When is $\left\lfloor \frac {7^n}{2^n} \right\rfloor \bmod {2^n} \ne 0\;$?

Question: Is
$$\left\lfloor \frac {7^n}{2^n} \right\rfloor \bmod{2^n} \ne 0\;$$
always true when $n \ge 3$.
Baker's theorem on transcendental numbers that provide bounds for diophantine equations may be useful, but I will leave that to the experts.
Comment: Did you manage to solve this, in the end?
Answer: One approach would be $7^n = (8 - 1)^n = (2^3 - 1)^n$. Doing binomial expansion, we get $7^n/2^n = 2^n x + k$ (k is sum of all binomial terms $i < n /3$). Little improved because it leaves less terms than above, but essentially same methodology.
Answer: The question can be restated whether $ 7^n <2^n \pmod {4^n}$
We can express this also in the number-system to base $2^n$, then
$\qquad 7^n \underset{\text{base } 2^n}{=} "c_n \  b_n  \ a_n" $ where $c_n , b_n, a_n$ are the "digits",
$\qquad \qquad$ and valid cases are where we have
$$\qquad 7^n-1 \underset{\text{base } 2^n}{=} "c_n \ 0 \ a_n" $$
As well we can ask, whether there is a number $m$ in the range $7^n -1 \ge m \ge 7^n - (2^n-1) $ such that $$ m= k \cdot 2^{2n} \tag 1 $$    The latter point of view shall be discussed below.

First we introduce the "residue" $r$ such that we write $ m_{n,r} =7^n-r$ where $1 \le r \le 2^n-1$ and $r$ is odd.
With this we find, that for the most residue classes the highest power of 2 occuring in $m_{n,r}$ is $3$, and this excludes then immediately a lot of nontrivial solutions.
Higher powers of $2$ occur only for residues $ r \equiv 1 \text{ or } r \equiv 7 \pmod {16} $ so we need only to test $m_{n,1}, m_{n,17}, m_{n,33},... m_{n,2^n-1}$ and $m_{n,7}, m_{n,23}, m_{n,49},... m_{n,2^n-9}$
If we test for the introducing example with residue $r=1$, literally "one step aside from the powers of $7$" we get the sequence $e_{n,1}$ of powers of $2$ which are factor as $7^n -1 = 2^{e_{n,1}} \cdot x$
$$ \begin{array} {r|rrrrrrrrrr}
 n&0&1&2&3&4&5&6&7&8&9&10&11&12&13&14&15&16&17& \cdots \\ \hline
 e&\cdot&1&4&1&5&1&4&1&6&1&4&1&5&1&4&1&7&1& \cdots
\end{array}$$
In this table, if we had a solution for your problem, the power of $2$ as factor at some $n$ should be $2^{2n}$ but we see, that after one solution at $n=2$ and $e_{n,1}=4=2n$ the growth of the exponents of 2 is much delayed: obviously (and in fact) the exponents grow only logarithmically with $n$. So we even know that after that single solution we shall have no more else. Here is a extended table with the required exponents:
$$ \begin{array} {r|rrrrrrrrrr}
 n&0&1&2&3&4&5&6&7&8&9& \cdots \\ \hline
m_n=7^n-1 &0&6&48&342 & \cdots\\
 e=\{m_n,2\}&\cdot&1&4&1&5&1&4&1&6&1& \cdots \\ \hline
\text{required e}=&0&2&4&6&8&10&12&14&16&18& \cdots
\end{array}$$
The possible key of the problem is then, that the similar effect occurs for all (interesting) residues $r$ which we have to look at, and these are only $1,17,33,49,...,1+16k,...$ and $7,23,39,...,7+16k $ because with all other residues $r$ we have at most powers of $2$ with exponent $3$ and thus we cannot have a solution with $e=2n$ for $n \gt 1$.
For some choice of $n$ we need check residue classes $r \lt 2^n$ and only two of them in each interval of $16$.
The problem which is not yet solved by this all is, that the tables for $n$ and $e$ have a certain perturbation of the entries $e$ so that higher powers can occur earlier. That this actually does not occur sufficiently strong and that it does not provide a solution in empirically accessible ranges illustrates the following table.

The table shows in the grey columns the residues $r$, and in the rows the occurences of $e_{n,r}$ . For instance, the row at residue $r=1$ contains the exponents of the powers of $2$ in  $7^n -1 $ First column refers to $\{7^1-1,2\}$ where the braces mean $e=\{n,p\}$ the exponent with which the primefactor $p$ is factor of $n$, so  $7^1-1=6$ has the primefactor 2 to the exponent 1. The same is valid for the values $n=1,3,5,7,...$  but is not documented in the table. The next column contains the exponent $\{7^2-1,2\} =4$ which is also valid for $n=2,6,10,14,...$. The third column contains the exponent $\{7^4-1,2\} =5$ which is also valid for $n=4 ,12,20,28,...$. And so on.
In general the columns follow only roughly(!) the powers of $2^c$ in $7^{2^c} $; the sequences of $n$ have with small perturbations compared with that of the sequences for residue $r=1$. However, a solution of the original problem could thus only occur, if the entries $e_{n,r}$ were about $2 \cdot 2^c$ and we see immediately, that for column-indexes $c \gt 4$ which would require $e_{n,r} = 2\cdot 2^4 = 32$ this very likely does not occur.
[update] Here is also an improved picture, where the lowest $n$ are made explicte with the exponents of the powers of $2$. I printed "n backtick e" in each cell. The yellow marked cells actually have $e_{n,r} \ge 2n$ and would give a solution $7^n-r \equiv 0 \pmod{4^n} $, but we ask only for solutions in the range $r \lt 2^n $ The ends of that ranges are marked by a bold underline and contain only the first entries of each columns down to that bold-underlined cells. Blue cell refer to $7^n-r$ which are negative and are not in the scope of our discussion.

Well, unfortunately this does not resolve the problem completely. But at least it gives a strong intuition - and possibly the path shown here can be followed later on.
Answer: The following may be a starting point:
Write $7^n \mod 4^n$:
$$ 7^n =a\cdot 4^n + b \quad b<4^n $$
$$ \left\lfloor \frac{7^n}{2^n} \right\rfloor \equiv \left\lfloor \frac b{2^n} \right\rfloor \pmod{2^n}$$
and this is $0$ iff $b<2^n$.
Well, $7^n=(2^3-1)^n=\displaystyle\sum_{0\le i\le n} \binom{n}{i} 2^{3i} \cdot (-1)^{n-i} $, and those with indices $3i\ge 2n$ vanish, thus
$$7^n \equiv (-1)^n\sum_{ i < 2n/3 } \binom ni (-8)^{i} = ... \pmod{4^n}$$
Comment: I don't think that working with the binomial notation can simplify the problem.
Answer: A little re-arrangement of the floored division in the counter-example yielded:
$7^{n}\ mod\ 2^{n} = 7^{n} + k\cdot 4^{n}\ ;\ k < 0$ or:
$7^{n}\ mod\ 2^{n} \equiv 7^{n}\left (mod\ 4^{n}\right )$
The first form: $(7^{n}\ mod\ 2^{n}) - 7^{n} = k\cdot 4^{n}$, requires the lhs to be divisible by $4^{n}$, or have $(2n)$ trailing zeroes in binary. A search from $n = 3$ to $n = 2^{17}$ failed to find a candidate. I'm sure there's more to be done with the first form...

So: $7^{n}$ would require bits: [n, 2n-1] to be zero.


Principle Component Analysis vs. Cholesky Decomposition for MonteCarlo

Question: Let's assume we have a portfolio containing large number (~500) of risk factors. We want to simulate the portfolio dynamics. PCA based simulation would be faster as we can reduce the dimensionality. Are there any other advantages of PCA-based approach Monte Carlo over Monte Carlo using Cholesky Decomposition (e.g. stability, more realistic dynamics)? I've seen papers dealing with seasonality effect in commodity forward curves, application to yield curves and an article here. However, I'm looking for some more in depth on the topic. Any references or practical experience is welcome.
Answer: Apart from numerical stability errors, Cholesky and PCA (without dim reduction) shall produce exactly the same distribution, they are two symmetric decomposition of the same covariance matrix and thus are equivalent for transforming a standard normal vector.
Of course when doing different things with PCA components, such as in dim reduction or quasi Monte Carlo sampling or related variance reduction methods, the equivalence is lost by definition, but it is there for standard sampling.
One advantage of Cholesky might be that storing and multiplying a triangular matrix requires less resources than a full square one. Pivoting is used for Cholesky if the covariance matrix is not PD (see this paper by Higham).
One source of confusion in the links might be the lack of clear separation between estimation and sampling. After estimation you shall have a PSD matrix and the decomposition used for sampling has nothing to do with it. (Methods for estimation can also be better than a naive sample covariance, there is a huge literature on this.)
Note that in the second link posted the procedure to "clean" non PSD matrices to get a correlation matrix forgets one step after zeroing negative eigenvalues: you must also scale rows&columns so as to recover ones on the diagonal. And there are also better methods to do that cleaning, this is not returning the nearest PSD correlation matrix.
Also that page is poorly written and confusing imho, if not ripe with errors, look for something else, e.g. Glasserman's Monte Carlo book.
Comment: +1 for the Higham method. It produces very reasonable PD matrices when you lack enough complete observations. Happens to be in new NAG release, I believe, if you have access to NAG. Or you could code it yourself (easy in Matlab).
Answer: When estimating covariance matrices, you run into problems as the number of assets/risk factors approaches or exceeds the number of observations. Some eigenvalues will go to zero, or be very small. This will mean that the covariance matrix is positive semi-definite instead of positive definite. Since the Cholesky decomposition requires a positive definite matrix, this leads to problems. However, you can adjust the eigenvalues in a PCA approach to change the covariance matrix to become positive definite. You could simulate from the PCA (for lack of a better way to phrase it) or use Cholesky on the adjusted covariance matrix.


Is it necessary for error messages to have cause and fix in them

Question: We are developing mobile applications, and our screen space is really limited. But our documentation guy is asking us to add long error messages that have cause.fix kinda format. So error messages are really getting very long and ugly. I wonder if there are best practices just for mobile applications with small screen space.
Answer: More Words Means Less Help
In general, you want to provide the user with the cause and the fix, especially that latter. However, you want to do this as concisely as possible. This applies to mobile, web, and desktop apps.
An error is an unexpected interruption that distracts the users from the task and frustrates achieving their goals. Users will naturally want to get back on task as quickly as possible, and will take shortcuts to do so. This means they will read as little as possible, skimming or scanning the message. They often do not read the error message at all. This is often optimal behavior. For example, if the user can simply recognize the message, they can guess the fix and not have to read the message. You want to use as few words as possible so experienced users know the fix at a quick glance, and inexperienced users can learn the fix by reading a few words. The longer the message, the less users read.
Okay to Imply Cause or Fix
This means you do not necessarily need to always follow a strict cause-fix format. If one is implied by the other, use only one. For example Don't say, "Problem: Entered qwerts exceeds the maximum allowed. Solution: Change your entered qwerts to be less than 76." Instead say, "Enter less than 76 qwerts." In some cases the fix is implied by the cause. For example, it's sufficient to say "Path C:\foo\bah not found." You don't have to say, "Check spelling of path." Users will tend to assume they mistyped it, or otherwise see the misspelling immediately in the error message anyway. Sometimes the cause is too technical to be comprehensible to users, so don't bother giving it. Just give the fix. Finally, sometimes there is no practical solution worth giving. If the users of a certain rank don't have permissions to delete, don't suggest they ask their boss for a promotion, or suggest they bribe Bob in the corner office to do it for them. Just say they don't have permission (or, often better, don't provide the delete control in the first place).
Optimize for Typical Case, Support Others
In writing your error message, assume a typical user with intermediate experience and knowledge, as indicated by your user research.  Messages with sufficient information for novices tend to be too long to be read by anyone. Assume the cause is the single most common one. Don't list multiple solutions. If two or more solutions are equally likely, then add code to determine which it is before showing any error message. Provide a "More help" link with the message to access modeless troubleshooting documentation for the edge cases of users with very low experience or unusual causes.
Format the message so that expert users can quickly recognize it. Put the key distinguishing words early in the message. Consider a unique icon for each error type (rather than the generic Error icon) that illustrates and distinguishes the problem.
Couple More Things...
As for ugliness, don't worry about that too much. When users hit an error, one of their least concerns is how pretty it looks.
And, of course, often the best looking and most helpful message box is no message box.
Answer: Keep to telling your users the essentials, like how they fix the problem. No need to feed them with information that they will forget as soon as they close the message, that will only make it more troublesome to read. And often (because of information overflow) even harder for the user to figure out what they're expected to do to actually fix the issue, since the generous amount of text suddenly made the problem look a lot more serious than it actually is.
Answer: If it is a simple field validation error, then simply highlight the field with 1-2 word phrase like 'Mandatory Field' or 'Only Numeric'
If it data-validation error from server, then show the message on top in red (also highlight failed fields)
If error is not because of user input, then show a small dialog box which will prompt them to respond, for example if network not available show dialog pop-up "Network not available, please try after sometime", or "Your Session expired, click OK to login again".
I wouldn't go with a fixed thumb rule on how to deal with errors, rather go case by case or even make sure that UI prevents the error than handling it.
Answer: I've observed something that I'd call error message blindness when users see an error and just abandon their task regardless of whether the situation is fixable or not.  This was with a high frequency, performance incentivized user group but I think that the lessons are generalizable.

Keep the message as short as possible.  Less is more.  Users tend to scan more than read error messages. If there isn't a clear simple action to take, the user may assume that they can't fix it and could abandon the task.
If possible, combine the cause and solution into one statement.  Some errors are simple and some are complex and require specific instructions for correcting them.  This is a judgement call and decisions should be validated with usability testing.
Create distinct styles for different error types.  For example, fixable errors should be visually communicated differently from unfixable ones.  Otherwise, users could learn to make quick wrong assumptions about whether or not they should abandon.  Users make decisions based on a lot of inputs and reading text is not always one of them, especially high frequency users.


accidentally placed oil in the coolant reservoir in a BMW 325i. How do I fix it and what is the cost?

Question: I accidentally added oil to my coolant reservoir. I have a BMW 325i.  The oil light came on and I figured my oil may be low. When the oil was added the oil light warning went off.  However, the service engine light came on. It was at this time, I checked the manual and discovered that although the cap where I added the oil stated use ATF oil only, per the manual this is the cap for coolant. Please tell me just how much trouble I'm in and what the cost will be to fix it? Thank you!
Answer: The very first thing that you should check is whether you actually made a mistake and, if so, which one.
A cap that says "ATF oil only" is for automatic transmission fluid.  If you're adding engine oil to the transmission, that's going to make your transmission very unhappy.  It is fixable: you'll need to drain the transmission fluid and replace it.
If you actually did add oil to your coolant reservoir, there was a similar situation discussed here:
Accidentally poured engine oil into the coolant reservoir
Essentially, the coolant will need to be flushed and replaced.  This isn't going to kill the car but it's best to keep driving to an absolute minimum until you've flushed the system.
Answer: Sounds like you actually poured you oil in the power steering reservoir, and should be easy to fix... If you didn't operate the vehicle long term, you can have it flushed, and have the reservoir refilled. Coolant tanks have a plastic cap, and are easy to see in your vehicle. Also, I believe most BMWs have sealed transmission, so unless you have an older BMW, you shouldn't be able to access the transmission that easily.


Galvanized steel off-flavor?

Question: I brewed my first beer with maris otter and it came out with an ashtray/cigarette flavor. At first I assumed it had something to do with the maris otter, but later I noticed my mash tun hose clamps where completely discolored. I guess they were galvanized not stainless. Is this the source of the off flavor? Is it safe to drink?
Comment: How much zinc is in your diet regularly?
Answer: Could the flavor be described as a burned flavor? Are you applying direct heat to the mash tun? Do you have a heating element in direct contact with the wort, like in a RIMS system? It sounds to me like you may have burned or scorched your mash or wort. Direct heat to the mash tun is fine if you have a false bottom, but be careful if the malt is at the floor of the tun. Scorching from RIMS can happen if the flow rate is too slow.
Or maybe someone played a trick and substituted some peated malt for Maris Otter? ;-)
Answer: It could be the source.  Also note that any time you have a mixture of metals, particularly when they are touching (because of production of electric current in a manner similar to a battery), you have the possibility of corrosion which can lead to metals dissolved in your batch.
I would be extremely surprised if the solubility was enough to cause acute toxicity and yet not enough to inhibit yeast growth.  In general if it doesn't taste that bad, I wouldn't expect it to be acutely toxic.  However, excess zinc can cause malabsorption of iron and some other nutrients so it may be one of those things to be careful about.  Anything in sufficient quantity is toxic.
My general rule is:  if it tastes bad enough to poison you with most (non-heavy!) metals, you wont drink it but that is me and not advice.  Do your own research on zinc toxicity and decide for yourself what level of risk you are comfortable with.
Answer: Ouch!  I've never used hose clamps inside my mash tun - copper friction fit works just fine for this old salt.
If you suspect zinc, put a magnet on the clamp(s).  Zinc is plated over steel, which contains iron and iron can foul a beer taste-wise in low doses.
However, short term exposure in a presumably high volume of wort to contact with the iron or zinc leads to the questions: what is your water profile?  And what is you malt bill?  Your ph can aggravate your flavors and attack metal.
Second thought, how old is your beer?  A million questions in an effort to defend Maris Otter, an otherwise solid malt.
Answer: I really doubt that's the source.  At one point, I had similar (although not galvanized) hose clamps in my tun.  I never noticed any off flavor from them.  If there was anything getting into the mash from them, the amount would be extremely small.  Then it would go through the boil and fermentation.  I can't imagine that any flavor would be left from it.  And I can't imagine how it could cause an ashtray/cigarette taste.
Answer: I too don't think it's the Marris Otter.  Malt made from Marris Otter barley is one of my favorites.
I also don't think the clamps would cause this particular problem, but you don't want steel or zinc in contact with your beer.  Iron and zinc are both toxic to yeast.  Go get some stainless hose clamps and replace the discolored ones.
When you say "ashtray" flavor, do you mean "smoky?"  If it's smoky, that character can be caused by some wild yeasts that produce phenolics.

Galvanized steel off-flavor?


How to Store Fresh Herbs

Question: What is the best way to store fresh herbs like parsley or cilantro?  I find I have about the same luck with them whether they are left in a plastic bag or I put them in a cup of water.
Comment: Make sure that the herbs are clean of dirt. Different herbs live differently. Show you can put in vases like flowers, rosemary and thyme don't need to be tightly covered and tarragon likes to be wrapped in a damp paper towel.
Comment: Easy, dry them out ;)
Answer: If you're going to store anything leafy in a plastic bag, I wrap it first in a paper towel, then in the plastic bag, so none of the leaves touch the bag.  This prevents the issue where the outer leaves turn to goo.  (I'm not sure what the actual biological issue is ... moisture/condensation? poor respiration?)
Don't wash it before storage, as the extra moisture will cause it to rot faster.
I think I've gotten as long as a month out of flat leaf parsley, when I buried them in the back of my crisper drawer and forgot about them.  (of course, I wasn't constantly opening the bag as you would when using them, and I'm not sure exactly when I placed it in there, as I had forgotten about it).
Comment: This works pretty well because your paper towel functions as a moisture buffer - absorbing water when there is too much, giving it off again when the atmosphere is dry.
Comment: Whenever I buy greens from the supermarket, they are always misted with water over there... They are rather damp. Should I dry them all out on a chopping board first? Also, does the rubber band around the stems have any negative effect?
Comment: @slav : Yes, you don't want to leave too much water on them, or they'll rot.  The rubber band doesn't help as it keeps everything tightly packted together, so any moisture that forms from transpiration  will have less air to evaporate.
Answer: Personally I think the best way to store fresh herbs is to use a small herb garden. I just planted one and found it very useful for things like thyme, rosemary, and parsley.
If you don't have room for a small herb garden then a plastic bag in the fridge is usually the next best thing.
Update: Cool link on popular mechanics on growing a garden in 5 gallon drywall buckets.
Comment: @Zaphoid: Isn't that the idea? :-)
Comment: @VinkoVrsalovic - This is only OK if the herbs are treated humanely.  For example, all my cilantro is free-range, cage-free, and have access to the outside.
Comment: I can't seem to grow Cilantro without killing it
Comment: This is the best thing I've done.  Nothing beats going out for fresh basil.  Or mint for your julips and mojitos ;)
Comment: I tried a herb garden. Mint tends to grow faster than I can use it, the roots catch fungus and moss develops on the soil. Cilantro takes a month to grow fully, and after flowering, it dies out quickly. Also, it tends to catch some kind of white powdery fungus on its leaves. I eventually threw away the grow-bags and just bought herbs from the store.
Answer: Basil: Make sure the leaves are dry! Use a papertowel to dry them off. Then, trim the end of each stem, and put the basil in a glass of water. Avoid having any leaves below the waterline. Change the water regularly. Keep it at room temperature.
Parsley and Cilantro: Same instructions except refrigerate with a baggie loosely over the herbs. Be sure they're not in an area of the fridge that gets extremely cold.
Rosemary: Wrap in a damp towel, and put it inside a baggie in the refrigerator.
However you store them, be sure to clean them up again after you get them out for use. Remove any yellowed leaves, give them fresh water, and make sure there's no leaves below the water line.
As others have mentioned, for longer storage, you can freeze herbs if longer storage time is needed.
Answer: Refrigerator storage methods
Some tender herbs (ex: cilantro/coriander and parsley) can be refrigerated by placing them in a cup of water (like a bouquet of flowers) and covering with a plastic bag. And like a bouquet, you'll want to change the water regularly. Ref: JustRightMenus, Michael Pryor
You can also get away with simply wrapping them in a paper towel and then in plastic, or wrapped with ice in paper. This will tend to work better for more hardy leaves (ex: rosemary, sage) Ref: Joe, Ryan Olson, TheComfortOfCooking.com
Freezer storage methods
For long-term storage, you can freeze cold-tolerant herbs. Seal in air-tight freezer bags, or submerse in liquid to prevent them from drying out, freeze as quickly as possible, and store as cold as possible. Try not to thaw before using. Ref: bubu, Kev
Room temperature storage methods
Some herbs (basil...) don't handle cold well. To keep these fresh, or if you simply don't have space in your fridge, you can try the same "flower bouquet" technique mentioned above, but without the bag over the top. Set out of direct sunlight and change the water periodically. Ref: JustRightMenus, Dinah, franko
You could also simply cultivate a miniature herb garden, and pick what you want when you need it - doesn't get any more fresh than that! Ref: Bryant
Other (not-so-fresh storage)
You can, with minimal effort, make a herb-flavored oil or vinegar by simply submerging fresh herbs in a good-quality oil or vinegar. Exercise caution when storing oils made with fresh herbs though, as if not properly refrigerated they can foster the growth of dangerous bacteria.
Drying is a great way to keep some herbs around for off-season use. Hang a bunch in a dark, dry place until thoroughly dried, then store in an air-tight container away from heat.
Comment: When you chop the herbs before freezing they are really easy to use. I try to always have frozen chopped parsley in the freezer.
Answer: I tend to wrap any leafy vegetables/herbs in paper towel or put them in a paper bag when putting them in the crisper. Instead of retaining the moisture, it lets it escape preventing the nasty sludgy rotting effect of dampness. It'll maybe give you a few extra days as the stuff will slowly dry out or wilt, but shouldn't become slimy.
Comment: I think I like this option the most but it does seem strange to  use paper towels like that.
Answer: StillTasty.com has good instructions for fresh cilantro and parsley.
BTW: the advice for these 2 happens to be the same but it's not the same for all herbs. For example, here's their advice for basil.
Their site has good advice for other herbs and foods as well. The one thing that they do that drives me crazy is disabling highlighting so I can't copy/paste.
Answer:
Take a cup and fill with water.
Put the cilantro in the cup (as if they were flowers)
Place a ziploc bag over the top of the cilantro and loosely fit it around the top of the cup
Place the cup in the fridge.

It should last a VERY long time like this.
I learned this from Joel.
Comment: I use this method. It allows cilantro to last about a week sometimes a week and a half.
Comment: @chrisjlee A week and a half doesn't sound like a very long time.
Answer: My method is similar to Joe's, but I skip the plastic bag entirely.  I wrap a bunch of herbs in a towel, then put a few ice cubes in a fold of the towel.  They melt slowly enough to keep the towel just a bit moist, and our herbs last for weeks.
Answer: Freeze it. Most herbs freezes well and do not lose the scent easily. The only caveat is that the color is usually lost. It is rather a trade off.
In a way, drying preserves more of the color and presentation of the herb, but freezing preserves more of its flavors.
In my opinion, get those resealable bags, put them in, squeeze the air out, put into fast-freeze compartment, take it back into the normal freezer compartment after 1 day, then store for up to 3 months.
Comment: Works better for some herbs than other. Basil fails completely with freezing. Parsley works great though.
Answer: i actually have had a bit of success keeping it in a small vase on the counter, out of a lot of direct sun! i change the water every day, and trim the ends of the stems a bit to keep the ends from going slimy.
Comment: If only there were a way to automate changing the water :)
Comment: well heck -- i was just randomly surfing some cooking blogs i frequent, and look what i found: http://comfortofcooking.blogspot.com/2010/07/how-to-store-fresh-herbs.html
Comment: +1 from me, it's my preferred method of keeping pretty much any herb that I use
Comment: It looks like the blog has moved, and the redirection didn't quite work.  This seems to be the relevant content : http://www.thecomfortofcooking.com/2010/07/how-to-store-and-freeze-fresh-herbs.html
Answer: I like the comment from @DaveVoutila best. I don't use a paper bag, though - just paper towels. The herbs will eventually wilt, but they'll still be fine for soups, stocks, etc. In fact, in time, they'll become rather similar to dried herbs.
Answer: Many herbs freeze quite well (works better if you have a fast chill compartment which reduces the chances of water crystals forming in the flesh).
When you come to use them prepare what you need right out of the freezer and straight into your dish.
Answer: If you only need to preserve them for a few days after getting them fresh, just using some aluminum foil to create a sealed package and store them on the fridge usually works out pretty well.
Answer: I've found that herbs packed in a vacuum, and then maybe put in the fridge, preserve their taste and smell for quite a long time.
Answer: You'll probably only get 10 days of freshness in the fridge, so consider freezing it.  You will lose some of the freshness, but it can still be useful for seasoning soups, stews, etc.  Freezing, as a means of preservation, works for lots of foods.
Answer: Freezing, or consider making a paste of it together with some oil (and store well). You'll lose the effect of fresh leaves, but it'll stay good a while longer.
Answer: Zaphoid, have you tried using special "Produce bags" sold in supermarkets? These have tiny perforations in the plastic that let the veggies or herbs breathe and also cut down on the excess moisture, they have a zipper and can be washed dried and reused. Do not use these bags for mushrooms which should go in small brown paper lunch bags.
Answer: oh well there is lot of ideas to make leafy vegetables fresh like spinach,cilantro etc if u want to keep it in fridge firstly roll them in newspaper then in plastic bag it will work and there is another idea you can keep leaffy vegetable in a pan n cover it properly n keep it in kitchen if its winter season u dont have to keep it in fridge,or you can just open it from bundle and spread it on large tray n keep it under sky in night it will be fresh because of dew drops which fell on it.
Answer: This is five years on & I recommend you put it in a brown paper bag (No sweating) and then place in the fridge - plastic bags are out - they cause moisture which causes rot to stems and leaves

How to Store Fresh Herbs


how can i carb multiple kegs at the same time?

Question: I have 5 kegs I want to carb with a single co2 tank, I have a splitter, but I don't know if I need to apply the same amount of pressure I apply to a single keg, I carb using the 40 20 method, which is 40 psi for 24 hours, then 20 psi for another 24 hours and finally at serving pressure, will I get the same results if I apply it to five kegs at the same time?
Answer: Yes, use the same pressure as for one keg. You can do this and it will work as expected I do it often - I have a primary regulator, 4 x secondary regulators, and each secondary feeds a 3 or 4 way manifold.  The fact that you are using a pressure regulator means that all kegs will be kept at the same pressure and will not overshoot or have any other problems. There is no difference between carbing one keg or 5 you use the same pressure, but of course, you use a larger quantity of co2.
If you don't have a check valve on each line of your splitter, be sure not to fill the keg too much, so that the liquid level is below the gas dip tube, or you can end up pushing beer out into other kegs.
Comment: Thank for clearing thing up
Comment: @mdma, do you have a picture of your system for share? I don't know if I understand well, do you have all this regulators attached to just one CO2 tank? Just being curious here. Thanks! (:
Answer: You should get the same results, though it will take longer for five kegs to come to the same pressure than for one (possibly minutes, rather than seconds).
The gas will flow from a location of high pressure to one of low pressure until it's all equalized.   It doesn't matter whether that location is one keg or if it's distributed across one hundred of them.   The only limiting factor is the amount of gas in the reservoir tank.   If there's not enough gas in the tank to get all five kegs filled, then they'll all equalize out at some lower pressure.


Is warm up exercise necessary for load-bearing and high impact exercise?

Question: I am new to fitness and will be doing load-bearing and high-impact exercises. It necessary to do warm-up exercises before starting load-bearing and high-impact exercises? If yes, then why it is necessary?
Comment: see definition of the tag "warm up"
Answer: A warmup is a very good idea, but it doesn't have to consist of what you normally think of as a warmup. The warmup should consist of low-key approximations of what you'll actually be doing. So for weights that might be going through the movements without any weights, then with lighter weights, before going to your work set. For running that would be walking first. For baseball it would be playing catch. And so on.
The biggest reason for doing a warmup is you'll be able to notice any problems before they become serious. If you notice some unusual pain or problems doing a bodyweight squat, that's a good indication you shouldn't be squatting with a heavy load on your shoulders. That might just be stiffness, and if you do a bit of a longer warmup you work the kinks out, but it might also be an injury (from anything, could even be just sleeping badly) and you're best off just not doing that exercise at all that day.
Answer: From what I've read, warm ups are good for getting your body warmed up and your muscles ready for stress.  Think of your muscles like rubber bands.  When a rubber band is cold, it has a tough time stretching and is prone to snapping if you put too much pressure on it.  Now, take that same rubber band and warm it up to a decent temperature and it'll stretch just fine.


Security of GPG encryption with AES and MD5 if MD5 is broken

Question: I have a file encrypted with gpg, using AES256 and MD5. Suppose that the MD5 hash function is broken, but not the AES cipher. Does that make it easy to crack decrypt the file?
Comment: Could you provide more details, like which cipher did you used. Are you sure your talking about hash, not key?
Comment: What is the hash use for? Signing?
Comment: lets say thats there is a file encrypted by gpg used AES256 and MD5 ... if MD5 cracked will the file decrypted easily or not
Answer: Depending upon to what extent MD5 is "broken", a break of MD5 might enable chosen-ciphertext attacks.  However, as far as I know, it won't enable purely passive eavesdropping.
That said, the likelihood of a catastrophic break of MD5 (bad enough to compromise the secrecy of your gpg-encrypted data) is probably much lower than other risks your system faces.  I think it's unlikely that this is the weakest link in your system, or that this is anywhere near the biggest risk in your system.  This risk is likely nearly negligible, compared to other kinds of risks that tend to be present in most information systems.
Answer: If MD5 is used to create the key that AES uses, then if MD5 is broken, someone else can re-create the key used by AES, and thus be able to decrypt the file.
Not unless MD5 is used with something else, like an iterated key derivation function.
MD5 is considered broken. So I suggest to not use it anymore.
Comment: side question, did hash store my key in the encrypted file, is this the header.


Scheduled Mail in asp.net

Question: Hai Guys,
         My application deals scheduled mail concept (i.e) every morning 6.00 am my users gets a remainder mail about their activities for the day... I dont know how to do this.... Many told use windows service but i will host my website on a shared server i may not get rights to do windows service... Is there any dll for sending mails at a schduled time through asp.net application ..please help me out guys......
Answer: ASP.NET doesn't have a built in scheduler, but there are ways of starting background threads even in a web application. However my advice would be to keep it simple, and have the emailer web page send emails on demand. Then you can schedule a task from any computer to visit that web page. You might want to protect the mailer application with some form of authentication to avoid abuse of the system where hackers could invoke the emailer.
This has the added side effect (advantage) that the scheduled task is always run in your time zone.
Answer: There are some solutions but they are all far from being ideal for your situation (because you want this on a shared host). I highly recommend you change to virtual hosting if possible, so that you can use Windows Scheduler. There are hosts that offer very cheap virtual hosting plans (starting from $40).
If this not possible, you can use a background thread as suggested in the previous answer. You may also call a page periodically on your website, for example using a website monitoring service. Both solutions are not really reliable but I'm afraid you don't have many options with a shared host.
Edit: I believe some shared hosts offer you scheduled tasks in their control panel, I remember I saw this with some host some time ago. Well, in this case you can find a host that offers this service and the problem is solved, it shouldn't be very hard with a little searching.
Answer: We just set up a cache object that expires every 24 hours. Initialize it in global.asax You can set the callback method to do your batch processing. Make sure when it's done, it re-fills the cache up with the dummy object that will call the callback again in another 24 hours.
Comment: This will work as long as your AppPool (IIS worker process) doesn't recycle during that 24-hr time period.
Answer: I am not sure if you are able to or not, considering the hosting environments, but it would definitely be worth your while to look into Quartz.NET for this sort of thing.  You create a job, and schedule it to run at 6:00 AM every morning.  It's a rather impressive tool, all-in-all.

Scheduled Mail in asp.net


other wording for a Select button?

Question: I have multiple Select buttons next to player's names in order for a user to choose which player they want in a game.  A user can't just click on a player's name because that gives additional stats, which is why there needs to be a select button.  They are rather ugly but I also don't want checkboxes.  If anyone can think of something more appealing to use I'm open to hear it.
Comment: What's the platform (e.g. Windows, Flash, iPad)? Can you post a screenshot?
Comment: Piggybacking off of Patrick's question...what technology are you using?  Need to understand how rich of an experience this is.  E.g.  Is it an HTML page with character choices or is it something highly interactive and animated like a Flash game?
Answer: Not a direct answer - but have a look at the way many of the arcade video games handled multiplayer selection.
There are lots of screenshots online - here's one:

Or, better yet - go down to the video arcade and see how they work.
Why do this?
Because arcade video games are in the harshest commercial market - anything that degrades the user experience leads directly to lost revenue because the player goes to another game machine and plays there instead.
Of course, you'll need to do some adaptation - your players are unlikely to have four joysticks attached to the machine, but video games don't usually have keyboards, and so on.
Answer: If possible, I would use just one button called "Continue", or "Go", or "Play".
This button would be beneath the entire list. Clicking on a player displays the stats and highlights that player and then once the button is pushed, the selection is made.
This avoids repeating the button and provides a natural flow - when I find a player with the stats I like, I stop looking and press the action button to select.
If that's not possible, consider whether viewing the stats is the main action in this screen?
Will most of your users be just viewing stats most of the time?
It sounds like after viewing the stats once or twice, their main focus on the page would be selecting the player.
Answer: I would give the user a 'token' (small circle with "user", "P1", etc... inside) that selects their player and the user drags/drops on the player they would like to use.
This allows them to select the player they want while still viewing that player's stats and without cluttering up the screen with more checkboxes or buttons.
Answer: You can have a "highlight" of some sort follow the mouse.  Imaginge this:
[1] 2 3 4 5 6
The numbers are your character images.  When you move the mouse the bracket follows it. Clicking your mouse 'selects' that character.  You'll have to figure out another way to communicate that a particular character has been selected.
Answer: We could use more information about how the screen is organized. Assuming it's split (horizontally/vertically) between the list of characters and a stats panel - why not place one Select button in the stats panel? You could click through the list of characters, the stats would update according to current selection, and the Select button would stay in one place.
Answer: You could display the information when the mouse hovers over and select on click.
Another way would be to display information on single click and select on double click.

other wording for a Select button?


Why does OAEP have 2 rounds with 2 random oracles?

Question: I strive into understanding why OAEP has two rounds of computations and not just one. I.e: Wouldn't it be safe to hash the random number r and XOR it with the original message?What security risks if any that padding scheme violates?
Comment: This is essentially an [all-or-nothing transform](http://en.wikipedia.org/wiki/All-or-nothing_transform).
Answer: This variant of OAEP would be malleable if the underlying trapdoor permutation is malleable, and hence would not be chosen-ciphertext secure.  This is a major theoretical weakness, as I explain below, and one that may lead to attacks in practice.
In more detail, suppose $G$ is the (lone) hash function and $f$ is trapdoor permutation used, so the formula for the encryption algorithm of this variant of OAEP is
$$f(m\oplus G(r)\|r).$$
Suppose you have are given the output of the encryption algorithm (call it $y$) for some unknown message $m$.  If $f$ is malleable, it may be feasible to come up with $y'$ that is an encryption of $m$ with a bit flipped, meaning $$y' = f(m'\oplus G(r)\|r)$$ for $m'$ equal to $m$ with a bit flipped.  If one obtains a decryption of $y'$ (as is allowed in a chosen-ciphertext attack) then one learns $m'$ and hence $m$.
The extra round of OAEP is to ensure that such ciphertexts decrypt to unrelated messages that do not help an attacker.  You may want to look at SAEP and SAEP+ [1] for some more results on one-round variants of OAEP that are secure.
[1] D. Boneh.  Simplified OAEP for the RSA and Rabin functions. In proceedings of Crypto '2001, Lecture Notes in Computer Science, Vol. 2139, Springer-Verlag, pp. 275-291, 2001
Answer: Adding to David Cash's answer, besides SAEP and SAEP+ by Boneh, there is another paper that improves OAEP using only a one-round Feistel structure and has an additional feature: redundancy-free encryption (which none of OAEP, SAEP and SAEP+ have). Read Verified Security of Redundancy-Free Encryption from Rabin and RSA by Barthe, Poitcheval and Beguelin (2012).


What is the difference between deb packages and tar balls ? What are the advantages/disadvantages of each?

Question: I don't know about tar balls. Most packages are available in the tar ball forms but Ubuntu packages are Debian packages.
What is the difference between deb packages and tar balls ?
What are the advantages/disadvantages of each ?
Answer: Tar balls are usually source code that you have to compile. Debs are pre-compiled programs, already built and configured for Ubuntu/Debian.
I would strongly suggest using debs when available, as they are easier, and they integrate with the package manager, so you can easily uninstall them.
Debs will also install any dependencies needed. Installing from source can lead to what is affectionately called "dependency hell". Most open-source programs depend on several other programs/libraries to function. When installing from source, it will not install these, and will instead (hopefully) complain that a dependency is not met. You then try to install that dependency and then it bombs out, requiring another dependency, etc, etc.
Installing from source can also put your files in unexpected places, as different distros lay things out slightly different.
When I need to install a program, I try my options in this order:

Look in the Software Center. This is obviously the easiest, although the Software Center is not all-inclusive and is not up-to-date with the latest versions.
Try to find a repository that provides it. Adding a repository will make the program show up in the Software Center, receive timely upgrades, etc.
Look for a .deb package.
Install from source (tar ball).
Answer: tar balls are just another form of compression like zip. Although the formats and techniques of compression differ, it is basically a container for a group of files and folders.
Usually, the source code and the files needed by it will be made available on the internet by the person/group who wrote the software in the form of a tar ball. So you can download it, untar it, compile the software and install it.
However, what deb packages do is to make this installation process easy for you by maintaining a standard. The software available on the internet will be taken by Debian package maintainers, made into their corresponding .deb packages and put into the Debian repository.

You can read about it from a Debian Package maintainer's blog here : http://www.j4v4m4n.in/2012/05/01/debian-utsavam-at-mes-kuttippuram-kerala-2/
As for the advantages and disadvantages, .deb packages are managed by package managers such as apt and aptitude. So whenever you install a software with it, they will automatically figure out if you have the dependencies that are required to run that software on your system and will install them for you.
But if you are using a tar ball install it, you will have to figure out what that software depends on and each time you will have to check manually whether the dependencies of the software you are installing were already installed previously.
But apt does all this for you.
Also, installing from source (installing from tar balls) will have different methods for different software. There is the GNU philosophy of configure-make-make install and there are other methods depending on how the software is written.
However, converting them into deb completely removes all these differences and makes it easier for the user to install and use the software.
One more point. When do you need to install from source? That is from a tar ball? There are basically two situations.

If the debian packaging team has not yet packaged a software.
If you want to contribute to the project. That means you can make changes to the source code, compile it and test the changes.

If you would like to know more about debian packaging, you can read it from here : http://www.debian.org/doc/manuals/maint-guide/
Hope this helps.
Answer: Debian (and hence Ubuntu) packages are collection of binaries and related instructions for their installation. This means that the package itself knows how and where to install, and it also knows the list of packages it depends on.
Source tarballs (files with extension .tar.gz or .tar.bz2 - or even .tgz or .tbz2) are simply sets of files and directories that have been packed together with the tar utility and also compressed with either gzip or bzip2. To build the source code you have to:

unpack the files with tar xvfz file.tar.gz or tar xvfj file.tar.bz2 (in an empty directory)
configure the package with ./configure (the package tests the system to see if everything is ok before starting the compilation)
start the compilation with make
if you want to, run make install to install the application to its "default" locatioon (usually in /usr/{s}bin or /usr/local/{s}bin but it depends on the application and on the distribution)

The main advantages of Debian/Ubuntu packages with respect to source tarballs are that packages are "self-contained" and their binaries are tracked. This means that the unpacking process is transparent to the user who just sees (roughly) one package per application. The user doesn't even need to remember what files a given application has installed and where, so the installation/removal of applications becomes (mostly) a one instruction process.
The main advantages of source tarballs with respect to binary packages are that in the first case the source code is compiled directly on the target machine and can then be optimized accordingly. Moreover, even the best package system can broke in particular cases (e.g. software packages too new or too old) and usually official packages are purged by servers when they become too old. In these cases one has to manually search the Internet for the desired application and for the specific libraries at specific versions to satisfy all its dependencies.
Comment: A small point. The "configure, make, make install" steps are for those Softwares that use the GNU automake build philosophy. There are Softwares that can be built from source (from tar balls) in various ways. So it might not be correct saying "To build the source, do configure, make, make install". The best way to put it might be, "To install from source, read the README or INSTALL file within the source and follow the steps mentioned there within. Do refer to this : http://sosaysharis.wordpress.com/2011/11/28/installing-a-software-from-source-in-ubuntu-untarring-a-tar-tar-gz-file/
Comment: Yes, I just talked about this kind of method because it's adopted by the vast majority of source tarballs.
Comment: No debate there. :)
Answer: I can see some pretty good answers already posted. But there are a few things that need to be addressed.
Contrary to what is known as "dependency hell" when it comes to compiling from source, you can actually configure Ubuntu in such a way that it automatically installs those dependencies when you are compiling from a tarball/ any source.
Read how to do this here:
http://www.howtogeek.com/106526/how-to-resolve-dependencies-while-compiling-software-on-ubuntu/
Also, if you keep that dependency problem aside, the good thing about tarballs is that you can configure lot of install related things like where to install etc, very easily in case of installing from source.
Also, the word "Debian Packages" could confuse you in this context. Remember that Debian packages come in two types like it says here:
http://www.debian.org/doc/manuals/debian-faq/ch-pkg_basics.en.html
Of course, if you are talking only about deb files, then they generally are those compiled software like the above answers already said.


Search site getting 404 error

Question: The log says nothing. I am getting 404 when accessing from browser. I can see the whole sub site using sharepoint manager 2010. By the way it was always working. Just stopped working about 12 hours ago.
What else should I be doing?
Comment: Is it pointing to a correct URL to the Search center, when you click on Search? May be somebody had a typo in the URL, in search settings of site settings.
Answer: 404 means NOT FOUND; you have to check the Search settings under Site Actions > Site Settings. The URL there is where the user goes when Search is clicked. This is a common issue when you aren't using the default Search site (basic), someone has moved it or you deployed the enterprise search site.
Simply check it by running a search and noting the URL - should be very easy to spot what the issue is. Worst case, simply deploy a new Search Site, set the URL's properly in the Site Settings and you'll be good (no effect on Index).
NOTE: You should also check the Search site settings in the User Profile application (Central Admin site > Application Management > Manage Service Applications). The My Site settings specify the URL to the search site.
David Sterling
davidmsterling.blogspot.com
www.sterling-consulting.com
www.sharepoint-blog.com
Answer: Open IIS Manager (Start => type IIS => press Enter) and make sure that the site is running.

If it is not (like as it shown in the screenshot), and you can't start it, the reason for this could be that some other application occupied the same port, and it prevents IIS from starting the site.
It could be Skype or security application or smth like this.
You can determine the application by running netstat -ano, find the port, and lookup the corresponding PID. Then, you can resolve the actual application name in the Task Manager (you might need to add the PID column from menu, View => Select columns...).
Also, a good idea would be to check Windows Event Viewer logs after trying to restart the site.
Answer: What are the configuration settings for Anonymous Authentication in IIS?  Right click on Anonymous Authentication in IIS and choose settings.  Then check to see if it is configured to use the Application Pool Account or the IUSR account.  I've found that if it is the former - application pool account - within SharePoint 2010 everything will go straight to hell.
I think this has to do with the changes to SPNEGO that were implemented in Windows Server 2008 R2, which is the same reason Kernel mode authentication is not supported in SharePoint 2010.  (That's right, it's not supported anymore.  Don't configuring Windows Authentication to use application pool credentials anymore:  http://www.harbar.net/archive/2008/05/18/Using-Kerberos-with-SharePoint-on-Windows-Server-2008.aspx).

Search site getting 404 error


Where can I see in which country a patent is valid?

Question: I am looking through Google Patents and reading the paperwork of various patents. In what section can I see under which country the patent is valid?
Answer: While any single granted patent is granted in a specific jurisdiction and only enforceable there, the applicant may very well have filed duplicate applications in any number of other countries.
EDIT
Not every patent document is an issued patent. If the number has an "A" at the end it is an application. If it ends in a "B" that indicates an issued patent. But issued may not mean enforceable. It may have expired at the end of its term or renewal fees may not have been paid and it may have expired early. The two letter country code and the A or B suffix are international standards.
Google patents will not necessarily show all related patents. One way to get a bigger picture is to use the INAPOC database. You can get to it in several ways. One free patent search site, The Lens, says it covers 90 patent jurisdictions. When you look up and find a patent document it has a series of tabs. From the tabs you can seen where it has been filed (if it is a matter of public record at the time) and it also shows if renewal fees have been paid. A screen shot shows a map of the world showing the coverage of a particular semi-random pick.
Answer: Patents are only valid in the country that issues the patent.  There are no international patents.
So, a US patent is only valid in the US.  Likewise, a Japanese patent is only valid in Japan.  Same with a German patent or a French patent or whatever.
To see what country issued the patent, check the front page of the patent.  Typically the top of the front page will identify the type of document.  Like "United States Patent" or similar.
Comment: Thanks, I wasnt sure if that was document language code up there.
Comment: To add to George's comment above - you can usually tell the country which issued the patent from the two letter [prefix of the patent](http://patft.uspto.gov/netahtml/PTO/help/helpctry.htm)
Comment: Please forgive me for switching the chosen answer. But George White provides additional information. This does not mean your answer is not spot on.


Have there been any mechanisms proposed for normalization in probabilistic population codes?

Question: I heard a talk yesterday by Dora Angelaki about multi-sensory integration.  Part of the talk was about bayesian inference with multiple noisy sources of information.  I know that there has been a lot of theoretical work done on bayesian inference and population coding, but I was wondering if there have been any biological mechanisms proposed for the population activity normalization necessary for these computations?
Answer: It depends what you mean by a biological mechanism. If you mean that there should be a protein cascade that implements normalization, that doesn't seem plausible, in my opinion. Normalization in probabilistic population codes is just one of many computations that can be performed in a neural system.
If you're okay with the notion that there's nothing biologically unique about normalization, then Normalization for probabilistic inference with neurons (a paper written by my supervisor, Chris Eliasmith) proposes a spiking neural network performs normalization on probability density functions.


Can I display Facebook Page status on my website?

Question: Is it possible to let my website show the status message of my facebook page? How can this be done?
Comment: Can you share more information about your website? There are different ways of doing this on wordpress-based websites, for example, than on just an HTML page.
Answer: There was a discussion about this on the Facebook Developer's forum that might help. The main recommendation is to use the Like Box plugin on your website - although I recommend you have a look at the Profile badges as well.
Answer: It's now possible to export your Facebook status as an RSS feed, which means you can add it to your own choice site.
The hard part is finding your personal status "feed." Go to your Facebook Profile page and look for the "Mini-Feed" box. Click on the "See all" link. On the right rail of the resulting page is a list of links; one of them is "Status stories." That's the one you want. Click it.
Now you have a page labeled "My Mini-Feed" that is limited to your own status updates. Look in the right rail for an RSS icon and a label, "Subscribe to these stories." There's your RSS link.
Grab the URL and add it to the Aggregator on your website. Set the refresh time to the lowest possible value (15 minutes) and make sure cron runs at least that frequently.


What is the difference between the wiper motor and the wiper motor control? Caddilac CTS 2006

Question: What is the difference between the wiper motor and the wiper motor control? Does the wiper motor control work the relay switch, in other words if your wipers wont shut off is that a wiper motor control problem?
Answer: Sounds like you have the problem described here.  Indications are replacing the motor is a fix.  This indicates there is some sort of module on the back of the motor, that might be what is actually broke.
Not sure how this works, I'd have to see a wiring diagram.  Power to the wiper motor is going to be going through a relay, but as far as what can cause that relay to engage, you'd need a diagram or trace the wiring.
Answer: I recently had a problem in which the wipers would not turn off when I told them to. The fix involved replacing the motor itself, not some sort of external control system or relay. I took the old motor apart, and it definitely seems that there is an embedded control mechanism, which explains the necessity of replacing the whole motor. I found this preferable, however, to tearing apart my dash to replace something in there.


Tapewound strings on an electric bass

Question: Recently tried Veillette and Rob Allen basses, both incredible instruments.  Unfortunately, they're also incredibly expensive.  Part of what I loved was the feel of the tapewound strings.  What would happen if I changed my steel roundwounds on an American Lakland bass to tapewound strings?  In other words, what kind of sound could I expect vs. the two basses I tried?
Comment: Interesting. I didn't actually know you could use these with pickups. Will have to try out a set now.
Comment: Guitarists can use them too! http://music.stackexchange.com/questions/9502/how-do-tape-wound-strings-compare-to-metal-flatwounds
Comment: I put a set of tapewounds on my Jazz Bass in 1973, and every time I take it ot of the case it's rarin' to go. I take it in for routine maintenance, other cats play it, nobody ever asks how old the strings are or have anything negative to say about the sound!
Answer: Tapewound strings are similar in construction to other wound bass strings; the difference is that they have a length (or 'tape') of nylon wrapped around a metal core.
This makes them feel less tough on fingers, and the tone they produce does not quickly degrade in time, as standard round/flatwound strings will.
The Sound they produce is different as well. They deliver a warmer, rounder, softer and smoother tone (because they will produce less string noise). Another word you will hear a lot when describing tapewound strings is 'thump.' For this reason, they are said to produce the closest sound to an upright bass that can be produced on an electric bass.
I have never come into contact with either of these basses, but from a spot of research I understand that they both have a 'semi-hollow' body design and construction. I would presume that this would add a fair amount to the sound, but the strings would also contribute a lot as well.
Replacing your current strings with tapewounds is likely to have a noticeable effect on the sound, but the body construction and the tonewoods that are used are also likely to be a major contributing feature to the bass's tone and sound.
Hope this helps.
Sources: Rob Allen Guitars and Veillette Guitars
Answer: I see a lot of instrumentalists confuse tapewounds and flatwounds from roundwounds and other material strings.
Flatwounds are regular roundwounds that are ground-down, in fact, you usually have to wipe off the excess machining from them before installing or else your fingers will blacken.
Tapewounds are correctly described above.
Tapewounds will inherently seem a little "softer" or have less attack since they are wrapped in a material that doesn't fundamentally ring true to the original string.  Flatwounds give you a very similar feel to tapewounds (which feel great for jazz guitar too, BTW) but have a bit more metallic sound to them, and will sustain a bit longer as well, since there is no softer nylon material to deaden vibration.
All bass strings are expensive, especially ones that require extra work aside form the winding.  A good wipe down every once in a while, and after a serious session will extend the life of them as gunk tends to get into the crevasses of the metal windings and corrode.
But here's some pricing examples of the two:
Tapewounds are indeed more labor intensive, but you may be able to find a more affordable set of flat-wounds which are more comfortable on your fingers and slightly less work to produce, therefore cheaper.

Tapewound strings on an electric bass


How should I store oak cubes to be used later?

Question: I ordered more oak cubes than I currently need from an online store, since my local store stopped carrying them.
Are there any special considerations for storing these, and is there a shelf life?
Answer: There could potentially be a transfer of water between the air and wood if not kept in bag (e.g. controlled environment), but I don't know if this matters. Moreover, white oak anatomy includes closed tyloses which are cells that resist water and rot and are why white oaks are used in cooperage.
I don't imagine there would be much loss of functionality (i.e. oaky-ness) over the time scale you would likely keep them.  I would store them in the dark in a zip-top bag.  If you are concerned about a loss of flavor, make a tea and taste it before you toss them in you brew after prolonged storage.


Which is better to sauté with, stainless steel or Teflon?

Question: Lots of times in recipes, they'll specify using a stainless steel pan, but I find the non-stick aspect of Teflon to be an advantage. Is stainless steel really better, and if so ,What about it makes it a better choice?
Answer: Also, you can get uncoated steel a lot hotter than you can get teflon (which will break down -- it's basically plastic). So you can sear meats at a much higher temperature than you can cook them on teflon. For some things it doesn't matter, like sweating vegetables, but anything where you want to get some real heat involved to develop browned flavors, you're better off without the teflon.
A good compromise is well-seasoned cast iron, which you can heat incredibly hot, and stuff doesn't really stick to it much. Those pans are cheap, too, and last forever.
On the other hand, if you're cooking eggs, you definitely want the teflon, or cleaning the pan will be very frustrating!
Comment: Agreed on no high heat for teflon, as saute is a high-heat cooking method -- but saute is 'jump' and requires flipping food (typically, a curved-side pan), which isn't typical for most cast-iron (except for some smaller enamalized cast iron).  If you need an alternative to stainless, I'd go with thick anodized aluminum.
Comment: +1 not only will teflon breakdown at high temps, the breakdown products are not exactly pleasant (or harmless)!
Answer: The advantage of using stainless steel is the fond (tasty brown bits) that form in the pan.  It both flavors whatever you are sauteing and is often used as the base for a pan sauce.
Answer: As a follow-up to Harlan - I do my eggs in either a stainless steel pan (scrambled and poached) or an enamelled omelette pan (which is technically a kind of non-stick) - which cleans like a dream. Which is to say, I don't even see the need for Teflon for eggs.
The only cleaning difficulty is if you leave eggy residue in a stainless steel pan - but at least you feel you can attack it when cleaning, without fear.
Caveat : I've not spent the same money on non-stick cookware, and I am pretty good at having cooking accidents like putting an empty pan back down on a ring that is still on - the kind of thing that destroys non-stick coating.
Comment: I've been reading lots on this site about what pan is best for eggs, b/c I can't seem to keep a nonstick pan alive for more than a year. My mom had an enamel omelette pan that she wouldn't use for anything else. Seeing that you have one also, I may look into this more.
Comment: +1. I have never had a problem cleaning stainless steel pan that I have cooked eggs in. If you have burned egg on your pan you cooked them too long or got the pan too hot :D.
Comment: I use a cheap non-stick for eggs, and occasionally pancakes when I don't feel like breaking out the griddle, that I figure I will be replacing every year or two.  Otherwise I use stainless.  I will have to look into enamled pans.
Answer: There is a common misconception in the stainless steel vs. non-stick discussion that one of the two must be "better" than the other, but this doesn't necessarily have to be the case. It is perhaps more constructive to frame the question in terms of which is "more appropriate" for your regular cooking style. Stainless steel and non-stick cookware both have different strengths and shortcomings, but each one can prove equally beneficial when used in the right way. Give this article a quick read for information about the differences between the two and the sorts of situations in which each type is more appropriate.
Usually, a combination of stainless steel and non-stick cookware is the best way to cover your bases in the kitchen. For example, stock pots and sauce pans generally do not need to be non-stick, as their contents will most often be liquid-based. Frying pans, on the other hand, often benefit greatly from non-stick coatings, as they usually take a lot of the hassle out of cooking dry ingredients. While you don't necessarily need both types of cookware around, it does improve the overall usefulness of your kitchen and will leave you ready to cook just about anything.


patent Infringement question

Question: Received a Design Patent from the USPTO a three years ago. Put the Design on the market for licensing. Noted a Major Manufacturers applied for published application in 2013 for a invention to be installed in their product. A portion of their invention looks like a portion of my design. If they are granted the patent for their invention and use portion of my design. Is that consider patent infringement by using non-expired design for their invention.
Answer: Your question appears to blur the distinction between a third party patent publication and a product of the third party.  A patent might effectively block the implementation of that which is described and/or claimed in another patent publication, but a patent publication cannot "infringe" a patent.  Patent infringement generally requires the making, using, offering to sell, selling of a patented invention within the US or the importation of a patented invention into the US.  See 35 USC Section 271.
If the manufacturers you noted above actually incorporate your patented design into a product, then you may have grounds for a patent infringement action, but I note you indicate the manufacturers use a "portion" of your design.  While one need not incorporate an exact copy of your design into a product to infringe, the design of the product would need to appear to an ordinary observer, taking into account the prior art, to be the substantially same as your patented design.

patent Infringement question


Spatial reference for dummies?

Question: Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems?
We are a small team of programmers working with GIS technology, and we often get snagged when working with data in different SRS/CS because we don't understand the concepts.
Comment: spatial referencing isn't for dummies :-)
Comment: Many of the answers to [What strategies, criteria, or rules to use for selecting coordinate systems?](http://gis.stackexchange.com/questions/2769) also fit perfectly here.
Answer: Personally, for the cliff's notes I find the ESRI ArcGIS desktop software help system useful, and and also the ESRI book Understanding Map Projections, its first 30 pages are not unlike a short textbook, followed by ~70 pages of appendix on individual projections, their uses, strengths, weaknesses, etc.
From these, you'll quickly understand all the pieces of a complete SR - spheroid + datum + meridian + unit of measure => GCS; and projection + parameters + unit of measure + GCS => PCS.
For all the math, try the classic USGS Professional Paper 1395 by John P. Synder - Map Projections - A Working Manual. You might find a PDF somewhere if you google it.
Finally, take a look at the 'documentation' links at the bottom of the page for the Proj.4 library.
And as a DB of spatial references, I tend to refer to http://www.spatialreference.org/ or another ESRI list provided as part of the docs for their ArcGIS Server REST API.
Hope that helps.
Answer: Answering a question about the difference between a projection and a datum, Bill Huber links to his article in the Directions Magazine where he gives introductory explanations of georeferencing, datums, spheroids, and the like.
As short and concise as it can be!
Answer: I think Carlos Furuti's tutorial is a really good resource.
http://www.progonos.com/furuti/MapProj/CartIndex/cartIndex.html
Answer: The PostGIS in action book has a great chapter, 6 - Spatial reference system considerations,  on these subjects, although it is (of course) a bit targeted at PostGIS use. Well worth checking out.
Answer: The OGP have lots of useful information on geodesy, try:
http://www.ogp.org.uk/pubs/373-01.pdf
They also have a GIGS (Geospatial Integrity of GeoScience Software) program, more info here and also via OGP:
http://www.cain-barnes.com/index.php/geospatial-integrity-of-geoscience-software
Answer: I just ran across NOAA's "What is a Datum".
They seem to have more info on vertical datums than other sites I've seen.
(I guess data is no longer the plural form of datum.)
Answer: Here's one for Arc that goes through several scenarios using vector data:
http://blog.geographyforever.org/2013/03/25/working-with-spatial-reference-systems-in-arcgis/

Spatial reference for dummies?


What's the most complete way to erase all the data from my phone so it cannot be recovered?

Question: I just got my replacement Droid and will be sending my current Droid back to Motorola.  I'm sure they are going to refurbish it and resell it.  I've backed up everything and I'm going to be keeping my microSD card, but how to ensure that all the data is completely wiped off the internal memory so there is no chance that it can be recovered by someone else?
Answer: Keeping the microSD is probably the main thing, so since that's the plan already it's just the phone to go.
I couldn't swear to this, but I used it when selling my g1:
uninstall everything - except astro file browser or similar
Use astro to wipe out any app related folders
remove astro
Use the "factory data reset" (on 2.2 its under Privacy)
Power up and check it's greeting you as a new user
Power off
Remove sim card
Power up and check it does even less
Power off & send
Answer: Perform a factory reset then write to the memory and reset again.  This is the best way I have found to prevent data remnance.
I was aware that with a magnetic based drive there is almost always data remnanace.  I believe the standard to effectively erase info on a magnetic drive is erasing and re-writing over the drive 7-20 times (don't quote me on those number).  I was under the impression that once you erased data from flash storage it was gone for good but recalled the story of a woman finding porn on her refurbished Evo. So, I asked about data remnance at Superuser on flash memory and found that data sometimes can remain after it is deleted.  The recommendation there was: formatting, writing to the memory and formatting again.
To format, as the answers above suggested, I performed a factory reset.  This can be done one of two ways on the Droid:

Go to the "Settings" menu, choose "Privacy" then choose "Factory Data Reset"
Do a hard reset

Ultimately I just did the Factory Reset because I was too lazy to load the system memory up and I suspect that 99.99% the Factory Reset is sufficient, but it's good to know what the risks are.
Answer: Keep in mind that creating a copy of your data and destroying the original data is a not a backup, just a transport action.
Create a copy of you data on another device/usb stick from your phone and use the move command. This will create another 'copy' and essentially makes sure you didn't forgot anything to move. Moving the data also 'deletes' is from the original device. (better save then sorry)
Now make a list of all things you don't want them to get and make sure they are deleted/removed. After this execute a factory data reset (from settings or boot menu) and check you phone if its really clean.
Answer: As I understand it, factory reset only "deletes" user specific files and databases. They still could be recovered if not overwritten at least once.
Also internal android flash memory is partitioned into several areas with independent file system. Some of these partitions are not directly writable.
I would do the following:
1. Make a factory reset.
2. Install as many apps as possible to overwrite almost all of the data blocks in the "data" partition.
3. Make another factory reset.
If there were a stock ROM to overwrite the currently installed ROM, I would reinstall that ROM, too.


Meaning of ἡ κοινωνία τῆς πίστεώς σου in Philemon 6

Question: What is the meaning of ἡ κοινωνία τῆς πίστεώς σου in Philemon 6? I have seen it rendered fellowship, sharing, communication, et cetera, but I haven't been able to clearly ascertain Paul's meaning—especially its connection to the following phrase, which we might translate that it will be effective to work in you the knowledge of all the good things you have in Christ. I am familiar with John's use of κοινωνία as fellowship or communion between a number of persons, human and divine. That seems to be the sense when Paul uses this word again in verse 17; but how is it best interpreted or translated in this verse?
Answer: For all the NT occurances of κοινωνία (and some translations) see here.
When Paul says κοινωνία ("fellowship" or "partnership") he is using a word taken from the world of business. Think of partners today in a law firm. They share in the responsibility to make the business work, to make money. They share in the risk that it might fail—and if it fails then all will suffer. They share in the success that it brings, and the profits they make. They have a partnership because they all take responsibility and they all work towards a shared goal—not just because they meet together.
So the emphasis here is on the shared nature of the Christian faith, the partnership of the faith. Paul doesn't just want to say "your faith", but he somehow wants to convey the idea that Philemon's faith is the same as Paul's faith—and their shared faith makes them partners in Christ.
The NET Bible translates it well:

I pray that the faith you share with us may deepen your understanding
  of every blessing that belongs to you in Christ.
Answer: Murray Harris in his commentary gives an in-depth consideration of this question. The renderings he offers which seem most plausible to me are:

"Your fellowship with Christ that is characterizes by faith"
"Your sharing in the faith"
"Our fellowship with you as believers"
"Your faith, that enables you to share in Christ"
"Your generosity, which arises from your faith"

The option I have listed here as 5 is the one that Harris prefers, and Peter O'Brien as well, among others. Harris cites Romans 15:26; 2 Corinthians 8:4; 9:13; and Hebrews 13:16 to show that κοινωνία can mean charitable contributions or almsgiving. This argument makes some sense to me, since Paul speaks elsewhere of boasting about the generosity of Christians, and because it seems to be a reading which requires less contortion of phrase.

Meaning of ἡ κοινωνία τῆς πίστεώς σου in Philemon 6


Files not accepted by SkyDrive

Question: Which file types will not upload and open in Microsoft's SkyDrive?
Answer: I don't think there any restriction of the type of files you can upload but you can only edit or create Office files in the browser.
Answer: Each file is limited to 50 MB in size, or it will not upload.  Check your file size...
Answer: They will accept any type of file. On my SkyDrive account I have MP4 files, ZIPs, RARs, Tar.gz's and all kind of archive, but it's for upload, for editing, just Office files and plain text. But the files needs to be -50MB in size.
PS: I've stored all my podcast media there and I had no problem

Files not accepted by SkyDrive


Check of SQL Server upgrade success

Question: I have performed SQL Server upgrade from 2005 to SQL Server 2008. Is there any tools/possibilities to check, whether the upgrade from SQL Server 2005 to SQL Server 2008 has been accomplished successfully?
Answer: There are no tools, so to speak. At least not that I am aware. The best thing to do is to test your code, verify your configurations and ensure that SQL Server is functioning optimally. I am hoping that you did this upgrade in a dev or test environment first and that you followed a process with steps that you can repeat again in production. If that's the case, do a full test of your code that interacts with SQL Server. Ensure everything functions as it did before and make sure that all of your maintenance works and that everyone can connect to it at as before.
I would also look in your SQL Server Error Logs and see if there are any issues. Same thing with your windows event logs (particularly your system and application event log)
I recently gave an answer here that talks a whole lot more about SQL Server Upgrades. Lastly, have you considered what you'll do about DB Compatibility Level? If you haven't, you might want to think about changing that for your databases to SQL 2008 and seeing if all works after a regression test. But please make sure you are in a dev or test. I do not advise just changing this in production, nor do I advise starting with an upgrade in production.
Answer: Check the log file that the installer creates.  If it says that it was done successfully then it was.  If there are errors reported they will be in there.
Also a pretty good check is if the instance starts and reports the correct version number.
Answer: Does this query work?
<code>select * from
(values(1),(2),(3)) X(a)
</code>
If so, you are in 2008. :-)

Check of SQL Server upgrade success


Closed form Information measure on a dataset

Question: Given a set of points ( 1-Dimensional), Can we get a measurement of the entropy of the data without calculating the underlying distribution. I mean , Is there a closed form for measuring entropy given a set of data-points. The closed form need not give me exact entropy..but any measure of information content would help.
Comment: it would probably be helpful if you could give more insight as to what "measures of information content" were acceptable
Answer: It's not really well defined. What you need is an estimate of the cdf from which you get an estimate of the density. The "easiest" way to do this is to bin the points into intervals, maintain the counts within each interval and use that to get an estimate. All of this is horribly nonrigorous, but in the limit as the bin sizes go to zero, you will get some kind of estimate.
The problem though is that such estimates are known to not be consistent, even if the underlying distribution is discrete (i.e defined over a discrete support). The above estimate is related to the MLE, and the typical problem is how to assign probabilities to empty bins. There's a wealth of literature on this topic, and at least for the discrete case, you should take a look at Liam Paninski's article:
Paninski, L. (2003). Estimation of entropy and mutual information. Neural Computation 15: 1191-1253.
Answer: The only other way that I am aware of for calculating entropy requires knowing the number of configurations of the system, i.e. the multiplicity.  This is often equivalent to knowing the distribution, but can, in some cases, be found without knowing the distribution, per se.  In this case the entropy is simply the log (to your favorite base) of the multiplicity.
Answer: I'm not sure I entirely understand the statement of the question, but it sounds to me as though it's similar to the question, "If you have access to a time series of observations/data coming from some dynamical system, but know nothing about the underlying system itself, what properties of that system can you determine based solely on your observations?"
Some of the key words relating to this question are "correlation dimension" and "correlation entropy", which originate in work of Grassberger and Procaccia ("Measuring the Strangeness of Strange Attractors", Physica D: Nonlinear Phenomena 9, 1983, 189‒208).  These let you determine certain properties of the system (analogous to Hausdorff dimension of the attractor or Kolmogorov-Sinai entropy) based only on the time series, without knowing anything about the underlying dynamics, which seems not unrelated to your original question.
Answer: there are quite a few methods for estimating the entropy without estimating the underlying distribution. this is particularly important for data that are not independent, since then you run out of data pretty quickly. some discussion and a lot of references are given here: http://pages.cs.aueb.gr/users/yiannisk/PAPERS/neuro.pdf
yiannis


How to host a single website on multiple servers?

Question: I'm planning on releasing an iOS app that downloads video from my server. If hundreds of people on the launch day try to do this, then my website and the services that my server provides will clearly go down. How do you host a website on multiple servers? When someone tries to access my site, how is their request passed to an available server? How do Apple and Google do it? Thanks for your help.
Comment: [http://en.wikipedia.org/wiki/Load_balancing_(computing)](http://en.wikipedia.org/wiki/Load_balancing_(computing))
Comment: Check my answer it's a very popular program to scale, and monitor servers
Answer: You can do load balancing as per @PeeHaa's link to Wikipedia's article for info here.  This requires some know how and money and time to setup.  Large companies like Google and Apple use technology they have written for themselves and trying to mimic them is an expensive and an overkill solution.  If you do load balancing you will want to use something much smaller than what they do.
Or you can use cloud servers to host your videos or other content.  They are called Content Distribution Networks (CDNS) and they can do much more than simple file hosting now. The benefit of these sites is that they use technology like what Google has created to create load balancing and they sell you the service based off of exactly the amount of data or cycles you consume on their servers.  This means your cost will grow at the same rate as you usage so as long as you have good revenue model you will always have funds to pay for the service.  Some great companies for smaller users are:

Amazon Web Services - http://aws.amazon.com/
Microsoft Azue - http://www.windowsazure.com/en-us/
Rackspace - http://www.rackspace.com/cloud/

They are many more than these three.  Also, the other benefit of CDN is that you content is no on one server but on a network across the globe.  The CDNs do this so that the content always comes from the server closest to the user.  Setting up 2+ servers in one location will never give you the same delivery speed benefits that a CDN can.
For the record, I don't work for any of these companies. I have used Amazon's Web Services for video hosting on my companies website and it has been a huge benefit.
Answer: Well as for the big guys (Google, Apple, etc.) they have sophisticated, and expensive, hardware the routes traffic.
A simpler solution would be to setup your multiple hosts and have a single host that rotates the requests.
Say we have 5 servers for hosting the video, named VideoHostN and we have a single server separate from those that keeps track of them being used name RoutingHost.
The first iOS client requests the address to get the video from RoutingHost.
RoutingHost returns the address on VideoHost1.
Second iOS client requests.
RoutingHost replies with VideoHost2.
So on till it hits our hypothetical max, VideoHost5, and resets to VideoHost1.
Just need some simple server side code keep track of which VideoHost to use next and returns the address to it.
It's a cheap and easy way to spread users out. This doesn't guarantee that you won't get some users clogged up on any given VideoHost. It's random chance that several users with slow connections could all end up pulling from the same location, but it's a start.
Comment: Sure, http://zoneedit.com/
Comment: Thanks for your help! I'm using a service called Zone Edit. I set up the DNS for my entire site with them today and they offer round robin DNS (I believe that's what it's called) along with "failover services". This monitors the servers that DNS points to and sends requests to available servers and pulls out the ones that are packed with requests. It's about $12 per year, so I'll just stick with them instead of figuring all this out. But thanks a lot for your help!
Comment: Yea, at $12/yr for a better solution. Can you drop the URL to that service for future reference?
Answer: A free load balancer software such as ZenLoader would do the trick. It's an open source software, you only pay if you need support.
I hear it will cover your requirements if you already have purchased the servers.
Answer: I would use Scalr on ec2 to monitor your servers automatically, it's open source and works very well with AWS services. So if your app server starts to get hit with too much traffic Scalr will automatically bring up more servers and balance the load for you. It will also automatically backup your databases if one goes down bringing up slaves as masters. So your application servers and database servers are all monitored and scaled as needed.

Scaling websites is hard and expensive. Using the power of Cloud
  Computing, Scalr automatically scales your website infrastructure: it
  scales your database, scales your app servers, and even adds and
  configures load balancing and caching servers!

http://code.google.com/p/scalr/


How make .qgs files open in QGIS automatically on a Mac?

Question: When saving a project my copy of QGIS used to assign file extension .qgis automatically.  Now it assigns .qgs automatically, which means that I can't reopen it.   All my old projects have also been given new extensions .qgs.
Does anyone know what's wrong and how can I fix it?
Answer: With most computer operating systems, there should be a function to assign a file extension to open with a particular application. This sort of problem is usually an Operating System level problem.
To correct this, as an example on my computer running Mac OS 10.7:
From the File menu -> Open With -> Other...
Browse to your Applications folder and click QGIS. At the bottom of the Window, click the "Always Open With" check box.
Click Open. At this point, all .qgs files should now open with QGIS.
Even if you don't have a Mac, the steps involved are similar with most operating systems. Usually the screen required to make the change is accessible by right clicking on the file.

If on a Mac and the above did not work, try running the two following terminal commands:
<code>/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -u /Applications/QGIS.app
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -f /Applications/QGIS.app
</code>
(The Terminal application can be found in the Utilities folder. The Utilities folder can be accessed from the Go Menu while in Finder.)
If you have QGIS located in a different spot other than the Applications folder, you will need to adjust the path accordingly. These two commands will unregister all filetype associations then force the Application to re-register them.
Once you have run the second command, you should be able to double click on .qgs files and have them open correctly.
Information courtesy of: http://krypted.com/mac-os-x/lsregister-associating-file-types-in-mac-os-x/
Comment: Thanks for that - I'm on a Mac - but unfortunately it didn't work.  Is it possible that the problem is caused by using Wroclaw 1.7.4 when the old projects were created with 1.7.1?
Comment: I added a portion onto the bottom of my original answer. Try giving that a whirl. I do not know explicitly if any file extension changes occurred though I am very doubtful.
Comment: You may also want to reset 'Launchservices' on your Mac using a utility like Onyx; this removes non-standard links between apps and docs. You can then try the suggestions above again.
Answer: using windows the steps are as follws:
right click any projectfile with the extension .qgs and click "open with" and brose to your qgis-folder. select qgis.bat. checkmark box "file-type allways open with selected program!


Will LEDs work with a point & shoot camera for light booth digital photography?

Question: I am planning on using multiple strips of LEDs to light up a 2 ft x 2 ft x 2 ft light booth for taking pictures of small items.  LED output is Cool White 6500k.  Digital camera is low cost 5 megapixel HP.  Are these lights and camera compatible?
Answer: In the most basic sense, yes. The colour temperature of the LEDs is well within the range of normal daylight, and just about any camera can cope with that.
The problem is that it's highly unlikely that the LEDs you are planning to use have a good colour rendering index (CRI). All of the consumer LEDs I have seen have a CRI in the low 80s at best. That means that there are substantial portions of the spectrum that are missing and/or over-emphasized, and you won't be able to fix the colour problems in your pictures by adjusting either the colour temperature or tint settings for the photos. The light isn't there, so the data aren't recorded. There are LEDs with reasonably good CRIs (you need something in the 90s at least), but they tend to be painfully expensive.
If possible, fluorescent or incandescent lighting would be better from a bang-for-the-buck point of view. Incandescent lighting is great, but there can be some significant heat problems, especially in a confined space. (Remember the Easy-Bake oven?) Fluorescents are bulky and a bit more expensive, but you can usually find bulbs with good-enough colour rendition at something approaching reasonable prices.
Comment: Also, a lot of LEDs with high CRI numbers are still terrible in the real world; the CRI score is based on assessment of a small number of color patches, and the manufacturers cheat by making sure those specific colors are rendered well. The expensive LEDs _are_ still better, but they're not as good as the numbers sound.
Answer: 6500K is roughly equivalent to outdoor, overcast, conditions. So, if the version of camera you have (you didn't specify which camera and HP has a few 5mp cameras) supports an option such as shade or overcast, that is probably what you want. Better yet, if it lets you specify the temperature to use, via custom white balance, do that.
HP does make the camera manuals available online. Just go to Google and type in something like "HP Photosmart E327 camera manual" and you'll get an immediate result. By the way, if that's the one you have... http://h10032.www1.hp.com/ctg/Manual/c00599504.pdf (see Page 39 for white balance settings).
Answer: I work as an assistant and also do my own photography. We use an LED video light much like this one
http://www.adorama.com/FPVL160.html?gclid=CLCRvtrTmLYCFW2oPAod81IAbg
It works great, has a dimmer on the back so you can adjust how much light you want. That might be the problem with your LEDs, being unable to adjust the brightness. I highly recommend getting a video light, they're not that expensive. They also come with filters to put on the front of them which allow you to make the light more yellow or blue as needed.
Answer: I would NOT use LED lighting if colors needed to look "real".  You can find a white ballance easily enough by doing test scene with a known white object, but that doesn't fix all the in-between colors.  The problem with LED lighting is the the light power is concentrated in a few relatively narrow spectral lines, not spread out like black-body radiation.
Take a look at a collection of colored objects under "white" LED lighting and sunlight.  The colors will look quite different relative to each other, even after your visual systems ballances for white.
If it just has to look plausible such that there doesn't appear to be any particular color cast and nobody knows the exact color of things you are photographing anyway, then it doesn't matter.  If your object contain a logo or something people are familiar with the color of, then LED lighting is not a good idea.


Making a "heavier-than-air" craft float

Question: How big would a hollow rigid object need to be to float, (not in water but in air) if all of the air was vacuumed out and the container sealed?
Answer: Another way to look at this is to solve for what weight/area you are allowed to use.  Assume a spherical craft.  Surface area goes up in proportion to r^2.  Volume (which will generate your lift) is proportional to r^3.  If you do the math, you find that you are allowed to use (r x 0.4)kg/m^2, or about (r x 0.88) lbs/m^2.  So the problem gets easier to solve as the craft gets bigger.
The force experienced by a totally evacuated body at sea level, would be about 14.7 psi, which is about 11.4 ~TONS~ per m^2.  (Don't you just love mixing metric and English units?  I do...)
At r = 1m, you can only use 0.88 lbs of material for skin and structure to hold back that massive force (good luck with that).
At r = 10m, you get 8.8 lbs/m^2.  That equates to a (1/17) inch thick aluminum skin and no internal supporting structure. ---> Still a no-go.
At r = 100m, you are allowed 88 lbs/m^2. ... O.K., now we are talking. 1/8 inch aluminum plate weighs about 19lb./m^2.  That leaves 69 lbs./m^2 for ridigization of the skin panels and internal structure.  Something that approximated a monocoque structure (like an egg shell: able to take tremendous pressure with no deep internal bracing) might work.  As an engineer, I'd be willing to take on that challenge; but... that is a H-U-G-E craft!  OVER two football field lengths in diameter, and weighing in at about 5 million kg before evacuation!
Maybe someone would be able to do it for r = 50m, which would be a budget of 44lbs./m^3.  My guess is that technical feasibility lies somewhere in the design area of 50m < r < 100m.
Answer: Just to flesh out Jim's answer.
Assume you made a cube (makes the math easier!)  1m x 1m x 1m
Aluminium has a density of 2700kg/m^3
And you need the cubeto have a mass of less than 1.2Kg
 - so can use (1.2/2700) m^3 of material
The surface area is 6m^2 then you can have a thickness of (1.2/2700)m^3 / 6m^2 = 70um
Or about half the thickness of a hair!
Answer: Since air weighs about 1.2 kilograms per cubic meter, if you could make your Magdeburg hemispheres strong enough and they enclosed one cubic meter and weighed less than 1.2 kilograms, they ought to float like a helium balloon
Comment: The big problem is making the container strong enough.  It has to withstand that 15 pounds per square inch air pressure and not collapse.
Comment: you can [edit your answer](http://physics.stackexchange.com/posts/8678/edit) to add additional details rather than adding comments

Making a "heavier-than-air" craft float