Truncations of E_infinity algebras

Question: In section 4.1 of Lurie's DAG VIII, he implies the existence of an $E_\infty$-ring spectrum $A$ such that the coconnective truncation $\tau_{\leq 0} (A)$ does not admit the structure of an $E_\infty$-ring spectrum. What is an explicit example? Is it possible to give an intuitive explanation for why this fails? Also, does this phenomenon occur for other similar categories, such as commutative dg algebras over $\mathbb{Q}$?
Answer: In general the issue is that the natural map $A \to \tau_{\leq 0} A$ often cannot be compatible with a ring structure, because on the level of homotopy groups or homology groups it acts as a quotient map that destroys all elements in positive degree.  This is often not compatible with the multiplicative structure.
A direct example is to consider the graded ring $A = \Bbb Z[u^{\pm 1}]$ with $|u|=2$, viewed as a (commutative) differential graded algebra with zero differential.  The map $A \to \tau_{\leq 0} A$ annihilates the positive powers of $u$ but leaves the negative powers alone, and this can't arise as the homology of a map of chain complexes because it doesn't respect the relation $u \cdot u^{-1} = 0$.
Your question doesn't immediately ask for the multiplicative structure on $\tau_{\leq 0} A$ to have anything to do with the multiplicative structure on $A$, and so we might have to work a little harder to come up with something like that.  I don't have one from homological algebra, because it is hard to write down a chain complex whose homology is a ring but which admits no multiplication.  The periodic $K$-theory spectrum $KU$ has $\tau_{\leq 0} KU \wedge \tau_{\leq 0} KU$ a rational spectrum, and this obstructs the possibility of getting a unital multiplication.
Comment: I assume you mean $u \cdot u^{-1} = 1$ in the relation? In any case, thank you! I was indeed wondering about compatible $E_\infty$-structures, so your example is wonderful. (And I feel stupid!)
Comment: Whoops.  Yes, that's a ridiculous mistake, I did mean $u \cdot u^{-1} = 1$.
Comment: @TylerLawson : I think it's not true that $\tau_{\leq 0}KU\wedge \tau_{\leq 0}KU$ is rational; but the example still works (if $\tau_{\leq 0}KU$ had a ring structure it would be a module over its $\pi_0$, i.e. an Eilenberg-MacLane spectrum; but its $k$-invariants are the same as those of $KU$, so it's not an EM spectrum). The reason I think it's not rational is because $KU\wedge \tau_{\leq 0}KU$ *is* rational (it's a homotopy colimit of extensions of $KU\wedge H\mathbb Z$ which is rational), and so it would imply that $ku\wedge \tau_{\leq 0}KU$ is also rational. (1/2)
Comment: But that would imply that $ku\wedge H\mathbb Z$ is also rational, which it's not (2/2)
Answer: In addition to Tyler's example, a very nice example has been provided at the end of Section 6 in the paper "Localization of algebras over coloured operads" by Casacuberta, Gutierrez, Moerdijk, and Vogt. The idea is again to truncate the unit. The authors prohibit this behavior by insisting that the localization is stable (commutes with suspension). Alternately, they prove in Theorem 6.5 that you can get away with unstable localizations if you assume some connectivity hypotheses on the ring you are localizing.
Another excellent example was presented by Mike Hill at Oberwolfach in 2011. In this example a localization of equivariant ring spectra is given which destroys genuine $E_\infty$ structure but preserves naive $E_\infty$-structure. In my thesis I try to understand this example in maximum generality. It turns out the failure is again a failure of the localization to be stable (this time with respect to non-trivial representation spheres). The fact that the localization does preserve naive $E_\infty$ structure follows from the fact that it is stable with respect to the monoidal unit. In my thesis I describe other ways to view what is going on in this example, I introduce the notion of a monoidal Bousfield localization (these will in particular preserve the structure of algebras over $\Sigma$-cofibrant operads such as $E_\infty$), and I characterize monoidal Bousfield localizations via the following:
Theorem: Let $M$ be a cofibrantly generated, left proper, monoidal model category in which cofibrant objects are flat. Let $C$ be a class of maps such that the Bousfield localization $L_C(M)$ exists. Then $L_C(M)$ has cofibrant objects flat and satisfies the pushout product axiom if and only if $L_C$ is a monoidal Bousfield localization.
This is the maximum generality in which I can answer the OP's question. In the examples section I treat separately the cases of localizations of spaces (also addressed in this mathoverflow question), spectra, equivariant spectra, and chain complexes. I characterize Bousfield localizations of chain complexes and devote particular attention to the case of CDGAs over fields of characteristic zero. I hope to have this work up on arXiv sometime soon, but I also welcome emails from people who want to see it now. Many details can be found in my research statement.

Truncations of E_infinity algebras


How to track / monitor changes in an online PDF file?

Question: How to track / monitor changes in an on-line PDF file? Need to be notified when that happens.
Answer: May be you can retrieve something like the headers and see the modified date? but you will need a script to do that.
You could use the response of a service like http://www.rexswain.com/httpview.html
And read the line:
<code>Last-Modified:·Thu,·31·Jan·2008·15:58:57·GMT(CR)(LF)
</code>
Answer: Probably there is no easy way to do it.
You can consider using LaTex for PDF creation - you will be able to track the "source code" of the PDF as any other source (SVN/Git/ etc.).
You can also use use the pyPdf lib to convert PDF contents to plain text (which is easily track-able).
Answer: Sounds like you're trying to use a basic version of source control. This might be a bit too large/complicated for your needs, but have you considered checking in the file to a CVS/SVN repository and then having the users access it through a web interface?


Is there a downside to leaving cavity in wall behind mirror?

Question: I took the bathroom mirror off the exterior wall and discovered a cavity roughly 12" wide, 16" tall.  I'm guessing this used to be for a small recessed medicine cabinet.
Is there a problem leaving this cavity here?
Comment: none whatsoever
Answer: If the cavity is not insulated, your mirror will be cold and fog-up more when you take a shower.  Also, if your mirror is not sealed to the wall, water vapor may enter the cavity and cause condensation and mold.  If there is insulation and is sealed from water vapor, you will have no problems.
Answer: Being its an outside wall, insulation and drywall would add some energy efficiency.
In my Michigan climate, that recess would get quite cold.


Conditional Probability

Question: 1)  A card is drawn from a standard deck of $52$ cards. The card is drawn from the pack and not replaced.  A second card is then drawn from the deck. Determine the probability:
$a)$    that the second card is a spade, given that the first card is a spade.
$b)$    That both cards are hearts.
$c)$    the first card is a diamond and the second card is a heart.
For part $a$, I put $P(\frac{S1}{S2})= \frac{4}{51}$
And part $c$, $\frac{4}{52}$ divides $\frac{4}{51}$ = $\frac{51}{52}$
I'm confused with part $b$ and will appreciate some help and can you guys kindly check over my part $a$ and $c$?
Thank you very much.
Comment: For (a) surely you mean $12/51$. For (c) it should be $(13/52)(13/51)$. Maybe now you can tackle (b).
Comment: From where are you plucking the number $4$ in your answer? $~$ Are you perhaps thinking that as there are $4$ suits it must be part of the answer? $~$ Think again; this is all about the number of cards in each suit ($13$).
Answer: $b)$ $P(\text{1st card is heart & second card is also heart})= \dfrac{13}{52}\cdot \dfrac{12}{51}= \dfrac{1}{17}$
For checking $a)$, the probability should be $\dfrac{12}{51}$ or $\dfrac{4}{17}$
For $c)$, the probability is $\dfrac{13}{52}\cdot \dfrac{13}{51} = \dfrac{13}{204}$
Answer:
b) That both cards are hearts:

The number of ways to draw $2$ out of $52$ cards is $\binom{52}{2}=1326$
The number of ways to draw $2$ out of $13$ hearts is $\binom{13}{2}=78$
Hence the probability of drawing $2$ hearts is $\frac{78}{1326}\approx5.88\%$
Answer:
a) that the second card is a spade, given that the first card is a spade.

If you remove one card from the deck and it is a spade, then there are $12$ spades left in the deck of $51$ remaining cards.   So therefore the (conditional) probability that the next card is also a spade when given that the first card is a spade is:-

b) That both cards are hearts.

It is the probability that the first card is one of the $13$ hearts times the (conditional) probability that the second card is also a heart when given that the first was.

c) the first card is a diamond and the second card is a heart.

Similar, although this time removing one of the $13$ diamonds does not reduce the number of hearts left in the deck (just the size of the deck).

Conditional Probability


MMP of geometries

Question: MBR is used for extent of geometries.. then what is the use of MMP..
is it for visualization the objects?
Comment: Could you provide a definition of MMP ?
Answer: It's hard to determine from that link what MMP actually is.
It seems to me it's like this.
You want to know whether the line intersects the polygon
Standard practice is to create a bounding box and see if they overlap. If not, there can be no intersection. If they do then it may intersect and you do a full intersection test to check.
With MMP you replace the start/end point of the line with point features and test if they are inside the polygon. If only one is then you know there is an intersection. If neither or both are then you then do the full intersection test to check.
So it's basically a way to reduce the need to do full intersection tests. At least that's how I read it. Quite a good method really, though whether it warrants a patent I'm not sure.
Comment: +1 for nice illustrations and interpretation of the patent
Answer: I couldn't find much on MMPs (Minimum Maximum Points) and geometries in a GIS context.
According to a patent text found here: http://www.freepatentsonline.com/6438269.html, MMPs are a generalization describing geometries (lines and/or polygons) in a way to increase performance of spatial filters.

MMP of geometries


What's the best lens for shooting baby and kids with a DX Nikon?

Question: I have a Nikon D5100 and want to see whats the best lens for shooting pictures of a baby and kids running around inside and outside?  I would like to stay under $1,000.  Thanks for the help.
Comment: Also see [Prime lens or flash: which upgrade will most improve baby photos?](http://photo.stackexchange.com/q/6250/1943)
Answer: For daylight outdoors, I mostly agree with Joanne C: If you already have the DX Nikkor 18-55mm f/3.5-5.6 kit zoom, use that. Otherwise the 18-105mm or 18-200mm DX zooms give more flexibility in focal length, and the 24-120mm f/4 FX zoom is a step up in image quality.
For indoors, the low light is a problem. I consider typical indoors to be around LV 4, which means that you would need 1/30s exposure at f/4 and ISO 3200. That's too slow for moving subjects, and ISO 3200 is about as high as the D5100 can go while still giving passable photos.
So for indoors and other low-light situations I'd suggest the AF-S DX NIKKOR
35mm f/1.8G. You sacrifice zoom, but gain two stops of low-light performance. Those stops also help with autofocus speed and accuracy in low light.
With a $1,000 budget, I would go for both: One of the zooms for general purpose use, and the 35mm DX prime for low-light situations.
Answer: I have always liked prime lenses, but found zoom lenses to be far more practical -- so that's what I used. However, after having a kid I learned of two huge advantages prime lenses have: there is no zoom ring to fiddle with, and they are lighter (perhaps only slightly, depending upon your lens selections). A prime lens most likely will have a faster aperture which is invaluable to help get the shot when you can't mess around with flash because of the fast-moving kid, too.
Both reasons are related, of course. Being lighter, it's easier to hold the camera one-handed for extended periods of time. This is important when I'm holding the kid with one arm, and only have one free to shoot. Shooting at the kid's eye level is important to making an engaging photo, which means getting on the floor/ground. Having one hand to help move and balance on the floor while still being able to shoot makes it possible to get shots much easier. And of course, without a zoom ring, I'm always at the expected focal length so it's easy to recognize how to move to frame a shot.
I'm guessing you already have a lens (the kit zoom?) and have used it some. Before buying a prime, I would try to determine how you have used the lens you have to decide what focal length(s) of primes to use. The way I do this is with Lightroom, and review metadata to see what focal lengths are most-used. (Other programs likely offer such functionality.) Alternatively, try setting the lens at a specific focal length and shooting the kids for a while to see how you like it. I have found a two-lens prime kit to be hugely versatile: something on the wide end and something mildly-telephoto.
Personally, on a crop-sensor camera like the 5100 I would want a 24mm lens (which equates to 36 mm focal length in the traditional 35 mm format). I think the only option is Nikon's 24mm f1.4; a fantastic lens, but well outside your budget. I haven't used Nikon's new 28mm f1.8 ($700), however that is likely a good lens/focal length for getting shots of the kids. Sigma offers a 30mm f1.4 ($400) that is also a fine choice. Nikon's 35mm f1.8 is cheap ($200) and well-reviewed, however I find this focal length very uninteresting and simply don't use it (roughly 50 mm in the 35 mm format).
On the more telephoto end, I think the easy choice is a Nikon 50mm f1.8 ($200) or f1.4 ($500) (75mm in the 35 mm format). This focal length is too long to shoot kids who are next to you. That is, if you're holding the baby or entertaining the kid, you won't be able to use this lens -- in the time it'll take you to back up far enough to get things into the frame the moment will have passed. However, for "sneaking" a candid from the other room or outside in a wide open space, it may be just the right choice. To be honest, I waffle between using an old 50mm 1.8 and an 85mm 1.4; the 85 is often too long, but I just like the lens so much I try to make it work.
So, finally after all that justification, with a $1000 budget, I would choose the 28mm f1.8 and the 50mm f1.8.
Answer: I'm not sure where you're located, but if you're willing to go a little above the $1000 mark, the AF-S Nikkor 24-120mm f/4 lens is a great option as a good general purpose, do most things, kind of lens. I have one for my D800 and I've been very happy with it and it's good enough to be on the recommended list for the D800 and that's saying something.
If you're firm on the sub-$1000 mark, then something like the AF-S DX Nikkor 18-200mm f/3.5-5.6 might be a decent choice, though I think I would be more inclined to the AF-S DX Nikkor 18-105mm f/3.5-5.6 since, in my experience, the shorter the zoom range, the better the lens and the Photozone tests bear that out.
Still, I'd shell out the extra money for the the 24-120mm option. Not only is it a better lens, it's an FX lens and it future-proofs you should you ever decide to go to an FX sensor. That possibility is becoming increasingly more realistic as the price drops, so don't quickly dismiss the idea.
Answer: So, just as Dan Wolfgang asked, I too would like to know what is your current lens and how do you use it.
I suppose you have the kit lens, the Nikon 18-55mm f/3.5-5.6G. to be honest it isn't a good lens, you may be satisfied with it but you will be amazed by the result that you can get by using a better lens on D5100.
So you got about $1000 to spend...
So you know your budget but you need a good plan to spend it.
First thing to do, review all your old photos and see what is your most used focal length.
By your current lens you're limited to 18mm and 55mm, is that ok for you?
At the wide end, the 18mm should be enough for most of your needs, that is photographing kids/people.
But what about the longer end?
Anyway, my point is you should know what is your desired focal length.
My recommendation
Nikon 18-105mm f/3.5-5.6G ED VR AF-S DX for $396.95 is much better and brighter than D5100's kit lens.
The 18-55mm reaches f/5.6 at 55mm and it's not useful for indoor shots at all.
Tamron 17-50mm f/2.8 for $499.00, yes! a third-party lens but it's a great lens, very good for landscape and useful for portraits. the constant f/2.8 aperture is a great plus, that means sharper and brighter photos in low light situations and of course better bokeh!
Nikon 50mm f/1.8 G AF for $216.95 is a great lens for portrait photography, it is brighter than the Tamron above but the negative side is that it's a prime and you may need to change it for another shot.
Nikon 18-200mm f/3.5-5.6G AF-S DX ED VR II for $846.95 is an all around lens, you probably don't need to take it off your camera.
Comment: I'd recommend the 50mm f1.8G over the D version simply because it'll autofocus on the 5100. It's nearly double the price, but AF is worth it for most people, I think.
Comment: Oh right, I almost forgot about lack of focus motor on D5100, thanks, I edited my answer.
Comment: I second the Tamron 17-50mm. Had a very good first year with my kid and others (baby swimming) with it indoors.


How do I reset a self-hosted Wordpress URL?

Question: i was using a wordpress install on an ubuntu server virtual machine.  At first the adapter was host-only at an address of 192.168.55.55.  The host had this on a vboxnet0 subnet.
i changed to bridged adapter to try port forwarding from the router, and now i cant access the page with the new address.
the new address is 192.168.1.5 and everything appears fine on routing tables of host.
i also cleared the dnsCache on the host.
but when i type in:
192.168.1.5/wordpress
in the browser, the activity bar shows it is trying to contact the old ip of 192.168.55.55, which was the vboxnet0 host-only adapter.
Answer: The easiest way to do this is by using copy&replace in the SQL file. Export the database. Use your favorite text editor and do a copy&replace and import it into a new database.
Then you go to wp-config.php and you change the WP_HOME and WP_SITEURL to the new host. Then you change the databasename. You also need to ensure that the same db user has access to the database.
Btw: There is a separate stackexchange for wordpress. Check out How do I move a Wordpress site to another server?
Answer: You can use this script to do the database find and replace without needing to do the SQL dump. Usual caveats apply - take a backup and delete the script after use. It's actually a better option that the text editor find & replace as it accounts for serialized arrays, which a text editor find & replace doesn't.
Wordpress (and others) search and replace tool
You'll still need to make the wpconfig.php edits manually.


strategies for dealing with machine epsilon

Question: Say you have a situation where you divide and then multiply a float, and you need to guarantee that it survives macheps (ie multiplication output equals division input). What are known strategies for guaranteeing this? Rounding would work, but anything else?
Comment: Use a different type that represents numbers as fractions. Then you can represent all rational numbers exactly.
Answer: Traditionally, you multiply FIRST, and THEN you divide.
If your hardware and compiler are smart enough, the instructions emitted will preserve the full double-width result of the multiplication, for processing by the division.
Dividing first and then multiplying, you can't really do that.  (Your compiler MIGHT at that point be smart enough to reorder the operations, but you are usually safer doing it yourself.)
Read Hamming's Numerical Methods for Scientists and Engineers.  Early in the book, he goes into considerable detail on reorganizing your computations to reduce this kind of trouble.  It's available from Dover.  (If technical literature is your fetish, like it is mine, Dover is your FRIEND!)
Answer: Actually this error happens not only because of multiplication, it can be reproduced by a simplier way: 0.1 + 0.2
There is a special website for this issue: http://floating-point-gui.de/

What can I do to avoid this problem?
That depends on what kind of calculations you're doing.

If you really need your results to add up exactly, especially when you work with money: use a special decimal datatype.
If you just don't want to see all those extra decimal places: simply format your result rounded to a fixed number of decimal places
  when displaying it.
If you have no decimal datatype available, an alternative is to work with integers, e.g. do money calculations entirely in cents. But
  this is more work and has some drawbacks.
Answer: You can't guarantee that.  Not while using floats, anyway.  As the comment says, if you need a guarantee, you can use arbitrary-precision fractions.
In general, rounding doesn't offer such a guarantee, either -- you need to do some actual math before you can be confident it works within the range of your particular application.
The real question is:  why do you think you need a guarantee?  Your question suggests that you need to actually, seriously devote some effort to considering this, because its answer is likely the most relevant and important part of actually solving your problem, and you have not provided enough information to enable any more detailed constructive advice.


What sums should everyone know?

Question: Well, everyone is an overstatement. Qualifying it: I'm interested in algorithms (complexity) and probabilistic processes/models and I often see sums converge to a certain value in the books I'm reading (algorithm iterations and finite and infinite series of probabilities etc.). I'm looking for a reference (website for example) that contains common sums and their convergence values (infinite or finite) that are often times encountered in these subjects.
Comment: [This](http://www.tug.org/texshowcase/cheat.pdf) possibly contains all you need.
Comment: Gradshteyn and Ryzhik's Table of Integrals, Series, and Products may be useful
Answer: Perhaps we can interest you in the book Concrete Mathematics. For an enthusiastic student who has not necessarily mastered similar material before, it teaches quite a variety of summation techniques with algorithm analysis in mind.
Answer: Geometric Series and its derivatives are very common in complexity problems as well as probabilistic models.
$$a+ar+ar^2+\cdots+ar^{n-1}=\frac{a(r^n-1)}{r-1}$$
For $|r|<1,$ infinite geometric series converges
$$a+ar+ar^2+\cdots =\frac{a}{1-r}$$
Binomial expansion is also common
$$(a+b)^n={n\choose 0}a^{n}b^{0}+{n\choose 1}a^{n-1}b^{1}+\cdots+{n\choose k}a^{n-k}b^{k}+\cdots +{n\choose n}a^{0}b^{n} $$

What sums should everyone know?


I had SSL certificate on my site but still it has been hacked...how to prevent this from happening?

Question: I used SSL certificate on my site but still it has been hacked.
How do I prevent this from happening?
Do SSL certificate come with a waranty which would compensate me because my site was hacked?
Comment: Security is full of misconceptions. SSL = security = why am I hacked? If you know don't know what else to consider, it actually is a logical statement. (Be nice to the new guy.)
Comment: If you can give context over what the hack method was then you could ask specific questions and get good guidance. SSL is not designed to prevent a website being hacked - as both Jeff and Mike said, it just protects communications.
Comment: I have a sword, does that mean the bully wouldn't be able to beat me?
Comment: You have to consider also, MITM attacks like `sslstrip`, session hijack, and so on.
Answer: An SSL certificate protects users of your site from having their communications intercepted by a 3rd party. I think it is likely that when you say your site was hacked, this isn't what you're talking about. An SSL certificate does not validate the content of your site, nor does it prevent anyone from accessing it as intended or otherwise. Controls for these are outside the realm of SSL.
There is no warranty regarding SSL certificates other than potential civil liability. Unless your certificate itself was compromised by actions of the issuer, you have no case against them and no warranty is implied.
As far as figuring out what was insecure about your site, how you were compromised, or what needs to be addressed to fix it, you need to have forensic analysis performed on your compromised machine. A review of the website code for the site in question may also be in order.
Comment: A minor clarification, SSL protects your communication from being understood, but an adversary could still intercept your communication.
Comment: Actually, an SSL **certificate** only certifies users that they're talking to your server, and is used by TLS for key exchange. What version of TLS, encryption algorithm and and a whole lot of other TLS security settings are all dependent on the server. For example, I may have a perfectly valid certificate but still be hacked at the communication level because I still have SSLv3 enabled.
Answer: SSL certificates don't do anything to prevent your site from being hacked, so you're not going to be able to claim compensation. If properly implemented, they prevent your users' traffic from being intercepted by third parties, which is not the same thing at all.
To stop your site from being hacked again, you need to employ or become an expert in Internet security -- there's no other way. There are so many different ways that your site could be vulnerable that I couldn't even begin to list them all here.
Comment: Minor clarification, SSL protects your communication from being understood, but an adversary could still intercept your communication.
Answer: I've never heard of a warranty on SSL certificates, and even so, it wouldn't be that your site wouldn't be broken into - it'd be a warranty concerning the link between your server and your user's computer.
You may be thinking of those (ridiculous) "verified by XXX" logos you see on websites. Those are intended to give visitors confidence that the site is indeed secure, but again, they don't function as an assertion that nobody can break into your site, as much as an indication that the site is using SSL to protect communications.
There are other logos out there that sometimes show up on websites, sometimes from the same companies that sell certificates, that purport to speak to the security of the site itself, but even so I haven't heard of any of them warranting that claim. Far from it, usually - almost everyone inserts gigantic disclaimers in their license agreements.
Answer: Let's say you have SSL, but an outdated OS, poor passwords, your house/work network compromised, not only by you, but by others that also make use of it. How can your server be secure?
There are so many technical paths a malicious guy can try, and social engineering to do. An SSL certificate, can only protected the communication preventing it to be transmitted as plain text and checking if the parts are who they are claiming to be. It's the same say to the user: "Your information will be transmitted by a verified organization locked in a box with one key to lock and another to open. Only you and I have the keys".
But this doesn't mean that no one will be able to exploit that key during the transmission. For example, the attacker can invalidate the HTTPS transmission before the user even note, forcing the information to be transmitted as plain text (e.g sslstrip).
Second, let's say that everything is ok, but you built your page with Wordpress or Joomla for example, with a feel plugins. If you do not have the appropriate guy to check your code, is just a matter of time to someone break in, since exploits for applications and plugins made by those organizations and their users pop out every day on exploits databases.
Just an example, the same can be done on in-house applications, even with automated tools.
SSL is just the tip of the iceberg.


Should I install an indoor or outdoor sump pump, or both?

Question: I have a full basement in a cold climate (North Dakota).   The previous owner had a raw hole broken out of the cement floor that must have served as an emergency sump pump hole.  We haven't had water in 8 years and did landscaping around the house to slope water away from house.  Due to Radon issues, we filled and sealed the hole and finished the installed a subfloor with Dry Core in the event of moisture in the basement.  This year we have a really high water table and water is in the basement - had to rip up carpet, etc.   Now I am wondering if I should break through the floor again to install a sump pump.  A contractor said he could do an outdoor sump pump for us, but I do not have an electrical source nearby, which will raise the costs and headache.  I am also uncertain if the cold climate will require me to remove the pump every year or what kind of hassles are associated with an outdoor sump pump.   What would you do?  Start over in the basement or put in an outdoor pump.  My Radon mitigation system is also a worry if we install a pump inside the house-- not sure how this will effect the deal.
Comment: Do you actually have a Radon mitigation system with a vent pipe installed in your house already?  Or did you just seal the basement?
Answer: I wouldn't even consider one or the other... both.
An outdoor sump pump in our could climate (I'm in Minnesota) is a real pain in the neck. A good friend of mine has one in his old house and he has to bring it in every winter and put it back out when the snow starts melting, which often means a few hours digging to find the top of the sump pit, then every couple days checking and adjusting the position of the pump as the solid ice on the bottom of the pit melts. Worse was the year it melted, then re-froze with the pump in it... I recall he had a number of very unpleasant things to say about it the next day at work. ;)
Depending on your levels of radon, the mitigation could be pretty simple. Several of my co-workers have a small bathroom exhaust fan in the utility room where there sump is located that ducts out of the house. It's on a timer that runs it for X minutes every Y hours, depending on what the levels were in their house. Most of us agreed that that was better than having to deal with flooded basements every few years.
Comment: An exterior pump would only be effective if there's a drain tile loop in place, and would only be needed if the drain tile doesn't benefit from gravity.
Answer: If your basement is flooding, and you live in freezing climates, an indoor sump pump is a pretty important.  A high water table also means a finished basement is going to be difficult.
If you are installing the sump pump to deal with the water table, and you also need to mitigate Radon, look at a sealed sump pump basin. It is sealed from above so Radon gas won't come into the house, but still has holes for the Radon vent pipe and the water discharge.
Note that you will want to install the sump basin in a location that works well for both the Radon vent pipe and the water discharge.  (This may not be where the previous owner's sump hole was installed before.)
Also, note that this style of sump basin won't give you an open pit that you can easily dump water into, because it's sealed on top.  For example, you can't run an overflow hose from your water softener over to the sump pit.  If you put open holes in the pit, you will undo the seal that blocks the Radon.  (You might be able to attach a drain line with a P-trap, but the radon vent pipe suction would probably empty the trap over time.)
Not sure about your state, but in a lot of places, Radon work has to done by a licensed contractor.  So, it would probably be a good idea to talk to a few Radon contractors and explain your sitution (which is a little more complex than a typical Radon system).
If you haven't researched Radon mitigation systems yet, you really should do so.
Answer: I'm not understanding the connection between the two issues. They really are different systems. As for Radon, not sure if it varies from state to state, but in MN they come in drill holes in your basement slab, then run PVC pipes from that up and out your roof with a low-power fan continually venting the system. The goals is to put negative pressure on your slab so that Radon doesn't enter your space. Since it sounds like you want a finished basement, I'd definitely go that route.
As for the water issue, if you have a high water table, maybe finishing the basement isn't the best idea. One thing I did with our old house is I didn't put down any flooring material and instead acid-stained the concrete. Not a look everyone likes, but I'll never have to deal with tearing out wet carpet. ;)
Answer: In Minnesota (a very similar climate), rarely are sumps installed outside the foundation. Typically there's a drain tile network that runs to a lower area away from the home. It's only when the home is in a low area that a pump is needed outside.
I would reinstall the interior pump, but its effectiveness may be limited by the lack of a proper drain tile network under the slab. If you have good washed rock as a substrate it may work well.
Regarding the radon system, you simply need to install a sealed cover over your pit or pail. By using rubber grommets around the exit pipe and power cord you allow the radon mitigation fan to create adequate vacuum under the slab. Such covers are readily available from online radon specialty companies.


Fourier transform for dummies

Question: So ... what is the Fourier transform? What does it do? Why is it useful (both in math and in engineering, physics, etc)?
(Answers at any level of sophistication are welcome.)
Comment: Isn't this the prototypical question not to ask on MO? :-)
Comment: Probably :-). I posted this a while ago, when MO was just getting started. I don't mind if people vote to close this.
Comment: Closed, at Kevin's suggestion. This one has bounced back to the front page enough times. http://tea.mathoverflow.net/discussion/210
Answer: One of the main uses of Fourier transforms is to diagonalize convolutions. In fact, many of the most useful properties of the Fourier transform can be summarized in the sentence "the Fourier transform is a unitary change of basis for functions (or distributions) that diagonalizes all convolution operators." I've been ambiguous about the domain of the functions and the inner product. The domain is an abelian group, and the inner product is the L2 inner product with respect to Haar measure. (There are more general definitions of the Fourier transform, but I won't attempt to deal with those.)
I think a good way to motivate the definition of convolution (and thus eventually of the Fourier transform) starts with probability theory. Let's say we have an abelian group (G, +, -, 0) and two independent random variables X and Y that take values in G, and we are interested in the value of X + Y. For simplicity, let's assume G = {x1, ..., xn} is finite. For example, X and Y could be (possibly biased) six-sided dice, which we can roll to get two independent elements of Z/6Z. The sum of the die rolls mod 6 gives another element of the group.
For x ∈ G, let f(x) be the probability P(X = x), and let g(x) = P(Y = x). What we care about is h(x) := P(X + Y = x). We can compute this as a sum of joint probabilities:
h(x) = P(X + Y = x) = Σy+z=xP(X = y & Y = z)
However, since X and Y are independent, P(X = y & Y = z) = P(X = y)P(Y = z) = f(y)g(z), so the sum is actually
h(x) = Σy+z=xf(y)g(z) = Σy∈Gf(y)g(x-y).
This is called the convolution of f and g and denoted by f*g. In words, the convolution of two probability distributions is the probability distribution of the sum of two independent random variables having those respective distributions. From that, one can deduce easily that convolution satisfies nice properties: commutativity, associativity, and the existence of an identity. Moreover, convolution has the same relationship to addition and scalar multiplication as pointwise multiplication does (namely, bilinearity). In the finite setting, there's also an obvious L2 inner product on distributions, with respect to which, for each f, the transformation g -> f * g is normal. Since such transformations also commute, recalling a big theorem from finite-dimensional linear algebra, we know there's an orthonormal basis with respect to which all of them are diagonal. It's not difficult to deduce then that in such a basis, convolution must be represented by coordinatewise multiplication. That basis is the Fourier basis, and the process of obtaining the coordinates in the Fourier basis from coordinates in the standard basis (the values f(x) for x ∈ G) is the Fourier transform. Since both bases are orthonormal, that transformation is unitary.
If G is infinite, then much of the above has to be modified, but a lot of it still works. (Most importantly, for now, the intuition works.) For example, if G = Rn, then the sum Σy∈Gf(y)g(x-y) must be replaced by the integral ∫y∈Gf(y)g(x-y)dy to define convolution, or even more generally, by Haar integration over G. The Fourier "basis" still has the important property of representing convolution by "coordinatewise" (or pointwise) multiplication and therefore of diagonalizing all convolution operators.
The fact that the Fourier transform diagonalizes convolutions has more implications than may appear at first. Sometimes, as above, the operation of convolution is itself of interest, but sometimes one of the arguments (say f) is fixed, and we want to study the transformation T(g) := f*g as a linear transformation of g. A lot of common operators fall into this category. For example:

Translation: T(g)(x) = g(x-a) for some fixed a. This is convolution with a "unit mass" at a.
Differentiation: T(g)(x) = g'(x). This is convolution with the derivative of a negative unit mass at 0.
Indefinite integration (say on R): T(g)(x) = ∫x-infinityg(t)dt. This is convolution with the Heaviside step function.

In the Fourier basis, all of those are therefore represented by pointwise multiplication by an appropriate function (namely the Fourier transform of the respective convolution kernel). That makes Fourier analysis very useful, for example, in studying differential operators.
Comment: Quite a nice answer! I came upon it by reading your post http://mathoverflow.net/questions/2117/solutions-to-the-diffusion-equation/2151#2151 At some level, I already understood "Fourier transformation diagonalizes the Laplace operator" as a mathematical principle. Your post here makes me want to go and read more harmonic analysis! ha!
Answer: Wikipedia article - very long, has explicit formulas, graphics, applications, etc.
A Fourier transform is a map from a space of functions on a (locally compact topological) abelian group A to functions on the Pontryagin dual group A' = Hom(A, U(1)), also a locally compact topological abelian group.  If the chosen space of functions is good, like L^2 or smooth with rapid decay, then the map is an isomorphism.  It is defined by integration against a canonical exponential kernel.  When A = R, then so is A', and the a function f(t) is taken to a function F(s), defined as the integral of f(t)e^(-2i pi st) dt.
Here is an application in signal processing: Say you have a quantity that varies in time, like the ambient air pressure at some location (describing a sound wave).  This is expressed as a function f(t), and taking the Fourier transform (A = time, A' = frequency), F(s) describes the decomposition into frequency components.  If f(t) = sin(2 pi t), then it is a combination of pure exponentials with frequencies -1 and +1, and the Fourier transform is a sum of delta functions supported at -1 and 1.  F isn't smooth, because f did not have rapid decay at infinity, so I'm implicitly using an extension of the transform to a larger space, like tempered distributions.  Alternatively, if you're only working with periodic input, you can quotient the time domain A to a circle R/Z, and the frequency domain A' becomes a copy of the integers.  In this case, the Fourier transform of sin(2 pi t) is a function supported at -1 and 1 with values i/2 and -i/2, respectively.
When A is finite, you get a discrete Fourier transform, which is amenable to computation because of the existence of fast algorithms (fft).  One example of its use is in JPEG image compression, decomposing image data into a sum of waves (which actually uses cosines instead of exponentials).  You can also multiply large integers quickly by pretending the sequence of digits is a signal.  Multiplication is the same as convolving the signals, and it amounts to pointwise multiplication on the Fourier transforms.
I'm not really prepared to discuss the mathematical uses - it's big in harmonic analysis, but I only really see the part that touches number theory, like in Tate's thesis and automorphic forms in general.
Answer: I basically agree with the other answers so far, but here's the answer in a nutshell: The Fourier transform (and also Fourier series) writes a function as a superposition of functions of the form exp(iax). These exponential functions are eigenvectors both for translation and differentiation operators. It is because these operators are so natural and ubiquitous that one often wants to work in a "basis" adapted to them.
Answer: A representation of an arbitrary sheaf from derived category of sheaves on a stack G/G (action by conjugacy) in terms of "dual" basis. Abelian case — Fourier-Mukai transform for abelian varieties which relates sheaves on A with sheaves on Av using the correspondence A\times Av.
(there's some important property of Fourier missing above — I'll return to this tomorrow). It's something about relationship between G/G and G^\wedge/G^\wedge.
After passing to functions, you may think about the resulting version as rewriting an arbitrary conjugate-invariant function as a sum by characters. That specializes to abelian case — where all functions are conjugate-invariant.
As an example, for the real line you have to present f(x) as an integral of e^{2\lambda ix} (well, L^2, i and the appearance of integral are some important technical details because of non-compactness). The correspondence after all becomes integration with the kernel K(x, \lambda)  = e^{2\lambda ix}.
Comment: Looking forward to hearing more about Fourier-Mukai! :-)
Comment: I'm not an expert, so what I know is simple. Perhaps you should post a question so others will share as well?
Comment: http://mathoverflow.net/questions/9834/heuristic-behind-the-fourier-mukai-transform
Answer: In algebraic geometry, there is a Deligne-Fourier transform, from the bounded derived category of $\ell$-adic sheaves on the affine line over a finite field, say $\mathbb F_q,$ to itself. This operation depends on the choice of an additive character of $\mathbb F_q$ (into $\bar{\mathbb Q}\_{\ell}^*$), and it is an important technique in Laumon's simplified proof for Weil II. Under the sheaf-function correspondence this Fourier transform gives the classical Fourier transform for $\mathbb F_q.$
For instance, if $\chi$ is a multiplicative complex-valued character of $\mathbb F_q,$ then its Fourier transform is known as the Gauss sum. While $\chi$ takes values in roots of unity, which have absolute value 1 and hence weight 0, its Gauss sum takes values in weight 1 numbers.
Answer: As well as all the abstract reasons above, one of the reasons the discrete Fourier transform is so widely used in signal and image analysis is the existence of Fast Fourier Transforms (of which there are many versions), all of which compute the FT very speedily.  This means that for convolution of large signals or images with large filters, it is much more efficient to use the FFT and the convolution theorem than a direct convolution.  You may like to look at Fastest Fourier Transform in the West, which is the library used by Matlab.
Answer: Nobody seems to have said anything about Physics.
It underlies the Heisenberg uncertainty principle in quantum mechanics, which can be paraphrased as the fact that a function and its Fourier transform cannot both have compact support.
Answer: When you say "for dummies", this one is a very intuitive and step-by-step explanation:
http://techhouse.brown.edu/~dmorris/projects/tutorials/fourier_tutorial.pdf
Answer: The electrical engineering answer goes something like this...
It converts your time domain to frequency domain.
It's quite good for cleaning up signals by removing certain parts of the signal, usually the very high frequency aspects, though you have to do so in very careful ways, b/c if you're not careful you'll remove a lot of good information.
Oh, it also allows you to pull out some interesting information very easily, like
it's linear
you can pull out translations by a constant like
F(f(x + x_0)) = CF(f(x)) (where c is power of e, it's specific but kind of messy)
you can pull out dilations as
F(f(ax)) = 1/|a|F(f(x/a))
Answer: In mathematical physics many differential equations may be transformed by FT and gives some relations which may be solved algebraically. It is specially useful for analysing periodic structures and propagations of charges within it, for wave equation and many many others.
Also in Quantum Field Theory in path integral formulation formal power series approximation is easier in momentum space than in coordinate space, and relation between them is by FT.

Fourier transform for dummies


youtube and soundcloud

Question: Do u use youtube.com and soundcloud.com to show your work?
Answer: Video
I use both Vimeo & Youtube to upload, reason being is I'm never sure which one will catch on and might get a little bit of traction. That said, I always use Vimeo to display my work, it looks better and now works on iPhones.
Audio
Soundcloud for sure! I quite like audioBoo to show quick snippets of sounds I like from a random place (recorded on iPhone) - not for professional use, just to share quickly.
Answer: I use Soundcloud for my business (sound libraries) and it's been absolutely great. Not only does it drive my work pretty much directly to one of my main customer bases (musicians), it's also serving as a great way to get feedback on my work, along with all the other sharing and viral word-of-mouth stuff that comes with a social platform. It's very tightly focused on one kind of content and that's why it works so well. You can also get very granular with things like permissions, sharing, comments, etc. It even has built-in Creative Commons licenses - if you want them. Their "Premium" account has proven to be well worth it for me.
YouTube, not so much. Unlike Soundcloud, it's like the Wild West. The demographic is, um, everyone in the world. And you have to face a double-sided sword of choosing to either lock down comments and lose out on potential viral spread and community type stuff, or open them up to the wide world of internet morons. I used it for a bit but didn't find it to be of any value. Your mileage may vary.
Vimeo, on the other hand, I like quite a lot. It's rare that I have the need to present video but when I do I use Vimeo. It's got a much higher signal-to-noise ratio and the audience there tends to be seeking out high quality material with genuine interest. Lots of artists and creative types on there.
As an aside, I also like tumblr for both video and audio. Free, easy and a built-in audience of several bazillion people. Very nice platform.
What's nice is that so many of these services talk to each other, so you can post content to one place and it automagically just ends up everywhere. Fun times we live in, the present is so futurey.
Comment: SoundCloud and Vimeo are my choices as well. Vimeo offers a lot more player customization and options than YouTube as well, and the UI is far cleaner for those who hit the site directly, as opposed to watching videos inline on your own site.
Answer: SoundCloud and Vimeo for me. Youtube is too open, Vimeo gives you more access in my opinion.
Answer: theres a good saying: "fish where the fish are"
& i agree with it ;)
Answer: I use YouTube and SoundCloud. Mostly to host files for my website.
Answer: Going to look into SoundCloud. Not familiar with it.
Vimeo I liked the reliability of their embed player - except you couldn't customize how it looked. More importantly, you have to subscribe to their service to post HD videos - in turn this limits the sound quality you can have on your presented work online.  Youtube allows most HD types which grants you the ability to put a wider range of audio formats with your video.  Vimeo makes you pay for this. Youtube also allows the privatization of your own personal channel and only your embedded player on your website will play the video. It wont show up in searches on Youtube.
Answer: Sound cloud and Vimeo - I try to avoid YouTube for my own work. Vimeo just feels more proffessional somehow if you're sending people links.
Answer: Yep, Soundcloud and Vimeo here too! I love how easy it is to post a soundcloud recording/clip on a blog. Plus the sample rate and bit depth are not limited, it's only the length in time. This is a big advantage.
Answer: I prefer vimeo to youtube. Youtube places a 15 minute limit on videos you upload. Vimeo does not have this length restriction. You are restriced by file size... but it's a fairly generous file size.
Answer: I use YouTube as another social outlet to show my work. I'm starting to use SoundCloud. I'm all for trying to make it easier for my clients. They can send me the files I need without having to log in to an ftp. I'm trying to add it to my Facebook account... but this is no picnic!
Answer: I use Vimeo and Soundcloud. Its great because these sites are so quick easy to upload a video and track. I use them both to get quick advice and comments on my works and to share files with others. Plus they look nicer than youtube. Also Soundcloud looks good and is easy to use right there without following a link when you put it up on facebook.
Answer: For sound designers, there is fantastic exposure available on youtube.  Because, this is where the filmmakers go .. right?  Who do you want to promote yourself to as a sound designer?  Filmmakers, film producers, video editors.
Sure, there are tons of irrelevant visitors but who knows what opportunities lurk in those visits.
Personally I post free sfx on youtube and have had over 300,000 views this year alone which is great for branding and driving traffic to my sound effects site.
Check it out, completely free promo and branding.
http://www.youtube.com/sfxsource
Soundcloud is an amazing service and site.  But, if you are looking for exposure to video editors, filmmakers etc .. folks who might hire you, its not necessarily the most direct option .. I get a sense its a fantastic platform for composers or for generating a fan base if you are a musician

youtube and soundcloud


TV commercials that start with a voice over, and later cut to the narrator

Question: I've noticed several TV commercials that start with a voice over, and later cut to the narrator. There is a unique audio effect, that makes the voice still sound like an overdub, but the lips are in sync. How is this done?
Answer: Most ads use ADR for the audio.
@gauss256 is correct; the easiest way is to record both audio and video of the narrator at the same time. However, sometimes this is not the best option for the audio. For example, if the narrator was walking along a beach while speaking, the recoded audio would not be clean. So in that case, they would record the audio as a guide track and then get the actor into a studio for an ADR session. This way they can record perfectly clear audio which they can edit to obtain that 'authoritative' 'voice of God' type sound.
As for the example you posted in your question, I'm not too sure if that's ADR or not. There's only about a second of footage of the narrator so it's difficult to see if his lips match perfectly with the audio. However, as the background is just pure black, I would assume they'd have recorded his sound and vision in a studio – so as to kill two birds with one stone.
In terms of how to achieve that 'voice of God' sound, I couldn't give exact instructions. You would just have to experiment with pitch shifting and equalizers in your chosen audio editing program.
Answer: That typical kind of sound is usually achieved by recording the voice in the near-field of a large-diaphragm condenser microphone. That gives you

very little room influence, so it sounds very direct.
strong, but focused bass response due to the proximity effect.

Since this recording technique requires the speaker to have a fat microphone and pop killer right in front of their face, usually no video is taken from such recordings; as it's so short it's really not a problem to do that with ADR, which they probably did in this clip.
Answer: The easiest way is to just record both audio and video of the narrator.  During editing, use the entire audio track from that recording but just a portion of the video track.  It's known as an L cut.
http://en.wikipedia.org/wiki/L_cut


Writing a shader once without using CG?

Question: Is there a tool that can convert a fragment shader from hlsl to glsl or glsl to hlsl? I do not want to use cg since it is not able to work on mobile platforms.
Is there a tool that can make it so I only write a shader once?
Thanks
Answer: Shiny is a new library that aims to make material management and portable shader writing easy. This is achieved mostly with a preprocessor meta language, that can output any of CG, HLSL or GLSL. It is currently geared towards usage with Ogre graphics engine, but that part is abstracted into a separate component, so it shouldn't be hard to plug in any other engine. The library has been / is being integrated into OpenMV and Stunt Rally (disclaimer: I'm a member of the latter).
There is a lengthy introduction here.
Answer: I can't vouch for either one, but there is a utility available here for going from HLSL to GLSL: https://github.com/aras-p/hlsl2glslfork
and here for going the other direction:
http://code.google.com/p/angleproject/
The first one is explained more here:
http://aras-p.info/blog/2010/05/21/compiling-hlsl-into-glsl-in-2010/
Answer: There's the tool MojoShader which accomplishes what you want: http://icculus.org/mojoshader/

Writing a shader once without using CG?


Dust is coming into my Ford Contour 1998 2.5L when the window is closed

Question: dust comes into my vehicle when the window is closed, looks like it comes from the passenger feet side. there is a peice of fabric that came off where the glove compartment is, could it be coming from there? where else would it come from? there are worn rubber strips along the front passenger door. dust also collects in the trunk; my doors are also started to wear out, can't open the driver side door from the outside and the passenger door won't open unless you open it from the outside and inside. i opened the driver side panel to see what the problem was, couldn't tell, but there is a small metal piece sticking out looking useless where the latch is.
Comment: Welcome to the site: are you asking two different questions at the same time?  It sounds like you have a vehicle filling with dust and a stuck door.
Answer: For the dust entry:  The fabric you mention is probably insulation over the blower motor.  It could be coming in from the outside to that location from the air intake in the cowl near the wipers on the passenger side.  It's possible the seal around the cabin air filter is gone.  There should be instructions for changing the cabin air filter in your owners manual.  You don't actually need to remove the wiper arms if you can get them stopped around 12 o'clock.  You could also be getting dust in through the door / trunk seals if they're shot.  That should be an easy fix with aftermarket material (Ford parts are probably discontinued).
As for your doors, I've recently been into the driver's door on a Contour.  The passenger side is the same, just flipped.  There is a cable that runs from the handle on the inside to the latch mechanism.  It could be stretched or broken.  You need to pull the foam panel to see it.  The cable was worn / stretched for a long time on the one I was working on and needed to have the outside and inside handles jiggled to lock the door from the inside before it eventually broke (either that or the mechanism just needed to be lubricated, which I did when I had everything off).  The outside handle is connected to the latch via a rod.  See Driver side front inside door handle does not work on a 1998 Ford Contour LX.  I've got more pictures I've got to upload yet which might help you out.  The door control cable is long discontinued (and there are none in dealer inventory or at Vintage Parts), I had to get one from a junkyard.  They sometimes show up on Ebay.  Looks like the control rod is discontinued, too.  If you can find the part number, you might be able to get it from Vintage Parts.  This is where I usually take doughnuts down to the local Ford Dealer parts department to get them to look up part numbers.  Team Ford might be able to help you out, too.


Can I use oil spray as a salad dressing?

Question: I have been using organic, all natural no-stick cooking spray (organic canola oil) for cooking recently. I know it is good for frying but I'd like to know if I can extend the usage of it. Can I use it as a salad dressing?
Answer: It won't have much flavor: unlike Olive, Canola Oil is rather bland, which makes it good for frying and lubricating when you don't want to add to the taste. You'll probably just end up with oily salad.
Answer: Well, it won't kill you.
It probably is going to just taste like oily salad.  Additionally, spray oil is rather expensive in terms of oil - if you're looking for oil on salad at least go for olive or another flavorful oil in normal liquid form.
Answer: Because it is a neutral medium, canola is not ideal for flavoring a salad with the oil in and of itself. However, neutral oils can be used as carriers for other flavors.
The spray application (assuming you are referring to a pre-packaged non-stick spray) will effectively nullify your ability to infuse flavors. Also, if you are using something like Pam canola cooking spray, there will be corn alcohol that won't cook off as it would in a baking/frying application (unless you saute your lettuce, of course), which may contribute a non-trivial flavor or effect.
Perhaps you find spray oil convenient, and canola preferable to other more flavorful oils. In this case you can use canola oil to add flavor. If you are using a pump-spray type mister you could infuse the oil with other flavors (herbs, other oils, spices, or garlic).


Turning Ubuntu 12.04 entirely Grey/B&W/Monoscale

Question: Does anyone know a way to change the color settings of the entire display to grey (or saturation to zero)? I have compiz Settings Manager installed if that helps but don't know how to do it there.
Answer: I've been playing around with the "Opacity, Brightness and Saturation" option under Accessibility in ccsm and have been able to set all windows to a saturation of 0, but the Dock and Dash don't seem to be affected by the change. A work around might be to change the Icon set to one of the High contrast versions that exist on the system or by finding one of your liking on the internet.
Here's how. CCSM-> Accessibility-> (Enable) Opacity, Brightness and Saturation. This will cause Compiz to have a little fit, give it time and it will repair itself.
In the OBaS settings go to the saturation tab. Under "Window specific settings" click New, in the next dialog box enter "type=any" without quotes, and set the Window values to 0. Click close and the results should be instantaneous.
Comment: It doesn't change anything when I implement what you've said.
Answer: You can play with gamma:
<code>> xgamma -gamma 0.9
</code>


Where do synthetics go after the Reapers have cleared the galaxy of organics?

Question: So the Reapers' purpose is to clear the galaxy of organic life so that synthetics won't annihilate organics, then where does the synthetic life go after the cycle is up?
Answer: Reapers hide in Dark Space, the space between Galaxies to avoid detection by races within the Galaxies. They depend on the Mass Relay network to get back into Galactic space to make their assault. The linked Wiki article has a ton of information on the process.
If you mean what happens to other synthetic life like the Geth, I assume they're culled along with the organics, given the Reaper's true purpose.

 Given the ending of ME3 the Reapers surely must remove all Synthetic life from the Galaxy as well, to avoid it from taking over Organic life. I would assume they treat them like raw material just like organics.
Answer: Obviously, given the lack of information about the Reapers origins and their overall purpose, it is nearly impossible to answer this question with absolute certainty. Going off what I have experienced in the games, I would venture to guess that all synthetics would either be persuaded to join the Reapers or enslaved if they refused. If you take a look at how the Geth were taken over by the Reapers in ME3, you see that they weren't forced to serve the Reapers, but persuaded to join. As explained by Legion, the Geth allowed themselves to be taken over by the Reapers in order to defend themselves againest the Quarian attack. Basically, what I believe is that the Reapers at first try to persuade other synthetics to join them and if the synthetics refuse they simply take them over anyway. If you think about, despite the lack of info on the Reapers we do know that they need to harvest advanced civilizations of organics in order to create more Reapers (which was found out in ME2) and if there were synthetics running around the galaxy wiping out organics before they could became advanced enough for the Reapers, then this would go againest the Reapers interests. So pretty much I think synthetics are offered two choses by the Reapers: join willingly or be enslaved. Of course, this is just my opinion because, like I said in the beginning, there simply isn't enough info to really give a truely accurate answer. I hoped this answers your question well enough.


How do I set a price for advertising on my website?

Question: I have a website that I would like to advertise directly to advertisers (without using adsense, doubleclick, etc..).  How do I find out a ballpark figure of what I should ask for in terms of CPC or CPM?  Are there any published reports or averages I can refer to?  Any advice in setting/negotiating a starting point for price?
Answer: You not necessarily need to deal with CPM or CPC when it comes to direct advertising. You can work off your analytics and industry, and close a time-based deal -- like a outdoor advertising banner.
That's how DaringFireball.net and many others do. This is much simpler for advertisers and more predictable for you.
Answer: It varies greatly from industry to industry, country to country, and, especially CPM, from site to site. The easiest would be to see how much adWords charges for the keywords related to your site.
If I can get X click-thrus or ad impressions by spending $Y on adWords, then I'm not likely to pay more than $Y/X per click/impression on advertising on a website unless it's a very well known site in my industry or they have past ad performance data showing that their ad space is more effective.


What is attentuation?

Question: What is attentuation?
How does it effect beer flavor and quality?
How is is calculated and why do I need to know it?
Answer: Attenuation is a measurement of a beer's drop in specific gravity during fermentation. It is expressed as a percentage of original gravity and calculated by (OG - FG) / OG. We measure apparent attenuation because the alcohol produced during fermentation is lighter than water meaning OG readings are not truly measurements of the sugars in beer.
Most often homebrewers use the apparent attenuation listed by their yeast supplier to predict final gravity, the stopping point of fermentation. Suppose you brewed a pre-prohibition lager with an OG of 11.4 ºPlato and chose WYeast 2206 (Bavarian Lager). WYeast lists the attenuation range at 73-77%. From this you know that fermentation will cease when the beer's FG is between 8.3 & 8.7 ºP.
Attenuation is a more true measurement of fermentation activity than anything else.
When designing beers you can use attenuation to influence the flavor of the finished product.  The higher a strain's attenuation, the drier the resultant beer. Say, for example, you want to turn your favorite IPA, made with White Labs WLP001, into a Double IPA.  Knowing that you need a maltier beer to balance the big hop flavor you could choose WLP008 which has a lower attenuation range, but similar flavor profile.
Comment: Nice complete answer.
Answer: Attenuation is the percentage of fermentables actually consumed by your yeast.  It's easiest to calculate "apparent attenuation," which is simply (OG - FG) / OG.  This is called apparent because it does not take into account the specific gravity of the alcohol that has been produced.
Commercially available homebrewer's yeast always lists it's expected attenuation range.  From this range, you can can calculate what your expected final gravity will be based on your starting gravity.  It's important to know this because it's a way of making sure you don't bottle too early.  If you bottled when airlock activity stopped without knowing the attenuation of your brew, you might find out that the bottling activity woke up some sleeping yeast, who then found plenty of yummy fermentables to eat in addition to your priming sugar, and you'll wake up one night to the sounds of exploding glass.
Comment: How about pondering how it effect beer flavor and quality before I give you THE answer check? :)

What is attentuation?


How does google treat domains that were once used for adult content but no longer are?

Question: I'm considering placing some adult xxx stub content and links on one of my unused domains. Depending on the outcome of the experiment, perhaps I would like to go back to non adult content in a few months for this domain. What can I expect in terms of google position after this move? Will I be penalized? If so, for how long? The targeted search phrase will be the same for both adult and non-adult version.
Answer: As John Conde noted, it's a long standing myth that Google penalizes a web site for having adult content. They don't. The myth came about because so many adult webmasters resorted to blackhat tactics to try and rank in a highly competitive niche. They routinely get their sites penalized or deindexed because of these tactics, not their content.
There is some potential harm that could hold over from this, beyond a pre-existing penalty. First of all, your domain may still rank for adult terms. Now if you want that traffic, that's fine, but if you don't, it can be a pain to deal with. Another part of this is that your site may be filtered out if someone is filtering out adult content on Google and your domain may still be filtered for a while until the new content is spidered full and old content is deindexed.
Also, your domain may be on an "adult content" list operated by "net nanny" programs and corporate firewall software. This, while not directly dealing with Google, can cause you problems depending on your target traffic.
Answer: Having adult content does not cause Google to penalize a website or domain as having porn on a website is not against their terms of service. If you change the content to be non-adult in nature Google will adjust the rankings for those pages as it crawls and discovers the new content. So making that change won't be an issue if you do decide to do something like that.


I have an idea for a card game. How can I best start testing it?

Question: I've been playing around with an idea for a card game for some time, and I think I've finally got the idea fairly well in place. How can I best start testing it out to refine it?
Comment: Is this a question about the card game design lifecycle or about prototyping card game (materials, etc.)?
Comment: I don't want the whole cycle per say, just the "I have a game planned" to start testing it.
Answer: There are different stages to testing.
You need to make sure the core idea and gameplay is workable.  You can do some of this by playing through a few games with just you playing for each other player.
Then you need to start creating the game.  This will be an iterative process.  You get the game together, and draft some instructions, and get some friends round to play it.
Take many notes!  See how they understand the instructions; make notes of any oddities during play; see if they understand the game in the way you intend.
Make changes, and do this again.  Do this a few times.
Eventually you'll get a game that's ready for beta testing with people who don't know you; maybe as a print and play download. Make sure people know it's a beta test, and make sure they have some good method for reporting problems they have and getting help.
You'll also want to think about asking people to try to break the game; trying to use weird strategies to win or "king making" or rushing or such.
Comment: You can also build prototypes in pretty much any office suite or desktop publishing software.  Create something bare-bones but functional, print on card stock and cut.  You don't need to get fancy with it at this stage.
Answer: If you think you'll have to frequently change cards you could use card sleeves instead of glue/tape. Simply print out a new version and swap. You'll probably have to add some kind of real card to the sleeve to give it stability.
As for the actual testing, just ask people to try it out with you and tell you what they think. You'll probably want to have a core group of testers that play more frequently so they can examine advanced strategies.
Once you're confident in your game you should have some blind playtesting: See how people handle the game with nothing more than the cards and the rulebook.
Answer: Buy normal playing cards (maybe more than one deck if you have a lot of cards in your game), print your special cards on normal paper (or write something on pieces of paper) and simply tape/glue them on the cards you bought. They will all look the same from the back and won't require you to make them on expensive paper.
Note: when you finally make the game, thing about cuttong the corners of the cards in rounded shape to avoid them to be destroyed too easely.
Answer: One Solution would be to start with index cards. No need to look fancy until you are sure you are happy with what you have got. (this could depend on the kind of card game. Like if you are using a game that can use standard playing cards then go with the obvious, however if you are making a trading card game or something then this solution could work for you.)
Once you have your cards and whatever extra stuff such as dice and what not that you need then gather up a few people and give them a rough overview of your game. Once you pique their interests bring them to a place where they can play, give them a set of rules. It's important that you don't play with them while they test it.
Instead of playing, keep a notebook with you and note down different details about how the players interact with your game. What makes them frustrated?, do they understand the rules?, are they enjoying themselves?, do they quit?, if so why?, and what not.
Also make the players feel that they can stop playing at any time so that they don't continue to play just out of respect for you, or out of the feeling of being trapped.
As you take notes also keep in mind the personalty of those you have playing. Are they your intended audience for your game? If so are you appealing to your audience? Also if they are not your intended audience do they find interest in your game? If so how can you maybe expand play to include their style and maybe broaden your market?
After you get these notes down be sure to look over your game and make revisions where necessary. Once revisions are made try to have a play test with the same players and see if you have improved the experience at all. Try the game with different people, and see what comes out of it.
Answer: You can purchase blank faced playing cards that are perfect for prototyping. Just write whatever text you need on the face of the card and start playing. It's a good idea to keep extras on hand for use as you need to add/remove/change the cards in your deck.
I could list a few sources, but your best bet is to check out Google Products to see what fits your needs the best.


What is a good barrier between grout and wood?

Question: A side of a tile flooring project abuts a strip of wood. How should I handle the side where the tile meets the wood so the wood won't absorb all the water from the grout?
Answer: You may not want to grout that joint.  Caulking (using a matching color with the grout) may be the better solution.  This way it will not crack as the wood expands and contracts over time with temp/humidity changes.
Comment: +1. Typically you'll want to use caulk or leave the gap empty, then cover it with a transition piece.
Comment: Some grout brands also sell caulk that's made to match the grout colors/textures.
Answer: In our house where tile meets wood, the tile installer inserted a thin metal strip between the tile and wood. I think there is grout on the tile side of the metal strip and the wood has very narrow space between it and the metal strip.
There is no transition piece that covers the joint and the top of the wood is flush with the top of the tile.
I've sat here for ten minutes trying to remember what that metal strip was called, but it escapes me.
Comment: Was it called a profile?
Answer: Whenever you have materials of different types butting up against each other, you always want to leave space for expansion because they'll expand at different rates.
Use transition pieces wherever you have these material joins - these are finish pieces that sit over top of the transition to hide it while giving that finished look.
In the case of tile meeting wood, as others have said, leave the space empty, or caulk with a material that will remain flexible made for the specific join (I can't think of one off hand, so I'd leave it empty) and cover the join with quarter round or shoe for a professionally finished look.
Like so: (Not my project)
Comment: Don't use 1/4 round when tiling to the wall, remove the base board, Tile, then use the base board to cover the gap.


Learning a new language and framework, should I spike a project, or first ground myself in the language fundamentals?

Question: I've got substantial J2EE experience, have worked with Grails, and am comfortable with several languages (Perl, PHP, Smalltalk). I've decided to try a new project using Ruby on Rails. For those who've decided to migrate to a new technology stack, how do you make the transition? Do you learn the details of Ruby first (I've done a few tutorials, and feel like I've got a decent enough grasp of the language to start doing some basic work) or do you do a full Ruby on Rails tutorial, and expand your knowledge from there. I'm leaning towards the latter approach because I feel like I can delve into details of the language as I encounter them. For those who work in Ruby on Rails, how did you learn, and which resources do you recommend?
Answer: I learned Rails by going through the Agile Web Development with Rails book and immediately applied everything that I learned to a real web project. I ended up with a rather substantial application (mykidslibrary.com) and a deep understanding of the framework.
Answer: There's that saying that if you spend 10,000 hours at a task you'll become an expert.  So I'd say "get coding!"  If you've done the tutorial then write some code to scratch an itch or join an open source ruby on rails project.
If your employer is brave/trusts you - perhaps you can build a small but useful real world project as well.
Answer: The best way to learn a new language is simply to use it (reading tutorials won't make it 'click') and one way that I've been assured is fantastic is through writing tests.  I'm yet to try this myself (and will do so this weekend) but give Ruby Koans a go and let me know how you get on :)
Comment: I really like the daily practice this offers. And rather than just learning new syntax, helps keep you sharp by asking you to think.
Answer: A crucial part of any project is the purpose it is aimed to satisfy. If you are just reading about a language or copying some program, the purpose isn't there, and it's just like painting by numbers.
Choose a project of your own initiative (though you can get ideas from others), not a big one, and tackle that. That way all parts of your brain will be engaged, you'll have fun, and everything you learn will be grounded in a purpose.
Answer: Read the tutorial, then go and write a 1,000 lines of code in the language. That will not make you a master but after 1k lines you should have a pretty good feel for it.
And don't be afraid to make stupid mistakes, as long as you learn from them!


Plurals: finance, spending, receipts

Question: My topic is money, budgeting and public finance(s?).

Do you say public finance or public finances? (like in http://news.bbc.co.uk/1/hi/business/8573128.stm)
Budget has two sides, spending and receipts? Why is one singular and second plural?
Answer: In response to your first question, I believe that finances (plural) have to do with the funds of the government (i.e. the little gold we have left int the Treasury), whereas  public finance is the management of those funds.
If you type in "define: finance" on google, you get:

Finance is the science of funds management.

whereas if you perform the same search on "finances", it outputs:

funds: assets in the form of money

In response to your second question (spending vs. receipts, plurality),
see the wikipedia page  on classification of nouns. One could be considered non-concrete and one concrete, or perhaps one is uncountable and the other countable.
Hope that helps!

Plurals: finance, spending, receipts


Utsuri goshi vs ushiro goshi usage

Question: They're both similar in execution and used as counters against hip techniques. Are there any reasons to prefer using one instead of the other in various situations?
Comment: #9 in [this highlight](https://www.facebook.com/ijudo/videos/10154355200783536/) (circa -5:47, or ~3:40 in) is an absolutely stunning utsuri goshi that highlights Thierry's point and demonstrates how it's appropriate when ushiro goshi is not.
Answer: I can't comment, so I'll answer it here instead.
As @Dave Liepmann said, it depends on your strengh and your ability. Utsuri Goshi is hard to do. The hardest move I've done, seriously.
Using the "right" move is always a decision based on your opponent's reaction.
If you start and manage to raise him off his feet (which is the first step of both moves) as set-up for ushiro goshi, 99% of the competitors will use their right leg to "hook" the inside of yours to prevent you from shifting correctly and easily over your shoulder/to your side, and often your grip isn't ideal and they will slip, turn, and try/manage to fall on you if you still try to get the move off.
I was a huge Harai goshi user, and got ushiro goshi used a lot against me... And you train yourself a lot to counter it. It's obvious when someone tries it, and not too hard to counter. I'd say in 14 or 15 years of competitions, it has been successfully used less than 10 times against me, and threw that about 2 or 3 times for anything higher than yuko.
On the other side, Utsuri ghosi gives you more control over your opponent, since once you manage to raise him off his feet, his first reflex will be to press or push against you, thus making it easier to pass in front of him, and once you do, you cannot miss scoring Ippon. Plus it's a hugely spectacular move to pull off.
But most of all, it's counterintuitive for someone to really block you correctly, and it has a big surprise factor. I was training with the elite team here, and I've never seen anyone practice how to counter or dodge utsuri goshi, because it is seriously hard to do.
Answer: I don't have an utsuri goshi, but I like ushiro goshi when my opponent hasn't broken my balance forward. After a successful hip block, ushiro goshi often feels like just an extra little "pop" of my hips to send someone up.
My understanding is that utsuri goshi is a somewhat more difficult and skillful throw, but it seems to afford a greater deal of control over the person being thrown. That is, uke can be controlled longer during utsuri goshi than with ushiro goshi, since uke can be carried on the hip and connected to your center further along the trip to the ground. Then again, like I said, I don't use the throw.

Utsuri goshi vs ushiro goshi usage


USB Keyboard doesn't work server installation 12.10

Question: USB Keyboard doesn't work server installation 12.10. I can get till the language selection screen and later no response to keyboard. Need help.
Answer: Since there's not much info to go on I'll give some general troubleshooting tips.
Try:
-Using a different usb port
-Turning the computer off and on
-Using a different keyboard, if you have one, to see if it's the computer's fault
That's the best I can give you. More info on the computer(laptop or desktop, previous OS's etc.) and the keyboard(has it worked before, does it work on other computers etc.) would be appreciated for a more specific answer.
Answer: Try looking for "USB Legacy Support" in your motherboard's BIOS options.  Setting this to "on" may be necessary in order to get the keyboard working before the OS is fully booted.
Sadly, it may also be necessary to plug in a PS/2 keyboard to GET to the BIOS options in the first place... but usually (usually!) not.


Are Xna XACT audio cues accurately timed enough for a loop sequencer?

Question: Would it be possible to make an audio seqencer using XNA that works by triggering XACT cues periodically using a timer. Would the timing be precise enough to synchronize several audio clips into one loop? (Think Ableton Live)
Answer: Not sure if you'd be able to, but on the bright side, you most likely don't have to.
If you're just trying to create a series of sounds to play in a row (and even loop that series) that can all be done in XACT.
When you have the XACT project open and all of the wavs added and corresponding Sounds for them, just drag the sounds onto the Cue that you want to use.  In the bottom-left panel, you can control how the cue uses the selection of sounds.
For instance, Random will just play one of the sounds with certain probability, but it sounds like you want "Ordered" or "Ordered from Random" so it will play all of the sounds.
"Interactive" gives you other freedoms as well. See this thread for more info.


Conjecture that two nested convex curves have a point with the same slope

Question: I'm trying to prove a conjecture and need some help.
Consider a continuous, twice differentiable function $p(a)$ such that $p(0) = 0$ and $\forall a$, $p'(a) > 0$ and $p''(a) < 0$ and $p$ is bounded above by 1. I believe it's the case that for $\gamma > 1$, $\exists a' | p'(a) = \gamma p'(\gamma a)$. Another way of stating that is that if you have two functions, $p(a)$ and $p(\gamma a)$, there is some point $a'$ where the slopes of the two curves are the same.
I'm trying to prove this conjecture but I'm not making much progress. I feel like I'm making this harder than it is, but in in terms of a proof sketch / intuition, I think one approach would be to:

Show that $\gamma p'(0) - p'(0) > 0$
Show that $p(a)$ and $p(\gamma a)$
both have to converge some the same
value, say $B$.
Argue that for the $p(a)$ curve to "catch up" to $p(\gamma a)$---because they converge to $B$ and the $p(a)$ curve is everywhere below the $p(\gamma a)$ curve---there has to be some point $\hat{a}$ where $p'(\hat{a}) > \gamma p(\gamma \hat{a})$ and hence $\gamma p'(\gamma \hat{a}) - p'(\hat{a}) < 0$ and so by the IVT, there has to be some $a'$ such that $\gamma p'(\gamma a') - p'(a') = 0$, which is what I'm looking for.

While I think this (might) work, the "catch up" notion is really informal and I suspect there's some much simpler, more rigorous way of showing that it's true. Thanks.
Comment: The differentiable function $x\mapsto  p(\gamma x)-p(x)$ vanishes at zero and at infinity, and it is non-negative because $p$ is increasing, so it has a maximum point $a$, which is what you want.
Comment: Of course - thank you! If you migrate this to an answer, I can approve it.
Answer: The differentiable function $x\mapsto p(\gamma x)−p(x)$ vanishes at zero and at infinity, and it is non-negative because p is increasing, so it has a maximum point a, which is what you want.


How to disable Airplay on IPad?

Question: Is it possible to disable Airplay on an iPad?  I recently bought a Denon receiver that supports Airplay.  The other day my 2 year old niece decided to stream what she was watching on the iPad to my stereo at an extremely high volume level.  As you could imagine, trying to tell a 2 year old not to do something can be impossible at times, so I'd like to disable the Airplay feature from the iPad so my niece, and others, can't use it.
Answer: No it is not possible to disable AirPlay.
However you could add a volume limit with Restrictions. Also with iOS 6 you can have more control over how kids control the iPad with Guided Access. You can limit the iPad to just the current app and lock off parts of the screen.
Answer: Or.., buy a router with a seperate guest network and have the kids toy access the Internet via this. Only solution for the ipod .
Answer: There aren't any AirPlay-specific restrictions available on the iOS side yet. Another approach would be to either disable or password-protect AirPlay on your home theather's end, not on the iPad.
Apple TV provides both of these options, for example. Unfortunately, based on my research, it doesn't appear to be possible to disable or password protect AirPlay on Denon receivers  at this time.

How to disable Airplay on IPad?


Gmail Unread Messages Favicons

Question: How can you get Gmail to show the number of unread messages in the favicon? Specifically, are there any plugins for Chrome that allow me to do it with both regular Gmail and Google Apps? I've used Better Gmail and Gmail Alert (both of which use the same underlying script) but they only work on one, only show up to "3+" new messages, and are often out of date.
Answer: The Gmail Favicon Alerts 3 user script works on Chrome, as well as Firefox and Opera (although I haven't tested Opera). It will show up to 999 new messages, and works on Gmail and Google Apps, even if both are opened in tabs.
Answer: The "Unread message icon" option in Gmail Labs can do this, as well.  (It doesn't show an exact number after you have more than 10 unread messages, but it will show something like 10+, 20+, 70+, 100+, etc.)  No browser extensions/plug-ins are needed for this method.
You can enable this for each individual Gmail or Apps account by going to Settings -> Labs -> Unread message icon and clicking Enable.
This works well with Chrome's "pin tab" feature to always show your e-mail in the corner of the screen.
More information: http://gmailblog.blogspot.com/2011/01/new-in-labs-unread-message-icon.html
Answer: The best of these I've found is the Better Gmail 2 extension for Firefox. Otherwise, the best extension out there for Chrome is the Better Gmail extension you mentioned, which is actually inspired by the Firefox one.

Gmail Unread Messages Favicons


Error on wiki page - Is it ok?

Question: Taken from Wikipedia on Windows and Linux

However such an approach has indeed produced several vulnerabilities,
  although this is a rare case

Is that statement logically correct because it seems to contradict itself or am I just reading it wrong.
Answer: You're absolutely correct that the sentence could be better written, and other answers have given good suggestions.
If you're looking for a logical contradiction between several and rare, though, there is none. Several refers to the number of things (more than a few) whereas rare refers to a proportion of some population. If the population is large enough, than you can have rare things of which there are several: for example, several NBA players have been under six feet, but they are rare. In a very large population, rare cases can have even many instances: many people have eyes of different colours, but they are rare too!
Answer: I think that sentence sounds confusing because it shifts from plural (several vulnerabilities) to singular (case).
A better way to phrase it would be

However, in several rare cases, such an approach has produced vulnerabilities.
Answer: Agreed, it makes no sense as written.
Better expressed:

However, such an approach has indeed produced several vulnerabilities, although these are  rare.
Answer: Indeed, considering the context:

Anyone with programming experience is free to fix bugs and submit them for inclusion in future releases and updates. However such an approach has indeed produced several vulnerabilities, although this is a rare case.

It could have been misunderstood to mean that "allowing anyone with programming experience to fix bugs" as a rare case, whereas in actuality, the sentence means "the vulnerabilities are rare cases, they do not happen often."
Yes, this sentence is ambiguous.

Error on wiki page - Is it ok?


Should we leave our contact details in source code?

Question: I usually leave my email address as a courtesy in case someone wants to ask me a question about it later. Do other people leave more or less information than that? Does anyone leave a phone number??
Comment: ****** No. ******
Comment: @Joel - ****** Hell No. ******  I remember some of the code I have unleashed upon the world and I would rather try to forget it than to be reminded of it 10 years from now by someone asking me WTF! =P
Answer: I almost never leave my name nor e-mail address :

It tends to get copy-pasted (yeah, bad practice) ; and I end up with people contacting me for code I didn't write
When the code is modified, the contact info is not removed nor update ; and I end up with people contacting me about code that has changed so much I don't even recognize it.

Instead, I prefer pointing people to the code repository (SVN, Git, ...) : there, they can have the full history -- and find out who wrote / modified the portion they have a question about.
Answer: I use to be in the habit of leaving my name or initials in comment headers, with a revision number and a brief description of the change.
I've recently gotten out of that habit given the fact the this is redundant with version control, e.g. any one interested in who made what changes can see the entire history of the source code in version control.
Comment: Aha! Time to complain to NetBeans about their default templates.
Answer: If you are developing software professionally, you are most probably using some version control system (svn, hg, git, etc). In this case, I find it redundant to leave your personal information inside the code since you already have a coder account (with that information) to be able to commit code on the project.
However, some people from the open source community find it interesting to leave a name and email address for contact. This is not a bad idea at all. Check this examples:
From FFmpeg:
<code>/*
 * Interplay C93 video decoder
 * Copyright (c) 2007 Anssi Hannula <email@example.com>
 *
 * This file is part of FFmpeg.
 */
</code>
From DirectFB:
<code>/*
   (c) Copyright 2001-2009  The world wide DirectFB Open Source Community (directfb.org)
   (c) Copyright 2000-2004  Convergence (integrated media) GmbH

   All rights reserved.

   Written by Denis Oliver Kropp <email@example.com>,
              Andreas Hundt <firstname.lastname@example.com>,
              Sven Neumann <email@example.com>,
              Ville Syrjälä <firstname.lastname@example.com> and
              Claudio Ciccani <firstname.lastname@example.com>.
*/
</code>
Answer: But surely leaving my name and or email would mean i was supposed to write comments in my code??
Sorry was not an answer. In reality  i usually leave doctype comments ...
<code>/**
* @author PurplePilot
* @package
* @etc
*/
</code>
with my name but not email address. Yes this code can get cut and pasted but if the copier does not change the author name they won't change anything else and it becomes obvious it is an unmaintained comment.
I have an email sig i use from time to time which goes
<code>/* Anything you put in comments is not tested and easily goes out of date. */
</code>
which seems to be a general reflection of many of the other posts in this thread. However as there are not rules on the subject a programmer needs to do what they feel the most comfortable with.
Comment: @Anna - Err.... I think it's supposed to be a joke.
Comment: Err... what? I think this should've been a comment.
Comment: @Slomojo Yeah, I got that. Still think it's more appropriate as a comment, though. It's cute, but a non-answer.
Comment: @Anna, oh I see, perhaps, but it works as an answer to the question, when I read it.
Answer: I often leave my initials in comments (where appropriate), but I don't see any reason to leave anything more. If the I'm still working at the company that owns the code, people should know how to get in touch with me.
If I've left the company and work elsewhere, it's not really fair on my new employer if I'm taking calls about software at my last company (who could be a competitor!).
If the code was shared in some other way (eg. open-source, posted online), then it's possibly worthwhile having your contact details, but if the code was passed on another way, the person you gave it to will likely already have your contact details, and would you really want a random stranger calling asking about code you wrote years earlier?
Comment: For publicly released code, I'd probably but my name/url/email in the header. I'd probably use a unique email alias so I could filter/block mail if it ended up being spammed due to being posted online publicly.
Comment: Yep inside a company that makes sense. I was more thinking of code released into the public domain.
Answer: There's a line of thought that says: Don't put in your source code stuff that should be in the source control.
Authorship information is one of these things, since over time, code will be modified by many people at less than file granularity. A blame log should tell you everything you need to know.
That being said, many companies follow the transition of listing the original file author and never changing it. Whether it's really useful (as people leave companies), I don't know.
I suspect that the main value is building awareness. You will not go and ask the IDE to tell you who authored each file that you see, but by encountering these over time in your group's codebase, you get an idea of responsibilities and expertise in the project.
For public domain - the benefit is "advertising", the downside is that someone could wreck your file in the future but it would still be bearing your name.
Answer: After 3 decades of programming and maintaing and converting software, I can safely say that the author information in source code is worthless.
I have never had a use for it.  It can't be trusted.  None of the people are still employed by the company.  Half the names are contractors.
Answer: I never leave my contact details in the code.  It always get out of date and seems to cause more problems then it solves.
Other people have pointed out quite a few of the problems, but I wanted to mention one that I think is the most insidious effects.
It can destroy team work and code quality.
How may you ask, well it all has to do with collective code ownership.  If you put your name of the code, then the next person coming in will say "that isn't my code, I will just X" where X can be hack it, ignore it, etc.  Then if they do fix it, they of course want to put their name on the code because they improved it.  But then you may think, hey I spent weeks on this code and they spent 10 minutes why do they get to have their name right by mine.  Over time this cycle continues and people argue about who should get credit (or blame) for the code.
It just doesn't work out well for the team. Instead if the team focused on collective ownership and making all the code great with no ownership you can focus on what is really important which is the quality of the system.  If you do need to track down who has worked on it you can always use the VCS to get the details.
Note: Even copyright headers can have this destructive impact if it has the name of a developer, especially if the developer is not as active as other contributors.  That is why on Open Source projects I try to only mention authors in an AUTHORS or contributors file one place in the project.
Comment: I think your issues stem more from poorly minded coworkers than the comments themselves.
Comment: Great answer, some open-source projects even forbid to write author information in files because it is breaking collective code ownership.
Answer: I don't tend to leave my contact information in source code as my VCS takes care of accountability for me.
That said, it's advisable to have your contact information somewhere so that people who use the code can contact you directly to provide feedback.  A link to a project website in the README file is generally good practice.
The convention comes from the era when Usenet and IRC were used regularly to share source code.  Since the code was rarely linked from a VCS and more often sent directly, if you wanted feedback you would have to include your contact information somewhere.
Answer: I leave my name in SQL scripts, as they will mostly be fetched directly from the database, not from source control.