Examples of Mixed Hodge Structures

Question: Does anyone know a user-friendly, example-laden introduction to mixed Hodge structures?  I get from Wikipedia how to calculate for a punctured and pinched curve (http://en.wikipedia.org/wiki/Hodge_structure#Mixed_Hodge_structures), but I want more!  I want tables and numbers and everything explicit and spoonfed.  Thanks!
Comment: Thanks for the responses so far.  I will dig in before accepting an answer.  (Hint:  active links most likely to get the vote.  When I say spoonfed, I mean spoonfed.  [Yeah, I'm talkin' to you, Emerton!])
Comment: Within our department, have you asked Sam?  He's spent a lot of time learning Hodge theory.
Comment: even I am looking for some thing like that.
Answer: I just noticed the question. The references mentioned so far are good. So I'll just do
the example that I normally do on a blackboard when anyone asks me.
Take a smooth complex projective variety $X$ with a smooth divisor $D$. Set $U=X-D$. There's
a long exact sequence
$$ \ldots H^i(X)\to H^i(U)\to H^{i-1}(D)\to H^{i+1}(X)\ldots$$
say with rational or complex coefficients. What are the maps?
The first is restriction, the second using $\mathbb{C}$ coefficients is a residue map,
and the third is  the Gysin map which is of type $(1,1)$ (or you want to want to get
fancy you need a Tate twist here). The mixed Hodge theory of $U$ can be read off from this.
For example, for the Hodge numbers
$$\dim H^{pq}(U)= \dim im[H^{p-1,q-1}(D)\to H^{pq}(X)]+\dim ker[H^{pq}(D)\to H^{p+1,q+1}(X)]$$
and so on. (By the way, $H^{pq}$ is taken to be the $(p,q)$ part of the $p+q$
weight graded  quotient.)
OK, let me make it more concrete. Let $X$ be a surface with irregularity $q=0$, perhaps $\mathbb{P}^2$, then $D \subset X$ is a curve of say genus $g$.
Then from above, the interesting Hodge numbers are
$$h^{20}(U)=h^{02}(U)=h^{20}(X)$$
$$h^{11}(U)=h^{11}(X)-1$$
$$h^{12}(U)=h^{21}(U)=g$$
 Maybe that's enough for now.
I can't resist squeezing in one more example. Suppose $D$ on  the above surface $X$
can be contracted to a point in a normal surface $Y$. So for example, $Y$ might be a cone over a plane curve, and $X$ the blow up of the vertex. Using duality  and the  standard exact sequence for compactly supported cohomology, we can  conclude
$$H^i(Y)=H_c^i(U)= H^{4-i}(U)^*(-2),\quad i>0$$
As far as Hodge numbers are concerned, the  dual means $(p,q)\mapsto (-p,-q)$ and $(-2)$ means shift by $(2,2)$.
Answer: I can't believe nobody has yet mentioned the book Period mappings and period domains by Carlson, Müller-Stach and Peters. Chapter 1, the introduction, is written almost as a story, starting with the pure Hodge structure on the cohomology of a Riemann surface and introducing mixed Hodge structures by looking at degenerations. Further niceties await the reader in subsequent chapters.
Comment:
This was the easiest reference for the basic ideas, gently spoonfed -- thanks!  It's probably enough for my purposes -- i.e., constructing a filtration on the cohomology of some complex which should be the cohomology of a singular algebraic variety qua central fiber, hence have a mixed Hodge structure.  Thanks to the others, too.
Answer: Dear Zaz,
If you look at Deligne's "Hodge I" article (actually an ICM talk, maybe from 1970 or thereabouts, which should be available at the IMU's electronic database of ICM talks),
you will find a table giving at least some info about weights and Hodge numbers in
various contexts (smooth but open, proper but possibly singular, etc.); more precisely,
he states the ranges that the various numbers can lie in.
Otherwise, the basic principle is that (say in the case of a smooth variety first)
you compactify your variety, write down the various long exact sequences that come to
mind relating the cohomology of the open variety to that of its compactification,
and then use the fact the maps of MHS are strict for weight and Hodge filtrations,
so that you can read of the numbers of the MHS you care about (the cohomology of the
open variety) from the MHS of other things appearing (which are compact, and so in
some sense known: more precisely, the compactification is compact and smooth, so
is known --- in principle --- by usual Hodge theory, while the boundary will be
a normal crossings divisor, so is compact but possibly singular --- but in the mildest
possible way --- and is also of lower dimension, so you can imagine that you know
it by induction on dimension and/or because it's compact and very close to being
smooth).
This is not the same as giving you a table, unfortunately; you wanted fish and I am giving
you (at best) some kind of fishing implement (or maybe a spoon).  Sorry about that.
Comment: Sometimes you just want your fish on a spoon!  I don't need to know what the carburetor does just to drive to the mall.
Comment: Matt, thanks for all the fish(y things). 42.
Answer: Clare Voisin's book "Hodge Theory and Complex Algebraic Geometry I" goes over the case of a smooth (noncompact) variety in quite an elementary way. I also found Peters and Steenbrink's book "Mixed Hodge Structures" to be useful - it has a lot of detail and takes you all the way from Hodge theory of compact Kahler manifolds to mixed Hodge modules.
I think these are written in a slightly more elementary/textbook style than Deligne's papers (though I also recommend looking at these).
I second Matt's remark on calculating mixed Hodge numbers. If you can find long exact sequences relating the cohomology of your variety to that of other varieties whose Hodge structure you know, then you can use the fact that the maps in the LES are maps of mixed Hodge structures to try to read off mixed Hodge numbers.
Answer: This lecture by Sam Payne is a very nice introduction:
http://archive.msri.org/communications/vmath/VMathVideos/VideoInfo/4162/LV/LaunchVideo?videoid=13602
Comment: I'll vouch for that; it was a great talk.  The video links at MSRI have changed; I think the video Jim is referring to is now at http://www.msri.org/web/msri/online-videos/-/video/showVideo/3674
Answer: A.H. Durfee, ``A naive guide to mixed Hodge theory,'' Singularities, Part 1 (Arcata, Calif., 1981), 313-320, Proc. Sympos. Pure Math., 40, Amer. Math. Soc., Providence, RI, 1983.
is quite nice to read, but probably doesn't handle any more cases than you already know.
Answer: Deligne's long "Fundamental group of the projective line minus three points" paper has several examples of mixed motives right near the beginning (in section 2, "examples") whose associated mixed Hodge structures are described very explicitly.  That's where I learned what a mixed Hodge structure was, at any rate.
http://www.math.ias.edu/files/deligne/GaloisGroups.pdf

Examples of Mixed Hodge Structures


Secondary size?

Question: When moving a 5 gallon batch into secondary does it make a difference if it is into a 5 gallon carboy or a 6.5?
Comment: Cleaning up tags: Change secondray to secondary
Answer: I say use any size it fits in.
In the secondary, there is unlikely to be any significant foaming unless you add a fermentable flavor such as a fruit juice. A five gallon carboy will serve fine.
Concerns about oxygenation in larger carboys, in my opinion, are largely unfounded. Small amounts of fermentation are still occurring in the secondary as well as natural outgassing from racking the beer out of the primary.  Because CO2 is heavier than air, it forms a protective blanket over your beer, protecting it from oxidation.
The real danger of oxidation in the secondary is excessive splashing during transfer, not exposure while sitting still. But that is easy to minimize and doesn't have any bearing on the carboy size.
Comment: I never thought about CO2 being heavier than air. That makes complete sense. Thanks!
Answer: The current thinking among homebrew "experts" such as John Palmer and Jamil Zainasheff, as well as Wyeast and White Labs, is not to use secondary at all unless you're doing a true secondary fermentation by adding fruit or something like that.  Just leave the beer in primary for 3-4 weeks, then package.  That's the ultimate solution about what to use for a secondary!
Comment: This is Denny C., his answer counts as an authoritative article!
Comment: do you have links to specific articles?
Comment: I believe in [this podcast](http://www.thebrewingnetwork.com/shows/Brew-Strong/Brew-Strong-12-08-08-Dry-Hopping), Palmer explains that he no longer thinks yeast autolysis is as big a concern as his original book. The hosts use a secondary for conditioning and dry hopping.
Comment: If you're an AHA member, you can read his take on it here...http://www.homebrewersassociation.org/pages/lets-brew/ask-the-experts/john-palmer
Answer: I've never had a problem. I only use 6.5gal carboys, have for over 4 years.
Comment: Excellent! Thats what I was hoping to hear.
Answer: I mentioned in a beer storage question that oxygen is one of the two beer spoilers. Minimize the exposure to oxygen by leaving little head space in your secondary vessel.  If you keg, you can flood the secondary with CO2 before transferring. Carbon dioxide is heavier than air and will protect your beer from oxidation.
That being said, there's not much reason to chase a problem that doesn't exist.  Oxidized beer has a wet cardboard or stale cracker flavor.  If you don't taste those flavors, relax, don't worry and have a non-oxidized homebrew.
Answer: Doesn't matter much; but some will advocate having as little airspace as possible.
Answer: I use 5 gal carboys for secondary... when I use a secondary.  Lately I have gotten lazy, except for lagers, I only use a primary.
Answer: I wouldn't put 1 gallon of finished beer in a 6 gallon carboy for sure, but 5 gallons in 6 or 6.5... probably not a big deal.  And I never had a problem.
For the record I don't secondary that often anymore anyway.
Answer: I took a class at a local homebrew supply.. the person in charge of the class said the "beer" should almost fill the carboy, leaving little air in the carboy and limiting the chances of contamination. I followed this direction and the fermentation that took place started to enter bubbler..... so I poored a few oz out. Thanks to this episode I will not leave a good amount of room in the carboy for fermentation to take place.
Comment: The guy at your local was likely talking about secondary.  You should leave plenty of headspace in the carboy for primary fermentation.
Comment: Like TinCoyote mentioned in his answer, I try to ensure there is enough room in my carboy to hold all of my beer.

Secondary size?


Annual Rate of Occurrence (ARO) and Exposure Factor (EF) Data

Question: I'm calculating loss expectancy (SLE/ALE) but where or how does one get data on annual rates of occurrences for various things? From simple hard-drive failure rates to something complex like the exploitation of client browsers? Or how about the effectiveness of controls and how much they can reduce the exposure factor? An example being using Snort Sourcefire VRT Certified Rules over default/non-subscription ones.
Answer: I think you may find that this question is so huge in function and scope that you won't find such definitive lists (though I'd also love to see one.)
Publicly, you are more likely to find mean-(time-to or between)-failure of hardware than for software simply because physical engineering will be concerned with those figures during the life-cycle.  Of course, Google's study on their consumer-grade disk drives was interesting, but again, very focused and clearly shows that even if you know the stats for physical hardware, sometimes reality paints a different (or at least "more complete") picture.
With all of this said, I can think of two organizations that love to deal with probabilities of failures: the government/military and insurance companies.  Maybe this can help in the search process?
Comment: You might find the following article interesting reading: http://c2.com/cgi/wiki?MeanTimeBetweenFailureForSoftware
Comment: Perhaps hard drives were a bit too simple of an example. Although I thought it was common knowledge that MTBF for hard drives were completely unrealistic?
Answer: You might want to look at Veris


Freelance web development vs. design

Question: Do web design freelancers (I'm thinking individuals, not companies) typically do all development and design work themselves? What are the options for those with a strong base in back-end web development but less with web design, color schemes, layouts, graphic design, etc.?
Comment: It'd be interesting to see the answers from this SE compare with the UX SE.
Answer: As a freelancer myself, this is what I do. I normally talk to the person who is giving me the project and get myself a designer. The designer designs the UI and provides me with all the necessary HTML, CSS etc etc. Using that as the base, I change plain vanilla HTML to server components (ASP.Net) and I start working on the design and then start development. My design methodology is mostly agile, as in freelance projects (depending upon the scale), you normally don't have separation of phases. So agile works well for me.
Answer: Some people do try and do both.. and in most cases I have seen they do one well and the other... not so much.  Designing and Programming generally take two different types of people.  Often I've seen designers subcontract the programming work and focus on the designing aspects.
Personally I consider myself formost a programmer.  I understand the basic aspects of designing web pages but I would rather let somone else deal with those details.
Answer: I'm up front about not doing any design work. I handle only the programming side. However, I keep all HTML seperate from the rest of the code, in easy to identify template files (e.g header.php, footer.php, signup.php, etc), so its very easy for them to get a designer and have him change it without having to deal with much code.
Answer: I typically get all of my design work sub-contracted. That is, I'll hire a designer to build a photoshop version of the site, usually getting it 90% of the way there and then either get someone to cut up that design into HTML & CSS, or do that myself (depending on a number of factors).
There are many options for getting the initial design. I tend to use the same designer that I've used in the past, but you can use sites like 99designs.com or more generic freelance sites like elance.com to find designers. I would tend to prefer the designer-specific 99designs.com, they're more expensive but the quality is generally higher.
In the past, I've also sub-contracted out the HTML/CSS cutting, but I find that is more hit-and-miss than the designs themselves. I usually prefer to do the cutting myself, since I can tailor the HTML/CSS to fit better with the server-side generation of the HTML. I find that many companies which provide HTML/CSS cutting don't take tweaking or modifications into account and making changes to the layout or slight tweaks later on can be very painful. I've been burnt by that often enough - it's ended up costing me more time tweaking a badly cut design than if I had just done the whole thing from scratch - that I don't even bother much any more.

Freelance web development vs. design


Improperly installed or nonexistent brick ties in a wall

Question: Is there as easy way to repair a brick wall that isn't properly attached to the wall behind it?  There are no cracks inside the house but there is a large vertical gap between the corner brick - these come out further than the wall - and the wall brick.  The brick wall will move slightly when you push against it.  When the house was being bricked I noticed one day that there were no brick ties on the wall.  I called the builder extremely upset and when I came by the house later brick ties were being used.  I don't have any idea how much of the work had been done before I saw they were not using the ties.  All the brick work done is terrible!  My dad was a stone mason so I might be overly picky, but there is mortar falling out in a number of places, patio Colima are not straight, fireplace brick inside has some joints that are more than an inch wide!  If I could afford it I would have it all taken down and redone . . .  The house was built after the original house was destroyed by a tornado.  Lots of shoddy work was done in the area at the time.  Looking back I should never allowed myself to be pressured into accepting such poor quality of workmanship.  Any help will be greatly appreciated!!
Answer: Obviously the ideal solution if the birckwork is generally poor is to rebuild the wall.
In this case this doens't seem to be an option. To replace existing ties that have problems or sections of the wall where ties are missing you can get drill and fix wall ties. I believe you can get this type of system from Helifix in the UK but I'm sure similar systems exist around the world. You can get systems that rely on some fairly unattractive face plates but other systems do not rely on this but have a resin bond to the brickwork. You will probably need specialist advice on what the right system for you is and to identify if there are any other issues associated with the poorly constructed wall other than the lack of ties.
Answer: If this is work in progress then talk to the builder and get him to redo the work properly.
Withhold some (or all) of the money you owe him until he puts it right.
Take photos of the poor workmanship so you have evidence to back up your claims.
Comment: The work was done in 2000 when the house was built.  The original was destroyed by a tornado.  It was a chaotic time trying to "get back home" so I know we let the builder get by with things that we shouldn't have.  At the time we were bring pressured by the insurance company to move in the new house so they could stop paying our rent; our kids wanted to go "home"; there was a shortage of contractors, workmen, even supplies at times.  The better workers were lured away by promises of more money, contractors were inflating the cost of everything, etc.  Now we are paying the price.
Comment: @Ann - what sort of guarantees (if any) came with the rebuild?


Error:[Brasero Disk Burner]: You do not have the required permissions to use this drive

Question: I just installed Ubuntu 11.04 and then installed some programs. Now, When I run the "Brasero Disk Burner" for  creating an image from a DVD, It gives me an error:

The image could not be created at the specified location. Do you want to
  specify another location for this session or retry with the current
  location?
You do not have the required permissions to use this drive.

I checked the permissions for my home directory and it shows nothing wrong:

Folder access: Create and delete files

I tried to create the image on different folders in vain. I wonder what the problem is?
Comment: Start Brasero via the terminal and see if there are any other errors. Also check /var/log/syslog
Answer: Problem self solved

I just noticed that I am able to put the image in the "Documents" folder.


Can an image have a full 3D effect without using special glasses?

Question: Can we put 3D effect in an image and watch this without using any coloured glasses ?
Answer: You are really asking two completely different questions.

Can we put 3D effect in an image?
Can I watch a 3D image without using any coloured glasses?

For #1, consider that 3D images are not a single image, the 3D effect is achieved by having two different images taken from a slightly different point of view. To see the 3D effect you have to feed these two images one to each eye. This approximates how we see the real world.
So really, if you have a single image you cannot see 3D. Though you can use post-production techniques to generate two images from your single image. This is how some 2D movies are "converted" to 3D.
There is good information about 3D imagery in the Stereoscopy page on Wikipedia.
Regarding #2, there are a few ways to see 3D images without glasses. But most require either glasses (to filter the two images being displayed and provide a single image to each eye) or specialized display hardware (to split the two images based on the angle of view each eye is at with respect to the display).
There is one interesting method that doesn't require any special hardware nor glasses and that is quite easy to achieve. It's commonly called "Wiggle 3D". This question has a pretty good example of this technique, and my answer there points to a tutorial on how to make them.
Answer: Yes, holography would be one example. Here's on explanation of "How Holograms Work".
Also, on a smartphone, it would be possible to use a combination of anamorphosis and the phone's gyroscopic sensors to achieve this effect.
Answer: Try wiggle stereoscopy or wiggle 3D. See Wikipedia for the explanations.
In short: Take two pictures with a normal 2D camera. Just shift the camera between the pictures. Then load the two images in an image editing software in two separated layers, adjust the position and rotation, crop them and export them.
The first difficulty is to adjust both images as very slight shifting or rotating will spoil the 3D effect.
The second difficulty is to produce a convenient output. Animated GIF produces big files, specially if you are using a transition effect between the both images. But, you can also use two images or one side by side and use Java Script or CSS to display and hide one image on a web page (see example link below).
The third difficulty is the time spent per image. Only a few percentage of the images is suitable for wiggling. And you will see the results only when all the work is done.
There is software around easing this process. I am related to one of the company so I can't put any link here.
But I put some examples of adjusted wiggle 3D images, displayed out of two JPEG images wiggling with CSS, on my private web site http://www.tomic.ch/wiggletest/
Comment: Thanks for expanding your answers. It's actually okay to link to your company when it's relevant -- you just need to mention that connection, and also (as you have) give answers that are helpful in themselves. (Also, you can put whatever links you want in your personal profile page.) And welcome to Stack Exchange!


Why does Rebbe Yehoshua need a passuk?

Question: The Gemara (Nazir 65b) says that Rabbi Yehoshua learns from the passuk of לטהרו או לטמאו that the case of ספק שיער לבן קדם ספק בהרת קדמה the halacha is טהור. The question is why he needs a passuk to say this if the Gemara (Kesubos 75b) says that the reasoning of Rebbe Yehoshua is because he holds that we go after חזקת הגוף?
Answer: One clarification:  R' Yehoshua is saying that all of the tanna kamma's cases are tahor, not just the safek case.
That should clear things up:
The pasuk comes to tell us the lesser chidush unless otherwise indicated.
If R' Yehoshua did not hold of chezkas haguf, then a case of white hair before baheres would be a safek and the chidush of the pasuk is that it is tahor, but baheres b/f white hair would remain a safek.  Since R' Yehoshua holds of chezkas haguf, white hair b/f baheres is tahor without the pasuk.  So the chidush of the pasuk is that baheres b/f white hair is also tahor.
(see Tos' iy hachi who uses the above structure when applying R' Yehudah/Rav to nizkak l'tumah above)

Why does Rebbe Yehoshua need a passuk?


Which type of pan can you recommend for pan-frying tofu?

Question: Which type of pan can you recommend for pan-frying tofu, stainless, aluminum, or carbon steel?
Answer: Cast iron rules! but if i was to choose from the options you provided i would pick the heaviest / thickest one regardless of the material.
Answer: The correct pan is the one you're most comfortable with.  Any of those materials can give you good results if used correctly, and you might even get away with cast-iron or nonstick cookware.
In fact, this is true for most cooking tasks. Exception: if the food will ruin your pan, as with acid on cast iron/carbon steel, and eggs with many materials, if not oiled enough.
Answer: For a beginner, I'd recommend a non-stick pan, and a wide one. Otherwise, you're liable to have the crust on the fried tofu stick to the pan.  Most tofu is fairly delicate.
Two tips:
1. dry and press the tofu before frying it
2. do not crowd the pan.
If you're an experienced cook, see BobMcGee's answer.


charging in power off

Question: I am using ipad 1 and I have some charging problem in it so,I want to ask that is there any problem if I charge my ipad in power off mode.
If yes yes what can be the problems that can be seen in my ipad
Can I use Chinese chargers for charging it.
Comment: What are some of the problems you are having?
Answer: You can charge your iPad 1 while in power off mode.
With regard to using a Chinese non-Apple branded charger, this is possible. However you should be aware that Apple's chargers are recommended. The price difference between a non-Apple branded charger and Apple's own charger is significant; that difference is because of Apple's design costs and additional safety features.
Ken Shirriff's article showing the inside of an Apple iPhone charger demonstrates why the price difference exists.
Answer: there are no problems with this. You can swap chargers however you want, although it is recommended that you use ones that are manufactured by apple.
Answer: The iPad is designed to draw more than the 500mA specified for USB. It even exceeds past 1A that is not unusual anymore these days but still not exactly standard USB2 current.
So, with the Apple charger for the iPad you get 10W at 5V and 2A. With any iPhone charger the iPad will only receive 5W at 1A, and most USB2 ports only deliver 500mA, resulting in only 2.5W. The iPad will charge with all of these currents, but it will take longer the lower the current falls.
Make sure you get a charger that safely delivers at least 1A, better 2A.
And yes, you can charge it when its off. It should be even quicker than charging while turned on.

charging in power off


What are the best ways to lose a zombie?

Question: When starting up, you have no weapon and no mean to defeat zombies at all. Are there ways to lose a zombie aggro or multiple zombies, even?
Answer: Run!
Run some more!
Lather, rinse, repeat. Eventually, zombies will stop chasing you.  According to the DayZ wiki:

Zombies stop chasing players when they are more than 300m away

Breaking line of sight is paramount.  Sometimes simply going prone can throw a zombie off you scent.  Another important thing to remember is zombies cannot run in buildings.  Taking a route through a building with multiple exits will allow you to slow down your pursuer significantly.  If you have the ammo and don't mind attracting the attention, this will also allow you to easily take them out with a well placed shot to the head.
Other alternatives include swimming, climbing, and closing doors.  Although zombies can do all these things as well, it can slow them down.
Comment: Adding to the above comment, Zombies also fall and conveniently die when running down hills, however this hill has to be steep enough for the zombie to fall.
Comment: You forgot to say [**RUN!!**](http://www.youtube.com/watch?v=DlT6owR5Ytg)
Comment: I would also add running up hills, zig zagging through trees and around buildings and then going prone and crawling off.
Answer: In my opinion the best way is to get inside buildings with 2 entrances, like large barns. You get inside, wait until all of the zeds are inside walking slowly and leave by the other entrance.
If you want to make really sure you lost them, after leaving go prone and take some distance.
Almost never fails, unless some zombie decides to go in by the second entrance.
Answer: There are a few key things to know about Zombies when trying to run away from them (from the DayZ wiki)

Zombies can only walk through buildings
Zombies can be lost by breaking their line of sight, but they will continue to investigate players' last known locations and the area

Given this, the methods I find best are
Run through buildings
Zombies can't run through buildings, so a good tactic is to either run through a building, or run into a building, wait for the Zombies to move away from the entrance and then peg it out the way you came in.
Make sure that you don't try this in small buildings with only one entrance as you will probably just back yourself into a corner.  Also be careful - zombies can attack (and sometimes even walk through) walls and closed doors.
Run up or down hills
If you manage to find a hill steep enough so that you slow to a walk going up it then try zig-zagging up the hill - the Zombie too will slow to a walk and running up hills in a zig-zag is much faster that trying to walk directly up the hill, so using this method is a quick way to loose your Zombie if you have any suitable hills nearby.
You can also give this a try on steep downards hills - last time I tried this the Zombies comically threw themselves off the hill to their deaths.
Run through bushes
Bushes and some trees can break line of sight - running through a dense line of trees or bushes can in itself be enough to loose a Zombie if there are enough bushes.
Run around buildings
If you don't have any suitable buildings / bushes / hills nearby then if you are desparate you can just try running around a building / fences.  Remember that the goal is to break line of sight, and then get far enough away so that the Zombie doesn't find you again.  This method is less than reliable, but can sometimes work if you are lucky.

In all cases as soon as you see that the Zombie has stopped running after you switch yourself to a crouch walk (so they don't just immediately spot you again / to stop you attracting even more zombies) and get away as fast as you can.
Answer: Once you break Line of sight zombies will stop chasing you. A common looting tactic is to just sprint into town take what you need and then wind around some buildings and run away. Right now this works because they took out the fatigue system. I don't know if there are plans to put it back in.
Also be aware that due to a bug, zombies glitch through closed doors.
Answer: Best thing to do is abort if you aggro zombies, they all disappear when you log back in.


Standards for HTML access keys

Question: Wanted to see if anyone has done some research on standard HTML access key. I have notices after doing some research many sites including Apple have incorporated the accesskey="s" on its search box. I find this extreamly usable if used properly and wanted to get input from the community.
Comment: +1 And for an authoritative answer, see http://xkcd.com/927/
Answer: I think the latest guidance is to not bother with them.  They often compete with other navigation aids, JAWS for example. I believe people like the BBC in the UK have dropped access keys, and I recently helped build a central government UK site without these access keys.
Comment: Yep. Too much conflict. For most situations there are better approaches to accessibility. Still potential to add skip to content links or similar where appropriate.
Answer: There's no list of accepted accesskey delegations. WebAIM say that both the UK and Canadian govermnents attempted it and they provide that list on their website. I notice "S" is used as "Skip navigation" there, not "Search" too. Wikipedia use "f" as their search accesskey.
In my state government there is also a standard, but that differs from the UK and Canadian model as well. I think the key is: if you are going to use accesskeys provide information on them for your users (usually a list in your accessibility statement). Hope that helps!
Answer: The unfortunate answer is that there is are too many "standards" for any one to legitimately be standard.
There are a few useful write-ups here and here, and note the age of the second. Not much has changed in nine years.

Standards for HTML access keys


How well does VirtualBox perform when compared to VMWare Fusion for Linux guests?

Question: I'm looking to do some Linux development, which includes some live testing of my application. I need pretty decent performance, but maybe not pedal to the metal performance, at least not for testing. However, I don't want a VM that is going to drag me down, or use more of my Mac's resources than needed. How well does VirtualBox perform on Snow Leopard?
Answer: Having extensively used VMware Fusion (all the versions from 1 beta till 3.1), Parallels (from their first public release till 5.x -haven't yet upgraded to 6) and a lot of VirtualBox versions (Although I stopped using it six months ago), I can say that for Windows both Parallels and VMware ran circles around VirtualBox in terms of features, compatibility and speed.
I used to compile .NET code inside those Windows and the speed of VMware and Parallels was superior (I went ahead and clocked different timings).
VirtualBox's advantage was (and still is) price. For a lot of stuff VirtualBox is enough, but it's still (as far as I understand) slower than its two (only) competitors.
The advantage you have is that VirtualBox is free, so you can start trying it now, and both VMware and Parallels offer trial versions you can try. If you're serious about finding the best virtualization solution for your scenario, I suggest you take the appropriate time to test all three options yourself.
I'm personally using Parallels 5 these months, because it worked better than VMware 3.1 for my Visual Studio C# very big solution. However, I've used VMware and skipped Parallels 3 and 4 because they were more unstable and slow (for me).
I didn't want to upgrade to Parallels 6 because they annoy me with their $49 upgrade price that you have to pay every year.
Comment: This answer gets my vote. I used VirtualBox for a couple of years as my LAMP (+ Lighttpd, Litespeed, C++, whatever) dev environment and had the occasional issue where a NFS share, virtual network adapter, etc., would stop working after a reboot; I also had to do some voodoo to get LAN sharing + external internet working consistently. It was also too memory hungry. I switched to VMware Fusion about 4 months ago and wish I had done it much, much sooner. Network "just works" and is protected from external requests, it uses my Macbook's /etc/hosts file, easier to setup shares, etc.
Answer: I cannot compare to VMWare, but VirtualBox and Linux work just fine on my laptop. I run computationally expensive code on the Linux VM. It only has 1 CPU whereas the laptop is Core 2 Duo. The laptop has 8GB RAM and the VM gets 2 of those.
One slight performance improvement is to boot the VM headlessly, then ssh in, if your application isn't a GUI.
Answer: I run Ubuntu Desktop 10.10 as a guest in VirtualBox Mac, and can say that it runs about as fast as when I ran it in Fusion. It is definitely slower that in Fusion for things that open a lot of files (such as recompiling the kernel), but in the same range for normal desktop Linux use, at least in my case.


How does "smile shot" work in cameras?

Question: Nowadays some advanced cameras have the feature of "smile shot" without the photographer pressing the shutter. How do the cameras achieve this? How does it recognise the smile?
Answer: It is the same cameras that have face detection. Even though the face detection is shows as a box around the faces, it internally has a model for the eyes and mouth, so it already knows where the mouth is. The shape of the mouth is then used to detect the smile by computing a single "probability of a smile" parameter. You set a threshold for when it should be considered a smile. When the parameter is above this threshold, it will take a photo. The sensitivity and accuracy of this parameter varies from person to person, so you have to adjust the threshold accordingly.
Answer: I have worked on image processing and image recognition. Not for smile recognition on picture; but the process might be this one:
An algorithm analyzes the video stream in real time (the "live preview" display on the rear screen for a point and shot camera) to detect people face, and then to detect if there is a smile on the detected faces or not.
If you are interested in face detection, you can read this article on Wikipedia.

How does "smile shot" work in cameras?


(Non?)-linearity of the consistency strength ordering in ZF

Question: Much of the research taking place in set theory, is related to the classification of sentences according to their consistency strength relative to ZF. In order to be more specific, we say that for all sentences $\sigma,\tau\in Sent$, $\sigma$ has less consistency strength than $\tau$ (or $\sigma\leq_{cons}\tau$) iff $cons(ZF+\tau)\rightarrow cons(ZF+\sigma)$. My main question (which I believe should have a negative answer) is the following:
$$\mbox{ Is } \leq_{cons}\mbox{ linear? If not is there a natural counterexample?}$$
In fact I have several similar questions concerning $\leq_{cons}$ and I would be glad if someone could provide me with some references. Thanks!
Comment: Google gave me this: http://websupport1.citytech.cuny.edu/faculty/vgitman/images/diagram.jpg
I believe it is the same one as in Kanamori.
Comment: I'm not even close to know enough for a proper answer, but I know that some large cardinal axioms might not be linearly ordered. You can find a graph in Kanamori's The Higher Infinite, and see there for yourself some of the possibly-non-linear sentences.
Answer: Marios, this is indeed a fascinating topic.
The consistency strength hierarchy is not linearly ordered. One can produce counterexamples by variants of Gödel sentences or of Rosser sentences. It is actually an interesting exercise to produce explicit examples of a pair of Rosser-like sentences $\phi,\psi$ both independent of ZFC, such that ZFC$+\phi$ and ZFC$+\psi$ are incomparable, by letting $\phi$ refer to the length of proofs of consistency of ZFC$+\psi$, and letting $\psi$ refer to the length of proofs of the consistency of ZFC$+\phi$. Explicit examples can be found, I believe, in Per Lindström's "Aspects of Incompleteness" (Lecture Notes in Logic 10).
Harvey Friedman has worked on this question, and expanded on the idea above. I believe it is his result that one can even embed a universal countable partial order in the consistency strength degrees or in the degrees of interpretability. I'm pretty sure he has commented on this in the FOM list, but I don't seem to be able to find his relevant postings right now. (I once gave a talk on this years ago, but cannot find my slides either. Old age...)
On the other hand, everybody agrees that these examples are not natural (see for example, the beginning of the section "The Gödel hierarchy" in this paper by Simpson, or page 54 of "Fixing Frege" by John P. Burgess). It is a remarkable empirical phenomenon that we indeed have comparability for natural theories. We expect this to always be the case, and a significant amount of work in inner model theory is guided by this belief. But although we have many striking partial results in this direction, it is not quite a theorem, in part because natural is not a formal concept.
The standard way by which we establish comparability of statements is by using forcing and the technique of inner models to measure a given statement against the large cardinal hierarchy, identifying this way the large cardinal companion of the statement. Different statement can then be compared by comparing their companions.
Hugh Woodin, in his book on Pmax suggests a way of formalizing this observation, by explaining how to associate Universally Baire sets to theories, the point being that under appropriate determinacy assumptions, the Wadge degrees of any two such sets are comparable, and the resulting ordering coincides precisely with the interpretability or consistency strength orderings. (The universally Baire sets ultimately trace back to the complexity of certain iteration strategies.) This, of course, requires that we work under additional large cardinal assumptions beyond ZFC, so it only applies to theories of high consistency strength (past $\omega$ Woodin cardinals, for example). This remarkable approach has thus the drawback that it does not explain why we find the phenomenon in the low levels of the hierarchy, the ones that are precisely amenable to current inner model theoretic techniques.
At the moment there are a few notable examples of theories that we do not quite know how to fit into the linear ordering of consistency strength. This is most likely due to our present technical limitations. For example, strongly compact cardinals are expected to either coincide or sit just below supercompact cardinals consistency-wise. However, their behavior is rather atypical and they are not really as well understood as other (strong) large cardinals.
For a nice introduction to these ideas, examples, and a far reaching program that touchesof Woodin's recent work on "ultimate $L$", see these slides of a talk by John Steel at the Workshop on Set Theory and the Philosophy of Mathematics, Oct. 2010.
Comment: Thank you very much Andres! This is truely a very fascinating part of mathematics I wasn't aware of. It provides motivation and a nice background for what is taking place in set theory.
Answer: The order $\le_{cons}$ isn't linear. There are Godel Lob provability logic $GL$. It's a modal logic with one modality. $GL$ is complete with respect to arithmetic semantic. It was shown by Solovay. Formula $\square(\Diamond p \to \Diamond q) \lor \square(\Diamond q \to \Diamond p)$ is not theorem of $GL$. So by completeness theorem (it can be proved for $ZF$) there are propositions $A$ and $B$ such that $ZF \not \vdash (Con({\ulcorner} A{\urcorner}) \to Con({\ulcorner} B{\urcorner}))$ and $ZF\not \vdash (Con({\ulcorner} B{\urcorner}) \to Con({\ulcorner} A{\urcorner}))$
But such $A$ and $B$ provided by Solovay proof are complex. I don't know any "natural" example.
Answer: There are some results of Woodin that indicate why large cardinal axioms of a
certain kind might indeed be linearly ordered by consistency strength.  In Kanamori's chart there are some possibilities for nonlinearity, but I think this is just lack of knowledge.
I am not aware of any result that actually says that two natural statements are incomparable in consistency strength over ZF.
Note however that this might be a problem of our current proof technology.
We have good technology to show that the consistency of a statement $\sigma$ implies the consistency of $\tau$ (all over ZF).  Namely, start with a model of ZF+$\sigma$ and use forcing and/or inner models to construct a model of ZF+$\tau$.
The second incompleteness theorem tells us how we can get a stronger theory from a consistent theory $T$, namely by adding the axiom "$T$ is consistent".
But how could we prove that two given statements are incomparable in consistency strength?
Answer: For theories one can define their proof theoretic ordinal, which is a countable ordinal that is (roughly) the smallest ordinal that the theory cannot prove is well ordered. If one orders theories by the size of the proof theoretic ordinal, this gives a total order on theories because ordinals are totally ordered. In practice the size of the proof-theoretic ordinal is a good measure of the consistency strength of a theory (roughly speaking, proving that the proof theoretic ordinal is well ordered tends to be about as strong as proving that the theory is consistent) so consistency strength  usually gives a total order on theories.
Answer: Unlike - seemingly - all the answers above, and since strangely he seems to have missed this question (as not so often), Pr. J.D. Hamkins claims he has natural statements that contradict the pre-linearity of this pre-ordering!
He will talk about them on 25 January at 7pm UTC:
http://jdh.hamkins.org/natural-instances-of-nonlinearity-in-the-hierarchy-of-consistency-strength-uwm-logic-seminar-january-2021/
Comment: A draft version of my article is now available at http://jdh.hamkins.org/nonlinearity-in-the-hierarchy-of-consistency-strength/. I shall update with the final version when it is ready.
Comment: Upvoting to counteract incorrect claim "from review" that this isn't an answer.
Answer: My understanding is that the large cardinals are indeed linearly ordered, which is a remarkable fact. Of course, it is not a theorem (nor could it ever be?), but merely an empirical fact; still, there is no known explanation for this completely surprising coincidence.
On the other hand, there are sentences $\sigma$ such that $T+\sigma>T$ and $T+\neg\sigma>T$. These are called "Double jump sentences" and though they are rare, a number of them exist. Thus, $\le_{cons}$ is not linear, though the counterexamples are quite contrived (none of the known ones would be called "natural" by a mathematician).
You can read more about Double jump sentences (and find references) here:
http://plato.stanford.edu/entries/independence-large-cardinals/#IntHie
I hope this answers your question to your satisfaction!
Comment: Terminological note: "Orey sentence" isn't another name for a double jump sentence.  It refers instead to when there is no jump: $T + \sigma \equiv T + \neg\sigma \equiv T$.
Comment: You are entirely right; I stand corrected.
Answer: Here is the relevant posting on the FOM list by Harvy Friedman can be found here:
http://www.cs.nyu.edu/pipermail/fom/1998-August/001929.html
The result that the consistency strength ordering has an infinite set of incomparable elements is found in corollary 4. It seems to me by the way that his proof of corollary 4 only holds for models of PA+Con(PA), not models of PA+notCon(PA)


How a free (no ads) site maintain itself?

Question: The past few years a trend has grown concerning a startup creating a webapp, paying a staff and priced hosting and yet offering a service for free and with no ads. Sites like droptask, Geeklist, koding and many others are practicing this kind of business and I don't know what are they planning in terms of revenue. There might be a huge interest path I'm not seeing, but it's clearly not obvious. Do you know the paths theses companies are taking to make profit out of those applications?
Comment: Koding is currently in beta; they will be introducing paid plans after the launch
Answer: It's on case by case basis, but I would say that they are trying to build a user base first and monetize later on. Perhaps they have Venture Capital (VC) funding that is keeping them going for the moment.
A prime example of this is Instagram, never made a penny, sold for $1bn, they effectively sold their user base to Facebook.
Tumblr is another great example of this to date its raised $125m of VC funding, and until the last year or so had no solid revenue streams, but what they do have is a great active user base. More recently they have branched out to running targeted ads on their site, only available to larger premium advertisers. According to Quantcast they have around 300M+ page views a day. Now they could easily cake the site in AdSense ads, if they got a CPM of $0.50 they would be generating $150,000 per day (these are very loose workings).
But because of the way that they have taken their time to build a passionate user base, they will now be likely be able to make a much stronger advertising offering.
So the simple answer to your question would be that the sites you gave as examples have funding in place or are bootstrapped and they are playing the long game, trying to develop a maturer company to monetize.
Comment: i think i would also vote to move this to the onstartups stackexchange
Comment: Thanks @sam ! I tried asking it there, but the answer got closed as not a question for the site, so I figured out this would be the best place! Your answer was very good! The amount of money a startup raises is what I'm thinking about now. I wonder how (sometimes) a group of five dudes with an idea raise thousands of dollars to maintain themselves for a long term goal, paying hundreds on hosting, staff and everything else. Loans for these kind of ventures aren't the easiest I guess...
Comment: @AndréLucas - they almost always tend not to be loans, instead its seed / venture capital funding - in exchange for equity.
Answer: Maybe not yet, I remember when Youtube and Facebook put no ads on their pages and video (pleade CMIIW but at least in my country was).
But there are many ways for startup to pay the bill: donation, pro product, member or page promotion (e.g in your Twitter suggestion, page suggestion).
Money is not always part of the main purpose.
My friend told me that a big company should not take profit from their small project but rather to use their small project to promote their big project. Maybe many big company does.


Difference between Baritone and Euphonium

Question: What is the difference between a baritone and a euphonium, and how can you tell? My band director sometimes uses them interchangeably, but I am pretty sure that is not correct. All I know is that this has to do with different valving.
Comment: No one mentioned this, but there's a difference in the mouthpieces as well.
Answer: In the British Brass Band Tradition, the Baritone is a member of the Saxhorn family, whereas the Euphonium is a member of the Tuba family.
The Euphonium has a wider bore and a more conical flare over more of the instrument's length, compared to the smaller, shorter Baritone flare. Generally, most Reasonable Euphoniums in the UK will have 4 Valves, arranged 3 upright and one on the side, whereas Baritones would have 3 Valves, although 4 Valve Baritones are now available and used in some Brass Bands.
In standard British Brass Bands, there are 2 Euphoniums and 2 Baritones, usually sitting together and frequently playing the same part. Because of the difference in bore and bell size, the Euphonium tends to have a more mellow sound, although the instruments do blend very effectively in the middle of the Band.
Modern Composers are starting to write for the Baritone as a separate instrument, often as a downward extension of the Tenor Horn section. The Euphoniums, likewise, tend to be written as an upward extension of the Tuba (Bass) Section.
In British Brass Bands, both instruments are written as Bb instruments in Treble Clef.
The old trick (in the UK) for telling the difference between a 3 Valve Baritone and a 3 Valve Euphonium was to take out the main Tuning Slide, turn it round, and try to insert the slide with the legs in the opposite hole. If it fits, it's a Baritone. If it doesn't, it's a Euphonium. This may not apply in other locations! :-)
Dave Werden's Site makes a good reference to differences and similarities between the two instruments and also has pictures of the different British and American Instruments..
Darryl (Played Baritone in Brass Bands for 5 years, Euphonium for 2)
EEb Bass Tuba, Shepherd Group Brass Band, York UK
Answer: While not disagreeing with tubadaz's great answer, historians often quibble about the origins of various brass horns, and these horns have no shortage of ambiguity over their history. It's no secret that the terms are commonly mixed; a Google Image search for "Baritone Horn" yields a large number of instruments more correctly called euphoniums.
The modern baritone horn is derived from a family of narrowly-conically-bored instruments known as saxhorns. tubadaz says they are cylindrically-bored instruments, but he's technically incorrect on that; they're just not as conical as a horn, euphonium or tuba (though more so than the trumpet or trombone, which are typically held up as examples of "cylindrical bores").
They were invented in the early 1830s by Adolphe Sax, also the father of the saxophone. His vision was to replace the menagerie of brass horns, all of varying regional and cultural origin, with one system of instrument design and construction; 3 edge-mounted dual-piston valves, circular piping arrangement, long straight conical bell, played with a circular cup mouthpiece. The resulting instruments could then be switched between more easily by players as the need arose, unlike the differing mouthpieces, valve designs and orientations of other brass families
He was modestly successful; the family contains ancestors of the modern cornet (sopranino), flugelhorn (soprano), and mellophone (alto), as well as the alto/tenor horn and baritone horn which have changed very little (the main change being a switch from horizontal orientation with rearward bells, popular in marching bands in the Civil War era, to vertical orientation with upward- or forward-facing bells). The bass saxhorn has fallen into disuse, though elements of its design can be seen in some styles of tuba. The baritone horn falls in a gradient of tone with other instruments of the same general range; it's slightly more conically-bored and therefore slightly warmer-sounding than the cylindrically-bored trombone, but brighter and edgier than the Wagner tuba and euphonium.
The euphonium has a different design path; the intent, from the beginning, was to create a baritone-range instrument with a warmer, sweeter timbre than that of existing tenor instruments like the trombone and saxhorns, more like the French horn and its contrabass helicon cousin (the predecessor to the modern sousaphone and ultimately the concert tuba). This was accomplished by scaling down and rearranging the helicon's circular construction while keeping its wide conical cross-section. Wagner had the same idea after hearing Sax's baritone saxhorn; his creation was the Wagner tuba, achieved by scaling up the French horn Wagner sought to emulate at lower registers. Some euphoniums have three valves, similar to the baritone horn, but the majority nowadays have four, adding the "trigger" valve from the French horn and "double Wagner tuba" which lowers the instruments fundamental by a perfect fourth. As the thumb is typically needed to support a euphonium near the valve tree, this fourth valve is usually either a "pinky valve" similar to modern tubas, or a "compensating" valve on the side of the instrument, used by the index finger of the "non-valve" hand.
So, the big differences between a true baritone horn and a euphonium are:

Baritone horn virtually always has three valves, in standard configuration; modern euphoniums almost always have four, the extra being more or less the same total length as the first and third combined
Baritone horn has a narrower bore than the euphonium for most of its length, with the conical expansion becoming most prevalent only at the bell
Baritone horn is typically more compactly coiled, with valves exposed over the top of the downtube leading to the bell, while euphoniums typically have their valves placed underneath the topmost section of the main pipe
Baritone horn has a more focused, edgy tone than the mellower euphonium
Baritone horn is lighter; for this reason it's more often given to beginning students to learn on, before "graduating" to the euphonium's greater weight and extra valve
Baritone horns typically cost less due to less material and surface area to be worked during construction (this is a rather broad statement and there is considerable overlap; you can find many examples of euphoniums costing less than baritones if you look, but these are generally not "apples to apples" comparisons in terms of features and build quality)
Baritone horns cannot play their fundamental frequency, which for a Bb instrument is the Bb two leger lines and a space below the bass staff; this is a side effect of the narrower cross section. Euphoniums can play this note without valves; tubas have the same written fundamental note, but like the double bass they sound an octave lower than traditionally scored

The similarities:

Core range is virtually identical, other than the loss of the fundamental partial on the baritone; they can be used interchangeably for most military band arrangements.
Both can be scored on bass or treble clef (historically the "tenor clef" was also used; this clef is still seen from time to time for trombone but is seldom used for horns).
Basic technique, embouchure, breath supply needed, etc are all more or less identical. Again, this makes the baritone horn a good first step for low brass students
Comment: Ah, the answer I've been longing for! Excellent! Can you perhaps refer to sources for further reading?
Answer: Baritone

Smaller Bore
Cylindrical

Tubing size stays same until it reaches the bell

3 valves
Usually only found in brass bands
Cutting and "solo" sound

Euphonium

Common to find bass clef parts
Conical

Tubing progressively gets wider as it approaches the bell

4 valves
Deeper cut mouthpiece
Darker sound
Traditional concert instrument

Similarities

Both may read Treble or Bass Clef
Comment: Some of your differences seem not quite right, so both instruments belong to the saxhorn family and have a conical-bore, also the number of valves allows no reliable distinction. I'll try an update after some research.
Comment: Also, a baritone is conical, like other Sax horns, not cylindrical. You can clearly see this in your photo!
Answer: Cody's summary of the differences between what you will generally find in an instrument called a "Euphonium" vs. one called a "baritone" is mostly spot on for today, but traditionally there really wasn't a difference between the two and it is a recent phenomenon where the high-end instruments are called euphoniums while cheaper student instruments are called baritones. There were 3-valve euphoniums for a long time, though now 4 vs. 3 valves is the most common differentiation among the two. The baritone horn also exists in a front-facing, compact "marching baritone" style which looks quite different but plays similarly. British band composers tended to label their parts "euphonium" since around the turn of the century, while American composers seem to more often have gone with "baritone" often as "baritone (T.C.)" or "baritone (B.C.)" to accommodate performers who were used to reading in either treble or bass clef. Holst's Euphonium part in the First Suite is written in bass clef in the score; but he provides parts in both treble and bass clefs.  Notably while the score says "Euphonium" the parts say "Euphonium (Baritone)." When written in treble clef, both the baritone and euphonium play as transposing B-flat instruments (sounding down a Major-9th, like a bass clarinet or tenor saxophone). In bass clef, they sound as written.
EDIT: Here's an ad from from Boosey & Hawkes which used to make instruments including euphoniums (and sexist ads, apparently) showing a three-valve instrument called a euphonium.
Comment: The pic above shows a B&H compensating 4-valve euphonium (3+1 configuration). The lady's left hand is covering the side 4th valve, so you can only see 3 valves. The 4th valve circuit doubles as the thumb rest for her right hand. It's a strange design, in that, the main tuning slide touches her left elbow (rather than being in the middle); so then, what looks like main slide is actually the slide for the 4th valve. Maybe B&H just wanted to trick us or maybe wanted 3-valve musicians to feel as equals with the 4-valve instruments; the world may never know  their intentions lol.
Comment: Thank you @russian_spy -- did not see that.  Will probably remove the photo then from the edit, since it doesn't justify keeping a sexist photo if it doesn't illustrate the main point of the argument.
Answer: There's some good information above, as well as some confusing details, in this perennial discussion, but many errors still persist.
For example, at the end of one quote above --
Baritone horns cannot play their fundamental frequency *[-- Actually, they can! -- see below * ] which for a Bb instrument is the Bb two leger lines and a space below the bass staff; this is a side effect of the narrower cross section. [If they CAN play the fundamental, then the supposed side effect is a moot point.]   Euphoniums can play this note without valves; tubas have the same written fundamental note [NO! a BBb tuba sounds BBb, contra Bb as a fundamental note for its "open" 18-foot tube length], but like the double bass they sound an octave lower than traditionally scored  [NO, they sound at actual pitch and are written one octave below the baritone/euphonium.  Treble clef is a different story -- octave-above-the-fundamental middle c, for a Bb cornet sounds Bb 1 step below; for a baritone/euph it sounds a major 9th lower, and for a BBb tuba, it sounds 2 octaves and one step lower. ]*
*Of course the baritone can play the fundamental!  It may depend on the player, however.  The bore size and shape have nothing to do with that!  I can play that same fundamental on a baroque trumpet crooked to Bb (9-foot sounding length), and, comparatively, it's bore is much smaller, and so is the mouthpiece.  Mouthpiece cup shape and size, and bore shape and size, might make it easier or more difficult, but it doesn't preclude the fundamental being played.  In fact, you can get the fundamental on any lip-vibrated aerophone merely by tapping the mouthpiece with the palm of your hand!
Also -- let's add the "North American" terminology into the discussion -- What about the tenor horn?  Even narrower bore than the baritone.  And many old band parts just say "baritone" meaning whatever plays in that range.  Often the distinction was more what clef it played -- treble clef = baritone, bass clef = euphonium.
Another misconception - Tubas are also saxhorns, and all saxhorns are flugelhorns (meaning more or less conical in bore shape).  Here are more terms to define  (or maybe NOT!    :-)   ) -- Bass tuba; Contra bass tuba (in my book the same thing); Bb Bass (in mid-19th century, a wide bore "euphonium" often over-the-shoulder); Bb Baritone (in mid-19th century, a medium-wide bore "baritone" often over-the-shoulder); Bb Tenor (in mid-19th century, a more narrow bore "baritone" or tenor horn, often over-the-shoulder); "Bb Tenor" could also imply a treble clef valved (or not) trombone! a term often used in British brass band arrangements; Bb alto is sometimes a name given to the Bb cornet, and/or Flugelhorn.
I have many instruments in my collection in the 9-foot and 18-foot range (and in between) that would defy being pigeonholed into anyone's preset terminology.  I have a right-shouldered (but still right handed for valves) helicon, a baritone Centennial horn (which might be classed as a valved bass trombone), and German Band instruments in oval shape with small and large bores.  The original name for a double belled euphonium was the doublophone and it was classed as a euphonium and valve trombone in one instrument.   I played it today at our Tuba Christmas concert and got brighter sounds from the small bell, and darker sounds from the big bell.  It is a York, and it would probably be termed a baritone by the pigeonholers.  I also have Bueschers and Conns with 4 and 5 valves, with otherwise identical bore shapes and diameters, and additional DB euphs by other makers.
So let's just make music on the things, and stop arguing about terminology (but let's get the acoustic facts correct).
Just my two cents, from a guy with 6000 instruments, who plays in vintage brass bands, and leads the Plumbing Factory Brass Band in London Canada.
Answer: To put a slightly finer point on the family relationships:
1) Tuba-EUPHONIUM- Flugelhorn
2) BARITONE HORN-Tenor horn- Alto horn- Cornet
Trumpets and Trombones are in a family of their own
Answer: Baritones in a typical British heritage brass band (as here in Australia) are Cylindrical bore in the same manner that trumpets (as opposed to cornets) and trombones are, while Euphoniums are conical bore.
Baritones are also generally smaller than Euphoniums allowing them to have a high range for the average player.
Having said all of that, I'm a firm believer that Euphoniums produce a much nicer sound in the ensemble on the baritone parts if the player is up to it.
In a concert band the Euphonium is universally called a Baritone due to its register only.
Answer: The 'euphoniums' were ment as 'high bass-horns' comparable with the 'cello' group in the Symphony orchestra's, in French: 'Tuba Basses' The 'Baritone's' are mere a form 'inbetween' the wide-mensured 'saxhorns' used in Brass/Reed bands.
In Italian Opera orchestra's, Giuseppe Verdi and his contemporary's/ancesters like Rossini Donizetti & Bellini, preferred though NARROW-mensured trombone-like instruments, valve- operated. This has to do with the sound-formants around 150-300 Hz. The 'broad-warm' couloring of tone is well accepted in windbands, but now-way in the Symphony- opera orchestra's in the 'pit' underneath forwards the podium. This is also the reason, why Giuseppe Verdi together with Atelier Giuseppe Peletti (Milan)ultimately developed a so called 'trombone basso "Verdi"
This is a BBb Contrabass-valve trombone -very- narrow mensured long Cylindric chort conic, likewise each Trombone.
All these 'bass-horns' were developed out from the bass-valve horns like
'Serpents d'L'Eglise, and 'Ophicleide's sur-named 'C'im-basso (Corno in Basso) wereupon the name 'Cimbasso' is derivated nowadays.
Though, Bariton-horns enlarged from Bb to FF together with 'fourth' valve are together with the slid-/-valve trombone's a perfect substitute in stead of the 'Cimbasso', nowadays build as a Contrabass- valvetrombone with the bell forward pointed.
(source: The tuba family Clifford Beavan, Renato Meucci The Peletti instruments)
Harlingen,       Friesland NL
Answer: The differences between a Baritone and a Euphonium is that a baritone is the same size tubing until the very end, then it gets wider. A euphonium gradually gets bigger throughout the horn. If an instrument has four valves, it is usually a euphonium.
Answer: Dr. Hank got it right. Comparing a baritone horn and a euphonium is similar to comparing a trumpet and cornet, the trumpet being relatively cylindrical, a fad the cornet conical. Both baritones and euphoniums may have 3, 4, or 5 valves. I once had a Conn 5 valve, double bell instrument, from the early 1900's, which was a baritone horn, smaller bore, smaller bell, shorter in height, and relatively more cylindrical, than Conn's double bell euphoniums of the same period. The difference in appearance is obvious and the Conn case for the baritone was about an inch shorter, and too small for a euphonium. All of the American made euphoniums that I have seen or played have an 11 or 11 and 1/2 inch bell, the only exception being the Martin, bell front model, and one only Conn 3 front action valves, upright bell, which must have been custom made at Conn, because the other horns with the same model number had 11inch bells. Also, the serial number of this particular euphonium put it in a period where the engraving would have been close to the time of transition between the script lettering Conn and the lady face Conn, but the engraving was the later 1950's and 1960's engraving. In summary the baritone is relatively more cylindrical than a euphonium, or the euphonium is relatively more conical than the baritone.
Answer: I don't think conicality is really the determining criterion. All of my Baritones are very conical, and my 3-valve (1963 Olds Studio)  passes the aforementioned "Euphonium" test on the tuning slide (my 2-valves both have the tuning slide on the lead-pipe side of the valves, so the test cannot be applied). I remember the distinction on for the 1979 2-valve King Baritone G-Bugle vs the Euphonium model was bore size and more notably weight. I was a skinny kid back in the day — I could blow enough air to make the Euphonium sound good if I was standing still, whereas with the Baritone I could still put out great sound on the march.


Essential maintenance for my bike whilst on a long distance tour

Question: I am thinking about what I need to do for maintenance whilst on a long distance tour I am planning. can anyone help me out with this?
Answer: This will depend on what kind of conditions you're riding in, what condition your bike is in, etc, but I think these are the basics:

Air up tires daily.
Lube chain. How often will depend on what kind of lube you use, which is one of those religious debates I prefer to avoid.
Check headset for looseness. This actually was an issue for me. Also check bearing cones (if you have loose bearings) on your hubs.
Check wheels for trueness, spokes for tension.
When you get a flat, make sure to remove the offending pointy thing from your tire. This can be harder than it sounds.
Check frequently (every time you stop) for slow leaks. I destroyed a tire prematurely because of a slow leak.
Check tightness of rack fixtures daily.

Naturally other things can go wrong, but I think these are the main things that you can rely on going wrong or needing attention.
And don't forget maintenance on your body. Be prepared for sunburn, saddle sores, hotspots on your feet, muscle aches, etc.
Comment: Check all QR's at the start of every day. Pick the (unloaded) bike up and drop it from about 10-20cm, listening to what it sounds like. Surprising how many gremlins you can hear with this simple test.....
Answer: Mainly air the tires daily and fix flats.  You should also give the bike a once-over about once a day checking for loose bolts & fittings, etc.  In particular, check for loose cranks, as a loose crank can muck things up really quickly.  Check the pressure in your tires (squeeze them with your hand) every few hours.
You should have the bike serviced before you start, so that the headset and wheel bearings are properly adjusted -- they should not need adjustment on the ride, though it doesn't hurt to check them from time to time for looseness.
The chain might need cleaning, depending on conditions and how far you ride.  Generally for a 1-week, 500 mile ride the chain should be fine.  Longer distances or exceptionally dusty/muddy conditions may require cleaning, and the chain should generally be replaced after about 2000 miles.
If there is a mechanic supporting the ride you don't need much in the way of tools.  Otherwise, you should have some basic tools and spare spokes and repair links for the chain (plus tools to deal with both).  And some spare bolts, etc.  I've had rack bolts go walkabout, eg.  Some tape (electrical, medical "adhesive", or, my favorite, hockey tape) is good to have, along with some "zip ties", for making emergency repairs.  (I recall one rider who did about 20 miles with a tire repaired with adhesive tape.)
Comment: Good tips. I recommend checking chain wear with a gauge, not by distance ridden, since there might be extreme variations in the distance a chain can cover during its lifespan, depending on weather and road/trail conditions.
Comment: Yeah, a gauge should be used, but it would be unusual for a chain to need replacing in less than 1500 miles or for one to last more than 3000 miles.  And, on a 1-2 week bike trip, if you start off with a fairly new chain, it's highly unlikely that it would need replacing before the end.
Comment: @heltonbiker - To most cyclists "touring" means 50-100 miles a day with loaded panniers, camping overnight. It may rain, of course, and sometimes the roads were less than ideal, but rarely was it off-road.  (Though in recent years it's gotten to more often be "supported" touring with a truck/van to haul one's gear.)
Comment: When people talk about "touring", I always imagine (being a former enthusiast of off-road adventures) something similar to the images shown when you google-image "muddy bike"... :o) When I was into that, 500 miles (of course not every of them in these condidions) were enough to finish a chain. Actually, one single mud puddle can "ruin" the whole day, regarding chain wear, not to mention wet weather.
Comment: Weird, my hybrid chain lasted some 13 years and 6000 miles. I can't say I was careful with it. If it looked mucky I wiped it with a cloth, sometimes I put wet lube (Finish line) on.
Comment: @JamesBradbury most drivetrains would last 6000 miles, the problem is: the whole drivetrain would probably need to be replaced then. In order to replace just the chain (and spare the money and trouble of replacing cassette and chainrings), the chain has to be replaced relatively often.
Answer: If you're talking about regular maintenance (instead of fixing stuff), then I'd say the most important thing to do is to clean the chain, and lube it after cleaning. The chain is by far the part of the bike with fastest turnover, and the right maintenance can more than double the lifespan of the chain and, most important, of the whole drivetrain. This is specially important if you ride off-road, but also if you ride wet weather where road grime is thrown on the drivetrain by the wheels.
Second to that, it is important to have your bike prepared PRIOR to the trip, and that means mostly wheels: properly installed tubes and tires, with protective strip inside the rim, well tensioned spokes, and hubs. Hubs should be preferrably waterproof (rubber washings), with clean grease and right adjustment (not too tight, and with no significant lateral play).
Attachment of luggage/racks can become a great problem if you don't ride the smoothest of pavements, and it might be a good idea to carry some bungee-cords to make eventually shaky panniers more firm (wrapping them around the bike), and using thread-locking products (loc-tite) in the pannier bolts can spare you a lot of trouble (I have lost countless bolts due to vibration).
I'm not sure being over-cautious with air pressure does more good than harm. Messing too much with pumping and inflation can stress the valve system, and usually even not-ideal tubes can be ridden fine being inflated only once a week. Usually, you can just lift and drop the bike over its tires, from one inch or two high, and the bounciness will give you a hint if the tire pressure "feels right". Sitting over it and bouncing yourself on the saddle and on the bars will make an underinflated tire immediately show off, and it is a very natural and function-related way of checking tire pressure, after you get used to what "the right pressure" is supposed to be, and how it looks and feels.
Depending on weather, another issue is brake cables and conduites. If you get too much dust and/or rain and mud, the braking power can be much reduced due to inner friction in the cabling system of the brakes, with levers becoming hard to activate. While cleaning helps, replacing everything is guaranteed to give back the best braking performance.
From personal experience, I think that's it, hope this helps!
Comment: +1 for luggage racks and common-sense approach to tyres.
Answer: I'm surprised no one has mentioned brake blocks. In my experience these wear faster than tyres or chain. I get maybe 800-1000 miles from a set of brake blocks.
I've now switched to the v-brake "insert" kind, which are marginally cheaper and much quicker to replace.
Always carry replacements and keep an eye on wear. When they are nearly worn down, carry two full sets (front and back).


Retiling a fireplace

Question: I want to re-tile our fireplace. It is an old home built in 1935. I am able to find lots of information online on how to tile a brick fireplace but nothing on re-tiling. I assume I just take a hammer and break away the tile that is there and try and get back to the (I'm assuming) original brick. Are there any additional things i need to be concerned with? Are there an online guides available?
Answer: You need to be very careful when removing the tile, as you don't want to break the substrate.  Taking a large hammer to the tiles is a great way to break the brick that is behind the existing tile.
My recommendation would be to get a tile chisel, and use that to break/pry up the existing tiles.  You'll likely be left with a very uneven surface.  Using the chisel, take off as many of the high points as possible.  However, even with lots of attention, you'll likely still have a pretty rough/uneven surface.  To take care of this, use some leveling mortar- apply the mortar in a thin layer, making sure to leave as smooth a surface as you can get with the trowel.  The point being to raise the surface to be flush with the highest points left after you chisel out the tiles.  Let it cure.  After it is dry, use some medium grit sandpaper to make the surface smooth.
Now you have a nice, flat, smooth surface to tile over.  Use a good wall tile adhesive, and tile away.
Answer: In addition to MarkD's answer, also remember that if fireplace will be used for a fire (as opposed to purely decorative or an electric insert), you must get a tile designed for a fireplace. Wall or floor tiles will just crack or bust the first time they are exposed to a fire.

Retiling a fireplace


How do I locate and defend against cloaked Geth Hunters?

Question: Geth Hunters make heavy use of cloaks and are almost impossible to detect, unless you observe keenly or shoot at them. Are there any ways to highlight them and find out where they are?
Answer: All cloaked enemies "shimmer" slightly, which can help you find them if you know approximately where they're moving.
If you just don't have a clue, open up with an automatic weapon and walk your fire across the general area.  Area of effect attacks are pretty good at exposing them as well.  Weapons like grenades or mines, or powers like Singularity can help.
In general, once you've done damage, their cloak will fail temporarily, giving you an opportunity to target them and do serious damage.
Another tactic which kind of works "by default" is to just wait for them to flank you - if you know they're coming, stay in cover and wait for them, and then target them with short range, high power attacks when they decloak and start to attack.  It's risky, but if you're low on ammo/grenades and can't employ these other strategies, you might not have many other options.
Answer: Equiping the Javelin sniper rifle  can help, as it highlights cloaked enemies in a purple outline (similar to how the Sniper Rifle Enhanced Scope upgrade allows you to see enemies through smoke).
Additionally, since Hunters will temporarily decloak after taking damage, spamming powers with a wide impact radius or homing capabilities (i.e. Incinerate) might also prove to be an effective way to weed them out before they're on top of you.
That said, I found that they usually weren't too hard to detect if you look down range through a scope since you can typically see their distortions as they move across your field of view. After that, it just takes at most a few shots to expose them, and then some directed fire to lay them down.
Answer: Shimmers are the best method of detecting Hunters. If one decloaks, it's in shotgun range so move. If they decloak it will take time for their cloak to reactivate. AoE powers are useful if they're in close proximity. If a cloaked hunter takes a hit, it will provide a target lock for homing powers such as biotics, tech, and impact (carnage, and concussion shot) powers. The window for this is small so make sure you hit it the second you can see the health bar.
Also if a Geth Hunter doesn't have shields, IT CAN'T CLOAK. So if you see a Hunter without shields, DO NOT let it regenerate those shields even by 1% or it will be able to cloak again.


Question about n-forms and $d^2 = 0$

Question: In my late question the answer was great, but I didn't understand what is the 0-form, 1-form and 2-form. Are this can be genralized for any natural $n$?

they are both special cases of the fact that $d^2=0$

What this formula mean?
Answer: Linear $n$-form is a function $L$ which maps $n$ vectors from $\mathbb{R}^m$ to a scalar $L(v_1,v_2,\dots,v_n) = a \in \mathbb R$ and has the linearity property: $$L(\alpha v_1 + \beta u_1, v_2, \dots, v_n) = \alpha L(v_1, v_2, \dots, v_n) + \beta L(u_1, v_2, \dots, v_n),$$
and so on for each $n$.
An alternating $n$-form is a linear form $L(v_1,\dots,v_n)$ such that if two vector arguments are equal, then $L=0$. For example, an alternating $2$-form is a linear form $L(v_1,v_2)$ such that $L(v,v)=0$ for every $v \in \mathbb{R}^3$.
If $v_1=(x_1,y_1,z_1)$ and $v_2 = (x_2,y_2,z_2)$ we use following denotations for some basic $n$-forms: $dx(v_1) = x_1$ is a $1$-form; $dx \wedge dy(v_1,v_2) = x_1 y_2 - x_2 y_1$ is an alternating $2$-form. Similarly we have $1$-forms $dy,dz$ and $2$-forms $dy \wedge dz, dz \wedge dx$.
If $\alpha$ and $\beta$ are $1$-forms, we define their wedge product $$(\alpha \wedge \beta) (v_1,v_2) = \alpha(v_1) \beta(v_2) - \alpha(v_2) \beta(v_1),$$
which is an alternating $2$-form. It's easily seen that $\alpha \wedge \beta = - \beta \wedge \alpha$ and $\alpha \wedge \alpha = 0$. The wedge product can be generalized to arbitrary forms: if $\alpha$ is an $m$-form and $\beta$ is an $n$-form, then $\alpha \wedge \beta$ is an alternating $(m+n)$-form. The generalization is a bit technical, and for now it's sufficient for you to know that the wedge product $\wedge$ is associative and anti-commutative.
A differential $n$-form (the type of form you are interested in) is made when you associate an alternating $n$-form to every point $(x,y,z) \in \mathbb{R}^3$ in a smooth way. For example, if $f,g$ and $h$ are smooth functions, then
$$ \omega_1 = f(x,y,z) dx + g(x,y,z) dy + h(x,y,z) dz $$
is a differential $1$-form,
$$ \omega_2 = f(x,y,z) dx \wedge dy + g(x,y,z) dy \wedge dz + h(x,y,z) dz \wedge dx $$
is a differential $2$-form and
$$ \omega_3 = f(x,y,z) dx \wedge dy \wedge dz$$
is a differential $3$-form. A differential $0$-form is defined to be a scalar field on $\mathbb{R}^3$. When working on $\mathbb{R}^3$ we are only interested in $0,1,2$ and $3$ forms, since for $n \geq 4$ every $n$-form is equal to $0$.
The exterior derivative of a form takes an $n$-form to an $(n+1)$-form. If $f$ is a $0$-form (that is a scalar field) then the exterior derivative is the same thing as the total differential:
$$ df = f_x dx + f_y dy + f_z dz $$
where $f_{x_i}$ denotes the partial derivative. If $\omega = f dx$ is a $1$-form, then
$$d \omega = d f \wedge dx = (f_x d x + f_y d y + f_z dz) \wedge dx = - f_y dx \wedge d y + f_z dz \wedge dx$$
(bear in mind that $d x \wedge dx = 0$). And for $\omega = f dx \wedge dy$ a two form:
$$d \omega = d f \wedge dx \wedge dy = f_z dz \wedge dx \wedge d y = f_z dx \wedge dy \wedge dz.$$
Now you can check for yourself that for every form $\omega$, $d^2 \omega = d(d \omega) = 0$.
Differential forms can be generalized to every $n$-dimensional differentiable manifold. We can develop integration theory for differential forms which leads us to a generalized Stokes' theorem and de Rham's theorem.
In $\mathbb{R}^3$ is a natural correspondence between vector fields and $1$-forms (or $2$-forms). To every vector field $V(x,y,z) = (V_1, V_2, V_3)$ we can associate a $1$-form
$$\omega_{1,V} = V_1 dx + V_2 d_y + V_3 dz$$
and a $2$-form
$$\omega_{2,V} = V_1 dy \wedge dz + V_2 dz \wedge dx + V_3 dx \wedge dy.$$
If $U = \mathrm{curl}\, V$, then $\omega_{2,U} = d \omega_{1,V}$. If $f = \mathrm{div}\, V$ then $d \omega_{2,V} = f dx \wedge dy \wedge dz$.
Hope this helps.
Answer: $d^2 = 0$ is a restatement of the equality of mixed partial derivatives.
Differential forms may be more easily understood in terms of a geometric approach.  In an N-dimensional real vector space, one typically only deals with vectors and scalars.  Scalars form their own 0-dimensional "vector" space, as all elements are just multiples of each other.  Vectors describe various directions, or lines through the origin that are oriented--pointing one way or another.
But there is more to the world than just scalars and vectors.  How would you describe, for example, a plane through the origin?  There is an equation for a plane, yes, but in terms of vectors?  In 3D, each plane has a unique normal vector, but for $N$ dimensions, that is no longer the case.
The solution to this problem is the wedge product, which is anticommutative (like the cross product), but the wedge product of two vectors is not another vector.  Rather, it is called a bivector.
Let me be concrete and talk about a 3D vector space.  Let there be three basis vectors, $e_x, e_y, e_z$, corresponding to the $xyz$ axes, respectively.
In this space, one has scalars, which form their own 0-dimensional vector space.
One also has vectors, which are linear combinations of the three basis vectors. A direction could be given as $x e_x + y e_y + z e_z$, for instance.
One has bivectors, which are oriented planes in the space.  The basis planes are $e_x \wedge e_y, e_x \wedge e_z, e_y \wedge e_z$--3 in total.  Note that $e_i \wedge e_i = 0$ for any of the three dimensions.  It's interesting that there are only 3 basis planes in 3D.  This illustrates how each plane has a unique normal vector, but again, in other dimensions such a relationship doesn't hold.  This relationship between bivectors and vectors in 3d is called duality.
Finally, there is a single trivector, also called the pseudoscalar because it forms a one-dimensional vector space like the scalars but is negated on reflections.  The basis pseudoscalar is $e_x \wedge e_y \wedge e_z$.  The pseudosclar corresponds to an oriented volume.
In 3D, this can seem like a lot of extra bookkeeping--instead of just scalar and vector fields, we have bivector and trivector (pseudoscalar) fields, but the ease with which this approach generalizes to any number of dimensions makes it useful, and the additional complexity isn't too bad.
Now that we've established the framework of multivectors, we can talk about $\nabla$.  It takes on a similar role to what you're used to in ordinary vector calculus.  $\nabla = e^x \partial_x + e^y \partial_y + e^z \partial_z$.  We can form two derivative operators on a vector field $A$ with this symbol--$\nabla \cdot A$ uses the familiar dot product and produces a scalar field.  $\nabla \wedge A$ uses the new wedge product and produces a bivector field, but it is very similar to the curl.  Both of these operators have a unique property:
$$\nabla \cdot \nabla \cdot A = \nabla \wedge \nabla \wedge A = 0$$
Differential forms parlance could call $\nabla \cdot A \equiv \delta A$ and $\nabla \wedge A\equiv dA$, but it's all really saying the same thing.
What does this mean?  Well, $\nabla \cdot \nabla \cdot A = 0$ is trivial.  Once you have $\nabla \cdot A$, a scalar field, you can't dot product it with anything anymore.  $\nabla \wedge \nabla \wedge A$, however, is interesting.  Let's expand that in terms of components.  Let $A = A_x e^x + A_y e^y + A_z e^z$, and we get
$$\nabla \wedge \nabla \wedge A = (e^x \wedge e^y \wedge e^z) \left[(\partial_x \partial_y - \partial_y \partial_x) A_z + (\partial_z \partial_x -\partial_x \partial_z) A_y + (\partial_y \partial_z - \partial_z \partial_y) A_x \right]$$
There are a lot of mixed partial derivatives here, and what do we know about mixed partials?  They're equal!  So all these terms cancel each other out, and you get 0.  $d^2 = 0$ is a restatement of the equality of mixed partial derivatives.

Question about n-forms and $d^2 = 0$


Can extract brewing achieve professional results?

Question: I was recently on vacation and I toured a brewpub in the Chicago area.  I was surprised to find out that they are extract brewers.  Is this common practice for small brewpubs?  Would this place a limit on caliber of beer you could produce?
Answer: I don't think its common practice, but there are several extract breweries out there.
The most important factor influencing beer quality at the homebrew and the professional level is fermentation control.  That includes temperatures, ptiching rate and yeast health and management.
These things would be the same for an extract brewery or an all grain brewery.  I am certain then that if those aspects are being mastered there is not limit to the quality of the beer they can produce.
The only limitations with extracts is recipes that require the addition of mashed adjuncts or of ingredients (oats or other flaked cereals come to mind).  Extract brewing limits the amount of control you have over the wort's mash profile.  You can always thin an extract a bit with sugars or careful control of pure amylase enzyme additions.  However, the opposite is a bit tougher; although I am sure you could order pure dextrins and the like to boost body if need be.
But if you amend the styles of beer you want to put out of your brew house, there is no reason to think you can't produce award winning beer with extracts at any scale of operation.
Answer: I think the number of beer competition medals won by both commercial and homebrew extract beers proves that you can certainly brew excellent beer from extract.
That being said, I think you do have to have a bit more advanced technique than an all-extract homebrewer might use. For example:

Use full volume boils (no topping off)
Do a partial mash/mini mash with specialty grains to add complexity
Find a good source for the freshest extract you can possibly find
Try techniques such as late-boil extract additions

Extract doesn't have to mean simple.
Answer: I know of one place in the entire San Francisco Bay Area, the Pacific Coast Brewing Co, that brews extract beers.  The brewhouse is tiny.  They've been doing it that way for 20 years.  Many of their beers were decorated with bronze & silver medals from GABF in the mid-90s.  While uncommon, you can make good beer.
I visited Oakland in 2008 to judge the Sam Adams Longshot competition right across the street from Pacific Coast.  I was not impressed with their beers and most of the other judges poo-pooed them for brewing extract.  People who know beer may turn up their noses when they find out your brewpub "cheats".
Comment: Ahh... when beer geeks become beer snobs.


Most important musical concepts for writing songs on acoustic guitar

Question: I want to be able to write catchy/"cool sounding" guitar parts for songs. I am currently studying music theory extensively. I am just wondering, are there any guitar-specific musical concepts that I should look into to be able to write good songs, or is it mostly just feeling? I've been told that formulating a song with an emphasis on sound musical theory can make it sound sort of "manufactured". Any answers would be greatly appreciated.
Comment: I think the circle of fifths is something you would find helpful, check this answer out http://music.stackexchange.com/questions/1809/any-advice-for-a-novice-composer/1811#1811
Answer: As a guitarist, I love both my electrics and my acoustics. I find they have different, but overlapping, sonic spaces.
The main difference I would note between acoustic and electric, besides the obvious differences in tone, is that the acoustic is much more of a percussion instrument. Yes it has strings and a neck, but it produces its sound through this big wooden box, which will amplify anything else you do to or around it. So, rythmic tapping or slapping on the box, even as part of strumming, makes the acoustic a much more rhythmically expressive solo instrument than an electric, which although the vibrations and tonal characteristics of the entire instrument are important, is much more focused on the sound produced by the pickup transducers responding the the strings' vibration.
For evidence, take a look at what Michael Hedges, Kaki King, and Erik Mongrain do to their instruments when playing a song. Slap it, tap it, drum your fingers across it, it reacts to these inputs almost as much as to the strings. Even when just strumming, the rhythmic quality of pick hitting string and arm brushing past is reflected in the sound of an acoustic to a far greater degree than an electric.
One other thing is that your average acoustic guitar has strings of a heavier gauge than an electric. This is because the changing tension of the string as it vibrates is important to an acoustic; you can think of the top of an acoustic as a speaker cone which is being "driven" by the strings. A light-gauge string will not properly "drive" the top. However, heavier strings mean more pressure necessary to make the notes speak clearly, which generally means slower digitation; it takes better technique to be fast on an acoustic. Most acoustic players, compared to electric players, don't bother; they use more chords and create movement through rhythm and through simpler manipulations of the strings, which makes songs a bit more repetitive but also much richer tonally.
Lastly, I've also found acoustics to be much more forgiving of dissonance than electrics; the overall effect of close or uncommon intervals is more pleasing. Make no mistake, you have to tune it, but chords involving major and even minor seconds, tritones, etc sound more organic as all the various overtones of the strings' vibrational interactions are reproduced more fully than with an electric. So, "jazz chords" and other non-traditional voicings may find a better place on acoustic than electric.
Answer: Why not choose both? Knowledge AND feeling.  I'd expect increased knowledge of music theory to give you more ideas to try, expanding the range of possibilities available to you.  Use your feeling for the music to help you choose between them.
For creating 'catchy' parts on guitar look into:
The DESH (a major chord with a descending bass line) which The Beatles used to catchy effect. http://www.washedashore.com/music/desh.html
Counterpoint (melody parts moving independently) http://en.wikipedia.org/wiki/Counterpoint
I'd also suggest you study a bit of harmony and figure out all the different types of chords there are for you to use, otherwise you could be missing out on some emotive options.  Then figure out all the different ways they can be voiced on the guitar (with and without open strings).  It might take a while but I can guarantee you'll discover some 'cool sounding' options along the way.
And when you've learnt lots of theory don't forget that rules are made to be broken!
Answer: The central concept for guitar accompaniment is the "riff". This is the "atom" from which you build up cadences like molecules. The cadences will often correspond one-to-one with verses or phraes of the song.
The riffs themselves are little "nuggets" of rhythm and harmony that provide the backbone of the song (by defining the framework of the musical space). By analyzing your favorite riffs from your favorite songs, you can discover what "makes them tick" and then build completely different riffs using the newly discovered principles. Many of the best songs came about from failed attempts to learn other people's songs because this analysis/construct-new-riff phenomenon can often happen by itself, in the fingers, without conscious control! Being human is spooky.


multiple person aproval workflow - how can I tell if everyone approved

Question: I have a need for a workflow where multiple people will need to approve something.  They are all on the same level and should get the same task at the same time.  When each person has accepted, I want something to happen.  How can I do this?
Answer: After the tasks have been assigned, you will want to do the "each person" tasks in parallel actions (as opposed to serial).  My assumption is that you are using SharePoint Designer 2010.  See if this page helps: http://office.microsoft.com/en-us/sharepoint-designer-help/understand-approval-workflows-in-sharepoint-2010-HA101857172.aspx


Illustrating an encrypted image

Question: How would you illustrate that an image is encrypted? I want to show the original image and then the "encrypted" one. I want people to see that it's based on the original photo but I don't want it to look like the encryption is too insecure. This is a bit tricky, since it always is insecure if you can recognize that it is based on the original image but using "real" encryption would make the illustration less effective.
Comment: What type of encryption? You could do a color encryption... where certain parts only show up under a red or green filter.
Answer: If you're trying to communicate the message that the encrypted image is unrecognisable as the original image, with a 'before' and 'after' pair, then at least part of the 'after' image has to be unrecognisable as the original.
Assuming it has to be both unrecognizable, and immediately recognisable, that sounds impossible... but one way to do it would be showing the transition from one state to the other.
Here's a really crude example. You'll know best how to make the general principle fit what you're trying to do.

(source for mammoth)
Another option would be have one complete state at one end, one at the other, and one or more intermediary states between them, so it's clear that that state 1 becomes state 2, without compromising state 1 or state 2.
Or maybe 3 images: original [arrow->] 100% encrypted [arrow->] original, and so it's the flow of the diagram that says that the encrypted image is still the original.
Answer: I think the only answer, given your constraints, is to obscure the image as far as can be without making it totally unrecognisable.
I would suggest applying a colour noise filter over the top and then reducing its opacity until the image can just be discerned.

Illustrating an encrypted image