How do you configure a mail enabled Exchange 2007 public folder so the Reply button is a normal mail reply and not a 'Post' reply?

Question: Right now, using Outlook 2007, the users have to open the item before 'Reply' acts as an email reply.  If they simply click the email and read it in the reading pain, the reply button in the Outlook toolbar shows 'Post Reply'. This simply posts a message back to the public folder.
Answer: Outlook 2007 maintains the Reply\Reply to All\Forward commands even in public folders, but adds the Post Reply to the left of Reply.  You can simply customize the standard toolbar when in a public folder and remove the Post Reply button.
Comment: Wow.  So many of my users missed this fact that I completely overlooked it as well.  I guess the real question should be 'How do you globally remove the 'Post Reply' button from public folders in Outlook.
Answer: I usually just do Alt+R, that gives me Reply. Alt+L is Reply All and Alt+W Forwards it. I rarely use the buttons. Not the best solution but it works like this all over Outlook.


Is there online corpus for the Chinese language?

Question: Is there online corpus for the Chinese language? What I mean is something like the Brown Corpus for American English.
Comment: Please clarify what kinds of queries you need to run. For instance, why wouldn't google meet your purposes (you can limit to Chinese results only)?
Comment: The primary disadvantage of the Google approach is that they don't have a search API and actively detect and block scraping. It would be suitable for any human needs, but probably not for what drobnbobn is after.
Answer: For a big-data Chinese corpus, have a look at this one:

(Taiwan) Academia Sinica Balanced Corpus of Modern Chinese 台灣 中央研究院 中文詞知識庫小組 現代漢語平衡語料庫

A million-word level corpus
Contact: Miss Su-Chu Lin (林素朱), firstname.lastname@example.com
Introduction in Chinese
Not sure if you can download it for free
Answer: I haven't found a large corpus, but I have used the results of some projects that analysed all Usenet newsgroups from 1993-1994. You could probably contact Shih-Kun Huang for information about the original corpus.
The files I used were a list of character frequencies and a list of word frequencies.
It's probably smaller than you want, and it only contains individual sentences, but you might find the translations at tatoeba.org interesting. You can download the raw data.
I don't know if they can be downloaded, but there are lots of example sentences on jukuu.com.
Answer: You can download all of the Chinese language Wikipedia. (you would probably want: zhwiki-latest-pages-meta-current.xml.bz2)
Another source that may or may not be suitable depending on the specific project is Project Gutenberg's collection of Chinese language books. The downside of this source is that most of them will be quite old.
Comment: What character set does the xml file use, traditional or simplified? If it is a mix, that's an issue.


Generate a PGP key with DSA key size of 1024 bits and El Gamal key size of 2048 bits using Mac GPG 2.0

Question: Can somebody please tell me how to generate a PGP key with Mac GPG 2.0 that uses a DSA key for signing with a length of 1024 bits, and an El Gamal key for encryption with a length of 2048 bits ? I've tried using the tool both through the GUI and the command line, and it seems it only lets you generate keys that have symmetric lengths (ie 1024 or 2048 for both).  I need the one specified above to communicate with somebody using a similar key.
Answer: I THINK you can do this by creating the signing key with the "sign only" option and then adding an encryption subkey with the settings you want afterwards.
However I would STRONGLY advise against generating 1024 bit RSA or DSA keys unless you have absolutely no other option. The spook can probablly crack them now and they are likely to get further weakened over time both by improvements in the mathematical algorithms used to crack them and by increases in computing power.
If your correspondent really is running a version of gnupg so ancient it can't handle a 4096/4096 RSA/RSA key then you should really tell them to upgrade.


Key and possible missing "tonic chord"

Question: I just figured out in this tune the chords F major and e minor fit, and they are repeated all over. Surely its a simple and repetitive piece, but what I am wondering is, the only key where both chords fit is C major. So is this in C major? But then nowhere a C major chord is played, is this normal? I somehow have the feeling a C major should be played to establish it as a C major key, but maybe I am wrong. Could someone explain? And if it is C major, then does it happen often that music is written in some key, but the "tonic chord" is not played?
Comment: I think the melody would clear that up.  These chords could perhaps be in the same minor key (melodic or harmonic).  But like the answer states, songs do need to be in a key.  Melody is "key" here.
Comment: Maybe it's not E minor. Maybe it's C major 7 with no C and E in the bass.
Answer: The first thing to clear up is music doesn't need to be in a key.
In this case it may be better to say Em and F both fit into the key signature of 0 sharps/flats.
You could call this C major, but why not call it A minor? Both chords fit into either "key."

    Em  F
 C: iii IV
Am: v   VI

The dominant chord really defines a key. (You could alternately say the leading tone defines the key.) Nevertheless, it would be unusual to not have the tonic chord as you have pointed out.
Interestingly with this case, neither the tonic nor the leading tone for either C major or A minor are used. Any claim that it is in a key would be weak unless additional musical context defined a key.
For practical purposes of notation you would use a key signature of 0 sharps/flats for this music.

I notice that your YouTube link drops into the middle of a long Chillwave recording. I didn't try to figure out the chords from the recording. I only answered regarding the two chords you listed in your question. But, you may want to consider a larger selection of that track when considering what key it might be in. The harmonic pace in Chillwave is often slow and repetitive so a larger selection may be needed to get the complete harmonic picture.
Answer: Maybe you could say that the key is Phrygian E minor. The key signature for Phrygian E minor would be just like C major and A minor, no sharps and no flats.
The part of the track you linked to has a strong minor feeling and when the bass note change from E to F the F feels like a leading tone down to E, and it does go down from F to E again and again.
Note that in the two chords E minor and FMaj7 the tone E is "persistent" in that it is there all the time at the top of the chords while the base goes E-F-E-F-E etc and the chords follow the bas line of course, but the top is an E.
All in all it gives a strong feeling of E as a tonic, thus you can argue that the key is Phrygian E minor.
EDIT:
Just like @Michael Curtis I am only relating to that part of the track where those two chords are alternating again and again. I listened to that part but did not listen to the whole track.
Answer: I can hear either E minor or F major as the tonic chord in that music.  But it doesn't really matter.  Functional harmony isn't the game this piece is playing.
Answer: With the major chord being Fmaj7, the second one could easily be Cmaj7, with an E bass. Em and Cmaj7 are easily confused for each other. If that's the case, then it's similar to Erik Satie's Gymnopedie.
Having said all that, it's music that's painting a picture, a mood scene, and there's no compunction for it to have a particular key base, just a pallette of sounds which interact with each other; no-ones going to be whistling or humming it, although I suspect it's actually C major.

Key and possible missing "tonic chord"


Does a washer really increase static friction force?

Question: Suppose I have a bolt that goes through a hole in a plate and is under tension. If I place a washer between the bolt head and the plate, does static frictional force (torque actually) really double? I'm assuming the bolt, washer, and plate are all of the same material for simplicity.
Answer: No it doesn't, and it isn't meant for that either. A standard flat washer, that is. It's meant to give the nuts and bolts a better support, and it protects the material against the nut which may otherwise scratch it upon tightening.
A washer may even reduce the friction on the nut, since the fastened material may in many cases have a higher friction against the nut than the washer does. That's why we either use lock washers, or nylock nuts, flange serrated nuts, or other types of self securing nuts.
For your good understanding, it doesn't matter what kind or how many washers or nuts you apply, the one with the least friction determines the total friction. Like the weakest link determines the strength of a chain.
Answer: You have made a very common mistake - if you want to increase the static friction, you have to decrease the torque! So yes, a well designed fastener system that includes washers can significantly reduce the torque needed to achieve a given tension on the bolt. And it is the tension, not the torque applied to get there, that provides the friction and stiction. This is done by controlling the radius of the pressure. It is common practice to want the blind side to stick more than the side being turned. Easy to do if you think about it. Also, for torque critical applications, washers provide a more consistent torque to tension relationship.


In the 2012 movie Compliance why was the maintenance man the only one with sense?

Question: Sandra, the manager, and several employees went along with a man on the phone and put Becky through a strip search ordeal.  Why was the maintenance man, Harold, who came in later in the day, the only one who saw that what they were doing was wrong?
Answer: I am not entirely sure this is the right place to answer those questions.  The movie is apparently based on a true story, about a prank caller who it is believed made a number of similar calls to fast-food restaurants over a number of years, the most significant incident of which appears to be the source material for the movie.  Some of the people involved in this true life event ended up with criminal convictions from the actions they took that day.  The victim and at least one of the members of staff subsequently sued the restaurant chain - making claims such as adequate staff training, and that they had not warned staff about prior incidents of hoax calls.
It is simply the fact from this incident that the Maintenance Man was the first person to refuse what the caller was demanding.
Your question is why?  Its hard to be specific about the people here.  Unfortunately it boils down to the fact that even when put in a stressful situation, psychologists have demonstrated in experiments that when being ordered by someone in authority a majority of people will do as they are told - to the point of believing they have caused significant pain, even harm to another.  They key example is the Milgram Experiment from the early 1960's where subjects believed they were administering increasingly large electric shocks to someone else in an experiment about learning.
The result from this experiment and others performed shows that as many as 66% of people would follow orders to inflict what would be fatal voltages on others when ordered and/or reassured by someone in authority - even if simultaneously they are clearly stressed by the actions they are being asked to take.  Amazingly in the Miligram Experiment even when the subject loses communication with the person they believe they are shocking, apparently unconscious, many still administered the final (fake) 450 volt shock.
Comment: FYI - I've not seen the movie, but I did listen to an interview with the director earlier today.


Is it dangerous to have Tor exit node?

Question: If I buy VPS and create Tor exit node there what would happen if someone did bad thing using my exit node? (terrorism, hacking goverment sites etc) VPS provider will share information about me to FBI or another goverment organizations or just will send abuse and block my VPS because it's obviously that I'm just an operator of exit node, not terrorist?
Answer: It depends on your definition of dangerous. Since I assume you aren't going to save any logs even if you're subpoenaed you don't have anything to turn over. It's not dangerous, but it certainly might be a hassle. Exit nodes are typically run by non-profits or those entities that have the time and money to address any issues that come up. Individuals are typically better off running a guard or middle node. If you're willing to deal with the hassle, please go for the exit! They are by far the most needed.
Comment: Addendum: Boingboing has a pretty good response too: https://boingboing.net/2015/08/04/what-happened-when-the-fbi-sub.html
Answer: If you're worried about running an exit relay, and legalities involved, the following may help put your mind at rest:

The Tor blog has an entry on how to run an exit node with minimal harassment
The EFF has a page on the legalities involved in Tor, including a specific section on exit relays

If you do run an exit relay (which is a great thing to do!), and you do get a take-down request from your ISP, then the Tor wiki has some templates that you can use to create a well-worded response. (This is linked to from the Tor FAQ.)

Is it dangerous to have Tor exit node?


Should I bother teaching buffer overflows any more?

Question: The students are skeptical that turning off non-executable stacks, turning off canaries and turning off ASLR represents a realistic environment.  If PaX, DEP, W^X, etc., are effective at stopping buffer overflow exploits, is there still value in learning about them?
Comment: @mrnap I've been teaching buffer overflows and shellcode writing for 13 years.  As most people in the security arena know, this was once the #1 vulnerability (5-10 years ago) and has since been supplanted by other vulnerabilities.  I asked the question above to poll professionals on the continued value of teaching these techniques (which takes a lot of time) when other topics are becoming more relevant.  You criticize me for even asking the question: believe me, if I'm not constantly questioning the impact of what I'm teaching, then I'm not doing my job.
Comment: @mrnap, whether the clear answer is a resounding "YES" or not, it is *always* a legitimate question to ask. In fact, someone that *doesn't* constantly question the current conventional wisdom is the one that shouldnt be teaching a class on security. As we all know, questioning assumptions is one of the best tools in our toolbox, and most often leads to finding vulnerabilities.
Comment: @avid nicely said!  @mrnap, please also note the great advice in our faq: *Be nice. Treat others with the same respect you'd want them to treat you.*  :)
Comment: @mrnap We get 10 weeks to teach a security class
Comment: @Fixee  I'm going to be brutally honest here, if you really are questioning the idea of teaching buffer overflows, I really don't think you should be "teaching" a class about security.  Considering they are one of the most basic and universal security exploits, buffer overflows should be an integral part of understanding and teaching how to attack ANY system.
Comment: @Fixee I see your point, but I still think my original point that they are a fundamental aspect of exploitation stands.  Anyone up to date and reading anything on the industry or understanding security in any fundamental way understands that BOs will exist as long as bad coding exists.  I would think by the cacophony of Yes' following this would be pretty apparent.
Comment: Since when has your car's operating system used PaX? When was the last time you saw an NIC firmware which had W^X? Did you ever see a MIPS32 router with DEP? While big bloaty desktops and servers may have these protections, **not all modern devices do.**
Answer: Absolutely.  ASLR and DEP are defense-in-depth measures.  There are exploits that exist that can bypass each of them (for a real-world example, look at Peter Vreugdenhil's Pwn2Own exploit that he used against IE).
All you need to bypass ASLR for Windows is an information disclosure vulnerability that will let you know the base address of a loaded DLL in the process (that was the first vuln that Vreugdenhil exploited).  From that, you can use a ret-to-libc attack to call any function in that DLL.
The bottom line: stack (and heap) overflows are absolutely still relevant today.  They're harder to exploit than they used to be but they're still relevant.
Comment: To complement, in a few specific contexts buffer overflows can be easier to exploit because of [memory layout leaks, e.g. in kernels](http://security.stackexchange.com/questions/69054/does-kaslr-really-provide-more-security-against-exploits). Heartbleed was also caused by a buffer overflow, and this will happen again because we still write and will continue writing low-level code for hardware interfaces and OS libraries...
Answer: Besides @Larry's and @SteveS's excellent concise answers, I want to point out a very important point:

The students are skeptical that turning off non-executable stacks, turning off canaries and turning off ASLR represents a realistic environment.

Hopefully this is true for your students' systems.
In the rest of the world, however, this is still very common, unfortunately. Besides the platforms that don't support these, there are always poorly build products that require shutting these off, older versions of OS, and even just bad misconfigurations.
Still very realistic, sadly.
On top of all that, 2 more comments from an educatory pov:
1. somebody has to build those defenses, right?
2. Even if hypothetically they were right - you only need pointers in C/C++ doesnt mean a Java developer shouldnt learn how these things work, inside the computer, right?
Answer: Yes. Apart from the systems where buffer overflows lead to successful exploits, full explanations on buffer overflows are always a great way to demonstrate how you should think about security. Instead on concentrating on how the application should run, see what can be done in order to make the application derail.
Also, regardless of stack execution and how many screaming canaries you install, a buffer overflow is a bug. All those security features simply alter the consequences of the bug: instead of a remote shell, you "just" get an immediate application crash. Not caring about application crashes (in particular crashes which can be triggered remotely) is, at best, very sloppy programming. Not on my watch!
For completeness, non-executable stacks and canaries do not prevent buffer overflows; they just shut off some of the easy ways to exploit buffer overflows. The traditional buffer overflow is about replacing the return address with a pointer to malicious code which is loaded as part of the data which overflowed the buffer; the malicious code gets executed when the function returns. The non-executable stack means that the attacker will not be able to place his code on the stack (he will have to arrange for a jump into some library code, e.g. the execve() implementation in standard library). The canary prevents the return address from being used if a stack buffer was overflowed (assuming the overflow is "simple": a contiguous chunk of data). But the overflow may also overwrite some other data, including function pointers (in particular in the context of C++).
Comment: Great post, few extra points:  1. People have to learn to write less buggy code, not blindly rely on mitigations (as the author correctly indicated, the stack based buffer overflows have not been eliminated, only made harder).  2.  How are they supposed to undertand what DEP, ASLR do, if they don't understand the attacks that made these protections necessary in the first place?  3.  Looking for bugs makes them a better coder, as they trust themselves and the system less, thus pay attention to behaviors that happen not only when things work properly, but also when they go awry.
Answer: Absolutely.  It shouldn't be enough that they know these are solutions to the problem, they should know how and why they are solutions to the problem.
Besides, not all platforms support these technologies.
Answer: There are already great answers here, so I won't try to re-cover them. However, since we're talking about mechanisms that prevent buffer overflow, I'd like to emphasize something that you might like to pass on to your students:
Just because a program is written in Java does not mean there are no buffer overflows. The Java Virtual Machine itself is not implemented in Java; it is implemented in (probably) C or C++, which are just as prone to buffer overflows as any other program.
On top of that there are many implementations of the JVM. For every one you fix, there are ten more that are likely still vulnerable.
I hope I didn't just trip all over my soap box.... :-)
Answer: I'd like to answer from the point of view of a student who has recently started learning about Buffer Overflow Attacks in depth. I too had the same concerns and had doubt in the benefits of learning about buffer overflow attacks but considering how much I have learned to get to the meat of it, I am very glad that I chose to do it.
I have so far had to:

Learn x86 assembly - mainly Ubuntu based
Learn some C programming
Become a ninja with gdb
Understand shell code
Look for every IT security forum I possibly can and learn the process of making software/operating systems safer

These skills are very transferable and I have no regrets. Unfortunately, I do not have someone teaching me this. I have had to rough it out with video tutorials and example codes for my Master's project. Buffer overflow attacks may be less of an IT security concern than it was 5-10 years ago but it can definitely serve as a stepping stone to learn about more complex or contemporary threats.
Answer: No, don't teach buffer overflows.  Teach memory corruption.  Teach exploit primitives.  Yes, they need to know the history as well, but it shouldn't take up more than half of the class.  I say when it comes to actual homework, give them challenges that have all of the memory protections enabled, but maybe make the vulnerable server weaker, with some memory disclosures that give hints at various offsets.
They should also understand that many memory protections are mostly gimmicks, and often times the "random offsets" aren't really as random as you might think they are.  They should learn to recognize bugs, and use the bugs they have to poke at the things they know, so that they can get towards things that they want.
They should be thinking in terms of overwriting function pointers rather than return addresses, and be jumping into known executable code (ret2libc, ROP) rather than jumping into shellcode on the stack/heap.
Answer: Being a college student fresh out of a C++ class—yes, I know it's not the same, but my professor made sure to put extra emphasis on teaching about buffer overflows and how to prevent them, and I really encourage you to continue teaching about buffer overflows in any course you teach programming. It can't harm them to do so.


IDA - save work on kernel mode debugging

Question: I'm working with IDA pro on a kernel mode function (VMware + windbg) and I'm a annoying because I can't save the workstation state. IDA crash after 3 hours when I "quit and save memory status".
Is there a plugin or anything else that could make me able to save my work (variables rename, commentaries and  others) ?
Thanks for reading (and answers =)
Answer: Did you try debug IDA?  You may save your work via IDA snapshot feature.
Comment: I don't understand you (oh, my bad English). Did you try simple dump IDA db to IDC file?? (File->Produce file->"Dump data base to IDC file")
Comment: sorry wrong send, here is the full comment :
Hi, thanks for your answer ! I tried with the snapshot functionality but an initial database is requiered.
In order :
  - I start my virual machine
  - I attach IDA with winDBG to start kernel mode debbugging
  - I place comments and wanna save them for next session
My problem is that I only have a temporary database and I can't save it because it's only a live work session.
Any idea how to solve that ?
Comment: (I'm probably hard to read, I'm french and my english is not awesome !) I never used IDC file, and I don't understand how it works for loading them. In my last message I mean that I try to save a live analysis state. So I probably need to save all the memory state of my current virtual machine if I wanna keep my comments and modifications. Is this message more clear ?
Comment: I'm never had some problem. I do understand you. Sorry but I'm thinking what I can't help you. Did you try read [this]?(http://www.hexblog.com/?p=92).  What version of IDA are you using?
Answer: I solved my problem with IDC files and VM snapshot =)
I'm on IDA 6.4 and the snapshot function doesn't work in live debugging.
My solution is to take a snapshot of my virtual machine (on VMware workstation) to have everytime the same kernel state. When I wanna reload my work, I begin to load the virtual machine snapshot then I attach IDA to my virtual machine with windbg and finally I can load my IDC file using the script file option.
Thank you very much for you answer, it really was helpful !


How does the Windows Native API communicate with the kernel?

Question: The windows Native API (Ntdll.dll) is a user-mode library. However, it is the final user-mode library that interfaces with the kernel. How does it actually interface with the kernel and bridge the gap from user-mode into kernel-mode? For example, if I write a standard usermode application, I cannot directly call ntoskrnl.exe functions. Does Ntdll.dll in fact directly call ntoskrnl.exe functions? If so, how does it have permissions to do so being a user-mode library?
Comment: Can *any* application make such a call to invoke SSDT funcs or just Ntdll?
Comment: @blabb I don't view it as the answer to this question. I viewed your other answer and while it is related, there is no mention of int 2e or sysenter/syscall in it. This is fine as they are 2 separate questions and your answer was for the other one. However, you did answer this one in the comments. If you want to elaborate as an answer, feel free!
Answer: ntdll.dll is not privileged in any sense and can't do anything that your user mode library can't. So no, it doesn't have "permission" do directly call kernel-mode code and it doesn't do that.
What it does is pass through one special interface the kernel provides in order to receive user mode calls. Depending on the version and on the CPU, the ntdll functions load a couple of registers with (a) a number representing the id of the requested operation, and (b) the address of the stack, containing arguments for this operation. The it does something special (see below) that causes the CPU to transition into kernel-mode, and start executing the entry point for system calls.
This code is basically a switch statement on the index, which calls the correct appropriate kernel-mode function (and copies arguments).
The "something special" ntdll does is either invoke a software interrupt (int 0x2e) or, in modern versions of Windows, use a specialized instruction for system calls (syscall or sysenter). What both these things do is transition into ring 0 and start executing a given address from a given stack. The difference is that dispatching the interrupt requires consulting a table stored in memory (the IDT), while the specialized instructions don't.
That's where the magic happens. Nothing really prevents you from preparing the right arguments on the stack, loading eax and edx with the right values and performing an int 2e (or the appropriate stuff for x64).


What is the Difference between Maple and Rosewood Fretboards

Question: Is there a difference that's based on feel or sound - why are they the two most widely used choices?
Comment: Don't forget Ebony, which is used in a huge number of high-end guitars. It's my fingerboard of choice because it's very tight grained and resonant.
Comment: I think in the end it simply comes down to feel. For live playing the rosewood will absorb some sweat also.
Answer: Maple boards are typically placed on Swamp Ash or brighter wood bodies and it lends a snap to the tone of the guitar. Rosewood is known to be much mellower, and usually makes it's way on mahogany bodies and necks. They definitely feel different too. A maple neck is harder and feels very smooth under your fingers, while rosewood has some sponginess to it due to the porous properties of the wood.
There are plenty of guitars out there that don't follow these traditional approaches so your mileage may vary. As to why they are chosen? I'd say tradition, along with the availability of the wood itself. It is however well known that woods lend specific tones to an instrument, so possibly years of experience and use by high quality luthiers have lent to the reputation of maple and rosewood. There are plenty of other fingerboard woods out there to choose from, but these two seem to be industry standards.
Warmoth has a stellar site dedicated to the distinction between different tonewoods (neck and body). Here's the neck site. Enjoy!
Comment: +1 for the Warmoth link.  Although I'm a bit skeptical of the claim that the fretboard makes much of a sonic difference, especially on an electric, since it makes up such a small percentage of the wood used.
Comment: Superstition.  I'd love to see you in a blindfold test of different fretboard sounds.
Comment: I would tend to agree with you Alex. I would love to see an empirical test of the differences between a rosewood and maple neck on the exact same body. Lots of people (some quite prominent) say it makes a difference though.
Comment: Yeah +1 for Warmoth too!  As soon as I get my tax return I'm getting my first custom guitar from there.  Also to add,  To me Maple vs. Rosewood is an esthetic choice.  I have not been able to feel the difference.  I prefer ebony though.  I need to play on more maple fretboards to see if I can really tell the difference.
Comment: I agree w/ Alex as well. The string doesn't make enough contact w/ the FB for it to have a dramatic difference. The sure do feel & look different tho.
Comment: More than anything, the feel of a finished maple neck seems to drag under my fingers, where rosewood and ebony seem smoother and, without the finish, more organic. The string doesn't really rub against the wood, but our finger pads do, and some people like the smooth finish, and others like the wood.
Comment: It does make a difference on an otherwise identical guitar! But ultimately touch and look matter more to me. I'm team rosewood.
Answer: One difference is how you treat and care for one or the other as a guitar owner.
Maple fretboards are usually varnished with the same finish (nitrocellulose, polyethylene, or other finishes) used on the rest of the neck. Thus they are sealed.
Rosewood fretboards have no finish on them, and should be treated periodically with a wood conditioning oil. Also, on guitars that are exposed to extreme seasonal changes in humidity due to climate, a rosewood fingerboard may expand or contract in size, causing problems with the seating of the metal frets. So if you live in certain climates, you should use a guitar humidifier to prevent those kinds of problems.
Another note: Some luthiers are now using a heat-treated maple fingerboard (sometimes called "roasted maple") in place of rosewood. Gibson has been doing a lot of this in the last year due to their acute shortage of rosewood (it's a long story). So now there are Les Pauls and SGs with roasted maple fingerboards instead of rosewood. Some recent Gibson models use fingerboards of granadillo (Dalbergia retusa) which also goes by names including cocobolo and palisander.
Comment: Would you not want to use a Dehumidifier? Adding humidity to the environment does not seem like a good idea.
Comment: Using a guitar humidifier is essential to keeping the wood in acoustic guitars from shrinking and cracking at low-humidity times of the year in most climates in the world. Guitars and violins and such must be humidified all year long in many arid places. If you don't, your guitar may be ruined. I live in Atlanta, Georgia, USA, where it is rarely necessary to use a humidifier, but to people in most other parts of the USA it is essential. Smart guitarists use a hygrometer to measure humidity and a humidifier to keep the humidity at at a constant level inside the case.
Comment: Visit a store that sells expensive acoustic guitars in the USA or Europe, and I guarantee you will find humidifiers running to keep the moisture level in the air higher so the guitars do not crack.
Comment: http://www.guitarcenter.com/search?Ns=r&Ntt=humidifier
Comment: Usually if the air is very dry, you always keep the guitar inside its case when it is not being played, and you only humidify the inside of the guitar case, and measure and monitor the humidity inside the case. You usually don't worry about humidifying your whole room or whole house, unless you are in an extremely dry environment.
Answer: It makes no difference to the sound or playability of an electric guitar whether you have rosewood or maple for the fingerboard.
 Did you know that the human eye has a blind spot that your brain fills in for you? Your hearing can be influenced by a number of factors. People lose high frequencies as they age. Volume changes what we hear and fatigue can set in as well. Our hearing can also be influenced by what we see. If I'm in a crowded room I can focus my hearing better by looking at someone directly.
   There's many phenomena that fool our senses: colors look different depending on the light source, mirages that look like water on the road but isn't. It looks like the sun travels across the sky but it doesn't. Sound frequencies can add up or cancel out and this can be heard differently depending on where you are in a room. Rooms sound very different.
    The sound and feel of a guitar depends much more on the material striking the string, how that string is vibrating (perpendicular or parallel to the top), the gauge, length and tuning of the strings and whatever the string directly contacts (the bridge and nut). The sound is supremely influenced by pickups, amps, speakers, the room and volume.
    Think about it for a moment. Which sound is the true sound of an electric guitar- the neck pickup or the bridge or both? Out of phase or in phase? Does it bother you that the pickup is sensing a relatively small portion of the string length? Single coil or humbucker?
    I have a Les Paul that sounds big, fat and warm through my tube amp/1x12 cab and thin and bright through a Yamaha practice amp with tiny speakers. Which one is the true sound of that guitar? When I split the neck pickup to a single coil the sound gets thinner and snappier even through the tube amp. Does the rosewood fingerboard have anything to do with either?
    I can get a warm fat sound or a thin snapping sound just by manipulating the string- but that was me, not the fingerboard.
    The only thing to be concerned about is caring for the wood and the way it looks when considering maple or rosewood.
   Guitarists also tend to think all maple sounds the same when it actually varies quite a bit in hardness.
   You'll never be able to identify a fingerboard wood just by listening.
Comment: *on different guitars*
Comment: I own maple, rosewood, and ebony fingerboards on different guitars, and I can't even begin to agree that it "makes no difference to the sound or playability".
Answer: I know this is an old thread, but I'd like to add something I think hasn't been mentioned much. In my younger days, I hated maple fingerboards purely out of looks. I just never was a fan of that bright looking fingerboard on guitars. I always have been a rock guy, blues and metal type music. So for me I always liked the looks of rosewood or ebony boards.
I did own a few guitars with maple fingerboards, but I never played them much really to give them good break ins. But, I did notice for myself, all the types of things I like to play, were like butter on a maple fingerboard. All the hammer ons and pull offs, slides, bends and taps.. all of it seemed so easy to play and execute on maple fingerboards. When I'd go back to my rosewood fingerboard guitars, I found I was having to work just a lil extra to pull the same things off. I never noticed before how much "work" I actually having to put into playing certain types of things.
However I still wasn't wanting to switch to maple fingerboards yet. Fast forward 20 years later, I'm older now and have arthritis in my hands now. So, the things I used to love to play were getting more painful and hard to play. A fellow guitar player Kenny Blue Ray gave me a maple neck with maple fingerboard to try out. He has some tendon problems in his hand and had surgery, since then he's been playing more maple boards and dropped down to a set of 9's when he plays now.
I tried the neck out and man was it back to like butter! Personally I don't get the playing problem even with sweating on my hands and on the fingerboard. It still feels effortless to play on. On my rosewoods, its a struggle with arthritis now. So I've found with arthritis Maple is tops for playing! No fatigue in my hands or pains. However, I was still kind of turned off by the looks of these blond necks on my good lookin' gits. So I did the next best thing, I started finishing my rosewood fingerboards like maple boards.
I know some are going to cringe and some going to say I've ruined a Fender or something, I don't give a Rat's Bass what you think Lol I got arthritis and just want to play, not worry what the wine cork sniffers think. What I do to mine so they seal properly, most argue the porous grain on rosewood is too difficult to try and fill before sealing. But what I do is take the board and clean it, then wearing gloves, I mix a small amount of clear 5 minute set epoxy. I take a finger of my glove and take a little dab of epoxy and wipe it into the grain of the fingerboard smooth. I work the whole length of the board until its just got a thin layer over it.
But the key is to work it into the grain to fill the majority of the grain. Once I feel its filled enough the way I want it, I let it cure. After curing I then spray down some coats of lacquer sanding sealer. In between coats I use fine steel wool and smooth out each coat. Doing this gives me a level board with filled in grain. It ends up feeling just like a finished maple board. Now you can either shoot some gloss lacquer over it all if you want that shine on it. I just leave the sanding sealer as is, it leaves a natural sheen I think that looks more close to a new natural polished up rosewood fingerboard.
Again, I ain't a cork sniffer and don't care about keeping things stock, and don't worry these mods are not on vintage guitars just everyday new players and home builds. But as I got older and my hands wanted to see what Arthritis is all about, finished fingerboards are the way to go for me now. All the guitars I have with unfinished rosewood fingerboards, they kill my hands and set my arthritis off! But the rosewood boards I've finished and sealed, they bend like butter and my fingertips glide across I have no problems playing anything anymore, even on a bad day of arthritis!
In my young days I would told you rosewood all day till I die. Now that I'm older and been knocked down a lil, give me a maple fingerboard or a finished rosewood board. Oh and I should note, I also only install Dunlop 6100 fretwire. That also has helped tremendously in my playing since my arthritis has gotten worse. Finished fingerboards and big frets are key if have the same issued as I do. Good luck to all out there, keep playing and find what works for you!
Comment: I would love to see a photo of one of these finished rosewood necks (up close and further away) if you happen to have any. Curious if it changes the look much.
Comment: Rickenbacker have used rosewood on occasion, though they favour Bubinga for fretboards. These are commonly finished with a high-gloss lacquer. My only issue with lacquering rosewood would be natural oils in the wood unseating the lacquer over time. I've seen old Rickenbackers with delaminating lacquer on the neck, possibly as a result of this.
Answer: The fret dividers vibrate differently on each type of wood, but anybody who is pro will tell you that each instrument becomes a personal choice based off the sound, looks, and overall playability. A lead guitarist would most likely prefer a maple board because of the brightness, as a rythimist would prefer ebony or rosewood. It's all preference and your ability to enforce it.
Answer: It will make a bit of difference to the sound - one ond of the string is resting on the bridge, and the vibration goes through that into the body.
The other end is on a fret, so the sound there goes through the metal of the fret, through the wood it's mounted in (maple/rosewood), and down the neck and into the body. It'll affect sustain and tone quality, although to be honest other factors like the type of string, pickup and body make much more difference.
In my experience Maple necks are more varnished, whcih also might make a difference to the tone. I prefer Rosewood peronally - mostly cos that's what my current guitar has (and it's brilliant!)
Answer: Since one answer provided a shout-out for Warmoth, I would like to reciprocate with a recommendation for Musikraft for Fender-licensed bodies and necks. I am simply satisfied consumer with a project built from a quartersawn 22-fret 1-piece maple "Strat" neck and a quilted maple over mahogany "Tele" hollow-body (a hybrid between the Thinline and the standard style).
Maple with tung oil provides a finish that polishes wonderfully over time, yielding a slick neck. (Some sources also call this "gunstock" oil.)
Answer: I have been playing guitar since 1964.  For a long time I played a rosewood fingerboard.  A few years back I picked up a couple Fenders with maple fingerboards.  I'd played a dark fingerboard for so long it took me a while to get used to the maple color when moving up and down the neck, but that was more of a visual thing than anything mechanical.  As for tone or feel, I don't notice any difference.  I think the use of clear finish makes the fingerboard more slippery and I like that, but that has nothing to do with the wood type.  I like both.
Answer: I am not sure how to say this but I think I hear the difference. Once I ordered an LP style guitar. They had 2 types in store. One with rosewood and one with maple fretboard. I ordered the maple to try but they sent the wrong guitar. (again-same model different fretboard). I tried the rosewood and recorded a track digitally then sent it back. When they sent the maple one I did the same with the same exact settings I saved to my digital setup. They differ. And it is audible.
-The rosewood had more bottom end
-The maple sounded more nasally.
ALL THESE ARE EASY TO MANIPULATE IN MIXING BUT IT IS TRUE. I HEARD THEM AND RECORDED THEM...again. It also matters what time of the day you record and how you sit in you chair..yes..but these were sure audible. (You can find there guitar on the guitarfetish website. There they are with different fretboards)
Answer: The difference is simple: nothing that can be isolated sufficiently to draw any solid conclusions. Rosewood and maple look different, but when guitarists state that rosewood sounds 'darker' they are hearing with their eyes in the main. What comes out of your amplifier, ultimately, is a low-fidelity approximation of the vibration of the length of guitar string from bridge saddle to fret, as picked up by a high impedance pickup, routed through all sorts of exciting tonestack and gain stage circuitry, then fired back out of one or a number of 12-inch speakers. With this in mind it is impossible to isolate the influence of fretboard material in the overall tone of the instrument. Using Fender neck construction as the baseline, how would this tonal variation come about, simply and solely from the 5/16" of material glued to the top of a maple neck blank? For one thing Leo Fender didn't move from Maple to Rosewood fretboards for any tonal reason. He went on record stating that he didn't like the way nitro-lacquered maple fretboards were holding up and appeared dirty when shown on black and white television.
Comparing two separate instruments automatically invalidates any claims you might be trying to make, even if they are of the same model. There are far too many variables at stake, and no amount of empirical evidence can compensate for that, ultimately. Comparing Les Pauls with rosewood necks to Stratocasters with maple necks is simply bad science.
Comment: Your 30+ years of owning two Stratocasters equates to exactly nothing in this debate. Even unscrewing the neck from one and adding the neck from the other wouldn't be 'proof' of any sort. You can adjust the tone of a Strat by tightening or slackening off the neck bolts (and if they are '70s Strats with that micro-tilt garbage, or a folded up bus ticket acting as a crude shim, then all bets are off). As for the frets being set in either maple or rosewood, show me the money! The data isn't there.
Answer: The funny thing is; when you play the guitar, your fingers don't touch the fingerboard, and the strings don't touch it either. Your strings touch the frets, and your fingers touch the strings. Neither of them touch the fingerboard.
Try it, fret a string, or have someone else fret a string, and watch it from the side. You can clearly see that string and finger float above the fingerboard.
Unless your guitar is setup real bad, that is.
If you bend the string; same thing.
So if one neck feels smoother than the other, it must have smoother frets. It can't be the fingerboard.
As for the difference in sound; it must make some difference, but very little. I am sure I could not hear the difference between two fingerboards, and I think most guitarplayers can not hear it either.
So it all comes down to looks. Which ones looks better to you?
Comment: If you never touch the fingerboard how does it end up dirty/worn on frets you use a lot?
Answer: Obviously, there is a tonal difference. Listen to a Paul Standard with rosewood, and a Paul Custom with ebony. Same guitar, different fretboards, and the Custom has a bit of a snappier, more articulate attack. Listen to a tele with a rosewood board, and one with a maple one. in this case, the maple has the snap. Anyone who says there's no difference, doesn't listen tot eh guitar without the amp. Anyone who says the fingers don't touch the board, doesn't "play" guitar. your fingers touch it, the strings touch it, the strings touch the frets that are IMBEDDED in the board..... of course to wood imparts something to the tone. to think otherwise is idiotic.
Comment: I don't know whether to upvote this for having some good information about fingerboard woods or flag it for unnecessary unkindness in the last two sentences. Would you consider editing the last two sentences (maybe even removing the last one) and keep it about guitars and not about people who have views that are different from yours?
Answer: Just put a spectrum analyser infront of the amp, and you will read a different frequence responce with maple vs rosewood. So simple is it.
Comment: You will almost certainly plot a different frequency response for different instruments, but you cannot even begin to claim that the difference is the result of fretboard material. The fretboard material might be a contributing factor, but impossible to isolate. Guitarists shouldn't pretend to be scientists.


run installer on all machines on domain

Question: is it reasonable to automatically run an installer (for an activex control) as administrator on all machines in my domain, using an out-of-the-box windows (any version)?
Answer: It depends a lot on the context.
What do you mean by "run an installer as administrator on all machines"? How are you going to actually run it? By logging on to all machines and clicking on it? By sceduling a task? By using a script? By group policy?
Or are you asking exactly for this, i.e. "how can I run an installer as administrator on all machines in the domain?"?
Please give more details, it's just not possible to answer this question as it is presently stated.
Comment: Also, if it's the latter "how can I run an installer", what kind of installer? EXE, MSI, etc?
Comment: You missed an option, which is to sit at each machine, log on as an admin and then run the installer via a logon script. There is no mention in the OP's question of wanting to run this remotely. ;)
Answer: Active X controls often need to be installed as administrator in order for Internet Explorer to download and install the Active X control to the special "Downloaded Program Files" folder (normally C:\WINNT\Downloaded Program Files - it is a super hidden folder in windows explorer). In addition several registry keys are written to ensure that the Active X control file version used locally is the same as the file version in the installation source URL. I believe IE checks this on every launch. If the file versions match no installation action is triggered.
In most cases I have been able to package Active X controls by capturing its installation while logged in and installing as an administrator and then creating an MSI file that can be run on the other machines and be installed by normal user accounts. See my answer here for some further details: http://forum.installsite.net/index.php?showtopic=20642&hl=

run installer on all machines on domain


Is there a scriptural basis for treating the non-Gospel books of the New Testament as scripture?

Question: Without citing any books of the New Testament besides the Gospels as evidence (since that would be self-referential), is there a scriptural basis (either in the Gospels or in the Old Testament) for treating any book of the New Testament besides the Gospels as scripture rather than as supplemental history/commentary/scholarship in the tradition of the Jewish Talmud?
Comment: Without citing any books of the New Testament besides the epistles of Peter and James as evidence (since that would be self-referential), is there a scriptural basis for treating any books of the New Testament besides the epistles of Peter and James as scripture? (My point is that you've separated the gospels from the other books, without giving a reason for that separation; any other separation would seem equally (un)justified.)
Comment: The epistles were written before the gospels, so it makes more sense to me that the gospels may reference them in a roundabout way. As far as I know, however, they do not.
Comment: I drew that distinction on the theory that at least one account of Jesus's life and teachings has to be treated as scripture in order for Christianity to function as a religion (otherwise, what's the point?) - but you could have a Christian faith (albeit a different one) if the rest of the NT were not scriptural.

This looks to me to be a similar relationship to that between the Jewish Torah and Talmud - the Torah can still produce a coherent religion without treating the Talmud as an authoritative text (as proven by the Reform Judaism folks), the Talmud without the Torah arguably could not.
Comment: @Jeff Actually, all you need to go on is the account of the resurrection, which is referenced (for example) in Acts, or Romans, and perhaps (especially for Catholics) the account of the institution of the Eucharist in 1 Corinthians. Acts and 1 Corinthians together could definitely give you a Christian faith.
Comment: @MattGutting - So you would argue that all of Jesus' personal teachings prior to the last supper are not foundational to a meaningfully Christian faith?
Comment: Depends on how you define "meaningful". The most important *events* in his life were the passion and resurrection, and his institution of the Eucharist.
Answer:
Is there a scriptural basis for treating the non-Gospel books of the New Testament as scripture?

Short answer: yes.
Jesus commissioned 12 of his disciples as 'apostles' and gave them authority to teach. If you accept Jesus' words as scripture (as recorded in the gospels), you should accept the words of his apostles as scripture as well, as He said to them:

18 ..."All authority in heaven and on earth has been given to me. 19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age." - Matthew 28:18-20 NIV (emphasis added)
Again Jesus said, "Peace be with you! As the Father has sent me, I am sending you." - John 20:21 NIV

Jesus specifically authorized His apostles to teach, and to do that in the authority that He Himself had received from His Heavenly Father. For this reason, the early church placed particular importance on what were judged to be authentic writings of the apostles (as well as their companions who were believed to have acted as scribes for them - e.g. Mark and Luke). The gospels themselves actually fit in this category - the early church trusted that the (canonical) gospels were accurate because of their author's apostolic credentials. For this reason, there is no legitimate basis for separating the gospels into a different category of 'scripture' that does not equally apply to the rest of the New Testament1.

1. In broad terms at least. There were some arguments about the authenticity of individual books that later came to be accepted (or excluded) from the New Testament canon. However these arguments centred around whether they were authentic in regards to their apostolic credentials. See http://en.wikipedia.org/wiki/Antilegomena for further information on these disputes.
Comment: I think this is an interesting argument, and certainly supports the legitimate role of the apostles as agents in spreading the early Christian faith - but I don't see anything in it to suggest that their personal ideas should be given the same implied weight as what they describe (through the gospels) as Jesus' direct teachings. To draw a different parallel than the Talmud, most of what we have of Socrates we get through Plato - but that does not imply that Socrates would lay claim to all of Plato's own ideas.
Comment: Giving the Apostles equal standing with Jesus as teachers also seems a bit awkward in light of Matthew 23:8-12. Any thoughts on that?
Comment: That passage is speaking about titles and attitudes - to interpret it as downgrading apostolic authority to teach conflicts with passages of scripture like Matthew 10:40 as well as the ones previously cited. To interpet the epistles as containing the apostles "personal ideas" is incorrect as well - they were men full of the Holy Spirit (that had been promised to them by Jesus) and wrote accordingly. In contrast to the Old Testament period, the Spirit was given to the apostles "without measure", so their authority should certainly not be seen as lower than that of the Old Testament writers.


What FAA sources of weather information can pilots use to mitigate the risk of flying in icing conditions?

Question: Pilots flying under the FAA jurisdiction have many official sources of weather information available to them. Specifically as it relates to icing conditions, what official sources of weather information can pilots refer to in order to avoid or mitigate the risk of flying in icing conditions?
Answer: Here's a list of official FAA weather information sources that pilots can analyze to avoid or mitigate icing risks:
AIRMET Zulu
An AIRMET Zulu will be issued for areas where icing conditions are forecast to be light or moderate.
SIGMET
A SIGMET will be issued for icing conditions forecast to be severe.
PIREPs
PIREPs are the best source of icing information. Unlike weather information sources which are forecasts, PIREPs are reports from pilots flying in the actual conditions and should be considered the most accurate source of icing information.
Here's an example of a PIREP where a pilot of a TBM-700 was descending into Atlanta. He reported a cloud layer topping at 7900 feet down to 500 feet AGL and picking up light rime ice between 7900 and 5000 feet.
<code>UA /OV ATL /TM 1200 /FLUNKN /TP TBM7 /SK OVC015-TOP079 /IC LGT RIME 050-079 /RM DURD
</code>
Significant Weather Prognostic Charts
The top two panes of a prog chart help pilots visualize the freezing level. A zig zag line shows when freezing level is at the surface and height contours for the highest freezing level are drawn at 4000 foot intervals with dashed lines. This information gives pilots a forecast of temperatures which when combined with known precipitation can predict ice and help to avoid it.

Area Forecast (FA)
An FA is an additional source of information about where cloud tops and bottoms are. If you know that along with the freezing level you can get a better idea of where icing conditions are most likely.
Comment: If I asked someone, "what sources of weather information are available" and they answered "temperature," I'd be fairly certain that we hadn't successfully communicated with each other. Temperature is a piece of information in the weather sources, but it is not a **source** of weather information.
Comment: good answer but you forgot one very important source: the temperature. can't have icing unless you're close to or above the freezing level.
Comment: "The temperature" isn't directly part of the answer. The question is about source of weather published by the FAA. The temperature isn't a source of weather. The forecasted freezing level is described in Airmets and is graphically depicted on prog charts. It is also available from FD forecasts, but is most readily available as an indication in the airplane, which isn't directly relevant when discussing weather sources.
Comment: in what universe is temperature not part of the weather forecast? its on the TAF, and you can calculate the freezing level using the lapse rate.
Answer: You can get it from Airmen's Meteorological Information or Significant Meteorological Information, a compiled graphical version of which can be found at Aviation Weather Center. FAA Advisory Circular 91-74A, Pilot Guide: Flight In Icing Conditions, notes

Aviation meteorologists at the NWS Aviation Weather Center (AWC), local NWS
  Field Offices, major airlines, and private companies prepare icing forecasts. In addition, guidance products are available on the Web. Icing AIRMETs, prepared at AWC, cover a 6-hour forecast window and are updated four times daily.

Also it notes the importance of Pilot Reports (PIREP),

PIREPs remain the major source of information for icing location and severity

Note that FAA requires the weather sources to be approved by US National Weather Service. As far as icing conditions go, to the best of my knowledge FAA doesn't mandate any particular source.


Can a Muslim woman leave her burqa in the West?

Question: It has been noted that Muslim women who wear garments that cover from head to toe may suffer from Vitamin D deficiency and obesity. Now, suppose a Muslim girl and her family moves to a Western country. Is it permissible then in Islam for a girl to leave her burqa, or must she wear a burqa at all times as an observant adherent? Is there any wiggle room in the law? Can the girl wear a hijab instead so that her face is shown in the sun?
Answer: First of all I want to say that the burqa is a cultural dress, not the Islamic hijab. I am not saying that the woman who wears it should not wear it as it is  the best dress for practicing hijab.
Secondly women wears burqa only when they are  out of home, when in front of na-mahram/non-mahram and not all the day. Therefore I found all those research as ridiculous and fishy, they are just a propaganda against Islamic dressing.
So even a person of just average common sense can make out that there is no relation between burqa and vitamin deficiency/obesity.
To know the minimum hijab requirment in Islam you can refer to brother Al Ummat's answer in this question.
And based on his answer a woman can show her face in the West.
Comment: [Capitalization](http://en.wikipedia.org/wiki/Capitalization#By_context)
Answer: Women in Arab; women in West
You're taking this to the wrong side a bit. Islam was never a religion for just Arab people. Islam is a complete code of conduct for humanity. So what do you expect? A woman from Arab will have to wear the Hijab where its alot hot and humid temp, and a woman won't need to wear hers burkha in West where temp is bearable just because her complexity is being not fair? Just because her doctor is telling her that remove the burkha and you'll be fair in color? How can that happen. Allah would never do injustice to his creature.
What is burkha
Burkha was never meant to be something that is black in color; which starts covering female body from her head, lets say hairs, and goes down all the way to her feet even covering her shoes. That's a cultural burkha not the islamic one. That burkha was used by people of tribes. They tried to hide their women from anyone, their females had to wear burkha even in the homes.
Where to wear a burkha
Islam wants a woman to be covered when she is infront of a person that not a mehram for her. Lets say, female's father, brother, mother and all these relatives don't need to meet her only when she is wearing her burkha. Burkha is asked to wear once she is outside where anyone from public can see her. Then burkha needs to be wore.
Living in West? still wear burkha
Going to west doesn't mean to leave your burkha; burkha is a part of our Islamic culture, not the part of eastern culture! :) However, even if a girl is wearing Hijab she is half covered; that's enough for her if she feels uncomfortable in burkha. You need to take your culture with you, and keep it in your heart. Respect your culture like they do respect their own.
What I might share
The best answer would be, Allah knows how his creatures feels in a condition. And will never punish them for the sins or discrimination of the religion that they have no control over. Just like you mentioned Vitamin D and all other symptons, I am not well aware of these things but if a female feels uncomfortable, she can replace burkha with Hijab, but she must be covered.
Answer: First of all, hijab is the actual type of covering, which woman should do. It has some basic criteria that except hands and eyes, whole body should be covered. (Most scholars recommend covering the face as well, although that does not make it obligatory, but iff done it's mutabahab). And there is no "burqa" in Islam, although the burqa is one form of hijab.
In any case, a woman is NOT allowed to leave hijab, UNLESS she has to face very serious consequences for it or following it may create serious issues for her. Otherwise, leaving hijab is in no way allowed in Islam.
Also, you have to know that you don't have to do complete hijab in your home. In the boundary of home, you still have a lot of sunlight coming inside your home, so can't you get sunlight from there?


How does a lander get from orbit to the ground?

Question: I've played a lot of Kerbal Space Program and always wondered: When in orbit around a body without an atmosphere, which trajectory does a lander take to approach and land using minimum delta-v, without wasting too much time, and landing at the exact right place that has been chosen during mission planning?
Comment: Very, very carefully.
Comment: You can easily exercise "suicide-burn" landing in KSP with [KER](http://www.curse.com/ksp-mods/kerbal/222685-kerbal-engineer-redux) mod, it calculates (approximate) suicide-burn duration.(And then your mission fails as your lander rolls down some crater ;p)
Comment: Are you talking about a landing on a body without an atmosphere or an atmospheric re-entry on Earth?
Comment: *"using minimum delta-v"*  That would be to reduce the perihelion (not sure of the term as it applies to random masses, that is more about stars) to a point where the orbiting object is not coming back out of the atmosphere due to drag.  The vector to fire the engines would be in the direction the craft is moving (to slow it down and reduce the perihelion of the orbit).  The place to do that burn is pretty much the exact opposite side of the larger object that is being orbited, to where you intend to reach the perihelion.  But really I think this question is 'too broad' for a single answer.
Comment: @AndrewThompson "periapsis" is the general term, "perihelion" refers specifically to the low point on orbits around our sun.
Comment: @1337joe  Thanks for the detail I was missing.  :)
Comment: I never mentionned any atmosphere, but both cases are interesting
Comment: @MagixKiller Both cases are completely different and would be enough for an own question. I would recommend you to ask a separate question about atmospheric reentry and rewrite this one to explicitly specify a non-atmospheric landing.
Answer: The minimum $\Delta V$ is effectively a Hohmann transfer.  You would de-orbit just enough to barely touch the surface at periapsis, and right at the surface you would do an instantaneous impulsive burn (also known as a "suicide burn") to exactly cancel your velocity relative to the surface.  Done!  A perfect landing.
In the real world however you don't have instantaneous burns.  So you need to start sometime before you get to the surface and do a gravity turn to minimize the gravity loss during the finite burn.  The higher your thrust-to-weight ratio, the shorter the burn and the less gravity loss that you'll have.
Then the time it takes will be the time it takes.  If your objective is to minimize $\Delta V$, then you can neither "waste" time nor be more efficient with the time.
As for the accuracy, you want to have the landing site in the plane of the orbit.  Then its just a matter of timing your de-orbit properly.  The residual error can be taken out with a smidge more $\Delta V$ and some means of sensing your location relative to the intended landing point, ideally before you start your landing burn.
Comment: @MagixKiller: Also note that a minimum-ΔV landing trajectory is commonly called (particularly in KSP jargon, although the term itself is far older) a "suicide burn". The reason being that minimizing ΔV means delaying the burn to the last second possible and then burning at maximum thrust, so that you'll have no safety margin, very little time to react, and no easy way to abort the landing (since your thrust is already maxed) if you find that you've miscalculated. There's a reason why real-world landing trajectories don't usually go for absolute minimum ΔV.
Comment: Well, you can start with the instantaneous impulse required and divide by the thrust.  That will get you in the ballpark.  Then you'll need to numerically integrate the trajectory to get the actual burn time.
Comment: I like the term "suicide burn".  The way it's really done is to bring the lander to some height above the landing location, measured in meters, and to go down from there with a constant velocity to the surface. That allows for some uncertainty in that height.
Comment: Is there a way to calculate the landing burn time depending on the TWR ?
Answer: If the body on which you want to land has no atmosphere, you need to reduce the spacecraft velocity using the onboard propulsion system.
If you perform an Hohmann-like manoeuvre you end up having a touch down which is not vertical and the resulting $\Delta$v is actually an underestimation of the real value.

Instead, if you try to perfom a landing like the one shown in the second figure, you will have a vertical terminal trajectory but the $\Delta$v required for the break makes this manoeuvre unfeasible.

A better estimation of the actual $\Delta$v needed can be found applying an optimal control theory, which will lead to a trajectory more like the one in the third picture.

EDIT: The optimal control theory approach
Like any optimization problem, you need to set a goal (what you want to optimize, in this case could be the amount of fuel used for the manoeuvre), then choose a model for the process and parameterize it (to have a finite number of parameters to be tuned). Finally tou have to define a cost function and some constraints.
The third case I have presented represents a 2-phases landing:

coasting phase, which is ballistic
powered descent phase

For this case, you need also to make some assumptions about the panet gravity field (which is assumed to be perfectly spherical) and also you have to assume the the manoeuvre is 2D and that during the power descent the magnitude of the thrust is constant.
When you have set all these things you are ready for the numerical optimization which will give you the resulting trajectory which will minimize the amount of fuel needed.
All what I have told you was part of a lecture I had last year. The lecturer had developed all this during his master thesis and you can download it here:
http://hdl.handle.net/10589/79781


Does a generator potential pass along a nerve the same way an action potential does?

Question: I have read that a generator potential is a localized depolarization of a membrane. Does that mean that it does not pass along a neuron the same way an action potential does ? If not, then how do generator potentials from multiple rods in our eyes add up (converge) and trigger an action potential in a sensory neurone ?
Answer: Generator potentials (GP) are meant to generate action potentials (AP). An action potential results, whenever the level of depolarisation at a particular place crosses a threshold. This "place" is usually the beginning of an axon of a typical receptor, since it is equipped with all the channels required to begin and propagate an action potential. The purpose of the receptor architecture, then, is to make the threshold go off in a naturally meaningful situation.
There are two possible ways this is done. Say the neuron is transmitting information about the location of a stimulus. Then the "naturally meaningful threshold" would be some spatial cutoff, a minimum area that needs to be stimulated for the action potential to go off. Then, the receptor would have several GP-producing dendrites spread out, each generator potential being summed at the meeting place of the dendrites, which happens to be the cell body and the beginning place of the axon. So the individual generator potential in each dendrite will contribute to the sum, which will be summated and the cellular decision-making process (or a crude example of it) be affected as this summation.
Another way is temporal summation, something which has, for example only one GP-producing dendrite and the axon. Then, for the summated potential at the cell body to cross the threshold, the stimulus must stay, or be summated across, for some time-cutoff. GPs have some decay time, before which if another GP reaches there, it adds up. This would be meaningful in things like the presence or absence of a touch, the cutoff preventing against minor fluctuations.
This said, the situation in the eye in much much more complex. There are several layers of neurons and each neuron performs a lot of different functions and has a specialised architecture for it. The Rods and Cones actually produce hyperpolarizations and not depolarisations (theoretically, both are propagated in the same way, but hyperpolarisations themselves do not initiate AP).
To complicate further, most receptor systems alter the frequency of AP and thus have some basal frequency, this modulation also being important for encoding the message.
An image of GP:
Comment: Some of this answer is good but it has major problems. Photoreceptors do not fire action potentials, for example. It is also misleading to talk about "10 layers" of the retina in terms of how many "layers of neurons" there are. There are only 3 in the chain: photoreceptors, bipolar cells, and retinal ganglion cells. Amacrine and horizontal cells also modulate the activity in other cells, but they are not part of the serial transmission chain to the brain.
Comment: I would suggest adding that action potentials are transmitted actively (trough activation of sodium and potassium channels), but localized potentials are transmitted passively with a time and space constant (cable theory).
Comment: @BryanKrause I never said that they do. I did mention the modulation of frequency at the end of the paragraph as a general complication in several receptor systems. I did mention the 10 layers to only show the complexity, hence the caveat 10 layers of 'retina' and not neurons. Edited in the answer.
Comment: It seemed difficult to explain the retinal neural mechanism in a simple way. Hence, the preceding part is a general way in which GP work. Do let me know if anything needs correction.


What's the brightness of Alpha Centauri from Proxima Centauri?

Question: Self-explanatory, but I would like a comparison as well. Is the light enough to see by? How disrupted will the pitch darkness on the spot opposite of the 'solar pole' be?
Comment: #JustForInformation: I guess by *solar pole* you mean the point where the sun is directly overhead? The real name for that is the *subsolar point*. So the opposite to that would be the *antipodes of the subsolar point*.
Answer: Not close to being able to read by.
Proxima Centauri is about 13,000 AU from the two binary Centari stars.   Together they have about twice the luminosity of the sun but at 13,000 AU, that's roughly 2/169,000,000 the visible light that the Earth gets from the Sun.
The brightness variation of the full moon to the Sun is about 1 to 440,000, so, some rough math, the two stars would shine about 1/190th as bright as the full moon.   That would make those 2 stars by far the brightest stars in the Proxima Centauri sky, but far short of reading light.   Together, the two stars would be about 10 times as bright as Venus at Venus' peak.  (Venus is about 1/2000th as bright as the moon, -4.4 apparent magnitude to -12.6 for the moon).
That would, I think, be bright enough to be visible during the day under an earth like sky a lot of the time.
The two stars would be quite close to each other too, maximum visible distance between them would be roughly 1/4 the diameter of the full moon, where they would still be visible separate stars when far apart, but they would pass close to each other too, perhaps appearing to touch to the naked eye.
The two stars complete a full orbit around each other in 79.9 years, so the variation would be noticeable over a human lifetime.
Comment: Hmm... I expect a human lifetime on Proxima Centauri would be rather short. ;)
Comment: @reirab : wouldn't it be better if we all assumed both the question and the answer mean "from a planet orbiting Proxima Centauri" instead of "from the surface of Proxima Centauri"? :)


Are plants actual oxygen factories?

Question: Is the oxygen exhaled by plants during the day compensated by inhalation of carbon dioxide at night?
Comment: Green-plant respirate (O2 ---> CO2 ) throughout day and night. But the total rate of photosynthesis (that happens only at day) throughout world is so greater than respiration of animals+plants for (day+night) is so grater, that  CO2 can't accumulate. speed of photosynthesis is greater than the plant's own respiration otherwise it could not be able to accumulate foods and  grow.
Comment: The confusion takes place because it is not about stoichiometry (chemical arithmetic) or balance; but it is about reaction-rate (speed) with time.
Comment: In night, the plant do-not intake any CO2. You can consider them like animals when it is night.
Comment: Are you confused about "dark-phase" of photosynthesis (where CO2) is taken? The term is misleading and another synonym for it is "light independent phase". All school-textbook on photosynthesis-chapter; mentions it so-far I can recall.
Comment: If you block the light; there would be a deficit of pre-requisit-compounds for another-phase (so-called dark-phase).  So with turning off light, within very short, momentary time the dark-phase stops. Dark-phase (light-independent phase) though indirectly, dependent on light.
Comment: Both phases of the reaction, i.e. 1.  the light-phase and 2.  light-independent-phase, both take place only in presence of light. On dark, both turns off.
Answer: All green plants do Photosynthesis as well as Respiration.
Plants respire during the day and night, but they only photosynthesis during the day when it is light:
there is equations for aerobic respiration and photosynthesis:
C6H12O6 + 6O2 → 6CO2 + 6H2O (aerobic respiration)
6CO2 + 6H2O → C6H12O6 + 6O2 (photosynthesis)
In terms of reactants and products, they are the reverse of each other. In terms of gas exchange:
Process        -------Carbon dioxide    -----------------Oxygen
Respiration     -----------Out  ----------------------------    In
Photosynthesis  -------In         ----------------------------    Out

Photosynthesis is only in the presence of Sunlight . So it occurs only during the day .
For photosynthesis they require Carbon Dioxide gas ( CO2 gas )
This gas enters the leaves through tiny pores on them called stomata .
The byproduct of photosynthesis is Oxygen gas ( O2 gas )
It is either passes out through the same stomata OR used for respiration

For respiration they require O2 gas .
It enters the leaves through the same pores or stomata .
The by product of respiration is CO2 gas .
During day time it is immediately used for photosynthesis .
During night time the CO2 gas is released in the atmosphere

Net gas exchange
The net (overall) effect depends on the time of day and the light intensity. Photosynthesis doesn't occur at night. When there is no photosynthesis, there is a net release of carbon dioxide and a net uptake of oxygen.
If there is enough light during the day, then:
<code>the rate of photosynthesis is higher than the rate of respiration
there is a net release of oxygen and a net uptake of carbon dioxide
</code>
(consider CAM plants)
in a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO2)
https://en.wikipedia.org/wiki/Crassulacean_acid_metabolism#During_the_night

this link help you understand the process better by simple language :
http://www.bbc.co.uk/education/guides/zxtcwmn/revision/1
Answer: It's impossible for a plant to use more oxygen in the long term. As @BlueFoxy explained, whenever a plant is using oxygen it is to oxidise sugar ($C_6H_{12}O_6$). These sugars were made by the plant itself using $CO_2$, $H_2O$ and sunlight, so it can't oxidise more sugar than it produced in the first place.
If the plant is growing then some of the carbon removed from $CO_2$ will be used to form the plant's tissues, causing a net increase in oxygen in the atmosphere. If the plant isn't growing it'll probably be oxygen neutral.
There are probably some weird parasitic plants that break this pattern by stealing other plants' carbon, but in general the rule holds.
Comment: "There are probably some weird parasitic plants that break this pattern by stealing other plants' carbon" - [*Monotropha uniflora*](https://en.wikipedia.org/wiki/Monotropa_uniflora) is parasitic on mycorrhizal fungi, so does this indirectly.
Comment: @arboviral *Cuscuta reflexa* or anysuch parasitic plant would be more direct example because they donot require mediators like mycorrhizal fungi.
Comment: @AlwaysConfused good catch - I'd forgotten about dodder. However, *Cuscuta reflexa* can actually photosynthesize a bit; a species which is thought to be entirely dependent on the host plants for nutrition such as *C*. *europaea* would be an even better example.
Comment: @arboviral Thanks I did not knew *C. reflexa* can do little amount of photosynthesis. Great info!

Are plants actual oxygen factories?


Bra–ket notation & Schrödinger's cat intepretation

Question: Can anyone explain to me the meaning of this picture? I Know that the argument is Quantum Physics and that cat is the Schrödinger's cat, but I don't know how to interpret the bra–ket notation and also the two numerical coefficients...
Comment: A ket (not related to the cat :D) is a mathematical object, which describes the state. Kets are denoted using special pair of brackets $| \phantom{a} \rangle$ and everything inside this brackets is just a label. The superposition of two states is represented as a linear combination of the corresponding kets.
Comment: So the combination of this two states $\frac{1}{\sqrt{2}}|\mathrm{Alive}\rangle +\frac{1}{\sqrt{2}}|\mathrm{Dead}\rangle$ result in a superposition that show that the cat is something between alive and dead, right? Thank you WildKET ;-)
Answer: The expression in the picture contains kets only. Kets represent states of a system. In this case, the "alive" state is the first one and the "dead" state the second.
The numerical factors are there for normalisation. It is assumed both states are equally likely, so they have the same numerical factor. If we call the expression in the picture $|\Psi\rangle$, the inner product$^1$ (analogous to the scalar product of two vectors)
$$\langle\Psi|\Psi\rangle = \int{\Psi^*(\vec{r})\Psi(\vec{r})d\vec{r}}$$
should be equal to $1$. This is because we interpret the wavefunction $\Psi(\vec{r})$ as a probability amplitude distribution and hence the scalar product of the wavefunction with itself as a probability distribution. Integrating a probability distribution over the entire space (I used the position space here, but you could just as well integrate over an abstract state space for example) should always give $1$, due to the nature of probability theory. This expresses the idea that the system (cat) must be in some state.
Now, there's a problem with this expression and that problem is also the resolution of the issue associated with Schrödinger's cat (the criticism that according to QM the cat would be both dead and alive at the same time). And that is that the cat is not a quantum system. A common mistake is that a conscious observer is needed for the "collapse" of the wavefunction, as it is described in the Copenhagen interpretation. This is not true. The cat will not be in a superposition of both dead and alive but in one particular state (see also decoherence).

$^1$ Some more information on the inner product $\langle\Psi|\Psi\rangle$.
Let's consider a general ket in some state space $\mathcal{V}$ (which is just a special kind of vector space and kets are special column vectors), say $|a\rangle$. Let's assume the dimension $d$ of this space is finite. It doesn't have to be, but it makes things conceptually easier to understand. Because then a finite basis $|e_i\rangle$ (with $i = 1\ldots d$) exists for this vector space, meaning we can write every ket in $\mathcal{V}$ as
$$|a\rangle = \sum_{i}^{d}{a_i|e_i\rangle}.\quad\quad(1)$$
For a ket space of infinite dimension (like position space) this sum becomes an integral.
Now we can construct a dual vector space $\mathcal{V^*}$ which contains all the linear functions $f(|a\rangle)$ mapping the kets in $\mathcal{V}$ to the complex numbers $\mathbb{C}$. We denote these functions as $\langle f|$ and call them bra's. You can think of these bra's as row vectors. The common notation therefore isn't $f(|a\rangle)$ but rather $\langle f|a\rangle$, a bra-ket, which can in turn be seen as a scalar (inner) product between a row vector and a column vector.
The elements of $\mathcal{V}^*$ are constructed in a special way. We choose the basis $\langle e_i|$ for this dual space such that for every $\langle e_i|$ it holds that $\langle e_i|a\rangle = a_i^*$ and therefore $\langle e_i|e_j\rangle = \delta_{ij}$ (orthonormality property). This allows us to associate a single bra $\langle a|$ with each ket $|a\rangle$ as follows
$$\langle a| = \sum_{i}^{d}{a_i^*\langle e_i|}.\quad\quad(2)$$
Again this sum becomes an integral if we consider a continuous label such as position instead of the discrete $i$'s.
Now the inner product of two kets in $\mathcal{V}$ is defined as
$$\left(|a\rangle\right) \cdot \left(|b\rangle\right) \equiv \langle a|b\rangle$$
which can be rewritten using $(1)$, $(2)$ and the orthonormality property, yielding:
$$\langle a|b\rangle = \sum_{i}^{d}{a_i^*b_i}$$
where the sum again becomes an integral in e.g. position space, recovering the expression I used above.
The difference between an expression of the form $\langle a|b\rangle$ and one of the form $c|b\rangle$ should now also be clear. In the first case we actually have a function $\langle a|$ with the ket $|b\rangle$ as its argument, the result of which is a complex number. In the second case we have a (possibly complex) number $c$ in front of a ket $|b\rangle$, the result of which is still a ket. And this ket still represents the same state as long as $c$ is a constant.
Comment: Why have you used the notation $\langle X|X\rangle$ and not only $X|X\rangle$ as in my picture? Because this $\langle X|X\rangle$ is a bra-ket and this $X|X\rangle$ is only a ket? What's the difference?
Comment: @FormlessCloud I've added a discussion of how the bra-ket is constructed with a paragraph pointing out the difference between expressions of the form $\langle X|X\rangle$ and ones of the form $x|X\rangle$. If there are still things that aren't clear, let me know.
Answer: Ket(s) and Bra(s) represent state of a system. The simplest interpretation is to see kets and states as (complex) vectors. In your case, the state could be described by the vector :
$$\vec S = \frac{1}{\sqrt{2}} \vec{alive} + \frac{1}{\sqrt{2}} \vec{dead}$$
Here, $\vec{alive}$ and $\vec{dead}$ are a basis for the states, so they are orthogonal vectors : $\vec{alive}.\vec{dead} = 0$, and they are normed : $|\vec{alive}|=|\vec{dead}|=1$
A general state could be written: $$\vec S = a  *~ \vec{alive} + b *~\vec{dead}$$ where $a$ and $b$ are $2$ complex numbers.
Generally, we want a normed state, that is $|a|^2 +|b|^2=1$, and this is the case in your particular state.
Now, if I take this general state, the probability that the cat is alive is $|a|^2$, and the probability that the cat is dead is $|b|^2$.
Said differently, the coefficients $a,b$ are probabilites amplitudes, there are not probabilities.
Answer: The easy part is the numerical coefficients which are there so the state is normalized, which means $\langle \psi | \psi \rangle=1$.
The easier part is what's written in the kets, one of them illustrates the state of a dead cat and the other a living one. The point is, due to the canonical form of quantum mechanics, before doing a measurement the cat's state is neither alive or dead; it's a linear superposition of them. When you do a measurement the cat's state will collapse in either one of them(but not both :-).
Answer: There are two states (in QM with ket's $\left|\phantom{H}\right>$ we mark possible states) of the Schrödinger's cat. 1st state means (the one on the left) the cat is alive and 2nd state (the one on the right) means it is dead. We could write this down like this:
$$\underbrace{\frac{1}{\sqrt{2}}}_{\llap{\text{amplitude for first state}}} \,\,\left|\text{alive}\right> + \underbrace{\frac{1}{\sqrt{2}}}_{\rlap{\text{amplitude for second state}}}\,\, \left|\text{dead}\right>$$
If you would deal with this problem in a classical way you would write probabilities instead of amplitudes like this (no square roots):
$$\underbrace{\frac{1}{2}}_{\llap{\text{probability for first state}}} \,\,\left|\text{alive}\right> + \underbrace{\frac{1}{2}}_{\rlap{\text{probability for second state}}}\,\, \left|\text{dead}\right> = \underbrace{1}_{\rlap{\text{total probability is allways 1}}}$$
For understanding the connection between probability and QM amplitude please read the accepted anwser to my own question which helped me to understand this: QM formalism is one big confusion - lack of geometrical explaination with images.
Comment: The second equal sign is merely suggestive. The object you've written down on the left hand side isn't a number, it's more of a list. Only the sum of the *entries* of that list is $1$.
Comment: Thank you for the comment. I am still learning QM myself.
Answer: I have provided an answer to this question in this video.
Your question was helpful for me to think about my understanding of QM notation since I am still learning myself.


How can I check if a key image has been imported into a view wallet?

Question: How can I check if a key image has been successfully imported into a view wallet, particularly a cold wallet that has never spent any of the funds it has received?
Answer: The easiest thing to do, in my view (due to it being the most thorough), is to set up a normal wallet and daemon on an air-gapped computer (one not connected to the internet).  Your air-gapped wallet will contain both the private viewkey and the private spendkey.
You can periodically save a copy of the blockchain from an internet-facing computer, transfer it via USB or whatever to the air-gapped computer, and have the wallet sync to that.  During the sync process, this method will create key images for all outputs owned by that wallet (and, of course, it'll also check whether the key images have been spent).
This is the most thorough way of knowing that all key images are accounted for, since the wallet will create any that are missing.  In fact, this is arguably the only way for a cold wallet to "know" it reflects an accurate balance, because it has the private spendkey to do the key image work.
If you have an internet-facing wallet which only contains a private viewkey, but does not contain a private spendkey, then this task may be more of a manual process. If you know the key image of a particular deposit, and you think you've imported the key image but you're not sure, you can run incoming_transfers_verbose to see the list of key images currently in the wallet.  See this thread for more details on looking up key images.
Answer: If the view key has been successfully imported you should be able to see your balance.
Comment: I think he meant, how do you tell the difference, ie you see some balance even without importing, for 'virgin' wallets it will be the same after the import, so how can you tell whether you've successfully imported a key image for each output you 'own', spent or unspent.
Comment: @JollyMort Yep.


How does mutation cause natural selection? and is it common in protists or prokaryotes?

Question: Why is it inevitable that evolution by mutations alone should be a common cause of evolutionary change in most natural populations? And do you expect mutation-driven evolution to be more common in typical protists or typical prokaryotes? Why?
Comment: What other causes of evolutionary change are you comparing mutations to? If you get right down to it, **every** change is a mutation of some sort...
Comment: I edited your title because of the close votes- hope this helps - feel free to change this back.
Answer: Your question, as I understand it, concerns the relative role (compare to natural selection and drift probably) of mutation in evolution. But evolution is not one process. Mutation and natural selection are processes that influence populations in very a different manners. At first sight, it seems to me that it does not make sense to weight the important of mutation versus other processes such as selection. But again, in what term would weight these processes?
Answer: Prokaryotes have very high reproductive rate. So, they develop mutants far more faster than multicellular eukaryotes.
Answer: Your question doesn't make a lot of sense.
Mutation is the process whereby new alleles are created, by the DNA chemically changing its sequence.  Natural selection is the process where in a population, alleles change frequency over time due to differing survival rates.  (And there are lots of other kinds of selection, and allele frequencies can change just due to chance, too)
So I don't think "evolution by mutation alone" makes much sense.  In sexually reproducing eukaryotes, variety can be created by mixing and matching different alleles in the population in different combinations, which isn't something that prokaryotes really do, so I guess that's a difference in the importance of mutations between sexually reproducing eukaryotes and prokaryotes.
Answer: A good post about "mixing", which means that a population generally harbors multitude of different versions of a gene, called alleles. So one organism, like a human, has a unique combination of which two alleles out of thousands possible represent each gene in its body. Besides this, major changes are often made not so much by mutations as by changes in the level of gene expression. For example, a mutation in one gene that produces a protein important for regulation of the expression of 50 other genes can cause a lot of change in body development (morphology) and physiology by simply affecting the expression level (amount of protein produced) by these 50 genes. In turn, changed levels of these 50 proteins can make substantial changes in the whole protein interaction network in cells. If you think why sharks look different than elephants, for instance, it's much more because of differential gene expression (including the timing of the expression during body development) than differences brought about by mutations causing functional changes in the coding regions of multiple genes.
And yes, mutations only provide raw material for evolution - diversity to select from. Mutations are a supermarket for evolution, selection is what evolution tends to buy more frequently in this supermarket or what's in demand currently. It is thus selection and drift that work to increase the frequency of certain mutant alleles that actually result in evolution.
The mechanism of selection is simple. The functional diversity in populations created by mutations in particular creates different survival rates for particular phenotypes/genotypes based on how well the combination of the alleles representing its genome can create a phenotype that matches environment. For example, in a bacterial population adapted to neutral media there's still a random diversity in the range of pH tolerance. If the medium becomes more acidic, cells that happen to have better tolerance to low pH gradually increase in frequency over time.
The difference between prokaryotes, like bacteria, and eukaryotes (like humans) mostly lies in that due to meiosis eukaryotes randomly shuffle alleles, so that they "intermix" in a population creating more possible phenotypes to select from. Bacteria do not have this mechanism and can only diverge by cell division, creating diversity only by mutations. However, it is not completely true, as now it is well known that bacteria share a lot of genes via horizontal gene transfer - direct exchange of genes between bacterial cells. This process is often aided by viruses. Horizontal gene transfer, just like meiosis, works to shuffle genes in the population, creating more diversity.
Comment: Can you break up this wall of text?