Why learn scales? What are they for?

Question: I tried Googling but it seems there is no answer for this one. So the internet assumes everyone knows what scales are for? Why should I learn them? Are they important to be a good guitarist?
Answer: Scales are important for a guitarist, just as learning good grammar is important to speaking properly.
If you are intent on "playing" guitar then learning the language of music is going to be inevitable.
From my own personal and teaching standpoint, guitar music should start with Chords.  As opposed to notes.  To me they are the most practical form of music as they are immediate.  Consider chords to be words.
So like a child, you are taught "MUM", "DAD", "YES", "NO" - so you might learn the chords G, C and D.  That may suffice you if all the conversations you will ever want to do on guitar is in the Key of G, eg.   But soon you will want to know other things, like Em, Am and now the intensity and complexity of MORE KNOWLEDGE comes into play.
Well that's where SCALES comes in.  They are the alphabet of the chords that you play.  It can make a difference from a chord progression / accompaniement sounding like "GOOD MORNING" to "GOOD MORNING, HOW ARE YOU? I FEEL FINE!, ISN'T IT A GREAT DAY TODAY?"
Scales can set the tone.  Knowledge of this alphabet allows you to add twiddles and trinkets to your rhythm work... that is, adding little fills based on your knowledge of scale shapes or forms or even better - true music theory where you know whether a particular note is a flat 3rd or diminished 5th and whether it is a Lydian or a Phrygian mode of a scale.   All this KNOWLEDGE of SCALES allows you to set the mood and tone of your playing.
Now the connotation of scales is another thing entirely.  In my mind, metal and hard rock styles have tinged the learning of scales slightly as SCALES often gets equated to SHRED.  But that's not the case.  Even styles like Blues and Jazz and Latin all have their tones and styles completely defined by the SCALES that are dominant in their music structure.
Last week, for example, I was explaining to one of my students the elusive difference of the MAJOR and MINOR scale change of a Blues progression.  This was invaluable information to him - because it now explains what he can hear in records/songs.  He knew there was something going on but he didn't have the vocabulary to explain it - which translates into better technique and conscious choice in what notes to play.
SCALES will lead to understanding; the ability to know and recall relationships between notes; this leads towards understanding the relationship between chords and how this sets an emotional mood; this leads towards understanding good composition and song writing; this leads towards good technique and more interesting rhythm work; this leads towards a roadmap for soloing and knowing various melodies to play over the right chords at the right time; this leads to complete mastery of the guitar.
LEARNING SCALES can do this for you.  It's invaluable and will open up the guitar for you.
Answer: Scales are the foundation to building the chords. Each scale, whether it be major, minor, dominant, Lydian Dominant, Harmonic minor, pentatonic and on, enables you to construct different set of chords, because of its structure, i.e., the intervals between notes of the scales.
In this case scales are then the backbone of chord building and harmony.
And, reversed, when you see the chord and you know from which scale it has been constructed, you can use this scale to improvise or compose a melody over that chord.
So if you see a G7 chord, it's a C major scale chord, or G mixolydian if we were talking about modes. So you can more or less play notes of the C major scale and they will sound good over this chord, but not all of them equally good.
So, you can use scales with melody and improvisation.
Considering both statements above, scale knowledge facilitates composition a lot.
It tells you which note will be diatonic, i.e., a scale notes, and which one will not be, which can be used to build tension for example.
Scales can be thought as one of the systems to organize and get to know well your fretboard.
Many rock, blues, metal players rely on this system solely.
If you are curious, there is the "CAGED" system, based around chord shapes popular amongst jazz players, but there other systems as well.
Answer: I'd also add that practicing scales allows you to concentrate on learning the physical motions of going from note to note (this is why interval practice is useful as well). As with any other physical action, more practice allows you to spend less cognitive resource on "let's see, C to D is that, and D to G is that, and...", allowing you to think, "oh, C-D-G, right", with the notes occurring as fast as you can think them - and as you practice further, without even the subvocalizations of note names: the note becomes the action without your thinking about taking the action at all.
This will greatly enhance your ability to sight-read and improvise, and to concentrate on other aspects of your performance - e.g., tone, dynamics, and expression - because you will have the cognitive resources to do so.
Comment: This is a very important point, and the main reason to practice scales. While the other answers here points out good theory on what scales are, and why they are significant, this answer gives the reason to why you should _practice_ scales. When you can play scales without thinking on what you play, you can play almost anything. This is also the way to improve your speed.
Comment: [This](http://music.stackexchange.com/questions/1995/permuations-or-scales-for-building-up-speed) and
[this](http://music.stackexchange.com/questions/4106/logical-way-to-learn-movable-scales-on-guitar) are questions that have some good advice on practicing scales on guitar.
Answer: I'm not a theorist, nor do I have a proper musical background, but from my experience, scales are the basis for the composition.
In other words:
The scale is the structure and everything moves around it. For example, a guitar solo can follow one or more scales, and for the layman/listener it may seem random notes being played, but in fact those notes follow a structure.
If you would like to be very picky, this structures can be found everywhere, so in my opinion, a scale is a structure that you follow. In an extreme, a very complex solo, that seems it not following any scale, can be following a mix of scales or even variations of scales, but this can be refuted by some, saying that a random play is just that: random... I don't agree, I'm one of those maniacs that think of a structure behind everything :)
Knowing this, if you learn scales, it will help you improve your playing (may it be composing or improvising). Many people try to step out of the normal scales and make variations, that's the beauty of it, because then they sound different but still come from a familiar origin. Mixing scales is also very useful and can give a nice twist to your solo.
Solos aren't the only thing based on scales, a rithm/chord also has the basis on a scale. Knowing scales also helps you with the chords.
I'm probably not very accurate/may not have used the correct terms, but I think this answer will at least contribute with the view of a self-learnt player (someone more theoretical will give you a better answer).
Answer: Let's take one scale, C major, C, D, E, F, G, A, B, chosen so we don't have to deal with majors and minors and naturals and all that confusion. You may know that as "do rey me fa so la ti do".
Let's take every other note, C, E, G. Those are the root, third, and fifth, the building blocks of chords. Skip forward a few to F. F, A, C. One more, to G. G, B, D. Those are the root, fourth and fifth chords. I, IV, V are the three major chords, which are all you need for a whole lot of songs. The same processes will get you D minor, E minor and A minor. Plus B diminished, which is beyond what I want to handle today.
A rule of harmony is that, for every note in a melody, you play a chord that contains that note. (Not everything does this, but it's a way to work it.) So, "Twinkle Twinkle Little Star" is C C G G A A G | F F E E D D C. First, once you have a sense of the scale, you can identify it as part of the C major scale. (Actually, I think I could have hit this part first, but ahh well.) So, chordally, you might play the chords C C G G F F G over those notes, or C C C C F F C. C C G G Am Am G. C C Em Em Am Am G. All sorts of fun choices.
So, knowing scales help you know how to take apart a song and know what you can play behind it.
Comment: I found this the most helpful in a similar question of mine, since it had a worked-out example.
Answer: Two points to complement the other answers:

Playing one note at a time, whether in scales, arpeggios, melodies, etc., helps you fine-tune your sound/tone.
Especially when you are new to the guitar, practicing various scales can help strengthen your fretting hand and will allow you to move between various chord shapes/voicings more easily.
Answer: As a practical observation, when my guitar students obviously and consistently practiced their scales, all their skills appeared to improve. When reading music, knowledge of where the notes should be was improved by knowledge of the scales.
When playing notes the practice of scale playing (Typically more repetitive and intense muscle work then learning to play a melody/riff etc.) improved the dexterity in both right hand and left. Such practice helps on getting the timing of finger placement to be more precise (use a metronome for greater effect). The left hand needs to be in place before the note is plucked by the right, but if it is too early and you interfere with the previous note. Finger placement effects the tone of your playing.
It is actual physical exercise for your fingers. The finger strength improves and control of your fingers improves. Your speed and precision improves. I would sometimes note an improved ability for students to play barre chords.
On truly special occasions I have noticed these differences from one week of a student's practice. It can take students longer to notice the same results.
Never mind that the direct knowledge you get from scales allows you to do a better job making up music (improvising or composition), and picking up music by ear (ear training, and playing by ear).
Scales multiply the power of all other practice, when you consistently practice them. It is like normal exercise however: when you slack off in your practice the benefits atrophy. For best/intense results, spend 15 minutes a day or more working a variety of scales and sequences (ordered patterns within scales). If you feel pain in your wrist or forearm, then stop practice for the day and perhaps the next to prevent injury.
Comment: I'm a banjo student, and this has been true for me.  Although scales don't seem to have anything to do with playing music, that's an illusion: my playing improves to the extent that I practice scales.  My fingers are more sure of themselves, it's easier to plant them accurately even when moving up and down the neck, and the notes I play sound better.
Answer: When I was a kid I learned to play piano first, then a bit of trumpet, then picked up guitar in my teens. Piano taught me to read scales, and I learned a bit about how melody and chords work. Guitar is my favorite, and I played it in jazz, country and rock bands for years.
I decided to take some music theory classes at the local community college, which, with what I'd learned from my jazz and piano, really opened up my understanding of what makes music work, and allowed me to be a lot more expressive.
Instead of guessing what notes would work, or learning riffs without understanding why they sounded good, I knew what a riff did, how to transpose it, enhance it, modify it to fit with a different scale, etc.
In other words, my understanding of what makes all music tick suddenly grew, and it's made me a lot better musician, and gave me a lot better appreciation of more forms of music.
Knowing scales and how they fit with chords gave me the tools to try to sound like me, not like someone else, and what I play is mine, not someone else's riffs regurgitated. I like that a lot.
Answer: I am an amateur piano player, took lessons for 6 months...been playing for 3 years not. My instructor did not bother having me learn scales, due to my age(60). We went right into learning songs.
However, I taught myself the major scales in one night;
just remember "fat cats go down alleys eating birds", and "beadg". This makes it very easy. Do some research for a more detailed explanation; Google "circle of fifths" and read and understand it. That is what I did.
You will have spent more time worrying about learning them, than it takes to learn them. Good luck to you.
Answer: You are playing a guitar. All the notes on your guitar (piano etc) are in a scale - the chromatic scale. From my outside perspective if you play some notes together it is a chord, and if you play tunes on a restricted set of notes (ie not playing all the notes) that would be a scale. If you use the same set of notes again you will save time by giving the scale a name to help remember it. If you play with other people, as they all call those scales the same thing it might help to learn their names for scales.
 I worked out the maths of music in the 1980s and I would argue that there are 57 main Keys based on 7 scales (I'm sure many people here would argue about that) but you would want to learn one scale at a time. Once you can play a scale pattern you can slide the same pattern along the neck by one fret (or more) to play in a new key (still the same scale though - keys are named after the note they 'start' with, scales can start anywhere). Good luck with your music.

Why learn scales? What are they for?


Why did this character in Prometheus kill without apparent reason?

Question: At the end of Prometheus, why did the Engineer kill the humans? What is that thing that killed the Engineer?
Comment: Edited the title to clarify that 'Alien' means 'Engineer' not the creatures from the Alien franchise.  ALso, please keep spoilers from the title of a question.
Answer: The Alien you are saying is actually an "Engineer" and they developed the so called "parasite plague" to end the planet earth (which they created in the first place).
If you remember the alien or parasite plague agent that killed "engineer" was forcefully taken out by Elizabeth (Eli) from her stomach in the med pod. She actually froze it using decontamination gas of the med pod but it survived and tried to come out of that room at the end and the "engineer" was accidentally present there at the same time. The alien killed the engineer and supposedly impregnated him and that's why you see a new alien born at the end of the movie.
Check this post which gives an insight into the whole plot.
Answer: So I have been doing a lot of thinking and I realized that Elizabeth wanted to kill the alien inside of her as soon as she found out about it. Maybe the engineers made us by mistake just as Elizabeth and Holloway did. Maybe they thought they would create something else!


Are barberries edible?

Question: Barberries are so common around here that there would be enough for a fruit serving a day for quite a while. But there is a problem: I do not know whether or not they are edible. Are they edible in any quantity?
Comment: Where do you live?  Also, do you know which species of barberry you have near you?
Comment: I am in southeastern PA. I actually have no idea what species it is.
Comment: That's cool.  What color are the berries?  What month do you usually see the blooms?  (Tryin' to figure out what species you might have, though I've read so far that most of them are edible.)
Comment: The berries are red and elongated, about 1/4"x 1/8".
Answer: I often found myself following these steps from Lofty Wiseman's Survival Guide, even though I was not in a life or death emergency situation, and never had any problems. It allows you to safe check all vegetation. These methods have proved themselves on several occasions during my time in the army.
I am not encouraging anyone to use this method in a non-survival situation, unless he/she feels comfortable doing so.
Always adopt the following procedure when trying out potential new food plants, only one person testing each plant. NEVER take short cuts – complete the whole test. If in any doubt, do NOT eat the plant. Should stomach trouble occur, relief can be gained by drinking plenty of hot water; do not eat again until the pain goes. If it is severe, induce vomiting by tickling the back of the throat. Charcoal is a useful emetic. Swallowing some will induce vomiting and the charcoal may also absorb the poison. White wood ash mixed to a paste with water will relieve stomach pain.
INSPECT
Try to identify. Ensure that a plant is not slimy or worm-eaten. It will be past its best, with little food value other than the grubs or worms upon it. Some plants, when old, change their chemical content and become toxic.
SMELL
Crush a small portion. If it smells of bitter almonds or peaches – DISCARD.
SKIN IRRITATION
Rub slightly or squeeze some of the juice onto a tender part of the body (under the arm between armpit and elbow, for instance). If any discomfort, rash or swelling is experienced – DISCARD, reject in future.
LIPS, TONGUE, MOUTH
If there is no irritation to the skin proceed in the following stages, going on to the next only after waiting five seconds to check that there is no unpleasant reaction:
• Place a small portion on the lips
• Place a small portion in the corner of the mouth
• Place a small portion on the tip of the tongue
• Place a small portion under the tongue
• Chew a small portion
In all cases: if any discomfort is felt, such as soreness to the throat, irritation or stinging or burning sensations – DISCARD, reject in future.
SWALLOW
Swallow a small amount and WAIT FIVE HOURS. During this period eat or drink NOTHING else.
EATING
If no reactions such as soreness to the mouth, repeated belching, nausea, sickness, stomach pains, griping pains in the lower abdomen or any other distressing symptoms are experienced, you may consider the plant safe.
WARNING
POISON! There are two fairly common poisons in the plant world, but both are easily detectable:
Hydrocyanic acid (Prussic acid) has the taste and smell of bitter almonds or peaches. Most notable example is the cherry laurel (Prunus laurocerasus), with laurel-like leaves, which contains a closely allied poison. Crush the leaves and remember the smell. Discard ALL plants with this smell.
Oxalic acid, whose salts (oxalates) occur naturally in some plants, for instance wild rhubarb (mostly in the leaves) and wood sorrel (Oxalis acetosella). Recognizable by the sharp, dry, stinging or burning sensation when applied to the skin or tongue. Discard ALL plants which fit this description.
• AVOID any plant with a milky sap, unless positively identified as safe (such as dandelion).
• AVOID red plants, unless positively identified, especially in the tropics. The red-streaked stalk of wild rhubarb is edible but its leaf is poisonous. Hemlock has reddish-purple splotches on its stem.
• AVOID fruit which is divided into five segments, unless positively identified as a safe species.
• AVOID grasses and other plants with tiny barbs on their stems and leaves. With a magnifying glass you can see them as hooks rather than straight hairs and they will irritate the mouth and digestive tract.
• AVOID old or wilted leaves. The leaves of some trees and plants develop deadly hydrocyanic acid when they wilt – including blackberry, raspberry, cherry, peach and plum. All may be safely eaten when young, fresh and dry.
• AVOID mature bracken (Pteridium aguilinium). It destroys vitamin B in the body, setting up a peculiar blood condition which can cause death.
Answer: Yes, although they can be a bit sour. They are popular in Persian cuisine, where they are known as zereshk.
Comment: Can you flesh this out any?  I know it's a simple yes no question, but other topics to cover to make this more complete for the outdoors would include:  Are there any similar looking plants such that it could be easily misidentified.  Do you have to make sure they are completely ripe and if so, how do you know?  etc.
Answer: I have bought dried barberries for cooking at Persian stores for many years.
One Green World has two varieties that can be bought for the fruit.

Are barberries edible?


What is the significance of negative frequency in Fourier transform?

Question: What is the significance of negative frequency in Fourier transform? Why we include the band widths of the negative frequency also while calculating band width of the signal.
Comment: Isn't frequency in a Fourier transform imaginary? Why should +i be any more real than -i?
Comment: @PeterShor, if the frequency were imaginary, it wouldn't need an *i* (or *j* if you're an EE) in front of it.  Recall:  $e^{i\omega}=cos(\omega) + isin(\omega)$.  $\  \omega$ is *real*.
Comment: You can actually observe the negative and positive frequency components appear (shifted in frequency) as the sidebands due to amplitude modulation:  http://en.wikipedia.org/wiki/Amplitude_modulation#Spectrum
Answer: If you have a real function of time $x(t)$, which may represent, for example, a modulated carrier, you can, if you wish, avoid negative frequencies by using the Fourier Sine Transform $$X_s(\omega)=\int_{-\infty}^{\infty}{x(t)\sin\omega t dt} $$  and Fourier Cosine Transform  $$X_c(\omega)=\int_{-\infty}^{\infty}{x(t)\cos\omega t dt} $$ because then, the inverse transforms can be written (ignoring factors of 2s and $\pi$s): $$x(t)=\int_{0}^{\infty}X_c(\omega)\cos \omega t + \int_{0}^{\infty}X_s(\omega)\sin \omega t $$ i.e no negative frequencies are present.
However, it's much neater to work with the complex exponential representation of modulated signals. A generic modulated signal, in the time domain will have its amplitude and phase varying as a function of time $$x(t)=A(t)\cos(\omega_c t+\phi(t)) $$ We can write this as the real part of a complex signal $$ x(t)=\Re\{A(t)\cos(\omega_c t+\phi(t))+jA(t)\sin(\omega_c t+\phi(t))\}$$  Now I could have written any old rubbish in the imaginary part, and the formula would still have been correct, but the choice I made makes it extremely convenient - mainly because I can write it in exponential form $$ x(t)=\Re\{A(t)\exp(j(\omega_c t+\phi(t)))\}$$  and this makes it really easy for me to "factor out" the carrier frequency  $$ x(t)=\Re\{X_B(t)\exp(j(\omega_c t))\} $$ where $X_B(t)$ is the "baseband equivalent" signal.  "Baseband" meaning "effectively at 0Hz carrier frequency".  The baseband  equivalent signal is just $$X_B(t)=A(t)\exp(j(\phi (t))) $$ and is complex and contains the "interesting" information contained in the modulation (the carrier itself being not so interesting!).
Working with these exponential forms, it now seems much more natural to define the Fourier transform in terms of exponentials in the normal way: $$X(\omega) = \int_{-\infty}^{\infty}{x(t)\exp(-j\omega t)}dt $$  together with the inverse transform $$x(t) = \int_{-\infty}^{\infty}{X(\omega)\exp(j\omega t)}d\omega $$ The Fourier transform of the baseband equivalent signal $X_B(t)$ is not symmetric about zero - you can't specify it by giving its values for positive frequencies and invoking symmetry.  So if you want to work with this formalism then negative frequencies are fundamental.

The actual spectrum of the signal centred at $+\omega_c$ is the one you'd get if you swept a very narrowband filter over the frequency range.  It's not necessarily symmetric about $+\omega_c$ and this gets translated to the complex baseband one (shown dotted) which is now not symmetric about zero, so negative frequencies are needed.
Answer: Choose a square root of negative one.
And now throw it out because statisticians hate complex numbers and negative frequencies, and never use them if we can help it.  For us, the power spectrum really measures the variance of the data, we use the word «power» because these concepts were started by physicists and engineers who were studying light or signals.  The power spectrum is a kind of analysis of variance, which attributes different parts of the variance of the data to the different frequencies.  There is no such thing as imaginary data, ummm, well it should be stamped out of course, it's fraud... and no such thing as non-commutative data...
If we look at the power spectrum (even of light, even in optics) the phase makes no difference, so the distinction between polarised one way or another way is irrelevant.  And the actual lab analysers measure the power, ignoring the phase.  (But if one is measuring cross-correlations between two different light beams, then the relative phases do make a difference since they affect the coherency of the two beams with each other.)
So there is no need to use complex numbers and Shuster did not do so.
The only reason negative frequencies would be needed is if you use complex numbers instead of sines and cosines.  Now many scientists prefer to use complex numbers because it makes the proofs simpler, it makes the Fourier inversion formulae more elegant, and more manageable too, and it encodes the phase information in the angle of the complex number.  But then this has the disadvantage that when you want to translate it back into the actual physical terms your lab bench instruments put out in the print out, you always have to combine the contributions due to the positive frequency $\lambda$ with those due to the negative one $-\lambda$ simply because $\cos (\lambda t)$, which (along with its phase shifted sine term) is made up out of two complex exponenetials, one with positive frequency and one with negative frequency, viz., $e^{i\lambda} + e^{-i\lambda}$.
Your initial choice of a square root of negative one, which was arbitrary, is reflected in the choice of a direction of motion in time.  (The same formula for the propagator will propagate you backwards in time if you choose the other square root, but then you can call backwards «forwards» and then that fixes everything...if you are a theorist...)
Answer: All monochromatic waves can be made from the linear combination of two counter-rotating helical waves,
$$ c\, e^{i f t} = \frac{a}{2} e^{i f t} + \frac{b}{2} e^{-i f t} ,$$
where $t$ is the time, $f$ is the frequency, and $a,b,c$ are complex.
In optics, positive frequencies (the first term) represent right-hand (dextro) circularly polarized light, and negative frequencies (the second term) represent left-handed (levo) circularly polarized light. Circularly polarized light carries angular momentum that causes a torque when it is absorbed. The sense of the torque corresponds to the sign of the frequency.
Linearly polarized light consists of two equal but oppositely rotating helical waves. Linearly polarized light does not carry angular momentum because the angular momenta of the two counter-rotating waves cancel.
Comment: This is plainly wrong. The LHS of the displayed equation is a solution of the ODE $(\partial_t-if)g(t)=0$ and the RHS is not. The post bumblingly tries to get at concepts that are ultimately correct, but their realization here isn't.


Can you use a wormhole to travel through space not time?

Question: I want to know if you could theoretically travel from your house to work via a wormhole but stay in the present day...without changing time. Kind of like teleportation but harnessing the energy of a black hole or wormhole. My background is chemistry not physics so I'd prefer a mathematical explanation. Thanks.
Comment: Related: http://physics.stackexchange.com/q/19754/2451
Answer: Any motion in "space" is between an entry and an exit point. If the wormhole is a handle linking two distant regions, you will enter at one point and emerge at another. The entry and exit events can have three possible relations:

The exit is strictly past of the entry
The exit is spacelike from the entry (you move in space to a distant location faster than light).
The exit point is to the future of the entry point.

Possibility 1 allows you to kill your grandfather. Possibility 2, together with relativity, is tantamount to possibility 1, since you can boost the two exits of the wormhole and make another copy of the wormhole boosted in the other direction, and by traversing the two copies suitably, you can rearrange possibility 1. So the only sensible possibility is possibility 3.
But in this case, the two ends of the wormhole are always causally linked--- you can't separate the entry and exit so that they are spacelike to each other. This means that the wormhole is nothing more than a room--- it is equivalent to entering and exiting the same region later, and there is nothing mysterious at all going on.
Such wormholes are known to exist in the extremal continued Reissner Nordstrom solution (charged black hole) and the exactly analogous Kerr solution (rotating black hole). The maximal extension of rotating/charged (or rotating and charged) black holes are tunnels to other branches, and the only barrier to crossing the tunnel is a Cauchy horizon which is possibly singular.
The Cauchy horizon in exact solutions is not singular at all, you just cross it. But Penrose speculates that the full solution will become singular as matter piles up on the Cauchy horizon (which sees the entire future of the black hole). This picture has not been supported by detailed calculations, which show the Cauchy horizon is a little hard, perhaps like a potential step, but not singular enough to disallow matter from crossing.
The result is that crossing a charged/rotating black hole is entering and leaving a "wormhole" that just spits you out of the same black hole. It has to be in our universe, since there is no information loss. Nobody knows how this works in detail, because the actual process classically spits you out in another universe.
That the "other universe" or wormehole interpretation is nonsense can be seen by a simple physical argument--- if you have two ends of a wormhole, they have to have matching radius, since they are continuations of each other. If you throw an object in, it increases the horizon area as it crosses, and when it leaves the other side, it decreases the horizon area, so they no longer match. The only sensible resolution is that it leaves in the same patch it enters, which means that strictly speaking, in a Penrose diagram, it crosses its own past. But if the traversal time is always positive, the outgoing object will not be able to see its incoming version, since it will already be behind the "brick wall" when the object comes out.
This resolution is not believed by anyone except me. Other people believe something must be going on in the interior to make the Cauchy horizon singular, so that the black hole is a one-way surface.
Comment: You just crushed my dreams. No suitable space-faring wormhole-aided travel.
Answer: I believe that space cannot be isolated from time once matter enters the wormhole. Time is bound to the third dimension, so time would enter from the same point of matter (the end assumes the nature of the entry, compromising the wormhole's integrity); kept open I believe it would behave as a tube as long as the wormhole (similar to last, post but less specific). I thought about having a wormhole inside of a wormhole to keep the integrity of the outer tube, but you are still compromising the inner tube and ignoring any effect from the outer tube. I believe that anything that enters physically brings space/time with itself by definition: either it doesn't enter, or it doesn't exit.
Answer: According to current knowledge no wormhole allowing survival durning passage can exist, so - no.
Comment: I think they can, as long as you keep yourself heavy. Kip Thorne has described this by talking about a "lead lifesaver ring" that reduces the effect of tidal forces. Unless you're talking about the fact that wormholes break off within the Planck time. That can be fixed by an infinitely advanced civilization by using vacuum fluctuations.
Comment: This is just plain incorrect--- ordinary Reissner Nordstrom wormholes are traversable, unless the Cauchy horizon is a singularity, which is unsupported by current calculations.
Answer: In fact that's the only way to use a wormhole. You won't stay exactly in the present time, you'll go a tiny bit into the future, since a wormhole takes some time to traverse as well. Then again, time is relative; but basically you won't go too far. Remember, wormholes are still hypothetical, and theory predicts their properties but not how they may be generated.
Any wormhole that can travel through time destroys itself, as a beam of vacuum fluctuations (virtual particles) will circulate through it, building upon itself till it reaches infinite intensity and destroys the wormhole.
A black hole would be a Very Bad Idea. Unless all black holes are wormholes (unknown; doubtful), you'd be spaghettified and reduced to a singularity. Not a good way to go. Not a good way to go to work, either :P.
I myself can't give a mathematical explanation; but I fail to see why a chemist would want one. All this stuff deals with tensors and whatnot, and gets pretty confusing to a non-physicist. I've come across statements like this: "consider a four-dimensional matrix of four dimensional matrices". Ouch.
Comment: Spinning or charged black holes of sufficiently large mass will not cause sphagettification, and the singularity actually is repulsive in its neighborhood.
Comment: @JerrySchirmer Isn't it unknown about the insides of spinning/charged holes?
Comment: No less so than the massive case.  You can see it discussed in Wald of MTW.
Answer: No, but not because of anything special about the wormhole itself. The problem is with the implicit idea of simultaneity you have invoked.
Travelling some distance will inherently mess up the idea of when 'now' is.
Depending on the observer's reference frame you will arrive before you left, after you left and simultaneously with when you left. And each observer would be "right" in some sense.


X does not start after removing parameters quiet splash

Question: I would like to remove the splash screen. Kubuntu 12.04 runs on my laptop with KDE 4.11 (I use the backports offered by the Kubuntu community).
In order to remove the splash at boot time,  I removed the kernel parameters quiet  splash in /etc/default/grub and did execute update-grub.
However, the result of this is that X does not start correctly anymore. I end up at the console login prompt. I can login and execute startx, which brings me to the KDE desktop.
Of course, this behaviour was not intended by me. How can I solve this issue?
Edit: I reverted the grub config file, i.e. added the parameters quiet splash again, which results in a correct boot (without boot messages).
Answer: Interesting. Did you edit /etc/default/grub from GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to GRUB_CMDLINE_LINUX_DEFAULT="" I have Ubuntu 12.04 with KDE 4.11 using backports and I removed the parameters. It starts correctly.


What are "Implied Odds" in Texas Hold'em Poker?

Question: What are "Implied Odds" in Texas Hold'em Poker?
Answer: Implied odds or implied pot odds are calculated the same way as pot odds, but consider future betting. You figure implied odds in situations where you expect to fold in the next round if you don't make your draw. You lose no more bets if you miss, but can expect to gain extra bets if you hit the draw.
An example. Say you see the flop with 2 other players acting before you in a NL game. You flop a gutshot straight draw. The first player bets and the second calls and now the pot is laying you 7:1. For a gutshot you want 10:1 or better; however, if you hit your straight on the turn, you stand to stack off one or both of your opponents. Thus your implied odds are considerably greater than 7:1, so you call.
Implied odds with a flush draw can be dicier. Namely because you can hit your flush on the turn and that kills the action. And your implied odds.
The example is a very simple one. If you were in the same scenario, but 2nd to act instead of last; you would be in a much different situation in that the last player could raise and ruin (or not) your implied odds. Additionally, stack sizes matter. If your opponents are short stacked you may not have the odds for the call. So, when considering implied odds be very aware of the situation.
Answer: While @wdypdx22's definition is correct, implied odds cannot be explained completely on a Q&A site.  To fully understand the concept requires an immense amount of study and you will spend the rest of your life refining them.
A better example of when they effect the outcome of the hand more is for hidden draws.  For instance, if two to a suit come up on the flop, but the turn and river give you a runner runner straight, your opponent is far less likely to put you on the hand you actually made and pay you off more.
Calculating implied odds is more of an art than a science.
Comment: Exactly! As I completed the answer I realized that I'd waded into deep mud... :~) I play in live games and I've chuckled many times when overhearing a player comment on how they had the implied odds to make a call...
Comment: You overhear that sort of remark ***often***??!!! (and, were you intended to overhear it?)
Answer: Consider calling a weak tight players preflop raise with a small pocket pair at Holdem. You only intend to continue in the hand if you flop a set. You will make a set about 1 time in 8. The amount of money you will win on average each time you flop a set needs to be at least 7 times your investment to justify calling and playing he hand this way because for every time you hit your set you will miss it seven times.
You are being laid a price to call a small amount now to win the pot plus extra action if you connect. That price (taking into account the expected future action) is your implied odds.
Most people over estimate their implied odds - you won't always get very much when you hit and hitting doesn't guarantee winning the pot.
Answer: Implied odds vary greatly between limit and no limit hold 'em. In either case, they occur when you are drawing to something like a straight or flush, particularly after the "turn" (fourth) card.
In limit, if you make your hand on the "river" card, and bet, you can pretty much count on each opponent to call your hand for one more (big) bet, to "keep you honest." Hence, you can mentally add these "implied" opponents' calls of your fifth card bet in calculating the size of the pot as of the fourth card.
No limit is trickier, and depends on the character of your opponents. Some (timid) NL players will call nothing after the fifth card if it looks like you made your hand. Then your implied odds after the fourth card are the same as the pot odds.
In other cases, you will have HUGE implied odds if a novice or reckless player "goes for broke" betting (or calling) that you're bluffing after the fifth card.
Most likely the result will "intermediate" to the two above. In any case, your implied odds after the fourth card depend on your ability to charge "what the market will bear" after the fifth card.


Extending Wald's equation to two classes of i.d. random variables?

Question: I try to adopt Wald's equation to a slightly more complex problem. In fact, after a full day, I found some solution now, but it has a confusing argument in the middle. Perhaps somebody can help me at that point? Perhaps I am even wrong with my conjecture? If the conjecture holds, it is a quite helpful tool.
Let $(X_n)_{n\in\mathbb{N}}$ be a series of real-valued random variables from within $[-c, c]$ for some constant $c$. They are neither independent nor identically distributed. However, there are only two different types of distributions: $A$ and $B$. Whether $X_i$ belongs to $A$ or $B$ depends on the realization of $X_i$ and all other $X_j$'s, thus, there is no fixed assignment to these classes, i.e., each realization also defines some random labeling $\ell: \{X_1, X_2, \ldots, ...\} \rightarrow \{A, B\}$, where I write $X_i \in A$ for $\ell(X_i) = A$. For example, it might be that $X_1, X_4, X_5, ... \in A$ and $X_2, X_3, X_6, ... \in B$, while for another realization the $X_i$'s might be mapped totally different. Further, let $T$ be a stopping time for $(X_n)_{n\in\mathbb{N}}$. Thus, the event $\{T \geq j\}$ does only depend on $X_1, \ldots, X_j$, but is independent of $X_{j+1}, \ldots$.
I am interested in an upper bound on $\mathbb{E}\left(\sum_{i=1}^T X_i\right)$. Since the $X_i$'s are not i.d., it is not possible to apply Wald's equation to get something like $\ldots = \mathbb{E}(T)\mathbb{E}(X)$.
For deriving a similar result, I already have that $\mathbb{E}\left(X|X \in A\right) < -2$ and $\mathbb{E}\left(X|X \in B\right) < 1$. Further, I have that $|B_T| \leq |A_T|$, with $A_T := \{X_i \in A | i=1,\ldots,T\}$, and $B_T$ analogous. Thus, it is intuitively clear, that an upper bound should be given by $\mathbb{E}\left(\sum_{i=1}^T X_i\right) < -\mathbb{E}\left(T\right)/2$, since any positive contribution ($<1$) of some random variable in $B_T$ is overcompensated ($<-2$) by some other in $A_T$, and we have that $|A_T|=|B_T|=T/2$ in the worst case. In fact, I suppose that it holds that
conjecture: $\mathbb{E}\left(\sum_{i=1}^T X_i\right) < \mathbb{E}\left(|A|\right) \cdot \mathbb{E}\left(X|X \in A\right) + \mathbb{E}\left(|B|\right) \cdot \mathbb{E}\left(X|X \in B\right)$.
It is easy to show a similar result for fixed $T$, but things get very complicated for $T$ being a stopping time.
So, perhaps you already know a solution to this? Then please share your knowledge!
Here is my approach incl. the confusing detail: With $N_a = |A_T|$ and $N_b = |B_T|$ the random variables with $N_a + N_b = T$, and from above $N_b \leq N_a$, we have that:
$\mathbb{E}\left(\sum_{i=1}^T X_i\right) = \mathbb{E}\left(\sum_{i=1}^{N_a} X_{a(i)} + \sum_{i=1}^{N_b} X_{b(i)}\right) = \mathbb{E}\left(\sum_{i=1}^{N_a} X_{a(i)}\right) + \mathbb{E}\left(\sum_{i=1}^{N_b} X_{b(i)}\right)$, where the indices $a(i)$ and $b(i)$ partition the indicies $1, 2, \ldots$ in order corresponding to $A$ and $B$, especially, $\{X_1, \ldots, X_T\} = \{X_{a(1)}, \ldots, X_{a(N_a)}\} \dot\cup \{X_{b(1)}, \ldots, X_{b(N_b)}\}$.
Now I think that the following argument is correct, but I have some doubts about it (and not the deep understanding or a formal method to prove it):
claim: $N_a$ is independent of $(X_{a(N_a)+i})_{i\in\mathbb{N}}$.
(same for $N_b$).
If this argument is correct, then we can just apply Wald's equation for the both sums independently, and get the final result.
But: I somehow get lost in accepting that this independency holds, since it might be that for example $T \gg a(N_a)$. Thus, $N_a$ somehow also depends on the fact that $X_i \in B$ for $i \in \{ a(N_a)+1, \ldots, T\}$. But, on the other hand side, this dependency is totally transparent due to seperating all these random variables into two separate 'streams'. Further, there 'should' be no dependency on $X_{a(N_a+1)}$ and later, since $a(N_a+1) > T$.
Do you see the reason for my confusion? Perhaps can you help me with that? Further, I read something about filterings in this context (although this concept is totally new to me), perhaps something like that can be applied here?
Answer: After carefully reviewing this question, I was able to work out the details and answer it by myself: The above claim is ill-formulated.
For applying Wald's equation to each summand, one would need that the event $\{N_a = j\}$ is independent of $(X_{a(j + 1)}, X_{a(j + 2)}, ...)$, not just independency of indices above $a(N_a)$.
Well, and unfortunately this is not satisfied, since indeed $\{N_a = j\}$ also depends on $X_{a(j + 1)}, ..., X_{T-1}$, thus, on the remaining part up to the stopping time $T$.
Thus, without additional assumptions, especially on $\ell$, it is more than doubtful whether just grouping the random variables by their distribution $A$ or $B$ and counting the number of each type leads to the above conjecture.


www subdomain for my webpage

Question: How many customer do I lose if my webpage is not accessible from www subdomain. Can anyone who has webpage analytics with large number of visitors provide me statistic how many users use www.domain.com and how many only domain.com? Thanks a lot
Answer: Not too many.
Most modern browsers (chrome, ie10, safari) will do a dns correction for you.
So if you type in www.yoursite.com but a www record does not exist, then they will try their best to figure out the correct place to send your visitor.  IN browsers that have search/address bar like chrome, the worst case is that google or whatever search is set as default will come up with results that put you at top.
Now, there is no reason to do this. In almost all hosting scenarios you will be able to redirect www to non www or vice versa.  If you are on IIS (windows) or Apache or Nginx all three support rewrite rules that can set this up for you almost instantly.   These are done with 301 redirects, which tell the browser that the site has been permanently moved.
If you tell us what type of server you are on, we can probably help you out.   In some scenarios (windows azure, heroku, and EC2 without a static ip), you will have to get a little more creative with dns to resolve this issue.  This is because they do not allow redirecting of naked domains, and dont always offer a static ip address.   In those scenarios dns redirects are used where the dns records are set to mirror or auto update.
Comment: thanks for answer. I know, how to set up environment to be accessible with / without www.
Is there any statistic that can provide me information how many users use it with www and how many without?

www subdomain for my webpage


Non-displaying objects in illustrator and photoshop

Question: So I'm trying to set up templates for other designers to use to adhere to design guidelines, and I want to know if there is any way to specify objects in illustrator and photoshop that do not show up when the image is exported or printed. I know it is possible to make non-printing objects in photoshop, however I would like the objects not to show up when using save for web or exporting a pdf/eps also.
Answer: Illustrator:

Create a new layer
Add stuff to layer you want visible, but not exported
Go to View > Guides > Make Guides

This outlines everything in a new color, locks the layer, and doesn't save for web or export.
Photoshop:
There isn't anything like the guide layer in Photoshop. However, you can add notes:

Click and hold on Eyedropper tool to expand sub-menu.
Select Note Tool
Click on screen and enter a note.
Answer: The fact that non-printing items export for web is a bug in my opinion. I'm not aware of any way around it.
I isolate anything extra on a dedicated layer(s). I've had very little trouble with the approach using a distributed team of designers.
Standard UI items, color palettes, brand elements, grids, notes, whatever, it's all there. I tag the layer "extras" with sublayers for different categories of items, when appropriate. When some items need to be below the main art, I just create another layer called "extras-SomethingOrOther".
The trick is to get designers used to looking for the extras layer(s) when they open a file. They should check there first for any instructions or guidelines, then deactivate it when they have things set-up properly. Usually the layer has so much on it that it's easy to remember to deactivate it.
The thing I like about this isolated layer approach is that I don't have to worry about required elements accidentally ending up with a "no print" attribute.
Answer: Illustrator has multiple options for layers: lock, non-printng.
You can display the following dialog by double-clicking on the layer:
http://screencast.com/t/hipAF1jS
Photoshop does not have the non-printing option, you can only lock layers.


What page numbering conventions are there for front matters (prelims) of books?

Question: When a book uses arabic page numbering, the usual habit is to treat the front cover as a page number 1, and start the book itself by page number 3. However, sometimes the front-matter of the book is numbered seperately by roman numbers. In such case, should the first page be i = 1 or iii = 3?
Answer: In my experience it depends upon binding.
If a piece is a self-cover, then often the cover will be considered page 1. In addition, if there is no table of contents or forward, or other information not directly related to internal contents, there would be no need to number differently.
If a piece is not a self-cover, contains a table of contents, or a forward, or prologue, then I often start the front matter with lower canse roman numerals (i, ii, iii, iv) and begin content with page 1.
One aspect many forget is that page numbering should always begin on the right side page for US/English left to right reading content.
Comment: There _is_ a need for seperate front-matter numbering. If I didn't have ToC or forward or so, I wouldn't have a front-matter at all, would I?
Comment: Sometimes there are simple publication copyright and date pages with an extra internal title page. Those aren't traditionally numbered in any sense, but could comprise 3-5 pages of front matter. You seem poised to argue with any answer :)
Comment: Sorry, I do not argue, I only try to explain myself in more details. My apologies for sounding negative.
Answer: There is some variation in this technique. The cover itself is often left out of the numbering. One tradition is to start the numbering with the inside front cover, often the title page.
There's no reason the numbering tradition should change based on the numbering style.
Answer: Front matters (a.k.a prelims) of hardcover and some softcover books produced in a traditional fashion comprise:
A) Page 1: The half title page (always on the right side of the page spread)
B) Page 2: The back side of the half title page, called the half-title verso.
C) Page 3: The main title page (always on the right side of the page spread)
D) Page 4: The imprint page (which is the main title verso)
E) Page 5–x: The table of contents
F) Page y: dedication and/or acknowledgements
G) Page z: preface/foreword
Paperbacks and self-produced books may omit the half title page and its verso (reverse side) – it's a relict from an earlier era of book production when books were shipped only with a paper jacket. Nowadays it's for the tradition. If omitted, the page count starts with C., the main title page.
If you choose to use separate page numbering for the front matters, you use Roman numerals.
However, the page number is not printed on any of the title pages and their reverse sides (A–D), they are counted nonetheless. So the next page after the imprint page would be paginated V (or III, if you omit the half title page.)
The new page count of the main text part starts with 1, but the page number is not printed on the first page if page numbers are positioned at the top of the pages.

Partly based on two German books about book production and typography:
Blana, H. (1991). Die Herstellung
Gulbins, J. & Kahrmann, C. (1992). Mut zur Typografie
Answer: English-language books most commonly begin page numbering on the half title page, unless that is omitted (as in some soft cover editions). Lowercase roman numerals are the standard for front matter folios. These are strong conventions, particularly for non-fiction works.
When you are working with a publisher, there will usually be a house style that you will follow. Otherwise, the best advice is to stick with the convention. The two most commonly used style references in North America are the Chicago and Associated Press. The excellent New Oxford Style Manual is the gold standard for Commonwealth English.


What is the acceptable success score for user testing?

Question: I'm just wondering how high of a success rate does the outcome of a user-testing have to be before you can consider it successful. I know that 100% is the target but if time and budget are limited, what's the minimum acceptable score? Given that 100 is the highest possible score.
Comment: There are way to many unknown variables here to just throw out a specific number. The point of a usability test isn't necessarily pass/fail the product but rather to find areas of the product to improve.
Answer: Why do you want to test?
Typically, usability analysts test a product's usability to see if the mental model works, if the workflow works, if the interaction (controls) are discoverable, if a task can be completed within a certain time, how many participants succeed at a given task (which is what you're after, I think), and so on.
The answer, as usual, is "It depends."

How critical is the task? (What's at stake if the user fails?)
How fast must the task be completed correctly to be deemed a success?
If the user fails, will they recognize the failure or will they believe the task succeeded?
If the user can recover from a failure (an error state), is that success with a longer time on task, or a failure?
And so on.

It's not unreasonable to expect a very high success rate. But it's also not uncommon to get lower success rates, if the GUI or design needs to be fixed.
In case you're new to usability testing, Gabriel, I'll add one tip. Make sure you give your participants realistic scenarios that don't lead the participants toward the desired outcome. For example, don't ask the users to "click the Save button," but instead ask them to "make sure you can use this document again, when you next use this program."
Answer: It is a teeny weeny bit analogous to service level agreements (SLAs), or disaster recovery...."how much do I spend"....and the answer, with regards to UX matters, is "what's the cost to your organisation of failure".
If your application is mission critical (e.g. nuclear power station control panel) or a medical device (e.g. X-ray machine) then the cost of failure is massive and the pass levels need to be nigh on 100% for all users to prevent lethal mistakes.
If your application is eCommerce related, I'd put the success rate up at 90% or somewhere reasonable around there.  You need your users to be able to achieve organisational goals (e.g. buy stuff, meet targets/plans etc) but also need to recognise that the audience will be significantly different from a medical or military application.
Much less than 90% and you have to question whether your interaction design is appropriate....imho :)
N
Answer: How are you even scoring "success"? The purpose of user testing is to reveal weak points in a design, not to get a high score. Reducing the results to a number makes the entire process useless; why not just put it up on Mechanical Turk and see what comes of it?
In fact, you could argue if you get a good 'score', you are wasting everyone's time. It means the testing was done much too late in the process to be useful, or was unnecessary at that stage.
IMHO the most useful usability tests are the ones where users do get through all the tasks, but reveal many previously unknown things about your system along the way.
Comment: I believe Nick Fine understood where I was coming from with this.

It's more of finding out if you were able to do your job well after the project is completed.


Toyota 4-runner front axle

Question: I recently ran into a big problem with my driver side front axle on my 1995 toyota 4-runner. for some reason its not wanting to act right. I replaced the axle, bearings, rotor, sway bar, bushings and everything. For some reason the axle is still messing up, assuming its the axle itself, can I just remove it and drive it in 2 wheel drive. I don't need 4 wheel, I just need it to work. Is this okay to do?
Comment: Can you explain "not wanting to act right",do you mean won't engage,grinds,locks up?
Answer: There is likely a seal that holds your gear oil in place on the shaft. Also, assuming you bought these online and installed yourself, did you verify them to be the same length and also that the shaft sat all the way into its seat? If it did not seat it could have wiggle room that allows it to slide in and out, instead of flex.

Toyota 4-runner front axle


If I change the event throttling in the diagnostic logs (ULS), do I also need to restart the Tracing Service?

Question: If I make a change to the event throttling (for example, increase it show show only high-level events for all events), do I need to restart the Tracing service (in Windows Services) in order to apply this change? I don't want to restart it if it's not necessary and I don't want to not restart it if it's required.
Answer: You should not need to restart any services. It should take into effect shortly after you click OK in Central Admin > Operations > Diagnostic Logging.
Notice how I use the word "should". It worked in my test farm, but from some research I've done, these changes don't always take into effect instantly like they were designed to. This previous post (https://sharepoint.stackexchange.com/questions/2297/how-can-can-i-disable-verbose-logging) explains that sometimes the tracing service may have to be restarted..You will have to check the log file and see if your changes have been made.
If you like doing items via stsadm you can follow the commands here to make your changes as well:
http://technet.microsoft.com/en-us/library/cc261740(v=office.12).aspx
Answer: As mentioned already, you "Should" not have to restart the service, though you will find times where it does get stuck. I tend to restart it anyway as it gives me a nice clean break in my logging so I can tell based on the time stamp which log contains the events from when I made my changes to the logging levels. So for example, if I set logging to verbose, I tend to restart the service so that I know that the new logs generated from that point will have the verbose logging info. It may also be useful to use the stsadm/powershell commands to restart the service whenever you are about to reproduce an issue for the same reasons. That way I can get a log with as little additional noise as possible making it easier to generate logs that cover just the time period of the issue reproduction. Just my 2 cents, hope this helps.


provable security and sandboxes

Question: Maybe this can be answered by an answer to a more general question, such as what programs can be proven secure.
Can it be (or has it been) formally proven that a sandbox is secure?
Answer: The term "sandbox" is wide, generic, and often misused and misunderstood.
Let's consider a type of sandbox, a virtual machine running under control of an hypervisor. The guest system is nominally isolated and cannot "see" the host system. However, this is relative to the implementation of the hypervisor, which is a combination of software and hardware, both of which being susceptible to bugs (hardware is always involved in that the whole thing, ultimately, runs on a CPU; I am not speaking about using or not using the AMD-V/Intel-VT opcodes). Escapes from hypervisors have happened. "Proving" the hypervisor to be correct would mean proving that it is bug-free. Proving that software is free of bugs has been a rather elusive goal for the last half century... and for hardware, even more so.
Moreover, sandboxes do not equate to safety. For a sandbox to be useful, it must have a few open doors: you run some software in the sandbox, but you will want to see the result, be it something displayed, files saved somewhere, or some network activity. When people use a Web browser in a sandbox, they want the browser to, say, actually browse the Web, so external network connections from the sandbox must be allowed; and the sandboxed browser must also have the possibility to display things, so it has an access to the graphic hardware (possibly a controlled access, but if you want 3D acceleration, strict controls become difficult). You want a sandbox because you suspect that the browser could be subverted and hijacked by an attacker. But, at that point, you have already lost (not the whole war, but significant battles nonetheless): the subverted browser, sandbox or not, is network-able and can be used as relay to attack other sites or send spam, seemingly originating from your address.
In more succint words, amputation is not the ultimately advisable type of medicine.
Let's see another kind of sandbox, the Java Virtual Machine and its support for applets. It has two main facets:

The "code" is not raw binary code for the local CPU, but "bytecode": opcodes for a conceptual, abstract machine, which lives in a non-hardware world where generic pointer arithmetics are not allowed. References have unescapable types, and array accesses are bounds-checked.
The external access facilities for the applet code are restricted: network connections can be made only to the originating server; local files cannot be read or written to; and so on.

When the bytecode must be run, it is first analyzed: the JVM implementation does a control flow analysis which formally proves (yes, in the sense of "provable security") that the code complies to the type rules for bytecode (namely, that it never calls a method on an object which does not feature that method). This allows for translation to efficient native code, without needing specialized virtualization hardware. Moreover, it protects against many types of subversion (buffer overflows are reliably detected, there is no dangling pointer or double-free because of GC-based memory management...). This kind of protection is not sufficient for "security" because you still want the access controls (e.g. blocking external connections except to the originating server) which are enforced by the system classes. The bytecode analysis is there to ensure that only the system classes are used, and are used correctly; the rest is up to the system classes.
Of course, over the history of Java, both the bytecode analyzer and system classes implementations have been found to have flaws. They are not intrinsic: what they try to achieve is not mathematically impossible. But, let's face it: bugs happen. The JVM is a rather complex piece of software which is far from being proven to be bug free. Also, the JVM runs within an operating system and on some tangible hardware, neither of which being bug-free either.
This illustrates my points:

A sandbox provides "provable security" only insofar as its implementation has no bugs. That's somewhat utopic.
What the sandbox actually provides is enforcement of a set of rules which may or, more often, may not, embody what you really mean by "security". As usual, the first step of proper security is to define clearly what you want.
Comment: Well written essay.  :P
Answer: Assume that you have proven that your sandbox is immune to all attacks.  If this proof where made about 10 years ago it would have not taken into consideration dangling pointer and padding oracle attacks because these methods of exploitation where unknown at the time.  Therefor you could not have proven that this sandbox was totally secure,  as that would be a contradiction -><-
Answer: Your question seems to indicate a misunderstanding of what security is. Proven security is an oxymoron.  Nothing can ever be completely secure, or as the old IT security joke goes, the only provably secure storage is writing to dev/null (ie, destruction).  Security is simply a game of resources and costs.  It tries to balance the need of legitimate users getting at information while preventing attackers from doing the same, but with any allowable access, given sufficient resources and time, it will always be possible or at least feasible to break the system and gain access.
Self destructive systems are an attempt to avoid this problem by limiting the amount of access that can be done, but inventive means can circumvent most of these as well given significant enough resources and effort (sometimes down to the level of actually dissolving layers of chips, layer by layer).
The question really needs more clarification to be answerable.  Do you perhaps mean, can protection against a particular type of attack be proven?  If so, what kinds of attacks are you worried about?
Answer: It depends what kind of provable security you talk abot (for either for its impossible  and nonsense). But in security algorithms provable security means that in order to break your algorithm someone needs to break underlaying crypto. Thus if we think of our crypto-alg as secure one, and you write a proof that only by breaking the crypto you will be able to break your algorithm then it does not mean anything, it's just something that can be researched and published nothing more. And I agree with Rook attack patterns are evolving something proof for now will not be secure within a decade or so.

provable security and sandboxes


Techniques to develop vibrato in singing

Question: Is vibrato gifted or is it developed by constant practice? Are there any exercises or techniques to develop a good vibrato in singing?
Comment: It can be developed. Find a Jo Estill teacher, who can help you on that.
Comment: Related: http://music.stackexchange.com/q/6328/1678
Answer: From a personal perspective, my vibrato started coming out after learning good breath support from the diaghram.  If I kept my throat relaxed and held a note in a comfortable area of my voice range, the vibrato would kick in.
It almost felt like hitting a sweet spot - a balance between diaghram control and vocal chord control.  Once I could evoke it reliably, I was able to start controlling it.
For the specifics on how to actually start the process, step-by-step, you might want to read this on Wiki-how:
http://m.wikihow.com/Sing-With-Vocal-Vibrato
Best of luck!
Answer: Vibrato is your friend. All singers, in any style of music, could benefit from learning to use a little vibrato because singing with vibrato is less fatiguing on the voice than singing with nothing but a "straight tone". When singers suffer vocal damage, it's often because they have sung for years with no vibrato and don't know how to use vibrato and control it.
When they start out, in their untrained voice, most singers, men and women, find themselves with very little vibrato. They need to develop vibrato (and how to control it) through practice. Any good voice teacher can work with you on this. It's fundamental to singing lessons. When you learn to produce and control vibrato, you can decide when and when not to use it, and how much, depending on the style of music you are singing.
For some reason I was the opposite: my natural untrained voice when I was young had a great deal of uncontrolled, wobbly vibrato. My voice teachers (I started studying voice at the age of 22 years) had to do a little work to show me how to reduce the vibrato and control the degree of vibrato. It's actually always been harder for me to sing pop or jazz (rather than classical or opera) because pop and jazz are supposed to be sung with very little vibrato.
Answer: I have told many of my friends and colleagues this technique to help you understand where vibrato comes from.
A good example is to imagine vibrato to be laughter.
Eg: Ha. ha. ha. ha. The "haha's" is actually a broken vibrato. A vibrato that is not connected or wavy. Once you understand this, you can begin working on trying to connect each 'ha ha' with a soft push of air. Till the haha's stop sounding percussive and begin sounding smooth and more wavy.
Once you manage understanding and doing this, you can begin trying to do this with different variations in tempo.
Good Luck


Unhate-able Villains

Question: There are so many guides on how to make a villain your players will truly hate, but I am trying to make a villain that the characters will feel for. How can I create a "good" villain, like someone who has the best intentions for all the races, but just doesn't quite seem to get the "good guy" act down, because of his methods? The villain does not have to be super-evil, just evil-ish and opposed to the characters.
Comment: Please do not answer in the comments.
Comment: Comments are not for extended discussion.  I am pruning comments significantly per user request.
Answer: The Road to Hell is paved with good intentions
In the Screwtape Letters, Screwtape toasts at a banquet stating that all the best sinners were failed saints. Men and women with a powerful will and a strong virtue, such as justice or defending the natural world, whose zeal crossed the line or had their virtue perverted. Villains should have goals that, at face value, seem noble, even commendable, its just the means to achieving their ends that makes them terrible. Hitler rose to power promising to end the harsh war reparations, raise the standard of living, and restore to Germany its former reputation and glory. He managed to achieve those goals, but his methods (and true goals) were horrifying, as history shows.
An Antagonist should be a foil
Every great Villain is a distortion of the Hero. Examine the rogue's gallery of someone like Batman. All the major villains hold a reflection of an aspect of the Hero's personality, methods, and/or identity. This is not so easy to accomplish in a party campaign setting, but your villain can have a similar background or shared experience with the party to underline the comparison. He/She could be the NPC that helped the party in an adventure, an NPC they rescued from danger, or an adventurer like the party. The villain's misdeeds should mirror some of the party's past actions. As Dampne suggests, a past party member (PC) whom a player got bored with or the GM was playing before becoming GM can make an excellent villain as well.
He/She is not Stupid Evil
While they will do terrible things in the name of their goals, the villain should display good and laudable qualities in other ways. They could be incredibly dedicated to their underlings, repaying their loyalty. They may burn down a village for logging in the forest, but at the same time help a sick traveler on the road. Above all they should not be evil for the sake of being evil or even personal gain, but evil for the "greater good" that they are seeking to accomplish.
Comment: I think Raz al-ghul and Bane from Nolan's Batman exemplify this (Joker can't because he is actually stupid/crazy evil). They both have elements which mirror Bruce/Batman's identity and background, but are decidedly different in what they seek. A villain should always be written as a hero who chose the wrong path.
Comment: This is a great answer. I would, however, add one other section. Ex-PCs tend to make fantastic villains. One of the best recurring villains in one of my own campaigns is a Bard who's player left the game early on. He was part of the group, and but for a day's worth of travel the other PC's would probably be on his side.
Answer: The difference between heroes and villains is often their methods, rather than their motivations.
Think about the end result, and make it as "honourable" as possible; world peace, destruction of an evil artifact, stopping another super villain etc.
Then think about how a normal hero would achieve these end results, if they ever could; getting everyone around a table and talking, safe removal and storage of the artifact, incarceration and rehabilitation of the super villain etc.
A villain would not consider these options first (if at all), with their own justifications (its never worked in the past, it would take to long, the risk is still there etc.) and would normally use force or other extreme methods to achieve the end result.
As you haven't offered a system or setting, I'm going with easily demonstrable examples:
Doctor Doom has moments where his intentions are "good"; retaking his throne from an usurper, considering killing Hitler, solving most of the world's problems etc.
Ozymandias wanted to cause a catastrophic event to deceive the world into uniting against a common enemy, and thus avert nuclear war.
EDIT: to follow from Doc's comment about Magneto, a lot of the Brotherhood of Mutants ended up trying to be good guys - Quicksilver eventually became an Avenger, Bandit was on both teams, Scarlet Witch went between being a hero and a villain, Emma Frost had her heroic ups and downs etc. Then there is the Hellfire Club, with all the complicated politics that had...
Comment: Magneto, from the X-Men series often had good intentions but just went about it in the wrong way.  In fact, he even teamed up with the X-Men on multiple occasions.
Answer: One more key:
Layers of secrets
I don't think I have seen this listed yet - if it has been, sorry. (Adam Davis' answer is similar to a degree, I know, but there's one crucial difference: free will. What I'll detail below leaves the "villain" in control of their own actions. They could quit it practically any minute. But they don't. They don't want to, for their own special reason. So, let's see what I'm talking about.)
Let me begin with an example: Have you read / seen the Harry Potter series? Remember Snape? Wasn't he the type of villain you're looking for? He hurt a lot of people. He killed important people. He was hated by the protagonists, the readers, and the viewers universally... until almost the very end. I won't spoil the story, but I guess you know what I'm referring to: His Secrets. His part he willingly took upon himself.
So, the method: Introduce your villain. Have him do villainy things. Slowly reveal, though, and only to the PCs, if possible, that he's not exactly what he seems, and neither are his doings...
He had a whole village slaughtered. Yes, they were all tainted with incurable lycanthropy, and would've suffered terribly in the coming weeks, spreading the disease everywhere. He had a town's well poisoned. Yes, because this way he immunized, to a degree, the townsfolk to the poisonous snakes the evil witches he's said to be in league with unleashed on the town. He murdered the King. Yes, at the King's own request, so that the King's death could lift a curse from the country.
...and he cannot tell anyone, because he was sworn not to, and because revealing his own real motives would blow his cover amongst the ranks of the Evil Army (or simply opposing army.) And, when your players discover his real motives, they realize they can't, or at least shouldn't reveal his secrets either. What's more, they have to keep on fighting him. For everyone's sake.
Answer: Establish clear limits your villain won't cross, don't make his evil acts hit too close to home for the PC's.
As Stalin is believed to have said "A single death is a tragedy; a million deaths is a statistic." make sure to keep the villains evil actions in the realm of statistics.
So the kingdom has just sent a 10000 strong army to push back the villains undead hoard ... and they all died, the PC's won't care unless they had personal NPC friends which died with that army.
The villain needs information from a NPC, torture is not something you should have the villain do, for the villain to remain sympathetic have him use dark magic to instantly get the information.
Rape is of course out of the question, racism as well and nobody likes sexism.
You should establish that the villain is as opposed to these evils as the PC's are in fact ...
The villain should share much of the motivations of the PC's (players) but take them too far.
Let's say your players are in college and frustrated by the various setbacks we all go through there, your villain can be a wizard turned evil because his masters at the tower were holding him back and applying arbitrary old timey restrictions against him.
So he slaughters all the old masters and starts to rebuild a evil mage order/take over the world.
Your players or the PC obviously have tons of motives why they can't punch their teachers in the face, but the villain can have their same woes (identifying with the villain is the key) and just decide to turn his masters into liche servants (or potted plants) at the same time giving the players the contentment in knowing that they're better than the villain in keeping their cool  and giving them the satisfaction in seeing the in-game representation of their woes being destroyed.
And best part they don't need to support the consequences for the villains outbreak they can get some of the buzz without the consequences which the villain will foot the tab for (he's a known evil mage now).
Are your players worried about the environment/animal lovers ?
Evil druid who kills all the hunters/woodcuters around the forest, by the time the PC's stop her (say it with me killing humans is bad) everyone is too afraid to go logging any more and the forest can recuperate.
Maybe there's a kingdom in which the king is obviously incompetent and the prince has the same complaints as the PC's but he decides enough is enough coup time, the PC's fight the coup because it's still against the law but they don't fault the prince.
Love is another good motivator for a villain which can make him/her likeable especially if the love is requited but society/the death of the partner is what it's keeping this from being a happy story.
What wouldn't you do for your loved one knowing that a life together is possible and the only barriers is some crusty old timers mumbling about "forbidden magics"/"demonic pacts".
Another villain might be a fantasy communist revolutionary, the realm is faltering and the richest merchants own nearly everything and twist the laws so that they can't be touched.
Fantasy Lenin might launch a surprise revolution and overrun the wealthiest most corrupt merchants.
By the time the PC's defeat him the tricky problems are solved, the greedy untouchables have been killed and the PC's defeated Lenin before he started getting to the sympathetic people.
More specific to RPG's have the villain build the PC's up as a way to get them on his side...
"Oh yes please take this artefact sword, I don't use swords anyway and once you use it you will see the true power of evil."
"Yes I do know the forbidden monkey stance here check it out ... very good you've mastered it ... now leave your master and join my temple and we will dominate the Chi ... here is my card for when you feel ready to give me a call."
"Look I understand your paladin's oath does not allow you to kill prisoners even this guy who will just escape and come back ... that's why I just threw a dagger into his heart ... yes yes there was nothing you could have done to stop me ... bye now"
Answer: Character motivation boils down to "What do they want?" and "What will they do to make it happen?"
The way you've phrased it is somewhat backwards - there are tons of media villains who want to "Save everyone" but will do horrible things to get there and they're not sympathetic at all.
The sympathetic villains may have evil goals, but won't cross important lines.  The key to a sympathetic villain is that they're not really a villain at all.  They're heroic, but they have crossing goals to the heroes.  The trick is that the players should be able to see it from the villain's perspective and say, "Well, if I was in the same situation, I'd do the same thing."
The easiest way to do this is show the villain helping others.  Not manipulating, not secretly corrupting, but actually, genuinely helping.
See the both of the Idealist archetypes I describe in the Seven Types of Antagonists.
Comment: You do not need to quote the question in your answer
Answer: I tend to lean towards some hints from 7th Sea.  Characters that get an individual identity have the option to pick up what are called Arcana.  If/When they pick this one and only one feature, it can swing positive or negative.  Heroes have the opportunity to take Righteous which allows the GM to make a genuine hero take an unsavory action because the end justifies the means.  Villains have the opportunity to take Mislead, which allows the players to cause them to hesitate because they think they're doing the right thing but are really doing something awful.  While this game draws a nice thick line between the "hero" and "villain" categories, there is no shortage of gray area on either side of it.
Ultimately, your best tool is TIME
To pull back the microscope a bit, to me it's all about integration.  If you park someone in front of the players and tell them that this is the villain or give them a name of someone and a laundry list of problems they cause, it's a mechanical problem.  This is just a bullseye with a name.  Give them a person not a character and they will be more inclined to identify with them or help them.

Show them the fledgling hero that's just a little too idealistic or heavy handed for the party.  As the rift grows, Plucky over there decides to start his own adventuring group/enterprise/empire.  His goals will coincide with or cross the party's path and he's not even out to get them - his lackeys might skirmish but when Plucky knows its the party he yanks the leash and goes about the rest of his work.
Give them the villain with style and panache.  They may perform
atrocities but they do it with undeniable flair.  Pay attention to
the things the party loves to see and do.  And then create a villain
with an expertise for exactly those things and put him on stage for
them.  But don't just make everything cinematic or they get bored
because they're not involved.  Oftentimes the players will look
forward to the villain's cameos if you keep them brief enough.
Lastly, and a personal favorite: give them the recovering villain. Whether or not it's working, this villain is genuinely trying to do things differently.  True effort is being put into arresting other villains but this one's been there and would rather obliterate their quarry knowing how crafty they can be.  When the players disagree, this villain gets irritated and just winds up doing something terrible on the side to blow off steam.  Ultimately, this character gets results whether the players like it or not.

In the end, having the likeable villain is a product of giving the players something to like enough that they won't kill on sight.  Which brings up an important point: The System needs to be one with rewards that aren't based solely on slaughter.  If you have games that reward by abstract values such as who acted the best, best idea, etc. or just a blanket "thanks for coming out" lump of XP players are more willing to take their time and get to know their villains.  Once again, 7th Sea can be paramount because the players are supposed to be heroes and thus no matter how they overcome the villain, they still get the awards and the game very strongly discourages killing anyone - just knocking them out.
Answer: I believe one of the most important parts is the way the character gets introduced - and it goes both ways. If you've read "A song of Fire & Ice" - take someone like Jaime Lannister. He seems almost like a villian at first, but once the reader sees the world from Jaimie's perspective he likely sympathizes with the character even. The same for the purposes of a villian can be used the other way around. The villian could be a very charming daredevil who enjoys games, betting, feasts etc., but once the players get to know him better they'll learn about some vile motives and alike. Or they'll meet and get to know the villian as someone who cares a lot for his sickly father and eventually they'll find out about all the dark deeds he partakes.
Answer: Another option is to consider the villain that had no alternative or choice in their means and methods.
Take, for example, a queen with a destructive power or curse she cannot control.  As it grows she finds it threatens the lives of those around her, and after a "straw that broke the camel's back" moment she flees her kingdom, but in the process destroys much of her realm, again unintentionally.  She's gotten away, and she may even pose no further threat, but the townspeople certainly won't see it that way, and the later rulers may find themselves compelled by their subjects to rid their kingdom of the possibility of attack later.
She may put up a fortress, find servants to take care of her (she knows no other life than that of a queen), and provide for the defense of herself and those around her.  But this looks awfully threatening to her previous kingdom, and some of her new subjects may be living better lives than they were before, but to the perspective of others they may be stolen, or slaves, or conspirators.
While ignorance, lack of control, and many other attributes don't excuse evil deeds, they are immediately understandable, and saddening to those who have a larger perspective.  They can make one sympathize with the evil character, enough to hesitate at the final moment when faced with the choice of passing judgement on a person who wasn't bad, but who cannot be otherwise stopped from hurting others.
Answer: Keep Q ever in mind: heavy is the burden of being me.
At the fringe are elements of

the jinn in Wish Master, "unlimited" power constrained by a plot element or world structure;
A. Lucard , Angel, or Nick Knight the vampires on course to redemption;
Londo of Babylon 5, a self aggrandizing egotist below a veneer of civility with occasional streaks of kindness amidst true cruelty (as opposed to the not-cruelty of killing animals (which have no rights): the moral context is not within the dead puppy but the heart of man).

Since you're developing an evil character within an RPG construct you might not have difficulty embracing the nascent evil in dungeons and dragons to access their chaotic-[evil|neutral|good] model.
Comment: +1 for Babylon 5 reference. Even the Shadows were not Stupid Evil, they too wanted progress.
Answer: Tragedy can also be a good tool.  If you can give the villain a truly lamentable life and make him a victim of his surroundings it will probably have an effect on the players.  Additionally you may wish to actually make the things that make the villain a villain simply traits that the player's (not their characters) themselves actually have, just magnified to a fault.  You might have a player who's a little bit of a procrastinator, fine.  Give you villain that trait, but make it extreme enough that it becomes something that makes him evil.  eg: Maybe he has to do despicable things because of how much he procrastinated something important.  etc...
Just be careful, you don't really want the player's to know where you got your inspiration...they might be a little offended if they do figure it out.  :P
Answer: I've played with a couple of interesting variations of this, though I'm not sure if either is exactly what you are looking for.
One is a "villain" who basically foils the P.C.s at every turn.  The annoying thing about him is that, even though events have placed him in opposition to the "good guys", he's actually a much better man than they are.
So, he might do things like K.O. or kill the entire party, arrange for them to get healed, and leave a note apologizing for the whole thing ("I really admire the work you've done in the past, but I think you're mistaken about this particular issue.  I hope someday we will be in a position to work together.").  He even returns their possessions.  Or the characters finally have a victory by beating him to perform some task, then find out he was delayed by his noble side-quest (possibly the same one the players passed up).  And so on.
The players probably won't like him though - they'll hate him more than anyone, possibly.  But they will feel for him and respect him.
Another variation is the charming rogue.  The GM I played with did this really well, and it's probably not easy to pull off.  He was super friendly, often helpful, but he would also sometimes trick you and steal stuff from you (never enough to really ruin your life - he was an ego-maniac who really wanted people to like him).
The way the GM pulled some of it off was to improvise, but allow the Charming Rogue to (retro-actively) have prepared just the right thing for the situation to trick the PCs  (within reason of what his abilities could have accomplished).  Some players could really object to this, but I enjoyed it.
The thing about the Charming Rogue is that, at the end of day, as much as he wants to be liked, it's all about him.  Every now and then somebody opposing something the Charming Rogue was doing would end up dead.  It was a little bit shocking when that happened, because he was such a fun character.
This worked well, but I think it partially depended on the GM being able to role-play a charming character.
Answer: The hero of almost any tragedy is responsible for all of the woes that befall him, and usually the radius of influence is much larger than themselves. Tragic heroes should be subdued or killed, but they are also typically very sympathetic.
Consider as a model, without reading too much into my own opinion of the man, Edward Snowden.

Unhate-able Villains


Is it a good idea to paint during Winter?

Question: I heard that interior painting is not a very good idea during winter.  How accurate is this statement and why?
Comment: You might want to clarify what area you live in.
Answer: Absolutely not accurate!!!!!!   There is no reason not to paint inside as long as temps are above 60F. Today's latex acrylic paints dry fast, adhere well, and apply well in moderate temps.( we always use some flowtrol to make it work longer and spread smoother) Actually, in winter the relative humidity is usually lower, so paint dries faster than in the heat and humidity of summer. Longer dry times lets more dust adhere.   Go for it during the winter, then you will have more time to enjoy the out of doors come summer time!!!!
Comment: BTW, today's paints have much lower VOC levels so fumes are not bad at all.  We run a fan in the painted room to move air and find that it is dry in less than 2 hours on average. Actually, I love the smell of a freshly painted room, but then, I thrive on that kind of thing.   lol
Answer: The main reason I don't paint in the winter is ventilation.  If you're indoors, temperature shouldn't be an issue.  However, I like to leave the windows open while painting to get some fresh air, and that's a huge waste in the middle of winter or summer.
Comment: Even the Low VOC paint produces more fumes than I can stand, after having tried painting in late fall. It's still a fair weather activity for the reasons you mention.
Answer: Temperature and humidity can affect how well the paint adheres to the surface being painted. I imagine that using a low-quality paint in a humid environment could create a problem, especially if trying to apply multiple coats.
Quality paints (and paint is, in my experience, something to spend the money on) have pretty wide tolerances though; I wouldn't hesitate to paint in the winter.
Answer: All paints have a range of temperatures and humidities at which they work best and you may experience problems with it taking longer for the paint to dry etc. if you work outside these ranges. This applies to high temperature as well as low temperature, though it's usually high humidity that's more of a problem (as shirlock mentions).
So check the data on the side of the can to see what the manufacturer recommends. If you're concerned that the temperature might be outside the range try a small area (or paint a spare board) and see how well the paint goes on and how long it takes to dry before tackling the whole room.
If the paint you have does cause you problems and you really have to paint in "extreme" conditions go back to the store and see if there's a different kind of paint that meets your requirements.
The main problem I find with painting during winter is the shortness of the daylight hours. I find it difficult to get even and complete coverage of wall and ceilings in artificial light so I much prefer painting in the spring and summer.


View competitors popular web pages

Question: Just wanted to know if there is an online tool that shows a website most popular pages from highest to least.
Answer: I don't know of any tool that does this, and if someone claimed to, I'd be highly skeptical.  Compete/Quantcast/Hitwise can't even get it right for an entire domain, let alone a page.
That said, SEMRush may be able to help you identify which specific pages rank highly for certain high traffic keywords, which would approximate what you want.
Comment: The way Hitwise et al say they do it is to get data from the ISPs (which I consider to be a little bit suspicious, but I like my internet connection and I don't really want to fork out to run my own ISP).
Answer: If you mean your own website, then yes, there are tools for this. Any decent analytics tool like Google Analytics or Awstats can easily tell you this information.
If you mean for another website that is not yours, then no, there is no way to get this information. This information is only available if you have tracking software on a website's web pages or access to the site's access logs.
Answer: There is no way of reliably analysing the traffic being driven to pages of another website unless you have access to their analytics software.
There are tools that attempt to estimate the traffic statistics of other pages with data gathered through toolbars, browsers, search engines, etc that they have control over. Chances are this information won't be very reliable unless you have en extremely large user base to sample your data from - and even then it's still not everyone.

View competitors popular web pages


How important is temperature when adding pectic enzyme?

Question: I added pectic enzyme when the must of my rhubarb wine was too warm after I misread the directions in the book where I found the recipe. I didn't notice until after the next day when I had already pitched the yeast. Will the pectic enzyme still help the wine clear? Should I re add it again at some other point?wine
Comment: Great question, I wish I had the answer.  I'd guess that if you were wine making it would be hard to be to warm for the enzyme.
Answer: I'm making plum wine right now and was wondering about this.  While this may not be an official "answer" here, I have read that you can pretty much add pectic enzyme at any point in the process, but it's supposedly best to add it in the beginning.  Pectic enzyme effectively un-does the work pectin does in your wine-- pectin wants to make it into a gel, but you want a clear wine in the end.  Pectic enzyme works to shorten the molecular chains that pectin forms in your must and wine-- while most fruit doesn't have enough pectin to make a gel on its own, those chains cause haze later.
My experience making wine tells me that if you're aging your wine in oak or in a carboy with oak chips for at least a few months, you can add the enzyme powder whenever you want and it'll do its work over time, similar to the way malolactic bacteria work on your wine once its in oak to covert malic acid into lactic.  I'm pitching yeast tonight after a day long fruit rest and don't have any pectic enzyme on-hand, so I'm going to add it midway through fermentation and will report back on how it goes.
Comment: How did it go?  I'm about to try pectic enzyme for a fruit-based soda, and am wondering about the temperature range for it, too.
Answer: It is best added when the must is at room temperature, you don't say what temp it was added so to be on the safe side I would add another dose. A double dose won't harm the resulting wine.
Answer: The optimal temperature for Pectic Enzyme (Pectinase) is about 45 degrees Celsius. Any temperature above that will decrease the rate of enzyme action because the enzyme will become denatured.
Comment: What about the effects of temperature below 45°C ? Please add as much details as possible to get a complete answer to the questions asked.
Comment: Would you happen to have a reference for this?


Conversion rate of topical Retinol to Retinoic Acid (Tretinoin)?

Question: I'm wondering if someone out there has more information than me. Retinoids have well known metabolic pathways in vivo, and it's usually something like: Retinyl Palmitate --> Retinol --> Retinaldehyde (Retinal) --> Retinoic Acid (Tretinoin) which is the biologically active form of the Retinoids.
Retinoids are used in cosmetics all the time, and while Retinol is available OTC, Retinoic Acid (Tretinoin - a.k.a. "Retin-A" by brand) is available by prescription only since it is a 'stronger' version of Retinol. It's not difficult to find 1% Retinol creams or higher, but Retinoic Acid treatments top out at 0.1%.
However, I can't help but wonder 'why'? One study I was able to dig up was here: Retinoic Acid Biosynthesis and Metabolism PDF. The table on page 5 shows Physiological Concentrations - starting at 50 microM for Retinol and ending at "<50nM?" suggesting an ultimate conversion rate of a little less than 10% which would make the 1% Retinol treatments roughly equivalent to a 0.1% Retinoic Acid treatment (and a 2% Retinol treatment to a 0.2% Retinoic Acid treatment - double what's available by prescription).
Do other studies/other evidence support the rate of conversion of Retinol to Retinoic Acid to be roughly 10% or suggest than a 1% Retinol topical treatment is equivalent to a 0.1% Retinoic Acid topical treatment? Or are there some other interfering factors that reduce the utilization of Retinol to Retinoic Acid that I'm missing?
Answer: My guess is that the effect you describe is due to compartmentalisation: both retinol and retinoate are practically lipophils and so will localize in membranes and other lipid "pools", while both human retinal dehydrogenase enzymes are cytosolic. Probably the only occasion they have to get at their substrate is when it's bound to RBP. This however introduces another factor complicating the simple model.