I was curious, why do they specify the differential of Work using an lowercase delta symbol $\delta$ as in  &quot;$\delta W$&quot;, instead of using a $d$, as in $dW$.  For example: $$\delta W=\vec{F} \cdot d\vec{s}$$ Does that have anything to do with the idea of absolute differentiation from tensor calculus?  Example: $$\frac{\delta T^i}{\delta t} = \frac{dT^i}{dt} + \Gamma^i_{rs} T^r \frac{dx^s}{dt}$$ If I convert this formula into a absolute differential, by multiplying both sides by $\delta t$, then I get: $$\delta T^i = dT^i + \Gamma^i_{rs} T^r dx^s$$ I would interpret this to mean that if you are using Cartesian coordinates then $\delta T^i = dT^i$ since the christoffel symbols of the second kind $\Gamma^i_{rs}$ are all zero for Cartesian coordinates. I was just curious if this has a similar means for the physics formula: $$\delta W=\vec{F} \cdot d\vec{s}$$ how would you apply this formula in cylindrical coordinates instead of Cartesian coordinates for example. (see   where i found the formula for work differential)  If I look in my tensor book i find that the christoffel symbols of the second kind for cylinderical coordinates: $\Gamma^r = \begin{bmatrix}0&amp;0&amp;0 \\ 0&amp;-r&amp;0\\0&amp;0&amp;0\end{bmatrix}$ $\Gamma^\theta = \begin{bmatrix}0&amp; 1/r&amp;0 \\ 1/r &amp;0&amp;0 \\ 0&amp;0&amp;0 \end{bmatrix}$ $\Gamma^{z} = \begin{bmatrix}0&amp;0&amp;0\\0&amp;0&amp;0\\0&amp;0&amp;0 \end{bmatrix}$ so in this case the absolute differential would have a none zero second term.  Another possibility that using under case $\delta$ as in $\delta W$ has nothing to do with absolute differentiation because work is a scalar? I just was wondering if it is somehow linked to $\delta$ absolution differentiation operator in tensors class...  The textbook i'm looking at says nothing about tensors... but it does tell me that if you are using cylindrical coordinates then the formula for a differential is different which sounds very tensor like to me.  Example: $ds = dr \frac{ds}{dr} + r~d\theta \frac{ds}{d\theta} + dz \frac{ds}{dz}$ Normally, in Cartesian coordinates the formula for a differential would be: $ds = \frac{\partial s}{\partial x}dx + \frac{\partial s}{\partial y}dy + \frac{\partial s}{\partial z}dy$
What is the exact use of the symbols $\partial$, $\delta$ and $\mathrm{d}$ in derivatives in physics? How are they different and when are they used? It would be nice to get that settled once and for all.  $$\frac{\partial y}{\partial x}, \frac{\delta y}{\delta x}, \frac{\mathrm{d} y}{\mathrm{d} x}$$   For what I know, $\mathrm{d}$ is used as a small infinitisemal change (and I guess the straight-up letter $\mathrm{d}$ is usual notation instead of italic $d$, simply to tell the difference from a variable). Of course we also have the big delta $\Delta$ to describe a finite (non-negligible) difference. And I have some vague idea that $\partial$ is used for partial derivatives in case of e.g. three-dimensional variables. Same goes for $\delta$, which I would have sworn was the same as $\partial$ until reading this answer on Math.SE:    Then to make the confusion total I noticed an equation like $\delta Q=\mathrm{d}U+\delta W$ and read in a physics text book that:     The fact that the amount of heat [added between two states] is dependent on the path is indicated by the symbol $\delta$...   So it seems $\delta$ means something more? The text book continues and says that:     a function [like the change in internal energy] is called a state function and its change is indicated by the symbol $\mathrm{d}$...   Here I am unsure of exactly why a $\mathrm d$ refers to a state function.   So to sum it up: down to the bone of it, what is $\delta$, $\partial$ and $\mathrm{d}$ exactly, when we are talking derivatives in physics.  Addition  Especially when reading a mathematical process on a physical equation like this procedure:  $$\delta Q=\mathrm{d}U+p\mathrm{d}V \Rightarrow\\ Q=\Delta U+\int_1^2 p \mathrm{d}V$$  It appears that $\delta$ and $\mathrm{d}$ are the same thing. An integral operation handles it the same way apparently?
$pq\mid pn^q+qn^p+kn$ for some $k,\,$ if $p,q$ are primes I'm trying to find a way to automatically clean/delete the temporary files from C:\Documents and Settings\user\Local Settings\Temp\ at shutdown/boot on my Windows XP Professional x64 SP2 machine.  The main reason for this is to clean Local Settings/Temp to remove old junk automatically. (I had thought I had this covered through Firefox settings, but I was only clearing temporary Internet files). Currently, there's around 3&nbsp;GB of temporary files, and I'd like to prevent this build up without having to remember to do anything on my part.  I have already looked at using  (explained in Super User question ), but it doesn't seem to touch that directory.  I'm aware of programs such as , but I would ideally like to use a solution that doesn't require additional software (so, I expect, something using a scheduled BAT/CMD script would be what I'm looking for).  One of the potential issues, I believe, is that there may be legitimate files in the Temp folder that may be needed on the next boot (for software installations or updates, for example) and the perfect solution would be able to distinguish those and leave them until they weren't needed (Note: I realise this perfect solution may not be reasonably possible).  I've already set up Disk Cleaner on a shutdown script, but when cleaning temporary files, Disk Cleaner doesn't clean this particular directory, and so I'm looking for alternative options (see Super User question  for a little more detail).  So, what are my options for automatically deleting the temp files from C:\Documents and Settings\user\Local Settings\Temp? Aiming at specific body parts How often do ewoks eat sentients? In Return of the Jedi, the ewoks plan on eating Luke, Han and Chewie.     THREEPIO: I'm rather embarrassed, General Solo, but it appears you are to be the main course at a banquet in my honor.   At this point, the tribe had already met and befriended Leia, and had encountered the Imperials in the past, making it fairly likely that they knew humans were .  This raises the question of how often they ate sentients. Was it a one-off thing, to honor an extremely rare visit from a god, or was this fairly common? What's the purpose (if any) of "javascript:" in event handler tags? I've been making a concerted effort to improve my javascript skills lately by reading as much javascript code as I can. In doing this I've sometimes seen the javascript: prefix appended to the front of event handler attributes in HTML element tags. What's the purpose of this prefix? Basically, is there any appreciable difference between:  onchange="javascript: myFunction(this)"   and  onchange="myFunction(this)"   ? The reminder email says:     We noticed you have not accepted our invitation to join Stack Overflow Careers. Only 3 days remain before it expires [...]      But please act soon: this invitation expires in 14 days [...]   Is it 3 days or 14 days now? Will ESM also become available for Ubuntu 14.04? ESM is available for 12.04, which enables Advantage customers to keep receiving kernel updates and updates for many user space packages. In our case it's very important to know if we'll be able tot use Ubuntu 14.04 safely after April '19, because it is not possible to upgrade our application and migrate it to say, 16.04. Android: No icon for Notification How come the year doesn't show here? If my data is overdispersed when binomial but not when Poisson does that alone mean I should use Poisson GLM? Top is Poisson, bottom is Binomial Source of variation is different people observed over a week long period. 118 people to be exact.  want to make predictions about the proportion of days/week one exercises if they wake up at a given time.  &gt; summary(FMR7)  Call: glm(formula = No.Days.Ex ~ WaketimeStand, family = poisson, data = PSD)  Deviance Residuals:       Min        1Q    Median        3Q       Max   -2.99043  -0.64677  -0.03492   0.67393   1.51943    Coefficients:               Estimate Std. Error z value Pr(&gt;|z|)     (Intercept)    1.36991    0.04689  29.218   &lt;2e-16 *** WaketimeStand -0.08309    0.04806  -1.729   0.0839 .   --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  (Dispersion parameter for poisson family taken to be 1)      Null deviance: 124.55  on 115  degrees of freedom Residual deviance: 121.51  on 114  degrees of freedom AIC: 479.71  Number of Fisher Scoring iterations: 4  &gt; summary(FMR6)  Call: glm(formula = cbind(No.Days.Ex, No.Days.NotEx) ~ WaketimeStand,      family = quasibinomial(link = logit), data = PSD)  Deviance Residuals:      Min       1Q   Median       3Q      Max   -3.7483  -0.9585  -0.0625   1.0428   2.9739    Coefficients:               Estimate Std. Error t value Pr(&gt;|t|)   (Intercept)     0.2595     0.1009   2.571   0.0114 * WaketimeStand  -0.1869     0.1020  -1.832   0.0695 . --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  (Dispersion parameter for quasibinomial family taken to be 2.015388)      Null deviance: 288.42  on 115  degrees of freedom Residual deviance: 281.57  on 114  degrees of freedom AIC: NA  Number of Fisher Scoring iterations: 4  Quite clear that there is much more overdispersion on the quasibinomial than the poisson. The response variable is no.days exercise per week and so my original thought was to analyse with binomial GLM as it is the proportion of days in a week someone exercises. However, when modelled with a Poisson GLM it is much less overdispersed. Is this a sign I am using the wrong distribution. Do small title edits constitute trivial edits? Time Manager (QGIS) date format I've been through associated answers but cannot quite seem to find something which works!  I'm having trouble getting TimeManager to recognise a simple data field (this is in QGIS2 - but I've had this error in earlier versions). I have these fields formatted in what appears to be one of the acceptable formats:    ... here is a screenshot of the field properties:    The format appears to be recognised in QGIS as I've worked out days difference between two dates (the "Time on Market" field shown in the image).  However ... I always end up with:   The Twitter.shp file works fine as a test, so I don't think this is an issue with the install / phyton conflict.  Any thoughts welcome! Can I Turn Off or Remove Map Layers in QGIS Print Composer The title pretty much says it all.  I have a base map in QGIS that I am using with several Print Composers.  In one of the Print Composers, I don't want one of the layers to show up.  Is there any way to accomplish this? Alright so I've seen some postings about loop cuts and done some research. I am very new to blender and modeling overall. I am trying to loop cut this concrete barrier. Now I'm following a tutorial and kind of did my own thing in some areas. I cleaned it up following some instructions in another answer here on stack exchange.  I can't for the life of me figure out why I can loop cut around the whole bottom:   ...but not the whole middle:   I see this marked as answered by another question. That question refers to ngons and inside faces. Now once again I'm totally new to this. I looked on the inside. I don't believe I have inside faces or any ngons by the terms I've read online in my research.  Here is a wireframe picture and the inside view:     Maybe I'm missing something the answers on other posts are saying. If so and you know what it is I'd be very appreciative of what it is. I get      every few minutes on Kubuntu (KDE), and the panels disappear.  It restarts itself automatically, so it's not a real problem, just an annoyance, but it is a big annoyance.  I've tried sudo apt install --reinstall plasmashell plasma-desktop, but that made no difference.  When I try a backtrace from the error message, it says it's unable to produce a useful backtrace. How to send emails and avoid them being classified as spam? This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating? How to connect a GUI button to function? I found this , but I am not sure if this is the same issue.  On , I did some reformatting of the indentation in the code block to make it a bit more readable and it was  for peer review. A few minutes later, it appears the OP made an edit that added some additional code. It looks like my suggested edit was applied when the OP saved his/her edit, and it looks like he got the "credit" for the edit.  I'm not really concerned about the 2 rep points; I'm more curious why this happened and if this is a bug (or limitation) in the editing feature, or if this is known/intended behavior?  Note that this is not a suggested edit that's overridden by a concurrent edit: the recorded edit starts from the post-suggested edit state (and in fact can be identical to it, as in  ). In Breaking Bad, Walter White chooses to go by Heisenberg. I know that there has to be some significance behind both why Walt chose the name and why the writers chose that name as opposed to any other physicist's. It would make sense for it to have something to do with Heisenberg's uncertainty principle, which postulates (in broad strokes) that any system is fundamentally unstable on a short enough time frame. The connection between that and Walt's specific character eludes me though. Which personal pronoun is appropriate in single-author papers - 'I' or 'we'? Could the use of 'I' be considered egotistical? Or will the use of 'we' be considered to be grammatically incorrect?