This bike is over 17 years old and not particularly high quality, but it does not make sense to replace the whole thing over one shifter. So I am looking to repair it if possible. I'm confident with most aspects of maintenance, but I've no idea what goes on inside these things.    When changing 'down' to an easier gear with the thumb, the lever slips and the gears do not change. The lever moves further than is expected, with no resistance. By simultaneously applying lots of upwards pressure with the thumb, you can sometimes get it to shift. Once it does shift, the rear functions happily. I've had no other derallier issues.    There's an allen key fitting on the top, and a screw on the bottom. I have not opened it up, worrying that springs will ping out and all will be lost!    I've no idea if it needs more lubrication... or all the gunk cleaning out. Go tighter... or looser?  Thank you.
I've got a road bike with brake lever shifters, and it's developed a small problem with age: sometimes, the shifter doesn't catch the first time or two I push it. It'll move easily, with no resistance, since it's not actually pulling on the cable, then after a few tries, catch and work normally. The colder the temperature, the more often this happens.  I don't know how the mechanism works internally, so I'm curious what would cause this, and also whether it's (as I suspect) gradual wear of some part of the mechanism, and if it's likely to fail catastrophically, or gradually worsen.
¿Can you help me with axiom of regularity? I understand that if we define a set such that $A=\{A\}$ we have then a contradiction because of regularity axiom, thus, a set can not be a member of itself. My question is; how can it be so, if I define a set $A=\{A,b\}$ ($b$ disjoint from $A$)?  Thanks. I am trying to solve the following exercise:     Prove that complex multiplication does not extend to a multiplication   on $\mathbb R^3$ so as to make $\mathbb R^3$ into a real division   algebra.   I am aware of Frobenius' theorem that there are only three finite dimensional real associative division algebras. But the exercise would be pointless if the theorem was assumed.   Let $x,y \in \mathbb R^3$. Since $x y$ has to extend the complex multiplication:  $$xy = (x_1y_1-x_2y_2, x_1y_2 + x_2 y_1, ?)$$  I have no idea how I can proceed from here. Could someone tell me how to do this? It should be easy as the other exercises I did so far were also easy. '+' and 's' in permission strings If the ls -l command gives me a permission string like  rwsr-s--x   What does the 's' mean? The only sources I found mention that it can be present sometimes but do not elaborate.  What does a '+' instead of a '-' mean? I have found mentions of 'extended permission' but nothing clear. How to decide whether to replace or repair? Analyzing $\biggl\lfloor{\frac{x}{5}}\bigg\rfloor=\bigg\lfloor{\frac{x}{7}}\bigg\rfloor$ How many non negative integral values of $x$ satisfy the equation :$$\biggl\lfloor{\dfrac{x}{5}}\bigg\rfloor=\bigg\lfloor{\dfrac{x}{7}}\bigg\rfloor$$.   My try:  Writing few numbers and putting in the required equation.  $\underbrace{0,1,2,3,4}_{\implies 0=0},\underbrace{5,6}_{\displaystyle\times},\underbrace{7,8,9}_{\implies 1=1},\underbrace{10,11,12,13}_{\displaystyle\times} ,\underbrace{14}_{\implies 2=2},\underbrace{15,16,17,18,19,20}_{\text{LHS gives 3 but RHS gives 2}},\underbrace{21,22,23,24}_{\text{LHS gives 4 but RHS gives 3}}$.  The point which I wish to make here is that after $14$ we'll get $5's$ multiple before than $7's$, hence $\forall x \geq 15 \implies \biggl\lfloor{\dfrac{x}{5}}\bigg\rfloor&gt;\bigg\lfloor{\dfrac{x}{7}}\bigg\rfloor$  Hence the only solution are: $\{0,1,2,3,4,7,8,9,14\}$. Does these make sense?  I need to know other solutions that don't incorporate such analyzing, means using some properties and framing it to solve above. I want to write a query like this:  SELECT o.OrderId, MAX(o.NegotiatedPrice, o.SuggestedPrice) FROM Order o   But this isn't how the MAX function works, right?  It is an aggregate function so it expects a single parameter and then returns the MAX of all rows.     Does anyone know how to do it my way? Extra semicolon near answers header On all the SE sites that I checked, the text that normally says something like “1 Answer” now says “1 Answer;” (with a semicolon seemingly in superscript):    The HTML for that part of the page looks like this (the semicolon is on the fourth line from bottom):              &lt;div id="answers"&gt;                  &lt;a name="tab-top"&gt;&lt;/a&gt;                 &lt;div id="answers-header"&gt;                     &lt;div class="subheader answers-subheader"&gt;                         &lt;h2&gt;                                 1 Answer                         &lt;/h2&gt;                         &lt;div&gt;                             &lt;div id="tabs"&gt;         &lt;a href="/questions/18587301/which-is-good-il-editor?answertab=active#tab-top" title="Answers with the latest activity first"&gt;             active         &lt;/a&gt;         &lt;a href="/questions/18587301/which-is-good-il-editor?answertab=oldest#tab-top" title="Answers in the order they were provided"&gt;             oldest         &lt;/a&gt;         &lt;a class="youarehere" href="/questions/18587301/which-is-good-il-editor?answertab=votes#tab-top" title="Answers with the highest score first"&gt;             votes         &lt;/a&gt; &lt;/div&gt; ;                         &lt;/div&gt;                     &lt;/div&gt;                 &lt;/div&gt; What USB drive filesystem works out of the box on Windows, Linux, and OS X? How do I print my Java object without getting "SomeType@2f92e0f4"? What's the best way to do a backwards loop in C/C#/C++? I need to move backwards through an array, so I have code like this:  for (int i = myArray.Length - 1; i &gt;= 0; i--) {     // Do something     myArray[i] = 42; }   Is there a better way of doing this?  Update: I was hoping that maybe C# had some built-in mechanism for this like:  foreachbackwards (int i in myArray) {     // so easy }   Update 2: There are better ways. Rune takes the prize with:  for (int i = myArray.Length; i-- &gt; 0; ) {         //do something } //or for (int i = myArray.Length; i --&gt; 0; ) {     // do something }   which looks even better in regular C (thanks to Twotymz):  for (int i = lengthOfArray; i--; ) {         //do something } I'm using Dataloader to Upsert a Child Account to Parent Account using an external ID.  When the Upsert is complete, the Child overwrites the parent, it's not not connecting the Child Account to the Parent Account.  ((See Answer Below)) I want to log out of Stack Overflow or any Stack Exchange site, but always it shows me logged in!  How do I log out of this site?  Note: I have yet to register; the site currently always shows my name and default email. I wish to log out so that I may start a new session! How to create a text file in a folder In windows I right click and then there is an option to create a text file.  How to do so in mac? Why can we distinguish different pitches in a chord but not different hues of light? In music, when two or more pitches are played together at the same time, they form a chord. If each pitch has a corresponding wave frequency (a pure, or fundamental, tone), the pitches played together make a , which is obtained by simple addition. This wave is no longer a pure sinusoidal wave.  For example, when you play a low note and a high note on a piano, the resulting sound has a wave that is the mathematical sum of the waves of each note. The same is true for light: when you shine a 500nm wavelength (green light) and a 700nm wavelength (red light) at the same spot on a white surface, the reflection will be a superposition waveform that is the sum of green and red.  My question is about our perception of these combinations. When we hear a chord on a piano, we’re able to discern the pitches that comprise that chord. We’re able to “pick out” that there are two (or three, etc) notes in the chord, and some of us who are musically inclined are even able to sing back each note, and even name it. It could be said that we’re able to decompose a Fourier Series of sound.  But it seems we cannot do this with light. When you shine green and red light together, the reflection appears to be yellow, a “pure hue” of 600nm, rather than an overlay of red and green. We can’t “pick out” the individual colors that were combined. Why is this?  Why can’t we see two hues of light in the same way we’re able to hear two pitches of sound? Is this a characteristic of human psychology? Animal physiology? Or is this due to a fundamental characteristic of electromagnetism? Ignoring programming style and design, is it "safe" to call delete on a variable allocated on the stack?  For example:     int nAmount;    delete &amp;nAmount;   or  class sample { public:     sample();     ~sample() { delete &amp;nAmount;}     int nAmount; } Ubuntu 18.04 can't resume after hibernate Hibernate worked correctly when I had been using Ubuntu 17.04. After upgrade to 17.10 I couldn't resume because of black screen after resume ().   After upgrade to 18.04 if I try to start my computer after hibernation it boots as if there was no hibernation done. Is every sub-lattice of $\mathcal P(X)$ isomorphic to a sub-lattice of $\mathcal P(X')$ containing singleton sets? In what order do multiple readied actions with the same trigger resolve? Why do we need a diagonal matrix? Apart from simplifying matrix powers, why do want to diagonalize a matrix? Do they have any appealing application which can be used to motivate to study diagonal matrices.  Thanks for any answers. Possible Duplicate:             TL;DR: sudo apt-get install ... saying "Unable to correct problems, you have held broken packages."   The problem  I was trying to get the WebApps feature for PP and QQ following .  I ran the sudo add-apt-repository ppa:webapps/preview command to add the repository, but i got a connection error. Since I know my current ISP gives a shaky connection, I tried again and sure enough, it worked.  Then I ran sudo apt-get install unity-webapps-preview, but I realized we had to update apt-get first, so I hit Ctrl + C to stop it. Then I ran sudo apt-get update which worked w/o a fuss, but when I ran sudo apt-get install unity-webapps-preview again later, it showed an error message. Here's the dump:  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  unity-webapps-preview : Depends: xul-ext-unity but it is not going to be installed                          Depends: xul-ext-websites-integration but it is not going to be installed                          Depends: xul-ext-webaccounts but it is not going to be installed E: Unable to correct problems, you have held broken packages.   I think this might be because of me interrupting the earlier command. It hadn't got a chance to output anything, though — I stopped it pretty fast.  What I tried  Commands  I tried these:-   sudo apt-get install --fix-broken sudo apt-get autoclean sudo apt-get autoremove sudo apt-get -f install   But even after running sudo apt-get upgrade after every try, none of them worked.  Purging  I tried purging the repository, but that didn't work either. First, I got the package using sudoapt-get install ppa-purgeand then tried to purge the WebApps repo usingsudo ppa-purge ppa:webapps/preview`.  Manually installing dependencies  If you look at the error dump carefully, it says:     Depends: xul-ext-unity but it is not going to be installed   Depends: xul-ext-websites-integration but it is not going to be installed   Depends: xul-ext-webaccounts but it is not going to be installed   So I tried installing them manually. I ran sudo apt-get install xul-ext-unity, but got this:     Depends: xul-ext-websites-integration but it is not going to be installed   Breaks: firefox (>= 15.+) but 16.0~b6+build1-0ubuntu0.12.04.1~mfn4 is to be installed   I have no idea what the second part means, but I tried resolving the first. Running sudo apt-get install xul-ext-websites-integration gave:     xul-ext-websites-integration : Breaks: firefox (>= 15.+) but 16.0~b6+build1-0ubuntu0.12.04.1~mfn4 is to be installed   As a last resort, I tried sudo apt-get install xul-ext-webaccounts, but that gave the sane message too:     Breaks: firefox (>= 14.+) but 16.0~b6+build1-0ubuntu0.12.04.1~mfn4 is to be installed   What does Breaks: firefox (&gt;= 14.+) but 16.0~b6+build1-0ubuntu0.12.04.1~mfn4 is to be installed mean?  Research  I tried searching , looking at a couple of , looking at  and searching on AU, but to no avail. Help would be appreciated.