Initial algebra is "unique up to isomorphism"?
What does it mean for something to hold "up to isomorphism"?
Simple past or present perfect? Which is preferable, simple past or present perfect, in situations like this one: I had a conversation with my friend and we planned to do something; shortly afterwards I call him back to announce the accomplishments. My biggest doubt about simple past is that perfect aspect is used to indicate past action (accomplishment) with current relevance, at the same time I'm not sure if I'm allowed to use present perfect, because there's a gap between accomplishing and the current moment, which is a characteristic of simple past. The  of March 01, 2013 put it's distance at 14 hrs 04 mins 23 secs of light-travel time from Earth. A  (earlier today) tweet says it is 14 hrs 04 mins 22 secs of light-travel time from Earth. An  tweet put it still further out at 14 hrs 04 mins 25 secs of light-travel time.  The Voyager 2 tweets on Voyager 1's proximity to Earth too has reduced similarly to  earlier today from  reported on Feb 28 2013  It could quite simply be a typo ... If not a typo then my curiosity is piqued; I was under the impression the Voyagers are outbound from the Solar System now without any major in-system activities now.   How is it the Voyagers are closer to Earth than before? From what I understand, the frequency of light coming from the source moving towards an observer increases. From $ E=hv $ , this implies increase in energy of photon.  What really is confusing, is where does that extra energy come from? And also where is the energy is lost during opposite Doppler effect (red shift)? Why doesn't this violate the conservation of energy? This is fairly easy.  If I go to https://webserver.com/someurl?a=b, will the someurl?a=b part be protected, or just the contents of the site? Moving from SQL 2005 [SQL_Latin1_General_CP1_CI_AS] to 2008 - will I lose any features by using 'backwards compatibility' Edit Mail rules manually Why don't we treat rubbish the same as spam? Spam gets fairly heavily punished - 100 reputation penalty, if I recall correctly, and the content itself gets hidden in the revision history.  Now if we just have some rubbish:     dfajiojaifojadiofjadhigaowkokaomdiovnuiyhioqejgioqejgio   I'm not talking about someone posting a question or comment as an answer (i.e. possibly just not knowing the rules or being frustrated with not having the required privileges), or someone making some really horrible attempt at answering the question, I'm talking about an answer that clearly shows absolutely no observation of any content on the page.  This, in my opinion, causes a similar amount of harm to the site - I'm inclined to say the fact that someone posts spam isn't as important as the fact that they're posting something that needs to be deleted, since we're likely going to delete it pretty quickly, and they're (likely) behaving maliciously, or am I wrong?  Why don't we treat this equally harshly, or why do we treat spam as harshly as we do?    Side notes:  I'm sure I've seen a few times where users get punished for posting spam when their link is likely actually relevant to the question and useful (should I flag these? They are still link-only answers, so they shouldn't really come back, and often I'm just not sure enough). While false positives are bad, it seems worse that we're treating worse behaviour better.  I'm assuming that's not what "abusive" in this reason is referring to: (I'm also not sure, off the top of my head, how this one gets treated)     It is offensive, abusive, or hate speech How to find information about the system/machine in Unix? I have always found it difficult to find information about the system itself in Unix, whether it be   Which OS I am using (version number and all, to compare it with the latest available builds)? Which Desktop Environment am I using? If I am using KDE, most of the programs begin with a K and I can say I am using KDE, but there should be some way to query this, say from a script. Which kernel version am I using? (For example, I am using Fedora, and I want to know what Linux kernel version I am using)   Basically, what I miss is a single point/utility that can get all this information for me. Most of the times the solutions to the above would themselves be OS specific. Then, you are stuck. Why more (and varying number of) logical reads with read ahead (prefetch)? After creating tpch database in my SQL Server, I tried below query:      set statistics io on     DBCC DROPCLEANBUFFERS;             select top 100 * from dbo.lineitem order by l_partkey;   The table lineitem has a non-clustered index on l_partkey. I issued the above queries for several times and found out that the logical reads vary each time:      Table 'lineitem'. Scan count 1, logical reads 1019, physical reads 4, read-ahead reads 1760, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.     Table 'lineitem'. Scan count 1, logical reads 1007, physical reads 4, read-ahead reads 1720, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.     Table 'lineitem'. Scan count 1, logical reads 1030, physical reads 4, read-ahead reads 1792, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.   From the post here: , I know it could be caused by read ahead behavior.  BUT exactly why read ahead could cause more logical reads? How does it change the SQL Server behavior? Like SQL Server may read more index page since it's in cache anyway?  Anyway, I disabled read ahead and issue the above query again. Now it reports the same amount of logical reads each time. BUT the logical reads is much smaller!!      Table 'lineitem'. Scan count 1, logical reads 404, physical reads 160, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.   So my question is, why the read ahead feature could cause many more and various logical reads count?  Out of curiosity, I tried another query without the "order by":      select top 100 * from dbo.lineitem   Here's the result without read ahead:      Table 'lineitem'. Scan count 1, logical reads 5, physical reads 3, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.   Here's the result with read ahead:      Table 'lineitem'. Scan count 1, logical reads 15, physical reads 2, read-ahead reads 3416, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.   The one with read ahead still has more logical reads. So, why? tmux: enable mouse only when shift pressed Community user "stealing" tags? Living potato clock? Change the title size in scrartcl I'd like to use a smaller title. I'm using the scrartcl documentclass from the . I can change it's color font but not it's size.  \setkomafont{title}{\normalfont\bfseries\small}   Everything works exept the size. Anyone know a way to immediately show the seconds of a file's date modified property in the GUI? So if you create a file, any file in any directory, right-click and choose Properties, the date modified (if it's recent) will say something like "dd/mm/yyy hh:mm, one minute ago" - reminder this is in Windows 7. Windows XP did it normally. Then they changed something.  If you wait a while, eventually you'll see the seconds, I'm not sure how long a while is, but this is incredibly annoying if you want to troubleshoot something that relies on the seconds of timestamps... is there a setting? registry key I can change perhaps?  I'm literally using Chrome, pasting in the path of the directory to be able to see the seconds quickly (as a workaround) but would be nice to be able to use Win7. It has been said that RSA uses a modulus product of two prime numbers for security reasons. But does RSA even work correctly if we allow composite integers instead?  I think that the answer is "NO".  Define “work correctly” as:   allows encryption and decryption to be carried out as in normal RSA, yielding the original message (message padding and unpadding can remain unspecified, or absent as in texbook RSA); a security level can be given in terms of the key generation process (which may have alternate requirements to testing that $p$ and $q$ are prime). How to revert to GNOME Classic Desktop? I'm used to GNOME Classic and personally don't want to change to anything else, but it seems there is no more GNOME Classic in the Oneiric release. After apt-get installed gnome-session and all, though there comes back the GNOME Classic option in the session listbox, however, after logged in, it seems not the expected one.  There is no System menu in the top bar, and I couldn't customize panels at all. I want to change the appearance(theme), but I can't find Appearance menu at all. And much more differences to my previous experience of GNOME classic shell.    There are multiple valid answers for this question spanning over several versions of Ubuntu. For your convenience an index of each below:    and up      &amp; Same mesh with different colors How do I fix a NoSuchMethodError? I tried to add a new repository to software sources, but "add source" button is unavailable. I can't click on it.  I also tried to add a new software source from the terminal, but it didn't work.  sudo‬‬ ‫‪add-apt-repository‬‬ ‫‪ppa:n-muench/burg‬‬   s‫‪udo‬‬: command not found     I also tried these commands:  ‫‪sudo‬‬ ‫‪add-apt-repository‬‬ ‫‪deb‬‬ ‫‪http://ppa.launchpad.net/n-muench/burg/ubuntu‬‬ natty‬‬ ‫‪main‬‬   sudo‬‬: command not found What are your tips for improving overall system performance on ubuntu? Inspired by this  I realized that some default settings may be rather conservative on Ubuntu and that it's possible to tweak it with little or no risk if you wish to make it faster.  This is not meant to be application specific (e.g. make firefox load pages faster), but system wide.  Preferably 1 tip per answer, with enough detail for people to implement it.  A couple of mine would be:   Install  (via Software Center or sudo apt-get install preload); Change  value - "which controls the degree to which the kernel prefers to swap when it tries to free memory";   What are yours?  PS: Since this is not intended to have a unique answer but rather, several useful tips, I'm making this community wiki out-of-the-box.