Universe Updated +Created
Wikipedia dumps Updated +Created
Per-table dumps created with mysqldump and listed at: dumps.wikimedia.org/. Most notably, for the English Wikipedia: dumps.wikimedia.org/enwiki/latest/
A few of the files are not actual tables but derived data, notably dumps.wikimedia.org/enwiki/latest/enwiki-latest-all-titles-in-ns0.gz from Download titles of all Wikipedia articles
The tables are "documented" under: www.mediawiki.org/wiki/Manual:Database_layout, e.g. the central "page" table: www.mediawiki.org/wiki/Manual:Page_table. But in many cases it is impossible to deduce what fields are from those docs.
X-10 Graphite Reactor Updated +Created
This was an intermediate step between the nuclear chain reaction prototype Chicago Pile-1 and the full blown plutonium mass production at Hanford site. Located in the Oak Ridge National Laboratory.
Figure 1.
Exterior of the X-10 Graphite Reactor in 1950
. Source.
Figure 2.
Workers loading Uranium into the X-10 Graphite Reactor with a rod
. Source.
Bicycle maintenance Updated +Created
Bicycle vocabulary Updated +Created
club.domain.cn Updated +Created
TODO what does this Chinese forum track? New registrations? Their focus seems to be domain name speculation
Some of the threads contain domain dumps. We haven't yet seen a scrapable URL pattern, but their data goes way back and did have various hits. The forum seems to have started in 2006: club.domain.cn/forum.php?mod=forumdisplay&fid=41&page=10127
club.domain.cn/forum.php?mod=viewthread&tid=241704 "【国际域名拟删除列表】2007年06月16日" is the earliest list we could find. It is an expired domain list.
Some hits:
  • club.domain.cn/forum.php?mod=viewthread&tid=709388 contains alljohnny.com The thread title is "2009.5.04". The post date 2009-04-30
    Breadcrumb nav: 域名论坛 > 域名增值交易区 > 国际域名专栏 (domain name forum > area for domain names increasing in value > international domais)
Energy operator Updated +Created
Appears directly on Schrödinger equation! And in particular in the time-independent Schrödinger equation.
MAC address Updated +Created
Hardcoded and unique network addresses for every single device on Earth.
Started with 48 bits (6 bytes), usually given as 01:23:45:67:89:AB but people now encouraged to use 64-bit ones.
How they are assigned: www.quora.com/How-are-MAC-addresses-assigned Basically IEEE gives out the 3 first bytes to device manufacturers that register, this is called the organizationally unique identifier, and then each manufacturer keeps their own devices unique.
Magarena Updated +Created
Open source MtG engine implementation written in Java.
Seems to have an option to download art from internet as well.
Ciro Santilli wonders how legal it is. They very explicitly do not mention the words Magic: The Gathering anywhere.
Their UI does a good job at being self explanatory. Space is the shortcut to skip phases.
No online play.
TODO it appears to parse card functionality out of the human readable text! That's genius, as it helps automatically get new cards working, and squirt around legal issues.
Application Updated +Created
Paging makes it easier to compile and run two programs or threads at the same time on a single computer.
For example, when you compile two programs, the compiler does not know if they are going to be running at the same time or not.
So nothing prevents it from using the same RAM address, say, 0x1234, to store a global variable.
And thread stacks, that must be contiguous and keep growing down until they overwrite each other, are an even bigger issue!
But if two programs use the same address and run at the same time, this is obviously going to break them!
Paging solves this problem beautifully by adding one degree of indirection:
(logical) ------------> (physical)
             paging
Where:
  • logical addresses are what userland programs see, e.g. the contents of rsi in mov eax, [rsi].
    They are often called "virtual" addresses as well.
  • physical addresses can be though of the values that go to physical RAM index wires.
    But keep in mind that this is not 100% true because of further indirections such as:
Compilers don't need to worry about other programs: they just use simple logical addresses.
As far as programs are concerned, they think they can use any address between 0 and 4GiB (2^32, FFFFFFFF) on 32-bit systems.
The OS then sets up paging so that identical logical addresses will go into different physical addresses and not overwrite each other.
This makes it much simpler to compile programs and run them at the same time.
Paging achieves that goal, and in addition:
  • the switch between programs is very fast, because it is implemented by hardware
  • the memory of both programs can grow and shrink as needed without too much fragmentation
  • one program can never access the memory of another program, even if it wanted to.
    This is good both for security, and to prevent bugs in one program from crashing other programs.
Or if you like non-funny jokes:
Figure 1.
Comparison between the Linux kernel userland memory virtualization and The Matrix
. Source. Is this RAM real?
Epoch (astronomy) Updated +Created
If looking through these don't make you think of the Book of Genesis then nothing will.
Exception to the Madelung energy ordering rule Updated +Created
The most notable exception is the borrowing of 3d-orbital electrons to 4s as in chromium, leading to a 3d5 4s1 configuration instead of the 3d4 4s2 we would have with the rule. TODO how is that observed observed experimentally?
Magnetic flux quantum Updated +Created
TODO is there any relationship between this and the Josephson effect?
This appears to happen to any superconducting loop, because the superconducting wave function has to be continuous.
Video "Superconducting Qubit by NTT SCL (2015)" suggests that anything in between gets cancelled out by a superposition of current in both directions.
Mathematics and Computer science course of the University of Oxford Updated +Created
A mixed cross department course with the Mathematical Institute of the University of Oxford.. Its corresponding masters is known as Oxford MMathCompSci. The handbook is together with the computer science one: Section "Computer science course of the University of Oxford".
Video 1.
Mathematics and Computer Science at Oxford University by University of Oxford (2017)
Source.
Recombination (cosmology) Updated +Created
Waring-Goldbach problem Updated +Created
It is exactly what you'd expect from the name, Waring was watching Netflix with Goldbach, when they suddenly came up with this.
Basic TLB operation Updated +Created
After a translation between linear and physical address happens, it is stored on the TLB. For example, a 4 entry TLB starts in the following state:
  valid  linear  physical
  -----  ------  --------
> 0      00000   00000
  0      00000   00000
  0      00000   00000
  0      00000   00000
The > indicates the current entry to be replaced.
And after a page linear address 00003 is translated to a physical address 00005, the TLB becomes:
  valid  linear  physical
  -----  ------  --------
  1      00003   00005
> 0      00000   00000
  0      00000   00000
  0      00000   00000
and after a second translation of 00007 to 00009 it becomes:
  valid  linear  physical
  -----  ------  --------
  1      00003   00005
  1      00007   00009
> 0      00000   00000
  0      00000   00000
Now if 00003 needs to be translated again, hardware first looks up the TLB and finds out its address with a single RAM access 00003 --> 00005.
Of course, 00000 is not on the TLB since no valid entry contains 00000 as a key.
2006 Nobel Prize in Physics Updated +Created
Cosmic microwave background anisotropy Updated +Created
There is a slight variation in temperature of CMB across the sky of the order of 200 microKelvin. It is small to the ~2.7 K average temperature, but it can be measured.
If the initial conditions of the Big Bang and the laws of physics were perfectly symmetric, then we could expect the Universe to just be one perfectly uniform boring soup.
But instead some asymetry made all the fun weird things we see today happen eventually, like galaxies and life.
And the cosmic microwave background serves as a way for us to look back in time to the early conditions of the universe, as it was set in stone as soon as the universe became transparent to this light during recombination.
Or if you want to get poetic, it is the closest we can ever get to listening to the original word of God when he setup the initial conditions of the universe.
The ansiotropies of CMB is the ultimate astronomical compass we will ever have, as it is the thing with the least proper motion.

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