Nuclear magnetic resonance spectroscopy Updated 2025-07-16
Used to identify organic compounds.
Seems to be based on the effects that electrons around the nuclei (shielding electrons) have on the outcome of NMR.
So it is a bit unlike MRI where you are interested in the position of certain nuclei in space (of course, these being atoms, you can't see their positions in space).
What's Nuclear Magnetic Resonance by Bruker Corporation (2020)
Source. Good 3D animations showing the structure of the NMR machine. We understand that it is very bulky largely due to the cryogenic system. It then talks a bit about organic compound identification by talking about ethanol, i.e. this is NMR spectroscopy, but it is a bit too much to follow closely. Basically the electron configuration alters the nuclear response somehow, and allows identifying functional groups. Nuclear weapon Updated 2025-07-16
A weapons-grade ring of electrorefined plutonium, typical of the rings refined at Los Alamos and sent to Rocky Flats for fabrication
. Source. The ring has a purity of 99.96%, weighs 5.3 kg, and is approx 11 cm in diameter. It is enough plutonium for one bomb core. Which city shall we blow up today?
Ciro Santilli is mildly obsessed by nuclear reactions, because they are so quirky. How can a little ball destroy a city? How can putting too much of it together produce criticality and kill people like in the Slotin accident or the Tokaimura criticality accident. It is mind blowing really.
More fun nuclear stuff to watch:
- Dr. Strangelove (1964)
- en.wikipedia.org/wiki/Chernobyl_(miniseries)
- The World Of Enrico Fermi by Harvard Project Physics (1970)
- Fat Man and Little Boy (1987) shows a possibly reasonably realistic of the history of the development of the Trinity
The Ultimate Guide to Nuclear Weapons by hypohystericalhistory (2022)
Source. Good overall summary. Some interesting points:- youtu.be/8uIPQBOCJ64?t=2946 talks about the difference between tactical and strategic nuclear weapons
- youtu.be/8uIPQBOCJ64?t=3291 mentions variable yield devices, this is the main new thing Ciro Santilli learned from this video
- youtu.be/8uIPQBOCJ64?t=3416 discusses if a strategic nuclear weapon usage would inevitably lead to tactical nuclear weapon escalation. It then mentions one case in which a possibly comparable escalation didn't happen: the abstinence of using chemical weapon during World War II.
ELF Hello World Tutorial
.strtab Updated 2025-07-16Holds strings for the symbol table.
This section has
sh_type == SHT_STRTAB.It is pointed to by outputs:
sh_link == 5 of the .symtab section.readelf -x .strtab hello_world.oHex dump of section '.strtab':
0x00000000 0068656c 6c6f5f77 6f726c64 2e61736d .hello_world.asm
0x00000010 0068656c 6c6f5f77 6f726c64 0068656c .hello_world.hel
0x00000020 6c6f5f77 6f726c64 5f6c656e 005f7374 lo_world_len._st
0x00000030 61727400 art.This implies that it is an ELF level limitation that global variables cannot contain NUL characters.
ELF Hello World Tutorial
STT_NOTYPE Updated 2025-07-16Then come the most important symbols:
Num: Value Size Type Bind Vis Ndx Name
4: 0000000000000000 0 NOTYPE LOCAL DEFAULT 1 hello_world
5: 000000000000000d 0 NOTYPE LOCAL DEFAULT ABS hello_world_len
6: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 2 _start ELF Hello World Tutorial
.text section Updated 2025-07-16Now that we've done one section manually, let's graduate and use the
readelf -S of the other sections: [Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 2] .text PROGBITS 0000000000000000 00000210
0000000000000027 0000000000000000 AX 0 0 16.text is executable but not writable: if we try to write to it Linux segfaults. Let's see if we really have some code there:objdump -d hello_world.ohello_world.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <_start>:
0: b8 01 00 00 00 mov $0x1,%eax
5: bf 01 00 00 00 mov $0x1,%edi
a: 48 be 00 00 00 00 00 movabs $0x0,%rsi
11: 00 00 00
14: ba 0d 00 00 00 mov $0xd,%edx
19: 0f 05 syscall
1b: b8 3c 00 00 00 mov $0x3c,%eax
20: bf 00 00 00 00 mov $0x0,%edi
25: 0f 05 syscallIf we grep
b8 01 00 00 on the hd, we see that this only occurs at 00000210, which is what the section says. And the Size is 27, which matches as well. So we must be talking about the right section.The most interesting part is line to pass the address of the string to the system call. Currently, the This modification is possible because of the data of the
a which does:movabs $0x0,%rsi0x0 is just a placeholder. After linking happens, it will be modified to contain:4000ba: 48 be d8 00 60 00 00 movabs $0x6000d8,%rsi.rela.text section. Elliptic geometry Updated 2025-07-16
Elliptic partial differential equation Updated 2025-07-16
Emission theory (vision) Updated 2025-07-16
It is so mind blowing that people believed in this theory. How can you think that, when you turn on a lamp and then you see? Obviously, the lamp must be emitting something!!!
Then comes along this epic 2002 paper: pubmed.ncbi.nlm.nih.gov/12094435/ "Fundamentally misunderstanding visual perception. Adults' belief in visual emissions". TODO review methods...
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Aprender em Comunidade by Prof. José Pacheco
. Source. In Portuguese. Title translation: "Learn in community". Essential nutrient Updated 2025-07-16
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Europe Updated 2025-07-16
For the most part, a great pseudo-country to live in with lots of cultural diversity, art and safety.
However, Europe is in economic decline after all its Jewish and German geniuses fled in/after World War II and due to having more than one natural language is bad for the world.
Ciro Santilli moved to Europe in 2010.
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