JCVI-syn3A Updated +Created
essential metabolism for a minimal cell (2019) mentions:
JCVI-syn3A, a robust minimal cell with a 543 kbp genome and 493 genes, provides a versatile platform to study the basics of life.
Based on JCVI-syn3.0, they've added a few genes back to give better phenotypes, including slightly faster duplication time. Because the development cycle time is your God is also true in biology.
As of essential metabolism for a minimal cell (2019) it had only 91 genes of unknown function! So funny.
Bibliograpy:
Figure 1.
JCVI-syn3A during cell division by David Goodsell (2022)
Source. A description is present at: cdn.rcsb.org/pdb101/goodsell/2022_JCVI-syn3A.pdf Integrative Illustration of a JCVI-syn3A Minimal Cell by David Goodsell (2022) which describes everything in the picture.
JCVI-syn3B Updated +Created
www.biorxiv.org/content/10.1101/2022.09.19.508583v1.full
CVI-syn3B strains differ from JCVI-syn3.0 by the presence of 19 additional non-essential genes that result in a more easily manipulated cell. JCVI-syn3B additionally includes a dual loxP landing pad that enables easy Cre recombinase mediated insertion of genes
It is also interesting to see how they are interested in co-culture with HeLa cells, presumably to enable infectious bacterial disease studies.
At biology.indiana.edu/news-events/news/2023/lennon-minimal-cells.html (2023) they let it re-evove to it it would regain some fitness, and it did.
Jean-Luc Ponty Updated +Created
Video 1.
Jean-Luc Ponty Live in Chicago on "Soundstage" (1976)
Source.
Jena SPARQL hello world Updated +Created
Once you've done the Apache Jena CLI tools setup we can query all users with Full Name (FN) "John Smith" directly fom the rdf/vcard.ttl Turtle RDF file with the rdf/vcard.rq SPARQL query:
sparql --data=rdf/vcard.ttl --query=rdf/vcard.rq
and that outputs:
---------------------------------
| x                             |
=================================
| <http://somewhere/JohnSmith/> |
---------------------------------
Jerry Sanders Updated +Created
Video 1.
AMD Founder Jerry Sanders Interview (2002)
Source. Source: exhibits.stanford.edu/silicongenesis/catalog/hr396zc0393. Fun to watch.
Jimmy Wales Updated +Created
One thing to note is that Jimmy was a finance worker before starting wikipdia, e.g. he had capital to hire Larry Sanger.
Maybe that's the way to go about it, make money first, and later on change the world.
Starting just after the beginning of the Internet can't hurt either. Though tooling must have been insane back then.
Joan Feynman Updated +Created
Video 1.
My brother, Richard: How he came to be so smart interview with Joan Feynman by Web of Stories (2019)
Source. Ah, shame to see Joan so old. Some good stories. The tiles game thing was not mentioned in Genius: Richard Feynman and Modern Physics by James Gleick (1994) I think.
John Bardeen Updated +Created
Video 1.
The Story of John Bardeen at the University of Illinois (2010)
Source.
ELF Hello World Tutorial / Section header table Updated +Created
Array of Elf64_Shdr structs.
Each entry contains metadata about a given section.
e_shoff of the ELF header gives the starting position, 0x40 here.
e_shentsize and e_shnum from the ELF header say that we have 7 entries, each 0x40 bytes long.
So the table takes bytes from 0x40 to 0x40 + 7 + 0x40 - 1 = 0x1FF.
Some section names are reserved for certain section types: www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#special_sections e.g. .text requires a SHT_PROGBITS type and SHF_ALLOC + SHF_EXECINSTR
Running:
readelf -S hello_world.o
outputs:
There are 7 section headers, starting at offset 0x40:

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .data             PROGBITS         0000000000000000  00000200
       000000000000000d  0000000000000000  WA       0     0     4
  [ 2] .text             PROGBITS         0000000000000000  00000210
       0000000000000027  0000000000000000  AX       0     0     16
  [ 3] .shstrtab         STRTAB           0000000000000000  00000240
       0000000000000032  0000000000000000           0     0     1
  [ 4] .symtab           SYMTAB           0000000000000000  00000280
       00000000000000a8  0000000000000018           5     6     4
  [ 5] .strtab           STRTAB           0000000000000000  00000330
       0000000000000034  0000000000000000           0     0     1
  [ 6] .rela.text        RELA             0000000000000000  00000370
       0000000000000018  0000000000000018           4     2     4
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)
The struct represented by each entry is:
typedef struct {
    Elf64_Word  sh_name;
    Elf64_Word  sh_type;
    Elf64_Xword sh_flags;
    Elf64_Addr  sh_addr;
    Elf64_Off   sh_offset;
    Elf64_Xword sh_size;
    Elf64_Word  sh_link;
    Elf64_Word  sh_info;
    Elf64_Xword sh_addralign;
    Elf64_Xword sh_entsize;
} Elf64_Shdr;
ELF Hello World Tutorial / Section vs segment Updated +Created
We will get into more detail later, but it is good to have it in mind now:
  • section: exists before linking, in object files.
    One ore more sections will be put inside a single segment by the linker.
    Major information sections contain for the linker: is this section:
    • raw data to be loaded into memory, e.g. .data, .text, etc.
    • or metadata about other sections, that will be used by the linker, but disappear at runtime e.g. .symtab, .srttab, .rela.text
  • segment: exists after linking, in the executable file.
    Contains information about how each segment should be loaded into memory by the OS, notably location and permissions.
ELF Hello World Tutorial / Specified file formats Updated +Created
The ELF standard specifies multiple file formats:
  • Object files (.o).
    Intermediate step to generating executables and other formats:
    Source code
    
        |
        | Compilation
        |
        v
    
    Object file
    
        |
        | Linking
        |
        v
    
    Executable
    Object files exist to make compilation faster: with make, we only have to recompile the modified source files based on timestamps.
    We have to do the linking step every time, but it is much less expensive.
  • Executable files (no standard Linux extension).
    This is what the Linux kernel can actually run.
  • Shared object files (.so).
    Libraries meant to be loaded when the executable starts running.
  • Core dumps.
    Such files may be generated by the Linux kernel when the program does naughty things, e.g. segfault.
    They exist to help debugging the program.
In this tutorial, we consider only object and executable files.
ELF Hello World Tutorial / Standards Updated +Created
The LSB basically links to other standards with minor extensions, in particular:
A handy summary can be found at:
man elf
ELF Hello World Tutorial / STT_FILE Updated +Created
Entry 1 has ELF64_R_TYPE == STT_FILE. ELF64_R_TYPE is continued inside of st_info.
  • 10 8: st_name = 01000000 = character 1 in the .strtab, which until the following \0 makes hello_world.asm
    This piece of information file may be used by the linker to decide on which segment sections go: e.g. in ld linker script we write:
    segment_name :
    {
        file(section)
    }
    to pick a section from a given file.
    Most of the time however, we will just dump all sections with a given name together with:
    segment_name :
    {
        *(section)
    }
  • 10 12: st_info = 04
    Bits 0-3 = ELF64_R_TYPE = Type = 4 = STT_FILE: the main purpose of this entry is to use st_name to indicate the name of the file which generated this object file.
    Bits 4-7 = ELF64_ST_BIND = Binding = 0 = STB_LOCAL. Required value for STT_FILE.
  • 10 13: st_shndx = Symbol Table Section header Index = f1ff = SHN_ABS. Required for STT_FILE.
  • 20 0: st_value = 8x 00: required for value for STT_FILE
  • 20 8: st_size = 8x 00: no allocated size
Now from the readelf, we interpret the others quickly.
ELF Hello World Tutorial / .symtab Updated +Created
Section type: sh_type == SHT_SYMTAB.
Common name: "symbol table".
First the we note that:
  • sh_link = 5
  • sh_info = 6
For SHT_SYMTAB sections, those numbers mean that:
  • strings that give symbol names are in section 5, .strtab
  • the relocation data is in section 6, .rela.text
A good high level tool to disassemble that section is:
nm hello_world.o
which gives:
0000000000000000 T _start
0000000000000000 d hello_world
000000000000000d a hello_world_len
This is however a high level view that omits some types of symbols and in which the symbol types . A more detailed disassembly can be obtained with:
readelf -s hello_world.o
which gives:
Symbol table '.symtab' contains 7 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS hello_world.asm
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1
     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    2
     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
The binary format of the table is documented at www.sco.com/developers/gabi/2003-12-17/ch4.symtab.html
The data is:
readelf -x .symtab hello_world.o
which gives:
Hex dump of section '.symtab':
  0x00000000 00000000 00000000 00000000 00000000 ................
  0x00000010 00000000 00000000 01000000 0400f1ff ................
  0x00000020 00000000 00000000 00000000 00000000 ................
  0x00000030 00000000 03000100 00000000 00000000 ................
  0x00000040 00000000 00000000 00000000 03000200 ................
  0x00000050 00000000 00000000 00000000 00000000 ................
  0x00000060 11000000 00000100 00000000 00000000 ................
  0x00000070 00000000 00000000 1d000000 0000f1ff ................
  0x00000080 0d000000 00000000 00000000 00000000 ................
  0x00000090 2d000000 10000200 00000000 00000000 -...............
  0x000000a0 00000000 00000000                   ........
The entries are of type:
typedef struct {
    Elf64_Word  st_name;
    unsigned char   st_info;
    unsigned char   st_other;
    Elf64_Half  st_shndx;
    Elf64_Addr  st_value;
    Elf64_Xword st_size;
} Elf64_Sym;
Like in the section table, the first entry is magical and set to a fixed meaningless values.
Eli Benderski Updated +Created
Amazing systems programming tutorials. Whenever you Google a hard topic, his blog comes up.
Also has many great contributions on Stack Overflow: stackoverflow.com/users/8206/eli-bendersky
As of 2016, Eli worked at Google (reference). TODO before that, I had found his earlier info previously but lost it.
Eli focuses mostly on compiler toolchains.
Eligius pool Updated +Created
Created by Luke Dashjr.
The pool is named after Saint Eligius, patron of miners[ref]
Eligius also means to "choose" or "chosen" in Latin: en.wiktionary.org/wiki/Eligius, same root as "to elect" in modern English presumably.
Figure 1.
Saint Eligius by Petrus Christus
. Source. Eligius pool is named after Saint Eligius, patron of goldsmiths and miners[ref]
Elis Regina Updated +Created
Mostly interpreter of songs written by others. But she's just too amazing, many of her interpretations are better than the original.
God, even Ciro Santilli is slightly shocked by her death, which happened before he was born, can you imagine it at the time? She was MPB's golden girl...
Video 1.
Atrás da Porta performed by Elis Regina
. Source. Composed by Francis Hime and Chico Buarque.
Video 2.
Águas de março performed by Elis Regina
. Source. From the 1972 eponymous album. Composed by Antônio Carlos Jobim.
Elliptic-curve Diffie-Hellman Updated +Created
The algorithm is completely analogous to Diffie-Hellman key exchange in that you efficiently raise a number to a power times and send the result over while keeping as private key.
The only difference is that a different group is used: instead of using the cyclic group, we use the elliptic curve group of an elliptic curve over a finite field.
Video 1.
Elliptic curves by Computerphile (2018)
Source. youtu.be/NF1pwjL9-DE?t=143 shows the continuous group well, but then fails to explain the discrete part.

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