Cavalcade of Mammals

Can a waterjet be made from a centrifuge?

A waterjet is fast moving water:
waterjet water speed at 40,000 psi = 680 m/s
waterjet water speed at 60,000 psi = 1021 m/s

A pressure washer gives water a speed of 110 m/s.

How fast can a centrifuge spin? Ultracentrifuge speed:
centrifuge spins at 1e5 rpm, has a 10 cm radius rotor.
This give a speed at the rim of:
45 cm rotor circumference at the bottom of the tube
1e5/60 rotations / sec
0.45m/60 x 1e5 = 7.5e2 m/s
So a centrifuge does get water moving fast enough to act as a waterjet.

To turn the rotor spin into a line of water drops, open a door in the bottom of the rotor as the rotor passes a certain point in every spin (1000-2000 times / sec).

If the door is open for 10 us, the rotor will spin 1.5mm.
If the door is open for 1 us, the rotor will spin 0.15 mm.
The water stream will come out in a line, so the resolution in the other dimension can be finer, with the waterjet spread out along the direction of the cut.

A door can’t be mechanically opened and closed that fast, 1 ms is likely the limit.

But a reasonable solution is a rotating (or vibrating) plate with a hole, say spinning 1000/s (or 100/s, opening only every tenth pass), and synchronized with the main rotor spin so opening appeared at the same point along the edge. This would tend to torque the main rotor, but it might be tolerable.

This would give a waterjet with slower cutting–the drop density is 1:1000 or 1:10,000 of a stream.

The rotor would need to be refilled and have enough power to accelerate the new water, and solidly built enough to overcome vibration/torque. And fast centrifuges are expensive.

A micofuge will only give a water speed of 125 m/s.







Using cron to mute sound in Ubuntu 20.04

I wanted to turn off audio at night automatically using cron.

I saw suggestions to use amixer:
export DISPLAY=:0 && /usr/bin/amixer -D pulse sset Master,0 0%
but this gave an error:

ALSA lib pulse.c:242:(pulse_connect) PulseAudio: Unable to connect: Connection refused
amixer: Mixer attach pulse error: Connection refused

This works, add this line to /etc/crontab:

* 23<tab>* * *<tab>jiml<tab>DISPLAY=:0.0 pactl --server unix:/run/user/1000/pulse/native set-sink-mute @DEFAULT_SINK@ true

and restart cron:
service cron restart

jiml is the user with the open desktop.
‘1000’ is the uid of user ‘jiml’, this can be found by:

ls /run/user
or
id -u jiml

and restart cron:
service cron restart


jiml is the user with the open desktop.
‘1000’ is the uid of user ‘jiml’, this can be found by:

ls /run/user
or
id -u jiml

Links for July 2021

Four-day week ‘an overwhelming success’ in Iceland
Nature’s Metropolis: Chicago and the Great West by William Cronon
The Death and Life of the Great Lakes by Dan Egan


Linux Fu: PDF For Penguins
Editing PDFs, PDFEscape
pdfedit, qpdf, pdfTk, Pandoc, ps2pdf, pdfxup
pdfshuffler, pdfslicer

Distinct colors
List of 20 Simple, Distinct Colors
Red #e6194B1, Green #3cb44b2, Yellow #ffe1193, Blue #4363d84, Orange #f582315, Purple #911eb46, Cyan #42d4f47, Magenta #f032e68, Lime #bfef459, Pink #fabed410, Teal #46999011, Lavender #dcbeff12, Brown #9A632413, Beige #fffac814, Maroon #80000015, Mint #aaffc316, Olive #80800017, Apricot #ffd8b118, Navy #00007519, Grey #a9a9a920

Generate visually distinct palettes of optimally distinct colors.

gray #808080, darkolivegreen #556b2f, forestgreen #228b22, maroon #800000, darkslateblue #483d8b, darkgoldenrod #b8860b, darkcyan #008b8b, steelblue #4682b4, darkblue #00008b, limegreen #32cd32, darkseagreen #8fbc8f, darkmagenta #8b008b, red #ff0000, darkorange #ff8c00, lime #00ff00, blueviolet #8a2be2, aqua #00ffff, blue #0000ff, greenyellow #adff2f, tomato #ff6347, fuchsia #ff00ff, dodgerblue #1e90ff, palevioletred #db7093, laserlemon #ffff54, powderblue #b0e0e6, lightgreen #90ee90, deeppink #ff1493, mediumslateblue #7b68ee, lightsalmon #ffa07a, wheat #f5deb3, violet #ee82ee, pink #ffc0cb


Links for June 2021

“Predicting the probability of death using proteomics”. Eiriksdottir et al, 2021. Nat Comm Bio.
“We could identify the 5% at highest risk in a group of 60-80 years old, where 88% died within ten years and 5% at the lowest risk where only 1% died.”

Appendix N: Inspirational and Educational Reading is a section at the back of the AD&D Dungeon Masters Guide (1e) (1979), p.224.

Why Are Billionaires Presumed Innocent? by David Sirota

Mechanical Singing-Bird Tabatieres: From 1785-1996
by Geoffrey T. Mayson

Books on Automata and Related Subjects
Flights of Fancy: Mechanical Singing Birds by Christian Bailly

How to Make Borneo’s “Breakfast of the Gods

DIY Book Scanner
ScanTailor – batch book image processing
Scan to OCR -ed PDF workflow.
Tesseract OCR

Dungeons & Deceptions: The First D&D Players Push Back On The Legend Of Gary Gygax by Cecilia D’Anastasio

Automata
The Incredible Mechanical Artistry Of François Junod
, Junod website
Bowes Museum Silver Swan


Links for April 2021


MTHFR Testing and Estrogen. If your provider orders this, walk out the door. Here’s why. by Dr. Jen Gunter
What the heck happened to John Ioannidis? by David Gorski
Tl; dr: went from skeptic to COVI-19 pandemic denier.

How the Top 0.01 Percent Became America’s Criminal Class
An underfunded and overworked IRS has enabled a handful of plutocratic tax cheats to live large at the expense of everyone else.
b
y Timothy Noah
A few interesting bits, but not a great article. This didn’t just happen, back when Newt Gingrich was majority leader, the Republicans attacked the IRS for auditing rich folks, and forced them to instead focus on auditing poor families.
CDC Morbidity and Mortality Weekly Report: Community Transmission of SARS-CoV-2 Associated with a Local Bar Opening Event — Illinois, February 2021
Remarkable Women: The Life and Times of Virginia Hall (Part 2) by Ginny Burges
Incredible account of an Americans women spying and running the resistance in occupied France in WWII.
Glendon, Alberta: World’s largest pierogi sculpture

Secrets of LEGO Designer by Michele Debczak

First-of-its-kind study pits psilocybin against a common antidepressant. by Erin Brodwin
Super bee photos by Sam Droege at USGS, BIML Lab Macro photo guide
Dimitri Tishchenko — magnetic ball sculptures, fractals

I Once Tried to Cheat Sleep, and For a Year I Succeeded by Akshat Rathi
Studio Ghibli wallpapers

Links for March 2021

Thousands of starlings fly together to make an enormous bird. by Gage Li
This amazing photograph (still from a video) was taken by James Crombie in Ireland. It shows a murmuration of thousands of starlings acting like a single giant creature to confuse predators.
The Seven Lady Godivas: The True Facts Concerning History’s Barest Family by Dr. Seuss
35M Americans have health insurance due to Obamacare. 12M directly on ACA plans, 14M due to the Medicaid expansion, a couple million young adults on their parents plans, and 10M covered due to the employer mandate.
Assemblies of putative SARS-CoV2-spike-encoding mRNA sequences for vaccines BNT-162b2 and mRNA-1273
College students are falling in love with white supremacy. Rep. Paul Gosar is helping. by Talia Lavin
Abraham Lincoln (1860-02-27): Cooper Union Address
“The sum of the whole is, that of our thirty-nine fathers who framed the original Constitution, twenty-one—a clear majority of the whole—certainly understood that no proper division of local from federal authority, nor any part of the Constitution, forbade the Federal Government to control slavery in the federal territories; while all the rest probably had the same understanding. Such, unquestionably, was the understanding of our fathers who framed the original Constitution; and the text affirms that they understood the question “better than we.””

“Now, and here, let me guard a little against being misunderstood. I do not mean to say we are bound to follow implicitly in whatever our fathers did. To do so, would be to discard all the lights of current experience—to reject all progress—all improvement. What I do say is, that if we would supplant the opinions and policy of our fathers in any case, we should do so upon evidence so conclusive, and argument so clear, that even their great authority, fairly considered and weighed, cannot stand; and most surely not in a case whereof we ourselves declare they understood the question better than we.”

“If any man at this day sincerely believes that a proper division of local from federal authority, or any part of the Constitution, forbids the Federal Government to control as to slavery in the federal territories, he is right to say so, and to enforce his position by all truthful evidence and fair argument which he can. But he has no right to mislead others, who have less access to history, and less leisure to study it, into the false belief that “our fathers who framed the Government under which we live” were of the same opinion—thus substituting falsehood and deception for truthful evidence and fair argument.”


Time, an XKCD comic, time-lapse video
When the Electric Car Is King, Less Energy Is More by Liam Denning and Elaine He

Strict firearm laws reduce gun deaths: here’s the evidence by Nick Evershed

Links for February 2021

The Real Origins of the Religious Right: They’ll tell you it was abortion. Sorry, the historical record’s clear: It was segregation. by RANDALL BALMER
Pro-Trump Rioters Tear Down American Flag, Replace it With Trump Flag at U.S. Capitol Building. by Morgan Smith and Virginia Chamlee
Amid the Wildfires: Mike Davis’s forecast for the left. by Micah Uetricht
City of Quartz (1990). Los Angeles’s history, politics, culture, architecture, policing, immigration
Late Victorian Holocausts (200). About famines that swept India, China, and Brazil from 1870 to 1914, resulting in tens of millions of deaths.
Freedom from the Market by Mike Konczal.
Remakes the American debate about freedom, draws on examples from their own, largely forgotten history.
What Do We Do About John James Audubon? The founding father of American birding soared on the wings of white privilege. The birding community and organizations that bear his name must grapple with this racist legacy to create a more just, inclusive world. by J. Drew Lanham
‘I Miss My Mom’: Children Of QAnon Believers Are Desperately Trying To Deradicalize Their Own Parents: Here’s what it’s like to lose the person who raised you to a far-right cult. by Jesselyn Cook
Cities Spend Millions On Police Misconduct Every Year. Here’s Why It’s So Difficult to Hold Departments Accountable. by Amelia Thomson-DeVeaux, Laura Bronner and Damini Sharma