tingilinde

a thought for the day - 412 years

 

The secondary mirror on the JWST has successfully deployed, so technically it's a telescope.  

 

 

 

newton's birthday

 

 

It's also fitting that the JWST launched on his birthday as he invented the reflector telescope.

 

an update on the antikythera mechanism

This device continues to amaze.  

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Much of the mechanism’s design relies on wisdom from earlier Middle Eastern scientists. Astronomy in particular went through a transformation during the first millennium B.C.E. in Babylon and Uruk (both in modern-day Iraq). The Babylonians recorded the daily positions of the astronomical bodies on clay tablets, which revealed that the sun, moon and planets moved in repeating cycles—a fact that was critical for making predictions. The moon, for instance, goes through 254 cycles against the backdrop of the stars every 19 years—an example of a so-called period relation. The Antikythera mechanism’s design uses several of the Babylonian period relations.

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salk's patenting the sun comment

There's more to the story than I knew.

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It’s a topical question during this COVID-19 pandemic: why are the companies that developed the vaccines against the coronavirus not giving away their patent on the vaccines for the greater good? Why aren’t governments forcing pharmaceutical companies to license other companies to share their patented invention under a compulsory license arrangement?

To support that idea, people like to bring to memory the history of the invention of the vaccine against polio. Heard of Jonas Salk or Albert Sabin? Jonas Salk became a hero when he invented the vaccine against polio, a worldwide disease affecting young children, paralyzing between 20,000 and 50,000 children annually. Although it was the first polio vaccine, it was not to be the last, as Albert Sabin introduced an oral vaccine in the 1960s that replaced Salk’s.

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why were van leeuwenhoek's microscopes so good?

Looking at the lens is key, but taking one out might damage important museum pieces.  Finally instruments were imaged using neutron tomography.  It turns out he was a superb craftsman. 

 

The paper in ScienceAdvances has some nice images. 

 

Neutron tomography of Van Leeuwenhoek’s microscopes

TIEMEN COCQUYT,  ZHOU ZHOU, JEROEN PLOM, AND LAMBERT VAN EIJCK

 

Abstract

The technique of neutron tomography has, after 350 years, enabled a first look inside the iconic single-lens microscopes of Antoni van Leeuwenhoek. Van Leeuwenhoek’s 17th-century discovery of “animalcules” marks the birth of microbiology. His skillfully self-produced microscope lenses remained unsurpassed for over 150 years. Neutron tomography now enabled us to reveal the lens types Van Leeuwenhoek used. We argue that Van Leeuwenhoek’s instruments incorporate some innovations that testify to an awareness of concurrent developments. In particular, our analysis shows that for making his best-performing microscopes, Van Leeuwenhoek deployed a lens-making procedure popularized in 1678 by Robert Hooke. This is notable, as Hooke always wanted to find the secret of Van Leeuwenhoek’s lenses, but never managed to do so. Therefore, Van Leeuwenhoek was far from the isolated scholar he is often claimed to be; rather, his secrecy about his lenses was motivated by an attempt to conceal his indebtedness to Hooke.

 

 

 

from oxford's history of science museum

Short videos of old, but still working, scientific apparatus. 

 

the adventures of charles townes

How the laser happened .. an excerpt from his book

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lewelyn H. Thomas, a noted Columbia theorist, told me that the maser flatly could not, due to basic physics principles, provide a pure frequency with the performance I predicted. So certain was he that he more or less refused to listen to my explanations. After it did work, he just stopped talking to me. A younger physicist in the department, even after the first suc­cessful operation of the device, bet me a bottle of scotch that it was not doing what we said it would (he paid up).

Shortly after we built a second maser and showed that the frequency was indeed remarkably pure, I visited Denmark and saw Niels Bohr, the great physicist and pioneer in the development of quantum mechanics. As we were walking along the street together, he quite naturally asked what I was doing. I described the maser and its performance. “But that is not possible,” he exclaimed. I assured him it was. Similarly, at a cock­tail party in Princeton, New Jersey, the Hungarian mathematician John von Neumann asked what I was working on. After I told him about the maser and the purity of its frequency, he declared, “That can’t be right!” But it was, I replied, and told him it was already demonstrated.

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tabby cats and a reaction diffusion process

Turing appears to have been on the right track

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The question of how cat stripes and splotches are made touches on some of the deepest theoretical puzzles of biology. How does a blob of cells organize itself into a fruit fly, or a panda? What tells the bones in a limb to become a hand, or paw, or the ribbing of a leathery wing? What tells some skin cells to grow dark hair and others lighter hair?

A team of geneticists reported Tuesday in the journal Nature Communications that it had identified a gene in domestic cats that plays a key role in creating the traditional tabby stripe pattern, and that the pattern is evident in embryonic tissue even before hair follicles start to grow.

The inheritance of cat coats — how to breed for this or that pattern — is well known. But how patterns emerge in a growing embryo “really has been an unsolved mystery,” said Dr. Gregory S. Barsh, an author of the new report.

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Here's the paper.  Turing considered his reaction-diffusion patterning mechanism to be his most important work.

 

Developmental genetics of color pattern establishment in cats

 

Christopher B. Kaelin, Kelly A. McGowan & Gregory S. Barsh
Nature Communications volume 12, Article number: 5127 (2021)

Abstract
Intricate color patterns are a defining aspect of morphological diversity in the Felidae. We applied morphological and single-cell gene expression analysis to fetal skin of domestic cats to identify when, where, and how, during fetal development, felid color patterns are established. Early in development, we identify stripe-like alterations in epidermal thickness preceded by a gene expression pre-pattern. The secreted Wnt inhibitor encoded by Dickkopf 4 plays a central role in this process, and is mutated in cats with the Ticked pattern type. Our results bring molecular understanding to how the leopard got its spots, suggest that similar mechanisms underlie periodic color pattern and periodic hair follicle spacing, and identify targets for diverse pattern variation in other mammals.

 

 

 

jocelyn bell burnell

The NY Times has a video on Jocelyn Bell Burnell

She's a star in astrophysics these days, but early on had a Nobel stolen..  

 

honing the capacity to destroy humanity