How zebrafish get their stripes


This video from the USA says about itself:

6 November 2014

In the clip, a 10-day-old zebrafish gets its stripes in this series of images taken one a day for 30 days. Credit required: D Parichy Lab/University of Washington.

From Cardiff University in Wales:

How do zebrafish develop their stripes?

Cardiff University mathematician discovers key aspect underlining distinctive patterns of the zebrafish

September 28, 2017

A Cardiff University mathematician has thrown new light on the longstanding mystery of how zebrafish develop the distinctive striped patterns on their skin.

In a new study, Dr Thomas Woolley has simulated the intricate process that sees the pigmented skin cells of the zebrafish engaged in a game of cat and mouse as they chase after each in the early developmental stages before resting to create a final pattern.

Dr Woolley discovered that a key factor is the angles at which the cells chase after each other, and these angles can determine whether a zebrafish develops its distinctive stripes, broken stripes, polka-dot patterns or sometimes no pattern at all.

The findings have been presented in the journal Physical Review E.

Rather than have a pattern ingrained in their genetic code, zebrafish start their lives as transparent embryos before developing iconic patterns over time as they grow into adults. As is often the case in nature, many possible mutations exist and this can dictate the pattern that develops in the zebrafish.

Several researchers have studied how and why these pattern form and have concluded that it’s a result of three types of pigment cells interacting with one other. More specifically, black pigment cells (melanophores), yellow pigment cells (xanthophores) and silvery pigment cells (iridophores), chase after each other until a final pattern is reached.

As hundreds of these chases play out, the yellow cells eventually push the black cells into a position to form a distinct pattern.

Dr Woolley, from Cardiff University’s School of Mathematics, said: “Experimentalists have demonstrated that when these two types of cells are placed in a petri dish, they appear to chase after each other, a bit like pacman chasing the ghosts. However, rather than chase each other in straight lines, they appear to be chasing each other in a spiral.

“My new research has shown that the angle at which the cells chase after each other is crucial to determining the final pattern that we see on different types of zebrafish.”

In his study, Dr Woolley performed a number of computer simulations that took a broad view of how cells move and interact when the zebrafish is just a few weeks old. Different patterns were then spontaneously generated depending on the chasing rules.

By experimenting with different chasing angles in his simulations, Dr Woolley was able to successfully recreate the different patterns that are exhibited by zebrafish.

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Babylonians, world’s oldest trigonometrists discovery


This video says about itself:

Ancient Babylonian tablet – world’s first trig table

24 August 2017

UNSW Sydney scientists have discovered the purpose of a famous 3700-year old Babylonian clay tablet, revealing it is the world’s oldest and most accurate trigonometric table, most likely used by ancient mathematical scribes to calculate how to construct palaces, temples and stepped pyramids.

Read more here.

Plimpton 322, the most famous of Old Babylonian tablets (1900-1600 BC), is the world’s oldest trigonometric table, possibly used by Babylonian scholars to calculate how to construct stepped pyramids, palaces and temples, according to a duo of researchers from the School of Mathematics and Statistics at the University of New South Wales (UNSW), Sydney, Australia: here.

African American women at NASA


This video from the USA says about itself:

14 August 2016

Watch the new trailer for Hidden Figures, based on the incredible untold true story. Starring Taraji P. Henson, Octavia Spencer & Janelle Monáe. In theaters this January.

HIDDEN FIGURES is the incredible untold story of Katherine G. Johnson (Taraji P. Henson), Dorothy Vaughan (Octavia Spencer) and Mary Jackson (Janelle Monáe)—brilliant African-American women working at NASA, who served as the brains behind one of the greatest operations in history: the launch of astronaut John Glenn into orbit, a stunning achievement that restored the nation’s confidence, turned around the Space Race, and galvanized the world. The visionary trio crossed all gender and race lines to inspire generations to dream big.

In Theaters – January 6, 2017

From Science News:

Hidden Figures highlights three black women who were vital to the U.S. space program

Despite racism and sexism, female “computers” put John Glenn into orbit

By Emily Conover

6:00am, December 23, 2016

Hollywood space flicks typically feature one type of hero: astronauts who defy the odds to soar into space and back again. But now a group of behind-the-scenes heroes from the early days of the U.S. space program are getting their due. Black female mathematicians performed essential calculations to safely send astronauts to and from Earth’s surface — in defiance of flagrant racism and sexism.

These “computers” — as they were known before the electronic computer came into widespread use — are the subject of Hidden Figures. The film focuses on three black women — Katherine Johnson (played by Taraji P. Henson), Dorothy Vaughan (Octavia Spencer) and Mary Jackson (Janelle Monáe) — and their work at NASA’s Langley Research Center in Hampton, Va., during the run-up to John Glenn’s orbit of the Earth in 1962.

A mathematics virtuoso, Katherine Johnson calculated or verified the flight trajectories for many of the nation’s space milestones. The film showcases her work on two: the first American in space (Alan Shepard), and the first American to orbit the Earth (John Glenn). But Johnson also had a hand in sending the first men to the moon, during the Apollo 11 mission, and when the Apollo 13 astronauts ran into trouble, Johnson worked on the calculations that helped them get home safely.

Mary Jackson worked on wind tunnel experiments at Langley, where she tested how spacecraft performed under high winds. The film follows Jackson as she overcomes obstacles of the Jim Crow era to become NASA’s first black female engineer. Though the movie focuses on her triumphant rise, after decades in that role, Jackson grew frustrated with the remaining glass ceilings and moved into an administrative role, helping women and minorities to advance their careers at NASA.

Johnson and Jackson got their start under the leadership of Dorothy Vaughan, who led the segregated group of “colored computers,” assigning black women to assist with calculations in various departments. As electronic computers became more essential Vaughan recognized their importance and became an expert programmer. A scene where she surreptitiously takes a book from whites-only section of a public library — a guide to the computing language FORTRAN — is a nod to Vaughan’s prowess with the language.

Electronic computers were so unfamiliar in the 1960s that everyone from engineers to astronauts felt more confident when a human computer calculated the numbers. After a room-sized IBM mainframe spits out figures for his trajectory, John Glenn requests, “Get the girl to check the numbers” — meaning Johnson. In the film, that request culminates in Johnson running a frantic last-minute check of the numbers and sprinting across the Langley campus while Glenn waits. In reality, that process took a day and a half.

For spaceflight fans, Hidden Figures provides an opportunity to be immersed in a neglected perspective. The women’s stories are uplifting, their resilience impressive and their retorts in response to those who underestimate them, witty.

But viewers should be aware that, although the main facts underpinning the plot are correct, liberties have been taken. Some of the NASA higher-ups in the film — including Johnson’s supervisor Al Harrison (Kevin Costner) — are not real people. And presumably because number crunching tends to be a bit thin in the suspense department, the filmmakers have dramatized some scenes — Johnson is pictured in Mission Control during Glenn’s flight, but in reality she watched it on television — which seems a shame because the contributions of these women don’t need to be exaggerated to sound momentous.

‘Mathematics is terrorism’ in American Airlines planes


This video from Canada says about itself:

How racial profiling hurts everyone, including the police | Jamil Jivani | TEDxToronto

8 October 2014

This talk was given at a local TEDx event, produced independently of the TED Conferences. Police forces around the world have often been criticized for racial profiling and for acting with unnecessary force. After being a victim of racial profiling himself, activist Jami Jivani wanted to change the way that the police engage with local citizens. In his TEDxToronto talk, Jamil discusses the importance of mediating the relationship between the police and the public. Though there may be fundamental flaws in the system, Jamil believes that by developing a dialogues with police officials, we can initiate positive change.

Jami Jivani is a 2014-15 articling student at Torys LLP and founder of the Policing Literacy Initiative. He formerly worked as a consultant for businesses and charities across Canada. While in law school, Jamil taught constitutional law as a part-time high school teacher and was President of the Yale Black Law Students Association. Jamil’s community involvement in Toronto includes serving on the Board of Directors of the Children’s Aid Society of Toronto. He is a graduate of Yale Law School, York University, and Humber College.

From daily The Independent in Britain:

Ivy League economist ‘suspected of terrorism‘ while doing maths aboard American Airlines plane

His seat neighbour incorrectly identified his equations for another language or code

Feliks Garcia, New York

7 May 2016

An Ivy League economist was escorted off an American Airlines plane after a fellow passenger incorrectly identified the mathematical equations he was scrawling for Arabic script, and suspected him of terrorism.

Italian economist Guido Menzio, 40, was en route to Syracuse to catch a connecting flight to Ontario, where he was scheduled to present a paper at Queen’s University. His neighbor had witnessed him scribbling the equations and subsequently handed a flight attendant a note. The unidentified passenger had tried to make small talk with Mr Menzio, who was too focused on working out the maths he was about to present at the university, according to the Washington Post.

The plane remained on the tarmac for an extended period of time, as the passenger wary of Mr Menzio had feigned sickness, and the pilots steered the craft back to the gate. Airline personnel escorted the passenger off, but shortly after requested Mr Menzio to also step out of the plane.

American Airlines spokesman Casey Norton told the Post that the passenger, whom he was not at liberty to identify over privacy concerns, revealed that she had felt ill because of the perceived behaviour of her neighbour, Mr Menzio, an associate professor of economics at the University of Pennsylvania.

Mr Menzio was questioned by “some sort of agent” who told him he was suspected of terrorism, but he was ultimately deemed not a “credible threat” after showing what he had been writing.

Although Mr Menzio said he was “treated respectfully throughout”, he criticised airline protocols that fail to collect sufficient intelligence in situations like these. Airlines have “a security protocol that is too rigid – in the sense that once the whistle is blown everything stops without checks – and relies on the input of people who may be completely clueless,” he said.

In April, Southwest Airlines came under scrutiny after ejecting a University of California, Berkeley student, Khairuldeen Makhzoomi, who passengers overheard speaking Arabic before takeoff.

Mr Makhzoomi did not sue the airline, however; he only wanted an apology.

“Human dignity is the most valuable thing in the world, not money,” he said. “If they apologised, maybe it would teach them to treat people equally.”

DELTA IS THE LATEST AIRLINE TO FIND ITSELF IN HOT WATER After kicking a family off an overbooked flight over their 2-year-old’s seat.

Florida Islamophobe’s crusade against Arabic numerals


This video says about itself:

3 September 2013

Hank unravels the fascinating yarn of how the world came to use so-called Arabic numerals — from the scholarship of ancient Hindu mathematicians, to Muslim scientist Al-Khwarizmi, to the merchants of medieval Italy.

By Tom Boggioni in the USA:

Conservative Florida mom vows to stop her children from learning about Islam and Arabic numerals

06 Oct 2015 at 14:29 ET

A Florida mom posted a rambling 15 minute video to her Facebook account complaining that her son’s high school world history class textbook spends an entire chapter on Muslims and advances in the Islamic world, including the “origin of Ay-rabic numerals.”

According to the post by Christian Kayla Normandin, she had previously promised to share a video detailing objections she has with the history book being used in her son’s class. …

Touching upon developments in education, astronomy, architecture, art, agriculture, science and mathematics in the Islamic world, Normandin drew attention to the development of the Arabic numeric system — the most common numeric system used in the world today.

“It even has the origin of ‘Ay-rabic’ numerals,” she read from the book …

Following her review of the chapter, Normandin asserted, “We need to stand up against this, y’all. Our children don’t need to be taught this. It’s not teaching them facts. It’s not teaching them truth. It’s basically telling them that this is going to be the way of life.”

She went on to state that she will go as far as she needs to go to get the textbook pulled, saying, “My children aren’t going to learn this.”

Starling murmurations, new research


This video is about a starling murmuration in Britain.

From Science:

How bird flocks are like liquid helium

By Marcus Woo

27 July 2014 1:00 pm

A flock of starlings flies as one, a spectacular display in which each bird flits about as if in a well-choreographed dance. Everyone seems to know exactly when and where to turn. Now, for the first time, researchers have measured how that knowledge moves through the flock—a behavior that mirrors certain quantum phenomena of liquid helium.

“This is one of the first studies that gets to the details of how groups move in unison,” says David Sumpter of Uppsala University in Sweden, who was not part of the study.

The remarkable accord with which starling flocks fly has long puzzled researchers and bird watchers alike. In the 1930s, the ornithologist Edmund Selous even suggested that the birds cooperate via telepathy. Researchers have since turned to more scientifically sound ideas, using mathematical models.

In the 1990s, physicist Tamás Vicsek of Eötvös Loránd University in Budapest came up with one of the more successful models, which is based on the principle that each bird flies in the same direction as its neighbors. If a bird angles right, the ones next to it will turn to stay aligned. Although this model reproduces many features well—how a flock swiftly aligns itself from a random arrangement, for example—a team of researchers from Italy and Argentina has now discovered that it doesn’t accurately describe in detail how flocks turn.

In their new study, the team, led by physicists Andrea Cavagna and Asja Jelic of the Institute for Complex Systems in Rome, used high-speed cameras to film starlings—which are common in Rome and form spectacular flocks—flying near a local train station. Using tracking software on the recorded video, the team could pinpoint when and where individuals decide to turn, information that enabled them to follow how the decision sweeps through the flock. The tracking data showed that the message to turn started from a handful of birds and swept through the flock at a constant speed between 20 and 40 meters per second. That means that for a group of 400 birds, it takes just a little more than a half-second for the whole flock to turn.

“It’s a real tour de force of measurement,” says Sriram Ramaswamy of the Tata Institute of Fundamental Research’s Centre for Interdisciplinary Sciences in Hyderabad, India, who wasn’t part of the research.

The fact that the information telling each bird to turn moves at a constant speed contradicts the Vicsek model, Cavagna says. That model predicts that the information dissipates, he explains. If it were correct, not all the birds would get the message to turn in time, and the flock wouldn’t be able to fly as one.

The team proposes that instead of copying the direction in which a neighbor flies, a bird copies how sharply a neighbor turns. The researchers derived a mathematical description of how a turn moves through the flock. They assumed each bird had a property called spin, similar to the spins of elementary particles in physics. By matching one another’s spin, the birds conserved the total spin of the flock. As a result of that conservation, the equations showed that the information telling birds to change direction travels through the flock at a constant speed—exactly as the researchers observed. It’s this constant speed that enables everyone to turn in near-unison, the team reports online today in Nature Physics.

The new model also predicts that information travels faster if the flock is well aligned—something else the team observed, Cavagna says. Other models don’t predict or explain that relationship. “This could be the evolutionary drive to have an ordered flock,” he says, because the birds would be able to maneuver more rapidly and elude potential predators, among other things.

Interestingly, Cavagna adds, the new model is mathematically identical to the equations that describe superfluid helium. When helium is cooled close to absolute zero, it becomes a liquid with no viscosity at all, as dictated by the laws of quantum physics. Every atom in the superfluid is in the same quantum state, exhibiting a cohesion that’s mathematically similar to a starling flock.

The similarities are an example of how deep principles in physics and math apply to many physical systems, Cavagna says. Indeed, the theory could apply to other types of group behavior, such as fish schools or assemblages of moving cells, Sumpter says.

Other models, such as the Vicsek model or others that treat the flock as a sort of fluid, probably still describe flock behavior over longer time and length scales, Ramaswamy says. But it’s notable that the new model, which is still based on relatively simple principles, can accurately reproduce behavior at shorter scales. “I think that’s cool,” he says. “That’s an achievement, really.”

Sumpter agrees. “It’s kind of reassuring we don’t need to think about the telepathic explanation,” he says.

See also here.