Scanning tunneling microscopy is used to observe signatures of Majorana states at the ends of iron atom chains. [Also see Perspective by Lee] Authors: Stevan Nadj-Perge, Ilya K. Drozdov, Jian Li, Hua Chen, Sangjun Jeon, Jungpil Seo, Allan H. MacDonald, B. Andrei Bernevig, Ali Yazdani

Article

Acoustic diodes and circulators operate on the principle that a mechanical signal is used to control the flow of mechanical energy through a solid. Here, the authors demonstrate an acoustic switch composed of a chain of spherical particles, and study the underpinning mechanism behind the process.

Nature Communications doi: 10.1038/ncomms6311

Authors: Feng Li, Paul Anzel, Jinkyu Yang, Panayotis G. Kevrekidis, Chiara Daraio

Hipsters are becoming more common, in both major senses of the word common, suggests this study:

“The hipster effect: When anticonformists all look the same,” Jonathan Touboul, arXiv:1410.8001, October 29, 2014.

The author explains:

“In such different domains as statistical physics and spin glasses, neurosciences, social science, economics and finance, large ensemble of interacting individuals taking their decisions either in accordance (mainstream) or against (hipsters) the majority are ubiquitous. Yet, trying hard to be different often ends up in hipsters consistently taking the same decisions, in other words all looking alike. We resolve this apparent paradox studying a canonical model of statistical physics, enriched by incorporating the delays necessary for information to be communicated. We show a generic phase transition in the system: when hipsters are too slow in detecting the trends, they will keep making the same choices and therefore remain correlated as time goes by, while their trend evolves in time as a periodic function. This is true as long as the majority of the population is made of hipsters. Otherwise, hipsters will be, again, largely aligned, towards a constant direction which is imposed by the mainstream choices. Beyond the choice of the best suit to wear this winter, this study may have important implications in understanding dynamics of inhibitory networks of the brain or investment strategies finance, or the understanding of emergent dynamics in social science, domains in which delays of communication and the geometry of the systems are prominent.”

Touboul is, in his own words: Principal Investigator “of the Mathematical Neuroscience Team, part of the Center for Interdisciplinary Research in Biology of the Collège de France. I am researcher at Inria (Paris), in the MYCENAE Team.” He writes, in this paper, in the royal we. He does not explicitly self-identify as a hipster.

(Thanks to investigator Leah Branch for bringing this to our attention).

The top 100 papers

Nature 514, 7524 (2014). http://www.nature.com/doifinder/10.1038/514550a

Authors: Richard Van Noorden, Brendan Maher & Regina Nuzzo

Nature explores the most-cited research of all time.

Author(s): Julian Barbour, Tim Koslowski, and Flavio Mercati

Masses evolving under Newtonian gravity have a preferred direction of time without special initial conditions.

[Phys. Rev. Lett. 113, 181101] Published Wed Oct 29, 2014

DeepMind has built a neural network that can access an external memory like a conventional Turing machine. The result is a computer that mimics the short-term memory of the human brain.

One of the great challenges of neuroscience is to understand the short-term working memory in the human brain. At the same time, computer scientists would dearly love to reproduce the same kind of memory in silico.

The best way to describe Sprout, an ambitious new desktop from HP, is that it's unlike any PC the company has ever made. The second-best way: It's an all-in-one computer with a touch mat that acts as a second screen, and an overhead projector/camera...

GLlrhghghhhh

Author(s): A. Hinke Schokker and A. Femius Koenderink

This paper reports a comprehensive experimental study of silver and gold plasmonic crystal lasers. Such periodic plasmon particle systems have recently triggered large attention due to the fact that localized plasmons and collective lattice resonances conspire to give large light-matter interaction strength in narrow resonances. The authors provide a detailed report on the conditions required for lasing, and a complete analysis of the underlying plasmonic lattice band structure.

[Phys. Rev. B 90, 155452] Published Tue Oct 28, 2014

Piled Higher & Deeper by Jorge Cham		www.phdcomics.com
title: "Not write" - originally published 10/29/2014 For the latest news in PHD Comics, CLICK HERE!

POW!

Author(s): Evgenii E. Narimanov

A design for a photonic crystal made with so-called hyperbolic metamaterials could provide unprecedented control of light waves confined to the surface.

[Phys. Rev. X 4, 041014] Published Mon Oct 27, 2014

A new microscope allows three-dimensional imaging of living systems at very high resolution in real time. Authors: Bi-Chang Chen, Wesley R. Legant, Kai Wang, Lin Shao, Daniel E. Milkie, Michael W. Davidson, Chris Janetopoulos, Xufeng S. Wu, John A. Hammer, Zhe Liu, Brian P. English, Yuko Mimori-Kiyosue, Daniel P. Romero, Alex T. Ritter, Jennifer Lippincott-Schwartz, Lillian Fritz-Laylin, R. Dyche Mullins, Diana M. Mitchell, Joshua N. Bembenek, Anne-Cecile Reymann, Ralph Böhme, Stephan W. Grill, Jennifer T. Wang, Geraldine Seydoux, U. Serdar Tulu, Daniel P. Kiehart, Eric Betzig

A bitter dispute lays bare questionable practices in China's foreign-talent programs. Author: Mara Hvistendahl

Author(s):

[Phys. Rev. X 4, 040002] Published Thu Oct 23, 2014

Piled Higher & Deeper by Jorge Cham		www.phdcomics.com
title: "Written Estimate" - originally published 10/22/2014 For the latest news in PHD Comics, CLICK HERE!

Distant Death

What is the farthest from Earth that any Earth thing has died?

—Amy from NZ

With Halloween approaching, I guess it's the season for death-related questions.

The farthest from Earth that any human has died is about 167 kilometers,[1]Plus or minus a kilometer. when three cosmonauts on Soyuz 11—Vladislav Volkov, Viktor Patsayev, and Georgi Dobrovolsky—suffered a depressurization accident while returning to Earth. They were moving at about 7,755 meters per second at the time, which is also the highest forward speed at which any human has ever died.

Volkov, Patsayev, and Dobrovolsky are the only humans who have died in space. Every other fatal space accident—and, for that matter, every other human death of any kind—happened within 70 kilometers of the surface.[2]Morbid list from my notes: The crew of Columbia died at just over 60 km, Pyotr Dolgov died at roughly 24 km, James Zwayer died at 23 km, Michael J. Adams died at 20 km, Ying Chin Wang died at 20 km, and Rudolf Anderson died at between 18 and 23 km. Jack Weeks presumably died somewhere between 20 and 0 km the ocean surface.

But humans don't hold this record.

For starters, there are plenty of test animals which have died in space. But, to be honest, I can't bring myself to collect statistics about them. I mean, at least the human pilots who died had all volunteered and understood what was happening to them. So instead, I'm going to skip straight to the organisms that are the real answer to Amy's question: Microbes.

Spacecraft carry bacteria, although we do our best to sterilize them before and during launch. This sterilization is important, because we don't want to contaminate another planet or Moon with Earth bacteria. There are two big reasons for this—one ethical and one practical. The ethical one is that we don't want to accidentally introduce Earth life that disrupts and/or destroys a native ecosystem. The practical one is that if we find life on some other planet, we don't want to have to struggle to figure out whether it was contamination from one of our probes.

But sterilizing spacecraft is hard. NASA has an employee specifically assigned to this task, and she has possibly the best job title of all time: Planetary Protection Officer.[3]Another competitor for this title is Philip M. Breedlove, who has the job title Supreme Allied Commander.

The Planetary Protection Officer is responsible for avoiding spacecraft contamination, although there are occasionally problems.

A 2008 study of lunar missions estimated that spacecraft carried 1.98x10¹¹ viable microorganisms per vehicle. Spacecraft such as the Voyagers and Pioneers, which were ultimately headed for deep space, were also not fully sterilized—the official planetary protection strategy was "try not to hit any planets."

Voyager certainly carries lots of bacterial spores. If we take the number from the 2008 paper as a (very rough) estimate of the number of microbes Voyager might carry, we can try to figure out how many might still be alive.

Some microorganisms can survive for a long time in a vacuum. One study found that the majority of bacteria that spent six years in space survived—though only if a shade protected them from the Sun's UV light. Other studies have agreed that radiation is the main thing to worry about, and the radiation environment inside a spacecraft is complex. The bottom line is that we just don't know for sure how long bacteria can survive in deep space.

But we can still give part of an answer Amy's question. If we assume that 1 in 1,000 bacterial spores on Voyager were of a space-tolerant variety, and 1 in 10 of those is somewhere on the craft where UV light doesn't reach it, then that still leaves on the order of 10 million viable bacterial spores traveling on Voyager.

If they suffer a death rate of 30% per six years, as in one of the studies, then there would still be a million of them alive after 50 years, dying at a rate of 1 every 10 minutes. On the other hand, the author of the 2008 study speculated that microbes could avoid hits from cosmic radiation for extremely long time periods, and other sources have speculated about survival for thousands or even millions of years. But no one really knows.

For our Voyager bacteria, there's a higher death rate at first, for spores in more exposed positions, and a much lower one for the more protected ones. Today, it's quite possible there are thousands of bacterial spores still alive on Voyager 1 and 2, lurking quietly in the dead of space. Every few hours, days, or months, one of them degrades enough to no longer be viable.

And each one sets a new record for the most distant Earth thing to die.

Nei due anni e passa dedicati - altri, fra cui forse io, direbbero "persi" - a tentare di fermare il declino italiano, che continua invece inesorabile, mi son fatto spesso coinvolgere in sciocchi dibattiti con personaggi di dubbia fama che i media italiani hanno, in 4+4=8, trasformato in guru economici. No, non vi tedierò oggi con la solita dottoressa Loretta, non ne vale la pena. Nè ritornerò a dibattere di austriaci ed alsaziani: la questione che mi interessa è quantitativa e seria, la polemica con altri è solo una meschina motivazione addizionale.

leggi tutto

Symmetry Magazine did a nice article about me and BAHFest.

There’s a new journal in town. Inference’s first issue includes a lengthy review of a laboratory by a tennis instructor, a set of caricatures, and an exchange of emails from 1996 that is “perhaps, less remarkable for what it says than for the fact that it took place at all.” In short, its editors — […]

Author(s): Benoît Gérardin, Jérôme Laurent, Arnaud Derode, Claire Prada, and Alexandre Aubry

A normally opaque medium can become fully transparent to properly tailored acoustic waves.

[Phys. Rev. Lett. 113, 173901] Published Tue Oct 21, 2014

Author(s): Ross T. Howie, Ioan B. Magdău, Alexander F. Goncharov, Graeme J. Ackland, and Eugene Gregoryanz

Localized vibration phonon modes are observed in a dense hydrogen-deuterium mixture, due to mass distribution disorder from the different isotope masses in the mixture.

[Phys. Rev. Lett. 113, 175501] Published Tue Oct 21, 2014

A normally opaque medium can become fully transparent to properly tailored acoustic waves.

Published Tue Oct 21, 2014

Condividi

Author(s): Sang Hoon Lee (이상훈), Robyn Ffrancon, Daniel M. Abrams, Beom Jun Kim (김범준), and Mason A. Porter

Few quantitative studies of historic human migration exist because of a dearth of data. Now, using geographical information from Korean family books, scientists develop a physics-based analyses of clan migration.

[Phys. Rev. X 4, 041009] Published Thu Oct 16, 2014