Science

Head spin: does the brain behave like a spin glass? Spin-glass-like states that occur in models of neural networks can provide important insights into states of low and high brain activity that have been observed in mammals. That is the claim of a team of theoretical biophysicists in Spain who are the first to show that disordered states in neurological networks could have a functional role in living brains. In familiar magnetic materials such as ferromagnets, the interaction between individual spin magnetic moments causes all of the spins to point in the same direction of magnetization. In spin-glass states, the interaction between spins does not allow individual spins to point in the same direction as their neighbours. This leads to “frustration”, whereby no direction of magnetization exists and the spins point in random directions. Brains are not magnetic systems and their working cells – neurons – do not resemble magnetic moments, but mathematically they behave …

A debate has raged for decades over whether male fertility is declining, according to some analyses of studies from recent decades. It’s an alarming possibility, and likely one reason at-home semen analysis is a growing field of research and product development. The latest study of a new at-home test kit, published today in Science Translational Medicine, found that even untrained users were able to measure sperm count and concentration as well as motility (the percentage of actively moving sperm), detecting abnormal semen with 97 percent accuracy compared with traditional lab testing. Developed by researchers at Harvard Medical School, the system uses a smartphone app with a 3-D–printed optical attachment to record a video of sperm cells in a sample. Software algorithms then analyze the video to count the sperm and assess their movement. The user simply slides the brick-shaped magnifying optical attachment onto the back of a smartphone, then loads a semen sample into a …

The brain contains a built-in GPS that relies on memories of past navigation experiences to simulate future ones. But how does it represent new environments in order to determine how to navigate them successfully? And what happens in the brain when we enter a new space, or use satellite navigation (SatNav) technology to help us find our way around? Research published Tuesday in Nature Communications reveals two distinct brain regions that cooperate to simulate the topology of one’s environment and plan future paths through it when one is actively navigating. In addition, the research suggests both regions become inactive when people follow SatNav instructions instead of using their spatial memories. In a previous study researchers at University College London took participants on a guided tour through the streets of London’s Soho district and then used functional magnetic resonance imaging (fMRI) to scan their brains as they watched 10 different simulations of navigating those streets. Some …

Symmetry is easily recognizable in art, architecture, even anatomy. But the concept of symmetry in physics is hard to wrap one’s head around. Yet it is here that symmetry has played one of its most important roles, unlocking the secrets of the forces in nature and of the fundamental particles that inhabit our universe. “The biggest conceptual change over the last 100 years in the way physicists think about the world is symmetry,” says theoretical physicist Lawrence Krauss of Arizona State University. Mathematical symmetry, which Krauss describes as a kind of rule book of nature, has guided scientists to discover the quarks that make up the protons and neutrons in atoms, the gluons that bind them, and eventually the current crowning achievement of particle physics: the Higgs boson that explains how particles get their mass. It has allowed researchers to unify some of the forces in nature—for instance uniting electricity and magnetism into electromagnetism and …

For nearly 40 years scientists have observed their self-imposed ban on doing research on human embryos in the lab beyond the first two weeks after fertilization. Their initial reasoning was somewhat arbitrary: 14 days is when a band of cells known as a primitive streak, which will ultimately give rise to adult tissues, forms in an embryo. It is also roughly the last time a human embryo can divide and create more than one person, and a few days before the nervous system begins to develop. But the so-called 14-day rule has held up all this time partly because scientists could not get an embryo to grow that long outside its mother’s body. Researchers in the U.K. and U.S. recently succeeded for the first time in growing embryos in the lab for nearly two weeks before terminating them, showing that the so-called 14-day rule is no longer a scientific limitation—although it remains a cultural one. …

In a twist: artist’s impression of plasmons with orbital angular momentum Plasmons in 10 different angular-momentum states have been created and characterized by physicists in Israel and Germany. Created by firing laser pulses at a specially designed gold surface, movies of the plasmons in motion were made with an electron microscope. The researchers believe their work could lead to the development of tiny devices that encode information in the angular momentum of the plasmons. Plasmons, which are collective oscillations of electrons in metals that behave like quantum-mechanical particles, can be created by firing light at a metal target. They behave much like the photons that created them but have much shorter wavelengths and so could be used to create tiny “plasmonic” circuits that can process optical signals while taking up much less space than conventional optics. Capacity boost The new work builds on physicists’ ability to create beams of “twisted” light that carry orbital angular …

The dream of the flying car could come down to earth before it gets off the ground. Rising in its place: a network of self-flying drones big enough to ferry individual commuters around town. That’s the future envisioned by several start-ups that are developing so-called “passenger drones,” which could shrink commute times from hours to minutes. At first blush, human-carrying drones sound no more realistic than flying cars. Until recently inventors had never been able to marry automobiles and aircraft in a practical way. Yet a few companies have kept at it: Woburn, Mass.–based Terrafugia, for example, has since 2006 been developing Transition, a “roadable aircraft” that resembles a small airplane that can fold its wings and drive on roads. A personal flying car in every garage has proved to be a tough sell, however, and there are serious safety concerns about asking the average commuter to train for a pilot’s license and take to …

Moiré is better: the self-assembly of block copolymers A new way of using self-assembling block copolymers (BCPs) to create patterned nanostructures has been unveiled by researchers in Canada. They found that arrays of BCPs with different lattice spacings can align preferentially to create well-defined moiré superstructures. These superstructures could be used to create optoelectronic devices that self-assemble, allowing device features to be much smaller than are currently possible using conventional fabrication techniques. BCPs comprise two or more chemically distinct polymer chains connected via covalent bonds. By tuning the molecular weight, chemical composition and the volume fraction of the blocks, researchers can make BCPs that self-assemble into periodic nanopatterns such as arrays of parallel lines and hexagonal dot patterns on a variety of surfaces. Directed self-assembly (DSA) of BCPs by pre-defined templates could lead to patterning capabilities beyond the resolution limits of conventional optical lithography. This could result in components with feature sizes well below 20 nm …

In touch: John Madden (left) and Mirza Saquib Sarwar with their sensor A flexible touch sensor that can distinguish between being touched and being stretched has been developed by researchers in Canada. The devices could be integrated into clothing and could even be used to create “skin” for robots. Touch sensors are ubiquitous and are used in a range of technologies from smartphone screens to robotic limbs. Researchers are now looking at creating flexible, stretchable sensors that can be used where traditional sensors are not suitable. This raises a challenging problem: if a touch sensor is deformable, how does it know whether it is being touched or stretched? Mirza Saquib Sarwar, John Madden and colleagues at the University of British Columbia (UBC) now think they have an answer, with a sensor with a capacitance that increases when you stretch it and decreases when you touch it. Delicate touch Capacitive touch sensors are used on applications …

On a recent expedition into southeastern Georgia’s backwoods, after 137 hours of searching through blackwater ponds with nets, amphibian specialist Mark Mandica came away with two flatwoods salamander larvae, a federally endangered species. Although only a meager find, the larval pair was “unfortunately considered a huge success,” the executive director of the Amphibian Foundation laments. Flatwoods are extremely rare: Since 2000 populations have declined by 90 percent throughout their range in the U.S. Southeast. Habitat loss is one key cause. Only 3 percent of their natural territory, longleaf pines, remains. Another is forest fire prevention: Flatwoods hibernate underground during the summer fire season but humans have been setting controlled burns in the winter, roasting the poor creatures. To combat their decline, Mandica plans to rear the larvae and ultimately breed flatwoods in captivity, the first attempt with this species, but it is an act of desperation. “It’s their only shot,” Mandica says. Yet flatwoods are …

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