Amazing Science

Physicists have experimentally demonstrated an optical system based on an unconventional class of quantum mechanical systems that could lead to the development of new quantum optical devices. The system is called a "PT-symmetric quantum walk," since it consists of single photons that occupy a superposition of states, called quantum walks, that obey parity-time (PT) symmetry—the property in which a system's coordinates in space and time can have their signs reversed without inherently changing the system.

Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

 These new details about how the climate could have dramatically changed following the impact of a 10-kilometer-wide asteroid will be published Aug. 21 in the Proceedings of the National Academy of Sciences. The study, led by the National Center for Atmospheric Research (NCAR) with support from NASA and the University of Colorado Boulder, used a world-class computer model to paint a rich picture of how Earth's conditions might have looked at the end of the Cretaceous Period, information that paleobiologists may be able to use to better understand why some species died, especially in the oceans, while others survived.

Scientists estimate that more than three-quarters of all species on Earth, including all non-avian dinosaurs, disappeared at the boundary of the Cretaceous-Paleogene periods, an event known as the K-Pg extinction. Evidence shows that the extinction occurred at the same time that a large asteroid hit Earth in what is now the Yucatán Peninsula. The collision would have triggered earthquakes, tsunamis, and even volcanic eruptions.

Scientists also calculate that the force of the impact would have launched vaporized rock high above Earth's surface, where it would have condensed into small particles known as spherules. As the spherules fell back to Earth, they would have been heated by friction to temperatures high enough to spark global fires and broil Earth's surface. A thin layer of spherules can be found worldwide in the geologic record.

"The extinction of many of the large animals on land could have been caused by the immediate aftermath of the impact, but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived," said NCAR scientist Charles Bardeen, who led the study. "Our study picks up the story after the initial effects—after the earthquakes and the tsunamis and the broiling. We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left."

250+ math theorems. Can you solve some of them?

Columbia Engineering researchers are first to reproducibly achieve the current blockade effect using atomically precise molecules at room temperature, a result that could lead to shrinking electrical components and boosting data storage and computing power.

A major goal in the field of molecular electronics, which aims to use single molecules as electronic components, is to make a device where a quantized, controllable flow of charge can be achieved at room temperature. A first step in this field is for researchers to demonstrate that single molecules can function as reproducible circuit elements such as transistors or diodes that can easily operate at room temperature.

A team led by Latha Venkataraman, professor of applied physics and chemistry at Columbia Engineeringand Xavier Roy, assistant professor of chemistry (Arts & Sciences), published a study (DOI 10.1038/nnano.2017.156) today in Nature Nanotechnology that is the first to reproducibly demonstrate current blockade—the ability to switch a device from the insulating to the conducting state where charge is added and removed one electron at a time—using atomically precise molecular clusters at room temperature.

Bonnie Choi, a graduate student in the Roy group and co-lead author of the work, created a single cluster of geometrically ordered atoms with an inorganic core made of just 14 atoms—resulting in a diameter of about 0.5 nanometers—and positioned linkers that wired the core to two gold electrodes, much as a resistor is soldered to two metal electrodes to form a macroscopic electrical circuit (e.g. the filament in a light bulb).

The researchers used a scanning tunneling microscope technique that they have pioneered to make junctions comprising a single cluster connected to the two gold electrodes, which enabled them to characterize its electrical response as they varied the applied bias voltage. The technique allows them to fabricate and measure thousands of junctions with reproducible transport characteristics. “We found that these clusters can perform very well as room-temperature nanoscale diodes whose electrical response we can tailor by changing their chemical composition,” says Venkataraman.

“Theoretically, a single atom is the smallest limit, but single-atom devices cannot be fabricated and stabilized at room temperature. With these molecular clusters, we have complete control over their structure with atomic precision and can change the elemental composition and structure in a controllable manner to elicit certain electrical response.”

This is a picture of the algebraic numbers in the complex plane, made by David Moore based on earlier work by Stephen J. Brooks, and available along with other neat stuff at Moore’s site Math and Code.

Algebraic numbers are roots of polynomials with integer coefficients. The integers 0 and 1 are the big dots near the bottom, while ii is near the top. In this picture, the color of a point indicates the degree of the polynomial of which it’s a root:

• red = roots of linear polynomials, i.e. rational numbers,

• green = roots of quadratic polynomials,

• blue = roots of cubic polynomials,

• yellow = roots of quartic polynomials, and so on.

The size of a point decreases exponentially with the ‘complexity’ of the simplest polynomial with integer coefficient of which it’s a root. Here the complexity is the sum of the absolute values of the coefficients of that polynomial.

There are many patterns in this picture that call for explanation! For example, look near the point ii. Can you describe some of these patterns, formulate some conjectures about them, and prove some theorems? Maybe you can dream up a stronger version of Roth’s theorem, which says roughly that algebraic numbers tend to ‘repel’ rational numbers of low complexity.

David Moore made this image using software created by Stephen J. Brooks on Wikipedia. 

Heatwaves amplified by high humidity can reach above 40°C and may occur as often as every two years, leading to serious risks for human health. If global temperatures rise with 4°C, a new super heatwave of 55°C can hit regularly many parts of the world, including Europe, warn researchers.

For the first time, a primitive movie has been encoded in – and then played back from – DNA in living cells. Scientists funded by the National Institutes of Health say it is a major step toward a “molecular recorder” that may someday make it possible to get read-outs, for example, of the changing internal states of neurons as they develop.

“We want to turn cells into historians,” explained neuroscientist Seth Shipman, Ph.D. , a post-doctoral fellow at Harvard Medical School, Boston. “We envision a biological memory system that’s much smaller and more versatile than today’s technologies, which will track many events non-intrusively over time.”

Shipman, Harvard’s Drs. George Church , Jeffrey Macklis  andJeff Nivala  report on their proof-of-concept for a futuristic “molecular ticker tape” online July 12, in the journal Nature. The work was funded by NIH’s National Institute of Mental Health, National Institute of Neurological Disorders and Stroke, and the National Human Genome Research Institute.

The ability to record such sequential events like a movie at the molecular level is key to the idea of reinventing the very concept of recording using molecular engineering, say the researchers. In this scheme, cells themselves could be induced to record molecular events – such as changes in gene expression over time – in their own genomes. Then the information could be retrieved simply by sequencing the genomes of the cells it is stored in.

“If we had those transcriptional steps, we could potentially use them like a recipe to engineer similar cells,” added Shipman. “These could be used to model disease – or even in therapies.”

For starters, the researchers had to show that DNA can be used to encode not just genetic information, but any arbitrary sequential information into a genome. For this they turned to the cutting-edge, NIH-funded gene editing technology CRISPR . They first demonstrated that they could encode and retrieve an image of the human hand in DNA inserted into bacteria. They then similarly encoded and reconstructed frames from a classic 1870s race horse in motion  sequence of photos – an early forerunner of moving pictures.

The researchers had previously shown that they could use CRISPR to store sequences of DNA in bacteria. CRISPR is a group of proteins and DNA that act as an immune system in some bacteria, vaccinating them with genetic memories of viral infections. When a virus infects a bacterium, CRISPR cuts out part of the foreign DNA and stores it in the bacteria’s own genome. The bacterium then uses the stored DNA to recognize the virus and defend against future attacks. “The sequential nature of CRISPR makes it an appealing system for recording events over time,” explained Shipman.

The researchers then similarly translated five frames from the race horse in motion photo sequence into DNA. Over the course of five days, they sequentially treated bacteria with a frame of translated DNA. Afterwards, they were able to reconstruct the movie with 90 percent accuracy by sequencing the bacterial DNA.

Although this technology could be used in a variety of ways, the researchers ultimately hope to use it to study the brain. “We want to use neurons to record a molecular history of the brain through development,” said Shipman. “Such a molecular recorder will allow us to eventually collect data from every cell in the brain at once, without the need to gain access, to observe the cells directly, or disrupt the system to extract genetic material or proteins.”

PTScientists, one of the companies that originally signed up for the Google Lunar X Prize competition, is planning to deliver two rovers to the Moon, using their ALINA (Autonomous Landing and Navigation) module. The rovers, developed in partnership with Audi, will have four-wheel electrical drive chains, rechargeable batteries, solar panels, and HD cameras. And they'll also need a way to transmit their data back to Earth. To that end, the German-based team is planning to use a simple, already existing solution called LTE technology - the same wireless communications system we use here on Earth for chattering on our mobile phones.

LTE has a big advantage over typical radio transmissions - it requires way less power, which means that the rovers can spend more battery juice on exploring and less on communicating.

"We will be collecting a lot of scientific data on the Moon and the high-speed data connectivity that LTE gives us will enable the rovers to communicate with ALINA to send that valuable data back to Earth," the team's electrical engineer Karsten Becker told Abigail Beall at Wired.

The lunar rovers are designed to draw about 90 watts of energy from their solar panels, and they will need half of that for getting around. Radio transmissions would need to use the other half, but LTE is going to conserve a lot of that leftover power.

Right now PTScientists is aiming to be the first private company to set any kind of boot - including robotic - on the Moon. As reported previously, they have already signed a contract to hitch a ride on a SpaceX rocket. But, as Tereza Pultarova reports for Space.com, the team has withdrawn from participating in the Lunar X race, believing that none of the participants are likely to meet the goal to launch by December 2017.

If PTScientists succeed in their mission, they are hoping that the trial of using LTE for lunar mission comms could indeed set course for building a whole telecommunications network up there. "We are trying to show that you can use the most widespread means of communication .. on the surface of the Moon, to execute missions there," Becker told Space.com. "We are aiming to provide cost-effective solutions to problems that are arising in terms of building the lunar village." We'll have to watch this space to see whether the mission goes as planned, with ALINA touching down next year. But one way or another, it certainly looks like humans will be putting gear and boots on the Moon once again - and very soon.

Neuroscientists want to understand how tangles of neurons produce complex behaviors, but even the simplest networks defy understanding.

Marta Zlatic owns what could be the most tedious film collection ever. In her laboratory at the Janelia Research Campus in Ashburn, Virginia, the neuroscientist has stored more than 20,000 hours of black-and-white video featuring fruit-fly (Drosophila) larvae. The stars of these films are doing mundane maggoty things, such as wriggling and crawling about, but the footage is helping to answer one of the biggest questions in modern neuroscience: how the circuitry of the brain creates behavior. It's a major goal across the field: to work out how neurons wire up, how signals move through the networks and how these signals work together to pilot an animal around, to make decisions or — in humans — to express emotions and create consciousness.

Even under the most humdrum conditions — “normal lighting; no sensory cues; they're not hungry”, says Zlatic — her fly larvae can be made to perform 30 different actions, including retracting or turning their heads, or rolling. The actions are generated by a brain comprising just 15,000 neurons. That is nothing compared with the 86 billion in a human brain, which is one of the reasons Zlatic and her teammates like the maggots so much.

“At the moment, really, the Drosophila larva is the sweet spot,” says Albert Cardona, Zlatic's collaborator and husband, who is also at Janelia. “If you can get the wiring diagram, you have an excellent starting point for seeing how the central nervous system works.”

Zlatic and Cardona lead two of the dozens of groups around the world that are generating detailed wiring diagrams for brains of model organisms. New tools and techniques for slicing up brains and tracing their connections have hastened progress over the past few years. And the resulting neural-network diagrams are yielding surprises — showing, for example, that a brain can use one network in multiple ways to create the same behaviors.

But understanding even the simplest of circuits — orders of magnitude smaller than those in Zlatic's maggots — presents a host of challenges. Circuits vary in layout and function from animal to animal. The systems have redundancy that makes it difficult to pin one function to one circuit. Plus, wiring alone doesn't fully explain how circuits generate behaviors; other factors, such as neurochemicals, have to be considered. “I try to avoid using the word 'understand',” says Florian Engert, who is putting together an atlas of the zebrafish brain at Harvard University in Cambridge, Massachusetts. “What do you even mean when you say you understand how something works? If you map it out, you haven't really understood anything.”

Still, scientists are beginning to detect patterns in simple circuits that may operate in more complex brains. “This is what we hope,” says Willie Tobin, a neuroscientist at Harvard Medical School in Boston, Massachusetts: “that we can come across general principles that can help us understand larger systems.”

A team of researchers from Princeton University, the Scripps Institution of Oceanography, the University of Maine and Oregon State University has drilled and retrieved a 2.7-million-year-old ice core from a spot in Antarctica.

Until recently, scientists believed that ice core samples taken from either pole had an age limit of approximately 800,000 years—this was because ice at the bottom melted due to heat from inside the Earth. But a team at Princeton discovered a few year ago that another type of ice could hold much older ice known as blue ice. It forms on glaciers due to snowfall which, over time, becomes compressed, squeezing out air bubbles, making the ice look blue. But it also has another characteristic—over time, the ice at the bottom is pushed upwards, protecting it from melting. In this new effort, the team drilled at a site called the Allan Hills, near McMurdo Station.

Ice cores taken from glaciers present problems because they are more difficult to date—cores from other places are dated by counting their layers. The older ice, it was found, could be dated by studying trace amounts of potassium and argon—though not as precise as layer counting, the researchers believe it is accurate to within 100,000 years. One of the first teams to take a core sample from the older ice drilled to a depth of 128 meters. In this latest effort, the team drilled to 205 meters and found ice that was nearly twice as old.

Ice cores are important because they contain very small air bubbles that are samples of atmospheric conditions. Air bubbles from 2.7 million years ago offer evidence of climactic conditions during the time before the ice ages began, perhaps offering clues as to why they occurred. Already, the team has found that atmospheric carbon dioxide levels were at approximately 300 ppm, which is considerably lower than today's 400 ppm. But the team notes that the core sample represents something perhaps even more exciting—the possibility of finding core samples that are much older, perhaps as old as 5 million years.

In an experiment designed to mimic the conditions deep inside the icy giant planets of our solar system, scientists were able to observe "diamond rain" for the first time as it formed in high-pressure conditions.

The glittering precipitation has long been hypothesized to arise more than 5,000 miles below the surface of Uranus and Neptune, created from commonly found mixtures of just hydrogen and carbon. The interiors of these planets are similar—both contain solid cores surrounded by a dense slush of different ices. With the icy planets in our solar system, "ice" refers to hydrogen molecules connected to lighter elements, such as carbon, oxygen and/or nitrogen.

Researchers simulated the environment found inside these planets by creating shock waves in plastic with an intense optical laser at the Matter in Extreme Conditions (MEC) instrument at SLAC National Accelerator Laboratory's X-ray free-electron laser, the Linac Coherent Light Source (LCLS).

In the experiment, they were able to see that nearly every carbon atom of the original plastic was incorporated into small diamond structures up to a few nanometers wide. On Uranus and Neptune, the study authors predict that diamonds would become much larger, maybe millions of carats in weight. Researchers also think it's possible that over thousands of years, the diamonds slowly sink through the planets' ice layers and assemble into a thick layer around the core.

The research was published in Nature Astronomy on August 21, 2017.

During the minutes during which the sun is completely blocked, observers experience the exquisitely odd and wondrous sensation of solar emissions, both visible and invisible, vanishing right in the middle of the day.

A bumper crop of Earth-size planets huddled around an ultra-cool, red dwarf star could be little more than chunks of rock blasted by radiation, or cloud-covered worlds as broiling hot as Venus.

Or they could harbor exotic lifeforms, thriving under skies of ruddy twilight.

Scientists are pondering the possibilities after this week’s announcement: the discovery of seven worlds orbiting a small, cool star some 40 light-years away, all of them in the ballpark of our home planet in terms of their heft (mass) and size (diameter). Three of the planets reside in the “habitable zone” around their star, TRAPPIST-1, where calculations suggest that conditions might be right for liquid water to exist on their surfaces—though follow-up observations are needed to be sure.

All seven are early ambassadors of a new generation of planet-hunting targets.

Red dwarf stars -- also called “M-dwarfs” -- outnumber others, including yellow stars like our sun, by a factor of three to one, comprising nearly 75 percent of the stars in our galaxy. They also last far longer. And their planets are proportionally larger compared to the small stars they orbit. That means small, rocky worlds orbiting the nearest red dwarfs will be primary targets for new, powerful telescopes coming online in the years ahead, both in space and on the ground.

“The majority of stars are M-dwarfs, which are faint and small and not very luminous,” said Martin Still, program scientist at NASA headquarters in Washington. “So the majority of places where you would look for planets are around these cool, small stars. We are interested in the nearest stars, and the nearest stars are mostly M-dwarfs.”

But these are sure to be perplexing planets, with strange properties that must be teased out by careful observation as well as computer simulations. Finding out whether they can support some form of life, and what kind, likely will keep astrobiologists working overtime, perhaps attempting to recreate in the laboratory some of the conditions on these red-tinged worlds.

“We’re definitely all working overtime now,” said Nancy Kiang, an astrobiologist at NASA’s Goddard Institute for Space Studies in New York City.

During the last decade, commercial brain-training programs have risen in popularity, offering people the hope of improving their cognitive abilities through the routine performance of various “brain games” that tap cognitive functions such as memory, attention and cognitive flexibility.

But a recent study at the University of Pennsylvania found that, not only did commercial brain training with Lumosity™ have no effect on decision-making, it also had no effect on cognitive function beyond practice effects on the training tasks.

The findings were published in the Journal of Neuroscience.

Seeking evidence for an intervention that could reduce the likelihood that people will engage in unhealthy behaviors such as smoking or overeating, a team of researchers at Penn, co-led by Joseph Kable, PhD, the Baird Term associate professor in the department of Psychology in the School of Arts & Sciences, and Caryn Lerman, PhD, the vice dean for Strategic Initiatives and the John H. Glick professor in Cancer Research in the Perelman School of Medicine, examined whether, through the claimed beneficial effect on cognitive function, commercial brain training regimes could reduce individuals’ propensity to make risky or impulsive choices.

Lerman’s prior work had shown that engagement of brain circuits involved in self-control predicts whether people can refrain from smoking. This work provided the foundation for examining whether modulating these circuits through brain training could lead to behavior change. 

“Our motivation,” Kable said, “was that there are enough hints in the literature that cognitive training deserved a real, rigorous, full-scale test. Especially given the addiction angle, we're looking for things that will help people make the changes in their lives that they want to make, one of which is being more future-oriented.”

Swansea University scientists working at CERN have again made a landmark finding, taking them one step closer to answering the question of why matter exists and illuminating the mysteries of the Big Bang and the birth of the Universe.

In their recent paper published in Nature the physicists from the University’s College of Science, working with an international collaborative team at CERN, describe the first observation of spectral line shapes in antihydrogen, the antimatter equivalent of hydrogen.

Professor Mike Charlton said: “The existence of antimatter is well established in physics, and it is buried deep in the heart of some of the most successful theories ever developed. But we have yet to answer a central question of why didn’t matter and antimatter, which it is believed were created in equal amounts when the Big Bang started the Universe, mutually self-annihilate? “We also have yet to address why there is any matter left in the Universe at all. This conundrum is one of the central open questions in fundamental science, and one way to search for the answer is to bring the power of precision atomic physics to bear upon antimatter.”

It has long been established that any excited atom will reach its lowest state by emitting photons, and the spectrum of light and microwaves emitted from them represents a kind of atomic fingerprint and it is a unique identifier. The most familiar everyday example is the orange of the sodium streetlights. Hydrogen has its own spectrum and, as the simplest and most abundant atom in the Universe, it holds a special place in physics. The properties of the hydrogen atom are known with high accuracy. The one looked at in this paper concerns the so-called hyperfine splitting, which in the case of hydrogen has been determined with a precision of one part in ten trillion. This transition is used these days in modern navigation and geo-positioning.

The team have made antihydrogen by replacing the proton nucleus of the ordinary atom by an antiproton, while the electron has been substituted by a positron. Last year, in ground-breaking work published inNature, the team used UV light to detect the so-called 1S-2S transition between positron energy levels.  Now, the team has used microwaves to flip the spin of the positron. This resulted not only in the first precise determination of the antihydrogen hyperfine splitting, but also the first antimatter transition line shape, a plot of the spin flip probability versus the microwave frequency. If there is a difference between matter and antimatter, it could be found in tiny differences between this line shape in hydrogen and antihydrogen.

Datasets which are identical over a number of statistical properties, yet produce dissimilar graphs, are frequently used to illustrate the importance of graphical representations when exploring data. A recent paper presents a novel method for generating such datasets, along with several examples. This technique varies from previous approaches in that new datasets are iteratively generated from a seed dataset through random perturbations of individual data points, and can be directed towards a desired outcome through a simulated annealing optimization strategy.