Photon twins of unequal origin

The quantum dots of the Basel researchers are different, but send out exactly identical light particles.
Credit: University of Basel, Department of Physics

Researchers have created identical light particles with different quantum dots - an important step for applications such as tap-proof communication.

Many technologies that take advantage of quantum effects are based on exactly the same photons. However, it is extremely difficult to manufacture them. Not only must the wavelength (color) of the photons exactly match, but also their shape and polarization.

A team of researchers from the University of Basel around Richard Warburton, in collaboration with colleagues from the Ruhr University in Bochum, has now succeeded in producing identical photons that come from different, widely separated sources.

Individual photons from quantum dots

In their experiments, physicists use so-called quantum dots, i.e. structures a few nanometers in semiconductor materials. Electrons are trapped in these quantum dots, which only assume very specific energy levels and can emit light when moving from one level to another. With the help of a laser pulse that triggers such a transition, individual photons can be produced at the push of a button.

Eternal matter waves

The central part of the experiment in which the coherent matter waves are created. Fresh atoms (blue) fall in and make their way to the Bose-Einstein Condensate in the center. In reality, the atoms are not visible to the naked eye.
Image processing by Scixel.

Imagining our everyday life without lasers is difficult. We use lasers in printers, CD players, pointers, measuring devices, and so on. What makes lasers so special is that they use coherent waves of light: all the light inside a laser vibrates completely in sync. Meanwhile, quantum mechanics tells us that particles like atoms should also be thought of as waves. As a result, we can build ‘atom lasers’ containing coherent waves of matter. But can we make these matter waves last, so that they may be used in applications? In research that was published in Nature this week, a team of Amsterdam physicists shows that the answer to this question is affirmative.

Getting bosons to march in sync

The concept that underlies the atom laser is the so-called Bose-Einstein Condensate, or BEC for short. Elementary particles in nature occur in two types: fermions and bosons. Fermions are particles like electrons and quarks – the building blocks of the matter that we are made of. Bosons are very different in nature: they are not hard like fermions, but soft: for example, they can move through one another without a problem. The best-known example of a boson is the photon, the smallest possible quantity of light. But matter particles can also combine to form bosons – in fact, entire atoms can behave just like particles of light. What makes bosons so special is that they can all be in the exact same state at the exact same time, or phrased in more technical terms: they can ‘condense’ into a coherent wave. When this type of condensation happens for matter particles, physicists call the resulting substance a Bose-Einstein Condensate.

Thin-film photovoltaics: Efficient and versatile in a double pack

Perowskit / CIS tandem solar cells are already converting a relatively large proportion of the incident light into electricity. Future developments can further improve efficiency.
Photo Credit: Marco A. Ruiz-Preciado, KIT

Stacking solar cells on top of each other increases efficiency. Researchers at the Karlsruhe Institute of Technology (KIT), together with partners in the EU project PERCISTAND, have now produced perovskite / CIS tandem solar cells with an efficiency of almost 25 percent - the highest for this technology to date. In addition, the material combination ensures lightness and versatility, so that the use of these tandem solar cells is also conceivable on vehicles, portable devices and foldable or rollable devices. The researchers present their work in the ACS Energy Letters journal.

Perovskite solar cells have undergone a steep development in just ten years. In terms of efficiency, they can already be compared with the long-established silicon solar cells. Perovskites are innovative materials with a special crystal structure. Researchers worldwide are currently working on making perovskite photovoltaics ready for practical use. The more electricity they generate per unit area, the more attractive solar cells are for end users.

The efficiency can be increased by stacking two or more solar cells. If each solar cell absorbs a different part of the sunlight spectrum particularly efficiently, inherent losses can be reduced and efficiency increases. This indicates how much of the incident light is converted into electricity. Thanks to their versatility, perovskite solar cells are ideal as part of such tandems. Tandem solar cells made of perovskites and silicon have achieved a record efficiency of over 29 percent - significantly higher than that of individual cells made of perovskites (25.7 percent) and silicon (26.7 percent).

Real-time Imaging of Dynamic Atom-atom Interactions

In a breakthrough, Tokyo Tech researchers have managed to observe and characterize dynamic assembly of metallic atoms using an ingenious combination of scanning transmission electron microscopy and video-based tracking. By visualizing short-lived molecules, such as metallic dimers and trimers, that cannot be observed using traditional methods, the researchers open up the possibility of observing more such dynamic structures predicted by simulations.

Chemistry is the study of bond formation (or dissociation) between atoms. The knowledge of how chemical bonds form is, in fact, fundamental to not just all of chemistry but also fields like materials science. However, traditional chemistry has been largely limited to the study of stable compounds. The study of dynamic assembly between atoms during a chemical reaction has received little attention. With recent advances in computational chemistry, however, dynamic, short-lived structures are gaining importance. Experimental observation and characterization of dynamic bonding predicted between atoms, such as the formation of metallic dimers, could open up new research frontiers in chemistry and materials science.

However, observing this bond dynamics also requires the development of a new methodology. This is because conventional characterization techniques only provide time-averaged structural information and are, thus, inadequate for observing the bonds as they are formed.

Extreme weather and climate events likely to drive an increase in gender-based violence

Aftermath of Hurricane Katrina 
Credit: NOAA Images

In a study published in The Lancet Planetary Health, a team led by a researcher at the University of Cambridge analyzed current scientific literature and found that the evidence paints a bleak picture for the future as extreme events drive economic instability, food insecurity, and mental stress, and disrupt infrastructure and exacerbate gender inequality.

Between 2000 and 2019, floods, droughts, and storms alone affected nearly 4 billion people worldwide, costing over 300,000 lives. The occurrences of these extreme events represent a drastic change, with the frequency of floods increasing by 134%, storms by 40%, and droughts by 29% over the past two decades. These figures are expected to rise further as climate change progresses.

Extreme weather and climate events have been seen to increase gender-based violence, due to socioeconomic instability, structural power inequalities, health-care inaccessibility, resource scarcity and breakdowns in safety and law enforcement, among other reasons. This violence can lead to long-term consequences including physical injury, unwanted pregnancy, exposure to HIV or other sexually transmitted infections, fertility problems, internalized stigma, mental health conditions, and ramifications for children.

A Glimpse into the Dog’s Mind: A New Study Reveals How Dogs Think of Their Toys

Many dog lovers want to know what goes on in their furry friends’ minds. Now scientists are finally getting closer to the answer. In a new study just published in the journal of Animal Cognition, researchers from the Family Dog Project (Eötvös Loránd University, University, Budapest) found out that dogs have a “multi-modal mental image” of their familiar objects. This means that, when thinking about an object, dogs imagine the object’s different sensory features. For instance, the way it looks or the way it smells.

The group of scientists assumed that the senses dogs use to identify objects, such as their toys, reflect the way the objects are represented in their minds. “If we can understand which senses dogs use while searching for a toy, this may reveal how they think about it” explains Shany Dror, one of the leading researchers of this study. “When dogs use olfaction or sight while searching for a toy, this indicates that they know how that toy smells or looks like”.

In previous studies, the researchers discovered that only a few uniquely gifted dogs can learn the names of objects. “These Gifted Word Learner dogs give us a glimpse into their minds, and we can discover what they think about when we ask them - Where is your Teddy Bear? – “explains Dr. Andrea Sommese, the second leading researcher.

Mastodon tusk chemical analysis reveals first evidence of one extinct animal’s annual migration

A mounted skeleton of the Buesching mastodon, based on casts of individual bones produced in fiberglass, on public display at the University of Michigan Museum of Natural History in Ann Arbor. The Buesching mastodon is a nearly complete skeleton of an adult male recovered in 1998 from a peat farm near Fort Wayne, Indiana. A new study, led by Joshua Miller of the University of Cincinnati and Daniel Fisher of the University of Michigan, uses oxygen and strontium isotopes from the mastodon’s right tusk to reconstruct changing patterns of landscape use during its lifetime.
Image credit: Eric Bronson, Michigan Photography

Around 13,200 years ago, a roving male mastodon died in a bloody mating-season battle with a rival in what today is northeast Indiana, nearly 100 miles from his home territory, according to the first study to document the annual migration of an individual animal from an extinct species.

The 8-ton adult, known as the Buesching mastodon, was killed when an opponent punctured the right side of his skull with a tusk tip, a mortal wound that was revealed to researchers when the animal’s remains were recovered from a peat farm near Fort Wayne in 1998.

Northeast Indiana was likely a preferred summer mating ground for this solitary rambler, who made the trek annually during the last three years of his life, venturing north from his cold-season home, according to a paper scheduled for online publication June 13 in Proceedings of the National Academy of Sciences.

Wandering star disrupts stellar nursery

A young protostar in L483 and its signature outflow peeks out through a shroud of dust in this infrared image from NASA's Spitzer Space Telescope. Stars are known to form from collapsing clumps of gas and dust, or envelopes, seen here around a forming star system as a dark blob, or shadow, against a dusty background. The greenish color shows jets coming away from the young star within. The envelope is roughly 100 times the size of our solar system.
Credit: NASA/JPL-Caltech/J.Tobin University of Michigan

From a zoomed out, distant view, star-forming cloud L483 appears normal. But when a Northwestern University-led team of astrophysicists zoomed in closer and closer, things became weirder and weirder.

As the researchers peered closer into the cloud, they noticed that its magnetic field was curiously twisted. And then — as they examined a newborn star within the cloud — they spotted a hidden star, tucked behind it.

“It’s the star’s sibling, basically,” said Northwestern’s Erin Cox, who led the new study. “We think these stars formed far apart, and one moved closer to the other to form a binary. When the star traveled closer to its sibling, it shifted the dynamics of the cloud to twist its magnetic field.”

The new findings provide insight into binary star formation and how magnetic fields influence the earliest stages of developing stars.

Cox presented this research at the 240th meeting of the American Astronomical Society (AAS) in Pasadena, California. “The Twisted Magnetic Field of L483” will take place on Tuesday, June 14, as a part of a session on “Magnetic Fields and Galaxies.” The Astrophysical Journal will also publish the study next week.

Speed and dense gas bend jets of matter streaming away from some galaxy centers

Paired jets of matter streaming away from supermassive black holes at the center of galaxies usually extend away in opposite directions along the black hole’s axis of spin — as in the two bottom galaxy images. But some, like the two top galaxies, have jets bent at odd angles.
Credit: Melissa Morris, Uw–Madison

The most active and gluttonous black holes in the universe can often be found with two jets of matter streaming from their centers. These jets accelerate with astounding speed out into space in opposite directions, and they are usually lined up along the axis of the spinning black hole. But not always.

Some of these supermassive black galaxy hearts, called active galactic nuclei, have jets bent at mysteriously odd angles. New research from astronomers at the University of Wisconsin–Madison, published recently in The Astronomical Journal, shows that these jets are probably bent by a combination of their galaxies moving at tremendous velocity and by drag on the jets as they pass through clouds of intergalactic gas.

“These active galactic nuclei are a subset of black holes that are — even for black holes — really quickly gobbling up an enormous amount of matter,” says Melissa Morris, a UW–Madison astronomy graduate student and lead author of the new study. “They’re being fueled so quickly that a ton of energy is released in the area around the black hole. That’s what causes these wild AGN jets.”

Study Finds No Benefit to Taking Ivermectin for COVID-19 Symptoms

A study led by the Duke Clinical Research Institute (DCRI) in partnership with Vanderbilt University found no differences in relief of mild-to-moderate COVID-19 symptoms between participants taking ivermectin and participants taking a placebo.

“There was no significant benefit in our primary endpoint of resolution of symptoms in mild-to-moderate COVID-19 illness,” said Adrian Hernandez, M.D., the study’s administrative principal investigator and executive director of the DCRI. “Overall, most people improved their symptoms whether they took ivermectin or not. Given these results, there does not appear to be a role for ivermectin outside of a clinical trial setting, especially considering other available options with proven reduction in hospitalizations and death.”

There was also no difference observed in the number of hospitalizations or emergency room visits. Findings appear on medRxiv, a pre-publication server, and have been submitted to a peer-reviewed journal.

ACTIV-6 -- “The Randomized Trial to Evaluate Efficacy of Repurposed Medications” -- is a nationwide double-blind study that has enrolled more than 4,000 participants. The trial continues to enroll with plans to include nearly 15,000 participants from across the United States.

Ivermectin, a medication used to treat parasitic infections, is one of three repurposed medications currently being tested in ACTIV-6. Repurposed medications are those already approved by the U.S. Food and Drug Administration (FDA) for other medical indications.