In experiments at Washington State University, scientists have developed a technique to see these matter wave caustics by placing attractive or repulsive obstacles in the path of a cold atom laser. The results are curving cusps or folds, upward or downward “V” shapes, which the researchers describe in a paper for Nature Communications.

While it is foundational research, these caustics have potential applications for highly precise measurement or timing devices such as interferometers and atomic clocks.

“It’s a beautiful demonstration of how we can manipulate matter waves in a way that is very similar to how one would manipulate light,” said Peter Engels, WSU Yount distinguished professor and the paper’s senior author. “An atom is accelerated by gravity, so therefore, we can mimic effects that would be very difficult to see with light. Also, since atoms respond to many different things, we can potentially exploit this for new types of sensors that are particularly good at detecting magnetic fields, gradients in electric fields or in gravity.”

To achieve these effects, first the scientists had to create one of the coldest places on Earth, which they were able to accomplish in the Fundamental Quantum Physics lab at WSU. Engels and his colleagues used optical lasers to take energy out of an atomic cloud trapped inside a vacuum chamber, cooling it very close to absolute zero (?273.15 degrees Celsius or ?459.67 degrees Fahrenheit).

This extreme cold makes atoms behave quantum mechanically in ways very different from the familiar laws of nature. In these conditions, instead of behaving like particles of matter, the atoms move like waves. Clouds formed of such atoms are known as Bose-Einstein condensates, named after the theorists whose work first predicted this state of matter, Albert Einstein and Satyendra Nath Bose.

In the process of exploring these condensates, the researchers at WSU created a cold atom laser, meaning the wave-like atoms started lining up in a column and moving together.

“A light laser is a collimated, coherent stream of photons, and we’re essentially doing that with atoms,” said Maren Mossman, the paper’s first author who worked on the project as a WSU post-doctoral fellow and is now the Clare Boothe Luce assistant professor of physics at the University of San Diego. “The atoms sort of walk together and behave as one object. So then, we decided to see what happens if we poked this.”

For this study, the researchers ‘poked’ at the atom laser by putting optical obstacles in its path, essentially shining specific wavelengths of laser lights onto the accelerating stream of atoms. One obstacle type repelled the atoms and made caustics in downward fold shapes; another attracted them making caustics in upward cusp shapes.

The system is also very tunable, the researchers said, meaning they can change how fast the atoms accelerate.

“Caustics in atom lasers have never really been studied with this flexibility,” said Engels.

In addition to Engels and Mossman, the co-authors include Michael Forbes, WSU associate professor in the Department of Physics and Astronomy and Thomas Bersano, a former WSU post-doctoral fellow now at Los Alamos National Laboratory.

This study was supported by grants from the National Science Foundation.

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Materials provided by Washington State University. Original written by Sara Zaske. Note: Content may be edited for style and length.

Rooftop photovoltaics (PVs) integrated with electric vehicles (EVs) has the potential to deeply decarbonize urban energy systems in a cost-effective way. The SolarEV City Concept suggested that the rooftop PV plus EV systems can supply 54-95% of electricity demand within cities in Japan, reducing CO₂ emission 54-95% (Kobashi et al., Environmental Research Letters, 16, 024042,2021). However, it was not clear which district in city could consume, generate, and store the PV electricity, as each district has different load patterns, building structures, and number of parked cars. Therefore, we performed techno-economic analyses on rooftop PV systems integrated with stand-alone batteries or EVs in residential and commercial districts in Japan from 2020 to 2040.

We found that rooftop PV systems in 2020 are already cost competitive relative to existing energy systems in Japan. However, “PV + EV” systems in residential houses rapidly increases its economic advantage over commercial districts due to greater rooftop space and higher number of available vehicles towards 2030. Moreover, energy sharing in the districts significantly improved the decarbonization potential. By 2025, energy cost savings, payback periods, and internal rate of return (IRR) of residential “PV + EV” systems respectively reached 23%, 9 years, and 11%, and continued improving in subsequent years. CO₂ emissions from electricity and gasoline consumption was reduced by 88%, and the system was capable to supplying 89% of electricity demand.

The results indicate that residential “PV + EV” systems are a potential source for significant renewable energy generation and storage that can also produce increasingly dispatchable electricity. Policy makers, industries, and communities should prepare to establish these systems through regulatory reform and demonstration projects to scale-up after 2025.

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Materials provided by National Institute for Environmental Studies. Note: Content may be edited for style and length.

An international team of scientists — led by the Natural History Museum and the University of Plymouth — carried out the first detailed analysis of gene sequence data for any species of the so-called “blindsnakes” (Scolecophidia), a group of small-eyed burrowers.

They found that seven of the 12 genes associated with bright-light vision in most snakes and lizards species are not present in scolecophidians.

This, they say, demonstrates extensive vision gene loss over tens of millions of years of evolutionary history, similar to that which has also been observed in burrowing mammals with reduced vision.

It also challenges the hypothesis that all snakes living across the world today evolved from extreme burrowers, because the vision genes lost in scolecophidians are present in most other living snakes. The researchers say it would be extremely unlikely for such genetic deficiencies to have been reversed through evolution.

Scolecophidians are dedicated burrowers and form one half of the oldest divergence in the snake tree. They comprise approximately 460 of the approximately 3,850 currently recognised living snake species, and likely diverged from their closest living relatives (Alethinophidia, which includes all other living snakes) more than 65 million years ago.

Scolecophidians are typically small, cylindrical, burrowing snakes with reduced eyes and small mouths, strikingly different from the more familiar alethinophidians, which include pythons, vipers, and cobras.

For this research, published in Genome Biology and Evolution, scientists generated new gene-sequence data for the dark-spined blind snake (Anilios bicolor) and the prong-snouted blind snake (Anilios bituberculatus), both of which are common across southern Australia.

They then compared their results with similar data for functional vision genes among other species of snakes and lizards.

Lead author Dr David Gower, Head of the Life Sciences Vertebrates Division at the Natural History Museum, said: “Our data and analytical results provide clear evidence for very substantial reduction of elements of the visual system of burrowing scolecophidian snakes. We already knew that snakes lost some vision genes and eye structures during their evolution from lizards, but most were nonetheless retained. It is highly unlikely that functional copies of a large number of vision genes were lost from the ancestral snake but subsequently re-evolved in most living snakes. As a result, our study strongly suggests that the ancestor of all living snakes was unlikely to have been as extreme a burrower as living scolecophidian snakes.”

The same team of researchers published a study in May 2020, which revealed that the visual systems of sea snakes have undergone remarkable adaptation to life underwater for 15 million years.

Dr Bruno Simões, Lecturer in Animal Biology at the University of Plymouth, led that research and is senior author on the current study. He said: “The nature of the ancestral snake has been highly debated. It has been suggested that it had evolved a reduced visual system as a result of a possible burrowing ecology. Our research provides new information on the likely ecology and environment of the ancestral snake and suggests that the highly subterranean lives and reduced eyes of living scolecophidian snakes likely evolved as specialisms rather than being the retention of primitive characteristics. This study also shows convergent evolution between subterranean snakes and burrowing mammals with the loss of similar genes, especially those associated with bright-light and colour vision.”

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Materials provided by University of Plymouth. Original written by Alan Williams. Note: Content may be edited for style and length.

The team conducted a set of 100 global Earth system model simulations over 1850-2100, working with a “business-as-usual” scenario for relatively strong emissions of greenhouse gases over the 21^st century. The runs were given different initial conditions, and by virtue of the butterfly effect they were able to represent a broad envelope of possible climate states over 1850-2100, enabling sophisticated analyses of changes in the variability of the Earth system over time. The nominally one-degree (~100km) resolution of the model, in conjunction with the 100-member set of runs, represented an unprecedented set of technical challenges that needed to be met before advancing to the goal of assessing how climate variability is impacted by sustained anthropogenic changes to the climate system. “We met these challenges by using the IBS/ICCP supercomputer Aleph, one of Korea’s fastest supercomputers” says Dr. Sun-Seon Lee from the ICCP, a co-author of the study who ran the simulations together with her NCAR colleague Dr. Nan Rosenbloom. For the project, approximately 80 million hours of supercomputer time were used, and approximately 5 Petabytes of disc space (approximately 5000 normal hard discs) were required for storage of the model output.

The main finding of the study is that the impact of climate change is apparent in nearly all aspects of climate variability, ranging from temperature and precipitation extremes over land to increased number of fires in California, to changes in bloom amplitude for phytoplankton in the North Atlantic Ocean. Each of these changes has important impacts for sustainable resource management. As an example, occurrences of extreme precipitation events over the 21^st century (between 2000-2009 and 2090-2099) indicate that extremes are expected to become more commonplace over many regions. These projected changes in precipitation extremes are in fact representative of the omnipresence of changes in extremes in the future across a broad range of climate and ecosystem variables, which has important implications for future adaptation strategies.

“In addition to large-scale changes in extreme events, our study also identified large-scale changes in the structure of the seasonal cycle over the 21^st century, showing an enhanced growing season length over the continental regions north of 50°N,” says Dr. Keith Rodgers from the ICCP, first author of the study and a co-lead of the CESM2 Large Ensemble Project. Largely due to mean state warming and ensuing changes in the timing of the retreat and advance of winter snow cover, by the end of the 21^st century growing season length is projected to increase by three weeks.

Taken together, the computer simulations reveal that across our planet we can expect widespread changes in climate variability, ranging in timescales from synoptic storms to seasons to that of El Niño to decades. Dr. Gokhan Danabasoglu, a co-author of the study and a co-lead of the project, says “an important step moving forward will be to identify more fully the potential societal impacts and to communicate the implications for adaptation strategies.” This broader study has already motivated a number of more specialized scientific investigations using the tremendous volume of output from the simulations, spanning topics from marine ecosystem impacts to hydrological changes that affect water supply.

The National Center for Atmospheric Research is sponsored by the US National Science Foundation and managed by the University Corporation for Atmospheric Research.

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Materials provided by Institute for Basic Science. Note: Content may be edited for style and length.