Breaking the scaling limits of analog computing

MIT researchers have developed a technique that greatly reduces the error in an optical neural network, which uses light to process data instead of electrical signals. With their technique, the larger an optical neural network becomes, the lower the error in its computations. This could enable them to scale these devices up so they would be large enough for commercial uses.
Credit: SFLORG stock photo

As machine-learning models become larger and more complex, they require faster and more energy-efficient hardware to perform computations. Conventional digital computers are struggling to keep up.

An analog optical neural network could perform the same tasks as a digital one, such as image classification or speech recognition, but because computations are performed using light instead of electrical signals, optical neural networks can run many times faster while consuming less energy.

However, these analog devices are prone to hardware errors that can make computations less precise. Microscopic imperfections in hardware components are one cause of these errors. In an optical neural network that has many connected components, errors can quickly accumulate.

Even with error-correction techniques, due to fundamental properties of the devices that make up an optical neural network, some amount of error is unavoidable. A network that is large enough to be implemented in the real world would be far too imprecise to be effective.

MIT researchers have overcome this hurdle and found a way to effectively scale an optical neural network. By adding a tiny hardware component to the optical switches that form the network’s architecture, they can reduce even the uncorrectable errors that would otherwise accumulate in the device.

Cognitive flexibility enhances mathematical reasoning

Multiple categorizations involves presenting students with mathematical problems that can be solved from different perspectives.
Illustration Credit: Calliste Scheibling-Sève

At school or in everyday life, proportional reasoning is essential for many activities. This type of reasoning allows us to adapt the quantity of ingredients in a recipe or to calculate the distance traveled as a function of speed by relying on ratios and proportions. In school settings, certain intuitive conceptions of proportions can mislead students and hinder their learning. A team from the University of Geneva (UNIGE) shows that multiple categorizations in mathematical problems - the ability to adopt several points of view on the same problem - makes it possible to go past this obstacle. These results open up new perspectives for the learning of mathematics but also for other disciplines. They can be found in the Journal of Numerical Cognition.

Proportional reasoning is a cognitive process that involves ratios and proportions to solve a mathematical problem. This reasoning is regularly practiced and applied in school, but it is also very useful in our daily lives. It allows us to calculate the price of certain products when we shop, to adapt the quantity of ingredients in a recipe, and to convert foreign currencies. It is at play when we understand that a speed of 30mph is equivalent to a distance of 15 miles travelled in 30 minutes. It is also involved in assessing our risk-taking: for example, when we make choices about our health by weighing the effectiveness of a treatment or vaccine against the risks of the disease.

Lychee Peel Powder Can Remove Persistent Dye from Wastewater

The peel of the lychee makes up about 15% of the weight of the fruit.
Photo Credit: Jamie Trinh

The international team of scientists, which includes chemists from the Ural Federal University, found out that chemically modified lychee peel eliminates a very persistent red dye from wastewater. The researchers have developed a new method that can be used to clean wastewater near textile production facilities in an environmentally friendly and cheap way. By doing so, it can prevent disease in humans and save animals, fish and birds that interact with dyed water. It will also help make the world's dirtiest rivers cleaner: the Buringanga River in Bangladesh, the Ganges in India, and the Chintarum in Indonesia, for example. A description of the new method and the results of the experiments were published in the Journal of Molecular Liquids.

"Red dyes emitted in various industries such as textiles, cosmetics, leather, food and plastic are dangerous environmental pollutants. From 20 to 40% of persistent dyes remain in wastewater and cause a critical increase in its acidity and alkalinity. The key factor here is the nature of these dyes. They contribute to increased deposition of calcium salts in organs, are considered highly toxic and pose a serious threat to humans, causing various cancers and mutagenic phenomena at cellular and molecular levels," explains Grigory Zyryanov, Professor of the Department of Organic and Biomolecular Chemistry at the Ural Federal University.

Novel sex-determination mechanism revealed in mammals

Amami spiny rat
Photo Credit: Asato Kuroiwa

In mammals, the distinction between male and female at the chromosomal level is due to the X and Y chromosomes. Typically, females have two X chromosomes (XX) while males have an X and a Y chromosome (XY). The Sry gene on the Y chromosome triggers the formation of the testes. However, there exist a handful of rodent species in which the Y chromosome has disappeared, taking with it the Sry gene. The mechanism by which testes development occurs in these species is not fully understood, and is subject to much research.

A team of researchers led by Professor Asato Kuroiwa at Hokkaido University has uncovered the genetic basis for sexual differentiation in the Amami spiny rat, one of the species the lacks a Y chromosome and the Sry gene. Their discoveries were published in the journal Proceedings of the National Academy of Sciences.

The Amami spiny rat is an endangered rodent found only on Amami Oshima, Japan. It is one of just four mammals known to lack a Y chromosome, alongside its close relative the Tokunoshima spiny rat, as well as the Transcaucasian mole vole and the Zaisan mole vole. In the Amami spiny rat, the the Sry gene is completely absent; thus, it has evolved a novel, unknown sex-determining mechanism independent of Sry.

Blood thinning drug to treat recovery from severe COVID-19 is not effective

The HEAL-COVID trial (Helping to Alleviate the Longer-term consequences of COVID-19) is funded by the National Institute for Health and Care Research (NIHR) and the Cambridge NIHR Biomedical Research Centre. To date, more than a thousand NHS patients hospitalized with COVID have taken part in HEAL-COVID, a platform trial that is aiming to find treatments to reduce the number who die or are readmitted following their time in hospital.

In these first results from HEAL-COVID, it’s been shown that prescribing the oral anticoagulant Apixaban does not stop COVID patients from later dying or being readmitted to hospital over the following year (Apixaban 29.1%, versus standard care 30.8%).

As well as not being beneficial, anticoagulant therapy has known serious side effects, and these were experienced by participants in the trial with a small number of the 402 participants receiving Apixaban having major bleeding that required them to discontinue the treatment.

There was also no benefit from Apixaban in terms of the number of days alive and out of hospital at day 60 after randomization (Apixaban 59 days, versus standard care 59 days).

Following these results, the trial will continue to test another drug called Atorvastatin, a widely used lipid lowering drug (‘a statin’) that acts on other mechanisms of disease that are thought to be important in COVID.

Rock Samples from the Floor of Jezero Crater Show Significant Contact with Water Together with Possible Organic Compounds

A photo of Jezero Crater on Mars. It was taken by instruments on NASA's Mars Reconnaissance Orbiter (MRO), which regularly takes images of potential landing sites for future missions.
Hi-Res Full-Size Image
Credit: NASA/JPL-Caltech/MSSS/JHU-APL

Analysis of multiple rocks found at the bottom of Jezero Crater on Mars, where the Perseverance rover landed in 2020, reveals significant interaction between the rocks and liquid water, according to a study published in the journal Science. Those rocks also contain evidence consistent with the presence of organic compounds.

The existence of organic compounds (chemical compounds with carbon–hydrogen bonds) is not direct evidence of life, as these compounds can be created through nonbiological processes.

Perseverance previously found organic compounds at Jezero's delta. Deltas are fan-shaped geologic formations created at the intersection of a river and a lake at the edge of the crater. Mars 2020 mission scientists had been particularly interested in the Jezero delta because such formations are created when a river transporting fine-grained sediments enter a deeper, slower-moving body of water. As the river water spreads out, it abruptly slows down, depositing the sediments it is carrying—and in so doing, traps and preserves any microorganisms that may exist in the water.

Astrophysicists Hunt for Second-Closest Supermassive Black Hole

Illustration Credit: Scott Anttila Anttler

Two astrophysicists at the Center for Astrophysics | Harvard & Smithsonian have suggested a way to observe what could be the second-closest supermassive black hole to Earth: a behemoth 3 million times the mass of the Sun, hosted by the dwarf galaxy Leo I.

The supermassive black hole, labeled Leo I*, was first proposed by an independent team of astronomers in late 2021. The team noticed stars picking up speed as they approached the center of the galaxy — evidence for a black hole — but directly imaging emission from the black hole was not possible.

Now, CfA astrophysicists Fabio Pacucci and Avi Loeb suggest a new way to verify the supermassive black hole's existence; their work is described in a study published today in The Astrophysical Journal Letters.

"Black holes are very elusive objects, and sometimes they enjoy playing hide-and-seek with us," says Fabio Pacucci, lead author of the ApJ Letters study. "Rays of light cannot escape their event horizons, but the environment around them can be extremely bright — if enough material falls into their gravitational well. But if a black hole is not accreting mass, instead, it emits no light and becomes impossible to find with our telescopes."

New device can control light at unprecedented speeds

Scientists have developed a programmable, wireless spatial light modulator that can manipulate light at the wavelength scale with orders-of-magnitude faster response than existing devices.
Illustration Credit: Sampson Wilcox

In a scene from “Star Wars: Episode IV — A New Hope,” R2D2 projects a three-dimensional hologram of Princess Leia making a desperate plea for help. That scene, filmed more than 45 years ago, involved a bit of movie magic — even today, we don’t have the technology to create such realistic and dynamic holograms.

Generating a freestanding 3D hologram would require extremely precise and fast control of light beyond the capabilities of existing technologies, which are based on liquid crystals or micromirrors.

An international group of researchers, led by a team at MIT, spent more than four years tackling this problem of high-speed optical beam forming. They have now demonstrated a programmable, wireless device that can control light, such as by focusing a beam in a specific direction or manipulating the light’s intensity, and do it orders of magnitude more quickly than commercial devices.

They also pioneered a fabrication process that ensures the device quality remains near-perfect when it is manufactured at scale. This would make their device more feasible to implement in real-world settings.

Study finds that big rains bring big algae blooms… eventually

Center for Limnology system engineer Mark Gahler, right, co-author of a new study on the relationship between big storms and algae blooms, and colleague Jonathon Thom collect Lake Mendota data from instruments aboard David Buoy.
Photo Credit: Paul Schramm / University of Wisconsin–Madison

In the lake-rich regions of the world, algae blooms are a growing problem. Not only are the floating green scums a nuisance for anyone hoping to enjoy the water, they can turn toxic and threaten public health.

The main driver behind these blooms is phosphorus, an element used widely in agriculture to fertilize crops, that can run from the land and into lakes — especially during heavy rains. A new study from the University of Wisconsin–Madison shows how soon after a storm phosphorous “loading” sparks algae explosions, but also describes the many other factors that weigh on when and whether the lake reaches a tipping point.

“The fact that you just had a big storm doesn’t mean now you’re going to get a big [algae] bloom. The blooms are much more complicated.” says Steve Carpenter, lead author of a report published in the Proceedings of the National Academy of the Sciences.

Ancient Iowan super predator got big by front-loading its growth in its youth

Co-author Ben Otoo with a life-size illustration of Whatcheeria.
Photo Credit: Courtesy of Ben Otoo.

The Field Museum in Chicago is home to the best, most-complete fossils of a prehistoric superpredator-- but one that lived hundreds of millions of years before SUE the T. rex. Whatcheeria was a six-foot-long lake-dwelling creature with a salamander-like body and a long, narrow head; its fossils were discovered in a limestone quarry near the town of What Cheer, Iowa. There are around 350 Whatcheeria specimens, ranging from single bones to complete skeletons, that have been unearthed, and every last one of them resides in the Field Museum’s collections. In a new study in Communications Biology, these specimens helped reveal how Whatcheeria grew big enough to menace its fishy prey: instead of growing “slow and steady” the way that many modern reptiles and amphibians do, it grew rapidly in its youth.

“If you saw Whatcheeria in life, it would probably look like a big crocodile-shaped salamander, with a narrow head and lots of teeth,” says Ben Otoo, a co-author of the study and a PhD student at the University of Chicago and the Field Museum. “If it really curled up, probably to an uncomfortable extent, it could fit in your bathtub, but neither you nor it would want it to be there.”