A team of scientists, including Professor C. David Wright from the University of Exeter, has explored the future potential for computer systems by using photonics in place of conventional electronics.

The article is published today (January 29th 2021) in the journal Nature Photonics.

The study focuses on potential solutions to one of the world’s most pressing computing problems — how to develop computing technologies to process this data in a fast and energy efficient way.

Contemporary computers are based on the von Neumann architecture in which the fast Central Processing Unit (CPU) is physically separated from the much slower program and data memory.

This means computing speed is limited and power is wasted by the need to continuously transfer data to and from the memory and processor over bandwidth-limited and energy-inefficient electrical interconnects — known as the von Neumann bottleneck.

As a result, it has been estimated that more than 50 % of the power of modern computing systems is wasted simply in this moving around of data.

Professor C David Wright, from the University of Exeter’s Department of Engineering, and one of the co-authors of the study explains “Clearly, a new approach is needed — one that can fuse together the core information processing tasks of computing and memory, one that can incorporate directly in hardware the ability to learn, adapt and evolve, and one that does away with energy-sapping and speed-limiting electrical interconnects.”

Photonic neuromorphic computing is one such approach. Here, signals are communicated and processed using light rather than electrons, giving access to much higher bandwidths (processor speeds) and vastly reducing energy losses.

Moreover, the researchers try to make the computing hardware itself isomorphic with biological processing system (brains), by developing devices to directly mimic the basic functions of brain neurons and synapses, then connecting these together in networks that can offer fast, parallelised, adaptive processing for artificial intelligence and machine learning applications.

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The image of the traffic light is transferred from our eyes to the visual cortex, which, in turn, communicates to the premotor cortex — a section of the brain involved in preparing and executing limb movements. A signal is then sent to our foot to step on the brake. However, brain region that helps the body go from “seeing” to “stepping” is still a mystery, frustrating neuroscientists and psychologists.

To unpack this “black box,” a team of neuroscientists at the University of California, Riverside, has experimented on mice to identify the brain region that functions beyond sensory encoding and motor encoding, potentially opening up new directions to studying the cellular and circuit mechanisms of sensory-motor transformations. The researchers report a cortical region traditionally defined as whisker motor cortex in mice is most directly related to the transformation process.

In the lab, the researchers trained mice to sense a slight deflection on one side of their whiskers, and report if they sensed it by licking a water port.

“We recorded the neuronal activity of some brain regions that might convey this sensory-motor transformation by using the ‘language of neurons’ — the electrical signals — generated as the mouse performs the task of stimulus detection,” said Zhaoran Zhang, a graduate student in the Neuroscience Graduate Program and a co-first author of the research paper published in eNeuro, an open-access journal of the Society of Neuroscience.

Behzad Zareian, a graduate student in the Department of Psychology and a co-first author of the research paper, explained the team used simple but intuitive mathematical tools to transform the neurons’ electrical activities to numbers that describe how much the neurons sense the sensory input, how much they reflect the upcoming movement outputs, and how well they predict whether the sensory information can be successfully transformed to a correct behavior.

“We located a brain region traditionally defined as the whisker motor cortex, which was previously believed to influence how a mouse moves its whiskers,” Zareian said, “We found this cortical region is capable of transforming the sensory input from whisker deflection to a more general movement action — licking in this case — rather than just moving whiskers.”

Corresponding author Edward Zagha, an assistant professor of psychology and the team’s principle investigator, explained that one difficulty in finding brain regions operating the sensory-motor transformation is that although scientists can measure the sensory- and motor-related brain activities easily in the lab, the inner process that conducts the sensory-motor transformation in the brain is elusive and hard to quantify.

“Our brain represents sensory and motor information in more than one place and often in a redundant manner for multiple purposes such as fine-tuning future movements, enhancing perception or memory storage,” Zagha said. “Thus, scientists are now able to distinguish the location of transformation and the regions that merely reflect the sensory or motor information for other purposes. This can vastly improve the use of targeted therapy for patients with sensory- and motor-related brain deficits.”

Next, the team plans to focus its research on whisker motor cortex to show what happens within this region to enable the transformation process.

“Interestingly, each cortical region consists of multiple layers and multiple subtype of neurons such as excitatory and inhibitory neurons that are subject to research,” Zagha said. “Thus, this expands our knowledge of the neurobiological circuits performing sensory-motor transformations and identifies sites of potential therapeutic intervention to modulate these brain functions.”

The research was funded by grants from the Whitehall Foundation and National Institutes of Health.

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Materials provided by University of California – Riverside. Original written by Iqbal Pittalwala. Note: Content may be edited for style and length.

Adaptation is a fundamental biological process driving organisms to change their traits and behavior to better fit their environment, whether it be the famed diversity of finches observed by pioneering biologist Charles Darwin or the many varieties of bacteria that humans coexist with. While antibiotics have long helped people prevent and cure bacterial infections, many species of bacteria have increasingly been able to adapt to resist antibiotic treatments.

Banerjee’s research at Carnegie Mellon and in his previous position at the University College London (UCL) has focused on the mechanics and physics behind various cellular processes, and a common theme in his work has been that the shape of a cell can have major effects on its reproduction and survival. Along with researchers at the University of Chicago, he decided to dig into how exposure to antibiotics affects the growth and morphologies of the bacterium Caulobacter crescentus, a commonly used model organism.

“Using single-cell experiments and theoretical modelling, we demonstrate that cell shape changes act as a feedback strategy to make bacteria more adaptive to surviving antibiotics,” Banerjee said of what he and his collaborators found.

When exposed to less than lethal doses of the antibiotic chloramphenicol over multiple generations, the researchers found that the bacteria dramatically changed their shape by becoming wider and more curved.

“These shape changes enable bacteria to overcome the stress of antibiotics and resume fast growth,” Banerjee said. The researchers came to this conclusion by developing a theoretical model to show how these physical changes allow the bacteria to attain a higher curvature and lower surface-to-volume ratio, which would allow fewer antibiotic particles to pass through their cellular surfaces as they grow.

“This insight is of great consequence to human health and will likely stimulate numerous further molecular studies into the role of cell shape on bacterial growth and antibiotic resistance,” Banerjee said.

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Materials provided by Carnegie Mellon University. Original written by Ben Panko. Note: Content may be edited for style and length.

Shigeki Watanabe of Johns Hopkins University School of Medicine, a familiar face at the Marine Biological Laboratory (MBL) as a faculty member and researcher, is hot on the trail of describing how glutamate signaling works in the brain to enable neuronal communication. In a paper last fall, Watanabe (along with several MBL Neurobiology course students) described how glutamate is released from neural synapses after the neuron fires. And today, Watanabe published a follow-up study in Nature Communications.

“With this paper, we uncover how signals are transmitted across synapses to turn on the switch for plasticity,” Watanabe says. “We demonstrate that glutamate is first released near AMPA-type glutamate receptors, to relay the signal from one neuron to the next, and then near NMDA-type receptors immediately after the first signal to activate the switch for synaptic plasticity.”

This new study was also partly conducted in the MBL Neurobiology course, where Watanabe is a faculty member. “It began in 2018 with (course students) Raul Ramos and Hanieh Falahati, and then we followed up in 2019 with Stephen Alexander Lee and Christine Prater. Shuo Li, the first author, was my teaching assistant for the Neurobiology course for both years,” Watanabe says. He will be returning to the MBL this summer to teach in the course — and discover more.

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Materials provided by Marine Biological Laboratory. Original written by Diana Kenney. Note: Content may be edited for style and length.

Now chemists at the U.S. Department of Energy’s Pacific Northwest National Laboratory have developed a simple and reliable method that holds promise for transforming how ultra-trace elements are separated and detected. Low levels of troublesome naturally occurring radioactive elements like uranium and thorium atoms are often tucked among valuable metals like gold and copper. It has been extraordinarily difficult, impractical, or even impossible, in some cases, to tease out how much is found in samples of ore mined across the globe.

Yet sourcing materials with very low levels of natural radiation is essential for certain types of sensitive instruments and detectors, like those searching for evidence of currently undetected particles that many physicists believe actually comprise most of the universe.

“We are really pushing the envelope on detection,” said chemist Khadouja Harouaka. “We want to measure very low levels of thorium and uranium in components that go into some of the most sensitive detectors in the world. It is particularly difficult to measure low levels of thorium and uranium in precious metals like the gold that goes into the electrical components of these detectors. With this new technique, we can overcome that challenge and achieve detection limits as low as 10 parts per trillion in gold.”

That’s like trying to find one four-leaf clover in about 100 thousand acres of clover?an area larger than New Orleans.

Colliding worlds of particles

The scientists locate their extraordinarily rare “four-leaf clover” atoms from the huge field of ordinary atoms by sending their samples through a series of isolation chambers. These chambers first filter and then collide the rare atoms with simple oxygen, creating a “tagged” molecule of a unique molecular weight that can then be separated by its size and charge.

The effect is like finding a way to tie a helium balloon to each target thorium or uranium atom so that it floats above the sea of gold sample and can be counted. In this case, the sophisticated counter is a mass spectrometer. The research is featured on the cover of the December 2020 issue of Journal of Analytical Atomic Spectrometry.

The central innovation is the collision cell chamber, where charged atoms of thorium and uranium react with oxygen, increasing their molecular weight and allowing them to separate from other overlapping signals that can disguise their presence.

“I had an aha moment,” said Greg Eiden, the original PNNL inventor of the patented collision cell, which is used to perform these reactions, thereby reducing unwanted interference in the instrument readout by a factor of a million. “It was this miracle chemistry that gets rid of the bad stuff you don’t want in your sample so you can see what you want to see.”

In the current study, Harouaka and her mentor Isaac Arnquist leveraged Eiden’s work to tease out the vanishingly small number of radioactive atoms that can nonetheless ruin sensitive electronic detection equipment. Among other uses, the innovation may allow chemists, led by senior chemist Eric Hoppe and his team at PNNL, to further hone the chemistry that produces the world’s purest electroformed copper. The copper forms a key component of sensitive physics detectors, including those used for international nuclear treaty verification.

Neutrino listening tour

Stanford physicist Giorgio Gratta helps lead a global quest to capture evidence for the fundamental building blocks of the universe. The nEXO experiment, now in the planning stages, is pushing the detection boundaries for evidence of these elusive particles, called Majorana Fermions. The signals they seek come from exceedingly rare events. To detect such an event, the experiments require exquisitely sensitive detectors that are free of stray radiation pings introduced through the materials that make up the detector. That includes the metals in the electronics required to record the exceedingly rare events that trigger detection.

“PNNL is a global leader in ultra-trace radiation detection,” said Gratta. “Their unique mix of innovation and application provide an important contribution that enables sensitive experiments like nEXO.”

Physicist Steve Elliott of Los Alamos National Laboratory emphasized the lengths to which researchers must go to ensure a scrupulously clean environment for rare particle detection.

“In experimental programs where even human fingerprints are too radioactive and must be avoided, techniques to measure ultra-low radioactive impurity levels are critical,” he said, adding that this method could provide an important way to source materials for another of the next generation of rare neutrino event detectors, called LEGEND, being planned for deployment in an underground location in Europe.

Cleaning semiconductors and quantum computers

Semiconductors, the basic building blocks of modern electronics, including integrated circuits, microchips, transistors, sensors and quantum computers are also sensitive to the presence of stray radiation. And the innovation cycle demands each generation pack more and more into ever tinier microchips.

“As the architecture gets smaller and smaller, radiation contamination is an ever-bigger issue that manufacturers have been working around by changing the architecture inside the chips,” said Hoppe. “But there’s only so far you can go with that, and you really start to become limited by the purity of some of those materials. The industry has set targets for itself that right now it can’t achieve, so having a measurement technique like this could make some of those targets achievable.”

More broadly, Eiden added, “in the big world of the periodic table there’s probably applications for any element that you care about. And what Eric, Khadouja and Isaac are going after here is analyzing any trace impurity in any ultra-pure material.”

Landscapes around the world are increasingly affected by rapid urbanization, deforestation and similar developments driven by human activity. So far, data collection has largely focused on measuring properties of the land — such as agriculture, urbanization, forestland, crops, or elevation. Other impacts from people are usually lumped together in categories such as population density, or distance from settlements or roads. The researchers propose that it is not merely the presence, absence, or number of people, but what the people are actually doing which affects wildlife movement. In fact, a range of psychological and socioeconomic factors can play a part in ‘anthropogenic resistance’. Some examples of these factors include hunting, poaching or supplementary feeding.

For their study, the researchers looked at three case studies in detail: wolves in Washington State; leopards in Iran; and large carnivores in central India. The same concept can be applied to other species: for example the Eurasian lynx, which are returning to their historical ranges; or roe deer who use croplands for both shelter and food but reduce their presence during the hunting season. In some parts of the world, cultural and religious beliefs can result in the tolerance of large carnivores, such as tigers and lions, despite substantial livestock losses and threats to human life. The researchers considered effects from beliefs, values and traditions to wildlife in different areas. The authors claim these nuanced differences in human behaviour strongly determine where wildlife may move and persist in a landscape.

Professor Niko Balkenhol, from Wildlife Sciences at the University of Göttingen, explains, “Anthropogenic resistance is also relevant to the BearConnect project, which aims to understand the factors that determine connectivity in European populations of the brown bear. Bears are capable of moving across huge distances, as shown by bear JJ1, better known as ‘Bruno’, who travelled from the Italian Trento region all the way to Bavaria, where he was shot. It is important to note that, although Bruno was able to cross the physical landscape, he was stopped by the severe ‘anthropogenic resistance’ provided by humans who could not tolerate his behaviour.”

“Our paper shows that ‘anthropogenic resistance’ is an important piece of the puzzle for connectivity-planning to ensure the functionality of corridors for wildlife and people,” says Dr Trishna Dutta, senior author of the study, also from Wildlife Sciences at the University of Göttingen. Dutta goes on to say: “It reveals that there are advantages for social and natural scientists to collaborate in understanding the effects of ‘anthropogenic resistance’ in future studies.”

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Materials provided by University of Göttingen. Note: Content may be edited for style and length.