Aurelia Butler

In a study that confirms its promise as the next-generation semiconductor material, UC Santa Barbara researchers have directly visualized the photocarrier transport properties of cubic boron arsenide single crystals.
“We were able to visualize how the charge moves in our sample,” said Bolin Liao, an assistant professor of mechanical engineering in the College of Engineering. Using the only scanning ultrafast electron microscopy (SUEM) setup in operation at a U.S. university, he and his team were able to make “movies” of the generation and transport processes of a photoexcited charge in this relatively little-studied III-V semiconductor material, which has recently been recognized as having extraordinary electrical and thermal properties. In the process, they found another, beneficial property that adds to the material’s potential as the next great semiconductor.
Their research, conducted in collaboration with physics professor Zhifeng Ren’s group at the University of Houston, who specialize in fabricating high-quality single crystals of cubic boron arsenide, appears in the journal Matter.
‘Ringing the Bell’
Boron arsenide is being eyed as a potential candidate to replace silicon, the computer world’s staple semiconductor material, due to its promising performance. For one thing, with an improved charge mobility over silicon, it easily conducts current (electrons and their positively charged counterpart, “holes”). However, unlike silicon, it also conducts heat with ease.
“This material actually has 10 times higher thermal conductivity than silicon,” Liao said. This heat conducting — and releasing — ability is particularly important as electronic components become smaller and more densely packed, and pooled heat threatens the devices’ performance, he explained. More

Using a simple set of magnets, MIT researchers have come up with a sophisticated way to monitor muscle movements, which they hope will make it easier for people with amputations to control their prosthetic limbs.
In a new pair of papers, the researchers demonstrated the accuracy and safety of their magnet-based system, which can track the length of muscles during movement. The studies, performed in animals, offer hope that this strategy could be used to help people with prosthetic devices control them in a way that more closely mimics natural limb movement.
“These recent results demonstrate that this tool can be used outside the lab to track muscle movement during natural activity, and they also suggest that the magnetic implants are stable and biocompatible and that they don’t cause discomfort,” says Cameron Taylor, an MIT research scientist and co-lead author of both papers.
In one of the studies, the researchers showed that they could accurately measure the lengths of turkeys’ calf muscles as the birds ran, jumped, and performed other natural movements. In the other study, they showed that the small magnetic beads used for the measurements do not cause inflammation or other adverse effects when implanted in muscle.
“I am very excited for the clinical potential of this new technology to improve the control and efficacy of bionic limbs for persons with limb-loss,” says Hugh Herr, a professor of media arts and sciences, co-director of the K. Lisa Yang Center for Bionics at MIT, and an associate member of MIT’s McGovern Institute for Brain Research.
Herr is a senior author of both papers, which appear today in the journal Frontiers in Bioengineering and Biotechnology. Thomas Roberts, a professor of ecology, evolution, and organismal biology at Brown University, is a senior author of the measurement study. More

Extreme miniaturization of infrared (IR) detectors is critical for their integration into next-generation consumer electronics, wearables and ultra-small satellites. Thus far, however, IR detectors have relied on bulky (and expensive) materials and technologies. A team of scientists lead by Empa researcher Ivan Shorubalko now succeeded in developing a cost-effective miniaturization process for IR spectrometers based on a quantum dot photodetector, which can be integrated on a single chip, as they report in Nature Photonics.
Miniaturization of infrared spectrometers will lead to their wider use in consumer electronics, such as smartphones enabling food control, the detection of hazardous chemicals, air pollution monitoring and wearable electronics. They can be used for the quick and easy detection of certain chemicals without using laboratory equipment. Moreover, they can be useful for the detection of counterfeit medical drugs as well as of greenhouse gases such as methane and CO2.
A team of scientists at Empa, ETH Zurich, EPFL, the University of Salamanca, Spain, the European Space Agency (ESA) and the University of Basel now built a proof-of-concept miniaturized Fourier-transform waveguide spectrometer that incorporates a subwavelength photodetector as a light sensor, consisting of colloidal mercury telluride quantum dot (Hg Te) and compatible with complementary metal-oxide-semiconductor (CMOS) technology, as they report in the recent issue of Nature Photonics.
Tremendous effects on spectrometers of different kinds — and in various fields
The resulting spectrometer exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm−1 at a total active spectrometer volume below 100 μm × 100 μm × 100 μm. This ultra-compact spectrometer design allows the integration of optical-analytical measurement instruments into consumer electronics and space devices. “The monolithic integration of subwavelength IR photodetectors has a tremendous effect on the scaling of Fourier-transform waveguide spectrometers,” says Empa researcher Ivan Shorubalko. “But this may also be of great interest for miniaturized Raman spectrometers, biosensors and lab-on-a-chip devices as well as the development of high-resolution snapshot hyperspectral cameras.”
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Materials provided by Swiss Federal Laboratories for Materials Science and Technology (EMPA). Note: Content may be edited for style and length. More

A new paper in Cell Systems explores the importance of using multiple data types in drug discovery. The paper screens over 1,000 drugs tested in six doses and demonstrates that gene expression and cell morphology provide different information for drug prioritization.
Led by biomedical data scientist Gregory Way, PhD, MS, the study showcases that by using these two data types simultaneously, scientists can measure fundamentally different aspects of the drug’s biology.
“We believe these two popular methods can be used to our advantage in designing drugs that address the full complexity of biology,” said Way, who is an assistant professor in biomedical informatics at the University of Colorado Anschutz Medical Campus.
Way and a team of data scientists found that the two data types provide a partially shared but also complementary view of drug mechanisms. They said using both approaches can advance drug discovery, functional genomics and precision medicine in unique directions.
“While labeling drugs based on mechanism of action is incredibly powerful, the approach risks missing a bigger picture. Both data types, collected via phenotypic drug screening, embrace the complexity of biology and can allow scientists to study and leverage the multifaceted effects drugs can offer,” Way adds.
Their paper shows how the assays compare with each other on useful biological tasks (e.g., mechanism of action prediction) given all the sources of variation/noise and current best practices in data processing. The phenotypic drug screening approach allows researchers to measure thousands of features of thousands of different drugs in a single experiment.
“We hope our analysis can guide researchers in experimental design and in understanding the limitations of their particular profiling modality to provide more consistent measurements and maximize potential for drug discovery successes,” Way said.
The paper guides scientists in planning experiments that profile cells for reversing disease phenotypes, quantifying cell response to chemical or genetic perturbation and querying drug mechanisms.
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Materials provided by University of Colorado Anschutz Medical Campus. Original written by Julia Milzer. Note: Content may be edited for style and length. More

If you’ve ever played the claw game at an arcade, you know how hard it is to grab and hold onto objects using robotics grippers. Imagine how much more nerve-wracking that game would be if, instead of plush stuffed animals, you were trying to grab a fragile piece of endangered coral or a priceless artifact from a sunken ship.
Most of today’s robotic grippers rely on embedded sensors, complex feedback loops, or advanced machine learning algorithms, combined with the skill of the operator, to grasp fragile or irregularly shaped objects. But researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have demonstrated an easier way.
Taking inspiration from nature, they designed a new type of soft, robotic gripper that uses a collection of thin tentacles to entangle and ensnare objects, similar to how jellyfish collect stunned prey. Alone, individual tentacles, or filaments, are weak. But together, the collection of filaments can grasp and securely hold heavy and oddly shaped objects. The gripper relies on simple inflation to wrap around objects and doesn’t require sensing, planning, or feedback control.
The research was published in the Proceedings of the National Academy of Sciences (PNAS).
“With this research, we wanted to reimagine how we interact with objects,” said Kaitlyn Becker, former graduate student and postdoctoral fellow at SEAS and first author of the paper. “By taking advantage of the natural compliance of soft robotics and enhancing it with a compliant structure, we designed a gripper that is greater than the sum of its parts and a grasping strategy that can adapt to a range of complex objects with minimal planning and perception.”
Becker is currently an Assistant Professor of Mechanical Engineering at MIT. More

A new study released in the American Cancer Society journal Cancer reconsiders guidelines for when to start screening with mammograms if a woman has a mother, sister, or daughter who was diagnosed with breast cancer.
Women with a first-degree family relative diagnosed with breast cancer, who are otherwise at average risk, are often advised to get screened 10 years earlier than the relative’s diagnosis age. However, there is little evidence to support the long-standing recommendation.
UC Davis Comprehensive Cancer Center researcher Diana Miglioretti joined Danielle Durham, with the Department of Radiology at University of North Carolina at Chapel Hill, and five other researchers on the study. They analyzed data from the Breast Cancer Surveillance Consortium on screening mammograms conducted from 1996-2016 to evaluate when screenings should begin for women with a family history of breast cancer.
More than 300,000 women were included in the national study. Researchers compared cumulative 5-year breast cancer incidence among women with and without a first-degree family history of breast cancer by relative’s age at diagnosis and screening age.
“The study concluded that a woman with a relative diagnosed at or before age 45 may wish to consider, in consultation with her doctor, initiating screening 5-8 years earlier than their relative’s diagnosis age, rather than a decade earlier. That puts them at a risk that is equal to that of an average-risk woman who is age 50, which is the most recommended age for starting mammograms,” said Durham.
BRCA gene mutation carriers may benefit from starting screenings earlier. Women ages 30-39 with more than one first-degree relative diagnosed with breast cancer may wish to consider genetic counseling.
Increasing the age for initiating screening could reduce the potential harms of starting breast cancer screenings too early. These include increased radiation exposure and false positive results that require women to return to the clinic for diagnostic imaging and possibly invasive procedures, but do not result in a breast cancer diagnosis. The earlier a woman starts receiving mammograms, the more screenings they will undergo over their lifetime — and that increases the chances of experiencing these harms.
“Mammography also may not perform as well in younger women because they are more likely to have dense breasts which increase the difficulty of finding cancer on the images and results in more false-positives,” Miglioretti said.
The other authors on this study include Linn A. Abraham, Kaiser Permanente Washington Health Research Institute; Megan C. Roberts, UNC Eshelman School of Pharmacy; Carly P. Khan, Patient-Centered Outcomes Research Institute; Robert A. Smith, American Cancer Society and Karla Kerlikowske, UCSF Health. Miglioretti is an affiliate investigator with UC Davis Center for Healthcare Policy and Research and Kaiser Permanente Washington Health Research.
The study was supported through funding by the Cancer Prevention Fellowship Program, Division of Cancer Prevention and the National Cancer Institute (NCI) at the National Institutes of Health. Data collection by the Breast Cancer Surveillance Consortium was funded by the NCI (grant numbers P01CA154292, U54CA163303 and PCS-1504-30370).
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Materials provided by University of California – Davis Health. Original written by Stephanie Winn. Note: Content may be edited for style and length. More

Quantum computers are powerful computational devices that rely on quantum mechanics, or the science of how particles like electrons and atoms interact with the world around them. These devices could potentially be used to solve certain kinds of computational problems in a much shorter amount of time. Scientists have long hoped that quantum computing could be the next great advance in computing; however, existing limitations have prevented the technology from hitting its true potential. For these computers to work, the basic unit of information integral to their operation, known as quantum bits, or qubits, need to be stable and fast.
Qubits are represented both by simple binary quantum states and by various physical implementations. One promising candidate is a trapped electron that levitates in a vacuum. However, controlling the quantum states, especially the vibrational motions, of trapped electrons can be difficult.
In a paper published in Physical Review Research, researchers identified possible solutions to some of the limitations of qubits for quantum computing. They looked at two different hybrid quantum systems: an electron-superconducting circuit and an electron-ion coupled system. Both systems were able to control the temperature and the movement of the electron.
“We found a way to cool down and measure the motion of an electron levitated in a vacuum, or a trapped electron, both in the quantum regime,” said Assistant Professor Alto Osada at the Komaba Institute for Science at the University of Tokyo. “With the feasibility of quantum-level control of the motion of trapped electrons, the trapped electron becomes more promising and attractive for quantum-technology applications, such as quantum computing.”
The proposed systems that the researchers focused on included an electron trapped in a vacuum called a Paul trap interacting with superconducting circuits and a trapped ion. Because ions are positively charged and electrons are negatively charged, when they are trapped together, they move toward each other because of a phenomenon called Coulomb attraction. Because the electron has such a light mass, the interactions between the electron and circuit and the electron and the ion were particularly strong. They also found that they were able to control the temperature of the electron using microwave fields and optical lasers.
Another important metric that the researchers used to measure the success of their calculations was the phonon mode of the electron. Phonon refers to a unit of energy that characterizes a vibration, or, in this case, the oscillation of the trapped electron. The desirable result was a single-phonon readout and ground-state cooling. Ground-state cooling refers to the frozen state of the electron. Researchers were able to accomplish these through their two hybrid systems they analyzed. “Highly efficient and high-fidelity quantum operations are available in the trapped-electron system,” said Osada. “This novel system manifests itself as a new playground for the development of quantum technologies.”
Looking ahead, researchers note that additional experimental research will need to be done to see if their methods can be implemented and applied to quantum computing. For example, they plan to demonstrate their idea with a proof-of-concept experiment. “We are planning to examine our schemes using electrons trapped in a microwave cavity,” said Osada. “Through this research, we will be able to get another step closer toward precise quantum operations and toward the implementation of quantum computation.”
The JST ERATO MQM project, JSPS KAKENHI and JST SPRING supported this research.
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Materials provided by University of Tokyo. Note: Content may be edited for style and length. More