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An electrical trigger fires single, identical photons

The precisely controlled photon source, made from an atomically thin semiconducting material, could aid the development of advanced quantum communicationCredit:…

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The precisely controlled photon source, made from an atomically thin semiconducting material, could aid the development of advanced quantum communication

Secure telecommunications networks and rapid information processing make much of modern life possible. To provide more secure, faster, and higher-performance information sharing than is currently possible, scientists and engineers are designing next-generation devices that harness the rules of quantum physics. Those designs rely on single photons to encode and transmit information across quantum networks and between quantum chips. However, tools for generating single photons do not yet offer the precision and stability required for quantum information technology.

Now, as reported recently in the journal Science Advances, researchers have found a way to generate single, identical photons on demand. By positioning a metallic probe over a designated point in a common 2D semiconductor material, the team led by researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has triggered a photon emission electrically. The photon’s properties may be simply adjusted by changing the applied voltage.

“The demonstration of electrically driven single-photon emission at a precise point constitutes a big step in the quest for integrable quantum technologies,” said Alex Weber-Bargioni, a staff scientist at Berkeley Lab’s Molecular Foundry who led the project. The research is part of the Center for Novel Pathways to Quantum Coherence in Materials (NPQC), an Energy Frontier Research Center sponsored by the Department of Energy, whose overarching goal is to find new approaches to protect and control quantum memory that can provide new insights into novel materials and designs for quantum computing technology.

Photons are one of the most robust carriers of quantum information and can travel long distances without losing their memory, or so-called coherence. To date, most established schemes for secure communication transfer that will power large-scale quantum communications require light sources to generate one photon at a time. Each photon must have a precisely defined wavelength and orientation. The new photon emitter demonstrated at Berkeley Lab achieves that control and precision. It could be used for transferring information between quantum processors on different chips, and ultimately scaled up to larger processors and a future quantum internet that links sophisticated computers around the world.

The photon emitter is based on a common 2D semiconductor material (tungsten disulfide, WS2), which has a sulfur atom removed from its crystal structure. That carefully located atomic imperfection, or defect, serves as a point where the photon can be generated through application of an electric current.

The challenge is not how to generate single photons, but how to make them truly identical and produce them on demand. Photon-emitting devices, like the semiconductor nanoparticles or “quantum dots” that light up QLED TVs, that are fabricated by lithography are subject to inherent variability, since no pattern-based system can be identical down to a single atom. Researchers working with Weber-Bargioni took a different approach by growing a thin-film material on a sheet of graphene. Any impurities introduced to the thin film’s atomic structure are repeated and identical throughout the sample. Through simulations and experiments, the team determined just where to introduce an imperfection to the otherwise uniform structure. Then, by applying an electrical contact to that location, they were able to trigger the material to emit a photon and control its energy with the applied voltage. That photon is then available to carry information to a distant location.

“Single-photon emitters are like a terminal where carefully prepared but fragile quantum information is sent on a journey into a lightning-fast, sturdy box,” said Bruno Schuler, a postdoctoral researcher at the Molecular Foundry (now a research scientist at Empa – the Swiss Federal Laboratories for Materials Science and Technology) and lead author of the work.

Key to the experiment is the gold-coated tip of a scanning tunnelling microscope that can be positioned exactly over the defect site in the thin film material. When a voltage is applied between the probe tip and the sample, the tip injects an electron into the defect. When the electron travels or tunnels from the probe tip, a well-defined part of its energy gets transformed into a single photon. Finally, the probe tip acts as an antenna that helps guide the emitted photon to an optical detector which records its wavelength and position.

By mapping the photons emitted from thin films made to include various defects, the researchers were able to pinpoint the correlation between the injected electron, local atomic structure, and the emitted photon. Usually, the optical resolution of such a map is limited to a few hundred nanometers. Thanks to extremely localized electron injection, combined with state-of-the-art microscopy tools, the Berkeley Lab team could determine where in the material a photon emerged with a resolution below 1 angstrom, about the diameter of a single atom. The detailed photon maps were crucial to pinpointing and understanding the electron-triggered photon emission mechanism.

“In terms of technique, this work has been a great breakthrough because we can map light emission from a single defect with sub-nanometer resolution. We visualize light emission with atomic resolution,” said Katherine Cochrane, a postdoctoral researcher at the Molecular Foundry and a lead author on the paper.

Defining single-photon light sources in two-dimensional materials with atomic precision provides unprecedented insight critical to understanding how those sources work, and provides a strategy for making groups of perfectly identical ones. The work is part of NPQC’s focus on exploring novel quantum phenomena in nonhomogenous 2D materials.

Two-dimensional materials are leading the way as a powerful platform for next-generation photon emitters. The thin films are flexible and easily integrated with other structures, and now provide a systematic way for introducing unparalleled control over photon emission. Based on the new results, the researchers plan to work on employing new materials to use as photon sources in quantum networks and quantum simulations.

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This research was supported by the DOE Office of Science and grants from the Swiss National Science Foundation.

The Molecular Foundry is a DOE Office of Science user facility located at Berkeley Lab.

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 14 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy’s Office of Science.

Source: https://bioengineer.org/an-electrical-trigger-fires-single-identical-photons/

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Reduced microbial stability linked to soil carbon loss in active layer under alpine permafrost degra

Credit: NIEER Chinese researchers have recently discovered links between reduction in microbial stability and soil carbon loss in the active

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Chinese researchers have recently discovered links between reduction in microbial stability and soil carbon loss in the active layer of degraded alpine permafrost on the Qinghai-Tibet Plateau (QTP).

The researchers, headed by Prof. CHEN Shengyun from the Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences (CAS), and XUE Kai from University of Chinese Academy of Sciences, conducted a combined in-depth analysis of soil microbial communities and their co-occurrence networks in the active permafrost layer along an extensive gradient of permafrost degradation.

The QTP encompasses the largest extent of high-altitude mountain permafrost in the world. This permafrost is different than high-latitude permafrost and stores massive soil carbon. An often ignored characteristic of permafrost is that the carbon pool in the active layer soil is more active and directly affected by climate change, compared to deeper layers.

Triggered by climate warming, permafrost degradation may decrease soil carbon stability and induce massive carbon loss, thus leading to positive carbon-climate feedback. However, microbial-mediated mechanisms for carbon loss from the active layer soil in degraded permafrost still remain unclear.

In this study, the researchers found that alpine permafrost degradation reduced the stability of active layer microbial communities as evidenced by increased sensitivity of microbial composition to environmental change, promoted destabilizing network properties and reduced resistance to node or edge attacking of the microbial network.

They discovered that soil organic carbon loss in severely degraded permafrost is associated with increased microbial dissimilarity, thereby potentially contributing to a positive carbon feedback in alpine permafrost on the QTP.

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The results were published in PNAS in an article entitled “Reduced microbial stability in the active layer is associated with carbon loss under alpine permafrost degradation”.

This research was financially supported by the National Natural Science Foundation of China, the Strategic Priority Research Program (A) of CAS and the Second Tibetan Plateau Scientific Expedition and Research Program.

Triggered by climate warming, permafrost degradation may decrease soil carbon stability and induce massive carbon loss, thus leading to positive carbon-climate feedback. However, microbial-mediated mechanisms for carbon loss from the active layer soil in degraded permafrost still remain unclear.

Source: https://bioengineer.org/reduced-microbial-stability-linked-to-soil-carbon-loss-in-active-layer-under-alpine-permafrost-degra/

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SNMMI Image of the Year: PET imaging measures cognitive impairment in COVID-19 patients

Credit: G Blazhenets et al., Department of Nuclear Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of

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Credit: G Blazhenets et al., Department of Nuclear Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg.

Reston, VA–The effects of COVID-19 on the brain can be accurately measured with positron emission tomography (PET), according to research presented at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2021 Annual Meeting. In the study, newly diagnosed COVID-19 patients, who required inpatient treatment and underwent PET brain scans, were found to have deficits in neuronal function and accompanying cognitive impairment, and in some, this impairment continued six months after their diagnosis. The detailed depiction of areas of cognitive impairment, neurological symptoms and comparison of impairment over a six-month time frame has been selected as SNMMI’s 2021 Image of the Year.

Each year, SNMMI chooses an image that best exemplifies the most promising advances in the field of nuclear medicine and molecular imaging. The state-of-the-art technologies captured in these images demonstrate the capacity to improve patient care by detecting disease, aiding diagnosis, improving clinical confidence, and providing a means of selecting appropriate treatments. This year, the SNMMI Henry N. Wagner, Jr., Image of the Year was chosen from more than 1,280 abstracts submitted to the meeting and voted on by reviewers and the society leadership.

“As the SARS-CoV-2 pandemic proceeds, it has become increasingly clear that neurocognitive long-term consequences occur not only in severe COVID-19 cases, but in mild and moderate cases as well. Neurocognitive deficits like impaired memory, disturbed concentration and cognitive problems may persist well beyond the acute phase of the disease,” said Ganna Blazhenets, PhD, a post-doctoral researcher in Medical Imaging at the University Medical Center Freiburg, in Freiburg, Germany.

To study cognitive impairment associated with COVID-19, researchers carried out a prospective study on recently diagnosed COVID-19 patients who required inpatient treatment for non-neurological complaints. A cognitive assessment was performed, followed by imaging with 18F-FDG PET if at least two new neurological symptoms were present. By comparing COVID-19 patients to controls, the Freiburg group established a COVID-19-related covariance pattern of brain metabolism with most prominent decreases in cortical regions. Across patients, the expression of this pattern showed a very high correlation with the patients’ cognitive performance.

Follow-up PET imaging was performed six months after the initial COVID-19 diagnosis. Imaging results showed a significant improvement in the neurocognitive deficits in most patients, accompanied by an almost complete normalization of the brain metabolism.

“We can clearly state that a significant recovery of regional neuronal function and cognition occurs for most COVID-19 patients based on the results of this study. However, it is important to recognize the evidence of longer-lasting deficits in neuronal function and accompanying cognitive deficits is still measurable in some patients six months after manifestation of disease,” noted Blazhenets. “As a result, post-COVID-19 patients with persistent cognitive complaints should be presented to a neurologist and possibly allocated to cognitive rehabilitation programs.”

“18F-FDG PET is an established biomarker of neuronal function and neuronal injury,” stated SNMMI’s Scientific Program Committee chair, Umar Mahmood, MD, PhD. “As shown the Image of the Year, it can be applied to unravel neuronal correlates of the cognitive decline in patients after COVID-19. Since 18F-FDG PET is widely available, it may therefore aid in the diagnostic work-up and follow-up in patients with persistent cognitive impairment after COVID-19.”

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Abstract 41. “Altered regional cerebral function and its association with cognitive impairment in COVID 19: A prospective FDG PET study.” Ganna Blazhenets, Johannes Thurow, Lars Frings and Philipp Meyer, Department of Nuclear Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Nils Schroeter, Tobias Bormann, Cornelius Weiller, Andrea Dressing and Jonas Hosp; Department of Neurology and Clinical Neuroscience, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany; and Dirk Wagner, Department of Internal Medicine, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.

All 2021 SNMMI Annual Meeting abstracts can be found online at https://jnm.snmjournals.org/content/62/supplement_1.

About the Society of Nuclear Medicine and Molecular Imaging

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and medical organization dedicated to advancing nuclear medicine and molecular imaging, vital elements of precision medicine that allow diagnosis and treatment to be tailored to individual patients in order to achieve the best possible outcomes.

SNMMI’s members set the standard for molecular imaging and nuclear medicine practice by creating guidelines, sharing information through journals and meetings and leading advocacy on key issues that affect molecular imaging and therapy research and practice. For more information, visit http://www.snmmi.org.

“As the SARS-CoV-2 pandemic proceeds, it has become increasingly clear that neurocognitive long-term consequences occur not only in severe COVID-19 cases, but in mild and moderate cases as well. Neurocognitive deficits like impaired memory, disturbed concentration and cognitive problems may persist well beyond the acute phase of the disease,” said Ganna Blazhenets, PhD, a post-doctoral researcher in Medical Imaging at the University Medical Center Freiburg, in Freiburg, Germany.

Source: https://bioengineer.org/snmmi-image-of-the-year-pet-imaging-measures-cognitive-impairment-in-covid-19-patients/

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Scientists demonstrate promising new approach for treating cystic fibrosis

Scientists led by UNC School of Medicine researchers Silvia Kreda, Ph.D., and Rudolph Juliano, Ph.D., created an improved oligonucleotide therapy

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Scientists led by UNC School of Medicine researchers Silvia Kreda, Ph.D., and Rudolph Juliano, Ph.D., created an improved oligonucleotide therapy strategy with the potential for treating other pulmonary diseases, such as COPD and asthma

CHAPEL HILL, NC – UNC School of Medicine scientists led a collaboration of researchers to demonstrate a potentially powerful new strategy for treating cystic fibrosis (CF) and potentially a wide range of other diseases. It involves small, nucleic acid molecules called oligonucleotides that can correct some of the gene defects that underlie CF but are not addressed by existing modulator therapies. The researchers used a new delivery method that overcomes traditional obstacles of getting oligonucleotides into lung cells.

As the scientists reported in the journal Nucleic Acids Research, they demonstrated the striking effectiveness of their approach in cells derived from a CF patient and in mice.

“With our oligonucleotide delivery platform, we were able to restore the activity of the protein that does not work normally in CF, and we saw a prolonged effect with just one modest dose, so we’re really excited about the potential of this strategy,” said study senior author Silvia Kreda, PhD, an associate professor in the UNC Department of Medicine and the UNC Department Biochemistry & Biophysics, and a member of the Marsico Lung Institute at the UNC School of Medicine.

Kreda and her lab collaborated on the study with a team headed by Rudolph Juliano, PhD, Boshamer Distinguished Professor Emeritus in the UNC Department of Pharmacology, and co-founder and Chief Scientific Officer of the biotech startup Initos Pharmaceuticals.

About 30,000 people in the United States have CF, an inherited disorder in which gene mutations cause the functional absence of an important protein called CFTR. Absent CFTR, the mucus lining the lungs and upper airways becomes dehydrated and highly susceptible to bacterial infections, which occur frequently and lead to progressive lung damage.

Treatments for CF now include CFTR modulator drugs, which effectively restore partial CFTR function in many cases. However, CFTR modulators cannot help roughly ten percent of CF patients, often because the underlying gene defect is of the type known as a splicing defect.

CF and splicing defects

Splicing is a process that occurs when genes are copied out – or transcribed – into temporary strands of RNA. A complex of enzymes and other molecules then chops up the RNA strand and re-assembles them, typically after deleting certain unwanted segments. Splicing occurs for most human genes, and cells can re-assemble the RNA segments in different ways so different versions of a protein can be made from a single gene. However, defects in splicing can lead to many diseases – including CF when CFTR’s gene transcript is mis-spliced.

In principle, properly designed oligonucleotides can correct some kinds of splicing defects. In recent years the U.S. Food and Drug Administration has approved two “splice switching oligonucleotide” therapies for inherited muscular diseases.

In practice, though, getting oligonucleotides into cells, and to the locations within cells where they can correct RNA splicing defects, has been extremely challenging for some organs.

“It has been especially difficult to get significant concentrations of oligonucleotides into the lungs to target pulmonary diseases,” Kreda said.

Therapeutic oligonucleotides, when injected into the blood, have to run a long gauntlet of biological systems that are designed to keep the body safe from viruses and other unwanted molecules. Even when oligonucleotides get into cells, the most usually are trapped within vesicles called endosomes, and are sent back outside the cell or degraded by enzymes before they can ever do their work.

A new delivery strategy

The strategy developed by Kreda, Juliano, and their colleagues overcomes these obstacles by adding two new features to splice switching oligonucleotides: Firstly, the oligonucleotides are connected to short, protein-like molecules called peptides that are designed to help them to distribute in the body and get into cells. Secondly, there is a separate treatment with small molecules called OECs, developed by Juliano and Initos, which help the therapeutic oligonucleotides escape their entrapment within endosomes.

The researchers demonstrated this combined approach in cultured airway cells from a human CF patient with a common splicing-defect mutation.

“Adding it just once to these cells, at a relatively low concentration, essentially corrected CFTR to a normal level of functioning, with no evidence of toxicity to the cells,” Kreda said.

The results were much better with than without OECs, and improved with OEC dose.

There is no mouse model for splicing-defect CF, but the researchers successfully tested their general approach using a different oligonucleotide in a mouse model of a splicing defect affecting a reporter gene. In these experiments, the researchers observed that the correction of the splicing defect in the mouse lungs lasted for at least three weeks after a single treatment – hinting that patients taking such therapies might need only sporadic dosing.

The researchers now plan further preclinical studies of their potential CF treatment in preparation for possible clinical trials.

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Yan Dang, Catharina van Heusden, Veronica Nickerson, Felicity Chung, Yang Wang, Nancy Quinney, Martina Gentzsch, and Scott Randell were other contributors to this study from the Marsico Lung Institute; Ryszard Kole a co-author from the UNC Department of Pharmacology.

The Cystic Fibrosis Foundation and the National Institutes of Health supported this work.

Scientists Demonstrate Promising New Approach for Treating Cystic Fibrosis

Source: https://bioengineer.org/scientists-demonstrate-promising-new-approach-for-treating-cystic-fibrosis/

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