(Press-News.org) Professor Konstantin Arutyunov of the HSE Tikhonov Moscow Institute of Electronics and Mathematics (MIEM HSE), together with Chinese researchers, has developed a graphene-based mechanical resonator, in which coherent emission of sound energy quanta, or phonons, has been induced. Such devices, called phonon lasers, have wide potential for application in information processing, as well as classical and quantum sensing of materials. The study is published in the journal Optics Express.
Using an analogy with photons, quanta of the electromagnetic spectrum, there are also particles of sound energy, phonons. In fact, these are artificially introduced objects in physics - quasi-particles, which correspond to vibrations of the crystal lattice of matter.
Some substances, when irradiated, emit photons of the same wavelength, phase, and polarisation. This process, called stimulated emission, was predicted by Albert Einstein over a century ago and is the basis of the device we all know - the laser. The first lasers were constructed about sixty years ago, and they have become firmly established in our lives in various fields.
A similar process, involving the emission of 'identical' phonons, underlies a device called, by analogy, a phonon laser, or saser. In fact, it was predicted at the same time as lasers, but only a few experimental realisations have been developed over a long period of time, and none of them have been widely used in the industry.
Magnesium ions, semiconductors, composite systems with microcavities, electromechanical resonators, nanoparticles, and many other substances and systems have been used as active media for phonon lasers over the last decade. Unlike previous studies, the present study used graphene to create coherent acoustic excitations. Due to the unique properties of graphene, such resonators can potentially be widely used.
The graphene resonator was produced by microlithography: a photo-sensitive polymer film is deposited on a silicon substrate. Using ultraviolet light, a certain structure is 'drawn' on the substrate, which subsequently allows the formation of a repeating system of micro-cavities by means of plasma treatment. The treated substrate is covered with a layer of graphene, and this system of 'drums' behaves like a resonator, i.e. it amplifies external vibrations if they are generated with a certain frequency.
If such a 'drum' is irradiated with laser light at a specific wavelength, photons are repeatedly reflected between the silicon backing and the graphene, thereby forming optical cavities where mechanical vibrations of the appropriate frequency are produced.
'Experimentally, we have examined a nanostructure, which is a fixed membrane made of a monatomic layer of carbon, or a graphene. Vibrations of atoms, or phonons, were activated in it through exposure to external optical radiation,' says Konstantin Arutyunov. 'The research is expected to continue, as it is of considerable interest both for physics of ultra small objects and has the potential to create a new generation of quantum optomechanical sensors and transducers.'
INFORMATION:
Geologic activity on Earth appears to follow a 27.5-million-year cycle, giving the planet a "pulse," according to a new study published in the journal Geoscience Frontiers.
"Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random," said Michael Rampino, a geologist and professor in New York University's Department of Biology, as well as the study's lead author.
Over the past five decades, researchers have proposed cycles ...
A new paper in Scientific Reports led by researchers at William & Mary's Virginia Institute of Marine Science challenges increased salinity and seawater temperatures as the established explanation for a decades-long increase in the prevalence and deadliness of a major oyster disease in the coastal waters of the mid-Atlantic.
Dr. Ryan Carnegie, the paper's lead author, says "We present an entirely new lens through which we can view our last 35 years of oyster history in the Chesapeake Bay region. We now know the great intensification of Dermo disease in the 1980s wasn't simply due to drought. It was more fundamentally due to the emergence of a new and highly virulent form of Perkinsus marinus, the parasite that causes Dermo."
In an unusual twist, the team's evidence ...
The Axial Spondyloarthritis International Federation (ASIF) set out to coordinate a comprehensive evidence-based global review of the factors influencing the current diagnosis delay in axSpA, and to produce a definitive report that shines a light on these barriers, as well as providing a resource that can ultimately empower a range of international stakeholders to reduce this delay.
At the 2021 EULAR congress, Wendy Gerhart and colleagues report the results of a full literature review and two virtual global forum events, involving patients and patient group ...
Ben Mulhearn and colleagues estimated the incidence of GCA seen during the COVID-19 pandemic and compared it to data from 2019, before the pandemic hit. The two distinct peaks of COVID-19 reflected by UK hospital admissions of COVID-19-positive patients allowed the authors to investigate the relationship in time between COVID-19 and GCA incidence.
At the Royal National Hospital for Rheumatic Diseases in Bath, UK, there were 61 probable or definite GCA diagnoses made in 2020 compared to 28 in 2019- representing an excess of 33 cases in 2020, or an increase of 118%.Taking into account the fact that41% of the ...
Arani Vivekanantham and colleagues investigated the association between RA and the risk of COVID-19 diagnosis, hospitalization with COVID-19,and COVID-19-related death. This population-based cohort study including all individuals registered in the Information System for Research in Primary Care (SIDIAP)- which covers over80% of the population of Catalonia, Spain. This information was linked to region-wide SARS-CoV-2 testing, hospital and mortality records. Outpatient diagnoses of COVID-19, hospitalizations and deaths with COVID-19 were identified between 1st March and 6th May 2020.
A total of 5,586,565 ...
MINNEAPOLIS/ST. PAUL (06/18/2021) -- Two recent studies led by researchers from the University of Minnesota Medical School add new evidence to the impact of how drug price increases affect U.S. patients and the overall cost of health care.
The first study, published today in the JAMA Network Open, provides new data on how dramatic increases in anti-infective drug prices altered the overall cost of outpatient health care and decreased patient access to appropriate drug treatment. The study protocol was reviewed by the U.S. Centers for Disease Control and Prevention and scanned ...
As part of the MAINSTREAM project, Favalli and colleagues conducted a seroprevalence cross-sectional study between 4th May and 16th June 2020toestimate the prevalence of anti-SARS-CoV-2 antibodies in a large cohort of people with rheumatoid arthritis (RA) or spondyloarthritis (SpA) treated with biologic or targeted synthetic disease modifying anti rheumatic drugs (b/tsDMARDs) in a COVID-19 high-endemic area (Lombardy, Italy). Over this time, 300 people were tested for IgG, IgM and IgA antibodies against three viral antigens-nucleoprotein, spike protein, and the receptor-binding domain. These data were compared with those observed in the healthy population in the same period and region. Everyone taking part also completed a questionnaire to collect information about symptoms consistent ...
A research group including Professor MATSUDA Tetsuya of Tamagawa University's Brain Science Institute (Machida City, Tokyo; Director: SAKAGAMI Masamichi) and Assistant Professor ISHIHARA Toru from Kobe University's Graduate School of Human Development and Environment has illuminated the changes in the brain's neural network and cortex structure that underlie the positive association between childhood exercise and the maintenance and promotion of cognitive function in later life.
These results were published in the academic journal NeuroImage on May 23, 2021.
Main Points
The researchers showed that people who are physically active during childhood (up to 12 years of age) have ...
That is the conclusion of new research published in the journal Geriatrics, which examined studies on several "telehealth" applications - smartphone apps used by patients and healthcare professionals to manage their condition.
Researchers found that smartphone apps and telehealth initiatives have the potential to improve the effectiveness and efficiency of healthcare systems and patients' quality of life in relation to pain management
The authors also emphasise that user involvement in development and construction of smartphone apps and telehealth initiatives is ...
Graphene consists of carbon atoms arranged in a chicken-wire like pattern. This one-atom-thick material is famous for its many extraordinary properties, such as extreme strength and remarkable capability to conduct electricity. Since its discovery, researchers have looked for ways to further tailor graphene through controlled manipulation of its atomic structure. However, until now, such modifications have been only confirmed locally, because of challenges in atomic-resolution imaging of large samples and analysis of large datasets.
Now a team around Jani Kotakoski at the University of ...
