Several systems in the solid state have been suggested as promising candidates for spin-based quantum information processing. In spite of significant progress during the last decade, there is a ...search for new systems with higher potential D. DiVincenzo, Nat. Mater. 9, 468 (2010). We report that silicon vacancy defects in silicon carbide comprise the technological advantages of semiconductor quantum dots and the unique spin properties of the nitrogen-vacancy defects in diamond. Similar to atoms, the silicon vacancy qubits can be controlled under the double radio-optical resonance conditions, allowing for their selective addressing and manipulation. Furthermore, we reveal their long spin memory using pulsed magnetic resonance technique. All these results make silicon vacancy defects in silicon carbide very attractive for quantum applications.
This article deals with the concept, architecture, and scientific-organizational problems of creating a new generation of integrated software intended for predictive modeling in engineering, energy, ...materials science, biology, medicine, economics, nature management, ecology, sociology, etc. Mathematical formulations include interdisciplinary direct and inverse extremely resource-intensive tasks, which are solved using computational methods and technologies of scalable parallelization by hybrid programming on heterogeneous supercomputers with distributed and hierarchical shared memory. The project concept includes the development of an instrumental computational environment that supports all stages of a large-scale machine experiment: geometric and functional modeling, generating of adaptive unstructured grids of various types and orders, approximation of initial equations, solution of emerging algebraic problems, postprocessing of the obtained results, optimization methods for inverse tasks, and machine learning and decision-making on the results of calculations. The effective functionality of the instrumented computing environment is based on high-performance computing and intelligent big data tools. The architecture of the instrumental computational environment provides for automated expansion of the composition of implemented models and applied algorithms, adaptation to the evolution of supercomputer platforms, user-friendly interfaces and active reuse of external software products, and coordinated participation of different groups of developers, which together should provide a long life cycle and demand for the created ecosystem by a wide range of users from different professional fields.
Abstract
The rotation rates of main-sequence stars slow over time as they gradually lose angular momentum to their magnetized stellar winds. The rate of angular momentum loss depends on the strength ...and morphology of the magnetic field, the mass-loss rate, and the stellar rotation period, mass, and radius. Previous observations suggested a shift in magnetic morphology between two F-type stars with similar rotation rates but very different ages (88 Leo and
ρ
CrB). In this Letter, we identify a comparable transition in an evolutionary sequence of solar analogs with ages between 2–7 Gyr. We present new spectropolarimetry of 18 Sco and 16 Cyg A and B from the Large Binocular Telescope, and we reanalyze previously published Zeeman Doppler images of HD 76151 and 18 Sco, providing additional constraints on the nature and timing of this transition. We combine archival X-ray observations with updated distances from Gaia to estimate mass-loss rates, and we adopt precise stellar properties from asteroseismology and other sources. We then calculate the wind braking torque for each star in the evolutionary sequence, demonstrating that the rate of angular momentum loss drops by more than an order of magnitude between the ages of HD 76151 and 18 Sco (2.6–3.7 Gyr) and continues to decrease modestly to the age of 16 Cyg A and B (7 Gyr). We suggest that this magnetic transition may represent a disruption of the global dynamo arising from weaker differential rotation, and we outline plans to probe this phenomenon in additional stars spanning a wide range of spectral types.
CompHEP 4.4—automatic computations from Lagrangians to events Boos, E.; Bunichev, V.; Dubinin, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2004, Volume:
534, Issue:
1
Journal Article
Peer reviewed
Open access
We present a new version of the CompHEP program (version 4.4). We describe shortly new issues implemented in this version, namely, simplification of quark flavor combinatorics for the evaluation of ...hadronic processes, Les Houches Accord-based CompHEP-PYTHIA interface, processing the color configurations of events, implementation of MSSM, symbolical and numerical batch modes, etc. We discuss how the CompHEP program is used for preparing event generators for various physical processes. We mention a few concrete physics examples for CompHEP-based generators prepared for the LHC and Tevatron.
Ion implantation is a key technology without alternative for doping silicon carbide SiC in the manufacturing processes of SiC devices. SiC technology has a number of distinctive features in ...comparison with Si-ion doping technology. This paper provides a systematic analysis of modern technical solutions aimed at the formation of local doped regions by the method of ion implantation for various purposes for SiC-based high-power electronic devices. The results of research conducted at the St. Petersburg State Electrotechnical University LETI are presented. This research is focused on the development and selection of modes of aluminum- and phosphorus-ion implantation into 4H-SiC structures that provide specified concentrations of doping impurities and geometric dimensions of local ion-doped regions. The developed ion-implantation modes are successfully implemented in the manufacture of samples of high-power 4H-SiC metal–insulator–semiconductor (MIS) transistors with operating voltages of up to 1200 V.
The most common diseases of the upper limb are osteoarthritis (OA) of the joints of the hands, lateral epiconlitis, tendinitis of the shoulder muscles, adhesive capsulitis. OA of the shoulder and ...acromioclavicular joints is less common. The development of acute and subacute pain in the elbow and shoulder joints in the vast majority of cases is determined by the pathology of soft tissues: muscles, ligamentous apparatus and related synovial bags, making it difficult to diagnose. A clinical and radiological heterogeneity of OA of the joints of the hands is a very complex pathology for the study, and also to create a unified algorithms for therapy. Therapy nonsteroidal anti-inflammatory drugs are effective in the short term, but it has several side effects. Despite a variety of attempts at therapy with successful and unsuccessful outcome, the attention of researchers for several decades converted to the injection therapy with hyaluronic acid. The article presents the data of studies demonstrating the anti-inflammatory effect of hyaluronic acid in the treatment of OA, as well as the results of clinical trials and data system of meta-analysis demonstrating the effectiveness of intra-articular and extra-articular therapy tendinopathy of the upper limb. Most of the cited studies demonstrated the efficacy and good tolerance of 1% sodium hyaluronate. In the domestic market it is presented in the drug Flexotron Forte. The authors provide the results of the study results, demonstrating the efficacy and safety of using Flexotron Forte to clinical practice.
Interface dynamics Abarzhi, Snezhana I.; Ilyin, Daniil V.; Goddar, William A. ...
Proceedings of the National Academy of Sciences - PNAS,
09/2019, Volume:
116, Issue:
37
Journal Article
Peer reviewed
Open access
Interfacial mixing and transport are nonequilibrium processes coupling kinetic to macroscopic scales. They occur in fluids, plasmas, and materials over celestial events to atoms. Grasping their ...fundamentals can advance a broad range of disciplines in science, mathematics, and engineering. This paper focuses on the long-standing classic problem of stability of a phase boundary—a fluid interface that has a mass flow across it. We briefly review the recent advances in theoretical and experimental studies, develop the general theoretical framework directly linking the microscopic interfacial transport to the macroscopic flow fields, discover mechanisms of interface stabilization and destabilization that have not been discussed before for both inertial and accelerated dynamics, and chart perspectives for future research.
Context. LQ Hya is one of the most frequently studied young solar analogue stars. Recently, it has been observed to show intriguing behaviour when analysing long-term photometry. For instance, from ...2003–2009, a coherent spot structure migrating in the rotational frame was reported by various authors. However, ever since, the star has entered a chaotic state where coherent structures seem to have disappeared and rapid phase jumps of the photometric minima occur irregularly over time. Aims. LQ Hya is one of the stars included in the SOFIN/FIES long-term monitoring campaign extending over 25 yr. Here, we publish new temperature maps for the star during 2006–2017, covering the chaotic state of the star. Methods. We used a Doppler imaging technique to derive surface temperature maps from high-resolution spectra. Results. From the mean temperatures of the Doppler maps, we see a weak but systematic increase in the surface temperature of the star. This is consistent with the simultaneously increasing photometric magnitude. During nearly all observing seasons, we see a high-latitude spot structure which is clearly non-axisymmetric. The phase behaviour of this structure is very chaotic but agrees reasonably well with the photometry. Equatorial spots are also frequently seen, but we interpret many of them to be artefacts due to the poor to moderate phase coverage. Conclusions. Even during the chaotic phase of the star, the spot topology has remained very similar to the higher activity epochs with more coherent and long-lived spot structures. In particular, we see high-latitude and equatorial spot activity, the mid latitude range still being most often void of spots. We interpret the erratic jumps and drifts in phase of the photometric minima to be caused by changes in the high-latitude spot structure rather than the equatorial spots.
Abstract
During the first half of their main-sequence lifetimes, stars rapidly lose angular momentum to their magnetized winds, a process known as magnetic braking. Recent observations suggest a ...substantial decrease in the magnetic braking efficiency when stars reach a critical value of the Rossby number, the stellar rotation period normalized by the convective overturn timescale. Cooler stars have deeper convection zones with longer overturn times, reaching this critical Rossby number at slower rotation rates. The nature and timing of the transition to weakened magnetic braking have previously been constrained by several solar analogs and two slightly hotter stars. In this Letter, we derive the first direct constraints from stars cooler than the Sun. We present new spectropolarimetry of the old G8 dwarf
τ
Cet from the Large Binocular Telescope, and we reanalyze a published Zeeman Doppler image of the younger G8 star 61 UMa, yielding the large-scale magnetic field strengths and morphologies. We estimate mass-loss rates using archival X-ray observations and inferences from Ly
α
measurements, and we adopt other stellar properties from asteroseismology and spectral energy distribution fitting. The resulting calculations of the wind braking torque demonstrate that the rate of angular momentum loss drops by a factor of 300 between the ages of these two stars (1.4–9 Gyr), well above theoretical expectations. We summarize the available data to help constrain the value of the critical Rossby number, and we identify a new signature of the long-period detection edge in recent measurements from the Kepler mission.
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