Interface charged impurity scattering in semiconductor MOSFETs and MODFETs: temperature dependent resistivity and 2D "metallic" behavior

We present the results on the anomalous 2D transport behavior by employing Drude-Boltzmann transport theory and taking into account the realistic charge impurity scattering effects. Our results show quantitative agreement with the existing experimental data in several different systems and address the origin of the strong and non-monotonic temperature dependent resistivity.Comment: Presented at SIMD, Dec. 1999 in Hawaii. To be published in Superlattices and Microstructures, May 2000 issu

Latsidipiin arteriaalse hüpertensiooni ravis: kirjanduse ülevaade ja kasutamiskogemused Eesti raviasutustes

Arteriaalse hüpertensiooni (AH) all kannatavate haigete pikaajaliseks raviks kasutatakse tänapäeval mitut gruppi ravimpreparaate. AH ravi esimese valiku preparaatideks, mis sobivad nii mono- kui ka kombineeritud teraapiaks, peetakse diureetikume, α α α α α- ja β β β β β-blokaatoreid, AKE inhibiitoreid, AT1-retseptorite ja kaltsiumiantagoniste. Artiklis on käsitletud kaltsiumiantagonistide kolme põlvkonna preparaatide antihüpertensiivse toime iseärasusi ning lähemalt kolmanda põlvkonna preparaadi latsidipiini omadusi ja kasutamise kogemusi

Minimizing the Ground Effect for Photophoretically Levitating Disks

Photophoretic levitation is a propulsion mechanism in which lightweight objects can be lifted and controlled through their interactions with light. Since photophoretic forces on macroscopic objects are usually maximized at low pressures, they may be tested in vacuum chambers in close proximity to the chamber floor and walls. We report here experimental evidence that the terrain under levitating microflyers, including the chamber floor or the launchpad from which microflyers lift off, can greatly increase the photophoretic lift forces relative to their free-space (mid-air) values. To characterize this so-called "ground effect" during vacuum chamber tests, we introduced a new miniature launchpad composed of three J-shaped (candy-cane-like) wires that minimized a microflyer's extraneous interactions with underlying surfaces. We compared our new launchpads to previously used wire-mesh launchpads for simple levitating mylar-based disks with diameters of 2, 4, and 8 cm. Importantly, wire-mesh launchpads increased the photophoretic lift force by up to sixfold. A significant ground effect was also associated with the bottom of the vacuum chamber, particularly when the distance to the bottom surface was less than the diameter of the levitating disk. We provide guidelines to minimize the ground effect in vacuum chamber experiments, which are necessary to test photophoretic microflyers intended for high-altitude exploration and surveillance on Earth or on Mars.Comment: 7 pages, 7 figures, including the Supplemental Materia

Possible Applications of Dissolution Dynamic Nuclear Polarization in Conjunction with Zero- to Ultralow-Field Nuclear Magnetic Resonance

The combination of a powerful and broadly applicable nuclear hyperpolarization technique with emerging (near-)zero-field modalities offer novel opportunities in a broad range of nuclear magnetic resonance spectroscopy and imaging applications, including biomedical diagnostics, monitoring catalytic reactions within metal reactors and many others. These are discussed along with a roadmap for future developments.Comment: 12 pages, 5 figure

The HST/ACS Grism Parallel Survey: II. First Results and a Catalog of Faint Emission-Line Galaxies at z < 1.6

We present the first results from the HST/ACS Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. We report on 11 high Galactic latitude fields here, each with grism integration times >12 ks. We identify 601 compact emission line galaxies at z 5 E-18 ergs/cm^2/s (3 sigma). We determine redshifts by cross correlation of the target spectra with template spectra, followed by visual inspection. We measure star formation rates from the observed [OII] 3727, [OIII] 5007 and Halpha line fluxes. Follow-up observations with the Keck telescope of one of the survey fields confirms our classification and redshifts with sigma(z)~0.02. This is one of the deepest emission line surveys to date, covering a total area of 121 arcmin^2. The rough estimate of the co-moving number density of emission-line galaxies in our survey at 0.3 < z < 1.3 is ~4.5 E-3 h^{-3}_70 Mpc^{-3}. We reach deeper into the emission-line luminosity function than either the STIS or NICMOS grism parallel surveys, finding an apparent space density of emission line galaxies several times higher than those surveys. Because of the ACS high spatial resolution, our survey is very sensitive to faint, compact galaxies with strong emission lines and weak continua. The ACS grism survey provides the co-moving star formation density at z < 1.6 at a high level of completeness.Comment: 20 pages, 12 figures, Accepted to the Astronomical Journal, Also available at: http://www.astro.spbu.ru/staff/dio/ACS_G800L/ACS_G800L.htm

Room-temperature optically detected magnetic resonance of single defects in hexagonal boron nitride

Optically addressable spins in materials are important platforms for quantum technologies, such as repeaters and sensors. Identification of such systems in two-dimensional (2d) layered materials offers advantages over their bulk counterparts, as their reduced dimensionality enables more feasible on-chip integration into devices. Here, we report optically detected magnetic resonance (ODMR) from previously identified carbon-related defects in 2d hexagonal boron nitride (hBN). We show that single-defect ODMR contrast can be as strong as 6% and displays a magnetic-field dependence with both positive or negative sign per defect. This bipolarity can shed light into low contrast reported recently for ensemble ODMR measurements for these defects. Further, the ODMR lineshape comprises a doublet resonance, suggesting either low zero-field splitting or hyperfine coupling. Our results offer a promising route towards realising a room-temperature spin-photon quantum interface in hexagonal boron nitride

A luminous X-ray transient in SDSS J143359.16+400636.0: a likely tidal disruption event

We present the discovery of a luminous X-ray transient, serendipitously detected by Swift's X-ray Telescope (XRT) on 2020 February 5, located in the nucleus of the galaxy SDSS J143359.16+400636.0 at z=0.099 (luminosity distance $D_{\rm L}=456$ Mpc). The transient was observed to reach a peak luminosity of $\sim10^{44}$ erg s$^{-1}$ in the 0.3--10 keV X-ray band, which was $\sim20$ times more than the peak optical/UV luminosity. Optical, UV, and X-ray lightcurves from the Zwicky Transient Facility (ZTF) and Swift show a decline in flux from the source consistent with $t^{-5/3}$, and observations with NuSTAR and Chandra show a soft X-ray spectrum with photon index $\Gamma=2.9\pm0.1$. The X-ray/UV properties are inconsistent with well known AGN properties and have more in common with known X-ray tidal disruption events (TDE), leading us to conclude that it was likely a TDE. The broadband spectral energy distribution (SED) can be described well by a disk blackbody model with an inner disk temperature of $7.3^{+0.3}_{-0.8}\times10^{5}$ K, with a large fraction ($>40$%) of the disk emission up-scattered into the X-ray band. An optical spectrum taken with Keck/LRIS after the X-ray detection reveals LINER line ratios in the host galaxy, suggesting low-level accretion on to the supermassive black hole prior to the event, but no broad lines or other indications of a TDE were seen. The stellar velocity dispersion implies the mass of the supermassive black hole powering the event is log($M_{\rm BH}$/$M_{\odot}$)$=7.41\pm0.41$, and we estimate that at peak the Eddington fraction of this event was $\sim$50%. This likely TDE was not identified by wide-field optical surveys, nor optical spectroscopy, indicating that more events like this would be missed without wide-field UV or X-ray surveys.Comment: Accepted for publication by ApJ. Accepted version now replaces initial submissio

A quantum coherent spin in a two-dimensional material at room temperature

Quantum networks and sensing require solid-state spin-photon interfaces that combine single-photon generation and long-lived spin coherence with scalable device integration, ideally at ambient conditions. Despite rapid progress reported across several candidate systems, those possessing quantum coherent single spins at room temperature remain extremely rare. Here, we report quantum coherent control under ambient conditions of a single-photon emitting defect spin in a a two-dimensional material, hexagonal boron nitride. We identify that the carbon-related defect has a spin-triplet electronic ground-state manifold. We demonstrate that the spin coherence is governed predominantly by coupling to only a few proximal nuclei and is prolonged by decoupling protocols. Our results allow for a room-temperature spin qubit coupled to a multi-qubit quantum register or quantum sensor with nanoscale sample proximity

Increased DAPK1 but decreased CCL2 plasma levels of nucleic acids in patients with stable angina

Introduction: We hypothesized that patients with stable angina have increased plasma levels of mRNA from genes responsible for atherosclerotic plaque development and destabilisation, i.e. from death-associated protein kinase (DAPK1) and monocyte chemotactic protein-1 (CCL2). Materials and methods: Nucleic acids were isolated from plasma of patients with stabile angina and healthy subjects as controls. mRNAs were transcribed to cDNAs, quantified by real-time PCR and standardized to the amount of a reference gene. Reagents for PCR quantification are declared to be mRNA specific, but in our test conditions DNA was found to interfere in both assays. Results: Patients had 5.1-times higher plasma level of DAPK1 nucleic acids (mRNA and DNA) than controls (P < 0.001) and the highest levels were associated with the presence of diabetes. However, plasma levels of CCL2 tended to be lower than in controls, and in statin-treated patients the decre-ment reached significance (-66.3%; P = 0.041). Conclusion: The estimated levels are explicable in terms of current knowledge. Further studies with specific assays for mRNA PCR quantification are reasonable to access whether this approach offers non-invasive in vivo assessment and monitoring of gene expression profile in atherosclerotic vascular beds

Mercury in the marine environment of the Canadian Arctic: Review of recent findings

AbstractThis review summarizes data and information which have been generated on mercury (Hg) in the marine environment of the Canadian Arctic since the previous Canadian Arctic Contaminants Assessment Report (CACAR) was released in 2003. Much new information has been collected on Hg concentrations in marine water, snow and ice in the Canadian Arctic. The first measurements of methylation rates in Arctic seawater indicate that the water column is an important site for Hg methylation. Arctic marine waters were also found to be a substantial source of gaseous Hg to the atmosphere during the ice-free season. High Hg concentrations have been found in marine snow as a result of deposition following atmospheric mercury depletion events, although much of this Hg is photoreduced and re-emitted back to the atmosphere. The most extensive sampling of marine sediments in the Canadian Arctic was carried out in Hudson Bay where sediment total Hg (THg) concentrations were low compared with other marine regions in the circumpolar Arctic. Mass balance models have been developed to provide quantitative estimates of THg fluxes into and out of the Arctic Ocean and Hudson Bay.Several recent studies on Hg biomagnification have improved our understanding of trophic transfer of Hg through marine food webs. Over the past several decades, Hg concentrations have increased in some marine biota, while other populations showed no temporal change. Marine biota also exhibited considerable geographic variation in Hg concentrations with ringed seals, beluga and polar bears from the Beaufort Sea region having higher Hg concentrations compared with other parts of the Canadian Arctic. The drivers of these variable patterns of Hg bioaccumulation, both regionally and temporally, within the Canadian Arctic remain unclear. Further research is needed to identify the underlying processes including the interplay between biogeochemical and food web processes and climate change