1,851 research outputs found
Pseudo spin-orbit coupling of Dirac particles in graphene spintronics
We study the pseudo spin-orbital (SO) effects experienced by massive Dirac
particles in graphene, which can potentially be of a larger magnitude compared
to the conventional Rashba SO effects experienced by particles in a 2DEG
semiconductor heterostructure. In order to generate a uniform vertical pseudo
SO field, we propose an artificial atomic structure, consisting of a graphene
ring and a charged nanodot at the center which produces a large radial electric
field. In this structure, a large pseudo SO coupling strength can be achieved
by accelerating the Dirac particles around the ring, due to the small energy
gap in graphene and the large radial electric field emanating from the charged
nanodot. We discuss the theoretical possibility of harnessing the pseudo SO
effects in mesoscopic applications, e.g. pseudo spin relaxation and switching.Comment: 12 pages, 1 figur
Overlapping-gate architecture for silicon Hall bar MOSFET devices in the low electron density regime
We report the fabrication and study of Hall bar MOSFET devices in which an
overlapping-gate architecture allows four-terminal measurements of low-density
2D electron systems, while maintaining a high density at the ohmic contacts.
Comparison with devices made using a standard single gate show that
measurements can be performed at much lower densities and higher channel
resistances, despite a reduced peak mobility. We also observe a voltage
threshold shift which we attribute to negative oxide charge, injected during
electron-beam lithography processing.Comment: 4 pages, 4 figures, submitted for Applied Physics Letter
Ethyl cyanide on Titan: Spectroscopic detection and mapping using ALMA
We report the first spectroscopic detection of ethyl cyanide (CHCN)
in Titan's atmosphere, obtained using spectrally and spatially resolved
observations of multiple emission lines with the Atacama Large
Millimeter/submillimeter array (ALMA). The presence of CHCN in Titan's
ionosphere was previously inferred from Cassini ion mass spectrometry
measurements of CHCNH. Here we report the detection of 27
rotational lines from CHCN (in 19 separate emission features detected
at confidence), in the frequency range 222-241 GHz. Simultaneous
detections of multiple emission lines from HCN, CHCN and CHCCH were
also obtained. In contrast to HCN, CHCN and CHCCH, which peak in
Titan's northern (spring) hemisphere, the emission from CHCN is found
to be concentrated in the southern (autumn) hemisphere, suggesting a distinctly
different chemistry for this species, consistent with a relatively short
chemical lifetime for CHCN. Radiative transfer models show that most of
the CHCN is concentrated at altitudes 300-600 km, suggesting production
predominantly in the mesosphere and above. Vertical column densities are found
to be in the range (2-5) cm.Comment: Published in 2015, ApJL, 800, L1
A Simple Protein Precipitation-based Simultaneous Quantification of Lovastatin and Its Active Metabolite Lovastatin Acid in Human Plasma by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry using Polarity Switching
Lovastatin is an anti-cholesterol lactone drug indicated for the treatment of hyperlipidemia and to reduce the risk of coronary heart disease. It is converted to the β-hydroxy acid form (lovastatin acid) in vivo, which is the major pharmacologically active metabolite. Here, we describe the development and validation of an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based method utilizing polarity switching for the simultaneous quantification of lovastatin and lovastatin acid in human plasma. Simple protein precipitation extraction and direct injection of the extracted samples without drying/reconstitution showed good recoveries of both analytes (~70%). The developed method exhibited satisfactory intra-day and inter-day accuracy and precision. The interconversion between lovastatin and lovastatin acid during sample preparation and storage was minimal (< 1.9%). The lower limits of quantification were 0.5 and 0.2 nM (or 0.2 and 0.084 ng/mL) for lovastatin and lovastatin acid, respectively, using only 50 μL of plasma during extraction. The validated method was successfully applied to analyze plasma samples obtained from a healthy human subject who enrolled in a clinical drug interaction study involving lovastatin
Ground-Based Centimeter, Millimeter, and Submillimeter Observations of Comet 103P/Hartley 2
Comets provide important clues to the physical and chemical processes that occurred during the formation and early evolution of the Solar System, and could also have been important for initiating prebiotic chemistry on the early Earth [1]. Comets are comprised of molecular ices, that may be pristine interstellar remnants of Solar System formation, along with high-temperature crystalline silicate dust that is indicative of a more thermally varied history in the protosolar nebula [2]. Comparing abundances of cometary parent volatiles, and isotopic fractionation ratios, to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection [3]. We have conducted observations, at primarily millimeter and submillimeter wavelengths, where molecular emission is easily resolved, towards comets to determine important cosmogonic quantities, such as the ortl1o:pal'a ratio and isotope ratios, as well as probe the origin of cometary organics. Comets provide important clues to the processes that occurred during the formation and early evolution of the Solar System. Past observations, as well as laboratory measurements of cometary material obtained from Stardust, have shown that comets appear to contain a mixture of the products from both interstellar and nebular chemistries. A major observational challenge in cometary science is to quantify the extent to which chemical compounds can be linked to either reservoir
Retrovirology: 3 at age 2
Retrovirology announces new editorial board members and reprises progress over the first two years of publishing
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