1,451 research outputs found
Tailoring the carrier mobility of semiconducting nanowires by remote dielectrics
The dielectric environment of thin semiconductor nanowires can affect the
charge transport properties inside the wire. In this work, it is shown that
Coulomb impurity scattering inside thin nanowires can be damped strongly by
coating the wire with a high-k dielectric. This will lead to an increase in the
mobility of free charges inside the wire.Comment: 4 pages, 3 figure
Very high two-dimensional hole gas mobilities in strained silicon germanium
We report on the growth by solid source MBE and characterization of remote doped Si/SiGe/Si two-dimensional hole gas structures. It has been found that by reducing the Ge composition to <=13% and limiting the thickness of the alloy layer, growth temperatures can be increased up to 950 °C for these structures while maintaining good structural integrity and planar interfaces. Record mobilities of 19 820 cm2 V−1 s−1 at 7 K were obtained in normal structures. Our calculations suggest that alloy scattering is not important in these structures and that interface roughness and interface charge scattering limit the low temperature mobilities
In Vivo Intracellular Oxygen Dynamics in Murine Brain Glioma and Immunotherapeutic Response of Cytotoxic T Cells Observed by Fluorine-19 Magnetic Resonance Imaging
Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC) molecules, combined with quantitative 19F spin-lattice relaxation rate (R1) measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS) GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R1 of 19F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO2) was ascertained. Three days after tumor implantation, mice were treated with 2×107 cytotoxic T cells intravenously. At day five, a transient spike in pO2 was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO2 was causally related to the T cells infiltration. Surprisingly, the pO2 spike was detected even though few (∼4×104) T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models. © 2013 Zhong et al
Willmore Surfaces of Constant Moebius Curvature
We study Willmore surfaces of constant Moebius curvature in . It is
proved that such a surface in must be part of a minimal surface in
or the Clifford torus. Another result in this paper is that an isotropic
surface (hence also Willmore) in of constant could only be part of a
complex curve in or the Veronese 2-sphere in . It is
conjectured that they are the only examples possible. The main ingredients of
the proofs are over-determined systems and isoparametric functions.Comment: 16 pages. Mistakes occured in the proof to the main theorem (Thm 3.6)
has been correcte
Low-supervision urgency detection and transfer in short crisis messages
Humanitarian disasters have been on the rise in recent years due to the
effects of climate change and socio-political situations such as the refugee
crisis. Technology can be used to best mobilize resources such as food and
water in the event of a natural disaster, by semi-automatically flagging tweets
and short messages as indicating an urgent need. The problem is challenging not
just because of the sparseness of data in the immediate aftermath of a
disaster, but because of the varying characteristics of disasters in developing
countries (making it difficult to train just one system) and the noise and
quirks in social media. In this paper, we present a robust, low-supervision
social media urgency system that adapts to arbitrary crises by leveraging both
labeled and unlabeled data in an ensemble setting. The system is also able to
adapt to new crises where an unlabeled background corpus may not be available
yet by utilizing a simple and effective transfer learning methodology.
Experimentally, our transfer learning and low-supervision approaches are found
to outperform viable baselines with high significance on myriad disaster
datasets.Comment: 8 pages, short version published in ASONAM 201
Green's function approach to transport through a gate-all-around Si nanowire under impurity scattering
We investigate transport properties of gate-all-around Si nanowires using
non-equilibrium Green's function technique. By taking into account of the
ionized impurity scattering we calculate Green's functions self-consistently
and examine the effects of ionized impurity scattering on electron densities
and currents. For nano-scale Si wires, it is found that, due to the impurity
scattering, the local density of state profiles loose it's interference
oscillations as well as is broaden and shifted. In addition, the impurity
scattering gives rise to a different transconductance as functions of
temperature and impurity scattering strength when compared with the
transconductance without impurity scattering.Comment: 8 pages, 4 figure
Herbicide-Resistant Tobacco Plants Expressing the Fused Enzyme between Rat Cytochrome P4501A1 (CYP1A1) and Yeast NADPH-Cytochrome P450 Oxidoreductase
Energy partitioning on intermolecular interactions: ab initio Monte Carlo study of water dimer
Ab initio Monte Carlo computations were carried out on H₂O dimer system. By introducing the energy partitioning
scheme that we have developed recently, ab initio calculated H₂O–H₂O interaction can be analyzed
from the viewpoint of atom-atom interaction. The electronic polarization caused by the interaction and its
temperature dependence are also discussed. To our best knowledge, this is the first report on the thermal
distribution of electronic distortion energy assigned to a molecule.Виконанi ab initio Монте Карло розрахунки для H2O димерної системи. Вводячи розроблену ранiше схему роздiлення енергiї, ab initio розрахована взаємодiя H2O–H2O може бути проаналiзована з точки зору атом-атомної взаємодiї. Обговорюється електронна поляризацiя, обумовлена взаємодiєю, та її температурна залежнiсть. З точки зору наших вiдомостей, це є перше повiдомлення про термiчний розподiл електронної змiни енергiї, переданої молекулi
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