247 research outputs found
Large Electronic Anisotropy and Enhanced Chemical Activity of Highly Rippled Phosphorene
We investigate the electronic structure and chemical activity of rippled
phosphorene induced by large compressive strains via first-principles
calculation. It is found that phosphorene is extraordinarily bendable, enabling
the accommodation of ripples with large curvatures. Such highly rippled
phosphorene shows a strong anisotropy in electronic properties. For ripples
along the armchair direction, the band gap changes from 0.84 to 0.51 eV for the
compressive strain up to -20% and further compression shows no significant
effect, for ripples along the zigzag direction, semiconductor to metal
transition occurs. Within the rippled phosphorene, the local electronic
properties, such as the modulated band gap and the alignments of frontier
orbitals, are found to be highly spatially dependent, which may be used for
modulating the injection and confinement of carriers for optical and
photovoltaic applications. The examination of the interaction of a physisorbed
NO molecule with the rippled phosphorene under different compressive strains
shows that the chemical activities of the phosphorene are significantly
enhanced at the top and bottom peaks of the ripples, indicated by the enhanced
adsorption and charge transfer between them. All these features can be ascribed
to the effect of curvatures, which modifies the orbital coupling between atoms
at the ripple peaks
Range Spectral Filtering in SAR Interferometry: Methods and Limitations
A geometrical decorrelation constitutes one of the sources of noise present in Synthetic Aperture Radar (SAR) interferograms. It comes from the different incidence angles of the two images used to form the interferograms, which cause a spectral (frequency) shift between them. A geometrical decorrelation must be compensated by a specific filtering technique known as range filtering, the goal of which is to estimate this spectral displacement and retain only the common parts of the images’ spectra, reducing the noise and improving the quality of the interferograms. Multiple range filters have been proposed in the literature. The most widely used methods are an adaptive filter approach, which estimates the spectral shift directly from the data; a method based on orbital information, which assumes a constant-slope (or flat) terrain; and slope-adaptive algorithms, which consider both orbital information and auxiliary topographic data. Their advantages and limitations are analyzed in this manuscript and, additionally, a new, more refined approach is proposed. Its goal is to enhance the filtering process by automatically adapting the filter to all types of surface variations using a multi-scale strategy. A pair of RADARSAT-2 images that mapped the mountainous area around the Etna volcano (Italy) are used for the study. The results show that filtering accuracy is improved with the new method including the steepest areas and vegetation-covered regions in which the performance of the original methods is limited.This work was supported by the Spanish Ministry of Science and Innovation (State Agency of Research, AEI) and the European Funds for Regional Development (ERFD) under Projects PID2020-117303GB-C21 and PID2020-117303-C22
Pharmacological interactions and menopausal hormone therapy a review
Importance and Objective: Menopausal hormone therapy (HT) is widely used, and there are several statements of international scientific societies to guide prescribers; however, a summary of existing literature about possible drug interactions with HT does not exist, although many midlife women take medications for other conditions. Therefore, our objective was to create a document that presents and synthesizes the most relevant interactions. The impact of the interaction itself and the number of candidates for HTwho are likely to use other treatments are considered based on the best available evidence.
Methods: A systematic review was performed to determine the best evidence of interaction effects on relevant outcomes of interest for decision making. Aworking framework was developed to formulate explicit and reasoned recommendations according to four predefined categories for coadministration: (1) can be used without expected risks, (2) acceptable use (no evidence of negative interaction), (3) alternative treatment should be considered, and (4) nonuse without express justification. The project protocolwas registered in the Open Science Framework platform (doi: 10.17605/OSF.IO/J6WBC) and in PROSPERO (registration number CRD42020166658).
Results: Studies targeting our objective are scarce, but 23 pharmacological groups were assigned to one of the predefined categories of recommendation for concomitant use of HT. Vaginal HTwas assigned to category 1 for 21 of the analyzed pharmacological groups. For oral and transdermal HT (estrogen-only or combined) and tibolone, there were 12 pharmacological groups assigned to category 1, 12 to category 2, 5 to category 3, and 4 to category 4. Results are shown in crossed-tables that are useful for counseling and prescription.
Discussion and conclusions: Available evidence of HT interactions with other drugs is scarce and mainly indirect. It comes from biological plausibility, knowledge of extensive concomitant use without reported incidents, and/or extrapolation from hormonal contraception, but there are pharmacological groups in all categories showing that information is useful. These eligibility criteria summarize it and can help in the decision process of HT coadministration with other drugs. Decisions should be taken based on these recommendations but also individualized risk/benefit evaluation, according to underlying pathology, patient's clinical requirements, and the existence or nonexistence of alternatives
An Improved Phase Filter for Differential SAR Interferometry Based on an Iterative Method
Phase quality is a key element in the analysis of the deformation of the Earth's surface carried out with differential synthetic aperture radar interferometry. Various decorrelation sources may degrade the surface deformation estimates, and thus, phase filters are needed for this kind of application. The well-known Goldstein filter is the most widely used due to its simple implementation and computational efficiency. In the past years, improved filters have been proposed, which are based on this filter but introduce variations in the data processing. The effectiveness of these filters mostly depends on the size of the filtering window, the weight of the smoothed spectrum, and the kernel used to filter the spectrum. In this paper, we evaluate the performance of four of these filters and present a new method that outperforms all of them. The proposed filter is based on an iterative method in which the original phase is denoised progressively with adaptive filtering windows of different sizes. The effectiveness of the filter is controlled by the interferometric coherence, a direct indicator of the phase quality. Moreover, we introduce some modifications regarding the processing of the power spectrum. Specifically, we propose to smooth the original phase using a new filter which is based on a Chebyshev interpolation scheme. The performance of the new filter has been tested on both simulated and real interferograms, acquired by RADARSAT-2 and the Uninhabited Aerial Vehicle Synthetic Aperture Radar, which mapped two different geological events that caused surface deformation.This work was supported in part by the Spanish Ministry of Economy, Industry and Competitiveness, in part by the State Agency of Research (AEI), in part by the European Funds for Regional Development under Project TIN2014-55413-C2-2-P and Project TEC2017-85244-C2-1-P, in part by the U.K. Natural Environmental Research Council through the Looking Inside the Continents under Grant NE/K011006/1, in part by the Rapid deployment of a seismic array in Ecuador following the April 16th 2016 M7.8 Pedernales earthquake under Grant NE/P008828/1, and in part by the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics under Grant COMET, GA/13/M/031
Semiconductor channel mediated photodoping in h-BN encapsulated monolayer MoSe2 phototransistors
In optically excited two-dimensional phototransistors, charge transport is
often affected by photodoping effects. Recently, it was shown that such effects
are especially strong and persistent for graphene/h-BN heterostructures, and
that they can be used to controllably tune the charge neutrality point of
graphene. In this work we investigate how this technique can be extended to h
BN encapsulated monolayer MoSe_2 phototransistors at room temperature. By
exposing the sample to 785 nm laser excitation we can controllably increase the
charge carrier density of the MoSe_2 channel by {\Delta}n {\approx} 4.45
{\times} 10^{12} cm^{-2}, equivalent to applying a back gate voltage of 60 V.
We also evaluate the efficiency of photodoping at different illumination
wavelengths, finding that it is strongly correlated with the light absorption
by the MoSe_2 layer, and maximizes for excitation on-resonance with the A
exciton absorption. This indicates that the photodoping process involves
optical absorption by the MoSe_2 channel, in contrast with the mechanism
earlier described for graphene/h-BN heterostroctures
Estrogen-related genes and postmenopausal osteoporosis risk
Background To date, more than 150 candidate genes related to osteoporosis have been described, but osteoporosis has increasingly been considered a polygenic disease modulated by environmental factors. It is
thought that osteoporosis predisposition, pathology, and treatment response depend on the interaction
between different genes or between genes and environmental factors.
Objective The aim of this study was to evaluate the relationship between the presence of single nucleotide
polymorphisms (SNPs) in the estrogen metabolic pathway and the development of osteoporosis and to determine whether this relationship is monogenic or whether interactions between genes exist.
Materials and methods A multicentric study with 1980 postmenopausal Spanish women in fi ve Spanish
communities was conducted. The women completed a specifi c questionnaire that inquired about risk factors
for osteoporosis. Data on participants ’ bone mineral density were obtained with dual-energy X-ray densitometers, and genetic data were obtained from frozen peripheral blood.
Results The digenic protection combinations indicated involvement of the wild-type genotype (WT) of the
3 UTR marker for the CYP19A1 gene, the IVS4 marker of the same gene, and the BMP15 and FSHR genes.
Among patients who carried two or more of the genotypes considered ‘ risky ’ , the triple combination among
markers of the ESR2 and NRIP1 genes with any of the two mutations of the analyzed markers of the BMP15
gene gave a mean T -score value of 2.32 0.91 ( p 0.02).
Conclusion Variants of the new candidate genes ( NRIP and BMP15 ) can predispose patients to osteoporosis
O Processo de coloração a seco de porcelanato. Parte 1: Variáveis envolvidas e influência sobre as propriedades das peças
Dentre as tipologias de revestimentos cerâmicos atualmente produzidos o porcelanato tem se destacado pela grande expansão em sua produção, observada nos últimos anos. O sucesso do produto se deve pelas propriedades técnicas e estéticas oferecidas. Dentro deste contexto a técnica de coloração a seco surge como alternativa a ser adotada no processamento da massa do material, pois confere ao produto características estéticas que podem ser obtidas através de uma simples mistura de pigmentos e grânulos atomizados. Entretanto, pouco se conhece sobre as variáveis envolvidas neste processo de mistura e a real interferência de cada uma delas nas propriedades apresentadas pelo produto queimado. Este trabalho apresenta o resultado de um estudo que revela o efeito das principais variáveis relacionadas à mistura do pigmento com os grânulos atomizados sobre as propriedades apresentadas pelo produto fina
Bilayer h-BN barriers for tunneling contacts in fully-encapsulated monolayer MoSe2 field-effect transistors
The performance of electronic and spintronic devices based on two-dimensional
semiconductors (2D SC) is largely dependent on the quality and resistance of
the metal/SC electrical contacts, as well as preservation of the intrinsic
properties of the SC channel. Direct Metal/SC interaction results in highly
resistive contacts due to formation of large Schottky barriers and considerably
affects the properties of the 2D SC. In this work, we address these two
important issues in monolayer Field-Effect transistors
(FETs). We encapsulate the channel with hexagonal Boron
Nitride (h-BN), using bilayer h-BN at the metal/SC interface. The bilayer h-BN
eliminates the metal/ chemical interactions, preserves the
electrical properties of and reduces the contact resistances
by prevention of Fermi-level pinning. We investigate electrical transport in
the monolayer FETs that yields close to intrinsic electron
mobilities () even at room
temperature. Moreover, we experimentally study the charge transport through
Metal/h-BN/ tunnel contacts and we explicitly show that the
dielectric bilayer of h-BN provides highly efficient gating (tuning the Fermi
energy) of the channel at the contact regions even with small
biases. Also we provide a theoretical model that allows to understand and
reproduce the experimental characteristics of the contacts. These
observations give an insight into the electrical behavior of the metal/h-BN/2D
SC heterostructure and introduce bilayer h-BN as a suitable choice for high
quality tunneling contacts that allows for low energy charge and spin
transport.Comment: 23 pages, 10 figures (including supporting information
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