1,070 research outputs found
Analysis of a diffusive effective mass model for nanowires
We propose in this paper to derive and analyze a self-consistent model
describing the diffusive transport in a nanowire. From a physical point of
view, it describes the electron transport in an ultra-scaled confined
structure, taking in account the interactions of charged particles with
phonons. The transport direction is assumed to be large compared to the wire
section and is described by a drift-diffusion equation including effective
quantities computed from a Bloch problem in the crystal lattice. The
electrostatic potential solves a Poisson equation where the particle density
couples on each energy band a two dimensional confinement density with the
monodimensional transport density given by the Boltzmann statistics. On the one
hand, we study the derivation of this Nanowire Drift-Diffusion Poisson model
from a kinetic level description. On the other hand, we present an existence
result for this model in a bounded domain
Evaluation of antimicrobial and antioxidant properties of leaves of Emex spinosa and fruits of Citrillus colocynthis from Saudi Arabia
The crude methanol extract of Citrullus colocynthis fruit and Emex spinosa leaves were examined for antimicrobial and antioxidant potentialities. The phytochemical analysis revealed presence of some bioactive principles, such as alkaloids, flavonoids and anthraquinones for E. spinosa and saponin, flavonoids, terpenoids and alkaloids for C. colocynthis. The antimicrobial activities were determined against seven bacterial strains (Proteus vulgaris NCTC 8196, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumonia ATCC 53651, Salmonella typhi NCTC 0650, Staphylococcus aureus ATCC 25923 and Bacillus cereus NCTC 8236) and one fungal strain (Candida albicans ATCC 7596). E. spinosa leaf methanol extract was most active against fungus, whileC. colocynthis fruit methanol extract was most active against bacteria, particularly E. coli ATCC 25922 and P. aeruginosa ATCC 27853. The antioxidant properties of extracts were investigated in vitro using1,1-diphenyl, 2-picryl hydrazyl (DPPH) radical scavenging assay and in vivo in rats using serological and enzymatic tests. Both plant extracts showed considerable antioxidant activities. The promising findings of this investigation could be used as a novel natural antimicrobial and antioxidant agents.Keywords: Emex spinosa, Citrillus colocynthis, antimicrobial, antioxidant activity.African Journal of Biotechnology Vol. 12(34), pp. 5308-531
An effective mass theorem for the bidimensional electron gas in a strong magnetic field
We study the limiting behavior of a singularly perturbed
Schr\"odinger-Poisson system describing a 3-dimensional electron gas strongly
confined in the vicinity of a plane and subject to a strong uniform
magnetic field in the plane of the gas. The coupled effects of the confinement
and of the magnetic field induce fast oscillations in time that need to be
averaged out. We obtain at the limit a system of 2-dimensional Schr\"odinger
equations in the plane , coupled through an effective selfconsistent
electrical potential. In the direction perpendicular to the magnetic field, the
electron mass is modified by the field, as the result of an averaging of the
cyclotron motion. The main tools of the analysis are the adaptation of the
second order long-time averaging theory of ODEs to our PDEs context, and the
use of a Sobolev scale adapted to the confinement operator
Towards a black body for near-field thermal radiation
We study the near-field heat exchange between hyperbolic materials and
demonstrate that these media are able to support broadband frustrated modes
which transport heat by photon tunnelling with a high efficiency close to the
theoretical limit. We predict that hyperbolic materials can be designed to be
perfect thermal emitters at nanoscale and derive the near-field analog of the
blackbody limit
Bayesian Signal Subspace Estimation with Compound Gaussian Sources
International audienceIn this paper, we consider the problem of low dimensional signal subspace estimation in a Bayesian con- text. We focus on compound Gaussian signals embedded in white Gaussian noise, which is a realistic modeling for various array processing applications. Following the Bayesian framework, we derive two algorithms to compute the maximum a posteriori (MAP) estimator and the so-called minimum mean square distance (MMSD) estimator, which minimizes the average natural distance between the true range space of interest and its estimate. Such approaches have shown their interests for signal subspace esti- mation in the small sample support and/or low signal to noise ratio contexts. As a byproduct, we also introduce a generalized version of the complex Bingham Langevin distribution in order to model the prior on the subspace orthonormal basis. Finally, numerical simulations illustrate the performance of the proposed algorithms
Signal subspace change detection in structured covariance matrices
International audienceTesting common properties between covariance matricesis a relevant approach in a plethora of applications. In thispaper, we derive a new statistical test in the context of structuredcovariance matrices. Specifically, we consider low rank signalcomponent plus white Gaussian noise structure. Our aim is totest the equality of the principal subspace, i.e., subspace spannedby the principal eigenvectors of a group of covariance matrices. Adecision statistic is derived using the generalized likelihood ratiotest. As the formulation of the proposed test implies a non-trivialoptimization problem, we derive an appropriate majorizationminimizationalgorithm. Finally, numerical simulations illustratethe properties of the newly proposed detector compared to thestate of the art
Birefringence in nonlinear anisotropic dielectric media
Light propagation is investigated in the context of local anisotropic
nonlinear dielectric media at rest with the dielectric coefficients
and constant ,
in the limit of geometrical optics. Birefringence was examined and the general
conditions for its occurrence were presented. A toy model is exhibited, in
which uniaxial birefringent media with nonlinear dielectric properties could be
driven by external fields in such way that birefringence may be artificially
controlled. The effective geometry interpretation is also addressed.Comment: 5 pages, 1 figur
First documented presence of Galeocerdo cuvier (Péron & Lesueur, 1822) (ELASMOBRANCHII, CARCHARHINIDAE) in the Mediterranean basin (Libyan waters)
One male and one female specimen of tiger shark, Galeocerdo cuvier (Peron & Lesueur, 1822), were accidentally caught by a drifting longline for swordfish in the south Mediterranean (Libyan waters). This finding confirms beyond any doubt that the tiger shark may be encountered in the waters of the Mediterranean Sea. Although records of this species has previously been reported, the information is partial or dubious, due to the lack of a description of the individuals found or the uncertain provenance of preserved material. Our finding confirms the record of this species in the southern part of the Mediterranean basin. Images, as well as morphometrics and information on stomach contents are given. Based on the size of the individuals, it is considered that the two specimens were born recently, presumably inside the Mediterranean Sea and likely close to the area where the individuals were found
Study protocol for the Anesthesiology Control Tower—Feedback Alerts to Supplement Treatments (ACTFAST-3) trial: A pilot randomized controlled trial in intraoperative telemedicine [version 1; referees: 2 approved]
Background: Each year, over 300 million people undergo surgical procedures worldwide. Despite efforts to improve outcomes, postoperative morbidity and mortality are common. Many patients experience complications as a result of either medical error or failure to adhere to established clinical practice guidelines. This protocol describes a clinical trial comparing a telemedicine-based decision support system, the Anesthesiology Control Tower (ACT), with enhanced standard intraoperative care. Methods: This study is a pragmatic, comparative effectiveness trial that will randomize approximately 12,000 adult surgical patients on an operating room (OR) level to a control or to an intervention group. All OR clinicians will have access to decision support software within the OR as a part of enhanced standard intraoperative care. The ACT will monitor patients in both groups and will provide additional support to the clinicians assigned to intervention ORs. Primary outcomes include blood glucose management and temperature management. Secondary outcomes will include surrogate, clinical, and economic outcomes, such as incidence of intraoperative hypotension, postoperative respiratory compromise, acute kidney injury, delirium, and volatile anesthetic utilization. Ethics and dissemination: The ACTFAST-3 study has been approved by the Human Resource Protection Office (HRPO) at Washington University in St. Louis and is registered at clinicaltrials.gov (NCT02830126). Recruitment for this protocol began in April 2017 and will end in December 2018. Dissemination of the findings of this study will occur via presentations at academic conferences, journal publications, and educational materials
Comparative Genomic and Transcriptomic Analyses of Mycobacterium kansasii Subtypes Provide New Insights Into Their Pathogenicity and Taxonomy
Mycobacterium kansasii is an important opportunistic pathogen of humans and has a
close phylogenetic relationship with Mycobacterium tuberculosis. Seven subtypes (I–VII)
have been identified using molecular biology approaches, of which subtype I is the
most frequent causative agent of human disease. To investigate the genotypes and
pathogenic components of M. kansasii, we sequenced and compared the complete
base-perfect genomes of different M. kansasii subtypes. Our findings support the
proposition that M. kansasii “subtypes” I-VI, whose assemblies are currently available,
should be considered as different species. Furthermore, we identified the exclusive
presence of the espACD operon in M. kansasii subtype I, and we confirmed its role in the
pathogenicity of M. kansasii in a cell infection model. The espACD operon is exclusively
present in mycobacterial species that induce phagosomal rupture in host phagocytes
and is known to be a major determinant of ESX1-mediated virulence in pathogenic
mycobacteria. Comparative transcriptome analysis of the M. kansasii I-V strains identified
genes potentially associated with virulence. Using a comparative genomics approach,
we designed primers for PCR genotyping of M. kansasii subtypes I-V and tested their
efficacy using clinically relevant strains of M. kansasii.Work in AP's laboratory was supported by the KAUST faculty baseline fund (BAS/1/1020-01- 01
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