Nonlinear hole transport and nonequilibrium thermodynamics in group III-nitrides under the influence of electric fields

A theoretical study on the nonlinear transport of holes and of the nonequilibrium thermodynamic characteristics of p-doped wurtzite gallium nitride (GaN), aluminium nitride (AlN), and indium nitride (InN), under the influence of moderate to high electric fields, is presented. It is based on a nonlinear quantum kinetic theory which provides a description of the dissipative phenomena developing in the system. The ultrafast time evolution of the hole drift velocity and of the quasitemperatures of holes and longitudinal optical phonons are obtained. The steady state is analyzed by determining the dependence on the electric field of the nonequilibrium thermodynamic state and of the non-Ohmic mobility. A velocity overshoot is evidenced. (C) 2007 American Institute of Physics.102

Health promoting potential of herbal teas and tinctures from Artemisia campestris subsp maritima: from traditional remedies to prospective products

This work explored the biotechnological potential of the medicinal halophyte Artemisia campestris subsp. maritima (dune wormwood) as a source of health promoting commodities. For that purpose, infusions, decoctions and tinctures were prepared from roots and aerial-organs and evaluated for in vitro antioxidant, anti-diabetic and tyrosinase-inhibitory potential, and also for polyphenolic and mineral contents and toxicity. The dune wormwood extracts had high polyphenolic content and several phenolics were identified by ultra-high performance liquid chromatography-photodiode array-mass-spectrometry (UHPLC-PDA-MS). The main compounds were quinic, chlorogenic and caffeic acids, coumarin sulfates and dicaffeoylquinic acids; several of the identified phytoconstituents are here firstly reported in this A. campestris subspecies. Results obtained with this plant's extracts point to nutritional applications as mineral supplementary source, safe for human consumption, as suggested by the moderate to low toxicity of the extracts towards mammalian cell lines. The dune wormwood extracts had in general high antioxidant activity and also the capacity to inhibit a-glucosidase and tyrosinase. In summary, dune wormwood extracts are a significant source of polyphenolic and mineral constituents, antioxidants and a-glucosidase and tyrosinase inhibitors, and thus, relevant for different commercial segments like the pharmaceutical, cosmetic and/or food industries.FCT - Foundation for Science and Technology [CCMAR/Multi/04326/2013]; Portuguese National Budget; FCT [IF/00049/2012, SFRH/BD/94407/2013]; Research Foundation - Flanders (FWO) [12M8315N]info:eu-repo/semantics/publishedVersio

Velocity overshoot onset in nitride semiconductors

A theoretical study on the electron drift velocity and some nonequilibrium thermodynamic characteristics of wurtzite GaN, AlN, and InN is presented. It is based on a nonlinear quantum kinetic theory which provides a description of the dissipative phenomena developing in the system. The ultrafast time evolution of the electron drift velocity and quasitemperature is obtained, and overshoot effects are evidenced on both. The overshoot onsets are shown to occur at 20 kV/cm in GaN, 60 kV/cm in AlN, and 10 kV/cm in InN, electric field intensities which are considerably smaller than those that have been recently derived resorting to Monte Carlo simulations. (C) 2000 American Institute of Physics. [S0003-6951(00)03914-0].76141893189

Nonlinear transport properties of III-nitrides in electric field

We consider the transport properties of polar direct-gap semiconductors in an electric field, specializing the numerical calculation of the general theory to the case of n-doped III-nitrides, in particular, GaN, AlN, and InN. The nonequilibrium thermodynamic state of these materials-characterized by the variables so-called quasitemperature, quasichemical potential, and drift velocity of the carriers, and the quasitemperatures of longitudinal optical and acoustical phonons-is studied. The evolution equations of these variables-which are highly nonlinear-are derived, and the transient regime and the ensuing steady state are analyzed. The nonlinear transport is characterized and its main properties are discussed. In one case comparison with a recent Monte Carlo calculation is made and good agreement is obtained. In this paper we mainly consider the ultrafast transient, and in the following paper the steady state. (c) 2005 American Institute of Physics.98

Hot-phonon bottleneck in the photoinjected plasma in GaN

The evolution on the picosecond scale of the macroscopic (nonequilibrium thermodynamic) state of a highly excited photoinjected plasma in bulk GaN is analyzed. We present the equations of evolution for the quasitemperature (level of excitation) of the hot carriers and of the optical phonons. A hot-phonon temperature overshoot is evidenced, as well as a preferential production of phonons in excess of equilibrium in a reduced off-center region of the Brillouin zone. A comparative analysis of the influence of the length of the exciting laser pulse is also performed. (C) 2003 American Institute of Physics.82152455245

Nonlinear transport properties of doped III-N and GaAs polar semiconductors: A comparison

In the previous article we have presented a study of the transport properties of doped direct-gap inverted-band polar semiconductors III-nitrides and GaAs in the steady state, calculated with a nonlinear quantum transport theory based on a nonequilibrium ensemble formalism. In the present one such results are compared with calculations using Monte Carlo-modeling simulations and with experimental measurements. Materials of the n-type and p-type dopings in the presence of intermediate to high electric fields, and for several temperatures of the external reservoir, are considered. The agreement between the results obtained using the nonlinear quantum kinetic theory, with those of Monte Carlo calculations and experimental data is remarkably good, thus satisfactorily validating this powerful, concise, and physically sound formalism. (c) 2005 American Institute of Physics.98

Characteristics of Dysphagia in Infants with Microcephaly Caused by Congenital Zika Virus Infection, Brazil, 2015.

We summarize the characteristics of dysphagia in 9 infants in Brazil with microcephaly caused by congenital Zika virus infection. The Schedule for Oral Motor Assessment, fiberoptic endoscopic evaluation of swallowing, and the videofluoroscopic swallowing study were used as noninstrumental and instrumental assessments. All infants had a degree of neurologic damage and showed abnormalities in the oral phase. Of the 9 infants, 8 lacked oral and upper respiratory tract sensitivity, leading to delays in initiation of the pharyngeal phase of swallowing. Those delays, combined with marked oral dysfunction, increased the risk for aspiration of food, particularly liquid foods. Dysphagia resulting from congenital Zika virus syndrome microcephaly can develop in infants >3 months of age and is severe

Hole mobility in zincblende c-GaN

We consider the nonequilibrium thermodynamic state of carriers in III-nitrides, and calculate the mobility of holes in cubic GaN layers under electric fields of low intensity. The contribution of different scattering mechanisms to the mobility is analyzed, and the relevance of each one is characterized. Satisfactory agreement with recently published experimental data is obtained. (C) 2004 American Institute of Physics.9594914491

Intracerebral infection with dengue-3 virus induces meningoencephalitis and behavioral changes that precede lethality in mice

<p>Abstract</p> <p>Background</p> <p>Dengue, one of the most important arboviral diseases of humans, may cause severe systemic disease. Although dengue virus (DENV) has been considered to be a non-neurotropic virus, dengue infection has been associated recently with a series of neurological syndromes, including encephalitis. In this work, we evaluated behavioral changes and inflammatory parameters in C57BL/6 mice infected with non-adapted dengue virus 3 (DENV-3) genotype I.</p> <p>Methods</p> <p>C57BL/6 mice received 4 × 10³PFU of DENV-3 by an intracranial route. We evaluated the trafficking of leukocytes in brain microvasculature using intravital microscopy, and evaluated chemokine and cytokine profiling by an ELISA test at 3 and 6 days post infection (p.i.). Furthermore, we determined myeloperoxidase activity and immune cell populations, and also performed histopathological analysis and immunostaining for the virus in brain tissue.</p> <p>Results</p> <p>All animals developed signs of encephalitis and died by day 8 p.i. Motor behavior and muscle tone and strength parameters declined at day 7 p.i. We observed increased leukocyte rolling and adhesion in brain microvasculature of infected mice at days 3 and 6 p.i. The infection was followed by significant increases in IFN-γ, TNF-α, CCL2, CCL5, CXCL1, and CXCL2. Histological analysis showed evidence of meningoencephalitis and reactive gliosis. Increased numbers of neutrophils, CD4⁺and CD8⁺T cells were detected in brain of infected animals, notably at day 6 p.i. Cells immunoreactive for anti-NS-3 were visualized throughout the brain.</p> <p>Conclusion</p> <p>Intracerebral infection with non-adapted DENV-3 induces encephalitis and behavioral changes that precede lethality in mice.</p

Quantification of key retinal features in early and late age-related macular degeneration using deep learning

PURPOSE: To develop and validate a deep learning model for segmentation of 13 features associated with neovascular and atrophic age-related macular degeneration (AMD). DESIGN: Development and validation of a deep-learning model for feature segmentation METHODS: Data for model development were obtained from 307 optical coherence tomography volumes. Eight experienced graders manually delineated all abnormalities in 2,712 B-scans. A deep neural network was trained with this data to perform voxel-level segmentation of the 13 most common abnormalities (features). For evaluation, 112 B-scans from 112 patients with a diagnosis of neovascular AMD were annotated by four independent observers. Main outcome measures were Dice score, intra-class correlation coefficient (ICC), and free-response receiver operating characteristic (FROC) curve. RESULTS: On 11 of the 13 features, the model obtained a mean Dice score of 0.63 ± 0.15, compared to 0.61 ± 0.17 for the observers. The mean ICC for the model was 0.66 ± 0.22, compared to 0.62 ± 0.21 for the observers. Two features were not evaluated quantitatively due to lack of data. FROC analysis demonstrated that the model scored similar or higher sensitivity per false positives compared to the observers. CONCLUSIONS: The quality of the automatic segmentation matches that of experienced graders for most features, exceeding human performance for some features. The quantified parameters provided by the model can be used in the current clinical routine and open possibilities for further research into treatment response outside clinical trials