Hydrodynamic subband model for semiconductors based on the maximum entropy principle

A hydrodynamic subband model for semiconductors is formulated by closing the moment system derived from the Schr¨odinger-Poisson-Boltzmann equations on the basis the maximum entropy principle. Explicit closure relations for fluxes and production terms are obtained taking into account scattering of electrons with acoustic and nonpolar optical phonons and surface scattering

Charge transport and mobility in monolayer graphene

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Electromagnetic analysis of the plasma chamber of an ECR-based charge breeder.

The optimization of the efficiency of an ECR-based charge breeder is a twofold task: efforts must be paid to maximize the capture of the injected 1+ ions by the confined plasma and to produce high charge states to allow post-acceleration at high energies. Both tasks must be faced by studying in detail the electrons heating dynamics, influenced by the microwave-to-plasma coupling mechanism. Numerical simulations are a powerful tools for obtaining quantitative information about the wave-to-plasma interaction process: this paper presents a numerical study of the microwaves propagation and absorption inside the plasma chamber of the PHOENIX charge breeder, which the selective production of exotic species project, under construction at Legnaro National Laboratories, will adopt as charge breeder. Calculations were carried out with a commercial 3D FEM solver: first, all the resonant frequencies were determined by considering a simplified plasma chamber; then, the realistic geometry was taken into account, including a cold plasma model of increasing complexity. The results gave important information about the power absorption and losses and will allow the improvement of the plasma model to be used in a refined step of calculation reproducing the breeding process itself

Electron cyclotron resonance ion source plasma characterization by energy dispersive x-ray imaging

Pinhole and CCD based quasi-optical x-ray imaging technique was applied to investigate the plasma of an electron cyclotron resonance ion source (ECRIS). Spectrally integrated and energy resolved images were taken from an axial perspective. The comparison of integrated images taken of argon plasma highlights the structural changes affected by some ECRIS setting parameters, like strength of the axial magnetic confinement, RF frequency and microwave power. Photon counting analysis gives precise intensity distribution of the x-ray emitted by the argon plasma and by the plasma chamber walls. This advanced technique points out that the spatial positions of the electron losses are strongly determined by the kinetic energy of the electrons themselves to be lost and also shows evidences how strongly the plasma distribution is affected by slight changes in the RF frequency. © 2017 IOP Publishing Ltd

Task-Related modulations of BOLD low-frequency fluctuations within the default mode Network

Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33 ± 6 years, 8 F/12 M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the continuous execution of a working memory n-back task. We found that task execution impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to continuous task execution, can contribute to a better understanding of how brain networks rearrange themselves in response to a task

Human mummification practices among the Ibaloy of Kabayan, North Luzon, the Philippines

The province of Benguet, situated in North Luzon, the Philippines, holds a large number of ancient mummified remains, mostly located within the municipality of Kabayan. Such bodies are mainly associated to the Ibaloy – one of the indigenous groups collectively known as Igorot – and are stored in natural rockshelters or caves carved into the stone, inside wooden coffins often obtained from hollowed pine tree segments. Recent inspections of some of these corpses, carried out in 2002 and 2012, indicated the nature of their mummification process as well as some details regarding their bioanthropological features. Although very little information was initially available on these bodies, the authors have gathered significant oral information on funerary rituals and attitudes towards the ancestors via interviews with the local elders, as well as data on the vegetal materials employed and the practice of tattooing. This paper is the first critical evaluation of these mummies and demonstrates the uniqueness and preciousness of this biocultural heritage now in danger

Information theory in the study of anisotropic radiation

Information theory is used to perform a thermodynamic study of non equilibrium anisotropic radiation. We limit our analysis to a second-order truncation of the moments, obtaining a distribution function which leads to a natural closure of the hierarchy of radiative transfer equations in the so-called variable Eddington factor scheme. Some Eddington factors appearing in the literature can be recovered as particular cases of our two-parameter Eddington factor. We focus our attention in the study of the thermodynamic properties of such systems and relate it to recent nonequilibrium thermodynamic theories. Finally we comment the possibility of introducing a nonequilibrium chemical potential for photons.Comment: 1 eps figure upon request by e-mail, to appear in Journal of Physics

Copropagating schemes for dielectric laser accelerators

f of principle electrons laser acceleration experiments, car- ried out by several groups, have demonstrated accelerating gradients larger than 200 MeV/m. However, the adopted configurations (free space coupled gratings, dual pillar, phase reset devices) cannot be easily scaled in length, because they require a transversely incident laser light, impinging laterally along the whole in- teraction dielectric structure. In this paper, extended interaction structures with collinear propagation of the accelerating electromagnetic field and the particles to be accelerated are described: both 2D and 3D photonic-crystals-based structures and slot hollow-core waveguides are compared in terms of accelerating gradient and characteristic interaction impedance, a fundamental quality parameter for Dielectric Laser Accelerators (DLAs)