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In this paper, the structural and electronic properties of epitaxial graphene (EG) grown on 8 degrees-off 4H-SiC (0001) by high temperature thermal processes have been extensively investigated by a combination of several high resolution characterization techniques. The increase in the number of graphene layers with the growth temperature (from 1600 to 1700 degrees C) was studied by microRaman spectroscopy and high resolution transmission electron microscopy (HRTEM) on cross sectioned samples. The few layers of graphene reside on a stepped SiC surface with alternating (0001) terraces and (11 - 2n) facets. Peculiar corrugations (wrinkles) in the graphene membrane preferentially oriented perpendicularly to the substrate steps were also observed. Motivated by recent atomic resolution studies of the EG/SiC interface revealing a local delamination of the interfacial C buffer from the (11 - 2n) facets, we searched for a correlation of these interfacial structural properties with the macroscopic electronic transport in EG field effect transistors (FETs). In particular, electrical characterization of EG Lop gated FETs fabricated with the channel length parallel or perpendicular to the substrate steps revealed a peculiar anisotropy of the channel conductance with respect to the steps orientation. This effect was explained in terms of a local enhancement of EG resistance on the (11-2n) facets with respect to the (0001) basal plane, which is consistent with a reduced doping due to the local buffer layer delamination from those facets. Furthermore, scanning probe microscopy-based local electron mean free path measurements on EG showed a similar to 3 x enhancement of mean free path On the buffer-layer-free (11-2n) facets with respect to (0001) terraces, probably associated to a strong reduction of Coulomb scattering effects on graphene's electrons. (C) 2013 Elsevier B.V. All rights reserved.

""In this paper we present a detailed study of the intersubband absorption occurring between electron states confined in strained Ge multi-quantum wells as a function of the temperature. The high structural quality of the samples is reflected by the very narrow absorption line-shape constant with temperature. We observe a temperature driven charge transfer occurring between the ground and the first excited subband which, in turn, induces a change in the depolarization shift and consequently in the energy of the absorbance peak. The experimental observations are well accounted for by a multi-valley k center dot p model.""

In this paper, silicon nanoparticles dispersed into a silica phase by sol–gel processing has been investigated by structural and nonlinear-optical characterization. The structural characterization has been performed by energy filtered and scanning transmission electron microscopy. A silicon nanoparticles mean radius of about 49 nm and a nanoparticle density of about 1.62 × 108 dots/cm2 have been obtained. Regarding nonlinear optics characterization, the observation of stimulated Raman scattering and the realization of a Raman amplifier based on silicon nanocomposites are described. Using a 1427 nm cw pump laser, amplification of Stokes signal, at 1542.2 nm, up to 1.4 dB/cm is demonstrated. A preliminary valuation of approximately a fivefold enhancement of the gain coefficient a significant reduction of threshold power are reported. Our findings have a potential interest for silicon-based Raman lasers.

Background While the haemodynamic benefits of DDDR pacing compared with DDD pacing in patients with brady– tachy syndrome and chronotropic incompetence (CI) are well demonstrated, the antiarrhythmic advantage is controversial and so far not clearly demonstrated. Aim We have performed a prospective, randomized, multicentre study to evaluate the efficacy of DDDR and DDD pacing modes in preventing paroxysmal atrial fibrillation (PAF) episodes in patients with brady–tachy syndrome and CI. Methods and Results Seventy-eight patients were included in the study. All patients had a dual chamber pacemaker implanted and were randomly programmed to DDD or DDDR with a cross over (DDD DDDR or vice versa) at 3 months. The final evaluation was performed at 6 months by means of two self-administered symptom questionnaires to evaluate activity. Symptoms of palpitations were analysed and scored. The patients were less symptomatic with the DDDR mode. The number of modeswitch activations compared with symptomatic episodes of PAF confirmed the high rate of asymptomatic PAF episodes in patients with brady–tachy syndrome. We conclude that in a small but well defined population of patients affected by sick sinus syndrome with CI and severely symptomatic PAF, DDDR pacing compared with DDD pacing may offer an additional antiarrhythmic benefit and should be considered the primary mode of pacing. (Europace 1999; 1: 220–225)

Introduction Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen. The objective of this study was to verify the proregenerative effects of VEGF in an experimental model of acute liver failure. Materials and methods Sixty four rats that underwent intraperitoneal injection of carbon tetrachloride (CCl 4 ) were randomly divided into two groups: group B animals received intravenous injection of VEGF 164 1 hour following CCl 4 poisoning. Group A hosts were untreated. To obtain daily liver function tests (LFTs) and histological samples, on each day up to 8 days we sacrificed four rats in each group. Results The laboratory examinations showed notable alteration of LFTs in group A, while group B revealed only slight changes. The histological examination showed greater liver damage in group A compared with group B. Conclusion Our results suggest that administration of exogenous VEGF protects the liver from CCl 4 -induced acute hepatic failure. Further studies are underway to assess whether exogenous VEGF is effective in other liver injuries.

Holographic measurements to determine deviations of the 32m Noto antenna with respect to an ideal parabolic surface have been performed at 11.5 GHz. An 'ad hoc' system including a reference secondary antenna was built, and digital beacons coming from commercial TV satellites were used as signal sources. Results clearly showed significant deformations of the dish.

The Square Kilometer Array (SKA) project aims at building the world’s largest radio observatory to observe the sky with unprecedented sensitivity and collecting area. In the first phase of the project (SKA1), an array of dishes, SKA1-MID, will be built in South Africa. It will consist of 133 15m-dishes, which will include the MeerKAT array, for the 0.350-20 GHz frequency band observations. Each antenna will be provided with a local monitor and control system (LMC), enabling operations both to the Telescope Manager remote system, and to the engineers and maintenance staff; it provides different environment for the telescope control (positioning, pointing, observational bands), metadata collection for monitoring and database storaging, operational modes and functional states management for all the telescope capabilities. In this paper we present the LMC software architecture designed for the detailed design phase (DD), where we describe functional and physical interfaces with monitored and controlled sub-elements, and highlight the data flow between each LMC modules and its sub-element controllers from one side, and Telescope Manager on the other side. We also describe the complete Product Breakdown Structure (PBS) created in order to optimize resources allocation in terms of calculus and memory, able to perform required task for each element according to the proper requirements. Among them, time response and system reliability are the most important, considering the complexity of SKA dish network and its isolated placement. Performances obtained by software implementation using TANGO framework will be discussed, matching them with technical requirements derived by SKA science drivers.

We have used Raman spectroscopy, transmission electron microscopy, x-ray diffraction, and x-ray photoemission spectroscopy to investigate strain relaxation mechanism of Si(0.22)Ge(0.78) heteroepitaxial layer deposited on Si substrates in tensile, neutral, and compressive strain conditions. The three regimes have been obtained by interposing between the SiGe layer and the substrate a fully relaxed Ge layer, a partially relaxed Ge layer, or growing directly the alloy on Si. We found that the deposition of a Ge buffer layer prior to the growth of the SiGe is very promising in view of the realization of thin virtual substrates on silicon to be used for the deposition of strain-controlled high Ge content SiGe alloys. We demonstrate that this is mainly due to the strain relaxation mechanism in the Ge layer occurring via insertion of pure edge 90 degrees misfit dislocations (MDs) and to the confinement of threading arms in to the Ge layer due to a second MD network formed at the SiGe/Ge heterointerface.