Dielectric mismatch and shallow donor impurities in GaN/HfO2 quantum wells

In this work we investigate electron-impurity binding energy in GaN/HfO$_2$ quantum wells. The calculation considers simultaneously all energy contributions caused by the dielectric mismatch: (i) image self-energy (i.e., interaction between electron and its image charge), (ii) the direct Coulomb interaction between the electron-impurity and (iii) the interactions among electron and impurity image charges. The theoretical model account for the solution of the time-dependent Schr\"odinger equation and the results shows how the magnitude of the electron-impurity binding energy depends on the position of impurity in the well-barrier system. The role of the large dielectric constant in the barrier region is exposed with the comparison of the results for GaN/HfO$_2$ with those of a more typical GaN/AlN system, for two different confinement regimes: narrow and wide quantum wells.Comment: 6 Pages, 7 figure

Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include

Metatarsal Salmonella enteritidis osteomyelitis in a healthy child

Non-typhoidal Salmonella osteomyelitis in healthy children is a very rare condition. A previously healthy 7-year-old boy presented with foot pain following a small injury. Local inflammatory signs of the foot were observed, with a normal radiograph. Two weeks before, he had had gastroenteritis. Assuming cellulitis, flucloxacillin was began. Early during admission, surgical subcutaneous abscess drainage was performed and Salmonella enteritidis was identified. According to bacterial susceptibility, antibiotherapy was changed to ceftriaxone. A foot radiograph and an MRI scan, performed on the 9th and the 12th days, revealed findings suggestive of osteomyelitis of the metaphysis of the fifth metatarsal. Clinical worsening persisted and surgical extensive debridement was needed. A 6-week antibiotic treatment was completed, with a good outcome. Osteomyelitis with a poor evolution in children with risk factors (prior gastrointestinal illness, warm weather and previous exposure to antibiotics) can raise the possibility of a non-typhoidal Salmonella infection.info:eu-repo/semantics/publishedVersio

FOREVER: Fault/intrusiOn REmoVal through Evolution & Recovery

The goal of the FOREVER project is to develop a service for Fault/intrusiOn REmoVal through Evolution & Recovery. In order to achieve this goal, our work addresses three main tasks: the definition of the FOREVER service architecture; the analysis of how diversity techniques can improve resilience; and the evaluation of the FOREVER service. The FOREVER service is an important contribution to intrustion-tolerant replication middleware and significantly enhances the resilience

Understanding social enterprises in the United Kingdom: the case of South Yorkshire

Purpose-- This study analyses the development of social enterprises in the UK, in the context of the increased need for creative solutions to ameliorate deprivation and deliver effective public services. Design/methodology/approach-- The investigation draws on a mixed method approach, using a postal survey of 102 social enterprises complemented by detailed analysis of two selected cases and key informant interviews. Findings-- The results of the study show that there is a paradigm shift in the practice and conceptualisation of social enterprises in South Yorkshire as they are increasingly taking a more corporate approach to achieve their outcomes. Research limitations/implications-- The study is limited to social enterprises in South Yorkshire, UK. Further comparative analysis in other regions and social contexts is required in order to explore if these results are widely applicable. Practical implications-- This study is of potential benefit to researchers and those involved in formulating policies for the development and support of social enterprise. Originality/value-- The study contributes to the extant literature by investigation of the development of social enterprise in competitive markets, which is an area that requires further academic scrutiny. The South Yorkshire region presents an interesting case that extends our understanding of the operations of social enterprises in the UK given the high levels of deprivation due to the steady decline of its industrial base ( Bache and Chapman, 2008)

Silicon nitride thin-films by RF sputtering : application on solid state lithium batteries

Silicon nitride is the most common barrier material to protect microsystems from atmosphere, usually deposited through CVD techniques. In this paper our aim is to highlight the advantages brought by using PVD techniques, namely RF sputtering, to deposit silicon nitride thin-films. In particular, we intend to protect microsystems fabricated only by PVD techniques and avoid the necessity of a second CVD chamber to do the microsystem coating. The influence of gases (Ar/N2) during deposition was correlated with film composition and with measured electrical and optical properties. Featuring electric resistivity of 9.51E11 Ω.cm, a breakdown field of 1.67 MV/cm and refractive index between 1.92 and 1.84 (measured at 650 nm) silicon nitride deposited by RF sputtering is a good complementary layer of Li3PO4 or Ti for the protection of metallic lithium anode of solid state lithium batteries.This work was financial supported by FCT funds with the project PTDC/EEAELC/114713/2009, second author scholarship SFRH/BD/78217/2011 and strategic project from Algoritmi Centre FCOMP-01-0124-FEDER-02267

Negative Energy Densities in Extended Sources Generating Closed Timelike Curves in General Relativity with and without Torsion

Near a spinning point particle in (2+1)-dimensional gravity (or near an infinitely thin, straight, spinning string in 3+1 dimensions) there is a region of space-time with closed timelike curves. Exact solutions for extended sources with apparently physically acceptable energy-momentum tensors, have produced the same exterior space-time structure. Here it is pointed out that in the case with torsion, closed timelike curves appear only for spin densities so high that the spin energy density is higher than the net effective energy density. In models without torsion, the presence of closed time-like curves is related to a heat flow of unphysical magnitude. This corroborates earlier arguments against the possibility of closed timelike curves in space-time geometries generated by physical sources.Comment: (to be published in Phys. Rev. D), 5 pages, REVTEX 3.0, NORDITA 93/62 A (Sept. 10/Revised Nov. 1, 1993

Electric-field control of spin waves at room temperature in multiferroic BiFeO3

To face the challenges lying beyond current CMOS-based technology, new paradigms for information processing are required. Magnonics proposes to use spin waves to carry and process information, in analogy with photonics that relies on light waves, with several advantageous features such as potential operation in the THz range and excellent coupling to spintronics. Several magnonic analog and digital logic devices have been proposed, and some demonstrated. Just as for spintronics, a key issue for magnonics is the large power required to control/write information (conventionally achieved through magnetic fields applied by strip lines, or by spin transfer from large spin-polarized currents). Here we show that in BiFeO3, a room-temperature magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned electrically by over 30%, in a non-volatile way and with virtually no power dissipation. Theoretical calculations indicate that this effect originates from a linear magnetoelectric effect related to spin-orbit coupling induced by the applied electric field. We argue that these properties make BiFeO3 a promising medium for spin wave generation, conversion and control in future magnonics architectures.Comment: 3 figure

First report of Hakea sericea leaf infection caused by Pestalotiopsis funerea in Portugal

[Excerpt] The woody shrub Hakea sericea (Proteaceae) is native of south-eastern Australia and has been considered as an invader of natural habitats. In northern Portugal, dense stands of this plant are rapidly spreading usually after intense forest fires (Fig. 1a). In May 2003, unusual leaf spots were observed on these naturally growing plants. Infected plants exhibit reddish leaves bearing black circular lesions with 1-3 mm in diameter (Fig. 1b,c). Leaf sections containing necrotic lesions were plated onto PDA (potato dextrose agar) and eight fungi isolates were obtained. Pure cultures exhibit pinkish mycelium bearing compact acervuli containing black and slimy spore masses (Fig. 2a). Microscopic observation revealed typical Pestalotiopsis sp. 5-celled spores (3 coloured median and 2 hyaline end cells) with 3-4 apical and 1 basal appendages (Fig. 2b,c). The identification of Pestalotiopsis at species level is difficult and has been based on morphological characteristics of conidia (Guba, 1961). Recently, molecular approaches have been reported based on sequencing the internal transcribed spacer region (ITS) of the ribosomal RNA operon and comparision of the sequenced region to its orthologs of already identified Pestalotiopsis species (Jeewon et al., 2002). In this work, genomic DNA from fungi isolates was purified using DNeasy ® Plant Mini Kit (Qiagen), and used as template in thermocyclic amplifications using Ready-To-GoTM PCR Beads (Amersham Biosciences) with ITS5 and ITS4 universal primers (White et al., 1990). The amplified sequences (599bp) were then analysed together with other Pestalotiopsis ITS sequences already edited in databases, using the programs ClustalX (alignment of sequences), GeneDoc (manual correction of the alignment) and Phylip (phylogenetic tree construction). The results showed that ITS sequences from all fungi isolates were identical to each other and 99.3% similar to Pestalotiopsis funerea (Fig. 3). To confirm the pathogenecity of Pestalotiopsis funerea towards Hakea sericea, 6 weeks-old plants grown in vitro were infected with a suspension containing 105 spores/ml and maintained at 22°C, under 16 h lightphotoperiod. After 6 days, in vitro plants exhibited tissue lesions identical to those observed in field plants, bearing fungus spores identical to those from original isolates. [...]Fundação para a Ciência e a Tecnologia (FCT) - grant ref. SFRH/BD/10899/2002