Defect study of GaInP/GaAs based heterojunction bipolar transistor emitter layer

Defects in the emitter region of Ga0.51In0.49P/GaAs heterojunction bipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 degreesC, 5 min) and as grown metalorganic chemical vapor deposition epitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be 0.87+/-0.05 eV below the conduction band, the capture cross section 3x10(-14) cm(2) and the defect density of the order of 10(14) cm(-3). This defect was also found to be localized at the emitter-base interface

Standardization of F-18 by digital b-(LS)-g coincidence counting

The nuclide 18F disintegrates to 18O by β + emission (96.86%) and electron capture (3.14%) with a half-life of 1.8288 h. It is widely used in nuclear medicine for positron emission tomography (PET). Because of its short half-life this nuclide requires the development of fast measuring methods to be standardized. The combination of LSC methods with digital techniques proves to be a good alternative to get low uncertainties for this, and other, short lived nuclides. A radioactive solution of 18F has been standardized by coincidence counting with a LSC, using the logical sum of double coincidences in a TDCR array and a NaI scintillation detector. The results show good consistency with other techniques like 4πγ and LSC.Fil: Rodrigues Ferreira Maltez, Dario Pablo. Comision Nacional de Energia Atomica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia D/aplicaciones y Tec de Radioisotopos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Balpardo, Christian Guillermo. Comision Nacional de Energia Atomica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia D/aplicaciones y Tec de Radioisotopos; ArgentinaFil: Cassette, P.. Laboratoire National Henri Becquerel; FranciaFil: Arenillas, Pablo. Comision Nacional de Energia Atomica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia D/aplicaciones y Tec de Radioisotopos; ArgentinaFil: Capoulat, Maria Eugenia. Comision Nacional de Energia Atomica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia D/aplicaciones y Tec de Radioisotopos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ceruti, Gabriela. Comision Nacional de Energia Atomica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia D/aplicaciones y Tec de Radioisotopos; ArgentinaFil: Garcia Toraño, Eduado. Laboratorio de Metrología de Radiaciones Ionizantes; Españ

Impact of target site distribution for Type I restriction enzymes on the evolution of methicillin-resistant Staphylococcus aureus (MRSA) populations.

A limited number of Methicillin-resistant Staphylococcus aureus (MRSA) clones are responsible for MRSA infections worldwide, and those of different lineages carry unique Type I restriction-modification (RM) variants. We have identified the specific DNA sequence targets for the dominant MRSA lineages CC1, CC5, CC8 and ST239. We experimentally demonstrate that this RM system is sufficient to block horizontal gene transfer between clinically important MRSA, confirming the bioinformatic evidence that each lineage is evolving independently. Target sites are distributed randomly in S. aureus genomes, except in a set of large conjugative plasmids encoding resistance genes that show evidence of spreading between two successful MRSA lineages. This analysis of the identification and distribution of target sites explains evolutionary patterns in a pathogenic bacterium. We show that a lack of specific target sites enables plasmids to evade the Type I RM system thereby contributing to the evolution of increasingly resistant community and hospital MRSA

Detection of novel chromosome-SCCmec variants in Methicillin Resistant Staphylococcus aureus and their inclusion in PCR based screening

Findings. To facilitate automation, a novel DNA extraction method for MRSA was adopted. The MRSA specific chromosome-SCCmec PCR was adapted, additional primers were added, and the performance was validated. From various laboratories in The Netherlands we received a total of 86 MRSA clinical isolates, that were negative in commercially available tests. We identified 14 MRSA strains with new variant chromosome-SCCmec junctions by sequence analysis. These MRSA strains appeared to carry SCCmec sequences with a high degree of homology to SCC regions of S. epidermidis and S. haemolyticus. All were included for detection in chromosome-SCCmec based PCR. Background: Efficient management of Methicillin Resistant Staphylococcus aureus (MRSA) in the hospital is needed to prevent dissemination. It is important that MRSA can be rapidly identified, and effective infection control measures can be initiated. Equally important is a rapid MRSA negative report, especially for patients in isolation. For negative screening we implemented fully automated high through-put molecular screening for MRSA. Conclusions: Fourteen variant chromosome-SCCmec junctions in MRSA, that are not detected in commercially available MRSA detection kits were added to our PCR to detect all currently known variant SCC-mec types of MRSA

Decentralization and regional government size in Spain

The aim of this paper is to investigate the impact of fiscal decen- tralization on the size of regional governments in Spain, by controlling for economies of scale, interregional heterogeneity and institutional framework. We study it over 1985 to 2004 using a panel dataset of seventeen spanish regions. The results can be easily summarized. Firstly, it supports the classic public goods theory of a trade-off-between the economic benefits of size and the costs of heterogeneity. Secondly, it doesn’t reject the “Leviathan” hypoth- esis and neither does the “common pool” hypothesis. Thirdly, by contrast, the paper partly rejects the “Wallis”’ hypothesis. It argues that government size is mediated by financial resources obtained through intergovernmental grants, consistent with welfare economics and positive economic policies. We conclude that later advances in the decentralisation process must be compatible with the goal of reducing fiscal imbalances that emanate from the vertical structure of fiscal power.info:eu-repo/semantics/publishedVersio

Comparison of Activity Measurements of 63-Ni and 55-Fe in the Framework of the EUROMET 297 Project.

The purpose of the EUROMET project 297 was to compare the standardisation of 63-Ni and 55-Fe by liquid scintillation counting (LSC) and especially to test the main LSC activity measurement methods currently used in radionuclides metrology and exchange models and ideas on LSC. Eleven laboratories participated in thids action coordinated by LPRI, France.JRC.D-Institute for Reference Materials and Measurements (Geel

Experimental study of the influence of the counter and scintillator on the universal curves in the cross-efficiency method in LSC

International audienceThe cross-efficiency method in LSC is one of the approaches proposed for the extension of the Système International de Référence (SIR) to radionuclides emitting no gamma radiation. This method is based on a so-called "universal cross-efficiency curve", establishing a relationship between the detection efficiency of the radionuclide to be measured and the detection efficiency of a suitable tracer. This paper reports a study at LNHB on the influence of the scintillator and of the LS counter on the cross-efficiency curves. This was done by measuring the cross-efficiency curves obtained for 63Ni and 55Fe vs. 3H, using three different commercial LS counters (Guardian 1414, Tricarb 3170 and Quantulus 1220), three different liquid scintillator cocktails (Ultima Gold, Hionic Fluor and PicoFluor 15 from Perkin Elmer(®)), and for chemical and colour-quenched sources. This study shows that these cross-efficiency curves are dependent on the scintillator, on the counter used and on the nature of the quenching phenomenon, and thus cannot definitively be considered as "universal"

Influence of rejection of a fraction of the single photoelectron peak in liquid scintillation counting.

Zero discrimination level setting of liquid scintillation systems for counting of all single photoelectron pulses is required by both triple-to-double coincidence ratio (TDCR) and CIEMAT/NIST methods. However, this requirement may not be able to be met in some circumstances. The influence of rejection of a fraction of the single photoelectron peak has been studied both theoretically and experimentally on 3H, 63Ni, 14C and 90Sr/90Y for both the TDCR and CIEMAT/NIST methods. A modified formula for calculation of efficiency is given in consideration of the rejected fraction of the single photoelectron peak. © 2006, Elsevier Ltd