Ion implantation and low-temperature epitaxial regrowth of GaAs

Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ion‐implanted GaAs and the crystal quality following capless furnace annealing at low temperature (∼400 °C). The implantation‐induced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 Å. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (<400 Å) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the low‐temperature annealing of GaAs

Public Perception of Visual Quality of Cut Mutia Mosque Park as Public Space in Jakarta

Cut Mutia Park is a city park which is an integral part and attached to the main courtyard of the mosque cut mutia. This park is a green open space that serves as a public space and generate the aesthetics of the city. There are seven critical elements that need to be studied to determine the public\u27s perception of the park. Knowledgeable public perception of these elements, useful for city authorities in the development of city parks for future. The results of the research showed that of the seven elements studied, only two elements of which will be a positive perception, namely aspects of cleanliness and coolness, while five other aspects got a negative perception. As a result, generally Cut Mutia Parks research object only gets the value perception of -0.24. Details of the value obtained by each of these aspects are: -0.52 for comfortability; +0.13 for cleanliness; -0.003 for freshness; +0.26 for coolness; -0.77 for harmony level; -0.42 for beauty level; and -0.32 for interesting presented. Low perception from respondents indicated that Cut Mutia Park need better design such that it can give added value to the mosque and the environment surrounding. At the end can be said that the city authorities need to further improve attention in structuring of the park, to makes Cut Mutia Park become more comfortable, interesting and favored by the public, and also strengthening the power of the mosque as the central point

Pulsed electron beam induced recrystallization and damage in GaAs

Single-pulse electron-beam irradiations of 300-keV 10^(15)Kr+/cm^2 or 300-keV 3×10^(12)Se+/cm^2 implanted layers in unencapsulated GaAs are studied as a function of the electron beam fluence. The electron beam pulse had a mean electron energy of ~-20 keV and a time duration of ~-10^(–7) s. Analyses by means of MeV He + channeling and TEM show the existence of narrow fluence window (0.4–0.7 J/cm^2) within which amorphous layers can be sucessfully recrystallized, presumably in the liquid phase regime. Too high a fluence produces extensive deep damage and loss of As

Steady-state thermally annealed GaAs with room-temperature-implanted Si

Semi-insulating Cr-doped single-crystal GaAs samples were implanted at room temperature with 300-keV Si ions in the dose range of (0.17–2.0)×1015 cm–2 and were subsequently steady-state annealed at 900 and 950°C for 30 min in a H2 ambient with a Si3N4 coating. Differential Hall measurements showed that an upper threshold of about 2×1018/cm3 exists for the free-electron concentration. The as-implanted atomic-Si profile measured by SIMS follows the theoretical prediction, but is altered during annealing. The Cr distribution also changes, and a band of dislocation loops ~2–3 kÅ wide is revealed by cross-sectional TEM at a mean depth of Rp~3 kÅ. Incomplete electrical activation of the Si is shown to be the primary cause for the effect

Epitaxial regrowth of thin amorphous GaAs layers

Channeling and transmission electron microscopy have been used to investigate the parameters that govern the crystal quality following capless funace annealing at low temperature (~ 400 °C) in ion-implanted GaAs. From the results obtained, we concluded that the crystal quality after annealing depends strongly on the thickness of the amorphous layer generated by ion implantation and the number of residual defects increases linearly with the thickness of the implanted layer. Single-crystal regrowth free of defects detectable by megaelectron volt He + channeling was achieved for a very thin amorphous layer (<~ 400 Å)

Simple oxidation of pyrimidinylhydrazones to triazolopyrimidines and their inhibition of Shiga toxin trafficking

The oxidative cyclisation of a range of benzothieno[2,3-d]pyrimidine hydrazones (7a–j) to the 1,2,4-triazolo[4,3-c]pyrimidines (8a–j) catalysed by lithium iodide or to the 1,2,4-triazolo[1,5-c]pyrimidines (10a–j) with sodium carbonate is presented. A complementary synthesis of the 1,2,4-triazolo[1,5-c]pyrimidines starting from the amino imine 11 is also reported. The effect of these compounds on Shiga toxin (STx) trafficking in HeLa cells and comparison to the previously reported Exo2 is also detailed

Criteria for multiplicity for complex biochemical reactions

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Monitoring and evaluation of human resources for health: an international perspective

BACKGROUND: Despite the undoubted importance of human resources to the functions of health systems, there is little consistency between countries in how human resource strategies are monitored and evaluated. This paper presents an integrated approach for developing an evidence base on human resources for health (HRH) to support decision-making, drawing on a framework for health systems performance assessment. METHODS: Conceptual and methodological issues for selecting indicators for HRH monitoring and evaluation are discussed, and a range of primary and secondary data sources that might be used to generate indicators are reviewed. Descriptive analyses are conducted drawing primarily on one type of source, namely routinely reported data on the numbers of health personnel and medical schools as covered by national reporting systems and compiled by the World Health Organization. Regression techniques are used to triangulate a given HRH indicator calculated from different data sources across multiple countries. RESULTS: Major variations in the supply of health personnel and training opportunities are found to occur by region. However, certain discrepancies are also observed in measuring the same indicator from different sources, possibly related to the occupational classification or to the sources' representation. CONCLUSION: Evidence-based information is needed to better understand trends in HRH. Although a range of sources exist that can potentially be used for HRH assessment, the information that can be derived from many of these individual sources precludes refined analysis. A variety of data sources and analytical approaches, each with its own strengths and limitations, is required to reflect the complexity of HRH issues. In order to enhance cross-national comparability, data collection efforts should be processed through the use of internationally standardized classifications (in particular, for occupation, industry and education) at the greatest level of detail possible

An acid-stable laccase from sclerotium rolfsii with potential for wool dye decolourization

The plant pathogen basidiomycete S. rolfsii secretes two laccases (SRL1 and SRL2) with molecular weights of 55 and 86 kDa, respectively. Laccase production was shown to be inducible by the addition of 2,5-xylidine to the cultural media. After treatment with a combination of chitinase and -1,3-glucanase, two different laccases were isolated from the sclerotia depending on the stage of sclerotia development. The more prominent laccase, SRL1, was purified and found to decolourize the industrially important wool azo dye Diamond Black PV 200 without the addition of redox mediators. The enzyme (pI 5.2) was active in the acidic pH range, showing an optimal activity at pH 2.4, with ABTS as substrate. The optimum temperature for activity was determined to be 62 ◦C. Enzyme stability studies revealed that SRL1 was notably stable at 18 ◦C and pH 4.5, retaining almost full activity after a week. Oxidation of tyrosine was not detectable under the reaction conditions but the enzyme did oxidize a variety of the usual laccase substrates. SRL1 was strongly inhibited by sodium azide and fluoride. Dye solutions decolourized with the immobilized laccase were successfully used for redyeing.(undefined