Influence of Bi and Mn on the green luminescence of ZnO ceramics

The effect of the addition of Bi and Mn on the photoluminescence from ZnO ceramics has been investigated. The effect of the presence of impurities on the green luminescence band can be compared to the effect of oxidizing treatments. A narrow green band has been observed in Mn‐doped samples

Influenza in long-term Dutch travelers in the tropics: symptoms and infections

Influenza is a common infection among travelers, and attack rates are well documented in short-term travelers and holiday makers. Little data exists on long-term, non-expatriate travelers. This was a prospective mono-centre study of immunocompetent, Dutch travelers aged ≥18 to 64 years. It was conducted at the Public Health Service travel clinic in Amsterdam from December 2008 to September 2011, and included all travelers intending to travel to a tropical or sub-tropical country. Among 602 Dutch long-term travelers to tropical regions, 82 % had protective influenza antibody titres pre-travel. The influenza attack rate of serologically confirmed infection during travel was 15 %, and of symptomatic infection was 6.3 % (fever alone) and 2 % (ILI), respectively. The attack rate in this study is similar to seasonal rates of infection in the general population. Influenza vaccination pre-travel is therefore most important for people at risk of medical complications due to influenz

The origin of the red luminescence in Mg-doped GaN

Optically-detected magnetic resonance (ODMR) and positron annihilation spectroscopy (PAS) experiments have been employed to study magnesium-doped GaN layers grown by metal-organic vapor phase epitaxy. As the Mg doping level is changed, the combined experiments reveal a strong correlation between the vacancy concentrations and the intensity of the red photoluminescence band at 1.8 eV. The analysis provides strong evidence that the emission is due to recombination in which electrons both from effective mass donors and from deeper donors recombine with deep centers, the deep centers being vacancy-related defects.Comment: 4 pages, 3 figure

The Physiological Variation of the Retinal Nerve Fiber Layer Thickness and Macular Volume in Humans as Assessed by Spectral Domain-Optical Coherence Tomography

Purpose.: With the introduction of spectral domain–optical coherence tomography (SD-OCT), changes in retinal nerve fiber layer (RNFL) thickness and macular volume (MV) can be detected with high precision. The aim of this study was to determine whether there is a physiological quantifiable degree of variation of these structures in humans. Methods.: This study took place during a 10-km charity run at VU University Medical Center Amsterdam. Weight, height, hydration status, RNFL thickness (ring scan, 12° around the optic nerve head), and MV (20° × 20°) were assessed in 69 subjects (44 runners, 25 controls) using SD-OCT with eye-tracking function. The SD-OCT scans were assessed before running (normal status), after running (more dehydrated status), and 1 to 1.5 hours after finishing the run (rehydrated status). Controls were measured at the same time intervals as the runners but did not participate in the running event. Changes over time were assessed by general linear models, correcting for repeated measurements. Results.: In runners, a significant increase in both RNFL thickness (94.4 μm [baseline] to 95.2 μm [rehydration], P = 0.04) and MV (288.9 μm [baseline] to 291.0 μm [rehydration], P < 0.001) over time was observed. Controls did not show significant changes over time. Anatomically, the physiological change of RNFL thickness was most marked in the nasal sectors. Conclusions.: This prospective study demonstrated a significant physiological variation of the RNFL thickness and MV at a proportion that, on an individual patient level, may be relevant for longitudinal studies in neurodegenerative diseases

Maar-diatreme geometry and deposits: Subsurface blast experiments with variable explosion depth

Basaltic maar-diatreme volcanoes, which have craters cut into preeruption landscapes (maars) underlain by downward-tapering bodies of fragmental material commonly cut by hypabyssal intrusions (diatremes), are produced by multiple subsurface phreatomagmatic explosions. Although many maar-diatremes have been studied, the link between explosion dynamics and the resulting deposit architecture is still poorly understood. Scaled experiments employed multiple buried explosions of known energies and depths within layered aggregates in order to assess the effects of explosion depth, and the morphology and compaction of the host on the distribution of host materials in resulting ejecta, the development of subcrater structures and deposits, and the relationships between them. Experimental craters were 1–2 m wide. Analysis of high-speed video shows that explosion jets had heights and shapes that were strongly influenced by scaled depth (physical depth scaled against explosion energy) and by the presence or absence of a crater. Jet properties in turn controlled the distribution of ejecta deposits outside the craters, and we infer that this is also reflected in the diverse range of deposit types at natural maars. Ejecta were dominated by material that originated above the explosion site, and the shallowest material was dispersed the farthest. Subcrater deposits illustrate progressive vertical mixing of host materials through successive explosions. We conclude that the progressive appearance of deeper-seated material stratigraphically upward in deposits of natural maars probably records the length and time scale for upward mixing through multiple explosions with ejection by shallow blasts, rather than progressive deepening of explosion sites in response to draw down of aquifers

Formation of oriented particles in an amorphous host: ZnS nanocrystals in silicon

Processes for incorporating randomly oriented crystalline precipitates in an amorphous host can be traced back to the 17th century when Cassius produced “gold ruby” glass. In this glass, octahedral colloidal precipitates of gold scatter light by the Mie process to produce a deep red color. In contrast to gold ruby glass, we describe a type of material in which the crystalline precipitates are crystallographically aligned in a coherent manner—even though they are dispersed in an amorphous matrix. Ion implantation and thermal processing are first used to form zinc sulfide nanocrystals that are coherently oriented with respect to a crystalline Si host. The Si is then amorphized by ion irradiation leaving the highly radiation-resistant ZnS precipitates in an aligned crystalline state. The process is anticipated to find applications in the creation of surfaces with unique optoelectronic properties. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69678/2/APPLAB-74-5-697-1.pd

Targeting drought-tolerant maize varieties in southern Africa: a geospatial crop modeling approach using big data

Maize is a major staple food crop in southern Africa and stress tolerant improved varieties have the potential to increase productivity, enhance livelihoods and reduce food insecurity. This study uses big data in refining the geospatial targeting of new drought-tolerant (DT) maize varieties in Malawi, Mozambique, Zambia, and Zimbabwe. Results indicate that more than 1.0 million hectares (Mha) of maize in the study countries is exposed to a seasonal drought frequency exceeding 20% while an additional 1.6 Mha experience a drought occurrence of 10–20%. Spatial modeling indicates that new DT varieties could give a yield advantage of 5–40% over the commercial check variety across drought environments while crop management and input costs are kept equal. Results indicate a huge potential for DT maize seed production and marketing in the study countries. The study demonstrates how big data and analytical tools enhance the targeting and uptake of new agricultural technologies for boosting rural livelihoods, agribusiness development and food security in developing countries

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) among travellers to Africa : destination-specific data pooled from three European prospective studies

Abstract Background One third of travellers to low- and middle-income regions of the tropics and subtropics become colonized by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE). The risk varies by destination and, for each traveller, may be substantially further increased by travellers’ diarrhoea (TD) and antibiotic use. Despite the risk of TD in Africa, ESBL-PE acquisition rates in all studies are lower there than in Asia. Africa has become increasingly popular as a destination for international travellers, yet minimal data are available from the continent’s subregions and countries. Methods We analysed subregion- and country-specific data on carriage and risk factors for ESBL-PE colonization pooled from three prospective studies conducted between 2009 and 2013 among Finnish and Dutch travellers. The data were subjected to multivariable analysis of risk factors. In addition, we compared our data to two recent large investigations reporting data by subregion and country. Results Our joint analysis comprised data on 396 travellers. The ESBL-PE colonization rate was highest in Northern Africa, followed by Middle and Eastern Africa, and lowest in Southern and Western Africa. Of individual countries with more than 15 visitors, the highest rates were seen for Egypt (12/17; 70.6%), Ghana (6/23; 26.1%), and Tanzania (14/81; 17.3%); the rates among travellers to Egypt were comparable to those reported in South and Southeast Asia. In a pooled multivariable analysis, travel destination, age, overnight hospitalisation abroad, TD, and use of fluoroquinolones were independently associated with increased ESBL-PE colonization rates. Conlusions Even in areas with relatively low risk of colonization, antimicrobials clearly predispose to colonization with ESBL-PE. Travellers to Africa should be cautioned against unnecessary use of antibiotics

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) among travellers to Africa : destination-specific data pooled from three European prospective studies

Background: One third of travellers to low- and middle-income regions of the tropics and subtropics become colonized by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE). The risk varies by destination and, for each traveller, may be substantially further increased by travellers' diarrhoea (TD) and antibiotic use. Despite the risk of TD in Africa, ESBL-PE acquisition rates in all studies are lower there than in Asia. Africa has become increasingly popular as a destination for international travellers, yet minimal data are available from the continent's subregions and countries. Methods: We analysed subregion- and country-specific data on carriage and risk factors for ESBL-PE colonization pooled from three prospective studies conducted between 2009 and 2013 among Finnish and Dutch travellers. The data were subjected to multivariable analysis of risk factors. In addition, we compared our data to two recent large investigations reporting data by subregion and country. Results: Our joint analysis comprised data on 396 travellers. The ESBL-PE colonization rate was highest in Northern Africa, followed by Middle and Eastern Africa, and lowest in Southern and Western Africa. Of individual countries with more than 15 visitors, the highest rates were seen for Egypt (12/17; 70.6%), Ghana (6/23; 26.1%), and Tanzania (14/81; 17.3%); the rates among travellers to Egypt were comparable to those reported in South and Southeast Asia. In a pooled multivariable analysis, travel destination, age, overnight hospitalisation abroad, TD, and use of fluoroquinolones were independently associated with increased ESBL-PE colonization rates. Conlusions: Even in areas with relatively low risk of colonization, antimicrobials clearly predispose to colonization with ESBL-PE. Travellers to Africa should be cautioned against unnecessary use of antibiotics.Peer reviewe