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

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

Background: 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. Methods: 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. Results: 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. Conclusions: 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 influenza

Conduit flow experiments help constraining the regime of explosive eruptions

It is currently impractical to measure what happens in a volcano during an explosive eruption, and up to now much of our knowledge depends on theoretical models. Here we show, by means of large‐scale experiments, that the regime of explosive events can be constrained on the basis of the characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose results are consistent with the literature, is a simple tool for defining the conditions at conduit exit that control the most hazardous volcanic regimes. Besides the well‐known convective plume regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which form when the eruptive gas‐particle mixture exits from the vent at overpressure with respect to atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favors the formation of density currents resembling natural base surges. We conclude that a quantitative knowledge of magma fragmentation, i.e., particle size, fragmentation energy, and fragmentation speed, is critical for determining the eruption regime.Research was partially funded by DPC-INGV agreement 07‐09 and MUR PRIN 06.PublishedB042043.6. Fisica del vulcanismoJCR Journalrestricte

Climate impact and adaptation to heat and drought stress of regional and global wheat production

Wheat (Triticum aestivum) is the most widely grown food crop in the world threatened by future climate change. In this study, we simulated climate change impacts and adaptation strategies for wheat globally using new crop genetic traits (CGT), including increased heat tolerance, early vigor to increase early crop water use, late flowering to reverse an earlier anthesis in warmer conditions, and the combined traits with additional nitrogen (N) fertilizer applications, as an option to maximize genetic gains. These simulations were completed using three wheat crop models and five Global Climate Models (GCM) for RCP 8.5 at mid-century. Crop simulations were compared with country, US state, and US county grain yield and production. Wheat yield and production from high-yielding and low-yielding countries were mostly captured by the model ensemble mean. However, US state and county yields and production were often poorly reproduced, with large variability in the models, which is likely due to poor soil and crop management input data at this scale. Climate change is projected to decrease global wheat production by −1.9% by mid-century. However, the most negative impacts are projected to affect developing countries in tropical regions. The model ensemble mean suggests large negative yield impacts for African and Southern Asian countries where food security is already a problem. Yields are predicted to decline by −15% in African countries and −16% in Southern Asian countries by 2050. Introducing CGT as an adaptation to climate change improved wheat yield in many regions, but due to poor nutrient management, many developing countries only benefited from adaptation from CGT when combined with additional N fertilizer. As growing conditions and the impact from climate change on wheat vary across the globe, region-specific adaptation strategies need to be explored to increase the possible benefits of adaptations to climate change in the future.info:eu-repo/semantics/publishedVersio

Conduit flow experiments help constraining the regime of explosive eruptions

It is currently impractical to measure what happens in a volcano during an explosive eruption, and up to now much of our knowledge depends on theoretical models. Here we show, by means of large‐scale experiments, that the regime of explosive events can be constrained on the basis of the characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose results are consistent with the literature, is a simple tool for defining the conditions at conduit exit that control the most hazardous volcanic regimes. Besides the well‐known convective plume regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which form when the eruptive gas‐particle mixture exits from the vent at overpressure with respect to atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favors the formation of density currents resembling natural base surges. We conclude that a quantitative knowledge of magma fragmentation, i.e., particle size, fragmentation energy, and fragmentation speed, is critical for determining the eruption regime

Sexually transmitted infections: challenges ahead.

WHO estimated that nearly 1 million people become infected every day with any of four curable sexually transmitted infections (STIs): chlamydia, gonorrhoea, syphilis, and trichomoniasis. Despite their high global incidence, STIs remain a neglected area of research. In this Commission, we have prioritised five areas that represent particular challenges in STI treatment and control. Chlamydia remains the most commonly diagnosed bacterial STI in high-income countries despite widespread testing recommendations, sensitive and specific non-invasive testing techniques, and cheap effective therapy. We discuss the challenges for chlamydia control and evidence to support a shift from the current focus on infection-based screening to improved management of diagnosed cases and of chlamydial morbidity, such as pelvic inflammatory disease. The emergence and spread of antimicrobial resistance in Neisseria gonorrhoeae is globally recognised. We review current and potential future control and treatment strategies, with a focus on novel antimicrobials. Bacterial vaginosis is the most common vaginal disorder in women, but current treatments are associated with frequent recurrence. Recurrence after treatment might relate to evidence that suggests sexual transmission is integral to the pathogenesis of bacterial vaginosis, which has substantial implications for the development of effective management approaches. STIs disproportionately affect low-income and middle-income countries. We review strategies for case management, focusing on point-of-care tests that hold considerable potential for improving STI control. Lastly, STIs in men who have sex with men have increased since the late 1990s. We discuss the contribution of new biomedical HIV prevention strategies and risk compensation. Overall, this Commission aims to enhance the understanding of some of the key challenges facing the field of STIs, and outlines new approaches to improve the clinical management of STIs and public health

Do Two Symmetry Breaking Transitions in Photosynthetic Light Harvesting Complexes Form One, Two or More Kibble Zurek Model Topological Defects?

Kibble and Zurek proposed that rapid symmetry breaking transitions in the hot, early universe could result in causally disconnected topological defects such as cosmic strings. This type of first order transition has analogues in certain second order transitions present in condensed matter such as liquid crystals, super fluids, and charge density waves in terms of flux tubes or vortices. Recently, we discovered that Rhodopseudomonas acidophilus photosynthetic light harvesting complex might have different types of coherent ground and excited states, suggesting that there are two different symmetry breaking transitions. The B 850 ground states comprise eight identical rings each containing 18 bacteriochlorophyll components, and each ring has undergone a Bose Einstein phase transition to a charge density wave that lowers the energy. The excited state coherence results from polariton formation from the non-crossing of bosons, here an extension of exciton theory. The result is short-lived quasi-particles with very low mass that can form an unusual BEC. We suggest the oriented, circular B 850 and enclosed singlet B 875 compounds create a new cavity structure with some attributes of a nano pillar. Since both the ground and excited states should contain solitons, we envisage three fast light pulse experiments could be able to map both the Kibble Zurek Model phase transitions and energy transfers as a function of light intensity and time in this complex at room temperature

Conduit flow experiments help constraining the regime of explosive eruptions

It is currently impractical to measure what happens in a volcano during an explosive eruption, and up to now much of our knowledge depends on theoretical models. Here we show, by means of large-scale experiments, that the regime of explosive events can be constrained based on the characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose results are consistent with the literature, is a simple tool for defining the conditions at conduit exit that control the most hazardous volcanic regimes. Besides the well-known convective plume regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which form when the eruptive gas-particle mixture exits from the vent at overpressure with respect to atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favours the formation of density currents resembling natural base surges. We conclude that a quantitative knowledge of magma fragmentation, i.e. particle size, fragmentation energy and fragmentation speed, is critical for determining the eruption regime

Effect of travel on influenza epidemiology

To assess the attack and incidence rates for influenza virus infections, during October 2006-October 2007 we prospectively studied 1,190 adult short-term travelers from the Netherlands to tropical and subtropical countries. Participants donated blood samples before and after travel and kept a travel diary. The samples were serologically tested for the epidemic strains during the study period. The attack rate for all infections was 7% (86 travelers) and for influenza-like illness (ILI), 0.8%. The incidence rate for all infections was 8.9 per 100 person-months and for ILI, 0.9%. Risk factors for infection were birth in a non-Western country, age 55-64 years, and ILI. In 15 travelers with fever or ILI, influenza virus infection was serologically confirmed; 7 of these travelers were considered contagious or incubating the infection while traveling home. Given the large number of travelers to (sub)tropical countries, travel-related infection most likely contributes to importation and further influenza spread worldwide

White Paper: Shifting the goal post - from high impact journals to high impact data

The purpose of this white paper is to provide an overview of the ongoing initiatives at center level to respond to changing public expectations and to the challenge of improving the conduct of science by making research data widely available. We also attempt to provide a framework for implementing open access for research data to maximize CGIAR’s impact on development. The remainder of this paper proceeds as follows; firstly a summary of the diversity of research data produced by the centers is given, followed by an overview of the existing infrastructure for data management for each Center. Secondly, some of the limitations and barriers faced by the centers in their process to mainstream research data publishing are addressed. The paper concludes with recommendations for how these limitations and barriers can be tackled