The aging of tungsten filaments and its effect on wire surface kinetics in hot-wire chemical vapor deposition

Wire-desorbed radicals present during hot-wire chemical vapor deposition growth have been measured by quadrupole mass spectrometry. New wires produce Si as the predominant radical for temperatures above 1500 K, with a minor contribution from SiH3, consistent with previous measurements; the activation energy for the SiH3 signal suggests its formation is catalyzed. Aged wires also produce Si as the predominant radical (above 2100 K), but show profoundly different radical desorption kinetics. In particular, the Si signal exhibits a high temperature activation energy consistent with evaporation from liquid silicon. The relative abundance of the other SiHx species suggests that heterogeneous pyrolysis of SiH4 on the wire may be occurring to some extent. Chemical analysis of aged wires by Auger electron spectroscopy suggests that the aging process is related to the formation of a silicide at the surface, with silicon surface concentrations as high as 15 at. %. A limited amount (2 at. %) of silicon is observed in the interior as well, suggesting that diffusion into the wire occurs. Calculation of the relative rates for the various wire kinetic processes, coupled with experimental observations, reveals that silicon diffusion through the silicide is the slowest process, followed by Si evaporation, with SiH4 decomposition being the fastest

The effect of current inhomogeneity on the performance and degradation of Li-S batteries

The effect of thermal gradients on the performance and cycle life of Li-S batteries is studied using bespoke single-layer Li-S cells, with isothermal boundary conditions maintained by Peltier elements. A temperature difference is shown to cause significant current imbalance between parallel connected single-layer cells, causing the hotter cell to provide more charge and discharge capacities during cycling. During charge, significant shuttle is induced in the hotter Li-S cell, causing accelerated degradation of it. A bespoke multi-tab cell in which the inner layers are electrically connected to different tabs versus the outer layers, is used to demonstrate that noticeable current inhomogeneity occurs during the operation of practical multilayer Li-S pouch cells, which is expected to affect their performance and degradation. The observed thermal and current inhomogeneity should have a direct consequence on battery pack and thermal management system design for real world Li-S battery packs

Solid state doping of CdxHg₁₋xTe epitaxial layers with elements of V group

Presented here are the results of studying the controlled doping with elements of V group of the periodic table, arsenic As and antimony Sb, of narrow gap CdxHg₁₋xTe epitaxial layers during the isothermal growth from the vapour phase by the evaporation-condensation-diffusion method. Three types of impurity sources have been used for solid state doping: homogeneously doped with As(Sb) single crystal substrates of CdTe, As doped buffer CdyHg₁₋yTe (y > x) epitaxial layers obtained by RF sputtering in mercury glow discharge onto undoped CdTe substrates, and As(Sb) implanted undoped CdTe substrates. The results of comparative analysis of galvano-magnetic measurements and SIMS spectra indicated very high, practically nearly ~100 %, electrical activity of dopants in the CdxHg₁₋xTe epitaxially grown layers

Mathematically Gifted Adolescents Have Deficiencies in Social Valuation and Mentalization

Many mathematically gifted adolescents are characterized as being indolent, underachieving and unsuccessful despite their high cognitive ability. This is often due to difficulties with social and emotional development. However, research on social and emotional interactions in gifted adolescents has been limited. The purpose of this study was to observe differences in complex social strategic behaviors between gifted and average adolescents of the same age using the repeated Ultimatum Game. Twenty-two gifted adolescents and 24 average adolescents participated in the Ultimatum Game. Two adolescents participate in the game, one as a proposer and the other as a responder. Because of its simplicity, the Ultimatum Game is an apt tool for investigating complex human emotional and cognitive decision-making in an empirical setting. We observed strategic but socially impaired offers from gifted proposers and lower acceptance rates from gifted responders, resulting in lower total earnings in the Ultimatum Game. Thus, our results indicate that mathematically gifted adolescents have deficiencies in social valuation and mentalization

Accumulation and annealing of radiation donor defects in arsenic-implanted Hg0.7Cd0.3Te films

Processes of accumulation and annealing of radiation-induced donor defects in arsenic-implanted Hg0.7Cd0.3Te films were studied with the use of the Hall-effect measurements with processing the data with mobility spectrum analysis. A substantial difference in the effects of arsenic implantation and post-implantation activation annealing on the properties of implanted layers and photodiode ‘base’ layers in Hg0.7Cd0.3Te and Hg0.8Cd0.2Te films was established and tentatively explained

Optimizing HVAC Control to Improve Building Comfort and Energy Performance

This paper demonstrates the benefits of optimal control in well-designed and operated buildings using a case study. The case study building was built in 2001. The HVAC and control systems have been installed with state-of-the-art equipment which include a terminal box temperature integrated minimum airflow reset. The building has been used and operated based on the design intents. This paper presents both the existing and the optimal control schedules, which include the VAV box operation schedule, AHUs optimal control, chiller and chilled water pump control, and boiler and hot water pump control. The measured hourly HVAC electricity consumption shows that annual savings of up to 40% can be achieved with an optimal control schedule

Extensive sampling sheds light on species-level diversity in Palearctic Placobdella (Annelida: Clitellata: Glossiphoniiformes)

The bloodfeeding leech genus Placobdella is dominated by North American diversity, with only a single nominal species known from Central America and one from the Palearctic region. This is likely due to considerable underestimation of Palearctic biodiversity, but investigations into potential hidden diversity are lacking. To shed light on this, the present study introduces new data for specimens initially identified as Placobdella costata from Ukraine (close to the type locality), Italy, Germany, Latvia, Montenegro, Bulgaria, Slovenia, Turkey, Azerbaijan, Tunisia, and Algeria, and uses both nuclear (Internal Transcribed Spacer [ITS] region) and mitochondrial (cytochrome c oxidase subunit I [COI]) sequence data in phylogenetic and DNA barcoding frameworks, in order to better understand species-level diversity. Seven independent lineages are present in the trees, five of which show adequate separation at the COI locus to suggest their unique species-level status (COI distances between these clades range from 4.86 to 8.10%). However, the ITS data suggest that speciation is recent or incipient in these clades, and that not enough time has passed for clear separation at this locus. We discuss the evolutionary and taxonomic implications of our findings and speculate on dispersal events that may have contributed to shaping this pattern of geographic distribution

Impact of COVID-19 on Formal Education: An International Review of Practices and Potentials of Open Education at a Distance.

In terms of scale, shock, and disenfranchisement, the disruption to formal education arising from COVID-19 has been unprecedented. Anecdotally, responses from teachers and educators around the world range from heightened caution to being inspired by distance education as the 'new normal.' Of all the challenges, face-to-face and formal teaching have been most heavily affected. Despite some education systems demonstrating resilience, a major challenge is sustaining quality and inclusiveness in formal education suddenly delivered at a distance. In probing these issues, this article profiles international perspectives on the role of open education in responding to the impact on formal school and higher education caused by the COVID-19 pandemic. We proceed by highlighting and analysing practices and case studies from 13 countries representing all global regions, identifying and discussing the challenges and opportunities that have presented themselves. Reports cover the period from the beginning of 2020 until 11 March 2021, the first anniversary of the COVID-19 outbreak as declared by the World Health Organization. In our comparative study, we identify seven key aspects of which three (missing infrastructure and sharing OER, open education and access to OER, and urgent need for professional development and training for teachers) are directly related to open education at a distance. After comparing examples of existing practice, we make recommendations and offer insights into how open education strategies can lead to interventions that are effective and innovative¿to improve formal education at a distance in schools and universities in the future

The frontline antibiotic vancomycin induces a zinc starvation response in bacteria by binding to Zn(II).

Vancomycin is a front-line antibiotic used for the treatment of nosocomial infections, particularly those caused by methicillin-resistant Staphylococcus aureus. Despite its clinical importance the global effects of vancomycin exposure on bacterial physiology are poorly understood. In a previous transcriptomic analysis we identified a number of Zur regulon genes which were highly but transiently up-regulated by vancomycin in Streptomyces coelicolor. Here, we show that vancomycin also induces similar zinc homeostasis systems in a range of other bacteria and demonstrate that vancomycin binds to Zn(II) in vitro. This implies that vancomycin treatment sequesters zinc from bacterial cells thereby triggering a Zur-dependent zinc starvation response. The Kd value of the binding between vancomycin and Zn(II) was calculated using a novel fluorometric assay, and NMR was used to identify the binding site. These findings highlight a new biologically relevant aspect of the chemical property of vancomycin as a zinc chelator.This work was supported by funding from the Royal Society, UK (516002.K5877/ROG), the Medical Research Council, UK (G0700141). A.Z. was supported from the Said foundation and Cambridge Trust.This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep1960