Interface Studies of Molecular Beam Epitaxy (MBE) Grown ZnSe-GaAs Heterovalent Structures

Comprehensive investigations on ZnSe/GaAs and GaAs/ZnSe interfaces were carried out by photoluminescence (PL) and transmission electron microscopy (TEM), as a part of realizing high quality ZnSe-GaAs (100) hetero-valent structures (HS). The nature of ZnSe/GaAs interface under different surface terminations of GaAs was examined. The ZnSe/Ga-terminated GaAs was found to have a superior optical and microstructural quality, with a chemical interface consisting of a mixture of both the GaAs and ZnSe atomic constituents. For GaAs/ZnSe interface studies, a low-temperature migration enhanced epitaxy (LT-MEE) growth technique was used to grow GaAs layers under the conditions compatible to the growth of ZnSe. Both Ga and As-initialized LT-MEE GaAs/ZnSe interfaces were investigated. A defective transition layer was observed along the As-initialized GaAs/ZnSe interface, which may be attributed to the formation Zn$_3$As$_2$ compound. The correlation between the observed optical as well as structural properties of both the (GaAs/ZnSe and ZnSe/GaAs) interfaces and the growth conditions used in this study are discussed in detail. This study could provide a valuable insight on the interface nature of ZnSe-GaAs HS

Self-Dual Yang-Mills and Vector-Spinor Fields, Nilpotent Fermionic Symmetry, and Supersymmetric Integrable Systems

We present a system of a self-dual Yang-Mills field and a self-dual vector-spinor field with nilpotent fermionic symmetry (but not supersymmetry) in 2+2 dimensions, that generates supersymmetric integrable systems in lower dimensions. Our field content is (A_\mu{}^I, \psi_\mu{}^I, \chi^{I J}), where I and J are the adjoint indices of arbitrary gauge group. The \chi^{I J} is a Stueckelberg field for consistency. The system has local nilpotent fermionic symmetry with the algebra \{N_\alpha{}^I, N_\beta{}^J \} = 0. This system generates supersymmetric Kadomtsev-Petviashvili equations in D=2+1, and supersymmetric Korteweg-de Vries equations in D=1+1 after appropriate dimensional reductions. We also show that a similar self-dual system in seven dimensions generates self-dual system in four dimensions. Based on our results we conjecture that lower-dimensional supersymmetric integral models can be generated by non-supersymmetric self-dual systems in higher dimensions only with nilpotent fermionic symmetries.Comment: 15 pages, no figure

Evaluating the effectiveness of the Emergency Neurological Life Support educational framework in low-income countries.

BackgroundThe Emergency Neurological Life Support (ENLS) is an educational initiative designed to improve the acute management of neurological injuries. However, the applicability of the course in low-income countries in unknown. We evaluated the impact of the course on knowledge, decision-making skills and preparedness to manage neurological emergencies in a resource-limited country.MethodsA prospective cohort study design was implemented for the first ENLS course held in Asia. Knowledge and decision-making skills for neurological emergencies were assessed at baseline, post-course and at 6 months following course completion. To determine perceived knowledge and preparedness, data were collected using surveys administered immediately post-course and 6 months later.ResultsA total of 34 acute care physicians from across Nepal attended the course. Knowledge and decision-making skills significantly improved following the course (p=0.0008). Knowledge and decision-making skills remained significantly improved after 6 months, compared with before the course (p=0.02), with no significant loss of skills immediately following the course to the 6-month follow-up (p=0.16). At 6 months, the willingness to participate in continuing medical education activities remained evident, with 77% (10/13) of participants reporting a change in their clinical practice and decision-making, with the repeated use of ENLS protocols as the main driver of change.ConclusionsUsing the ENLS framework, neurocritical care education can be delivered in low-income countries to improve knowledge uptake, with evidence of knowledge retention up to 6 months

Water Quality and Pollution Status of Lararpur Reservoir with Special Reference to Bacterial Contamination

Laharpur dam was constructed in the southwest of Bhopal city, M.P., India with an objective to store water for irrigational purpose. At the time of planning and construction of the reservoir it was in the outskirts of township but now, with the expansion of the city the reservoir has come well within the settlement. The developmental activities and occupancy in the area is exerting pressure on the water body. Surface water in urban water bodies almost always contains some degree of contamination. This is due to exposure to animals, humans, aquatic life, etc. In addition to this, variety of other human activities resulted in increasing the bacterial concentration of reservoir. Many of these bacteria are pathogenic and spread diseases like typhoid, paratyphoid, gastroenteritis etc. Inflow of sewage in the surface water may play an important role in the transmission of pathogenic agents discharged through feces. Some pathogenic bacteria like Actinomyces sp., Aerobacter aerogenes, A. cloacae, Micrococcus sp., Salmonella sp., Staphylococcus aureus, Bacillussp, and Shigella species indicate the higher level of fecal contamination of water. This untreated water poses a serious threat to the health of consumers and therefore, calls for urgent intervention by government.
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ASASSN-18tb: A Most Unusual Type Ia Supernova Observed by TESS and SALT

We present photometric and spectroscopic observations of the unusual Type Ia supernova ASASSN-18tb, including a series of SALT spectra obtained over the course of nearly six months and the first observations of a supernova by the Transiting Exoplanet Survey Satellite (TESS). We confirm a previous observation by Kollmeier et al. (2019) showing that ASASSN-18tb is the first relatively normal Type Ia supernova to exhibit clear broad ($\sim1000$ km s$^{-1}$) H$\alpha$ emission in its nebular phase spectra. We find that this event is best explained as a sub-Chandrasekhar mass explosion with $M_{Ni} \approx 0.3\; \rm{M}_\odot$. Despite the strong H$\alpha$ signature at late times, we find that the early rise of the supernova shows no evidence for deviations from a single-component power-law and is best fit with a moderately shallow power-law of index $1.69\pm0.04$. We find that the H$\alpha$ luminosity remains approximately constant after its initial detection at phase +37 d, and that the H$\alpha$ velocity evolution does not trace that of the Fe~III$~\lambda4660$ emission. These suggest that the H$\alpha$ emission arises from circumstellar medium (CSM) rather than swept up material from a non-degenerate companion. However, ASASSN-18tb is strikingly different from other known CSM-interacting Type Ia supernovae in a number of significant ways. Those objects typically show an H$\alpha$ luminosity two orders of magnitude higher than what is seen in ASASSN-18tb, pushing them away from the empirical light-curve relations that define "normal" Type Ia supernovae. Conversely, ASASSN-18tb exhibits a fairly typical light curve and luminosity for an underluminous or transitional SN Ia, with $M_R \approx -18.1$ mag. Moreover, ASASSN-18tb is the only SN Ia showing H$\alpha$ from CSM interaction to be discovered in an early-type galaxy.Comment: 13 pages, 8 figure

Macroeconomic Interdependence and Integration in Africa

There is a renewed interest in the debate on integration in Africa since the creation of the Africa Union in 2002. This study investigates the feasibility of a full-fledge union in Africa from an economic standpoint. Towards this goal, we examine both the contemporaneous and dynamic relations in the short- and long-run among six key macro variables--consumer price level, gross domestic product, consumption, investment, trade flows and government expenditures--in eight African countries. In the quarterly data from 1976 to 2005, we observe the existence of common trends in real output, price level, private consumption, government consumption, investment and trade flows among these eight countries. In addition, we also note that there exist common cycles in real output, investment and trade flows for these countries. These two critical findings indicate the existence of some macroeconomic interdependence among these countries. Thus, the chances for success of integration in Africa driven by these eight countries are appreciable