Photocatalytic Degradation of Rhodamine B Dye and Hydrogen Evolution by Hydrothermally Synthesized NaBH4-Spiked ZnS Nanostructures.

Metal sulphides, including zinc sulphide (ZnS), are semiconductor photocatalysts that have been investigated for the photocatalytic degradation of organic pollutants as well as their activity during the hydrogen evolution reaction and water splitting. However, devising ZnS photocatalysts with a high overall quantum efficiency has been a challenge due to the rapid recombination rates of charge carriers. Various strategies, including the control of size and morphology of ZnS nanoparticles, have been proposed to overcome these drawbacks. In this work, ZnS samples with different morphologies were prepared from zinc and sulphur powders via a facile hydrothermal method by varying the amount of sodium borohydride used as a reducing agent. The structural properties of the ZnS nanoparticles were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. All-electron hybrid density functional theory calculations were employed to elucidate the effect of sulphur and zinc vacancies occurring in the bulk as well as (220) surface on the overall electronic properties and absorption of ZnS. Considerable differences in the defect level positions were observed between the bulk and surface of ZnS while the adsorption of NaBH4 was found to be highly favourable but without any significant effect on the band gap of ZnS. The photocatalytic activity of ZnS was evaluated for the degradation of rhodamine B dye under UV irradiation and hydrogen generation from water. The ZnS nanoparticles photo-catalytically degraded Rhodamine B dye effectively, with the sample containing 0.01 mol NaBH4 being the most efficient. The samples also showed activity for hydrogen evolution, but with less H2 produced compared to when untreated samples of ZnS were used. These findings suggest that ZnS nanoparticles are effective photocatalysts for the degradation of rhodamine B dyes as well as the hydrogen evolution, but rapid recombination of charge carriers remains a factor that needs future optimization.

The role of surface oxidation and Fe-Ni synergy in Fe-Ni-S catalysts for CO2 hydrogenation.

Increasing carbon dioxide (CO2) emissions, resulting in climate change, have driven the motivation to achieve the effective and sustainable conversion of CO2 into useful chemicals and fuels. Taking inspiration from biological processes, synthetic iron-nickel-sulfides have been proposed as suitable catalysts for the hydrogenation of CO2. In order to experimentally validate this hypothesis, here we report violarite (Fe,Ni)3S4 as a cheap and economically viable catalyst for the hydrogenation of CO2 into formate under mild, alkaline conditions at 125 °C and 20 bar (CO2 : H2 = 1 : 1). Calcination of violarite at 200 °C resulted in excellent catalytic activity, far superior to that of Fe-only and Ni-only sulfides. We further report first principles simulations of the CO2 conversion on the partially oxidised (001) and (111) surfaces of stoichiometric violarite (FeNi2S4) and polydymite (Ni3S4) to rationalise the experimentally observed trends. We have obtained the thermodynamic and kinetic profiles for the reaction of carbon dioxide (CO2) and water (H2O) on the catalyst surfaces via substitution and dissociation mechanisms. We report that the partially oxidised (111) surface of FeNi2S4 is the best catalyst in the series and that the dissociation mechanism is the most favourable. Our study reveals that the partial oxidation of the FeNi2S4 surface, as well as the synergy of the Fe and Ni ions, are important in the catalytic activity of the material for the effective hydrogenation of CO2 to formate.

Examining Summer Laboratory Research Apprenticeships for High School Students as a Factor in Entry to MD/PhD Programs at Matriculation.

Do summer laboratory research apprenticeships during high school have an impact on entry into MD/PhD programs? Apart from the nearly decade-long span of time between high school and matriculation into an MD/PhD program, young people have many life-shaping experiences that presumably impact their education and career trajectories. This quantitative study (n = 236,432) examines the connection between early laboratory research apprenticeship experiences at the high school level and matriculation into one of the more rigorous educational programs for scientific research training. The span of time covered by this analysis reaches across more than a decade, examining the potential importance of research experiences during the precollege years in the educational trajectory of young people. Intertwined with this question on research experiences is a second major concern regarding diversity in the life sciences research corps. Diversity in this wide-ranging discipline refers specifically to the underrepresentation of Blacks/African Americans, Hispanics/Latino/as, and American Indians/Alaska Natives among the ranks of research scientists. Thus, this study includes analyses that specifically focus on research apprenticeships of Blacks/African Americans and Hispanics/Latino/as and their entrance into MD/PhD programs.

Esophegeal replacement in children with AIDS.

We report 2 human immunodeficiency virus-positive patients with refractory esophageal strictures secondary to candidiasis. They presented with progressive dysphagia and had suffered from oropharyngeal and/or esophageal candidiasis within the preceding 3 months. Both failed conservative management of these strictures, including systemic antifungal therapy, administration of proton pump inhibitors, and numerous attempts at stricture dilation, ultimately progressing to open transhiatal esophagectomy. Although challenging in the immunocompromised host, successful treatment of these strictures by gastric interposition is achievable with minimal morbidity.

A general organocatalytic enantioselective malonate addition to alpha,beta-unsaturated enones.

A general enantioselective organocatalytic conjugate addition procedure of a variety of malonates to alpha,beta-unsaturated enone systems is presented. The reaction is efficiently catalysed by the pyrrolidinyl tetrazole catalyst 1. Cyclic, acyclic and aromatic enones can be used and the reaction with ethyl malonates 3 b provides the Michael addition products in high yields with good to excellent enantioselectivities. Since only 1.5 equivalents of malonate are used as a reagent, the reaction is readily scaled and practical to operate. Furthermore, the malonate addition products can be easily mono decarboxylated without loss in enantiomeric excess by enzymatic or sodium hydroxide mediated methods.

Convergent extension, planar-cell-polarity signalling and initiation of mouse neural tube closure.

Planar-cell-polarity (PCP) signalling is necessary for initiation of neural tube closure in higher vertebrates. In mice with PCP gene mutations, a broad embryonic midline prevents the onset of neurulation through wide spacing of the neural folds. In order to evaluate the role of convergent extension in this defect, we vitally labelled the midline of loop-tail (Lp) embryos mutant for the PCP gene Vangl2. Injection of DiI into the node, and electroporation of a GFP expression vector into the midline neural plate, revealed defective convergent extension in both axial mesoderm and neuroepithelium, before the onset of neurulation. Chimeras containing both wild-type and Lp-mutant cells exhibited mainly wild-type cells in the midline neural plate and notochordal plate, consistent with a cell-autonomous disturbance of convergent extension. Inhibitor studies in whole-embryo culture demonstrated a requirement for signalling via RhoA-Rho kinase, but not jun N-terminal kinase, in convergent extension and the onset of neural tube closure. These findings identify a cell-autonomous defect of convergent extension, requiring PCP signalling via RhoA-Rho kinase, during the development of severe neural tube defects in the mouse.

An efficient, asymmetric organocatalyst-mediated conjugate addition of nitroalkanes to unsaturated cyclic and acyclic ketones.

5-Pyrrolidin-2-yltetrazole is a versatile organocatalyst for the asymmetric conjugate addition of nitroalkanes to enones. Using this catalyst, this transformation requires short reaction times, tolerates a broad substrate scope, and possibly proceeds via generation of an iminium species.

Asymmetric organocatalytic conjugate addition of malonates to enones using a proline tetrazole catalyst.

5-Pyrrolidin-2-yltetrazole performs as a useful organocatalyst for the asymmetric addition of malonates to a range of enones, with good to excellent enantioselectivities.

A versatile organocatalyst for the asymmetric conjugate addition of nitroalkanes to enones.

5-Pyrrolidin-2-yltetrazole performs as an improved catalyst for the asymmetric addition of a range of nitroalkanes to cyclic and acyclic enones, with good to excellent enantioselectivity.