Observation of a registered phase in Cs/W(110)

RHEED and AES studies at room temperature have revealed a new metastable state of Cs ad-atoms on W(110) which are in registry at least along [1̄10] W. The ad-atom density in this state is 0.81 ± 0.03 ML, where 1 ML corresponds to the final density of Cs atoms in the saturated close packed hexagonal structure. This new structure has been observed as the final structure in dynamic deposition conditions, i.e. under the constant pressure of the Cs beam. The previously observed 1 ML structure arises when deposition and AES observations are alternated. The possibility that impurities provide the means of overcoming a nucleation barrier to this final structure is discussed.     

Appraisal of radioactivity and associated radiation hazards in sand samples of four rivers of Punjab province,Pakistan

Natural and anthropogenic radioactivity of sand and water samples collected from the four big rivers of Punjab province, Pakistan, was measured using a high-purity germanium detector coupled with a high resolution multichannel analyser. The average concentration of the naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K in all the sand samples from the rivers Jhelum, Chenab, Ravi and Indus was found to be 22±0.6, 36±1 and 287±10 Bq?kg ^?1, respectively, while the concentration of the anthropogenic radionuclide ¹³⁷Cs was found to be below the minimum detectable activity, i.e. ～ 1.2 Bq?kg ^?1. All the sand samples have Ra_eq concentrations lower than the limit of 370 Bq?kg ^?1. Indoor (H _in) and outdoor (H _out) radiation hazard indices were calculated for the samples to assess the radiation hazards arising due to the use of this sand in construction, and were found to be less than unity in the study area. Calculated values of the absorbed dose rate were less than the typical world average value of 59 nGy?h ^?1, and the annual effective dose rate was also less than the typical world value of 70 μSv, except in the Indus river, in which it is slightly higher then the world average. Results show that the measured values are comparable with other global radioactivity measurements. None of the studied riverbeds was considered a radiological hazard, and their sand can be safely used in construction.     

Growth optimization and characterization of lattice-matched Al0.82In0.18N optical confinement layer for edge emitting nitride laser diodes

We present the growth optimization and the doping by the metal organic chemical vapor deposition of lattice-matched Al_0.82In_0.18N bottom optical confinement layers for edge emitting laser diodes. Due to the increasing size and density of V-shaped defects in Al_1?xIn_xN with increasing thickness, we have designed an Al_1?xIn_xN/GaN multilayer structure by optimizing the growth and thickness of the GaN interlayer. The Al_1?xIn_xN and GaN interlayers in the multilayer structure were both doped using the same SiH₄ flow, while the Si levels in both layers were found to be significantly different by SIMS. The optimized 8×(Al_0.82In_0.18N/GaN=54/6 nm) multilayer structures grown on free-standing GaN substrates were characterized by high resolution X-ray diffraction, atomic force microscopy and transmission electron microscopy, along with the in-situ measurements of stress evolution during growth. Finally, lasing was obtained from the UV (394 nm) to blue (436 nm) wavelengths, in electrically injected, edge-emitting, cleaved-facet laser diodes with 480 nm thick Si-doped Al_1?xIn_xN/GaN multilayers as bottom waveguide claddings.     

Synthesis,in vitro $$\alpha $$-glucosidase inhibitory activity,and in silico study of ( E)-thiosemicarbazones and ( E)-2-(2-(arylmethylene)hydrazinyl)-4-arylthiazole derivatives

This study is focused on the identification of thiazole-based inhibitors for the \(\alpha \)-glucosidase enzyme. For that purpose, (E)-2-(2-(arylmethylene)hydrazinyl)-4-arylthiazole derivatives were synthesized in two steps and characterized by various spectroscopic techniques. All derivatives and intermediates were evaluated for their in vitro \(\alpha \)-glucosidase inhibitory activity. Thiosemicarbazones 20 and 35, and cyclized thiazole derivatives 2, 5–11, 13, 15, 21–24, 27–31, and 36–37 showed significant inhibitory potential in the range of \(\hbox {IC}_{50}=6.2\pm 0.19\)–\(43.6\pm 0.23~\upmu \hbox {M}\) as compared to standard acarbose (\(\hbox {IC}_{50}=37.7\pm 0.19~\upmu \hbox {M}\)). A molecular modeling study was carried out to understand the binding interactions of compounds with the active site of enzyme.     

New flavonol glycosides from the leaves of Caragana brachyantha

Two new flavonol glycosides, brachysides C and D, together with three known flavonol glycosides, were isolated from the leaves of Caragana brachyantha. The structures of brachysides C and D were elucidated on the basis of detailed spectroscopic analysis as quercetin 5-O-[α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside]-7-O-[α-l-rhamnopyranoside] and quercetin 5-O-[α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside]-7-O-[α-l-rhamnopyranoside]-4′-O-[α-l-rhamnopyranoside], respectively. The presence of flavonol tetra- and triglycosides bearing a sugar moiety at position 5 was the first report from this genus Caragana.     

Biodiesel Production from Alkali-Catalyzed Transesterification of Tamarindus indica Seed Oil and Optimization of Process Conditions

Biodiesel is considered a sustainable alternative to petro-diesel owing to several favorable characteristics. However, higher production costs, primarily due to the use of costly edible oils as raw materials, are a chief impediment to its pecuniary feasibility. Exploring non-edible oils as raw material for biodiesel is an attractive strategy that would address the economic constraints associated with biodiesel production. This research aims to optimize the reaction conditions for the production of biodiesel through an alkali-catalyzed transesterification of Tamarindus indica seed oil. The Taguchi method was applied to optimize performance parameters such as alcohol-to-oil molar ratio, catalyst amount, and reaction time. The fatty acid content of both oil and biodiesel was determined using gas chromatography. The optimized conditions of alcohol-to-oil molar ratio (6:1), catalyst (1.5% w/w), and reaction time 1 h afforded biodiesel with 93.5% yield. The most considerable contribution came from the molar ratio of alcohol to oil (75.9%) followed by the amount of catalyst (20.7%). In another case, alcohol to oil molar ratio (9:1), catalyst (1.5% w/w) and reaction time 1.5 h afforded biodiesel 82.5% yield. The fuel properties of Tamarindus indica methyl esters produced under ideal conditions were within ASTM D6751 biodiesel specified limits. Findings of the study indicate that Tamarindus indica may be chosen as a prospective and viable option for large-scale production of biodiesel, making it a substitute for petro-diesel.     

Rapid Photolysis-Mediated Folding of Disulfide-Rich Peptides

Structure–activity relationship studies are a highly time-consuming aspect of peptide-based drug development, particularly in the assembly of disulfide-rich peptides, which often requires multiple synthetic steps and purifications. Therefore, it is vital to develop rapid and efficient chemical methods to readily access the desired peptides. We have developed a photolysis-mediated “one-pot” strategy for regioselective disulfide bond formation. The new pairing system utilises two ortho-nitroveratryl protected cysteines to generate two disulfide bridges in less than one hour in good yield. This strategy was applied to the synthesis of complex disulfide-rich peptides such as Rho-conotoxin ρ-TIA and native human insulin.     

An improved method of synthesis of N-protected L-amino acids as their benzoxymethyl esters

An improved method for the synthesis of L-amino acids as their benzoxymethyl esters has been reported. All the synthesized compounds were characterized by (1)H NMR, EI-MS and IR spectroscopic methods.