Photoluminescence studies of heteroepitaxial gaas on si

We present a systematic study of the photoluminescence of undoped GaAs layers deposited by MOCVD on Si substrates. The study includes an examination of substrate and layer thickness effects in thin GaAs layers, and a detailed investigation of the stress effects on the intrinsic band-edge transitions in thicker samples. For sample thickness,t ≤ 0.5(μm), we observe strong midgap emission bands associated with defects close to the interface. These bands depend strongly on the nature of the Si substrate. The crystal quality improves with sample thickness, and fort ≥ 0.5 μm the emission is dominated by lines in the band edge region which are relatively independent of substrate preparation. Photoluminescence excitation spectra reveal that the highest energy line is due to an intrinsic exciton transition, and that a splitting of this line observed fort ≥ 2 μm reflects the presence of two different regions of strain in the material. The magnitude of the strain is estimated from the shift of the exciton lines relative to unstrained GaAs, and is found to be consistent with an upper limit provided by the thermal expansion mismatch between GaAs and Si.     

Reappraisal of neutron scattering results on micellar solutions of dodecylhexaoxyethylene glycol monoether (C12E6)

SANS data on micellar solutions of C₁₂E₆ as a function of temperature have been reanalysed using a cylinder growth model. Reasonably good fits to the experimental curves were obtained using only the rod length as an adjustable parameter. The effect of polydispersity in the micelle size on the scattering profile was also investigated. Our main conclusion is that SANS is not a sufficiently sensitive technique to allow a clear identification of the micelle structure(s) at elevated temperatures.     

Antimony oxide–PVC synergism: Laser pyrolysis studies of the interaction mechanism

Laser-probe pyrolysis is used to investigate the synergistic flame-retardancy effect observed for antimony oxide (Sb₂O₃)–PVC combinations. Molecular beam-mass analysis detection techniques permit direct sampling of the laser-vaporized species without the need for intermediate product collection stages. Laser pyrolysis of a PVC formulation containing 3 phr Sb₂O₃ provides the first direct evidence for the production of volatile SbCl₃ during thermal decomposition. Selective laser irradiation of PVC in the presence of unheated Sb₂O₃ in the sample cell reveals that HCl evolved from the polymer substrate rapidly reacts with Sb₂O₃(s) to form the volatile flame-retardant species SbCl₃. Similar results are observed for SbOCl(s). These reactions are distinct from those previously proposed, which involve the formation and subsequent thermal decomposition of intermediate solid-phase antimony oxychlorides, and demonstrate that the antimony compounds, rather than serving only as inert sources for SbCl₃, readily participate in direct chemical reactions with HCl. In addition to the composition of the reaction products, information is also obtained on their evolution characteristics from the sample cell.     

Stress corrosion cracking of alloy C-22 and Ti Gr-12 using double-cantilever-beam technique

Susceptibility to stress corrosion cracking (SCC) of two candidate alloys for the inner container of the multi-barrier nuclear waste package was evaluated by using wedge-loaded precracked double-cantilever-beam (DCB) specimens in deaerated acidic brine (pH≈2.70) at 90°C. Materials tested included Alloy C-22 and Ti Grade-12. Duplicate samples of each material were loaded at different initial stress intensity factor (K_I) values ranging between 22 and 43 MPa√m. Both metallography and the compliance methods were used to determine the final crack length. The final stress intensity for SCC (K_f) was computed from the measured final wedge load and the average crack length. The results indicate that, in general, the final crack lengths measured by metallography and compliance agreed well with one another, thus, providing very similar K_f values. The alloy C-22 showed higher susceptibility to SCC than Ti Grade-12 in terms of the average crack growth. Fractographic evaluation by scanning electron microscopy (SEM) of broken DCB specimens revealed three distinct regions showing the characteristics of fatigue precrack, SCC, and fast fracture.     

Genistein: A Potential Natural Lead Molecule for New Drug Design and Development for Treating Memory Impairment

Genistein is a naturally occurring polyphenolic molecule in the isoflavones group which is well known for its neuroprotection. In this review, we summarize the efficacy of genistein in attenuating the effects of memory impairment (MI) in animals. Scopus, PubMed, and Web of Science databases were used to find the relevant articles and discuss the effects of genistein in the brain, including its pharmacokinetics, bioavailability, behavioral effects, and some of the potential mechanisms of action on memory in several animal models. The results of the preclinical studies highly suggested that genistein is highly effective in enhancing the cognitive performance of the MI animal models, specifically in the memory domain, including spatial, recognition, retention, and reference memories, through its ability to reduce oxidative stress and attenuate neuroinflammation. This review also highlighted challenges and opportunities to improve the drug delivery of genistein for treating MI. Along with that, the possible structural modifications and derivatives of genistein to improve its physicochemical and drug-likeness properties are also discussed. The outcomes of the review proved that genistein can enhance the cognitive performance and ameliorate MI in different preclinical studies, thus indicating its potential as a natural lead for the design and development of a novel neuroprotective drug.     

Chemistry,Biosynthesis and Pharmacology of Sarsasapogenin: A Potential Natural Steroid Molecule for New Drug Design,Development and Therapy

Sarsasapogenin is a natural steroidal sapogenin molecule obtained mainly from Anemarrhena asphodeloides Bunge. Among the various phytosteroids present, sarsasapogenin has emerged as a promising molecule due to the fact of its diverse pharmacological activities. In this review, the chemistry, biosynthesis and pharmacological potentials of sarsasapogenin are summarised. Between 1996 and the present, the relevant literature regarding sarsasapogenin was obtained from scientific databases including PubMed, ScienceDirect, Scopus, and Google Scholar. Overall, sarsasapogenin is a potent molecule with anti-inflammatory, anticancer, antidiabetic, anti-osteoclastogenic and neuroprotective activities. It is also a potential molecule in the treatment for precocious puberty. This review also discusses the metabolism, pharmacokinetics and possible structural modifications as well as obstacles and opportunities for sarsasapogenin to become a drug molecule in the near future. More comprehensive preclinical studies, clinical trials, drug delivery, formulations of effective doses in pharmacokinetics studies, evaluation of adverse effects and potential synergistic effects with other drugs need to be thoroughly investigated to make sarsasapogenin a potential molecule for future drug development.     

Antibacterial Potential of Bacopa monnieri (L.) Wettst. and Its Bioactive Molecules against Uropathogens—An In Silico Study to Identify Potential Lead Molecule(s) for the Development of New Drugs to Treat Urinary Tract Infections

Urinary tract infections (UTIs) are becoming more common, requiring extensive protection from antimicrobials. The global expansion of multi-drug resistance uropathogens in the past decade emphasizes the necessity of newer antibiotic treatments and prevention strategies for UTIs. Medicinal plants have wide therapeutic applications in both the prevention and management of many ailments. Bacopa monnieri is a medicinal plant that is found in the warmer and wetlands regions of the world. It has been used in Ayurvedic systems for centuries. The present study aimed to investigate the antibacterial potential of the extract of B. monnieri leaves and its bioactive molecules against UTIs that are caused by Klebsiella pneumoniae and Proteus mirabilis. This in vitro experimental study was conducted by an agar well diffusion method to evaluate the antimicrobial effect of 80% methanol, 96% ethanol, and aqueous extracts of B. monnieri leaves on uropathogens. Then, further screening of their phytochemicals was carried out using standard methods. To validate the bioactive molecules and the microbe interactions, AutoDock Vina software was used for molecular docking with the Klebsiella pneumoniae fosfomycin resistance protein (5WEW) and the Zn-dependent receptor-binding domain of Proteus mirabilis MR/P fimbrial adhesin MrpH (6Y4F). Toxicity prediction and drug likeness were predicted using ProTox-II and Molinspiration, respectively. A molecular dynamics (MD) simulation was carried out to study the protein ligand complexes. The methanolic leaves extract of B. monnieri revealed a 22.3 mm ± 0.6 mm to 25.0 mm ± 0.5 mm inhibition zone, while ethanolic extract seemed to produce 19.3 mm ± 0.8 mm to 23.0 mm ± 0.4 mm inhibition zones against K. pneumoniae with the use of increasing concentrations. In the case of P. mirabilis activity, the methanolic extracts showed a 21.0 mm ± 0.8 mm to 24.0 mm ± 0.6 mm zone of inhibition and the ethanol extract produced a 17.0 mm ± 0.9 mm to 23.0 mm ± 0.7 mm inhibition zone with increasing concentrations. Carbohydrates, flavonoids, saponin, phenolic, and terpenoid were common phytoconstituents identified in B. monnieri extracts. Oroxindin showed the best interactions with the binding energies with 5WEW and 6Y4F, −7.5 kcal/mol and −7.4 kcal/mol, respectively. Oroxindin, a bioactive molecule, followed Lipinski’s rule of five and exhibited stability in the MD simulation. The overall results suggest that Oroxindin from B. monnieri can be a potent inhibitor for the effective killing of K. pneumoniae and P. mirabilis. Additionally, its safety has been established, indicating its potential for future drug discovery and development in the treatment for UTIs.     

Wood property relationships and survival models in reliability

We study the relationship between lumber strength properties and their visual grading characteristics. This topic is central to the analysis of the reliability of lumber products in that it underlies the calculation of structural design values. The approaches described in the paper are adaptations of survival analysis methods commonly used in medical studies. Because each piece of lumber can only be tested to destruction with one method (i.e., each piece cannot be broken twice), modeling these strengths distributions simultaneously can be challenging. In the past, this kind of problem has been solved by subjectively matching pieces of lumber, but the quality of this approach is then an issue. The objective of our analysis is to build a predictive model that relates the strength properties to the recorded characteristics. The paper concludes that type of wood defect (knot), a lumber grade status (off‐grade: yes/no), and a lumber's module of elasticity have statistically significant effects on wood strength. We find that the Weibull accelerated failure time model provides a better fit than the Cox proportional hazards model in our dataset. Copyright © 2016 John Wiley & Sons, Ltd.