Photoluminescence enhancement in CdS quantum dots by thermal annealing

ABSTRACT: The photoluminescence behavior of CdS quantum dots in initial growth stage was studied in connection with an annealing process. Compared to the as-synthesized CdS quantum dots (quantum efficiency approximately equal to 1%), the heat-treated sample showed enhanced luminescence properties (quantum efficiency approximately equal to 29%) with a narrow band-edge emission. The simple annealing process diminished the accumulated defect states within the nanoparticles and thereby reduced the nonradiative recombination, which was confirmed by diffraction, absorption, and time-resolved photoluminescence. Consequently, the highly luminescent and defect-free nanoparticles were obtained by a facile and straightforward process.     

Vapor-liquid equilibra for cyclohexane+2-propoxyethanol and cyclohexane+2-butoxyethanol systems

2-propoxyethanol (C₃E₁) and 2-butoxyethanol (C₄E₁) are nonionic surfactants which are a particularly interesting class of substances due to both inter-molecular and intra-molecular association, related to the presence of O and OH in the same molecule. Binary (vapor+liquid) equilibrium data were measured for cyclohexane+2-propoxyethanol and cyclohexane+2-butoxy ethanol systems at temperatures ranging from 303.15 K to 323.15 K at 10 K intervals. A static apparatus was used in this study. Two systems show positive deviation from Raoult’s law and no azeotrope. The experimental data were correlated well with Peng-Robinson-Stryjek-Vera equation of state using Wong-Sandler mixing rule incorporating the non-random-two-liquid model.     

Synthesis and characterization of proton exchange poly (phenylenebenzophenone)s membranes grafted with propane sulfonic acid on pendant phenyl groups

A series of poly(phenylenebenzophenone)s with sulfonic acid groups via long alkyl side chains, SPPBPs, were successfully prepared as proton exchange membranes for fuel cells. The new monomer, 1,4-dichloro-2,5 diphenylenemethoxybenzophenone (PMBP) was synthesized by the Friedel–Crafts reaction of tetrachloroterephthalate with anisole and copolymerized with 1,4-dichloro-2,5-diphenylenebenzophenone (PBP) to prepare poly(phenylenebenzophenone)s copolymers containing dimethoxy groups (sPPMBP). After converting the methoxy group to the reactive hydroxyl group, the resulting side-chain-type sulfonated copolymers (SPPBP) were obtained by a sulfopropylation reaction. These SPPBP series membranes showed high proton conductivity in the range of 98.4–162.1 mS/cm 80 °C under 90% hydrated conditions. SPPBP-40 (IEC = 2.45 meq./g) showed comparable higher proton conductivity (162.1 mS/cm) than Nafion 211 (130.2 mS/cm) in the 90% hydrated state. The membranes were studied by ¹H NMR spectroscopy, thermo-gravimetric analysis, ionic exchange capacity, water uptake, and proton conductivity. Also surface morphologies were assessed by atomic force microscope (AFM).     

Gleditsia sinensis Thorn Attenuates the Collagen-Based Migration of PC3 Prostate Cancer Cells through the Suppression of α2β1 Integrin Expression

Gleditsia sinensis thorns (GST) have been used as a traditional medicine for carbuncles and skin diseases. The purpose of this study was to decide whether non-toxicological levels of water extract of GST (WEGST) are effective in inhibiting the progress of prostate cancer formation and to identify the target molecule involved in the WEGST-mediated inhibitory process of prostate cancer cell migration and in vivo tumor formation. Through the Boyden chamber migration assay, we found that non-toxic levels of WEGST could not attenuate the PC3 migration to the bottom area coated with serum but significantly inhibited PC3 cell migration to the collagen-coated bottom area. We also found that non-toxic levels of WEGST significantly attenuated collagen against adhesion. Interestingly, ectopic administration of WEGST could not affect the expression of α2β1 integrin, which is known as a receptor of collagen. However, when the PC3 cells adhered to a collagen-coated plate, the expression of α2 integrin but not that of β1 integrin was significantly inhibited by the administration of non-toxic levels of WEGST, leading to the inhibition of focal adhesion kinase (FAK) phosphorylation. Furthermore, oral administration of WEGST (25 mg/kg/day) significantly inhibited the size of a PC3 cell-xenografted tumor. Taken together, these results suggest a novel molecular mechanism for WEGST to inhibit prostate cancer progression at particular stages, such as collagen-mediated adhesion and migration, and it might provide further development for the therapeutic use of WEGST in the treatment of prostate cancer progression.     

Study on nuclear accident precursors using AHP and BBN,a case study of Fukushima accident

Most of the nuclear accident reports used to indicate the implicit precursors which are not quantified earlier as underlying factors. The current Probabilistic Safety Assessment is capable of quantifying the importance of accident causes in limited scope. It was, therefore, difficult to achieve quantifiable decision making for resource allocation. In this study, the methodology which facilitates to quantify these precursors and a case study of Fukushima accident has been presented. First, four implicit precursors have been obtained by evaluating the causality and hierarchy structure of various accident factors. Eventually, it turned out they represent the lack of knowledge. After four precursors are selected, sub‐precursors have been investigated and their cause–consequence relationship has been implemented by using Bayesian Belief Network (BBN). To prioritize the precursors, the prior probability is initially estimated by expert judgment and updated upon observations. The pair‐wise importance between precursors is calculated by Analytic Hierarchy Process (AHP) and the results are converted into Node Probability Tables in the BBN model. Using this method, the sensitivity and the posterior probability of each precursor can be analyzed so that it enables to make prioritization for the factors. The lessons learned from Fukushima accident to demonstrate the feasibility of the proposed methodology have been implemented. Copyright © 2014 John Wiley & Sons, Ltd.     

Pseudo-cyclic renewal systems

A finite set W of words over an alphabet A is cyclic if, whenever u,v∈A^∗ and uv,vu∈W^∗, we have u,v∈W^∗. If it is only assumed that the property holds for all u,v∈A^∗ with a large length, then W is called pseudo-cyclic, that is, there is N∈N such that, whenever u,v∈A^∗ with |u|, |v|≥N and uv,vu∈W^∗, we have u,v∈W^∗. We analyze the class of pseudo-cyclic sets and describe how it is related to the open question which asks whether every irreducible shift of finite type is conjugate to a renewal system.     

Effect of acid-pretreatment on hydrogen fermentation of food waste: Microbial community analysis by next generation sequencing

This work presents the effect of acid-pretreatment on H₂ fermentation of food waste with detailed microbial information by next generation sequencing. The pretreated food waste at pH 1.0–4.0 was cultivated under mesophilic conditions without external inoculum addition. From the food waste acid-pretreated at pH 1–3, H₂ yields in the range of 1.37–1.74 mol H₂/mol hexose_added were achieved, attaining the highest value at pH 2. Clostridium sp. such as Clostridium acetobutylicum ATCC 824 and Clostridium perfringens occupied more than 70% of total number of sequences at pH 1–3. On the other hand, in the control (no pretreatment) and at pH 4, lactic acid bacteria such as Lactobacillus and Streptococcus were found to be the dominant genus (>90% of total number of sequences), resulting in a low H₂ yield. In addition, the effect of substrate concentration on H₂ fermentation was investigated, and the maximum H₂ productivity was estimated to be 27.2 L H₂/L/d by Andrew's model.