Greener synthesis of dimethyl carbonate using a novel tin-zirconia/graphene nanocomposite catalyst

© 2017 A green, rapid and continuous hydrothermal flow synthesis (CHFS) route has been employed to synthesise highly efficient and active novel heterogeneous catalysts. Tin doped zirconia (Zr–Sn–O) and tin doped zirconia/graphene nanocomposite (Zr–Sn/GO) have been assessed as suitable heterogeneous catalysts for the synthesis of dimethyl carbonate (DMC). The catalysts have been extensively characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area measurement and X-ray photoelectron spectroscopy (XPS) analysis. Extensive batch studies for the synthesis of DMC via the transesterification of propylene carbonate (PC) and methanol (MeOH) using Zr–Sn/GO catalyst in a solvent free process were also conducted. The effect of various reaction conditions such as reactant molar ratio, catalyst loading, reaction temperature and reaction time has been extensively evaluated. Response surface methodology based on Box-Behneken Design (BBD) was employed to derive optimum conditions for maximising PC conversion and DMC yield. The correlations and interactions between various variables such as MeOH:PC ratio, catalyst loading, reaction temperature, reaction time and stirring speed were extensively studied. A quadratic model by multiple regression analysis for the PC conversion and DMC yield was developed and verified by several methods BBD revealed that optimum conditions for high yield values of DMC are 12.33:1 MeOH:PC molar ratio, 446.7 K, 4.08 h and 300 rpm using 2.9% (w/w) Zr–Sn/GO nanocomposite. The maximum predicted responses at the optimum conditions are 85.1% and 81% for PC conversion and yield of DMC respectively. Experimental results at optimum model predicted reaction conditions agree very well with the model predicted response, where 82.4% PC conversion and 78.2% yield of DMC were obtained. Catalyst reusability and stability studies have been conducted at optimum reaction condition to investigate the long term stability of Zr–Sn/GO and it has been found that the catalyst could be reused more than six times (about 42 h) without losing its catalytic activity. These experimental and model predicted values showed an excellent agreement for tin doped zirconia/graphene nanocomposite as a heterogeneous catalyst for the synthesis of DMC from PC and MeOH

Effect of Ramadan fasting on glucose, glycosylated haemoglobin, insulin, lipids and proteinous concentrations in women with non-insulin dependent diabetes mellitus

The objective of this study was to investigate the effect of Ramadan fasting on body mass index (BMI) and on certain biochemical parameters of serum in women patients with non-insulin dependent diabetes mellitus. Sixty-six subjects from 3 regions located in the west of Algeria participated in this study. All participating patients were studied a week before Ramadan and at the third week of Ramadan fasting. No statistically significant fluctuations were noted in BMI either during Ramadan or in nonfasting days. However, the rates of glycosylated haemoglobin (HbA1c) decreased slightly (P < 0.05) during the last week of the month of Ramadan among the diabetic patients. Also, the glucose levelswere significantly (p < 0.05) higher in the serum subjects of patients during the fasting period when compared to the level before Ramadan. This could be due to the significant decrease (P < 0.05) of insulin levels in patients during the fasting period. The rates of HDL cholesterol recorded in the blood among patients rose significantly (p < 0.05) during the Ramadan than during the non-fasting period. The statistically significant increase in HDL-cholesterol explains clearly the beneficial effect of Ramadan fasting on diabetic’s serum lipids. Moreover, serum total cholesterol, triglyceride, LDL cholesterol and VLDL cholesterol levels decreased significantly (p < 0.05) during the third week of Ramadan than nonfasting day. As for proteinous compounds (protein, creatin and urea), their plasmatic rates all increased substantially (p < 0.05) in patients during the fasting period of the month of Ramadan

Carbonic Anhydrase Activators: Gold Nanoparticles Coated with Derivatized Histamine, Histidine, and Carnosine Show Enhanced Activatory Effects on Several Mammalian Isoforms.

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Structure and Strength of Dislocation Junctions: An Atomic Level Analysis

The quasicontinuum method is used to simulate three-dimensional Lomer-Cottrell junctions both in the absence and in the presence of an applied stress. The simulations show that this type of junction is destroyed by an unzipping mechanism in which the dislocations that form the junction are gradually pulled apart along the junction segment. The calculated critical stress needed for breaking the junction is comparable to that predicted by line tension models. The simulations also demonstrate a strong influence of the initial dislocation line directions on the breaking mechanism, an effect that is neglected in the macroscopic treatment of the hardening effect of junctions.Comment: 4 pages, 3 figure

Analysis of some networks with local interaction

Projet MEVALIn this paper we study a stochastic network model introduced recently in the analysis of neural networks. In this model the interaction between the nodes of the network is local : to each node is associated some real number (the inhibition in the language of neural networks) which is decreasing linearly with time. When this number reaches 0, it sends out some random input to its neighbors (a spike) and restarts with some random value. We are interested in the asymptotic behavior of the network, that is under which conditions the nodes do not die (i.e. their inhibition is not converging to infinity). When these conditions are not satisfied, we analyze the set of nodes which are likely to die. We consider networks with a finite number of nodes and two kind of topologies, the fully connected network and related graphs and the linear network where the nodes are located on a line. A quantity p is associated to this network and the stability properties of the network depend only on it. For the fully connected network, we give the necessary and sufficient condition for the stability of the network (p < 1) as well as the explicit expression for the invariant measure of the Markov process associated to this model. For the stability of the linear network of size N, we prove that the critical value for p is 1/2 if N is odd, otherwise it is the constant.F(1;2cos p/(N+1)). When the network is not stable, the set of possible asymptotic states is analyzed

Techno-Functional properties of whey protein concentrates

Introduction. Whey proteins are well known for their nutritional value but also their functional properties because of their gelling and inter-facial properties. Objective. To extract whey protein concentrates and to study some techno-functional properties of these proteins. Material and methods. The whey proteins were obtained by thermo-precipitation. The techno-functional properties of these proteins (solubility, foaming and emulsification) were evaluated by comparison with bovine serum albumin (BSA). Results. The whey protein concentrates were soluble at pH 4 and 7. The foam expansion of whey proteins (7.00%) was significantly lower than that of BSA (73.33%) whereas the foam stability of whey proteins was significantly higher than that of BSA (p<0.01). The emulsifying properties of the whey protein concentrates were maximal at pH 4 and the emulsifying stability rating was maximal at pH 2. Conclusion. The whey protein concentrates are characterized by a very good solubility and an excellent emulsifying properties and foam stability. The whey proteins could also be useful in food manufacturing due to their functionalit

Mesoscopic Analysis of Structure and Strength of Dislocation Junctions in FCC Metals

We develop a finite element based dislocation dynamics model to simulate the structure and strength of dislocation junctions in FCC crystals. The model is based on anisotropic elasticity theory supplemented by the explicit inclusion of the separation of perfect dislocations into partial dislocations bounding a stacking fault. We demonstrate that the model reproduces in precise detail the structure of the Lomer-Cottrell lock already obtained from atomistic simulations. In light of this success, we also examine the strength of junctions culminating in a stress-strength diagram which is the locus of points in stress space corresponding to dissolution of the junction.Comment: 9 Pages + 4 Figure

Analysis of a neural network model

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Limits on the neutrino magnetic moment from the MUNU experiment

The MUNU experiment was carried out at the Bugey nuclear power reactor. The aim was the study of electron antineutrino-electron elastic scattering at low energy. The recoil electrons were recorded in a gas time projection chamber, immersed in a tank filled with liquid scintillator serving as veto detector, suppressing in particular Compton electrons. The measured electron recoil spectrum is presented. Upper limits on the neutrino magnetic moment were derived and are discussed.Comment: 9 pages, 7 figures Added reference: p.3, 1st col., TEXONO Added sentence: p.4, 1st col., electron attachement Modified sentence: p.5, 1st col., readout sequence Added sentence: p.5, 1st col., fast rise time cu

Screening for Active Small Molecules in Mitochondrial Complex I Deficient Patient's Fibroblasts, Reveals AICAR as the Most Beneficial Compound

Congenital deficiency of the mitochondrial respiratory chain complex I (CI) is a common defect of oxidative phosphorylation (OXPHOS). Despite major advances in the biochemical and molecular diagnostics and the deciphering of CI structure, function assembly and pathomechanism, there is currently no satisfactory cure for patients with mitochondrial complex I defects. Small molecules provide one feasible therapeutic option, however their use has not been systematically evaluated using a standardized experimental system. In order to evaluate potentially therapeutic compounds, we set up a relatively simple system measuring different parameters using only a small amount of patient's fibroblasts, in glucose free medium, where growth is highly OXPOS dependent. Ten different compounds were screened using fibroblasts derived from seven CI patients, harboring different mutations