Reaction Interface for Heterogeneous Oxidation of Aluminum Powders

Heterogeneous oxidation of aluminum is rate limited by diffusion through a growing aluminum oxide layer. If inward diffusion of oxygen ions is faster than outward diffusion of aluminum, the reaction will occur at the inner interface of the oxide. Conversely, the reaction will occur at the outer oxide surface if outward diffusion of aluminum is faster. The location of the heterogeneous reaction is identified processing results of thermogravimetric measurements for two oxidizing spherical aluminum powders with different but overlapping particle size distribution. For each experiment, the measured weight gain is distributed among particles of different sizes assuming that the rate of oxidation is proportional to the reactive interface area. Different models are considered to determine the interface area. For a ductile oxide shell, when there is no void between oxide and aluminum, two cases with the reaction occurring at both inner and outer surfaces of the shell were evaluated. In addition, a case with the reaction at the outer surface of a rigid oxide shell is considered, for which a void inside the particle forms when the aluminum core is shrinking. Oxidation weight gains for the same size particles present in different aluminum powders are expected to be identical to each other when the calculated reactive interface area reflects the true oxidation mechanism. It is concluded that the reaction at the outer surface of a rigid oxide shell describes the experiments most accurately. Thus, the outward diffusion of aluminum ions controls the rate of heterogeneous oxidation of aluminum in a wide range of temperatures of approximately 400–1500 °C. The conclusion is further supported by the electron microscopy of particles quenched at different temperatures, showing oxide surface features consistent with the identified reaction mechanism

Defect Chemistry of the Metal Cation Defects in the p- and n‑Doped SnO₂ Nanocrystalline Films

Cationic interstitial and substitutional defects, which serve as a key role in shaping the material’s performance, are considered as two kinds of important defect structures in the doped SnO₂. To give a clear characterization of such metal cation defects, temperature-dependent electrical conduction measurement by the high throughput screening platform of gas-sensing materials is carried out, for the first time, to perform the defect structure studies of the p-type (Li⁺, Cd²⁺, Al³⁺), isovalent (Ti⁴⁺), and n-type (Nb⁵⁺, W⁶⁺) doped SnO₂ nanocrystalline films in the oxygen-free atmosphere. The temperature-dependent measurements indicate that subtle induced impurities are capable of evidently modifying the electrical conduction mechanism of the SnO₂. In terms of the small-polaron hopping mechanism, an improved defect chemical model is proposed in which the properties of the metal cation defects are explicitly depicted. Values for the ionization energy (Δ<i>E_D</i>) of the metal cation defects and electron hopping energy (<i>E_H</i>) in the doped SnO₂ are extracted by fitting the experimental data to the defect model. These data that reflect the nature of the metal cation defects and their effects on the electronic structure of the SnO₂ are first introduced here, and the validity of these data are confirmed. What’s more, the Δ<i>E_D</i> calculated here is of critical importance for understanding the defect structure of the metal dopants in the SnO₂

Synchronously Deriving Electron Concentration and Mobility by Temperature- and Oxygen-Dependent Conductivity of Porous ZnO Nanocrystalline Film

A simple and effective way to get electron concentration and mobility accurately is significant for the electronic and photoelectric applications of porous ZnO nanocrystalline film. On the basis of the defect ionization and the electron scattering, we proposed here a new temperature-programmed-dependent conductivity-based synchronous derivation method (TPDCBSD) to evaluate electron concentration and mobility of porous ZnO nanocrystalline film independently. The obtained results were consistent with others. Compared with the commonly used Hall-effect measurements, the TPDCBSD method is much more simple, has lower noise, and is convenient to couple external fields. More importantly, the extracted electron concentration and electron mobility are relatively independent. Besides, a series of physical parameters related to the effects of temperature and oxygen partial pressure were obtained, and the coupling effect of temperature and oxygen was discussed in this work, which are inspiring for the applications of porous ZnO nanocrystalline film

Additional file 2: of A novel approach for metabolic pathway optimization: Oligo-linker mediated assembly (OLMA) method

Sequence of lac Z module and genes involved in lycopene synthetic pathway. (DOC 204 kb

Influence of Vitamin E Supplementation on Glycaemic Control: A Meta-Analysis of Randomised Controlled Trials

<div><p>Observational studies have revealed that higher serum vitamin E concentrations and increased vitamin E intake and vitamin E supplementation are associated with beneficial effects on glycaemic control in type 2 diabetes mellitus (T2DM). However, whether vitamin E supplementation exerts a definitive effect on glycaemic control remains unclear. This article involves a meta-analysis of randomised controlled trials of vitamin E to better characterise its impact on HbA1c, fasting glucose and fasting insulin. PubMed, EMBASE and the Cochrane Library were electronically searched from the earliest possible date through April 2013 for all relevant studies. Weighted mean difference (WMD) was calculated for net changes using fixed-effects or random-effects models. Standard methods for assessing statistical heterogeneity and publication bias were used. Fourteen randomised controlled trials involving individual data on 714 subjects were collected in this meta-analysis. Increased vitamin E supplementation did not result in significant benefits in glycaemic control as measured by reductions in HbA1c, fasting glucose and fasting insulin. Subgroup analyses revealed a significant reduction in HbA1c (−0.58%, 95% CI −0.83 to −0.34) and fasting insulin (−9.0 pmol/l, 95% CI −15.90 to −2.10) compared with controls in patients with low baseline vitamin E status. Subgroup analyses also demonstrated that the outcomes may have been influenced by the vitamin E dosage, study duration, ethnic group, serum HbA1c concentration, and fasting glucose control status. In conclusion, there is currently insufficient evidence to support a potential beneficial effect of vitamin E supplementation on improvements of HbA1c and fasting glucose and insulin concentrations in subjects with T2DM.</p></div

Additional file 1: of A novel approach for metabolic pathway optimization: Oligo-linker mediated assembly (OLMA) method

Supplemental figures and tables used in this study. (DOC 1492 kb

Quality assessment of included studies.

<p>Y, yes; U, unclear; Randomisation:the study described as randomized; Random sequence generation: the correct method for generation of random numbers computer random numbers table, shuffled cards or tossed coins, and minimization; Allocation concealment: Adequate concealment was that up to the point of treatment (eg, central randomisation); Double-blinding: masking to both researchers and patients; Reporting of withdrawals: The numbers and reasons for withdrawal in each group had to be stated for a point to be awarded.</p

Summary of effect sizes (weighted mean difference) for secondary outcomes.

<p>HOMA, homeostasis model assessment; Total-C, total cholesterol; HDL-C, high-density lipoprotein-cholesterol;LDL-C, low-density lipoprotein-cholesterol; CI, confidence interval. T: treatment group; C: control group.</p

Forest plot of randomised controlled trials investigate the effect of vitamin E supplementation on fasting glucose.

<p>Forest plot of randomised controlled trials investigate the effect of vitamin E supplementation on fasting glucose.</p

Forest plot of randomised controlled trials investigate the effect of vitamin E supplementation on fasting insulin.

<p>Forest plot of randomised controlled trials investigate the effect of vitamin E supplementation on fasting insulin.</p