Direct evidence of oxygen evolution from Li1+ x (Ni1/3Mn1/3Co1/3)1? x O2 at high potentials

Li_1+x (Ni_1/3Mn_1/3Co_1/3)_1−x O₂ (NMC) oxides are among the most promising positive electrode materials for future lithium–ion batteries. A voltage “plateau” was observed on the first galvanostatic charging curve of NMC in the extended voltage region positive to 4.5 V vs. Li/Li⁺ for compounds with x > 0 (overlithiated compounds). Differences were observed in the cycling stability of the overlithiated and stoichiometric (x = 0) NMC oxides in this potential region. A differential plot of the charge vs. potential profile in the first cycle revealed that, for the overlithiated compounds, a large irreversible oxidative peak arises positive to 4.5 V vs. Li/Li⁺, while in the same potential region only a small peak due to the electrolyte oxidation is detected for the stoichiometric material. Differential Electrochemical Mass Spectrometry (DEMS) was used to investigate the high voltage region for both compounds and experimental evidence for oxygen evolution was provided for the overlithiated compounds at potentials positive to 4.5 V vs. Li/Li⁺. No oxygen evolution was detected for the stoichiometric compound.     

Aerobic exercise and normotensive adults: a meta-analysis

Using the meta-analytic approach, the purpose of this study was to examine the effects of aerobic exercise on resting systolic (SYS) and diastolic (DIA) blood pressure in normotensive adults: The results of 35 human clinical training studies published in English-language journals between 1963 and 1992 and representing 1,076 subjects (800 exercise, 276 control) met criteria for inclusion. Across all categories and designs, statistically significant post-exercise reductions were found for both SYS and DIA blood pressure (mean +/- SD, SYS: -4.4 +/- 6.6 mm Hg, 95% CI, -6.2 to -2.6 mm Hg; DIA: -3.2 +/- 3.2 mm Hg, 95% CI, -4.0 to -2.2 mm Hg). When partitioned according to type of study: 1) (randomized controlled trials (RCT), 2) controlled trials (CT), and 3) no controls (NC), the following changes were noted: RCT, SYS: -4.5 +/- 7.2 mm Hg, 95% CI, -7.1 to -1.2 mm Hg; DIA: -3.8 +/- 2.9 mm Hg, 95% CI, -5.0 to -2.6 mm Hg; CT, SYS: -2.8 +/- 6.9 mm Hg, 95% CI, -10.0 to 4.4 mm Hg; DIA: -5.0 +/- 3.7 mm Hg, 95% CI, -8.9 to -1.1 mm Hg; NC, SYS: -4.7 +/- 6.1 mm Hg, 95% CI, -7.5 to 1.9 mm Hg; DIA: -1.7 +/- 3.0 mm Hg, 95% CI, -3.2 to -0.36 mm Hg. We concluded that aerobic exercise results in small reductions in resting SYS and DIA blood pressure among normotensive adults.     

Near-infrared spectrometric determination of di- and tripeptides synthesized by a combinatorial solid-phase method

A new method based on near-infrared (NIR) spectrometry and partial least-squares analysis has been developed for the noninvasive and nondestructive determination of the identity and sequences of amino acid residues in di- and tripeptides. The di- and tripeptides were synthesized from six amino acids with similar structures (Gly, Ala, Leu, Met, Phe, Val) on two different polymer beads (bead with and without a linker) using the solid-phase peptide synthetic method. The developed NIR method is capable of determining the identity of sequences of these di- and tripeptides (with and without the Fmoc protecting group) directly on the polymer beads. It can distinguish not only dipeptides from tripeptides but also peptides with very similar structures (e.g., bead-Gly-Ala-Ala, bead-Gly-Ala-Phe, bead-Gly-Ala-Leu, bead-Gly-Ala-Val, and bead-Gly-Ala-Met). More importantly, the method is capable of distinguishing di- and tripeptides with the same amino acid residues but different sequences (e.g., bead-Gly-Leu-Val from bead-Gly-Val-Leu).     

Sum of arbitrarily correlated Gamma variates and performance of wireless communication systems over Nakagami-m fading channels

The probability density function (PDF) and the moment generating function (MGF) of a sum of squares of arbitrarily correlated, non-identically distributed Nakagami-m random variates, with non-identical and non-integer fading orders are derived. The authors proposed a simple method to determine a good truncation of the PDFs infinite sum and the associated truncation error. The derived results can be used to analyse a number of performance measures of diversity combining techniques in wireless communication systems over Nakagami-m fading channels.     

New tools for electromechanical characterisation of piezoceramics

This paper presents three methods that can be used to characterise piezoelectric integrated structures or materials, based on the resolution of an inverse problem. Analytical models that describe the electrical and/or mechanical behaviour of the material or structure as a function of piezoelastic properties are developed, and the appropriate measurements are carried out on the piezoelectric materials. The fitting of these models with experimental data allows the piezoelastic properties to be determined. Three characterisation methods are described. The first one is based on the electrical impedance measurement of piezoelectric integrated structures. The second one, purely acoustic, is based on the measurement of transmission coefficients of a plane wave through a piezoelectric plate. The third method uses the principle of resonance ultrasound spectroscopy of a piezoelectric cube combined with Laser detection.     

钢渣对水溶液中砷的吸附动力学和热力学特性试验

以炼钢厂固体废弃物钢渣为材料,通过批量平衡吸附法,并结合宏观热力学和动力模型应用,分析和研究了钢渣对水溶As(III)的吸附特征。结果表明钢渣在吸附As(III)过程中,初始阶段吸附量迅速增加,随着浓度的增加,吸附逐渐趋于饱和,最后达到平衡,具有"快速吸附、缓慢平衡"的特点。钢渣吸附材料具有极高的最大吸附容量,高达3.58×104mg/kg。钢渣对As(III)的吸附均符合Langmuir和Freundlich吸附等温线,其中钢渣对As(III)的吸附特征与Freundlich等温吸附方程吻合性最好,相关系数(R2)达到0.99以上。钢渣对As(III)的吸附动力学数据均符合一级动力学方程、Elovich方程和双常数方程,拟合优度用相关系数(R2)为0.92~0.98,相比较而言,钢渣对As(III)的吸附以Elovich方程为最佳模型。