Quantification of Se-Methylselenocysteine and Its γ-Glutamyl Derivative from Naturally Se-Enriched Green Bean (Phaseolus vulgaris vulgaris) After HPLC-ESI-TOF-MS and Orbitrap MS n -Based Identification

Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-methylselenocysteine and γ-glutamyl-Se-methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes.     

Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system.     

The mechanism of oxidation of copper in alkaline solutions

The formation of Cu₂O by the oxidation of Cu in alkaline solutions under various controlled potential conditions has been studied by potentiodynamic methods, the rotating ring disc technique and by employing colloidal Cu(OH)₂ electrodes supported on vitreous carbon.The kinetics of the electrochemical reactions, both anodic and cathodic, are interpreted in terms of a complex reaction mechanism involving various intermediates participating in the phase oxide formation, (e.g. adsorbed OH, soluble Cu(I) and metal sites of different activity).Besides the electrochemical reactions the model includes various ageing and surface restructuring processes. The growth mechanism is envisaged to depend on the conditions of oxidation.     

Dietary intakes and food sources of fatty acids for Belgian women, focused on n-6 and n-3 polyunsaturated fatty acids

The intake of fat, saturated and monounsaturated FA (SFA and MUFA), and omega-6 and omega-3 PUFA has been estimated in 641 Belgian women (age 18-39 y). Their food intake was recorded using a 2-d food diary. The PUFA included were linoleic (LA), alpha-linolenic (LNA), arachidonic (AA), eicosapentaeonoic (EPA), docosapentaenoic (DPA) and docosahexaenoic (DHA) acids. The mean total fat intake corresponded to 34.3% of total energy intake (E). The mean intake of the FA groups corresponded to 13.7%, 13.1%, and 6.0% of E, for SFA, MUFA, and PUFA, respectively. The mean intake of LA was 5.3% of E and of LNA was 0.6% of E, with a mean LA/LNA ratio of 8.7. The mean intake of AA was 0.03% of E. The mean intake of EPA, DPA, and DHA was 0.4%, 0.01%, and 0.06% of E, respectively. According to the Belgian recommendations, the total fat and SFA intake was too high for about three-quarters of the population. The mean LA and overall n-6 PUFA intake corresponded with the recommendation, with part of the population exceeding the upper level. Conversely, the population showed a large deficit for LNA and n-3 PUFA. The major food source for LA and LNA was fats and oils, followed by cereal products. The main sources of long-chain PUFA were fish and seafood, and meat, poultry, and eggs. From a public health perspective, it seems desirable to tackle the problem of low n-3 PUFA intake.     

Coke Formation on Pt?CSn/Al2O3 Catalyst in Propane Dehydrogenation: Coke Characterization and Kinetic Study

The influences of gas compositions on the rates of coke formation over a Pt?CSn/Al₂O₃ catalyst are studied. The coke formed on the catalyst is characterized by thermal gravimetric analysis, IR spectroscopy, Raman spectroscopy and elemental analysis. Two kinds of coke are identified from the TPO profiles and assigned to the coke on the metal and the coke on the support, respectively. The coke formed on the metal is softer (containing more hydrogen) than that formed on the support. The rate of coke formation on the metal is weakly dependent on the propylene and hydrogen pressures but increasing with the propane pressure, while the rate of coke formation on the support is increasing with the propane and propylene pressures and decreasing with the hydrogen pressure. Based on the kinetic analysis, a mechanism for the coke formation on the Pt?CSn/Al₂O₃ catalyst is proposed, and the dimerization of adsorbed C₃H₆ is identified to be the kinetic relevant step for coke formation on the metal.     

氨气/甲烷贫预混旋转湍流火焰稳定性及NO生成

为了研究氨气/甲烷掺混燃气在贫预混旋转湍流状态下的火焰稳定性及NO的排放特性,设计建造了一个可视化的旋转湍流燃烧装置,开展了一系列的实验测量研究。研究表明：随着当量比增大,氨气火焰稳定燃烧的范围有所扩大,但当氨气掺混比大于0.60时火焰出现上下振荡现象,继续增加将导致火焰吹熄;NO的排放水平随当量比增加而提高;但在相同的当量比下,NO的排放随氨气掺混比的增加先升高再下降。此外,分别采用化学反应器网络（CRN）方法和一维层流预混火焰计算方法,对相应的火焰状态进行了数值计算分析,虽然计算结果与实验结果误差较大,但其预测的NO排放特性随氨气掺混比、当量比的变化趋势是一致的,对三者之间误差的来源进行了分析。     

我国地域经济差异与人口迁移研究

改革开放后的区域经济差异持续扩大是促动我国人口迁移空前活跃的主要因素,而日趋活跃的人口迁移亦对区域经济差异产生均衡作用。本文通过测算我国1985-2000年各省区在人口迁移前后“人口—GDP”的基尼系数变化,验证了人口迁移对区域经济发展不均衡的减缓作用。在此基础上,测算区域经济达到均衡状态下的各省区理论人口和人口迁移潜力,并重点分析了县一级行政地域的理论人口和人口迁移潜力分布。     

A digital system for surface roughness analysis of plane and cylindrical parts

This paper describes an on-line system for digital analysis of surfaces where the electrical signal from a surface roughness instrument is converted and input into a desk-top computer which also controls the traversing. Special fixtures integrated with the system and dedicated software permit two- and three-dimensional tracings to be carried out on plane as well as on cylindrical parts. The surface profiles can be plotted in different ways. Roughness parameters, frequency spectra etc, can be computed digitally and all results can be stored. Scratches and irregularities on the surface can be identified and processed separately from the rest of the surface. The desk-top computer is connected to the university mainframe computer through a modem, this being of advantage in connection with graphic data processing. The capability of the equipment has been investigated and results from calibration are presented.     

Analytical and experimental characterisation of high-precision flexural pivots subjected to lateral loads

This work addresses the parasitic motion of high-precision rotation mechanisms based on flexural pivots subjected to lateral loads. This case has great importance from the mechanical design point of view, since generally flexural pivots support mechanical elements of considerable weight and their rotation is obtained by loading the pivot with a force instead of a pure couple.

From an analytical point of view, the problem is approached by studying the large deflections of an elastic frame. The equilibrium equations are considered and a solution based on the Newton–Raphson method is proposed. This approach is compared with other theoretical approaches. An experimental assessment performed by using laser interferometric techniques is presented. It is shown that the proposed solution allows the influence of lateral loads to be clearly established and proves to be adequate when the most common cases of limited lateral loads and rotations are considered.