Some properties and applications of cumulative Kullback–Leibler information

The cumulative Kullback–Leibler information has been proposed recently as a suitable extension of Kullback–Leibler information to the cumulative distribution function. In this paper, we obtain various results on such a measure, with reference to its relation with other information measures and notions of reliability theory. We also provide some lower and upper bounds. A dynamic version of the cumulative Kullback–Leibler information is then proposed for past lifetimes. Furthermore, we investigate its monotonicity property, which is related to some new concepts of relative aging. Moreover, we propose an application to the failure of nanocomponents. Finally, in order to provide an application in image analysis, we introduce the empirical cumulative Kullback–Leibler information and prove an asymptotic result. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemometric and trend analysis of water quality of the South Chennai lakes: an integrated environmental study

In order to bring out the nature of the factors influencing lake water composition, multivariate statistical analysis and trend analysis were performed based on the hydrochemical data of the study area, namely, South Chennai. Change in land use pattern and settlements along the banks of the lakes alters the quality and quantity of the surface water. In the present study, the R‐mode factor analysis and cluster analysis were applied to the geochemical parameters of the water to identify the factors affecting the chemical composition of the lake water. Dendograms of both the seasons give three major clusters, reflecting the groups of unpolluted to moderately polluted, polluted, and heavily polluted stations. The movement of stations from one cluster to another clearly brings out the seasonal variation in the chemical composition of the lake water. The complex hydrochemical data of the surface water were interpreted by condensing them into three major factors. Factor score analysis was used successfully to delineate the stations under study and the role of the contributing factors, and the nature of factors responsible for the variation in chemical composition of the water has been clearly brought out. Results of trend analysis using ArcGIS clearly indicate that the trend in water quality is deteriorating at a faster rate in the eastern part of the study area. It is understood that although natural shifts probably can account for some of the variation, it is most likely that human activities play a major role in affecting the water quality on a regional scale. Copyright © 2014 John Wiley & Sons, Ltd.     

A Chemical Test for Determining Biological Availability of Aged Chemicals in Soil

Abstract

Aging is one of several processes that are known to affect exposure of chemicals to organisms by decreasing the available fraction of chemical contaminants in soil. This phenomenon has important implications in the assessment of the hazards of chemicals and regulations for soil cleanup. Passive sampling devices (PSDs) are potentially direct chemical indicators for assessing bioavailability of pesticides (and other chemicals). PSDs consist of lipophilic material within a semi-permeable membrane, similar to biological systems. In this study, a pesticide mixture was aged in soil for up to eight months. Earthworms and PSDs were placed in soil and chemical uptake into both was determined over time. Uptake rates into PSDs and maximum concentrations were observed to positively correlate with uptake rates and maximum concentrations in earthworms for both of the soil types studied (sandy loam, silt loam). These results indicate that PSDs may be used as a surrogate for earthworms and provide a chemical technique for assessing the availability of aged chemical residues in soil.     

基于离子液体的超级电容在3 V及65 oC老化条件下的铝碳界面效应

相比于传统乙腈电解液体系的超级电容器,离子液体基超级电容器具有工作窗口电压高,能量密度大,不可燃等优点,适用于碳中和时代清洁但不稳定电力领域的大规模储能。然而,目前的工作主要集中在对纽扣型离子液体-超级电容器的研究上,有关软包式离子液体-超级电容器的长循环寿命评测的报道较少。构建可靠的超级电容器用于长时间测试或在高温下开展加速老化测试,应考虑集流体/电极界面的良好接触,以最小化电荷转移电阻。本文以包覆不同碳层的泡沫铝为集流体,研究了超级电容器新系统中的碳-铝界面效应。通过环氧树脂薄膜碳化得到的均匀无定形碳层,相比通过PVDF粘附石墨烯碳层,赋予了铝相和碳相更强的相互作用。此外,为了充分挖掘大离子尺寸的离子液体电解液的潜力,本文采用介孔碳电极实现离子在介孔间的快速扩散。因此,本工作首次制备了由介孔碳电极、离子液体电解液和覆碳三维泡沫铝集流体组成的新结构软包式超级电容器。以自制的容量为37 F的不同软包式超级电容器件,通过3 V、65 ^oC、500 h加速老化试验,研究了其时间依赖性的电化学性能,包括CV测试、恒流充放电测试、电容值、接触电阻、电化学阻抗谱等。相比石墨烯包覆的泡沫铝基器件,无定形碳层包覆的泡沫铝基器件表现出更高的电容保持率。此外,我们还对ESR进行了等效电路拟合,并深入分析了接触电阻、电荷转移电阻、韦伯电阻,研究了C-Al界面对高能量密度超级电容器的高性能和稳定性的影响。500小时老化测试前后的极片表征证实了上述结果。高温、高压条件使粘附石墨烯碳层的泡沫铝界面结构不可靠。而泡沫铝表面原位包覆的碳层在老化过程中表现出较强的相互作用和稳定的结构。这些坚实的数据为面向高能量密度、高功率密度和长循环寿命,进一步优化高窗口电压超级电容器提供了充足的信息。     

Evolution of Cu(In,Ga)Se2 surfaces under water immersion monitored by X-ray photoelectron spectroscopy

Cu(In,Ga)Se₂ absorbers were immerged in deionized water for different times, and specific chemical evolutions were monitored thanks to X-ray photoemission spectroscopy. Cu(In,Ga)Se₂ related dissolution products were studied in water through induced coupled plasma optical emission spectroscopy. From those analyses, specific surface network disorganization was observed, with Cu migration towards the surface, leading to different kinetics of oxidation and dissolution for each element that could be quantified.     

Dos(e)Age: Role of Dose and Age in the Long-Term Effect of Cannabinoids on Cognition

Cannabis is still the most widely used illicit drug around the world. While its use has always been prevalent among adolescents, recent evidence suggests that its consumption is also increasing among other population groups, such as pregnant women and aged people. Given the known impact of cannabis on brain development and behavior, it is important to dissect the possible long-term impact of its use across different age groups, especially on measures of cognitive performance. Animal models of cannabinoid exposure have represented a fundamental tool to characterize the long-lasting consequences of cannabinoids on cognitive performance and helped to identify possible factors that could modulate cannabinoids effects in the long term, such as the age of exposure and doses administered. This scoping review was systematically conducted using PubMed and includes papers published from 2015 to December 2021 that examined the effects of cannabinoids, either natural or synthetic, on cognitive performance in animal models where exposure occurred in the prenatal period, during adolescence, or in older animals. Overall, available data clearly point to a crucial role of age in determining the long-term effect of cannabinoid on cognition, highlighting possible detrimental consequences during brain development (prenatal and adolescent exposure) and beneficial outcomes in old age. In contrast, despite the recent advances in the field, it appears difficult to clearly establish a possible role of dosage in the effects of cannabinoids on cognition, especially when the adolescent period is taken into account.     

有机玻璃自然老化和人工老化疲劳寿命的当量关系

根据有机玻璃人工加速老化的机理与自然老化的机理保持一致的原则,导出有机玻璃在应力作用下,其疲劳寿命与所接受的太阳紫外总辐射量及作用在其上应力之间的关系式;将该关系式应用于工程上,大大减少老化试验次数.将自然老化后与未老化的有机玻璃的疲劳强度进行比较,建立其疲劳强度下降率的变化规律关系式,可以估算在不同自然老化时期和在不同疲劳寿命下的疲劳强度下降率或疲劳强度.     

Enthalpy relaxation in a partially cured epoxy resin

The enthalpy relaxation of a partially cured (70%) epoxy resin, derived from diglycidyl ether of bisphenol-A cured by methyl-tetrahydrophthalic anhydride with accelerator, has been investigated. The key parameters of the structural relaxation (the apparent activation energy Δh*, the nonlinearity parameter x, and the nonexponentiality parameter β) are compared with those of the fully cured epoxy resin. The aging rates, characterized by the dependences of the enthalpy loss and peak temperature on log(annealing time), are greater in the partially cured epoxy than they are in the fully cured resin at an equivalent aging temperature (T_a = T_g − 20°C). There is a significant reduction in Δh*, from 1100 kJ mol⁻¹ for the fully cured system to 615 kJ mol⁻¹, as the degree of cure is reduced. The parameter x determined by the peak-shift method appears essentially independent of the degree of cure (x = 0.41 ± 0.03 for the partially cured resin compared with 0.42 ± 0.03 obtained previously for the fully cured resin), and does not follow the usually observed correlation of increasing x as Δh* decreases. This invariability of the parameter x seems to indicate that it is determined essentially by the local chemical structure of the backbone chain, and rather little by the supramolecular structure. On the other hand, the estimated nonexponentiality parameter β lies between 0.3 and 0.456, which is significantly lower than in the fully cured epoxy (β ≅ 0.5), indicative of a broadening of the distribution of relaxation times as the degree of cross-linking is reduced. Like the parameter x, this also does not follow the usual correlation with Δh*. These results are discussed in the framework of strong and fragile behavior of glass-forming systems, but it is difficult to reconcile these results in any simple way with the concept of strength and fragility. © 1996 John Wiley & Sons, Inc.     

STUDY ON THE PROPERTIES OF BLEND OF NATURAL RUBBER LATEX/METHYL METHACRYLATE GRAFTED RUBBER LATEX BY GAMMA RADIATION

Natural rubber latex(NRL)and methyl methacrylate(MMA)grafted rubber latex were blended in different ratios and irradiated at various absorbed doses by gamma rays from Co-60 source at room temperature.The tensile properties, swelling ratio and permanent set were measured.The maximum tensile strength and modulus at 500% elongation were obtained at an absorbed dose of 8 kGy.Modulus increases from 6.99 MPa to 9.87 MPa for an increase in proportion of MMA grafted rubber from 40% to 60% in the blend at similar absorbed dose.Elongation at break and swelling ratio decrease with increasing absorbed dose as well as the MMA grafted rubber content in the blends.The decreasing trend of permanent set is high up to 5 kGy absorbed dose,and beyond that dose,it becomes almost flat.