Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.     

纤维缠绕复合材料环形容器设计优化(英文)

纤维缠绕环形容器可充分利用空间,节省结构质量和消除系统质心漂移,目前在很多工业领域中发挥着日益重要的作用。本文基于复合材料层合理论和测地线缠绕原理,提出了纤维缠绕环形压力容器的线型优化设计方法。应用微分几何,导出了圆环面上测地缠绕轨迹和纤维不架空判据。以初始缠绕角和缠绕层厚度为变量,对结构重量进行最小化设计,得到了对应于不同管径比的优化缠绕线型。对优化线型进行了计算机缠绕仿真,并给出了缠绕铺层的各向正轴应力分布。结果表明,优化设计的缠绕线型模式精确可靠,满足纤维缠绕的基本要求。纤维缠绕角度大小更趋于合理,从而能充分发挥缠绕结构的力学性能,减经系统重量,使优化得到的环形容器结构性能比传统测地线缠绕环形容器有很大提高。本文的设计计算方法可直接用于复合材料环形气瓶的初步设计。     

A single administration of testosterone induces cardiac accelerative responses to angry faces in healthy young women.

Recently, it was demonstrated how individuals with high levels of testosterone selectively attend toward angry faces. It was argued that this suggests that high levels of testosterone are associated with an aggressive, dominating personality style. In this study, the authors used a double-blind, placebo-controlled design to examine whether exogenous testosterone would induce cardiac acceleration in response to angry faces. Participants (healthy young women) were exposed to neutral, happy, or angry faces. Administration of a single dosage of testosterone (0.5 mg) induced an accelerative cardiac response to angry faces. It is argued that this effect is due to the encouragement of dominance behavior and the inclination toward aggression. Possible mechanisms behind testosterone-driven changes in behavior are discussed with relevance to steroid-responsive networks in the limbic system that drive and control motivational and physiological aspects of social behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Novelty-dependent learning and topological mapping

Unsupervised topological ordering, similar to Kohonen's (1982, Biological Cybernetics, 43: 59-69) self-organizing feature map, was achieved in a connectionist module for competitive learning (a CALM Map) by internally regulating the learning rate and the size of the active neighbourhood on the basis of input novelty. In this module, winner-take-all competition and the 'activity bubble' are due tograded lateral inhibition between units. It tends to separate representations as far apart as possible, which leads to interpolation abilities and an absence of catastrophic interference when the interfering set of patterns forms an interpolated set of the initial data set. More than the Kohonen maps, these maps provide an opportunity for building psychologically and neurophysiologically motivated multimodular connectionist models. As an example, the dual pathway connectionist model for fear conditioning by Armony et al. (1997, Trends in Cognitive Science, 1: 28-34) was rebuilt and extended with CALM Maps. If the detection of novelty enhances memory encoding in a canonical circuit, such as the CALM Map, this could explain the finding of large distributed networks for novelty detection (e.g. Knight and Scabini, 1998, Journal of Clinical Neurophysiology, 15: 3-13) in the brain.     

Evaluation of (4‐Arylpiperidin‐1‐yl)cyclopentanecarboxamides As High‐Affinity and Long‐Residence‐Time Antagonists for the CCR2 Receptor

Animal models suggest that the chemokine ligand 2/CC‐chemokine receptor 2 (CCL2/CCR2) axis plays an important role in the development of inflammatory diseases. However, CCR2 antagonists have failed in clinical trials because of a lack of efficacy. We previously described a new approach for the design of CCR2 antagonists by the use of structure–kinetics relationships (SKRs). Herein we report new findings on the structure–affinity relationships (SARs) and SKRs of the reference compound MK‐0483, its diastereomers, and its structural analogues as CCR2 antagonists. The SARs of the 4‐arylpiperidine group suggest that lipophilic hydrogen‐bond‐accepting substituents at the 3‐position are favorable. However, the SKRs suggest that a lipophilic group with a certain size is desired [e.g., 3‐Br: K_i=2.8 nM , residence time (t_res)=243 min; 3‐iPr: K_i=3.6 nM , t_res=266 min]. Alternatively, additional substituents and further optimization of the molecule, while keeping a carboxylic acid at the 3‐position, can also prolong t_res; this was most prominently observed in MK‐0483 (K_i=1.2 nM , t_res=724 min) and a close analogue (K_i=7.8 nM ) with a short residence time.     

Morphology and thermal properties of maleic anhydride grafted polypropylene/ethylene–vinyl acetate copolymer/wood powder blend composites

Maleic anhydride grafted polypropylene (MAPP) was blended with ethylene–vinyl acetate (EVA) copolymer to form MAPP/EVA polymer blends. Wood powder (WP) was mixed into these blends at different weight fractions to form MAPP/EVA/WP blend composites. Differential scanning calorimetry (DSC) analysis of the blends showed small melting peaks between those of EVA and MAPP, which indicated interaction and cocrystallization of fractions of EVA and MAPP. The presence of MAPP influenced the EVA crystallization behavior, whereas the MAPP crystallization was not affected by the presence of EVA. Scanning electron microscopy, Fourier transform infrared spectroscopy, and DSC results show that the WP particles in the MAPP/EVA blend were in contact with both the MAPP and EVA phases and that there seemed to be chemical interaction between the different functional groups. This influenced the crystallization behavior, especially of the MAPP phase. The thermogravimetric analysis results show that the MAPP/EVA blend had two degradation steps. An increase in the WP content in the blend composite led to an increase in the onset of the second degradation step but a decrease in onset of the first degradation step. The presence of WP in the blend led to an increase in the modulus but had almost no influence on the tensile strength of the blend. The dynamic mechanical analysis results confirm the interaction between EVA and MAPP and show that the presence of WP only slightly influenced the dynamic mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ruthenacycles and Iridacycles as Catalysts for Asymmetric Transfer Hydrogenation and Racemisation

Ruthenacycles, which are easily prepared in a single step by reaction between enantiopure aromatic amines and [Ru(arene)Cl₂]₂ in the presence of NaOH and KPF₆, are very good asymmetric transfer hydrogenation catalysts. A range of aromatic ketones were reduced using isopropanol in good yields with ee’s up to 98%. Iridacycles, which are prepared in similar fashion from [IrCp*Cl₂]₂ are excellent catalysts for the racemisation of secondary alcohols and chlorohydrins at room temperature. This allowed the development of a new dynamic kinetic resolution of chlorohydrins to the enantiopure epoxides in up to 90% yield and 98% enantiomeric excess (ee) using a mutant of the enzyme Haloalcohol dehalogenase C and an iridacycle as racemisation catalyst.     

Hemicellulose Removal from Hardwood Chips in the Pre-Hydrolysis Step of the Kraft-Based Dissolving Pulp Production Process

Abstract

A pre-hydrolysis step to remove hemicelluloses from mixed hardwood chips consisting of maple, aspen, and birch with a ratio of 7:2:1 has been carried out. The effects of parameters on the pre-hydrolysis such as time, temperature, acetic acid addition, and raw material species, were determined. Different sugars, acetic acid, and furfural formation in the pre-hydrolysis liquor were quantified. The results showed that the pre-hydrolysis is a dynamic process, in which the removal of hemicelluloses increased with time while the conversion of extracted hemicelluloses to monosaccharides due to acid hydrolysis increased and part of the xylose was converted to furfural. The maximum temperature was the most critical parameter for hemicelluloses extraction and conversion, and a temperature of 170°C was the optimum for hemicelluloses extraction with relatively low conversion of xylose to furfural. About 11% of the xylan (in both monomeric and oligomeric forms) was removed at 170°C. Due to the presence of a high amount of xylan, birch produced the highest amount of xylose, followed by maple, and then aspen.     

Regulatory road maps for the integration of intermittent electricity generation: Methodology development and the case of The Netherlands

The envisaged increase in the share of electricity generation from intermittent renewable energy sources (RES-E) like wind and photovoltaics will pose challenges to the existing electricity system. A successful integration of these sources requires a cost-efficient use of system flexibility. The literature on the options to improve system flexibility, and thus the costs of successfully integrating intermittent electricity generating units, is still growing but what is lacking is an overarching systematic view on when to adopt which option in particular energy systems. This paper aims to bridge this gap in literature. We use existing insights on market and network integration of intermittent electricity sources within a regulatory road map framework. The framework allows policy makers and other electricity system stakeholders to arrive at a consistent strategy in dealing with integration issues over a longer period of time. In this contribution we present and explain the framework and apply it for the case of The Netherlands.     

User response and equity considerations regarding emission cap-and-trade schemes for travel

In most countries with greenhouse gas emission reduction commitments, transportation has been relatively spared, thus, far in the targeting of reduction obligations, owing to the supposedly high marginal cost. With the prospect of tightening reduction targets, pressure is, however, mounting to address transportation more seriously in the near term and not to rely solely on medium to long-term breakthroughs of alternative fuel technologies. This means stricter policies at the demand side of the mobility market. In addition to fiscal and spatial policies, cap-and-trade systems have been put forward as a new option that deserves serious consideration. This paper reviews the possibilities and pitfalls of such a system applied to passenger transport. Key concerns are the transaction costs of the system and trade-offs between transaction cost and equity effects. A simple system with low(er) transaction cost is more likely to invoke politically sensitive equity effects. On the basis of the recent upsurge in monitoring and feedback studies, one may also conclude that the organisation and tailoring of the information interfaces for the household/traveller requires still elaborate study and testing.