Solid-state grafting of maleic anhydride onto polypropylene: The influence of morphology of polypropylene on heterogeneous reaction

Polypropylene (PP) was modified with maleic anhydride (MAH) via heterogeneous solid-state radical grafting performed in a fluidized polymerization reactor. The effect of PP morphology and different concentration of initiator (dibenzoyl peroxide, DBP) on the course of the reaction and grafting efficiency was evaluated with using infrared spectroscopy, scanning electron microscopy (SEM) and particle surface analysis (BET method). With respect to obtained results, the reaction course can be strongly affected by the reaction conditions and PP morphology. Unlike the reactive modification in melt, heterogeneous reaction exhibits lower extent of β-scission albeit the reaction conversion is lower. Solid-state grafting can be used as an alternative method for the surface modification of nonpolar surfaces with polar monomers under mild conditions.     

硫氧化还原酶热稳定性的结构基础(英文)

The thermostability of three sulfur oxygenase reductases(SORs) was investigated from thermoaci-dophilic achaea Acidianus tengchongensis(SORAT) and Sulfolobus tokodaii(SORST) as well as the moderately thermophilic bacterium Acidithiobacillus sp.SM-1(SORSB).The optimal temperatures for catalyzing sulfur oxida-tion were 80 °C(SORAT),85 °C(SORST),and 70 °C(SORSB),respectively.The half-lives of the three SORs at their optimal catalytic conditions were 100 min(SORAT),58 min(SORST),and 37 min(SORSB).In order to reveal the structural basis of the thermostability of these SORs,three-dimensional structural models of them were generated by homology modeling using the previously reported high-resolution X-ray structure of SORAA(from Acidianus ambivalens) as a template.The results suggest that thermostability was dependent on:(a) high number of the charged amino acid glutamic acid and the flexible amino acid proline,(b) low number of the thermolabile amino acid glutamine,(c) increased number of ion pairs,(d) decreased ratio of hydrophobic accessible solvent surface area(ASA) to charged ASA,and(e) increased volumes of the cavity.The number of cavities and the number of hydro-gen bonds did not significantly affect the thermostability of SORs,whereas the cavity volumes increased as the thermal stability increased.     

Ionic Liquids and their Polymers in Lithium‐Sulfur Batteries

Future optimized lithium‐sulfur batteries may promise higher energy densities than the current standard. However, there are many barriers which hinder their commercialization. In this review we describe how ionic liquids (ILs) and their polymers are utilized in different components of the battery to address some of these issues. For example, IL‐based electrolytes have the potential to reduce the solubility of polysulfides compared to conventional organic electrolytes. Polymerizing ILs directly on the surface of the Li‐metal anode is suggested as an approach to protect the surface of this electrode. Finally, using poly(ionic liquids) (PILs) as binders for the cathode active material may increase the performance of the cathode as compared to polyvinylidene difluoride (PVdF) and could inhibit swelling‐induced degradation. These results demonstrate the advantages of ILs and their polymers for improving the performance of Li?S batteries.     

Gemini Surfactants with Polymethylene Spacer: Supramolecular Structures at Solid Surface and Aggregation in Aqueous Solution

Aggregation of α,ω-bisammonium cationic gemini surfactants with a variable polymethylene spacer and two dodecyl chains has been studied on a solid surface and in aqueous solution. Scanning electron microscopy and dynamic light scattering with the time-resolved fluorescence quenching technique were used for the experiments on the solid surface and in aqueous solution, respectively. As the results from the scanning electron microscopy indicate, the morphology of supramolecular structures of gemini surfactants at the solid surface depends on the spacer length. In aqueous solution, gemini surfactants with spacers consisting of 4, 6, 8, 10, and 12 CH₂ groups form spherical micelles with diameters between 2 and 3.5 nm. Micelles of gemini surfactant with a short ethylene spacer show an increase in size up to 13 nm at the maximum concentration investigated. The aggregation number of micelles determined by time resolved fluorescence quenching was found to be in the range 14–25 for the spacer lengths from 6 to 12 CH₂ groups with only a moderate increase with surfactant concentration. For micelles of gemini surfactants with the short ethylene spacer, the increase of the aggregation number up to 50 at the maximum concentration was observed. The findings support micellar growth of gemini surfactants with short ethylene spacer.     

Fuel cells for civil aircraft application: On-board production of power, water and inert gas

Fuel cell systems are regarded as a promising solution for future electrical energy generation on board of commercial aircraft. In addition to an improved efficiency such systems offer the opportunity of producing water usable for on-board purposes and provide additional functions such as inerting (providing a non-inflammable atmosphere) of the jet fuel tank. This paper presents an evaluation and assessment of different system architectures as well as experimental results demonstrating the feasibility of the multiple functions in a laboratory set-up. First, the conventional system requirements and the results reported by the Federal Aviation Administration (FAA) are discussed. A system design evaluation based on simulating cruise and ground operation of aircraft is performed demonstrating the benefits of systems with pressurized hydrogen tank storage and cabin air use. The requirements for a fuel cell system regarding aircraft inerting function are calculated based on the FAA analysis. Experimental results based on laboratory systems confirm the feasibility of the implementation of various functions with a single fuel cell system. Test platforms for further investigation of the systems are shortly described.     

Innovations in disaster mental health: Psychological first aid.

Professional psychologists are called upon to deal with a broad array of crises and traumatic events. However, training and expertise in crisis response varies widely among practitioners, and there has been considerable controversy about the value of widely disseminated mental health crisis intervention protocols that include "debriefing" as an essential feature. This article gives an overview of the developmental process, guiding principles, and core actions of the Psychological First Aid Field Operations Guide (PFA Guide), which provides guidance for practitioners in responding to immediate mental health needs of children, adults, and families who have recently experienced a disaster or terrorist event. Issues in training, provider self-care, and evaluation research are also presented. The PFA Guide presents approaches thought to be most consistently supported by current research and practice so that they can be taught, used, and evaluated in field settings. Although we expect further refinement as more systematic research becomes available, the PFA Guide represents a sustained collaborative effort to define current evidence-informed best practices that can be utilized now by practitioners involved in disaster mental health responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

带结晶器电磁搅拌的大圆坯连铸的数值模拟

在圆坯连铸中,结晶器电磁搅拌器(M-EMS)是常见的改善钢流内流场的手段。众所周知,液芯的流动对最终产品的质量有着重要影响,用M-EMS能优化凝固前沿的流速,进一步促进柱状晶向等轴晶的转变,进而改善铸坯的表面和皮下缺陷。在奥钢联多纳维茨钢厂,绝大多数产品的生产都应用了M-EMS。由于在奥钢联多纳维茨钢厂的恶劣环境下难于进行测量,因此研究采用数值模拟的方法。连铸过程1:1比例的物理模拟也很难实现,因为水的传导率太低,且液态金属不透明或金属处理难,因此数值模拟就成为获得整个过程较好的重要手段。数值模型考虑了流场和电磁场的完全耦合,许多物理问题都用最优参数进行模拟,流场用商业有限元CFD编码软件FLUENT进行计算,电磁场用商业有限元求解器ANSYSEMAG计算。采用这种方法可以研究各种参数对流场和凝固组织的影响,也能揭示搅拌频率和搅拌强度的变化对液芯内部流场的影响。应用数值模拟能够加深对电磁场下连铸过程的认识,也能够找到优化的参数。     

On average and highest number of flips in pancake sorting

We are given a stack of pancakes of different sizes and the only allowed operation is to take several pancakes from the top and flip them. The unburnt version requires the pancakes to be sorted by their sizes at the end, while in the burnt version they additionally need to be oriented burnt-side down. We are interested in the largest value of the number of flips needed to sort a stack of $n$ pancakes, both in the unburnt version ($f\left(n\right)$) and in the burnt version ($g\left(n\right)$).We present exact values of $f\left(n\right)$ up to $n=19$ and of $g\left(n\right)$ up to $n=17$ and disprove a conjecture of Cohen and Blum by showing that the burnt stack $?I_{15}$ is not the hardest to sort for $n=15$.We also show that sorting a random stack of $n$ unburnt pancakes can be done with at most $17n/12+O\left(1\right)$ flips on average. The average number of flips of the optimal algorithm for sorting stacks of $n$ burnt pancakes is shown to be between $n+\Omega (n/logn)$ and $7n/4+O\left(1\right)$ and we conjecture that it is $n+\Theta (n/logn)$.Finally we show that sorting the stack $?I_n$ needs at least $?(3n+3)/2?$ flips, which slightly increases the lower bound on $g\left(n\right)$. This bound together with the upper bound for sorting $?I_n$ found by Heydari and Sudborough in 1997 [10] gives the exact number of flips to sort it for $n\equiv 3(mod4)$ and $n\ge 15$.     

In vitro production of specific polysaccharides: isolation and structure of an antitumor active β-glucan from Phytophthora parasitica

Polysaccharides are known to be an important group of biological polymers which are of great interest for industrial use. Besides their physical properties, their chemical structures can be the base for specific applications in medicine. Various polysaccharides are known to exhibit an antitumor activity, which is thought to be host mediated by a stimulation of the host's immune system. A β-1.3/1.6-glucan P isolated from the cell walls of Phytophthora parasitica Dastur (Mating type A1, 1828) exhibited strong antitumor activity against Sarcoma-180 in mice. Growth of the fungus was markedly stimulated by β-sitosterol and calcium ions. The fungus was shown to be thiamine heterotroph. At optimal growth conditions up to 30 g (dry weight) of fungal mycelium could be harvested within 5 days in 81 of culture medium, which represented ~6 g of cell wall material. A specific water-soluble cell wall glucan P was isolated by extraction with hot water and purification by ion-exchange and Con A chromatography. By methylation analysis it was shown that the β-glucan consisted of 1.3-, 1.3.6- and terminal-glucose residues in a molar ratio of 5:1:1. Sequential Smith degradations combined with methylation analyses showed the presence of mono- as well as di- and trisaccharides as side chain constituents in a ratio of 9:2:3. A structure of the antitumor active β-1.3/1.6-glucan P is proposed.