One-step synthesis of graphene supported platinum nanoparticles as electrocatalyst for PEM fuel cells

Here in, we describe an ultrafast, single-step microwave irradiation route (MW) to prepare graphene supported Pt nanoparticles, during which the small Pt nanoparticles are distributed uniformly on a reduced graphene oxide surface. This route provides evident advantages namely low cost, easiness, low time consuming and high yield in comparison to actual chemical methods to develop efficient Pt/rGO catalyst with Pt content close to state-of-the-art commercial composition. The structure and composition of prepared samples have been studied by specific techniques, while the electrocatalytic stability has been studied using ex-situ and in-situ measurements. High performance and electrochemically stable catalyst for PEM fuel cells was developed using the sample with highest loading and good dispersion. The fabricated Pt-rGO-based MEA was investigated for durability under fuel starvation in comparison with commercial Pt/C-based MEA. The electrocatalytic activity was investigated and the electrochemical response revealed the higher stability during accelerated degradation test under fuel starvation in comparison with commercial Pt/C. This study promotes the applicability of described preparation method to noble or transition metal nanoparticles embedded on graphene-based materials.     

Phytoextraction technologies for mercury- and chromium-contaminated soil: a review

Mercury and chromium represent two important elements of environmental concern and with a strong impact on human health. Several technologies are available to clean up the environment from these kinds of contaminants, but most of them are costly and difficult to use to get optimum results. Currently, phytoextraction is an effective and affordable technological solution used to extract or remove metals from contaminated soil and water by the use of plants as tools. This technology is environment-friendly and potentially cost-effective. This paper aims to compile some information about the two metals mercury and chromium, their effects and their possible treatment by phytoextraction, a branch of phytoremediation technologies aimed to confront metal/metalloid pollution. © 2019 Society of Chemical Industry     

Street names in Dakar-Plateau: a colonial and post-colonial perspective

ABSTRACT

This article revolves around the naming of streets in Dakar-Plateau. This was borne in mind as analysis considered the system of urban nomenclature applied in the colonial era, when the city was founded and shaped by France’s colonial administration; as well as the (re)naming process ongoing after Senegal’s independence. The approach thus applied quantitative verification methods to a thesis oft-repeated in the subject literature, that a French glossary of toponyms dominates the system by which streets in Dakar are named. Quantitative analysis here shows unequivocally that there is only a slight numerical prevalence of colonial-era names of streets over new names. Beyond that, clear evidence is offered for the idea that, in both colonial days and today, the symbolic urban landscape expressed with the aid of urbanonyms was shaped by authorities in a conscious manner, being pressed into the service of political objectives. To indicate the strength of this kind of linkage, the article engages in the detailed discussion of each change of name that certain streets have been through; the bases for this approach being reference to the historical town/city plans present in the Archives Nationales du Sénégal, as well as fieldwork carried out in the Senegalese capital.     

Study of thermal behavior of polyimides containing pendent-substituted azobenzene units

Thermal stability and degradation kinetic of the polyimides containing pendent-substituted azobenzene units were investigated by thermogravimetric analysis in nitrogen at different heating rates. Freeman–Carroll, Coats–Redfern and Flynn–Wall–Ozawa methods were utilized to obtain the kinetic parameters (activation energy E _a, pre-exponential factor A and order of reaction n) or variation of activation energy with conversion degree from thermogravimetric and derivative thermogravimetric curves. The thermogravimetric analysis revealed that the decomposition of azopolyimides proceeds in three or four stages, regardless of heating rate.     

Cancer Stem Cells: Biological Functions and Therapeutically Targeting

Almost all tumors are composed of a heterogeneous cell population, making them difficult to treat. A small cancer stem cell population with a low proliferation rate and a high tumorigenic potential is thought to be responsible for cancer development, metastasis and resistance to therapy. Stem cells were reported to be involved in both normal development and carcinogenesis, some molecular mechanisms being common in both processes. No less controversial, stem cells are considered to be important in treatment of malignant diseases both as targets and drug carriers. The efforts to understand the role of different signalling in cancer stem cells requires in depth knowledge about the mechanisms that control their self-renewal, differentiation and malignant potential. The aim of this paper is to discuss insights into cancer stem cells historical background and to provide a brief review of the new therapeutic strategies for targeting cancer stem cells.     

High Frequency Ultrasonic Investigation for Ceramic Materials to Test the Manufacturing Process

Abstract

High frequency ultrasonic techniques for nondestructive tests of fine grained ceramic materials are presented. Green and partially sintered are considered. To this purpose, ultrasonic velocities and attenuation were measured and correlated to the porosity degree reached in different phases of the manufacturing process. A physical understanding of the experimental results is achieved by comparing them with the theoretical predictions provided by a self consistent scattering theory introduced in the 1980s. Finally, porosity maps are proposed since they give a comprehensive view of the process quality.     

从结构主义到想象艺术

正家具最早出现在人类生活中时,是作为提高生活效率的"器具"使用的,它具备基础的功能性,外型和整体架构都十分简单。随着人类社会的不断演变,家具的存在早已被附上一层又一层的定义,设计师们的想象力通过家具的外型得以展现;而它的内部结构,成为展示制造工艺的最好平台;它的质感与视觉效果,通过材料的异同展现出不一样的姿态。荷兰设计师Oato所设计的Stuck Chair映射了工     

Influence of partial dealcoholization by reverse osmosis on red wine composition and sensory characteristics

Two red wines with a very high ethanol content were partially dealcoholized by reverse osmosis, so that the influence of this technique on wine color, chemical composition and sensory quality could be studied. No statistically significant differences were found in pH, color intensity, total phenolic index, proanthocyanidin concentration and their mean degree of polymerization between control wines and partially dealcoholized wines (?1 and ?2 vol. %). Some slight but significant differences were found in titratable acidity, anthocyanins, CIELab coordinates and polysaccharides. However, these differences were really quite small and only significant in a few cases. Moreover, a trained panel of tasters had severe difficulty in distinguishing between control and partially dealcoholized wines in triangular tests, and results were statistically significant only in some of the comparisons. It is concluded that this technique can be very useful for the partial dealcoholization of red wines because they hardly alter their composition and sensory characteristics.     

Nanocomposite piezoelectric films of P(VDF‐TrFE)/LiNbO3

Piezoelectric films were prepared by incorporation of lithium niobate (LiNbO₃) nanoparticles into copolymer of vinylidene difluoride and trifluoroethylene. Nanoparticles of LiNbO₃ with ferroelectric phase were successfully synthesized and dispersed homogenously by ultrasonication in the copolymer matrix without any surfactant or surface functionalization. The nanocomposites were fully characterized by electronic microscopy, X‐ray diffraction, differential scanning calorimetry, dynamical mechanical analysis, and piezometer. Surprisingly, the copolymer matrix crystallinity and morphology were not affected by the incorporation of nanoparticles. Therefore the nanocomposites remained good mechanicals properties and high ferroelectricity coupled to nonlinear optical activity thanks to the noncentro symmetric space group of lithium niobate. This could be a novel approach to develop new multifunctional materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013