Sulfonated derivatives of polyparaphenylene as proton conducting membranes for direct methanol fuel cell application

Proton conducting polymers derived from polybenzoyl-1,4-phenylene (PBP) and poly-p-phenoxybenzoyl-1,4-phenylene (PPBP) were synthesized by the Colon synthesis technique. The sulfonation of these proton conducting polymers was carried out using either sulphuric acid or tetramethylsiliylchlorosulfonate (TMSCl) as sulfonating agent, and their thermal properties were evaluated. Both sulfonated PBP and PPBP are thermally stable up to at least 215 °C. The sulfonated sPPBP exhibited good conductivity as proton conducting membranes at room temperature and were tested as electrolyte membranes for a single direct methanol fuel cell (DMFC) in terms of water absorption, methanol permeability and electrical performance. The water uptake of the sPPBP was found to be larger than that of the sPBP, i.e., 65 and 43 mol%, respectively. The permeability to methanol was found to be 10 times lower than sPPBP and sPBP compared to a Nafion^® membrane. In spite of this, performance in a single DMFC was found to be twice inferior to that with Nafion^® 117. Optimisation of the sulfonation level and of the electrode-membrane interfaces was lead to better results.     

Roadmap for the design of a superconducting electron cyclotron resonance ion source for Spiral2

A review of today achieved A∕Q = 3 heavy ions beams is proposed. The daily operation A∕Q = 3 ion beam intensities expected at Spiral2 are at the limit or above best record 3rd generation electron cyclotron resonance ion source (ECRIS) intensities. The necessity to build a new fully superconducting to fulfill these requirements is outlined. A discussion on the volume of the future source is proposed and the minimum value of 12 liters is derived. An analysis of the x-ray absorption superconducting ECRIS is presented based on VENUS experimental data and geometry. This study underlines the necessity to include a complete x-ray study at the time of source conception. The specifications foreseen for the new ECRIS are presented, followed with the roadmap for the design.     

Enhancing spatial estimates of metal pollutants in raw wastewater irrigated fields using a topsoil organic carbon map predicted from aerial photography

Various approaches have been used to estimate metal pollutant element (TE) contents at unsampled locations in a 15-ha contaminated site located in the plain of Pierrelaye-Bessancourt (about 24 km Northwest of Paris). 87 samples of soil plough layer were randomly sampled at each mesh of a regular square grid over the whole study area and the total contents of Cd, Cr, Cu, Ni, Pb, and Zn were measured. A first set of 50 measurements, randomly selected from the 87 samples, was used for the prediction and another set of 37 measurements was kept for the validation. Topsoil organic carbon contents (SOC) were measured at 75 sites with 50 measurements sharing the same locations as TE. An aerial photography of the study area showing bare soils was selected for relating brightness intensities and SOC. Mapping procedures used were ordinary kriging (OK), cokriging (COK), collocated cokriging (CC), and kriging with external drift (KED). SOC maps used as exhaustively sampled information in KED and CC of TE were obtained by KED and CC procedures, respectively, accounting for 75 SOC measurements and the brightness intensities of numerical counts provided by the visible bands of the aerial photograph bare soils. Consequently, for each TE, four maps were generated: two maps resulting from KED and CC procedures (KED-SOC75P, CC-SOC75P), another one provided by standard cokriging (COK-TE50SOC75) accounting for TE prediction set plus 75 SOC measurements, and the last one corresponding to that estimated by ordinary kriging from only prediction set measurements (OK50). Three indices: (1) the mean prediction error (ME) and the mean absolute prediction error (|ME|); (2) the root mean square error (RMSE); and (3) the relative improvement (RI) of accuracy, as well as residuals analysis, were computed from the validation set (observed data) and predicted values. On the 37 test data, the results showed that the more accurate predictions were systematically those obtained by kriging accounting for SOC map predicted by KED from 75 SOC measurements and brightness values of the aerial photo (KED-SOC75P) followed closely by CC-SOC75P procedure, except for Cu and Zn where CC-SOC75P appeared to be slightly more accurate than KED-SOC75P. In regard to the RI of accuracy between prediction methods, the results confirmed once for all the benefit of accounting for SOC data set plus the exhaustively sampled information provided by the aerial photography regardless of the considered TE. Nevertheless, for Cd, Pb, and Zn, the RI of accuracy was less than 20% between the two most accurate methods (KED-SOC75P and CC-SOC75P) and standard cokriging in which the information provided by the aerial photography is ignored when mapping. The sensitivity of KED-SOC75P and CC-SOC75P approaches to the sampling density of the target variables (TE) was assessed using 10 random subsets of different sizes (25 and 33 observations) drawn from a prediction set that includes 50 data. Results have shown that the TE estimates by KED-SOC75P and CC-SOC75P approaches using only 25 TE samples were much more accurate than the estimates performed by OK50 and COK-TE50SOC75 approaches that use the whole samples of the prediction set. Moreover, the RI of accuracy was reduced by less than 15% if the original sampling density was reduced by a third.     

The role of within-dimension singleton priming in visual search.

The authors report a newly identified intertrial priming phenomenon, within-dimension singleton priming, by which search for a target that happens to be a singleton on the current trial is faster when the target on the previous trial had also been a singleton on the same dimension rather than a nonsingleton. This effect was replicated in 6 experiments with different procedures, with singletons on various dimensions, when the featural contrast defining the singleton remained the same or changed within a dimension from one trial to the next, and when the target was a singleton on a target-defining dimension or on an irrelevant dimension. These findings cannot be explained by previously demonstrated intertrial repetition effects such as dimension-specific priming or priming of popout. Theoretical implications of the within-dimension singleton priming phenomenon are discussed relative to the dimension-weighting hypothesis, the role of stimulus-driven salience in feature-guided search, and the roles of intertrial priming and goal-directed factors in visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trace element partitioning and soil particle characterisation around mining and smelting areas at Tharsis, Ríotinto and Huelva, SW Spain

Trace elements may present an environmental hazard in the vicinity of mining and smelting activities. However, the factors controlling trace element distribution in soils around ancient and modern mining and smelting areas are not always clear. Tharsis, Ríotinto and Huelva are located in the Iberian Pyrite Belt in SW Spain. Tharsis and Ríotinto mines have been exploited since 2500 B.C., with intensive smelting taking place. Huelva, established in 1970 and using the Flash Furnace Outokumpu process, is currently one of the largest smelter in the world. Pyrite and chalcopyrite ore have been intensively smelted for Cu. However, unusually for smelters and mines of a similar size, the elevated trace element concentrations in soils were found to be restricted to the immediate vicinity of the mines and smelters, being found up to a maximum of 2 km from the mines and smelters at Tharsis, Ríotinto and Huelva. Trace element partitioning (over 2/3 of trace elements found in the residual immobile fraction of soils at Tharsis) and soil particles examination by SEM-EDX showed that trace elements were not adsorbed onto soil particles, but were included within the matrix of large trace element-rich Fe silicate slag particles (i.e. 1 mm ? at least 1 wt.% As, Cu and Zn, and 2 wt.% Pb). Slag particle large size (1 mm ?) was found to control the geographically restricted trace element distribution in soils at Tharsis, Ríotinto and Huelva, since large heavy particles could not have been transported long distances. Distribution and partitioning indicated that impacts to the environment as a result of mining and smelting should remain minimal in the region.     

Electrocatalytic oxidation of aliphatic alcohols: Application to the direct alcohol fuel cell (DAFC)

The electrooxidation of some low molecular weight alcohols, such as ethanol, ethylene glycol and n-propanol, is discussed in terms of reaction mechanisms and catalytic activity of the anode material. Some examples of a single cell, using a proton exchange membrane (PEM) as electrolyte, are given to illustrate interesting results, particularly for the direct electrooxidation of ethanol. This alcohol may replace methanol in a direct alcohol fuel cell.     

Possible in vivo tolerance of human polymorphonuclear neutrophil to low-grade exercise-induced endotoxaemia

Splenic injury is the most common abdominal organ injury in children who sustain blunt trauma and may result from apparently minor injuries. We present two cases of delayed diagnosis of splenic injury in children who fell from a moderate height of less than 10 feet. Careful physical examination and close follow-up with reevaluation are necessary to identify children with possible splenic injury after relatively minor blunt trauma.     

Nitroxyls for scorch suppression,cure control,and functionalization in free-radical crosslinking of polyethylene

This paper describes the use of 2,2,6,6-tetramethylpiperidinyl-oxy (TEMPO) derivatives for scorch suppression, cure control, and functionalization in peroxide crosslinking of polyethylene. When 4-hydroxy 2,2,6,6-tetramethylpiperidin-1-oxyl was used for scorch suppression, there was often a loss in ultimate degree of crosslinking. In contrast, with bis(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)sebacate, both scorch suppression and ultimate degree of crosslinking were enhanced. A model study in hexadecane showed that TEMPO radicals terminate with carbon-centered radicals formed as a consequence of peroxide homolysis and propagation steps. This termination occurs preferentially over peroxide-initiated crosslinking and results in TEMPO-grafted polymer. In addition to polymer radical formation, several additional reaction pathways are available following thermal homolysis of the peroxide, including unimolecular disassociation of the peroxy radical to yield a methyl radical and a ketone, and proton extraction from one of several substrates by the peroxy radical to yield an alkyl radical and an alcohol. This study reveals that the reaction rate is limited by the rate of peroxide homolysis, and proceeds to statistical products with little or no preference for any specific species. The implication is that choice of peroxide is a dominant controlling factor over whether the TEMPO derivatives are ultimately grafted to the polymer or are bound to small alkyl radicals. POLYM. ENG. SCI., 47:50–61, 2007. © 2006 Society of Plastics Engineers