A high performance direct borohydride fuel cell employing cross-linked chitosan membrane

A cross-linked chitosan (CCS) membrane has been prepared by a solution casting method using sulfuric acid as cross-linking agent. The CCS membrane was used as the polymer electrolyte and separator in a direct borohydride fuel cell (DBFC). Ionic conductivity and borohydride crossover rate have been measured for the CCS membrane. The DBFC used in this study employed nickel-based composite as anode catalyst and Nafion^® as anode binder. The power performance of the CCS membrane-based DBFC was compared with a similar DBFC employing Nafion^® 212 (N212) membrane as electrolyte /separator. The CCS membrane-based DBFC exhibited better power performance as compared to N212 membrane-based DBFC. Encouraged by this result, chitosan chemical hydrogel (CCH) was prepared and used as binder for anode catalysts. A DBFC comprising CCS membrane and CCH as anode binder was studied and found to exhibit even better power performance at all temperatures in this study. A maximum peak power density of 450 mW cm⁻² was observed at 60 ?C for DBFC employing CCS membrane and CCH binder-based anode. The chitosan-based DBFC was operated continuously for 100 h and its performance stability was recorded.     

Variation in blood pressure is associated with white matter microstructure but not cognition in African Americans.

Although hypertension is a major risk factor for cerebrovascular disease (CVD) and is highly prevalent in African Americans, little is known about how blood pressure (BP) affects brain–behavior relationships in this population. In predominantly Caucasian populations, high BP is associated with alterations in frontal–subcortical white matter and in executive functioning aspects of cognition. We investigated associations among BP, brain structure, and neuropsychological functioning in 52 middle–older-age African Americans without diagnosed history of CVD. All participants underwent diffusion tensor imaging for examination of white matter integrity, indexed by fractional anisotropy (FA). Three regions of interest were derived in the anterior (genu) and posterior (splenium) corpus callosum and across the whole brain. A brief neuropsychological battery was administered from which composite scores of executive function and memory were derived. Blood pressure was characterized by mean arterial blood pressure (MABP). When controlling for age, higher MABP was associated with lower FA in the genu, and there was a trend for this same relationship with regard to whole-brain FA. When the sample was broken into groups on the basis of treatment for BP regulation (medicated vs. nonmedicated), MABP was related to genu and whole-brain FA only in the nonmedicated group. Neither MABP nor FA was significantly related to either neuropsychological composite score regardless of medication use. These data provide important evidence that variation in BP may contribute to significant alterations in specific neural regions of white matter in nonmedicated individuals without symptoms of overt CVD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Study of Two Phase Emulsion Systems

Two phase emulsion is widely used to increase the reaction efficiency. Slag–metal emulsion is used widely in metallurgy to increase the efficiency of the process. Previously, Pb–salt emulsion system at high temperature has been studied experimentally and mathematically. In this work the study has been extended to Al–salt and Sn–salt systems to cover wider physical properties at much higher temperature, both experimentally as well as mathematically. Further the mathematical model has been verified against various published emulsion systems, having a wide variety of physical properties. Using this model, the effect of various physical properties of slag and iron, such as viscosity, density and drop size, on the iron–slag emulsion system has been studied. It is found that the iron droplets of the size of 100 µm or lesser may be entrapped in the slag if sufficient time is not allowed to settle them into the metal phase.     

Human gene control by vital oncogenes: revisiting a theoretical model and its implications for targeted cancer therapy

An important assumption of our current understanding of the mechanisms of carcinogenesis has been the belief that clarification of the cancer process would inevitably reveal some of the crucial mechanisms of normal human gene regulation. Since the momentous work of Bishop and Varmus, both the molecular and the biochemical processes underlying the events in the development of cancer have become increasingly clear. The identification of cellular signaling pathways and the role of protein kinases in the events leading to gene activation have been critical to our understanding not only of normal cellular gene control mechanisms, but also have clarified some of the important molecular and biochemical events occurring within a cancer cell. We now know that oncogenes are dysfunctional proto-oncogenes and that dysfunctional tumor suppressor genes contribute to the cancer process. Furthermore, Weinstein and others have hypothesized the phenomenon of oncogene addiction as a distinct characteristic of the malignant cell. It can be assumed that cancer cells, indeed, become dependent on such vital oncogenes. The products of these vital oncogenes, such as c-myc, may well be the Achilles heel by which targeted molecular therapy may lead to truly personalized cancer therapy. The remaining problem is the need to introduce relevant molecular diagnostic tests such as genome microarray analysis and proteomic methods, especially protein kinase identification arrays, for each individual patient. Genome wide association studies on cancers with gene analysis of single nucleotide and other mutations in functional proto-oncogenes will, hopefully, identify dysfunctional proto-oncogenes and allow the development of more specific targeted drugs directed against the protein products of these vital oncogenes. In 1984 Willis proposed a molecular and biochemical model for eukaryotic gene regulation suggesting how proto-oncogenes might function within the normal cell. That model predicted the existence of vital oncogenes and can now be used to hypothesize the biochemical and molecular mechanisms that drive the processes leading to disruption of the gene regulatory machinery, resulting in the transformation of normal cells into cancer.     

Gold Catalysis: β‐Ketonaphthalenes via Molecular Gymnastics of 1,6‐Diyne‐4‐en‐3‐ols

1,6‐Diyne‐4‐en‐3‐ols with one terminal alkyne were applied as test substrates for a possible dual catalyzed cyclization. Instead of a dual catalysis cycle, naphthyl ketone derivatives were obtained as single products. The regioselectivity of the obtained products is unprecedented. Instead of the expected naphthyl ketones bearing the keto group in the α‐position, the keto group is positioned in the ß‐position of the naphthyl skeleton by a complex rearrangement of the starting materials.     

A digitally temperature-compensated crystal oscillator

The base frequency of oscillators used in the Global System for Mobile Communication (GSM) network or Global Positioning System (GPS) receiver applications needs to be very stable with respect to temperature and supply-voltage variations. One approach to obtain extremely good frequency stability is the use of oven-stabilized crystal oscillators. With this kind of oscillator, a frequency stability versus temperature of a few ppb versus the standard temperature range can be achieved. In this paper, a digitally compensated crystal oscillator is described. The system provides a frequency stability of (Δf)/f<1.5 ppm for a temperature range of -40°C to 90°C compared to about ±20 ppm for a noncompensated crystal. The core of the system is an application-specified integrated circuit (ASIC) fabricated in a standard 0.8-μm CMOS process. The power consumption for the oscillator running at 13 MHz is 100 mW. The final device equipped with the ASIC, crystal blank, and a few external components fits into a 14×9×3 mm³ package     

Effektiver Algorithmus zur Lösung von inversen Aufgabenstellungen – Anwendung in der Geomechanik

Effective algorithm for solving inverse problems – geomechanical application. When working with numerical models, it is essential to determine model parameters which are as realistic as possible. Optimization techniques are being employed more and more frequently for solving this task. However, using these methods may lead to very high time costs – in particular, if rather complicated forward calculations are involved. In this paper, we present a class of methods that allows estimating the solution of this kind of optimization problems based on relatively few sampling points. We put very weak constraints on the sampling point distribution; hence, they may be taken from previous forward calculations as well as from alternative sources. Starting from an introduction into the theoretical approach, a strategy for speeding up inverse optimization problems is introduced which is illustrated by an example geomechanics.