Carbon supported nano-sized Pt-Pd and Pt-Co electrocatalysts for proton exchange membrane fuel cells

Cataloged from PDF version of article.Nano-sized Pt-Pd/C and Pt-Co/C electrocatalysts have been synthesized and characterized by an alcohol-reduction process using ethylene glycol as the solvent and Vulcan XC-72R as the supporting material. While the Pt-Pd/C electrodes were compared with Pt/C (20 wt.% E-TEK) in terms of electrocatalytic activity towards oxidation of H(2), CO and H(2)-CO mixtures, the Pt-Co/C electrodes were evaluated towards oxygen reduction reaction (ORR) and compared with Pt/C (20 wt% E-TEK) and Pt-Co/C (20 wt.% E-TEK) and Pt/C (46 wt.% TKK) in a single cell. in addition, the Pt-Pd/C and Pt-Co/C electrocatalyst samples Were characterized by XRD, XPS, TEM and electroanalytical methods. The TEM images of the carbon supported platinum alloy electrocatalysts show homogenous catalyst distribution with a particle size of about 3-4 nm it was found that while the Pt-Pd/C electrocatalyst has superior CO tolerance compared to commercial catalyst, Pt-Co/C synthesized by polyol method has shown better activity and stability up to 60 degrees C compared to commercial catalysts Single cell tests using the alloy catalysts coated on Nafion-212 membranes with H(2) and O(2) gases showed that the fuel cell performance in the activation and the ohmic regions are almost similar comparing conventional electrodes to Pt-Pd anode electrodes However, conventional electrodes give a better performance in the ohmic region comparing to Pt-Co cathode. It is worth mentioning that these catalysts are less expensive compared to the commercial catalysts if only the platinum contents were considered. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Sustainable tourism and identity model in the context of contemporary requirements

İnsanların yaşam süreçleri içerisinde birtakım değerlerin değişmesi çok olağan bir olgudur. Değişmek, vazgeçilmez bir süreçtir, ancak değişimin boyutu, koşulları ve sonuçları dikkate alındığında birtakım değerlerin değişmesi sırasında sürdürülebilir olanların da korunması ve sürekliliğinin sağlanması gerekmektedir. Çalışma kapsamında çok boyutlu, çok katılımlı bir sistematik geliştirilerek, bölgesel-kimlik analizi çerçevesinde oluşturulan model ile kimlik analiz envanterini ne kadar (ölçek), niçin, neden (içerik), nasıl, kimin tarafından (davranış) korunup-sürdürüleceğinin ve/veya değiştirilip geliştirileceğinin boyutları incelenmiştir. Sonuç olarak, sürdürülebilir turizm ve kimlik gelişiminin holistik yapısında bölge ile ilgili tespitler, katılımcıların bölge hakkındaki kararları ve uygulamaları ile karşılaştırılmak üzere tez-anti tez olarak sorgulanmıştır. Anahtar Kelimeler: Fiziksel çevre, holistik model, kimlik, sürdürülebilir turizm.The aim of this study is to present a systematic approach in investigation of the contradiction between the contemporary necessities and cultural continuity in the context of sustainable tourism in the light of sustainability for the use of next generations to preserve natural, cultural and environmental identity of tourism areas. Change in values of human beings? lives is a usual occurrence. Change is an inevitable fact but when its dimensions, conditions and the consequences are taken into consideration protection of sustainable ones and providing the cultural continuity are required during the development of the values. The need of examination of human?s communication and an interaction on the same platform with the local-regional identity is an element of culture in the formation of physical environment. In this study, inventory of the identity analysis was investigated in different dimensions as what, how much (scale), why, what for (content), how and by whom (behavior) should be conserved and protected and/or changed and developed by  the model formed in the framework of regional-identity analysis based on a multi-dimensional and multi-participation systematic approach. Consequently, for comparison with the decisions and applications of the participants about the region, the findings about the region in the holistic structure of development of sustainable tourism and identity were examined. With this model the decisions of the participants were systematically investigated by means of the data. Keywords: Physical environment, holistic model, identity, sustainable tourism

Organic acids, sugars, vitamin C, antioxidant capacity and phenolic compounds in fruits of white (<i>Morus alba</i> L.) and black (<i>Morus nigra</i> L.) mulberry genotypes

Mulberries (Morus spp) are historically grown in particular microclimatic regions in Eastern Anatolia, including Aras valley. In the valley, mulberries are one of the ancient crop and used for several purposes by local people. The aim of the present study was to first time evaluate organic acids, sugars, vitamin C, antioxidant capacity (TEAC assay, Trolox Equivalent Antioxidant Capacity). and phenolic compounds of the historical black and white mulberry genotypes growing Aras valley in Turkey. Results showed that, species and genotypes strongly influenced the chemical content and antioxidant capacity (p<0.05). Malic acid was the main organic acid in all genotypes and ranged from 1.130 to 3.040 g/100 g. Among sugars, fructose and glucose are predominant and were between 4.177 and 7.700 g/100g and 5.337 and 8.573 g/100g in all mulberry genotypes, respectively. The black mulberry genotypes showed remarkably higher antioxidant capacity determined by TEAC assay (10.167 to 14.400 µ mol TE/g) compared to white mulberry genotypes (6.170 to 9.273 µmol TE/g). Chlorogenic acid and rutin was the main phenolic compound

Upregulation of virulence genes promotes Vibrio cholerae biofilm hyperinfectivity

Vibrio cholerae remains a major global health threat, disproportionately impacting parts of the world without adequate infrastructure and sanitation resources. In aquatic environments, V. cholerae exists both as planktonic cells and as biofilms, which are held together by an extracellular matrix. V. cholerae biofilms have been shown to be hyperinfective, but the mechanism of hyperinfectivity is unclear. Here we show that biofilm-grown cells, irrespective of the surfaces on which they are formed, are able to markedly outcompete planktonic-grown cells in the infant mouse. Using an imaging technique designed to render intestinal tissue optically transparent and preserve the spatial integrity of infected intestines, we reveal and compare three-dimensional V. cholerae colonization patterns of planktonic-grown and biofilm-grown cells. Quantitative image analyses show that V. cholerae colonizes mainly the medial portion of the small intestine and that both the abundance and localization patterns of biofilm-grown cells differ from that of planktonic-grown cells. In vitro biofilm-grown cells activate expression of the virulence cascade, including the toxin coregulated pilus (TCP), and are able to acquire the cholera toxin-carrying CTXФ phage. Overall, virulence factor gene expression is also higher in vivo when infected with biofilm-grown cells, and modulation of their regulation is sufficient to cause the biofilm hyperinfectivity phenotype. Together, these results indicate that the altered biogeography of biofilm-grown cells and their enhanced production of virulence factors in the intestine underpin the biofilm hyperinfectivity phenotype

Cellular Levels and Binding of c-di-GMP Control Subcellular Localization and Activity of the Vibrio cholerae Transcriptional Regulator VpsT

The second messenger, cyclic diguanylate (c-di-GMP), regulates diverse cellular processes in bacteria. C-di-GMP is produced by diguanylate cyclases (DGCs), degraded by phosphodiesterases (PDEs), and receptors couple c-di-GMP production to cellular responses. In many bacteria, including Vibrio cholerae, multiple DGCs and PDEs contribute to c-di-GMP signaling, and it is currently unclear whether the compartmentalization of c-di-GMP signaling components is required to mediate c-di-GMP signal transduction. In this study we show that the transcriptional regulator, VpsT, requires c-di-GMP binding for subcellular localization and activity. Only the additive deletion of five DGCs markedly decreases the localization of VpsT, while single deletions of each DGC do not impact VpsT localization. Moreover, mutations in residues required for c-di-GMP binding, c-di-GMP-stabilized dimerization and DNA binding of VpsT abrogate wild type localization and activity. VpsT does not co-localize or interact with DGCs suggesting that c-di-GMP from these DGCs diffuses to VpsT, supporting a model in which c-di-GMP acts at a distance. Furthermore, VpsT localization in a heterologous host, Escherichia coli, requires a catalytically active DGC and is enhanced by the presence of VpsT-target sequences. Our data show that c-di-GMP signaling can be executed through an additive cellular c-di-GMP level from multiple DGCs affecting the localization and activity of a c-di-GMP receptor and furthers our understanding of the mechanisms of second messenger signaling

Verticalization of bacterial biofilms

Biofilms are communities of bacteria adhered to surfaces. Recently, biofilms of rod-shaped bacteria were observed at single-cell resolution and shown to develop from a disordered, two-dimensional layer of founder cells into a three-dimensional structure with a vertically-aligned core. Here, we elucidate the physical mechanism underpinning this transition using a combination of agent-based and continuum modeling. We find that verticalization proceeds through a series of localized mechanical instabilities on the cellular scale. For short cells, these instabilities are primarily triggered by cell division, whereas long cells are more likely to be peeled off the surface by nearby vertical cells, creating an "inverse domino effect". The interplay between cell growth and cell verticalization gives rise to an exotic mechanical state in which the effective surface pressure becomes constant throughout the growing core of the biofilm surface layer. This dynamical isobaricity determines the expansion speed of a biofilm cluster and thereby governs how cells access the third dimension. In particular, theory predicts that a longer average cell length yields more rapidly expanding, flatter biofilms. We experimentally show that such changes in biofilm development occur by exploiting chemicals that modulate cell length.Comment: Main text 10 pages, 4 figures; Supplementary Information 35 pages, 15 figure

Digitally enabled health service for the integrated management of hypertension: A participatory user-centred design process

This article describes a user-centred approach taken by a group of five procurers to set specifications for the procurement of value-based research and development services for IT-sup-ported integrated hypertension management. The approach considered the unmet needs of patients and health systems of the involved regions. The procurers established a framework for requirements and a solution design consisting of nine building blocks, divided into three domains: service delivery, devices and integration, and health care organisation. The approach included the development of questionnaires, capturing patients’ and professionals’ views on possible system functionalities, and a template collecting information about the organisation of healthcare, professionals involved and existing IT systems at the procurers’ premises. A total of 28 patients diagnosed with hypertension and 26 professionals were interviewed. The interviewees identified 98 functional requirements, grouped in the nine building blocks. A total of nine use cases and their corresponding process models were defined by the procurers’ working group. As result, a digitally enabled integrated approach to hypertension has been designed to allow citizens to learn how to prevent the development of hypertension and lead a healthy lifestyle, and to receive comprehensive, individualised treatment in close collaboration with healthcare professionals

Reprogrammed Transcriptome in Rhesus-Bovine Interspecies Somatic Cell Nuclear Transfer Embryos

Global activation of the embryonic genome (EGA), one of the most critical steps in early mammalian embryo development, is recognized as the time when interspecies somatic cell nuclear transfer (iSCNT) embryos fail to thrive.In this study, we analyzed the EGA-related transcriptome of rhesus-bovine iSCNT 8- to 16-cell embryos and dissected the reprogramming process in terms of embryonic gene activation, somatic gene silencing, and maternal RNA degradation. Compared with fibroblast donor cells, two thousand and seven genes were activated in iSCNT embryos, one quarter of them reaching expression levels comparable to those found in in vitro fertilized (IVF) rhesus embryos. This suggested that EGA in iSCNT embryos had partially recapitulated rhesus embryonic development. Eight hundred and sixty somatic genes were not silenced properly and continued to be expressed in iSCNT embryos, which indicated incomplete nuclear reprogramming. We compared maternal RNA degradation in bovine oocytes between bovine-bovine SCNT and iSCNT embryos. While maternal RNA degradation occurred in both SCNT and iSCNT embryos, we saw more limited overall degradation of maternal RNA in iSCNT embryos than in SCNT embryos. Several important maternal RNAs, like GPF9, were not properly processed in SCNT embryos.Our data suggested that iSCNT embryos are capable of triggering EGA, while a portion of somatic cell-associated genes maintain their expression. Maternal RNA degradation seems to be impaired in iSCNT embryos. Further understanding of the biological roles of these genes, networks, and pathways revealed by iSCNT may expand our knowledge about cell reprogramming, pluripotency, and differentiation

Structural Basis for c-di-GMP-Mediated Inside-Out Signaling Controlling Periplasmic Proteolysis

X-ray crystallographic structural analyses of the bacterial transmembrane receptor LapD identify conserved molecular mechanisms that control biofilm formation in response to changes in the intracellular levels of the second messenger c-di-GMP