bluuebunny/crossref_metadata_2025 huggingface dataset:
DUPLICATED RNA GENES IN TELEOST FISH GENOMES
Authors: ROSE DOMINIC , JÖRIS JULIAN , HACKERMÜLLER JÖRG , REICHE KRISTIN , LI QIANG , STADLER PETER F.
Published: December 2008

Teleost fishes share a duplication of their entire genomes. We report here on a computational survey of structured non-coding RNAs (ncRNAs) in teleost genomes, focusing on the fate of fish-specific duplicates. As in other metazoan groups, we find evidence of a large number (11,543) of structured RNAs, most of which (~86%) are clade-specific or evolve so fast that their tetrapod homologs cannot be detected. In surprising contrast to protein-coding genes, the fish-specific genome duplication did not lead to a large number of paralogous ncRNAs: only 188 candidates, mostly microRNAs, appear in a larger copy number in teleosts than in tetrapods, suggesting that large-scale gene duplications do not play a major role in the expansion of the vertebrate ncRNA inventory.
DEVELOPMENT OF AN AFFINITY EVALUATION AND PREDICTION SYSTEM BY USING THE SHAPE COMPLEMENTARITY CHARACTERISTIC BETWEEN PROTEINS
Authors: TSUKAMOTO KOKI , YOSHIKAWA TATSUYA , HOURAI YUICHIRO , FUKUI KAZUHIKO , AKIYAMA YUTAKA
Published: December 2008

A system was developed to evaluate and predict the interaction between protein pairs by using the widely used shape complementarity search method as the algorithm for docking simulations between the proteins. This system, which we call the affinity evaluation and prediction (AEP) system, was used to evaluate the interaction between 20 protein pairs. The system first executes a "round robin" shape complementarity search of the target protein group, and evaluates the interaction of the complex structures obtained by shape complementarity search. These complex structures are selected by using a statistical procedure that we developed called "grouping". At a low prevalence of 5.0%, our AEP system predicted protein–protein interaction with 65.0% recall, 15.1% precision, 80.0% accuracy, and had an area under the curve (AUC) of 0.74. By optimizing the grouping process, our AEP system successfully predicted 13 protein pairs (among 20 pairs) that were biologically significant combinations. Our ultimate goal is to construct an affinity database that will provide crucial information obtained using our AEP system to cell biologists and drug designers.
INDIAN OCEAN TSUNAMI ON 26 DECEMBER 2004: NUMERICAL MODELING OF INUNDATION IN THREE CITIES ON THE SOUTH COAST OF SRI LANKA
Authors: WIJETUNGE J. J. , WANG XIAOMING , LIU PHILIP L.-F.
Published: December 2008

The 2004 Indian Ocean tsunami caused enormous loss of lives and damage to property in Sri Lanka and in several other countries bordering the Indian Ocean. One way of mitigating potential loss of lives from a similar event in the future is through early warning and quick evacuation of vulnerable coastal communities to safer areas, and such evacuation planning is usually carried out based on inundation maps. Accordingly, the present paper outlines the numerical modelling carried out to develop tsunami inundation maps on a grid of 10 m resolution for three cities on the south coast of Sri Lanka. The results give the tsunami arrival time contours and the spatial distribution of the extent of inundation, the maximum flow velocities as well as the hydrodynamic force in these three cities due to an event similar to the 2004 tsunami.
Almost-tight hardness of directed congestion minimization
Authors: Andrews Matthew , Zhang Lisa
Published: December 2008

Given a set of demands in a directed graph, the
directed congestion minimization
problem is to route every demand with the objective of minimizing the heaviest load over all edges. We show that for any constant ε > 0, there is no Ω(log
1−ε
M
)-approximation algorithm on networks of size
M
unless
NP
⊆
ZPTIME
(
n

polylog
n

). This bound is almost tight given the
O
(log
M
/log log
M
)-approximation via randomized rounding due to Raghavan and Thompson.
Vigilante
Authors: Costa Manuel , Crowcroft Jon , Castro Miguel , Rowstron Antony , Zhou Lidong , Zhang Lintao , Barham Paul
Published: December 2008

Worm containment must be automatic because worms can spread too fast for humans to respond. Recent work proposed network-level techniques to automate worm containment; these techniques have limitations because there is no information about the vulnerabilities exploited by worms at the network level. We propose Vigilante, a new end-to-end architecture to contain worms automatically that addresses these limitations.

In Vigilante, hosts detect worms by instrumenting vulnerable programs to analyze infection attempts. We introduce
dynamic data-flow analysis
: a broad-coverage host-based algorithm that can detect unknown worms by tracking the flow of data from network messages and disallowing unsafe uses of this data. We also show how to integrate other host-based detection mechanisms into the Vigilante architecture. Upon detection, hosts generate
self-certifying alerts
(SCAs), a new type of security alert that can be inexpensively verified by any vulnerable host. Using SCAs, hosts can cooperate to contain an outbreak, without having to trust each other. Vigilante broadcasts SCAs over an overlay network that propagates alerts rapidly and resiliently. Hosts receiving an SCA protect themselves by generating filters with
vulnerability condition slicing
: an algorithm that performs dynamic analysis of the vulnerable program to identify control-flow conditions that lead to successful attacks. These filters block the worm attack and all its polymorphic mutations that follow the execution path identified by the SCA.

Our results show that Vigilante can contain fast-spreading worms that exploit unknown vulnerabilities, and that Vigilante's filters introduce a negligible performance overhead. Vigilante does not require any changes to hardware, compilers, operating systems, or the source code of vulnerable programs; therefore, it can be used to protect current software binaries.
Enforcing Safety and Consistency Constraints in Policy-Based Authorization Systems
Authors: Lee Adam J. , Winslett Marianne
Published: December 2008

In trust negotiation and other forms of distributed proving, networked entities cooperate to form proofs of authorization that are justified by collections of certified attribute credentials. These attributes may be obtained through interactions with any number of external entities and are collected and validated over an extended period of time. Although these collections of credentials in some ways resemble partial system snapshots, current trust negotiation and distributed proving systems lack the notion of a consistent global state in which the satisfaction of authorization policies should be checked. In this article, we argue that unlike the notions of consistency studied in other areas of distributed computing, the level of consistency required during policy evaluation is predicated solely upon the security requirements of the policy evaluator. As such, there is little incentive for entities to participate in complicated consistency preservation schemes like those used in distributed computing, distributed databases, and distributed shared memory. We go on to show that the most intuitive notion of consistency fails to provide basic safety guarantees under certain circumstances and then propose several more refined notions of consistency that provide stronger safety guarantees. We provide algorithms that allow each of these refined notions of consistency to be attained in practice with minimal overheads and formally prove several security and privacy properties of these algorithms. Lastly, we explore the notion of strategic design trade-offs in the consistency enforcement algorithm space and propose several modifications to the core algorithms presented in this article. These modifications enhance the privacy-preservation or completeness properties of these algorithms without altering the consistency constraints that they enforce.
The Corrosion of a Stainless Steel in High Temperature Phosphoric Acid
Authors: Wang Heli , Turner John A.
Published: December 2008

The experiments described in this article were designed to evaluate 904L stainless steel as a candidate for replacing carbon composite in a phosphoric acid fuel cell (PAFC) bipolar plate application. We investigated the 904L steel in phosphoric acid purged with air or hydrogen gas at 170° C. Dynamic polarization showed that the steel experienced passivation with high currents. A depth profile obtained using X-ray photoelectron spectroscopy indicated that the surface film of 904L consists of an outer layer rich in Fe-oxide and an inner layer rich in Cr-oxide. After polarization, the Fe-oxide layer was selectively dissolved and Cr-oxide dominated the passive film. The Cr-oxide layer also experienced corrosion, but at a much lower rate. After 3 hours of polarization, the Fe-oxide was almost totally depleted, and phosphorus was incorporated into the passive film, changing its chemical composition. We concluded that 904L steel is an excellent candidate for use in PAFC applications.
Recent Developments in Borohydride Fuel Cells
Authors: Ponce de Leon Carlos , Walsh Frank C. , Bessette Russell R. , Patrissi Charles J. , Medeiros Maria G. , Rose Abigail , Browning Darren , Lakeman John B. , Reeve Robert W.
Published: December 2008

Developments in direct borohydride fuel cells (DBFC) are considered together with electrolyte stability and the choice of membrane and electrode materials. The cyclic voltammetry of borohydride oxidation was studied at three electrodes: a) gold on carbon, Au/C, b) gold on titanate nanotubes, Au/TiN and (c) gold foil. Similar currents were observed from the three electrodes. A DBFC in a single, 2- and 4-bipolar cell configuration with Au/C anode and Pt/C cathode produced 2.2, 3.2 and 9.6 W showed cell voltages of 1.06, 0.81 and 3 V, respectively. In another single cell, the reduction of peroxide on a Pd/Ir coated microfibrous carbon cathode was catalytically more active than a platinised-carbon one. The maximum power density achieved was 78 mW cm-2 at a cell voltage of 1.09 V. The need for further research is highlighted, particularly into new electrocatalyst materials.
Evaluation of Coated Stainless Steels for Bipolar Plates in Fuel Cells Type PEM
Authors: Rendón Belmonte Mariela , Pérez-Quiroz Jose T. , Porcayo-Calderón J. , Orozco German
Published: December 2008

According to the electrochemical study of Ni20Cr, NiCrAlY and Cr3C2(NiCr) alloys in coating form made with the Tafel extrapolation and Resistance techniques to polarization, the icorr values obtained for Ni20Cr and NiCrAlY coatings, the material dissolution, and the little resistance to corrosion discard the possibility to consider them as candidates to be used as bipolar plates for fuel cells type PEM; however with the Cr3C2(NiCr) coating, icorr values below 1.6X10-5A/cm2 were obtained. Materials must fulfill this criterion to be considered as candidates in applications such as a bipolar plate.
Synthesis and Characterization of Cryptomelane for use in Electrochemical Capacitors
Authors: Ramirez-Castro Claudia , Torres-Gonzalez Luis C.
Published: December 2008

Cryptomelane was synthesized by a solid state with low temperature technique and tested as active material for an electrochemical capacitor. X-ray diffraction peaks are in good agreement with the standard pattern of tetragonal cryptomelane. Surface area and pore sized distribution shows 292 m2/g and 6.12nm respectively which show a mesopore structure. Two different aqueous electrolytes were tested K2SO4 0.1M and Na2SO4 0.1M both of them present an ideal capacitive behavior, being more interesting capacitance values with Na2SO4 0.1M electrolyte. Further testing using this electrolyte with different scan rates presents capacitor behavior under 5mV/s.
Defect Chemistry and Electrical Conductivity in the Mg and Y Doped-CeNb3O9 Perovskite
Authors: Ruiz Trejo Enrique , Gómez-García José Francisco
Published: December 2008

We studied the electrical conductivity of nominally pure, Mg- and Y- doped CeNb3O9. First, we determined by Rietveld refinement the most probable crystal structure. We then measured by 4-point dc conductivity the transport properties in a variety of atmospheres and temperatures to determine the nature of the charge carrier. We propose that the higher conductivity of CeNb3O9 in the LnNb3O9 series is due to a displacement of Ce into the Nb sites that brings about oxygen vacancies. We present a defect chemistry model for this system
Influence of Structure Transformations over the Growth and Semiconductor Properties of Ti Anodic Films in 0.1 M NaOH
Authors: Acevedo-Peña Próspero , Vázquez Gerardo , Laverde Dionisio , Pedraza-Rosas Julio E. , González Ignacio
Published: December 2008

The electrochemical characterization of Ti anodic films during their growth in 0.1 M NaOH indicates structural changes related to the formation of different oxides i.e. TiO, Ti2O3 and TiO2. These transformations do not affect the growth kinetics, since the film thickness showed a linear relation vs. the formation potential (Ef). On the other hand the exponential dependence of the density of donors (Nd), within the whole potential range of Ef, is associated with the distribution of different oxides inside the film. The oxide with low oxidation state is near to the metal/oxide film interface and as going to the oxide film/solution interface, the oxides with higher oxidation state appeared (Ti2O3 to TiO2). Furthermore, the dependence of the flat band potential (Efb) with Ef, is attributed to the composition of the oxide films formed by a mix of Ti oxides.
Effects of the Coordination Sphere in Zinc Deposition from NH4Cl Solutions
Authors: Hernández Karla , Vazquez-Arenas Jorge G. , Cruz Roel
Published: December 2008

The effect of the coordination sphere in the zinc deposition from different bulk complexes has been analyzed through electrochemical studies in chloride ammonium - ammonia baths. In acid zone, hydrogen evolution reaction (HER) was found to be coupled with the main reduction of zinc chloro-complexes. Neutral region of pH is characterized by a reduction mechanism merging of the coexisting chloro-amino-complexes, whereas in alkaline pH values, amino-complexes are the main pathway for depositing metallic zinc. The main role of chlorides is acting as inhibitors adsorbed to the substrate, and not bonded to the complex. This last fact is given by the promptly substitution of chlorides by ammonia ions in the zinc complexes, which may offer higher resistance to the charge tunneling, as well as detaching from the complex atmosphere. The reduction process in alkaline zone is additionally settled on the interaction between hydroxyl ions and ammonia.
Fractal Analysis of the Corrosion Inhibition of Carbon Steel in a Bromide Solution by Molybdates
Authors: Sarmiento E. , Gonzalez-Rodriquez Jose Gonzalo , Urichurtu J.
Published: December 2008

Electrochemical noise results were obtained for mild steel corrosion in a lithium bromide-ethylene glycol solution with different concentrations of lithium molybdate (LiMoO3) as corrosion inhibitor. The evaluation was performed from the fractal dimension of the electrochemical noise-time series obtained using the so called Rescale Range Analysis (R/S) proposed by Hurst. The steel under different inhibitor concentrations were exposed to a lithium bromide environment and electrochemical potential/current noise measurements were performed. Afterwards, the fractal dimensions were calculated from the time series obtained for different condition. This dimension was obtained from the empirical law R/S = (τ/2)H where R represents the difference between the maximum and minimum values of the variable, S the standard deviation of the time series, τ the period of time measured and H the Hurst exponent (0 < H < 1). The calculation of Hurst exponent and fractal dimension of the time series comes from the slope of R/S plot. Electrochemical impedance spectroscopy was also performed for comparison. The fractal analysis of electrochemical noise helps to evaluate the inhibitor protection performance under the tested corrosion conditions.
Electrochemical Evaluation of Zn-22 wt.% Al- x wt.% Ag (x = 2, 4, 6) Sacrificial Anodes
Authors: Hernandez Laura A. , Hernandez Luis S. , Arce Elsa M. , Cabrera-Sierra Roman
Published: December 2008

The object of the present work was to determine the possibility that Zn-Al eutectoid alloys (Zn-22 wt.% Al), with silver contents of 2, 4 and 6 wt.%, could be used as sacrificial anodes for cathodic protection of steel structures in two test aqueous solutions: substitute ocean water and 0.5 M NaCl. Besides the as-cast condition, some samples were homogenized at 350 oC during 96 h and air-cooled. A short-term electrochemical test, DNV RP B401, as well as electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and electrochemical capacity of the anodes, and to reveal any tendencies to passivation. The experimental results suggest that the Zn-Al-Ag sacrificial anodes, with both microstructures, showed a passive behavior in substitute ocean water. However, these alloys exhibited adequate potentials and electrochemical capacities to work as sacrificial anodes in 0.5 M NaCl.
Behavior of Corrosion of Steel Embedded in Ternary Concretes
Authors: Maldonado Erick , Almeraya Calderon Facundo , Bastidas David M. , Gaona Citlalli , Bastidas Jose M. , Martinez Villafañe Alberto
Published: December 2008

The electrochemical characterization of the behavior of reinforced concrete using ternary mixtures was carried out with the objective of decreasing the degradation rate of reinforced concrete structures caused by corrosion. The materials used were: Fly ash, micro-silica, and ground granulated blast furnace. During the experimental process, 11 ternary concrete mixtures where up to 20% wt. of Portland cement was substituted with two of the previously mentioned additives in different percentages in each mixture. Then two low carbon steel rebars that functioned as electrodes were embedded into the mixtures. Afterwards, a 3.5% wt. NaCl solution was placed on the sample for 13 months. Through the use of electrochemical techniques, it was observed that the mixture of 5% flying ash + 15% micro-silica + 80% Portland cement presented the best protection of the reinforcing bar, decreasing the corrosion rate with respect to a control mixture of 100% Portland cement.
Carbon Electrodes Surface Modification in Hexane/CTAB-CTAmodified-butanol/Water System
Authors: Carreon Gutierrez Carlos A. , Gallegos Covarrubias Belinda , Estrada-Vargas Arturo , Barcena Soto Maximiliano , Casillas Norberto
Published: December 2008

The modification of graphite electrode surfaces with different hardness using hexane/CTAB-CTAmodified-butanol/water microemulsion forming system with inverse micelles (W/O) is presented. CTAB is modified by exchanging bromide ions of the surfactant with ferrocyanide ions in a salt solution. Carbon electrodes are modified by immersing them into a W/O microemulsion, followed by a rinsing step with pure water, and a potential cycling in a ferrocyanide solution. After this treatment, electrodes display two redox peaks, characteristic of strongly adsorbed species. The amount of adsorbed material at the electrode surface is greater for soft graphite electrodes than for hard ones. FTIR spectra of carbon electrodes before and after modification not show signal of C-C bonds and the increase of C-N signal from ferrocyanide ions attached to the surfactant. These results support the formation of a new bond between the surfactants tail and the carbon surface.
Electrochemical Study of the Chemiadsorption, Chemical Protection and Desorption of Cysteine in Gold and Copper Electrodes
Authors: González-Mares Mariana O. , García-Jiménez M. G. , De León Rodríguez L. M.
Published: December 2008

Au and Cu selective adsoprtion and monolayer formation of thiol containing molecules makes them attractive as materials to study the selective adsorption followed by in situ chemical modification of cysteine, an important aminoacid in peptide synthesis. Therefore, in this work it was demonstrated that chemiadsorbed cysteine in gold and copper electrodes can be chemically protected with CBZ and Fmoc protecting groups. This was supported by comparison of the electrochemical desorption voltamperograms, infrared spectra and contact angle values of metal monolayers with protected and non-protected cysteine.
Ionically Conducting Ceramics as Alternative Catalyst Supports
Authors: Vernoux Philippe , Guth Michel , Li Xingang
Published: December 2008

Pt/YSZ nanodispersed catalysts were prepared and characterized by TEM and O2-Temperature Programmed Desorption. The thermal migration of O2- ionic species from the ionic ceramic support to the Pt particles surface was evidenced by O2-TPD. Catalytic performance measurements for propane deep oxidation have shown that the thermal-induced backspillover of O2- ionic species can promote the propane combustion, confirming that oxide ions are effective promoting species for propane deep oxidation. These results demonstrate that Electrochemical Promotion of Catalysis (EPOC) can be induced without any electrical polarization by using nanoparticles of metallic catalysts supported on ionically conducting ceramics.
Ionic and Electronic Conductivities for Ln9.33+xSi6O26+1.5x under Various Conditions
Authors: Nakao Takayuki , Mineshige Atsushi , Ohnishi Yoshiki , Kobune Masafumi , Yazawa Tetsuo , Yoshioka Hideki
Published: December 2008

Electrical properties of an apatite-type oxide ionic conductor, lanthanide silicates (Ln9.33+xSi6O26+1.5x, LnSO; Ln = La or Nd) which are expected as novel solid electrolytes for the intermediate-temperature solid oxide fuel cell (IT-SOFC) have been investigated in detail. Its total electrical conductivity was almost P(O2)-independent, while a slight dependence of the conductivity on P(O2) was observed under high P(O2) conditions at high temperatures. The conductivity for La10Si6O27 was much higher than that for Nd10Si6O27. This was probably due to a difference in an accepting capacity of excess oxide ions. The excess oxide ions, formed by introducing the excess Ln elements (x), play an important part in oxide ion conduction. In the case of Ln = Nd system, formation of the excess oxide ions was blocked probably due to its smaller lattice volume than that of Ln = La system.
Impedance Spectroscopy Analysis of Zirconia:10 mol% Scandia Solid Electrolytes During and After Sintering
Authors: Costa Gustavo , Muccillo Reginaldo
Published: December 2008

ZrO2:10 mol%Sc2O3 (10ScSZ) powders were synthesized by the polyacrylamide technique (route I) and the polymeric precursor technique (route II). Attrition milling was used to break up powder agglomerates. The evolution of the distribution of particle size upon attrition milling was evaluated by laser scattering. Impedance spectroscopy measurements were carried out in cold-pressed powders in the 500oC-1400oC range during sintering and in the 300-500oC range after sintering. Upon sintering, the decrease of the total electrical resistivity of the specimens prepared with both powders is similar. Nanosize ZrO2:10 mol% Sc2O3 powders synthesized by route I are less sinteractive than powders synthesized by route II due to formation of agglomerates, which produce, upon sintering, pellets with intragranular pores. Sintered pellets using powders prepared by route I have lower electrical conductivity than pellets using powders prepared by route II.
Electrochemical Investigation of LSGMC-Composite Cathodes on LSGM-Substrate
Authors: Do Anh-Tuan , Guo James , Lu Xinyu , Pine Thomas , Bae Joongmyeon , Brouwer Jacob
Published: December 2008

As potential intermediate-temperature SOFC cathodes, perovskite composite cathode materials were evaluated in combination with a La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte. Various cathode materials La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), and Pr0.3Sr0.7Co0.8Fe0.2O3-δ (PSCF) were compounded with La0.8Sr0.2Ga0.8Mg0.1Co0.1O3-δ (LSGMC) as a mixed conducting composite element. All powders were synthesized by the glycine-nitrate process (GNP). XRD analysis found resistive phases of LaSrGaO4 and LaSrGa3O7 present in the calcined layer of composite cathodes on LSGM. A bulk ohmic resistance of 3.81 Ω•cm2 and an interfacial resistance value of 0.16 Ω were measured for LSCF/LSGMC composite cathode on LSGM substrate at 800ºC in air. Low-frequency secondary arcs in the impedance spectra of LSCF/LSGMC cathode coupled with low current density and low cathode porosity suggested possible mass transfer limitations. The LSCF/LSGMC composite electrode performed best at 800ºC (0.11 A/cm2 at 0.045 V overpotential) while the BSCF/LSGMC performed best at the lowest temperature investigated (0.1 A/cm2 at 700ºC and 0.04 V overpotential).
Strontium Titanate-based Composite Anodes for Solid Oxide Fuel Cells
Authors: Blennow Peter , Kammer Hansen Kent , Wallenberg L. Reine , Mogensen Mogens
Published: December 2008

Surfactant-assisted infiltration of Gd-doped ceria (CGO) in Nb-doped SrTiO3 (STN) was investigated as a potential fuel electrode for solid oxide fuel cells (SOFC). An electronically conductive backbone structure of STN was first fabricated at high temperatures and then combined with the mixed conducting and electrochemically active nano-sized CGO phase at low temperatures. Symmetrical cell measurements at open circuit voltage (OCV), showed that the electrochemical activity was maintained or even improved compared to Ni/YSZ fuel electrodes. The novel electrode had an electrode polarization resistance of 0.12 Ωcm2 and 0.44 Ωcm2 in humidified H2 at 850 ºC and 650 ºC, respectively. In addition, the ceramic composite electrode was shown to be redox stable. The electrode was actually activated with redox cycles at 650 ºC. The ceramic electrode structure thus presents a potential solution to overcome some of the major limitations of the current Ni-YSZ cermet SOFC anodes.
X-Ray Absorption Spectroscopic Studies on Electronic Structure in La0.6Sr0.4Co0.8Fe0.2O3-δ Perovskite-Type Oxides
Authors: Orikasa Yuki , Ina Toshiaki , Fukutsuka Tomokazu , Amezawa Koji , Kawada Tatsuya , Uchimoto Yoshiharu
Published: December 2008

In order to investigate the variation of the electronic structure of La0.6Sr0.4Co0.8Fe0.2O3-δ depending on its oxygen nonstoichiometry, X-ray absorption spectroscopy of the material annealed under various oxygen partial pressures was performed. Co/Fe L-edge XANES spectra indicated that the mean valence of Co ion decreased with decreasing oxygen partial pressure, while that of Fe ion was almost independent of oxygen partial pressure. This suggested that Co ion rather than Fe ion preferentially compensated the charges caused by the formation of oxygen vacancies.
Characterizations of double perovskite Sr2Fe1-xCoxNbO6-δ system as cathode materials for intermediate temperature solid oxide fuel cells (ITSOFCs)
Authors: Xia Tian , Wang Jingping , Lin Nan , Zhao Hui , Huo Lihua , Cao Xueqiang , Meng Jian
Published: December 2008

Sr2Fe1-xCoxNbO6-δ (SFCN) (0 {less than or equal to} x {less than or equal to} 0.9) electrode has been prepared by a solid-state reaction. The XRD patterns showed that these materials are single phases with a double perovskite structure. SFCN (x = 0.9) has the highest electrical conductivity among all these composites with = 5.7 S cm-1 at 800 oC. The p-type electronic conduction was dominant in an oxygen partial pressure range of 1-10-15 atm. SEM results showed that the composite electrode formed good contact with Zr0.92Y0.08O2-δ (8YSZ) electrolyte after sintering at 1200 oC for 12 h. Ac impedance spectroscopy and dc polarization measurements were used to study the composite electrode performances in air. The polarization resistance decreased with increasing the Co contents. The area specific resistance (ASR) of SFCN (x = 0.9) was 0.67 ohm cm2 at 800 oC in air. These results suggested that the SFCN composite electrode was a promising cathode material in ITSOFC.
Reactions at a Porous Ni Electrode Concurrent with Hydrogen evolution
Authors: Villa Marco , Salvi Paolo , Verardi Erwin , Zangari G.
Published: December 2008

We summarize some of the difficulties we had in understanding the behavior of Ni electrodes, and Raney Ni in particular, in the hydrogen evolution reaction. We give a preliminary presentation of a set of experiments where the behavior of smooth or porous electrodes are compared after being conditioned with different protocols of polarization or of oxidation/reduction cycles
Intermediate Temperature Solid Oxide Fuel Cells Based on Nano-Composite Cathode Structures
Authors: Kharlamova Tamara , Smirnova Alevtina , Sadykov Vladislav , Zarubina V. , Krieger T. , Batuev L. , Ishchenko A. , Salanov A. , Uvarov N.
Published: December 2008

The present study is focused on the development of new SOFC cathode structures based on YSZ electrolyte and operating in the temperature range of 600-800oC. The corresponding cathode materials were manufactured from La0.8Sr0.2Fe0.6Ni0.4O3-δ and La0.8Sr0.2Fe0.6Ni0.4O3-δ/ Ce0.9Gd0.1O2 composites. Thin electrolyte diffusion barrier layer of Ce0.9Gd0.1O2 was deposited between the cathode and the electrolyte to prevent possible formation of low conducting phases. The electrochemical characterization and SEM study of SOFCs demonstrated an improved performance of the nano-composite SOFC cathode structures.
Oxygen Nonstoichiometry and Defect Chemistry Modelling of Ce0.8PrxTb0.2-xO2-δ
Authors: Chatzichristodoulou Christodoulos , Hendriksen Peter V. , Hagen Anke , Grivel Jean-Claude
Published: December 2008

Powders of Ce_{0.8}Pr_{x}Tb_{0.2-x}O_{2-δ} solid solutions (x = 0, 0.05, 0.10, 0.15, 0.20) were synthesized by co-precipitation. After sintering at 1500^{o}C in Air for 12h and subsequent annealing in either reducing or oxidizing conditions, the powders were observed by XRD to be single phase fluorites. The oxygen nonstoichiometry was determined over a wide PO2 range at 600/700/800/900^{o}C by coulometric titration and validated for the x = 0.20 composition by thermogravimetry. XANES measurements were performed at the Ce/Pr/Tb L3 and L2 edges. The valence state of each dopant was found to be affected by the presence of the co-dopant. The total 4-valent dopant fraction obtained from XANES, matches well the one determined by coulometric titration. A defect model was developed that accounts well for the determined oxygen nonstoichiometry Ce_{0.8}Pr_{x}Tb_{0.2-x}O_{2-δ} over the entire P_{O2} range.
La0.7Sr0.3Cu0.2Fe0.8O3-x as Oxygen Transport Membrane for Producing Hydrogen via Water Splitting
Authors: Park Chan Young , Lee Tae H. , Dorris Steve E. , Balachandran U. (Balu)
Published: December 2008

Oxygen transport membranes (OTMs) made of mixed oxygen ionelectron conductors can generate significant amounts of hydrogen and oxygen via water splitting at moderate temperatures (500- 900{degree sign}C). Hydrogen production by this method is nongalvanic, and the separated hydrogen is of high purity. This study focuses on results that were obtained with La0.7Sr0.3Cu0.2Fe0.8O3-δ (LSCF7328), one potential OTM material. This material is easily prepared, exhibits good mechanical properties, and is stable in severe gas conditions. In tests of LSCF7328 membranes, the measured hydrogen production rates varied linearly with temperature, indicating that the material undergoes no phase transition, while the thin-film LSCF7328 sample shows a slightly different slope change in the Arrhenius plot. Also determined were the effects of membrane thickness and a Pt-porous layer and the microstructure before and after the measurements. The highest hydrogen production rate, ≈11.4 cm3/min-cm2, was obtained with a ≈50 μmthick LSCF7328 membrane via water splitting at 900{degree sign}C. The effects of surface oxygen exchange kinetics and the importance of porous substrate materials are discussed.
Preparation and Characterization of the PVA/MMT Composite Polymer Membrane for DMFC
Authors: Yang Chun-Chen , Lee Yuan-Jen
Published: December 2008

A novel composite polymer electrolyte membrane composed of PVA polymer matrix and nanosized Montmorillonite (MMT) filler (2~20wt.%), was prepared by a solution casting method. The characteristic properties of the PVA/MMT composite polymer membrane were investigated using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), atomic force microscopy (AFM), micro-Raman spectroscopy, and the AC impedance method. The PVA/MMT composite polymer membrane showed good thermal and mechanical properties, ionic conductivity. The PVA/10wt.%MMT composite polymer membrane with the highest ionic conductivity was around 0.0368 S cm-1 at 30oC. The methanol permeability (P) values were 3~4×10-6 cm2 s-1, which are smaller than that of Nafion 117 membrane of 5.8×10-6 cm2 s-1. It was revealed that the addition of nanosized MMT fillers into the PVA matrix could markedly improve the electrochemical properties of the PVA/MMT composite membrane; it can be accomplished by a simple blend method. As a result, the PVA/MMT composite polymer appears to be a potential candidate for the DMFC applications.
Enhanced PEMFC Cathode Kinetics at 120{degree sign}C and Low Relative Humidity Using Heteropolyacid Additives
Authors: Brooker Robert P. , Baker Phillip , Kunz H. Russell , Bonville Leonard , Parnas Richard
Published: December 2008

Operation of polymer electrolyte membrane fuel cells (PEMFCs) at elevated temperatures and low relative humidity is limited by the electrolyte's dependence on water. Addition of heteropolyacids, specifically silicotungstic acid (STA), is shown to increase activity by nearly 35% at 118{degree sign}C/40%RH. Additionally, activity for STA-containing cells is improved at 118{degree sign}C/40%RH over the activity of the same cells at 78{degree sign}C/100%RH. Electrochemically active areas are not affected by addition of STA, implying a mechanism other than increased wetting of the Platinum catalyst, is responsible for the increased activity.
Temperature Gradient Induced Water Transport in Polymer Electrolyte Fuel Cells
Authors: Kim Soowhan , Mench Matthew M.
Published: December 2008

The objective of this work is to investigate water transport of polymer electrolyte fuel cell (PEFC) materials subjected to a temperature gradient. Direct thermo-osmotic experiments on different polymer membrane types (non-reinforced Nafion®, reinforced A, and reinforced B membrane) were performed using an in-house fuel cell fixture with a parallel flow field. Thermo-osmotic flow was observed in all membranes, and the water flow direction (in the membrane only) was determined to always flow from the cold side to the hot side. The water flux was found to be proportional to temperature gradient and increased with average temperature. The dependency of the thermo-osmotic diffusivity on average temperature showed predictable Arrhenius-type behavior. For the membrane electrode assembly (MEA), net flow was determined to be from the hot to cold side due to a phase-change effect, which will be discussed in detail in a later publication. Interface temperatures of membrane were estimated using 2-dimensional thermal model, leading to empirical relations of thermo-osmotic diffusivity across the membrane.
Fenofibrate reduces serum retinol-binding protein-4 by suppressing its expression in adipose tissue
Authors: Wu Haiya , Wei Li , Bao Yuqian , Lu Junxi , Huang Ping , Liu Yong , Jia Weiping , Xiang Kunsan
Published: December 2008

Fenofibrate is a peroxisome proliferator-activated receptor-α (PPARα) activator that has been clinically used to treat dyslipidemia and insulin resistance. To better understand the molecular mechanisms underlying fenofibrate action, we investigated whether fenofibrate affects serum levels of retinol-binding protein-4 (RBP4), an adipocytokine that has recently been shown to link obesity and insulin resistance. Fenofibrate treatment significantly decreased serum RBP4 levels of dyslipidemic patients, which correlated with reduced body weight and increased insulin sensitivity. To elucidate the biochemical mechanisms of fenofibrate action, we investigated the effect of fenofibrate on RBP4 expression in obese rats. Fenofibrate greatly decreased RBP4 mRNA levels in adipose tissue but not in the liver, which correlated with decreased serum RBP4 levels and increased insulin sensitivity in obese rats. Consistent with a direct effect on RBP4 expression, fenofibrate treatment significantly reduced the mRNA expression levels of RPB4 in 3T3-L1 adipocytes. Together, our results demonstrate for the first time that fenofibrate inhibits RPB4 expression in dyslipidemic human subjects and suggest that inhibition of RBP4 expression in adipocytes may provide a mechanism by which fenofibrate improves insulin sensitivity in dyslipidemic patients.
Histamine induces postprandial tachycardia through a direct effect on cardiac H2-receptors in pythons
Authors: Skovgaard Nini , Møller Kate , Gesser Hans , Wang Tobias
Published: December 2008

The intrinsic heart rate of most vertebrates studied, including humans, is elevated during digestion, suggesting that a nonadrenergic-noncholinergic factor contributes to the postprandial tachycardia. The regulating factor, however, remains elusive and difficult to identify. Pythons can ingest very large meals, and digestion is associated with a marked rise in metabolism that is sustained for several days. The metabolic rise causes more than a doubling of heart rate and a fourfold rise in cardiac output. This makes the python an interesting model to investigate the postprandial tachycardia. We measured blood pressure and heart rate in fasting Python regius, and at 24 and 48 h after ingestion of a meal amounting to 25% of body wt. Digestion caused heart rate to increase from 25 to 56 min, whereas blood pressure was unchanged. The postprandial rise in heart rate was partially due to a doubling of intrinsic heart rate. The H2-antagonist did not affect heart rate of fasting snakes but decreased heart rate by 15–20 min at 24 h into digestion, whereas it had no effects at 48 h. Thus, the histaminergic tone on the heart rose from none to 30% at 24 h but vanished after 48 h. In anesthetized snakes, histamine caused a systemic vasodilatation and a marked increase in heart rate and cardiac output mediated through a direct effect on H2- receptors. Our study strongly indicates that histamine regulates heart rate during the initial phase of digestion in pythons. This study describes a novel regulation of the vertebrate heart.
Cyclosporine stimulates the renal epithelial sodium channel by elevating cholesterol
Authors: Wang Jing , Zhang Zhi-Ren , Chou Chu-Fang , Liang You-You , Gu Yuchun , Ma He-Ping
Published: December 2008

Cyclosporine A (CsA) is an efficient immunosuppressant used for reducing allograft rejection but with a severe side effect of causing hypertension. We hypothesize that the renal epithelial sodium channel (ENaC) may participate in CsA-induced hypertension. In the present study, we used the patch-clamp cell-attached configuration to examine whether and how CsA stimulates ENaC in A6 distal nephron cells. The data showed that CsA significantly increased ENaC open probability. Since CsA is an inhibitor of the ATP-binding cassette A1 (ABCA1) transporter, we employed 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), another ABCA1 inhibitor, and found that DIDS mimicked the effects of CsA on ENaC basal and cholesterol-induced activity but without any additive effect if combined with CsA. CsA and DIDS also had an identical effect on reduced ENaC activity caused by cholesterol extraction. ABCA1 protein was detected in A6 cells by Western blot analysis. Confocal microscopy data showed that both CsA and DIDS facilitated A6 cells to uptake cholesterol. Since enhanced ENaC activity is known to cause hypertension, these data together suggest that CsA may cause hypertension by stimulating ENaC through a pathway associated with inhibition of ABCA1 and consequent elevation of cholesterol in the cells.
Viscosity Approximation Methods for Generalized Mixed Equilibrium Problems and Fixed Points of a Sequence of Nonexpansive Mappings
Authors: Zeng Wei-You , Huang Nan-Jing , Zhao Chang-Wen
Published: December 2008

We introduce an iterative scheme by the viscosity approximation method for finding a common element of the set of common solutions for generalized mixed equilibrium problems and the set of common fixed points of a sequence of nonexpansive mappings in Hilbert spaces. We show a strong convergence theorem under some suitable conditions.
Humans and chimpanzees differ in their cellular response to DNA damage and non-coding sequence elements of DNA repair-associated genes
Authors: Weis E. , Galetzka D. , Herlyn H. , Schneider E. , Haaf T.
Published: December 2008

Compared to humans, chimpanzees appear to be less susceptible to many types of cancer. Because DNA repair defects lead to accumulation of gene and chromosomal mutations, species differences in DNA repair are one plausible explanation. Here we analyzed the repair kinetics of human and chimpanzee cells after cisplatin treatment and irradiation. Dot blots for the quantification of single-stranded (ss) DNA repair intermediates revealed a biphasic response of human and chimpanzee lymphoblasts to cisplatin-induced damage. The early phase of DNA repair was identical in both species with a peak of ssDNA intermediates at 1 h after DNA damage induction. However, the late phase differed between species. Human cells showed a second peak of ssDNA intermediates at 6 h, chimpanzee cells at 5 h. One of four analyzed DNA repair-associated genes, UBE2A, was differentially expressed in human and chimpanzee cells at 5 h after cisplatin treatment. Immunofluorescent staining of γH2AX foci demonstrated equally high numbers of DNA strand breaks in human and chimpanzee cells at 30 min after irradiation and equally low numbers at 2 h. However, at 1 h chimpanzee cells had significantly less DNA breaks than human cells. Comparative sequence analyses of approximately 100 DNA repair-associated genes in human and chimpanzee revealed 13% and 32% genes, respectively, with evidence for an accelerated evolution in promoter regions and introns. This is strikingly contrasting to the 3% of DNA repair-associated genes with positive selection in the coding sequence. Compared to the rhesus macaque as an outgroup, chimpanzees have a higher accelerated evolution in non-coding sequences than humans. The TRF1-interacting, ankyrin-related ADP-ribose polymerase (TNKS) gene showed an accelerated intraspecific evolution among humans. Our results are consistent with the view that chimpanzee cells repair different types of DNA damage faster than human cells, whereas the overall repair capacity is similar in both species. Genetic differences in non-coding sequence elements may affect gene regulation in the DNA repair network and thus contribute to species differences in DNA repair and cancer susceptibility.
Synteny conservation of the Z chromosome in 14 avian species (11 families) supports a role for Z dosage in avian sex determination
Authors: Nanda I. , Schlegelmilch K. , Haaf T. , Schartl M. , Schmid M.
Published: December 2008

In order to determine synteny conservation of the avian Z chromosome, a chicken (Gallus gallus, GGA) Z chromosome painting probe was hybridized to the chromosomes of 14 bird species belonging to 11 different families. The GGAZ painted the Z chromosomes in all species analyzed, suggesting strong conservation of its gene content among the different avian lineages. This was confirmed by the mapping of five GGAZ-orthologous genes (DMRT1, GHR, CHRNB3, ALDOB, B4GALT1) to the Z chromosomes of eight other species. The shuffled order of these genes on different Z chromosomes can be explained by the prevalence of intrachromosomal rearrangements during avian evolution. Synteny conservation of the mammalian X is generally thought to be the result of X chromosome inactivation. The absence of Z chromosome inactivation implies sex-specific dosage differences of a highly conserved array of Z-linked genes in birds. The evolutionary conservation of the entire Z chromosome among avian lineages supports the idea that avian sex determination and/or sex-specific functions are largely based on sex chromosome dosage. We propose that the accumulation of male-specific genes on the Z chromosome confers selective pressure on the Z to conserve its synteny.
XX/XY heteromorphic sex chromosome systems in two bullhead catfish species, Liobagrusmarginatus and L. styani (Amblycipitidae, Siluriformes)
Authors: Chen J. , Fu Y. , Xiang D. , Zhao G. , Long H. , Liu J. , Yu Q.
Published: December 2008

Karyotypes and chromosomal characteristics of two species of bullhead catfish of the genus Liobagrus, namely L. marginatus and L. styani were examined by means of conventional (Giemsa and CMA3 staining) and molecular (FISH with telomeric, 5S and 18S rDNA probes, respectively) cytogenetic techniques. The diploid numbers of L. marginatus and L. styani were 2n = 24 and 30 respectively. The karyotypes were: L. marginatus, 20m+2sm+2st in females and 19m+2sm+2st+1a in males; L. styani, 16m+ 10sm+4st in both sexes. The karyotypes of the two species and the delayed-pairing of synaptonemal complexes in meiosis of L. marginatus suggested the presence of heteromorphic XX/XY sex chromosome systems. The results of (TTAGGG)nFISH and CMA3-staining suggested that Robertsonian fusion might play an important role in chromosome differentiation among these species of Liobagrus. The 5S rDNA situated on the sex chromosomes of L. marginatus and 18S rDNA on the sex chromosomes of L. styani were located by FISH, and the origins of heteromorphic sex chromosomes via chromosomal reversion or unequal crossing over of heterochromatin were hypothesized.
Characterization of 11p14-p12 deletion in WAGR syndrome by array CGH for identifying genes contributing to mental retardation and autism
Authors: Xu S. , Han J.C. , Morales A. , Menzie C.M. , Williams K. , Fan Y.-S.
Published: December 2008

WAGR (Wilms tumor, Aniridia, Genitourinary malformations and mental Retardation) syndrome is a rare genomic disorder caused by deletion of the 11p14-p12 chromosome region. The majority of WAGR patients have mental retardation and behavioral problems, and more than 20% of the patients also have features of autism. While the Wilms tumor/genitourinary anomalies and aniridia are caused by deletion of WT1 and PAX6 respectively, the genomic cause of mental retardation and autism in WAGR syndrome remains unknown. Using oligonucleotide arrays, we have characterized the 11p14-p12 deletions in 31 patients and identified all the genes involved in each deletion. The deletions had sizes ranging from 4.9 to 23 Mb that encompass 18–62 genes (40 on average). In addition to WT1 and PAX6, all the patients had deletion of PRRG4 (transmembrane gamma-carboxyglutamic acid protein 4). The majority of them had deletion of BDNF (brain-derived neurotrophic factor) and SLC1A2 [solute carrier family 1 (glial high affinity glutamate transporter) member 2]. Deletion of BDNF and SLC1A2 occurred in patients with autism more frequently than in those without autism. Literature review on the functions of the genes suggests that haploinsufficiency of SLC1A2, PRRG4, and BDNF may contribute to mental retardation and behavioral problems. In particular, BDNF may modulate the risk of autism in WAGR patients as suggested by its link with Rett syndrome as a target of MECP2. We observed that all the de novo deletions occurred in the chromosome 11 inherited from the father in the families genotyped, implying a predisposition for de novo mutations occurring in spermatogenesis and possible involvement of imprinting in cognitive impairment in WAGR patients.