bluuebunny/crossref_metadata_2025 huggingface dataset:
Upper limit concentrations of trapped xenon in individual interplanetary dust particles from the stratosphere
Authors: KEHM K. , CROWTHER S. , GILMOUR J. D. , MOHAPATRA R. K. , HOHENBERG C. M.
Published: January 2010

Abstract— The Xe contents in 25 individual stratospheric interplanetary dust particles were measured in two different laboratories using focused laser micro‐gas extraction and (1) a conventional low‐blank magnetic sector mass spectrometer (Washington University), and (2) a resonance ionization time of flight mass spectrometer (RELAX‐University of Manchester). Data from both laboratories yielded a remarkably similar upper‐limit 132Xe concentration in the IDPs (>2.7, 6.8 and 2.2 × 10−8ccSTP/g for Washington University Run 1, Washington University Run 2 and University of Manchester analyses, respectively), which is up to a factor of five smaller than previous estimates. The upper‐limit 132Xe/36Ar ratio in the IDPs (132Xe/36Ar > ˜8 × 10−4for Run 1 and 132Xe/36Ar > ˜19 × 10−4for Run 2), computed using 36Ar concentration data reported elsewhere is consistent with a mixture between implanted solar wind, primordial, and atmospheric noble gases. Most significantly, there is no evidence that IDPs are particularly enriched in primordial noble gases compared to chondritic meteorites, as implied by previous work.
The Meteoritical Bulletin, No. 95
Authors: WEISBERG Michael K. , SMITH Caroline , BENEDIX Gretchen , FOLCO Luigi , RIGHTER Kevin , ZIPFEL Jutta , YAMAGUCHI Akira , AOUDJEHANE Hasnaa CHENNAOUI
Published: January 2010

Abstract— The Meteoritical Bulletin No. 95 reports 1093 (282 non‐Antarctic and 801 Antarctic) newly approved meteorite names and their recovery histories, macroscopic descriptions, petrography, mineral compositions and geochemistry. Meteorites reported include lunar meteorites, eucrites, mesosiderites, angrites, ureilites, an acapulcoite, and H, L, LL, R, CO, CM, CK and CV chondrites. Three new falls, the Bunburra Rockhole (Australia) eucrite and the recent (Nov., 2008) Buzzard Coulee (Canada) H4 chondrite, and Tamdakht (Morocco) H5 chondrite are reported.
Refractory inclusions and aluminum‐rich chondrules in Sayh al Uhaymir 290 CH chondrite: Petrography and mineralogy
Authors: ZHANG Aicheng , HSU Weibiao
Published: January 2010

Abstract— Here we report the petrography, mineralogy, and bulk compositions of Ca,Al‐rich inclusions (CAIs), amoeboid olivine aggregate (AOA), and Al‐rich chondrules (ARCs) in Sayh al Uhaymir (SaU) 290 CH chondrite. Eighty‐two CAIs (0.1% of the section surface area) were found. They are hibonite‐rich (9%), grossite‐rich (18%), melilite ± spinel‐rich (48%), fassaite ± spinel‐rich (15%), and fassaite‐anorthite‐rich (10%) refractory inclusions. Most CAIs are rounded in shape and small in size (average = 40 μm). They are more refractory than those of other groups of chondrites. CAIs in SaU 290 might have experienced higher peak heating temperatures, which could be due to the formation region closer to the center of protoplanetary disk or have formed earlier than those of other groups of chondrites. In SaU 290, refractory inclusions with a layered texture could have formed by gas‐solid condensation from the solar nebula and those with an igneous texture could have crystallized from melt droplets or experienced subsequent melting of pre‐existing condensates from the solar nebula. One refractory inclusion represents an evaporation product of pre‐existing refractory solid on the basis of its layered texture and melting temperature of constituting minerals. Only one AOA is observed (75 μm across). It consists of olivine, Al‐diopside, anorthite, and minor spinel with a layered texture. CAIs and AOA show no significant low‐temperature aqueous alteration. ARCs in SaU 290 consist of diopside, forsterite, anorthite, Al‐enstatite, spinel, and mesostasis or glass. They can be divided into diopside‐rich, Al‐enstatite‐rich, glass‐rich, and anorthite‐rich chondrules. Bulk compositions of most ARCs are consistent with a mixture origin of CAIs and ferromagnesian chondrules. Anorthite and Al‐enstatite do not coexist in a given ARC, implying a kinetic effect on their formation.
Meteorite finds from southern Tunisia
Authors: OUAZAA N. LARIDHI , PERCHIAZZI N. , KASSAA S. , ZEOLI A. , GHANMIM M. , FOLCO L.
Published: January 2010

Abstract— We report on the meteorite search campaign of April 2008, conducted by a joint Tunisian‐Italian scientific expedition in southern Tunisia (Dahar region). Nine likely unpaired meteorites (seven H‐class and two L‐class chondrites) totalling ?1.3 kg were recovered by exploring an approximately 45 km2area, therefore demonstrating that southern Tunisia is a suitable terrain for systematic searches for meteorites.
Transformation textures, mechanisms of formation of high‐pressure minerals in shock melt veins of L6 chondrites, and pressure‐temperature conditions of the shock events
Authors: Ozawa Shin , Ohtani Eiji , Miyahara Masaaki , Suzuki Akio , Kimura Makoto , Ito Yoshinori
Published: January 2010

Abstract— The high‐pressure polymorphs of olivine, pyroxene, and plagioclase in or adjacent to shock melt veins (SMVs) in two L6 chondrites (Sahara 98222 and Yamato 74445) were investigated to clarify the related transformation mechanisms and to estimate the pressure‐temperature conditions of the shock events. Wadsleyite and jadeite were identified in Sahara 98222. Wadsleyite, ringwoodite, majorite, akimotoite, jadeite, and lingunite (NaAlSi3O8‐hollandite) were identified in Yamato 74445. Wadsleyite nucleated along the grain boundaries and fractures of original olivine. The nucleation and growth of ringwoodite occurred along the grain boundaries of original olivine, and as intracrystalline ringwoodite lamellae within original olivine. The nucleation and growth of majorite took place along the grain boundaries or fractures in original enstatite. Jadeite‐containing assemblages have complicated textures containing “particle‐like,” “stringer‐like,” and “polycrystalline‐like” phases. Coexistence of lingunite and jadeite‐containing assemblages shows a vein‐like texture. We discuss these transformation mechanisms based on our textural observations and chemical composition analyses. The shock pressure and temperature conditions in the SMVs of these meteorites were also estimated based on the mineral assemblages in the SMVs and in comparison with static high‐pressure experimental results as follows: 13–16 GPa, >1900 °C for Sahara 98222 and 17–24 GPa, >2100 °C for Yamato 74445.
Characteristic foliation on a hypersurface of general type in a projective symplectic manifold
Authors: Hwang Jun-Muk , Viehweg Eckart
Published: January 2010

A foliation on a non-singular projective variety is algebraically integrable if all leaves are algebraic subvarieties. A non-singular hypersurface X in a non-singular projective variety M equipped with a symplectic form has a naturally defined foliation, called the characteristic foliation on X. We show that if X is of general type and dim M≥4, then the characteristic foliation on X cannot be algebraically integrable. This is a consequence of a more general result on Iitaka dimensions of certain invertible sheaves associated with algebraically integrable foliations by curves. The latter is proved using the positivity of direct image sheaves associated to families of curves.
Magnetic Field Effect on the Hydronium Diffusivity at an Enzymatic Biofuel Cell Anode via Atomistic Analysis
Authors: Chiu C. P. , Hong C. W.
Published: January 2010

This paper investigates how a constant magnetic field between the anode catalyst and the electrode surface affects the performance of an enzymatic biofuel cell. Molecular dynamics techniques were employed to observe the nanoscale proton transport phenomenon. The simulation model comprised a Au electrode, pyrroloquinoline quinine, flavin adenine dinucleotide, and glucose macromolecules with hydronium ions in aqueous solution. A constant magnetic field was applied parallel to the anode electrode surface in the simulation process. It is found that the magnetic field is able to enhance the hydronium mobility in the solution and the rate of the biochemical reaction increased. Simulation results show that the hydronium diffusivity increases from 3.80×10−9 m2/s to a maximum 19.91×10−9 m2/s at a glucose concentration of 27 mM and from 13.02×10−9 m2/s to a maximum 36.44×10−9 m2/s at a glucose concentration of 82 mM.
Characterization of Scandia Stabilized Zirconia Doped With Various Bi2O3 Additions as an Intermediate Temperature Solid Oxide Fuel Cell Electrolyte
Authors: Bai Bing , Sammes Nigel M. , Smirnova Alevtina L. , Tompsett Geoff
Published: January 2010

Bi 2 O 3 doped scandia stabilized zirconia systems have shown promise for use as electrolytes in intermediate temperature solid oxide fuel cells (IT-SOFC's). Sintering properties, crystal phase transformation, and electrical conductivity of the Bi2O3 doped Sc2O3–ZrO2 systems were investigated. The effect of Bi2O3 doping from 0 mol % to 2.0 mol % and different sintering temperatures on the properties and performance of the electrolyte were examined. The presence of Bi2O3 aided the sintering process and better sintering for the doped system was achieved at lower temperatures. The cubic phase was successfully stabilized at room temperature with concentrations of 1 mol % and 2 mol %Bi2O3 sintered at 1100–1400°C. The achievement of a cubic structure depends on both the Bi2O3 concentration and the sintering temperature. Higher electrical conductivity was achieved with Bi2O3 doped Sc2O3–ZrO2 systems than 10ScSZ below 600°C. A maximum conductivity of 1.68×10−2 S/cm at 700°C was obtained for 2 mol %Bi2O3 doped sample sintered at 1100°C.
Degradation of Solid Oxide Fuel Cell Cathodes Accelerated at a High Water Vapor Concentration
Authors: Kim S. H. , Shim K. B. , Kim C. S. , Chou J. T. , Oshima T. , Shiratori Y. , Ito K. , Sasaki K.
Published: January 2010

The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800°C and 1000°C. Cell voltage change was negligible at 1000°C, while considerable voltage drop was observed at 800°C accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La2O3 formed on the (La0.8Sr0.2)0.98MnO3 surface, which is assumed to be the reason for a large voltage drop.
Performance of Proton Exchange Membrane Fuel Cells Using Pt/MWNT–Pt/C Composites as Electrocatalysts for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells
Authors: Reddy A. Leela Mohana , Shaijumon M. M. , Rajalakshmi N. , Ramaprabhu S.
Published: January 2010

Multiwalled carbon nanotubes (MWNTs) have been synthesized by the pyrolysis of acetylene using hydrogen decrepitated Mischmetal based AB3 alloy hydride catalyst. Structural, morphological, and vibrational characterizations have been carried out using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) spectroscopy. Pt-supported MWNTs (Pt/MWNTs) have been prepared by chemical reduction method using functionalized MWNTs. Composites of Pt/MWNTs and Pt/C in different weight proportions have been used as electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cell (PEMFC) and the performance on the accessibility of Pt electrocatalysts for the oxygen reduction reaction in PEMFC has been systematically studied. The cyclic voltammetric studies of the electrodes have been performed in order to understand the factors influencing the elecetrocatalytic activity and fuel cell performance and the results have been discussed.
Hybrid System Test Rig: Start-up and Shutdown Physical Emulation
Authors: Ferrari Mario L. , Pascenti Matteo , Magistri Loredana , Massardo Aristide F.
Published: January 2010

The University of Genoa (TPG) has designed and developed an innovative test rig for high temperature fuel cell hybrid system physical emulation. It is based on the coupling of a modified commercial 100 kW recuperated micro gas turbine to a special modular volume designed for the experimental analysis of the interaction between different dimension fuel cell stacks and turbomachines. This new experimental approach that generates reliable results as a complete test rig also allows investigation of high risk situations with more flexibility without serious and expensive consequences to the equipment and at a very low cost compared with real hybrid configurations. The rig, developed with the support of the European Integrated Project “FELICITAS,” is under exploitation and improvement in the framework of the new European Integrated Project “LARGE-SOFC” started in January 2007. The layout of the system (connecting pipes, valves, and instrumentation) was carefully designed to minimize the pressure loss between compressor outlet and turbine inlet to have the highest plant flexibility. Furthermore, the servocontrolled valves are useful for performing tests at different operative conditions (i.e., pressures, temperatures, and pressure losses), focusing the attention on surge and thermal stress prevention. This work shows the preliminary data obtained with the machine connected to the volume for the test rig safe management to avoid surge or excessive stress, especially during the critical operative phases (i.e., start-up and shutdown). Finally, the attention is focused on the valve control system developed to emulate the start-up and shutdown phases for high temperature fuel cell hybrid systems. It is necessary to manage the flows in the connecting pipes, including an apt recuperator bypass, to perform a gradual heating up and cooling down as requested during these phases. It is an essential requirement to avoid thermal stress for the fuel cell stack. For this reason, during the start-up, the volume is gradually heated by the compressor outlet flow followed by a well managed recuperator outlet flow and vice versa for the shutdown. Furthermore, operating with a constant rotational speed control system, the machine load is used to reach higher temperature values typical of these kinds of systems.
Optimization of Passive Air Breathing Fuel Cell Cathodes
Authors: Babcock Bryan , Tupper A. J. , Clark Dan , Fabian Tibor , O’Hayre Ryan
Published: January 2010

Air-breathing polymer electrolyte membrane fuel cells (ABFCs) use free convection airflow to supply oxygen to their cathodes. These cells are typically characterized by low output power densities compared with forced-convection fuel cells. Because ABFC designs rely on natural convection air delivery, cathode performance is often the performance bottleneck. This paper specifically examines the tradeoff between mass transport losses and ohmic electrical resistance losses for an optimal ABFC cathode design. Optimization is nontrivial because the simultaneous requirements for excellent cell compression, current collection, and gas access are often in contradiction. Simple scaling analysis and experimental observations suggest that the tradeoff between lateral mass transport resistance losses and cathode/gas diffusion layer (GDL) contact resistance losses determines the optimal ABFC cathode design. In order to quantitatively study these effects, we have tested a series of different cathode geometries in a standardized ABFC. Using high frequency resistance measurements and fast-scan polarization measurements, we have been able to interrogate both the ohmic and mass transport losses associated with each cathode configuration. We have also used pressure sensitive foils to examine the pressure distribution for representative configurations, providing a quantitative link between pressure distribution and cell resistance. Finally, we have studied the effect of deploying a current collecting contact layer between the cathode and the GDL. Results indicate that the deployment of a sufficiently stiff yet highly porous contact layer significantly reduces contact resistance losses while imposing minimal additional mass transport losses. A stiff yet porous contact layer reduces the contact resistance losses by increasing the total contact surface area and providing a more even distribution of pressure across the face of the cell. By minimizing contact resistance losses, this strategy enables the deployment of ABFC cathode structures with greater than 90% open area, thereby leading to an enhanced ABFC performance, particularly at high current densities.
Effect of Compression on the Water Management of a Proton Exchange Membrane Fuel Cell With Different Gas Diffusion Layers
Authors: Shi Zhongying , Wang Xia , Guessous Laila
Published: January 2010

The gas diffusion layer (GDL) plays an important role in maintaining suitable water management in a proton exchange membrane fuel cell. The properties of the gas diffusion layer, such as its porosity, permeability, wettability, and thickness, are affected by the shoulders of the bipolar plates due to the compression applied in the assembly process. Compression therefore influences the water management inside fuel cells. A two-phase fuel cell model was used to study the water management problem in a proton exchange membrane fuel cell with interdigitated flow channels. The effect of the compression on the fuel cell performance was numerically investigated for a variety of GDL parameters. This paper focuses on studying the water management of fuel cells under compression for various types of gas diffusion layers. First, the deformation of a gas diffusion layer due to compression applied from the shoulders of the bipolar plates was modeled as a plain-strain problem and was determined using finite element analysis (FEA). The porosity and the permeability of the gas diffusion layer were then recalculated based on the deformation results. Next, the deformed domain from the FEA model was coupled with a fuel cell model, and the effects of the compression during the assembly process on the water management and fuel cell performance were studied for gas diffusion layers with different thicknesses, porosities, and compressive moduli. It was found that the deformation of the GDL results in a low oxygen concentration at the reaction site. The saturation level of liquid water increases along the flow direction, and is higher when the compression effect is considered in the simulation.
Plasma Nitrided Type 349 Stainless Steel for Polymer Electrolyte Membrane Fuel Cell Bipolar Plate—Part I: Nitrided in Nitrogen Plasma
Authors: Wang Heli , Teeter Glenn , Turner John A.
Published: January 2010

An austenite 349 stainless steel was nitrided via nitrogen plasma. Glancing angle X-ray diffraction patterns suggest that the nitrided layer is amorphous. X-ray photoelectron spectroscopy analysis indicated that the plasma nitridation process produced bulk-type nitrides in the surface layer. In general, the nitrided layer was composed of iron oxide in the outer layer and chromium oxide in the inner layers. Contaminations of vanadium and tin were detected in the as-grown nitrided layer; these dissolved away after polarization. The influence of these contaminants on the corrosion resistance of the nitrided layer in polymer electrolyte membrane fuel cell (PEMFC) environments is not considered significant. The nitrided sample had a much higher contact resistance than the bare one and the contact resistance increased with the nitriding time. The high interfacial contact resistance values can be related to the thicker oxide film after plasma nitridation. The corrosion resistances obtained for the 1 h nitrided and bare stainless steels in simulated PEMFC environments were similar. The outmost nitrided layer dissolved after polarization in the PEMFC environments leaving a passive film (modified with nitrides), similar to that of bare stainless steel under the same conditions. The passive film thickness was 3.7 nm for nitrided steel in PEMFC cathode environment and 4.2 nm for nitrided steel in PEMFC anode environment.
Plasma Nitrided Type 349 Stainless Steel for Polymer Electrolyte Membrane Fuel Cell Bipolar Plate—Part II: Nitrided in Ammonia Plasma
Authors: Wang Heli , Teeter Glenn , Turner John A.
Published: January 2010

Austenitic 349 stainless steel was nitrided in an NH3 plasma. A low interfacial contact resistance was obtained with the nitrided steel. Glancing angle X-ray diffraction suggests that the nitrided layer is very thin and possibly amorphous. X-ray photoelectron spectroscopy (XPS) studies show that the nitrided layer is composed of mixed oxides and nitrides of Fe3+ and Cr3+. Contaminations of V and Sn were also observed, though their influence on the as-nitrided surface conductivity is not clear. The nitrided samples were investigated in a simulated polymer electrolyte membrane fuel cell (PEMFC) environment, and showed excellent corrosion resistance. The XPS depth profile indicated that the passive film, which formed on the plasma-nitrided steel in the PEMFC anode environment, is composed of mixed oxides and nitrides, in which chromium oxide/nitride dominates the surface chemistry. No V or Sn was detected on the surface after the polarization tests. For the PEMFC bipolar plate application, nitridation in NH3 plasma is a promising surface treatment approach, though more research is needed to investigate the influence of the plasma density and substrate bias on the surface conductivity and performance of the nitrided steel in PEMFC environments.
Evaluation of Bi2V0.9Cu0.1O5.35—an Aurivillius-Type Conducting Oxide—as a Cathode Material for Single-Chamber Solid-Oxide Fuel Cells
Authors: Shao Zongping , Mederos Jennifer , Kwak Chan , Haile Sossina M.
Published: January 2010

The compound Bi2V0.9Cu0.1O5.35, a typical Aurivillius-type fast oxygen ion conductor, was evaluated as a possible cathode material for single-chamber solid-oxide fuel cells operated under mixed propane and oxygen. The material was found to be structurally stable under various C3H8+O2 environments over a wide temperature range and furthermore displayed low catalytic activity for propane oxidation. However, at temperatures above 650°C, detrimental reactions between the cathode and the ceria electrolyte occurred, producing low conductivity interfacial phases. At these high temperatures the cathode additionally underwent extensive sintering and loss of porosity and, thus, stable fuel cell operation was limited to furnace temperatures of <600°C. Even under such conditions, however, the partial oxidation occurring at the anode (a ceria nickel cermet) resulted in cell temperatures as much as 70–110°C higher than the gas-phase temperature. This explains the sharp decrease in fuel cell performance with time during operation at a furnace temperature of 586°C. Under optimized conditions, a peak power density of ∼60 mW/cm2 was obtained, which does not compete with recent values obtained from higher activity cathodes. Thus, the poor electrochemical activity of Bi2V0.9Cu0.1O5.35, combined with its chemical instability at higher temperatures, discourages further consideration of this material as a cathode in single-chamber fuel cells.
La 0.8 Sr 0.2 Co 1 − x Mn x O 3 Cathode and Its Application to Metal-Supported Solid Oxide Fuel Cells
Authors: Lee Changbo , Bae Joongmyeon , Kim Jung Hyun , Baek Seung-Wook
Published: January 2010

Cathode properties of La0.8Sr0.2Co1−xMnxO3 (LSCM) perovskite oxides were investigated for their application to metal-supported solid oxide fuel cells (SOFCs). La0.8Sr0.2Co0.4Mn0.6O3 (LSCM-8246) had the lowest impedance on Zr0.85Y0.15O2 (YSZ) electrolyte among various compositions because the properties of the cathodic reaction kinetics, thermal expansion compatibility, and chemical reactivity were optimized. A Ce0.9Gd0.1O2 (CGO) interlayer was introduced between LSCM and YSZ to inhibit the formation of resistive phases at the interface. The cathode impedance was decreased to about 1/3 of the noninterlayer samples. The study of the partial oxygen pressure dependence and activation energy of LSCM-8246 on CGO-layered YSZ showed that the ionization of the adsorbed oxygen is the rate-determining step of the cathode reaction at the general operation condition of SOFCs. Metal-supported single cell SOFCs with LSCM-8246 cathode were fabricated and characterized. The single cell impedance was much greater than values expected from the half cell test because the cathode in the single cell was sintered in situ during the measurement. The effect of cathode sintering was observed by measuring the current-voltage (I-V) curves and impedance spectra with time.
Surface topography and physicochemistry of silver containing titanium nitride nanocomposite coatings
Authors: Whitehead Kathryn , Kelly Peter , Li Heqing , Verran Joanna
Published: January 2010

Titanium nitride (TiN) is a hard, wear-resistant coating material, which is widely applied to components operating in an abrasive wear environment. When codeposited with silver, the coating forms a nanocomposite structure consisting of nanoparticles of silver embedded in a TiN matrix. TiN/Ag coatings were deposited by cosputtering onto bright annealed stainless steel substrates. By control of the target powers, the silver content of the films was varied in the range of 0–16.7 at. %. The films were characterized using scanning electron microscopy (structure), energy dispersive x-ray spectroscopy (chemical composition), white light profilometry (roughness), atomic force microscopy (topography), and physicochemistry (ΔGiwi, γs, γsLW, γsAB, γs+, and γs−). Silver was heterogeneously distributed throughout the TiN matrix, and increasing the silver content in the TiN surfaces resulted in changes in surface nanotopographies with respect to surface features, grain sizes, and physicochemistry. In particular, a silver concentration of 16.7 at. % resulted in a distinct change in surface nanotopography and features, which were qualitatively demonstrated using visual images, linear profiles, and quantitatively using Rp, Rpm, Rz, and Rt roughness parameters. There were also some changes in γs− with increased silver content. When producing novel surfaces, changes in surface chemistry affect other surface parameters. A thorough analysis of surface parameters is essential since changes may affect the potential end use of the product.
Turned On by the Cold
Authors: Gough Nancy R.
Published: January 2010

Cold triggers a rearrangement of the
cspA
mRNA that promotes translation.
Making Connections
Authors: Zahn Laura
Published: January 2010

A genome-wide interaction map of yeast identifies genetic interactions, networks, and function.
Opacity Proteins Increase
Neisseria gonorrhoeae
Fitness in the Female Genital Tract Due to a Factor under Ovarian Control
Authors: Cole Jessica G. , Fulcher Nanette B. , Jerse Ann E.
Published: January 2010

The neisserial opacity (Opa) proteins are a family of antigenically distinct outer membrane proteins that undergo phase-variable expression. Opa
+
variants of
Neisseria gonorrhoeae
strain FA1090 are selected in a cyclical pattern from the lower genital tract of estradiol-treated mice. Here we show that cyclical recovery of Opa
+
gonococci does not occur in ovariectomized mice; therefore, the reproductive cycle plays a role in the selection kinetics
in vivo
. As predicted by the selection pattern shown by wild-type gonococci, we demonstrated that a constitutive Opa-expressing strain was more fit than an Opa-deficient mutant in the early and late phases of infection. We found no evidence that Opa-mediated colonization selects for Opa
+
variants during murine infection based on adherence assays with cultured murine epithelial cells. We also tested the hypothesis that complement selects for Opa protein expression during infection. Although some Opa
+
variants of a serum-sensitive derivative of strain FA1090 were more resistant to the bactericidal activity of normal human serum, selection for Opa expression was not abrogated in C3-depleted mice. Finally, as previously reported, Opa
+
gonococci were more sensitive to serine proteases. Thus, proteases or protease inhibitors may contribute to the observed
in vivo
selection pattern. We concluded that Opa proteins promote persistence of
N. gonorrhoeae
in the female genital tract and that
opa
gene phase variation allows gonococci to evade or capitalize upon unidentified host factors of the mammalian reproductive cycle. This work revealed an intimate interaction between pathogen and host and provides evidence that hormonally related factors shape bacterial adaptation.
Loss of Ability To Self-Heal Malaria upon Taurine Transporter Deletion
Authors: Delić Denis , Warskulat Ulrich , Borsch Elena , Al-Qahtani Saad , Al-Quraishi Saleh , Häussinger Dieter , Wunderlich Frank
Published: January 2010

Deletion of the taurine transporter gene (taut) results in lowered levels of taurine, the most abundant amino acid in mammals. Here, we show thattaut−/−mice have lost their ability to self-heal blood-stage infections withPlasmodium chabaudimalaria. Alltaut−/−mice succumb to infections during crisis, while about 90% of the controltaut+/+mice survive. The latter retain unchanged taurine levels even at peak parasitemia. Deletion oftaut, however, results in the lowering of circulating taurine levels from 540 to 264 μmol/liter, and infections cause additional lowering to 192 μmol/liter. Peak parasitemia levels intaut−/−mice are approximately 60% higher than those intaut+/+mice, an elevation that is associated with increased systemic tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) levels, as well as with liver injuries. The latter manifest as increased systemic ammonia levels, a perturbed capacity to entrap injected particles, and increased expression of genes encoding TNF-α, IL-1β, IL-6, inducible nitric oxide synthase (iNOS), NF-κB, and vitamin D receptor (VDR). Autopsy reveals multiorgan failure as the cause of death for malaria-infectedtaut−/−mice. Our data indicate thattaut-controlled taurine homeostasis is essential for resistance toP. chabaudimalaria. Taurine deficiency due totautdeletion, however, impairs the eryptosis ofP. chabaudi-parasitized erythrocytes and expedites increases in systemic TNF-α, IL-1β, and ammonia levels, presumably contributing to multiorgan failure inP. chabaudi-infectedtaut−/−mice.
SEMICLASSICAL METHODS FOR HAWKING RADIATION FROM A VAIDYA BLACK HOLE
Authors: SIAHAAN HARYANTO M. , TRIYANTA
Published: January 2010

We derive the general form of Hawking temperature for Vaidya black hole in the tunneling pictures. This type of black hole is regarded as the description of a more realistic one compared to static case such as Schwarzschild's solution. The black hole mass in Vaidya solution is time dependent and decreasing due to evaporation process. Clearly, the temperature would be time dependent as our findings show. We use the semiclassical methods, namely radial null geodesic and complex paths methods. Both methods are found to give the same results. Then, we discuss the possible form of the corresponding entropy.
RADIATIVE CORRECTIONS IN VECTOR-TENSOR MODELS
Authors: BUCHEL A. , CHISHTIE F. A. , HANIF M. T. , HOMAYOUNI S. , JIA JUNJI , McKEON D. G. C.
Published: January 2010

We consider a two-form antisymmetric tensor field ϕ minimally coupled to a non-Abelian vector field with a field strength F. Canonical analysis suggests that a pseudoscalar mass term [Formula: see text] for the tensor field eliminates degrees of freedom associated with this field. Explicit one-loop calculations show that an additional coupling m Tr (ϕ ∧ F) (which can be eliminated classically by a tensor field shift) reintroduces tensor field degrees of freedom. We attribute this to the lack of the renormalizability in our vector-tensor model. We also explore a vector-tensor model with a tensor field scalar mass term [Formula: see text] and coupling m Tr (ϕ ∧ ⋆F). We comment on the Stueckelberg mechanism for mass generation in the Abelian version of the latter model.
WMAP5 OBSERVATIONAL CONSTRAINTS ON BRANEWORLD NEW INFLATION MODEL
Authors: ZARROUKI R. , SAKHI Z. , BENNAI M.
Published: January 2010

We study a new inflation potential in the framework of the Randall–Sundrum type II braneworld model. Using the technic developed in Ref. 1, we consider both a monomial and a new inflation potentials and apply the slow-roll approximation in high energy limit, to derive analytical expression of relevant perturbation spectrum. We show that for some values of the parameter n in the potential [Formula: see text] we obtain a perturbation spectrum which gives a good agreement with the recent WMAP5 observations.
ON THE SIGN PROBLEM IN DENSE QCD
Authors: HSU STEPHEN D. H. , REEB DAVID
Published: January 2010

We investigate the Euclidean path integral formulation of QCD at finite baryon density and temperature. We show that the partition function Z can be written as a difference between two sums Z+ and Z-, each of which defines a partition function with positive weights. We call the sign problem severe if the ratio Z-/Z+ is nonzero in the infinite volume limit. This occurs only if, and generically always if, the associated free energy densities F± are equal in this limit. We present strong evidence here that the sign problem is severe at almost all points in the phase diagram, with the exception of special cases like exactly zero chemical potential (ordinary QCD), which requires a particular order of limits. Part of our reasoning is based on the analyticity of free energy densities within their open phase regions. Finally, we describe a Monte Carlo technique to simulate finite-density QCD in regions where Z-/Z+ is small.
QCD FACTORIZATION BASED ON SIX-QUARK OPERATOR EFFECTIVE HAMILTONIAN FROM PERTURBATIVE QCD AND CHARMLESS BOTTOM MESON DECAYS B(s)→ππ, πK, KK
Authors: SU FANG , WU YUE-LIANG , YANG YI-BO , ZHUANG CI
Published: January 2010

The charmless bottom meson decays are systematically investigated based on an approximate six-quark operator effective Hamiltonian from perturbative QCD. It is shown that within this framework the naive QCD factorization method provides a simple way to evaluate the hadronic matrix elements of two-body mesonic decays. The singularities caused by on mass-shell quark propagator and gluon exchanging interaction are appropriately treated. Such a simple framework allows us to make theoretical predictions for the decay amplitudes with reasonable input parameters. The resulting theoretical predictions for all the branching ratios and CP asymmetries in the charmless B0, B+, Bs → ππ, πK, KK decays are found to be consistent with the current experimental data except for a few decay modes. The observed large branching ratio in B→π0π0 decay remains a puzzle though the predicted branching ratio may be significantly improved by considering the large vertex corrections in the effective Wilson coefficients. More precise measurements of charmless bottom meson decays, especially on CP violations in B → KK and Bs → ππ, πK, KK decay modes, will provide a useful test and guide us to a better understanding on perturbative and nonperturbative QCD.
THE CASE FOR A DIRECTIONAL DARK MATTER DETECTOR AND THE STATUS OF CURRENT EXPERIMENTAL EFFORTS
Authors: AHLEN S. , AFSHORDI N. , BATTAT J. B. R. , BILLARD J. , BOZORGNIA N. , BURGOS S. , CALDWELL T. , CARMONA J. M. , CEBRIAN S. , COLAS P. , DAFNI T. , DAW E. , DUJMIC D. , DUSHKIN A. , FEDUS W. , FERRER E. , FINKBEINER D. , FISHER P. H. , FORBES J. , FUSAYASU T. , GALAN J. , GAMBLE T. , GHAG C. , GIOMATARIS I. , GOLD M. , GOMEZ H. , GOMEZ M. E. , GONDOLO P. , GREEN A. , GRIGNON C. , GUILLAUDIN O. , HAGEMANN C. , HATTORI K. , HENDERSON S. , HIGASHI N. , IDA C. , IGUAZ F. J. , INGLIS A. , IRASTORZA I. G. , IWAKI S. , KABOTH A. , KABUKI S. , KADYK J. , KALLIVAYALIL N. , KUBO H. , KUROSAWA S. , KUDRYAVTSEV V. A. , LAMY T. , LANZA R. , LAWSON T. B. , LEE A. , LEE E. R. , LIN T. , LOOMBA D. , LOPEZ J. , LUZON G. , MANOBU T. , MARTOFF J. , MAYET F. , McCLUSKEY B. , MILLER E. , MIUCHI K. , MONROE J. , MORGAN B. , MUNA D. , MURPHY A. St. J. , NAKA T. , NAKAMURA K. , NAKAMURA M. , NAKANO T. , NICKLIN G. G. , NISHIMURA H. , NIWA K. , PALING S. M. , PARKER J. , PETKOV A. , PIPE M. , PUSHKIN K. , ROBINSON M. , RODRIGUEZ A. , RODRIGUEZ-QUINTERO J. , SAHIN T. , SANDERSON R. , SANGHI N. , SANTOS D. , SATO O. , SAWANO T. , SCIOLLA G. , SEKIYA H. , SLATYER T. R. , SNOWDEN-IFFT D. P. , SPOONER N. J. C. , SUGIYAMA A. , TAKADA A. , TAKAHASHI M. , TAKEDA A. , TANIMORI T. , TANIUE K. , TOMAS A. , TOMITA H. , TSUCHIYA K. , TURK J. , TZIAFERI E. , UENO K. , VAHSEN S. , VANDERSPEK R. , VERGADOS J. , VILLAR J. A. , WELLENSTEIN H. , WOLFE I. , YAMAMOTO R. K. , YEGORYAN H.
Published: January 2010

We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.
MODELING DYNAMIC CORRELATIONS AND SPILLOVER EFFECTS OF COUNTRY RISK: EVIDENCE FROM RUSSIA AND KAZAKHSTAN
Authors: LI JIANPING , SUN XIAOLEI , HE WAN , TANG LING , XU WEIXUAN
Published: January 2010

Oil economies in the Former Soviet Union (FSU) region, with geographical proximity to each other, are usually impacted by some common risk factors, which make their country risks closely correlated. This paper focuses on correlation between country risks and investigates the spillovers of country risk returns (CRR). Taking Russia and Kazakhstan for example, firstly, this paper identifies the structural breaks in CRR series, using iterated cumulative sums of squares (ICSS) algorithm. Secondly, on the assumption that there may be similarity in structural breaks of CRR series of the two countries, Vector Autoregression (VAR) process and Granger causality test are used to identify whether there are mean spillovers of CRR series. Finally, the volatility spillovers are captured by using multivariate conditional volatility models in the framework of the BEKK models. Empirical results show that (1) there are significant unidirectional mean spillovers from Russia to Kazakhstan; (2) there are asymmetric bidirectional volatility spillovers between Russia and Kazakhstan; and volatility spillover effects from Russia to Kazakhstan are stronger.
A PIECEWISE-DEFINED SEVERITY DISTRIBUTION-BASED LOSS DISTRIBUTION APPROACH TO ESTIMATE OPERATIONAL RISK: EVIDENCE FROM CHINESE NATIONAL COMMERCIAL BANKS
Authors: LI JIANPING , FENG JICHUANG , CHEN JIANMING
Published: January 2010

Following the Basel II Accord, with the increased focus on operational risk as an aspect distinct from credit and market risk, quantification of operational risk has been a major challenge for banks. This paper analyzes implications of the advanced measurement approach to estimate the operational risk. When modeling the severity of losses in a realistic manner, our preliminary tests indicate that classic distributions are unable to fit the entire range of operational risk data samples (collected from public information sources) well. Then, we propose a piecewise-defined severity distribution (PSD) that combines a parameter form for ordinary losses and a generalized Pareto distribution (GPD) for large losses, and estimate operational risk by the loss distribution approach (LDA) with Monte Carlo simulation. We compare the operational risk measured with piecewise-defined severity distribution based LDA (PSD-LDA) with those obtained from the basic indicator approach (BIA), and the ratios of operational risk regulatory capital of some major international banks with those of Chinese commercial banks. The empirical results reveal the rationality and promise of application of the PSD-LDA for Chinese national commercial banks.
LIMITATIONS OF CANCER MARGIN DELINEATION BY MEANS OF AUTOFLUORESCENCE IMAGING UNDER CONDITIONS OF LASER SURGERY
Authors: DOUPLIK ALEXANDRE , ZAM AZHAR , HOHENSTEIN RALPH , KALITZEOS ANGELOS , NKENKE EMEKA , STELZLE FLORIAN
Published: January 2010

Limitations of cancer margin delineation and surgical guidance by means of autofluorescence imaging under conditions of laser ablation were investigated and preliminary results are presented. PinPoint™ (Novadaq Technologies Inc., Canada) was used to capture digital images and Er:YAG laser (2.94 μm, Glissando, WaveLight™, Germany) was exploited to cause laser ablation on both normal and cancer sites of the specimen. It was shown that changes of the autofluorescence image after ablation extend beyond the actual sizes of the ablation loci. The tumor tissue after the laser ablation starts to emit fluorescent light within the green wavelength band (490–550 nm) similar to normal tissue stating that the current technology of in-process tissue classification fails. However, when the autofluorescence was collected in the red range (600–750 nm), then the abnormal/normal contrast was reduced, but still present even after the laser ablation. The present study highlights the importance of finding a proper technology for surgical navigation of cancer removal under conditions of high power effects in biological tissues.
An interview with Michael Rabin
Authors: Shasha Dennis , Rabin Michael
Published: January 2010

Michael O. Rabin, co-recipient of the 1976 ACM A.M. Turing Award, discusses his innovative algorithmic work with Dennis Shasha.
Post-silicon bug localization for processors using IFRA
Authors: Park Sung-Boem , Mitra Subhasish
Published: January 2010

IFRA, an acronym for Instruction Footprint Recording and Analysis, overcomes major challenges associated with a very expensive step in post-silicon validation of processors---pinpointing a bug location and the instruction sequence that exposes the bug from a system failure, such as a crash. Special on-chip recorders, inserted in a processor during design, collect instruction footprints---special information about flows of instructions, and what the instructions did as they passed through various microarchitectural blocks of the processor. The recording is done concurrently during the normal operation of the processor in a post-silicon system validation setup. Upon detection of a system failure, the recorded information is scanned out and analyzed offline for bug localization. Special self-consistency-based program analysis techniques, together with the test-program binary of the application executed during post-silicon validation, are used for this purpose. Major benefits of using IFRA over traditional techniques for post-silicon bug localization are (1) it does not require full system-level reproduction of bugs, and (2) it does not require full system-level simulation. Hence, it can overcome major hurdles that limit the scalability of traditional post-silicon validation methodologies. Simulation results on a complex superscalar processor demonstrate that IFRA is effective in accurately localizing electrical bugs with 1% chip-level area impact.
DSPs, BRAMs, and a Pinch of Logic
Authors: Drimer Saar , Güneysu Tim , Paar Christof
Published: January 2010

We present three lookup-table-based AES implementations that efficiently use the BlockRAM and DSP units embedded within Xilinx Virtex-5 FPGAs. An iterative module outputs a 32-bit AES round column every clock cycle, with a throughput of 1.67 Gbit/s when processing two 128-bit inputs. This construct is then replicated four times to provide a complete AES round per cycle with 6.7 Gbit/s throughput when processing eight input streams. This, in turn, is replicated ten times for a fully unrolled design providing over 52 Gbit/s of throughput. We also present implementations of a BRAM-based AES key-expansion, CMAC, and CTR modes of operation. Results for designs where DSPs are replaced by regular logic are also presented. The combination and arrangement of the specialized embedded functions available in the FPGA allows us to implement our designs using very few traditional user logic elements such as flip-flops and lookup tables, yet still achieve these high throughputs. HDL source code, simulation testbenches, and software tool commands to reproduce reported results for the three AES variants and CMAC mode are made publicly available. Our contribution concludes with a discussion on comparing cipher implementations in the literature, and why these comparisons can be meaningless without a common reporting methodology, or within the context of a constrained target application.
Performance Analysis Framework for High-Level Language Applications in Reconfigurable Computing
Authors: Curreri John , Koehler Seth , George Alan D. , Holland Brian , Garcia Rafael
Published: January 2010

High-Level Languages (HLLs) for Field-Programmable Gate Arrays (FPGAs) facilitate the use of reconfigurable computing resources for application developers by using familiar, higher-level syntax, semantics, and abstractions, typically enabling faster development times than with traditional Hardware Description Languages (HDLs). However, programming at a higher level of abstraction is typically accompanied by some loss of performance as well as reduced transparency of application behavior, making it difficult to understand and improve application performance. While runtime tools for performance analysis are often featured in development with traditional HLLs for sequential and parallel programming, HLL-based development for FPGAs has an equal or greater need yet lacks these tools. This article presents a novel and portable framework for runtime performance analysis of HLL applications for FPGAs, including an automated tool for performance analysis of designs created with Impulse C, a commercial HLL for FPGAs. As a case study, this tool is used to successfully locate performance bottlenecks in a molecular dynamics kernel in order to gain speedup.
An encryption system in assembly language
Authors: Goulding Tom
Published: January 2010

This case study discusses the incorporation of encryption systems development into the educational journey of undergraduate computer science or game development majors. We discuss the experience of first semester Daniel Webster College sophomores who attempted to develop the German WWII ENIGMA encryption system in assembly language. By incorporating a real world encryption system project into a beginning computer architecture class students become deeply immersed in numbering systems, hardware logic design, operating system services and, of course instruction set architectures. Of necessity, they also must refine and develop their programming skills to an extraordinary degree. During the past seven years we have found that most students can develop a complete software version of the complex and amazing ENIGMA encryption system. We outline in this paper the strategy that seems to lead to a successful outcome for most students.
The assignment problem
Authors: Rolfe Timothy J.
Published: January 2010

The linear assignment problem requires the determination of an optimal permutation vector for the assignment of tasks to agents. Even the backtracking implementation supports a rather powerful bounding function. An earlier article discussed the fundamental problem and executing the backtracking in parallel. This article addresses the branch-and-bound approach and shows transforming that into a parallel algorithm.
The software engineering class builds a GUI for subversion
Authors: Santore John , Lorenzen Torben , Creed Robert , Murphy David , Orcutt Roger
Published: January 2010

The authors describe a software engineering course in which undergraduate students produced a GUI frontend to Subversion, a popular open source version control system. Three teams implemented the project by shelling out to the command line and one team used TkSVN. A download of the course materials and a project implementation are provided.