bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanofluid Suspensions as Derivative of Interface Heat Transfer Modeling in Porous Media
Authors: Vadasz Peter
Published: June 2010

Spectacular heat transfer enhancement has been measured in nanofluid suspensions. Attempts in explaining these experimental results did not yield yet a definite answer. Modeling the heat conduction process in nanofluid suspensions is being shown to be a special case of heat conduction in porous media subject to Lack of Local thermal equilibrium (LaLotheq). The topic of heat conduction in porous media subject to Lack of Local thermal equilibrium (LaLotheq) is reviewed, introducing one of the most accurate methods of measuring the thermal conductivity, the transient hot wire method, and discusses its possible application to dual-phase systems. Maxwell’s concept of effective thermal conductivity is then introduced and theoretical results applicable for nanofluid suspensions are compared with published experimental data.
Mathematical Modelling of Fire and Smoke Characteristics in Ventilated Rooms
Authors: Khalil Essam E.
Published: June 2010

This paper presents a preliminary investigation of transient flow characteristics and heat release in a ventilated compartment fire. This study aims at enhancing current understanding of fire propagation in the compartment and its influence on the air flow characteristics. The present paper demonstrated through the application of numerical techniques the results of different ventilation scenarios for single fire scenario. It is recommended to use the smoke extract fans in designated locations in the spaces that could be exposed to the fire hazards. Corridor smoke extract fan provides the safe escape for the occupancy. Quantitative parametric studies are carried out for various situations, to enhance our knowledge about the fire behaviour. The fire field models based on CFD are useful tools that can greatly support this target.
Simulation of Traffic Jam Formation in Fast Axonal Transport
Authors: Kuznetsov A. V. , Avramenko A. A. , Blinov D. G.
Published: June 2010

Many neurodegenerative diseases, such as Alzheimer’s disease, are linked to swellings occurring in long arms of neurons. Many scientists believe that these swellings result from traffic jams caused by the failure of intracellular machinery responsible for fast axonal transport; such traffic jam can plug an axon and prevent the sufficient amount of organelles to be delivered toward the synapse of the axon. Mechanistic explanation of the formation of traffic jams in axons induced by overexpression of tau protein is based on the hypothesis that the traffic jam is caused not by the failure of molecular motors to transport organelles along individual microtubules but rather by the disruption of the microtubule system in an axon, by the formation of a swirl of disoriented microtubules at a certain location in the axon. This paper investigates whether a microtubule swirl itself, without introducing into the model microtubule discontinuities in the traffic jam region, is capable of capturing the traffic jam formation. The answer to this question can provide important insight into the mechanics of the formation of traffic jams in axons.
Symbolic Calculation for Free Convection in a Circular Cavity With Periodic Heat Generation
Authors: Mansour Kamyar
Published: June 2010

We consider the two-dimensional problem of steady natural convection in a circular cavity with periodic heat generation filled with viscous fluid subject to cosine temperature variation on the boundary. The solution is expanded for low Rayleigh number and extended to 16 terms by computer. Analysis of these expansions allows the exact computation for arbitrarily accuracy up to 50000 figures. Although the range of the radius of convergence is small but pade approximation leads our result to be good even for higher value of the similarity parameter.
An Experimental Investigation on the Effects of Heat and Mass Flux on Vapor Bubble Growth Characteristics in a Microchannel
Authors: Edel Zachary , Mukherjee Abhijit
Published: June 2010

Micro heat exchangers are emerging as one of the most effective cooling technologies for high power-density applications. The design of micro heat exchangers is complicated by the presence of alternating flow regimes, which give way to flow boiling instability. Bubble formation inside microchannels can be correlated directly to flow boiling instability and can regulate flow characteristics and wall heat transfer when the bubbles grow to reach the microchannel hydraulic diameter. In this study, the growth of vapor bubbles in a single microchannel was examined using an experimental setup capable of measuring coolant flow rate, inlet and outlet liquid temperatures, and channel wall surface temperature. Liquid flow rate and wall heat flux were systematically varied while a high-speed camera was used to capture images of vapor bubbles forming in the channel. These images were used to compare bubble growth rates for a constant flow rate. The results provide fundamental understanding of the bubble growth process.
CFD Analysis of Coal Combustion With Oxygen/CO2/H2O Mixture
Authors: Ghenai Chaouki
Published: June 2010

Coal combustion with oxygen is considered one of the most effective methods to improve thermal efficiency, reduce pollutant emissions such as NOX, and facilitate capture of CO2 pollutant from flue gas. This paper presents calculations of oxygen coal combustion with flue gas recirculation. The coal is burned in oxygen/CO2/H20 mixture. In addition to solving transport equations for the continuous phase (gas), a discrete second phase (spherical particles) is simulated in the Lagrangian frame of reference. Reaction is modeled by a mixture fractions/PDF approach. Discrete phase modeling is used for the prediction of discrete phase trajectory and heat and mass transfer to/from particles. Drayton coal with a lower heating value of 27.8 MJ/Kg is used in this study. Coal is burned in oxygen/CO2/H20 mixture with a composition of VC02+H20/VO2 = 0 to 4. The results obtained in this study show clearly the benefit of burning coal with oxygen/CO2/H20 mixture compared to coal combustion with air. The CO2 emissions increases which will help to reduce the cost of CO2 capture, NOX emissions will also decrease because of the replacement of nitrogen in air by CO2/H20 mixture, and better devolatization and burnout of coal particles for coal combustion with oxygen/CO2/H20 mixture. In addition to that, with a CO2/H20 to oxygen volume ratio of 0.67, the gas temperature is the same as the gas temperature for coal combustion with air. No modifications of the combustor materials is required during the retrofitting of power plant with oxygen coal combustion systems.
Experimental Study of Effects of Non-Condensable on Condensation in a Vertical Tube Bundle
Authors: Zhou Wenzhong , Henderson Gavin , Revankar Shripad T.
Published: June 2010

One of the engineered safety systems in the advanced boiling water reactor is a passive containment cooling system (PCCS) which is composed of a number of vertical heat exchanger. After a loss of coolant accident, the pressurized steam discharged from the reactor and the noncondensable (NC) gases mixture flows into the PCCS condenser tube. The PCCS condenser must be able to remove sufficient energy from the reactor containment to prevent containment from exceeding its design pressure. The efficient performance of the PCCS condenser is thus vital to the safety of the reactor. In PCCS condenser tube three flow conditions are expected namely the forced flow, cyclic venting and complete condensation modes. The PCCS test facility consists of steam generator (SG), instrumented condenser with secondary pool boiling section, condensation tank, suppression pool, storage tank, air supply line, and associated piping and instrumentation. The specific design of condensing tube is based on scaling analysis from the PCCS design of ESBWR. The scaled PCCS is made of four tubes of diameter 52.5mm and height 1.8 m arranged in square pitch. Steam air mixture condensation tests were carried out in a through flow mode of operation where the mixture flows through the condenser tube with some steam condensation. Data on condensation heat transfer were obtained for two nominal pressures, 225 kPa and 275 kPa and for air concentration fraction from 0 to 13%. Test results showed that with increase in pressure the condensation heat transfer increased. The presence of the air in the steam decreased the condensation heat transfer coefficient from 10 to 45% depending on air fraction in the steam.
Measurements of Mean Heat Transfer Coefficients for Turbulent Forced Convection in a Rectangular Duct With Uniformly Spaced Plate Inserts
Authors: Camargo Lorena , Gitsham Matthew , Baliga B. Rabi
Published: June 2010

An experimental investigation of turbulent forced convection from single and multiple heated plates in the spatially-periodic fully-developed region of air flows in a straight rectangular duct with uniformly spaced plate inserts is described. The focus in this work is on measurements of temporally- and spatially-averaged heat transfer coefficients on the surfaces of the aforementioned plates. The experimental technique is based on a lumped parameter analysis. Six different heated plates were specially designed, constructed, and instrumented for this work. Each of these heated plates was made up of a central metal section (brass, aluminum, or copper) and two plastic end sections (Ertalyte): the metal section was constructed from a top part and a bottom part, with grooves milled in the bottom part to accommodate three thermocouples and an electrical heating wire; the plastic sections were used to reduce the rates of heat loss from the ends to negligible amounts compared to that due to forced convection from the lateral surfaces of the metal section to the air. The Reynolds number used in the presentation of the results is based on the time-mean average streamwise velocity in the minimum cross-sectional area of the duct and a hydraulic diameter: its values ranged from 2,000 to 30,000. Details of the experimental technique used and the results obtained are presented and discussed.
Flow Visualization in Boiling Water Flows Leading Up to Departure From Nucleate Boiling in an Electrically-Heated Duct
Authors: Krenitsky Helene A. , Hurlburt Evan T. , Fore Larry B. , McKeown Paul T. , Williams Richard B.
Published: June 2010

A fundamental departure from nucleate boiling (DNB) flow visualization experiment was designed to obtain a better understanding of flow boiling by visually capturing the mechanisms leading up to and including DNB for subcooled vertical flow boiling. At the critical heat flux (CHF) the heat transfer coefficient between the wall and fluid is greatly reduced, entering an inefficient heat transfer region that can cause a rapid increase in wall temperature. Most of the visual data on DNB in the open literature comes from experiments conducted with refrigerants or with water at relatively low pressure. One goal of this test was to capture high-quality photographs leading up to DNB for water at higher pressures, higher mass fluxes, and larger inlet subcooling than most of the data in the open literature. The fundamental DNB experiment consisted of three different run stages: incipient boiling, subcooled boiling, and CHF runs, which were intended to capture the behavior leading up to and including a departure from nucleate boiling crisis. At high heat flux conditions, the steep temperature and refractive-index gradients in the water near the wall act like lenses and bend the light away from the wall, which is the region of interest for discerning the DNB mechanism. By frosting the inner surface of the window on the light source side, the nearly collimated light was diffused as it entered the test section and enabled better visualization near the wall region. A high speed camera was used in testing. A typical run consisted of a 2 second image data set, with a resolution of 512 by 160 pixels, at 10,000 frames per second. Three excursive CHF runs were achieved, the last of which melted the test section. The trigger function on the camera captured images from before and after the power trip for the last CHF run. A trend can be seen of an increasing two-phase friction factor with power that begins to increase more rapidly at test section powers greater than 64.5kW. The 1995 Groenevel, et al. (1996) look-up table proved to be a good estimate of the heat flux at DNB.
Experimental Evidence of Density and Mechanical Properties Enhancement of Binary Alloys by Solidification Subject to Vibrations
Authors: Vadasz J. , Meyer J. P. , Govender S. , Andrick M. , Carter W. , Ebrahim H. , Naidoo A. , Ngubane I. , Ogle M.
Published: June 2010

Preliminary evidence of density and mechanical properties enhancement of binary alloys by solidification subject to vibrations is presented. The frequency of vibrations was increased from 0 to 100 Hz by using sound waves as the vibration source. The latter shows that the solidified microstructure, the ultimate tensile strength, and the hardness improve as the frequency increases. The chosen alloy for this study was Pb-Sb 4.4% (lead antimony 4.4%) and was selected because of its low melting temperature. The cast chosen was of a rod shape having a diameter of 10mm and a length 500mm. This choice is consistent with assuming an infinite length and therefore ignoring boundary effects in a planned theoretical follow-up analysis. Also due to the geometry of the mould it can be assumed that the cast was cooled due to conduction alone.
The electron propagator in external electromagnetic fields in low dimensions
Authors: Murguía Gabriela , Raya Alfredo , Sánchez Ángel , Reyes Edward
Published: June 2010

We study the electron propagator in quantum electrodynamics in one and two spatial dimensions in the presence of external electromagnetic fields. In this case, the propagator is not diagonal in momentum space. We obtain the propagator on the basis of the eigenfunctions of the operator (γ⋅Π)2 in terms of which the propagator acquires a free form. Πμ is the canonical momentum operator and γμ are the Dirac matrices. In two dimensions, we work with an irreducible representation of the Clifford algebra and consider to all orders the effects of an arbitrary magnetic field perpendicular to the plane of motion of the electrons. We then discuss the special cases of a uniform magnetic field and an exponentially damped static magnetic field. These cases are relevant to graphene in the massless limit. We further consider the electron propagator for the massive Schwinger model and incorporate the effects of a constant electric field to all orders.
Impact of multimedia learning modules on an introductory course on electricity and magnetism
Authors: Stelzer Timothy , Brookes David T. , Gladding Gary , Mestre José P.
Published: June 2010

Web-based multimedia learning modules were added as prelectures to our reformed introductory electricity and magnetism course. Each module consisted of approximately 20 min of narrated animation, and students were given credit for completing them before lecture. To compensate for this additional time, lectures were reduced from 75 to 50 min. In addition to a modest increase in exam performance, the changes dramatically improved student attitudes toward the course in general and lectures in particular.
Berry phases near degeneracies: Beyond the simplest case
Authors: Garg Anupam
Published: June 2010

The Berry phase is reviewed with emphasis on the Berry curvature and the Chern number. The behavior of these quantities and the analytic properties of adiabatically continued wave functions in the vicinity of degeneracies are discussed. An example of a spin Hamiltonian is given in which the Chern numbers associated with the states involved in a double degeneracy are ±2 rather than ±1, as is usually the case. Degeneracies in the spectrum of magnetic molecular solids are discussed.
Three ways to obtain flat rotation curves: A problem in undergraduate computational physics
Authors: Bacon M. E. , Sharrar Amber
Published: June 2010

We have addressed the need to introduce undergraduates to computational methods in physics by making computation an integral part of our intermediate laboratory experience. We discuss an example of a senior project that follows an introduction to a suite of computational tools in our intermediate laboratory and focuses on a topic in astrophysics. We report on computations of flat rotation curves for spiral galaxies using three models and compare the results to the available data for the spiral galaxy NGC 3198. The models are the “standard” exponential disk+dark matter halo model, the modified Newtonian dynamic model, and a general computational procedure that allows for testing arbitrary nonstandard surface mass density distributions. The models can also be applied to other spiral galaxies for which data are readily available.
Virus-Induced Ca
2+
Influx Extends Survival of West Nile Virus-Infected Cells
Authors: Scherbik Svetlana V. , Brinton Margo A.
Published: June 2010

West Nile virus (WNV) infection leads to rapid and sustained Ca
2+
influx. This influx was observed with different strains of WNV and in different types of cells. Entry during virion endocytosis as well as through calcium channels contributed to the Ca
2+
influx observed in WNV-infected cells. Ca
2+
influx was not detected after infection with vesicular stomatitis virus (VSV) and occurred only through endocytosis in Sindbis virus-infected cells. Caspase 3 cleavage and activation of several kinases, including focal adhesion kinase (FAK), mitogen-activated extracellular signal-regulated protein kinase (ERK1/2), and protein-serine kinase B alpha (Akt), at early times after WNV infection were shown to be dependent on Ca
2+
influx. Although the activation of these kinases was sustained in virus-infected cells throughout infection, UV-inactivated WNV induced only a transient activation of FAK and ERK1/2 at early times after infection. The Ca
2+
-dependent FAK activation observed in WNV-infected cells was not mediated by αvβ3 integrins. Reduction of Ca
2+
influx at early times of infection by various treatments decreased the viral yield and delayed both the early transient caspase 3 cleavage and the activation of FAK, Akt, and ERK signaling. The results indicate that Ca
2+
influx is required for early infection events needed for efficient viral replication, possibly for virus-induced rearrangement of the endoplasmic reticulum (ER) membrane. Increased caspase 3 cleavage at both early (transient) and late times of infection correlated with decreased activation of the FAK and ERK1/2 pathways, indicating a role for these kinases in extending the survival of flavivirus-infected cells.
Continued Evolution of H5N1 Influenza Viruses in Wild Birds, Domestic Poultry, and Humans in China from 2004 to 2009
Authors: Li Yanbing , Shi Jianzhong , Zhong Gongxun , Deng Guohua , Tian Guobin , Ge Jinying , Zeng Xianying , Song Jiasheng , Zhao Dongming , Liu Liling , Jiang Yongping , Guan Yuntao , Bu Zhigao , Chen Hualan
Published: June 2010

Despite substantial efforts to control H5N1 avian influenza viruses (AIVs), the viruses have continued to evolve and cause disease outbreaks in poultry and infections in humans. In this report, we analyzed 51 representative H5N1 AIVs isolated from domestic poultry, wild birds, and humans in China during 2004 to 2009, and 21 genotypes were detected based on whole-genome sequences. Twelve genotypes of AIVs in southern China bear similar H5 hemagglutinin (HA) genes (clade 2.3). These AIVs did not display antigenic drift and could be completely protected against by the A/goose/Guangdong/1/96 (GS/GD/1/96)-based oil-adjuvanted killed vaccine and recombinant Newcastle disease virus vaccine, which have been used in China. In addition, antigenically drifted H5N1 viruses, represented by A/chicken/Shanxi/2/06 (CK/SX/2/06), were detected in chickens from several provinces in northern China. The CK/SX/2/06-like viruses are reassortants with newly emerged HA, NA, and PB1 genes that could not be protected against by the GS/GD/1/96-based vaccines. These viruses also reacted poorly with antisera generated from clade 2.2 and 2.3 viruses. The majority of the viruses isolated from southern China were lethal in mice and ducks, while the CK/SX/2/06-like viruses caused mild disease in mice and could not replicate in ducks. Our results demonstrate that the H5N1 AIVs circulating in nature have complex biological characteristics and pose a continued challenge for disease control and pandemic preparedness.
Hit-and-Run Stimulation: a Novel Concept To Reactivate Latent HIV-1 Infection without Cytokine Gene Induction
Authors: Wolschendorf Frank , Duverger Alexandra , Jones Jennifer , Wagner Frederic H. , Huff Jason , Benjamin William H. , Saag Michael S. , Niederweis Michael , Kutsch Olaf
Published: June 2010

Current antiretroviral therapy (ART) efficiently controls HIV-1 replication but fails to eradicate the virus. Even after years of successful ART, HIV-1 can conceal itself in a latent state in long-lived CD4
+
memory T cells. From this latent reservoir, HIV-1 rebounds during treatment interruptions. Attempts to therapeutically eradicate this viral reservoir have yielded disappointing results. A major problem with previously utilized activating agents is that at the concentrations required for efficient HIV-1 reactivation, these stimuli trigger high-level cytokine gene expression (hypercytokinemia). Therapeutically relevant HIV-1-reactivating agents will have to trigger HIV-1 reactivation without the induction of cytokine expression. We present here a proof-of-principle study showing that this is a possibility. In a high-throughput screening effort, we identified an HIV-1-reactivating protein factor (HRF) secreted by the nonpathogenic bacterium
Massilia timonae
. In primary T cells and T-cell lines, HRF triggered a high but nonsustained peak of nuclear factor kappa B (NF-κB) activity. While this short NF-κB peak potently reactivated latent HIV-1 infection, it failed to induce gene expression of several proinflammatory NF-κB-dependent cellular genes, such as those for tumor necrosis factor alpha (TNF-α), interleukin-8 (IL-8), and gamma interferon (IFN-γ). Dissociation of cellular and viral gene induction was achievable, as minimum amounts of Tat protein, synthesized following application of a short NF-κB pulse, triggered HIV-1 transactivation and subsequent self-perpetuated HIV-1 expression. In the absence of such a positive feedback mechanism, cellular gene expression was not sustained, suggesting that strategies modulating the NF-κB activity profile could be used to selectively trigger HIV-1 reactivation.
An Adjuvant for the Induction of Potent, Protective Humoral Responses to an H5N1 Influenza Virus Vaccine with Antigen-Sparing Effect in Mice
Authors: Lau Yuk-Fai , Tang Lay-Hoon , McCall Amber W. , Ooi Eng-Eong , Subbarao Kanta
Published: June 2010

Intramuscular administration of inactivated influenza virus vaccine is the main vaccine platform used for the prevention of seasonal influenza virus infection. In clinical trials, inactivated H5N1 vaccines have been shown to be safe and capable of eliciting immune correlates of protection. However, the H5N1 vaccines are poorly immunogenic compared to seasonal influenza virus vaccines. Needle-free vaccination would be more efficient and economical in a pandemic, and the development of an effective and safe mucosal adjuvant will be an important milestone. A stabilized chemical analog of double-stranded RNA, PIKA, was previously reported to be a potent mucosal adjuvant in a murine model. While PIKA stimulates dendritic cells
in vitro
, little was known about its receptor and adjuvanting mechanism
in vivo
. In this study, we demonstrated that the immunostimulatory effect of PIKA resulted in an increased number of mature antigen-presenting cells, with the induction of proinflammatory cytokines at the inoculation site. In addition, coadministration of PIKA with a poorly immunogenic H5N1 subunit vaccine led to antigen sparing and quantitative and qualitative improvements of the immune responses over those achieved with an unadjuvanted vaccine in mice. The adjuvanted vaccine provided protection against lethal challenge with homologous and heterologous H5N1 wild-type viruses. Mice lacking functional TLR3 showed diminished cytokine production with PIKA stimulation, diminished antibody responses, and reduced protective efficacy against wild-type virus challenge following vaccination. These data suggest that TLR3 is important for the optimal performance of PIKA as an adjuvant. With its good safety profile and antigen-sparing effect, PIKA could be an attractive adjuvant for use in future pandemics.
Vaccinia Virus A25 and A26 Proteins Are Fusion Suppressors for Mature Virions and Determine Strain-Specific Virus Entry Pathways into HeLa, CHO-K1, and L Cells
Authors: Chang Shu-Jung , Chang Yu-Xun , Izmailyan Roza , Tang Yin-Liang , Chang Wen
Published: June 2010

Mature vaccinia virus enters cells through either fluid-phase endocytosis/macropinocytosis or plasma membrane fusion. This may explain the wide range of host cell susceptibilities to vaccinia virus entry; however, it is not known how vaccinia virus chooses between these two pathways and which viral envelope proteins determine such processes. By screening several recombinant viruses and different strains, we found that mature virions containing the vaccinia virus A25 and A26 proteins entered HeLa cells preferentially through a bafilomycin-sensitive entry pathway, whereas virions lacking these two proteins entered through a bafilomycin-resistant pathway. To investigate whether the A25 and A26 proteins contribute to entry pathway specificity, two mutant vaccinia viruses, WRΔA25L and WRΔA26L, were subsequently generated from the wild-type WR strain. In contrast to the WR strain, both the WRΔA25L and WRΔA26L viruses became resistant to bafilomycin, suggesting that the removal of the A25 and A26 proteins bypassed the low-pH endosomal requirement for mature virion entry. Indeed, WRΔA25L and WRΔA26L virus infections of HeLa, CHO-K1, and L cells immediately triggered cell-to-cell fusion at a neutral pH at 1 to 2 h postinfection (p.i.), providing direct evidence that viral fusion machinery is readily activated after the removal of the A25 and A26 proteins to allow virus entry through the plasma membrane. In summary, our data support a model that on vaccinia mature virions, the viral A25 and A26 proteins are low-pH-sensitive fusion suppressors whose inactivation during the endocytic route results in viral and cell membrane fusion. Our results also suggest that during virion morphogenesis, the incorporation of the A25 and A26 proteins into mature virions may help restrain viral fusion activity until the time of infections.
Identification of an
l
-Rhamnose Synthetic Pathway in Two Nucleocytoplasmic Large DNA Viruses
Authors: Parakkottil Chothi Madhu , Duncan Garry A. , Armirotti Andrea , Abergel Chantal , Gurnon James R. , Van Etten James L. , Bernardi Cinzia , Damonte Gianluca , Tonetti Michela
Published: June 2010

Nucleocytoplasmic large DNA viruses (NCLDVs) are characterized by large genomes that often encode proteins not commonly found in viruses. Two species in this group are
Acanthocystis turfacea
chlorella virus 1 (ATCV-1) (family
Phycodnaviridae
, genus
Chlorovirus
) and
Acanthamoeba polyphaga
mimivirus (family
Mimiviridae
), commonly known as mimivirus. ATCV-1 and other chlorovirus members encode enzymes involved in the synthesis and glycosylation of their structural proteins. In this study, we identified and characterized three enzymes responsible for the synthesis of the sugar
l
-rhamnose: two UDP-
d
-glucose 4,6-dehydratases (UGDs) encoded by ATCV-1 and mimivirus and a bifunctional UDP-4-keto-6-deoxy-
d
-glucose epimerase/reductase (UGER) from mimivirus. Phylogenetic analysis indicated that ATCV-1 probably acquired its UGD gene via a recent horizontal gene transfer (HGT) from a green algal host, while an earlier HGT event involving the complete pathway (UGD and UGER) probably occurred between a protozoan ancestor and mimivirus. While ATCV-1 lacks an epimerase/reductase gene, its
Chlorella
host may encode this enzyme. Both UGDs and UGER are expressed as late genes, which is consistent with their role in posttranslational modification of capsid proteins. The data in this study provide additional support for the hypothesis that chloroviruses, and maybe mimivirus, encode most, if not all, of the glycosylation machinery involved in the synthesis of specific glycan structures essential for virus replication and infection.
Molecular Basis of Neurovirulence of Flury Rabies Virus Vaccine Strains: Importance of the Polymerase and the Glycoprotein R333Q Mutation
Authors: Tao Lihong , Ge Jinying , Wang Xijun , Zhai Hongyue , Hua Tao , Zhao Bolin , Kong Dongni , Yang Chinglai , Chen Hualan , Bu Zhigao
Published: June 2010

The molecular mechanisms associated with rabies virus (RV) virulence are not fully understood. In this study, the RV Flury low-egg-passage (LEP) and high-egg-passage (HEP) strains were used as models to explore the attenuation mechanism of RV. The results of our studies confirmed that the R333Q mutation in the glycoprotein (GR333Q) is crucial for the attenuation of Flury RV in mice. The R333Q mutation is stably maintained in the HEP genome background but not in the LEP genome background during replication in mouse brain tissue or cell culture. Further investigation using chimeric viruses revealed that the polymerase L gene determines the genetic stability of the GR333Qmutation during replication. Moreover, a recombinant RV containing the LEP G protein with the R333Q mutation and the HEP L gene showed significant attenuation, genetic stability, enhancement of apoptosis, and immunogenicity. These results indicate that attenuation of the RV Flury strain results from the coevolution of G and L elements and provide important information for the generation of safer and more effective modified live rabies vaccine.
The PB2 Subunit of the Influenza Virus RNA Polymerase Affects Virulence by Interacting with the Mitochondrial Antiviral Signaling Protein and Inhibiting Expression of Beta Interferon
Authors: Graef Katy M. , Vreede Frank T. , Lau Yuk-Fai , McCall Amber W. , Carr Simon M. , Subbarao Kanta , Fodor Ervin
Published: June 2010

The PB2 subunit of the influenza virus RNA polymerase is a major virulence determinant of influenza viruses. However, the molecular mechanisms involved remain unknown. It was previously shown that the PB2 protein, in addition to its nuclear localization, also accumulates in the mitochondria. Here, we demonstrate that the PB2 protein interacts with the mitochondrial antiviral signaling protein, MAVS (also known as IPS-1, VISA, or Cardif), and inhibits MAVS-mediated beta interferon (IFN-β) expression. In addition, we show that PB2 proteins of influenza viruses differ in their abilities to associate with the mitochondria. In particular, the PB2 proteins of seasonal human influenza viruses localize to the mitochondria while PB2 proteins of avian influenza viruses are nonmitochondrial. This difference in localization is caused by a single amino acid polymorphism in the PB2 mitochondrial targeting signal. In order to address the functional significance of the mitochondrial localization of the PB2 protein
in vivo
, we have generated two recombinant human influenza viruses encoding either mitochondrial or nonmitochondrial PB2 proteins. We found that the difference in the mitochondrial localization of the PB2 proteins does not affect the growth of these viruses in cell culture. However, the virus encoding the nonmitochondrial PB2 protein induces higher levels of IFN-β and, in an animal model, is attenuated compared to the isogenic virus encoding a mitochondrial PB2. Overall this study implicates the PB2 protein in the regulation of host antiviral innate immune pathways and suggests an important role for the mitochondrial association of the PB2 protein in determining virulence.
Crystal Structure of PG16 and Chimeric Dissection with Somatically Related PG9: Structure-Function Analysis of Two Quaternary-Specific Antibodies That Effectively Neutralize HIV-1
Authors: Pancera Marie , McLellan Jason S. , Wu Xueling , Zhu Jiang , Changela Anita , Schmidt Stephen D. , Yang Yongping , Zhou Tongqing , Phogat Sanjay , Mascola John R. , Kwong Peter D.
Published: June 2010

HIV-1 resists neutralization by most antibodies. Two somatically related human antibodies, PG9 and PG16, however, each neutralize 70 to 80% of circulating HIV-1 isolates. Here we present the structure of the antigen-binding fragment of PG16 in monoclinic and orthorhombic lattices at 2.4 and 4.0 Å, respectively, and use a combination of structural analysis, paratope dissection, and neutralization assessment to determine the functional relevance of three unusual PG9/PG16 features: N-linked glycosylation, extensive affinity maturation, and a heavy chain-third complementarity-determining region (CDR H3) that is one of the longest observed in human antibodies. Glycosylation extended off the side of the light chain variable domain and was not required for neutralization. The CDR H3 formed an axe-shaped subdomain, which comprised 42% of the CDR surface, with the axe head looming ∼20 Å above the other combining loops. Comprehensive sets of chimeric swaps between PG9 and PG16 of light chain, heavy chain, and CDR H3 were employed to decipher structure-function relationships. Chimeric swaps generally complemented functionally, with differences in PG9/PG16 neutralization related primarily to residue differences in CDR H3. Meanwhile, chimeric reversions to genomic V genes showed isolate-dependent effects, with affinity maturation playing a significant role in augmenting neutralization breadth (
P
= 0.036) and potency (
P
< 0.0001). The structural and functional details of extraordinary CDR H3 and extensive affinity maturation provide insights into the neutralization mechanism of and the elicitation pathway for broadly neutralizing antibodies like PG9 and PG16.
‘Football for Health’—a football-based health-promotion programme for children in South Africa: a parallel cohort study
Authors: Fuller Colin W , Junge Astrid , DeCelles Jeff , Donald James , Jankelowitz Ryan , Dvorak Jiri
Published: June 2010

Objectives

To develop, implement and assess an interactive, football-based health education programme for children in South Africa.

Design

Prospective cohort study with control group.

Setting

Two schools in Khayelitsha township, South Africa.

Participants

370 children making up two intervention groups (Grade 6: 125; Grade 7: 131) and one control group (Grade 7: 114).

Intervention

Eleven 90 min sessions, each divided into two 45 min halves of Play Football (football skills) and Play Fair (health issues), each session focused on one specific health risk factor.

Main outcome measures

Health knowledge using a 20-item questionnaire; coaches' attitudes towards their training programme using a 10-item questionnaire and children's attitudes towards the health education programme using a six-item questionnaire.

Results

Children in the Grade 7 intervention group showed significant (p<0.05) increases in the proportion of correct responses for nine of the 20 health knowledge questions postintervention, and these increases were maintained at 3 months postintervention. The Grade 6 intervention group showed significant increases in the proportion of correct responses for 15 of the 20 health knowledge questions postintervention. The Grade 7 control group showed a significant increase in the proportion of correct responses to one of the 20 health knowledge questions post-Play Football sessions and nine of 20 questions post-Play Fair sessions. Over 90% of the children provided positive attitude responses to the health-education programme.

Conclusions

The programme demonstrated that it was possible to implement a football-based health-education programme for children in Africa that achieved significant increases in health knowledge and that was also well received by participants.
Lateral sacral artery aneurysm of the lumbar spine: hemorrhage resulting in cauda equina syndrome
Authors: Nogueira Raul G , Kasper Ekkehard , Walcott Brian P , Nahed Brian V , Redjal Navid , Coumans Jean-Valery , Hirsch Joshua A
Published: June 2010

Objective

To describe the effective treatment of a ruptured lateral sacral artery aneurysm presenting as a spinal epidural hematoma.

Design

Case report and literature review.

Setting

University teaching hospital, neurovascular center.

Participant

A man with a history of renal allograft who presented with sudden onset low back pain.

Intervention

The patient underwent emergent decompressive surgery, diagnostic angiogram and endovascular embolization.

Main outcome measure

Obliteration of aneurysm and restoration of neurological function.

Results

Surgery resulted in decompression of the cauda equina. The patient's aneurysm was endovascularly obliterated. There was complete restoration of neurological function.

Conclusion

Lateral sacral artery aneurysm formation and rupture is a rare cause of epidural hemorrhage and one described only in patients who have undergone renal transplantation. It may be caused by high flow from transpelvic collaterals between both internal iliac arteries. Treatment includes endovascular obliteration and may necessitate operative decompression in the setting of neurological compromise.
AN EXPANDING 4D UNIVERSE IN A 5D KALUZA–KLEIN COSMOLOGY WITH HIGHER DIMENSIONAL MATTER
Authors: DARABI F.
Published: June 2010

In the framework of Kaluza–Klein theory, we investigate a (4+1)-dimensional universe consisting of a (4+1)-dimensional Robertson–Walker type metric coupled with a (4+1)-dimensional energy–momentum tensor. The matter part consists of an energy density together with a pressure subject to 4D part of the (4+1)-dimensional energy–momentum tensor. The dark part consists of just a dark pressure [Formula: see text], corresponding to the extra-dimension endowed by a scalar field, with no element of dark energy. It is shown that the reduced Einstein field equations are free of 4D pressure and are just affected by an effective pressure produced by the 4D energy density and dark pressure. It is then proposed that the expansion of the universe may be controlled by the equation of state in higher dimension rather than four dimensions. This may account for the current acceleration at the beginning or in the middle of matter dominant era.
A METAL–INSULATOR TRANSITION IN 2D: ESTABLISHED FACTS AND OPEN QUESTIONS
Authors: Kravchenko S. V. , Sarachik M. P.
Published: June 2010

The discovery of a metallic state and a metal–insulator transition (MIT) in two-dimensional (2D) electron systems challenges one of the most influential paradigms of modern mesoscopic physics, namely, that "there is no true metallic behavior in two dimensions". However, this conclusion was drawn for systems of noninteracting or weakly interacting carriers, while in all 2D systems exhibiting the metal–insulator transition, the interaction energy greatly exceeds all other energy scales. We review the main experimental findings and show that, although significant progress has been achieved in our understanding of the MIT in 2D, many open questions remain.
FINANCIAL TSUNAMI, ECONOMIC INSECURITY AND SOCIAL PROTECTION: THE CASE OF HONG KONG
Authors: LEE KIM MING , CHENG CHING YIN
Published: June 2010

Rising economic inequality becomes an important concern for both advanced and developing countries. Nonetheless, political and business elites around the world never question the neoliberal agenda, despite economic crises happening every now and then. The year 2007 may mark the turning point of neoliberal globalisation. As the global financial tsunami kicked off from the burst of the subprime mortgage bubble in the United States in 2007, the global economy is facing an economic hardship never heard of since the Great Depression in the 1930s. Hong Kong as a highly open economy is also severely hurt by the financial tsunami. In every economic recession, all Hong Kong people suffer, but lower classes suffer most. This raises a serious question about whether the current social protection system adequately protects people against an increasingly risky global economic environment. By examining the social policy package adopted by the HK government in fighting against the financial tsunami, we show the lack of long-term strategies and commitments of the government in protecting HK people against globalisation risks and economic insecurity. By drawing experiences from other countries, we suggest that active labour market policies (ALMPs) may be the social policy tools the government can use to reform the social protection system.
日出山莊輔導有濫藥習慣的青少年成效評估調查
Authors: 司徒 明旺 , 陳 志慧 , 陳 永芳
Published: June 2010

香港基督教服務處賽馬會日出山莊 ( 下稱 ⌈日出山莊⌋ ) 於2003年3月成立, 旨在為30歲以下濫用鴉片類藥物和濫用多種藥物人士, 提供一站式的人性化戒毒治療和康復服務, 重點並不單放在解決服務使用者的濫藥問題, 並更著重在他們的成長過程中加以協助, 期望他們能更有效地處理目前與將來要面對的種種問題, 故此, 中心著力於營造一個充滿愛的治療環境及製造機會供服務使用者成長. 日出山莊於06至08年間以量化和質性的混合研究模式評估服務成效. 透過客觀的數據分析和受訪者主觀的評價, 我們印證了日出山莊的服務確能使服務使用者戒除藥癮和獲得正面成長的效果

Hong Kong Christian Service Jockey Club Lodge of Rising Sun (LRS) has commenced its operation in 2003. The centre aims at providing one-stop and humanistic drug treatment and rehabilitation service for opiate and poly-drug abusers aged under 30. The focus of the treatment method adopted by the center is not merely to solve the clients' addiction problem. Rather, it is to assist the clients in their growth process, so that they can cope with current problems as well as future problems better. All effort aims at building a loving environment and creating opportunity for clients' growth. An evaluative research, which was done from 2006 to 2008, aimed at evaluating the effectiveness of the service provided by LRS through using a quantitative-qualitative mixed mode method. The result revealed that the service users have a significant improvement in their drug problems, and growth and development after receiving humanistic service provided by LRS.
A Unified Character-Based Tagging Framework for Chinese Word Segmentation
Authors: Zhao Hai , Huang Chang-Ning , Li Mu , Lu Bao-Liang
Published: June 2010

Chinese word segmentation is an active area in Chinese language processing though it is suffering from the argument about what precisely is a word in Chinese. Based on corpus-based segmentation standard, we launched this study. In detail, we regard Chinese word segmentation as a character-based tagging problem. We show that there has been a potent trend of using a character-based tagging approach in this field. In particular, learning from segmented corpus with or without additional linguistic resources is treated in a unified way in which the only difference depends on how the feature template set is selected. It differs from existing work in that both feature template selection and tag set selection are considered in our approach, instead of the previous feature template focus only technique. We show that there is a significant performance difference as different tag sets are selected. This is especially applied to a six-tag set, which is good enough for most current segmented corpora. The linguistic meaning of a tag set is also discussed. Our results show that a simple learning system with six
n
-gram feature templates and a six-tag set can obtain competitive performance in the cases of learning only from a training corpus. In cases when additional linguistic resources are available, an ensemble learning technique, assistant segmenter, is proposed and its effectiveness is verified. Assistant segmenter is also proven to be an effective method as segmentation standard adaptation that outperforms existing ones. Based on the proposed approach, our system provides state-of-the-art performance in all 12 corpora of three international Chinese word segmentation bakeoffs.
Topic-Dependent Language Model with Voting on Noun History
Authors: Naptali Welly , Tsuchiya Masatoshi , Nakagawa Seiichi
Published: June 2010

Language models (LMs) are an important field of study in automatic speech recognition (ASR) systems. LM helps acoustic models find the corresponding word sequence of a given speech signal. Without it, ASR systems would not understand the language and it would be hard to find the correct word sequence. During the past few years, researchers have tried to incorporate long-range dependencies into statistical word-based
n
-gram LMs. One of these long-range dependencies is topic. Unlike words, topic is unobservable. Thus, it is required to find the meanings behind the words to get into the topic. This research is based on the belief that nouns contain topic information. We propose a new approach for a topic-dependent LM, where the topic is decided in an unsupervised manner. Latent Semantic Analysis (LSA) is employed to reveal hidden (latent) relations among nouns in the context words. To decide the topic of an event, a fixed size word history sequence (window) is observed, and voting is then carried out based on noun class occurrences weighted by a confidence measure. Experiments were conducted on an English corpus and a Japanese corpus:
The Wall Street Journal
corpus and
Mainichi Shimbun
(Japanese newspaper) corpus. The results show that our proposed method gives better perplexity than the comparative baselines, including a word-based/class-based
n
-gram LM, their interpolated LM, a cache-based LM, a topic-dependent LM based on
n
-gram, and a topic-dependent LM based on Latent Dirichlet Allocation (LDA). The
n
-best list rescoring was conducted to validate its application in ASR systems.
SIGWEB
Authors: Munson Ethan
Published: June 2010

This is my penultimate Annual Report to the SIGWEB Membership and I continue to be lucky in having good news to report. As is traditional, there will also be a face-to-face SIGWEB Town Meeting on June 15 during Hypertext 2010 in Toronto, Canada.

SIGWEB is sound financially and has a solid pool of volunteers working on the SIG and its conferences. Membership has been rising recently, too. The Executive Committee is supporting a number of new initiatives including Student Travel Awards and increased communication and publicity efforts. A particularly exciting development is that SIGWEB is close to completing an agreement to be the primary sponsor of the Web Science conference series.
Interview with Peter Brusilovsky
Authors: Atzenbeck Claus
Published: June 2010

Peter Brusilovsky has been working in the field of adaptive hypermedia and adaptive Web-based systems for more than 20 years. He served as a co-editor of several books and a guest editor of several special journal issues on adaptive hypermedia and the adaptive Web. He co-founded the Adaptive Hypermedia conference series and chaired several conferences and multiple workshops on adaptive hypermedia, adaptive Web-based systems, and User Modeling. He is Associate Editor-in-Chief of IEEE Transactions on Learning Technologies and a board member for several journals. He is also the current President of User Modeling Inc., a professional organization of user modeling researchers. Dr. Brusilovsky is currently an Associate Professor of Information Science and Intelligent Systems at the University of Pittsburgh, where he leads Personalized and Adaptive Web Systems Lab.
A note on disjunctive form tautologies
Authors: Bauer M. , Brand D. , Fischer M. , Meyer A. , Paterson M.
Published: June 2010

Cook [1] and Karp [2] have shown that a large class of combinatorial decision problems can be solved in time bounded by a polynomial in the size of the problem iff there is a polynomial time procedure for deciding whether a disjunctive formula with at most three literals per disjunct in the propositional calculus is a tautology.
On some direct encodings of nondeterministic Turing machines operating in polynomial time into p-complete problems
Authors: Galil Zvi
Published: June 2010

Cook [1] and Karp [2] introduced the notion of complete problems. Meyer and Stockmeyer [3] showed that some problems require exponential time. All these problems have a common property which in the latter case implies that they cannot be solved in polynomial time.