bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of membrane potential, SR Ca2+ content and RyR responsiveness on systolic Ca2+ alternans in rat ventricular myocytes
Authors: Li Yatong , Díaz Mary E. , Eisner David A. , O'Neill Stephen
Published: January 2009

Previous work has shown that small depolarizing pulses produce a beat to beat alternation in the amplitude of the systolic Ca2+ transient in ventricular myocytes. The aim of the present work was to investigate the role of changes of SR Ca2+ content and L‐type Ca2+ current in this alternans. As the amplitude of the depolarizing pulse was increased from 10 to 30 mV the magnitude of alternans decreased. Confocal linescan studies showed that this was accompanied by an increase in the number of sites from which Ca2+ waves propagated. A sudden decrease in the depolarisation amplitude resulted in three classes of behaviour: (1) a gradual decrease in Ca2+ transient amplitude before alternans developed accompanied by a loss of SR Ca2+, (2) a gradual increase in Ca2+ transient amplitude before alternans accompanied by a gain of SR Ca2+, and (3) immediate development of alternans with no change of SR content. We conclude that alternans develops if the combination of decreased opening of L‐type channels and change of SR Ca2+ content results in spatially fragmented release from the SR as long as there is sufficient Ca2+ in the SR to sustain wave propagation. Potentiation of the opening of the ryanodine receptor (RyR) by low concentrations of caffeine (100 μm) abolished alternans for a few pulses but the alternans then redeveloped once SR Ca2+ content fell to the new threshold for wave propagation. Finally we show evidence that inhibiting L‐type Ca2+ current with 200 μm Cd2+ produces alternans by means of a similar fragmentation of the Ca2+ release profile and propagation of mini‐waves of Ca2+ release.
The spatial pattern of exocytosis and post‐exocytic mobility of synaptopHluorin in mouse motor nerve terminals
Authors: Gaffield Michael A. , Tabares Lucia , Betz William J.
Published: January 2009

We monitored the spatial distribution of exo‐ and endocytosis at 37°C in mouse motor nerve terminals expressing synaptopHluorin (spH), confirming and extending earlier work at room temperature, which had revealed fluorescent ‘hot spots’ appearing in repeatable locations during tetanic stimulation. We also tested whether hot spots appeared during mild stimulation. Averaged responses from single shocks showed a clear fluorescence jump, but revealed no sign of hot spots; instead, fluorescence rose uniformly across the terminal. Only after 5–25 stimuli given at high frequency did hot spots appear, suggesting a novel initiation mechanism. Experiments showed that about half of the surface spH molecules were mobile, and that spH movement occurred out of hot spots, demonstrating their origin as exocytic sources, not endocytic sinks. Taken together, our results suggest that synaptic vesicles exocytose equally throughout the terminal with mild stimulation, but preferentially exocytose at specific, repeatable locations during tetanic stimulation.
Severe Acute Respiratory Syndrome Coronavirus nsp9 Dimerization Is Essential for Efficient Viral Growth
Authors: Miknis Zachary J. , Donaldson Eric F. , Umland Timothy C. , Rimmer Ryan A. , Baric Ralph S. , Schultz L. Wayne
Published: January 2009

The severe acute respiratory syndrome coronavirus (SARS-CoV) devotes a significant portion of its genome to producing nonstructural proteins required for viral replication. SARS-CoV nonstructural protein 9 (nsp9) was identified as an essential protein with RNA/DNA-binding activity, and yet its biological function within the replication complex remains unknown. Nsp9 forms a dimer through the interaction of parallel α-helices containing the protein-protein interaction motif GXXXG. In order to study the role of the nsp9 dimer in viral reproduction, residues G100 and G104 at the helix interface were targeted for mutation. Multi-angle light scattering measurements indicated that G100E, G104E, and G104V mutants are monomeric in solution, thereby disrupting the dimer. However, electrophoretic mobility assays revealed that the mutants bound RNA with similar affinity. Further experiments using fluorescence anisotropy showed a 10-fold reduction in RNA binding in the G100E and G104E mutants, whereas the G104V mutant had only a 4-fold reduction. The structure of G104E nsp9 was determined to 2.6-Å resolution, revealing significant changes at the dimer interface. The nsp9 mutations were introduced into SARS-CoV using a reverse genetics approach, and the G100E and G104E mutations were found to be lethal to the virus. The G104V mutant produced highly debilitated virus and eventually reverted back to the wild-type protein sequence through a codon transversion. Together, these data indicate that dimerization of SARS-CoV nsp9 at the GXXXG motif is not critical for RNA binding but is necessary for viral replication.
Characterization of Lassa Virus Cell Entry and Neutralization with Lassa Virus Pseudoparticles
Authors: Cosset François-Loic , Marianneau Philippe , Verney Geraldine , Gallais Fabrice , Tordo Noel , Pécheur Eve-Isabelle , ter Meulen Jan , Deubel Vincent , Bartosch Birke
Published: January 2009

The cell entry and humoral immune response of the human pathogen Lassa virus (LV), a biosafety level 4 (BSL4) Old World arenavirus, are not well characterized. LV pseudoparticles (LVpp) are a surrogate model system that has been used to decipher factors and routes involved in LV cell entry under BSL2 conditions. Here, we describe LVpp, which are highly infectious, with titers approaching those obtained with pseudoparticles displaying G protein of vesicular stomatitis virus and their the use for the characterization of LV cell entry and neutralization. Upon cell attachment, LVpp utilize endocytic vesicles for cell entry as described for many pH-dependent viruses. However, the fusion of the LV glycoproteins is activated at unusually low pH values, with optimal fusion occurring between pH 4.5 and 3, a pH range at which fusion characteristics of viral glycoproteins have so far remained largely unexplored. Consistent with a shifted pH optimum for fusion activation, we found wild-type LV and LVpp to display a remarkable resistance to exposure to low pH. Finally, LVpp allow the fast and quantifiable detection of neutralizing antibodies in human and animal sera and will thus facilitate the study of the humoral immune response in LV infections.
Ebola Virus Protein VP35 Impairs the Function of Interferon Regulatory Factor-Activating Kinases IKKε and TBK-1
Authors: Prins Kathleen C. , Cárdenas Washington B. , Basler Christopher F.
Published: January 2009

The Ebola virus (EBOV) VP35 protein antagonizes the early antiviral alpha/beta interferon (IFN-α/β) response. We previously demonstrated that VP35 inhibits the virus-induced activation of the IFN-β promoter by blocking the phosphorylation of IFN-regulatory factor 3 (IRF-3), a transcription factor that is crucial for the induction of IFN-α/β expression. Furthermore, VP35 blocks IFN-β promoter activation induced by any of several components of the retinoic acid-inducible gene I (RIG-I)/melanoma differentiation-associated gene 5 (MDA-5)-activated signaling pathways including RIG-I, IFN-β promoter stimulator 1 (IPS-1), TANK-binding kinase 1 (TBK-1), and IκB kinase epsilon (IKKε). These results suggested that VP35 may target the IRF kinases TBK-1 and ΙΚΚε. Coimmunoprecipitation experiments now demonstrate physical interactions of VP35 with ΙΚΚε and TBK-1, and the use of an ΙΚΚε deletion construct further demonstrates that the amino-terminal kinase domain of ΙΚΚε is sufficient for interactions with either IRF-3 or VP35. In vitro, either ΙΚΚε or TBK-1 phosphorylates not only IRF-3 but also VP35. Moreover, VP35 overexpression impairs ΙΚΚε-IRF-3, ΙΚΚε-IRF-7, and ΙΚΚε-IPS-1 interactions. Finally, lysates from cells overexpressing IKKε contain kinase activity that can phosphorylate IRF-3 in vitro. When VP35 is expressed in the IKKε-expressing cells, this kinase activity is suppressed. These data suggest that VP35 exerts its IFN-antagonist function, at least in part, by blocking necessary interactions between the kinases ΙΚΚε and TBK-1 and their normal interaction partners, including their substrates, IRF-3 and IRF-7.
E7 Oncoprotein of Novel Human Papillomavirus Type 108 Lacking the E6 Gene Induces Dysplasia in Organotypic Keratinocyte Cultures
Authors: Nobre Rui Jorge , Herráez-Hernández Elsa , Fei Jian-Wei , Langbein Lutz , Kaden Sylvia , Gröne Hermann-Josef , de Villiers Ethel-Michele
Published: January 2009

The genome organization of the novel human papillomavirus type 108 (HPV108), isolated from a low-grade cervical lesion, deviates from those of other HPVs in lacking an E6 gene. The three related HPV types HPV103, HPV108, and HPV101 were isolated from cervicovaginal cells taken from normal genital mucosa (HPV103) and low-grade (HPV108) and high-grade cervical (HPV101) intraepithelial neoplasia (Z. Chen, M. Schiffman, R. Herrero, R. DeSalle, and R. D. Burk, Virology
360:
447-453, 2007, and this report). Their unusual genome organization, against the background of considerable phylogenetic distance from the other HPV types usually associated with lesions of the genital tract, prompted us to investigate whether HPV108 E7 per se is sufficient to induce the above-mentioned clinical lesions. Expression of HPV108 E7 in organotypic keratinocyte cultures increases proliferation and apoptosis, focal nuclear polymorphism, and polychromasia. This is associated with irregular intra- and extracellular lipid accumulation and loss of the epithelial barrier. These alterations are linked to HPV108 E7 binding to pRb and inducing its decrease, an increase in PCNA expression, and BrdU incorporation, as well as increased p53 and p21
CIP1
protein levels. A delay in keratin K10 expression, increased expression of keratins K14 and K16, and loss of the corneal proteins involucrin and loricrin have also been noted. These modifications are suggestive of infection by a high-risk papillomavirus.
HR-2 Mutations in Human Immunodeficiency Virus Type 1 gp41 Restore Fusion Kinetics Delayed by HR-1 Mutations That Cause Clinical Resistance to Enfuvirtide
Authors: Ray Neelanjana , Blackburn Leslie A. , Doms Robert W.
Published: January 2009

Enfuvirtide (ENF) prevents the entry of human immunodeficiency virus type 1 (HIV-1) into cells by binding to the HR-1 region of the viral envelope (Env) protein gp41 subunit. Resistance to ENF arises via mutations in the drug binding site in HR-1. In addition, HR-2 mutations are commonly observed in ENF-resistant Env proteins, though their role remains unclear. We explored the mechanistic basis for clinical resistance to ENF and the role of HR-2 mutations. Using panels of ENF resistance-associated mutants for two patients, we found that mutations in HR-1 slowed the fusion kinetics and that mutations in HR-2 restored fusion rates. We assessed the differences in the rates of fusion of these mutants from a temperature-arrested state and observed similar trends, suggesting that the step of delay occurs after coreceptor engagement. Sensitivity to neutralizing antibodies was unchanged by the HR-1 and HR-2 mutants in each panel. Since this result was in contrast to those of a previous in vitro analysis where enhanced sensitivity to neutralization was demonstrated for heterologous Envs with ENF resistance-associated HR-1 changes, we examined the context dependence of HR-1 and HR-2 mutations by transferring the mutations seen in one patient into the Env context of another. These studies revealed that some, but not all, HR-1 mutations, when placed out of context (i.e., in a patient Env where they did not originally arise), enhance sensitivity to neutralizing antibodies. However, in most cases, HR-1 mutations in ENF-treated patients evolve in a manner that preserves pretreatment neutralization sensitivity so as to evade the pressures of the immune system.
Evidence for general base catalysis by protic solvents in a kinetic study of alcoholyses and hydrolyses of 1-(phenoxycarbonyl)pyridinium ions under both solvolytic and non-solvolytic conditions
Authors: Kevill Dennis N. , Park Byoung-Chun , Kyong Jin Burm
Published: January 2009

The kinetics of nucleophilic substitution reactions of 1-(phenoxycarbonyl)pyridinium ions, prepared with the essentially non-nucleophilic/non-basic fluoroborate as the counterion, have been studied using up to 1.60 M methanol in acetonitrile as solvent and under solvolytic conditions in 2,2,2-trifluoroethan-1-ol (TFE) and its mixtures with water. Under the non- solvolytic conditions, the parent and three pyridine-ring-substituted derivatives were studied. Both second-order (first-order in methanol) and third-order (second-order in methanol) kinetic contributions were observed. In the solvolysis studies, since solvent ionizing power values were almost constant over the range of aqueous TFE studied, a Grunwald–Winstein equation treatment of the specific rates of solvolysis for the parent and the 4-methoxy derivative could be carried out in terms of variations in solvent nucleophilicity, and an appreciable sensitivity to changes in solvent nucleophilicity was found.
A sea-level curve for the Canadian Beaufort Shelf
Authors: Hill Philip R. , Mudie Peta J. , Moran Kate , Blasco Steve M.
Published: January 2009

Radiocarbon-dated peat and peaty clay samples from geotechnical boreholes in the Canadian Beaufort continental shelf have been used to reconstruct a late Quaternary relative sea-level (RSL) curve. The samples were carefully selected and evaluated using palynological techniques, to ensure that reasonable age error limits could be given to each sample. The dated samples were then related to the local geological setting, using seismic profiles to determine the environment of deposition. The resulting data show a rise of 140 m in RSL since 27 000 years BP. A minor lowering of RSL at some time between 20 000 and 10 000 years BP is inferred from acoustic data. Contributions from basin subsidence, sediment loading, and consolidation account for 35 m of the total RSL rise. The RSL curve is interpreted in the light of recent models of the isostatic and eustatic responses of the Earth's crust at the Laurentide ice-sheet margin. Ice may have been more extensive during the middle Wisconsinan than previously thought and may have caused the major lowering of sea level in the shelf area. This ice may have advanced to within several hundred kilometres of the Mackenzie Delta – Tuktoyaktuk Peninsula coast. An ice readvance of late Wisconsinan age probably caused a subsequent minor lowering of RSL.
Phyto- and chronostratigraphical correlations between the late Pennsylvanian Morien Group (Sydney, Nova Scotia) and the Silesian Pennant Measures (south Wales)
Authors: Zodrow Erwin L. , Cleal Chris J.
Published: January 2009

Three macrofloral interval zones, Lobatopteris vestita, L. micromiltoni, and Linopteris bunburii, recognized in the Westphalian D and the cantabrica Biozone in the Stephanian of Europe, are also present in the Morien Group (Pictou Group) of Sydney Coalfield, Nova Scotia. These zones allow a more refined correlation to be made between sequences of the same age in the Sydney and south Wales coalfields and thus between western Europe and North America in general.
A debris flow triggered by the breaching of a moraine-dammed lake, Klattasine Creek, British Columbia
Authors: Clague John J. , Evans S. G. , Blown Iain G.
Published: January 2009

A very large debris flow of unusual origin occurred in the basin of Klattasine Creek (southern Coast Mountains, British Columbia) between June 1971 and September 1973. The flow was triggered by the sudden release of up to 1.7 × 106 m3 of water from a moraine-dammed lake at the head of a tributary of Klattasine Creek. Water escaping from the lake mobilized large quantities of unconsolidated sediment in the valley below and thus produced a debris flow that travelled in one or, more likely, several surges 8 km downvalley on an average gradient of 10° to the mouth of the stream. Here, the flow deposited a sheet of coarse bouldery debris up to about 20 m thick, which temporarily blocked Homathko River. Slumps, slides, and debris avalanches occurred on the walls of the valley both during and in years following the debris flow. Several secondary debris flows of relatively small size have swept down Klattasine Creek in the 12–14 years since Klattasine Lake drained.
Estimates of terrestrial heat flow in offshore eastern Canada
Authors: Reiter Marshall , Jessop Alan M.
Published: January 2009

From available bottom-hole temperatures and conductivities estimated from lithologic descriptions, heat-flow estimates are calculated for 72 sites on the Canadian Atlantic Shelf. The resulting data suggest a pattern of low heat flow (~055 mW/m2) within the Paleozoic basins in proximity to land areas and generally intermediate heat flow (~60–80 mW/m2) along the outer half of the continental shelf. Higher heat flows (~90 mW/m2) are estimated along the shelf edge in some areas, e.g., the southwestern Scotian Shelf and the eastern Newfoundland and Labrador shelves. Radioactive heat generation in sediments that thicken seawards probably does not account for the observed increase in heat flow. The possibility that higher heat flows in some areas may arise because of fluid movement from depth is suggested. Various other causes for the high heat flows, e.g., tectonic or magmatic activity, are considered less likely.
Occurrence and significance of Late Silurian reefs in New Brunswick, Canada
Authors: Noble J. P. A.
Published: January 2009

Detailed studies of scattered outcrops and small quarries in the interior of northern New Brunswick have revealed the presence of small stromatoporoidal–stromatolitic reefs in a unit informally named the Laplante unit, of Pridolian age. The reefs consist mainly of laminar stromatoporoids and stromatolitic algae in a boundstone framework, but these are associated with tabulate coral bafflestones and also with stromatolitic algae, mudstones, and extensive biogenic and polymict breccias. The characteristics of the faunas and sediments suggest deposition as small reef mounds in relatively low-energy environments, and the associated internal breccias and mass flows suggest that these reef mounds were deposited on the upper slope at the margin of a narrow shelf, probably in a compressional tectonic regime with associated uplift. Several facies in the Laplante unit are similar to the Colline Daniel Facies of the West Point reef complex in southern Gaspé and suggest the possibility of a reef belt with sporadically developed reef mounds extending beneath Chaleur Bay. The reefal sediments are presently located in the basin between the Elmtree Inlier to the north and the Mirimichi Massif to the south, but there is some evidence that they are allochthonous. If so, they have not been transported very far. Evidence also suggests that emergence occurred and caused the development of solution features not long after deposition. This emergence was probably related to the phase of Pridolian tectonic compression and uplift.
40Ar/39Ar dating of micas from the East Kemptville tin deposit, Yarmouth County, Nova Scotia
Authors: Zentilli M. , Reynolds P. H.
Published: January 2009

The East Kemptville tin deposit in Nova Scotia, the largest known tin deposit in North America, lies in a greisen zone within the Davis Lake Pluton, generally considered to be part of the Devonian South Mountain Batholith. Our dating of micas from within the deposit suggests that the greisenization process that accompanied mineralization took place about 295 ± 5 Ma ago, that is, ca. 60 Ma after the emplacement of the batholith.Hydrothermal alteration–mineralization activity in southern Nova Scotia coincided with extensive shearing and tectonism throughout the Hercynian orogen. The East Kemptville deposit appears to be approximately coeval with similar mineralization in southwest England, the Iberian peninsula, and northwest Africa and much younger than the Devonian Acadian orogeny.
Tectonic strain determined from pillow selvages: accuracy and the cut effect
Authors: Borradaile Graham J.
Published: January 2009

Tectonic strain ratios on a surface passing through the centre of a deformed, pod-shaped lava pillow are close to the ratio of the maximum/minimum selvage thicknesses. This approximation is valid for a variety of cases with an accuracy of 20% even where the section does not pass through the centre of the pillow but as long as the section passes through the central third of the pillow. Variation in selvage thickness is unlikely to provide a meaningful estimate of strain where the pillow shape was originally tubular.
A new locality for primary xenolith-bearing nephelinites in northwestern British Columbia
Authors: Higgins Michael D. , Allen John M.
Published: January 2009

High Ni abundances (420–500 ppm) and Mg* values (100 × Mg/(Mg + Fe2+) = 69–71) and the presence of mantle-derived xenoliths indicate that a subvolcanic nephelinite intrusion in northwestern British Columbia represents an unmodified primary magma. A separate, closely associated nephelinite intrusion shows evidence of minor olivine fractionation from a similar composition. Only three other occurrences of primary nephelinite have been described. This new occurrence suggests that these magmas may not be so rare as previously supposed. The trace-element abundances closely resemble those of primary nephelinites of similar La content from Freemans Cove, Canada. Such compositions are usually taken as evidence of intraplate rifting and doming. Therefore, these rocks are further evidence of late Tertiary or Quaternary rifting in the Stikine volcanic belt.
FANO INTERFERENCE IN THE QUANTUM WELL–QUANTUM DOT SYSTEM
Authors: ABRAMOV A. A. , LIN C.-H. , LIU C. W.
Published: January 2009

The interaction between the quantum dot (QD) level and the 2D continuum of a quantum well (QW) is investigated theoretically. Due to interference from these states, the Fano-like resonance states appear in the 2D continuum of the QW. Also, the free-electron energy band of the QW is changed because of QD potential influence. We have calculated the position and the broadening of Fano resonances, and also modified the band structure of free states in the QW. The obtained results are used further for research on tunneling from the QW to the QD.
MAGNETIC STUDIES OF METAL–INSULATOR TRANSITION IN A QUANTUM WELL SYSTEM
Authors: PETER A. JOHN , SUGIRTHAM L. CAROLINE
Published: January 2009

Metal–insulator transition in doped semiconductors is investigated in the presence of intense magnetic fields. A variational procedure within the effective mass approximation is employed using the Thomas–Fermi screening function and the exact quasi-Q2D Lindhard dielectric function. The Hubbard model results are justified using an effective mass that depends on interimpurity separation. The nonparabolicity of the subband is included using an energy-dependent effective mass. Though an increase of ionization energy with a magnetic field is observed for isolated donor models, the metallization occurs with an intense magnetic field at a higher concentration for a particular well width. The diamagnetic susceptibility of a hydrogenic donor impurity in GaAs / Ga 1 - x Al x As quantum well systems is discovered in the observation of metal–insulator transition. It is shown that the diamagnetic susceptibility diverges for all critical concentrations for a given well width. The large diamagnetic susceptibility (> 6) is observed at the transition. All the calculations are carried out for infinite and finite barriers, and the results are compared with the existing literature.
BEHAVIOR OF THE CONFINED HARD-SPHERE FLUID WITHIN NANOSLITS: A FUNDAMENTAL-MEASURE DENSITY-FUNCTIONAL THEORY STUDY
Authors: KAMALVAND MOHAMMAD , KESHAVARZI TAHMINEH (EZZAT) , MANSOORI G. ALI
Published: January 2009

A property of central interest for theoretical study of nanoconfined fluids is the density distribution of molecules. The density profile of the hard-sphere fluids confined within nanoslit pores is a key quantity for understanding the configurational behavior of confined real molecules. In this report, we produce the density profile of the hard-sphere fluid confined within nanoslit pores using the fundamental-measure density-functional theory (FM-DFT). FM-DFT is a powerful approach to studying the structure and the phase behavior of nanoconfined fluids. We report the computational procedure and the calculated data for nanoslits with different widths and for a wide range of hard-sphere fluid densities. The high accuracy of the resulting density profiles and optimum grid-size values in numerical integration are verified. The data reveal a number of interesting features of hard spheres in nanoslits, which are different from the bulk hard-sphere systems. These data are also useful for a variety of purposes, including obtaining the shear stress, thermal conductivity, adsorption, solvation forces, free volume and prediction of phase transitions.
MODIFIED EXFOLIATED GRAPHITE AS A MATERIAL FOR SHIELDING AGAINST ELECTROMAGNETIC RADIATION
Authors: VOVCHENKO LYUDMILA , MATZUI LYUDMILA , OLIYNYK VIKTOR , LAUNETZ VILEN , PRYLUTSKYY YURIY , HUI DAVID , STRZHEMECHNY YURI M.
Published: January 2009

We report on the structure and morphology of thermoexfoliated graphite (TEG) powders and TEG–metal ( Co , Cu , Ni ) powders. Electrodynamic parameters of the compacted TEG and TEG–metal specimens have been studied along the compacting axis (c axis) within the range of electromagnetic radiation frequencies between 25.5 and 37.5 GHz. Metal particles attached to the surface of the TEG particles yield enhanced radiation shielding within the entire frequency range. Moreover, it is observed that the absorption coefficient increases with the increase in conductivity of the metal particles and is enhanced due to a high concentration of TEG–metal boundaries, which promote multiple reflections.
INVESTIGATION OF MAGNETIZATION BEHAVIORS OF IONIC FERROFLUIDS BASED ON CoFe2O4 NANOPARTICLES
Authors: LI JIAN , LIN YUEQIANG , LIU XIAODONG , GAO RONGLI , HAN SHAONA
Published: January 2009

The average density of CoFe 2 O 4 particles treated by using ferric nitrate is decided from specific saturation magnetization of both untreated and treated particles. Besides, some characteristic parameters, depending on the density of particles, are determined for CoFe 2 O 4 ionic ferrofluids. The magnetization of the ferrofluids exhibits abnormal behaviors and is interpreted in relation to aggregates self-assembled from particles in the ferrofluids. Ringlike aggregates in which particles' moments linked into closed flux cause the saturation magnetization measured to be less than the theoretical value. The aggregates with opposed-parallel moments ordering will break up into isolated particles in the first magnetization process, so that the second magnetization will be easier than the first. For the aggregates with head-to-tail linked moments ordering, the magnetization behavior of the self-assembly structure may be hard to distinguish from field-induced aggregates.
GEOMETRICALLY NONLINEAR ANALYSIS OF MICROSWITCHES USING THE LOCAL MESHFREE METHOD
Authors: GU Y. T.
Published: January 2009

In the modeling and simulation of microelectromechanical system (MEMS) devices, such as the microswitch, the large deformation or the geometrical nonlinearity should be considered. Due to the issue of mesh distortion, the finite element method (FEM) is not effective for this large deformation analysis. In this paper, a local meshfree formulation is developed for geometrically nonlinear analysis of MEMS devices. The moving least squares approximation (MLSA) is employed to construct the meshfree shape functions based on the arbitrarily distributed field nodes and the spline weight function. The discrete system of equations for two-dimensional MEMS analysis is obtained using the weighted local weak form, and based on the total Lagrangian (TL) approach, which refers all variables to the initial configuration. The Newton–Raphson iteration technique is used to get the final results. Several typical microswitches are simulated by the developed nonlinear local meshfree method. Some important parameters of these microswitches, e.g. the pull-in voltage, are studied. Compared with the experimental results and results obtained by linear analysis, nonlinear meshfree analysis of microswitches is accurate and efficient. It has demonstrated that the present nonlinear local meshfree formulation is very effective for geometrically nonlinear analysis of MEMS devices, because it totally avoids the issue of mesh distortion in the FEM.
SIMULATION OF VEHICLE–BRIDGE COUPLING VIBRATION CONSIDERING THE TRANSIENT JUMP OF THE WHEEL
Authors: LIU XUE-WEN , LUO HAN-ZHONG , HUANG XING-CHUN
Published: January 2009

The transient jump of the wheel is a possible phenomenon in the actual running of light transit. But it is seldom considered in the analysis of vehicle–bridge coupling vibration. In this paper, the so-called alterable element method (AEM) is employed to deal with the coupling interaction of vehicle and bridge considering the actual transient jump of the wheel, and so the classical "contact all along" assumption, which regards wheels and lower structures as being always in contact with each other, is abandoned. In the numerical study, different moving vehicle models where the effects of random and abrupt corrugation are taken into consideration are presented. Also, the effect of velocity on the transient jump is investigated. The numerical solutions compare favorably with the results obtained by alternative methods when no jump phenomenon exists. By using the present method, the transient jump of the wheel with abrupt irregularity is studied. Compared with results of the semianalytical method, the validity of the simulation is confirmed.
APPLICATION OF GENETIC ALGORITHM FOR PSS AND FACTS-BASED CONTROLLER DESIGN
Authors: PANDA SIDHARTHA , PADHY NARAYANA PRASAD
Published: January 2009

This paper investigates the application of genetic algorithm (GA) for the design of a power system stabilizer (PSS) and a flexible ac transmission system (FACTS)–based controller to enhance power system stability. The design problem of the proposed controllers is formulated as an optimization problem and the GA optimization technique is employed to search for optimal controller parameters. The proposed controllers are tested on a weakly connected power system under various disturbances and loading conditions, and compared with a conventional PSS (CPSS). The eigenvalue analysis and nonlinear simulation results show the effectiveness and robustness of the proposed controllers.
EDGE-BASED SMOOTHED POINT INTERPOLATION METHODS
Authors: LIU G. R. , ZHANG G. Y.
Published: January 2009

This paper formulates an edge-based smoothed point interpolation method (ES-PIM) for solid mechanics using three-node triangular meshes. In the ES-PIM, displacement fields are construed using the point interpolation method (polynomial PIM or radial PIM), and hence the shape functions possess the Kronecker delta property, facilitates the enforcement of Dirichlet boundary conditions. Strains are obtained through smoothing operation over each smoothing domain associated with edges of the triangular background cells. The generalized smoothed Galerkin weak form is then used to create the discretized system equations and the formation is weakened weak formulation. Four schemes of selecting nodes for interpolation using the PIM have been introduced in detail and ES-PIM models using these four schemes have been developed. Numerical studies have demonstrated that the ES-PIM possesses the following good properties: (1) the ES-PIM models have a close-to-exact stiffness, which is much softer than for the overly-stiff FEM model and much stiffer than for the overly-soft node-based smoothed point interpolation method (NS-PIM) model; (2) results of ES-PIMs are generally of superconvergence and "ultra-accurate"; (3) no additional degrees of freedom are introduced, the implementation of the method is straightforward, and the method can achieve much better efficiency than the FEM using the same set of triangular meshes.
SIGGRAPH debuts in Asia
Authors: Kroeker Kirk L.
Published: January 2009

ACM's premier computer graphics conference hosts its first-ever graphics event in Asia, with a more global focus.
EducationHuman computing skills
Authors: Fletcher George H. L. , Lu James J.
Published: January 2009

Establishing the fundamentals of computational thinking is essential to improving computer science education.
Privacy and securityInternational communications surveillance
Authors: Irion Kristina
Published: January 2009

Aren't we all foreigners when our Internet traffic transits through other countries and is subject to regional intelligence-gathering policies?
Toward 2

W

, beyond web 2.0
Authors: Raman T. V.
Published: January 2009

2

W

is a result of the exponentially growing Web building on itself to move from a Web of content to a Web of applications.
Compiler research
Authors: Hall Mary , Padua David , Pingali Keshav
Published: January 2009

Research and education in compiler technology is more important than ever.
A sneak peek at Windows 7
Authors: Greiner Lynn
Published: January 2009

For those burned by Windows Vista, Microsoft's next OS may just be the welcomed salve we needed.
Do not crawl in the DUST
Authors: Bar-Yossef Ziv , Keidar Idit , Schonfeld Uri
Published: January 2009

We consider the problem of DUST: Different URLs with Similar Text. Such duplicate URLs are prevalent in Web sites, as Web server software often uses aliases and redirections, and dynamically generates the same page from various different URL requests. We present a novel algorithm,
DustBuster
, for uncovering DUST; that is, for discovering rules that transform a given URL to others that are likely to have similar content. DustBuster mines DUST effectively from previous crawl logs or Web server logs,
without
/examining page contents. Verifying these rules via sampling requires fetching few actual Web pages. Search engines can benefit from information about DUST to increase the effectiveness of crawling, reduce indexing overhead, and improve the quality of popularity statistics such as PageRank.
Browsing on small displays by transforming Web pages into hierarchically structured subpages
Authors: Xiao Xiangye , Luo Qiong , Hong Dan , Fu Hongbo , Xie Xing , Ma Wei-Ying
Published: January 2009

We propose a new Web page transformation method to facilitate Web browsing on handheld devices such as Personal Digital Assistants (PDAs). In our approach, an original Web page that does not fit on the screen is transformed into a set of subpages, each of which fits on the screen. This transformation is done through slicing the original page into page blocks iteratively, with several factors considered. These factors include the size of the screen, the size of each page block, the number of blocks in each transformed page, the depth of the tree hierarchy that the transformed pages form, as well as the semantic coherence between blocks. We call the tree hierarchy of the transformed pages an SP-tree. In an SP-tree, an internal node consists of a textually enhanced thumbnail image with hyperlinks, and a leaf node is a block extracted from a subpage of the original Web page. We adaptively adjust the fanout and the height of the SP-tree so that each thumbnail image is clear enough for users to read, while at the same time, the number of clicks needed to reach a leaf page is few. Through this transformation algorithm, we preserve the contextual information in the original Web page and reduce scrolling. We have implemented this transformation module on a proxy server and have conducted usability studies on its performance. Our system achieved a shorter task completion time compared with that of transformations from the Opera browser in nine of ten tasks. The average improvement on familiar pages was 44%. The average improvement on unfamiliar pages was 37%. Subjective responses were positive.
Characterizing truthful mechanisms with convex type spaces
Authors: Archer Aaron , Kleinberg Robert
Published: January 2009

Mechanism design studies the implementation of allocation functions (sometimes called social choice functions) when relevant information resides with self-interested agents who may misreport their information if it is rational to do so. A central question in the field is to characterize which allocation functions are truthful, meaning that they can be combined with a payment function that induces players to report their preferences truthfully. Characterization theorems for truthful mechanisms, when they exist, are a boon to the mechanism designer since they allow us to reduce problems of optimal mechanism design to algorithm design problems in which the algorithm that computes the allocation function is required to satisfy additional constraints.
Improving wireless security through network diversity
Authors: Ye Tao , Veitch Darryl , Bolot Jean
Published: January 2009

Data confidentiality over mobile devices can be difficult to secure due to a lack of computing power and weak supporting encryption components. However, modern devices often have multiple wireless interfaces with diverse channel capacities and security capabilities. We show that the availability of diverse, heterogeneous links (physical or logical) between nodes in a network can be used to increase data confidentiality, on top of the availability or strength of underlying encryption techniques. We introduce a new security approach using multiple channels to transmit data securely, based on the idea of deliberate corruption, and information reduction, and analyze its security using the information theoretic concept of secrecy capacity, and the wiretap channel. Our work introduces the idea of channel
design
with security in mind.
Wireless innovation through software radios
Authors: Saha Dola , Grunwald Dirk , Sicker Douglas
Published: January 2009

Advances in networking have been accelerated by the use of abstractions, such as "layering", and the ability to apply those abstractions across multiple communication media. Wireless communication provides the greatest challenge to these clean abstractions because of the lossy communication media. For many networking researchers, wireless communications hardware starts and ends with WiFi, or 802.11 compliant hardware.

However, there has been a recent growth in software defined radio, which allows the basic radio medium to be manipulated by programs. This mutable radio layer has allowed researchers to exploit the physical properties of radio communication to overcome some of the challenges of the radio media; in certain cases, researchers have been able to develop mechanisms that are difficult to implement in electrical or optical media. In this paper, we describe the different design variants for software radios, their programming methods and survey some of the more cutting edge uses of those radios.
APOE-4 Genotype and Neurophysiological Vulnerability to Alzheimer's and Cognitive Aging
Authors: Bookheimer Susan , Burggren Alison
Published: January 2009

Many years before receiving a clinical diagnosis of Alzheimer's disease (AD), patients experience evidence of cognitive decline. Recent studies using a variety of brain imaging technologies have detected subtle changes in brain structure and function in normal adults with a genetic risk for AD; these brain changes have similar pathological features as AD, and some appear to be predictive of future cognitive decline. This review examines the most recent data on brain changes in genetic risk for AD and discusses the benefits and potential risks of detecting individuals at risk.
The Development of LinguaBytes: An Interactive Tangible Play and Learning System to Stimulate the Language Development of Toddlers with Multiple Disabilities
Authors: Hengeveld Bart , Voort Riny , Hummels Caroline , Moor Jan de , van Balkom Hans , Overbeeke Kees , van der Helm Aadjan
Published: January 2009

Young children with multiple disabilities (e.g., both cognitive and motor disabilities) are confronted with severe limitations in language development from birth and later on. Stimulating the adult-child communication can decrease these limitations. WithinLinguaBytes, a three-year research program, we try to stimulate language development by developing an interactive and adaptive play and learning environment, incorporating tangible objects and multimedia content, based on interactive storytelling and anchored instruction. The development of a product for such a heterogeneous user group presents substantial challenges. We use a Research-through-Design method, that is, an iterative process of developing subsequent experiential prototypes and then testing them in real-life settings, for example, a center for rehabilitation medicine. This article gives an outline of the development of theLinguaBytesplay and learning environment from the earliest studies up to the current prototype,CLICK-IT.
M-CSF and GM-CSF Regulation of STAT5 Activation and DNA Binding in Myeloid Cell Differentiation is Disrupted in Nonobese Diabetic Mice
Authors: Rumore-Maton B. , Elf J. , Belkin N. , Stutevoss B. , Seydel F. , Garrigan E. , Litherland S. A.
Published: January 2009

Defects in macrophage colony-stimulating factor (M-CSF) signaling disrupt myeloid cell differentiation in nonobese diabetic (NOD) mice, blocking myeloid maturation into tolerogenic antigen-presenting cells (APCs). In the absence of M-CSF signaling, NOD myeloid cells have abnormally high granulocyte macrophage colony-stimulating factor (GM-CSF) expression, and as a result, persistent activation of signal transducer/activator of transcription 5 (STAT5). Persistent STAT5 phosphorylation found in NOD macrophages is not affected by inhibiting GM-CSF. However, STAT5 phosphorylation in NOD bone marrow cells is diminished if GM-CSF signaling is blocked. Moreover, if M-CSF signaling is inhibited, GM-CSF stimulationin vitrocan promote STAT5 phosphorylation in nonautoimmune C57BL/6 mouse bone marrow cultures to levels seen in the NOD. These findings suggest that excessive GM-CSF production in the NOD bone marrow may interfere with the temporal sequence of GM-CSF and M-CSF signaling needed to mediate normal STAT5 function in myeloid cell differentiation gene regulation.
Epigenetic Alterations in Cholangiocarcinoma-Sustained IL-6/STAT3 Signaling in Cholangio- carcinoma due to SOCS3 Epigenetic Silencing
Authors: Isomoto Hajime
Published: January 2009

Cholangiocarcinoma (CCA) is a highly lethal malignant tumor arising from the biliary tract epithelium, characterized by its typically late clinical presentation and lack of effective therapeutic modalities. Chronic inflammatory conditions, including primary sclerosing cholangitis, liver fluke infestation and hepatolithiasis, are listed in the risk factors, but for most cases of CCA the cause is unknown. Recent advances in molecular pathogenesis have highlighted the importance of epigenetic alterations including promoter hypermethylation and histone deacetylation in addition to genetic changes in the process of cholangiocarcinogenesis. This review provides a comprehensive overview of the genes hypermethylated in CCA to date and their putative roles in cholangiocarcinogenesis. Among genes hypermethylated, we found the CpG island hypermethylation in suppressor of cytokine signaling 3 (SOCS3) gene promoter in CCA. Interleukin-6 (IL-6)-mediated signal transducers and activators of transcription 3 (STAT3) activation are aberrantly sustained in CCA cells, resulting in resistance to apoptosis. SOCS3 controls the IL-6/STAT3 signaling pathway by a classic feedback loop. Indeed, SOCS3 epigenetic silencing is responsible for sustained IL-6/STAT3 signaling in CCA. These findings provide new perspectives for epigenetic therapy to restore SOCS3 in this cancer.
Stepwise Diagnosis and Treatment from Uninvestigated Dyspepsia to Functional Dyspepsia in Clinical Practice in Japan: Proposal of a 4-Step Algorithm
Authors: Nakajima Shigemi
Published: January 2009

Background/Aim: Management of dyspepsia may differ between countries. In Japan, Helicobacter pylori infection should be considered because of the high prevalence of the infection and the related diseases. I tried to propose an algorithm for stepwise diagnosis and treatment from uninvestigated dyspepsia to functional dyspepsia in clinical practice in Japan. Methods: A proposal was made from my personal review of published studies. Results: A 4-step algorithm was proposed. In the first step, organic, systemic or metabolic diseases are excluded and nonulcer dyspepsia (NUD) is diagnosed. The second step is to test and treat H. pylori infection for NUD patients. In the third step, proton pump inhibitor (PPI)-responsive NUD is discriminated by PPI. Nonresponsive patients in the third step are diagnosed as having PPI-resistant NUD. In the fourth step, functional dyspepsia is diagnosed with the Rome III questionnaire. In this algorithm, it is not necessary to do special function tests for functional gastrointestinal disorders. Treatment options are automatically restricted in each step. Conclusions: The proposed 4-step algorithm may be useful in clinical practice for the diagnosis from uninvestigated dyspepsia to functional dyspepsia in Japan. With this stepwise algorithm, treatment options are restricted in each step and the management of dyspepsia may be easier.
Adiposity and Gastrointestinal Malignancy
Authors: Kitayama Joji , Tabuchi Masafumi , Tsurita Giichiro , Ishikawa Makoto , Otani Kensuke , Nagawa Hirokazu
Published: January 2009

Recent epidemiologic studies have shown a positive association between obesity and certain cancers. Our retrospective studies show that hypertriglyceridemia is an independent risk factor for the development of colonic adenoma and nodal metastasis in early gastric and esophageal cancer in men. High-fat condition may be favorable for the growth of malignant cells. Serum level of adiponectin is reduced in patients with advanced gastric cancer, which may be associated with the positive link between adiposity and cancer. In early gastric cancer, patients with undifferentiated type have lower fat volume than those with differentiated type. Adiposity appears to be closely related with various aspects in pathophysiology of gastrointestinal malignancy.
Ectopic Fat Deposition and the Metabolic Syndrome in Obese Children and Adolescents
Authors: Cali Anna M.G. , Caprio Sonia
Published: January 2009

Aims: We examined the impact of varying degrees of obesity on the prevalence of the metabolic syndrome and its relation to ectopic fat deposition in a large, multi-ethnic cohort of children and adolescents. Methods: A standard glucose tolerance test was administered to 438 obese, 31 overweight and 20 nonobese children and adolescents. Baseline measures included blood pressure and plasma lipid and insulin levels. In a subset of 118 subjects, abdominal fat distribution was measured by magnetic resonance imaging (MRI) and further stratified into tertiles based on the proportion of abdominal fat in the visceral depot. Liver fat was measured by fast MRI and intramyocellular fat by proton magnetic resonance spectroscopy. Results: Overall, the prevalence of the metabolic syndrome increased with the severity of obesity. In the subset of 118 obese adolescents undergoing MRI, there were no differences in age or body mass index z-scores across tertiles. However, as the proportion of visceral fat increased, subcutaneous fat decreased. There were significant increases in the occurrence of hepatic steatosis, insulin resistance and metabolic syndrome, with subjects in tertile 3 being 5.2-times more likely to have the metabolic syndrome than those in tertile 1. Conclusions: The prevalence of the metabolic syndrome is high in obese children and adolescents and increases with worsening obesity. Obese adolescents with a high proportion of visceral fat and relatively low abdominal subcutaneous fat have a phenotype reminiscent of partial lipodystrophy: hepatic steatosis, profound insulin resistance and an increased risk of the metabolic syndrome.