bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Tensioner Dry Friction on the Vibration of Belt Drives With Belt Bending Stiffness
Authors: Zhu Farong , Parker Robert G.
Published: February 2008

A model of dry friction tensioner in a belt-pulley system considering transverse belt vibration is developed, and the influence of the dry friction on the system dynamics is examined. The discretized formulation is divided into a linear subsystem including linear coordinates and a nonlinear subsystem addressing tensioner arm vibration, which reduces the dimension of the iteration matrices when employing the harmonic balance method. The Coulomb damping at the tensioner arm pivot mitigates the tensioner arm vibration but not necessarily the vibrations of other system components. The extent of the mitigation varies for different excitation frequency ranges. The critical amplitude of the dry friction torque beyond which the system operates with a locked arm is determined analytically. Superharmonic resonances are observed in the responses of the generalized span coordinates, but their amplitudes are small. The energy dissipation at the tensioner arm hub is discussed, and the stick-slip phenomena of the arm are reflected in the velocity reversals near the arm extreme location. Dependence of the span tension fluctuations on Coulomb torque is explored.
Effect of Boundary Conditions on Nonlinear Vibration and Flutter of Laminated Cylindrical Shells
Authors: Jansen E. L.
Published: February 2008

A nonlinear vibration analysis of laminated cylindrical shells is presented in which the effect of the specified boundary conditions at the shell edges, including nonlinear fundamental state deformations, can be accurately taken into account. The method is based on a perturbation expansion for both the frequency parameter and the dependent variables. The present theory includes the effects of finite vibration amplitudes, initial geometric imperfections, and a nonlinear static deformation. Nonlinear Donnell-type equations formulated in terms of the radial displacement W and an Airy stress function F are used, and classical lamination theory is employed. Furthermore, an extension of the theory is presented to analyze linearized flutter in supersonic flow, based on piston theory. The effect of different types of boundary conditions on the nonlinear vibration and linearized flutter behavior of cylindrical shells is illustrated for several characteristic cases.
Dynamic Stiffness Analysis of a Beam Based on Trigonometric Shear Deformation Theory
Authors: Li Jun , Hua Hongxing , Shen Rongying
Published: February 2008

The dynamic stiffness matrix of a uniform isotropic beam element based on trigonometric shear deformation theory is developed in this paper. The theoretical expressions for the dynamic stiffness matrix elements are found directly, in an exact sense, by solving the governing differential equations of motion that describe the deformations of the beam element according to the trigonometric shear deformation theory, which include the sinusoidal variation of the axial displacement over the cross section of the beam. The application of the dynamic stiffness matrix to calculate the natural frequencies and normal mode shapes of two rectangular beams is discussed. The numerical results obtained are compared to the available solutions wherever possible and validate the accuracy and efficiency of the present approach.
Self-Identification Experiments Using Variable Inertia Systems for Flexible Beam Structures
Authors: Senba Atsuhiko , Furuya Hiroshi
Published: February 2008

The concept of self-identification and its feasibility are experimentally investigated. The modal parameters changed by the variable inertia systems, which are controlled by control input, are used to obtain linear equations about unknown structural parameters to overcome the lack of modes in vibration testing. We derive the controllability of the modal parameters as the requested conditions for implementing self-identification using sensitivity analyses of the modal parameters with respect to the control input. Also, a criterion for the self-identification is proposed to measure the controllability. To examine the present method, the self-identification experiments are performed using a flexible cantilevered beam with controllable additional mass attached to the beam. In the experiments, we simulate the self-identification of a flexible structure with variable inertia systems, where lower vibration modes are changed by the variable inertia system adapting to the lack of modes in identification of unknown parameters. It is shown that the identification error of the bending stiffness and mass per unit length of the beam are ranging from about 8% to 12% and 1% to 7%, respectively, and they depend on the mode number because the mode shape estimation from strain sensors and cubic spline interpolation also depends on the mode. Furthermore, the factor for the identification error is discussed in detail through numerical analysis, and the results show the clear relationship between the present criterion and the identification accuracy in experiments.
Heat Conduction Through Heat Exchanger Tubes of Noncircular Cross
Section
Authors: Moharana Manoj Ku. , Das Prasanta Ku.
Published: February 2008

Conduction through shaped tubes with circular inner surface and hydrodynamically shaped outer surface has been analyzed by two different techniques. A two-dimensional analysis has been made by a semianalytical technique using boundary collocation at the outer periphery. A one-dimensional approximate technique called sector method shows a closed agreement with the two-dimensional analysis. The present work gives an improvement on the analysis of Li et al. (2004, “Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis,” ASME J. Heat Transfer, 126, pp. 211–218) who solved the same problem using a one-dimensional approximation following the methodology of fin analysis. Both the present methods relax some of the approximations taken by Li et al. Further, the suggested one-dimensional sector method is simple and requires limited computational effort.
Heatline Visualization of Natural Convection in a Porous Cavity Occupied by a Fluid With Temperature-Dependent Viscosity
Authors: Hooman K. , Gurgenci H.
Published: February 2008

Temperature-dependent viscosity effect in buoyancy driven flow of a gas or a liquid in an enclosure filled with a porous medium is studied numerically based on the general model of momentum transfer in a porous medium. The exponential form of viscosity-temperature relation is applied to examine three cases of viscosity-temperature relation: constant, decreasing, and increasing. Application of arithmetic and harmonic mean values of the viscosity is also investigated for their ability to represent the Nusselt number versus the effective Rayleigh number. Heat lines are illustrated for a more comprehensive investigation of the problem.
The Critical Heat Flux Condition With Water in a Uniformly Heated Microtube
Authors: Roday A. P. , Borca-Tasçiuc T. , Jensen M. K.
Published: February 2008

The critical heat flux (CHF) condition needs to be well understood for designing miniature devices involving two-phase flow. Experiments were performed to determine the CHF condition for a single stainless steel tube having an inside diameter of 0.427mm subjected to uniform heat flux boundary conditions. The effects of mass flux, pressure, and exit quality on the CHF were investigated. The experimental results show that the CHF increases with an increase in mass flux and exit pressure. For all exit pressures, the CHF decreased with an increase in quality in the subcooled region, but with a further increase in quality (near zero quality and above), the CHF was found to have an increasing trend with quality (up to about 25% quality). CHF values in this region were much higher than those in the subcooled region. This suggests that even at very low qualities, the void fraction becomes appreciable, which results in an increase in the average velocity, thereby increasing the CHF limit.
Heat Transfer From a Rotating Disk to Fluids for a Wide Range of Prandtl Numbers Using the Asymptotic Model
Authors: Awad M. M.
Published: February 2008

A simple method for calculating heat transfer from a rotating disk to fluids for a wide range of Prandtl numbers using asymptotic analysis is presented. Nusselt numbers for a heated rotating disk for different Prandtl numbers is expressed in terms of the asymptotic Nusselt numbers corresponding to a very small value of Prandtl numbers and Nusselt numbers corresponding to a very large value of Prandtl numbers. The proposed model uses a concave downward asymptotic correlation method to develop a robust compact model. Using the methods discussed by Churchill and Usagi (1972, “General Expression for the Correlation of Rates of Transfer and Other Phenomena,” AIChE J., 18(6), pp. 1121–1128), the fitting parameter in the proposed model can be determined at Prandtl numbers corresponding to the intersection of the two asymptotes.
Impact of Interface Resistance on Pulsed Thermoelectric Cooling
Authors: Ju Y. Sungtaek
Published: February 2008

Pulsed thermoelectric cooling is an attractive approach for the site specific thermal management of infrared sensors and other low-heat flux devices. Intense Joule heating caused by electrical interface resistance, however, can severely degrade pulsed cooling performance. Numerical simulations are used to quantify the impact of the interface resistance on pulsed thermoelectric cooling. The degradation in performance is most pronounced for microcoolers that have small bulk resistivity at high pulse amplitudes. Our work also forms a basis for new techniques to probe interfaces in TE devices for energy harvesting as well as cooling applications.
A Light Transmission Based Liquid Crystal Thermography System
Authors: Roth Timothy B. , Anderson Ann M.
Published: February 2008

This paper presents results from a study aimed at developing a novel thermochromic liquid crystal (TLC) temperature measurement system that uses light transmission instead of light reflection to measure surface temperature fields. In previous work, we reported on the effect of temperature on light transmission through TLCs as measured with a spectrophotometer [Roth, T. B., and Anderson, A. M., 2005, “Light Transmission Characteristics of Thermochromic Liquid Crystals,” Proceedings of IMECE2005, Orlando, FL, Paper No. IMECE2005-81812;Roth, T. B., and Anderson, A. M., 2007, “The Effects of Film Thickness, Light Polarization and Light Intensity on the Light Transmission Characteristics of Thermochromic Liquid Crystals,” ASME J. Heat Transfer, 129(3), pp. 372–378]. Here we report on results obtained using a charge coupled device (CCD) camera and polychromatic light setup that is similar to the type of equipment used in TLC reflection thermography. We tested three different light sources, a white electroluminescent light, a green electroluminescent light, and a halogen fiber optic light, using both direct and remote lighting techniques. We found that the green signal (as detected by the CCD camera) of the green electroluminescent light makes the best temperature sensor, because under remote lighting conditions it showed a 500% linear signal increase as the temperature of the R25C10W TLCs was raised from 30°to48°C. We further found that the angle of the CCD camera relative to the light did not significantly affect the results for angles up to 10deg for remote lighting and 15deg for direct lighting. The effect of light intensity variation was not significant for intensities up to 40% of the original level when normalized on the intensity at 19°C (a temperature outside the active range of the TLCs). The use of light transmission results in a larger range of temperature over which the TLCs can be calibrated and offers opportunities for more uniform lighting conditions, which may help overcome some of the problems associated with light reflection.
Optimization of a Two Degree of Freedom System Acting as a Dynamic Vibration Absorber
Authors: Febbo M. , Vera S. A.
Published: February 2008

This paper deals with the problem of finding the optimal stiffnesses and damping coefficients of a two degree of freedom (2DOF) system acting as a dynamic vibration absorber (DVA) on a beam structure. In this sense, a heuristic criterion for the optimization problem will be developed to contemplate this particular type of DVA. Accordingly, it is planned to minimize the amplitude of vibration in predetermined points of the main structure. Two optimizations will be proposed for two DVAs of 1DOF to compare their performances with the optimized 2DOF system. A simulated annealing algorithm is used to obtain the DVA’s optimal parameters for minimum amplitude in a given point of the beam. The best configuration depends on the location of the absorbers on the beam and, for a fixed location, on the distribution of the stiffness constants.
Insights into Phases of Liquid Water from Study of Its Unusual Glass-Forming Properties
Authors: Angell C. Austen
Published: February 2008

The vitrification of pure water is compared with that of molecular solutions rich in water, and gross differences are noted. Thermodynamic reasoning and direct observations on noncrystallizing nanoconfined water indicate that the glass transition in ambient-pressure water is qualitatively distinct from that found in the usual molecular liquids. It belongs instead to the order-disorder class of transition seen in molecular and ionic crystalline materials. The distinctive “folding funnel” energy landscape for this type of system explains the extreme weakness of the glass transition of water as well as the consequent confusion that has characterized its scientific history; it also explains the very small excess entropy at the glass transition temperature. The relation of confined water behavior to that of bulk is discussed, and the “fragile-to-strong” transition for supercooled water is interpreted by adding a “critical point–free” scenario to the two competing scenarios for understanding supercooled bulk water.
Comment on "Saturation of the Southern Ocean CO
2
Sink Due to Recent Climate Change"
Authors: Zickfeld Kirsten , Fyfe John C. , Eby Michael , Weaver Andrew J.
Published: February 2008

We disagree with the conclusion of Le Quéré
et al
. (Reports, 22 June 2007, p. 1735) that poleward intensifying winds could continue to weaken the Southern Ocean sink in the future. We argue that altered winds, along with rising atmospheric carbon dioxide, will likely increase the efficiency of this sink in the 21st century.
Response to Comments on "Saturation of the Southern Ocean CO
2
Sink Due to Recent Climate Change"
Authors: Le Quéré Corinne , Rödenbeck Christian , Buitenhuis Erik T. , Conway Thomas J. , Langenfelds Ray , Gomez Antony , Labuschagne Casper , Ramonet Michel , Nakazawa Takakiyo , Metzl Nicolas , Gillett Nathan P. , Heimann Martin
Published: February 2008

We estimated a weakening of the Southern Ocean carbon dioxide (CO
2
) sink since 1981 relative to the trend expected from the large increase in atmospheric CO
2
. We agree with Law
et al
. that network choice increases the uncertainty of trend estimates but argue that their network of five locations is too small to be reliable. A future reversal of Southern Ocean CO
2
saturation as suggested by Zickfeld
et al
. is possible, but only at high atmospheric CO
2
concentrations, and the effect would be temporary.
Comment on "Saturation of the Southern Ocean CO
2
Sink Due to Recent Climate Change"
Authors: Law Rachel M. , Matear Richard J. , Francey Roger J.
Published: February 2008

Unlike Le Quéré
et al
. (Reports, 22 June 2007, p. 1735), we do not find a saturating Southern Ocean carbon sink due to recent climate change. In our ocean model, observed wind forcing causes reduced carbon uptake, but heat and freshwater flux forcing cause increased uptake. Our inversions of atmospheric carbon dioxide show that the Southern Ocean sink trend is dependent on network choice.
Profiling Essential Genes in Human Mammary Cells by Multiplex RNAi Screening
Authors: Silva Jose M. , Marran Krista , Parker Joel S. , Silva Javier , Golding Michael , Schlabach Michael R. , Elledge Stephen J. , Hannon Gregory J. , Chang Kenneth
Published: February 2008

By virtue of their accumulated genetic alterations, tumor cells may acquire vulnerabilities that create opportunities for therapeutic intervention. We have devised a massively parallel strategy for screening short hairpin RNA (shRNA) collections for stable loss-of-function phenotypes. We assayed from 6000 to 20,000 shRNAs simultaneously to identify genes important for the proliferation and survival of five cell lines derived from human mammary tissue. Lethal shRNAs common to these cell lines targeted many known cell-cycle regulatory networks. Cell line–specific sensitivities to suppression of protein complexes and biological pathways also emerged, and these could be validated by RNA interference (RNAi) and pharmacologically. These studies establish a practical platform for genome-scale screening of complex phenotypes in mammalian cells and demonstrate that RNAi can be used to expose genotype-specific sensitivities.
Cancer Proliferation Gene Discovery Through Functional Genomics
Authors: Schlabach Michael R. , Luo Ji , Solimini Nicole L. , Hu Guang , Xu Qikai , Li Mamie Z. , Zhao Zhenming , Smogorzewska Agata , Sowa Mathew E. , Ang Xiaolu L. , Westbrook Thomas F. , Liang Anthony C. , Chang Kenneth , Hackett Jennifer A. , Harper J. Wade , Hannon Gregory J. , Elledge Stephen J.
Published: February 2008

Retroviral short hairpin RNA (shRNA)–mediated genetic screens in mammalian cells are powerful tools for discovering loss-of-function phenotypes. We describe a highly parallel multiplex methodology for screening large pools of shRNAs using half-hairpin barcodes for microarray deconvolution. We carried out dropout screens for shRNAs that affect cell proliferation and viability in cancer cells and normal cells. We identified many shRNAs to be antiproliferative that target core cellular processes, such as the cell cycle and protein translation, in all cells examined. Moreover, we identified genes that are selectively required for proliferation and survival in different cell lines. Our platform enables rapid and cost-effective genome-wide screens to identify cancer proliferation and survival genes for target discovery. Such efforts are complementary to the Cancer Genome Atlas and provide an alternative functional view of cancer cells.
Languages Evolve in Punctuational Bursts
Authors: Atkinson Quentin D. , Meade Andrew , Venditti Chris , Greenhill Simon J. , Pagel Mark
Published: February 2008

Linguists speculate that human languages often evolve in rapid or punctuational bursts, sometimes associated with their emergence from other languages, but this phenomenon has never been demonstrated. We used vocabulary data from three of the world's major language groups—Bantu, Indo-European, and Austronesian—to show that 10 to 33% of the overall vocabulary differences among these languages arose from rapid bursts of change associated with language-splitting events. Our findings identify a general tendency for increased rates of linguistic evolution in fledgling languages, perhaps arising from a linguistic founder effect or a desire to establish a distinct social identity.
Systemic Leukocyte-Directed siRNA Delivery Revealing Cyclin D1 as an Anti-Inflammatory Target
Authors: Peer Dan , Park Eun Jeong , Morishita Yoshiyuki , Carman Christopher V. , Shimaoka Motomu
Published: February 2008

Cyclin D1 (CyD1) is a pivotal cell cycle–regulatory molecule and a well-studied therapeutic target for cancer. Although CyD1 is also strongly up-regulated at sites of inflammation, its exact roles in this context remain uncharacterized. To address this question, we developed a strategy for selectively silencing CyD1 in leukocytes in vivo. Targeted stabilized nanoparticles (tsNPs) were loaded with CyD1–small interfering RNA (siRNA). Antibodies to β
7
integrin (β
7
I) were then used to target specific leukocyte subsets involved in gut inflammation. Systemic application of β
7
I-tsNPs silenced CyD1 in leukocytes and reversed experimentally induced colitis in mice by suppressing leukocyte proliferation and T helper cell 1 cytokine expression. This study reveals CyD1 to be a potential anti-inflammatory target, and suggests that the application of similar modes of targeting by siRNA may be feasible in other therapeutic settings.
Cathepsin K-Dependent Toll-Like Receptor 9 Signaling Revealed in Experimental Arthritis
Authors: Asagiri Masataka , Hirai Toshitake , Kunigami Toshihiro , Kamano Shunya , Gober Hans-Jürgen , Okamoto Kazuo , Nishikawa Keizo , Latz Eicke , Golenbock Douglas T. , Aoki Kazuhiro , Ohya Keiichi , Imai Yuuki , Morishita Yasuyuki , Miyazono Kohei , Kato Shigeaki , Saftig Paul , Takayanagi Hiroshi
Published: February 2008

Cathepsin K was originally identified as an osteoclast-specific lysosomal protease, the inhibitor of which has been considered might have therapeutic potential. We show that inhibition of cathepsin K could potently suppress autoimmune inflammation of the joints as well as osteoclastic bone resorption in autoimmune arthritis. Furthermore,
cathepsin K
–/–
mice were resistant to experimental autoimmune encephalomyelitis. Pharmacological inhibition or targeted disruption of cathepsin K resulted in defective Toll-like receptor 9 signaling in dendritic cells in response to unmethylated CpG DNA, which in turn led to attenuated induction of T helper 17 cells, without affecting the antigen-presenting ability of dendritic cells. These results suggest that cathepsin K plays an important role in the immune system and may serve as a valid therapeutic target in autoimmune diseases.
Abiogenic Hydrocarbon Production at Lost City Hydrothermal Field
Authors: Proskurowski Giora , Lilley Marvin D. , Seewald Jeffery S. , Früh-Green Gretchen L. , Olson Eric J. , Lupton John E. , Sylva Sean P. , Kelley Deborah S.
Published: February 2008

Low-molecular-weight hydrocarbons in natural hydrothermal fluids have been attributed to abiogenic production by Fischer-Tropsch type (FTT) reactions, although clear evidence for such a process has been elusive. Here, we present concentration, and stable and radiocarbon isotope, data from hydrocarbons dissolved in hydrogen-rich fluids venting at the ultramafic-hosted Lost City Hydrothermal Field. A distinct “inverse” trend in the stable carbon and hydrogen isotopic composition of C
1
to C
4
hydrocarbons is compatible with FTT genesis. Radiocarbon evidence rules out seawater bicarbonate as the carbon source for FTT reactions, suggesting that a mantle-derived inorganic carbon source is leached from the host rocks. Our findings illustrate that the abiotic synthesis of hydrocarbons in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat.
Measuring the Surface Dynamics of Glassy Polymers
Authors: Fakhraai Z. , Forrest J. A.
Published: February 2008

The motion of polymer chain segments cooled below the glass transition temperature slows markedly; with sufficient cooling, segmental motion becomes completely arrested. There is debate as to whether the chain segments near the free surface, or in thin films, are affected in the same way as the bulk material. By partially embedding and then removing gold nanospheres, we produced a high surface coverage of well-defined nanodeformations on a polystyrene surface; to probe the surface dynamics, we measured the time-dependent relaxation of these surface deformations as a function of temperature from 277 to 369 kelvin. Surface relaxation was observed at all temperatures, providing strong direct evidence for enhanced surface mobility relative to the bulk. The deviation from bulk α relaxation became more pronounced as the temperature was decreased below the bulk glass transition temperature. The temperature dependence of the relaxation time was much weaker than that of the bulk α relaxation of polystyrene, and the process exhibited no discernible temperature dependence between 277 and 307 kelvin.
Single-Molecule Cut-and-Paste Surface Assembly
Authors: Kufer S. K. , Puchner E. M. , Gumpp H. , Liedl T. , Gaub H. E.
Published: February 2008

We introduce a method for the bottom-up assembly of biomolecular structures that combines the precision of the atomic force microscope (AFM) with the selectivity of DNA hybridization. Functional units coupled to DNA oligomers were picked up from a depot area by means of a complementary DNA strand bound to an AFM tip. These units were transferred to and deposited on a target area to create basic geometrical structures, assembled from units with different functions. Each of these cut-and-paste events was characterized by single-molecule force spectroscopy and single-molecule fluorescence microscopy. Transport and deposition of more than 5000 units were achieved, with less than 10% loss in transfer efficiency.
Oocyte-Specific Deletion of
Pten
Causes Premature Activation of the Primordial Follicle Pool
Authors: Reddy Pradeep , Liu Lian , Adhikari Deepak , Jagarlamudi Krishna , Rajareddy Singareddy , Shen Yan , Du Chun , Tang Wenli , Hämäläinen Tuula , Peng Stanford L. , Lan Zi-Jian , Cooney Austin J. , Huhtaniemi Ilpo , Liu Kui
Published: February 2008

In the mammalian ovary, progressive activation of primordial follicles from the dormant pool serves as the source of fertilizable ova. Menopause, or the end of female reproductive life, occurs when the primordial follicle pool is exhausted. However, the molecular mechanisms underlying follicle activation are poorly understood. We provide genetic evidence that in mice lacking PTEN (phosphatase and tensin homolog deleted on chromosome 10) in oocytes, a major negative regulator of phosphatidylinositol 3-kinase (PI3K), the entire primordial follicle pool becomes activated. Subsequently, all primordial follicles become depleted in early adulthood, causing premature ovarian failure (POF). Our results show that the mammalian oocyte serves as the headquarters of programming of follicle activation and that the oocyte PTEN-PI3K pathway governs follicle activation through control of initiation of oocyte growth.
Prioritizing Climate Change Adaptation Needs for Food Security in 2030
Authors: Lobell David B. , Burke Marshall B. , Tebaldi Claudia , Mastrandrea Michael D. , Falcon Walter P. , Naylor Rosamond L.
Published: February 2008

Investments aimed at improving agricultural adaptation to climate change inevitably favor some crops and regions over others. An analysis of climate risks for crops in 12 food-insecure regions was conducted to identify adaptation priorities, based on statistical crop models and climate projections for 2030 from 20 general circulation models. Results indicate South Asia and Southern Africa as two regions that, without sufficient adaptation measures, will likely suffer negative impacts on several crops that are important to large food-insecure human populations. We also find that uncertainties vary widely by crop, and therefore priorities will depend on the risk attitudes of investment institutions.
Give Way to the Migrants
Authors: Alerstam Thomas
Published: February 2008

No Way Home
. The Decline of the World's Great Animal Migrations.
By David S. Wilcove
. Island Press, Washington, DC, 2008. 253 pp. $24.95. ISBN 9781559639859.

The author discusses long-distance movements of animals---in the air, on land, and in the water---as well as the growing threats these migrants face from human activities and environmental changes
Sulfated K5
Escherichia coli
Polysaccharide Derivatives as Wide-Range Inhibitors of Genital Types of Human Papillomavirus
Authors: Lembo David , Donalisio Manuela , Rusnati Marco , Bugatti Antonella , Cornaglia Maura , Cappello Paola , Giovarelli Mirella , Oreste Pasqua , Landolfo Santo
Published: February 2008

Genital human papillomaviruses (HPV) represent the most common sexually transmitted agents and are classified into low or high risk by their propensity to cause genital warts or cervical cancer, respectively. Topical microbicides against HPV may be a useful adjunct to the newly licensed HPV vaccine. A main objective in the development of novel microbicides is to block HPV entry into epithelial cells through cell surface heparan sulfate proteoglycans. In this study, selective chemical modification of the
Escherichia coli
K5 capsular polysaccharide was integrated with innovative biochemical and biological assays to prepare a collection of sulfated K5 derivatives with a backbone structure resembling the heparin/heparan biosynthetic precursor and to test them for their anti-HPV activity. Surface plasmon resonance assays revealed that O-sulfated K5 with a high degree of sulfation [K5-OS(H)] and N,O-sulfated K5 with a high [K5-N,OS(H)] or low [K5-N,OS(L)] sulfation degree, but not unmodified K5, N-sulfated K5, and O-sulfated K5 with low levels of sulfation, prevented the interaction between HPV-16 pseudovirions and immobilized heparin. In cell-based assays, K5-OS(H), K5-N,OS(H), and K5-N,OS(L) inhibited HPV-16, HPV-18, and HPV-6 pseudovirion infection. Their 50% inhibitory concentration was between 0.1 and 0.9 μg/ml, without evidence of cytotoxicity. These findings provide insights into the design of novel, safe, and broad-spectrum microbicides against genital HPV infections.
Roles of Trypanothione
S
-Transferase and Tryparedoxin Peroxidase in Resistance to Antimonials
Authors: Wyllie Susan , Vickers Tim J. , Fairlamb Alan H.
Published: February 2008

The clinical value of antimonial drugs, the mainstay therapy for leishmaniasis, is now threatened by the emergence of acquired drug resistance, and a comprehensive understanding of the underlying mechanisms is required. Using the model organism
Leishmania tarentolae
, we have examined the role of trypanothione
S
-transferase (TST) in trivalent antimony [Sb(III)] resistance. TST has
S
-transferase activity with substrates such as chlorodinitrobenzene as well as peroxidase activity with alkyl and aryl hydroperoxides but not with hydrogen peroxide. Although
S
-transferase activity and TST protein levels were unchanged in Sb(III)-sensitive and -resistant lines, rates of metabolism of hydrogen peroxide,
t
-butyl hydroperoxide, and cumene hydroperoxide were significantly increased. Elevated peroxidase activities were shown to be both trypanothione and tryparedoxin dependent and were associated with the overexpression of classical tryparedoxin peroxidase (TryP) in the cytosol of
L. tarentolae
. The role of TryP in Sb(III) resistance was verified by overexpression of the recombinant
Leishmania major
protein in Sb(III)-sensitive promastigotes. An approximate twofold increase in the level of TryP activity in this transgenic cell line was accompanied by a significant decrease in sensitivity to Sb(III) (twofold;
P
< 0.001). Overexpression of an enzymatically inactive TryP failed to result in Sb(III) resistance. This indicates that TryP-dependent resistance is not due to sequestration of Sb(III) and suggests that enhanced antioxidant defenses may well be a key feature of mechanisms of clinical resistance to antimonial drugs.
The Presence of Capsule inCryptococcus neoformansInfluences the Gene Expression Profile in Dendritic Cells during Interaction with the Fungus
Authors: Lupo P. , Chang Y. C. , Kelsall B. L. , Farber J. M. , Pietrella D. , Vecchiarelli A. , Leon F. , Kwon-Chung K. J.
Published: February 2008

The aim of this investigation was to study the effect of polysaccharide capsule on the gene expression in dendritic cells (DC) during their interaction withCryptococcus neoformans. To this end, we used an encapsulated virulent strain ofC. neoformansand acap59gene-disrupted acapsular avirulent strain derived from the same genetic background. DC were exposed to encapsulated and acapsularC. neoformansstrains for 4 h and 18 h, and their transcriptional profiles were analyzed using the Affymetrix mouse gene chip U74Av2. A large number of DC genes were up-regulated after treatment with the acapsular strain. In particular, we observed the up-regulation of the genes involved in DC maturation, such as cell surface receptors, cytokines, and chemokines (interleukin-12 [IL-12], IL-2, IL-1α, IL-1β, IL-6, IL-10, tumor necrosis factor alpha, CCR7, CCL17, CCL22, CCL3, CCL4, CCL7, and CXCL10), membrane proteins, and the genes involved in antigen processing and presentation as well as cell cycle or apoptosis. The chemokine gene expression data were confirmed by real-time reverse transcription-PCR, while the expression of cytokine genes was correlated with their secretion. A completely different pattern of gene expression was observed for DC treated with an encapsulated strain ofC. neoformans. In particular, no significant induction was observed in the expression of the genes mentioned above. Moreover, a number of genes, such as those coding for chemokines, were down-regulated. These results suggest that the polysaccharide capsule shrouding the cell wall ofC. neoformansplays a fundamental role in inducing DC response, highlighting the molecular basis of the true nature of immune silencing exerted by capsular material.
Proteomic Characterization of the Whole Secretome of
Legionella pneumophila
and Functional Analysis of Outer Membrane Vesicles
Authors: Galka Frank , Wai Sun Nyunt , Kusch Harald , Engelmann Susanne , Hecker Michael , Schmeck Bernd , Hippenstiel Stefan , Uhlin Bernt Eric , Steinert Michael
Published: February 2008

Secretion of effector molecules is one of the major mechanisms by which the intracellular human pathogen
Legionella pneumophila
interacts with host cells during infection. Specific secretion machineries which are responsible for the subfraction of secreted proteins (soluble supernatant proteins [SSPs]) and the production of bacterial outer membrane vesicles (OMVs) both contribute to the protein composition of the extracellular milieu of this lung pathogen. Here we present comprehensive proteome reference maps for both SSPs and OMVs. Protein identification and assignment analyses revealed a total of 181 supernatant proteins, 107 of which were specific to the SSP fraction and 33 of which were specific to OMVs. A functional classification showed that a large proportion of the identified OMV proteins are involved in the pathogenesis of Legionnaires' disease. Zymography and enzyme assays demonstrated that the SSP and OMV fractions possess proteolytic and lipolytic enzyme activities which may contribute to the destruction of the alveolar lining during infection. Furthermore, it was shown that OMVs do not kill host cells but specifically modulate their cytokine response. Binding of immunofluorescently stained OMVs to alveolar epithelial cells, as visualized by confocal laser scanning microscopy, suggested that there is delivery of a large and complex group of proteins and lipids in the infected tissue in association with OMVs. On the basis of these new findings, we discuss the relevance of protein sorting and compartmentalization of virulence factors, as well as environmental aspects of the vesicle-mediated secretion.
Elevated Gamma Interferon-Producing NK Cells, CD45RO Memory-Like T Cells, and CD4 T Cells Are Associated with Protection against Malaria Infection in Pregnancy
Authors: Othoro Caroline , Moore Julie M. , Wannemuehler Kathleen A. , Moses Sichangi , Lal Altaf , Otieno Juliana , Nahlen Bernard , Slutsker Laurence , Shi Ya Ping
Published: February 2008

Previous studies have shown that gamma interferon (IFN-γ) production in the placenta is associated with protection against placental malaria. However, it remains unknown which IFN-γ-producing cell subpopulations are involved in this protection and whether the cellular immune components of protection are the same in the peripheral and the placental blood compartments. We investigated cell subpopulations for CD4, CD8, and CD45RO memory-like T cells and CD56+/CD3−natural killer (NK) cells and for IFN-γ production by these cells in maternal peripheral and placental intervillous blood in relation to the status of malaria infection in pregnancy. Of 52 human immunodeficiency virus-negative enrolled pregnant women residing in Western Kenya, 20 had placental parasitemia. We found that the percentages of CD45RO memory-like and CD4 T cells were significantly higher in the periphery than in the placenta, while the CD56/CD3−NK-cell percentage was higher in the placenta than in the periphery, suggesting differences in immune cell profiles between the two blood compartments. Furthermore, the percentages of peripheral CD45RO memory-like and CD4 T cells were significantly elevated in aparasitemic women compared to levels in the parasitemic group, with aparasitemic multigravid women having the highest percentages of CD45RO memory-like and CD4 T cells. In contrast, at the placental level, IFN-γ production by innate NK cells was significantly increased in aparasitemic women compared to parasitemic women, regardless of gravidity. These results suggest that the elevated IFN-γ-producing NK cells in the placenta and CD45RO memory-like and CD4 T cells in peripheral blood may be involved in protection against malaria infection in pregnancy.
Evidence for Globally Shared, Cross-Reacting Polymorphic Epitopes in the Pregnancy-Associated Malaria Vaccine Candidate VAR2CSA
Authors: Avril Marion , Kulasekara Bridget R. , Gose Severin O. , Rowe Chris , Dahlbäck Madeleine , Duffy Patrick E. , Fried Michal , Salanti Ali , Misher Lynda , Narum David L. , Smith Joseph D.
Published: February 2008

Pregnancy-associated malaria (PAM) is characterized by the placental sequestration of
Plasmodium falciparum
-infected erythrocytes (IEs) with the ability to bind to chondroitin sulfate A (CSA). VAR2CSA is a leading candidate for a pregnancy malaria vaccine, but its large size (∼350 kDa) and extensive polymorphism may pose a challenge to vaccine development. In this study, rabbits were immunized with individual VAR2CSA Duffy binding-like (DBL) domains expressed in
Pichia pastoris
or
var2csa
plasmid DNA and sera were screened on different CSA-binding parasite lines. Rabbit antibodies to three recombinant proteins (DBL1, DBL3, and DBL6) and four plasmid DNAs (DBL1, DBL3, DBL5, and DBL6) reacted with homologous FCR3-CSA IEs. By comparison, antibodies to the DBL4 domain were unable to react with native VAR2CSA protein unless it was first partially proteolyzed with trypsin or chymotrypsin. To investigate the antigenic relationship of geographically diverse CSA-binding isolates, rabbit immune sera were screened on four heterologous CSA-binding lines from different continental origins. Antibodies did not target conserved epitopes exposed in all VAR2CSA alleles; however, antisera to several DBL domains cross-reacted on parasite isolates that had polymorphic loops in common with the homologous immunogen. This study demonstrates that VAR2CSA contains common polymorphic epitopes that are shared between geographically diverse CSA-binding lines.
Vibrio vulnificus rtxE
Is Important for Virulence, and Its Expression Is Induced by Exposure to Host Cells
Authors: Lee Byung Cheol , Lee Jeong Hyun , Kim Myung Won , Kim Byoung Sik , Oh Man Hwan , Kim Kun-Soo , Kim Tae Sung , Choi Sang Ho
Published: February 2008

Numerous secreted virulence factors have been proposed to account for the fulminating and destructive nature of
Vibrio vulnificus
infections. A mutant of
V. vulnificus
that exhibited less cytotoxicity to INT-407 human intestinal epithelial cells was screened from a library of mutants constructed by random transposon mutagenesis. A transposon-tagging method was used to identify and clone an open reading frame encoding an RTX toxin secretion ATP binding protein, RtxE, from
V. vulnificus
. The deduced amino acid sequence of RtxE from
V. vulnificus
was 91% identical to that reported from
Vibrio cholerae
. Functions of the
rtxE
gene in virulence were assessed by constructing an isogenic mutant whose
rtxE
gene was inactivated by allelic exchanges and by evaluating the differences between its virulence phenotype and that of the wild type in vitro and in mice. The disruption of
rtxE
blocked secretion of RtxA to the cell exterior and resulted in a significant reduction in cytotoxic activity against epithelial cells in vitro. Also, the intraperitoneal 50% lethal dose of the
rtxE
mutant was 10
4
to 10
5
times higher than that of the parental wild type, indicating that RtxE is essential for the virulence of
V. vulnificus
. Furthermore, the present study demonstrated that the
rtxBDE
genes are transcribed as one transcriptional unit under the control of a single promoter, P

rtxBDE

. The activity of
V. vulnificus
P

rtxBDE

is induced by exposure to INT-407 cells, and the induction requires direct contact of the bacteria with the host cells.
SATURATED ACTIONS BY FINITE-DIMENSIONAL HOPF *-ALGEBRAS ON C*-ALGEBRAS
Authors: JEONG JA A. , PARK GI HYUN
Published: February 2008

If a finite group action α on a unital C*-algebra M is saturated, the canonical conditional expectation E : M → Mα onto the fixed point algebra is known to be of index finite type with Index (E) = |G| in the sense of Watatani. More generally, if a finite-dimensional Hopf *-algebra A acts on M and the action is saturated, the same is true with Index (E) = dim (A). In this paper, we prove that the converse is true. Especially in case M is a commutative C*-algebra C(X) and α is a finite group action, we give an equivalent condition in order that the expectation E : C(X) → C(X)α is of index finite type, from which we obtain that α is saturated if and only if G acts freely on X. Actions by compact groups are also considered to show that the gauge action γ on a graph C*-algebra C*(E) associated with a locally finite directed graph E is saturated.
THE POLE DIAGRAM AND THE MIYAZAWA POLYNOMIAL
Authors: ISHII ATSUSHI
Published: February 2008

We introduce the pole diagram, which helps to retrieve information from a knot diagram when we smooth crossings. By using the notion, we define a bracket polynomial for the Miyazawa polynomial. The bracket polynomial gives a simple definition and evaluation for the Miyazawa polynomial. Then we show that the virtual crossing number of a virtualized alternating link is determined by its diagram. Furthermore, we construct infinitely many virtual link diagrams which attain the minimal real and virtual crossing numbers together.
IRREDUCIBLE HEEGNER DIVISORS IN THE PERIOD SPACE OF ENRIQUES SURFACES
Authors: KOCA CANER , SERTÖZ ALİ SİNAN
Published: February 2008

Reflection walls of certain primitive vectors in the anti-invariant sublattice of the K3 lattice define Heegner divisors in the period space of Enriques surfaces. We show that depending on the norm of these primitive vectors, these Heegner divisors are either irreducible or have two irreducible components. The two components are obtained as the walls orthogonal to primitive vectors of the same norm but of different type as ordinary or characteristic.
ON THE PICARD NUMBER OF ALMOST FANO THREEFOLDS WITH PSEUDO-INDEX > 1
Authors: CASAGRANDE CINZIA , JAHNKE PRISKA , RADLOFF IVO
Published: February 2008

We study Gorenstein almost Fano threefolds X with canonical singularities and pseudoindex > 1. We show that the maximal Picard number of X is 10 in general, 3 if X is Fano, and 8 if X is toric. Moreover, we characterize the boundary cases. In the Fano case, we prove that the generalized Mukai conjecture holds.
ENDOMORPHISMS OF THE PLANE PRESERVING A PENCIL OF CURVES
Authors: DABIJA MARIUS , JONSSON MATTIAS
Published: February 2008

We classify endomorphisms of the plane that preserve a pencil of curves.
A GEANT-BASED STUDY OF ATMOSPHERIC NEUTRINO OSCILLATION PARAMETERS AT INO
Authors: SAMANTA ABHIJIT , BHATTACHARYA SUDEB , GHOSAL AMBAR , KAR KAMALES , MAJUMDAR DEBASISH , RAYCHAUDHURI AMITAVA
Published: February 2008

We have studied the dependence of the allowed space of the atmospheric neutrino oscillation parameters on the time of exposure for a magnetized Iron CALorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We have performed a Monte Carlo simulation for a 50 kTon ICAL detector generating events by the neutrino generator NUANCE and simulating the detector response by GEANT. A chi-square analysis for the ratio of the up-going and down-going neutrinos as a function of L/E is performed and the allowed regions at 90% and 99% CL are displayed. These results are found to be better than the current experimental results of MINOS and Super-K. The possibilities of further improvement have also been discussed.
SIMULATIONS OF EXTENSIVE AIR SHOWERS FOR THE ESTIMATION OF THE NUMBER OF PHOTOELECTRONS OF A SETUP OF P. AUGER FLUORESCENCE DETECTOR
Authors: GERANIOS A. , FOKITIS E. , MALTEZOS S. , PATRINOS K. , ROZAKI-MAVROULI H.
Published: February 2008

The efficiency of a pixel detector using optical UV filters is determined in this work. Based on the Auger fluorescence detector geometry, we have calculated the overall efficiency of the pixel detector using an appropriate method that takes into account the particular spectral functions and the dependence on the angle of incidence of the optical filter used. Assuming extensive air shower (EAS) events developed with various inclinations generated by AIRES code, we calculated the number of electrons and positrons produced during the development of the EAS's. The detection efficiency of the pixel detector is taken into account in estimating the recorded signal (number of photoelectrons) for two sets of EAS simulations, corresponding to protons and iron nuclei, as primary particles.
ON SUPERGROUPS WITH ODD CLIFFORD PARAMETERS AND SUPERSYMMETRY WITH MODIFIED LEIBNIZ RULE
Authors: KUZNETSOVA Z. , ROJAS M. , TOPPAN F.
Published: February 2008

We investigate supergroups with Grassmann parameters replaced by odd Clifford parameters. The connection with nonanticommutative supersymmetry is discussed. A Berezin-like calculus for odd Clifford variables is introduced. Fermionic covariant derivatives for supergroups with odd Clifford variables are derived. Applications to supersymmetric quantum mechanics are made. Deformations of the original supersymmetric theories are encountered when the fermionic covariant derivatives do not obey the graded Leibniz property. The simplest nontrivial example is given by the N = 2 supersymmetric quantum mechanics with a real (1, 2, 1) multiplet and a cubic potential. The action is real. Depending on the overall sign ("Euclidean" or "Lorentzian") of the deformation, a Bender–Boettcher pseudo-Hermitian Hamiltonian is encountered when solving the equations of motions of the auxiliary field. A possible connection of our framework with the Drinfeld twist deformation of supersymmetry is pointed out.
GREEN FUNCTIONS AND NONLINEAR SYSTEMS: SHORT TIME EXPANSION
Authors: FRASCA MARCO
Published: February 2008

We show that Green function methods can be straightforwardly applied to nonlinear equations appearing as the leading order of a short time expansion. Higher-order corrections can be then computed giving a satisfactory agreement with numerical results. The relevance of these results relies on the possibility of fully exploiting a gradient expansion in both classical and quantum field theory granting the existence of a strong coupling expansion. Having a Green function in this regime in quantum field theory amounts to obtain the corresponding spectrum of the theory.
FURTHER COMMENTS ON THE SYMMETRIC SUBTRACTION OF THE NONLINEAR SIGMA MODEL
Authors: BETTINELLI DANIELE , FERRARI RUGGERO , QUADRI ANDREA
Published: February 2008

Recently a perturbative theory has been constructed, starting from the Feynman rules of the nonlinear sigma model at the tree level in the presence of an external vector source coupled to the flat connection and of a scalar source coupled to the nonlinear sigma model constraint (flat connection formalism). The construction is based on a local functional equation, which overcomes the problems due to the presence (already at one loop) of nonchiral symmetric divergences. The subtraction procedure of the divergences in the loop expansion is performed by means of minimal subtraction of properly normalized amplitudes in dimensional regularization. In this paper we complete the study of this subtraction procedure by giving the formal proof that it is symmetric to all orders in the loopwise expansion. We provide further arguments on the issue that, within our subtraction strategy, only two parameters can be consistently used as physical constants.