bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Characteristics of Simply Supported Thick Skew Plates in Three-Dimensional Setting
Authors: Liew K. M. , Hung K. C. , Lim M. K.
Published: February 2008

A procedure is presented for determining the three-dimensional elasticity solutions for free vibration analysis of simply supported thick skew plates. The exact expressions of strain and kinetic energies are derived from linear, small-strain, three-dimensional elasticity theory. To allow the treatment of soft and hard simple support conditions, sets of three-dimensional spatial displacement functions are expressed in terms of unit normals to the edges. By virtue of the three-dimensional elasticity theory, the present method does not require a special treatment for stress singularity at the obtuse corners. This method is also demonstrated to be free from shear locking phenomena. The significant difference in the vibration response of skew plates with soft and hard simple support conditions is highlighted. The influence of skew angle on the eigenvalues of thick skew plate is discussed in the context of the three-dimensional elasticity solutions.
Out-of-Plane Impact at the Tip of a Right-Angled Bent Cantilever Beam
Authors: Wang B. , Yu T. X. , Reid S. R.
Published: February 2008

The present paper provides an analysis of the response of a right-angled bent cantilever beam subjected to an out-of-plane impulsive load (i.e., suddenly imposed velocity) applied to concentrated mass at its tip. If T0 and M0 are the fully plastic torque and bending moment, respectively, of the cross section, it is shown that for the case T0/M0 < 1, a double hinge mechanism is required, with a pure bending hinge in the first segment of the beam and a combined bending-torsion hinge in the second segment. The history of deformation is described following impartation of the load.
Taylor-Couette Instability With a Continuous Spectrum
Authors: Yao L. S. , Ghosh Moulic S.
Published: February 2008

Nonlinear evolution of a continuous spectrum of unstable waves near the first bifurcation point in circular Couette flow has been investigated. The disturbance is represented by a Fourier integral over all possible axial wave numbers, and an integrodif-ferential equation for the amplitude-density function of a continuous spectrum is derived. The equations describing the evolution of monochromatic waves and slowly varying wave packets of classical weakly nonlinear instability theories are shown to be special limiting cases. Numerical integration of the integrodifferential equation shows that the final equilibrium state depends on the initial disturbance, as observed experimentally, and it is not unique. In all cases, the final equilibrium state consists of a single dominant mode and its harmonics of smaller amplitudes. The predicted range of wave numbers for stable supercritical Taylor vortices is found to be narrower than the span of the neutral curve from linear theory. Taylor-vortex flows with wave numbers outside this range are found to be unstable and to decay, but to excite another wave inside the narrow band. This result is in agreement with the Eckhaus and Benjamin-Feir sideband instability. The results also show that a linearly stable long wave can excite a short unstable wave through nonlinear wave interaction. An important implication of the existence of nonunique equilibrium states is that the torque induced by the fluid motion cannot be determined uniquely. The numerical results show that the uncertainty, associated with nonuniqueness, of using any accurately measured Taylor-vortex torque slightly above the first bifurcation point in engineering practice can be as large as ten percent. The presence of multiple solutions at a fixed Reynolds number for a given geometry in Taylor-Couette flows has been known since Coles’ monumental contribution in 1965. A theoretical confirmation has come only 30 years later. It is worthwhile to point out that the existence of multiple solutions, found by Coles, differs from current popular bifurcation theories. The current study indicates that the state of flows on a stable bifurcation branch can involve any wave number within a finite band and can not be determined uniquely. The multiple solutions in Coles’ sense have also been found for mixed-convection flows (Yao and Ghosh Moulic, 1993, 1994) besides the Taylor-Couette flows. We believe that the nonuniqueness of Coles sense, which complements the bifurcation theories, is a generic property for all fluid flows.
Complete Solution of the Linear Magnetoelasticity and the Magnetic Fields in a Magnetized Elastic Half-Space
Authors: Ke-Fu Huang , Min-Zhong Wang
Published: February 2008

In this paper, a general solution of the equations in the linearized theory of magnetoe-lasticity, which was developed by Pao and Yeh (1973) on the basis of Brown’s phenomenological theory of magnetoelasticity (1966), is obtained. As in some applications, the magnetic fields caused by the mechanical singularities in a magnetized elastic half-space are considered. Using the general solution and the Mindlin state of the elastic half-space (1936), the exact three-dimensional solutions for the generated magnetic fields due to various mechanical singularities, such as a single force and a doublet, are obtained in closed form.
Attitude Behavior of a Variable Mass Cylinder
Authors: Eke F. O. , Wang Song-Min
Published: February 2008

This paper examines the attitude motion of a cylindrical body with mass loss. It is found that mass variation can have a substantial influence on the behavior of such a system. Specifically, the initial dimensions as well as the manner in which mass loss affects system inertia are found to be key factors in the determination of the characteristics of the lateral motion of the system. In great contrast to the attitude behavior of spinning rigid bodies, oblate variable mass cylinders exhibit divergent transverse attitude motion, while the transverse motion of prolate variable mass cylinders is found to be bounded in general.
Boundary of the Basin of Attraction for Weakly Damped Primary Resonance
Authors: Haberman R. , Ho E. K.
Published: February 2008

The dissipatively perturbed Hamiltonian system corresponding to primary resonance is analyzed in the case in which two competing stable periodic responses exist. The method of averaging fails as the trajectory approaches the unperturbed homoclinic orbit (separatrix). By using the small dissipation of the Hamiltonian (the Melnikov integral) near the homoclinic orbit, the boundaries of the basin of attraction are determined analytically in an asymptotically accurate way. The selection of the two competing periodic responses is influenced by small changes in the initial conditions. The analytic formula is shown to agree well with numerical computations.
The Stiffest Wire
Authors: Schulgasser K.
Published: February 2008

We consider a polycrystal constituted from orthorhombic single crystals for which one particular principal axis of the crystallites is always oriented parallel to a particular direction; in the plane perpendicular to this direction the crystallites are randomly oriented. Bounds are found for the Young’s modulus in the axial direction. The lower bound on the Young’s modulus, which is realizable, is found to be that of the individual crystallite in the aligned direction. The upper bound determined is necessarily realizable when the single crystal elastic constants satisfy a certain condition. When this condition is not satisfied a bound is found; whether or not this bound is realizable must be examined using the specific elastic constants of the crystal being considered. For all physical examples considered the upper bound was indeed found to be realizable. Thus, generally speaking, a wire constituted as above, with the stiffest direction of the individual crystallites being along the wire, will have a higher Young’s modulus than the maximum modulus of the individual crystallites of which it is composed.
Rotational Dynamics of Axisymmetric Variable Mass Systems
Authors: Wang S.-M. , Eke F. O.
Published: February 2008

This paper studies the attitude dynamics of variable mass systems that have axisymmetric mass distribution and that are subjected to continuous mass variation while in motion. The equations of rotational motion for such systems are solved analytically under the assumption of zero external torque. It is found that such systems can spin up or spin down in free motion, and that the transverse angular velocity magnitude can increase or decrease with time. The analytical conditions for growth or decay of spin rate and lateral angular speed are presented, and these conditions are related to practical design criteria for rocket-type systems.
Analysis of Ring-Stiffened Cylindrical Shells
Authors: Yang Bingen , Zhout Jianping
Published: February 2008

A new analytical and numerical method is presented for modeling and analysis of cylindrical shells stiffened by circumferential rings. This method treats the shell and ring stiffeners as individual structural components, and considers the ring eccentricity with respect to the shell middle surface. Through use of the distributed transfer functions of the structural components, various static and dynamic problems of stiffened shells are systematically formulated. With this transfer function formulation, the static and dynamic response, natural frequencies and mode shapes, and buckling loads of general stiffened cylindrical shells under arbitrary external excitations and boundary conditions can be determined in exact and closed form. The proposed method is illustrated on a Donnell-Mushtari shell, and compared with finite element method and two other modeling techniques.
Elastic Moduli of Composites Reinforced by Multiphase Particles
Authors: Dunn M. L. , Ledbetter H.
Published: February 2008

A theoretical approach is proposed to estimate the elastic moduli of three-phase composites consisting of a matrix phase reinforced by two-phase particles. The theoretical predictions are based on a simple extension to nondilute concentrations of the mechanical concentration factors obtained from the recent analysis of the average elastic fields in a double inclusion by Hori and Nemat-Nasser (1993). The proposed micromechanics theory can account for the effects of shapes and concentrations of both the particles and the dispersed phase in the particles. Theoretical estimates of the concentration factors and the effective elastic moduli are obtained in closed form and are diagonally symmetric and fall within the Hashin-Shtrikman-Walpole bounds for all cases considered. The theoretical predictions are in excellent agreement with experimental results obtained from pulse-echo and rod-resonance measurements of the elastic moduli of a three-phase composite consisting of an aluminum matrix reinforced by mullite/alumina particles.
An Energy Approach to the Plasticity of a Two-Phase Composite Containing Aligned Inclusions
Authors: Qiu Y. P. , Weng G. J.
Published: February 2008

Based on a linear comparison composite (Tandon and Weng, 1988) and an energy criterion for the effective stress of the ductile matrix (Qiu and Weng, 1992), a nonlinear theory is developed to estimate the strain potential and the overall stressstrain relations of a two-phase composite containing aligned spheroidal inclusions. The plastic state of the ductile matrix under a given external load is determined by solving two simultaneous equations, one being its constitutive equation and the other the expression of its effective stress as a function of its secant shear modulus. Then by means of the effective properties of the linear comparison composite, the overall strain and strain potential of the nonlinear system are evaluated. It is demonstrated that, for an elastically incompressible matrix containing either aligned voids or rigid inclusions, the derived strain potential is exactly equal to Ponte Castaneda’s (1991) bound or estimate, respectively, of Willis’ (1977) type. Comparison with an exact solution of a fiber-reinforced composite under the plane-strain biaxial loading also shows an excellent agreement. The theory is generally intended for the condition when the concentration is not high, and is finally applied to examine the aspect-ratio dependence of the overall response for a silicon carbide/aluminum system. It is found that, more so than the elastic behavior, the nonlinear plastic response of the twophase composite is very sensitive to the inclusion shape under most types of loading.
Symmetrical Propagation of a Central Crack in Orthotropic Material
Authors: Tsai Y. M.
Published: February 2008

A central crack which propagates symmetrically in an orthotropic composite plate is investigated using the techniques of Fourier and Laplace transforms. The crack is located along one of the principal axes of the material. Complete contour integrations are carried out in the evaluation of the Laplace inversion integrals. For the crack tips running at a constant speed, exact expressions for the dynamic crack shape and the dynamic stress distribution with singularities in the crack plane are obtained in terms of anisotropic material constants and crack speed. The dynamic expressions are evaluated numerically by using graphite/epoxy and glass/ epoxy composites and an isotropic material as sample materials. The dynamic solution reduces to the static solution at zero crack speed. During crack propagation, the deviation between dynamic and static solutions is governed by dynamic correction factors which are nondimensional functions of the ratios among anisotropic material constants and the ratio of crack speed to shear-wave speed. Values of these dynamic factors are obtained for the sample composites at a large range of crack speed. The dynamic stress intensity factor vanishes at the corresponding Rayleigh wave speed.
Realizability of Negative Pore Compressibility in Poroelastic Composites
Authors: Berge P. A. , Berryman J. G.
Published: February 2008

For elastic materials containing fluid-saturated porosity, the pore compressibility is a measure of the deformation of a unit pore volume in response to a change in fluid pressure. Rather than being measured, this quantity has been routinely set equal to an effective solid compressibility, since this equality is exact whenever a single solid component is present. However, we show that the pore compressibility and solid compressibility may be uncorrelated in general. In certain special circumstances they do not even share the same sign. Although thermodynamic and mechanical stability constraints cause solid and drained-frame bulk moduli of a porous composite to be positive and bounded by component properties, the pore compressibility is unconstrained and, therefore, can have negative values. For special realizable model materials, the value of the pore compressibility can be found using an exact expression valid for a composite made up of one fluid and two solid components, i.e., two porous components. In order to quantify how various factors affect the sign and magnitude of the pore compressibility, pore compressibilities were calculated for models that used two porous components having the microgeometry of an assemblage of concentric spheres. This model implicitly assumes the pores are on a much smaller length scale than the concentric spheres. Modeling results show that with the stiffer porous material forming the outer shells of the concentric spheres, the pore compressibility of such materials is negative when solid component bulk moduli differ by at least a factor of 5, if, in addition, the porosities and drained frame moduli of the two porous components are relatively low. Negative pore compressibilities were found for realizable models whose two porous constituents had the properties of silicon nitride and either sandstone or clay. For models using combinations of alumina and glass foam properties, pore compressibilities were non-negative but smaller than the compressibilities of the solid components.
Transient Thermal Stresses in a Multilayered Anisotropic Medium
Authors: Chen Tei-Chen , Jang Horng-I , Tseng Ampere A.
Published: February 2008

A transient thermoelasticity problem of a multilayered anisotropic medium under the state of generalized plane deformation is considered in this note. The flexibility/stiffness matrix method is adopted here to obtain the complete solution of the entire layered medium by introducing the thermal and mechanical boundary and layer interface conditions in the Fourier and Laplace transform domains. As a numerical illustration, the distributions of transient temperatures and thermal stresses in a laminated anisotropic slab subjected to a uniform surface temperature rise are presented for some stacking sequences of fiber-reinforced layers.
Rapid Neural Coding in the Retina with Relative Spike Latencies
Authors: Gollisch Tim , Meister Markus
Published: February 2008

Natural vision is a highly dynamic process. Frequent body, head, and eye movements constantly bring new images onto the retina for brief periods, challenging our understanding of the neural code for vision. We report that certain retinal ganglion cells encode the spatial structure of a briefly presented image in the relative timing of their first spikes. This code is found to be largely invariant to stimulus contrast and robust to noisy fluctuations in response latencies. Mechanistically, the observed response characteristics result from different kinetics in two retinal pathways (“ON” and “OFF”) that converge onto ganglion cells. This mechanism allows the retina to rapidly and reliably transmit new spatial information with the very first spikes emitted by a neural population.
Juvenile Hormone Regulates Butterfly Larval Pattern Switches
Authors: Futahashi Ryo , Fujiwara Haruhiko
Published: February 2008

Insect color patterns can be very diverse. This variation is also seen among many larval instar stages, which can take on vastly different phenotypes. Young caterpillars of the swallowtail butterfly,
Papilio xuthus
, are mimics of bird droppings, whereas the fifth larval instar is camouflaged among the leaves of host plants (cryptic pattern). We find that juvenile hormone (JH) titers decrease during the fourth larval instar. Furthermore, treatment with JH analog at the beginning of the fourth instar stage resulted in reproducing the mimetic pattern instead of the usual cryptic one and likewise altered gene expression patterns to that associated with the mimetic pattern. These findings suggest that JH regulates the progressive larval pattern switch of this insect.
The Force Needed to Move an Atom on a Surface
Authors: Ternes Markus , Lutz Christopher P. , Hirjibehedin Cyrus F. , Giessibl Franz J. , Heinrich Andreas J.
Published: February 2008

Manipulation of individual atoms and molecules by scanning probe microscopy offers the ability of controlled assembly at the single-atom scale. However, the driving forces behind atomic manipulation have not yet been measured. We used an atomic force microscope to measure the vertical and lateral forces exerted on individual adsorbed atoms or molecules by the probe tip. We found that the force that it takes to move an atom depends strongly on the adsorbate and the surface. Our results indicate that for moving metal atoms on metal surfaces, the lateral force component plays the dominant role. Furthermore, measuring spatial maps of the forces during manipulation yielded the full potential energy landscape of the tip-sample interaction.
NADP Regulates the Yeast
GAL
Induction System
Authors: Kumar P. Rajesh , Yu Yao , Sternglanz Rolf , Johnston Stephen Albert , Joshua-Tor Leemor
Published: February 2008

Transcriptional regulation of the galactose-metabolizing genes in
Saccharomyces cerevisiae
depends on three core proteins: Gal4p, the transcriptional activator that binds to upstream activating DNA sequences (UAS
GAL
); Gal80p, a repressor that binds to the carboxyl terminus of Gal4p and inhibits transcription; and Gal3p, a cytoplasmic transducer that, upon binding galactose and adenosine 5′-triphosphate, relieves Gal80p repression. The current model of induction relies on Gal3p sequestering Gal80p in the cytoplasm. However, the rapid induction of this system implies that there is a missing factor. Our structure of Gal80p in complex with a peptide from the carboxyl-terminal activation domain of Gal4p reveals the existence of a dinucleotide that mediates the interaction between the two. Biochemical and in vivo experiments suggests that nicotinamide adenine dinucleotide phosphate (NADP) plays a key role in the initial induction event.
Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation
Authors: Li Jun Z. , Absher Devin M. , Tang Hua , Southwick Audrey M. , Casto Amanda M. , Ramachandran Sohini , Cann Howard M. , Barsh Gregory S. , Feldman Marcus , Cavalli-Sforza Luigi L. , Myers Richard M.
Published: February 2008

Human genetic diversity is shaped by both demographic and biological factors and has fundamental implications for understanding the genetic basis of diseases. We studied 938 unrelated individuals from 51 populations of the Human Genome Diversity Panel at 650,000 common single-nucleotide polymorphism loci. Individual ancestry and population substructure were detectable with very high resolution. The relationship between haplotype heterozygosity and geography was consistent with the hypothesis of a serial founder effect with a single origin in sub-Saharan Africa. In addition, we observed a pattern of ancestral allele frequency distributions that reflects variation in population dynamics among geographic regions. This data set allows the most comprehensive characterization to date of human genetic variation.
Optimal Blood Mononuclear Cell Isolation Procedures for Gamma Interferon Enzyme-Linked Immunospot Testing of Healthy Swedish and Tanzanian Subjects
Authors: Nilsson C. , Aboud S. , Karlén K. , Hejdeman B. , Urassa W. , Biberfeld G.
Published: February 2008

Determination of antigen-specific T-cell responses is an important part of vaccine assessment. High levels of recovery, viability, and functionality of peripheral blood mononuclear cells (PBMCs) are essential for reliable assessment of cell-mediated immune responses. Here, we sought to find the cell preparation technique best suited for two clinical vaccine trial sites: Stockholm, Sweden, and Dar es Salaam, Tanzania. Standard Ficoll-Paque gradient centrifugation, BD Vacutainer cell preparation tube (CPT), and Greiner Bio-One LeucoSep tube techniques were tested. Cell yield and viability were recorded. Gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) testing was used to assess cell functionality. No differences in mean recovery or mean viability of fresh PBMCs were observed between Ficoll-Paque gradient centrifugation and CPT techniques as used in Stockholm. In Dar es Salaam, recovery of PBMCs isolated by use of the Ficoll-Paque gradient technique was higher than that seen with CPT (1.58 ± 0.6 versus 1.34 ± 0.4 million cells/ml of blood [
P
= 0.0469]), and the viability of PBMCs processed by Ficoll-Paque gradient was higher than that seen with CPT-purified cells (95.8% ± 2.3% versus 92.6% ± 4.8% [
P
= 0.0081]). Furthermore, LeucoSep cell separation gave higher levels of yield (1.10 ± 0.3 versus 0.92 ± 0.3 million cells/ml of blood [
P
= 0.0022]) and viability (95.7% ± 2.0% versus 93.4% ± 3.2% [
P
= 0.0012]) than Ficoll-Paque cell separation. The cells purified by the different techniques at the two sites performed equally well in IFN-γ ELISPOT assays. Both techniques generated cell preparations with excellent yield, viability, and functionality in Stockholm. In Dar es Salaam, CPT did not perform as well as Ficoll-Paque separation. In a subsequent comparison, LeucoSep performed better than Ficoll-Paque separation. Our findings emphasize the need for on-site assessment of PBMC purification techniques for optimal evaluation of cell-mediated immune responses.
Serological Reactivity and Biochemical Characterization of Methylated and Unmethylated Forms of a Recombinant Protein Fragment Derived from Outer Membrane Protein B of
Rickettsia typhi
Authors: Chao Chien-Chung , Zhang Zhiwen , Wang Hui , Alkhalil Abdulnaser , Ching Wei-Mei
Published: February 2008

Rickettsia typhi
, an obligate intracellular bacterium that causes murine typhus, possesses a heavily methylated outer membrane protein B (OmpB) antigen. This immunodominant antigen is responsible for serological reactions and is capable of eliciting protective immune responses with a guinea pig model. Western blot analysis of partially digested OmpB with patient sera revealed that most of the reactive fragments are larger than 20 kDa. One of these fragments, which is located at the N terminus (amino acids 33 to 273), fragment A (At), has been expressed in
Escherichia coli
. The expressed protein (rAt) was purified by chromatography and properly refolded by sequential dialysis. The refolded rAt protein was recognized by at least 87% of the typhus group patient sera as determined by enzyme-linked immunosorbent assay (ELISA). However, the titers were lower than those obtained with OmpB of
R. typhi
. Since native OmpB is hypermethylated at lysine residues, we chemically methylated the lysine residues in rAt. The methylation was confirmed by amino acid composition analysis, and the methylation pattern of the methylated rAt (mrAt) protein was similar to that of native At from OmpB, as revealed by liquid chromatography-mass spectrometry analysis. Both rAt and mrAt were evaluated in an ELISA for their serological reactivity with patient sera. Among patient sera tested, 83% exhibited higher titers with mrAt than with rAt. These results suggest that rAt, with or without methylation, can potentially replace rickettsia-derived OmpB or whole-cell antigen for the diagnosis of
R. typhi
infection.
Comparative Analysis of Human and Canine
Campylobacter upsaliensis
Isolates by Amplified Fragment Length Polymorphism
Authors: Damborg Peter , Guardabassi Luca , Pedersen Karl , Kokotovic Branko
Published: February 2008

Human (
n
= 33) and canine (
n
= 53)
Campylobacter upsaliensis
isolates from seven countries were genotyped by a new amplified fragment length polymorphism method. We observed 100% typeability and high overall diversity. The majority of human strains (23/33) clustered separately from canine strains, indicating that dogs may not be the main source of human infection.
Comparison of Reverse Hybridization, Microarray, and Sequence Analysis for Genotyping Hepatitis B Virus
Authors: Pas Suzan D. , Tran Nathalie , de Man Robert A. , Burghoorn-Maas C. , Vernet Guy , Niesters Hubert G. M.
Published: February 2008

Hepatitis B virus (HBV) genotyping has become important in epidemiological and clinical diagnoses, given the relationship between the viral genotype and the progression of disease or the appearance of antiviral resistance. Since genotyping by sequence and phylogenetic analyses is not convenient in the clinical setting, we evaluated InnoLipa HBV genotyping (Innogenetics, Belgium) and an HBV DNA-Chip (bioMerieux, France) prototype assay and compared their sequencing of the gold standard S gene, using a cohort of 275 individual patient samples. All but two samples, belonging to distant and individual subgroups within a single genotype, were detected by InnoLipa HBV assay. Four samples with dual infections belonging to genotypes A and G were identified only by InnoLipa HBV assay. Using an HBV DNA-Chip assay, one sample could not be amplified due to a low viral load. Four samples were identified as genotype C and two as genotype D by sequencing but were classified as genotype A (two samples) and D (two samples) and as A (one sample) and G (one sample) by the DNA-Chip assay. In conclusion, the InnoLipa HBV genotyping strip assay detected dual infections and was an easy and quick tool for genotyping, with a sensitivity of 99.3% and a specificity of 100% compared to sequence analysis. HBV DNA-Chip assay showed a sensitivity and specificity of 97.5 and 97.8%, respectively.
Population Structure of Invasive and Colonizing Strains of
Streptococcus agalactiae
from Neonates of Six U.S. Academic Centers from 1995 to 1999
Authors: Bohnsack John F. , Whiting April , Gottschalk Marcelo , Dunn Diane Marie , Weiss Robert , Azimi Parvin H. , Philips Joseph B. , Weisman Leonard E. , Rhoads George G. , Lin Feng-Ying C.
Published: February 2008

The purpose of this study was to describe the population structure of group B streptococci (GBS) isolated from infected and colonized neonates during a prospective active-surveillance study of early-onset disease in six centers in the United States from July 1995 to June 1999 and to examine its relationship to bovine strains of GBS. The phylogenetic lineage of each GBS isolate was determined by multilocus sequence typing, and isolates were clustered into clonal complexes (CCs) using the eBURST software program. A total of 899 neonatal GBS isolates were studied, of which 129 were associated with invasive disease. Serotype Ia, Ib, and V isolates were highly clonal, with 92% to 96% of serotype Ia, Ib, and V isolates being confined to single clonal clusters. In contrast, serotype II and III isolates were each comprised of two major clones, with 39% of serotype II and 41% of serotype III isolates in CC 17 and 41% of serotype II and 54% of serotype III isolates in CC 19. Further analysis demonstrates that the CC 17 serotype II and III GBS are closely related to a previously described “ancestral” lineage of bovine GBS. While 120 (93%) of invasive GBS were confined to the same lineages that colonized neonates, 9 (7%) of the invasive GBS isolates were from rare lineages that comprised only 2.7% of colonizing lineages. These results are consistent with those for other geographic regions that demonstrate the highly clonal nature of GBS infecting and colonizing human neonates.
Impact of Human Bocavirus on Children and Their Families
Authors: Esposito Susanna , Bosis Samantha , Niesters Hubert G. M. , Tremolati Elena , Sabatini Caterina , Porta Alessandro , Fossali Emilio , Osterhaus Albert D. M. E. , Principi Nicola
Published: February 2008

This study was planned to investigate the prevalence and clinical features of the illnesses associated with human bocavirus (hBoV) in children with acute disease. We prospectively enrolled all subjects aged less than 15 years attending an emergency room in Milan, Italy, on Wednesdays and Sundays between 1 November 2004 and 31 March 2005 for any acute medical reason, excluding surgical diseases and trauma. Nasopharyngeal swabs were collected at admission to detect hBoV; influenza A and B viruses; respiratory syncytial virus; human metapneumovirus; parainfluenza viruses 1, 2, 3, and 4; rhinovirus; adenovirus; and coronaviruses 229E, OC43, NL63, and HKU1 by real-time PCR. Among the 1,332 enrolled children, hBoV was the fifth most frequently detected virus (7.4%). The rate of hBoV coinfections with other viruses was significantly higher than for the other viruses (50.5% versus 27.5%;
P
< 0.0001). Eighty-nine of the 99 hBoV-positive children (89.9%) had a respiratory tract infection, and 10 (10.1%) had gastroenteritis. hBoV coinfections had a significantly greater clinical and socioeconomic impact on the infected children and their households than hBoV infection alone. In conclusion, these findings show that the role of hBoV infection alone seems marginal in children attending an emergency room for acute disease; its clinical and socioeconomic importance becomes relevant only when it is associated with other viruses.
High-Capacity Adenovirus Vector-Mediated Anti-Glioma Gene Therapy in the Presence of Systemic Antiadenovirus Immunity
Authors: King Gwendalyn D. , Muhammad A. K. M. Ghulam , Xiong Weidong , Kroeger Kurt M. , Puntel Mariana , Larocque Daniel , Palmer Donna , Ng Philip , Lowenstein Pedro R. , Castro Maria G.
Published: February 2008

Gene therapy is proposed as a novel therapeutic strategy for treating glioblastoma multiforme (GBM), a devastating brain cancer. In the clinic, antivector immune responses pose formidable challenges. Herein we demonstrate that high-capacity adenovirus vectors (HC-Ads) carrying the conditional cytotoxic gene herpes simplex virus type 1-thymidine kinase (TK) induce tumor regression and long-term survival in an intracranial glioma model, even in the presence of systemic antiadenovirus immunity, as could be encountered in patients. First-generation Ad-TK failed to elicit tumor regression in this model. These results pave the way for implementing HC-Ad-TK-mediated gene therapy as a powerful adjuvant for treating GBM.
Inhibition of CD1 Antigen Presentation by Human Cytomegalovirus
Authors: Raftery Martin J. , Hitzler Manuel , Winau Florian , Giese Thomas , Plachter Bodo , Kaufmann Stefan H. E. , Schönrich Günther
Published: February 2008

The betaherpesvirus human cytomegalovirus (HCMV) encodes several molecules that block antigen presentation by the major histocompatibility complex (MHC) proteins. Humans also possess one other family of antigen-presenting molecules, the CD1 family; however, the effect of HCMV on CD1 expression is unknown. The majority of CD1 molecules are classified on the basis of homology as group 1 CD1 and are present almost exclusively on professional antigen-presenting cells such as dendritic cells, which are a major target for HCMV infection and latency. We have determined that HCMV encodes multiple blocking strategies targeting group 1 CD1 molecules. CD1 transcription is strongly inhibited by the HCMV interleukin-10 homologue cmvIL-10. HCMV also blocks CD1 antigen presentation posttranscriptionally by the inhibition of CD1 localization to the cell surface. This function is not performed by a known HCMV MHC class I-blocking molecule and is substantially stronger than the blockage induced by herpes simplex virus type 1. Antigen presentation by CD1 is important for the development of the antiviral immune response and the generation of mature antigen-presenting cells. HCMV present in antigen-presenting cells thus blunts the immune response by the blockage of CD1 molecules.
The GLN Family of Murine Endogenous Retroviruses Contains an Element Competent for Infectious Viral Particle Formation
Authors: Ribet David , Harper Francis , Esnault Cécile , Pierron Gérard , Heidmann Thierry
Published: February 2008

Several families of endogenous retroviruses (ERVs) have been identified in the mouse genome, in several instances by in silico searches, but for many of them it remains to be determined whether there are elements that can still encode functional retroviral particles. Here, we identify, within the GLN family of highly reiterated ERVs, one, and only one, copy that encodes retroviral particles prone to infection of mouse cells. We show that its envelope protein confers an ecotropic host range and recognizes a receptor different from mCAT1 and mSMIT1, the two previously identified receptors for other ecotropic mouse retroviruses. Electron microscopy disclosed viral particle assembly and budding at the cell membrane, as well as release of mature particles into the extracellular space. These particles are closely related to murine leukemia virus (MLV) particles, with which they have most probably been confused in the past. This study, therefore, identifies a new class of infectious mouse ERVs belonging to the family
Gammaretroviridae
, with one family member still functional today. This family is in addition to the two MLV and mouse mammary tumor virus families of active mouse ERVs with an extracellular life cycle.
Theiler's Virus-Induced Intrinsic Apoptosis in M1-D Macrophages Is Bax Mediated and Restricts Virus Infectivity: a Mechanism for Persistence of a Cytolytic Virus
Authors: Son Kyung-No , Becker Robert P. , Kallio Patricia , Lipton Howard L.
Published: February 2008

Theiler's murine encephalomyelitis virus (TMEV), a member of theCardiovirusgenus in the familyPicornaviridae, is a highly cytolytic virus that produces necrotic death in rodent cells except for macrophages, which undergo apoptosis. In the present study we have analyzed the kinetics of BeAn virus infection in M1-D cells, in order to temporally relate virus replication to the apoptotic signaling events. Apoptosis was associated with early exponential virus growth from 1 to 12 h postinfection (p.i.); however, ≥80% of peak infectivity was lost by 16 to 24 h p.i. The pan-caspase inhibitor qVD-OPh led to significantly higher virus yields, while zVAD-fmk completely inhibited virus replication until 10 h p.i., precluding its assessment in apoptosis. In contrast, while zVAD-fmk significantly inhibited BeAn virus replication in BHK-21 cells at 12 and 16 h p.i., virus replication at these time points was not altered by qVD-OPh. Bax translocation into mitochondria, efflux of cytochromecinto the cytoplasm, and activation of caspases 9 and 3 between ∼8 and 12 h p.i. (all hallmarks of the intrinsic apoptotic pathway) were transiently inhibited by expression of Bcl-2, which is not expressed in M1-D cells. Thus, BeAn virus infection in M1-D macrophages, which restricts virus replication, provides a potential mechanism for modulating TMEV neurovirulence during persistence in the mouse central nervous system.
Measles Virus Infects both Polarized Epithelial and Immune Cells by Using Distinctive Receptor-Binding Sites on Its Hemagglutinin
Authors: Tahara Maino , Takeda Makoto , Shirogane Yuta , Hashiguchi Takao , Ohno Shinji , Yanagi Yusuke
Published: February 2008

Measles is one of the most contagious human infectious diseases and remains a major cause of childhood morbidity and mortality worldwide. The signaling lymphocyte activation molecule (SLAM), also called CD150, is a cellular receptor for measles virus (MV), presumably accounting for its tropism for immune cells and its immunosuppressive properties. On the other hand, pathological studies have shown that MV also infects epithelial cells at a later stage of infection, although its mechanism has so far been unknown. In this study, we show that wild-type MV can infect and produce syncytia in human polarized epithelial cell lines independently of SLAM and CD46 (a receptor for the vaccine strains of MV). Progeny viral particles are released exclusively from the apical surface of these polarized epithelial cell lines. We have also identified amino acid residues on the MV attachment protein that are likely to interact with a putative receptor on epithelial cells. All of these residues have aromatic side chains and may form a receptor-binding pocket located in a different position from the putative SLAM- and CD46-binding sites on the MV attachment protein. Thus, our results indicate that MV has an intrinsic ability to infect both polarized epithelial and immune cells by using distinctive receptor-binding sites on the attachment protein corresponding to each of their respective receptors. The ability of MV to infect polarized epithelial cells and its exclusive release from the apical surface may facilitate its efficient transmission via aerosol droplets, resulting in its highly contagious nature.
Phoma cyperi sp.nov., a sew pathogen of Cyperus iria, its vegetative and reproductive structures and production of phytotoxins
Authors: Upadhyay Rajeev K. , Strobel Gary A. , Hess Wilford M.
Published: February 2008

Phoma cyperi sp.nov. is described as a new pathogen of Cyperus iria L. It differed characteristically in culture, conidiomata, abortive cells, chlamydospores, and dictyochlamydospores from four closely related species of Phoma. Phoma cyperi showed specificity towards nut sedges and produced at least one phytotoxin. Key words: Phoma cyperi sp.nov., Cyperus iria, new pathogen, chlamydospore, dictyochlamydospore, phytotoxin.
Some mechanisms involved in growth stimulation of ectomycorrhizal fungi by bacteria
Authors: Duponnois R. , Garbaye J.
Published: February 2008

The stimulating effect of some soil bacteria on the growth of two ectomycorrhizal fungi (Hebeloma crustuliniforme Bull. Saint Amans and Paxillus involutus Batsch. ex Fr.) is considered. Two mechanisms are involved: a direct trophic effect of the bacteria on the fungi, and an indirect effect by detoxication of the fungal culture medium. This is supported by observations that (i) some organic acids (citric acid, malic acid), released by the bacteria, stimulate the growth of the two fungi, and (ii) Paxillus involutus releases polyphenolic substances that are toxic to itself but are metabolized by the bacteria. These first results suggest that some bacteria can have beneficial effects during the saprophytic phase of ectomycorrhizal fungi before mycorrhizal infection.
A histological study of the invasive and developmental processes of the aphid pathogen Erynia neoaphidis (Zygomycotina: Entomophthorales) in the pea aphid Acyrthosiphon pisum
Authors: Butt T. M. , Beckett A. , Wilding N.
Published: February 2008

On landing on the surface of an aphid host, the primary conidium of Erynia neoaphidis produced either a secondary conidium, a germ tube, or an appressorium. Appressoria were usually globose or clavate and each produced a single penetration peg. A circular bore hole marked the penetration site. Once the fungus had breached the cuticle, it formed protoplasts that failed to elicit an obvious immune response and multiplied rapidly in the haemocoel and in tissues. When the body of the host was occluded (about 3 days after penetration at 20 °C), the protoplasts regenerated a wall and differentiated into rhizoids, which were confined to the midventral region of the dead insect, pseudocystidia, and conidiophores. The rhizoids terminated in a digitate holdfast that adhered firmly to the plant cuticle but did not penetrate it. Conidiophores appeared to break out through the host cuticle using a combination of enzymatic and mechanical means. Key words: Erynia neoaphidis, Entomophthorales, infection, development, aphid.
Effets de l'irradiation γ directe de plantules de tabac sur leur morphologie générale et sur les chloroplastes et la teneur nucléaire en ADN de leur tissu chlorenchymateux
Authors: Muhanna S. , Souvre A. , Albertini L.
Published: February 2008

Plantlets of Nicotiana tabacum var. xanthi and of its Dulieu chlorophyll mutant showed a reduced growth and became yellowish when treated with different γ-ray doses (100–1000 Gy). In bom varieties, the size of the cotyledons and of the first leaves was increased and their aspect was modified after irradiation at 500 and, especially, 100 Gy. Furthermore, in the cotyledon green tissue where chloroplast replication is inhibited by irradiation, a marked dose-dependent increase in chloroplast size and starch storage was observed: in the Dulieu variety, at 500 and 1000 Gy, the chloroplast mean area was respectively 74 and 121 times larger than the control area, whereas the starch granule mean area was respectively 28 and 39 times superior to that of the control. Direct irradition of plantlets induced a nucleus endopolyploidization process directly related to the nucleus size in the green tissue of the cotyledons and first leaves of these two tobacco varieties; the endopolyploidization level was very high at 100 Gy (8C, 16C, and > 16C), high at 500 Gy (8C → 16C), and lower but still significant at 1000 Gy (8C). In this tissue, the G2 → M transition point was more sensitive to strong γ irradiation (100–1000 Gy) than the G1 → S transition point. In conclusion, the plantlets of the two tobacco varieties did not show any significant differences in response to strong γ irradiation. Key words: plant morphology, γ irradiation, chloroplasts, nuclear DNA, cytophotometry.
Studies on the systematics of ectomycorrhizal fungi in axenic culture. V. Linear growth response to standard extreme temperatures used as a taxonomic character
Authors: Hutchison Leonard J.
Published: February 2008

Ectomycorrhizal fungi showed characteristic differences in linear growth rate reduction when grown on modified Melin–Norkrans agar at 7 and 30 °C. The two standard temperature extremes differentiated ectomycorrhizal fungi into three growth response categories which reflected taxonomic affinity: sensitive, semitolerant, and tolerant. At 7 °C, species of Laccaria and Hebeloma generally exhibited tolerant or semitolerant growth, whereas at 30 °C growth tended to be restricted to species of Amanita, Laccaria, Suillus, and a few gasteromycetous fungi (e.g., Rhizopogon, Scleroderma, and Pisolithus). The results reveal the potential value of standard extreme temperatures as a taxonomic character for differentiating species or genera of ectomycorrhizal fungi in vitro. Tolerance or sensitivity to 30 °C by ectomycorrhizal fungi may reflect their association with specific host trees. Key words: ectomycorrhizal fungi, temperature, sensitivity, tolerance, cultures, identification.
A checklist of the subfamily Maloideae (Rosaceae)
Authors: Phipps James B. , Robertson Kenneth R. , Smith Paul G. , Rohrer Joseph R.
Published: February 2008

A checklist of the economically and ecologically important subfamily Maloideae (Rosaceae) is presented. One thousand one hundred and ten species are recognised in 23 genera, as well as 33 species in 13 intergeneric hybrid genera. An alphabetic arrangement is used within each taxonomic rank. The larger genera are subdivided into infrageneric groupings to represent structure. Several new infrageneric taxa were created to reconcile different sources. This checklist is believed to be complete to 1986 and represents the compilation and synthesis of over 170 publications. The following new names are published: Crataegus series Henryanae Phipps, ser.nov. et stat.nov.; Crataegus section Hupehensis Phipps, sect.nov.; Crataegus series Hupehenses Phipps, ser.nov.; Crataegus section Lacrimatae Phipps, sect, et stat.nov.; Malacomeles paniculata (Rehder) Phipps, comb.nov.; Sorbus subgen. Micromeles (Decne.) Phipps, Robertson & Spongberg, subgen. et stat.nov.; Sorbus section Albo-carmesini H.A. McAllister, sect.nov.
Cranberry black rot fungi: Allantophomopsis cytisporea and Allantophomopsis lycopodina
Authors: Carris L. M.
Published: February 2008

The coelomycete genus Allantophomopsis was erected in 1925 by Petrak based on Sphaeria cytisporea, a species described by Fries in 1823 from leaves of Vaccinium vitis-idaea in Sweden. Apostrasseria, erected by Nag Raj in 1983, is based on Ceuthospora lunata, a coelomycetous species described by Shear in 1907 and one of the causal agents of black rot of cranberry (Vaccinium macrocarpon). Examination of type specimens confirmed that Allantophomopsis cytisporea and Apostrasseria lunata are conspecific. A study of light and dark strains of the cranberry black rot fungus provided new evidence to support the recognition of two distinct species. The species are readily separated by cultural, morphological, and cytoiogical characteristics. Allantophomopsis lycopodina, comb.nov. is proposed for collections corresponding to the dark stain wife binu-cleate conidia 8–15 μm long. Allantophomopsis cytisporea is retained for the light strain with uninucleate conidia measuring 6–10 μm in length. Key words: Apostrasseria, Ceuthospora lunata, Vaccinium fungi.
Strength design against brittle fracture of structures of medium strength steels
Authors: Kennedy D. J. L. , Magued M. H.
Published: February 2008

A series of notched static tension tests was carried out over a range of temperatures to study the influence on the fracture behaviour of a medium strength steel of such parameters as the width of the specimen, the depth of the notch, the thickness of the specimen, the notch location, the root radius of the notch, and residual stresses. Based on these tests, the concept of strength interaction surfaces has been developed. The major portion of such a surface, called the strength cirque, determined empirically, was found to be dependent on the temperature, notch depth, and specimen width and thickness. Strain rate and residual stresses are also expected to affect this surface.From the strength interaction surfaces, the critical flaw size can be estimated as a function of such parameters as temperatue, member width, and thickness, to satisfy the criterion that, at the lowest operating temperature, general yielding of the member at an unflawed section should occur prior to fracture across the flawed section in series with it. Thus a procedure is proposed to prevent the fracture in service of medium strength structural steel (up to 350 MPa yield strength) members containing flaws and subject to low ambient temperatures (down to −60 °C).