bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimum Damping Selection by Statistical Energy Analysis
Authors: Lu Leo K. H.
Published: June 2008

It is widely accepted that for mitigating the vibration developed in structures, damping should be applied to the components with the largest response and be added at locations in the components’ energy transmission paths. However, it is difficult to determine the optimum damping location for some complicated dynamic systems. In this paper, the SEA concept is used to prove mathematically the reason for damping application and also to provide a convenient procedure for selecting the location of the damping treatment.
Transient Response by Component Modal Synthesis Method
Authors: Yee Eric K. L. , Tsuei Y. G.
Published: June 2008

A method for determining the transient responses of a system is introduced. This method is an extension of the component modal synthesis technique. The transient responses of the system are computed based on the substructure modal parameters, the geometric compatibility, and the force equilibrium equations between substructures. The eigensolutions of the final system are not required. In the process of calculation, the interconnecting force vectors between substructures are determined at each time step. The system responses are then computed from the force response equations. The external force vectors are approximated as the step function vectors in each time step. The transient responses of several systems are investigated. The solutions are compared to the close form solutions. The results indicate that the proposed method accurately determines the system responses and is numerically efficient.
Effect of Transverse Shear and Rotary Inertia on Vibrations of Stepped Thickness Plates
Authors: Aksu G.
Published: June 2008

The free vibration characteristics of stepped thickness plates by including the effect of transverse shear deformation and rotary inertia is presented. A method based on the variational procedure in conjunction with the finite difference technique is used to determine the natural frequencies and mode shapes. The convergence characteristics of the present method is studied and the results are compared with existing solutions based on the classical thin plate theory. The effects of the stepped thickness and relative thickness ratio on the vibration characteristics are studied.
Dynamic Green’s Function of Finite Media by Finite Difference Method
Authors: Fukunaga Y. , Enoki M. , Kishi T. , Kihara J.
Published: June 2008

A three-dimensional finite difference method (FDM) has been developed for the computation of elastic wave propagation in finite media containing a macrocrack, with a new treatment of boundary conditions of surfaces. The method can be used for the simulation of dynamic Green’s functions of an arbitrary rectangular parallelepiped medium with a macrocrack such as a compact tension (CT) specimen. The validity of the method has been confirmed by comparison with theoretical solutions of the plate problem for a monopole source and a double source. The method was then applied to the computation of Green’s functions for a seismic moment in CT specimen. Evaluation of Green’s function by this three-dimensional FDM leads to more accurate acoustic emission (AE) source characterization.
Matching Finite Element Models to Modal Data
Authors: Minas C. , Inman D. J.
Published: June 2008

A technique is proposed which systematically adjusts a finite element model of a structure to produce an updated model in agreement with measured modal results. The approach suggested here is to consider the desired perturbations in stiffness and damping matrices as gain matrices in a feedback control algorithm designed to perform eigenstructure assignment. The improved stiffness and damping matrices combined with the analytical mass matrix, more closely predict the modal test results. The technique is applicable to undamped, proportionally damped, as well as non-proportionally damped models. The proposed method assumes that the analytical mass, damping and stiffness matrices are known and that vibration test data is available in the form of natural frequencies, damping ratios, and mode shapes.
Some Aspects of Aeroacoustics: From Rayleigh Until Today
Authors: Powell A.
Published: June 2008

An overview of aeroacoustics is provided, beginning with a discussion of the properties of point sources of sound of various orders. This is followed by treatment of the sound generated by a free aerodynamic flow (in the absence of rigid surfaces), and finally by a discussion of the effects of surfaces—very small (aeolian tones), very large (boundary layers), and the important effect of the edge of a large surface (trailing edge noise). In the first part, it is assumed that the aerodynamic flow is given, and that the sound produced by the flow does not act on the flow itself. In the second part, there is a reaction on the flow, and the effect is first order. Then a flow resonance occurs, even though no physical resonator is present; and of course, a physical resonator can be present, as in the familiar case of the organ pipe.
Effects of Shear Deformation and Rotary Inertia on the Nonlinear Dynamics of Rotating Curved Beams
Authors: Gau Wei-Hsin , Shabana A. A.
Published: June 2008

In this investigation a method for the dynamic analysis of initially curved Timoshenko beams that undergo finite rotations is presented. The combined effect of rotary inertia, shear deformation, and initial curvature is examined. The kinetic energy is first developed for the curved beam and the beam mass matrix is identified. It is shown that the form of the mass matrix as well as the nonlinear inertia terms that represent the coupling between the rigid body motion and the elastic deformation can be expressed in terms of a set of invariants that depend on the assumed displacement field, rotary inertia, shear deformation, and the initial beam curvature. A nonlinear finite element formulation is then developed for Timoshenko beams that undergo finite rotations. The nonlinear formulation presented in this paper is applied to multibody dynamics where mechanical systems consist of an interconnected set of rigid and deformable bodies, each of which may undergo finite rotations. The equations of motion are developed using Lagrange’s equation and nonlinear algebraic constraint equations that mathematically describe mechanical joints and specified trajectories are adjoined to the system differential equations using the vector of Lagrange multipliers.
Axisymmetric Nonlinear Dynamic Response of Bimodulus Annular Plates
Authors: Srinivasan R. S. , Ramachandra L. S.
Published: June 2008

In the present study, the geometrically nonlinear dynamic response of bimodulus annular and circular plates is obtained. The governing equations of the problem are formulated using the energy method and are solved by using annular finite elements spacewise. The integration in the time domain is accomplished by the Wilson θ method. Numerical work has been done for different hole sizes under various edge conditions and loadings.
Statistical Energy Analysis for the Time-Integrated Transient Response of Vibrating Systems
Authors: Lai M. L. , Soom A.
Published: June 2008

For more than twenty years, statistical energy analysis (SEA) has been used for the analysis of steady-state response distributions in complex coupled structures and sound-structure systems. However, the steady-state SEA formalism is not directly applicable to the analysis of transient vibrations. In this paper, energy relations, analogous to steady-state SEA power flow relations, are derived for the time-integrated transient response of each oscillator. These energy flow relations can be combined using statistical concepts, to obtain a set of energy balance equations for N coupled multimodal subsystems. It is shown that the time-integrated response of each subsystem can be described in terms of transient input energies and conventional SEA parameters, i.e., modal densities, loss factors and coupling loss factors. By solving the energy balance equations, the time-integrated response of each subsystem can be obtained. The results of experiments, conducted on a coupled structure consisting of two welded plates, are presented to illustrate the applicability of these relations.
A Study on the Mechanics of Fatigue-Dominated Friction Noise
Authors: Mohamed Mohamed Abdel-Salam , Ahmadi Goodarz , Loo Francis T. C.
Published: June 2008

The generation of friction noise for fatigue-dominated interfaces is studied. A special experimental set up for studying the effects of various parameters on the generation of noise by dry friction under different running conditions of load and speed is constructed. The noise and vibration response signatures are simultaneously measured and statistically analyzed. A simplified model for the friction interface and the supporting structure is also developed, and is used to simulate the vibration and acoustic responses. It is shown that the simulation predictions are in good agreement with the experimental data. The results show that the friction noise signatures have a well defined structure with randomly occuring sharp pulses. For fatigue-dominated interfaces, the departure of the noise signature from a Gaussian process increases as acoustic radiation due to roughness interaction effects becomes more significant. The noise power spectra contain a broad frequency band with a continuous peak level extending over the high frequency range of 2–20 kHz due to the effects of impacts between surface asperities.
Transient Finite Element Analysis of the Exterior Structural Acoustics Problem
Authors: Pinsky P. M. , Abboud N. N.
Published: June 2008

Considerable progress has been made in the development of numerical methods for the time-harmonic exterior structural acoustics problem involving solution of the coupled Helmholtz equation. In contrast, numerical solution procedures for the transient case have not been studied so extensively. In this paper a finite element formulation is proposed for solution of the time-dependent coupled wave equation over an infinite fluid domain. The formulation is based on a finite computational fluid domain surrounding the structure and incorporates a sequence of boundary operators on the fluid truncation boundary. These operators are designed to minimize reflection of outgoing waves and are based on an asymptotic expansion of the exact solution for the time-dependent problem. In the fluid domain, a mixed two-field finite element approximation, based on a specialization of the Hu-Washizu principle for elasticity, is proposed and employs pressure and displacement potential as independent fields. Since radiation dissipation renders the coupled system nonconservative, a variational formalism based on the Morse and Feshbach concept of a “mirror-image” adjoint system is used. The variational formalism also accommodates viscoelastic dissipation in the structure (or its coatings) and this is considered in the paper. Very accurate results for model problems involving a single layer of fluid elements have been obtained and are discussed in detail.
Uniqueness of Solutions to Variationally Formulated Acoustic Radiation Problems
Authors: Wu Xiao-Feng , Pierce Allan D.
Published: June 2008

Determination of the surface acoustic pressure given the surface velocity of a vibrating body can be formulated in various ways. However, for some such formulations such as the surface Helmholtz integral equation, solutions are not unique at certain discrete frequencies. Such uniqueness problems can also be present for variational formulations of the problem, but the variational formulation based on the normal derivative of the Kirchhoff integral theorem has unique solutions for vibrating disks and plate-like bodies. For bodies of finite volume, but for which each surface point is vibrating in phase, the total radiated acoustic power is always unique, even though the pressure may not be. The latter conclusion is supported by numerical calculations based on the Rayleigh-Ritz technique for the case of a finite cylinder vibrating as a rigid body in the axial direction.
Development of a General Procedure to Formulate Four Pole Parameters by Modal Expansion and Its Application to Three-Dimensional Cavities
Authors: Kim J. , Soedel W.
Published: June 2008

If an acoustic system has one or more large dimensions compared to the shortest wave length of interest, the pressure responses which are necessary to formulate four pole parameters have to be obtained by solving the continuous wave equation of the system. In this paper, a general procedure is established to derive four pole parameters from the pressure response solutions utilizing modal series expansion. As an example, four pole parameters of a cylindrically annular cavity are obtained. The validity of the procedure is proven by applying it also to a one-dimensional pipe whose four pole parameters are available by direct method. The comparison is made in terms of four pole parameters and pressure profiles along the pipe. The comparison allows interesting observations with regard to the equivalence of the two approaches. The theory was further generalized to be applied to more complex acoustic systems, namely multiply connected systems. A cylindrically annular cavity connected by two pipes to a small lumped parameter cavity is taken as an example of the application. Noise control by either mode cancellation or wave cancellation is explored.
State Space Representation of the Nonself-Adjoint Acoustic Duct System
Authors: Hull A. J. , Radcliffe C. J. , Miklavcˇicˇ M. , MacCluer C. R.
Published: June 2008

One-dimensional acoustic response of ducts is a classical engineering problem. The acoustic response in a hard-walled duct with a dissipative end condition can be visualized as a combination of standing and propagating wave response. A modal decomposition based on the system eigenvalues derived here produces an infinite order state space model incorporating this behavior. This allows computation of system transient response as well as frequency response. The shapes of duct characteristic response derived here are in stark contrast to those previously available for ducts. It is shown that the traditionally employed sinusoidal responses cannot be used to compute duct response for dissipative ends. A comparison between the frequency response of a finite order truncation of the new state space model and a previous exact frequency response is included. The new transient response of the truncated state space model is demonstrated and truncation error investigated. High frequency behavior of the state space model is discussed.
Eigen-Analysis of a Tip-Loaded Beam Attached to a Rotating Joint
Authors: Low K. H.
Published: June 2008

In this paper, a method of eigen-analysis for a vibrating elastic system is presented. The model analyzed is a Bernoulli-Euler beam having a slender payload at the free end and being attached at the other end to a compliant, rotating hub. The system equations with the complete boundary conditions are derived. The corresponding frequency equation in a dimensionless form is solved by using the secant method. Agreement with other works not only verifies the accuracy of the results, but also demonstrates the generality of the model.
Experimental Investigations of Rotor Whirl Excitation Forces Induced by Labyrinth Seal Flow
Authors: Rajakumar C. , Sisto F.
Published: June 2008

The labyrinth seal flow-induced forces have been identified as one of the causes of rotordynamic instabilities in the recent literature. The eccentricity of the rotor center relative to the seal center introduces asymmetry in the seal clearance flow causing circumferential variation of the pressure in seal cavities. Experimentally-measured seal cavity pressure distributions for different rotor eccentricities are presented in this paper. Resultant seal forces obtained by integrating the circumferential pressures over the rotor surface are presented as a function of rotor eccentricity. The experimental results are also used to validate the analytically predicted seal pressure distributions and forces.
Lateral Excitation of a Rotating Shaft Driven by a Universal Joint With Friction
Authors: Kato Masayoshi , Ota Hiroshi
Published: June 2008

The relative angular motion between a cross-pin and yokes of a universal joint gives rise to viscous and Coulomb’s frictions. A driven rotating shaft resultingly undergoes a moment caused by these frictions. This moment about a joint center has a component perpendicular to the driven shaft, and might be responsible for introducing lateral vibrations of the driven shaft. Analysis of these excitation components, supplemented with experimental results, confirms that excitations due to viscous friction enlarge with an increase in the joint angle, but are extremely small in practice, and that the excitations due to Coulomb’s friction are independent of the joint angle.
Torsional Vibrations in Turbogenerators Due to Network Disturbances
Authors: Schwibinger P. , Nordmann R.
Published: June 2008

Large steam-turbine generators in operation may be stimulated to torsional vibrations by dynamic moments at the generator due to electrical system transients. The induced torsional stresses in the shaft have drawn growing attention over the past few years. To solve the torsional vibration problem the turbogenerator shaft is modelled by the finite element method. This paper presents the results for a 600 MW turbogenerator set. To verify the quality of the used finite element model measurements were carried out and compared with the analytical results. For some applications it is desirable to have a torsional model with a reduced number of degrees of freedom, which reproduces the finite element model only in the lower eigenfrequencies and modes. This paper describes a method on how to find the most accurate reduced torsional model with discrete masses and springs from the finite element model.
Efficient Loads Analyses of Shuttle-Payloads Using Dynamic Models With Linear Or Nonlinear Interfaces
Authors: Spanos P. D. , Cao T. T. , Nelson D. A. R. , Hamilton D. A.
Published: June 2008

A technique is presented for conducting efficient loads analyses of Shuttle-payloads systems with linear or nonlinear attachment interfaces. The technique relies on representing the Space Shuttle and the payloads with physical and modal coordinates. Further, by invoking a standard algorithm of numerical integration of equations of motion, the kinematics of the interface degrees of freedom at a given time are determined without calculating the modes of the combined system involving the Space Shuttle and the payload. If the Shuttle-payloads interface coupling induces a linear dynamic model for the loads analysis, the equations of motion of the Shuttle and the payload are integrated separately step-by-step in time. If the dynamic model is nonlinear, the equations of motion of the Shuttle and the payload are again integrated separately. However, in the latter case an iterative procedure is used within a time step to converge to reliable values of the nonlinear terms of the equations of motion. The usefulness of the proposed technique is demonstrated by conducting a loads analysis for the Shuttle abort landing event with the Inertia Upper Stage (IUS) booster carrying a Tracking and Data Relay Satellite (TDRS) in the payload bay. This combined system has at its interface dry friction and hydraulic nonlinear dampers. For the analysis of this system, the discontinuous signum function used traditionally in modeling dry friction is replaced by an expeditious continuous approximation. Because of its efficiency and versatility, the new technique deserves serious consideration for becoming a standard tool for linear or nonlinear analysis of combined systems, in general, and of Shuttle-payloads systems, in particular.
Two-Dimensional Radiation and Scattering at Short Wave Length
Authors: Yoon W. S. , Park J. M. , Eversman W.
Published: June 2008

The problem of radiation and scattering by objects in the case when the wave length is much smaller than the characteristic dimension of the radiator or scatterer is investigated. The boundary element method is used with the goal of obtaining accurate results in an efficient computational scheme for wave lengths less than 5 percent of the object characteristic dimension. With a systematic application of conventional boundary element techniques it is found that the modelling of such problems leads to excessive computation time due to the large number of elements, demands on Gaussian Quadrature, evaluation of the fundamental solution, and the resulting large nonsymmetric matrix equation. The approach is to use cubic elements, approximate polynomial and asymptotic evaluations of the fundamental solution, and to tailor the order of the Gaussian Quadrature according to the local demands dictated by the distance between sending and receiving points. In addition, out of core equation solvers are investigated. It is found that results can be obtained which are as accurate as those obtained using conventional Boundary Element techniques, but at greatly reduced cost. The potential application is to problems involving propagation of relatively low frequency sound over large terrain features.
An Improved Formulation for Acoustic Eigenmode Extraction from Boundary Element Models
Authors: Coyette J. P. , Fyfe K. R.
Published: June 2008

The acoustic boundary element method has been utilized primarily as a direct response analysis technique. Recently, methodologies have been published that enable the formulation of an eigenvalue problem from a boundary element model. These techniques, however, have been very slow due to the inefficient synthesis techniques used in solving the algebraic problems. In this paper, an alternative procedure is obtained which indirectly calculates the desired acoustic variables. This technique greatly enhances the calculation speed in setting up the eigenvalue problem and in determining the field pressures. A subspace iteration technique is outlined to solve the generalized unsymmetric eigenvalue problem. Examples are presented to show the accuracy of the method.
A Recursive Pole Placement Method for Large Flexible Structures
Authors: Baruh H.
Published: June 2008

This paper presents a recursive method to accomplish pole placement for control of large-order vibrating systems. The pole placement is based on matrix perturbation theory, where the controls are considered as a perturbation on the uncontrolled system. The difference between the open-loop poles and the desired closed-loop poles is divided into regions small enough to maintain validity of the perturbation assumption. Control gains are then calculated in each region, resulting in a stepwise design.
Auxin Gradients Are Associated with Polarity Changes in Trees
Authors: Kramer Eric M. , Lewandowski Michael , Beri Satvik , Bernard Jessica , Borkowski Matthew , Borkowski Michael H. , Burchfield Laura Ann , Mathisen Brenda , Normanly Jennifer
Published: June 2008

Models of plant growth and development propose that changes in cell polarity are mediated by gradients of the plant hormone auxin. With use of gas chromatography‐mass spectrometry, we measured the redistribution of endogenous auxin in stems of quaking apen trees (Populus tremuloides) after wounding. Persistent (lasting at least 24 hours) auxin gradients were observed in the region of the cambium where cell polarity was changing. A computer model of the auxin redistribution shows agreement with measured concentrations.
Biological Activities of Anti-Merozoite Surface Protein-1 Antibodies Induced by Adjuvant-Assisted Immunizations in Mice with Different Immune Gene Knockouts
Authors: Hui George , Choe Dan , Hashimoto Caryn
Published: June 2008

Immunizations withPlasmodium falciparumMSP1-42 or MSP1-19 induce antibodies that inhibit parasites in vitro, which correlates with in vivo protective immunity by vaccination. We previously showed that several adjuvant formulations can induce anti-MSP1-19 antibodies in interleukin-6, intercellular adhesion molecule 1, CD80, and CD86 knockout (KO) mice and at levels similar to those obtained in the healthy uninfected hosts. Here, we determine whether these immune gene KOs or the immunopotentiating activities of the adjuvants have a more important influence on the induction of parasite-inhibitory anti-MSP1-19 antibodies. Results showed that the biological activities of the anti-MSP1-19 antibodies induced by these adjuvants were not affected by the immune gene KOs. All adjuvant formulations that induced significant inhibitory antibody responses (i.e., >50% inhibition of parasite growth) contained monophosphoryl lipid A (MPL) in emulsion carriers, whereas MPL or emulsion carriers alone were ineffective. The ability to retain vaccine efficacy by the MSP1-19 and adjuvant formulations in the altered immunological background is a valuable and significant attribute in light of many instances of skewed immune status in the targeted vaccine populations.
Evidence of Multiple
Treponema
Phylotypes Involved in Bovine Digital Dermatitis as Shown by 16S rRNA Gene Analysis and Fluorescence In Situ Hybridization
Authors: Klitgaard Kirstine , Boye Mette , Capion Nynne , Jensen Tim K.
Published: June 2008

The etiopathogenesis of the skin disease digital dermatitis (DD), an important cause of lameness in cattle, remains uncertain. Microscopically, the disease appears to be polymicrobial, with spirochetes as the predominant bacteria. The objective of this study was to identify the main part of the bacteria involved in DD lesions of cattle by using culture-independent molecular methods. Ten different phylotypes of
Treponema
were identified either by 16S rRNA gene sequencing of bacteria from DD lesions or by fluorescence in situ hybridization (FISH) analysis using phylotype-specific 16S rRNA-directed oligonucleotide probes. Two phylotypes, phylotype 1 (PT1) and PT2, were not closely related to any characterized treponemal species. PT7 was 99.3% identical to
Treponema denticola
, while PT9 resembled
T. vincentii
by 96%. The remaining phylotypes, PT3, PT4, PT5, PT6, and PT8, and
Treponema brennaborense
had previously been isolated from DD lesions. Forty DD biopsy specimens were examined for
Treponema
by FISH. With one exception, all of the biopsy specimens revealed epidermotropic, intermingled infection with three or more different phylotypes (mean, 4.7). The most prevalent species were PT1 (95%), PT6 (93%), and PT3 (85%). While colonization by PT3 was confined to the surface of the epidermis, both PT1 and PT6 invaded deep into the stratum spinosum and were seen in ulcerated dermal papillae. In two cases, all 10 phylotypes were demonstrated. Furthermore, FISH with a
Treponema
group-specific probe showed that
Treponema
accounted for more than 90% of the total bacterial population in the biopsy specimens. These data strongly suggest that a group of apparently symbiotic
Treponema
species are involved as primary bacterial pathogens in DD.
Higher Homologous and Lower Cross-Reactive Gag-Specific T-Cell Responses in Human Immunodeficiency Virus Type 2 (HIV-2) Than in HIV-1 Infection
Authors: Jennes Wim , Camara Makhtar , Dièye Tandakha , Mboup Souleymane , Kestens Luc
Published: June 2008

Human immunodeficiency virus type 2 (HIV-2) infection results in slower CD4+T-cell decline, lower plasma viral load levels, and hence slower progression of the disease than does HIV-1 infection. Although the reasons for this are not clear, it is possible that HIV-2 replication is more effectively controlled by host responses. We used aligned pools of overlapping HIV-1 and HIV-2 Gag peptides in an enhanced gamma interferon enzyme-linked immunospot assay to compare the levels of homologous and cross-reactive Gag-specific T-cell responses between HIV-1- and HIV-2-infected patients. HIV-2-infected patients showed broader and stronger homologous Gag-specific T-cell responses than HIV-1-infected patients. In contrast, the cross-reactive T-cell responses in HIV-2-infected patients were both narrower and weaker than those in HIV-1-infected patients, in line with overall weaker correlations between homologous and heterologous T-cell responses among HIV-2-infected patients than among HIV-1-infected patients. Cross-reactive responses in HIV-2-infected patients tended to correlate directly with HIV-1/HIV-2 Gag sequence similarities; this was not found in HIV-1-infected patients. The CD4+T-cell counts of HIV-2-infected patients correlated directly with homologous responses and inversely with cross-reactive responses; this was not found in HIV-1-infected patients. Our data support a model whereby high-level HIV-2-specific T-cell responses control the replication of HIV-2, thus limiting viral diversification and priming of HIV-1 cross-reactive T-cell responses over time. However, we cannot exclude the possibility that HIV-2 replication is controlled by other host factors and that HIV-2-specific T-cell responses are better maintained in the context of slow viral divergence and a less damaged immune system. Understanding the nature of immune control of HIV-2 infection could be crucial for HIV vaccine design.
The Epstein-Barr Virus LF2 Protein Inhibits Viral Replication
Authors: Calderwood Michael A. , Holthaus Amy M. , Johannsen Eric
Published: June 2008

The switch from Epstein-Barr virus (EBV) latent infection to lytic replication is governed by two transcriptional regulators, Zta and Rta. We previously reported that the EBV protein encoded by the LF2 gene binds to Rta and can inhibit Rta activity in reporter gene assays. We now report that LF2 associates with Rta in the context of EBV-infected cells induced for lytic replication. LF2 inhibition of Rta occurs in both epithelial and B cells, and this downregulation is promoter specific: LF2 decreases Rta activation of the BALF2, BMLF1, and BMRF1 promoters by 60 to 90% but does not significantly decrease Rta activation of its own promoter (Rp). LF2 decreases Rta activation by at least two mechanisms: decreased DNA binding and interference with transcriptional activation by the Rta acidic activation domain. Coexpression of LF2 also specifically induces modification of Rta by the small ubiquitin-like modifiers SUMO2 and SUMO3. We further demonstrate that LF2 overexpression blocks lytic activation in EBV-infected cells induced with Rta or Zta. Our results demonstrate that LF2, a gene deleted from the EBV reference strain B95-8, encodes a potent inhibitor of EBV replication, and they suggest that future studies of EBV replication need to account for the potential effects of LF2 on Rta activity.
Association of Hepatitis C Virus Replication Complexes with Microtubules and Actin Filaments Is Dependent on the Interaction of NS3 and NS5A
Authors: Lai Chao-Kuen , Jeng King-Song , Machida Keigo , Lai Michael M. C.
Published: June 2008

The hepatitis C virus (HCV) RNA replication complex (RC), which is composed of viral nonstructural (NS) proteins and host cellular proteins, replicates the viral RNA genome in association with intracellular membranes. Two viral NS proteins, NS3 and NS5A, are essential elements of the RC. Here, by using immunoprecipitation and fluorescence resonance energy transfer assays, we demonstrated that NS3 and NS5A interact with tubulin and actin. Furthermore, immunofluorescence microscopy and electron microscopy revealed that HCV RCs were aligned along microtubules and actin filaments in both HCV replicon cells and HCV-infected cells. In addition, the movement of RCs was inhibited when microtubules or actin filaments were depolymerized by colchicine and cytochalasin B, respectively. Based on our observations, we propose that microtubules and actin filaments provide the tracks for the movement of HCV RCs to other regions in the cell, and the molecular interactions between RCs and microtubules, or RCs and actin filaments, are mediated by NS3 and NS5A.
Structural Analysis Reveals an Amyloid Form of the Human Papillomavirus Type 16 E1
∧
E4 Protein and Provides a Molecular Basis for Its Accumulation
Authors: McIntosh Pauline B. , Martin Stephen R. , Jackson Deborah J. , Khan Jameela , Isaacson Erin R. , Calder Lesley , Raj Kenneth , Griffin Heather M. , Wang Qian , Laskey Peter , Eccleston John F. , Doorbar John
Published: June 2008

The abundant human papillomavirus (HPV) type 16 E4 protein exists as two distinct structural forms in differentiating epithelial cells. Monomeric full-length 16E1
∧
E4 contains a limited tertiary fold constrained by the N and C termini. N-terminal deletions facilitate the assembly of E1
∧
E4 into amyloid-like fibrils, which bind to thioflavin T. The C-terminal region is highly amyloidogenic, and its deletion abolishes amyloid staining and prevents E1
∧
E4 accumulation. Amyloid-imaging probes can detect 16E1
∧
E4 in biopsy material, as well as 18E1
∧
E4 and 33E1
∧
E4 in monolayer cells, indicating structural conservation. Our results suggest a role for fibril formation in facilitating the accumulation of E1
∧
E4 during HPV infection.
Nonstructural Proteins 1 and 2 of Respiratory Syncytial Virus Suppress Maturation of Human Dendritic Cells
Authors: Munir Shirin , Le Nouen Cyril , Luongo Cindy , Buchholz Ursula J. , Collins Peter L. , Bukreyev Alexander
Published: June 2008

Human respiratory syncytial virus (RSV) is the most important agent of serious pediatric respiratory tract disease worldwide. One of the main characteristics of RSV is that it readily reinfects and causes disease throughout life without the need for significant antigenic change. The virus encodes nonstructural protein 1 (NS1) and NS2, which are known to suppress type I interferon (IFN) production and signaling. In the present study, we monitored the maturation of human monocyte-derived myeloid dendritic cells (DC) following inoculation with recombinant RSVs bearing deletions of the NS1 and/or NS2 proteins and expressing enhanced green fluorescent protein. Deletion of the NS1 protein resulted in increased expression of cell surface markers of DC maturation and an increase in the expression of multiple cytokines and chemokines. This effect was enhanced somewhat by further deletion of the NS2 protein, although deletion of NS2 alone did not have a significant effect. The upregulation was largely inhibited by pretreatment with a blocking antibody against the type I IFN receptor, suggesting that suppression of DC maturation by NS1/2 is, at least in part, a result of IFN antagonism mediated by these proteins. Therefore, this study identified another effect of the NS1 and NS2 proteins. The observed suppression of DC maturation may result in decreased antigen presentation and T-lymphocyte activation, leading to incomplete and/or weak immune responses that might contribute to RSV reinfection.
Gibberellin-like activity from organs of Tulipa Gesneriana
Authors: Einert A. E. , Staby G. L. , Hertogh A. A. De
Published: June 2008

Quantitative determinations of extractable gibberellin-like substances (GA's) were made from various organs of Tulipa Gesneriana L. cv. 'Elmus' during cooling and forcing. The barley half-seed and dwarf pea bioassays were used to determine the activity. Shoot tissue contained the greatest levels of GA activity followed by scale and then root tissue. Further division of the shoot and scale tissues showed that the developing flower and bulblets contained the majority of the GA's in these tissues. Quantitative and also qualitative changes, as assessed by chromatogram comparisons, occurred in GA's during the cooling and forcing treatments. The exact pattern of changes within each organ was dependent on the bioassay used. Shoot tissue appeared to be the most sensitive organ to changes in temperature.
Studies in the Arundinelleae (Gramineae). XIII. Taximetrics of the loudetioid, tristachyoid, and danthoniopsoid groups
Authors: Phipps J. B.
Published: June 2008

This paper describes the phenetic taximetrics of the 'main groups' of the tribe Arundinelleae (Gramineae) on the basis of 106 characters. At the higher levels of classification the loudetioid, tristachyoid, and danthoniopsoid groups are recognizable in a general way, though the tristachyoids are split into Tristachya, sens. str., and others, in which case Tristachya allies with loudetioids. Another somewhat miscellaneous group, consisting of certain Loudetiopsis, sens. lat., and some tristachyoid monotypics, is frequently observable. At the more detailed level of classification Loudetia section Loudetia subsections Typicae and Densispicae may be generally identified as may Tristachya, sens. str., and Danthoniopsis, sens. str. The genus Loudetiopsis, sens, lat., is strongly fragmented and certain monotypic genera, Gilgiochloa, Muantijamvella, and Rattraya, are shown to be moderately isolated. This paper strongly clarifies the tentative groupings provided in an earlier paper (Phipps 1970) based on a systematic sample of half the tribe.
Toxicity levels of mercury, lead, copper, and zinc in tissue culture systems of cauliflower, lettuce, potato, and carrot
Authors: Barker W. G.
Published: June 2008

Explanted tissues of cauliflower, carrot, potato, and lettuce have been grown in media containing Zn, Cu, Hg, and Pb. Toxicity levels have been established for each of these elements and a considerable uniformity was noted. Lettuce tissue responds occasionally to high levels of Zn by making extraordinarily prolific growth, a matter that has yet to be explained.
Repeated germination of sclerotia of Botrytis convoluta to produce successive crops of conidia
Authors: Jackson R. S.
Published: June 2008

Six successive crops of mature conidia were produced at 5 °C by sclerotia of Botrytis convoluta when each sporulation was preceded by a 24-h exposure to near-ultraviolet (n.uv.) radiation. Conidial production during these sporulations was greatest during the second sporulation while the largest number of conidia produced per unit of weight lost during the sporulations occurred during the third sporulation. Sporulation began to decline after the dry weight of the sclerotia had fallen to 32% of its initial level.The improved sporulation that occurred during the second sporulation was more marked at 10 °C than at any other temperature tested. It resulted in a shift in the optimum temperature for sporulation from 5 °C during the first sporulation to 10 °C during the second sporulation.At 5 °C, sclerotia were able to produce at least four crops of conidia after only a single, initial 24-h exposure to n.uv. radiation. The total number of spores produced during these sporulations was 11% below that of sclerotia exposed to n.uv. radiation before each of the four sporulations. When sclerotia were placed at 25 °C for the first sporulation, however, they did not sporulate again at either 5 °C or 25 °C without additional exposure to n.uv. radiation.When conidia and conidiophores of one sporulation were left intact on the sclerotia, they did not produce further crops of conidia under otherwise favorable conditions. The suppression of repeated sporulation was lifted by the removal of the conidia. Removal of the conidiophores as well as the conidia did not further influence the number of conidia produced during the subsequent resporulation.
Formation of mycorrhizae in monoxenic culture by pond pine (Pinus serotina)
Authors: Suggs Edna G. , Grand Larry F.
Published: June 2008

Ectomycorrhizae were formed by pond pine after 4 months in monoxenic culture with Amanita muscaria, Cenococcum graniforme, Laccaria laccata, Pisolithus tinctorius, Suillus brevipes, S. cothurnatus, S. granulatus, S. hirtellus, and S. pictus. Phylloporus rhodoxanthus formed a fungal mantle but no Hartig net. Macroscopic characteristics which were used for distinguishing among species of fungi forming mycorrhizae in this study were type of branching, color of mycorrhizae, and production of rhizomorphic strands.
A new species of Eupropolella Höhnel
Authors: Morgan-Jones G.
Published: June 2008

A new species of Eupropolella Höhnel is described and illustrated from leaves of Prunus laurocerasus in the British Isles. It is compared with E. vaccinii (Rehm) Höhnel, the type species.
Relationship of Erwinia herbicola to Erwinia amylovora
Authors: Riggle J. H. , Klos E. J.
Published: June 2008

A yellow bacterium which had inhibited Erwinia amylovora was identified as Erwinia herbicola. Erwinia herbicola occurred on leaf surfaces in large numbers on apple, cherry, and apricot trees, but in small numbers on pear leaves. It was not pathogenic, but was a secondary invader of diseased tissues. Fire blight branch cankers were examined for occurrence and location of E. amylovora and E. herbicola. Erwinia herbicola occurred mixed with E. amylovora. Both bacteria were isolated at maximum frequency about 7.6 cm above the edge of downward advancing cankers.Partial control of fire blight was obtained in the greenhouse and field plots by inoculation of pear blossoms with E. herbicola 24 h before inoculation with a virulent suspension of E. amylovora. The inhibitory effect could occur in pear blossom nectar. On media containing sugar concentrations comparable to pear nectar, E. herbicola consumed all organic nitrogen in the medium and reduced the pH to a level inhibitory to E. amylovora.
Histopathology of Pythium infected strawberry roots
Authors: Nemec S.
Published: June 2008

Host–parasite interactions between eight Pythium species, previously isolated from necrotic strawberry root tissue, and Fragaria × ananassa Duch. runner plant main roots were studied. When excised roots were placed in water on petri dish cultures, P. rostratum and P. hypogenum infection was limited to the root tip epidermis. Pythium irregulare, P. perniciosum, P. dissotocum, P. sylvaticum, P. ultimum, and unidentified isolate 1E penetrated the epidermis several centimeters along the zone of maturation. Penetration occurred most frequently through root hairs by hyphae; resulting infections usually stopped in the epidermis or adjacent cortex, and here hyphae formed sporangium-like structures, oogonia, and oospores. Extensive cortical infection by hyphae was primarily limited to the zone of elongation. Extent of epidermal and cortical infection in roots grown in soil with P. irregulare, P. dissotocum, and P. sylvaticum was similar to petri dish test results. Stelar infection by P. sylvaticum and P. dissotocum occurred mainly in phloem cells, but did not advance far into the region of maturation. Numerous oogonia formed in infected steles and usually in adjacent cortical cells. Infected roots ranged from a white to grey, water-soaked color. Extensively infected root tips typically were unhealthy, succulent, and thin.
Bryology in arctic and boreal North America and Greenland
Authors: Schofield W. B.
Published: June 2008

Bryological research in boreal and arctic North America is in very preliminary stages. Although the flora is moderately well documented, details are lacking in much of the region. Greenland, Alaska, and Ellesmere Island are better understood than the rest of the area. Much of the information has been accumulated as casual collections and observations and incidental to other research. Bryophyte cover in arctic regions is less than that of vascular plants; in boreal regions wetlands are often dominated by bryophytes and open forests have extensive moss carpets. Turfs dominate the growth forms in the arctic while in boreal regions whorled-branched turfs, wefts, and compact mats become the predominant growth forms. Bryophytes are important in plant community structure and dynamics of both boreal and arctic regions, but detailed studies are few. Cytology of arctic and boreal bryophytes in North America rests on a single paper, thus any generalizations are hazardous. Physiology of bryophytes in northern North America has been inadequately documented. The sexuality, reproductive cycles, growth rates, and metabolic activities of bryophytes are areas that could yield intriguing results. Reproduction in bryophytes in northern regions appears not to be greatly different from that of more southern regions. In spite of the shorter growing season and the terrain and climate favoring wind dispersal, this had not led to an increase in the incidence of asexual reproduction in spite of the fact that more than 60% of the bryophytes are dioicous. Bryogeographic patterns are similar to those of the vascular flora but the presence of western North American taxa in the easternmost arctic and their absence in intervening areas is highly suggestive of eastern refugia. Glacial refugia are supported by the bryophyte distributions; their presence in unglaciated Alaska–Yukon, Ellesmere Island, and parts of Greenland seems best documented. Thirty-six maps are given showing bryophyte distribution patterns in the region under discussion.
Distribution and chromatography of Polygonatum in Ontario
Authors: Cruise J. E. , Haber E.
Published: June 2008

The distributional and chromatographic patterns of the multiflowered forms of both Polygonatum biflorum and P. pubescens yield no apparent differences from the respective normal-flowered forms, whereas P. biflorum is readily distinguished from P. pubescens by the presence in its flowers and fruits of a number of flavonoids which are absent from the same structures of the latter species. Polygonatum pubescens in both its normal and multiflowered forms extends, in Ontario, considerably northward of the range of P. biflorum.
Intraspecific variability of isozymes of the lichen Umbilicaria mammulata
Authors: Hageman C. , Fahselt D.
Published: June 2008

Thalli of the lichen Umbilicaria mammulata (Ach.) Tuck, were collected from six geographically distinct locations and extracts of these were analyzed by isoelectric focusing to test for isozyme variability within and between sites. A total of 58 bands were resolved representing eight different enzyme systems; some enzymes exhibited mostly constant electromorphs, and the remainder were highly polymorphic with many variable bands. Other enzyme systems were not reliably detectable in U. mammulata. Sums of squares agglomeration and principal-components analysis of the molecular data showed the existence of distinct groups corresponding to sets of thalli collected at each of the collection sites. There was a positive correlation between the phenctie distance between sites, based on isozyme distribution, and physical intersite distance.
A checklist of marine algae of eastern Canada, second revision
Authors: South G. Robin
Published: June 2008

A revised checklist of 354 species, subspecies, and varieties of benthic marine algae from eastern Canada is given, consisting of 128 Rhodophyceae, 128 Phaeophyceae, 90 Chlorophyceae, 7 species of Vaucheria (Xanthophyceae), and 1 of Phaeosaccion (Chrysophyceae). Records for the entire coastline from Cape Chidley, Labrador, in the north to the New Brunswick – Maine border in the south are included, as well as from Anticosti Island, Magdalen Island, Sable Island, and St. Pierre and Miquelon. Additions include Waerniella lucifuga (Kuck.) Kylin; Phloeospora curta (Fosl.) Jaasund; Striaria attenuata (Grev.) Grev.; Fucus distichus L. subsp. anceps (Harv. et Ward ex Carm.) Powell (Phaeophyta); Pilinia ? rimosa Kütz.; and Tellamia contorta Batt. (Chlorophyta).
Pyropyxis, a new pyrophilous operculate discomycete with a Dichobotrys anamorph
Authors: Egger Keith N.
Published: June 2008

The monotypic genus Pyropyxis is described based upon the type species, Peziza rubra Peck. Pyropyxis is distinguished by deeply cupulate, sessile, pink to reddish-orange apothecia. The ectal excipulum is composed of thick-walled cells forming a textura angularis tissue with the outer layer of cells occasionally giving rise to hyaline, moniliform hairs. The hymenium contains two types of paraphyses; most are hyaline, but some are filled with orange, crystalline pigments. The ascospores are eguttulate when fully mature but contain two small polar guttules when immature. A Dichobotrys anamorph is produced in axenic culture.