bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Acoustic Vibration Criteria Compared to In-Service Experience With Steam Generator In-Line Tube Banks
Authors: Eisinger F. L. , Sullivan R. E. , Francis J. T.
Published: June 2008

Tube banks of operating steam generators were evaluated for resonant acoustic vibration in the transverse acoustic mode, using a number of published vibration criteria and a range of Strouhal numbers. Theoretical predictions based on computer simulations were compared to available experimental data for nonvibrating and vibrating banks. It is shown that large differences exist among the predictive methods, and most do not fully predict acoustic resonances. On a relative basis, prediction criteria of Y. N. Chen and Grotz and Arnold, with Fitzhugh-Strouhal numbers, offer the best results for steam generator tube banks.
An Approach to Account for Negative R-Ratio Effects in Fatigue Crack Growth Calculations for Pressure Vessels Based on Crack Closure Concepts
Authors: Bloom J. M.
Published: June 2008

Current fatigue crack growth procedures in the commercial nuclear industry do not clearly specify how compressive loads are to be handled and, therefore, regulatory agencies usually recommend a conservative approach requiring full consideration of the loads. This paper demonstrates that a more realistic approach to account for compressive loads can be formulated using crack closure concepts. Several empirical plasticity-induced crack closure models were evaluated. An approach in the Section XI ASME Code for tensile loading only has been extended and evaluated for negative R-ratios. However, the paper shows this approach to be overly conservative. The approaches using crack closure models are shown to be more accurate. An analytically based crack closure model, while more complicated, is shown to give a theoretical basis to the empirically derived crack closure models. The paper concludes with a recommendation for modifying the current ASME Code practices consistent with the crack closure models and fatigue crack growth data from negative R-ratio tests.
Loading and Unloading of Thick-Walled Cylindrical Pressure Vessels of Strain-Hardening Material
Authors: Loghman A. , Wahab M. A.
Published: June 2008

A thick-walled closed-end cylinder of isotropic, homogeneous and strain-hardening material is considered in this study. Loading is assumed to consist of a temperature gradient as well as an internal pressure. Unloading is completely elastic without considering a Bauschinger effect. A generalized plane strain case in which the material obeys Von Mises yield criterion is studied. Using the yield criterion, critical conditions for a wide range of loading combinations and thickness ratios are investigated. After the critical condition is established, load is increased beyond the critical values and calculations are made for plastic stresses and strains and progress of plastic zone using an incremental theory of plasticity. Residual stresses are obtained as the cylinder is unloaded from a 25 and 50-percent overstrained condition. Reverse yielding is not considered while the residual stresses at the onset of reverse yielding are calculated. Loading function is assumed to follow the stress-strain curve of SUS 304 at a constant temperature of 400°C, which is selected from the experimental work of earlier researchers.
Simplified Methods for Calculation of Redundant Moments and Forces at the Discontinuities in Pressure Vessels—Part II: Hemisphere—Shell and Shells of Different Thicknesses
Authors: Chen H. , Zhou K.
Published: June 2008

Following a similar idea as described in Part I of this paper, the redundant bending moment and the redundant shearing force at the junctures of hemispherical/cylindrical shells and of cylindrical shells of different thicknesses are shown to be unique functions of λ (ratio of the thickness of the joint members) and η (ratio of the thickness of the cylindrical shell to its mean diameter). Thereby, simplification of the calculation for the redundant moment and the redundant force is proposed and demonstrated to possess a good accuracy.
An Approximate Procedure for Solving Base-Isolated Structures
Authors: Mohraz B. , Jian Y. C.
Published: June 2008

Dynamic analysis of several shear-type structures with base isolation indicates that the response of these structures follows their fundamental mode shape. Based on this observation, this paper uses an approximate procedure for computing the response of base-isolated structures. The procedure consists of modeling the structure and its base by a two-degree of freedom system, one representing the base and the other the structure. The response from the two-degree of freedom model and mode shapes of the structure are used to compute the response of the structure to earthquake excitation. The approximate procedure is simple, requires substantially less computational time than other methods, and gives results that are in excellent agreement with those from direct integration. Nonlinear properties and nonproportional damping are easily included in the model. Savings of approximately 54–77 percent in computational time result by using the approximate model.
A Summary of NRC Generic Safety Issue 113: Dynamic Qualification and Testing of Large Bore Hydraulic Snubbers
Authors: Ware A. G. , Nitzel M. E. , Page J. D.
Published: June 2008

The Nuclear Regulatory Commission (NRC) developed Generic Safety Issue 113, “Dynamic Qualification and Testing of Large Bore Hydraulic Snubbers (LBHSs),” with the objective of evaluating the reliability of LBHS in operating commercial nuclear power plants. This paper provides a summary of the important findings of the Generic Safety Issue-113 research program and a discussion of the recommendations that were made in NUREG/CR-5416. Fifteen potential improvements in LBHS reliability were identified, covering the areas of design, environmental (including dynamic) qualification, functional testing, visual inspection, and personnel training.
Effectiveness of Anti-Liquefaction Techniques for Buried
Pipelines
Authors: Akiyoshi T. , Fuchida K. , Shirinashihama S. , Tsutsumi T.
Published: June 2008

In this paper, effectiveness of several existing anti-liquefaction methods for preventing large deformations of pipelines for lateral flow of liquefied grounds during earthquakes are investigated and compared, as well as a proposed method which fixes pipelines with expansion joints parallel to auxiliary continuous pipes using iron tie-plates. Stiffness of liquefied soils around pipes is represented as a static coefficient of subgrade reaction, based on the experiments on the interaction between liquefied sand deposits and pipes. Pipeline-spring systems which are characterized by those coefficients are analyzed based on the theory of “a beam on an elastic foundation” and transfer matrix method. Computations are performed with respect to the key parameters of pipes, coefficient of subgrade reaction, and several fixing conditions between pipes and underground structures. The sliding displacements of pipelines, rotational angles of joints, and stresses of pipelines are compared for such anti-liquefaction methods as soil-improving methods (sand-compaction pile or ballast-replaced soil methods) and structural-stiffening methods (parallel pipe or pile-supporting methods).
Allowable Shape Deviation in a Pressurized Cylinder
Authors: Ong L. S.
Published: June 2008

Presence of initial shape imperfection causes additional bending stresses to be developed in a pressurized cylinder. Although the bending stress will initially increase with pressure, it will finally settle down to a certain value. This article derives the maximum bending stress associated with the geometric shape imperfection. It also discusses the implication of this additional bending stress on the design stress and allowable shape tolerance. Finally, it is concluded that a 1-percent diametral deviation, as commonly specified by most design codes, is adequate and sound for the internally pressurized cylinder.
Risk-Based Considerations in Developing Strategies to Ensure Pipeline
Integrity—Part II: Applications
Authors: Rahman S. , Leis B. N.
Published: June 2008

This is the second in series of two papers generated from a recent study on risk-based analysis for developing strategies to ensure pipeline integrity. This paper (Part II—Applications) focuses on the applications of the proposed deterministic and probabilistic models presented in the first paper (Part I—Theory) (Leis and Rahman, 1994) for stochastic pipe fracture evaluations. Using these models, numerical predictions are made for line-pipe steel typically used in gas transmission pipelines and are compared with the available test data. Thereafter, the paper explores the significance of the random variables related to serviceability in pipelines subjected to flaw growth in service. The results are discussed in the light of a hydrotest-based approach to ensure pipeline integrity. It is concluded that analysis of hydrotest strategies to optimize safety for such populations (e.g., Leis and Brust, 1992) should be based on a probabilistic analysis that permits risk assessments associated with pipeline operating decisions and the type and frequency of hydrotests done to ensure continued safe operation of the line. This same probabilistic framework could be used to assess the operating and safety implications for flaw populations characterized by in-line inspection.
Structural Integrity Assessment of Carbon and Low-Alloy Steel
Pressure Vessels Using a Simplified Fracture Mechanics Procedure
Authors: Rana M. D.
Published: June 2008

This paper describes a simplified fracture analysis procedure which was developed by Pellini to quantify fracture critical-crack sizes and crack-arrest temperatures of carbon and low-alloy steel pressure vessels. Fracture analysis diagrams have been developed using the simplified analysis procedure for various grades of carbon and low-alloy steels used in the construction of ASME, Section VIII, Division 1 pressure vessels. Structural integrity assessments have been conducted from the analysis diagrams.
Stress Analysis of Ellipsoidal Shell With Nozzle Under Internal Pressure Loading
Authors: Skopinsky V. N. , Berkov N. A.
Published: June 2008

This paper presents the numerical procedure for the stress analysis of the intersecting shells consisting of an ellipsoidal shell and nozzle. Thin shell theory and finite element method are used. The developed special-purpose computer program SAIS is employed for elastic stress analysis of the model joints of the ellipsoidal shell with nozzle. The parametric study of the joints under internal pressure loading was performed. The results are presented in graphical form. Nondimensional geometric parameters are considered to analyze the effects of changing these parameters on the maximum effective stresses in the shells.
The “Self-Rescue” Capacity of Wrapped Vessels—A Theoretical and Experimental Analysis
Authors: Wang Y. , Soler A. I. , Chen G.-L.
Published: June 2008

The highest risk of longitudinal welds in a wrapped multi-layer vessel is analyzed by assuming all internal lengthwise seams unwelded except for the inner most and the outer most layers. The friction behaviors between layers are investigated. The mechanical analysis is within the elastic domain. A formula is provided to estimate the lowest bursting strength of a wrapped vessel. Two small three-layer cylinders have been tested to verify the theory. A seven-layer bench-scale practical vessel has also been tested to show the application.
Some Results on Axisymmetric Vibration of Spherical Shells of Variable Thickness
Authors: Singh A. V. , Mirza S.
Published: June 2008

Natural frequencies and mode shapes are presented for the free axisymmetric vibration of spherical shells with linearly varying thickness along the meridian. Clamped and hinged edges corresponding to opening angles 30, 45, 60 and 90 deg have been considered in this technical brief to cover a wide range from shallow to deep spherical shells. Variations in thickness are seen to have very pronounced effects on the frequencies and mode shapes.
On the Use of the Momentum Balance in the Impact Analysis of Constrained Elastic Systems
Authors: Rismantab-Sany J. , Shabana A. A.
Published: June 2008

In elastic systems, impulsive forces that act at a point on a deformable body produce stress waves that travel with finite speeds. This paper examines, both theoretically and numerically, the validity of using the generalized impulse momentum approach in modeling impact or collisions in the constrained motion of deformable bodies. The generalized impulse momentum equations that involve the coefficient of restitution and the kinematic constraint Jacobian matrix are used to predict the jump discontinuity in the velocity vector as well as the joint reaction forces. The series solutions obtained by solving these algebraic equations are used to establish a closed form relationship between the jump discontinuity in velocities and joint reactions due to impact and the number of elastic degrees of freedom. It is shown that by increasing the number of elastic coordinates these series converge to their limits. The convergence of these series is used to prove that the generalized impulse momentum equations with the coefficient of restitution can be used with confidence to study impact problems in constrained multibody systems consisting of interconnected rigid and deformable bodies. The results obtained are compared with the classical treatment of the impact problems in the theory of elasticity wherein the case of perfectly plastic impact is assumed.
A Dynamic Model on a Single-Link Flexible Manipulator
Authors: Chang Liang-Wey , Gannon K. P.
Published: June 2008

An enhanced Equivalent Rigid Link System (ERLS) model using natural-mode shape function for flexible manipulators is developed. An experimental validation of the model is performed on a single-link manipulator. The Lagrangian dynamics and the Finite Element Method are used to derive the equations of motion. Joint variables and nodal displacements are chosen being generalized coordinates. The model well describes the dynamic behavior of manipulator systems and allows for applications to design a robust motion control.
Linear Dynamics of a Translating String on an Elastic Foundation
Authors: Perkins N. C.
Published: June 2008

This paper examines the free and forced linear response of a string which is translating across an elastic foundation. Exact solutions are derived for the free vibration of the string which translates between fixed eyelets and across elastic foundations represented by (1) a single interior spring and (2) a uniform step foundation. Results illustrate the dependence of the string natural frequencies and mode shapes on the foundation stiffness, the foundation geometry, and the string translation speed. The forced response of the string to harmonic end excitation is computed in closed form for the case of a complete uniform foundation. A cutoff frequency separates three distinct solution forms. For excitation frequencies below the cutoff frequency, the response amplitude decays exponentially with distance from the driven end.
Tracking Dynamics of Read/Write Head Suspensions in High-Performance Small Form Factor Rigid Disk Drives
Authors: Miu D. K. , Frees G. M. , Gompertz R. S.
Published: June 2008

Recording density of rigid disk drives is related to both linear and track density. High linear density requires submicron recording spacing which is made possible by using a gas-lubricated slider bearing to support the read/write transducer. This critical component has inspired much research effort in the past, both in industry and in academia. On the other hand, a major limitation in increasing the track density is the structural resonance of the suspension which connects the slider bearing to the actuator arm. In this paper, a nonintrusive measurement technique using a Laser Doppler Vibrometer is utilized to measure the submicron suspension vibration. Excitation of the suspension is provided by a miniature air-hammer, a piezoelectric transducer, and the voice-coil motor in commercial disk drives during normal operation. Natural frequencies and mode shapes are extracted from the measurements and compared with numerical data from finite element analysis. Correlation between suspension dynamics and off-track error is presented. Research shows that even for linear actuators, torsional vibration of the suspension causes substantial lateral head motions and contributes significantly to tracking error.
Dynamic Response of a Read/Write Head Floppy Disk System Subjected to Axial Excitation
Authors: Jiang Z. W. , Chonan S. , Abe´ H.
Published: June 2008

The paper is concerned with the forced vibration of a read/write head floppy disk system subjected to axial excitation. The solution is obtained by applying the modal expansion method together with the Galerkin method to the disk governing equations. Numerical results are presented for a 5.25 in. floppy disk rotating at 300 rpm. The effects of the excitation frequency and the head location on the response amplitude of disk are studied in detail.
Earthquake-Induced Instability of a Rotor Supported by Oil Film Bearings
Authors: Hori Y. , Kato T.
Published: June 2008

The effect of seismic waves on the stability of a Jeffcott rotor supported by oil film bearings is investigated by calculating loci of the centers of the journal and the disk using the Runge-Kutta-Gill method. It will be shown that a linearly stable rotor can become unstable under a strong artificial shock and a real seismic wave, if it is running at speeds above twice the first critical speed, which is close to the natural frequency of the rotor. Thus, it will be pointed out that the linear analysis is insufficient to examine the stability of a rotor-bearing system if the rotor is operated above twice the critical speed and a strong shock such as due to an earthquake is expected.
Probabilistic Method to Compute the Optimal Slip Load for a Mistuned Bladed Disk Assembly With Friction Dampers
Authors: Chen S. , Sinha A.
Published: June 2008

In this paper, an analytical technique has been developed to compute the statistics of forced response of a mistuned bladed disk assembly with friction dampers (blade-to-blade or blade-to-ground). The method is based on the statistical linearization approach and predicts the probability distribution function of a blade’s amplitude. The validity of this technique has been corroborated by comparison with the results from numerical simulations. Using this technique, the optimal value of the slip load at the friction joint has been computed to minimize the probability that a blade’s amplitude will exceed a critical value.
Numerical Evaluation of the Performance of Active Noise Control Systems
Authors: Mollo C. G. , Bernhard R. J.
Published: June 2008

Most of the approaches to the prediction of the effectiveness of active noise control systems are analytical in nature. Analytical approaches are limited to active noise control systems where a solution to the governing acoustic wave equation is available. The objective of the investigation presented in this paper was to develop a generalized numerical technique for evaluating the optimal performance of active noise controllers. The numerical technique used as the basis of the numerical analysis is the indirect boundary element method (IBEM). Boundary element methods have been shown to be straightforward and accurate numerical methods for the prediction of the acoustic response of a system. The IBEM numerical procedures are used here to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the noise source strengths or the enclosure boundary description may not be known. Detectors are introduced into the system to deduce the unknown noise source strengths. The performance prediction for a single input, single output system is presented. Analysis of the stability and observability of the active noise control system employing detectors is also presented.
Pseudo-High-Speed Balancing
Authors: Ehrich F. F.
Published: June 2008

In industries like the aircraft gas turbine, trans-critical or super-critical operating speeds are quite common, and rotating machinery must be mass produced with very demanding precision in balance effectiveness, generally without recourse to high-speed balance procedures. A procedure has been developed which permits high-speed multi-plane (i.e., three or more plane) balance correction to be made on rotors in simple conventional low-speed balance machines (Patent Applied For). The procedure accomplishes most of the benefits of actual high-speed or modal or true multi-plane balancing by utilizing other known or available data on the particular rotor’s generic dynamic behavior (i.e., its natural or critical mode shapes) and data on the particular rotor’s generic design and manufacture (i.e., its perceived generic patterns of unbalance distribution). For (N) balance planes, the procedure involves the specification of a Balancing Rule wherein a sequence of (J) low speed balance steps is specified (where J equals the integer part of [(N + 7)/2]). At each of these steps, some fraction (called a Balancing Factor) of the measured two plane unbalance vectors is applied to one or two of the other balance correction planes, before final correction is made on the last two correction planes themselves. A procedure is derived to predetermine those (I) Balance Factors (where I equals [N-2]). The procedure involves an iterative sequence for computing the optimized Balance Factors, with convergence driven by the Newton Raphson procedure, and requires the specification of (I) pairs of generic unbalance distributions and natural mode shapes. The analytically derived Balancing Factors are designed to null the vibration response of the rotor excited by each of the specified generic unbalance distributions at the critical speed associated with the specified mode shape with which the generic unbalance distribution is paired.
Analytical and Experimental Study of the Vibration of Bonded Beams With a Lap Joint
Authors: Rao M. D. , Crocker M. J.
Published: June 2008

A theoretical model to study the flexural vibration of a bonded lap joint system is described in this paper. First, equations of motion at the joint region are derived using a differential element approach. The transverse displacements of the upper and lower beam are considered to be different. The adhesive is assumed to be linearly viscoelastic and the widely used Kelvin-Voight model is used to represent the viscoelastic behavior of the adhesive. The shear force at the interface between the adhesive and the beam is obtained from the simple bending motion equations of the two beams. The resulting equations of motion are combined with the equations of transverse vibration of the beams in the unjointed regions. These are later solved as a boundary value problem to obtain the eigenvalues and eigenvectors of the system. The model can be used to predict the natural frequencies, modal damping ratios, and mode shapes of the system for free vibration. Good agreement between numerical and experimental results was obtained for a system of graphite epoxy beams lap-jointed by an epoxy adhesive.
Experimental Evaluation of Wide Band Active Vibration Controllers
Authors: Metcalfe A. V. , Burdess J. S.
Published: June 2008

Two methods for estimating unknown forces applied to a structure are incorporated into a design technique for wide-band vibration controllers. Their practical performances are compared by experiments on one and two mode test structures.
A Fast Rational Model Approach to Parametric Spectral Estimation—Part I: The Algorithm
Authors: Fassois S. D.
Published: June 2008

A novel, fast rational model (ARMA) approach to parametric spectral estimation, based on correlation-type and guaranteed-stability versions of the Suboptimum Maximum Likelihood scheme that utilizes a quadratic approximation of the negative log-likelihood about an initial estimate in the MA parameter subspace, inverse function estimates, and fundamental ARMA process properties, is introduced. The proposed approach is exclusively based on linear operations, uses the autocovariance function as a “sufficient statistic,” and overcomes the main drawbacks/limitations of alternative approaches by offering high accuracy, minimal computational and memory storage requirements, no need for a priori information, mathematically guaranteed stability (and therefore the capability of estimating all types of spectra, including those characterized by sharp valleys), and complete elimination of the local extrema problem by yielding a unique estimate that is shown to asymptotically converge to the true spectrum. The paper is divided into two parts: The basic form of the proposed approach is derived in the first part, whereas in the second (Fassois, 1990), its consistency is proven, two guaranteed-stability versions developed, and its performance evaluated via numerical simulations and comparisons with standard techniques.
On the Vibration of a Translating String Coupled to Hydrodynamic Bearings
Authors: Tan C. A. , Yang B. , Mote C. D.
Published: June 2008

The vibration of a translating string, controlled through hydrodynamic bearing forces, is analyzed by the transfer function method. Interactions between the string response and the bearing film are described by the bearing impedance function. This function depends on the string translation speed, the frequency of the film thickness variation, and the spatial location of the bearings. The control system consists of the translating string, bearings, actuators and sensors, and feedback elements. An integral formulation of the controlled system response is proposed that leads to the closed-loop transfer function. The frequency response of the control system is studied in the system parameter space. The feasibility of adding active control to improve the bearing force control is also considered.
Bending Vibrations of a Plate Combination Subject to Point Excitation
Authors: Gibbs B. M. , Shen Y.
Published: June 2008

The bending vibration of a structure composed of five rectangular thin plates, subject to point excitation, is investigated theoretically and experimentally. In the theoretical description the displacement amplitude function vector of the global system of combined plates is expressed as a linear combination of coordinate function vectors which satisfy all boundary conditions. The solution is not general since rotation only is allowed at the plate edges but a complex rotational stiffness can be assigned to all noncoupled edges such that constraints ranging continuously from the simply supported to the clamped condition can be modelled on computer. The results of prediction and scale model measurement are presented in the form of point and transfer accelerances and promising agreement is obtained both in terms of level and phase difference.
Policies Designed for Self-Interested Citizens May Undermine "The Moral Sentiments": Evidence from Economic Experiments
Authors: Bowles Samuel
Published: June 2008

High-performance organizations and economies work on the basis not only of material interests but also of Adam Smith's “moral sentiments.” Well-designed laws and public policies can harness self-interest for the common good. However, incentives that appeal to self-interest may fail when they undermine the moral values that lead people to act altruistically or in other public-spirited ways. Behavioral experiments reviewed here suggest that economic incentives may be counterproductive when they signal that selfishness is an appropriate response; constitute a learning environment through which over time people come to adopt more self-interested motivations; compromise the individual's sense of self-determination and thereby degrade intrinsic motivations; or convey a message of distrust, disrespect, and unfair intent. Many of these unintended effects of incentives occur because people act not only to acquire economic goods and services but also to constitute themselves as dignified, autonomous, and moral individuals. Good organizational and institutional design can channel the material interests for the achievement of social goals while also enhancing the contribution of the moral sentiments to the same ends.
Proliferating Cells Express mRNAs with Shortened 3' Untranslated Regions and Fewer MicroRNA Target Sites
Authors: Sandberg Rickard , Neilson Joel R. , Sarma Arup , Sharp Phillip A. , Burge Christopher B.
Published: June 2008

Messenger RNA (mRNA) stability, localization, and translation are largely determined by sequences in the 3′ untranslated region (3′UTR). We found a conserved increase in expression of mRNAs terminating at upstream polyadenylation sites after activation of primary murine CD4
+
T lymphocytes. This program, resulting in shorter 3′UTRs, is a characteristic of gene expression during immune cell activation and correlates with proliferation across diverse cell types and tissues. Forced expression of full-length 3′UTRs conferred reduced protein expression. In some cases the reduction in protein expression could be reversed by deletion of predicted microRNA target sites in the variably included region. Our data indicate that gene expression is coordinately regulated, such that states of increased proliferation are associated with widespread reductions in the 3′UTR-based regulatory capacity of mRNAs.
Learning Much from a Bug's Life
Authors: Rankin Daniel J.
Published: June 2008

Microcosm
.
E. coli
and the New Science of Life.
By Carl Zimmer
. Pantheon, New York, 2008. 255 pp. $25.95, C$30. ISBN 9780375424304.

Through stories on the biology, studies, and uses of Escherichia coli bacteria, the author offers lay readers an illuminating perspective on life, evolution, bioscience, and biotechnology.
For a Redefinition of God
Authors: Noble Denis
Published: June 2008

Reinventing the Sacred
. A New View of Science, Reason, and Religion.
By Stuart A. Kauffman
. Basic Books, New York, 2008. 334 pp. $27, C$28.95. ISBN 9780465003006.

The author argues for his emergence-based view of the world and "that the qualities of divinity that we hold sacred-creativity, meaning, purposeful action-are in fact properties of the universe that can be investigated scientifically."
Multicenter Evaluation of the Vitek 2 Anaerobe and
Corynebacterium
Identification Card
Authors: Rennie Robert P. , Brosnikoff Cheryl , Turnbull LeeAnn , Reller L. Barth , Mirrett Stanley , Janda William , Ristow Kathy , Krilcich Ann
Published: June 2008

The new anaerobe and
Corynebacterium
(ANC) identification card for Vitek 2 was compared with a 16S rRNA gene sequencing (16S) reference method for accuracy in the identification of corynebacteria and anaerobic species. Testing was performed on a Vitek 2 XL system with modified software at three clinical trial laboratories. Reproducibility was determined with nine ATCC quality control strains that were tested 20 times over a minimum of 10 days at all three sites. A challenge set of 50 well-characterized strains and 365 recent fresh and frozen clinical isolates were included in the study. The expected positive and negative biochemical well reactions were also evaluated for substrate reproducibility. All strains were tested with the ANC card, and clinical isolates were saved for 16S rRNA gene sequencing. All reproducibility tests yielded expected results within a 95% confidence interval, except for that with
Corynebacterium striatum
ATCC 6940, for which identification failed at one trial site. For the challenge isolates, there was 98% correct identification, 5% low discrimination, and 2% incorrect identification, and 0% were unidentified. For clinical strains, there was 95.1% correct identification, 4.9% low discrimination, and 4.6% incorrect identification, and 0.3% were unidentified. The 4.6% (17/365) of clinical isolates that were incorrectly identified consisted of 14 isolates that were correct at the genus level and three that were incorrect at the genus level. The new ANC card met all performance criteria within a 95% confidence interval compared to the identification performance by 16S rRNA gene sequencing.
In Vitro Survey of Triazole Cross-Resistance among More than 700 Clinical Isolates of
Aspergillus
Species
Authors: Pfaller M. A. , Messer S. A. , Boyken L. , Rice C. , Tendolkar S. , Hollis R. J. , Diekema D. J.
Published: June 2008

Few data exist to describe in vitro patterns of cross-resistance among large collections of clinical
Aspergillus
isolates, including those of species other than
Aspergillus fumigatus
. We examined 771
Aspergillus
spp. clinical isolates collected from 2000 to 2006 as part of a global antifungal surveillance program (553
A. fumigatus
, 76
A. flavus
, 59
A. niger
, 35
A. terreus
, and 24
A. versicolor
isolates and 24 isolates of other
Aspergillus
species). Antifungal susceptibility testing was performed by the Clinical and Laboratory Standards Institute (CLSI) M38-A broth dilution method with itraconazole (ITR), posaconazole (POS), ravuconazole (RAV), and voriconazole (VOR). We examined the potential for cross-resistance by using measures of correlation overall and by species. For most
Aspergillus
isolates (from 88% of isolates for ITR to 98% of isolates for VOR and POS), MICs of each triazole were ≤1 μg/ml. When all 771 isolates were examined, there were statistically significant correlations for all six triazole-triazole pairs. For
A. fumigatus
, the strongest correlations seen were those between VOR and RAV MICs (
r
= 0.7) and ITR and POS MICs (
r
= 0.4). Similarly, for
A. flavus
, only VOR and RAV MICs and ITR and POS MICs demonstrated statistically significant positive correlations. We have demonstrated correlations among triazole MICs for
Aspergillus
, which for the most common species (
A. fumigatus
and
A. flavus
) were strongest between VOR and RAV MICs and ITR and POS MICs. However,
Aspergillus
species for which MICs of VOR or POS were >2 μg/ml remain extremely rare (<1% of isolates).
A Replication-Defective Gammaherpesvirus Efficiently Establishes Long-Term Latency in Macrophages but Not in B Cells In Vivo
Authors: Li Haiyan , Ikuta Kazufumi , Sixbey John W. , Tibbetts Scott A.
Published: June 2008

Murine gammaherpesvirus 68 (γHV68 or MHV68) is genetically related to the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), providing a useful system for in vivo studies of the virus-host relationship. To begin to address fundamental questions about the mechanisms of the establishment of gammaherpesvirus latency, we previously generated a replication-defective γHV68 lacking the expression of the single-stranded DNA binding protein encoded by
orf6
. In work presented here, we demonstrate that this mutant virus established a long-term infection in vivo that was molecularly identical to wild-type virus latency. Thus, despite the absence of an acute phase of lytic replication, the mutant virus established a chronic infection in which the viral genome (i) was maintained as an episome and (ii) expressed latency-associated, but not lytic replication-associated, genes. Macrophages purified from mice infected with the replication-defective virus harbored viral genome at a frequency that was nearly identical to that of wild-type γHV68; however, the frequency of B cells harboring viral genome was greatly reduced in the absence of lytic replication. Thus, this replication-defective gammaherpesvirus efficiently established in vivo infection in macrophages that was molecularly indistinguishable from wild-type virus latency. These data point to a critical role for lytic replication or reactivation in the establishment or maintenance of latent infection in B cells.
A Functional F Analogue of
Autographa californica
Nucleopolyhedrovirus GP64 from the
Agrotis segetum
Granulovirus
Authors: Yin Feifei , Wang Manli , Tan Ying , Deng Fei , Vlak Just M. , Hu Zhihong , Wang Hualin
Published: June 2008

The envelope fusion protein F of
Plutella xylostella
granulovirus is a computational analogue of the GP64 envelope fusion protein of
Autographa californica
nucleopolyhedrovirus (AcMNPV). Granulovirus (GV) F proteins were thought to be unable to functionally replace GP64 in the AcMNPV pseudotyping system. In the present study the F protein of
Agrotis segetum
GV (AgseGV) was identified experimentally as the first functional GP64 analogue from GVs. AgseF can rescue virion propagation and infectivity of
gp64
-null AcMNPV. The AgseF-pseudotyped AcMNPV also induced syncytium formation as a consequence of low-pH-induced membrane fusion.
Characterization of Dengue Virus Complex-Specific Neutralizing Epitopes on Envelope Protein Domain III of Dengue 2 Virus
Authors: Gromowski Gregory D. , Barrett Nicholas D. , Barrett Alan D. T.
Published: June 2008

The surface of the mature dengue virus (DENV) particle is covered with 180 envelope (E) proteins arranged as homodimers that lie relatively flat on the virion surface. Each monomer consists of three domains (ED1, ED2, and ED3), of which ED3 contains the critical neutralization determinant(s). In this study, a large panel of DENV-2 recombinant ED3 mutant proteins was used to physically and biologically map the epitopes of five DENV complex-specific monoclonal antibodies (MAbs). All five MAbs recognized a single antigenic site that includes residues K310, I312, P332, L389, and W391. The DENV complex antigenic site was located on an upper lateral surface of ED3 that was distinct but overlapped with a previously described DENV-2 type-specific antigenic site on ED3. The DENV complex-specific MAbs required significantly higher occupancy levels of available ED3 binding sites on the virion, compared to DENV-2 type-specific MAbs, in order to neutralize virus infectivity. Additionally, there was a great deal of variability in the neutralization efficacy of the DENV complex-specific MAbs with representative strains of the four DENVs. Overall, the differences in physical binding and potency of neutralization observed between DENV complex- and type-specific MAbs in this study demonstrate the critical role of the DENV type-specific antibodies in the neutralization of virus infectivity.
T Lymphocytes Contribute to Antiviral Immunity and Pathogenesis in Experimental Human Metapneumovirus Infection
Authors: Kolli Deepthi , Bataki Efthalia L. , Spetch LeAnne , Guerrero-Plata Antonieta , Jewell Alan M. , Piedra Pedro A. , Milligan Gregg N. , Garofalo Roberto P. , Casola Antonella
Published: June 2008

Human metapneumovirus (hMPV), a member of the familyParamyxoviridae, is a leading cause of lower respiratory tract infections in children, the elderly, and immunocompromised patients. Virus- and host-specific mechanisms of pathogenesis and immune protection are not fully understood. By an intranasal inoculation model, we show that hMPV-infected BALB/c mice developed clinical disease, including airway obstruction and hyperresponsiveness (AHR), along with histopathologic evidence of lung inflammation and viral replication. hMPV infection protected mice against subsequent viral challenge, as demonstrated by undetectable viral titers, lack of body weight loss, and a significant reduction in the level of lung inflammation. No cross-protection with other paramyxoviruses, such as respiratory syncytial virus, was observed. T-lymphocyte depletion studies showed that CD4+and CD8+T cells cooperate synergistically in hMPV eradication during primary infection, but CD4+more than CD8+T cells also enhanced clinical disease and lung pathology. Concurrent depletion of CD4+and CD8+T cells completely blocked airway obstruction as well as AHR. Despite impaired generation of neutralizing anti-hMPV antibodies in the absence of CD4+T cells, mice had undetectable viral replication after hMPV challenge and were protected from clinical disease, suggesting that protection can be provided by an intact CD8+T-cell compartment. Whether these findings have implications for naturally acquired human infections remains to be determined.
KINETIC STUDIES OF PLANT DECARBOXYLASES AND CARBONIC ANHYDRASE
Authors: Hansl N. , Waygood E. R.
Published: June 2008

Spinach leaf carbonic anhydrase has been used as a tool in the Krebs-Roughton technique to determine whether several plant decarboxylase systems give rise to carbon dioxide or bicarbonate as the primary end product. The results show that in addition to the urease – urea and yeast carboxylase – pyruvic systems, the plant enzyme systems decarboxylating pyruvic, oxalacetic, glutamic, and α-ketoglutaric acids produce carbon dioxide and not bicarbonate as the primary end product.
CULTURAL VARIABILITY IN SEPTORIA AVENAE FRANK
Authors: Johnson T.
Published: June 2008

Cultures from field collections of Septoria avenae Frank produce "wild type" colonies of rather uniform appearance—a creamy-white mycelium, a brown substrate, and few, if any, pycnidia. Subculturing on potato sucrose agar usually leads to the production of a great variety of variants that fall into two broad classes: mycelial and pycnidial, the latter usually producing scant mycelium, many pycnidia, and a blue-green substrate pigment. In some cultures, staling, i.e., cessation of growth, occurs commonly but is generally followed, after an interval of time, by renewed growth. Cultures of the pycnidia! type show a marked tendency to produce mycelial type variants and, conversely, cultures of the mycelial type will give rise to pycnidial type variants. In certain cultures, strains have arisen that predominantly produce small pycnidia containing spermatium-like microspores, but which are still capable of producing macro-spores. Cultures from microspores show several distinct types including dark-pigmented cultures, albino cultures with dark pycnidia, albino cultures with colorless pycnidia, and cultures of purely mycelial type. Attempts to demonstrate that the microspores perform a function in the production of the perfect stage of the organism were unsuccessful.
FURTHER STUDIES ON THE NITROGEN SOURCE FOR THE PRODUCTION OF AMYLOLYTIC ENZYMES BY SUBMERGED CULTURE OF ASPERGILLUS NIGER
Authors: Shu Ping
Published: June 2008

The experimental results obtained in this study indicate that proteins or amino acids are not necessary for the production of high yields of the amylolytic enzymes, alpha-amylase, maltase, and limit dextrinase. However, in cultures which produce appreciable transient acids during the fermentation the use of a nitrogen source which is a potential alkali donor greatly increases the yield of alpha-amylase. Ammonium acetate fulfills this requirement, and under appropriate conditions it gives high yields of alpha-amylase, maltase, and limit dextrinase. The accumulation of maltase and limit dextrinase is inhibited when the pH of the medium rises above eight, whereas an acid pH as low as four is still suitable for their production.
STUDIES OF FUNGI IMPERFECTI: I. PHIALOPHORA
Authors: Cain Roy F.
Published: June 2008

Some notes are given concerning the structure and occurrence of phialides and phialospores and their relationship with spermatia. The genus Phialophora is not sharply delimited and with many transitional species gradually merges with several genera of the Fungi Imperfecti. A new species Phialophora radicicola Cain, is described from the roots of corn in Ontario.
Cytochemical localization of peroxidase activity in wound vessel members of Coleus
Authors: Hepler Peter K. , Rice Rita M. , Terranova William A.
Published: June 2008

Peroxidase activity has been localized in the cell walls and cytoplasm of wound vessel elements of Coleus which had been fixed in glutaraldehyde, incubated in diaminobenzidine (DAB) and H2O2, and postfixed in OSO4. Electron microscopic investigations revealed prominent staining in the reticulate secondary wall and in the primary wall where the secondary thickenings attach. The stain in the secondary wall is finely textured and heavier towards its periphery than towards its core. The staining of the primary wall, however, is coarsely granular. In the cytoplasm of differentiating vessel elements electron-opaque deposits are observed in the plasmalemma, especially where it overlies the secondary thickening, and in the dictyosomes and their associated vesicles. Staining also occurs on the internal membranes of developing chloroplasts where it is most likely the result of photooxidation of DAB.Staining, except in chloroplasts, appears to be due specifically to peroxidase, since either removal of H2O2 or preincubation with KCN markedly reduces staining, whereas preincubation with aminotriazole, an inhibitor of catalase, does not. The similarity of localization of peroxidase and lignin in the walls of Coleus wound vessel elements supports the postulate that the enzyme participates in lignification.
Plant community responses to disturbances in the western Canadian Arctic
Authors: Bliss L. C. , Wein Ross W.
Published: June 2008

Data are presented on several current studies being conducted in the Mackenzie Delta and the Arctic Archipelago in relation to oil and gas exploration. Tundra fires destroy most of the aboveground plant cover and result in significant increases in depth of the active layer. Fire stimulated the growth and flowering of Eriophorum vaginatum subsp. spissum and Calamagrostis canadensis. The recovery of dwarf heath shrubs from rhizomes was relatively rapid while lichens and mosses showed no early recovery. Crude oil spilled in different plant communities killed the leaves of all species, yet regrowth occurred on some woody species the same summer and more species showed regrowth the second summer. Oil spilled in early winter (October) and in wet sedge communities in summer appeared to be most detrimental.Percentage plant removal has been significantly reduced with changed seismic technology in the past 6 years. Native species, often from rhizomes, reinvade all lines though recovery on peats and by native grasses appears most rapid. Winter roads of compacted snow were less detrimental to wetland sedge communities than to upland dwarf shrub – sedge – heath ones. Upland sites, which were dry in summer, were more difficult to revegetate. The revegetation studies indicated that 100 kg/ha of elemental nitrogen and 200 kg/ha of phosphorus treatment was best and that early spring or late fall seeding was essential. About five perennial plus two annual grass species in varying mixtures grew best in the reseeding trials. The supply of available nitrogen appears to strongly limit plant growth of native species while phosphorus does not. Most of these nutrients are retained in the organic mat, thus any disturbance that destroys this mat will seriously modify normal nutrient cycling and greatly increase the need for fertilizer in revegetation.In the High Arctic most soils are wet during snow melt and thus subject to surface disturbance by vehicles. In the polar deserts, silty and sandy soils dry rather rapidly and show less evidence of disturbance later in summer. Lowland areas where there is a more complete cover of plants on wet shallow peats or silty soils are subject to rutting throughout the summer as in the Low Arctic. With surface disturbance there is much less thaw of the permafrost than occurs in the Delta.The different plant community – topographic – soil – ground ice landscape units or systems respond differentially to the different surface disturbances tested to date. This is true in both the Low and High Arctic.
Distribution patterns of American Arctic lichens
Authors: Thomson John W.
Published: June 2008

Maps showing typical American Arctic lichen distribution patterns are given, including broad ranging circumpolar, boreal forest outlier, Appalachian extensions, arcto-Pacific (Beringian), amphi-Atlantic, American Arctic endemic, Great Plains and Arctic, and western states and eastern arctic disjuncts. Discussion of dispersion mechanisms suggests wind over snow cover as most important. The origin of the arctic lichens is suggested as being in tectonic uplifts of the Miocene giving alpine tundras from which spread into arctic tundras occurred in pre-Pleistocene and subsequently. Possible sites of origin are the Rocky Mountains and the mountains of eastern Siberia. The question is posed of whether the distribution patterns reflect equiformal spread from centers of origin or if they reflect patterns of distribution of environmental conditions.