bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Characterization of a Flip-Chip Solder Joint
Authors: Patra S. K. , Sritharan S. S. , Lee Y. C.
Published: February 2008

Based on an energy minimization principle, a mathematical/numerical model has been developed to study the impact of design and process variations associated with flip-chip solder joint on its ability to align in lateral and axial direction. The minimum-energy shape needed for joint evaluation is computed by a novel numerical method based on motion by mean curvature. The analysis shows that (1) the magnitude of the reaction force in lateral and axial direction reduces with increase in solder volume, (2) the normal reaction is an order of magnitude higher compared to the lateral reaction (restoring force) thus making the joint more susceptible to lateral misalignment compared to the axial misalignment, and (3) the axial misalignment is primarily dictated by the accuracy of the solder deposition height.
A Time Domain Substructure Synthesis Method for Viscoelastic Structures
Authors: Qian Duan , Hansen J. S.
Published: February 2008

The method of substructure synthesis, originally conceived for undamped and viscously damped systems, has been extended to systems with viscoelastic damping in the hereditary integral form. Based on a new variational principle, the substructure synthesis method is formulated in the time domain. The displacement in each substructure is represented by a set of real admissible trial vectors. The traditional state space formulation is avoided by the proposed method so that the approach is independent of the form of viscoelastic models. Effectiveness of the method is illustrated through numerical examples.
Rotational Representation of a Plate Made of Grioli-Toupin Material
Authors: Jemielita G.
Published: February 2008

A solenoidal part of displacement field appearing in a plate made of material with constraints has been determined. The semi-inverse method has been applied to description. The results being obtained together with the already known biharmonic representation (Jemielita, 1992) might be useful in a new micropolar plate theory formulation.
Bending of Superelastic Wires, Part I: Experimental Aspects
Authors: Berg B. T.
Published: February 2008

A pure-bending apparatus is used to measure the constitutive relationship between applied pure bending moments and the resulting curvatures of a few superelastic alloy wires. The sample nickel-titanium alloy (NiTi) wires change phase when ample bending moments are imposed. Like the material’s uniaxial tension stress-strain relationship, the measured moment-curvature relationship shows plateaus of constant moment and hysteresis. The bent shape is circular, except in the mixed phase region where it is composed of a phase mixture of circles. An example of the applications of the measured moment-curvature relations is presented in Part II of this paper where the three-point bending problem is considered.
Poincare Linear Interpolated Cell Mapping: Method for Global Analysis of Oscillating Systems
Authors: Levitas J. , Weller T.
Published: February 2008

A method for global analysis of nonlinear dynamical oscillating systems was developed. The method is based on the idea of introducing a Poincare section into a multidimensional state space of the dynamical system and combine it with an interpolation procedure within the cells which constitute the discretized problem domain of interest. The proposed method was applied to study the global behavior of two nonlinear coupled van der Pol oscillators. Significant saving in calculation time, in comparison with both direct numerical integration and Poincare-like simple cell mapping, is demonstrated.
Lagrange’s Equations, Hamilton’s Equations, and Kane’s Equations: Interrelations, Energy Integrals, and a Variational Principle
Authors: Mingori D. L.
Published: February 2008

A new viewpoint is suggested for expressing the governing equations of analytical mechanics. This viewpoint establishes a convenient framework for examining the relationships among Lagrange’s equations, Hamilton’s equations, and Kane’s equations. The conditions which must be satisfied for the existence of an energy integral in the context of Kane’s equations are clarified, and a generalized form of Hamilton’s Principle is presented. Generalized speeds replace generalized velocities as the velocity variables in the formulation. The development considers holonomic systems in which the generalized forces are derivable from a potential function.
On the Partly Bonded Thermoelastic Circular Inhomogeneity
Authors: Kattis M. A. , Meguid S. A.
Published: February 2008

The thermoelastic problem of an infinite elastic plane containing a partly bonded circular inhomogeneity of different thermomechanical properties is considered. Based upon the solution of a perfectly bonded inhomogeneity established in the current work, the complex stress intensity factor of the interfacial crack problem is obtained for full heat-conductive conditions of an “open” crack and for a linear temperature change at infinity.
Analysis of Shear Band Development in a Viscoplastic Double Slip, Single Crystal in Tension
Authors: Yang S. , Rey C.
Published: February 2008

Using an idealized planar single crystal model undergoing symmetrical double slip in tension, the effect of rate sensitivity on shear band initiation and on shear band development is analysed. The behavior of the crystal is assumed to be rigid-viscoplastic. By analysing the kinematics and statics of shear banding, the deformation modes involving shear banding pattern are formulated. By a linearized stability analysis, the critical condition for shear band initiation is obtained. To study shear band development, the formulated constitutive equations are numerically solved, and the maximum value of the localized shear is predicted. The results show three different stages of shear band development. The first corresponds to a slow progression of shear localization in the band, the second to a rapid shear localization accompanied with an unloading of surrounding material, and the third to a resumption of deformation in the surrounding material and to a progressive saturation of the shear band. All three stages depend strongly on rate sensitivity, especially the first stage which does not exist in the rigid-plastic case. Even very small rate sensitivity can delay significantly or even preclude the shear band formation. Finally a discussion of the results illustrates how a macroscopic shear band forms and propagates.
Out-of-Plane Buckling of Fiber-Reinforced Thermoplastic Sheets Under Homogeneous Biaxial Conditions
Authors: Christie G. R. , Collins I. F. , Bhattacharyya D.
Published: February 2008

The mechanical behavior of fiber-reinforced composite thermoplastic sheets during forming processes is modelled as a viscous fluid with inextensibility and incompressibility constraints. Techniques of linear stability analysis are used to study the growth or decay of initial imperfections in plane sheets reinforced by two families of fibers subjected to biaxial strains. This theory delimits situations when buckles can be expected to form during forming operations.
Intermittency Route to Chaos of a Cantilevered Pipe Conveying Fluid With a Mass Defect at the Free End
Authors: Semler C. , Pai¨doussis M. P.
Published: February 2008

The nonlinear equations for planar motions of a vertical cantilevered pipe conveying fluid are modified to take into account a small lumped mass added at the free end. The resultant equations contain nonlinear inertial terms; by discretizing the system first and inverting the inertia matrix, these terms are transferred into other matrices. In this paper, the dynamics of the system is examined when the added mass is negative (a mass defect), by means of numerical computations and by the software package AUTO. The system loses stability by a Hopf bifurcation, and the resultant limit cycle undergoes pitchfork and period-doubling bifurcations. Subsequently, as shown by the computation of Floquet multipliers, a type I intermittency route to chaos is followed—as illustrated further by a Lorenz return map, revealing the well-known normal form for this type of bifurcation. The period between “turbulent bursts” of nonperiodic oscillations is computed numerically, as well as Lyapunov exponents. Remarkable qualitative agreement, in both cases, is obtained with analytical results.
Stability of Cohesive Crack Model: Part II—Eigenvalue Analysis of Size Effect on Strength and Ductility of Structures
Authors: Bazˇant Z. P. , Li Yuan-Neng
Published: February 2008

The preceding paper is extended to the analysis of size effect on strength and ductility of structures. For the case of geometrically similar structures of different sizes, the criterion of stability limit is transformed to an eigenvalue problem for a homogeneous Fredholm integral equation, with the structure size as the eigenvalue. Under the assumption of a linear softening stress-displacement relation for the cohesive crack, the eigenvalue problem is linear. The maximum load of structure under load control, as well as the maximum deflection under displacement control (which characterizes ductility of the structure), can be solved explicitly in terms of the eigenfunction of the aforementioned integral equation.
Optimal Design Problems in Mechanics of Growing Composite Solids, Part I: Preload Optimization
Authors: Drozdov A. D. , Kalamkarov A. L.
Published: February 2008

Optimal design problems arising in mechanics of growing composite viscoelastic and elastic solids subjected to aging are considered. The growth means a continuous mass influx to the body surface. Due to this process, the size of the body increases in time. The mass influx with pretensioning causes the rise of stresses in the growing body. The purpose of the current study is to propose a new class of the optimal design problems for the growing viscoelastic composite solids subjected to aging, and to solve the mechanical design problems of this new type. In the current paper, we analyze the optimal preload distribution in the winding process for cylindrical solids. The proposed approach and the obtained new solutions are of a special interest and importance for the optimization of winding of composite pressure vessels.
The Contact Problem at Delamination
Authors: Giannakopoulos A. E. , Nilsson K.-F. , Tsamasphyros G.
Published: February 2008

The important phenomenon of delamination buckling is examined subjected to the condition of frictionless contact. Buckled delamination is examined in particular, because in-plane compressive loading is typical and detrimental. Two types of contact can be distinguished, local and global. The latter may occur everywhere in the plate while the local contact is limited to the crack front (negative KI stress intensity factors). Both local and global contact conditions were considered using a finite element scheme which employed nonlinear plate theory. The global contact problem is formulated as it appears in post-buckling of delamination. The case of simultaneous buckling and contact is also addressed in this paper. Two particularly interesting examples of thin film delaminations are presented. In the first, the contact at buckling is due to the material anisotropy. In this case the bucking load and the post-bucking analysis were very well supported by experiments. In the second example, contact at buckling arises because of a pin that holds down the delaminated layer at its center. The treated cases indicated that contact may significantly affect the fracture parameters along the delamination front, and is, therefore, important for delamination arrest.
Displacement and Strain Fields for a Bimetallic Strip Under Remote Tension
Authors: Epstein J. S. , Graham S. M. , Perry K. E. , Reuter W. G.
Published: February 2008

Experimental displacement and strain fields are presented for a generalized plane stress tensile specimen consisting of commercially pure titanium diffusion bonded to 6Al-4V titanium. Plastic flow initiates at the intersection of the interface with the specimen free edge. Further deformation results in concentrated shear bands emanating from the interface at both free edges. Interactions of the interface-free edge shear bands force a state of plane strain in the center of the specimen. These interface constraint effects have practical relevance on the testing of joined metals with property mismatch.
Transient Analysis of Dynamic Crack Propagation With Boundary Effect
Authors: Ma Chien-Ching , Ing Yi-Shyong
Published: February 2008

In this study, a dynamic antiplane crack propagation with constant velocity in a configuration with boundary is investigated in detail. The reflected cylindrical waves which are generated from the free boundary will interact with the propagating crack and make the problem extremely difficult to analyze. A useful fundamental solution is proposed in this study and the solution is determined by superposition of the fundamental solution in the Laplace transform domain. The proposed fundamental problem is the problem of applying exponentially distributed traction (in the Laplace transform domain) on the propagating crack faces. The Cagniard’s method for Laplace inversion is used to obtain the transient solution in time domain. Numerical results of dynamic stress intensity factors for the propagation crack are evaluated in detail.
Anisotrophy of the Vigdergauz Microstructure
Authors: Grabovsky Y. , Kohn R. V.
Published: February 2008

A recent article by Vigdergauz considered two-component, linearly elastic plates. It showed the existence of spatially periodic microstructures producing plates of extremal rigidity. For the microstructures which maximize or minimize the effective bulk modulus, Vigdergauz asserted that the effective behavior was isotropic. We show this is wrong: the effective tensor is in fact anisotropic.
Nuclear Coupling and Polarization in Molecular Transport Junctions: Beyond Tunneling to Function
Authors: Galperin Michael , Ratner Mark A. , Nitzan Abraham , Troisi Alessandro
Published: February 2008

Much current experimental research on transport in molecular junctions focuses on finite voltages, where substantial polarization-induced nonlinearities may result in technologically relevant device-type responses. Because molecules have strong polarization responses to changing charge state or external field, molecules isolated between electrodes can show strongly nonlinear current-voltage responses. For small applied voltages (up to ∼0.3 volt), weak interaction between transporting electrons and molecular vibrations provides the basis for inelastic electron tunneling spectroscopy. At higher voltages and for certain time scale regimes, strong coupling effects occur, including Coulomb blockade, negative differential resistance, dynamical switching and switching noise, current hysteresis, heating, and chemical reactions. We discuss a general picture for such phenomena that arise from charging, strong correlation, and polarization (electronic and vibrational) effects in the molecule and at the interface.
Bioinspired Design and Assembly of Platelet Reinforced Polymer Films
Authors: Bonderer Lorenz J. , Studart André R. , Gauckler Ludwig J.
Published: February 2008

Although strong and stiff human-made composites have long been developed, the microstructure of today's most advanced composites has yet to achieve the order and sophisticated hierarchy of hybrid materials built up by living organisms in nature. Clay-based nanocomposites with layered structure can reach notable stiffness and strength, but these properties are usually not accompanied by the ductility and flaw tolerance found in the structures generated by natural hybrid materials. By using principles found in natural composites, we showed that layered hybrid films combining high tensile strength and ductile behavior can be obtained through the bottom-up colloidal assembly of strong submicrometer-thick ceramic platelets within a ductile polymer matrix.
Extending Earthquakes' Reach Through Cascading
Authors: Marsan David , Lengliné Olivier
Published: February 2008

Earthquakes, whatever their size, can trigger other earthquakes. Mainshocks cause aftershocks to occur, which in turn activate their own local aftershock sequences, resulting in a cascade of triggering that extends the reach of the initial mainshock. A long-lasting difficulty is to determine which earthquakes are connected, either directly or indirectly. Here we show that this causal structure can be found probabilistically, with no a priori model nor parameterization. Large regional earthquakes are found to have a short direct influence in comparison to the overall aftershock sequence duration. Relative to these large mainshocks, small earthquakes collectively have a greater effect on triggering. Hence, cascade triggering is a key component in earthquake interactions.
Atomic-Scale Chemical Imaging of Composition and Bonding by Aberration-Corrected Microscopy
Authors: Muller D. A. , Kourkoutis L. Fitting , Murfitt M. , Song J. H. , Hwang H. Y. , Silcox J. , Dellby N. , Krivanek O. L.
Published: February 2008

Using a fifth-order aberration-corrected scanning transmission electron microscope, which provides a factor of 100 increase in signal over an uncorrected instrument, we demonstrated two-dimensional elemental and valence-sensitive imaging at atomic resolution by means of electron energy-loss spectroscopy, with acquisition times of well under a minute (for a 4096-pixel image). Applying this method to the study of a La
0.7
Sr
0.3
MnO
3
/SrTiO
3
multilayer, we found an asymmetry between the chemical intermixing on the manganese-titanium and lanthanum-strontium sublattices. The measured changes in the titanium bonding as the local environment changed allowed us to distinguish chemical interdiffusion from imaging artifacts.
Spine-Type-Specific Recruitment of Newly Synthesized AMPA Receptors with Learning
Authors: Matsuo Naoki , Reijmers Leon , Mayford Mark
Published: February 2008

The stabilization of long-term memories requires de novo protein synthesis. How can proteins, synthesized in the soma, act on specific synapses that participate in a given memory? We studied the dynamics of newly synthesized AMPA-type glutamate receptors (AMPARs) induced with learning using transgenic mice expressing the GluR1 subunit fused to green fluorescent protein (GFP-GluR1) under control of the
c-fos
promoter. We found learning-associated recruitment of newly synthesized GFP-GluR1 selectively to mushroom-type spines in adult hippocampal CA1 neurons 24 hours after fear conditioning. Our results are consistent with a “synaptic tagging” model to allow activated synapses to subsequently capture newly synthesized receptor and also demonstrate a critical functional distinction in the mushroom spines with learning.
Predicting Human Interactive Learning by Regret-Driven Neural Networks
Authors: Marchiori Davide , Warglien Massimo
Published: February 2008

Much of human learning in a social context has an interactive nature: What an individual learns is affected by what other individuals are learning at the same time. Games represent a widely accepted paradigm for representing interactive decision-making. We explored the potential value of neural networks for modeling and predicting human interactive learning in repeated games. We found that even very simple learning networks, driven by regret-based feedback, accurately predict observed human behavior in different experiments on 21 games with unique equilibria in mixed strategies. Introducing regret in the feedback dramatically improved the performance of the neural network. We show that regret-based models provide better predictions of learning than established economic models.
Comment on "International Conservation Policy Delivers Benefits for Birds in Europe"
Authors: Rodríguez-Muñoz Rolando , Ojanguren Alfredo F. , Tregenza Tom
Published: February 2008

Donald
et al
. (Reports, 10 August 2007, p. 810) assessed the impact of the European Union's Birds Directive, a conservation policy enacted in 1979, and reported evidence for positive population changes in targeted species. We argue that their conclusions are overstatements based on unsuitable data and inappropriate analyses.
Response to Comment on "International Conservation Policy Delivers Benefits for Birds in Europe"
Authors: Donald Paul F. , Sanderson Fiona J. , Burfield Ian J. , Bierman Stijn M. , Gregory Richard D. , Waliczky Zoltan
Published: February 2008

Rodríguez-Muñoz
et al
. raise concerns about our study on the effectiveness of the European Union's Birds Directive, based on the provenance of the trend data used and on the predictions that were tested. Here, we show that our results are robust to different assumptions of uncertainty surrounding trend estimates and that criticisms of the methods stem largely from misunderstandings of the original paper.
A Photon Turnstile Dynamically Regulated by One Atom
Authors: Dayan Barak , Parkins A. S. , Aoki Takao , Ostby E. P. , Vahala K. J. , Kimble H. J.
Published: February 2008

Beyond traditional nonlinear optics with large numbers of atoms and photons, qualitatively new phenomena arise in a quantum regime of strong interactions between single atoms and photons. By using a microscopic optical resonator, we achieved such interactions and demonstrated a robust, efficient mechanism for the regulated transport of photons one by one. With critical coupling of the input light, a single atom within the resonator dynamically controls the cavity output conditioned on the photon number at the input, thereby functioning as a photon turnstile. We verified the transformation from a Poissonian to a sub-Poissonian photon stream by photon counting measurements of the input and output fields. The results have applications in quantum information science, including for controlled interactions of single light quanta and for scalable quantum processing on atom chips.
Dose-Dependent Protection against or Exacerbation of Disease by a Polylactide Glycolide Microparticle-Adsorbed, Alphavirus-Based Measles Virus DNA Vaccine in Rhesus Macaques
Authors: Pan Chien-Hsiung , Nair Nitya , Adams Robert J. , Zink M. Christine , Lee Eun-Young , Polack Fernando P. , Singh Manmohan , O'Hagan Derek T. , Griffin Diane E.
Published: February 2008

Measles remains an important cause of vaccine-preventable child mortality. Development of a low-cost, heat-stable vaccine for infants under the age of 6 months could improve measles control by facilitating delivery at the time of other vaccines and by closing a window of susceptibility prior to immunization at 9 months of age. DNA vaccines hold promise for development, but achieving protective levels of antibody has been difficult and there is an incomplete understanding of protective immunity. In the current study, we evaluated the use of a layered alphavirus DNA/RNA vector encoding measles virus H (SINCP-H) adsorbed onto polylactide glycolide (PLG) microparticles. In mice, antibody and T-cell responses to PLG-formulated DNA were substantially improved compared to those to naked DNA. Rhesus macaques received two doses of PLG/SINCP-H delivered either intramuscularly (0.5 mg) or intradermally (0.5 or 0.1 mg). Antibody and T-cell responses were induced but not sustained. On challenge, the intramuscularly vaccinated monkeys did not develop rashes and had lower viremias than vector-treated control monkeys. Monkeys vaccinated with the same dose intradermally developed rashes and viremia. Monkeys vaccinated intradermally with the low dose developed more severe rashes, with histopathologic evidence of syncytia and intense dermal and epidermal inflammation, eosinophilia, and higher viremia compared to vector-treated control monkeys. Protection after challenge correlated with gamma interferon-producing T cells and with early production of high-avidity antibody that bound wild-type H protein. We conclude that PLG/SINCP-H is most efficacious when delivered intramuscularly but does not provide an advantage over standard DNA vaccines for protection against measles.
Seroprevalences of Herpes Simplex Virus Type 2, Five Oncogenic Human Papillomaviruses, and
Chlamydia trachomatis
in Katowice, Poland
Authors: Görander Staffan , Lagergård Teresa , Romanik Malgorzata , Viscidi Raphael P. , Martirosian Gayane , Liljeqvist Jan-Åke
Published: February 2008

Herpes simplex virus type 2 (HSV-2), human papillomaviruses (HPVs), and
Chlamydia trachomatis
are the most common pathogens causing sexually transmitted infections (STIs). There is limited information about the prevalences of these STIs in Poland. Here, we estimated the occurrence of immunoglobulin G (IgG) antibodies against HSV-2, HPV, and
C. trachomatis
in 199 blood donors and 110 patients of both genders attending an STI clinic in Katowice in southern Poland. The seroprevalences of HSV-2 were 5% for blood donors and 14% in the STI cohort. The seroprevalences of the five potentially oncogenic HPV types 16, 18, 31, 35, and 51 were 15%, 7%, 5%, 5%, and 17%, respectively, in blood donors and 37%, 8%, 12%, 5%, and 21%, respectively, in the STI cohort. The majority of HPV-infected individuals showed antibodies against more than one type, i.e., had been infected with multiple HPV types. Anti-
C. trachomatis
IgG antibodies were detected in 6% of blood donors and 13% of individuals attending the STI clinic. The relatively high prevalence of HPV-51 may have implications for future vaccine programs, as the newly introduced HPV vaccines are based on the potentially oncogenic HPV types 16 and 18.
Detection of
Histoplasma capsulatum
Antigen in Panamanian Patients with Disseminated Histoplasmosis and AIDS
Authors: Gutierrez Maria Eugenia , Canton Alfredo , Connolly Patricia , Zarnowski Robert , Wheat L. Joseph
Published: February 2008

Histoplasmosis is a common endemic mycosis in the Americas, often causing severe disease in patients with AIDS. Antigen detection has become an important method for rapid diagnosis of histoplasmosis in the United States but not in Central or South America. Isolates from patients in the United States are predominantly found to be class 2 isolates when typed using the nuclear gene
YPS3
, while isolates from Latin America are predominantly typed as class 5 or class 6. Whether infection with these Latin American genotypes produces positive results in the
Histoplasma
antigen assay has not been reported. In this study, we have compared the sensitivity of antigen detection for AIDS patients from Panama who had progressive disseminated histoplasmosis to that for those in the United States. Antigenuria was detected in the MVista
Histoplasma
antigen enzyme immunoassay (EIA) in 95.2% of Panamanian cases versus 100% of U.S. cases. Antigenemia was detected in 94.7% of the Panamanian cases versus 92% of the U.S. cases. Two clinical isolates from Panama were typed using
YPS3
and were found to be restriction fragment length polymorphism class 6. We conclude that the MVista
Histoplasma
antigen EIA is a sensitive method for diagnosis of histoplasmosis in Panama.
Rapid and Accurate Identification of
Candida albicans
Isolates by Use of PNA FISH
Flow
Authors: Trnovsky Jan , Merz William , Della-Latta Phyllis , Wu Fann , Arendrup Maiken Cavling , Stender Henrik
Published: February 2008

We developed the simple, rapid (1 h), and accurate PNA FISH
Flow
method for the identification of
Candida albicans
. The method exploits unique in solution in situ hybridization conditions under which the cells are simultaneously fixed and hybridized. This method facilitates the accurate identification of clinical yeast isolates using two scoring techniques: flow cytometry and fluorescence microscopy.
Increased Sporulation Rate of Epidemic
Clostridium difficile
Type 027/NAP1
Authors: Åkerlund Thomas , Persson Ingela , Unemo Magnus , Norén Torbjörn , Svenungsson Bo , Wullt Marlene , Burman Lars G.
Published: February 2008

Clostridium difficile
PCR ribotype 027 comprised 0.2% of a collection of Swedish isolates in 1997-2001 (3 of 1,325 isolates). These isolates had lower moxifloxacin MICs than the epidemic type 027 isolates, but they had the same
tcdC
sequence and toxin yield. Type 027 produced 3- to 13-fold more toxin than did major Swedish types. One epidemic strain (027/NAP1a) sporulated more than did other type 027 isolates, a feature that should contribute to its survival and spread.
Etiological Analysis of Initial Colonization of Periodontal Pathogens in Oral Cavity
Authors: Cortelli Jose Roberto , Aquino Davi Romeiro , Cortelli Sheila Cavalca , Fernandes Camila Borges , de Carvalho-Filho Jonas , Franco Gilson César Nobre , Costa Fernando Oliveira , Kawai Toshihisa
Published: February 2008

It is unclear when the initial colonization by periodontal pathogens occurs in the oral cavity. Therefore, we report here the association between specific age groups and the time when the initial colonization by periodontal pathogens occurs in the oral cavity in such groups. Findings are based on an epidemiological analysis of the prevalence of five periodontal pathogens in the oral cavities of a wide range of age populations, from newborn to elderly, who were randomly selected in a geographic region of Brazil. These periodontal pathogens include
Campylobacter rectus
,
Porphyromonas gingivalis
,
Aggregatibacter actinomycetemcomitans
,
Prevotella intermedia
, and
Tannerella forsythia
and were analyzed in the bacterial samples isolated from gingival sulcus, the dorsum of the tongue, and cheek mucosa of diverse age groups, using a bacterial DNA-specific PCR method. Results indicated that there are distinct age-related groups where initial colonization by the five periodontal pathogens examined in this study can be detected and that the presence of teeth is a permissive factor for colonization by
P. gingivalis
,
P. intermedia
, and
T. forsythia
. Although it remains unclear exactly how or when target pathogens colonize healthy subjects, an understanding of age-related groups does provide a potentially useful tool in the early detection and prevention of periodontitis in healthy individuals.
Fatal Levofloxacin Failure in Treatment of a Bacteremic Patient Infected with
Streptococcus pneumoniae
with a Preexisting
parC
Mutation
Authors: de Cueto M. , Rodríguez J. M. , Soriano M. J. , López-Cerero L. , Venero J. , Pascual A.
Published: February 2008

The fatal outcome of levofloxacin treatment in a patient with bacteremic pneumonia caused by
Streptococcus pneumoniae
with a preexisting
parC
mutation is reported. Failure was due to the emergence of a
gyrA
mutation after 4 days of therapy. Problems encountered in detecting first-step mutation isolates are discussed.
Improved Detection of Circulating
Aspergillus
Antigen by Use of a Modified Pretreatment Procedure
Authors: Mennink-Kersten Monique A. S. H. , Ruegebrink Dorien , Klont Rocus R. , Warris Adilia , Blijlevens Nicole M. A. , Donnelly J. Peter , Verweij Paul E.
Published: February 2008

Detection of circulating galactofuranose (gal
f
) antigens, including galactomannan (GM), by the Platelia
Aspergillus
(PA) enzyme-linked immunosorbent assay (ELISA) is an important tool in the early diagnosis of invasive aspergillosis (IA). We used a modified pretreatment technique (MT) on consecutive negative PA ELISA plasma samples from IA patients in order to improve the detection of the fungal components present. Plasma samples (52) were collected from healthy donors, and 174 plasma samples with a galactomannan index (GMI) below 0.5 were collected from 25 unclassifiable and 23 IA patients. The PA ELISA reactivity of pretreated samples was determined before (conventional technique [CT]) and after (MT) filtration using a Microcon filter with a 50-kDa cutoff (Millipore). For the MT, the sensitivity of the PA ELISA increased from 42.9% (CT) to 78.6% (MT) using a cutoff for the GMI of 1.5 in the probable and proven group, whereas specificity slightly decreased from 98.7% to 96.1% in the control group. The 10-fold concentration step increased the GMI as high as 121-fold. The MT resulted not only in positive reactivity in samples that tested negative with the CT but also in the earlier detection of antigen by 2 to 17 days.
Acute Infantile Gastroenteritis Associated with Human Enteric Viruses in Tunisia
Authors: Sdiri-Loulizi Khira , Gharbi-Khélifi Hakima , de Rougemont Alexis , Chouchane Slaheddine , Sakly Nabil , Ambert-Balay Katia , Hassine Mouna , Guédiche Mohamed Neji , Aouni Mahjoub , Pothier Pierre
Published: February 2008

This prospective study, conducted from January 2003 to June 2005, investigated the incidence and the clinical role of various enteric viruses responsible for infantile gastroenteritis in 632 Tunisian children presenting in dispensaries (380 children) or hospitalized (252 children) for acute diarrhea. At least one enteric virus was found in each of 276 samples (43.7%). A single pathogen was observed in 234 samples, and mixed infections were found in 42 samples. In terms of frequency, rotavirus and norovirus were detected in 22.5 and 17.4% of the samples, respectively, followed by astrovirus (4.1%), Aichi virus (3.5%), adenovirus types 40 and 41 (2.7%), and sapovirus (1.0%). The seasonal distribution of viral gastroenteritis showed a winter peak but also an unusual peak from May to September. The severity of the diarrhea was evaluated for hospitalized infants. No significant differences were observed between rotavirus and norovirus infections with regard to the incidence and the clinical severity of the disease, especially in dehydration.
Prosthetic Hip Infection Caused by
Tropheryma whipplei
Authors: Cremniter Julie , Bauer Thomas , Lortat-Jacob Alain , Vodovar Dominique , Le Parc Jean-Marie , Emile Jean-François , Franc Brigitte , Sebbag Pierre , Gaillard Jean-Louis , Heym Beate
Published: February 2008

We report a case of prosthetic hip infection due to
Tropheryma whipplei
in a 74-year-old man not previously known to have Whipple's disease. Diagnosis was based on systematic 16S rRNA gene amplification and sequencing of samples obtained during revision hip arthroplasty.
Validation of Virulence and Epidemiology DNA Microarray for Identification and Characterization of
Staphylococcus aureus
Isolates
Authors: Spence Richard P. , Wright Victoria , Ala-Aldeen Dlawer A. A. , Turner David P. , Wooldridge Karl G. , James Richard
Published: February 2008

The human pathogen
Staphylococcus aureus
is isolated and characterized using traditional culture and sensitivity methodologies that are slow and offer limited information on the organism. In contrast, DNA microarray technology can provide detailed, clinically relevant information on the isolate by detecting the presence or absence of a large number of virulence-associated genes simultaneously in a single assay. We have developed and validated a novel, cost-effective multiwell microarray for the identification and characterization of
Staphylococcus aureus
. The array comprises 84 gene targets, including species-specific, antibiotic resistance, toxin, and other virulence-associated genes, and is capable of examining 13 different isolates simultaneously, together with a reference control strain. Analysis of
S. aureus
isolates whose complete genome sequences have been determined (Mu50, N315, MW2, MRSA252, MSSA476) demonstrated that the array can reliably detect the combination of genes known to be present in these isolates. Characterization of a further 43
S. aureus
isolates by the microarray and pulsed-field gel electrophoresis has demonstrated the ability of the array to differentiate between isolates representative of a spectrum of
S. aureus
types, including methicillin-susceptible, methicillin-resistant, community-acquired, and vancomycin-resistant
S. aureus
, and to simultaneously detect clinically relevant virulence determinants.
Vaccinia Virus E2L Null Mutants Exhibit a Major Reduction in Extracellular Virion Formation and Virus Spread
Authors: Domi Arban , Weisberg Andrea S. , Moss Bernard
Published: February 2008

The vaccinia virus E2L (VACWR058) gene is conserved in all sequenced chordopoxviruses and is predicted to encode an 86-kDa protein with no recognizable functional motifs or nonpoxvirus homologs. Although the region immediately upstream of the open reading frame lacked optimal consensus promoter motifs, expression of the E2 protein occurred after viral DNA replication. Transfection studies, however, indicated that the promoter was weak compared to well-characterized intermediate and late promoters. The E2 protein was present in mature virions purified from infected cells but was more abundant in extracellular enveloped forms. Despite the conservation of the E2L gene in chordopoxviruses, deletion mutants could be isolated from both the WR and IHD-J strains of vaccinia virus. These null mutants produced very small plaques in all cell lines tested, reduced amounts of mature infectious virions, and very low numbers of extracellular virions. Nevertheless, viral protein synthesis appeared qualitatively and quantitatively normal. The defect in extracellular virus formation was corroborated by electron microscopy, which also showed some aberration in the wrapping of virions by cisternal membranes. Extracellular virions that did form, however, were able to induce actin tail formation.
Identification of a GP64 Subdomain Involved in Receptor Binding by Budded Virions of the Baculovirus
Autographica californica
Multicapsid Nucleopolyhedrovirus
Authors: Zhou Jian , Blissard Gary W.
Published: February 2008

Enveloped virus entry into host cells is typically initiated by an interaction between a viral envelope glycoprotein and a host cell receptor. For budded virions of the baculovirus
Autographa californica
multicapsid nucleopolyhedrovirus, the envelope glycoprotein GP64 is involved in host cell receptor binding, and GP64 is sufficient to mediate low-pH-triggered membrane fusion. To better define the role of GP64 in receptor binding, we generated and characterized a panel of antisera against subdomains of GP64. Eight subdomain-specific antisera were generated, and their reactivities with GP64 proteins and neutralization of virus infectivity and binding were examined. Antibodies directed against the N-terminal region of GP64 (amino acids 21 to 159) showed strong neutralization of infectivity and effectively inhibited binding of
35
S-labeled budded virions to Sf9 cells. In addition, we generated virions displaying truncated GP64 constructs. A construct displaying the N-terminal 274 amino acids (residues 21 to 294) of the ectodomain was sufficient to mediate virion binding. Additional studies of antisera directed against small subdomains revealed that an antiserum against a 40-amino-acid region (residues 121 to 160) neutralized virus infectivity. Site-directed mutagenesis was subsequently used for functional analysis of that region. Recombinant viruses expressing GP64 proteins with single amino acid substitutions within amino acids 120 to 124 and 142 to 148 replicated to high titers, suggesting that those amino acids were not critical for receptor binding or other important GP64 functions. In contrast, GP64 proteins with single amino acid substitutions of residues 153 and 156 were unable to substitute for wild-type GP64 and did not rescue a
gp64
knockout virus. Further analysis showed that these substitutions substantially reduced binding of recombinant virus to Sf9 cells. Thus, the amino acid region from positions 21 to 159 was identified as a putative receptor binding domain, and amino acids 153 and 156 appear to be important for receptor binding.
Alveolar Macrophages Are a Major Determinant of Early Responses to Viral Lung Infection but Do Not Influence Subsequent Disease Development
Authors: Pribul Philippa K. , Harker James , Wang Belinda , Wang Hongwei , Tregoning John S. , Schwarze Jürgen , Openshaw Peter J. M.
Published: February 2008

Macrophages are abundant in the lower respiratory tract. They play a central role in the innate response to infection but may also modulate excessive inflammation. Both macrophages and ciliated epithelial cells respond to infection by releasing soluble mediators, leading to the recruitment of innate and adaptive effector cells. To study the role of lung macrophages in acute respiratory viral infection, we depleted them by the inhalation of clodronate liposomes in an established mouse model of respiratory syncytial virus (RSV) disease. Infection caused an immediate local release of inflammatory cytokines and chemokines, peaking on day 1, which was virtually abolished by clodronate liposome treatment. Macrophage depletion inhibited the activation (days 1 to 2) and recruitment (day 4) of natural killer (NK) cells and enhanced peak viral load in the lung (day 4). However, macrophage depletion did not affect the recruitment of activated CD4 or CD8 T cells, weight loss, or virus-induced changes in lung function. Therefore, lung macrophages play a central role in the early responses to viral infection but have remarkably little effect on the adaptive response occurring at the time of peak disease severity.
Alveolar Macrophages Are Indispensable for Controlling Influenza Viruses in Lungs of Pigs
Authors: Kim Heui Man , Lee Young-Won , Lee Ki-Ja , Kim Hyun Soo , Cho Sung Whan , van Rooijen Nico , Guan Yi , Seo Sang Heui
Published: February 2008

Alveolar macrophages constitutively reside in the respiratory tracts of pigs and humans. An in vivo role of alveolar macrophages in defending against influenza viruses in mice infected with a reassorted influenza virus, 1918 HA/NA:Tx/91, was reported, but there has been no report on an in vivo role of alveolar macrophages in a natural host such as a pig using currently circulating human influenza virus. Here we show that in vivo depletion of alveolar macrophages in pigs by dichloromethylene diphosphonate (MDPCL2) treatment results in 40% mortality when pigs are infected with currently circulating human H1N1 influenza viruses, while none of the infected control pigs died. All infected pigs depleted of alveolar macrophages suffered from more severe respiratory signs than infected control pigs. Induction of tumor necrosis factor alpha in the infected pigs depleted of alveolar macrophages was significantly lower than that in the lungs of infected control pigs, and the induction of interleukin-10, an immunosuppressive cytokine, significantly increased in the lungs of infected pigs depleted of alveolar macrophages compared to infected control pigs. When we measured antibody titers and CD8
+
T lymphocytes expressing gamma interferon (IFN-γ), lower antibody titers and a lower percentage of CD8
+
T lymphocytes expressing IFN-γ were detectable in MDPCL2-treated infected pigs than in phosphate-buffered saline- and liposome-treated and infected pigs. Taken together, our findings suggest that alveolar macrophages are essential for controlling H1N1 influenza viruses in pigs.
Biomasse et espèces de lichens terrestres disponibles pour le caribou dans le nord du Québec
Authors: Crête Michel , Morneau Claude , Nault René
Published: February 2008

Following a two-stage sampling plan, 44 1-km2 primary units were systematically allocated between 53 and 59 ° latitude throughout northern Québec to estimate the biomass of terrestrial lichens. Lichens were collected in two secondary units (0.25 m2) located in parts of each primary unit where lichens were visible from a helicopter (lichen stratum). Overall, the lichen stratum covered 51% of the study area and lichen biomass averaged 1223 kg/ha (dry weight; SE = 201; n = 44). Almost 85% of the variance of this mean was attributable to variability between primary units. The biomass in the west was greater than in the east; it was the highest in the [Formula: see text]700-mm precipitation zone and the lowest in the 500- to 599-mm zone. Data on percent plant cover indicated mat mosses increased in importance over lichens in the east. There was a clear relationship between lichen biomass in secondary units on one hand and mat thickness and percent lichen ground cover on the other. Cladinia stellaris (Opiz) Brodo was the most common species; Alectoria ochroleuca (Hoffm.) Mass. and Cornicularia divergens Ach. were typical of the north, whereas Cladina mitis (Sandst.) Hustich characterized the south of the study area. The annual consumption of lichens by caribou was probably 0.5-0.9% of the available biomass in 1987. Key words: biomass, caribou, Cladina, lichens, Quebec.
Post-spate development of epilithic algal communities in different current environments
Authors: Peterson Christopher G. , Stevenson R. Jan
Published: February 2008

Development of epilithic algal communities was monitored in fast- (29 cm∙s−1) and slow-current (12 cm∙s−1) outdoor experimental stream channels for 33 d following a simulated spate. Disturbance reduced diatom densities in both current regimes to equal levels, but recovery was more rapid in slow current. Maximum algal abundances, which seemed to reach carrying capacity in both current environments, were lower in fast current than in slow. The percentage of live cells in diatom assemblages decreased during community development. The small, monoraphid diatom Achnanthes minutissima Kütz. dominated communities in both current regimes from 0 to 12 d, principally because of its persistence on substrata through disturbance. Post-spate diatom accumulation was more rapid in slow current, presumably due to higher cell export in fast current. Differences in community structure between current regimes during early (0–6 d) recovery were attributed to differences in attachment strength and growth form of persistent species. In both current regimes, initial dominance by A. minutissima shifted to dominance by Synedra spp. and dense, floating mats of zygnematalean green algae. Zygnematalean mats enhanced diatom deposition and probably reduced water-column nutrient concentrations, altered light availability, and increased habitat heterogeneity. Zygnematalean proliferation affected diatom succession in slow but not in fast currents, suggesting that autogenic changes were more pronounced in slow-current habitats. Key words: benthic algae, current, disturbance, recovery, streams, succession.
Embryo sac development in soybean: cellularization and egg apparatus expansion
Authors: Folsom M. W. , Cass D. D.
Published: February 2008

An ultrastructural study of soybean embryo sac development was performed. Prior to the final mitotic division and cellularization a nuclear rearrangement occurs that involves the chalazal movement of one of the two micropylar nuclei. During cellularization this nucleus divides to form the egg and micropylar polar nuclei and produces the wall that separates the central ceil from title space occupied by the egg apparatus. Within this space the other nucleus divides to form the two synergid nuclei and one of the two walls that separate the egg and synergid cells from one another. Egg apparatus cells are initially densely cytoplasmic, each is enclosed by thick, highly dissected walls, and they are all similar with respect to distribution of organelles except that synergid nuclei are micropylar to the egg nucleus. There is a progressive thinning and segmentation of egg apparatus walls during cellular expansion until they resemble the beaded chain structure seen in the mature egg and synergid cell walls. Taken as a whole these observations suggest that the chalazal movement of one of the two micropylar nuclei during the 4-nucleate stage is pivotal in determining future patterns of egg apparatus development.