bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Associated with Fissure Sealant Delegation: Dentist Characteristics and Office Staffing Patterns
Authors: Farghaly Mahassen M. , Lang W. Paul , Woolfolk Marilyn W. , Faja Barbara W. , Ziemiecki Thomas L. , Pritzel Susan J.
Published: September 2007

The purpose of this research was to identify dentist characteristics and dental office staffing patterns related to delegation of sealant applications. Results from a 1989 ma/led survey were used to characterize Michigan general dentists (N =300) who did or did not delegate sealant applications to auxiliaries and to identify factors associated with delegation. Nearly 50 percent of respondents were applying all sealants themselves. In offices that delegated the procedure, the mean proportion of sealants being applied by dentists was 39.9 percent. Registered dental hygienists were applying 51 percent, while registered dental assistants were applying 6.5 percent. Delegating dentists were more knowledgeable about sealant procedures, held more favorable attitudes, treated more young patients, placed more sealants, and were better informed about the legality of delegation according to the state practice act. Logistic regression analysis found that employing a registered dental hygienist was the most significant factor associated with sealant delegation, followed by employing a registered dental assistant. Findings suggest that dental auxiliaries, and particularly registered dental assistants, are underutilized for applying sealants. Approaches to increasing delegation of sealants may include changing dentists' traditional hiring patterns, highlighting the skills of auxiliaries such as the registered dental hygienist (RDH) and the registered dental assistant (RDA), and increasing awareness of legally allowable procedures that RDHs and RDAs can perform.
Effects of Molybdenum Content and Heat Treatment on Mechanical and Tribological Properties of a Low-Carbon Stellite® Alloy
Authors: Huang Ping , Liu Rong , Wu Xijia , Yao Matthew X.
Published: September 2007

The chemical composition of Stellite® 21 alloy was modified by doubling the molybdenum (Mo) content for enhanced corrosion and wear resistance. The specimens were fabricated using a casting technique. Half of the specimens experienced a heat treatment at 1050°C for an hour. The microstructure and phase analyses of the specimens were conducted using electron scanning microscopy and X-ray diffraction. The mechanical properties of the specimens were determined in terms of the ASTM Standard Test Method for Tension Testing of Metallic Materials (E8-96). The mechanical behaviors of individual phases in the specimen materials were investigated using a nano-indentation technique. The wear resistance of the specimens was evaluated on a ball-on-disk tribometer. The experimental results revealed that the increased Mo content had significant effects on the mechanical and tribological properties of the low-carbon Stellite® alloy and the heat treatment also influenced these properties.
An Experimental Determination of Optimum Processing Parameters for Al∕SiC Metal Matrix Composites Made Using Ultrasonic Consolidation
Authors: Yang Y. , Janaki Ram G. D. , Stucker B. E.
Published: September 2007

Ultrasonic consolidation, an emerging additive manufacturing technology, is one of the most recent technologies considered for fabrication of metal matrix composites (MMCs). This study was performed to identify the optimum combination of processing parameters, including oscillation amplitude, welding speed, normal force, operating temperature, and fiber orientation, for manufacture of long-fiber-reinforced MMCs. A design of experiments approach (Taguchi L25 orthogonal array) was adopted to statistically determine the influences of individual process parameters. SiC fibers of 0.1mm diameter were successfully embedded into an Al 3003 metal matrix. Push-out testing was employed to evaluate the bond strength between the fiber and the matrix. Data from push-out tests and microstructural studies were analyzed and an optimum combination of parameters was achieved. The effects of process parameters on bond formation and fiber/matrix bond strength are discussed.
Characterization of the Core Properties of a Shock Absorbing Composite
Authors: Georgiades G. , Oyadiji S. O. , Zhu X. Q. , Wright J. R. , Turner J. T.
Published: September 2007

This paper is on the characterization of the mechanical properties of Newtonian-type shock absorbing elastomeric composites. This composite material is a blend of elastomeric capsules or beads in a matrix of a Newtonian liquid. The material can be considered as a liquid analogy to elastomeric foams. It exhibits bulk compression characteristics and acts like an elastic liquid during an impact, unlike elastic foams, which exhibit uniaxial compression characteristics. A test cell consisting of an instrumented metal cylinder and a piston was designed. A sample of the material was placed in the instrumented cylinder, which was located at the base of a drop test rig. A drop mass of 17.3kg was subsequently released from a desired height to impact the piston. From measurements of the acceleration histories of the drop mass and the piston, and from the displacement history of the piston, the force-displacement curves and the associated impact energies absorbed were derived. These are compared to the corresponding characteristics derived from measurements of pressure of the fluid medium inside the cylinder. The results are compared for blends of different bead types, and the different aspects contributing to their performance are discussed. It is shown that the performance curves derived from the accelerometer measurements matched those derived from the pressure measurements. Blends of this composite material of different types of beads showed distinctively different characteristics.
Experimental Technique for Elevated Temperature Mode I Fatigue Crack Growth Testing of Ni-Base Metal Foils
Authors: Liu L. , Holmes J. W.
Published: September 2007

Details are provided for an experimental approach to study the tensile fatigue crack growth behavior of very thin metallic foils. The technique utilizes a center-notched specimen and a hemispherical bearing alignment system to minimize bending strains. To illustrate the technique, the constant amplitude fatigue crack growth behavior of a Ni-base superalloy foil was studied at temperatures from 20°C to 760°C. The constant amplitude fatigue tests were performed at a frequency of 2Hz and stress ratio of 0.2. The crack growth rate versus stress intensity range data followed a Paris relation with a stress intensity range exponent m between 5 and 6; this exponent is significantly higher than what is commonly observed for thicker materials and indicates very rapid fatigue crack propagation rates can occur in thin metallic foils.
Constitutive Modeling of Metals Based on the Evolution of the Strain-Hardening Rate
Authors: Durrenberger L. , Klepaczko J. R. , Rusinek A.
Published: September 2007

The mechanical threshold stress (MTS) model is not commonly used in industrial applications due to its complexity. The Zener–Hollomon parameter Z was utilized to develop a simplified and compact formulation similar to the MTS model. The predictions of the proposed formulation are compared to the results obtained by the original MTS model and experimental data. The flow stresses of three cold-rolled steels frequently used in automotive industries were analyzed for both formulations over a wide range of strain rates (8.10−3s−1≤ε¯̇p≤103s−1).
Modeling of Elastic Waves in Dynamically Loaded NiAl Bicrystals
Authors: Loomis Eric , Peralta Pedro , Swift Damian C.
Published: September 2007

Two methods have been used to simulate 2D elastic wave scattering in nickel aluminide (NiAl) bicrystals to study effects of grain boundaries and material anisotropy on elastic wave propagation. Scattering angles and amplitude ratios of the reflected and refracted waves produced at the grain boundary were calculated via slowness curves for both grains, which were plotted in the plane of incidence containing the grain boundary normal. From these curves, scattering angles were measured graphically and amplitude ratios were calculated based on the continuity of tractions and displacements at the boundary. To support these calculations, finite element simulations were performed with ABAQUS/EXPLICIT to obtain time- and space-dependent stresses. The results of each method correlated well with each other for four bicrystals. It was found that for bicrystals where the transmitted quasi-longitudinal (TQL) wave amplitude decreased across the boundary, diminished stresses were found in the finite element models for the same bicrystal. Conversely, where an increase in amplitude of the TQL wave was found, the finite element simulations showed that stress under the boundary increased. In general, the amplitude of the TQL wave was found to have a strong connection to the ratio of incident and TQL sound speeds. However, other directions in each grain are believed to contribute strongly to the overall scattering process since the pairs of bicrystals in this investigation had somewhat similar sound speeds. These findings correlated well with free surface cracking observed in a previous paper (Loomis, E., Peralta, P., Swift, D., and McClellan, K., 2005, Mater. Sci. Eng., Ser. A., 404(1-2), pp. 291–300), where cracks nucleated and propagated due to the focusing of scattered waves at the boundary. Specifically, in bicrystals oriented for shielding, the grain boundary was protected forcing cracks to grow outside of the shielded region.
Initiation and Propagation of Stress-Assisted Corrosion (SAC) Cracks in Carbon Steel Boiler Tubes
Authors: Yang Dong , Singh Preet M. , Neu Richard W.
Published: September 2007

Industrial boilers experience bulbous cracks in carbon steel water-wall tubes and other water-touched surfaces. Because these cracks are blunt and different from sharp fatigue cracks, they are generally referred to as stress-assisted corrosion (SAC) cracks. The performance of carbon steels in industrial boilers strongly depends on the formation and stability of the magnetite film on the waterside surface. To understand the mechanism for SAC crack initiation and propagation, slow strain rate tests were conducted in a recirculation autoclave under industrial boiler water conditions. The dissolved oxygen in the water was maintained from a negligible amount (5ppb) to 3ppm. The SAC crack initiation and propagation mechanism involves magnetite film damage and requires the presence of dissolved oxygen in the water. Increasing the test temperature accelerates the process. A mechanism for SAC cracking is proposed, and interrupted slow strain rate tests were carried out to validate this mechanism. Temperature and dissolved oxygen in boiler water are important factors in initiation and propagation of stress assisted corrosion cracks. SAC in boilers can be controlled by controlling the dissolved oxygen levels around 5ppb.
Effects of Strain Hardening and Initial Yield Strength on Machining-Induced Residual Stresses
Authors: Nasr Mohamed N.A. , Ng E.-G. , Elbestawi M. A.
Published: September 2007

Finite element analysis was used in the current study to examine the effects of strain hardening and initial yield strength of workpiece material on machining-induced residual stresses (RS). An arbitrary–Lagrangian–Eulerian finite element model was built to simulate orthogonal dry cutting with continuous chip formation, then a pure Lagrangian analysis was used to predict the induced RS. The current work was validated by comparing the predicted RS profiles in four workpiece materials to their corresponding experimental profiles obtained under similar cutting conditions. These materials were AISI H13 tool steel, AISI 316L stainless steel, AISI 52100 hardened steel, and AISI 4340 steel. The Johnson–Cook (J–C) constitutive equation was used to model the plastic behavior of the workpiece material. Different values were assigned to the J-C parameters representing the studied properties. Three values were assigned to each of the initial yield strength (A) and strain hardening coefficient (B), and two values were assigned to the strain hardening exponent (n). Therefore, the full test matrix had 18 different materials, covering a wide range of commercial steels. The yield strength and strain hardening properties had opposite effects on RS, where higher A and lower B or n decreased the tendency for surface tensile RS. Because of the opposite effects of A and (B and n), maximum surface tensile RS was induced in the material with minimum A and maximum B and n values. A physical explanation was provided for the effects of A, B, and n on cutting temperatures, strains, and stresses, which was subsequently used to explain their effects on RS. Finally, the current results were used to predict the type of surface RS in different workpiece materials based on their A, B, and n values.
On the Reference Length and Mode Mixity for a Bimaterial Interface
Authors: Agrawal A. , Karlsson A. M.
Published: September 2007

We investigate properties that govern interfacial fracture within the framework of linear elastic fracture mechanics, including interfacial fracture toughness, mode mixity, and the associated reference length. The reference length describes the arbitrary location where the mode mixity is evaluated, ahead of the crack tip, in a bimaterial system. A method for establishing a reference length that is fixed for a given bimaterial system is proposed. This is referred to as the “characteristic reference length,” with the associated “characteristic mode mixity.” The proposed method is illustrated with an experimental investigation, utilizing a four-point bend test of a bimaterial system.
Spherical Rare-Earth Magnets in Introductory Physics
Authors: Adams Al
Published: September 2007

Permanent magnets have long been used in both traditional laboratory exercises1,2 and in inquiry-based learning activities.3 These pedagogical applications are typically timed to correspond to the early coverage of magnetism in the second-semester sequence of introductory physics. At the initial level the concepts relate to the magnetic field of the Earth, the magnetic forces on a magnetic dipole, the various classes of magnetic materials, the nature of the magnetic field in the vicinity of a permanent magnet, and perhaps the use of magnetic fields to produce electric currents. Although there are examples of quantitative experiments in magnetism and electromagnetism using permanent magnets,4,5 very rarely are these laboratories made part of the introductory laboratory experience.
Student Selection of the Textbook for an Introductory Physics Course
Authors: Dake L. S.
Published: September 2007

Several years ago I had to select a new textbook for my calculus-based introductory physics class. I subscribe to Just-in-Time Teaching methods,1 which require students to read the book before the material is covered in class. Thus, the readability of the text by the students is critical. However, I did not feel that I was the best judge of this factor, so I turned the textbook selection into a class project. The students unanimously chose one textbook, which I have now successfully used for three years. The project was decidedly worthwhile, and I gained considerable insight into what students prefer in a textbook.
Index of Refraction Using Total Internal Reflection
Authors: Greenslade Thomas B.
Published: September 2007

Here is a quick way to measure the index of refraction of water using the phenomenon of total internal reflection.
Physics Northwest: An Academic Alliance
Authors: Hicks James L.
Published: September 2007

It's a weekday in mid-October, late at night and with another teaching assignment not far below the horizon. Yet 40 teachers are laughing, joking, and sharing in the fun that is associated with physics teaching. The event: a Physics Northwest (PNW) meeting, an organization that is in its 20th year and thriving. “Physics Northwest meetings are not only interesting, educational, and a source of great ideas for physics demonstrations, they are also Phun,” says David Thiessen. David's response appears to be universal among PNW members and he continues to attend PNW meetings even though he is into his ninth year of retirement. Patti Sievert of Northern Illinois University tells us, “I'm here tonight to learn how to form a Physics Northwest in the Rock River Valley,” and immediately three people from PNW volunteer to be there to help with her first meeting. Yes, this happened and continues to happen monthly in many northwest Illinois suburban high schools. The history of this prosperous organization and its sister organization, the Illinois State Physics Project (ISPP),1 can be gleaned from the website in Ref. 2.
Another Look at the Wine Butler
Authors: DeWeerd Alan J.
Published: September 2007

In a recent article, Iain MacInnes analyzed the static equilibrium of a system consisting of a wine bottle and a wine butler.1 After discussing that composite system, students can be asked to consider only the bottle (and its contents) as the system. An interesting challenge for them is to describe the forces on the bottle in static equilibrium.
The Magnetic Torque Oscillator and the Magnetic Piston
Authors: Connors Martin , Al-Shamali Farook
Published: September 2007

A magnet suspended in a uniform magnetic field like that of the Earth can be made to oscillate about the field. The frequency of oscillation depends on the strength (magnetic moment) of the magnet, that of the external field, and the moment of inertia of the magnet. It is easily shown and verified by experiment that a simple but nontrivial expression represents this motion well, but that only the product of the magnetic moment and magnetic field can be determined. The repulsion of two magnets can be used to determine the magnetic moment, and in turn the external field can be determined. The results are reasonably good considering the very simple equipment required, and the experiment allows quantitative investigation of magnetism.
Energy Ambiguity and the Inductive Rail Oscillator
Authors: Hecking Patrick C.
Published: September 2007

In electric or mixed electric-mechanic systems, the distinction between potential and kinetic energy is not as clear as in purely mechanical systems. A solution for the motion of an inductively loaded rail generator is presented. In this case, the magnetic field energy (½)Li2 can be written formally in terms of a potential energy, while physically it is something different. The analogy between mechanical and electric oscillators has limits, and harmonic oscillators can operate without potential energy, both of which must be pointed out by physics teachers.
Population Pharmacokinetics of Lamivudine in Human Immunodeficiency Virus-Exposed and -Infected Infants
Authors: Tremoulet Adriana H. , Capparelli Edmund V. , Patel Parul , Acosta Edward P. , Luzuriaga Katherine , Bryson Yvonne , Wara Diane , Zorrilla Carmen , Holland Diane , Mirochnick Mark
Published: September 2007

This study aimed to determine lamivudine disposition in infants and to construct an appropriate dose adjustment for age, given the widespread use of lamivudine for both the prevention of mother-to-child transmission of human immunodeficiency virus (HIV) and the treatment of HIV-infected infants. Using a pooled-population approach, the pharmacokinetics of lamivudine in HIV-exposed or -infected infants from four Pediatric AIDS Clinical Trials Group studies were assessed. Ninety-nine infants provided 559 plasma samples for measurement of lamivudine concentrations. All infants received combination antiretroviral therapy including lamivudine dosed at 2 mg/kg of body weight every 12 h (q12h) for the first 4 to 6 weeks of life and at 4 mg/kg q12h thereafter. Lamivudine's apparent clearance was 0.25 liter/h/kg at birth, doubling by 28 days. In the final model, age and weight were the only significant covariates for lamivudine clearance. While lamivudine is predominantly renally eliminated, the serum creatinine level was not an independent covariate in the final model, possibly because it was confounded by age. Inclusion of interoccasion variability for bioavailability improved the individual subject clearance prediction over the age range studies. Simulations based on the final model predicted that by the age of 4 weeks, 90% of infant lamivudine concentrations with the standard 2 mg/kg dose of lamivudine fell below the adult median concentration. This population pharmacokinetic analysis affirms that adjusting the dose of lamivudine from 2 mg/kg to 4 mg/kg q12 h at the age of 4 weeks for infants with normal maturation of renal function will provide optimal lamivudine exposure, potentially contributing to more successful therapy.
BK Virus Replication In Vitro: Limited Effect of Drugs Interfering with Viral Uptake and Intracellular Transport
Authors: Randhawa Parmjeet , Farasati Noush Afarin , Huang Yuchen
Published: September 2007

BK virus is an important pathogen in kidney transplant recipients. In vitro studies demonstrated slight antiviral activity for chloroquine and nystatin. A sialic acid derivative, BTB11968, was identified as a lead compound for further development.
Sel1 Repeat Protein LpnE Is a
Legionella pneumophila
Virulence Determinant That Influences Vacuolar Trafficking
Authors: Newton Hayley J. , Sansom Fiona M. , Dao Jenny , McAlister Adrian D. , Sloan Joan , Cianciotto Nicholas P. , Hartland Elizabeth L.
Published: September 2007

The environmental pathogen
Legionella pneumophila
possesses five proteins with Sel1 repeats (SLRs) from the tetratricopeptide repeat protein family. Three of these proteins, LpnE, EnhC, and LidL, have been implicated in the ability of
L. pneumophila
to efficiently establish infection and/or manipulate host cell trafficking events. Previously, we showed that LpnE is important for
L. pneumophila
entry into macrophages and epithelial cells. In further virulence studies here, we show that LpnE is also required for efficient infection of
Acanthamoeba castellanii
by
L. pneumophila
and for replication of
L. pneumophila
in the lungs of A/J mice. In addition, we found that the role of LpnE in host cell invasion is dependent on the eight SLR regions of the protein. A truncated form of LpnE lacking the two C-terminal SLR domains was unable to complement the invasion defect of an
lpnE
mutant of
L. pneumophila
130b in both the A549 and THP-1 cell lines. The
lpnE
mutant displayed impaired avoidance of LAMP-1 association, suggesting that LpnE influenced trafficking of the
L. pneumophila
vacuole, similar to the case for EnhC and LidL. We also found that LpnE was present in
L. pneumophila
culture supernatants and that its export was independent of both the Lsp type II secretion system and the Dot/Icm type IV secretion system. The fact that LpnE was exported suggested that the protein may interact with a eukaryotic protein. Using LpnE as bait, we screened a HeLa cell cDNA library for interacting partners, using the yeast two-hybrid system. Examination of the protein-protein interaction between LpnE and a eukaryotic protein, obscurin-like protein 1, suggested that LpnE can interact with eukaryotic proteins containing immunoglobulin-like folds via the SLR regions. This investigation has further characterized the contribution of LpnE to
L. pneumophila
virulence and, more specifically, the importance of the SLR regions to LpnE function.
Genome Differences between
Treponema pallidum
subsp.
pallidum
Strain Nichols and
T. paraluiscuniculi
Strain Cuniculi A
Authors: Strouhal Michal , Šmajs David , Matějková Petra , Sodergren Erica , Amin Anita G. , Howell Jerrilyn K. , Norris Steven J. , Weinstock George M.
Published: September 2007

The genome of
Treponema paraluiscuniculi
strain Cuniculi A was compared to the genome of the syphilis spirochete
Treponema pallidum
subsp.
pallidum
strain Nichols using DNA microarray hybridization, whole-genome fingerprinting, and DNA sequencing. A DNA microarray of
T. pallidum
subsp.
pallidum
Nichols containing all 1,039 predicted open reading frame PCR products was used to identify deletions and major sequence changes in the Cuniculi A genome. Using these approaches, deletions, insertions, and prominent sequence changes were found in 38 gene homologs and six intergenic regions of the Cuniculi A genome when it was compared to the genome of
T. pallidum
subsp.
pallidum
Nichols. Most of the observed differences were localized in
tpr
loci and the vicinity of these loci. In addition, 14 other genes were found to contain frameshift mutations resulting in major changes in protein sequences. Analysis of restriction target sites representing 0.34% of the total genome length and DNA sequencing of three PCR products (0.46% of the total genome length) amplified from Cuniculi A chromosomal regions and comparison to the Nichols genome revealed a sequence similarity of 98.6 to 99.3%. These results are consistent with a close genetic relationship among the
T. pallidum
strains and subspecies and a strong, but relatively divergent connection between the human and rabbit pathogens.
Transgenic Mice Expressing Human Transferrin as a Model for Meningococcal Infection
Authors: Zarantonelli Maria-Leticia , Szatanik Marek , Giorgini Dario , Hong Eva , Huerre Michel , Guillou Florian , Alonso Jean-Michel , Taha Muhamed-Kheir
Published: September 2007

The pathogenesis of meningococcal disease is poorly understood due to the lack of a relevant animal model. Moreover, the use of animal models is not optimal as most meningococcal virulence determinants recognize receptors that are specifically expressed in human tissues. One major element of the host specificity is the system of meningococcal iron uptake by transferrin-binding proteins that bind specifically human transferrin but not murine transferrin. We developed a new mouse model for experimental meningococcal infection using transgenic mice expressing human transferrin. Intraperitoneal challenge of transgenic mice induced bacteremia for at least 48 h with an early stage of multiplication, whereas the initial inoculum was rapidly cleared from blood in wild-type mice. Inflammation in the subarachnoidal space with a high influx of polymorphonuclear cells was observed only in transgenic mice. Meningococcal mutants that were unable to use transferrin as a source of iron were rapidly cleared from both wild-type and transgenic mice. Thus, transgenic mice expressing human transferrin may represent an important advance as a new mouse model for in vivo studies of meningococcal virulence and immunogenicity factors.
AttenuatedCoxiella burnetiiPhase II Causes a Febrile Response in Gamma Interferon Knockout and Toll-Like Receptor 2 Knockout Mice and Protects against Reinfection
Authors: Ochoa-Repáraz Javier , Sentissi Jami , Trunkle Theresa , Riccardi Carol , Pascual David W.
Published: September 2007

Coxiella burnetiiis a highly infectious obligate intracellular bacterium. The phase I form is responsible for Q fever, a febrile illness with flu-like symptoms that often goes undiagnosed. The attenuatedC. burnetiiphase II (having a truncated “O” chain of its lipopolysaccharide) does not cause disease in immunocompetent animals; however, phase II organisms remain infectious, and we questioned whether disease could be produced in immunodeficient mice. To studyC. burnetiiphase II infections, febrile responses in gamma interferon knockout (IFN-γ−/−), BALB/c, Toll-like receptor 2 knockout (TLR2−/−), and C57BL/6 mice were measured using the Nine Mile phase II (NMII) strain ofC. burnetii. Immunocompetent mice showed minimal febrile responses, unlike those obtained with IFN-γ−/−and TLR2−/−mice, which showed elevated rectal temperatures that were sustained for ∼15 days with transient increases in splenic weights. Reinfection of IFN-γ−/−and TLR2−/−mice withC. burnetiiNMII 30 days after primary infection protected mice as evident by reduced febrile responses and a lack of splenic inflammation. Although minimal detection ofCoxiellain TLR2−/−mouse spleens was observed, greater colonization was evident in the IFN-γ−/−mice. Cytokine analysis was performed on infected peritoneal macrophages isolated from these mice, and immunocompetent macrophages showed robust tumor necrosis factor alpha, IFN-γ, and granulocyte-macrophage colony-stimulating factor (GM-CSF) but no interleukin-12 (IL-12) responses. IFN-γ−/−macrophages produced elevated levels of IL-6, IL-10, and IL-12, while TLR2−/−macrophages produced GM-CSF, IL-12, and minimal IL-10. To distinguish immunity conferred by innate or adaptive systems, adoptive transfer studies were performed and showed that immune lymphocytes obtained from immunocompetent mice protected against a subsequent challenge with NMII, indicating that adaptive immunity mediates the observed protection. Thus, our data show that NMII is capable of eliciting disease in immunocompromised mice, which may help in evaluation of vaccine candidates as well as the study of host-pathogen interactions.
Role of
Streptococcus gordonii
Surface Proteins SspA/SspB and Hsa in Platelet Function
Authors: Kerrigan Steven W. , Jakubovics Nicholas S. , Keane Ciara , Maguire Patricia , Wynne Kieran , Jenkinson Howard F. , Cox Dermot
Published: September 2007

Streptococcus gordonii
colonization of damaged heart surfaces in infective endocarditis is dependent upon the recognition of host receptors by specific bacterial surface proteins. However, despite several attempts to identify the mechanisms involved in this interaction, the nature of the bacterial proteins required remains poorly understood. This study provides clear evidence that several
S. gordonii
surface proteins participate in the interaction with platelets to support platelet adhesion and induce platelet aggregation.
S. gordonii
strains were found to support strong (DL1-Challis, SK12, SK184, and Blackburn) or moderate (UB1545 Δ
hsa
and CH1-Challis) adhesion or failed to support platelet adhesion (M5, M99, and Channon). In addition, under flow conditions, platelets rolled and subsequently adhered to immobilized
S. gordonii
at low shear (50 s
−1
) in an Hsa-dependent manner but did not interact with
S. gordonii
DL1 at any shear rate of >50 s
−1
.
S. gordonii
strains either induced (DL1-Challis, SK12, SK184, UB1545 Δ
hsa
, and M99) or failed to induce (M5, CH1-Challis, Channon, and Blackburn) platelet aggregation. Using a proteomic approach to identify differential cell wall protein expression between aggregating (DL1) and nonaggregating (Blackburn) strains, we identified antigen I/antigen II family proteins SspA and SspB. The overexpression of SspA or SspB in platelet-nonreactive
Lactococcus lactis
induced GPIIb/GPIIIa-dependent platelet aggregation similar to that seen with
S. gordonii
DL1. However, they failed to support platelet adhesion. Thus,
S. gordonii
has distinct mechanisms for supporting platelet adhesion and inducing platelet aggregation. Differential protein expression between strains may be important for the pathogenesis of invasive diseases such as infective endocarditis.
The Extracellular Signal-Regulated Kinase/Mitogen-Activated Protein Kinase Pathway Induces the Inflammatory Factor Interleukin-8 followingChlamydia trachomatisInfection
Authors: Buchholz Kerry R. , Stephens Richard S.
Published: September 2007

Diseases associated withChlamydiainfection, such as pelvic inflammatory disease and ectopic pregnancy, are due to inflammation-mediated tissue damage and scarring that occur after chronic or repeated infections. The inflammatory chemokine interleukin-8 (IL-8) is produced byChlamydia-infected cells through an endogenous mechanism of activation, independent of soluble factors in the supernatant. The host signaling pathways necessary for this response are not understood, but the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK) has been shown to be activated at similar times as IL-8 mRNA up-regulation. The purpose of this study was to elucidate the MAPK pathways necessary to induce the endogenous IL-8 response toChlamydia trachomatisinfection of epithelial cells. IL-8 induced by infection withC. trachomatisL2 was shown to be dependent on ERK and independent of p38 and Jun N-terminal MAPK by use of chemical inhibitors of the signaling pathways. Persistent ERK activation during IL-8 mRNA production at 24 h postinfection was necessary to maintain the response.C. trachomatisserovar D also induced IL-8 in an ERK-dependent manner. We concluded that IL-8 induced during infection of epithelial cells is dependent on continual activation of ERK byC. trachomatis.
Systematics of Vitaceae in South AmericaThis article is one of a selection of papers presented at the symposium onVitisat the XVII International Botanical Congress held in Vienna, Austria, in 2005.
Authors: Lombardi Julio Antonio
Published: September 2007

In South America, the family Vitaceae is represented by 65 species divided into 2 genera: Cissus contains 64 species, whereas Vitis consists of only 1 species. Recent studies on the Neotropical Cissus reveal that with regard to species delimitation, trichome types and the morphology of fruits and seeds are more important than the traditionally used trichome density and leaf shape. Fifteen provisional species groups are recognized for South America, excluding one species whose grouping is uncertain. Future research in this area should incorporate other data (e.g., anatomical, histological, and molecular) to identify a subgeneric division in Cissus.
An updated estimate of intergeneric phylogenetic relationships in the Australian VitaceaeThis article is one of a selection of papers presented at the symposium onVitisat the XVII International Botanical Congress held in Vienna, Austria, in 2005.
Authors: Rossetto Maurizio , Crayn Darren M. , Jackes Betsy R. , Porter Carolyn
Published: September 2007

Previous molecular studies have suggested that the genus Cissus (Vitaceae) is not monophyletic. The majority of species are grouped, but four Australian taxa ( Cissus antarctica Vent., Cissus hypoglauca A. Gray, Cissus oblonga (Benth.) Planch., and Cissus sterculiifolia (F. Muell. ex Benth.) Planch.) form a distinct clade and Cissus opaca has now been recognized as belonging to the genus Clematicissus ( Clematicissus opaca (F. Muell.) Jackes & Rossetto). Here, we investigate relationships among the Australian Vitaceae by parsimony and Bayesian analysis of plastid trnL-trnF and nuclear internal transcribed spacer sequences and include a range of taxa that had not been previously investigated. We find no support for a close relationship between Nothocissus and the four distinct Australian Cissus, as suggested in previous morphology-based treatments. We find a robust sister relationship between Clematicissus and at least two southern American Cissus ( Cissus tweediana (Baker) Planch. and Cissus striata Ruiz & Pav.), suggesting a possible origin from an ancient southern progenitor. Finally, this study confirms the paraphyletic nature of Cayratia , with species occurring in two clades, both with Australian and non-Australian species. The necessity in future studies for data from additional and more tractable nuclear loci is also noted.
Costa Rican species ofNematoctonus(anamorphic Pleurotaceae)
Authors: Koziak Alexandra T.E. , Diaz Felipe Chavarria , Diaz Joel , Garcia Maria , Janzen Daniel H. , Thorn R. Greg
Published: September 2007

Nematoctonus (Hyphomycetes) and Hohenbuehelia (Agaricales, Pleurotaceae) are the names for the asexual and sexual stages of a genus of nematode-destroying fungi (Basidiomycota). Six morphospecies of Nematoctonus, all previously described, were isolated from fruiting bodies of Hohenbuehelia and from 439 samples of soil and organic debris collected in all 12 Holdridge life zones in Costa Rica. Nematoctonus was recorded in all but three life zones at the lowest and highest altitudes: tropical dry forest, tropical moist forest, and subalpine rain paramó. Isolates of Nematoctonus were identified by the micromorphology of their conidia and adhesive knobs, which are usually an hourglass-shaped secretory cell surrounded by a drop of mucilage. Adhesive knobs were found either exclusively on hyphae in predatory species ( Nematoctonus robustus F.R. Jones), exclusively on germinated conidia in parasitoid species ( Nematoctonus leptosporus Drechsler, Nematoctonus pachysporus Drechsler, and Nematoctonus tylosporus Drechsler) or on both hyphae and germinated conidia in a group we term “intermediate predators” ( Nematoctonus angustatus Thorn & G.L. Barron, Nematoctonus geogenius Thorn & G.L. Barron, and one monokaryotic isolate of N. robustus). Teleomorph–anamorph connections, made by culturing the anamorph from a teleomorph fruiting body, were made for N. angustatus (Hohenbuehelia angustata (Berk.) Singer), N. geogenius (Hohenbuehelia petalodes (Fr.) Schulz.), N. leptosporus (an unidentified Hohenbuehelia), and N. robustus ( Hohenbuehelia grisea (Peck) Singer).
Evolution of the grapevine (Vitis viniferaL.) imprinted by natural and human factorsThis review is one of a selection of papers presented at the symposium onVitisat the XVII International Botanical Congress held in Vienna, Austria, in 2005.
Authors: Bessis Roger
Published: September 2007

This paper is concerned with vegetative reproduction, which is the only mode of propagation in cultivated grapevines. After a brief summary of the systematics of the Vitaceae the question of the nomenclature of cultivated grapevines is discussed. Intra-varietal variability is discussed using morphological and molecular characteristics. The origins of variation are presented: mutations, foreign nucleic acids, and memory of previous environmental conditions. Grapevines provide characteristic products, leading viticulturalists to make selections among the diversity observed in the vineyard, thus decreasing diversity. Grapevines interact with various environmental agents. One example, the natural defence provided by resveratrol, is analysed, showing its direct effects against parasitic fungi and its indirect effects, both metabolic and genetic, on other organisms. Thus, the grapevine, viticulturalists, and their environment form a web of biological interactions.
Phylogeny of Vitaceae based on the nuclearGAI1gene sequencesThis article is one of a selection of papers presented at the symposium onVitisat the XVII International Botanical Congress held in Vienna, Austria, in 2005.
Authors: Wen Jun , Nie Ze-Long , Soejima Akiko , Meng Ying
Published: September 2007

Phylogenetic analysis of 105 nuclear GAI1 sequences of Vitaceae provided a fairly robust phylogeny, largely congruent with the recently published chloroplast data of the family. In the GAI1 phylogeny, Cayratia Juss., Tetrastigma (Miq.) Planch., and Cyphostemma (Planch.) Alston form a clade. Cyphostemma and Tetrastigma are both monophyletic, and Cayratia is paraphyletic. Ampelopsis Michx is paraphyletic with the African Rhoicissus Planch. and the South American Cissus striata Ruiz & Pav. and its close relatives (e.g., Cissus simsiana Roem. & Schult.) nested within it. The pinnately leaved Ampelopsis forms a subclade, and the simple and palmately leaved Ampelopsis constitutes another subclade. All species of Cissus L. sampled from Asia, Africa, and Central and South America (except the C. striata complex) form a monophyletic group. Pterisanthes Blume of southeastern Asia forms a clade with the Asian Ampelocissus Planch. Vitis  L. is monophyletic and forms a larger clade with the tropical Ampelocissus and Pterisanthes . Parthenocissus Planch., forms a clade with Yua C.L. Li, with each genus reportedly monophyletic. Cissus from the Old World is paraphyletic with the neotropical core Cissus nested within it. The basal grade of Cissus consists of taxa from Africa. The African-Asian biogeographic relationships are complex, with several intercontinental disjunctions. The Northern Hemisphere Ampelopsis is most closely related to the South American C. striata complex and the African Rhoicissus .
Phylogenetic analyses of Nematoctonus and Hohenbuehelia (Pleurotaceae)
Authors: Koziak Alexandra T.E. , Cheng Kei Chin , Thorn R. Greg
Published: September 2007

Hohenbuehelia (Agaricales, Pleurotaceae) and Nematoctonus (Hyphomycetes) are the names for the sexual and asexual stages of a genus of nematode-destroying fungi (Basidiomycota). We obtained partial sequences of nuclear ribosomal DNA, including the internal transcribed spacer region and the 5′ end of the large subunit, of 37 isolates of Hohenbuehelia and Nematoctonus representing 13 of the 16 described species in Nematoctonus. Phylogenetic analyses support Hohenbuehelia–Nematoctonus as a monophyletic clade of the Pleurotaceae, within which the species were placed in five main subclades. Exclusively predatory species ( Nematoctonus brevisporus Thorn & G.L. Barron, Nematoctonus campylosporus Drechsler, Nematoctonus robustus F.R. Jones, and Nematoctonus sp. UAMH 5317) appear to be basal. In these species, adhesive knobs to capture prey are produced on their hyphae but not on their conidia. A single mycelial individual may feed on many nematodes. From these have arisen both exclusively parasitoid species ( Nematoctonus cylindrosporus Thorn & G.L. Barron, Nematoctonus leiosporus Drechsler, Nematoctonus leptosporus Drechsler, Nematoctonus pachysporus Drechsler, Nematoctonus tylosporus Drechsler), and species that we call intermediate predators ( Nematoctonus angustatus Thorn & G.L. Barron, Nematoctonus concurrens Drechsler, Nematoctonus geogenius Thorn & GL. Barron, Nematoctonus hamatus Thorn & G.L. Barron, and Nematoctonus subreniformis Thorn & G.L. Barron). Exclusively parasitoid species have conidia that germinate to form sticky knobs that attach to passing nematodes but lack adhesive knobs on the hyphae. Each mycelial individual feeds on only one nematode. Intermediate predators have adhesive knobs both on hyphae and on germinated conidia and can act in both predatory and parasitoid modes. Most morphospecies are resolved as monophyletic, but sequences of additional gene regions are required to clarify species limits within the N. angustatus – N. geogenius group.
State–space model for light-based tracking of marine animals
Authors: Nielsen Anders , Sibert John R
Published: September 2007

A coherent model is presented to estimate the most probable track of geographic positions directly from a series of light measurements. The model estimates two geographic positions per day, without reducing the daily light data to two threshold crossing times, its covariance structure is designed to handle high correlations due to for instance local weather conditions, and it can estimate the yearly pattern in latitudinal precision by propagating the data uncertainties through the geolocation process. The model is applied to one mooring study, one GPS drifter buoy study, and numerous simulated cases. The simulations are performed with realistic assumptions about the relationship between solar altitude and light and with realistic uncertainty parameters (all taken from real data). The simulations showed that all model parameters were identifiable, and that all tracks could be reconstructed within 1° or 2° latitude and 0.5° or 1° longitude. The mooring and drifter buoy data showed that the tracks could be reliably estimated, even in cases where the other methods had completely failed.
Slow dam passage in adult Columbia River salmonids associated with unsuccessful migration: delayed negative effects of passage obstacles or condition-dependent mortality?
Authors: Caudill Christopher C , Daigle William R , Keefer Matthew L , Boggs Charles T , Jepson Michael A , Burke Brian J , Zabel Richard W , Bjornn Theodore C , Peery Christopher A
Published: September 2007

The relationships among behavior, environment, and migration success in anadromous fishes are poorly understood. We monitored migration behavior at eight Columbia and Snake river dams for 18 286 adult Chinook salmon (Oncorhynchus tshawytscha) and steelhead (sea-run Oncorhynchus mykiss) over 7 years using radiotelemetry. When statistically controlling for variation in flow, temperature, fisheries take, and other environmental variables, we observed that unsuccessful individuals — those not observed to reach spawning areas — had longer passage times at nearly all dams than fish that eventually reached tributaries. In many cases, times were also longer for unsuccessful adults passing through a multiple-dam reach. Four ecological mechanisms may have contributed to these patterns: (i) environmental factors not accounted for in the analyses; (ii) inefficient responses by some fish to passage conditions at dams that resulted in slowed passage, energetic depletion, and unsuccessful migration; (iii) ongoing selection for traits needed to pass obstructions; and (or) (iv) passage rate was not directly linked to migration success, but rather, both resulted from relatively poor phenotypic condition upon river entry in unsuccessful migrants. Overall, these results illustrate the need for a mechanistic understanding of the factors that influence migration success and the need for fitness-based criteria to assess the effects of dams on anadromous fishes.
Regional trends in fish mean length at age: components of variance and the statistical power to detect trends
Authors: Wagner Tyler , Bence James R , Bremigan Mary T , Hayes Daniel B , Wilberg Michael J
Published: September 2007

We examined statewide time series (1940s–2002) of mean length at ages 2, 3, and 4 for seven fish species sampled from Michigan and Wisconsin inland lakes for temporal trends. We used a components of variance approach to examine how total variation in mean length at age was partitioned into lake-to-lake, coherent temporal, ephemeral temporal, trend, and residual variation. Using these estimated variance components, we simulated the effects of different variance structures on the power to detect trends in mean length at age. Of the 42 data sets examined, only four demonstrated significant regional (statewide) trends: age 4 largemouth bass (Micropterus salmoides) from Wisconsin lakes increased about 0.7 mm·year–1 in mean length at age, and ages 2, 3, and 4 walleye (Sander vitreus) from Wisconsin lakes decreased between 0.5 and 0.9 mm·year–1 in mean length at age. The structure of variation differed substantially among data sets, and these differences strongly affected the power to detect trends. Of particular note was that even modest levels of coherent temporal variation led to substantial decreases in power for detecting trends. To maximize trend detection capabilities, fisheries management agencies should consider variance structures prior to choosing indices for monitoring and realize that trend detection capabilities are species- and region-specific.
Simplification of seagrass food webs across a gradient of nutrient enrichment
Authors: Tewfik Alexander , Rasmussen Joseph B , McCann Kevin S
Published: September 2007

Anthropogenic nutrient enrichment has resulted in significant changes in food web structure. Although such changes have been associated with the loss of diversity and ecosystem services, little empirical work has been done to study food webs of similar systems across a nutrient enrichment gradient. We examined 11 seagrass beds along a gradient of increasing δ15N of primary consumers, where δ15N is used as an indicator of sewage-derived nutrients. Observations across this gradient revealed corresponding increases in consumer density and changes in distinct functional groups, whereas consumer diversity, seagrass canopy, and macrodetrital biomass decreased. However, maximum overall primary consumer diversity and minimum density occurred at intermediate levels along the nutrient gradient. We hypothesize that higher species diversity at low to moderate levels of nutrient enrichment depends on the persistence of grazer-resistant seagrass. This seagrass canopy, and the significant macrodetritus it generates, facilitates a variety of food and shelter resources. Overgrazed and simplified habitats may occur when densities of generalist urchins, capable of direct producer consumption, are no longer controlled through competition, predation, and intraguild predation. We hypothesize that high and stable urchin populations appear possible with the increased availability of allochthonous phytoplankton and associated particulate detritus that is a well-known consequence of nutrient enrichment in aquatic systems.