bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics and Control of Adaptive Nonlinear Piezothermoelastic Structures With Coupled Electric, Thermal and Mechanical Fields: A Finite Element Approach
Authors: Tzou H. S. , Wang D. W.
Published: May 2008

Piezoelectric sensors and actuators are widely used in smart structures, mechatronic and structronic systems, etc. This paper is to investigate the dynamics and control of nonlinear laminated piezothermoelastic shell structures subjected to the combined mechanical, electrical, and thermal excitations by the finite element method. Governing relations of nonlinear strain-displacement, electric field-electric potential, and temperature gradient-temperature field for a piezothermoelastic shell are presented in a curvilinear coordinate system. Based on the layerwise constant shear angle theory, a generic curved triangular laminated piezothermoelastic shell element is developed. Generic nonlinear finite element formulations for vibration sensing and control analysis of laminated piezoelectric shell structures are derived based on the virtual work principle. Dynamic system equations, equations of electric potential output, and feedback control force are derived and discussed. The modified Newton-Raphson method is used for efficient nonlinear dynamic analysis of complex nonlinear piezoelectric/elastic/control structural systems. For vibration sensing and control, various control algorithms are implemented. The developed nonlinear piezothermoelastic shell element and finite element code are validated and applied to analysis of nonlinear flexible structronic systems. Vibration sensing and control of constant/non-constant curvature piezoelectric shell structures are studied. Thermal effect to static deflection, dynamic response, and control is investigated.
Processing Characteristics of Layered Silicate Nanocomposites With Application to Blown Film
Authors: Dirama Taner E. , Goettler Lloyd A.
Published: May 2008

The aim of this study is to investigate the film blowing processing of various polyamide 6-based layered silicate nanocomposites (LSN’s) and to correlate their processing behaviors to the underlying rheology and structure. In-situ polymerized nanocomposites were found to possess a wider processing window compared to the base PA6. Shear and dynamic rheological measurements were employed to correlate the rheological behavior of the nanocomposites to the bubble formation and stability in the film blowing process. The in-situ plymerized LSN melts having higher elastic modulus (G′) were found to perform better in the film blowing process. DSC measurements indicated that nanoclays induce the γ type of crystallinity, which may also play a role in film blowing behavior.
Multi-Input Multi-Output Modal Testing Techniques for a Gossamer Structure
Authors: Ruggiero Eric , Park Gyuhae , Inman Daniel J. , Wright Jan
Published: May 2008

Inflated space-based structures have become popular over the past three decades due to their minimal launch-mass and launch-volume. Once inflated, these space structures are subject to vibrations induced by guidance systems and space debris as well as from variable amounts of direct sunlight. Understanding the dynamic behavior of space-based structures is critical to ensuring their desired performance. Inflated materials, however, pose special problems when testing and trying to control their vibrations because of their lightweight, flexibility, and high damping. Traditional modal testing techniques, based on single-input, single-output (SISO) methods, are limited for a variety of reasons when compared to their multiple counterparts. More specifically, SISO modal testing techniques are unable to reliably distinguish between pairs of modes that are inherent to axi-symmetric structures (such as an inflated torus, a critical component of a gossamer spacecraft). Furthermore, it is questionable as to whether a single actuator could reliably excite the global modes of a true gossamer craft, such as a 25 m diameter torus. In this study, we demonstrate the feasibility of using a multiple-input multiple-output (MIMO) modal testing technique on an inflated torus. In particular, the refined modal testing methodology focuses on using Macro-Fiber Composite (MFC®) patches (from NASA Langley Research Center) as both actuators and sensors. MFC® patches can be integrated in an unobtrusive way into the skin of the torus, and can be used to find a gossamer structure’s modal parameters. Furthermore, MFC® excitation produces less interference with suspension modes of the free-free torus than excitations from a conventional shaker. The use of multiple actuators is shown to properly excite the global modes of the structure and distinguish between pairs of modes at nearly identical resonant frequencies. Formulation of the MIMO test as well as the required postprocessing techniques are explained and successfully applied to an inflated Kapton® torus.
Design of a Functionally Binary Pinned-Pinned Segment for Use as a Tension-Compression Spring in Compliant Micro Mechanisms
Authors: Wittwer Jonathan W. , Howell Larry L.
Published: May 2008

As mechanisms approach the micro scale, manufacture and assembly of linear coil springs becomes nearly impossible. For this reason, compliant functionally binary pinned-pinned segments are frequently used in place of them. A new pseudo-rigid-body model (PRBM) is presented for circular functionally binary pinned-pinned (FBPP) segments that undergo large, nonlinear deflections for both tension and compression. A new method of evaluating the maximum moment in the beam is presented, called the focal moment method, which significantly increases the accuracy of the force for a given displacement. This paper also shows how some FBPP segments can be modeled as simple linear tension/compression springs. The deflection limits for a given maximum error can be determined analytically, thereby making it possible to use optimization algorithms in the design of these springs. The effect of the size of the rigid pin joints is also discussed.
Strain and Current Responses During Electron Flux Excitation of Piezoelectric Ceramics
Authors: Hadinata Philip C. , Main John A.
Published: May 2008

The electric field induced strain in piezoelectric materials subjected to an electron flux is examined in this paper. An analysis using quantum mechanics indicates that stable and controllable strains with very low current draw should be achievable over a range of positive and negative control potentials. The model also predicts an instability in the internal electric field at larger negative potentials. The model was evaluated by observing the strain output of PZT5h plates subjected to an electron flux on one face and voltage inputs from a single electrode on the opposite face. The strain response and current flow were measured as a function of electrode potential and electron energy. All of the significant predictions of the model were verified by the experimental results. Further experiments were performed to examine the time response of the strain induced in the plate. It was found that the location and potential of the electron collector dramatically influences the dynamic response of the system.
Topology Optimization of Constrained Damping Layer Treatments
Authors: Lumsdaine Arnold
Published: May 2008

The aim of this research is to determine the optimal shape of a constrained viscoelastic damping layer on an elastic beam by means of topology optimization. The optimization objective is to maximize the system loss factor for the first resonance frequency of the base beam. All previous optimal design studies on viscoelastic lamina have been size or shape optimization studies, assuming a certain topology for the damping treatment. In this study, this assumption is relaxed, allowing an optimal topology to emerge. The loss factor is computed using the Modal Strain Energy method in the optimization process. Loss factor results are validated by using the half-power bandwidth method, which requires obtaining the forced response of the structure. The ABAQUS finite element code is used to model the structure with two-dimensional continuum elements. The optimization code uses a Sequential Quadratic Programming algorithm. Results show that significant improvements in damping performance, on the order of 100% to 300%, are obtained by optimizing the constrained damping layer topology. A novel topology for the constraining layer emerges through the optimization process.
The Manufacture of NiTi Foams
Authors: Shaw John A. , Gremillet Antoine , Grummon David S.
Published: May 2008

Ongoing research is presented on processing of NiTi-based shape memory alloy (SMA) foams. The aim is to demonstrate a new class of materials that combine the advantages of light-weight metallic foams with the strain recovery and energy-dissipation capability of SMAs. There are a number of potential novel structural and biomedical applications that could be enabled by the unusual passive and active properties of such a material. This paper presents initial results on our attempt to fabricate functional prototype specimens using a polymeric foam precursor and a powder metallurgy process to produce NiTi foams with user-selected topology and relative density. It is shown that open-cell NiTi foams with relative density less than 5% can be produced with this technique. While definite martensitic transformational behavior has been achieved in the prototypes, the quality of the foams are found to be sensitive to the sintering temperature, the binder system employed, and the levels of interstitial contamination. Further work is needed before good superelastic and shape-memory properties can be demonstrated. Nevertheless, the current technique appears promising, since the method is capable of producing NiTi foam with a more regular structure and at a relative density nearly an order of magnitude less than other techniques currently used to produce porous NiTi.
Numerical Modeling of Formation of High-Speed Water Slugs
Authors: Petrenko O. , Geskin E. S. , Atanov G. A. , Semko A. , Goldenberg G. A. B.
Published: May 2008

The objective of this study is to investigate the phenomena that occur in the course of energy injection into water at an extremely high rate. In this study energy was injected via the powder explosion. In the course of this study a numerical model was constructed and used for process investigation. The model describes powder combustion, energy exchange between combustion products and the water load, formation of the shock waves in the water and superposition of waves. It was assumed that powder combustion is a stationary process, and the description of this process was used to determine the variation of the pressure exerted on the water. The 1D space approximation was used for description of the dynamics of the water motion. The velocity and pressure fields were determined for a fixed instant of time. The characteristic method was used to relate the velocity and pressure distributions in the instants t and t+Δt. The pressure, velocity and density fields in the course of slug formation were calculated and used to evaluate the design characteristics of the device for water acceleration termed the water cannon.
Effect of Moisture Absorption on Mechanical Properties of Resin Transfer Molded Composites
Authors: Aktas Levent , Hamidi Youssef , Altan M. Cengiz
Published: May 2008

Fiber reinforced polymer composites are highly susceptible to environmental conditions despite their favorable properties. Among various environmental factors, moisture absorption is known to have significant adverse effects on such materials. This work investigates the effects of accelerated moisture absorption on the mechanical properties of resin transfer molded glass/epoxy composites. 152.4 mm diameter disk-shaped parts are fabricated using EPON 815C resin and EPICURE 3282 curing agent. Reinforcement is provided by four layers of randomly oriented planar glass fiber preforms with 0.459 kg/m2 surface density, yielding approximately 21.2% fiber volume fraction. Samples cut from the molded disks are immersed into boiling water for accelerated aging. The masses of the specimens are measured at periodic intervals to quantity the amount of water absorbed. Tensile and short beam shear tests are performed at different levels of moisture absorption. Mechanical properties are found to decrease as moisture diffused into the material. Fiber pullouts on the surfaces of tested samples show fiber loosening as the cause of material weakening. To investigate the desorption and characteristics, part of the samples are dried at 65°C after the maximum moisture absorption is reached. Total stiffness recovery is observed after desorption but ultimate tensile strenth only recovered by 27.7%, which is 33.4% lower than the initial value.
Simulation Model of an Axial Piston Pump Inclusive of Cavitation
Authors: Berta G. L. , Casoli P. , Vacca A. , Guidetti M.
Published: May 2008

A mathematical model of an axial piston pump is presented. The numerical model is based on a finite volume concept. The pump has been divided in different volumes where fluid properties are assumed homogeneous. Since the reduction of the pressure pulsations is one of the most important aims of pump builders, the effects of the port plate relief groove design have been carefully modelled. The gaseous cavitation has been considered in a simplified manner. The pump has been modified in order to measure the fluid pressure inside one of the cylinders; therefore a conduit has been realized to connect the cylinder chamber to a pressure transducer that is placed in a non-rotating position. The fluid pressure inside the conduit has been modelled with a one dimensional scheme for unsteady flow. The code has been tested and calibrated by comparing its numerical results with a set of experimental data. The potentials of the code are presented, spanning over different geometries.
Torque Control of a Water Hydraulic Vane Actuator Using Pressure Feedback
Authors: Raneda Albert , Siuko Mikko , Virvalo Tapio
Published: May 2008

In this paper the torque control properties of a water hydraulic rotary actuator are theoretically and experimentally studied and the results are analyzed and compared with oil hydraulics. If the same performance levels can be achieved with water and oil hydraulics, water as the pressure medium is preferred in applications where external oil leakage is not allowed or applications that take place in fire hazardous environments. The analysis carried out in this paper uses a linear model of the hydraulic drive which is first verified against experimental tests. The linear model allows to study the effect of valve saturation and the effect of using pressure transducers for torque feedback in torque control applications. Two torque control cases are studied: torque control with the boom end in a fixed location and boom end free to move with desired torque set to zero (backdrivable system). Experimental results are presented and compared with simulated results. Results show that in torque control applications, the use of water as the pressure medium does not cause any special control problems and a similar performance than with oil is obtained. Also, pressure sensors can be used for providing torque feedback without causing significant problems.
Practical Implementation of a Dead Zone Inverse on a Hydraulic Wrist
Authors: Fortgang Joel D. , George Lynnane E. , Book Wayne J.
Published: May 2008

This paper presents practical aspects of implementing a dead zone inverse on a hydraulic wrist. A dead zone occurs over a range of small input values for which a system does not respond. It was desirable to use the most straightforward method available to achieve improved system performance while requiring the least amount of modification to the controller. Thus a fixed parameter dead zone inverse (DZI) was added to an existing proportional-integral (PI) controller. First, the parameters of the dead zone were characterized from open loop testing. These parameters are the break points, or input values between which the system does not respond at all, and the slope of the system’s response just outside the break points. The DZI augments the PI signal input to the plant, effectively adding or subtracting a constant equal to the size of the dead zone break points and scaling the input by its slope. Simulations predicted perfect system tracking, but implementation on the hardware revealed several practical issues. First, the dead zone slope parameters vary throughout the robot’s workspace. Overestimation can lead to non-ideal system performance, but the more extreme problem is underestimation, which effectively increases control loop gain and can lead to system instability. However, performance is not affected significantly unless these parameters are off by an order of magnitude. Overall the system performance is relatively robust to modeling errors in the slope parameters. The second issue is that noise can be magnified by the dead zone inverse and cause chattering. This problem was very noticeable in the wrist when the estimated dead zone break points were used in the DZI. This problem can be eliminated by reducing the dead zone break points or reintroducing a small artificial dead zone back into the control loop to envelope the expected noise level. The requirements for successful implementation of the DZI were found to be a basic characterization of the dead zone and an understanding of practical system issues that can be accentuated by its use. The effectiveness of the technique was tested through simulations and experiments on the wrist.
The Variable Structure Filter
Authors: Habibi S. R. , Burton R.
Published: May 2008

This paper presents a new strategy for estimation of state variables. The strategy may be applied to linear systems and is referred to as the Variable Structure Filter. The filter is considered for discrete-time systems subject to random disturbances and measurement noise. A proof of stability for the filter is provided. For stability, this filtering concept requires a specification of an upper bound for the random disturbances and measurement noise. The filter requires a parametric model and can be formulated to accommodate model uncertainties. The application of this filter to a third order linear system is demonstrated.
Turbulent Natural Convection in Enclosures With Clear Fluid and Completely Filled With Porous Material
Authors: Braga Edimilson J. , de Lemos Marcelo J. S.
Published: May 2008

Steady laminar and turbulent natural convection in a two-dimensional square cavity, isothermally heated from the left side and cooled from the opposing side, is numerically analyzed using the finite volume method. Benchmark results for laminar and turbulent flows are compared with similar numerical solutions in the literature. The cases of clear and porous media are considered. Governing equations are written in terms of primitive variables and are recast into a general form. The effects of Rayleigh number on flow pattern and energy transport are investigated for Ra ranging from 103 to 1010 for clear media and 101 to 106 for porous media. The turbulence model used was the standard k–ε along with the wall function approach. All results presented herein showed reasonable agreement with calculations presented in the literature. Critical values for the Rayleigh number for the onset of turbulence are suggested. The main objective of this work is to validate a numerical tool for simulating turbulent natural convection in both clear and porous media.
A Heuristic Thermodynamic Interpretation of a Mechanism Responsible for the Selection of Solidification Microstructures
Authors: Sekulic Dusan P.
Published: May 2008

This paper offers a heuristic thermodynamic analysis of the selection of solidification microstructures formed during re-solidification of micro layers of molten metal driven by surface tension. This study explores empirical evidence obtained by performing a tightly controlled heating-dwell-cooling materials processing cycle that causes melting followed by re-solidification of micro layers of an Al + Si alloy in ultra high purity nitrogen. Identification of characteristic process parameters responsible for crystal pattern formation of the α-phase solid solution during associated rapid quench is discussed. The focus of the inquiry is ultimately directed toward solid solution dendrites population morphology. A transition from a scarce (even single or non existent) dendrite formation toward chaotically distributed α-phase dendrites imbedded in two-phase eutectic is identified. A heuristic approach has been established to interpret alpha phase dendrite pattern formation during solidification phenomena driven by entropy generation at the liquid-solid interfaces.
Predicting Human Brain Activity Associated with the Meanings of Nouns
Authors: Mitchell Tom M. , Shinkareva Svetlana V. , Carlson Andrew , Chang Kai-Min , Malave Vicente L. , Mason Robert A. , Just Marcel Adam
Published: May 2008

The question of how the human brain represents conceptual knowledge has been debated in many scientific fields. Brain imaging studies have shown that different spatial patterns of neural activation are associated with thinking about different semantic categories of pictures and words (for example, tools, buildings, and animals). We present a computational model that predicts the functional magnetic resonance imaging (fMRI) neural activation associated with words for which fMRI data are not yet available. This model is trained with a combination of data from a trillion-word text corpus and observed fMRI data associated with viewing several dozen concrete nouns. Once trained, the model predicts fMRI activation for thousands of other concrete nouns in the text corpus, with highly significant accuracies over the 60 nouns for which we currently have fMRI data.
Response to Comment on "Mixed-Layer Deepening During Heinrich Events: A Multi-Planktonic Foraminiferal δ
18
O Approach"
Authors: Rashid Harunur , Boyle Edward A.
Published: May 2008

Hillaire-Marcel and de Vernal question our hypothesis of the “homogenization of the upper water masses” of the North Atlantic during Heinrich events 0, 1, and 4. Here, we respond to their specific points and synthesize data from the southern Labrador Sea cores, the basic tenet of Hillaire-Marcel and de Vernal's arguments.
Ancestral Monogamy Shows Kin Selection Is Key to the Evolution of Eusociality
Authors: Hughes William O. H. , Oldroyd Benjamin P. , Beekman Madeleine , Ratnieks Francis L. W.
Published: May 2008

Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry (>2 effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory.
Development of an Immunofluorescence Assay Using Recombinant Proteins Expressed in Insect Cells To Screen and Confirm Presence of Human Herpesvirus 8-Specific Antibodies
Authors: Minhas Veenu , Crosby Lynsey N. , Crabtree Kay L. , Phiri Saul , M'soka Tendai J. , Kankasa Chipepo , Harrington William J. , Mitchell Charles D. , Wood Charles
Published: May 2008

Human herpesvirus 8 (HHV-8), or Kaposi's sarcoma (KS)-associated herpesvirus, has been linked to all forms of KS. The results of most current serological assays for the detection of HHV-8-specific antibodies have low levels of concordance among themselves. To establish a sensitive and specific testing strategy that can be used to screen for HHV-8-specific antibodies, three HHV-8 proteins, ORF65, ORF73, and K8.1A, were expressed by using baculoviral vectors in insect cells and incorporated into a monoclonal antibody-enhanced immunofluorescence assay (mIFA) termed the Sf9 three-antigen mIFA. The results obtained by this mIFA were compared to those obtained by a standard mIFA with an HHV-8-infected B-cell line (BC3 mIFA). Test sera were obtained from patients diagnosed with KS, human immunodeficiency virus type 1-infected patients at high risk for HHV-8 infection, and healthy controls from a local blood bank. The combined use of both assays had a sensitivity of 94% and a specificity of 96%. The performance of these two assays when they were used together indicates that they may be useful for the reliable detection of HHV-8-specific immunoglobulin G antibodies in a population.
Molecular Epidemiology of Methicillin-Resistant
Staphylococcus aureus
Bloodstream Isolates in Urban Detroit
Authors: Chua Thea , Moore Carol L. , Perri Mary B. , Donabedian Susan M. , Masch William , Vager Dora , Davis Susan L. , Lulek Kaitlin , Zimnicki Benjamin , Zervos Marcus J.
Published: May 2008

To gain a better understanding of epidemiology of resistance in
Staphylococcus aureus
, we describe the molecular epidemiology of methicillin-resistant
Staphylococcus aureus
bloodstream isolates in urban Detroit. Bloodstream isolates from July 2005 to February 2007 were characterized. Two hundred ten bloodstream isolates from 201 patients were evaluated. Patient characteristics were as follows: median age, 54 years; 56% male; and 71% African-American. Seventy-six percent of infections were health care associated, with 55% being community-onset infections and 21% hospital acquired, and 24% were community associated. The most common sources were skin/wound (25%), central venous catheters (24%), unknown source (20%), and endocarditis (9%). Ninety percent and 5% of isolates had a MIC of vancomycin of ≤1.0 mg/liter, using automated dilution testing and E-test, respectively. Six percent of isolates showed heteroresistance to vancomycin, all occurring with isolates having a vancomycin E-test MIC of ≥1.5 mg/liter. Results of pulsed-field gel electrophoresis showed 17 strain types. The predominant strains were USA100 (104 isolates) and USA300 (74 isolates). Forty-nine percent of the isolates had staphylococcal cassette chromosome
mec
II, and 56% had
agr
II. All USA300 isolates were positive for the Panton-Valentine leukocidin toxin genes and
agr
I. Forty-seven percent of USA300 bloodstream infections were health care associated (35% community onset and 12% hospital onset). USA300 strains were more common in injection drug users with skin/wound as the predominant source of infection. Thirty percent of the USA100 strains were closely related to vancomycin-resistant
Staphylococcus aureus
isolates. The results of this study show that vancomycin MICs using automated dilution testing with Vitek-2 and E-test were highly discordant. Most methicillin-resistant
S. aureus
strains causing bacteremia are health care associated, commonly have MICs of vancomycin that are high within the susceptible range are not detected by routine automated dilution testing, and have significant diversity of molecular characteristics. USA100 strains that are closely related to vancomycin-resistant
S. aureus
(VRSA) isolates and USA300 strains are common as causes of both hospital and community-onset infection. Infection control measures should focus not only on prevention of the spread of community strains in the hospital but also prevention of the spread of hospital strains associated with VRSA into the community.
Identification of a Novel
Babesia
sp. from a Sable Antelope (
Hippotragus niger
Harris, 1838)
Authors: Oosthuizen Marinda C. , Zweygarth Erich , Collins Nicola E. , Troskie Milana , Penzhorn Banie L.
Published: May 2008

Babesiosis in a sable antelope (
Hippotragus niger
Harris, 1838) was first reported in 1930; the parasite was named
Babesia irvinesmithi
. Recently, specimens from an adult sable that presented with a sudden onset of disease and that subsequently died during immobilization were submitted for molecular characterization. Microscopic examination of thin blood smears revealed the presence of small piroplasms. DNA was extracted from blood samples; the V4 variable region of the 18S rRNA gene was amplified and analyzed using the reverse line blot (RLB) assay. Amplicons did not hybridize with any of the
Babesia
or
Theileria
species-specific probes present on the blot and hybridized only with a
Babesia
or
Theileria
genus-specific probe, suggesting the presence of a novel species. The full-length 18S rRNA gene sequence was obtained and aligned with published sequences of related genera, and phylogenetic trees were constructed. Sequence similarity analyses indicated that a
Babesia
species, designated
Babesia
sp. (sable), was present. The sequence showed its highest similarity to
B. orientalis
and to an unnamed
Babesia
species previously detected in bovine samples. The latter was later established to be
Babesia occultans
. A
Babesia
sp. (sable)-specific RLB oligonucleotide probe was designed and used to screen 200 South African sable samples, but so far, no other sample has been found to be positive for the presence of
Babesia
sp. (sable) DNA. In summary, we identified a novel piroplasm parasite from a sable antelope that died from an unknown illness. While the parasite was observed in blood smears, there is no direct evidence that it was the cause of death.
Distribution, Organization, and Ecology of Bacteria in Chronic Wounds
Authors: Kirketerp-Møller Klaus , Jensen Peter Ø. , Fazli Mustafa , Madsen Kit G. , Pedersen Jette , Moser Claus , Tolker-Nielsen Tim , Høiby Niels , Givskov Michael , Bjarnsholt Thomas
Published: May 2008

Between 1 and 2% of the population in the developed world experiences a nonhealing or chronic wound characterized by an apparent arrest in a stage dominated by inflammatory processes. Lately, research groups have proposed that bacteria might be involved in and contribute to the lack of healing of these wounds. To investigate this, we collected and examined samples from chronic wounds obtained from 22 different patients, all selected because of suspicion of
Pseudomonas aeruginosa
colonization. These wound samples were investigated by standard culturing methods and peptide nucleic acid-based fluorescence in situ hybridization (PNA FISH) for direct identification of bacteria. By means of the culturing methods,
Staphylococcus aureus
was detected in the majority of the wounds, whereas
P. aeruginosa
was observed less frequently. In contrast, using PNA FISH, we found that a large fraction of the wounds contained
P. aeruginosa
. Furthermore, PNA FISH revealed the structural organization of bacteria in the samples. It appeared that
P. aeruginosa
aggregated as microcolonies imbedded in the matrix component alginate, which is a characteristic hallmark of the biofilm mode of growth. The present investigation suggests that bacteria present within these wounds tend to be aggregated in microcolonies imbedded in a self-produced matrix, characteristic of the biofilm mode of growth. Additionally, we must conclude that there exists no good correlation between bacteria detected by standard culturing methods and those detected by direct detection methods such as PNA FISH. This strongly supports the development of new diagnostic and treatment strategies for chronic wounds.
Biological and Molecular Characteristics of
Mycobacterium tuberculosis
Clinical Isolates with Low-Level Resistance to Isoniazid in Japan
Authors: Abe Chiyoji , Kobayashi Ikuo , Mitarai Satoshi , Wada Masako , Kawabe Yoshiko , Takashima Tetsuya , Suzuki Katsuhiro , Sng Li-Hwei , Wang Suxing , Htay Hla Hla , Ogata Hideo
Published: May 2008

We reevaluated the BACTEC MGIT 960 antimicrobial susceptibility testing system (MGIT 960 AST) by using 1,112 isolates of
Mycobacterium tuberculosis
. When the results of MGIT 960 AST were compared with that of the proportion method using Ogawa medium (Ogawa PM), discrepant results were obtained for 30 strains with isoniazid, all resistant by MGIT 960 AST but susceptible by Ogawa PM. For 93% of the strains that produced discrepant results, the MIC was 0.4 or 0.8 μg/ml, showing resistance by the proportion method using Middlebrook agar plates. Furthermore, it was also established by analyses of the
katG
and
inhA
genes that strains resistant only by MGIT 960 AST have a low level of isoniazid (INH) resistance, indicating that MGIT 960 AST is a reliable method. Ninety-six strains were resistant to 0.1 μg/ml INH by MGIT 960 AST. When they were divided into three groups, Low-S (susceptible at 0.2 μg/ml), Low-R (resistant at 0.2 μg/ml), and High-R (resistant at 1.0 μg/ml), by Ogawa PM, 43.3% of the Low-S strains had mutations in the promoter region of
inhA
and no mutations were detected in
katG
codon 315, while 61.7% of the High-R strains had
katG
codon 315 mutations or a gross deletion of
katG
. These results suggest that mutations in
inhA
are associated with low-level resistance to INH and
katG
codon 315 mutations are associated with high-level resistance to INH. In addition, the analyses demonstrated some relationship of mutations in the
inhA
gene with ethionamide resistance for the Low-S strains, but not for the High-R strains.
Molecular Characterization of Porcine Picobirnaviruses and Development of a Specific Reverse Transcription-PCR Assay
Authors: Carruyo Gabriela M. , Mateu Guaniri , Martínez Laura C. , Pujol Flor H. , Nates Silvia V. , Liprandi Ferdinando , Ludert Juan E.
Published: May 2008

The molecular characterization of partial- length genomic segment 2 of porcine picobirnavirus (PBV) strains and the development of a specific reverse transcription-PCR (RT-PCR) assay for detection of virus in feces are reported. Phylogenetic analysis indicated that the studied porcine isolates were more closely related (>85% identity) to human PBV belonging to genogroup I than to the other porcine PBV described so far. Analysis by RT-PCR and polyacrylamide gel electrophoresis of fecal samples collected in Venezuela and Argentina showed that PBV circulate at high frequencies in piglets.
Genetic Diversity and Zoonotic Potential ofCryptosporidium parvumCausing Foal Diarrhea
Authors: Grinberg A. , Learmonth J. , Kwan E. , Pomroy W. , Lopez Villalobos N. , Gibson I. , Widmer G.
Published: May 2008

Cryptosporidiumisolates from diarrheic foals in New Zealand (n= 9) were identified asC. parvum, subtyped at two polymorphic loci, and compared with human (n= 45) and bovine (n= 8) isolates. FoalC. parvumisolates were genetically diverse, markedly similar to human and bovine isolates, and carried GP60 IIaA18G3R1 alleles, indicating a zoonotic potential.
Reovirus Serotypes Elicit Distinctive Patterns of Recall Immunity in Humans
Authors: Douville Renée N. , Su Ruey-Chyi , Coombs Kevin M. , Simons F. Estelle R. , HayGlass Kent T.
Published: May 2008

Mammalian orthoreoviruses (reoviruses) are ubiquitous viral agents that infect cells in respiratory and enteric tracts. The frequency and nature of human cellular immunoregulatory responses against reovirus are unknown. Here we establish systems to detect and quantify reovirus-induced cytokine and chemokine recall responses using primary cultures of virus-infected peripheral blood mononuclear cells (PBMC) and two widely used reovirus serotypes, type 1 Lang (T1L) and type 3 Dearing (T3D) reexposure in vitro. In cultures from 44 healthy adults, reovirus induced exceptionally strong CD4 and CD8 T-cell-dependent gamma interferon (IFN-γ) recall responses concomitant with intense interleukin 10 (IL-10) production. These responses were elicited independently of viral replication. Surprisingly, paired analyses of subject responses to these two common serotypes revealed that while both elicit intense Th1-dominated immunity, median T3D-driven responses were 2.2-fold weaker (P= 0.0004) than those elicited by T1L. Recall responses evoked by these viral serotypes differed markedly in their mechanism of regulation. T3D IL-10 and IFN-γ responses were CD4 and CD8 dependent and blocked by interfering with CD86 costimulation but were CD80 independent. T1L responses were consistently CD28 and CD80/86 independent. Thus, despite extensive genetic and morphological similarities between reovirus serotypes, the nature and intensity of the human recall responses as well as the control mechanisms regulating them are clearly distinct.
Dysregulation of TLR3 Impairs the Innate Immune Response to West Nile Virus in the Elderly
Authors: Kong Kok-Fai , Delroux Karine , Wang Xiaomei , Qian Feng , Arjona Alvaro , Malawista Stephen E. , Fikrig Erol , Montgomery Ruth R.
Published: May 2008

West Nile virus (WNV), a mosquito-borne flavivirus, has recently emerged in North America, and the elderly are particularly susceptible to severe neurological disease and death from infection with this virus. We have investigated the innate immune response of primary human macrophages to WNV in vitro and have found significant differences between the responsiveness of macrophages derived from younger donors and that from older donors. Binding of the glycosylated WNV envelope protein to the C-type lectin dendritic cell-specific intercellular adhesion molecule 3 (ICAM3) grabbing nonintegrin (DC-SIGN) leads to a reduction in the expression of Toll-like receptor 3 (TLR3) in macrophages from young donors via the signal transducer and activator of transcription 1 (STAT1)-mediated pathway. This signaling is impaired in the elderly, and the elevated levels of TLR3 result in an elevation of cytokine levels. This alteration of the innate immune response with aging may contribute to the permeability of the blood-brain barrier and suggests a possible mechanism for the increased severity of WNV infection in older individuals.
Dengue Virus Replicon Expressing the Nonstructural Proteins Suffices To Enhance Membrane Expression of HLA Class I and Inhibit Lysis by Human NK Cells
Authors: Hershkovitz Oren , Zilka Alon , Bar-Ilan Ahuva , Abutbul Shai , Davidson Andrew , Mazzon Michela , Kümmerer Beate M. , Monsoengo Alon , Jacobs Michael , Porgador Angel
Published: May 2008

Many viruses escape the cellular immune response by downregulating cell surface expression of major histocompatibility complex (MHC) class I molecules. However, infection of cells with flaviviruses can upregulate the expression of these molecules. In this study we analyzed the expression of MHC class I in K562 and THP-1 human cell lines that were stably transfected with self-replicating subgenomic dengue virus RNA (replicons) and express all the dengue virus nonstructural proteins together. We show that MHC class I expression is upregulated in the dengue virus replicon-expressing cells and that the binding of natural killer (NK) inhibitory receptors to these cells is augmented. This upregulation results in reduced susceptibility of the dengue virus replicon-expressing cells to NK lysis, indicating a possible mechanism for evasion of the dengue virus from NK cell recognition. Visualizing MHC class I expression in replicon-containing K562 and THP-1 cells by confocal microscopy demonstrated aggregation of MHC class I molecules on the cell surface. Finally, replicon-expressing K562 cells manifested increased TAP (transporter associated with antigen processing) and LMP (low-molecular-mass protein) gene transcription, while replicon-expressing THP-1 cells manifested increased NF-κB activity and MHC class I transcription. We suggest that expression of dengue virus nonstructural proteins is sufficient to induce MHC class I upregulation through both TAP-dependent and -independent mechanisms. Additionally, aggregation of MHC class I molecules on the cell membrane also contributes to significantly higher binding of low-affinity NK inhibitory receptors, resulting in lower sensitivity to lysis by NK cells.
“Living apart together”: moral frictions between two coexisting organ transplantation schemes
Authors: Hilhorst M T
Published: May 2008

Cadaveric transplantation and living transplantation exist side by side. Both practices help to alleviate organ need. They provide us with two separate moral schemes. Is it rational to keep them apart? The cadaveric system is organised along strict, impartial lines, while the living system is inherently partial and local. The ethical justification for this partial scheme seems to be that it merely supplements the cadaveric scheme: partial transplants do not come at the expense of cadaveric impartiality, but in fact significantly reduce the waiting time for patients on the list for a cadaveric transplant.

This seemingly peaceful coexistence is challenged by new initiatives, among them living donation list exchange, and also the LifeSharers initiative, leading to practices that undermine cadaveric impartiality. Should we bemoan this fact, or should we move on towards a new balance in the relationship between cadaveric and living transplantation practices, towards a new moral weighing of impartial and partial values? I argue, against the background of a rapid growth of living donations, that we have good, ethical reasons—not only utilitarian ones—for giving the value of partiality a more prominent place in our policies.
“Eugenics talk” and the language of bioethics
Authors: Wilkinson S
Published: May 2008

In bioethical discussions of preimplantation genetic diagnosis and prenatal screening, accusations of eugenics are commonplace, as are counter-claims that talk of eugenics is misleading and unhelpful. This paper asks whether “eugenics talk”, in this context, is legitimate and useful or something to be avoided. It also looks at the extent to which this linguistic question can be answered without first answering relevant substantive moral questions. Its main conclusion is that the best and most non-partisan argument for avoiding eugenics talk is the Autonomy Argument. According to this, eugenics talk per se is not wrong, but there is something wrong with using its emotive power as a means of circumventing people’s critical–rational faculties. The Autonomy Argument does not, however, tell against eugenics talk when such language is used to shock people into critical–rational thought. These conclusions do not depend on unique features of eugenics: similar considerations apply to emotive language throughout bioethics.
Ethics and the pitchside physician
Authors: Salkeld L R
Published: May 2008

Sports medicine is a rapidly expanding area of clinical practice. The pitchside physician faces many ethical challenges in managing the injuries and wellbeing of sports men and women. This brief essay describes some of the dilemmas frequently encountered by the pitchside physician and calls for a discussion of the issues raised.
Caring for risky patients: duty or virtue?
Authors: Tomlinson T
Published: May 2008

The emergence several years ago of SARS, with its high rate of infection and death among healthcare workers, resurrected a recurring ethical question: do health professionals have a duty to provide care to patients with deadly infectious diseases, even at some substantial risk to themselves and their families? The conventional answer, repeated on the heels of the SARS epidemic, is that they do. In this paper, I argue that the arguments in support of such a duty are wanting in significant respects, and that the language of duty is simply not adequate to an understanding of all the moral dimensions of professional responses to the care of risky patients. Instead, we should speak the language of virtues and ideals if we want to do justice to the complexity of such harrowing circumstances.
Intrabullous blood injection for lung volume reduction
Authors: Kanoh S , Kobayashi H , Motoyoshi K
Published: May 2008

Bronchoscopic treatment for emphysematous lung diseases has attracted clinical attention, and several different approaches are being investigated. We present a case of emphysematous bullae that was effectively treated with a newly developed bronchoscopic intervention, autologous blood injection. A 59-year-old man was referred to our institution with exertional dyspnoea. Chest CT showed emphysema and bullae with a diameter of 12 cm in the right upper lobe. Bronchoscopic treatment was introduced as an alternative to surgery. Autologous blood and fibrinogen solution were infused into bullae via the transbronchial catheter, under fluoroscopic guidance. Post-treatment CT showed marked contraction of bullae to a diameter of 3 cm, corresponding to a volume reduction of 800 ml on body plethysmography. A significant reduction in dyspnoea was also noted. This therapeutic approach is less invasive and may represent a good option for reducing lung volume.
Length-at-Age Analysis: Can You Get What You See?
Authors: Mulligan T. J. , Leaman B. M.
Published: May 2008

Observations at a single point in time of length-at-age (LAA) for a long-lived rockfish (Sebastes alutus) show that old fish are shorter than intermediate-aged fish. Fitting of a von Bertalanffy growth model to these data produces a systematic trend in the residual of observed versus calculated LAA. We examined how such LAA data can lead to erroneous conclusions about individual growth, and whether asymptotic growth can give rise to such data. We considered two hypotheses: (i) that a time trend in growth rate resulted in larger fish in more recent years and (ii) that there are multiple growth types, where growth and mortality rates are directly related. Using a general growth model that incorporated both (i) and (ii), we show that both hypotheses can generate data identical to those for the rockfish. A single set of LAA data is inadequate for describing individual growth; however, if sufficient data are available, model ambiguity can be resolved and reasonable parameter estimates obtained. Analysis of the rockfish data indicates that (ii) is more likely to explain the observations than (i). We show how fisheries on such species may preclude our understanding these biological relationships.
Foraging and Prey Search Behaviour of Golden Shiner (Notemigonus crysoleucas) Larvae
Authors: Browman Howard I. , O'Brien W. John
Published: May 2008

The juveniles of several species of freshwater fish search for zooplankton prey using a strategy intermediate between cruise and ambush: "saltatory search" (SS) or "pause–travel" search. Unlike ambush or cruise search, saltatory search involves scanning for prey throughout the search space and only during the brief stationary periods that punctuate repositioning movements. If no prey are located, these fish swim a short distance, stop, and scan again. In this paper, we describe the ontogeny of prey search in a cyprinid, the golden shiner (Notemigonus crysoleucas), a species whose search pattern has not been examined. Swimming and pursuit speeds and prey location distances increased with fish size. Golden shiner larvae searched for prey throughout the search space and only during the pauses that punctuated swimming movements. Only 1–10% of all of the stationary pauses that punctuated swimming movements were followed by attacks on prey. We conclude that golden shiner larvae employ a saltatory-search strategy similar to that described in other zooplanktivorous fish and their larvae.