bluuebunny/crossref_metadata_2025 huggingface dataset:
Remote Health Monitoring Increases Reliability and Condition-Based Maintenance
Authors: Green Bruce , Hull George , Hurtado Juan , Harvill Mark
Published: July 2009

This paper presents the technical approach taken to develop and implement a real-time health monitoring system to enable condition-based maintenance and remote health monitoring of two electric fleets operated by Amtrak. The monitoring devices and accompanying software, fault logic, rule sets, documentation manuals, and training forums assist mechanical maintenance crews, field service technicians, and onboard personnel to determine locomotive and consist train health and to take necessary maintenance actions as needed to maintain optimal equipment availability, reliability, and On Time Performance (OTP). This paper provides the status of that rollout and is designed to invite comment and discussion from others in the industry developing similar programs and processes to enable condition based maintenance.
Characterization and Modeling of CNT Based Actuators
Authors: Riemenschneider Johannes
Published: July 2009

In order to get an understanding of the general characteristics of Carbon Nanotube (CNT) based actuators, the system response of the actuator was analyzed. Special techniques were developed in order to generate a reproducible characteristic measure for the material: the R-Curve. On top, the dynamic response of the system was evaluated in different states of the actuator. A model was generated to capture the general behavior of the system. At last an actuator incorporating solid electrolyte was built and tested, showing similar characteristics as the actuator in aqueous electrolyte.
Effect of Crystal Orientation on Polarization in Piezoelectric Materials
Authors: Qidwai M. A. Siddiq , DeGiorgi V. G.
Published: July 2009

This work highlights the computational application of a nonlinear constitutive model to determine the impact of crystal orientation with respect to both initial poling direction and applied electrical fields. Misalignment between material axes and loading axes can occur during the fabrication process and may exhibit desirable performance feature for actuator design. The analysis showed that small angles of loading and material axes misalignment such as may occur in fabrication (less than 5 degrees) have minor impact on material performance, and that the liner response range of these materials can be expanded by increased levels of constraint at the cost of maximum actuation strain. For larger angles, variations in loading and material axes misalignment angles can have a significant impact on performance.
Hysteresis and Viscoelastic Modeling of a Piezo-Optic Voltage Sensor
Authors: Seeley Charles E. , Koste Glen , Stringer Craig
Published: July 2009

There is growing interest in sensor technology that is immune to electro-magnetic interference. By nature, development of this technology covers multiple physical domains including electronics, optics, mechanics and materials. This paper discusses development of a mathematical model to compensate for the hysteresis and viscoelastic effects of a piezo-optic voltage sensor. The sensor utilizes piezoelectric fibers with interdigitated electrodes coupled to an optical wave guide via a dielectric matrix. The unknown voltage energizes the piezoelectric fibers to deform fiber Bragg gratings (FBGs) on the waveguide. Therefore, a measurable change in wavelength is related to the unknown voltage. The hysteresis model is based on Rayleigh’s Law of magnetization that is adapted for the coupled piezoelectric and optic response, and the viscoelastic model is based on the standard linear solid model using springs and dashpots in combination. Model results compare favorably with experimental results.
Improved Prediction of Electrodes’ Mass Loading Effect on MEMS FBAR Structure in Longitudinal Resonance
Authors: Ruimi Annie , Liang Yueming , McMeeking Robert M.
Published: July 2009

In this paper, we derive an exact one-dimensional rule for predicting mass loading effect due to electrodes by analyzing a FBAR structure consisting of a piezoelectric layer and two electrodes in longitudinal resonance. We validate the numerical scheme using aluminum nitride as the piezoelectric material and gold and aluminum for the top and bottom electrodes respectively. Results are compared with three-dimensional finite elements simulations obtained earlier. It is seen that the new rule predicts higher values of the resonant frequency and constitutes an improvement over an elementary rule particularly for electrodes thicknesses greater than 20% of the piezoelectric layer thickness.
Design and Testing of a PMN-PT Based Compact Hybrid Actuator
Authors: Chaudhuri A. , Wereley N. M.
Published: July 2009

Substantial research has been conducted in the development of hybrid hydraulic actuators driven by various smart materials. The basic operation of these actuators involves high frequency bidirectional length change of an active material stack (rod) which is converted to unidirectional motion of a hydraulic fluid by a set of active or passive valves. In this paper, we present the design and experimental test results of a compact hybrid actuation driven by the electrostrictive material PMN. The active material was actuated at different frequencies, with variations in the applied voltage and fluid bias pressure to study their effects on performance. The tests were carried out under no-load conditions and also with external weights to find the maximum flow rate and blocked force respectively. The maximum actuator velocity was calculated to be 330 mm/s and the corresponding flow rate was 42.5 cc/s. The blocked force of the actuator was found to be 63 N and the maximum power output was 8 W. Dynamic tests were also conducted to find the PMN stack response without any fluid loads. Results of the experiments are presented and compared with simulation data.
Characterization of the Magnetostriction of Magnetorheological Elastomers
Authors: Aga Zelalem , Faidley LeAnn
Published: July 2009

Magnetorheological Elastomers (MREs) are polymer composites comprised of an elastomer matrix material with a filler of magnetic particles. The interaction of the filler particles when exposed to a magnetic field can result in a change in stiffness and a strain. However, the main focus of previous research has been on field induced change in stiffness. The goal of this study is therefore to characterize the magnetostriction (field induced strain) of these materials. The measurement of the magnetostriction of MRE was carried out by placing the specimens in a magnetic field produced by a solenoid coil and measuring the resulting strain using a capacitive sensor. A one cycle sinusoidal voltage was input to the solenoid coil that surrounded the MRE specimen to produce the magnetic field. In order to study the effect of mass percentage of iron filler particles on magnetostriction, specimens with different iron filler composition varying from 10 to 30% were produced. The effect of bulk stiffness of the specimen and the magnitude of applied magnetic field on magnetostriction properties has also been studied. The results reveal that increasing the mass percentage of iron in the specimen increases the magnitude of the magnetostriction. In addition, the magnetostriction of MRE showed dependence on the level of applied magnetic field and on the bulk stiffness of the MRE specimens.
Energy Harvesting Utilizing Single Crystal PMN-PT Material
Authors: Song Hyun Jeong , Choi Young-Tai , Wang Gang , Wereley Norman M.
Published: July 2009

This study compares the measured and predicted characteristics of an energy harvester utilizing single crystal lead magnesium niobate-lead titanate (PMN-PT) material. The energy harvester is composed of a cantilever beam with a single crystal PMN-PT patch, a tip mass, a rectifier and an electric load. Characteristics of the energy harvester were studied via both analysis and experiment. A theoretical model was established and experimentally validated. Natural frequency of energy harvester was fixed with tip mass. The generated power was also experimentally obtained for different levels of acceleration. The energy harvester was also used to drive an accelerometer using only energy harvested from ambient vibration.
Testing and Simulation of Stress-Stiffening Extreme Poisson’s Ratio Twisted Fiber-Reinforced Elastomer Composites
Authors: Peel Larry D. , Lingala Madhuri
Published: July 2009

Laminates that exhibit high and negative Poisson’s ratios can be used as solid-state actuators, passive and active vibration dampers, and for morphing aircraft structures. Recently, fiber-reinforced elastomer (FRE) laminates have been fabricated that exhibit extreme (high and negative) Poisson’s ratios [1]. The current research explores twisted fiber bundle elastomeric laminates (both single and double helix) which are being investigated using experimentation, linear and non-linear finite element analysis (FEA). Twisted fiber bundles can be made from carbon fibers, fiberglass, etc, but for simplicity the current work uses twisted cotton string. It is observed that uniaxial fiber-reinforced elastomer laminates, where the fibers are twisted as shown in Figure 1, exhibit stress stiffening. Negative Poisson’s ratios may be produced if the fiber bundles have a double helical path as simulated by a series of laminated tubes. Future auxetic FRE laminates may be developed that do experience extreme shear.
Cyclic Actuator Behavior of Ferrogels
Authors: Faidley LeAnn , Macias David , Harrington Eric
Published: July 2009

Ferrogels are low modulus polymer materials with embedded magnetic powder filler giving them the capability to strain in a magnetic field. The large strains, high energy densities, and fast response that have been reported make these materials attractive for actuator applications, however, a full understanding of the dynamic behavior is lacking. In this work the following behaviors are characterized: (1) the effect of gravity is determined by comparing behavior in two configurations, (2) the effect of compositions is investigated for 9 samples of different matrix and filler compositions, (3) the effect of frequency is determined for sinusoidal inputs between 0.1 and 80 Hz and, (4) the instantaneous and long-term strain behavior is discussed based on the ferrogel response to step inputs of magnitudes up to 2200 Gauss. It was found that the highest strains are achieved for the most flexible samples with the highest amount of magnetic filler tested in a configuration in which gravity acts in opposition to the magnetic attraction. Lower frequencies allow for larger strains because more time is allowed for visco-elastic motion. Finally, the step response shows that the strain occurs in two types. First, is an instantaneous strain; second, is a visco-elastic deformation that takes place over an extended period of time.
Loading Rate Effect on the Domain Switching of Ferroelectric Materials
Authors: Achuthan Ajit , Sun Chin-Teh
Published: July 2009

A method to characterize the strain electric field butterfly behavior based on the underlying domain switching mechanism is presented at first. The effect of loading rate on the different characteristics of the strain electric-field-butterfly behavior is then studied. By comparing the changes in these characteristics under different loading rates, it is established that the loading rate dependence of the strain electric field butterfly behavior is mainly due to two factors, 1) the dependence of the switching of individual domains on the magnitude and duration of the loading time and 2) the variation of the transition electric field with the loading rate. Several interesting attributes of the domain switching behavior that may shed light on understanding the underlying mechanism of domain switching further is illustrated in the present study. The present study also demonstrates that the method of characterizing the strain electric butterfly based on the underlying domain switching mechanism is very effective in studying ferroelectric behavior under different loading conditions.
Frequency Response of Piezoelectric and Magnetostrictive Hysteretic Nonlinear Systems
Authors: Stuebner Michael , Atulasimha Jayasimha , Smith Ralph C.
Published: July 2009

Piezoelectric and magnetostrictive materials exhibit high energy densities and broadband drive capabilities enabling compact actuator designs. These applications include acoustic transducers, nano-positioning systems such as Atomic Force Microscopes (AFM) and other smart actuators for precise control of displacement. However, these materials exhibit hysteresis and constitutive nonlinearities at all drive levels. Quantification and understanding these effects on the frequency domain behavior of the materials is necessary for precise control of displacement as well as developing control strategies to alleviate the higher harmonics produced during operation. Whereas considerable effort has been made on model development and understanding these materials in parameter space and time domain, a comprehensive understanding in frequency domain is lacking. Here we quantify the effect of hysteresis, nonlinearities, bias fields and AC drive levels on the frequency domain behavior.
The Smart Joint: Model and Optimization of a Shape Memory Alloy/Shape Memory Polymer Composite Actuator
Authors: Manzo Justin E. , Garcia Ephrahim
Published: July 2009

The Smart Joint, developed at Cornell University, is a composite device which functions as both a structural element and shape changing mechanism. Through resistive heating, the device will provide a tip deflection on the order of 5–20% of its undeflected length, with a high specific work capability. The joint possesses sufficient stiffness to function as a load-carrying element on a structure, inspired by the need to consume minimal energy through passive rigidity. An overview of Smart Joint operation is provided, followed by an improved model encompassing embedded actuators, applicable to many strain actuation systems. Previous work has developed a model that describes the shape change capability of the joint as a function of composition and layering structure, and the revised model is an extension of that work, agreeing well with finite element analysis. Benchmarking is conducted through a heuristic optimization study, providing a framework for selecting joint structure to match desired application by joint composition family. Implementation on a bat-like morphing wing is proposed that uses the Smart Joints as self-actuated hinge structures along the skeleton, capable of providing increased wing camber and tip deflections while in flight.
Evaluation of Analogs of Reutericyclin as Prospective Candidates for Treatment of Staphylococcal Skin Infections
Authors: Hurdle Julian G. , Yendapally Raghunandan , Sun Dianqing , Lee Richard E.
Published: July 2009

The potential for reutericyclin derivatives to be used as topical antibiotics to treat staphylococcal skin infections was investigated. All reutericyclins inhibited the growth of clinical isolates of drug-resistant
Staphylococcus aureus
. Unlike the standard topical agent mupirocin, most reutericyclin derivatives eradicated staphylococcal biofilms. Moreover, two compounds formulated in hydrophilic petrolatum (10%, wt/wt) were efficacious in treating
S. aureus
superficial skin infections in mice. These data exemplify the prospect of developing reutericyclins as new topical antibiotics.
Didanosine Population Pharmacokinetics in West African Human Immunodeficiency Virus-Infected Children Administered Once-Daily Tablets in Relation to Efficacy after One Year of Treatment
Authors: Hirt Déborah , Bardin Christophe , Diagbouga Serge , Nacro Boubacar , Hien Hervé , Zoure Emmanuelle , Rouet François , Ouiminga Adama , Urien Saik , Foulongne Vincent , Van De Perre Philippe , Tréluyer Jean-Marc , Msellati Philippe
Published: July 2009

Our objective was to study didanosine pharmacokinetics in children after the administration of tablets, the only formulation available in Burkina Faso for which data are missing, and to establish relationships between doses, plasma drug concentrations, and treatment effects (efficacy/toxicity). Didanosine concentrations were measured for 40 children after 2 weeks and for 9 children after 2 to 5 months of treatment with a didanosine-lamivudine-efavirenz combination. A population pharmacokinetic model was developed with NONMEM. The link between the maximal concentration of the drug in plasma (Cmax), the area under the concentration-time curve (AUC), and the decrease in human immunodeficiency virus (HIV) type 1 RNA levels after 12 months of treatment was evaluated. The threshold AUC that improved efficacy was determined by the use of a Wilcoxon test for HIV RNA, and an optimized dosing schedule was simulated. Didanosine pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. The apparent clearance and volume of distribution were higher for tablets, probably due to a lower bioavailability with tablets than with pediatric powder. The decrease in the viral load after 12 months of treatment was significantly correlated with the didanosine AUC andCmax(P≤ 0.02) during the first weeks of treatment. An AUC of >0.60 mg/liter·h was significantly linked to a greater decrease in the viral load (a decrease of 3 log10versus 2.4 log10copies/ml;P= 0.03) than that with a lower AUC. A didanosine dose of 360 mg/m2administered as tablets should be a more appropriate dose than 240 mg/m2to improve efficacy for these children. However, data on adverse events with this dosage are missing.
Identification of Amino Acid Residues Responsible for the Enantioselectivity and Amide Formation Capacity of the Arylacetonitrilase fromPseudomonas fluorescensEBC191
Authors: Kiziak Christoph , Stolz Andreas
Published: July 2009

The nitrilase fromPseudomonas fluorescensEBC191 converted (R,S)-mandelonitrile with a low enantioselectivity to (R)-mandelic acid and (S)-mandeloamide in a ratio of about 4:1. In contrast, the same substrate was hydrolyzed by the homologous nitrilase fromAlcaligenes faecalisATCC 8750 almost exclusively to (R)-mandelic acid. A chimeric enzyme between both nitrilases was constructed, which represented in total 16 amino acid exchanges in the central part of the nitrilase fromP. fluorescensEBC191. The chimeric enzyme clearly resembled the nitrilase fromA. faecalisATCC 8750 in its turnover characteristics for (R,S)-mandelonitrile and (R,S)-2-phenylpropionitrile (2-PPN) and demonstrated an even higher enantioselectivity for the formation of (R)-mandelic acid than the nitrilase fromA. faecalis. An alanine residue (Ala165) in direct proximity to the catalytically active cysteine residue was replaced in the nitrilase fromP. fluorescensby a tryptophan residue (as found in the nitrilase fromA. faecalisATCC 8750 and most other bacterial nitrilases) and several other amino acid residues. Those enzyme variants that possessed a larger substituent in position 165 (tryptophan, phenylalanine, tyrosine, or histidine) converted racemic mandelonitrile and 2-PPN to increased amounts of theRenantiomers of the corresponding acids. The enzyme variant Ala165His showed a significantly increased relative activity for mandelonitrile (compared to 2-PPN), and the opposite was found for the enzyme variants carrying aromatic residues in the relevant position. The mutant forms carrying an aromatic substituent in position 165 generally formed significantly reduced amounts of mandeloamide from mandelonitrile. The important effect of the corresponding amino acid residue on the reaction specificity and enantiospecificity of arylacetonitrilases was confirmed by the construction of a Trp164Ala variant of the nitrilase fromA. faecalisATCC 8750. This point mutation converted the highlyR-specific nitrilase into an enzyme that converted (R,S)-mandelonitrile preferentially to (S)-mandeloamide.
Prevalence of Antibiotic Resistance in Drinking Water Treatment and Distribution Systems
Authors: Xi Chuanwu , Zhang Yongli , Marrs Carl F. , Ye Wen , Simon Carl , Foxman Betsy , Nriagu Jerome
Published: July 2009

The occurrence and spread of antibiotic-resistant bacteria (ARB) are pressing public health problems worldwide, and aquatic ecosystems are a recognized reservoir for ARB. We used culture-dependent methods and quantitative molecular techniques to detect and quantify ARB and antibiotic resistance genes (ARGs) in source waters, drinking water treatment plants, and tap water from several cities in Michigan and Ohio. We found ARGs and heterotrophic ARB in all finished water and tap water tested, although the amounts were small. The quantities of most ARGs were greater in tap water than in finished water and source water. In general, the levels of bacteria were higher in source water than in tap water, and the levels of ARB were higher in tap water than in finished water, indicating that there was regrowth of bacteria in drinking water distribution systems. Elevated resistance to some antibiotics was observed during water treatment and in tap water. Water treatment might increase the antibiotic resistance of surviving bacteria, and water distribution systems may serve as an important reservoir for the spread of antibiotic resistance to opportunistic pathogens.
Genetic Analysis of a NovelXylella fastidiosaSubspecies Found in the Southwestern United States
Authors: Randall Jennifer J. , Goldberg Natalie P. , Kemp John D. , Radionenko Maxim , French Jason M. , Olsen Mary W. , Hanson Stephen F.
Published: July 2009

Xylella fastidiosa, the causal agent of several scorch diseases, is associated with leaf scorch symptoms inChitalpa tashkentensis, a common ornamental landscape plant used throughout the southwestern United States. For a number of years, many chitalpa trees in southern New Mexico and Arizona exhibited leaf scorch symptoms, and the results from a regional survey show that chitalpa trees from New Mexico, Arizona, and California are frequently infected withX. fastidiosa.Phylogenetic analysis of multiple loci was used to compare theX. fastidiosainfecting chitalpa strains from New Mexico, Arizona, and trees imported into New Mexico nurseries with previously reportedX. fastidiosastrains. Loci analyzed included the 16S ribosome, 16S-23S ribosomal intergenic spacer region, gyrase-B, simple sequence repeat sequences,X. fastidiosa-specific sequences, and the virulence-associated protein (VapD). This analysis indicates that theX. fastidiosaisolates associated with infected chitalpa trees in the Southwest are a highly related group that is distinct from the four previously defined taxonsX. fastidiosasubsp.fastidiosa(piercei),X. fastidiosasubsp.multiplex,X. fastidiosasubsp.sandyi, andX. fastidiosasubsp.pauca. Therefore, the classification proposed for this new subspecies isX. fastidiosasubsp.tashke.
Role of AP-1 in Developmentally Regulated Lysosomal Trafficking in
Trypanosoma brucei
Authors: Tazeh Ngii N. , Silverman Jason S. , Schwartz Kevin J. , Sevova Elitza S. , Sutterwala Shaheen S. , Bangs James D.
Published: July 2009

African trypanosomes are the causative agents of human trypanosomiasis (sleeping sickness). The pathogenic stage of the parasite has unique adaptations to life in the bloodstream of the mammalian host, including upregulation of endocytic and lysosomal activities. We investigated stage-specific requirements for cytoplasmic adaptor/clathrin machinery in post-Golgi apparatus biosynthetic sorting to the lysosome using RNA interference silencing of the Tbμ1 subunit of adaptor complex 1 (AP-1), in conjunction with immunolocalization, kinetic analyses of reporter transport, and quantitative endocytosis assays. Tbμ1 silencing was lethal in both stages, indicating a critical function(s) for the AP-1 machinery. Transport of soluble and membrane-bound secretory cargoes was Tbμ1 independent in both stages. In procyclic parasites, trafficking of the lysosomal membrane protein, p67, was disrupted, leading to cell surface mislocalization. The lysosomal protease trypanopain was also secreted, suggesting a transmembrane-sorting receptor for this soluble hydrolase. In bloodstream trypanosomes, both p67 and trypanopain trafficking were unaffected by Tbμ1 silencing, suggesting that AP-1 is not necessary for biosynthetic lysosomal trafficking. Endocytosis in bloodstream cells was also unaffected, indicating that AP-1 does not function at the flagellar pocket. These results indicate that post-Golgi apparatus sorting to the lysosome is critically dependent on the AP-1/clathrin machinery in procyclic trypanosomes but that this machinery is not necessary in bloodstream parasites. We propose a simple model for stage-specific default secretory trafficking in trypanosomes that is consistent with the behavior of other soluble and glycosylphosphatidylinositol-anchored cargos and which is influenced by upregulation of endocytosis in bloodstream parasites as an adaptation to life in the mammalian bloodstream.
Plasminogen Acquisition and Activation at the Surface of
Leptospira
Species Lead to Fibronectin Degradation
Authors: Vieira Monica L. , Vasconcellos Silvio A. , Gonçales Amane P. , de Morais Zenaide M. , Nascimento Ana L. T. O.
Published: July 2009

Pathogenic
Leptospira
species are the etiological agents of leptospirosis, a widespread disease of human and veterinary concern. In this study, we report that
Leptospira
species are capable of binding plasminogen (PLG) in vitro. The binding to the leptospiral surface was demonstrated by indirect immunofluorescence confocal microscopy with living bacteria. The PLG binding to the bacteria seems to occur via lysine residues because the ligation is inhibited by addition of the lysine analog 6-aminocaproic acid. Exogenously provided urokinase-type PLG activator (uPA) converts surface-bound PLG into enzymatically active plasmin, as evaluated by the reaction with the chromogenic plasmin substrate
d
-Val-Leu-Lys 4-nitroanilide dihydrochloridein. The PLG activation system on the surface of
Leptospira
is PLG dose dependent and does not cause injury to the organism, as cellular growth in culture was not impaired. The generation of active plasmin within
Leptospira
was observed with several nonvirulent high-passage strains and with the nonpathogenic saprophytic organism
Leptospira biflexa
. Statistically significant higher activation of plasmin was detected with a low-passage infectious strain of
Leptospira
. Plasmin-coated virulent
Leptospira interrogans
bacteria were capable of degrading purified extracellular matrix fibronectin. The breakdown of fibronectin was not observed with untreated bacteria. Our data provide for the first time in vitro evidence for the generation of active plasmin on the surface of
Leptospira
, a step that may contribute to leptospiral invasiveness.
The RNA Binding Protein CsrA Is a Pleiotropic Regulator of the Locus of Enterocyte Effacement Pathogenicity Island of Enteropathogenic
Escherichia coli
Authors: Bhatt Shantanu , Edwards Adrianne Nehrling , Nguyen Hang Thi Thu , Merlin Didier , Romeo Tony , Kalman Daniel
Published: July 2009

The
a
ttaching and
e
ffacing (A/E) pathogen enteropathogenic
Escherichia coli
(EPEC) forms characteristic actin-filled membranous protrusions upon infection of host cells termed pedestals. Here we examine the role of the RNA binding protein CsrA in the expression of virulence genes and proteins that are necessary for pedestal formation. The
csrA
mutant was defective in forming actin pedestals on epithelial cells and in disrupting transepithelial resistance across polarized epithelial cells. Consistent with reduced pedestal formation, secretion of the translocators EspA, EspB, and EspD and the effector Tir was substantially reduced in the
csrA
mutant. Purified CsrA specifically bound to the
sepL espADB
mRNA leader, and the corresponding transcript levels were reduced in the
csrA
mutant. In contrast, Tir synthesis was unaffected in the
csrA
mutant. Reduced secretion of Tir appeared to be in part due to decreased synthesis of EscD, an inner membrane architectural protein of the type III secretion system (TTSS) and EscF, a protein that forms the protruding needle complex of the TTSS. These effects were not mediated through the
l
ocus of
e
nterocyte
e
ffacement (LEE) transcriptional regulator GrlA or Ler. In contrast to the
csrA
mutant, multicopy expression of
csrA
repressed transcription from
LEE1
,
grlRA
,
LEE2
,
LEE5
,
escD
, and
LEE4
, an effect mediated by GrlA and Ler. Consistent with its role in other organisms, CsrA also regulated flagellar motility and glycogen levels. Our findings suggest that CsrA governs virulence factor expression in an A/E pathogen by regulating mRNAs encoding translocators, effectors, or transcription factors.
Relevant Role of Fibronectin-Binding Proteins in
Staphylococcus aureus
Biofilm-Associated Foreign-Body Infections
Authors: Vergara-Irigaray Marta , Valle Jaione , Merino Nekane , Latasa Cristina , García Begoña , Ruiz de los Mozos Igor , Solano Cristina , Toledo-Arana Alejandro , Penadés José R. , Lasa Iñigo
Published: July 2009

Staphylococcus aureus
can establish chronic infections on implanted medical devices due to its capacity to form biofilms. Analysis of the factors that assemble cells into a biofilm has revealed the occurrence of strains that produce either a polysaccharide intercellular adhesin/poly-
N
-acetylglucosamine (PIA/PNAG) exopolysaccharide- or a protein-dependent biofilm. Examination of the influence of matrix nature on the biofilm capacities of embedded bacteria has remained elusive, because a natural strain that readily converts between a polysaccharide- and a protein-based biofilm has not been studied. Here, we have investigated the clinical methicillin (meticillin)-resistant
Staphylococcus aureus
strain 132, which is able to alternate between a proteinaceous and an exopolysaccharidic biofilm matrix, depending on environmental conditions. Systematic disruption of each member of the LPXTG surface protein family identified fibronectin-binding proteins (FnBPs) as components of a proteinaceous biofilm formed in Trypticase soy broth-glucose, whereas a PIA/PNAG-dependent biofilm was produced under osmotic stress conditions. The induction of FnBP levels due to a spontaneous
agr
deficiency present in strain 132 and the activation of a LexA-dependent SOS response or FnBP overexpression from a multicopy plasmid enhanced biofilm development, suggesting a direct relationship between the FnBP levels and the strength of the multicellular phenotype. Scanning electron microscopy revealed that cells growing in the FnBP-mediated biofilm formed highly dense aggregates without any detectable extracellular matrix, whereas cells in a PIA/PNAG-dependent biofilm were embedded in an abundant extracellular material. Finally, studies of the contribution of each type of biofilm matrix to subcutaneous catheter colonization revealed that an FnBP mutant displayed a significantly lower capacity to develop biofilm on implanted catheters than the isogenic PIA/PNAG-deficient mutant.
The Electron Transfer System of Syntrophically Grown
Desulfovibrio vulgaris
Authors: Walker Christopher B. , He Zhili , Yang Zamin K. , Ringbauer Joseph A. , He Qiang , Zhou Jizhong , Voordouw Gerrit , Wall Judy D. , Arkin Adam P. , Hazen Terry C. , Stolyar Sergey , Stahl David A.
Published: July 2009

Interspecies hydrogen transfer between organisms producing and consuming hydrogen promotes the decomposition of organic matter in most anoxic environments. Although syntrophic coupling between hydrogen producers and consumers is a major feature of the carbon cycle, mechanisms for energy recovery at the extremely low free energies of reactions typical of these anaerobic communities have not been established. In this study, comparative transcriptional analysis of a model sulfate-reducing microbe,
Desulfovibrio vulgaris
Hildenborough, suggested the use of alternative electron transfer systems dependent on growth modality. During syntrophic growth on lactate with a hydrogenotrophic methanogen, numerous genes involved in electron transfer and energy generation were upregulated in
D. vulgaris
compared with their expression in sulfate-limited monocultures. In particular, genes coding for the putative membrane-bound Coo hydrogenase, two periplasmic hydrogenases (Hyd and Hyn), and the well-characterized high-molecular-weight cytochrome (Hmc) were among the most highly expressed and upregulated genes. Additionally, a predicted operon containing genes involved in lactate transport and oxidation exhibited upregulation, further suggesting an alternative pathway for electrons derived from lactate oxidation during syntrophic growth. Mutations in a subset of genes coding for Coo, Hmc, Hyd, and Hyn impaired or severely limited syntrophic growth but had little effect on growth via sulfate respiration. These results demonstrate that syntrophic growth and sulfate respiration use largely independent energy generation pathways and imply that to understand microbial processes that sustain nutrient cycling, lifestyles not captured in pure culture must be considered.
Bifurcated Degradative Pathway of 3-Sulfolactate in
Roseovarius nubinhibens
ISM via Sulfoacetaldehyde Acetyltransferase and (
S
)-Cysteate Sulfolyase
Authors: Denger Karin , Mayer Jutta , Buhmann Matthias , Weinitschke Sonja , Smits Theo H. M. , Cook Alasdair M.
Published: July 2009

Data from the genome sequence of the aerobic, marine bacterium
Roseovarius nubinhibens
ISM were interpreted such that 3-sulfolactate would be degraded as a sole source of carbon and energy for growth via a novel bifurcated pathway including two known desulfonative enzymes, sulfoacetaldehyde acetyltransferase (EC 2.3.3.15) (Xsc) and cysteate sulfo-lyase (EC 4.4.1.25) (CuyA). Strain ISM utilized sulfolactate quantitatively with stoichiometric excretion of the sulfonate sulfur as sulfate. A combination of enzyme assays, analytical chemistry, enzyme purification, peptide mass fingerprinting, and reverse transcription-PCR data supported the presence of an inducible, tripartite sulfolactate uptake system (SlcHFG), and a membrane-bound sulfolactate dehydrogenase (SlcD) which generated 3-sulfopyruvate, the point of bifurcation. 3-Sulfopyruvate was in part decarboxylated by 3-sulfopyruvate decarboxylase (EC 4.1.1.79) (ComDE), which was purified. The sulfoacetaldehyde that was formed was desulfonated by Xsc, which was identified, and the acetyl phosphate was converted to acetyl-coenzyme A by phosphate acetyltransferase (Pta). The other portion of the 3-sulfopyruvate was transaminated to (
S
)-cysteate, which was desulfonated by CuyA, which was identified. The sulfite that was formed was presumably exported by CuyZ (TC 9.B.7.1.1 in the transport classification system), and a periplasmic sulfite dehydrogenase is presumed. Bioinformatic analyses indicated that transporter SlcHFG is rare but that SlcD is involved in three different combinations of pathways, the bifurcated pathway shown here, via CuyA alone, and via Xsc alone. This novel pathway involves ComDE in biodegradation, whereas it was discovered in the biosynthesis of coenzyme M. The different pathways of desulfonation of sulfolactate presumably represent final steps in the biodegradation of sulfoquinovose (and exudates derived from it) in marine and aquatic environments.
An A257V Mutation in the
Bacillus subtilis
Response Regulator Spo0A Prevents Regulated Expression of Promoters with Low-Consensus Binding Sites
Authors: Seredick Steve D. , Seredick Barbara M. , Baker David , Spiegelman George B.
Published: July 2009

In
Bacillus
species, the master regulator of sporulation is Spo0A. Spo0A functions by both activating and repressing transcription initiation from target promoters that contain 0A boxes, the binding sites for Spo0A. Several classes of
spo0A
mutants have been isolated, and the molecular basis for their phenotypes has been determined. However, the molecular basis of the Spo0A(A257V) substitution, representative of an unusual phenotypic class, is not understood. Spo0A(A257V) is unusual in that it abolishes sporulation; in vivo, it fails to activate transcription from key stage II promoters yet retains the ability to repress the
abrB
promoter. To determine how Spo0A(A257V) retains the ability to repress but not stimulate transcription, we performed a series of in vitro and in vivo assays. We found unexpectedly that the mutant protein both stimulated transcription from the
spoIIG
promoter and repressed transcription from the
abrB
promoter, albeit twofold less than the wild type. A DNA binding analysis of Spo0A(A257V) showed that the mutant protein was less able to tolerate alterations in the sequence and arrangement of its DNA binding sites than the wild-type protein. In addition, we found that Spo0A(A257V) could stimulate transcription of a mutant
spoIIG
promoter in vivo in which low-consensus binding sites were replaced by high-consensus binding sites. We conclude that Spo0A(A257V) is able to bind to and regulate the expression of only genes whose promoters contain high-consensus binding sites and that this effect is sufficient to explain the observed sporulation defect.
Short-Chain Chromate Ion Transporter Proteins from
Bacillus subtilis
Confer Chromate Resistance in
Escherichia coli
Authors: Díaz-Magaña Amada , Aguilar-Barajas Esther , Moreno-Sánchez Rafael , Ramírez-Díaz Martha I. , Riveros-Rosas Héctor , Vargas Eréndira , Cervantes Carlos
Published: July 2009

Tandem paired genes encoding putative short-chain monodomain protein members of the chromate ion transporter (CHR) superfamily (
ywrB
and
ywrA
) were cloned from genomic DNA of
Bacillus subtilis
strain 168. The transcription of the paired genes, renamed
chr3N
and
chr3C
, respectively, was shown to occur via a bicistronic mRNA generated from a promoter upstream of the
chr3N
gene. The
chr3N
and
chr3C
genes conferred chromate resistance when expressed in
Escherichia coli
strain W3110. The cloned
chr3N
gene alone did not confer chromate resistance on
E. coli
, suggesting that both
chr3N
and
chr3C
genes are required for function.
E. coli
cells expressing paired
chr3N
and
chr3C
genes demonstrated diminished uptake of chromate compared to that by a vector-only control strain. These results suggest that short-chain CHR proteins form heterodimer transporters which efflux chromate ions from the cytoplasm.
The paleomagnetism of Huronian red beds and Nipissing diabase; Post-Huronian Igneous Events and apparent polar path for the interval −2300 to −1500 Ma for Laurentia
Authors: Roy J. L. , Lapointe P. L.
Published: July 2009

Thermal, chemical, and alternating field (and two-stage) cleaning treatments of Huronian sediments and Nipissing diabase (which intrudes the sediments) from the Cobalt area yield five directions of magnetizations (A–E) of high stability; A, B, C, and E are found in the sediments, and C, D, and E in the diabase. It is suggested that magnetization B (337°, +52°; α95 = 8°; pole 158 °E, 67 °N) was acquired shortly after deposition of the Firstbrook beds [Formula: see text]; magnetization C (259°, +82°; α95 = 5°; pole 258 °E, 42 °N), found in both the diabase and sediments in contact with the diabase, was acquired during cooling following emplacement of the diabase [Formula: see text]; and magnetizations D and E, yielding poles at 264 °E, 15 °S and 000°, 09 °N respectively, were produced during the Hudsonian orogeny (−1850 to −1700 Ma). This interpretation resolves the previous inconsistencies between poles and age determinations. Good agreement between results from the Nipissing diabase and other igneous bodies indicate that widespread igneous events occurred in the time range approximately −2200 to −2100 Ma, immediately following deposition of Huronian sediments. This is referred to as 'Post-Huronian Igneous Events'. A proposed apparent polar path relative to Laurentia shows two distinct motions; for the 2300–1850 Ma interval, a latitudinal change (roughly along longitude 250° E) from high [Formula: see text] to low [Formula: see text] latitudes and, for the 1850–1500 Ma interval, a displacement along the present-day equator with first an eastward motion to about 000° longitude followed by a westward motion to 240° E longitude; the apex of the eastward excursion is given a date of [Formula: see text]. It is possible that this reflects a rotation of Laurentia about a vertical axis at the time of and following the Hudsonian orogeny. Subsequent uplift and cooling would explain the many overprinted stable magnetizations yielding poles distributed along the equator (track 4). Latitude maps indicate that Laurentia was in high latitudes from 2200–2000 Ma and in intermediate to low latitudes from 1900–1500 Ma.
Cupriferous reduction spheres in Upper Mississippian redbeds of the Hopewell Group at Dorchester Cape, New Brunswick
Authors: Poll H. W. van de , Sutherland J. K.
Published: July 2009

Concentrations of copper (cuprite, native copper), silver and mercury (schachnerite), and vanadium (roscoelite) occur in greyish, dark-cored reduction spheres in Upper Mississippian redbeds of the Hopewell Group in southeastern New Brunswick. The mineralized reduction spheres range from approximately 1 to 6 cm in diameter. Analytical work indicates that organic matter is not present in either the mineralized cores or their enclosing spheres.Tentative results from this investigation support the conclusion that some if not all of the metallic minerals present in the reduction spheres were introduced in the environment during or shortly after deposition of the strata. This type of mineral association in redbeds has apparently not previously been described in the literature.
Morphologic variation and stratigraphic significance of Triangulatisporites rootsii Chaloner
Authors: Chi B. I. , Hills L. V.
Published: July 2009

The morphologic variation in Triangulatisporites rootsii is described and illustrated, and five new varieties (rootsii, irregularis, reticulatus, regulatus, and var. A) are erected. Stratigraphic evidence presented indicates that this species is indicative of Frasnian Age in the Canadian Arctic.
Comparison of some tectonostratigraphic zones in the Appalachians of Newfoundland and New Brunswick
Authors: Rast N. , Kennedy M. J. , Blackwood R. F.
Published: July 2009

Whereas rocks of the Avalon Zone in Newfoundland are in fault contact with those of the Gander Zone, rocks identifiable as equivalents of the Gander Zone in New Brunswick are separated from the Avalon Zone by a 65 km wide belt of Silurian, Ordovician, and older rocks. This belt, referred to as the Fredericton Zone, contains a number of fault bounded blocks, each containing contrasting depositional, structural, and metamorphic histories. It is concluded that the Gander/Avalon Zone boundary in southern New Brunswick has controlled the development of subsequent basins, which have been deformed by Taconic and Acadian movements. In Newfoundland, the same boundary has remained essentially inactive in Paleozoic times.
Optimization in gravimetric terrain corrections
Authors: Blais J. A. R. , Ferland R.
Published: July 2009

Terrain corrections for gravimetric measurements require topographical data of appropriate accuracy and density. The situation is clearly dependent on the ruggedness of the topography and the accuracy specifications for the terrain corrections. From the optimization point of view, this computational problem has been investigated and computer software developed for the near, intermediate, and distant zones surrounding the gravity stations. Test results indicate that the general accuracy objective of 1.0–1.5 mGal (10–15 μm s−2) for the gravimetric terrain corrections is easily achievable in practice with appropriate topographical data. For geophysical applications, higher accuracies are certainly achievable with the method, even in rugged areas.
The direction of ice-wedge cracking in permafrost: downward or upward?
Authors: Mackay J. Ross
Published: July 2009

Field studies have been carried out along the western arctic coast of Canada in an attempt to determine whether all ice-wedge cracks originate at the ground surface and therefore propagate downward or whether some cracks originate near the top of permafrost and then propagate both upward and downward. The field studies have been concentrated upon (1) low- and high-centred tundra polygons a few thousand years old; and (2) ice wedges, growing for the first time, on the bottom of a lake experimentally drained in 1978. The field instrumentation has included electronic crack direction indicators, electronic elapsed timers, and continuous temperature measurements. The field studies reveal that many of the ice-wedge cracks originated near the top of permafrost and then propagated upward to the ground surface as well as downward into ice-wedge ice. For the 1974–1982 period, the field observations showed that about 57% of the ice wedges cracked from the ground surface downward and 43% cracked both upward and downward. Furthermore, the vertical direction of ice-wedge cracking was not consistent for any given wedge, presumably because of year-to-year variations in the physical and thermal conditions of the polygons and their troughs.
Petrology and tectonic significance of Gates Formation (early Cretaceous) sediments in northeast British Columbia
Authors: Leckie Dale
Published: July 2009

Moosebar–Gates sandstones are predominantly litharenites, with some feldspathic litharenites. Both the light- and heavy-mineral suites indicate a mixed source characterized by clastic and carbonate sedimentary rocks, acidic to intermediate plutonic and volcanic igneous rocks, and metamorphic rocks. The sediment sources all fall within a recycled orogenic provenance grouping. Histograms showing stratigraphic variation of mineral content do not indicate any significant progressive unroofing of more deeply buried source rocks.The source area was very extensive regionally and extended well into the Omineca Crystalline Belt and eastern margins of the Intermontane Belt. Zebraic chalcedony was derived from evaporitic rocks of the Charlie Lake Formation, situated east of the Rocky Mountain Trench. Kyanite and almandine garnet were probably derived from the Omineca Crystalline Belt west of the Rocky Mountain Trench. Regional paleoslope dipped towards the north-northwest. Restoration of strike-slip on the Rocky Mountain Trench places potential source areas to the south of the depocentre; this supports paleoslope data. During Moosebar–Gates time the Tenakihi Group in the Omineca Crystalline Belt would have been hundreds of kilometres south of its present location and south of the study area, where it could have provided sediment. Volcanic rocks were derived from west of the Rocky Mountain Trench. Source rocks in the Omineca Crystalline Belt were being eroded as early as late early Albian and providing sediment into the foreland basin to the east.