bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal variation and impact factors of available phosphorus in typical paddy soils of Taihu Lake region, China
Authors: Chen Xiaomin , Fang Kun , Chen Can
Published: December 2011

Phosphorus loss from soil can play an important role in eutrophication of aquatic bodies. The seasonal variation of available phosphorus in soil profiles of three major paddy soils (Bai soil, Huangni soil and Wushan soil) during wheat and rice growth seasons was studied in the Taihu Lake region of China. The results were as follows: the available phosphorus contents differed in the three paddy soils. Available phosphorus content in Bai soil was the lowest in these soils. The available phosphorus content decreases rapidly with depth from the soil surface and reach the minimum value at approximately 45 cm before increasing slightly near the groundwater. The contents of available phosphorus were higher in February (tillering and shooting period of wheat) and in September (full heading time of rice) than in other months. The total phosphorus content strongly affects available phosphorus content in the studied soils. During the period of wheat cultivation, they show a typical power function relationship with correlation coefficient r = 0.6492** (n = 13), a significant positive linear correlation. In addition, available phosphorus content has a remarkable positive linear correlation with organic matter content, r = 0.9111** (n = 13), and a remarkable negative linear correlation with pH value, r = −0.5945* (n = 13). In Wushan soil, there is a negative linear correlation between clay content and available phosphorus content, r = −0.9289* (n = 4). Therefore, total phosphorus content, organic matter content and pH value are major impact factors on available phosphorus content in these soils.
The evaluation of low‐cost biosorbents for removal of an azo dye from aqueous solution
Authors: Kahraman Sibel , Yalcin Pelin , Kahraman Hüseyin
Published: December 2011

There is a need to develop innovative and alternative technologies that can remove dyes from wastewater. In this study, low‐cost and locally available two renewable biosorbents (cotton stalk and apricot seed) were investigated to remove of Astrazone Black from aqueous solution. The effects of various experimental parameters such as dye concentration, adsorbent amount, adsorbent particle size and initial pH were tested, and optimal experimental conditions were examined. The results showed that as the amount of adsorbent was increased, the percentage of dye removal increased accordingly. The ratios of dye sorbed increased as the adsorbent particle size decreased. In addition, antibacterial effect of untreated and treated (decolourized) dye on a soil bacterium, Pseudomonas aeruginosa, was determined. The removal of this dye with agricultural wastes reduced the toxic effect on P. aeruginosa. This reduction in toxic effect is important both in respect of environmental biotechnology and waste detoxification.
The prefrontal cortex and hybrid learning during iterative competitive games
Authors: Abe Hiroshi , Seo Hyojung , Lee Daeyeol
Published: December 2011

Behavioral changes driven by reinforcement and punishment are referred to as simple or model‐free reinforcement learning. Animals can also change their behaviors by observing events that are neither appetitive nor aversive when these events provide new information about payoffs available from alternative actions. This is an example of model‐based reinforcement learning and can be accomplished by incorporating hypothetical reward signals into the value functions for specific actions. Recent neuroimaging and single‐neuron recording studies showed that the prefrontal cortex and the striatum are involved not only in reinforcement and punishment, but also in model‐based reinforcement learning. We found evidence for both types of learning, and hence hybrid learning, in monkeys during simulated competitive games. In addition, in both the dorsolateral prefrontal cortex and orbitofrontal cortex, individual neurons heterogeneously encoded signals related to actual and hypothetical outcomes from specific actions, suggesting that both areas might contribute to hybrid learning.
The orbitofrontal cortex and the computation of subjective value: consolidated concepts and new perspectives
Authors: Padoa‐Schioppa Camillo , Cai Xinying
Published: December 2011

Remarkable progress has been made in recent years toward understanding the functions of the orbitofrontal cortex (OFC). The finding that neurons in this area encode the subjective value monkeys assign to different goods while making choices has been confirmed and extended by numerous studies using both primate neurophysiology and human imaging. Moreover, new lesion studies demonstrated that subjective values computed in the OFC are causally and specifically related to choice behavior. Importantly, values in the OFC are attached to goods, not to actions or to spatial locations. Furthermore, subjective values appear to be computed in this area even if the situation does not require a choice. In the light of this growing body of work, we propose that the primary function of the OFC is the computation of good identities and subjective values in an abstract representation. In this view, OFC neurons compute the subjective value of a good whenever that good is behaviorally relevant.
Financial Distress in the Great Depression
Authors: Graham John R. , Hazarika Sonali , Narasimhan Krishnamoorthy
Published: December 2011

We use firm‐level data to study corporate performance during the Great Depression era for all industrial firms on the NYSE. Our goal is to identify the factors that contribute to business insolvency and valuation changes during the period 1928‐1938. We find that firms with more debt and lower bond ratings in 1928 became financially distressed more frequently during the Depression, consistent with the trade‐off theory of leverage and the information production role of credit rating agencies. We also document for the first time that firms responded to tax incentives to use debt during the Depression era but that the extra debt used in response to this tax‐driven “debt bias” did not contribute significantly to the occurrence of distress. Finally, we conduct an out‐of‐sample test during the recent 2008‐2009 Recession and find that higher leverage and lower bond ratings also increased the occurrence of financial distress during this period.
An Empirical Examination of the Stated Purposes of Issuer Tender Offers to Purchase Common Stock
Authors: Dunn Jessica Kay , Fayman Alex , McNutt Jamie John
Published: December 2011

This paper documents the purposes of issuer tender offers to repurchase stock, as stated in Securities and Exchange Commission (SEC) disclosures, over the period 1994‐2006. We explore whether stated purposes relate to announcement period returns and find returns are significantly lower when repurchases replace dividends, distribute cash from unspecified sources, or occur subsequent to third‐party tender offers. Announcement period returns are significantly higher when repurchases are viewed by management as the best investment opportunity available or when they occur subsequent to previous repurchase programs. Finally, we find evidence in support of signaling theory and Jensen's (1986) agency cost of free cash flow theory.
Validation of Assessment for Learning Questionnaires for teachers and students
Authors: Pat‐El Ron Jonathan , Tillema Harm , Segers Mien , Vedder Paul
Published: December 2011

Background. Assessment can be a powerful force in promoting student learning. Still, few measures exist to gauge Assessment for Learning (AFL) in the classroom. Literature on AFL suggests that it encompasses both a monitor to track student progress as well as a scaffold to show or help students recognize in what areas they need to improve.

Aims. Based on a review of recent attempts to measure the AFL, we constructed Assessment for Learning Questionnaires for Teachers (TAFL‐Q) and for students (SAFL‐Q) for evaluating perceptions regarding AFL practices in classrooms using matching items.

Sample. The total sample included 1,422 students (49% girls, 51% boys) and 237 teachers (43% females, 57% males) in lower vocational secondary education.

Methods. The 28‐item questionnaires were examined by means of confirmatory factor analysis (CFA) using EQS on one random half of the sample. The CFA was cross‐validated on the second half. Measurement invariance tests were conducted to compare the students and teacher versions of the questionnaires.

Results. CFA revealed a stable second‐order two‐factor structure that was cross‐validated: perceived monitoring, and perceived scaffolding subsumed under a common factor: AFL. Tests for measurement invariance showed that the parallel constructs were measured similarly for both students and teachers.

Conclusion. The TAFL‐Q and SAFL‐Q capture the construct AFL in two subscales: Monitoring and Scaffolding, and allows for comparisons between teacher and student perceptions. The instruments can be useful tools for teachers and students alike to identify and scrutinize assessment practices in classroom.
Perceiving people as group members: The role of fit in the salience of social categorizations
Authors: Oakes Penelope J. , Turner John C. , Haslam S. Alexander
Published: December 2011

It was hypothesized that the perceived social category membership of others becomes salient as a description and explanation of their behaviour where their attitudes ‘fit’ the social categorization. Fit is defined as the degree to which the attributes of others are perceived to correlate with group membership in a normatively consistent direction. In Expt 1 subjects viewed tape—slide presentations of six‐person groups where gender composition (‘solo’ or ‘collective’) and the pattern of agreement (‘deviance’ or ‘conflict’) were manipulated in a 2 × 2 design to produce a correlation between gender and attitudes in the solo/deviance and collective/conflict conditions. In Expt 2, subjects viewed videos of a group of three arts and three science students in which the normative consistency of an arts target person (‘consistent’ or ‘inconsistent’) and the pattern of agreement (‘consensus' or ‘conflict’ or ‘deviance’) were manipulated in a 2 × 3 design to produce a normative correlation between faculty membership and attitudes in the consistent/conflict condition. Salience was measured by stereotyping in terms of, and attributions to, social category memberships. The results of both experiments were largely consistent with predictions.
Intergroup violence and intergroup attributions
Authors: Hunter J. A. , Stringer M. , Watson R. P.
Published: December 2011

Pettigrew's (1979) prediction that relative to in‐group behaviour, negative out‐group behaviour would be attributed to internal characteristics, was tested in the context of Northern Ireland's continued conflict. Catholic and Protestant respondents were presented with newsreel footage depicting scenes of in‐ and out‐group violence. One showed a Protestant attack on mourners at a Catholic funeral. The other showed a Catholic attack on a car containing two plain clothes soldiers at a Catholic funeral. Using a free response format, subjects' explanations were classified into internal and external attributions. The results showed strong support for Pettigrew's hypothesis. The implications of these findings with regard to the maintenance of intergroup conflict are discussed.
Empathy, effectiveness and donations to charity: Social psychology's contribution
Authors: Warren Peter E. , Walker Iain
Published: December 2011

Charity organizations often use mailed requests to solicit donations from the public. This is not an efficient way to raise large amounts of money. The challenge addressed in this study was to use social psychology's knowledge of helping processes to make mailed requests more effective. Two constructs were identified as possibly useful: empathy and perceived effectiveness of helping. These were manipulated in a field experiment in a 2 times 2 × 2 factorial design (two levels of empathy, two of need extent, and two of need persistence—the last two factors operationalized perceived effectiveness). Letters soliciting donations to a well‐known charity were mailed to a random sample of 2648 people in Perth, Western Australia. Manipulations of the three variables were embedded in the letters. The two effectiveness manipulations produced significant main effects, whereas the empathy manipulation was ineffective. We argue that social psychology's knowledge of helping processes is too confined to narrow, theoretical, laboratory‐based phenomena to be directly and immediately applicable to the practices of charities.
Attitudes and attraction: A test of the similarity‐attraction and dissimilarity‐repulsion hypotheses
Authors: Singh Ramadhar , Tan Lynne S. C.
Published: December 2011

It is widely held that similarity of attitudes promotes interpersonal attraction. However, Rosenbaum (1986a) argued that the relationship between attitudinal similarity and attraction is actually a relationship between attitudinal dissimilarity and repulsion. Contrasting predictions of the similarity‐attraction and dissimilarity‐repulsion hypotheses were tested in a main within‐subjects experiment. Ninety subjects first judged a stranger, a randomly sampled same‐sex university student, in a no‐attitude information control condition. Later they judged the same student again, knowing that the stranger shared 0.00, 0.50 or 1.00 proportion of similar attitudes with them (N = 30). As predicted by the similarity‐attraction hypothesis, both similar and dissimilar attitudes affected attraction. Moreover, the effects of similar and dissimilar attitudes were contingent upon the level of similarity of attitudes assumed by the subjects in the no‐attitude information control condition. In an auxiliary between‐subjects experiment, attraction response was also higher in the experimental condition of similar attitudes (N = 19) than in the control condition of no‐attitude information (N = 20). These results reaffirm the similarity‐attraction relationship but reject the dissimilarity‐repulsion hypothesis. In addition, they call attention to the proper consideration of assumed similarity in Byrne's (1971) reinforcement‐affect model.
Modelling and suicide: A test of the Werther effect
Authors: Jonas Klaus
Published: December 2011

The present study investigates whether news about suicides of prominent persons evokes an imitative effect. To this end, daily overall suicide frequencies of a German federal state, Baden‐Württemberg, were examined for the years 1968 to 1980 and were related to prominent suicides that were publicized in major newspapers. Data were analysed quasi‐experimentally and by means of a time series regression analysis. These methods yielded significant or marginally significant increases, respectively, for the week following the news. Alternative social psychological explanations were examined, and possible statistical artifacts were taken into account. The results are on the whole consistent with the assumption of an imitative effect.
Recognizing group diversity: Individualist‐collectivist and autonomous‐relational social orientations and their implications for intergroup processes
Authors: Brown Rupert , Hinkle Steve , Ely Pamela G. , Fox‐Cardamone Lee , Maras Pam , Taylor Laurie A.
Published: December 2011

A recently proposed taxonomy describes four basic types of groups or group members by crossing the individualist‐collectivist distinction with autonomous versus relational group orientations (Hinkle & Brown, 1990). The model posits that many of the basic relationships derived from Social Identity Theory will be most readily observed amongst collectivist groups with relational orientations. Three investigations (two laboratory experiments and one field study) were conducted to examine the orthogonality of the individualist‐collectivist and autonomous‐relational dimensions and test the hypothesis that significant, positive correlations between in‐group identification and in‐group bias are most apt to occur amongst collectivists with relational orientations. In all three studies, research participants completed an individualist‐collectivist inventory and measures of autonomous versus relational group orientations, in‐group identification, and in‐group favouritism. As expected, correlations between individualism‐collectivism and the measure of autonomous‐relational orientations were quite low; the two dimensions manifested little overlap. Responses to the individualist‐collectivist inventory and autonomous versus relational group orientations scale were used to divide the research participants into the taxonomy's four categories. As hypothesized, in all three studies significant, positive identification/in‐group favouritism correlations were observed for collectivists with relational orientations, whilst these same correlations amongst individualists with autonomous orientations were zero. The results from these studies support predictions derived from Hinkle & Brown's (1990) group taxonomy. The use of different paradigms, subject populations and measures of key constructs in the laboratory and field studies speaks to the model's generalizability. The general implication of these findings for Social Identity Theory and intergroup relations research is that our theoretical understanding and predictive precision can be enhanced by recognizing that the relevant psychological processes can vary across different types of groups and group members.
Groups as problem‐solving units: Toward a new meaning of social cognition
Authors: Larson James R. , Christensen Caryn
Published: December 2011

In this paper we take the position that cognition can be meaningfully understood at the group level of analysis. We refer to group‐level cognitive activity as social cognition, a term that we apply collectively to those social processes involved in the acquisition, storage, transmission, manipulation and use of information for the purpose of creating a group‐level intellective product. In this context, the word ‘social’ is used to denote how cognition is accomplished, not its content. It is proposed that at least some social cognition occurs in every kind of group problem‐solving situation, though the amount and type depends on the specific problem‐solving functions that need to be addressed in order to reach a problem solution. We examine a number of these functions, and consider how they are served by various group member actions. This analysis is informed (though not determined) by certain functional analogies that can be found between individual‐level and group‐level (i.e. social) cognition. The benefits of adopting a functional orientation to understanding group problem solving are discussed.
Shared concepts in group decision making: A model for decisions based on qualitative data
Authors: Wilson Margaret , Canter David
Published: December 2011

This paper presents a methodology for modelling the process of group decision making based on qualitative data. It is hypothesized that group decisions can be modelled in terms of the sharing and negotiation of the individual construct systems of the group members. Individual construct systems are elicited from each group member prior to the group decision using an open‐ended sorting procedure (Canter, Brown & Groat, 1985). The combined construct system of the group is represented using a non‐metric multidimensional scaling technique known as Multidimensional Scalogram Analysis (MSA). Each stage of the elicitation and representation of the construct systems is illustrated using a worked example taken from an experimental decision‐making group choosing houses for student accommodation. The decision reached by the group is compared to the multidimensional model. The potential of the model for social processes research is discussed.
Individual differences and common dimensions in Implicit Personality Theory
Authors: Vonk Roos
Published: December 2011

This paper starts from the assumption that the dimensions of meaning revealed by studies on Implicit Personality Theory (IPT) are primarily determined by the particular traits under consideration; there are individual differences in the traits that are personally relevant to subjects and hence are an integrated part of their IPT. The study of collective trait sets selected by the researcher magnifies the emergence of ‘universal’ IPT dimensions and conceals individual differences in the dimensional structure of IPT. This argument is supported by the results of two studies. In the first study, subjects judged the perceived associations among their personally relevant attributes. Considerable individual differences were found in (a) the attribute sets; (b) the dimensions of judgement; and (c) the relations between these dimensions. In the second study, subjects judged a collective set of traits. Several structural analyses indicated that individual differences were virtually absent.
The theory of reasoned action and cooperative behaviour: It takes two to use a condom
Authors: Kashima Yoshihisa , Gallois Cynthia , McCamish Malcolm
Published: December 2011

The applicability of the Theories of Reasoned Action and Planned Behaviour to the cooperative behaviour of condom use were examined. Seventy‐one male and 78 female students, all sexually active unmarried heterosexuals aged 17 to 21 years, gave information about their intentions for the next sexual encounter, as well as their attitude, subjective norm, expectancy‐value attitude and subjective norm (including normative beliefs for their sexual partner), and their past behaviour with respect to condom use. After their next sexual encounter, they completed a questionnaire on their actual condom use. Results indicated that when behavioural conditions including the availability of a condom and an agreement with the partner to use it were satisfied, intention interacted with past behaviour to predict actual behaviour. These results imply that intentions which are consistent with past behaviour are stable enough to be carried out in the face of the interpersonal dynamics of a sexual encounter. Further, normative belief for the sexual partner had a direct influence on attitudes, subjective norm and intention. Neither the Theory of Reasoned Action nor the Theory of Planned Behaviour can fully explain these results, which point to the need for further theoretical inquiry into the dynamics of cooperative behaviour.
The determinants of differential group evaluations in distinctiveness‐based illusory correlations in stereotyping
Authors: Johnson Craig , Mullen Brian
Published: December 2011

A meta‐analytic strategy was utilized to examine the determinants of differential group evaluations in the distinctiveness‐based illusory correlation paradigm. Illusory correlations measured by the estimation task proved to be a much stronger predictor of differential group evaluations than illusory correlations measured by the assignment task. Moreover, differential group evaluations seemed more dependent upon affective responses than upon cognitive load. These findings are discussed in terms of their implications regarding the mechanism(s) underlying the illusory correlation effect.
Linguistic intergroup bias and implicit attributions
Authors: Arcuri Luciano , Maass Anne , Portelli Giovanna
Published: December 2011

This experiment addresses the relation between the ‘Linguistic intergroup bias’ (that is, the tendency to describe positive in‐group and negative out‐group behaviours in more abstract terms than negative in‐group and positive out‐group behaviours) and the locus of causality and stability implicit in verbs. Subjects were presented with episodes of successful and unsuccessful interactions involving in‐group or out‐group protagonists. Applying Semin & Fiedler's (1988) ‘Linguistic category model’, subjects were asked to choose between two explanations of each episode, one expressed in more concrete interpretive action verbs (implying high subject causation but low stability), the other expressed in more abstract state verbs (implying low subject causation but high stability). Results show that negative in‐group and positive out‐group behaviours were described in more concrete terms despite the greater subject causation implicit in such verbs.
Corrosion Effects on Reliability of Flat Plates in Tension
Authors: Yu Weiwei , Karr Dale G. , Vargas Pedro M.
Published: December 2011

Neuber’s theory of elastic and inelastic stress concentration factors are applied to the pit corrosion of plates. The finite element method is then employed to model the problem numerically and to calculate the stress concentration factors for semioblate spheroidal pits. Furthermore, corrosion development is a process with many random factors such as the geometry and the growth rate. A realistic reflection of corrosion effects on structural failure is to consider it within the framework of reliability analysis. By knowing the analytical formula of stress concentration factor, reliability analyses are conducted to calculate the reliability safety index of the panel based on a strain-based limit state. The structural failure can then be directly related to the reliability safety index. The reliability procedure is demonstrated in an example of a highly deformed bottom shell panel during ship grounding. Partial safety factors of two random variables which describe pit corrosion geometry and the effective nominal strain level are also calculated. Recommendations for using partial safety factors are provided.
Optimizing Ultrasonic Additive Manufactured Al 3003 Properties With Statistical Modeling
Authors: Hopkins C. D. , Wolcott P. J. , Dapino M. J. , Truog A. G. , Babu S. S. , Fernandez S. A.
Published: December 2011

Ultrasonic additive manufacturing (UAM) has proven useful in the solid-state, low tempe’rature fabrication of layered solid metal structures. It is necessary to optimize the various process variables that affect the quality of bonding between layers through investigation of the mechanical strength of various UAM builds. We investigate the effect of the process parameters tack force, weld force, oscillation amplitude, and weld rate on the ultimate shear strength (USS) and ultimate transverse tensile strength (UTTS) of 3003-H18 aluminum UAM built samples. A multifactorial experiment was designed and an analysis of variance was performed to obtain an optimal set of process parameters for maximizing mechanical strength for the tested factors. The statistical analyses indicate that a relatively high mechanical strength can be achieved with a process window bounded by a 350 N tack force, 1000 N weld force, 26 μm oscillation amplitude, and about 42 mm/s weld rate. Optical analyses of bond characterization did not show a consistent correlation linking linear weld density and bonded area of fractured surfaces to mechanical strength. Therefore, scanning electronmicroscopy (SEM) was conducted on fractured samples showing a good correlation between mechanical strength and area fraction that shows ductile failure.
Real-time spectroscopic ellipsometric investigation of adsorption and desorption in atomic layer deposition: A case study for the strontium bis(tri-isopropylcyclopentadienyl)/water process
Authors: Wang Han , Jiang Xiaoqiang , Willis Brian G.
Published: December 2011

The atomic layer deposition (ALD) of SrO thin films from Sr(C5iPr3H2)2 (g) and H2O (g) was studied using real-time spectroscopic ellipsometry (SE) investigations of adsorption and desorption during each half cycle. Adsorption of Sr(C5iPr3H2)2 was self-terminating at deposition temperatures of 150–350 °C and the saturated growth per cycle (GPC) highly depended on the deposition temperature, ranging from 0.05 to 0.33 nm/cycle at the lower and upper limits, respectively. Submonolayer sensitivity of SE was demonstrated by examining changes in the ellipsometric parameters and apparent thickness before and after precursor pulses. A comparison between experimental GPC and available theoretical models demonstrates that the deposition temperature has a marked effect on the reaction mechanism and indicates more than one operation regime for the ALD process of Sr(C5iPr3H2)2 and H2O.
Identification of New Antileishmanial Leads from Hits Obtained by High-Throughput Screening
Authors: Zhu Xiaohua , Pandharkar Trupti , Werbovetz Karl
Published: December 2011

A previous screen of ∼200,000 compounds from the PubChem database identified 70 compounds possessing 50% effective concentrations (EC
50
s) below 1 μM against
Leishmania major
promastigotes that were not toxic to mammalian epithelial cancer cells at this concentration (E. Sharlow et al., PLoS Negl. Trop. Dis. 3:e540, 2009). Based on availability and chemical exclusion criteria, 31 of these compounds were purchased from commercial suppliers and evaluated for
in vitro
activity against intracellular
L. donovani
and
L. amazonensis
parasites. Benzothiazole cyanine compounds (PubChem 16196319 and 16196223) displayed potent activity against intracellular amastigotes, prompting a search for commercially available compounds that were structurally related. Pubchem 123859 (the cyanine dye thiazole orange) showed exceptionally potent activity against intracellular
L. donovani in vitro
(50% inhibitory concentration [IC
50
] = 21 ± 12 nM) and low cytotoxicity against Vero cells (IC
50
= 7,800 ± 200 nM). Administration of 123859 and 16196319 at a dose of 1 mg/kg of body weight intraperitoneally (i.p.) daily for 5 days resulted in 44% ± 4% and 42% ± 3% suppression of liver parasitemia in
L. donovani
-infected BALB/c mice, respectively, compared to the untreated control group (the reductions in liver parasitemia were 30% ± 5% and 27% ± 4%, respectively, compared to the (2-hydroxypropyl)-β-cyclodextrin solution (HPβCD) vehicle control, which itself displayed some antileishmanial activity). Benzothiazole-containing cyanine dyes are thus potential lead compounds for the discovery of novel antileishmanial agents.
Aerosolized Gentamicin Reduces the Burden of Tuberculosis in a Murine Model
Authors: Roy Chad J. , Sivasubramani Satheesh K. , Dutta Noton K. , Mehra Smriti , Golden Nadia A. , Killeen Stephanie , Talton James D. , Hammoud Badre E. , Didier Peter J. , Kaushal Deepak
Published: December 2011

Tuberculosis (TB) is a major infectious disease problem: 1.7 million people annually die due to TB. Emergence of drug-resistant
Mycobacterium tuberculosis
and the lack of new antibiotics have exacerbated the situation. There is an urgent need to develop or repurpose drugs against TB. We evaluated inhaled gentamicin as direct respiratory system-targeted therapy in a murine model of TB. Aerosolized-gentamicin-treated mice showed significantly reduced lung
M. tuberculosis
loads and fewer granulomas relative to untreated controls. These results suggest that direct delivery of antibiotics to the respiratory system may provide therapeutic benefit to conventional treatment regimes for treatment of pulmonary TB.
Molecular Analyses of TEM Genes and Their Corresponding Penicillinase-Producing Neisseria gonorrhoeae Isolates in Bangkok, Thailand
Authors: Nakayama Shu-ichi , Tribuddharat Chanwit , Prombhul Sasiprapa , Shimuta Ken , Srifuengfung Somporn , Unemo Magnus , Ohnishi Makoto
Published: December 2011

Neisseria gonorrhoeaeis a major public health problem globally, especially because the bacterium has developed resistance to most antimicrobials introduced for first-line treatment of gonorrhea. In the present study, 96N. gonorrhoeaeisolates with high-level resistance to penicillin from 121 clinical isolates in Thailand were examined to investigate changes related to their plasmid-mediated penicillin resistance and their molecular epidemiological relationships. A β-lactamase (TEM) gene variant,blaTEM-135, that may be a precursor in the transitional stage of a traditionalblaTEM-1gene into an extended-spectrum β-lactamase (ESBL), possibly causing high resistance to all extended-spectrum cephalosporins inN. gonorrhoeae, was identified. Clonal analysis using multilocus sequence typing (MLST) andN. gonorrhoeaemultiantigen sequence typing (NG-MAST) revealed the existence of a sexual network among patients from Japan and Thailand. Molecular analysis of theblaTEM-135gene showed that the emergence of this allele might not be a rare genetic event and that the allele has evolved in different plasmid backgrounds, which results possibly indicate that it is selected due to antimicrobial pressure. The presence of theblaTEM-135allele in the penicillinase-producingN. gonorrhoeaepopulation may call for monitoring for the possible emergence of ESBL-producingN. gonorrhoeaein the future. This study identified ablaTEMvariant (blaTEM-135) that is a possible intermediate precursor for an ESBL, which warrants international awareness.
Resistance to Linezolid Caused by Modifications at Its Binding Site on the Ribosome
Authors: Long Katherine S. , Vester Birte
Published: December 2011

Linezolid is an oxazolidinone antibiotic in clinical use for the treatment of serious infections of resistant Gram-positive bacteria. It inhibits protein synthesis by binding to the peptidyl transferase center on the ribosome. Almost all known resistance mechanisms involve small alterations to the linezolid binding site, so this review will therefore focus on the various changes that can adversely affect drug binding and confer resistance. High-resolution structures of linezolid bound to the 50S ribosomal subunit show that it binds in a deep cleft that is surrounded by 23S rRNA nucleotides. Mutation of 23S rRNA has for some time been established as a linezolid resistance mechanism. Although ribosomal proteins L3 and L4 are located further away from the bound drug, mutations in specific regions of these proteins are increasingly being associated with linezolid resistance. However, very little evidence has been presented to confirm this. Furthermore, recent findings on the Cfr methyltransferase underscore the modification of 23S rRNA as a highly effective and transferable form of linezolid resistance. On a positive note, detailed knowledge of the linezolid binding site has facilitated the design of a new generation of oxazolidinones that show improved properties against the known resistance mechanisms.
Immobilization of Antibacterial Dihydropyrrol-2-ones on Functional Polymer Supports To Prevent Bacterial Infections
In Vivo
Authors: Ho Kitty Ka Kit , Cole Nerida , Chen Renxun , Willcox Mark D. P. , Rice Scott A. , Kumar Naresh
Published: December 2011

Antibiotic-resistant
Staphylococcus aureus
is of great concern, as it causes a wide range of life-threatening infections. The current study demonstrates that dihydropyrrolone (DHP)-coated polyacrylamide substrates are effective in reducing the number of culturable clinical isolates of
S. aureus
in vitro
in a dose-dependent manner and are able to reduce the pathogenic potential of staphylococcal infection in a subcutaneous infection model. Covalently bound DHPs therefore show great potential for use as an antimicrobial strategy in device-related applications.
Live Attenuated Salmonella Vaccines Displaying Regulated Delayed Lysis and Delayed Antigen Synthesis To Confer Protection against Mycobacterium tuberculosis
Authors: Juárez-Rodríguez María Dolores , Yang Jiseon , Kader Rebin , Alamuri Praveen , Curtiss Roy , Clark-Curtiss Josephine E.
Published: December 2011

Live recombinant attenuatedSalmonellavaccine (RASV) strains have great potential to induce protective immunity againstMycobacterium tuberculosisby deliveringM. tuberculosisantigens. Recently, we reported that, in orally immunized mice, RASV strains delivering theM. tuberculosisearly secreted antigenic target 6-kDa (ESAT-6) protein and culture filtrate protein 10 (CFP-10) antigens via theSalmonellatype III secretion system (SopE amino-terminal region residues 1 to 80 with two copies of ESAT-6 and one copy of CFP-10 [SopENt80-E2C]) afforded protection against aerosol challenge withM. tuberculosis. Here, we constructed and evaluated an improvedSalmonellavaccine againstM. tuberculosis. We constructed translational fusions for the synthesis of two copies of ESAT-6 plus CFP-10 fused to the OmpC signal sequence (OmpCSS-E2C) and amino acids 44 to 338 of antigen 85A (Ag85A294) flanked by the signal sequence (SS) and C-terminal peptide (CT) of β-lactamase (BlaSS-Ag85A294-BlaCT) to enable delivery via theSalmonellatype II secretion system. The genes expressing these proteins were cloned as an operon transcribed from Ptrcinto isogenic Asd+/MurA+pYA3681 lysis vector derivatives with different replication origins (pBR, p15A, pSC101), resulting in pYA4890, pYA4891, and pYA4892 for SopENt80-E2C/Ag85A294synthesis and pYA4893 and pYA4894 for OmpCSS-E2C/Ag85A294synthesis. Mice orally immunized with the RASV χ11021 strain engineered to display regulated delayed lysis and regulated delayed antigen synthesisin vivoand harboring pYA4891, pYA4893, or pYA4894 elicited significantly greater humoral and cellular immune responses, and the RASV χ11021 strain afforded a greater degree of protection againstM. tuberculosisaerosol challenge in mice than RASVs harboring any other Asd+/MurA+lysis plasmid and immunization withM. bovisBCG, demonstrating that RASV strains displaying regulated delayed lysis with delayed antigen synthesis resulted in highly immunogenic delivery vectors for oral vaccination againstM. tuberculosisinfection.
Sialylation of Lipooligosaccharides Is Dispensable for the Virulence of Haemophilus ducreyi in Humans
Authors: Spinola Stanley M. , Li Wei , Fortney Kate R. , Janowicz Diane M. , Zwickl Beth , Katz Barry P. , Munson Robert S.
Published: December 2011

Sialylated glycoconjugates on the surfaces of mammalian cells play important roles in intercellular communication and self-recognition. The sialic acid preferentially expressed in human tissues is
N
-acetylneuraminic acid (Neu5Ac). In a process called molecular mimicry, many bacterial pathogens decorate their cell surface glycolipids with Neu5Ac. Incorporation of Neu5Ac into bacterial glycolipids promotes bacterial interactions with host cell receptors called Siglecs. These interactions affect bacterial adherence, resistance to serum killing and phagocytosis, and innate immune responses.
Haemophilus ducreyi
, the etiologic agent of chancroid, expresses lipooligosaccharides (LOS) that are highly sialylated. However, an
H. ducreyi
sialyltransferase (
lst
) mutant, whose LOS contain reduced levels of Neu5Ac, is fully virulent in human volunteers. Recently, a second sialyltransferase gene (
Hd0053
) was discovered in
H. ducreyi
, raising the possibility that
Hd0053
compensated for the loss of
lst
during human infection. CMP-Neu5Ac is the obligate nucleotide sugar donor for all bacterial sialyltransferases; LOS derived from an
H. ducreyi
CMP-Neu5Ac synthetase (
neuA
) mutant has no detectable Neu5Ac. Here, we compared an
H. ducreyi neuA
mutant to its wild-type parent in several models of pathogenesis. In human inoculation experiments, the
neuA
mutant formed papules and pustules at rates that were no different than those of its parent. When grown in media with and without Neu5Ac supplementation, the
neuA
mutant and its parent had similar phenotypes in bactericidal, macrophage uptake, and dendritic cell activation assays. Although we cannot preclude a contribution of LOS sialylation to ulcerative disease, these data strongly suggest that sialylation of LOS is dispensable for
H. ducreyi
pathogenesis in humans.
Effects of Amino Acid Supplementation on Porin Expression and ToxR Levels in Vibrio cholerae
Authors: Mey Alexandra R. , Craig Stephanie A. , Payne Shelley M.
Published: December 2011

Vibrio cholerae
responds to environmental changes by altering the protein composition of its outer membrane. In rich medium,
V. cholerae
expresses almost exclusively the outer membrane porin OmpU, whereas in minimal medium, OmpT is the dominant porin. The supplementation of a minimal medium with a mixture of asparagine, arginine, glutamic acid, and serine (NRES) promotes OmpU production and OmpT repression at levels similar to those seen with rich media. Here we show that the altered Omp profile is not due to an increase in the growth rate in the presence of supplemental amino acids but requires the addition of specific amino acids. The effects of the NRES mix on Omp production were mediated by ToxR, a known regulator of
omp
gene expression. No changes in the Omp profile were detected in a
toxR
mutant. Supplementation with the NRES mix resulted in significantly higher levels of ToxR, and the elevated ToxR levels were sufficient to cause a switch in Omp synthesis. The increase in the level of the ToxR protein correlated with an increase in
toxR
mRNA levels and was observed only when
toxR
was expressed from its native promoter. ToxS, which is required for ToxR activity, was necessary for NRES-mediated
omp
gene regulation but not for the increase in ToxR levels. The growth of
V. cholerae
in the presence of bile acids also resulted in Omp switching, and this required ToxR. However, unlike the NRES mix, bile acids did not increase either ToxR protein or
toxR
mRNA levels, suggesting a different mechanism of
omp
gene regulation by bile than that by amino acids.
Molecular Mechanisms That Mediate Colonization of Shiga Toxin-Producing Escherichia coli Strains
Authors: Farfan Mauricio J. , Torres Alfredo G.
Published: December 2011

Shiga toxin-producing
Escherichia coli
(STEC) is a group of pathogens which cause gastrointestinal disease in humans and have been associated with numerous food-borne outbreaks worldwide. The intimin adhesin has been considered for many years to be the only colonization factor in these strains. However, the rapid progress in whole-genome sequencing of different STEC serotypes has accelerated the discovery of other adhesins (fimbrial and afimbrial), which have emerged as important contributors to the intestinal colonization occurring during STEC infection. This review summarizes recent progress to identify and characterize, at the molecular level, novel adhesion and colonization factors in STEC strains, with an emphasis on their contribution to virulence traits, their host-pathogen interactions, the regulatory mechanisms controlling their expression, and their role as targets eliciting immune responses in the host.
The epidemiology of new versus recurrent sports concussions among high school athletes, 2005–2010
Authors: Castile Lianne , Collins Christy L , McIlvain Natalie M , Comstock R Dawn
Published: December 2011

Objectives

To compare new versus recurrent concussions with respect to constellation of symptoms, symptom severity, symptom resolution; evaluate potential subset differences with respect to gender and sport; and to compare mechanisms and activities associated with new versus recurrent concussions.

Methods

Sports-related injury and exposure data were collected for nine sports from 2005 to 2010 from 100 nationally representative US high schools.

Results

Nationally, an estimated 732,805 concussions occurred. Of these reported concussions, 13.2% were recurrent. The rate of new concussions was 22.2 per 100,000 athletic exposures while the rate of recurrent concussions was 3.1 per 100,000 athletic exposures (RR 7.23, 95% CI 6.39 to 8.17, p<0.001). While 0.6% of new concussion symptoms took >1 month to resolve, 6.5% of recurrent concussion symptoms took >1 month to resolve (IPR 10.35; 95% CI 4.62 to 23.16; p<0.001). Loss of consciousness was reported more often with recurrent (7.7%) than new concussions (4.4%) (IPR 1.76; 95% CI 1.02 to 3.03; p=0.043). A greater proportion of athletes sustaining recurrent concussions returned to play in >3 weeks (7.5%) or were medically disqualified (16.2%) than athletes sustaining new concussions (3.8%; IPR 1.95; 95% CI 1.01 to 3.77; p=0.047 and 2.9%; IPR 5.58; 95% CI 3.50 to 8.88; p<0.001, respectively). The majority of new and recurrent concussions resulted from contact with another person (73.4% and 77.9%, respectively).

Conclusions

Athletes sustaining recurrent concussions had longer symptom resolution times, were kept out of play longer and reported loss of consciousness more frequently than athletes sustaining new concussions. With the possibility of long-term impairment and other negative sequelae, proper management and prevention of concussions at the high school level is imperative.
Which domains of childhood physical activity predict physical activity in adulthood? A 20-year prospective tracking study
Authors: Cleland Verity , Dwyer Terence , Venn Alison
Published: December 2011

Purpose

It is important to examine how childhood physical activity is related to adult physical activity in order to best tailor physical activity-promotion strategies. The time- and resource-intensive nature of studies spanning childhood into adulthood means the understanding of physical activity trajectories over this time span is limited. This study aimed to determine whether childhood domain-specific physical activities predict domain-specific physical activity 20 years later in adulthood, and whether age and sex play a role in these trajectories.

Methods

In 1985, 6412 children of age 9–15 years self-reported frequency and duration of discretionary sport and exercise (leisure activity), transport activity, school sport and physical education (PE) in the past week and number of sports played in the past year. In 2004–2006, 2201 of these participants (aged 26–36 years) completed the long International Physical Activity Questionnaire and/or wore a Yamax pedometer. Analyses included partial correlation coefficients and log-binomial regression.

Results

Childhood and adult activity were weakly correlated (r=−0.08–0.14). Total weekly physical activity in childhood did not predict adult activity. School PE predicted adult total weekly physical activity and daily steps (older females), while school sport demonstrated inconsistent associations. Leisure and transport activity in childhood predicted adult leisure activity among younger males and older females, respectively. Childhood past year sport participation positively predicted adult physical activity (younger males and older females).

Conclusions

Despite modest associations between childhood and adult physical activity that varied by domain, age and sex, promoting a range of physical activities to children of all ages is warranted.
Stenting of complete vertebral artery ostial occlusion in a patient with medically refractory vertebrobasilar ischemia
Authors: Noorian Ali Reza , Gupta Rishi , Nogueira Raul Gomes
Published: December 2011

The case history is described of a man in his late 50s who presented with recurrent vertebrobasilar ischemic events despite maximal medical treatment in the setting of a complete left vertebral artery ostial occlusion. The complete occlusion was successfully treated with a drug-eluting stent. The patient has been symptom-free for 6 months. Stenting of vertebral artery ostial occlusion is technically feasible in well-selected cases.