bluuebunny/crossref_metadata_2025 huggingface dataset:
Modified wire array underwater electrical explosion
Authors: Gilburd L. , Efimov S. , Fedotov Gefen A. , Gurovich V. Tz. , Bazalitski G. , Antonov O. , Krasik Ya. E.
Published: March 2012

The results of experiments involving underwater electrical explosion of different wire arrays using an outer metallic cylinder as a shock reflector are presented. A pulse generator with a stored energy of about 6 kJ, current amplitude ≤ 500 kA, and rise time of 350 ns was used for the wire array explosion. The results of the experiments and of hydrodynamic simulations showed that in the case of a Cu wire array explosion, the addition of the reflector increases the pressure and temperature of the water in the vicinity of the implosion axis about 1.38 and about 1.33 times, respectively. Also, it was shown that in the case of an Al wire array explosion with stainless steel reflector, Al combustion results, and, accordingly, additional energy is delivered to the converging water flow generating about 540 GPa pressure in the vicinity of the explosion axis. Finally, it was found that microsecond time scale light emission that appears with microsecond time scale delay with respect to the nanosecond time scale self-light emission of the compressed water in the vicinity of the implosion axis is related to water bubbles formation which scattered light of exploded wires.
THE TIMING OF ISLAND EFFECTS IN NONNATIVE SENTENCE PROCESSING
Authors: Felser Claudia , Cunnings Ian , Batterham Claire , Clahsen Harald
Published: March 2012

Using the eye-movement monitoring technique in two reading comprehension experiments, this study investigated the timing of constraints on wh-dependencies (so-called island constraints) in first- and second-language (L1 and L2) sentence processing. The results show that both L1 and L2 speakers of English are sensitive to extraction islands during processing, suggesting that memory storage limitations affect L1 and L2 comprehenders in essentially the same way. Furthermore, these results show that the timing of island effects in L1 compared to L2 sentence comprehension is affected differently by the type of cue (semantic fit versus filled gaps) signaling whether dependency formation is possible at a potential gap site. Even though L1 English speakers showed immediate sensitivity to filled gaps but not to lack of semantic fit, proficient German-speaking learners of English as a L2 showed the opposite sensitivity pattern. This indicates that initial wh-dependency formation in L2 processing is based on semantic feature matching rather than being structurally mediated as in L1 comprehension.
VOWEL EPENTHESIS AND SEGMENT IDENTITY IN KOREAN LEARNERS OF ENGLISH
Authors: de Jong Kenneth , Park Hanyong
Published: March 2012

Recent literature has sought to understand the presence of epenthetic vowels after the productions of postvocalic word-final consonants by second language (L2) learners whose first languages (L1s) restrict the presence of obstruents in coda position. Previous models include those in which epenthesis is seen as a strategy to mitigate the effects of coda licensing restrictions in the L1; others see epenthesis as a result of misperception of consonant releases in the L2 as indicating the presence of an additional syllable nucleus. The current study examines segmental identification and syllable counting in inexperienced Korean learners of English as a foreign language. Across stimuli, two effects were found. Increased perceptual epenthesis correlated with increased identification of a segment as voiceless, indicating a joint perception of voicelessness and an epenthetic vowel. Also, rate of epenthesis increased with accuracy of detecting sibilants and coronal segments, sounds characterized by salient consonant noise. Taken together, these results indicate a perceptual mechanism that evaluates segmental content and prosodic structure from an integrated percept. Analyses across individual listeners do not support a model in which perceptual epenthesis is a strategy to increase segmental accuracy; rather, they support models in which both syllable counting and segmental identification are skills that are reflections of increased proficiency in the L2. These results are discussed with respect to models of L2 phonology that rely on the robust encoding of lexical items.
THE GROWTH OF RACE AND CULTURE IN NINETEENTH-CENTURY GERMANY: GUSTAV KLEMM AND THE UNIVERSAL HISTORY OF HUMANITY
Authors: MANIAS CHRIS
Published: March 2012

The German ethnologist Gustav Klemm (1802–67) occupies a rather problematic position in the history of ideas, alternately hailed as a seminal figure in the development of concepts of race and culture, or belittled as a rather derivative marginal thinker. This article seeks to clarify Klemm's significance by rooting his theories in their contemporary intellectual and social context. It argues that his system, a linear model of human development driven by the interworkings of race and culture, grew from an attempt to synthesize Enlightenment notions of universal progress with major shifts of the mid-nineteenth century, including experiences of dramatic social, political and technological change, commitments to constitutional liberalism, and changes in contemporary ethnology and museology. His works therefore illustrate the complex manners in which ideas of heredity, environment, civilization, development and gender could be blended in this often neglected period, and how their meanings and implications altered as syntheses were built.
ANTI-ESSENTIALIST FEMINISM VERSUS MISOGYNIST SEXOLOGY INFIN DE SIECLEVIENNA
Authors: LECK RALPH
Published: March 2012

As the foundational contributions of thefin de sièclesexual science movement to research on sexuality continue to be fleshed out, new avenues of understanding this important movement will continue to emerge. This essay uncovers the explosive intersection of early sexual science and strains of first-wave feminism in Vienna and charts the emergence of anti-essentialist feminism from this intersection. The first section offers an interpretation of how the discipline of sexual science emerged from medical criminology and how these origins contributed to the misogynist inflection of early sexology. The essay then chronicles the intersection of first-wave feminism and this misogynist sexual science. The central argument is that feminists’ encounters with sexual science dialectically produced an anti-essentialist variant of feminism. This microscopic interpretation of historical context, it will be argued, provides a new vista from which to view the larger tableau of modern European, especially Austrian, intellectual history.
THE CLASSICAL TURN IN ENLIGHTENMENT STUDIES
Authors: EDELSTEIN DAN
Published: March 2012

Antiquity is back. In some respects, it is surprising it ever went away: for the last forty years, Peter Gay's magisterial survey, which connected the “little flock” ofphilosopheswith “pagan” authors, has loomed large over the field of Enlightenment studies. But shortly after its publication, a methodological sea change pulled the field in an opposite direction. Robert Darnton hailed this rising tide of social and cultural history in a 1971 largely critical review of Gay's two volumes. The hyper-longue duréeof Gay's historical panorama, which extended from the age of Virgil to that of Voltaire, was soon to be displaced by more focused inquiries into the history of the book, forms of enlightened sociability, and national difference. Intellectual history, particularly of Gay's epic brand, soon became scarce, despite the lasting presence of Gay's two volumes on bibliographies and course syllabi.
RISE,GRUBENHUND: ON PROVINCIALIZING KUHN
Authors: COEN DEBORAH R.
Published: March 2012

Bilingualism was Kuhn's solution to the problem of relativism, the problem raised by his own theory of incommensurability. InThe Structure of Scientific Revolutions, he argued that scientific theories are separated by gulfs of mutual incomprehension. There is no neutral ground from which to judge one theory fitter than another. Each is formulated in its own language and cannot be translated into the idiom of another. Yet, like many Americans, Kuhn never had the experience of moving comfortably between languages. “I've never been any good really at foreign languages,” he admitted in an interview soon before his death. “I can read French, I can read German, if I'm dropped into one of those countries I can stammer along for a while, but my command of foreign languages is not good, and never has been, which makes it somewhat ironic that much of my thought these days goes to language.” Kuhn may have been confessing to more than a personal weakness. His linguistic ineptitude seems to be a clue to his overweening emphasis on the difficulty of “transworld travel.” Multilingualism remained for him an abstraction. In this respect, I will argue, Kuhn engendered a peculiarly American turn in the history of science. Kuhn's argument for the dependence of science on the norms of particular communities has been central to the development of studies of scienceinandasculture since the 1980s. Recent work on the mutual construction of science and nationalism, for instance, is undeniably in Kuhn's debt. Nonetheless, the Kuhnian revolution cut off other avenues of research. In this essay, I draw on the counterexample of the physician–historian Ludwik Fleck, as well as on critiques by Steve Fuller and Ted Porter, to suggest one way to situate Kuhn within the broader history of the history of science. To echo Kuhn's own visual metaphors, one of the profound effects ofThe Structure of Scientific Revolutionson the field of history of science was to render certain modes of knowledge production virtually invisible.
BACKWARDS TO THE FUTURE: THE CULTURAL TURN AND THE WISDOM OF INTELLECTUAL HISTORY
Authors: HALL DAVID D.
Published: March 2012

Unlike the memory of the querulous and time-bending White Queen inThrough the Looking Glass, mine befits her complaint, inclined as I am to thinking backwards when asked to contemplate the state of our field. Backwards, then, I go in the first section of this essay, after a few opening comments on the situation of our field at the present moment. Thereafter, I describe the emergence of cultural history and summarize some of its strengths and weaknesses, to the end of reflecting on its implications for intellectual history.
Transnational Access to Environmental Information
Authors: Krämer Ludwig
Published: March 2012

This paper traces back the efforts, in particular in Europe, to promote transnational legal provisions which grant a right of access to environmental information. Initiatives in the 1970s failed to establish a fundamental right to a clean environment. However, the establishment of fundamental procedural rights of access to information, participation in decision-making and access to justice in environmental matters has been more successful – culminating in the 1998 Aarhus Convention. This paper describes the – until now unsuccessful – attempts to extend the territorial scope of application of the Aarhus Convention to non-European countries and regions, and ultimately the conclusion of a global convention on access to environmental information.
Internet Addiction and Personality in First-Person-Shooter Video Gamers
Authors: Montag Christian , Flierl Matthias , Markett Sebastian , Walter Nora , Jurkiewicz Magdalena , Reuter Martin
Published: March 2012

The present study investigated the influence on Internet addiction of numerous variables ranging from personality to psychological and physical well-being, in a large and highly ecologically valid sample of mainly male adolescent online computer gamers (first-person-shooter video gamers) in Germany. Low Self-Directedness could be linked to a high Internet Addiction Test score in the present study, and the data yielded a continuum model indicating that low Self-Directedness is highly correlated with Internet Addiction Score, not only in students but also in first-person-shooter video gamers.
Sex Differences in Mass Media Preferences Across Four Asian Countries
Authors: Ratnasingam Malini , Ellis Lee
Published: March 2012

Background. Nearly all of the research on sex differences in mass media utilization has been based on samples from the United States and a few other Western countries. Aim. The present study examines sex differences in mass media utilization in four Asian countries (Japan, Malaysia, South Korea, and Singapore). Methods. College students self-reported the frequency with which they accessed the following five mass media outlets: television dramas, televised news and documentaries, music, newspapers and magazines, and the Internet. Results. Two significant sex differences were found when participants from the four countries were considered as a whole: Women watched television dramas more than did men; and in Japan, female students listened to music more than did their male counterparts. Limitations. A wider array of mass media outlets could have been explored. Conclusions. Findings were largely consistent with results from studies conducted elsewhere in the world, particularly regarding sex differences in television drama viewing. A neurohormonal evolutionary explanation is offered for the basic findings.
Nonlinear dynamical triggering of slow slip on simulated earthquake faults with implications to Earth
Authors: Johnson P. A. , Carpenter B. , Knuth M. , Kaproth B. M. , Le Bas P.‐Y. , Daub E. G. , Marone C.
Published: March 2012

Among the most fascinating, recent discoveries in seismology are the phenomena of dynamically triggered fault slip, including earthquakes, tremor, slow and silent slip—during which little seismic energy is radiated—and low frequency earthquakes. Dynamic triggering refers to the initiation of fault slip by a transient deformation perturbation, most often in the form of passing seismic waves. Determining the frictional constitutive laws and the physical mechanism(s) governing triggered faulting is extremely challenging because slip nucleation depths for tectonic faults cannot be probed directly. Of the spectrum of slip behaviors, triggered slow slip is particularly difficult to characterize due to the absence of significant seismic radiation, implying mechanical conditions different from triggered earthquakes. Slow slip is often accompanied by nonvolcanic tremor in close spatial and temporal proximity. The causal relationship between them has implications for the properties and physics governing the fault slip behavior. We are characterizing the physical controls of triggered slow slip via laboratory experiments using sheared granular media to simulate fault gouge. Granular rock and glass beads are sheared under constant normal stress, while subjected to transient stress perturbation by acoustic waves. Here we describe experiments with glass beads, showing that slow and silent slip can be dynamically triggered on laboratory faults by ultrasonic waves. The laboratory triggering may take place during stable sliding (constant friction and slip velocity) and/or early in the slip cycle, during unstable sliding (stick‐slip). Experimental evidence indicates that the nonlinear‐dynamical response of the gouge material is responsible for the triggered slow slip.
Analysis of matrix effects critical to microbial transport in organic waste‐affected soils across laboratory and field scales
Authors: Unc Adrian , Goss Michael J. , Cook Simon , Li Xunde , Atwill Edward R. , Harter Thomas
Published: March 2012

Organic waste applications to soil (manure, various wastewaters, and biosolids) are among the most significant sources of bacterial contamination in surface and groundwater. Transport of bacteria through the vadose zone depends on flow path geometry and stability and is mitigated by interaction between soil, soil solution, air‐water interfaces, and characteristics of microbial surfaces. After initial entry, the transport through soil depends on continued entrainment of bacteria and resuspension of those retained in the porous structure. We evaluated the retention of bacteria‐sized artificial microspheres, varying in diameter and surface charge and applied in different suspending solutions, by a range of sieved soils contained in minicolumns, the transport of hydrophobic bacteria‐sized microspheres through undisturbed soil columns as affected by waste type under simulated rainfall, and the field‐scale transport of Enterococcus spp. to an unconfined sandy aquifer after the application of liquid manure. Microsphere retention reflected microsphere properties. The soil type and suspending solution affected retention of hydrophilic but not hydrophobic particles. Retention was not necessarily facilitated by manure‐microsphere‐soil interactions but by manure‐soil interactions. Undisturbed column studies confirmed the governing role of waste type on vadose‐zone microsphere transport. Filtration theory applied as an integrated analysis of transport across length scales showed that effective collision efficiency depended on the distance of travel. It followed a power law behavior with the power coefficient varying from ∼0.4 over short distances to >0.9 over 1 m (i.e., very little filtration for a finite fraction of biocolloids), consistent with reduced influence of soil solution and biocolloid properties at longer travel distances.
Heterogeneity of biogenic gas ebullition in subtropical peat soils is revealed using time‐lapse cameras
Authors: Comas Xavier , Wright William
Published: March 2012

We tested a set of biogenic gas traps combined with time‐lapse cameras to investigate the heterogeneous nature of biogenic gas ebullition events in subtropical peat soils at both the laboratory and field scale. The main findings are: (1) ebullition events in peat soils are highly heterogeneous; (2) estimates of flux rate are directly influenced by temporal scale of measurement with rapid (i.e., hourly) releasing events exceeding daily averages by one order of magnitude; and (3) increases in atmospheric pressure result in gas release from shallow peat soils into the atmosphere (i.e., ebullition), as indicated by a positive linear relation between changes in biogenic gas content and changes in atmospheric pressure. These results suggest that biogenic gas releases from shallow subtropical peat soils are not constant with larger than average daily fluxes being potentially released within hours during periods of increased atmospheric pressure. Furthermore, this study also shows the potential of time‐lapse cameras for autonomously assessing the temporal variation in biogenic gas flux to the atmosphere from peatlands, and questions what temporal scale of measurement should be appropriate to infer dynamics of biogenic gas release in peat soils.
The biology of happiness
Authors: Kováč Ladislav
Published: March 2012

Happiness has become a major topic of interest for the social sciences and economists, yet biology has had little to say about this elusive emotion. As humans evolved to seek pleasure and avoid pain, how did this ancient survival mechanism determine human destiny in modern societies.
Transcription goes digital
Authors: Lionnet Timothée , Singer Robert H
Published: March 2012

Transcription is a complex process that integrates the state of the cell and its environment to generate adequate responses for cell fitness and survival. Recent microscopy experiments have been able to monitor transcription from single genes in individual cells. These observations have revealed two striking features: transcriptional activity can vary markedly from one cell to another, and is subject to large changes over time, sometimes within minutes. How the chromatin structure, transcription machinery assembly and signalling networks generate such patterns is still unclear. In this review, we present the techniques used to investigate transcription from single genes, introduce quantitative modelling tools, and discuss transcription mechanisms and their implications for gene expression regulation.
The Effect of Articulatory Adjustment on Reducing Hypernasality
Authors: Rong Panying , Kuehn David
Published: March 2012

Purpose

With the goal of using articulatory adjustments to reduce hypernasality, this study utilized an articulatory synthesis model (Childers, 2000) to simulate the adjustment of articulatory configurations with an open velopharynx to achieve the same acoustic goal as normal speech simulated with a closed velopharynx.

Method

To examine the effect of articulatory adjustment on perceived nasality, this study used an articulatory synthesis model (Childers, 2000) to synthesize 18 oral /i/ vowels, 18 nasal /i/ vowels, and 18 nasal /i/ vowels with computer-generated articulatory adjustments; these vowels were then presented to 7 listeners for perceptual ratings of nasality following the direct magnitude estimation method.

Results

Comparisons of nasality ratings of nasal vowels showed a significant reduction of perceived nasality after articulatory adjustment. Moreover, the acoustic features associated with nasal resonances were attenuated and the oral formant structures changed by nasalization were restored after articulatory adjustment, which confirmed findings in Rong and Kuehn (2010).

Conclusion

Appropriate articulatory adjustments are able to reduce the nasality of synthetic nasal /i/ vowels by compensating for the acoustic deviations caused by excessive velopharyngeal opening. Such compensatory interarticulator coordination may have an application in using articulatory adjustments to reduce hypernasality in clinical speech therapies.
The Consonant-Weighted Envelope Difference Index (cEDI): A Proposed Technique for Quantifying Envelope Distortion
Authors: Hoover Eric C. , Souza Pamela E. , Gallun Frederick J.
Published: March 2012

Purpose

The benefits of amplitude compression in hearing aids may be limited by distortion resulting from rapid gain adjustment. To evaluate this, it is convenient to quantify distortion by using a metric that is sensitive to the changes in the processed signal that decrease consonant recognition, such as the Envelope Difference Index (EDI; Fortune, Woodruff, & Preves, 1994). However, the EDI relies on the entire duration of the signal, including portions irrelevant to consonant recognition.

Method

This note describes a computationally efficient method of automatically segmenting speech in time according to the syllable structure. Our technique uses the 1st derivative of the envelope as a basis. Peaks located in the derivative were used to generate a weighting function for the computation of a metric of signal distortion.

Results

The weighting function significantly improved the variance explained in consonant recognition scores over previous methods. However, only 3.2% of the variance was explained in the revised model.

Conclusion

This technique was effective in focusing the analysis of distortion on specific segments of the signal. Use of the technique has implications for speech analysis. The difference in the amplitude envelope of consonants is not a robust model of the effect of hearing aid compression on consonant recognition.
New Sentence Recognition Materials Developed Using a Basic Non-Native English Lexicon
Authors: Calandruccio Lauren , Smiljanic Rajka
Published: March 2012

Purpose

The objective of this project was to develop new sentence test materials drawing on a basic non-native English lexicon that could be used to test speech recognition for various listener populations. These materials have been designed to provide a test tool that is less linguistically biased, compared with materials that are currently available, for sentence recognition for non-native as well as native speakers of English.

Method

One hundred non-native speakers of English were interviewed on a range of 20 conversational topics. Over 26 hr of recorded non-native English speech were transcribed. These transcriptions were used to create a lexicon of over 4,000 unique words. The words from this lexicon were used to create the new materials based on a simple syntactic sentence structure frame.

Results

Twenty lists of 25 sentences were developed. Each sentence has 4 keywords, providing 100 keywords per list. Lists were equated for rate of occurrence of keywords in lexicon, high-frequency count (total number of affricates and fricatives), number of syllables, and distribution of syntactic structure. Listening-in-noise results for native-English-speaking, normal-hearing listeners indicated similar performance across lists.

Conclusion

The Basic English Lexicon materials provide a large set of sentences for native and non-native English speech-recognition testing.

Supplemental Material

https://doi.org/10.23641/asha.6170381
Armagh and Feminist Strategy: Campaigns around Republican Women Prisoners in Armagh Jail
Authors: Loughran Christina
Published: March 2012

The priorities for women in England are not automatically ours. There is a war going on in Ireland, we are living in a country divided by British rule. (Rita O'Hare, Women's Department Sinn Fein, in Collins, 1985:115)
Transforming Socialist-Feminism: The Challenge of Racism
Authors: Bhavnani Kum-Kum , Coulson Margaret
Published: March 2012

Feminism is the political theory and practice that struggles to free all women: women of colour, working class women, poor women, disabled women, lesbians, old women – as well as white economically privileged, heterosexual women. (Smith, 1982:49)
More than Just a Memory: Some Political Implications of Women's Involvement in the Miners’ Strike, 1984–85
Authors: Rowbotham Sheila , McCrindle Jean
Published: March 2012

Jean McCrindle is treasurer of Women Against Pit Closures. In November 1985 Sheila Rowbotham interviewed her on the process through which women became involved in the strike, the impact of this on miners and the trade union officials, and the specific problems of a movement in support of a mainly men's strike which also expresses the autonomous needs of the women. Jean McCrindle reflects on the socialist-feminist politics she brought into her support of the miners’ strike, the interaction, sometimes highly suspicious, sometimes enthusiastic, between the women in the coalfields and feminism, and the implications of the experience for socialism.
Difference: ‘A Special Third World Women Issue’
Authors: Minh-ha Trinh T.
Published: March 2012

It is thrilling to think – to know that for any act of mine, I shall get twice as much praise or twice as much blame. It is quite exciting to hold the center of the national stage, with the spectators not knowing whether to laugh or to weep. (Zora Neale Hurston, ‘How It Feels to Be Colored Me')
Future Insecure: Women and Income Maintenance under a Third Tory Term
Authors: Lister Ruth
Published: March 2012

The Conservative Manifesto has to be scoured for policies which might improve the lives of women as a sex. There is a section on animal welfare but nothing on the welfare of women. Little attention is paid to women's special problems either at work or as carers in the home. Yet much Conservative social policy depends on women as unpaid carers. (St-John Brooks, 1987)
Geometric Specification of Dynamics: Learning to Visually Perceive Kinetic Quantities from Static Images
Authors: Michaels Claire F , Romaniak-Gross Carissa A
Published: March 2012

In a single experiment, perceivers viewed computer-generated hammer-like objects and estimated a kinetic property. Each hammer comprised a cylinder of some diameter and height, attached to a handle—a second cylinder of fixed diameter and variable length. On 5 blocks of trials, three groups of perceivers reported a property reflecting mass, torque, or moment of inertia. Blocks 2–4 were training blocks on which numerical feedback was given. On blocks 6 and 7, perceivers were asked to report the kinetic properties not reported on blocks 1–5. We were interested in how geometrical object properties affected the perception of kinetic properties, and how that perception changed with experience. To determine how geometrical object properties informed reports of kinetics, a continuous information space of head diameter and height, and handle length was created, and perceivers’ loci within that space were determined. Perceivers began at various distances from the optimum for the to-be-reported property and were closer to the optimum after training. On blocks 6 and 7, performance did not reflect transfer from training on another property. The results were interpreted in the context of the theory of direct learning.
New Twists for an Old Turning Illusion
Authors: Chappell Mark , Hawke Johanne L
Published: March 2012

A Vernier-offset illusion induced by rotating lines, introduced by Matin et al (1976 Perception & Psychophysics20 138–142) was re-examined using onset, offset, and reverse trajectories inspired by flash-lag illusion research, with both Vernier and alignment-with-vertical judgments being recorded. The pattern of illusions found was generally in agreement with a differential latency of stimulus ends account described by those authors, although certain variants of modern spatial projection theories, and a differential latency of attribute account, could also accommodate much of the data.
Synthesis of Silver Nanoparticles with Monovalently Functionalized Self-Assembled Monolayers
Authors: Free P. , Paramelle D. , Bosman M. , Hobley J. , Fernig D. G.
Published: March 2012

The importance of having nanoparticles that are soluble, stable, and that have no non-specific binding is often overlooked, but essential for their use in biology. This is particularly prominent with silver nanoparticles that are susceptible to the effects of aggregation and metal-surface reactivity. Here we use a combination of several small peptidols and short alkanethiol ethylene glycol ligands to develop a ligand shell that is reasonably resistant to ligand exchange and non-specific binding to groups common in biological molecules. The stability of the nanoparticles is not affected by the inclusion of a functional ligand, which is done in the same preparative step. The stoichiometry of the nanoparticles is controlled, such that monofunctional silver nanoparticles can be obtained. Two different sets of nanoparticles, functionalized with either Tris-nitrilotriacetic acid or a hexa-histidine peptide sequence, readily form dimers/oligomers, depending on their stoichiometry of functionalization.
Coarse-Grained Simulations of the Effects of Chain Length, Solvent Quality, and Chemical Defects on the Solution-Phase Morphology of MEH-PPV Conjugated Polymers
Authors: Chiu Ming , Kee Tak W. , Huang David M.
Published: March 2012

A mesoscale coarse-grained model of the conjugated polymer poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) in implicit solvent is developed. The model is parametrized to reproduce the local structure and dynamics of an atomistic simulation model and accounts for the effects of solvent quality and saturation chemical defects on the polymer structure. Polymers with defect concentrations of 0 to 10 % are simulated using Langevin dynamics in tetrahydrofuran (THF) and in a model poor solvent for chain lengths and solution concentrations used experimentally. The polymer chains are extended in THF and collapse into compact structures in the poor solvent. The radius of gyration decreases with defect content in THF and agrees quantitatively with experiment. The structures formed in poor solvent by chains with 300 monomer units change from toroidal to cylindrical with increasing defect content, while chains containing 1000 monomers form cylinders regardless of defect content. These results have implications for energy transfer in MEH-PPV.
Are male germ cells of the arid-zone hopping mouse (Notomys alexis) sensitive to high environmental temperatures?
Authors: Wechalekar H. , Setchell B. P. , Peirce E. , Leigh C. , Breed W. G.
Published: March 2012

In most mammalian species, the temperature of scrotal testes is several degrees lower than that of core body temperature due to the presence of a counter-current heat exchange between the coiled testicular artery and the pampiniform plexus of veins. Here we ask: have hopping mice developed a highly efficient cooling mechanism within their scrotal sac and/or germ cell resistance to high environmental temperatures? To investigate this, adult male sexually mature Notomys alexis were used to determine: (1) the temperature of the testes; (2) the extent of coiling of the testicular artery; (3) the effect of artificially induced cryptorchidism on spermatogenesis up to three weeks after surgery; and (4) the effect of whole body heat exposure of 37−38°C for 8 h per day for three consecutive days on germ cell apoptosis. The results showed that in hopping mice the testicular artery, unlike that in most other mammalian species, is not coiled although the temperature in the scrotum was found to be ~2°C lower than that of the abdomen. In cryptorchid males, 21 days after surgery, testes weights were reduced in three of five individuals but there was no statistically significant decrease after 16 h exposure to whole body heat (P = 0.07). Nevertheless, some impairment of spermatogenesis was evident in both the cryptorchid testes and in the testes after whole body heating. These results show that in hopping mice developing male germ cells are susceptible to degeneration when testes are exposed to high environmental temperatures. Thus adaptations of Notomys alexis to the arid zone have not involved any special adaptations for male germ cell survival in a hot environment. Behavioural adaptations may play a pivotal role in maintaining maximal male fertility in such extreme environmental conditions.
Changes in urinary testosterone and corticosterone metabolites during short-term confinement with repeated handling in wild male cane toads (Rhinella marina)
Authors: Narayan Edward J. , Molinia Frank C. , Cockrem John F. , Hero Jean-Marc
Published: March 2012

Stressors generally decrease testosterone secretion and inhibit reproduction in animals. Urinary testosterone and corticosterone metabolite concentrations were measured in adult male cane toads (Rhinella marina) at the time of capture from the wild and during 24 h of confinement with repeated handling. Mean urinary testosterone concentrations increased 2 h after capture, were significantly elevated above initial concentrations at 5 h, and then declined. Mean testosterone concentrations remained elevated 24 h after capture. Mean urinary corticosterone concentrations increased after capture, were significantly elevated above initial concentrations at 2 h, and remained elevated thereafter. This is the first report in amphibians of an increase in testosterone excretion after capture from the wild, with previous studies showing either no change or decline in testosterone. This finding may be associated with the mating strategy and maintenance of reproductive effort in the cane toad, a species that shows explosive breeding and agonistic male–male interactions during breeding. The finding that testosterone excretion increases rather than decreases after capture in male cane toads shows that it should not be generally assumed that reproductive hormone secretion will decrease after capture in amphibians.
In vitro modeling of respiratory syncytial virus infection of pediatric bronchial epithelium, the primary target of infection in vivo
Authors: Villenave Rémi , Thavagnanam Surendran , Sarlang Severine , Parker Jeremy , Douglas Isobel , Skibinski Grzegorz , Heaney Liam G. , McKaigue James P. , Coyle Peter V. , Shields Michael D. , Power Ultan F.
Published: March 2012

Respiratory syncytial virus (RSV) is the major viral cause of severe pulmonary disease in young infants worldwide. However, the mechanisms by which RSV causes disease in humans remain poorly understood. To help bridge this gap, we developed an ex vivo/in vitro model of RSV infection based on well-differentiated primary pediatric bronchial epithelial cells (WD-PBECs), the primary targets of RSV infection in vivo. Our RSV/WD-PBEC model demonstrated remarkable similarities to hallmarks of RSV infection in infant lungs. These hallmarks included restriction of infection to noncontiguous or small clumps of apical ciliated and occasional nonciliated epithelial cells, apoptosis and sloughing of apical epithelial cells, occasional syncytium formation, goblet cell hyperplasia/metaplasia, and mucus hypersecretion. RSV was shed exclusively from the apical surface at titers consistent with those in airway aspirates from hospitalized infants. Furthermore, secretion of proinflammatory chemokines such as CXCL10, CCL5, IL-6, and CXCL8 reflected those chemokines present in airway aspirates. Interestingly, a recent RSV clinical isolate induced more cytopathogenesis than the prototypic A2 strain. Our findings indicate that this RSV/WD-PBEC model provides an authentic surrogate for RSV infection of airway epithelium in vivo. As such, this model may provide insights into RSV pathogenesis in humans that ultimately lead to successful RSV vaccines or therapeutics.
Myelin-derived ephrinB3 restricts axonal regeneration and recovery after adult CNS injury
Authors: Duffy Philip , Wang Xingxing , Siegel Chad S. , Tu Nathan , Henkemeyer Mark , Cafferty William B. J. , Strittmatter Stephen M.
Published: March 2012

Recovery of neurological function after traumatic injury of the adult mammalian central nervous system is limited by lack of axonal growth. Myelin-derived inhibitors contribute to axonal growth restriction, with ephrinB3 being a developmentally important axonal guidance cue whose expression in mature oligodendrocytes suggests a role in regeneration. Here we explored the in vivo regeneration role of ephrinB3 using mice lacking a functional
ephrinB3
gene. We confirm that ephrinB3 accounts for a substantial portion of detergent-resistant myelin-derived inhibition in vitro. To assess in vivo regeneration, we crushed the optic nerve and examined retinal ganglion fibers extending past the crush site. Significantly increased axonal regeneration is detected in
ephrinB3
−/−
mice. Studies of spinal cord injury in
ephrinB3
−/−
mice must take into account altered spinal cord development and an abnormal hopping gait before injury. In a near-total thoracic transection model,
ephrinB3
−/−
mice show greater spasticity than wild-type mice for 2 mo, with slightly greater hindlimb function at later time points, but no evidence for axonal regeneration. After a dorsal hemisection injury, increased corticospinal and raphespinal growth in the caudal spinal cord are detected by 6 wk. This increased axonal growth is accompanied by improved locomotor performance measured in the open field and by kinematic analysis. Thus, ephrinB3 contributes to myelin-derived axonal growth inhibition and limits recovery from adult CNS trauma.
Lateral mobility of individual integrin nanoclusters orchestrates the onset for leukocyte adhesion
Authors: Bakker Gert Jan , Eich Christina , Torreno-Pina Juan A. , Diez-Ahedo Ruth , Perez-Samper Gemma , van Zanten Thomas S. , Figdor Carl G. , Cambi Alessandra , Garcia-Parajo Maria F.
Published: March 2012

Integrins are cell membrane adhesion receptors involved in morphogenesis, immunity, tissue healing, and metastasis. A central, yet unresolved question regarding the function of integrins is how these receptors regulate both their conformation and dynamic nanoscale organization on the membrane to generate adhesion-competent microclusters upon ligand binding. Here we exploit the high spatial (nanometer) accuracy and temporal resolution of single-dye tracking to dissect the relationship between conformational state, lateral mobility, and microclustering of the integrin receptor lymphocyte function-associated antigen 1 (LFA-1) expressed on immune cells. We recently showed that in quiescent monocytes, LFA-1 preorganizes in nanoclusters proximal to nanoscale raft components. We now show that these nanoclusters are primarily mobile on the cell surface with a small (ca.5%) subset of conformational-active LFA-1 nanoclusters preanchored to the cytoskeleton. Lateral mobility resulted crucial for the formation of microclusters upon ligand binding and for stable adhesion under shear flow. Activation of high-affinity LFA-1 by extracellular Ca2+resulted in an eightfold increase on the percentage of immobile nanoclusters and cytoskeleton anchorage. Although having the ability to bind to their ligands, these active nanoclusters failed to support firm adhesion in static and low shear-flow conditions because mobility and clustering capacity were highly compromised. Altogether, our work demonstrates an intricate coupling between conformation and lateral diffusion of LFA-1 and further underscores the crucial role of mobility for the onset of LFA-1 mediated leukocyte adhesion.
Cofactor-specific photochemical function resolved by ultrafast spectroscopy in photosynthetic reaction center crystals
Authors: Huang Libai , Ponomarenko Nina , Wiederrecht Gary P. , Tiede David M.
Published: March 2012

High-resolution mapping of cofactor-specific photochemistry in photosynthetic reaction centers (RCs) from
Rhodobacter sphaeroides
was achieved by polarization selective ultrafast spectroscopy in single crystals at cryogenic temperature. By exploiting the fixed orientation of cofactors within crystals, we isolated a single transition within the multicofactor manifold, and elucidated the site-specific photochemical functions of the cofactors associated with the symmetry-related active A and inactive B branches. Transient spectra associated with the initial excited states were found to involve a set of cofactors that differ depending upon whether the monomeric bacteriochlorophylls, BChl
A
, BChl
B
, or the special pair bacteriochlorophyll dimer, P, was chosen for excitation. Proceeding from these initial excited states, characteristic photochemical functions were resolved. Specifically, our measurements provide direct evidence for an alternative charge separation pathway initiated by excitation of BChl
A
that does not involve P*. Conversely, the initial excited state produced by excitation of BChl
B
was found to decay by energy transfer to P. A clear sequential kinetic resolution of BChl
A
and the A-side bacteriopheophytin, BPh
A
, in the electron transfer proceeding from P* was achieved. These experiments demonstrate the opportunity to resolve photochemical function of individual cofactors within the multicofactor RC complexes using single crystal spectroscopy.
Cancer-associated epithelial cell adhesion molecule (EpCAM; CD326) enables epidermal Langerhans cell motility and migration in vivo
Authors: Gaiser Maria R. , Lämmermann Tim , Feng Xu , Igyarto Botond Z. , Kaplan Daniel H. , Tessarollo Lino , Germain Ronald N. , Udey Mark C.
Published: March 2012

After activation, Langerhans cells (LC), a distinct subpopulation of epidermis-resident dendritic cells, migrate from skin to lymph nodes where they regulate the magnitude and quality of immune responses initiated by epicutaneously applied antigens. Modulation of LC–keratinocyte adhesion is likely to be central to regulation of LC migration. LC express high levels of epithelial cell adhesion molecule (EpCAM; CD326), a cell-surface protein that is characteristic of some epithelia and many carcinomas and that has been implicated in intercellular adhesion and metastasis. To gain insight into EpCAM function in a physiologic context in vivo, we generated conditional knockout mice with EpCAM-deficient LC and characterized them. Epidermis from these mice contained increased numbers of LC with normal levels of MHC and costimulatory molecules and T-cell–stimulatory activity in vitro. Migration of EpCAM-deficient LC from skin explants was inhibited, but chemotaxis of dissociated LC was not. Correspondingly, the ability of contact allergen-stimulated, EpCAM-deficient LC to exit epidermis in vivo was delayed, and strikingly fewer hapten-bearing LC subsequently accumulated in lymph nodes. Attenuated migration of EpCAM-deficient LC resulted in enhanced contact hypersensitivity responses as previously described in LC-deficient mice. Intravital microscopy revealed reduced translocation and dendrite motility in EpCAM-deficient LC in vivo in contact allergen-treated mice. These results conclusively link EpCAM expression to LC motility/migration and LC migration to immune regulation. EpCAM appears to promote LC migration from epidermis by decreasing LC–keratinocyte adhesion and may modulate intercellular adhesion and cell movement within in epithelia during development and carcinogenesis in an analogous fashion.
Initiation factor 2, tRNA, and 50S subunits cooperatively stabilize mRNAs on the ribosome during initiation
Authors: Masuda Tomoaki , Petrov Alexey N. , Iizuka Ryo , Funatsu Takashi , Puglisi Joseph D. , Uemura Sotaro
Published: March 2012

Initiation factor 2 (IF2) is a key factor in initiation of bacterial protein synthesis. It recruits initiator tRNA to the small ribosomal subunit and facilitates joining of the large ribosomal subunit. Using reconstituted translation system of
Escherichia coli
and optical tweezers, we directly measure the rupture force between single ribosomal complexes and mRNAs for initiation complexes in the presence and the absence of IF2. We demonstrate that IF2 together with codon recognition by initiator tRNA increases the force required to dislocate mRNA from the ribosome complexes; mRNA stabilization by IF2 required the presence of a joined 50S subunit, and was independent of bound guanine nucleotide. IF2 thus helps lock the 70S ribosome over the start codon during initiation, thus maintaining reading frame. Our results show how mRNA is progressively stabilized on the ribosome through distinct steps of initiation.
Structural basis for the enhanced stability of highly fluorinated proteins
Authors: Buer Benjamin C. , Meagher Jennifer L. , Stuckey Jeanne A. , Marsh E. Neil G.
Published: March 2012

Noncanonical amino acids have proved extremely useful for modifying the properties of proteins. Among them, extensively fluorinated (fluorous) amino acids seem particularly effective in increasing protein stability; however, in the absence of structural data, the basis of this stabilizing effect remains poorly understood. To address this problem, we solved X-ray structures for three small proteins with hydrophobic cores that are packed with either fluorocarbon or hydrocarbon side chains and compared their stabilities. Although larger, the fluorinated residues are accommodated within the protein with minimal structural perturbation, because they closely match the shape of the hydrocarbon side chains that they replace. Thus, stability increases seem to be better explained by increases in buried hydrophobic surface area that accompany fluorination than by specific fluorous interactions between fluorinated side chains. This finding is illustrated by the design of a highly fluorinated protein that, by compensating for the larger volume and surface area of the fluorinated side chains, exhibits similar stability to its nonfluorinated counterpart. These structure-based observations should inform efforts to rationally modulate protein function using noncanonical amino acids.