bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating epidemiology and toxicology in neurotoxicity risk assessment
Authors: Boyes William K , Moser Virginia C , Geller Andrew M , Benignus Vernon A , Bushnell Philip J , Kamel Freya
Published: July 2007

Neurotoxicity risk assessments depend on the best available scientific information, including data from animal toxicity studies, human experimental studies and human epidemiology studies. There are several factors to consider when evaluating the comparability of data from studies. Regarding the epidemiology literature, issues include choice of study design, use of appropriate controls, methods of exposure assessment, subjective or objective evaluation of neurological status, and assessment and statistical control of potential confounding factors, including co-exposure to other agents. Animal experiments must be evaluated regarding factors such as dose level and duration, procedures used to assess neurological or behavioural status, and appropriateness of inference from the animal model to human neurotoxicity. Major factors that may explain apparent differences between animal and human studies include: animal neurological status may be evaluated with different procedures than those used in humans; animal studies may involve shorter exposure durations and higher dose levels; and most animal studies evaluate a single substance whereas humans typically are exposed to multiple agents. The comparability of measured outcomes in animals and humans may be improved by considering functional domains rather than individual test measures. The application of predictive models, weight of evidence considerations and meta-analysis can help evaluate the consistency of outcomes across studies. An appropriate blend of scientific information from toxicology and epidemiology studies is necessary to evaluate potential human risks of exposure to neurotoxic substances. Human & Experimental Toxicology (2007) 26, 283-293
Effects of acute alcohol intoxication on visuospatial attention
Authors: do Canto-Pereira Luiz Henrique M , David Isabel de PA , Machado-Pinheiro Walter , Ranvaud Ronald D
Published: July 2007

The aim of the present study was to examine the effects of acute alcohol intoxication on the spatial distribution of visual attention measured with simple reaction times (RTs) to targets presented over an extended region of the visual field. Control (n =10) and alcohol groups (n =14) were tested with the same protocol. Participants were tested in two different conditions; in Experiment I, participants were instructed to direct their visual attention to the centre, while in Experiment II they were asked to orient their attention covertly to both right and left, but not to the centre. Throughout participants were required to fixate a small cross in the centre of the computer screen. In the alcohol group, participants received an alcohol dose of 0.4 g/kg so as to produce a blood alcohol concentration (BAC) in the range of 0.08% during the experiments. The spatial distribution of RTs was analysed graphically with geostatistical methods and statistically through analysis of variance of particular regions of the visual field. Results showed that controls were able to direct their attention tightly towards the centre (Expt I) and also to divide attention (Expt II) to the right and left. Participants in the alcohol group fixed their attention more diffusely in the centre (Expt I) and were unable to disengage attention from the centre in Experiment II. We conclude that acute alcohol intoxication impairs the ability to dissociate attention from gaze. Human & Experimental Toxicology (2007) 26, 311-319
Animal models of chronic pesticide neurotoxicity
Authors: Moser Virginia C
Published: July 2007

There is a wealth of literature on neurotoxicological outcomes of acute and short-term exposure to pesticides in laboratory animals, but there are relatively few studies of- long-term exposure. Many reports in the literature describing `chronic' exposures to pesticides are, in fact, as short as five days and rarely longer than three months. Furthermore, routes of administration range from subcutaneous to dietary. Doses used in many of the studies produce signs of acute or overt toxicity. In contrast, human symptoms have been reported following exposures that are prolonged and often without obvious toxic effects. A survey of the literature was conducted to identify rodent studies with neurobehavioral and neurophysiological endpoints of pesticide exposures lasting 30 days or longer. This survey indicated that the majority of studies concentrate on cholinesterase inhibitors (organophosphorus and carbamate insecticides). Various neuromotor, cholinergic, physiological, affective and cognitive disorders were reported at doses producing cholinesterase inhibition; however, there were a fewer effects at non-inhibiting doses. Other classes of pesticides produced similar effects, with the exception of cholinergic signs. In many studies, the changes were subtle, which may correspond to the nonspecific changes in psychomotor and cognitive function reported in humans. It appears, then, that the data from animal and human pesticide exposures are generally comparable, but the specific outcomes are influenced by many experimental differences. Future research should concentrate on analogous exposures and outcomes to facilitate interpretation. Human & Experimental Toxicology (2007) 26, 321—331
Colour vision defects in occupational chronic solvent encephalopathy
Authors: Päällysaho Juha , Näsänen Risto , Mäntyjärvi Maija , Kaukiainen Ari , Sainio Markku
Published: July 2007

Occupational chronic solvent encephalopathy (CSE) is associated with a number of neurobehaviuoral disorders including defects of visual perception. The purpose of this study was to characterize colour vision defects in CSE patients. Colour vision was tested in bright illumination with the Farnsworth-Munsell 100-hue test in workers who had CSE due to occupational exposure to common industrial solvents. Before assessing colour vision, the subjects' ocular health and visual functions were evaluated. On the basis of this evaluation, 36 subjects with healthy eyes were selected and their colour vision was tested monocularly. The colour vision performance of the patient group was, statistically, significantly inferior to that of a control group matched by age at a group level. A mixed form of reduced colour sensitivity was found in 42% ( n = 15/36) of the cases, affecting the entire range of Munsell hues. No association was found between the length and intensity of exposure and colour vision performance. Our results show that CSE patients can have significantly impaired colour discrimination ability, although their eyes are healthy and their other visual functions are normal. This may indicate toxic damage to higher level visual processing, possibly the colour selective regions of the cerebral cortex. Human & Experimental Toxicology (2007) 26: 375— 383
Video-Based Research Made “Easy”: Methodological Lessons Learned from the TIMSS Video Studies
Authors: Jacobs Jennifer K. , Hollingsworth Hilary , Givvin Karen B.
Published: July 2007

In this article, the authors share some of the methodological lessons learned from the Third International Mathematics and Science Study (TIMSS) 1995 and TIMSS 1999 Video Studies. They focus on their experiences overseeing these large-scale, video-based, cross-national surveys of teaching. The article documents some of the progress the authors made, as well as some of the obstacles they encountered. The authors hope that the ideas shared here help prevent possible missteps, enhance the quality of projects, and encourage researchers to advance the use of video as a methodology.
Grabbing the Audience: Correlates of Contactability in Visitor Studies
Authors: Roose Henk
Published: July 2007

Visitor studies using standardized questionnaires are popular in marketing-oriented research. Yet these surveys often contend with high nonresponse rates because of the peculiarity of the survey context. Spectators are contacted and persuaded to participate in a survey when they are attending—sometimes en masse—an event outdoors. In this article, the particular correlates of contactability in visitor studies are explored. More specifically, correlates of contactability in audience research in cultural institutions staging music, theater, opera, and dance are analyzed. The resulting model offers practical guidelines for conducting arts-related research in terms of the number of interviewers required to achieve a desired contact rate—given an expected audience size and a planned method for data collection.
An exploratory study of teachers' knowledge about the symptoms of depression in young people with and without intellectual disabilities
Authors: Taggart L. , Mcmullan P.
Published: July 2007

Research has shown that children and young people with intellectual disabilities are at a greater risk of developing a psychiatric disorder than their non-disabled peers. However, no information exists regarding teachers' knowledge of the signs and symptoms of these conditions. Using a postal questionnaire, 36 teachers working within schools for children and young people with severe intellectual disabilities in one part of the UK were asked about their knowledge of depression. Results indicated that the teachers reported few signs and symptoms. Furthermore, the teachers also highlighted a lack of confidence in working with this doubly disadvantaged population. This study shows that teachers have a vital role to play in the early recognition of psychiatric signs and symptoms in young people with intellectual disabilities. Teachers must also receive the appropriate education and training in an attempt to prompt early referral to specialists for a detailed and comprehensive psychiatric assessment rather than continuing to manage such young people's challenging behaviours.
The development of a questionnaire to assess the perceptions of care staff towards people with intellectual disabilities who display challenging behaviour
Authors: Williams Ruth J. , Rose John L.
Published: July 2007

The perceptions of staff about challenging behaviour may be a key factor in designing successful behavioural interventions. There is a lack of robust psychometric instruments designed to assess staff attributions towards incidents of challenging behaviour. The aim of this research was to develop a scale based upon the self-regulation theory of illness behaviour. Two staff focus groups identified and clarified relevant constructs to be included in the Challenging Behaviour Perception Questionnaire (CBPQ), which was then completed by 51 staff. Some correlations between the CBPQ and the Attributional Style Questionnaire were found. A significant amount of the variance in the perception of challenging behaviour was explained by the subscales of the new questionnaire. In particular, episodic timeline would seem to be a promising area for further investigation.
KIT is required for hepatic function during mouse post-natal development
Authors: Magnol Laetitia , Chevallier Marie-Clémence , Nalesso Valérie , Retif Stéphanie , Fuchs Helmut , Klempt Martina , Pereira Patricia , Riottot Michel , Andrzejewski Sandra , Doan Bich-Thuy , Panthier Jean-Jacques , Puech Anne , Beloeil Jean-Claude , de Angelis Martin Hrabe , Hérault Yann
Published: July 2007

Background

The Kit gene encodes a receptor tyrosine kinase involved in various biological processes including melanogenesis, hematopoiesis and gametogenesis in mice and human. A large number of Kit mutants has been described so far showing the pleiotropic phenotypes associated with partial loss-of-function of the gene. Hypomorphic mutations can induce a light coat color phenotype while complete lack of KIT function interferes with embryogenesis. Interestingly several intermediate hypomorphic mutations induced in addition growth retardation and post-natal mortality.

Results

In this report we investigated the post-natal role of Kit by using a panel of chemically-induced hypomorphic mutations recently isolated in the mouse. We found that, in addition to the classical phenotypes, mutations of Kit induced juvenile steatosis, associated with the downregulation of the three genes, VldlR, Lpin1 and Lpl, controlling lipid metabolism in the post-natal liver. Hence, Kit loss-of-functions mimicked the inactivation of genes controlling the hepatic metabolism of triglycerides, the major source of energy from maternal milk, leading to growth and viability defects during neonatal development.

Conclusion

This is a first report involving KIT in the control of lipid metabolism in neonates and opening new perspectives for understanding juvenile steatosis. Moreover, it reinforces the role of Kit during development of the liver and underscores the caution that should be exerted in using KIT inhibitors during anti-cancer treatment.
Systematic reviews of adverse effects: framework for a structured approach
Authors: Loke Yoon K , Price Deirdre , Herxheimer Andrew ,   the Cochrane Adverse Effects Methods Group
Published: July 2007

Background

As every healthcare intervention carries some risk of harm, clinical decision making needs to be supported by a systematic assessment of the balance of benefit to harm. A systematic review that considers only the favourable outcomes of an intervention, without also assessing the adverse effects, can mislead by introducing a bias favouring the intervention.

Much of the current guidance on systematic reviews is directed towards the evaluation of effectiveness; but this differs in important ways from the methods used in assessing the safety and tolerability of an intervention. A detailed discussion of why, how and when to include adverse effects in a systematic review, is required.

Methods

This discussion paper, which presupposes a basic knowledge of systematic review methodology, was developed by consensus among experienced reviewers, members of the Adverse Effects Subgroup of The Cochrane Collaboration, and supplemented by a consultation of content experts in reviews methodology, as well as those working in drug safety.

Results

A logical framework for making decisions in reviews that incorporate adverse effects is provided. We explore situations where a comprehensive investigation of adverse effects is warranted and suggest strategies to identify practicable and clinically useful outcomes. The advantages and disadvantages of including observational and experimental study designs are reviewed. The consequences of including separate studies for intended and unintended effects are explained. Detailed advice is given on designing electronic searches for studies with adverse effects data. Reviewers of adverse effects are given general guidance on the assessment of study bias, data collection, analysis, presentation and the interpretation of harms in a systematic review.

Conclusion

Readers need to be able to recognize how strategic choices made in the review process determine what harms are found, and how the findings may affect clinical decisions. Researchers undertaking a systematic review that incorporates adverse effect data should understand the rationale for the suggested methods and be able to implement them in their review.
Procalcitonin guided antibiotic therapy and hospitalization in patients with lower respiratory tract infections: a prospective, multicenter, randomized controlled trial
Authors: Schuetz Philipp , Christ-Crain Mirjam , Wolbers Marcel , Schild Ursula , Thomann Robert , Falconnier Claudine , Widmer Isabelle , Neidert Stefanie , Blum Claudine A , Schönenberger Ronald , Henzen Christoph , Bregenzer Thomas , Hoess Claus , Krause Martin , Bucher Heiner C , Zimmerli Werner , Müller Beat ,   the ProHOSP study group
Published: July 2007

Background:

Lower respiratory tract infections like acute bronchitis, exacerbated chronic obstructive pulmonary disease and community-acquired pneumonia are often unnecessarily treated with antibiotics, mainly because of physicians' difficulties to distinguish viral from bacterial cause and to estimate disease-severity. The goal of this trial is to compare medical outcomes, use of antibiotics and hospital resources in a strategy based on enforced evidence-based guidelines versus procalcitonin guided antibiotic therapy in patients with lower respiratory tract infections.

Methods and design:

We describe a prospective randomized controlled non-inferiority trial with an open intervention. We aim to randomize over a fixed recruitment period of 18 months a minimal number of 1002 patients from 6 hospitals in Switzerland. Patients must be >18 years of age with a lower respiratory tract infections <28 days of duration. Patients with no informed consent, not fluent in German, a previous hospital stay within 14 days, severe immunosuppression or chronic infection, intravenous drug use or a terminal condition are excluded. Randomization to either guidelines-enforced management or procalcitonin-guided antibiotic therapy is stratified by centre and type of lower respiratory tract infections. During hospitalization, all patients are reassessed at days 3, 5, 7 and at the day of discharge. After 30 and 180 days, structured phone interviews by blinded medical students are conducted. Depending on the randomization allocation, initiation and discontinuation of antibiotics is encouraged or discouraged based on evidence-based guidelines or procalcitonin cut off ranges, respectively. The primary endpoint is the risk of combined disease-specific failure after 30 days. Secondary outcomes are antibiotic exposure, side effects from antibiotics, rate and duration of hospitalization, time to clinical stability, disease activity scores and cost effectiveness. The study hypothesis is that procalcitonin-guidance is non-inferior (i.e., at worst a 7.5% higher combined failure rate) to the management with enforced guidelines, but is associated with a reduced total antibiotic use and length of hospital stay.

Discussion:

Use of and prolonged exposure to antibiotics in lower respiratory tract infections is high. The proposed trial investigates whether procalcitonin-guidance may safely reduce antibiotic consumption along with reductions in hospitalization costs and antibiotic resistance. It will additionally generate insights for improved prognostic assessment of patients with lower respiratory tract infections.

Trial registration:

ISRCTN95122877
Nuclear Factor 90(NF90) targeted to TAR RNA inhibits transcriptional activation of HIV-1
Authors: Agbottah Emmanuel T , Traviss Christine , McArdle James , Karki Sambhav , St Laurent Georges C , Kumar Ajit
Published: July 2007

Background

Examination of host cell-based inhibitors of HIV-1 transcription may be important for attenuating viral replication. We describe properties of a cellular double-stranded RNA binding protein with intrinsic affinity for HIV-1 TAR RNA that interferes with Tat/TAR interaction and inhibits viral gene expression.

Results

Utilizing TAR affinity fractionation, North-Western blotting, and mobility-shift assays, we show that the C-terminal variant of nuclear factor 90 (NF90ctv) with strong affinity for the TAR RNA, competes with Tat/TAR interaction in vitro. Analysis of the effect of NF90ctv-TAR RNA interaction in vivo showed significant inhibition of Tat-transactivation of HIV-1 LTR in cells expressing NF90ctv, as well as changes in histone H3 lysine-4 and lysine-9 methylation of HIV chromatin that are consistent with the epigenetic changes in transcriptionally repressed gene.

Conclusion

Structural integrity of the TAR element is crucial in HIV-1 gene expression. Our results show that perturbation Tat/TAR RNA interaction by the dsRNA binding protein is sufficient to inhibit transcriptional activation of HIV-1.
Cardiopulmonary bypass via common carotid artery cannulation in redo sternotomy
Authors: Bhudia Sunil K , Vohra Hunaid A , Hassan Asif , Abid Qamar
Published: July 2007

There are certain situations in redo cardiac surgery in adults where it may not be possible to use alternate arterial cannulation sites like the common femoral artery and axillary artery. We report a case where we established safe cardiopulmonary bypass with common carotid artery cannulation in an adult patient. The patient underwent aortic valve replacement for severe aortic regurgitation 8 months after repair of type A aortic dissection plus aortic valve resuspension.
A proteome-wide protein interaction map for Campylobacter jejuni
Authors: Parrish Jodi R , Yu Jingkai , Liu Guozhen , Hines Julie A , Chan Jason E , Mangiola Bernie A , Zhang Huamei , Pacifico Svetlana , Fotouhi Farshad , DiRita Victor J , Ideker Trey , Andrews Phillip , Finley Russell L
Published: July 2007

Background

Data from large-scale protein interaction screens for humans and model eukaryotes have been invaluable for developing systems-level models of biological processes. Despite this value, only a limited amount of interaction data is available for prokaryotes. Here we report the systematic identification of protein interactions for the bacterium Campylobacter jejuni, a food-borne pathogen and a major cause of gastroenteritis worldwide.

Results

Using high-throughput yeast two-hybrid screens we detected and reproduced 11,687 interactions. The resulting interaction map includes 80% of the predicted C. jejuni NCTC11168 proteins and places a large number of poorly characterized proteins into networks that provide initial clues about their functions. We used the map to identify a number of conserved subnetworks by comparison to protein networks from Escherichia coli and Saccharomyces cerevisiae. We also demonstrate the value of the interactome data for mapping biological pathways by identifying the C. jejuni chemotaxis pathway. Finally, the interaction map also includes a large subnetwork of putative essential genes that may be used to identify potential new antimicrobial drug targets for C. jejuni and related organisms.

Conclusion

The C. jejuni protein interaction map is one of the most comprehensive yet determined for a free-living organism and nearly doubles the binary interactions available for the prokaryotic kingdom. This high level of coverage facilitates pathway mapping and function prediction for a large number of C. jejuni proteins as well as orthologous proteins from other organisms. The broad coverage also facilitates cross-species comparisons for the identification of evolutionarily conserved subnetworks of protein interactions.
Evolutionary conservation of regulated longevity assurance mechanisms
Authors: McElwee Joshua J , Schuster Eugene , Blanc Eric , Piper Matthew D , Thomas James H , Patel Dhaval S , Selman Colin , Withers Dominic J , Thornton Janet M , Partridge Linda , Gems David
Published: July 2007

Background

To what extent are the determinants of aging in animal species universal? Insulin/insulin-like growth factor (IGF)-1 signaling (IIS) is an evolutionarily conserved (public) regulator of longevity; yet it remains unclear whether the genes and biochemical processes through which IIS acts on aging are public or private (that is, lineage specific). To address this, we have applied a novel, multi-level cross-species comparative analysis to compare gene expression changes accompanying increased longevity in mutant nematodes, fruitflies and mice with reduced IIS.

Results

Surprisingly, there is little evolutionary conservation at the level of individual, orthologous genes or paralogous genes under IIS regulation. However, a number of gene categories are significantly enriched for genes whose expression changes in long-lived animals of all three species. Down-regulated categories include protein biosynthesis-associated genes. Up-regulated categories include sugar catabolism, energy generation, glutathione-S-transferases (GSTs) and several other categories linked to cellular detoxification (that is, phase 1 and phase 2 metabolism of xenobiotic and endobiotic toxins). Protein biosynthesis and GST activity have recently been linked to aging and longevity assurance, respectively.

Conclusion

These processes represent candidate, regulated mechanisms of longevity-control that are conserved across animal species. The longevity assurance mechanisms via which IIS acts appear to be lineage-specific at the gene level (private), but conserved at the process level (or semi-public). In the case of GSTs, and cellular detoxification generally, this suggests that the mechanisms of aging against which longevity assurance mechanisms act are, to some extent, lineage specific.
A model study for estimating optimum upward-continuation height for gravity separation with application to a Bouguer gravity anomaly over a mineral deposit, Jilin province, northeast China
Authors: Zeng Hualin , Xu Deshu , Tan Handong
Published: July 2007

Upward continuation can be used to separate a regional gravity anomaly resulting from deep sources from the observed gravity. We present a practical method, based on model studies, to derive an optimum upward continuation height for regional-residual gravity separation. Using this method we can calculate an optimal height for upward continuation. Although mathematically there is no optimum height, this method provides an objective procedure to calculate a best height for upward continuation. We initially use a 2D model to calculate an optimum separation height, as given by the maximum crosscorrelation between the upward continuation of the observed gravity and a known regional anomaly. For an unknown regional field, we calculate a series of crosscorrelations between the upward continuations at two successive heights. The average height of the maximum deflection of these crosscorrelation values yields the optimum height for regional-residual separation. The method was applied to the Bouguer gravity anomaly over a mineral deposit in the Jilin province in northeast China. When we subtract the estimated regional anomaly obtained in this manner from the Bouguer anomaly, we can obtain a residual anomaly that clearly shows the location of two known iron bodies.
Induced polarization and surface electrochemistry
Authors: Merriam J. B.
Published: July 2007

Induced-polarization (IP) responses arising from activation overvoltage are investigated, with the goal of relating established electrochemical properties and processes to IP time constants. In activation overvoltage, an electrical double layer with a well-defined areal capacitance forms at the mineral-electrolyte interface. This study shows that the known capacitance of the interface is compatible with observed initial time constants for the decay of electrode polarization. Furthermore, because the electrical double-layer capacitance is determined largely by the electrolyte and not the mineral, the conclusion is that, although the polarization is caused by the presence of the mineral, the time constants of the decay are determined primarily by the electrolyte and not the mineral. The dependence of the capacitance on the sign and magnitude of the potential implies that the effective decay time constant will be small at the start of depolarization and will progress to larger values as the decay proceeds.
Waveform inversion by one-way wavefield extrapolation
Authors: Shragge Jeff
Published: July 2007

One-way Riemannian wavefield extrapolation (RWE) on computational meshes conforming to the direction of turning-wave propagation is an alternative forward-modeling procedure for waveform inversion. Forward-modeling tests demonstrate that the RWE approach may be a sufficiently accurate approximation for calculating the wavefield phases important for early-arrival waveform inversion. Initial results indicate that RWE waveforms are well matched at wide offsets to finite-difference data, and can be used in a waveform inversion scheme to invert synthetic data for moderate 1D velocity perturbations.
P-wave seismic attenuation by slow-wave diffusion: Numerical experiments in partially saturated rocks
Authors: Picotti Stefano , Carcione José M. , Germán Rubino J. , Santos Juan E.
Published: July 2007

P-wave attenuation by slow-wave diffusion is a significant loss mechanism at seismic frequencies. This effect is known as mesoscopic loss, because it is a consequence of fluid flow at mesoscopic-scale inhomogeneities. These are larger than the pore size but smaller than the wavelength, typically tens of centimeters, and are due to local variations in lithological properties or to patches of immiscible fluids. Basically, a P-wave traveling in a porous medium induces a fluid-pressure gradient in regions of different properties, such as patches saturated with different fluids, generating slow P-waves, which diffuse away from the interfaces separating the fluids. This mechanism can be explained by the combined effect of mesoscopic-scale inhomogeneities and mode conversion at interfaces. We consider a periodically stratified medium and perform numerical experiments to determine the P-wave quality factor in partially saturated rocks. The modeling method is an iterative domain-decomposition 2D finite-element algorithm for solving Biot equations of motion in a parallel computer, which is a requirement to run the numerical experiments at seismic frequencies. The simulated pulses show evidence of the mesoscopic-loss mechanism, and the quality factors estimated with the spectral-ratio and frequency-shift methods are in good agreement with the theoretical values predicted by the White theory. Errors in the estimation of the quality factor are less than 5% (spectral ratio) and 3% (frequency shift).
Improving crosshole radar velocity tomograms: A new approach to incorporating high-angle traveltime data
Authors: Irving James D. , Knoll Michael D. , Knight Rosemary J.
Published: July 2007

To obtain the highest-resolution ray-based tomographic images from crosshole ground-penetrating radar (GPR) data, wide angular ray coverage of the region between the two boreholes is required. Unfortunately, at borehole spacings on the order of a few meters, high-angle traveltime data (i.e., traveltime data corresponding to transmitter-receiver angles greater than approximately 50° from the horizontal) are notoriously difficult to incorporate into crosshole GPR inversions. This is because (1) low signal-to-noise ratios make the accurate picking of first-arrival times at high angles extremely difficult, and (2) significant tomographic artifacts commonly appear when high- and low-angle ray data are inverted together. We address and overcome thesetwo issues for a crosshole GPR data example collected at the Boise Hydrogeophysical Research Site (BHRS). To estimate first-arrival times on noisy, high-angle gathers, we develop a robust and automatic picking strategy based on crosscorrelations, where reference waveforms are determined from the data through the stacking of common-ray-angle gathers. To overcome incompatibility issues between high- and low-angle data, we modify the standard tomographic inversion strategy to estimate, in addition to subsurface velocities, parameters that describe a traveltime ‘correction curve’ as a function of angle. Application of our modified inversion strategy, to both synthetic data and the BHRS data set, shows that it allows the successful incorporation of all available traveltime data to obtain significantly improved subsurface velocity images.
Translational control of meiotic cell cycle progression and spermatid differentiation in male germ cells by a novel eIF4G homolog
Authors: Baker Catherine C. , Fuller Margaret T.
Published: July 2007

Translational control is crucial for proper timing of developmental events that take place in the absence of transcription, as in meiotic activation in oocytes, early embryogenesis in many organisms, and spermatogenesis. Here we show that a novel form of the translation initiation complex component eIF4G in Drosophila, eIF4G2, is required specifically for male germ cells to undergo meiotic division and proper spermatid differentiation. Flies mutant for eIF4G2 are viable and female fertile but male sterile. Spermatocytes form, but the germ cells in mutant males skip the major events of the meiotic divisions and form aberrant spermatids with large nuclei. Consistent with the failure to undergo the meiotic divisions, function of eIF4G2 is required post-transcriptionally for normal accumulation of the core cell cycle regulatory proteins Twine and CycB in mature spermatocytes. Loss of eIF4G2 function also causes widespread defects in spermatid differentiation. Although differentiation markers Dj and Fzo are expressed in late-stage eIF4G2 mutant germ cells, several key steps of spermatid differentiation fail, including formation of a compact mitochondrial derivative and full elongation. Our results suggest that an alternate form of the translation initiation machinery may be required for regulation and execution of key steps in male germ cell differentiation.
Conserved pattern of tangential neuronal migration during forebrain development
Authors: Métin Christine , Alvarez Chantal , Moudoux David , Vitalis Tania , Pieau Claude , Molnár Zoltán
Published: July 2007

Origin, timing and direction of neuronal migration during brain development determine the distinct organization of adult structures. Changes in these processes might have driven the evolution of the forebrain in vertebrates. GABAergic neurons originate from the ganglionic eminence in mammals and migrate tangentially to the cortex. We are interested in differences and similarities in tangential migration patterns across corresponding telencephalic territories in mammals and reptiles. Using morphological criteria and expression patterns of Darpp-32, Tbr1, Nkx2.1 and Pax6 genes, we show in slice cultures of turtle embryos that early cohorts of tangentially migrating cells are released from the medial ganglionic eminence between stages 14 and 18. Additional populations migrate tangentially from the dorsal subpallium. Large cohorts of tangentially migrating neurons originate ventral to the dorsal ventricular ridge at stage 14 and from the lateral ganglionic eminence from stage 15. Release of GABAergic cells from these regions was investigated further in explant cultures. Tangential migration in turtle proceeds in a fashion similar to mammals. In chimeric slice culture and in ovo graft experiments, the tangentially migrating cells behaved according to the host environment -turtle cells responded to the available cues in mouse slices and mouse cells assumed characteristic migratory routes in turtle brains, indicating highly conserved embryonic signals between these distant species. Our study contributes to the evaluation of theories on the origin of the dorsal cortex and indicates that tangential migration is universal in mammals and sauropsids.
Early developmental specification of the thyroid gland depends onhan-expressing surrounding tissue and on FGF signals
Authors: Wendl Thomas , Adzic Dejan , Schoenebeck Jeffrey J. , Scholpp Steffen , Brand Michael , Yelon Deborah , Rohr Klaus B.
Published: July 2007

The thyroid is an endocrine gland in all vertebrates that develops from the ventral floor of the anterior pharyngeal endoderm. Unravelling the molecular mechanisms of thyroid development helps to understand congenital hypothyroidism caused by the absence or reduction of this gland in newborn humans. Severely reduced or absent thyroid-specific developmental genes concomitant with the complete loss of the functional gland in the zebrafish hands off (han, hand2) mutant reveals the han gene as playing a novel, crucial role in thyroid development. han-expressing tissues surround the thyroid primordium throughout development. Fate mapping reveals that, even before the onset of thyroid-specific developmental gene expression, thyroid precursor cells are in close contact with han-expressing cardiac lateral plate mesoderm. Grafting experiments show that han is required in surrounding tissue,and not in a cell-autonomous manner, for thyroid development. Loss of han expression in the branchial arches and arch-associated cells after morpholino knock-down of upstream regulator genes does not impair thyroid development, indicating that other han-expressing structures,most probably cardiac mesoderm, are responsible for the thyroid defects in han mutants. The zebrafish ace (fgf8) mutant has similar thyroid defects as han mutants, and chemical suppression of fibroblast growth factor (FGF) signalling confirms that this pathway is required for thyroid development. FGF-soaked beads can restore thyroid development in han mutants, showing that FGFs act downstream of or in parallel to han. These data suggest that loss of FGF-expressing tissue in han mutants is responsible for the thyroid defects.
TheDrosophilaHMG-domain proteins SoxNeuro and Dichaete direct trichome formation via the activation ofshavenbabyand the restriction of Wingless pathway activity
Authors: Overton Paul M. , Chia William , Buescher Marita
Published: July 2007

Trichomes are cytoplasmic extrusions of epidermal cells. The molecular mechanisms that govern the differentiation of trichome-producing cells are conserved across species as distantly related as mice and flies. Several signaling pathways converge onto the regulation of a conserved target gene, shavenbaby (svb, ovo), which, in turn, stimulates trichome formation. The Drosophila ventral epidermis consists of the segmental alternation of two cell types that produce either naked cuticle or trichomes called denticles. The binary choice to produce naked cuticle or denticles is affected by the transcriptional regulation of svb, which is sufficient to cell-autonomously direct denticle formation. The expression of svb is regulated by the opposing gradients of two signaling molecules- the epidermal growth factor receptor (Egfr) ligand Spitz (Spi), which activates svb expression, and Wingless (Wg), which represses it. It has remained unclear how these opposing signals are integrated to establish a distinct domain of svb expression. We show that the expression of the high mobility group (HMG)-domain protein SoxNeuro (SoxN) is activated by Spi,and repressed by Wg, signaling. SoxN is necessary and sufficient to cell-autonomously direct the expression of svb. The closely related protein Dichaete is co-regulated with SoxN and has a partially redundant function in the activation of svb expression. In addition, we show that SoxN and Dichaete function upstream of Wg and antagonize Wg pathway activity. This suggests that the expression of svb in a discreet domain is resolved at the level of SoxN and Dichaete.
Radial-displacement solution for a rotating disc with a hyperbolic thickness profile
Authors: Holland M
Published: July 2007

The general solution for radial displacement, and thereby radial and circumferential stresses, in a rotating disc having a thickness governed by the law t = Ar−n (which has become generally known as the disc with a hyperbolic profile) covers all cases but one. It is shown in this note that there is a unique thickness profile, produced when n=8/3+ v, at which the displacements and stresses become indeterminate. The special solution required for this case is developed below.
Combined tension-torsion studies on polymers: Apparatus and preliminary results for polythene
Authors: Ewing P D , Turner S , Williams J G
Published: July 2007

The general concept of equivalent stress and strain is examined with a view to its application in combined tension-torsion creep testing of polymers. A description of the apparatus used and the necessary refinements and precautions to give satisfactory results is given. Comparison of data using the equivalence concept generally supports its use as a method of simplifying data. Further results are given for both loading and unloading at various times during the creep test and the inherent problem of describing unloading is highlighted.
Stiffness characteristics of rubber impact absorbers
Authors: Bakirzis E A
Published: July 2007

Classical elasticity theory, together with a knowledge of the behaviour of solid-rubber pads under compression, is employed to predict the force-deflection characteristics of hollow rubber units used as impact absorbers. Various parameters are predicted theoretically and agreement with theory is found to be satisfactory for a wide range of shapes and ratios of cross-sectional dimensions.
Shrinkage stresses near a discontinuity in a fibre composite material
Authors: Asamoah N K , Wood W G
Published: July 2007

The technique of photothermoelasticity has been used to analyse the shrinkage stresses near to a discontinuity in a model of a fibre composite material. The axial-shrinkage stresses away from the discontinuity are tensile in the matrix and compressive in the fibre, while, between the ends of the discontinuous fibre they are wholly compressive. Under an applied axial tensile stress the presence of shrinkage stresses would therefore tend to reduce the tendency for matrix cracking to occur in the gap between the fibre ends where the tensile-stress concentration is high. However, if the fibres are close together the shrinkage stresses can themselves cause matrix cracking. These observations are reinforced by the results of other work on the strength of single- and multiple-fibre composites.
Axiality of loading in the tensile test
Authors: Grant C
Published: July 2007

Axiality of loading is very important in the tensile test, particularly under creep conditions. An experimental evaluation of bending of the test section using resistance strain gauges has been devised. This test showed that excessive bending was present in spite of the adoption of a coupling design recommended in the literature. The cause of bending was found to be solely due to a friction moment exerted by the pin joints which formed the essential feature of the couplings. A crossed knife-edge design was substituted for them with satisfactory results. Analysis of the pin joint showed it to be unsuitable for specimen alignment in the tensile test.
Shell analysis using a simple facet element
Authors: Dawe D J
Published: July 2007

The use of a simple triangular facet element in the analysis of shells by the displacement method is described. The element stiffness incorporates a recently proposed displacement formulation of the constant-moment element to represent bending behaviour and the well known constant-stress element to represent membrane behaviour. The analysis is a reformulation of an earlier approach based on a mixed variational principle. The results of two numerical applications are included.
Estimation of creep and fatigue behaviour under cyclic loading
Authors: Tilly G P
Published: July 2007

Equations to estimate creep behaviour under cyclic stressing have been developed from the assumption of strain hardening. Reasonable correlations were obtained with experimental data for tensile-stress cycling of a nickel alloy and an 11 per cent chromium steel at elevated temperatures. A cyclic hardening effect was identified which lowers rates of strain accumulation and leads to unexpectedly long endurances, particularly at the higher loading rates and temperatures. However, this causes estimated lives to err on the safe side. Behaviour is predominantly fatigue-dependent at the lower temperatures but either creep or fatigue may predominate at intermediate temperatures. Assumption of linear damage enabled reasonable estimates of lives to be made for different loading rates and stresses by use of readily available creep and plain fatigue data. There was no evidence of any creep-fatigue interaction that could cause reduced endurances.
Plastic design of regular orthotropic grids with two adjacent edges fixed, free, or hinged
Authors: Grigorian M
Published: July 2007

Lower-bound solutions to the problem of collapse of regular rectangular, orthotropic grids with two adjacent edges clamped and the other two either free or simply supported and carrying a uniform concentration of normal nodal forces are developed. The virtual-work method of plastic analysis is used to derive generalized formulae for grids composed of cantilevered and propped-cantilevered beams. The uniqueness of the work-method solutions are confirmed by use of the techniques of discrete field mechanics. The present study is restricted to flat grids with uniform members possessing no torsional resistance. An example is provided to illustrate the applications of the proposed solutions.
Out-of-circularity effects in a pipe bend subjected to pressure and bending loads
Authors: Kitching R , Bond M P
Published: July 2007

When a 2-foot-diameter three-weld right-angled pipe bend (pipe factor 0.0319) was subjected to in-plane bending moments, the stress distributions and flexibility factors compared well with theoretical predictions. When internal pressure was applied alone, and then combined with the bending loads, significant non-linear elastic behaviour was observed and was attributed to the initial out-of-circular shape of the pipe section. An approximate method of assessing this behaviour is discussed.
A new strain meter for concrete
Authors: Marshall A L
Published: July 2007

The manufacture and evaluation of a new strain meter is described. It is cheap and simple to make. The considerations involved in its assessment which are described should prove useful in the evaluation of internal strain meters for concrete.
Parameters governing load trasnfer for single reinforcing members
Authors: Remedios N C , Wood W G
Published: July 2007

The diffusion of stress between a single reinforcing member and a matrix is shown to be a function of three main parameters. These are: position along the stiffener; a stiffness parameter which is the product of the ratio of stiffener to matrix modulus and the aspect ratio of the stiffener; a matrix-width parameter. The effects of variations in Poisson's ratio are found to be small so that similar patterns of stress transfer occur in plane-stress and plane-strain systems if the governing parameters for the systems are the same. No quantitative comparison can be made between stress diffusion in plane and axisymmetric systems.
Response of the integrated polariscope
Authors: Pindera J T , Straka P
Published: July 2007

A new photoelastic technique has been developed for simultaneous recording of the amount of birefringence in transmitted and in scattered light. This paper presents the basic theories of transmission and scattered-light polariscopes and hence deduces the theoretical foundation of the method and technique of the developed integrated polariscope.

A laser is used as light source, or two identical lasers are used. In a one-laser system the linearly polarized ray is split into two beams, one of which is expanded and passes through the standard transmission polariscope, and the other, being about 1 mm in diameter, enters the photoelastic object parallel to its middle plane. An ‘integrating prism’ has been developed for simultaneous recording of the standard isochromatics and of three scattered light beams; a beam scattered parallel to the polariscope axis and two complementary beams scattered at angels of − π/4 and + π/4.
Reinforced discontinuous bend subjected to uniform internal pressure: Effect of reinforcing ring stiffness
Authors: Holland M , Barlow N , Mitchell H
Published: July 2007

This paper deals with the results of an experimental study undertaken to assess the stress-reducing effect of internally bracing a traditional constant-depth elliptical reinforcing ring.

Stress profiles, calculated from strain readings recorded by electrical-resistance foil strain gauges bonded to inner and outer surfaces of the cylindrical limbs of model Araldite bends, are presented for four reinforcement conditions: constant-depth (traditional) elliptical ring; constant-depth ring with internal cruciform bracing; constant-depth ring with a single brace across the minor diameter; perfectly rigid reinforcing plate.

When a traditional reinforcing ring was used the greatest stress-concentration factor (referring to circumferential membrane stress remote from the discontinuity as unity) was found to be 4.15. This was reduced to 2.90 by the use of a ring with a single minor-diameter brace and was further reduced to 2.70 when a ring having a cruciform brace set across major and minor diameters was used. The effect of an infinitely rigid reinforcement was to reduce the maximum stress-concentration factor to 2.60.