bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonia‐oxidizing Crenarchaeota and nitrification inside the tissue of a colonial ascidian
Authors: Martínez‐García Manuel , Stief Peter , Díaz‐Valdés Marta , Wanner Gerhard , Ramos‐Esplá Alfonso , Dubilier Nicole , Antón Josefa
Published: September 2008

Marine Crenarchaeota represent an abundant component of the oceanic microbiota that play an important role in the global nitrogen cycle. Here we report the association of the colonial ascidian Cystodytes dellechiajei with putative ammonia‐oxidizing Crenarchaeota that could actively be involved in nitrification inside the animal tissue. As shown by 16S rRNA gene analysis, the ascidian‐associated Crenarchaeota were phylogenetically related to Nitrosopumilus maritimus, the first marine archaeon isolated in pure culture that grows chemolithoautotrophically oxidizing ammonia to nitrite aerobically. Catalysed reporter deposition (CARD)‐FISH revealed that the Crenarchaeota were specifically located inside the tunic tissue of the colony, where moreover the expression of amoA gene was detected. The amoA gene encodes the alpha‐subunit of ammonia monooxygenase, which is involved in the first step of nitrification, the oxidation of ammonia to nitrite. Sequencing of amoA gene showed that they were phylogenetically related to amoA genes of N. maritimus and other putative ammonia‐oxidizing marine Crenarchaeota. In order to track the suspected nitrification activity inside the ascidian colony under in vivo conditions, microsensor profiles were measured through the tunic tissue. Net NOx production was detected in the tunic layer 1200–1800 μm with rates of 58–90 nmol cm−3 h−1. Oxygen and pH microsensor profiles showed that the layer of net NOx production coincided with O2 concentrations of 103–116 μM and pH value of 5.2. Together, molecular and microsensor data indicate that Crenarchaeota could oxidize ammonia to nitrite aerobically, and thus be involved in nitrification inside the ascidian tissue.
Reduced GFR and microalbuminuria are independently associated with prevalent cardiovascular disease in Type 2 diabetes: JDDM study 16
Authors: Yokoyama H. , Oishi M. , Kawai K. , Sone H. ,   on behalf of the Japan Diabetes Clinical Data Management Study Group
Published: September 2008

Aims  We investigated whether a reduced estimated glomerular filtration rate (eGFR) was associated with cardiovascular disease (CVD) prevalence, independent of the effect of microalbuminuria in patients with diabetes.

Methods  In a multicentre, large‐scale cohort including 3002 Japanese patients with Type 2 diabetes without macroalbuminuria, the relationship of a reduced eGFR and microalbuminuria with CVD was investigated.

Results  Of those patients, 4.8% had a reduced eGFR and microalbuminuria, 12.7% had a reduced eGFR without microalbuminuria and 18.7% had microalbuminuria but normal eGFR. A reduced eGFR and microalbuminuria were each associated with a doubling of the prevalence of CVD. Compared with patients with no microalbuminuria/normal eGFR [odds ratio (OR) 1.0], the OR for CVD was significantly higher in those with a reduced eGFR without microalbuminuria (OR 1.97) and similarly higher in those with microalbuminuria without a reduced eGFR (OR 1.85). The OR was highest in those with both a reduced eGFR and microalbuminuria (OR 3.97, 95% confidence interval 2.55–6.20). The OR for CVD remained significant after adjustments for age, sex, hypertension, dyslipidaemia, smoking, body mass index, glycated haemoglobin and the duration of diabetes, and remained significant if the cut‐off point for microalbuminuria was set at the median albumin : creatinine ratio (13.7 mg/g creatinine). In patients without microalbuminuria, a reduced eGFR was associated with CVD only in the older and male groups.

Conclusion  A reduced eGFR and the presence of microalbuminuria were each associated with a near doubling of the prevalence of CVD, independently of traditional CVD risk factors and glycaemic control in patients with Type 2 diabetes.
Performance‐vested Stock Options and Earnings Management*
Authors: Kuang Yu Flora
Published: September 2008

Abstract:  This paper investigates the effects of performance‐vested stock options (PVSOs) on the propensity of managers to engage in earnings management. Using observations from the 240 largest non‐financial firms in the UK, I show that managers are more likely to engage in earnings management when they hold a larger proportion of their compensation in PVSOs. When categorizing PVSOs on the basis of their distance from the end of performance periods, the results show that managerial incentives to manage earnings mainly stem from PVSOs that are granted in prior years but within a performance evaluation period (i.e., PVSOs before vesting). Moreover, vesting targets influence the relationship between earnings management and PVSO compensation. The findings are consistent with the earnings smoothing hypothesis: confronted with more ambitious vesting targets, managers who are heavily loaded with PVSOs before vesting will report higher performance by generating greater accounting accruals, whereas in years with good performance, these managers will have incentives to reduce current reported performance by managing earnings downward so they can increase earnings as needed in the future.
Does Competition Improve Health Care Quality?
Authors: Scanlon Dennis P. , Swaminathan Shailender , Lee Woolton , Chernew Michael
Published: September 2008

Objective. To identify the effect of competition on health maintenance organizations' (HMOs) quality measures.

Study Design. Longitudinal analysis of a 5‐year panel of the Healthcare Effectiveness Data and Information Set (HEDIS) and Consumer Assessment of Health Plans Survey® (CAHPS) data (calendar years 1998–2002). All plans submitting data to the National Committee for Quality Assurance (NCQA) were included regardless of their decision to allow NCQA to disclose their results publicly.

Data Sources. NCQA, Interstudy, the Area Resource File, and the Bureau of Labor Statistics.

Methods. Fixed‐effects models were estimated that relate HMO competition to HMO quality controlling for an unmeasured, time‐invariant plan, and market traits. Results are compared with estimates from models reliant on cross‐sectional variation.

Principal Findings. Estimates suggest that plan quality does not improve with increased levels of HMO competition (as measured by either the Herfindahl index or the number of HMOs). Similarly, increased HMO penetration is generally not associated with improved quality. Cross‐sectional models tend to suggest an inverse relationship between competition and quality.

Conclusions. The strategies that promote competition among HMOs in the current market setting may not lead to improved HMO quality. It is possible that price competition dominates, with purchasers and consumers preferring lower premiums at the expense of improved quality, as measured by HEDIS and CAHPS. It is also possible that the fragmentation associated with competition hinders quality improvement.
The Effect of Community‐Level Unemployment on Preventive Oral Health Care Utilization
Authors: Quinn Brian C. , Catalano Ralph A. , Felber Eugene
Published: September 2008

Objective. To test the hypothesis that high community‐level unemployment is associated with reduced use of preventive dental care services by a dentally insured population.

Data. The study uses monthly data on population dental visits and unemployment in the Seattle and Spokane areas from 1995 to 2004. Utilization data come from Washington Dental Services. Unemployment data were obtained from the Bureau of Labor Statistics and Washington's Employment Security Department.

Study Design. The study uses a Box–Jenkins Autoregressive Integrated Moving Average (ARIMA) method to measure the association between the variables over time. The approach controls for the effects of autocorrelation, seasonality, and confounding variables.

Findings. In the Seattle area, an unexpected 10,000 unit increase in the number of unemployed individuals is associated with a 1.24 percent decrease in preventive visits during the month ( p=.0043). In the Spokane area, a similar increase in unemployment is associated with a 5.95 percent decrease in preventive visits ( p=.0326). The findings persist when the independent variable is the number of initial unemployment insurance claims.

Conclusions. The analysis suggests that utilization of preventive dental care declines during periods of high community‐level unemployment. Community‐level unemployment may impede or distract populations from utilizing preventive dental services. The study's findings have implications for insurers, dentists, policy makers, and researchers.
Benchmark Duration of Work Hours for Development of Fatigue Symptoms in Japanese Workers with Adjustment for Job‐Related Stress
Authors: Suwazono Yasushi , Dochi Mirei , Kobayashi Etsuko , Oishi Mitsuhiro , Okubo Yasushi , Tanaka Kumihiko , Sakata Kouichi
Published: September 2008

The objective of this study was to calculate benchmark durations and lower 95% confidence limits for benchmark durations of working hours associated with subjective fatigue symptoms by applying the benchmark dose approach while adjusting for job‐related stress using multiple logistic regression analyses. A self‐administered questionnaire was completed by 3,069 male and 412 female daytime workers (age 18–67 years) in a Japanese steel company. The eight dependent variables in the Cumulative Fatigue Symptoms Index were decreased vitality, general fatigue, physical disorders, irritability, decreased willingness to work, anxiety, depressive feelings, and chronic tiredness. Independent variables were daily working hours, four subscales (job demand, job control, interpersonal relationship, and job suitability) of the Brief Job Stress Questionnaire, and other potential covariates. Using significant parameters for working hours and those for other covariates, the benchmark durations of working hours were calculated for the corresponding Index property. Benchmark response was set at 5% or 10%. Assuming a condition of worst job stress, the benchmark duration/lower 95% confidence limit for benchmark duration of working hours per day with a benchmark response of 5% or 10% were 10.0/9.4 or 11.7/10.7 (irritability) and 9.2/8.9 or 10.4/9.8 (chronic tiredness) in men and 8.9/8.4 or 9.8/8.9 (chronic tiredness) in women. The threshold amounts of working hours for fatigue symptoms under the worst job‐related stress were very close to the standard daily working hours in Japan. The results strongly suggest that special attention should be paid to employees whose working hours exceed threshold amounts based on individual levels of job‐related stress.
Hormesis Without Cell Killing
Authors: Cox, Jr Louis Anthony (Tony)
Published: September 2008

Stochastic two‐stage clonal expansion (TSCE) models of carcinogenesis offer the following clear theoretical explanation for U‐shaped cancer dose‐response relations. Low doses that kill initiated (premalignant) cells thereby create a protective effect. At higher doses, this effect is overwhelmed by an increase in the net number of initiated cells. The sum of these two effects, from cell killing and cell proliferation, gives a U‐shaped or J‐shaped dose‐response relation. This article shows that exposures that do not kill, repair, or decrease cell populations, but that only hasten transitions that lead to cancer, can also generate U‐shaped and J‐shaped dose‐response relations in a competing‐risk (modified TSCE) framework where exposures disproportionately hasten transitions into carcinogenic pathways with relatively long times to tumor. Quantitative modeling of the competing effects of more transitions toward carcinogenesis (risk increasing) and a higher proportion of transitions into the slower pathway (risk reducing) shows that a J‐shaped dose‐response relation can occur even if exposure increases the number of initiated cells at every positive dose level. This suggests a possible new explanation for hormetic dose‐response relations in response to carcinogenic exposures that do not have protective (cell‐killing) effects. In addition, the examples presented emphasize the role of time in hormesis: exposures that monotonically increase risks at younger ages may nonetheless produce a U‐shaped or J‐shaped dose‐response relation for lifetime risk of cancer.
Surgical closure of the patent ductus arteriosus and its effect on the cerebral tissue oxygenation
Authors: Vanderhaegen J , De Smet D , Meyns B , Van De Velde M , Van Huffel S , Naulaers G
Published: September 2008

Aim: Surgical patent ductus arteriosus (PDA) ligation is considered after failure or contraindication of medical treatment. Till now ligation of the PDA has been associated with low morbidity and mortality although recently concerns have been raised about the possible association of ductal clipping and neurodevelopmental abnormalities later in life. By means of near‐infrared spectroscopy (NIRS), we analysed the changes in the cerebral tissue oxygenation index (TOI) and fractional tissue oxygen extraction (FTOE) at the time of clipping as well as after clipping.

Method: Ten preterm infants with a symptomatic PDA who underwent surgical ligation were continuously monitored for heart rate (HR), mean arterial blood pressure (MABP), peripheral oxygen saturation (SaO2) and TOI from 1 h before up to 1 h after clipping. FTOE and haemoglobin difference (HbD) were calculated. Changes in parameters at 5 min after ligation represent the effect of the clipping itself whereas changes up to 1 h‐post‐clipping represent the post‐clipping effect.

Results: At the exact time of clipping, over the entire group, we found a significant increase in TOI of 2.9% (p = 0.037), in HbD of 12.5 μmol/l (p = 0.047) and in HR of 6.5 bpm (p = 0.012). FTOE significantly decreased by 0.02% (p = 0.013). One hour post‐clipping, the cerebral and peripheral parameters were not significantly different from the control values before clipping.

Conclusion: The ductal clipping in se has no negative effect on the cerebral oxygenation.
Development and growth in very preterm infants in relation to NIDCAP in a Dutch NICU: two years of follow‐up
Authors: Wielenga JM , Smit BJ , Merkus MP , Wolf MJ , Van Sonderen L , Kok JH
Published: September 2008

Aim: To study development and growth in relation to newborn individualized developmental and assessment program (NIDCAP®) for infants born with a gestational age of less than 30 weeks.

Methods: Developmental outcome of surviving infants, 25 in the NIDCAP group and 24 in the conventional care group, in a prospective phase‐lag cohort study performed in a Dutch level III neonatal intensive care unit (NICU) was compared. Main outcome measure was the Bayley scales of infant development‐II (BSID‐II) at 24 months corrected age. Secondary outcomes were neurobehavioral and developmental outcome and growth at term, 6, 12 and 24 months.

Results: Accounting for group differences and known outcome predictors no significant differences were seen between both care groups in BSID‐II at 24 months. At term age NIDCAP infants scored statistically significant lower on neurobehavioral competence; motor system (median [IQR] 4.8 [2.9–5.0] vs. 5.2 [4.3–5.7], p = 0.021) and autonomic stability (median [IQR] 5.7 [4.8–6.7] vs. 7.0 [6.0–7.7], p = 0.001). No differences were seen in other developmental outcomes. After adjustment for background differences, growth parameters were comparable between groups during the first 24 months of life.

Conclusion: At present, the strength of conclusions to be drawn about the effect of NIDCAP on developmental outcome or growth at 24 months of age is restricted. Further studies employing standardized assessment approaches including choice of measurement instruments and time points are needed.
Differential binding of factor XII and activated factor XII to soluble and immobilized fibronectin – localization of the Hep‐1/Fib‐1 binding site for activated factor XII
Authors: Schousboe Inger , Nystrøm Birthe T. , Hansen Gert H.
Published: September 2008

Fibronectins (FNs) are dimeric glycoproteins that adopt a globular conformation when present in plasma and solution and an extended conformation in the extracellular matrix. Factor XII (FXII) is a zymogen of the proteolytically active FXIIa that plays a role in thrombus stabilization by enhancing clot formation and in inflammation by enhancing bradykinin formation. To investigate whether the extracellular matrix could play a role in these events, we have recently shown that FXIIa, but not FXII, binds to the extracellular matrix (ECM), and suggested that FN may be the target for the binding. Immunofluorescence microscopy has in the present investigation confirmed that FXIIa added to the ECM colocalizes with FN deposited during growth of human umbilical vein endothelial cells. The aim of the present study, therefore, was to further elucidate the interaction between FXIIa and FN by the use of a solid face binding assay. This showed, like the binding to the ECM, that FXIIa, but not FXII, binds in a Zn2+‐independent manner to immobilized FN. The KD for the binding was 8.5 ± 0.9 nm (n = 3). The binding was specific for the immobilized FN, as the binding could not be inhibited by soluble FN. Furthermore, soluble FN did not bind to immobilized FXIIa. However, soluble FN could bind to FXII, and this binding inhibited the surface‐induced autoactivation of FXII and subsequent binding of the generated FXIIa to immobilized FN. The presence of FXII in an anti‐FN immunoprecipitate of plasma indicated that some FXII in plasma circulates bound to FN. The binding of FXIIa to FN was inhibited by gelatine and fibrin but not by heparin, indicating that FXIIa binds to immobilized FN through the type I repeat modules. Accordingly, FXIIa was found to bind to immobilized fragments of FN containing the type I repeat modules in the N‐terminal domain to which fibrin and gelatine bind.
Multigene analysis for differentiation of aster yellows phytoplasmas infecting carrots in Serbia
Authors: Duduk B. , Calari A. , Paltrinieri S. , Duduk N. , Bertaccini A.
Published: September 2008

During a survey of large carrot fields in Serbia, plants showing leaf reddening and/or yellowing, adventitious shoot production and reduction in taproot size and quality were observed in a low percentage of plants. To verify phytoplasma association with the described symptoms and to carry out pathogen differentiation, PCR assays followed by restriction fragment length polymorphism (RFLP) analyses and/or sequencing of phytoplasma 16Sr DNA and ribosomal protein genes l22 and s3, tuf, putative aa kinase plus ribosomal recycling factor genes and DNA helicase gene were carried out. Phytoplasmas belonging to 16SrI‐A and 16SrI‐B ribosomal subgroups and to rpI‐A and rpI‐B ribosomal protein subgroups, respectively, were identified by RFLP analyses in 13 of 15 symptomatic plants tested. No amplification was obtained with non‐symptomatic carrot samples. The identification was confirmed by sequence analyses of the phytoplasma genes studied. In two carrot samples, presence of interoperon sequence heterogeneity was detected and phytoplasma strains were identified as belonging to 16SrI group but were not assigned to any 16S rRNA or ribosomal protein subgroup. This research allowed the first molecular identification of phytoplasmas infecting carrot in Serbia using several molecular markers, and it indicates that under field conditions in non‐epidemic outbreaks a certain amount of genetic mutation may occur in conserved genes of these prokaryotes.
Rice root colonisation by mycorrhizal and endophytic fungi in aerobic soil
Authors: Vallino M. , Greppi D. , Novero M. , Bonfante P. , Lupotto E.
Published: September 2008

Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts that form intimate associations with the majority of plants growing in aerobic soil; fungal endophytes live internally, either intercellularly or intracellularly, and asymptomatically within plant tissues. Their presence is correlated with an increased response to biotic and abiotic stress. The populations of AM and of endophytic fungi were studied in the roots of different rice varieties grown in aerobic condition, in experimental fields in Vercelli, North Italy. All the rice varieties resulted colonised by AM fungi with a percentage of arbuscularisation ranging between 4% and 28%. Preliminary molecular analyses on some rice varieties showed that the AM population was composed of fungi identified as Glomus intraradices, on the basis of 18S ribosomal gene. All the varieties analysed but one resulted in colonisation by endophytic fungi. About 300 fungal isolates were obtained, belonging mainly to the genera Neotyphodium, Stagonospora and Penicillium.
Sound waves in the intracluster medium of the Centaurus cluster
Authors: Sanders J. S. , Fabian A. C.
Published: September 2008

We report the discovery of ripple-like X-ray surface brightness oscillations in the core of the Centaurus cluster of galaxies, found with 200 ks of Chandra observations. The features are between 3 and 5 per cent variations in surface brightness with a wavelength of around 9 kpc. If, as has been conjectured for the Perseus cluster, these are sound waves generated by the repetitive inflation of central radio bubbles, they represent around 5 × 1042 erg s−1 of spherical sound wave power at a radius of 30 kpc. The period of the waves would be 107 yr. If their power is dissipated in the core of the cluster, it would balance much of the radiative cooling by X-ray emission, which is around 1.3 × 1043 erg s−1 within the inner 30 kpc. The power of the sound waves would be a factor of 4 smaller that the heating power of the central radio bubbles, which means that energy is converted into sound waves efficiently.
Truncated Plurigaussian Simulations to Characterize Aquifer Heterogeneity
Authors: Mariethoz Grégoire , Renard Philippe , Cornaton Fabien , Jaquet Olivier
Published: September 2008

Integrating geological concepts, such as relative positions and proportions of the different lithofacies, is of highest importance in order to render realistic geological patterns. The truncated plurigaussian simulation method provides a way of using both local and conceptual geological information to infer the distributions of the facies and then those of hydraulic parameters. The method (Le Loc’h and Galli 1994) is based on the idea of truncating at least two underlying multi‐Gaussian simulations in order to create maps of categorical variable. In this article, we show how this technique can be used to assess contaminant migration in highly heterogeneous media. We illustrate its application on the biggest contaminated site of Switzerland. It consists of a contaminant plume located in the lower fresh water Molasse on the western Swiss Plateau. The highly heterogeneous character of this formation calls for efficient stochastic methods in order to characterize transport processes.
Using Semivariogram Parameter Uncertainty in Hydrogeological Applications
Authors: Pardo‐Igúzquiza Eulogio , Chica‐Olmo Mario , Garcia‐Soldado Maria Jose , Luque‐Espinar Juan A.
Published: September 2008

Geostatistical estimation (kriging) and geostatistical simulation are routinely used in ground water hydrology for optimal spatial interpolation and Monte Carlo risk assessment, respectively. Both techniques are based on a model of spatial variability (semivariogram or covariance) that generally is not known but must be inferred from the experimental data. Where the number of experimental data is small (say, several tens), as is not unusual in ground water hydrology, the model fitted to the empirical semivariogram entails considerable uncertainty. If all the practical results are based on this unique fitted model, the final results will be biased. We propose that, instead of using a unique semivariogram model, the full range of models that are inside a given confidence region should be used, and the weight that each semivariogram model has on the final result should depend on its plausibility. The first task, then, is to evaluate the uncertainty of the model, which can be efficiently done by using maximum likelihood inference. The second task is to use the range of plausible models in applications and to show the effect observed on the final results. This procedure is put forth here with kriging and simulation applications, where the uncertainty in semivariogram parameters is propagated into the final results (e.g., the prediction of ground water head). A case study using log‐transmissivity data from the Vega de Granada aquifer, in southern Spain, is given to illustrate the methodology.
How Much Can Be Gained by More Systematic Prevention of Stroke?
Authors: Goldstein Larry B.
Published: September 2008

Clinical trials and observational studies provide evidence for a wide range of interventions of proven value for preventing a first or recurrent stroke. The available data indicate that strategies for primordial, primary and secondary stroke prevention are not being optimally implemented. Although specific estimates are difficult to calculate, the impact of improving the use of the wide array of effective stroke preventive interventions would be substantial.
Human Security and Food Security in Geographical Study: Pragmatic Concepts or Elusive Theory?
Authors: Huish Robert
Published: September 2008

This article explores how the concepts of ‘food security’ and ‘human security’ build common language between action‐based researchers and policy‐makers for effective knowledge translation. Both concepts are important examples of how research can inform policy aimed at social justice. While human security is still building a sense of itself, the concept of food security demonstrates how broader issues can be excluded from the common language and how this limits dialogue. In the process of building common language between researchers and policy‐makers, the agreed definition of food security excluded many important issues. As a result, the excluded, more radical issues have been pursued by off‐shoot movements that do less to directly engage the policy‐making process. Human security is a similar concept that is at risk of abandoning its radical origins in order to be considered workable by policy‐makers and academics alike. I argue that social justice theorization must maintain the audacity to envision radical improvements to the human condition, albeit pursuing working definitions for policy‐makers. Social justice and action‐based research should not shy away from theory that seeks to overcome inequity and injustice; it should work to meet the needs of people rather than meet the needs of existing policy‐making technocracy.
Gentrification: What It Is, Why It Is, and What Can Be Done about It
Authors: Shaw Kate
Published: September 2008

This article outlines the key contemporary debates on gentrification, most of which arise from variations in the process: in interpretations, assessments of displacement, the agents involved and the forms that gentrified cities take. The variations are so extensive that some scholars argue that gentrification has become too broad a concept to retain analytical coherency. Others counter that the logic of gentrification is now so generalised that the concept captures no less than the fundamental state and market‐driven ‘class remake’ of cities throughout the world. The article agrees with the latter position and proposes that gentrification should be considered part of a broader continuum of social and economic geographic change, replacing the useful but out‐dated stage model but still accommodating the myriad of variations within its underlying logics. Understanding gentrification as a complex but coherent concept highlights the importance of time and place in the viability of progressive policy responses to gentrification's inequitable effects.
Effects of volitional contraction on intracortical inhibition and facilitation in the human motor cortex
Authors: Ortu Enzo , Deriu Franca , Suppa Antonio , Tolu Eusebio , Rothwell John C.
Published: September 2008

Short‐interval intracortical inhibition (SICI), intracortical facilitation (ICF) and short‐interval intracortical facilitation (SICF) were assessed in the cortical motor area of the first dorsal interosseous muscle (FDI) of 16 healthy subjects. Paired‐pulse TMS was delivered to the left hemisphere at the following interstimulus intervals (ISIs): 2 and 3 ms for SICI, 10 and 15 ms for ICF and 1–5 ms for SICF. Motor‐evoked potentials were recorded from the resting and active right FDI. The effects exerted on SICI and ICF by four intensities (60–90% of active motor threshold, AMT) of the conditioning stimulus (S1) and by three levels of muscle contraction (10%, 25%, 50% of maximal voluntary contraction, MVC) were evaluated. The effects exerted on SICF were evaluated with two intensities (90% and 70% of AMT) of the test stimulus (S2) and with the same levels of muscle contraction. Results showed that: (i) during 10% MVC, maximum SICI was observed with S1 = 70% AMT; (ii) the amount of SICI obtained with S1 = 70% AMT was the same at rest as during 10% MVC, but decreased at higher contraction levels; (iii) ICF was observed only at rest with S1 = 90% AMT; (iv) SICF was facilitated at 10% and 25% MVC, but not at 50% MVC. We conclude that during muscle activation, intracortical excitability reflects a balance between activation of SICI and SICF systems. Part of the reduction in SICI during contraction is due to superimposed recruitment of SICF. Low intensity (70% AMT) conditioning stimuli can test SICI independently of effects on SICF at low contraction levels.
Smooth muscle cell calcium activation mechanisms
Authors: Berridge Michael J.
Published: September 2008

Smooth muscle cell (SMC) contraction is controlled by the Ca2+and Rho kinase signalling pathways. While the SMC Rho kinase system seems to be reasonably constant, there is enormous variation with regard to the mechanisms responsible for generating Ca2+signals. One way of dealing with this diversity is to consider how this system has been adapted to control different SMC functions. Phasic SMCs (vas deferens, uterus and bladder) rely on membrane depolarization to drive Ca2+influx across the plasma membrane. This depolarization can be induced by neurotransmitters or through the operation of a membrane oscillator. Many tonic SMCs (vascular, airway and corpus cavernosum) are driven by a cytosolic Ca2+oscillator that generates periodic pulses of Ca2+. A similar oscillator is present in pacemaker cells such as the interstitial cells of Cajal (ICCs) and atypical SMCs that control other tonic SMCs (gastrointestinal, urethra, ureter). The changes in membrane potential induced by these cytosolic oscillators does not drive contraction directly but it functions to couple together individual oscillators to provide the synchronization that is a characteristic feature of many tonic SMCs.
Amino‐termini isoforms of the Slack K+ channel, regulated by alternative promoters, differentially modulate rhythmic firing and adaptation
Authors: Brown Maile R. , Kronengold Jack , Gazula Valeswara‐Rao , Spilianakis Charalampos G. , Flavell Richard A. , Von Hehn Christian A. A. , Bhattacharjee Arin , Kaczmarek Leonard K.
Published: September 2008

The rates of activation and unitary properties of Na+‐activated K+ (KNa) currents have been found to vary substantially in different types of neurones. One class of KNa channels is encoded by the Slack gene. We have now determined that alternative RNA splicing gives rise to at least five different transcripts for Slack, which produce Slack channels that differ in their predicted cytoplasmic amino‐termini and in their kinetic properties. Two of these, termed Slack‐A channels, contain an amino‐terminus domain closely resembling that of another class of KNa channels encoded by the Slick gene. Neuronal expression of Slack‐A channels and of the previously described Slack isoform, now called Slack‐B, are driven by independent promoters. Slack‐A mRNAs were enriched in the brainstem and olfactory bulb and detected at significant levels in four different brain regions. When expressed in CHO cells, Slack‐A channels activate rapidly upon depolarization and, in single channel recordings in Xenopus oocytes, are characterized by multiple subconductance states with only brief transient openings to the fully open state. In contrast, Slack‐B channels activate slowly over hundreds of milliseconds, with openings to the fully open state that are ∼6‐fold longer than those for Slack‐A channels. In numerical simulations, neurones in which outward currents are dominated by a Slack‐A‐like conductance adapt very rapidly to repeated or maintained stimulation over a wide range of stimulus strengths. In contrast, Slack‐B currents promote rhythmic firing during maintained stimulation, and allow adaptation rate to vary with stimulus strength. Using an antibody that recognizes all amino‐termini isoforms of Slack, Slack immunoreactivity is present at locations that have no Slack‐B‐specific staining, including olfactory bulb glomeruli and the dendrites of hippocampal neurones, suggesting that Slack channels with alternate amino‐termini such as Slack‐A channels are present at these locations. Our data suggest that alternative promoters of the Slack gene differentially modulate the properties of neurones.
Design of a High Efficiency Fuel Cell dc/dc Converter Dedicated to Transportation Applications
Authors: Narjiss Abdellah , Depernet Daniel , Gustin Frédéric , Hissel Daniel , Berthon Alain
Published: September 2008

This work consists in a theoretical and practical study of a dc/dc converter designed to be coupled to a fuel cell stack in transport applications. It also proposes analysis and control of the whole system using digital signal processor (DSP) controller. The research is focused on the integration of a polymer electrolyte fuel cell (PEFC) stack in an embedded system. The fuel cell is characterized by a low-voltage high-current electrical power deliverty. Therefore, it is obvious that a dedicated power interface is necessary to adapt and fix voltage and current levels accordingly to the application requirements. In our case, the power conversion will be done by a high-frequency-transformer-based DC/DC converter. The use of a high frequency transformer allows obtaining significant output voltage ratio (approximately 12 in our case), high efficiency, reduce compactness of used elements and limited semi-conductors losses.
Study on the Polymer Membrane-Type Fuel Cell and Hybrid Hydrogenation Engine System Considering Improvement of Efficiency for Partial-Load Operation
Authors: Obara Shin’ya , Tanno Itaru
Published: September 2008

Power demand patterns, such as for houses, fluctuate sharply. Therefore, if fuel cell cogeneration is installed in a house, partial-load operations with low efficiency frequently occur. On the other hand, if the hydrogen rate of hydrogenation gas-engine generation is increased at the time of low load, emission cleanup and brake thermal efficiency improve. So, in this paper, a hybrid cogeneration system that combines a hydrogenation gas engine and a solid polymer membrane-type fuel cell is proposed. So, operation of a fuel cell or a gas engine with the threshold value of load is investigated. In this paper, four systems were investigated by numerical analysis: independent hydrogenation gas-engine operation, solid polymer membrane-type fuel cell independent operation, that operates a fuel cell or a gas engine with the threshold value of load, and operation using a fuel cell to a base load. As a result, the operating method corresponding to a base load in polymer membrane-type fuel cell had the highest total efficiency. In this case, gas-engine generator (NEG) is operated corresponding to load fluctuation. Moreover, in the comparison results of carbon dioxide emissions, the hydrogenation operation of NEG achieved the best result.
Deformation of a Droplet in a Channel Flow
Authors: Shirani Ebrahim , Masoomi Shila
Published: September 2008

Formation of droplets especially in microchannels, micro-electro-mechanical systems (MEMS) and polymer electrolyte membrane fuel cells and their effects on the performance of these devises, as well as scientific aspect of the droplet behavior in the fluid flow motion, makes the subject of the droplet deformation and motion an attractive problem. In this work, we numerically simulate the deformation of a drop of water attached to the wall of a channel flow using full two-dimensional Navier–Stokes equation and the volume-of-fluid method for capturing the interface. The effects of channel inlet velocity, the density and viscosity of the surrounding fluid, and the surface tension coefficient on the flow structures both inside and outside of the droplet as well as the deformation of the droplets are examined. Several test cases, which cover rather wide range of the Reynolds and capillary numbers, based on the surrounding fluid properties and the diameter of the droplet are performed. The Reynolds number, Re, range is from 24 to 1800 and the capillary number, Ca, is from 0.014 to 0.219. It is found that the droplet shape changes and depending on the capillary and Reynolds numbers, it eventually reaches an equilibrium state when there is balance between the surface tension, inertia, and the viscous forces. It is also found that the deformation of the droplet does not depend on the capillary numbers, when Ca is small, but it is a strong function of Ca, when it is large.
Electrochemical Impedance Parameters for the Diagnosis of a Polymer Electrolyte Fuel Cell Poisoned by Carbon Monoxide in Reformed Hydrogen Fuel
Authors: Nakajima Hironori , Konomi Toshiaki , Kitahara Tatsumi , Tachibana Hideaki
Published: September 2008

We have investigated the behavior of an operating polymer electrolyte fuel cell (PEFC) with supplying a mixture of carbon monoxide (CO) and hydrogen (H2) gases into the anode to develop the PEFC diagnosis method for anode CO poisoning by reformed hydrogen fuel. We analyze the characteristics of the CO poisoned anode of the PEFC at 80°C including CO adsorption and electro-oxidation behaviors by current-voltage (I‐V) measurement and electrochemical impedance spectroscopy (EIS) to find parameters useful for the diagnosis. I‐V curves show the dependence of the output voltage on the CO adsorption and electro-oxidation. EIS analyses are performed with an equivalent circuit model consisting of several resistances and capacitances attributed to the activation, diffusion, and adsorption∕desorption processes. As the result, those resistances and capacitances are shown to change with current density and anode overpotential depending on the CO adsorption and electro-oxidation. The characteristic changes of those parameters show that they can be used for the diagnosis of the CO poisoning.
Numerical Simulation and Experimental Study of Residual Stresses in Compression Molding of Precision Glass Optical Components
Authors: Chen Yang , Yi Allen Y. , Su Lijuan , Klocke Fritz , Pongs Guido
Published: September 2008

Compression molding of glass optical components is a high volume near net-shape precision fabrication method. Residual stresses incurred during postmolding cooling are an important quality indicator for these components. In this research, residual stresses frozen inside molded glass lenses under different cooling conditions were investigated using both experimental approach and numerical simulation with a commercial finite element method program. In addition, optical birefringence method was also employed to verify the residual stress distribution in molded glass lenses. Specifically, optical retardations caused by the residual stresses in the glass lenses that were molded with different cooling rates were measured using a plane polariscope. The measured residual stresses of the molded glass lenses were compared with numerical simulation as a validation of the modeling approach. Furthermore, a methodology for optimizing annealing process was proposed using the residual stress simulation results.
Analysis of the High Performance Drilling Process: Influence of Shape and Profile of the Cutting Edge of Twist Drills
Authors: Koehler W.
Published: September 2008

The aims of the investigations presented in this paper were to measure the tool load under conditions of high performance drilling and to analyze if changes of the tool edge shape as well as the edge profile significantly influence the edge stresses. The described methods to analyze the influences of edge shape modifications will contribute to the optimization of drilling tools. Based on a specific cutting edge shape of a drilling tool, systematic changes to the tool’s chamfer and the transition from the chisel edge to the cutting edge were made. Forces and temperatures on the cutting edge were measured as well as the heat flow into the chips and the workpiece. Using a quick-stop device, chip roots of the different drill tools under conditions of high performance machining were made in order to analyze the chip formation. The contact between chip and rake face could be made visible by a so called contact area analysis. It could be shown that the modification of the transition from the chisel to the cutting edge influences the orientation of the forces on the drill. Machining with a rounded cutting edge shape compared to a chamfered edge reduces the mechanical and thermal tool load. This is confirmed by the fact that the deformation zone in front of the cutting edge is smaller as shown by the crosssections of the chip roots. The presented experimental methods show the possibility of determining influences of modified cutting edge shapes and to adapt the drill to the needs of the high performance drilling.
Numerical Analysis on the Start-Up Flow Past a Resonant Cavity
Authors: Filippone Antonio
Published: September 2008

This paper presents the results of a computational analysis on a three-dimensional unsteady flow inside a resonant cavity. The cavity was fully immersed in a channel flow, had a squared cross section, and a spanwise aspect ratio equal to 3. It was partly closed to the inflow by slits upstream and downstream. The lid was 1∕4 of the cavity length. The Reynolds number was Re=8000 based on the freestream velocity. The numerical simulations were carried out for flow times up to 380 units. Results are presented for a symmetric cavity with respect to the normal to the freestream. The analysis shows complex three-dimensional vortex structures, with Taylor–Görtler-type vortices, filament vortices, and other secondary vortices, some having a relatively short life-span. It is shown that the flow is substantially symmetric, with small spanwise instabilities. It is further shown that there is an asymptotic tendency to an unsteady flow with large wavelengths. A primary vortex establishes at the center of the cavity. Most vortex regions disappear and that they depend on the type of geometry and the state of the boundary layer at the inlet.
Performance Characteristics of a Microscale Ranque–Hilsch Vortex Tube
Authors: Hamoudi A. F. , Fartaj A. , Rankin G. W.
Published: September 2008

The results of an experimental investigation of the energy separation performance of a microscale Ranque–Hilsch vortex tube are presented. The supply channel Reynolds number of a microscale Ranque–Hilsch vortex tube is varied over a considerable range, which extends into the laminar flow regime in order to determine the minimum conditions for cooling. Experiments are conducted for a fixed geometry and control valve setting. At low Reynolds numbers based on the inlet tube hydraulic diameter and average velocity, the results exhibit an increase in dimensionless temperature in both the hot and cold outlets as the Reynolds number is increased from zero, reaching maximum values below 500 and 1000, respectively. The hot outlet dimensionless temperature decreases after reaching its maximum and achieves a minimum value at a Reynolds number below 1500. It then increases steadily with further increases in Reynolds number. The cold outlet dimensionless temperature decreases steadily after the maximum to become negative at a Reynolds number of approximately 1800. This implies that the cooling effect occurs at Reynolds numbers consistent with turbulent flow. The performance characteristics of the microscale vortex tube operating at higher inlet pressures of 200kPa, 300kPa, and 400kPa with an average inlet temperature of 293.6K are also presented for cold air mass ratio values over the range of 0.05–0.95. An increase in the inlet pressure causes the values of the dimensionless cold temperature difference to increase over the whole range of the cold air mass fraction. An unstable operation is observed at a length to diameter ratio of approximately 10, causing radial mixing between the cold and hot flow streams and a dramatic change in the cold mass flow fraction plot.
Estimation of Cavitation Limits From Local Head Loss Coefficient
Authors: Sánchez Raúl , Juana Luis , Laguna Francisco V. , Rodríguez-Sinobas Leonor
Published: September 2008

Cavitation effects in valves and other sudden transitions in water distribution systems are studied as their better understanding and quantification is needed for design and analysis purposes and for predicting and controlling their operation. Two dimensionless coefficients are used to characterize and verify local effects under cavitating flow conditions: the coefficient of local head losses and the minimum value of the cavitation number. In principle, both coefficients must be determined experimentally, but a semianalytical relationship between them is here proposed so that if one of them is known, its value can be used to estimate the corresponding value of the other one. This relationship is experimentally contrasted by measuring head losses and flow rates. It is also shown that cavitation number values, called cavitation limits, such as the critical cavitation limit, can be related in a simple but practical way with the mentioned minimum cavitation number and with a given pressure fluctuation level. Head losses under conditions of cavitation in sharp-edged orifices and valves are predicted for changes in upstream and downstream boundary conditions. An experimental determination of the coefficient of local head losses and the minimum value of the cavitation number is not dependent on the boundary conditions even if vapor cavity extends far enough to reach a downstream pressure tap. Also, the effects of cavitation and displacement of moving parts of valves on head losses can be split. A relatively simple formulation for local head losses including cavitation influence is presented. It can be incorporated to water distribution analysis models to improve their results when cavitation occurs. Likewise, it can also be used to elaborate information about validity limits of head losses in valves and other sudden transitions and to interpret the results of head loss tests.
Wall-Modeled Large-Eddy Simulations of Flows With Curvature and Mild Separation
Authors: Radhakrishnan Senthilkumaran , Piomelli Ugo , Keating Anthony
Published: September 2008

The performance of wall-modeled large-eddy simulation (WMLES) based on hybrid models, in which the inner region is modeled by Reynolds-averaged Navier–Stokes (RANS) equation and the outer region is resolved by large-eddy simulation (LES), can make the application of LES attainable at high Reynolds numbers. In previous work by various authors, it was found that in most cases a buffer region exists between the RANS and LES zones, in which the velocity gradient is too high; this leads to an inaccurate prediction of the skin-friction coefficient. Artificially perturbing the RANS∕LES interface has been demonstrated to be effective in removing the buffer region. In this work, WMLES has been performed with stochastic forcing at the interface, following the previous work by our group on two nonequilibrium complex flows. From the two flows studied, we conclude that the application of stochastic forcing results in improvements in the prediction of the skin-friction coefficient in the equilibrium regions of these flows, a better agreement with the experiments of the Reynolds stresses in the adverse pressure gradient and the recovery region, and a good agreement of the mean velocity field with experiments in the separation region. Some limitations of this method, especially in terms of CPU requirements, will be discussed.