891 resultados para maximal voluntary contraction


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In recent decades there has been an ethical turn in expectations of how African mineral production and trade should be conducted. Good labour conditions, the absence of conflict and mining’s potential for securing economic, social and environmental benefits are being demanded in the jewellery trade. As a consequence the quality of precious and semi-precious metals and gemstones is now being judged on their ethical credentials in addition to their aesthetic and mineral qualities. Mineral production for industrial manufacture, particularly in the electronics industry, is also coming under scrutiny. Adding value through ethics is closely associated with the use of voluntary (non-state) regulation. This includes standards and associated certification and labels, which have been widely adopted by the minerals and metals sector in efforts to ensure improvements in the social and environmental conditions of production and to enable access to the profitable and expanding global ‘ethical market’. In this chapter, we focus on ethical trading schemes that incorporate voluntary regulation, by using artisanal gold mining in Tanzania and the sale of gold through international fair trade markets as an exemplar to consider the development dynamics that emerge from ethical schemes.

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A severe complication of spinal cord injury is loss of bladder function (neurogenic bladder), which is characterized by loss of bladder sensation and voluntary control of micturition (urination), and spontaneous hyperreflexive voiding against a closed sphincter (detrusor-sphincter dyssynergia). A sacral anterior root stimulator at low frequency can drive volitional bladder voiding, but surgical rhizotomy of the lumbosacral dorsal roots is needed to prevent spontaneous voiding and dyssynergia. However, rhizotomy is irreversible and eliminates sexual function, and the stimulator gives no information on bladder fullness. We designed a closed-loop neuroprosthetic interface that measures bladder fullness and prevents spontaneous voiding episodes without the need for dorsal rhizotomy in a rat model. To obtain bladder sensory information, we implanted teased dorsal roots (rootlets) within the rat vertebral column into microchannel electrodes, which provided signal amplification and noise suppression. As long as they were attached to the spinal cord, these rootlets survived for up to 3 months and contained axons and blood vessels. Electrophysiological recordings showed that half of the rootlets propagated action potentials, with firing frequency correlated to bladder fullness. When the bladder became full enough to initiate spontaneous voiding, high-frequency/amplitude sensory activity was detected. Voiding was abolished using a high-frequency depolarizing block to the ventral roots. A ventral root stimulator initiated bladder emptying at low frequency and prevented unwanted contraction at high frequency. These data suggest that sensory information from the dorsal root together with a ventral root stimulator could form the basis for a closed-loop bladder neuroprosthetic. Copyright © 2013, American Association for the Advancement of Science

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Although contraction of human isolated bronchi is mediated mainly by tachykinin NK2 receptors, NK1 receptors, via prostanoid release, contract small-size (approximately 1 mm in diameter) bronchi. Here, we have investigated the presence and biological responses of NK1 receptors in medium-size (2-5 mm in diameter) human isolated bronchi. Specific staining was seen in bronchial sections with an antibody directed against the human NK1 receptor. The selective NK1 receptor agonist, [Sar(9), Met(O2)(11)]SP, contracted about 60% of human isolated bronchial rings. This effect was reduced by two different NK1 receptor antagonists, CP-99,994 and SR 140333. Contraction induced by [Sar(9), Met(O2)(11)]SP was independent of acetylcholine and histamine release and epithelium removal, and was not affected by nitric oxide synthase and cyclooxygenase (COX) inhibition. [Sar(9), Met(O2)(11)]SP increased inositol phosphate (IP) levels, and SR 140333 blocked this increase, in segments of medium- and small-size (approximately 1 mm in diameter) human bronchi. COX inhibition blocked the IP increase induced by [Sar(9), Met(O2)(11)]SP in small-size, but not in medium-size, bronchi. NK1 receptors mediated bronchoconstriction in a large proportion of medium-size human bronchi. Unlike small-size bronchi this effect is independent of prostanoid release, and the results are suggestive of a direct activation of smooth muscle receptors and IP release.

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Alkyl esters of p–hydroxybenzoic acid (parabens) are widely used as preservatives in personal care products, foods and pharmaceuticals. Their oestrogenic activity, their measurement in human breast tissue and their ability to drive proliferation of oestrogen-responsive human breast cancer cells has opened a debate on their potential to influence breast cancer development. Since proliferation is not the only hallmark of cancer cells, we have investigated the effects of exposure to parabens at concentrations of maximal proliferative response on migratory and invasive properties using three oestrogen-responsive human breast cancer cell lines (MCF-7, T-47-D, ZR-75-1). Cells were maintained short-term (1 week) or long-term (20±2 weeks) in phenol-red-free medium containing 5% charcoal-stripped serum with no addition, 10-8M 17-oestradiol, 1-5x10-4M methylparaben, 10-5M n-propylparaben or 10-5M n-butylparaben. Long-term exposure (20±2 weeks) of MCF-7 cells to methylparaben, n-propylparaben or n-butylparaben increased migration as measured using a scratch assay, time-lapse microscopy and xCELLigence technology: invasive properties were found to increase in matrix degradation assays and migration through matrigel on xCELLigence. Western immunoblotting showed an associated downregulation of E-cadherin and -catenin in the long-term paraben-exposed cells which could be consistent with a mechanism involving epithelial to mesenchymal transition. Increased migratory activity was demonstrated also in long-term paraben-exposed T-47-D and ZR-75-1 cells using a scratch assay and time-lapse microscopy. This is the first report that in vitro, parabens can influence not only proliferation but also migratory and invasive properties of human breast cancer cells.

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Grassroots innovations (GI) are promising examples of deliberate transformation of socio-technical systems towards resilience and sustainability. However, evidence is needed on the factors that limit or enable their success. This paper set out to study how GI use narratives to empower innovation in the face of incumbent socio-technical regimes. Institutional documents were comparatively analyzed to assess how the narratives influence the structure, form of action and external interactions of two Italian grassroots networks, Bilanci di Giustizia and Transition Network Italy. The paper finds an internal consistency between narratives and strategies for each of the two networks. The paper also highlights core similarities, but also significant differences in the ethical basis of the two narratives, and in the organizations and strategies. Such differences determine different forms of innovation empowerment and expose the niche to different potentials to transform incumbent regimes, or to the risk of being co-opted by them.

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The rise in international markets of new, productive Japanese car manufacturers provoked intense world competition, which created serious doubts about the economic sustainability of an industry mostly dominated until the 1970s by European and North-American multinational companies. Ultimately, this crisis provoked a deep transformation of the industry, with consequences that had a permanent impact on European companies in the sector. American and later European manufacturers were successful in lobbying governments to provide protection. Using a rich source of data from the UK, I show that the ‘new trade policy’, voluntary export restraint (VER), placed on Japanese exports of new cars from 1977 to December 1999, was binding. This case study illustrates the strategies used by Japanese manufacturers to gain access to the European market through the UK market via strategic alliances and later through transplant production, against which continental European nation states were unable to fully insulate themselves. It is also shown that the policy had a profound effect on the nature of Japanese products, as Japanese firms responded to the quantity restraints by radically altering the product characteristics of their automobiles and shifting towards larger autos and new goods, to maximise their profits subject to the binding constraint.

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I evaluate the voluntary export restraint placed on Japanese automobile exports from 1977 to 1999 by the UK. I show that the policy failed to assist the British domestic car industry. Instead, UK-based US multi-nationals and Japanese manufacturers were the primary beneficiaries, at a substantial cost to UK consumers. Whilst there are a number of caveats, the policy was on balance damaging to the UK economy in welfare terms.

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Purpose – This paper aims to make a comparison, different from existing literature solely focusing on voluntary earnings forecasts and ex post earnings surprise, between the effects of mandatory earnings surprise warnings and voluntary information disclosure issued by management teams on financial analysts in terms of the number of followings and the accuracy of earnings forecasts. Design/methodology/approach – This paper uses panel data analysis with fixed effects on data collected from Chinese public firms between 2006 and 2010. It uses an exogenous regulation enforcement to minimise the endogeneity problem. Findings – This paper finds that financial analysts are less likely to follow firms which mandatorily issue earnings surprise warnings ex ante than those voluntarily issue earnings forecasts. Moreover, ex post, they issue less accurate and more dispersed forecasts on former firms. The results support Brown et al.’s (2009) finding in the USA and suggest that the earnings surprise warnings affect information asymmetries. Practical implications – This paper justifies the mandatory earnings surprise warnings policy issued by Chinese Securities Regulatory Commission in 2006. Originality/value – Mandatory earnings surprise is a unique practical regulation for publicly listed firms in China. This paper, for the first time, provides empirical evaluation on the effectiveness of a mandatory information disclosure policy in China. Consistent with existing literature on information disclosure by public firms in other countries, this paper finds that, in China, voluntary information disclosure captures more private information than mandatory information disclosure on corporate earnings ability.

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The contraction of a species’ distribution range, which results from the extirpation of local populations, generally precedes its extinction. Therefore, understanding drivers of range contraction is important for conservation and management. Although there are many processes that can potentially lead to local extirpation and range contraction, three main null models have been proposed: demographic, contagion, and refuge. The first two models postulate that the probability of local extirpation for a given area depends on its relative position within the range; but these models generate distinct spatial predictions because they assume either a ubiquitous (demographic) or a clinal (contagion) distribution of threats. The third model (refuge) postulates that extirpations are determined by the intensity of human impacts, leading to heterogeneous spatial predictions potentially compatible with those made by the other two null models. A few previous studies have explored the generality of some of these null models, but we present here the first comprehensive evaluation of all three models. Using descriptive indices and regression analyses we contrast the predictions made by each of the null models using empirical spatial data describing range contraction in 386 terrestrial vertebrates (mammals, birds, amphibians, and reptiles) distributed across the World. Observed contraction patterns do not consistently conform to the predictions of any of the three models, suggesting that these may not be adequate null models to evaluate range contraction dynamics among terrestrial vertebrates. Instead, our results support alternative null models that account for both relative position and intensity of human impacts. These new models provide a better multifactorial baseline to describe range contraction patterns in vertebrates. This general baseline can be used to explore how additional factors influence contraction, and ultimately extinction for particular areas or species as well as to predict future changes in light of current and new threats.

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The present study describes the enzymatic properties and molecular identification of 5`-nucleotidase in soluble and microsomal fractions from rat cardiac ventricles. Using AMP as a substrate, the results showed that the cation and the concentration required for maximal activity in the two fractions was magnesium at a final concentration of 1 mM. The pH optimum for both fractions was 9.5. The apparent K-m (Michaelis constant) values calculated from the Eadie-Hofstee plot were 59.7 +/- 10.4 mu M and 134.8 +/- 32.1 mu M, with V-max values of 6.7 +/- 0.4 and 143.8 +/- 23.8 nmol P-i/min/mg of protein (means +/- S.D., n = 4) from soluble and microsomal fractions respectively. Western blotting analysis of ecto-5`-nucleotidase revealed a 70 kDa protein in both fractions, with the major proportion present in the microsomal fraction. The presence of these enzymes in the heart probably has a physiological function in adenosine signalling. Furthermore, the presence of ecto-5`-nucleotidase in the microsomal fraction could have a role in the modulation of the excitation-contraction-coupling process through involvement of the Ca2+ influx into the sarcoplasmic reticulum. The measurement of maximal enzyme activities in the two fractions highlights the potential capacity of the different pathways of purine metabolism in the heart.

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Previous studies have documented temporal attraction in perceived times of actions and their effects. While some authors argue that voluntary action is a necessary condition for this phenomenon, others claim that the causal relationship between action and effect is the crucial ingredient. In the present study, we investigate voluntary action and causality as the necessary and sufficient conditions for temporal binding. We used a variation of the launching effect proposed by Michotte, in which participants controlled the launch stimulus in some blocks. Volunteers reported causality ratings and estimated the interval between the two events. Our results show dissociations between causality ratings and temporal estimation. While causality ratings are not affected by voluntary action, temporal bindings were only found in the presence of both voluntary action and high causality. Our results indicate that voluntary action and causality are both necessary for the emergence of temporal binding.

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Objective: It was the aim of this study to evaluate whether chronic pain in athletes is related to performance, measured by the maximum oxygen consumption and production of hormones and cytokines. Methods: Fifty-five athletes with a mean age of 31.9 +/- 4.2 years engaged in regular competition and showing no symptoms of acute inflammation, particularly fever, were studied. They were divided into 2 subgroups according to the occurrence of pain. Plasma concentrations of adrenaline, noradrenaline, cortisol, prolactin, growth hormone and dopamine were measured by radioimmunoassay, and the production of the cytokines interleukin (IL)-1, IL-2, IL-4, IL-6, tumor necrosis factor-alpha, interferon-alpha and prostaglandin E-2 by whole-blood culture. Maximal oxygen consumption was determined during an incremental treadmill test. Results: There was no change in the concentration of stress hormones, but the athletes with chronic pain showed a reduction in maximum oxygen consumption (22%) and total consumption at the anaerobic threshold (25%), as well as increased cytokine production. Increases of 2.7-, 8.1-, 1.7- and 3.7-fold were observed for IL-1, IL-2, tumor necrosis factor-alpha and interferon-alpha, respectively. Conclusions: Our data show that athletes with chronic pain have enhanced production of proinflammatory cytokines and lipid mediators and reduced performance in the ergospirometric test. Copyright (c) 2008 S. Karger AG, Basel.