16,425 research outputs found

    Enzyme kinetics for a two-step enzymic reaction with comparable initial enzyme-substrate ratios

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    We extend the validity of the quasi-steady state assumption for a model double intermediate enzyme-substrate reaction to include the case where the ratio of initial enzyme to substrate concentration is not necessarily small. Simple analytical solutions are obtained when the reaction rates and the initial substrate concentration satisfy a certain condition. These analytical solutions compare favourably with numerical solutions of the full system of differential equations describing the reaction. Experimental methods are suggested which might permit the application of the quasi-steady state assumption to reactions where it may not have been obviously applicable before

    Selective Deletion of Sodium Salt Taste during Development Leads to Expanded Terminal Fields of Gustatory Nerves in the Adult Mouse Nucleus of the Solitary Tract.

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    Neuronal activity plays a key role in the development of sensory circuits in the mammalian brain. In the gustatory system, experimental manipulations now exist, through genetic manipulations of specific taste transduction processes, to examine how specific taste qualities (i.e., basic tastes) impact the functional and structural development of gustatory circuits. Here, we used a mouse knock-out model in which the transduction component used to discriminate sodium salts from other taste stimuli was deleted in taste bud cells throughout development. We used this model to test the hypothesis that the lack of activity elicited by sodium salt taste impacts the terminal field organization of nerves that carry taste information from taste buds to the nucleus of the solitary tract (NST) in the medulla. The glossopharyngeal, chorda tympani, and greater superficial petrosal nerves were labeled to examine their terminal fields in adult control mice and in adult mice in which the α-subunit of the epithelial sodium channel was conditionally deleted in taste buds (αENaC knockout). The terminal fields of all three nerves in the NST were up to 2.7 times greater in αENaC knock-out mice compared with the respective field volumes in control mice. The shapes of the fields were similar between the two groups; however, the density and spread of labels were greater in αENaC knock-out mice. Overall, our results show that disruption of the afferent taste signal to sodium salts disrupts the normal age-dependent "pruning" of all terminal fields, which could lead to alterations in sensory coding and taste-related behaviors. Neural activity plays a major role in the development of sensory circuits in the mammalian brain. To date, there has been no direct test of whether taste-elicited neural activity has a role in shaping central gustatory circuits. However, recently developed genetic tools now allow an assessment of how specific taste stimuli, in this case sodium salt taste, play a role in the maturation of the terminal fields in the mouse brainstem. We found that the specific deletion of sodium salt taste during development produced terminal fields in adults that were dramatically larger than in control mice, demonstrating for the first time that sodium salt taste-elicited activity is necessary for the normal maturation of gustatory inputs into the brain

    Sport, glocalization and the new Indian middle class

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    Focusing on the structure and influence of transnational sport - namely the Commonwealth Games and fitness culture within the context of contemporary India - we draw on observations derived from empirical research to explore the complex interrelationships between economic liberalization, globalization, and consumer capitalism. Our argument centres on the processes through which contemporary Indian sport culture is being re-made within the image of India's new middle class; a set of processes that simultaneously contributes toward the hegemony of India's protuberant new middle class and thereby patently re-inscribes the social inequities and polarities evident within Indian life more generally. Through a contextual consideration of the economic liberalization policies and allied neoliberal ideologies that propelled the emergence of the new middle class (Antonio, 2007), and the consumer culture through which its identities are substantiated and boundaries demarcated (Bauman, 2001), we point to those bodies valorized (productive, consumptive and functional) and those pathologized (impoverished, underserved and disposable) within a transnational sporting culture that espouses the dictates of neoliberal polity, policy and body politics. © The Author(s) 2013

    You Can Change the World With a Haircut”: Evaluating the Feasibility of a Barber-led Intervention for Men of Black and Ethnic Minority Heritage to Manage High Blood Pressure

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    Background: People of Black, Asian and minority ethnic (BAME) heritage have a higher-than-average incidence of, and mortality from hypertension and stroke. Therefore, it is important to identify new settings for engaging people at risk of high blood pressure (BP). Aim: This feasibility study aimed to evaluate if barbers in a London borough can support and educate men of BAME heritage to manage their BP. Following UK Medical Research Council guidance, the RE-AIM (reach, effectiveness, adoption, implementation, maintenance) framework was used to guide study objectives and feasibility outcomes. Methods: We collaborated with 8 barbers who were part of an existing BAME barber network. Barbers were trained online (1.5 h) and face-to-face (3 h) to provide BP healthcare advice and take customers BP readings. Qualitative field notes were collected to assess how best to recruit and train barbers, and to understand how to maintain motivation and retention of barbers. BP readings were recorded between June 2021 and March 2022. Results: Both online and face-to-face training were effective, however, greater focus on how to start conversations about BP with clients was needed. We found that motivation, incentivization and regular contact with barbers were important for recruitment, retention, and sustained BP measurement. Obtaining BP readings was challenging due to client concerns about recording their data and the impracticalities of recording results. We captured 236 BP recordings, of which 39 (16.53%) were over 140/90 mmHg; of these, 5 were over 180/100 mmHg. Conclusion: The combined data showed that educating barbers to take BP readings and deliver healthcare advice about BP is a viable intervention for rollout in a large-scale study. It has demonstrated the need to identify strategies to motivate barbers for sustained recruitment and retention, as well as further efforts to build trust among customers for long-term BP surveillance

    Accelerated Projected Gradient Method for Linear Inverse Problems with Sparsity Constraints

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    Regularization of ill-posed linear inverse problems via 1\ell_1 penalization has been proposed for cases where the solution is known to be (almost) sparse. One way to obtain the minimizer of such an 1\ell_1 penalized functional is via an iterative soft-thresholding algorithm. We propose an alternative implementation to 1\ell_1-constraints, using a gradient method, with projection on 1\ell_1-balls. The corresponding algorithm uses again iterative soft-thresholding, now with a variable thresholding parameter. We also propose accelerated versions of this iterative method, using ingredients of the (linear) steepest descent method. We prove convergence in norm for one of these projected gradient methods, without and with acceleration.Comment: 24 pages, 5 figures. v2: added reference, some amendments, 27 page

    The Magnificent Seven: Magnetic fields and surface temperature distributions

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    Presently seven nearby radio-quiet isolated neutron stars discovered in ROSAT data and characterized by thermal X-ray spectra are known. They exhibit very similar properties and despite intensive searches their number remained constant since 2001 which led to their name ``The Magnificent Seven''. Five of the stars exhibit pulsations in their X-ray flux with periods in the range of 3.4 s to 11.4 s. XMM-Newton observations revealed broad absorption lines in the X-ray spectra which are interpreted as cyclotron resonance absorption lines by protons or heavy ions and / or atomic transitions shifted to X-ray energies by strong magnetic fields of the order of 10^13 G. New XMM-Newton observations indicate more complex X-ray spectra with multiple absorption lines. Pulse-phase spectroscopy of the best studied pulsars RX J0720.4-3125 and RBS 1223 reveals variations in derived emission temperature and absorption line depth with pulse phase. Moreover, RX J0720.4-3125 shows long-term spectral changes which are interpreted as due to free precession of the neutron star. Modeling of the pulse profiles of RX J0720.4-3125 and RBS 1223 provides information about the surface temperature distribution of the neutron stars indicating hot polar caps which have different temperatures, different sizes and are probably not located in antipodal positions.Comment: 10 pages, 8 figures, to appear in Astrophysics and Space Science, in the proceedings of "Isolated Neutron Stars: from the Interior to the Surface", edited by D. Page, R. Turolla and S. Zan

    Characterisation of the effects of salicylidene acylhydrazide compounds on type three secretion in Escherichia coli O157:H7

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    Recent work has highlighted a number of compounds that target bacterial virulence by affecting gene regulation. In this work, we show that small-molecule inhibitors affect the expression of the type III secretion system (T3SS) of <i>Escherichia coli</i> O157:H7 in liquid culture and when the bacteria are attached to bovine epithelial cells. The inhibition of T3SS expression resulted in a reduction in the capacity of the bacteria to form attaching and effacing lesions. Our results show a marked variation in the ability of four structurally-related compounds to inhibit the T3SS of a panel of isolates. Using transcriptomics, we provide a comprehensive analysis of the conserved- and inhibitor-specific transcriptional responses to the four compounds. These analyses of gene expression show that numerous virulence genes, located on horizontally-acquired DNA elements, are affected by the compounds but the number of genes significantly affected varied markedly between the compounds. Overall, we highlight the importance of assessing the effect of such "anti-virulence" agents on a range of isolates and discuss the possible mechanisms which may lead to the co-ordinate down-regulation of horizontally acquired virulence genes

    Reconstructing stakeholder relationships using ‘corporate social responsibility’ as a response strategy to cases of corporate irresponsibility: The case of the 2010 BP spill in the Gulf of Mexico.

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    Purpose When organisations behave irresponsibly, a question remains: Can they use a messaging strategy based in the organisation’s commitment social responsibility to effectively respond to the crisis? The purpose of this chapter is to analyse stakeholder attitudes and their antecedents in such a case. Because of its scope, magnitude and use of a response strategy based on messages of social responsibility, the 2010 BP oil spill in the Gulf of Mexico serves as an excellent case for measuring the effectiveness of such a messaging strategy. Methodology/approach The present study drew from two data sources: a content analysis of interactions on BP’s Facebook page (N=1,515) as well as an image survey of BP (N=749). Findings BP’s messaging strategy had limited positive effects in terms of (1) being viewed as a ‘socially responsible’ organisation and (2) creating significant good will towards the company. However, these data also reveal that BP has effectively opened lines of communication between stakeholders and the company. Practical and social implications This study has two central implications. First, for both organisations and activists, personal investment and the relevance of issues are both critical in order to change stakeholder attitudes about organisations. Second, based on this research, we can begin to develop stakeholder profiles based on age, sex and political identity. Originality/value In the last couple of years, considerable attention has been paid to describing and analysing the response strategies that organisations deploy; however, scant attention has been paid to measuring stakeholder evaluations of those crisis response strategies

    Spontaneous circadian rhythms in a cold-Adapted natural isolate of Aureobasidium pullulans

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    Indexación: Scopus.Circadian systems enable organisms to synchronize their physiology to daily and seasonal environmental changes relying on endogenous pacemakers that oscillate with a period close to 24 h even in the absence of external timing cues. The oscillations are achieved by intracellular transcriptional/translational feedback loops thoroughly characterized for many organisms, but still little is known about the presence and characteristics of circadian clocks in fungi other than Neurospora crassa. We sought to characterize the circadian system of a natural isolate of Aureobasidium pullulans, a cold-Adapted yeast bearing great biotechnological potential. A. pullulans formed daily concentric rings that were synchronized by light/dark cycles and were also formed in constant darkness with a period of 24.5 h. Moreover, these rhythms were temperature compensated, as evidenced by experiments conducted at temperatures as low as 10 °C. Finally, the expression of clock-essential genes, frequency, white collar-1, white collar-2 and vivid was confirmed. In summary, our results indicate the existence of a functional circadian clock in A. pullulans, capable of sustaining rhythms at very low temperatures and, based on the presence of conserved clock-gene homologues, suggest a molecular and functional relationship to well-described circadian systems.https://www.nature.com/articles/s41598-017-14085-
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