High-resolution 3D whole-heart coronary MRA: a study on the combination of data acquisition in multiple breath-holds and 1D residual respiratory motion compensation.

OBJECT: To study a scan protocol for coronary magnetic resonance angiography based on multiple breath-holds featuring 1D motion compensation and to compare the resulting image quality to a navigator-gated free-breathing acquisition. Image reconstruction was performed using L1 regularized iterative SENSE. MATERIALS AND METHODS: The effects of respiratory motion on the Cartesian sampling scheme were minimized by performing data acquisition in multiple breath-holds. During the scan, repetitive readouts through a k-space center were used to detect and correct the respiratory displacement of the heart by exploiting the self-navigation principle in image reconstruction. In vivo experiments were performed in nine healthy volunteers and the resulting image quality was compared to a navigator-gated reference in terms of vessel length and sharpness. RESULTS: Acquisition in breath-hold is an effective method to reduce the scan time by more than 30 % compared to the navigator-gated reference. Although an equivalent mean image quality with respect to the reference was achieved with the proposed method, the 1D motion compensation did not work equally well in all cases. CONCLUSION: In general, the image quality scaled with the robustness of the motion compensation. Nevertheless, the featured setup provides a positive basis for future extension with more advanced motion compensation methods.

Financial protection of patients through compensation of providers: the impact of health equity funds in Cambodia

Public providers have no financial incentive to respect their legal obligation to exempt the poor from user fees. Health Equity Funds (HEFs) aim to make exemptions effective by giving NGOs responsibility for assessing eligibility and compensating providers for lost revenue. We use the geographic spread of HEFs in Cambodia to identify their impact on out-of-pocket (OOP) payments. Among households with some OOP payment, HEFs reduce the amount by 29%, on average. The effect is larger for households that are poorer, mainly use public health care and live closer to a district hospital. HEFs are more effective in reducing OOP payments when they are operated by a NGO, rather than the government, and when they operate in conjunction with the contracting of public health services. HEFs reduce households' health-related debt by around 25%, on average. There is no significant impact on non-medical consumption and health care utilisation

Mechanisms and evolutionary patterns of mammalian and avian dosage compensation.

As a result of sex chromosome differentiation from ancestral autosomes, male mammalian cells only contain one X chromosome. It has long been hypothesized that X-linked gene expression levels have become doubled in males to restore the original transcriptional output, and that the resulting X overexpression in females then drove the evolution of X inactivation (XCI). However, this model has never been directly tested and patterns and mechanisms of dosage compensation across different mammals and birds generally remain little understood. Here we trace the evolution of dosage compensation using extensive transcriptome data from males and females representing all major mammalian lineages and birds. Our analyses suggest that the X has become globally upregulated in marsupials, whereas we do not detect a global upregulation of this chromosome in placental mammals. However, we find that a subset of autosomal genes interacting with X-linked genes have become downregulated in placentals upon the emergence of sex chromosomes. Thus, different driving forces may underlie the evolution of XCI and the highly efficient equilibration of X expression levels between the sexes observed for both of these lineages. In the egg-laying monotremes and birds, which have partially homologous sex chromosome systems, partial upregulation of the X (Z in birds) evolved but is largely restricted to the heterogametic sex, which provides an explanation for the partially sex-biased X (Z) expression and lack of global inactivation mechanisms in these lineages. Our findings suggest that dosage reductions imposed by sex chromosome differentiation events in amniotes were resolved in strikingly different ways.

Reservoir compensation releases : impact on the macroinvertebrate community of the Derwent River, Northumberland, UK-A longitudinal

River regulation for the purposes of public water supply causes the flow regime downstream of a dam to change. Traditionally, in the UK, such regulation was accompanied by requirements for reservoir releases to compensate downstream water users (e.g. industry) for the loss of natural flow (compensation flows). In this article, we compare a unique pre-impoundment macroinvertebrate data set for a regulated upland river with survey data post-impoundment. This allows a longitudinal assessment of the response of the system to regulation. The Derwent River, Northumberland, was impounded in 1966. Impacts on the hydrological regime were quantified by comparing long-term hydrographs, flow duration curves, flow ranges and flashiness indices for the pre-impoundment and post-impoundment periods. The comparison of changes in macroinvertebrate richness and diversity post-impoundment showed that the change in flow regime has had limited effect on the ecological community structure. The flow regime of the Derwent River has become less flashy with fewer extreme events, and the richness and the diversity of macroinvertebrates have, in some cases, increased and at worst have not deteriorated. We suggest that this reflects the strict compensation regime, which has guaranteed minimum flows at all times. Copyright (c) 2012 John Wiley & Sons, Ltd.

Functional compensation of motor function in pre-symptomatic Huntington's disease.

Involuntary choreiform movements are a clinical hallmark of Huntington's disease. Studies in clinically affected patients suggest a shift of motor activations to parietal cortices in response to progressive neurodegeneration. Here, we studied pre-symptomatic gene carriers to examine the compensatory mechanisms that underlie the phenomenon of retained motor function in the presence of degenerative change. Fifteen pre-symptomatic gene carriers and 12 matched controls performed button presses paced by a metronome at either 0.5 or 2 Hz with four fingers of the right hand whilst being scanned with functional magnetic resonance imaging. Subjects pressed buttons either in the order of a previously learnt 10-item finger sequence, from left to right, or kept still. Error rates ranged from 2% to 7% in the pre-symptomatic gene carriers and from 0.5% to 4% in controls, depending on the condition. No significant difference in task performance was found between groups for any of the conditions. Activations in the supplementary motor area (SMA) and superior parietal lobe differed with gene status. Compared with healthy controls, gene carriers showed greater activations of left caudal SMA with all movement conditions. Activations correlated with increasing speed of movement were greater the closer the gene carriers were to estimated clinical diagnosis, defined by the onset of unequivocal motor signs. Activations associated with increased movement complexity (i.e. with the pre-learnt 10-item sequence) decreased in the rostral SMA with nearing diagnostic onset. The left superior parietal lobe showed reduced activation with increased movement complexity in gene carriers compared with controls, and in the right superior parietal lobe showed greater activations with all but the most demanding movements. We identified a complex pattern of motor compensation in pre-symptomatic gene carriers. The results show that preclinical compensation goes beyond a simple shift of activity from premotor to parietal regions involving multiple compensatory mechanisms in executive and cognitive motor areas. Critically, the pattern of motor compensation is flexible depending on the actual task demands on motor control.

Role of MicroRNAs in Islet Beta-Cell Compensation and Failure during Diabetes.

Pancreatic beta-cell function and mass are markedly adaptive to compensate for the changes in insulin requirement observed during several situations such as pregnancy, obesity, glucocorticoids excess, or administration. This requires a beta-cell compensation which is achieved through a gain of beta-cell mass and function. Elucidating the physiological mechanisms that promote functional beta-cell mass expansion and that protect cells against death, is a key therapeutic target for diabetes. In this respect, several recent studies have emphasized the instrumental role of microRNAs in the control of beta-cell function. MicroRNAs are negative regulators of gene expression, and are pivotal for the control of beta-cell proliferation, function, and survival. On the one hand, changes in specific microRNA levels have been associated with beta-cell compensation and are triggered by hormones or bioactive peptides that promote beta-cell survival and function. Conversely, modifications in the expression of other specific microRNAs contribute to beta-cell dysfunction and death elicited by diabetogenic factors including, cytokines, chronic hyperlipidemia, hyperglycemia, and oxidized LDL. This review underlines the importance of targeting the microRNA network for future innovative therapies aiming at preventing the beta-cell decline in diabetes.

Living with an imperfect cell wall: compensation of femAB inactivation in Staphylococcus aureus.

BACKGROUND: Synthesis of the Staphylococcus aureus peptidoglycan pentaglycine interpeptide bridge is catalyzed by the nonribosomal peptidyl transferases FemX, FemA and FemB. Inactivation of the femAB operon reduces the interpeptide to a monoglycine, leading to a poorly crosslinked peptidoglycan. femAB mutants show a reduced growth rate and are hypersusceptible to virtually all antibiotics, including methicillin, making FemAB a potential target to restore beta-lactam susceptibility in methicillin-resistant S. aureus (MRSA). Cis-complementation with wild type femAB only restores synthesis of the pentaglycine interpeptide and methicillin resistance, but the growth rate remains low. This study characterizes the adaptations that ensured survival of the cells after femAB inactivation. RESULTS: In addition to slow growth, the cis-complemented femAB mutant showed temperature sensitivity and a higher methicillin resistance than the wild type. Transcriptional profiling paired with reporter metabolite analysis revealed multiple changes in the global transcriptome. A number of transporters for sugars, glycerol, and glycine betaine, some of which could serve as osmoprotectants, were upregulated. Striking differences were found in the transcription of several genes involved in nitrogen metabolism and the arginine-deiminase pathway, an alternative for ATP production. In addition, microarray data indicated enhanced expression of virulence factors that correlated with premature expression of the global regulators sae, sarA, and agr. CONCLUSION: Survival under conditions preventing normal cell wall formation triggered complex adaptations that incurred a fitness cost, showing the remarkable flexibility of S. aureus to circumvent cell wall damage. Potential FemAB inhibitors would have to be used in combination with other antibiotics to prevent selection of resistant survivors.

On solving fair exchange and related distributed problems in Byzantine environments

Abstract The solvability of the problem of fair exchange in a synchronous system subject to Byzantine failures is investigated in this work. The fair exchange problem arises when a group of processes are required to exchange digital items in a fair manner, which means that either each process obtains the item it was expecting or no process obtains any information on, the inputs of others. After introducing a novel specification of fair exchange that clearly separates safety and liveness, we give an overview of the difficulty of solving such a problem in the context of a fully-connected topology. On one hand, we show that no solution to fair exchange exists in the absence of an identified process that every process can trust a priori; on the other, a well-known solution to fair exchange relying on a trusted third party is recalled. These two results lead us to complete our system model with a flexible representation of the notion of trust. We then show that fair exchange is solvable if and only if a connectivity condition, named the reachable majority condition, is satisfied. The necessity of the condition is proven by an impossibility result and its sufficiency by presenting a general solution to fair exchange relying on a set of trusted processes. The focus is then turned towards a specific network topology in order to provide a fully decentralized, yet realistic, solution to fair exchange. The general solution mentioned above is optimized by reducing the computational load assumed by trusted processes as far as possible. Accordingly, our fair exchange protocol relies on trusted tamperproof modules that have limited communication abilities and are only required in key steps of the algorithm. This modular solution is then implemented in the context of a pedagogical application developed for illustrating and apprehending the complexity of fair exchange. This application, which also includes the implementation of a wide range of Byzantine behaviors, allows executions of the algorithm to be set up and monitored through a graphical display. Surprisingly, some of our results on fair exchange seem contradictory with those found in the literature of secure multiparty computation, a problem from the field of modern cryptography, although the two problems have much in common. Both problems are closely related to the notion of trusted third party, but their approaches and descriptions differ greatly. By introducing a common specification framework, a comparison is proposed in order to clarify their differences and the possible origins of the confusion between them. This leads us to introduce the problem of generalized fair computation, a generalization of fair exchange. Finally, a solution to this new problem is given by generalizing our modular solution to fair exchange

Plant sex chromosomes: lost genes with little compensation.

In many animals, gene loss on Y chromosomes is compensated through altered expression of their X-chromosome homologue. Now, however, a new study in plants finds that even genes deleted from the Y show no dosage compensation.

Evolution of dosage compensation under sexual selection differs between X and Z chromosomes.

Complete sex chromosome dosage compensation has more often been observed in XY than ZW species. In this study, using a population genetic model and the chicken transcriptome, we assess whether sexual conflict can account for this difference. Sexual conflict over expression is inevitable when mutation effects are correlated across the sexes, as compensatory mutations in the heterogametic sex lead to hyperexpression in the homogametic sex. Coupled with stronger selection and greater reproductive variance in males, this results in slower and less complete evolution of Z compared with X dosage compensation. Using expression variance as a measure of selection strength, we find that, as predicted by the model, dosage compensation in the chicken is most pronounced in genes that are under strong selection biased towards females. Our study explains the pattern of weak dosage compensation in ZW systems, and suggests that sexual selection plays a major role in shaping sex chromosome dosage compensation.

La compensation écologique : marché ou marchandage ?

Les "banques de conservation" sont fréquemment présentées comme de nouveaux instruments de marché au service de la conservation de la biodiversité. Il s'agit d'une modalité de mise en oeuvre de la compensation écologique d'abord développée aux Etats-Unis au début des années 2000 avant d'être plus globalement diffusée. Ce dispositif est perçu par ses promoteurs comme un marché en devenir, tandis que ses détracteurs y voient le dernier avatar du projet de marchandisation de la nature au coeur des politiques environnementales depuis deux décennies. Au-delà des discours, les arrangements institutionnels en jeu dans les banques de conservation sont mal connus. Cet article se propose de revenir sur leur statut économique en analysant le dispositif tel que décrit dans la réglementation fédérale qui lui est consacrée aux Etats-Unis et en évaluant sa mise en place à l'aune de critères et attributs constitutifs d'un marché, qui auront été préalablement définis.

Management Control for Corporate Sustainability Execution: The Role of Employee Compensation

The research described in this thesis examines the characteristics, the benefits and the challenges associated with the implementation of management accounting systems in the field of Corporate Social Responsibility (CSR). Applied to the CSR context, management accounting relates to the identification, elaboration and communication of information about an organization's interactions with the society and the environment. Based on this information, firms are able to make decisions to achieve social and environmental objectives and provide evidence justifying the benefits and the costs of such actions. The study begins by focusing on green management and exploring the characteristics of Environmental Management Accounting (EMA) systems within firms. The first chapter informs the reader about the growing body of EMA research and reveals unexplored relevant aspects that need to be further investigated. The work also emphasizes the importance of developing new theoretical hypotheses and appropriate research designs to empirically tackle new aspects of EMA and gain understanding on the use of these practices. Subsequently, given the acknowledged importance of control systems in influencing the behaviour of individuals within organizations, the remaining two chapters of the dissertation focus on the functioning of CSR-linked incentives assigned to employees in the form of compensation plans. The second chapter examines the determinants influencing corporate provision of incentives for the attainment of environmental targets. Empirical analysis of a sample of international firms reveals that companies are likely to use green incentives as mechanisms to increase the efficacy in contracting with their employees as well as to respond to social influences. Finally, the third chapter investigates the effectiveness of contracting associated with the use of CSR-linked executive compensation. Empirical analysis of a sample of US-based companies shows that corporate choice to tie senior executives' pay to CSR targets promotes the firm's CSR performance. Cette thèse examine les caractéristiques, avantages et défis associés à l'utilisation des systèmes de contrôle de gestion dans le domaine de la Responsabilité Sociale des Entreprises (RSE). Dans le contexte de la RSE, les activités du contrôle de gestion impliquent l'identification, l'élaboration et la communication d'informations qui concernent les interactions des organisations avec la société et l'environnement. Avec ces informations les entreprises sont en mesure de prendre des décisions visant à atteindre les objectifs sociaux et environnementaux de l'organisation et de documenter les bénéfices et coûts de ces actions. Dès le début, la thèse se concentre sur les caractéristiques des systèmes de contrôle de gestion environnementale au sein des entreprises. Le premier chapitre passe en revue la littérature existante et révèle des aspects inexplorés. Pour ce faire, le travail suggère le développement de nouvelles théories ainsi que l'utilisation de méthodes appropriées. Ces dernières doivent permettre d'aborder empiriquement de nouveaux aspects des systèmes de contrôle environnemental et faciliter la compréhension sur l'utilisation de ces pratiques. Considérant l'importance des systèmes de contrôle pour influencer le comportement des individus au sein des organisations, la suite du travail se concentre sur le fonctionnement des contrats de rémunération des employées liées aux résultats de la RSE. Plus particulièrement, le deuxième chapitre examine les facteurs qui influencent la décision des entreprises d'assigner des objectifs environnementaux aux employées. L'analyse empirique d'un échantillon d'entreprises internationales montre que les entreprises sont susceptibles d'utiliser des mécanismes incitatifs écologiques pour augmenter l'efficacité des contrats ainsi que pour répondre aux influences sociales. Finalement, le troisième chapitre analyse l'efficacité des contrats de rémunération des dirigeants liés aux résultats de la RSE. L'analyse empirique d'un échantillon de sociétés américaines indique que le choix de l'entreprise de lier la rémunération des dirigeants à des objectifs de la RSE favorise la performance RSE de l'organisation.