Energy loss and thermalization of heavy quarks in a strongly-coupled plasma

Using the AdS/CFT correspondence, we compute the medium-induced energy loss of a decelerating heavy quark moving through a strongly-coupled supersymmetric Yang Mills plasma. In the regime where the deceleration is small, a perturbative calculation is possible and we obtain the first two corrections to the energy-loss rate of a heavy quark with constant velocity. The thermalization of the heavy quark is also discussed.Comment: 4 pages, no figures, Proceedings of the 21st International Conference on Ultra-Relativistic Nucleus Nucleus Collisions (QM09), Knoxville, USA, March 30-April 4 200

Study of the reproductive biology and chemical communication of sea cucumbers (Holothuria arguinensis and H. mammata)

New sea cucumber fisheries are emerging in the Mediterranean Sea and Atlantic Ocean in response to a strong Chinese market demand. However, little is known about the biology of the new target species, hindering decisions on their management. The main objective of the present thesis was to study the reproductive biology and the role played by chemical communication and chemosensory systems in Holothuria arguinensis and Holothuria mammata. The different populations sampled in a narrow range along the Iberian Peninsula varied in size/weight, gonadal production, and maturity profile within each species, suggesting the influence of singular features of each location. However, they had all the same general reproductive pattern with a summer-autumn spawning. These results, essential to manage populations, were also useful to determine when to develop bioassays to test whether and how these species communicate during reproduction. Male sea cucumbers, but not females, release chemicals that attract and induce spawning in both sexes. A preliminary analysis of the male spawning water suggests a pheromone with multiple components, among them possibly phosphatidylcholine derivatives. Histology, histochemistry and immunohistochemistry of the potential chemosensory structures involved in the detection of these cues – tentacles, papillae and tube feet – show no obvious differences between them. However, the disc was the most specialized area, with a specific nerve arrangement, rich in nitric oxide synthase and containing numerous cells some of which are likely sensory neurons. The analysis of tissue transcriptomes revealed the presence of at least 591 G-protein-coupled receptors among them at least seven putative odorant receptors distributed mainly in the tentacles, oral cavity, calcareous ring and, papillae and tegument. Overall, this thesis gives valuable insights for sea cucumber fisheries management in the region and a better understanding of how sea cucumbers communicate during reproduction.Estão a emergir novas pescarias de pepinos do mar no mar Mediterrâneo e Oceano Atlântico em resposta à forte procura do mercado chinês. Contudo, sabe-se pouco sobre a biologia e história de vida destas novas espécies alvo, o que prejudica as decisões sobre a sua gestão. O principal objectivo desta tese é o estudo da biologia reprodutiva e o papel da comunicação química e sistema quimiosensorial em Holothuria arguinensis e Holothuria mammata. Sabe-se que a comunicação química está envolvida nos processos reproductivos em vários invertebrados marinhos. No entanto, tem sido pouco investigada nos equinodermes e sabe-se pouco acerca da natureza química dos compostos e dos mecanismos sensoriais envolvidos, assim como dos efeitos que desencadeia. Esta tese tem como objectivos específicos: i) adquirir conhecimentos sobre as características reprodutivas das espécies de interesse, ii) determiner se e como os pepinos do mar comunicam durante a reprodução e procurar identificar os compostos envolvidos, iii) caracterizar as estruturas em contacto directo com o ambiente que potencialmente estão envolvidas na detecção de sinais químicos, e iv) caracterizar o reportório de quimioreceptores e identificar possíveis receptores de odorantes nos tecidos analisados. As populações de H. arguinensis e H. mammata amostradas numa estreita faixa territorial da Peninsula Ibérica variaram tamanho, perfil de produção e maturação das gónadas, o que sugere a influência de características únicas de cada local. Havia maiores indivíduos de H. arguinensis e com gónadas mais pesadas em Sagres e na Ria Formosa comparado com Olhos de Água onde se encontraram mais indivíduos imaturos. A gametogénese e a postura era mais longa em Sagres o que pode ser devido a condições nutricionais e de maré (subtidal vs intertidal). Os indivíduos de H. mammata na Ria Formosa também eram maiores e com gónadas mais pesadas do que em Murcia e Olhos de Água, possivelmente ligado a diferenças n alimentação devido ao tipo de substrato (vasa/areia vs rochas). Estes resultados, incluindo o tamanho à primeira maturação e fecundidade, são importantes para a gestão das espécies nestas regiões. Além disso, sabendo quendo estas espécies se reproduzem permitiu determiner quando deviam ser feitos os bioensaios para estudar a comunicação química nos pepinos de mar. Os bioensaios tiveram como objectivo testar a hipótese de que os pepinos de mar libertam químicos durante a agregação e postura. Os resultados mostram que a água condicionada por machos, mas não homogenatos de gónada ou fluido celómico, atrai machos e fêmeas. Também, a água condicionada de macho, com ou sem espermatozóides, induziu a postura em ambos o sexos, sendo que a água de fêmea não teve qualquer efeito. Isto mostrou claramente que os machos atraem e induzem a postura em ambos os sexos. A água de macho foi analisada através de cromatografia líquida associada a espectrometria de massa, sendo identificada a presença de derivados de fosfatidil colina; contudo, a sua função potencial como feromonas necessita de confirmação experimental. As estruturas corporais em contacto difecto com o ambiente – os tentáculos, as papilas e os pés ambulacrários – e potencialmente envolvidos ma detecção de estímulos químicos foram caracterizadas através de histologia, histoquímica e imunocitoquímica para identificar terminais nervosos que pudessem ser utilizados para electrofisiologia e fazer a triagem dos possíveis coompostos feromonais. Não se encontraram diferenças óbvias na organização nervosa e tecidular. Contudo, o disco na extremidade destas estruturas parece ser um candidato promissor para ensaios electrofisiológicos futuros pois confirma-se ser a área snsorial de cada estrutura.Ó disco caracteriza-s por um arranjo nervoso específico, incluindo uma placa nervosa distinta, rica em óxido nitroso e contendo abundantes células, muitas das quais positivas para sinaptotagmina e serotonina, provavelmente neurónios sensoriais anteriormemte descritos. Finalmente, para melhor compreender como a percepção sensorial ocorre nos pepinos do mar, o reportório de receptores acoplados a proteínas G (GPCR) foram analisados em seis bibliotecas de transcriptómica de diferentes tecidos (tentáculos, ovário, testículo, cavidade oral, anel calcáreo, papila e tegumento). Foram identificados 591 GPCR através de pesquisa de sequências por semelhança; contudo não foram encontrados ortólogos de receptores de odorantes humanos. Através da análise filogenética, que incluiu sequências proteicas de humano, enguia anfioxo, ouriço marinho e anémona, pelo menos sete receptores de odorantes foram encontrados no pepino do mar. Estas sequências pertencem a dois grupos, um mais próximo do ouriço do mar e outro mais próximo da anémona, o que sugere origem de diferentes ancestrais. Foram encontrados amino ácidos conservados característicos da assinatura de receptores de odorantes de metazoários. Além disso, estes estavam presentes principalmente nos tentáculos, cavidade oral, anel calcário, papila e tegumento, em acordo com uma potencial função sensorial. No seu conjunto, esta tese fornece nova e importante informação para a gestão dos pepinos do mar e para melhor compreender como comunicam durante a reprodução

Next-to-leading BFKL phenomenology of forward-jet cross sections at HERA

We show that the forward-jet measurements performed at HERA allow for a detailed study of corrections due to next-to-leading logarithms (NLL) in the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach. While the description of the d\sigma/dx data shows small sensitivity to NLL-BFKL corrections, these can be tested by the triple differential cross section d\sigma/dxdk_T^2dQ^2 recently measured. These data can be successfully described using a renormalization-group improved NLL kernel while the standard next-to-leading-order QCD or leading-logarithm BFKL approaches fail to describe the same data in the whole kinematic range. We present a detailed analysis of the NLL scheme and renormalization-scale dependences and also discuss the photon impact factors.Comment: 15 pages, 9 figures, new title, NLL-BFKL saddle-point approximation replaced by exact integratio

Population pharmacokinetics of mycophenolic acid in pediatric renal transplant patients using parametric and nonparametric approaches.

International audienceMycophenolic acid (MPA) is an immunosuppressive drug widely used in the prevention of acute rejection in pediatric renal transplant recipients and is characterized by a wide inter-individual variability in its pharmacokinetics. The aim of this study was to compare population pharmacokinetic modeling of MPA in pediatric renal transplant recipients given mycophenolate mofetil, the ester prodrug of MPA, using parametric and nonparametric population methods. The data from 34 pediatric renal transplants (73 full pharmacokinetic profiles obtained on day 21, months 3, 6 and 9 post-transplant) were analyzed using both the nonlinear mixed-effect modeling (NONMEM) and nonparametric adaptive grid (NPAG) approaches, based on a two-compartment model with first order lagged time absorption and first order elimination. The predictive performance of the two models was evaluated in a separate group of 32 patients. Higher mean population parameter values and ranges of individual pharmacokinetic parameters were obtained with NPAG, especially for the elimination constant ke: mean 1.16 h(-1) (0.26-4.33 h(-1)) and 0.78 h(-1) (0.66-1.15 h(-1)) with NPAG and NONMEM, respectively. With NPAG, the skewness and kurtosis values for ke (2.03 and 7.80, respectively) were far from the theoretical values expected for normal distributions. Such a non-normal distribution could explain the high value of shrinkage (35%) obtained for this parameter with the parametric NONMEM method. Bayesian forecasting of mycophenolic acid exposure using the NPAG population pharmacokinetic parameters as priors yielded a better predictive performance, with a significantly smaller bias than with the NONMEM model (-1.68% vs -9.53%, p<0.0001). In conclusion, in the present study, NPAG was found to be the most adequate population pharmacokinetic method to describe the pharmacokinetics of MPA in pediatric renal transplant recipients

The concept of instrumental conflict: an application of the theory of activity to computer-supported teaching-learning situations

The purpose of this chapter is to define and to illustrate the concept of instrumental conflict, as a tool to a better understanding of the difficulties that learners encounter while using ICT (Information and Communication Technologies). An instrumental conflict takes its meaning within the framework of Rabardel’s theory of instruments, which in itself is a part of the more general theory of activity. The main idea is that VLE (Virtual Learning Environments) associate three different types of artefacts: didactical, pedagogical and technical. These artefacts must be correctly combined, so that learners can have access to knowledge, which is embedded in the device. We point out the usefulness of such a concept. We thus describe how scientific communities, which focus on didactics of Mathematics and computer science, and on ICT in education and training in particular, deal with difficulties of implementation and exploitation of ICT. It appears that some objects called either didactical objects or pedagogical objects represent a reality, which is similar and extremely wide at the same time. In fact, this ambiguity justifies the distinction between didactical artefacts, pedagogical artefacts and technical artefacts. We finally give some examples of obstacles that can be considered as instrumental conflicts as well as some possible developments offered by the concept of instrumental conflict

Flexibility within the middle ears of vertebrates

Introduction and aims: Tympanic middle ears have evolved multiple times independently among vertebrates, and share common features. We review flexibility within tympanic middle ears and consider its physiological and clinical implications. Comparative anatomy: The chain of conducting elements is flexible: even the ‘single ossicle’ ears of most non-mammalian tetrapods are functionally ‘double ossicle’ ears due to mobile articulations between the stapes and extrastapes; there may also be bending within individual elements. Simple models: Simple models suggest that flexibility will generally reduce the transmission of sound energy through the middle ear, although in certain theoretical situations flexibility within or between conducting elements might improve transmission. The most obvious role of middle-ear flexibility is to protect the inner ear from high-amplitude displacements. Clinical implications: Inter-ossicular joint dysfunction is associated with a number of pathologies in humans. We examine attempts to improve prosthesis design by incorporating flexible components

The low Q

The JLAB EIC (JLEIC) design includes a chicane after the interaction point to detect electron associated with production of quasi-real photon at the interaction. This chicane layout can also be used for Compton polarimetry to measure the electron beam polarization. This proceeding will present the layout of the low Q2 chicane and the implementation and current R&D of a Compton polarimeter which would be located in the middle of this chicane

Effects of Crime Type and Location on Park Use Behavior

Crime and the fear of crime can be a barrier to park use, and locations of crimes can have varied effects. Unsafe areas in or around the park, around the residence, or along the route to the park can alter park use behavior. Our study aimed to examine associations between objective measures of types and location of crimes and park use behaviors. In 2013 we surveyed a sample (N = 230) of residents in Greensboro, North Carolina, about park use, with responses matched to objective crime and spatial measures. We measured all crimes and violent crimes near home, near the closest park, and along the shortest route between home and park. By using ordered and binary logistic modeling, we examined the relationships between the locations of crime and park use and duration of park visit, park rating, and never visiting parks. Additional models included distance to the closest park. Increased crime in parks and near home was associated with fewer park visits. Greater violent crime in all locations was related to fewer park visits. Park ratings were lower for parks with high violent crime rates. Given the importance of parks as settings for outdoor recreation and physical activity, crime may have a detrimental effect on physical activity and, therefore, public health

Dielectrophoresis of charged colloidal suspensions

We present a theoretical study of dielectrophoretic (DEP) crossover spectrum of two polarizable particles under the action of a nonuniform AC electric field. For two approaching particles, the mutual polarization interaction yields a change in their respective dipole moments, and hence, in the DEP crossover spectrum. The induced polarization effects are captured by the multiple image method. Using spectral representation theory, an analytic expression for the DEP force is derived. We find that the mutual polarization effects can change the crossover frequency at which the DEP force changes sign. The results are found to be in agreement with recent experimental observation and as they go beyond the standard theory, they help to clarify the important question of the underlying polarization mechanisms