Controlled stratification for quantile estimation

In this paper we propose and discuss variance reduction techniques for the estimation of quantiles of the output of a complex model with random input parameters. These techniques are based on the use of a reduced model, such as a metamodel or a response surface. The reduced model can be used as a control variate; or a rejection method can be implemented to sample the realizations of the input parameters in prescribed relevant strata; or the reduced model can be used to determine a good biased distribution of the input parameters for the implementation of an importance sampling strategy. The different strategies are analyzed and the asymptotic variances are computed, which shows the benefit of an adaptive controlled stratification method. This method is finally applied to a real example (computation of the peak cladding temperature during a large-break loss of coolant accident in a nuclear reactor).Comment: Published in at http://dx.doi.org/10.1214/08-AOAS186 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Simulating microbial degradation of organic matter in a simple porous system using the 3-D diffusion-based model MOSAIC

This paper deals with the simulation of microbial degradation of organic matter in soil within the pore space at a microscopic scale. Pore space was analysed with micro-computed tomography and described using a sphere network coming from a geometrical modelling algorithm. The biological model was improved regarding previous work in order to include the transformation of dissolved organic compounds and diffusion processes. We tested our model using experimental results of a simple substrate decomposition experiment (fructose) within a simple medium (sand) in the presence of different bacterial strains. Separate incubations were carried out in microcosms using five different bacterial communities at two different water potentials of −10 and −100 cm of water. We calibrated the biological parameters by means of experimental data obtained at high water content, and we tested the model without changing any parameters at low water content. Same as for the experimental data, our simulation results showed that the decrease in water content caused a decrease of mineralization rate. The model was able to simulate the decrease of connectivity between substrate and microorganism due the decrease of water content

Soin des corps, soin des âmes : genre et pouvoirs dans les hôpitaux de France et de Nouvelle-France aux XVIIe et XVIIIe siècles

Thèse réalisée en cotutelle avec l'université Clermont 2 (Clermont-Ferrand, France)Comment les établissements hospitaliers d’Ancien Régime marquent-ils les corps des personnes qui y séjournent et y officient ? À partir du milieu du XVIIe siècle, l’espace français fait l’objet d’une réforme hospitalière menée de concert par l’Église de la Réforme catholique et l’État en voie d’absolutisme. La création des Hôpitaux Généraux dans l’ensemble du royaume, jusqu’en terre coloniale, a pour effet de progressivement préciser le rôle des Hôtels-Dieu, et de contribuer à la mise en place d’un réseau d’institutions hospitalières au sein desquelles se côtoient laïcs et religieux, soignants et malades, hommes et femmes. Afin d’appréhender les principales situations où ce processus se met en place, nous avons analysé les établissements parisiens sur lesquels les volontés étatique et religieuse s’expriment pleinement, un territoire provincial – l’Auvergne – qui, éloigné du centre du pouvoir royal, adapte le fonctionnement hospitalier à son territoire, et un espace colonial – la vallée du Saint-Laurent au Canada – où l’implantation des institutions hospitalières répond à la fois à la volonté de l’Église missionnaire et des autorités coloniales, tout en devant répondre aux besoins d’une population particulière. Notre thèse propose de montrer comment ces différents pouvoirs que sont l’Église, la volonté soignante et le genre s’entremêlent au sein des hôpitaux, et s’exercent sur l’ensemble des personnes qui participent à la vie des établissements depuis le début de cette réforme hospitalière jusqu’à la fin du XVIIIe siècle Pour ce faire, cette thèse convoque des documents divers issus des fonds d’archives des hôpitaux et des communautés hospitalières. En croisant les textes prescriptifs et les sources témoignant des pratiques hospitalières, ce travail montre que les corps des agents de l’institution comme ceux des usagers subissent un processus de disciplinement relativement similaire, tout particulièrement dans le domaine religieux. Elle souligne de plus la répartition du pouvoir entre les femmes et les hommes qui évolue, au cours de la période étudiée, au bénéfice de ces derniers sous l’effet d’un phénomène de professionnalisation des métiers soignants encadrés par les autorités laïques. En comparant trois territoires, cette thèse montre de plus comment les institutions s’adaptent à des contextes différents. Elle permet ainsi de faire ressortir, notamment à travers une analyse de l’espace hospitalier, les similitudes entre la situation auvergnate et la situation canadienne, du moins au cours des décennies de paix pour la colonie. En revanche, la colonie se distingue nettement de la métropole par le primat accordé au religieux tout au long de la période, qui s’achève avec la Conquête, tandis que les établissements métropolitains, d’abord ceux de Paris puis d’Auvergne, témoignent d’une orientation qui accorde de plus en plus de place et de pouvoir aux questions médicales laïques.How did Ancien Régime hospitals mark and regulate the bodies of its inhabitants and its officers? From the mid-seventeenth century, the French colonial space was the subject of a hospital reform implemented in collaboration with Church and the State, the latter in the process of absolutism. The creation of the General Hospitals across the kingdom, throughout colonial land, had the effect of gradually clarifying the role of Hôtel-Dieu, and thus contributed to the establishment of a network of health institutions where secular and religious, caregivers and patients, men and women worked alongside each other. In order to capture the primary settings where this process took place, the dissertation analyzes the Parisian establishments under which state and religious wishes were fully expressed, a provincial territory - Auvergne - which, far from the center of royal power adapted the workings of hospital to its territory and colonial space - St. Lawrence Valley in Canada - where the implementation of hospital institutions responded both to the will of the missionary Church and colonial authorities as well as to meet the needs of a particular population. The project demonstrates how the powers of the Church, the caregiver and the dynamics of gender intertwined in hospitals and acting on all those involved in the hospital life from the Earlier this hospital reform until the end of the eighteenth century For this, this thesis brings together various documents from the archives of hospitals and hospital communities. By crossing the prescriptive texts and documents showing hospital practice, this thesis shows that the bodies of the institution's staff and those of the users underwent a process of disciplining relatively similar, especially in the religious sphere. It also shows that the distribution of power between men and women that evolves during the study period for the benefit of mankind as a result of a phenomenon of professional caregivers trades framed by the secular authorities. Comparing the three territories, this thesis, furthermore, shows how institutions adapt to different contexts. It helps to emphasize, in particular through an analysis of hospital space, the similarities between the Auvergne and the Canadian contexts, at least during the decades of peace for the colony. However, the colony is clearly distinguishable from the metropolis by the primacy accorded to religious throughout the period, which ended with the conquest, while the metropolitan institutions, first those of Paris and the Auvergne, testify to the increasingly power given to lay medical issues

Qui sont les associés d’audit des cabinets Big 4 ? : Une lecture interactionniste des carrières des auditeurs dans les cabinets Big 4 en France

This PhD studies the process of becoming a partner in professional services firms, envisaged through the lens of the building of the partner identity. To this end, it implements the concept of « career » developed by interactionist sociology to analyse the making of a partner in the context of the Big 4 international audit firms. Becoming a partner is a process that starts right after recruitment and which is governed by complex and largely informal mechanisms and political manoeuvring. We characterize these mechanisms with the help of the notion of “stable”, whose purpose is to understand procedures of co-option in their unofficial dimension but also to account for the structuration of the partner level in firms and the role played by hierarchies within this level in post-partner career progression. We come to the conclusion that auditors actually become partners much earlier than their official promotion to the rank, from the moment they consider themselves as such. This awakening is yet only the first turning point on the road to partnership. It is only when they are officially co-opted that auditors become the partners they were, by being recognised as such by their peers, completing therefore their identity conversion.This work contributes to the literature in the sociology of professions and organizational theory fields by investigating how professionals are socialized and how their identity is constructed and by grasping more accurately the organization of professional services firmsCette thèse entend contribuer à l’étude des carrières des associés des firmes professionnelles en s’intéressant en particulier au processus de construction de l’identité d’associé. En nous appuyant sur le concept interactionniste de carrière nous analysons le « devenir associé » dans le contexte des grands cabinets d’audit internationaux (les Big 4). Ce devenir est un processus qui débute quasiment dès le recrutement et qui relève de mécanismes informels et tacites et de manœuvres politiques. Nous caractérisons ces mécanismes par la notion « d’écurie » qui permet à la fois de comprendre le fonctionnement des procédures de cooptation dans sa dimension non-officielle, mais également la hiérarchisation de la partnershipet le déroulement des carrières en son sein, une fois le stade de l’association passé. La conclusion à laquelle nous parvenons est que l’auditeur devient associé bien avant sa cooptation, en se reconnaissant lui-même comme un professionnel. Ce turning point n’est cependant que le premier sur le chemin qui mène à la partnership car c’est seulement au moment où il rejoint cette dernière que l’auditeur devient l’associé qu’il était, en se faisant reconnaître comme tel par ses pairs, achevant ainsi sa conversion identitaire d’auditeur en associé. Par notre travail, nous nous inscrivons dans la lignée des études en sociologie des professions et en théorie des organisations qui ont exploré le champ de la socialisation des professionnels de l’audit et de la construction de leur identité ainsi que le fonctionnement des grands cabinets internationau

Gravitational Wilson Lines in 3D de Sitter

We construct local probes in the static patch of Euclidean dS$_3$ gravity. These probes are Wilson line operators, designed by exploiting the Chern-Simons formulation of 3D gravity. Our prescription uses non-unitary representations of $so(4)\simeq su(2)_L\times su(2)_R$, and we evaluate the Wilson line for states satisfying a singlet condition. We discuss how to reproduce the Green's functions of massive scalar fields in dS$_3$, the construction of bulk fields, and the quasinormal mode spectrum. We also discuss the interpretation of our construction in Lorentzian signature in the inflationary patch, via $SL(2,\mathbb{C})$ Chern-Simons theory.Comment: 46 pages, 1 figure; v2: final version for JHEP, minor edit

EB1 regulates microtubule dynamics and tubulin sheet closure in vitro.

International audienceEnd binding 1 (EB1) is a plus-end-tracking protein (+TIP) that localizes to microtubule plus ends where it modulates their dynamics and interactions with intracellular organelles. Although the regulating activity of EB1 on microtubule dynamics has been studied in cells and purified systems, the molecular mechanisms involved in its specific activity are still unclear. Here, we describe how EB1 regulates the dynamics and structure of microtubules assembled from pure tubulin. We found that EB1 stimulates spontaneous nucleation and growth of microtubules, and promotes both catastrophes (transitions from growth to shrinkage) and rescues (reverse events). Electron cryomicroscopy showed that EB1 induces the initial formation of tubulin sheets, which rapidly close into the common 13-protofilament-microtubule architecture. Our results suggest that EB1 favours the lateral association of free tubulin at microtubule-sheet edges, thereby stimulating nucleation, sheet growth and closure. The reduction of sheet length at microtubule growing-ends together with the elimination of stressed microtubule lattices may account for catastrophes. Conversely, occasional binding of EB1 to the microtubule lattice may induce rescues

Modeling the effect of soil meso- and macropores topology on the biodegradation of a soluble carbon substrate

Soil structure and interactions between biotic and abiotic processes are increasingly recognized as important for explaining the large uncertainties in the outputs of macroscopic SOM decomposition models. We present a numerical analysis to assess the role of meso- and macropore topology on the biodegradation of a soluble carbon substrate in variably water saturated and pure diffusion conditions . Our analysis was built as a complete factorial design and used a new 3D pore-scale model, LBioS, that couples a diffusion Lattice-Boltzmann model and a compartmental biodegradation model. The scenarios combined contrasted modalities of four factors: meso- and macropore space geometry, water saturation, bacterial distribution and physiology. A global sensitivity analysis of these factors highlighted the role of physical factors in the biodegradation kinetics of our scenarios. Bacteria location explained 28% of the total variance in substrate concentration in all scenarios, while the interactions among location, saturation and geometry explained up to 51% of it

Men’s Experiences of Paternity Leaves in Accounting Firms

Accounting researchers and practitioners have made strides in addressing persistent gender inequalities in the accounting profession. However, these efforts have largely sidestepped men and masculinities. Our study considers the role of men and masculinities in gender inequalities by exploring how men in accounting experience paternity leaves. We conduct interviews with thirteen men in audit firms in France. We find that fathers are reluctant to take leaves which they view as vacation periods incompatible with their professional work. They see audit firms as offering less support to fathers than mothers, with support for fathers growing but still marginal. Finally, they experience a variety of emotions, including positive emotions around fatherhood and negative emotions around difficulties in reconciling fatherhood with professional responsibilities and paternity leaves. Practically, our findings imply that to address gender inequalities further, accounting firms need to change the norms around care work, including paternity leaves