146 research outputs found
Contribution to the inner tracker design and penguin sensitivity studies for the measurement of sin 2Ă in LHCb
LHCb is one of the four large experiments hosted at the Large Hadron Collider (LHC) at CERN in Geneva. It will start taking data in September 2008, and will then operate for several years. It consists of a single-arm forward spectrometer dedicated to precise measurements of CP violation and rare decays in the B sector, with the aim of testing the Standard Model and possibly of discovering the first signatures of New Physics. Building such a large experiment as LHCb is a challenge, and many contributions are needed. The Lausanne lab is responsible for the design and the production of the Silicon Inner Tracker (IT) of LHCb. This detector is made of Silicon sensors which need to be cooled to avoid thermal runaway. We present here a contribution to the design of this sub-detector and a description of the production steps. In particular, a study of the cooling of the Inner Tracker is described. It is shown that the cooling abilities of the IT can avoid thermal runaway. CP violation in B meson decays was first observed in the measurement of the so-called "golden channel", in which a Bd0 meson decays into a J/Ï and a Îs0 . The time-dependent CP asymmetry in Bd0 â J/ÏÎs0 allows to measure the angle ÎČ of the (d, b) unitary triangle. This parameter is now known with 4% accuracy at B factories. However, this determination of sin 2ÎČ is made under the assumption that there is only a single amplitude present in this decay : this means that penguin diagrams which might be present have been neglected. In 1999, Robert Fleischer [29] proposed a theoretical method to access those penguin diagrams in the Bd0 â J/ÏÎs0 decay, using the Bs0â J/ÏÎs0 channel. This method relies on U-Spin symmetry and also allows to determine the Îł angle of the (d, b) unitary triangle. We have developed a selection method for the Bd0 â J/ÏÎs0 channel in order to strongly suppress the background and to allow the separation of the Bs0 and Bd0 peaks. We obtained mass resolution of 8 MeV/c2 and a B/S ratio for the channel Bd0 â J/ÏÎs0 estimated to belong to [0, 0.039] at 90% confidence level in a ±2Ï mass window around the Bd0 mass, after the first level of trigger (L0). For the channel Bs0 â J/ÏÎs0 , the B/S ratio is calculated from the result for Bd0 â J/ÏÎs0 assuming known branching fractions. It lies in the interval [0, 3.33] at 90% CL. The annual yield is expected to be around 300 events for an integrated luminosity of 2 fb-1. We have simulated with fast Monte Carlo the Bs0 â J/ÏÎs0 signal using the parametrization proposed in [29] and taking as input the results of selection obtained for Bd0 â J/ÏÎs0 . The simulation has been repeated several times for different integrated luminosities and B/S ratios. We conclude that after 5 years of normal running, LHCb will be able to determine the penguin contribution in the Bd0 â J/ÏÎs0 decay with a sensitivity of (0.172 ± 0.004) using this method based on U-spin symmetry
Achieving Food System Resilience Requires Challenging Dominant Land Property Regimes
Although evidence continues to indicate an urgent need to transition food systems away
from industrialized monocultures and toward agroecological production, there is little
sign of significant policy commitment toward food system transformation in global North
geographies. The authors, a consortium of researchers studying the land-food nexus in
global North geographies, argue that a key lock-in explaining the lack of reform arises
from how most food system interventions work through dominant logics of property
to achieve their goals of agroecological production. Doing so fails to recognize how
land tenure systems, codified by law and performed by society, construct agricultural
land use outcomes. In this perspective, the authors argue that achieving food system
âresilienceâ requires urgent attention to the underlying property norms that drive land
access regimes, especially where norms of property appear hegemonic. This paper first
reviews research from political ecology, critical property law, and human geography to
show how entrenched property relations in the global North frustrate the advancement
of alternative models like food sovereignty and agroecology, and work to mediate
acceptable forms of âsustainable agriculture.â Drawing on emerging cases of land tenure
reform from the authorsâ collective experience working in Scotland, France, Australia,
Canada, and Japan, we next observe how contesting dominant logics of property
creates space to forge deep and equitable food system transformation. Equally, these
cases demonstrate how powerful actors in the food system attempt to leverage legal
and cultural norms of property to legitimize their control over the resources that drive
agricultural production. Our formulation suggests that visions for food system âresilienceâ
must embrace the reform of property relations as much as it does diversified farming
practices. This work calls for a joint cultural and legal reimagination of our relation to land
in places where property functions as an epistemic and apex entitlement
Achieving food system resilience requires challenging dominant land property regimes
International audienceAlthough evidence continues to indicate an urgent need to transition food systems away from industrialized monocultures and toward agroecological production, there is little sign of significant policy commitment toward food system transformation in global North geographies. The authors, a consortium of researchers studying the land-food nexus in global North geographies, argue that a key lock-in explaining the lack of reform arises from how most food system interventions work through dominant logics of property to achieve their goals of agroecological production. Doing so fails to recognize how land tenure systems, codified by law and performed by society, construct agricultural land use outcomes. In this perspective, the authors argue that achieving food system âresilienceâ requires urgent attention to the underlying property norms that drive land access regimes, especially where norms of property appear hegemonic. This paper first reviews research from political ecology, critical property law, and human geography to show how entrenched property relations in the global North frustrate the advancement of alternative models like food sovereignty and agroecology, and work to mediate acceptable forms of âsustainable agriculture.â Drawing on emerging cases of land tenure reform from the authors' collective experience working in Scotland, France, Australia, Canada, and Japan, we next observe how contesting dominant logics of property creates space to forge deep and equitable food system transformation. Equally, these cases demonstrate how powerful actors in the food system attempt to leverage legal and cultural norms of property to legitimize their control over the resources that drive agricultural production. Our formulation suggests that visions for food system âresilienceâ must embrace the reform of property relations as much as it does diversified farming practices. This work calls for a joint cultural and legal reimagination of our relation to land in places where property functions as an epistemic and apex entitlement
Atom probe tomographic study of L10 martensite in a Pt-modified NiCoCrAlYTa bond coating
The L10 martensite formed in a Pt-modified NiCoCrAlYTa bond coating has been investigated by atom probe tomography. It was found that obvious segregation of Co and Cr occurred in the micro-twins zone inside the martensite lath. Based upon the compositional analysis, it is known that Pt destabilizes the ÎČ phase and Co and Cr act as ÎČ stabilizers with respect to the ÎČâL10 martensitic transformation. In addition, some α-Cr particles precipitated inside the martensite lath
Th1 Disabled Function in Response to TLR4 Stimulation of Monocyte-Derived DC from Patients Chronically-Infected by Hepatitis C Virus
Background: Lack of protective antibodies and inefficient cytotoxic responses are characteristics of chronic hepatitis C infection. A defect in dendritic cell (DC) function has thus been suspected, but this remains a controversial issue. Methods and Findings: Here we show that monocyte-derived DC (MoDC) from chronically-infected patients can mature in response to TLR1/2, TLR2/6 or TLR3 ligands. In contrast, when stimulated with the TLR4 ligand LPS, MoDC from patients show a profound defect in inducing IFNc secretion by allogeneic T cells. This defect is not due to defective phenotypic maturation or to the presence of HCV-RNA in DC or monocytes but is correlated to reduced IL-12 secretion by DC. Restoration of DC ability to stimulate IFNc secretion can be obtained by blocking MEK activation in DC, indicating that MEK/ ERK pathway is involved in the Th1 defect of MoDC. Monocytes from HCV patients present increased spontaneous secretion of cytokines and chemokines, especially MIP-1b. Addition of MIP-1b on healthy monocytes during differentiation results in DC that have Th1 defect characteristic of MoDC from HCV patients, suggesting that MIP-1b secretion by HCV monocytes participates in the Th1 defect of DC. Conclusions: Our data indicate that monocytes from HCV patients are activated in vivo. This interferes with their differentiation into DC, leading to deficient TLR4 signaling in these cells that are enable to induce a Th1 response. Thi
Favoriser lâinsertion professionnelle et lâaccĂšs Ă lâemploi
Cherchant Ă adapter leurs services Ă lâactualitĂ© sociale et aux besoins rĂ©els de leur public, de plus en plus de bibliothĂšques se prĂ©occupent dâoffrir des services orientĂ©s vers lâinsertion professionnelle et la recherche dâemploi. Quâelle soit universitaire ou publique, la bibliothĂšque constitue une ressource essentielle de la formation tout au long de la vie, Ă©lĂ©ment primordial Ă lâadaptation permanente au monde du travail. Cet ouvrage aborde cette nouvelle problĂ©matique pour les Ă©tablissements sous trois angles diffĂ©rents, selon les besoins des publics : travailler, se former, entreprendre. Les conditions dâaccueil des publics concernĂ©s, lâadaptation de lâoffre suivant la dimension de la bibliothĂšque, la constitution des collections spĂ©cialisĂ©es dans ce domaine, la qualitĂ© des propositions en matiĂšre dâautoformation, les atouts des diffĂ©rents partenariats dans le domaine de la recherche dâemploi, tels sont les Ă©lĂ©ments traitĂ©s ici pour favoriser le succĂšs de la mise en place et du dĂ©veloppement dâune offre propre Ă Ă©largir avec efficacitĂ© les champs dâintervention des bibliothĂšques aujourdâhui. CoordonnĂ© par Georges Perrin, inspecteur gĂ©nĂ©ral honoraire des bibliothĂšques, ce volume collectif rĂ©unit des professionnels spĂ©cialisĂ©s dans le domaine Ă©ducatif, social et culturel
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