Effect of local treatments of convection upon the solar p-mode excitation rates

We compute, for several solar models, the rates P at which the solar radial p modes are expected to be excited. The solar models are computed with two different local treatments of convection : the classical mixing-length theory (MLT hereafter) and Canuto, Goldmann and Mazzitelli(1996, CGM hereafter)'s formulation. For one set of solar models (EMLT and ECGM models), the atmosphere is gray and assumes Eddington's approximation. For a second set of models (KMLT and KCGM models), the atmosphere is built using a T(tau) law which has been obtained from a Kurucz's model atmosphere computed with the same local treatment of convection. The mixing-length parameter in the model atmosphere is chosen so as to provide a good agreement between synthetic and observed Balmer line profiles, while the mixing-length parameter in the interior model is calibrated so that the model reproduces the solar radius at solar age. For the MLT treatment, the rates P do depend significantly on the properties of the atmosphere. On the other hand, for the CGM treatment, differences in P between the ECGM and the KCGM models are very small compared to the error bars attached to the seismic measurements. The excitation rates P for modes from the EMLT model are significantly under-estimated compared with the solar seismic constraints. The KMLT model results in intermediate values for P and shows also an important discontinuity in the temperature gradient and the convective velocity. On the other hand, the KCGM model and the ECGM model yield values for P closer to the seismic data than the EMLT and KMLT models. We conclude that the solar p-mode excitation rates provide valuable constraints and according to the present investigation cleary favor the CGM treatment with respect to the MLT.Comment: 4 pages, 3 figures, proceedings of the SOHO14/GONG 2004 workshop "Helio- and Asteroseismology: Towards a Golden Future" from July 12-16 2004 at New Haven CT (USA

Stellar Fluxes as Probes of Convection in Stellar Atmospheres

Convection and turbulence in stellar atmospheres have a significant effect on the emergent flux from late-type stars. The theoretical advancements in convection modelling over recent years have proved challenging for the observers to obtain measurements with sufficient precision and accuracy to allow discrimination between the various predictions. An overview of the current observational techniques used to evaluate various convection theories is presented, including photometry, spectrophotometry, and spectroscopy. The results from these techniques are discussed, along with their successes and limitations. The prospects for improved observations of stellar fluxes are also given.Comment: 3 pages, 1 figure; to appear in Convection in Astrophysics, Proc. IAUS 239, F.Kupka, I.W. Roxburgh, K.L. Chan ed

Influence of local treatments of convection upon solar p mode excitation rates

We compute the rates P at which acoustic energy is injected into the solar radial p modes for several solar models. The solar models are computed with two different local treatments of convection: the classical mixing-length theory (MLT hereafter) and Canuto et al (1996)'s formulation (CGM hereafter). Among the models investigated here, our best models reproduce both the solar radius and the solar luminosity at solar age and the observed Balmer line profiles. For the MLT treatment, the rates P do depend significantly on the properties of the atmosphere whereas for the CGM's treatment the dependence of P on the properties of the atmosphere is found smaller than the error bars attached to the seismic measurements. The excitation rates P for modes associated with the MLT models are significantly underestimated compared with the solar seismic constraints. The CGM models yield values for P closer to the seismic data than the MLT models. We conclude that the solar p-mode excitation rates provide valuable constraints and according to the present investigation clearly favor the CGM treatment with respect to the MLT, although neither of them yields values of P as close to the observations as recently found for 3D numerical simulations.Comment: 11 pages, 7 figures, accepted for publication in Astronomy & Astrophysic

Role of Kappa-Opioid Receptors in Stress-Induced Behaviors

The development of anxiety and mood disorders often coincides with exposure to stress. Accumulating evidence indicates that both corticotropin-releasing factor (CRF) and dynorphin, the endogenous ligand for the kappa-opioid receptor (KOR), can mediate the effects of stress. My dissertation research utilized laboratory animals to investigate the role of KORs in stress-induced increases in the acoustic startle response, a metric often used to study stress effects in humans. Using wild-type mice, I first demonstrated that systemic administration of a KOR antagonist produced an anxiolytic-like effect on acoustic startle following central (intracerebroventricular) infusion of CRF. Immunohistochemical analysis revealed that KOR blockade decreased c-Fos cell counts in the dentate gyrus of the hippocampus in both vehicle- and CRF-treated mice, and reduced CRF-induced increases in the ventral tegmental area (VTA). Within the VTA, reductions were predominantly in dopaminergic neurons. KOR antagonist pretreatment also produced anxiolytic-like effects on footshock-potentiated startle, a model that quantifies context-specific fear conditioning. To complement the antagonist studies, we developed constitutive knockout mice that lack KORs throughout the brain (KOR-/-), and conditional KOs that lack KORs only within dopaminergic neurons (DAT-KORlox/lox). Initial characterization demonstrated that these two mutant lines did not differ from controls in hearing, vision, weight gain, and locomotor activity. KOR-/- mice were similar to controls in unconditioned anxiety-like behavior, but DAT-KORlox/lox mice displayed nominal decreases in anxiety-like behavior in the open field and light/dark box. Unexpectedly, KOR ablation did not affect CRF-induced increases in startle in either mutant line. Importantly, however, KOR antagonist treatment did not alter CRF-induced increases in startle in KOR-/- mice, suggesting that KOR antagonist effects in wild-type mice are due to blockade of KORs. These findings raise the possibility that differences in KOR antagonist and KOR-/- studies may be related to brief KOR blockade during adulthood versus a lack of KORs during the entire lifespan. In the footshock-potentiated startle paradigm, KOR-/- mice were comparable to littermate controls, whereas DAT-KORlox/lox mice showed attenuated effects of footshock. My findings confirm a role for KORs in fear and anxiety-like behavior in rodents, and implicate KORs expressed on dopaminergic neurons in modulating important aspects of stress-related behavior

Microarray technology and its effect on breast cancer (re)classification and prediction of outcome

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Prognostic Gene Expression Profile That Predicts Circulating Tumor Cell Presence in Breast Cancer Patients

The detection of circulating tumor cells (CTCs) in the peripheral blood and microarray gene expression profiling of the primary tumor are two promising new technologies able to provide valuable prognostic data for patients with breast cancer. Meta-analyses of several established prognostic breast cancer gene expression profiles in large patient cohorts have demonstrated that despite sharing few genes, their delineation of patients into “good prognosis” or “poor prognosis” are frequently very highly correlated, and combining prognostic profiles does not increase prognostic power. In the current study, we aimed to develop a novel profile which provided independent prognostic data by building a signature predictive of CTC status rather than outcome. Microarray gene expression data from an initial training cohort of 72 breast cancer patients for which CTC status had been determined in a previous study using a multimarker QPCR-based assay was used to develop a CTC-predictive profile. The generated profile was validated in two independent datasets of 49 and 123 patients and confirmed to be both predictive of CTC status, and independently prognostic. Importantly, the “CTC profile” also provided prognostic information independent of the well-established and powerful ‘70-gene’ prognostic breast cancer signature. This profile therefore has the potential to not only add prognostic information to currently-available microarray tests but in some circumstances even replace blood-based prognostic CTC tests at time of diagnosis for those patients already undergoing testing by multigene assays