Dust environment and dynamical history of a sample of short-period comets: II. 81P/Wild 2 and 103P/Hartley 2

Aims. This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods. As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the Afρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results. From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 109 kg yr-1 and (0.4-1.5) × 109 kg yr-1, respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ~40 yr in the case of 81P/Wild 2 and ~1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed

Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research

Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes

Behavioural correlates of dopaminergic manipulations of the striatum

SIGLEAvailable from British Library Document Supply Centre-DSC:D197182 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Adult Neurogenesis, Chronic Stress and Depression

A major risk factor for depression in vulnerable individuals is exposure to stress during critical periods. Stress affects mood and cognition and is also one of the best known inhibitors of adult neurogenesis that has been associated with hippocampal changes and atrophy, common findings in major depression (models). While the effects of acute or mild stress are generally short-lived and recover quickly, chronic and severe stress can induce longer lasting reductions in neurogenesis that, depending on the age of exposure, can affect hippocampal structure and function, alter hippocampal plasticity, and increase vulnerability to psychopathology. Stress-induced reductions in neurogenesis can in part be normalized by positive stimuli for plasticity such as exercise, by drugs targeting the stress system, and by some, but not all, antidepressants. Exposure to stress during sensitive periods of (early) life increases the risk for developing cognitive or anxiety symptoms, common to many brain diseases, including depression. Recruiting the plasticity still present in the adult brain, e.g., through normalization of neurogenesis, may be required for a successful treatment response and recovery

Molecular diagnosis of Strongyloides stercoralis in faecal samples using real-time PCR (vol 103, pg 342, 2009)

Host-parasite interactio