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A definition of resilience is the capacity to resist mental disorders despite exposure to stress. Little is known about its biological concomitants. In adults, biochemical and hormonal factors have been advocated. Smaller Corpus Callosum (CC) volume and lower Fractional Anisotropy (FA) have been observed in psychiatric and stress-related conditions. There is no Diffusion Tensor Imaging (DTI) study of resilience in adolescence, a critical lifetime period for neural and psychological maturation. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents.
Three community groups were compared: resilient adolescents – with low risk of mental disorder despite high exposure to lifetime stress, adolescents at risk of mental disorder exposed to the same level of stress, and controls. Personality was assessed by NEO Five Factor Inventory (NEO-FFI) and cognitive function by a battery of tests. Voxelwise statistics of DTI values in CC were obtained using Tract-Based Spatial Statistic. Regional projections were identified by probabilistic tractography.
Higher FA values were detected in the anterior CC of resilient compared with both non-resilient and control adolescents. FA values varied according to resilience capacity. Regional changes in CC were in regions that project onto anterior cingulated and frontal cortex. Neuroticism and three other personality factors differentiated at risk adolescents from the other two groups.
High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk in adolescents was associated with personality characteristics. Resilience in adolescence may be a dimension embedding white matter features.
L’instabilité émotionnelle est fréquente à l’adolescence et peut parfois être considérée comme un trouble de l’humeur subsyndromique. Or, les tableaux subsyndromiques de manie ou de dépression à l’adolescence évoluent souvent vers des troubles de l’humeur. Nous avons recherché, chez des adolescents « subsyndromiques », s’il existait des modifications cérébrales voisines de celles retrouvées dans les troubles de l’humeur avérés. Les participants étaient tous issus de la cohorte IMAGEN qui a rassemblé des données de plus de 2000 adolescents européens scolarisés en classes de 4e et 3e. Ils avaient été examinés en imagerie cérébrale anatomique (IRM T1 et de diffusion) et évalués par un entretien diagnostique informatisé permettant l’évaluation d’éventuels symptômes. Une première étude a comparé la microstructure de la substance blanche et le volume de substance grise chez des participants présentant des symptômes bipolaires maniaques subsyndromiques comparés à des adolescents pris comme témoins. Une deuxième étude a été menée chez des adolescents ayant des symptômes subsyndromiques de dépression. L’analyse des images a mis en évidence chez les adolescents à bipolarité subsyndromique des variations de la microstructure de la substance blanche dans plusieurs faisceaux en cours de maturation, et un moindre volume de substance grise dans des régions du cerveau contribuant à la régulation émotionnelle. Chez les adolescents « subdéprimés », des modifications étaient également présentes dans le réseau fronto-striatal. Pour la première fois, des modifications de la structure cérébrale de régions impliquées dans les troubles de l’humeur ont été mises en évidence chez des adolescents scolarisés ayant des symptômes subsyndromiques. Ces résultats suggèrent des particularités de maturation cérébrale à l’adolescence qui pourraient entraîner une vulnérabilité aux troubles de l’humeur.
Although neuroimaging studies suggest brain regional abnormalities in depressive disorders, it remains unclear whether abnormalities are present at illness onset or reflect disease progression.
We hypothesized that cerebral variations were present in adolescents with subthreshold depression known to be at high risk for later full-blown depression.
We examined brain structural and diffusion-weighted magnetic resonance images of adolescents with subthreshold depression.
The participants were extracted from the European IMAGEN study cohort of healthy adolescents recruited at age 14. Subthreshold depression was defined as a distinct period of abnormally depressed or irritable mood, or loss of interest, plus two or more depressive symptoms but without diagnosis of Major Depressive Episode. Comparisons were performed between adolescents meeting these criteria and control adolescents within the T1-weighted imaging modality (118 and 475 adolescents respectively) using voxel-based morphometry and the diffusion tensor imaging modality (89 ad 422 adolescents respectively) using tract-based spatial statistics. Whole brain analyses were performed with a statistical threshold set to p< 0.05 corrected for multiple comparisons.
Compared with controls, adolescents with subthreshold depression had smaller gray matter volume in caudate nuclei, medial frontal and cingulate cortices; smaller white matter volume in anterior limb of internal capsules, left forceps minor and right cingulum; and lower fractional anisotropy and higher radial diffusivity in the genu of corpus callosum.
The findings suggest that adolescents with subthreshold depression have volumetric and microstructural gray and white matter changes in the emotion regulation frontal-striatal-limbic network.
The role that vitamin D plays in pulmonary function remains uncertain. Epidemiological studies reported mixed findings for serum 25-hydroxyvitamin D (25(OH)D)–pulmonary function association. We conducted the largest cross-sectional meta-analysis of the 25(OH)D–pulmonary function association to date, based on nine European ancestry (EA) cohorts (n 22 838) and five African ancestry (AA) cohorts (n 4290) in the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium. Data were analysed using linear models by cohort and ancestry. Effect modification by smoking status (current/former/never) was tested. Results were combined using fixed-effects meta-analysis. Mean serum 25(OH)D was 68 (sd 29) nmol/l for EA and 49 (sd 21) nmol/l for AA. For each 1 nmol/l higher 25(OH)D, forced expiratory volume in the 1st second (FEV1) was higher by 1·1 ml in EA (95 % CI 0·9, 1·3; P<0·0001) and 1·8 ml (95 % CI 1·1, 2·5; P<0·0001) in AA (Prace difference=0·06), and forced vital capacity (FVC) was higher by 1·3 ml in EA (95 % CI 1·0, 1·6; P<0·0001) and 1·5 ml (95 % CI 0·8, 2·3; P=0·0001) in AA (Prace difference=0·56). Among EA, the 25(OH)D–FVC association was stronger in smokers: per 1 nmol/l higher 25(OH)D, FVC was higher by 1·7 ml (95 % CI 1·1, 2·3) for current smokers and 1·7 ml (95 % CI 1·2, 2·1) for former smokers, compared with 0·8 ml (95 % CI 0·4, 1·2) for never smokers. In summary, the 25(OH)D associations with FEV1 and FVC were positive in both ancestries. In EA, a stronger association was observed for smokers compared with never smokers, which supports the importance of vitamin D in vulnerable populations.
Resilience is the capacity of individuals to resist mental disorders despite exposure to stress. Little is known about its neural underpinnings. The putative variation of white-matter microstructure with resilience in adolescence, a critical period for brain maturation and onset of high-prevalence mental disorders, has not been assessed by diffusion tensor imaging (DTI). Lower fractional anisotropy (FA) though, has been reported in the corpus callosum (CC), the brain's largest white-matter structure, in psychiatric and stress-related conditions. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents.
Three groups of adolescents recruited from the community were compared: resilient with low risk of mental disorder despite high exposure to lifetime stress (n = 55), at-risk of mental disorder exposed to the same level of stress (n = 68), and controls (n = 123). Personality was assessed by the NEO-Five Factor Inventory (NEO-FFI). Voxelwise statistics of DTI values in CC were obtained using tract-based spatial statistics. Regional projections were identified by probabilistic tractography.
Higher FA values were detected in the anterior CC of resilient compared to both non-resilient and control adolescents. FA values varied according to resilience capacity. Seed regional changes in anterior CC projected onto anterior cingulate and frontal cortex. Neuroticism and three other NEO-FFI factor scores differentiated non-resilient participants from the other two groups.
High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk was associated with personality characteristics. Resilience in adolescence may be related to white-matter microstructure.
Hill stability cannot be easily established in the classical 3-body problem with point masses, as sufficient energy for escape of one of the bodies can always be extracted from the gravitational potential energy. For the finite density, so-called Full 3-body problem the lower limits on the gravitational potential energy ensure that Hill stability can exist. For the equal mass Full 3-body problem this can be easily established, with the result that for any equal mass, finite density 3-body problem in or near a contact equilibrium, none of the components of the system can escape in the ensuing motion.
We analyze the trajectory of near-Earth asteroid 2009~BD, which is a candidate target of the NASA Asteroid Redirect Mission. The small size of 2009 BD and its Earth-like orbit pose challenges to understanding the dynamical properties of 2009 BD. In particular, nongravitational perturbations, such as solar radiation pressure and the Yarkovsky effect, are essential to match observational data and provide reliable predictions. By using Spitzer Space Telescope IRAC observations and our model for the thermophysical properties and the nongravitational forces acting on 2009 BD we obtain probabilistic derivations of the physical properties of this object. We find two physically possible solutions. The first solution shows 2009 BD as a 2.9 ± 0.3 m diameter rocky body with an extremely high albedo that is covered with regolith-like material, causing it to exhibit a low thermal inertia. The second solution suggests 2009 BD to be a 4 ± 1 m diameter asteroid with albedo 0.45 ± 0.35 that consists of a collection of individual bare rock slabs. We are unable to rule out either solution based on physical reasoning. 2009 BD is the smallest asteroid for which physical properties have been constrained, providing unique information on the physical properties of objects in the size range smaller than 10 m.
In the standard model of core accretion, the cores of the giant planets form by the accretion of planetesimals. In this scenario, the evolution of the planetesimal population plays an important role in the formation of massive cores. Recently, we studied the role of planetesimal fragmentation in the in situ formation of a giant planet. However, the exchange of angular momentum between the planet and the gaseous disk causes the migration of the planet in the disk. In this new work, we incorporate the migration of the planet and study the role of planet migration in the formation of a massive core when the population of planetesimals evolves by planet accretion, migration, and fragmentation.
The University of Florida (UF) have recently collaborated with Raith Inc. to modify Raith’s ion beam lithography, nanofabrication and engineering (ionLiNE) station that utilizes only Ga ions, into a multi-ion beam system (MionLiNE) by adding the capabilities to use liquid metal alloy sources (LMAIS) to access a variety of ions and an EXB filter for mass separation. The MionLiNE modifications discussed below provide a wide range of spatial and temporal precision that can be used to investigate ion solid interactions under extended boundary conditions, as well as for ion lithography and nanofabrication. Here we demonstrate the ion beam lithographic capabilities of the MionLiNE for fabricating patterned arrays of Au and Si nanocrystals, with nanoscale dimensions, in SiO2 substrates, by direct implantation; and show that the same directwrite/maskless-implantation features can be used for in situ fabrication of nanoelectronic devices. Additionally, the spatial and temporal capabilities of the MionLiNE are used to explore the effects of dose rate on the long-standing surface morphological transformation that occurs in ion bombarded Ge.
The interplay of the disc and the dark halo resonances governs the secular evolution of disc galaxies, and the properties of their bar component (Athanassoula 2002). Martinez-Valpuesta et al. (2006), Ceverino & Klypin (2007) and Athanassoula (2007b) confirm and extend this work. Ceverino & Klypin (2007) calculate the orbital frequencies of each particle over the whole temporal evolution, and thus find much broader frequency peaks. In all cases, it is the same resonances that come into play, and, as in Athanassoula 2002, the angular momentum is emitted by near-resonant material in the bar region and absorbed by near-resonant material in the halo and the outer disc. The relative importance of each resonance, however, varies from one case to another. Furthermore, the second and third of the above mentioned studies examine the location of resonant orbits in configuration space and find compatible results.
A total of 16 among the new IAU members have asked to join Commission 20; they are: Jerome Berthier, Nicholas J. Cooper, Marco Delbò, Romina P. Di Sisto, Michael W. Evans, Tetsuharu Fuse, Ludmila Hudkova, Yurij N. Krugly, Elena N. Polyakhova, Zhanna Pozhalova, Alessandro Rossi, Qi Rui, Jonathan D. Shanklin, Slawomira E. Szutowicz, Gino Tuccari and Hong-Suh Yim. Moreover, two requests to join the Commission have been received by astronomers that are already IAU members: Peter De Cat and Ricardo A. Gil-Hutton.
In his address to the Commission, the outgoing president A. Milani explained what he considers have been done well in the past triennium, what has been done only in part, and what has not been done at all. Among the things in which the performance was rated good, he mentioned the successful sponsorship and/or co-sponsorship of four meetings (IAU Colloquia 196 and 197, and Symposia 229 and 236) which have been held in the previous period, as well as of the Symposium on exoplanets to be held next year in China. The only failure in this respect was the proposed meeting in India, which failed already at the proposal definition stage. Also, Milani expressed his satisfaction with the triennial report which has been compiled for the occasion, and his gratitude to the collaborating authors.
The orbital fits of multi-planetary systems from radial velocity data has proved to be a complex task. In some cases, different orbital solutions provide similarly good fits, especially when two planets are near mean-motion resonances. Ferraz-Mello et al (2005) and Goździewski et al (2005) showed that the published best fits of systems HD82932 and HD160691 are dynamically unstable, and re-determined their orbital parameters with Monte Carlo and genetic algorithms. In both cases dynamically stable orbits were found with RMS similar to the published orbits. It was also shown that uncertainties in the stellar mass Ferraz Mello et al (2005) and the stellar jitter Gozdziewski et al (2005) can significantly affect the orbital determination. Ford (2005) used a Markov chain Monte Carlo technique to quantify the orbit uncertainties. For some planetary systems he found a strong correlation between the orbital elements and/or significant non-Gaussian error distribution in the parameter space. As a consequence, the actual uncertainties in the orbital fits can be much larger (or smaller) than those published.
The past triennium has continued to see a huge influx of astrometric positions of small solar system bodies provided by near-Earth object (NEO) surveys. As a result, the size of the orbital databases of all populations of small solar system bodies continues to increase dramatically, and this in turn allows finer and finer analyses of the types of motion in various regions of the orbital elements space.
Metallic copper nanostructured particles were synthesised by thermal decomposition of a CuC2O4 precursor obtained via the precipitation reaction between Cu(NO3)2·6H2O and Na2C2O4 in the present of hydroxyl propyl methyl cellulose (HPMC). X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and thermogravimetric analysis (TG) were used to characterise the particles and their evolution during the transformation to metallic copper. We highlight the nanostructured nature of the oxalate precursor, which is made up of anisotropic nanosized buildings blocks (25nm by 40nm). These produce an anisotropy in the oxalate particle and influence the decomposition pathway. The results show the evolution of the nanostructure as a function of degree of reaction and a possible kinetic model is discussed.
Quelles sont les valeurs qui caractérisent sur le territoire français les rayonnements
ionisants et les radionucléides d'origine naturelle ? Comment distinguer dans le résultat
d'une mesure la part qui résulte éventuellement d'une activité humaine ? Afin d'essayer
de répondre à ces questions, un questionnaire a été adressé aux différents organismes
qui effectuent en France des mesures de radioactivité dans l'environnement. Les informations
mentionnées dans cette étude se rapportent exclusivement à des observations faites dans
l'environnement à l'extérieur des bâtiments et du périmètre des installations nucléaires
de base (INB). En outre, elles ne concernent, sauf cas particuliers signalés, que des
mesures de rayonnements ou de radioéléments d'origine naturelle dont les résultats
n'ont pas été perturbés par l'action de l'homme. L'enquête montre la difficulté actuelle
de dresser en France un bilan exhaustif des connaissances acquises concernant les
caractéristiques du bruit de fond radioactif d'origine naturelle dans l'environnement.
Aujourd'hui en France, dans le domaine de la radioactivité naturelle, les efforts
consentis manquent de coordination et d'orientation vers certaines priorités. À ce
titre, les mesures des 238U et 232Th précurseurs des 226Ra et 228Ra,
des descendants solides émetteurs alpha du radon (par la mesure des EAP du 222Rn
et 220Rn), des émetteurs gamma post émanation (214Pb, 214Bi, 212Pb),
du 210Pb, 210Po et du 14C doivent être privilégiées.
Les préoccupations concernant la présence de substances radioactives dans
l'environnement conduisent régulièrement à des expertises sur les niveaux
d'activité des radionucléides dans l'environnement et à des évaluations de
leurs impacts radiologiques sur les populations humaines. La crédibilité de
ces expertises repose en partie sur la qualité et la fiabilité des mesurages.
Ce document présente les systèmes d'organisations de la normalisation, nationale et
internationale, ainsi que les documents normatifs publiés et les travaux de
normalisation en cours relatifs à la métrologie des radionucléides présents
dans les matrices environnementales.
Recent advances in surgical techniques have made it possible to study the changes that are known as degeneration of the intervertebral disc (IVD) in greater depth than ever before. This is an important area of study because degeneration of the lumbar IVDs is associated, perhaps causally, with low back pain: one of the most common and debilitating conditions in the western world. The term degeneration implies an inevitable progression that is characteristic of wear-and-tear-associated conditions. However, modern research on human tissue has shown that this is not the case. Here, disruption of the micro-anatomy that is described as degeneration is an active process, which is probably regulated by locally produced cytokines. This one observation opens up the possibility of inhibiting or even reversing the processes of degeneration. The immediate question is how can the slowly progressive changes of degeneration be treated, particularly as connective tissue repair is thought to be a slow and highly regulated process. In this review, the possibility of using gene therapy as a single-shot, long-lasting therapeutic strategy is discussed, together with an outline of developments in this area to date.
Research in Celestial Mechanics, for the past three years, has mainly focused on the understanding of Chaos on all its aspects. The always larger number of potential applications (meteors, KBO, NEA, asteroids of the main belt but also exoplanets or galactic motions) and the development of new efficient tools, like the symplectic integrators, have allowed the passage from QUALITATIVE models (for example the transfer mechanisms) to real QUANTITATIVE results (like the calculation of lifetimes). This important step has contributed to (re)create collaborations between theoreticians and observers (for example, in the prediction of catastrophic impacts) and to situate the Celestial Mechanics in a wider scientific context.