Consommation de substances psychoactives, troubles du comportement et sentiments dépressifs à l'adolescence

Cet article examine la cooccurrence de trois types de problèmes d'adaptation à l'adolescence : la consommation problématique de psychotropes, les troubles du comportement (trouble oppositionnel et trouble des conduites) et les sentiments dépressifs (dépression et dysthymie). Il examine aussi les caractéristiques comportementales et sociofamiliales qui, au cours de l'enfance, distinguent les jeunes avec plusieurs problèmes d'adaptation de ceux avec un seul problème ou aucun problème. Plus de 1600 jeunes de toutes les régions du Québec ont participé à l'étude. Ces jeunes étaient âgés en moyenne de 15,7 ans lorsqu'ils ont participé à une entrevue visant à déterminer la présence possible d'une consommation problématique de psychotropes, de problèmes de comportement et de sentiments dépressifs. Leurs caractéristiques comportementales et sociofamiliales avaient été évaluées au préalable (entre l'âge de 6 et 12 ans) à l'aide de questionnaires remplis par les parents et les enseignants. Les résultats révèlent que près de 10 % des jeunes éprouvent deux ou trois problèmes d'adaptation. Ces jeunes se distinguent de ceux avec un seul problème sur diverses dimensions personnelles et sociofamiliales au cours de l'enfance. Les jeunes avec un seul problème représentent un peu plus de 25 % de l'échantillon. À leur tour, ils se distinguent du groupe sans problème sur plusieurs variables. Le groupe des jeunes qui affichent seulement un problème de consommation de psychotropes fait toutefois exception. La discussion souligne l'importance de connaître s'il y a présence simultanée de plusieurs problèmes et propose d'intervenir préventivement auprès des jeunes qui risquent de présenter plusieurs problèmes.Psychoactive substance abuse, behavioral disorder and depression during adolescence This article examines coocurrence of three types of problems of adaptation during adolescence : abuse of psychotropic drugs, behavioral disorder (oppositional and behavioral disorders) and feelings of depression (depression and dysthymia). The study also examines behavioral, social as well as family characteristics which, during childhood, distinguish youths with many adaptation problems from those with only one or no problem. More than 1600 youths from all regions of Quebec participated in the study. These youths were around 15,7 years old when they completed an interview aiming at determining the possible presence of abusive use of psychotropic drugs, behavioral problems and feelings of depression. Their behavioral and sociofamilial characteristics had been previously evaluated (between the ages of 6 and 12) with questionnaires answered by parents and teachers. Results reveal that almost 10 % of youths experience two or three adaptation problems. These youths distinguish themselves from those with only one problem on various personal and sociofamilial dimensions in the course of childhood. Those with one problem represent a little more than 25 % of the sample. They also distinguish themselves from the group of youth with no problem on several variables. However, the group of youths with a problem of substance abuse only, is an exception. The discussion underlines the importance of knowing if there is simultaneous presence of several problems and proposes to intervene in a preventive fashion with youths who risk experiencing many problems.Consumo de sustancias psicoactivas, turbios de comportamiento y sentimiento depresivos durante el adolescencia Este artículo examina el acontecimiento de tres tipos de problemas de adaptación durante la adolescencia: el consumo problemático de psicótropos, turbios de comportamiento (turbios oposicional y turbio de conductas) y sentimientos depresivos (depresion y distemia). Examina también caracteristicas comportamentales y sociofamiliares cuales, durante la enfancia, distinguen los jovenes con varios problemas de adaptación de los con un solo problema o sin problema. Más de 1600 jóvenes de cada region del Québec participaron al estudio. Estos jovenes tenian en medida 15,7 años cuando participaron a una entrevista para determinar la presencia posible de un consumo problemático de psicótropos, de problemas de comportamiento y de sentimientos depresivos. Sus caracteristicas comportamentales habian sido evaluadas previamente (entre 6 y 12 años de edad) con la ayuda de cuestionarios llenados por los padres y los profesores. Los resultados revelan que cerca de 10% de jovenes sufren de dos o tres problemas de adaptación. Estos jovenes se distingan de los con un problema sobre varias dimensiones personales y sociofamiliares durante la enfancia. Jovenes con un problema representan un poco mas de 25% del escantillón. A su vez se distingan del grupo sin problema sobre varias variables. El grupo de jovenes con un problema de consumo de psicótropos hace sin embargo excepción. La discusión subraya la importancia de conocer si hay presencia simultanea de varios problemas y propone una intervención preventiva con jovenes quienes riesgan presentar varios problemas

Regulation and the Evolution of Corporate Boards: Monitoring, Advising or Window Dressing?

An earlier version of this paper was entitled “Deregulation and Board Composition: Evidence on the Value of the Revolving Door.”It is generally agreed that boards are endogenously determined institutions that serve both oversight and advisory roles in a firm. While the oversight role of boards has been extensively studied, relatively few studies have examined the advisory role of corporate boards. We examine the participation of political directors on the boards of natural gas companies between 1930 and 1998. We focus on the expansion of federal regulation of the natural gas industry in 1938 and 1954 and subsequent partial deregulation in 1986. Using data sets covering the periods from 1930 to 1990 and 1978 to 1998, we test whether regulation and deregulation altered the composition of companies' boards as the firms' environment changed. In particular, did regulation cause an increase and deregulation a decrease in the number of political directors on corporate boards? We find evidence that the number of political directors increases as firms shift from market to political competition. Specifically, the regulation of natural gas is associated with an increase in the number of political directors and deregulation is associated with a decrease in the number of political directors on boards

Origin and evolution of the light nuclides

After a short historical (and highly subjective) introduction to the field, I discuss our current understanding of the origin and evolution of the light nuclides D, He-3, He-4, Li-6, Li-7, Be-9, B-10 and B-11. Despite considerable observational and theoretical progress, important uncertainties still persist for each and every one of those nuclides. The present-day abundance of D in the local interstellar medium is currently uncertain, making it difficult to infer the recent chemical evolution of the solar neighborhood. To account for the observed quasi-constancy of He-3 abundance from the Big Bang to our days, the stellar production of that nuclide must be negligible; however, the scarce observations of its abundance in planetary nebulae seem to contradict this idea. The observed Be and B evolution as primaries suggests that the source composition of cosmic rays has remained quasi-constant since the early days of the Galaxy, a suggestion with far reaching implications for the origin of cosmic rays; however, the main idea proposed to account for that constancy, namely that superbubbles are at the source of cosmic rays, encounters some serious difficulties. The best explanation for the mismatch between primordial Li and the observed "Spite-plateau" in halo stars appears to be depletion of Li in stellar envelopes, by some yet poorly understood mechanism. But this explanation impacts on the level of the recently discovered early ``Li-6 plateau'', which (if confirmed), seriously challenges current ideas of cosmic ray nucleosynthesis.Comment: 18 pages, 9 figs. Invited Review in "Symposium on the Composition of Matter", honoring Johannes Geiss on the occasion of his 80th birthday (Grindelwald, Switzerland, Sept. 2006), to be published in Space Science Series of ISS

Bayesian analysis of weak gravitational lensing and Sunyaev-Zel'dovich data for six galaxy clusters

We present an analysis of observations made with the Arcminute Microkelvin Imager (AMI) and the Canada-France-Hawaii Telescope (CFHT) of six galaxy clusters in a redshift range of 0.16--0.41. The cluster gas is modelled using the Sunyaev--Zel'dovich (SZ) data provided by AMI, while the total mass is modelled using the lensing data from the CFHT. In this paper, we: i) find very good agreement between SZ measurements (assuming large-scale virialisation and a gas-fraction prior) and lensing measurements of the total cluster masses out to r_200; ii) perform the first multiple-component weak-lensing analysis of A115; iii) confirm the unusual separation between the gas and mass components in A1914; iv) jointly analyse the SZ and lensing data for the relaxed cluster A611, confirming our use of a simulation-derived mass-temperature relation for parameterizing measurements of the SZ effect.Comment: 22 pages, 12 figures, 12 tables, published by MNRA

Detailed SZ study of 19 LoCuSS galaxy clusters: masses and temperatures out to the virial radius

We present 16-GHz AMI SZ observations of 19 clusters with L_X >7x10^37 W (h50=1) selected from the LoCuS survey (0.142<z<0.295) and of A1758b, in the FoV of A1758a. We detect 17 clusters with 5-23sigma peak surface brightnesses. Cluster parameters are obtained using a Bayesian cluster analysis. We fit isothermal beta-models to our data and assume the clusters are virialized (with all the kinetic energy in gas internal energy). Our gas temperature, T_AMI, is derived from AMI SZ data, not from X-ray spectroscopy. Cluster parameters internal to r500 are derived assuming HSE. We find: (i) Different gNFW parameterizations yield significantly different parameter degeneracies. (ii) For h70 = 1, we find the virial radius r200 to be typically 1.6+/-0.1 Mpc and the total mass M_T(r200) typically to be 2.0-2.5xM_T(r500).(iii) Where we have found M_T X-ray (X) and weak-lensing (WL) values in the literature, there is good agreement between WL and AMI estimates (with M_{T,AMI}/M_{T,WL} =1.2^{+0.2}_{-0.3} and =1.0+/-0.1 for r500 and r200, respectively). In comparison, most Suzaku/Chandra estimates are higher than for AMI (with M_{T,X}/M_{T,AMI}=1.7+/-0.2 within r500), particularly for the stronger mergers.(iv) Comparison of T_AMI to T_X sheds light on high X-ray masses: even at large r, T_X can substantially exceed T_AMI in mergers. The use of these higher T_X values will give higher X-ray masses. We stress that large-r T_SZ and T_X data are scarce and must be increased. (v) Despite the paucity of data, there is an indication of a relation between merger activity and SZ ellipticity. (vi) At small radius (but away from any cooling flow) the SZ signal (and T_AMI) is less sensitive to ICM disturbance than the X-ray signal (and T_X) and, even at high r, mergers affect n^2-weighted X-ray data more than n-weighted SZ, implying significant shocking or clumping or both occur even in the outer parts of mergers.Comment: 45 pages, 33 figures, 13 tables Accepted for publication in MNRA

Sunyaev-Zel'dovich observations of galaxy clusters out to the virial radius with the Arcminute Microkelvin Imager

We present observations using the Small Array of the Arcminute Microkelvin Imager (AMI; 14-18 GHz) of four Abell and three MACS clusters spanning 0.171-0.686 in redshift. We detect Sunyaev-Zel'dovich (SZ) signals in five of these without any attempt at source subtraction, although strong source contamination is present. With radio-source measurements from high-resolution observations, and under the assumptions of spherical $\beta$-model, isothermality and hydrostatic equilibrium, a Bayesian analysis of the data in the visibility plane detects extended SZ decrements in all seven clusters over and above receiver noise, radio sources and primary CMB imprints. Bayesian evidence ratios range from 10^{11}:1 to 10^{43}:1 for six of the clusters and 3000:1 for one with substantially less data than the others. We present posterior probability distributions for, e.g., total mass and gas fraction averaged over radii internal to which the mean overdensity is 1000, 500 and 200, r_200 being the virial radius. Reaching r_200 involves some extrapolation for the nearer clusters but not for the more-distant ones. We find that our estimates of gas fraction are low (compared with most in the literature) and decrease with increasing radius. These results appear to be consistent with the notion that gas temperature in fact falls with distance (away from near the cluster centre) out to the virial radius.Comment: 18 pages, 10 figures, submitted to MNRAS (updated authors and fixed Figure 1

Cluster Lenses

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author

The UK clinical eye research strategy: refreshing research priorities for clinical eye research in the UK

To validate and update the 2013 James Lind Alliance (JLA) Sight Loss and Vision Priority Setting Partnership (PSP)'s research priorities for Ophthalmology, as part of the UK Clinical Eye Research Strategy. Twelve ophthalmology research themes were identified from the JLA report. They were allocated to five Clinical Study Groups of diverse stakeholders who reviewed the top 10 research priorities for each theme. Using an online survey (April 2021-February 2023), respondents were invited to complete one or more of nine subspecialty surveys. Respondents indicated which of the research questions they considered important and subsequently ranked them. In total, 2240 people responded to the survey (mean age, 59.3 years), from across the UK. 68.1% were female. 68.2% were patients, 22.3% healthcare professionals or vision researchers, 7.1% carers, and 2.1% were charity support workers. Highest ranked questions by subspecialty: Cataract (prevention), Cornea (improving microbial keratitis treatment), Optometric (impact of integration of ophthalmic primary and secondary care via community optometric care pathways), Refractive (factors influencing development and/or progression of refractive error), Childhood onset (improving early detection of visual disorders), Glaucoma (effective and improved treatments), Neuro-ophthalmology (improvements in prevention, diagnosis and treatment of neurodegeneration affecting vision), Retina (improving prevention, diagnosis and treatment of dry age-related macular degeneration), Uveitis (effective treatments for ocular and orbital inflammatory diseases). A decade after the initial PSP, the results refocus the most important research questions for each subspecialty, and prime targeted research proposals within Ophthalmology, a chronically underfunded specialty given the substantial burden of disability caused by eye disease. [Abstract copyright: © 2024. The Author(s).