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We present preliminary analysis of new HST observations of the transiting extrasolar planet HD 209458b. Photometric observations were obtained with the Fine Guidance Sensor (FGS) on the Hubble Space Telescope (HST), providing milli-mag precision and high time resolution (40 Hz). The FGS photometry allows us to derive precise stellar/orbital parameters (ephemeris, inclination, limb darkening) and planetary radius, and also allows a search for the presence of planetary rings and satellites. We discuss preliminary results and two approaches to modelling the observations.
Many studies have shown associations between a history of childhood trauma and more severe or complex clinical features of bipolar disorders (BD), including suicide attempts and earlier illness onset. However, the psychopathological mechanisms underlying these associations are still unknown. Here, we investigated whether affective lability mediates the relationship between childhood trauma and the severe clinical features of BD.
A total of 342 participants with BD were recruited from France and Norway. Diagnosis and clinical characteristics were assessed using the Diagnostic Interview for Genetic Studies (DIGS) or the Structured Clinical Interview for DSM-IV Axis I disorders (SCID-I). Affective lability was measured using the short form of the Affective Lability Scale (ALS-SF). A history of childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ). Mediation analyses were performed using the SPSS process macro.
Using the mediation model and covariation for the lifetime number of major mood episodes, affective lability was found to statistically mediate the relationship between childhood trauma experiences and several clinical variables, including suicide attempts, mixed episodes and anxiety disorders. No significant mediation effects were found for rapid cycling or age at onset.
Our data suggest that affective lability may represent a psychological dimension that mediates the association between childhood traumatic experiences and the risk of a more severe or complex clinical expression of BD.
Previous studies of bipolar disorders indicate that childhood abuse and substance abuse are associated with the disorder. Whether both influence the clinical picture, or if one is mediating the association of the other, has not previously been investigated.
A total of 587 patients with bipolar disorders were recruited from Norway and France. A history of childhood abuse was obtained using the Childhood Trauma Questionnaire. Diagnosis and clinical variables, including substance abuse, were based on structured clinical interviews (Structured Clinical Interview for DSM-IV Axis I disorders or French version of the Diagnostic Interview for Genetic Studies).
Cannabis abuse was significantly associated with childhood abuse, specifically emotional and sexual abuse (χ2 = 8.63, p = 0.003 and χ2 = 7.55, p = 0.006, respectively). Cannabis abuse was significantly associated with earlier onset of the illness (z = −4.17, p < 0.001), lifetime history of at least one suicide attempt (χ2 = 11.16, p = 0.001) and a trend for rapid cycling (χ2 = 3.45, p = 0.06). Alcohol dependence was associated with suicide attempt (χ2 = 10.28, p = 0.001), but not with age at onset or rapid cycling. After correcting for possible confounders and multiple testing, a trend was observed for an interaction between cannabis abuse and childhood abuse and suicide attempt (logistic regression: r2 = 0.06, p = 0.039). Significant additive effects were also observed between cannabis abuse and childhood abuse on earlier age at onset (p < 0.001), increased rapid cycling and suicide attempt (logistic regression: r2 = 0.03–0.04, p < 0.001). No mediation effects were observed; childhood abuse and cannabis abuse were independently associated with the disorder.
Our study is the first to demonstrate significant additive effects, but no mediation effects, between childhood abuse and cannabis abuse on increased clinical expressions of bipolar disorders.
One of the central results in Einstein’s theory of Brownian motion is that the mean
square displacement of a randomly moving Brownian particle scales linearly with time. Over
the past few decades sophisticated experiments and data collection in numerous biological,
physical and financial systems have revealed anomalous sub-diffusion in which the mean
square displacement grows slower than linearly with time. A major theoretical challenge
has been to derive the appropriate evolution equation for the probability density function
of sub-diffusion taking into account further complications from force fields and
reactions. Here we present a derivation of the generalised master equation for an ensemble
of particles undergoing reactions whilst being subject to an external force field. From
this general equation we show reductions to a range of well known special cases, including
the fractional reaction diffusion equation and the fractional Fokker-Planck equation.
This issue of the Journal features collaborative follow-up studies of two unique pregnancy cohorts recruited during 1959–1966 in the United States. Here we introduce the Early Determinants of Adult Health (EDAH) study. EDAH was designed to compare health outcomes in midlife (age 40s) for same-sex siblings discordant on birthweight for gestational age. A sufficient sample of discordant siblings could only be obtained by combining these two cohorts in a single follow-up study. All of the subsequent six papers are either based upon the EDAH sample or are related to it in various ways. For example, three papers report results from studies that significantly extended the ‘core’ EDAH sample to address specific questions.
We first present the overall design of and rationale for the EDAH study. Then we offer a synopsis of past work with the two cohorts to provide a context for both EDAH and the related studies. Next, we describe the recruitment and assessment procedures for the core EDAH sample. This includes the process of sampling and recruitment of potential participants; a comparison of those who were assessed and not assessed based on archived data; the methods used in the adult follow-up assessment; and the characteristics at follow-up of those who were assessed. We provide online supplementary tables with much further detail. Finally, we note further work in progress on EDAH and related studies, and draw attention to the broader implications of this endeavor.
We carefully consider numerous explanations for the sulfur abundance anomaly in planetary nebulae. No one rationale appears to be satisfactory, and we suggest that the ultimate explanation is likely to be a heretofore unidentified feature of the nebular gas which significantly impacts the sulfur ionization correction factor.
Since the introduction of zone-melting recrystallization (ZMR)for silicon-on-insulator (SOI) films, subboundaries (low-angle grain boundaries) have been the major crystalline defects in recrystallized films. By using an improved ZMR procedure, subboundaries have been eliminated over large areas. The improvements include the use of 1-µm-thick polycrystalline-Si films deposited on 2-µm-thick thermal SiO2 film (instead of 0.5-µm-thick Si and SiO2 films), a new encapsulation technique, and improved control of the thermal gradient during ZMR. Recrystallized SOI films without subboundaries contain isolated dislocations with densities <2 × 106 cm−2.
The radiative recombination processes of the two-dimensional hole gas formed in SiGe quantum wells (QWs) due to modulation doping are studied in details by photoluminescence (PL) spectroscopy. Boron-modulation-doped Si/Sil−xGex/Si heterostructures grown by molecular beam epitaxy (MBE) are studied. It is shown that charge transfer of holes from the doped Si layers causes the filling of the SiGe QWs leading to an appearance of a broad asymmetric PL band with a characteristic sharp high energy cut-off and enhanced recombination near the Fermi edge. A reduction of this PL enhancement is observed with an increase of measuring temperature. The PL bandwidth and the high energy cut-off are found to vary with either the doping level or the spatial separation between the delta-doped layers and the QWs. This PL band is argued to arise from the recombination of the holes in the QWs and electrons confined near the QWs as a result of the band bending induced by the delta-doping. The shape of the PL band with enhanced intensity near the Fermi edge are discussed in terms of the phase space filling and many-body effects.
Ion bombardment of polycrystalline Ge, Si, and Au films leads to rates of grain boundary motion that greatly exceed rates of thermally-induced motion at the same temperature and which exhibit a weak temperature dependence. The enhanced migration rate is proportional to the rate of energy deposition in nuclear collisions at or very near the grain boundary. Experimental work is reviewed, and a transition state model is presented which accounts for the observed kinetics of grain boundary migration during bombardment. This model suggests that the rate limiting step in grain boundary motion may be thermally-induced migration of a bombardment-generated defect across the boundary. Also, the ratio of atomic jumps at grain boundaries to the local collision-induced Frenkel defect generation rate is shown to be characteristic of each material, but independent of ion mass and ion flux. The model is extended to the motion of an interface between two phases, and applications to crystallization during ion bombardment are discussed.
We carry out an investigation of grown-in nonradiative defects in Si and SiGe/Si heterostructures grown by molecular-beam-epitaxy (MBE). A number of such defects are observed by the optical detection of magnetic resonance (ODMR) technique, in samples with various structures and growth conditions. These defects are shown to provide efficient nonradiative shunt paths for carrier recombination, competing with and reducing radiative recombination processes. It is revealed that the dominant nonradiative defect is a low-symmetry vacancy-related complex, evident from a characteristic hyperfine structure due to 29Si ligands (with nuclear spin I=1/2 and natural abundance of 4.67 %) connected to the dangling bonds. The introduction of these defects is believed to be largely due to a low surface adatom mobility during the low temperature growth. By varying the substrate bias during the MBE growth, it is shown that the formation of these nonradiative defects can be effectively enhanced by exposure to accelerated positive ions, presumably dominated by the Si+ ions. Effects of hydrogenation on these defects are also studied.
Defect characterization in n-type silicon after the reactive ion etching (RIE) in low-pressure plasmas containing fluorine and oxygen is performed by using photoluminescence (PL) and deep level transient spectroscopies (DLTS). It is shown that RIE treatment results in the formation of (i) luminescence centers giving rise to the C- and G- excitonic lines and broad emission bands related to radiation-induced defect complexes and extended defects and (ii) several electron traps located at 0.16 eV, 0.26 eV, 0.43 eV and 0.58 eV below the conduction band. The addition of oxygen to the SF6 and CF4 plasma is shown to cause nonuniform stress in the near surface region. This stress is responsible for the experimentally observed splitting of the C- and G-excitonic lines, a low energy shift of the phosphorous bound exciton lines, as well as the splitting of the DLTS spectra. It is shown that the stress field is highly inhomogeneous across the wafer, and is rather related to the RIE-induced extended defects than caused by the reaction layer formed on the Si surface.
The use of zone melting recrystallization (ZMR) to prepare large-grain(and in some cases single-crystal) semiconductor films is reviewed, with emphasis on recent work on Si on SiO2. Encapsulants are generally required to minimize contamination and decomposition, induce a crystalline texture,improve surface morphology and prevent agglomeration. In the case of Si, the solid-liquid interface is faceted, which gives rise to subboundaries. These can be entrained by laterally modulating the temperature through the use of an optical absorber on top of the encapsulant. Control of thermal gradients and in-plane crystallographic orientation are important for reliable entrainment.
Bacillus subtilis swarms rapidly over the surface of a synthetic medium
creating remarkable hyperbranched dendritic communities. Models to reproduce such effects
have been proposed under the form of parabolic Partial Differential Equations representing
the dynamics of the active cells (both motile and multiplying), the passive cells
(non-motile and non-growing) and nutrient concentration. We test the numerical behavior of
such models and compare them to relevant experimental data together with a critical
analysis of the validity of the models based on recent observations of the swarming
bacteria which show that nutrients are not limitating but distinct subpopulations growing
at different rates are likely present.
The CRESST-II direct Dark Matter search is located in the Gran Sasso underground laboratories, Italy. CaWO4 crystals are used as scintillating targets for WIMP (weakly interacting massive particle) interactions. They are operated as cryogenic calorimeters in combination with a second cryogenic detector used to measure the scintillation light produced in the target crystal. For each particle interaction, the combination of phonon and light signals provides an event by event discrimination which allows to distinguish known particles (alphas, betas, gammas, neutrons) from the expected signal of WIMPs. A major upgrade of the setup comprises modifications of the shielding, installation of a muon-veto, and new read out electronics, as well as a new detector-support structure to accommodate up to 33 detector modules, i.e. 10 kg of target mass. The experiment was thereafter successfully commissioned in 2007. Data obtained during this commissioning phase from 2 detector modules are presented here. Combining the data collected with these two detector modules with data from one single module obtained during the CRESST-I phase, the experiment could already place a limit of ~6 × 10-7 pb for the spin independent WIMP-nucleon scattering cross section at a WIMP mass of ~60 GeV/c2.
EURECA (European Underground Rare Event Calorimeter Array) is an
astro-particle physics facility aiming to directly detect galactic dark
matter. The Laboratoire Souterrain de Modane has been selected as host
laboratory. The EURECA collaboration unites CRESST, EDELWEISS and the
Spanish-French experiment ROSEBUD, thus concentrating and focussing effort
on cryogenic detector research in Europe into a single facility. EURECA will
use a target mass of up to one ton, enough to explore WIMP – nucleon scalar
scattering cross sections in the region of 10-9 – 10-10 picobarn.
A major advantage of EURECA is the planned use of more than just one target
material (multi target experiment for WIMP identification).