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Mass loss generated by radiatively damped acoustic waves is investigated. We find that a persistent wave energy flux leads to extended chromospheres. Mass loss is quite likely produced if the wave field retains a transient character and if large wave periods are used.
Cannabis use shows a robust dose-dependent relationship with psychosis risk among the general population. Despite this, it has been difficult to link cannabis use with risk for transitioning to a psychotic disorder among individuals at ultra-high risk (UHR) for psychosis. The present study examined UHR transition risk as a function of cannabis use characteristics which vary substantially between individuals including age of first use, cannabis abuse severity and a history of cannabis-induced attenuated psychotic symptoms (APS).
Participants were 190 UHR individuals (76 males) recruited at entry to treatment between 2000 and 2006. They completed a comprehensive baseline assessment including a survey of cannabis use characteristics during the period of heaviest use. Outcome was transition to a psychotic disorder, with mean time to follow-up of 5.0 years (range 2.4–8.7 years).
A history of cannabis abuse was reported in 58% of the sample. Of these, 26% reported a history of cannabis-induced APS. These individuals were 4.90 (95% confidence interval 1.93–12.44) times more likely to transition to a psychotic disorder (p = 0.001). Greater severity of cannabis abuse also predicted transition to psychosis (p = 0.036). However, this effect was mediated by higher abuse severity among individuals with a history of cannabis-induced APS.
Findings suggest that cannabis use poses risk in a subpopulation of UHR individuals who manifest cannabis-induced APS. Whether this reflects underlying genetic vulnerability requires further study. Nevertheless, findings reveal an important early marker of risk with potentially significant prognostic utility for UHR individuals.
We investigated particle acceleration and shock structure associated with an unmagnetized
relativistic jet propagating into an unmagnetized plasma. Strong magnetic fields generated
in the trailing shock contribute to the electrons transverse deflection and acceleration.
We have calculated, self-consistently, the radiation from electrons accelerated in these
turbulent magnetic fields. We found that the synthetic spectra depend on the bulk Lorentz
factor of the jet, its temperature and strength of the generated magnetic fields. We have
also investigated accelerated electrons in strong magnetic fields generated by kinetic
shear (Kelvin-Helmholtz) instabilities. The calculated properties of the emerging
radiation will guide our understanding of the complex time evolution and/or spectral
structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.
Poor sleep is a risk factor for depression, but little is known about the underlying mechanisms.
Disentangling potential mechanisms by which sleep may be related to depression by zooming downto the ‘micro-level’ of within-person daily life patterns of subjective sleep and affect usingthe experience sampling method (ESM).
A population-based twin sample consisting of 553 women underwent a 5-day baseline ESM protocolassessing subjective sleep and affect together with four follow-up assessments of depression.
Sleep was associated with affect during the next day, especially positive affect. Daytime negative affect was not associated with subsequent night-time sleep. Baseline sleep predicted depressive symptoms across the follow-up period.
The subtle, repetitive impact of sleep on affect on a daily basis, rather than the subtle repetitive impact of affect on sleep, may be one of the factors on the pathway to depression in women.
Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron's transverse deflection behind the shock. The “jitter” radiation from deflected electrons in turbulent magnetic fields has properties different from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We present synthetic spectra to compare with the spectra obtained from Fermi observations.
Previously published articles have shown that co-implanted fluorine reduces transient enhanced diffusion of boron. However, it is not yet elucidated whether this effect is due to interaction of fluorine with point-defects or boron atoms. In this work, we have used boron redistribution in a shallow Delta-doped Si structures in order to get some insights into the role of fluorine in the boron diffusion. The structures consisted of 3 boron-doped layers separated by 40nm-thick undoped silicon. The samples were given to Ge preamorphization and F co-implant. SIMS depth profiling was used to analyse boron redistribution after annealing. The results we obtained strongly suggest that fluorine is not interacting with point-defects. The reduction in boron TED is most probably due to boron-fluorine interaction.
Strained Silicon On Insulator wafers are today envisioned as a natural and powerfulenhancement to standard SOI and/or bulk-like strained Si layers. For MOSFETs applications, thisnew technology potentially combines enhanced devices scalability allowed by thin films andenhanced electron and hole mobility in strained silicon. This paper is intended to demonstrate byexperimental results how a layer transfer technique such as the Smart Cut™ technology can be usedto obtain good quality tensile Strained Silicon On insulator wafers. Detailed experiments andcharacterizations will be used to characterize these engineered substrates and show that they arecompatible with the applications.
Ge-based photodetectors operating in the telecommunication wavelength range (1.3-1.6 μm) of silica fibers are highly desirable for the development of optical interconnections on SOI substrates. We have therefore investigated the structural and optical properties of Ge thick films grown directly onto Si(001) substrates using a production-compatible Reduced Pressure Chemical Vapor Deposition system. The thick Ge layers grown using a low-temperature / high temperature approach are in a definite tensile-strain configuration, with a threading dislocation density for as-grown layers of the order of 3×107 cm−2. The surface of those Ge thick layers is rather smooth, especially when considering the large lattice mismatch in-between Ge and Si. The root mean square roughness is indeed of the order of 2 nm only for as-grown layers. The layers produced are of high optical quality. An absorption coefficient α ≈10000 cm−1 @ 1.3μm (4500 cm−1 @ 1.55μm) has been found at room temperature for our Ge thick layers. A 30 meV bandgap shrinkage with respect to bulk Ge (0.77 eV ≎ 0.80 eV) is observed as well in those tensilestrained Ge epilayers.
First results on formation of thin film GeOI structures by the Smart Cut™ technology are presented in this paper. Thin single crystal layers of Ge have been successfully transferred, via oxide bonding layer, onto standard Si substrates with diameters ranging from 100 to 200 mm. Compared to SOI manufacturing, the development of GeOI requires adaptation to the available germanium material, since the starting material can be either bulk Ge or an epitaxial layer. Some results will be presented for GeOI formation according to the different technological options. Germanium splitting kinetics will be discussed and compared to already published results. To show good quality of the GeOI structures, detailed characterization has been done by TEM cross sections for defect densities, interfaces abruptness and layers homogeneities evaluation. AFM was used for surface roughness measurements. These results help define procedures that are required to achieve large diameter high quality GeOI structures.
This paper presents proposals for the synthesis of several group III metal organics (In, Ga, Al compounds) and preliminary results on their use in the MOVPE (metal organic vapor phase epitaxy) of III-V semiconductors. The common feature of all these precursors is that they are saturated by interor intramolecular coordination. They are even non-pyrophoric and air resistant which is an interesting aspect with respect to safe handling. In addition, the compounds are liquid at room temperature with a low but sufficient vapor pressure for MOVPE without additional heating of the source.
A coating apparatus which combines two material modification techniques, sputter coating and plasma immersion ion implantation, is described. The plasma is generated by an electron cyclotron resonance microwave plasma source. In the upper part of the vacuum chamber, the plasma is confined in a magnetic field by means of a solenoid. In the lower part, a magnetron sputter cathode is mounted which is used for depositing thin films on the sample. The sample is clamped onto a water-cooled sample holder which can be moved in vertical direction. It is connected to a semiconductor-based high voltage pulse generator which provides negative voltage pulses. In this apparatus, a substrate can be pre-implanted by plasma immersion ion implantation, then it can be coated by sputtering. Finally, the sputtered film can be modified by another ion implantation step.
Carbon silicon nitride (CSixNy), and carbon boron nitride (CBxNy) thin films have been grown by pulsed laser deposition (PLD) of various carbon (silicon/boron) (nitride) targets using an additional nitrogen RF plasma source on  oriented silicon substrates without additional heating. The CSixNy and CBxNy thin films were amorphous and showed nano hardness up to 23 GPa compared to 14 GPa for silicon and maximum nitrogen content of 30 at%. The maximum nanohardness was achieved for 10% Si and 10% B content in the films. The lower hardness of this films compared to the nanohardness of 30-50 GPa of DLC films indicates a lower amount of covalent carbon-nitrogen bonding in the films. However, in contrast to DLC films, the CSixNy and CBxNy films can be grown to thickness above 3 μm due to lower internal compressive stress. XPS of CSixNy and CBxNy film surfaces shows clear correlation of binding energy and intensity of N ls, C ls, and Si 2p peaks to composition of the PLD-targets and to nitrogen flow through plasma source, indicating soft changes of binding structure due to variation of PLD parameters. The results demonstrate the capability of the plasma assisted PLD process to deposit hard amorphous CSixNy, and CBxNy thin films with adjustable properties.