The mental health experiences and needs of methamphetamine users in Cape Town: A mixed-methods study

Background. South Africa (SA) has a burgeoning problem of methamphetamine use, particularly in the Western Cape Province. Although methamphetamine has been associated with elevated psychological distress, there has been little examination of the mental health needs of out-of-treatment methamphetamine users in SA.Objective. To describe the mental health experiences and needs of out-of-treatment methamphetamine users in Cape Town.Methods. Active methamphetamine users were recruited using respondent-driven sampling techniques. Eligible participants (N=360) completed a computer-assisted assessment and clinical interview, where they provided data on mental health symptoms and treatmentseeking behaviour. A subset of 30 participants completed qualitative in-depth interviews in which they provided narrative accounts of their mental health experiences and needs. Analysis of the mixed-methods data was conducted using a concurrent triangulation strategy whereby both methods contributed equally to the analysis and were used for cross-validation.Results. About half of the participants met screening criteria for depression and traumatic stress, and there were some indications of paranoia. Using substances to cope with psychological distress was common, with participants talking about using methamphetamine to numb their feelings or forget stressful memories. One-third of women and 13% of men had previously tried to commit suicide. Despite the huge mental health burden in this population, very few had ever received mental health treatment.Conclusion. The data indicate a need for integrated care that addresses both substance use and psychiatric needs in this population. Mental health and drug treatment services targeting methamphetamine users should include a concerted focus on suicide prevention

100 GHz resonant cavity enhanced Schottky photodiodes

Cataloged from PDF version of article.Resonant cavity enhanced (RCE) photodiodes are promising candidates for applications in optical communications and interconnects where ultrafast high-efficiency detection is desirable. We have designed and fabricated RCE Schottky photodiodes in the (Al, In) GaAs material system for 900-nm wavelength. The observed temporal response with 10-ps pulsewidth was limited by the measurement setup and a conservative estimation of the bandwidth corresponds to more than 100 GHz. A direct comparison of RCE versus conventional detector performance was performed by high speed measurements under optical excitation at resonant wavelength (895 nm) and at 840 nm where the device functions as a single-pass conventional photodiode. A more than two-fold bandwidth enhancement with the RCE detection scheme was demonstrated

Design and Optimization of High-Speed Resonant Cavity Enhanced Schottky Photodiodes

Cataloged from PDF version of article.Resonant cavity enhanced (RCE) photodiodes (PD’s) are promising candidates for applications in optical communications and interconnects where high-speed high-efficiency photodetection is desirable. In RCE structures, the electrical properties of the photodetector remain mostly unchanged; however, the presence of the microcavity causes wavelength selectivity accompanied by a drastic increase of the optical field at the resonant wavelengths. The enhanced optical field allows to maintain a high efficiency for faster transit-time limited PD’s with thinner absorption regions. The combination of an RCE detection scheme with Schottky PD’s allows for the fabrication of high-performance photodetectors with relatively simple material structures and fabrication processes. In top-illuminated RCE Schottky PD’s, a semitransparent Schottky contact can also serve as the top reflector of the resonant cavity. We present theoretical and experimental results on spectral and high-speed properties of GaAs–AlAs–InGaAs RCE Schottky PD’s designed for 900-nm wavelength

Fabrication of high-speed resonant cavity enhanced schottky photodiodes

We report the fabrication and testing of a GaAs-based high-speed resonant cavity enhanced (RCE) Schottky photodiode. The top-illuminated RCE detector is constructed by integrating a Schottky contact, a thin absorption region (In0.8Ga0.92As) and a distributed AlAs-GaAs Bragg mirror. The Schottky contact metal serves as a high-reflectivity top mirror in the RCE detector structure. The devices were fabricated by using a microwave-compatible fabrication process. The resulting spectral photo response had a resonance around 895 nm, in good agreement with our simulations. The full-width-at-half-maximum (FWHM) was 15 nm, and the enhancement factor was in excess of 6. The photodiode had an experimental setup limited temporal response of 18 ps FWHM, corresponding to a 3-dB bandwidth of 20 GHz

One Sided Radiographic Inspection Using Backscatter Imaging

Radiographic inspection, where access is limited to one side of the part, can be performed by the use of backscatter imaging techniques. Compton scattering is the primary source of the backscattered signal strength with some contribution from x-ray fluorescence. A variety of approaches have been used in both medicine and industry to create the images [1–25]. The flying spot technique which uses a collimated beam of x-rays, and a large area detector has been used in the work reported here. The backscatter imaging is particular useful in the inspection of low-density, composite materials.</p

Heterostructures for Optical Devices

Contains research objectives and reports on eight research projects.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAALO3-89-C-0001)National Science Foundation (Grant EET 87-03404)Charles Stark Draper Laboratory (Contract DL-H-315251)Xerox Corporation FellowshipMIT Fund

The laser-hybrid accelerator for radiobiological applications

The `Laser-hybrid Accelerator for Radiobiological Applications', LhARA, is conceived as a novel, uniquely-flexible facility dedicated to the study of radiobiology. The technologies demonstrated in LhARA, which have wide application, will be developed to allow particle-beam therapy to be delivered in a completely new regime, combining a variety of ion species in a single treatment fraction and exploiting ultra-high dose rates. LhARA will be a hybrid accelerator system in which laser interactions drive the creation of a large flux of protons or light ions that are captured using a plasma (Gabor) lens and formed into a beam. The laser-driven source allows protons and ions to be captured at energies significantly above those that pertain in conventional facilities, thus evading the current space-charge limit on the instantaneous dose rate that can be delivered. The laser-hybrid approach, therefore, will allow the vast ``terra incognita'' of the radiobiology that determines the response of tissue to ionising radiation to be studied with protons and light ions using a wide variety of time structures, spectral distributions, and spatial configurations at instantaneous dose rates up to and significantly beyond the ultra-high dose-rate `FLASH' regime. It is proposed that LhARA be developed in two stages. In the first stage, a programme of in vitro radiobiology will be served with proton beams with energies between 10MeV and 15MeV. In stage two, the beam will be accelerated using a fixed-field accelerator (FFA). This will allow experiments to be carried out in vitro and in vivo with proton beam energies of up to 127MeV. In addition, ion beams with energies up to 33.4MeV per nucleon will be available for in vitro and in vivo experiments. This paper presents the conceptual design for LhARA and the R&D programme by which the LhARA consortium seeks to establish the facility

Heterostructures for High Performance Devices

Contains an introduction and reports on ten research projects.Charles S. Draper Laboratory, Contract DL-H-315251Joint Services Electronics Program, Contract DAAL03-89-C-0001National Science Foundation Grant, Grant EET 87-03404MIT FundsInternational Business Machines CorporationNational Science Foundation Grant ECS 84-1317