Recombination lifetimes in gamma-irradiated P-type float zone silicon

Electron decay rate and absorption cross sections for electron holes and recombination in gamma irradiated n-type silico

Radiation effects on lasers Technical report, Jul. 1, 1965 - May 31, 1966

Effects of space radiation on laser

A Bose-Einstein Condensate in a Uniform Light-induced Vector Potential

We use a two-photon dressing field to create an effective vector gauge potential for Bose-condensed Rb atoms in the F=1 hyperfine ground state. The dressed states in this Raman field are spin and momentum superpositions, and we adiabatically load the atoms into the lowest energy dressed state. The effective Hamiltonian of these neutral atoms is like that of charged particles in a uniform magnetic vector potential, whose magnitude is set by the strength and detuning of Raman coupling. The spin and momentum decomposition of the dressed states reveals the strength of the effective vector potential, and our measurements agree quantitatively with a simple single-particle model. While the uniform effective vector potential described here corresponds to zero magnetic field, our technique can be extended to non-uniform vector potentials, giving non-zero effective magnetic fields.Comment: 5 pages, submitted to Physical Review Letter

Quantitative localized proton-promoted dissolution kinetics of calcite using scanning electrochemical microscopy (SECM)

Scanning electrochemical microscopy (SECM) has been used to determine quantitatively the kinetics of proton-promoted dissolution of the calcite (101̅4) cleavage surface (from natural “Iceland Spar”) at the microscopic scale. By working under conditions where the probe size is much less than the characteristic dislocation spacing (as revealed from etching), it has been possible to measure kinetics mainly in regions of the surface which are free from dislocations, for the first time. To clearly reveal the locations of measurements, studies focused on cleaved “mirror” surfaces, where one of the two faces produced by cleavage was etched freely to reveal defects intersecting the surface, while the other (mirror) face was etched locally (and quantitatively) using SECM to generate high proton fluxes with a 25 μm diameter Pt disk ultramicroelectrode (UME) positioned at a defined (known) distance from a crystal surface. The etch pits formed at various etch times were measured using white light interferometry to ascertain pit dimensions. To determine quantitative dissolution kinetics, a moving boundary finite element model was formulated in which experimental time-dependent pit expansion data formed the input for simulations, from which solution and interfacial concentrations of key chemical species, and interfacial fluxes, could then be determined and visualized. This novel analysis allowed the rate constant for proton attack on calcite, and the order of the reaction with respect to the interfacial proton concentration, to be determined unambiguously. The process was found to be first order in terms of interfacial proton concentration with a rate constant k = 6.3 (± 1.3) × 10–4 m s–1. Significantly, this value is similar to previous macroscopic rate measurements of calcite dissolution which averaged over large areas and many dislocation sites, and where such sites provided a continuous source of steps for dissolution. Since the local measurements reported herein are mainly made in regions without dislocations, this study demonstrates that dislocations and steps that arise from such sites are not needed for fast proton-promoted calcite dissolution. Other sites, such as point defects, which are naturally abundant in calcite, are likely to be key reaction sites

Carers matter: promoting the inclusion of families within acute inpatient settings

Despite their important contributions, many carers report feeling excluded by mental health services. Admission to a psychiatric ward can be a traumatic experience for both clients and their carers. Inpatient teams play a crucial role in engaging families but they report a lack of time, skills and confidence. This pilot study evaluated the feasibility, acceptability and potential benefits of introducing a family service across three acute wards. This comprised staff training, individual carer support and family intervention (FI). The service was found to be acceptable and feasible to implement. Family meetings on the ward increased following staff training, along with reported confidence in working with families. Following FI, significant improvements were found in carer distress, wellbeing, burden and negative illness perceptions and more carers reported having someone to confide in. The total number of ward complaints decreased following introduction of the service. Despite the difficulties implementing family work on the wards, it remains highly indicated. This pilot has shown it is possible to implement an effective and much needed service in an acute setting

Non-radial oscillations in M-giant semi-regular variables: Stellar models and Kepler observations

The success of asteroseismology relies heavily on our ability to identify the frequency patterns of stellar oscillation modes. For stars like the Sun this is relatively easy because the mode frequencies follow a regular pattern described by a well-founded asymptotic relation. When a solar like star evolves off the main sequence and onto the red giant branch its structure changes dramatically resulting in changes in the frequency pattern of the modes. We follow the evolution of the adiabatic frequency pattern from the main sequence to near the tip of the red giant branch for a series of models. We find a significant departure from the asymptotic relation for the non-radial modes near the red giant branch tip, resulting in a triplet frequency pattern. To support our investigation we analyze almost four years of Kepler data of the most luminous stars in the field (late K and early M type) and find that their frequency spectra indeed show a triplet pattern dominated by dipole modes even for the most luminous stars in our sample. Our identification explains previous results from ground-based observations reporting fine structure in the Petersen diagram and sub ridges in the period-luminosity diagram. Finally, we find `new ridges' of non-radial modes with frequencies below the fundamental mode in our model calculations, and we speculate they are related to f modes.Comment: 8 page, 5 figures, accepted by ApJL (ApJ, 788, L10

Variability of M giant stars based on Kepler photometry: general characteristics

M giants are among the longest-period pulsating stars which is why their studies were traditionally restricted to analyses of low-precision visual observations, and more recently, accurate ground-based data. Here we present an overview of M giant variability on a wide range of time-scales (hours to years), based on analysis of thirteen quarters of Kepler long-cadence observations (one point per every 29.4 minutes), with a total time-span of over 1000 days. About two-thirds of the sample stars have been selected from the ASAS-North survey of the Kepler field, with the rest supplemented from a randomly chosen M giant control sample. We first describe the correction of the light curves from different quarters, which was found to be essential. We use Fourier analysis to calculate multiple frequencies for all stars in the sample. Over 50 stars show a relatively strong signal with a period equal to the Kepler-year and a characteristic phase dependence across the whole field-of-view. We interpret this as a so far unidentified systematic effect in the Kepler data. We discuss the presence of regular patterns in the distribution of multiple periodicities and amplitudes. In the period-amplitude plane we find that it is possible to distinguish between solar-like oscillations and larger amplitude pulsations which are characteristic for Mira/SR stars. This may indicate the region of the transition between two types of oscillations as we move upward along the giant branch.Comment: 12 pages, 13 figures, accepted for publication in MNRAS. The normalized light curves are available upon reques

BRAIN TOPiC Study: Assessing Variability in Traumatic Brain Injury (TBI) Outcome Prognostication – Do Self-Fulfilling Prophecies Exist in TBI, Too?

OBJECTIVE: In this study, we surveyed clinicians caring for patients with moderate-severe traumatic brain injury (msTBI) to assess (1) possible variability in outcome prognostication in TBI, varying by clinicians level of training and medical specialty, (2) possible biases and self-fulfilling prophecies, and (3) whether specific ICU medical complications may influence clinicians in their outcome prognostication. BACKGROUND: Patients with msTBI commonly die from withdrawal of support, likely as a consequence of an unfavorable outcome prognosis provided to the family by the treating physician. It is unknown whether prognostication may lead to self-fulfilling prophecies, and whether the presence of intensive care unit (ICU) complications may accentuate possible provider bias. DESIGN/METHODS: We conducted an anonymous electronic survey of clinicians, including faculty members (Neurology, Neurosurgery, Trauma, Anesthesia/Critical Care), neurology house staff, ICU affiliate practitioners and neuroICU nurses at a single Level I trauma center. The survey included three TBI case vignettes and their respective ICU courses. Questions were designed to assess the utilization of known TBI prognostic models, relative importance of ICU complications for outcome prognostication and aggressiveness of care recommended by the survey participant. RESULTS: The survey response rate was 72% (106 surveys returned). In all 3 cases, the majority of participants did not recommend withdrawal of care, but did predict unfavorable 6-month outcomes. 51% of participants consider medical ICU complications as very important in TBI prognostication. Age, ICU course and head CT findings are the prognostic variables considered most important to outcomes. CONCLUSIONS: We have discovered great variability in outcome predictions made by clinicians with different levels of experience in treating msTBI. Self-fulfilling prophecies may exist in msTBI outcomes. Outcome estimates should focus not only on admission variables, but also on ICU complications in order to guide clinicians in providing prognostication