Geant4 Applications for Modeling Molecular Transport in Complex Vacuum Geometries

We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment, in the molecular flow regime. The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elementary particles within complex detector systems. Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical. The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation. We discuss the use of an application with a very complicated geometry, that of the Large Synoptic Survey Telescope camera cryostat, to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.Comment: 7 pages, 4 figures, 2 tables, to appear in IJMSSC, updated to accepted versio

Western equatorial Pacific climate variability from restricted basins: Century scale changes in Kau Bay to glacial-interglacial changes in the Sulu Sea

The surface ocean in the western equatorial Pacific contains some of the warmest water on the planet in the western Pacific warm pool (WPWP). Changes in the size and scope of the warm pool have a significant impact on global climate. With the concern of changes in the extent of this body of water as a result of anthropomorphic changes in atmospheric composition, it is vital to investigate prior changes to the WPWP, the causes of such changes, and resultant effects. For my dissertation, I used several proxies to analyze sediments from Kau Bay and the Sulu Sea in Indonesia to examine changes within the WPWP over century and glacial-interglacial time scales, respectively. Organic matter proxies (δ15N, δ13C, C/N, relative composition and δ13C of fatty acids and alkanes) were analyzed at century-scale resolution from a core from Kau Bay, Halmahera, that spanned over the last ∼3,500 years. These proxies were used to decipher the flushing history of the basin and its relation to El Niño events and warm pool dynamics. Pteropod shells (Creseis acicula) were analyzed from the same cores from Kau Bay for δ 18O, δ13C, and Sr/Ca in order to test the utility of pteropod shells in paleoclimate studies and to determine possible changes in the hydrological cycle within Kau Bay and its relation to equatorial Pacific climate. The C. acicula data showed that Kau Bay water and, therefore, WPWP surface water, was likely warmer 3,000yrBP than throughout the last 2,200 years. Comparisons of this data to other records from the equatorial Pacific and South China Sea revealed that zonal dynamics and the EAM may have had an effect on WPWP and global climate throughout the late Holocene and that ENSO may affect climate change at this resolution. In the Sulu Sea, the δ18O of thermocline dwelling foraminifera, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, was analyzed and compared to mixed layer foraminifera to determine that the mixed layer was probably more shallow during interglacial stages than during glacial stages over the last 800kyr, likely in response to changes in sea level and monsoon intensity

Western equatorial Pacific climate variability from restricted basins: Century scale changes in Kau Bay to glacial-interglacial changes in the Sulu Sea

The surface ocean in the western equatorial Pacific contains some of the warmest water on the planet in the western Pacific warm pool (WPWP). Changes in the size and scope of the warm pool have a significant impact on global climate. With the concern of changes in the extent of this body of water as a result of anthropomorphic changes in atmospheric composition, it is vital to investigate prior changes to the WPWP, the causes of such changes, and resultant effects. For my dissertation, I used several proxies to analyze sediments from Kau Bay and the Sulu Sea in Indonesia to examine changes within the WPWP over century and glacial-interglacial time scales, respectively. Organic matter proxies (δ15N, δ13C, C/N, relative composition and δ13C of fatty acids and alkanes) were analyzed at century-scale resolution from a core from Kau Bay, Halmahera, that spanned over the last ∼3,500 years. These proxies were used to decipher the flushing history of the basin and its relation to El Niño events and warm pool dynamics. Pteropod shells (Creseis acicula) were analyzed from the same cores from Kau Bay for δ 18O, δ13C, and Sr/Ca in order to test the utility of pteropod shells in paleoclimate studies and to determine possible changes in the hydrological cycle within Kau Bay and its relation to equatorial Pacific climate. The C. acicula data showed that Kau Bay water and, therefore, WPWP surface water, was likely warmer 3,000yrBP than throughout the last 2,200 years. Comparisons of this data to other records from the equatorial Pacific and South China Sea revealed that zonal dynamics and the EAM may have had an effect on WPWP and global climate throughout the late Holocene and that ENSO may affect climate change at this resolution. In the Sulu Sea, the δ18O of thermocline dwelling foraminifera, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, was analyzed and compared to mixed layer foraminifera to determine that the mixed layer was probably more shallow during interglacial stages than during glacial stages over the last 800kyr, likely in response to changes in sea level and monsoon intensity

Dismissive incomprehension: a use of purported ignorance to undermine others

This paper analyses a particular social phenomenon whereby a speaker purports ignorance of the meaning of another speaker’s speech in order to undermine that other speaker: dismissive incomprehension. It develops a speech act theory of the phenomenon, and develops its distinctive, and sometimes problematic perlocutionary character. After taking a look at some of the issues surrounding the phenomenon, the paper compares it to more fully studied features of our social lives, including epistemic injustice and gaslighting. It ends with some thoughts on counteracting the problematic cases of dismissive incomprehension

Does a micro-grooved trunnion stem surface finish improve fixation and reduce fretting wear at the taper junction of total hip replacements? A finite element evaluation.

The generation of particulate debris at the taper junction of total hip replacements (THRs), can cause failure of the artificial hip. The taper surfaces of femoral heads and trunnions of femoral stems are generally machined to a certain roughness to enhance fixation. However, the effect of the surface roughness of these surfaces on the fixation, wear and consequently clinical outcomes of the design is largely unknown. In this study, we asked whether a micro-grooved trunnion surface finish (1) improves the fixation and (2) reduces the wear rate at the taper junction of THRs. We used 3D finite element (FE) models of THRs to, firstly, investigate the effect of initial fixation of a Cobalt-Chromium femoral head with a smooth taper surface mated with a Titanium (1) micro-grooved and (2) smooth, trunnion surface finishes. Secondly, we used a computational FE wear model to compare the wear evolution between the models, which was then validated against wear measurements of the taper surface of explanted femoral heads. The fixation at the taper junction was found to be better for the smooth couplings. Over a 7 million load cycle analysis in-silico, the linear wear depth and the total material loss was around 3.2 and 1.4 times higher for the femoral heads mated with micro-grooved trunnions. It was therefore concluded that smooth taper and trunnion surfaces will provide better fixation at the taper junction and reduce the volumetric wear rates

Access to and experience of education for children and adolescents with cancer: a scoping review protocol

BACKGROUND: Cancer diagnosis in childhood or adolescence impacts significantly on school attendance, experience and educational outcomes. While there is longstanding recognition in clinical practice that these effects span the whole illness trajectory and continue beyond treatment completion, further clarity is required on the specific barriers and facilitators to education during cancer treatment and beyond, as well as on the experiences of children and adolescents across the full range of education settings (hospital, home, virtual, original school of enrolment), in order to determine which interventions are successful in improving access and experience from their perspective. The aim of this review is to identify what is known from the existing literature about access to and experience of education for children and adolescents with cancer during and post treatment. METHODS: We have planned a scoping literature review searching the following databases from inception onwards: MEDLINE (Ovid), Embase and Embase Classic, Web of Science Core Collection, Education Resources Index, Sociological Abstracts, APA PsycINFO, SCOPUS, CINAHL Plus, Emcare and The Cochrane Library. In addition, DARE, conference abstracts, key journals, and institutional websites will be searched. Arksey and O'Malley's six-step process will be followed, including a consultation exercise. Studies, reports and policies from any country providing care and treatment for children and adolescents with cancer published in English will be considered eligible for inclusion. Two reviewers will independently screen all citations, full-text articles and abstract data. A narrative summary of findings will be conducted. Data analysis will involve quantitative (e.g., frequencies) and qualitative (e.g., content and thematic analysis) methods. DISCUSSION: This is a timely examination given the increased incidence of childhood cancer, more intensive treatment regimens and improved survival rates for childhood cancer. The inclusion of a substantive consultation exercise with families and professionals will provide an important opportunity to examine the scoping review outputs. Findings will assist the childhood cancer community in developing a comprehensive evidence-based understanding of a significant associated bio-psychosocial impact of cancer diagnosis and treatment and will form the first step towards developing effective interventions and policies to mitigate identified detrimental effects. SYSTEMATIC REVIEW REGISTRATION: Open Science Framework (osf/io/yc4wt)

Investigation of queueing parameters for evaluating Boston Housing Authority maintnenance [sic] operations

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1984.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.Bibliography: leaf 88.by Theodore James Langton.M.C.P

Constraints on the Atmospheric Circulation and Variability of the Eccentric Hot Jupiter XO-3b

We report secondary eclipse photometry of the hot Jupiter XO-3b in the 4.5~$\mu$m band taken with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We measure individual eclipse depths and center of eclipse times for a total of twelve secondary eclipses. We fit these data simultaneously with two transits observed in the same band in order to obtain a global best-fit secondary eclipse depth of $0.1580\pm 0.0036\%$ and a center of eclipse phase of $0.67004\pm 0.00013$. We assess the relative magnitude of variations in the dayside brightness of the planet by measuring the size of the residuals during ingress and egress from fitting the combined eclipse light curve with a uniform disk model and place an upper limit of 0.05$\%$. The new secondary eclipse observations extend the total baseline from one and a half years to nearly three years, allowing us to place an upper limit on the periastron precession rate of $2.9\times 10^{-3}$ degrees/day the tightest constraint to date on the periastron precession rate of a hot Jupiter. We use the new transit observations to calculate improved estimates for the system properties, including an updated orbital ephemeris. We also use the large number of secondary eclipses to obtain the most stringent limits to date on the orbit-to-orbit variability of an eccentric hot Jupiter and demonstrate the consistency of multiple-epoch Spitzer observations.Comment: 14 pages, 11 figures, published by Ap

Atmospheric Circulation of Eccentric Hot Neptune GJ436b

GJ436b is a unique member of the transiting extrasolar planet population being one of the smallest and least irradiated and possessing an eccentric orbit. Because of its size, mass and density, GJ436b could plausibly have an atmospheric metallicity similar to Neptune (20-60 times solar abundances), which makes it an ideal target to study the effects of atmospheric metallicity on dynamics and radiative transfer in an extrasolar planetary atmosphere. We present three-dimensional atmospheric circulation models that include realistic non-gray radiative transfer for 1, 3, 10, 30, and 50 times solar atmospheric metallicity cases of GJ436b. Low metallicity models (1 and 3 times solar) show little day/night temperature variation and strong high-latitude jets. In contrast, higher metallicity models (30 and 50 times solar) exhibit day/night temperature variations and a strong equatorial jet. Spectra and light curves produced from these simulations show strong orbital phase dependencies in the 50 times solar case and negligible variations with orbital phase in the 1 times solar case. Comparisons between the predicted planet/star flux ratio from these models and current secondary eclipse measurements support a high metallicity atmosphere (30-50 times solar abundances) with disequilibrium carbon chemistry at play for GJ436b. Regardless of the actual atmospheric composition of GJ436b, our models serve to illuminate how metallicity influences the atmospheric circulation for a broad range of warm extrasolar planets.Comment: 25 pages, 13 figure