The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems

We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The current limit for activity-age relations found for M dwarfs in open clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for the exploration of this relationship at ages older than 4 Gyr. The general trend of stars remaining active for a longer time at later spectral type is confirmed. However, our larger sample and greater age range reveals additional complexity in assigning age based on activity alone. We find that M dwarfs in wide binaries older than 4 Gyr depart from the log-linear relation for clusters and are found to have activity at magnitudes, colors and masses which are brighter, bluer and more massive than predicted by the cluster relation. In addition to our activity-age results, we present the measured radial velocities and complete space motions for 161 white dwarf stars in wide binaries.Comment: 22 pages including 9 figures and 5 tables. Accepted for publication in The Astronomical Journa

The FHD/ε\boldsymbol{\varepsilon}ppsilon Epoch of Reionization Power Spectrum Pipeline

Epoch of Reionization data analysis requires unprecedented levels of accuracy in radio interferometer pipelines. We have developed an imaging power spectrum analysis to meet these requirements and generate robust 21 cm EoR measurements. In this work, we build a signal path framework to mathematically describe each step in the analysis, from data reduction in the FHD package to power spectrum generation in the $\varepsilon$ppsilon package. In particular, we focus on the distinguishing characteristics of FHD/$\varepsilon$ppsilon: highly accurate spectral calibration, extensive data verification products, and end-to-end error propagation. We present our key data analysis products in detail to facilitate understanding of the prominent systematics in image-based power spectrum analyses. As a verification to our analysis, we also highlight a full-pipeline analysis simulation to demonstrate signal preservation and lack of signal loss. This careful treatment ensures that the FHD/$\varepsilon$ppsilon power spectrum pipeline can reduce radio interferometric data to produce credible 21 cm EoR measurements.Comment: 21 pages, 10 figures, accepted by PAS

Measurements and Predictions on the Elkhart Greek Culvert

This paper describes field measurements and analysis carried out on the Elkhart Creek soil arch culvert structure in British Columbia, Canada. The structure has a span of 13.4 m, a rise of 7.3 m, and a soil cover of 9.6 m. The original structure collapsed during backfilling in October 1987. A new structure of the same design was built in the Fall of 1989, and because of controversy regarding the design thrust value, it was instrumented to measure thrust, moment, and displacements in the arch. Displacements and stresses in the soil were also measured. The measured thrust values were much lower than expected and indicated that significant positive soil-arching occurred. A nonlinear finite element analysis of the soil-structure system was carried out simulating the construction procedures used, and the computed response compared with the measurements. The computed and observed responses were in reasonable agreement in terms of thrust, moment, displacements and soil stresses provided an allowance was made for slip at the bolted connections

Evidence for Accretion in the High-resolution X-ray Spectrum of the T Tauri Star System Hen 3-600

We present high-resolution X-ray spectra of the multiple T Tauri star system Hen 3-600, obtained with the High Energy Transmission Grating Spectrograph on the Chandra X-ray Observatory. Two binary components were detected in the zeroth-order image. Hen 3-600-A, which has a large mid-infrared excess, is a 2-3 times fainter in X-rays than Hen 3-600-B, due to a large flare on B. The dispersed X-ray spectra of the two primary components overlap spatially; spectral analysis was performed on the combined system. Analysis of the individual spectra was limited to regions where the contributions of A and B can be disentangled. This analysis results in two lines of evidence indicating that the X-ray emission from Hen 3-600 is derived from accretion processes: line ratios of O VII indicate that the characteristic density of its X-ray-emitting plasma is large; a significant component of low-temperature plasma is present and is stronger in component A. These results are consistent with results obtained from X-ray gratings spectroscopy of more rapidly accreting systems. All of the signatures of Hen 3-600 that are potential diagnostics of accretion activity -- X-ray emission, UV excess, H-alpha emission, and weak infrared excess -- suggest that its components represent a transition phase between rapidly accreting, classical T Tauri stars and non-accreting, weak-lined T Tauri stars.Comment: latex, 27 pages, 12 figures, 6 tables; accepted by Ap

The perception and management of risk in UK office property development

Risk is an ever-present aspect of business, and risk taking is necessary for profit and economic progress. Speculative property development is popularly perceived as a 'risky business' yet, like other entrepreneurs, developers have opportunities to manage the risks they face; techniques include phasing and joint ventures. The associated areas of investment portfolio risk, development risk analysis and construction risk management have all been addressed by research. This article presents new knowledge about how developers perceive risks and the means they subsequently adopt to manage them. The developers of office projects across the UK were sent questionnaires by post. Respondents were asked about their perceptions of risks at the first appraisal stage and currently and about the risk management techniques that they had adopted. In-depth interviews with a selection of respondents were then used to discuss and augment the findings. Developers were most concerned about market-based risks at both stages. Concern about production-orientated risks was lower and fell significantly between the two stages. A fixed price contract was the most common risk management technique. Risk management techniques were used more often outside London and the South East. Developer type affects both the perception and management of risk. While developers do manage risk, decisions are made on the basis of professional and business experience. These findings should help development companies manage risk in a more objective and analytical way

Evaluation of a Revised Curriculum: A Four-Year Qualitative Study of Student Perceptions

Following curricular revisions at the Virginia Commonwealth University School of Dentistry, this longitudinal study was designed to determine students\u27 perceptions of their educational experience in the revised curriculum. A SWOT (Strengths, Weaknesses, Opportunities, and Threats) open-ended response questionnaire was administered to students in the class of 2011 (N=89) in January of each academic year, 2008 through 2011, followed by focus groups three months prior to graduation. The overall response rate for the questionnaire was 69 percent, and a total of fourteen students participated in four focus groups. Cumulatively, 1,382 responses (SWOT=984 and focus groups=398) were qualitatively analyzed, and five themes emerged: 1) early clinical experiences led to a perceived readiness for direct patient care; 2) the pace and organization of the revised condensed preclinical curriculum were perceived as hectic yet were appreciated as necessary preparation for patient care; 3) most faculty members were seen as committed to student learning, but a few were reported to have poor teaching skills and attitudes when interacting with students; 4) a perceived lack of patients led to fewer clinical experiences and a decrease in student confidence; and 5) some curricular content was seen to be redundant and irrelevant to future practice. The results indicate that the students were satisfied with aspects of their educational experience, suggesting the revised curriculum\u27s preliminary success in meeting its goals of earlier patient care, a condensed preclinical curriculum, and a student-friendly environment. As the curriculum is adapted in response to student feedback, ongoing evaluation is necessary and should be complemented by other evaluation indicators such as faculty perceptions and student learning outcomes

Spatial Regulation of Membrane Fusion Controlled by Modification of Phosphoinositides

Membrane fusion plays a central role in many cell processes from vesicular transport to nuclear envelope reconstitution at mitosis but the mechanisms that underlie fusion of natural membranes are not well understood. Studies with synthetic membranes and theoretical considerations indicate that accumulation of lipids characterised by negative curvature such as diacylglycerol (DAG) facilitate fusion. However, the specific role of lipids in membrane fusion of natural membranes is not well established. Nuclear envelope (NE) assembly was used as a model for membrane fusion. A natural membrane population highly enriched in the enzyme and substrate needed to produce DAG has been isolated and is required for fusions leading to nuclear envelope formation, although it contributes only a small amount of the membrane eventually incorporated into the NE. It was postulated to initiate and regulate membrane fusion. Here we use a multidisciplinary approach including subcellular membrane purification, fluorescence spectroscopy and Förster resonance energy transfer (FRET)/two-photon fluorescence lifetime imaging microscopy (FLIM) to demonstrate that initiation of vesicle fusion arises from two unique sites where these vesicles bind to chromatin. Fusion is subsequently propagated to the endoplasmic reticulum-derived membranes that make up the bulk of the NE to ultimately enclose the chromatin. We show how initiation of multiple vesicle fusions can be controlled by localised production of DAG and propagated bidirectionally. Phospholipase C (PLCγ), GTP hydrolysis and (phosphatidylinsositol-(4,5)-bisphosphate (PtdIns(4,5)P2) are required for the latter process. We discuss the general implications of membrane fusion regulation and spatial control utilising such a mechanism

Understanding students’ motivation towards proactive career behaviours through goal-setting theory and the job demands–resources model

The graduate labour market is highly competitive but little is known about why students vary in their development of employability. This study contributes to the literature by applying goal-setting theory and the job demands–resources model to investigate how motivational processes influence students’ proactive career behaviours. We tested four hypotheses using structural equation modelling and moderation/mediation analysis using a nested model approach; 432 undergraduates from 21 UK universities participated in this cross-sectional study. The results showed that students higher in mastery approach had greater perceived employability mediated by two proactive career behaviours (skill development and network building). Students’ career goal commitment was associated with all four proactive career behaviours (career planning, skill development, career consultation and network building). Students’ academic and employment workloads did not negatively impact their proactive career behaviours. University tutors and career services should therefore encourage students to set challenging career goals that reflect mastery approach