29,204 research outputs found

    Linking teaching and research in disciplines and departments

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    This paper supports the effective links between teaching and discipline-based research in disciplinary communities and in academic departments. It is authored by Alan Jenkins, Mick Healey and Roger Zetter

    Flat device for heat concentration or dispersion

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    Device provides low-cost unit for efficiently transferring heat between, either to or from, flat surface and central point or region. It is based upon vapor heat transfer principle and therefore, extends applicability of heat pipe

    The 5g yields 4f pionic transition in Th 232 and U 238

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    X ray energy measurements in 5g yields 4f pionic transitions of Th-232 and U-23

    Maximum A Posteriori Resampling of Noisy, Spatially Correlated Data

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    In any geologic application, noisy data are sources of consternation for researchers, inhibiting interpretability and marring images with unsightly and unrealistic artifacts. Filtering is the typical solution to dealing with noisy data. However, filtering commonly suffers from ad hoc (i.e., uncalibrated, ungoverned) application. We present here an alternative to filtering: a newly developed method for correcting noise in data by finding the “best” value given available information. The motivating rationale is that data points that are close to each other in space cannot differ by “too much,” where “too much” is governed by the field covariance. Data with large uncertainties will frequently violate this condition and therefore ought to be corrected, or “resampled.” Our solution for resampling is determined by the maximum of the a posteriori density function defined by the intersection of (1) the data error probability density function (pdf) and (2) the conditional pdf, determined by the geostatistical kriging algorithm applied to proximal data values. A maximum a posteriori solution can be computed sequentially going through all the data, but the solution depends on the order in which the data are examined. We approximate the global a posteriori solution by randomizing this order and taking the average. A test with a synthetic data set sampled from a known field demonstrates quantitatively and qualitatively the improvement provided by the maximum a posteriori resampling algorithm. The method is also applied to three marine geology/geophysics data examples, demonstrating the viability of the method for diverse applications: (1) three generations of bathymetric data on the New Jersey shelf with disparate data uncertainties; (2) mean grain size data from the Adriatic Sea, which is a combination of both analytic (low uncertainty) and word-based (higher uncertainty) sources; and (3) side-scan backscatter data from the Martha\u27s Vineyard Coastal Observatory which are, as is typical for such data, affected by speckle noise. Compared to filtering, maximum a posteriori resampling provides an objective and optimal method for reducing noise, and better preservation of the statistical properties of the sampled field. The primary disadvantage is that maximum a posteriori resampling is a computationally expensive procedure

    A Search for Lost Planets in the Kepler Multi-planet Systems and the Discovery of the Long-period, Neptune-sized Exoplanet Kepler-150 f

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    The vast majority of the 4700 confirmed planets and planet candidates discovered by the Kepler mission were first found by the Kepler pipeline. In the pipeline, after a transit signal is found, all data points associated with those transits are removed, creating a "Swiss cheese"-like light curve full of holes, which is then used for subsequent transit searches. These holes could render an additional planet undetectable (or "lost"). We examine a sample of 114 stars with 3+3+ confirmed planets to evaluate the effect of this "Swiss cheesing". A simulation determines that the probability that a transiting planet is lost due to the transit masking is low, but non-negligible, reaching a plateau at 3.3%\sim3.3\% lost in the period range of P=400500P=400-500 days. We then model all planet transits and subtract out the transit signals for each star, restoring the in-transit data points, and use the Kepler pipeline to search the transit-subtracted (i.e., transit-cleaned) light curves. However, the pipeline did not discover any credible new transit signals. This demonstrates the validity and robustness of the Kepler pipeline's choice to use transit masking over transit subtraction. However, a follow-up visual search through all the transit-subtracted data, which allows for easier visual identification of new transits, revealed the existence of a new, Neptune-sized exoplanet (Kepler-150 f) and a potential single transit of a likely false positive (Kepler-208). Kepler-150 f (P=637.2P=637.2 days, RP=3.640.39+0.52R_{\rm{P}}=3.64^{+0.52}_{-0.39} R_{\oplus}) is confirmed with >99.998%>99.998\% confidence using a combination of the planet multiplicity argument, a false positive probability analysis, and a transit duration analysis.Comment: 11 pages, 5 figures, 2 tables. Accepted into A

    Deriving Iodine-free spectra for high-resolution echelle spectrographs

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    We describe a new method to derive clean, iodine-free spectra directly from observations acquired using high-resolution echelle spectrographs equipped with iodine cells. The main motivation to obtain iodine-free spectra is to use portions of the spectrum that are superimposed with the dense forest of iodine absorption lines, in order to retrieve lines that can be used to monitor the magnetic activity of the star, helping to validate candidate planets. In short, we provide a straight-forward methodology to clean the spectra by using the forward model used to derive radial velocities, the Line Spread Function information plus the stellar spectrum without iodine to reconstruct and subtract the iodine spectrum from the observations. We show our results using observations of the star τ\tau Ceti acquired with the PFS, HIRES and UCLES spectrographs, reaching an iodine-free spectrum correction at the \sim1% RMS level. We additionally discuss the limitations and further applications of the method.Comment: 15 pages, 7 figures. Accepted for publication in A

    On the structure of large N cancellations in baryon chiral perturbation theory

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    We show how to compute loop graphs in heavy baryon chiral perturbation theory including the full functional dependence on the ratio of the Delta--nucleon mass difference to the pion mass, while at the same time automatically incorporating the 1/N cancellations that follow from the large-N spin-flavor symmetry of baryons in QCD. The one-loop renormalization of the baryon axial vector current is studied to demonstrate the procedure. A new cancellation is identified in the one-loop contribution to the baryon axial vector current. We show that loop corrections to the axial vector currents are exceptionally sensitive to deviations of the ratios of baryon-pion axial couplings from SU(6) values

    Climate change as a confounding factor in reversibility of acidification: RAIN and CLIMEX projects

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    The RAIN and CLIMEX experiments at Risdalsheia, southernmost Norway, together cover 17 years (1984-2000) of whole-catchment manipulation of acid deposition and climate. A 1200 m<sup>2</sup> roof placed over the forest canopy at KIM catchment excluded about 80% of ambient acid deposition; clean rain was sprinkled under the roof. A climate change treatment (3.7&#176;C increase in air temperature and increase in air carbon dioxide concentrations to 560 ppmv) was superimposed on the clean rain treatment for four years (1995-1998). Sea-salt inputs and temperature are climate-related factors that influence water chemistry and can confound long-term trends caused by changes in deposition of sulphur and nitrogen. The RAIN and CLIMEX experiments at Risdalsheia provided direct experimental data that allow quantitative assessment of these factors. Run-off chemistry responded rapidly to the decreased acid deposition. Sulphate concentrations decreased by 50% within three years; nitrate and ammonium concentrations decreased to new steady-state levels within the first year. Acid neutralising capacity increased and hydrogen ion and inorganic aluminium decreased. Similar recovery from acidification was also observed at the reference catchment, ROLF, in response to the general 50% reduction in sulphate deposition over southern Norway in the late 1980s and 1990s. Variations in sea-salt deposition caused large variations in run-off chemistry at the reference catchment ROLF and the year-to-year noise in acid neutralising capacity was as large as the overall trend over the period. These variations were absent at KIM catchment because the sea-salt inputs were held constant over the entire 17 years of the clean rain treatment. The climate change experiment at KIM catchment resulted in increased leaching of inorganic nitrogen, probably due to increased mineralisation and nitrification rates in the soils.</p> <p style='line-height: 20px;'><b>Keywords:</b> acid deposition, global change, water, soil, catchment, experiment, Norway

    The reported use and effectiveness of Hypericum (St John’s wort) on affective symptoms in a depression self-help group

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    A recent meta-analysis suggested that Hypericum perforatum (St John’s wort) is an effective treatment for mild to moderate depression and may have a superior side-effect profile to some antidepressant drugs. The aim of this study was to assess the use of herbal remedies in treating depressive and anxiety symptoms, as reported by members of the UK self-help organization Depression Alliance using self-completed questionnaires. More than 50% of the 452 respondents reported using Hypericum, onequarter of whom also reported concurrent use of traditional antidepressants. Most of the sample reported sufficient symptoms for warranting a diagnosis of major depression, with the majority also describing symptoms suggestive of co-morbid psychiatric conditions. One-half of the Hypericum users experienced symptom improvement, which for most occurred within the first 4 weeks of use. Response was better for those with mild as compared to severe symptoms and poorer for those taking Hypericum alongside other antidepressants. The responders were generally older than non-responders. Adverse effects were reported by one-quarter of users and were mostly psychological in nature. This retrospective survey indicated that use of herbal remedies was common in this population. Although often helpful in relieving symptoms, particularly in those with mild depression, there is a risk of adverse events and drug interaction
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