Possible detection of a magnetic field in T Tauri

Medium-resolution $(R\simeq 15000)$ circular spectropolarimetry of T Tauri is presented. The star was observed twice: on November 11, 1996 and January 22, 2002. Weak circular polarization has been found in photospheric absorption lines, indicating a mean surface longitudinal magnetic field $B_{\|}$ of $160\pm 40$ G and $140\pm 50$ G at the epoch of the first and second observations respectively. While these values are near the detection limit of our apparatus, we belive that they are real. In any case one can conclude from our data that $B_{\|}$ of T Tau does not significantly exceed 200 G, which is much less than surface magnetic field strength of the star ($>2.3$ kG) found by Guenther et al. (1999) and Johns-Krull et al. (2000). We discuss possible reasons of this difference.Comment: 5 pages, 3 figure

Natural nitrogen-15 abundance of soil and plant samples

Includes bibliographical references (page 50).Nitrogen isotope analysis of total soil N and soil-derived nitrate for nine selected Chernozemic and Luvisolic Ap horizons showed mean δa15N values based on atmospheric abundance of 8.8. Luvisolic soils were characterized by a relatively low level of the heavier isotope. Isotope enrichment of the total N reached a maximum in the lower B horizon. Subsoil nitrate (180-cm depth) had a δa15N value 1/3 that of the Ap horizon. The δa15N of subsurface soil horizons containing residual fertilizer N were low (−5.2) compared to the surface horizon (7.0). The δa15N of NH4-N in commercial fertilizers is close to that of atmospheric-N whereas the NO3-N has higher values. The data suggest that variations in δ15N abundance between horizons of the same soil, or between different soils, may be of real use in evaluating stresses which have been placed in the nitrogen cycle due to man's activities in the past. Similarly, differences in 15N abundance of soil, legume and air samples may provide an integrated estimation of symbiotic nitrogen fixation under field conditions. More detailed understanding of biological and other processes which control the N isotope concentrations must be obtained before the data reported can be further interpreted

The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk

We measure the temperature of warm gas at planet-forming radii in the disk around the classical T Tauri star (CTTS) TW Hya by modelling the H2 fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission irradiates a warm disk surface within 2 AU of the central star and pumps certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to estimate fluxes for the 140 observed H2 emission lines and to reconstruct the Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Ly-alpha profile incident upon the warm H2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics, we estimate that the warm disk surface has a column density of log N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling factor of H2, as seen by the source of Ly-alpha emission, of 0.25\pm0.08 (all 2-sigma error bars). TW Hya produces approximately 10^{-3} L_\odot in the FUV, about 85% of which is in the Ly-alpha emission line. From the H I absorption observed in the Ly-alpha emission, we infer that dust extinction in our line of sight to TW Hya is negligible.Comment: Accepted by ApJ. 26 pages, 17 figures, 6 table

Delineating the role of βIV-Tubulins in pancreatic cancer: βIVb-tubulin inhibition sensitizes pancreatic cancer cells to vinca alkaloids

Pancreatic cancer (PC) is a lethal disease which is characterized by chemoresistance. Components of the cell cytoskeleton are therapeutic targets in cancer. βIV-tubulin is one such component that has two isotypes—βIVa and βIVb. βIVa and βIVb isotypes only differ in two amino acids at their C-terminus. Studies have implicated βIVa-tubulin or βIVb-tubulin expression with chemoresistance in prostate, breast, ovarian and lung cancer. However, no studies have examined the role of βIV-tubulin in PC or attempted to identify isotype specific roles in regulating cancer cell growth and chemosensitivity. We aimed to determine the role of βIVa- or βIVb-tubulin on PC growth and chemosensitivity. PC cells (MiaPaCa-2, HPAF-II, AsPC1) were treated with siRNA (control, βIVa-tubulin or βIVb-tubulin). The ability of PC cells to form colonies in the presence or absence of chemotherapy was measured by clonogenic assays. Inhibition of βIVa-tubulin in PC cells had no effect chemosensitivity. In contrast, inhibition of βIVb-tubulin in PC cells sensitized to vinca alkaloids (Vincristine, Vinorelbine and Vinblastine), which was accompanied by increased apoptosis and enhanced cell cycle arrest. We show for the first time that βIVb-tubulin, but not βIVa-tubulin, plays a role in regulating vinca alkaloid chemosensitivity in PC cells. The results from this study suggest βIVb-tubulin may be a novel therapeutic target and predictor of vinca alkaloid sensitivity for PC and warrants further investigation

Upper ocean manifestations of a reducing meridional overturning circulation

Most climate models predict a slowing down of the Atlantic Meridional Overturning Circulation during the 21st century. Using a 100year climate change integration of a high resolution coupled climate model, we show that a 5.3Sv reduction in the deep southward transport in the subtropical North Atlantic is balanced solely by a weakening of the northward surface western boundary current, and not by an increase in the southward transport integrated across the interior ocean away from the western boundary. This is consistent with Sverdrup balance holding to a good approximation outside of the western boundary region on decadal time scales, and may help to spatially constrain past and future change in the overturning circulation. The subtropical gyre weakens by 3.4Sv over the same period due to a weakened wind stress curl. These changes combine to give a net 8.7Sv reduction in upper western boundary transport. © 2012. American Geophysical Union. All Rights Reserved

Cool Jupiters greatly outnumber their toasty siblings : Occurrence rates from the Anglo-Australian Planet Search

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©2019 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Our understanding of planetary systems different to our own has grown dramatically in the past 30 yr. However, our efforts to ascertain the degree to which the Solar system is abnormal or unique have been hindered by the observational biases inherent to the methods that have yielded the greatest exoplanet hauls. On the basis of such surveys, one might consider our planetary system highly unusual - but the reality is that we are only now beginning to uncover the true picture. In this work, we use the full 18-yr archive of data from the Anglo-Australian Planet Search to examine the abundance of 'cool Jupiters' - analogues to the Solar system's giant planets, Jupiter and Saturn. We find that such planets are intrinsically far more common through the cosmos than their siblings, the hot Jupiters.We find that the occurrence rate of such 'cool Jupiters' is 6.73 +2.09 -1.13 per cent, almost an order of magnitude higher than the occurrence of hot Jupiters (at 0.84 +0.70 -0.20 per cent). We also find that the occurrence rate of giant planets is essentially constant beyond orbital distances of ~1 au. Our results reinforce the importance of legacy radial velocity surveys for the understanding of the Solar system's place in the cosmos.Peer reviewe

Modelling the molecular Zeeman effect in M-dwarfs: methods and first results

We present first quantitative results of the surface magnetic field measurements in selected M-dwarfs based on detailed spectra synthesis conducted simultaneously in atomic and molecular lines of the FeH Wing-Ford $F^4\,\Delta-X^4\,\Delta$ transitions. A modified version of the Molecular Zeeman Library (MZL) was used to compute Land\'e g-factors for FeH lines in different Hund's cases. Magnetic spectra synthesis was performed with the Synmast code. We show that the implementation of different Hund's case for FeH states depending on their quantum numbers allows us to achieve a good fit to the majority of lines in a sunspot spectrum in an automatic regime. Strong magnetic fields are confirmed via the modelling of atomic and FeH lines for three M-dwarfs YZ~CMi, EV~Lac, and AD~Leo, but their mean intensities are found to be systematically lower than previously reported. A much weaker field ($1.7-2$~kG against $2.7$~kG) is required to fit FeH lines in the spectra of GJ~1224. Our method allows us to measure average magnetic fields in very low-mass stars from polarized radiative transfer. The obtained results indicate that the fields reported in earlier works were probably overestimated by about $15-30$\%. Higher quality observations are needed for more definite results.Comment: Accepted by A&A, 13 pages, 7 figures, 1 tabl

The Areal Extent and Hydraulic Continuity of Perched Ground Water in the Vicinity of the Pantex Plant

Groundwater contamination at the Pantex Plant is currently restricted to a perched aquifer(s) above the regional Ogallala aquifer water table. Therefore, the areal extent and hydraulic continuity of this unit are critical factors in the overall hydrologic characterization required for the design of effective remediation activities. Another important question is determining whether any privately owned domestic wells are producing from the perched aquifer(s) in areas downgradient from and hydrologically connected to known or possible contaminated areas on the Pantex Plant. It should be noted, however, that a continuous saturated zone is not the only scenario by which point-source and non-point-source contaminants could migrate. All recharging groundwater that is perched will eventually move through the fine-grained, low-permeability zone that underlies the perched aquifer(s) and resume a downward track to the Ogallala aquifer. In addition, the results of this study clearly illustrate areas where there is no perched aquifer(s), and thus there may be no perching layer, within the boundary of the Pantex Plant. In these areas where a perching layer is absent, there will be no retarding effect created by the perched aquifer(s) on the vertical movement of recharge to the Ogallala aquifer.Bureau of Economic Geolog

The role of ultrasound imaging in the management of partial placental retention after third trimester livebirth

Objectives: To evaluate the impact of different ultrasound signs in the management and the role of ultrasound guidance in the surgical evacuation of partial placental tissue retention.Methods: This is an observational cohort study and retrospective case assessment of 82 patients with clinical symptoms of partial placental retention following a third trimester singleton livebirth between January 2013 and May 2019. The ultrasound signs were recorded using a standardized protocol and the outcome of the management strategy and the use of ultrasound guidance during any surgical procedure was evaluated.Results: Out of the 64 patients who had a vaginal birth, 25 (39.1%) had a manual removal of the placenta at delivery. Fifteen patients were confirmed as not having retained placental tissue and did not require further treatment. Four patients were referred after failed surgical management and four after failed conservative management. All surgical procedures were vacuum aspiration and forceps removal under continuous ultrasound guidance. A significantly lower gestational age at delivery (p < .05), shorter interval between delivery and ultrasound diagnosis (p < .05) and lower number of patients presenting with heavy bleeding was found in the conservative compared to the surgical management subgroups (p < .05). The incidence of feeding vessels was significantly (p < .05) higher in the surgical than in the conservative management subgroups and associated with increased myometrial vascularity. Six patients developed intra-uterine adhesions. In four of these cases, ultrasound examination showed a hyperechoic mass surrounded by normal myometrial vascularity and no feeding vessel.Conclusions: Ultrasound imaging accurately differentiated between patient with and without partial placental retention after third trimester livebirth. Ultrasound-guided vacuum aspiration is safe and efficient in these cases

Stationarity, soft ergodicity, and entropy in relativistic systems

Recent molecular dynamics simulations show that a dilute relativistic gas equilibrates to a Juettner velocity distribution if ensemble velocities are measured simultaneously in the observer frame. The analysis of relativistic Brownian motion processes, on the other hand, implies that stationary one-particle distributions can differ depending on the underlying time-parameterizations. Using molecular dynamics simulations, we demonstrate how this relativistic phenomenon can be understood within a deterministic model system. We show that, depending on the time-parameterization, one can distinguish different types of soft ergodicity on the level of the one-particle distributions. Our analysis further reveals a close connection between time parameters and entropy in special relativity. A combination of different time-parameterizations can potentially be useful in simulations that combine molecular dynamics algorithms with randomized particle creation, annihilation, or decay processes.Comment: 4 page