The use of contemporary and historic diatom assemblages in the derivation of reference state communities for rivers in KwaZulu-Natal, South Africa

Reference state conditions of minimally disturbed headwaters were identified from present-day and historic diatom data of key rivers within the selected study area, with the main purpose of establishing diatom reference state communities

No detectable radio emission from the magnetar-like pulsar in Kes 75

The rotation-powered pulsar PSR J1846-0258 in the supernova remnant Kes 75 was recently shown to have exhibited magnetar-like X-ray bursts in mid-2006. Radio emission has not yet been observed from this source, but other magnetar-like sources have exhibited transient radio emission following X-ray bursts. We report on a deep 1.9 GHz radio observation of PSR J1846-0258 with the 100-m Green Bank Telescope in late 2007 designed to search for radio pulsations or bursts from this target. We have also analyzed three shorter serendipitous 1.4 GHz radio observations of the source taken with the 64-m Parkes telescope during the 2006 bursting period. We detected no radio emission from PSR J1846-0258 in either the Green Bank or Parkes datasets. We place an upper limit of 4.9 \mu Jy on coherent pulsed emission from PSR J1846-0258 based on the 2007 November 2 observation, and an upper limit of 27 \mu Jy around the time of the X-ray bursts. Serendipitously, we observed radio pulses from the nearby RRAT J1846-02, and place a 3\sigma confidence level upper limit on its period derivative of 1.7 * 10^{-13}, implying its surface dipole magnetic field is less than 2.6 * 10^{13} G.Comment: 15 pages, 2 figures, submitted to Ap

Plans for a Neutron EDM Experiment at SNS

The electric dipole moment of the neutron, leptons, and atoms provide a unique window to Physics Beyond the Standard Model. We are currently developing a new neutron EDM experiment (the nEDM Experiment). This experiment, which will be run at the 8.9 A Neutron Line at the Fundamental Neutron Physics Beamline (FNPB) at the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory, will search for the neutron EDM with a sensitivity two orders of magnitude better than the present limit. In this paper, the motivation for the experiment, the experimental method, and the present status of the experiment are discussed.Comment: 9 Pages, 4 Figures, submitted to the proceedings of the Second Meeting of the APS Topical Group on Hadronic Physics, Nashville, TN, October 22-24, 200

X-ray Observations of XSS J12270-4859 in a New Low State: A Transformation to a Disk-Free Rotation-Powered Pulsar Binary

We present XMM-Newton and Chandra observations of the low-mass X-ray binary XSS J12270--4859, which experienced a dramatic decline in optical/X-ray brightness at the end of 2012, indicative of the disappearance of its accretion disk. In this new state, the system exhibits previously absent orbital-phase-dependent, large-amplitude X-ray modulations with a decline in flux at superior conjunction. The X-ray emission remains predominantly non-thermal but with an order of magnitude lower mean luminosity and significantly harder spectrum relative to the previous high flux state. This phenomenology is identical to the behavior of the radio millisecond pulsar binary PSR J1023+0038 in the absence of an accretion disk, where the X-ray emission is produced in an intra-binary shock driven by the pulsar wind. This further demonstrates that XSS J12270-4859 no longer has an accretion disk and has transformed to a full-fledged eclipsing "redback" system that hosts an active rotation-powered millisecond pulsar. There is no evidence for diffuse X-ray emission associated with the binary that may arise due to outflows or a wind nebula. An extended source situated 1.5' from XSS J12270--4859 is unlikely to be associated, and is probably a previously uncatalogued galaxy cluster.Comment: 8 pages, 6 figures; accepted for publication in the Astrophysical Journa

Comment on ``Measurement of the 3^3He mass diffusion coefficient in superfluid 4^4He over the 0.45--0.95 K temperature range

The role of 3He-3He collisions in our diffusion experiment is addressed and shown to not be relevant to the measurement of 3He diffusion against phonons in superfluid helium.Comment: Two pages, in Europhysics Letters forma

Evidence of strong stabilizing effects on the evolution of boreoeutherian (Mammalia) dental proportions.

The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar-molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals

Measurement of the 3He mass diffusion coefficient in superfluid 4He over the 0.45-0.95 K temperature range

We have measured the mass diffusion coefficient D of 3He in superfluid 4He at temperatures lower than were previously possible. The experimental technique utilizes scintillation light produced when neutron react with 3He nuclei, and allows measurement of the 3He density integrated along the trajectory of a well-defined neutron beam. By measuring the change in 3He density near a heater as a function of applied heat current, we are able to infer values of D with 20% accuracy. At temperatures below 0.7 K and for concentrations of order 10^{-4} we find D=(2.0+2.4-1.2)T^-(6.5 -/+ 1.2) cm^2/s, in agreement with a theoretical approximation.Comment: 8 pages, 5 figures. Submitted to Europhysics Letters and prepared in that journal's forma

Acid-yield measurements of the gas-phase ozonolysis of ethene as a function of humidity using Chemical Ionisation Mass Spectrometry (CIMS)

Gas-phase ethene ozonolysis experiments were conducted at room temperature to determine formic acid yields as a function of relative humidity (RH) using the integrated EXTreme RAnge chamber-Chemical Ionisation Mass Spectrometry technique, employing a CH<sub>3</sub>I ionisation scheme. RHs studied were <1, 11, 21, 27, 30 % and formic acid yields of (0.07±0.01) and (0.41±0.07) were determined at <1 % RH and 30 % RH respectively, showing a strong water dependence. It has been possible to estimate the ratio of the rate coefficient for the reaction of the Criegee biradical, CH<sub>2</sub>OO with water compared with decomposition. This analysis suggests that the rate of reaction with water ranges between 1×10<sup>−12</sup>–1×10<sup>−15</sup> cm<sup>3</sup> molecule<sup>−1</sup> s<sup>−1</sup> and will therefore dominate its loss with respect to bimolecular processes in the atmosphere. Global model integrations suggest that this reaction between CH<sub>2</sub>OO and water may dominate the production of HC(O)OH in the atmosphere

The Green Bank Northern Celestial Cap Pulsar Survey - I: Survey Description, Data Analysis, and Initial Results

We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts (FRBs), at 350 MHz using the Green Bank Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4,096 channels every 81.92 $\mu s$. This survey will cover the entire sky visible to the Green Bank Telescope ($\delta > -40^\circ$, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure ($<$30 $\mathrm{pc\,cm^{-3}}$) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of $-$1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214$+$5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636$+$5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 $M_\mathrm{J}$). PSR J0645$+$5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434$+$7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816$+$4510 is an eclipsing MSP in a short-period orbit (8.7 hours) and may have recently completed its spin-up phase.Comment: 18 pages, 10 figures, 5 tables, accepted by Ap