A Dedicated M-Dwarf Planet Search Using The Hobby-Eberly Telescope

We present first results of our planet search program using the 9.2 meter Hobby-Eberly Telescope (HET) at McDonald Observatory to detect planets around M-type dwarf stars via high-precision radial velocity (RV) measurements. Although more than 100 extrasolar planets have been found around solar-type stars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosse et al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetary system. With the current incompleteness of Doppler surveys with respect to M-dwarfs, it is not yet possible to decide whether this is due to a fundamental difference in the formation history and overall frequency of planetary systems in the low-mass regime of the Hertzsprung-Russell diagram, or simply an observational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in the next 3 to 4 years with the primary goal to answer this question. Here we present the results from the first year of the survey which show that our routine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 are binary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveal a high RV-scatter and represent candidates for having short-periodic planetary companions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtained follow-up observations but no periodic signal is present in the RV-data.Comment: 12 pages, 14 figures, accepted for publication in the Astronomical Journa

Quantifying regional biodiversity in the tropics : a case study of freshwater fish in Trinidad and Tobago

Funding: European Research Council (AdG BioTIME 250189 and PoC BioCHANGE 727440) (AEM).Extinction rates are predicted to accelerate during the Anthropocene. Quantifying and mitigating these extinctions demands robust data on distributions of species and the diversity of taxa in regional biotas. However, many assemblages, particularly those in the tropics, are poorly characterized. Targeted surveys and historical museum collections are increasingly being used to meet the urgent need for accurate information, but the extent to which these contrasting data sources support meaningful inferences about biodiversity change in regional assemblages remains unclear. Here, we seek to elucidate uncertainty surrounding regional biodiversity estimates by evaluating the performance of these alternative methods in estimating the species richness and assemblage composition of the freshwater fish of Trinidad & Tobago. We compared estimates of regional species richness derived from two freshwater fish datasets: a targeted two year survey of Trinidad & Tobago rivers and historical museum collection records submitted to The University of the West Indies Zoology Museum. Richness was estimated using rarefaction and extrapolation, and assemblage composition was benchmarked against a recent literature review. Both datasets provided similar estimates of regional freshwater fish species richness (50 and 46 species, respectively), with a large overlap (85%) in species identities. Regional species richness estimates based on survey and museum data are thus comparable, and consistent in the species they include. Our results suggest that museum collection data are a viable option for setting reliable baselines in many tropical systems, thereby widening options for meaningful monitoring and evaluation of temporal trends.PostprintPeer reviewe

The California-Kepler Survey V. Peas in a Pod: Planets in a Kepler Multi-planet System are Similar in Size and Regularly Spaced

We have established precise planet radii, semimajor axes, incident stellar fluxes, and stellar masses for 909 planets in 355 multi-planet systems discovered by Kepler. In this sample, we find that planets within a single multi-planet system have correlated sizes: each planet is more likely to be the size of its neighbor than a size drawn at random from the distribution of observed planet sizes. In systems with three or more planets, the planets tend to have a regular spacing: the orbital period ratios of adjacent pairs of planets are correlated. Furthermore, the orbital period ratios are smaller in systems with smaller planets, suggesting that the patterns in planet sizes and spacing are linked through formation and/or subsequent orbital dynamics. Yet, we find that essentially no planets have orbital period ratios smaller than $1.2$, regardless of planet size. Using empirical mass-radius relationships, we estimate the mutual Hill separations of planet pairs. We find that $93\%$ of the planet pairs are at least 10 mutual Hill radii apart, and that a spacing of $\sim20$ mutual Hill radii is most common. We also find that when comparing planet sizes, the outer planet is larger in $65 \pm 0.4\%$ of cases, and the typical ratio of the outer to inner planet size is positively correlated with the temperature difference between the planets. This could be the result of photo-evaporation.Comment: Published in The Astronomical Journal. 15 pages, 17 figure

Selective Precipitation and Purification of Monovalent Proteins Using Oligovalent Ligands and Ammonium Sulfate

This paper describes a method for the selective precipitation and purification of a monovalent protein (carbonic anhydrase is used as a demonstration) from cellular lysate using ammonium sulfate and oligovalent ligands. The oligovalent ligands induce the formation of protein–ligand aggregates, and at an appropriate concentration of dissolved ammonium sulfate, these complexes precipitate. The purification involves three steps: (i) the removal of high-molecular-weight impurities through the addition of ammonium sulfate to the crude cell lysate; (ii) the introduction of an oligovalent ligand and the selective precipitation of the target protein–ligand aggregates from solution; and (iii) the removal of the oligovalent ligand from the precipitate by dialysis to release the target protein. The increase of mass and volume of the proteins upon aggregate formation reduces their solubility, and results in the selective precipitation of these aggregates. We recovered human carbonic anhydrase, from crude cellular lysate, in 82% yield and 95% purity with a trivalent benzene sulfonamide ligand. This method provides a chromatography-free strategy of purifying monovalent proteins—for which appropriate oligovalent ligands can be synthesized—and combines the selectivity of affinity-based purification with the convenience of salt-induced precipitation.Chemistry and Chemical Biolog

N-Terminal Pro–B-Type Natriuretic Peptide in the Emergency Department: The ICON-RELOADED Study

Background Contemporary reconsideration of diagnostic N-terminal pro–B-type natriuretic peptide (NT-proBNP) cutoffs for diagnosis of heart failure (HF) is needed. Objectives This study sought to evaluate the diagnostic performance of NT-proBNP for acute HF in patients with dyspnea in the emergency department (ED) setting. Methods Dyspneic patients presenting to 19 EDs in North America were enrolled and had blood drawn for subsequent NT-proBNP measurement. Primary endpoints were positive predictive values of age-stratified cutoffs (450, 900, and 1,800 pg/ml) for diagnosis of acute HF and negative predictive value of the rule-out cutoff to exclude acute HF. Secondary endpoints included sensitivity, specificity, and positive (+) and negative (−) likelihood ratios (LRs) for acute HF. Results Of 1,461 subjects, 277 (19%) were adjudicated as having acute HF. The area under the receiver-operating characteristic curve for diagnosis of acute HF was 0.91 (95% confidence interval [CI]: 0.90 to 0.93; p < 0.001). Sensitivity for age stratified cutoffs of 450, 900, and 1,800 pg/ml was 85.7%, 79.3%, and 75.9%, respectively; specificity was 93.9%, 84.0%, and 75.0%, respectively. Positive predictive values were 53.6%, 58.4%, and 62.0%, respectively. Overall LR+ across age-dependent cutoffs was 5.99 (95% CI: 5.05 to 6.93); individual LR+ for age-dependent cutoffs was 14.08, 4.95, and 3.03, respectively. The sensitivity and negative predictive value for the rule-out cutoff of 300 pg/ml were 93.9% and 98.0%, respectively; LR− was 0.09 (95% CI: 0.05 to 0.13). Conclusions In acutely dyspneic patients seen in the ED setting, age-stratified NT-proBNP cutpoints may aid in the diagnosis of acute HF. An NT-proBNP <300 pg/ml strongly excludes the presence of acute HF

Enhancement of nonclassical properties of two qubits via deformed operators

We explore the dynamics of two atoms interacting with a cavity field via deformed operators. Properties of the asymptotic regularization of entanglement measures proving, for example, purity cost, regularized fidelity and accuracy of information transfer are analyzed. We show that the robustness of a bipartite system having a finite number of quantum states vanishes at finite photon numbers, for arbitrary interactions between its constituents and with cavity field. Finally it is shown that the stability of the purity and the fidelity is improved in the absence of the deformation parameters

Vergence-Mediated Changes in Listing&apos;s Plane Do Not Occur in an Eye with Superior Oblique Palsy

PURPOSE. As a normal subject looks from far to near, Listing&apos;s plane rotates temporally in each eye. Since Listing&apos;s plane relates to the control of torsional eye position, mostly by the oblique eye muscles, the current study was conducted to test the hypothesis that a patient with isolated superior oblique palsy would have a problem controlling Listing&apos;s plane. METHOD. Using the three-dimensional scleral search coil technique, binocular Listing&apos;s plane was measured in four patients with congenital and in four patients with acquired unilateral superior oblique palsy during far-(94 cm) and near-(15 cm) viewing. The results were compared to previously published Listing&apos;s plane data collected under exactly the same conditions from 10 normal subjects. RESULTS. In patients with unilateral superior oblique palsy, either congenital or acquired, Listing&apos;s plane in the normal eye rotated temporally on near-viewing, as in normal subjects, while in the paretic eye it failed to do so. In patients with acquired superior oblique palsy, Listing&apos;s plane was already rotated temporally during far-viewing and failed to rotate any farther on near-viewing, whereas in patients with congenital superior oblique palsy Listing&apos;s plane in the paretic eye was oriented normally during far-viewing and failed to rotate any farther on near-viewing. CONCLUSIONS. These results suggest that the superior oblique muscle, at least in part, is responsible for the temporal rotation of Listing&apos;s plane that occurs in normal subjects on convergence. (Invest Ophthalmol Vis Sci. 2004;45:3043-3047) DOI:10.1167/iovs.04-0014 A lthough the eye can rotate with three degrees of freedom, during visual fixation, smooth pursuit, and saccades, it exercises only two: horizontal and vertical. Furthermore, when the head is not moving and there is no vestibular input, horizontal and vertical eye-in-head position (gaze position) determines how much the eye has rotated about its line of sight (i.e., the amount of torsion). This relationship between torsional eye position and gaze position is described by Listing&apos;s law. During visual fixation, smooth pursuit, 1 and saccades, 2 Listing&apos;s law correctly predicts that the tips of the rotation vectors used to describe eye positions all lie in a plane called the displacement plane. 3 The displacement plane is determined by Listing&apos;s plane (LP), which is head fixed and changes orientation under few conditions. For example, LP changes orientation during prolonged fusion of an imposed vertical disparity 4 and during prismatically induced horizontal and vertical vergence. 6 -9 LP rotates in each eye around a point that is not at the origin of the coordinate system describing eye position. Consequently, it is only during downward gaze that torsional eye position changes significantly on near-viewing. Temporal rotation of LP on near-viewing approximately aligns the three-dimensional eye rotation axes during saccades and, as a consequence, eye eccentricity is minimized. 11 However, another line of evidence suggests that the vergence-mediated change in LP may be due to relaxation of one extraocular muscle, the superior oblique. Eye torsion is produced mainly by the oblique eye muscles. There could be some structural differences between congenital and acquired SOPs. One study reported imaging of abnormalities of the superior oblique tendon in congenital SOP in contrast to atrophy of the superior oblique muscle in acquired SOP, 15 but this result was not replicated

Generating Temperature Flow for eta/s with Higher Derivatives: From Lifshitz to AdS

We consider charged dilatonic black branes in AdS_5 and examine the effects of perturbative higher derivative corrections on the ratio of shear viscosity to entropy density eta/s of the dual plasma. The structure of eta/s is controlled by the relative hierarchy between the two scales in the plasma, the temperature and the chemical potential. In this model the background near-horizon geometry interpolates between a Lifshitz-like brane at low temperature, and an AdS brane at high temperatures -- with AdS asymptotics in both cases. As a result, in this construction the viscosity to entropy ratio flows as a function of temperature, from a value in the IR which is sensitive to the dynamical exponent z, to the simple result expected for an AdS brane in the UV. Coupling the scalar directly to the higher derivative terms generates additional temperature dependence, and leads to a particularly interesting structure for eta/s in the IR.Comment: Plots and references added. Journal version of the pape

Rare behavior of growth processes via umbrella sampling of trajectories

We compute probability distributions of trajectory observables for reversible and irreversible growth processes. These results reveal a correspondence between reversible and irreversible processes, at particular points in parameter space, in terms of their typical and atypical trajectories. Thus key features of growth processes can be insensitive to the precise form of the rate constants used to generate them, recalling the insensitivity to microscopic details of certain equilibrium behavior. We obtained these results using a sampling method, inspired by the “s-ensemble” large-deviation formalism, that amounts to umbrella sampling in trajectory space. The method is a simple variant of existing approaches, and applies to ensembles of trajectories controlled by the total number of events. It can be used to determine large-deviation rate functions for trajectory observables in or out of equilibrium