Solar-like oscillations in the metal-poor subgiant nu Indi: II. Acoustic spectrum and mode lifetime

Convection in stars excites resonant acoustic waves which depend on the sound speed inside the star, which in turn depends on properties of the stellar interior. Therefore, asteroseismology is an unrivaled method to probe the internal structure of a star. We made a seismic study of the metal-poor subgiant star nu Indi with the goal of constraining its interior structure. Our study is based on a time series of 1201 radial velocity measurements spread over 14 nights obtained from two sites, Siding Spring Observatory in Australia and ESO La Silla Observatory in Chile. The power spectrum of the high precision velocity time series clearly presents several identifiable peaks between 200 and 500 uHz showing regularity with a large and small spacing of 25.14 +- 0.09 uHz and 2.96 +- 0.22 uHz at 330 uHz. Thirteen individual modes have been identified with amplitudes in the range 53 to 173 cm/s. The mode damping time is estimated to be about 16 days (1-sigma range between 9 and 50 days), substantially longer than in other stars like the Sun, the alpha Cen system or the giant xi Hya.Comment: 5 pages, 7 figures, A&A accepte

Structure-reactivity relationship in pyrolysis of plastics. A comparison with natural polymers

Recent advances in plastics recycling confirm the high potential of pyrolysis technologies to enhance recovery and selectivity rates. Modelling the kinetics of this complex process to stimulate scaling-up opportunities remains a major challenge.This study is an attempt to develop practical quantitative reactivity indices for the pyrolysis of natural and synthetic polymers. Representative samples from both categories (coal and pine vs. PET, PE and PMMA) were selected. Their weight loss during pyrolysis was determined experimentally and analyzed using judicious lumping procedures for its initiation, propagation and termination steps. The combined experimental and theoretical approach allowed us to determine apparent activation energies using the isoconversional Friedman method; and the use of Benson’s group contribution method generated reaction enthalpies for the initiation reactions. Increasing activation energies with conversion in each case indicated that bond scission proceeds in order of increasing bond strength. The greater chemical complexity of natural polymers was reflected in the higher coefficients of variability for activation energy and wider ranges of reaction enthalpies. A structure-reactivity relationship based on the Evans-Polanyi theory was used to test the hypothesis that primary pyrolysis kinetics is controlled by cleavage of weakest chemical bonds. While the results show that this approach is promising, especially if confirmed by extension to a larger data set, they also suggest the need to compare the relative kinetic importance of initiation and propagation steps in the sequence of polymer pyrolysis reactions

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate their fundamental parameters and the abundances of 16 chemical species in a self-consistent manner. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general abundance trends as a function of the metallicity observed in stars of the Galactic disk. After an allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN cycle. A contamination by NeNa-cycled material in the most massive stars is also discussed. With the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low- and intermediate-mass stars.Comment: Accepted for publication in A&A, 25 pages, 13 colour figures (revised version after language editing

An Economic Analysis of What Role Monetary Contributions Play in How a Government Representative Will Vote

As a result of polarizing election outcomes, controversial legislative actions, and the general stigma that elected officials are corrupt, many Americans are questioning whether their representatives in government have the best interest of their constituents at heart, or are considering more self-centered motives. One point of contention is that political action committees and lobbyists contribute hundreds of thousands of dollars to legislators\u27 campaigns in return for consideration of their viewpoints. This study seeks to determine exactly how much weight members of the House of Representatives give to monetary contributions when considering how to vote on a bill by using voting records and control variables associated with the Patient Protection and Affordable Care Act. After testing how party, ideology, monetary contributions, constituent income, percent of votes received in the election, and the size of the election margin impacted how each Representative voted on the ACA it was unclear whether any variables had significant impacts on the dependent variable. However, when only the data from the Democrats was considered, it was possible to conclude that both ideology and monetary contributions were major contributing factors for the vote

Pubertal development of penile Nitric Oxide Synthase (NOS)-containing nerve fibers in the rat

Objectives: To evaluate the expression of nitric oxide synthase (NOS)-containing nerve fibers in penile tissue in different age groups in the rat and to measure serum testosterone levels during this developmental process. Material and Methods: Fifteen male Sprague-Dawley (SD) rats divided into 3 equally numbered groups of different age (40 days (d), 54d and 65d) were used in this study. Penile erection was evaluated using cavernous nerve electrostimulation. Before sacrificing the rats, a penile midshaft specimen was taken for nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining and blood samples were collected to evaluate the testosterone levels. Results: Electrostimulation of the cavernous nerve revealed no significant difference in the maximal intracavernous pressure in the different age groups (44.9 ± 6.4, 54.8 ± 24.8, 45.9 ± 16.8 cm H2O, respectively; p>0.05), but the latency of the response to electrostimulation was significantly shorter in 54d and 65d than in 40d-old rats (5.4 ± 0.8 and 5.0 ± 0.7 vs. 9.0 ± 5.4 sec., respectively;

Core properties of alpha Cen A using asteroseismology

A set of long and nearly continuous observations of alpha Centauri A should allow us to derive an accurate set of asteroseismic constraints to compare to models, and make inferences on the internal structure of our closest stellar neighbour. We intend to improve the knowledge of the interior of alpha Centauri A by determining the nature of its core. We combined the radial velocity time series obtained in May 2001 with three spectrographs in Chile and Australia: CORALIE, UVES, and UCLES. The resulting combined time series has a length of 12.45 days and contains over 10,000 data points and allows to greatly reduce the daily alias peaks in the power spectral window. We detected 44 frequencies that are in good overall agreement with previous studies, and found that 14 of these show possible rotational splittings. New values for the large and small separations have been derived. A comparison with stellar models indicates that the asteroseismic constraints determined in this study allows us to set an upper limit to the amount of convective-core overshooting needed to model stars of mass and metallicity similar to those of alpha Cen A.Comment: 8 pages, 11 figures, A&A accepte

Model-assisted measurements of suspension-feeding flow velocities

Author Posting. © Company of Biologists, 2017. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 220 (2017): 2096-2107, doi:10.1242/jeb.147934.Benthic marine suspension feeders provide an important link between benthic and pelagic ecosystems. The strength of this link is determined by suspension-feeding rates. Many studies have measured suspension-feeding rates using indirect clearance-rate methods, which are based on the depletion of suspended particles. Direct methods that measure the flow of water itself are less common, but they can be more broadly applied because, unlike indirect methods, direct methods are not affected by properties of the cleared particles. We present pumping rates for three species of suspension feeders, the clams Mya arenaria and Mercenaria mercenaria and the tunicate Ciona intestinalis, measured using a direct method based on particle image velocimetry (PIV). Past uses of PIV in suspension-feeding studies have been limited by strong laser reflections that interfere with velocity measurements proximate to the siphon. We used a new approach based on fitting PIV-based velocity profile measurements to theoretical profiles from computational fluid dynamic (CFD) models, which allowed us to calculate inhalant siphon Reynolds numbers (Re). We used these inhalant Re and measurements of siphon diameters to calculate exhalant Re, pumping rates, and mean inlet and outlet velocities. For the three species studied, inhalant Re ranged from 8 to 520, and exhalant Re ranged from 15 to 1073. Volumetric pumping rates ranged from 1.7 to 7.4 l h−1 for M. arenaria, 0.3 to 3.6 l h−1 for M. mercenaria and 0.07 to 0.97 l h−1 for C. intestinalis. We also used CFD models based on measured pumping rates to calculate capture regions, which reveal the spatial extent of pumped water. Combining PIV data with CFD models may be a valuable approach for future suspension-feeding studies.This research is part of a collaborative project (National Science Foundation grant OCE-1260232 to P.A.J., and grant OCE-1260199 to J. Crimaldi, University of Colorado). Funding was also provided by NSF grant OIA-1355457 to Maine EPSCoR at the University of Maine (D.C.B.).2018-05-3