Psychrometric Properties of Humid Air from Multi-Fluid Helmholtz-Energy-Explicit Models

Psychrometric properties of humid air are widely used in the analysis and modeling of thermal systems. In this work we present a method for obtaining these properties from the multi-fluid mixture formulation of the GERG mixture model. This mixture model was originally developed to model the thermodynamics of natural gas mixtures, and now has been extended to model thermodynamic properties relevant for carbon capture and storage. The primary advantage of this formulation is that the dry air composition is not fixed, and can be adjusted to suit the application, for instance in submarines, for Martian atmospheres, etc. We present an algorithm that can be used to calculate the saturated vapor water composition in vapor-liquid equilibrium, and other properties that arise out of this equilibrium calculation, such as relative humidity and dewpoints. Solid-vapor equilibrium is not considered, and neither is the calculation of wet-bulb temperatures

A Helmholtz Energy Equation of State for Trifluoroethylene (R-1123)

A first fundamental equation of state explicit in the Helmholtz energy is presented for trifluoroethylene (R-1123). Much attention has been given to this novel refrigerant due to its preferable characteristics for working fluids in residential air conditioners. The independent variables of the equation of state are temperature and density. All thermodynamic properties can be derived as derivatives of the Helmholtz energy. The equation of state is composed of two parts; one is the ideal-gas part representing ideal-gas properties, and the other is the residual part corresponding to the influence of intermolecular forces. The ideal-gas part is analytically formulated from a correlation for the ideal-gas isobaric heat capacity. The correlation comes from sound speed data in the vapor phase. The residual part is empirically determined from experimental data for the critical parameters, vapor pressures, vapor sound speeds, and liquid and vapor densities, including those at saturation. Following recent trends in the development of accurate equations of state, a functional form that includes Gaussian bell-shaped terms was optimized with the use of nonlinear least-squares fitting to the experimental data. Numerous thermodynamic constraints were applied to control the slope and curvature of derived properties from the equation of state. The equation is valid for temperatures from 273 K to 450 K and for pressures up to 10 MPa. Typical uncertainties over the range of validity are 0.1 % for vapor pressures, 0.1 % for liquid densities, and 0.5 % for vapor densities, except in the critical region where larger deviations up to about 2 % are observed in densities. At temperatures below 300 K, deviations in vapor pressures are larger due to higher experimental uncertainties. The equation shows reasonable extrapolation behavior in regions away from the experimental data. Although the equation is based on limited experimental data, it is the best currently available for the calculation of thermodynamic properties for R-1123. The equation of state will be incorporated in the ongoing development of a multi-fluid mixture model for the R-32/1123 mixture

Quantifying the spatiotemporal dynamics in a chorus frog (Pseudacris) hybrid zone over 30 years

© 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. Although theory suggests that hybrid zones can move or change structure over time, studies supported by direct empirical evidence for these changes are relatively limited. We present a spatiotemporal genetic study of a hybrid zone between Pseudacris nigrita and P. fouquettei across the Pearl River between Louisiana and Mississippi. This hybrid zone was initially characterized in 1980 as a narrow and steep “tension zone,” in which hybrid populations were inferior to parentals and were maintained through a balance between selection and dispersal. We reanalyzed historical tissue samples and compared them to samples of recently collected individuals using microsatellites. Clinal analyses indicate that the cline has not shifted in roughly 30 years but has widened significantly. Anthropogenic and natural changes may have affected selective pressure or dispersal, and our results suggest that the zone may no longer best be described as a tension zone. To the best of our knowledge, this study provides the first evidence of significant widening of a hybrid cline but stasis of its center. Continued empirical study of dynamic hybrid zones will provide insight into the forces shaping their structure and the evolutionary potential they possess for the elimination or generation of species

Off-target capture data, endosymbiont genes and morphology reveal a relict lineage that is sister to all other singing cicadas

Phylogenetic asymmetry is common throughout the tree of life and results from contrasting patterns of speciation and extinction in the paired descendant lineages of ancestral nodes. On the depauperate side of a node, we find extant ´relict´ taxa that sit atop long, unbranched lineages. Here, we show that a tiny, pale green, inconspicuous and poorly known cicada in the genus Derotettix, endemic to degraded salt-plain habitats in arid regions of central Argentina, is a relict lineage that is sister to all other modern cicadas. Nuclear and mitochondrial phylogenies of cicadas inferred from probe-based genomic hybrid capture data of both target and non-target loci and a morphological cladogram support this hypothesis. We strengthen this conclusion with genomic data from one of the cicada nutritional bacterial endosymbionts, Sulcia, an ancient and obligate endosymbiont of the larger plant-sucking bugs (Auchenorrhyncha) and an important source of maternally inherited phylogenetic data. We establish Derotettiginae subfam. nov. as a new, monogeneric, fifth cicada subfamily, and compile existing and new data on the distribution, ecology and diet of Derotettix. Our consideration of the palaeoenvironmental literature and host-plant phylogenetics allows us to predict what might have led to the relict status of Derotettix over 100 Myr of habitat change in South America.Fil: Simon, Chris. University of Connecticut; Estados UnidosFil: Gordon, Eric R. L.. University of Connecticut; Estados UnidosFil: Moulds, M.S.. Australian Museum Research Institute; AustraliaFil: Cole, Jeffrey A.. Pasadena City College; Estados UnidosFil: Haji, Diler. University of Connecticut; Estados UnidosFil: Lemmon, Alan R.. Florida State University; Estados UnidosFil: Lemmon, Emily Moriarty. Florida State University; Estados UnidosFil: Kortyna, Michelle. Florida State University; Estados UnidosFil: Nazario, Katherine. University of Connecticut; Estados UnidosFil: Wade, Elizabeth J.. Curry College. Department of Natural Sciences and Mathematics; Estados Unidos. University of Connecticut; Estados UnidosFil: Meister, Russell C.. University of Connecticut; Estados UnidosFil: Goemans, Geert. University of Connecticut; Estados UnidosFil: Chiswell, Stephen M.. National Institute of Water and Atmospheric Research; Nueva ZelandaFil: Pessacq, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagónica. Universidad Nacional de la Patagonia "San Juan Bosco". Centro de Investigación Esquel de Montaña y Estepa Patagónica; ArgentinaFil: Veloso, Claudio. Universidad de Chile; ChileFil: McCutcheon, John P.. University of Montana; Estados UnidosFil: Lukasik, Piotr. University of Montana; Estados Unidos. Swedish Museum of Natural History. Department of Bioinformatics and Genetics; Sueci

Why are convertible bond announcements associated with increasingly negative issuer stock returns? An arbitrage-based explanation

While convertible offerings announced between 1984 and 1999 induce average abnormal stock returns of −1.69%, convertible announcement effects over the period 2000–2008 are more than twice as negative (−4.59%). We hypothesize that this evolution is attributable to a shift in the convertible bond investor base from long-only investors towards convertible arbitrage funds. These funds buy convertibles and short the underlying stocks, causing downward price pressure. Consistent with this hypothesis, we find that the differences in announcement returns between the Traditional Investor period (1984–1999) and the Arbitrage period (2000–September 2008) disappear when controlling for arbitrage-induced short selling associated with a range of hedging strategies. Post-issuance stock returns are also in line with the arbitrage explanation. Average announcement effects of convertibles issued during the Global Financial Crisis are even more negative (−9.12%), due to a combination of short-selling price pressure and issuer, issue, and macroeconomic characteristics associated with these offerings