Thermodynamic fluid equations-of-state

As experimental measurements of thermodynamic properties have improved in accuracy, to five or six figures, over the decades, cubic equations that are widely used for modern thermodynamic fluid property data banks require ever-increasing numbers of terms with more fitted parameters. Functional forms with continuity for Gibbs density surface (p,T) which accommodate a critical-point singularity are fundamentally inappropriate in the vicinity of the critical temperature (T-c) and pressure (p(c)) and in the supercritical density mid-range between gas- and liquid-like states. A mesophase, confined within percolation transition loci that bound the gas- and liquid-state by third-order discontinuities in derivatives of the Gibbs energy, has been identified. There is no critical-point singularity at T-c on Gibbs density surface and no continuity of gas and liquid. When appropriate functional forms are used for each state separately, we find that the mesophase pressure functions are linear. The negative and positive deviations, for both gas and liquid states, on either side of the mesophase, are accurately represented by three or four-term virial expansions. All gaseous states require only known virial coefficients, and physical constants belonging to the fluid, i.e., Boyle temperature (T-B), critical temperature (T-c), critical pressure (p(c)) and coexisting densities of gas ((cG)) and liquid ((cL)) along the critical isotherm. A notable finding for simple fluids is that for all gaseous states below T-B, the contribution of the fourth virial term is negligible within experimental uncertainty. Use may be made of a symmetry between gas and liquid states in the state function rigidity (dp/d)(T) to specify lower-order liquid-state coefficients. Preliminary results for selected isotherms and isochores are presented for the exemplary fluids, CO2, argon, water and SF6, with focus on the supercritical mesophase and critical region.info:eu-repo/semantics/publishedVersio

Nonlinear Fluid Dynamics Description of non-Newtonian Fluids

Nonlinear hydrodynamic equations for visco-elastic media are discussed. We start from the recently derived fully hydrodynamic nonlinear description of permanent elasticity that utilizes the (Eulerian) strain tensor. The reversible quadratic nonlinearities in the strain tensor dynamics are of the 'lower convected' type, unambiguously. Replacing the (often neglected) strain diffusion by a relaxation of the strain as a minimal ingredient, a generalized hydrodynamic description of viscoelasticity is obtained. This can be used to get a nonlinear dynamic equation for the stress tensor (sometimes called constitutive equation) in terms of a power series in the variables. The form of this equation and in particular the form of the nonlinear convective term is not universal but depends on various material parameters. A comparison with existing phenomenological models is given. In particular we discuss how these ad-hoc models fit into the hydrodynamic description and where the various non-Newtonian contributions are coming from.Comment: Acta Rheologic

Characterization of short- and long-term morbidity and mortality of goat kids born to does with pregnancy toxemia

Pregnancy Toxemia is a common peri-parturient disease of negative energy balance seen in sheep and goats in the last trimester of pregnancy. Although several studies have evaluated outcomes for dams with pregnancy toxemia, there is a gap in knowledge for its effects on the lambs and kids after parturition. The aim of this study was to characterize the short- and long-term morbidity and mortality of kids born to pregnancy toxemia does. A secondary aim was to evaluate common biochemical and hematologic parameters to find a difference between perinatal adaptation in kids from pregnancy toxemia dams (PT) and control kids (CON) from healthy dams. Serial measurements of blood L-lactate, glucose, beta-hydroxybutyrate, arterial blood gases, hematocrit, total protein, non-esterified fatty acids, and body weight were compared across groups over the first 72 hours of life. Long-term follow up was performed at 3 months. PT kids had a higher short- and long-term mortality compared to CON kids. PT kids were more likely to have a difficult birth, and more likely to require tube feeding due to abnormal nursing behavior. PT kids were much more acidemic and lactatemic at birth, and were less able to maintain their blood glucose compared to CON kids. PT kids were more likely to lose weight in the first 72 hours of life and this was associated with an increased risk of non-survival at 3 months. Overall PT kids showed a decreased ability to ventilate, mobilize energy substrates and adequately perfuse tissues in the peri-natal period which may contribute to their overall weakness and increased mortality. Clinically, these kids would benefit from prolonged oxygen supplementation and need to be monitored for weight gain and milk intake in the first few days of life. Weight loss in the first few days could be a useful predictor of future poor performance

Intraocular pressure measurement in the conscious rat

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74866/1/j.1600-0420.1999.770108.x.pd