Chemical Association via Exact Thermodynamic Formulations

It can be fruitful to view two-component physical systems of attractive monomers, A and B, ``chemically'' in terms of a reaction A + B C, where C = AB is an associated pair or complex. We show how to construct free energies in the three-component or chemical picture which, under mass-action equilibration, exactly reproduce any given two-component or ``physical'' thermodynamics. Order-by-order matching conditions and closed-form chemical representations reveal the freedom available to modify the A-C, B-C, and C-C interactions and to adjust the association constant. The theory (in the simpler one-component, i.e., A = B, case) is illustrated by treating a van der Waals fluid.Comment: 15 double-spaced pages (RevTeX), including 1 eps figur

Impairments in motor coordination without major changes in cerebellar plasticity in the Tc1 mouse model of Down syndrome

Down syndrome (DS) is a genetic disorder arising from the presence of a third copy of human chromosome 21 (Hsa21). Recently, O’Doherty et al. [An aneuploid mouse strain carrying human chromosome 21 with Down syndrome phenotypes. Science 309 (2005) 2033–2037] generated a trans-species aneuploid mouse line (Tc1) that carries an almost complete Hsa21. The Tc1 mouse is the most complete animal model for DS currently available. Tc1 mice show many features that relate to human DS, including alterations in memory, synaptic plasticity, cerebellar neuronal number, heart development and mandible size. Because motor deficits are one of the most frequently occurring features of DS, we have undertaken a detailed analysis of motor behaviour in cerebellum-dependent learning tasks that require high motor coordination and balance. In addition, basic electrophysiological properties of cerebellar circuitry and synaptic plasticity have been investigated. Our results reveal that, compared with controls, Tc1 mice exhibit a higher spontaneous locomotor activity, a reduced ability to habituate to their environments, a different gait and major deficits on several measures of motor coordination and balance in the rota rod and static rod tests. Moreover, cerebellar long-term depression is essentially normal in Tc1 mice, with only a slight difference in time course. Our observations provide further evidence that support the validity of the Tc1 mouse as a model for DS, which will help us to provide insights into the causal factors responsible for motor deficits observed in persons with DS

Measurements of Oil Retention in a Microchannel Condenser for AC Systems

In a refrigeration cycle, a small portion of the compressor oil circulates with the refrigerant flow through the cycle components, while most of the oil stays in the compressor. The presence of the lubricant affects the performance of heat exchangers by increasing the pressure losses and adding a thermal resistance to the heat transfer exchange process. The oil effects on microchannel heat exchangers are unique due to their relatively small scale geometry and manifold configuration. In this paper, oil retention in a microchannel type condenser was measured and its effects on heat transfer and pressure drop characteristics are presented. The heat exchanger was a 2 passes, aluminum louvered-fin type condenser that consisted of multiports rectangular microchannels with hydraulic diameter of 0.06 inch (1.7 mm). The refrigerant and oil flow rates were varied and actual operating conditions of an air conditioning condenser for R410A systems were replicated in laboratory. The refrigerant R410A and Polyolester oil mixture was studied at saturation temperature from 85 to 130 °F (29 to 54 °C) and two refrigerant mass flux that are common for a 4 ton nominal capacity AC system for residential applications. Oil mass fraction (OMF) in circulation with the refrigerant was varied from 0.5 to 5.6 in wt.%. The results indicated that at OMFs of 0.5 wt.% to 1 wt.%, which are common ranges in typical air conditioning systems, the oil retention in the microchannel condenser was less than 5% of the microchannel condenser internal volume for all saturation temperatures and all mass fluxes studied in this work. The oil retained in the condenser increased if the OMF increases and it was measured up to 23% of the total microchannel condenser internal volume when the OMF was 5.4 wt. %. The superheated vapor refrigerant section of the condenser held small amount of oil due to high refrigerant vapor superficial velocities inside the microchannel tubes. At OMFs of 0.5 wt. % the heat transfer capacity of the coil was the same of that of oil free conditions. At high saturation temperature of 130 °F (54 °C). and high mass flux, the heat transfer capacity of the coil decreased as the OMF increased and some penalization of refrigerant-side heat transfer rate was observed at OMFs as low as 1 wt. %. If OMF increased then the heat transfer capacity of the heat exchanger was penalized by up to 9% and the pressure drops across the condenser was augmented up to 19% with respect to the oil free case

Blue Swimmer Crab ( Portunus armatus ) and Mud Crab Scylla serrata and Scylla olivacea ) Resources in the North Coast and Gascoyne Coast Bioregions, Western Australia

Blue swimmer crab (Portunus armatus) are found along the entire Western Australia (WA) coast, in a range of estuarine, inshore and continental shelf areas (\u3c50 m). In the North Coast Bioregion (NCB), commercial fishing primarily occurs as part of the Pilbara Crab Managed Fishery (PCMF) which spans the inshore waters from Onslow through to Port Hedland, with most fishing activity taking place around Nickol Bay

Blue Swimmer Crab ( Portunus armatus ) Resource in the West Coast Bioregion, Western Australia Part 1: Peel Harvey Estuary, Cockburn Sound and Swan Canning Estuary

Blue swimmer crabs (Portunus armatus) are found along the entire coastline of Western Australia in a range of estuarine, inshore and continental shelf areas (\u3c50 m). In the West Coast Bioregion (WCB), crab fisheries are centred in estuaries and coastal embayments from Geographe Bay to the Swan River. Commercial fisheries include the Cockburn Sound Crab Managed Fishery (CSCMF), the Warnbro Sound Crab Managed Fishery, the Swan-Canning Estuary (SCE) Crab Fishery (Area 1 of the West Coast Estuarine Managed Fishery (WCEMF)), Peel-Harvey Crab Fishery (Area 2 of the WCEMF), Hardy Inlet (Area 3 of the WCEMF) and the Mandurah to Bunbury Developing Crab Fishery (Area 1, Comet Bay and Area 2, Mandurah-Bunbury)

On the finite-size behavior of systems with asymptotically large critical shift

Exact results of the finite-size behavior of the susceptibility in three-dimensional mean spherical model films under Dirichlet-Dirichlet, Dirichlet-Neumann and Neumann-Neumann boundary conditions are presented. The corresponding scaling functions are explicitly derived and their asymptotics close to, above and below the bulk critical temperature $T_c$ are obtained. The results can be incorporated in the framework of the finite-size scaling theory where the exponent $\lambda$ characterizing the shift of the finite-size critical temperature with respect to $T_c$ is smaller than $1/\nu$, with $\nu$ being the critical exponent of the bulk correlation length.Comment: 24 pages, late

Modeling of Lubricant Effects in a Microchannel Type Condenser

In HVAC and refrigeration systems, a small portion of the oil circulates with the refrigerant flow through the cycle components, while most of the oil stays in the compressor. The circulating oil can form a fairly homogeneous mixture with the liquid refrigerant, or it can exist as a separate oil-rich film inside the small tubes and headers of a microchannel heat exchanger; the amount of oil held up is affected by the system conditions. The oil retention in the microchannel type condenser is of particular interest as the amount of oil in excess in this component affects the heat transfer capacity and increases the frictional pressure losses. This paper presents a new physics-based model of the oil retention in microchannel-type condensers. The model calculates the local thermodynamic properties in each section for the refrigerant R-410A and Polyester (POE) oil mixture based on the local oil concentration, pressure, temperature, and mass flux. Then the model, which was experimentally validated, predicts the refrigerant-side heat transfer coefficient and pressure drop. The simulation results indicated that the pressure losses increased by over 20% when the oil mass flow rate fraction increased up to 5 weight percent. The augmented mixture viscosity resulted in high frictional pressure drops and shear stress during the two phase flow condensation. The refrigerant side correlations were validated against literature data for in-tube two-phase flow condensation but further investigation is needed for the single-phase annular type flow in microchannel with refrigerant vapor and oil. At low degree of superheat the heat transfer coefficient of the refrigerant and oil mixture was basically unaffected by the oil mass fraction up to 3 weight percent. When the oil mass fraction was higher than 3 weight percent, then the heat transfer capacity of the condenser decreased. At high degree of superheat, the heat transfer coefficient of the oil and refrigerant mixture was penalized when the Oil Mass Fraction (OMF) was higher than 2 weight percent. Further investigation is needed on the suitability and accuracy of the heat transfer coefficients correlations to be adopted with superheated vapor refrigerant and lubricant film in annular flow at the inlet section of the microchannel type condenser

Thermodynamic Casimir effects involving interacting field theories with zero modes

Systems with an O(n) symmetrical Hamiltonian are considered in a $d$-dimensional slab geometry of macroscopic lateral extension and finite thickness $L$ that undergo a continuous bulk phase transition in the limit $L\to\infty$. The effective forces induced by thermal fluctuations at and above the bulk critical temperature $T_{c,\infty}$ (thermodynamic Casimir effect) are investigated below the upper critical dimension $d^*=4$ by means of field-theoretic renormalization group methods for the case of periodic and special-special boundary conditions, where the latter correspond to the critical enhancement of the surface interactions on both boundary planes. As shown previously [\textit{Europhys. Lett.} \textbf{75}, 241 (2006)], the zero modes that are present in Landau theory at $T_{c,\infty}$ make conventional RG-improved perturbation theory in $4-\epsilon$ dimensions ill-defined. The revised expansion introduced there is utilized to compute the scaling functions of the excess free energy and the Casimir force for temperatures T\geqT_{c,\infty} as functions of $\mathsf{L}\equiv L/\xi_\infty$, where $\xi_\infty$ is the bulk correlation length. Scaling functions of the $L$-dependent residual free energy per area are obtained whose $\mathsf{L}\to0$ limits are in conformity with previous results for the Casimir amplitudes $\Delta_C$ to $O(\epsilon^{3/2})$ and display a more reasonable small-$\mathsf{L}$ behavior inasmuch as they approach the critical value $\Delta_C$ monotonically as $\mathsf{L}\to 0$.Comment: 23 pages, 10 figure