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

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)

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

Asymmetric Primitive-Model Electrolytes: Debye-Huckel Theory, Criticality and Energy Bounds

Debye-Huckel (DH) theory is extended to treat two-component size- and charge-asymmetric primitive models, focussing primarily on the 1:1 additive hard-sphere electrolyte with, say, negative ion diameters, a--, larger than the positive ion diameters, a++. The treatment highlights the crucial importance of the charge-unbalanced ``border zones'' around each ion into which other ions of only one species may penetrate. Extensions of the DH approach which describe the border zones in a physically reasonable way are exact at high $T$ and low density, $\rho$, and, furthermore, are also in substantial agreement with recent simulation predictions for \emph{trends} in the critical parameters, $T_c$ and $\rho_c$, with increasing size asymmetry. Conversely, the simplest linear asymmetric DH description, which fails to account for physically expected behavior in the border zones at low $T$, can violate a new lower bound on the energy (which applies generally to models asymmetric in both charge and size). Other recent theories, including those based on the mean spherical approximation, have predicted trends in the critical parameters quite opposite to those established by the simulations.Comment: to appear in Physical Review