Bronchoalveolar lavage fluid from both lungs in horses: Diagnostic reliability of cytology from pooled samples.

Cytology of bronchoalveolar lavage fluid (BALF) from one lung may not predict findings in the contralateral lung of the same horse. The aim of this study was to determine whether a pooled BALF from both lungs was representative of corresponding individual samples. Fifty-one horses referred for poor performance and/or respiratory signs and for which a BALF was collected from both lungs, were included in the study. Cytology of pooled and individual BALF samples were performed using a masked protocol. Based on clinical signs and individual BALF cytologies, horses were classified as control (CTL), mild equine asthma (mEA), severe equine asthma (sEA) and/or exercise-induced pulmonary haemorrhage (EIPH). No significant difference was observed between pooled and individual BALF samples for all cell types (P>0.05). Correlations between pooled and individual BALF samples were good (r≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio, and moderate (r≥0.4) for metachromatic cell and eosinophil proportions. Similarly, intraclass correlation coefficient (ICC) were good (ICC≥0.9) for neutrophil proportions and haemosiderophages/macrophages ratio and substantial (ICC≥0.6) for metachromatic cell proportions. Based on threshold values for pooled samples as determined by receiver operating characteristic (ROC) analysis, categorical agreements were good (κ≥0.97) for diagnosis of mEA/sEA, and substantial (κ=0.74) for EIPH. Using a pooled BALF sample, only one horse was incorrectly classified as CTL instead of mEA and three horses were classified as EIPH instead of CTL. In conclusion, BALF cytology from pooled sample is representative of both individual lungs, and constitutes a valid method to diagnose EA.

Single nucleotide polymorphisms in the REG-CTNNA2 region of chromosome 2 and NEIL3 associated with impulsivity in a Native American sample.

Impulsivity is a multi-faceted construct that, while characterized by a set of correlated dimensions, is centered around a core definition that involves acting suddenly in an unplanned manner without consideration for the consequences of such behavior. Several psychiatric disorders include impulsivity as a criterion, and thus it has been suggested that it may link a number of different behavioral disorders, including substance abuse. Native Americans (NA) experience some of the highest rates of substance abuse of all the US ethnic groups. The described analyses used data from a low-coverage whole genome sequence scan to conduct a genome-wide association study (GWAS) of an impulsivity phenotype in an American Indian community sample (n = 658). Demographic and clinical information were obtained using a semi-structured interview. Impulsivity was assessed using a scale derived from the Maudsley personality inventory that combines both novelty seeking and lack of planning items. The impulsivity score was tested for association with each variant adjusted for demographic variables, and corrected for ancestry and kinship, using emmax. Simulations were conducted to calculate empirical P-values. Genome-wide significant findings were observed for a variant 50-kb upstream from catenin cadherin-associated protein, alpha 2 (CTNNA2), a neuronal-specific catenin, in the REG gene cluster. A meta-analysis of GWAS had previously identified common variants in CTNNA2 as being associated with excitement seeking. A second locus upstream of nei endonuclease VIII-like 3 (NEIL3) on chromosome 4 also achieved genome-wide significance. The association between sequence variants in these regions suggests their potential roles in the genetic regulation of this phenotype in this population.

Phase bubbles and spatiotemporal chaos in granular patterns.

We use inelastic hard sphere molecular dynamics simulations and laboratory experiments to study patterns in vertically oscillated granular layers. The simulations and experiments reveal that phase bubbles spontaneously nucleate in the patterns when the container acceleration amplitude exceeds a critical value, about 7 g, where the pattern is approximately hexagonal, oscillating at one-fourth the driving frequency (f/4). A phase bubble is a localized region that oscillates with a phase opposite (differing by pi) to that of the surrounding pattern; a localized phase shift is often called an arching in studies of two-dimensional systems. The simulations show that the formation of phase bubbles is triggered by undulation at the bottom of the layer on a large length scale compared to the wavelength of the pattern. Once formed, a phase bubble shrinks as if it had a surface tension, and disappears in tens to hundreds of cycles. We find that there is an oscillatory momentum transfer across a kink, and the shrinking is caused by a net collisional momentum inward across the boundary enclosing the bubble. At increasing acceleration amplitudes, the patterns evolve into randomly moving labyrinthian kinks (spatiotemporal chaos). We observe in the simulations that f/3 and f/6 subharmonic patterns emerge as primary instabilities, but that they are unstable to the undulation of the layer. Our experiments confirm the existence of transient f/3 and f/6 patterns.

Plume dynamics in quasi-2D turbulent convection.

We have studied turbulent convection in a vertical thin (Hele-Shaw) cell at very high Rayleigh numbers (up to 7x10(4) times the value for convective onset) through experiment, simulation, and analysis. Experimentally, convection is driven by an imposed concentration gradient in an isothermal cell. Model equations treat the fields in two dimensions, with the reduced dimension exerting its influence through a linear wall friction. Linear stability analysis of these equations demonstrates that as the thickness of the cell tends to zero, the critical Rayleigh number and wave number for convective onset do not depend on the velocity conditions at the top and bottom boundaries (i.e., no-slip or stress-free). At finite cell thickness delta, however, solutions with different boundary conditions behave differently. We simulate the model equations numerically for both types of boundary conditions. Time sequences of the full concentration fields from experiment and simulation display a large number of solutal plumes that are born in thin concentration boundary layers, merge to form vertical channels, and sometimes split at their tips via a Rayleigh-Taylor instability. Power spectra of the concentration field reveal scaling regions with slopes that depend on the Rayleigh number. We examine the scaling of nondimensional heat flux (the Nusselt number, Nu) and rms vertical velocity (the Peclet number, Pe) with the Rayleigh number (Ra(*)) for the simulations. Both no-slip and stress-free solutions exhibit the scaling NuRa(*) approximately Pe(2) that we develop from simple arguments involving dynamics in the interior, away from cell boundaries. In addition, for stress-free solutions a second relation, Nu approximately nPe, is dictated by stagnation-point flows occurring at the horizontal boundaries; n is the number of plumes per unit length. No-slip solutions exhibit no such organization of the boundary flow and the results appear to agree with Priestley's prediction of Nu approximately Ra(1/3). (c) 1997 American Institute of Physics.

Linear stability analysis of a vertically oscillated granular layer.

We present a linear stability analysis of an oscillating granular layer, treating it as an isothermal incompressible fluid with zero surface tension, which undergoes periodic collisions with and separations from an oscillating plate. Because the viscosity of the granular layer is unknown, we use the experimental value of the critical acceleration for the transition from a flat to patterned layer as input for the theory, and use the analysis to calculate the granular viscosity and the wavelength of the most unstable mode. The wavelength compares favorably with the experimental pattern wavelength. Further, we find that the wavelengths are controlled by the viscosity of the granular layer.

Instability of the Kolmogorov flow in a soap film.

We examine the instability of a soap film flow driven by a time-independent force that is spatially periodic in the direction perpendicular to the forcing (Kolmogorov flow). Linear stability analysis of an idealized model of this flow predicts a critical Reynolds number R(c) is approximately equal to the square root of 2. In our soap film experiment, we find a critical value R(c) is approximately equal to 70. This discrepancy can be ascribed to frictional effects from viscous coupling of gas to the film, which is neglected in the idealized model. The kinematic viscosity of the surrounding gas and the thickness of gas layers on each side of the soap film are varied in the experiments to better understand these frictional effects. Our observations indicate that flow in the soap film cannot be decoupled from flow in the surrounding gas.

Transport coefficients for granular media from molecular dynamics simulations.

Under many conditions, macroscopic grains flow like a fluid; kinetic theory predicts continuum equations of motion for this granular fluid. In order to test the theory, we perform event-driven molecular simulations of a two-dimensional gas of inelastic hard disks, driven by contact with a heat bath. Even for strong dissipation, high densities, and small numbers of particles, we find that continuum theory describes the system well. With a bath that heats the gas homogeneously, strong velocity correlations produce a slightly smaller energy loss due to inelastic collisions than that predicted by kinetic theory. With an inhomogeneous heat bath, thermal or velocity gradients are induced. Determination of the resulting fluxes allows calculation of the thermal conductivity and shear viscosity, which are compared to the predictions of granular kinetic theory, and which can be used in continuum modeling of granular flows. The shear viscosity is close to the prediction of kinetic theory, while the thermal conductivity can be overestimated by a factor of 2; in each case, transport is lowered with increasing inelasticity.