Observations and a model of gravity-wave variability in the middle atmosphere

A major goal was to determine what portion of the gravity-wave frequency spectrum accounted for the majority of the momentum flux and divergence, as this has important implications for the middle atmosphere response. It was found that approx. 70% of the total flux and divergence was due to wave motions with observed periods less than 1 hour, consistent with expectations based on the shape of the observed gravity-wave spectrum (FrItts, 1984). This dominance of the momentum flux and divergence by high-frequency motions implies a potential for the modulation of those quantities by large-amplitude motions at lower frequencies. A second, striking aspect of the velocity and momentum flux data is its dramatic diurnal variability, particularly at certain levels. This variability is illustrated with the momentum flux, computed in 8-hr blocks. The dominant contributions here are due to waves with periods less than 1 hr. The variability with height and size of the mean square velocity in the west beam and the momentum flux, energed over the 3-day period. A detailed analysis of the various tidal motions present during this data interval was performed, and it was determined that variations in the zontal wind profile imposed by the diurnal tidal motion are probably responsible for the modulation of the gravity-wave amplitudes and momentum fluxes

Flow rate--pressure drop relation for deformable shallow microfluidic channels

Laminar flow in devices fabricated from soft materials causes deformation of the passage geometry, which affects the flow rate--pressure drop relation. For a given pressure drop, in channels with narrow rectangular cross-section, the flow rate varies as the cube of the channel height, so deformation can produce significant quantitative effects, including nonlinear dependence on the pressure drop [{Gervais, T., El-Ali, J., G\"unther, A. \& Jensen, K.\ F.}\ 2006 Flow-induced deformation of shallow microfluidic channels.\ \textit{Lab Chip} \textbf{6}, 500--507]. Gervais et. al. proposed a successful model of the deformation-induced change in the flow rate by heuristically coupling a Hookean elastic response with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbation approach for the flow rate--pressure drop relation in a shallow deformable microchannel using the theory of isotropic quasi-static plate bending and the Stokes equations under a lubrication approximation (specifically, the ratio of the channel's height to its width and of the channel's height to its length are both assumed small). Our result contains no free parameters and confirms Gervais et. al.'s observation that the flow rate is a quartic polynomial of the pressure drop. The derived flow rate--pressure drop relation compares favorably with experimental measurements.Comment: 20 pages, 6 figures; v2 minor revisions, accepted for publication in the Journal of Fluid Mechanic

The social geography of childcare: 'making up' the middle class child

Childcare is a condensate of disparate social forces and social processes. It is gendered and classed. It is subject to an excess of policy and political discourse. It is increasingly a focus for commercial exploitation. This is a paper reporting on work in progress in an ESRC funded research project (R000239232) on the choice and provision of pre-school childcare by middle class (service class) families in two contrasting London locations. Drawing on recent work in class analysis the paper examines the relationships between childcare choice, middle class fractions and locality. It suggests that on the evidence of the findings to date, there is some evidence of systematic differences between fractions in terms of values, perspectives and preferences for childcare, but a more powerful case for intra-class similarities, particularly when it comes to putting preferences into practice in the 'making up of a middle class child' through care and education

Chemical modification of poly(p-phenylene) for use in ablative compositions

Development of ablative materials based on modification of polyphenylene compounds is discussed. Chemical and physical properties are analyzed for application as heat resistant materials. Synthesis of linear polyphenylenes is described. Effects of exposure to oxyacetylene flame and composition of resultant char layer are presented

A simple construction of elliptic RR-matrices

We show that Belavin's solutions of the quantum Yang--Baxter equation can be obtained by restricting an infinite $R$-matrix to suitable finite dimensional subspaces. This infinite $R$-matrix is a modified version of the Shibukawa--Ueno $R$-matrix acting on functions of two variables.Comment: 6 page

Error analysis for Mariner Venus/Mercury 1973 conducted at the JPL Mesa west antenna range

Theoretical analysis and experimental data are combined to yield the errors to be used with antenna gain, antenna patterns, and RF cable insertion loss measurements for the Mariner Venus-Mercury 1973 Flight Project. These errors apply to measurements conducted at the JPL Mesa, West Antenna Range, on the high gain antenna, low gain antenna, and RF coaxial cables

Sensitivity Kernels for Flows in Time-Distance Helioseismology: Extension to Spherical Geometry

We extend an existing Born approximation method for calculating the linear sensitivity of helioseismic travel times to flows from Cartesian to spherical geometry. This development is necessary for using the Born approximation for inferring large-scale flows in the deep solar interior. In a first sanity check, we compare two $f-$mode kernels from our spherical method and from an existing Cartesian method. The horizontal and total integrals agree to within 0.3 %. As a second consistency test, we consider a uniformly rotating Sun and a travel distance of 42 degrees. The analytical travel-time difference agrees with the forward-modelled travel-time difference to within 2 %. In addition, we evaluate the impact of different choices of filter functions on the kernels for a meridional travel distance of 42 degrees. For all filters, the sensitivity is found to be distributed over a large fraction of the convection zone. We show that the kernels depend on the filter function employed in the data analysis process. If modes of higher harmonic degree ($90\lesssim l \lesssim 170$) are permitted, a noisy pattern of a spatial scale corresponding to $l\approx 260$ appears near the surface. When mainly low-degree modes are used ($l\lesssim70$), the sensitivity is concentrated in the deepest regions and it visually resembles a ray-path-like structure. Among the different low-degree filters used, we find the kernel for phase-speed filtered measurements to be best localized in depth.Comment: 17 pages, 5 figures, 2 tables, accepted for publication in ApJ. v2: typo in arXiv author list correcte