Flexible dielectric waveguides with powder cores

Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz using thin-wall polymer tubing filled with low-loss, high-dielectric-constant powders. Absorptive losses of the order of 10 dB/m were measured at 94 GHz. with nickel-aluminium titanate and barium tetratitanate powder in polytetrafluoroethylene (PTFE) lightweight electrical tubing. Bending losses at 94 GHz were negligible for curvature radii greater than 4 cm. M.H. Kuhn's (1974) theory of three-region cylindrical dielectric waveguide was used to calculate dispersion curves for the lower-order modes for several combinations of dimensions and dielectric constants. Good agreement was obtained between experimental and theoretical values of guide wavelength. A scheme is proposed for classifying hybrid modes of three-region guides based on the ratio |Ez/Hz|. For two-region guides, this reduces to E. Snitzer's (1961) familiar scheme

We thought it might encourage participation.” Using lottery incentives to improve LibQUAL+(TM) response rates among students

Libraries deploying the LibQUAL+™ survey can offer a lottery incentive and many do in the hope of increasing response rates. Other libraries may be prohibited from offering one because of Institutional Review Board restrictions, as is the case at [institution name]. We wanted to discover why libraries offer lottery incentives and what kinds and if they believe these incentives have a positive impact on their response rates. The responding libraries hold a general belief that lottery incentives are effective but base this on feeling rather than research. We examine what the literature says about lottery incentives and student populations

Iterative-deepening heuristic search for optimal and semi-optimal resource allocation

It is demonstrated that when iterative-deepening A asterisk (IDA asterisk) is applied to one type of resource allocation problem, it uses far less storage than A asterisk, but opens far more nodes and thus has unacceptable time complexity. This is shown to be due, at least in part, to the low-valued effective branching factor that is a characteristic of problems with real-valued cost functions. The semi-optimal, epsilon-admissible IDA asterisk sub epsilon search algorithm that the authors described was shown to open fewer nodes than both A asterisk and IDA asterisk with storage complexity proportional to the depth of the search tree

Halite and stable chlorine isotopes in the Zag H3-6 breccia

Zag is an H3-6 chondrite regolith breccia within which we have studied 14 halite grains ?3mm. The purity of the associated NaCl-H2O brine is implied by freezing characteristics of fluid inclusions in the halite and EPMA analyses together with a lack of other evaporite-like phases in the Zag H3-6 component. This is inconsistent with multistage evolution of the fluid involving scavenging of cations in the Zag region of the parent body. We suggest that the halite grains are clastic and did not crystallise in situ. Halite and water-soluble extracts from Zag have light Cl isotopic compositions, ?37-Cl = -1.4 to '2.8 �. Previously reported bulk carbonaceous chondrite values are approximately ?37-Cl = +3 to +4 �. This difference is too great to be the result of fractionation during evaporation and instead we suggest that Cl isotopes in chondrites are fractionated between a light reservoir associated with fluids and a heavier reservoir associated with higher temperature phases such as phosphates and silicates. Extraterrestrial carbon released at 600 degrees Celsius from the H3-4 matrix has ?13-C = -20 �, consistent with poorly graphitised material being introduced into the matrix rather than indigenous carbonate derived from a brine. We have also examined 28 other H-chondrite falls in order to ascertain how widespread halite or evaporite-like mineral assemblages are in ordinary chondrites. We did not find any more to add to Zag (H3-6) and Monahans (H5), which suggests that such highly soluble phases were not usually preserved on the parent bodies

Markov chain Monte Carlo analysis of Bianchi VII_h models

We have extended the analysis of Jaffe et al. to a complete Markov chain Monte Carlo (MCMC) study of the Bianchi type ${\rm VII_h}$ models including a dark energy density, using 1-year and 3-year Wilkinson Microwave Anisotropy Probe (WMAP) cosmic microwave background (CMB) data. Since we perform the analysis in a Bayesian framework our entire inference is contained in the multidimensional posterior distribution from which we can extract marginalised parameter constraints and the comparative Bayesian evidence. Treating the left-handed Bianchi CMB anisotropy as a template centred upon the `cold-spot' in the southern hemisphere, the parameter estimates derived for the total energy density, `tightness' and vorticity from 3-year data are found to be: $\Omega_{tot} = 0.43\pm 0.04$, $h = 0.32^{+0.02}_{-0.13}$, $\omega = 9.7^{+1.6}_{-1.5}\times 10^{-10}$ with orientation $\gamma = {337^{\circ}}^{+17}_{-23}$). This template is preferred by a factor of roughly unity in log-evidence over a concordance cosmology alone. A Bianchi type template is supported by the data only if its position on the sky is heavily restricted. The low total energy density of the preferred template, implies a geometry that is incompatible with cosmologies inferred from recent CMB observations. Jaffe et al. found that extending the Bianchi model to include a term in $\Omega_{\Lambda}$ creates a degeneracy in the $\Omega_m - \Omega_{\Lambda}$ plane. We explore this region fully by MCMC and find that the degenerate likelihood contours do not intersect areas of parameter space that 1 or 3 year WMAP data would prefer at any significance above $2\sigma$. Thus we can confirm that a physical Bianchi ${\rm VII_h}$ model is not responsible for this signature.Comment: 8 pages, 10 figures, significant update to include more accurate results and conclusions to match version accepted by MNRA

SCUBA Observations of NGC 1275

Deep SCUBA observations of NGC 1275 at 450 micron and 850 micron along with the application of deconvolution algorithms have permitted us to separate the strong core emission in this galaxy from the fainter extended emission around it. The core has a steep spectral index and is likely due primarily to the AGN. The faint emission has a positive spectral index and is clearly due to extended dust in a patchy distribution out to a radius of $\sim$ 20 kpc from the nucleus. These observations have now revealed that a large quantity of dust, $\sim$ 6 $\times$ 10$^7$ $M_\odot$, 2 orders of magnitude larger than that inferred from previous optical absorption measurements, exists in this galaxy. We estimate the temperature of this dust to be $\sim$ 20 K (using an emissivity index of $\beta$ = 1.3) and the gas/dust ratio to be 360. These values are typical of spiral galaxies. The dust emission correlates spatially with the hot X-ray emitting gas which may be due to collisional heating of broadly distributed dust by electrons. Since the destruction timescale is short, the dust cannot be replenished by stellar mass loss and must be externally supplied, either via the infalling galaxy or the cooling flow itself.Comment: 13 pages, 4 figures. Figure 4 is colou