Lightweight composite reflector panels

The Hexel Corp. has produced additional composite panels, based on JPL designs, that: (1) have increased the panel size from 0.15 to 0.40 meters, (2) have improved the as-manufactured surface precision 3.0 to approx. 1.0 micron RMS, (3) have utilized different numbers of face sheet plys, (4) have improved face sheet fiber orientation, (5) have variations of aluminum honeycomb core cell size, (6) have combined graphite/epoxy (Gr/Ep) face sheets with E-glass honeycomb cores, and (7) have used standard aluminum core with face sheets composed of combinations of glass, Kevlar, and carbon fibers. Additionally, JPL has identified candidate alternate materials for the facesheets and core, modified the baseline polymer panel matrix material, and developed new concepts for panel composite cores. Dornier designed and fabricated three 0.6 meter Gr/Ep panels, that were evaluated by JPL. Results of both the Hexel and Dornier panel work were used to characterize the state-of-the-art for Gr/Ep mirrors

Inhomogeneous charge textures stabilized by electron-phonon interactions in the t-J model

We study the effect of diagonal and off-diagonal electron-phonon coupling in the ground state properties of the t-J model. Adiabatic and quantum phonons are considered using Lanczos techniques. Charge tiles and stripe phases with mobile holes (localized holes) are observed at intermediate (large) values of the diagonal electron-phonon coupling. The stripes are stabilized by half-breathing modes, while the tiles arise due to the development of extended breathing modes. Off-diagonal terms destabilize the charge inhomogeneous structures with mobile holes by renormalizing the diagonal coupling but do not produce new phases. Buckling modes are also studied and they seem to induce a gradual phase separation between hole rich and hole poor regions. The pairing correlations are strongly suppressed when the holes are localized. However, in charge inhomogeneous states with mobile holes no dramatic changes, compared with the uniform state, are observed in the pairing correlations indicating that D-wave pairing and moderate electron-phonon interactions can coexist.Comment: minor changes; to appear in Physical Review

Making automation pay - cost & throughput trade-offs in the manufacture of large composite components

The automation of complex manufacturing operations can provide significant savings over manual processes, and there remains much scope for increasing automation in the production of large scale structural composites. However the relationships between driving variables are complex, and the achievable throughput rate and corresponding cost for a given design are often not apparent. The deposition rate, number of machines required and unit production rates needed are interrelated and consequently the optimum unit cost is difficult to predict. A detailed study of the costs involved for a series of composite wing cover panels with different manufacturing requirements was undertaken. Panels were sized to account for manufacturing requirements and structural load requirements allowing both manual and automated lay-up procedures to influence design. It was discovered that the introduction of automated tape lay-up can significantly reduce material unit cost, and improve material utilisation, however higher production rates are needed to see this benefit

Charge Ordered RVB States in the Doped Cuprates

We study charge ordered d-wave resonating valence bond states (dRVB) in the doped cuprates, and estimate the energies of these states in a generalized $t-J$ model by using a renormalized mean field theory. The long range Coulomb potential tends to modulate the charge density in favor of the charge ordered RVB state. The possible relevance to the recently observed $4 \times 4$ checkerboard patterns in tunnelling conductance in high $T_c$ cuprates is discussed.Comment: 4 pages, 4 figures, 3 table

Quantitative bounds on morphodynamics and implications for reading the sedimentary record

Sedimentary rocks are the archives of environmental conditions and ancient planetary surface processes that led to their formation. Reconstructions of Earth’s past surface behaviour from the physical sedimentary record remain controversial, however, in part because we lack a quantitative framework to deconvolve internal dynamics of sediment-transport systems from environmental signal preservation. Internal dynamics of landscapes—a consequence of the coupling between bed topography, sediment transport and flow dynamics (morphodynamics)—result in regular and quasiperiodic landforms that abound on the Earth and other planets. Here, using theory and a data compilation of morphodynamic landforms that span a wide range of terrestrial, marine and planetary depositional systems, we show that the advection length for settling sediment sets bounds on the scales over which internal landscape dynamics operate. These bounds provide a universal palaeohydraulic reconstruction tool on planetary surfaces and allow for quantitative identification of depositional systems that may preserve tectonic, climatic and anthropogenic signals

Performance of Foundations and Retaining Structures

The design, construction, and performance of several building foundations and temporary earth retaining structures located in the downtown area of White Plains, New York are presented in this paper. High rise structures were supported on shallow mat or spread foundations bearing on erratic saturated alluvial silt and sand deposits. Additionally, the construction of two and three level underground parking structures required the use of cantilevered and braced excavation support systems to retain the adjacent streets and utilities. Several assumptions were required to design and predict the performance of the building foundations and retaining structures. The accuracy of these assumptions was verified through the use of precise field measurements during and after construction. The results of these field measurements and comparison with predicted values are presented and discussed

Prevalence of mixed genotype hepatitis C virus infections in the UK as determined by genotype‐specific PCR and deep sequencing

The incidence of mixed genotype hepatitis C virus infections in the UK is largely unknown. As the efficacy of direct acting antivirals is variable across different genotypes, treatment regimens are tailored to the infecting genotype, which may pose issues for the treatment of underlying genotypes within undiagnosed mixed genotype HCV infections. There is therefore a need to accurately diagnose mixed genotype infections prior to treatment. PCR-based diagnostic tools were developed to screen for the occurrence of mixed genotype infections caused by the most common UK genotypes, 1a and 3, in a cohort of 506 individuals diagnosed with either of these genotypes. The overall prevalence rate of mixed infection was 3.8% however this rate was unevenly distributed, with 6.7% of individuals diagnosed with genotype 3 harbouring genotype 1a strains and only 0.8% of samples from genotype 1a patients harbouring genotype 3 (p<0.05). Mixed infection samples consisted of a major and a minor genotype, with the latter constituting less than 21% of the total viral load and, in 67% of cases, less than 1% of the viral load. Analysis of a subset of the cohort by Illumina PCR-next generation sequencing resulted in a much greater incidence rate than obtained by PCR. This may have occurred due to the non-quantitative nature of the technique and despite the designation of false positive thresholds based on negative controls

Statin prescribing in Australia: socioeconomic and sex differences - A cross-sectional study

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included.OBJECTIVE: To assess if there are any differences in statin prescribing across Australia by socioeconomic status or sex and to relate prescribing rates to coronary heart disease (CHD) mortality rates. DESIGN: Cross-sectional study using data on statin prescribing by age, sex and patient postcode for the period May to December 2002. SETTING AND PARTICIPANTS: The Australian population, stratified by sex and quintile of Index of Relative Socio-Economic Disadvantage (IRSD). MAIN OUTCOME MEASURES: Age-standardised rates of statin scripts per 1000 population per month for each sex and IRSD quintile. RESULTS: 9.1 million prescriptions for statins were supplied between May and December 2002, for a total cost of $570 million. The age-standardised rates for statin prescribing in women varied from 56.9 (95% CI, 56.6–57.2) scripts per 1000 population per month in the most disadvantaged socioeconomic quintile through 53.4 (95% CI, 53.0–53.7), 50.3 (95% CI, 50.0–50.6), 48.4 (95% CI, 48.1–48.7) to 46.3 (95% CI, 46.0–46.6) in the least disadvantaged quintile. For men the figures were 52.6 (95% CI, 52.3–52.9), 50.9 (95% CI, 50.6–51.2), 48.8 (95% CI, 48.6–49.1), 47.7 (95% CI, 47.4–47.9), and 51.9 (95% CI, 51.6–52.2). There was a significant linear association between statin prescribing and CHD mortality by quintile of socioeconomic disadvantage in women (weighted least squares slope, 0.380; 95% CI, 0.366 to 0.395; P < 0.0001), but not in men (slope, −0.002; 95% CI, −0.010 to 0.006; P = 0.65). Conclusions: Our results suggest that in men there is either overprescribing of statins in the highest socioeconomic quintile or underprescribing in the lowest. Furthermore, contrary to expectation, women — relative to men — are prescribed statins at higher rates at lower levels of risk (using CHD deaths as a proxy MJA 2004; 180: 229–231 measure of risk).Nigel P Stocks, Philip Ryan, Heather McElroy and James Alla