Underwater optical wireless communications : depth dependent variations in attenuation

Depth variations in the attenuation coefficient for light in the ocean were calculated using a one-parameter model based on the chlorophyll-a concentration Cc and experimentally-determined Gaussian chlorophyll-depth profiles. The depth profiles were related to surface chlorophyll levels for the range 0–4  mg/m2, representing clear, open ocean. The depth where Cc became negligible was calculated to be shallower for places of high surface chlorophyll; 111.5 m for surface chlorophyll 0.8<Cc<2.2  mg/m3 compared with 415.5 m for surface Cc<0.04  mg/m3. Below this depth is the absolute minimum attenuation for underwater ocean communication links, calculated to be 0.0092  m−1 at a wavelength of 430 nm. By combining this with satellite surface-chlorophyll data, it is possible to quantify the attenuation between any two locations in the ocean, with applications for low-noise or secure underwater communications and vertical links from the ocean surface

Sow and Litter Performance of Individual Crate and Group Hoop Barn Gestation Housing Systems: A Progress Report

The effects of swine gestation housing on sow and litter performance were evaluated at the Iowa State University Lauren Christian Swine Research and Demonstration Farm near Atlantic, IA. The gestation housing systems were 1) individual gestation crates in a mechanically ventilated, partially slatted floor, manure flush confinement building (CRATE); and 2) group pens in deep-bedded, naturally ventilated hoop structures (HOOP). The HOOP sows were fed in individual feed stalls. The sow genotypes were 1/4 Hampshire x 1/2 Yorkshire x 1/4 Landrace. Farrowing occurred every 2 weeks throughout the year

Pultrusion Die Assembly

This invention relates generally to pultrusion die assemblies, and more particularly, to a pultrusion die assembly which incorporates a plurality of functions in order to produce a continuous, thin composite fiber reinforced thermoplastic material. The invention is useful for making high performance thermoplastic composite materials in sheets which can be coiled on a spool and stored for further processing

Hotel Asset and Equity Risk Before, During, and After the Global Financial Crisis

In this paper, we use asset betas and equity betas over the period January 2000 through December 2015 to investigate the operating and financial risk of hotel industry REITs and C-Corps. We conclude that, on average over our sample period, the operating risk of C-Corps exceeds that of REITs. One interpretation of this result is that management contracts between REITs and C-Corps allocate more operating risk to C-Corps than to REITs. We also find that, on average, during our sample period, the equity betas of C-Corps exceed those of REITs. However, the difference between the average equity risk of the two sectors is much smaller than is the sectors’ difference in operating risk. Because equity betas capture both operating and financial risk, these results imply that REITs have significantly less operating risk than C-Corps and offset their lower business risk with higher financial leverage. During the global financial crisis, operating risk increases in both hotel industry subsectors, and the amount by which C-Corp asset betas exceed REIT asset betas is roughly proportionate to that observed in noncrisis periods. During the financial crisis, however, REITs experienced a greater increase in finan- cial leverage than did C-Corps, with the result being that the normal relation reverses, i.e., during the global financial crisis, REIT average equity betas significantly exceeded the average equity betas of C-Corps

Virtual histology of transgenic mouse embryos for high-throughput phenotyping.

Journal ArticleA bold new effort to disrupt every gene in the mouse genome necessitates systematic, interdisciplinary approaches to analyzing patterning defects in the mouse embryo. We present a novel, rapid, and inexpensive method for obtaining high-resolution virtual histology for phenotypic assessment of mouse embryos. Using osmium tetroxide to differentially stain tissues followed by volumetric X-ray computed tomography to image whole embryos, isometric resolutions of 27 mum or 8 mum were achieved with scan times of 2 h or 12 h, respectively, using mid-gestation E9.5-E12.5 embryos. The datasets generated by this method are immediately amenable to state-of-the-art computational methods of organ patterning analysis. This technique to assess embryo anatomy represents a significant improvement in resolution, time, and expense for the quantitative, three-dimensional analysis of developmental patterning defects attributed to genetically engineered mutations and chemically induced embryotoxicity

Temporal Evolution of Financial Market Correlations

We investigate financial market correlations using random matrix theory and principal component analysis. We use random matrix theory to demonstrate that correlation matrices of asset price changes contain structure that is incompatible with uncorrelated random price changes. We then identify the principal components of these correlation matrices and demonstrate that a small number of components accounts for a large proportion of the variability of the markets that we consider. We then characterize the time-evolving relationships between the different assets by investigating the correlations between the asset price time series and principal components. Using this approach, we uncover notable changes that occurred in financial markets and identify the assets that were significantly affected by these changes. We show in particular that there was an increase in the strength of the relationships between several different markets following the 2007--2008 credit and liquidity crisis.Comment: 15 pages, 10 figures, 1 table. Accepted for publication in Phys. Rev. E. v2 includes additional section