Paraxial ray optics cloaking

Despite much interest and progress in optical spatial cloaking, a three-dimensional (3D), transmitting, continuously multidirectional cloak in the visible regime has not yet been demonstrated. Here we experimentally demonstrate such a cloak using ray optics, albeit with some edge effects. Our device requires no new materials, uses isotropic off-the-shelf optics, scales easily to cloak arbitrarily large objects, and is as broadband as the choice of optical material, all of which have been challenges for current cloaking schemes. In addition, we provide a concise formalism that quantifies and produces perfect optical cloaks in the small-angle (`paraxial') limit

Paraxial full-field cloaking

We complete the `paraxial' (small-angle) ray optics cloaking formalism presented previously [Choi and Howell, Opt. Express 22, 29465 (2014)], by extending it to the full-field of light. Omnidirectionality is then the only relaxed parameter of what may be considered an ideal, broadband, field cloak. We show that an isotropic plate of uniform thickness, with appropriately designed refractive index and dispersion, can match the phase over the whole visible spectrum. Our results support the fundamental limits on cloaking for broadband vs. omnidirectionality, and provide insights into when anisotropy may be required

Work and the Disability Transition in 20th Century America

Using data from Union Army pensioners and from the National Health Interview Surveys, we estimate that work-disability among white males aged 45-64 was 3.5 times as high in the late 19th century than at the end of the 20th century, including a decline and flattening of the age-profile since 1970. We present a descriptive model of disability that can account for a) the secular decline in prevalence; b) changes in slope of the age-profile; and c) periods of increasing prevalence. The high level and relatively flat slope of the historical disability age-profile is consistent with the early onset of chronic conditions and with high mortality associated with a subset of those conditions. We show that many common conditions in the 19th century have been either eliminated, delayed to later ages, or rendered less disabling by treatment innovations and the transformation of the workplace. These improvements have swamped the effect of declining mortality, which put upward pressure on disability prevalence. Given the low rate of mortality prior to age 65, technological changes will likely induce further reductions in work-disability, though recent increases in the prevalence of asthma and obesity may eventually work against this trend.

Letter from Joseph Howell

Letter concerning the bill that went to the House of Representatives concerning the National Educational Association

Quadruple Simulations of Thermographic Inspections of Impacted Composites

Thermography has been shown to be a viable technique for inspection of composites. Impact damage in composites typically contains multiple overlapping delaminations at different depths. Understanding the limitations of the thermographic inspection is enhanced by performing simulations of the technique. Most simulations of composite thermographic inspections have focused on simulations of a single delamination at a fixed depth. The quadrupole method has been shown as a viable technique for rapid three-dimensional thermographic simulations of a delamination. This method is expanded to enable rapid simulation of multiple overlapping delaminations at different depths. Quadrupole simulations are compared to finite element simulations of multiple delaminations at different depths. The simulations are also compared to the thermographic measurements on impacted composites where shape and depth of the delaminations are known from x-ray computed tomography data

Financing -- A Major Problem of Small Business

It is imperative that a definitive study of small business include a discourse on financing.\u27 Generally, the first consideration of a prospective entrepreneur is the availability of sufficient capital, borrowed or paid-in, to support the activity of his business. Of paramount importance, however, to those who attempt to assess the prospects of survival and future growth of a company is the recognition that all considerations are secondary to the human factor. The careful banker, while requiring collateral to secure a loan, depends on his estimation of the applicant\u27s personality traits. While the adequacy of capital contributes to the success of a business, without alert, imaginative,and competent management, the chances for survival are slight. In essence the problems of financing a small business are problems of personalities, mutual confidence, and capacity; they are not merely problems of percentages, figures or working capital

Exploring Infrared Properties of Giant Low Surface Brightness Galaxies

Abridged: We present analysis of Spitzer Space Telescope observations of the three low surface brightness (LSB) optical giant galaxies Malin 1, UGC 6614 and UGC 9024. Mid- and far-infrared morphology, spectral energy distributions, and integrated colors are used to derive the dust mass, dust-to-gas mass ratio, total infrared luminosity, and star formation rate (SFR). The 8 micron images indicate that polycyclic aromatic hydrocarbon molecules are present in the central regions of all three metal-poor LSB galaxies. The diffuse optical disks of Malin 1 and UGC 9024 remain undetected at mid- and far-infrared wavelengths. The dustiest of the three LSB galaxies, UGC 6614, has infrared morphology that varies significantly with wavelength. The 8 and 24 micron emission is co-spatial with H\alpha emission previously observed in the outer ring of UGC 6614. The estimated dust-to-gas ratios, from less than 10^{-3} to 10^{-2}, support previous indications that the LSB galaxies are relatively dust poor compared to the HSB galaxies. The total infrared luminosities are approximately 1/3 to 1/2 the blue band luminosities, suggesting that old stellar populations are the primary source of dust heating in these LSB objects. The SFR estimated from the infrared data ranges ~0.01-0.88 M_sun yr^{-1}, consistent with results from optical studies.Comment: Accepted in ApJ (2007, July 20 issue), 34 pages, 10 postscript figures, 2 table

A Case Study Of Determinants Of An Effective Cloud Computing Strategy

The cloud continues to be an area of information systems that is being adopted cautiously by business firms. The authors of this study analyze factors that can determine the effectiveness of a cloud strategy as firms invest in this computing method. The authors examine cloud computing strategy from a detailed case study and statistical interpretation of a sample of projects of firms and organizations. The findings impute that technical factors are driving cloud computing projects more than procedural factors and that projects in the study exhibit less discipline in methodology than might otherwise be helpful in enabling an initial cloud computing strategy. This study contributes a framework for a prudent cloud computing strategy that can help firms as they further invest in this method of technology

Multicolour Entanglement

The entanglement of squeezed light beams is critical for quantum optical applications, but has so far been achieved with only two light beams. Now, researchers have surpassed this restriction and achieved entanglement with three beams of different colours. They also report a finite loss level for disentanglement of one beam from the other two

Paraxial Full-Field Cloaking

We complete the ‘paraxial’ (small-angle) ray optics cloaking formalism presented previously [Opt. Express 22, 29465 (2014)], by extending it to the full-field of light. Omnidirectionality is then the only relaxed parameter of what may be considered an ideal, broadband, field cloak. We show that an isotropic plate of uniform thickness, with appropriately designed refractive index and dispersion, can match the phase over the whole visible spectrum. Our results support the fundamental limits on cloaking for broadband vs. omnidirectionality, and provide insights into when anisotropy may be required