No abstract

We report the development of a diffuse reflecting material with measured reflectivity values as high as 0.99919 at 532 nm and 0.99686 at 266 nm. This material is a high-purity fumed silica, or quartz powder, with particle sizes on the order of 40 nm. We demonstrate that this material can be used to produce surfaces with nearly Lambertian behavior, which in turn can be used to form the inner walls of high-reflectivity integrating cavities. Light reflecting off such a surface penetrates into the material. This means there will be an effective "wall time" for each reflection off the walls in an integrating cavity. We measure this wall time and show that it can be on the order of several picoseconds. Finally, we introduce a technique for absorption spectroscopy in an integrating cavity based on cavity ring-down spectroscopy. We call this technique integrating cavity ring-down spectroscopy.

No abstract

Clean water is paramount to human health. In this article, we present a technique for detection of trace amounts of human or animal waste products in water using fluorescence emission cavity-enhanced spectroscopy. The detection of femtomolar concentrations of urobilin, a metabolic byproduct of heme metabolism that is excreted in both human and animal waste in water, was achieved through the use of an integrating cavity. This technique could allow for real-time assessment of water quality without the need for expensive laboratory equipment.water contamination | fluorescence spectroscopy | femtomolar detection

No abstract

A new technique using nickel-chromium wire, called the NiCr (Nichrome R ) wire technique, has been presented in a rst paper describing the technique [1]. This second paper focuses on the results obtained when this new technique is applied to ballistic fabrics. Strain distributions on the layer impacted, as well as in dierent layers, are presented. An energy balance based on the strains is shown to provide reasonable values for the elastic energy stored by the yarns. Failure times of the rst layer as a function of impact velocity are discussed and a simple momentum balance is shown to predict well the deection history of the fabric. Ultra-high-speed photography and high-speed videos allowed recording of fabric deection vs. time.The combination of the four diagnostic techniques, including X-rays, delivers a very complete picture of the impact mechanics in fabrics, both for early-time and latetime phenomena.

No abstract

No abstract