Antireflective transparent covers for solar devices

Promising solutions for low-cost antireflective (AR) covers for solar receivers are based on the principle of mixing bulk material with air on a subwavelength scale in order to obtain very low effective refractive indices. Possibilities to achieve this are given by porous media and by periodic or stochastic subwavelength surface-relief structures. In this work, the mentioned approaches were investigated experimentally. Subwavelength surface-relief structures were embossed in organically modified sol–gel materials or in acrylic materials, and porous sol–gel coatings were produced by dip-coating. It is shown that the solar transmittance of a transparent cover can be improved by up to 6% with a porous sol–gel coating at normal incidence. This improvement of the solar transmittance increases with larger angles of incidence.     

Microstructure and ferroelectric properties of soft-doped sol–gel derived PZT/SKN fibers

Sol–gel derived PZT/SKN fibers with a final composition of 0.98(PbO)_1+z (Zr_0.53Ti_0.47)O₂-0.02Sr(K_0.25Nb_0.75)O₃ and a PbO content of z = +0.04 and +0.14 in the spinning sol were sintered at different temperatures. Fiber stoichiometry, phase content and microstructure as well as the physical properties of the fibers were investigated. A fully densified microstructure independent from the initial PbO content was obtained for fibers sintered at 950 °C or higher. Enhanced porosity was found only for fibers sintered at 900 °C. The densification of the fiber batches at the lower temperatures is dominated by solid state sintering, while liquid phase sintering is promoted by sintering at temperatures above 900 °C. TEM investigations confirmed the homogeneous nature of the PZT/SKN fibers devoid of compositional gradients. Typical dielectric permittivity is in the range of 650–1000. The ferroelectric hysteresis loops are well pronounced showing typical soft-doped behavior with remanent polarization values in the range of 15 and 34 μC/cm² and coercivities of about 1.9 V/μm.     

The E1A oncogene induces resistance to the effects of 1,25-dihydroxyvitamin D3 on inhibition of growth of mouse keratinocytes

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] inhibited DNA synthesis in transformed mouse keratinocytes (Pam212) in a time- and dose-dependent manner as measured by [3H]thymidine incorporation. To investigate the mechanism through which 1,25-(OH)2D3 acts, we examined its effects on Pam212 cells further transformed with the E1A oncogene. Here, we show that transformation of the cells with the E1A oncogene induced resistance to the effects of 1,25-(OH)2D3 on inhibition of growth of Pam212 cells. While 1,25-(OH)2D3 treatment increased the level of expression of vitamin D receptor mRNA 20-fold in parental cells, the E1A-transformed cells failed to express vitamin D receptor mRNA even after treatment with 1,25-(OH)2D3. Transfection of the E1A-transformed cell line with an expression construct encoding the vitamin D receptor restored receptor expression as well as the inhibition of growth by 1,25-(OH)2D3. These results suggest that one of the mechanisms for acquisition of 1,25-(OH)2D3 resistance induced by E1A may involve loss of vitamin D receptor inducibility by 1,25-(OH)2D3.     

Lentil aspiration pneumonia: radiographic and CT findings

We studied 10 healthy volunteers given itraconazole 200 mg orally, once daily or placebo for 4 days in a crossover study. i.v. fentanyl 3 micrograms kg-1 was given on day 4. Plasma concentrations of fentanyl were measured by radioimmunoassay and ventilatory frequency and peripheral arteriolar oxygen saturation were also measured. Fentanyl-induced subjective effects (drowsiness, itching, nausea, performance, feeling of drug effect) were measured by visual analogue scales. The pharmacokinetics and pharmacodynamics of fentanyl were similar after both itraconazole and placebo. Thus although itraconazole is a strong inhibitor of the cytochrome 3A enzymes responsible for metabolism of fentanyl in vitro, it did not affect the i.v. pharmacokinetics of fentanyl in humans.     

Review and Recent Development of Angle-Resolved Low-Coherence Interferometry for Detection of Precancerous Cells in Human Esophageal Epithelium

The combination of low-coherence interferometry with angle-resolved light scattering measurements has been shown to be a powerful method for determining the structure of cell nuclei within intact tissue samples. The nuclear morphology data have been used as a biomarker of neoplastic change in a wide range of settings. Here, we review the development of angle-resolved low-coherence interferometry (a/LCI) for assessing the health status of human esophageal epithelial tissues based on depth-resolved measurements of the morphology of cell nuclei. The design and implementation of clinical instrumentation are reviewed, and results from ex vivo human tissue measurements are presented to validate the capabilities of the technique. In addition to the review of earlier papers, new results are presented, which demonstrate the first application of a portable a/LCI system with a flexible endoscopic probe to assessing depth-resolved nuclear morphology in a clinical setting. High sensitivity for the detection of precancerous tissues is demonstrated.     

Bipolar strain hysteresis of poled composites with Nd–Mn-doped PZT fibres

Nd–Mn-doped PZT fibres were produced using the sol–gel process. The PZT was doped with 2 mol% neodymium and an amount of 1.1 mol% or 0.75 mol% manganese. The fibres were investigated with respect to microstructure, composition after sintering and phase content. Strain and polarisation were measured after imbedding the fibres in a polymer matrix.The resulting 1–3-composites were poled with constant electric field. Measurements of strain and polarisation were done using a sinusoidal voltage of high amplitude. Instead of a shifted strain hysteresis (butterfly loop) an asymmetric strain–field relation was observed. The asymmetry depends on the direction of the applied voltage. For the half wave with voltage parallel to former poling voltage the strain curve is linear. For the other half wave the strain curve inflates and there is a region with no change of strain. Possible explanations for the asymmetric strain behaviour are discussed.