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Effective medium theory was used to model optical properties in the 0.3 - 30 µm wavelength range for films comprised of nanoparticles of a transparent conducting oxide that are connected in a percolating network characterized by a filling factor f. The model is based on charge carrier density n[sub e] and resistivity ρ of the particles, and it enables analyses of these microscopic parameters upon posttreatment of the film. The theory was used to interpret data on spin coated layers consisting of nanoparticles of indium tin oxide (i.e., In[sub 2]O[sub 3]:Sn) with f close to the percolation limit. It showed that the as-deposited film contained nanoparticles with n[sub e] as large as ∼5 × 10[sup 20] cm[sup -3] and ρ≈5 × 10[sup -4] Ω cm. The model also provided important data on f, n[sub e], and ρ after heat treatment of the film. [ABSTRACT FROM AUTHOR]

Provides information on the influence of xenon buffer gas on the shape of the self-reversed sodium (Na)-D lines emitted by high-pressure Na arcs. Value of the Na resonance broadening constant; Influence of the collisional Na-D line-broadening by xenon; Method to derive values for the sodium, mercury and xenon pressures from experimental values of the wavelength positions.

Presents a study that determined the efficiency of second-harmonic generation at 425 nm in periodically segmented waveguides in undoped and 120 ppm scandium&sup3+;-doped c-axis-oriented KTiOPO[sub4] (KTP) plates. Representative measurements of ionic conductivity; Nonlinear characteristics of waveguides fabricated in undoped KTP; Information on crystal growth and waveguide fabrication.

Presents a study that examined the negative fluorescence in high-pressure sodium/mercury arcs. Methodology; Effect of the chopper frequency on the laser-induced fluorescence; Discussion on the reliability of using laser-induced fluorescence for diagnostics in high-pressure arcs.

Electrical and optical properties were investigated in porous thin films consisting of In2O3:Sn (indium tin oxide; ITO) nanoparticles. The temperature-dependent resistivity was successfully described by a fluctuation-induced tunneling model, indicating a sample morphology dominated by clusters of ITO nanoparticles separated by insulating barriers. An effective-medium model, including the effect of ionized impurity scattering, was successfully fitted to measured reflectance and transmittance. Post-deposition treatments were carried out at 773 K for 2 h in both air and vacuum. It is shown that vacuum annealing increases either the barrier width or the area between two conducting clusters in the samples and, furthermore, an extra optical absorption occurs close to the band gap. A subsequent air annealing then reduces the effect of the barriers on the electrical properties and diminishes the absorption close to the band gap. [ABSTRACT FROM AUTHOR]

Meiosis in seven interspecific Cucumis hybrids has been analysed i.a. in C. metuliferus × C. zeyheri, where the parents belong to different sections. In the triploid hybrids a remarkably high number of trivalents has been found. Additional data from literature on geographical distribution, cucurbitacins, flavonoid patterns, isozymes, C-banding, genome size, DNA amount and chloroplast DNA are used to discuss species relationships and evolution. The African cross-compatible group is divided into the Myriocarpus subgroup with the diploid species C. africanus, C. myriocarpus subsp. leptodermis and subsp. myriocarpus, and the Anguria subgroup with C. anguria, C. dipsaceus, C. ficifolius, C. prophetarum, C. zeyheri and all polyploids (except C. heptadactylus). It is argued that the Asian subg. Melo with x = 7 is derived from the African subg. Cucumis with x = 12; the latter contains all the polyploid species and has the most common basic chromosome number of the Cucurbitaceae. This phylogenetic advance is interpreted with concepts of the quantum model of evolution. [ABSTRACT FROM AUTHOR]

A two-part study was designed to investigate the efficacy of using UVC to prevent biofouling in the context of ship hull coatings. The first study determined the frequency of UVC required for a coating that does not have any additives (epoxy). It was found that 1 min/day was effective at preventing hard fouling but not biofilm development. The second study addressed several variables: coating type (epoxy, copper, fouling release), frequency of UVC (no exposure, continuous exposure, 1min/6h, 1 min/day), and distance from the lamp (25 and 50 mm). Continuous UVC exposure resulted in no biofouling settlement but it did damage the copper coating. Intermittent UVC exposure was effective at preventing biofouling recruitment to both the copper and the fouling release coatings. Variations were observed with regards to the fouling composition, especially biofilms, sedimentary tubeworms and barnacles, suggesting tolerances within the community.

It is now well established that epidermis, like many other tissues, contains a phospholipase A2 that is responsible for the initiation of the arachidonic acid cascade. Here we report that human epidermis also contains a second, quite distinct enzyme of the phospholipase A2 group, which is unique in its extreme activity against phospholipids in true solution. It also differs from the classic cutaneous enzyme in that (a) its activity is not reduced by pretreatment of the skin with corticosteroids in vivo nor by treatment of the epidermal homogenate with alkaline phosphatase in vitro, and (b) its activity is reduced, rather than increased, in the lesions of inflammatory diseases such as psoriasis. The enzyme seems to occur mainly in fully differentiated keratinocytes, its level being low in the basal cell layer of epidermis and in keratinocytes cultured in vitro. On the basis of these observations, we suggest that this new phospholipase A2 is responsible for the degradation of phospholipids that accompanies the terminal keratinization process.

We describe a new approach to the quantification of tissue phospholipase A2 based on the observation that the Vmax is increased by several orders of magnitude in the presence of high concentrations of dimethyl sulphoxide. The enzyme from human skin showed optimal activity at 30% dimethyl sulphoxide and pH 6-7.5, and had an absolute dependence on Ca2+ (apparent Km = 1.4 mmol/l). The relationship between reaction velocity and substrate concentration did not follow Michaelis-Menten kinetics. The enzyme was inhibited by p-bromophenacyl bromide, half-maximal inhibition occurring at 2.4 mumol/l. Surprisingly, assay of specimens of various human tissues indicated that, with the exception of pancreas, skin contained higher levels of phospholipase A2 activity than any other tissue investigated. Equally surprising was that primate skin (in particular human) seems considerably more active than that of other mammals. Speculatively, these findings may be related to the high levels of free fatty acids occurring on the skin surface.