Laser Treatment of Nanoparticulated Metal Thin Films for Ceramic Tile Decoration.

This paper presents a new method for the fabrication of metal-like decorative layers on glazed ceramic tiles. It consists of the laser treatment of Cu thin films prepared by electron-beam evaporation at glancing angles. A thin film of discontinuous Cu nanoparticles was electron-beam-evaporated in an oblique angle configuration onto ceramic tiles and an ample palette of colors obtained by laser treatment both in air and in vacuum. Scanning electron microscopy along with UV-vis-near-IR spectroscopy and time-of-flight secondary ion mass spectrometry analysis were used to characterize the differently colored layers. On the basis of these analyses, color development has been accounted for by a simple model considering surface melting phenomena and different microstructural and chemical transformations of the outmost surface layers of the samples.

High speed inscription of uniform, large-area laser-induced periodic surface structures in Cr films using a high repetition rate fs laser.

We report on the fabrication of laser-induced periodic surface structures in Cr films upon high repetition rate fs laser irradiation (up to 1 MHz, 500 fs, 1030 nm), employing beam scanning. Highly regular large-area (9 cm2) gratings with a relative diffraction efficiency of 42% can be produced within less than 6 min. The ripple period at moderate and high fluences is 0.9 µm, with a small period of 0.5 µm appearing at lower energies. The role of the irradiation parameters on the characteristics of the laser-induced periodic surface structures (LIPSS) is studied and discussed in the frame of the models presently used. We have identified the polarization vector orientation with respect to the scan direction as a key parameter for the fabrication of high-quality, large-area LIPSS, which, for perpendicular orientation, allows the coherent extension of the sub-wavelength structure over macroscopic distances. The processing strategy is robust in terms of broad parameter windows and applicable to other materials featuring LIPSS.

Prevalence and distribution of HHV-8 in different subpopulations, with and without HIV infection, in Spain.

OBJECTIVE: To estimate the seroprevalence of HHV-8 in several Spanish subpopulations with different risk levels of acquiring HIV-1 infection and from different geographical regions. DESIGN: Cross-sectional seroprevalence study. METHODS: A total of 1699 serum samples from blood donors (613), children under the age of 12 years (100), injecting drug users (IDU) (382), heterosexuals attending a sexually transmitted disease (STD) clinic (273) and homosexual men attending a STD clinic or a HIV-based hospital unit (331) were analysed for anti-HHV-8 antibodies. The presence of antibodies against HHV-8 was tested with an indirect immunofluorescence assay (IFA). A subsample of HHV-8-positive samples was also tested for antibody titre against HHV-8. RESULTS: The overall seroprevalence of antibodies against HHV-8 for the blood donor population was 6.5% (7.0% in Andalusia, 8.0% in Catalonia and 4.5% in the Basque Country). None of the children tested positive for HHV-8. The HHV-8 prevalence was 86.7% in HIV-positive homosexual men and 28.0% in HIV-negative homosexual men (P < 0.001). Of heterosexual men attending STD clinics, 17.2% tested positive for HHV-8; 11.5% of IDU tested positive for HHV-8. HHV-8 antibody titres by groups parallel the distribution of HHV-8 prevalence. No association between HHV-8 antibody titres and CD4 cell count or HIV viral load was identified. CONCLUSIONS: The HHV-8 prevalence among blood donors in Spain is higher than in Northern Europe and the USA, but is similar to that in Northern Italy. The distribution of HHV-8 is compatible with a sexually transmitted agent. The distribution of HHV-8 correlates with that of Kaposi's sarcoma but factors other than HHV-8 seem to explain the Kaposi sarcoma distribution.

Production of some enzymes in the autolysis of the white-rot fungus Coriolus versicolor in fermenter.

The autolysis and production of some extracellular enzymes by Coriolus versicolor was studied in submerged cultures. After 48 days of incubation the fungus lost 31% of its maximum dry weight. 1.3-beta-glucanase was excreted at the beginning of autolysis and proteases were present during the course of the experiment. On the other hand, laccase was produced in very small amount in the first days of incubation, reaching the maximum activity at the 8th-day of autolysis.

The kinetics of the autolytic phase of growth in cultures of Aspergillus niger.

The kinetics of the autolytic phase of growth in cultures of Aspergillus niger has been studied. Two different autolytic periods could be distinguished. One, consisting of a rapid (exponential) loss (62%) of mycelial weight, occurred between 36 and 117 hours of incubation. A second, consisting of a slow autolysis, occurred between the 117th and the 190th hour of incubation; the mycelial loss here being 5%. Based on the degree of autolysis (alpha = 67.0%), 92.5% and 7.5% are lost during the first and the second autolytic periods, respectively.

Liberation of electrolytes during the induced autolysis of Aspergillus niger.

The induced autolysis of Aspergillus niger was studied by suspending mycelia in water; after 120 hours there was a 50% reduction in dry weight. The kinetics of the liberation of electrolytes during autolysis was studied, and a positive correlation was observed between the electrical conductivity of the autolizate and autolysis loss of mycelium dry weight.

Lytic enzyme activity in autolysing mycelium of Aspergillus niger.

We have studied changes in the activity of some lytic enzymes contained in mycelium of Aspergillus niger in cultures relative to the autolytic phase of growth. Acid phosphatase, polygalacturonidase and alpha-amylase activity reached its highest level (40.7, and 8 U/sample, respectively) at the initiation of the autolytic phase of growth. 1.3-beta-Glucanase and beta-N-acetylglucosaminidase reached its highest level (3.5 and 2 U/sample, respectively) during the first days of autolysis. Alkaline phosphatase, cellulase, invertase, esterase, chitinase and proteolytic activity is also present in autolysing mycelium of A. niger, though comparatively low. Their maximum activity coincided with the beginning of the autolytic phase of growth. In all enzymes studied here, as autolyis proceeded, enzyme activity decreased by about 90%. Only esterase activity remained nearly constant throughout the whole period of autolysis described here.

Cell wall degradation in the autolysis of filamentous fungi.

A systematic study on autolysis of the cell walls of fungi has been made on Neurospora crassa, Botrytis cinerea, Polystictus versicolor, Aspergillus nidulans, Schizophyllum commune, Aspergillus niger, and Mucor mucedo. During autolysis each fungus produces the necessary lytic enzymes for its autodegradation. From autolyzed cultures of each fungus enzymatic precipitates were obtained. The degree of lysis of the cell walls, obtained from non-autolyzed mycelia, was studied by incubating these cell walls with and without a supply of their own lytic enzymes. The degree of lysis increased with the incubation time and generally was higher with a supply of lytic enzymes. Cell walls from mycelia of different ages were obtained. A higher degree of lysis was always found, in young cell walls than in older cell walls, when exogenous lytic enzymes were present. In all the fungi studied, there is lysis of the cell walls during autolysis. This is confirmed by the change of the cell wall structure as well as by the degree of lysis reached by the cell wall and the release of substances, principally glucose and N-acetylglucosamine in the medium.

Lytic enzymes in the autolysis of Schizophyllum commune with special reference to 1,3-alpha-glucanase.

In the autolytic phase of growth Schizophyllum commune lost 62% of its dry weight in 70 days of incubation. The variations in the activity of some lytic enzymes were studied in the culture fluid and mycelial extracts during growth and autolysis of this fungus. The enzymes 1,3-beta-glucanase (exoglucanase), 1,3(4)-beta-glucanase (endoglucanase), alpha-amylase, and invertase behaved in the same way in culture fluid and mycelial extract, but their activities were much higher in the culture fluid. The enzyme activities increased during autolysis, but then decreased at the end of this period except in the case of alpha-amylase which remained high. It was only possible to detect 1,6-beta-glucanase, cellulase, and polygalacturonase activities at certain times during the autolytic phase of growth. The enzyme chitinase was not detected and 1,3-alpha-glucanase (S-glucanase) occurred in the mycelial extract at a higher concentration than in the culture fluid. A decrease in the activity of this enzyme in the mycelial extract and an increase in the culture fluid occurred during autolysis. The enzyme 1,3-alpha-glucanase exhibited two optima pH, one at 6.0 and the other at 8.0. The Km value for the latter was 0.02 M at pH 5.5 in borate-citrate-phosphate buffer.

Lytic enzymes in the autolysis of filamentous fungi.

The degrees of autolysis attained by five different genera of filamentous fungi during an incubation period of 60 days, under the same culture conditions were: 87.3% for Penicillium oxalicum; 65.9% for Neurospora crassa; 62.7% for Polystictus versicolor; 51.7% for Aspergillus niger and 23.5% for Nectria galligena. N. crassa, A. niger and P. versicolor reached the end of the autolysis during this incubation period (60 days), whereas P. oxalicum and N. galligena did not. The excretion of the lytic enzymes beta-N-acetylglucosaminidase, beta -1-3 glucanase, chitinase, invertase and acid phosphatase into the culture medium during growth and autolysis was investigated. The excretion of these enzymes was consistent with the degree of autolysis reached, the maximum excretion belonging to P. oxalicum and the minimum to N. galligena. The N. crassa invertase was excreted into the culture liquid at levels very much higher than the other enzymes studied, and at levels very much higher than the invertases excreted by the other fungi.

Liberation of protoplasts from mycelium of Neurospora crassa by means of enzymes obtained from autolyzed cultures of this fungus.

Spherical protoplast-like structures were released from Neuropsora crassa mycelia under the influence of cell-wall-lytic enzymes obtained from autolyzed cultures of this fungus, in 50 mM borate-citrate-phosphate buffer, pH 5.5 with 0.5-0.8 M mannitol for appropriate osmotic pressure. The protoplasts retain their morphological aspect for several days at 4 C, or for a longer time when they are washed by centrifugation and incubated with 0.8 M mannitol. The free protoplasts are sensitive to osmotic shock and lyse immediately when placed in distilled water; the vacuoles and other cytoplasmatic material remain intact for some time.