Large-scale, reliable and robust SERS-active nanowire substrates prepared using porous alumina templates.

nanowire arrays for surface-enhanced Raman scattering applications. These nanowire films were synthesized via electrodeposition using porous alumina templates of varying order, thickness and pore diameters. Mechanical polishing has been shown to be a very effective method to prepare nanowire arrays with monodisperse length over comprehensively large dimensions. On the other hand, a convenient synthesis route has been suggested that allows the formation of nanoparticle rrays using very thin and/or large area porous alumina films. It is reckoned that even films with the smallest obtainable pore sizes can be utilized to prepare large area, fine nanoparticle arrays. Such arrays may also find use in other areas, such as solar cells and electrochemistry. Preliminary Raman experiments indicated that the nanowire/nanoparticle arrays are indeed surface-enhanced Raman scattering-active. Finally, the potentials offered by the reported processing methods for fabricating substrates with predictable and high Raman amplifications are discussed.

On the transformation behaviour, mechanical properties and biocompatibility of two niti-based shape memory alloys: NiTi42 and NiTi42Cu7.

The transformation behaviour, mechanical properties and cytotoxicity of a binary NiTi42 and a ternary NiTi42Cu7 alloy have been investigated. The transformation temperatures were determined via differential scanning calorimetry, the mechanical properties have been investigated in 3-point bending tests in the temperature range between 6 and 60 degrees C. The cytotoxicity tests were performed on both alloys in cultured epithelial cells from human gingiva. The cytotoxicity investigations included both MTT tests and morphological observations. It is shown that although the ternary alloy is characterised by a narrower hysteresis and superior mechanical properties, including fatigue resistance, its cytotoxicity is higher than that of the binary alloy. This is thought to arise from the release of copper ions in the medium, which upon atomic absorption spectroscopy measurements amount to approximately 2.8 microg cm(-2) for an incubation period of 7 days.

Torque transmission between square wire and bracket as a function of measurement, form and hardness parameters.

The aim of the study was to investigate the influence of cross section, edge geometry and structural hardness on torque transmission between square wire and bracket. For this purpose, 5 different brands of stainless steel square wire in 3 dimensions (0.016" x 0.016", 0.016" x 0.022" and 0.017" x 0.025") were inserted into edgewise brackets with a slot size of 0.018" and loaded with different torques (1 and 3 Ncm). The slot and wire geometries were analyzed by computer on ground specimens before and after loading. In addition, the Vickers hardness and micro-hardness of the unstressed and stressed metal surfaces were determined. While the slot size was very accurately maintained, the wire dimensions deviated downwards by an average of 10%. Torque transmission led to notching and bending-up phenomena on the bracket slot flanks. A torque loading of 3 Ncm increased the torque play of 0.016" x 0.022" wires by 3.6 degrees, and of 0.017" x 0.025" wires by 3.7 degrees. In the case of 0.016" x 0.016" wires, an effective torque transmission was no longer possible. The average Vickers hardness of the wires was 533 kp/mm2, and that of the brackets 145 kp/mm2. The micro-hardness in the deformation area of stressed internal slot walls increased with increasing load transmission from 204 to 338 kp/mm2. As a result of excessively small wire dimensions and plastic deformation of the brackets, a relatively large torque play occurs. Deformation and notching in the area of the internal slot walls are inconsistent with demands for recycling brackets. A standardization of bracket wire systems stating the actual torque play would be desirable.

Stimulation of peroxisomal palmitoyl-CoA oxidase activity by ciprofibrate in hepatic cell lines: comparative studies in Fao, MH1C1 and HepG2 cells.

The response of two rat cell lines, Fao and MH1C1, and one human cell line, HepG2, to the peroxisome proliferator ciprofibrate, was studied. Using a fluorometric assay for palmitoyl-CoA oxidase, the dose- and time-dependent increase of this enzymatic activity was determined. From the lowest concentration (100 microM) stimulation is evident in the two rat cell lines. In the Fao line, the activity was stimulated reaching a seven-fold increase over the control level at 250 microM after 72 h of treatment. In the MH1C1 line, the maximum stimulation, four- to five-fold, was obtained at 250 and 500 microM after 72 h. In the HepG2 cell line, activity increased two-fold at 250 microM after 72 h reaching a three-fold increase at 1000 microM after 48 h. Ciprofibrate was more toxic to Fao cells than to MH1C1 and HepG2 cells which is also the order of the acyl-CoA oxidase stimulation by ciprofibrate. These preliminary results suggest that the two rat cell lines are appropriate for investigating the induction of peroxisomal beta-oxidation enzymes and the expression of their genes. The HepG2 cell line is a complementary model for the study of interspecies differences in the response to peroxisomal proliferators and of the peroxisomal functions implied in the lipid metabolism of human liver.

18-hydroxylation in the Y-1 adrenal cell line: response to ACTH and to culture conditions.

The 18-hydroxylation of deoxycorticosterone in the Y-1 adrenal cell line was studied under various incubation and cell culture conditions and compared to 11 beta-hydroxylation. Repeated incubation of the substrate increased both 18- and 11 beta-hydroxylation in the Y-1 cells. Furthermore, both 18- and 11 beta-hydroxylation were increased with increased serum concentration and prolonged incubation time. While the increase in 11 beta-hydroxylation seemed to be independent of the type of serum, 18-hydroxylation was much more important in cells cultured in fetal or newborn calf serum supplemented medium than in those cultured in horse serum supplemented medium. As expected, ACTH treatment increased 11 beta-hydroxylation; however, it decreased 18-hydroxylation. The different regulation of these two hydroxylating pathways by ACTH, point to a heterogeneity of the cytochrome P-450(11) beta of the Y-1 cell line.

Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.

The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms of 20 alpha-dihydroaldosterone as the MO-TMS derivatives; that is, the 18-aldehyde, the 18,11 beta-hemiacetal, and the 11 beta:18,18:20 alpha-acetal. The possible origin of these different forms is discussed as a function of these results and of the results obtained by complementary analysis on high-performance liquid chromatography.

19-Hydroxylated steroids, new metabolites produced by the Y1 adrenal cell line.

The expression of 19-hydroxylase activity in the Y1 adrenal cell line is reported here for the first time. Two new metabolites from the incubation of deoxycorticosterone (DOC) with these cells, 19-hydroxy-20 alpha-dihydroDOC and 19-hydroxy-20 alpha-dihydrocorticosterone, have been identified. The most important of the two is the 11 beta,19-dihydroxylated metabolite, which is produced in smaller amounts than 18-hydroxy-20 alpha-dihydrocorticosterone. A third 19-hydroxylated metabolite was identified as 19-hydroxy-20 alpha-dihydroprogesterone, produced from the cholesterol in the serum supplemented medium. These results show that the cytochrome P-450(11)beta of this cell line expresses 19-hydroxylase activity in addition to 11 beta- and 18-hydroxylase activities, as do those of other species.

18-Hydroxylase activity in the Y1 adrenal cell line.

18-Hydroxylase activity, reported here for the first time in the mouse adrenal tumor cell line (Y1), was expressed in the metabolism of 11-deoxycorticosterone (DOC) and corticosterone (B). Detected after 24 h of incubation, it was more evident after 48 h and produced mostly 18-hydroxy-20 alpha-DHB from these exogenous substrates. However, 18-hydroxylation was quantitatively less significant than the metabolism of 20 alpha-reduction and 11 beta-hydroxylation (of DOC). The latter is also the predominant metabolism of progesterone in this cell line, during the conversion of cholesterol from the serum-supplemented culture media. The cytochrome P-450 11 beta activity of the Y1 cells is similar to that of the mouse in vivo which catalyzes the production of an 11 beta 18-dihydroxylated metabolite as the principal 18-hydroxylated steroid. It is different from that of other species, such as the rat and the bovine, both in terms of the ratio of 11 beta- to 18-hydroxylated metabolites and of the structure of these metabolites.