Spray method: Dependence of deposition efficiency on substrate temperature

Application of the spray method for the deposition of thin films has shown that the deposition efficiency is a decreasing function of the substrate temperature. The forces which determine the path and the time the droplets take to go from the nozzle to the substrate are analyzed. A theoretical curve of the deposition efficiency as a function of the substrate temperature has been obtained by a successive-approximation method. Experimental values of the efficiency obtained from the growth rate of the films are always a function of the substrate temperature. The good agreement of the theoretical curve with the experimental data confirms the validity of the method applied for our analysis.Work supported by Ministero della Universitá e della Ricerca Scientifica and Centro Regionale Ricerche Nucleari e Struttura della Materia     

Electrocatalytic oxidation of reduced nicotinamide coenzymes by graphite electrodes modified with an adsorbed phenoxazinium salt,meldola blue

Meldola Blue (7-dimethylamino-1,2-benzophenoxazine) can be adsorbed on graphite to give chemically modified electrodes. The electrochemical redox reactions of the phenoxazine are fairly reversible at low coverages with an E′^o of ?175 mV vs. SCE at pH 7.0. The electrode was most stable in acid solutions, at pH 6.0 its electrochemical activity decreased by 15% during 2h. The adsorbed compound mediated electron transfer in the electrocatalytic oxidation of the nicotinamide coenzymes (NADH and NADPH). The formation of a charge transfer complex between Meldola Blue and the coenzyme is demonstrated by experiments with a rotating disk electrode. The complex decomposes in a rate limiting step (k₊₂=30 s^?1) to the oxidized coenzyme and the reduced Meldola Blue. The latter can be reoxidized in a fast electrochemical step. The overall result is an electrocatalytic oxidation at a voltage which is about 500 mV lower than at an unmodified electrode.     

Measurement of toxic volatile organic compounds in indoor air of semiconductor foundries using multisorbent adsorption/thermal desorption coupled with gas chromatography-mass spectrometry

A method for the qualitative and quantitative analysis of volatile organic compounds (VOCs) in the air of class-100 clean rooms at semiconductor fabrication facilities was developed. Air samples from two semiconductor factories were collected each hour on multisorbent tubes (including Carbopack B, Carbopack C, and Carbosieve SIII) with a 24-h automatic active sampling system and analyzed using adsorption/thermal desorption coupled with gas chromatography-mass spectrometry. Experimental parameters, including thermal desorption temperature, desorption time, and cryofocusing temperature, were optimized. The average recoveries and the method detection limits for the target compounds were in the range 94-101% and 0.31-0.89 ppb, respectively, under the conditions of a 1 L sampling volume and 80% relative humidity. VOCs such as acetone, isopropyl alcohol, 2-heptanone, and toluene, which are commonly used in the semiconductor and electronics industries, were detected and accurately quantified with the established method. Temporal variations of the analyte concentrations observed were attributed to the improper use of organic solvents during operation.     

Determination of remoxipride in human plasma and urine by reversed-phase ion-pair high-performance liquid chromatography.

A sensitive method is described for the measurement of remoxipride in human plasma and urine. Remoxipride and its internal standard are extracted from plasma or urine at pH 12 with a mixture of hexane and methyl tert.-butyl ether. After washing the organic phase with base, the compounds are extracted into acid and analyzed on a C18 column with ultraviolet detection at 214 nm. The mobile phase is composed of acetonitrile and aqueous buffer (sodium perchlorate and phosphoric acid, pH 1.7). The limits of reliable quantitation for remoxipride are 12.5 and 50 ng/ml for plasma and urine, respectively. The run times are 6 min for plasma and 3 min for urine. The method has been successfully used to assay remoxipride clinical study samples. This mobile phase has also been successfully applied to the analysis of other basic drugs such as cimetidine, codeine, diltiazem and quinidine with minor modifications.     

Micelles of SDS Surfactants in Concentrated NaCl Solutions

We investigated the aggregation behavior of rod-like micelles of sodium dodecyl sulfate (SDS) in concentrated NaCl solution by quasi-elastic light scattering (QLS) and viscosity measurement over a range of temperature (25 °C to 50 °C) and NaCl concentration. The reduced viscosity of aqueous SDS in the presence of NaCl has been measured by an Ubbelohde-type capillary viscometer. We show mean hydrodynamic radius of micelles can be determined from viscosity data. We also determined mean hydrodynamic radius using quasi-elastic light scattering. Micellar size decreases with increasing temperature, whereas it increases with increasing ionic strength. The results of viscosity and dynamic light-scattering measurements are interpreted as the extension of length of rod-like micelles. We compare viscosity and light scattering experimental results.     

Congruence theorems for compact hypersurfaces of a riemannian manifold

Summary Let M^m, ^m be two m-dimensional compact oriented hypersurfaces of class C³ immersed in a Riemannian manifold R^m+1 of constant sectional curvature. Suppose that R^m+1 admits a one-parameter continuous group G of conformal transformations satisfying a certain condition (which holds automatically when G is a group of isometric transformations). Suppose further that there is a1 − 1 transformation T_τ ∈ G between M^m and ^m such that for each P ∈ M^m and each ^m. If the r-th mean curvature for any r, 1 ⩽ r ⩽ m, of M^m at each point P ∈ M^m is equal to that of ^m at the corresponding point , together with other conditions, then M^m and ^m are congruent mod G. This is a generalization of a joint theorem ofH. Hopf andY. Katsurada [5] in which G is a group of isometric transformations. Entrata in Redazione il 13 Giugno 1975. The first author was partially supported by the National Science Foundation grant GP-33944.