Quadratic spline interpolation on uniform meshes

The interpolation problem at uniform mesh points of a quadratic splines(x _i)=f _i,i=0, 1,...,N ands(x ₀)=f₀ is considered. It is known that s–f=O(h ³) and s–f=O(h ²), whereh is the step size, and that these orders cannot be improved. Contrary to recently published results we prove that superconvergence cannot occur for any particular point independent off other than mesh points wheres=f by assumption. Best error bounds for some compound formulae approximatingf _i andf _i ⁽³⁾ are also derived.     

Transient creep during transformation in Cd-Zn alloys

Transient creep of Cd-2 wt. % Zn and Cd-17·4 wt. % Zn alloys has been studied under different constant stresses ranging from 6·4 MPa to 12·7 MPa near the transformation temperature. The results of both compositions showed two transient deformation regions, the low temperature region (below 483 K) and the high temperature region (above 483 K). From the transient creep described by the equation _tr=Bt ⁿ, where _tr andt are the transient creep strain and time. The parametersB andn were calculated. The parameterB was found to change with the applied stress from 0·3×10^–4 to 3×10^–4 and from 0·6×10^–4 to 18×10^–4 for Cd-2 wt. % Zn and Cd-17·4 wt. % Zn, respectively. The exponentn was found to change from 0·8 to 0·95 for both alloys. The parameterB was related to the steady state creep rate through the equation , the exponent was found to be 0·5 for Cd-2 wt. % Zn and 0·6 for the eutectic composition. The activation energies of transient creep in the vicinity of the transformation regions (above 483 K) were found to be 50·2 kJ/mole for Cd-2 wt. % Zn and 104·7 kJ/mole for the eutectic composition characterizing the mechanisms of grain boundary diffusion and volume diffusion in Cd, respectively.     

Properties of RF sputtered ZnxCd1−xS thin films

Zn _x Cd_1–x S thin films (0x0.20) were prepared using rf sputtering in argon atmosphere and characterized using X-ray diffraction, optical transmission, electrical resistivity and photoconductive decay measurements. The films were found to possess hexagonal structure. The crystallite size and degree of preferential orientation were found to decrease with the increase ofx and to improve upon annealing in vacuum at 250 °C. The transmission edge shifted towards shorter wavelengths with the increase ofx in agreement with the expected shift in the energy band gap. The films were found to exhibit room temperature resistivity in the range 100–1000 cm. The obtained values of long wavelength transmission (70–80%) and minority carrier diffusion length (30 m) are high enough for the application of these films in the field of solar cells.     

Spectrofluorimetric determination of guanethidine sulphate,guanfacine hydrochloride,guanoclor sulphate and guanoxan sulphate in tablets and biological fluids,using benzoin

A sensitive and rapid Spectrofluorimetric method for the determination of guanethidine sulphate, guanfacine hydrochloride, guanoclor sulphate and guanoxan sulphate in tablets and spiked human serum and urine samples is described. The method is based on the reaction of monosubstituted guanidino compounds in an aqueous potassium hydroxide solution with benzoin, in the presence of -mercaptoethanol and sodium sulphite. Highly fluorescent derivatives were obtained, with excitation and emission maximum wavelengths around 325 and 430 nm, respectively. In optimal reaction conditions, the linearity ranges were 0.04–0.28 g/ml, with relative standard deviations less than 2%. The method has been successfully applied to the determination of these drugs in tablets. The results are highly correlated with the B.P. method. Chloroform (or for guanoxan dichloromethane) was used to extract the drugs from serum and urine at basic pH, followed by the proposed fluorimetric method. The limit of detection is 0.02 g/ml for the selected drugs.     

Synthesis of condensed systems containing the tetrazole ring by base-catalyzed intramolecular cyclization of quaternary ammonium salts

Quaternary ammonium salts containing propargyl and 3-(2-methyltetrazol-5-yl)propargyl groups undergo base-catalyzed cyclization at room temperature with self heating to form condensed heterocyclic systems containing the tetrazole ring. Heating at 90–92°C for 2 h is necessary to cyclize the allyl analogs of the starting salts.Communication 234 of the series Research on Amines and Ammonium Compounds. For 233, see [1].Institute of Organic Chemistry, National Academy of Sciences of the Republic of Armenia, Erevan 375094. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 390–394, March, 1999.