Study of acid-base properties of a SiO2?AlPO4 (80∶20 W/W) catalyst

2-Methyl-3-butyn-2-ol (MBOH) transformation was used as a test reaction in order to determine the acid-base properties of a SiO₂/AlPO₄ (80∶20 w/w) catalyst. Experiments were carried out in a microcatalytic pulse reactor and in a continuous-flow reactorvia Temperature Programmed Surface Reactions-Mass Spectrometry (TPSR-MS). Results are compared to acid-base properties calculated by other instrumental techniques.     

Incubation process in polyimid upon UV photoablation

The incubation process in polyimid was investigated at 337.1 nm UV photoablation. The threshold number of incubation pulses needed to start the ablation is proportional to a reciprocal cubic function of the fluence and does not depend on the repetition rate of the laser between 0 and 20 pps. A simple model is presented to explain these characteristics.     

Directional and wavelength sweep of distributed-feedback dye-laser pulses

Directional and wavelength sweep of a pulse train from a distributed-feedback dye laser is studied and found not to be a thermal effect, rather a gain-induced one. The directional sweep can be used for single-pulse selection.     

Factors for ¦N,pn;δ¦k summability of Fourier series

In this paper two theorems on | N,p_n;δ|_k summability factors, which generalize the results of Bor [4] on | N,p_n|k summability factors, have been proved.     

On the\left| {\bar N,p_n } \right|_k summability factors for infinite seriessummability factors for infinite series

In this paper a theorem on \(\left| {\bar N,p_n } \right|_k \) summability factors of infinite series, which generalizes a theorem of Bor [2], has been proved.     

Time-resolved study of ArF-excimer-laser ablation processes of polymethylmethacrylate

The processes of the ArF-excimer-laser ablation of PolyMethylMethAcrylate (PMMA) has been investigated. We studied the surface reflection of the polymer sample during UV photoablation. It was observed that a dark spot appeared in the reflected probe nitrogen laser beam (the reflection decreased below 4%) with about 5 ns delay after the onset of the ablating excimer pulse, while the transmitted probe laser intensity was increased to about 104%.A fast stroboscopic photographic arrangement was built for investigation of the ejection. A protuberance developed on the irradiated surface at about 100 ns delay. This expanded with about 600 m/s average velocity until 4 s, then contracted slowly, and finally at 16–18 s delay the ejection started. We also examined the process of the UV photoablation of PMMA in the vacuum chamber. In this case, the protuberance also appeared, but it left the surface nearly in one block at 3 s delay.Using a double-flash exposure photographic arrangement based on a dye laser, the propagation velocity of the shock waves developed in the air above the surface of the PMMA sample as a function of time was measured, and good agreement with shock wave theory was found. The pressure in the shock front can be as high as 1939 bar.     

Determination of low molecular weight organic acids in soil solution by HPLC

An HPLC method employing an ion exclusion column was developed for the determination of low molecular weight organic acids in soil solution. The method includes extensive sample pretreatment using ultrafiltration and cation exchange. The method showed linear calibration graphs (r>0.99) and the limits of detection in the range 0.1-26 muM. The recovery of eleven added acids ranged from 89 to 102%. Soil solutions of five horizons of a podzolised soil were analysed. The results showed that these compounds made up 1-3% of the dissolved organic carbon and 0-14% of the acidity. Identification of the major acids was also carried out by capillary zone electrophoresis.     

Reactions of 2-aminothiobenzamide with isocyanates: A new synthesis of 2, 3-dihydroimidazo[1, 2-c]quinazolin-5(6H)-one and 3, 4-Dihydro-2H-pyrimido[1, 2-c]quinazolin-6(7H)-one

2-(2-Chloroethylureido)- and 2-(3-chloropropylureido)thiobenzamides 5a, b were prepared in good yields by treating 2-aminothiobenzamide with 2-chloroethyl and 3-chloropropyl isocyanates respectively. Subsequent treatment of compound 5a and 5b either with alkali or mineral acid led to the formation of 2, 3-dihydro-imidazo[1, 2-c]quinazolin-5(6H)-one 7a and 3, 4-Dihydro-2H-pyrimido[1, 2-c]quinazolin-6(7H)-one 7b .     

Studies on Polymerization of Vinyl Compounds Initiated by Metal Chelate II Kinetics of Polymerization of Methyl Methacrylate Initiated by Nickel Ethyl Acetoacetate in the Presence and the Absence of Aromatic Amines

The kintetic studies of polymerization of methyl methacrylate initiated with nickel ethyl acetoacetate gave the following equations. R_p=K₁[Monomer]^1.4[Chelate]^0.5, in the absence ox aniline R_p=K₂[Monomer]^1.2[Chelate]^0.5 [Aniline]^0,5, in the presence of aniline. Some aromatic amines such as aniline markedly accelerated the polymerization, while pyridine had no such effect. The activation energy of initiation was 24.8 kcal/mol in the absence of aniline, and 8.8 kcal/mol in the presence of aniline. Both the kinetic data and the infrared spectra of the polymer indicated that the polymerization was radical in nature. The reaction order against monomer varied, as the temperature differed. The spectrophotometric investigation indicated formation of a complex between the chelate and the monomer, or amines. It also showed that the formation of a complex was not a factor which controlled the rate of initiation. A scheme of initiation mechanism was presented on the basis of the above experimental evidence.