On the evaluation of the nonisothermal kinetic parameters of (GeS2)0.3(Sb2S3)0.7 crystallization using the IKP method

The isoconversional method suggested by Friedman and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the nonisothermal crystallization of (GeS₂)_0.3(Sb₂S₃)_0.7. The objective of the paper is to show the usefulness of the IKP method both for determining the activation parameters as well as the model of the investigated process. It was shown that the kinetic triplet [(E, A, f(α), where E is the activation energy, A is the preexponential factor, and f(α) is the differential function of conversion], which results through the application of the IKP method, depends on the set of kinetic models considered. For different sets of kinetic models, proportional values of f(α) are obtained. A criterion for the selection of this set, the use of which lead to the true kinetic triplet corresponding to the analyzed process (E = 163.2 kJ mol^?1; A = 2.47 × 10¹² min^?1 and the Avrami‐Erofeev model, A_m, for m = 2.5–2.6 was suggested. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 309–315, 2004     

Silyl modification of biologically active compounds 5. Hydrolytic stability and biological activity of the trialkylsilyl derivatives of some heterocyclic bases

The kinetics of the desilylation of the triorganosilyl derivatives of some biologically active heterocyclic bases and uridine were investigated by¹H NMR spectroscopy. A correlation was established between the relative rates of desilylation and the steric environment of the silicon atom. In trials on locomotor activity and muscular tone, the effect on memory processes, and the Porsolt test it was found that tris(tert-butylmethylsilyl)barbituric acid has higher sedative activity than barbituric acid. In contrast to uridine, 5-O-tert-butyldimethylsilyluridine exhibits antitumor activity, suppressing the development of fibrosarcoma in human lungs (HT-1080) and fibroblasts in mice.For communication 4, see [1].Latvian Institute of Organic Synthesis, Riga, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1253–1258, September, 1998.     

Silyl modification of biologically active compounds. 3. organosilicon derivatives of aminoalcohols in the series of tetrahydroquinoline,tetrahydroisoquinoline, and tetrahydrosilaisoquinoline

The N-(2-hydroxyethyl)-1, 2, 3, 4-tetrahydroquinoline, -isoquinoline, and -silaisoquinoline, and their trimethyland triethylsilyl derivatives and the corresponding methiodides were synthesized. The acute toxicity and psychotropic activity of the compounds synthesized were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 793–799, June, 1996. Original article submitted April 25, 1996.     

Fluxional behaviour of π-bonded acetylenes

Some cationic five coordinate complexes of formula [Os(CO)(NO)L₂A]PF₆ (L = tertiary phosphine, A = an acetylene) have been prepared by reaction of the appropriate acetylene with [Os(CO)(NO)L₂(acetone)]PF₆; the variable temperature ¹H NMR spectra of some of these indicate that the coordinated π-acetylene undergoes fluxional behaviour.     

Non-isothermal kinetic study of the solid-gas thermal decompositions of some coordination compounds of CoII and NiII

Using a method developed by us, a non-isothermal kinetic study of the thermal decomposition of some coordination compounds (CC) with the general formula Me^IIL_pX₂, where

, was performed.     

TG and DSC investigation of the dehydration of the extra large pore aluminophosphate molecular sieve VPI-5 and related materials

The dehydration of a series of VPI-5 and H3 samples, synthesized under various conditions, as well as the solid state transformation of VPI-5 to AlPO₄-8 have been investigated using combined TG-DTG-DSC and high-resolution solid state³¹P-NMR. The TG curves show a quasi-continuous release of water, the total loss being characteristic for each sample. Complete dehydration is achieved when the samples are heated from 20°C to about 150°C at various beating rates. Besides the main dehydration effect, several weak endothermic peaks are observed. These generally non-reproducible modulated peaks, recorded at high heating rates, are presumably due to the interactions of the water molecules leaving the channels of VPI-5 with the randomly positioned fragments stemming from the destruction of the water triple helix assemblage. The non-isothermal kinetic parameters of the dehydration have been evaluated from the TG and DTG curves recorded at low heating rates. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Gel-permeation chromatography and cellulose. I. Effect of degree of nitration of cellulose on molecular weight distribution data

Consideration is given to the effect on gel-permeation chromatographic (GPC) data of the extent of substitution in nitrated cellulose. GPC parameters for samples containing 13.55–13.81% nitrogen (14.14% corresponds to complete substitution, DS = 3) were hardly affected by this variation in substitution. Variations that were observed are considered to arise within the samples themselves. Experiments with low molecular weight organic iodides, nitrates, and hydroxyl compounds indicate longer chain lengths than actual; this is attributed to extensive solvation of the substituent groups. The very long chain lengths obtained for cellulose nitrate by the present GPC procedure may arise from such an affect.     

Synthesis and characterization of nanoparticles with an iron oxide magnetic core and a biologically active trialkylsilylated aliphatic alkanolamine shell

Water-soluble double-coated magnetic nanoparticles (NPs) containing cytotoxic decyldimethyl(β$\beta$-dimethylaminoethoxy)silane methiodide (AA) molecule sorbed at biocompatible magnetic particles, which consist of magnetite pre-coated with oleic acid (OA), have been prepared. X-ray line profile broadening analysis was used for crystallite size determination. The method of magnetogranulometry has been used for determination of diameter of iron oxide magnetic core and magnetic properties of NPs prepared. In vitro cytotoxicity on monolayer tumor cell lines HT-1080 (human fibrosarcoma), MG-22A (mouse hepatoma) and normal mouse fibroblasts (NIH 3T3) has been studied. It was revealed that all the water-based colloidal solutions obtained are non-toxic and possess high NO-induction ability.     

Hydrodynamic stability of the spherical front of a reaction accompanied by a strong increase in viscosity

The hydrodynamic stability of the steady spherical front of a reaction accompanied by a strong increase in viscosity taking place in a radial, centrally symmetric flow of condensed reaction medium is considered. The flow is assumed to be bounded by two permeable concentric spherical surfaces. The stability is investigated in the linear approximation with respect to small perturbations. A relation is obtained for the dependence of the perturbation growth rate on the parameters of the problem: the viscosity ratio of the medium at the front, the ratio of the boundary surface radii to the radius of the front, and the dimensionless hydrodynamic resistances of the boundary surfaces. It is shown that the front is stable over almost the entire physical region of variation of the parameters and that instability occurs only in the case of a low hydrodynamic resistance of the outer boundary surface as the front approaches.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 46–53, May–June, 1988.