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991.
Agustín Urretabizkaia Gurutze Arzamendi María J. Unzu Jos M. Asua 《Journal of polymer science. Part A, Polymer chemistry》1994,32(9):1779-1788
A method for the calculation of the optimal monomer addition policies for polymer composition control in emulsion terpolymerization is developed. The method is applied to reactors with and without limited heat removal capacity. A mathematical model that incorporates the main features of the vinyl acetate/methyl methacrylate/butyl acrylate high solids content emulsion terpolymerization system allows the calculation of the composition of the initial charge of the reactor and the time-dependent monomer addition rates required. © 1994 John Wiley & Sons, Inc. 相似文献
992.
The unrestricted Hartree-Fock (UHF) method of Snyder and Amos is used to calculate, in the -electron approximation, the spin density distributions in radical anions of heterocyclic amine N-oxides. The computed spin densities are observed to be in good agreement with the experimental values. The computed spin density distribution of the radical anion of pyridine N-oxide is consistent with the greater susceptibility of pyridine N-oxide relative to pyridine to electrophilic nitration. Also, the calculations are consistent with the lower basicity of the N-oxides relative to the parent bases. 相似文献
993.
Goryunov E. I. Petrovskii P. V. Shcherbina T. M. Zakharov L. S. 《Russian Chemical Bulletin》2001,50(6):1085-1087
Catalytic phosphorylation of -trifluoromethylbenzyl alcohols with POCl3 taken in a ratio of 3 : 1 under particular temperature conditions afforded predominantly symmetrical tris(-trifluoromethylbenzyl) phosphates. The latter were obtained as mixtures of two diastereomers with a statistical ratio of the components. 相似文献
994.
This paper summarizes our research in the preparation of chain end functionalized isotactic polypropylene (PP) having a terminal functional group, such as Cl, OH, and NH2. The chemistry involves metallocene-mediated propylene polymerization using rac-Me2Si[2-Me-4-Ph(Ind)]2ZrCl2/MAO complex in the presence of styrene derivatives (St-f) and hydrogen, which serve as the chain transfer agents. The molecular weight of the resulting PP polymers with a terminal Cl, OH and NH2 group (i.e., PP-t-Cl, PP-t-OH and PP-t-NH2) are inversely proportional to the molar ratio of [St-f]/[propylene]. Despite the extremely low concentration of functional group, the high molecular weight chain end functionalized PP-t-OH and exhibit a distinctive advantage over other functional PP polymers containing side chain functional groups or long functional blocks. The terminal hydrophilic OH and cations, with good mobility and reactivity, effectively hydrogen bond and ion-exchange the cations (Li+, Na+, etc.) located between the clay interlayers, respectively. Such interactions anchor the PP chain to the clay surfaces. On the other hand, the remaining rest of the unperturbed end-tethered high molecular weight PP tail exfoliates the clay layers. This exfoliated structure is maintained even after further mixing of the PP-bearing platelets with pure neat PP polymers. 相似文献
995.
Hamdi N. Feutelais Y. Yagoubi N. de Girolamo D. Legendre B. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):985-1001
Indomethacin is known to exhibit polymorphism and solvates, the different forms obtained do not exhibit the same solubility
and their bioavailabilities are different. It is of a prime importance to identify the various polymorphic and solvated forms.
This study was carried out by: DSC (different scanning calorimetry), TG (thermogravimetric analysis), X-ray diffraction and
thermomicroscopy. Seven solvates, with acetone, benzene, dichloromethane, tetrahydrofurane, propanol, chloroform and diethylether,
were isolated and studied. Their formulae have been determined by thermogravimetric analysis and their X-ray patterns on powder
are presented, by DSC their behaviour after desolvation is recorded, the temperature and the enthalpy of fusion are measured
and by this way the form obtained is deduced.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
997.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
998.
Macrocycle opening in derivatives of benzocrown ethers under the action of amines is affected by the nature of the heteroatoms in the macrocycle, the nature of the functional group in the benzene ring of the crown ether, and the length, branching, and number of hydrocarbon radicals at the amine nitrogen atom. A distinguishing feature of this reaction is the template effect of MeNH3
+, Me2NH2
+, Na+, and K+ ions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 687–692, March, 1996.For Part I see Ref. 1. 相似文献
999.
1000.