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991.
J. Kaloustian Paulette Lechene De La Porte T. El-Moselhy H. Lafont H. Portugal 《Journal of Thermal Analysis and Calorimetry》2005,82(2):331-338
Summary Cholesterol constitutes the major component of most gallstones. It was identified and determined in gallstones by thermal
analysis technique (DSC and TG-DTA), mainly by the use of the melting temperature (Tonset=145°C and Tmax=149°C) and by DTG peak decomposition (Tmax=364°C). Cholesterol anhydrous (ChA), which showed endothermic polymorphic peak, Tmax=40°C, without mass loss, was differentiated from cholesterol monohydrate (ChH), which showed a broad endothermic peak, Tmax=59°C, attributed to loss of water of crystallization (theoretical 4.45%). Morphological studies of gallstones were performed
by optical microscopy and scanning electron microscopy (SEM). The stones consisted of a pigmented core with a variably-sized
irregular central cavity, surrounded by a radially arranged deposits of plate-like ChH. The outer part of the stones showed
ChA crystal arborescences. X-ray microanalysis gave a typical spectrum rich in C and O, and in some instances the presence
of P, which was attributed to the presence of phospholipids. CaCO3 was easily characterized by TG with the use of DTG decomposition peak at 674°C. 相似文献
992.
Maria L. Foresti Francesco Pergola Rolando Guidelli 《Journal of Electroanalytical Chemistry》1980,107(2):307-321
Both the oxidation of Cu0 at dropping amalgam electrodes immersed in solutions of benzotriazole (BTA) and the reduction of CuII at a dropping mercury electrode from BTA solutions have been investigated by the single potential-step chronocoulometric technique. The dependence of the charge Q(t) flowing as a consequence of a given potential jump Ei→Ef upon the initial and final potentials Ei and Ef, as well as upon the time t elapsed from the instant of the potential jump provides direct evidence for the presence of a single adsorbed monolayer of a CuI compound on a mercury electrode immersed in a CuII solution containing BTA, at applied potentials positive to ≈?0.4 V/SCE. Analogous measurements carried out at dropping amalgam electrodes reveal the presence of a single adsorbed monolayer of a CuI compound, or else of an adsorbed multilayer, depending on the potential range investigated. The results of the chronocoulometric measurements are in agreement with those of the polarographic measurements of Part I. 相似文献
993.
Renato Noto Giuseppe Werber Francesco Buccheri Caterina Arnone 《Journal of heterocyclic chemistry》1987,24(5):1457-1459
The dissociation constants (K1) of both acids 4a-c and esters 5a-c and the rate constants of the decarboxylation reaction of acids 4a-c have been measured at various high concentrations of hydrochloric acid (0.5-8.0 M range). The results obtained have enabled us to suggest the probable structure of the zwitterion which undergoes decarboxylation. 相似文献
994.
In this paper, zinc tetraaminophthalocyanine (Zn-APc) was immobilized on cellulosic fiber by covalent bond to obtain a novel cellulosic fiber supported metallophthalocyanine, named Zn-TDTAPc-F. At pH 11, upon visible light irradiation for 6 h in the presence of O2, Zn-TDTAPc-F was found to be highly effective for the degradation of phenol in aqueous solution, and the degradation rate of phenol was more than 95%. HPLC was used to confirm formic acid, fumaric acid and maleic acid as its main degradation products. 相似文献
995.
“Simple” energetic patterns, where simple means the use of parameters derived only from the stoichiometry of these species,
are relatively rarely discussed in the literature. In addition, entropy studies have been dominated by derivation of the absolute
quantity S° rather than the entropy of formation (TΔf
S
o). Relationships between the entropy of formation and different parameters such as negative value of the charge of the species,
the number of oxygen atoms, the natural logarithm of the molecular weight, the total number of atoms and the number of central
atoms that are gases were recently discussed by us for aqueous polynuclear oxyanions. As shown here hydrogen containing anions
do not follow this pattern. In this study, new approaches for the estimation of the entropy of formation of aqueous hydrogen
containing mono and polynuclear oxyanions are suggested, evaluated and recommended. 相似文献
996.
Van den Eynde I Van Rompaey K Lazzaro F Tourwé D 《Journal of combinatorial chemistry》2004,6(4):468-473
Starting from Boc-o-aminomethylphenylalanine, a solution-phase parallel synthesis of 2,4-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones is described. This heterocycle has two nitrogen functions, which are differentiated and can be selectively substituted. The sources of diversity are aldehydes for the R(1) position and carboxylic acids, sulfonyl chlorides, or isocyanates for the R(2) position. High-throughput synthesis and purification of this multistep synthetic sequence was accomplished using polymer-bound reagents and scavengers and liquid-liquid extraction protocols, and a small library of compounds was prepared. Polymer-bound cyanoborohydride was found to work well for the reductive amination. Scavenging of excess of amine was performed by polymer-bound benzaldehyde, and cyclization was performed in the presence of polymer-bound coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). After Boc-deprotection, the second nitrogen can be acylated using carboxylic acids, sulfonylated or converted to a urea. The acylation is again performed by polymer-bound EDC. Excellent yields and purities were obtained. 相似文献
997.
Dragan Mihailovic 《Monatshefte für Chemie / Chemical Monthly》2003,134(2):137-147
Ferromagnetism in fullerene-based systems doped with metallocenes is reviewed. These compounds form a ferromagnetic state
by spin-coupling between π electrons on fullerene units, while the metallocene molecules do not contribute to the spin ordering.
One of these compounds has the highest critical temperature (19 K) for this class of compound. The magnetic properties of
these materials are very strongly dependent on the crystallization conditions.
Corresponding author. E-mail: Dragan.Mihailovic@ijs.si
Received September 4, 2002; accepted September 6, 2002 相似文献
998.
Jonathan Rosenhead 《The Journal of the Operational Research Society》1978,29(2):105-111
A case study is presented of the application of robustness analysis to the choice of examination subjects to be made by a 14-year-old girl. The analysis is conducted in terms of the desirable future career options which may be preserved by different combinations of subjects, and also of the balance with topics selected for their intrinsic interest. The approach, which employs very limited technical apparatus, is justified on a number of grounds-in particular, the crucial importance of uncertainty, and the need for understanding and acceptance by a "client" very unlike the corporate manager. Some tentative conclusions are reached on the extension of such methods to other cases of decision-makers with little, if any, resources to control except their own lives. 相似文献
999.
Helmut Schneider 《The Journal of the Operational Research Society》1978,29(12):1181-193
This paper deals with a periodic review inventory system. Methods are discussed for determining the re-order point s of an (s, S) order policy, when a certain service level is required. The results differ from those presented for a (Q, s) model which is usually considered in literature and implemented in practice. Methods are discussed for determining the re-order point of an (s, S) policy when demand is normal or gamma distributed. A numerical investigation demonstrates the applicability of the described methods. In particular, it is shown that these methods are superior to a formula that is implemented in many inventory control systems. 相似文献
1000.
Ji-Lai Li Cai-Yun Geng Xu-Ri Huang Chia-Chung Sun 《Theoretical chemistry accounts》2007,117(3):417-429
The reaction of atomic radical F with propyne has been studied theoretically using ab initio quantum chemistry methods and
transition state theory. The potential energy surface was calculated at the CCSD(T)/aug-cc-pVDZ (single-point) level using
the UMP2/6-311++G(d,p) optimized structures. Two reaction mechanisms including the addition–isomerization–elimination reaction
mechanism and the directed hydrogen abstraction reaction mechanism are considered. For the hydrogen abstraction reactions,
i.e., the most probable evolution pathway in the title reaction, the HF formation occurs via direct abstraction mechanism
dominantly and the H atom picked up by the atomic radical F should come mostly from the methyl group of normal propyne. On
the other hand, for the addition–isomerization–elimination mechanism, the most feasible pathway should be the atomic radical
F attacking on the C≡C triple bond in propyne (CH3C≡CH) to form a weakly-bound adduct A1 with no barrier, followed by F addition to the C≡C triple bond to form the low-lying
intermediate isomer 5. Subsequently, isomer 5 directly dissociates to P3 H2CCCHF + H via transition state TS5/P3. The other reaction pathways on the doublet PES are less competitive due to thermodynamical or kinetic factors. Furthermore,
based on the analysis of the kinetics of all channels through which the addition and abstraction reaction proceed, we expect
that the competitive power of reaction channels may vary with experimental conditions for the title reaction. The present
work will provide useful information for understanding the processes of atomic radical F reaction with other unsaturated hydrocarbons.
This material is available from author via E-mail. 相似文献