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991.
The coordination compound [Co(C10H7COO)2(H2O)3]2n
· 4nH2O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized
by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers
are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions.
The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can
be assigned to the intraligand electronic transfer. 相似文献
992.
Yong Li 《Theoretical chemistry accounts》2007,117(1):163-165
We present the theoretical results for the positions and widths of the initial anticrossing between Stark manifold n and n + 1 in sodium, obtained by using the method of diagonalization in which zero-field wave functions are chosen from a kind of atomic potential model. These results can provide the quantitative information for understanding the microwave ionization process, whose rate-limiting step is probably the n to n + 1 transition performed at the first crossing between the outermost states of these two manifolds. 相似文献
993.
Antonio Fernández-Ramos Benjamin A. Ellingson Rubén Meana-Pañeda Jorge M. C. Marques Donald G. Truhlar 《Theoretical chemistry accounts》2007,118(4):813-826
This article shows how to evaluate rotational symmetry numbers for different molecular configurations and how to apply them
to transition state theory. In general, the symmetry number is given by the ratio of the reactant and transition state rotational
symmetry numbers. However, special care is advised in the evaluation of symmetry numbers in the following situations: (i)
if the reaction is symmetric, (ii) if reactants and/or transition states are chiral, (iii) if the reaction has multiple conformers
for reactants and/or transition states and, (iv) if there is an internal rotation of part of the molecular system. All these
four situations are treated systematically and analyzed in detail in the present article. We also include a large number of
examples to clarify some complicated situations, and in the last section we discuss an example involving an achiral diasteroisomer. 相似文献
994.
Nitrile butadiene rubber, NBR, structural foam of different apparent densities was obtained by using different concentrations of foaming agent, azodicarbonamide, ADC/K. The true stress-strain characteristics, in case of compression, of foamed samples after the application of cyclic stress-strain were measured. The effect of the cyclic stress-strain on strain energy density of ADC/K foaming agent-filled NBR rubber composites was studied. The mechanical parameters were found to depend on the foaming agent concentration and on the pre-cyclic fatigue number. Results also indicated that the strain energy decreased with filler concentration.The effects of the cyclic stress-strain on the conductivity of ADC/K foaming agent-filled NBR rubber composites were studied. The electrical properties were found to depend on the foaming agent concentration, the strain amplitude and the number of stress-strain cycles of pre-strain. This study was assisted by the current-voltage characteristics which were measured under the effect of different compression ratios: 0%, 5%, 10%, 15%, 20%, 25% and 30%. The free current carrier mobility and the equilibrium concentration of charge carriers in the conduction band were produced as functions of compressive strain. Results also indicate that there is a linear variation between pressure and conductivity for all samples, which means that these samples can be used as a pressure sensor. 相似文献
995.
Wiesława Nocuń-Wczelik 《Journal of Thermal Analysis and Calorimetry》2007,88(1):291-294
The effect of PbO on cement hydration kinetics by calorimetric method
was evaluated as a first step in this project. Substantial retardation of
reaction with water at early stages with subsequent intensification of the
process was found. As the next step, the model systems covering pure cement
minerals and their mixtures of various composition as well as soluble Pb salts
were taken into account to elucidate the mechanism of delayed, by quite good
formation of products in the so-called post-induction period. The precipitation
of sulphate, forming very thin impermeable layer seems to be responsible for
this delaying effect in case of cement, however the other reactions of Pb
compounds in alkaline environment of hydrating calcium silicate are not out
of importance. In order to prove this, the studies of chemical composition
in small areas were also carried out. 相似文献
996.
S. V. Volkov S. V. Kutyakov A. N. Levov E. I. Polyakova Le Tuan An S. A. Soldatova P. B. Terentiev A. T. Soldatenkov 《Chemistry of Heterocyclic Compounds》2007,43(10):1260-1268
It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of
arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation
of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles
and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has
been studied.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007. 相似文献
997.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
998.
Haggag Awad Abd El Mageed K. F. El Sahhar Kenneth R. Robertson Ramin Parham Constantin A. Rebeiz 《Photochemistry and photobiology》1997,66(1):89-96
Abstract— On the basis of the steady-state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl-light divinyl (DDV-LDV), dark monovinyl-light divinyl (DMV-LDV) and dark monovinyl-light monovinyl (DMV-LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211-220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV-LDV and DMV-LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re-darkening, this greening group is designated as a light-dark MV (LDMV) subgroup. In DDV-LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light-dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4-vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase-A (POR-A) may be active in LDDV plants, while POR-B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed. 相似文献
999.
Sorption equilibrium of methanol on new composite sorbents “CaCl<Subscript>2</Subscript>/silica gel”
Yuri I. Aristov Larissa G. Gordeeva Yuri D. Pankratiev Ludmila M. Plyasova I. V. Bikova Angelo Freni Giovanni Restuccia 《Adsorption》2007,13(2):121-127
This paper presents experimental data on methanol sorption on new composite sorbents which consist of mesoporous silica gels
and calcium chloride confined to their pores. Sorption isobars and XRD analysis showed the formation of a solid crystalline
solvate CaCl2⋅2MeOH at low methanol uptake, while at higher uptake the formation of the CaCl2–methanol solution occurred. The solution confined to the silica pores showed the sorption properties similar to those of
the CaCl2–methanol bulk solution. Calorimetric and isosteric analyses showed that the heat of methanol sorption depends on the methanol
uptake, ranging from 38±2 kJ/mol for the solution to 81±4 kJ/mol for the solid crystalline phase CaCl2⋅2MeOH. The above mentioned characterizations allowed the evaluation of the methanol sorption and the energy storage capacities,
clearly showing that the optimal applications of these new composite sorbents are the methanol removal from gaseous mixtures,
heat storage and sorption cooling driven by low temperature heat. 相似文献
1000.
Tatjana Topalovic Vincent A. Nierstrasz Lorenzo Bautista Dragan Jocic Antonio Navarro Marijn M. C. G. Warmoeskerken 《Cellulose (London, England)》2007,14(4):385-400
Hydrogen peroxide can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating dinuclear tri-μ-oxo
bridged manganese(IV) complex of the ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (MnTACN) as the catalyst in the bleaching
solution. The catalytic system was found to be more selective under the conditions applied than the non-catalytic H2O2 system, showing better bleaching performance while causing slightly lower decrease in degree of polymerization (DP) of cellulose.
In order to gain fundamental knowledge of the bleach effect on cotton fibers and cellulose as its main component, especially
after catalytic bleaching, X-ray Photoelectron Spectroscopy (XPS) was used to study surface chemical effects. The Washburn
method was applied to investigate wetting properties, and liquid porosity was used to obtain pore volume distribution (PVD)
plots. Parallel analyzes performed on model cotton fabric, i.e. “clean” cotton fabric stained with morin - a pigment regularly
found in native cotton fiber, helped to differentiate between pigment oxidation and other bleaching effects produced on the
(regular) industrially scoured cotton fabric. Bleaching was not limited to the chemical action but also affected cotton fiber
capillary parameters most likely due to the removal of non-cellulosic materials as well as chain-shortened cellulose. 相似文献