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111.
Jan W. Bats Andreas Rivas Nass A. Stephen K. Hashmi 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):814-817
The crystal structure of the title compound, (2,2′‐bipyridyl‐κ2N,N′)(tetraallyl 3,3,3′,3′‐tetramethyl‐1,1′‐bicyclopropane‐1,1′,2,2′‐tetracarboxylato‐κ2C2,C2′)palladium(II), [Pd(C26H32O8)(C10H8N2)], is disordered above 194 K. A doubling of the unit cell is observed on cooling. The structure at 143 K contains two ordered molecules related by a pseudo‐translation vector of approximately (0.44,0.00,0.50) or a pseudo‐inversion center at approximately (0.22,0.00,0.25). Weak intermolecular C—H?O interactions are enhanced in the low‐temperature structure. 相似文献
112.
Guadalupe del C. Pizarro Oscar G. Marambio Manuel Jeria‐Orell Bernabé L. Rivas Wolf D. Habicher 《先进技术聚合物》2011,22(6):1024-1031
The present work reports the incorporation of the ZnO doped diblock copolymer matrix and its conversion into a self‐assembled structure. The diblock P(HEMA)80‐b‐P(N‐PhMI)20 and P(HEMA)90‐b‐P(St)10 copolymers consist of a majority (HEMA) and minority (N‐PhMI or St) block. The copolymers were synthesized with a block repeat unit ratio by atom‐transfer radical polymerization (ATRP) using a poly(2‐hydroxyethylmethacrylate)‐Cl/CuBr/bipyridine initiating system. The P(HEMA)‐Cl was prepared by reverse ATRP1. The average theoretical number molecular weight (Mn,th) was calculated from the feed capacity. The composite of the inorganic nanoparticles was achieved at room temperature in the liquid phase, using ZnCl2 precursor dopant and wet chemical processing to convert to ZnO nanoparticle films. Thermal characterization was performed using differential scanning calorimetry (DSC) and thermogravimetry (TG). The proton/area relationship confirmed the block copolymer compositions calculated by elemental analysis, consisting of a majority and minority blocks. Morphology properties of the polymer samples were investigated by scanning electron microscopy (SEM). The microphotographs of the film's surfaces show that the film's upper surfaces were generally smooth with ordered structure morphology. FT‐IR spectroscopy confirmed the association of the ZnCl2 precursor with the majority block and the formation of ZnO, the white SEM showed the morphology of ZnO nanoparticles' films when the surface relief changes principally due to surface loss rather than its orientation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
113.
Karina Nesprias Mariángeles Iglesias Sonia Rivas Elida Alvarez Gastón Barreto Nora Eyler Adriana Cañizo 《国际化学动力学杂志》2011,43(11):657-666
Cyclic organic peroxides have interesting pharmacological properties and are used at industrial level as polyfunctional initiators of polymerization, and so their preparation through novel methods has attracted the attention of numerous researchers. White crystals of 4‐heptanone cyclic diperoxide (HDP) can be obtained in acidic media at ?1°C by a reaction between 4‐heptanone and hydrogen peroxide. Its thermal decomposition was studied in acetone, cyclohexane, acetonitrile, ethyl acetate, ethanol, 2‐propanol, 2‐butanol, and 1,4‐dioxane at temperatures higher than 120°C, showing a behavior accordingly with a pseudo‐first‐order kinetic law up to at least 80% HDP conversion. It was demonstrated that an increase in solvent polarity is accompanied by an increase in reaction rates. The effect of solvent polarity on the thermal decomposition rate constant values can be associated with a reaction mechanism involving a more dipolar‐activated complex than the diperoxide initial molecule. The activation parameters varied widely from 31.2 to 46.6 kcal mol?1 and ?1.33 to 31.7 cal mol?1 K?1 when going from ethanol to cyclohexane as reaction solvents, respectively. An enthalpy–entropy compensation effect was observed in all solvents. Specific interactions between the oxygen atoms from the peroxidic bond and the hydrogen atom bonded to C2 and/or from the OH group can be taken into account to explain that the existence of the compensation effect does not mean that an isokinetic relationship consequently can be established. The kinetic results showed that an isokinetic relationship is observed only for a group of solvents. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 657–666, 2011 相似文献
114.
Xiomara Gutierrez Felix Silva Manuel Chirinos Javier Leiva Hercilio Rivas 《Journal of Dispersion Science and Technology》2013,34(1-3):405-418
This paper describes the most relevant issues associated with the development of a technology; the formation of highly concentrated bitumen-in-water emulsions. Viscosity values for bitumen-in-water emulsions, containing between 70 and 85% (v/v) of bitumen, have been found to be several order of magnitude lower than the viscosity of the hydrocarbon itself. Thus, these emulsions, have potential applications in the processes of production, transportation, handling and commercialization of these extremely highly viscous hydrocarbons. The emulsions, the properties of which are discussed in this paper, were stabilized with mixtures of nonionic and natural surfactants (1,2) and formed using the HIPR (high internal phase ratio) technique (3). Information on the conditions required to produce emulsions with very narrow droplet diameter distributions is given. Results indicate that the mean droplet diameter, the droplet diameter distribution, and the bitumen volume fraction, significantly modify the rheological behavior. Emulsion stability was measured by following changes in the mean droplet diameter and in the rheological parameters with storage time. 相似文献
115.
Tiina Nypelö Carlos Rodriguez-Abreu José Rivas Michael D. Dickey Orlando J. Rojas 《Cellulose (London, England)》2014,21(4):2557-2566
We fabricated self-standing films of cellulose nanocrystals (CNC) and electrospun composite fibers with CNC and polyvinyl alcohol both with magnetic properties arising from cobalt iron oxide nanoparticles in the CNC matrix. Aqueous dispersions of cobalt-iron oxide nanoparticles (10–80 nm diameter) and CNCs (ca. 150 nm length) were used as precursor systems for the films and composite fibers. The properties of the hybrid material were determined by electron and atomic force microscopy, X-ray diffraction, thermogravimetry and magnetometry. The CNC-inorganic system was ferromagnetic, with a saturation magnetization of ca. 20 emu g?1 of the magnetic phase. We demonstrate potential applications of the precursor dispersions, including magnetic fluid hyperthermia and highlight possible uses of the CNC-based magneto-responsive systems in biomedical and magneto-optical components. 相似文献
116.
Gisele A. B. Canuto Emerson A. Castilho-Martins Marina F. M. Tavares Luis Rivas Coral Barbas Ángeles López-Gonzálvez 《Analytical and bioanalytical chemistry》2014,406(14):3459-3476
Miltefosine (MT) (hexadecylphosphocholine) was implemented to cope with resistance against antimonials, the classical treatment in Leishmaniasis. Given the scarcity of anti- Leishmania (L) drugs and the increasing appearance of resistance, there is an obvious need for understanding the mechanism of action and development of such resistance. Metabolomics is an increasingly popular tool in the life sciences due to it being a relatively fast and accurate technique that can be applied either with a particular focus or in a global manner to reveal new knowledge about biological systems. Three analytical platforms, gas chromatography (GC), liquid chromatography (LC) and capillary electrophoresis (CE) have been coupled to mass spectrometry (MS) to obtain a broad picture of metabolic changes in the parasite. Impairment of the polyamine metabolism from arginine (Arg) to trypanothione in susceptible parasites treated with MT was in some way expected, considering the reactive oxygen species (ROS) production described for MT. Importantly, in resistant parasites an increase in the levels of amino acids was the most outstanding feature, probably related to the adaptation of the resistant strain for its survival inside the parasitophorous vacuole. Online Abstract Figure
? 相似文献
117.
M. P. Breijo C. Rey S. Castro M. Sánchez M. A. Señarís-Rodríguez J. Mira A. Fondado J. Rivas 《Ionics》1998,4(3-4):267-274
We have used three soft-chemistry methods for the efficient preparation of Ln1−xSrxCoO3 samples, adapting the combustion and the liquid-mix methods for the synthesis of the Ln = La and Gd compounds, respectively,
and the preparation of Nd1−xSrxCoO3 by the nitrate decomposition method.
We report the magnetic and electrical properties of these relatively small particle-size materials, specially in the case
of the Ln = La and Ln = Nd series (d≈0.2 μm and 0.5 μm, respectively), and we compare them to those displayed by the corresponding
compounds prepared at higher temperatures. The compounds here obtained are ferromagnetic for x≥0.15 when Ln = La and for x≥0.20
when Ln = Nd and Gd. Their resistivity decreases as the doping degree increases. And, very interestingly, for compositions
0.20<x≤0.45, when Ln = La, and for x=0.40, when Ln = Nd, they show M-I transitions as the temperature rises. These are very
sensitive to the application of electrical current and its polarity and the presence of magnetic fields, displaying peculiar
behaviors.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
118.
119.
The temperature, heat and entropy of fusion and the temperature of decomposition of oxetanes derived from photochemical reaction between the five-membered heterocyclics, containing O, N and S, respectively, as the hetero-atom and several excited carbonyl compounds have been measured. These characteristics are intended to serve as supplemental data for the identification of this type of compound. Furthermore, this investigation establishes the general pattern in the thermal behavior of this family of compounds containing as a common feature a four-membered ring with an oxygen atom. 相似文献
120.
J. A. Martínez M. C. Caracoche A. M. Rodríguez P. C. Rivas A. R. López García 《Hyperfine Interactions》1983,14(2):135-138
Time-differential perturbed angular correlation (TDPAC) measurements in NH4Hf2F9 were performed between 15 and 580 K. The compound was found to be stable in the whole temperature range and no phase transitions were observed. Experimental results could be explained assuming two equally populated quadrupole interactions which suggest a neat inequivalence between the two sites occupied by the hafnium atoms in the molecule. 相似文献