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排序方式: 共有120条查询结果,搜索用时 156 毫秒
1.
Diana I. Martin Elena Mateescu Gabriela Craciun Daniel Ighigeanu Adelina Ighigeanu 《Radiation Physics and Chemistry》2002,64(5-6):423-428
Results obtained by accelerated electron beam, microwave and simultaneous microwave and electron beam application in the chemistry of acrylamide and acrylic acid copolymers (polymeric flocculants used for wastewater treatment) are presented. Comparative results concerning the molecular weight and Huggins’ constant for the acrylamide and acrylic acid copolymers obtained by classical heating, microwave heating, electron beam irradiation and simultaneous microwave and electron beam treatment are reported. Microwave heating produces high water solubility of the polymeric flocculants but median molecular weight values. Electron beam irradiation gives high molecular weight values but associated with a cross-linked structure (poor water solubility) while microwave energy addition to electron beam energy gives simultaneously high molecular weight values and high water solubility. 相似文献
2.
The thermochemical behavior of the coordination compound [Fe(urea)6](NO3)3 was studied by simultaneous CG–TG–DTG–DTA and mass spectrometry methods non-isothermal conditions. The compound decomposes at 200 °C into a mixture of spinel-type oxides and hematite. The nature and particle size of the final decomposition products are strongly associated with the conditions during the thermal treatments, in particular the heating rate and the calcination temperature. A certain fraction of the products are formed as nanometric particles; they show superparamagnetic behavior at room temperature. The comparably low temperature of the calcination treatments of this compound is a promising perspective to attain small sized magnetic powders. 相似文献
3.
Carp O. Patron L. Mindru I. Marinescu G. Diamandescu L. Banuta A. 《Journal of Thermal Analysis and Calorimetry》2003,74(3):789-799
The thermal behaviour of three coordination compounds, potential precursors of nickel ferrite [Fe2Ni(C4H4O5)2.5(OH)2]NO3·5H2O,[Fe2Ni(C4H8O3N2)4](NO3)8·24H2O and (NH4)[Fe2Ni(C4H4O5)3(OH)3]·3H2O has been investigated to evaluate their suitability as precursors for nickel ferrite. For a complete and reliable assignment of the thermal transformations, the isolable solid intermediates and end products were characterized by IR, X-ray diffraction and Mössbauer investigations. A decomposition scheme is proposed. 相似文献
4.
Choi S Cooley RB Voutchkova A Leung CH Vastag L Knowles DE 《Journal of the American Chemical Society》2005,127(6):1773-1781
Many transition-metal complexes mediate DNA oxidation in the presence of oxidizing radiation, photosensitizers, or oxidants. The DNA oxidation products depend on the nature of the metal complex and the structure of the DNA. Earlier we reported trans-d,l-1,2-diaminocyclohexanetetrachloroplatinum (trans-Pt(d,l)(1,2-(NH(2))(2)C(6)H(10))Cl(4), [Pt(IV)Cl(4)(dach)]; dach = diaminocyclohexane) oxidizes 2'-deoxyguanosine 5'-monophosphate (5'-dGMP) to 7,8-dihydro-8-oxo-2'-deoxyguanosine 5'-monophosphate (8-oxo-5'-dGMP) stoichiometrically. In this paper we report that [Pt(IV)Cl(4)(dach)] also oxidizes 2'-deoxyguanosine 3'-monophosphate (3'-dGMP) stoichiometrically. The final oxidation product is not 8-oxo-3'-dGMP, but cyclic (5'-O-C8)-3'-dGMP. The reaction was studied by high-performance liquid chromatography, (1)H and (31)P nuclear magnetic resonance, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The proposed mechanism involves Pt(IV) binding to N7 of 3'-dGMP followed by nucleophilic attack of a 5'-hydroxyl oxygen to C8 of G and an inner-sphere, 2e(-) transfer to produce cyclic (5'-O-C8)-3'-dGMP and [Pt(II)Cl(2)(dach)]. The same mechanism applies to 5'-d[GTTTT]-3', where the 5'-dG is oxidized to cyclic (5'-O-C8)-dG. The Pt(IV) complex binds to N7 of guanine in cGMP, 9-Mxan, 5'-d[TTGTT]-3', and 5'-d[TTTTG]-3', but no subsequent transfer of electrons occurs in these. The results indicate that a good nucleophilic group at the 5' position is required for the redox reaction between guanosine and the Pt(IV) complex. 相似文献
5.
Molins Elies Roig Anna Miravitlles Carlos Moreno-Mañas Marcial Vallribera Adelina Gálvez Nicanor Serra Neus 《Structural chemistry》1998,9(3):203-208
The crystal and molecular structure of (BzlMe3N)
2
+
[Fe2OCl6]2- has been determined. The asymmetric unit contains two benzyltrimethylammonium cations and two half -oxo-bis(trichloro-iron(III)) anions. The bridging -oxygen atoms of these anions are located over crystallographic symmetry elements. Therefore, the two anions resulting from the symmetry operations correspond to two different conformers presenting angular and linear dispositions of the Fe-O-Fe bond angle. Mössbauer spectrum consists of two asymmetric lines that are adequately simulated by two equally populated quadrupole doublets associated with the two iron sites. 相似文献
6.
7.
Jairo Amortegui Alexander Rodríguez-López Deicy Rodríguez Ana K. Carrascal Carlos J. Alméciga-Díaz Adelina del P. Melendez Oscar F. Sánchez 《Applied biochemistry and biotechnology》2014,172(7):3374-3389
Bacteriocins are low molecular peptides with antimicrobial activity, which are of great interest as food bio-preservatives and for treating diseases caused by pathogenic bacteria. In this study, we present the characterization of bacteriocins produced by Lactobacillus plantarum LE5 and LE27 isolated from ensiled corn. Bacteriocins were purified through ammonium sulfate precipitation and double dialysis by using 12- and 1-kDa membranes. Bacteriocins showed activity against Listeria innocua, Listeria monocytogenes, and Enteroccocus faecalis. Molecular weight was estimated through Tricine-SDS-PAGE and overloading the gel onto Mueller-Hinton agar seeded with L. monocytogenes, showing an inhibition zone between 5 and 10 kDa. NanoLC-MS/MS analysis allowed the identification of UPF0291 protein (UniProtKB/Swiss-Prot Q88VI7), which is also presented in other lactic acid bacteria without assigned function. Ab initio modeling showed it has an α-helix-rich structure and a large positive-charged region. Bacteriocins were stable between 4 and 121 °C and pH 2 and 12, and the activity was inhibited by SDS and proteases. Mode of action assay suggests that the bacteriocin causes of target microorganism. Taken together, these results describe a possible new class IIa bacteriocin produced by L. plantarum, which has a wide stability to physicochemical conditions, and that could be used as an alternative for the control of foodborne diseases. 相似文献
8.
9.
Oana Carp Luminita Patron Daniela C. Culita Petru Budrugeac Marcel Feder Lucian Diamandescu 《Journal of Thermal Analysis and Calorimetry》2010,101(1):181-187
The thermal stability of two kinds of dextran-coated magnetite (dextran with molecular weight of 40,000 (Dex40) and 70,000
(Dex70)), obtained by dextran adsorption onto the magnetite surface is investigated in comparison with free dextran in air
and argon atmosphere. The thermal behavior of the two free dextran types and corresponding coated magnetites is similar, but
atmosphere dependent. The magnetite catalyzes the thermal decomposition of dextran, the adsorbed dextran displaying lower
initial decomposition temperatures comparative with the free one in both working atmospheres. The dextran adsorbed onto the
magnetite surface decomposes in air through a strong sharp exothermic process up to ~450 °C while in argon atmosphere two
endothermic stages are identified, one in the temperature range 160–450 °C and the other at 530–800 °C. 相似文献
10.
L. Patron O. Carp I. Mandru G. Grasa 《Journal of Thermal Analysis and Calorimetry》1999,56(2):597-602
New Nd-Co based polynuclear coordination compounds containing as ligand polyhydrocarboxylic acid as tartaric, malic and gluconic
acids were prepared, namely: [NdCo(tart)3]·4H2O, (NH4)[NdCo0.5Cu0.5(tart)3]·4H2O, (NH4)[NdCo(malic)3]·4H2O, (NH4)[NdCo0.5Cu0.5(malic)3]·4H2O, [NdCo(gluc)4]·4H2O and [Nd2CoCu(gluc)7]·5H2O. A comparison between the thermal behaviour of the studied polynuclear coordination compounds concerning thermal stability
and thermal decomposition stoichiometry was inferred. Oxalic and malonic intermediates were identified at about 300°C in the
thermal decomposition of tartaric and malic compounds. In all the decomposition processes at about 400°C the presence of oxocarbonate
is shown. The residual products are mixed oxides of perovskite type.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献