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91.
Magdalena Ćwikowska Florian P. Pruchnik Oleksiy Pavlyuk Frédéric Lafolet Sylvie Chardon-Noblat Alain Deronzier 《Polyhedron》2010
Binuclear Rh(II) compounds [Rh2(μ-OOCCH3)2(dbbpy)2(H2O)2](CH3COO)2 (1) (dbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), [Rh2(μ-OOCCH3)2(dbbpy)2(H2O)2](BF4)2·H2O·CH3CN (2), [Rh2(CH3COO)2(C18H24N2)2(CH3CN)2](BF4)2·4CH3CN (3) and {[Rh2(μ-OOCCH3)2(dbbpy)2][BF4]}n (4) have been synthesized and characterized with spectroscopic methods. Structure of complex 3 has been determined using X-ray crystallography. Rhodium atoms in compound 3 have distorted octahedral coordination with O and N atoms in equatorial positions and Rh atom and CH3CN molecule in axial coordination sites. Reduction of rhodium(II) compounds with aqueous 2-propanol leads to the formation of polymetallic compound {[Rh2(μ-OOCCH3)2(dbbpy)2][BF4]}n (4) containing [Rh2]3+ core. Compound 4 shows strong antiferromagnetic properties, μ = 0.18–1.73 M.B. in the range 1.8–300 K, J = −597 cm−1. Electrochemistry of compounds 3 and 4 in CH3CN has been investigated. Compound 4 exhibits a poorly reversible oxidation system at E1/2 = −0.92 V (ΔEp = 0.19 V) and in solution in DMF is slowly oxidized to 3 even in total absence of oxygen. Complex 3 is irreversibly oxidized to Rh(III) compound at Epa = 1.48 V and irreversibly reduced at Epc = −1.02 V to lead to the unstable polynuclear complex 4 in CH3CN. 相似文献
92.
Catalytic properties and surface activity of nitrogen containing polymeric organic material (N‐POM) were analyzed by constant current chronopotentiometric stripping analysis (CPSA) and alternating current (AC) voltammetry in sodium chloride solution (pH 8) and seawater. CPSA proved to be a suitable method for determination of low concentrations of N‐POM in seawater by measuring its ‘presodium’ catalytic peak H. A protein human serum albumin (HSA) (15% of N) was used as a model compound and the concentration of N‐POM from natural seawater samples was expressed in HSA concentration equivalents. Peak H represents an additional parameter for characterization of natural organic matter. 相似文献
93.
Marković Gordana Marinović-Cincović Milena Vodnik Vesna Radovanović Blaga Budinski-Simendić Jaroslava Veljković Olivera 《Journal of Thermal Analysis and Calorimetry》2009,97(3):999-1006
The properties of chlorosulphonated polyethylene (CSM) rubber, acrylonitrile rubber (NBR) and their blend (50/50 w/w) were
studied. Fourier transform infrared (FTIR) studies supported that CSM/NBR rubber blend is self curable, when cross-linking
takes place between acrylonitrile groups of NBR and –SO2Cl groups or in situ generated allyl chloride moieties of CSM. The thermal stability of vulcanizates was analyzed in nitrogen
by thermogravimetry. It was found that the initial degradation temperature of elastomer based on CSM rubber is lower than
of pure NBR rubber. By adding NBR to CSM rubbers, the degradation temperature of crosslinked material increased, indicating
higher thermal stability. The activation energy for the degradation are determined using the Arrhenius equation The activation
energies for the rubber blends are higher than for elastomers based on pure rubbers. It was found that the mass loss of the
blends at any temperature was between those of the pure rubbers. The differential scanning calorimetry (DSC) was used for
the glass transition temperature determination. It is estimated thermodynamic immiscibility of NBR/CSM blend based on noticed
two different glass transition temperatures, corresponding to CSM and NBR rubbers. 相似文献
94.
Enantiodivergent formal synthesis of (+)- and (−)-muricatacins from d-xylose has been accomplished through utilization of the latent plane of symmetry present in the starting monosaccharide. This approach was extended to the preparation of two novel (+)- and (−)-muricatacin 7-oxa analogs (2 and ent-2, respectively), which showed in vitro antitumor activity toward some human malignant cells. The analog ent-2 showed a powerful antiproliferative activity against the K562 cell line, being 36-fold more potent than the standard cytotoxic agent, doxorubicin. Compound 2, however, showed a powerful cytotoxic activity against HL-60 cells, being more than 17-fold more potent with respect to the reference compound. 相似文献
95.
Cerkvenik-Flajs V 《Biomedical chromatography : BMC》2006,20(10):985-992
Validation of an analytical method for determining chloramphenicol residues in muscle tissue by gas chromatography-electron capture detection (GC-ECD) was performed according to the latest European Union criteria for the analysis of veterinary drugs in food, laid down by Commission Decision 2002/657/EC. The method using the meta isomer of chloramphenicol as an internal standard proved to be very selective, specific to other related phenicols and accurate to within +3.6% at a concentration level of 8.9 microg/kg, as present in the certified reference material available. The correlation coefficient of the calibration curve was 0.9991. At all three fortification levels studied (0.3, 0.45 and 0.6 microg/kg), repeatability and intra-laboratory reproducibility were <8 and < or =9%, respectively. The decision limit (CCalpha) and detection capability (CCbeta) were 0.07 and 0.12 microg/kg, respectively. The validation results and the results of participation in an international inter-laboratory proficiency test indicate that the method presented is completely suited for regulatory control to screen and quantify chloramphenicol residues in various muscle tissues on a routine basis. 相似文献
96.
CH/pi interactions between the coordinated acetylacetonato ligand and phenyl rings were analyzed in the crystal structures from the Cambridge Structural Database and by quantum chemical calculations. The acetylacetonato ligand may engage in two types of interactions: it can be hydrogen atom donor or acceptor. The analysis of crystal structures and calculations show that interactions with the acetylacetonato ligand acting as hydrogen atom donor depend on the metal in an acetylacetonato chelate ring; the chelate rings with soft metals make stronger interactions. The same trend was not observed in the interactions where the acetylacetonato chelate ring acts as the hydrogen atom acceptor. 相似文献
97.
Stankov-Jovanović VP Nikolić-Mandić SD Mandić LM Mitić VD 《Analytical and bioanalytical chemistry》2006,385(8):1462-1469
Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine
acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine.
Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine
chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten’s constant KM=0.40 mmol/L, maximal reaction rate Vmax=52.2 μmol/L min, inhibition constant Ki=0,56 μmol/L and IC50=1.31 μmol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20–68.25 nmol/L,
which corresponds to the real sample concentrations from 0.328 to 2.730 μmol/L. The method detection and quantification limits
were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70,
29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15–7.45%. Accuracy was examined by standard
addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed
method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery.
The method has good sensitivity, accuracy, precision and it is suitable for clinical practice.
相似文献
98.
Hemorrhage control in arteries using high-intensity focused ultrasound: a survival study 总被引:5,自引:0,他引:5
Zderic V Keshavarzi A Noble ML Paun M Sharar SR Crum LA Martin RW Vaezy S 《Ultrasonics》2006,44(1):46-53
High-intensity focused ultrasound (HIFU) has been shown to provide an effective method for hemorrhage control of blood vessels in acute animal studies. The objective of the current study was to investigate the long-term effects of HIFU-induced hemostasis in punctured arteries. The femoral arteries ( approximately 2mm in diameter) of 25 adult anesthetized rabbits were surgically exposed, and either punctured and treated with HIFU (n=15), served as control (no puncture and no HIFU application: n=7), or were punctured and left untreated (n=3). Treated animals were allowed to recover, and examined and/or sacrificed on days 0, 1, 3, 7, 14, 28, and 60 after treatment to obtain ultrasound images and samples of blood and tissue. Hemostasis (arrest of bleeding) was achieved in all 15 of the HIFU-treated arteries. Eleven of the arteries were patent after HIFU treatment, and four arteries were occluded, as determined by Doppler ultrasound. The median HIFU application time to achieve hemostasis was 20s (range 7-55 s) for the patent arteries and 110 s (range 50-134 s) for the occluded arteries. In untreated animals, bleeding had not stopped after 120 s. One of the occluded arteries had reopened by day 14. No immediate or delayed re-bleeding was observed after HIFU treatment. Maximal blood flow velocities were similar in HIFU-treated patent vessels and control vessels. No significant difference in hematocrits was found between HIFU-treated and control groups at different time points after the procedure. Light microscopy observations of the HIFU-treated arteries showed disorganization of adventitia, and coagulation and thinning of the tunica media. The general organization of the adventitia and tunica media recovered to normal appearance within 28 days, with some thinning of the tunica media observed up to day 60. Neointimal hyperplasia was observed on days 14 and 28. The results show that HIFU can produce effective and long-term (up to 60 days) hemostasis of punctured femoral arteries while preserving normal blood flow and vessel wall structure in the majority of vessels. 相似文献
99.
In this paper we define the radical ϱ
k
(k∈Z
+) of a relation ϱ on an arbitrary semigroup. Also, we define various types of k-regularity of semigroups and various types of k-Archimedness of semigroups. Using these notions we describe the structure of semigroups in which ρ
k
is a band (semilattice) congruence for some Green’s relation. 相似文献
100.