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排序方式: 共有326条查询结果,搜索用时 62 毫秒
321.
Leszek Pazderski Jaromír Touek Andrzej Wojtczak Jerzy Sitkowski Lech Kozerski Edward Szyk 《Polyhedron》2008,27(14):3067-3078
The crystal and molecular structure of potassium aquapentachloroiridate(III) (K2[Ir(H2O)Cl5]) was reported. The [Ir(H2O)Cl5]2− anions are nearly octahedral, the axial Ir–Cl bond (2.322(2) Å) being shorter than the equatorial ones (2.346(2)–2.360(2) Å); the Ir–O bond length is 2.090(4) Å. Ir(III) chloride complexes with 2,2′-bipyridine (LL = bpy) or 1,10-phenanthroline (LL = phen), of the general formulae K[Ir(LL)Cl4] and cis-[Ir(LL)2Cl2]Cl, were studied by far-IR and 1H–13C, 1H–15N HMBC/HMQC/HSQC–NMR. High-frequency 1H NMR coordination shifts (Δ1Hcoord = δ1Hcomplex − δ1Hligand; max. ca. +1 ppm) were noted for [Ir(LL)Cl4]− anions, while for cis-[Ir(LL)2Cl2]+ cations they had variable sign and magnitude (max. ca. ±1 ppm); they were dependent on the proton position, being mostly expressed for the nitrogen-adjacent hydrogens (H(6) for bpy, H(2) for phen). 13C NMR signals were high-frequency shifted (by max. ca. 8 ppm), whereas all 15N nuclei were shifted to the lower frequency (by ca. 105–120 ppm). The experimental 1H, 13C, 15N NMR chemical shifts were reproduced by semi-empirical quantum-chemical calculations (B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*). 相似文献
322.
It is shown that if two submeasures on that are lim sup's of sequences of measures have the same zero sets, and one is nonatomic, so is the other, and they are (ε-δ)-equivalent. Moreover, if a submeasure η is the lim sup of a sequence of lower semi-continuous (lsc) submeasures and is 0-dominated by the so-called core γ• of an lsc submeasure γ, then η is also (ε-δ)-dominated by γ•. And if a submeasure η of this type is 0-dominated by a nonatomic submeasure, then it is nonatomic as well. 相似文献
323.
LJ Hubble E Chow JS Cooper M Webster KH Müller L Wieczorek B Raguse 《Lab on a chip》2012,12(17):3040-3048
Functionalised gold nanoparticle (Au(NP)) chemiresistors are investigated for direct sensing of small organic molecules in biological fluids. The principle reason that Au(NP) chemiresistors, and many other sensing devices, have limited operation in biological fluids is due to protein and lipid fouling deactivating the sensing mechanism. In order to extend the capability of such chemiresistor sensors to operate directly in biofluids, it is essential to minimise undesirable matrix effects due to protein and lipidic components. Ultrafiltration membranes were investigated as semi-permeable size-selective barriers to prevent large biomolecule interactions with Au(NP) chemiresistors operating in protein-loaded biofluids. All of the ultrafiltration membranes protected the Au(NP) chemiresistors from fouling by the globular biomolecules, with the 10 kDa molecular weight cut-off size being optimum for operation in biofluids. Titrations of toluene in different protein-loaded fluids indicated that small molecule detection was possible. A sensor array consisting of six different thiolate-functionalised Au(NP) chemiresistors protected with a size-selective ultrafiltration membrane successfully identified, and discriminated the spoilage of pasteurised bovine milk. This proof-of-principle study demonstrates the on-chip protein separation and small metabolite detection capability, illustrating the potential for this technology in the field of microbial metabolomics. Overall, these results demonstrate that a sensor array can be protected from protein fouling with the use of a membrane, significantly increasing the possible application areas of Au(NP) chemiresistors ranging from the food industry to health services. 相似文献
324.
Dagmara Jacewicz Dariusz Wyrzykowski Krzysztof ?amoj? Diana Czerwińska Paulina Czaja Lech Chmurzyński 《Structural chemistry》2012,23(2):333-340
The thermal decomposition of trans-K[Cr(C2O4)2(OH2)2]·3H2O and cis-K[Cr(C2O4)2(OH2)2] has been studied using the TG–MS technique. The measurements were carried out in an argon atmosphere over the temperature
range of 293–873 K. The influence of the complex structures and configurational geometry on the stability of the transition
products and the pathways of thermal transformations has been discussed. Furthermore, the kinetics of the isomerization reactions
of the [Cr(C2O4)2(OH2)2]− complex ion catalyzed by five different metal ions: Be2+, Mg2+, Ca2+, Sr2+ and Ba2+ have been studied. The isomerization reactions were studied in aqueous solution at five various temperatures (283–303 K),
at constant concentration of metal ions (C = 0.1 M) and the constant ionic strength of solution (Na+, NO3
−) I = 2.4 M. The rates of the isomerization reaction were determined spectrophotometrically by monitoring of absorbance changes
at 410 nm. 相似文献
325.
A Pratesi G Giuli MR Cicconi S Della Longa TC Weng M Ginanneschi 《Inorganic chemistry》2012,51(15):7969-7976
A former spectroscopic study of Cu(II) coordination by the 13-membered ring cyclic tetrapeptide c(Lys-dHis-βAla-His) (DK13), revealed the presence, at alkaline pH, of a stable peptide/Cu(III) complex formed in solution by atmospheric dioxygen oxidation. To understand the nature of this coordination compound and to investigate the role of the His residues in the Cu(III) species formation, Cu K-edge XANES, and EXAFS spectra have been collected for DK13 and two other 13-membered cyclo-peptides: the diastereoisomer c(Lys-His-βAla-His) (LK13), and c(Gly-βAla-Gly-Lys) (GK13), devoid of His residues. Comparison of pre-edge peak features with those of Cu model compounds, allowed us to get information on copper oxidation state in two of the three peptides, DK13 and GK13: DK13 contains only Cu(III) ions in the experimental conditions, while GK13 binds only with Cu(II). For LK13/Cu complex, EXAFS spectrum suggested and UV-vis analysis confirmed the presence of a mixture of Cu(II) and Cu(III) coordinated species. Theoretical XANES spectra have been calculated by means of the MXAN code. The good agreement between theoretical and experimental XANES data collected for DK13, suggests that the refined structure, at least in the first coordination shell around Cu, is a good approximation of the DK13/Cu(III) coordination species present at strongly alkaline pH. All the data are consistent with a slightly distorted pyramidal CuN(4) unit, coming from the peptide bonds. Surprisingly, the His side-chains seemed not involved in the final, stable, Cu(III) scaffold. 相似文献
326.
Lech Zarȩba 《NoDEA : Nonlinear Differential Equations and Applications》2009,16(4):445-467
In this paper we consider the mixed problem for the equation u
tt
+ A
1
u + A
2(u
t
) + g(u
t
) = f(x, t) in unbounded domain, where A
1 is a linear elliptic operator of the fourth order and A
2 is a nonlinear elliptic operator of the second order. Under natural assumptions on the equation coefficients and f we proof existence of a solution. This result contains, as a special case, some of known before theorems of existence. Essentially,
in difference up to previous results we prove theorems of existence without the additional assumption on behavior of solution
at infinity.
相似文献