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171.
Valeriu Mereacre Denis Prodius Ayuk M. Ako Narpinder Kaur Janusz Lipkowski Charles Simmons Naresh Dalal Ion Geru Christopher E. Anson Annie K. Powell Constantin Turta 《Polyhedron》2008
Reaction of manganese acetate and lanthanide nitrates in the presence of excess of PhCOOH affords highly asymmetric dodecanuclear mixed-metal [Mn10Ln2(OH)(O)8(PhCOOH)(PhCOO)19] (Ln = PrIII (1), NdIII (2)) clusters. The similar reaction, but with only 2 equiv. of PhCOOH resulted in the compounds with higher nuclearity [Mn11Eu4(O)8(OH)8(PhCOO)18(NO3)2(H2O)6]NO3 · 4CH3CN (3). Variable-temperature solid-state magnetic susceptibility of 1 and 2 in the temperature range 1.8–300 K were carried out, and for both complexes antiferromagnetic exchange interactions between the metal centers were observed, giving an estimated S = 17/2 ground state. AC magnetic susceptibility data have revealed out-of-phase signals, which suggest that these complexes exhibit a slow relaxation of magnetization as observed in single-molecule magnets. 相似文献
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173.
Fatma Türkyilmaz Dr. Gerald Kehr Dr. Jun Li Dr. Constantin G. Daniliuc Matthias Tesch Prof. Armido Studer Prof. Gerhard Erker 《Angewandte Chemie (International ed. in English)》2016,55(4):1470-1473
B(C6F5)2‐containing boryldienes 4 underwent the addition of two molar equivalents of TEMPO to give N,O‐bonded four‐membered heterocyclic products 7 . The reaction is a metal‐free example of the generation of reactive nitrogen‐centered TEMPO radical derivatives, in this case by the addition of TEMPO to the borane, followed by carbon–nitrogen bond formation and subsequent trapping of the resulting allyl radical by the second equivalent of TEMPO. 相似文献
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175.
George Fragkiadakis Michael Doumpos Constantin Zopounidis Christophe Germain 《Annals of Operations Research》2016,247(2):787-806
The continuous growth of hospital costs has driven governments in many countries to seek ways to improve their efficiency. In Greece, this has consistently been a major issue for almost two decades, as efficiency assessment and monitoring systems are lacking. In response to this need, the evaluation of the National Health System hospitals’ efficiency level is a precondition for planning, implementing and monitoring any promising reform. In this paper, a non-parametric modeling approach is employed to assess and analyze the efficiency of 87 Greek public hospitals over the period 2005–2009, using data envelopment analysis. The operational and economic aspects of the hospitals’ operation are considered on the basis of their service/case mix and cost structure. We also investigate the efficiency trends over time with the Malmquist index and a second stage regression analysis is performed to explain the operational and economic efficiency results in terms of the hospitals’ operating characteristics and the environment in which they operate. 相似文献
176.
177.
Chemical Twinning of Salt and Metal in the Subnitridometalates Ba23Na11(MN4)4 with M=V,Nb, Ta
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Matthias Wörsching Frank Tambornino Stefan Datz Dr. Constantin Hoch 《Angewandte Chemie (International ed. in English)》2016,55(36):10868-10871
The subnitridometalates Ba23Na11(MN4)4 (M=V, Nb, Ta) crystallize in a new structure type, which shows ionic ortho‐nitridometalate anions and motifs from simple (inter)metallic packings: Na‐centered [Na8] cubes as cutouts of the bcc structure of elemental Na and Na‐centered [Ba10Na2] icosahedra as found in Laves phases, for example. Single‐crystal and powder X‐ray diffraction studies in combination with quantum‐chemical calculations of the electronic structure and Raman spectroscopy support the characterization of the subnitridometalates as “chemical twins”. They consist of independent building units with locally prevalent ionic or metallic bonding in an overall metallic compound. 相似文献
178.
Delivering Structural Information on the Polar Face of Membrane‐Active Peptides: 19F‐NMR Labels with a Cationic Side Chain
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Oleg M. Michurin Dr. Sergii Afonin Dr. Marina Berditsch Dr. Constantin G. Daniliuc Prof. Anne S. Ulrich Prof. Igor V. Komarov Dr. Dmytro S. Radchenko 《Angewandte Chemie (International ed. in English)》2016,55(47):14595-14599
Conformationally constrained non‐racemizing trifluoromethyl‐substituted lysine isosteres [(E)‐ and (Z)‐TCBLys] with charged side chains are presented as a new type of 19F‐NMR labels for peptide studies. Design of the labels, their synthesis, incorporation into peptides and experimental demonstration of their application for solid state NMR studies of membrane‐active peptides are described. A series of fluorine‐labeled analogues of the helical amphipathic antimicrobial peptide PGLa(Nle) was obtained, in which different lysine residues in the original peptide sequence were replaced, one at a time, by either (E)‐ or (Z)‐TCBLys. Antimicrobial activities of the synthesized analogues were practically the same as those of the parent peptide. The structural and orientational parameters of the helical PGLa(Nle) peptide in model bilayers, as determined using the novel labels confirmed and refined the previously known structure. (E)‐ and (Z)‐TCBLys, as a set of cationic 19F‐NMR labels, were shown to deliver structural information about the charged face of amphipathic peptides by solid state 19F‐NMR, previously inaccessible by this method. 相似文献
179.
The use of metallocenes in many stoichiometric and catalytic processes has been the impetus for the development of new organometallic complexes, especially those containing early transition metals. The formation of coordinative unsaturated complexes using allylic, benzamidinate and aminopyridine families is presented. The synthesis and structural parameters of the new complexes, their activation and use in the polymerization of alpha-olefins and dienes, in the dehydrogenative coupling of silanes and in the hydroamination reactions comprise the objectives of this review. 相似文献
180.
Hatziieremia S Kostomitsopoulos N Balafas V Tamvakopoulos C 《Rapid communications in mass spectrometry : RCM》2007,21(15):2431-2438
Melanotan-II (MT-II), a synthetic analogue of the natural melanocortin peptide, alpha-melanocyte-stimulating hormone (alpha-MSH), is well known for the anorexic effects it elicits in rodents. These effects are, at least partly, associated with agonistic action on the centrally located melanocortin receptors, MC3R and MC4R. Whether MT-II exerts this effect via brain penetration still remains unclear. In order to address this question we administered MT-II in rodents at efficacious doses and then employed a sensitive methodology for the determination of MT-II in plasma and brain samples. MT-II was extracted from mouse plasma and brain tissue by acetonitrile precipitation followed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis. The described assay improved significantly previously reported MT-II levels of quantification in rat plasma and brain. The lower limits of quantification (LLOQs) of 0.5 ng/mL and 2.5 ng/g were obtained in 50 microL plasma and 100 microL brain homogenate, respectively. The calibration curve was linear over the concentration range of 0.5-500 ng/mL for plasma and 2.5-250 ng/g for brain tissue. The method was successfully applied in measuring levels of MT-II in plasma and brain tissue following intraperitoneal (ip) administration of 1 mg/kg of peptide in mice. Following administration of MT-II, clearance from plasma was rapid. The sensitivity of the assay allowed the determination of low concentrations of MT-II (11.4 +/- 5.5 ng/g) in brain homogenate at 30 min after dosing. However, the brain concentrations when compared with the high plasma levels of MT-II at the same time point confirmed the low penetrability of the peptide in mouse brain. 相似文献