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61.
Maj‐Britt Suhr Kirketerp Michael Åxman Petersen Dr. Marius Wanko Dr. Leonardo Andres Espinosa Leal Henning Zettergren Dr. Françisco M. Raymo Prof. Angel Rubio Prof. Mogens Brøndsted Nielsen Prof. Steen Brøndsted Nielsen Prof. 《Chemphyschem》2009,10(8):1207-1209
From blue to red: While four π‐conjugated nitrophenolates absorb within a relatively narrow region in solution, they cover the entire visible spectrum when isolated in vacuo (see picture). The work combines gas‐ and solution‐phase spectroscopy and provides the first benchmark of theoretical excitation energies for nitrophenolates.
62.
We introduce a new approach to the model theory of metric structures by defining the notion of a metric abstract elementary class (MAEC) closely resembling the notion of an abstract elementary class. Further we define the framework of a homogeneous MAEC were we additionally assume the existence of arbitrarily large models, joint embedding, amalgamation, homogeneity and a property which we call the perturbation property. We also assume that the Löwenheim-Skolem number, which in this setting refers to the density character of the set instead of the cardinality, is ${\aleph_0}$ . In these settings we prove an analogue of Morley’s categoricity transfer theorem. We also give concrete examples of homogeneous MAECs. 相似文献
63.
ABSTRACTCore–valence double-electron ionisation spectra of a few small molecules – carbon monoxide, ammonia, methyl fluoride and thiophene – are presented and analysed using the self-consistent field algorithm introduced by Hans Jørgen Jensen 30 years ago. It confirms the utility of this algorithm, frequently employed to obtain stable and sharp convergence of wave functions for the benefit of calculations of a great variety of molecular properties, thus also for optimisation of core–valence states and for the interpretation of the corresponding spectra. 相似文献
64.
A new and general procedure is described for a detailed analysis of time-resolved fluorescence depolarisation data in the presence of electronic energy migration. An isotropic ensemble of bifluorophoric molecules (D(1)-R-D(2)) has been studied to demonstrate its utility. Intramolecular donor-donor energy migration occurs between the two donor groups (D), which are covalently connected to a rigid linker group (R). These groups undergo restricted reorientational motions with respect to the R group. The analysis of depolarisation data basically involves the search for best-fit parameters which describe the local reorientational motions, the intermolecular D(1)-D(2) distance, as well as the mutual orientations of the donors. For this, the analysis is partly performed on the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process has been described by using Monte Carlo simulations and an extended F?rster theory (EFT). It is found that the EFT provides the least time-consuming computational method. Since one-photon and two-photon excited fluorescence experiments can be applied for energy migration studies, a general and unified theoretical formulation is given. 相似文献
65.
66.
Oscar Verho Marléne D. V. Dilenstam Markus D. Kärkäs Dr. Eric V. Johnston Dr. Torbjörn Åkermark Prof. Jan‐E. Bäckvall Prof. Björn Åkermark 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(52):16947-16954
By using a dimeric ruthenium complex in combination with tert‐butyl hydrogen peroxide (TBHP) as stoichiometric oxidant, a mild and efficient protocol for the oxidation of secondary benzylic alcohols was obtained, thereby giving the corresponding ketones in high yields within 4 h. However, in the oxidation of aliphatic alcohols, the TBHP protocol suffered from low conversions owing to a competing Ru‐catalyzed disproportionation of the oxidant. Gratifyingly, by switching to Oxone (2 KHSO5 ? KHSO4 ? K2SO4 triple salt) as stoichiometric oxidant, a more efficient and robust system was obtained that allowed for the oxidation of a wide range of aliphatic and benzylic secondary alcohols, giving the corresponding ketones in excellent yields. The mechanism for these reactions is believed to involve a high‐valent RuV–oxo species. We provide support for such an intermediate by means of mechanistic studies. 相似文献
67.
Beatrix C. Hiesmayr Antonio Di Domenico Catalina Curceanu Andreas Gabriel Marcus Huber Jan-Åke Larsson Pawel Moskal 《The European Physical Journal C - Particles and Fields》2012,72(1):1856
Entanglement and its consequences—in particular the violation of Bell inequalities, which defies our concepts of realism and
locality—have been proven to play key roles in Nature by many experiments for various quantum systems. Entanglement can also
be found in systems not consisting of ordinary matter and light, i.e. in massive meson–antimeson systems. Bell inequalities
have been discussed for these systems, but up to date no direct experimental test to conclusively exclude local realism was
found. This mainly stems from the fact that one only has access to a restricted class of observables and that these systems
are also decaying. In this Letter we put forward a Bell inequality for unstable systems which can be tested at accelerator
facilities with current technology. Herewith, the long awaited proof that such systems at different energy scales can reveal
the sophisticated “dynamical” nonlocal feature of Nature in a direct experiment gets feasible. Moreover, the role of entanglement and CP\mathcal{CP} violation, an asymmetry between matter and antimatter, is explored, a special feature offered only by these meson–antimeson
systems. 相似文献
68.
A method based on hollow fiber liquid phase microextraction (HF-LPME) for analysis of pinic acid and pinonic acid was developed and for the first time successfully applied to ambient aerosol samples. In this method, the aerosol samples were dissolved in 0.05 M H2SO4 and the solution was extracted using three-phase HF-LPME where donor phase was 0.1 M (NH4)2CO3. Different parameters like type of organic solvent for membrane phase, extraction time and stirring speed etc. were optimized. Optimum extraction time was 4.5 h and optimum-stirring speed was found to be 900 rpm. We used 6-undecanone as organic phase along with tri-n-octylphosphine oxide (optimum TOPO contents was 15% w/v), which gave an enormous enrichment for both pinic and pinonic acid. Enrichment factors of 28,050 and 27,400 times were obtained for pinonic acid and pinic acid, respectively, that are the highest ever published. The extraction efficiency for pinic acid and pinonic acid were 68.5% and 70.1%, respectively. Very low limits of detection were obtained. Values of 1.0 ng L?1 and 0.5 ng L?1 in aqueous solutions, corresponding to 24 pg m?3 and 12 pg m?3 in aerosol samples were the limits of detections for pinonic acid and pinic acid, respectively. Both pinonic acid and pinic acid were found in all aerosol samples analyzed. 相似文献
69.
We present a detailed investigation of the perturbation approach for calculating zero-point vibrational contributions to
molecular properties. It is demonstrated that if the sum of the potential energy and the zero-point vibrational energy is
regarded as an effective potential energy, the leading contribution to the first-order wave function vanishes in the perturbation
approach. Two different perturbation approaches have been investigated numerically by calculations of some magnetic properties
for a few diatomic molecules and the results obtained have been compared to the exact numerical results. It is shown that
only a few terms need to be included in a perturbation expansion to obtain an accuracy in the calculated rovibrational contribution
better than the quality normally obtained for the potential and property surfaces in electronic structure calculations.
Received: 16 April 1999 / Accepted: 1 July 1999 / Published online: 4 October 1999 相似文献
70.
Anthony Prandina Sylvie Radix Marc Le Borgne Lars Petter Jordheim Zineb Bousfiha Christopher Fröhlich Hanna-Kirsti S. Leiros Ørjan Samuelsen Espen Frøvold Pål Rongved Ove Alexander Høgmoen Åstrand 《Tetrahedron》2019,75(11):1525-1540
Antibiotics are key drugs in modern healthcare, especially in hospitals, where multiresistant bacteria resides and is a potential threat to human health. In the present work, a new series of adjuvants working synergistically with the carbapenem meropenem, in which a selective zinc-chelating agent was covalently linked to the small bacterial peptide D-Ala-D-Ala, was synthesized and tested against VIM-2 and NDM-1 metallo-β-lactamases (MBLs). The nature of the linker was modified in a structure-activity relationship study. Compound 1i, having an ethyl piperidine linker, lowered the MIC of meropenem from 32 to 64?mg/L to 2 and 1–2?mg/L against VIM-2- and NDM-1-producing clinical isolates, respectively. The IC50 value of 1i against VIM-2 was 9.8 and 2.2?μM after 5 and 20?min, respectively. Compound 1i also showed intrinsic toxicity against three eukaryotic human tumoral cell lines between 50 and 120?μM. 相似文献