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排序方式: 共有158条查询结果,搜索用时 15 毫秒
51.
Dean Weldor Tina D. Poulsen Kurt V. Mikkelsen Peter R. Ogilby 《Photochemistry and photobiology》1999,70(4):369-379
The lowest excited electronic state of molecular oxygen, O2(a1-DLg), is often called simply singlet oxygen. This singlet delta state is an acknowledged and well-studied intermediate in many solution-phase photosystems. However, the second excited electronic state of oxygen, O2(b1δg+), is also a singlet. It has recently become possible to monitor this singlet sigma state in solution, which, in combination with studies of the singlet delta state, contributes to a better understanding of a variety of general problems in chemistry. 相似文献
52.
A. Jourdan P. Doussi re D. Leclerc S. Gurib F. Masetti N. Vodjdani F. Ratovelomanana A. Enard G. Morthier R. Baets C. J rgensen T. Durhuus B. Mikkelsen S. L. Danielsen K. Stubjkaer M. Schilling K. Wü nstel W. Idler D. Chiaroni 《Fiber and Integrated Optics》1996,15(3):193-210
We present the latest results about all-optical wavelength conversion obtained within the European Union—funded RACE ATMOS project. In particular, solutions based on carrier depletion in Distributed Brag Reflector lasers have reached penalty-free polarization-insensitive operation at up to 2.5 Gbit/s, while solutions based on Semiconductor Optical Amplifiers (SOAS) under cross-gain modulation have been demonstrated at more than 20 Gbit/s. The study of cross-phase modulation in SOAs has also been performed, leading to the monolithic integration of SOAs within an interferometer, according to structures proposed by the project. Penalty-free operation at up to 10 Gbit/s as well as signal reshaping have been obtained with such devices. Besides the study of components, wavelength converters have been used in several demonstrators assessing their maturity and compatibility with photonic-switching applications. 相似文献
53.
Wang JG Li WX Borg M Gustafson J Mikkelsen A Pedersen TM Lundgren E Weissenrieder J Klikovits J Schmid M Hammer B Andersen JN 《Physical review letters》2005,95(25):256102
Using core-level spectroscopy and density functional theory we show that a one-dimensional (1D) oxide structure forms at the steps of the Pt(332) surface after exposure. The 1D oxide is found to be stable in an oxygen pressure range, where bulk oxides are only metastable, and is therefore argued to be a precursor to the Pt oxidation. As an example of the consequences of such a precursor exclusively present at the steps, we investigate the reaction of CO with oxygen covered Pt(332). Albeit more strongly bound, the oxidic oxygen is found to react more easily with CO than oxygen chemisorbed on the Pt terraces. 相似文献
54.
Se vapor pressures were measured by the dew point method for the binary system Ga1·xSex, 0.60 < x < 1.00 (Ga2Se3-Se), between 700 and 1050°C. The Se vapor pressure was found to decrease rapidly near x = 60 atomic% Se. The T-X and P-X liquidus curves are thermodymanically modelled by a regular associated solution model for the liquid phase, with the associate, Ga2Se3. The best fit to the data was obtained with 4000 cal/mole of Ga2Se3 for the regular solution interaction parameter and 0.10 for the degree of dissociation in the stoichiometric liquid (x = 0.60). 相似文献
55.
From measurements on single crystals of Li2Ti3O7, the conductivity is determined to be predominately ionic with an anisotropy of and . This anisotropy is significant but is not sufficient to classify this channel-structured ramsdellite material as a one-dimensional conductor. A conduction path through the ramsdellite crystal structure consistent with the determined anisotropy is presented. 相似文献
56.
57.
Viktor Bliksted Roug Pedersen Jeppe Granhøj Andreas Erbs Hillers-Bendtsen Prof. Dr. Anders Kadziola Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(32):8315-8324
Polycyclic aromatic hydrocarbons (PAHs) have found strong interest for their electronic properties and as model systems for graphene. While PAHs have been studied intensively as single units, here PAHs were constructed in ladder-type arrangements using cross-conjugated fulvalene and dithiafulvalene motifs as connecting units and moving forward a convenient synthetic approach for dimerizing (thio)ketones into olefins by the action of Lawesson's reagent. Some of the PAHs can also be regarded as “super-extended” tetrathiafulvalenes (TTFs) with some of the largest cores ever explored, being multi-redox systems that exhibit both reversible oxidations and reductions. Concomitant absorption redshifts were observed when expanding the ladder-type structures from one to two to three indenofluorene units, and optical and electrochemical HOMO-LUMO gaps were found to correlate linearly. Various conformations (and solid-state packing arrangements) were studied by X-ray crystallography and computations. 相似文献
58.
Alvis Mengots Andreas Erbs Hillers-Bendtsen Dr. Sandra Doria Frederik Ørsted Kjeldal Nicolai Machholdt Høyer Dr. Anne Ugleholdt Petersen Prof. Dr. Kurt V. Mikkelsen Dr. Mariangela Di Donato Prof. Dr. Martina Cacciarini Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12437-12446
Photoswitch triads comprising two dihydroazulene (DHA) units in conjugation with a central trans-azobenzene (AZB) unit were prepared in stepwise protocols starting from meta- and para-disubstituted azobenzenes. The para-connected triad had significantly altered optical properties and lacked the photoactivity of the separate photochromes. In contrast, for the meta-connected triad, all three photochromes could be photoisomerized to generate an isomer with two vinylheptafulvene (VHF) units and a cis-azobenzene unit. Ultrafast spectroscopy of the photoisomerizations revealed a fast DHA-to-VHF photoisomerization and a slower trans-to-cis AZB photoisomerization. This meta triad underwent thermal VHF-to-DHA back-conversion with a similar rate of all VHFs, independent of the identity of the neighboring units, and in parallel thermal cis-to-trans AZB conversion. The experimental observations were supported by computation (excitation spectra and orbital analysis of the transitions). 相似文献
59.
Bondesson L Mikkelsen KV Luo Y Garberg P Agren H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(2):213-224
Infrared and Raman spectra of three drug molecules, aspirin, caffeine and ibuprofen, in gas phase and in aqueous solution have been simulated using hybrid density functional theory. The long range solvent effect is modelled by the polarizable continuum model, while the short range hydrogen bonding effects are taken care of by the super-molecular approach with explicit inclusion of water molecules. The calculated spectra are found to compare well with available experimental results. The agreement obtained make grounds for proposing theoretical modeling as a tool for characterizing changes in the bonding environments of drug molecules in terms of particular variations in their IR and Raman spectra. 相似文献
60.
Si-Qian Chen Deirdre Mikkelsen Patricia Lopez-Sanchez Dongjie Wang Marta Martinez-Sanz Elliot P. Gilbert Bernadine M. Flanagan Michael J. Gidley 《Cellulose (London, England)》2017,24(3):1211-1226
This study investigated cellulose production and microstructure variation from six Komagataeibacter strains (ATCC 53524, ATCC 10245, ATCC 23769, ATCC 700178, NBRC 13693 and KTH 5655). Strain KTH 5655 produced the highest cellulose yields (10.39 g/l) after 9 days cultivation. Nuclear magnetic resonance spectroscopy and X-ray diffraction revealed that strain ATCC 23769 synthesised cellulose with the lowest crystallinity and decreased ratio of Iα/Iβ allomorph, whilst strain KTH 5655 produced a relatively ordered cellulose structure. However, the average widths of cellulose ribbons were similar (30–50 nm) for all types of cellulose. Phylogenetic analysis of the 16S rRNA gene indicated that these strains shared a high level of genetic similarity (ranging from 88 to 98%). All strains were used to produce cellulose in the presence of arabinoxylan or xyloglucan as simplified cell wall analogues. Our results provide guidance for the selection of cellulose-producing strains for specific biotechnological and research applications. 相似文献