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921.
We consider point sets in the m-dimensional affine space where each squared Euclidean distance of two points is a square in Fq. It turns out that the situation in is rather similar to the one of integral distances in Euclidean spaces. Therefore we expect the results over finite fields to be useful for the Euclidean case.We completely determine the automorphism group of these spaces which preserves integral distances. For some small parameters m and q we determine the maximum cardinality I(m,q) of integral point sets in . We provide upper bounds and lower bounds on I(m,q). If we map integral distances to edges in a graph, we can define a graph Gm,q with vertex set . It turns out that Gm,q is strongly regular for some cases. 相似文献
922.
The ability of hearing-impaired (HI) listeners to use high-rate envelope information in a competing-talker situation was assessed. In experiment 1, signals were tone vocoded and the cutoff frequency (f(c)) of the envelope extraction filter was either 50?Hz (E filter) or 200?Hz (P filter). The channels for which the P or E filter was used were varied. Intelligibility was higher with the P filter regardless of whether it was used for low or high center frequencies. Performance was best when the P filter was used for all channels. Experiment 2 explored the dynamic range over which HI listeners made use of high-rate cues. In each channel of a vocoder, the envelope extracted using f(c)?=?16?Hz was replaced by the envelope extracted using f(c)?=?300?Hz, either at the peaks or valleys, with a parametrically varied "switching threshold." For a target-to-background ratio of +5?dB, changes in speech intelligibility occurred mainly when the switching threshold was between -8 and +8?dB relative to the channel root-mean-square level. This range is similar in width to, but about 3?dB higher in absolute level than, that found for normal-hearing listeners, despite the reduced dynamic range of the HI listeners. 相似文献
923.
The spontaneous formation of clusters of synchronized spiking in a structureless ensemble of equal stochastically perturbed excitable neurons with delayed coupling is demonstrated for the first time. The effect is a consequence of a subtle interplay between interaction delays, noise, and the excitable character of a single neuron. The dependence of the cluster properties on the time lag, noise intensity, and the synaptic strength is investigated. 相似文献
924.
Meyer K Ott C Raith P Kaldun A Jiang Y Senftleben A Kurka M Moshammer R Ullrich J Pfeifer T 《Physical review letters》2012,108(9):098302
Time-resolved measurements of quantum dynamics are based on the availability of controlled events that are shorter than the typical evolution time scale of the processes to be observed. Here we introduce the concept of noise-enhanced pump-probe spectroscopy, allowing the measurement of dynamics significantly shorter than the average pulse duration by exploiting randomly varying, partially coherent light fields consisting of bunched colored noise. These fields are shown to be superior by more than a factor of 10 to frequency-stabilized fields, with important implications for time-resolved experiments at x-ray free-electron lasers and, in general, for measurements at the frontiers of temporal resolution (e.g., attosecond spectroscopy). As an example application, the concept is used to explain the recent experimental observation of vibrational wave-packet motion in D(2)(+) on time scales shorter than the average pulse duration. 相似文献
925.
Ekaterina V. Ilgisonis Raisa Shalina Nigyar Kasum-Zade Kristina G. Burkova Oxana P. Trifonova Dmitry L. Maslov Anna L. Kaysheva Sergey S. Markin 《Molecules (Basel, Switzerland)》2022,27(8)
We sought to identify the characteristic metabolite profile of blood plasma samples obtained from patients with preeclampsia. Direct high-resolution mass spectrometry was used to analyze samples from 79 pregnant women, 34 of whom had preeclampsia. We performed a comparative analysis of the metabolite profiles and found that they differed between pregnant women with and without preeclampsia. Lipids and sugars were identified as components of the metabolite profile that are likely to be associated with the development of preeclampsia. While PE was established only in the third trimester, a set of metabolites specific for the third trimester, including 2-(acetylamino)-1,5-anhydro-2-deoxy-4-O-b-D-galactopyranosyl-D-arabino-Hex-1-enitol, N-Acetyl-D-glucosaminyldiphosphodolichol, Cer(d18:0/20:0), and allolithocholic acid, was already traced in the first trimester. These components are also likely involved in lipid metabolism disorders and the development of oxidative stress. 相似文献
926.
Mikhail V. Kalyaev Dmitry S. Ryabukhin Marina A. Borisova Alexander Yu. Ivanov Irina A. Boyarskaya Kristina E. Borovkova Lia R. Nikiforova Julia V. Salmova Nikolay V. Ulyanovskii Dmitry S. Kosyakov Aleksander V. Vasilyev 《Molecules (Basel, Switzerland)》2022,27(14)
Reactions of 3-(furan-2-yl)propenoic acids and their esters with arenes in Brønsted superacid TfOH affords products of hydroarylation of the carbon–carbon double bond, 3-aryl-3-(furan-2-yl)propenoic acid derivatives. According to NMR and DFT studies, the corresponding O,C-diprotonated forms of the starting furan acids and esters should be reactive electrophilic species in these transformations. Starting compounds and their hydroarylation products, at a concentration of 64 µg/mL, demonstrate good antimicrobial activity against yeast-like fungi Candida albicans. Apart from that, these compounds suppress Escherichia coli and Staphylococcus aureus. 相似文献
927.
928.
Kristina B. Simeonova Ana I. Koleva Anna-Mariya R. Zlatanova Nevena I. Petkova-Yankova Hristiyan A. Aleksandrov Petko St. Petkov Rositca D. Nikolova 《Molecules (Basel, Switzerland)》2022,27(21)
In the present study, the reaction conditions for homodimerization process of 3-acetylcoumarin were achieved under sonication using combination of zinc and metallic salt (ZnCl2 or Zn(OAc)2). Appropriate frequency and sound amplitude have been identified as significant variables for the initiation of the reaction. On the base of first principal calculations and experimental results, the mechanism of the reaction was investigated. The relative stability of the possible intermediates has been compared, including evaluation on the ionic and radical reaction pathways for the dimerization process. Theoretical results suggested that the radical mechanism is more favorable. The C-C bond formation between the calculated radical intermediates occurs spontaneously (∆G = −214 kJ/mol for ZnCl2, −163 kJ/mol in the case of Zn(OAc)2), which proves the possibility for the homodimerization of 3-acetylcoumarin via formation of radical species. Both experimental and theoretical data clarified the activation role of the solvent on the reactivity of the Zn-salt. The formation of complexes of solvent molecules with Zn-atom from the ZnCl2 reduces the energy barrier for the dissociation of Zn-Cl bond and facilitate the formation of the dimeric product. 相似文献
929.
F. Reiss Fr. I. Herz F. Scholler F. Bolm K. Vogt S. Rothenfußer W. Wedemann E. Pozzi-Escot A. O. Dahlberg O. Kurz O. Baumann G. Gahrtz J. Drost G. Koestler B. van der Burg C. A. Koppejan Wilhelm Müller I. Bang A. Bakke D. W. Horn F. v. Fillinger Julius Freund 《Analytical and bioanalytical chemistry》1925,67(4):169-176
930.
Dr. Vasily Sivchik Aleksandr Kochetov Toni Eskelinen Dr. Kristina S. Kisel Dr. Anastasia I. Solomatina Dr. Elena V. Grachova Dr. Sergey P. Tunik Dr. Pipsa Hirva Dr. Igor O. Koshevoy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1787-1794
Luminescent cyclometalated complexes [M(C^N^N)CN] (M=Pt, Pd; HC^N^N=pyridinyl- (M=Pt 1 , Pd 5 ), benzyltriazolyl- (M=Pt 2 ), indazolyl- (M=Pt 3 , Pd 6 ), pyrazolyl-phenylpyridine (M=Pt 4 )) decorated with cyanide ligand, have been explored as nucleophilic building blocks for the construction of halogen-bonded (XB) adducts using IC6F5 as an XB donor. The negative electrostatic potential of the CN group afforded CN⋅⋅⋅I noncovalent interactions for platinum complexes 1 – 3 ; the energies of XB contacts are comparable to those of metallophilic bonding according to QTAIM analysis. Embedding the chromophore units into XB adducts 1 – 3 ⋅⋅⋅IC6F5 has little effect on the charge distribution, but strongly affects Pt⋅⋅⋅Pt bonding and π-stacking, which lead to excited states of MMLCT (metal–metal-to-ligand charge transfer) origin. The energies of these states and the photoemissive properties of the crystalline materials are primarily determined by the degree of aggregation of the luminophores via metal–metal interactions. The adduct formation depends on the nature of the metal and the structure of the metalated ligand, the variation of which can yield dynamic XB-supported systems, exemplified by thermally regulated transition 3 ↔ 3 ⋅⋅⋅IC6F5. 相似文献