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91.
Optical Bloch equations are widely used for describing dynamics in a system consisting molecules, electromagnetic waves, and a thermal bath. We analyze applicability of these equations to a single molecule imbedded in a solid matrix. Classical Bloch equations and the limits of their applicability are derived from more general master equations. Simple and intuitively appealing picture based on stochastic Bloch equations shows that at low temperatures, contrary to common believes, a strong driving field can not only suppress but can also increase decay rates of Rabi oscillations. A physical system where predicted effects can be observed experimentally is suggested. 相似文献
92.
93.
We prove that a locally compact ANR-space X is a Q-manifold if and only if it has the Disjoint Disk Property (DDP), all points of X are homological Z∞-points and X has the countable-dimensional approximation property (cd-AP), which means that each map f:K→X of a compact polyhedron can be approximated by a map with the countable-dimensional image. As an application we prove that a space X with DDP and cd-AP is a Q-manifold if some finite power of X is a Q-manifold. If some finite power of a space X with cd-AP is a Q-manifold, then X2 and X×[0,1] are Q-manifolds as well. We construct a countable familyχof spaces with DDP and cd-AP such that no space X∈χis homeomorphic to the Hilbert cube Q whereas the product X×Y of any different spaces X, Y∈χis homeomorphic to Q. We also show that no uncountable familyχwith such properties exists. 相似文献
94.
Taras Plakhotnik 《Journal of luminescence》2007,127(1):235-238
We propose a new methodology for probing transport of just one electron, a process of great importance both in nature and in artificial devices. Our idea for locating a single electron is analogues to the conventional GPS where signals from several satellites are used to locate a macro object. Using fluorescent molecules as tiny sensors, it is possible to determine 3D displacement vector of an electron. 相似文献
95.
We prove that if an ultrafilter ${\mathcal{L}}$ is not coherent to a Q-point, then each analytic non-??-bounded topological group G admits an increasing chain ${\langle G_\alpha:\alpha < \mathfrak b(\mathcal L)\rangle}$ of its proper subgroups such that: (i) ${\bigcup_{\alpha}G_\alpha=G}$ ; and (ii) For every ??-bounded subgroup H of G there exists ?? such that ${H\subset G_\alpha}$ . In case of the group Sym(??) of all permutations of ?? with the topology inherited from ?? ?? this improves upon earlier results of S. Thomas. 相似文献
96.
Taras Gula Carolyn Hoessler 《International Journal of Mathematical Education in Science & Technology》2013,44(8):1130-1148
Many students enter the Canadian college system with insufficient mathematical ability and leave the system with little improvement. Those students who enter with poor mathematics ability typically take a developmental mathematics course as their first and possibly only mathematics course. The educational experiences that comprise a developmental mathematics course vary widely and are, too often, ineffective at improving students’ ability. This trend is concerning, since low mathematics ability is known to be related to lower rates of success in subsequent courses. To date, little attention has been paid to the selection of an instructional approach to consistently apply across developmental mathematics courses. Prior research suggests that an appropriate instructional method would involve explicit instruction and practising mathematical procedures linked to a mathematical concept. This study reports on a randomized field trial of a developmental mathematics approach at a college in Ontario, Canada. The new approach is an adaptation of the JUMP Math program, an explicit instruction method designed for primary and secondary school curriculae, to the college learning environment. In this study, a subset of courses was assigned to JUMP Math and the remainder was taught in the same style as in the previous years. We found consistent, modest improvement in the JUMP Math sections compared to the non-JUMP sections, after accounting for potential covariates. The findings from this randomized field trial, along with prior research on effective education for developmental mathematics students, suggest that JUMP Math is a promising way to improve college student outcomes. 相似文献
97.
We study the asymptotic behavior of eigenvalues and eigenfunctions of the Laplacian in a 2D thick cascade junction with heavy concentrated masses. We present two-term asymptotic approximations, as ε→0, for the eigenelements in the case of “slightly heavy”, “moderate heavy”, and “super heavy” concentrated masses. Asymptotics of high-frequency cell-vibrations are found as well. 相似文献
98.
Chemistry of Heterocyclic Compounds - Diversity-oriented synthesis embodied in a strategy of pairing vinyl sulfonamide moiety with other functional groups resulted in an array of skeletally diverse... 相似文献
99.
Kateryna Fominova Taras Diachuk Dmitry Granat Taras Savchuk Vladyslav Vilchynskyi Oleksiy Svitlychnyi Vladyslav Meliantsev Igor Kovalchuk Eduard Litskan Vadym
V. Levterov Valentyn R. Badlo Ruslan I. Vaskevych Alla I. Vaskevych Andrii V. Bolbut Volodymyr V. Semeno Rustam Iminov Kostiantyn Shvydenko Anastasiia S. Kuznetsova Yurii V. Dmytriv Daniil Vysochyn Vasyl Ripenko Andrei A. Tolmachev Olexandra Pavlova Halyna Kuznietsova Iryna Pishel Petro Borysko Pavel K. Mykhailiuk 《Chemical science》2021,12(34):11294
A general approach to a new generation of spirocyclic molecules – oxa-spirocycles – was developed. The key synthetic step was iodocyclization. More than 150 oxa-spirocyclic compounds were prepared. Incorporation of an oxygen atom into the spirocyclic unit dramatically improved water solubility (by up to 40 times) and lowered lipophilicity. More potent oxa-spirocyclic analogues of antihypertensive drug terazosin were synthesized and studied in vivo.A general practical approach to a new generation of spirocyclic molecules – oxa-spirocycles – is developed. 相似文献
100.
Taras K. Antal Wayne Lo William H. Armstrong Esa Tyystjärvi 《Photochemistry and photobiology》2009,85(3):663-668
We measured the photosensitivity of an artificial tetranuclear oxo–Mn(IV) complex, [Mn4 O6 (bpea)4 ]Br4 , which has an adamantane-shaped {Mn4 O6 }4+ core. Illumination caused changes in the absorption spectrum of the compound consistent with a one-electron reduction in the compound. Bromide appears to be the most probable electron donor in the reaction system. Chemical modification of the cluster appears to destabilize it, predisposing it to reductive degradation. UV light was more efficient than visible light in causing the changes. The data support the suggestion that the natural oxygen-evolving Mn complex is photosensitive and can oxidize components of the oxygen-evolving complex in its excited state causing photoinhibition, and that photostability is an important issue in designing Mn complexes for artificial photosynthesis. Furthermore, light-induced oxidation of bromide by [Mn4 O6 (bpea)4 ]4+ may suggest that oxidation of chloride is involved in natural water splitting or has been involved during the evolution of the water-splitting enzyme. 相似文献