Search results for "Function"
showing 10 items of 14432 documents
Many-body Green's function theory of electrons and nuclei beyond the Born-Oppenheimer approximation
2020
The method of many-body Green's functions is developed for arbitrary systems of electrons and nuclei starting from the full (beyond Born-Oppenheimer) Hamiltonian of Coulomb interactions and kinetic energies. The theory presented here resolves the problems arising from the translational and rotational invariance of this Hamiltonian that afflict the existing many-body Green's function theories. We derive a coupled set of exact equations for the electronic and nuclear Green's functions and provide a systematic way to approximately compute the properties of arbitrary many-body systems of electrons and nuclei beyond the Born-Oppenheimer approximation. The case of crystalline solids is discussed …
Driven Bose-Hubbard Model with a Parametrically Modulated Harmonic Trap
2016
We investigate a one-dimensional Bose–Hubbard model in a parametrically driven global harmonic trap. The delicate interplay of both the local interaction of the atoms in the lattice and the driving of the global trap allows us to control the dynamical stability of the trapped quantum many-body state. The impact of the atomic interaction on the dynamical stability of the driven quantum many-body state is revealed in the regime of weak interaction by analyzing a discretized Gross–Pitaevskii equation within a Gaussian variational ansatz, yielding a Mathieu equation for the condensate width. The parametric resonance condition is shown to be modified by the atom interaction strength. In particul…
Correlation Dynamics During a Slow Interaction Quench in a One-Dimensional Bose Gas
2014
We investigate the response of a one-dimensional Bose gas to a slow increase of its interaction strength. We focus on the rich dynamics of equal-time single-particle correlations treating the Lieb-Liniger model within a bosonization approach and the Bose-Hubbard model using the time-dependent density-matrix renormalization group method. For short distances, correlations follow a power-law with distance with an exponent given by the adiabatic approximation. In contrast, for long distances, correlations decay algebraically with an exponent understood within the sudden quench approximation. This long distance regime is separated from an intermediate distance one by a generalized Lieb-Robinson …
On the structure of 3-acetylamino-5-methyl- 1,2,4-oxadiazole and on the fully degenerate rearrangements (FDR) of its anion: a stimulating comparison …
2009
An accurate crystal structure determination has provided evidence for a planar conformation for 3-acetylamino-5-methyl-1,2,4-oxadiazole (5), in agreement with quantum-mechanical calculations in the gas phase. In the crystal, a series of strong intermolecular N7H7...O9 hydrogen bonds link the amido groups of different molecules, causing the formation of infinite parallel ordered chains. The effect of the DMSO solvent on the energy and charge distribution of compound 5 and on its relevant 5S anion, involved in a fully degenerate rearrangement (FDR), has been deepened by quantum-mechanical DFT calculations. The calculated energy barrier for the FDR increases in going from in vacuo to DMSO, in …
Государственная граница как пограничный объект в сети трансграничного сотрудничества: случай границы Латвии, Эстонии и России
2019
Цель публикации – раскрыть функции государственной границы в качестве пограничного объекта в сети трансграничного сотрудничества в случае внутренней и внешней границы ЕС.Теоретическое обрамление публикации составляет теория пограничных объектов – производное теории сети агентов, которую в своей работе «Институциональная экология, «интерпретация» и пограничные объекты: любители и профессионалы в зоологическом музее позвоночных в Беркли» (1989) развивали Сьюзaн Ли Стар и Джеймс Гриземер.Пограничные объекты как теоретическое понятие были созданы на основании взаимодействия различных социальных миров друг с другом и на точке, когда им необходима взаимная интерпретация (Worrall, 2010). Пограничн…
Bounded and unbounded solutions for a class of quasi-linear elliptic problems with a quadratic gradient term
2001
Abstract Our aim in this article is to study the following nonlinear elliptic Dirichlet problem: − div [a(x,u)·∇u]+b(x,u,∇u)=f, in Ω; u=0, on ∂Ω; where Ω is a bounded open subset of RN, with N>2, f∈L m (Ω) . Under wide conditions on functions a and b, we prove that there exists a type of solution for this problem; this is a bounded weak solution for m>N/2, and an unbounded entropy solution for N/2>m⩾2N/(N+2). Moreover, we show when this entropy solution is a weak one and when can be taken as test function in the weak formulation. We also study the summability of the solutions.
Boundary angles, cusps and conformal mappings
1986
Let f be a conformal mapping of a bounded Jordan domain D in the complex plane onto the unit disk . This paper examines the consequences for the local geometry of D near a boundary point z 0 of the mapping f-or, to be more precise, of the homeomorphic extension of this mapping to the closure of D—satisfying a Holder condition at z 0 or, alternatively, of its inverse satisfying a Holder condition at the point f(z 0). In particular, the compatibility of Holder conditions with the presence of cusps in the boundary of D is investigated.
Progressive Development of Renal Vascular Dysfunction in Brain Death Implicates Reversible Alterations of Nitric Oxide Metabolism
2011
Vascular endothelial dysfunction occurs in the kidney graft from marginal brain death (BD) donors and may be responsible for a low success rate after transplantation.BD was induced in 16 dogs for 6 hours. Immediately after the inflation of the intracranial balloon, the treated group (n = 8) received 40 mg/kg bolus followed by 3 mg/kg/min infusion of L-arginine for 30 minutes. Renal vascular function and hemodynamic and biochemical parameters were determined.BD caused vasoconstriction, increase in renal venous nitrite (4.9 ± 0.8 versus 2.6 ± 0.1, P.05) and myeloperoxidase levels (1.43 ± 0.04 versus 2.43 ± 0.23, P.001), and reduced vasodilatation of renal artery to acetylcholine. Larginine di…
Target point calculation in the computerized tomography. Comparison of different stereotactic methods
1995
The adaptation of computerized tomography for stereotactic operations requires the transformation of the coordinates of the target point from the CT image space into the stereotactic frame space. Two basic solutions for this transformation are realized in the most of the contemporary stereotactical systems. The indirect geometric method adjusts the frame coordinate system mechanically and identifies its origin in the CT image. There are 6 degrees of freedom: 3 of rotation and 3 of translation which have to be taken into consideration. The second method is a based on direct algebraic coordinate transformation and is independent of the explicite knowledge of the relationship between the image…
Mildronate treatment improves functional recovery following middle cerebral artery occlusion in rats
2011
Mildronate (3-(2,2,2-trimethylhydrazinium) propionate) is an inhibitor of l-carnitine biosynthesis and an anti-ischemic drug. In the present study, we investigated the effects of mildronate in rats following focal cerebral ischemia. Male Wistar rats were subjected to transient occlusion of the middle cerebral artery (MCAO) for 90min, followed by the intraperitoneal administration of mildronate at doses of 100 and 200mg/kg 2h after reperfusion and then daily for an additional 14days. The beam-walking, rota-rod and cylinder tests were used to assess sensorimotor function, and vibrissae-evoked forelimb-placing and limb-placing tests examined responses to tactile and proprioceptive stimulation.…