The influence of a spherical boundary on the vacuum fluctuations of a massive scalar field is investigated in the background of a ( D + 1 ) -dimensional Milne universe, assuming that the field obeys ...Robin boundary conditions on the sphere. The normalized mode functions are derived for the regions inside and outside the sphere and different vacuum states are discussed. For the conformal vacuum, the Hadamard function is decomposed into boundary-free and sphere-induced contributions and an integral representation is obtained for the latter in both the interior and exterior regions. As important local characteristics of the vacuum state, the vacuum expectation values (VEVs) of the field squared and of the energy-momentum tensor are investigated. It is shown that the vacuum energy-momentum tensor has an off-diagonal component that corresponds to the energy flux along the radial direction. Depending on the coefficient in Robin boundary conditions, the sphere-induced contribution to the vacuum energy and the energy flux can be either positive or negative. At late stages of the expansion and for a massive field the decay of the sphere-induced VEVs, as functions of time, is damping oscillatory. The geometry under consideration is conformally related to that for a static spacetime with negative constant curvature space and the sphere-induced contributions in the corresponding VEVs are compared.
Time-periodic imbalances in the kinetic and magnetic energies at the conservation of the total energy have been found for three-dimensional homogeneous magnetohydrodynamic turbulence in the presence ...of rotation and an external magnetic field. It has been shown that these imbalances are caused by the collisions of Alfvén wave packets that arise because of the external magnetic field. It has been shown that no periodic imbalances of the kinetic and magnetic energies occur in the system at certain threshold values of the angular velocity of rotation and external magnetic field.
A scale for two-dimensional β-plane magnetohydrodynamic turbulence is proposed that characterizes an upper bound of the energy containing interval similar to a classical Rhines scale for neutral ...fluid turbulence on a -plane. It is found that only unsteady zonal flows with complex temporal dynamics are formed in two-dimensional magnetohydrodynamic turbulence on the -plane. It is shown that flow nonstationarity is due to the appearance of isotropic magnetic islands caused by the Lorentz force in the system. The characteristic dimensions of a flow are in agreement with the proposed scale.
L-Cysteinium⋯L-Cysteine Phosphite Ghazaryan, V. V.; Giester, G.; Minkov, V. S. ...
Journal of structural chemistry,
2024/6, Letnik:
65, Številka:
6
Journal Article
Recenzirano
In the system L-cysteine-H
3
PO
3
–H
2
O, a new salt with a dimeric cation, (L-CysH⋯L-Cys)(H
2
PO
3
), has been obtained. The compound exhibits incongruent solubility and is synthesized using an ...equimolar ratio of L-cysteine and phosphorous acid. It crystallizes in the orthorhombic space group
P
2
1
2
1
2
1
. The dimeric (L-CysH⋯L-Cys) cation is formed due to a strong O–H⋯O hydrogen bond with an O⋯O distance of 2.498(2) Å. Phosphite anions in the structure are linked to infinite chains. An IR spectrum is recorded and discussed based on its structure.
In this work we present our preliminary results on the systematic search for salts of amino acids with hexafluorosilicate (SiF62−) anion. Three types of simple salts have been obtained: 2A+·SiF62− ...(2Gly+·SiF62−, 2l-Phe+·SiF62−, 2l-Val+·SiF62−, 2l-Glu+·SiF62−, 2l-His+·SiF62−), A2+·SiF62− (l-His2+·SiF62−, l-Lys2+·SiF62−, l-Orn2+·SiF62−) and 2(A···A+)·SiF62− (2(Bet···Bet+)·SiF62−). Furthermore, one example of mixed salts with different anions, including SiF62−, viz. 2l-His2+·2BF4−·SiF62−·2H2O is presented. It was found that the salts of amino acids with SiF62− anion tend to form crystal hydrates and the SiF62− anion is often disordered within the structures.
► First report on a new class of amino acids salts with hexafluorosilicate anion. ► Crystals of three types of simple salts are reported. ► An example of mixed salts with different anions is presented.
We report a comorbid patient after redo Frozen Elephant Trunk procedure followed by recurrent infection of thoracic aortic prosthesis, deep sternal wound infection and extensive soft tissue defect. ...Closure with skin-muscle thoracodorsal flap and graft-sparing technique with omentoplasty is an alternative to total graft replacement for thoracic aortic graft infection in comorbid patients with concomitant extensive defect of the chest wall or recurrent infection in early postoperative period.
The orientation fluctuations of the director of a liquid crystal are measured, by a sensitive polarization interferometer, close to the Fréedericksz transition, which is a second-order transition ...driven by an electric field. We show that, near the critical value of the field, the spatially averaged order parameter has a generalized Gumbel distribution instead of a Gaussian one. The latter is recovered away from the critical point. The relevance of slow modes is pointed out. The parameter of the generalized Gumbel distribution is related to the effective number of degrees of freedom.
Transmission through descending pathways to lumbar motoneurons, although important for voluntary walking in humans and rats, has not been fully understood at the cellular level in contusion models. ...Major descending pathways innervating lumbar motoneurons include those at corticospinal tract (CST) and ventrolateral funiculus (VLF). We examined transmission and plasticity at synaptic pathways from dorsal (d)CST and VLF to individual motoneurons located in ventral horn and interneurons located in dorsomedial gray matter at lumbar segments after thoracic chronic contusion in adult anesthetized rats. To accomplish this, we used intracellular electrophysiological recordings and performed acute focal spinal lesions during the recordings. We directly demonstrate that after thoracic T10 chronic contusion the disrupted dCST axons spontaneously form new synaptic contacts with individual motoneurons, extending around the contusion cavity, through spared ventrolateral white matter. These detour synaptic connections are very weak, and strengthening these connections in order to improve function may be a target for therapeutic interventions after spinal cord injury (SCI). We found that degradation of scar-related chondroitin sulfate proteoglycans with the enzyme chondroitinase ABC (ChABC) combined with adeno-associated viral (AAV) vector-mediated prolonged delivery of neurotrophin NT-3 (AAV-NT3) strengthened these spontaneously formed connections in contused spinal cord. Moreover, ChABC/AAV-NT3 treatment induced the appearance of additional detour synaptic pathways innervating dorsomedial interneurons. Improved transmission in ChABC/AAV-NT3-treated animals was associated with increased immunoreactivity of 5-HT-positive fibers in lumbar dorsal and ventral horns. Improved locomotor function assessed with automated CatWalk highlights the physiological significance of these novel connections.
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