Tidal forces in Kottler spacetimes Vandeev, V. P.; Semenova, A. N.
European physical journal. C, Particles and fields,
07/2021, Letnik:
81, Številka:
7
Journal Article
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Odprti dostop
The article considers tidal forces in the vicinity of the Kottler black hole. We find a solution of the geodesic deviation equation for radially falling bodies, which is determined by elliptic ...integrals. And also the asymptotic behavior of all spatial geodesic deviation vector components were found. We demonstrate that the radial component of the tidal force changes sign outside the single event horizon for any negative values of the cosmological constant, in contrast to the Schwarzschild black hole, where all the components of the tidal force are sign-constant. We also find the similarity between the Kottler black hole and the Reissner–Nordström black hole, because we indicate the value of the cosmological constant, which ensures the existence of two horizons of the black hole, between which the angular components of the tidal force change sign. It was possible to detect non-analytical behavior of geodesic deviation vector components in anti-de Sitter spacetime and to describe it locally.
The investigation of in-vitro response of cell cultures derived from tumor material of individual patients with similar tumor localizations to photodynamic treatment is presented. Tumor types ...included in the research were renal cell carcinoma, melanoma and alveolar, synovial, lypo- and osteo- sarcomas. Long-term observations of treatment-induced morphological changes in cells were performed by means of digital holographic microscopy. A substantial variance in response of cells of individual patients with similar tumor types and localizations to photodynamic treatment with the same dose has been observed. These peculiarities are indicative of the demand to personalized protocols of photodynamic treatment. The elevated resistance of cells of some patients to treatment at high doses highlights potential limitations of photodynamic therapy for some patients. Digital holographic microscopy is shown to be an informative label-free noninvasive tool allowing for long-term monitoring of cell samples in vitro and providing quantitative information on necrosis rate and loss of cellular dry mass. The developed methodology can be generalized for analysis of cellular response to various therapies.
•Tumor cells of patients with the same malignancy show different response to PDT.•PDT can be inefficient for treatment of some patients.•Digital holography is informative in assessment of cells death dynamics.•Average phase shift and dry mass decrease exponentially in a course of cell necrosis.•Proliferative activity of cells does not correlate with their resistivity to PDT.
Long-length ultrafine-grained (UFG) Ti rods are produced by equal-channel angular pressing via the conform scheme (ECAP-C) at 200°C, which is followed by drawing at 200°C. The evolution of ...microstructure, macrotexture, and mechanical properties (yield strength, ultimate tensile strength, failure stress, uniform elongation, elongation to failure) of pure Ti during this thermo-mechanical processing is studied. Special attention is also paid to the effect of microstructure on the mechanical behavior of the material after macrolocalization of plastic flow. The number of ECAP-C passes varies in the range of 1–10. The microstructure is more refined with increasing number of ECAP-C passes. Formation of homogeneous microstructure with a grain/subgrain size of 200nm and its saturation after 6 ECAP-C passes are observed. Strength properties increase with increasing number of ECAP passes and saturate after 6 ECAP-C passes to a yield strength of 973MPa, an ultimate tensile strength of 1035MPa, and a true failure stress of 1400MPa (from 625, 750, and 1150MPa in the as-received condition). The true strain at failure failure decreases after ECAP-C processing. The reduction of area and true strain to failure values do not decrease after ECAP-C processing. The sample after 6 ECAP-C passes is subjected to drawing at 200¯C resulting in reduction of a grain/subgrain size to 150nm, formation of (101¯0) fiber texture with respect to the rod axis, and further increase of the yield strength up to 1190MPa, the ultimate tensile strength up to 1230MPa and the true failure stress up to 1600MPa. It is demonstrated that UFG CP Ti has low resistance to macrolocalization of plastic deformation and high resistance to crack formation after necking.
The decomposition and mineralization of various plant residues (oak and aspen leaves, pine needles, small branches and thin roots of trees, aboveground biomass and roots of meadow grasses, ...aboveground biomass and roots of clover, and straw and roots of barley) were investigated in the laboratory experiments by quantitative measurement of produced C–CO
2
. The plant residues were mixed with vermiculite or gray forest soil (Greyzemic Phaeozems Albic) and incubated under constant temperature and moisture conditions. After a year of incubation, 25–67% of C
org
in plant residues were mineralized. Oak leaves, aboveground mass of meadow grasses, and aboveground mass and roots of clover were characterized by a three-pool structure of organic matter with moderate (0.1 >
k
1
> 0.01 day
–1
), slow (0.01 >
k
2
> 0.001 day
–1
), and very slow (
k
3
< 0.001 day
–1
) mineralization rates, while the other types of plant residues had only a two-pool structure with slow and very slow mineralization rates. An opposite relationship between the decomposition rate and the C : N ratio in the plant residues was found. Poorly decomposable types of plant residues were the main source for particulate organic matter (C
POM
) in the soil, while highly decomposable types were the main source for microbial biomass (C
mic
). The content of potentially mineralizable organic matter in the soil with plant residues correlated positively with C
POM
and with C
mic
.
The antiquark-diquark-diquark model describes pentaquark states both in terms of quarks and hadrons. We discuss pentaquark states with hidden charm
P
(
c
¯
c
u
u
d
)
discovered in the
J
/
Ψ
p
...spectrum by the LHCb collaboration. We consider three pentaquark states as members of the lowest (
S
-wave) multiplet and discuss the mass splitting scheme. The latest LHCb data for pentaquarks with hidden charm provide an opportunity to make an assumption about the diquark content of the pentaquark states. We give a classification for the LHCb pentaquarks and define recombination channels for these states.
The dependence of the absorbed energy of ultrafine-grained (UFG) Ti-6Al-4V alloy on the test temperature is studied. Tensile tests and Charpy tests were carried out at room temperature, cryogenic ...temperature, and temperatures elevated up to 500 °С. A UFG state was produced by equal-channel angular pressing. For the sake of comparison, coarse-grained (CG) alloy was subjected to heat treatment to produce a duplex structure. The UFG alloy demonstrates enhanced strength and reduced ductility-related properties at room temperature. It is shown that at operating temperatures of 200 and 300 °С, the best balance between high strength and absorbed energy is achieved in the UFG alloy. The UFG alloy demonstrates higher strength compared to the CG alloy at the liquid nitrogen temperature, but their absorbed energy is practically the same. The failure mechanisms of CG and UFG alloy and promising engineering applications of UFG alloy are discussed.
Polymeric and supramolecular models of humic substances (HSs) are considered. It has been noted that the HSs in natural objects can simultaneously occur in the forms of macromolecular polymers and ...supramolecularly organized monomers; macromolecular polymers of HSs can have some properties of suprastructures or be associated into aggregates, and covalent bonds can be formed between the monomers of supramolecules. Mineral particles of soil act as catalysts in chemical reactions between individual compounds, sorbents of biomolecules, and a surface for self-assembling HSs. It is supposed that the combination of such physicochemical processes and phenomena in soil as cementation, charring, incrustation, occlusion, sedimentation, sorption, coagulation, flocculation, encapsulation, complexation, and intercalation, as well as the entrapment of macroorganic, particulate, and soluble organic substances in micropores, can be as important for the stabilization of organic matter as the interactions between biomolecules with the formation of HSs.
Atlantic walruses (
Odobenus rosmarus rosmarus
) are still poorly studied in the easternmost part of their range, especially in the Kara Sea. Therefore, any new data from this region on the biology ...and ecology of the subspecies are highly important. In autumn 2019, the largest coastal assemblage of walruses ever found in the Kara Sea was observed on the northwestern coast of the Yamal Peninsula. This assemblage was surveyed using a drone-mounted digital camera (from 5 m in altitude) on 17 October 2019. The herd comprised 1062 (± 17 SE) walruses. Approximately one-sixth of the assemblage consisted of dependent calves (0–2 years old), one-sixth consisted of mature bulls, one-third consisted of independent immature animals, and one-third consisted of mature females and young (mature) males. A considerable but not estimated number of walruses was also observed in nearshore water. Satellite imagery and an opportunistic visit to the site revealed that walruses used this haul-out from mid-September until at least the end of October. Satellite tracking of two tagged walruses showed that animals stayed within 200 km of the coastline in shallow water (not deeper than 20–25 m) throughout their tracking periods (8 and 9 days). In addition to the main haul-out, three more sites on this part of the Yamal Peninsula coast were identified as areas where walruses came ashore. These new abundance and distribution data from the Kara Sea add significantly to our knowledge regarding Atlantic walruses in this region. Considering the rapid and large-scale industrial development in the region, proactive measures should be taken to protect key walrus habitats in the Yamal Peninsula area.
The paper studies experimentally and theoretically the interference structure of the low-frequency spatial amplitude and phase responses of the scalar field and three projections of the vibrational ...velocity vector formed by tone signals from towed omnidirectional acoustic sources in zones near the interference maxima and minima of the sound pressure. The experimental dependences of these field characteristics on the distance obtained by four-component vector-scalar receivers when the sources are towed are compared with the calculated ones within the Pekeris model and waveguide model with a three-layer seafloor, the parameters of which were calculated based on acoustic calibration of the operations area. Satisfactory agreement was established between the amplitude and phase responses of the field, calculated by acoustic calibration and measured experimentally. It is shown that in the zones of maxima, a slow change in the angle of arrival is observed and the phase gradients are “smooth”, while in the zones of the minimum, sharp jumps in the amplitudes and phases form in the horizontal and vertical planes, leading for deep minima to the formation of circulations: local vortices around the poles. Numerical analysis of the fine structure of the sound pressure and vibrational velocity projections in the acoustic vortex zone is carried out, and hodographs of the vibrational velocity and phase gradients of the sound pressure are calculated, confirming the formation of vortices in the vertical plane in the zone of the poles.
The aim of this paper is to investigate tidal forces in multidimensional spherically simmetric spacetimes. We consider geodesic deviation equation in Schwarzschild–Tangherlini metric and its ...electrically charged version. We show that these equations can be solved explicity for radial geodesics as quadratures in spaces of any dimension. In the cases of five, six and seven dimensional spaces, these solutions can be represented in terms of elliptic integrals. For spacetimes of higher dimension asymptotics of the solution are found instead. We established that the greater the dimension of space is, the stronger the tidal stretch along the radial direction in the vicinity of physical singularity is, whereas the tidal compression in direction transverse to the radial one, does not change in the leading order starting from a certain dimension. Also, in the case of non-radial geodesics, the presence of black hole electric charge does not affect the force of transverse compression in the leading order. Finally, for non-radial geodesics with nonzero angular momentum, the local properties of solutions of geodesic deviation equations in the vicinity of a singularity are studied.
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