29 research outputs found
Periapsis shifts in dark matter distribution around a black hole
We consider the periapsis shifts of bound orbits of stars on static clouds
around a black hole. The background spacetime is constructed from a
Schwarzschild black hole surrounded by a static and spherically symmetric
self-gravitating system of massive particles, which satisfies all the standard
energy conditions and physically models the gravitational effect of dark matter
distribution around a nonrotating black hole. Using nearly circular bound
orbits of stars, we obtain a simple formula for the precession rate. This
formula explicitly shows that the precession rate is determined by a positive
contribution (i.e., a prograde shift) from the conventional
general-relativistic effect and a negative contribution (i.e., a retrograde
shift) from the local matter density. The four quantities for such an orbit
(i.e., the orbital shift angle, the radial oscillation period, the redshift,
and the star position mapped onto the celestial sphere) determine the local
values of the background model functions. Furthermore, we not only evaluate the
precession rate of nearly circular bound orbits in several specific models but
also simulate several bound orbits with large eccentricity and their periapsis
shifts. The present exact model demonstrates that the retrograde precession
does not mean any exotic central objects such as naked singularities or
wormholes but simply the existence of significant energy density of matters on
the star orbit around the black hole.Comment: 30 pages, 7 figures; v2: added Tables, a few paragraphs in
Introduction, and references, accepted for publication in the International
Journal of Modern Physics
General formulae for the periapsis shift of a quasi-circular orbit in a static spherically symmetric spacetime and the active gravitational mass density
We study the periapsis shift of a quasi-circular orbit in a general static
spherically symmetric spacetime. We derive two formulae in full order with
respect to the gravitational field, one in terms of the gravitational mass
and the Einstein tensor and the other in terms of the orbital angular velocity
and the Einstein tensor. These formulae reproduce the well-known ones for the
forward shift in the Schwarzschild spacetime. In a general case, the shift
deviates from that in the vacuum spacetime due to a particular combination of
the components of the Einstein tensor at the radius of the orbit. The
formulae give a backward shift due to the extended-mass effect in Newtonian
gravity. In general relativity, in the weak-field and diffuse regime, the
active gravitational mass density, ,
plays an important role, where , , and are the energy
density, the radial stress, and the tangential stress of the matter field,
respectively. We show that the shift is backward if is beyond a
critical value \rho_{c}\simeq 2.8\times 10^{-15} \mbox{g}/\mbox{cm}^{3}
(m/M_{\odot})^{2}(r/\mbox{au})^{-4}, while a forward shift greater than that
in the vacuum spacetime instead implies , i.e., the violation of
the strong energy condition, and thereby provides evidence for dark energy.Comment: 24 pages, minor revision, title and terminology modified, references
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Effect of quercetin on the permeability of N-acetyl 5-aminosalicylic acid on Caco-2 cells.
The aim of this study was to investigate the transporter-mediated transport of N-acetyl 5-aminosalicylic acid (Ac-5-ASA) and the effect of quercetin on Ac-5-ASA transport.Caco-2 cell monolayers grown in Transwells were used to study the transport of Ac-5-ASA in the absence or presence of quercetin, and apical-to-basolateral and basolateral-to-apical apparent permeability (PappAB and PappBA values, respectively) was determined. The effect of transporter inhibitors, such as MK571, quinidine and mitoxantrone, on the transport of Ac-5-ASA was investigated.In the absence of transporter mediators, the transport of Ac-5-ASA was much higher in the basolateral-to-apical direction than in the opposite direction. The PappBA/PappAB ratio of Ac-5-ASA was 4.89. Quercetin inhibited the apical efflux of Ac-5-ASA and decreased the PappBA/PappAB ratio to 1.05. Of the transporter inhibitors, MK571 decreased the PappBA/PappAB ratio to 1.07; however, neither quinidine nor mitoxantrone had an effect on Ac-5-ASA transport.Ac-5-ASA was excreted by multidrug resistance-associated protein 2 from Caco-2 cells, and its transport was inhibited by quercetin. Our findings suggest that dose levels of sulfasalazine or 5-aminosalicylic acid can be decreased by coadministration of quercetin, leading to improved pharmaceutical care for inflammatory bowel diseases.The aim of this study was to investigate the transporter-mediated transport of N-acetyl 5-aminosalicylic acid (Ac-5-ASA) and the effect of quercetin on Ac-5-ASA transport.Caco-2 cell monolayers grown in Transwells were used to study the transport of Ac-5-ASA in the absence or presence of quercetin, and apical-to-basolateral and basolateral-to-apical apparent permeability (PappAB and PappBA values, respectively) was determined. The effect of transporter inhibitors, such as MK571, quinidine and mitoxantrone, on the transport of Ac-5-ASA was investigated.In the absence of transporter mediators, the transport of Ac-5-ASA was much higher in the basolateral-to-apical direction than in the opposite direction. The PappBA/PappAB ratio of Ac-5-ASA was 4.89. Quercetin inhibited the apical efflux of Ac-5-ASA and decreased the PappBA/PappAB ratio to 1.05. Of the transporter inhibitors, MK571 decreased the PappBA/PappAB ratio to 1.07; however, neither quinidine nor mitoxantrone had an effect on Ac-5-ASA transport.Ac-5-ASA was excreted by multidrug resistance-associated protein 2 from Caco-2 cells, and its transport was inhibited by quercetin. Our findings suggest that dose levels of sulfasalazine or 5-aminosalicylic acid can be decreased by coadministration of quercetin, leading to improved pharmaceutical care for inflammatory bowel diseases
Origin of an Orbiting Star Around the Galactic Supermassive Black Hole
The tremendous tidal force that is linked to the supermassive black hole
(SMBH) at the center of our galaxy is expected to strongly subdue star
formation in its vicinity. Stars within 1" from the SMBH thus likely formed
further from the SMBH and migrated to their current positions. In this study,
spectroscopic observations of the star S0-6/S10, one of the closest (projected
distance from the SMBH of about 0.3") late-type stars were conducted. Using
metal absorption lines in the spectra of S0-6, the radial velocity of S0-6 from
2014 to 2021 was measured, and a marginal acceleration was detected, which
indicated that S0-6 is close to the SMBH. The S0-6 spectra were employed to
determine its stellar parameters including temperature, chemical abundances
([M/H], [Fe/H], [alpha/Fe], [Ca/Fe], [Mg/Fe], [Ti/Fe]), and age. As suggested
by the results of this study, S0-6 is very old (> ~10 Gyr) and has an origin
different from that of stars born in the central pc region.Comment: 15 pages, 6 figures, 10 tables, accepted for publication in
Proceedings of the Japan Academy, Ser. B, Physical and Biological Science
Effects of Oral Glucosamine Hydrochloride Administration on Plasma Free Amino Acid Concentrations in Dogs
We examined the effects of oral glucosamine hydrochloride (GlcN), N-acetyl-d-glucosamine (GlcNAc) and d-glucose (Glc) administration on plasma total free amino acid (PFAA) concentrations in dogs. The PFAA concentrations increased in the control group and the GlcNAc group at one hour after feeding, and each amino acid concentration increased. On the other hand, in the GlcN group and the Glc group PFAA concentrations decreased at one hour after feeding. A significant decrease in amino acid concentration was observed for glutamate, glycine and alanine. Our results suggest the existence of differences in PFAA dynamics after oral administration of GlcN and GlcNAc in dogs
PO-112 The exploration of constitutively expressed myokines utilizing tissue-engineered skeletal muscle
Objective Recent evidence has identified skeletal muscle as a secretory organ. Many myokines, which are bioactive substances secreted from skeletal muscle, have been identified in plane muscle culture cells. Compared to the plane muscle culture cells, the tissue-engineered muscle is an excellent model as culture system mimicked native skeletal muscle. However, constitutively expressed genes and secreted compounds from tissue-engineered muscle have not been analyzed sufficiently. The purposes of this study were 1) to clarify kinetics of constitutively secreted compounds, and 2) to explore constitutively expressed genes in the tissue-engineered muscle.
Methods C2C12 cells embedded within collagen gel solution were placed between two tendons made up of elastase-treated acelluar porcine blood vessel. The constructs were cultured in growth media for 2 days and cultured in differentiation media for 6 days. To compare with plane culture cells, C2C12 cells were cultured in plane under the same condition as the construct. The culture media were obtained, and analyzed by MALDI-TOF Mass Spectrometry. Furthermore, constitutively up-regulated genes in tissue-engineered skeletal muscle were explored based on microarray analysis and confirmed by RT-PCR.
Results MALDI-TOF Mass Spectrometry revealed that the number of detected peaks in tissue-engineered muscle was abundant compared to that of plane muscle culture cells, especially at range of low molecular weight. Furthermore, the detected peaks were substantially different among these culture media and specific peaks were identified in tissue-engineered muscle. Based on microarray analysis, the transcription of cholecystokinin identified, and confirmed the up-regulation in tissue-engineered skeletal muscle by RT-PCR.
Conclusions These results suggested that the tissue-engineered muscle constitutively secreted many compounds compared to plane culture cells, especially at range of low molecular weight. Furthermore, the transcription of cholecystokinin was up-regulated in tissue-engineered skeletal muscle. Besides of the plane muscle culture cells, it is possible to expect to obtain novel myokines utilizing tissue-engineered muscle
The Japanese space gravitational wave antenna; DECIGO
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future
Japanese space gravitational wave antenna. DECIGO is expected to open a new window of
observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing
various mysteries of the universe such as dark energy, formation mechanism of supermassive
black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of
three drag-free spacecraft, whose relative displacements are measured by a differential Fabry–
Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre-
DECIGO first and finally DECIGO in 2024
DECIGO pathfinder
DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article
Current status of space gravitational wave antenna DECIGO and B-DECIGO
Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is the
future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO
aims at the detection of primordial gravitational waves, which could be
produced during the inflationary period right after the birth of the universe.
There are many other scientific objectives of DECIGO, including the direct
measurement of the acceleration of the expansion of the universe, and reliable
and accurate predictions of the timing and locations of neutron star/black hole
binary coalescences. DECIGO consists of four clusters of observatories placed
in the heliocentric orbit. Each cluster consists of three spacecraft, which
form three Fabry-Perot Michelson interferometers with an arm length of 1,000
km. Three clusters of DECIGO will be placed far from each other, and the fourth
cluster will be placed in the same position as one of the three clusters to
obtain the correlation signals for the detection of the primordial
gravitational waves. We plan to launch B-DECIGO, which is a scientific
pathfinder of DECIGO, before DECIGO in the 2030s to demonstrate the
technologies required for DECIGO, as well as to obtain fruitful scientific
results to further expand the multi-messenger astronomy.Comment: 10 pages, 3 figure