235 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
adde
健常高齢者における神経心理学検査の測定値 : 年齢・教育年数の影響
取得学位 : 博士(保健学), 学位授与番号 : 医博甲第1785号, 学位授与年月日 : 平成18年3月22日, 学位授与大学 : 金沢大学, 主査 : 能登谷 晶子, 副査 :生田 宗博, 染矢 富士
Factors Predicting Bone Mineral Density (BMD) Changes in Young Women over A One-year Study:Changes in Body Weight and Bone Metabolic Markers during the Menstrual Cycle and Their Effects on BMD
Currently, 26% of Japanese women in their twenties are under weight, and therefore at risk of developing
various metabolic abnormalities due to an inadequate nutrient intake, which in turn affects the acquisition of a peak bone mineral density (BMD). In this study, we aimed to clarify the effects of menstrual cycle-related changes in body weight and bone metabolic marker levels on the BMD changes. The subjects were 42 women (19.6±0.8 years). The levels of osteocalcin (OC), BAP, s-NTx, u-DPD, and E2 in the menstrual and ovulatory phases were measured. The associations between dependent variables (BMD changes/year in the lumbar spine, femur, femoral neck) and explanatory variables (body weight changes/year, the levels of OC, BAP, s-NTx, u-DPD) were evaluated using multiple regression analysis. Analysis of the correlations between the changes in bone metabolic markers
and changes in BMD showed a correlation between the OC level in the menstrual phase and changes in the BMD of the entire femur, suggesting that a high OC level protects against BMD reduction,
probably by promoting osteoblast activity, and that bone formation activity suppresses the decrease in BMD. These results suggest that, to predict BMD changes from bone metabolic markers in young women, it is necessary to measure OC levels in the menstrual phase
Black hole evaporation in a heat bath as a nonequilibrium process and its final fate
When a black hole evaporates, there arises a net energy flow from black hole
into its outside environment (heat bath). The existence of energy flow means
that the thermodynamic state of the whole system, which consists of the black
hole and the heat bath, is in a nonequilibrium state. Therefore, in order to
study the detail of evaporation process, the nonequilibrium effects of the
energy flow should be taken into account. Using the nonequilibrium
thermodynamics which has been formulated recently, this paper shows the
following: (1) Time scale of black hole evaporation in a heat bath becomes
shorter than that of the evaporation in an empty space (a situation without
heat bath), because a nonequilibrium effect of temperature difference between
the black hole and heat bath appears as a strong energy extraction from the
black hole by the heat bath. (2) Consequently a huge energy burst (stronger
than that of the evaporation in an empty space) arises at the end of
semi-classical stage of evaporation. (3) It is suggested that a remnant of
Planck size remains after the quantum stage of evaporation in order to
guarantee the increase of total entropy of the whole system
Tim23–Tim50 pair coordinates functions of translocators and motor proteins in mitochondrial protein import
Mitochondrial protein traffic requires coordinated operation of protein translocator complexes in the mitochondrial membrane. The TIM23 complex translocates and inserts proteins into the mitochondrial inner membrane. Here we analyze the intermembrane space (IMS) domains of Tim23 and Tim50, which are essential subunits of the TIM23 complex, in these functions. We find that interactions of Tim23 and Tim50 in the IMS facilitate transfer of precursor proteins from the TOM40 complex, a general protein translocator in the outer membrane, to the TIM23 complex. Tim23–Tim50 interactions also facilitate a late step of protein translocation across the inner membrane by promoting motor functions of mitochondrial Hsp70 in the matrix. Therefore, the Tim23–Tim50 pair coordinates the actions of the TOM40 and TIM23 complexes together with motor proteins for mitochondrial protein import
Parkinson\u27s disease showing progressive conduction aphasia
Patients with Parkinson\u27s disease (PD) may develop progressive dementia late in their clinical course. Dementia in PD is mostly related to neuropathological findings of extensive Lewy bodies (LBs), with or without the coexistence of Alzheimer\u27s disease (AD) pathology. Aphasia has been reported in patients with LB diseases with AD pathology; however, there have been no reports of typical PD patients developing progressive aphasia during their clinical course. We describe a female PD patient who later developed progressive conduction aphasia characterized by phonemic paraphasia and disturbance in repetition of short sentences without disturbance in writing or auditory comprehension. No episodes of fluctuations of attention, memory complaints, or planning errors were observed. She experienced episodes of visual hallucination. Her low scores on the Mini-Mental State Examination suggested impairment of orientation and attention, and her scores on Raven\u27s Coloured Progressive Matrices test indicated impaired visuospatial functions. However, her cognitive deficits were not sufficiently severe to impair her daily life. Brain magnetic resonance images revealed atrophy of the left superior temporal gyrus and widening of the left sylvian fissure. [18F]-fluorodeoxyglucose positron emission tomography revealed glucose hypometabolism in the left cerebral hemisphere. These findings may be related to conduction aphasia. During the progression of PD lesions, the brainstem LB is assumed to take an upward course, extend to the limbic system, and then extend to the neocortex. Conduction aphasia observed in our patient may be associated with an unusual progression of the LB pathology from the brainstem to the left temporoparietal lobe. © 2011 Springer-Verlag
Five-point Likert scaling on MRI predicts clinically significant prostate carcinoma
Background: To clarify the relationship between the probability of prostate cancer scaled using a 5-point Likert system and the biological characteristics of corresponding tumor foci. Methods: The present study involved 44 patients undergoing 3.0-Tesla multiparametric MRI before laparoscopic radical prostatectomy. Tracing based on pathological and MRI findings was performed. The relationship between the probability of cancer scaled using the 5-point Likert system and the biological characteristics of corresponding tumor foci was evaluated. Results: A total of 102 tumor foci were identified histologically from the 44 specimens. Of the 102 tumors, 55 were assigned a score based on MRI findings (score 1: n = 3; score 2: n = 3; score 3: n = 16; score 4: n = 11 score 5: n = 22), while 47 were not pointed out on MRI. The tracing study revealed that the proportion of >0.5 cm3 tumors increased according to the upgrade of Likert scores (score 1 or 2: 33 %; score 3: 68.8 %; score 4 or 5: 90.9 %, χ2 test, p 7 also increased from scale 2 to scale 5 (scale 2: 0 %; scale 3: 56.3 %; scale 4: 72.7 %; 5: 90.9 %, χ2 test, p = 0.0001). On using score 3 or higher as the threshold of cancer detection on MRI, the detection rate markedly improved if the tumor volume exceeded 0.5 cm3 (<0.2 cm3: 10.3 %; 0.2-0.5 cm3: 25 %; 0.5-1.0 cm3: 66.7 %; 1.0 < cm3: 92.1 %). Conclusions: Each Likert scale favobably reflected the corresponding tumor’s volume and Gleason score. Our observations show that “score 3 or higher” could be a useful threshold to predict clinically significant carcinoma when considering treatment options
Concomitant Nrf2- and ATF4-Activation by Carnosic Acid Cooperatively Induces Expression of Cytoprotective Genes
Carnosic acid (CA) is a phytochemical found in some dietary herbs, such as Rosmarinus officinalis L., and possesses antioxidative and anti-microbial properties. We previously demonstrated that CA functions as an activator of nuclear factor, erythroid 2 (NF-E2)-related factor 2 (Nrf2), an oxidative stress-responsive transcription factor in human and rodent cells. CA enhances the expression of nerve growth factor (NGF) and antioxidant genes, such as HO-1 in an Nrf2-dependent manner in U373MG human astrocytoma cells. However, CA also induces NGF gene expression in an Nrf2-independent manner, since 50 μM of CA administration showed striking NGF gene induction compared with the classical Nrf2 inducer tert-butylhydroquinone (tBHQ) in U373MG cells. By comparative transcriptome analysis, we found that CA activates activating transcription factor 4 (ATF4) in addition to Nrf2 at high doses. CA activated ATF4 in phospho-eIF2α- and heme-regulated inhibitor kinase (HRI)-dependent manners, indicating that CA activates ATF4 through the integrated stress response (ISR) pathway. Furthermore, CA activated Nrf2 and ATF4 cooperatively enhanced the expression of NGF and many antioxidant genes while acting independently to certain client genes. Taken together, these results represent a novel mechanism of CA-mediated gene regulation evoked by Nrf2 and ATF4 cooperation
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