Self-force Regularization in the Schwarzschild Spacetime

We discuss the gravitational self-force on a particle in a black hole space-time. For a point particle, the full (bare) self-force diverges. The metric perturbation induced by a particle can be divided into two parts, the direct part (or the S part) and the tail part (or the R part), in the harmonic gauge, and the regularized self-force is derived from the R part which is regular and satisfies the source-free perturbed Einstein equations. But this formulation is abstract, so when we apply to black hole-particle systems, there are many problems to be overcome in order to derive a concrete self-force. These problems are roughly divided into two parts. They are the problem of regularizing the divergent self-force, i.e., ``subtraction problem'' and the problem of the singularity in gauge transformation, i.e., ``gauge problem''. In this paper, we discuss these problems in the Schwarzschild background and report some recent progress.Comment: 34 pages, 2 figures, submitted to CQG, special volume for Radiation Reaction (CAPRA7

Secondary BRCA1 Mutations in BRCA1-Mutated Ovarian carcinomas with platinum resistance.

Although ovarian carcinomas with mutated BRCA1 or BRCA2 are sensitive to platinum compounds, such carcinomas eventually develop platinum resistance. Previously, we showed that acquired resistance to cisplatin in BRCA2-mutated tumors can be mediated by secondary intragenic mutations in BRCA2 that restore the wild-type BRCA2 reading frame. Here, we show that secondary mutations of BRCA1 also occur in BRCA1-mutated ovarian cancer with platinum resistance. We evaluated nine recurrent BRCA1-mutated ovarian cancers previously treated with platinum compounds, including five with acquired platinum resistance, one with primary platinum resistance, and three with platinum sensitivity. Four of the six recurrent platinum-resistant tumors had developed secondary genetic changes in BRCA1 that restored the reading frame of the BRCA1 protein, whereas none of the three platinum-sensitive recurrent tumors developed BRCA1 sequence alterations. We immunohistochemically confirmed restored expression of BRCA1 protein in two cases with secondary mutations. Intriguingly, the case with primary platinum resistance showed back mutation of BRCA1 in the primary tumor and showed another secondary mutation in the recurrent tumor. Our results suggest that secondary mutations in BRCA1 can mediate resistance to platinum in BRCA1-mutated ovarian tumors

``Flux'' state in double exchange model

We study the ground state properties of the double-exchange systems. The phase factor of the hopping matrix elements arises from $t_{2g}$ spin texture in two or more dimensions. A novel ``flux'' state is stabilized against the canted antiferromagnetic and spiral spin states. In a certain range of hole doping, the phase separation occurs between the ``flux'' state and antiferromagnetic states. Constructing a trial state which provides the rigorous upper bound on the ground state, we show that the metallic canted antiferromagnetic state is not stable in the double exchange model.Comment: REVTEX, 8 pages and 4 PS figure

Optical Identification of the Hardest X-ray Source in the ASCA Large Sky Survey

We report the optical identification of the hardest X-ray source (AX J131501+3141) detected in an unbiased wide-area survey in the 0.5--10 keV band, the ASCA Large Sky Survey. The X-ray spectrum of the source is very hard and is well reproduced by a power-law component (Gamma = 1.5^+0.7_-0.6) with N_H = 6^+4_-2 *10^22 cm^-2 (Sakano et al. 1998). We have found a galaxy with R=15.62 mag near the center of the error circle for the X-ray source. The optical spectrum of the galaxy shows only narrow emission lines whose ratios correspond to those of a type 2 Seyfert galaxy at z = 0.072, implying an absorption-corrected X-ray luminosity of 2*10^43 erg sec^-1 (2--10 keV) and M_B = -20.93 mag. A radio point source is also associated with the center of the galaxy. We thus identify the X-ray source with this galaxy as an obscured AGN. The hidden nature of the nucleus of the galaxy in the optical band is consistent with the X-ray spectrum. These results support the idea that the obscured AGNs/QSOs contribute significantly to the cosmic X-ray background in the hard band at the faint flux level.Comment: 20 pages with 5 postscript figures, uses aaspp4.sty, Ap.J. Accepte

Low temperature transport in AC-driven Quantum Dots in the Kondo regime

We present a fully nonequilibrium calculation of the low temperature transport properties of a quantum dot in the Kondo regime when an AC potential is applied to the gate voltage. We solve a time dependent Anderson model with finite on-site Coulomb interaction. The interaction self-energy is calculated up to second order in perturbation theory in the on-site interaction, in the context of the Keldysh non-equilibrium technique, and the effect of the AC voltage is taken into account exactly for all ranges of AC frequencies and AC intensities. The obtained linear conductance and time-averaged density of states of the quantum dot evolve in a non trivial way as a function of the AC frequency and AC intensity of the harmonic modulation.Comment: 30 pages,7 figure

Evidence for a companion to BM Gem, a silicate carbon star

Balmer and Paschen continuum emission as well as Balmer series lines of P Cygni-type profile from H_gamma through H_23 are revealed in the violet spectra of BM Gem, a carbon star associated with an oxygen-rich circumstellar shell (`silicate carbon star') observed with the high dispersion spectrograph (HDS) on the Subaru telescope. The blue-shifted absorption in the Balmer lines indicates the presence of an outflow, the line of sight velocity of which is at least 400 km s^-1, which is the highest outflow velocity observed to date in a carbon star. We argue that the observed unusual features in BM Gem are strong evidence for the presence of a companion, which should form an accretion disk that gives rise to both an ionized gas region and a high velocity, variable outflow. The estimated luminosity of ~0.2 (0.03-0.6) L_sun for the ionized gas can be maintained by a mass accretion rate to a dwarf companion of ~10^-8 M_sun yr^-1, while ~10^-10 M_sun yr^-1 is sufficient for accretion to a white dwarf companion. These accretion rates are feasible for some detached binary configurations on the basis of the Bond-Hoyle type accretion process. We concluded that the carbon star BM Gem is in a detached binary system with a companion of low mass and low luminosity. However, we are unable to determine whether this companion object is a dwarf or a white dwarf. The upper limits for binary separation are 210 AU and 930 AU for a dwarf and a white dwarf, respectively. We also note that the observed features of BM Gem mimic those of Mira (omi Cet), which may suggest actual similarities in their binary configurations and circumstellar structures.Comment: 11 pages, 2 figures, 1 table, accepted for publication in Ap

Effect of predictive sign of acceleration on heart rate variability in passive translation situation: preliminary evidence using visual and vestibular stimuli in VR environment

<p>Abstract</p> <p>Objective</p> <p>We studied the effects of the presentation of a visual sign that warned subjects of acceleration around the yaw and pitch axes in virtual reality (VR) on their heart rate variability.</p> <p>Methods</p> <p>Synchronization of the immersive virtual reality equipment (CAVE) and motion base system generated a driving scene and provided subjects with dynamic and wide-ranging depth information and vestibular input. The heart rate variability of 21 subjects was measured while the subjects observed a simulated driving scene for 16 minutes under three different conditions.</p> <p>Results</p> <p>When the predictive sign of the acceleration appeared 3500 ms before the acceleration, the index of the activity of the autonomic nervous system (low/high frequency ratio; LF/HF ratio) of subjects did not change much, whereas when no sign appeared the LF/HF ratio increased over the observation time. When the predictive sign of the acceleration appeared 750 ms before the acceleration, no systematic change occurred.</p> <p>Conclusion</p> <p>The visual sign which informed subjects of the acceleration affected the activity of the autonomic nervous system when it appeared long enough before the acceleration. Also, our results showed the importance of the interval between the sign and the event and the relationship between the gradual representation of events and their quantity.</p

Small-angle X-ray diffraction studies of a molluscan smooth muscle in the catch state

Small-angle X-ray diffraction patterns from the anterior byssus retractor muscle of Mytilus edulis in the resting, active, and catch states were examined closely to elucidate the structural features of catch. The specimens were isometrically contracted by stimulation with acetylcholine. The specimens that produced strong tensions in both the active and catch states showed noticeable structural change in the thick filaments. Although the tension was weaker in the catch state than in the active state, the axial spacings of the 14.5 nm meridional reflection and its higher order reflections from the thick filaments were more elongated in the catch state than in the active state. This means that the thick filaments were stretched more strongly in the catch state than in the active state