70 research outputs found
Stress Shielding Minimized In Femoral Hip Implants A Finite Element Model Optimized By Virtual Compatibility
Bone mechanics and traditional implant materials produce a recurring problem for patients of total hip arthroplasty (THA): the bone is “shielded” from the loading it has become accustomed to over many years of development. Bone adheres to what is called “Wolff’s Law”, meaning it is an adaptive structure which adjusts its geometry based on the loads experienced over its life (Pearson; Goldstein). As the new femoral hip implant transmits reduced stresses to the remaining bone, bone tissue atrophies at the interface, permitting loosening of the implant, pain, and thereby obliging additional surgery to correct the issue (Meade). In the present work, a methodology is endeavored for creating an innovative design for femoral hip implants. The approach uncouples the finite element implant model from the bone model, in order to focus solely on expected behavior within the implant while considering the varying material behavior in unique directions and locations. The implant’s internal geometry is optimized in order to better match typical, intact bone conditions. The eventual design reduces extreme changes in stresses within remnant bone such that the implant will remain implanted for greater periods of time without additional surgical attention
Search for Outer Massive Bodies around Transiting Planetary Systems: Candidates of Faint Stellar Companions around HAT-P-7
We present results of direct imaging observations for HAT-P-7 taken with the
Subaru HiCIAO and the Calar Alto AstraLux. Since the close-in transiting planet
HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as
giant planets, brown dwarfs, or a binary star are expected to exist in the
outer region of this system. We show that there are indeed two candidates for
distant faint stellar companions around HAT-P-7. We discuss possible roles
played by such companions on the orbital evolution of HAT-P-7b. We conclude
that as there is a third body in the system as reported by Winn et al. (2009,
ApJL, 763, L99), the Kozai migration is less likely while planet-planet
scattering is possible.Comment: 8 pages, 3 figures, 2 tables, PASJ in pres
A Substellar Companion to Pleiades HII 3441
We find a new substellar companion to the Pleiades member star, Pleiades HII
3441, using the Subaru telescope with adaptive optics. The discovery is made as
part of the high-contrast imaging survey to search for planetary-mass and
substellar companions in the Pleiades and young moving groups. The companion
has a projected separation of 0".49 +/- 0".02 (66 +/- 2 AU) and a mass of 68
+/- 5 M_J based on three observations in the J-, H-, and K_S-band. The spectral
type is estimated to be M7 (~2700 K), and thus no methane absorption is
detected in the H band. Our Pleiades observations result in the detection of
two substellar companions including one previously reported among 20 observed
Pleiades stars, and indicate that the fraction of substellar companions in the
Pleiades is about 10.0 +26.1/-8.8 %. This is consistent with multiplicity
studies of both the Pleiades stars and other open clusters.Comment: Main text (14 pages, 4 figures, 4 tables), and Supplementary data (8
pages, 3 tables). Accepted for Publications of Astronomical Society of Japa
Radial decoupling of small and large dust grains in the transitional disk RX J1615.3-3255
We present H-band (1.6 {\mu}m) scattered light observations of the
transitional disk RX J1615.3-3255, located in the ~1 Myr old Lupus association.
From a polarized intensity image, taken with the HiCIAO instrument of the
Subaru Telescope, we deduce the position angle and the inclination angle of the
disk. The disk is found to extend out to 68 12 AU in scattered light and
no clear structure is observed. Our inner working angle of 24 AU does not allow
us to detect a central decrease in intensity similar to that seen at 30 AU in
the 880 {\mu}m continuum observations. We compare the observations with
multiple disk models based on the Spectral Energy Distribution (SED) and submm
interferometry and find that an inner rim of the outer disk at 30 AU containing
small silicate grains produces a polarized intensity signal which is an order
of magnitude larger than observed. We show that a model in which the small dust
grains extend smoothly into the cavity found for large grains is closer to the
actual H-band observations. A comparison of models with different dust size
distributions suggests that the dust in the disk might have undergone
significant processing compared to the interstellar medium.Comment: 8 pages, 7 figures, 4 tables. Accepted for publication in A&
Extreme Asymmetry in the Disk of V1247 Ori
We present the first near-infrared scattered-light detection of the
transitional disk around V1247 Ori, which was obtained using high-resolution
polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging
in the H band reveals the disk morphology at separations of ~0.14"-0.86"
(54-330 au) from the central star. The polarized intensity (PI) image shows a
remarkable arc-like structure toward the southeast of the star, whereas the
fainter northwest region does not exhibit any notable features. The shape of
the arm is consistent with an arc of 0.28" 0.09" in radius (108 au from
the star), although the possibility of a spiral arm with a small pitch angle
cannot be excluded. V1247 Ori features an exceptionally large azimuthal
contrast in scattered, polarized light; the radial peak of the southeastern arc
is about three times brighter than the northwestern disk measured at the same
distance from the star. Combined with the previous indication of an
inhomogeneous density distribution in the gap at 46 au, the notable
asymmetry in the outer disk suggests the presence of unseen companions and/or
planet-forming processes ongoing in the arc.Comment: 21 pages, 5 figures, accepted for publication in PAS
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