4,142 research outputs found
Candidate Members and Age Estimate of the Family of Kuiper Belt Object 2003 EL61
The collisional family of Kuiper belt object (KBO) 2003 EL61 opens the
possibility for many interesting new studies of processes important in the
formation and evolution of the outer solar system. As the first family in the
Kuiper belt, it can be studied using techniques developed for studying asteroid
families, although some modifications are necessary. Applying these modified
techniques allows for a dynamical study of the 2003 EL61 family. The velocity
required to change orbits is used to quantitatively identify objects near the
collision. A method for identifying family members that have potentially
diffused in resonances (like 2003 EL61) is also developed. Known family members
are among the very closest KBOs to the collision and two new likely family
members are identified: 2003 UZ117 and 1999 OY3. We also give tables of
candidate family members which require future observations to confirm
membership. We estimate that a minimum of ~1 GYr is needed for resonance
diffusion to produce the current position of 2003 EL61, implying that the
family is likely primordial. Future refinement of the age estimate is possible
once (many) more resonant objects are identified. The ancient nature of the
collision contrasts with the seemingly fresh surfaces of known family members,
suggesting that our understanding of outer solar system surfaces is incomplete.Comment: 22 pages, 5 figures, accepted to AJ, author's cv available at
http://www.gps.caltech.edu/~dari
Discovery of a Binary Centaur
We have identified a binary companion to (42355) 2002 CR46 in our ongoing
deep survey using the Hubble Space Telescope's High Resolution Camera. It is
the first companion to be found around an object in a non-resonant orbit that
crosses the orbits of giant planets. Objects in orbits of this kind, the
Centaurs, have experienced repeated strong scattering with one or more giant
planets and therefore the survival of binaries in this transient population has
been in question. Monte Carlo simulations suggest, however, that binaries in
(42355) 2002 CR46 -like heliocentric orbits have a high probability of survival
for reasonable estimates of the binary's still-unknown system mass and
separation. Because Centaurs are thought to be precursors to short period
comets, the question of the existence of binary comets naturally arises; none
has yet been definitively identified. The discovery of one binary in a sample
of eight observed by HST suggests that binaries in this population may not be
uncommon.Comment: 20 pages, 4 figures, 1 table accepted for publication in Icaru
The Mutual Orbit, Mass, and Density of Transneptunian Binary Gknhmdm (229762 2007 UK126)
We present high spatial resolution images of the binary transneptunian object Gkn'hmdm (229762 2007 UK126) obtained with the Hubble Space Telescope and with the Keck observatory on Mauna Kea to determine the orbit of G' hG' h, the much smaller and redder satellite. G' h orbits in a prograde sense, on a circular or near-circular orbit with a period of 11.3 days and a semimajor axis of 6000 km. Tidal evolution is expected to be slow, so it is likely that the system formed already in a low-eccentricity configuration, and possibly also with the orbit plane of the satellite in or close to the plane of Gkn'hmdm's equator. From the orbital parameters we can compute the system mass to be 1.4 10(exp 20) kg. Combined with estimates of the size of Gkn'hmdm from thermal observations and stellar occultations, we can estimate the bulk density as about 1 g cm(exp 3). This low density is indicative of an ice-rich composition, unless there is substantial internal porosity. We consider the hypothesis that the composition is not unusually ice-rich compared with larger TNOs and comet nuclei, and instead the porosity is high, suggesting that mid-sized objects in the 400 to 1000 km diameter range mark the transition between small, porous objects and larger objects that have collapsed their internal void space as a result of their much higher internal pressures and temperatures
Functional Relaxation and Guided Imagery as Complementary Therapy in Asthma: A Randomized Controlled Clinical Trial
Background: Asthma is a frequently disabling and almost invariably distressing disease that has a high overall prevalence. Although relaxation techniques and hypnotherapeutic interventions have proven their effectiveness in numerous trials, relaxation therapies are still not recommended in treatment guidelines due to a lack of methodological quality in many of the trials. Therefore, this study aims to investigate the efficacy of the brief relaxation technique of functional relaxation (FR) and guided imagery (GI) in adult asthmatics in a randomized controlled trial. Methods: 64 patients with extrinsic bronchial asthma were treated over a 4-week period and assessed at baseline, after treatment and after 4 months, for follow-up. 16 patients completed FR, 14 GI, 15 both FR and GI (FR/GI) and 13 received a placebo relaxation technique as the control intervention (CI). The forced expiratory volume in the first second (FEV 1) as well as the specific airway resistance (sR(aw)) were employed as primary outcome measures. Results: Participation in FR, GI and FR/GI led to increases in FEV 1 (% predicted) of 7.6 +/- 13.2, 3.3 +/- 9.8, and 8.3 +/- 21.0, respectively, as compared to -1.8 +/- 11.1 in the CI group at the end of the therapy. After follow-up, the increases in FEV 1 were 6.9 +/- 10.3 in the FR group, 4.4 +/- 7.3 in the GI and 4.5 +/- 8.1 in the FR/GI, compared to -2.8 +/- 9.2 in the CI. Improvements in sR(aw) (% predicted) were in keeping with the changes in FEV 1 in all groups. Conclusions: Our study confirms a positive effect of FR on respiratory parameters and suggests a clinically relevant long-term benefit from FR as a nonpharmacological and complementary therapy treatment option. Copyright (C) 2009 S. Karger AG, Base
Geothermal probabilistic cost study
A tool is presented to quantify the risks of geothermal projects, the Geothermal Probabilistic Cost Model (GPCM). The GPCM model was used to evaluate a geothermal reservoir for a binary-cycle electric plant at Heber, California. Three institutional aspects of the geothermal risk which can shift the risk among different agents was analyzed. The leasing of geothermal land, contracting between the producer and the user of the geothermal heat, and insurance against faulty performance were examined
Spectroscopic Detection of Carbon Monoxide in Two Late-type T Dwarfs
M band spectra of two late-type T dwarfs, 2MASS J09373487+2931409, and Gliese
570D, confirm evidence from photometry that photospheric CO is present at
abundance levels far in excess of those predicted from chemical equilibrium.
These new and unambiguous detections of CO, together with an earlier
spectroscopic detection of CO in Gliese 229B and existing M band photometry of
a large selection of T dwarfs, suggest that vertical mixing in the photosphere
drives the CO abundance out of chemical equilibrium and is a common, and likely
universal feature of mid-to-late type T dwarfs. The M band spectra allow
determinations of the time scale of vertical mixing in the atmosphere of each
object, the first such measurements of this important parameter in late T
dwarfs. A detailed analysis of the spectral energy distribution of 2MASS
J09373487+2931409 results in the following values for metallicity, temperature,
surface gravity, and luminosity: [M/H]~-0.3, T_eff=925-975K, log g=5.20-5.47,
log L/L_sun=-5.308 +/- 0.027. The age is 3-10 Gyr and the mass is in the range
45-69 M_Jup.Comment: 36 pages incl. 12 figures and 3 tables, accepted by Ap
The Orbit of Transneptunian Binary Manw\"e and Thorondor and their Upcoming Mutual Events
A new Hubble Space Telescope observation of the 7:4 resonant transneptunian
binary system (385446) Manw\"e has shown that, of two previously reported
solutions for the orbit of its satellite Thorondor, the prograde one is
correct. The orbit has a period of 110.18 0.02 days, semimajor axis of
6670 40 km, and an eccentricity of 0.563 0.007. It will be viewable
edge-on from the inner solar system during 2015-2017, presenting opportunities
to observe mutual occultation and eclipse events. However, the number of
observable events will be small, owing to the long orbital period and expected
small sizes of the bodies relative to their separation. This paper presents
predictions for events observable from Earth-based telescopes and discusses the
associated uncertainties and challenges.Comment: 15 pages, 3 figures, 5 table
Use of Energy Consumption during Milling to Fill a Measurement Gap in Hybrid Additive Manufacturing
Coupling additive manufacturing (AM) with interlayer peening introduces bulk anisotropic properties within a build across several centimeters. Current methods to map high resolution anisotropy and heterogeneity are either destructive or have a limited penetration depth using a nondestructive method. An alternative pseudo-nondestructive method to map high-resolution anisotropy and heterogeneity is through energy consumption during milling. Previous research has shown energy consumption during milling correlates with surface integrity. Since surface milling of additively manufactured parts is often required for post-processing to improve dimensional accuracy, an opportunity is available to use surface milling as an alternative method to measure mechanical properties and build quality. The variation of energy consumption during the machining of additive parts, as well as hybrid AM parts, is poorly understood. In this study, the use of net cutting specific energy was proposed as a suitable metric for measuring mechanical properties after interlayer ultrasonic peening of 316 stainless steel. Energy consumption was mapped throughout half of a cuboidal build volume. Results indicated the variation of net cutting specific energy increased farther away from the surface and was higher for hybrid AM compared to as-printed and wrought. The average lateral and layer variation of the net cutting specific energy for printed samples was 81% higher than the control, which indicated a significantly higher degree of heterogeneity. Further, it was found that energy consumption was an effective process signature exhibiting strong correlations with microhardness. Anisotropy based on residual strains were measured using net cutting specific energy and validated by hole drilling. The proposed technique contributes to filling part of the measure gap in hybrid additive manufacturing and capitalizes on the preexisting need for machining of AM parts to achieve both goals of surface finish and quality assessment in one milling operation
Abundances of ammonia and carbon disulfide in the Jovian stratosphere following the impact of comet Shoemaker‐Levy 9
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95648/1/grl8459.pd
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