Observations of radar speckle patterns tied to the rotation of Mercury establish that the planet occupies a Cassini state with obliquity of 2.11 ± 0.1 arc minutes. The measurements show that the ...planet exhibits librations in longitude that are forced at the 88-day orbital period, as predicted by theory. The large amplitude of the oscillations, 35.8 ± 2 arc seconds, together with the Mariner 10 determination of the gravitational harmonic coefficient C₂₂, indicates that the mantle of Mercury is decoupled from a core that is at least partially molten.
Families and other carers report widespread dissatisfaction with general hospital care for confused older people.
We undertook a qualitative interviews study of 35 family carers of 34 confused older ...patients to ascertain their experiences of care on geriatric and general medical, and orthopaedic wards of a large English hospital. Transcripts were analysed using a grounded theory approach. Themes identified in interviews were categorised, and used to build a model explaining dissatisfaction with care.
The experience of hospital care was often negative. Key themes were events (illness leading to admission, experiences in the hospital, adverse occurrences including deterioration in health, or perceived poor care); expectations (which were sometimes unrealistic, usually unexplored by staff, and largely unmet from the carers' perspective); and relationships with staff (poor communication and conflict over care). Expectations were influenced by prior experience. A cycle of discontent is proposed. Events (or 'crises') are associated with expectations. When these are unmet, carers become uncertain or suspicious, which leads to a period of 'hyper vigilant monitoring' during which carers seek out evidence of poor care, culminating in challenge, conflict with staff, or withdrawal, itself a crisis. The cycle could be completed early during the admission pathway, and multiple cycles within a single admission were seen.
People with dementia who have family carers should be considered together as a unit. Family carers are often stressed and tired, and need engaging and reassuring. They need to give and receive information about the care of the person with dementia, and offered the opportunity to participate in care whilst in hospital. Understanding the perspective of the family carer, and recognising elements of the 'cycle of discontent', could help ward staff anticipate carer needs, enable relationship building, to pre-empt or avoid dissatisfaction or conflict.
Dynamical simulations of the coupled rotational and orbital dynamics of binary near-Earth asteroid 66391 (1999 KW4) suggest that it is excited as a result of perturbations from the Sun during ...perihelion passages. Excitation of the mutual orbit will stimulate complex fluctuations in the orbit and rotation of both components, inducing the attitude of the smaller component to have large variation within some orbits and to hardly vary within others. The primary's proximity to its rotational stability limit suggests an origin from spin-up and disruption of a loosely bound precursor within the past million years.
Binary Asteroids in the Near-Earth Object Population Margot, J. L.; Nolan, M. C.; Benner, L. A. M. ...
Science (American Association for the Advancement of Science),
05/2002, Letnik:
296, Številka:
5572
Journal Article
Recenzirano
Radar images of near-Earth asteroid 2000 DP107 show that it is composed of an ∼800-meter-diameter primary and an ∼300-meter-diameter secondary revolving around their common center of mass. The ...orbital period of 1.755 ± 0.007 days and semimajor axis of 2620 ± 160 meters constrain the total mass of the system to 4.6 ± 0.5 × 10
11
kilograms and the bulk density of the primary to 1.7 ± 1.1 grams per cubic centimeter. This system and other binary near-Earth asteroids have spheroidal primaries spinning near the breakup point for strengthless bodies, suggesting that the binaries formed by spin-up and fission, probably as a result of tidal disruption during close planetary encounters. About 16% of near-Earth asteroids larger than 200 meters in diameter may be binary systems.
Integration of the orbit of asteroid (29075) 1950 DA, which is based on radar and optical measurements spanning 51 years, reveals a 20-minute interval in March 2880 when there could be a ...nonnegligible probability of the 1-kilometer object colliding with Earth. Trajectory knowledge remains accurate until then because of extensive astrometric data, an inclined orbit geometry that reduces in-plane perturbations, and an orbit uncertainty space modulated by gravitational resonance. The approach distance uncertainty in 2880 is determined primarily by uncertainty in the accelerations arising from thermal re-radiation of solar energy absorbed by the asteroid. Those accelerations depend on the spin axis, composition, and surface properties of the asteroid, so that refining the collision probability may require direct inspection by a spacecraft.
Detailed topographic maps of the lunar poles have been obtained by Earth-based radar interferometry with the 3.5-centimeter wavelength Goldstone Solar System Radar. The interferometer provided maps ...300 kilometers by 1000 kilometers of both polar regions at 150-meter spatial resolution and 50-meter height resolution. Using ray tracing, these digital elevation models were used to locate regions that are in permanent shadow from solar illumination and may harbor ice deposits. Estimates of the total extent of shadowed areas poleward of 87.5 degrees latitude are 1030 and 2550 square kilometers for the north and south poles, respectively.
Radar observations of 214 near-Earth asteroids (NEAs) reveal a very strong correlation of circular polarization ratio with visible–infrared taxonomic class, establishing distinct differences in the ...centimeter-to-several-decimeter structural complexity of objects in different spectral classes. The correlation may be due to the intrinsic mechanical properties of different mineralogical assemblages but also may reflect very different formation ages and collisional histories. The highest ratios are measured for groups associated with achondritic igneous rocky meteorites: the E class, whose parent body may be 3103 Eger, and the V class, derived from the mainbelt asteroid (and Dawn mission target) 4 Vesta.
Abstract The surgical treatment of mandibular condyle fractures currently offers several possibilities for stable internal fixation. In this study, a finite element model evaluation was performed of ...three different methods for osteosynthesis of low subcondylar fractures: (1) two four-hole straight plates, (2) one seven-hole lambda plate, and (3) one four-hole trapezoidal plate. The finite element model evaluation considered a load applied to the first molar on the contralateral side to the fracture. Results showed that, although the three methods are capable of withstanding functional loading, the lambda plate displayed a more homogeneous stress distribution for both osteosynthesis material and bone and may be a better method when single-plate fixation is the option.
We report 8510-MHz (3.5-cm) radar observations of the Earth-crossing asteroid (ECA) 6489 Golevka (1991 JX) obtained between June 3 and June 15, 1995, at Goldstone, the Very Large Array and the ...Evpatoria (Ukraine) and Kashima (Japan) radio antennas. One-dimensional Doppler spectra are used to estimate the object's convex hull, refine the ephemeris, and yield four possible pole directions. Three-dimensional modeling using two-dimensional delay-Doppler images and published lightcurves unambiguously defines the pole and reveals an extraordinarily angular shape with flat sides, sharp edges and corners, and peculiar concavities. The equivalent diameter of the object is 530±30 m, with moments of inertia about the (long, intermediate, short) axes proportional to (1.00, 1.38, 1.39) ±0.1. The asteroid's pole direction is λ=202±5°, β=−45±5°, and its sidereal period is
P=6.0289±0.0001 h.
The asteroid's circular polarization ratio, SC/OC=0.23±0.02, is lower than the average for radar-detected near-Earth asteroids and reveals only a modest degree of near-surface roughness at scales near the 3.5-cm wavelength. However, the approximately Lambertian radar scattering law implies considerable surface roughness at larger scales. The asteroid's radar scattering law is modeled as ρcos
n
θ, with ρ=0.25±0.12 and
n=1.7±0.7 giving an equivalent spherical albedo of 0.18±0.09. This value is in the middle of the distribution of albedos of S-class asteroid's previously imaged by radar. The Hapke parameters describing the object's optical scattering properties are
w=0.173±0.006,
h=0.024±0.012,
B
0=1.03±0.45,
g=−0.34±0.02, and
θ
=20±5°. Both the optical and the radar scattering properties are consistent with those of a typical S-class asteroid.
Goldstone-VLA plane-of-sky images do not resolve the asteroid but do provide astrometry with uncertainties less than 0.1 arcsec. Integration of an orbit based on all available radar and optical astrometry shows that Golevka has an insignificant probability of collision with any planet during at least the next nine centuries.
We investigate Golevka's dynamical environment, assuming uniform density. Some areas of the surface are characterized by large enough slopes that we expect that they are exposed, solid, monolithic rock.
Near-Earth Asteroid (29075) 1950 DA may closely encounter Earth in 2880. The probability of Earth impact may be as high as 1/300, but the outcome of the encounter depends critically on the physical ...properties of the asteroid Giorgini et al., 2002. Science 196, 132–136. We have used Arecibo and Goldstone radar data and optical lightcurves to estimate the shape, spin state, and surface structure of 1950 DA. The data allow two distinct models. One rotates prograde and is roughly spheroidal with mean diameter
1.16
±
0.12
km
. The other rotates retrograde and is oblate and about 30% larger. Both models suggest a nickel–iron or enstatite chondritic composition. Ground-based observations should be able to determine which model is correct within the next several decades.
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