3,012 research outputs found
Circular 45
This circular provides guidance on fertilizing native hay meadows of
bluejoint reedgrass (Calamagrostis canadensis) on the lower Kenai Peninsula.
It is based on a num ber o f experim ental trials conducted by the authors on
Kachemak silt loam soil at various sites near Homer
An orbital window into the ancient Sun's mass
Models of the Sun's long-term evolution suggest that its luminosity was
substantially reduced 2-4 billion years ago, which is inconsistent with
substantial evidence for warm and wet conditions in the geological records of
both ancient Earth and Mars. Typical solutions to this so-called "faint young
Sun paradox" consider changes in the atmospheric composition of Earth and Mars,
and while attractive, geological verification of these ideas is generally
lacking-particularly for Mars. One possible underexplored solution to the faint
young Sun paradox is that the Sun has simply lost a few percent of its mass
during its lifetime. If correct, this would slow, or potentially even offset
the increase in luminosity expected from a constant-mass model. However, this
hypothesis is challenging to test. Here, we propose a novel observational proxy
of the Sun's ancient mass that may be readily measured from accumulation
patterns in sedimentary rocks on Earth and Mars. We show that the orbital
parameters of the Solar system planets undergo quasi-cyclic oscillations at a
frequency, given by secular mode g_2-g_5, that scales approximately linearly
with the Sun's mass. Thus by examining the cadence of sediment accumulation in
ancient basins, it is possible distinguish between the cases of a constant mass
Sun and a more massive ancient Sun to a precision of greater than about 1 per
cent. This approach provides an avenue toward verification, or of
falsification, of the massive early Sun hypothesis.Comment: 7 pages, 4 Figures. Accepted to The Astrophysical Journal Letter
Traffic control system and method
Frequency of carrier received by aircraft is measured and compared with reference to indicate magnitude of Doppler shift. One Doppler frequency range is selected and indicated by digital signal. Difference between frequency is offset of apparent carrier frequency transmitted by aircraft
Traffic control system and method Patent
Traffic control system for supersonic transports using synchronous satellite for data relay between vehicles and ground statio
Remote sensing of the atmosphere from environmental satellites
Various applications of satellite remote sensing of the earth are reviewed, including (1) the use of meteorological satellites to obtain photographic and radiometric data for determining weather conditions; (2) determination of the earth radiation budget from measurements of reflected solar radiation and emitted long wave terrestrial radiation; (3) the use of microwave imagery for measuring ice and snow cover; (4) LANDSAT visual and near infrared observation of floods and crop growth; and (5) the use of the Nimbus 4 backscatter ultraviolet instrument to measure total ozone and vertical ozone distribution. Plans for future activities are also discussed
Laughlin type wave function for two-dimensional anyon fields in a KMS-state
The correlation functions of two-dimensional anyon fields in a KMS-state are
studied. For T=0 the -particle wave functions of noncanonical fermions of
level , odd, are shown to be of Laughlin type of order
. For they are given by a simple finite-temperature
generalization of Laughlin's wave function. This relates the first and second
quantized pictures of the fractional quantum Hall effect.Comment: 9 pages, LaTeX, comments and references added (version to appear in
Physics Letters B
A determination of the spin-orbit alignment of the anomalously dense planet orbiting HD 149026
We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15
were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities
provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably small planetary radius, the planetary mass, and the orbital inclination, found to be Rp/RJup = 0.718 ± 0.065, Mp/MJup = 0.352 ± 0.025, and I = 86.1° ± 1.4°, respectively. Together the planetary mass and radius determinations imply a mean planetary density
of 1.18(-0.30)(+0.38)g cm(-3). The new data also allow for the determination of the angle between the apparent stellar equator and the orbital plane, which we constrain to be λ = -12° ± 15°
Magnetic Instability in Strongly Correlated Superconductors
Recently a new phenomenological Hamiltonian has been proposed to describe the
superconducting cuprates. This so-called Gossamer Hamiltonian is an apt model
for a superconductor with strong on-site Coulomb repulsion betweenthe
electrons. It is shown that as one approaches half-filling the Gossamer
superconductor, and hence the superconducting state, with strong repulsion is
unstable toward an antiferromagnetic insulator an can undergo a quantum phase
transition to such an insulator if one increases the on-site Coulomb repulsion
Testing the locality of transport in self-gravitating accretion discs - II. The massive disc case
In this paper, we extend our previous analysis (Lodato & Rice 2004) of the
transport properties induced by gravitational instabilities in cooling, gaseous
accretion discs to the case where the disc mass is comparable to the central
object. In order to do so, we have performed global, three-dimensional smoothed
particle hydrodynamics simulations of massive discs. These new simulations show
a much more complex temporal evolution with respect to the less massive case.
Whereas in the low disc mass case a self-regulated, marginally stable state
(characterized by an approximately constant radial profile of the stability
parameter ) is easily established, in the high disc mass case we observe the
development of an initial transient and subsequent settling down in a
self-regulated state in some simulations, or a series or recurrent spiral
episodes, with low azimuthal wave number , in others. Accretion in this last
case can therefore be a highly variable process. On the other hand, we find
that the secular evolution of the disc is relatively slow. In fact, the
time-average of the stress induced by self-gravity results in accretion
time-scales much longer than the dynamical timescale, in contrast with previous
isothermal simulations of massive accretion discs. We have also compared the
resulting stress tensor with the expectations based on a local theory of
transport, finding no significant evidence for global wave energy transport.Comment: MNRAS, accepted (higher quality, colour figures can be found at
http://www.ast.cam.ac.uk/~giuseppe/Publications/Locality_II/
A Study of the Effects of Quick Freezing on Saturated Fragments of Rocks
Quick freezing of a fragment of rock which is fully saturated with water is, perhaps, the most rigorous of all tests for soundness, durability, or resistance to weathering. So-called soundness or quality tests employed currently, or heretofore, for evaluating concrete aggregates are usually less rigorous inasmuch as the state of saturation at the outset of freezing is not at a critical level. Hence, the number of freeze-thaw cycles endured by a rock specimen undergoing freezing and thawing in the presence of available water may merely reflect the duration of the exposure before the rock becomes vulnerable to damage -- i.e., time required for critical saturation. Damage arises wholly from the combined effects of the volume dilation accompanying the freezing of absorbed water, the dilation pressure induced, and the inherent restraining strength of the aggregate particle. Thus, the severest freezing condition, to which rock or concrete may be exposed, occurs after long periods of sustained wetting -- when the degree of saturation is the highest
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