1,274 research outputs found
Mariner Mars 1971 optical navigation demonstration
The feasibility of using a combination of spacecraft-based optical data and earth-based Doppler data to perform near-real-time approach navigation was demonstrated by the Mariner Mars 71 Project. The important findings, conclusions, and recommendations are documented. A summary along with publications and papers giving additional details on the objectives of the demonstration are provided. Instrument calibration and performance as well as navigation and science results are reported
Report from solar physics
A discussion of the nature of solar physics is followed by a brief review of recent advances in the field. These advances include: the first direct experimental confirmation of the central role played by thermonuclear processes in stars; the discovery that the 5-minute oscillations of the Sun are a global seismic phenomenon that can be used as a probe of the structure and dynamical behavior of the solar interior; the discovery that the solar magnetic field is subdivided into individual flux tubes with field strength exceeding 1000 gauss. Also covered was a science strategy for pure solar physics. Brief discussions are given of solar-terrestrial physics, solar/stellar relationships, and suggested space missions
Orbitally tuned timescale and astronomical forcing in the middle Eocene to early Oligocene
Deciphering the driving mechanisms of Earth system processes, including the
climate dynamics expressed as paleoceanographic events, requires a complete,
continuous, and high-resolution stratigraphy that is very accurately dated.
In this study, a robust astronomically calibrated age model was constructed
for the middle Eocene to early Oligocene interval (31â43 Ma) in
order to permit more detailed study of the exceptional climatic events that
occurred during this time, including the middle Eocene climate optimum and
the EoceneâOligocene transition. A goal of this effort is to accurately date
the middle Eocene to early Oligocene composite section cored during the
Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic
framework for the new timescale is based on the identification of the stable
long eccentricity cycle in published and new high-resolution records
encompassing bulk and benthic stable isotope, calibrated XRF core scanning,
and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218,
and 207-1260 as well as IODP Sites 320-U1333, and 320-U1334 spanning magnetic
polarity Chrons C12n to C20n. Subsequently orbital tuning of the records to
the La2011 orbital solution was conducted. The resulting new timescale
revises and refines the existing orbitally tuned age model and the
geomagnetic polarity timescale from 31 to 43 Ma. The newly defined
absolute age for the EoceneâOligocene boundary validates the astronomical
tuned age of 33.89 Ma identified at the Massignano, Italy, global
stratotype section and point. The compilation of geochemical records of
climate-controlled variability in sedimentation through the middle-to-late
Eocene and early Oligocene demonstrates strong power in the eccentricity band
that is readily tuned to the latest astronomical solution. Obliquity driven
cyclicity is only apparent during 2.4 myr eccentricity cycle minima
around 35.5, 38.3, and 40.1 Ma
Stochastic Analysis of Dimerization Systems
The process of dimerization, in which two monomers bind to each other and
form a dimer, is common in nature. This process can be modeled using rate
equations, from which the average copy numbers of the reacting monomers and of
the product dimers can then be obtained. However, the rate equations apply only
when these copy numbers are large. In the limit of small copy numbers the
system becomes dominated by fluctuations, which are not accounted for by the
rate equations. In this limit one must use stochastic methods such as direct
integration of the master equation or Monte Carlo simulations. These methods
are computationally intensive and rarely succumb to analytical solutions. Here
we use the recently introduced moment equations which provide a highly
simplified stochastic treatment of the dimerization process. Using this
approach, we obtain an analytical solution for the copy numbers and reaction
rates both under steady state conditions and in the time-dependent case. We
analyze three different dimerization processes: dimerization without
dissociation, dimerization with dissociation and hetero-dimer formation. To
validate the results we compare them with the results obtained from the master
equation in the stochastic limit and with those obtained from the rate
equations in the deterministic limit. Potential applications of the results in
different physical contexts are discussed.Comment: 10 figure
Sunspot observations from the SOUP instrument on Spacelab 2
A series of white light images obtained by the SOUP instrument on Spacelab 2 of active region 4682 on August 5, 1985 were analyzed in the area containing sunspots. Although the umbra of the spot is underexposed, the film is well exposed in the penumbral regions. These data were digitally processed to remove noise and to separate p-mode oscillations from low velocity material motions. The results of this preliminary investigation include: (1) proper motion measurements of a radial outflow in the photospheric granulation pattern just outside the penumbra; (2) discovery of occasional bright structures (streakers) that appear to be ejected outward from the penumbra; (3) broad dark clouds moving outward in the penumbra in addition to the well known bright penumbral grains moving inward; (4) apparent extensions and contractions of penumbral filaments over the photosphere; and (5) observation of a faint bubble or loop-like structure which seems to expand from two bright penumbral filaments into the photosphere
Quark-Gluon Jet Differences at LEP
A new method to identify the gluon jet in 3-jet ``{\bf Y}'' decays of
is presented. The method is based on differences in particle multiplicity
between quark jets and gluon jets, and is more effective than tagging by
leptonic decay. An experimental test of the method and its application to a
study of the ``string effect'' are proposed. Various jet-finding schemes for
3-jet events are compared.Comment: 11 pages, LaTeX, 4 PostScript figures availble from the author
([email protected]), MSUTH-92-0
Pion and Kaon Production in and Collisions at Next-to-Leading Order
We present new sets of fragmentation functions for charged pions and kaons,
both at leading and next-to-leading order. They are fitted to data on inclusive
charged-hadron production in annihilation taken by TPC at PEP (~GeV) and to similar data by ALEPH at LEP, who discriminated between
events with charm, bottom, and light- flavour fragmentation in their
charged-hadron sample. We treat all partons independently and to properly
incorporate the charm and bottom thresholds. Due to the sizeable energy gap
between PEP and LEP, we are sensitive to the scaling violation in the
fragmentation process, which allows us to extract a value for the asymptotic
scale parameter of QCD, . Recent data on inclusive charged-hadron
production in tagged three-jet events by OPAL and similar data for longitudinal
electron polarization by ALEPH allow us to pin down the gluon fragmentation
functions. Our new fragmentation functions lead to an excellent description of
a multitude of other data on inclusive charged-hadron production,
ranging from ~GeV to LEP energy. In addition, they agree nicely
with the transverse-momentum spectra of single charged hadrons measured by H1
and ZEUS in photoproduction at the collider HERA, which represents a
nontrivial check of the factorization theorem of the QCD-improved parton model.Comment: 22 pages, latex, 13 compressed ps figures in separate fil
Director configuration of planar solitons in nematic liquid crystals
The director configuration of disclination lines in nematic liquid crystals
in the presence of an external magnetic field is evaluated. Our method is a
combination of a polynomial expansion for the director and of further
analytical approximations which are tested against a numerical shooting method.
The results are particularly simple when the elastic constants are equal, but
we discuss the general case of elastic anisotropy. The director field is
continuous everywhere apart from a straight line segment whose length depends
on the value of the magnetic field. This indicates the possibility of an
elongated defect core for disclination lines in nematics due to an external
magnetic field.Comment: 12 pages, Revtex, 8 postscript figure
Impact of R-Parity Violation on Supersymmetry Searches at the Tevatron
We evaluate cross sections for \eslt, 1 and various dilepton and
multilepton event topologies that result from the simultaneous production of
all sparticles at the Tevatron collider, both within the minimal model
framework as well as in two different -parity violating scenarios. Our
analysis assumes that these -violating couplings are small, and that their
sole effect is to cause the lightest supersymmetric particle to decay inside
the detector. We reassess future strategies for sparticle searches at the
Tevatron, and quantify by how much the various signals for supersymmetry could
differ from their minimal model expectations, if -parity is not conserved
due to either baryon number or lepton number violating operators. We also
evaluate the Tevatron reach in for the various models, and find that
rate-limited multilepton signals ultimately provide the largest reach for both
-parity conserving and -parity violating cases.Comment: preprint nos. FSU-HEP-941001, UR-1387, ER-40685-836 and
UH-511-807-94, 13 pages (REVTEX) plus 3 uuencoded figures attache
Multiplicity dependence of identical particle correlations in the quantum optical approach
Identical particle correlations at fixed multiplicity are consideres in the
presence of chaotic and coherent fields. The multiplicity distribution,
one-particle momentum density, and two-particle correlation function are
obtained based on the diagrammatic representation for cmulants in
semi-inclusive events. Our formulation is applied to the analysis of the
experimental data on the multiplicity dependence of correlation functions
reported by the UA1 and the OPAL Collaborations.Comment: 14 pages, 7 figure
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