29,573 research outputs found
The last disconnection events in Comet Halley in April 1986
Disconnection event (DE) in cometary plasma physics is the regular loss of the entire plasma tail and the growth of the new one. Analysis of a sequence of DEs that occurred 13-18 April, 1986 shows that they correlate well with a magnetic, sector-boundary crossing and a complex magnetic structure in the solar wind with polarity reversals that occurred about one day later. These events are entirely consistent with sunward, magnetic reconnection as the DE mechanism
Latitudinal properties of the solar wind from studies of ionic comet tails
A statistical analysis is presented of the orientations of ionic comet tails in the solar wind. The analysis indicates that the radial solar wind speed is not necessarily higher near the solar poles than near the equator. The results refer to a long-term, global flow pattern and do not refer to short-term variations of solar wind speed
Evolution on large-scale plasma structures in comets: Kinematics and physics
The disconnection event (DE) consists of the periodic loss of a comet's entire plasma tail and the growth of a new one. This spectacular phenomenon is not understood. The strategy was to assemble a data base of specific events studied in detail, determine the solar wind conditions responsible for DEs, and develop a consistent physical model. Analysis is complete for the sequence of DEs that took place during 13 to 18 April 1986. The first DE correlates well with a sector boundary crossing for the comet and a group of DEs that occurred approximately a day later could have produced by polarity reversals seen in the IMP-8 data. Thus, these DEs are consistent with the frontside, magnetic reconnection mechanism
Review: Observations of recent comets, ion tails
Photographic plates of the moving structures in the cometary tail are examined. Several divergent explanations for the case of comet Kohoutek are presented. It is suggested that these hypotheses be tested by observing the motion of the material spectroscopically by means of the Doppler effect
Evolution of large-sclae plasma structures in comets: Kinematics and physics
Disconnection Events are the dramatic part of the periodic morphology involving the separation of the entire plasma tail from the head region of the comet and the growth of a new plasma. The coordinated observations of Comet Halley recorded approximately 30 DEs during the 7 months of plasma activity; 19 of these are obvious. The plasma physics of these events were approached via a detailed, kinematic investigation of specific DEs and the solar-wind environment associated with it. As the detailed investigations are completed, researchers should be able to answer the question of a single or multiple mechanism(s) for DEs and determine which mechanism(s) are important. At present, the mechanism of sunward magnetic reconnection caused by interplanetary sector boundary crossing in consistent with the data available
Acetazolamide in the treatment of acute mania - A case report
Several antiepileptic drugs are also being used in affective disorders. There are some hints that also the carbonic anhydrase inhibitor acetazolamide might be useful in the treatment of bipolar affective disorder. We report a 39-year-old male patient with a history of bipolar affective disorder who presented with his second manic episode. Acetazolamide was added to a low dose of valproic acid and to perazine. A marked decrease of the BRMAS score was achieved. The implications of this case are discussed
Statics and Dynamics of Vortex Liquid Crystals
Using numerical simulations we examine the static and dynamic properties of
the recently proposed vortex liquid crystal state. We confirm the existence of
a smectic-A phase in the absence of pinning. Quenched disorder can induce a
smectic state even at T=0. When an external drive is applied, a variety of
anisotropic dynamical flow states with distinct voltage signatures occur,
including elastic depinning in the hard direction and plastic depinning in the
easy direction. We discuss the implications of the anisotropic transport for
other systems which exhibit depinning phenomena, such as stripes and electron
liquid crystals.Comment: 4 pages, 4 postscript figure
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Microbial mats of the Tswaing impact crater: results of a South African exobiology expedition and implications for the search for biological molecules on Mars
We describe microbial mats from the Tswaing impact crater in South Africa. The mats provide insights into the unique biological characteristics of impact craters and can help strategies for the search for biomolecules on Mars
Non-Quadratic Gauge Fixing and Global Gauge Invariance in the Effective Action
The possibility of having a gauge fixing term in the effective Lagrangian
that is not a quadratic expression has been explored in spin-two theories so as
to have a propagator that is both traceless and transverse. We first show how
this same approach can be used in spontaneously broken gauge theories as an
alternate to the 't Hooft gauge fixing which avoids terms quadratic in the
scalar fields. This "non-quadratic" gauge fixing in the effective action
results in there being two complex Fermionic and one real Bosonic ghost fields.
A global gauge invariance involving a Fermionic gauge parameter, analogous to
the usual BRST invariance, is present in this effective action.Comment: 4 pages, revtex4 (submitted to Phys. Rev. D
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