2,104 research outputs found
Triplet Superconductors from the Viewpoint of Basic Elements for Quantum Computers
We discuss possibilities of utilizing superconductors with Cooper condensates
in triplet pairing states (where the spin of condensate pairs is S=1) for
practical realization of quantum computers. Superconductors with triplet
pairing condensates have features that are unique and cannot be found in the
usual (singlet pairing, S=0) superconductors. The symmetry of the order
parameter in some triplet superconductors (e.g., ruthenates) corresponds to
doubly-degenerate chiral states. These states can serve as qubit base states
for quantum computing.Comment: 4 pages, 5 figures, will be presented at ASC-2002 and submitted to
IEEE Trans. Appl. Supercon
X ray timing observations and gravitational physics
Photon-rich x ray observations on bright compact galactic sources will make it possible to detect many fast processes that may occur in these systems on millisecond and submillisecond timescales. Many of these processes are of direct relevance to gravitational physics because they arise in regions of strong gravity near neutron stars and black holes where the dynamical timescales for compact objects of stellar mass are milliseconds. To date, such observations have been limited by the detector area and telemetry rates available. However, instruments such as the proposed X ray Large Array (XLA) would achieve collecting areas of about 100 sq m. This instrument has been described elsewhere (Wood and Michelson 1988) and was the subject of a recent prephase A feasibility study at Marshall Space Flight Center. Observations with an XLA class instrument will directly impact five primary areas of astrophysics research: the attempt to detect gravitational radiation, the study of black holes, the physics of mass accretion onto compact objects, the structure of neutron stars and nuclear matter, and the characterization of dark matter in the universe. Those observations are discussed that are most directly relevant to gravitational physics: the search for millisecond x ray pulsars that are potential sources of continuous gravitational radiation; and the use of x ray timing observations to probe the physical conditions in extreme relativistic regions of space near black holes, both stellar-sized and supermassive
Harm Reduction Measures in Substance Use Disorder (SUD)
This literature review aims to comprehensively analyze harm reduction strategies employed in addressing Substance Use Disorder (SUD). Focusing on key interventions such as fentanyl testing strips, naloxone distribution, syringe exchange programs, and methadone/buprenorphine clinics, the study seeks to evaluate the effectiveness of these approaches in reducing the associated harms of substance misuse
X-Ray Eclipse Timing in the LMXB EXO0748-676
Orbital period changes are an important diagnostic for understanding low mass
X-ray binary (LMXB) accretion-induced angular momentum exchange and overall
system evolution. We present our most recent results for the eclipse timing of
the LMXB EXO0748-676. Since its discovery in 1985 it has apparently undergone
three distinct orbital period "epochs", each characterized by a different
orbital period than the previous epoch. We outline the orbital period behavior
for EXO0748-676 over the past 18 years and discuss the implications of this
behavior in light of current theoretical ideas for LMXB evolution.Comment: 4 Pages, 3 Figures, Submitted to the X-Ray Timing 2003: Rossi and
Beyond conference, November 200
On the Low and High Frequency Correlation in Quasi-Periodic Oscillations Among White Dwarfs, Neutron Star and Black Hole Binaries
We interpret the correlation over five orders of magnitude between high
frequency and low frequency in a quasi-periodic oscillations (QPO) found by
Psaltis, Belloni & van der Klis (1999) for black hole (BH), neutron star (NS)
systems and then extended by Mauche (2002) to white dwarf (WD) binaries. We
argue that the observed correlation is a natural consequence of the Keplerian
disk flow adjustment to the innermost sub-Keplerian boundary conditions near
the central object. In the framework of the transition layer model the high
frequency is related to the Keplerian frequency at the outer (adjustment)
radius and the low frequency is related to the magnetoacoustic oscillation (MA)
frequency. Using a relation between the MA frequency the magnetic and gas
pressure and the density and the hydrostatic equilibrium condition in the disk
we infer a linear correlation the Keplerian frequency and the MA frequency. We
estimate the magnetic field strength near the TL outer radius for BHs NSs and
WDs. The fact that the observed high-low frequency correlation over five orders
of magnitude is valid for BHs, NSs, and down to WDs strongly rules out
relativistic models for QPO phenomena. We come to the conclusion that the QPOs
observations indicate the adjustment of the geometrically thin disk to
sub-Keplerian motion near the central object. This effect is a common feature
for a wide class of systems, starting from white dwarf binaries up to black
hole binaries.Comment: 8 pages, 1 figure, accepted for publication in the ApJ. Letters 2002
August
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Possible Magnetic Activity in the Low Mass X-ray Binary EXO 0748-676
We report evidence of magnetic activity associated with the secondary star in
the EXO 0748-676 low mass X-ray binary system. An analysis of a sequence of
five consecutive X-ray eclipses observed during December 2003 with the RXTE
satellite brings out a feature occurring during ingress we interpret as the
X-ray photoelectric absorption shadow, as seen by an observer at Earth, of a
plasma structure suspended above the surface of the secondary star. The light
curve feature consists of an initial drop in count rate to near zero (the
absorption shadow) with a very short rebound to a significant fraction of the
pre-ingress count rate and then a final plunge to totality over a total time
scale of ~25 s. The ingress feature persists for at least 5 consecutive orbital
periods (a total of ~19 hr), and possibly up to 5 days in our data. Our data
also show significant post-egress dipping during this eclipse sequence, unusual
for this source, indicating possible secondary star mass ejection during this
episode.Comment: Accepted by Astrophysical Journal Letters; 11 Pages including 3
figures and 1 tabl
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