28,491 research outputs found
Fast switching current detection at low critical currents
A pulse-and-hold technique is used to measure the switching of small critical
current Josephson junctions. This technique allows one to achieve a good binary
detection and therefore measure switching probabilities. The technique
overcomes limitations on simple square pulses and allows for the measurement of
junctions with critical currents of the order of 10nA with bias pulses of the
order of 100ns. A correlation analysis of the switching events is performed to
show how the switching probability depends on the wait time between repeated
bias pulses.Comment: Changed abstract Added reference 1
Incorporation of amino acids into the outer and inner membrane of isolated rat liver mitochondria II
The Integral Burst Alert System (IBAS)
We describe the INTEGRAL Burst Alert System (IBAS): the automatic software
for the rapid distribution of the coordinates of the Gamma-Ray Bursts detected
by INTEGRAL. IBAS is implemented as a ground based system, working on the
near-real time telemetry stream. During the first six months of operations, six
GRB have been detected in the field of view of the INTEGRAL instruments and
localized by IBAS. Positions with an accuracy of a few arcminutes are currently
distributed by IBAS to the community for follow-up observations within a few
tens of seconds of the event.Comment: 7 pages, latex, 5 figures, Accepted for publication on A&A Special
Issue on First Science with INTEGRA
EPR of Cu\u3csup\u3e2+\u3c/sup\u3e Prion Protein Constructs at 2 GHz Using the \u3cem\u3eg\u3c/em\u3e\u3csub\u3e⊥\u3c/sub\u3e Region to Characterize Nitrogen Ligation
A double octarepeat prion protein construct, which has two histidines, mixed with copper sulfate in a 3:2 molar ratio provides at most three imidazole ligands to each copper ion to form a square-planar Cu2+ complex. This work is concerned with identification of the fourth ligand. A new (to our knowledge) electron paramagnetic resonance method based on analysis of the intense features of the electron paramagnetic resonance spectrum in the g⊥ region at 2 GHz is introduced to distinguish between three and four nitrogen ligands. The methodology was established by studies of a model system consisting of histidine imidazole ligation to Cu2+. In this spectral region at 2 GHz (S-band), g-strain and broadening from the possible rhombic character of the Zeeman interaction are small. The most intense line is identified with the MI = +1/2 extra absorption peak. Spectral simulation demonstrated that this peak is insensitive to cupric Ax and Ay hyperfine interaction. The spectral region to the high-field side of this peak is uncluttered and suitable for analysis of nitrogen superhyperfine couplings to determine the number of nitrogens. The spectral region to the low-field side of the intense extra absorption peak in the g⊥ part of the spectrum is sensitive to the rhombic distortion parameters Ax and Ay. Application of the method to the prion protein system indicates that two species are present and that the dominant species contains four nitrogen ligands. A new loop-gap microwave resonator is described that contains ∼1 mL of frozen sample
Ozone measurements from the NOAA-9 and the Nimbus-7 satellites: Implications of short and long term variabilities
An overview is given of the measurements of total ozne and ozone profiles by the SBUV/2 instrument on the NOAA-9 spacecraft relative to similar measurements from the SBUV and TOMS instruments on Nimbus-7. It is shown that during the three year period from March 14, 1985, to February 28, 1988, when these data sets overlap, there have been significant changes in the calibrations of the three instruments which may be attributed to the drift of the NOSS-9 orbit to later equator crossing times (for SBUV/2). These changes in instrument characteristics have affected the absolute values of the trends derived from the three instruments, but their geophysical characteristics and response to short term variations are accurate and correlate well among the three instruments. For example, the total column ozone measured by the three instruments shows excellent agreement with respect to its day to day, seasonal, and latitudinal variabilities. At high latitudes, the day to day fluctuations in total ozone show a strong positive correlation with temperature in the lower stratosphere, as one might expect from the dynamical coupling of the two parameters at these latitudes
Dirac fermion wave guide networks on topological insulator surfaces
Magnetic texturing on the surface of a topological insulator allows the
design of wave guide networks and beam splitters for domain-wall Dirac
fermions. Guided by simple analytic arguments we model a Dirac fermion
interferometer consisting of two parallel pathways, whereby a newly developed
staggered-grid leap-frog discretization scheme in 2+1 dimensions with absorbing
boundary conditions is employed. The net transmission can be tuned between
constructive to destructive interference, either by variation of the
magnetization (path length) or an applied bias (wave length). Based on this
principle, a Dirac fermion transistor is proposed. Extensions to more general
networks are discussed.Comment: Submitted to PR
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