506 research outputs found
Gravitational lens candidates in the E-CDFS
We report ten lens candidates in the E-CDFS from the GEMS survey. Nine of the
systems are new detections and only one of the candidates is a known lens
system. For the most promising five systems including the known lens system, we
present results from preliminary lens mass modelling, which tests if the
candidates are plausible lens systems. Photometric redshifts of the candidate
lens galaxies are obtained from the COMBO-17 galaxy catalog. Stellar masses of
the candidate lens galaxies within the Einstein radius are obtained by using
the -band luminosity and the color-based stellar mass-to-light ratios.
As expected, the lensing masses are found to be larger than the stellar masses
of the candidate lens galaxies. These candidates have similar dark matter
fractions as compared to lenses in SLACS and COSMOS. They also roughly follow
the halo mass-stellar mass relation predicted by the subhalo abundance matching
technique. One of the candidate lens galaxies qualifies as a LIRG and may not
be a true lens because the arc-like feature in the system is likely to be an
active region of star formation in the candidate lens galaxy. Amongst the five
best candidates, one is a confirmed lens system, one is a likely lens system,
two are less likely to be lenses and the status of one of the candidates is
ambiguous. Spectroscopic follow-up of these systems is still required to
confirm lensing and/or for more accurate determination of the lens masses and
mass density profiles.Comment: 12 pages, 5 figures, 3 tables, ApJ accepte
High performance magnetic field sensor based on Superconducting Quantum Interference Filters
We have developed an absolute magnetic field sensor using Superconducting
Quantum Interference Filter (SQIF) made of high-T_c grain boundary Josephson
junctions. The device shows the typical magnetic field dependent voltage
response V(B), which is sharp delta-like dip in the vicinity of zero magnetic
field. When the SQIF is cooled with magnetic shield, and then the shield is
removed, the presence of the ambient magnetic field induces a shift of the dip
position from B_0 ~ 0 to a value B ~ B_1, which is about the average value of
the earth magnetic field, at our latitude. When the SQIF is cooled in the
ambient field without shielding, the dip is first found at B ~ B_1, and the
further shielding of the SQIF results in a shift of the dip towards B_0 ~ 0.
The low hysteresis observed in the sequence of experiments (less than 5% of
B_1) makes SQIFs suitable for high precision measurements of the absolute
magnetic field. The experimental results are discussed in view of potential
applications of high-T_c SQIFs in magnetometry.Comment: 4 pages, 2 figure
Nineteenth Century Rosa Parks? Assessing Elizabeth Jennings\u27 Legacy as a Teacher and Civil Rights Pioneer in Antebellum America
Elizabeth Jennings should be recognized as more than a Rosa Parks figure in Antebellum New York City history. Both Jennings\u27 and Parks\u27 experiences with segregation on public transportation are similar, but they are not the same. Jennings\u27 ejection from a New York streetcar was not deliberately planned, nor did her removal from the streetcar lead to mass protests or boycotts in New York City or throughout the country. Similarly though, as many African Americans endured violence during the Civil Rights movement of the 1950s and 1960s, Elizabeth Jennings also survived the New York City Draft Riots in 1863. Overall, both women deserve their own respective place in United States history because they were emblematic of the socio-political issues of their time - Jennings in the Antebellum Era and Parks in the post-World War II civil rights movement
Quadratic Mixing of Radio Frequency Signals using Superconducting Quantum Interference Filters
The authors demonstrate quadratic mixing of weak time harmonic
electromagnetic fields applied to Superconducting Quantum Interference Filters,
manufactured from high- grain boundary Josephson junctions and
operated in active microcooler. The authors use the parabolic shape of the dip
in the dc-voltage output around B=0 to mix \emph{quadratically} two external
rf-signals, at frequencies and well below the
Josephson frequency , and detect the corresponding mixing
signal at . Quadratic mixing takes also place when the SQIF
is operated without magnetic shield. The experimental results are well
described by a simple analytical model based on the adiabatic approximation.Comment: 3 pages, 3 figure
Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures
The Queen Charlotte fault (QCF) is a dextral transform system located offshore of southeastern Alaska and western Canada, accommodating similar to 4.4 cm/yr of relative motion between the Pacific and North American plates. Oblique convergence along the fault increases southward, and how this convergence is accommodated is still debated. Using seismic reflection data, we interpret offshore basement structure, faulting, and stratigraphy to provide a geological context for two recent earthquakes, an M-w 7.5 strike-slip event near Craig, Alaska, and an M-w 7.8 thrust event near Haida Gwaii, Canada. We map downwarped Pacific oceanic crust near 54 degrees N, between the two rupture zones. Observed downwarping decreases north and south of 54 degrees N, parallel to the strike of the QCF. Bending of the Pacific plate here may have initiated with increased convergence rates due to a plate motion change at similar to 6 Ma. Tectonic reconstruction implies convergence-driven Pacific plate flexure, beginning at 6 Ma south of a 10 degrees bend the QCF (which is currently at 53.2 degrees N) and lasting until the plate translated past the bend by similar to 2 Ma. Normal-faulted approximately late Miocene sediment above the deep flexural depression at 54 degrees N, topped by relatively undeformed Pleistocene and younger sediment, supports this model. Aftershocks of the Haida Gwaii event indicate a normal-faulting stress regime, suggesting present-day plate flexure and underthrusting, which is also consistent with reconstruction of past conditions. We thus favor a Pacific plate underthrusting model to initiate flexure and accommodation space for sediment loading. In addition, mapped structures indicate two possible fault segment boundaries along the QCF at 53.2 degrees N and at 56 degrees N.USGS Earthquake Hazards External Grants ProgramNational Earthquake Hazards Reduction ProgramUTIG Ewing/Worzel FellowshipInstitute for Geophysic
Effects of magnetic field on two-dimensional Superconducting Quantum Interference Filters
We present an experimental study of two-dimensional superconducting quantum
interference filters (2D-SQIFs) in the presence of a magnetic field B. The
dependences of the dc voltage on the applied magnetic field are characterized
by a unique delta-like dip at B=0, which depends on the distribution of the
areas of the individual loops, and on the bias current. The voltage span of the
dip scales proportional to the number of rows simultaneously operating at the
same working point. In addition, the voltage response of the 2D-SQIF is
sensitive to a field gradient generated by a control line and superimposed to
the homogeneous field coil. This feature opens the possibility to use 2D
superconducting quantum interference filters as highly sensitive detectors of
spatial gradients of magnetic field.Comment: 3 pages, 4 figures, submitted to AP
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