11,800 research outputs found
Heat flow and thermal processes in the Jornada delMuerto, New Mexico
Most heat flow data in rifts are uncertain largely because of hydrologic disturbances in regions of extensive fracturing. Estimates of heat flow in deep petroleum tests within a large basin of the Rio Grande rift, which has suffered little syn-rift fracturing, may begin to provide clearer insight into the relationships between high heat flow and crustal thinning processes. The Jornada del Muerto is a large basin located in the Rio Grande rift of south central New Mexico. The region of interest within the Jornada del Muerto is centered about 30 km east of the town of Truth or Consequences, and is approximately 60 km north-south by 30 km east-west. High heat flows are estimated for the region. Values increase from about 90 mWm(-2) in the northern part of the study area to about 125 mWm(-2) in the southern part. These high heat flows are rather enigmatic because in the immediate vicinities of the sites there is little evidence of Cenozoic volcanism or syn-rift extensional tectonics. It is suggested that the geothermal anomaly in the southern Jornada del Muerto (approx. 125 to approx. 95 mWm(-2) results from some type of mass movement-heat transfer mechanism operating in the crust just below the elastic layer. This conclusion is consistent with the geologic and geophysical data which describe a thin crust, apparently devoid of features indicative of extensional-tectonics in the upper part of the lastic crust
The ADA and Collective Bargaining Issues
This brochure on collective bargaining and the American with Disabilities Act (ADA) is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, SPHR, Director, Program on Employment and Disability, School of Industrial and Labor Relations – Extension Division, Cornell University
Ancient eruptions of Eta Carinae: A tale written in proper motions
We analyze eight epochs of Hubble Space Telescope H+[N II] imaging of
Eta Carinae's outer ejecta. Proper motions of nearly 800 knots reveal that the
detected ejecta are divided into three apparent age groups, dating to around
1250 A.D., to around 1550 A.D., and to during or shortly before the Great
Eruption of the 1840s. Ejecta from these groups reside in different locations
and provide a firm constraint that Eta Car experienced multiple major eruptions
prior to the 19th century. The 1250 and 1550 events did not share the same
axisymmetry as the Homunculus; the 1250 event was particularly asymmetric, even
one-sided. In addition, the ejecta in the S ridge, which have been associated
with the Great Eruption, appear to predate the ejection of the Homunculus by
several decades. We detect essentially ballistic expansion across multiple
epochs. We find no evidence for large-scale deceleration of the observed knots
that could power the soft X-ray shell by plowing into surrounding material,
suggesting that the observed X-rays arise instead from fast, rarefied ejecta
from the 1840s overtaking the older dense knots. Early deceleration and
subsequent coasting cannot explain the origin of the older outer
ejecta---significant episodic mass loss prior to the 19th century is required.
The timescale and geometry of the past eruptions provide important constraints
for any theoretical physical mechanisms driving Eta Car's behavior.
Non-repeating mechanisms such as the merger of a close binary in a triple
system would require additional complexities to explain the observations.Comment: 14 pages, 11 figures, accepted for publication in MNRA
Dissipative preparation of entanglement in optical cavities
We propose a novel scheme for the preparation of a maximally entangled state
of two atoms in an optical cavity. Starting from an arbitrary initial state, a
singlet state is prepared as the unique fixed point of a dissipative quantum
dynamical process. In our scheme, cavity decay is no longer undesirable, but
plays an integral part in the dynamics. As a result, we get a qualitative
improvement in the scaling of the fidelity with the cavity parameters. Our
analysis indicates that dissipative state preparation is more than just a new
conceptual approach, but can allow for significant improvement as compared to
preparation protocols based on coherent unitary dynamics.Comment: 4 pages, 2 figure
A Survey of Irradiated Pillars, Globules, and Jets in the Carina Nebul
We present wide-field, deep narrowband H, Br, H, [S II],
[O III], and broadband I and K-band images of the Carina star formation region.
The new images provide a large-scale overview of all the H and Br
emission present in over a square degree centered on this signature star
forming complex. By comparing these images with archival HST and Spitzer images
we observe how intense UV radiation from O and B stars affects star formation
in molecular clouds. We use the images to locate new candidate outflows and
identify the principal shock waves and irradiated interfaces within dozens of
distinct areas of star-forming activity. Shocked molecular gas in jets traces
the parts of the flow that are most shielded from the intense UV radiation.
Combining the H and optical images gives a more complete view of the jets,
which are sometimes only visible in H. The Carina region hosts several
compact young clusters, and the gas within these clusters is affected by
radiation from both the cluster stars and the massive stars nearby. The Carina
Nebula is ideal for studying the physics of young H II regions and PDR's, as it
contains multiple examples of walls and irradiated pillars at various stages of
development. Some of the pillars have detached from their host molecular clouds
to form proplyds. Fluorescent H outlines the interfaces between the ionized
and molecular gas, and after removing continuum, we detect spatial offsets
between the Br and H emission along the irradiated interfaces.
These spatial offsets can be used to test current models of PDRs once synthetic
maps of these lines become available.Comment: Accepted in the Astronomical Journa
Mediation and Title I of the ADA
This brochure on mediation and Title I of the American with Disabilities Act (ADA) is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, SPHR, Director, Program on Employment and Disability, School of Industrial and Labor Relations – Extension Division, Cornell University. Cornell University was funded in the early 1990’s by the U.S. Department of Education National Institute on Disability and Rehabilitation Research as a National Materials Development Project on the employment provisions (Title I) of the ADA (Grant #H133D10155). These updates, and the development of new brochures, have been funded by Cornell’s Program on Employment and Disability, the Pacific Disability and Business Technical Assistance Center, and other supporters
Proper motions of collimated jets from intermediate-mass protostars in the Carina Nebula
We present proper motion measurements of 37 jets and HH objects in the Carina
Nebula measured in two epochs of H images obtained yrs apart
with HST/ACS. Transverse velocities in all but one jet are faster than km s, confirming that the jet-like H features identified by
Smith et al. (2010) trace outflowing gas. Proper motions constrain the location
of the jet-driving source and provide kinematic confirmation of the
intermediate-mass protostars that we identify for 20/37 jets. Jet velocities do
not correlate with the estimated protostar mass and embedded driving sources do
not have slower jets. Instead, transverse velocities (median km
s) are similar to those in jets from low-mass stars. Assuming a constant
velocity since launch, we compute jet dynamical ages (median yr).
If continuous emission from inner jets traces the duration of the most recent
accretion bursts, then these episodes are sustained longer (median
yr) than the typical decay time of an FU Orionis outburst. These jets can carry
appreciable momentum that may be injected into the surrounding environment. The
resulting outflow force, , lies between that measured in low- and
high-mass sources, despite the very different observational tracers used.
Smooth scaling of the outflow force argues for a common physical process
underlying outflows from protostars of all masses. This latest kinematic result
adds to a growing body of evidence that intermediate-mass star formation
proceeds like a scaled-up version of the formation of low-mass stars.Comment: accepted to MNRAS, 29 pages, 30 figures, 3 table
A model for melting of confined DNA
When DNA molecules are heated they denature. This occurs locally so that
loops of molten single DNA strands form, connected by intact double-stranded
DNA pieces. The properties of this "melting" transition have been intensively
investigated. Recently there has been a surge of interest in this question,
caused by experiments determining the properties of partially bound DNA
confined to nanochannels. But how does such confinement affect the melting
transition? To answer this question we introduce, and solve a model predicting
how confinement affects the melting transition for a simple model system by
first disregarding the effect of self-avoidance. We find that the transition is
smoother for narrower channels. By means of Monte-Carlo simulations we then
show that a model incorporating self-avoidance shows qualitatively the same
behaviour and that the effect of confinement is stronger than in the ideal
case.Comment: 5 pages, 4 figures, supplementary materia
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