25,425 research outputs found
High Resolution CO and H2 Molecular Line Imaging of a Cometary Globule in the Helix Nebula
We report high resolution imaging of a prominent cometary globule in the
Helix nebula in the CO J=1-0 (2.6 mm) and H2 v=1-0 S(1) (2.12 micron) lines.
The observations confirm that globules consist of dense condensations of
molecular gas embedded in the ionized nebula. The head of the globule is seen
as a peak in the CO emission with an extremely narrow line width (0.5 km/s) and
is outlined by a limb-brightened surface of H2 emission facing the central star
and lying within the photo-ionized halo. The emission from both molecular
species extends into the tail region. The presence of this extended molecular
emission provides new constraints on the structure of the tails, and on the
origin and evolution of the globules.Comment: 12 pages, 3 figures. To appear in The Astrophysical Journal Letter
High frequency sampling of the 1984 spring bloom within the mid-Atlantic Bight: Synoptic shipboard, aircraft, and in situ perspectives of the SEEP-I experiment
Moorings of current meters, thermistors, transmissometers, and fluorometers on the mid-Atlantic shelf, south of Long Island, suggest a cumulative seaward export of perhaps 0.35 g C/sq m/day between the 80 and 120 m isobaths during February-April 1984. Such a horizontal loss of algal carbon over the lower third of the water column would be 23 to 78% of the March-April 1984 primary production. This physical carbon loss is similar to daily grazing losses from zooplankton of 32-40% of the algal fixation of carbon. Metabolic demands of the benthos could be met by just the estimated fecal pellet flux, without direct consumption of algal carbon, while bacterioplankton needs could be served by excretory release of dissolved organic matter during photosynthesis. Sediment traps tethered 10 m off the bottom at the 120 m isobath and 50 m above the 500 m isobath caught as much as 0.16 to 0.26 g C /sq m/day during March-April 1984, in reasonable agreement with the flux estimated from the other moored instruments
Wide-field Magnetic Field and Temperature Imaging using Nanoscale Quantum Sensors
The simultaneous imaging of magnetic fields and temperature (MT) is important
in a range of applications, including studies of carrier transport, solid-state
material dynamics, and semiconductor device characterization. Techniques exist
for separately measuring temperature (e.g., infrared (IR) microscopy,
micro-Raman spectroscopy, and thermo-reflectance microscopy) and magnetic
fields (e.g., scanning probe magnetic force microscopy and superconducting
quantum interference devices). However, these techniques cannot measure
magnetic fields and temperature simultaneously. Here, we use the exceptional
temperature and magnetic field sensitivity of nitrogen vacancy (NV) spins in
conformally-coated nanodiamonds to realize simultaneous wide-field MT imaging.
Our "quantum conformally-attached thermo-magnetic" (Q-CAT) imaging enables (i)
wide-field, high-frame-rate imaging (100 - 1000 Hz); (ii) high sensitivity; and
(iii) compatibility with standard microscopes. We apply this technique to study
the industrially important problem of characterizing multifinger gallium
nitride high-electron-mobility transistors (GaN HEMTs). We spatially and
temporally resolve the electric current distribution and resulting temperature
rise, elucidating functional device behavior at the microscopic level. The
general applicability of Q-CAT imaging serves as an important tool for
understanding complex MT phenomena in material science, device physics, and
related fields
Making Meaning Together: An Exploratory Study of Therapeutic Conversation Between Helping Professionals and Homeless Shelter Residents
This exploratory study examined the nature of therapeutic conversation between helping professionals and homeless persons as an intervention to optimize health. Meaningful conversation occurred in relationships where there was a sense of connection and the presence of rapport. Emergent facilitators of therapeutic conversation included respectful engagement, casual nature of conversation, alternative settings for therapeutic conversation, effective listening, and establishing trust. Barriers included prejudging homeless persons, fear of punishment and authority, and academic and professional intimidation. Central to the study findings was the acknowledgement of the client’s personhood. Acknowledgement of personhood is a critical element in engagement between homeless persons and helping professionals
Making Meaning Together: An Exploratory Study of Therapeutic Conversation between Helping Professionals and Homeless Shelter Residents
This exploratory study examined the nature of therapeutic conversation between helping professionals and homeless persons as an intervention to optimize health. Meaningful conversation occurred in relationships where there was a sense of connection and the presence of rapport. Emergent facilitators of therapeutic conversation included respectful engagement, casual nature of conversation, alternative settings for therapeutic conversation, effective listening, and establishing trust. Barriers included prejudging homeless persons, fear of punishment and authority, and academic and professional intimidation. Central to the study findings was the acknowledgement of the client\u27s personhood. Acknowledgement of personhood is a critical element in engagement between homeless persons and helping professionals
Stars in the Hubble Ultra Deep Field
We identified 46 unresolved source candidates in the Hubble Ultra Deep Field,
down to i775 = 29.5. Unresolved objects were identified using a parameter S,
which measures the deviation from the curve-of-growth of a point source.
Extensive testing of this parameter was carried out, including the effects of
decreasing signal-to-noise and of the apparent motions of stars, which
demonstrated that stars brighter than i775 = 27.0 could be robustly identified.
Low resolution grism spectra of the 28 objects brighter than i775 = 27.0
identify 18 M and later stellar type dwarfs, 2 candidate L-dwarfs, 2 QSOs, and
4 white dwarfs. Using the observed population of dwarfs with spectral type M4
or later, we derive a Galactic disk scale height of 400 \pm 100 pc for M and L
stars. The local white dwarf density is computed to be as high as (1.1 \pm 0.3)
x10^(-2) stars/pc^3. Based on observations taken 73 days apart, we determined
that no object in the field has a proper motion larger than 0.027"/year (3
sigma detection limit). No high velocity white dwarfs were identified in the
HUDF, and all four candidates appear more likely to be part of the Galactic
thick disk. The lack of detected halo white dwarfs implies that, if the dark
matter halo is 12 Gyr old, white dwarfs account for less than 10% of the dark
matter halo mass.Comment: 35 pages, 11 figures, accepted by Ap
Scattered Nuclear Continuum and Broad H-alpha in Cygnus A
We have discovered scattered broad Balmer emission lines in the spectrum of
Cygnus A, using the Keck II telescope. Broad H-alpha appears in polarized flux
from components on either side of the nucleus, and to a lesser extent in the
nucleus. The full-width at half-maximum of broad H-alpha is 26,000 km/s,
comparable to the widest emission lines seen in broad-line radio galaxies.
Scattered AGN light provides a significant contribution to the total flux at
3800 Angstroms (rest) of the western component, where the polarization rises to
16%. The spatially integrated flux of Cygnus A at 5500 Angstroms can be
decomposed into an elliptical galaxy fraction (Fg=0.70), a highly polarized
blue component (FC1=0.15), a less polarized red component (FC=0.09), and a
contribution from the nebular continuum (0.06). Imaging polarimetry shows a
double fan of polarization vectors with circular symmetry which corresponds to
the ionization cone seen in HST images. Our results are consistent with
scattering of light from a hidden quasar of modest luminosity by an extended,
dusty narrow-line region.Comment: 13 pages, 4 figures, Latex, to appear in ApJ Letter
Two-electron processes in multiple ionization under strong soft-x-ray radiation
In a combined experimental and theoretical study we have investigated the ionization of atomic argon upon irradiation with intense soft-x-ray pulses of 105 eV photon energy from the free-electron laser FLASH. The measured ion yields show charge states up to Ar7+. The comparison with the theoretical study of the underlying photoionization dynamics highlights the importance of excited states in general and of processes governed by electron correlation in particular, namely, ionization with excitation and shake-off, processes usually inaccessible by measurements of ionic yields only. The Ar7+ yield shows a clear deviation from the predictions of the commonly used model of sequential ionization via single-electron processes and the observed signal can only be explained by taking into account the full multiplet structure of the involved configurations and by inclusion of two-electron processes. The competing process of two-photon ionization from the ground state of Ar6+ is calculated to be orders of magnitude smaller
Polarization and kinematics in Cygnus A
From optical spectropolarimetry of Cygnus A we conclude that the scattering
medium in the ionization cones in Cygnus A is moving outward at a speed of
170+-34 km/s, and that the required momentum can be supplied by the radiation
pressure of an average quasar. Such a process could produce a structure
resembling the observed ionization cones, which are thought to result from
shadowing by a circumnuclear dust torus. We detect a polarized red wing in the
[O III] emission lines arising from the central kiloparsec of Cygnus A. This
wing is consistent with line emission created close to the boundary of the
broad-line region.Comment: 5 pages, accepted for publication in MNRAS letter
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