5,778 research outputs found
Process for preparing polyimide adhesives
High bonding strengths are obtained for metals and fiber-reinforced organic resin composites with no significant loss in thermo-oxidative stability of the adhesive resin
The influence of infant irritability on maternal sensitivity in a sample of very premature infants
The relationship between maternal sensitivity and infant irritability was investigated in a short-term
longitudinal study of 29 very preterm infants. Infant irritability was assessed at term with the Brazelton
NBAS, the Mother and Baby Scales (MABS) and the Crying Pattern Questionnaire (CPQ). Maternal
sensitivity was assessed by nurses' ratings in the neonatal care unit and at three months during motherinfant
interaction observation. Cross-lagged panel analysis indicated that neonatal irritability did not
influence sensitivity at 3 months nor did maternal sensitivity in the newborn period lead to reduced
irritability at 3 months. Both irritability and maternal sensitivity showed moderate stability over time (r=.55
and r=.60, respectively). It is concluded that in early infancy maternal sensitivity shows little influence on
infant irritability in very preterm infants
Investigating planet formation in circumstellar disks: CARMA observations of RY Tau and DG Tau
(Abridged) We present CARMA observations of the thermal dust emission from
the circumstellar disks around the young stars RYTau and DGTau at wavelengths
of 1.3mm and 2.8mm. The angular resolution of the maps is as high as
0.15arcsec, or 20AU at the distance of the Taurus cloud, which is a factor of 2
higher than has been achieved to date at these wavelengths. The unprecedented
detail of the resulting disk images enables us to address three important
questions related to the formation of planets. (1) What is the radial
distribution of the circumstellar dust? (2) Does the dust emission show any
indication of gaps that might signify the presence of (proto-)planets? (3) Do
the dust properties depend on the orbital radius? We find that modeling the
disk surface density in terms of either a classical power law or the similarity
solution for viscous disk evolution, reproduces the observations well. The
1.3mm image from RYTau shows two peaks separated by 0.2arcsec with a decline in
the dust emission toward the stellar position, which is significant at about
2-4sigma. For both RYTau and DGTau, the dust emission at radii larger than 15
AU displays no significant deviation from an unperturbed viscous disk model. In
particular, no radial gaps in the dust distribution are detected. Under
reasonable assumptions, we exclude the presence of planets more massive than 5
Jupiter masses orbiting either star at distances between about 10 and 60 AU.
The radial variation of the dust opacity slope, beta, was investigated by
comparing the 1.3mm and 2.8mm observations. We find mean values of beta of 0.5
and 0.7 for DGTau and RYTau respectively. Variations in beta are smaller than
0.7 between 20 and 70 AU. These results confirm that the circumstellar dust
throughout these disks differs significantly from dust in the interstellar
medium.Comment: ApJ in press
Preliminary simulations of internal waves and mixing generated by finite amplitude tidal flow over isolated topography
Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 53 (2006): 140-156, doi:10.1016/j.dsr2.2005.09.014.Much recent observational evidence suggests that energy from the barotropic tides may be used for mixing in the deep ocean. Here the process of internal tide generation and dissipation by tidal flow over an isolated Gaussian topography is examined, using 2-dimensional numerical simulations
employing the MITgcm. Four different topographies are considered, for five different amplitudes of barotropic forcing, thereby allowing a variety of combinations of key nondimensional parameters.
While much recent attention has focused on the role of relative topographic steepness and height in modifying the rate of conversion of energy from barotropic to baroclinic modes, here attention is
focused on parameters dependent on the
flow amplitude. For narrow topography, large amplitude forcing gives rise to baroclinic responses at higher harmonics of the forcing frequency. Tall narrow topographies are found to be the most conducive to mixing. Dissipation rates in these calculations
are most efficient for the narrowest topography.KH was supported by a Summer Student Fellowship at Woods Hole Oceanographic Institution.
SL was supported by Office of Naval Research grant N00014-03-1-0336
Comparison of deep-ocean finescale shear at two sites along the Mid-Atlantic Ridge
Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 53 (2006): 207-225, doi:10.1016/j.dsr2.2005.08.021.Four drifting floats were used to measure the magnitude of the vertical derivative
of horizontal velocity in waters above the rough bathymetry of the Mid Atlantic
Ridge. This derivative is typically the dominant component of the velocity gradient
(the shear). Two floats were at the site of the Brazil Basin Tracer Release Experiment
(BBTRE) in the South Atlantic, and two were near the site of the Guiana Abyssal
Gyre Experiment (GAGE) in the North Atlantic. Floats operated for one year except
for one BBTRE float which operated for 100 days. Shear was measured over a vertical
span of 9.5 m using drag elements that caused the floats to rotate slowly in response
to shear. For each float, the first, second and fourth moments of shear were elevated
above levels associated with the Garrett-Munk model internal-wave spectrum. Three
of the four floats were tracked as they moved over mountainous terrain, allowing
shear intensity to be measured as a function of height above the bottom. A deep
BBTRE float showed enhancement of rms shear near the bottom. Floats at both
areas provided measurements at 2000 m above the bottom, with differing results: The
GAGE site had a lower fourth moment of shear (diapycnal diffusivity proxy) than the
BBTRE site. However, application of normalization factors accounting for differences between the sites in bottom roughness, latitude-dependent internal-wave dynamics, and tidal current speeds brings the results into agreement.This work was funded
by the National Science Foundation under grants OCE9416014 and OCE9906685
Photometric Properties of Six Local Volume Dwarf Galaxies from Deep Near-Infrared Observations
We have obtained deep near-infrared - (1.25 m), - (1.65m)
and -band (2.15 m) imaging for a sample of six dwarf galaxies
(M_B\ga-17 mag) in the Local Volume (LV, D\la10 Mpc). The sample consists
mainly of early-type dwarf galaxies found in various environments in the LV.
Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the
near-infrared for the first time. The deep near-infrared images allow for a
detailed study of the photometric and structural properties of each galaxy. The
surface brightness profiles of the galaxies are detected down to the ~ isophote in the - and -bands, and in
the -band. The total magnitudes of the galaxies are derived in the three
wavelength bands. For the brightest galaxies (M_B\la-15.5 mag) in the sample,
we find that the Two Micron All Sky Survey (2MASS) underestimates the total
magnitudes of these systems by up to \la0.5 mag. The radial surface
brightness profiles of the galaxies are fitted with an exponential (for those
galaxies having a stellar disk) or S\'ersic law to derive the structure of the
underlying stellar component. In particular, the effective surface brightness
() and effective radius () are determined from the analytic fits to
the surface brightness profile. The - colours for the galaxies have
been measured to explore the luminosity-metallicity relation for early-type
dwarfs. In addition, the - colours of the galaxies are used to assess
their evolutionary state relative to other galaxy morphologies. The total
stellar masses of the dwarf galaxies are derived from the -band photometric
measurements. These will later be compared to the dynamical mass estimates for
the galaxies to determine their dark matter content.Comment: 14 pages, 8 figures, submitted to MNRA
Neutron to proton ratios of quasiprojectile and midrapidity emission in the Zn + Zn reaction at 45 MeV/nucleon
Simultaneous measurement of both neutrons and charged particles emitted in
the reaction Zn + Zn at 45 MeV/nucleon allows comparison of the
neutron to proton ratio at midrapidity with that at projectile rapidity. The
evolution of N/Z in both rapidity regimes with increasing centrality is
examined. For the completely re-constructed midrapidity material one finds that
the neutron-to-proton ratio is above that of the overall Zn + Zn
system. In contrast, the re-constructed ratio for the quasiprojectile is below
that of the overall system. This difference provides the most complete evidence
to date of neutron enrichment of midrapidity nuclear matter at the expense of
the quasiprojectile
NASA's Internal Space Weather Working Group
Measurements from many of NASA's scientific spacecraft are used routinely by space weather forecasters, both in the U.S. and internationally. ACE, SOHO (an ESA/NASA collaboration), STEREO, and SDO provide images and in situ measurements that are assimilated into models and cited in alerts and warnings. A number of years ago, the Space Weather laboratory was established at NASA-Goddard, along with the Community Coordinated Modeling Center. Within that organization, a space weather service center has begun issuing alerts for NASA's operational users. NASA's operational user community includes flight operations for human and robotic explorers; atmospheric drag concerns for low-Earth orbit; interplanetary navigation and communication; and the fleet of unmanned aerial vehicles, high altitude aircraft, and launch vehicles. Over the past three years we have identified internal stakeholders within NASA and formed a Working Group to better coordinate their expertise and their needs. In this presentation we will describe this activity and some of the challenges in forming a diverse working group
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