3,170 research outputs found
Untangling the Recombination Line Emission from HII Regions with Multiple Velocity Components
HII regions are the ionized spheres surrounding high-mass stars. They are
ideal targets for tracing Galactic structure because they are predominantly
found in spiral arms and have high luminosities at infrared and radio
wavelengths. In the Green Bank Telescope HII Region Discovery Survey (GBT HRDS)
we found that >30% of first Galactic quadrant HII regions have multiple
hydrogen radio recombination line (RRL) velocities, which makes determining
their Galactic locations and physical properties impossible. Here we make
additional GBT RRL observations to determine the discrete HII region velocity
for all 117 multiple-velocity sources within 18deg. < l < 65deg. The
multiple-velocity sources are concentrated in the zone 22deg. < l < 32deg.,
coinciding with the largest regions of massive star formation, which implies
that the diffuse emission is caused by leaked ionizing photons. We combine our
observations with analyses of the electron temperature, molecular gas, and
carbon recombination lines to determine the source velocities for 103 discrete
H II regions (88% of the sample). With the source velocities known, we resolve
the kinematic distance ambiguity for 47 regions, and thus determine their
heliocentric distances.Comment: 44 pages, 5 figures, 16 pages of tables; Accepted by ApJ
Tele-methylhistamine 1 distribution in rat brain
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65997/1/j.1471-4159.1979.tb02303.x.pd
The Kepler equation for inspiralling compact binaries
Compact binaries consisting of neutron stars / black holes on eccentric orbit
undergo a perturbed Keplerian motion. The perturbations are either of
relativistic origin or are related to the spin, mass quadrupole and magnetic
dipole moments of the binary components. The post-Newtonian motion of such
systems decouples into radial and angular parts. We present here for the first
time the radial motion of such a binary encoded in a generalized Kepler
equation, with the inclusion of all above-mentioned contributions, up to linear
order in the perturbations. Together with suitably introduced parametrizations,
the radial motion is solved completely
The Gbt 67â93.6 Ghz Spectral Line Survey Of Orion-Kl
We present a 67--93.6 GHz spectral line survey of Orion-KL with the new 4 mm Receiver on the Green Bank Telescope (GBT). The survey reaches unprecedented depths and covers the low-frequency end of the 3 mm atmospheric window which has been relatively unexplored previously. The entire spectral-line survey is published electronically for general use by the astronomical community. The calibration and performance of 4 mm Receiver on the GBT is also summarized
Speakers Raise their Hands and Head during Self-Repairs in Dyadic Conversations
People often encounter difficulties in building shared understanding during everyday conversation. The most common symptom of these difficulties are self-repairs, when a speaker restarts, edits or amends their utterances mid-turn. Previous work has focused on the verbal signals of self-repair, i.e. speech disfluences (filled pauses, truncated words and phrases, word substitutions or reformulations), and computational tools now exist that can automatically detect these verbal phenomena. However, face-to-face conversation also exploits rich non-verbal resources and previous research suggests that self-repairs are associated with distinct hand movement patterns. This paper extends those results by exploring head and hand movements of both speakers and listeners using two motion parameters: height (vertical position) and 3D velocity. The results show that speech sequences containing self-repairs are distinguishable from fluent ones: speakers raise their hands and head more (and move more rapidly) during self-repairs. We obtain these results by analysing data from a corpus of 13 unscripted dialogues, and we discuss how these findings could support the creation of improved cognitive artificial systems for natural human-machine and human-robot interaction
A histidine residue and a tetranuclear cuprousâthiolate cluster dominate the copper loading landscape of a copper storage protein from Streptomyces lividans
The chemical basis for protecting organisms against the toxic effect imposed by excess cuprous ions is to constrain this through highâaffinity binding sites that use cuprousâthiolate coordination chemistry. In bacteria, a family of cysteine rich fourâhelix bundle proteins utilise thiolate chemistry to bind up to 80 cuprous ions. These proteins have been termed copper storage proteins (Csp). The present study investigates cuprous ion loading to the Csp from Streptomyces lividans (SlCsp) using a combination of Xâray crystallography, siteâdirected mutagenesis and stoppedâflow reaction kinetics with either aquatic cuprous ions or a chelating donor. We illustrate that at low cuprous ion concentrations, copper is loaded exclusively into an outer core region of SlCsp via one end of the fourâhelix bundle, facilitated by a set of three histidine residues. Xâray crystallography reveals the existence of polynuclear cuprousâthiolate clusters culminating in the assembly of a tetranuclear [Cu4(ÎŒ2âSâCys)4(ÎÎŽ1âHis)] cluster in the outer core. As more cuprous ions are loaded, the cysteine lined inner core of SlCsp fills with cuprous ions but in a fluxional and dynamic manner with no evidence for the assembly of further intermediate polynuclear cuprousâthiolate clusters as observed in the outer core. Using siteâdirected mutagenesis a key role for His107 in the efficient loading of cuprous ions from a donor is established. A model of copper loading to SlCsp is proposed and discussed
Untangling The Recombination Line Emission From H Ii Regions With Multiple Velocity Components
H ii regions are the ionized spheres surrounding high-mass stars. They are ideal targets for tracing Galactic structure because they are predominantly found in spiral arms and have high luminosities at infrared and radio wavelengths. In the Green Bank Telescope H ii Region Discovery Survey (GBT HRDS), we found that of first Galactic quadrant H ii regions have multiple hydrogen radio recombination line (RRL) velocities, which makes determining their Galactic locations and physical properties impossible. Here we make additional GBT RRL observations to determine the discrete H ii region velocity for all 117 multiple-velocity sources within . The multiple-velocity sources are concentrated in the zone , coinciding with the largest regions of massive star formation, which implies that the diffuse emission is caused by leaked ionizing photons. We combine our observations with analyses of the electron temperature, molecular gas, and carbon recombination lines to determine the source velocities for 103 discrete H ii regions ( of the sample). With the source velocities known, we resolve the kinematic distance ambiguity for 47 regions, and thus determine their heliocentric distances
High Resolution Millimeter-Wave Mapping of Linearly Polarized Dust Emission: Magnetic Field Structure in Orion
We present 1.3 and 3.3 mm polarization maps of Orion-KL obtained with the
BIMA array at approximately 4 arcsec resolution. Thermal emission from
magnetically aligned dust grains produces the polarization. Along the Orion
``ridge'' the polarization position angle varies smoothly from about 10 degrees
to 40 degrees, in agreement with previous lower resolution maps. In a small
region south of the Orion ``hot core,'' however, the position angle changes by
90 degrees. This abrupt change in polarization direction is not necessarily the
signpost of a twisted magnetic field. Rather, in this localized region
processes other than the usual Davis-Greenstein mechanism might align the dust
grains with their long axes parallel with the field, orthogonal to their normal
orientation.Comment: AAS preprint:14 pages, 2 figures (3mm.eps and 1mm.eps); requires
aaspp4.sty To be published in Astrophysical Journal Letter
Equation of motion for relativistic compact binaries with the strong field point particle limit : the second and half post-Newtonian order
We study the equation of motion appropriate to an inspiralling binary star
system whose constituent stars have strong internal gravity. We use the
post-Newtonian approximation with the strong field point particle limit by
which we can introduce into general relativity a notion of a point-like
particle with strong internal gravity without using Dirac delta distribution.
Besides this limit, to deal with strong internal gravity we express the
equation of motion in surface integral forms and calculate these integrals
explicitly. As a result we obtain the equation of motion for a binary of
compact bodies accurate through the second and half post-Newtonian (2.5 PN)
order. This equation is derived in the harmonic coordinate. Our resulting
equation perfectly agrees with Damour and Deruelle 2.5 PN equation of motion.
Hence it is found that the 2.5 PN equation of motion is applicable to a
relativistic compact binary.Comment: 48 pages, revtex, accepted for publication in Phys. Rev.
Equation of motion for relativistic compact binaries with the strong field point particle limit : Formulation, the first post-Newtonian and multipole terms
We derive the equation of motion for the relativistic compact binaries in the
post-Newtonian approximation taking explicitly their strong internal gravity
into account. For this purpose we adopt the method of the point particle limit
where the equation of motion is expressed in terms of the surface integrals. We
examine carefully the behavior of the surface integrals in the derivation. As a
result, we obtain the Einstein-Infeld-Hoffman equation of motion at the first
post-Newtonian (1PN) order, and a part of the 2PN order which depends on the
quadrupole moments and the spins of component stars. Hence, it is found that
the equation of motion in the post-Newtonian approximation is valid for the
compact binaries by a suitable definition of the mass, spin and quadrupole
moment.Comment: revised version. 27pages, three tables, revtex. Some errors have been
corrected and some explanations have been adde
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