3,364 research outputs found
Ontogenetic changes in shape and growth rate during postnatal development in false killer whales (<i>Pseudorca crassidens</i>) vertebral column
Intraspecific variation in cetacean vertebral anatomy as a result of ageing, growth, and sexual dimorphism is poorly understood. Using 3D geometric morphometrics, we investigated allometric patterns, sexual dimorphism, and ontogenetic trajectories in the vertebral column of false killer whale (Pseudorca crassidens). Our data set includes thoracic, lumbar, and caudal vertebrae of 30 specimens, including neonates, juveniles, and adults of both sexes. Vertebral shape was significantly correlated with size within each region. Neonatal vertebral shape differed significantly from juveniles and adults, displaying ontogenetic shape change. Allometric and growth patterns of the vertebral regions, particularly of the lumbar region with the thoracic and caudal regions, differed significantly, which may influence the function and mobility patterns of the vertebral regions during different life stages. Using quantitative methods, we could not conclude that the Pseudorca vertebrae are sexually dimorphic. This study describes for the first time intraspecific vertebral patterns in a cetacean species across ontogenetic stages. Pseudorca individuals live in large pods and swim together, sharing the same swimming mode. The neonates have a more flexible column and swim less efficiently following their mothers to nurse
Test of the Running of in Decays
The decay rate into hadrons of invariant mass smaller than
can be calculated in QCD assuming global
quark--hadron duality. It is shown that this assumption holds for
~GeV. From measurements of the hadronic mass distribution, the
running coupling constant is extracted in the range
0.7~GeV. At , the result is
. The running of is in good
agreement with the QCD prediction.Comment: 9 pages, 3 figures appended; shortened version with new figures, to
appear in Physical Review Letters (April 1996
Measurements of hydrogen cyanide (HCN) and acetylene (C2H2) from the Infrared Atmospheric Sounding Interferometer (IASI)
Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm−1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009–2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform InfraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values
Gamma-Ray Burst Sequences in Hardness Ratio-Peak Energy Plane
The narrowness of the distribution of the peak energy of
spectrum of gamma-ray bursts (GRBs) and the unification of GRB population are
great puzzles yet to be solved. We investigate the two puzzles based on the
global spectral behaviors of different GRB population in the
plane (HR the spectral hardness ratio) with BATSE and HETE-2 observations. It
is found that long GRBs and XRFs observed by HETE-2 seem to follow the same
sequence in the plane, with the XRFs at the low end of this
sequence. The long and short GRBs observed by BATSE follow significantly
different sequences in the plane, with most of the short GRBs
having a larger hardness ratio than the long GRBs at a given .
These results indicate that the global spectral behaviors of the long GRB
sample and the XRF sample are similar, while that of short GRBs is different.
The short GRBs seem to be a unique subclass of GRBs, and they are not the
higher energy extension of the long GRBs (abridged).Comment: 9 pages, 3 figure
The Minimal Supersymmetric Standard Model: Group Summary Report
CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4.
Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6.
Experimental Bounds on SUSY Particle Masses, 7. References.Comment: 121 pages, latex + epsfig, graphicx, axodraw, Report of the MSSM
working group for the Workshop "GDR-Supersym\'etrie",France. Rep. PM/98-4
On the nature of the Be star HR 7409 (7 Vul)
HR 7409 (7 Vul) is a newly identified Be star possibly part of the Gould Belt
and is the massive component of a 69-day spectroscopic binary. The binary
parameters and properties of the Be star measured using high-dispersion spectra
obtained at Ondrejov Observatory and at Rozhen Observatory imply the presence
of a low mass companion (~ 0.5-0.8 M_sun). If the pair is relatively young
(<50-80 Myr), then the companion is a K V star, but, following another, older
evolutionary scenario, the companion is a horizontal-branch star or possibly a
white dwarf star. In the latter scenario, a past episode of mass transfer from
an evolved star onto a less massive dwarf star would be responsible for the
peculiar nature of the present-day, fast-rotating Be star.Comment: Accepted for publication in MNRA
Spectroscopic analysis of the B/Be visual binary HR 1847
We studied both components of a slightly overlooked visual binary HR 1847
spectroscopically to determine its basic physical and orbital parameters. Basic
stellar parameters were determined by comparing synthetic spectra to the
observed echelle spectra, which cover both the optical and near-IR regions. New
observations of this system used the Ond\v{r}ejov and Rozhen 2-m telescopes and
their coud\'e spectrographs. Radial velocities from individual spectra were
measured and then analysed with the code {\FOTEL} to determine orbital
parameters. The spectroscopic orbit of HR 1847A is presented for the first
time. It is a single-lined spectroscopic binary with a B-type primary, a period
of 719.79 days, and a highly eccentric orbit with e=0.7. We confirmed that HR
1847B is a Be star. Its H\alpha emission significantly decreased from 2003 to
2008. Both components have a spectral type B7-8 and luminosity class IV-V.Comment: Astronomy and Astrophysics, accepte
The OSACA Database and a Kinematic Analysis of Stars in the Solar Neighborhood
We transformed radial velocities compiled from more than 1400 published
sources, including the Geneva--Copenhagen survey of the solar neighborhood
(CORAVEL-CfA), into a uniform system based on the radial velocities of 854
standard stars in our list. This enabled us to calculate the average weighted
radial velocities for more than 25~000 HIPPARCOS stars located in the local
Galactic spiral arm (Orion arm) with a median error of +-1 km/s. We use these
radial velocities together with the stars' coordinates, parallaxes, and proper
motions to determine their Galactic coordinates and space velocities. These
quantities, along with other parameters of the stars, are available from the
continuously updated Orion Spiral Arm CAtalogue (OSACA) and the associated
database. We perform a kinematic analysis of the stars by applying an
Ogorodnikov-Milne model to the OSACA data. The kinematics of the nearest single
and multiple main-sequence stars differ substantially. We used distant
(r\approx 0.2 kpc) stars of mixed spectral composition to estimate the angular
velocity of the Galactic rotation -25.7+-1.2 km/s/kpc, and the vertex
deviation,l=13+-2 degrees, and detect a negative K effect. This negative K
effect is most conspicuous in the motion of A0-A5 giants, and is equal to
K=-13.1+-2.0 km/s/kpc.Comment: 16 pages, 8 figure
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