486 research outputs found
Discussing some basic critique on Journal Impact Factors: revision of earlier comments
In this study the issue of the validity of the argument against the applied length of citation windows in Journal Impact Factors calculations is critically re-analyzed. While previous studies argued against the relatively short citation window of 1ā2Ā years, this study shows that the relative short term citation impact measured in the window underlying the Journal Impact Factor is a good predictor of the citation impact of the journals in the next years to come. Possible exceptions to this observation relate to journals with relatively low numbers of publications, and the citation impact related to publications in the year of publication. The study focuses on five Journal Subject Categories from the science and social sciences, on normal articles published in these journals, in the 2Ā years 2000 and 2004
Ehrenfest relations at the glass transition: solution to an old paradox
In order to find out whether there exists a thermodynamic description of the
glass phase, the Ehrenfest relations along the glass transition line are
reconsidered. It is explained that the one involving the compressibility is
always satisfied, and that the one involving the specific heat is principally
incorrect.
Thermodynamical relations are presented for non-ergodic systems with a
one-level tree in phase space. They are derived for a spin glass model, checked
for other models, and expected to apply, e.g., to glass forming liquids. The
second Ehrenfest relation gets a contribution from the configurational entropy.Comment: 4 pages revtex, to appear in Phys. Rev. Let
HD 144432: a young triple system
We present new imaging and spectroscopic data of the young Herbig star HD
144432 A, which was known to be a binary star with a separation of 1.47 arcsec.
High-resolution NIR imaging data obtained with NACO at the VLT reveal that HD
144432 B itself is a close binary pair with a separation of 0.1 arcsec.
High-resolution optical spectra, acquired with FEROS at the 2.2m MPG/ESO
telescope in La Silla, of the primary star and its co-moving companions were
used to determine their main stellar parameters such as effective temperature,
surface gravity, radial velocity, and projected rotational velocity by fitting
synthetic spectra to the observed stellar spectra. The two companions, HD
144432 B and HD 144432 C, are identified as low-mass T Tauri stars of spectral
type K7V and M1V, respectively. From the position in the HRD the triple system
appears to be co-eval with a system age of 6+/-3 Myr.Comment: Accepted for publication in Astronomy & Astrophysics, 4 pages, 4
figure
āSPLITā Pancreaticojejunostomy in the Surgical Treatment of Chronic Pancreatitis
āSplitā pancreaticojejunostomy is a procedure consisting of vertical transection of the pancreas
and anastomosis of both sides of the cut pancreatic duct with an interposed, Roux-en-Y jejunal
loop. In this paper we report the long term results of this procedure in the treatment of eight
patients with chronic pancreatitis (CP)
A spectral atlas of post-main-sequence stars in omega Centauri: kinematics, evolution, enrichment and interstellar medium
We present a spectral atlas of the post-main-sequence population of the most
massive Galactic globular cluster, omega Centauri. Spectra were obtained of
more than 1500 stars selected as uniformly as possible from across the (B, B-V)
colour-magnitude diagram of the proper motion cluster member candidates of van
Leeuwen et al. (2000). The spectra were obtained with the 2dF multi-fibre
spectrograph at the Anglo Australian Telescope, and cover the approximate range
lambda~3840-4940 Angstroem. We measure the radial velocities, effective
temperatures, metallicities and surface gravities by fitting ATLAS9 stellar
atmosphere models. We analyse the cluster membership and stellar kinematics,
interstellar absorption in the Ca II K line at 3933 Angstroem, the RR Lyrae
instability strip and the extreme horizontal branch, the metallicity spread and
bimodal CN abundance distribution of red giants, nitrogen and s-process
enrichment, carbon stars, pulsation-induced Balmer line emission on the
asymptotic giant branch (AGB), and the nature of the post-AGB and UV-bright
stars. Membership is confirmed for the vast majority of stars, and the radial
velocities clearly show the rotation of the cluster core. We identify
long-period RR Lyrae-type variables with low gravity, and low-amplitude
variables coinciding with warm RR Lyrae stars. A barium enhancement in the
coolest red giants indicates that 3rd dredge-up operates in AGB stars in omega
Cen. This is distinguished from the pre-enrichment by more massive AGB stars,
which is also seen in our data. The properties of the AGB, post-AGB and
UV-bright stars suggest that RGB mass loss may be less efficient at very low
metallicity, [Fe/H]<<-1, increasing the importance of mass loss on the AGB. The
catalogue and spectra are made available via CDS.Comment: accepted for publication in MNRA
Local exchange-correlation vector potential with memory in Time-Dependent Density Functional Theory: the generalized hydrodynamics approach
Using Landau Fermi liquid theory we derive a nonlinear non-adiabatic
approximation for the exchange-correlation (xc) vector potential defined by the
xc stress tensor. The stress tensor is a local nonlinear functional of two
basic variables - the displacement vector and the second-rank tensor which
describes the evolution of momentum in a local frame moving with Eulerian
velocity. For irrotational motion and equilibrium initial state the dependence
on the tensor variable reduces to that on a metrics generated by a dynamical
deformation of the system.Comment: RevTex, 5 pages, no figures. Final version published in PR
Bone mineral density assessed by phalangeal radiographic absorptiometry before and during long-term growth hormone treatment in girls with Turner's syndrome participating in a randomized dose-response study
To assess bone mineral density (BMD) in girls with Turner's syndrome
before and during long-term treatment with GH, longitudinal measurements
using phalangeal radiographic absorptiometry were performed in 68 girls
with Turner's syndrome. These previously untreated girls, age 2-11 y,
participating in a randomized, dose-response trial, were randomly assigned
to one of three GH dosage groups: group A, 4 IU/m(2)/d ( approximately
0.045 mg/kg/d); group B, first year 4 IU/m(2)/d, thereafter 6 IU/m(2)/d (
approximately 0.0675 mg/kg/d); or group C, first year 4 IU/m(2)/d, second
year 6 IU/m(2)/d, thereafter 8 IU/m(2)/d ( approximately 0.090 mg/kg/d).
In the first 4 y of GH treatment, no estrogens for pubertal induction were
prescribed to the girls. Thereafter, girls started with 17beta-estradiol
(5 microg/kg body weight/d, orally) when they had reached the age of 12 y.
BMD results were adjusted for bone age and sex, and expressed as SD scores
using reference values of healthy Dutch girls. At baseline, almost every
individual BMD value of bone consisting predominantly of cortical bone, as
well as that of bone consisting predominantly of trabecular bone, was
within the normal range of healthy girls and the SD scores were not
significantly different from zero [mean (SE) 0.38 (0.22) and -0.04
(0.13)]. During 7 y of GH treatment, BMD SD scores showed a significant
increase to values significantly higher than zero [mean (SE) 0.87 (0.15)
and 0.95 (0.14)]. The increment in BMD SD score of bone consisting
predominantly of cortical bone was significantly higher in group C
compared with that of the other two GH dosage groups. The pretreatment
bone age was significantly negatively related to the increment in BMD SD
score. We found no significant influence of spontaneous puberty or the use
of low-dose estrogens in the last 3 y of the study period on the increment
in BMD SD score during 7 y of GH treatment. In conclusion, most untreated
young girls with Turner's syndrome have a normal volumetric BMD. During 7
y of GH treatment with 4, 6, or 8 IU/m(2)/d, the BMD SD score increased
significantly
Ellipsoidal primary of the RS CVn binary zeta And: Investigation using high-resolution spectroscopy and optical interferometry
We have obtained high-resolution spectroscopy, optical interferometry, and
long-term broad band photometry of the ellipsoidal primary of the RS CVn-type
binary system zeta And. Based on the optical interferometry the apparent limb
darkened diameter of zeta And is 2.55 +/- 0.09 mas using a uniform disk fit.
The Hipparcos distance and the limb-darkened diameter obtained with a uniform
disk fit give stellar radius of 15.9 +/- 0.8 Rsolar, and combined with
bolometric luminosity, it implies an effective temperature of 4665 +/- 140 K.
The temperature maps obtained from high resolution spectra using Doppler
imaging show a strong belt of equatorial spots and hints of a cool polar cap.
The equatorial spots show a concentration around the phase 0.75. This spot
configuration is reminiscent of the one seen in the earlier published
temperature maps of zeta And. Investigation of the Halpha line reveals both
prominences and cool clouds in the chromosphere. Long-term photometry spanning
12 years shows hints of a spot activity cycle, which is also implied by the
Doppler images, but the cycle length cannot be reliably determined from the
current data.Comment: 9 pages, 9 figures, accepted for A&
True protein digestibility and amounts of endogenous protein measured with the 15N-dilution technique in piglet feed on peas (Pisum sativum) and common beans (Phaseolus vulgaris)
Observation of Nonspreading Wave Packets in an Imaginary Potential
We propose and experimentally demonstrate a method to prepare a nonspreading
atomic wave packet. Our technique relies on a spatially modulated absorption
constantly chiseling away from an initially broad de Broglie wave. The
resulting contraction is balanced by dispersion due to Heisenberg's uncertainty
principle. This quantum evolution results in the formation of a nonspreading
wave packet of Gaussian form with a spatially quadratic phase. Experimentally,
we confirm these predictions by observing the evolution of the momentum
distribution. Moreover, by employing interferometric techniques, we measure the
predicted quadratic phase across the wave packet. Nonspreading wave packets of
this kind also exist in two space dimensions and we can control their amplitude
and phase using optical elements.Comment: 4 figure
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