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Effects of ultrasound on the growth and function of bone and periodontal ligament cells <i>in vitro</i>
The effects of therapeutic ultrasound (US) on tissue healing processes in vivo are likely to involve US-induced changes in key cellular functions. However, these have not yet been clearly delineated and the present study has, therefore, examined the effects of a single 5-min CW exposure of 3.00-MHz US on the growth and functional activity of a human osteoblast-like cell line (MG63 cells) and human periodontal ligament (PDL) cells in vitro. Although cell proliferation was found to be largely unaffected by spatial average intensity (ISA) values of between 140â990 mW/cm2, flow cytometry (FCM) analysis showed that there were pronounced and differential effects on cell function. Thus, bone-associated proteins were down-regulated, whereas collagen type I (COL I) was unaffected and fibronectin (FN) was up-regulated at low intensities in MG63 cells. In contrast, bone protein expression was found to be dose-dependent, and FN and COL I were down-regulated in PDL cells. These results show that US has potentially important effects on the functional activities of connective tissue cells in vitro, which could markedly influence tissue repair and regeneration processes in vivo
Can the frequency-dependent specific heat be measured by thermal effusion methods?
It has recently been shown that plane-plate heat effusion methods devised for
wide-frequency specific-heat spectroscopy do not give the isobaric specific
heat, but rather the so-called longitudinal specific heat. Here it is shown
that heat effusion in a spherical symmetric geometry also involves the
longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex
Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding
The usage of Stromgren photometry in studies of Local Group Dwarf Spheroidal Galaxies - Application to Draco: a new catalogue of Draco members and a study of the metallicity distribution function and radial gradients
In this paper we demonstrate how Stromgren uvby photometry can be efficiently
used to: 1. Identify red giant branch stars that are members in a dwarf
spheroidal galaxy. 2. Derive age-independent metallicities for the same stars
and quantify the associated errors. Stromgren uvby photometry in a 11 x 22
arcmin field centered on the Draco dwarf spheroidal galaxy was obtained using
the Isaac Newton Telescope on La Palma. Members of the Draco dSph galaxy were
identified using the surface gravity sensitive c_1 index which discriminates
between red giant and dwarf stars. Thus enabling us to distinguish the (red
giant branch) members of the dwarf spheroidal galaxy from the foreground dwarf
stars in our galaxy. The method is evaluated through a comparison of our
membership list with membership classifications in the literature based on
radial velocities and proper motions. The metallicity sensitive m_1 index was
used to derive individual and age-independent metallicities for the members of
the Draco dSph galaxy. The derived metallicities are compared to studies based
on high resolution spectroscopy and the agreement is found to be very good. We
present metallicities for 169 members of the red giant branch in the Draco
dwarf spheroidal galaxy (the largest sample to date). The metallicity
distribution function for the Draco dSph galaxy shows a mean [Fe/H] = -1.74 dex
with a spread of 0.24 dex. The correlation between metallicity and colour for
the stars on the red giant branch is consistent with a dominant old, and coeval
population. There is a possible spatial population gradient over the field with
the most metal-rich stars being more centrally concentrated than the metal-poor
stars.Comment: Accepted for publication in A&A. 26 pages, 27 figures (some at
reduced resolution). High resolution version available at
http://www.astro.lu.se/~daniel/draco/faria.p
uvby-Hbeta CCD photometry and membership segregation of the open cluster NGC 2548; Gaps in the Main Sequence of open clusters
Deep CCD photometry in the uvby-Hbeta intermediate-band system is presented
for the cluster NGC 2548 (M 48). A complete membership analysis based on
astrometric and photometric criteria is applied. The photometric analysis of a
selected sample of stars yields a reddening value of E(b-y)=0.06\pm0.03, a
distance modulus of V_0-M_V=9.3\pm0.5 (725 pc) and a metallicity of [Fe/H]=
-0.24\pm0.27. Through isochrone fitting we find an age of log t = 8.6\pm0.1
(400 Myr). Our optical photometry and JHK from 2MASS are combined to derive
effective temperatures of cluster member stars. The effective temperature
distribution along the main sequence of the cluster shows several gaps. A test
to study the significance of these gaps in the main sequence of the HR diagram
has been applied. The method is also applied to several other open clusters
(Pleiades, Hyades, NGC 1817 and M 67) to construct a sequence of metallicities
and ages. The comparison of the results of each cluster gives four gaps with
high significance (one of them, centred at 4900 K, has not been previously
reported).Comment: 11 pages, 8 figures, A&A in press. Corrected typos on Table
Soft band X/K luminosity ratios for gas-poor early-type galaxies
We aim to place upper limits on the combined X-ray emission from the
population of steady nuclear-burning white dwarfs in galaxies. In the framework
of the single-degenerate scenario these systems are believed to be likely
progenitors of Type Ia supernovae. From the Chandra archive, we selected normal
early-type galaxies with the point source detection sensitivity better than
10^37 erg/s to minimize the contribution of unresolved low-mass X-ray binaries.
The galaxies, contaminated by emission from ionized ISM, were identified based
on the analysis of radial surface brightness profiles and energy spectra. The
sample was complemented by the bulge of M31 and the data for the solar
neighborhood. To cover a broad range of ages, we also included NGC3377 and
NGC3585. Our final sample includes eight gas-poor galaxies for which we
determine L_X/L_K ratios in the 0.3-0.7 keV energy band. In computing the L_X
we included both unresolved emission and soft resolved sources with the color
temperature of kT_bb <= 200 eV. We find that the X/K luminosity ratios are in
the range of (1.7-3.2) x 10^27 erg/s/L_K,sun. The data show no obvious trends
with mass, age, or metallicity of the host galaxy, although a weak
anti-correlation with the Galactic NH appears to exist. It is much flatter than
predicted for a blackbody emission spectrum with temperature of ~50-75 eV,
suggesting that sources with such soft spectra contribute significantly less
than a half to the observed X/K ratios. However, the correlation of the X/K
ratios with NH has a significant scatter and in the strict statistical sense
cannot be adequately described by a superposition of a power law and a
blackbody components with reasonable parameters, thus precluding quantitative
constraints on the contribution from soft sources. (abbr.)Comment: 9 pages, 5 figures, 4 tables, accepted for publication in Astronomy
and Astrophysic
A photometric and spectroscopic study of the new dwarf spheroidal galaxy in Hercules
Our aim is to provide as clean and as complete a sample as possible of red
giant branch stars that are members of the Hercules dSph galaxy. With this
sample we explore the velocity dispersion and the metallicity of the system.
Stromgren photometry and multi-fibre spectroscopy are combined to provide
information about the evolutionary state of the stars (via the Stromgren c_1
index) and their radial velocities. Based on this information we have selected
a clean sample of red giant branch stars, and show that foreground
contamination by Milky Way dwarf stars can greatly distort the results. Our
final sample consists of 28 red giant branch stars in the Hercules dSph galaxy.
Based on these stars we find a mean photometric metallicity of -2.35 dex which
is consistent with previous studies. We find evidence for an abundance spread.
Using those stars for which we have determined radial velocities we find a
systemic velocity of 45.2 km/s with a dispersion of 3.72 km/s, this is lower
than values found in the literature. Furthermore we identify the horizontal
branch and estimate the mean magnitude of the horizontal branch of the Hercules
dSph galaxy to be V_0=21.17, which corresponds to a distance of 147 kpc. We
have shown that a proper cleaning of the sample results in a smaller value for
the velocity dispersion of the system. This has implications for galaxy
properties derived from such velocity dispersions.Comment: 24 pages, 28 figure
On the Origin of the Kinematical Differences Between the Stellar Halo and the Old Globular Cluster System in the Large Magellanic Cloud
We discuss structural and kinematical properties of the stellar halo and the
old globular cluster system (GCS) in the Large Magellanic Cloud (LMC) based on
numerical simulations of the LMC formation. We particularly discuss the
observed possible GCS's rotational kinematics (V/sigma > 2) that appears to be
significantly different from the stellar halo's one with a large velocity
dispersion (~50 km/s). We consider that both halo field stars and old GCs can
originate from low-mass subhalos virialized at high redshifts (z >6). We
investigate the final dynamical properties of the two old components in the
LMC's halo formed from merging of low-mass subhalos with field stars and GCs.
We find that the GCS composed of old globular clusters (GCs) formed at high
redshifts (z > 6) has little rotation (V/sigma ~0.4) and structure and
kinematics similar to those of the stellar halo. This inconsistency between the
simulated GCS's kinematics and the observed one is found to be seen in models
with different parameters. This inconsistency therefore implies that if old,
metal-poor GCs in the LMC have rotational kinematics, they are highly unlikely
to originate from the low-mass subhalos that formed the stellar halo. We thus
discuss a scenario in which the stellar halo was formed from low-mass subhalos
with no/few GCs whereas the GCS was formed at the very early epoch of the LMC's
disk formation via dissipative minor and major merging of gas-rich subhalos and
gas infall. We suggest that there can be a threshold subhalo mass above which
GCs can be formed within subhalos at high redshifts and thus that this
threshold causes differences in physical properties between stellar halos and
GCSs in less luminous galaxies like the LMC.Comment: 10 pages, 8 figures, accepted by MNRA
The VMC survey - XVII : The proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae
In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motion of different stellar populations in a tile of 1.5 deg sq. in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Stars of the three main stellar components are selected from their spatial distribution and their distribution in colour-magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple Ks-band observations for stars as faint as Ks=19 mag. Proper motions are derived from the slope of the best-fitting line among 10 VMC epochs over a time baseline of ~1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. The resulting absolute proper motion of 47 Tuc is (mu_alpha cos(delta), mu_delta)=(+7.26+/-0.03, -1.25+/-0.03) mas/yr. This measurement refers to about 35000 sources distributed between 10 and 60 arcmin from the cluster centre. For the SMC we obtain (mu_alpha cos(delta), mu_delta)=(+1.16+/-0.07, -0.81+/-0.07) mas/yr from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line-of-sight (l =305.9, b =-44.9) of this VISTA tile is (mu_alpha cos(delta), mu_delta)=(+10.22+/-0.14, -1.27+/-0.12) mas/yr and results from about 4000 sources. Systematic uncertainties associated to the astrometric reference system are 0.18 mas/yr. Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.Peer reviewe
Biogeography and Character Evolution of the Ciliate Genus Euplotes (Spirotrichea, Euplotia), with Description of Euplotes curdsi sp. nov.
Ciliates comprise a diverse and ecologically important phylum of unicellular protists. One of
the most specious and best-defined genera is Euplotes, which constitutes more than 70
morphospecies, many of which have never been molecularly tested. The increasing number
of described Euplotes taxa emphasizes the importance for detailed characterizations of
new ones, requiring standardized morphological observations, sequencing of molecular
markers and careful comparison with previous literature. Here we describe Euplotes curdsi
sp. nov., distinguishable by the combination of the following features: 45±65 Όm length,
oval or elongated shape with both ends rounded, narrow peristome with 25±34 adoral
membranelles, conspicuous paroral membrane, double-eurystomus dorsal argyrome type,
6±7 dorsolateral kineties and 10 frontoventral cirri. Three populations of the novel species
have been found in brackish and marine samples in the Mediterranean and the White Sea.
We provide the SSU rRNA gene sequences of these populations, and an updated phylogeny
of the genus Euplotes. Using the molecular phylogenetic tree, we inferred aspects of
the biogeographical history of the genus and the evolution of its most important taxonomic
characters in order to provide a frame for future descriptions. Ultimately, these data reveal
recurrent trends of freshwater invasion and highlight the dynamic, yet convergent, morphological
evolution of Euplotes
The star formation and chemical evolution history of the sculptor dwarf spheroidal galaxy
We have combined deep photometry in the B,V and I bands from CTIO/MOSAIC of
the Sculptor dwarf spheroidal galaxy, going down to the oldest Main Sequence
Turn-Offs, with spectroscopic metallicity distributions of Red Giant Branch
stars. This allows us to obtain the most detailed and complete Star Formation
History to date, as well as an accurate timescale for chemical enrichment. The
Star Formation History shows that Sculptor is dominated by old (10 Gyr),
metal-poor stars, but that younger, more metal-rich populations are also
present. Using Star Formation Histories determined at different radii from the
centre we show that Sculptor formed stars with an increasing central
concentration with time. The old, metal-poor populations are present at all
radii, while more metal-rich, younger stars are more centrally concentrated. We
find that within an elliptical radius of 1 degree, or 1.5 kpc from the centre,
a total mass in stars of 7.8 M was formed, between 14
and 7 Gyr ago, with a peak at 1314 Gyr ago. We use the detailed Star
Formation History to determine age estimates for individual Red Giant Branch
stars with high resolution spectroscopic abundances. Thus, for the first time,
we can directly determine detailed timescales for the evolution of individual
chemical elements. We find that the trends in alpha-elements match what is
expected from an extended, relatively uninterrupted period of star formation
continuing for 67 Gyr. The knee in the alpha-element distribution occurs at
an age of 10.91Gyr, suggesting that SNe Ia enrichment began
1Gyr after the start of star formation in Sculptor.Comment: 23 pages, 23 figure
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