Histomorphometric Analysis of the Rat Proximal Tibial Metaphysis by “Linear Scanning”

Twenty-four female Sprague-Dawley rats (10 weeks old, 200g BW) were either sham-operated (n = 6) or ovariectomized (ovx). Ovx rats were divided into 3 groups (n = 6 each) : ovx; ovx + 1,25(OH) 2D3; ovx + l,25(OH)2D3 + 1,24,25(OH)3D3. The vitamin D metabolites were fed orally starting the day after surgery. After 7 weeks all rats were sacrificed and the proximal tibiae were processed undecalcified for quantitative histomorphometry. Conventional histomorphometric analysis of the distal zone (\u3e 1 mm from the growth cartilage) of the tibial metaphysis revealed a dramatic loss of cancellous bone mass in ovx rats. Both l,25(OH)2D3 and the combination of l,25(OH)2D3 with l,24,25(OH)3D3 prevented the bone loss in the distal zone in ovx animals. Measurements in the proximal zone (\u3c 1 mm from the growth cartilage) of the tibial metaphysis were performed with a newly developed technique that utilizes the advantages of automatic image analysis, and that we propose to name linear scanning . This method revealed a significantly decreased hard tissue mass at about 100 μm and within 800 to 950 μm distance from the growth plate in ovx rats. However, ovx rats reached normal amounts of hard tissue within 250 to 450 μm from the growth plate. The results obtained by linear scanning suggest that the obvious loss of cancellous bone mass in the distal zone of the tibial metaphysis in growing ovx rats is not a consequence of structural changes in the proximal zone

Kinematic modeling of disk galaxies III. The warped "Spindle" NGC 2685

This is the third of a series of papers in which the structure and kinematics of disk galaxies is studied. Employing direct tilted-ring fits to the data cube as introduced in Paper I, we perform an analysis of the "Spindle" galaxy NGC 2685, previously regarded as two-ringed polar ring galaxy. Deep HI and optical (i'-band) observations are presented. The HI observations strongly suggest that the gaseous structure of NGC 2685 does not consist of two separate mutually inclined regions, but forms a coherent, extremely warped disk, the appearance of two rings being due to projection effects. By comparing the HI total-intensity maps with the optical image we demonstrate that at large radii a faint stellar disk is well aligned with the outer HI disk. The shape of the dust-lanes obscuring the NE part of the inner stellar body indicates that also at smaller radii NGC 2685 possesses a disk containing gas, dust, and stars in which the various constituents are aligned. At smaller radii, this disk is kinematically decoupled from the central stellar body. Hence, in the region of the bright, central stellar body, NGC 2685 appears to consist of two disks that share a common centre, but have different orientation: a bright stellar lenticular body apparently devoid of dust and gas, and a heavily warped low-surface brightness disk containing stars, gas and dust. The low-surface-brightness disk changes its orientation gradually and at large radii assumes the orientation of the central stellar S0 disk. Since, according to our analysis, the intrinsic orientation of the low-surface-brightness disk changes through 70 degrees, the gaseous disk is coherent, and is at no radius orientated perpendicularly with respect to the central stellar body, NGC 2685 is likely not a classical polar-ring galaxy.Comment: 26 pages, 14 figures, 6 tables, accepted for publication in Astronomy & Astrophysics. For a high-resolution version see http://www.astron.nl/~jozsa/publications

The star formation rate history in the FORS Deep and GOODS South Fields

We measure the star formation rate (SFR) as a function of redshift z up to z \~4.5, based on B, I and (I+B) selected galaxy catalogues from the FORS Deep Field (FDF) and the K-selected catalogue from the GOODS-South field. Distances are computed from spectroscopically calibrated photometric redshifts accurate to (Delta_z / (z_spec+1)) ~0.03 for the FDF and ~0.056 for the GOODS-South field. The SFRs are derived from the luminosities at 1500 Angstroem. We find that the total SFR estimates derived from B, I and I+B catalogues agree very well (\lsim 0.1 dex) while the SFR from the K catalogue is lower by ~0.2 dex. We show that the latter is solely due to the lower star-forming activity of K-selected intermediate and low luminosity (L<L_*) galaxies. The SFR of bright (L>L_*) galaxies is independent of the selection band, i.e. the same for B, I, (I+B), and K-selected galaxy samples. At all redshifts, luminous galaxies (L>L_*) contribute only ~1/3 to the total SFR. There is no evidence for significant cosmic variance between the SFRs in the FDF and GOODs-South field, ~0.1 dex, consistent with theoretical expectations. The SFRs derived here are in excellent agreement with previous measurements provided we assume the same faint-end slope of the luminosity function as previous works (alpha ~ -1.6). However, our deep FDF data indicate a shallower slope of alpha=-1.07, implying a SFR lower by ~0.3 dex. We find the SFR to be roughly constant up to z ~4 and then to decline slowly beyond, if dust extinctions are assumed to be constant with redshift.Comment: 6 pages, 2 figures, Accepted for publication in ApJ

Is Gravitational Lensing by Intercluster Filaments Always Negligible?

Intercluster filaments negligibly contribute to the weak lensing signal in general relativity (GR), $\gamma_{N}\sim 10^{-4}-10^{-3}$. In the context of relativistic modified Newtonian dynamics (MOND) introduced by Bekenstein, however, a single filament inclined by $\approx 45^\circ$ from the line of sight can cause substantial distortion of background sources pointing towards the filament's axis ($\kappa=\gamma=(1-A^{-1})/2\sim 0.01$); this is rigorous for infinitely long uniform filaments, but also qualitatively true for short filaments ($\sim 30$Mpc), and even in regions where the projected matter density of the filament is equal to zero. Since galaxies and galaxy clusters are generally embedded in filaments or are projected on such structures, this contribution complicates the interpretation of the weak lensing shear map in the context of MOND. While our analysis is of mainly theoretical interest providing order-of-magnitude estimates only, it seems safe to conclude that when modeling systems with anomalous weak lensing signals, e.g. the "bullet cluster" of Clowe et al., the "cosmic train wreck" of Abell 520 from Mahdavi et al., and the "dark clusters" of Erben et al., filamentary structures might contribute in a significant and likely complex fashion. On the other hand, our predictions of a (conceptual) difference in the weak lensing signal could, in principle, be used to falsify MOND/TeVeS and its variations.Comment: 11 pages, 6 figures, published versio

Introducing BAX: a database for X-ray clusters and groups of galaxies

We present BAX, Base de Donnees Amas de Galaxies X (http://webast.ast.obs-mip.fr/bax), a multi-wavelength database dedicated to X-ray clusters and groups of galaxies allowing detailed information retrieval. BAX is designed to support astronomical research by providing access to published measurements of the main physical quantities and to the related bibliographic references: basic data stored in the database are cluster/group identifiers, equatorial coordinates, redshift, flux, X-ray luminosity (in the ROSAT band) and temperature, and links to additional linked parameters (in X-rays, such as spatial profile parameters, as well as SZ parameters of the hot gas, lensing measurements,and data at other wavelengths, such as optical and radio). The clusters and groups in BAX can be queried by the basic parameters as well as the linked parameters or combinations of these. We expect BAX to become an important tool for the astronomical community. BAX will optimize various aspects of the scientific analysis of X-ray clusters and groups of galaxies, from proposal planning to data collection, interpretation and publication, from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM-Newton, Chandra and Planck.Comment: Accepted for publication in Astronomy and Astrophysics Journal. Contains 4 pages and 1 figur

Recruitment, augmentation and apoptosis of rat osteoclasts in 1,25-(OH)2D3 response to short-term treatment with 1,25-dihydroxyvitamin D3in vivo

Background Although much is known about the regulation of osteoclast (OC) formation and activity, little is known about OC senescence. In particular, the fate of of OC seen after 1,25-(OH)2D3 administration in vivo is unclear. There is evidence that the normal fate of OC is to undergo apoptosis (programmed cell death). We have investigated the effect of short-term application of high dose 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on OC apoptosis in an experimental rat model. Methods OC recruitment, augmentation and apoptosis was visualised and quantitated by staining histochemically for tartrate resistant acid phosphatase (TRAP), double staining for TRAP/ED1 or TRAP/DAPI, in situ DNA fragmentation end labelling and histomorphometric analysis. Results Short-term treatment with high-dose 1,25-(OH)2D3 increased the recruitment of OC precursors in the bone marrow resulting in a short-lived increase in OC numbers. This was rapidly followed by an increase in the number of apoptotic OC and their subsequent removal. The response of OC to 1,25-(OH)2D3 treatment was dose and site dependent; higher doses producing stronger, more rapid responses and the response in the tibiae being consistently stronger and more rapid than in the vertebrae. Conclusions This study demonstrates that (1) after recruitment, OC are removed from the resorption site by apoptosis (2) the combined use of TRAP and ED1 can be used to identify OC and their precursors in vivo (3) double staining for TRAP and DAPI or in situ DNA fragmentation end labelling can be used to identify apoptotic OC in vivo

XMMU J100750.5+125818: A strong lensing cluster at z=1.082

We report on the discovery of the X-ray luminous cluster XMMU J100750.5+125818 at redshift 1.082 based on 19 spectroscopic members, which displays several strong lensing features. SED modeling of the lensed arc features from multicolor imaging with the VLT and the LBT reveals likely redshifts ~2.7 for the most prominent of the lensed background galaxies. Mass estimates are derived for different radii from the velocity dispersion of the cluster members, M_200 ~ 1.8 10^{14} Msun, from the X-ray spectral parameters, M_500 ~ 1.0 10^{14} Msun, and the largest lensing arc, M_SL ~ 2.3 10^{13} Msun. The projected spatial distribution of cluster galaxies appears to be elongated, and the brightest galaxy lies off center with respect to the X-ray emission indicating a not yet relaxed structure. XMMU J100750.5+125818 offers excellent diagnostics of the inner mass distribution of a distant cluster with a combination of strong and weak lensing, optical and X-ray spectroscopy.Comment: A&A, accepted for publicatio