A NEW DIAGNOSTIC OF THE RADIAL DENSITY STRUCTURE OF Be DISKS

We analyze the intrinsic polarization of two classical Be stars in the process of losing their circumstellar disks via a Be to normal B star transition originally reported by Wisniewski et al. During each of five polarimetric outbursts which interrupt these disk-loss events, we find that the ratio of the polarization across the Balmer jump (BJ+/BJ-) versus the V-band polarization traces a distinct loop structure as a function of time. Since the polarization change across the Balmer jump is a tracer of the innermost disk density whereas the V-band polarization is a tracer of the total scattering mass of the disk, we suggest that such correlated loop structures in Balmer jump-V-band polarization diagrams (BJV diagrams) provide a unique diagnostic of the radial distribution of mass within Be disks. We use the three-dimensional Monte Carlo radiation transfer code HDUST to reproduce the observed clockwise loops simply by turning ""on/off"" the mass decretion from the disk. We speculate that counterclockwise loop structures we observe in BJV diagrams might be caused by the mass decretion rate changing between subsequent ""on/off"" sequences. Applying this new diagnostic to a larger sample of Be disk systems will provide insight into the time-dependent nature of each system's stellar decretion rate.

Probing the Galactic thick disc vertical properties and interfaces

Aims. This work investigates the properties (metallicity and kinematics) and interfaces of the Galactic thick disc as a function of height above the Galactic plane. The main aim is to study the thick disc in a place where it is the main component of the sample. Methods. We take advantage of former astrometric work in two fields of several square degrees in which accurate proper motions were measured down to V-magnitudes of 18.5 in two directions, one near the north galactic pole and the other at a galactic latitude of 46 degrees and galactic longitude near 0 degrees. Spectroscopic observations have been acquired in these two fields for a total of about 400 stars down to magnitude 18.0, at spectral resolutions of 3.5 to 6.25 angstrom. The spectra have been analysed with the code ETOILE, comparing the target stellar spectra with a grid of 1400 reference stellar spectra. This comparison allowed us to derive the parameters effective temperature, gravity, [Fe/H] and absolute magnitude for each target star. Results. The Metallicity Distribution Function (MDF) of the thin-thick-disc-halo system is derived for several height intervals between 0 and 5 kpc above the Galactic plane. The MDFs show a decrease of the ratio of the thin to thick disc stars between the first and second kilo-parsec. This is consistent with the classical modelling of the vertical density profile of the disc with 2 populations with different scale heights. A vertical metallicity gradient, partial derivative[Fe/H]/partial derivative z = -0.068 +/- 0.009 dex kpc(-1), is observed in the thick disc. It is discussed in terms of scenarios of formation of the thick disc.

Age distribution of the central stars of galactic disk planetary nebulae

Context. Determination of the ages of central stars of planetary nebulae (CSPN) is a complex problem, and there is presently no single method that can be generally applied. We have developed several methods of estimating the ages of CSPN, based on both the observed nebular properties and some properties of the stars themselves. Aims. Our aim is to estimate the ages and the age distribution of CSPN and to compare the derived results with mass and age determinations of CSPN and white dwarfs based on empirical determinations of these quantities. Methods. We considered a sample of planetary nebulae in the galactic disk, most of which (similar to 69%) are located in the solar neighbourhood, within 3 kpc from the Sun. We discuss several methods of deriving the age distribution of CSPN, namely; (i) the use of an age-metallicity relation that also depends on the galactocentric distance; (ii) the use of an age-metallicity relation obtained for the galactic disk; and (iii) the determination of ages from the central star masses obtained from the observed nitrogen abundances. Results. We estimated the age distribution of CSPN with average uncertainties of 1-2 Gyr, and compared our results with the expected distribution based both on the observed mass distribution of white dwarfs and on the age distribution derived from available mass distributions of CSPN. Based on our derived age distributions, we conclude that most CSPN in the galactic disk have ages under 6 Gyr, and that the age distribution is peaked around 2-4 Gyr.

MASS DISTRIBUTION IN HICKSON COMPACT GROUPS OF GALAXIES

This study presents the mass distribution for a sample of 18 late-type galaxies in nine Hickson compact groups. We used Ha rotation curves (RCs) from high-resolution two-dimensional velocity fields of Fabry-Perot observations and the J-band photometry from the Two Micron All Sky Survey, in order to determine the dark halo and the visible matter distributions. The study compares two halo density profiles, an isothermal core-like distribution, and a cuspy one. We also compare their visible and dark matter distributions with those of galaxies belonging to cluster and field galaxies coming from two samples: 40 cluster galaxies of Barnes et al. and 35 field galaxies of Spano et al. The central halo surface density is found to be constant with respect to the total absolute magnitude similar to what is found for the isolated galaxies. This suggests that the halo density is independent of galaxy type and environment. We have found that core-like density profiles better fit the RCs than cuspy-like ones. No major differences have been found between field, cluster, and compact group galaxies with respect to their dark halo density profiles.

HR Del REMNANT ANATOMY USING TWO-DIMENSIONAL SPECTRAL DATA AND THREE-DIMENSIONAL PHOTOIONIZATION SHELL MODELS

The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in H alpha, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman & O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of three-dimensional clumpy models including a disk-shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10(-4) M(circle dot) is derived from these models. We estimate that 50%-70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.

Galaxy distribution and evolution around a sample of 2dF groups

Context. We study galaxy evolution and spatial patterns in the surroundings of a sample of 2dF groups. Aims. Our aim is to find evidence of galaxy evolution and clustering out to 10 times the virial radius of the groups and so redefine their properties according to the spatial patterns in the fields and relate them to galaxy evolution. Methods. Group members and interlopers were redefined after the identification of gaps in the redshift distribution. We then used exploratory spatial statistics based on the the second moment of the Ripley function to probe the anisotropy in the galaxy distribution around the groups. Results. We found an important anticorrelation between anisotropy around groups and the fraction of early-type galaxies in these fields. Our results illustrate how the dynamical state of galaxy groups can be ascertained by the systematic study of their neighborhoods. This is an important achievement, since the correct estimate of the extent to which galaxies are affected by the group environment and follow large-scale filamentary structure is relevant to understanding the process of galaxy clustering and evolution in the Universe.

Hormone-regulated expression and distribution of versican in mouse uterine tissues

Background: Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination. Methods: Uteri from mice in all phases of the estrous cycle, and animals subjected to ovariectomy and hormone replacement were collected for immunoperoxidase staining for versican, as well as PCR and quantitative Real Time PCR. Results: In diestrus and proestrus, VER was exclusively expressed in the endometrial stroma. In estrus and metaestrus, VER was present in both endometrial stroma and myometrium. In OVX mice, VER immunoreaction was abolished in all uterine tissues. VER expression was restored by E2, MPA and E2+MPA treatments. Real Time PCR analysis showed that VER expression increases considerably in the MPA-treated group. Analysis of mRNA identified isoforms V0, V1 and V3 in the mouse uterus. Conclusion: These results show that the expression of versican in uterine tissues is modulated by ovarian steroid hormones, in a tissue-specific manner. VER is induced in the myometrium exclusively by E2, whereas MPA induces VER deposition only in the endometrial stroma.

Mechanisms of Vascular Damage by Hemorrhagic Snake Venom Metalloproteinases: Tissue Distribution and In Situ Hydrolysis

Background: Envenoming by viper snakes constitutes an important public health problem in Brazil and other developing countries. Local hemorrhage is an important symptom of these accidents and is correlated with the action of snake venom metalloproteinases (SVMPs). The degradation of vascular basement membrane has been proposed as a key event for the capillary vessel disruption. However, SVMPs that present similar catalytic activity towards extracellular matrix proteins differ in their hemorrhagic activity, suggesting that other mechanisms might be contributing to the accumulation of SVMPs at the snakebite area allowing capillary disruption. Methodology/Principal Findings: In this work, we compared the tissue distribution and degradation of extracellular matrix proteins induced by jararhagin (highly hemorrhagic SVMP) and BnP1 (weakly hemorrhagic SVMP) using the mouse skin as experimental model. Jararhagin induced strong hemorrhage accompanied by hydrolysis of collagen fibers in the hypodermis and a marked degradation of type IV collagen at the vascular basement membrane. In contrast, BnP1 induced only a mild hemorrhage and did not disrupt collagen fibers or type IV collagen. Injection of Alexa488-labeled jararhagin revealed fluorescent staining around capillary vessels and co-localization with basement membrane type IV collagen. The same distribution pattern was detected with jararhagin-C (disintegrin-like/cysteine-rich domains of jararhagin). In opposition, BnP1 did not accumulate in the tissues. Conclusions/Significance: These results show a particular tissue distribution of hemorrhagic toxins accumulating at the basement membrane. This probably occurs through binding to collagens, which are drastically hydrolyzed at the sites of hemorrhagic lesions. Toxin accumulation near blood vessels explains enhanced catalysis of basement membrane components, resulting in the strong hemorrhagic activity of SVMPs. This is a novel mechanism that underlies the difference between hemorrhagic and non-hemorrhagic SVMPs, improving the understanding of snakebite pathology.

Characterization of subgraph relationships and distribution in complex networks

A network can be analyzed at different topological scales, ranging from single nodes to motifs, communities, up to the complete structure. We propose a novel approach which extends from single nodes to the whole network level by considering non-overlapping subgraphs (i.e. connected components) and their interrelationships and distribution through the network. Though such subgraphs can be completely general, our methodology focuses on the cases in which the nodes of these subgraphs share some special feature, such as being critical for the proper operation of the network. The methodology of subgraph characterization involves two main aspects: (i) the generation of histograms of subgraph sizes and distances between subgraphs and (ii) a merging algorithm, developed to assess the relevance of nodes outside subgraphs by progressively merging subgraphs until the whole network is covered. The latter procedure complements the histograms by taking into account the nodes lying between subgraphs, as well as the relevance of these nodes to the overall subgraph interconnectivity. Experiments were carried out using four types of network models and five instances of real-world networks, in order to illustrate how subgraph characterization can help complementing complex network-based studies.

Relationship Between Surface Topography and Energy Density Distribution of Er,Cr:YSGG Beam on Irradiated Dentin: An Atomic Force Microscopy Study

Objective: The aim of this study was to assess by atomic force microscopy (AFM) the effect of Er,Cr:YSGG laser application on the surface microtopography of radicular dentin. Background: Lasers have been used for various purposes in dentistry, where they are clinically effective when used in an appropriate manner. The Er, Cr: YSGG laser can be used for caries prevention when settings are below the ablation threshold. Materials and Methods: Four specimens of bovine dentin were irradiated using an Er, Cr:YSGG laser (lambda = 2.78 mu m), at a repetition rate of 20 Hz, with a 750-mu m-diameter sapphire tip and energy density of 2.8 J/cm(2) (12.5 mJ/pulse). After irradiation, surface topography was analyzed by AFM using a Si probe in tapping mode. Quantitative and qualitative information concerning the arithmetic average roughness (Ra) and power spectral density analyses were obtained from central, intermediate, and peripheral areas of laser pulses and compared with data from nonirradiated samples. Results: Dentin Ra for different areas were as follows: central, 261.26 (+/- 21.65) nm; intermediate, 83.48 (+/- 6.34) nm; peripheral, 45.8 (+/- 13.47) nm; and nonirradiated, 35.18 (+/- 2.9) nm. The central region of laser pulses presented higher ablation of intertubular dentin, with about 340-760 nm height, while intermediate, peripheral, and nonirradiated regions presented no difference in height of peritubular and interperitubular dentin. Conclusion: According to these results, we can assume that even when used at a low-energy density parameter, Er, Cr: YSGG laser can significantly alter the microtopography of radicular dentin, which is an important characteristic to be considered when laser is used for clinical applications.

Synchrotron X-ray powder diffraction and extended X-ray absorption fine structure spectroscopy studies on nanocrystalline ZrO(2)-CaO solid solutions

The crystal structure and the local atomic order of a series of nanocrystalline ZrO(2)-CaO solid solutions with varying CaO content were studied by synchrotron radiation X-ray powder diffraction and extended X-ray absorption fine structure (EXAFS) spectroscopy. These samples were synthesized by a pH-controlled nitrate-glycine gel-combustion process. For CaO contents up to 8 mol%, the t' form of the tetragonal phase (c/a > 1) was identified, whereas for 10 and 12 mol% CaO, the t '' form (c/a=1; oxygen anions displaced from their ideal positions in the cubic phase) was detected. Finally, the cubic phase was observed for solid solutions with CaO content of 14 mol% CaO or higher. The t'/t '' and t ''/cubic compositional boundaries were determined to be at 9 (1) and 13 (1) mol% CaO, respectively. The EXAFS study demonstrated that this transition is related to a tetragonal-to-cubic symmetry change of the first oxygen coordination shell around the Zr atoms.

Robust relations between CCN and the vertical evolution of cloud drop size distribution in deep convective clouds

In-situ measurements in convective clouds (up to the freezing level) over the Amazon basin show that smoke from deforestation fires prevents clouds from precipitating until they acquire a vertical development of at least 4 km, compared to only 1-2 km in clean clouds. The average cloud depth required for the onset of warm rain increased by similar to 350 m for each additional 100 cloud condensation nuclei per cm(3) at a super-saturation of 0.5% (CCN0.5%). In polluted clouds, the diameter of modal liquid water content grows much slower with cloud depth (at least by a factor of similar to 2), due to the large number of droplets that compete for available water and to the suppressed coalescence processes. Contrary to what other studies have suggested, we did not observe this effect to reach saturation at 3000 or more accumulation mode particles per cm(3). The CCN0.5% concentration was found to be a very good predictor for the cloud depth required for the onset of warm precipitation and other microphysical factors, leaving only a secondary role for the updraft velocities in determining the cloud drop size distributions. The effective radius of the cloud droplets (r(e)) was found to be a quite robust parameter for a given environment and cloud depth, showing only a small effect of partial droplet evaporation from the cloud's mixing with its drier environment. This supports one of the basic assumptions of satellite analysis of cloud microphysical processes: the ability to look at different cloud top heights in the same region and regard their r(e) as if they had been measured inside one well developed cloud. The dependence of r(e) on the adiabatic fraction decreased higher in the clouds, especially for cleaner conditions, and disappeared at r(e)>=similar to 10 mu m. We propose that droplet coalescence, which is at its peak when warm rain is formed in the cloud at r(e)=similar to 10 mu m, continues to be significant during the cloud's mixing with the entrained air, cancelling out the decrease in r(e) due to evaporation.

Precise measurements of direct CP violation, CPT symmetry, and other parameters in the neutral kaon system

We present precise tests of CP and CPT symmetry based on the full data set of K -> pi pi decays collected by the KTeV experiment at Fermi National Accelerator Laboratory during 1996, 1997, and 1999. This data set contains 16 x 10(6) K -> pi(0)pi(0) and 69 x 10(6) K -> pi(+)pi(-) decays. We measure the direct CP violation parameter Re(epsilon'/epsilon) = (19.2 +/- 2.1) x 10(-4). We find the K(L) -> K(S) mass difference Delta m = (5270 +/- 12) x 10(6) (h) over tilde s(-1) and the K(S) lifetime tau(S) = (89.62 +/- 0.05) x 10(-12) s. We also measure several parameters that test CPT invariance. We find the difference between the phase of the indirect CP violation parameter epsilon and the superweak phase: phi(epsilon) - phi(SW) =(0.40 +/- 0.56)degrees. We measure the difference of the relative phases between the CP violating and CP conserving decay amplitudes for K -> pi(+)pi(-) (phi(+-)) and for K -> pi(0)pi(0) (phi(00)): Delta phi = (0.30 +/- 0.35)degrees. From these phase measurements, we place a limit on the mass difference between K(0) and (K) over bar (0): Delta M < 4.8 x 10(-19) GeV/c(2) at 95% C.L. These results are consistent with those of other experiments, our own earlier measurements, and CPT symmetry.

Supergraph techniques for D=3, N=1 broken supersymmetric theories

We enlarge the usual D = 3 N = 1 supergraph techniques to include the case of (explicitly or spontaneously) broken supersymmetric gauge theories. To illustrate the utility of these techniques, we calculate the two-loop effective potential of the SQED(3) by using the tadpole and the vacuum bubble methods. In these methods, to investigate the possibility of supersymmetry breaking, the superfields must be shifted by theta(alpha) dependent classical superfields (vacuum expectation values), what implies in the explicit breakdown of supersymmetry in the intermediate steps of the calculation. Nevertheless, after studying the minimum of the resulting effective potential, we find that supersymmetry is conserved, while gauge symmetry is dynamically broken, with a mass generated for the gauge superfield.

Noncommutativity due to spin

Using the Berezin-Marinov pseudoclassical formulation of the spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spatial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external electromagnetic field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, Delta x Delta y >= theta(2)/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.