24,606 research outputs found
Osteoblast interactions within a biomimetic apatite microenvironment.
Numerous reports have shown that accelerated apatites can mediate osteoblastic differentiation in vitro and bone formation in vivo. However, how cells interact within the apatite microenvironment remains largely unclear, despite the vast literature available today. In response, this study evaluates the in vitro interactions of a well-characterized osteoblast cell line (MC3T3-E1) with the apatite microenvironment. Specifically, cell attachment, spreading, and viability were evaluated in the presence and absence of serum proteins. Proteins were found to be critical in the mediation of cell-apatite interactions, as adherence of MC3T3-E1 cells to apatite surfaces without protein coatings resulted in significant levels of cell death within 24 h in serum-free media. In the absence of protein-apatite interaction, cell viability could be "rescued" upon treatment of MC3T3-E1 cells with inhibitors to phosphate (PO(4) (3-)) transport, suggesting that PO(4) (3-) uptake may play a role in viability. In contrast, rescue was not observed upon treatment with calcium (Ca(2+)) channel inhibitors. Interestingly, a rapid "pull-down" of extracellular Ca(2+) and PO(4) (3-) ions onto the apatite surface could be measured upon the incubation of apatites with α-MEM, suggesting that cells may be subject to changing levels of Ca(2+) and PO(4) (3-) within their microenvironment. Therefore, the biomimetic apatite surface may significantly alter the microenvironment of adherent osteoblasts and, as such, be capable of affecting both cell survival and differentiation
The distance to a star forming region in the Outer arm of the Galaxy
We performed astrometric observations with the VLBA of WB89-437, an H2O maser
source in the Outer spiral arm of the Galaxy. We measure an annual parallax of
0.167 +/- 0.006 mas, corresponding to a heliocentric distance of 6.0 +/- 0.2
kpc or a Galactocentric distance of 13.4 +/- 0.2 kpc. This value for the
heliocentric distance is considerably smaller than the kinematic distance of
8.6 kpc. This confirms the presence of a faint Outer arm toward l = 135
degrees. We also measured the full space motion of the object and find a large
peculiar motion of ~20 km/s toward the Galactic center. This peculiar motion
explains the large error in the kinematic distance estimate. We also find that
WB89-437 has the same rotation speed as the LSR, providing more evidence for a
flat rotation curve and thus the presence of dark matter in the outer Galaxy.Comment: The Astrophysical Journal, accepted, 16 pages, 4 Figure
Disease risks from foods, England and Wales, 1996-2000.
Data from population-based studies and national surveillance systems were collated and analyzed to estimate the impact of disease and risks associated with eating different foods in England and Wales. From 1996 to 2000, an estimated 1,724,315 cases of indigenous foodborne disease per year resulted in 21,997 hospitalizations and 687 deaths. The greatest impact on the healthcare sector arose from foodborne Campylobacter infection (160,788 primary care visits and 15,918 hospitalizations), while salmonellosis caused the most deaths (209). The most important cause of indigenous foodborne disease was contaminated chicken (398,420 cases, risk [cases/million servings] = 111; case-fatality rate [deaths/100,000 cases] = 35, deaths = 141). Red meat (beef, lamb, and pork) contributed heavily to deaths, despite lower levels of risk (287,485 cases, risk = 24, case-fatality rate = 57, deaths = 164). Reducing the impact of indigenous foodborne disease is mainly dependent on controlling the contamination of chicken
AEGIS: Extinction and Star Formation Tracers from Line Emission
Strong nebular emission lines are a sensitive probe of star formation and
extinction in galaxies, and the [O II] line detects star forming populations
out to z>1. However, star formation rates from emission lines depend on
calibration of extinction and the [O II]/H-alpha line ratio, and separating
star formation from AGN emission. We use calibrated line luminosities from the
DEEP2 survey and Palomar K magnitudes to show that the behavior of emission
line ratios depends on galaxy magnitude and color. For galaxies on the blue
side of the color bimodality, the vast majority show emission signatures of
star formation, and there are strong correlations of extinction and [O
II]/H-alpha with restframe H magnitude. The conversion of [O II] to
extinction-corrected H-alpha and thus to star formation rate has a significant
slope with M_H, 0.23 dex/mag. Red galaxies with emission lines have a much
higher scatter in their line ratios, and more than half show AGN signatures. We
use 24 micron fluxes from Spitzer/MIPS to demonstrate the differing populations
probed by nebular emission and by mid-IR luminosity. Although extinction is
correlated with luminosity, 98% of IR-luminous galaxies at z~1 are still
detected in the [O II] line. Mid-IR detected galaxies are mostly bright and
intermediate color, while fainter, bluer galaxies with high [O II] luminosity
are rarely detected at 24 microns.Comment: 4 pages, 3 figures. Accepted for publication in ApJ Letters AEGIS
special editio
Kinematic Effects of Tidal Interaction on Galaxy Rotation Curves
We use self-consistent N-body models, in conjunction with models of test
particles moving in galaxy potentials, to explore the initial effects of
interactions on the rotation curves of spiral galaxies. Using nearly
self-consistent disk/bulge/halo galaxy models (Kuijken & Dubinski 1995), we
simulate the first pass of galaxies on nearly parabolic orbits; we vary orbit
inclinations, galaxy halo masses and impact parameters. For each simulation, we
mimic observed rotation curves of the model galaxies. Transient
interaction-induced features of the curves include distinctly rising or falling
profiles at large radii and pronounced bumps in the central regions. Remarkably
similar features occur in our statistical sample of optical emission-line
rotation curves of spiral galaxies in tight pairs and n-tuples.Comment: 9 pages, 2 figures, accepted for publication in ApJ Letter
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