49,337 research outputs found
Mediators of mechanotransduction between bone cells
Mechanical forces are known to regulate the function of tissues in the body, including bone. Bone adapts to its mechanical environment by altering its shape and increasing its size in response to increases in mechanical load associated with exercise, and by decreasing its size in response to decreases in mechanical load associated with microgravity or prolonged bed rest. Changes in bone size and shape are produced by a cooperative action of two main types of the bone cells - osteoclasts that destroy bone and osteoblasts that build bone. These cell types come from different developmental origins, and vary greatly in their characteristics, such as size, shape, and expression of receptor subtypes, which potentially may affect their responses to mechanical stimuli. The objective of this study is to compare the responses of osteoclasts and osteoblasts to mechanical stimulation.
This study has allowed us to conclude the following:
1. A mediator is released from a single source cell.
2. The response to the mediator changes with distance.
3. The value of the apparent diffusion coeficient increases with distance.
4. A plausible proposed mechanism is that ATP is released and degrades to ADP.
5. Future experiments are required to confim that ATP is the mediator as suggested
Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with WMAP and the COSMOSOMAS Experiment
We present evidence for anomalous microwave emission (AME) in the Pleiades
reflection nebula, using data from the seven-year release of the Wilkinson
Microwave Anisotropy Probe (WMAP) and from the COSMOSOMAS experiment. The flux
integrated in a 1-degree radius around R.A.=56.24^{\circ}, Dec.=23.78^{\circ}
(J2000) is 2.15 +/- 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data
show no significant emission, but allow to set upper limits of 0.94 and 1.58 Jy
(99.7% C.L.) respectively at 10.9 and 14.7 GHz, which are crucial to pin down
the AME spectrum at these frequencies, and to discard any other emission
mechanisms which could have an important contribution to the signal detected at
22.8 GHz. We estimate the expected level of free-free emission from an
extinction-corrected H-alpha template, while the thermal dust emission is
characterized from infrared DIRBE data and extrapolated to microwave
frequencies. When we deduct the contribution from these two components at 22.8
GHz the residual flux, associated with AME, is 2.12 +/- 0.12 Jy (17.7-sigma).
The spectral energy distribution from 10 to 60 GHz can be accurately fitted
with a model of electric dipole emission from small spinning dust grains
distributed in two separated phases of molecular and atomic gas, respectively.
The dust emissivity, calculated by correlating the 22.8 GHz data with
100-micron data, is found to be 4.36+/-0.17 muK/MJy/sr, a value that is rather
low compared with typical values in dust clouds. The physical properties of the
Pleiades nebula indicate that this is indeed a much less opaque object than
others were AME has usually been detected. This fact, together with the broad
knowledge of the stellar content of this region, provides an excellent testbed
for AME characterization in physical conditions different from those generally
explored up to now.Comment: Accepted for publication in ApJ. 12 pages, 8 figure
A Layman's guide to SUSY GUTs
The determination of the most straightforward evidence for the existence of
the Superworld requires a guide for non-experts (especially experimental
physicists) for them to make their own judgement on the value of such
predictions. For this purpose we review the most basic results of Super-Grand
unification in a simple and clear way. We focus the attention on two specific
models and their predictions. These two models represent an example of a direct
comparison between a traditional unified-theory and a string-inspired approach
to the solution of the many open problems of the Standard Model. We emphasize
that viable models must satisfy {\em all} available experimental constraints
and be as simple as theoretically possible. The two well defined supergravity
models, and , can be described in terms of only a few
parameters (five and three respectively) instead of the more than twenty needed
in the MSSM model, \ie, the Minimal Supersymmetric extension of the Standard
Model. A case of special interest is the strict no-scale
supergravity where all predictions depend on only one parameter (plus the
top-quark mass). A general consequence of these analyses is that supersymmetric
particles can be at the verge of discovery, lurking around the corner at
present and near future facilities. This review should help anyone distinguish
between well motivated predictions and predictions based on arbitrary choices
of parameters in undefined models.Comment: 25 pages, Latex, 11 figures (not included), CERN-TH.7077/93,
CTP-TAMU-65/93. A complete ps file (1.31MB) with embedded figures is
available by request from [email protected]
Threading the spindle: a geometric study of chiral liquid crystal polymer microparticles
Polymeric particles are strong candidates for designing artificial materials
capable of emulating the complex twisting-based functionality observed in
biological systems. In this letter, we provide the first detailed investigation
of the swelling behavior of bipolar polymer liquid crystalline microparticles.
Deswelling from the spherical bipolar configuration causes the microparticle to
contract anisotropically and twist in the process, resulting in a twisted
spindle shaped structure. We propose a model to describe the observed spiral
patterns and twisting behavior
Spatially resolved kinematics, galactic wind, and quenching of star formation in the luminous infrared galaxy IRAS F11506-3851
We present a multi-wavelength integral field spectroscopic study of the low-z
LIRG IRAS F11506-3851, on the basis of VIMOS and SINFONI (ESO-VLT)
observations. The morphology and the 2D kinematics of the gaseous (neutral and
ionized) and stellar components have been mapped using the NaD doublet, the
H line, and the near-IR CO(2-0) and CO(3-1) bands. The kinematics of
the ionized gas and the stars are dominated by rotation, with large observed
velocity amplitudes and centrally peaked velocity dispersion maps. The stars
lag behind the warm gas and represent a dynamically hotter system, as indicated
by the observed dynamical ratios. Thanks to these IFS data we have disentangled
the contribution of the stars and the ISM to the NaD feature, finding that it
is dominated by the absorption of neutral gas clouds in the ISM. The neutral
gas 2D kinematics shows a complex structure dominated by two components. On the
one hand, the thick slowly rotating disk lags significantly compared to the
ionized gas and the stars, with an irregular and off-center velocity dispersion
map. On the other hand, a kpc-scale neutral gas outflow is observed along the
semi-minor axis of the galaxy, as revealed by large blueshifted velocities
(30-154 km/s). We derive an outflowing mass rate in neutral gas of about 48
/yr. Although this implies a global mass loading factor of
1.4, the 2D distribution of the ongoing SF suggests a much larger value of mass
loading factor associated with the inner regions (R200 pc), where the
current SF represents only 3 percent of the total. All together these results
strongly suggest that we are witnessing (nuclear) quenching due to SF feedback
in IRAS F11506-3851. However, the relatively large mass of molecular gas
detected in the nuclear region via the H2 1-0 S(1) line suggests that further
episodes of SF may take place again
Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae
The HAWC Gamma-Ray Observatory has reported the discovery of TeV gamma-ray
emission extending several degrees around the positions of Geminga and B0656+14
pulsars. Assuming these gamma rays are produced by inverse Compton scattering
off low-energy photons in electron halos around the pulsars, we determine the
diffusion of electrons and positrons in the local interstellar medium. We will
present the morphological and spectral studies of these two VHE gamma-ray
sources and the derived positron spectrum at Earth.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017),
Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution
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