847 research outputs found
Strategies for articular cartilage repair and regeneration
Articular cartilage is an avascular tissue, with limited ability to repair and self-renew. Defects in articular cartilage can induce debilitating degenerative joint diseases such as osteoarthritis. Currently, clinical treatments have limited ability to repair, for they often result in the formation of mechanically inferior cartilage. In this review, we discuss the factors that affect cartilage homeostasis and function, and describe the emerging regenerative approaches that are informing the future treatment options
On-Line Structure Detection and Parameter Estimation with Exponential Windowing for Nonlinear Systems
A new recursive orthogonal estimation algorithm is derived which updates both the model structure and the parameters of nonlinear models on-line. Techniques developed for linear systems are not generally suitable when nonlinear models are considered because the complexity of nonlinear systems and the demands of recursive processing make on-line structure detection much more difficult..........
Growth and properties of ferromagnetic In(1-x)Mn(x)Sb alloys
We discuss a new narrow-gap ferromagnetic (FM) semiconductor alloy,
In(1-x)Mn(x)Sb, and its growth by low-temperature molecular-beam epitaxy. The
magnetic properties were investigated by direct magnetization measurements,
electrical transport, magnetic circular dichroism, and the magneto-optical Kerr
effect. These data clearly indicate that In(1-x)Mn(x)Sb possesses all the
attributes of a system with carrier-mediated FM interactions, including
well-defined hysteresis loops, a cusp in the temperature dependence of the
resistivity, strong negative magnetoresistance, and a large anomalous Hall
effect. The Curie temperatures in samples investigated thus far range up to 8.5
K, which are consistent with a mean-field-theory simulation of the
carrier-induced ferromagnetism based on the 8-band effective band-orbital
method.Comment: Invited talk at 11th International Conference on Narrow Gap
Semiconductors, Buffalo, New York, U.S.A., June 16 - 20, 200
An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field-South: The AGN Fraction and X-Ray Properties of Submillimeter Galaxies
The large gas and dust reservoirs of submillimeter galaxies (SMGs) could potentially provide ample fuel to trigger an active galactic nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with Atacama Large Millimeter/submillimeter Array (ALMA) and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submillimeter-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey. We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which eight were identified as AGNs using several techniques that enable cross-checking. The other two X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their star formation activity. Six of the eight SMG-AGNs are moderately/highly absorbed, with N H > 1023 cm?2. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of for AGNs with rest-frame 0.5-8?keV absorption-corrected luminosity ?7.8 × 1042?erg?s?1; we provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and we found four potential SMG-AGNs in our stacking sample
Betacellulin drives therapy resistance in glioblastoma
Background: The transcription factor signal transducer and activator of transcription 3 (STAT3) drives progression in glioblastoma (GBM), suggesting STAT3 as a therapeutic target. Surprisingly however, GBM cells generally show primary resistance to STAT3 blockade. Methods: Human glioblastoma cell lines LN229, U87, SF767, and U373, and patient-derived xenografts (PDXs) GBM8 and GBM43 were used to evaluate epidermal growth factor receptor (EGFR) activation during STAT3 inhibition. Protein and gene expression experiments, protein stability assays, cytokine arrays, phospho-tyrosine arrays and EGFR-ligand protein arrays were performed on STAT3 inhibitor-treated cells. To evaluate antitumor activity, we administered a betacellulin (BTC)-neutralizing antibody alone and in combination with STAT3 inhibition. BTC is an EGFR ligand. We therefore treated mice with orthotopic xenografts using the third-generation EGFR inhibitor osimertinib, with or without STAT3 knockdown. Results: We demonstrate that both small-molecule inhibitors and knockdown of STAT3 led to expression and secretion of the EGFR ligand BTC, resulting in activation of EGFR and subsequent downstream phosphorylation of nuclear factor-kappaB (NF-κB). Neutralizing antibody against BTC abrogated activation of both EGFR and NF-κB in response to inhibition of STAT3; with combinatorial blockade of STAT3 and BTC inducing apoptosis in GBM cells. Blocking EGFR and STAT3 together inhibited tumor growth, improving survival in mice bearing orthotopic GBM PDXs in vivo. Conclusion: These data reveal a feedback loop among STAT3, EGFR, and NF-κB that mediates primary resistance to STAT3 blockade and suggest strategies for therapeutic intervention
Magnetic fields in cosmic particle acceleration sources
We review here some magnetic phenomena in astrophysical particle accelerators
associated with collisionless shocks in supernova remnants, radio galaxies and
clusters of galaxies. A specific feature is that the accelerated particles can
play an important role in magnetic field evolution in the objects. We discuss a
number of CR-driven, magnetic field amplification processes that are likely to
operate when diffusive shock acceleration (DSA) becomes efficient and
nonlinear. The turbulent magnetic fields produced by these processes determine
the maximum energies of accelerated particles and result in specific features
in the observed photon radiation of the sources. Equally important, magnetic
field amplification by the CR currents and pressure anisotropies may affect the
shocked gas temperatures and compression, both in the shock precursor and in
the downstream flow, if the shock is an efficient CR accelerator. Strong
fluctuations of the magnetic field on scales above the radiation formation
length in the shock vicinity result in intermittent structures observable in
synchrotron emission images. Resonant and non-resonant CR streaming
instabilities in the shock precursor can generate mesoscale magnetic fields
with scale-sizes comparable to supernova remnants and even superbubbles. This
opens the possibility that magnetic fields in the earliest galaxies were
produced by the first generation Population III supernova remnants and by
clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review
Thermodynamic Measurements in a Strongly Interacting Fermi Gas
We conduct a series of measurements on the thermodynamic properties of an
optically-trapped strongly interacting Fermi gas, including the energy ,
entropy , and sound velocity . Our model-independent measurements of
and enable a precision study of the finite temperature thermodynamics. The
data are directly compared to several recent predictions. The
temperature in both the superfluid and normal fluid regime is obtained from the
fundamental thermodynamic relation by parameterizing
the data. Our data are also used to experimentally calibrate the
endpoint temperatures obtained for adiabatic sweeps of the magnetic field
between the ideal and strongly interacting regimes. This enables the first
experimental calibration of the temperature scale used in experiments on
fermionic pair condensation. Our calibration shows that the ideal gas
temperature measured for the onset of pair condensation corresponds closely to
the critical temperature estimated in the strongly interacting regime from the
fits to our data. The results are in very good agreement with recent
predictions. Finally, using universal thermodynamic relations, we estimate the
chemical potential and heat capacity of the trapped gas from the data.Comment: 29 pages, 12 figures. To appear in JLTP online, and in the January,
2009 volum
Various correlations in a Heisenberg XXZ spin chain both in thermal equilibrium and under the intrinsic decoherence
In this paper we discuss various correlations measured by the concurrence
(C), classical correlation (CC), quantum discord (QD), and geometric measure of
discord (GMD) in a two-qubit Heisenberg XXZ spin chain in the presence of
external magnetic field and Dzyaloshinskii-Moriya (DM) anisotropic
antisymmetric interaction. Based on the analytically derived expressions for
the correlations for the cases of thermal equilibrium and the inclusion of
intrinsic decoherence, we discuss and compare the effects of various system
parameters on the correlations in different cases. The results show that the
anisotropy Jz is considerably crucial for the correlations in thermal
equilibrium at zero temperature limit but ineffective under the consideration
of the intrinsic decoherence, and these quantities decrease as temperature T
rises on the whole. Besides, J turned out to be constructive, but B be
detrimental in the manipulation and control of various quantities both in
thermal equilibrium and under the intrinsic decoherence which can be avoided by
tuning other system parameters, while D is constructive in thermal equilibrium,
but destructive in the case of intrinsic decoherence in general. In addition,
for the initial state , all
the correlations except the CC, exhibit a damping oscillation to a stable value
larger than zero following the time, while for the initial state , all the correlations monotonously
decrease, but CC still remains maximum. Moreover, there is not a definite
ordering of these quantities in thermal equilibrium, whereas there is a
descending order of the CC, C, GMD and QD under the intrinsic decoherence with
a nonnull B when the initial state is .Comment: 8 pages, 7 figure
Origins of the Ambient Solar Wind: Implications for Space Weather
The Sun's outer atmosphere is heated to temperatures of millions of degrees,
and solar plasma flows out into interplanetary space at supersonic speeds. This
paper reviews our current understanding of these interrelated problems: coronal
heating and the acceleration of the ambient solar wind. We also discuss where
the community stands in its ability to forecast how variations in the solar
wind (i.e., fast and slow wind streams) impact the Earth. Although the last few
decades have seen significant progress in observations and modeling, we still
do not have a complete understanding of the relevant physical processes, nor do
we have a quantitatively precise census of which coronal structures contribute
to specific types of solar wind. Fast streams are known to be connected to the
central regions of large coronal holes. Slow streams, however, appear to come
from a wide range of sources, including streamers, pseudostreamers, coronal
loops, active regions, and coronal hole boundaries. Complicating our
understanding even more is the fact that processes such as turbulence,
stream-stream interactions, and Coulomb collisions can make it difficult to
unambiguously map a parcel measured at 1 AU back down to its coronal source. We
also review recent progress -- in theoretical modeling, observational data
analysis, and forecasting techniques that sit at the interface between data and
theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue
connected with a 2016 ISSI workshop on "The Scientific Foundations of Space
Weather." 44 pages, 9 figure
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
- …