1,436 research outputs found
Review: emerging concepts in the pathogenesis of tendinopathy
Tendinopathy is a common clinical problem and has a significant disease burden attached, not only in terms of health care costs, but also for patients directly in terms of time off work and impact upon quality of life. Controversy surrounds the pathogenesis of tendinopathy, however the recent systematic analysis of the evidence has demonstrated that many of the claims of an absence of inflammation in tendinopathy were more based around belief than robust scientific data. This review is a summary of the emerging research in this topical area, with a particular focus on the role of neuronal regulation and inflammation in tendinopathy
Stringy Effects During Inflation and Reheating
We consider inflationary cosmology in the context of string compactifications
with multiple throats. In scenarios where the warping differs significantly
between throats, string and Kaluza-Klein physics can generate potentially
observable corrections to the cosmology of inflation and reheating. First we
demonstrate that a very low string scale in the ground state compactification
is incompatible with a high Hubble scale during inflation, and we propose that
the compactification geometry is altered during inflation. In this
configuration, the lowest scale is just above the Hubble scale, which is
compatible with effective field theory but still leads to potentially
observable CMB corrections. Also in the appropriate region of parameter space,
we find that reheating leads to a phase of long open strings in the Standard
Model sector (before the usual radiation-dominated phase). We sketch the
cosmology of the long string phase and we discuss possible observational
consequences.Comment: 33pp, RevTeX4, v2. minor changes, added ref
Analysis of Carbon across the Cenomanian-Turonian Boundary
Following the work of Wolbach et al., who studied reduced carbon across the 65 Ma-old Cretaceous-Tertiary extinction boundary, a study was conducted to analyze reduced carbon across the 92 Ma-old Cenomanian-Turonian (C-T) extinction horizon, in the hope that evidence could be gathered which might support a particular mechanism for these extinction events. Currently two sample sites are being analyzed for reduced carbon content at the C-T boundary: Red Wash, New Mexico and Chispa Summit, Texas. Both sample sites are from the Western Interior Basin of North America. During the time of the extinctions 92 million years ago, the basin was an inland sea. Preliminary data suggest a decrease in the amount of carbonaceous residue found at the boundary at both sample sites. This would indicate that the extinction event was not rapid, as lower amounts of reduced carbon are generally more characteristic of extinctions caused by slow changes in climate vs sudden changes caused by catastrophic events. Slow climate changes would allow microorganisms time to digest (oxidize) the carbon in dead plankton before sedimentation, thus decreasing the amount of reduced carbon preserved in the rock. A mechanism for the C-T extinctions consistent with previous data as well as preliminary results obtained in this study is the opening of deep sea fissures at the ocean floor, increasing certain metal concentrations in seawater, and, more importantly, increasing water temperatures. Plankton unable to adapt to these new conditions would become extinct
Seasonal Climatology of Hydrographic Conditions in the Upwelling Region Off Northern Chile
Over 30 years of hydrographic data from the northern Chile (18 degreesS-24 degreesS) upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore. The data are interpolated to a grid with sufficient spatial resolution to preserve cross-shelf gradients and then presented as means within four seasons: austral winter (July-September), spring (October-December), summer (January-March), and fall (April-June). Climatological monthly wind forcing, surface temperature, and sea level from three coastal stations indicate equatorward (upwelling favorable) winds throughout the year, weakest in the north. Seasonal maximum alongshore wind stress is in late spring and summer (December-March). Major water masses of the region are identified in climatological T-S plots and their sources and implied circulation discussed. Surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year-round, strongest in summer and weakest in winter, bringing relatively fresh water to the surface nearshore. Surface geostrophic flow nearshore is equatorward throughout the year. During summer, an anticyclonic circulation feature in the north which extends to at least 200 m depth is evident in geopotential anomaly and in both temperature and geopotential variance fields. Subsurface fields indicate generally poleward flow throughout the year, strongest in an undercurrent near the coast. This undercurrent is strongest in summer and most persistent and organized in the south (south of 21 degreesS), A subsurface oxygen minimum, centered at similar to 250 m, is strongest at lower latitudes. Low-salinity subsurface water intrudes into the study area near 100 m, predominantly in offshore regions, strongest during summer and fall and in the southernmost portion of the region. The climatological fields are compared to features off Baja within the somewhat analogous California Current and to measurements from higher latitudes within the Chile-Peru Current system
Satellite-Measured Chlorophyll and Temperature Variability Off Northern Chile During the 1996-1998 La Niña and El Niño
Time series of satellite measurements are used to describe patterns of surface temperature and chlorophyll associated with the 1996 cold La Nina phase and the 1997-1998 warm El Nino phase of the El Nino - Southern Oscillation cycle in the upwelling region off northern Chile. Surface temperature data are available through the entire study period. Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data first became available in September 1997 during a relaxation in El Nino conditions identified by in situ hydrographic data. Over the time period of coincident satellite data, chlorophyll patterns closely track surface temperature patterns. Increases both in nearshore chlorophyll concentration and in cross-shelf extension of elevated concentrations are associated with decreased coastal temperatures during both the relaxation in El Nino conditions in September-November 1997 and the recovery from EI Nino conditions after March 1998. Between these two periods during austral summer (December 1997 to March 1998) and maximum El Nino temperature anomalies, temperature patterns normally associated with upwelling were absent and chlorophyll concentrations were minimal. Cross-shelf chlorophyll distributions appear to be modulated by surface temperature frontal zones and are positively correlated with a satellite-derived upwelling index. Frontal zone patterns and the upwelling index in 1996 imply an austral summer nearshore chlorophyll maximum, consistent with SeaWiFS data from I 1998-1999, after the El Nino. SeaWiFS retrievals in the data set used here are higher than in situ measurements by a factor of 2-4; however, consistency in the offset suggests relative patterns are valid
Critical collapse and the primordial black hole initial mass function
It has normally been assumed that primordial black holes (PBHs) always form
with mass approximately equal to the mass contained within the horizon at that
time. Recent work studying the application of critical phenomena in
gravitational collapse to PBH formation has shown that in fact, at a fixed
time, PBHs with a range of masses are formed. When calculating the PBH initial
mass function it is usually assumed that all PBHs form at the same horizon
mass. It is not clear, however, that it is consistent to consider the spread in
the mass of PBHs formed at a single horizon mass, whilst neglecting the range
of horizon masses at which PBHs can form. We use the excursion set formalism to
compute the PBH initial mass function, allowing for PBH formation at a range of
horizon masses, for two forms of the density perturbation spectrum. First we
examine power-law spectra with , where PBHs form on small scales. We find
that, in the limit where the number of PBHs formed is small enough to satisfy
the observational constraints on their initial abundance, the mass function
approaches that found by Niemeyer and Jedamzik under the assumption that all
PBHs form at a single horizon mass. Second, we consider a flat perturbation
spectrum with a spike at a scale corresponding to horizon mass , and compare the resulting PBH mass function with that of the MACHOs
(MAssive Compact Halo Objects) detected by microlensing observations. The
predicted mass spectrum appears significantly wider than the steeply-falling
spectrum found observationally.Comment: 8 pages RevTeX file with ten figures incorporated (uses RevTeX and
epsf). Minor changes to dicussion onl
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