13,618 research outputs found
Multiple Equilibria in a Single-Column Model of the Tropical Atmosphere
A single-column model run under the weak temperature gradient approximation,
a parameterization of large-scale dynamics appropriate for the tropical
atmosphere, is shown to have multiple stable equilibria. Under conditions
permitting persistent deep convection, the model has a statistically steady
state in which such convection occurs, as well as an extremely dry state in
which convection does not occur. Which state is reached depends on the initial
moisture profile.Comment: Submitted to Geophysical Research Letter
Bisphosphonate's and Intermittent Parathyroid Hormone's Effect on Human Spinal Fusion: A Systematic Review of the Literature.
There has been a conscious effort to address osteoporosis in the aging population. As bisphosphonate and intermittent parathyroid hormone (PTH) therapy become more widely prescribed to treat osteoporosis, it is important to understand their effects on other physiologic processes, particularly the impact on spinal fusion. Despite early animal model studies and more recent clinical studies, the impact of these medications on spinal fusion is not fully understood. Previous animal studies suggest that bisphosphonate therapy resulted in inhibition of fusion mass with impeded maturity and an unknown effect on biomechanical strength. Prior animal studies demonstrate an improved fusion rate and fusion mass microstructure with the use of intermittent PTH. The purpose of this study was to determine if bisphosphonates and intermittent PTH treatment have impact on human spinal fusion. A systematic review of the literature published between 1980 and 2015 was conducted using major electronic databases. Studies reporting outcomes of human subjects undergoing 1, 2, or 3-level spinal fusion while receiving bisphosphonates and/or intermittent PTH treatment were included. The results of relevant human studies were analyzed for consensus on the effects of these medications in regards to spinal fusion. There were nine human studies evaluating the impact of these medications on spinal fusion. Improved fusion rates were noted in patients receiving bisphosphonates compared to control groups, and greater fusion rates in patients receiving PTH compared to control groups. Prior studies involving animal models found an improved fusion rate and fusion mass microstructure with the use of intermittent PTH. No significant complications were demonstrated in any study included in the analysis. Bisphosphonate use in humans may not be a deterrent to spinal fusion. Intermittent parathyroid use has shown early promise to increase fusion mass in both animal and human studies but further studies are needed to support routine use
Calorimetric Investigation of CeRu2Ge2 up to 8 GPa
We have developed a calorimeter able to give a qualitative picture of the
specific heat of a sample under high pressure up to approximately 10 GPa. The
principle of ac-calorimetry was adapted to the conditions in a high pressure
clamp. The performance of this technique was successfully tested with the
measurement of the specific heat of CeRu2Ge2 in the temperature range 1.5
K<T<12 K. The phase diagram of its magnetic phases is consistent with previous
transport measurements.Comment: 5 pages, 4 figure
Recommended from our members
Biomarkers and overall survival in patients with advanced hepatocellular carcinoma treated with TGF-βRI inhibitor galunisertib.
BackgroundTransforming growth factor beta (TGF-β) signalling is involved in the development of hepatocellular carcinoma (HCC). We followed changes in biomarkers during treatment of patients with HCC with the TGF-βRI/ALK5 inhibitor galunisertib.MethodsThis phase 2 study (NCT01246986) enrolled second-line patients with advanced HCC into one of two cohorts of baseline serum alpha-fetoprotein (AFP): Part A (AFP ≥1.5x ULN) or Part B (AFP <1.5x ULN). Baseline and postbaseline levels of AFP, TGF-β1, E-cadherin, selected miRNAs, and other plasma proteins were monitored.ResultsThe study enrolled 149 patients (Part A, 109; Part B, 40). Median OS was 7.3 months in Part A and 16.8 months in Part B. Baseline AFP, TGF-β1, E-cadherin, and an additional 16 plasma proteins (such as M-CSF, IL-6, ErbB3, ANG-2, neuropilin-1, MIP-3 alpha, KIM-1, uPA, IL-8, TIMP-1, ICAM-1, Apo A-1, CA-125, osteopontin, tetranectin, and IGFBP-1) were found to correlate with OS. In addition, a range of miRs were found to be associated with OS. In AFP responders (21% of patients in Part A with decrease of >20% from baseline) versus non-responders, median OS was 21.5 months versus 6.8 months (p = 0.0015). In TGF-β1 responders (51% of all patients) versus non-responders, median OS was 11.2 months versus 5.3 months (p = 0.0036).ConclusionsConsistent with previous findings, both baseline levels and changes from baseline of circulating AFP and TGF-β1 function as prognostic indicators of survival. Future trials are needed to confirm and extend these results
Controlling laser spectra in a phaseonium photonic crystal using maser
We study the control of quantum resonances in photonic crystals with
electromagnetically induced transparency driven by microwave field. In addition
to the control laser, the intensity and phase of the maser can alter the
transmission and reflection spectra in interesting ways, producing hyperfine
resonances through the combined effects of multiple scattering in the
superstructure.Comment: 7 pages, 4 figure
Compressibility of lithium hexafluorophosphate solutions in two carbonate solvents
Speed-of-sound measurements are performed to establish how the isentropic bulk modulus Ks of the electrolyte system comprising lithium hexafluorophospate (LiPF6) in blends of propylene carbonate (PC) and ethyl methyl carbonate (EMC) varies with salt molality m, mass fraction of PC in the PC:EMC cosolvent f, and temperature T. Bulk moduli are calculated by combining acoustic time-of-flight data between parallel walls of a liquid-filled cuvette with densitometric data for a sequence of binary and ternary salt solutions. Correlations are presented to yield Ks (m, f, T) accurately for nine compositions spanning the range m = 0–2 mol kg–1 and f = 0–1, at temperatures T ranging from 283.15 to 313.15 K. Electrolyte compressibility varies most with solvent ratio, followed by salt content and temperature, with Ks ranging from 1 to 3 GPa. Composition-dependent acoustical properties elucidate the nature of speciation and solvation states in bulk electrolytes, and could be useful to identify the features of individual phases within solution-permeated porous electrodes
The gas density around SN 1006
The density of the ambient medium where the supernova remnant evolves is a
relevant parameter for its hydrodynamical evolution, for the mechanism of
particle acceleration, and for the emission at TeV energies. Using XMM-Newton
X-ray observations, we present a study of the ambient medium density of the
historical supernova remnant SN 1006. We modelled the post-shock thermal
emission to constrain the ambient medium density. Our study is focused on the
North-West and the South-East rims of the remnant, where the thermal emission
dominates. We used a plane-parallel shock plasma model plus another component
for the ejecta that are not negligible in the regions of our study. The
importance of the synchrotron component is also studied. In order to improve
statistics, we combined several observations of the remnant.
The density found in the South-East rim is low, roughly 0.05 cm-3, and seems
to be representative of the rest of the remnant. However, in the North-West rim
(close to the bright optical filament), the density is significantly higher
(about 0.15-0.25 cm-3). This confirms a picture of SN 1006 evolving in a
tenuous ambient medium, except in the North-West where the remnant has recently
encountered a denser region.
A density this low is compatible with the non-detection of the remnant by the
HESS gamma-ray observatory. The lower density in the South-East implies a
higher shock speed of 4900 km/s, higher than that of 2890 km/s measured in the
North-West. This new estimate of the velocity could increase the maximum energy
that accelerated particles can reach to energies of about 1 PeV.Comment: 8 pages, 4 figures, accepted for publication in A&A, Figure 3
correcte
X-ray Line Emission from Supernova Ejecta Fragments
We show that fast moving isolated fragments of a supernova ejecta composed of
heavy elements should be sources of K_alpha X-ray line emission of the SN
nuclear-processed products. Supersonic motion of the knots in the intercloud
medium will result in a bow-shock/knot-shock structure creation. Fast
nonthermal particles accelerated by Fermi mechanism in the MHD collisionless
shocks diffuse through a cold metallic knot, producing the X-ray emission. We
modeled the X-ray emission from a fast moving knot of a mass M ~ 10^{-3} \Msun,
containing about 10^{-4} \Msun of any metal impurities like Si, S, Ar, Ca, Fe.
The fast electron distribution was simulated using the kinetic description. We
accounted for nonlinear effects of shock modification by the nonthermal
particles pressure. The K_alpha line emission is most prominent for the knots
propagating through dense molecular clouds. The bow shock should be a radiative
wave with a prominent infrared and optical emission. In that case the X-ray
line spectrum of an ejecta fragment is dominated by the low ionization states
of the ions with the metal line luminosities reaching L_x \gsim 10^{31} erg/s.
High resolution XMM and Chandra observations are able to detect the line
emission from the knots at distances up to a few kpcs. The knots propagating
through tenuous interstellar matter are of much fainter surface brightness but
long-lived. The line spectra with higher ionization states of the ions are
expected in that case. Compact dense knots could be opaque for some X-ray lines
and that is important for their abundances interpretation. The ensemble of
unresolved knots of galactic supernovae can contribute substantially to the
iron line emission observed from the Galactic Center region and the Galactic
ridge.Comment: 9 pages, 1 figure; Astronomy and Astrophysics (in press
Effects of Neutron Irradiation on Carbon Doped MgB2 Wire Segments
We have studied the evolution of superconducting and normal state properties
of neutron irradiated Mg(BC) wire segments as a function
of post exposure annealing time and temperature. The initial fluence fully
suppressed superconductivity and resulted in an anisotropic expansion of the
unit cell. Superconductivity was restored by post-exposure annealing. The upper
critical field, H(T=0), approximately scales with T starting with an
undamaged T near 37 K and H(T=0) near 32 T. Up to an annealing
temperature of 400 C the recovery of T tends to coincide with a
decrease in the normal state resistivity and a systematic recovery of the
lattice parameters. Above 400 C a decrease in order along the c- direction
coincides with an increase in resistivity, but no apparent change in the
evolution of T and H. To first order, it appears that carbon doping
and neutron damaging effect the superconducting properties of MgB
independently
- …