269 research outputs found
The initial conditions of the universe: how much isocurvature is allowed?
We investigate the constraints imposed by the current data on correlated
mixtures of adiabatic and non-adiabatic primordial perturbations. We discover
subtle flat directions in parameter space that tolerate large (~60%)
contributions of non-adiabatic fluctuations. In particular, larger values of
the baryon density and a spectral tilt are allowed. The cancellations in the
degenerate directions are explored and the role of priors elucidated.Comment: 4 pages, 4 figures. Submitted to PR
A Histological Assessment of the Mechanism of Early-Stage Healing of a Biphasic Calcium Phosphate in an \u3cem\u3eIn vivo\u3c/em\u3e Rabbit Model
The healing mechanism of osteoconductive biphasic calcium phosphate granules was investigated by a histological assessment of early-stage bone deposition and remodeling. The deposition of de novo bone on the scaffold granules was observed to initiate at the defect periphery by week one and in the bulk of the defect incorporating the granules by week four. New bone tissue was deposited in the space provided by the macroporosity and was observed in direct apposition to the implanted material confirming the bioactivity of the biphasic calcium phosphate. The granules were removed through a cell-mediated resorption process that was observed to begin as early as week two following surgery. Mature lamellar bone, fatty bone marrow, and vascularization was observed throughout the bulk of the defect with the cortical shell healed by week twelve. This healing mechanism was found to balance bone formation and implant resorption resulting in complete healing of the corticocancellous defect in the rabbit femoral condyle
CMBPol Mission Concept Study: A Mission to Map our Origins
Quantum mechanical metric fluctuations during an early inflationary phase of
the universe leave a characteristic imprint in the polarization of the cosmic
microwave background (CMB). The amplitude of this signal depends on the energy
scale at which inflation occurred. Detailed observations by a dedicated
satellite mission (CMBPol) therefore provide information about energy scales as
high as GeV, twelve orders of magnitude greater than the highest
energies accessible to particle accelerators, and probe the earliest moments in
the history of the universe. This summary provides an overview of a set of
studies exploring the scientific payoff of CMBPol in diverse areas of modern
cosmology, such as the physics of inflation, gravitational lensing and cosmic
reionization, as well as foreground science and removal .Comment: 6 pages, 3 figure
Constraints on isocurvature models from the WMAP first-year data
We investigate the constraints imposed by the first-year WMAP CMB data
extended to higher multipole by data from ACBAR, BOOMERANG, CBI and the VSA and
by the LSS data from the 2dF galaxy redshift survey on the possible amplitude
of primordial isocurvature modes. A flat universe with CDM and Lambda is
assumed, and the baryon, CDM (CI), and neutrino density (NID) and velocity
(NIV) isocurvature modes are considered. Constraints on the allowed
isocurvature contributions are established from the data for various
combinations of the adiabatic mode and one, two, and three isocurvature modes,
with intermode cross-correlations allowed. Since baryon and CDM isocurvature
are observationally virtually indistinguishable, these modes are not considered
separately. We find that when just a single isocurvature mode is added, the
present data allows an isocurvature fraction as large as 13+-6, 7+-4, and 13+-7
percent for adiabatic plus the CI, NID, and NIV modes, respectively. When two
isocurvature modes plus the adiabatic mode and cross-correlations are allowed,
these percentages rise to 47+-16, 34+-12, and 44+-12 for the combinations
CI+NID, CI+NIV, and NID+NIV, respectively. Finally, when all three isocurvature
modes and cross-correlations are allowed, the admissible isocurvature fraction
rises to 57+-9 per cent. The sensitivity of the results to the choice of prior
probability distribution is examined.Comment: 20 pages, 24 figures. Submitted to PR
Primary membranous glomerulonephritis with negative serum PLA2R in haemophilia : a successfully managed with rituximab : case report and review of the literature
Background: Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) cause a wide range of glomerular pathologies. In people with haemophilia, transfusion-associated infections with these viruses are common and definitive pathological diagnosis in this population is complicated by the difficulty of safely obtaining a renal biopsy. Membranous nephropathy (MN) is a common cause of adult onset nephrotic syndrome occurring in both primary and secondary forms. Primary MN is associated with podocyte autoantibodies, predominantly against phospholipase A2 receptor (PLA2R). Secondary disease is often associated with viral infection; however, infrequently with HIV or HCV. Distinguishing these entities from each other and other viral glomerular disease is vital as treatment strategies are disparate. Case presentation: We present the case of a 48-year-old man with moderate haemophilia A and well-controlled transfusion-associated HCV and HIV coinfection who presented with sudden onset nephrotic range proteinuria. Renal biopsy demonstrated grade two membranous nephropathy with associated negative serum PLA2R testing. Light and electron microscopic appearances were indeterminant of a primary or secondary cause. Given his extremely stable co-morbidities, treatment with rituximab and subsequent angiotensin receptor blockade was initiated for suspected primary MN and the patient had sustained resolution in proteinuria over the following 18 months. Subsequent testing demonstrated PLA2R positive glomerular immunohistochemistry despite multiple negative serum results. Conclusions: Pursuing histological diagnosis is important in complex cases of MN as the treatment strategies between primary and secondary vary significantly. Serum PLA2R testing alone may be insufficient in the presence of multiple potential causes of secondary MN
Spatial Correlations in the Helium-Ionizing Background
After quasars ionize intergalactic HeII at z~3, a large radiation field
builds up above the HeII ionization edge. Unlike the background responsible for
HI ionizations, this field should be highly variable, thanks to the scarcity of
bright quasars and the relatively short attenuation lengths (~50 Mpc) of these
high-energy photons. Recent observations of the HeII and HI Lyman-alpha forests
show that this background does indeed vary strongly, with substantial
fluctuations on scales as small as ~2 Mpc. Here we show that such spatial
fluctuation scales are naturally expected in any model in which the sources are
as rare as bright quasars, so long as the attenuation length is relatively
small. The correlation length itself is comparable to the attenuation length
(~10 Mpc) for the most plausible physical scenarios, but we find
order-of-magnitude fluctuations on all scales smaller than ~6 Mpc. Moreover,
aliasing along the one-dimensional skewers probed by the HeII and HI
Lyman-alpha forests exaggerates these variations, so that order-of-magnitude
fluctuations should be observed on all scales smaller than ~20 Mpc. Complex
radiative transfer is therefore not required to explain the observed
fluctuations, at least at the level of current data.Comment: 6 pages, 3 figures, submitted to Ap
Anti-glycoprotein VI mediated immune thrombocytopenia: An under-recognized and significant entity?
Idiopathic immune thrombocytopenia (ITP) is an autoimmune disorder characterized by relapsing/remitting thrombocytopenia. Bleeding complications are infrequent with platelet counts above 30x10(9)/L, and this level is commonly used as a threshold for treatment. The question of another/co-existent diagnosis or an alternate mechanism of platelet destruction arises when bleeding is experienced with platelet counts above this threshold. We report a case of anti-GPVI mediated ITP that was diagnosed following investigations performed to address this key clinical question. A patient with ITP experienced exaggerated bruising symptoms despite a platelet count of 91x10(9)/L. Platelet functional testing showed an isolated platelet defect of collagen-induced aggregation. Next generation sequencing excluded a pathogenic variant of GP6, and anti-GPVI antibodies that curtailed GPVI function were confirmed by extended platelet phenotyping. We propose that anti-GPVI mediated ITP may be under-recognized, and that inclusion of GPVI in antibody detection assays may improve their diagnostic utility and in turn, facilitate a better understanding of ITP pathophysiology and aid individualized treatment approaches
Power-law Template for Infrared Point-source Clustering
We perform a combined fit to angular power spectra of unresolved infrared (IR) point sources from the Planck
satellite (at 217, 353, 545, and 857 GHz, over angular scales 100 ⟠â ⟠2200), the Balloon-borne Large-Aperture
Submillimeter Telescope (BLAST; 250, 350, and 500ÎŒm; 1000 ⟠â ⟠9000), and from correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps. We find that the clustered power over the range of angular scales and frequencies considered is well fitted by a simple power law of the form C^(clust)_â â â^(-n) with n = 1.25 ± 0.06. While the IR sources are understood to lie at a range of redshifts, with a variety of dust properties, we find that the frequency dependence of the clustering power can be described by the square of a modified blackbody, Îœ^(ÎČ)B(Îœ, T_(eff)), with a single emissivity index ÎČ = 2.20 ± 0.07 and effective temperature T_(eff) = 9.7 K. Our predictions for the clustering amplitude are consistent with existing ACT and South Pole Telescope results at around 150 and 220 GHz, as is our prediction for the effective dust spectral index, which we find to be α_(150â220) = 3.68±0.07 between 150 and 220 GHz. Our constraints on the clustering shape and frequency dependence can be used to model the IR clustering as a contaminant in cosmic microwave background anisotropy measurements. The combined Planck and BLAST data also rule out a linear bias clustering model
CMBPol Mission Concept Study: Gravitational Lensing
Gravitational lensing of the cosmic microwave background by large-scale
structure in the late universe is both a source of cosmological information and
a potential contaminant of primordial gravity waves. Because lensing imprints
growth of structure in the late universe on the CMB, measurements of CMB
lensing will constrain parameters to which the CMB would not otherwise be
sensitive, such as neutrino mass.
If the instrumental noise is sufficiently small (<~ 5 uK-arcmin), the
gravitational lensing contribution to the large-scale B-mode will be the
limiting source of contamination when constraining a stochastic background of
gravity waves in the early universe, one of the most exciting prospects for
future CMB polarization experiments. High-sensitivity measurements of
small-scale B-modes can reduce this contamination through a lens reconstruction
technique that separates the lensing and primordial contributions to the B-mode
on large scales.
A fundamental design decision for a future CMB polarization experiment such
as CMBpol is whether to have coarse angular resolution so that only the
large-scale B-mode (and the large-scale E-mode from reionization) is measured,
or high resolution to additionally measure CMB lensing. The purpose of this
white paper is to evaluate the science case for CMB lensing in polarization:
constraints on cosmological parameters, increased sensitivity to the gravity
wave B-mode via lens reconstruction, expected level of contamination from
non-CMB foregrounds, and required control of beam systematics
BFORE: The B-mode Foreground Experiment
The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project
designed to make optimal use of the sub-orbital platform by concentrating on
three dust foreground bands (270, 350, and 600 GHz) that complement
ground-based cosmic microwave background (CMB) programs. BFORE will survey ~1/4
of the sky with 1.7 - 3.7 arcminute resolution, enabling precise
characterization of the Galactic dust that now limits constraints on inflation
from CMB B-mode polarization measurements. In addition, BFORE's combination of
frequency coverage, large survey area, and angular resolution enables science
far beyond the critical goal of measuring foregrounds. BFORE will constrain the
velocities of thousands of galaxy clusters, provide a new window on the cosmic
infrared background, and probe magnetic fields in the interstellar medium. We
review the BFORE science case, timeline, and instrument design, which is based
on a compact off-axis telescope coupled to >10,000 superconducting detectors.Comment: 7 pages, 4 figures, conference proceedings published in Journal of
Low Temperature Physic
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