115 research outputs found
Whole egg consumption and cortical bone in healthy children
Eggs contain bioactive compounds thought to benefit pediatric bone. This cross-sectional study shows a positive link between childhood egg intake and radius cortical bone. If randomized trials confirm our findings, incorporating eggs into children's diets could have a significant impact in preventing childhood fractures and reducing the risk of osteoporosis.
INTRODUCTION:
This study examined the relationships between egg consumption and cortical bone in children.
METHODS:
The cross-sectional study design included 294 9-13-year-old black and white males and females. Three-day diet records determined daily egg consumption. Peripheral quantitative computed tomography measured radius and tibia cortical bone. Body composition and biomarkers of bone turnover were assessed using dual-energy X-ray absorptiometry and ELISA, respectively.
RESULTS:
Egg intake was positively correlated with radius and tibia cortical bone mineral content (Ct.BMC), total bone area, cortical area, cortical thickness, periosteal circumference, and polar strength strain index in unadjusted models (r = 0.144-0.224, all P < 0.050). After adjusting for differences in race, sex, maturation, fat-free soft tissue mass (FFST), and protein intakes, tibia relationships were nullified; however, egg intake remained positively correlated with radius Ct.BMC (r = 0.138, P = 0.031). Egg intake positively correlated with total body bone mineral density, BMC, and bone area in the unadjusted models only (r = 0.119-0.224; all P < 0.050). After adjusting for covariates, egg intake was a positive predictor of radius FFST (β = 0.113, P < 0.050) and FFST was a positive predictor of Ct.BMC (β = 0.556, P < 0.050) in path analyses. There was a direct influence of egg on radius Ct.BMC (β = 0.099, P = 0.035), even after adjusting for the mediator, FFST (β = 0.137, P = 0.020). Egg intake was positively correlated with osteocalcin in both the unadjusted (P = 0.005) and adjusted (P = 0.049) models.
CONCLUSION:
If the positive influence of eggs on Ct.BMC observed in this study is confirmed through future randomized controlled trials, whole eggs may represent a viable strategy to promote pediatric bone development and prevent fractures
Particle Acceleration at Relativistic Shocks
I review the current status of Fermi acceleration theory at relativistic
shocks. I first discuss the relativistic shock jump conditions, then describe
the non-relativistic Fermi mechanism and the differences introduced by
relativistic flows. I present numerical calculations of the accelerated
particle spectrum, and examine the maximum energy attainable by this process. I
briefly consider the minimum energy for Fermi acceleration, and a possible
electron pre-acceleration mechanism.Comment: 17 pages, 4 figures. To appear in "Relativistic Flows in
Astrophysics", A.W. Guthmann, M. Georganopoulos, A. Marcowith and K.
Manolokou, eds., Lecture Notes in Pysics, Springer Verla
Three-Point Correlations in Weak Lensing Surveys: Model Predictions and Applications
We use the halo model of clustering to compute two- and three-point
correlation functions for weak lensing, and apply them in a new statistical
technique to measure properties of massive halos. We present analytical results
on the eight shear three-point correlation functions constructed using
combination of the two shear components at each vertex of a triangle. We
compare the amplitude and configuration dependence of the functions with
ray-tracing simulations and find excellent agreement for different scales and
models. These results are promising, since shear statistics are easier to
measure than the convergence. In addition, the symmetry properties of the shear
three-point functions provide a new and precise way of disentangling the
lensing E-mode from the B-mode due to possible systematic errors.
We develop an approach based on correlation functions to measure the
properties of galaxy-group and cluster halos from lensing surveys. Shear
correlations on small scales arise from the lensing matter within halos of mass
M > 10^13 solar masses. Thus the measurement of two- and three-point
correlations can be used to extract information on halo density profiles,
primarily the inner slope and halo concentration. We demonstrate the
feasibility of such an analysis for forthcoming surveys. We include covariances
in the correlation functions due to sample variance and intrinsic ellipticity
noise to show that 10% accuracy on profile parameters is achievable with
surveys like the CFHT Legacy survey, and significantly better with future
surveys. Our statistical approach is complementary to the standard approach of
identifying individual objects in survey data and measuring their properties.Comment: 30 pages, 21 figures. Corrected typos in equations (23) and (28).
Matches version for publication in MNRA
Cosmology at the Millennium
One hundred years ago we did not know how stars generate energy, the age of
the Universe was thought to be only millions of years, and our Milky Way galaxy
was the only galaxy known. Today, we know that we live in an evolving and
expanding Universe comprising billions of galaxies, all held together by dark
matter. With the hot big-bang model, we can trace the evolution of the Universe
from the hot soup of quarks and leptons that existed a fraction of a second
after the beginning to the formation of galaxies a few billion years later, and
finally to the Universe we see today 13 billion years after the big bang, with
its clusters of galaxies, superclusters, voids, and great walls. The attractive
force of gravity acting on tiny primeval inhomogeneities in the distribution of
matter gave rise to all the structure seen today. A paradigm based upon deep
connections between cosmology and elementary particle physics -- inflation +
cold dark matter -- holds the promise of extending our understanding to an even
more fundamental level and much earlier times, as well as shedding light on the
unification of the forces and particles of nature. As we enter the 21st
century, a flood of observations is testing this paradigm.Comment: 44 pages LaTeX with 14 eps figures. To be published in the Centennial
Volume of Reviews of Modern Physic
Isocurvature and Adiabatic Fluctuations of Axion in Chaotic Inflation Models and Large Scale Structure
In the chaotic inflation models, quantum fluctuations for axion fields lead
to the overproduction of domain walls and too large isocurvature fluctuations
which is inconsistent with the observations of cosmic microwave background
anisotropies. These problems are solved by assuming a very flat potential for
the Peccei-Quinn scalar. As the simplest possibility, we consider a model where
the Peccei-Quinn scalar is an inflaton itself and show that the isocurvature
fluctuations can be comparable with the adiabatic ones. We investigate
cosmological implications in the case that both adiabatic and isocurvature
fluctuations exist and find that the amplitude of the matter spectrum becomes
smaller than that for the pure adiabatic case. This leads to relatively high
bias parameter () which is favoured by the current observations.Comment: 5 pages, uudecoded postscript file with figure
Three-Dimensional Mapping of the Dark Matter
We study the prospects for three-dimensional mapping of the dark matter to
high redshift through the shearing of faint galaxies images at multiple
distances by gravitational lensing. Such maps could provide invaluable
information on the nature of the dark energy and dark matter. While in
principle well-posed, mapping by direct inversion introduces exceedingly large,
but usefully correlated noise into the reconstruction. By carefully propagating
the noise covariance, we show that lensing contains substantial information,
both direct and statistical, on the large-scale radial evolution of the density
field. This information can be efficiently distilled into low-order
signal-to-noise eigenmodes which may be used to compress the data by over an
order of magnitude. Such compression will be useful for the statistical
analysis of future large data sets. The reconstructed map also contains useful
information on the localization of individual massive dark matter halos, and
hence the dark energy from halo number counts, but its extraction depends
strongly on prior assumptions. We outline a procedure for maximum entropy and
point-source regularization of the maps that can identify alternate
reconstructions.Comment: 11 pages, 5 figures, submitted to PR
History of clinical transplantation
How transplantation came to be a clinical discipline can be pieced together by perusing two volumes of reminiscences collected by Paul I. Terasaki in 1991-1992 from many of the persons who were directly involved. One volume was devoted to the discovery of the major histocompatibility complex (MHC), with particular reference to the human leukocyte antigens (HLAs) that are widely used today for tissue matching.1 The other focused on milestones in the development of clinical transplantation.2 All the contributions described in both volumes can be traced back in one way or other to the demonstration in the mid-1940s by Peter Brian Medawar that the rejection of allografts is an immunological phenomenon.3,4 © 2008 Springer New York
Genetic Sharing with Cardiovascular Disease Risk Factors and Diabetes Reveals Novel Bone Mineral Density Loci.
Bone Mineral Density (BMD) is a highly heritable trait, but genome-wide association studies have identified few genetic risk factors. Epidemiological studies suggest associations between BMD and several traits and diseases, but the nature of the suggestive comorbidity is still unknown. We used a novel genetic pleiotropy-informed conditional False Discovery Rate (FDR) method to identify single nucleotide polymorphisms (SNPs) associated with BMD by leveraging cardiovascular disease (CVD) associated disorders and metabolic traits. By conditioning on SNPs associated with the CVD-related phenotypes, type 1 diabetes, type 2 diabetes, systolic blood pressure, diastolic blood pressure, high density lipoprotein, low density lipoprotein, triglycerides and waist hip ratio, we identified 65 novel independent BMD loci (26 with femoral neck BMD and 47 with lumbar spine BMD) at conditional FDR < 0.01. Many of the loci were confirmed in genetic expression studies. Genes validated at the mRNA levels were characteristic for the osteoblast/osteocyte lineage, Wnt signaling pathway and bone metabolism. The results provide new insight into genetic mechanisms of variability in BMD, and a better understanding of the genetic underpinnings of clinical comorbidity
Natural circular dichroism in X-ray spectroscopy
The measurement of natural circular dichroism has been extended to the X-ray region. XNCD spectra have been measured for uniaxial single crystals of the chiral coordination compounds Na3[Nd(digly)3]·2NaBF4·6H2O (digly = 2,2‘-oxydiacetate) and {[Co(en)3]Cl3}2·NaCl·6H2O (en = ethane-1,2-diamine) and for ionic crystals such as LiIO3. The XANES part of the XNCD shows circular dichroism corresponding to chiral multiple scattering paths of the photoelectron. In addition, both the Nd(III) and Co(III) compounds show quadrupole allowed pre-edge features (2p → 4f for Nd and 1s → 3d for Co) which have exceptionally large Kuhn dissymmetry factors. The theory of XNCD is discussed and the circular dichroism is shown to be due to the interference between allowed electric dipole and electric quadrupole transition moments (E1−E2 mechanism). This new spectroscopy represents a useful extension to techniques for the study of both molecular and crystal structural enantiomorphism
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