1,513 research outputs found
Plant cell walls: impact on nutrient bioaccessibility and digestibility
Cell walls are important structural components of plants, affecting both the bioaccessibility and subsequent digestibility of the nutrients that plant-based foods contain. These supramolecular structures are composed of complex heterogeneous networks primarily consisting of cellulose, and hemicellulosic and pectic polysaccharides. The composition and organization of these different polysaccharides vary depending on the type of plant tissue, imparting them with specific physicochemical properties. These properties dictate how the cell walls behave in the human gastrointestinal tract, and how amenable they are to digestion, thereby modulating nutrient release from the plant tissue. This short narrative review presents an overview of our current knowledge on cell walls and how they impact nutrient bioaccessibility and digestibility. Some of the most relevant methods currently used to characterize the food matrix and the cell walls are also described
The metabolic syndrome - What is it and how should it be managed?
A cluster of metabolic factors have been merged into an entity named the metabolic syndrome. Although the characteristics of this syndrome have varied over time the presently used definition was established in 2009. The presence of three abnormal findings out of five components qualifies a person for the metabolic syndrome: elevated waist circumference, elevated triglycerides, reduced high-density lipoprotein cholesterol, elevated blood pressure and elevated fasting plasma glucose. Cut points have been defined for all components apart from waist circumference, for which national or regional values are used. The metabolic syndrome predicts cardiovascular disease and type 2 diabetes. This associated risk does not exceed its components whereof elevated blood pressure is the most frequent. A successful management should, however, address all factors involved. The management is always based on healthy lifestyle choices but has not infrequently to be supported by pharmacological treatment, especially blood pressure lowering drugs. The metabolic syndrome is a useful example of the importance of multiple targets for preventive interventions. To be successful management has to be individualized not the least when it comes to pharmacological therapy. Frail elderly people should not be over-treated. Knowledge transfer of how risk factors act should be accompanied by continuous trust building and motivation. In complex situations with a mix of biological risk factors, adverse social conditions and unhealthy lifestyle, everything cannot be changed at once. It is better to aim for small steps that are lasting than large, unsustainable steps with relapses to unhealthy behaviours. A person with the metabolic syndrome will always be afflicted by its components, which is the reason that management has to be sustained over a very long time. This review summarizes the knowledge on the metabolic syndrome and its management according to present state of the art.Peer reviewe
Halo Shapes, Dynamics and Environment
In the hierarchical structure formation model cosmic halos are supposed to
form by accretion of smaller units along anisotropic direction, defined by
large-scale filamentary structures. After the epoch of primary mass aggregation
(which depend on the cosmological model), violent relaxation processes will
tend to alter the halo phase-space configuration producing quasi-spherical
halos with a relatively smooth density profiles.
Here we attempt to investigate the relation between halos shapes, their
environment and their dynamical state. To this end we have run a large ( Mpc, particles) N-body simulation of a flat low-density
cold dark matter model with a matter density , Hubble constant km s
Mpc and a normalization parameter of . The particle mass
is comparable to the mass of
one single galaxy. The halos are defined using a friends-of-friend algorithm
with a linking length given by where is the mean
density. This linking length corresponds to an overdensity at the present epoch () and the total number of halos
with more than 130 particles () is 57524.Comment: To be published in "Groups Of Galaxies In The Nearby Universe", held
in Chile, December 2005, edited by I.Saviane, V.Ivanov and J.Borissova.
Springer-Verlag series "ESO Astrophysics Symposia
NGC 4138 - A Case Study in Counterrotating Disk Formation
The Sa(r) galaxy NGC 4138 has been recently found to contain an extensive
counterrotating disk which appears to be still forming. Up to a third of the
stars in the disk system may be on retrograde orbits. A counterrotating ring of
H II regions, along with extended counterrotating H I gas, suggests that the
retrograde material has been recently acquired in the gas phase and is still
trickling in. Using numerical simulations, we have attempted to model the
process by which the counterrotating mass has been accreted by this galaxy. We
investigate two possibilities: continuous retrograde infall of gas, and a
retrograde merger with a gas-rich dwarf galaxy. Both processes are successful
in producing a counterrotating disk of the observed mass and dimensions without
heating up the primary significantly. Contrary to our experience with a
fiducial cold, thin primary disk, the gas-rich merger works well for the
massive, compact primary disk of NGC 4138 even though the mass of the dwarf
galaxy is a significant fraction of the mass of the primary disk. Although we
have restricted ourselves mainly to coplanar infall and mergers, we report on
one inclined infall simulation as well. We also explore the possibility that
the H-alpha ring seen in the inner half of the disk is a consequence of
counterrotating gas clouds colliding with corotating gas already present in the
disk and forming stars in the process.Comment: To appear in ApJ, 21 pages, LaTeX (aaspp4) format, 17 figs (gzipped
tar file) also available at ftp://bessel.mps.ohio-state.edu/pub/thakar/cr2/
or at http://www-astronomy.mps.ohio-state.edu/~thakar
Robust, data-driven inference in non-linear cosmostatistics
We discuss two projects in non-linear cosmostatistics applicable to very
large surveys of galaxies. The first is a Bayesian reconstruction of galaxy
redshifts and their number density distribution from approximate, photometric
redshift data. The second focuses on cosmic voids and uses them to construct
cosmic spheres that allow reconstructing the expansion history of the Universe
using the Alcock-Paczynski test. In both cases we find that non-linearities
enable the methods or enhance the results: non-linear gravitational evolution
creates voids and our photo-z reconstruction works best in the highest density
(and hence most non-linear) portions of our simulations.Comment: 14 pages, 10 figures. Talk given at "Statistical Challenges in Modern
Astronomy V," held at Penn Stat
Non-radial motion and the NFW profile
The self-similar infall model (SSIM) is normally discussed in the context of
radial orbits in spherical symmetry. However it is possible to retain the
spherical symmetry while permitting the particles to move in Keplerian
ellipses, each having the squared angular momentum peculiar to their 'shell'.
The spherical 'shell', defined for example by the particles turning at a given
radius, then moves according to the radial equation of motion of a 'shell'
particle. The 'shell' itself has no physical existence except as an ensemble of
particles, but it is convenient to sometimes refer to the shells since it is
they that are followed by a shell code. In this note we find the distribution
of squared angular momentum as a function of radius that yields the NFW density
profile for the final dark matter halo. It transpires that this distribution is
amply motivated dimensionally. An effective 'lambda' spin parameter is roughly
constant over the shells. We also study the effects of angular momentum on the
relaxation of a dark matter system using a three dimensional representation of
the relaxed phase space.Comment: accepted for publication in Astronomy and Astrophysics. date
received: 31-03-03 date accepted: 10-06-0
Detailed Surface Photometry of Dwarf Elliptical and Dwarf S0 Galaxies in the Virgo Cluster
We analyze new V-band images of 14 dwarf S0 galaxies and 10 dwarf elliptical galaxies in the Virgo Cluster, in combination with R-band images of 70 dwarf elliptical galaxies from an earlier paper. We compute the intensity-weighted mean ellipticity, the mean deviations from elliptical isophotes, and a newly defined parameter to measure isophotal twists. We also fit each major-axis profile to a power law Σ(a) α exp[-(a/as)n], where n is allowed to vary. Consistent with other studies of the Virgo dwarf ellipticals, we find that the profile shapes for the entire sample is strongly peaked near n=1 (exponential profiles) and that no galaxies have n=1/4 (de Vaucouleurs profile). The faintest galaxies all have nearly exponential profiles, while the brighter ones on average have n<1. The correlation between ellipticity and the boxy/disky parameter is similar to that of large elliptical galaxies, suggesting that dwarfs may also be divided into two groups with differing internal dynamics. The Virgo dEs also show a greater degree of isophotal twisting than more luminous elliptical galaxies. There does not seem to be any combination of parameters from the surface photometry that statistically correlates with the dE/dS0 designation: in particular, the dS0 galaxies do not, on average, have more pointed (disky) isophotes than the dEs
The Ellipticity of the Disks of Spiral Galaxies
The disks of spiral galaxies are generally elliptical rather than circular.
The distribution of ellipticities can be fit with a log-normal distribution.
For a sample of 12,764 galaxies from the Sloan Digital Sky Survey Data Release
1 (SDSS DR1), the distribution of apparent axis ratios in the i band is best
fit by a log-normal distribution of intrinsic ellipticities with ln epsilon =
-1.85 +/- 0.89. For a sample of nearly face-on spiral galaxies, analyzed by
Andersen and Bershady using both photometric and spectroscopic data, the best
fitting distribution of ellipticities has ln epsilon = -2.29 +/- 1.04. Given
the small size of the Andersen-Bershady sample, the two distribution are not
necessarily inconsistent. If the ellipticity of the potential were equal to
that of the light distribution of the SDSS DR1 galaxies, it would produce 1.0
magnitudes of scatter in the Tully-Fisher relation, greater than is observed.
The Andersen-Bershady results, however, are consistent with a scatter as small
as 0.25 magnitudes in the Tully-Fisher relation.Comment: 19 pages, 5 figures; ApJ, accepte
Hadley V. Baxendale: Still Crazy After All These Years? Panel Discussion
The following discussion about Hadley v. Baxendale took place on June 8, 2004, at the Conference on The Common Law of Contracts as a World Force in Two Ages of Revolution, held at the Oxstalls Campus of the University of Gloucestershire, in Gloucester, England. The Conference marked the 150th anniversary of Hadley. The following discussion was intended to be a free-ranging exploration of Hadley, its rule, its role in legal pedagogy, and its likely future
A Bogomol`nyi equation for intersecting domain walls
We argue that the Wess-Zumino model with quartic superpotential admits static
solutions in which three domain walls intersect at a junction. We derive an
energy bound for such junctions and show that configurations saturating it
preserve 1/4 supersymmetry.Comment: 4 pages revtex. No figures. Revised version to appear in Physical
Review Letters includes discussion of the supersymmetry algebr
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