1,320 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 Shapes of Dense Cores and Bok Globules
The shapes of isolated Bok globules and embedded dense cores of molecular
clouds are analyzed using a nonparametric method, under the alternate
hypotheses that they are randomly oriented prolate objects or that they are
randomly oriented oblate objects. In all cases, the prolate hypothesis gives a
better fit to the data. If Bok globules are oblate, they must be very flat; the
average axis ratio is b/a = 0.3, and few or no globules can have b/a > 0.7. If
Bok globules are prolate, then the mean axis ratio is b/a = 0.5. For most data
samples of dense cores, the randomly-oriented oblate hypothesis can be rejected
at the 99% confidence level. If the dense cores are prolate, their mean axis
ratio is approximately 0.4 to 0.5. Dense cores are significantly different in
shape from the clouds in which they are embedded; clouds have flatter apparent
shapes, and are inconsistent with a population of randomly oriented
axisymmetric objects.Comment: 26 pages (LaTeX) including 8 postscript figures; to appear in Ap
A solar cycle of spacecraft anomalies due to internal charging
International audienceIt is important to appreciate how the morphology of internal charging of spacecraft systems, due to penetrating electrons, differs from that of the more common surface charging, due to electrons with lower energy. A specific and recurrent anomaly on a geostationary communication satellite has been tracked for ten years so that solar cycle and seasonal dependencies can be clearly established. Concurrent measurements of sunspot number, solar wind speed and 2-day >2 MeV electron fluence are presented to highlight pertinent space weather relationships, and the importance of understanding the complex particle interaction processes involved
On formation of domain wall lattices
We study the formation of domain walls in a phase transition in which an
S_5\times Z_2 symmetry is spontaneously broken to S_3\times S_2. In one compact
spatial dimension we observe the formation of a stable domain wall lattice. In
two spatial dimensions we find that the walls form a network with junctions,
there being six walls to every junction. The network of domain walls evolves so
that junctions annihilate anti-junctions. The final state of the evolution
depends on the relative dimensions of the simulation domain. In particular we
never observe the formation of a stable lattice of domain walls for the case of
a square domain but we do observe a lattice if one dimension is somewhat
smaller than the other. During the evolution, the total wall length in the
network decays with time as t^{-0.71}, as opposed to the usual t^{-1} scaling
typical of regular Z_2 networks.Comment: 7 pages, 4 figures. Minor changes, final version accepted for
publication in Phys. Rev.
An entirely analytical cosmological model
The purpose of the present study is to show that in a particular cosmological
model, with an affine equation of state, one can obtain, besides the background
given by the scale factor, Hubble and deceleration parameters, a representation
in terms of scalar fields and, more important, explicit mathematical
expressions for the density contrast and the power spectrum. Although the model
so obtained is not realistic, it reproduces features observed in some previous
numerical studies and, therefore, it may be useful in the testing of numerical
codes and as a pedagogical tool.Comment: 4 pages (revtex4), 4 figure
The glucose triad and its role in comprehensive glycaemic control: current status, future management
The prevalence of type 2 diabetes across the world has been described as a global pandemic. Despite significant efforts to limit both the increase in the number of cases and the long-term impact on morbidity and mortality, the total number of people with diabetes is projected to continue to rise and most patients still fail to achieve adequate glycaemic control. Optimal management of type 2 diabetes requires an understanding of the relationships between glycosylated haemoglobin (HbA1c), fasting plasma glucose and postprandial glucose (the glucose triad), and how these change during development and progression of the disease. Early and sustained control of glycaemia remains important in the management of type 2 diabetes. The contribution of postprandial glucose levels to overall glycaemic control and the role of postprandial glucose targets in disease management are currently debated. However, many patients do not reach HbA1C targets set according to published guidelines. As recent data suggest, if driving HbA1C down to lower target levels is not the answer, what other factors involved in glucose homeostasis can or should be targeted? Has the time come to change the treatment paradigm to include awareness of the components of the glucose triad, the existence of glucose variability and their potential influence on the choice of pharmacological treatment? It is becomingly increasingly clear that physicians are likely to have to consider plasma glucose levels both after the overnight fast and after meals as well as the variability of glucose levels, in order to achieve optimal glycaemic control for each patient. When antidiabetic therapy is initiated, physicians may need to consider selection of agents that target both fasting and postprandial hyperglycaemia
Impact of string and monopole-type junctions on domain wall dynamics: implications for dark energy
We investigate the potential role of string and monopole-type junctions in
the frustration of domain wall networks using a velocity-dependent one-scale
model for the characteristic velocity, , and the characteristic length, ,
of the network. We show that, except for very special network configurations,
v^2 \lsim (HL)^2 \lsim (\rho_\sigma + \rho_\mu)/\rho_m where is the
Hubble parameter and , and are the average
density of domain walls, strings and monopole-type junctions. We further show
that if domain walls are to provide a significant contribution to the dark
energy without generating exceedingly large CMB temperature fluctuations then,
at the present time, the network must have a characteristic length L_0 \lsim
10 \Omega_{\sigma 0}^{-2/3} {\rm kpc} and a characteristic velocity v_0 \lsim
10^{-5} \Omega_{\sigma 0}^{-2/3} where and is the critical density. In order to satisfy these
constraints with , would have to be at
least 10 orders of magnitude larger than , which would be in
complete disagreement with observations. This result provides very strong
additional support for the conjecture that no natural frustration mechanism,
which could lead to a significant contribution of domain walls to the dark
energy budget, exists.Comment: 4 pages, 1 figur
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