284 research outputs found
Perinatal nutrient restriction reduces nephron endowment increasing renal morbidity in adulthood: A review
Perinatal malnutrition has been included among the causes of renal disease in adulthood. Here, we consider the relationships between early supply of specific nutrients (such as protein, fat, vitamins and electrolytes) and renal endowment. Prenatal and postnatal nutrition mismatch is also discussed. In addition, this article presents the role of nutrition of both mothers and pre-term infants on nephron endowment, with final practical considerations. (C) 2010 Elsevier Ireland Ltd. All rights reserved
Error-estimate-based adaptive integration for immersed isogeometric analysis
The Finite Cell Method (FCM) together with Isogeometric analysis (IGA) has been applied successfully in various problems in solid mechanics, in image-based analysis, fluid–structure interaction and in many other applications. A challenging aspect of the isogeometric finite cell method is the integration of cut cells. In particular in three-dimensional simulations the computational effort associated with integration can be the critical component of a simulation. A myriad of integration strategies has been proposed over the past years to ameliorate the difficulties associated with integration, but a general optimal integration framework that suits a broad class of engineering problems is not yet available. In this contribution we provide a thorough investigation of the accuracy and computational effort of the octree integration scheme. We quantify the contribution of the integration error using the theoretical basis provided by Strang's first lemma. Based on this study we propose an error-estimate-based adaptive integration procedure for immersed isogeometric analysis. Additionally, we present a detailed numerical investigation of the proposed optimal integration algorithm and its application to immersed isogeometric analysis using two- and three-dimensional linear elasticity problems
Skeleton-stabilized ImmersoGeometric Analysis for incompressible viscous flow problems
A Skeleton-stabilized ImmersoGeometric Analysis technique is proposed for
incompressible viscous flow problems with moderate Reynolds number. The
proposed formulation fits within the framework of the finite cell method, where
essential boundary conditions are imposed weakly using a Nitsche-type method.
The key idea of the proposed formulation is to stabilize the jumps of
high-order derivatives of variables over the skeleton of the background mesh.
The formulation allows the use of identical finite-dimensional spaces for the
approximation of the pressure and velocity fields in immersed domains. The
stability issues observed for inf-sup stable discretizations of immersed
incompressible flow problems are avoided with this formulation. For B-spline
basis functions of degree with highest regularity, only the derivative of
order has to be controlled, which requires specification of only a single
stabilization parameter for the pressure field. The Stokes and Navier-Stokes
equations are studied numerically in two and three dimensions using various
immersed test cases. Oscillation-free solutions and high-order optimal
convergence rates can be obtained. The formulation is shown to be stable even
in limit cases where almost every elements of the physical domain is cut, and
hence it does not require the existence of interior cells. In terms of the
sparsity pattern, the algebraic system has a considerably smaller stencil than
counterpart approaches based on Lagrange basis functions. This important
property makes the proposed skeleton-stabilized technique computationally
practical. To demonstrate the stability and robustness of the method, we
perform a simulation of fluid flow through a porous medium, of which the
geometry is directly extracted from 3D scan data
CULTURED EPIDERMIS IN THE TREATMENT OF LEG ULCER:EDGE EFFECT AND CORRELATION WITH KERATINOCYTE PROLIFERATION INDEX
Exploring cell surface markers and cell-cell interactions of human breast milk stem cells
Background: Breakthrough studies have shown that pluripotent stem cells are present in human breast milk. The expression of pluripotency markers by breast milk cells is heterogeneous, relating to cellular hierarchy, from early-stage multi-lineage stem cells to fully differentiated mammary epithelial cells, as well as weeks of gestation and days of lactation. Design and methods: Here, we qualitatively analyze cell marker expression in freshly isolated human breast milk cells, without any manipulation that could influence protein expression. Moreover, we use electron microscopy to investigate cell-cell networks in breast milk for the first time, providing evidence of active intercellular communication between cells expressing different cellular markers. Results: The immunocytochemistry results of human breast milk cells showed positive staining in all samples for CD44, CD45, CD133, and Ki67 markers. Variable positivity was present with P63, Tβ4 and CK14 markers. No immunostaining was detected for Wt1, nestin, Nanog, OCT4, SOX2, CK5, and CD34 markers. Cells isolated from human breast milk form intercellular connections, which together create a cell-to-cell communication network. Conclusions: Cells freshly isolated form human breast milk, without particular manipulations, show heterogeneous expression of stemness markers. The studied milk staminal cells show "pluripotency" at different stages of differentiation, and are present as single cells or grouped cells. The adjacent cell interactions are evidenced by electron microscopy, which showed the formation of intercellular connections, numerous contact regions, and thin pseudopods
Residual-based error estimation and adaptivity for stabilized immersed isogeometric analysis using truncated hierarchical B-splines
We propose an adaptive mesh refinement strategy for immersed isogeometric
analysis, with application to steady heat conduction and viscous flow problems.
The proposed strategy is based on residual-based error estimation, which has
been tailored to the immersed setting by the incorporation of appropriately
scaled stabilization and boundary terms. Element-wise error indicators are
elaborated for the Laplace and Stokes problems, and a THB-spline-based local
mesh refinement strategy is proposed. The error estimation .and adaptivity
procedure is applied to a series of benchmark problems, demonstrating the
suitability of the technique for a range of smooth and non-smooth problems. The
adaptivity strategy is also integrated in a scan-based analysis workflow,
capable of generating reliable, error-controlled, results from scan data,
without the need for extensive user interactions or interventions.Comment: Submitted to Journal of Mechanic
Error-estimate-based Adaptive Integration For Immersed Isogeometric Analysis
The Finite Cell Method (FCM) together with Isogeometric analysis (IGA) has
been applied successfully in various problems in solid mechanics, in
image-based analysis, fluid-structure interaction and in many other
applications. A challenging aspect of the isogeometric finite cell method is
the integration of cut cells. In particular in three-dimensional simulations
the computational effort associated with integration can be the critical
component of a simulation. A myriad of integration strategies has been proposed
over the past years to ameliorate the difficulties associated with integration,
but a general optimal integration framework that suits a broad class of
engineering problems is not yet available. In this contribution we provide a
thorough investigation of the accuracy and computational effort of the octree
integration scheme. We quantify the contribution of the integration error using
the theoretical basis provided by Strang's first lemma. Based on this study we
propose an error-estimate-based adaptive integration procedure for immersed
isogeometric analysis. Additionally, we present a detailed numerical
investigation of the proposed optimal integration algorithm and its application
to immersed isogeometric analysis using two- and three-dimensional linear
elasticity problems.Comment: To CAMW
Constructing Fresnel reflection coefficients by ruler and compass
A simple and intuitive geometical method to analyze Fresnel formulas is
presented. It applies to transparent media and is valid for perpendicular and
parallel polarizations. The approach gives a graphical characterization
particularly simple of the critical and Brewster angles. It also provides an
interpretation of the relation between the reflection coefficients for both
basic polarizations as a symmetry in the plane
The Flavor Asymmetry of the Light Quark Sea from Semi-inclusive Deep-inelastic Scattering
The flavor asymmetry of the light quark sea of the nucleon is determined in
the kinematic range 0.02<x<0.3 and 1 GeV^2<Q^2<10 GeV^2, for the first time
from semi-inclusive deep-inelastic scattering. The quantity
(dbar(x)-ubar(x))/(u(x)-d(x)) is derived from a relationship between the yields
of positive and negative pions from unpolarized hydrogen and deuterium targets.
The flavor asymmetry dbar-ubar is found to be non-zero and x dependent, showing
an excess of dbar over ubar quarks in the proton.Comment: 7 Pages, 2 figures, RevTeX format; slight revision in text, small
change in extraction of dbar-ubar and comparison with a high q2
parameterizatio
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