358 research outputs found
Evaluation of a Phosphate Management Protocol to Achieve Optimum Serum Phosphate Levels in Hemodialysis Patients
Original article can be found at: http://www.sciencedirect.com/science/journal/10512276 Copyright National Kidney Foundation, Inc. DOI: 10.1053/j.jrn.2008.05.003To evaluate the effectiveness of a protocol designed to optimize serum phosphate levels in patients undergoing regular hemodialysis (HD).Peer reviewe
Bimodal granulocyte transit time through the human lung demonstrated by deconvolution analysis
AbstractThe lungs are an important site of granulocyte pooling. The aim of the study is to quantify pulmonary vascular granulocyte transit time using deconvolution analysis, as has previously been performed to measure pulmonary red cell transit time. Granulocyte and red cell studies were performed in separate groups of patients. Both cell types were labelled with Tc-99m, which for granulocyte labelling was complexed with hexamethylpropyleneamine oxime (HMPAO). The red cell impulse response function (IRF) was monoexponential with a median transit time of 4·3 s. The granulocyte IRF was biexponential in 19 of 22 subjects, 18 of whom had systemic inflammation (inflammatory bowel disease, systemic vasculitis or graft-vs-host disease) and four were controls without inflammatory disease. The median transit time of the fast component ranged from 20 to 25 s and of the slow component 120â138 s in the four patient groups. The fraction of cells undergoing slow transit correlated significantly with (a) mean granulocyte transit time and (b) the fraction showing shape change in vitro. We conclude that granulocyte transit time through the pulmonary circulation is bimodal and that shape-changed (activated) cells transit more slowly that non-activated cells. The size of the fraction undergoing slow transit is closely related to mean granulocyte transit time and is an important determinant of the size of the pulmonary vascular granulocyte pool
From invasion percolation to flow in rock fracture networks
The main purpose of this work is to simulate two-phase flow in the form of
immiscible displacement through anisotropic, three-dimensional (3D) discrete
fracture networks (DFN). The considered DFNs are artificially generated, based
on a general distribution function or are conditioned on measured data from
deep geological investigations. We introduce several modifications to the
invasion percolation (MIP) to incorporate fracture inclinations, intersection
lines, as well as the hydraulic path length inside the fractures. Additionally
a trapping algorithm is implemented that forbids any advance of the invading
fluid into a region, where the defending fluid is completely encircled by the
invader and has no escape route. We study invasion, saturation, and flow
through artificial fracture networks, with varying anisotropy and size and
finally compare our findings to well studied, conditioned fracture networks.Comment: 18 pages, 10 figure
Euler configurations and quasi-polynomial systems
In the Newtonian 3-body problem, for any choice of the three masses, there
are exactly three Euler configurations (also known as the three Euler points).
In Helmholtz' problem of 3 point vortices in the plane, there are at most three
collinear relative equilibria. The "at most three" part is common to both
statements, but the respective arguments for it are usually so different that
one could think of a casual coincidence. By proving a statement on a
quasi-polynomial system, we show that the "at most three" holds in a general
context which includes both cases. We indicate some hard conjectures about the
configurations of relative equilibrium and suggest they could be attacked
within the quasi-polynomial framework.Comment: 21 pages, 6 figure
Tilt order parameters, polarity and inversion phenomena in smectic liquid crystals
The order parameters for the phenomenological description of the smectic-{\it
A} to smectic-{\it C} phase transition are formulated on the basis of molecular
symmetry and structure. It is shown that, unless the long molecular axis is an
axis of two-fold or higher rotational symmetry, the ordering of the molecules
in the smectic-{\it C} phase gives rise to more than one tilt order parameter
and to one or more polar order parameters. The latter describe the indigenous
polarity of the smectic-{\it C} phase, which is not related to molecular
chirality but underlies the appearance of spontaneous polarisation in chiral
smectics. A phenomenological theory of the phase transition is formulated by
means of a Landau expansion in two tilt order parameters (primary and
secondary) and an indigenous polarity order parameter. The coupling among these
order parameters determines the possibility of sign inversions in the
temperature dependence of the spontaneous polarisation and of the helical pitch
observed experimentally for some chiral smectic-{\it } materials. The
molecular interpretation of the inversion phenomena is examined in the light of
the new formulation.Comment: 12 pages, 5 figures, RevTe
Analytical results for coupled map lattices with long-range interactions
We obtain exact analytical results for lattices of maps with couplings that
decay with distance as . We analyze the effect of the coupling
range on the system dynamics through the Lyapunov spectrum. For lattices whose
elements are piecewise linear maps, we get an algebraic expression for the
Lyapunov spectrum. When the local dynamics is given by a nonlinear map, the
Lyapunov spectrum for a completely synchronized state is analytically obtained.
The critical lines characterizing the synchronization transition are determined
from the expression for the largest transversal Lyapunov exponent. In
particular, it is shown that in the thermodynamical limit, such transition is
only possible for sufficiently long-range interactions, namely, for , where is the lattice dimension.Comment: 4 pages, 2 figures, corrections included. Phys. Rev. E 68, 045202(R)
(2003); correction in pres
Collapsing shear-free perfect fluid spheres with heat flow
A global view is given upon the study of collapsing shear-free perfect fluid
spheres with heat flow. We apply a compact formalism, which simplifies the
isotropy condition and the condition for conformal flatness. This formalism
also presents the simplest possible version of the main junction condition,
demonstrated explicitly for conformally flat and geodesic solutions. It gives
the right functions to disentangle this condition into well known differential
equations like those of Abel, Riccati, Bernoulli and the linear one. It yields
an alternative derivation of the general solution with functionally dependent
metric components. We bring together the results for static and time- dependent
models to describe six generating functions of the general solution to the
isotropy equation. Their common features and relations between them are
elucidated. A general formula for separable solutions is given, incorporating
collapse to a black hole or to a naked singularity.Comment: 26 page
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio
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