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Search Results: 1 - 10 of 4773 matches for " Erik Eckhardt "
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Chylomicrons Promote Intestinal Absorption and Systemic Dissemination of Dietary Antigen (Ovalbumin) in Mice
Yuehui Wang,Sarbani Ghoshal,Martin Ward,Willem de Villiers,Jerold Woodward,Erik Eckhardt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008442
Abstract: A small fraction of dietary protein survives enzymatic degradation and is absorbed in potentially antigenic form. This can trigger inflammatory responses in patients with celiac disease or food allergies, but typically induces systemic immunological tolerance (oral tolerance). At present it is not clear how dietary antigens are absorbed. Most food staples, including those with common antigens such as peanuts, eggs, and milk, contain long-chain triglycerides (LCT), which stimulate mesenteric lymph flux and postprandial transport of chylomicrons through mesenteric lymph nodes (MLN) and blood. Most dietary antigens, like ovalbumin (OVA), are emulsifiers, predicting affinity for chylomicrons. We hypothesized that chylomicron formation promotes intestinal absorption and systemic dissemination of dietary antigens.
T-Lymphocyte Responses to Intestinally Absorbed Antigens Can Contribute to Adipose Tissue Inflammation and Glucose Intolerance during High Fat Feeding
Yuehui Wang,Jianing Li,Lihua Tang,Yu Wang,Richard Charnigo,Willem de Villiers,Erik Eckhardt
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013951
Abstract: Obesity is associated with inflammation of visceral adipose tissues, which increases the risk for insulin resistance. Animal models suggest that T-lymphocyte infiltration is an important early step, although it is unclear why these cells are attracted. We have recently demonstrated that dietary triglycerides, major components of high fat diets, promote intestinal absorption of a protein antigen (ovalbumin, “OVA”). The antigen was partly transported on chylomicrons, which are prominently cleared in adipose tissues. We hypothesized that intestinally absorbed gut antigens may cause T-lymphocyte associated inflammation in adipose tissue.
Technical Note: Analytical sensitivity analysis of a two parameter recursive digital baseflow separation filter
K. Eckhardt
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2012,
Abstract: A sensitivity analysis for a well-established baseflow separation technique, a two parameter recursive digital filter, is presented. The sensitivity of the calculated baseflow index to errors or uncertainties of the two filter parameters and of the initial baseflow value is analytically ascertained. It is found that the influence of the initial baseflow value is negligible for long time series. The propagation of errors or uncertainties of the two filter parameters into the baseflow index is expressed by a dimensionless sensitivity index, the ratio between the relative error of the baseflow index and the relative error of the respective parameter. Representative index values are derived by application of the resulting equations to 65 North American catchments. In the mean the parameter a, the recession constant, has a stronger influence on the calculated baseflow index than the second filter parameter BFImax. This is favourable in that a can be determined by a recession analysis and therefore should be less uncertain. Whether this finding also applies for a specific catchment can easily be checked by means of the derived equations.
Technical Note: Analytical sensitivity analysis of a two parameter recursive digital baseflow separation filter
K. Eckhardt
Hydrology and Earth System Sciences Discussions , 2011, DOI: 10.5194/hessd-8-9469-2011
Abstract: A sensitivity analysis for a well established baseflow separation technique, a two parameter recursive digital filter, is presented. The propagation of errors or uncertainties of the two filter parameters into the calculated baseflow index is analytically ascertained. Representative sensitivity indices (defined as the ratio between the relative error of the baseflow index and the relative error of the respective parameter) are derived by application of the resulting equations to a great number of catchments. It is found that in the mean the parameter a, the recession constant, has a stronger influence on the calculated baseflow index than the second filter parameter BFImax. This is favourable in that a can be determined by a recession analysis and therefore should be less uncertain. Whether this finding also applies for a specific catchment can easily be checked by means of the derived equations.
Periodic Orbit Theory
Bruno Eckhardt
Physics , 1993,
Abstract: [[ RM: A review paper on cycle expansions. I quote the introduction: in section (2) ]] I will summarize Gutzwiller's theory for the spectrum of eigenenergies and extend it to diagonal matrix elements as well. The derivation of the associated zeta function is given (2.2) and the identification of suitable scaling variables discussed (2.3). In section 3 tools necessary for the organization of chaos will be discussed: symbolic dynamics (3.1), the connectivity matrix (3.3), the topological zeta function (3.4) and general transfer matrices and zeta functions (3.5). Although illustrated for the case of hard collisions in a billiard, the symbolic dynamics can be extended to `smooth collisions' in smooth potentials (3.2). In systems with discrete symmetries, zeta functions factorize into zeta functions on invariant subspaces. This symmetry factorization and the associated reduction in symbolics is discussed in section 4. The ideas developed here are illustrated for the example of a free particle reflected elastically off three disks in section 5. Methods to find periodic orbits (5.1), the convergence of the trace formula (5.2), the semiclassical computation of scattering resonances (5.3), the convergence of the cycle expansion (5.4) and methods to obtain eigenvalues of the bounded billiard (5.5) are discussed. The relevant parts of a classical periodic orbit theory are developed in section 6.1, including a discussion of escape rates and the Hannay-Ozorio de Almeida sum rule (6.2). Finally, the issue of semiclassical matrix elements is taken up again and applications to experiments are discussed.
Order and chaos in quantum irregular scattering: Wigner's time delay
Bruno Eckhardt
Physics , 1993, DOI: 10.1016/0083-6656(93)90007-7
Abstract: Recent developments in the semiclassical analysis of chaotic systems are reviewed and illustrated for Wigner's time delay in elastic scattering of a point particle from three disks in the plane. The convergence of the cycle expanded periodic orbit expression for Wigners time delay is demonstrated. Different regimes in form factor (the Fourier transform of the two point correlation function) of the semiclassical time delay are identified and their relation to Berry's semiclassical theory of the spectral rigidity are discussed.
Eigenvalue statistics in quantum ideal gases
B. Eckhardt
Physics , 1998,
Abstract: The eigenvalue statistics of quantum ideal gases with single particle energies $e_n=n^\alpha$ are studied. A recursion relation for the partition function allows to calculate the mean density of states from the asymptotic expansion for the single particle density. For integer $\alpha>1$ one expects and finds number theoretic degeneracies and deviations from the Poissonian spacing distribution. By semiclassical arguments, the length spectrum of the classical system is shown to be related to sums of integers to the power $\alpha/(\alpha-1)$. In particular, for $\alpha=3/2$, the periodic orbits are related to sums of cubes, for which one again expects number theoretic degeneracies, with consequences for the two point correlation function.
Echoes in classical dynamical systems
Bruno Eckhardt
Physics , 2002, DOI: 10.1088/0305-4470/36/2/306
Abstract: Echoes arise when external manipulations to a system induce a reversal of its time evolution that leads to a more or less perfect recovery of the initial state. We discuss the accuracy with which a cloud of trajectories returns to the initial state in classical dynamical systems that are exposed to additive noise and small differences in the equations of motion for forward and backward evolution. The cases of integrable and chaotic motion and small or large noise are studied in some detail and many different dynamical laws are identified. Experimental tests in 2-d flows that show chaotic advection are proposed.
A Noncommutative Gauss map
Caleb Eckhardt
Mathematics , 2009,
Abstract: The aim of this paper is to transfer the Gauss map, which is a Bernoulli shift for continued fractions, to the noncommutative setting. We feel that a natural place for such a map to act is on the AF algebra $\mathfrak{A}$ considered separately by F. Boca and D. Mundici. The center of $\ga$ is isomorphic to $C[0,1]$, so we first consider the action of the Gauss map on $C[0,1]$ and then extend the map to $\mathfrak{A}$ and show that the extension inherits many desirable properties.
Perturbations of completely positive maps and strong NF algebras
Caleb Eckhardt
Mathematics , 2009, DOI: 10.1112/plms/pdq008
Abstract: Let $\phi:M_n\to B(H)$ be an injective, completely positive contraction with $\V\phi^{-1}:\phi(M_n)\to M_n\V_{cb}\leq1+\delta(\epsilon).$ We show that if either (i) $\phi(M_n)$ is faithful modulo the compact operators or (ii) $\phi(M_n)$ approximately contains a rank 1 projection, then there is a complete order embedding $\psi:M_n\to B(H)$ with $\V\phi-\psi\V_{cb}<\epsilon.$ We also give examples showing that such a perturbation does not exist in general. As an application, we show that every $C^*$-algebra $A$ with $\mathcal{OL}_\infty(A)=1$ and a finite separating family of primitive ideals is a strong NF algebra, providing a partial answer to a question of Junge, Ozawa and Ruan.
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