24 research outputs found
The Role of Hypothyroidism in the Etiology and Progression of Dilated Cardiomyopathy in Doberman Pinschers
Background: Hypothyroidism and dilated cardiomyopathy (DCM) are both common diseases in Doberman Pinschers. A possible influence of hypothyroidism on the etiology and progression of DCM is controversial.
Objectives: Evaluation of the role of hypothyroidism in etiology and progression of DCM.
Animals: A total of 175 Doberman Pinschers.
Methods: In this longitudinal prospective study, echocardiography and 24-hour ambulatory ECG recordings were performed in all dogs as screening tests for DCM. Total thyroxine (TT4) and thyroid ultrasonography served as initial screening tests for hypothyroidism and low TT4 values were followed up by a thyroid stimulating hormone (TSH) test or free total thyroxine (fT4)/cTSH measurements. Additionally, a follow-up study of dogs affected by both DCM and hypothyroidism under optimal treatment for hypothyroidism was conducted.
Results: A total of 107 dogs were healthy, 45 dogs had DCM, 11 hypothyroidism, and 12 dogs had both DCM and hypothyroidism. TT4 values as well as the thyroid volumes were equivalent in the healthy dogs and in those with DCM. Neither ventricular premature complexes nor echocardiographic parameters differed between healthy and hypothyroid dogs. Dogs with DCM had a 2.26-fold (CI0.95 = 1.1â4.8) higher risk of also being affected by hypothyroidism. Despite optimal thyroid treatment of dogs with hypothyroidism and DCM, there was a progression of the heart disease.
Conclusions and Clinical Importance: This study did not confirm a role of hypothyroidism in the etiology or progression of DCM. Treatment of hypothyroidism did not improve the clinical outcome
The Role of Hypothyroidism in the Etiology and Progression of Dilated Cardiomyopathy in Doberman Pinschers
Background: Hypothyroidism and dilated cardiomyopathy (DCM) are both common diseases in Doberman Pinschers. A possible influence of hypothyroidism on the etiology and progression of DCM is controversial.
Objectives: Evaluation of the role of hypothyroidism in etiology and progression of DCM.
Animals: A total of 175 Doberman Pinschers.
Methods: In this longitudinal prospective study, echocardiography and 24-hour ambulatory ECG recordings were performed in all dogs as screening tests for DCM. Total thyroxine (TT4) and thyroid ultrasonography served as initial screening tests for hypothyroidism and low TT4 values were followed up by a thyroid stimulating hormone (TSH) test or free total thyroxine (fT4)/cTSH measurements. Additionally, a follow-up study of dogs affected by both DCM and hypothyroidism under optimal treatment for hypothyroidism was conducted.
Results: A total of 107 dogs were healthy, 45 dogs had DCM, 11 hypothyroidism, and 12 dogs had both DCM and hypothyroidism. TT4 values as well as the thyroid volumes were equivalent in the healthy dogs and in those with DCM. Neither ventricular premature complexes nor echocardiographic parameters differed between healthy and hypothyroid dogs. Dogs with DCM had a 2.26-fold (CI0.95 = 1.1â4.8) higher risk of also being affected by hypothyroidism. Despite optimal thyroid treatment of dogs with hypothyroidism and DCM, there was a progression of the heart disease.
Conclusions and Clinical Importance: This study did not confirm a role of hypothyroidism in the etiology or progression of DCM. Treatment of hypothyroidism did not improve the clinical outcome
Quasi-exactly solvable cases of the N-dimensional symmetric quartic anharmonic oscillator
The O(N) invariant quartic anharmonic oscillator is shown to be exactly
solvable if the interaction parameter satisfies special conditions. The problem
is directly related to that of a quantum double well anharmonic oscillator in
an external field. A finite dimensional matrix equation for the problem is
constructed explicitly, along with analytical expressions for some excited
states in the system. The corresponding Niven equations for determining the
polynomial solutions for the problem are given.Comment: 7 pages, RevTeX4. A discussion on the N=1 case has been added with
the boundary condition properly treate
Short-range oscillators in power-series picture
A class of short-range potentials on the line is considered as an
asymptotically vanishing phenomenological alternative to the popular confining
polynomials. We propose a method which parallels the analytic Hill-Taylor
description of anharmonic oscillators and represents all our Jost solutions
non-numerically, in terms of certain infinite hypergeometric-like series. In
this way the well known solvable Rosen-Morse and scarf models are generalized.Comment: 23 pages, latex, submitted to J. Phys. A: Math. Ge
Pseudospectra in non-Hermitian quantum mechanics
We propose giving the mathematical concept of the pseudospectrum a central
role in quantum mechanics with non-Hermitian operators. We relate
pseudospectral properties to quasi-Hermiticity, similarity to self-adjoint
operators, and basis properties of eigenfunctions. The abstract results are
illustrated by unexpected wild properties of operators familiar from
PT-symmetric quantum mechanics.Comment: version accepted for publication in J. Math. Phys.: criterion
excluding basis property (Proposition 6) added, unbounded time-evolution
discussed, new reference
Leaky quantum graphs: approximations by point interaction Hamiltonians
We prove an approximation result showing how operators of the type in , where is a graph,
can be modeled in the strong resolvent sense by point-interaction Hamiltonians
with an appropriate arrangement of the potentials. The result is
illustrated on finding the spectral properties in cases when is a ring
or a star. Furthermore, we use this method to indicate that scattering on an
infinite curve which is locally close to a loop shape or has multiple
bends may exhibit resonances due to quantum tunneling or repeated reflections.Comment: LaTeX 2e, 31 pages with 18 postscript figure
Complex Calogero model with real energies
We show that and how PT symmetry (interpreted as a "weakened Hermiticity")
can be extended to the exactly solvable two- and three-particle Calogero model.Comment: 16 pages, 3 figures, submitted to J. Phys.
Non-Hermitian matrix description of the PT symmetric anharmonic oscillators
Schroedinger equation H \psi=E \psi with PT - symmetric differential operator
H=H(x) = p^2 + a x^4 + i \beta x^3 +c x^2+i \delta x = H^*(-x) on
L_2(-\infty,\infty) is re-arranged as a linear algebraic diagonalization at
a>0. The proof of this non-variational construction is given. Our Taylor series
form of \psi complements and completes the recent terminating solutions as
obtained for certain couplings \delta at the less common negative a.Comment: 18 pages, latex, no figures, thoroughly revised (incl. title), J.
Phys. A: Math. Gen., to appea
A single-mode quantum transport in serial-structure geometric scatterers
We study transport in quantum systems consisting of a finite array of N
identical single-channel scatterers. A general expression of the S matrix in
terms of the individual-element data obtained recently for potential scattering
is rederived in this wider context. It shows in particular how the band
spectrum of the infinite periodic system arises in the limit . We
illustrate the result on two kinds of examples. The first are serial graphs
obtained by chaining loops or T-junctions. A detailed discussion is presented
for a finite-periodic "comb"; we show how the resonance poles can be computed
within the Krein formula approach. Another example concerns geometric
scatterers where the individual element consists of a surface with a pair of
leads; we show that apart of the resonances coming from the decoupled-surface
eigenvalues such scatterers exhibit the high-energy behavior typical for the
delta' interaction for the physically interesting couplings.Comment: 36 pages, a LaTeX source file with 2 TeX drawings, 3 ps and 3 jpeg
figures attache
Bound states in open coupled asymmetrical waveguides and quantum wires
The behavior of bound states in asymmetric cross, T and L shaped
configurations is considered. Because of the symmetries of the wavefunctions,
the analysis can be reduced to the case of an electron localized at the
intersection of two orthogonal crossed wires of different width. Numerical
calculations show that the fundamental mode of this system remains bound for
the widths that we have been able to study directly; moreover, the
extrapolation of the results obtained for finite widths suggests that this
state remains bound even when the width of one arm becomes infinitesimal. We
provide a qualitative argument which explains this behavior and that can be
generalized to the lowest energy states in each symmetry class. In the case of
odd-odd states of the cross we find that the lowest mode is bounded when the
width of the two arms is the same and stays bound up to a critical value of the
ratio between the widths; in the case of the even-odd states we find that the
lowest mode is unbound up to a critical value of the ratio between the widths.
Our qualitative arguments suggest that the bound state survives as the width of
the vertical arm becomes infinitesimal.Comment: 11 pages, 19 figures, 3 table