bluuebunny/crossref_metadata_2025 huggingface dataset:
QUANTUM BI-HAMILTONIAN SYSTEMS
Authors: CARIÑENA JOSÉ F. , GRABOWSKI JANUSZ , MARMO GIUSEPPE
Published: August 2004

We define quantum bi-Hamiltonian systems, by analogy with the classical case, as derivations in operator algebras which are inner derivations with respect to two compatible associative structures. We find such structures by means of the associative version of Nijenhuis tensors. Explicit examples, e.g. for the harmonic oscillator, are given.
NONLOCAL TWO-DIMENSIONAL YANG–MILLS AND GENERALIZED YANG–MILLS THEORIES
Authors: SAAIDI KHALED , KHORRAMI MOHAMMAD
Published: August 2004

A generalization of the two-dimensional Yang–Mills and generalized Yang–Mills theory is introduced in which the building B-F theory is nonlocal in the auxiliary field. The classical and quantum properties of this nonlocal generalization are investigated and it is shown that for large gauge groups, there exists a simple correspondence between the properties of the nonlocal theory and its corresponding local theory.
ENERGY DISTRIBUTION IN MELVIN'S MAGNETIC UNIVERSE
Authors: XULU S. S.
Published: August 2004

We use the energy–momentum complexes of Landau and Lifshitz and Papapetrou to obtain the energy distribution in Melvin's magnetic universe. For this space–time we find that these definitions of energy give the same and convincing results. The energy distribution obtained here is the same as we obtained earlier for the same space–time using the energy–momentum complex of Einstein. These results uphold the usefulness of the energy–momentum complexes.
FUNCTIONAL BOSONIZATION OF NONRELATIVISTIC FERMIONS IN 2+1 DIMENSIONS
Authors: BARCI DANIEL G. , LINHARES C. A. , DE QUEIROZ A. F. , NETO J. F. MEDEIROS
Published: August 2004

We analyze the universality of the bosonization rules in nonrelativistic fermionic systems in (2+1)d. We show that, in the case of linear fermionic dispersion relations, a general fermionic theory can be mapped into a gauge theory in such a way that the fermionic density maps into a magnetic flux and the fermionic current maps into a transverse electric field. These are universal rules in the sense that they remain valid whatever the interaction considered. We also show that these rules are universal in the case of nonlinear dispersion relations provided we consider only density–density interactions. We apply the functional bosonization formalism to a nonrelativistic and nonlocal massive Thirring-like model and evaluate the spectrum of collective excitations in several limits. In the large mass limit, we are able to exactly calculate this spectrum for arbitrary density–density and current–current interactions. We also analyze the massless case and show that it has no collective excitations for any density–density potential in the Gaussian approximation. Moreover, the presence of current interactions may induce a gapless mode with a linear dispersion relation.
REGULAR R–R AND NS–NS BPS BLACK HOLES
Authors: BERTOLINI MATTEO , TRIGIANTE MARIO
Published: August 2004

We show in a precise group theoretical fashion how the generating solution of regular BPS black holes of N=8 supergravity, which is known to be a solution also of a simpler N=2 STU model truncation, can be characterized as purely NS–NS or R–R charged according to the way the corresponding STU model is embedded in the original N=8 theory. Of particular interest is the class of embeddings which yield regular BPS black hole solutions carrying only R–R charge and whose microscopic description can possibly be given in terms of bound states of D-branes only. The microscopic interpretation of the bosonic fields in this class of STU models relies on the solvable Lie algebra (SLA) method. In the present paper, we improve this mathematical technique in order to provide two distinct descriptions for type IIA and type IIB theories and an algebraic characterization of S×T-dual embeddings within the N=8, d=4 theory. This analysis will be applied to the particular example of a four parameter (dilatonic) solution of which both the full macroscopic and microscopic descriptions will be worked out.
GRAVITATIONAL THERMODYNAMICS AND BLACK-HOLE MERGERS
Authors: PORTEGIES ZWART SIMON F. , MCMILLAN STEPHEN L. W.
Published: August 2004

Black holes become the most massive objects early in the evolution of star clusters. Dynamical relaxation then causes them to sink to the cluster core, where they form binaries which become more tightly bound by superelastic encounters with other cluster members. Ultimately, these binaries are ejected from the cluster. The majority of escaping black-hole binaries have orbital periods short enough and eccentricities high enough that the emission of gravitational waves causes them to coalesce within a few billion years. The rate at which such collisions occur is on the order of 10-7 per year per cubic megaparsec. This implies event rates for gravitational-wave detectors substantially greater than current estimates of the corresponding rates from neutron-star mergers or black-hole mergers stemming from pure binary evolution.
RESOLVING THE BLACK HOLE INFORMATION PARADOX
Authors: MATHUR SAMIR D.
Published: August 2004

The recent progress in string theory strongly suggests that formation and evaporation of black holes is a unitary process. This fact makes it imperative that we find a flaw in the semiclassical reasoning that implies a loss of information. We propose a new criterion that limits the domain of classical gravity: the hypersurfaces of a foliation cannot be stretched too much. This conjectured criterion may have important consequences for the early universe.
HIGH-PRECISION CALCULATION OF MULTILOOP FEYNMAN INTEGRALS BY DIFFERENCE EQUATIONS
Authors: LAPORTA S.
Published: August 2004

We describe a new method of calculation of generic multiloop master integrals based on the numerical solution of systems of difference equations in one variable. We show algorithms for the construction of the systems using integration-by-parts identities and methods of solutions by means of expansions in factorial series and Laplace transformation. We also describe new algorithms for the identification of master integrals and the reduction of generic Feynman integrals to master integrals, and procedures for generating and solving systems of differential equations in masses and momenta for master integrals. We apply our method to the calculation of the master integrals of massive vacuum and self-energy diagrams up to three loops and of massive vertex and box diagrams up to two loops. Implementation in a computer program of our approach is described. Important features of the implementation are: the ability to deal with hundreds of master integrals and the ability to obtain very high precision results expanded at will in the number of dimensions.
BORN–INFELD COSMOLOGIES
Authors: GARCÍA-SALCEDO RICARDO , BRETÓN NORA
Published: August 2004

We present a model for an inhomogeneous and anisotropic early universe filled with a nonlinear electromagnetic field of Born–Infeld (BI) type. The effects of the BI field are compared with the linear case (Maxwell). Since the curvature invariants are well behaved then we conjecture that our model does not present an initial big bang singularity. The existence of the BI field modifies the curvature invariants at t=0 as well as sets bounds on the amplitude of the conformal metric function.
LARGE DIMENSIONS AND STRING PHYSICS IN FUTURE COLLIDERS
Authors: ANTONIADIS I. , BENAKLI K.
Published: August 2004

We review the status of low-scale string theories and large extra-dimensions. After an overview on different string realizations, we discuss some of the main important problems and we summarize present bounds on the size of possible extra-dimensions from collider experiments.
ON THE QUANTUM REFLECTION FACTOR FOR THE SINH–GORDON MODEL WITH GENERAL BOUNDARY CONDITIONS
Authors: CHENAGHLOU A.
Published: August 2004

The one loop quantum corrections to the classical reflection factor of the sinh–Gordon model are calculated partially for general boundary conditions. The model is studied under boundary conditions which are compatible with integrability, and in the framework of the conventional perturbation theory generalized to the affine Toda field theory. It is found that the general form of the related quantum corrections are hypergeometric functions.
NON-ABELIAN FRACTIONAL QUANTUM HALL STATES AND CHIRAL COSET CONFORMAL FIELD THEORIES
Authors: CABRA D. C. , FRADKIN E. , ROSSINI G. L. , SCHAPOSNIK F. A.
Published: August 2004

We propose an effective Lagrangian for the low energy theory of the Pfaffian states of the fractional quantum Hall effect in the bulk in terms of non-Abelian Chern–Simons (CS) actions. Our approach exploits the connection between the topological Chern–Simons theory and chiral conformal field theories. This construction can be used to describe a large class of non-Abelian FQH states.
QUANTIZATION OF POINTLIKE PARTICLES AND CONSISTENT RELATIVISTIC QUANTUM MECHANICS
Authors: GAVRILOV S. P. , GITMAN D. M.
Published: August 2004

We revise the problem of the quantization of relativistic particle models (spinless and spinning), presenting a modified consistent canonical scheme. One of the main point of the modification is related to a principally new realization of the Hilbert space. It allows one not only to include arbitrary backgrounds in the consideration but to get in the course of the quantization consistent relativistic quantum mechanics, which reproduces literally the behavior of the one-particle sector of the corresponding quantum field. In particular, in a physical sector of the Hilbert space, a complete positive spectrum of energies of relativistic particles and antiparticles is reproduced, and all state vectors have only positive norms.
ON THE η and f1(1420) COUPLINGS TO THE NUCLEON
Authors: NEUMEIER S. , KIRCHBACH M.
Published: August 2004

We consider neutral pseudoscalar, η, and axial vector, f1(1420), mesons in the OZI-rule-respecting flavor basis, [Formula: see text], and suggest a scenario for their coupling to the nucleon. Within this framework, the nonstrange parts of the ηN and f1N couplings are modeled by means of triangular a0πN, and KK*(Λ/Σ) vertices, while the strange ones partly proceed via Goldberger–Treiman relations, which have been concluded solely on the grounds of current universality. The suggested model explains the observed suppression of the ηN coupling with respect to the constituent quark model expectations, and predicts the coupling of f1with the nucleon.
SYMMETRIC VACUA IN HETEROTIC M THEORY
Authors: LUKAS ANDRÉ , OVRUT BURT A.
Published: August 2004

Symmetric vacua of heterotic M theory, characterized by vanishing cohomology classes of individual sources in the three-form Bianchi identity, are analyzed on smooth Calabi–Yau three-folds. We show that such vacua do not exist for elliptically fibered Calabi–Yau spaces. However, explicit examples are found for Calabi–Yau three-folds arising as intersections in both unweighted and weighted projective space. We show that such symmetric vacua can be combined with attractive phenomenological features such as three generations of quarks and leptons. Properties of the low energy effective actions associated with symmetric vacua are discussed. In particular, the gauge kinetic functions receive no perturbative threshold corrections, there are no corrections to the matter field Kähler metric and the associated five-dimensional effective theory admits flat space as its vacuum.
WAVES ON NONCOMMUTATIVE SPACE–TIME AND GAMMA-RAY BURSTS
Authors: AMELINO-CAMELIA GIOVANNI , MAJID SHAHN
Published: August 2004

Quantum group Fourier transform methods are applied to the study of processes on noncommutative Minkowski space–time [xi, t]=ιλxi. A natural wave equation is derived and the associated phenomena of in vacuo dispersion are discussed. Assuming the deformation scale λ is of the order of the Planck length one finds that the dispersion effects are large enough to be tested in experimental investigations of astrophysical phenomena such as gamma-ray bursts. We also outline a new approach to the construction of field theories on the noncommutative space–time, with the noncommutativity equivalent under Fourier transform to non-Abelianness of the "addition law" for momentum in Feynman diagrams. We argue that CPT violation effects of the type testable using the sensitive neutral-kaon system are to be expected in such a theory.
STRINGS AND BRANES IN NON-ABELIAN GAUGE THEORY
Authors: SCHMIDHUBER CHRISTOF
Published: August 2004

It is an old speculation that SU(N) gauge theory can alternatively be formulated as a string theory. Recently this subject has been revived, in the wake of the discovery of D-branes. In particular, it has been argued that at least some conformally invariant cousins of the theory have such a string representation. This is a pedagogical introduction to these developments for nonstring theorists. Some of the existing arguments are simplified.
NEUTRINO MASSES AND THE BARYON ASYMMETRY
Authors: BUCHMÜLLER W. , PlÜMACHER M.
Published: August 2004

Due to sphaleron processes in the high-temperature symmetric phase of the standard model the cosmological baryon asymmetry is related to neutrino properties. For hierarchical neutrino masses, with B-L broken at the unification scale ΛGUT~1016 GeV, the observed baryon asymmetry nB/s~10-10 can be naturally explained by the decay of heavy Majorana neutrinos. We illustrate this mechanism with two models of neutrino masses, consistent with the solar and atmospheric neutrino anomalies, which are based on the two symmetry groups SU(5)×U(1)F and SU(3)c×SU(3)L×SU(3)R×U(1)F. We also review related cosmological bounds on Majorana neutrino masses and the use of Boltzmann equations.
STUDY OF THE LOCAL TRANSPORT AND STRUCTURAL PROPERTIES OF MULTIFILAMENTARY Ag-SHEATHED Bi(2223) TAPES
Authors: STRANO G. , GUASCONI P. , MALAGOLI A. , BELLINGERI E. , SIRI A. S. , GRASSO G.
Published: August 2004

It is known that the current flow in high quality Ag-heathed (Bi,Pb) 2 Sr 2 CaCu 3 O 10+x tapes shows a clear inhomogeneous behavior, as demonstrated by earlier magneto-optical experiments. In order to study this effect in detail we have extracted single filaments from a multifilamentary Ag-sheathed Bi(2223) tape, prepared by the Oxide-Powder-In-Tube technique. The filaments have been isolated by chemical etching of the silver matrix, and individually characterised according to their position inside the conductor. Different series of measurements have been performed on each filament: magnetisation hysteresis loops and zero field cooled DC susceptibility by SQUID magnetometry, electrical resistivity by the four-probe method, Bi(2223) phase purity and texture by XRD analysis, and local stoichiometry by SEM/EDX analysis.

The microstructure analysis, in particular the study of the c-axis parameter and the microprobe analysis have revealed a higher Pb content (matching the starting stoichiometry) in the innermost filament. In addition to this result. It has been found by magnetisation measurements that the innermost filament carries a critical current density of 53 kA/cm 2 (at 77 K), i.e. a factor of two larger than for all the filaments of the outer shell (with j c ranging between 25 and 40 kA/cm 2). This result is in quantitative agreement with the room temperature electrical resistivity measurements performed on the same samples.
QUANTUM CHEMICAL STUDY ON THE DOPING MECHANISM OF CUPRATE SUPERCONDUCTORS
Authors: Tanaka Jiro
Published: August 2004

Molecular orbital calculations on the model clusters of cuprate superconductor are presented to show the mechanism of insulator to metal transition. Highest occupied molecular orbitals (HOMO) of the model clusters of one-dimensional chain showed that the metallic carrier will appear above 6% doping level, which is consistent with experimental results.
Growth hormone secretion in primary adrenal Cushing's syndrome is disorderly and inversely correlated with body mass index
Authors: van Aken Maarten O. , Pereira Alberto M. , Frölich Marijke , Romijn Johannes A. , Pijl Hanno , Veldhuis Johannes D. , Roelfsema Ferdinand
Published: August 2004

To evaluate the impact on the somatotropic axis of endogenous cortisol excess in the absence of primary pituitary disease, we investigated spontaneous 24-h growth hormone (GH) secretion in 12 adult patients with ACTH-independent hypercortisolism. Plasma GH concentration profiles (10-min samples) were analyzed by deconvolution to reconstruct secretion and approximate entropy to quantitate orderliness of the release process. Comparisons were made with a body mass index (BMI)-, age-, and gender-matched control group and an age- and gender-matched lean control group. GH secretion rates did not differ from BMI-matched controls but were twofold lower compared with lean subjects, mainly due to a 2.5-fold attenuation of the mean secretory burst mass ( P = 0.001). In hypercortisolemic patients, GH secretion was negatively correlated with BMI ( R = −0.55, P = 0.005) but not cortisol secretion. Total serum IGF-I concentrations were similar in the three groups. Approximate entropy (ApEn) was increased in patients with Cushing's syndrome compared with both control groups (vs. BMI-matched, P = 0.04; vs. lean, P = 0.001), denoting more irregular GH secretion patterns. ApEn in patients correlated directly with cortisol secretion ( R = 0.77, P = 0.003). Synchrony between cortisol and GH concentration series was analyzed by cross-correlation, cross-ApEn, and copulsatility analyses. Patients showed loss of pattern synchrony compared with BMI-matched controls, but copulsatility was unchanged. We conclude that hyposomatotropism in primary adrenal hypercortisolism is only partly explained (∼30%) by increased body weight and that increased GH secretory irregularity and loss of synchrony suggest altered coordinate regulation of GH release.
On the structure of Riemannian manifolds of almost nonnegative Ricci curvature
Authors: Yun Gabjin
Published: August 2004

We study the structure of manifolds with almost nonnegative Ricci curvature. We prove a compact Riemannian manifold with bounded curvature, diameter bounded from above, and Ricci curvature bounded from below by an almost nonnegative real number such that the first Betti number havingcodimension two is an infranilmanifold or a finite cover is a sphere bundle over a torus. Furthermore, if we assume the Ricci curvature is bounded and volume is bounded from below, then the manifold must be an infranilmanifold.
A note on a pair of derivations of semiprime rings
Authors: Chaudhry Muhammad Anwar , Thaheem A. B.
Published: August 2004

We study certain properties of derivations on semiprime rings. The main purpose is to prove the following result: let R be a semiprime ring with center Z(R), and let f, g be derivations of R such that f(x)x + xg(x) ∈ Z(R) for all x ∈ R, then f and g are central. As an application, we show that noncommutative semisimple Banach algebras do not admit nonzero linear derivations satisfying the above central property. We also show that every skew‐centralizing derivation f of a semiprime ring R is skew‐commuting.
Moduli space of filtered λ‐ringstructures over a filtered ring
Authors: Yau Donald
Published: August 2004

Motivated in part by recent works on the genus of classifying spaces of compact Lie groups, here we study the set of filtered λ‐ring structures over a filtered ring from a purely algebraic point of view. From a global perspective, we first show that this set has a canonical topology compatible with the filtration on the given filtered ring. For power series rings R[[x]], where R is between ℤ and ℚ, with the x‐adic filtration, we mimic the construction of the Lazard ring in formal group theory and show that the set of filtered λ‐ring structures over R[[x]] is canonically isomorphic to the set of ring maps from some “universal” ring U to R. From a local perspective, we demonstrate the existence of uncountably many mutually nonisomorphic filtered λ‐ring structures over some filtered rings, including rings of dual numbers over binomial domains, (truncated) polynomial, and power series rings over ℚ‐algebras.
Predictive Adaptive Responses to Maternal High-Fat Diet Prevent Endothelial Dysfunction but Not Hypertension in Adult Rat Offspring
Authors: Khan Imran , Dekou Vasia , Hanson Mark , Poston Lucilla , Taylor Paul
Published: August 2004

Background—

Population-based studies suggest that fetal adaptive responses to maternal dietary imbalance confer survival benefit when the postnatal diet remains suboptimal but increase susceptibility to cardiovascular disease when postnatal nutrition is improved. We have investigated “predictive adaptive” responses in a rodent model in which adult offspring of fat-fed dams develop characteristics of the metabolic syndrome.

Methods and Results—

Sprague-Dawley rats were fed a fat-rich diet or normal chow throughout pregnancy and weaning. Vascular endothelial function and blood pressure were determined in 180-day-old offspring of fat-fed dams raised on standard chow (FC) or on the fat-rich diet (FF) and in offspring of chow-fed dams raised on chow (CON). Small mesenteric artery endothelium-dependent dilation to acetylcholine was impaired in male and female FC (by ANOVA,
P
<0.001 versus CON) but similar to CON in FF (
P
=NS). Blood glucose was lower in FF versus FC. Heart rate was reduced in male FC versus CON (
P
<0.05) but not in FF. Plasma triglyceride concentrations were reduced in male FF compared with CON (
P
<0.05). Blood pressure was raised in female FC (systolic, 132.5±3.0 mm Hg versus CON, 119.0±3.8 mm Hg,
P
<0.05; diastolic, 91.2±1.7 mm Hg versus CON, 81.1±1.4 mm Hg,
P
<0.05) and in female FF (systolic, 132.5±4.2 mm Hg versus CON,
P
<0.05; diastolic, 91.0±1.9 mm Hg versus CON,
P
<0.05). Blood pressure was similar to CON in male FC and FF.

Conclusions—

Predictive adaptive responses prevent endothelial dysfunction and reduced heart rate in offspring of fat-fed dams if offspring are raised on the same diet but do not prevent development of raised blood pressure.
Effect of Isthmus Anatomy and Ablation Catheter on Radiofrequency Catheter Ablation of the Cavotricuspid Isthmus
Authors: Da Costa Antoine , Faure Emmanuel , Thévenin Jérôme , Messier Marc , Bernard Samuel , Abdel Kihel , Robin Christophe , Romeyer Cécile , Isaaz Karl
Published: August 2004

Background—

Cavotricuspid isthmus (CTI) characteristics are rarely documented when comparing catheters in radiofrequency ablation (RFA) of atrial flutter (AFL). Our objectives were (1) to evaluate the impact of CTI morphology and length on ablation procedures and (2) to compare the efficacy of an 8-mm-tip catheter with an irrigated cooled-tip RFA in the subgroup presumed to be more difficult to treat (with a long CTI, >35 mm).

Methods and Results—

Over a period of 17 months, 185 patients accepted the protocol and underwent an isthmogram in preparation for RFA. Groups were classified according to CTI length and CTI morphology. RFA was performed with an 8-mm-tip catheter for patients with a short CTI, ≤35 mm (n=123), whereas randomization between an 8-mm-tip and a cooled-tip catheter applied to patients with a longer CTI, >35 mm (n=62). For long CTI, 32 patients were assigned to an 8-mm catheter and 30 patients to the cooled-tip RFA ablation group. In this subset, RF application (18.2±17 versus 19±13 minutes) and x-ray exposure (20.8±18 versus 18±13 minutes) did not differ between the 8-mm-tip and the cooled-tip procedures. Number of applications (9.9±11 versus 18.6±15 minutes;
P
<0.0001) and x-ray exposure (11.7±11 versus 19.5±16 minutes,
P
=0.0001) differed significantly between patients with short and long CTIs. Patients with short and straight CTIs required 3 times fewer RFA applications and shorter x-ray exposure compared with other CTI morphologies (pouch-like recesses and concave characteristics).

Conclusions—

The number of RF applications required for a complete isthmus block in long CTIs is not influenced by the choice between an 8-mm or cooled-tip catheter. Procedure parameters, however, are significantly influenced by CTI length and morphology. Pouch-like recesses and concave characteristics account for much longer ablation times at all CTI lengths.
Estimation of the End of Ejection in Aortic Stenosis
Authors: Bermejo Javier , Rojo-Álvarez José Luis , Antoranz J. Carlos , Abel Monica , Burwash Ian G. , Yotti Raquel , Moreno Mar , García-Fernández Miguel A. , Lehmann Kenneth G. , Otto Catherine M.
Published: August 2004

Background—

All indices of aortic stenosis (AS) rely on measurements of mean transvalvular pressure gradient (
ΔP
) and flow rate. Because the gradient is reversed during late ejection, the late systolic left ventricular (LV)–aortic pressure crossover may be an erroneous landmark of end-ejection. The aortic incisura should be a better reference to calculate indices of AS invasively.

Methods and Results—

The accuracy of the pressure crossover and the incisura to define end-ejection was assessed in a chronic AS experimental model (9 dogs) with the use of an implantable flowmeter and Doppler echocardiography as reference. In 288 hemodynamic recordings analyzed (aortic valve area [AVA]: 0.74±0.46 cm
2
), ejection ended 37±29 ms after the pressure crossover but almost simultaneously with the incisura (2±17 ms). Pressure crossover error accounted for significant errors in the measurement of
ΔP
(95% limits of agreement, +0 to +7 mm Hg) and AVA (−0.1 to +0.2 cm
2
). These errors were reduced to less than half with the use of the incisura to define end-ejection. Additionally, the agreement with Doppler-derived AS indices was best with use of the incisura. Pressure crossover error was maximal in situations of higher output, moderate orifice narrowing, higher arterial compliance, and lower vascular resistance. In 32 consecutive patients undergoing cardiac catheterization for AS, the pressure crossover induced a clinically important overestimation of the
ΔP
from +22 to +50%. Errors in AVA estimation were considerably smaller (−2% to +6%) because of simultaneous and offsetting errors in the measurements of
ΔP
and flow.

Conclusions—

The aortic incisura and not the second pressure crossover should be used to obtain invasive indices of AS.
Fetal Ventricular Mass Determination on Three-Dimensional Echocardiography
Authors: Bhat Aarti Hejmadi , Corbett Virginia , Carpenter Nathan , Liu Nick , Liu Ruolan , Wu Anna , Hopkins Graham , Sohaey Roya , Winkler Carey , Sahn Christine S. , Sovinsky Valerie , Li Xiaokui , Sahn David J.
Published: August 2004

Background—

Estimation of ventricular volume and mass is important for baseline and serial evaluation of fetuses with normal or abnormal hearts. Direct measurement of chamber wall volumes and mass can be made without geometric assumptions by 3D fetal echocardiography. Our goals were to determine the feasibility of using fast nongated 3D echocardiography for fetal volumetric and mass assessments, to validate the accuracy of the ultrasound system and the measurement technique, and if satisfactory, to develop normal values for fetal ventricular mass during the second and third trimesters.

Methods and Results—

This was a prospective outpatient study of 90 consecutive normal pregnancies during routine obstetric services at Oregon Health & Science University (Portland). Optimized 3D volumes of the fetal thorax and cardiac chambers were rapidly acquired and later analyzed for right and left ventricular mass by radial summation technique from manual epicardial and endocardial traces. Experiments to validate the ultrasound system and measurement technique were performed with modified small balloon models and in vivo and ex vivo small animal experiments. Our study established the feasibility of fetal ventricular mass measurements with 3D ultrasound technology and developed normal values for right and left ventricular mass from 15 weeks’ gestation to term.

Conclusions—

Nongated fast 3D fetal echocardiography is an acceptable modality for determination of cardiac chamber wall volume and mass with good accuracy and acceptable interobserver variability. The method should be especially valuable as an objective serial measurement in clinical fetal studies with structurally or functionally abnormal hearts.
Secretoneurin, an Angiogenic Neuropeptide, Induces Postnatal Vasculogenesis
Authors: Kirchmair Rudolf , Egger Margot , Walter Dirk H. , Eisterer Wolfgang , Niederwanger Andreas , Woell Ewald , Nagl Markus , Pedrini Michael , Murayama Toshinori , Frauscher Silke , Hanley Allison , Silver Marcy , Brodmann Marianne , Sturm Wolfgang , Fischer-Colbrie Reiner , Losordo Douglas W. , Patsch Josef R. , Schratzberger Peter
Published: August 2004

Background—

Induction of postnatal vasculogenesis, the mobilization of bone marrow–derived endothelial progenitor cells and incorporation of these cells into sites of blood vessel formation, is a well-known feature of angiogenic cytokines such as vascular endothelial growth factor. We hypothesized that the angiogenic neuropeptide secretoneurin induces this kind of neovascularization.

Methods and Results—

Secretoneurin induced mobilization of endothelial progenitor cells to sites of vasculogenesis in vivo in the cornea neovascularization assay. Progenitor cells were incorporated into vascular structures or were located adjacent to them. Systemic injection of secretoneurin led to increase of circulating stem cells and endothelial progenitor cells. In vitro secretoneurin induced migration, exerted antiapoptotic effects, and increased the number of these cells. Furthermore, secretoneurin stimulated the mitogen-activated protein kinase system, as shown by phosphorylation of extracellular signal–regulated kinase, and activated the protein kinase B/Akt pathway. Activation of mitogen-activated protein kinase was necessary for increase of cell number and migration, whereas Akt seemed to play a role in migration of endothelial progenitor cells.

Conclusions—

These data show that the angiogenic neuropeptide secretoneurin stimulates postnatal vasculogenesis by mobilization, migration, and incorporation of endothelial progenitor cells.
Altered Age-Related Blood Pressure Pattern in Type 1 Diabetes
Authors: Rönnback Mats , Fagerudd Johan , Forsblom Carol , Pettersson-Fernholm Kim , Reunanen Antti , Groop Per-Henrik
Published: August 2004

Background—

Pulse pressure (PP) increases with age as a result of arterial stiffening and is a powerful predictor of cardiovascular disease. Type 1 diabetes is associated with excessive cardiovascular mortality and increased arterial stiffness. We examined whether the age-related blood pressure changes in type 1 diabetic patients differ from those of the nondiabetic background population.

Methods and Results—

We performed a cross-sectional, case-control study of 2988 consecutively selected diabetic subjects and 5486 randomly selected nondiabetic control subjects. Blood pressure was measured twice by mercury sphygmomanometry on a single occasion. Compared with controls, diabetic subjects had a higher systolic blood pressure in all age groups, whereas diastolic blood pressure was higher in those <40 years but lower in those >45 years of age. Consequently, diabetic subjects had a higher PP and a higher prevalence of isolated systolic hypertension. The early age-related rise in PP was more pronounced in subjects with diabetic nephropathy but was also evident in diabetic subjects with normal albumin excretion rate. In a multiple regression analysis, PP in diabetic patients was associated with age, male sex, duration of diabetes, and albuminuria.

Conclusions—

A higher systolic pressure and an earlier decrease in diastolic pressure result in a higher and more rapidly increasing PP in type 1 diabetic patients. Our findings indicate accelerated arterial aging, which may contribute to the higher cardiovascular morbidity and mortality in these patients.
Incremental Benefit of Myocardial Contrast to Combined Dipyridamole-Exercise Stress Echocardiography for the Assessment of Coronary Artery Disease
Authors: Moir Stuart , Haluska Brian A. , Jenkins Carly , Fathi Robert , Marwick Thomas H.
Published: August 2004

Background—

Although assessment of myocardial perfusion by myocardial contrast echocardiography (MCE) is feasible, its incremental benefit to stress echocardiography is not well defined. We examined whether the addition of MCE to combined dipyridamole-exercise echocardiography (DExE) provides incremental benefit for evaluation of coronary artery disease (CAD).

Methods and Results—

MCE was combined with DExE in 85 patients, 70 of whom were undergoing quantitative coronary angiography and 15 patients with a low probability of CAD. MCE was acquired by low-mechanical-index imaging in 3 apical views after acquisition of standard resting and poststress images. Wall motion, left ventricular opacification, and MCE components of the study were interpreted sequentially, blinded to other data. Significant (>50%) stenoses were present in 43 patients and involved 69 coronary territories. The addition of qualitative MCE improved sensitivity for the detection of CAD (91% versus 74%,
P
=0.02) and accurate recognition of disease extent (87% versus 65% of territories,
P
=0.003), with a nonsignificant reduction in specificity.

Conclusions—

The addition of low-mechanical-index MCE to standard imaging during DExE improves detection of CAD and enables a more accurate determination of disease extent.
The 1+1 Trial
Authors: Bänsch Dietmar , Steffgen Frank , Grönefeld Gerian , Wolpert Christian , Böcker Dirk , Mletzko Ralph-Uwe , Schöls Wolfgang , Seidl Karlheinz , Piel Michael , Ouyang Feifan , Hohnloser Stefan H. , Kuck Karl-Heinz
Published: August 2004

Background—

The tachycardia detection interval (TDI) in implantable cardioverter/defibrillators (ICDs) is conventionally programmed according to the slowest documented ventricular tachycardia (VT), with a safety margin of 30 to 60 ms. With this margin, VTs above the TDI may occur. However, longer TDIs are associated with an increased risk of inappropriate therapy. We hypothesized that patients with slow VTs (<200 bpm) may benefit from a long TDI and a dual-chamber detection algorithm compared with a conventionally programmed single-chamber ICD.

Methods and Results—

Patients with VTs <200 bpm were implanted with a dual-chamber ICD that was randomly programmed to a dual-chamber algorithm and a TDI of ≥469 ms or to a single-chamber algorithm with a TDI 30 to 60 ms above the slowest documented VT cycle length and the enhancement criteria of cycle length variation and acceleration. The primary combined end point was the number of all inappropriate therapies, VTs above the TDI, and VTs with significant therapy delay (>2 minutes). After 6 months, a crossover analysis was performed. Total follow-up was 1 year. One hundred two patients were included in the study. The programmed TDI was 500±36 ms during the dual-chamber phase and 424±63 ms during the single-chamber phase. For the primary end point (inappropriate therapies, VTs above the TDI, or VTs with detection delay), a moderate superiority of the dual-chamber mode was found: Mann-Whitney estimator=0.6661; 95% CI, 0.5565 to 0.7758;
P
=0.0040.

Conclusions—

Dual-chamber detection with a longer TDI improves VT detection and does not increase the rate of inappropriate therapies despite a considerable increase in tachycardia burden.
Early Statin Treatment in Patients With Acute Coronary Syndrome
Authors: Okazaki Shinya , Yokoyama Takayuki , Miyauchi Katsumi , Shimada Kazunori , Kurata Takeshi , Sato Hitoshi , Daida Hiroyuki
Published: August 2004

Background—

Recent clinical trials have demonstrated that aggressive lipid lowering by statins could prevent recurrent events after acute coronary syndrome (ACS). We hypothesized that this efficacy was caused by a significant reduction in plaque volume by aggressive LDL cholesterol (LCL-C) lowering. The present study investigated the effect of early statin treatment on plaque volume of a nonculprit lesion by serial volumetric intravascular ultrasound in patients with ACS.

Methods and Results—

Seventy patients with ACS were enrolled. All patients underwent emergency coronary angiography and percutaneous coronary intervention (PCI). They were randomized to intensive lipid-lowering therapy (n=35; atorvastatin 20 mg/d) or control (n=35) groups after PCI. Volumetric intravascular ultrasound analyses were performed at baseline and 6-month follow-up for a non-PCI site in 48 patients (atorvastatin, n=24; control, n=24). LDL-C level was significantly decreased by 41.7% in the atorvastatin group compared with the control group, in which LDL-C was increased by 0.7% (
P
<0.0001). Plaque volume was significantly reduced in the atorvastatin group (13.1±12.8% decrease) compared with the control group (8.7±14.9% increase;
P
<0.0001). Percent change in plaque volume showed a significant positive correlation with follow-up LDL-C level (
R
=0.456,
P
=0.0011) and percent LDL-C reduction (
R
=0.612,
P
<0.0001), even in patients with baseline LDL-C <125 mg/dL.

Conclusions—

Early aggressive lipid-lowering therapy by atorvastatin for 6 months significantly reduced the plaque volume in patients with ACS. Percent change in plaque volume showed a significant positive correlation with percent LDL-C reduction, even in patients with low baseline LDL-C.
Effects of Percutaneous Transluminal Angioplasty and Endovascular Brachytherapy on Vascular Remodeling of Human Femoropopliteal Artery by Noninvasive Magnetic Resonance Imaging
Authors: Wyttenbach Rolf , Gallino Augusto , Alerci Mario , Mahler Felix , Cozzi Luca , Di Valentino Marcello , Badimon Juan J. , Fuster Valentin , Corti Roberto
Published: August 2004

Background—

Percutaneous transluminal angioplasty (PTA) of severely stenotic peripheral vascular lesions is hampered by a higher restenosis rate. The effects of PTA on vascular wall as well as the effects of the antirestenotic properties of endovascular brachytherapy (EVBT) remain unclear. MRI allows in vivo noninvasive assessment of the vascular effects of such treatment strategies. We sought to elucidate the vascular effect of PTA and PTA+EVBT by serial MRI.

Methods and Results—

Twenty symptomatic patients with severe stenosis of the femoropopliteal artery were randomly assigned to PTA (n=10) or PTA+EVBT (n=10; 14 Gy by γ-irradiation source) and imaged by high-resolution MRI before and 24 hours and 3 months after intervention. An independent observer blinded to the procedure analyzed the MRI data. At 24 hours, cross-sectional MRI revealed that lumen area (86% and 67%) and total vessel area (47% and 34%) increased similarly in the PTA and PTA+EVBT groups, respectively. All patients showed severe splitting of the atherosclerotic plaque, resulting in an irregularly shaped lumen. At 3 months, MRI revealed a significant difference in lumen area change between the PTA and PTA+EVBT groups (40% and 106%, respectively;
P
=0.026) and in the total vessel area (14% and 39%, respectively;
P
=0.018). At 3 months, plaque disruption was still present in 50% of the patients treated with PTA+EVBT.

Conclusions—

After PTA, there is deep disruption of the atherosclerotic plaques and an extensive remodeling process of the arterial wall. Luminal loss after PTA is partially due to inward vessel remodeling. Brachytherapy prevents inward remodeling and induces an increase in lumen area but partially prevents healing of disrupted vessel surface.
Myocardial Perfusion Imaging Based on the Blood Oxygen Level–Dependent Effect Using T
2
-Prepared Steady-State Free-Precession Magnetic Resonance Imaging
Authors: Fieno David S. , Shea Steven M. , Li Yongzhong , Harris Kathleen R. , Finn J. Paul , Li Debiao
Published: August 2004

Background—

The decision to perform coronary revascularization procedures may hinge on assessment of myocardial perfusion reserve. Blood oxygen level–dependent (BOLD) MRI is a potential method to detect the effects of regional variations in myocardial blood flow during vasodilation.

Methods and Results—

We imaged dogs (n=13) on a 1.5-T whole-body MRI scanner using a new T
2
-prepared steady-state free-precession (SSFP) MRI pulse sequence sensitive to BOLD contrast. Images (in-plane resolution ≈1 mm
2
) of 5 short-axis and 2 long-axis slices of the heart were acquired during graded levels of adenosine infusion via a surgically placed left circumflex (LCx) catheter (n=11) or via a right atrial catheter in animals with an LCx occluder (n=2). Relative myocardial perfusion was measured with the use of fluorescent microspheres. Signal intensity changes in myocardium subtended by the left anterior descending coronary artery were compared with those in the LCx region. Unprocessed T
2
-weighted images revealed changes in signal intensity corresponding to areas of regional vasodilation or reduced myocardial perfusion reserve during systemic vasodilation. At maximal vasodilation, the signal intensity ratio in the LCx versus left anterior descending territories increased by 33±4% compared with baseline, corresponding to a 3.8±0.3-fold increase in relative perfusion (
P
<0.01). MR intensity at progressive levels of vasodilation demonstrated good agreement with microsphere flow (
R
=0.80,
P
<0.01).

Conclusions—

T
2
-prepared SSFP BOLD imaging is a promising method to determine an index of myocardial perfusion reserve in this animal model.
Impact of the Metabolic Syndrome on Mortality From Coronary Heart Disease, Cardiovascular Disease, and All Causes in United States Adults
Authors: Malik Shaista , Wong Nathan D. , Franklin Stanley S. , Kamath Tripthi V. , L’Italien Gilbert J. , Pio Jose R. , Williams G. Rhys
Published: August 2004

Background—

Mortality resulting from coronary heart disease (CHD), cardiovascular disease (CVD), and all causes in persons with diabetes and pre-existing CVD is high; however, these risks compared with those with metabolic syndrome (MetS) are unclear. We examined the impact of MetS on CHD, CVD, and overall mortality among US adults.

Methods and Results—

In a prospective cohort study, 6255 subjects 30 to 75 years of age (54% female) (representative of 64 million adults in the United States) from the Second National Health and Nutrition Examination Survey were followed for a mean±SD of 13.3±3.8 years. MetS was defined by modified National Cholesterol Education Program criteria. From sample-weighted multivariable Cox proportional-hazards regression, compared with those with neither MetS nor prior CVD, age-, gender-, and risk factor–adjusted hazard ratios (HRs) for CHD mortality were 2.02 (95% CI, 1.42 to 2.89) for those with MetS and 4.19 (95% CI, 3.04 to 5.79) for those with pre-existing CVD. For CVD mortality, HRs were 1.82 (95% CI, 1.40 to 2.37) and 3.14 (95% CI, 2.49 to 3.96), respectively; for overall mortality, HRs were 1.40 (95% CI, 1.19 to 1.66) and 1.87 (95% CI, 1.60 to 2.17), respectively. In persons with MetS but without diabetes, risks of CHD and CVD mortality remained elevated. Diabetes predicted all mortality end points. Those with even 1 to 2 MetS risk factors were at increased risk for mortality from CHD and CVD. Moreover, MetS more strongly predicts CHD, CVD, and total mortality than its individual components.

Conclusions—

CHD, CVD, and total mortality are significantly higher in US adults with than in those without MetS.
National Cholesterol Education Program Versus World Health Organization Metabolic Syndrome in Relation to All-Cause and Cardiovascular Mortality in the San Antonio Heart Study
Authors: Hunt Kelly J. , Resendez Roy G. , Williams Ken , Haffner Steve M. , Stern Michael P.
Published: August 2004

Background—

To assess the utility of clinical definitions of the metabolic syndrome (MetS) to identify individuals with increased cardiovascular risk, we examined the relation between the MetS, using both the National Cholesterol Education Program (NCEP) and the World Health Organization definitions, and all-cause and cardiovascular mortality in San Antonio Heart Study participants enrolled between 1984 and 1988.

Methods and Results—

Among 2815 participants, 25 to 64 years of age at enrollment, 509 met both criteria, 197 met NCEP criteria only, and 199 met WHO criteria only. Over an average of 12.7 years, 229 deaths occurred (117 from cardiovascular disease). Moreover, in the primary prevention population of 2372 participants (ie, those without diabetes or cardiovascular disease at baseline), 132 deaths occurred (50 from cardiovascular disease). In the primary prevention population, the only significant association adjusted for age, gender, and ethnic group was between NCEP-MetS and cardiovascular mortality (hazard ratio [HR], 2.01; 95% CI, 1.13–3.57). In the general population, all-cause mortality HRs were 1.47 (95% CI, 1.13–1.92) for NCEP-MetS and 1.27 (95% CI, 0.97–1.66) for WHO-MetS. Furthermore, for cardiovascular mortality, there was evidence that gender modified the predictive ability of the MetS. For women and men, respectively, HRs for NCEP-MetS were 4.65 (95% CI, 2.35–9.21) and 1.82 (95% CI, 1.14–2.91), whereas HRs for WHO-MetS were 2.83 (95% CI, 1.55–5.17) and 1.15 (95% CI, 0.72–1.86).

Conclusions—

In summary, although both definitions were predictive in the general population, the simpler NCEP definition tended to be more predictive in lower-risk subjects.
Protective Effect of Propylthiouracil Independent of Its Hypothyroid Effect on Atherogenesis in Cholesterol-Fed Rabbits
Authors: Chen Wei-Jan , Lin Kwang-Huei , Lai Ying-Ju , Yang Su-Hui , Pang Jong-Hwei S.
Published: August 2004

Background—

Propylthiouracil (PTU) is used to treat hyperthyroid patients by its hypothyroid effect. PTU also is found to have potent antioxidant and immunosuppressive effects. These findings suggest that PTU may play a role in the prevention of atherosclerosis.

Methods and Results—

This study evaluates the effect of PTU on atherosclerotic change in rabbits fed a high-cholesterol diet. The pronounced atherosclerotic lesions in the aortas of rabbits fed a 2% cholesterol diet for 12 weeks were significantly attenuated by the concurrent addition of 0.1% PTU to the drinking water. However, exogenous supplementation of thyroid hormone in hypothyroid PTU-treated rabbits did not abrogate the protective effect of PTU on atherogenesis. Immunohistochemical analysis showed that PTU administration apparently reduced the intimal smooth muscle cell/macrophage ratio in the atherosclerotic plaques of rabbits fed a 2% cholesterol diet. In vitro, the addition of PTU to the medium of cultured rat vascular smooth muscle cells led to a dose-dependent inhibition of cell proliferation and migration. Furthermore, this study confirmed that PTU dose-dependently increased expression of PTEN, a tumor suppressor gene known to be involved in the coordinate inhibition of VSMC proliferation and migration.

Conclusions—

This study demonstrated that PTU inhibited the development of atherosclerosis through a thyroid-independent mechanism that may be explained, at least in part, by the ability of PTU to inhibit vascular smooth muscle cell proliferation and migration. Furthermore, PTEN induction, via disruption of the phosphatidylinsitol 3–kinase–mediated pathway, plays a crucial role in mediating the inhibitory action on vascular smooth muscle cell proliferation and migration.