180 research outputs found

    Microscopic description of large-amplitude shape-mixing dynamics with inertial functions derived in local quasiparticle random-phase approximation

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    On the basis of the adiabatic self-consistent collective coordinate method, we develop an efficient microscopic method of deriving the five-dimensional quadrupole collective Hamiltonian and illustrate its usefulness by applying it to the oblate-prolate shape coexistence/mixing phenomena in proton-rich 68,70,72Se. In this method, the vibrational and rotational collective masses (inertial functions) are determined by local normal modes built on constrained Hartree-Fock-Bogoliubov states. Numerical calculations are carried out using the pairing-plus-quadrupole Hamiltonian including the quadrupole-pairing interaction. It is shown that the time-odd components of the moving mean-field significantly increase the vibrational and rotational collective masses in comparison with the Inglis-Belyaev cranking masses. Solving the collective Schroedinger equation, we evaluate excitation spectra, quadrupole transitions and moments. Results of the numerical calculation are in excellent agreement with recent experimental data and indicate that the low-lying states of these nuclei are characterized as an intermediate situation between the oblate-prolate shape coexistence and the so-called gamma unstable situation where large-amplitude triaxial-shape fluctuations play a dominant role.Comment: 17 pages, 16 figures, Submitted to Phys. Rev.

    Primary peripheral arterial stenoses and restenoses excised by transluminal atherectomy: A histopathologic study

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    Atherectomy is a new therapeutic intervention for the treatment of peripheral arterial disease, and permits the controlled excision and retrieval of portions of stenosing lesions. The gross and light microscopic features of 218 peripheral arterial stenoses resected from 100 patients by atherectomy were studied. One hundred seventy of these lesions were primary stenoses and 48 were restenoses subsequent to prior angioplasty or atherectomy. Microscopically, primary stenoses were composed of atherosclerotic plaque (150 lesions), fibrous intimai thickening (15 lesions) or thrombus alone (5 lesions). Atherosclerotic plaques had a variable morphology and, in one-third of cases, were accompanied by abundant surface thrombus that probably added to the severity of stenosis. Most patients with fibrous intimai thickening or thrombus alone had typical atherosclerotic plaque removed elsewhere from within the same artery.Intimai hyperplasia, with or without underlying residual plaque, was found at 36 sites of restenosis, the remaining 12 consisting of plaque only. Intimai hyperplasia had a distinctive histologic appearance and was due to smooth muscle cell proliferation within a loosely fibrous stroma. Superimposed thrombus may have contributed to arterial narrowing in 25% of hyperplastic and 8% of atherosclerotic restenoses (p = 0.41). Pathologic examination of tissues recovered by peripheral atherectomy is an important adjunct that may provide insight into the efficacy of vascular interventions and the phenomenon of postintervention restenosis

    The nuclear energy density functional formalism

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    The present document focuses on the theoretical foundations of the nuclear energy density functional (EDF) method. As such, it does not aim at reviewing the status of the field, at covering all possible ramifications of the approach or at presenting recent achievements and applications. The objective is to provide a modern account of the nuclear EDF formalism that is at variance with traditional presentations that rely, at one point or another, on a {\it Hamiltonian-based} picture. The latter is not general enough to encompass what the nuclear EDF method represents as of today. Specifically, the traditional Hamiltonian-based picture does not allow one to grasp the difficulties associated with the fact that currently available parametrizations of the energy kernel E[g′,g]E[g',g] at play in the method do not derive from a genuine Hamilton operator, would the latter be effective. The method is formulated from the outset through the most general multi-reference, i.e. beyond mean-field, implementation such that the single-reference, i.e. "mean-field", derives as a particular case. As such, a key point of the presentation provided here is to demonstrate that the multi-reference EDF method can indeed be formulated in a {\it mathematically} meaningful fashion even if E[g′,g]E[g',g] does {\it not} derive from a genuine Hamilton operator. In particular, the restoration of symmetries can be entirely formulated without making {\it any} reference to a projected state, i.e. within a genuine EDF framework. However, and as is illustrated in the present document, a mathematically meaningful formulation does not guarantee that the formalism is sound from a {\it physical} standpoint. The price at which the latter can be enforced as well in the future is eventually alluded to.Comment: 64 pages, 8 figures, submitted to Euroschool Lecture Notes in Physics Vol.IV, Christoph Scheidenberger and Marek Pfutzner editor

    The 9p21 susceptibility locus for coronary artery disease and the severity of coronary atherosclerosis

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    <p>Abstract</p> <p>Background</p> <p>Case-control Genome-Wide Association Studies (GWAS) have identified single nucleotide polymorphisms (SNPs) at the 9p21 locus as risk factors for coronary artery disease (CAD). The locus does not contain a clear candidate gene. Hence, the results of GWAS have raised an intense interest in delineating the basis for the observed association. We analyzed association of 4 SNPs at the 9p21 locus with the severity and progression of coronary atherosclerosis, as determined by serial quantitative coronary angiograms (QCA) in the well-characterized Lipoprotein Coronary Atherosclerosis Study (LCAS) population. The LCAS is a randomized placebo-control longitudinal follow-up study in patients with CAD conducted to test the effects of fluvastatin on progression or regression of coronary atherosclerosis.</p> <p>Methods</p> <p>Extensive plasma lipid levels were measured at the baseline and 2 1/2 years after randomization. Likewise serial QCA was performed at the baseline and upon completion of the study. We genotyped the population for 4 SNPs, previously identified as the susceptibility SNPs for CAD in GWAS, using fluorogenic 5' nuclease assays. We reconstructed the haplotypes using Phase 2, analyzed SNP and haplotype effects using the Thesias software as well as by the conventional statistical methods.</p> <p>Results</p> <p>Only Caucasians were included since they comprised 90% of the study population (332/371 with available DNA sample). The 4 SNPs at the 9p21 locus were in tight linkage disequilibrium, leading to 3 common haplotypes in the LCAS population. We found no significant association between quantitative indices of severity of coronary atherosclerosis, such as minimal lumen diameter and number of coronary lesions or occlusions and the 9p21 SNPs and haplotypes. Likewise, there was no association between quantitative indices of progression of coronary atherosclerosis and the SNPs or haplotypes. Similarly, we found no significant SNP or haplotype effect on severity and progression of coronary atherosclerosis.</p> <p>Conclusion</p> <p>We conclude the 4 SNPs at the 9p21 locus analyzed in this study do not impart major effects on the severity or progression of coronary atherosclerosis. The effect size may be very modest or the observed association of the CAD with SNPs at the 9p21 locus in the case-control GWAS reflect involvement of vascular mechanisms not directly related to the severity or progression of coronary atherosclerosis.</p

    Testing microscopically derived descriptions of nuclear collectivity : Coulomb excitation of 22Mg

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    Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be studied within a microscopic or ab initio framework without the use of effective charges; for example with the proper evolution of the E2 operator, or alternatively, through the use of an appropriate and manageable subset of particle–hole excitations. We present a precise determination of E2 strength in 22Mg and its mirror 22Ne by Coulomb excitation, allowing for rigorous comparisons with theory. No-core symplectic shell-model calculations were performed and agree with the new B(E2) values while in-medium similarity-renormalization-group calculations consistently underpredict the absolute strength, with the missing strength found to have both isoscalar and isovector components. The discrepancy between two microscopic models demonstrates the sensitivity of E2 strength to the choice of many-body approximation employed
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