Estimating Parameter Uncertainty in Binding-Energy Models by the Frequency-Domain Bootstrap.

We propose using the frequency-domain bootstrap (FDB) to estimate errors of modeling parameters when the modeling error is itself a major source of uncertainty. Unlike the usual bootstrap or the simple χ^{2} analysis, the FDB can take into account correlations between errors. It is also very fast compared to the Gaussian process Bayesian estimate as often implemented for computer model calibration. The method is illustrated with a simple example, the liquid drop model of nuclear binding energies. We find that the FDB gives a more conservative estimate of the uncertainty in liquid drop parameters than the χ^{2} method, and is in fair accord with more empirical estimates. For the nuclear physics application, there are no apparent obstacles to apply the method to the more accurate and detailed models based on density-functional theory.

Exit-Channel Suppression in Statistical Reaction Theory.

Statistical reaction theories such as the Hauser-Feshbach theory assume that branching ratios follow Bohr's compound nucleus hypothesis by factorizing into independent probabilities for different channels. Corrections to the factorization hypothesis are known in both nuclear theory and quantum transport theory, particularly an enhanced memory of the entrance channel. We apply the Gaussian orthogonal ensemble to study a complementary suppression of exit channel branching ratios. The combined effect of the width fluctuation and the limitation on the transmission coefficient can provide a lower bound on the number of exit channels. The bound is demonstrated for the branching ratio in neutron-induced reactions on a ^{235}U target.

Nuclear Matrix Elements for Tests of Local Lorentz Invariance Violation.

The nuclear matrix elements for the spin operator and the momentum quadrupole operator are important for the interpretation of precision atomic physics experiments that search for violations of local Lorentz and CPT symmetry and for new spin-dependent forces. We use the configuration-interaction nuclear shell model and self-consistent mean-field theory to calculate the momentum matrix elements for ^{21}Ne, ^{23}Na, ^{133}Cs, ^{173}Yb, and ^{201}Hg. We show that these momentum matrix are strongly suppressed by the many-body correlations, in contrast to the well-known enhancement of the spatial quadrupole nuclear matrix elements.

Nuclear deformation at finite temperature.

Deformation, a key concept in our understanding of heavy nuclei, is based on a mean-field description that breaks the rotational invariance of the nuclear many-body Hamiltonian. We present a method to analyze nuclear deformations at finite temperature in a framework that preserves rotational invariance. The auxiliary-field Monte Carlo method is used to generate a statistical ensemble and calculate the probability distribution associated with the quadrupole operator. Applying the technique to nuclei in the rare-earth region, we identify model-independent signatures of deformation and find that deformation effects persist to temperatures higher than the spherical-to-deformed shape phase-transition temperature of mean-field theory.

Nuclear correlations and the r process.

We show that long-range correlations for nuclear masses have a significant effect on the synthesis of heavy elements by the r process. As calculated by Delaroche et al. [Phys. Rev. C 81, 014303 (2010)], these correlations suppress magic number effects associated with minor shells. This impacts the calculated abundances before the third r-process peak (at mass number A≈195), where the abundances are low and form a trough. This trough and the position of the third abundance peak are strongly affected by the masses of nuclei in the transition region between deformed and spherical. Based on different astrophysical environments, our results demonstrate that a microscopic theory of nuclear masses including correlations naturally smoothens the separation energies, thus reducing the trough and improving the agreement with observed solar system abundances.

Symmetry restoration in Hartree-Fock-Bogoliubov based theories.

We present a Pfaffian formula for projection and symmetry restoration for wave functions of the general Bogoliubov form, including quasiparticle excited states and linear combinations of them. This solves a long-standing problem in calculating states of good symmetry, arising from the sign ambiguity of the commonly used determinant formula. A simple example is given of projecting a good particle number and angular momentum from a Bogoliubov wave function in the Fock space of a single j-shell.

Nonadiabatic generation of coherent phonons.

The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.

Mixed-spin pairing condensates in heavy nuclei.

We show that the Bogoliubov-de Gennes equations for nuclear ground-state wave functions support solutions in which the condensate has a mixture of spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates do not occur when there are equal numbers of neutrons and protons, but only when there is an isospin imbalance. Using a phenomenological Hamiltonian, we predict that such nuclei may occur in the physical region within the proton dripline. We also solve the Bogoliubov-de Gennes equations with variable constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei that exhibit this new pairing behavior, the resulting energy surface can be rather soft, suggesting that there may be low-lying excitations associated with the spin mixing.

Magnetic circular dichroism in real-time time-dependent density functional theory.

We apply the adiabatic time-dependent density functional theory to magnetic circular dichroism (MCD) spectra using the real-space, real-time computational method. The standard formulas for the MCD response and its A and B terms are derived from the observables in the time-dependent wave function. We find real-time method is well suited for calculating the overall spectrum, particularly at higher excitation energies where individual excited states are numerous and overlapping. The MCD sum rules are derived and intepreted in the real-time formalism; we find that they are very useful for normalization purposes and assessing the accuracy of the theory. The method is applied to MCD spectrum of C(60) using the adiabatic energy functional from the local density approximation. The theory correctly predicts the signs of the A and B terms for the lowest allowed excitations. However, the magnitudes of the terms only show qualitative agreement with experiment.

Porter-Thomas fluctuations in complex quantum systems.

The Gaussian orthogonal ensemble (GOE) of random matrices has been widely employed to describe diverse phenomena in strongly coupled quantum systems. In particular, it has often been invoked to explain the fluctuations in decay rates that follow the χ-squared distribution for one degree of freedom, as originally proposed by Brink and by Porter and Thomas. However, we find that the coupling to the decay channels can change the effective number of degrees of freedom from one to two. Our conclusions are based on a configuration-interaction Hamiltonian originally constructed to test the validity of transition-state theory, also known as the Rice-Ramsperger-Kassel-Marcus theory in chemistry. The internal Hamiltonian consists of two sets of GOE reservoirs connected by an internal channel. We find that the effective number of degrees of freedom depends on the control parameter ρΓ, where ρ is the level density in the first reservoir and Γ is the level decay width. The distribution for two degrees of freedom is a well-known property of the Gaussian unitary ensemble (GUE); our model demonstrates that the GUE fluctuations can be present under much milder conditions. Our treatment of the model permits an analytic derivation for ρΓ≳1.

Effective 3-body interaction for mean-field and density-functional theory.

Density functionals for nuclei usually include an effective 3-body interaction that depends on a fractional power of the density. Using insights from the many-body theory of the low-density two-component Fermi gas, we consider a new, nonlocal, form for the energy functional that is consistent with the Fock-space representation of interaction operators. In particular, there is a unique spatially nonlocal generalization of the contact form of the interaction that preserves the ρ(7/3) density dependence required by the many-body theory. We calculate the ground-state energies for particles in a harmonic trap by using the nonlocal induced 3-body interaction and compare them to numerically accurate Green's function Monte Carlo calculations. Using no free parameters, we find that a nonlocality in the space domain provides a better description of the weak-coupling regime than the local-density approximation.

Fire-setting behavior in the histories of a state hospital population.

Review of the records of 191 nongeriatric state hospital inpatients showed that 50 (26%) of the patients had engaged in some form of fire-setting behavior; half of this group had engaged in a single episode. As a group, persons who had engaged in fire-setting behavior were significantly more likely to have a history of nonlethal self-injurious behavior and had a significantly greater number of admissions to the state hospital. The data suggest that fire setting by any patient cannot be accurately predicted and that fire-setting behavior may be an example of destructive operant behavior.

Cardiac high-energy phosphate metabolism in patients with aortic valve disease assessed by 31P-magnetic resonance spectroscopy.

BACKGROUND: The purpose of this work was to determine the clinical and hemodynamic correlates of alterations in cardiac high-energy phosphate metabolism in patients with aortic stenosis and with aortic incompetence. METHODS: Fourteen volunteers, 13 patients with aortic stenosis, and 9 patients with aortic incompetence were included. Patients underwent echocardiography and left and right heart catheterization. 31P-MR spectra from the anterior myocardium were obtained with a 1.5 Tesla clinical MR system. RESULTS: Aortic stenosis and aortic incompetence patients had similar New York Heart Association (NYHA) classes (2.77 +/- 0.12 vs 2.44 +/- 0.18), ejection fractions (normal), left ventricular (LV) end-diastolic pressures, and LV wall thickness. In volunteers, phosphocreatine/adenosine triphosphate (ATP) ratios were 2.02 +/- 0.11. For all patients, phosphocreatine/ATP was significantly reduced (1.64 +/- 0.09; *p = 0.011 vs volunteers). Phosphocreatine/ATP decreased to 1.55 +/- 0.12 (*p = 0.008) in aortic stenosis, while in aortic incompetence, phosphocreatine/ATP only showed a trend for a reduction (1.77 +/- 0.12; p = 0.148). For all patients, phosphocreatine/ATP decreased significantly only with NYHA class III (1.51 +/- 0.09; *p = 0.001), but not with NYHA classes I and II (phosphocreatine/ATP 1.86 +/- 0.18). In aortic stenosis, phosphocreatine/ATP ratios decreased (1.13 +/- 0.03; *p = 0.019) only when LV end-diastolic pressures were > 15 mm Hg or when LV diastolic wall stress was > 20 kdyne cm-2 (1.13 +/- 0.03; *p = 0.024). CONCLUSIONS: For a similar clinical degree of heart failure in human myocardium, volume overload hypertrophy does not, but pressure overload does, induce significant impairment of cardiac high-energy phosphate metabolism. In aortic valve disease, alterations of high-energy phosphate metabolism are related to the degree of heart failure.

Detection of myocardial viability by low-dose dobutamine Cine MR imaging.

The purpose of this work was to test the diagnostic value of dobutamine stress magnetic resonance imaging (MRI) for predicting recovery of regional myocardial contractility after revascularization. Cardiac wall motion abnormalities are due to either non-viable and/or scarred, or viable, but hibernating, myocardial tissue. Dobutamine stress leads to increased systolic wall thickening only in viable myocardium. Twenty-five patients with akinetic or dyskinetic myocardial regions were examined with a Cine FLASH-2D sequence at rest and during dobutamine stress (10 microg/kg/min). Patients were re-examined at rest 3, and in case of persisting wall motion defects, 6 months after revascularization. Criterion of viability was increasing end-systolic wall thickening during stress and/or at follow-up. Akinetic regions related either to the LAD (n = 19) or to the RCA (n = 6) were judged viable if > or = 50% of the affected segments improved. MR studies were completed in all subjects without arrhythmia or need for early terminations due to symptoms. Sensitivity, specificity, and positive predictive value for the prediction of myocardial viability were 61%, 90%, and 87% for the segment-related analysis, and 76%, 100%, and 100% for the patient-related analysis based on coronary artery distribution, respectively. Dobutamine stress MRI allows to predict global functional recovery of akinetic myocardial regions after revascularization with a high positive predictive value and high specificity.

Isolation of full-size mRNA from cells sorted by flow cytometry.

Gene expression is one key mechanism to regulate cell growth and differentiation. It is usually determined by Northern blotting or RT-PCR. However, studies with primary cell cultures are frequently hampered due to contaminating cells such as fibroblasts. We have developed a method to isolate intact full-size mRNA from sorted cells. In many cell types, e.g. cardiac myocytes, cell sorting without prior fixation revealed complete RNA breakdown. Based on a murine fibroblast cell line (AKR-2B), ethanol and formaldehyde at various concentrations and pre-treatment with ribonuclease inactivating DEPC were compared with each other. Fixation with 75% ice-cold DEPC-pre-treated ethanol for 5 min yielded mostly intact RNA. In contrast, antibody staining prior to sorting required 15 min fixation. Addition of RNAse-free BSA (0.5%) and 2 mM CaCl2 optimised the cell recovery ratio and thus a better RNA yield (60% compared to control) after sorting than former studies. Northern blotting and RT-PCR show the intact mRNA species beta-actin. Furthermore, dependent on the cellular PCNA content, we have demonstrated the cell cycle dependent cdk2 and cyclin A expression. This fast and reliable method allows to isolate intact full-size mRNA species appropriate for Northern blotting and RT-PCR to monitor gene expression.