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Impulsive problems for mechanical systems subject to kinematic constraints are discussed in this paper. In addition to the applied impulses, there may exist suddenly changed constraints, or termed impulsive constraints. To describe the states of the system during the impulsive motion, three different phases, i.e., prior motion, virtual motion, and posterior motion, are defined which are subject to different sets of constraints, and thus have different degrees-of-freedom. A fundamental principle, i.e., the principle of velocity variation, for the constrained impulsive motion is enunciated as a foundation to derive the privileged impulse-momentum equations. It is shown that for a system with no applied impulse, a conservation law can be stated as the conservation of the virtual-privileged momenta. The proposed methodology provides a systematic scheme to deal with various types of impulsive constraints, which is illustrated in the paper by solving the constrained impulsive problems for the motion of a sleigh.

It was recently demonstrated that the empirical linear correlation of ${E(4}_{1}^{+})$ with ${E(2}_{1}^{+})$ is reproduced by the interacting boson model 1 (IBA-1) if a constant value for the coefficient $\ensuremath{\kappa}$ of the Q$\ensuremath{\cdot}$Q term is used. This constancy motivates the present investigation of whether it is possible to find sets of IBA-1 parameters, with fixed $\ensuremath{\kappa}$, that reproduce the data for a more general set of observables and a wide range of nuclei. A consistent procedure, based on contour plots of key observables, was used to extract $\ensuremath{\epsilon}$ and $\ensuremath{\chi}$ values for 145 nuclei spanning the $Z$ = 50--82 shell, which give reasonable overall agreement with the data with smoothly varying parameters. The constant $\ensuremath{\kappa}$ constraint sometimes leads to parameter values different than normal: finite $\ensuremath{\epsilon}$ values $(\ensuremath{\sim}$ 0.1 MeV) even for rotational nuclei and large $\ensuremath{\chi}$ values for transitional and vibrational nuclei that even increase towards the vibrational region. Finally, a systematic correlation of $\ensuremath{\epsilon}$ values with ${E(2}_{1}^{+})$ was found.

A new class of non‐holonomic constraints is proposed, namely, completely non‐holonomic, partially non‐ holonomic, and truly non‐holonomic. The classification is mainly based on the Frobenius condition and the existence of the integral surfaces of the constraints. The intrinsic properties of non‐holonomic constraints, such as the reachability property, vary with respect to different classes. In fact, some non‐holonomic constraints do not have the reachability property. The path‐planning problems for different classes of non‐holonomic constraints also become quite delicate. The paths from a point on one side of the critical surface to a point on the other side must pass through the singular points on the critical surface. The observation made in this paper gives a new outlook of non‐holonomic constraints, and may lead to a deeper understanding of the behaviour of systems with non‐holonomic constraints.

The low energy octupole states in {sup 134}Ba were examined using the inelastic scattering of 22 MeV protons. Strong fragmentation of the low energy octupole strength, which was observed in {sup 196,198}Pt and was identified as a signature of the O(6) dynamical symmetry limit of the interacting boson approximation (IBA), does {ital not} occur in {sup 134}Ba, which has been proposed to have O(6) structure. The model calculations demonstrate that there is, in fact, little difference in the structure of the low-lying positive parity levels between certain nuclei in a U(5){r_arrow}SU(3) (vibrator{r_arrow}rotor) transition and an O(6) nucleus ({gamma}-soft nucleus), but that the octupole fragmentation has an enhanced sensitivity to the d-boson composition of the wave functions and thereby reveals differences in structure that are not easily discernible with other observables. {copyright} {ital 1997} {ital The American Physical Society}

The 1987 evaluation of A=82 (87Mu01) has been revised using experimental decay and reaction data received by the cutoff date noted below.

The negative parity state of [sup 172[minus]180]Os are studied in the framework of the interacting boson approximation model. The negative parity states are formed by including one [ital f] boson or allowing one boson to break into two fermions which are placed in orbits with opposite parity. The calculated level energies and [ital B]([ital E]2)'s are in reasonable agreements with experiments. From the comparison of intrinsic structure it suggests that the relative energy of the quasiparticles may be the most important factor in the calculations.

A study of γ-band levels from Z = 30–82 allows an extension of a nearly-universal anharmonic vibrator description of nuclei to non-yrast states and shows that a multi-phonon picture gives an excellent description of the data.

The 1989 evaluation of A=72 (89Ki02) has been revised using experimental decay and reaction data received by the cutoff noted below.

The energies of [Formula: see text] states in even-even nuclei from Dy to W are shown to be linear in the P-factor and can be described using the same slope prescription for all these nuclei. Deviations are found for Os and Pt isotopes with Np. The results for N>104 give evidence for a more complex structural evolution beyond midneutron shell.

Energy staggering in negative-parity bands is studied in both vibrational and deformed regions. Good agreement is found between empirical signature patterns and those calculated in the IBA. It is shown that the calculations in each region depend essentially on only a single parameter. It is found that each kind of structural region displays unique and characteristic signature behaviour. In γ-soft [O(6)] nuclei the staggering is large and nearly independent of J. Octupole staggering can actually be used as a signature for this symmetry. In deformed regions, signature effects in K = 1− bands show a striking singularity as a function of the filling of a shell, which, both experimentally and theoretically, is shown to be due to the crossing and mixing of K = 0− and 1− bands. Finally, it is found that, albeit for different reasons in different structural regions, the signature splitting of low-lying negative-parity states in vibrational and deformed regions (K = 1− bands) is almost always opposite in phase with that of positive-parity γ-bands: the only exception is at the very beginning of deformed regions.

Level lifetimes were measured for the first time for the neutron-rich isotope $^{78}\mathrm{Ge}$ by the fast electronic scintillation timing technique and B(E2) values were extracted. The energies of the low-lying states and the B(E2) values between the ${0}^{+}$ and ${2}^{+}$ states disclose a rapidly changing structure near N=40, followed by a stabilization, with $^{74\mathrm{\ensuremath{-}}78}\mathrm{Ge}$ best understood as asymmetric rotors.

A comprehensive analysis is made of the experimental information on Gamow-Teller beta decay for the light (A\ensuremath{\le}18) nuclei. Experimental data on half-lives, Q values, and branching ratios are tabulated. Experimental logft values and beta-decay matrix elements are deduced from these data. The one-body-transition densities necessary to predict the beta-decay matrix elements are then calculated using a recently constructed shell-model Hamiltonian operating in the first four major shells. Using these parameters, effective Gamow-Teller operators are deduced for the 0p shell from a least-squares fit to 16 experimental matrix elements. The effective operators are used to calculate 83 decay matrix elements. Some specific decays are discussed.

An average resonance capture study of Te-124 was carried out by An average resonance capture study of Te-124 was carried out by

Lifetime measurements of levels near 2 MeV in 114 Cd give quantitative evidence for collective 3-phonon vibrational states. An analysis of the level scheme reveals a remarkable ambiguity with origins in the basic properties of quantum mechanical mixing.

It is shown that isotopic sequences of 21+ level energies, for elements from Zr to the actinides, are linear against the factor P = N p N n (N p +N n ) . This linearity is interpreted in terms of a simple two-level model. The P-factor also provides a linearization scheme for intruder 0+ energies in the Pb region.

A long-standing issue in the study of deformed nuclei is whether axial asymmetry occurs because of dynamic fluctuations (γ-softness) or as a stable shape (triaxial) component. This question can be conveniently addressed by exploiting certain properties of the IBA which allow the superposition of a γ-soft potential with the traditional hamiltonian via an additional (cubic) term that incorporates a contribution to V ( γ ) with a minimum at γ =30°. With such an approach, it has been shown that nuclei with large r.m.s. asymmetry are, in fact, extremely γ-soft. The present study concerns well deformed rare-earth nuclei with small r.m.s. γ ( γ ≃10°) and focuses on the sensitivity of ratios of β- and γ-band energies to the degree of γ-softness. It is found that a γ-rigid potential results in qualitative dis agreement with the data and, indeed, that the data for these nuclei consistently indicate that the inclusion of a cubic term (rigid triaxiality) makes the model predictions worse. In contrast, a γ-soft potential is in reasonable agreement with empirical results. For most of the nuclei studied, limits on the potential yield a γ min ⩽15° with a relative depth at the minimum of

The reaction58Ni(36Ar, 4p)90Mo has been studied at a beam energy of 149 MeV. A detector array consisting of the OSIRIS spectrometer (12 Compton-suppressed Ge detectors), four charged-particleδE detectors and seven NE-213 neutron detectors at the VICKSI accelerator in Berlin has been used to measure the gamma radiation inγγ- and particle-γγ-coincidence mode. An additional Ge detector was placed at 162‡ to the beam direction to provide information on DCO ratios. The level scheme of90Mo has been extended up to an excitation energy of about 12 MeV and probable spin 23ħ. Some 70 transitions and 40 levels have been newly identified. Spin assignments have been proposed on the basis of measured DCO ratios. Shell model calculations in a model space consisting of the proton 1f 5/2, 2p 3/2, 2p 1/2, and 1g 9/2 orbits and the neutron 2p 1/2, 1g 9/2, 1g 7/2, 2d 5/2, 2d 3/2, and 3s 1/2 orbits with some truncation were made for states above 9ħ and the predicted structure of these states is discussed.

Two-shell-model interactions are constructed in the model space of the five proton and six neutron orbits just above the double shell closure at $^{132}\mathrm{Sn}$. One interaction uses the two-body matrix elements calculated by Kuo and Herling for use near $^{208}\mathrm{Pb}$. For the other, the proton-proton two-body matrix elements are replaced with effective ones of Kruse and Wildenthal and selected proton-neutron matrix elements were varied in order to better reproduce the known energy spectra of $^{134}\mathrm{Sb}$. The main difficulty in this construction is the determination of the neutron single-particle energies. This determination was done by comparison of theoretical and experimental (d,p) spectroscopic factors for the N=83, Z=54, 56, and 58 isotones. The \ensuremath{\Delta}J\ensuremath{\ne}0 first-forbidden ${\mathrm{\ensuremath{\beta}}}^{\mathrm{\ensuremath{-}}}$ decays of $^{133}\mathrm{Sn}$(7/${2}^{\mathrm{\ensuremath{-}}}$), $^{134}\mathrm{Sn}$(${0}^{+}$), $^{134}\mathrm{Sb}$(${0}^{\mathrm{\ensuremath{-}}}$), and $^{134}\mathrm{Sb}$(${7}^{\mathrm{\ensuremath{-}}}$) were considered in order to exemplify the application of these interactions.

Calculations of the variations of residual proton-neutron (p-n) interaction matrix elements for three different mass regions are presented within the frameworks of two approaches, the Nilsson and shell models, which differ substantially in the basis states and interactions used. The excellent agreement obtained with experiment in both approaches points to the simplicity of the underlying physics in terms of orbital overlap arguments.

We present results of interacting-boson-fermion-fermion approximation (IBFFA) calculations for deformed odd-odd $^{176}\mathrm{Re}$ and $^{178}\mathrm{Re}$. Such calculations yield accurate structural information for many different rotational band types, including highly distorted and doubly decoupled bands. Thus, they can help in interpreting experimental data, predicting spin-parity assignments that agree with those obtained by other methods, and giving rather good predictions for interband transition energies. We also compare our previously published IBFFA predictions for $^{180}\mathrm{Re}$ with new experimental data.

The evolution of nuclear structure along the Xe and Ba isotopes with N{lt}82 is studied in comparison with that in the Pt-Os isotopes and with interacting boson approximation calculations. As is well known, the Pt isotopes from {sup 188{minus}196}Pt exhibit a stable structure very close to O(6), the lighter Pt isotopes and the Os nuclei evolve towards a rotor, and the heaviest Pt nuclei, {sup 198,200}Pt, show a tendency towards vibrational character. In contrast, we show that the Ba nuclei are best described by a trajectory from U(5) towards SU(3) that passes through an intermediate structure that resembles O(6) for N{approximately}72{endash}76. The Xe appears to evolve from U(5) to O(6)-like. {copyright} {ital 1998} {ital The American Physical Society}

Lifetimes of the first ${4}^{+}$ and ${6}^{+}$ states in ${}^{104}\mathrm{Mo}$ and ${}^{106}\mathrm{Mo}$ have been measured using the recoil distance method following spontaneous fission of ${}^{252}\mathrm{Cf}.$ The experiment was performed at the 88-inch cyclotron of the Lawrence Berkeley National Laboratory employing the Gammasphere array and the New Yale Plunger Device. Reduced transition probabilities in the ground state band of ${}^{104}\mathrm{Mo}$ are compared with predictions of the critical point symmetry X(5) for phase transitional nuclei between rotational and vibrational shape. While known level energies of ${}^{104}\mathrm{Mo}$ are in good agreement with the X(5) predictions, the analysis of the measured $B(E2)$ values favors a rotor interpretation.

In this paper states in ${}^{102}\mathrm{Pd}$ populated in the $\ensuremath{\epsilon}/{\ensuremath{\beta}}^{+}$ decay of ${}^{102}\mathrm{Ag},$ produced in the ${}^{89}\mathrm{Y}{(}^{16}\mathrm{O},3n)$ reaction, were studied with high efficiency Ge detectors. The level scheme of ${}^{102}\mathrm{Pd}$ is in good overall agreement with the predictions of the E(5) critical point symmetry, with the exception of the ${0}_{2}^{+}$ state, which may be of intruder character.

Introduction Long-term weight change since young-adulthood is a better indicator of distribution of body fat mass. We investigated weight change from age 20 in relation to the risk of CVD mortality, including specific causes of CVD, using data of a large population-based cohort study in Japan. Methods In 1994, 41 364 eligible individuals aged 40–79 years responded to the questionnaire survey. Participants were categorised by weight change: loss ≥10 kg and 5−9.9 kg, ±4.9 kg, gain 5−9.9 kg and ≥10 kg. During the follow-up period of 13.3 years, 1756 deaths of CVD were identified and risk analysis was done by Cox proportional hazards model. Results For all CVD mortality in men were significantly increased for weight loss more than 10 kg with the HR 1.52. Weight gain didn9t predict increased risk in our study. In women, U-shaped association was found while the HRs were 1.64 and 1.35 for those with 10 kg weight loss and weight gain, respectively. The risks for coronary and stroke mortality were also increased for women who lost their weight with the HRs 2.03 and 1.49. The risk trends were similar in subgroup analysis of elderly, non-smokers and early death deletion. Conclusion Weight loss since early adulthood was a predictor of death from CVD. Weight gain more than 10 kg was associated with increased risk of CVD mortality among women.

A simple compact correlation of the energies of the lowest ${0}^{+}$ excitation with the yrast energy ratio ${R}_{4/2}(\mathrm{g}.\mathrm{s}.)\ensuremath{\equiv}{E(4}_{1}^{+}{)/E(2}_{1}^{+})$ is found to characterize all collective nuclei, regardless of structure. This correlation can be reproduced by interacting bosom approximation calculations. Collective signature observables for the states based on ${0}_{2}^{+}$ excitations indicate a different structure than for the ground state configuration but systematic inconsistencies in their global behavior and discrepancies with calculations prevent a definite interpretation.

Lifetimes in the neutron-rich nuclei ${}^{104}\mathrm{Mo},$ ${}^{110}\mathrm{Ru},$ and ${}^{144}\mathrm{Ba}$ were measured using the differential recoil distance method. The experiment was performed with a ${}^{252}\mathrm{Cf}$ fission source inside the New Yale Plunger Device. $\ensuremath{\gamma}$ rays were detected by the SPEctrometer for Experiments with Doppler shifts at Yale (SPEEDY) while fission fragments with the appropriate kinematics were detected by an array of photocells.

It is shown that identical rotational energy spacings in pairs of even-even nuclei do not set these nuclei qualitatively apart from others. Rather, they represent the terminus or limiting case of a continuous range of spacings whose behavior is controlled by the balance between residual {ital p}-{ital n} pairing interactions and whose phenomenology can be simply described.

A systematic study of predictions of the interacting boson approximation (IBA)-2 model leads to the identification of two parameter invariants such that calculations with the same values of the invariants yield results that are identical in certain cases and show close similarities under a wider set of conditions. The invariants validate a much-used form of the IBA-2 Hamiltonian and provide a systematic method to simplify IBA-2 calculations by choosing a truncated Hamiltonian with the same invariant values as more general Hamiltonians. (c) 2000 The American Physical Society.

It is shown that the simple correlation of {ital E}(2{sub 1}{sup +}) and {ital E}(4{sub 1}{sup +}) energies can be a sensitive indicator of underlying shell structure and, in particular, that recent suggestions of radically different structure near the neutron drip line may be most easily signaled by this observable.

Exploiting the concept of {ital F} spin to link extended series of noncontiguous nuclei, it is proposed that {ital F}-spin multiplets ({ital F}=4.5, 5, and 5.5, respectively) commencing with {sup 158,160,162} Yb comprise series of nuclei with similar character resembling the O(6) dynamical symmetry or, at least, the {gamma}-soft O(5) subgroup. The evidence brought to bear on this stems from the yrast ground band levels, {ital B}({ital E}2) values, and signature effects in medium-spin negative-parity levels.

Energy staggering in octupole bands in deformed nuclei is studied. The data show dramatic variations, even reversals, and a singularity in the staggering, across the rare-earth region. A simple model analysis, which is almost parameter independent, is able to reproduce the phenomenology, including the discontinuity, and is amenable to a simple physical interpretation.

Low spin identical bands are found in sets of widely dispersed nuclei, spanning as much as 24 mass units. Moreover, they occur in regions of rapid structural and shape changes. A correlation ansatz to identify such nuclei, based on the concepts of {ital N}{sub {ital p}N{ital n}} and {ital F} spin, is discussed.

Odd-odd 174,176Re nuclei were studied via in-beam γ-ray spectroscopy with a variety of HI-induced reactions at both Michigan State University NSCL and SUNY Stony Brook. One of the most prominent features of each is the existence and very strong population of a doublydecoupled hand. These K = 1 bands result from the coupling of the h 9/2 1/2-[541] proton and an i 13/2 1/2- neutron state. Such doubly-decoupled bands exist in many nuclei in this region. The minimal variations in these structures from nucleus to nucleus implies a relatively weak coupling of the odd particles to the core. This offers hope of a more detailed understanding of p-n residual interactions in relatively high-mass systems. Other information about the character of the doubly-decoupled structures, backbending, and reaction mechanisms can also be learned from these nuclei. Our studies also yielded information on two rotational bands in 175Re, which had been entirely uncharacterized prior to our investigations. The bands are built on the decoupled h 9/2 1/2-[541] proton and a Δ I = 1 band based on the h 9/29/2-[514] proton.

Odd-odd nuclei have been calculated before in the framework of the IBA model. However, in order to keep the calculations tractable, they were done by using supersymmetries or were limited only to unique-parity orbits. We used computer codes for the interacting-bosonfermion-fermion approximation (IBFFA) model, which adopted a very efficient model-space trunction scheme, so no restriction needed to be made and complete calculations of the excitation energy spectra were obtained. We calculated a series of odd-odd isotopes, 176–184Re. The calculations started from even-even Os cores, where a simplified hamiltonian for the SU(3) limit in the IBA-1 model was used. Both negative-and positive-parity calculations for nearby odd-mass Re and Os isotopes have also been carried out. The detailed results of excitation energy spectra of all three types of calculations are presented, also some selected quadrupole and magnetic moments, and B(E2) and B(M1) values. All calculations are compared with experimental data. One of the successes of the IBFFA model is the prediction of the doubly-decoupled bands, which have been verified from experiments.

We present the detailed results of calculations of excitation-energy spectra, quadrupole and magnetic moments, and B(E2) and B(M1) values for the odd-odd 180,182,184Re isotopes in the framework of the interacting-boson-fermion-fermion approximation model. Also, calculations are presented for both positive- and negative-parity excitations in the nearby odd-mass Re and Os nuclides and for collective states in the even-even Os core nuclides. The calculated results are compared with experimental data.

High T c cuprate superconductors have been made by pyrolysis of metallorganic precursors incorporating the appropriate molar ratios of metal ions to form the desired copper oxide compounds. Twp processes have been described as representative examples of novel strategies to produce high T c superconductors in bulk and thin film form: pyrolysis of metallorganic powders for bulk processing and spray pyrolysis for thin film fabrication.

The interacting-boson-fermion-approximation and triaxial models were used to calculate excitation energies and mixing ratios for the {ital N}=80 nuclei, {sup 139}Pr, {sup 141}Pm, and {sup 143}Eu. For low-lying negative- and positive-parity states both models yield roughly the same numbers, in good agreement with experimental results. For high-lying states we find that the interacting-boson-fermion-approximation model describes the level structure considerably better than the triaxial model. On the other hand, the triaxial model gives more satisfactory results in predicting the mixing ratios.