A new method of alpha ray measurement using a Quadrupole Mass Spectrometer

We propose a new method of alpha($\alpha$)-ray measurement that detects helium atoms with a Quadrupole Mass Spectrometer(QMS). A demonstration is undertaken with a plastic-covered $^{241}$Am $\alpha$-emitting source to detect $\alpha$-rays stopped in the capsule. We successfully detect helium atoms that diffuse out of the capsule by accumulating them for one to 20 hours in a closed chamber. The detected amount is found to be proportional to the accumulation time. Our method is applicable to probe $\alpha$-emitting radioactivity in bulk material.Comment: 8 pages, 6 figure

Re‐examining content‐enriched access : its effect on usage and discovery

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Structure of 11Li in the cluster-orbital shell model for the 9Li+n +n system

The properties of 11Li are studied in detail in the cluster-orbital shell model assuming the structure of 9Li+n+n. The interactions acting between the constituent particles are carefully determined consistently with available data. Large and flexible bases for the valence neutrons are represented as a superposition of gaussian functions. The anomalously large radius of 11Li is nicely reproduced. The density distributions calculated clarify the picture of the neutron halo. The binding energy is, however, calculated to be 1-1.4 MeV short. A possible resolution of this point is discussed from the viewpoint of the di-neutron clustering. The quadrupole moment of 11Li is predicted to be almost the same as that of 9Li.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28629/1/0000443.pd

Microscopic multicluster description of neutron-halo nuclei with a stochastic variational method

To test a multicluster approach for halo nuclei, we give a unified description for the ground states of $^6$He and $^8$He in a model comprising an $\alpha$ cluster and single-neutron clusters. The intercluster wave function is taken a superposition of terms belonging to different arrangements, each defined by a set of Jacobi coordinates. Each term is then a superposition of products of gaussian functions of the individual Jacobi coordinates with different widths, projected to angular momenta $l=0$ or 1. To avoid excessively large dimensions and ``overcompleteness", stochastic methods were tested for selecting the gaussians spanning the basis. For $^6$He, we were able to calculate ground-state energies that are virtully exact within the subspace defined by the arrangements and $l$ values, and we found that preselected random sets of bases (with or without simulated annealing) yield excellent numerical convergence to this ``exact" value with thoroughly truncated bases. For $^8$He good energy convergence was achieved in a state space comprising three arrangements with all $l=0$, and there are indications showing that the contributions of other subspaces are likely to be small. The $^6$He and $^8$He energies are reproduced by the same effective force very well, and the matter radii obtained are similar to those of other sophisticated calculations.Comment: Latex , 8 figures available on request, ATOMKI-4-1993-

Determining the relative permeability and conductivity of thin materials

In order to determine the relative permeability and conductivity of thin materials that could not be found using traditional methods, we constructed a shield box and developed a measuring system to estimate the unknown electric parameters of exotic shielding materials such as thin cloths. Thin electromagnetic shielding sheets of both nonmagnetic materials and ferromagnetic materials were used. The shielding effectiveness of the materials was measured as a function of frequency, and the results were compared with the calculated solutions for a multilayered model that was evaluated using the Sommerfeld integral that expresses near-field spherical waves by a composition of cylindrical waves. In these calculations, the relative permeability and conductivity were varied to determine the solution closest to the measured results. The least squares method was used to determine the best fitted values. Initially the nominal values of relative permeability were assumed, and the conductivity was found using the fitting technique. Then this determined value of the conductivity was assumed, and the relative permeability was found using the fitting technique. For the nonmagnetic materials, the estimated relative permeability was the same as the nominal values. For the ferromagnetic materials, the estimated relative permeability varied 0 percent -30 percent from the nominal values. For both types of materials, the estimated conductivities were 0 percent -9.8 percent different from nominal values. This research details a new method for evaluating the attenuation of interfering electromagnetic waves for thin materials

Compatibility of localized wave packets and unrestricted single particle dynamics for cluster formation in nuclear collisions

Antisymmetrized molecular dynamics with quantum branching is generalized so as to allow finite time duration of the unrestricted coherent mean field propagation which is followed by the decoherence into wave packets. In this new model, the wave packet shrinking by the mean field propagation is respected as well as the diffusion, so that it predicts a one-body dynamics similar to that in mean field models. The shrinking effect is expected to change the diffusion property of nucleons in nuclear matter and the global one-body dynamics. The central \xenon+\tin collisions at 50 MeV/nucleon are calculated by the models with and without shrinking, and it is shown that the inclusion of the wave packet shrinking has a large effect on the multifragmentation in a big expanding system with a moderate expansion velocity.Comment: 16 pages, 7 figure

Cluster structure in stable and unstable nuclei

Cluster structure in stable and unstable nuclei has been studied. We report recent developments of theoretical studies on cluster aspect, which is essential for structure study of light unstable nuclei. We discuss negative parity bands in even-even Be and Ne isotopes and show the importance of cluster aspect. Three-body cluster structure and cluster crystallization are also introduced. It was found that the coexistence of cluster and mean-field aspect brings a variety of structures to unstable nuclei.Comment: 6 pages, 3 figures, submitted to Euro. Phys. J.

Three-Body Halos. II. from Two- to Three-Body Asymptotics

The large distance behavior of weakly bound three-body systems is investigated. The Schr\"{o}dinger equation and the Faddeev equations are reformulated by an expansion in eigenfunctions of the angular part of a corresponding operator. The resulting coupled set of effective radial equations are then derived. Both two- and three-body asymptotic behavior are possible and their relative importance is studied for systems where subsystems may be bound. The system of two nucleons outside a core is studied numerically in detail and the character of possible halo structure is pointed out and investigated.Comment: 16 pages, compressed and uuencoded PosrScript file, IFA-94/3

OAZ-t/OAZ3 Is Essential for Rigid Connection of Sperm Tails to Heads in Mouse

Polyamines are known to play important roles in the proliferation and differentiation of many types of cells. Although considerable amounts of polyamines are synthesized and stored in the testes, their roles remain unknown. Ornithine decarboxylase antizymes (OAZs) control the intracellular concentration of polyamines in a feedback manner. OAZ1 and OAZ2 are expressed ubiquitously, whereas OAZ-t/OAZ3 is expressed specifically in germline cells during spermiogenesis. OAZ-t reportedly binds to ornithine decarboxylase (ODC) and inactivates ODC activity. In a prior study, polyamines were capable of inducing a frameshift at the frameshift sequence of OAZ-t mRNA, resulting in the translation of OAZ-t. To investigate the physiological role of OAZ-t, we generated OAZ-t–disrupted mutant mice. Homozygous OAZ-t mutant males were infertile, although the polyamine concentrations of epididymides and testes were normal in these mice, and females were fertile. Sperm were successfully recovered from the epididymides of the mutant mice, but the heads and tails of the sperm cells were easily separated in culture medium during incubation. Results indicated that OAZ-t is essential for the formation of a rigid junction between the head and tail during spermatogenesis. The detached tails and heads were alive, and most of the headless tails showed straight forward movement. Although the tailless sperm failed to acrosome-react, the heads were capable of fertilizing eggs via intracytoplasmic sperm injection. OAZ-t likely plays a key role in haploid germ cell differentiation via the local concentration of polyamines

Correlations in a Many-Body Calculation of 11^{\bf 11}Li

A many-body calculation of $^{11}$Li is presented where the only input is the well-tested, finite-range {\it D1S} effective interaction of {\it Gogny}. Pairing correlations are included in a constrained Hartree-Fock-Bogolyubov calculation, while long-range collective correlations are introduced using a GCM derived calculation. Correlations are found to play an important role in describing $^{11}$Li. A substantive underlying $^9$Li core of $^{11}$Li is found, which has a different density profile than a free $^9$Li nucleus. This may have significant implications in the use of a three-body framework in studies of $^{11}$Li.Comment: 23 pages typeset in revtex 2.0 with 8 postscript figures in accompanying uuencoded fil