Development of a 64 × 64 CdZnTe array and associated readout integrated circuit for use in nuclear medicine

Previous work has shown that hybrid semiconductor detector arrays similar to those used in infrared focal-plane arrays are very attractive for use in nuclear medicine and other gamma-ray imaging applications. In this paper, we describe the development of a 64 × 64 readout multiplexer specifically for use in gamma-ray imaging; we also describe the construction of 64 × 64 CdZnTe hybrid detector arrays using the new readout. The readout and detector array are both about one inch square (2.5 cm × 2.5 cm) and have 380 μm pixel pitch. Some initial assembly problems have been resolved by stabilizing the hybrids with epoxy. Preliminary testing results are presented that verify that the 64 × 64 CdZnTe arrays perform as excellent imaging spectrometers.     

Polyelectrolyte contributions to transitions in electrostatic persistence length

The manner in which a conformational change determining the polyelectrolyte contribution to chain stiffness is incorporated into existing polyelectrolyte theory is discussed. The full Poisson-Boltzmann equation for the electrostatic potential (rather than a linear version) is incorporated into the calculation of the electrostatic persistence length. Changes in the electrostatic persistence length can then be demonstrated qualitatively to be controlled by the solution dielectric constant.     

Hidden configurations and effective interactions: A comparison of three different ways to construct renormalized hamiltonians for truncated shell-model calculations

We discuss in general some criteria and methods for constructing effective Hamiltonians. Then three different methods are compared for constructing an effective Hamiltonian to be used in nuclear shell-model calculations for A = 17–20, allowing (A-16) active nucleons in the d_5/2, s_1/2 vector space. For all three methods, the aim is to obtain a d_5/2, s_1/2 model which will simulate the results of a given full d_5/2, s_1/2, d_3/2 model. The three methods for finding the effective Hamiltonian are.

1. (a) conventional low-order perturbation theory;

2. (b) a projection technique, in which we construct a Hamiltonian whose eigenvalues excactly match a selected subset of d_5/2, s_1/2, d_3/2 eigenvalues, and whose eigenvectors excatly match the projections of d_5/2, s_1/2, d_3/2 eigenvectors on the d_5/2, s_1/2 space; and

3. (c) least-square fit to selected d_5/2, s_1/2, d_3/2 energies.

For all three methods, we first restrict the effective Hamiltonian to a linear combination of 1-body and 2-body operators. Then for the perturbation and projection techniques, we also calculate the 3-body-operator terms in the effective Hamiltonian.When the effective Hamiltonians are limited to 1-body and 2-body terms, the leastsquare method yields the best overall fit to the low-lying spectrum of d_5/2, s_1/2, d_3/2     

Some Examples of the Use of Simulation in U.S. and Canadian Agriculture

Mathematical simulation is a technique widely used by agricultural engineers to determine systems interactions, to evaluate technical feasibility, to determine economic feasibility, to design complex structures and to help with managing production. In the past, simulation has been used one level removed from the farmers who manage operation on a day-to-day basis. This is changing.Three completely different types of simulations are presented: (1) a static and deterministic simulation of on-farm ethanol production that models the conversion process and determines economic feasibility; (2) a dynamic and deterministic simulation of maize production, including harvest and drying that is weather dependent; (3) a static and stochastic simulation that uses Monte Carlo techniques to obtain information about strength and performance of glued-laminated beams.We believe that inexpensive computing capability will tremendously increase the use of simulation models, such as the three described, that will help farmers better manage their production systems.     

Large-basis no-core shell-model calculations and their application to10C →10B fermi beta decay

We use a 4ħΩ shell-model calculation with a two-body effective interaction derived microscopically from the Reid93 potential to calculate the isospin-mixing correction for the¹⁰C→¹⁰B superallowed Fermi transition. The effective interaction takes into account the Coulomb potential as well as the charge dependence ofT=1 partial waves. Our results suggest the isospin-mixing correctionδ _c ≈ 0.1%, which is compatible with previous calculations obtained by other methods. The obtainedδ _C correction is about a factor of four too small to obtain unitarity of the Cabibbo-Kobayashi-Maskawa matrix with the present experimental data. Presented by B.R. Barrett at the International Conference on “Atomic Nuclei and Metallic Clusters”, Prague, September 1–5, 1997. This work is supported in part by NSF grant No. PHY96-05192.