On a problem of B. Jónsson concerning subalgebras and endomorphisms

Presented by the R. W. Quackenbush.     

Time resolved on-line nuclear orientation (TR-OLNO): Principles and a review of existing experiments

This paper introduces the principles of a new method of making on-line nuclear orientation (OLNO) experiments. The source is pulsed and nuclear spin lattice relaxation is observed directly through the growth of anisotropy of angular distribution of emitted radiation with time after implantation. It is shown that Time Resolved studies (TR-OLNO) are necessary if useful analysis of orientation experiments is to be possible when relaxation times and half-lives become comparable. In the application of OLNO to decays following the initial implant, use of TR-OLNO can overcome difficulties which arise when polarisation is inherited from precursors in the decay chain. Such inheritance introduces ambiguity into analysis of continuous implantation, Time Integral (TI-OLNO), data. Two important features of the new method are discussed. TR-OLNO relaxation rates are sensitive measures of the nuclear g-factor, and combined with TI-OLNO can yield both nuclear spin and magnetic moment. A second feature is the ability to simplify complex spectra, to establish assignments of transitions to members of a decay chain with clarity and to establish the presence of long lived isomers. Experiments performed with TR-OLNO are briefly reviewed.     

Ground state magnetic moments of212,213Bi

The magnetic dipole moments of²¹²Bi and²¹³Bi have been measured and the results are interpreted within the framework of the shell model.     

Intra- and intersubject variability in acoustic measures of normal voice

Twenty-four normal adult women read part of the Rainbow Passage and sustained vowels three trials each. Utterances were assessed for selected parameters measured by Visi-Pitch (average and SD of fundamental frequency (F₀), average and SD of dBA, perturbation, and percent voiced/unvoiced/pause). Assessment of each parameter included measures of central tendency, dispersion, and distribution characteristics (skewness and kurtosis) of the data and of the ranges of values that would include 95% of the scores (95% fiduciary limits). Generally, differences for the group between the three trials were not significant. Intersubject variability for only a few parameters was less than 20% of the parameter's mean. For vowels, variability of jitter was 30–48% of the mean. Eight subjects provided performances 2 months later to obtain an estimate of intrasubject variability over time. There were desirable intrasubject correlations between performances for mean F₀, jitter in reading and on vowels /i/ and /a/, and percent of voicing. Inter- and intrasubject variability seems restricted and the data appear to resemble a normally distributed function for mean F₀ on reading, jitter on /i/, and percent of voicing. Thus, these parameters may have statistical merit for use in vocal testing.     

New directions in low temperature nuclear orientation

The basis of the low temperature nuclear orientation technique is summarized. The present limitations on accessible temperatures and the orders of magnitude of hyperfine interactions in the metallic systems currently studied are discussed briefly. The broad applicability to many elements and the high sensitivity of this singles counting method are emphasized. Specific recent developments are discussed in more detail. The use of a dilution refrigerator to cool to ≈ 10mK nuclei of isotopes far from stability ‘on-line’, after production in an accelerator and electromagnetic selection, is a major extension of the method. The minimum half-life is now limited by the nuclear spinlattice relaxation time, typically of order 10–100 s at 10 mK. Aspects of these experiments are considered and recent results given for Cs and I isotopes. Secondly, the extension of the related technique of nuclear magnetic resonance or oriented nuclei (NMR/ON) to antiferromagnetic insulators is described. A new cooling mechanism involving nuclear-magnon coupling gives access to much lower temperatures than previously reached in these systems. Recent precision work on MnCl₂, 4H₂O is discussed, along with its possible extension to nuclei of lanthanide elements. Finally, the use of nuclear orientation to study ordering below 10 mK of enhanced nuclear moment systems is briefly surveyed, with HoVO₄ as the test case. NMR/ON experiments at high pressure are proposed.     

Magnetic moments of85–90Y nuclei

Low temperature nuclear orientation (LTNO) of neutron deficient^{85m, 86m+}g,^{87m, 90m}Y nuclei is described. The magnetic moments are compared with those of neighbouring nuclei.     

The magnetic dipole moment of 55Co

The ground state g-factor for ⁵⁵Co has been measured as $\text{¦g¦= 1.378±0.001}$ by the technique of nuclear magnetic resonance on oriented nuclei. The temperature dependence of γ-ray anisotropy in the ⁵⁵Fe daughter decay determines both the 1408 keV level spin and the ⁵⁵Co ground state spin to be $\text{7}\text{2}$, and yields values of mixing ratios in the 1037 keV β-transition and the 477 keV γ-transition. The configuration mixing model is used to discuss 1f_{$\text{7}\text{2}$} moment systematics.     

Electronic laboratories for nuclear science education

We are developing electronic laboratories to help introduce students to nuclear science. An electronic laboratory is a collection of computer simulations of nuclear science experiments. Each program allows students to set experimental parameters, collect data, and analyze results. Experiments can easily be repeated because the computer can compress time. Electronic laboratories are useful for schools with existing nuclear science programs because they can prepare students for actual laboratory work. They are also useful for schools without specialized facilities, since they give students an empirical understanding of nuclear science but do not require specialized equipment. We present three electronic experiments.     

Representing endomorphisms and principal congruences

For every algebraU there is an algebraU ^* with (up to isomorphism) the same endomorphism, subalgebra and congruence structure as that ofU, for which every finitely generated subalgebra and every finitely generated congruence ofU ^* is singly generated. The theorem is proved in a somewhat more general category theoretic context.Presented by R. W. Quackenbush.This author's research was supported by an OTKA grant from Hungary.This author's research was supported by NSERC, The Natural Sciences and Engineering Research Council of Canada.