Circular 70

This report describes one aspect of successful air transport developed over the past 20 years in Alask

The degree of an eight-dimensional real quadratic division algebra is 1, 3, or 5

A celebrated theorem of Hopf, Bott, Milnor, and Kervaire states that every finite-dimensional real division algebra has dimension 1, 2, 4, or 8. While the real division algebras of dimension 1 or 2 and the real quadratic division algebras of dimension 4 have been classified, the problem of classifying all 8-dimensional real quadratic division algebras is still open. We contribute to a solution of that problem by proving that every 8-dimensional real quadratic division algebra has degree 1, 3, or 5. This statement is sharp.Comment: 8 page

Circular 75

Record keeping is an important tool in the management of any productive enterprise. In the area of reindeer herding, consistent and accurate record keeping can provide valuable information for making profitable herd management decisions. Making the right decisions can mean the difference between a non-productive herd and one that yields high profits. In this paper, it will be shown how keeping records can contribute to decision making and how computers can help the record keeping process

Circular 74

In 1985, members of the Applied Reindeer Research Project at the University of Alaska Fairbanks obtained and reviewed a Scandinavian instructional video1 on reindeer herding in Norway. This video described a structure that was developed and used by the Scandinavian reindeer industry to prevent injuries during corralling by segregating fawns from adults. The following is a description of how the fawn separator is built, how it works, and its current use in western Alaska

Relation between stress heterogeneity and aftershock rate in the rate-and-state model

We estimate the rate of aftershocks triggered by a heterogeneous stress change, using the rate-and-state model of Dieterich [1994].We show that an exponential stress distribution Pt(au) ~exp(-tautau_0) gives an Omori law decay of aftershocks with time ~1/t^p, with an exponent p=1-A sigma_n/tau_0, where A is a parameter of the rate-and-state friction law, and \sigma_n the normal stress. Omori exponent p thus decreases if the stress "heterogeneity" tau_0 decreases. We also invert the stress distribution P(tau) from the seismicity rate R(t), assuming that the stress does not change with time. We apply this method to a synthetic stress map, using the (modified) scale invariant "k^2" slip model [Herrero and Bernard, 1994]. We generate synthetic aftershock catalogs from this stress change.The seismicity rate on the rupture area shows a huge increase at short times, even if the stress decreases on average. Aftershocks are clustered in the regions of low slip, but the spatial distribution is more diffuse than for a simple slip dislocation. Because the stress field is very heterogeneous, there are many patches of positive stress changes everywhere on the fault.This stochastic slip model gives a Gaussian stress distribution, but nevertheless produces an aftershock rate which is very close to Omori's law, with an effective p<=1, which increases slowly with time. We obtain a good estimation of the stress distribution for realistic catalogs, when we constrain the shape of the distribution. However, there are probably other factors which also affect the temporal decay of aftershocks with time. In particular, heterogeneity of A\sigma_n can also modify the parameters p and c of Omori's law. Finally, we show that stress shadows are very difficult to observe in a heterogeneous stress context.Comment: In press in JG

Occasional Publications on Northern Life, No. 04

The need to exchange information on research in reindeer and caribou diseases became apparent to investigators attending the Second International Reindeer/Caribou Symposium in Roros, Norway, in 1979. Initially, bibliographies were to be exchanged by being submitted to and subsequently distributed by workers at the University of Alaska. When the bibliographies were submitted, it seemed sensible to computerize the lists to facilitate searches for specific information in the future. An apparently simple task became amazingly complex. This is the resultant collection of publications by reindeer/caribou disease researchers. Because researchers in wildlife diseases tend to work on more than one species or topic, out of interest or necessity, a decision was made to include all of a person's references rather than to limit them to strictly reindeer/caribou diseases. The authors hope this will provide a good basis for exchange of information among all those interested in reindeer/caribou diseases

Charge Transport in Polymer Ion Conductors: a Monte Carlo Study

Diffusion of ions through a fluctuating polymeric host is studied both by Monte Carlo simulation of the complete system dynamics and by dynamic bond percolation (DBP) theory. Comparison of both methods suggests a multiscale-like approach for calculating the diffusion coefficients of the ion