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Estimates of canine and feline euthanasia at U.S. animal shelters--largely based on voluntary surveys with low response rates--make it difficult to estimate the population from which the euthanized animals derive. Estimates of euthanasia rates (animals euthanized per unit of population) have varied widely and been available only sporadically. This study used requirements of Michigan state law (Pet Shops, Dog Pounds, and Animal Shelters Act, 1969) for animal shelters to collect admission and discharge data for all 176 Michigan-licensed animal shelters. In 2003, Michigan shelters discharged 140,653 dogs: Of these, 56,972 (40%) were euthanized; 40,005 (28%) were adopted. This annual euthanasia rate is 2.6% of the estimated 2003 Michigan dog population. Michigan shelters discharged 134,405 cats in 2003: 76,321 (57%) by euthanasia and (24%) by adoption. The estimated ratio of euthanized cats to cats who had owners was 3.1%. Small shelters and privately owned shelters were associated with higher adoption rates. Comparison with historical information from the past 10 to 20 years suggests the number of companion animals being euthanized in shelters has decreased and that progress has been made in reducing the companion animal overpopulation problem.

Computation of all possible frequency responses of a linear system that depends on m uncertain parameters is the subject of this paper. Using a brute force approach, this computation could be carried out using an (m + l)-dimensional parameter sweep, i.e. there is the usual frequency sweep plus one sweep for each uncertain parameter. A much simpler computational alternative is possible if the uncertain system's transfer function has a linear dependence on the parameters and if the set of possible parameter values has a polytopic structure. For this class of uncertain systems, it has previously been shown that, for a single fixed frequency, all possible responses can be determined using several 1-dimensional sweeps. Thus, for a range of frequencies, the obvious extension would involve several 2-dimensional sweeps. However, this obvious extension is not the simplest way to carry out the computation. Indeed, this paper will show that all possible responses for a range of frequencies can be determined...

The stability robustness of both continuous and discrete-time dynamical systems is tantamount to the stability of a whole family of (characteristic) polynomials. The authors treat such families as sets in coefficient space and examine some of their geometric properties. Specifically, they examine cases where the stability of the extreme points of a set implies the stability of the complete family. They are also concerned with the construction and convexity of the stability region in coefficient space.