Let R be the convex subset of x ∈ IRⁿ defined by q linear inequalities where x, a_j ∈ IRⁿ and b_j ∈ IR. Given a strictly positive vector ω; ∈ IR^q, the weighted analytic center x_ac(ω;) is the minimizer of the strictly convex function over the interior of R. We consider the linear programming problem (LP): max{c^Tx|x ∈ R}. We give an interior point method for solving the LP that uses weighted analytic centers. We test its performance and limitations using a variety of LP problems. We also compare the method with the well-known logarithmic barrier method.

The white-tailed hawk (Buteo albicaudatus) formerly nested in the American Southwest but no longer appears to do so. We hypothesize that the reason for the absence of this always-scarce species in Arizona and Sonora, Mexico, is the elimination of its grassland habitat caused by cessation of grass fires in the tropic-subtropic regions of these two states. Loss of subtropical grasslands in the Southwest was due to livestock grazing removing fine fuels for grassland fires. When grassland prey sources became scarce due to the reduction in grass cover, nutritional levels were no longer sufficient to allow the white-tailed hawk to successfully engage in nest-building, egg-laying and the rearing of young. These conditions, initiated in the 1880s, have continued through to the present day in both southern Arizona and Sonora.

The Rodeo-Chediski Wildfire, the largest in Arizona's history, damaged or destroyed ecosystem resources or disrupted ecosystem functioning in a mostly mosaic pattern throughout the ponderosa pine (Pinus ponderosa) forests exposed to the bum. Impacts of the wildfire on the occurrence of birds and their diversities were studied on two watersheds in the area, one burned by a high severity (stand-replacing) fire, while the other was burned by a low severity (stand-modifying) fire. This paper reports on the results of a five-year (2002–2007) evaluation of this wildfire on the bird species and numbers observed on these two watersheds to provide a record of the impacts of the historic fire on avifauna communities.

The Division of Mathematical and Natural Sciences at the West campus of Arizona State University has adopted a new curriculum leading to a B.S. degree in the Life Sciences. An innovative feature of this curriculum is the inclusion of experimental work with the desert tree lizard (Urosaursus ornatus) in multiple courses to link them together thematically. The experiments conducted in the core courses in Cell Biology and Fundamentals of Genetics are designed to introduce students to techniques in modern cell and molecular biology within the context of the lizard theme. In the laboratory for the Cell Biology course, students perform a 3-week project using SDS-polyacrylamide gel electrophoresis to compare the proteins found in various lizard organs including heart and liver. In the laboratory for the Fundamentals of Genetics course, students carry out a 2-week project using nondenaturing gel electrophoresis in agarose gels to study the occurrence of allozymes of aconitate hydratase (EC 4.2.1.3) and NADP -dependent malate dehydrogenase (EC 1.1.1.37) in different individuals in captive populations of desert tree lizards. In both cases, the students gain experience in casting and running gels, in staining and imaging gels digitally, and in analyzing the images quantitatively. By performing these two linked projects in separate courses, students can see the value of vertical and horizontal gel electrophoresis in different contexts and build on their technical skills as they move through the curriculum.

Pyrgulopsis trivialis is a western North American hydrobiid snail that is a candidate for federal listing under the Endangered Species Act as threatened or endangered. No literature regarding population size estimates for this species were found. This type of information is limited for aquatic gastropods, springsnails in particular, though it is important for addressing conservation issues. Density counts were used on samplers made of saltillo tile within a single springbrook to estimate population size of P. trivialis. Three population estimates were obtained over the study period in 2002: 129,135; 80,130; and 164,234 snails. These estimates were statistically comparable, though they may under-estimate the true population size. Nevertheless, this provides a reliable and repeatable method of estimating population size for P. trivialis and other hydrobiids that live in similar lotic habitats.