Plesippus francescana (Frick) from the late Pliocene, Coso Mountains, California, with a review of the genus Plesippus

Two mammalian types, occurring in a late Pliocene fauna from the Coso Mountains, California, have already been described. Among the more abundant forms in this assemblage are the horses of the genus Plesippus. These are of particular interest not only for purposes of correlation of the geologic horizon in which they occur, but also because of their phylogenetic relationships. Opportunity is taken therefore to make a comparative study of characters of the species from the Coso Mountains with reference to nearly related forms found in beds of similar age and to define more clearly, than has been previously attempted, the position of Plesippus in the lineage of the horse group

Site-saturation studies of β-lactamase: Production and characterization of mutant β-lactamases with all possible amino acid substitutions at residue 71

A mutagenic technique that "saturates" a particular site in a protein with all possible amino acid substitutions was used to study the role of residue 71 in β-lactamase (EC 3.5.2.6). Threonine is conserved at residue 71 in all class A β-lactamases and is adjacent to the active site Ser-70. All 19 mutants of the enzyme were characterized by the penam and cephem antibiotic resistance they provided to Escherichia coli LS1 cells. Surprisingly, cells producing any of 14 of the mutant β-lactamases displayed appreciable resistance to ampicillin; only cells with mutants having Tyr, Trp, Asp, Lys, or Arg at residue 71 had no observable resistance to ampicillin. However, the mutants are less stable to cellular proteases than wild-type enzyme is. These results suggest that Thr-71 is not essential for binding or catalysis but is important for stability of the β-lactamase protein. An apparent change in specificity indicates that residue 71 influences the region of the protein that accommodates the side chain attached to the β-lactam ring of the substrate

Technology development for lunar base water recycling

This paper will review previous and ongoing work in aerospace water recycling and identify research activities required to support development of a lunar base. The development of a water recycle system for use in the life support systems envisioned for a lunar base will require considerable research work. A review of previous work on aerospace water recycle systems indicates that more efficient physical and chemical processes are needed to reduce expendable and power requirements. Development work on biological processes that can be applied to microgravity and lunar environments also needs to be initiated. Biological processes are inherently more efficient than physical and chemical processes and may be used to minimize resupply and waste disposal requirements. Processes for recovering and recycling nutrients such as nitrogen, phosphorus, and sulfur also need to be developed to support plant growth units. The development of efficient water quality monitors to be used for process control and environmental monitoring also needs to be initiated

STEER AND HEIFER PRICE DIFFERENCES IN THE LIVE CATTLE AND CARCASS MARKETS

A dynamic model is used to estimate quarterly price differences between steers and heifers in the feeder, slaughter, and carcass markets. For cattle within the same weight and grade range, their price differences are hypothesized to be influenced by seasonal, economic, and partly reflecting time changes in evaluation of steer and heifer quality in the live cattle and dressed meat trades. Stochastic factors are less prevalent at the feeder level, although risk of placing pregnant heifers in feedlots and weather are important. Steer and heifer inventories, slaughter prices, cost of gain, and margins explained most of the variation in feeder steer and heifer price differences.Livestock Production/Industries, Marketing,

Galois module structure of Galois cohomology for embeddable cyclic extensions of degree p^n

Let p>2 be prime, and let n,m be positive integers. For cyclic field extensions E/F of degree p^n that contain a primitive pth root of unity, we show that the associated F_p[Gal(E/F)]-modules H^m(G_E,mu_p) have a sparse decomposition. When E/F is additionally a subextension of a cyclic, degree p^{n+1} extension E'/F, we give a more refined F_p[Gal(E/F)]-decomposition of H^m(G_E,mu_p)