Spatial Distribution of the Surface Geology and 1992 Land Use of the Buffalo River Watershed

The Buffalo River was established by Congress in 1972 as the first National River in the United States and is one of the few remaining free-flowing streams in Arkansas . The Buffalo River flows through the three major physiographic provinces of northern Arkansas, originating in the higher elevations of the Boston Mountains, and flowing generally northeastward to cut through the Springfield and Salem Plateaus. It drops from approximately 2000 feet in the headwaters to around 500 feet above sea level at its confluence with the White River in Marion County. The Buffalo River is considered to be one of Arkansas\u27 greatest natural treasures; thus there is strong interest in protecting it from undue anthropogenic influences. A general description of the area within the Buffalo River Watershed was given by Smith (1967)

Ionization behavior of the histidine residue in the catalytic triad of serine proteases

α-Lytic protease is a homologue of the mammalian serine proteases such as trypsin, chymotrypsin, and elastase, and its single histidine residue belongs to the Asp-His-Ser catalytic triad. This single histidine residue has been selectively enriched in the C-2 carbon with 13C. Magnetic resonance studies of the chemical shift and coupling constant (1Jch) behavior of this nucleus as a function of pH suggest that the imidazole ring is neutral above pH 5 and therefore that the group which is known to ionize with pKa near 6.7 must be the aspartic acid residue. Implications of these new pKa assignments for the catalytic mechanism of serine proteases are discussed and include the absence of any need to separate charge during catalysis. The histidine residue plays two roles. (a) It insulates the aspartic acid from an aqueous environment and accordingly raises its pKa. (b) It serves as a bidentate base to accept a proton from the serine at one of its nitrogens and concertedly transfer a proton from its other nitrogen to the buried carboxylate anion during formation of the tetrahedral intermediate

The molecular structure of isocyanic acid from microwave and infra-red absorption spectra

Experimental investigations of the infra-red and microwave spectra of the slightly asymmetric rotor, HNCO, have been made, and the structure of the molecule has been determined

Community acceptance and implementation of HIV prevention interventions for injection drug users

In 1997, the National Institutes of Health (NIH) reviewed evidence of the effectiveness of HIV prevention programs for injection drug users (IDUs) and recommended that three types ofinterventions be implemented to prevent transmission of HIV among IDUs: 1) community-based outreach, 2) expanded syringe access (including needle exchange programs [NEP] and pharmacy sales), and 3) drug treatment. Progress on increasing the acceptance and feasibility of implementing these programs has been made at the national level, but their implementation has been varied at the local level.Understanding the conditions under which communities accept and implement interventions can help guide effective strategies to foster the implementation of these interventions in areas where programs do not currently exist

Correlated Two-Electron Wave Functions of Any Symmetry

Using a procedure originally due to Hylleraas, a convenient expansion in coupled spherical harmonics which terminates in a very small number of terms is applied to the treatment of fully correlated two-electron wave functions of any symmetry (total angular momentum, parity, and spin). Coupled equations satisfied by these wave functions are derived which are well adapted to computation and which we discretize on a numerical lattice utilizing the basis-spline collocation method. Use of this method which relies on very flexible basis functions is intended to facilitate subsequently the consideration of time-dependent rearrangments such as autoionization, photoionization, and electron-impact excitation and ionization. Here, we describe the underlying theoretical and computational methods concerning our treatment of the two-electron problem, the lattice discretization, and partial eigensolution by damped relaxation. Results of explicit calculations are given regarding the ground state and two low-lying singly excited states of helium