Preimpoundment Ichthyofaunal Survey of the Piney Creek Watershed, Izard County, Arkansas

Piney Creek is a clear medium-size tributary of White River in a region of the Ozarks that is undergoing rapid environmental change. Piney Creek is characterized by a very diverse ichthyofauna, although increased sedimentation due to poor agricultural practices and gravel mining threatens to destroy much natural habitat and eventually may cause extirpation of some species. The wide diversity of 44 species is related to variety of habitat and the proximity of a large reservoir, and not to differences in the physicochemical environments. Fish density ranged from 15,100 to 21 fish/ha, greatest concentrations being in headwater pools. For the three most numerous cyprinids, mean weight per individual was greater in pools than in riffles. Okkelbergia aepyptera was collected for the second time in Arkansas (Harp and Matthews, in press), and a range extension for Notropis sabinae is reported

RANCH-LEVEL ECONOMIC IMPACTS OF GRAZING POLICY CHANGES: A CASE STUDY FROM OWYHEE COUNTY, IDAHO

Economic impacts often are cited as justification both for and against changes in grazing policy on public lands. A recent study conducted in Owyhee County, Idaho, illustrates a process to gather ranch-level economic information, develop economic models for different ranching systems, and use the models to estimate economic impacts of grazing policy changes. Ranch-level models were developed from producer panels and interviews within the county. Costs and returns, livestock production information, dependency on public lands, and other factors relative to ranch-level economics were gathered in four meetings with livestock producers and other interested parties. Results indicate that, as dependency on federal lands rise, both costs and returns fall. Ranch-level economic impacts of alternative grazing policy scenarios also are detailed.Land Economics/Use, Agricultural and Food Policy,

COHESION, INTEGRATION, AND ATTACHMENT IN OWYHEE COUNTY COMMUNITIES

How social change occurs is an important consideration when analyzing the effects of public land management policies on rural communities. This paper utilizes data from a recent study in Owyhee County, Idaho, to explore the combination of social attributes that contribute to community attitudes of cohesion, integration, and attachment in a set of rural communities. Specifically, we examine the importance of social networks and where a particular public land activity, ranching, fits into those networks. We then evaluate the role such networks play in determining respondent attitudes about the cohesiveness of their community, how they are integrated with people in their community, and how attached they are to where they live. The results indicate that increasing density of acquaintenship and intimate social connections to ranching and other local businesses increase the strength of cohesion and integration attitudes. Density of acquaintenship and intimate social connections to local businesses increase community attachment, but a social connection to ranching does not.Community/Rural/Urban Development, Land Economics/Use,

Numerical calculation of the internal flow field in a centrifugal compressor impeller

An iterative numerical method has been developed for the calculation of steady, three-dimensional, viscous, compressible flow fields in centrifugal compressor impellers. The computer code, which embodies the method, solves the steady three dimensional, compressible Navier-Stokes equations in rotating, curvilinear coordinates. The solution takes place on blade-to-blade surfaces of revolution which move from the hub to the shroud during each iteration

In-flight calibration of the Apollo 14 500 mm Hasselblad camera

In-flight calibration of 500-mm Hasselblad camera flown on Apollo 1

An evaluation of dry film lubricants and substrate materials for use on SSME gimbal bearings

Failure of the spherical bearing shaft of the Space Shuttle Main Engine (SSME) gimbal bearing assembly was encountered during Design Verification Specification testing of the full scale engine. Investigation revealed that the failure was caused by a deficiency in the lubrication system. Based upon the materials and gimbal operating conditions, a lubricant of MoS2 and graphite with a ceramic binder was the best lubricant candidate for this particular application; however, the decision to implement the change was not made without verification testing. Scaled down simulation testing was performed. Four different substrate materials and eight different dry film lubricants were subjected to tests under simulated SSME environmental and stress load conditions. The test specimens were evaluated for friction and operating life. Each test specimen was subjected to cyclic operation under load until failure. The force required to move the bearing surfaces relative to each other was monitored throughout the test, thus providing analytical data for derivation of the coefficient of friction. Results indicate that the MoS2/graphite lubricant with ceramic binder proved to be superior from the standpoint of endurance and also from the standpoint of friction reducing capabilities when applied to the titanium substrate material used on SSME. Endurance of this lubricant was approximately 16 times that of the lubricant which was being used when the SSME gimbal failed

Influence of tectonic folding on rockfall susceptibility, American Fork Canyon, Utah, USA

International audienceWe examine rockfall susceptibility of folded strata in the Sevier fold-thrust belt exposed in American Fork Canyon in north-central Utah. Large-scale geologic mapping, talus production data, rock-mass-quality measurements, and historical rockfall data indicate that rockfall susceptibility is correlated with limb dip and curvature of the folded, cliff-forming Mississippian limestones. On fold limbs, rockfall susceptibility increases as dip increases. This relation is controlled by several factors, including an increase in adverse dip conditions and apertures of discontinuities, and shearing by flexural slip during folding that has reduced the friction angles of discontinuities by smoothing surface asperities. Susceptibility is greater in fold hinge zones than on adjacent limbs primarily because there are greater numbers of discontinuities in hinge zones. We speculate that susceptibility increases in hinge zones as fold curvature becomes tighter