Grosse Ile and the Irish Memorial National Historic Site, Parks Canada: A Case Study

Focuses on values and their protection by examining the place of values in management. Grosse Ile's management is still evolving, and the eventful first phases of planning are still fresh in the minds of staff

Stationary Plasma Thruster Plume Characteristics

Stationary Plasma Thrusters (SPT's) are being investigated for application to a variety of near-term missions. This paper presents the results of a preliminary study of the thruster plume characteristics which are needed to assess spacecraft integration requirements. Langmuir probes, planar probes, Faraday cups, and a retarding potential analyzer were used to measure plume properties. For the design operating voltage of 300 V the centerline electron density was found to decrease from approximately 1.8 x 10 exp 17 cubic meters at a distance of 0.3 m to 1.8 X 10 exp 14 cubic meters at a distance of 4 m from the thruster. The electron temperature over the same region was between 1.7 and 3.5 eV. Ion current density measurements showed that the plume was sharply peaked, dropping by a factor of 2.6 within 22 degrees of centerline. The ion energy 4 m from the thruster and 15 degrees off-centerline was approximately 270 V. The thruster cathode flow rate and facility pressure were found to strongly affect the plume properties. In addition to the plume measurements, the data from the various probe types were used to assess the impact of probe design criteri

A convergent synthetic route to the tunicamycin antibiotics. Synthesis of (+)-tunicamycin V

The tunicamycins are a family of natural products represented generally by structure 1, wherein R indicates one of several long-chain branched, linear, saturated or unsaturated acyl substituents. They elicit a considerable range of biological responses including antimicrobial, antifungal, antiviral, and antitumor activities. Their ability to function as potent inhibitors of oligosaccharide synthesis in eukaryotic cells has established them as unique biochemical probes of the role of glycosylation on protein structure and function. In this work, we describe a concise synthetic route to the tunicamycins, illustrated by the preparation of (+)-tunicamycin V (1-V)

An Investigation Of The Recent Deterioration Of I-75 In Scott County

In early January of 1999, approximately 15 miles ofl-75 in Scott County began to rapidly deteriorate. The existing pavement exhibited several potholes and delaminations. The worst section of deterioration fell approximately between milepoints 125 and 133. In the latter part of January, the condition of the highway had declined to the point thatcorrective action was necessary. The worst sections were milled and patched with hotmixasphalt (HMA). Despite this temporary improvement to the pavement condition, adesire developed within the Department to investigate the cause of the deterioration inorder to prevent a future similar occurrence. Therefore, personnel from the Division of Materials and the Kentucky Transportation Center conducted an abbreviated investigation of the deteriorating pavement and theasphalt mixtures involved. The findings from this investigation, including analyses of thehistorical data for these mixtures and testing of the in-place pavement, revealed severalpossibilities for the premature pavement failure. These possibilities included questionable quality of the aggregates in the mixtures, lowasphalt contents and high dust contents, poor volumetric properties of the mixtures, andlow in-place densities and high permeability of the existing pavement. It was concludedthat no single deficiency caused the failure, but rather, a combination of several factors. A companion section of I-7 5 immediately south of the deteriorated Scott County portions,constructed about one year prior to the pavement presently in question, continues toperform well. Investigation of this pavement and the involved asphalt mixtures revealedhigher asphalt contents, better volumetric properties, higher in-place densities, and lowerpermeability. It is believed that recent revisions to the applicable asphalt mixture specifications have allbut eliminated the possibility of the recurrence of this type of failure. Mixtures designedcurrently under the Superpave system undergo greater scrutiny and must satisfy tougherspecifications. Also, asphalt mixtures are accepted differently today than when thispavement was originally constructed. It is highly unlikely that the mixtures that arecurrently deteriorating on I-75 could satisfy today\u27s specifications

Advanced aeroservoelastic stabilization techniques for hypersonic flight vehicles

Advanced high performance vehicles, including Single-Stage-To-Orbit (SSTO) hypersonic flight vehicles, that are statically unstable, require higher bandwidth flight control systems to compensate for the instability resulting in interactions between the flight control system, the engine/propulsion dynamics, and the low frequency structural modes. Military specifications, such as MIL-F-9490D and MIL-F-87242, tend to limit treatment of structural modes to conventional gain stabilization techniques. The conventional gain stabilization techniques, however, introduce low frequency effective time delays which can be troublesome from a flying qualities standpoint. These time delays can be alleviated by appropriate blending of gain and phase stabilization techniques (referred to as Hybrid Phase Stabilization or HPS) for the low frequency structural modes. The potential of using HPS for compensating structural mode interaction was previously explored. It was shown that effective time delay was significantly reduced with the use of HPS; however, the HPS design was seen to have greater residual response than a conventional gain stablized design. Additional work performed to advance and refine the HPS design procedure, to further develop residual response metrics as a basis for alternative structural stability specifications, and to develop strategies for validating HPS design and specification concepts in manned simulation is presented. Stabilization design sensitivity to structural uncertainties and aircraft-centered requirements are also assessed

Chaco Culture National Historical Park: A Case Study

Looks at the management of CCNHP by the National Park Service. The long history of CCNHP as a heritage site provides an excellent illustration of how values emerge and evolve with new knowledge

Radio Astronomy

Contains research objectives and summary of research on seven research projects and a report on one research project.Joint Services Electronics Program (Contract DAAB07-75-C-1346)National Science Foundation (Grant AST73-05042-AO2)National Institutes of Health (Grant 5 SO5 RR07047-10)U. S. Air Force - Electronic Systems Division (Contract F19628-75-C-0122)M.I.T. Sloan Fund for Basic ResearchNational Aeronautics and Space Administration (Contract NAS5-21980)National Aeronautics and Space Administration (Contract NAS5-22485

Radio Astronomy

Contains reports on three research projects.National Aeronautics and Space Administration (Grant NGL 22-009-016)National Aeronautics and Space Administration (Grant NGL 22-009-421)National Science Foundation (Grant GP-20769)California Institute of Technology Contract 952568Sloan Fund for Basic Research (M. I. T. Grant 241