Surface grid generation for complex three-dimensional geometries

An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code based on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry

Development of computerized analysis for solid propellant combustion (ISAP-2)

This report is an improvement of ISAP-1, SRB Vorticity-Acoustic Coupled Instability Analysis, September 1986. Included in this report are the automatic generation of all input data for grid configuration, boundary conditions for coupled acoustic and vortical field calculations, transformation of all dimensions to a parametric form, resulting in flexibility for the user to define the size of the problem (geometric configurations) with reduction in storage (15 to 65%) and computer run-time (50 to 75%). Additional research is required for the following areas: (1) turbulence effects; (2) nonlinear wave oscillations; and (3) chemistry upon combustion instability

A checklist of the hepatics and anthocerotes of Panamá

A brief account of the geography and floristic regions of Panamá is complemented with an historical account of the liverwort studies of this country. This is followed by an annotated checklist of 289 taxa, including 93 new for Panamá. Among these are four hornwort taxa that represent the first anthocerotes reported. Each checklist entry comprises proper taxon citation, collection data and/or bibliographic references.Una revisión de la geografía y regiones florísticas de Panamá es complementada con una nota histórica de los estudios sobre hepáticas de este país. Esto es seguido por una lista anotada de 289 taxa, incluyendo 93 que son nuevos para Panamá. Entre éstos se encuentran cuatro antocerotes que representan las primeras comunicaciones en esta División. Cada taxon ingresado contiene la citación apropiada, datos de colecta y/o referencias bibliográficas

A Review on the Alzheimer Disease Animal Models and Retinal Degeneration

Alzheimer’s disease (AD) is a chronic neurodegen- erative disease, serving as the most common form of dementia among the elderly population. AD targets various neurological processes in humans such as the visual pathway and hence resulting in various forms of visual abnormalities. Several studies have reported the loss of retinal ganglion cells, reduced thickness of nerve fibre layers (NFL) and damage of the optic nerve head and fiber layers. These findings suggest a putative link between AD and visual function deficits. As genetic defects have been found to be associated with AD, it is possible to experimentally mimic this condition in animal models. AD gene mutations discovered in human amyloid pre- cursor protein (APP), presenilin 1/2 (PS1/PS2) and microtubule- associated tau protein have been used to engineer AD animal models. In this review, we discuss the underlying molecular mecha- nisms of AD in terms of amyloidogenesis and tauopathies, as well as explain the pathological changes leading to vision loss in AD patients. Subsequently, the biology of the genes/proteins which have a causative link to AD, including APP, PS1 and PS2 will be discussed. Several recent reports of retinal degeneration in AD transgenic mouse models are selected to examine the relationship between AD and visual disturbance. We believe that a well- established method to generate transgenic mice will enhance our understanding of AD pathology and its correlation with retinal degeneration, leading to possible detection and treatment methods for AD

Hepatitis C Virus and Hepatocarcinogenesis

Hepatitis C virus (HCV) is an RNA virus that is unable to integrate into the host genome. However, its proteins interact with various host proteins and induce host responses. The oncogenic process of HCV infection is slow and insidious and probably requires multiple steps of genetic and epigenetic alterations, the activation of cellular oncogenes, the inactivation of tumor suppressor genes, and dysregulation of multiple signal transduction pathways. Stellate cells may transdifferentiate into progenitor cells and possibly be linked to the development of hepatocellular carcinoma (HCC). Viral proteins also have been implicated in several cellular signal transduction pathways that affect cell survival, proliferation, migration and transformation. Current advances in gene expression profile and selective messenger RNA analysis have improved approach to the pathogenesis of HCC. The heterogeneity of genetic events observed in HCV-related HCCs has suggested that complex mechanisms underlie malignant transformation induced by HCV infection. Considering the complexity and heterogeneity of HCCs of both etiological and genetic aspects, further molecular classification is required and an understanding of these molecular complexities may provide the opportunity for effective chemoprevention and personalized therapy for HCV-related HCC patients in the future. In this review, we summarize the current knowledge of the mechanisms of hepatocarcinogenesis induced by HCV infection

Maintenance cost studies of rotary wing commercial transport aircraft

December 1974Includes bibliographical references (p. 121-123)Introduction: The vertical take-off and landing (VTOL) aircraft market has had substantial growth in the period of the last ten years when one considers the overall number of aircraft in use. The military fleet has continued to increase, as have such operators as natural resource (petroleum and lumber) companies, and law enforcement agencies. (See Table 1.) In scheduled passenger service, however, the VTOL- market has not enjoyed sustained growth. Consider Table 2, the type and number of helicopters in passenger service during 1962-1972. Following the cessation of federal subsidies to helicopter operators in 1966 the number of aircraft (and total available seats) has been steadily declining. Table 3 shows the composition of the fleets of the certificated carriers since 1966. Los Angeles Airways has been in bankruptcy since 1969; Chicago Helicopter is now largely a charter operator, although retaining its certificate; New York Airways, after a period of experimentation with the fixed wing Twin Otter (DHC-6) in 1968-1969, finally made it into the black in 1973, flying Sikorsky S-61's; and SFO Helicopter has retrenched its passenger services severely, but is not yet profitable. Why is the state of scheduled passenger operations so bleak? Many answers to this question have been given. For example, it has been said that the aircraft used by the operators have been inadequate: that they have been designed for military use and are ill suited for civilians who have been used to a higher comfort level (especially since most flights taken on a helicopter are in conjunction with a ride on a large, comfortable jet transport). Alternatively, it has been said that the high cost of operating the current helicopter fleet has caused the ticket price to be too high to be attractive to the traveler. Sometimes the operators have been fingered as the culprits -- that they have not priced their product adequately and have structured their networks poorly, i.e., that the failure has been one of management and marketing. And from the purely technology minded, the answer has been that once the properly designed rotary wing aircraft arrives on the scene -- one designed for civilian use and having the proper payload-range configuration -- the market will boom as VTOL aircraft enter city-center to city-center service. Doubtless there is a kernel -of truth in all these explanations, and examples to sustain most of them can be found in the history of helicopter operations in the United States. The intent of the work described in this report was to explore one frequently cited cause of the problem of high operating costs of helicopters in scheduled service - to wit, high maintenance costs of rotary wing aircraft. This attempt was made to allow a look ahead and to predict trends in maintenance costs of future rotary wing aircraft.This work was performed under a NASA Contract for Ames Research Cente