Process for synthesizing and formulating condensed ring polymers

Chemical process for forming low molecular weight, fully cyclized heteroaromatic prepolymers under conditions which limit chain extension or branching is described. Exact procedures used in conducting chemical reaction are defined. Advantages of process over conventional methods are presented

Method for forming pyrrone molding powders and products of said method

The formation of pyrrone resins of the ladder or semiladder structure is described. The technique involves initial formation of fully cyclized prepolymers having an average degree of polymerization of about 1.5, one with acidic terminal groups, another with amine terminal groups. Thereafter the prepolymers are intimately admixed on a 1:1 stoichiometric basis. The resulting powder mixture is molded at elevated pressures and temperatures to form a fully cyclized resin

PRESSURE MEASUREMENT AT THE BALLAST-TIE INTERFACE OF RAILROAD TRACK USING MATRIX BASED TACTILE SURFACE SENSORS

The pressure distribution at the ballast-tie interface of railroad track plays a key role in overall track support. Failure of the ballast or tie can result from excessive loads that were not designed for, requiring increased maintenance and reducing railroad operating efficiency. Understanding the forces acting on the ballast and tie are required to design higher performance and longer lasting track. To further this understanding, the use of Matrix Based Tactile Surface Sensors (MBTSS) is employed to measure the actual pressure distribution at the ballast-tie interface, characterized by individual ballast particle contact points and non-uniform pressures. The research explores this application of MBTSS including the development of sensor protection and calibration procedures. Results from laboratory ballast box testing conducted at the Transportation Technology Center, Inc. (TTCI) are presented. Conservative estimates of peak pressure under a typical wheel load on new ballast averaged 1450 psi and on fouled ballast averaged 680 psi. Contact areas varied across the range of ballast gradations and are shown to increase under increased applied load. A parameter to describe the roughness of the ballast-tie pressure distribution is offered. Results from in-track testing performed at TTCI, including pressure distributions along ten test ties, are also presented

Risk factors for respiratory failure following operative stabilization of thoracic and lumbar spine fractures

Journal ArticleBackground: Respiratory failure is a serious complication that can adversely affect the hospital course and survival of multiply injured patients. Some studies have suggested that delayed surgical stabilization of spine fractures may increase the incidence of respiratory complications. However, the authors of these studies analyzed small sets of patients and did not assess the independent effects of multiple risk factors. Methods: A retrospective cohort study was conducted at a regional level-I trauma center to identify risk factors for respiratory failure in patients with surgically treated thoracic and lumbar spine fractures. Demographic, diagnostic, and procedural variables were identified. The incidence of respiratory failure was determined in an adult respiratory distress syndrome registry maintained concurrently at the same institution. Univariate and multivariate analyses were used to determine independent risk factors for respiratory failure. An algorithm was formulated to predict respiratory failure. Results: Respiratory failure developed in 140 of the 1032 patients in the study cohort. Patients with respiratory failure were older; had a higher mean Injury Severity Score (ISS) and Charlson Comorbidity Index Score; had greater incidences of pneumothorax, pulmonary contusion, and thoracic level injury; had a lower mean Glasgow Coma Score (GCS); were more likely to have had a posterior surgical approach; and had a longer mean time from admission to surgical stabilization than the patients without respiratory failure (p 25 points, a GCS of ≤12 points, blunt chest injury, and surgical stabilization performed more than two days after admission. An algorithm was created to determine, on the basis of the number of preoperative predictors present, the relative risk of respiratory failure when surgery was delayed for more than two days. Conclusions: Independent risk factors for respiratory failure were identified in an analysis of a large cohort of patients who had undergone operative stabilization of thoracic and lumbar spine fractures. Early operative stabilization of these fractures, the only risk factor that can be controlled by the physician, may decrease the risk of respiratory failure in multiply injured patients. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence

A Study of the "toss Factor" in the Impact Testing of Cermets by the Izod Pendulum Test

The test method presented shows that the "toss energy" contributed by the apparatus for brittle materials is negligible. The total toss energy is considered to consist of two components. (a) recovered stored elastic energy and (b) kinetic energy contributed directly by the apparatus. The results were verified by high-speed motion pictures of the test in operation. From these photographs, velocities of tossed specimens were obtained and toss energy computed. In addition, impact energies of some titanium carbide base cermets and high-temperature alloys, as measured by the low-capacity Izod pendulum test, compare well with impact energies measured by the NACA drop test

COLD-SAT feasibility study safety analysis

The Cryogenic On-orbit Liquid Depot-Storage, Acquisition, and Transfer (COLD-SAT) satellite presents some unique safety issues. The feasibility study conducted at NASA-Lewis desired a systems safety program that would be involved from the initial design in order to eliminate and/or control the inherent hazards. Because of this, a hazards analysis method was needed that: (1) identified issues that needed to be addressed for a feasibility assessment; and (2) identified all potential hazards that would need to be controlled and/or eliminated during the detailed design phases. The developed analysis method is presented as well as the results generated for the COLD-SAT system