[en] Winter and summer indoor radon measurements are reported for 121 houses in Freehold, New Jersey. When presented as winter:summer ratios of indoor radon, the data closely approximate a lognormal distribution. The geometric mean is 1.49. Freehold is located on the fairly flat coastal plain. The winter:summer ratios are believed to represent the norm for regions of the U.S. with cold winters and hot summers. The Freehold data set can be compared to corresponding data sets from other locations to suggest seasonal perturbations of indoor radon arising from unusual causes

[en] The present work reports on the characterization of AlCuFeCr based quasicrystalline approximant films produced via radio frequency and direct current sputtering from a powder composite target. Previous reports on similar Al-transition metal sputtered films indicated that amorphous coatings were produced at ambient temperatures. Annealing was required to develop the quasicrystalline approximant microstructure via a phase transformation. In this work, the nature of as-deposited AlCuFeCr coatings was studied using high-resolution grazing incidence X-ray scattering, radial distribution function analysis and simulated diffraction patterns based on a Scherrer line broadening model. Agreement was observed between these methods for an ordered approximant grain size of 25-50 A. A wide processing window was observed to produce as-deposited AlCuFeCr quasicrystalline approximant films

[en] The advent of relatively inexpensive microcomputers has opened up the possibility of producing self-testing and self-diagnostic equipment for applications which demand very high reliability. If correctly designed the use of a multi-microprocessor system could result in improved standards of reliability and availability as well as making the operations of commissioning, testing and routine maintenance much simpler. Described in this article is one implementation of a microprocessor-based guard line system installed as a 'shadow system' on the Universities Research Reactor at Risley. The basic unit developed for guard line operation consists of a dual microprocessor system designed so that one microprocessor is engaged in self-testing while the other is involved in performing the guard line operation. After the self-testing routine is completed the roles of the two microprocessors are changed over and the guard line operation continues. If the system detects a fault the nature of the fault and the corrective action required is communicated to the operator via a microprocessor-controlled data terminal while the microcomputer system recovers from the fault (if possible) and continues guard line operation. A minimum of interconnection has been used between the two microcomputers to reduce fault pollution and ease fault recovery. In the present system emphasis has been placed on self-testing the microprocessor section of the equipment and the actuator circuits for the reactor control rods. In future systems it is envisaged that automatic testing of transducers will be introduced which should result in enhancing the availability of the guard line circuit. (author)

[en] Marginal fractures of the tibial plateau are associated with a high incidence of soft tissue injuries to the stabilising structures of the knee joint. Injuries to the anterior cruciate ligament are associated with the Segond fracture and impingement fractures of the posteromedial tibial plateau. Recognition of these fractures aids diagnosis of these injuries. Marginal fractures of the tibial plateau associated with posterior cruciate ligament injuries are less common, though recently a ''reverse'' Segond fracture has been recognised. We describe a fracture of the anteromedial tibial plateau associated with complete disruption of the posterior cruciate ligament and posterolateral complex. (orig.)

[en] A new technique for visualizing the native coronary arteries is described using the high-resolution mode of an ultrafast CT scanner (Imatron C-100) combined with electrocardiogram gating and breath-holding. In 100 consecutive patients, successful visualization of the extramural coronary arteries was achieved. Coronary artery calcifications of varying density and size were visualized. High-resolution, off-axis reconstruction in oblique, sagittal, or coronal planes could also be obtained. This paper discusses the technical aspects of the technique and the image quality in the first 100 subjects studied

[en] The United States Department of Energy, Nuclear Energy Research Initiative (NERI) Direct Energy Conversion (DEC) project began in August of 1998 with the goal of developing a direct energy conversion process suitable for commercial development. With roughly two thirds of the project completed, we believe a viable direct energy device could be economic. This paper describes the financial basis behind that belief for one proposed DEC reactor, the magnetically insulated fission electric cell (FEC). It also illustrates the value of economic analysis even in these early phases of a research project. The financial basis consists of a conceptual level Economic Model comprised of five modules. The Design Model provides technical specification to other modules. The Fuel Cost Model estimates fuel expenses based on current spot market prices applied over a wide range of fuel enrichment. The Operating Cost Model uses published correlations to provide rough order of magnitude non-fuel operating costs. The Capital Cost model uses analogy and parametric estimating techniques to generate capital cost estimates for a DEC power plant. Finally, the financial model combines output from the other models to produce a Net Present Value analysis with cost of generation as the independent variable. Model results indicate that several FEC geometric configurations could be economic. Within these configurations, optimums exist. Finally, the model demonstrates that the most efficient design is not necessarily the most economic. (authors)

[en] The United States Department of Energy, Nuclear Energy Research Initiative (NERI) Direct Energy Conversion (DEC) project has as its goal the development of a direct energy conversion process suitable for commercial development. Direct energy conversion is defined as any fission process that returns usable energy without using an intermediate thermal process. This project includes the study of the fission electric cell (FEC). Inherent to the FEC is a cathode insulated from the rest of the cell by a vacuum. This arrangement has the potential to trap energy on the cathode, increasing temperatures and potentially causing structural problems and gas emissions. This paper describes the project efforts to address this and similar thermal issues. This paper describes the development of a Thermal Model that integrates thermodynamic and heat transfer considerations into an overall Design Model. The Thermal Model begins with the basic energy balance. It then applies heat transfer methods to these models to develop a general relationship between temperature and system operating parameters. Finally, the model uses published correlations to relate the general parameters to specific geometric configurations. The Thermal Model demonstrates that the low energy densities typical of fission electric cells result in assemblies whose available heat transfer mechanisms efficiently transport any waste heat the systems generate. This results in a design at this conceptual level with significant opportunities to optimize system operations and economics using operating temperature. The model also demonstrates that for the same reasons, heat buildup has a weak correlation with system operating voltage. (authors)

[en] An extension of dosemeter issue period brings significant economic and logistic benefits. Therefore, it is desirable to have an extended period as long as possible without significant loss of the quality of dose measurements. There are many studies devoted to the investigation of fading or reduction of the dose accumulated in dosemeters with time. However, this is one of many critical factors that need's to be taken into account when extending the dosemeter issue period. Background radiation is also a critical factor that needs to be appropriately accounted. In this report, a new approach has been suggested for evaluating the effect of background radiation on the lower limit of detection (LLD) of occupational radiation dose. This approach is based on the data collected from control dosemeters that are routinely used for subtraction of background radiation from occupational dose measurements. The results show that for LiF:Mg,Cu,P thermoluminescence dosemeters, variations in background radiation have a higher impact on the LLD than dose fading and the absolute value of background radiation. Although there is no significant dose fading in LiF:Mg,Cu,P for a dosemeter issue period up to 1 y, variations in background radiation during this period of time can significantly increase photon LLDs (up to 700 μSv) for workers operating in an environment of variable radiation background. (authors)

[en] In this work, we found that the interdiffusion of the CdS and Zn₂SnO₄ (ZTO) layers can occur either at high temperature (550--650^oC) in Ar or at lower temperature (400--420^oC) in a CdCl₂ atmosphere. By integrating a Zn₂SnO₄ film into a CdS/CdTe solar cell as a buffer layer, this interdiffusion feature can solve several critical issues and improve device performance and reproducibility of both SnO₂-based and Cd₂SnO₄-based CdTe cells. Interdiffusion consumes the CdS film from both the ZTO and CdTe sides during the device fabrication process and improves quantum efficiency at short wavelengths. The ZTO film acts as a Zn source to alloy with the CdS film, which results in increases in the band gap of the window layer and in short-circuit current density J_sc. Interdiffusion can also significantly improve device adhesion after CdCl₂ treatment, thus providing much greater process latitude when optimizing the CdCl₂ process step. The optimum CdCl₂-treated CdTe device has high quantum efficiency at long wavelength, because of its good junction properties and well-passivated CdTe film. We have fabricated a Cd₂SnO₄/Zn₂SnO₄/CdS/CdTe cell demonstrating an NREL-confirmed total-area efficiency of 15.8% (V_oc=844.3mV, J_sc=25.00mA/cm², and fill factor=74.82%). This high-performance cell is one of the best thin-film CdTe solar cells in the world

[en] Full text: We are currently developing an instrument -ultimately one that exploits the high radiation flux of a synchrotron source- that will record reflectivity measurements of fast, transient structural changes in chemical and biological processes at the air-water interface with sub-second resolution. Present methods for the study of materials that show no appreciable structural change are very powerful. However, there is a need to improve the time resolution of such studies from hours to fractions of one second (potentially to milliseconds with synchrotron radiation) so that faster chemical reactions and the relaxation processes of interfacial structures can be investigated in real time. Two energy dispersive analysers for the new reflectometer have been commissioned on our laboratory x-ray source: a commercial liquid nitrogen-cooled germanium detector (EG and G); and a Bragg rotor crystal analyser, designed and constructed at the Research School of Chemistry. Since reflectometry is a technique well suited to study the profile of solid state metal oxide and metal organic thin films, we will at no loss of generality, discuss the fundamental issues of the new spectrometer in the context of this application