Calibration of the Weibull stress scale parameter, σu, using the Master Curve

This work proposes that the Weibull stress scale parameter, σ_u, increases with temperature to reflect the increasing microscale toughness of ferritic steels caused by local events that include plastic shielding of microcracks, microcrack blunting, and microcrack arrest. The Weibull modulus, m, then characterizes the temperature invariant, random distribution of microcrack sizes in the material. Direct calibration of σ_u values at temperatures over the DBT region requires extensive sets of fracture toughness values. A more practical approach developed here utilizes the so-called Master Curve standardized in ASTM Test Method E1921-02 to provide the needed temperature vs. toughness dependence for a material using a minimum number of fracture tests conducted at one temperature. The calibration procedure then selects σ_u values that force the Weibull stress model to predict the Master Curve temperature dependence of K_Jc values for the material. At temperatures in mid-to-upper transition, the process becomes more complex as fracture test specimens undergo gradual constraint loss and the idealized conditions of high-constraint, small-scale yielding assumed in E1921-02 gradually degenerate. The paper develops the σ_u calibration process to incorporate these effects in addition to consideration of threshold toughness effects and the testing of fracture specimens with varying crack-front lengths. Initial illustrations of the calibration process for simpler conditions, i.e. 1T crack-front lengths, use the temperature dependent flow properties and a range of toughness levels for an A533B pressure vessel steel. Then using the extensive fracture toughness data sets for an A508 pressure vessel steel generated recently by Faleskog et al. [Engng. Fract. Mech., in press], the paper concludes with calibrations of both m and σ_u over the DBT region and assessments of the Master Curve calibration approach developed here.     

Statistical approach and benchmarking for modeling of multi-dimensional behavior in TRISO-coated fuel particles

The fundamental design for a gas-cooled reactor relies on the behavior of the coated particle fuel. The coating layers, termed the TRISO coating, act as a mini-pressure vessel that retains fission products. Results of US irradiation experiments show that many more fuel particles have failed than can be attributed to one-dimensional pressure vessel failures alone. Post-irradiation examinations indicate that multi-dimensional effects, such as the presence of irradiation-induced shrinkage cracks in the inner pyrolytic carbon layer, contribute to these failures. To address these effects, the methods of prior one-dimensional models are expanded to capture the stress intensification associated with multi-dimensional behavior. An approximation of the stress levels enables the treatment of statistical variations in numerous design parameters and Monte Carlo sampling over a large number of particles. The approach is shown to make reasonable predictions when used to calculate failure probabilities for irradiation experiments of the New Production - Modular High Temperature Gas Cooled Reactor Program.     

New urban forms: the crescents of Bath and Le Corbusier's plan for Rio de Janeiro

This article considers whether formal references in Le Corbusier's work may be traced to the eigtheenth century crescents of Bath and, in particular, Lansdowne Crescent. By exploring this line, it raises the possibility that in the work he produced for the Latin American context, this arch-modernist planner moved beyond the de-contextualized approach for which he is known and explored the possibility of integrating new urban forms with nature. The article also shows how Le Corbusier's plans for Rio de Janeiro allowed him to become an important formal reference point for successive generations of local architects and planners.     

The DOE advanced gas reactor fuel development and qualification program

The high outlet temperatures and high thermal-energy conversion efficiency of modular high-temperature gas-cooled reactors (HTGRs) enable an efficient and cost-effective integration of the reactor system with non-electricity-generation applications, such as process heat and/or hydrogen production, for the many petrochemical and other industrial processes that require temperatures between 300°C and 900°C. The U.S. Department of Energy (DOE) has selected the HTGR concept for the Next Generation Nuclear Plant (NGNP) Project as a transformative application of nuclear energy that will demonstrate emissions-free nuclear-assisted electricity, process heat, and hydrogen production, thereby reducing greenhouse-gas emissions and enhancing energy security. The objective of the DOE Advanced Gas Reactor (AGR) Fuel Development and Qualification program is to qualify tristructural isotropic (TRISO)-coated particle fuel for use in HTGRs. An overview of the program and recent progress is presented.     

Childhood obesity: a risk factor for traumatic injuries to anterior teeth

The relationship between obesity and traumatic dental injuries was evaluated in a study population of 938 6- to 11-year-old schoolchildren from Rome, Italy, and it was suggested by the lifestyle and the physical activity of obese children, which, according to many authors, is different from the lifestyle of other children. The subjects were examined at school: presence and type of dental injury, overjet, incisor protrusion, upper lip incompetence and presence of obesity were recorded. Trauma predisposition was evaluated with a questionnaire investigating the behaviour which may predispose to impacts. Six out of eight questions in this questionnaire concerned the children's lifestyle and the trauma predisposition score was therefore also considered an estimate of lifestyle and physical activity. The dental injury prevalence of the study population was 21.3% and obesity prevalence was 11.4%. Of the obese children 30.8% had dental injuries vs. only 20.0% of non-obese subjects (P = 0.007). Obese children had only enamel and enamel-dentine fractures and the main reported trauma cause was indoor play; conversely, lean children also had other types of injuries and the most frequently reported cause was outdoor play. The main predisposing factors significantly affecting the probability of dental injury, evaluated with multiple logistic regression, were upper lip uncoverage (OR: 1.23; P = 0.02), overjet larger than 3 mm (OR: 1.68; P = 0.001) and obesity (OR: 1.45; P = 0.01). Surprisingly, trauma predisposition was a protective factor (OR: 0.50; P = 0.00001). The results of this study were explained by the significant inverse correlation between obesity and trauma-predisposing behaviour, thus suggesting that subjects frequently playing sports and lively games were not only less obese but also more skillful and, for this reason, less prone to trauma when they fell or sustained impacts.     

Fractal characteristics of far-field diffraction patterns for two-dimensional Thue-Morse quasicrystals

We report a numerical method to analyze the fractal characteristics of far-field diffraction patterns for two-dimensional Thue-Morse (2-D TM) structures. The far-field diffraction patterns of the 2-D TM structures can be obtained by the numerical method, and they have a good agreement with the experimental ones. The analysis shows that the fractal characteristics of far-field diffraction patterns for the 2-D TM structures are determined by the inflation rule, which have potential applications in the design of optical diffraction devices.     

Therapy of acute myeloid leukemia: towards a patient-oriented, risk-adapted approach

BACKGROUND AND OBJECTIVE: The successful use of differentiating treatment for patients with acute promyelocytic leukemia (APL) suggests that other acute myeloid leukemias (AML) may benefit from tailored and subtype-specific therapy. Despite the fact that new drugs specifically targeting AML genetic lesions have not yet been developed, distinct karyotypic categories have been identified which may deserve differentiated treatment. In addition, molecular assays to assess response to therapy more sensitively are now available for several AML subsets. In this review, we discuss the role of genetic characterization in the therapy of AML, and the investigative efforts which we believe are still needed for the design of tailored treatment for each and every patient with this disease. DESIGN AND METHODS: The authors have been working in this field for many years and have contributed original papers, the data of which are incorporated in this article. In addition, the material analyzed in this overview includes articles and reviews covered by the Science Citation Index and Medline as well as some more recent unpublished personal observations. RESULTS: Modern therapeutic approaches to AML tend to differentiate post-induction treatment intensity according to cytogenetically defined risk categories. Such prognostic categorization is largely unsatisfactory. In fact, following the advent of newly developed molecular assays (e.g. RT-PCR and FISH), specific and prognostically relevant lesions are frequently found in patients with an apparently normal karyotype, and these patients are, therefore, re-assigned to more appropriate prognostic categories. In addition, recent studies suggest that some patients may benefit from an increase in induction intensity; rapid genetic characterization will be needed for future differentiation of initial therapy. However, preliminary investigation of AML by integrated karyotypic/molecular analyses show that no specific abnormalities are detectable in at least half of the cases. Therefore, use of genetic criteria for prognostic stratification is currently feasible in only a proportion of patients. INTERPRETATIONS AND CONCLUSIONS: The prognostic role of genetic lesions, currently identified by karyotypic studies, needs to be validated in large series of AML patients prospectively characterized by advanced molecular/cytogenetic analyses and treated uniformly. In addition, searches for new clinically relevant genetic abnormalities, and diagnostic tools for their rapid identification are urgently needed to identify prognostic categories better. Elucidation of AML gene alterations should foster basic investigation aimed at developing new drugs targeted to the specific lesion in the individual patient. Before these more specific therapeutic agents are developed, diagnostic genetic characterization should add to other well-established prognostic factors to optimize the use of the presently available therapies.     

Factors influencing survival after gamma knife radiosurgery for patients with single and multiple brain metastases

BACKGROUND: Significant changes are restructurng the U.S. health care delivery system. National health reform is now extending itself into the public sector. Increased health and medical costs by federal and state governments are forcing a reevaluation of major entitlement programs, especially Medicaid. METHODS/RESULTS: Because Medicaid is the single largest item in many state budgets, states are now enrolling Medicaid patients into managed and coordinated care arrangements as a means to control costs and increase access to care. HMOs are not only competing for private patients but also actively seeking the Medicaid population. Nationally, almost one-fourth of all Medicaid patients are now enrolled in managed care plans. Various models and approaches have been developed by individual states. CONCLUSIONS: Because managed care enrollment in the Medicaid program has increased substantially in recent years, selected services including vision care are no longer rendered by any practitioner willing to accept Medicaid fees. Freedom of choice is now restricted to pre-selected and panel practitioners participating with the managed care program. The rules, regulations, billing procedures, fees, and program requisites will differ under managed care programs. Private optometric practitioners must consider entering economic and organizational relationships and linkages that make them attractive to managed care organizations.     

Vertical p-i-n polysilicon diode with antifuse for stackable field-programmable ROM

A field-programmable, stackable memory cell using 0.15-/spl mu/m technology is demonstrated. Vertical polycrystalline silicon diodes are stacked on top of one another, with tungsten (with TiN adhesion film) interconnect wires. An SiO/sub 2/ antifuse film separates the top of each diode from the TiN-W films. The cell is programmed when sufficient biasing voltage is applied to break down the antifuse, connecting the diode to tungsten. The cell is unprogrammed when the antifuse is intact. Cell fabrication and performance are described.