Determination of 3‐D Alumina Grain Orientation,Size, Shape,and Growth Kinetics from 2‐D Data in Nextel™ 610 Fibers

Nextel^? 610 alumina fibers were heat‐treated at 1100°C–1500°C for 1–100 h in air. Grain size distributions (GSDs) and grain orientation distributions (ODs) with respect to the fiber axis were characterized by analysis of TEM images from longitudinal fiber sections. The 2‐D GSDs and ODs were characterized as ellipses. 3‐D GSDs and ODs were calculated by fitting distributions of oriented oblate ellipsoids to 2‐D GSDs and ODs formed by ellipsoid–section‐plane intersections. The standard deviations (SDs) of log‐normal GSDs consistently increased with grain size, which is not diagnostic of normal grain growth. The grain aspect ratio (α) and the tendency of the short grain axis to orient perpendicular to the fiber axis also increased with grain size, resulting in more textured fibers at larger grain sizes. Average 3‐D grain sizes were larger than 2‐D sizes for GSDs with small SDs, but smaller for GSDs with large SDs because of under sampling of small grains. 3‐D grain growth kinetics had the same 815 kJ/mol activation energy as that found by 2‐D analysis, but the grain growth exponent m of 6.0 was larger and the pre‐exponential factor much smaller. Expressions for 3‐D log‐normal GSDs as a function of heat treatment temperature and time were determined. α‐distributions and ODs were determined as a function of grain size. Methods for determining 3‐D GSDs are discussed.     

Fiber Strength After Grain Growth in Nextel™ 610 Alumina Fiber

Nextel^? 610 alumina fiber tows were heat‐treated at 1100°C–1500°C for 1 to 100 h in air. Tensile strengths and Weibull moduli were measured for 30 filaments after each heat‐treatment. 3‐D grain size and orientation distributions were described using oblate ellipsoids. The number of grains in a 1 inch gauge length and grains with the largest major and minor ellipsoid‐axes were determined from these distributions. The grain with the largest K_EFF for mixed‐mode fracture was also determined, using the maximum energy release rate criteria from grain‐size and orientation distributions. Grain‐size dependence of tensile strength and Weibull modulus was evaluated. Strength had no obvious dependence on grain size for fibers with average major‐axes smaller than 0.25 μm. For fibers with larger grains, grain‐size dependence may involve flaws originating from clumps of grains, rather than a single grain. Possible relationships between strength and grain‐size and other causes of strength degradation after heat‐treatment are discussed.     

EFFICIENCY OF A CONTROLLED-CYCLE EXTRACTOR

Experimental studies were performed with a 4.0 in. (10.2 cm.) diameter extraction column containing ten dualflow type trays and operated in a controlled cycling mode. The systems methyl isobutyl ketone/acetic acid/water and toluene/acetone/water were used. The overall stage efficiency was found to be a function of the ratio of the volume of a phase transferred during a cycle to the volume of that phase held up on the tray, of the feed-to-solvent ratio, and of the phase throughput rates. A non-equilibrium model was developed to represent the experimental data. For the HIBK/acetic acid/water system, overall stage efficiencies were in the range of 30 to 38 percent, corresponding to HETS values of 0.46 to 0.55 meters. For the toluene/acetone/water system, overall stage efficiencies were in the range of 20 to 31 percent, corresponding to HETS values of 0.55 to 0.95 meters.     

Ceramic Composites with Three-Dimensional Architectures Designed to Produce a Threshold Strength—II. Mechanical Observations

Finite element modeling and linear elastic fracture mechanics are used to model the residual stresses and failure stress of ceramic composites consisting of polyhedral alumina cores surrounded by thin alumina/mullite layers in residual compression. This type of composite architecture is expected to exhibit isotropic threshold strength behavior, in which the strength of the composite for a particular assumed flaw will be constant and independent of the orientation of tensile loading. The results of the modeling indicate that the strengths of such architectures will be higher than those of laminates of similar architectural dimensions that were previously found to exhibit threshold strength behavior for a particular flaw type. Flexural testing of the polyhedral architectures reveals that failure is dominated by processing defects found at junctions between the polyhedra. Fractography revealed the interaction of these defects with the residual stresses in the compressive layers that separate the polyhedra.     

Rheological Characterization of Nitrocellulose Gels

Various nitrocellulose, NC, based propellant formulations need to be processed using new and more environmentally friendly solvent combinations on the one hand and using continuous processing methodologies on the other hand. A detailed understanding of the significant changes that take place in the structure and hence the rheological behavior of NC based formulations during manufacture is required to minimize the use of organic solvents and to revert to safer and green solvents. Towards achieving these objectives, experimental methodologies were developed for the first time to enable the accurate characterization and thus fingerprinting of the rheological behavior of NC gels. In these methodologies linear viscoelastic measurements are employed. The concentration of the solvents existing in the gel sample during rheological characterization is concomitantly monitored to allow the documentation of the major source of error associated with the rapid loss of the typical solvents, which generally exhibit relatively high vapor pressures. These measurements have indicated that the source of the NC fibers and the treatment method alter the rheological behavior and can be tracked. The rheological properties of the NC gels can be linked to their manufacturability and such data can be used to pinpoint optimum geometries and processing conditions. The processability of the NC based formulations can also be tailored on the basis of rheological characterization, allowing the manufacturers greater latitude for reducing costs and environmental footprint during manufacture, as well as improving the quality of their NC based energetic formulations.     

Managing what you measure: creating outcome-driven systems of care for youth with serious emotional disturbances

This article presents the California System of Care Model for youth with severe emotional disturbances as an illustration of how ongoing assessment of the costs and outcomes of service delivery can be an integral part of a service delivery model. The core of this model, developed initially in Ventura County, California, is a five-step planning process that guides care system development and implementation. The implications of each stage of the planning process for evaluation and feedback at the child, family, and system levels are highlighted. A set of principles for selecting outcome measures deriving from the planning process are also presented that, in conjunction with the planning model, serve as guidelines for establishing outcome measures within care systems. The resulting specific plan for measuring system- and client-level outcomes deriving from this process, along with challenges to the implementation of the outcome management plan, is described.     

Precipitation Coating of Rare-Earth Orthophosphates on Woven Ceramic Fibers—Effect of Rare-Earth Cation on Coating Morphology and Coated Fiber Strength

Monazite (La, Ce, Nd, and GdPO₄) and xenotime (Tb, Dy, and YPO₄) coatings were deposited on woven Nextel^™ 610 and 720 fibers by heterogeneous precipitation from a rare-earth citrate/phosphoric acid precursor. Coating phases and microstructure were characterized by SEM and TEM, and coated fiber strength was measured after heat treatment at 1200°C for 2 h. Coated fiber strength increased with decreasing ionic radius of the rare-earth cation in the monazite and xenotime coatings, and correlates with the high-temperature weight loss and the densification rate of the coatings. Dense coatings with trapped porosity and high weight loss at a high temperature degrade fiber strength the most. The degradation is consistent with stress corrosion driven by thermal residual stress from coating precursor decomposition products trapped in the coating at a high temperature.     

Low Voltage Electrowetting-on-Dielectric Platform using Multi-Layer Insulators

A low voltage, two-level-metal, and multi-layer insulator electrowetting-on-dielectric (EWD) platform is presented. Dispensing 300pl droplets from 140nl closed on-chip reservoirs was accomplished with as little as 11.4V solely through EWD forces, and the actuation threshold voltage was 7.2V with a 1Hz voltage switching rate between electrodes. EWD devices were fabricated with a multilayer insulator consisting of 135nm sputtered tantalum pentoxide (Ta(2)O(5)) and 180nm parylene C coated with 70nm of CYTOP. Furthermore, the minimum actuation threshold voltage followed a previously published scaling model for the threshold voltage, V(T), which is proportional to (t/ε(r))(1/2), where t and ε(r) are the insulator thickness and dielectric constant respectively. Device threshold voltages are compared for several insulator thicknesses (200nm, 500nm, and 1μm), different dielectric materials (parylene C and tantalum pentoxide), and homogeneous versus heterogeneous compositions. Additionally, we used a two-level-metal fabrication process, which enables the fabrication of smaller and denser electrodes with high interconnect routing flexibility. We also have achieved low dispensing and actuation voltages for scaled devices with 30pl droplets.     

Pathological staging and biochemical recurrence after neoadjuvant androgen deprivation therapy in combination with radical prostatectomy in clinically localized prostate cancer: results of a phase II study

OBJECTIVES: To assess the pathological staging and biochemical progression-free survival (assessed using serum prostate-specific antigen level) of patients with clinically localized prostate cancer using neoadjuvant androgen deprivation therapy (ADT) in combination with radical retropubic prostatectomy (RRP). PATIENTS AND METHODS: A prospective study was carried out on 69 patients with localized prostate cancer who were enrolled in a trial of 3 months of ADT followed by RRP (group 1). These patients were compared with 72 patients matched for age and clinical stage who declined ADT therapy and had RRP concurrently (group 2). Assignment to the individual treatment groups was thus determined by the patient's preference and not the physician's selection. Pathological staging and biochemical progression-free recurrence were compared between the groups. RESULTS: The rate of organ-confined (pT2) tumours was 74% in group 1 and 49% in group 2 (P < 0.01), and the rate of margin-negative tumours was 87% in group 1 and 64% in group 2 (P < 0.01). Within a median follow-up of 35 months, there was no significant difference in biochemical failure between the groups (P = 0.37). Patients with pT2 disease, regardless of treatment, had similar biochemical failure rates. In the patients with margin-positive disease, there was a significantly higher biochemical failure rate in group 1 (P = 0.02). CONCLUSIONS: The rates of organ- and specimen-confined disease were higher among the patients treated with ADT. The preliminary follow-up suggested that patients with pT2 disease after ADT have a biochemical progression-free recurrence rate similar to pT2 patients treated with RRP alone. Additionally, high biochemical failure rates in patients with margin-positive disease after ADT may identify a subset of more biologically aggressive tumours in need of early adjuvant treatment.     

Low-frequency performance of guided scrambling DC-free codes

We analyze the effect of coding parameters on low-frequency suppression in guided scrambling (GS) dc-free codes based on computer simulation. Simple expressions to accurately estimate the sum variance and low-frequency spectrum-weight of these codes are developed. Systematic design of GS dc-free codes is discussed.