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Aluminum alloys containing small amounts of Zn, Bi, Te, ln, Ga, Pb, and TI, either individually or in various combinations, have been prepared and investigated as possible fuels for alkaline aluminum-air batteries. The binary alloys, containing generally <1% of the alloying elements, exhibit corrosion rates in 4 M KOH at 50 C that are higher than that for pure aluminum in the same medium. Addition of two or more alloying elements can result in a sharp reduction in the open circuit corrosion rate to well below that for aluminum, and several alloys containing Ga, ln, TI, and P that appear promising as high performance fuels were identified. Mechanical processing [cold working (CW)] was found to have little reproducible effect on the corrosion rate, except for Al-0.5% Ga in which case the corrosion rate was found to pass through a minimum at 50% CW. The corrosion rate data also demonstrate that very low concentrations of the alloying elements are sufficient to achieve inhibition and that little is gained by exceeding the critical levels.
We present a probabilistic model for a document corpus that combines many of the desirable features of previous models. The model is called "GaP" for Gamma-Poisson, the distributions of the first and last random variable. GaP is a factor model, that is it gives an approximate factorization of the document-term matrix into a product of matrices Λ and X. These factors have strictly non-negative terms. GaP is a generative probabilistic model that assigns finite probabilities to documents in a corpus. It can be computed with an efficient and simple EM recurrence. For a suitable choice of parameters, the GaP factorization maximizes independence between the factors. So it can be used as an independent-component algorithm adapted to document data. The form of the GaP model is empirically as well as analytically motivated. It gives very accurate results as a probabilistic model (measured via perplexity) and as a retrieval model. The GaP model projects documents and terms into a low-dimensional space of "themes," and models texts as "passages" of terms on the same theme.
We describe a new sample of Seyfert nuclei discovered during the course of an optical spectroscopic survey of nearby galaxies. The majority of the objects, many recognized for the first time, have luminosities much lower than those of classical Seyferts and populate the faint end of the AGN luminosity function. A significant fraction of the nuclei emit broad H-alpha emission qualitatively similar to the broad lines seen in classical Seyfert 1 nuclei and QSOs.
This document provides a description and technical summary of the Second International Engineering Foundation Conference/Workshop on Small Fatigue Cracks, held in Santa Barbara, California, 5-10 January, 1986. It provides a current assessment of the pertinent issues with respect to definition, differences in behavior compared to long cracks, environmental effects, driving forces for small crack extension, intrinsic thresholds, and the application of small crack methodology to life prediction and alloy design. A listing of the conference participants and the technical program are appended to the report.
Abstract not Available.
Transition metal ions as a template method has been widely used in the field of supramolecular chemistry. The metal complexation is advantageous in making complex supramocluar architectures because it pre-organizes the ligands into a desirable orientation which faciliatates the following ring-closing reaction, with shorter synthetic steps and generally higher yield. In a similar fashion, this synthetic strategy has recently been adopted to make extended materials by linking the metal-coordinated building blocks with design principles of reticular synthesis. Individual building units are stitched together through strong covalent bond formation to yield long covalent molecular threads that are woven two- or three-dimensionally (2D or 3D), at regular intervals templated by the metal ions. For example, by linking functionalized tetrahedrally-shaped metal complexes with linear links through reversible imine bond formation, crystalline 3D covalent organic frameworks with diamond topology, COF-505 and COF-112, have been constructed by design. In particular, the metal templates can be post-synthetically removed so that the threads have high degrees of freedom to move in respect to each other, which leads to unusal mechanical properties of the woven materials.
Purpose Despite the importance of training in ambulatory care settings for residents to acquire important competencies, little is known about the organizational and environmental factors influencing the relative amount of time primary care residents train in ambulatory care during residency. The authors examined factors associated with postgraduate year 1 (PGY-1) residents’ ambulatory care training time in Accreditation Council for Graduate Medical Education (ACGME)-accredited primary care programs. Method U.S.-accredited family medicine (FM) and internal medicine (IM) programs’ 2016–2017 National Graduate Medical Education (GME) Census data from 895 programs within 550 sponsoring institutions (representing 13,077 PGY-1s) were linked to the 2016 Centers for Medicare and Medicaid Services Cost Reports and 2015–2016 Area Health Resource File. Multilevel regression models examined the association of GME program characteristics, sponsoring institution characteristics, geography, and environmental factors with PGY-1 residents’ percentage of time spent in ambulatory care. Results PGY-1 mean (standard deviation, SD) percent time spent in ambulatory care was 25.4% (SD, 0.4) for both FM and IM programs. In adjusted analyses (% increase [standard error, SE]), larger faculty size (0.03% [SE, 0.01], P < .001), sponsoring institution’s receipt of Teaching Health Center (THC) funding (6.6% (SE, 2.7), P < .01), and accreditation warnings (4.8% [SE, 2.5], P < .05) were associated with a greater proportion of PGY-1 time spent in ambulatory care. Programs caring for higher proportions of Medicare beneficiaries spent relatively less time in ambulatory care (< 0.5% [SE, 0.2], P < .01). Conclusions Ambulatory care time for PGY-1s varies among ACGME-accredited primary care residency programs due to the complex context and factors primary care GME programs operate under. Larger ACGME-accredited FM and IM programs and those receiving federal THC GME funding had relatively more PGY-1 time spent in ambulatory care settings. These findings inform policies to increase resident exposure in ambulatory care, potentially improving learning, competency achievement, and primary care access.
The point defect model (PDM) has been used to derive the dependence of the pitting potential on the voltage scan rate. Relationships derived from the PDM predict that the observed pitting potential is a linear function of the square root of voltage scan rate at low scan rates, which agrees with experimental data reported in the literature. Furthermore, the critical concentration of condensed cation vacancies that give rise to passivity breakdown, as estimated from the sweep rate dependence of the pitting potential, is found to be in good agreement with that estimated from structural considerations. The PDM is also used to predict the probability distribution function in the induction time for pitting (tind), that is, the survival probability, by assuming that the maximum diffusivity of the cation vacancy in a population of specimens is log‐normally distributed. This calculated "external" distribution in the induction time is found to be in reasonable agreement with experimental induction time data for passivity breakdown on multiple specimens of single crystal (100) Ni and polycrystalline nickel buffered chloride solutions.
