Abstract Objectives To review the history, theory and current applications of Weibull analyses sufficient to make informed decisions regarding practical use of the analysis in dental material ...strength testing. Data References are made to examples in the engineering and dental literature, but this paper also includes illustrative analyses of Weibull plots, fractographic interpretations, and Weibull distribution parameters obtained for a dense alumina, two feldspathic porcelains, and a zirconia. Sources Informational sources include Weibull's original articles, later articles specific to applications and theoretical foundations of Weibull analysis, texts on statistics and fracture mechanics and the international standards literature. Study selection The chosen Weibull analyses are used to illustrate technique, the importance of flaw size distributions, physical meaning of Weibull parameters and concepts of “equivalent volumes” to compare measured strengths obtained from different test configurations. Conclusions Weibull analysis has a strong theoretical basis and can be of particular value in dental applications, primarily because of test specimen size limitations and the use of different test configurations. Also endemic to dental materials, however, is increased difficulty in satisfying application requirements, such as confirming fracture origin type and diligence in obtaining quality strength data.
We present an experimental investigation of flexible panels actuated with heave oscillations at their leading edge. Results are presented from kinematic video analysis, particle image velocimetry, ...and direct force measurements. Both the trailing edge amplitude and the mode shapes of the panel are found to scale with dimensionless parameters originating from the Euler–Bernoulli beam equation. The time-averaged net thrust increases with heaving frequency, but experiences localized boosts near resonant frequencies where the trailing edge amplitude is maximized. These boosts correspond to local maxima in the propulsive efficiency. For a constant heave amplitude, the time-averaged net thrust coefficient is shown to be a function of Strouhal number over a wide range of conditions. It appears, therefore, that self-propelled swimming (zero net thrust) only occurs over a small range of Strouhal numbers. Under these near-constant Strouhal number conditions, the propulsive economy increases with higher flexibilities and slower swimming speeds.
Experimental gradient-based optimization is used to maximize the propulsive efficiency of a heaving and pitching flexible panel. Optimum and near-optimum conditions are studied via direct force ...measurements and particle image velocimetry (PIV). The net thrust and power scale predictably with the frequency and amplitude of the leading edge, but the efficiency shows a complex multimodal response. Optimum pitch and heave motions are found to produce nearly twice the efficiencies of optimum heave-only motions. Efficiency is globally optimized when (i) the Strouhal number is within an optimal range that varies weakly with amplitude and boundary conditions; (ii) the panel is actuated at a resonant frequency of the fluid–panel system; (iii) heave amplitude is tuned such that trailing-edge amplitude is maximized while the flow along the body remains attached; and (iv) the maximum pitch angle and phase lag are chosen so that the effective angle of attack is minimized. The multi-dimensionality and multi-modality of the efficiency response demonstrate that experimental optimization is well-suited for the design of flexible underwater propulsors.
Climate change imposes physiological constraints on organisms particularly through changing thermoregulatory requirements. Bergmann's and Allen's rules suggest that body size and the size of ...thermoregulatory structures differ between warm and cold locations, where body size decreases with temperature and thermoregulatory structures increase. However, phenotypic plastic responses to malnutrition during development can result in the same patterns while lacking fitness benefits. The Gulf of Maine (GOM), located at the southern end of the Labrador current, is warming faster than most of the world's oceans, and many of the marine species that occupy these waters exist at the southern edge of their distributions including Atlantic puffins (Fratercula arctica; hereafter "puffin"). Monitoring of puffins in the GOM, at Machias Seal Island (MSI), has continued annually since 1995. We asked whether changes in adult puffin body size and the proportional size of bill to body have changed with observed rapid ocean warming. We found that the size of fledgling puffins is negatively related to sea surface temperature anomalies (warm conditions = small fledgers), adult puffin size is related to fledgling size (small fledgers = small adults), and adult puffins have decreased in size in recent years in response to malnutrition during development. We found an increase in the proportional size of bill to wing chord, likely in response to some mix of malnutrition during development and increasing air temperatures. Although studies have assessed clinal variation in seabird morphology with temperature, this is the first study addressing changes in seabird morphology in relation to ocean warming. Our results suggest that puffins nesting in the GOM have morphological plasticity that may help them acclimate to ocean warming.
The decision makers who approve or deny payment for health‐care services review many new technologies. Reimbursement for companion diagnostics for expensive drugs (“personalized medicine”) is already ...under close policy scrutiny, in line with long‐standing concerns about overuse of diagnostic tests. Evaluation of diagnostic tests adds some complexities to the payer's comparative‐effectiveness evaluation for drugs alone. Currently, decision‐making frameworks suitable for companion diagnostics are being developed for practical application by payer policy makers.
Clinical Pharmacology & Therapeutics (2010) 88 6, 751–754. doi: 10.1038/clpt.2010.234
Abstract Objectives Presentation of a methodological approach using stereo and scanning electron microscope examination for the failure analysis of an alumina all-ceramic premolar crown (Procera® ...AllCeram). Methods The recovered part of a fractured Procera alumina crown was examined utilizing first a stereomicroscope and second a scanning electron microscope (SEM). The stereomicroscope analysis was performed at low magnifications with oblique lighting in order to enhance spatial relationships and gross detection of crack features. A preliminary fracture surface map of the stereo observations was drawn and used as a guide for the SEM analysis that followed. Specific sites of interest identified under the stereo microscope were analyzed using the SEM at high magnifications searching for small fracture features such as wake hackle and twist hackle within the veneering ceramic in order to confirm the direction of crack propagation. Results At low magnifications and oblique illumination, the stereomicroscope analysis provided an excellent overview of the fractured topography, showing sites of major interest such as a primary edge chip at a margin, a compression curl indicating the end of the fracture event as well as larger hackle lines distributed over the cracked surface. The greater magnifications with the SEM analysis of the sites of interest showed the presence of wake and twist hackle, indicators of the crack propagation direction. A general map of the fracture events could be reconstructed starting with a primary veneer edge chip at the mesial margin. Hackle and wake hackle of the crack front emanating from this margin arose from hoop stresses and propagated through the full crown thickness towards the distal end of the restoration where the compression curl was located. Additional occlusal surface damage in the form of veneer chipping containing arrest lines and twist hackle running in the opposite direction as the main crack path were observed, but occurred as a secondary event without penetrating the alumina core material. Significance Stereo and scanning electron microscopy are complementary analysis techniques useful for the mapping and interpretation of the fracture surface. This case examination is intended to guide the clinical researcher in using qualitative (descriptive) fractography as a tool for understanding the failure process in brittle restorative materials, as well as for assessing possible design inadequacies.
The Research Collaboratory for Structural Bioinformatics Protein Data Bank (RCSB PDB) develops tools and resources that provide a structural view of biology for research and education. The RCSB PDB ...web site (http://www.rcsb.org) uses the curated 3D macromolecular data contained in the PDB archive to offer unique methods to access, report and visualize data. Recent activities have focused on improving methods for simple and complex searches of PDB data, creating specialized access to chemical component data and providing domain-based structural alignments. New educational resources are offered at the PDB-101 educational view of the main web site such as Author Profiles that display a researcher's PDB entries in a timeline. To promote different kinds of access to the RCSB PDB, Web Services have been expanded, and an RCSB PDB Mobile application for the iPhone/iPad has been released. These improvements enable new opportunities for analyzing and understanding structure data.
The RCSB Protein Data Bank (RCSB PDB) web site (http://www.pdb.org) has been redesigned to increase usability and to cater to a larger and more diverse user base. This article describes key ...enhancements and new features that fall into the following categories: (i) query and analysis tools for chemical structure searching, query refinement, tabulation and export of query results; (ii) web site customization and new structure alerts; (iii) pair-wise and representative protein structure alignments; (iv) visualization of large assemblies; (v) integration of structural data with the open access literature and binding affinity data; and (vi) web services and web widgets to facilitate integration of PDB data and tools with other resources. These improvements enable a range of new possibilities to analyze and understand structure data. The next generation of the RCSB PDB web site, as described here, provides a rich resource for research and education.
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