The heat generation from a notch during the compression-compression fatigue of a cellular Al alloy has been measured and compared with a model. The measure
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This technical note describes a detailed study on wax printing, a simple and inexpensive method for fabricating microfluidic devices in paper using a commercially available printer and hot plate. The printer prints patterns of solid wax on the surface of the paper, and the hot plate melts the wax so that it penetrates the full thickness of the paper. This process creates complete hydrophobic barriers in paper that define hydrophilic channels, fluid reservoirs, and reaction zones. The design of each device was based on a simple equation that accounts for the spreading of molten wax in paper.
Background: Because long-term weight gain typically occurs insidiously (~1 lb/y) it is very difficult to study in RCTs and prospective cohorts provide crucial evidence on its key contributors. Most prior studies have evaluated how baseline diet, rather than change in diet that may be more physiologically relevant, relates to future weight gain. Aim: To evaluate and compare different methodological approaches for investigating how diet relates to long-term weight gain. Methods: Participants from 3 separate cohorts, the Nurses Health Study (NHS, n=50,422), Nurses Health Study II (NHS II, n=47,898), and the Health Professionals Follow-up Study (HPFS, n=22,557), free of obesity and chronic diseases at baseline, were included and followed for up to 20 y. Lifestyle, health status, and weight were assessed by questionnaires every 2 y, and diet by validated FFQ every 4 y. We assessed 3 different analytic approaches, including relations of 1) baseline diet at the start of each 4 y with weight change in the next 4 y; 2) 4-y change in diet with weight change in the same 4 y; and 3) 4-y change in diet with lagged weight change in the next 4 y. We compared these approaches evaluating consistency across cohorts, magnitudes of associations, and biological plausibility of findings. Results: Across the three methods, consistent, robust, and biologically plausible associations were only seen between changes in diet and changes in weight in the same 4 y (Figure). Findings evaluating baseline diet and lagged dietary change were less consistent across cohorts, far smaller in magnitude, and often not biologically plausible, suggesting presence of both bias and misclassification of the true relevant dietary metric. Conclusions: The methods used to analyze dietary habits and long-term weight gain are crucial. The most robust, biologically relevant, and consistent findings are seen when evaluating dietary change and weight change in discrete periods.
The authors consider the performance of Schwarz splitting algorithms for partial differential equation problems on the hypothetical Multi-FLEX machine. The particular multi-FLEX considered consists of eight clusters of FLEX-32 multiprocessors. The concept of execution domains is introduced to model the three levels of memory on these machines: local, locally shared, and global. The method of stochastic high-level Petri nets (SHLPN) is appliedto model the performance of these PDE splitting algorithms on a Multi-FLEX machine. For very large, but realistic, applications potential speedup to 300 for 2D problems and more for 3D problems is projected, along with processor utilization of over 90%. Real computations on real machines can fall far short of this potential and still be very successful.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHoly Grails of ChemistryAllen J. Bard, George M. Whitesides, Richard N. Zare, and Fred W. McLaffertyCite this: Acc. Chem. Res. 1995, 28, 3, 91Publication Date (Print):March 1, 1995Publication History Published online1 May 2002Published inissue 1 March 1995https://pubs.acs.org/doi/10.1021/ar00051a001https://doi.org/10.1021/ar00051a001research-articleACS PublicationsRequest reuse permissionsArticle Views2874Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
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The role of micron-scale patterning on the interface toughness of bonded Cu-to-Cu nanometer-scale films is analyzed, motivated by experimental studies of Tadepalli, Turner and Thompson. In the experiments 400nm Cu films were deposited in various patterns on Si wafer substrates and then bonded together. Crack growth along the bond interface is here studied numerically using finite element analyses. The experiments have shown that plasticity in the Cu films makes a major contribution to the macroscopic interface toughness. To account for the size dependence of the plastic flow a strain gradient plasticity model is applied here for the metal. A cohesive zone model is applied to represent the crack growth along the bond between the two Cu films. This cohesive zone model incorporates the effect of higher order stresses in the continuum, such that the higher order tractions on the crack faces decay to zero values when the crack separation process takes place. The analyses focus on a pattern of Cu lines orthogonal to the crack growth direction, and the analyses are carried out for plane strain conditions with the assumption of small scale yielding under remote mode I loading. When crack growth over a Cu line initiates at the 90° edge on the Cu substrate the resistance curve shows a high peak before the toughness decays to a rather constant plateau. Later, when the crack tip approaches the 90° edge at the end of the Cu line, the fracture toughness decays below the plateau. It is found that both the toughness peak and the subsequent plateau level are highly sensitive to the value of the characteristic material length. A small material length, relative to the thickness of the Cu film, gives high toughness whereas a length comparable to the film thickness gives much reduced crack growth resistance.
