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We briefly review high-resolution electron energy loss spectroscopy (HREELS) studies of the low energy excitations in the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 8 . HREELS has been used to determine the magnitude and temperature dependence of the energy gap (2Δ) for Bi 2 Sr 2 CaCu 2 O 8 single crystals. Below the transition temperature low-energy excitations are detected in the energy loss spectra. Because the energy loss spectra are proportional to the real part of the frequency dependent resistivity, ρ R (ω), the energy gap can be determined directly from the HREEL data. At low temperature 2Δ = 6kT c and Δ develops sharply for T < T c . The constraints that these new results place on potential mechanisms of superconductivity are discussed.
We describe new families of random fractals, referred to as "V-variable", which are intermediate between the notions of deterministic and of standard random fractals. The parameter V describes the degree of "variability": at each magnification level any V-variable fractals has at most V key "forms" or "shapes". V-variable random fractals have the surprising property that they can be computed using a forward process. More precisely, a version of the usual Random Iteration Algorithm, operating on sets (or measures) rather than points, can be used to sample each family. To present this theory, we review relevant results on fractals (and fractal measures), both deterministic and random. Then our new results are obtained by constructing an iterated function system (a super IFS) from a collection of standard IFSs together with a corresponding set of probabilities. The attractor of the super IFS is called a superfractal; it is a collection of V-variable random fractals (sets or measures) together with an associated probability distribution on this collection. When the underlying space is for example ℝ 2 , and the transformations are computationally straightforward (such as affine transformations), the superfractal can be sampled by means of the algorithm, which is highly efficient in terms of memory usage. The algorithm is illustrated by some computed examples. Some variants, special cases, generalizations of the framework, and potential applications are mentioned.
Background: Studies suggest that higher consumption of added sugar is associated with cardiovascular risk factors in adolescents. However, these studies were subject to measurement error due to the lack of adjustment for day-to-day variability. Hypothesis: We hypothesized that higher usual percent of calories from added sugar is associated with dyslipidemia. Methods: We analyzed data on 3322 adolescents aged 12-19 years who were not on low fat/low cholesterol diet or on sugar free/low sugar diet from the 2005-2010 National Health and Nutrition Examination Surveys. We estimated the usual percent of calories from added sugar from the diet accounting for measurement error. Multivariable linear regression was used to examine the associations between the percent of calories from added sugar with lipids profile. Results: The average usual percent of calories from added sugar was 17.5%. Ninety-one percent and 11% adolescents had usual percent ≥10% and ≥25%, respectively. After adjustment for potential confounders (age, sex, race/ethnicity, body mass index, parental educational attainment, smoking status, physical activity, 2010 Health Eating Index score except sugar component, and total calorie intake), usual percent of calories from added sugar was inversely associated with high-density lipoprotein and positively associated with triglycerides and the ratio of total cholesterol to high-density lipoprotein. Among the lowest and the highest quintiles of intake, high-density lipoprotein were 52.4 mg/dL (95% CI: 50.9 to 53.9) and 49.0 (95% CI: 47.9 to 50.2) (P trend = 0.003), triglycerides were 80.2 mg/dL (95% CI: 70.5 to 90.0) and 100.4 mg/dL (95% CI: 86.7 to 114.2) (P trend = 0.028), and the ratio of total cholesterol to high-density lipoprotein were 3.16 (95% CI: 2.8 to 3.6) and 3.49 (95% CI: 3.0 to 4.0) (P trend =0.006), respectively. The patterns of association were largely consistent across gender, race/ethnicity, and body mass index (normal vs. overweight/obese) subgroups, except in non-Hispanic black and Mexican American, in which the magnitude of the association tended to be smaller. Sensitivity analysis showed that, when intake data from the 1 st 24-hour dietary recall was used, the association remained significant but attenuated substantially. No association was found for total cholesterol and low-density lipoprotein. Conclusions: Overwhelming majority of US adolescents consumed more added sugar than recommended for heart health. Increased intake of added sugar is associated with several measures of dyslipidemia, and reduction of added sugar consumption among adolescents might reduce the risk of developing cardiovascular disease in adults.
We present a procedure for modeling the initially quasi‐static upward progression of a zone of slip from some depth in the lithosphere toward the earth's surface, along a transform plate margin, culminating in a great crustal earthquake. Stress transmission in the lithosphere is analyzed with a generalized Elsasser model, in which elastic lithospheric plates undergo plane stress deformation and are coupled by an elementary foundation model to a Maxwellian viscoelastic asthenosphere. Upward progression of rupture over a finite length of plate boundary, corresponding to a seismic gap along strike, is analyzed by a method based on the ‘line‐spring’ concept, whereby a two‐dimensional antiplane analysis of the upward progression provides the relation between lithospheric thickness‐averaged stress and slip used as a boundary condition in the generalized Elsasser plate model. The formulation results in a nonlinear integral equation for the rupture progression as a function of time and distance along strike. A simpler approximate single degree of freedom analysis procedure is described and shown to lead to instability results that can be formulated in terms of the slip‐softening slope at the boundary falling below the elastic unloading stiffness of the surroundings. The results also indicate a delay of ultimate (seismic) instability due to the stiffer short versus long time asthenospheric response and predict a final period of self‐driven creep toward instability. The procedures for prediction of rupture progression and instability are illustrated in detail for an elastic‐brittle crack model of slip zone advance, and parameters of the model are chosen consistently with great earthquake slips and stress drops. For example, an effective crack fracture energy of the order 4×10 6 J/m 2 at the peak, 7 to 10 km below surface, of a Gaussian bell‐shaped distribution of fracture energy with depth, with variance of the order 5 km, simulating strength build‐up in a seismogenic layer, leads to prediction of nominal seismic stress drops of 30 to 60 bars and slips of 2 to 5 m in great strike slip earthquake ruptures breaking 100 to 400 km along strike. Precursory surface straining in the self‐driven stage is predicted to proceed at a distinctly higher rate over time intervals beginning 3 to 10 months before such an earthquake, this interval being greater for longer distances along strike over which the preseismic upward rupture progression takes place.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCorrelations between wettability and structure in monolayers of alkanethiols adsorbed on goldColin D. Bain and George M. WhitesidesCite this: J. Am. Chem. Soc. 1988, 110, 11, 3665–3666Publication Date (Print):May 1, 1988Publication History Published online1 May 2002Published inissue 1 May 1988https://pubs.acs.org/doi/10.1021/ja00219a055https://doi.org/10.1021/ja00219a055research-articleACS PublicationsRequest reuse permissionsArticle Views996Altmetric-Citations185LEARN 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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