Publications

Among diabetic women, increased physical activity, including regular walking, is associated with substantially reduced risk for cardiovascular events.

This chapter describes the mixed mode cracking in layered materials. There is ample experimental evidence that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip. An unloaded crack subsequently subject to a combination of modes I and II will initiate growth by kinking in such a direction that the advancing tip is in mode I. The chapter also elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness. The competition between crack advance within the interface and kinking out of the interface depends on the relative toughness of the interface to that of the adjoining material. The interface stress intensity factors play precisely the same role as their counterparts in elastic fracture mechanics for homogeneous, isotropic solids. When an interface between a bimaterial system is actually a very thin layer of a third phase, the details of the cracking morphology in the thin interface layer can also play a role in determining the mixed mode toughness. The elasticity solutions for cracks in multilayers are also elaborated.

The longitudinal thermal conductivity of a unidirectional fibre-reinforced composite containing an array of equally spaced transverse matrix cracks is calculated. The cracked composite is modelled by a cylindrical cell which accounts for altered heat transfer across the matrix cracks as well as through debonded portions of the fibre-matrix interface. Heat transfer mechanisms across the cracks and dedonded interfaces considered are contact, gaseous conduction, and radiation, and the relative importance of these mechanisms is discussed. Approximate closed form solutions to the cell model for the overall thermal conductivity are obtained using an approach reminiscent of the shear lag analysis of stiffness loss due to matrix cracking and debonding. Selected numerical results from a finite-element analysis of the cell model are presented to complement the analytical solutions. Both matrix cracking and interfacial debonding have the potential for significantly reducing the longitudinal thermal conductivity.

Cracks in ductile single crystals are analyzed here for geometries and orientations such that two-dimensional states of anti-plane shear constitute possible deformation fields. The crystals are modelled as ideally plastic and yield according to critical resolved shear stresses on their slip systems. Restrictions on the asymptotic forms of stress and deformation fields at crack tips are established for anti-plane loading of stationary and quasistatically growing cracks, and solutions are presented for several specific orientations in f.c.c. and b.c.c. crystals. The asymptotic solutions are complemented by complete elastic-plastic solutions for stationary and growing cracks under small scale yielding, based on previous work by Rice (1967, 1984) and Freund (1979). Remarkably, the plastic zone at a stationary crack tip collapses into discrete planes of displacement and stress discontinuity emanating from the tip; plastic flow consists of concentrated shear on the displacement discontinuities. For the growing crack these same planes, if not coincident with the crack plane, constitute collapsed plastic zones in which velocity and plastic strain discontinuities occur, but across which the stresses and anti-plane displacement are fully continuous. The planes of discontinuity are in several cases coincident with crystal slip planes but it is shown that this need not be the case, e.g., for orientations in which anti-plane yielding occurs by multi-slip, or for special orientations in which the crack tip and the discontinuity planes are perpendicular to the activated slip plane.

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

High‐carbin mcirostructures as components in microelectromechanical structures and microreactors are of particular interest because their mechanical, electrical, and chemical properties can be controlled by the temperature of preparation. The range of electrical properties is especially impressive. A method of fabricating microstructures of glassy carbon and other high‐carbon solids is presented, based on micromolding of polymers to form precursors to these structures and pyrolysis to yield the carbon solids. The advantages of the technique are discussed.

Background Observational studies have found beneficial effects of increased dairy intake on risk of high blood pressure (HBP). While it has been suggested that fermented dairy may provide even greater benefits, the independent effects yogurt, cheese, and milk have not been demonstrated. Objective To estimate the independent effects of total dairy, as well as yogurt, cheese, and milk, on risk of incident HBP among adults. A secondary objective was to evaluate effect modification by healthy diet patterns. Methods Data from three prospective studies of middle‐aged adults were used: the Nurses' Health Study (NHS) (ages 30–55 years, n=66,987), NHS II (ages 25–42, n=84,368), and the male Health Professionals Follow‐up Study (HPFS) (ages 40–75, n=30,512). Subjects without prevalent HBP, cardiovascular disease, cancer, or diabetes but with valid food frequency questionnaire data were included. NHS, NHS II, and HPFS participants were followed for a maximum of 30, 20, and 24 years, respectively, for development of physician diagnosed HBP self‐reported on biennial questionnaires. Time‐dependent Cox proportional hazards models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI), controlling for age, race, family history of HBP, smoking, physical activity, energy intake, protein, fruits and vegetables. Updated BMI was added in separate models to evaluate its potential mediating effect on HBP risk. A DASH (Dietary Approaches to Stop Hypertension) diet score was calculated to explore effect modification by diet quality. Fixed effects meta‐analysis was used to combine the results across the three cohorts. Results There were 81,909 total cases of incident HBP in the three cohorts; 41,585 cases occurred in the NHS, 26,134 cases in the NHS II, and 14,190 cases in the HPFS. Regular yogurt consumers (≥5 servings/week vs. <1 serving/month) in the NHS, NHS II, and HPFS cohorts respectively had 19% (95% CI: 0.75–0.86), 17% (95% CI: 0.76–0.89), and 7% (95% CI: 0.82–1.05) reductions in HBP risk. In pooled analyses, higher yogurt intake led to an 18% (95% CI: 0.78–0.86) reduction in risk of HBP. In contrast, we found 17% (95% CI: 0.80–0.85), 13% (95% CI: 0.85–0.89) and 8% (95% CI: 0.88–0.96) reductions in HBP risk with higher intakes of total dairy (3–<6 servings/day), milk (2–<6 servings/day), and cheese (1–4 servings/day), respectively. Controlling for BMI slightly attenuated (<5%) the effect of dairy in all forms. There was evidence of additive interaction between diet quality and yogurt intake; those with the highest yogurt intake and in the highest tertile of the DASH score across all three cohorts had a statistically significant 30% (95% CI: 0.65–0.74) lowered HBP risk. Conclusion Higher usual intakes of total dairy and all dairy subtypes (milk, cheese, and yogurt) were associated with a lower risk of HBP across three longitudinal cohorts. Yogurt consumption tended to confer a greater benefit than other forms of dairy. Our study adds solid evidence that higher long‐term dairy intake, and especially yogurt consumption, is linked with lower risk of HBP in middle‐aged adults. Support or Funding Information National Dairy Council and the Boston Nutrition and Obesity Research Center

There is indisputable evidence from epidemiologic and clinical studies that being overweight and obese elevates the risk of developing debilitating and costly chronic diseases, including hypertension, hypercholesterolemia, type 2 diabetes, cardiovascular diseases (CVD), and cancer (1). Nonetheless, the relationship between body mass index (BMI) and mortality remains the subject of much debate. A recent meta-analysis concluded that compared to those of normal weight (BMI<25.0), overweight individuals (BMI 25.0–29.9) had a significantly lower mortality risk (2). Even Class 1 obesity (BMI 30–34.9) was associated with marginally reduced mortality. In this Perspective, we discuss why this finding is likely to be an artifact of methodological limitations and what the clinical and public health implications may be.