The "epidemic" of breast cancer in the U.S.--determining the factors

Breast cancer incidence rates in the United States rose by 24% between 1973 and 1991. Mortality during this period, however, remained stable. Both the 5-year relative survival rate and the rates of in situ and stage I breast cancers have been increasing, while the incidence of later-stage cancers has been decreasing. Increased mammography screening may explain the documented jump in breast cancer incidence rates during the mid-1980s. Differences in the distribution of breast cancer risk factors may account, in part, for the temporal trends in breast cancer incidence. In particular, breast cancer risk factors may vary by birth cohort, including age at menarche, age at first birth, physical activity, obesity, diet, alcohol intake, estrogen therapy, and exposure to environmental organochlorines. After decades of epidemiologic research, a preventive approach to breast cancer that focuses on the physiologic effects of the sex steroid hormones, and their potential interactions with family history, is being carefully formulated.     

Comments on “The electromagnetic field of a vertical electricdipole over the Earth or sea” [and reply]

Yokoyama makes some comments on the “numerical distance” contained in the surface wave term in the paper by King and Sandler (see ibid., vol.42, p.383, 1994) comparing it with the one obtained by former authors. He comments on the parameter P in the Fresnel-integral term in the paper. Yokoyama concludes that for the calculation of such a problem in a semi-sphere, the spherical polar coordinate system is preferable to the cylindrical coordinate system including the case of lateral waves. King and Sandler reply to the Comment     

Polyvinylidene fluoride monofilament sutures: can they be used safely for long-term anastomoses in the thoracic aorta?

Polyvinylidene fluoride (PVDF) represents an attractive alternative to polypropylene as a monofilament vascular suture because of its satisfactory physicochemical properties, it ease of handling, and its good biocompatibility. However, the polymer's ability to remain mechanically and chemically stable when exposed to a mild hydrolytic environment over the long term has yet to be demonstrated. One in vitro study involved the comparison of the long-term relative resistance of PVDF and polypropylene sutures to hydrolysis for a period of 9 years. The PVDF suture showed major molecular rearrangements from the original ratio of three crystalline structures to the single beta crystalline phase. The observation of some surface oxidation and water inhibition did not significantly modify the tensile strength of the PVDF suture, which retained 92.5% of its original value. In contrast, the polypropylene sample did not undergo any recrystallization but was associated with more oxidation byproducts and more water molecules near the surface, which contributed to a 46.6% loss in initial tensile strength. An in vivo study confirmed that PVDF sutures are biocompatible and are able to maintain satisfactory biostability when used to anastomose thoracic aortic allografts for a period of 6 months in the dog. The cellular reaction of fresh allografts as well as the control autografts to PVDF sutures was minimal. In other allografts that had been preserved in a supplemented medium for 1 week prior to implantation, the PVDF sutures healed satisfactorily with the formation of neocollagen and few macrophages surrounding the monofilament. No evidence of instability at the allograft-host artery junction was observed, confirming that the PVDF sutures were able to ensure a secure anastomosis in the thoracic aorta. PVDF sutures have demonstrated superior long-term biostability in vitro and minimal tissue response in vivo. These are two essential requirements when evaluating the use of a suture for vascular surgery in general and thoracic aortic surgery in particular.     

Influence of regular aerobic exercise on psychological health: A randomized, controlled trial of healthy middle-aged adults.

Evaluated 120 healthy, sedentary, middle-aged adults randomly assigned to either a 6-mo home-based aerobic exercise training program or to an assessment-only control condition. Adherence across the 6-mo period by the exercise group was demonstrated by self-report and heart rate microprocessor methods to exceed 75%. A 14-item Likert rating scale was used to measure a variety of psychological variables. Significant between-groups differences favoring the exercise group were found on scale items closely associated with actual physical changes that occurred with exercise (satisfaction with shape/appearance, perceived fitness). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficacy and Safety Evaluation of Ozonation to Degrade Aflatoxin in Corn

ABSTRACT: This study determined the efficacy and safety of ozonation in degrading aflatoxin in corn. Ozonation (10 to 12 wt%) reduced aflatoxin levels by 92% and no reversion to the parent compound was observed. Ozonation had minimal effect on fatty acids of uncontaminated corn, but had significant effect on fatty acids of contaminated corn. Crude extracts showed no mutagenic potential in the Ames assay using TA98 and TA100. Clean-up using hexane increased their mutagenic potentials. Clean-up using Mycosep columns increased the mutagenic potentials 18 to 617%. Hexane extracts from ozone-treated contaminated corn had lower inhibitory effect. This suggested that a fat-soluble mutagen is being formed or natural inhibitors of mutagenicity are being destroyed.     

Compact conical antennas for wide-band coverage

A broadband antenna with a vertically polarized, omnidirectional electric field is studied. The design of the antenna and its feeding system in the wide frequency range from 20 to 1000 MHz is described and the driving-point impedance determined. Also calculated are the voltage standing-wave ratio (VSWR) and the input impedance of a transmission line connected to the antenna. More efficient operation at low frequencies is obtained by adding a length of transmission line to form a resonant section with the antenna. The effect of the different properties of the earth's surface on the field pattern is treated in a companion paper     

Effect of thermal residual stresses on fatigue crack opening and propagation behavior in an Al/SiC p metal matrix composite

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated. formerly Research Student, Department of Materials Science and Metallurgy, University of Cambridge formerly Lecturer, Department of Materials Science and Metallurgy, University of Cambridge This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the 1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint TMS-SMD/ASM-MSD Composite Materials Committee.