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Epitaxial NiO hillocks on the {111} and {001} facets of truncated octahedral nanoparticles of Ni have been directly observed by high-resolution transmission electron microscopy. These nanometer hillocks form a rough shell enclosing the Ni nanoparticle. The epitaxial relationships of NiO on nanoparticles of Ni are the same as those of NiO on bulk Ni {111} and {001} surfaces. The formation of hillocks is related to the relaxation of the compressive stress in NiO arising from the very large lattice mismatch between NiO and Ni. The compressively stressed epitaxial NiO shell provides effective protection to the nanoparticles of Ni against further oxidation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Remarkably oxidation-resistant nanoparticles of iron prepared at Tianjin University have been studied by electron diffraction and high-resolution transmission electron microscopy (HRTEM). HRTEM images clearly show the polyhedral epitaxy of γ-Fe[sub 2]O[sub 3] layers on equivalent {100} facets of the {100} truncated {110} rhombic dodecahedral nanoparticles of iron. Oxide layers on {110} facets are formed by the lateral extension of the epitaxial {100} γ-Fe[sub 2]O[sub 3] layers over adjacent {110} facets. The {110} oxide layers are bent and concave inward. The compressive γ-Fe[sub 2]O[sub 3] layers which are about 4 nm thick give effective protection, according to the theory of Caberra-Mott, to the iron core from further oxidation. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Background: Although noninvasive pharmacologic stress tests are widely used, their relative performance is not clear. We compared the performance of pharmacologic stress tests combined with echocardiography or nuclear imaging for the diagnosis of coronary disease., Methods: We performed a regression meta-analysis of published data. We included studies published between January 1975 and June 1999 in which subjects underwent echocardiographic or single-photon emission computed tomography (SPECT) stress testing with adenosine, dipyridamole, or dobutamine for diagnosis of coronary artery disease. All subjects also underwent coronary angiography. Two independent reviewers abstracted population characteristics, technical factors, methodologic factors, and results and calculated test sensitivity and specificity., Results: Eighty-two studies met the inclusion criteria. The sensitivity of dipyridamole SPECT imaging, 89% (95% CI, 84%-93%), was higher than that of dipyridamole echocardiography, but the specificity of dipyridamole SPECT imaging, 65% (95% CI, 54%-74%), was lower than that of dipyridamole echocardiography. Dipyridamole and adenosine tests had similar sensitivities and specificities. The sensitivity of dobutamine echocardiography, 80% (95% CI, 77%-83%) was similar to that of dobutamine SPECT imaging, but dobutamine echocardiography had a higher specificity, 84% (95% CI, 80%-86%) than dobutamine SPECT imaging did., Conclusions: The findings of our study can be used to guide the selection of the optimal pharmacologic stress test for each patient. Maximum sensitivity can be attained by use of a vasodilator combined with SPECT imaging. Maximum specificity can be attained by use of a vasodilator with echocardiography. The highest combination of sensitivity and specificity can be attained with dobutamine echocardiography.

Purpose: Randomized trials comparing medical and surgical therapies for the treatment of chronic stable angina were completed in the early 1980s. Therapies developed since then have decreased mortality and myocardial infarction rates from coronary artery disease. Using decision analysis and incorporating current recommendations for treatment, we simulated a trial comparing coronary artery bypass graft surgery and medical therapy., Methods: A Markov decision analysis model was constructed to compare the 5-year and 10-year outcomes of a simulated trial of medical therapy versus bypass surgery for stable chronic angina. Baseline data were obtained from a meta-analysis of trials comparing the two treatments. Data on risk reduction from contemporary therapies were obtained from randomized trials and meta-analyses., Results: All subgroups experienced modest gains in survival with current therapies. At 5 years, the survival rate was 90% in the medical group (an absolute gain of 6%) and 94% in the surgical group (an absolute gain of 4%). Similar results were obtained for patients with triple-vessel disease. Among patients with a low ejection fraction, the 5-year survival rate was 85% for medical patients and 92% for surgical patients. Sensitivity analyses did not substantially affect the conclusions., Conclusion: Advances in the treatment of chronic stable angina have improved the outcome both for patients treated initially with surgery and for those treated initially with medical therapy. The improvements were of similar magnitude in both groups, so the fundamental conclusions of the bypass trials are unchanged.

Background: Depot medroxyprogesterone acetate contraception is widely used in Navajo women, a high-risk population for diabetes mellitus. However, depot medroxyprogesterone may lead to weight gain and independently decrease insulin sensitivity. We studied the association between depot medroxyprogesterone and development of diabetes in Navajo women., Methods: We studied Navajo women aged 18 to 50 years who had seen a health care provider at a Navajo Area Indian Health Service clinic at least once in 1998. Diabetic cases (n = 284) and nondiabetic controls (n = 570) were matched by age. Medical records were reviewed to determine contraception use before the diagnosis date of diabetes., Results: Users of depot medroxyprogesterone were more likely to develop diabetes than patients who had used combination estrogen-progestin oral contraception only (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.8-7.9). The excess risk persisted after adjustment for body mass index (OR, 3.6; 95% CI, 1.6-7.9). Longer use was associated with greater risk of diabetes. Users of depot medroxyprogesterone were also more likely to develop diabetes than patients who had never used hormonal contraception, although excess risk was smaller (OR, 2.4; 95% CI, 1.4-3.6)., Conclusions: Depot medroxyprogesterone contraception was associated with a greater risk of diabetes compared with combination oral contraceptive use only. Risk was associated with length of use and persisted after adjustment for body mass index. Additional research is needed for confirmation, but this risk should be considered in contraceptive choice for women at high risk for diabetes.

Context: The use of Viagra (sildenafil) (Pfizer, New York, New York) for treating impotence has increased dramatically. However, the cost of the drug and philosophical questions about what defines a medical condition have sparked controversy over whether insurance policies should cover impotence treatment., Count: The utility of life with impotence at which Viagra meets the conventional criterion for cost-effectiveness (i.e., < $50,000 per quality-adjusted life-year [QALY])., Calculation: We solved the following equation for utility of life with impotence: [formula: see text], Results: Assuming that Viagra is used twice a week and that it costs $10 per pill, the utility of life with impotence would have to be less than 0.98 (compared with quality of life without impotence) for Viagra to meet the conventional criterion for cost-effectiveness. For patients using Viagra once or three times per week, the corresponding threshold utilities for impotence were 0.99 and 0.97, respectively., Conclusions: For men whose quality of life is sufficiently diminished by impotence, Viagra would be considered cost-effective relative to other commonly used health interventions.

Background: The optimal strategy for the diagnosis of coronary artery disease (CAD) in women is not well defined. We compared the cost-effectiveness of several strategies for diagnosing CAD in women with chest pain., Methods: We performed decision and cost-effectiveness analyses with simulations of 55-year-old ambulatory women with chest pain. With a Markov model, simulations of patients underwent exercise electrocardiography, exercise testing with thallium scintigraphy, exercise echocardiography, angiography, or no workup., Results: Diagnosis with angiography cost less than $17, 000 per quality-adjusted life-year compared with exercise echocardiography if the patient had definite angina and less than $76,000 per life-year if she had probable angina. If she had nonspecific chest pain, diagnosis with exercise echocardiography increased life-years compared with no testing., Conclusions: Cost-effectiveness of first-line diagnostic strategy for diagnosis of CAD in women varies mostly according to pretest probability of CAD. Diagnosis of coronary artery disease with angiography is cost-effective in 55-year-old women with definite angina. In 55-year-old women with probable angina, diagnosis with angiography would increase quality-adjusted life-years but significantly increase costs. Use of exercise echocardiography as a first-line diagnosis for CAD is cost effective in 55-year-old women with probable angina and nonspecific chest pain.

Background: Although the Indian Health Service provides extensive health care service to Navajo people, the role of native healers, or medicine men, has not been quantitatively described., Objective: To determine the prevalence of native healer use, the reasons for use, cost of use, and the nature of any conflict with conventional medicine., Methods: We conducted a cross-sectional interview of 300 Navajo patients seen consecutively in an ambulatory care clinic at a rural Indian Health Service hospital., Results: Sixty-two percent of Navajo patients had used native healers and 39% used native healers on a regular basis; users were not distinguishable from nonusers by age, education, income, fluency in English, identification of a primary provider, or compliance, but Pentecostal patients used native healers less than patients of other faiths. Patients consulted native healers for common medical conditions such as arthritis, depression, and diabetes mellitus as well as "bad luck." Perceived conflict between native healer advice and medical provider advice was rare. Cost was the main barrier to seeking native healer care., Conclusions: Among the Navajo, use of native healers for medical conditions is common and is not related to age, sex, or income but is inversely correlated with the Pentecostal faith; use of healers overlaps with use of medical providers for common medical conditions. Patients are willing to discuss use of native healers and rarely perceive conflict between native healer and conventional medicine. This corroborates other research suggesting that alternative medicine is widely used by many cultural groups for common diseases.