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BACKGROUND: We studied availability to mammography among Spanish women aged 40 to 70 years, variation in use of the mammography by autonomous community, and the situation and importance of breast cancer screening programs among other factors, in the access to mammography. SUBJECTS AND METHODS: A cross-sectional population survey was conducted in 1994 in a sample of 3,218 women. A questionnaire was used to collect data on the variable access (receipt of at least one mammogram in the last 2 years) as well as different access-related variables. Information on breast cancer screening programs was collected by contacting the responsible institutions. We considered that a program had total coverage if it included all the municipalities in the province and partial if it did not include all municipalities. RESULTS: Twenty-eight percent of women had performed a mammogram. This proportion varied among autonomous communities (AACC) from 11.5 to 73.8%. Breast cancer screening programs existed in 8 AACC. The multivariant analysis revealed an association between access to mammography and the existence of a screening program, especially when the later had total coverage (OR = 7.64; 95% CI = 5.24-11.10). An association was also found between access to mammography and physician-related factors, place of residence and attitudes of women toward mammography. CONCLUSIONS: Less than one third of women aged 40-70 have performed a mammography in the last 2 years, and this proportion varies among AACC. Gynecologist visits and the existence of breast cancer screening programs are fundamental factors in the access to mammography in Spain.  相似文献   
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It is very difficult to have a clear and homogeneous idea of the embryo metabolism. In fact it may vary from one species to another and also according to the embryonic stage: i.e. before and after genomic activation. Basic compounds such as glucose may be toxic, but obviously, it is more the problem of the quantity introduced in the culture media and an unsuitable balance between the metabolites which may impair the embryonic development. At low concentration glucose is actively metabolised by embryos. High levels of amino acids are deleterious (due to release of ammonia), but they are necessary at low concentrations. Addition of serum or other biological fluids is generally useless. Further knowledge on embryo metabolism is necessary to avoid culture medium related delay or developmental blocks. Sequential media are at least partly the answer.  相似文献   
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The direct electrooxidation of methanol in acid medium was studied on electrodes made of a perfluorinated membrane with small amounts of metal catalysts incorporated by chemical reduction. Platinum is a good electrocatalyst for this reaction, but needs to be modified by other metals in order to obtain oxidation potentials much more compatible with a working anode in a direct methanol fuel cell. Ruthenium and tin appear to give encouraging results, leading to a negative shift of more than 250 mV as compared to the potential obtained with pure platinum. Other parameters were investigated in this work, such as the working temperature, and the manner of introduction of the methanol into the cell. By gaseous supply, it was possible to carry out measurements at higher temperatures than with methanol in solution, and consequently to greatly improve the performance of the catalytic electrode.  相似文献   
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An in situ NMR study of tert-butanol dehydration in 95 and 85% sulfuric acid did not indicate the formation of tert-butyl cations as active reaction intermediates. Instead, only NMR lines from oxonium ions under the condition of fast exchange with water and the acid were observed. It is most likely that, in the concentrated acid, the active intermediates of this reaction are represented by tert-butyl sulfuric ester which probably is a precursor of invisible tert-butyl carbenium ions representing short-lived excited or transition states.  相似文献   
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An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli.  相似文献   
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