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Both caloric restriction and overeating have been shown to affect neural processes associated with reinforcement. Both preclinical and some clinical studies have provided evidence that food restriction may increase reward sensitivity, and while there are mixed findings regarding the effects of overeating on reward sensitivity, there is strong evidence linking this behavior with changes in reward-related brain regions. Evidence of these changes comes in part from findings that show that such eating patterns are associated with increased drug use. The data discussed here regarding the differential effects of various eating patterns on reward systems may be particularly relevant to the aging population, as this population has been shown to exhibit altered reward sensitivity and decreased caloric consumption. Moreover, members of this population appear to be increasingly affected by the current obesity epidemic. Food, like alcohol or drugs, can stimulate its own consumption and produce similar neurochemical changes in the brain. Age-related loss of appetite, decreased eating, and caloric restriction are hypothesized to be associated with changes in the prevalence of substance misuse, abuse, and dependence seen in this cohort. 相似文献
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以正交设计筛选处方,研制了安心酮注射剂,考察了制剂的稳定性,有效期为2.85年。采用酸性染料比色法测定注射剂中安心酮的含量,平均回收率为98.7%(RSD=0.44%)。本品对离体灌流豚鼠心脏的作用与原药相似。 相似文献
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Penny F Whiting Marie E Weswood Anne WS Rutjes Johannes B Reitsma Patrick NM Bossuyt Jos Kleijnen 《BMC medical research methodology》2006,6(1):1-8
Background
In clinical trials, both unequal randomization design and sequential analyses have ethical and economic advantages. In the single-stage-design (SSD), however, if the sample size is not adjusted based on unequal randomization, the power of the trial will decrease, whereas with sequential analysis the power will always remain constant. Our aim was to compare sequential boundaries approach with the SSD when the allocation ratio (R) was not equal. 相似文献47.
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A 1-mm-thick, stationary, ultrahigh-strip-density, focused grid was evaluated with respect to patient radiation dose and mammographic image quality as it affected the resolution of microcalcifications and masses. Radiographic technique was varied to determine the most useful alteration to improve image quality with the grid. Results from 89 patients demonstrated that no improvement in diagnostic ability was found in women with fatty breasts. As breast density increased, the advantage of the grid technique became more apparent. Grid mammography also often solved the problem of questionable microcalcifications with improved visualization of their number and geometry. 相似文献