Results from a computer simulation of the pulse radiolysis of water using an improved spur model which includes a novel hydrated electron distribution and a spur overlap approximation are reported. Data for hydrated electron decay at nanosecond and subnanosecond times following pulse radiolysis of air-free water are fit within experimental error by adjustments in the initial spatial distribution of spur intermediates and the energy deposited per average spur. Using the same parameters which are successful in modeling the hydrated electron decay kinetics, pulse radiolysis data for hydroxyl radical decay are also fit within experimental error. Again using the same model parameters, the hydrated electron decay data for variable pulse dose were computed for times from 10"12 to 10"6 s following the pulse. At a pulse dose of about 8000 rd the fit between computations and experimental data for hydrated electron concentration is within experimental error at all times from 100 ps to 1 ps. At several kilorad pulse doses there is qualitative agreement but at very low pulse doses (below 200 rd) the fit between computer predictions and experimental hydrated electron decay data is not even qualitatively similar at times longer than 10"7 s. The pulse-dose dependent deviations from our computer model predictions can be reconciled using Mozumder and Magee's "blobs" and/or "short tracks". The average spur density of these spatial regions is postulated to be on the order of that present in 8000-rd pulse-irradiated water.
The kinetics of the decay of hydrated electron absorbance in pure water has been studied as a function of time and radiation dose delivered by 20-ns pulses of 15-MeV electrons. In order to identify intraspur reactions of the hydrated electron, values of the function |[-d(eaq~)/(eaq")]/dí)¡ (= Qt) were investigated as a function of pulse dose and time. Qt represents the fraction óf hydrated electrons disappearing at any given time, t, following the pulse. Whereas Q has the same functional form as a first-order rate constant, it is not a constant, but decreases with increasing time following the pulse. However, the functional form of Qt vs. time remains the same at low pulse doses (37-380 rads) for relatively long periods of time (up to 1 ps). The dose independence of Q is interpreted as evidence for predominantly intraspur hydrated electron decay. A plot of Qt vs. the function [(time)1/2(dose)1/3] yields a relatively sharp transition from dose independent hydrated electron decay (interpreted as arising predominantly from intraspur reactions) to dose dependent decay (both interspur and intraspur decay).This transition region is interpreted as the onset of significant spur overlap. In the range 0-8000 rads per 20-ns pulse, an empirical constant: (approximate time of detectable overlap)1/2(dose)1/3 = 110 ± 10 ns1/2 rads1/s is obtained which correlates the onset of experimentally observable spur overlap. Based upon these results, implications regarding spur sizes and spatial distributions of spurs and the need to include spur overlap considerations in modeling studies are developed.
Background: Breast augmentation is one of the most frequently performed aesthetic procedures in the United States. Online information is often used by patients to make decisions when undergoing cosmetic procedures. It is vital that online medical information includes relevant decision-making factors and uses language that is understandable to broad patient audiences. Ideally, online resources should aid patient decisions in aesthetic surgical planning, especially implant size selection for breast augmentation. We describe patient decision-making factors and readability of breast implant size selection recommended by private practice plastic surgery webpages. Methods: Using a depersonalized, anonymous query to Google search engine, the terms "breast implant size factors" and "breast implant size decision" were searched, and 52 plastic surgery private practice webpages were identified. Webpages were analyzed for reported decision-making factors of implant size selection. Readability analyses of webpages were performed with Readability Studio and Hemingway Editor. Results:The two major decision-making factors for implant size selection reported by webpages were body/tissue-based measurements and surgeon input. Ten factors related to patient lifestyle, surgical goals, and procedural options were also identified. Average webpage scores for five readability measures exceeded recommended levels for medical information. Conclusions: Reported decision-making factors for implant size selection emphasize a plastic surgeon's expertise but may enhance the patient's role in preoperative planning. Webpages describing breast implant size selection exceed the sixth and eighth grade reading levels recommended by the AMA and NIH, respectively. Improving the readability of webpages will refine the role of online medical information in preoperative planning of breast augmentation.
which presents evidence to show that the cis-trans Isomerization of 2,3-dimethyl-1,3-pentadiene almost certainly proceeds via the intermediate formation of 1,2,3-trlmethylcyclobutane and not via a biradical mechanism. These workers also studied the cis-trans Isomerization of 1,3-pentadiene. The situation was less clear but again intermediate formation of a cyclobutane seemed more likely than a biradical mechanism. A similar pathway for 3-methyl-1,3-pentadiene seems likely. This paper was overlooked by Marley and Jeffers.
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