136 resultados para Effective-medium Approximation


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The intrinsic physical and radiobiological characteristics of High Dose Rate Brachytherapy (HDR-BT) are well suited to the treatment of prostate cancer. HDR-BT was initially used as a boost to external beam brachytherapy, but has subsequently been employed as the sole treatment, which is termed HDR monotherapy. This review summarizes the clinical outcomes and toxicity results of the principal studies and discusses the radiobiological basis supporting its use.

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Communication between trainer and trainee plays a central role in teaching and learning in the clinical environment. There are various strategies to frame the dialogue between trainee and trainer. These strategies allow trainers to be more effective in their supervision, which is important in our busy clinical environment. Communication strategies are well adapted to both in- and out-patient settings, to both under- and postgraduate contexts. This article presents three strategies that we think are particularly useful. They are meant to give feedback, to ask questions and to present a case.

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QUESTION UNDER STUDY: To test longitudinally differences in conventional cigarette use (cigarettes smoked, cessation, quit attempts) between vapers and nonvapers. METHODS: Fifteen months follow-up of a sample of 5 128 20-year-old Swiss men. The onset of conventional cigarette (CC) use among nonsmokers, and smoking cessation, quit attempts, changes in the number of CCs smoked among smokers at baseline were compared between vapers and nonvapers at follow-up, adjusted for nicotine dependence. RESULTS: Among baseline nonsmokers, vapers were more likely to start smoking at follow-up than nonvapers (odds ratio [OR] 6.02, 95% confidence interval [CI] 2.81, 12.88 for becoming occasional smokers, and OR = 12.69, 95% CI 4.00, 40.28 for becoming daily smokers). Vapers reported lower smoking cessation rates among occasional smokers at baseline (OR = 0.43 (0.19, 0.96); daily smokers: OR = 0.42 [0.15, 1.18]). Vapers compared with nonvapers were heavier CC users (62.53 vs 18.10 cigarettes per week, p <0.001) and had higher nicotine dependence levels (2.16 vs 0.75, p <0.001) at baseline. The number of CCs smoked increased between baseline and follow-up among occasional smokers (b = 6.06, 95% CI 4.44, 7.68) and decreased among daily smokers (b = -5.03, 95% CI -8.69, -1.38), but there were no differential changes between vapers and nonvapers. Vapers showed more quit attempts at follow-up compared with nonvapers for baseline occasional smokers (incidence rate ratio [IRR] 1.81, 95% CI 1.24, 2.64; daily smokers IRR 1.28, 95% CI 0.95, 1.73). CONCLUSIONS: We found no beneficial effects of vaping at follow-up for either smoking cessation or smoking reduction.

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This paper asks whether collective industrial relations can be promoted by means other than seeking change in public policy. Recent research points to the increasing significance of transnational private regulation (TPR) in developing economies. There is an emerging consensus that market incentives to improve wages and conditions of work can have a modest positive effect on measurable outcomes like hours of work, and health and safety. However, it appears that TPR has little impact on the capacity of workers to pursue such improvements for themselves via collective action. The paper takes a closer look at the potential of TPR to enhance worker voice and participation. It argues that this potential cannot be properly evaluated without understanding how local actors mobilise the social and political resources that TPR provides. The case studies presented show how different TPR schemes have been used by unions in Africa as a means to pursue the interests of members. The authors found that the scale of the impact of TPR in all of the contexts studied depended almost entirely on the existing capacities and resources of the unions involved. TPR led to the creation of collective industrial relations processes, or helped unions to ensure that certain enterprises participated in existing industrial relations processes, but did virtually nothing to enhance the political and organisational capacity of the unions to influence the outcomes of those processes in terms of wages and conditions of employment. The paper concludes that the potential of TPR to promote the emergence of collective industrial relations systems is very low.

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Screening mammography is the only imaging modality with proved decrease in breast cancer mortality. Ultrasound has been proposed as additional tool for screening. Controversies remain about the real value of sonography in this setting. In Caucasian women with dense breast, sonography improves significantly breast cancer detection, but also increases the false positive cases, biopsies and costs. A careful selection of women who may benefit from additional screening with sonography is mandatory.

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NlmCategory="UNASSIGNED">As opposed to the standard detective quantum efficiency (DQE), effective DQE (eDQE) is a figure of merit that allows comparing the performances of imaging systems in the presence of scatter rejection devices. The geometry of the EOS™ slot-scanning system is such that the detector is self-collimated and rejects scattered radiation. In this study, the EOS system was characterised using the eDQE in imaging conditions similar to those used in clinical practice: with phantoms of different widths placed in the X-ray beam, for various incident air kerma and tube voltages corresponding to the phantom thickness. Scatter fractions in EOS images were extremely low, around 2 % for all configurations. Maximum eDQE values spanned 9-14.8 % for a large range of air kerma at the detector plane from 0.01 to 1.34 µGy. These figures were obtained with non-optimised EOS setting but still over-performed most of the maximum eDQEs recently assessed for various computed radiology and digital radiology systems with antiscatter grids.