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11.
A standard protocol for the yellow-green-2 (yg2) forward mutation assay in Zea mays is proposed. A detailed calibration of the assay using 137Cs gamma rays and ethylmethanesulfonate (EMS) was conducted. Gamma ray-induced mutant sectors in leaves 4 and 5 exhibited one-hit kinetics. The radiation doses ranged from 25 to 500 rads. The mean induced mutation rate per rad of gamma radiation was 4.54 X 10(-6). This value was constant for the primordial cells of leaves 4 or 5. The induction of forward mutation by EMS also exhibited one-hit kinetics in the concentration range 0.25-20 mM (0.33-23.54 mumol EMS/kernel). The mean induced mutation rate per mM EMS was 1.79 X 10(-4), and the mean induced mutation rate per mumol of EMS per kernel was 1.52 X 10(-4). Using the induced mutation rates for gamma radiation and EMS, the rad equivalent was calculated. One rad of gamma radiation is equivalent to the exposure of a 2.53 X 10(-5) M EMS solution or to 2.99 X 10(-8) mol of EMS per kernel. 相似文献
12.
Dowd SB 《Applied radiology》1984,13(2):81-82
Most texts and studies analyzing risks and benefits of ionizing radiation use a "risk-comparison" method in which the benefits of ionizing radiation are not considered. This article describes a method designed to weigh both risks and benefits. 相似文献
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14.
We studied the effect of scheduled intern rotations on the cost and quality of inpatient care at one teaching hospital. For all discharges from the internal medicine service between 1980 and 1986, we identified 1,705 rotation patients and 3,141 no-rotation patients. Using linear or logistic regression analysis to control for baseline differences, we evaluated for the effect of rotation. We found that rotation was significantly related to longer length of hospital stay, b = 0.341 days, p = 0.001, and higher hospital charges (for log charges, b = 0.053, p = 0.016. Hospital deaths, nursing home placements, and 30-day readmissions were not significantly related to rotation, p > 0.1. These results suggest that the systematic discontinuity induced by scheduled intern rotations may be another source of increased health care costs experienced at teaching hospitals. 相似文献
15.
BACKGROUND: Forecasting the population health burden of chronic diseases requires models consistent with the relation, over time and in an uncertain environment, of risk factors and diseases at the individual level. There is now sufficient longitudinal data, and scientific understanding, of some chronic diseases to construct detailed process-models to better predict their population health burden and more realistically describe the effects of interventions. A crucial clement in constructing models is the way in which stochastic influences are described, e.g. are they allowed to interact over time with deterministic model features? METHODS: A review of statistical and forecasting models aimed to establish what ancillary data and scientific insights are necessary to describe multivariate stochastic health processes and their response to interventions. For circulatory diseases and cancer there exists sufficient longitudinal data and biological insight to construct stochastic multivariate process models. For other diseases, biological knowledge is less complete and there are fewer data sets where multiple risk factors are assessed longitudinally. Forecasting models for those diseases will then rely more heavily on theoretical assumptions about disease behaviour. 相似文献
16.
Malek AM Halbach VV Phatouros CC Higashida RT Dowd CF Wachhorst S Lawton MT 《Neurosurgery》1999,44(4):877-880
OBJECTIVE AND IMPORTANCE: A case of a spinal dural arteriovenous fistula (DAVF) with two associated feeding artery aneurysms is reported. Intradural spinal arteriovenous malformations have been associated with aneurysms that present with subarachnoid hemorrhage and with venous varices that produce mass effect, but spinal DAVFs have not previously been described in association with feeding artery aneurysms. CLINICAL PRESENTATION: A 71-year-old man presented with progressive spastic paraparesis, constipation, and overflow incontinence. Magnetic resonance imaging demonstrated a spinal vascular lesion and venous ischemia in the lower spinal cord. Diagnostic spinal angiography revealed a DAVF originating from the left T11 radicular artery and having the unusual feature of two proximal feeding artery aneurysms. INTERVENTION: The patient deteriorated neurologically after undergoing angiography, prompting emergent surgery. The DAVF was resected through a T11 transpedicular approach. One aneurysm was dolichoectatic and therefore unclippable, requiring proximal occlusion of the parent artery after establishing tolerance of test occlusion using somatosensory evoked potentials; the second aneurysm was adjacent to the fistula and was resected with the DAVF. CONCLUSION: Feeding artery aneurysms in association with spinal DAVFs have not been previously reported. They present additional risk to patients and, with simple modifications of the standard operative approaches, can easily be treated as part of the surgery for the DAVF. 相似文献
17.
In today's health care environment, many health care managers choose to move to a new setting. Because environments vary from setting to setting, a manager who plans to move needs to evaluate potential "fit" in the new locality. An evaluation of "fit" includes an assessment of both the job culture and persons in the environment. The Giger-Davidhizar transcultural assessment model provides a model for evaluating a new job culture. 相似文献
18.
Pathways to care for alcohol use disorders 总被引:1,自引:0,他引:1
19.
Child sexual abuse is a problem that often can be stopped or prevented if reported. This article summarizes child sexual abuse: its incidence, signs and symptoms. and legal and ethical issues. Through a case study, a five-step approach to the reporting of child sexual abuse is presented to help health care professionals and supervisors in fulfilling their ethical and legal obligations. 相似文献
20.
Hospital managers are making aggressive changes in their caregiver staffs to meet challenges such as reductions in utilization and capitated care. Managers are doing this to decrease the cost of care while maintaining or improving quality of care. However, the literature addressing the impact of hospital staffing practices on quality of care indicates that these changes may negatively influence quality. Department administrators must be cautious, yet proactive in their approach to patient care restructuring in order to ensure continued quality as well as cost-effectiveness. 相似文献