This paper examines the stability of long-term trends in the number of traffic fatalities in eight highly motorised countries: Norway, Sweden, Denmark, Finland, The Netherlands, Great Britain, Australia and The United States. In all these countries, the number of traffic fatalities reached a peak around 1970-1972 and has since declined. The decline has, however, been irregular and fairly long periods of stagnation or even increase in the number of fatalities have occurred in all countries. A stable trend is defined in this paper as a trend that remains unchanged and therefore can be used to successfully predict the future number of fatalities by means of extrapolation. It is concluded that the trends towards fewer fatalities in the countries selected have not been stable and that even trend lines that fit past trends very closely are usually worthless for predictive purposes. An attempt was made to identify factors influencing long-term trends by fitting negative binomial regression models to fatality data. Although some of the models fitted the data marginally better than simple trend lines, these models are not necessarily more useful for predicting future trends than simple trend lines, since using the models for prediction requires that future changes in all explanatory variables must be predicted. The chief lesson is that past trends do not provide a reliable basis for predicting future developments with respect to the number of traffic fatalities. 相似文献
National road safety programmes have been developed in many motorised countries. Some of these programmes contain estimates of the safety benefits that were expected to be realised if the programmes were fully implemented. When these estimates are compared to actual outcomes, it is not uncommon to find large differences. This paper argues that differences between the predicted and actual results of road safety programmes could be the result of a large, but generally unrecognised, uncertainty inherent in estimates of the effects of such programmes. Ten sources of uncertainty are identified and briefly described. The possibility of describing these sources of uncertainty numerically, and of estimating their joint contribution, is discussed. It is concluded that at the current state of knowledge, it is not possible to meaningfully estimate the total uncertainty inherent in road safety programmes. The prospects of reducing uncertainty by means of research are discussed. 相似文献
Quartz and carbonaceous materials, which are used in the production of silicon as well as electrodes and refractories in the silicon furnace, contain trace elements mostly in the form of oxides. These oxides can be reduced to gaseous compounds and leave the furnace or stay in the reaction products—metal and slag. This article examines the behavior of trace elements in hydrothermal quartz and quartzite in the reaction of SiO2 with Si or SiC. Mixtures of SiO2 (quartz or quartzite), SiC, and Si in forms of lumps or pellets were heated to 1923 K and 2123 K (1650°C and 1850°C) in high purity graphite crucibles under Argon gas flow. The gaseous compounds condensed in the inner lining of the tube attached to the crucible. The phases present in the reacted charge and the collected condensates were studied quantitatively by X-ray diffraction (XRD) and qualitatively by Electron Probe Micro Analyzer (EPMA). Contaminants in the charge materials, reacted charge and condensate were analyzed by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Muscovite in the mineral phase of quartz melted and formed two immiscible liquid phases: an Al-rich melt at the core of the mineral, and a SiO2-rich melt at the mineral boundaries. B, Mn, and Pb in quartz were removed during heating in reducing atmosphere at temperature above 1923 K (1650°C). Mn, Fe, Al and B diffused from quartz into silicon. P concentration was under the detection limit. Quartzite and hydrothermal quartz had different initial impurity levels: quartzite remained more impure after reduction experiment but approached purity of hydrothermal quartz upon silica reduction. 相似文献
This paper identifies nine characteristics of road safety problems that are all in principle amenable to numerical measurement. The nine characteristics identified are:
1. Magnitude
2. Severity
3. Externality
4. Inequity
5. Complexity
6. Spatial dispersion
7. Temporal stability
8. Perceived urgency
9. Amenability to treatment
The purpose of identifying these dimensions and of trying to measure them is to provide a basis for selecting problems for treatment by means of safety programmes. Selecting problems for treatment usually cannot be done on the basis of a single dimension, as it is the mix of characteristics that determine the prospects for successfully treating a problem. It is proposed that amenability to treatment is a function of complexity, perceived urgency and the availability of cost-effective treatments. Speed and speeding is used as an example of a road safety problem to illustrate how the various dimensions can be measured. 相似文献
The performance of a multi-slit Integrated Micro Packed Bed Reactor-Heat Exchanger (IMPBRHE) for methanol synthesis from synthesis gas over Cu/ZnO/support commercial catalyst was experimentally investigated from a reaction engineering perspective. Through establishment of a systematic comparison strategy, performance comparison with a laboratory scale tubular Fixed-Bed Reactor (FBR) with three different dilution ratios was made to evaluate the IMPBRHE. The productivity, thermal behavior, activity of body materials, pressure drop and residence time distribution (RTD) of the two reactor types were investigated. The IMPBRHE outperformed the undiluted FBR and gave CO conversions comparable to the diluted FBRs. The main difference is ascribed to superior heat exchange properties of the IMPBRHE, which can improve reactor performance for an exothermic reaction such as methanol synthesis. The results reveal advantages of the IMPBRHE for robust scale up. 相似文献
Abstract Southern pine and aspen flakes were acetylated with acetic anhydride alone without cosolvent or catalyst by a simple dip procedure. The new procedure greatly shortens reaction time and simplifies chemical recovery. Acetylation weight gains of 15% to 20% can be achieved in 1 to 3 hours with southern pine flakes and in 2 to 4 hours with aspen flakes. Flakeboards made from acetylated southern pine or aspen flakes absorbed much less water, both in water-soaking tests and when subjected to humid air, and swelled at a lower rate and to a lower extent than did control boards. Hygroscopicity of the resulting flakeboards decreased with increased level of wood acetylation. The equilibrium moisture content (EMC) for flakeboards made from acetylated flakes was lower at each relative humidity tested than that of control boards. 相似文献
Although early studies suggested that coffee consumption might increase risk of some cancers, more comprehensive epidemiological and experimental data now generally indicate either neutral or beneficial effects. In this review, we summarize the current evidence for associations between breast, prostate, colorectal, and liver cancers and the consumption of coffee, and discuss the experimental evidence for potential chemopreventive mechanisms of coffee and coffee constituents. The epidemiological evidence consistently indicates that coffee protects against liver cancer, and also point toward protective effects for risk of colorectal cancers (with relative risks of 0.50 (95% CI: 0.42–0.59) and 0.83 (95% CI: 0.75–0.92), respectively, in the most recent meta‐analyses). There seems to be no association between the overall risk of breast and prostate cancer and coffee intake. However, for subgroups such as postmenopausal breast cancers, advanced prostate cancers, and breast and prostate cancer survivors, an inverse association with coffee intake is indicated. Potential mechanisms for chemopreventive effects of coffee phytochemicals includes inhibition of oxidative stress and oxidative damage, regulation of DNA repair, phase II enzymatic activity, apoptosis, inflammation, as well as having antiproliferative, antiangiogenetic effects and antimetastatic effects. The experimental evidence for effects of coffee and coffee constituents on each of these processes is discussed. 相似文献
High-purity iron has been oxidized at 1000–1200° C in CO2 and in CO2 + CO with different compositions and at different total gas pressures (0.1–1 atm.). The experimental work has comprised thermogravimetric reaction rate measurements and characterization of the wüstite scales by metallography and x-ray diffraction. The overall results have been analyzed in terms of a classical model for coupled linear/parabolic kinetics, where it is assumed that the surface of growing wüstite scales has exactly the same defect structure and defect concentrations as that of bulk wüstite equilibrated in the same gaseous atmospheres. Important discrepancies are found between the predicted and the experimentally observed reaction behavior. Thus, both the linear and parabolic rate constants are found to be dependent on the partial pressure of CO2 and the total gas pressure of the CO2 + CO gas mixtures, and furthermore, the reaction in CO2 + CO is slower than in O2 and in H2O + H2 with the same oxygen activity. In order to explain the experimental results, it is suggested that CO and CO2 molecules interact with the wüstite surface and thereby affect the defect structure and defect concentrations in a thin surface layer, and that this, in turn, affects both the linear and parabolic reaction rates. 相似文献
In Norway, a national initiative is currently aiming at standardising the electronic patient record (EPR) content based on an openEHR framework. The openEHR architecture, offers users the capability to conduct standardisation and structuration of the EPR content in a distributed manner, through an internet-based tool. Systems based on this architecture, is expected to ensure universal (also internationally) interoperability among all forms of electronic data. A crude estimate is that it is necessary to define somewhere between 1000 and 2000 standardised elements or clinical concepts (so-called archetypes), to constitute a functioning EPR system. Altogether, the collection of defined archetypes constitutes a backbone of an interoperable EPR system lending on the openEHR architecture. We conceptualize the agreed-upon archetypes as a large-scale information infrastructure, and the process of developing the archetypes as a infrastructuring effort. With this as a backdrop, we focus on the following research question: What are the challenges of infrastructuring in a large-scale user-driven standardisation process in healthcare? This question is operationalized into three sub-questions: First, how are the openEHR-based archetypes standardised in practice? Second, what is the role of daily clinical practice, and existing systems in the process of developing archetypes? Third, how may related, but supposedly independent infrastructuring projects shape each other’s progress? We contribute with insight into how power relations and politics shape the infrastructuring process. Empirically, we have studied the formative process of establishing a national information infrastructure based on the openEHR approach in the period 2012–2016 in Norway. 相似文献