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1.
Atkinson [2006. Losing energy in classical, relativistic and quantum mechanics. in Studies in History and Philosophy of Modern Physics, 38 To appear.] has obtained some new results on supertasks and the violation of conservation laws. I discuss these results here, extending them from a different perspective, which, by focusing on considerations of indeterminism, facilitates the natural introduction in this context of the concept of dynamical attractor.  相似文献   

2.
Objectiveprobability in quantum mechanics is often thought to involve a stochastic process whereby an actual future is selected from a range of possibilities. Everett's seminal idea is that all possible definite futures on the pointer basis exist as components of a macroscopic linear superposition. I demonstrate that these two conceptions of what is involved in quantum processes are linked via two alternative interpretations of the mind-body relation. This leads to a fission, rather than divergence, interpretation of Everettian theory and to a novel explanation of why a principle of indifference does not apply to self-location uncertainty for a post-measurement, pre-observation subject, just as Sebens and Carroll claim. Their Epistemic Separability Principle is shown to arise out of this explanation and the derivation of the Born rule for Everettian theory is thereby put on a firmer footing.  相似文献   

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Zusammenfassung In Laboratoriumsuntersuchungen wurde der Einfluss von Aluminiumphosphat auf die «dose-response regression lines» des Impfstoffes gegen Keuchhusten untersucht.  相似文献   

6.
This paper is concerned primarily with the evaluation and comparison of objective and subjective weather forecasts. Operational forecasts of three weather elements are considered: (1) probability forecasts of precipitation occurrence, (2) categorical (i.e. non-probabilistic) forecasts of maximum and minimum temperatures and (3) categorical forecasts of cloud amount. The objective forecasts are prepared by numerical-statistical procedures, whereas the subjective forecasts are based on the judgements of individual forecasters. In formulating the latter, the forecasters consult information from a variety of sources, including the objective forecasts themselves. The precipitation probability forecasts are found to be both reliable and skilful, and evaluation of the temperature/cloud amount forecasts reveals that they are quite accurate/skilful. Comparison of the objective and subjective forecasts of precipitation occurrence indicates that the latter are generally more skilful than the former for shorter lead times (e.g. 12–24 hours), whereas the two types of forecasts are of approximately equal skill for longer lead times (e.g. 36–48 hours). Similar results are obtained for the maximum and minimum temperature forecasts. Objective cloud amount forecasts are more skilful than subjective cloud amount forecasts for all lead times. Examination of trends in performance over the last decade reveals that both types of forecasts for all three elements increased in skill (or accuracy) over the period, with improvements in objective forecasts equalling or exceeding improvements in subjective forecasts. The role and impact of the objective forecasts in the subjective weather forecasting process are discussed in some detail. The need to conduct controlled experiments and other studies of this process, with particular reference to the assimilation of information from different sources, is emphasized. Important characteristics of the forecasting system in meteorology are identified, and they are used to describe similarities and differences between weather forecasting and forecasting in other fields. Acquisition of some of these characteristics may be beneficial to other forecasting systems.  相似文献   

7.
有无植物条件下明渠水流紊动特性对比   总被引:2,自引:0,他引:2  
在可变坡水槽中,模拟了带枝杈植物对明渠水流的干扰作用,借助超声多普勒流速仪(ADV)测量了不同水深下垂线不同测点的瞬时流速,计算了各测点的三维时均流速、脉动强度及雷诺应力等紊动参数,通过与无植物干扰的明渠均匀流紊动特性进行对比,分析植物对水流紊动参数的影响规律。试验结果表明:在有植物明渠水流中,时均流速呈三区分布特征;脉动强度及雷诺应力均在植物顶部附近出现最大值;脉动强度明显增大,在3个方向上趋于接近;可以用植物顶部以上的雷诺应力分布推求摩阻流速。  相似文献   

8.
Summary Although trypsin-disaggregated embryonic chick neural retina cells are incapable while EDTA-disaggregated cells are capable of immediate aggregation in culture, cells from both populations exhibit equally negligible levels of cell surface proteolytic activity as measured by substrate assay. The trypsin-induced lag does not appear, therefore, to depend upon adsorbed enzyme.  相似文献   

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This article discusses the intersection of science and culture in the marketplace and explores the ways in which radium quack and medicinal products were packaged and labelled in the early twentieth century US. Although there is an interesting growing body of literature by art historians on package design, historians of science and medicine have paid little to no attention to the ways scientific and medical objects that were turned into commodities were packaged and commercialized. Thinking about packages not as mere containers but as multifunctional tools adds to historical accounts of science as a sociocultural enterprise and reminds us that science has always been part of consumer culture. This paper suggests that far from being receptacles that preserve their content and facilitate their transportation, bottles and boxes that contained radium products functioned as commercial and epistemic devices. It was the 1906 Pure Food and Drug Act that enforced such functions. Packages worked as commercial devices in the sense that they were used to boost sales. In addition, 'epistemic' points to the fact that the package is an artefact that ascribes meaning to and shapes its content while at the same time working as a device for distinguishing between patent and orthodox medicines.  相似文献   

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Summary No difference was observed during in vitro development between mouse single blastomeres with and without the zona, pellucida, isolated from 2- and 4-cell stage eggs.  相似文献   

11.
H Tojo  Z Ogita  Y Momose 《Experientia》1985,41(1):108-109
No difference was observed during in vitro development between mouse single blastomeres with and without the zona pellucida, isolated from 2- and 4-cell stage eggs.  相似文献   

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In this paper I critically evaluate the justification of the von Neumann–Lüders projection postulate for state changes in projective measurement contexts from the objective quantum Bayesian perspective. I point out that the justification provided so far for the von Neumann–Lüders projection postulate is insufficient. I argue that the best way to correct this problem is to make an assumption, Benign Realism, which is contradictory to the objective quantum Bayesian interpretation of quantum states.  相似文献   

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Zusammenfassung Dissoziierte Nervenzellen der Gehirnhemisphären von Hühnerembryonen wurden inRose-Kammern mit und ohne Cellophanmembran kultiviert. Die Differenzierung der Neurone wurde mit Phasenkontrast und histochemischen Methoden untersucht.

Chargée de Recherche au CNRS.  相似文献   

15.
Summary A helper factor can be detected in antigen-treated supernatants from spleen T and adherent cells of sensitized animals. This factor promotes an indirect hapten-specific plaque forming response of B cells, irrespective of the identity of the carrier, i.e. provides the Th-2 type of help. Factor production increases with age and occurs most rapidly in strains known to have an accelerated decrease of suppressor capacity. The reason for the inverse correlation between suppressor capacity and the Th-2 type of helper factor is discussed.Acknowledgments. Thanks are due to the Medical Research Council, the National Cancer Institute of Canada and the National Health Research and Development Program for financial support; T.M. is indebted to the Medical Research Council for personal support.  相似文献   

16.
Life without oxygen: what can and what cannot?   总被引:1,自引:0,他引:1  
A J Zehnder  B H Svensson 《Experientia》1986,42(11-12):1197-1205
The basic principles involved in the biotransformation of organic carbon compounds in the absence of molecular oxygen (dioxygen) are presented in this paper. The role of various electron acceptors during the breakdown of organic compounds is discussed and the metabolic end-products expected are summarized. The different biochemical possibilities and strategies for the anaerobic degradation of organic matter and the metabolic response of some organisms to anaerobiosis are elucidated. Positive and negative effects of anaerobiosis on environmentally relevant processes and their influence on man and on animals are reviewed. Finally, some examples of the biotechnological application of anaerobic processes are presented.  相似文献   

17.
This paper evaluates different procedures for selecting the order of a non-seasonal ARMA model. Specifically, it compares the forecasting accuracy of models developed by the personalized Box-Jenkins (BJ) methodology with models chosen by numerous automatic procedures. The study uses real series modelled by experts (textbook authors) in the BJ approach. Our results show that many objective selection criteria provide structures equal or superior to the time-consuming BJ method. For the sets of data used in this study, we also examine the influence of parsimony in time-series forecasting. Defining what models are too large or too small is sensitive to the forecast horizon. Automatic techniques that select the best models for forecasting are similar in size to BJ models although they often disagree on model order.  相似文献   

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Résumé Des substances inhibitrices de la croissance radiculaire sont présentés dans les téguments et les cotylédons des graines de Lentille. Leurs effets sont mis en évidence dans des germinations de graines préalablement imbibées et (ou) semées avec ou sans téguments.  相似文献   

20.
Résumé Les résultats obtenus suggèrent que la lésion de l'hypothalame provoquée par la microcoagulation accélère l'apparition de la puberté des rats totalement irradiés aux rayons X, ce qui est le cas aussi chez des rats normaux. Mais l'apparition de la puberté est retardée proportionnellement aux doses de rayons X appliquées, indépendamment de la microcoagulation.  相似文献   

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