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1.
This paper presents expressions for the variance of the forecast error for arbitrary lead times for both the additive and multiplicative Holt-Winters seasonal forecasting models. It is shown that even when the smoothing constants are chosen to have values between zero and one, when the period is greater than four, the variance may not be finite for some values of the smoothing constants. In addition, the regions where the variance becomes infinite are almost the same for both models. These results are of importance for practitioners, who may choose values for the smoothing constants arbitrarily, or by searching on the unit cube for values which minimize the sum of the squared errors when fitting the model to a data set. It is also shown that the variance of the forecast error for the multiplicative model is nonstationary and periodic.  相似文献   

2.
A standard approach to the combination of probabilistic opinions involves taking a weighted linear average of the individuals distributions. This paper reviews some of the possible interpretations that have been proposed for these weights in the literature on expert use. Several paradigms for selecting weights are also considered. Special attention is devoted to the Bayesian mechanism used for updating expert weights in the face of new information. An asymptotic result is proved which highlights the importance of choosing the initial weights carefully.  相似文献   

3.
A modified peptidoglycan (PG) wall is required for maintenance of spore core dehydration and the accompanying metabolic dormancy and heat resistance. Production of the spore PG depends on the cooperative expression of gene products within both the mother cell and forespore compartments of the sporangium. Structural elements that differentiate spore PG from vegetative cell PG include the presence of the modified sugar muramic-delta-lactam and a low level of peptide cross-links between the glycan strands. Detailed analyses of PG structure in dormant spores and in developing forespores of wild-type and mutant strains are providing data on factors required for introduction of these modifications and the importance of these structural elements in determining spore properties. Muramic-delta-lactam is not required for spore core dehydration but serves as a specificity factor for spore germination lytic enzymes. Cross-linking of spore PG can vary over a relatively wide range without significantly effecting spore core dehydration but does have an influence on the rate of spore germination and outgrowth. Future studies will examine how the two cells within the sporangium coordinate the production of this unique structure between themselves and how specific spore PG structural modifications are produced and participate in determining spore resistance properties.  相似文献   

4.
Summary The spike discharges in the EEG of the El mouse, a seizure-susceptible strain, were recorded during convulsive seizures. This fact provides evidence that those seizures are really epileptic convulsions.I thank Dr.K. Imaizumi and Dr.K. Nakano of National Institute of Health for their sharing the strain of El mouse to us and MissY. Nakamoto and Mr.N. Ozawa for their technical assistance and Mr.K. Moriyama for his care for the mice, and also thank Dr. H.Narabayashi for his criticism on this paper.  相似文献   

5.
Predicting the direction of central banks' target interest rates is important for various market participants. This paper advances procedures for predicting the direction of the federal funds target rate using a dynamic extension of the multinomial logit model. I find that the 6‐month Treasury bill spread relative to the federal funds rate, the unemployment rate and the real GDP growth rate have superior predictive content for the direction of the target a week to several months ahead. When these variables are employed, lagged target changes do not provide additional predictive power. This suggests that the apparent positive serial dependence of the target changes is due to the Fed's systematic response to autocorrelated macroeconomic variables. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

6.
Summary A precise method for the injection of drugs into the cerebroventricular system of small animals used for experimentation is described. This method, based on the intraventricular pressure record, gives absolute certainty for the injection of a drug into a previously selected site and thus avoids the subsequent histological studies.  相似文献   

7.
The peptide hormone relaxin is emerging as a multi-functional factor in a broad range of target tissues including several non-reproductive organs, in addition to its historical role as a hormone of pregnancy. This review discusses the evidence that collectively demonstrates the many diverse and vital roles of relaxin: the homeostatic role of endogenous relaxin in mammalian pregnancy and ageing; its gender-related effects; the therapeutic effects of relaxin in the treatment of fibrosis, inflammation, cardioprotection, vasodilation and wound healing (angiogenesis) amongst other pathophysiological conditions, and its potential mechanism of action. Furthermore, translational issues using experimental models (to humans) and its use in various clinical trials, are described, each with important lessons for the design of future trials involving relaxin. The diverse physiological and pathological roles for relaxin have led to the search for its significance in humans and highlight its potential as a drug of the future. Received 12 December 2006; received after revision 12 February 2007; accepted 15 March 2007  相似文献   

8.
Z Z Wahba  K F Soliman 《Experientia》1992,48(3):265-268
Choline acetyltransferase (ChAT) activity was determined in cerebral cortex, hypothalamus, hippocampus, cerebellum, medulla oblongata, midbrain and adrenal gland of rats exposed to acute or chronic stress. The exposure of animals to acute immobilization and cold stress (4 degrees C) for one hour resulted in a significant decline of ChAT activity in all brain regions examined except for the medulla oblongata. Moreover, the exposure to acute stress resulted in significant increase of the same enzyme in the adrenal gland. However, chronic exposure of animals to cold stress (4 degrees C) for 7 days resulted in no significant changes of ChAT activity in all tissues examined except for a decline in the midbrain and an increase in the medulla oblongata. The administration of corticosterone (2.0 mg/kg) 1 h prior to sacrificing caused an effect similar to that of acute stress on ChAT activity in all brain regions except for the hypothalamus and the cerebellum. It was concluded from this experiment that stress-induced changes in the ChAT activity of specific brain regions might be mediated by the adrenal steroids.  相似文献   

9.
The aim of this study was to answer the question of how the economic cycle affects the stability and efficiency of business failure prediction models, using bootstrap replacement method for validation. We analyse 2228 Spanish small and medium‐sized enterprises for the period 2001–2009, and divide it into three different phases of the economic cycle (growth, crisis, recession). We find that the structure and the ability of business failure prediction models are different according to the economic cycle. These findings are relevant for the debate on the most suitable financial ratios when developing business failure prediction models and to pose their accuracy level in these prediction models. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

10.
Choline acetyltransferase (ChAT) activity was determined in cerebral cortex, hypothalamus, hippocampus, cerebellum, medulla oblongata, midbrain and adrenal gland of rats exposed to acute or chronic stress. The exposure of animals to acute immobilization and cold stress (4°C) for one hour resulted in a significant decline of ChAT activity in all brain regions examined except for the medulla oblongata. Moreover, the exposure to acute stress resulted in significant increase of the same enzyme in the adrenal gland. However, chronic exposure of animals to cold stress (4°C) for 7 days resulted in no significant changes of ChAT activity in all tissues examined except for a decline in the midbrain and an increase in the medulla oblongata. The administration of corticosterone (2.0 mg/kg) 1 h prior to sacrificing caused an effect similar to that of acute stress on ChAT activity in all brain regions except for the hypothalamus and the cerebellum. It was concluded from this experiment that stress-induced changes in the ChAT activity of specific brain regions might be mediated by the adrenal steroids.This work was supported by a grant from the National Aeronautics and Space Administration (NSG 2183 and NAG 2-411), a grant from the National Institutes of Health (NIH RR 0811) and a grant from the Division of Research Resources (NIH grant RR 03020).  相似文献   

11.
Sydney Chapman is unanimously considered to have played a founding role in modern geomagnetism and to have opened up new lines of research in geophysics generally. Nevertheless, Chapman's conviction regarding the synthesis of the explanatory mechanisms of the atmosphere has gone practically unnoticed in the historiography of geophysics. This paper examines Chapman's contribution to ionospheric physics. It aims to understand Chapman's theory of ionospheric layer formation, and particularly its link to his theory of ozone formation. It deals first with the traits which characterized Chapman's personality, as a way of explaining—and even perhaps justifying— his quest for the integration and synthesis of geophysical knowledge. It then analyses Chapman's model of ionospheric layers and his suggestions regarding its use as an operational tool (without ontological connotations), before continuing with his account of the formation of the ozone layer, which seemed to constitute the missing link for understanding ionosphere layer formation. The paper concludes with Chapman's attempt to reconcile geomagnetic and radio evidence.  相似文献   

12.
Summary An artificial source for dowsing experiments is described. Investigations on the perceptibility of this source by turning on and off the water flow gives significant statistical results. The experiments for locating the source compared with blank experiments equally reveal perceptibility. An unexpected hysteresis in the reactions is observed when changing the source conditions in time and space. The behaviour of the sensitivity of the operator is deduced from many locating experiments.Acknowledgments. The author expresses his gratitude to the pharmaceutical company Hoffmann-La Roche for supporting this project, particularly to Prof. Dr A. Pletscher, the operators mentioned by the code names TR, RU, ER, ME, KO, RY and others, and all persons who contributed to this investigation.  相似文献   

13.
Zusammenfassung Es wird gezeigt, dass das Gift der Wespe Philanthus triangulum F. bei der Heuschrecke eine reversible Muskellähmung bewirkt, die auf einer Blockierung der Axon-Muskel-Synapse der «schnellen» Faser beruht. Die Synapse der langsamen und hemmenden Faser wird offenbar nicht beeinflusst.

This work has been supported in part by the European Research Office, United States Army, Frankfurt am Main, Germany.

Acknowledgments: I am indebted to Prof. Dr. C.van der Meer for his constant help and criticism and to Dr. R. T.Simon Thomas for providing the wasps. I wish to thank Mr. E.Engels for all the technical work.  相似文献   

14.
Summary Hemicastration in the skink induces change in the electrophoretic pattern of some enzymes like LDH, MDH, acid phosphatase and esterases.The authors wish to thank Prof. N.B. Krishnamurthy for his encouragment, UGC, New Delhi for their financial help to DTP and SM, and CSIR, New Delhi for MR.  相似文献   

15.
This article explores the relationship between epistemic relativism and Pyrrhonian scepticism. It is argued that a fundamental argument for contemporary epistemic relativism derives from the Pyrrhonian problem of the criterion. Pyrrhonian scepticism is compared and contrasted with Cartesian scepticism about the external world and Humean scepticism about induction. Epistemic relativism is characterized as relativism due to the variation of epistemic norms, and is contrasted with other forms of cognitive relativism, such as truth relativism, conceptual relativism and ontological relativism. An argument from the Pyrrhonian problem of the criterion to epistemic relativism is presented, and is contrasted with three other arguments for epistemic relativism. It is argued that the argument from the criterion is the most fundamental argument for epistemic relativism. Finally, it is noted how the argument of the present paper fits with the author’s previous suggestion that a particularist response to the Pyrrhonian sceptic may be combined with a naturalistic view of epistemic warrant to meet the challenge of epistemic relativism.  相似文献   

16.
Summary Concentrations of 4 trace amines in diencephalon and hippocampus of the rat were measured by integrated-ioncurrent mass spectrometry after administration of the antidepressant drug, tranylcypromine. Much larger increases were observed for 2-phenylethylamine and tryptamine than for m- and p-tyramine.Financial support has been provided by the Medical Research Council of Canada, the Psychiatric Services Branch, Province of Saskatchewan, the Alberta Mental health Research Fund, and the Special Services and Research Committee, University of Alberta Hospital.Acknowledgments. The authors wish to thank Dr B.A. Davis for synthesizing the deuterated internal standards and Dr D.A. Durden for supervising the mass spectral analyses. Expert technical assistance was provided by Mr R.C. Mag-Atas and Ms D.G. Calverley. The advice and encouragement of Professors W. G. Dewhurst and A. A. Boulton are gratefully acknowledged.  相似文献   

17.
Summary Reference is made to a procedure for evaluating certain incidental findings presented by particles of soot or dust on the adhesive strips of the Burkard pollen-and-spore trap or the slides of the similar Hirst apparatus. For this an evaluating device is recommended that is generally used for pherograms in large hospitals today. The often very noticeable streaks of soot or dust particles on the adhesive layer can be assessed with this method. Furthermore, it is possible to determine the time of the occurrence of the particles and possibly to relate them to the velocity and direction of the wind, and also eventually to detect the source of the polluting material.Acknowledgments. We would like to thank Prof. R. Schuppli, director of the Dermatological Department of the Basel Cantonal Hospital, for making it possible to carry out extended monitoring of airborne particles. Our special thanks go to Dr H.P. Rieder, head of the protein-testing laboratory of the Basel Cantonal Hospital, for enabling the examinations with the pherogram evaluator to be made. Finally, we wish to thank the Swiss National Foundation for the Advancement of Scientific Research who has made a grant-in-aid available to Dr R.M. Leuschner for monitoring airborne particles.  相似文献   

18.
The 111 series of the Makridakis competition are used to address a number of questions pertaining to use of the Box–Jenkins technique. The ARIMA models developed are compared to the ARIMA models developed independently by Andersen for the Makridakis competition. The time required to perform the analysis for each series is discussed in terms of model complexity. Forecast accuracy, measured as the MAPE for the one step ahead forecast, is discussed for different series lengths.  相似文献   

19.
A Bracht  A P Campello 《Experientia》1979,35(12):1559-1561
Increase of the ionic strength inhibits the catalytic activity of the mitochondrial MDH, reduces substrate inhibition and decreases the affinity of the substrates for the enzyme.  相似文献   

20.
This study addresses problems concerning the forecasting of net migration in the preparation of population forecasts. "As the width of forecast intervals for migration in single years differs strongly from that of an interval for average migration during the forecast period, it is important that the forecaster indicates which type of interval is presented. A comparison of forecast intervals for net migration obtained from an ARIMA model to intervals in official Dutch national population forecasts shows that the uncertainty on migration has been underestimated in past official forecasts."  相似文献   

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