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71.
72.
In this paper we show that optimal trading results can be achieved if we can forecast a key summary statistic of future prices. Consider the following optimization problem. Let the return ri (over time i=1, 2, ..., n) for the ith day be given and the investor has to make investment decision di on the ith day with di=1 representing a ‘long' position and di=0 a ‘neutral' position. The investment return is given by r=Σni=1ridi−cΣn+1i=1∣di−di−1∣, where c is the transaction cost. The mathematical programming problem of choosing d1, ..., dn to maximize r under a given transaction cost c is shown to have an analytic solution, which is a function of a key summary statistic called the largest change before reversal. The largest change before reversal is recommended to be used as an output in a neural network for the generation of trading signals. When neural network forecasting is applied to a dataset of Hang Seng Index Futures Contract traded in Hong Kong, it is shown that forecasting the largest change before reversal outperforms the k‐step‐ahead forecast in achieving higher trading profits. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
73.
There has been growing interest in exploiting potential forecast gains from the nonlinear structure of self‐exciting threshold autoregressive (SETAR) models. Statistical tests have been proposed in the literature to help analysts check for the presence of SETAR‐type nonlinearities in observed time series. However, previous studies show that classical nonlinearity tests are not robust to additive outliers. In practice, time series outliers are not uncommonly encountered. It is important to develop a more robust test for SETAR‐type nonlinearity in time series analysis and forecasting. In this paper we propose a new robust nonlinearity test and the asymptotic null distribution of the test statistic is derived. A Monte Carlo experiment is carried out to compare the power of the proposed test with other existing tests under the influence of time series outliers. The effects of additive outliers on nonlinearity tests with misspecification of the autoregressive order are also studied. The results indicate that the proposed method is preferable to the classical tests when the observations are contaminated with outliers. Finally, we provide illustrative examples by applying the statistical tests to three real datasets. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
74.
Chondroitinase ABC promotes functional recovery after spinal cord injury 总被引:82,自引:0,他引:82
Bradbury EJ Moon LD Popat RJ King VR Bennett GS Patel PN Fawcett JW McMahon SB 《Nature》2002,416(6881):636-640
The inability of axons to regenerate after a spinal cord injury in the adult mammalian central nervous system (CNS) can lead to permanent paralysis. At sites of CNS injury, a glial scar develops, containing extracellular matrix molecules including chondroitin sulphate proteoglycans (CSPGs). CSPGs are inhibitory to axon growth in vitro, and regenerating axons stop at CSPG-rich regions in vivo. Removing CSPG glycosaminoglycan (GAG) chains attenuates CSPG inhibitory activity. To test the functional effects of degrading chondroitin sulphate (CS)-GAG after spinal cord injury, we delivered chondroitinase ABC (ChABC) to the lesioned dorsal columns of adult rats. We show that intrathecal treatment with ChABC degraded CS-GAG at the injury site, upregulated a regeneration-associated protein in injured neurons, and promoted regeneration of both ascending sensory projections and descending corticospinal tract axons. ChABC treatment also restored post-synaptic activity below the lesion after electrical stimulation of corticospinal neurons, and promoted functional recovery of locomotor and proprioceptive behaviours. Our results demonstrate that CSPGs are important inhibitory molecules in vivo and suggest that their manipulation will be useful for treatment of human spinal injuries. 相似文献
75.
A. H. Davies T. M. Preston C. A. King 《Cellular and molecular life sciences : CMLS》1981,37(7):708-709
Summary The speed of amoeboid locomotion was the same for amoebae moving on the top surface and bottom surface of a horizontal perfusion chamber i.e. cell-substrate adhesive forces must be considerably greater than the gravitational force acting on the locomoting amoeba.Acknowledgments. We would like to thank Les Cooper for technical assistance, and the Science Research Council for support. 相似文献
76.
Sequence and expression of a frog brain complementary DNA encoding a kainate-binding protein 总被引:11,自引:0,他引:11
K Wada C J Dechesne S Shimasaki R G King K Kusano A Buonanno D R Hampson C Banner R J Wenthold Y Nakatani 《Nature》1989,342(6250):684-689
Excitatory amino acids (EAAs) are important neurotransmitters in the vertebrate central nervous system. Electrophysiological and ligand-binding studies indicate that at least three different receptor subtypes for EAAs exist--N-methyl-D-aspartate, kainate and quisqualate receptor subtypes--on the basis of the preferred agonist of the receptors. We recently purified a kainate-binding protein (KBP) from frog (Rana pipiens berlandieri) brain by domoic acid (a high-affinity kainate analogue) affinity chromatography, and showed that the kainate-binding activity was associated with a protein of relative molecular mass 48,000 (Mr 48 K). The pharmacological properties and the anatomical distribution of KBP were consistent with those of a kainate receptor-ionophore complex. We have now isolated a complementary DNA encoding KBP of Mr 48 K. The deduced amino-acid sequence of the KBP has similar hydrophobic profiles to those found in other ligand-gated ion channel subunits, and shows some amino-acid sequence similarities to the corresponding regions of brain nicotinic acetylcholine receptor subunits. Localization of the KBP messenger RNAs by in situ hybridization histochemistry is compatible with the results of immunohistochemistry and receptor autoradiography studies. COS-7 cells transfected with the cDNA encoding the KBP show high-affinity kainate-binding activity with pharmacological properties similar to those of the biochemically purified KBP. These results provide the first molecular characterization of an EAA-binding site and raise the possibility that the KBP cDNA encodes a ligand-binding subunit of a kainate receptor-ionophore complex. 相似文献
77.
The role of social stimulation in avian vocal learning is well documented. The separate contribution of social, as opposed to vocal, stimulation has been difficult to address, however, because in almost all cases both tutor and pupil sing. The opportunity to isolate such effects arose in cowbirds (Molothrus ater ater) after discovering that males housed with non-singing female cowbirds made vocal changes which related directly to the female preferences for native song. Here we report how females communicate with males about songs. We describe a visual display by females, a wing stroke, that is elicited by specific vocalizations. The songs that trigger wing strokes are in turn highly effective releasers of copulatory postures, and thus this previously unnoticed female display has biological significance. The data not only provide the first evidence of the tutorial role of male-female interactions during song ontogeny, they also clearly implicate visual stimulation in song learning, a process that has until now been assumed to be affected only by auditory information. 相似文献
78.
Mitochondrial DNA (mtDNA) was extracted from teeth stored from 3 months to 20 years, including teeth from the semi-skeletonized remains of a murder victim which had been buried for 10 months. Tooth donors and/or their maternal relatives provided blood or buccal cells, from which mtDNA was also extracted. Enzymatic amplification and direct sequencing of roughly 650 nucleotides from two highly polymorphic regions of mtDNA yielded identical sequences for each comparison of tooth and fresh DNA. Our results suggest that teeth provide an excellent source for high molecular weight mtDNA that can be valuable for extending the time in which decomposed human remains can be genetically identified. 相似文献
79.
A. S. King V. Molony J. McLelland D. R. Bowsher M. F. Mortimer 《Cellular and molecular life sciences : CMLS》1968,24(10):1017-1018
Résumé Nous avons enregistré 88 afférences respiratoires du nerf vague chez le poulet. Quelques unes se déclenchaient au cours de l'inspiration eupnéique, d'autres au cours de l'expiration. Jusqu'à présent, on a l'impression qu'il existe plus de types d'activité afférente respiratoire chez l'oiseau que chez le mammifère, mais de nouvelles analyses seront nécessaires pour mieux les préciser. Nous croyons que c'est ici la première preuve évidente de l'existence d'un contrôle afférent vagal de la respiration chez l'oiseau.
This work was supported by a grant from the British Egg Marketing Board. 相似文献
This work was supported by a grant from the British Egg Marketing Board. 相似文献
80.
Summary The drug trifluoperazine (TFP) inhibits the gliding motility of gregarine protozoans. This suggests that the Ca++ binding protein, calmodulin, plays a role in the motility process. However the presence of extracellular Ca++ was not required for gliding to occur.Acknowledgments. We should like to thank L. Cooper for technical assistance, Smith, Kline and French for the gift of trifluoperazine, and Terry Preston for valuable discussion. 相似文献