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1.
A Further Comparison of Splitting Rules for Decision-Tree Induction 总被引:10,自引:0,他引:10
One approach to learning classification rules from examples is to build decision trees. A review and comparison paper by Mingers (Mingers, 1989) looked at the first stage of tree building, which uses a splitting rule to grow trees with a greedy recursive partitioning algorithm. That paper considered a number of different measures and experimentally examined their behavior on four domains. The main conclusion was that a random splitting rule does not significantly decrease classificational accuracy. This note suggests an alternative experimental method and presents additional results on further domains. Our results indicate that random splitting leads to increased error. These results are at variance with those presented by Mingers. 相似文献
2.
Inhibition of the LHRH system appears to play an important role in preventing precocious activation of the hypothalamic-pituitary-gonadal axis. Evidence points to gamma-aminobutyric acid (GABA) as the major negative regulator of postnatal LHRH neuronal activity. Changes in LHRH messenger RNA (mRNA) levels after alterations of GABAergic activity have been reported in vivo. However, the extent to which GABA acts directly on LHRH neurons to effect LHRH mRNA levels has been difficult to ascertain. The present work evaluates the effect of GABAergic activity, via GABA(A) receptors, on LHRH neuropeptide gene expression in LHRH neurons maintained in olfactory explants generated from E11.5 mouse embryos. These explants maintain large numbers of primary LHRH neurons that migrate from bilateral olfactory pits in a directed manner. Using in situ hybridization histochemistry and single cell analysis, we report dramatic alterations in LHRH mRNA levels. Inhibition of spontaneous synaptic activity by GABA(A) antagonists, bicuculline (10(-5) M) or picrotoxin (10(-4) M), or of electrical activity by tetrodotoxin (TTX, 10(-6) M) significantly increased LHRH mRNA levels. In contrast, LHRH mRNA levels decreased in explants cultured with the GABA(A) receptor agonist, muscimol (10(-4) M), or KCl (50 mM). The observed responses suggest that LHRH neurons possess functional pathways linking GABA(A) receptors to repression of neuropeptide gene expression and indicate that gene expression in embryonic LHRH neurons, outside the CNS, is highly responsive to alterations in neuronal activity. 相似文献
3.
Science China Technological Sciences - We use 9 years data of Cluster to study the dependencies of plasma parameters and energy transport in the plasma sheet on the lasting time of... 相似文献
4.
K. Brad Wray 《Scientometrics》2009,81(3):757-764
I examine whether the professionalization of science, a process that unfolded between 1600 and 1899, afforded better opportunities
for young scientists to make significant discoveries. My analysis suggests that the professionalization of the sciences did
make it a little easier for scientists to make significant contributions at a younger age. But, I also argue that it is easy
to exaggerate the effects of professionalization. Older and middle age scientists continued to play an important role in making
significant discoveries throughout the history of modern science. 相似文献
5.
In previous work, we showed a robust gamma-aminobutyric acid (GABAergic) synaptic input onto embryonic luteinizing hormone-releasing hormone (LHRH) neurons maintained in olfactory explants. In this study, we identify GABAergic neurons in olfactory pit (OP) of embryonic mice in vivo and study, using patch-pipet whole-cell current and voltage clamp techniques, synaptic interactions of these neurons in explant cultures. In vivo, glutamate decarboxylase (GAD, the enzyme which synthesizes GABA) mRNA was first detected in nasal regions on Embryonic Day (E) 11.5. From E12.5 to E13.5, robust GAD expression was localized to cells primarily in the ventral aspect of the OP. GAD mRNA was not detected over dorsally located cells in olfactory sensory or respiratory epithelium. In addition, GAD mRNA was not observed in cells along olfactory axons. GAD mRNA was dramatically reduced in the OP/vomeronasal organ by E16.5. Using antibodies against both GABA and GAD, immunopositive axonal-like tracts were detected in the nasal septum on E12.5. GABAergic staining decreased by E13.5. To examine synaptic interactions of these GABAergic cells, embryonic olfactory explants were generated and maintained in serum-free media. As explants spread, neuron-like cells migrated into the periphery, sometimes forming ganglion-like clusters. Cells were recorded, marked intracellularly with Lucifer Yellow and post-fixation, immunocytochemically examined. Forty-six cells, typically multipolar, were GABAergic, had resting potentials around -50 mV, and exhibited spontaneous action potentials which were generated by spontaneous depolarizing GABAergic (GABAA) synaptic activity. OP neurons depolarized in response to GABA by increasing Cl- conductance. The biophysical properties of OP-derived GABAergic neurons were distinct from those reported for olfactory receptor neurons but similar to embryonic LHRH neurons. However, unlike LHRH neurons, GABAergic neurons did not migrate large distances in olfactory explants or appear to leave the olfactory pit in vivo. 相似文献
6.
This paper describes an experimental investigation of the mechanical behavior of a paper-filled-phenolic laminate widely used
in the electronics industry. Uniaxial tensile tests in three directions, sandwich-beam bending tests to determine the compressive
behavior, and cylindrical-punch punchability tests were conducted. Interesting phenomena observed included difference in tensile
and compressive behavior, consistent crack branching in tension, and strain mismatch during punching.
Based upon a thesis submitted by the first author in partial fulfillment of the requirements for the M.S. degreee in Mechanical
Engineering at the University of Oklahoma, December 1976. 相似文献
7.
A rule induction approach for determining the number of kanbans in A just-in-time production system 总被引:2,自引:0,他引:2
Ina S. Markham Richard G. Mathieu Barry A. Wray 《Computers & Industrial Engineering》1998,34(4):717-727
A procedure based on rule induction is presented which can be used to determine the number of kanbans while simultaneously determining the critical factors in a just-in-time (JIT) production system. In particular, the classification and regression tree (CART) technique developed by Brieman et al. [Breiman, L., Friedman, J., Olshen, R. and Stone, C. J., Classification and Regression Trees. Wadsworth, Belmont, CA, 1984.] is used to automatically generate rules from dynamic shop floor data. An example application of the methodology is presented and the advantages of a rule induction approach are explained. The paper concludes with a discussion of future research directions. 相似文献
8.
C Eder P Proksch V Wray K Steube G Bringmann RW van Soest Sudarsono E Ferdinandus LA Pattisina S Wiryowidagdo W Moka 《Canadian Metallurgical Quarterly》1999,62(1):184-187
Two samples of the marine sponge Stylissa carteri collected in Indonesia yielded two new bromopyrrole alkaloids: debromostevensine (1) and debromohymenin (2), as well as nine other known congeners (3-11). The structures of the new compounds were unambiguously established on the basis of their NMR and mass spectra. 相似文献
9.
10.
A partnership has been developed linking the United States Military Academy and Special People in the Northeast, a non-profit agency for the mentally and physically handicapped children and adults based in Philadelphia. The present work documents a student design team's design and construction of a ticket-tearing device for a young man in the advanced stages of cerebral palsy and concludes with an evaluation of the entire process. 相似文献