In the practice of English language teaching, great importance is attached to writing ability of second language learners. There are many difficulties existing in second language writing, and a variety of writing appr...
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In the practice of English language teaching, great importance is attached to writing ability of second language learners. There are many difficulties existing in second language writing, and a variety of writing approaches aim to help students solve these problems. The process approach has now attracted most attention.
The present research tries to find out the role of pre-writing activities, which is advocated by the process approach. It has been found out that these activities mainly help students develop meaning in their writing although different students reacted in a different way. And they also help students begin their writing more easily.
Another finding is the role of the teacher. They are expected to: 1) regard students as writers; 2) guide through pre-writing stage; 3) integrate receptive skills and productive skills. This research suggests the need for writing instruction by which students can experience writing as a creative process for exploring and communicating meaning.
Growth cones are highly motile structures at the end of neuronal processes, capable of receiving multiple types of guidance cues and transducing them into directed axonal growth. Thus, to guide the axon toward the app...
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A method of locating crop rows in image sequences is described. Unlike several previously reported algorithms, the method does not rely upon the segmentation of plant material from the background on the basis of absol...
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A method of locating crop rows in image sequences is described. Unlike several previously reported algorithms, the method does not rely upon the segmentation of plant material from the background on the basis of absolute brightness or colour. Rather, the periodic amplitude variation due to parallel crop rows is exploited. Given the geometry of the camera arrangement and the crop row spacing, a filter is derived which allows the crop rows to be extracted whilst attenuating the effects of partial shadowing and spurious features such as weeds. The position and orientation of the rows are tracked using an extended Kalman filter. The method has been used to guide a mechanical hoe in winter wheat with an RMS positional error of 15.6 mm at a speed of 1.6 ms-(1), despite the presence of complex shadows cast by the tractor in the imaged area. (C) 2000 Elsevier Science Ltd. All rights reserved.
In order to suppress residual vibrations, a general method is presented for preconditioning any guidance function prior to its application to a dynamic system, by convolving it with a sequence of impulses. The approac...
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In order to suppress residual vibrations, a general method is presented for preconditioning any guidance function prior to its application to a dynamic system, by convolving it with a sequence of impulses. The approach includes first the development of the necessary design specifications for the impulse sequence, so that the robustness properties cover the widest possible variation of the system natural frequencies. Three solution methods are proposed then, with special emphasis in the achievement of the minimum possible duration time of the impulse sequence. Numerical experiments verify the effectiveness of the robustness, not only with respect to variations of the natural frequency, but also with respect to variations of a range of other linear and non-linear variables.
The paper presents the relations that form the basis for the calculus models needed to study rolling guided missiles. The equations of the general motion are written within the Resal trihedral in a way that allows, af...
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The paper presents the relations that form the basis for the calculus models needed to study rolling guided missiles. The equations of the general motion are written within the Resal trihedral in a way that allows, after linearization, one to draw up a structural scheme of the controlled object, a scheme that will be used in the guided missile system analysis. Opposite to the flying machines with stabilized roll where the analysis is done after decoupling the channels, for the missile with rotation, the analysis of the scheme is done simultaneously on both channels, as terms used are complex terms. Furthermore, there will be presented some characteristics of this type of missile by analyzing a model close to the one of an antichariot missile with gasodynamic control.
To assess the value of accurate preoperative CT-guided needle localization of occult breast lesions, we reviewed a total of 39 needle-directed biopsies of breast tumors in 24 women. The average age was 52.9 years (ran...
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To assess the value of accurate preoperative CT-guided needle localization of occult breast lesions, we reviewed a total of 39 needle-directed biopsies of breast tumors in 24 women. The average age was 52.9 years (range 31-67). All lesions were nonpalpable and mammographically, as well as sonographically occult. They were solely seen on MR-images. After demonstrating the suspicious region on CT scans, a hookwire was inserted. The correct position was confirmed by a control scan. The subsequent histo pathological examination showed that 28 of the lesions (71.8%) were benign, among them mastopathy, fibrosis, fibroadenoma, papilloma, intramammary lymph node, liponecrosis and epitheliosis. Eleven lesions (28%) were malignant and showed either lobular, ductal or tubular cancer. Our results endorse that CT guided needle localization is a helpful method that allows a precise surgical excision of the suspect area with the removal of a minimal amount of breast tissue, (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.
Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP-alpha, PTP-delta, and LAR, are expressed in...
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Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP-alpha, PTP-delta, and LAR, are expressed in overlapping but distinct patterns in the developing Xenopus retina, including expression in retinal ganglion cells (RGCs) as they send axons to the tectum (Johnson KG, Holt CE. 2000. Expression of CRYP-alpha, LAR, PTP-delta, and PTP-rho in the developing Xenopus visual system. Mech Dev 92:291-294). In order to examine the role of these RPTPs in visual system development, putative dominant negative RPTP mutants (CS-CRYP-alpha, CS-PTP-delta, and CS-LAR) were expressed either singly or in combination in retinal No effect was found on either retinal cell fate determination or on gross RGC axon guidance to the tectum. However, expression of these CS-RPTP constructs differentially affected the rate of RGC axon outgrowth. In vivo, expression of all three CS-RPTPs or CS-PTP-delta alone inhibited RGC axon outgrowth, while CS-LAR and CS-CRYP-alpha had no significant effect. In vitro, expression of CS-CRYP-alpha enhanced neurite outgrowth, while CS-PTP-delta inhibited neurite outgrowth in a substrate-dependent manner. This study provides the first in vivo evidence that RPTPs regulate retinal axon outgrowth. (C) 2001 John Wiley & Sons, Inc.
The present Study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing cond...
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The present Study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing conditions, the information shown outside the gaze-contingent window was restricted to the feature or feature pair shared between the target and a particular distractor type. In the masking conditions, no stimulus features were shown outside the window. Significant cueing and masking effects on saccadic selectivity were observed for saccades directed at items within the window, where all features were visible across experimental conditions. Cueing a particular feature or feature pair biased saccadic selectivity towards this feature or feature pair, while masking generally reduced saccadic selectivity. These findings support the concept of visual guidance being a preattentive process that operates in parallel across the display. (C) 2001 Published by Elsevier Science Ltd.
On their way toward their synaptic targets, motor growth cones encounter multiple choice points, where they are confronted with trajectory choices. We have previously shown that the zebrafish unplugged gene acts as a ...
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On their way toward their synaptic targets, motor growth cones encounter multiple choice points, where they are confronted with trajectory choices. We have previously shown that the zebrafish unplugged gene acts as a somite-derived cue controlling pathway choice of primary motor axons. Here, we demonstrate that this trajectory choice is not exclusively controlled by a single unplugged-dependent process, but depends on the coordinated function of additional cues. We also show that secondary motor neurons, most similar to those in birds and mammals, depend on the unplugged gene to navigate a choice point, suggesting that primary and secondary motor neurons share common mechanisms controlling axonal path selection. Moreover, we show that the unplugged gene plays an additional role guiding secondary motor axons through a single segmental nerve. Finally, we report that unplugged larvae display a striking pharyngeal arch defect, consistent with a dual function of the unplugged gene in axonal guidance and cell Motility. (C) 2001 Elsevier Science.
Pathfinding by developing axons towards their proper targets is an essential step in establishing appropriate neuronal connections. Recent work involving cell culture assays and molecular biology strategies, including...
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Pathfinding by developing axons towards their proper targets is an essential step in establishing appropriate neuronal connections. Recent work involving cell culture assays and molecular biology strategies, including knockout animals, strongly indicates that a complex network of guidance signals regulates the formation of hippocampal connections during development. Outgrowing axons are routed towards the hippocampal formation by specific expression of long-range cues, which include secreted class 3 semaphorins, netrin 1 and Slit proteins. Local membrane- or substrate-anchored molecules, such as ligands of the ephrin A subclass, provide layer-specific positional information. Understanding the molecular mechanisms that underlie axonal guidance during hippocampal development might be of importance in making therapeutic use of sprouting fibers, which are produced following the loss of afferents in CNS lesion.
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