MKAS : A modular knockout ATM switch

Simple Knockout Switch [11 exhibits excellent traffic performance (cell loss, cell delay and maximum throughput etc.) under uniform as well as non-uniform traffic patterns (2-6). But being a single stage, its hardware complexity is directly proportional to the switch size N. This problem may bind its implementation for largescale requirements because of the technological and physical constraints of packaging (e. g. chip or board size). Here, we are proposing a two-stage Modular Knockout ATM Switch architecture, which is extendable to large-scale switch sizes without sacrificing any significant decrease in switch performance. The concept of Generalised Knockout Principle in conjunction with Simple Knockout Principle has been utilised to filter, route and resolve the output contention problems in distributed fashion. Using distributed address filtration and shared concentration techniques simplifies the switch functions and reduces the switch complexity to large extent in terms of filters, switching elements and input output interconnection wires

Los efectos negativos de enseñar algoritmos en grados primarios (1ro al 4to)

This article summarizes the evidence collected since the 1970s againts algorithm teaching, in order to promote the contrary: encounraging children to execute their thinking about arithmetic problems in order to construct knowledge. The harmful effects of teaching “carrying” and “borrowing” were demonstrated by asking second, third, and fourth graders to mentally solve problems like 7 + 52 + 186. The children who had not been taught these algorithms gave correct answers much more frequently, and the errors they make were much more reasonable (e.g., 235) than the errors made by students who were taught these rules (e.g., 989 and 29). It was concluded that teaching these rules is harmful to the great majority of students because (a) it makes students give up their own thinking, and (b) it “unteaches” place value. How to cite: Kamii, C., & Dominick, A. (2011). Los efectos negativos de enseñar algoritmos en grados primarios (1ro al 4to). (Trad. N. Zambrana). Pedagogía, 43(1), 59-73. Retrieved from https://revistas.upr.edu/index.php/educacion/article/view/16574Este trabajo resume la evidencia recopilada desde los años 1970 en contra de la enseñanza de algoritmos en escuela primaria, con el propósito de promover la idea contraria: que hay que estimular a los niños a aplicar sus propios procedimientos mentales en la solución de problemas aritméticos, para así fomentar la construcción de conocimiento. Las autoras demostraron los efectos perjudiciales que tiene enseñar mecánicamente a los niños de nivel elemental conceptos como “llevar” y “tomar prestado”. Estas observaron y documentaron que niños de segundo, tercero y cuarto grados inventan procedimientos para sumar, por ejemplo, 7 + 52 + 186, y obtienen respuestas correctas más frecuentemente que aquellos a quienes se les había enseñado mediante algoritmos. Las respuestas incorrectas de los alumnos que no usaron algortimos fueron más razonables (e.i. 235) que las de aquellos a quienes se les enseñaron los algoritmos (e.i., 989 y 29). Concluyeron que enseñar estas reglas es perjudicial para la mayoría de los niños porque (a) los desanima a pensar por ellos mismos y (b) no enseña apropiadamente el concepto de valor posicional del dígito. Cómo citar: Kamii, C., & Dominick, A. (2011). Los efectos negativos de enseñar algoritmos en grados primarios (1ro al 4to). (Trad. N. Zambrana). Pedagogía, 43(1), 59-73. Recuperado a partir de https://revistas.upr.edu/index.php/educacion/article/view/1657

Objects, actions, and images: a perspective on early number development

It is the purpose of this article to present a review of research evidence that indicates the existence of qualitatively different thinking in elementary number development. In doing so, the article summarizes empirical evidence obtained over a period of 10 years. This evidence first signaled qualitative differences in numerical processing, and was seminal in the development of the notion of procept. More recently, it examines the role of imagery in elementary number processing. Its conclusions indicate that in the abstraction of numerical concepts from numerical processes qualitatively different outcomes may arise because children concentrate on different objects or different aspects of the objects, which are components of numerical processing

Identifying the task characteristics that predict children's construction task performance

Construction tasks form a major part of children’s play and can be linked to achievement in maths and science. However there is a lack of understanding of construction task ability and development. Therefore, there is little foundation for the applied use of construction tasks, such as in teaching or research, as there are no apparent methods for assessing difficulty. This empirical research identifies four construction task characteristics that impact on cognition and predict construction task difficulty in children aged 7-8 and 10-11 years and adults. The results also reveal a developmental trajectory in construction ability. The research provides a method to quantify, predict and control the complexity of construction tasks for future research and to inform applied use

Nitric oxide in the medial prefrontal cortex contributes to the acquisition of cocaine place preference and synaptic plasticity in the laterodorsal tegmental nucleus

金沢大学医薬保健研究域薬学系Nitric oxide (NO), a gaseous neurotransmitter, is involved in a variety of brain functions, including drug addiction. Although previous studies have suggested that NO plays an important role in the development of cocaine addiction, the brain region(s) in which NO acts and how it contributes to cocaine addiction remain unclear. In this study, we examined these issues using a cocaine-induced conditioned place preference (CPP) paradigm and ex vivo electrophysiological recordings in rats. Specifically, we focused on the medial prefrontal cortex (mPFC) and laterodorsal tegmental nucleus (LDT), brain regions associated with cocaine CPP development and cocaine-induced plasticity. Intra-mPFC injection of the non-selective NO synthase (NOS) inhibitor L-NAME or the neuronal NOS (nNOS) selective inhibitor L-NPA during the conditioning phase disrupted cocaine CPP. Additionally, intra-mPFC injection of L-NPA prior to each cocaine injection prevented the induction of presynaptic plasticity, induced by repeated cocaine administration, in LDT cholinergic neurons. These findings indicate that NO generated in the mPFC contributes to the acquisition of cocaine CPP and the induction of neuroplasticity in LDT cholinergic neurons. Together with previous studies showing that NO induces membrane plasticity in mPFC neurons, that mPFC neurons project to the LDT, and that LDT activity is critical for the acquisition of cocaine CPP, the present findings suggest that NO-mediated neuroplasticity induced in the mPFC-LDT circuitry is critical for the development of cocaine addiction. © 2017 Elsevier B.V.Embargo Period 12 month

Stress augments the rewarding memory of cocaine via the activation of brainstem-reward circuitry

金沢大学医薬保健研究域薬学系Effects of stress on the reward system are well established in the literature. Although previous studies have revealed that stress can reinstate extinguished addictive behaviors related to cocaine, the effects of stress on the rewarding memory of cocaine are not fully understood. Here, we provide evidence that stress potentiates the expression of rewarding memory of cocaine via the activation of brainstem-reward circuitry using a cocaine-induced conditioned place preference (CPP) paradigm combined with restraint stress in rats. The rats exposed to 30-minute restraint stress immediately before posttest exhibited significantly larger CPP scores compared with non-stressed rats. Intra-laterodorsal tegmental nucleus (LDT) microinjection of a β or α2 adrenoceptor antagonist attenuated the stress-induced enhancement of cocaine CPP. Consistent with this observation, intra-LDT microinjection of a β or α2 adrenoceptor agonist before posttest increased cocaine CPP. Additionally, intra-ventral tegmental area (VTA) microinjection of antagonists for the muscarinic acetylcholine, nicotinic acetylcholine or glutamate receptors attenuated the stress-induced enhancement of cocaine CPP. Finally, intra-medial prefrontal cortex (mPFC) microinjection of a D1 receptor antagonist also reduced the stress-induced enhancement of cocaine CPP. These findings suggest a mechanism wherein the LDT is activated by noradrenergic input from the locus coeruleus, leading to the activation of VTA dopamine neurons via both cholinergic and glutamatergic transmission and the subsequent excitation of the mPFC to enhance the memory of cocaine-induced reward value. © 2018 Society for the Study of Addiction.Embargo Period 12 month