Educational Studies in Mathematics - The give-n task is widely used in developmental psychology to indicate young children’s knowledge or use of the cardinality principle (CP): the last... 相似文献
Although research suggests that the use of child-initiated vs. teacher-directed instructional practices in early childhood education has implications for learning and development, the precise nature of these effects remains unclear. Using data from the Midwest Child-Parent Center (CPC) Expansion Project, the present study examined the possibility that a blend of child- and teacher-directed practices best promotes school readiness among preschoolers experiencing high levels of sociodemographic risk and explored whether the optimal blend varies based on child characteristics. Sixty-two CPC preschool teachers reported their instructional practices throughout the year, using a newly developed questionnaire—the Classroom Activity Report (CAR). The average reported proportion of child-initiated instruction was examined in relation to students’ end-of-year performance on a routine school readiness assessment (N = 1289). Although there was no main effect of child-initiated instruction on school readiness, there was a significant interaction between instruction and student age. Four-year-olds’ school readiness generally improved as the proportion of child-initiated time increased, while 3-year-olds showed a U-shaped pattern. The present findings add to the evidence that child-initiated instruction might support preschoolers’ school readiness, although they also suggest this relation may not always be linear. They also point to the importance of examining instructional strategies in relation to student characteristics, in order to tailor strategies to the student population. The CAR has potential as a brief, practical measurement tool that can support program monitoring and professional development.
In this paper it is argued that virtual processes are dispensable fictions. The argument proceeds by a comparison with the phenomenon of quantum tunnelling. Building on an analysis of Lévy-Leblond and Balibar, it is argued that, although the phenomenon known as quantum tunnelling certainly occurs and is at the basis of many paradigmatic quantum effects, the implied conceptualization of it as a free particle burrowing through a potential barrier is flawed. An alpha particle, for example, does not exist as a free particle inside a uranium nucleus and then ??burrow through?? the massive potential barrier of the repulsive Coulomb potential: rather, it can be interpreted as existing in a bound state which gives it a corresponding (absolutely tiny, but) finite probability of appearing on the other side of the barrier. If the part of the state function representing the transmission through the barrier is conceived as representing a particle trajectory, the particle will have imaginary momentum and negative kinetic energy. A similar analysis then applies to virtual processes. For example, if (as in Hawking??s conception of black hole radiation) one imagines a pair of particles created at the Schwarzschild radius, one of which drops into the black hole, at its creation that particle will have imaginary momentum and negative kinetic energy; so will the pion that is imagined as mediating the nuclear exchange force on the standard model. In each case, it is argued, the phenomenon can be understood in terms of a finite probability of transmission predicted by quantum theory, without appealing to particle trajectories. The idea that a particle ??penetrates?? a barrier that it does not have the energy to surmount, or that a pair of particles is ??virtually?? produced one on either side of the Schwarzschild radius, in defiance of energy conservation, should be discarded as unphysical. 相似文献
To sum up our argument then: It is shown, in the first place, that the arrangement of the atoms in certain crystals, as determined by the X-ray spectra, indicates definitely that in these crystals there is no molecular structure.In extending the argument to all solid matter it is pointed out, from the dependence of crystal form on chemical composition, from a consideration of the Dulong-Petit law and of the nature of cohesion, and from the evidence of X-rays as to certain crystals, that each atom in a solid oscillates about a definite position of stable equilibrium.From a further examination of the nature of cohesion and of the forces concerned in chemical combination and especially from the general relation found between the atomic heat of formation of a substance and its melting-point it is found that the forces holding the atoms in their positions of stable equilibrium are of the same nature and comparable in magnitude with the forces binding together a chemical molecule.It is seen further that the atoms in a solid are very close together so that they often come in contact. And, since an atom attracts equally all atoms of another kind which are in contact with it, an atom cannot remain combined for more than an infinitesimal interval with any other particular atom ordinary temperatures.Finally, it was shown that, since in the solid state each atom has three degrees of translational freedom and is strongly attracted by atoms other than those of its own “molecule,” it must, on the average, exert equal attractions on all the neighboring atoms.From this the conclusion is drawn that in the particular molecules cannot be definitely defined.When those properties of solid matter which have been explained by molecules are considered, nothing is found which indicates at all definitely a molecular structure.We feel justified in concluding, therefore, that the structure of solid matter is not molecular. 相似文献
