Observation of magnetism in Au thin films

Direct magnetization measurements of thin gold films are presented. These measurements integrate the signal from the thin film under study and the magnetic contribution of the film's interface with the substrate. The diamagnetic contribution to the signal from the bulk substrate is of the same order as the noise level. we find that thin gold films can exhibit positive magnetization. The character of their magnetic behavior is strongly substrate dependent.Comment: 9 pages, 4 figure

NMR Time Reversal Experiments in Highly Polarised Liquid 3He-4He Mixtures

Long-range magnetic interactions in highly magnetised liquids (laser-polarised 3He-4He dilute mixtures at 1 K in our experiment) introduce a significant non-linear and non-local contribution to the evolution of nuclear magnetisation that leads to instabilities during free precession. We recently demonstrated that a multi-echo NMR sequence, based on the magic sandwich pulse scheme developed for solid-state NMR, can be used to stabilise the magnetisation against the effect of distant dipolar fields. Here, we report investigations of echo attenuation in an applied field gradient that show the potential of this NMR sequence for spin diffusion measurements at high magnetisation densities.Comment: Accepted for publication in the Journal of Low Temperature Physic

Number Sense and Mathematics: Which, When and How?

Individual differences in number sense correlate with mathematical ability and performance, although the presence and strength of this relationship differs across studies. Inconsistencies in the literature may stem from heterogeneity of number sense and mathematical ability constructs. Sample characteristics may also play a role as changes in the relationship between number sense and mathematics may differ across development and cultural contexts. In this study, 4,984 16-year-old students were assessed on estimation ability, one aspect of number sense. Estimation was measured using two different tasks: number line and dot-comparison. Using cognitive and achievement data previously collected from these students at ages 7, 9, 10, 12, and 14 years of age, the study explored for which of the measures and when in development these links are observed; how strong these links are and how much these links are moderated by other cognitive abilities. The two number sensemeasures correlated modestly with each other (r = .22), but moderately with mathematics at age 16. Both measures were also associated with earlier mathematics; but this association was uneven across development and was moderated by other cognitive abilities

Development and validation of a mathematics-number sense web-based test battery.

This study aimed to create and validate a web-based battery of tests, age appropriate for 16 year-olds, and designed to assess mathematical skills, general cognitive abilities and number sense. The first stage of the study involved the selection of 11 measures and their administration to a sample of 100 16 year-old students, either in pen and paper format, or on computers. Guided by reliability analyses conducted on the first phase's data, 6 of these tests were selected and implemented online. The new battery revealed to be a reliable tool of assessment showing good internal validity and reliability for all the measures

Best interpolation in a strip II: Reduction to unconstrained convex optimization

In this paper, we study the problem of finding a real-valued function f on the interval [0, 1] with minimal L 2 norm of the second derivative that interpolates the points ( t i , y i ) and satisfies e(t) ≤ f(t) ≤ d(t) for t ∈ [0, 1]. The functions e and d are continuous in each interval ( t i , t i +1) and at t 1 and t n but may be discontinuous at t i . Based on an earlier paper by the first author [7] we characterize the solution in the case when e and d are linear in each interval ( t i , t i +1). We present a method for the reduction of the problem to a convex finite-dimensional unconstrained minimization problem. When e and d are arbitrary continuous functions we approximate the problem by a sequence of finite-dimensional minimization problems and prove that the sequence of solutions to the approximating problems converges in the norm of W 2,2 to the solution of the original problem. Numerical examples are reported.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44775/1/10589_2004_Article_BF00248266.pd

Dynamic testing and transfer: An examination of children's problem-solving strategies

This study examined the problem-solving behaviour of 104 children (aged 7–8 years) when tackling construction-analogy tasks. Children were allocated to one of two conditions: either a form of unguided practice alone or this in combination with training based on graduated prompt techniques. Children's ability to solve figural open-ended analogy-problems was investigated as well as their ability to construct new analogy problems themselves. We examined children's progression in solving analogy problems and the variability in their strategy-use. Results showed that the group that received training made greater progress in solving analogy problems than children who only received unguided practice opportunities. However, the training appeared to give no additional improvement in performance on the transfer task over that of repeated unguided practice alone. Findings from this study demonstrate that an open construction task can provide additional information about children's cognitive learning potential