Child development - issues in early detection

Child development is a complex, non-linear process affected by multiple factors. In addition, there is a large degree of individual variation. Developmental delay is present when a child does not reach developmental milestones at the expected age (with adequate leeway for the broad variation among normal children). Although delay may result primarily from a biological factor such as a chromosomal disorder, or an environmental factor such as maternal depression, the principal model for the causes of developmental delay is a ‘transactional’ one. The process of development is viewed as a transaction between the child and the environment, in which each can have profound effects on the other. About 15% of children have developmental delay. Many, however, are not detected before commencing school, mainly because the disabilities are mild or because they relate to tasks only then attempted by the child. Of the 15%, a much smaller proportion has more severe disability. This group is more likely to present earlier because of the severity of their problems, because there is more often an associated medical condition, and because a number of them (such as those with extreme prematurity) are picked up by at-risk screening programs.&nbsp

Physically inspired interactive music machines: making contemporary composition accessible?

Much of what we might call "high-art music" occupies the difficult end of listening for contemporary audiences. Concepts such as pitch, meter and even musical instruments often have little to do with such music, where all sound is typically considered as possessing musical potential. As a result, such music can be challenging to educationalists, for students have few familiar pointers in discovering and understanding the gestures, relationships and structures in these works. This paper describes on-going projects at the University of Hertfordshire that adopt an approach of mapping interactions within visual spaces onto musical sound. These provide a causal explanation for the patterns and sequences heard, whilst incorporating web interoperability thus enabling potential for distance learning applications. While so far these have mainly driven pitch-based events using MIDI or audio files, it is hoped to extend the ideas using appropriate technology into fully developed composition tools, aiding the teaching of both appreciation/analysis and composition of contemporary music

Equilibrium Wage Dispersion: An Example

Search models with posting and match-specific heterogeneity generate wage dispersion. Given K values for the match-specific variable, it is known that there are K reservation wages that could be posted, but generically never more than two actually are posted in equilibrium. What is unknown is when we get two wages, and which wages are actually posted. For an example with K = 3, we show equilibrium is unique; may have one wage or two; and when there are two, the equilibrium can display any combination of posted reservation wages, depending on parameters. We also show how wages, profits, and unemployment depend on productivitySearch equilibrium, wage posting, wage dispersion, labor theory

Generalized search-theoretic models of monetary exchange

This paper extends the literature on search-theoretic models of money in several ways. It provides results for general bargaining parameters, whereas previous papers consider only special cases. It also presents one version of the model in which agents holding money cannot produce and another in which they can. The former has been used in essentially all the previous literature, although the latter seems more natural for some purposes and avoids several undesirable implications. Since very little is known about this version, the authors analyze it in detail.Monetary theory

Alternative Theories of Wage Dispersion

We analyze labor market models where the law of one price does not hold; i.e., models with equilibrium wage dispersion. We begin assuming workers are ex ante heterogeneous, and highlight a flaw with this approach: if search is costly, the market shuts down. We then assume workers are homogeneous but matches are ex post heterogeneous. This model is robust to search costs, and delivers equilibria equilibrium wage dispersion. However, we prove the law of two prices holds: generically we cannot get more than two wages. We explore several other models, including one combining ex ante and ex post heterogeneity; this model is robust, and can deliver more than two-point wage distributions.wages, search, distributions

Magnetic field effects in few-level quantum dots: theory, and application to experiment

We examine several effects of an applied magnetic field on Anderson-type models for both single- and two-level quantum dots, and make direct comparison between numerical renormalization group (NRG) calculations and recent conductance measurements. On the theoretical side the focus is on magnetization, single-particle dynamics and zero-bias conductance, with emphasis on the universality arising in strongly correlated regimes; including a method to obtain the scaling behavior of field-induced Kondo resonance shifts over a very wide field range. NRG is also used to interpret recent experiments on spin-1/2 and spin-1 quantum dots in a magnetic field, which we argue do not wholly probe universal regimes of behavior; and the calculations are shown to yield good qualitative agreement with essentially all features seen in experiment. The results capture in particular the observed field-dependence of the Kondo conductance peak in a spin-1/2 dot, with quantitative deviations from experiment occurring at fields in excess of $\sim$ 5 T, indicating the eventual inadequacy of using the equilibrium single-particle spectrum to calculate the conductance at finite bias.Comment: 15 pages, 12 figures. Version as published in PR

Correlated electron physics in multilevel quantum dots: phase transitions, transport, and experiment

We study correlated two-level quantum dots, coupled in effective 1-channel fashion to metallic leads; with electron interactions including on-level and inter-level Coulomb repulsions, as well as the inter-orbital Hund's rule exchange favoring the spin-1 state in the relevant sector of the free dot. For arbitrary dot occupancy, the underlying phases, quantum phase transitions (QPTs), thermodynamics, single-particle dynamics and electronic transport properties are considered; and direct comparison is made to conductance experiments on lateral quantum dots. Two distinct phases arise generically, one characterised by a normal Fermi liquid fixed point (FP), the other by an underscreened (USC) spin-1 FP. Associated QPTs, which occur in general in a mixed valent regime of non-integral dot charge, are found to consist of continuous lines of Kosterlitz-Thouless transitions, separated by first order level-crossing transitions at high symmetry points. A `Friedel-Luttinger sum rule' is derived and, together with a deduced generalization of Luttinger's theorem to the USC phase (a singular Fermi liquid), is used to obtain a general result for the T=0 zero-bias conductance, expressed solely in terms of the dot occupancy and applicable to both phases. Relatedly, dynamical signatures of the QPT show two broad classes of behavior, corresponding to the collapse of either a Kondo resonance, or antiresonance, as the transition is approached from the Fermi liquid phase; the latter behavior being apparent in experimental differential conductance maps. The problem is studied using the numerical renormalization group method, combined with analytical arguments.Comment: 22 pages, 18 figures, submitted for publicatio