A process model of children's early verb use

The verb-island hypothesis (Tomasello, 1992) states that children’s early grammars consist of sets of lexically-specific predicate structures (or verb-islands). However, Pine, Lieven and Rowland (1998) have found that children’s early language can also be built around lexical items other than verbs, such as pronouns (this contradicts a strict version of the verb-island hypothesis). This paper presents a computational model (called MOSAIC), which constructs a network of nodes and links based on a performance-limited distributional analysis of the input (mother’s speech). The results show that utterances generated from MOSAIC: (1) more closely resemble the child’s data than the child’s mother’s data on which MOSAIC is trained; and (2) can readily simulate both the verb-island and other-island phenomena which exist in the child’s data

Learning novel sound patterns

The acquisition of vocabulary represents a key phenomenon in language acquisition, yet it is still poorly understood. Gathercole and colleagues have recently provided a rigorous test of vocabulary knowledge (the nonword repetition test, Gathercole, Willis, Baddeley, & Emslie, 1994) and have adapted the phonological loop part of the working memory model (Baddeley & Hitch, 1974) to explain the nonword repetition findings (e.g. Gathercole & Baddeley, 1989). However, there are two major failings in their explanation: there is no description of how words are learned, and no definition of how the phonological loop interacts with long-term memory. We present an EPAM based computational model which overcomes these problems by combining the phonological loop approach with the EPAM/chunking approach (Feigenbaum & Simon, 1984). Trained on naturalistic phonemically coded speech (from mother’s utterances to 2-3 year old children), the model provides a good match to the nonword repetition data from 2-3 year old children. The model is also able to show the effect on nonword repetition when the model is trained using different sets of input. Implementing the phonological loop within EPAM represents a parsimonious approach to learning novel sound patterns and provides a more precise definition of how vocabulary acquisition may occur

Not just old and sick - the 'will to health' in later life

The end of the ‘Golden Age’ of welfare capitalism in the 1970s was the prelude to a period of greater individualisation within societies and was accompanied by an increase in the importance of consumption as a way of organising social relations. During the same period there was also an expansion in the discourses aimed at enhancing the government of the autonomous self. One such discourse operates around what has been termed the ‘will to health’: it suggests that health has become a required goal for individual behaviour and has become synonymous with health itself. The generational groups whose lifecourses were most exposed to these changes are now approaching later life. We explore the extent to which social transformations related to risk, consumption and individualisation are reflected in the construction of later-life identities around health and ageing. We examine how the growth in health-related ‘technologies of the self’ have fostered a distinction between natural and normal ageing, wherein the former is associated with coming to terms with physical decline and the latter associated with maintaining norms of self-care aimed at delaying such decline. Finally, we consider anti-ageing medicine as a developing arena for the construction of later-life identities and discuss the implications of the social changes for researching later life

Comment on ``New ansatz for metric operator calculation in pseudo-Hermitian field theory''

In a recent Brief Report by Shalaby a new first-order perturbative calculation of the metric operator for an $i\phi^3$ scalar field theory is given. It is claimed that the result is an improvement on a previous calculation by Bender, Brody and Jones because it is local. Unfortunately Shalaby's calculation is not valid because of sign errors.Comment: 2 pages, no figures. This comment replaces the previous comment on the Brief Report by Shalaby. In the previous comment we pointed out that Shalaby's calculation failed in all but 2 space-time dimensions. We have subsequently found additional errors which mean that the calculation is not valid even in that cas

Predicting costs of mental health care: a critical literature review

Cost evaluation research in the mental health field is being increasingly recognized as a way to achieve a more effective deployment of scarce resources. However, there is a paucity of studies that seek to identify predictors of psychiatric service utilization and costs. This paper aims to critically review the published research in the field of psychiatric service utilization and costs, and discusses current methodological developments in this field

Acceleration Rates and Injection Efficiencies in Oblique Shocks

The rate at which particles are accelerated by the first-order Fermi mechanism in shocks depends on the angle, \teq{\Tbone}, that the upstream magnetic field makes with the shock normal. The greater the obliquity the greater the rate, and in quasi-perpendicular shocks rates can be hundreds of times higher than those seen in parallel shocks. In many circumstances pertaining to evolving shocks (\eg, supernova blast waves and interplanetary traveling shocks), high acceleration rates imply high maximum particle energies and obliquity effects may have important astrophysical consequences. However, as is demonstrated here, the efficiency for injecting thermal particles into the acceleration mechanism also depends strongly on obliquity and, in general, varies inversely with \teq{\Tbone}. The degree of turbulence and the resulting cross-field diffusion strongly influences both injection efficiency and acceleration rates. The test particle \mc simulation of shock acceleration used here assumes large-angle scattering, computes particle orbits exactly in shocked, laminar, non-relativistic flows, and calculates the injection efficiency as a function of obliquity, Mach number, and degree of turbulence. We find that turbulence must be quite strong for high Mach number, highly oblique shocks to inject significant numbers of thermal particles and that only modest gains in acceleration rates can be expected for strong oblique shocks over parallel ones if the only source of seed particles is the thermal background.Comment: 24 pages including 6 encapsulated figures, as a compressed, uuencoded, Postscript file. Accepted for publication in the Astrophysical Journa

Must a Hamiltonian be Hermitian?

A consistent physical theory of quantum mechanics can be built on a complex Hamiltonian that is not Hermitian but instead satisfies the physical condition of space-time reflection symmetry (PT symmetry). Thus, there are infinitely many new Hamiltonians that one can construct that might explain experimental data. One would think that a quantum theory based on a non-Hermitian Hamiltonian violates unitarity. However, if PT symmetry is not broken, it is possible to use a previously unnoticed physical symmetry of the Hamiltonian to construct an inner product whose associated norm is positive definite. This construction is general and works for any PT-symmetric Hamiltonian. The dynamics is governed by unitary time evolution. This formulation does not conflict with the requirements of conventional quantum mechanics. There are many possible observable and experimental consequences of extending quantum mechanics into the complex domain, both in particle physics and in solid state physics.Comment: Revised version to appear in American Journal of Physic

Trade Preferences: Economic Issues and Policy Options

[Excerpt] Since 1974, Congress has created multiple trade preference programs designed to foster economic growth, reform, and development in less developed countries. These programs give temporary, non-reciprocal, duty-free U.S. market access to select exports of eligible countries. Congress conducts regular oversight of these programs, repeatedly revising and extending them. Two major issues face the 111th Congress: (1) the expiration of two preference programs by December 31, 2010; and (2) possible legislative action on broader reform of the preference programs based on comprehensive reviews in hearings held in both the House and the Senate earlier in this Congress. This report discusses the major U.S. trade preference programs, their possible economic effects, stakeholder interests, and legislative options