Good readers use context-sensitive grapheme-phoneme correspondences

Fifth-grade children were given a series of word reading tasks. First, two sets of 16 disyllabic words with medial VCV spellings, and with a long initial vowel were selected, varying in frequency but with similar word-initial segments. Nonwords were derived from these sets of words by exchanging initial onsets. Children read these nonwords in a first testing session. In a second test session, children were given the Woodcock Word Identification Test and the set of analogue words from which the nonwords were derived. Initial analyses examined only nonwords derived from words that were correctly read. Both sets of nonwords were more likely to be read with a long initial vowel than a short initial vowel, although this tendency was stronger in nonwords derived from high frequency words. Furthennore, Word Identification ability showed a strong relationship with the preference for long initial vowels in this type of disyllabic nonword, both for nonwords derived from known analogues and for nonwords derived from words that children could not read correctly. This preference was also correlated with the preference for context-sensitive grapheme-phoneme correspondences in the reading of ambiguous monosyllabic nonwords.These results have strong implications for current theories of word reading.

Utilizing encoding in scalable linear optics quantum computing

We present a scheme which offers a significant reduction in the resources required to implement linear optics quantum computing. The scheme is a variation of the proposal of Knill, Laflamme and Milburn, and makes use of an incremental approach to the error encoding to boost probability of success.

Unitary R-matrices for topological quantum computing

The main problem with current approaches to quantum computing is the difficulty of establishing and maintaining entanglement. A Topological Quantum Computer (TQC) aims to overcome this by using different physical processes that are topological in nature and which are less susceptible to disturbance by the environment. In a (2+1)-dimensional system, pseudoparticles called anyons have statistics that fall somewhere between bosons and fermions. The exchange of two anyons, an effect called braiding from knot theory, can occur in two different ways. The quantum states corresponding to the two elementary braids constitute a two-state system allowing the definition of a computational basis. Quantum gates can be built up from patterns of braids and for quantum computing it is essential that the operator describing the braiding-the R-matrix-be described by a unitary operator. The physics of anyonic systems is governed by quantum groups, in particular the quasi-triangular Hopf algebras obtained from finite groups by the application of the Drinfeld quantum double construction. Their representation theory has been described in detail by Gould and Tsohantjis, and in this review article we relate the work of Gould to TQC schemes, particularly that of Kauffman.

Mathematical constraints on a theory of human memory - Response

Colonius suggests that, in using standard set theory as the language in which to express our computational-level theory of human memory, we would need to violate the axiom of foundation in order to express meaningful memory bindings in which a context is identical to an item in the list. We circumvent Colonius's objection by allowing that a list item may serve as a label for a context without being identical to that context. This debate serves to highlight the value of specifying memory operations in set theoretic notation, as it would have been difficult if not impossible to formulate such an objection at the algorithmic level.

Family context and duration of untreated psychosis (DUP): Results from the Sao Paulo Study

Background: Duration of untreated psychosis (DUP) depends on several factors, including socio-demographic, socioeconomic, clinical and contextual circumstances, such as availability of mental health services. Living arrangements may also play a role, especially in low- and middle-income countries, where most people who develop psychosis live with their relatives. Methods: Population-based study of first-episode psychosis in Sao Paulo, Brazil. Participants were aged 18-64 years, lived in a defined geographic area of the city and had a first contact in life with mental health services due to a psychotic episode. Duration of untreated psychosis was defined as the period between onset of first psychotic symptom and first contact with health service due to psychosis. The median DUP was used to classify participants into short and long DUP. Psychopathology, social adjustment and psychiatric diagnoses were made with standardized assessments. Type of service sought and living arrangements were examined. Results: Two hundred participants were included (52% women, 61% non-affective psychoses). The median DUP was 4.1 weeks (inter-quartile range: 1.9-11.4), and was shorter for affective psychoses. Most participants had their first contact with psychiatric emergency services. Those who did not live with a relative (children older than 18 years, parents, partner) were more likely to present long DUP (OR: 2.63; 95%Cl: 0.98-7.04); p = 0.05). Conclusion: The DUP in Sao Paulo was shorter than expected. Living arrangements may play an important role in shortening the DUP in urban centres of low- and middle income countries that have a network of mental health services. (C) 2009 Elsevier B.V. All rights reserved.