Perfect single error-correcting codes in the Johnson Scheme

Delsarte conjectured in 1973 that there are no nontrivial pefect codes in the Johnson scheme. Etzion and Schwartz recently showed that perfect codes must be k-regular for large k, and used this to show that there are no perfect codes correcting single errors in J(n,w) for n <= 50000. In this paper we show that there are no perfect single error-correcting codes for n <= 2^250.Comment: 4 pages, revised, accepted for publication in IEEE Transactions on Information Theor

World reactions to the 1961 Paris Pogrom

On 17 October 1961 a peaceful protest of Algerians in Paris, against a night-time curfew which applied only to them, was organised by the Féderation de France of the Front de Libération National (FLN), near the end of its guerrilla war against the French authorities in Algeria (1954-1962). The march was brutally repressed by the police, with somewhere in the region of 200 fatalities. Long a taboo subject in France, these events have recently been the subject of public controversy, notably during the 1997-98 trial of Maurice Papon, the Paris prefect of police in 1961, for crimes carried out during the Second World War; and in Papon's unsuccessful 1999 libel action against the author of a prominent book on the 1961 massacre, Jean-Luc Einaudi.2 This article aims to investigate the neglected subject of international responses to the 1961 massacre

Human in vitro models for understanding mechanisms of autism spectrum disorder.

Early brain development is a critical epoch for the development of autism spectrum disorder (ASD). In vivo animal models have, until recently, been the principal tool used to study early brain development and the changes occurring in neurodevelopmental disorders such as ASD. In vitro models of brain development represent a significant advance in the field. Here, we review the main methods available to study human brain development in vitro and the applications of these models for studying ASD and other psychiatric disorders. We discuss the main findings from stem cell models to date focusing on cell cycle and proliferation, cell death, cell differentiation and maturation, and neuronal signaling and synaptic stimuli. To be able to generalize the results from these studies, we propose a framework of experimental design and power considerations for using in vitro models to study ASD. These include both technical issues such as reproducibility and power analysis and conceptual issues such as the brain region and cell types being modeled