Time-resolved characterization of the formation of a collisionless shock.

We report on the temporally and spatially resolved detection of the precursory stages that lead to the formation of an unmagnetized, supercritical collisionless shock in a laser-driven laboratory experiment. The measured evolution of the electrostatic potential associated with the shock unveils the transition from a current free double layer into a symmetric shock structure, stabilized by ion reflection at the shock front. Supported by a matching particle-in-cell simulation and theoretical considerations, we suggest that this process is analogous to ion reflection at supercritical collisionless shocks in supernova remnants.

Elevated plasma levels of alpha-1-anti-chymotrypsin in age-related cognitive decline and Alzheimer's disease: a potential therapeutic target.

alpha-1-antichymotrypsin (ACT), is an acute phase protein and a protease inhibitor produced by the liver and brain. ACT is involved in the pathogenesis of Alzheimer's disease (AD), since elevated ACT concentration was found in cerebrospinal fluid (CSF) and brain from AD. ACT has also been shown to influence amyloid deposition in vitro and in animal models of AD. In this investigation 830 healthy controls, 69 subjects with cognitive impairment and not dementia (CIND), 53 patients with severe clinical AD and 142 patients with mild AD were investigated. Plasma levels of ACT were measured with a new competitive immune enzyme linked immune-assay (ELISA). ACT levels were higher in AD patients than in CIND or controls. An age dependent increase of plasma ACT was present in both healthy elderly and CIND. Patients with mild clinical AD were followed up for two years and stratified according to the rate of clinical deterioration. CT plasma levels were elevated in AD patients that showed an accelerated rate of cognitive deterioration during the follow up; this increment being prominent in AD with the Apolipoprotein E (APOE) epsilon 4 allele. Therefore, increased peripheral ACT levels in APOE 4 positive patients appear to predict an accelerated clinical progression. Plasma ACT might be used as a surrogate marker to monitor the conversion of pre-dementia stages to AD and the progression of the disease. The development of compounds able to interfere with the ACT biological activity (protease inhibition and/or promotion of amyloid deposition) might have therapeutic relevance for the disease.