Mild Cognitive Impairment in the Elderly is Associated with Volume Loss of the Cholinergic Basal Forebrain Region

Background Cholinergic neurons within the basal forebrain are assumed to be an early (preclinical) manifestation site of pathological changes in Alzheimer's disease (AD). Methods We used morphometric magnetic resonance imaging (MRI) to detect and quantify atrophic changes in the basal forebrain of subjects suffering from amnestic mild cognitive impairment (aMCI). Three Tesla magnetic resonance (MR) data of 26 aMCI patients, 46 cognitively normal elderly control subjects (CO), and 12 patients suffering from Alzheimer's dementia were analyzed, including segmentation and quantification of brain tissue as well as a segmentation of basal forebrain structures (substantia innominata [SI]). Results We found the volume of the SI to be significantly different between groups in that control subjects showed the largest SI volumes, followed by aMCI and AD patients. Conclusions These results are in line with the hypothesis that cell loss within the cholinergic basal forebrain regions occurs already in the early (predementia) stage of AD. In vivo quantification of these changes might be of use as a novel neuroimaging marker of cholinergic neurodegeneration in AD

Distinct magnetic regimes through site-selective atom substitution in the frustrated quantum antiferromagnet Cs2_2CuCl4−x_{4-x}Brx_x

We report on a systematic study of the magnetic properties on single crystals of the solid solution Cs$_2$CuCl$_{4-x}$Br$_x$ (0 $\leq$ x $\leq$ 4), which include the two known end-member compounds Cs$_2$CuCl$_4$ and Cs$_2$CuBr$_4$, classified as quasi-two-dimensional quantum antiferromagnets with different degrees of magnetic frustration. By comparative measurements of the magnetic susceptibility $\chi$($T$) on as many as eighteen different Br concentrations, we found that the inplane and out-of-plane magnetic correlations, probed by the position and height of a maximum in the magnetic susceptibility, respectively, do not show a smooth variation with x. Instead three distinct concentration regimes can be identified, which are separated by critical concentrations x$_{c1}$ = 1 and x$_{c2}$ = 2. This unusual magnetic behavior can be explained by considering the structural peculiarities of the materials, especially the distorted Cu-halide tetrahedra, which support a site-selective replacement of Cl- by Br- ions. Consequently, the critical concentrations x$_{c1}$ (x$_{c2}$) mark particularly interesting systems, where one (two) halidesublattice positions are fully occupied.Comment: 15 pages, 4 figure

Flow and transport in the obstacle layer : First results of the micro-scale model MITRAS

A new obstacle resolving atmospheric micro-scale chemistry, transportand flow model MITRAS has been developed within the TroposphericResearch Program (TFS). MITRAS is an obstacle resolving model solvingsimultaneously the chemistry, pollutant transport including soot as well asflow and temperature field. The chemical reaction module is based on asimplified RACM mechanism. MITRAS has been carefully tested againstquality ensured wind tunnel data. The model results on soot and ozoneconcentrations as well as on the spatial representativity of measurementsites underline the necessity for high-resolution flow simulationsincluding temperature effects for case studies on close-to-sourcechemistry and pollutant transport within the urban canopy

Distinct magnetic regimes through site-selective atom substitution in the frustrated quantum antiferromagnet Cs 2CuCl 4-xBr x

We report on a systematic study of the magnetic properties on single crystals of the solid solution Cs 2CuCl 4-xBr x (0 ≤ x ≤ 4), which include the two known end-member compounds Cs 2CuCl 4 and Cs 2CuBr 4, classified as quasi-two-dimensional quantum antiferromagnets with different degrees of magnetic frustration. By comparative measurements of the magnetic susceptibility χ(T) on as many as 18 different Br concentrations, we found that the in-plane and out-of-plane magnetic correlations, probed by the position and height of a maximum in the magnetic susceptibility, respectively, do not show a smooth variation with x. Instead, three distinct concentration regimes can be identified, which are separated by critical concentrations x c1 =; 1 and x c2 =2. This unusual magnetic behavior can be explained by considering the structural peculiarities of the materials, especially the distorted Cu-halide tetrahedra, which support a site-selective replacement of Cl - by Br - ions. Consequently, the critical concentrations x c1 (x c2) mark particularly interesting systems, where one (two) halide-sublattice positions are fully occupied. © 2011 American Physical Society

Anatomical brain connectivity and positive symptoms of schizophrenia: a diffusion tensor imaging study

Structural brain changes in schizophrenia are well documented in the neuroimaging literature. The classical morphometric analyses of magnetic resonance imaging (MRI) data have recently been supplemented by diffusion tensor imaging (DTI), which mainly assesses changes in white matter (WM). DTI increasingly provides evidence for abnormal anatomical connectivity in schizophrenia, most often using fractional anisotropy (FA) as an indicator of the integrity of WM tracts. To better understand the clinical significance of such anatomical changes, we studied FA values in a whole-brain analysis comparing paranoid schizophrenic patients with a history of auditory hallucinations and matched healthy controls. The relationship of WM changes to psychopathology was assessed by correlating FA values with PANSS scores (positive symptoms and severity of auditory hallucinations) and with illness duration. Schizophrenic patients showed FA reductions indicating WM integrity disturbance in the prefrontal regions, external capsule, pyramidal tract, occipitofrontal fasciculus, superior and inferior longitudinal fasciculi, and corpus callosum. The arcuate fasciculus was the only tract which showed increased FA values in patients. Increased FA values in this region correlated with increased severity of auditory hallucinations and length of illness. Our results suggest that local changes in anatomical integrity of WM tracts in schizophrenia may be related to patients' clinical presentation