We have measured the branching fraction and photon energy spectrum for the radiative penguin process b-->s gamma. We find Beta(b-->s gamma) = (3.21+/-0.43+/-0.27(+0.18)(-0.10))x10(-4), where the ...errors are statistical, systematic, and from theory corrections. We obtain first and second moments of the photon energy spectrum above 2.0 GeV, <E( gamma)> = 2.346+/-0.032+/-0.011 GeV, and <E(2)(gamma)>-<E(gamma)>(2) = 0.0226+/-0.0066+/-0.0020 GeV(2), where the errors are statistical and systematic. From the first moment, we obtain (in the modified minimal subtraction renormalization scheme, to order 1/M(3)(B) and beta(0)alpha(2)(s)) the heavy quark effective theory parameter Lambda = 0.35+/-0.08+/-0.10 GeV.
Human behavior is surprisingly variable, even when facing the same problem under identical circumstances. A prominent example is risky decision making. Economic theories struggle to explain why ...humans are so inconsistent. Resting-state studies suggest that ongoing endogenous fluctuations in brain activity can influence low-level perceptual and motor processes, but it remains unknown whether endogenous fluctuations also influence high-level cognitive processes including decision making. Here, using real-time functional magnetic resonance imaging, we tested whether risky decision making is influenced by endogenous fluctuations in blood oxygenation level-dependent (BOLD) activity in the dopaminergic midbrain, encompassing ventral tegmental area and substantia nigra. We show that low prestimulus brain activity leads to increased risky choice in humans. Using computational modeling, we show that increased risk taking is explained by enhanced phasic responses to offers in a decision network. Our findings demonstrate that endogenous brain activity provides a physiological basis for variability in complex human behavior.
Abstract In this study, we investigate whether aberrant integrity of white matter (WM) fiber tracts represents a genetically determined biological marker of schizophrenia (SZ), and its relation with ...clinical symptoms. We collected brain DTI data from 28 SZ patients, 18 first-degree relatives and 22 matched controls and used voxel-based analysis with tract-based spatial statistics (TBSS) in order to compare fractional anisotropy (FA) between groups. Mean voxel-based FA values from the entire skeleton of each group were compared. We did a multiple regression analysis, followed by single post-hoc contrasts between groups. FA values were extracted from the statistically significant areas. The results showed significantly smaller FA values for SZ patients in comparison with controls in cortico-spinal tracts, in commissural fibers, in thalamic projections, in association fibers and in cingulum bundles. A significant increase of FA in SZ patients in comparison with healthy controls was only found in the arcuate fasciculus. Relatives had intermediate values between patients and controls which were deemed significant in the comparison to patients and controls in association fibers, arcuate fasciculus and cingulum bundles. Lower FA values in association fibers were significantly associated with predisposition toward hallucinations (in SZ patients and relatives), with higher PANSS scores of positive symptoms and with duration of illness (SZ patients). Our results suggest that clinical and subclinical presentations of psychotic symptoms are associated with aberrant integrity of multiple WM tracts. This association may represent an endophenotype of schizophrenia, since it is present in unaffected relatives as well. Such endophenotypes may serve as quantitative traits for future genetic studies and as candidate markers for early and preclinical identification of subjects at risk.
Abstract Structural brain changes are amongst the most robust biological alterations in schizophrenia, and their investigation in unaffected relatives is important for an assessment of the ...contribution of genetic factors. In this cross-sectional morphometry study we investigated whether volume changes in SZ are linked with genetic vulnerability and whether these effects are separated from secondary illness effects. We compared density of grey and white matter using high-resolution 3D-anatomical MRI imaging data in 31 SZ patients, 29 first-degree relatives and 38 matched healthy controls, using Voxel-Based Morphometry (VBM) with SPM8. Volume of basal ganglia was also compared by manual segmentation. We found increased grey matter in the striatum, globus pallidus internus and thalamus and decreased grey matter in the parahippocampal and cingulate gyri both in SZ patients and relatives. Additionally, SZ patients had decreased volume of temporal, frontal and limbic grey and white matter in comparison with relatives and controls. Relatives showed intermediate values in many of these areas. Increased volume in the thalamus and parts of the basal ganglia and decreased volume of cortical areas and underlying white matter were thus associated with schizophrenia and its genetic vulnerability. These results suggest that brain morphological changes associated with SZ are in part determined by genetic risk factors and are not entirely explained by effects of medication or changes secondary to illness.
First measurement of gamma(D(+)) Ahmed, S; Alam, M S; Athar, S B ...
Physical review letters,
12/2001, Letnik:
87, Številka:
25
Journal Article
Recenzirano
Odprti dostop
We present the first measurement of the D*(+) width using 9/fb of e(+)e(-) data collected near the Upsilon(4S) resonance by the CLEO II.V detector. Our method uses advanced tracking techniques and a ...reconstruction method that takes advantage of the small vertical size of the Cornell Electron-positron Storage Ring beam spot to measure the energy release distribution from the D*(+)-->D(0)pi(+) decay. We find gamma(D*(+)) = 96+/-4 (stat)+/-22 (syst) keV. We also measure the energy release in the decay and compute Delta m identical with m(D*(+))-m(D(0)) = 145.412+/-0.002 (stat)+/-0.012 (syst) MeV/c(2).
Using 13.7 fb(-1) of data recorded by the CLEO detector at the Cornell Electron Storage Ring, we investigate the spectrum of charmed baryons which decay into Lambda+(c)pi(-)pi(+) and are more massive ...than the Lambda+(c)(2625) baryon. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda+(c) baryon; the other is narrow with an invariant mass of 596+/-1+/-2 MeV above the Lambda+(c) mass.
Background
Image-quality assessment is a fundamental step before clinical evaluation of magnetic resonance images. The aim of this study was to introduce a visual scoring system that provides a ...quality control standard for arterial spin labeling (ASL) and that can be applied to cerebral blood flow (CBF) maps, as well as to ancillary ASL images.
Methods
The proposed image quality control (QC) system had two components: (1) contrast-based QC (cQC), describing the visual contrast between anatomical structures; and (2) artifact-based QC (aQC), evaluating image quality of the CBF map for the presence of common types of artifacts. Three raters evaluated cQC and aQC for 158 quantitative signal targeting with alternating radiofrequency labelling of arterial regions (QUASAR) ASL scans (CBF, T1 relaxation rate, arterial blood volume, and arterial transient time). Spearman correlation coefficient (
r
), intraclass correlation coefficients (ICC), and receiver operating characteristic analysis were used.
Results
Intra/inter-rater agreement ranged from moderate to excellent; inter-rater ICC was 0.72 for cQC, 0.60 for aQC, and 0.74 for the combined QC (cQC + aQC). Intra-rater ICC was 0.90 for cQC; 0.80 for aQC, and 0.90 for the combined QC. Strong correlations were found between aQC and CBF maps quality (
r
= 0.75), and between aQC and cQC (
r
= 0.70). A QC score of 18 was optimal to discriminate between high and low quality clinical scans.
Conclusions
The proposed QC system provided high reproducibility and a reliable threshold for discarding low quality scans. Future research should compare this visual QC system with an automatic QC system.
We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected ...with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.
Cerebral perfusion and O(2) metabolism are affected by physiologic age-related changes. High-resolution motion-corrected quantitative T2'-imaging and PASL were used to evaluate differences in ...deoxygenated hemoglobin and CBF of the gray matter between young and elderly healthy subjects. Further combined T2'-imaging and PASL were investigated breathing room air and 100% O(2) to evaluate age-related changes in cerebral autoregulation.
Twenty-two healthy volunteers 60-88 years of age were studied. Two scans of high-resolution motion-corrected T2'-imaging and PASL-MR imaging were obtained while subjects were either breathing room air or breathing 100% O(2). Manual and automated regions of interest were placed in the cerebral GM to extract values from the corresponding maps. Results were compared with those of a group of young healthy subjects previously scanned with the identical protocol as that used in the present study.
There was a significant decrease of cortical CBF (P < .001) and cortical T2' values (P < .001) between young and elderly healthy subjects. In both groups, T2' remained unchanged under hyperoxia compared with normoxia. Only in the younger but not in the elderly group could a significant (P = .02) hyperoxic-induced decrease of the CBF be shown.
T2'-mapping and PASL in the cerebral cortex of healthy subjects revealed a significant decrease of deoxygenated hemoglobin and of CBF with age. The constant deoxyHb level breathing 100% O(2) compared with normoxia in young and elderly GM suggests an age-appropriate cerebral autoregulation. At the younger age, hyperoxic-induced CBF decrease may protect the brain from hyperoxemia.
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