28,040 research outputs found

    Magnetooptical sum rules close to the Mott transition

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    We derive new sum rules for the real and imaginary parts of the frequency-dependent Hall constant and Hall conductivity. As an example, we discuss their relevance to the doped Mott insulator that we describe within the dynamical mean-field theory of strongly correlated electron systems.Comment: 4 pages, 4 ps figures; accepted for publication in PR

    Infrared Astronomical Satellite (IRAS) analysis of the transmittance of off-axis energy due to scattering and diffraction

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    Stray light transmittance is analyzed. Mathematical models are evaluated. The results of scatter and diffraction are considered separately, and the combined transmittance values evaluated

    Diagnostic performance of the specific uptake size index for semi-quantitative analysis of I-123-FP-CIT SPECT: harmonized multi-center research setting versus typical clinical single-camera setting

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    Introduction: The specific uptake size index (SUSI) of striatal FP-CIT uptake is independent of spatial resolution in the SPECT image, in contrast to the specific binding ratio (SBR). This suggests that the SUSI is particularly appropriate for multi-site/multi-camera settings in which camera-specific effects increase inter-subject variability of spatial resolution. However, the SUSI is sensitive to inter-subject variability of striatum size. Furthermore, it might be more sensitive to errors of the estimate of non-displaceable FP-CIT binding. This study compared SUSI and SBR in the multi-site/multi-camera (MULTI) setting of a prospective multi-center study and in a mono-site/mono-camera (MONO) setting representative of clinical routine. Methods: The MULTI setting included patients with Parkinson’s disease (PD, n = 438) and healthy controls (n = 207) from the Parkinson Progression Marker Initiative. The MONO setting included 122 patients from routine clinical patient care in whom FP-CIT SPECT had been performed with the same double-head SPECT system according to the same acquisition and reconstruction protocol. Patients were categorized as “neurodegenerative” (n = 84) or “non-neurodegenerative” (n = 38) based on follow-up data. FP-CIT SPECTs were stereotactically normalized to MNI space. SUSI and SBR were computed for caudate, putamen, and whole striatum using unilateral ROIs predefined in MNI space. SUSI analysis was repeated in native patient space in the MONO setting. The area (AUC) under the ROC curve for identification of PD/“neurodegenerative” cases was used as performance measure. Results: In both settings, the highest AUC was achieved by the putamen (minimum over both hemispheres), independent of the semi-quantitative method (SUSI or SBR). The putaminal SUSI provided slightly better performance with ROI analysis in MNI space compared to patient space (AUC = 0.969 vs. 0.961, p = 0.129). The SUSI (computed in MNI space) performed slightly better than the SBR in the MULTI setting (AUC = 0.993 vs. 0.991, p = 0. 207) and slightly worse in the MONO setting (AUC = 0.969 vs. AUC = 0.976, p = 0.259). There was a trend toward larger AUC difference between SUSI and SBR in the MULTI setting compared to the MONO setting (p = 0.073). Variability of voxel intensity in the reference region was larger in misclassified cases compared to correctly classified cases for both SUSI and SBR (MULTI setting: p = 0.007 and p = 0.012, respectively). Conclusions: The SUSI is particularly useful in MULTI settings. SPECT images should be stereotactically normalized prior to SUSI analysis. The putaminal SUSI provides better diagnostic performance than the SUSI of the whole striatum. Errors of the estimate of non-displaceable count density in the reference region can cause misclassification by both SUSI and SBR, particularly in borderline cases. These cases might be identified by visual checking FP-CIT uptake in the reference region for particularly high variability

    Estimating genetic and non-genetic components of variance for fasting glucose levels in pedigrees ascertained through non-insulin dependent diabetes

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    Fasting glucose levels measured on 337 individuals in 14 pedigrees ascertained through a proband with non-inuslin dependent diabetes were used to estimate genetic and non-genetic components of variance under a multifactorial model of inheritance. In this sample genetic factors were important in controlling variation in basal carbohydrate metabolism, as represented by age-adjusted log-fasting glucose. There was no evidence that arbitrary sib common environments or arbitrary parent common environments accounted for significant portions of the variability in fasting glucose in these data. An arbitrary environment shared by parent and offspring, however, had a marginally significant impact on the likelihood. Parameter estimates obtained from multifactorial models analysed in this manner are sensitive to extreme phenotypic values, however, and caution must be exerciese in estimating total genetic variation. While additive genetic factors did account for a significant proportion of the total variation in fasting glucose, a large proportion remained unexplained.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66167/1/j.1469-1809.1982.tb01586.x.pd

    Quasiperiodic Modulated-Spring Model

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    We study the classical vibration problem of a chain with spring constants which are modulated in a quasiperiodic manner, {\it i. e.}, a model in which the elastic energy is jkj(uj1uj)2\sum_j k_j( u_{j-1}-{u_j})^2, where kj=1+Δcos[2πσ(j1/2)+θ]k_j=1+\Delta cos[2\pi\sigma(j-1/2)+\theta] and σ\sigma is an irrational number. For Δ<1\Delta < 1, it is shown analytically that the spectrum is absolutely continuous, {\it i.e.}, all the eigen modes are extended. For Δ=1\Delta=1, numerical scaling analysis shows that the spectrum is purely singular continuous, {\it i.e.}, all the modes are critical.Comment: REV TeX fil

    L'estat actual de les Biblioteques del CSIC a Catalunya : objectius aconseguits i mancances

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    S'analitza l'estat actual de les biblioteques del Consell Superior d'Investigacions Científiques a Catalunya, en tant que pertanyents a la Xarxa de Biblioteques del CSIC, en particular la seva dependència de les comunicacions, els seus aspectes cooperatius, la informatització dels seus catàlegs, l'increment dels seus serveis, i la seva incorporació a les noves tecnologies de la informació. S'exposa la futura estructura de la Xarxa.Se analiza el estado actual de las bibliotecas del Consejo Superior de Investigaciones Científicas en Cataluña considerando que pertenecen a la Red de Bibliotecas del CSIC, en particular su dependencia de las comunicaciones, aspectos cooperativos, informatización de sus catálogos, incremento de sus servicios y la incorporación de nuevas tecnologías de la información. Se expone la futura estructura de la Red

    Model signatures and aridity indices enhance the accuracy of water balance estimations in a data-scarce Eastern Mediterranean catchment

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    Study region: Wadi Faria catchment, Palestine. Study focus: The upper part of the Faria catchment (139 km2) is a typical semi-arid karst catchment in the Eastern Mediterranean, where, up to recently, data availability has hindered the accurate assessment of renewable water resources. Newly available six-year time-series of rainfall and runoff data, combined with thorough field campaigns, enabled the application of the distributed TRAIN-ZIN watershed model. The model was constrained using seven hydrological signatures derived from the available time-series. New hydrological insights for the region: We found that the mean annual actual evapotranspiration was about 70% of precipitation, recharge was about 30% and natural runoff (excluding baseflow) 1%. Aggregated model results also supported aridity indicators that show the presence of Infiltration Excess (Hortonian) Overland Flow, as well as the importance of indirect groundwater recharge and evaporation from soil during dry months. In total, maximum annual water availability was of the same order of magnitude as actual demand estimates (23 MCM). However, high spatial and inter-annual variability, and the presence of karst features suggest that water resources in the region are highly vulnerable
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