Access Control and Retrieval Optimization Functions of the Supervisor for an Extended Data Management Facility

The purpose of the Supervisor in an Extended Data Management Facility (EDMF) is to direct the Facility\u27s handling of a user\u27s request for service. The Supervisor fulfills its task through the use of five main functions: Access Control, Retrieval Initialization, File Searching, Record Validating and Record Formatting. The major and most important component of the Retrieval Initialization phase is the Retrieval Optimization subfunction. This report is concerned mainly with the design and implementation of the Access Control and Retrieval Optimization functions. Macro instructions are the mechanism through which a user\u27s program can call upon the ECMF. The Authority Item check is the EDMF\u27s security control over file access while the Prime Keyword Search is the method used to optimize the retrieval strategy. The Authority Item check and the Prime Keyword Search are two of the major concepts of the Extended Data Management Facility

Exploring the Function of Neural Oscillations in Early Sensory Systems

Neuronal oscillations appear throughout the nervous system, in structures as diverse as the cerebral cortex, hippocampus, subcortical nuclei and sense organs. Whether neural rhythms contribute to normal function, are merely epiphenomena, or even interfere with physiological processing are topics of vigorous debate. Sensory pathways are ideal for investigation of oscillatory activity because their inputs can be defined. Thus, we will focus on sensory systems as we ask how neural oscillations arise and how they might encode information about the stimulus. We will highlight recent work in the early visual pathway that shows how oscillations can multiplex different types of signals to increase the amount of information that spike trains encode and transmit. Last, we will describe oscillation-based models of visual processing and explore how they might guide further research

Retinal oscillations carry visual information to cortex

Thalamic relay cells fire action potentials that transmit information from retina to cortex. The amount of information that spike trains encode is usually estimated from the precision of spike timing with respect to the stimulus. Sensory input, however, is only one factor that influences neural activity. For example, intrinsic dynamics, such as oscillations of networks of neurons, also modulate firing pattern. Here, we asked if retinal oscillations might help to convey information to neurons downstream. Specifically, we made whole-cell recordings from relay cells to reveal retinal inputs (EPSPs) and thalamic outputs (spikes) and analyzed these events with information theory. Our results show that thalamic spike trains operate as two multiplexed channels. One channel, which occupies a low frequency band (<30 Hz), is encoded by average firing rate with respect to the stimulus and carries information about local changes in the image over time. The other operates in the gamma frequency band (40-80 Hz) and is encoded by spike time relative to the retinal oscillations. Because these oscillations involve extensive areas of the retina, it is likely that the second channel transmits information about global features of the visual scene. At times, the second channel conveyed even more information than the first.Comment: 21 pages, 10 figures, submitted to Frontiers in Systems Neuroscienc

Statistical Wiring of Thalamic Receptive Fields Optimizes Spatial Sampling of the Retinal Image

SummaryIt is widely assumed that mosaics of retinal ganglion cells establish the optimal representation of visual space. However, relay cells in the visual thalamus often receive convergent input from several retinal afferents and, in cat, outnumber ganglion cells. To explore how the thalamus transforms the retinal image, we built a model of the retinothalamic circuit using experimental data and simple wiring rules. The model shows how the thalamus might form a resampled map of visual space with the potential to facilitate detection of stimulus position in the presence of sensor noise. Bayesian decoding conducted with the model provides support for this scenario. Despite its benefits, however, resampling introduces image blur, thus impairing edge perception. Whole-cell recordings obtained in vivo suggest that this problem is mitigated by arrangements of excitation and inhibition within the receptive field that effectively boost contrast borders, much like strategies used in digital image processing

Coronary calcium scoring on virtual non-contrast and virtual non-iodine reconstructions compared to true non-contrast images using photon-counting computed tomography

Objectives: To compare coronary artery calcification (CAC) scores measured on virtual non-contrast (VNC) and virtual non-iodine (VNI) reconstructions computed from coronary computed tomography angiography (CCTA) using photon-counting computed tomography (PCCT) to true non-contrast (TNC) images. Methods: We included 88 patients (mean age = 59 years ± 13.5, 69% male) who underwent a TNC coronary calcium scan followed by CCTA on PCCT. VNC images were reconstructed in 87 patients and VNI in 88 patients by virtually removing iodine from the CCTA images. For all reconstructions, CAC scores were determined, and patients were classified into risk categories. The overall agreement of the reconstructions was analyzed by Bland–Altman plots and the level of matching classifications. Results: The median CAC score on TNC was 27.8 [0–360.4] compared to 8.5 [0.2–101.6] (p &lt; 0.001) on VNC and 72.2 [1.3–398.8] (p &lt; 0.001) on VNI. Bland–Altman plots depicted a bias of 148.8 (ICC = 0.82, p &lt; 0.001) and − 57.7 (ICC = 0.95, p &lt; 0.001) for VNC and VNI, respectively. Of all patients with CAC TNC = 0, VNC reconstructions scored 63% of the patients correctly, while VNI scored 54% correctly. Of the patients with CAC TNC &gt; 0, VNC and VNI reconstructions detected the presence of coronary calcium in 90% and 92% of the patients. CAC VNC tended to underestimate CAC score, whereas CAC VNI overestimated, especially in the lower risk categories. According to the risk categories, VNC misclassified 55% of the patients, while VNI misclassified only 32%. Conclusion: Compared to TNC images, VNC underestimated and VNI overestimated the actual CAC scores. VNI reconstructions quantify and classify coronary calcification scores more accurately than VNC reconstructions. Clinical relevance statement: Photon-counting CT enables spectral imaging, which might obviate the need for non-contrast enhanced coronary calcium scoring, but optimization is necessary for the clinical implementation of the algorithms. Key Points: • Photon-counting computed tomography uses spectral information to virtually remove the signal of contrast agents from contrast-enhanced scans. • Virtual non-contrast reconstructions tend to underestimate coronary artery calcium scores compared to true non-contrast images, while virtual non-iodine reconstructions tend to overestimate the calcium scores. • Virtual non-iodine reconstructions might obviate the need for non-contrast enhanced calcium scoring, but optimization is necessary for the clinical implementation of the algorithms.</p

A Novel fry1 Allele Reveals the Existence of a Mutant Phenotype Unrelated to 5′->3′ Exoribonuclease (XRN) Activities in Arabidopsis thaliana Roots

BACKGROUND Mutations in the FRY1/SAL1 Arabidopsis locus are highly pleiotropic, affecting drought tolerance, leaf shape and root growth. FRY1 encodes a nucleotide phosphatase that in vitro has inositol polyphosphate 1-phosphatase and 3',(2'),5'-bisphosphate nucleotide phosphatase activities. It is not clear which activity mediates each of the diverse biological functions of FRY1 in planta. PRINCIPAL FINDINGS A fry1 mutant was identified in a genetic screen for Arabidopsis mutants deregulated in the expression of Pi High affinity Transporter 1;4 (PHT1;4). Histological analysis revealed that, in roots, FRY1 expression was restricted to the stele and meristems. The fry1 mutant displayed an altered root architecture phenotype and an increased drought tolerance. All of the phenotypes analyzed were complemented with the AHL gene encoding a protein that converts 3'-polyadenosine 5'-phosphate (PAP) into AMP and Pi. PAP is known to inhibit exoribonucleases (XRN) in vitro. Accordingly, an xrn triple mutant with mutations in all three XRNs shared the fry1 drought tolerance and root architecture phenotypes. Interestingly these two traits were also complemented by grafting, revealing that drought tolerance was primarily conferred by the rosette and that the root architecture can be complemented by long-distance regulation derived from leaves. By contrast, PHT1 expression was not altered in xrn mutants or in grafting experiments. Thus, PHT1 up-regulation probably resulted from a local depletion of Pi in the fry1 stele. This hypothesis is supported by the identification of other genes modulated by Pi deficiency in the stele, which are found induced in a fry1 background. CONCLUSIONS/SIGNIFICANCE Our results indicate that the 3',(2'),5'-bisphosphate nucleotide phosphatase activity of FRY1 is involved in long-distance as well as local regulatory activities in roots. The local up-regulation of PHT1 genes transcription in roots likely results from local depletion of Pi and is independent of the XRNs.This work was supported by an ANR-GENOPLANT grant (RIBOROOT-ANR06 GPLA 011) and the CEA agency. Array hybridizations have been partly supported by RNG (Réseau National des Génopoles, Evry, France). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding received for this study

Image quality assessment of coronary artery segments using ultra-high resolution dual source photon-counting detector computed tomography

Purpose: The study is intended to assess the image quality of ultra-high resolution (UHR) coronary computed tomography angiography (CCTA) performed on dual source photon-counting detector CT (PCD-CT). Method: Consecutive patients, who underwent clinically indicated CCTA on PCD-CT (UHR 120x 0.2 mm collimation), were included. CCTA images were reconstructed at 0.2 mm slice thickness with Bv40, Bv44, Bv48 and Bv56 kernels and quantum iterative reconstruction level 4. Contrast-to-noise (CNR) and signal-to-noise ratios (SNR) were quantified from contrast-enhanced blood and subcutaneous adipose tissue. All reconstructions were scored per coronary segment (18-segment model) for presence, image quality, motion artefacts, stack artefacts, plaque presence and composition, and stenosis degree. Image quality was scored by two independent observers. Results: Sixty patients were included (median age 62 [25th – 75th percentile: 53–67] years, 45% male, median calcium score 62 [0–217]). The mean heart rate during scanning was 71 ± 11 bpm. Median CTDIvol was 19 [16–22]mGy and median DLP 243 [198–327]mGy.cm. The SNR was 9.3 ± 2.3 and the CNR was 11.7 ± 2.6. Of the potential 1080 coronary segments (60 patients x 18 segments), 255/256 (reader1/reader2) segments could not be assessed for being absent or non-evaluable due to size. Both readers scored 85% of the segments as excellent or very good (Intraclass Correlation Coefficient: 0.88 (95% CI: 0.87–0.90). Motion artefacts were present in 45(5%) segments, stack artefacts in 60(7%) segments and metal artefacts in 9(1%) segments. Conclusion: UHR dual-source PCD-CT CCTA provides excellent or very good image quality in 85% of coronary segments at relatively high heart rates at moderate radiation dose with only limited stack artefacts.</p