A Unified Distributed DSP-Based Beam Diagnostics and Global Feedback System for Ramped Electron Storage Rings

In dieser Arbeit wurde ein verteiltes DSP-basiertes Feedbacksystem zur Echtzeitregelung von Strahlparametern wie Arbeitspunkt und globalem Orbit an gerampten Elektronenspeicherringen entwickelt. Darauf basierend wurde an Bodo, dem gerampten Full-Energy Booster der 1.5 GeV Synchrotronstrahlungsquelle Delta, ein Arbeitspunktfeedback aufgebaut, charakterisiert und erfolgreich in Betrieb genommen, das den transversalen Arbeitspunkt von Bodo waehrend beliebiger Energierampen in Echtzeit korrigiert. Weiterhin wurde mit dem DSP-System ein globales Orbitfeedbackaufgebaut, charakterisiert und erfolgreich kommissioniert, das den Orbit von Bodo mit einer Rate von 4 kHz mit Hilfe derSVD-Methode global korrigiert. Durch die Integration weitererMonitore zur Messung von Strahlverlusten, Strahlstrom, Lebensdauer und Netzgeraetstroemen sowie -spannungen in das DSP-System von Bodo wurde die Moeglichkeit demonstriert, mitdem entwickelten DSP-System 'interdisziplinaere' globale Feedbacks zu implementieren, die verschiedene Eigenschaftendes Elektronenstrahls in Boostern und Speicherringen unter Beruecksichtigung einer Vielzahl verschiedenartiger Monitore in Echtzeit optimieren koennen. Das generische Gesamtkonzeptdes entwickelten Systems erlaubt den zukuenftigen Einsatz an Delta oder an anderen Synchrotronstrahlungsquellen mit nur geringem Anpassungsaufwand bei Hardware und Software. Neben der Entwicklung einer Multiprozessor-VMEbus-DSP-Karte, eines neuartigen FPGA-basierten LWL-Multiprozessor-Netzwerks ('DeltaNet') zum globalen Echtzeit-Messdatentransfer (globales reflektives internes DSP-RAM), des BPM-Datenerfassungssystems sowie weiten Teilen des DSP-/DDS-basierten Arbeitspunktmesssystems wurden in der Arbeit auch die gesamten DSP Software, die Treiber zur Integration in das EPICS-Kontrollsystem sowie die graphischenBenutzeroberflaechen entwickelt. Durch die Entwicklung einerBodo-Strahloptik mit reduzierter Emittanz sowie DSP-basierterAnalyse und Optimierung der Strahlparameter von Bodo waehrendder Energierampe konnte die Fuellzeit des Speicherrings Deltaerheblich reduziert werden.The subject of this thesis is the development of a distributed DSP-based feedback system for the real-time correction of beam parameters like betatron tune and global orbit in ramped electron storage rings. Based on thissystem, a betatron tune feedback for Bodo, the 1.5 GeVfull energy booster of the synchrotron light source Delta,was constructed, characterised and successfully commissioned. The feedback is able to correct the betatrontunes in real-time during arbitrary beam energy ramps. Moreover, a global orbit feedback system was constructed that corrects the Bodo orbit globally in real-time with the SVD method, at a correction rate of 4 kHz. By integratingadditional monitors for beam loss, beam current, lifetime andpower supply currents and voltages into the DSP system, it was demonstrated that the system allows the implementation of global 'interdisciplinary' feedbacks that optimise different beam parameters simultaneously in real-time by using a variety of different monitor types. The generic hardware and software design concept enables the future use of the system at Delta or other synchrotron light sources with minor modifications. The work on this thesis includes the development of a multiprocessor VMEbus DSP board, of a novel FPGA-based fiber optic multiprocessor network ('DeltaNet') for global real-time measurement data transfer (global reflective internal DSP memory), of the BPM data acquisition system and of most parts of the DSP-/DDS-based betatron tune measurement system of Bodo. The software for the DSPs, for their integration into the EPICS control system and for the graphical user interfaces was alsodeveloped during the work on this thesis. The design of a Bodo beam optics with reduced emittance and the DSP-basedanalysis and optimisation of beam parameters during the Bodoenergy ramp allowed a significant reduction of the Deltafilling time

Sparse geometric graphs with small dilation

Given a set S of n points in R^D, and an integer k such that 0 <= k < n, we show that a geometric graph with vertex set S, at most n - 1 + k edges, maximum degree five, and dilation O(n / (k+1)) can be computed in time O(n log n). For any k, we also construct planar n-point sets for which any geometric graph with n-1+k edges has dilation Omega(n/(k+1)); a slightly weaker statement holds if the points of S are required to be in convex position

Representational similarity precedes category selectivity in the developing ventral visual pathway

© 2019 Many studies have investigated the development of face-, scene-, and body-selective regions in the ventral visual pathway. This work has primarily focused on comparing the size and univariate selectivity of these neural regions in children versus adults. In contrast, very few studies have investigated the developmental trajectory of more distributed activation patterns within and across neural regions. Here, we scanned both children (ages 5–7) and adults to test the hypothesis that distributed representational patterns arise before category selectivity (for faces, bodies, or scenes) in the ventral pathway. Consistent with this hypothesis, we found mature representational patterns in several ventral pathway regions (e.g., FFA, PPA, etc.), even in children who showed no hint of univariate selectivity. These results suggest that representational patterns emerge first in each region, perhaps forming a scaffold upon which univariate category selectivity can subsequently develop. More generally, our findings demonstrate an important dissociation between category selectivity and distributed response patterns, and raise questions about the relative roles of each in development and adult cognition

3D molecular MR imaging of liver fibrosis and response to rapamycin therapy in a bile duct ligation rat model

Background & Aims Liver biopsy, the gold standard for assessing liver fibrosis, suffers from limitations due to sampling error and invasiveness. There is therefore a critical need for methods to non-invasively quantify fibrosis throughout the entire liver. The goal of this study was to use molecular Magnetic Resonance Imaging (MRI) of Type I collagen to non-invasively image liver fibrosis and assess response to rapamycin therapy. Methods Liver fibrosis was induced in rats by bile duct ligation (BDL). MRI was performed 4, 10, or 18 days following BDL. Some BDL rats were treated daily with rapamycin starting on day 4 and imaged on day 18. A three-dimensional (3D) inversion recovery MRI sequence was used to quantify the change in liver longitudinal relaxation rate (ΔR1) induced by the collagen-targeted probe EP-3533. Liver tissue was subjected to pathologic scoring of fibrosis and analyzed for Sirius Red staining and hydroxyproline content. Results ΔR1 increased significantly with time following BDL compared to controls in agreement with ex vivo measures of increasing fibrosis. Receiver operating characteristic curve analysis demonstrated the ability of ΔR1 to detect liver fibrosis and distinguish intermediate and late stages of fibrosis. EP-3533 MRI correctly characterized the response to rapamycin in 11 out of 12 treated rats compared to the standard of collagen proportional area (CPA). 3D MRI enabled characterization of disease heterogeneity throughout the whole liver. Conclusions EP-3533 allowed for staging of liver fibrosis, assessment of response to rapamycin therapy, and demonstrated the ability to detect heterogeneity in liver fibrosis.National Cancer Institute (U.S.) (CA140861)National Institutes of Health. National Institute for Biomedical Imaging and Bioengineering (EB009062)Sanofi Aventis (Firm

An eight‐channel Tx dipole and 20‐channel Rx loop coil array for MRI of the cervical spinal cord at 7 tesla

RÉSUMÉ: The quality of cervical spinal cord images can be improved by the use of tailored radiofrequency (RF) coil solutions for ultrahigh field imaging; however, very few commercial and research 7-T RF coils currently exist for the spinal cord, and in particular, those with parallel transmission (pTx) capabilities. This work presents the design, testing, and validation of a pTx/Rx coil for the human neck and cervical/upper thoracic spinal cord. The pTx portion is composed of eight dipoles to ensure high homogeneity over this large region of the spinal cord. The Rx portion is made up of twenty semiadaptable overlapping loops to produce high signal-to-noise ratio (SNR) across the patient population. The coil housing is designed to facilitate patient positioning and comfort, while also being tight fitting to ensure high sensitivity. We demonstrate RF shimming capabilities to optimize B1+ uniformity, power efficiency, and/or specific absorption rate efficiency. B1+ homogeneity, SNR, and g-factor were evaluated in adult volunteers and demonstrated excellent performance from the occipital lobe down to the T4-T5 level. We compared the proposed coil with two state-of-the-art head and head/neck coils, confirming its superiority in the cervical and upper thoracic regions of the spinal cord. This coil solution therefore provides a convincing platform for producing the high image quality necessary for clinical and research scanning of the upper spinal cord

Model averaging in ecology: a review of Bayesian, information-theoretic and tactical approaches for predictive inference

In ecology, the true causal structure for a given problem is often not known, and several plausible models and thus model predictions exist. It has been claimed that using weighted averages of these models can reduce prediction error, as well as better reflect model selection uncertainty. These claims, however, are often demonstrated by isolated examples. Analysts must better understand under which conditions model averaging can improve predictions and their uncertainty estimates. Moreover, a large range of different model averaging methods exists, raising the question of how they differ in their behaviour and performance. Here, we review the mathematical foundations of model averaging along with the diversity of approaches available. We explain that the error in model‐averaged predictions depends on each model's predictive bias and variance, as well as the covariance in predictions between models, and uncertainty about model weights. We show that model averaging is particularly useful if the predictive error of contributing model predictions is dominated by variance, and if the covariance between models is low. For noisy data, which predominate in ecology, these conditions will often be met. Many different methods to derive averaging weights exist, from Bayesian over information‐theoretical to cross‐validation optimized and resampling approaches. A general recommendation is difficult, because the performance of methods is often context dependent. Importantly, estimating weights creates some additional uncertainty. As a result, estimated model weights may not always outperform arbitrary fixed weights, such as equal weights for all models. When averaging a set of models with many inadequate models, however, estimating model weights will typically be superior to equal weights. We also investigate the quality of the confidence intervals calculated for model‐averaged predictions, showing that they differ greatly in behaviour and seldom manage to achieve nominal coverage. Our overall recommendations stress the importance of non‐parametric methods such as cross‐validation for a reliable uncertainty quantification of model‐averaged predictions

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe