ATLAS pixel opto-electronics Arms, K.E.; Gan, K.K.; Jackson, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2005, Letnik:
554, Številka:
1
Journal Article
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We have developed two radiation-hard ASICs for optical data transmission in the ATLAS pixel detector at the LHC at CERN: a driver chip for a Vertical Cavity Surface Emitting Laser (VCSEL) diode for ...80
Mbit/s data transmission from the detector, and a Bi-Phase Mark decoder chip to recover the control data and 40
MHz clock received optically by a PIN diode. We have successfully implemented both ASICs in 0.25
μm CMOS technology using enclosed layout transistors and guard rings for increased radiation hardness. We present results of the performance of these chips, including irradiation with 24
GeV protons up to 61
Mrad (2.3×10
15
p/cm
2).
We present a workflow for kinetic modeling of biocatalytic reactions which combines methods from Bayesian learning and uncertainty quantification for model calibration, model selection, evaluation, ...and model reduction in a consistent statistical framework. Our workflow is particularly tailored to sparse data settings in which a considerable variability of the parameters remains after the models have been adapted to available data, a ubiquitous problem in many real‐world applications. Our workflow is exemplified on an enzyme‐catalyzed two‐substrate reaction mechanism describing the symmetric carboligation of 3,5‐dimethoxy‐benzaldehyde to (R)‐3,3′,5,5′‐tetramethoxybenzoin catalyzed by benzaldehyde lyase from Pseudomonas fluorescens. Results indicate a substrate‐dependent inactivation of enzyme, which is in accordance with other recent studies.
In contemporary control nets, random access schemes like CSMA are commonly used and are often enhanced by fixed priorities for some message types to guarantee an upper bound for the transmission time ...of high-priority messages. The introduction of priorities has a significant impact on the overall quality of service, which means that messages with a low priority may have long transmission times or high loss rates if the whole network is not adequately dimensioned. Thus, capacity planning includes as one of the first steps a model-based analysis of the network. This paper presents an approach to analyze the quality of service of CSMA-based control nets. Based on open queueing networks, analytical formulas are derived that allow one to compute performance measures like mean throughputs, loss rates, and response times in an extremely efficient way and with limited information about the system load. Particular emphasis is spent on the analysis of priorities in networks using a variant of the CSMA access scheme which has not been analyzed analytically before. Furthermore, the integration of timeouts and multicast communication into the analysis approach is outlined.
During the design of large technical systems, the use of analytic and simulative models to test and dimension the system before implementation is of practical importance for an efficient and reliable ...design process. However, setting up the necessary models is time-consuming and therefore often too expensive in practice. Usually most information for modeling is already available in the design tool used to develop such extensive systems and only needs to be extracted for automatic model building. This paper presents an automated modeling approach from an existing design database using the example of a network analysis for building automation fieldbuses. The analysis is based on an analytical decomposition approach that enables fast estimation of performance measures for large-scale networks. The combination of fast analytical algorithms with automatic model generation allows network performance engineering with minimized effort for model generation and analysis.
Retinal microvascular changes predict cardiovascular morbidity and mortality independent of classical risk factors. However, it is unclear which retinal changes characterize patients with established ...coronary artery disease (CAD), and in particular, with acute coronary syndromes (ACS). The aim of the present preliminary study was to assess retinopathy in these patients.
43 consecutive patients with ACS and 19 consecutive patients with stable CAD were investigated. Among the patient group with ACS, 20 patients presented with ST-Elevation Myocardial Infarction (STEMI) and 23 patients presented with Non-STEMI (NSTEMI). Standardized protocols were used and retinal fundus photography was taken within 48 h post-coronary angiography to assess retinopathy and general arteriolar narrowing as arterio-venous ratio (AVR). Clinical and laboratory cardiovascular risk factors were recorded.
Despite comparable age and comparable frequency of diabetes and hypertension, patients with ACS had a much higher likelihood for retinal microaneurysms and dot bleedings than patients with stable CAD (17 (40%) vs. 1 (5%) patients, OR 11.77; 95%CI 1.43–96.59; p
=
0.006). Performing multivariate analysis, this association remains significant (OR 20.5, 95%CI 1.6–255, p
=
0.019). CAD patients presented more often with focal signs of arteriovenous nicking / focal vasoconstriction (10 (53%) vs. 9 (21%) patients, OR 4.2; 95%CI 1.31–13.4; p
=
0.018), however after multivariate analysis this association lost significance. The AVR was comparably low in both groups.
Patients with ACS present more often with dot bleedings and microaneurysms. These findings provide preliminary evidence that retinal fundus examination may be useful to contribute to the risk profile of patients, enabling a more intensive survey and care.
The paper presents a class of numerical methods to compute the stationary distribution of Markov chains (MCs) with large and structured state spaces. A popular way of dealing with large state spaces ...in Markovian modeling and analysis is to employ Kronecker-based representations for the generator matrix and to exploit this matrix structure in numerical analysis methods. This paper presents various multilevel (ML) methods for a broad class of MCs with a hierarchcial Kronecker structure of the generator matrix. The particular ML methods are inspired by multigrid and aggregation-disaggregation techniques, and differ among each other by the type of multigrid cycle, the type of smoother, and the order of component aggregation they use. Numerical experiments demonstrate that so far ML methods with successive over-relaxation as smoother provide the most effective solvers for considerably large Markov chains modeled as HMMs with multiple macrostates. PUBLICATION ABSTRACT
We have designed an ASIC for use in a parallel optical engine for a new layer ofthe ATLAS pixel detector in the initial phase of the LHC luminosity upgrade. The ASIC is a 12-channel VCSEL (Vertical ...Cavity Surface Emitting Laser) array driver capable of operating up to5 Gb/s per channel. The ASIC is designed using a 130 nm CMOS process to enhance the radiationhardness.A scheme for redundancy has also been implemented to allow bypassing of a brokenVCSEL. The ASIC also contains a power-on reset circuit that sets the ASIC to a default configurationwith no signal steering. In addition, the bias and modulation currents of the individualchannels are programmable. We have received the ASIC and the performance up to 5 Gb/s is satisfactory.Furthermore, we are able to program the bias and modulation currents and to bypass abroken VCSEL channel. We are currently upgrading our design to allow operation at 10 Gb/s perchannel yielding an aggregated bandwidth of 120 Gb/s. Some preliminary results of the design willbe presented.
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