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Experiments in nuclear physics, biomedicine and astronomy often require pulse-counting electronics for large numbers of channels. This paper describes an event-counting system attached to 60 channels of an innovative monolithic array of Single-Photon Avalanche Diodes (SPADA) intended for astronomical use. The system can capture events with pulse-counting rates of up to 20 MHz, a minimum integration time of 10 [micro]s, which results in a data acquisition rate of 100 000 frames per second. It can also store several hours' worth of data. This performance is achieved in a system that offers a high degree of flexibility, is small in size and has a low cost. The implementation is based on a Commercial-Off-The-Shelf (COTS) single board, fitted with an FPGA and a DSP. This board is connected to a PC by means of an IEEE 1394 high-speed serial link which stores the collected data and functions as a TCP/IP server. The data acquisition parameters, as well as the collected data, can be accessed by means of a custom-designed interface running on a TCP/IP client. A proof-of-concept system has been assembled and some test stand results are presented and discussed. Index Terms--Astronomy, counting circuits, digital signal processors, field programmable gate arrays, imaging, radiation detectors.

A theoretical analysis of the effects of the delay-line differential nonlinearity (DNL) on the typical performance parameters of high-resolution time-to-digital converters (TDCs) based on delay-locked-loop (DLL) delay lines has been developed. The theoretical study is based on the knowledge of the delay-line nonlinearity values that can be measured, with the desired precision, by means of a statistical code-density test. In particular, the effects on the TDC time resolution and error standard deviation curve as a function of the measured time interval are investigated. An a posteriori linearization technique, consisting in a proper correction of the TDC readouts, is then analyzed and its advantages are theoretically demonstrated. Finally, the theoretical results are superimposed on experimental data coming from a real TDC. The measured deviations from the ideal behavior are thus justified and can just be ascribed to the delay-line nonlinearity. Index Terms--Delay-locked-loop (DLL) delay lines, differential nonlinearity (DNL), high-resolution time measurement, linearization technique, time-to-digital converter (TDC).

Experiments in nuclear physics, biomedicine and astronomy often require pulse-counting electronics for large numbers of channels. This paper describes an event-counting system attached to 60 channels of an innovative monolithic array of Single-Photon Avalanche Diodes (SPADA) intended for astronomical use. The system can capture events with pulse-counting rates of up to 20 MHz, a minimum integration time of 10 µs, which results in a data acquisition rate of 100 000 frames per second. It can also store several hours' worth of data. This performance is achieved in a system that offers a high degree of flexibility, is small in size and has a low cost. The implementation is based on a Commercial-Off-The-Shelf (COTS) single board, fitted with an FPGA and a DSP. This board is connected to a PC by means of an IEEE 1394 high-speed serial link which stores the collected data and functions as a TCP/IP server. The data acquisition parameters, as well as the collected data, can be accessed by means of a custom-designed interface running on a TCP/IP client. A proof-of-concept system has been assembled and some test stand results are presented and discussed. [ABSTRACT FROM AUTHOR]

A compact system for counting and time-tagging single photons is presented, based on a monolithic array sensor of 60 pixels able to detect single photons, namely the single-photon avalanche diode array (SPADA). First, the working principle and performance of the single-photon detector pixel is detailed, with particular attention paid to monolithic array integration. Then the electronics needed to quench each pixel after avalanche ignition, namely the active-quenching circuit (AQC) is discussed, since the features of this quenching electronics dramatically affect the operating conditions of the detector, hence its actual performance. The discussion then focuses on integration of the SPADA system into Astrophysics applications such as adaptive optics, fast-transient imaging and atmospheric layer sensing. The whole electronics necessary to control SPADA operating conditions and temperature is also described, together with the complete opto-mechanics used to focus the telescope pupil onto the detector. Finally, experimental results are reported. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Clinical scales evaluating arm function after stroke are weak at detecting quality of movement. Therefore a new scale, the Motor Evaluation Scale for Upper Extremity in Stroke Patients (MESUPES), was developed, comprising 22 items pertaining to arm and hand performance. The scale was investigated for validity and unidimensionality using the Rasch measurement model, and for inter-rater reliability. SETTING: Twelve hospitals and rehabilitation centres in Belgium, Germany and Switzerland. PATIENTS: There were 396 patients (average age 63.38+/-12.89 years) in the Rasch study and 56 patients (average age 65.68+/-12.75 years) in the reliability study. MAIN MEASURES: The scale was examined on its fit to the Rasch model, thereby evaluating the scale's unidimensionality and validity. Differential item functioning was performed to test the stability of item hierarchy on several variables. Inter-rater reliability was examined with kappa values, weighted percentage agreement and intraclass correlation coefficients (ICC). RESULTS: Based on Rasch analysis, five items were removed. The MESUPES was divided in two tests: the MESUPES-arm test (8 items) and MESUPES-hand test (9 items). Both scales fitted the Rasch model. All items were stable among the subgroups of the sample. ICCs were 0.95 (95% confidence interval (CI) 0.91 -0.97) and 0.97 (95% CI 0.95-0.98) for the total score on arm and hand test respectively. The scale was also reliable at item level (weighted kappa 0.62 -0.79, weighted percentage agreement 85.71 -98.21). CONCLUSION: The MESUPES-arm and MESUPES-hand meet the statistical properties of reliability, validity and unidimensionality. Both tests provide a useful clinical and research tool to qualitatively evaluate arm and hand function during recovery after stroke. [ABSTRACT FROM AUTHOR]