RESUMO
A 52-year-old man had altered a wooden folding chair by placing two electrodes and a circuit underneath the seat. Using a remote control, he was able to give electric shocks to a person sitting on the chair. He used this device on more than 50 children, video-taping their reactions for his own pleasure. There are no reports that any of the children suffered a lasting damage to their health. The construction as well as the function and the electrical parameters of the chair were examined by forensic specialists. According to their expertise, the construction was not able to cause a potentially life-threatening condition when used with healthy children. The perpetrator was convicted for bodily harm etc.
Assuntos
Abuso Sexual na Infância/legislação & jurisprudência , Traumatismos por Eletricidade/etiologia , Eletrochoque/instrumentação , Prova Pericial/legislação & jurisprudência , Pedofilia/diagnóstico , Adolescente , Criança , Desenho de Equipamento , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Precisely timed detection of single photons plays an important role in the field of quantum information processing and fluorescence sensing. The method of time-correlated single photon counting is therefore constantly evolving and the associated instrumentation is being improved with new ideas and technologies. Simultaneous, time tagged readout of multiple detector channels is invaluable in many applications, spanning from fluorescence lifetime imaging in biology to the measurement of quantum optical correlations in basic research. Here we present a new integrated design, providing up to three independent input channels, a very short dead time, very high throughput, and a timing resolution of 25 ps at reasonable cost and small size. Apart from design features and test results of the instrument, we show an application in quantum optics, namely, the measurement of the photon statistics of a heralded single photon source based on cavity-enhanced spontaneous parametric down-conversion.
RESUMO
Time-correlated single photon counting continues to gain importance in a wide range of applications. Most prominently, it is used for time-resolved fluorescence measurements with sensitivity down to the single molecule level. While the primary goal of the method used to be the determination of fluorescence lifetimes upon optical excitation by short light pulses, recent modifications and refinements of instrumentation and methodology allow for the recovery of much more information from the detected photons, and enable entirely new applications. This is achieved most successfully by continuously recording individually detected photons with their arrival time and detection channel information (time tagging), thus avoiding premature data reduction and concomitant loss of information. An important property of the instrumentation used is the number of detection channels and the way they interrelate. Here we present a new instrument architecture that allows scalability in terms of the number of input channels while all channels are synchronized to picoseconds of relative timing and yet operate independent of each other. This is achieved by means of a modular design with independent crystal-locked time digitizers and a central processing unit for sorting and processing of the timing data. The modules communicate through high speed serial links supporting the full throughput rate of the time digitizers. Event processing is implemented in programmable logic, permitting classical histogramming, as well as time tagging of individual photons and their temporally ordered streaming to the host computer. Based on the time-ordered event data, any algorithms and methods for the analysis of fluorescence dynamics can be implemented not only in postprocessing but also in real time. Results from recently emerging single molecule applications are presented to demonstrate the capabilities of the instrument.