Fast fluorescence dynamics in non-ratiometric calcium indicators

A fluorescence decay of high-affinity non-ratiometric Ca2+ indicator Oregon Green BAPTA-1 (OGB-1) is analyzed with unprecedented temporal resolution in the two-photon excitation regime. A triple exponential decay is shown to best fit the fluorescence dynamics of OGB-1. We provide a new model for accurate measurements of the free Ca2+ concentration and dissociation constants of non-ratiometric calcium indicators.Comment: 3 pages, 2 figures, figures revised, added chi-square goodness of fi

3D Imaging based on Single Photon Detectors

This paper introduces a mathematical model to evaluate fast and cost-effective 3D image sensors based on single photon detectors. The model will help engineers evaluate design parameters based on operating conditions and system performance. Ranging is based on the time-of-flight principle using TCSPC techniques. Two scenarios are discussed: (i) short-distance range indoors and (ii) medium-distance range outdoors. The model predicts an accuracy of 0.25cm at 5m with 0.5W of illumination and 1klux of background light. In the medium-range scenario, a precision of 0.5cm is predicted at 50m with 20W of illumination and 20klux of background light

Reduced order models of integrated RF spiral inductors with geometrical and technological automatic parameterization

In this paper a method is presented for automatically generating a parameterized model of integrated inductors accounting for geometry and substrate effects. A multiparameter Krylov-subspace based moment matching method is used to reduce the three-dimensional integral equations describing the EM behavior of the inductor over the substrate. Parameterization enables optimization of geometry and substrate technology simultaneously

Low Cost Earth Sensor Based on Oxygen Airglow (AIRES)

This project has demonstrated the feasibility of a low-cost Earth sensor based on imaging oxygen airglow, allowing 0.4° accuracy from GEO under any illumination condition. Available Earth Sensor (ES) are based on the measurement of the earth’s infrared radiation to determine the vector to the Earth’s centre. These designs provide excellent accuracies over a large field of view, but are often heavy, large, require cooling or temperature stabilization and are power hungry. In addition, the sensor concept for a LEO or GEO application ES differs significantly. We have developed a novel ES concept for applications where milli-degree accuracy is not required, but where low-cost is essential and lower (about 1 – 5°) accuracy is acceptable. Such a sensor could be used in new scenarios and to improve spacecraft reliability by providing a low-cost back-up sensor. Our Earth Sensor concept is based on imaging atmospheric oxygen emission at 762 nm using highly sensitive detectors. In both night-time and daytime there is continuous emission at 762 nm due to oxygen recombination. Low-noise active pixel sensors (APS) or low-light detector based on arrays of single photon avalanche diodes (SPAD) enables the ES to operate at night and day, over a wide temperature range, with a very compact optical system (aperture of 8 mm, focal length of 11 mm) and no scanning elements. A modular design allows designing similar instruments using the same wavelength band, the same detector technology, the same optics, the same power and data interfaces and similar algorithms for GEO and LEO applications, thus reducing the development cost. We have developed an Earth appearance model at 762 nm, which was used as input for the mechanical, optical and electric design of the Earth Sensor (conceptual design). In order to achieve a low-cost solution, simplicity and reduction of part count was a driving factor in the design trade-offs. Total mass for the GEO design is 845 g with a mean power consumption of 4 W. Algorithms were developed to determine the vector to the Earth from the images. A breadboard was built to display a simulated picture of the Earth under varying conditions, image those pictures at different temperatures with a radiation tolerant APS (LCMS), and verify the correct operation of the algorithms. In addition to the conceptual design and breadboard level demonstration of key technologies, a novel detector chip was designed and fabricated: a radiation-tolerant array of single photon avalanche photodiodes (SPAD) build using conventional 0.35 μm CMOS technology. The chip was tested under proton and gamma irradiation, and operated with only minor changes in dark current after 30 krad TID. Having shown the feasibility of such an Earth Sensor, this work concluded with a development plan to lead to a flight model