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An optically addressed spatial light modulator (OASLM) works by using the intensity of a ‘write’ light to modulate the phase of a ‘read’ light. OASLM using ZnO nanoparticles (NPs) as a photoconductor is important to holographic displays because of its record-high spatial resolution. However, its response time to the write light is long and the switch-off time (τoff) can take tens of seconds due to the trap states in the ZnO NP layer. This results in residual images and poses limitations to its application in dynamic holographic displays. In this work, a ZnO NP photoconductor was replaced by a solution-processed ZnO NP/PEDOT:PSS heterojunction photodiode and the τoff of OASLM was significantly reduced to about 0.6 s. Electrical and optical properties of the heterojunction were characterized and a barrier height of 0.604 eV was determined by CV measurement. The heterojunction-based OASLM was then fabricated and its light modulating performance was investigated by using a diffractive phase grating. Finally, impedance spectroscopy was used to analysis the device equivalent circuit and optimize the operation of the OASLM.

This study describes the development of paper-based devices for the determination of biothiols. The devices are inexpensive (composed of paper and silver halide particles), and the analytical protocol is easily executable with minimum technical expertise and without the need of specialized equipment; the user has to add a test sample, illuminate the device with a UV lamp, and read the color change of the sensing area using a simple imaging device (i.e., cell-phone camera) or a bare eye. The detection mechanism of the assay is based on the biothiols-mediated photoreduction of nanometer-sized silver chloride particles deposited on the surface of paper; photoreduced silver chloride particles have a grayish coloration that depends on the concentration of biothiols in the tested solution. This is the first time that the UV-mediated photoreduction of solid silver halides particles is used for analytical purposes. The performance of the devices has been tested on the detection of total biothiols content of artificial body fluids and protein–free human blood plasma samples, and the results were satisfactory in terms of sensitivity, selectivity, recoveries and reproducibility.

Aim of the study: The aim of this study was to describe a new functionality aimed at X-ray dose reduction, referred to as spot region of interest (Spot ROI) and to compare it with existing dose-saving functionalities, spot fluoroscopy (Spot F), and conventional collimation (CC). Material and methods: Dose area product, air kerma, and peak skin dose were measured for Spot ROI, Spot F, and CC in three different fields of view (FOVs) 20 × 20 cm, 15 × 15 cm, and 11 × 11 cm using an anthropomorphic head phantom RS-230T. The exposure sequence was 5 min of pulsed fluoroscopy (7.5 pulses per s) followed by 7× digital subtraction angiography (DSA) runs with 30 frames per DSA acquisition (3 fps × 10 s). The collimation in Spot F and CC was adjusted such that the size of the anatomical area exposed was as large as the Spot ROI area in each FOV. Results: The results for all FOVs were the following: for the fluoroscopy, all measured parameters for Spot ROI and Spot F were lower than corresponding values for CC. For DSA and DSA plus fluoroscopy, all measured parameters for Spot ROI were lower than corresponding parameters for Spot F and CC. Conclusion: Spot ROI is a promising dose-saving technology that can be applied in fluoroscopy and acquisition. The biggest benefit of Spot ROI is its ability to keep the entire FOV information always visible.

A biomimetic device for the reduction of Cu(II) to Cu(I) consisting of thioglycolic acid covalently grafted to cellulose paper was developed. The device displays exceptionally fast reducing properties allowing the reduction of Cu(II) in seconds and the formation of deeply colored Cu(I)-SCH2R complexes onto the cellulose paper. This biomimetic and biomaterial-based concept was exploited for the detection of copper in water samples with a limit of detection as low as 2 ppm.

Water quality assessment requires a continuous and strict analysis of samples to guarantee compliance with established standards. Nowadays, the increasing number of pollutants and their synergistic effects lead to the development general toxicity bioassays capable to analyse water pollution as a whole. Current general toxicity methods, e.g. Microtox(®), rely on long operation protocols, the use of complex and expensive instrumentation and sample pre-treatment, which should be transported to the laboratory for analysis. These requirements delay sample analysis and hence, the response to avoid an environmental catastrophe. In an attempt to solve it, a fast (15 min) and low-cost toxicity bioassay based on the chromatic changes associated to bacterial ferricyanide reduction is here presented. E. coli cells (used as model bacteria) were stably trapped on low-cost paper matrices (cellulose-based paper discs, PDs) and remained viable for long times (1 month at -20 °C). Apart from bacterial carrier, paper matrices also acted as a fluidic element, allowing fluid management without the need of external pumps. Bioassay evaluation was performed using copper as model toxic agent. Chromatic changes associated to bacterial ferricyanide reduction were determined by three different transduction methods, i.e. (i) optical reflectometry (as reference method), (ii) image analysis and (iii) visual inspection. In all cases, bioassay results (in terms of half maximal effective concentrations, EC50) were in agreement with already reported data, confirming the good performance of the bioassay. The validation of the bioassay was performed by analysis of real samples from natural sources, which were analysed and compared with a reference method (i.e. Microtox). Obtained results showed agreement for about 70% of toxic samples and 80% of non-toxic samples, which may validate the use of this simple and quick protocol in the determination of general toxicity. The minimum instrumentation requirements and the simplicity of the bioassay open the possibility of in-situ water toxicity assessment with a fast and low-cost protocol.

We show some of the specific problems for testing software introduced by the object-oriented features of Ada 95, and focus on specification-based testing, since this strategy is the key strategy for testing object-oriented software. We present a theory for testing software by refinement of an exhaustive test set into a finite test set using three reduction hypothesis. We also show how the Oracle problem can be partially solved using some particular features of Ada 95. Slides: http://lgl.epfl.ch/pub/Papers/barbey-testing_ada95_oop-slides.ps