The Agilent 1290 Infi nity II LC was used to analyze additives such as sweeteners, preservatives, and caffeine in various food products, beverages, and consumer toothpaste. The developed method facilitates accurate and sensitive determination of nine additives using a diode array detector (DAD) and an evaporative light scattering detector (ELSD) placed in series. After the DAD, a valve was inst...

When photon-counting detectors are calibrated in the presence of a background signal, deadtime effects can be significant and must be carefully accounted for to achieve high accuracy. We present a method for separating the correlated signal from the background signal that appropriately handles deadtime effects. This method includes consideration of pulse timing and afterpulsing issues that aris...

A closed-cell photothermal detector for aqueous analytes has been evaluated at 254 and 678 nm. We used a detector with a water meniscus as a pressure sensor, whose periodic deflection was measured using a low-finesse optical fiber Fabry-Perot interferometer. Performance was compared with a commercial diode array spectrometer and found to be similar for absorption measurements in nonturbid sampl...

The possible application of Schottky diodes as detector elements in receivers and image sensing systems operating in the THz frequency range has been demonstrated in the literature. In addition to metal-semiconductor (M-S) Schottky diodes, the use of heterojunction Schottky barrier diodes for detection and mixing applications has also been explored. Such diodes require lower d.c. bias voltages,...

We have developed a threedimensional imaging laser radar featuring 3-cm range resolution and single-photon sensitivity. This prototype direct-detection laser radar employs compact, all-solid-state technology for the laser and detector array. The source is a Nd:YAG microchip laser that is diode pumped, passively Q-switched, and frequency doubled. The detector is a gated, passively quenched, two-...

A novel type of millimeter/submillimeter wave sampler based on resonant tunneling diodes (RTDs) was proposed, and its operation was confirmed by circuit simulation. It consists of an RTD pulse generator and an RTD detector. Owing to the fuse-like nonlinear I-V curve, highly sensitive sampling can be obtained. We also found that the effects of nonideality in the I-V curve of the RTD can be corre...

Modulation frequency multiplexing provides a straightforward method, analogous to television or radio broadcasting, for performing simultaneous detection of multiple gases by use of wavelength modulation spectroscopy with diode lasers. When fiber-optic coupled lasers are used, our approach guarantees that all beams transit the same optical path and impinge on the same detector. Each laser is mo...

Standard commercial diode detectors over-respond within small radiation fields, an effect largely attributable to the relatively high mass-density of silicon. However, Monte Carlo studies can be used to optimise dosimeter designs and have demonstrated that 'mass-density compensation'-for example, introducing a low-density air-gap upstream of a diode's high-density silicon volume-can substantial...

The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte ...

Purpose: To investigate the energy dependence/spectral sensitivity of silicon diodes designed for small-field dosimetry and obtain response factors (RFs) for arbitrary photon spectra using Monte Carlo (MC) simulations.   Methods: The EGSnrc user-code DOSRZnrc was used to calculate the dose deposition in water and in the active volume of a stereotactic diode f...