Frequency-selectable dual-band wilkinson divider/combiner

A technique for realising a compact frequency-selectable dual-band Wilkinson divider/combiner is presented in this study. To provide a frequency-selection function, the band-pass transmission-line transformer (TLT) in a dual-band device is replaced with a tuneable band-reject TLT. To realise this tuneable device, a variable capacitively loaded spur-line filter is proposed for its compact size. The theory based on an ideal transmission-line circuit is developed to provide a design procedure. The proposed circuits are demonstrated with simulated and measured results of a Wilkinson divider/combiner fabricated on FR4 substrate

Differential six-port reflectometer for determining dry rubber content of latex

This study presents the application of a differential six-port reflectometer to the design of a portable system for measurement of the dry rubber content (DRC) of latex. The proposed DRC measurement system consists of a 1 GHz reflectometer used with an open-ended coaxial-probe sensor, a temperature sensor, a display and a microcontroller. The complex permittivity and temperature of the rubber latex are measured, and a temperature-dependent model for DRC determination based on a dielectric mixture theory is used. The reflectometer performance is verified by comparing the measured complex permittivity with the results obtained from a commercial dielectric measurement system. Finally, the accuracy of the DRC measurement system is assessed by comparing the measured DRCs from different latex samples over the range of 10–40°C with the standard oven-drying method

Quantifying Zinc Contamination from Laboratory Syringes

While many sources of contamination in chemical and biological laboratories are well understood and known, some are less so. To quantify the magnitude of the potential contamination of solutions by zinc in common laboratory syringes, a study was conducted on solutions stored in rubber-containing syringes in which the rubber was catalyzed by zinc. This study identified specific factors contributing to contamination from laboratory syringes, including the syringe brand, time, solution type, and pH. Two common syringe brands, Covidien and BD, were tested, and three time durations, 0 days, 1 day, and 14 days, were examined. The solutions tested included sucrose and tartaric acid, representing both covalent and ionic species. Additionally, this study employed a pH range of 2 to 13 to further explore zinc contamination across a wide range of conditions and factors. The zinc concentration from the syringes was measured using inductively coupled plasma mass spectrometry (ICP-MS). The results, which ranged from less than 20 to over 600 μg L−1, revealed increased zinc concentration at both extreme pH values, while remaining lower but measurable at neutral pH levels. Zinc contamination is important to study because its contamination in laboratory syringes could interfere with the detection of other elements, further skew laboratory data, unexpectedly catalyze reactions, and lead to inconsistencies in experimental conditions. This study further emphasizes the broader significance of understanding pollutants within laboratory settings. The findings highlight the intricate dynamics of zinc contamination, stressing the need for the control of environmental factors and the broad dissemination of lesser-known sources. Recognizing the potential impact of contaminants like zinc is crucial, as it not only influences analytical accuracy, but also mirrors the wider concern of pollutants compromising scientific integrity in diverse experimental conditions