The nature of the observed phenomenon of "starting resistance" is reviewed, along with the accompanying experimental evidence of high drive-level altering and sometime "curing" of the malady. A simple phenomenological model is proposed, and then it is shown that this model does indeed predict all of the observed properties of starting resistance with the exception of "high-drive curing". This same model is then shown to predict the low level intermodulation effects seen in monolithic crystal filters. The ability to predict both starting resistance and intermodulation phenomena with the same model is taken as an indication that both phenomena have a common cause. Explanations of high-drive level curing of the phenomena are contemplated.

Arsenic is a carcinogenic groundwater contaminant that is toxic even at the parts-per-billion (ppb) level and its on-site determination remains challenging. Colorimetric test strips, though cheap and widely used, often fail to give reliable quantitative data. On the other hand, electrochemical detection is sensitive and accurate but considerably more expensive at the onset. Here, we present a study on arsenic detection in groundwater using a low-cost, open-source potentiostat based on Arduino technology. We tested different types of gold electrodes (screen-printed and microwire) with anodic stripping voltammetry (ASV), achieving low detection limits (0.7 μg L-1). In a study of arsenic contaminated groundwaters in Mexico, the microwire technique provides greater accuracy than test strips (reducing the median error from -50% to +2.9%) and greater precision (reducing uncertainties from ±25% to ±4.9%). Most importantly, the rate of false negatives versus the World Health Organisation’s 10 μg L-1 limit was reduced from 50% to 0% (N = 13 samples). Arsenic determination using open-source potentiostats may offer a low-cost option for research groups and NGOs wishing to perform arsenic analysis in-house, yielding superior quantitative data than the more widely used colorimetric test strips.

No abstract

Over the past few years, Motorola, as well as several other companies around the world, have been developing a new type of flat panel display, called the field emission display (FED). The FED combines many of the advantages of its cousin, the cathode ray tube (CRT), including high brightness and contrast, wide angle viewability, and speed in a flat package that is only a few millimeters thick. A 14 cm diagonal FED prototype built at Motorola Flat Panel Display Division is shown below, in Figure 1.

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