In micro four-point probe measurements, three-way flexible L-shaped cantilever probes show significant advantages over conventional straight cantilever probes. The L-shaped cantilever allows static contact to the sample surface which reduces the frictional wear of the cantilever tips. We analyze the geometrical design space that must be fulfilled for the cantilevers to obtain static contact with the test sample. The design space relates the spring constant tensor of the cantilevers to the minimal value of the static tip-to-sample friction coefficient. Using an approximate model, we provide the analytical calculation of the compliance matrix of the L-shaped cantilever. Compared to results derived from finite element model simulations, the theoretical model provides a good qualitative analysis while deviations for the absolute values are seen. From a statistical analysis, the deviation is small for cantilevers with low effective spring constants, while the deviation is significant for large spring constants where the quasi one-dimensional approximation is no longer valid.
Background/Aim: Irritable bowel syndrome (IBS) affects about 15–20% of the population of the Western countries. Traditionally, IBS has been an exclusion diagnosis, but recently definitions have emerged from population-based research. The aim of this population-based study was to evaluate any association between gastrointestinal pathophysiology and IBS in subjects with symptoms of IBS compared to subjects with no abdominal complaints. Methods: From a random sample of 2,656 participants, subjects with IBS (32) together with subjects without abdominal complaints (26), were invited for further evaluation. IBS was defined as more than weekly experience of abdominal pain and distension, and in addition either borborygmia or altering stool consistency. The diagnostic work-up consisted of gastroscopy, manometry and 23-hour pH and pressure recordings of the oesophagus, lactose tolerance test, barium enema, measurement of colonic transit time, and rectoscopy. Results: Compared to the group without abdominal complaints significantly more subjects with IBS had spasms of the colon (OR = 10.2 (1.2–87.3)), and abnormal contractions of the oesophagus at manometry (OR = 9.1 (1.1–78.2)). Furthermore, there was a non-significant tendency towards spasms at 23-hour pH and pressure recordings (OR = 3.58 (0.4–35.2)), and more discomfort at lactose tolerance test (OR = 5.8 (0.6–51.3)) in persons with IBS compared to subjects without abdominal complaints. Conclusion: The results of this population-based study indicate that signs of gastrointestinal dysmotility and hyperperception are more prevalent in subjects with IBS than in subjects without abdominal complaints.
We have developed and fabricated a multi-sensor chip for fisheries’ research and demonstrated the functionality under controlled conditions. The outer dimensions of the sensor chip are 3.0 × 7.4 × 0.8 mm3 and both sides of the chip are utilized for sensors. Hereby a more compact chip is achieved that allows for direct exposure to the seawater and thereby more accurate measurements. The chip contains a piezo-resistive pressure sensor, a pn-junction photodiode sensitive to visible light, a four-terminal platinum resistor for temperature measurement and four conductivity electrodes for the determination of the salinity of saltwater. Pressure, light intensity, temperature and salinity are all essential parameters when mapping the migration route of fish. The pressure sensor has a sensitivity of S = 1.44 × 10−7 Pa−1 and is optimized to 20 bar pressure; the light sensor has a quantum efficiency between 52% and 74% in the range of visible light. The temperature sensor responds linearly with temperature and has a temperature coefficient of resistance of 2.9 × 10−3 K−1. The conductivity sensor can measure the salinity with an accuracy of ±0.1 psu. This is all together the smallest and best functioning fully integrated MEMS-based multi-sensor made to date for this specific application. However, each single-sensor performance can be optimized by introducing a considerably more complicated process sequence. In this paper, a new simpler process for integrating the four sensors on one single chip is presented in details for the first time. Further, an optimized performance of the individual sensors is presented.
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