In this paper, the impact of Lorentz forces and temperature on the natural frequencies of a piezoresistive sensor composed of two microcantilevers with integrated U-shaped thin-film aluminum heaters are investigated. Two types of experiments were performed. In the first, the sensor was placed in a magnetic field so that the current flowing in the heater, in addition to raising the temperature, produced Lorentz forces, inducing normal stresses in the plane of one of the microcantilevers. In the second, which were conducted without magnetic fields, only the temperature variation of the natural frequency was left. In processing of the results, the thermal variations were subtracted from the variations due to both Lorentz forces and temperature in the natural frequency, resulting in the influence of the Lorentz forces only. Theoretical relations for the Lorentz frequency offsets were derived. An indirect method of estimating the natural frequency of one of the cantilevers, through a particular cusp point in the amplitude–frequency response of the sensor, was used in the investigations. The findings show that for thin microcantilevers with silicon masses on the order of 4 × 10−7 g and currents of 25 µA, thermal eigenfrequency variations are dominant. The results may have applications in the design of similar microsensors with vibrational action.
- Award ID(s):
- 1955482
- PAR ID:
- 10435867
- Date Published:
- Journal Name:
- Science
- Volume:
- 380
- Issue:
- 6640
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 64 to 69
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
-
null (Ed.)This piece explores the history of medicine in Egypt, the roots of an Egyptian practice of biomedicine in particular, through its historiography. In the period after World War II, the term “biomedicine” came to describe a practice of medicine defined by the close relations among clinicians, biological laboratory research, and the pharmaceutical industry in Europe and the United States. The history of medicine in Egypt and other parts of the Middle East and North Africa has long possessed close links to that in regions of Europe. In Egypt too, biomedicine has deep historical roots shaped by the influence of the nineteenth-century Ottoman‐Egyptian state, the experience of colonialism, and the anti‐colonial objectives of the post‐colonial Egyptian state in the second half of the twentieth century. These influences were particularly important in relation to the treatment of schistosomiasis, one of Egypt's top-ranking health problems of the twentieth century. The history of schistosomiasis demonstrates the gaps in the historiography of medicine in modern Egypt as well as how we might begin to consider the emergence of biomedical knowledge and theory at sites in Global South.more » « less
-
This piece explores the history of medicine in Egypt, the roots of an Egyptian practice of biomedicine in particular, through its historiography. In the period after World War II, the term “biomedicine” came to describe a practice of medicine defined by the close relations among clinicians, biological laboratory research, and the pharmaceutical industry in Europe and the United States. The history of medicine in Egypt and other parts of the Middle East and North Africa has long possessed close links to that in regions of Europe. In Egypt too, biomedicine has deep historical roots shaped by the influence of the nineteenth-century Ottoman-Egyptian state, the experience of colonialism, and the anti-colonial objectives of the post-colonial Egyptian state in the second half of the twentieth century. These influences were particularly important in relation to the treatment of schistosomiasis, one of Egypt’s top-ranking health problems of the twentieth century. The history of schistosomiasis demonstrates the gaps in the historiography of medicine in modern Egypt as well as how we might begin to consider the emergence of biomedical knowledge and theory at sites in Global South.more » « less
-
more » « less
Abstract Corals of the eastern tropical Pacific live in a marginal and oceanographically dynamic environment. Along the Pacific coast of Panamá, stronger seasonal upwelling in the Gulf of Panamá in the east transitions to weaker upwelling in the Gulf of Chiriquí in the west, resulting in complex regional oceanographic conditions that drive differential coral‐reef growth. Over millennial timescales, reefs in the Gulf of Chiriquí recovered more quickly from climatic disturbances compared with reefs in the Gulf of Panamá. In recent decades, corals in the Gulf of Chiriquí have also had higher growth rates than in the Gulf of Panamá. As the ocean continues to warm, however, conditions could shift to favor the growth of corals in the Gulf of Panamá, where upwelling may confer protection from high‐temperature anomalies. Here we describe the recent spatial and temporal variability in surface oceanography of nearshore environments in Pacific Panamá and compare those conditions with the dynamics of contemporary coral‐reef communities during and after the 2016 coral‐bleaching event. Although both gulfs have warmed significantly over the last 150 yr, the annual thermal maximum in the Gulf of Chiriquí is increasing faster, and ocean temperatures there are becoming more variable than in the recent past. In contrast to historical trends, we found that coral cover, coral survival, and coral growth rates were all significantly higher in the Gulf of Panamá. Corals bleached extensively in the Gulf of Chiriquí following the 2015–2016 El Niño event, whereas upwelling in the Gulf of Panamá moderated the high temperatures caused by El Niño, allowing the corals largely to escape thermal stress. As the climate continues to warm, upwelling zones may offer a temporary and localized refuge from the thermal impacts of climate change, while reef growth in the rest of the eastern tropical Pacific continues to decline.
-
Climate warming in the Russian Arctic over the past 40 years shows a variety of patterns at different locations and time periods. In the second half of the 20th century, the maximum rates of warming were characteristic of the subarctic permafrost regions of Russia. But in the 21st century, the locations of the greatest rates of climate warming moved to the Arctic zone of Russia. It was one of the reasons for a sharp increase in permafrost temperatures, an increase in the depth of seasonal thaw, and the formation of closed taliks. It was found that as a result of climate change, the differences in permafrost temperatures between different cryogenic landscapes in the area of continuous and discontinuous permafrost distribution have decreased, and in the area of sporadic permafrost distribution are now practically absent. The thermal regime of the ground shows dramatic changes everywhere with a pronounced reduction in the depth of zero annual amplitude.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.adg4520
