An official website of the United States government
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.
more »
« less
One dislocation at a time
The direct observation of enhanced dislocation mobility in iron by in situ electron microscopy offers key insights and adds to the ongoing debate on the mechanisms of hydrogen embrittlement.
more »
« less
- Award ID(s):
- 2118522
- PAR ID:
- 10473647
- Publisher / Repository:
- Nature Materials
- Date Published:
- Journal Name:
- Nature Materials
- Volume:
- 22
- Issue:
- 6
- ISSN:
- 1476-1122
- Page Range / eLocation ID:
- 679 to 680
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
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
-
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
-
Abstract Mixing has been widely used in the interpretation of radiogenic isotope ratios and highly incompatible trace element variations in basalts produced by melting of a heterogeneous mantle. The binary mixing model is constructed by considering mass balance of endmember components, which is independent of physical state and spatial distribution of the endmembers in the mantle source. Variations of radiogenic isotope ratios and highly incompatible trace elements in basalts also depend on the size and spatial distribution of chemical and lithological heterogeneities in the mantle source. Here we present a new mixing model and a mixing scheme that take into account of the size, spatial location, and melting history of enriched mantle (EM) and depleted mantle (DM) parcels in the melting column. We show how Sr, Nd, and Hf concentrations and isotope ratios in the aggregated or pooled melt collected at the top of the melting column vary as a function of location of the EM parcel in the melting column. With changing location of the EM parcel in the upwelling melting column, compositions of the pooled melt do not follow a single mixing curve expected by the binary mixing model. Instead, they define a mixing loop that has an enriched branch and a depleted branch joined by two extreme points in composition space. The origin of the mixing loop can be traced back to four types of EM distribution or configuration in the melting column. The shape of the mixing loop depends on the relative melting rate of the EM to that of the DM and the number and spacing of EM parcels in the melting column. Probabilities of sampling the enriched and depleted branches in the pooled melt are proportional to volume fractions of the enriched and depleted materials in the mantle source. Mixing of pooled melts from a bundle of melting columns results in mixing envelopes in the isotope ratio correlation diagrams. The mixing envelope is a useful tool for studying chemical variations in mantle-derived melts. As an application, we consider scattered correlations in 87Sr/86Sr vs. 143Nd/144Nd and 143Nd/144Nd vs. 176Hf/177Hf in mid-ocean ridge basalts. We show that such correlations arise naturally from melting of a spatially heterogeneous mantle.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41563-023-01555-8
