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- Schüpbach, S., et al.
(författare)
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Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.
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- Nawaz, M., et al.
(författare)
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Assessment of High and Low Temperature Performance of SiC BJTs
- 2009
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2008. - STAFA-ZURICH : TRANS TECH PUBLICATIONS LTD. ; , s. 825-828
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the performance of SiC NPN Bipolar Junction Transistors (BJTs) at high and low temperature. A current gain of 50 at room temperature was obtained which decreases to 25 at 275 degrees C. A maximum current gain (beta) of 111 has been reported at -86 degrees C. At low temperature (below -86 degrees C), the current gain drops rapidly because of carrier freezout effect. At room temperature, a minimum on-resistance of 7 m Omega-cm(2) was obtained. This increases to 28 m Omega-cm(2) at 275 degrees C. The on-resistance of BJTs is approximately unaffected by lowering the temperature down to -86 degrees C front room temperature. Below -86 degrees C, the on-reststance JUMPS up rapidly because of carrier freezeout. Electrical performance of BJTs have been fairly stable during stress measurement at high temperature (120 hours at 100 degrees C) at a collector bias of 1000V (with open base) for devices with a breakdown voltage of 1200VA. The devices have been stressed further at low (i.e., 6) and high gain (i.e., 15) at room temperature. Initial degradation within first hour of stress test has been reported and then degradation stabilizes out. Packaged devices were tested Lip to 550 degrees C and performed admirably well up to that temperature.
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- Nevins, M., et al.
(författare)
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Equine-Derived Bone Mineral Matrix for Maxillary Sinus Floor Augmentation: A Clinical, Radiographic, Histologic, and Histomorphometric Case Series
- 2013
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Ingår i: International Journal of Periodontics & Restorative Dentistry. - : Quintessence Publishing. - 0198-7569 .- 1945-3388. ; 33:4, s. 483-490
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this proof-of-principle multicenter case series was to examine the bone regenerative potential of a newly introduced equine-derived bone mineral matrix (Equimatrix) to provide human sinus augmentation for the purpose of implant placement in the posterior maxilla. There were 10 patients requiring 12 maxillary sinus augmentations enrolled in this study. Histologic results at 6 months demonstrated abundant amounts of vital new bone in intimate contact with residual graft particles. Active bridging between residual graft particles with newly regenerated bone was routinely observed in intact core specimens. A mean value of 23.4% vital bone formation was observed at 6 months. This compared favorably with previous results using xenografts to produce bone in the maxillary sinus for the purpose of dental implant placement. Both the qualitative and quantitative results of this case series suggest comparable bone regenerative results at 6 months to bovine-derived xenografts.
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