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398 results on '"Hensel, J."'

102. Platelet-activating factor induction of activator protein-1 signaling in bronchial epithelial cells.

Author

D, LeVan T, W, Bloom J, G, Adams D, L, Hensel J, and M, Halonen

Abstract

Platelet-activating factor (PAF) has been implicated in the pathogenesis of allergic and inflammatory events in the airway. In the present study, we sought to determine if PAF receptors are present on human bronchial epithelial cells and whether PAF binding to these receptors leads to activation of activator protein-1 (AP-1)-mediated transcription. Radioligand binding studies demonstrated specific binding sites for the PAF antagonist [3H]WEB 2086 (3-[4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f]-[1,2,4]triazolo[4,3- a][1,4]diazepine-2-yl]-1-(4-morpholinyl)-1-propanone) on primary bronchial epithelial cells with an equilibrium dissociation constant (Kd) = 9.8 nM and maximal density of binding sites (Bmax) = 42.4 fmol/mg of protein. The expression of PAF receptors in these cells was further confirmed by reverse transcriptase-polymerase chain reaction, which revealed amplification products derived from PAF receptor mRNA corresponding to transcripts 1 and 2. In the bronchial epithelial cell line BEAS-2B transfected with an expression plasmid for the human PAF receptor, PAF stimulation increased AP-1 DNA binding activity as determined by electrophoretic mobility shift assays. The Fos and Jun family proteins were identified as components of the DNA-protein complexes by anti-peptide antibodies in gel supershift assays. Additionally, PAF significantly induced AP-1 mediated transcription which was dependent on the expression of PAF receptors. The PAF antagonist WEB 2086 blocked the PAF effect but not that induced by 12-O-tetradecanoyl phorbol-13-acetate, indicating the specificity of the PAF response. These results indicate that activation of airway epithelial cells through stimulation of PAF receptors includes up-regulation of the nuclear transcription factor AP-1 and AP-1 transcriptional activity.

Published
1998

104. Positron mobility in anthracene.

Author

Mills, A., Karl, N., Zuckerman, D., Passner, J., Hensel, J., and Beling, C.

Abstract

We have measured the positron mobility μ in a sample of scintillation grade anthracene at two temperatures. We obtain at 300 K: μ=(26.0±0.9±2.6) cmVs and at 77 K: μ=(33.4±1.1±3.3) cmVs, where the first error estimate is statistical and the second is systematic. We have also made preliminary measurements on a highly purified sample that yields μ=(130±3±20) cm V s at 300 K. The data are consistent with the hypothesis that the positron is scattered from both impurities and acoustic phonons in the first sample, and predominantly from photons in the second. It appears that positrons in pure anthracene crystals are delocalized and have a mean free path of about 85 Å at room temperature. [ABSTRACT FROM AUTHOR]

Published
1992
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105. Operation of the Si/CoSi2/Si heterostructure transistor.

Author

Hensel, J. C.

Subjects
*TRANSISTORS, *SEMICONDUCTORS
Abstract

A two-current path model is presented to describe the operation of the Si/CoSi2/Si epitaxial, heterostructure transistor. The model gives a good account of the device behavior and allows us to conclude that it works by activated charge control, in a formal sense like a bipolar transistor. The analysis further suggests that with the fine base dimensions made possible by the single crystal, vertical structure one can foresee devices with β’s of a 100 or more, at the same time maintaining a transconductance close to the optimal value 0.04 mhos/mA characteristic of a charge injection device. [ABSTRACT FROM AUTHOR]

Published
1986
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106. Transistor action in Si/CoSi2/Si heterostructures.

Author

Hensel, J. C., Levi, A. F. J., Tung, R. T., and Gibson, J. M.

Subjects
*HETEROSTRUCTURES, *SILICON, *COBALT compounds
Abstract

We report transistor action in a Si/CoSi[sub 2]/Si structure. The thin silicide layer (<100 Å), which acts as the base, is a single-crystal metal, essentially continuous and locally exhibiting atomically perfect interfaces with Si. The transistor action is manifested by a common base current gain a as high as 0.6 and a voltage gain greater than 10. [ABSTRACT FROM AUTHOR]

Published
1985
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107. Electrical transport properties of CoSi2 and NiSi2 thin films.

Author

Hensel, J. C., Tung, R. T., Poate, J. M., and Unterwald, F. C.

Subjects
*THIN films, *ELECTRIC conductivity, *TEMPERATURE, *STRENGTH of materials, *SILICIDES
Abstract

Transport studies have been performed on thin films of CoSi2 and NiSi2 in the temperature range 1-300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room-temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiessen's rule is obeyed over a remarkable range of bombardment doses. [ABSTRACT FROM AUTHOR]

Published
1984
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108. Electrical transport and in situ x-ray studies of the formation of TiSi2 thin films on Si.

Author

Hensel, J. C., Vandenberg, J. M., Unterwald, F. C., and Maury, A.

Subjects
*THIN films, *SILICON, *TITANIUM
Abstract

The formation of TiSi2 thin films on Si has been investigated by in situ x-ray diffraction and electrical transport. The x-ray results show unequivocally that the staging proceeds through two orthorhombic polytypes of TiSi2 according to the sequence: sputter-deposited metallic Ti or TiSix alloy films on Si(001)→TiSi2 (C49 structure)→TiSi2 (C54 structure), with no evidence of lower silicides. Electrical transport shows metallic behavior for all phases and distinctive features in the annealing curves which correlate with the structural transformations. Most important, the resistivity, characteristically very high for the C49 phase, undergoes a precipitous drop at the C49→C54 transition. In the C54 phase when fully annealed the resistivity is 12.4 μΩ cm at room temperature and 0.66 μΩ cm at 4.2 K. [ABSTRACT FROM AUTHOR]

Published
1987
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109. Electrical and structural characterization of ultrathin epitaxial CoSi2 on Si(111).

Author

Phillips, Julia M., Batstone, J. L., Hensel, J. C., and Cerullo, M.

Subjects
EPITAXY, SILICON, THIN films
Abstract

We report the fabrication of epitaxial CoSi2 layers on Si(111) as thin as 1 nm. The crystalline lattice of these layers is coherent with the Si lattice, and the silicide is electrically continuous. There are pronounced structural differences between films which are less than 3 nm thick and those which are thicker. The resistivity of the layers increases sharply with decreasing thickness. This is the first report of the growth of coherent, electrically continuous CoSi2 layers on Si. [ABSTRACT FROM AUTHOR]

Published
1987
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