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Novel high-performance, symmetrical metal-oxide-metal tunnel diodes (MOMTDs) in a quasiplanar configuration (US patent 4 549 194) have been successfully fabricated, and for the first time used as room-temperature detectors for the heterodyne mixing of two CO2 lasers operating on the P14 line near ? = 10.6 ?m. Using these devices, we have achieved state-of-the-art NEP (noise equivalent power) in the 4 to 6 × 10?16 W/Hz range and a D* of 5 × 106 cm Hz?/W. 相似文献
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Calviello J.A. Bie P.R. Hickman G. Pomian P. Cappello A. Costello W. 《Electronics letters》1986,22(10):510-512
An all-refractory-metal GaAs MESFET (ARFET) making use of a Ta Schottky barrier with a thick gold overlayer for the source, gate and drain, and very highly doped N+-layers (2x1019 cm-3) to achieve low-resistivity nonalloyed ohmic contacts, has been successfully fabricated. These have a 400 ?m gate periphery and 0.6 ?m gate length and measured an associated gain of 10.22 dB and a noise figure of 2.14 dB at 8 GHz. The ARFETs were fabricated on epitaxial layers grown by MBE. Only one mask was used to simultaneously define source, gate and drain regions via a plasma dry-etch technique. 相似文献
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A novel GaAs beam-lead Mott Schottky-barrier mixer device having a zero-bias junction capacitance near 10 fF, very low parasitic capacitance, ideality factor near or below 1.07, and a zero-bias cutoff frequency as high as 5000 GHz has been developed. The diode configuration makes use of a unique design in which the current distribution in the N+ layer at d.c. and at r.f. are equivalent, and thus, for the first time, it is possible to fully characterise mixer devices at d.c. Samples of these devices have been tested at 94 GHz in a broadband fin-line mixer structure, and realised a mixer conversion loss below 6.0 dB. This performance is representative of the best results achieved to date in a printed-circuit mount. 相似文献
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A highly reliable metallised GaAs Ta-Schottky-barrier diode with native-oxide passivation has been developed. The zero bias cutoff frequency of these diodes is greater than 1000 GHz when measured accurately near 60 GHz, with a zero-bias junction capacitance near 0·1 pF. This zero-bias cutoff frequency is approximately twice the value for a comparable nonmetallised device. The letter describes the r.f. properties and the structure of the device. 相似文献
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P Palozza G Calviello S Serini P Moscato GM Bartoli 《Canadian Metallurgical Quarterly》1998,128(11):1989-1994
The effects of oral doses of canthaxanthin on tissue distribution of alpha- and gamma-tocopherols were investigated in three experiments in male and female Balb/c mice. Mice were assigned to receive canthaxanthin [7 or 14 microg/(g body weight.d)] or placebo (olive oil) by gavage for different periods of time (0, 1, 2, 4 and 6 wk). A 2 wk-treatment with canthaxanthin resulted in incorporation of the carotenoid in all tissues analyzed, including liver, spleen, kidney, lung and heart. In liver, the maximum accumulation of the carotenoid was reached after 2 wk of dosing in female mice and after 6 wk in male mice. Canthaxanthin incorporation was accompanied by changes in alpha- and gamma-tocopherol concentrations in plasma and tissues. These included the following: 1) a significant increase (P < 0.001) in alpha-tocopherol concentration in spleen (21 and 27% in male and female mice, respectively) after 2 wk and in liver ( approximately 50% in both male and female mice) after 6 wk; 2) a significant decrease in gamma-tocopherol concentration in plasma (P < 0.05) and tissues (P < 0.001) after 2 wk of treatment. In female mice, this decrease was 55% in plasma, 43% in liver, 44% in kidney, 71% in lung and 70% in heart. In male mice, the decrease was observed only in plasma (30%), kidney (54%) and heart (46%). In liver, the decrease in gamma-tocopherol concentration was both dose- and time-dependent and significantly (P < 0.001) greater in female than in male mice. We conclude that dietary administration of canthaxanthin modifies tocopherol status in murine tissues. 相似文献
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Gabriella Calviello Paola Palozza Piergiorgio Franceschelli Gianna Maria Bartoli 《Lipids》1997,32(10):1075-1083
In view of the promising future for use of n-3 polyunsaturated fatty acids (PUFA) in the prevention of cancer and cardiovascular
diseases, it is necessary to ensure that their consumption does not result in detrimental oxidative effects. The aim of the
present work was to test a hypothesis that low doses of eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) do not induce
harmful modifications of oxidative cell metabolism, as modifications of membrane fatty acid composition occur. Wistar rats
received by gavage oleic acid, EPA, or DHA (360 mg/kg body weight/day) for a period of 1 or 4 wk. Fatty acid composition and
α-tocopherol content were determined for plasma, red blood cell (RBC) membranes, and liver, kidney, lung, and heart microsomal
membranes. Susceptibility to oxidative stress induced by tert-butylhydroperoxide was measured in RBC. EPA treatment increased EPA and docosapentaenoic acid (DPA) content in plasma and
in all the membranes studied. DHA treatment mainly increased DHA content. Both treatments decreased arachidonic acid content
and n-6/n-3 PUFA ratio in the membranes, without modifying the Unsaturation Index. No changes in tissue α-tocopherol content
and in RBC susceptibility to oxidative stress were induced by either EPA or DHA treatment. The data suggest that EPA and DHA
treatments can substantially modify membrane fatty acids, with-out increasing susceptibility to oxidative stress, when administered
at low doses. This opens the possibility for use of low doses of n-3 PUFA for chemoprevention without risk of detrimental
secondary effects. 相似文献
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Cell proliferation’ differentiation’ and apoptosis are modified by n−3 polyunsaturated fatty acids in normal colonic mucosa 总被引:4,自引:0,他引:4
Gabriella Calviello Paola Palozza Nicola Maggiano Elisabetta Piccioni Piergiorgio Franceschelli Andrea Frattucci Fiorella Di Nicuolo Gianna Maria Bartoh 《Lipids》1999,34(6):599-604
Supplementation with low doses of eicosapentaenoic (EPA) or docosahexaenoic (DHA) acid was used here to investigate changes
in epithelial proliferation’ differentiation’ and apoptosis in normal rat colonic mucosa. ACI/T rats received by oral administration
low doses of purified EPA or DHA ethyl esters (1g/kg body weight) and colonic mucosa was analyzed for cell proliferation’
differentiation’ and apoptosis. n−3 Polyunsaturated fatty acid incorporation into membrane phospholipids was investigated
as reflections of fatty acid metabolism. Both EPA and DHA suppressed colonocyle proliferation and increased the numbers of
differentiating and apoptotic cells without modification of the crypt morphology and the number of cells per crypt columns.
A significant incorporation of the supplemented fatty acids into total phospholipids was observed. This enrichment was accompanied
by a decreased content in arachidonic acid. The observation that EPA and DHA do not alter crypt morphology although they modify
cell turnover in normal colonic mucosa suggests a possible use of these fatty acids as dietary chemopreventive agents. 相似文献
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