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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 600-603 (Sept. 2008), p. 1321-1324 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We report on the 288 V-10 V DC- DC converter circuit using AlGaN/GaN HFETs forthe first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operationwas fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistancewas 70 mohm. The breakdown voltage was over 600 V. A DC-DC down-converter from input DC288 V to output DC 10 V was fabricated using these HFETs. It was confirmed that the switchingspeed of the AlGaN/GaN HFET was faster than that of Si MOSFET. The DC-DC down-converterwas fabricated using these HFETs. This converter was composed of a full bridge circuit using fourn-channel AlGaN/GaN HFETs. In the case of AlGaN/GaN HFET, a gate switching wave (Vgs) andsource-drain wave (Vds) were abrupt compared with those of using Si MOSFETs. In both cases, astable and constant output DC 10V was also obtained and the conversion efficiency of theconverters with AlGaN/GaN HFETs was 84%
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; tissue-isolated tumor ; intratumoral injection ; drug disposition ; perfusion experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to establish an experimental system for evaluation of the intratumoral behavior of drugs after intratumoral injection using perfused tissue-isolated tumor preparations of Walker 256 carcinoma (3.46–9.73g, n = 16). Methods. We quantified the recovery of Phenol Red (model drug) in the tumor, leakage from the tumor surface and the venous outflow after intratumoral injection using perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model in which the tumor tissue was assumed to be divided into two compartments, i.e., well- and poorly-perfused regions. Results. In small tumors (Type 1, 5.42 ± 0.39 g), the drug appeared immediately in the venous outflow, and the amount remaining in the tumor tissue at 2 hr after injection was small. In contrast, the venous appearance rate reached a significantly lower peak a few minutes after injection, and a large amount of injected drug remained in some large tumors (Type 2, 8.17 ± 0.51 g). Pharmacokinetic analysis revealed that there was a correlation between tumor weight and the rate constants of transfer from the poorly-perfused region to the well-perfused region, and between the rate constants of transfer from the well-perfused region to the venous outflow and dosing ratios into the well-perfused region. Conclusions. An experimental system and analytical method were established for the evaluation of the intratumoral behavior of drugs after intratumoral injection using a tissue-isolated tumor perfusion system. This experimental system will be useful in analyzing the antitumor drug disposition after intratumoral injection.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; tissue-isolated tumor ; liposome ; emulsion ; intratumoral injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Pharmacokinetic properties of various lipid carriers (liposome and emulsions) after intratumoral injection were studied in perfusion experiments using tissue-isolated tumor preparations of Walker 256 carcinosarcoma. Methods. Four types of lipid carriers, large emulsion (254 nm), small emulsion (85 nm), neutral liposomes (120 nm) and cationic liposomes (125 nm) were prepared. We quantified their recovery from the tumor, leakage from the tumor surface and venous outflow after intratumoral injection into perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model. Results. In contrast to the small emulsion and neutral liposomes, which immediately appeared in the venous outflow perfusate following intratumoral injection, the appearance of the cationic liposomes and the large emulsion was highly restricted, clearly demonstrating that intratumoral clearance of these formulations can be greatly retarded by the cationic charge and large particle size, respectively. The venous appearance rate-time profiles were fitted to equations derived from a two-compartment model by nonlinear regression analysis. When the calculated parameters were compared among these four formulations, the venous appearance rate did not exhibit such a large difference; however, the rate of transfer from the injected site to the compartment which involves clearance by venous outflow was all very different. Conclusions. The results of this study indicate that the determining factor which alters the pharmacokinetic properties of these lipid carriers after intratumoral injection is not the rate of transfer from the interstitial space to the vascular side but the rate of intratumoral transfer from the injection site to the well-vascularized region.
    Type of Medium: Electronic Resource
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