[en] To assess the effects of incorporation of a CF₂ group into the side chain of a 2-nitroimidazole derivative, the authors evaluated the in vitro and in vivo radiosensitizing activities of KU-2285 (a 2-nitroimidazole derivative with an N₁-substituent of -CH₂CF₂CONH(CH₂)nOH) and its related compounds in comparison with those of comparable nonfluorinated compounds. The pharmacokinetics of these compounds in murine tumors was also tested. KU-2285, KU-3202, and KU-3207 are fluorinated 2-nitroimidazole derivative compounds with similar structures. Etanidazole (a 2-nitroimidazole derivative with an N₁-substituent of -CH₂CONH(CH₂)nOH) and its related compounds, KU-3205 and KU-3206 were also tested. The in vivo radiosensitizing activities of each compound for hypoxic cells was evaluated with a standard colony formation method. The in vivo radiosensitizing activities of these compounds were tested in female C3H/He mice bearing SCCVII tumors using an in vivo/in vitro clonogenic assay. The pharmacokinetic studies were performed in C3H/He mice bearing the SCCVII tumor. Samples were analyzed by reversed-phase high-performance liquid chromatography. The in vitro radiosensitizing activities of fluorinated 2-nitroimidazoles were higher than those of the nonfluorinated compounds. Although the in vivo radiosensitizing activity of KU-2285 was higher than that of etanidazole, other fluorinated 2-nitroimidazoles showed less radiosensitizing activity than the comparable nonfluorinated compounds. The compound was eliminated from serum more rapidly with the increase in the number of CH₂ group in the side chain of the compound in each series. Although the in vitro sensitizing activity of the fluorinated compounds was higher than that of the comparable nonfluorinated compounds, the in vivo radiosensitizing activity of all fluorinated compounds but KU-2285 was lower than that of comparable etanidazole group compounds. 8 refs., 2 figs., 1 tab

[en] Because reoxygenation of solid tumors after irradiation with a hypoxic cell sensitizer has never previously been investigated, the authors assessed the reoxygenation in SCCVII tumors after treatment with KU-2285 plus single or fractionated irradiation. KU-2285 (100 mg/kg) was injected intraperitoneally into C3H mice bearing 1-cm SCCVII tumors at 30 min before a single dose of 12 Gy or three fractions of 5 Gy at 12 h intervals. Changes of the hypoxic fraction (HF) were then evaluated by the paired survival curve method. Since the radiosensitizing effect of KU-2285 was relatively persistent, the HF was only evaluable after 6 h of irradiation. The HF of untreated SCCVII tumors was 9.1%. After treatment with KU-2285 and 12 Gy, the HF was 25% at 6 h, 32% at 12 h, 24% at 24 h, and 7.6% at 72 h. The HF was lower at 6 h than that after radiation alone, but was similar at later periods. After three fractions of 5 Gy with or without KU-2285, the HF was 33% at 6 h in both groups, while it was 12% and 13% at 24 h for tumors pretreated with KU-2285 and those receiving radiation alone, respectively. However, a sensitizing effect of KU-2285 was indicated by the downward shift of the survival curves for tumors irradiated after exposure to this agent. Reoxygenation occurred quite efficiently in tumors receiving KU-2285 and 12 Gy. After fractionated irradiation, however, reoxygenation was similar in the KU-2285-pretreatment and irradiation alone groups. 11 refs., 4 figs

No abstract available

[en] In a clinical trial in which a 2-nitroimidazole radiosensitizer was administered repeatedly, the dose-limiting toxicity was found to be peripheral neuropathy. In the present study, the in vivo radiosensitizing activity of KU-2285 in combination with radiation dose fractionation, and the pharmacokinetics of cumulative dosing of KU-2285 in the peripheral nerves were examined. The ability of three nitroimidazoles, misonidazole (MISO), etanidazole (SR-2508) and KU-2285, to sensitize SCCVII tumors to radiation treatment has been compared for drug doses in the range 0-200 mg/kg. Single radiation doses or two different fractionation schedules (6 Gy/fractions x three fractions/48 h or 5 Gy/fractions x five fractions/48 h) were used; the tumor cell survival was determined using an in vivo/in vitro colony assay. The pharmacokinetics in the sciatic nerves were undertaken, when KU-2285 or etanidazole were injected at a dose of 200 mg/kg intravenously one, two, three, or four times at 2-h intervals. At less than 100 mg/kg, KU-2285 sensitized SCCVII tumors more than MISO and SR-2508 by fractionated irradiation. Evaluation of pharmacokinetics in the peripheral nerves showed that the apparent biological half-life of SR-2508 increased with the increases in the number of administrations, whereas that of KU-2285 became shorter. Since most clinical radiotherapy is given in small multiple fractions, KU-2285 appears to be a hypoxic cell radiosensitizer that could be useful in such regimens, and that poses no risk of chronic peripheral neurotoxicity. 12 refs., 5 figs., 1 tab

[en] The title compound (enol-hexafluoroacetylacetone) has an isotopic fractionation factor of 0.6 +- 0.1. This, and much other information about this compound, can be rationalized if the enolic hydrogen bridges between the two oxygens and is governed by a double minimum potential function with a central maximum of approx. 3000 cm^-1 (8 kcal/mol)

[en] Polyvinylidene fluoride or PVDF is a flexible, thin piezo film and long chain semicrystalline polymer containing repeated of CH/sub 2/ - CH/sub 2/. In order to obtain desired piezoelectric properties PVDF is poled by subjecting it to high electric field. In poled PVDF piezoelectric constants have different values for each axis and one constant per axis. PVDF polymer exhibits generator and motor action. Usually 1000 A /sup o/ thick vacuum-deposited aluminum electrodes are formed on both sides of the sheet. Polymer material of PVDF can be used as a sensing element with temperature range of -40 /sup 0/ C to 100 /sup 0/C and a frequency range of 10/sup -3/ to 10/sup -9/ Hz. This paper includes as experimental observation of exciting aluminium open-ended tube at its resonance using PVDF transducer and maintained in this condition using phase lock loop or PLL. The tube is free to resonate when 9-micrometer thin polyvinylidene fluoride transducer is energized. It is observed that a film of such material can easily be used to produced the requisite vibrations in the tube. (author)

[en] One hydrocarbon-based and two fluorocarbon-based magnetic fluid samples were tested under four different vacuum levels. The weight losses of the samples were measured and the evaporation rates calculated. It was found that under higher vacuum levels (lower pressure levels) the evaporation rate of each sample was significantly higher than under atmospheric conditions, gradually reaching a saturated level while the vacuum level kept increasing. The Langmuir equation is modified to theoretically explain this phenomenon. It was also found that the fluorocarbon-based magnetic fluids are more suitable for ultra-high-vacuum applications

No abstract available

[en] The influence of fluorobenzenes on the formation of o-Ps in the nonpolar benzene, 2,2,4-trimethylpentane and cyclohexane has been studied. In the fluorobenzene-cyclohexane system most of the additives give rise to a powerful enhancement of the o-Ps yield compared to pure solvent. This promoting behaviour of the substrates becomes much less pronounced in the other two solvents investigated. o-C₆H₄F₂ is the only additive which behaves as a typical inhibitor of o-Ps formation. The results are discussed in terms of existing models for formation of positronium. (Auth.)

[en] The temperature dependence of the low-energy electron attachment and autodetachment processes for c-C₄F₆ in a N₂ buffer gas has been studied in the temperature, T, range of 300 to 600 K and the mean electron energy, <ε>, range from 0.19 to 1.0 eV. The low-energy electron attachment rate constant for c-C₄F₆ shows only a slight dependence on gas temperature. In contrast, the autodetachment frequency increases by more than four orders of magnitude when T is increased from 300 to 600 K. This increase in autodetachment is due to the increase in the internal energy content of the c-C₄,F₆^- anion with increasing T. The autodetachment process under consideration is a heat-activated process and has an activation energy E* of 0.24 eV. Significance of these results to gaseous dielectrics is indicated