The combustion of methane with oxygen in supercritical homogeneous aqueous fluids has been investigated and stationary diffusion flames generated to pressures of 2000 bar. A reaction autoclave with sapphire windows contains high pressure homogeneous mixtures of water and methane to 500°C. A typical mixture composition is 70 to 30 mole percent of H2O and CH4. A quasi‐circular fluid flow permits the steady injection of oxygen through a 0.5 mm nozzle at rates of 1 — 10 mm3 s−1 at constant pressures. — Above 400°C spontaneous ignition of flames occurred. The flames were observed and recorded with microscope and video camera. Emission spectra in the UV‐region were obtained and samples could be taken for analysis. Below about 400°C flame‐less oxidation is detected. The stationary diffusion flames are cone‐shaped and typically about 3 mm high. Flame examples for pressures between 300 and 2000 bar are shown. Preliminary temperatures derived from OH‐spectra are close to 3200 K. — Water can be replaced by argon.

The response of a model brain tumor system in the rat to single doses of x irradiation has been studied. Solid tumors were exposed in situ, removed, dissociated into single cells, and grown in tissue culture. The fraction of surviving clonogenic cells was determined as a function of x-ray dose level for tumors irradiated in anesthetized, air-breathing rats, and for tumors irradiated in rats killed 5 minutes prior to irradiation by nitrogen gas asphyxiation. The parameters of the survival curve for tumors irradiated in air-breathing rats were: Do = 295 rads; D, = 350 rads; and n = 3.0. Similarly, the survival parameters for tumors irradiated in nitrogen gas asphyxiated rats were: Do = 625 rads; D, = 675 rads; and n = 3.0. The survival curve of these tumor cells when assayed in in vitro tissue culture only has parameters of: Do = 225 rads; D, = 350 rads; and n = 4.7. Data from the in vivo to in vitro tumor cell survival curves suggest that there is no significant hypoxic fraction in this brain tumor. HE MALIGNANT TUMORS ARISING IN BRAINT and spinal cord are rarely curable by radiation therapy.31 T h e question of why such tumors appear so resistant to radiation treatment would appear to be a n important area of investigation. In this regard, it would be desirable to obtain information on the cellular survival characteristics of such tumors after exposure to ionizing radiation.A n experimental brain tumor model system has been d e~e l o p e d ,~ and we have used this

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