PubMed · 3452465
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H Deconinck, J Libert. 1986. Fiber optic endolaser.. https://pubmed.ncbi.nlm.nih.gov/3452465/
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The use of an ion trap mass spectrometer with three different membrane inlet probes is described. Two methods of removing water from the sample are compared. One is the use of a PTFE-silicone rubber double membrane, PTFE is relatively impermeable to water and so reduces the amount entering with the gas sample (Probe A). The second is the use of a silicone rubber membrane covered long probe, which condenses water out of the sample (Probe B). Response times (100%) for dissolved N2O, O2, Ar and CO2 without He in the chamber vary from between 158 and 684 s with Probe A. For the same probe with He, the response times were between 283 and 551 s. In the gas phase response times were between 99 and 153 s with He and 117 and 122 s without He. Probe B had 100% response of between 122 and 152 s for dissolved gases. Further extension of the probe by 2 m slowed response times as did increasing the ionisation time. Response times for Probe B increased to between 99 and 340 s when ionisation time increased from 1000 to 24,930 microseconds. Plots of output against concentration showed the steepest line of response for the short single membrane covered probe with 1000 microseconds ionisation time. Increasing the ionisation time, extending the probe and the use of a double membrane all reduced the gradient of output against concentration for every gas tested. In an intact sediment core, concentrations of O2, N2O and CO2 rose at the start and the concentration of N2 fell. As the disturbed sediment settled, this was reversed. The initial increase in O2 concentration stimulated respiration and inhibited the final pathway in dentrification producing higher concentrations of N2O and reducing the concentration of N2.
Based on the observed cytoprotective effect of the intracellularly permeable radical scavenger cysteamine (+NH3CH2CH2SH) in cells exposed to ultrasound and the lack of protection by its oxidized cell-nonpermeable form, cystamine (+NH3CH2CH2S-SCH2CH2NH3+), it was suggested that inertial cavitation (the growth of small gas bubbles present in the liquid exposed to ultrasound and their subsequent violent collapse) and associated free radical production may occur intracellularly (Radiat. Res. 89:369; 1982). Here we demonstrate that high concentrations (> 10 mM) of the thiol cysteamine effectively lower H2O2 yields following ultrasound exposure in argon- and air-saturated phosphate buffered saline (PBS), while cystamine is less effective under argon and practically without effect in air-saturated PBS. Direct removal of H2O2 by cysteamine is the dominant mechanism while scavenging of the H2O2 precursors .OH and superoxide plays a lesser role. Since H2O2 is a known cytotoxic species capable of penetrating cells if produced extracellularly, these results offer an alternative hypothesis for the protective effect of cysteamine and the lack of protection by cystamine, based on their differential ability to lower ultrasound-dependent H2O2 yields, without the necessity of invoking intracellular cavitation.
The application of neutron emitting radioisotopes in brachytherapy facilitates the use of the higher biological effectiveness of neutrons compared to photons in treating some cancers. Different types of high intensity 252Cf sources are in use for the treatment of different cancers. To improve the therapy of bulky tumors the dose can be augmented by the additional use of the boron capture reaction of thermal neutrons. This requires information about the thermal neutron dose component around the Cf source. In this work, a Mg/Ar-ionization chamber internally coated with 10B was used to measure the thermal neutrons. These measurements were performed on two different 252Cf sources, one in use in the Gershenson Radiation Oncology Center at Harper Hospital in Detroit, MI, and one at the University Hospital of Chiang Mai in Chiang Mai, Thailand. The results of these measurements are compared and indicate that the differences in the construction of the sources influence the thermal dose component.