scholarly journals Significant changes in yields of 7-hydroxy-coumarin-3-carboxylic acid produced under FLASH radiotherapy conditions

RSC Advances ◽  
2020 ◽  
Vol 10 (63) ◽  
pp. 38709-38714
Author(s):  
Tamon Kusumoto ◽  
Hisashi Kitamura ◽  
Satoru Hojo ◽  
Teruaki Konishi ◽  
Satoshi Kodaira
Keyword(s):  
Carboxylic Acid ◽  
Dose Rate ◽  
Oxygen Depletion ◽  
Conventional Condition ◽  
Hydroxy Coumarin

Yield of 7-hydroxy-coumarin-3-carboxylic acid (7OH–C3CA) significantly decreases at FLASH condition with the dose rate of >40 Gy s−1, compared to that at conventional condition of 0.05 Gy s−1, due to the oxygen depletion in the solution.

scholarly journals A Computational Model for Oxygen Depletion Hypothesis in FLASH Effect

2021 ◽  
Author(s):  
Ankang Hu ◽  
Rui Qiu ◽  
Zhen Wu ◽  
Hui Zhang ◽  
Wei Bo Li ◽  
...  
Keyword(s):  
Computational Model ◽  
Dose Rate ◽  
Oxygen Concentration ◽  
Microvessel Density ◽  
Oxygen Depletion ◽  
Oxygen Distribution ◽  
Resistance Level ◽  
Negative Exponential Function ◽  
Normal Tissues ◽  
Negative Exponential

Experiments have reported low normal tissue toxicities during FLASH irradiation, but the mechanism has not been elaborated. Several hypotheses have been proposed to explain the mechanism. One hypothesis is oxygen depletion. We analyze the time-dependent change of oxygen concentration in the tissue to study the oxygen depletion hypothesis using a computational model. The effects of physical, chemical and physiological parameters on oxygen depletion were explored. The kinetic equation of the model is solved numerically using the finite difference method with rational boundary conditions. Results of oxygen distribution is supported by the experiments of oxygen-sensitivity electrodes and experiments on the expression and distribution of the hypoxia-inducible factors. The analysis of parameters shows that the steady-state oxygen distribution before irradiation is determined by the oxygen consumption rate of the tissue and the microvessel density. The change of oxygen concentration after irradiation has been found to follow a negative exponential function, and the time constant is mainly determined by the microvessel density. The change of oxygen during exposure increases with dose rate and tends to be saturated because of oxygen diffusion. When the dose rate is high enough, the same dose results in the same reduction of oxygen concentration regardless of dose rate. The analysis of the FLASH effect in the brain tissue based on this model does not support the explanation of the oxygen depletion hypothesis. The oxygen depletion hypothesis remains controversial because the oxygen in most normal tissues cannot be depleted to radiation resistance level by FLASH irradiation.

scholarly journals Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

2021 ◽  
Author(s):  
Jörg Pawelke ◽  
Michael Brand ◽  
Stefan Hans ◽  
Katalin Hideghéty ◽  
Leonhard Karsch ◽  
...  
Keyword(s):  
Dose Rate ◽  
Radiation Damage ◽  
Oxygen Depletion ◽  
Zebrafish Embryos ◽  
Electron Dose

Low-temperature annealing of YBa2Cu3O7-x

1992 ◽  
Vol 50 (1) ◽  
pp. 88-89
Author(s):  
R.L. Sabatini ◽  
Yimei Zhu ◽  
Masaki Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Oxygen Diffusion ◽  
Diffusion Rate ◽  
Oxygen Depletion ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Microstructural Effects ◽  
Oxygen Diffusion Rate

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.

Fibrinolytic Activity of Cerebro-Spinal Fluid and the Development of Artificial Cerebral Haematomas in Dogs

1969 ◽  
Vol 21 (02) ◽  
pp. 294-303 ◽  
Author(s):  
H Mihara ◽  
T Fujii ◽  
S Okamoto
Keyword(s):  
Cerebrospinal Fluid ◽  
Carboxylic Acid ◽  
Fibrinolytic Activity ◽  
Clinical Implications ◽  
Trans Form ◽  
Plate Method ◽  
Blood Samples ◽  
Fibrin Plate ◽  
The Brain

SummaryBlood was injected into the brains of dogs to produce artificial haematomas, and paraffin injected to produce intracerebral paraffin masses. Cerebrospinal fluid (CSF) and peripheral blood samples were withdrawn at regular intervals and their fibrinolytic activities estimated by the fibrin plate method. Trans-form aminomethylcyclohexane-carboxylic acid (t-AMCHA) was administered to some individuals. Genera] relationships were found between changes in CSF fibrinolytic activity, area of tissue damage and survival time. t-AMCHA was clearly beneficial to those animals given a programme of administration. Tissue activator was extracted from the brain tissue after death or sacrifice for haematoma examination. The possible role of tissue activator in relation to haematoma development, and clinical implications of the results, are discussed.

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