Ion lifetimes in gaseous radiolysis systems

1967 ◽  
Vol 45 (24) ◽  
pp. 3071-3078
Author(s):  
C. J. Wood ◽  
R. A. Back ◽  
D. H. Dawes
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Applied Field ◽  
Wave Period ◽  
Ion Currents ◽  
Square Wave ◽  
Dose Rates ◽  
Phase Combination

A technique is described for measuring ion lifetimes in irradiated gases. Gases were irradiated continuously, and lifetimes were determined by measuring average ion currents, obtained with an intermittent square-wave applied field, as a function of square-wave period. The dose rates, pressures, and vessel geometry were similar to those commonly used in radiolysis experiments, so that the information obtained can be applied directly to an understanding of radiolysis mechanisms. The theory of the method and analysis of ion-loss processes are discussed in some detail.Measurements in oxygen at pressures from 30 to 300 Torr and dose rates from 1.5 to 56 × 1010 eV cc−1 s−1 gave mean ion lifetimes ranging from 0.014 to 0.082 s. The dependence of lifetime on dose rate and pressure indicated that ion loss under these conditions was almost entirely by gas-phase combination. Values of α, the gas-phase combination coefficient, are compared with those measured by other methods.

Ion lifetimes in irradiated gaseous HCl

1967 ◽  
Vol 45 (24) ◽  
pp. 3079-3082 ◽  
Author(s):  
D. A. Armstrong ◽  
R. A. Back
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Gamma Rays ◽  
Half Life ◽  
Field Method ◽  
Dose Rates ◽  
Phase Combination

An intermittent-field method has been used to measure ion lifetimes in gaseous HCl during irradiation by gamma rays under conditions of pressure, dose rate, and vessel geometry similar to those employed in radiolysis studies. At 23 °C, with HCl pressures from 119 to 660 Torr and dose rates from 5.5 to 86 × 1010 eV cc−1 s−1, the ion half-life ranged from 6 to 30 ms. The dependence on dose rate and pressure strongly indicated that ion neutralization occurred almost entirely in the gas phase. Values of α, the gas-phase combination coefficient, were calculated; at pressures above 246 Torr the value was constant and equal to 3.1 ± 0.3 × 10−6 cc ions−1 s−1. The addition of SF6 had little effect on α, while reducing the temperature to −79 °C increased α to 5.1 × 10−6.

Isotope effects in the gas phase radiolysis of H2S and D2S

1976 ◽  
Vol 54 (17) ◽  
pp. 2767-2772
Author(s):  
Robert D. McAlpine ◽  
O. A. Miller ◽  
A. W. Boyd
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Isotope Effects ◽  
High Dose ◽  
Dose Rates ◽  
Kinetic Isotope ◽  
A Value ◽  
Straight Line ◽  
Separation Factors ◽  
Very High

Gas phase radiolysis studies have been carried out on mixtures of H2S and D2S using as irradiation sources, either a Gammacell or a Febetron 705 pulsed electron accelerator. Separation factors (α = (H/D)prod ÷ (H/D)react) were obtained for various values of xD (the mole fraction of D2S), dose rate and temperature, as well as with the addition of SF6. All of the observed α values, for 0.2 ≤ xD ≤ 0.8, fall on the following empirical straight line.[Formula: see text]The addition of neon to a D2S/H2S mixture gives a value of α which decreases as the partial pressure of neon increases. For a 70% D2S/30% H2S mixture, &([a-z]+); = 1.9 ± 0.1 for the pure mixture and 1.28 ± 0.08 when 90 kPa of neon has been added to 10 kPa of the mixture. The &([a-z]+); values described by eq. 1 are interpreted as arising from kinetic isotope effects in the reactions of (translationally) hot H or D atoms with H2S, HDS, or D2S to form H2, HD or D2.Hydrogen yields from the gas phase radiolysis of pure H2S and pure D2S have been determined for dose rates from 4 × 1016 to 2 × 1028 eV g−1 s−1. Using dose rates of up to 2 × 1027 eV g−1 s−1, ΔG = G(H2) − G(D2) = 0.5. For the highest dose rate used (2 × 1028 eV g−1 s−1), ΔG = 1.5. The larger value of ΔG at very high dose rates is thought to arise from the dissociative neutralization processes. A possible mechanism is discussed.

Radiation dosimetry with acetylene

1971 ◽  
Vol 24 (10) ◽  
pp. 2053
Author(s):  
KG McLaren
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
No Value ◽  
Free Radical Scavengers ◽  
Lower Yield ◽  
Γ Irradiation ◽  
Dose Rates ◽  
Wide Range ◽  
Absolute Basis ◽  
Dose Rate Effect

The suitability of acetylene as a gas-phase radiation dosimeter has been studied. Yields were obtained on an absolute basis, using ionization current dosimetry. Radiolysis of acetylene produces two products, benzene and polymer. The yield of benzene is dependent on dose, dose rate, presence of hydrogen or free radical scavengers, and temperature, and is of no value for estimating dose. ��� For 60Co γ irradiation at a dose rate of 4.1 x 1013 eV cm-3 mmHg-1 hr-1 and acetylene pressure 500 mmHg (6.6x104 N m-2) at 30�C, G(-C2H2) = 82.1�0.5. ��� 1-MeV electron irradiation at a dose rate of 3.9 x 1016 eV cm-3 mmHg-1 hr-1 gave a much lower yield, G(-C2H2) = 55.0�1.9, believed to be due to a dose rate effect. G(-C2H2) increased by about 67% when the temperature was increased from 25�C to 125-250�C. ��� Comparison with ethylene indicates the latter is the more useful dosimeter, as the yields do not vary significantly over a wide range of dose rates and temperatures.

THE EFFECT OF ELECTRIC FIELDS, AND A RELATED DEPENDENCE ON DOSE RATE, IN THE γ-RADIOLYSIS OF HYDROCARBON GASES

1963 ◽  
Vol 41 (6) ◽  
pp. 1463-1468 ◽  
Author(s):  
T. W. Woodward ◽  
R. A. Back
Keyword(s):  
Dose Rate ◽  
Gas Phase ◽  
Electric Fields ◽  
Low Dose ◽  
High Dose ◽  
Hydrogen Yield ◽  
Hydrocarbon Gases ◽  
Saturation Field ◽  
Dose Rates ◽  
And Diffusion

The effect of electric fields on the γ-radiolysis of ethane, propane, and the butanes has been investigated briefly at 800 mm pressure, with dose rates between 2 × 1010 and 400 × 1010 ev/cc sec. Yields of hydrogen were reduced when a saturation field was applied, except with ethane at low dose rate, where a slight increase in hydrogen yield was observed. With propane and n-butane, the yield of hydrogen in the presence of a saturation field was independent of dose rate, while with ethane, it decreased with decreasing dose rate. At the same time, a dose rate dependence was discovered in the simple radiolysis, in the absence of any field, of ethane, propane, and n-butane, a decrease in the yield of hydrogen at low dose rates being observed. An explanation of these observations is suggested in terms of a competition between neutralization of ions in the gas phase and diffusion of ions to the wall. High dose rates should favor the former process, and low dose rates the latter. At sufficiently high dose rates, all ions should be neutralized in the gas phase. At sufficiently low dose rates, all ions should diffuse to the wall before neutralization, and it is suggested that the radiolysis under these conditions should closely resemble that in the presence of a saturation field at higher dose rates.

scholarly journals Radiation Awareness for Endovascular Abdominal Aortic Aneurysm Repair in the Hybrid Operating Room: An Instant Operator Risk Chart for Daily Practice

2021 ◽  
pp. 152660282110074
Author(s):  
Quirina M. B. de Ruiter ◽  
Frans L. Moll ◽  
Constantijn E. V. B. Hazenberg ◽  
Joost A. van Herwaarden
Keyword(s):  
Radiation Dose ◽  
Dose Rate ◽  
Effect Size ◽  
Radiation Risk ◽  
Dose Limit ◽  
Access Site ◽  
Femoral Access ◽  
Dose Rates ◽  
Rate Prediction ◽  
Operator Dose

Introduction: While the operator radiation dose rates are correlated to patient radiation dose rates, discrepancies may exist in the effect size of each individual radiation dose predictors. An operator dose rate prediction model was developed, compared with the patient dose rate prediction model, and converted to an instant operator risk chart. Materials and Methods: The radiation dose rates (DRoperator for the operator and DRpatient for the patient) from 12,865 abdomen X-ray acquisitions were selected from 50 unique patients undergoing standard or complex endovascular aortic repair (EVAR) in the hybrid operating room with a fixed C-arm. The radiation dose rates were analyzed using a log-linear multivariable mixed model (with the patient as the random effect) and incorporated varying (patient and C-arm) radiation dose predictors combined with the vascular access site. The operator dose rate models were used to predict the expected radiation exposure duration until an operator may be at risk to reach the 20 mSv year dose limit. The dose rate prediction models were translated into an instant operator radiation risk chart. Results: In the multivariate patient and operator fluoroscopy dose rate models, lower DRoperator than DRpatient effect size was found for radiation protocol (2.06 for patient vs 1.4 for operator changing from low to medium protocol) and C-arm angulation. Comparable effect sizes for both DRoperator and DRpatient were found for body mass index (1.25 for patient and 1.27 for the operator) and irradiated field. A higher effect size for the DRoperator than DRpatient was found for C-arm rotation (1.24 for the patient vs 1.69 for the operator) and exchanging from femoral access site to brachial access (1.05 for patient vs 2.5 for the operator). Operators may reach their yearly 20 mSv year dose limit after 941 minutes from the femoral access vs 358 minutes of digital subtraction angiography radiation from the brachial access. Conclusion: The operator dose rates were correlated to patient dose rate; however, C-arm angulation and changing from femoral to brachial vascular access site may disproportionally increase the operator radiation risk compared with the patient radiation risk. An instant risk chart may improve operator dose awareness during EVAR.

Kinetics of DNA Repair Under Chronic Irradiation at Low and Medium Dose Rates in Repair Proficient and Repair Compromised Normal Fibroblasts

2021 ◽  
Author(s):  
Elena K. Zaharieva ◽  
Megumi Sasatani ◽  
Kenji Kamiya
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dose Rate ◽  
Dose Response ◽  
Chronic Irradiation ◽  
Dose Rates ◽  
Chronic Radiation ◽  
Damage Repair ◽  
Kinetics Of ◽  
Medium Dose

We present time and dose dependencies for the formation of 53BP1 and γH2AX DNA damage repair foci after chronic radiation exposure at dose rates of 140, 250 and 450 mGy/day from 3 to 96 h, in human and mouse repair proficient and ATM or DNA-PK deficient repair compromised cell models. We describe the time/dose-response curves using a mathematical equation which contains a linear component for the induction of DNA damage repair foci after irradiation, and an exponential component for their resolution. We show that under conditions of chronic irradiation at low and medium dose rates, the processes of DNA double-strand breaks (DSBs) induction and repair establish an equilibrium, which in repair proficient cells manifests as a plateau-shaped dose-response where the plateau is reached within the first 24 h postirradiation, and its height is proportionate to the radiation dose rate. In contrast, in repair compromised cells, where the rate of repair may be exceeded by the DSB induction rate, DNA damage accumulates with time of exposure and total absorbed dose. In addition, we discuss the biological meaning of the observed dependencies by presenting the frequency of micronuclei formation under the same irradiation conditions as a marker of radiation-induced genomic instability. We believe that the data and analysis presented here shed light on the kinetics of DNA repair under chronic radiation and are useful for future studies in the low-to-medium dose rate range.

scholarly journals Serum Metabolomic Alterations Associated with Cesium-137 Internal Emitter Delivered in Various Dose Rates

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 270
Author(s):  
Heng-Hong Li ◽  
Yun-Tien Lin ◽  
Evagelia C. Laiakis ◽  
Maryam Goudarzi ◽  
Waylon Weber ◽  
...  
Keyword(s):  
Dose Rate ◽  
Cumulative Dose ◽  
Low Dose ◽  
Biological Effects ◽  
Serum Samples ◽  
Dose Rates ◽  
Sphingosine 1 Phosphate ◽  
Cesium 137 ◽  
Dose Rate Effect ◽  
Medium Dose

Our laboratory and others have use radiation metabolomics to assess responses in order to develop biomarkers reflecting exposure and level of injury. To expand the types of exposure and compare to previously published results, metabolomic analysis has been carried out using serum samples from mice exposed to 137Cs internal emitters. Animals were injected intraperitoneally with 137CsCl solutions of varying radioactivity, and the absorbed doses were calculated. To determine the dose rate effect, serum samples were collected at 2, 3, 5, 7, and 14 days after injection. Based on the time for each group receiving the cumulative dose of 4 Gy, the dose rate for each group was determined. The dose rates analyzed were 0.16 Gy/day (low), 0.69 Gy/day (medium), and 1.25 Gy/day (high). The results indicated that at a cumulative dose of 4 Gy, the low dose rate group had the least number of statistically significantly differential spectral features. Some identified metabolites showed common changes for different dose rates. For example, significantly altered levels of oleamide and sphingosine 1-phosphate were seen in all three groups. On the other hand, the intensity of three amino acids, Isoleucine, Phenylalanine and Arginine, significantly decreased only in the medium dose rate group. These findings have the potential to be used in assessing the exposure and the biological effects of internal emitters.

scholarly journals Investigation of dose-rate effects and cell-cycle distribution under protracted exposure to ionizing radiation for various dose-rates

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Yusuke Matsuya ◽  
Stephen J. McMahon ◽  
Kaori Tsutsumi ◽  
Kohei Sasaki ◽  
Go Okuyama ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Ionizing Radiation ◽  
Dose Rate ◽  
Cell Cycle Distribution ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects

scholarly journals Sinusoidal voltage protocols for rapid characterisation of ion channel kinetics

2017 ◽  
Author(s):  
Kylie A. Beattie ◽  
Adam P. Hill ◽  
Rémi Bardenet ◽  
Yi Cui ◽  
Jamie I. Vandenberg ◽  
...  
Keyword(s):  
Ion Channel ◽  
Voltage Clamp ◽  
Ion Current ◽  
Ion Currents ◽  
Channel Kinetics ◽  
Sinusoidal Voltage ◽  
Square Wave ◽  
Voltage Clamps ◽  
Ion Channel Kinetics ◽  
Cell Cell

AbstractUnderstanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics — the voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fit a mathematical model to currents evoked by a novel 8 second sinusoidal voltage clamp in CHO cells over-expressing hERG1a. The model is then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step voltage clamps, and also a novel voltage clamp comprised of a collection of physiologically-relevant action potentials. We demonstrate that we can make predictive cell-specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell-cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches.Table of Contents CategoryTechniques for Physiology1Key PointsIon current kinetics are commonly represented by current-voltage relationships, time-constant voltage relationships, and subsequently mathematical models fitted to these. These experiments take substantial time which means they are rarely performed in the same cell.Rather than traditional square-wave voltage clamps, we fit a model to the current evoked by a novel sum-of-sinusoids voltage clamp that is only 8 seconds long.Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions.The new model predicts the current under traditional square-wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically-relevant series of action potential clamps is predicted extremely well.The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell-cell variability in current kinetics for the first time.

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