Evaluation of Air-Kerma and Absorbed Dose to Water for External Radiotherapy Beam Using Ionization Chamber

Radiotherapy is the most widely applied oncologic treatment modality utilizing ionizing radiation. A high degree of accuracy, reliability and reproducibility is required for a successful treatment outcome. Measurement using ionization chamber is a prerequisite for absorbed dose determination for external beam radiotherapy. Calibration coefficient is expressed in terms of air kerma and absorbed dose to water traceable to Secondary Standards Dosimetry Laboratory. The objective of this work was to evaluate the level of accuracy of ionization chamber used for clinical radiotherapy beam determination. Measurement and accuracy determination were carried out according to IAEA TRS 398 protocol. Clinical farmers type ionization chamber measurement and National Reference standard from Secondary Standards Dosimetry Laboratory were both exposed to cobalt-60 beam and measurement results compared under the same environmental conditions. The accuracy level between National Reference Standard and clinical radiotherapy standard was found to be −1.92% and −2.02% for air kerma and absorbed dose to water respectively. To minimize the effect of error and maximize therapeutic dose during treatment in order to achieve required clinical outcome, calibration factor was determined for air kerma (Nk) as 49.7 mGy/nC and absorbed dose to water ND, as 52.9 mGy/nC. The study established that radiotherapy beam measurement chain is prone to errors. Hence there is a need to independently verify the accuracy of radiation dose to ensure precision of dose delivery. The errors must be accounted for during clinical planning by factoring in calibration factor to minimize the systematic errors during treatment, and thereby providing enough room to achieve ±5% dose delivery to tumor target as recommended by ICRU.

Mechanism and Method of Testing Fracture Toughness and Impact Absorbed Energy of Ductile Metals by Spherical Indentation Tests

To address the problem of conventional approaches for mechanical property determination requiring destructive sampling, which may be unsuitable for in-service structures, the authors proposed a method for determining the quasi-static fracture toughness and impact absorbed energy of ductile metals from spherical indentation tests (SITs). The stress status and damage mechanism of SIT, mode I fracture, Charpy impact tests, and related tests were frst investigated through fnite element (FE) calculations and scanning electron microscopy (SEM) observations, respectively. It was found that the damage mechanism of SITs is diferent from that of mode I fractures, while mode I fractures and Charpy impact tests share the same damage mechanism. Considering the diference between SIT and mode I fractures, uniaxial tension and pure shear were introduced to correlate SIT with mode I fractures. Based on this, the widely used critical indentation energy (CIE) model for fracture toughness determination using SITs was modifed. The quasi-static fracture toughness determined from the modifed CIE model was used to evaluate the impact absorbed energy using the dynamic fracture toughness and energy for crack initiation. The efectiveness of the newly proposed method was verifed through experiments on four types of steels: Q345R, SA508-3, 18MnMoNbR, and S30408.

XPS study of surface absorbed oxygen of ABO_3 mixed oxides

Perovskite-type complex oxides ABO3 （A=Sr, La; B=Mn, Fe, Co） were prepared by citric acid method. The degradation of water-solubilized dyes was carried out using the mixed oxides as photocatalyst. The surface absorbed oxygen was analyzed using X-ray photoelectron spectroscopy （XPS）. The results indicated that there was a relationship between the photocatalytic activity and the content of the surface absorbed oxygen. The higher the content of the surface absorbed oxygen was, the better the performance of the photocatalyst.

Transferability of Charpy Absorbed Energy to Fracture Toughness Based on Weibull Stress Criterion

The relationship between Charpy absorbed energy and the fracture toughness by means of the (crack tip opening displacement (CTOD)) method was analyzed based on the Weibull stress criterion. The Charpy absorbed energy and the fracture toughness were measured for the SN490B steel under the ductile-brittle transition temperature region. For the instrumented Charpy impact test, the curves between the loading point displacement and the load against time were recorded. The critical Weibull stress was taken as a fracture controlled parameter, and it could not be affected by the specimen configuration and the loading pattern based on the local approach. The parameters controlled brittle fracture are obtained from the Charpy absorbed energy results, then the fracture toughness for the compact tension (CT) specimen is predicted. It is found that the results predicted are in good agreement with the experimental. The fracture toughness could be evaluated by the Charpy absorbed energy, because the local approach gives a good description for the brittle fracture even though the Charpy impact specimen or the CT specimen is used for the given material.

The Effect of the Size of Radiotherapy Photon Beams on the Absorbed Dose to an Al_2O_3 Dosimeter

The effect of the size of radiotherapy photon beams on the absorbed dose to an Al2O3 dosimeter was investigated using the Monte Carlo method. The EGSnrc/DOSRZnrc program code was used to simulate the absorbed dose to the Al2O3 dosimeter, as well as the absorbed dose to water at the corresponding position in the absence of the dosimeter. The incident beams were 60Co γ and 6 MV with a different beam radius ranging from 0.1 cm to 2 cm. Results revealed that the absorbed dose ratio factor depends on the size of the incident photon beam. When the radius of the incident beam is smaller than that of the dosimeter, the absorbed dose ratio factor decreases as the incident beam size increases. The absorbed dose ratio factor reaches its minimum when the radius of the incident beam is almost the same as that of the dosimeter. When the radius of the incident beam is larger than that of the dosimeter, the absorbed dose ratio factor increases as the incident beam size increases. The maximum difference among these absorbed dose ratio factors can be up to 14% in 60Co γ beams and 23% in 6 MV beams. However, when the size of the incident beam is much larger than that of the dosimeter, the effect of the incident beam size on the absorbed dose ratio factor becomes quite small. The maximum discrepancy between the absorbed dose ratio factors and the average value is not more than 1%.

DETERMINATION OF SUPERFICAL ABSORBED DOSE FROMEXTERNAL EXPOSURE OF WEAKLY PENETRATING RADEATIONS

The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported. The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D (0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.

Ensuring Uniformity of Measurements of Absorbed Doses of Intensive Photon and Electron Radiation in Radiation Technologies

Ensuring reliability and traceability of the unit of absorbed dose of intense photon and electron radiation, used in radiation technologies in industry, is based on the creation of a system of sample measures and methods of transmission with minimal loss of dimensional accuracy of the unit of absorbed dose from the sample tools to working dosimeters and is a necessary basis of yield growth, of increase of labour productivity and the introduction of innovative products. The measuring capabilities of the State primary special standard of power unit of absorbed dose of intensity photon, electron and beta radiation for radiation technologies and of the standards of the absorbed dose of photon and electron radiation, used for radiation monitoring of radiation pro- cesses.

Improvement of Impact Absorbed Energy of CFRPs on Adding the Nanoparticles into Epoxy Resins

The present study investigates the effect of the addition of nanoparticles into epoxy resins as the matrix on the impact absorbed energy of CFRP （carbon fiber reinforced polymer）. Impact absorbed energy is one of the main properties to evaluate the CFRP＇s performance for transportation and aerospace structures. Two types of nanoparticle, namely nanofibers and nano-silica beads, were added into the epoxy resin to improve the impact absorption capacity of the CFRP. Two modified additives and conventional epoxy resins were quantitatively compared. The impact test results showed that impact absorbed energy for nanofibers was higher than nano-silica beads, and nanofibers as the additive promoted about 11% of impact absorbed energy compared with neat epoxy resin.

Government Subsidies and Enterprise Innovation:Moderation Effect of Absorbed Slack

It is worth studying whether enterprises receiving government subsidies can transform them into innovative achievements under the constraints of enterprise resources.The data from the three industries of electronics,pharmaceuticals,and information technology during 2013-2016 were empirical tested to verify the moderating effect of the absorbed slack on the relationship between government subsidies and enterprise innovation.The results show that government subsidies can promote enterprise innovation;absorbed slack promotes enterprise innovation;the absorbed slack of enterprises plays a positive moderation role in the relationship between government subsidy and enterprise innovation.In other words,the enterprises with high absorbed slack can promote the innovation of enterprises by government subsidies.The conclusions provide theoretical guidance for government departments to select the most suitable enterprises which accept innovative subsidies.

International Recommendations on Calculation of Absorbed Dose in Biota:A Comprehensive Revue

Since the early times, radioprotection has been focused on the human being. Currently this approach has changed, being now also necessary to take care of the protection of the environment from unwanted effects of ionizing radiation. To this end, several institutions (UNSCEAR, ICRP, IAEA, DOE, ACRP) and consortia of institutions (FASSET, ERICA) have established procedures in order to protect the biota of such effects. Developed procedures are based on the calculation of the absorbed dose in biota (ICRP, DOE, IAEA), or on environmental risk assessment―ERA (DOE, ACRP, FASSET, ERICA);but even in this latter approach the parameters used are related to the absorbed doses in biota. The calculation of dose is the standard procedure in human radioprotection, and this points such an approach as the most interesting for providing a convergence between human and nonhuman (= biota) radioprotections. On the other hand, the ERA approach is easier to apply, because this methodology is used in several countries for non-radioactive contamination assessments. Since the world radioprotection system follows a number of institutions (UNSCEAR, ICRP, IAEA and regulatory institutions of member countries) that use dose calculation, this appears to be the way for biota radioprotection. We here review and comment the evolution of the concepts and approaches of the recommendations for radioprotection of non-human biota.

Capacity and degree of iodine absorbed and enriched by vegetable from soil

To understand the biogeochemical transfer of iodine, the absorbability and bioaccumulation of iodine in tested vegetables(radish, spinach and Chinese cabbage) are examined by applying iodic fertilizer composed of kelp and diatomaceous earth. The experimental results show that when iodine in soil is not excessive, the concentrations of iodine in tested vegetables increase as the content of iodine in soil increases. The absorbability and enrichment degree of iodine in various vegetables and in various parts of the same vegetable are different, which explains that the concentration of iodine in plant is determined by the plant type and the physiological action of plant. The patience order of tested vegetables to excessive iodine is Chinese cabbage>spinach>radish. These results have theoretical and practical significance in opening up a new way for ameliorating poor iodine environment with artificial means.

Promising Ultraviolet Absorbers——Novel Guanine Analogs Having Significantly Improved Ultraviolet Absorption Capacity and Dissipating the Energy of Absorbed Photons by Nonradiative Decay Mechanism

Structural properties of nucleobase underlie their ultrafast excited-state dynamics and low fluorescence quantum yields, which cause effectively nonradiative decay process and render them like sunscreens. Thus, eight guanine analogs[N-2-（2＇-nitrobenzoyl）-guanine, N-2-（3＇-nitrohenzoyl）-guanine, N-2-（4＇-nitrobenzoyl）-guanine, N-2-（2＇-hydroxybenzoyl）-guanine, N-2-（4＇-methoxylbenzoyl）-guanine, N-2-（4＇-chloricbenzoyl）-guanine, N-2-（4＇- me- thylicbenzoyl）-guanine and N-2-（3＇,5＇-dinitrobenzoyl）-guanine] with different substituted benzoyls, except N-2-（4＇-chloricbenzoyl）-guanine, were newly synthesized. In contrast with guanine, they exhibit wider ultraviolet absorbent range, higher molar extinction coefficient and lower fluorescence intensity.

Maximizing the Absorbed Power of A Point Absorber Using An FA-Based Optimized Model Predictive Control

This paper presents an extended model predictive controller for maximizing the absorbed power of a point absorber wave energy converter. Owing to the great influence of controller parameters upon the absorbed power, the optimization of these parameters is carried out for the first time by a firefly algorithm(FA). Error, the difference between output velocity of buoy and input wave speed which leads to power maximization in the optimized MPC is compared with the classical MPC. Simulation results indicate that given the high accuracy and acceptable speed of the algorithm, it can adjust the parameters of the controller to the point where system error decreased effectively and the absorbed energy increased about 4 MW.

Absorbed Bioactive Compounds Replicate GuanxinⅡ-Induced Endothelium-Associated in/ex vivo Vasodilation

Objective:To develop an interference-free and rapid method to elucidate GuanxinⅡ(GXⅡ)'s representative vasodilator absorbed bioactive compounds(ABCs)among enormous phytochemicals.Methods:The contents of ferulic acid,tanshinol,and hydroxysafflor yellow A(FTA)in GXⅡ/rat serum after the oral administration of GXⅡ(30 g/kg)were detected using ultra-performance liquid chromatography-mass spectrometry.Totally 18 rats were randomly assigned to the control group(0.9%normal saline),GXⅡ(30 g/kg)and FTA(5,28 and 77 mg/kg)by random number table method.Diastolic coronary flow velocity-time integral(VTI),i.e.,coronary flow or coronary flow-mediated dilation(CFMD),and endothelium-intact vascular tension of isolated aortic rings were measured.After 12 h of exposure to blank medium or 0.5 mmol/L H_(2)O_(2),endothelial cells(ECs)were treated with post-dose GXⅡof supernatant from deproteinized serum(PGSDS,300μL PGSDS per 1 m L of culture medium)or FTA(237,1539,and 1510 mg/m L)for 10 min as control,H_(2)O_(2),PGSDS and FTA groups.Nitric oxide(NO),vascular endothelial growth factor(VEGF),endothelin-1(ET-1),superoxide dismutase(SOD),malondialdehyde(MDA)and phosphorylated phosphoinositide 3 kinase(p-PI3K),phosphorylated protein kinase B(p-AKT),phosphorylated endothelial nitric oxide synthase(p-e NOS)were analyzed.PGSDS was developed as a GXⅡproxy of ex vivo herbal crude extracts.Results:PGSDS effectively eliminates false responses caused by crude GXⅡpreparations.When doses equaled the contents in GXⅡ/its post-dose serum,FTA accounted for 98.17%of GXⅡ-added CFMD and 92.99%of PGSDS-reduced vascular tension.In ECs,FTA/PGSDS was found to have significant antioxidant(lower MDA and higher SOD,P<0.01)and endothelial function-protective(lower VEGF,ET-1,P<0.01)effects.The increases in aortic relaxation,endothelial NO levels and phosphorylated PI3K/Akt/e NOS protein induced by FTA/PGSDS were markedly abolished by NG-nitro-L-arginine methyl ester(L-NA,e NOS inhibitor)and wortmannin(PI3K/AKT inhibitor),respectively,indicating an endothelium-dependent vasodilation via the PI3K/AKT-e NOS pathway(P<0.01).Conclusion:This study provides a strategy for rapidly and precisely elucidating GXⅡ's representative in/ex vivo cardioprotective absorbed bioactive compounds(ABCs)-FTA,suggesting its potential in advancing precision ethnomedicine.

Construction of voxel-based Portunus haanii phantom and its absorbed fractions and specific absorbed fractions calculation based on Monte Carlo simulations

Objective:To build the database of the absorbed fractions(AFs)and specific absorbed fractions(SAFs),in order to accurately assess the internal radiation dose in non-human biota.Methods:A voxel-based Portunus haanii phantom was established based on the computed tomography(CT)images.A set of AFs and SAFs were calculated with Monte Carlo toolkit Geant4 for the emission of monoenergetic photons and electrons with energies ranging from 10 keV to 5 MeV.Results:The mass of the voxel-based Portunus haanii phantom(392.2 g)was in agreement with the actual mass(389.2 g),indicating the reliability of the phantom.The calculated AFs and SAFs,based on the voxel-based Portunus haanii phantom,provided precise and reliable data for conducting internal radiation dose calculations specifically tailored to the Chinese Red Swimming Crab(Portunus haanii).The results indicated that the self-AFs and self-SAFs were affected by both the radiation energy and the mass of the source/target organ.Moreover,the AFs and SAFs for cross irradiation,were not only dependent on the energy and the mass of the target organ,but also on the relative position of the source and target organs.Conclusion:These results serve as a valuable resource for accurately evaluating the internal radiation exposure of this species.

Evaluation of Dosimetric Impact of Uncertainty of Measurement in Estimating External Radiotherapy Dose

Cancer is a major societal public health and economic problem, responsible for one in every six deaths. Radiotherapy is the main technique of treatment for more than half of cancer patients. To achieve a successful outcome, the radiation dose must be delivered accurately and precisely to the tumor, within ± 5% accuracy. Smaller uncertainties are required for better treatment outcome. The objective of the study is to investigate the uncertainty of measurement of external radiotherapy beam using a standard ionization chamber under reference conditions. Clinical farmers type ionization chamber measurement was compared against the National Reference standard, by exposing it in a beam 60Co gamma source. The measurement set up was carried out according to IAEA TRS 498 protocol and uncertainty of measurement evaluated according to GUM TEDDOC-1585. Evaluation and analysis were done for the identified subjects of uncertainty contributors. The expanded uncertainty associated with 56 mGy/nC ND,W was found to be 0.9% corresponding to a confidence level of approximately 95% with a coverage factor of k = 2. The study established the impact of dosimetry uncertainty of measurement in estimating external radiotherapy dose. The investigation established that the largest contributor of uncertainty is the stability of the ionization chamber at 36%, followed by temperature at 22% and positioning of the chamber in the beam at 8%. The effect of pressure, electrometer, resolution, and reproducibility were found to be minimal to the overall uncertainty. The study indicate that there is no flawless measurement, as there are many prospective sources of variation. Measurement results have component of unreliability and should be regarded as best estimates of the true value. .

Measurement of Radon Concentration and Estimation of Cancer Risk in Twenty-Four Model Houses in the Town of Koudougou

The objective of our study is to evaluate the concentration of radon (86Rn) inside houses in the town of Koudougou in order to estimate its impact on the health of the population. Indeed, when uranium-rich minerals are found near the surface of the ground, radon concentrations can reach tens of becquerels per cubic meter in enclosed spaces. Given the nature of the geological base of Burkina Faso, this situation is quite probable and certain places that are sometimes poorly ventilated (house, school, office, etc.) can have radon levels high enough to constitute a health problem for occupants. Thus, twenty-four (24) sample houses were identified. In each house, the Corentium digital detector was between 0.8 m and 2 m for at least one week in a place where the occupants estimate that they spend more time of time and measure the concentration of radon in the long term and short term. The recorded data allowed us to determine the Absorbed Dose and the Annual Effective Dose of radon gas for each house in order to estimate the Risk of Cancer and the probable Number of Cases of Lung Cancer per million inhabitants. Thus, the results indicate that the long-term radon concentration varies between 6 Bq/m3 and 285 Bq/m3 respectively in houses 11 and 4 compared to 1 Bq/m3 to 208 Bq/m3 in the short term in the same houses. Also, in the long term, in control houses 1, 3 and 4, the radon level is above the recommended threshold interval. For the short term, these are houses 1, 3, 4 and 17 respectively with 110 Bq/m3, 142 Bq/m3, 208 Bq/m3 and 105 Bq/m3. As for the long-term and short-term effective doses, only houses 1, 3, 4, 17 and 24 have values between 3 - 10 Sv/year. The estimation of the relative risk of lung cancer gives values relatively close to unity and between 1.006 and 1.142 with an average of 1.035 and that of the Number of Lung Cancer Cases per million inhabitants gives values between 8 and 166 with an average of 42. Thus, we can conclude that with the exception of houses 1, 3, 4 and 17, the radon concentrations are relatively low in the twenty-four control houses in the city of Koudougou. The lifestyle of the populations can well explain this situation when we know that people are in the habit of always leaving doors and windows open, especially when they are not sleeping. We can therefore say that the risk of population exposure to radon gas is relatively low in the town of Koudougou.

Multiphase Interfacial Regulation Based on Hierarchical Porous Molybdenum Selenide to Build Anticorrosive and Multiband Tailorable Absorbers

Electromagnetic wave(EMW)absorbing materials have an irreplaceable position in the field of military stealth as well as in the field of electromagnetic pollution control.And in order to cope with the complex electromagnetic environment,the design of multifunctional and multiband high efficiency EMW absorbers remains a tremendous challenge.In this work,we designed a three-dimensional porous structure via the salt melt synthesis strategy to optimize the impedance matching of the absorber.Also,through interfacial engineering,a molybdenum carbide transition layer was introduced between the molybdenum selenide nanoparticles and the three-dimensional porous carbon matrix to improve the absorption behavior of the absorber.The analysis indicates that the number and components of the heterogeneous interfaces have a significant impact on the EMW absorption performance of the absorber due to mechanisms such as interfacial polarization and conduction loss introduced by interfacial engineering.Wherein,the prepared MoSe_(2)/MoC/PNC composites showed excellent EMW absorption performance in C,X,and Ku bands,especially exhibiting a reflection loss of−59.09 dB and an effective absorption bandwidth of 6.96 GHz at 1.9 mm.The coordination between structure and components endows the absorber with strong absorption,broad bandwidth,thin thickness,and multi-frequency absorption characteristics.Remarkably,it can effectively reinforce the marine anticorrosion property of the epoxy resin coating on Q235 steel substrate.This study contributes to a deeper understanding of the relationship between interfacial engineering and the performance of EMW absorbers,and provides a reference for the design of multifunctional,multiband EMW absorption materials.

Vibration Reduction by a Partitioned Dynamic Vibration Absorber with Acoustic Black Hole Features

Vibration quality is a vital indicator for assessing the progress of modern equipment.The dynamic vibration absorber(DVA)based on the acoustic black hole(ABH)feature is a new passive control method that manipulates waves.It offers efficient energy focalization and broad-spectrum vibration suppression,making it highly promising for applications in large equipment such as aircraft,trains,and ships.Despite previous advancements in ABH-DVA development,certain challenges remain,particularly in ensuring effective coupling with host structures during control.To address these issues,this study proposes a partitioned ABH-featured dynamic vibration absorber(PABH-DVA)with partitions in the radial direction of the disc.By employing a plate as the host structure,simulations and experiments were conducted,demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance.The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping.Simulation results revealed that the PABH-DVA exhibits more coupled modes,occasionally with lower coupling coefficients than the symmetric ABH-DVA.The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance.Additionally,the study discussed the impact of the number of slits and their orientation.This research further explains the coupling mechanism between the ABH-DVA and the controlled structure,and provides new ideas for the further application of ABH in engineering.

Comprehensive profiling and characterization of the absorbed components and metabolites in mice serum and tissues following oral administration of Qing-Fei-Pai-Du decoction by UHPLC-Q-Exactive-Orbitrap HRMS

Qing-Fei-Pai-Du decoction(QFPDD)is a Chinese medicine compound formula recommended for combating corona virus disease 2019(COVID-19)by National Health Commission of the People's Republic of China.The latest clinical study showed that early treatment with QFPDD was associated with favorable outcomes for patient recovery,viral shedding,hospital stay,and course of the disease.However,the effective constituents of QFPDD remain unclear.In this study,an UHPLC-Q-Orbitrap HRMS based method was developed to identify the chemical constituents in QFPDD and the absorbed prototypes as well as the metabolites in mice serum and tissues following oral administration of QFPDD.A total of 405 chemicals,including 40 kinds of alkaloids,162 kinds of flavonoids,44 kinds of organic acids,71 kinds of triterpene saponins and 88 kinds of other compounds in the water extract of QFPDD were tentatively identified via comparison with the retention times and MS/MS spectra of the standards or refereed by literature.With the help of the standards and in vitro metabolites,195 chemical components(including 104 prototypes and 91 metabolites)were identified in mice serum after oral administration of QFPDD.In addition,165,177,112,120,44,53 constituents were identified in the lung,liver,heart,kidney,brain,and spleen of QFPDD-treated mice,respectively.These findings provided key information and guidance for further investigation on the pharmacologically active substances and clinical applications of QFPDD.