Solid Water Research Articles

A Comparison Study of the Solid Phantom and Water Phantom Using 6 MV and 15 MV Photon Energies, Depending on the Depth

Water is such an environmental element that is considered the best human body tissue equivalent. In the field of dosimetry studies, water is frequently used. This comparison study is conducted by a solid phantom and a water phantom with 6 MV and 15 MV photon energies, respectively. A cylindrical-type ionization chamber is used to collect charge when beams are on. The distance between the ray source and the surface of the phantom was fixed at 100 cm i.e. to SSD (Source to Surface Distance) of during the experiment. Chamber travels 1 cm to 20 cm in both phantoms and an electrometer is attached in the experimental set-up to measure the charge. The field size was 10x10 cm2. The relative deviation ratio of the solid phantom to the water phantom was calculated. In the result, the maximum deviation was 0.64%, while the minimum deviation was 0%, corresponding to the depths of 1 cm and 2.5 cm, respectively, for 6 MV and at 15 MV, maximum deviation and minimum deviation were 1.90% and 0.167% respectively, corresponding to the depths of 1.5 cm and 13 cm. Therefore, it can be said that the solid phantom can overcome the disadvantages of installation time required for the water phantom and problems while water level changing for depth measurement, simultaneously can used to measure the radiological dose precisely. Bangladesh J. Nuclear Med. 27(1): 34-38, 2024

Enhancement of mechanical properties, durability and service life of low carbon cement paste with super low w/c ratio by incorporating carbon fiber

The high strength and durability of cement-based materials are pivotal for energy conservation and carbon emission reduction. By employing solid water mixing technology, a cement-based material with a significantly high compressive strength was developed. However, the concurrent increase in brittleness prompted the exploration of carbon fiber as a potential bridging agent to improve toughness. This paper investigates the role of carbon fiber reinforcement in enhancing the mechanical properties, durability, and service life of cement paste with a super low water-to-cement (w/c) ratio. The results demonstrated that the addition of 0.3 vol% carbon fiber led to an 18.4 % increase in 28-day flexural strength compared to the control group, as well as a 15.3 % increase in flexural compression ratio. Furthermore, under the same carbon fiber content, the drying shrinkage rate after 150-day exhibited a decrease of 20.3 %, and there was a notable decrease of 35.80 % in compressive strength loss rate after 200 freezing-thawing cycles. Service life was significantly improved. It showed that carbon fiber could improve the toughness and durability of hardened cement paste.

Evaluation of cutout factors with small and narrow fields using various dosimetry detectors in electron beam keloid radiotherapy.

The inherent problems in the existence of electron equilibrium and steep dose fall-off pose difficulties for small- and narrow-field dosimetry. To investigate the cutout factors for keloid electron radiotherapy using various dosimetry detectors for small and narrow fields. The measurements were performed in a solid water phantom with nine different cutout shapes. Five dosimetry detectors were used in the study: pinpoint 3D ionization chamber, Farmer chamber, semiflex chamber, Classic Markus parallel plate chamber, and EBT3 film. The results demonstrated good agreement between the semiflex and pinpoint chambers. Furthermore, there was no difference between the Farmer and pinpoint chambers for large cutouts. For the EBT3 film, half of the cases had differences greater than 1%, and the maximum discrepancy compared with the reference chamber was greater than 2% for the narrow field. The parallel plate, semiflex chamber and EBT3 film are suitable dosimeters that are comparable with pinpoint 3D chambers in small and narrow electron fields. Notably, a semiflex chamber could be an alternative option to a pinpoint 3D chamber for cutout widths≥3 cm. It is very important to perform patient-specific cutout factor calibration with an appropriate dosimeter for keloid radiotherapy.

Skin dose investigations on a 0.5 T parallel rotating biplanar linac-MR using Monte Carlo simulations and measurements.

The Alberta rotating biplanar linac-MR has a 0.5 T magnetic field parallel to the beamline. When developing a new linac-MR system, interactions of charged particles with the magnetic field necessitate careful consideration of skin dose and tissue interface effects. To investigate the effect of the magnetic field on skin dose using measurements and Monte Carlo (MC) simulations. We develop an MC model of our linac-MR, which we validate by comparison with ion chamber measurements in a water tank. Additionally, MC simulation results are compared with radiochromic film surface dose measurements on solid water. Variations in surface dose as a function of field size are measured using a parallel plate ion chamber in solid water. Using an anthropomorphic computational phantom with a 2mm-thick skin layer, we investigate dose distributions resulting from three beam arrangements. Magnetic field on and off scenarios are considered for all measurements and simulations. For a 20×20cm2 field size, (the minimum dose to the hottest contiguous 0.2 cc volume) for the top 2mm of a simple water phantom is 72% when the magnetic field is on, compared to 34% with magnetic field off (values are normalized to the central axis dose maximum). Parallel plate ion chamber measurements demonstrate that the relative increase in surface dose due to the magnetic field decreases with increasing field size. For the anthropomorphic phantom, (minimum skin dose in the hottest 1×1×1 cm3 cube) shows relative increases of 20%-28% when the magnetic field is on compared to when it is off. With magnetic field off, skin is 71%, 56%, and 21% for medial-lateral tangents, anterior-posterior beams, and a five-field arrangement, respectively. For magnetic field on, the corresponding skin values are 91%, 67%, and 25%. Using a validated MC model of our linac-MR, surface doses are calculated in various scenarios. MC-calculated skin dose varies depending on field sizes, obliquity, and the number of beams. In general, the parallel linac-MR arrangement results in skin dose enhancement due to charged particles spiraling along magnetic field lines, which impedes lateral motion away from the central axis. Nonetheless, considering the results presented herein, treatment plans can be designed to minimize skin dose by, for example, avoiding oblique beams and using a larger number of fields.

Characterization of selected additive manufacturing materials for synchrotron monochromatic imaging and broad-beam radiotherapy at the Australian synchrotron-imaging and medical beamline

Objective. This study aims to characterize radiological properties of selected additive manufacturing (AM) materials utilizing both material extrusion and vat photopolymerization technologies. Monochromatic synchrotron x-ray images and synchrotron treatment beam dosimetry were acquired at the hutch 3B and 2B of the Australian Synchrotron-Imaging and Medical Beamline. Approach. Eight energies from 30 keV up to 65 keV were used to acquire the attenuation coefficients of the AM materials. Comparison of theoretical, and experimental attenuation data of AM materials and standard solid water for MV linac was performed. Broad-beam dosimetry experiment through attenuated dose measurement and a Geant4 Monte Carlo simulation were done for the studied materials to investigate its attenuation properties specific for a 4 tesla wiggler field with varying synchrotron radiation beam qualities. Main results. Polylactic acid (PLA) plus matches attenuation coefficients of both soft tissue and brain tissue, while acrylonitrile butadiene styrene, Acrylonitrile styrene acrylate, and Draft resin have close equivalence to adipose tissue. Lastly, PLA, co-polyester plus, thermoplastic polyurethane, and White resins are promising substitute materials for breast tissue. For broad-beam experiment and simulation, many of the studied materials were able to simulate RMI457 Solid Water and bolus within ±10% for the three synchrotron beam qualities. These results are useful in fabricating phantoms for synchrotron and other related medical radiation applications such as orthovoltage treatments. Significance and conclusion. These 3D printing materials were studied as potential substitutes for selected tissues such as breast tissue, adipose tissue, soft-tissue, and brain tissue useful in fabricating 3D printed phantoms for synchrotron imaging, therapy, and orthovoltage applications. Fabricating customizable heterogeneous anthropomorphic phantoms (e.g. breast, head, thorax) and pre-clinical animal phantoms (e.g. rodents, canine) for synchrotron imaging and radiotherapy using AM can be done based on the results of this study.

Streamflow seasonality in a snow-dwindling world.

Climate warming induces shifts from snow to rain in cold regions1, altering snowpack dynamics with consequent impacts on streamflow that raise challenges to many aspects of ecosystem services2-4. A straightforward conceptual model states that as the fraction of precipitation falling as snow (snowfall fraction) declines, less solid water is stored over the winter and both snowmelt and streamflow shift earlier in season. Yet the responses of streamflow patterns to shifts in snowfall fraction remain uncertain5-9. Here we show that as snowfall fraction declines, the timing of the centre of streamflow mass may be advanced or delayed. Our results, based on analysis of 1950-2020 streamflow measurements across 3,049 snow-affected catchments over the Northern Hemisphere, show that mean snowfall fraction modulates the seasonal response to reductions in snowfall fraction. Specifically, temporal changes in streamflow timing with declining snowfall fraction reveal a gradient from earlier streamflow in snow-rich catchments to delayed streamflow in less snowy catchments. Furthermore, interannual variability of streamflow timing and seasonal variation increase as snowfall fraction decreases across both space and time. Our findings revise the 'less snow equals earlier streamflow' heuristic and instead point towards a complex evolution of seasonal streamflow regimes in a snow-dwindling world.

Graphite foils as potential skin and epithelium dosimeters at therapeutic photon energies

This work builds upon a prior study, examining the dosimetric utility of pencil lead and thin graphitic sheets, focusing upon the measurement of skin doses within the mammographic regime. In recognizing the near soft-tissue equivalence of graphite and the earlier-observed favourable thermoluminescence yield of thin sheets of graphite, this has led to present study of 50 μm thick graphite for parameters typical of external beam fractionated radiotherapy and skin dose evaluations. The graphite layers were annealed and then stacked to form an assembly of 0.5 mm nominal thickness. Using a 6 MV photon beam and delivering doses from 2- to 60 Gy, irradiations were conducted, the assembly first forming a superficial layer to a solid water phantom and subsequently underlying a 1.5 cm bolus, seeking to circumvent the build-up to electronic equilibrium for skin treatments. Investigations were made of several dosimetric properties arising from the thermoluminescence yield of the 50 μm thick graphite slabs, in particular proportionality and sensitivity to dose. The results show excellent sensitivity within the dose range of interest, the thermoluminescence response varying with increasing depth through the stacked graphite layers, obtaining a coefficient of determination of 90%. Acknowledging there to be considerable challenge in accurately matching skin thickness with dose, the graphite sheets have nevertheless shown considerable promise as dosimeters of skin, sensitive in determination of dose from the surface of the graphite through to sub-dermal depth thicknesses.

Determination of kilovoltage x-ray therapy depth doses with open-ended applicators.

The purpose of this work was to determine percentage depth dose (PDD) curves for kilovoltage x-rays from the WOmed-T105 unit, with open-ended steel applicators and beam qualities ranging from 0.5 to 4.2mm Al. Measurements were made with parallel plate chambers in a water phantom, with extrapolation based on a fifth order polynomial used to estimate the surface dose. Measurements were also made with parallel plate chambers in a plastic water phantom, with thin plastic sheets used to obtain detailed measurements at shallow depths (less than 1mm). Monte Carlo simulations were performed using the EGSnrc package, with two different sources as input: a SpekPy simulation of the x-ray beam and a full simulation of the x-ray tube, treatment head and applicators. Results showed that all four methods (two measurements and two simulations) agreed within the measurement uncertainty at depths greater than 2mm. At shallow depths, significant differences were noted. At depths less than 0.1mm, the full Monte Carlo simulation and the solid water measurements showed a sharp spike in surface dose which is attributed to electron contamination, which was not seen in the SpekPy Monte Carlo simulation or the extrapolated water measurements. At depths between 0.1mm and 2mm, beyond the range of contaminant electrons, the extrapolated water measurements underestimate the dose by up to 13% compared to the full Monte Carlo simulation and the solid water measurements, attributed to fluorescent photons generated in the applicators. This work demonstrates that for open-ended applicators, measurement of depth doses in water with extrapolation of surface dose has the potential to significantly underestimate the dose at shallow depths between the surface and 2mm, even after eliminating electron contamination from the beam.

ДИСИПАЦІЯ ЕНЕРГІЇ НИЗЬКОМОЛЕКУЛЯРНИМИ РЕЧОВИНАМИ ПІД ЧАС ЗОНДУВАННЯ ЕЛЕКТРИЧНИМ ПОЛЕМ БАГАТОЖИЛЬНИХ КАБЕЛІВ АТОМНИХ ЕЛЕКТРИЧНИХ СТАНЦІЙ

A model of the piece-homogeneous interphase space of stranded cables is proposed, taking into account the influence of cracks oriented along the lines of force of the electric field. The cracks are filled with low molecular weight substances. The case of a probing electric field with a significant tangential component is considered.. The equivalent values of the tangent of the dielectric loss angle at various parameters of low molecular weight substances in the cracks of the polyethylene insulation of the conductor with a cross section of 2.5 mm2 were determined. The equivalent tangent of the angle of dielectric loss increases by (3-20) times when the dissipation of electrical energy by low molecular weight substances changes from 10% to 100% in a crack, which is 1% of the thickness of an intact section of polyethylene insulation. The distribution of the electric field for the general case of accumulation of low-molecular products in capillaries formed by slit-like gaps between isolated veins is obtained. A strong electric field in the smaller part of the gap between the insulated cores, which occurs at a core potential of 1 kV, contributes to the capillary absorption of decomposition products of both solid polyethylene insulation and water vapor from the atmosphere in the case of unshielded structures of multi-core cables. The asymmetric configuration of the probing electric field with a significant tangential component makes it possible to detect low-molecular decomposition products of solid polymer insulation, which are a sign of its aging. Differences experimentally observed in the value of tgδ with different schemes of examination of multi-core cables are related, to a greater extent, to the uneven distribution of substances dissipating electrical energy across the cross-section of the cable, and not to a change in the structure of the probing electric field. References 11, figure 5.

Operational Radiation Safety Considerations During Equine Superficial Radiation Treatment Using Portable X-Ray Devices

Abstract Veterinary personnel exposure due to scattered x rays, when present during superficial radiation treatment (SRT), was evaluated. Veterinary personnel presence is needed during SRT to minimize the degree of required aesthesia to horses. Animal treatment was simulated, and exposure rates determined for 50, 70, and 100 kV x rays using eight different SRT applicators. Exposure rates at the surface of a solid water phantom (SWP) phantom ranged from 3.9 mR h−1 to 396 mR h−1 for 50 kV, from 41 mR h−1 to 2,880 mR h−1 for 70 kV, and from 235 mR h−1 to 7,500 mR h−1, for 100 kV, respectively. A horse phantom was used to mimic SRT equine ocular treatment creating a spatial exposure field where the directional scatter was measured at 1 m. The minimum distance away from the source to reach < 2 mR h−1 varied with angular position and energy and was lowest for all energies directly behind the x-ray tube. The closest distance before exceeding 2 mR h−1 at 50 kVp was determined to 1.96 m. A worker could stand 1 m behind the x-ray tube at 50 kVp with 0.25 mm lead for 15,106 hours. Typical SRT treatment times for horse eyelid squamous cell carcinoma are less than 5 minutes, and radiation doses to practitioners are expected to be well below local administrative ALARA limits.

Physicochemical and Biological Properties of Land and Water Bodies Surrounding Major Dumpsites in Kolkata

In this paper we have investigated the data acquired from the analysis of the soil and water samples from and around the dump sites in Kolkata and North 24 Paragana district of West Bengal where the population density is extremely high. The treatment of disposal of municipal solid wastes and waste water has been inadequate to negligible in these areas and as a result the quality of soil and water bodies is subject to deterioration. We have made use of GPS enabled Satellite acquired images and its associated softwares to identify and demarcate the areas that come under the direct impact of the dumping sites, and which ultimately are the areas prone to diseases and degradation in the coming years. The pH, salinity, Total Dissolved Solvents and oxidation reduction potential has been investigated for the basic characterization of the samples. An estimate of heavy metals has also been made. Estimation of salts and oxides from the various sediments and soil samples were acquired. Identification of bacteria, under the purview of biological studies and the dependence of their growth on physiochemical parameters of the surrounding has portrayed an alarming result. Adjacent to these areas there are agricultural fields where leached water from the dumping site directly drain into and cause biomagnifications. Contamination of the ground water is also sizable. This research will help to control pollution and biological outbreaks as well as suggest areas where immediate care should be taken to set up environmental restoration. The findings of the paper will further enlighten the planning and designing of waste disposal in urban areas and assist in its policy making in urban areas and thereby improve the quality of life of the scavengers who are left to equate their survival with the garbage mounds.

Planar dose calculation of electron therapy

Purpose. The aim of this study is to determine the planar dose distribution of irregularly-shaped electron beams at their maximum dose depth (z max) using the modied lateral build-up ratio (LBR) and curve-fitting methods. Methods. Circular and irregular cutouts were created using Cerrobend alloy for a 14 × 14 cm2 applicator. Percentage depth dose (PDD) at the standard source-surface-distance (SSD = 100 cm) and point dose at different SSD were measured for each cutout. Orthogonal profiles of the cutouts were measured at z max. Data were collected for 6, 9, 12, and 15 MeV electron beam energies on a VERSA HDTM LINAC using the IBA Blue Phantom2 3D water phantom system. The planar dose distributions of the cutouts were also measured at z max in solid water using EDR2 films. Results. The measured PDD curves were normalized to a normalization depth (d 0) of 1 mm. The lateral-buildup-ratio (LBR), lateral spread parameter (σ R (z)), and effective SSD (SSD eff ) for each cutout were calculated using the PDD of the open applicator as the reference field. The modified LBR method was then employed to calculate the planar dose distribution of the irregular cutouts within the field at least 5 mm from the edge. A simple curve-fitting model was developed based on the profile shapes of the circular cutouts around the field edge. This model was used to calculate the planar dose distribution of the irregular cutouts in the region from 3 mm outside to 5 mm inside the field edge. Finally, the calculated planar dose distribution was compared with the film measurement. Conclusions. The planar dose distribution of electron therapy for irregular cutouts at z max was calculated using the improved LBR method and a simple curve-fitting model. The calculated profiles were within 3% of the measured values. The gamma passing rate with a 3%/3 mm and 10% dose threshold was more than 96%.

Gafchromic EBT3 film provides equivalent dosimetric performance to EBT-XD film for stereotactic radiosurgery dosimetry

The accurate assessment of film results is highly dependent on the methodology and techniques used to process film. This study aims to compare the performance of EBT3 and EBT-XD film for SRS dosimetry using two different film processing methods. Experiments were performed in a solid water slab and an anthropomorphic head phantom. For each experiment, the net optical density of the film was calculated using two different methods; taking the background (initial) optical density from 1) an unirradiated film from the same film lot as the irradiated film (stock to stock (S-S) method), and 2) a scan of the same piece of film taken prior to irradiation (film to film (F-F) method). EBT3 and EBT-XD performed similarly across the suite of experiments when using the green channel only or with triple channel RGB dosimetry. The dosimetric performance of EBT-XD was improved across all colour channels by using an F-F method, particularly for the blue channel. In contrast, EBT3 performed similarly well regardless of the net optical density method used. Across 21 SRS treatment plans, the average per-pixel agreement between EBT3 and EBT-XD films, normalised to the 20 Gy prescription dose, was within 2% and 4% for the non-target (2—10 Gy) and target (> 10 Gy) regions, respectively, when using the F-F method. At doses relevant to SRS, EBT3 provides comparable dosimetric performance to EBT-XD. In addition, an S-S dosimetry method is suitable for EBT3 while an F-F method should be adopted if using EBT-XD.

Flash melting amorphous ice.

Water can be vitrified if it is cooled at high rates, which makes it possible to outrun crystallization in so-called no man's land, a range of deeply supercooled temperatures where water crystallizes rapidly. Here, we study the reverse process in pure water samples by flash melting amorphous ice with microsecond laser pulses. Time-resolved electron diffraction reveals that the sample transiently crystallizes despite a heating rate of more than 5 × 106 K/s, even though under the same conditions, vitrification can be achieved with a similar cooling rate of 107 K/s. Moreover, we observe different crystallization kinetics for amorphous solid water and hyperquenched glassy water. These experiments open up new avenues for elucidating the crystallization mechanism of water and studying its dynamics in no man's land. They also add important insights into the laser melting and revitrification processes that are integral to the emerging field of microsecond time-resolved cryo-electron microscopy.

The effect of electron backscatter and charge build up in media on beam current transformer signal for ultra-high dose rate (FLASH) electron beam monitoring

Objective. Beam current transformers (BCT) are promising detectors for real-time beam monitoring in ultra-high dose rate (UHDR) electron radiotherapy. However, previous studies have reported a significant sensitivity of the BCT signal to changes in source-to-surface distance (SSD), field size, and phantom material which have until now been attributed to the fluctuating levels of electrons backscattered within the BCT. The purpose of this study is to evaluate this hypothesis, with the goal of understanding and mitigating the variations in BCT signal due to changes in irradiation conditions. Approach. Monte Carlo simulations and experimental measurements were conducted with a UHDR-capable intra-operative electron linear accelerator to analyze the impact of backscattered electrons on BCT signal. The potential influence of charge accumulation in media as a mechanism affecting BCT signal perturbation was further investigated by examining the effects of phantom conductivity and electrical grounding. Finally, the effectiveness of Faraday shielding to mitigate BCT signal variations is evaluated. Main Results. Monte Carlo simulations indicated that the fraction of electrons backscattered in water and on the collimator plastic at 6 and 9 MeV is lower than 1%, suggesting that backscattered electrons alone cannot account for the observed BCT signal variations. However, our experimental measurements confirmed previous findings of BCT response variation up to 15% for different field diameters. A significant impact of phantom type on BCT response was also observed, with variations in BCT signal as high as 14.1% when comparing measurements in water and solid water. The introduction of a Faraday shield to our applicators effectively mitigated the dependencies of BCT signal on SSD, field size, and phantom material. Significance. Our results indicate that variations in BCT signal as a function of SSD, field size, and phantom material are likely driven by an electric field originating in dielectric materials exposed to the UHDR electron beam. Strategies such as Faraday shielding were shown to effectively prevent these electric fields from affecting BCT signal, enabling reliable BCT-based electron UHDR beam monitoring.

Microphysical Characteristics of Precipitation Over Eastern China and Its Coastal Regions

AbstractMany studies have investigated the macro‐ and micro‐physical properties of precipitation, but few classified precipitation into warm‐ and cold‐topped, which affects precipitation phase and precipitation type significantly. Furthermore, the impact of moisture and dynamics on microphysical characteristics of precipitation has been less studied. Using precipitation data from the GPM 2A DPR between May and September from 2015 to 2023, this study conducts a systematic study on microphysical characteristics of precipitation over eastern China and its coastal areas. This study divides precipitation cases into 20 categories, including warm‐/cold‐topped (CTP/WTP) convective/stratiform light/moderate/heavy/extreme/the most extreme precipitation. The findings reveal distinct differences along with similarities in various precipitation categories between eastern China and its coastal regions. The convection ratio for CTP increases with higher precipitation intensity, while WTP is dominated by convective precipitation. The more CTP, the higher the solid water content. The heavier precipitation, the higher liquid water content contributes. The mass‐weighted diameter (Dm) for CTP shows three variations from high to low with little or slight decrease with altitude at upper‐layer, followed by a rapid increase at middle‐layer and finally decreasing slightly at low‐layer. The CTP Dm grows rapidly with temperature from −18.58 (−13.93)°C for convective (stratiform) precipitation and their maximum growth rate are almost located in melting layer. Dm (raindrop density) is larger (lower) over land than ocean and larger (lower) for CTP than WTP. Dm shows positive relation to vertical velocity and specific humidity, especially sensitive to the middle‐ and upper‐layers meteorological conditions.

The development of a cylindrical phantom for nanoDotTM calibration with multiple beam angles

Background: The nanoDotTM dosimeter, an optically stimulated luminescent dosimeter (OSLD), is compact and precise, ideal for various applications like radiation dosimetry. The nanoDotTM requires calibration before use with the detector alignment perpendicular to the central beam axis. It exhibits angular dependence that may impact the calibration factor, requiring the fabrication of a specific cylindrical phantom for the calibration procedure. Objective: This study aimed to develop a cylindrical phantom for nanoDotTM calibration to facilitate dose measurements in composite fields with various beam angles and to evaluate the nanoDotTM calibration factors for different plans. Materials and methods: The cylindrical phantom was constructed using cast nylon material to accommodate the nanoDotTM or a cylindrical ionization chamber (IC). The novel phantom underwent validation for physical characteristics, including dimensions, density, and uniformity. Validation for the calibration factor, using cylindrical phantom (CF cylin) under standard conditions with a 10x10 cm² field size at 10 cm depth was conducted with 6 MV X-rays, comparing it with calibration factor using slab solid water phantoms (CFsolid). The CFcylin for different numbers of beams were determined and validated against a reference IC in various planning conditions. Furthermore, angular correction factors were determined for their application in the single-beam calibration factor. Results: The cylindrical phantom had dimensions of 20 cm in diameter and 30 cm in length, a density of 1.145 g/cm³ and good uniformity. As a result of single beam, the CF cylin, agreed well with CFsolid, showing a difference of -0.069%. The CFcylin increased with the number of beams, ranging between 1.179 and 1.242. Additionally, the angular correction factor increased as the number of beams increased, peaking at 1.058 with 9 beams. When comparing the results to the IC, it was observed that with an increase in the number of beams to 4 beams, the single-beam calibration factor exhibited a variation of more than 2%. However, when applying the CF cylin specific to the number of beams or correcting for the angular correction factor, the dose differences between nanoDotTM and IC measurements were within 2%. Conclusion: The developed cylindrical phantom is suitable for nanoDotTM calibration under single beam angle and in composite fields with various beam angles. The new calibration factors for specific numbers of beams allow for accurate dose measurements using nanoDotTM, thus reducing the dose difference from the IC to acceptable levels. Further studies should investigate its application in clinical situations.

Water splitting via electrocatalysis and photocatalysis: Engineering stumbling blocks and advancements

Renewable green hydrogen is produced using solar or wind-powered photocatalysis and electrocatalysis of water. In today's world, more than a third of nations have national plans for widespread green hydrogen generation. A variety of electrocatalytic water splitting methods exist such as alkaline water electrolyzer (AWE), proton exchange membrane (PEM), anion exchange membrane (AEM), solid oxide water electrolyzer (SOWE), and proton conducting ceramic electrolyzer (PCCEL). Nowadays, the high cost of producing hydrogen is a major barrier to the broad adoption of PEC and PEM, even though these processes are more efficient than conventional water-splitting technologies. A variety of carbon dopants, including graphene oxide, graphitic-carbon nitride, nanosheets, nitrogen, and other non-noble metals, are discussed in the present work and their applications in PEC and PEM catalysts. Based on the literature review, it is noticed that the hydrogen's levelized production cost (LCOH) for PEC is 8.43 USD/kg, whereas that for electrochemical water splitting systems is just 6.22 USD/kg. As a result, scientists are still looking for better, cheaper ways to produce green hydrogen. When combined with carbon dopants in catalysts, green hydrogen shows promise way as a sustainable energy source that can help bring the world closer to climate neutrality.

Depth dose measurement by using Al2O3 OSL dosimeters in high energy photons in the presence of air cavity and density inhomogeneity

Air cavities and tissue density inhomogeneity significantly affects the distribution of radiation doses, potentially resulting in adverse consequences such as cancer recurrence. This research aims to assess the accuracy of Al2O3 optically stimulated luminescence (OSL) dosimeters in measuring doses within varying thicknesses of air cavities (3, 5, and 8 cm) and tissue inhomogeneity of low and high density simulated by the lung and bone phantoms. An expanded polystyrene (EPS) was employed in homogeneous solid water® phantoms to simulate the air cavity. The percentage depth-dose (PDD) curves at 6 MV photons were obtained in both presence of air cavity and density inhomogeneity and compared to that in the EBT3 radiochromic film dosimeters and treatment planning system (TPS). The results indicated that the presence of an air cavity and tissue inhomogeneity affected the depth dose measured in OSL dosimeters, EBT3 films and TPS. OSLD and TPS showed good agreement at the centre of the cavity, which is within ±5% but could not estimate scattered radiation to the distal and proximal surfaces of the air cavity. The obtained p-values showed no significant differences of dose measured in OSL dosimeters compared to those in EBT3 films and TPS. The Kruskal Wallis test and Mann-Whitney showed no significant difference between OSL dosimeters, EBT3 film and TPS in the measurement of depth doses in the presence of density inhomogeneity. The overall results indicated the suitability of OSL dosimeters as indirect dosimeters for the measurements of depth dose in the presence of air cavity and tissue density inhomogeneity

Plastic scintillator-based dosimeters for ultra-high dose rate (UHDR) electron radiotherapy

This paper reports the development of dosimeters based on plastic scintillating fibers imaged by a charge-coupled device camera, and their performance evaluation through irradiations with the electron Flash research accelerator located at the Centro Pisano Flash Radiotherapy. The dosimeter prototypes were composed of a piece of plastic scintillating fiber optically coupled to a clear optical fiber which transported the scintillation signal to the readout systems (an imaging system and a photodiode). The following properties were tested: linearity, capability to reconstruct the percentage depth dose curve in solid water and to sample in time the single beam pulse. The stem effect contribution was evaluated with three methods, and a proof-of-concept one-dimensional array was developed and tested for online beam profiling. Results show linearity up to 10 Gy per pulse, and good capability to reconstruct both the timing and spatial profiles of the beam, thus suggesting that plastic scintillating fibers may be good candidates for low-energy electron Flash dosimetry.