Homogeneous Irradiation Research Articles

A New Double-Step Process of Shortening Fibers without Change in Molding Equipment Followed by Electron Beam to Strengthen Short Glass Fiber Reinforced Polyester BMC.

It is vital to maximize the safety of outdoor constructions, airplanes, and space vehicles by protecting against the impact of airborne debris from increasing winds due to climate change, or from bird strikes or micrometeoroids. In a widely-used compression-molded short glass fiber polyester bulk-molded compound (SGFRP-BMC) with 55% wt. CaCO3 filler, the center of the mother panel has lower impact strength than the outer sections with solidification texture angles and short glass fiber (SGF) orientations being random from 0 to 90 degrees. Therefore, a new double-step process of: (1) reducing commercial fiber length without change in molding equipment; followed by a (2) 0.86 MGy dose of homogeneous low-voltage electron beam irradiation (HLEBI) to both sides of the finished samples requiring no chemicals or additives, which is shown to increase the Charpy impact value (auc) about 50% from 6.26 to 9.59 kJm-2 at median-accumulative probability of fracture, Pf = 0.500. Shortening the SGFs results in higher fiber spacing density, Sf, as the thermal compressive stress site proliferation by action of the CTE difference between the matrix and SGF while the composite cools and shrinks. To boost impact strength further, HLEBI provides additional nano-compressive stresses by generating dangling bonds (DBs) creating repulsive forces while increasing SGF/matrix adhesion. Increased internal cracking apparently occurs, raising the auc.

Preparation of Antioxidant and Antifouling Ultrafiltration Membrane by Co-blending Eugenol with Polyethylene Glycol-Modified Polyvinylidene Fluoride

Polyvinylidene fluoride-graft-polyethylene glycol methyl acrylate (PVDF-g-PEGMA) was prepared by grafting PEGMA onto PVDF using a homogeneous irradiation grafting method. After incorporating various concentrations of eugenol, a natural antioxidant component of clove oil, the membranes were fabricated through non-solvent induced phase separation. The results indicated that the addition of eugenol did not alter the inherent properties of the membrane but slightly reduced the pore size and water flux. The cyclic flux test showed that eugenol did not compromise the anti-fouling performance of the membrane, with the flux recovery ratio exceeding 93%. The antioxidant performance test revealed that eugenol enhanced the membrane’s capacity to remove free radicals and imparted oxidation resistance in NaClO solution, making the modified membrane suitable for use in oxidizing environments. This study successfully demonstrated a simple method to prepare a bifunctional membrane with anti-fouling and antioxidant properties, potentially extending its service life and applicability in oxidative contexts.

Antifouling and Antioxidant Properties of PVDF Membrane Modified with Polyethylene Glycol Methacrylate and Propyl Gallate.

In this study, molecules of propyl gallate (PG) and polyethylene glycol methacrylate (PEGMA) were covalently bonded via a transesterification reaction and subsequently grafted onto polyvinylidene fluoride substrates using a homogeneous radiation grafting technique. The enhancement of the membranes' hydrophilicity with the increment of the grafting rate was corroborated by scanning electron microscopy imaging and measurements of the water contact angle. At a grafting degree of 10.1% and after a duration of 4 min, the water contact angle could decrease to as low as 40.1°. Cyclic flux testing demonstrated that the membranes modified in this manner consistently achieved a flux recovery rate exceeding 90% across varying degrees of grafting, indicating robust anti-fouling capabilities. Furthermore, these modified membranes exhibited significant antioxidant ability while maintaining antifouling performance over 30 days. The ability of the modified membranes to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS+) free radicals remained nearly unchanged after being stored in pure water for 30 days, and the flux recovery rate remained above 95% after immersion in sodium hypochlorite solution for 30 days. Among the tested membranes, the PVDF-g-PEGMAG modified membrane with a grafting degree of 7.2% showed the best antioxidant effect.

Using the genomic adjusted radiation dose (GARD) to personalize the radiation dose in nasopharyngeal cancer

BackgroundLocally advanced nasopharyngeal cancer (NPC) patients undergoing radiotherapy are at risk of treatment failure, particularly locoregional recurrence. To optimize the individual radiation dose, we hypothesize that the genomic adjusted radiation dose (GARD) can be used to correlate with locoregional control. MethodsA total of 92 patients with American Joint Committee on Cancer / International Union Against Cancer stage III to stage IVB recruited in a randomized phase III trial were assessed (NPC-0501) (NCT00379262). Patients were treated with concurrent chemo-radiotherapy plus (neo) adjuvant chemotherapy. The primary endpoint is locoregional failure free rate (LRFFR). ResultsDespite the homogenous physical radiation dose prescribed (Median: 70 Gy, range 66–76 Gy), there was a wide range of GARD values (median: 50.7, range 31.1–67.8) in this cohort. In multivariable analysis, a GARD threshold (GARDT) of 45 was independently associated with LRFFR (p = 0.008). By evaluating the physical dose required to achieve the GARDT (RxRSI), three distinct clinical subgroups were identified: (1) radiosensitive tumors that RxRSI at dose < 66 Gy (N = 59, 64.1 %) (b) moderately radiosensitive tumors that RxRSI dose within the current standard of care range (66–74 Gy) (N = 20, 21.7 %), (c) radioresistant tumors that need a significant dose escalation above the current standard of care (>74 Gy) (N = 13, 14.1 %). ConclusionGARD is independently associated with locoregional control in radiotherapy-treated NPC patients from a Phase 3 clinical trial. GARD may be a potential framework to personalize radiotherapy dose for NPC patients.

A PEGylated PVDF Antifouling Membrane Prepared by Grafting of Methoxypolyethylene Glycol Acrylate in Gama-Irradiated Homogeneous Solution.

In this study, methoxypolyethylene glycol acrylate (mPEGA) served as a PEGylated monomer and was grafted onto polyvinylidene fluoride (PVDF) through homogeneous solution gamma irradiation. The grafting process was confirmed using several techniques, including infrared spectroscopy (FTIR), thermodynamic stability assessments, and rotational viscosity measurements. The degree of grafting (DG) was determined via the gravimetric method. By varying the monomer concentration, a range of DGs was achieved in the PVDF-g-mPEGA copolymers. Investigations into water contact angles and scanning electron microscopy (SEM) images indicated a direct correlation between increased hydrophilicity, membrane porosity, and higher DG levels in the PVDF-g-mPEGA membrane. Filtration tests demonstrated that enhanced DGs resulted in more permeable PVDF-g-mPEGA membranes, eliminating the need for pore-forming agents. Antifouling tests revealed that membranes with a lower DG maintained a high flux recovery rate, indicating that the innate properties of PVDF could be largely preserved.

Inflation alternative via the gravitational field of a singularity

We explore the scenario that the observable Universe emerged from the vicinity of a negative mass ring singularity, and all content of the Universe travels at the same group velocity close to the speed of light on a geodesic trajectory along the axis of rotation of the singularity. In appropriate coordinate parametrization and evaluated on the trajectory, we find that the metric tensor in the vicinity of the trajectory exhibits a conformal scale factor a(η) with contraction and subsequent expansion properties that solve the horizon problem. We then introduce a static flow of gravitating radiation along the trajectory (perturbatively with respect to the mass scale of the singularity) to model a homogeneous radiation dominated Universe. Solving the Einstein field equations with a physically motivated ansatz of metric perturbation then reveals that the effective conformal scale factor indeed grows asymptotically with the same power law as expected in a conventional radiation dominated Universe.

Enhanced RBE of Particle Radiation Depends on Beam Size in the Micrometer Range.

High-linear energy transfer (LET) radiation, such as heavy ions is associated with a higher relative biological effectiveness (RBE) than low-LET radiation, such as photons. Irradiation with low- and high-LET particles differ in the interaction with the cellular matter and therefore in the spatial dose distribution. When a single high-LET particle interacts with matter, it results in doses of up to thousands of gray (Gy) locally concentrated around the ion trajectory, whereas the mean dose averaged over the target, such as a cell nucleus is only in the range of a Gy. DNA damage therefore accumulates in this small volume. In contrast, up to hundreds of low-LET particle hits are required to achieve the same mean dose, resulting in a quasi-homogeneous damage distribution throughout the cell nucleus. In this study, we investigated the dependence of RBE from different spatial dose depositions using different focused beam spot sizes of proton radiation with respect to the induction of chromosome aberrations and clonogenic cell survival. Human-hamster hybrid (AL) as well as Chinese hamster ovary cells (CHO-K1) were irradiated with focused low LET protons of 20 MeV (LET = 2.6 keV/µm) beam energy with a mean dose of 1.7 Gy in a quadratic matrix pattern with point spacing of 5.4 × 5.4 µm2 and 117 protons per matrix point at the ion microbeam SNAKE using different beam spot sizes between 0.8 µm and 2.8 µm (full width at half maximum). The dose-response curves of X-ray reference radiation were used to determine the RBE after a 1.7 Gy dose of radiation. The RBE for the induction of dicentric chromosomes and cell inactivation was increased after irradiation with the smallest beam spot diameter (0.8 µm for chromosome aberration experiments and 1.0 µm for cell survival experiments) compared to homogeneous proton radiation but was still below the RBE of a corresponding high LET single ion hit. By increasing the spot size to 1.6-1.8 µm, the RBE decreased but was still higher than for homogeneously distributed protons. By further increasing the spot size to 2.7-2.8 µm, the RBE was no longer different from the homogeneous radiation. Our experiments demonstrate that varying spot size of low-LET radiation gradually modifies the RBE. This underlines that a substantial fraction of enhanced RBE originates from inhomogeneous energy concentrations on the µm scale (mean intertrack distances of low-LET particles below 0.1 µm) and quantifies the link between such energy concentration and RBE. The missing fraction of RBE enhancement when comparing with high-LET ions is attributed to the high inner track energy deposition on the nanometer scale. The results are compared with model results of PARTRAC and LEM for chromosomal aberration and cell survival, respectively, which suggest mechanistic interpretations of the observed radiation effects.

Combining photovoltaic modules and food crops: first agrovoltaic prototype in Belgium

Agrovoltaic systems (combination of biomass production and electricity production by photovoltaics (PV)) are typically installed in locations with high insolation and/or arid climates in order to protect the crops against drought and sunburn. However, even in Belgium with a temperate maritime climate, summers are getting warmer and dryer, with reduced crop yields as result. This paper describes the first agrivoltaic prototype in Belgium. By use of a coupled simulation program developed in Python, a checkerboard panel arrangement was selected as an initial validation, in order to have a homogeneous ground radiation and crop growth. Potatoes were grown below the PV modules and the microclimate was measured. Results show lower temperatures below the PV modules and less transpiration and evaporation from crop and soil. The leaf area of the potatoes was larger below the PV modules which indicates an adapted light harvesting capability. Night-time temperatures were not seen to be improved under the agrivoltaic checkerboard structure, which indicates that this arrangement may not provide much protection against frost.

A compact high‐gain slot antenna array with a bidirectional broadside radiation pattern

AbstractA novel bidirectional broadside slot antenna array is proposed in this letter. The outstanding merits of this antenna array lie in the minimum width and the highest gain‐to‐area ratio (G/A) compared to previous works. The ingenious combination of the radiation mode and the transmission mode of slots is adopted, eliminating the design of the feed network. Thus, a simple and compact configuration is obtained. Moreover, two metal plates are added vertically at the sides of the slot array, with a more homogeneous radiation aperture and a higher G/A. With the 3D structure, a compact volume of the antenna array is ensured. For performance evaluation, our proof‐of‐concept design is fabricated with a cuboid dimension of 1.94λ0 × 0.12λ0 × 0.12λ0, where λ0 denotes the wavelength in free space at the centre frequency. An impedance bandwidth of 2.38 to 2.49 GHz is achieved, with a maximum gain of 9.7 dBi and a higher G/A of 39.5. The advantages including compact size and high G/A are paving the path for the potential application of communications in long and narrow spaces.

The Roles of IL-18 in a Realistic Partial Body Irradiation with 5% Bone Marrow Sparing (PBI/BM5) Model.

IL-18 has been shown to play important roles in response to total body irradiation. However, homogenous total body irradiation is not a realistic model to reflect the radiation exposure in a real nuclear event. To further study the roles of IL-18 in a real nuclear scenario, we developed a mouse partial body irradiation with 5% bone marrow sparing (PBI/BM5) model to mimic the inhomogeneous radiation exposure. We established the dose response curves of PBI/BM5 using different radiation doses ranging from 12 to 16 Gy. Using the PBI/BM5 model, we showed that IL-18 knockout mice were significantly more radiation resistant than the wild-type mice at 14.73 Gy. We further studied the hematopoietic changes using a complete blood count, bone marrow colony-forming assays, and serum cytokine assays on the mice exposed to PBI/BM5 with IL-18BP treatment and wild-type/IL-18 knockout mice. In conclusion, our data suggest that IL-18 plays important roles in mouse survival in a realistic nuclear exposure model, potentially through the IL-18/IFNγ pathway.

Increasing Bending Strength of Polycarbonate Reinforced by Carbon Fiber Irradiated by Electron Beam.

In an interlayered carbon fiber-reinforced polycarbonate polymer (CFRPC) composite composed of three sized of CF plies, alternating between four PC sheets, designated [PC]4[CF]3, and a new process of activating CF cross-weave cloth plies directly on both sides with homogeneous low-energy electron beam irradiation (HLEBI) before lamination assembly and hot pressing at 6.0 MPa and 537 K for 8 min was produced. Experimental results show that a dose of 215 kGy of HLEBI raised the bending strength, σb, at each experimental accumulative probability, Pa, with the σb at a median Pa of 0.50, increasing by 25% over that of the untreated sample. Three-parameter Weibull analysis showed that when quality can be controlled, a dose of 215 kGy of HLEBI can raise the statistically lowest bending strength, σs, at Pa = 0 (94.3 Mpa), with a high correlation coefficient. This is because, although it had a higher bending strength than that in the other experimental conditions, the weakest sample of the 215 kGy data set had a much lower σb value than that of the others. Electron spin resonance (ESR) of the CF showed that naturally occurring dangling bonds in CF were increased at 215 kGy. Charge transfer to the PC occurs, apparently generating stronger bonds, which are possibly covalent, resulting in enhanced adhesion at the CF-PC interface.

A UVA light-emitting diode microreactor for the photocatalytic degradation of humic acids and the control of disinfection by-products formation potential

Chlorination is one of the most applied technologies for drinking water disinfection. However, the generation of disinfection by-products (DBPs) in the chlorination process is threatening drinking water safety, especially when the concentration of natural organic matter (NOM) is high in source water. Climate change increases the fluctuation of NOM in source water, which further challenges water safety in small and rural communities. In this study, environmental microfluidics was introduced to a UVA-LED photocatalytic oxidation system for a rapid oxidation of NOM. The results showed that HA adsorption and degradation, and DOC degradation were more favored in low pH. At pH 5, 56.9% of HA and 58.1% of dissolved organic carbon (DOC) were removed in 3.4 min by the microreactor. DBP formation potential was efficiently reduced, with the highest reduction of THM and HAA formation potentials by 76% and 70.7%, respectively. Compared with the bottle reactor, the degradation rate constants of HA and DOC by UVA-LED microreactor were increased by 2.99 – 15.8 times, and 6.8 – 170.2 times, respectively. Homogenous irradiation and rapid mass transfer in the microreactor accelerated the inhibited oxidation of HA in acidic and base solutions and increased the apparent quantum yields of photocatalysis. Further, the microfluidic photocatalytic oxidation was much more efficient in the reduction of DPBs formation potential in a source water sample. The process was rapid and had low chemical and energy consumption. Approaches on system scale-up, system simplification, and energy conservation would increase potential of microfluidic photocatalytic oxidation in water purification for households and small communities.

Chemical reaction and radiation impact on unsteady free convective flow through a porous medium past an infinite oscillatory vertical plate

AbstractThe current investigation is concerned with the effect of chemical reactions and radiation on unsteady free convective flow through a porous medium via an infinitely oscillating vertical plate. The primary goal of this study is to investigate the effects of first‐order homogeneous chemical reactions and thermal radiation on mass flow and heat transmission characteristics. The closed‐form Laplace transformation method is used to obtain exact solutions to the governing equations for concentration, energy and momentum. The impact of various non‐dimensional parameters on fluid velocity, temperature and concentration is graphically depicted. Furthermore, 3‐dimensional surface plots for the Nusselt number and Sherwood number are provided, and the equation for skin friction is derived and demonstrated in tabular form. Investigation simulates that the skin friction increases as the chemical reaction parameter hikes, whereas the fluid concentration reduces as the chemical reaction parameter increases. Further, it was revealed that the augmentation of the radiation parameter decreased the temperature and velocity pattern. It is seen that the primary and secondary velocities reduce due to the increment of the chemical reaction parameter.

Contrast-enhanced ultrasound imaging for monitoring the efficacy of near-infrared photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) is a promising cancer therapy combining NIR-light irradiation with an antibody and IR700DX, a light-sensitive substance, to destroy tumours. However, homogeneous irradiation is difficult because the light varies depending on the distance and tissue environment. Therefore, markers that indicate sufficient irradiation are necessary. Nanoparticles sized 10∼200nm show enhanced permeation and retention within tumours, which is further enhanced via NIR-PIT (super enhanced permeability and retention, SUPR). We aimed to monitor the effectiveness of NIR-PIT by measuring SUPR. A xenograft mouse tumour model was established by inoculating human cancer cells in both buttocks of Balb/C-nu/nu mice, and NIR-PIT was performed on only one side. To evaluate SUPR, fluorescent signal examination was performed using QD800-fluorescent nanoparticles and NIR-fluorescent poly (d,l-lactide-co-glycolic acid) (NIR-PLGA) microparticles. Harmonic signals were evaluated using micro-bubbles of the contrast agent Sonazoid and contrast-enhanced ultrasound (CEUS) imaging. The correlation between SUPR immediately after treatment and NIR-PIT effectiveness on the day after treatment was evaluated. QD800 fluorescent signals persisted only in the treated tumours, and the intensity of remaining signals showed high positive correlation with the therapeutic effect. NIR-PLGA fluorescent signals and Sonazoid-derived harmonic signals remained for a longer time in the treated tumours than in the controls, and the kE value of the two-compartment model correlated with NIR-PIT effectiveness. SUPR measurement using Sonazoid and CEUS imaging could be easily adapted for clinical use as a therapeutic image-based biomarker for monitoring and confirming of NIR-PIT efficacy. This research was supported by ARIM JAPAN of MEXT, the Program for Developing Next-generation Researchers (Japan Science and Technology Agency), KAKEN (18K15923, 21K07217) (JSPS), CREST (JPMJCR19H2, JST), and FOREST-Souhatsu (JST). Mochida Memorial Foundation for Medical and Pharmaceutical Research; Takeda Science Foundation; The Japan Health Foundation; and Princess Takamatsu Cancer Research Fund. Funders only provided financial support and had no role in the study design, data collection, data analysis, interpretation, and writing of the report.

Boron-10 stimulated helium production and accelerated radiation displacements for rapid development of fusion structural materials

Boron doping, combined with neutron capture in fission reactors, has been used to simulate the helium effect on fusion structural materials. However, inhomogeneous helium bubble formation was often observed due to boron segregation to grain boundaries. The excess radiation displacements due to 10B(n, α)7Li reaction, the high-energy lithium and helium ions, also were not accounted for, which can significantly accelerate the displacements-per-atom (dpa) accumulation alongside helium production (appm). Hereby an isotopically pure 10B doping approach is proposed to simulate the extreme environment inside fusion reactors with a high He appm-to-dpa ratio of about 10, which is about 102 × larger than in fission reactors. Computational modeling showed that ∼13% of total radiation displacement was induced by 10B(n, α)7 Li in the case of 1 000 appm 10B doped Fe samples, which becomes even greater with increasing 10B loading. Spatially homogenous radiation damage and helium generation are predicted for grain sizes less than 1 μm, even if the boron partially formed precipitates or segregates on grain boundaries. Feasibility studies with various 10B doping (and 235U-codoping) levels in research reactors showed the estimated helium generation and radiation damage would significantly mimic fusion conditions and greatly expedite fusion materials testing, from many years down to months.

Applicability of the NASA galactic cosmic ray simulator for mice, rats, and minipigs

Space radiation poses multiple health risks to astronauts including cancer, cardiovascular disease, and damage to the central nervous system. Radiation from galactic cosmic rays (GCR) is the main source of these risks for missions beyond low Earth orbit to the moon and beyond. A galactic cosmic ray simulator (GCRsim) was developed at the NASA Space Radiation Laboratory to better understand and mitigate these risks by simulating the complex mixed field of the GCR environment at a ground-based facility. The GCRsim delivers a radiation field to cell and animal models in a laboratory setting that is comparable to the shielded radiation environment within internal organs of astronauts in deep space missions. Previous verification studies using Monte Carlo simulations with mouse (Digimouse) and rat (Digirat) digital phantoms showed that the GCRsim yields acceptable dose homogeneity within the internal organs of these animals. Spectral characteristics of the intended space radiation environment are also accurately reproduced at radiosensitive sites in both phantoms. In this work, similar Monte Carlo simulations were performed in a minipig model (Digipig) to show the applicability and limitations of the current GCRsim for larger animal model systems. The results showed dose homogeneity in internal organs of the three animal models with GCRsim irradiation. While slightly lower average doses were seen in the minipig compared to the external beam dose, the individual voxel doses in slices of the phantoms were found to be within 6%–8% of the average voxel dose, establishing that the GCRsim can still provide a relatively homogeneous irradiation within larger animals. Furthermore, simulated dose and fluence spectral results across the relevant linear energy transfer (LET) range agreed well with the reference field in the most relevant regions of the spectra, further verifying that the GCRsim beam represents the reference field in larger animals.

A New Strengthening Process for Carbon-Fiber-Reinforced Thermoplastic Polyphenylene Sulfide (CFRTP-PPS) Interlayered Composite by Electron Beam Irradiation to PPS Prior to Lamination Assembly and Hot Press

Impact by hailstone, volcanic rock, bird strike, or also dropping tools can cause damage to aircraft materials. For maximum safety, the goal is to increase Charpy impact strength (auc) of a carbon-fiber-reinforced thermoplastic polyphenylene sulfide polymer (CFRTP-PPS) composite for potential application to commercial aircraft parts. The layup was three cross-weave CF plies alternating between four PPS plies, [PPS-CF-PPS-CF-PPS-CF-PPS], designated [PPS]4[CF]3. To strengthen, a new process for CFRP-PPS was employed applying homogeneous low voltage electron beam irradiation (HLEBI) to both sides of PPS plies prior to lamination assembly with untreated CF, followed by hot press under 4.0 MPa at 573 K for 8 min. Experimental results showed a 5 kGy HLEBI dose was at or near optimum, increasing auc at each accumulative probability, Pf. Optical microscopy of 5 kGy sample showed a reduction in main crack width with significantly reduced CF separation and pull-out; while, scanning electron microscopy (SEM) and electron dispersive X-ray (EDS) mapping showed PPS adhering to CF. Electron spin resonance (ESR) of a 5 kGy sample indicated lengthening of PPS chains as evidenced by a reduction in dangling bond peak. It Is assumed that 5 kGy HLEBI creates strong bonds at the interface while strengthening the PPS bulk. A model is proposed to illustrate the possible strengthening mechanism.

2D mapping of radiation dose and clonogenic survival for accurate assessment of in vitro X-ray GRID irradiation effects

Spatially fractionated radiation therapy (SFRT or GRID) is an approach to deliver high local radiation doses in an ‘on-off’ pattern. To better appraise the radiobiological effects from GRID, a framework to link local radiation dose to clonogenic survival needs to be developed. A549 lung cancer cells were irradiated in T25 cm2 flasks using 220 kV x-rays with an open field or through a tungsten GRID collimator with periodical 5 mm openings and 10 mm blockings. Delivered nominal doses were 2, 5, and 10 Gy. A novel approach for image segmentation was used to locate the centroid of surviving colonies in scanned images of the cell flasks. GafchromicTM film dosimetry (GFD) and FLUKA Monte Carlo (MC) simulations were employed to map the dose at each surviving colony centroid. Fitting the linear-quadratic (LQ) function to clonogenic survival data for open field irradiation, the expected survival level at a given dose level was calculated. The expected survival levels were then mapped together with the observed levels in the GRID-irradiated flasks. GFD and FLUKA MC gave similar dose distributions, with a mean peak-to-valley dose ratio of about 5. LQ-parameters for open field irradiation gave Gy−1 and Gy−2. The mean relative percentage deviation between observed and predicted survival in the (peak; valley) dose regions was (4.6; 3.1) %, (26.6; −1.0) %, and (129.8; −2.3) % for 2, 5 and 10 Gy, respectively. In conclusion, a framework for mapping of surviving colonies following GRID irradiation together with predicted survival levels from homogeneous irradiation was presented. For the given cell line, our findings indicate that GRID irradiation causes reduced survival in the peak regions compared to an open field configuration.

Evaluation of the RadCalc collapsed cone dose calculation algorithm against measured data.

This work describes the experimental validation of the RadCalc (Lifeline software Inc, Tyler) collapsed cone dose calculation algorithm against measured data for a range of scenarios. 6 MV photon beam data were measured in a large water tank on a Varian TrueBeam linear accelerator. These were input into the RadCalc software, in conjunction with head geometry and output calibration information, then used to create a collapsed cone beam model. The model performance was assessed by comparison against measurement, using a selection of homogeneous and inhomogeneous geometries not incorporated into the original beam model. Dose calculations generated using the collapsed cone algorithm are generally in good agreement with measurement. However, the primary collimating of the linac is not accounted for in the RadCalc model and hence dose in the corners of large fields is significantly overestimated. Percentage depth doses were within 0.5% beyond a depth of 2 cm. The dose in the build-up region was underestimated by RadCalc Version 7.1.4.1, with (Distance To Agreement) discrepancies of up to 3 mm which were corrected in Version 7.2.2.0. Beam profiles for homogeneous phantom comparisons were within 2% in the central 80% of the field with out of field dose underestimated by no more than 3%. Dose comparisons in heterogeneous geometries were acceptable and generally within 3.5%. The largest observed differences were found at density interfaces and a result of the RadCalc dose resolution of 2 mm against 1 mm measured. Absolute dose comparisons demonstrated that RadCalc agreed with measurement to within 1.2% under homogeneous media irradiation geometries. For static beam IMRT deliveries agreement was within 2% or 2 mm of measured data, and for complex VMAT deliveries within 3% or 2 mm. The implementation of the (model-based) photon collapsed cone algorithm in RadCalc shows generally good agreement with measured data over a range of simple and complex scenarios considered.

Design of an optical system equipped with blue LEDs for the irradiation of Drosophila melanogaster cultures

A longer exposure to blue light has negative effects on organisms, therefore we present an optical assembly based on a hexagonal design with blue LED light for homogeneous irradiation of cultures of Drosophila melanogaster, which has a variability range of illuminance controlled by the change of local current, useful for the evaluation of various factors under this parameter.