Irradiation Beam Research Articles

Comparison study of iron and iron-oxide nanoparticles for thermoplasmonic applications

The plasmonic nanoparticles have the properties of surface plasmon resonance (SPR) that can be used to heat up the surrounding by absorbing maximum light from an irradiated beam. Therefore, the present study reveals the photothermal effect of iron and iron-oxide nanosphere in different ambient environments with varying radii from 20 nm to 60 nm. Based on Mie’s theory, PyMieLab_V1.0 software is used to calculate the size-dependent absorption cross-section of spherical nanoparticles. The absorption spectra at λmax have been tuned from the UV to Infrared region of Fe nanoparticles in different surrounding environments while for Fe2O3 NPs, it reveals in the UV region. As the nanoparticle size increases, the absorption peak position of Fe and Fe2O3 NPs shifts towards the longer wavelength regime on the electromagnetic spectrum. It has been observed that the heat generation rate and the maximum temperature gradually increase with particle sizes and a 60 nm particle’s size has maximum heat generated as well as a maximum temperature increase further, iron NPs are more dominant than iron oxide NPs. At the resonance wavelength, the near-field enhancement is observed with the nanosphere's radii, but with variation in the value of refractive indices, it decreases. Thus, this simulated work opens potential applications in a newly emerging field like thermo-plasmonic and thermo-optic.

Effect of scanning speed on molten metal behaviour under angled irradiation with a continuous-wave laser

Laser processing is one of the most suitable technologies for fabricating controlled structures consisting of grooves or holes having a depth of several tens of micrometres on a metal surface. These structures are expected to improve the characteristics of the surface, such as its adhesiveness to metal and plastics. To control the surface structures, it is important to understand the dynamic behaviours during laser processing. Surface processing using an angled continuous-wave (CW) laser irradiation has been proposed for high-speed surface structuring. Distinct structures consisting of high upheavals on the incident side of the irradiated laser beam and wide grooves on the reflection side are formed on metal surfaces using this proposed method. The dynamic phenomena of molten metal during laser irradiation were investigated by examining the effect of scanning speed via experiments and thermal fluid analyses under the conditions of an average power of 200 W, an irradiation angle of 60°, and a scanning speed of 0.5–2.0 m/s. High-speed camera observations and fluid analysis revealed that the molten metal flow velocity from the reflection side to incident side significantly increased with an increase in scanning speed. Thus, the molten metal was dispersed on the reflection side and accumulated on the incident side. These asymmetric molten metal behaviours resulted in the formation of distinct surface structures. The detailed analyses of molten metal behaviours conducted in this study will help clarify the phenomena associated with high-speed laser surface structuring.

Electrostatic accelerator facilities and their applications at Peking University

<p indent="0mm">Electrostatic accelerators are powerful tools in many research fields, such as nuclear physics, materials science, and archaeology. Three electrostatic accelerators, the 1.7 MV tandem, the single stage Van de Graaff with a terminal voltage of 4.5 MV, and the EN tandem with a terminal voltage of 6 MV, were installed in 1980s and have been put into operation since the early 1990s at Peking University. The 1.7 MV tandem accelerator is equipped with a radio frequency charge exchange negative ion source and a cesium sputtering negative ion source, which can produce most of the ions from H to Au. It accelerates the ions to energies from several hundreds of keV to several MeV. The accelerator is used for ion irradiation, ion beam modification of materials, as well as ion beam analysis (IBA), such as Rutherford backscattering spectroscopy (RBS) and channeling. Many significant achievements have been made by using the ion irradiation beamline, especially in the research of nuclear materials. The superlattice steel containing a high density of B2-ordered Ni(Al, Fe) superlattice nanoprecipitates (NPs) was irradiated with <sc>6 MeV</sc> Au ions at different high temperatures. The superlattice steel exhibits extraordinary radiation tolerance, namely, zero void swelling at 400–600°C under an average radiation damage of up to <sc>2350 dpa,</sc> outperforming most of the other steels studied to date. This paper demonstrates a counterintuitive strategy to enhance the radiation resistance of metallic materials by simply ordered superlattice NPs. For the 4.5 MV electrostatic accelerator, the isotope ions of hydrogen or helium can be produced in the energy range of <sc>0.7–3.8 MeV,</sc> and continuous or pulsed quasi-monoenergetic neutron fields <sc>(0.03–7 MeV,</sc> <sc>14–19 MeV)</sc> can be generated by ion beam bombarding targets. The neutron fields have applied it to measure (n, α) reaction cross section. Based on the 4.5 MV electrostatic accelerator, a total-IBA system has been established. Total-IBA can obtain self-consistency results through analyzing spectra of different emission particles, without massive modification of equipment. RBS-nuclear reaction analysis (NRA)-particle-induced X-ray emission analysis (PIXE) integrated IBA experiment was carried out to study a Fe-based alloy. The incident particle is ³He⁺ under <sc>3.0 MeV.</sc> The integrated charge is obtained by fitting the RBS spectrum. The content and depth distribution of C element can be determined by analyzing the NRA spectrum. The signal of O element can also be observed in the NRA spectrum, and its depth distribution can be obtained by fitting RBS. More than ten trace elements are analyzed by PIXE, and P has the lowest content, which is <sc>158.2 ppm.</sc> The 6 MV EN tandem accelerator, which has supported much basic and application research at Peking University, was transferred from Oxford University, UK. It is suitable for accelerator mass spectrometry (AMS), ion irradiation and ion beam analysis. The accelerator can also be applied for detector calibration. CR-39 nuclear track detectors were irradiated by <sc>3–8 MeV</sc> mono-energetic protons and <sc>6–30 MeV</sc> mono-energetic carbon ions, which were produced by the 6 MV tandem accelerator. The relationships between particle energy and orbital diameter in CR-39 detectors are established. These data on CR-39 detectors will be useful for identifying reaction products in laser-plasma experiments with complex conditions. With the technique development such as modern ion beam analysis technology and multi-beam to one target, more attractive applications are expected.

Study on occupational exposure of medical staff caused by induced radioactivity in the treatment room of medical heavy-ion facility

Heavy-ion radiotherapy is currently recognized as the most advanced particle therapy method and is being vigorously promoted and applied worldwide. This method can rapidly generate radiation and induce radioactivity during treatment. However, the induced radioactivity, which is the primary source of exposure for medical staff, does not disappear following therapeutic application in the treatment room. In this study, we investigated the characteristics, dose rate distribution, and impact of this induced radioactivity on medical staff in the treatment room (uniform scanning mode) at Gansu Wuwei Tumor Hospital using experimental measurement and Monte Carlo simulation. We found that the exposure dose experienced by medical staff is predominantly related to the irradiated patients for single irradiation and the irradiated beam delivery system for long-term irradiation. The half-lives of the main radionuclides ranged from a few minutes to tens of minutes for single irradiation and from tens of days to hundreds of days for long-term irradiation. The primary radionuclide contributors are 15O, 11C, 176Ta, and 177W. We also estimated the personal dose experienced by the medical staff in the treatment room in relation to their working patterns. The results showed that the maximum annual exposure dose of medical staff in the horizontal treatment direction under the current model was 0.728 mSv. We hypothesized that an appropriate increase in the patient's treatment could reduce the annual exposure dose of medical staff to 0.650 mSv without changing the total treatment time per day. Finally, some suggestions were made to reduce the exposure of medical staff to unwanted radiation.

Exploring thermoplasmonic profiles of some noble metallic nanospheres

In the current study, we have described the photothermal effect of noble metal (Au, Ag, or Cu) nanospheres immersed in water (at ambient conditions) with the radius of nanospheres ranging from 10 nm to 50 nm. The theoretical simulation software MiePlot based on Mie’s theory is used to calculate the optical properties like absorption and scattering of light energy. In order to determine the heat generation by light energy absorption of nanospheres and temperature distribution by plasmonic nanospheres, we computed the steady using state heat transfer equation. The plasmonic nanoparticle have a property of surface plasmon resonance (SPR) that can be used to heat up the surrounding by absorbing maximum light from irradiated beam. Based on this, we calculated the absorption cross-section of noble metal nanosphere with various sizes. The surface plasmon resonance have been tuned from ultraviolet-visible (UV-vis) range by varying the size of these nanosphere. Since, the radius of the nanosphere had a significant impact on the temperature and the maximum temperature increase inside the nanoparticle is associated with its absorption cross-section. These theoretical studies seek to advance our fundamental knowledge of the heating process by plasmonic nano-heaters in UV-vis region, which has numerous practical uses. • The SPR for noble metals is tuned from Ultraviolet-visible range by varying the size of nanosphere. • The maximum absorption for Au, Ag, and Cu noble metals nanospheres is perceived at the wavelength of 543 nm, 390 nm, and 582 nm, respectively. • The temperature profiles of noble metal nanospheres with varying wavelength are reported. • The maximum temperature increase is found inside the nanosphere for different radii in the presence of water (n = 1.33) as surrounding medium.

Parametric triggering of vortices in toroidally trapped rotating Bose–Einstein condensates

We study the creation of vortices by triggering the rotating Bose–Einstein condensates in a toroidal trap with trap parameters such as laser beam waist and Gaussian potential depth. By numerically solving the time-dependent Gross–Pitaevskii equation in two dimensions, we observe a change in vortex structure and a considerable increase in the number of vortices when the waist of the irradiated laser beam is in consonance with the area of the condensate as we vary the Gaussian potential depth. By computing the root mean square radius of the condensate, we confirm the variation in the number of vortices generated as a function of the ratio between the root-mean-square radius of the condensate and the laser beam waist. In particular, the number of hidden vortices reaches the maximum value when the above ratio is close to the value 0.7. We find the variation in the number of vortices is rapid for deeper Gaussian potentials, and we conclude that the larger beam waist and deeper Gaussian potentials generate more vortices. Further, we calculate the number of vortices using the Feynman rule with Thomas Fermi approximation and compare them with the numerical results. We also observe that the critical rotation frequency decreases with an increase in depth of Gaussian potential.

Phantom Study of the Optimum Irradiation Angle for Proton Beam Therapy in Hepatocellular Carcinoma

<h3>Purpose/Objective(s)</h3> Passive proton beam therapy (PPBT) for hepatocellular carcinoma (HCC) has a higher local control rate than surgery or photon beam therapy. Moreover, it is attracting attention as one of the new treatment options. In the PPBT planning, the selection of the beam angle is determined according to the subjective judgment of the planner. Therefore, there are differences in the dose distribution depending on the planner. It has not yet been clarified which the irradiation angle can be selected to reduce unnecessary dose on the organ-at-risks and maintain the target coverage. The purpose of this study was to determining the optimal beam angle for liver S8 lesions. <h3>Materials/Methods</h3> The subjects were fifty-four treatment plans for HCC located in S8 irradiated using PPBT during the period of 2012.6-2021.3 at the National Cancer Center Hospital East. Tumor sizes were aggregated from the subjects. Clinical Target Volume (CTV) of the subject's liver ranged from 4 cm3 to 1370 cm3. Tumor sizes ranged from 132 cm to 655 cm3. From these results, the average CTV were represented on a virtual phantom, the dose distribution using PPBT was optimized using two irradiation angles. For the calculation of the optimum irradiation angle, the combination of the two beams rotated every 10 degrees and the best dose distribution was considered to be the optimum angle. The Conformity Index (CI) and Homogeneity Index (HI) of the CTV and the V30 (%) of the liver were calculated using the Dose volume histogram (DVH). <h3>Results</h3> The combination of beam angles showing 1 in the Conformity Index was 360 ° and 250 °, 350 ° and 230 °, 260 ° and 190 ° for small tumor volumes. Homogeneity Index and V30 averaged 1.06 and 28.0%, respectively. At the time of large tumor volume, it was 350 ° and 270 °, 350 ° and 250 °, 250 ° and 170 °. Homogeneity Index and V30 averaged 1.07 and 47.6%, respectively. The treatment schemes beam-arranged with a 70 ° difference in angle between the two beams were the most homogeneous with respect to the target. A significant difference was found in Conformity Index when compared to the most heterogeneous 190 ° difference (p <0.05). <h3>Conclusion</h3> Based on our findings, we recommend using a 2-beam configuration with a beam tilted by approximately 70 ° between the two beams for passive irradiation of hepatocellular carcinoma located in S8. This has the potential to achieve a uniform dose distribution within the target and at the same time reduce the hepatic dose. However, it should be noted that there is a difference in dose increase / decrease depending on the positional relationship of organs and tumors. Further treatment planning studies on aspects of respiration and organ movement need to be conducted.

New insight into anodization of aluminium with focused ion beam pre-patterning

The self-ordered anodic aluminium oxide (AAO) structure consists of micron-scale domains—defect-free areas with a hexagonal arrangement of pores. A substantial increase in domain size is possible solely by pre-patterning the aluminium surface in the form of a defect-free hexagonal array of concaves, which guide the pore growth during subsequent anodization. Among the numerous pre-patterning techniques, direct etching by focused gallium ion beam (Ga FIB) allows the preparation of AAO with a custom-made geometry through precise control of the irradiation positions, beam energy, and ion dosage. The main drawback of the FIB approach includes gallium contamination of the aluminium surface. Here, we propose a multi-step anodizing procedure to prevent gallium incorporation into the aluminium substrate. The suggested approach successfully covers a wide range of AAO interpore distances from 100 to 500 nm. In particular, anodization of FIB pre-patterned aluminium in 0.1 M phosphoric acid at 195 V to prepare AAO with the interpore distance of about 500 nm was demonstrated for the first time. The quantification of the degree of pore ordering reveals the fraction of pores in hexagonal coordination above 96% and the in-plane mosaicity below 3° over an area of about 1000 μm2. Large-scale defect-free AAO structures are promising for creating photonic crystals and hyperbolic metamaterials with distinct functional properties.

On-line optical absorption of electron-irradiated yttria-stabilized zirconia

The kinetics of color-center formation and decay in electron-irradiated cubic yttria-stabilized zirconia (ZrO2: Y3+) has been followed by on-line UV/Vis absorption spectroscopy. The growth and decay with time of absorption spectra have been measured upon electron irradiation and subsequent beam shut-off for energies of 0.8, 1.0, 1.75, and 2.5 MeV. Spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.8 eV for high beam current intensity. These bands are assigned to so-called T-centers, i.e. Zr3+ ions in trigonal point symmetry, which are produced by ionization processes induced by either photon irradiation or charged particle irradiation. A red-shift of the absorption spectra is observed for lower current intensities irrespective of electron energy: these spectra have been fitted with two broad absorption bands centered at about 3.0 eV and 3.3 eV. This modification is attributed to a change in the local environment of Zr3+ ions due to the formation of neighboring oxygen vacancies by elastic collisions, which depends on the electron energy and flux. A common behavior of an increase in differential absorbance to similar saturation values after accumulation of the irradiation dose and decays with time to similar non-zero asymptotic values has been observed, irrespective of the electron energy and flux. However, the rise time and lifetime deduced from the growth and decay curves of the absorbance are dependent on the electron energy. The increase and saturation of the T-center growth rate with electron energy can be attributed to competitive channels of hole trapping at the oxygen and zirconium vacancies induced by elastic collisions. The present on-line experiments reveal the complex process of point-defect generation resulting from the interplay of displacement damage and electronic excitation.

Temperature/pH-responsive carmofur-loaded nanogels rapidly prepared via one-pot laser-induced emulsion polymerization

Tumor microenvironment-responsive nanogels loading antitumor drugs can improve the chemotherapy efficiency due to their suitable size, great hydrophilicity, excellent biocompatibility, and sensitivity to specific stimulation. Herein, a simple and effective strategy of one-pot laser-induced emulsion polymerization at 532 nm was developed to prepare carmofur-loaded nanogels based on biocompatible and temperature/pH-sensitive monomers including polyethylene glycol diacrylate (PEGDA), N-vinylcaprolactam (NVCL), and 2-(dimethylamino) ethyl methacrylate (DMAEMA). The nanogels loading carmofur with dual-stimuli responsive drug release properties were rapidly obtained under laser irradiation (beam diameter 2.5 mm, laser power 60 mW) for only 100 s. These nanogels exhibited an average hydrodynamic diameter of 195.9 nm and a low polydispersity index of 0.115. The effect of monomer ratio on the size, morphology, double-bond conversion, and thermo/pH-sensitivity of nanogels was investigated. The cumulative carmofur release from nanogels at pH 5.0 within 48 h was nearly three times that at pH 7.4, while the release amount at 42 °C was twice that at 25 °C, showing the controlled and sustainable release with the change of pH and temperature. The in vitro release kinetics of carmofur was in accord with first-order release model.

Chemical identification of lithium compounds by reflection electron energy loss spectroscopy

This article shows that reflection electron energy loss spectroscopy can be used to identify Li compounds with comparable accuracy as X-ray absorption near edge structure by optimizing the energy and energy width of the irradiated electron beam. This method was applied to analyzing the solid–electrolyte interface of Li metal, and the chemical state of Li could be examined directly without being affected by surface contamination.

Aligned Stacking of Nanopatterned 2DMaterials for High-Resolution 3DDevice Fabrication.

Two-dimensional materials can be combined by placing individual layers on top of each other, so that they are bound only by their van der Waals interaction. The sequence of layers can be chosen arbitrarily, enabling an essentially atomic-level control of the material and thereby a wide choice of properties along one dimension. However, simultaneous control over the structure in the in-plane directions is so far still rather limited. Here, we combine spatially controlled modifications of 2D materials, using focused electron irradiation or electron beam induced etching, with the layer-by-layer assembly of van der Waals heterostructures. The presented assembly process makes it possible to structure each layer with an arbitrary pattern prior to the assembly into the heterostructure. Moreover, it enables a stacking of the layers with accurate lateral alignment, with an accuracy of currently 10 nm, under observation in an electron microscope. Together, this enables the fabrication of almost arbitrary 3D structures with highest spatial resolution.

The effect of radiolytic oxidation on the elastic properties of nuclear graphite measured by electronic speckle pattern interferometry

• Three-point bend measurement data characterised by ESPI and inverse modelling. • Static Young's modulus , Poisson's ratio and strength determined. • Measurements performed on 218 irradiated graphite beams taken from UK AGR stations. • Graphite samples (6 × 6 × 19 mm) cover dose range to 21.1 DPA and weight loss to 46%. • Modulus and strength correlate well with radiolytic weight loss. The Young's modulus, Poisson's ratio and flexural strength of 218 beams of radiolytically oxidised nuclear graphite have been determined by combining electronic speckle pattern interferometry, ESPI, and inverse finite element modelling techniques. The graphite was extracted from three operational advanced gas cooled reactor stations where it had been subjected to fast neutron irradiation and radiolytic oxidation resulting in mass loss. The 6 × 6 × 19 mm beam samples had densities ranging from 1063 – 1840 kg.m −3 , equivalent to weight losses up to 46%, with cumulative neutron doses of up to 161 × 10 20 n.cm −2 equivalent Dido nickel dose, or 21.1 displacements per atom, significantly extending the datasets available in the open literature to higher levels of both dose and oxidation. In situ ESPI measurements were collected during three-point bend tests, creating full field displacement maps of the evolving deformation to which simulations were matched by chi-squared minimisation of the elastic properties. Potential loading abnormalities were accounted for in the fitting process to ensure the simulations were representative, with total uncertainties in the determined Young's modulus and Poisson's ratio values of ± 4.5% and ± 0.08, respectively. Consistent trends were observed in the behaviour of the material from the different stations, with strong positive dependences on density for both the flexural strength and Young's modulus. The strength and Young's modulus remained well correlated even to high levels of oxidation mass loss. Conversely, the Poisson's ratio was practically invariant with oxidation with mean values of 0.21 ± 0.03, 0.24 ± 0.05 and 0.25 ± 0.05 for the three stations. The combined ESPI-finite element measurement approach is demonstrated as robust for irradiated small specimens, making it suitable for monitoring graphite in future reactors. The collected data support the safety assessments of the current reactors, enabling predictions of the responses to progressively higher mean core mass loss.

Flexible radiochromic dosimeters development for complex irradiation beams

In vivo dosimetry for patient radioprotection is a real challenge concerning new radiotherapy treatments. In this study we aim to develop a dosimeter based on tissue equivalent material, flexible and adaptable to the patient morphology in order to perform in vivo dosimetry for complex irradiation beams. Here, we report the evaluation in standard beams of highly flexible dosimeter composed of a silicone elastomer and containing leucomalachite green as radiochromic dye and give a first estimation of LMG-micelle hydrogel response. All results are compared to a commercially available PRESAGE® dosimeter.

Calculation of dose rates in loss of coolant accident due to double ended rupture of the experimental tangential irradiation beam tube of MTR reactor.

A MTR reactor is an open water pool reactor type. The water pool serves as a shield from radioactive radiations. The most serious accident in this type of reactor is the Loss of Coolant Accident (LOCA) due to rupture either of a primary coolant pipe or of any experimental beam tube. In the present work it has been assumed that pool water drains out due to double ended rupture of the tangential irradiation beam tube (TIC) which has a diameter 150 mm. For an operating power level of 22 MW, the equilibrium core would enter into melting conditions if the pool drain time is less than one hour. It was also assumed that Emergency Core Cooling System (chimney water injection system and siphon effect breaker were not working. The reactor interiors have been modeled using the Monte Carlo N-Particle Transport code MCNPX 2.7.0. The source term has been determined using the ORIGEN-2 code. The doses and dose rates calculations in different places of operator (as phantom of Tissue-Equivalent Material) inside of the reactor building were determined by using Monte Carlo N-Particle Transport (MCNPX).The results show that the dose rate in the control room would be 5.24557 SV/h, the dose rate in the reactor hall above the pools on the gate would be7.20137 SV/h and the dose rate in the Emergency control room would be 2.68239 SV/h. Those dose rates are extremely high and would lead to fatal doses in short time.

Calculation of dose rates in loss of coolant accident due to double ended rupture of the experimental tangential irradiation beam tube of MTR reactor

The doses and dose rates following a LOCA in MTR reactor have been studied. A MTR reactor is an open pool type. The water pool serves as a shield from radioactive radiations.The most serious accident in this type of reactor is the Loss of Coolant Accident (LOCA) due to rupture either of a primary coolant pipe or of any experimental beam tube. In the present work it has been assumed that pool water drains out due to double ended rupture of the tangential irradiation beam tube (TIC) which has a diameter 150 mm. For an operating power level of 22 MW, the equilibrium core will enter into melting conditions if the pool drain time is less than 1 h.It was also assumed that Emergency Core Cooling System (chimney water injection system and siphon effect breaker) were not working. Therefore, conservatively a severe damage (∼80%) is expected to occur to the core, either by a core uncover situation following extended boiling operation, or by a core covered situation with extended boiling.The reactor interiors have been modeled using the Monte Carlo N-Particle Transport code MCNPX 2.7.0. The source term has been determined using the ORIGEN-2 code. The doses and dose rates calculations in different places of operator (as phantom of Tissue-Equivalent Material) inside of the reactor building were determined by using Monte Carlo N-Particle Transport (MCNPX). The results show that the dose rate in the control room is 5.24 Sv/h, the dose rate in the reactor hall above the pools on the gate is 7.20Sv/h and the dose rate in the Emergency control room is 2.68Sv/h. Those dose rates are extremely high and would lead to fatal doses in short time.

Chronological Analysis of Acute Hematological Outcomes after Proton and Photon Beam Craniospinal Irradiation in Pediatric Brain Tumors.

PurposeThis study aimed to compare the early hematological dynamics and acute toxicities between proton beam craniospinal irradiation (PrCSI) and photon beam craniospinal irradiation (PhCSI) for pediatric brain tumors.Materials and MethodsWe retrospectively reviewed patients with pediatric brain tumors who received craniospinal irradiation (CSI). The average change in hemoglobin levels (ΔHbavg), absolute lymphocyte counts (ΔALCavg), and platelet counts (ΔPLTavg) from baseline values was evaluated and compared between the PrCSI and PhCSI groups at 1 and 2 weeks after the initiation of CSI, 1 week before and at the end of radiotherapy, and 3–4 weeks after the completion of radiotherapy using t-test and mixed-model analysis.ResultsThe PrCSI and PhCSI groups consisted of 36 and 30 patients, respectively. There were no significant differences in ΔHbavg between the two groups at any timepoint. However, ΔALCavg and ΔPLTavg were significantly lower in the PhCSI group than in PrCSI group at every timepoint, demonstrating that PrCSI resulted in a significantly lower rate of decline and better recovery of absolute lymphocyte and platelet counts. The rate of grade 3 acute anemia was significantly lower in the PrCSI group than in in the PhCSI group.ConclusionPrCSI showed a lower rate of decline and better recovery of absolute lymphocyte and platelet counts than PhCSI in the CSI for pediatric brain tumors. Grade 3 acute anemia was significantly less frequent in the PrCSI group than in the PhCSI group. Further large-scale studies are warranted to confirm these results.

Effects of Beam Conditions in Ground Irradiation Tests on Degradation of Photovoltaic Characteristics of Space Solar Cells

We investigated the effects of irradiation beam conditions on the performance degradation of silicon and triple-junction solar cells for use in space. The fluence rates of electron and proton beams were varied. Degradation did not depend on the fluence rate of protons for both cells. A higher fluence rate of electrons caused greater degradation of the Si cell, but the dependence was due to the temperature increase during irradiation. Two beam-area expansion methods, defocusing and scanning, were examined for proton irradiation of various energies (50 keV–10 MeV). In comparing the output degradation from irradiation with defocused and scanned proton beams, no significant difference in degradation was found for any proton energy. We plan to reflect these findings into ISO standard of irradiation test method of space solar cells.

Estimated clinical benefit of combining highly conformal target volumes with Volumetric-Modulated Arc Therapy (VMAT) versus conventional flank irradiation in pediatric renal tumors

BackgroundFor decades, Anterior-Posterior/Posterior-Anterior (AP/PA) photon beams were standard-of-care for flank irradiation in children with renal cancer. Recently, highly conformal flank target volumes were defined correcting for postoperative organ shift and intra-fraction motion.By radiotherapy treatment plan comparison, this study aims to estimate the clinical benefits and potential risks of combining highly conformal target volumes with Volumetric-Modulated Arc Therapy (VMAT) versus conventional target volumes with AP/PA beams for flank irradiation. Materials and MethodsTwenty consecutive renal tumor cases (left/right-sided:10/10; median age:3.2 years) were selected. Highly conformal flank target volumes were generated for VMAT, while conventional target volumes were used for AP/PA. For each case, the dose to the organs at risk (OARs) and Total Body Volume (TBV) was calculated to compare VMAT with AP/PA treatment plans for a prescribed dose (PD) of 14.4/1.8 Gy. Dose constraint violation of the tail of the pancreas and spleen (Dmean < 10 Gy), heart (D50 < 5 Gy) or mammary buds (Dmean < 10 Gy) were prioritized as potentially beneficial for clinics. ResultsHighly conformal Planning Target Volumes (PTV) were smaller than conventional volumes (mean ΔPTVAP/PA-PTVVMAT: 555 mL, Δ60%, p=<0.01). A mean dose reduction favoring VMAT was observed for almost all OARs. Dose constraints to the tail of the pancreas, spleen, heart and mammary buds were fulfilled in 8/20, 12/20, 16/20 and 19/20 cases with AP/PA, versus 14/20, 17/20, 20/20 and 20/20 cases with VMAT, respectively. In 12/20 cases, VMAT prevented the dose constraint violation of one or more OARs otherwise exceeded by AP/PA. VMAT increased the TBV receiving 10% of the PD, but reduced the amount of irradiated TBV for all higher doses. ConclusionCompared to 14.4 Gy flank irradiation using conventional AP/PA photon beams, an estimated clinical benefit by dose reduction to the OARs can be expected in 60% of the pediatric renal tumor cases using highly conformal flank target volumes combined with VMAT.

Different sterilization and disinfection methods used for human tendons \u2013 a systematic review using mechanical properties to evaluate tendon allografts

BackgroundIt is important to know the biomechanical properties of an allograft. This is because when looking to do a transplant of a tendon, the tendon must have very similar biomechanical properties to the original tendon. To use tendon allografts, it is critical to properly sterilize the tendon before implantation. In past decades, several sterilization procedures have been used. This study aimed to systematically evaluate the existing literature to compare the values of failure load/ultimate strength and Young’s modulus of elasticity of different sterilization methods on commonly used tendon allografts. Five major scientific literature databases (Web of Science, Science Direct, Scopus, PLOS ONE, Hindawi) and additional sources were used.ResultsStudies used had to show a particular sterilization method. Studies were identified to meet the following inclusion criteria: is a controlled laboratory study, gamma irradiation (dose reported), and other sterilization methods. Search for publications dated between 1991 and March 31st, 2020. The database search and additional sources resulted in 284 records. Two hundred thirty records eliminated during the screening for various reasons. The number of articles used in the final synthesis was 54.ConclusionsIdentified sterilization methods (gamma irradiation, ethylene oxid, supercritical carbon dioxide (SCCO2), BioCleanse, Electron Beam) are offered as a catalog of potential methods.As a result of the broadness of the present research, it provides an overview of sterilization methods and their effect on the mechanical properties (failure load and Young’s modulus of elasticity) of tendons. It does not stand for the state-of-the-art of any single process. Based on a systematic literature review, we recommend freezing and gamma irradiation or electron beam at 14.8–28.5 kGy. These methods are effective at keeping or improving the mechanical properties, while fully sterilizing the inside and the outside of the tendon. Other sterilization method (ethylene oxide, supercritical carbon dioxide (SCCO2), BioCleanse) deteriorated the mechanical properties. These methods are not recommended.