secondary radiation
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2022 ◽  
Vol 23 (2) ◽  
pp. 932
Author(s):  
Dmitry V. Korolev ◽  
Galina A. Shulmeyster ◽  
Natalia V. Evreinova ◽  
Maria S. Syrovatkina ◽  
Maria S. Istomina ◽  
...  

In this paper, we describe the synthesis of multilayer nanoparticles as a platform for the diagnosis and treatment of ischemic injuries. The platform is based on magnetite (MNP) and silica (SNP) nanoparticles, while quinacrine is used as an anti-ischemic agent. The synthesis includes the surface modification of nanoparticles with (3-glycidyloxypropyl)trimethoxysilane (GPMS), the immobilization of quinacrine, and the formation of a chitosan coating, which is used to fix the fluorophore indocyanine green (ICG) and colloidal quantum dots AgInS2/ZnS (CQDs), which serve as secondary radiation sources. The potential theranostic platform was studied in laboratory animals.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Tisi ◽  
V. Mares ◽  
J. Schreiber ◽  
F. S. Englbrecht ◽  
W. Rühm

AbstractAt the Center for Advanced Laser Applications (CALA), Garching, Germany, the LION (Laser-driven ION Acceleration) experiment is being commissioned, aiming at the production of laser-driven bunches of protons and light ions with multi-MeV energies and repetition frequency up to 1 Hz. A Geant4 Monte Carlo-based study of the secondary neutron and photon fields expected during LION’s different commissioning phases is presented. Goal of this study is the characterization of the secondary radiation environment present inside and outside the LION cave. Three different primary proton spectra, taken from experimental results reported in the literature and representative of three different future stages of the LION’s commissioning path are used. Together with protons, also electrons are emitted through laser-target interaction and are also responsible for the production of secondary radiation. For the electron component of the three source terms, a simplified exponential model is used. Moreover, in order to reduce the simulation complexity, a two-components simplified geometrical model of proton and electron sources is proposed. It has been found that the radiation environment inside the experimental cave is either dominated by photons or neutrons depending on the position in the room and the source term used. The higher the intensity of the source, the higher the neutron contribution to the total dose for all scored positions. Maximum neutron and photon ambient dose equivalent values normalized to 109 simulated incident primaries were calculated at the exit of the vacuum chamber, where values of about 85 nSv (109 primaries)−1 and 1.0 μSv (109 primaries)−1 were found.


Author(s):  
I. M. Kornilovskiy

Purpose: To consider new possibilities of refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Materials and Methods: Experimental (20 pork, 90 rabbit eyes) and clinical studies on photorefractive and phototherapeutic operations with saturation of the corneal stroma with riboflavin (610 operations) were analyzed. To activate riboflavin, secondary radiation induced by exposure to ablative and subablative energy densities was used. A quick transition to energy densities below the ablation threshold without additional calibrations was carried out using a “Microscan Visum-500” excimer laser (Optosystems, Russia). An objective assessment of the refractive keratomodelling effect and visual results was carried out according to the data of complex optometric studies. Results: Experimental and clinical studies have shown the advantages of refractive keratomodeling by theradiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin. Isotonic 0.25% riboflavin solution did not affect the accuracy of refractive ablation and blocked the negative effect of induced secondary radiation on keratocytes and corneal nerves. This reduced the aseptic inflammatory response and the risk of developing an irreversible form of fibroplasia. Ablation with riboflavin initiated a damped crosslinking effect, which increased the photoprotective and strength properties of the thinned cornea. A refractive keratomodelling effect was found when energy densities were applied below the stromal ablation threshold. The magnitude of this refractive effect depended on the total radiation dose and the topography of the affected area. This approach made it possible to implement laser-induced refractive keratomodeling without ablation of the corneal stroma. Conclusion: Refractive modeling of the cornea by the radiation of an argon-fluorine excimer laser in ablative and subablative modes after saturation of the stroma with riboflavin opens up new possibilities in laser correction of ametropia.


2021 ◽  
pp. 162-166
Author(s):  
Ioannis Vlachos ◽  
Ioannis Kandarakis ◽  
Giorgos Panayiotakis

Radiation protection for personnel working with X-rays is of vital importance. Several studies have been published regarding the secondary radiation and the shielding requirements to areas that are adjacent to the X-ray units. In this work, secondary radiation in a conventional radiographic room, in terms of dose rate (mSv/hr), as a function of different radiographic exposure factors has been studied. The measurements were performed with a 451P Fluke Biomedical survey meter on a Philips Medio 65 CP-H X-ray generator with a cylindrical water phantom. It was found that the dose rate from the scatter radiation decreases with distance. An added filtration of 2.0 mmAl at 100 kVp reduced the secondary dose rate further by 21.4%. The results of this study may be of value during exposure of personnel that are not protected by shielding materials. Highlights Ÿ It was found that the dose rate from the scatter radiation decreases with distance. An added filtration of 2.0 mmAl at 100 kVp reduced the secondary dose rate further by 21.4%. Ÿ The mean secondary X-ray energies for 60, 80, 100 and 100 kV with 2 mmAl added, were calculated as 34.41, 51.12, 69.03 and 71.29 keV respectively. Ÿ The results of this study are of value during exposure of people such as radiographers, and patients during the use of mobile X-ray units.


2021 ◽  
pp. 35-38
Author(s):  
I.M. Kornilovskiy ◽  

Purpose. To substantiate the expediency of using ablative and subablative energy densities of an argon-fluorine excimer laser for corneal crosslinking. Material and methods. In the period from 1 month to 6 years, the results of more than 500 photorefractive and phototherapeutic operations with saturation of the cornea with riboflavin and the effect of crosslinking were analyzed. To activate riboflavin, secondary radiation was used, induced by the use of ablative and subablative energy densities of an argon-fluorine excimer laser. For an objective assessment of the effect of excimer laser crosslinking, we used the techniques of computed keratotopography, aberrometry, optical coherence tomography, and densitometry. Results. Clinical observations have shown that in most cases of photorefractive surgery of the cornea for the prevention of keratoectasias, it is sufficient to carry out ablation after saturation of the corneal stroma with 0.25% isotonic riboflavin solution for 3-10 minutes, depending on the degree of ametropia and the volume of tissue removed. This provided photoprotective protection of deeper stromal structures from the negative effects of ablation-induced secondary radiation. At the same time, upon completion of ablation, secondary radiation initiated the effect of crosslinking in the adjacent layers, which did not violate the elastic properties of the cornea. In a number of cases, the cross-linking effect was enhanced by additional exposure to energy densities below the ablation threshold and the formation of a Bowman-like membrane structure on the ablation surface. For keratoconus and corneal pathology, without and in combination with keratoectasia, the technology of therapeutic cross-linking was used. This technology provided for the saturation of the stroma with 0.1% or 0.25% isotonic riboflavin solution and its activation by subablative radiation energy densities of an argon-fluorine excimer laser. During therapeutic crosslinking, according to OCT and densitometry, all the classic signs of traditional corneal crosslinking were revealed. Conclusion. The radiation of an argon-fluorine excimer laser with the use of ablative pulse energy densities can be recommended for prophylactic crosslinking in all cases of corneal thinning during photorefractive surgeries, while the use of energy densities below the ablation threshold allows for therapeutic crosslinking in keratoconus and corneal ectasias of various etiology. Key words: excimer laser crosslinking, cornea, keratoconus, photorefractive ablation, riboflavin.


Author(s):  
M.M. Sobirov ◽  

This article studies the polarization characteristics of diffusely reflected backward radiation when illuminating a semiinfinite, light-scattering medium with unpolarized radiation. The formation of neutral Babine, Brewster and Arago polarization points in the angular polarization characteristics of the secondary radiation is shown. Comparison between the results of exact numerical calculations and approximate analytical formulas has been carried out and physical conditions for the appearance of neutral points depending on the angles of illumination and the multiplicity of scattering have been analyzed.


2021 ◽  
Vol 81 (4) ◽  
Author(s):  
A. Göggelmann ◽  
J. Jochum ◽  
L. Gastaldo ◽  
C. Velte ◽  
F. Mantegazzini

AbstractFor above ground particle physics experiments, cosmic muons are common source of background, not only for direct detector hits, but also for secondary radiation created in neighboring materials. The ECHo experiment has been designed for the determination of the effective electron neutrino mass by the analysis of the endpoint region of the $$^{163}\text {Ho}$$ 163 Ho electron capture spectrum. The fraction of events occurring in the region of interest of 10 eV below the $$Q_{\mathrm {EC}}$$ Q EC value of about 2.8 keV is only of the order of $$10^{-9}$$ 10 - 9 . This means that the background in that region need to be studied, characterized and methods to suppress it need to be developed. We expect a major background contribution to be due to cosmic muons and radiation produced by muons traveling through material around the detectors. To determine the muon-related background in metallic magnetic calorimeters (MMCs) used in the ECHo experiment, we have performed an experiment in which a muon veto was installed around the cryostat used for the operation of the detectors. We analysed the acquired events to investigate the pulse shape of MMC events in coincidence with the muon veto and the rate of multiple coincidences among detector array pixels. With different methods used for identification of muon related events, we studied events generated by muons and secondary radiation depositing energy in the substrate close to the ECHo pixels. In addition, energy depositions of muons and secondary radiation in the detectors was studied via Monte Carlo simulation. At the present status of investigation, we conclude that muon related events will be a negligible background in the region of interest of the $$^{163}\text {Ho}$$ 163 Ho spectrum.


Author(s):  
Niloofar Azadegan ◽  
Mehdi Hassanpour ◽  
Mayeen Uddin Khandaker ◽  
Mohammad Rashed Iqbal Faruque ◽  
K.S. Al-mugren ◽  
...  

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