Modulation Of Radiation Research Articles

Nonlinear phenomena in femtosecond laser systems based on Yb: YAG thin-rod amplifiers

Nonlinear effects in a high-power laser amplification system based on thin-rod active elements are experimentally investigated. It is shown that the most important nonlinear effect is the Kerr effect leading to self-focusing and self-phase modulation of laser radiation. The observed luminescence in Yb : YAG crystals in the visible region of the spectrum is caused by the charge transfer luminescence effect, which, in turn, is due to multiphoton absorption of laser radiation. Second-order nonlinearity in the crystal is used to effectively convert femtosecond pulses to second harmonic and sum-frequency waves which exhibit radiations of green and UV spectra.

Auxiliary arbitrary waveform generator for fiber optic gyroscope

Phase modulation of laser radiation using an auxiliary generator makes it possible to improve the accuracy characteristics of fiber-optic gyroscopes. The authors propose a method for generating a phase modulation signal implemented on the basis of a parallel architecture with the possibility of dynamically changing the signal parameters. A prototype of a compact embedded generator for generating signals with frequencies up to 2.5 GHz is presented. The generator is implemented on a field-programmable gate array, which ensured a compact design and made it possible to include it in the design of a fiber-optic gyroscope. The dynamic change of the generated signal is carried out using a personal computer using the developed specialized software that allows generating arbitrary waveforms. For the developed generator, the spectra of a sinusoidal signal and white noise are presented.

Optical alignment and radiative flux characterization of a multi-source high-flux solar simulator

High-flux solar simulators are research-grade sources of artificial radiation mimicking optical characteristics of concentrating solar systems. They allow for experimental evaluation of high-temperature solar thermal devices and materials under controlled and reproducible conditions. In this study, we demonstrate the application of close-range photogrammetry in tandem with radiometry to optically align radiation modules of a multi-source high-flux solar simulator and to characterize its radiative output. The photogrammetric setup consists of photogrammetry targets, a digital camera and photogrammetry software. The radiometric measurements are conducted using mobile Lambertian targets, a heat flux gauge, and a complementary metal-oxide semi-conductor camera equipped with neutral density filters. An iterative procedure for adjusting lamp positions allows obtaining optical configurations of radiative modules meeting experimental requirements of high and ultra-high temperature solar thermal and thermochemical research. Close-range photogrammetry is demonstrated to be a convenient and effective method to obtain the as-built geometric configuration of the solar simulator setup. We report characteristics of an example radiative module configuration for a subset of six radiation modules. The peak and mean radiative fluxes over a 60-mm diameter flat target located in the focal plane are 3080kWm−2 and 1135kWm−2, respectively. The mean aiming error, defined as the average distance between theoretical and actual aiming points in the focal plane, is reduced from 37.20mm to 4.50mm for the pre- and post-alignment configurations, respectively.

Effects of Ambient Temperature and Solar Radiation on Solar Chimney Power Plants (SCPP) Performances

In this paper, the air flow inside the Solar Chimney Power Plants (SCPP) of Manzanares (Spain) has been investigated through numerical simulation, aiming to study the influence of environmental parameters on the SCPP performances. The electrical power produced by the SCPP of different regions in Algeria has been also compared in order to determine the best location for the installation of SCPP in Algeria. The resolution of Navier-Stokes equations that govern the air flow through the SCPP has been conducted using Ansys Fluent software. The k–ε RNG model and the standard wall mode have been selected to simulate the turbulent flow conditions, while the discrete ordinate model has been chosen for the thermal radiation modulation. The solar radiation had a direct effect on the output power while it had no effect on the effectiveness of the SCPP. The Ambient temperature has negatively affected the SCPP efficiency and the output power. Based on the results of this study, solar radiation and ambient temperature are the two main factors that could allow the possibility of adopting the SCPP system in a specific region. The global solar radiation is the dominant factor in the allocation of SCPP output power, relatively to the ambient temperature. It has been concluded that areas with high solar radiation and low ambient temperature are more appropriate for SCPP installation to increase electrical energy production.

Trapping of H ii regions in Population III star formation

ABSTRACT Radiative feedback from massive Population III (Pop III) stars in the form of ionizing and photodissociating photons is widely believed to play a central role in shutting off accretion on to these stars. Understanding whether and how this occurs is vital for predicting the final masses reached by these stars and the form of the Pop III stellar initial mass function. To help us better understand the impact of UV radiation from massive Pop III stars on the gas surrounding them, we carry out high-resolution simulations of the formation and early evolution of these stars, using the arepo moving-mesh code coupled with the innovative radiative transfer module sprai. Contrary to most previous results, we find that the ionizing radiation from these stars is trapped in the dense accretion disc surrounding them. Consequently, the inclusion of radiative feedback has no significant impact on either the number or the total mass of protostars formed during the 20 kyr period that we simulate. We show that the reason that we obtain qualitatively different results from previous studies of Pop III stellar feedback lies in how the radiation is injected into the simulation. H ii region trapping only occurs if the photons are injected on scales smaller than the local scale height of the accretion disc, a criterion not fulfilled in previous 3D simulations of this process. Finally, we speculate as to whether outflows driven by the magnetic field or by Lyman-α radiation pressure may be able to clear enough gas away from the star to allow the H ii region to escape from the disc.

Effects of Aerosol–Induced Snow Albedo Feedback on the Seasonal Snowmelt Over the Himalayan Region

AbstractAerosol‐induced snow darkening and its feedback on seasonal snow cover, snowmelt, and runoff were investigated using the Regional Climate Model (RegCM4.6) coupled with SNow, Ice, and Aerosol Radiation (SNICAR) and aerosol modules over the Himalayas during the melting season (March‐September). The snow albedo reduction due to the deposition of absorbing aerosols increases the 2 m air temperature (1.47°C) and thus decreases the snow cover (10.6%) over the Himalayas during spring. This aerosol‐induced excess warming accelerates the seasonal snowmelt (1.2 mm day−1), which reduces the number of snow‐covered periods by more than 20 days throughout the Himalayas. The accumulated total snowmelt also increased by 41.3% over the Himalayas during the melting season. The early snowmelt and increase in runoff due to aerosol forcing have significant implications on rivers originating from the western Himalayas (Indus Basin). The change in snowmelt distribution and doubling of snowmelt extremes due to aerosol‐induced snow darkening could also translate to an increase in flood risks across the Himalayan river basins. Therefore, the present study highlights the importance of aerosol‐induced snow albedo forcing and its feedback on snowmelt and runoff over the Himalayan region, which has further implications on water availability over the South Asian region.

Retrieval of aerosol properties using relative radiance measurements from an all-sky camera

Abstract. This paper explores the potential of all-sky cameras to retrieve aerosol properties with the GRASP code (Generalized Retrieval of Atmosphere and Surface Properties). To this end, normalized sky radiances (NSRs) extracted from an all-sky camera at three effective wavelengths (467, 536 and 605 nm) are used in this study. NSR observations are a set of relative (uncalibrated) sky radiances in arbitrary units. NSR observations have been simulated for different aerosol loads and types with the forward radiative transfer module of GRASP, indicating that NSR observations contain information about the aerosol type, as well as about the aerosol optical depth (AOD), at least for low and moderate aerosol loads. An additional sensitivity study with synthetic data has been carried out to quantify the theoretical accuracy and precision of the aerosol properties (AOD, size distribution parameters, etc.) retrieved by GRASP using NSR observations as input. As a result, the theoretical accuracy of AOD is within ±0.02 for AOD values lower than or equal to 0.4, while the theoretical precision goes from 0.01 to 0.05 when AOD at 467 nm varies from 0.1 to 0.5. NSR measurements recorded at Valladolid (Spain) with an all-sky camera for more than 2 years have been inverted with GRASP. The retrieved aerosol properties are compared with independent values provided by co-located AERONET (AErosol RObotic NETwork) measurements. AODs from both data sets correlate with determination coefficient (r2) values of about 0.87. Finally, the novel multi-pixel approach of GRASP is applied to daily camera radiances together by constraining the temporal variation in certain aerosol properties. This temporal linkage (multi-pixel approach) provides promising results, reducing the highly temporal variation in some aerosol properties retrieved with the standard (one by one or single-pixel) approach. This work implies an advance in the use of all-sky cameras for the retrieval of aerosol properties.

Non-equilibrium radiation modeling in a gas kinetic simulation code

Radiation modeling is implemented in the highly parallel gas kinetic, open-source plasma simulation suite PICLas. A photon Monte Carlo approach for three-dimensional radiative energy transfer is developed. Since these kind of solvers have the disadvantage of high computational costs and statistical fluctuations, these points are addressed by specific adaptations to the solver. An approach to simulate axisymmetric problems is presented as well as noise reducing methods. Results are compared to a semi-infinite black body radiating cylinder, where an analytical solution is known, and a good agreement for both, three-dimensional and axisymmetric simulations is demonstrated. It is also shown that the implemented noise reducing methods can reduce statistical fluctuations. To calculate radiative properties in terms of emission and absorption coefficients, a line-by-line method is implemented and compared with good agreement to results obtained with other well-established radiation codes. The FIRE II reentry is used as a test case for a simulation combined with DSMC. Unidirectional coupling with the developed radiation modules shows good results compared to measured values as well as in performance scaling.

A flexibly controllable high-flux solar simulator for concentrated solar energy research from extreme magnitudes to uniform distributions

High-flux solar simulator (HFSS) is a useful lab-scale equipment for material, device, and prototype characterizations and testing via creating stable and controllable irradiation environments close to real solar concentrators. This study presents the design, building, and characterization of a flexibly controllable 40 kWe HFSS consisted of 4 × 10 kWe radiation modules at SUSTech enabling applications from photothermal to photoelectrochemical devices. A cylindrical reflector was designed at the focal plane as the optical homogenizer for generating uniform flux profiles for concentrated photovoltaic and photoelectrochemical applications. Both indirect and direct calibration methods were performed, compared, and correlated. The measured results are shown a record high peak flux of 41.43 MW m−2, summing over all four lamps without the homogenizer, which is 91% higher than the highest value reported in the literature. The average flux and total power in a circular target with a radius of 50 mm are 2.25 MW m−2 and 17.57 kW, respectively, showing a high electricity-to-radiation efficiency of 43.93%. When adding the homogenizer, the total uniformity of the system was tripled. Highly uniform region with non-uniformity of only 1.76% can be identified meeting the ASTM class A standard in terms of spatial non-uniformity. In addition to solar thermal/thermochemical applications, this newly built HFSS enables applications in concentrated solar photovoltaics and photoelectrochemical devices and beyond.

Фотомодуляция люминесценции наносфер с квантовыми точками CdSe/ZnS в полимерных пленках

The results of studies of the spectral-kinetic (absorption and fluorescent) characteristics of the polymer nanospheres created by us (containing luminescent inorganic CdSe/ZnS quantum dots and photochromic diarylethene molecules) incorporated into a polymer film are presented. A reversible modulation of the fluorescence intensity of quantum dots, caused by the photoisomerization of diarylethene molecules, was found. It is shown that nanospheres in polymer matrices exhibit higher efficiencies of both photoinduced modulation of QD radiation and Förster resonance energy transfer (FRET) from QDs to the cyclic isomer of DAE as compared to solutions. The results can be used, for example, to create luminescent photocontrolled panels based on films containing fluorescent nanoparticles.

Luminescence photomodulation of nanospheres with CdSe/ZnS quantum dots in polymer films

The results of studies of the spectral-kinetic (absorption and fluorescent) characteristics of the polymer nanospheres created by us (containing luminescent inorganic CdSe/ZnS quantum dots and photochromic diarylethene molecules) incorporated into a polymer film are presented. A reversible modulation of the fluorescence intensity of quantum dots, caused by the photoisomerization of diarylethene molecules, was found. It is shown that nanospheres in polymer matrices exhibit higher efficiencies of both photoinduced modulation of QD radiation and Forster resonance energy transfer (FRET) from QDs to the cyclic isomer of DAE as compared to solutions. The results can be used, for example, to create luminescent photocontrolled panels based on films containing fluorescent nanoparticles. Keywords: photochromism, fluorescence, quantum dot, Forster resonance energy transfer, polymer nanospheres, polymer films

UV-Visible radiation modulation abilities of photon up-converting nanocapsules integrated with an oscillatory reaction

Oil-in-silica capsules enable triplet–triplet annihilation radiation up-conversion in air equilibrated conditions and their use to achieve controlled intensity modulated emission.

Radiation-hydrodynamics with MPI-AMRVAC

Context. Radiation controls the dynamics and energetics of many astrophysical environments. To capture the coupling between the radiation and matter, however, is often a physically complex and computationally expensive endeavor. Aims. We sought to develop a numerical tool to perform radiation-hydrodynamics simulations in various configurations at an affordable cost. Methods. We built upon the finite volume code MPI-AMRVAC to solve the equations of hydrodynamics on multi-dimensional adaptive meshes and introduce a new module to handle the coupling with radiation. A non-equilibrium, flux-limiting diffusion approximation was used to close the radiation momentum and energy equations. The time-dependent radiation energy equation was then solved within a flexible framework, fully accounting for radiation forces and work terms and further allowing the user to adopt a variety of descriptions for the radiation-matter interaction terms (“opacities”). Results. We validated the radiation module on a set of standard test cases for which different terms of the radiative energy equation predominate. As a preliminary application to a scientific case, we calculated spherically symmetric models of the radiation-driven and optically thick supersonic outflows from massive Wolf-Rayet stars. This also demonstrates our code’s flexibility, as the illustrated simulation combines opacities typically used in static stellar structure models with a parametrized form for the enhanced line-opacity expected in supersonic flows. Conclusions. This new module provides a convenient and versatile tool for performing multi-dimensional and high-resolution radiative-hydrodynamics simulations in optically thick environments with the MPI-AMRVAC code. The code is ready to be used for a variety of astrophysical applications, where our first target is set to be multi-dimensional simulations of stellar outflows from Wolf-Rayet stars.

Phytochemicals: Potential Therapeutic Modulators of Radiation Induced Signaling Pathways.

Ionizing radiation results in extensive damage to biological systems. The massive amount of ionizing radiation from nuclear accidents, radiation therapy (RT), space exploration, and the nuclear battlefield leads to damage to biological systems. Radiation injuries, such as inflammation, fibrosis, and atrophy, are characterized by genomic instability, apoptosis, necrosis, and oncogenic transformation, mediated by the activation or inhibition of specific signaling pathways. Exposure of tumors or normal cells to different doses of ionizing radiation could lead to the generation of free radical species, which can release signal mediators and lead to harmful effects. Although previous FDA-approved agents effectively mitigate radiation-associated toxicities, their use is limited due to their high cellular toxicities. Preclinical and clinical findings reveal that phytochemicals derived from plants that exhibit potent antioxidant activities efficiently target several signaling pathways. This review examined the prospective roles played by some phytochemicals in altering signal pathways associated with radiation response.

Synergistic modulation of solar and thermal radiation in dynamic energy-efficient windows

Current technologies about the dynamic window in buildings, vehicles, and greenhouses primarily focus on solar radiation modulation for interior lighting, heating and cooling regulation. Mid-infrared thermal radiation of windows, as another important factor for interior thermal load, can be dynamically optimized to further improve energy efficiency. However, it is challenging to achieve synergistic solar and thermal radiation modulation of a window for optimal energy efficiency management. Herein, based on the estimation of the energy-saving potential of a midrise building by controlling the window emissivity, we propose an energy-efficient dynamic window that can synergistically modulate solar and thermal radiation. The prototype of such windows with sequence photonic structures could perform the function of synergistic multiband modulation by loading mechanical strain, and achieve a broad modulation ranges up to 55% in solar transmittance and 25% in mid-infrared thermal emittance. The dynamic window can regulate the steady-state interior temperature of a chamber up to ~4 °C in real-time testing, which could potentially provide annual energy-saving from ~45.5 to ~166.5 MJ m−2 for a typical midrise building located in 11 cities around the world. The intelligent dynamic window system with fast response to the changing weather can further improve home convenience, comfort and artistry and realize an energy-saving residential setting.

Role of mTOR pathway in modulation of radiation induced bystander effects

Purpose Radiation-induced bystander effect (RIBE) is considered as an important consequence of radiation exposure. Based on the type of effect induced, it has important implications in radiation therapy. mTOR pathway, a key regulator of cell survival, plays an important role in radiation-induced damages. However, the role of mTOR signaling in the modulation of RIBE is still unclear. We evaluated the role of mTOR pathway in RIBE and its relationship with the radiation response of target cells. Materials and methods Direct and bystander effects were evaluated by using clonogenic and MTT assay in five different cell lines. Expression of mTOR pathway proteins in directly targeted and bystander cells was studied using western blotting. Results Among five different cell lines naïve HT1080 and A549 cells exhibited proliferative bystander effect induced by conditioned media and irradiated conditioned media, while no effect was observed in other cell lines. Everolimus significantly abolished the proliferative bystander effect induced in naïve cells. Conclusions These results suggested that the mTOR pathway plays an important role in RIBEs. These effects are cell type-specific and depending on the radiosensitivity of the target cells, therapeutic benefits of radiation may be modulated by treatment with mTOR inhibitors.

Features of modulation of high-power laser radiation for optical space control systems

In this work we justify the necessity of using shutter-type modulators to create laser radiation with the required parameters in fiber-optic systems.This is necessary to detect the fact of making changes in the optical system (unauthorized connection with the restoration of the function of communication channels). We have developed a shutter-type optical radiation modulator design. This modulator design has no fundamental limitations on the power of laser radiation, which is used to solve various problems. The investigation results of different work regime to the modulator are presented.

Application of gas analyzers for the control of fuel in the air environment of rocket and space industry enterprises

The presented work shows the necessity of organization of individual instrumental control of the content of rocket fuel and its products in the air of rocket-space industry enterprises. No accurate analysis of gas analyzers presented on the Russian market, providing individual instrumental control of concentrations of heptyl and its derivatives in the workplace air is available. Therefore, the task of express, automatic, selective and simultaneous monitoring of heptyl vapors and derivatives of its transformation in the air of industrial premises by one instrument and replacing the imported gas analyzers remains urgent. It is shown that the solution of the posed problem is possible on the basis of the optical absorption method. The requirements to be met by the gas analyzer are formulated. Approximate wavelengths at which simultaneous measurement of concentrations of heptyl and its derivatives in an air sample is possible have been determined. The ways of realization of individual gas analyzers having small mass-size characteristics are outlined. Structural schemes for infra-red gas analyzers have been proposed: multi-channel; single-channel (with frequency modulation of radiation). Tasks for further research are formulated.

Self-adaptive near-field radiative thermal modulation using a thermally sensitive bimaterial structure

The active control of the near-field radiative heat transfer has recently aroused significant attention. The common methods include utilizing phase-change materials, applying external electric or magnetic field and regulating the chemical potential. Herein, we propose a self-adaptive near-field radiative thermal modulation using a thermally sensitive bimaterial structure composed of gold and silicon nitride. Due to the huge differences between their Young's moduli and thermal expansion coefficients, the bimaterial structure has a bending tendency upon a sudden temperature change. The curved surface has a significant influence on the near-field radiative thermal transport, which largely depends on the separation gap between the two spaced objects. Two different bending scenarios are discussed, and the bimaterial structure can both spontaneously recover to its original planar state through self-adaptive thermal regulation. 24-fold and 4.4-fold variations in small-scale radiative heat transfer are demonstrated, respectively, for a 5 °C rise and 1 °C drop of the bimaterial. This work opens avenues for a dynamic and self-adaptive near-field radiative thermal modulation, and a large tuning range is worthy of expectation.

HIF2 Regulates Intestinal Wnt5a Expression.

Radiation therapy for abdominal tumors is challenging because the small intestine is exquisitely radiosensitive. Unfortunately, there are no FDA-approved therapies to prevent or mitigate GI radiotoxicity. The EGLN protein family are oxygen sensors that regulate cell survival and metabolism through the degradation of hypoxia-inducible factors (HIFs). Our group has previously shown that stabilization of HIF2 through genetic deletion or pharmacologic inhibition of the EGLNs mitigates and protects against GI radiotoxicity in mice by improving intestinal crypt stem cell survival. Here we aimed to elucidate the molecular mechanisms by which HIF2 confers GI radioprotection. We developed duodenal organoids from mice, transiently overexpressed non-degradable HIF2, and performed bulk RNA sequencing. Interestingly, HIF2 upregulated known radiation modulators and genes involved in GI homeostasis, including Wnt5a. Non-canonical Wnt5a signaling has been shown by other groups to improve intestinal crypt regeneration in response to injury. Here we show that HIF2 drives Wnt5a expression in multiple duodenal organoid models. Luciferase reporter assays performed in human cells showed that HIF2 directly activates the WNT5A promoter via a hypoxia response element. We then evaluated crypt regeneration using spheroid formation assays. Duodenal organoids that were pre-treated with recombinant Wnt5a had a higher cryptogenic capacity after irradiation, compared to vehicle-treated organoids. Conversely, we found that Wnt5a knockout decreased the cryptogenic potential of intestinal stem cells following irradiation. Treatment with recombinant Wnt5a prior to irradiation rescued the cryptogenic capacity of Wnt5a knockout organoids, indicating that Wnt5a is necessary and sufficient for duodenal radioprotection. Taken together, our results suggest that HIF2 radioprotects the GI tract by inducing Wnt5a expression.