Modulation Of Radiation Research Articles

Acousto-optic Modulation of Terahertz Radiation in Liquefied Sulfur Hexafluoride at Room Temperature

Acousto-optic modulation of terahertz free-electron laser radiation was investigated using diffraction on an acoustic wave in liquefied sulfur hexafluoride at room temperature. At the wavelength 130 μ m, the diffraction efficiency in Bragg regime of interaction 1% was obtained at 75 V driving electrical signal applied to the transducer terminals.

Тонкопленочные нелинейно-оптические кристаллы для внутрирезонаторной электрооптической модуляции

Methods for the preparation of DAST (4-N, N – dimethylamino–4'-N'-methyl stilbazolium tosylate) thin monocrystals with a thickness of a few micrometers, intended for electro-optics modulation were investigated. Thin-film single crystals are obtained, the shape and absorption spectrum of which confirms their crystalline structure of the “red” form DAST. Uniform color in the polarization contrast mode shows their monocrystallinity and uniform orientation. The materials are intended for intracavity modulation of laser radiation.

Pulsed modulation of multi-color argon laser radiation

Pulsed modulation of multi-color argon laser radiation

Theoretical Analysis of Parameter Optimization for Lower-Ionosphere Excitation ELF/VLF Waves Based on Chirp-BOK Modulated Heating

To improve the anti-interference for ELF/VLF communication based on modulated heating lower-ionosphere, chirp spread spectrum technology with strong anti-interference is combined with square wave amplitude modulation, a novel method of chirp-BOK modulated heating lower-ionosphere is proposed in this paper. On this basis, to improve the radiation efficiency of ELF/VLF, the effects of heating parameters (effective radiation power, pump frequency, polarization mode, modulation frequency, duty cycle, and bandwidth) on the radiation efficiency of ELF/VLF were analyzed. The results show that the radiation amplitude of ELF/VLF increases with the increase of effective radiation power, while the radiation efficiency increases first and then decreases; the X-mode is better than the O-mode; the radiation intensity of ELF/VLF decreases with the increase of pump wave frequency from 4MHz to 10MHz; the ELF/VLF equivalent dipole moments increase with the rise of modulation frequency from 500Hz to 5kHz; with the change of duty cycle from 10% to 90%, the dipole moments first increase and then decrease, and the optimal range of duty cycle is 40% to 70%; with the increase of bandwidth, the dipole moments are unchanged. Furthermore, the ELF/VLF dipole moments of square wave amplitude modulated heating ionosphere is unchanged before and after the chirp spread spectrum.

Estimation of an Optimal PV Panel Cleaning Strategy Based on Both Annual Radiation Profile and Module Degradation

This paper addresses a methodology to optimize PV panel cleaning schedule. PV system yield is impacted due to soiling on panel surface. This soiling changes during the system operation as a consequence of environmental conditions. In order to reduce the impact of soiling accumulation, the panel surface must be cleaned. However, cost and frequency of cleaning can affect plant revenue. Therefore, to enhance financial performance, an optimal cleaning strategy must be selected. This strategy depends mostly on energy cost, soiling rate, cleaning costs, and system efficiency. Hence, the model proposed in this work takes into account these variables in order to support the decisions during the assessment of PV yield. The methodology was evaluated through two irradiation profiles with different associated costs. As a result, the methodology made it possible to estimate a cleaning strategy optimizing the incomes under different scenarios.

Occurrence of micronuclei in exfoliated buccal mucosal cells in mobile phone users: A case-control study.

The use of mobile phones has increased enormously all over the world especially among young people. This technology is based upon electromagnetic radiation in the microwave frequency range [radiofrequency (RF) waves and microwaves]. The radiation frequency and modulation standards vary in the range of 300-2100 MHz, depending on the region in the world. To detect the presence of micronuclei in exfoliated buccal mucosal cells of mobile phone users as well as to carry out a quantitative analysis of micronuclei in exfoliated buccal mucosal cells of mobile phone users. A cross-sectional study was carried out in 100 individuals, out of which 50 were included under the test group and 50 under the control group. Buccal mucosal smears were obtained from each subject. Staining was done using papanicuolau (PAP) stain and the slides were examined for the presence of micronuclei. The mean duration of mobile phone usage in years was 5.32 years for the exposed and 2.42 years for the control. Mean duration of mobile phone usage per day in the test group was 94.8 min and 12.4 min in the control group. The frequency of micronucleated cells (MNC) in test and control groups ranged from 0 to 16 and 0 to 2 respectively. The data obtained were statistically analyzed using Student t-test and significant results were obtained at 0.0001 level. Our study concluded that there is an increased frequency of micronuclei in mobile phone users which is related to carcinogenesis.

Wide-Angle Polarization-Independent Paratellurite-Based Acousto-Optic Laser Radiation Modulator

High-efficiency wide-angle polarization-independent acousto-optic diffraction of laser radiation in a paratellurite-based modulator is experimentally studied. The previously published main theoretical principles are confirmed. We have shown that the angular aperture of the acousto-optic modulator can be ~8° in an ultrasonic frequency range of 135–68 MHz depending on the light wavelength and 2°–5° in the range of 20–30 MHz. A wide-angle acousto-optic depolarized laser radiation modulator has been created that operates at a wavelength λ = 1.06 μm with one output depolarized beam and an efficiency of no less than 90% for input radiation with an angular aperture of 30 mrad.

Super-Planckian Radiative Heat Transfer between Macroscale Surfaces with Vacuum Gaps Down to 190 nm Directly Created by SU-8 Posts and Characterized by Capacitance Method

In this work we experimentally demonstrated the near-field thermal radiation enhancement over the blackbody limit by 11 times between highly doped silicon chips with 1x1 cm2 size at a vacuum gap distance of 190 nm under a temperature difference of 74.7 K above room temperature. SU-8 polymer posts, which significantly reduced the conduction less than 6% of the total heat transfer due to its low thermal conductivity, were carefully fabricated with different heights to directly create vacuum gaps from 507 nm down to 190 nm precisely determined in-situ by capacitance measurement. Experimental results were validated by theoretical calculations based on fluctuational electrodynamics, which revealed the enhancement mechanism mainly as coupled surface plasmon polariton. The experimental method developed here will facilitate the potential applications of near-field radiative devices made of electrically conductive materials like metals, graphene, and transparent conductive oxide besides heavily doped semiconductors for thermal energy conversion, radiative thermal rectification, and radiative heat modulation.

Magritte, a modern software library for 3D radiative transfer: I. Non-LTE atomic and molecular line modelling

ABSTRACT Radiative transfer is a key component in almost all astrophysical and cosmological simulations. We present magritte: a modern open-source software library for 3D radiative transfer. It uses a deterministic ray-tracer and formal solver, i.e. it computes the radiation field by tracing rays through the model and solving the radiative transfer equation in its second-order form along a fixed set of rays originating from each point. magritte can handle structured and unstructured input meshes, as well as smoothed-particle hydrodynamics (SPH) particle data. In this first paper, we describe the numerical implementation, semi-analytic tests and cross-code benchmarks for the non-LTE line radiative transfer module of magritte. This module uses the radiative transfer solver to self-consistently determine the populations of the quantized energy levels of atoms and molecules using an accelerated Lambda iteration (ALI) scheme. We compare magritte with the established radiative transfer solvers ratran (1D) and lime (3D) on the van Zadelhoff benchmark and present a first application to a simple Keplerian disc model. Comparing with lime, we conclude that magritte produces more accurate and more precise results, especially at high optical depth, and that it is faster.

Thermal-responsive PNIPAm-acrylic/Ag NRs hybrid hydrogel with atmospheric window full-wavelength thermal management for smart windows

Smart windows with reversible regulation on solar radiation by altering their optical transmittance in response to thermal stimuli have been developed as a promising solution toward reducing energy consumption of buildings. This work presents a new strategy for doping Ag nanorods (NRs) with poly(N-isopropylacrylamide) (PNIPAm) hydrogel to achieve atmospheric window full-wavelength thermal management. PNIPAm as basic material was aimed to achieve solar radiation modulation among visible, near infrared (NIR), and middle infrared region. Acrylic was grafted on PNIPAm chains to enhance mechanical strength. While Ag NRs were the major factors that affected solar radiation modulation due to its structural changes driven by PNIPAm phase transition. The hybrid hydrogel showed a relatively high solar modulation ability (ΔTsol) of 59.24% while maintaining luminous transmittance (Tlum) of 61.36% under room temperature. The infrared emissivity kept a little increase from 0.947 to 0.958 during phase transition and caused a 12.7 °C reduction in temperature observed from the water-warming experiment. The innovative combination of Ag NRs and hydrogel indicated that metal nanorods may make positive effects when combining with hydrogels. This kind of new strategy based on atmospheric window full-wavelength thermal management exhibits to be an ideal candidate for applications in smart windows.

Numerical investigation of turbulent combustion with hybrid enrichment by hydrogen and oxygen

In this study, the NG + H2/air + O2 turbulent flame is numerically investigated using the Computational Fluid Dynamics CFD code. The modulation of combustion and radiation is performed respectively by the Eddy Dissipation Model and the Discrete Ordinate Model. The turbulence modeling is carried out by Shear Stress Transport (SST/k-ω) turbulence model. The H2 amount in the fuel mixture varies under constant volumetric fuel flow between 0 and 60% and the oxidant is composed by 80% air and 20% pure oxygen. The results obtained show the hydrogen addition to Natural Gas improves the mixing between the reactants, reduces their residence time and reduces the length and thickness of the flame. On the other hand, the hydrogen enrichment minimizes the CO2 and CO production and increases the NOx level.

Modulation of THz radiation via enhanced Dirac plasmon-dual phonon interaction

Imaging with terahertz (THz) radiation is a crucial technique that promotes its applications in security inspection, crack detection, biomedical imaging, and so forth. THz modulation is one of the critical factors (others include generation, propagation, and detection) of the THz fast imaging technique. In this work, an efficient THz radiation modulator is realized based on the as-grown Bi2Se3 nanowires. Different from the conventional metamaterials or plasmonic devices, fabrication of subwavelength structures is unnecessary in this manipulation. The modulation is facilitated via synergistic Fano-type interaction of topological surface plasmons with two phonons in Bi2Se3 nanowires. The comprehensive control of the modulation is realized in a direct optical manner. A high modulation depth of 1826% has been demonstrated in this modulator. The realization of such a THz modulator based on an as-grown system indicates the possibility of the modulation extricating from fabrication of complicated postgrowth micro/nanostructures.

Hybrid vibration sensor with conversion of a piezoelectric signal into modulation of optical radiation and its transmission through optical fiber

In this study, a hybrid vibration sensor is proposed and investigated, in which an electric signal from a primary piezoelectric vibration transducer is used to modulate optical radiation using an electro-optic modulator. The modulator is made using integrated-optics technology based on the Mach–Zehnder layout of a reflective type with combined input/output to an optical fiber with conservation of polarization. The measured threshold vibration sensitivity of the sensor was approximately ${{10}^{ - 5}}\;{\rm m}/{{\rm s}^2}$10−5m/s2 in the acoustic frequency range.

Studies on Charge Carrier Transport in an Injection Laser with Frequency Modulation of the Optical Radiation

One of the promising approaches to solve the problem of increasing the efficiency for interelement connections consists in the use of integrated optical switching systems, whose main elements represent injection lasers with functionally integrated optical radiation modulators. Injection lasers make it possible to modulate the laser radiation by subpicosecond controlling pulses at a constant pumping current, as well as making it possible to implement the sources and modulators of optical radiation in a united AIIIBV nanoheterostructure with second-type heterojunctions. This work is devoted to the studies concerning the transport of charge carriers within a functionally integrated modulator laser with internal frequency modulation of the generated optical radiation using a proposed two-dimensional diffusion-drift model and a numerical simulation technique. The results of the numerical simulation of charge carrier transport in a modulator laser when the pumping current is switched on, as well as under pulsed variation of the controlling voltage, take the structural features, the transport effects, the mechanisms of stimulated and spontaneous radiative recombination, and the photon lifetime into account. It is shown that the maximum modulation frequency of laser radiation is determined by the subpicosecond time of the controlled spatial relocation of the charge-carrier density maxima in the quantum zones of the modulator laser, as well as by the photon lifetime in the laser resonator, and corresponds to the terahertz range. To increase the maximum modulation frequency, it is necessary to reduce the photon lifetime in the active zone of the modulator laser to values lower than 3 ps by changing the resonator’s parameters in a corresponding manner. The proposed model and the method of numerical simulation make it possible to optimize the parameters of a functionally integrated modulator laser, and to provide the required relationships between the maximum modulation frequency of the optical radiation, the modulation coefficient, and the density of the threshold pumping current.

Evaluation of the genotoxicity of cell phone radiofrequency radiation in male and female rats and mice following subchronic exposure.

The National Toxicology Program tested two common radiofrequency radiation (RFR) modulations emitted by cellular telephones in a 2‐year rodent cancer bioassay that included interim assessments of additional animals for genotoxicity endpoints. Male and female Hsd:Sprague Dawley SD rats and B6C3F1/N mice were exposed from Gestation day 5 or Postnatal day 35, respectively, to code division multiple access (CDMA) or global system for mobile modulations over 18 hr/day, at 10‐min intervals, in reverberation chambers at specific absorption rates of 1.5, 3, or 6 W/kg (rats, 900 MHz) or 2.5, 5, or 10 W/kg (mice, 1,900 MHz). After 19 (rats) or 14 (mice) weeks of exposure, animals were examined for evidence of RFR‐associated genotoxicity using two different measures. Using the alkaline (pH > 13) comet assay, DNA damage was assessed in cells from three brain regions, liver cells, and peripheral blood leukocytes; using the micronucleus assay, chromosomal damage was assessed in immature and mature peripheral blood erythrocytes. Results of the comet assay showed significant increases in DNA damage in the frontal cortex of male mice (both modulations), leukocytes of female mice (CDMA only), and hippocampus of male rats (CDMA only). Increases in DNA damage judged to be equivocal were observed in several other tissues of rats and mice. No significant increases in micronucleated red blood cells were observed in rats or mice. In conclusion, these results suggest that exposure to RFR is associated with an increase in DNA damage. Environ. Mol. Mutagen. 61:276–290, 2020. © 2019 Wiley Periodicals, Inc.

Photoelastic Properties of Potassium Sulfate Crystals

The spectral dependences of the absolute piezooptic coefficients of potassium sulfate crystals are studied. It is established that their dispersion dependence is insignificant. The matrix of elastooptic coefficients pin of these crystals is filled using the elastic stiffness coefficients and the absolute piezooptic coefficients. The coefficient of acoustooptical efficiency M2 is calculated. It is shown that, considering the maximum values, it is more than an order of magnitude higher than that of quartz and strontium borate crystals. Potassium sulfate crystals are proposed for use for acoustooptic modulation of ultraviolet radiation, taking into account the short-wavelength limit of their transparent region (~170 nm).

Non-LTE radiation hydrodynamics in PLUTO

Context. Modeling the dynamics of most astrophysical structures requires an adequate description of the interaction of radiation and matter. Several numerical (magneto-) hydrodynamics codes were upgraded with a radiation module to fulfill this request. However, those that used either the flux-limited diffusion (FLD) or the M1 radiation moment approaches are restricted to local thermodynamic equilibrium (LTE). This assumption may not be valid in some astrophysical cases. Aims. We present an upgraded version of the LTE radiation-hydrodynamics (RHD) module implemented in the PLUTO code, which we have extended to handle non-LTE regimes. Methods. Starting from the general frequency-integrated comoving-frame equations of RHD, we have justified all the assumptions that were made to obtain the non-LTE equations that are implemented in the module under the FLD approximation. An operator-split method with two substeps was employed: the hydrodynamics part was solved with an explicit method by the solvers that are currently available in PLUTO, and the non-LTE radiation diffusion and energy exchange part was solved with an implicit method. The module was implemented in the PLUTO environment. It uses databases of radiative quantities that can be provided independently by the user: the radiative power loss, and the Planck and Rosseland mean opacities. In our case, these quantities were determined from a collisional-radiative steady-state model, and they are tabulated as functions of temperature and density. Results. Our implementation has been validated through different tests, in particular, radiative shock tests. The agreement with the semi-analytical solutions (when available) is good, with a maximum error of 7%. Moreover, we have proved that a non-LTE approach is of paramount importance to properly model accretion shock structures. Conclusion. Our radiation FLD module represents a step toward a general non-LTE RHD modeling.

Electronic Modulation of THz Radiation at NovoFEL: Technical Aspects and Possible Applications.

The Novosibirsk Free Electron Laser (NovoFEL) facility is able to produce high-power tunable terahertz (THz) laser radiation in quasi-continuous mode. The ability to control/shape this THz radiation is required in a number of user experiments. In this work we propose a modulation approach suitable for free electron lasers based on recuperation design. It allows for generating THz macropulses of a desirable length, down to several microseconds (limited by a quality factor of FEL optical resonator). Using this approach, macropulses in the time window from several microseconds to several hundred microseconds have been shown for three possible frequency ranges: mid-infrared (~1100 cm−1), far-infrared (~200 cm−1) and THz (~40 cm−1). In each case, the observed rise and decay of the macropulse have been measured and interpreted. The advantage of using short macropulses at the maximum peak power available has been demonstrated with the time-resolved Electron Paramagnetic Resonance (EPR) spectroscopy.

Mechanophysical Methods for Producing Optical Nanoceramics Based on Magnetic Semiconductors

This paper considers mechanophysical methods (shear under pressure and explosive loading) developed for producing high-density optical nanoceramics based on some oxide magnetic semiconductors and their optical properties. Advantages of these methods are the simplicity of implementation, a combination of nano-grinding and compaction of material in a single process, obtaining high-density (∼99%) stable materials, and the absence of external impurity. It is shown that copper oxide nanoceramics can be used as solar energy absorbers and iron-yttrium garnet nanoceramics as an optical element in electromagnetic radiation modulators.

Melatonin Modulation of Radiation and Chemotherapeutics-induced Changes on Differentiation of Breast Fibroblasts.

Melatonin exerts oncostatic actions and sensitizes tumor cells to chemotherapeutics or radiation. In our study, we investigated the effects of docetaxel, vinorelbine, and radiation on human breast fibroblasts and its modulation by melatonin. Docetaxel or vinorelbine inhibits proliferation and stimulates the differentiation of breast preadipocytes, by increasing C/EBPα and PPARγ expression and by downregulating tumor necrosis factor α (TNFα), interleukin 6 (IL-6), and IL-11 expression. Radiation inhibits both proliferation and differentiation through the downregulation of C/EBPα and PPARγ and by stimulating TNFα expression. In addition, docetaxel and radiation decrease aromatase activity and expression by decreasing aromatase promoter II and cyclooxygenases 1 and 2 (COX-1 and COX-2) expression. Melatonin potentiates the stimulatory effect of docetaxel and vinorelbine on differentiation and their inhibitory effects on aromatase activity and expression, by increasing the stimulatory effect on C/EBPα and PPARγ expression and the downregulation of antiadipogenic cytokines and COX expression. Melatonin also counteracts the inhibitory effect of radiation on differentiation of preadipocytes, by increasing C/EBPα and PPARγ expression and by decreasing TNFα expression. Melatonin also potentiates the inhibitory effect exerted by radiation on aromatase activity and expression by increasing the downregulation of promoter II, and COX-1 and COX-2 expression. Our findings suggest that melatonin modulates regulatory effects induced by chemotherapeutic drugs or radiation on preadipocytes, which makes it a promising adjuvant for chemotherapy and radiotherapy sensibilization.