Radiation Spectrum Research Articles

Singular Points of the Radiation Spectrum of Leaky Surface Magnon Polarons

Within the dissipation-free approach, for a magnetic layer separating two semi-bounded ideal fluids, it is shown that, at the point of the phonon radiation spectrum where leaky surface magnon polarons of the “dark” state are formed (of interference or symmetry-protected type) at the interface with an acoustically less dense medium, both the numerator and the denominator of the input wave impedance can independently become zero (at the very point of existence of a bound state in the continuum, they vanish simultaneously). The calculation was performed for a two-sublattice model of an antiferromagnet, which simultaneously takes into account magnetoelastic, inhomogeneous exchange, and hyperfine coupling. Conditions have been found under which the mechanisms of formation of bound states in the spectrum of phonon radiation of leaky magnon polarons involving quasi-electronic or quasi-nuclear magnons are fundamentally different: elastodynamic or elastostatic.

Effect of the method of excitation of the plasma antenna on the spectral characteristics of the radiated signal

The radiation of signal by the plasma asymmetrical vibrator antenna is studied for two methods of its excitation. Earlier, it was shown that the 2nd and 3rd harmonics of the input signal frequency in the radiation spectrum of the plasma antenna are 10—20 dB stronger than those of a metal antenna with the same geometry. In this work, we study experimentally and by computer simulations the effect of the method of excitation of the plasma asymmetrical vibrator antenna on the spectral characteristics of the signal that it radiates. For the two excitation methods of the antenna, through an electrode and through a coaxial coupler, it was shown that the strength of the signal components at the frequency of the radiated signal and its multiple harmonics is different. The introduction of the coaxial coupler in the antenna excitation scheme allowed us to improve the coupling at the input signal frequency and decrease its components at the 2nd and 3rd harmonics. For the plasma antenna with the coaxial coupler, the difference between the 1st and 2nd harmonics was increased by almost 6 dB, and between the 1st and the 3rd ones by almost 20 dB compared to the antenna excitation scheme through the electrode.

Effect of load-resisting force on photoisomerization mechanism of a single second generation light-driven molecular rotary motor.

A pivotal aspect of molecular motors is their capability to generate load capacity from a single entity. However, few studies have directly characterized the load-resisting force of a single light-driven molecular motor. This research provides a simulation analysis of the load-resisting force for a highly efficient, second-generation molecular motor developed by Feringa et al. We investigate the M-to-P photoinduced nonadiabatic molecular dynamics of 9-(2,3-dihydro-2-methyl-1H-benz[e]inden-1-ylidene)-9H-fluorene utilizing Tully's surface hopping method at the semi-empirical OM2/MRCI level under varying load-resisting forces. The findings indicate that the quantum yield remains relatively stable under forces up to 0.003a.u., with the photoisomerization mechanism functioning typically. Beyond this threshold, the quantum yield declines, and an alternative photoisomerization mechanism emerges, characterized by an inversion of the central double bond's twisting direction. The photoisomerization process stalls when the force attains a critical value of 0.012a.u. Moreover, the average lifetime of the excited state oscillates around that of the unperturbed system. The quantum yield and mean lifetime of the S1 excited state in the absence of external force are recorded at 0.54 and 877.9fs, respectively. In addition, we analyze a time-dependent fluorescence radiation spectrum, confirming the presence of a dark state and significant vibrations, as previously observed experimentally by Conyard et al.

Study of Neural Network Architectures for Determining Gas Concentrations by Spectra

A study of a number of neural networks of different architectures for determining gas concentrations from spectra obtained using an optical emission gas analyzer, which measures the spectrum of electromagnetic radiation emitted by gases when excited by an electric discharge, is presented. The neural network is trained on data from the optical spectroscopy laboratory and is able to predict gas concentrations from spectra at high speed. The research concerned the deep neural network architectures with convolutional and recurrent layers. Convolutional layers highlight the features of the spectra, while recurrent layers take into account the consistent structure of the data. The quality of the neural network is evaluated by the R2 coefficient of determination, and the comparison between networks by the RMSE indicator between the predicted and real gas concentrations.

Role of Humic Substances in the (Bio)Degradation of Synthetic Polymers under Environmental Conditions

Information on the detection of the presence and potential for degradation of synthetic polymers (SPs) under various environmental conditions is of increasing interest and concern to a wide range of specialists. At this stage, there is a need to understand the relationship between the main participants in the processes of (bio)degradation of SPs in various ecosystems (reservoirs with fresh and sea water, soils, etc.), namely the polymers themselves, the cells of microorganisms (MOs) participating in their degradation, and humic substances (HSs). HSs constitute a macrocomponent of natural non-living organic matter of aquatic and soil ecosystems, formed and transformed in the processes of mineralization of bio-organic substances in environmental conditions. Analysis of the main mechanisms of their influence on each other and the effects produced that accelerate or inhibit polymer degradation can create the basis for scientifically based approaches to the most effective solution to the problem of degradation of SPs, including in the form of microplastics. This review is aimed at comparing various aspects of interactions of SPs, MOs, and HSs in laboratory experiments (in vitro) and environmental investigations (in situ) aimed at the biodegradation of polymers, as well as pollutants (antibiotics and pesticides) that they absorb. Comparative calculations of the degradation velocity of different SPs in different environments are presented. A special place in the analysis is given to the elemental chemical composition of HSs, which are most successfully involved in the biodegradation of SPs. In addition, the role of photo-oxidation and photoaging of polymers under the influence of the ultraviolet spectrum of solar radiation under environmental conditions on the (bio)degradation of SPs in the presence of HSs is discussed.

Significantly enhanced energy efficiency through reflective materials integration in plant factories with artificial light

Plant factory with artificial light (PFAL) based on vertical farming is a promising technology for resource-efficient plant production, especially in urban areas or arid regions. However, the lighting system of PFAL requires a large amount of energy, which makes the total energy cost much higher than open-field and greenhouse farming. To address this issue, in this work, a cultivation system integrated with highly reflective materials is demonstrated in PFAL, which reduces light energy consumption by more than 36 %. A low-cost reflective film is fabricated with an overall reflectivity of 96.5 % in the entire photosynthetically active radiation spectrum. The effectiveness of this reflective film in reducing energy consumption is further demonstrated with optical simulation analysis and the corresponding computational fluid dynamics simulation based on an experimental cultivation rack. The corresponding field experiments of 3 different types of lettuce, Crunchy, Butterhead and Grand Rapids, under different light intensities are conducted in the cultivation unit. With reflective film properly installed, a 36 % reduction of light energy consumption is demonstrated while the dry weight and fresh weight still increase. An additional benefit is that the light reception area of lettuce becomes larger due to the more uniform lighting with the integration of reflective material. This work presents a simple yet reliable strategy for enhancing the energy efficiency in PFAL systems and can achieve the cost-effective daily production of lettuce with significantly reduced energy input.

Comparison of methods for changing the spectrum of radiation of a pulse x-ray source to determine the most effective two-energy image processing

For detecting substances with similar chemical composition and density, one of the promising methods of non-destructive testing is dual-energy processing of X-ray images. In particular, dual-energy transformation algorithms can be used to search for minerals hidden within barren rock. This method is most effective when the conditions for registering X-ray images and energy levels are properly selected. This study compares the effectiveness of image processing using the dual-energy method for three cases of spectral composition variation: firstly, as a result of adjusting the voltage on the X-ray tube; secondly, by attenuating low-energy radiation through the use of a copper filter; and thirdly, by combining these two methods. Beryl particles embedded in ground muscovite are used as samples for detection. The study utilizes a pulsed X-ray radiation source that generates radiation pulses of nanosecond duration. An original high-voltage generator scheme has been implemented for the method of regulating radiation energy by changing the peak voltage on the X-ray tube. The use of X-ray sources of this type enables the acquisition of high-resolution X-ray images of moving objects.

MEASUREMENT OF THE VELOCITY OF PULSED PLASMA FLOW AT THE PW-7 INSTALLATION

The paper considers two independent methods for measuring the velocity of the plasma flow generated in the PV-7 pulsed plasma accelerator: a method based on observation and evaluation of the Doppler shift of spectral lines, and a method of high-speed visualization of plasma motion. To record the plasma flow radiation spectrum, a monochromator M833 was used. High-speed video recording was carried out at 640,000 fps using a Phantom VEO710S CMOS camera. The results of measurements of the average flow velocity obtained at a working gas pressure of 2⋅10-2 Torr, capacitance and voltage of the capacitor bank of 400 μF and 4 kV are presented. The results obtained by two independent methods were compared with each other. Argon was used as the working gas in the experiments. It is shown that the value of the plasma flow velocity estimated by the first method is 12.5 m/s, and the value of the plasma flow velocity estimated by the second method is 16.7 m/s. From these data the measured flow velocity values have a small discrepancy. Thus, it has been established that high-speed video recording and Doppler shift methods make it possible to obtain comparable estimates of flow velocity within the measurement errors. Determining the magnitude of the plasma flow velocity is of great practical importance.

Multi-mode hybridization in the MXene tetramer metasurface for ultra-broadband solar energy utilization

MXene is promising in photothermal or photovoltaic conversion, while high-performance MXene metasurface solar absorbers based on simple and feasible structures are still lacking. This study aims to design a solar absorber with ultra-broadband absorption capability in the visible and near-infrared wavelength ranges based on the MXene nanoblock tetramer/silica film/MXene substrate structure. The average absorptivity of this proposed metasurface absorber is 96.9% in the wavelength range of 300–2500 nm covering the whole solar spectrum. The physics behind the high absorption results from multiple-mode hybridization in different resonant bands, including the coupling between the surface plasmons, cavity resonances, and guided-mode resonances. The broadband and high-absorption performance remains stable under large-angle incidence and structural parameter variations with the average absorption above 90% in the whole wavelength region of interest. The calculated energy absorption ratio of the AM1.5 solar radiation spectrum can reach up to 96.3%, indicating low solar energy loss and efficient solar energy capture. In summary, these results provide great application prospects in the fields of photothermal and photovoltaic conversion.

Fine and rough structure of the frequency spectrum of high-power laser diodes during slow degradation

It is shown that a fine and rough structure can be distinguished in the radiation spectrum of a powerful laser diode. The relationship between the spectrum characteristics and the internal parameters of the laser structure was established and experimentally verified, which was observed during the degradation of the device. The effect of losses in the resonator and coherence of laser radiation on both the fine and rough structure of its radiation spectrum is shown.

Computer simulation of the effect of focusing X rays by means of refractive-diffractive lens

The features of focusing X rays using a refractive-diffractive lens (RDL), which is a system of two asymmetrically reflecting crystals with asymmetry factors, the product of which is equal to unity, and a refractive lens with a large focal length, are theoretically studied. Crystals make it possible to shorten the focal length of the lens by b2 times, where b is the asymmetry factor of the second crystal. A detailed numerical simulation of the effect of radiation focusing using the RDL has been performed. The universal computer program XRWP was used which is created to calculate the effects of coherent X-ray optics. Analytical formulas are obtained for the optimal aperture and radius of curvature of the lens, as well as for the width of the radiation spectrum that can be focused.

PT-symmetry and radiation structure of high-power laser diodes

Possible conditions for the application of the quantum formalism of PT-symmetry in solving the wave equation in systems with pseudo-Hermitian Hamiltonian for determining the structure of the optical field and radiation spectra of modern high-power laser diodes are considered. The physical mechanisms affecting the spatial and spectral separation of radiation into separate generation channels are discussed.

An inexpensive way to introduce students to gamma spectroscopy

This paper presents two ways to introduce the student to some basic experimental concepts of gamma spectroscopy, without the use of expensive professional measurement equipment. For one, the complete experiment was simulated through several computer programs. Using this simulation, students are tasked with performing all the operations that must be performed in a real experimental setup, to obtain the spectrum of gamma radiation, as the expected result. For the second approach, equipment has been designed that looks and functions like real experimental equipment, and students can use it to perform completely identical procedures in the measurement process as with the real one. The central part of each component of a system designed in this way is a programmable microcontroller, set to perform a function analogous to that of the actual components. By working in these two ways, with a virtual experiment or a setup designed to fully imitate real measurement equipment, students can be introduced to the field of gamma spectroscopy and acquire a routine that can be repeated in real experiments. The main advantage of these two described methods is that they only require small investments.

Potential Use and Chemical Analysis of Some Natural Plant Extracts for Controlling Listeria spp. Growth In Vitro and in Food.

Listeria are Gram-negative intracellular foodborne pathogens that can cause invasive infections with high mortality rates. In this work, the antibacterial activity of ten essential oils, infusion extracts, and decoction extracts of some medicinal plants was tested against Listeria monocytogenes and listeria ivanovii strains. The effects of different physical conditions including temperature, pH, sodium chloride, and some organic acids were studied. The results showed that the water extracts gave the maximum bacterial inhibition, while ethanolic extract was inactive against the tested Listeria spp. The antibiotic sensitivity of L. monocytogenes LMG10470 and L. ivanovii LMZ11352 was tested against five antibiotics including imipenem, levofloxacin, amikacin, ampicillin, and amoxicillin. Imipenem was the most effective antibiotic, resulting in inhibition zones of 40 mm and 31 mm for L. monocytogenes and L. ivanovii, respectively. When imipenem mixed with Syzygium aromaticum oil, Salvia officinalis oil, Pimpinella anisum infusion, and Mentha piperita infusion each, the water extract of Moringa oleifera leaves and seeds against LMG10470 and LMZ11352 resulted in broader antibacterial activity. The antimicrobial activity of both Pimpinella anisum and Mentha piperita plant extracts is related to a variety of bioactive compounds indicated by gas chromatography-mass spectrometry analysis of these two plant extracts. These two plant extracts seemed to contain many chemical compounds elucidated by gas chromatography-mass spectrometry (GC-MS) and infrared radiation spectra. These compounds could be classified into different chemical groups such as ethers, heterocyclic compounds, aromatic aldehydes, condensed heterocyclic compounds, ketones, alicyclic compounds, aromatics, esters, herbicides, saturated fatty acids, and unsaturated fatty acids. The use of these natural compounds seems to be a useful technological adjuvant for the control of Listeria spp. in foods.

QCD-gravity double-copy in the Regge regime: Shock wave propagators

In a previous paper [H. Raj and R. Venugopalan, ], we demonstrated a double-copy relation between inclusive gluon radiation in shock wave collisions of ultrarelativistic nuclei and inclusive graviton radiation in trans-Planckian gravitational shock wave collisions. We compute here the corresponding gravitational shock wave propagators in general relativity and demonstrate that they too obey a double-copy relation to gluon shock wave propagators computed previously. These results provide key input in a renormalization group approach toward computing the high frequency radiation spectrum in close black hole encounters. Published by the American Physical Society 2024

Elevating electron energy gain and betatron x-ray emission in proton-driven wakefield acceleration

The long proton beams present at CERN have the potential to evolve into a train of microbunches through the self-modulation instability process. The resonant wakefield generated by a periodic train of proton microbunches can establish a high acceleration field within the plasma, facilitating electron acceleration. This paper investigates the impact of plasma density on resonant wakefield excitation, thus influencing the acceleration of a witness electron bunch and its corresponding betatron radiation within the wakefield. Various scenarios involving different plasma densities are explored through particle-in-cell simulations. The peak wakefield in each scenario is calculated by considering a long pre-modulated proton driver with a fixed peak current. Subsequently, the study delves into the witness beam acceleration in the peak wakefield and its radiation emission. Elevated plasma density increases both the number of microbunches and the accelerating gradient of each microbunch, consequently resulting in heightened resonant wakefield. Nevertheless, the scaling is disrupted by the saturation of the resonant wakefield due to the nonlinearities. The simulation results reveal that at high plasma densities, an intense and broadband radiation spectrum extending into the domain of the hard x-rays and gamma rays is generated. Furthermore, in such instances, the energy gain of the witness beam is significantly enhanced. The impact of wakefield on the witness energy gain and the corresponding radiation spectrum is clearly evident at elevated densities.

Different spectrum of space radiation induced cognitive impairments in radiation-naïve and adapted rats

NASA's decision to resume manned deep space mission, first to the Moon and then Mars, necessitated a detailed assessment of the potential health effects that astronauts may experience on long-duration missions. Multiple studies suggest that there may be significant space radiation (SR)-induced impairment of neurocognitive processes, including advanced executive functions. However, given the multitude of SR-induced changes in the CNS, it is possible that completely different SR-induced sequelae will be induced in previously exposed individuals. Thus, current risk estimates are likely to be pertinent only for the early stages of a deep space mission, and even then only for astronauts that have no previous experience in space.In this study, rats that maintained high attentional set shifting (ATSET) performance after an initial exposure to 10 cGy of SR (either 250 MeV/n He or GCRsim), were exposed to an additional dose of 10 cGy GCRsim and their ATSET performance reassessed. The re-irradiated rats exhibited significant impairment of ATSET performance, however, the performance decrements differed in two important aspects from those typically observed after single exposures. First, the decrements were manifested when the rats were required to perform set shifting, specifically in the IDR and EDS stages of the ATSET test. Secondly, the main performance decrement was in a loss of processing speed, which in the IDR stage resulted in the re-irradiated rats taking 2-fold more time to solve the problem than did Sham rats. The functional consequence of this decrement was that compared to Sham rats, 20 % fewer SR-exposed rats solved the IDS and EDR problems within 20 s.These data suggests that prior SR exposure alters nature of ATSET impairments from that observed in radiation-naïve individuals. Risk estimates derived from studies that use radiation naïve rats may thus not fully reflect the incidence and nature of ATSET performance deficits that could occur over the entire duration of a mission to Mars, or in astronauts who return to deep space on multiple occasions. It would thus be germane to conduct in-flight monitoring for cognitive performance decrements observed in both radiation naïve and exposed rats during the mission, and ensure that the crew has sufficient overlapping skill sets to minimize the operational impact of these additional cognitive impairments.

Tracking the Photoactivity At The Interface of SiC/Poly 2(2-Thienyl) Furan Thin Solid Film in Polymer Gel Electrolytes

Assemblies made by immobilizing nanoparticles SiC into poly 2(2-thienyl) furane (PTF) were subjected to optical and electrochemical investigation. The studies show that SiC, a molecular inorganic compound, and PTF produce reproducible photo responses. Optical studies show that the optical band gap of SiC is around 2.5 eV while PTF's is around 2.2 eV. The band gap values suggest these assemblies absorb the visible solar radiation spectra. Electrochemical studies in gel electrolytes indicate that PTF and PTF/SiC under illumination show p-p behavior, where hole accumulation dominates. SiC thin films lack such character. Electrochemical Impedance Spectroscopy (EIS) studies revealed that the PTF and PTF/SiC possess kinetic and diffusional charge transfer properties. The studied assemblies and the gel electrolyte showed stability and resistance to photodegradation as evidenced by the regeneration of the same photo response after a longer period of experimentation.

Effects of lead shielding on gamma radiation scatter energy spectrum during equine bone scintigraphy.

The main aim of this pilot study was to determine how the energy spectrum of scatter radiation emitted from horses after injection of the radiopharmaceutical 99mTechnetium-methyl diphosphonate (99mTc-MDP), changed behind lead shielding of varying thicknesses (0.25 mm, 0.35 mm, and 0.5 mm Pb thickness), and if beam hardening occurred. The effect lead shielding has on the emitted gamma radiation energy spectrum has not been documented. In particular, the presence of beam hardening effects behind lead shielding was investigated, to determine whether or not it could discourage the use of lead shields during bone scintigraphy in horses. Horses were injected intravenously with 99mTc-MDP, and energy spectra emitted from horses without lead shielding were recorded initially to determine the emitted scatter spectrum. Thereafter, different combinations of lead shields of the various thicknesses listed above, draped over the horse and on simulated personnel, were recorded. The energy spectra were obtained at different anatomical locations of five horses on five consecutive days with a pulse height (multichannel) analyser two and a half hours post-injection. Energy spectra recorded from horses without lead shielding showed polychromatic energy spectra that encompassed a large portion of predominantly lower scatter energies (averaging around the 88-94 keV peaks). Higher 99mTc- MDP peaks averaging at 139-143 keV (useful for gamma camera acquisition) were consistently seen in all recordings but made up a very small part of the emitted spectra. With the application of lead shielding, peaks of 83-86 keV, which coincided with K-edges of lead, occurred. No significant beam hardening effects behind lead shields of varying thicknesses were observed. Thus, the wearing of lead shields during bone scintigraphy of horses is encouraged.

Dynamical theory of single-photon transport through a qubit chain coupled to a one-dimensional nanophotonic waveguide

We study the dynamics of a single-photon pulse traveling through a linear qubit chain coupled to continuum modes in a one-dimensional (1D) photonic waveguide. We derive a time-dependent dynamical theory for qubits’ amplitudes and for transmitted and reflected spectra. We show that the requirement for the photon-qubit coupling to exist only for positive frequencies can significantly change the dynamics of the system. First, it leads to the additional photon-mediated dipole-dipole interaction between qubits which results in the violation of the phase coherence between them. Second, the spectral lines of transmitted and reflected spectra crucially depend on the shape of the incident pulse and on the initial distance between the pulse center and the first qubit in the chain. We apply our theory to one-qubit and two-qubit systems. For these cases we obtain the explicit expressions for the qubits’ amplitudes and for the photon radiation spectra as time tends to infinity. Specific calculations are performed for superconducting qubits operating in GHz frequency range. For the incident Gaussian wave packet we calculate the line shapes of transmitted and reflected photons.