Wavelength Of Radiation Research Articles

New developments in sunscreens.

Topical sunscreen application is one of the most important photoprotection tool to prevent sun damaging effects in human skin at the short and long term. Although its efficacy and cosmeticity have significantly improved in recent years, a better understanding of the biological and clinical effects of longer wavelength radiation, such as long ultraviolet A (UVA I) and blue light, has driven scientists and companies to search for effective and safe filters and substances to protect against these newly identified forms of radiation. New technologies have sought to imbue sunscreen with novel properties, such as the reduction of calorific radiation. Cutaneous penetration by sunscreens can also be reduced using hydrogels or nanocrystals that envelop the filters, or by binding filters to nanocarriers such as alginate microparticles, cyclodextrins, and methacrylate polymers. Finally, researchers have looked to nature as a source of healthier products, such as plant products (e.g., mycosporines, scytonemin, and various flavonoids) and even fungal and bacterial melanin, which could potentially be used as substitutes or enhancers of current filters.

Enhancement of Sulfur Source-Dependent Zn Vacancies in Different Photocatalytic Performances of ZnIn2S4 Nanoparticles.

This study focuses on the synthesis and investigation of ZnIn2S4 nanoparticle (NP) photocatalysts treated with different sulfur sources, thioacetamide (TAA), or thiourea (TU), to explore their wavelength-dependent photocatalytic activity. The research aims to understand the impact of Zn vacancies present on the surface of ZnIn2S4 NPs. The investigation involves electron spin resonance and in situ X-ray photoelectron spectroscopy to study the photocatalytic activity of ZnIn2S4-TU and ZnIn2S4-TAA NPs, following the characterization of surface morphology and electronic properties using high-resolution transmission electron microscopy and X-ray diffraction. Additionally, the study delves into the wavelength-dependent photocatalytic degradation (PCD) activity of the ZnIn2S4 NPs using 2,5-hydroxymethylfurfural (HMF) across a wide range. Notably, the selective oxidation of HMF using ZnIn2S4-TU NPs resulted in the formation of 2,5-furandicarboxylic acid (FDCA) via 2,5-diformylfuran, with an efficiency exceeding 40% over the broad wavelength range. The research demonstrates that the irradiation wavelength for PCD is influenced by the number of defect structures introduced into the ZnIn2S4 NPs through the sulfur source.

High Harmonic Generation near the Low-Frequency Edge of a Plateau under Nonlinear Propagation of 1.24-μm Near-Infrared Femtosecond Laser Radiation in a Dense Argon Jet

High (15–25) harmonic generation in the vacuum ultraviolet spectral range (83–50 nm) has been realized by focused (NA = 0.033) near-infrared femtosecond laser radiation (wavelength λ = 1.24 μm) with a vacuum intensity of ~7.5 × 1014 W/cm2 irradiating a dense gas jet. It has been shown experimentally that the use of such a high-numerical aperture focusing requires high (up to 10 bar) gas jet pressures to optimize phase matching. The use of the dense gas jet results in a noticeable manifestation of nonlinear propagation effects for generating radiation, which affect the generation process through the change in the phase matching conditions. Furthermore, it has been shown that the prechirping of the generating pulse makes it possible to compensate a chirp appearing due to self-phase modulation and to increase the harmonic generation efficiency because of the nonlinear compression of the generating pulse. This approach has allowed 17th (73 nm) harmonic generation with an energy of 2 pJ in a pulse and a generation efficiency of 5.4 × 10–9. The estimates obtained have shown that this radiation can be used for single-pulse maskless photolithography in the extreme ultraviolet range.

Investigation of the Effects of Dioctyl Sulfosuccinate on the Photodegradation of Benzo[a]Pyrene in Aqueous Solutions under Various Wavelength Regimes.

Due to the relatively high concentrations of polycyclic aromatic hydrocarbons (PAHs) in oil samples, oil spills in aquatic ecosystems release significant amounts of PAHs. Although remediation efforts often take place during or immediately after an oil spill incident, a portion of the released PAHs remains in the body of water. A natural phenomenon resulting from the direct exposure of PAHs to sunlight is photodegradation. This article investigates the effect of dioctyl sulfosuccinate (DOSS) on the photodegradation of benzo[a]pyrene (BaP), the most toxic PAH in the priority pollutants list of the US Environmental Protection Agency (EPA). DOSS is a surfactant typically used in the remediation of oil spills. Three lamps with maximum emission wavelengths at 350 nm, 419 nm, and 575 nm were individually and simultaneously used to irradiate aqueous solutions of BaP in the absence and the presence of DOSS. When irradiated with the 419 nm lamp or the 575 lamp, BaP showed no photodegradation. Upon irradiation with the 350 nm lamp and with the simultaneous use of the three lamps, the photodegradation of BaP followed first-order kinetics. Independent of the irradiation wavelength, the presence of DOSS increased the half-life of BaP in the aqueous solution. In the case of the 350 nm lamp, the rate constant of photodegradation in the absence and the presence of DOSS varied from (3.79 ± 0.97) × 10-3 min-1 to (1.10 ± 0.13) × 10-3 min-1, respectively. Under simultaneous irradiation with the lamps, the rate constant of photodegradation varied from (1.12 ± 0.35) × 10-3 min (no DOSS) to (3.30 ± 0.87) × 10-4 (with DOSS). Since the largest rate constants of photodegradation were observed in the absence of DOSS, the longer half-lives of BaP in the presence of surfactant were attributed to the incorporation of PAH molecules into the DOSS micelles.

Measurement setup to simultaneously explore the location and energy of trapped charges in thin polymer films

This research proposes a unique system that combines charge density measurements by the laser intensity modulation method with optically excited current acquisitions using the photo-stimulated discharge technique (PSD). The purpose of this setup is to investigate the relationship between space charge properties (such as density, spatial depth, and time evolution) and the photocurrent-associated energies in order to gain new insights into the trap population and detrapping mechanisms in thin polymer films. This paper presents a description of the technical principles of both methods as well as the whole combined system. The results on a 12 μm-thick polyethylene naphthalate film show pyroelectric currents, which after processing indicate the formation of homocharges whose magnitude and depth decrease after light irradiation. The PSD currents allow the identification of two major energy bands at 3.4 and 5.9 eV (360 and 207 nm, respectively), possibly related to charge detrapping. In addition, current transients during constant wavelength irradiation show that incident photons can interact differently with trapped charges depending on the applied field.

Effect of the use of inorganic- based photoluminescent materials in solar energy devices application

The dynamic processes that take place in life require energy. The main convenient source of energy even in living tissue are hydrocarbons. This is due to the high-carbon based energy source that eventually converts fossil fuels. The preferred fuels as the primarily and industrial fuel contribute to the observed negative effects which emit pollutants to our environments and result to global warming. To mitigate such energy dependence, solar radiation has been exploited to produce clean energy through the use of photovoltaic cells. Nevertheless, natural radiation varies depending on the season of the year. This study investigated the properties of inorganic materials that support fluorescence after the source of light has been withdrawn. The minerals Sb/Ca/Mn/Ag were prepared hydrothermally to cultivate luminescent properties. The resulting products were characterized using Fourier Transformed Infrared (FTIR) spectroscopy and then applied to extend radiation in a photoactive material of a photocell. Optimal values of the prepared luminescent substance were established to produce the best generated potential in the fabricated solar cells when the natural radiation was withdrawn. Established receptive layer composites (KI/I2: CX) were inserted into a molding dice on top of the photosensitive layer and joined together by pressing. The ensued inorganic luminescent cells optical characteristics were observed under UV radiation (320 - 400 nm) wavelength which produced sequential varying colorations from brown, light blue, blue to red before diminishing gradually as the incident radiation was removed. The open circuit potential voltage (VOC) and current density (JSC) generated parameters were observed. The (0.45, 0.4, and 0.086) V residue potential resulted due to shifting of IR by SbNO3, Sb-PO4, Sb-CO3 and Sb-O luminescent materials. The dopants had promising properties for radiation delay in photo voltaic devices application.

Unidirectional manipulation of Smith-Purcell radiation by phase-gradient metasurfaces.

Here, we present a new, to the best of our knowledge, approach to control Smith-Purcell radiation (SPR) via phase-gradient metasurfaces (PGMs), i.e., periodic grating structures with gradient phase modulation. We show that the phase gradient and the parity design of the PGM can efficiently manipulate higher order diffraction to achieve perfect unidirectional SPR, which significantly alters the SPR in the spectrum and the spatial distribution beyond traditional understanding. Specifically, the even-parity PGM results in incidence-free unidirectional radiation, while the odd-parity PGM enables incidence-locking unidirectional radiation. This unidirectional SPR is very robust, ensured by the parity-dependent diffraction rule in PGMs. A modified formula is presented to reveal the relationship between the radiation wavelength and the radiation angle. Our findings offer a new way to control the electromagnetic radiation of moving charged particles (CPs) with structured materials, which may lead to novel applications in tunable, efficient light sources and particle detectors.

Sub-wavelength effects in a free electron laser oscillator.

Previous simulation studies of cavity based free electron lasers (FELs) have utilised models which average the optical field in the FEL interaction over an integer number of radiation wavelengths. In this paper, two unaveraged simulation codes, OPC and Puffin, are combined to enable modelling, for the first time, of a cavity based FEL at the sub-wavelength scale. This enables modelling of effects such as coherent spontaneous emission from the electron beam and sub-wavelength cavity length detuning. A cavity FEL operating in the mid-infrared is modelled and it is shown that, for small sub-wavelength cavity detunings, the FEL can preferentially lase at the third harmonic of the fundamental FEL wavelength. This novel result suggests other modes of operation may be possible and opens up cavity-based FEL operation to investigation of further, potentially useful, modes of operation.

Study of the Effect of Laser Radiation Parameters on the Efficiency of Lithotripsy

In this article, we report on experimental studies of the influence of several laser radiation parameters, such as the duration of the laser pulse, the radiation wavelength, and the pulse energy, on the efficiency of the destruction of urinary calculi. The study used a laser lithotripter based on a fiber Tm laser generating at a wavelength of 1940 nm with pulses with a duration of about 1800 μs and pulse energy of up to 6 J, as well as a femtosecond solid-state Yb laser generating at a wavelength of 1032 nm with a pulse duration of about 250 fs and pulse energy of up to 400 μJ. A comparative analysis was carried out according to such criteria as the productivity of lasers when removing a unit mass of images and the amount of sample displacement resulting from the retropulsion effect. The results obtained in this work demonstrated that the femtosecond laser loses approximately two times its efficiency in terms of sample material removal. However, this shows the absolute advantage of the photoionization mechanism of femtosecond laser ablation in the study of retropulsion and thermal heating, which were completely absent in this case.

First insights into 6PPD-quinone formation from 6PPD photodegradation in water environment

p-Phenylenediamines (PPDs), an important type of rubber antioxidants, have received little study on their environmental fate, particularly for their vital photodegradation process in water environment. Accordingly, N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), as a representative of PPDs, was investigated experimentally and theoretically for its photodegradation in water. Rapid photodegradation occurred when 6PPD was exposed to illumination especially UV region irradiation. Under acidic conditions, the photodegradation of 6PPD accelerated mainly due to the increased absorption of long wavelength irradiation by ionized 6PPD. Nine photodegradation products (e.g., 6PPD-quinone (6PPDQ)) of 6PPD were identified by an ultra-performance liquid chromatography QTOF mass spectrometry. Molar yields of photoproducts such as 6PPDQ, aniline, 4-aminodiphenylamine, and 4-hydroxydiphenylamine were 0.03 ± 0.00, 0.10 ± 0.01, 0.03 ± 0.02, and 0.08 ± 0.01, respectively. Mechanisms involved in 6PPD photodegradation include photoexcitation, direct photolysis, self-sensitized photodegradation, and 1O2 oxidation, as demonstrated by electron paramagnetic resonance (EPR) analysis, scavenging experiments, and the time-dependent density functional theory (TD-DFT). Notably, the toxicity of the reaction solution formed during the photodegradation of 6PPD was increased by the formation of highly toxic products (e.g., 6PPDQ). This study provides the first explanation for photodegradation mechanisms of 6PPD and confirms the pathway of 6PPDQ produced by the photoreaction in water environment.

Comprehensive investigations of trans-cis-trans isomerization in the solid state for azo polyimides

This work describes the thermal cis-trans isomerization in the solid-state for poly(ether imide)s and poly(ester imide)s with azobenzene or azo pyridine moieties. The cis-trans relaxation was monitored for covalently functionalized polyimides (main-chain, side-chain, „T-type”) and “guest-host” azo systems. The obtained results from the investigations allow us to formulate some general relationships between material aspects such as polyimide structure, its molar mass, the content of azo dye, the value of d-spacing, the thickness of polymer film, and thermal cis-trans isomerization. The reversibility of the trans-cis-trans reaction was studied in 10 subsequent cycles and 100 cycles for the selected polymers. Studies of the reversibility of the trans-cis-trans reaction were realized by irradiation using two wavelengths of radiation λ = 365 nm (P = 2.9 W) and λ = 460 nm (P = 850 mW). To the best of our knowledge, this is the first article that comprehensively presents solid-state cis-trans isomerization for azo polyimides.

Effects of wavelength on the treatment of contaminants of emerging concern by UV-assisted homogeneous advanced oxidation/reduction processes

Pollutants of emerging concern in aqueous environments present a significant threat to both the aquatic ecosystem and human health due to their rapid transfer. Among the various treatment approaches to remove those pollutants, UV-assisted advanced oxidation/reduction processes are considered competent and cost-effective. The treatment effectiveness is highly dependent on the wavelength of the UV irradiation used. This article systematically discusses the wavelength dependency of direct photolysis, UV/peroxides, UV/chlor(am)ine, UV/ClO2, UV/natural organic matter, UV/nitrate, and UV/sulfite on the transformation of contaminants. Altering wavelengths affects the photolysis of target pollutants, photo-decay of the oxidant/reductant, and quantum yields of reactive species generated in the processes, which significantly impact the degradation rates and formation of disinfection byproducts. In general, the degradation of contaminants is most efficient when using wavelengths that closely match the highest molar absorption coefficients of the target pollutants or the oxidizing/reducing agents, and the contribution of pollutant absorption is generally more significant. By matching the wavelength with the peak absorbance of target compounds and oxidants/reductants, researchers and engineers have the potential to optimize the UV wavelengths used in UV-AO/RPs to effectively remove pollutants and control the formation of disinfection byproducts.

The biological effects of terahertz wave radiation-induced injury on neural stem cells

Terahertz (THz) is an electromagnetic wave with a radiation wavelength range of 30-3000μm and a frequency of 0.1-10 THz. With the development of new THz sources and devices, THz has been widely applied in various fields. However, there are few studies on biological effects of THz irradiation on the human neural stem cells (hNSCs) and mouse neural stem cells (mNSCs), which need to be further studied. We studied the biological effects of THz radiation on hNSCs and mNSCs. The effects of THz irradiation time and average output power on the proliferation, apoptosis, and DNA damage of NSCs were analyzed by flow cytometry and immunofluorescence. The results showed that the proliferation and apoptosis of NSCs were dose-dependently affected by THz irradiation time and average output power. The proliferation of hNSCs was more vulnerable to damage and apoptosis was more serious under the same terahertz irradiation conditions compared to those of mNSCs.

Efficacy of UV and UV-LEDs Irradiation Models for Microbial Inactivation Applicable to Automated Sterile Drug Compounding

LEDs development has attracted attention over conventional mercury lamps for the tiny size, high efficiency, long lifetime, low operating temperature. The antimicrobial effectiveness of traditional UV-lamps radiation (wavelength of 254 nm) compared to UV-C LEDs (LED1 wavelength range 275–286 nm and LED2 range 260–270 nm) was carried out, for possible applications to automated sterile drug compounding. The UV lamp and the tested UV-LED devices remarkably reduced microbial load, following a time-dose response, but the best performance was evidenced by LED1, which guaranteed the complete inactivation of high concentrations of bacteria, yeasts, and spores at doses between 200 and 2000 J/m2.

Mathematical Model of Fuse Effect Initiation in Fiber Core

This work focuses on the methods of creating in-fiber devices, such as sensors, filters, and scatterers, using the fiber fuse effect. The effect allows for the creation of structures in a fiber core. However, it is necessary to know exactly how this process works, when the plasma spark occurs, what size it reaches, and how it depends on external parameters such as power and wavelength of radiation. Thus, this present study aims to create the possibility of predicting the consequences of optical breakdown. This paper describes a mathematical model of the optical breakdown initiation in a fiber core based on the thermal conductivity equation. The breakdown generates a plasma spark, which subsequently moves along the fiber. The problem is solved in the axisymmetric formulation. The computational domain consists of four elements with different thermophysical properties at the boundaries of which conjugation conditions are fulfilled. The term describing the heat source in the model is determined by the wavelength of radiation and the refractive indices of the core and the shell and also includes the radiation absorption on the released electrons during the thermal ionization of the quartz glass. The temperature field distributions in the optical fiber are obtained. Based on the calculations, it is possible to estimate the occurrence times of various phase states inside the fiber, in particular, the plasma spark occurrence time.

Coherent information accumulation from virtual MIMO radars with multiple increase of interelement distances in the real MIMO radar

To reduce the number of air carriers when using MIMO radars, it is advisable to reduce the number of transmitting and receiving elements (TLE and RTE) of real MIMO radars, as well as the use of virtual MIMO radars. The reduction in the number of TLE and RTE can be achieved by increasing the distances between them to values significantly exceeding the average radiation wavelength. In this case, it is necessary to theoretically estimate the spatial resolution and accuracy of the measured coordinates in the selected system of virtual MIMO radars corresponding to real MIMO radars with spatially highly rarefied TLE and RTE. For short-range MIMO radars, using theoretical expressions for the generalized uncertainty function (GUF) in the case of a fixed point target, two-dimensional and one-dimensional sections of GUF in the “range–azimuth” plane are determined, which are compared for variants of moderate and highly rarefied two-dimensional arrangements of TLE and RTE of real and virtual MIMO antennas. The proposed mathematical technique allows you to quickly evaluate the resolution in range and azimuth in the development and creation of real and virtual MIMO radars with increased inter-element distances.

Role of Gas Pressure in Quasi-Phase Matching in High Harmonics Driven by Two-Color Laser Field

The results of a study on the effect of pressure in a medium consisting of a set of gas jets separated by vacuum gaps, interacting with two-color laser fields formed by the fundamental and the second harmonics of a laser, are presented herein. It has been demonstrated that a decrease in pressure leads to a shift in the region of harmonics where quasi-phase matching (QPM) occurs towards shorter wavelength radiation, accompanied by an increase in the efficiency of amplification of these harmonics. A feature of this process is the identical power-law character of the shift in the region and the increase in the efficiency of harmonic QPM amplification. Additionally, the study presents the results of the effect of inaccurately setting the width of the gas jets on the shape of the spectrum of harmonic QPM amplification.

Analyzing the Effectiveness of Support Vector Machine and Random Forest Classifiers in Delineating the Green Area

Due to human limitations in exploring the world, the existence of remote sensing technology has made it possible and affordable for humans to study the green cover in the modern world, especially over a large region. This is so that details of the objects can be captured and monitored by satellites or other aircraft by measuring the wavelengths of radiation that are both emitted and reflected from the area. For the past decades, various approaches have been utilized by researchers to detect green areas such as deep learning, machine learning, object based and pixel-based classification. Thus, this study aims to evaluate the effectiveness of machine learning classifiers such as Support Vector Machine (SVM) and Random Forest (RF) in detecting and delineating the green area in Universiti Teknologi Mara (UiTM) Shah Alam. Based on the study, the overall accuracy obtained by the SVM classifier is 80% with a 0.75 kappa coefficient, whereas the RF classifier managed to get 79% with a 0.74 kappa. Even though the result of both classifiers is almost the same, the accuracy of detecting green area by the SVM classifier is 93% which outperforms the RF classifier with an accuracy of 88%. This shows that the SVM classifier is more effective than the RF classifier. The detection and delineation of the green area using both machine learning approaches also showed using a map so that it is easier to be analyzed and observed.

Wideband Low-RCS Linear Polarized Array Based on Miniaturized Polarization Conversion Metasurface

Based on the proposed miniaturized polarization conversion metasurface (PCM), a checkerboard metasurface is designed, which can realize radar cross section (RCS) reduction in the ultra-wide range of 4.3~13.5 GHz (103%) by using the principle of reflection phase cancellation. The characteristic mode analysis (CMA) method is introduced to establish the checkerboard PCM as the radiation patch, and a wideband low-profile antenna for the C-band is achieved, with a bandwidth of 4.8~6 GHz (22.2%). The highlight and advantages are that the size of the checkerboard PCM is significantly reduced, and its side length is close to the radiation wavelength of the antenna. The antenna element based on this checkerboard PCM has the characteristics of small size and wide frequency range of RCS reduction, and the low-RCS antenna array can be realized by paving them seamlessly. Moreover, the checkerboard PCM not only suppresses scattering but also improves antenna performance, plays an important role in achieving wideband and enhancing radiation directivity.

Nonlinear optical properties of gold nanoparticles produced by laser ablation at two different radiation wavelengths

In this study, gold nanoparticles were synthesized by laser ablation of Au bulk in distilled water. The laser used is Nd: YAG laser, which has a fundamental harmonic wavelength (λ=1064nm) and second harmonic wavelength (λ=532nm). In order to control the size of Au nanoparticles (NPs), we used sodium citrate as a stabilizer. Morphology, structure and linear optical properties of Au NPs samples were characterized by transmission electron microscopy (TEM observation), XRD diffraction (XRD) and UV–Visible spectroscopy. Furthermore, the chemical structure in solution of Au NPs was studied by Fourier transform-infrared spectroscopy (FTIR). The nonlinear optical parameters of these Au NPs were studied using the Z-scan method. We found the optimal values of fluencies and laser pulse repetition rates to achieve the smallest size values and the most distribution of the produced gold nanoparticles. It is resulted that due to the very small size of NPs, the nonlinear optical parameters show larger values. It is 107 order of magnitude larger than what has been reported for the nonlinear refractive index in previous researches. In addition, gold nanoparticles that are produced with a laser wavelength of 1064 nm and have a high nonlinear refractive index can be used in chip-based sensors. Finally, the use of these Au NPs in optical switching devices was investigated by the two figures of merit method, which indicated that these Au NPs are practical tools for optical switching devices.