Search Results (56)

Myoglobin (Mb), a heme-containing protein, plays crucial roles in storing and transporting oxygen in muscle cells. Various Mb structures have been extensively determined using conventional cryogenic crystallography, providing valuable information for understanding the molecular mechanisms of the protein. However, this approach has limitations attributable to cryogenic temperatures and radiation damage. Serial femtosecond crystallography (SFX) using X-ray free-electron lasers is an emerging technique that enables the determination of biologically relevant room-temperature structures without causing radiation damage. In this study, we assessed the crystallization, collection, and processing of SFX diffraction data of Mb from equine skeletal muscle. Needle- and needle cluster-shaped Mb crystals were obtained using the microbatch method. Fixed-target SFX data collection was performed at the Pohang Accelerator Laboratory X-ray Free Electron Laser, yielding 1389 indexed diffraction patterns. The phase problem was solved by molecular replacement. The preliminary Mb structure determined at 2.3-Å resolution in this study exhibited subtle structural differences in the heme environment compared with previously reported Mb structures determined by SFX. These results both confirm the feasibility of myoglobin SFX experiments and establish a foundation for future time-resolved studies aiming to visualize ligand binding and oxygen transport. Full article

Preventing false signals of phantom pain after limb amputation is crucial. The development of neurointerfaces capable of bidirectional information exchange between the brain and external devices, along with long-term use, is a key research priority. The main problem with existing devices lies in the potential formation of scar tissue and the death of adjacent neurons. To address this issue, a polymer composite based on new composition: chitosan, bovine serum albumin, single-walled carbon nanotubes, and Eosin Y, which was created for the fabrication of a neurointerface. A polymer composite of the required shape was formed by two-photon polymerization. In studying its nonlinear optical properties, the new effect of phase self-modulation was discovered, which is observed after exposure to laser radiation prior to the formation of the composite. The time of appearance of diffraction rings was measured. This allowed optimization of laser parameters—scanner speed and intensity. The resulting homogeneous composite exhibited a specific conductivity of 20 mS × cm⁻¹, sufficient for electrophysiological signal transmission. Full article

Cracks due to stress corrosion cracking in stainless steels are becoming a problem not only in boiling water reactors but also in pressurized water reactor nuclear plants. Stress improvement measures have been implemented mainly for large-bore welded piping, but in the case of small-bore welded piping, post-welding stress improvement measures are often not possible due to dimensional restrictions, etc. Therefore, knowing the actual welding residual stresses of small-bore welded piping regardless of reactor type is essential for the safe and stable operation of nuclear power stations, but there are only a limited number of examples of measuring the residual stresses. In this study, austenitic stainless steel pipes with an outer diameter of 100 mm and a wall thickness of 11.1 mm were butt-welded. The residual stresses were measured by the strain scanning method using neutrons. Furthermore, to obtain detailed residual stresses near the penetration bead where the maximum stress is generated, the residual stresses near the inner surface of the weld were measured using the double-exposure method (DEM) with hard X-rays of synchrotron radiation. A method using a cross-correlation algorithm was proposed to determine the accurate diffraction angle from the complex diffraction patterns from the coarse grains, dendritic structures, and plastic zones. A quantum beam hybrid method (QBHM) was proposed that uses the circumferential residual stresses obtained by neutrons and the residual stresses obtained by the double-exposure method in a complementary use. The residual stress map of welded piping measured using the QBHM showed an area where the axial tensile residual stress exists from the neighborhood of the penetration bead toward the inside of the welded metal. This result could explain the occurrence of stress corrosion cracking in the butt-welded piping. A finite element analysis of the same butt-welded piping was performed and its results were compared. There is also a difference between the simulation results of residual stress using the finite element method and the measurement results using the QBHM. This difference is because the measured residual stress map also includes the effect of the stress of each crystal grain based on elastic anisotropy, that is, residual micro-stress. Full article

Water is the source of life on Earth. Therefore, water pollution is one of the greatest problems in the world. On this basis, the current study focuses on accelerating industrial pollutant removal from water using light by designing effective photocatalysts. This target was achieved through a triple-action effect. This effect depends on the integration of the doping process with nanotube formation in addition to the surface plasmon resonance of gold for titanium oxides. In this way, titanium oxide nanoparticles were prepared and converted to nanotubes during the doping process. These nanoparticles and nanotubes were supported by gold nanoparticles to use this triple-action effect for increasing charge carriers and active sites of the photocatalysts and preventing recombination reactions. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), Raman spectra, energy-dispersive X-ray spectrometer (EDX), and X-ray diffraction were used to clarify the triple-action effect on the structure of the photocatalysts. The optical properties and activity of the prepared photocatalysts were studied in terms of the photocatalytic degradation of the green dyes (acid green 1). The experimental results indicated that the triple-action effect has a strong positive role in increasing industrial pollutant removal with or without light. Here, the percentage of photocatalytic decomposition reached 100% after 17 min of light radiation. In addition, 27% of the pollutants were removed without light radiation. In conclusion, the current study indicated that the triple-action effect could solve the drawbacks of titanium oxide by creating new photo-active sites and novel tracks for charge carriers in addition to preventing recombination reactions. Full article

Radiation damage is an inherent problem in macromolecular crystallography because it impairs the diffraction quality of crystals and produces inaccurate structural information. Understanding radiation damage in protein structures is crucial for accurate structural interpretation and effective data collection. This study undertook X-ray data collection and structure determination of thermolysin (TLN), which contains Zn and Ca ions, by using three different X-ray doses to improve our understanding of the radiation damage phenomena on metal ions in proteins. Data processing revealed typical global radiation damage in TLN, such as an increase in unit cell volume, R_merge value, and Wilson B-factor. An analysis of the B-factor indicated that radiation damage at the Zn and Ca sites in TLN increased with higher X-ray doses. However, the distance between the metal ions and their interacting residues in TLN was not significantly affected, suggesting that radiation damage to the metal ions has a minimal effect on these interactions. Moreover, the increase in the B-factor of the metal ions according to the X-ray dose was similar to that in the B-factor of the residues interacting with the metal ions. These results expand our understanding of radiation damage phenomena in macromolecules and can be used to improve data collection strategies. Full article

We propose a task-specific method for calculating cascaded phase diffractive optical elements (DOEs) for focusing Q incident beams with different wavelengths to Q given points. Due to the utilization of a special optimization criterion, the proposed method makes it possible to calculate the elements of the cascaded DOE in a sequential way. In addition, the calculation of the diffractive microrelief of each DOE in the cascade is reduced to solving a set of independent and computationally simple “pointwise” optimization problems. Using the proposed method, cascades of two DOEs were designed to focus radiation of 11 different wavelengths to 11 different points. The presented numerical simulation results demonstrate good performance of the method. The chosen operating wavelengths correspond to a set of widely used vegetation indices enabling monitoring the vegetation status conditions and tracking the environmental stresses. This makes the obtained results promising for the application in remote sensing and smart agriculture. Full article

The principal objective of this investigation is to assess the hydrodynamic characteristics and the exciting forces induced by waves acting upon a shallowly submerged spheroid. This study focuses on an arbitrarily shaped spheroid body with a vertical axis, fully immersed beneath the free surface within waters of finite depth. The methodology outlined here necessitates solving the linear hydrodynamic diffraction and radiation problems, which entail discretizing the flow field around the body into ring-shaped fluid regions. Within each region, expansions of axisymmetric eigenfunctions of the velocity potential are employed. Complementing the theoretical framework, numerical methodologies are employed utilizing panel models across the wetted surface of the submerged body. Extensive numerical results concerning the exciting forces induced and the hydrodynamic coefficients are presented in the framework of frequency domain formulations. Through the current analysis, the phenomenon of negative added mass and rapid variations in the added mass and damping coefficients is confirmed, attributed to the free surface effect elucidated in terms of the presence of near-resonant standing waves above the submerged body. Full article

Currently, one of the most important problems of environmental protection is the deep and complex processing of mineral raw materials. This problem is especially relevant when processing substandard ores and production waste, one of which is phosphogypsum. This study examines the process of CaSO₄/CaS composite material formation during the reduction of phosphogypsum with citric acid. The composite structure formation mechanism is proposed. The resulting materials are characterized using various methods, including X-ray diffraction (XRD), transmission electron microscopy, the Scherrer method, thermogravimetric analysis (TGA), and FT-IR spectroscopy. The reduced sample emits orange radiation in the range of 500–750 nm with a quantum yield of 0.17. Experimental results showed that the sample decomposition process in the solid state consisted of two components with a predominant contribution from the long-lived component (~46 ns). The optimal conditions for producing luminescent materials by reducing phosphogypsum with citric acid were determined: a heat treatment temperature of 1073 K, a holding time of 60 min, and a reducing agent mole fraction of 37%. It was found that an increase in temperature with a simultaneous decrease in heat treatment time, as well as a decrease in temperature with a simultaneous increase in heat treatment time, led to a decrease in the luminescent properties of the synthesized material compared to optimal values. The results can be used to develop technology for recycling large-tonnage waste from the chemical industry into luminescent materials. Full article

Recently, many floating renewable energy platforms have been deployed in coastal regions, where sloping bottoms are an important factor when evaluating their safety. In this article, a simplified method coupling an eigenfunction matching method (EMM) and a finite-depth Green’s function (FDGF) is developed to evaluate floating-body motion responses over a sloping bottom for which bathymetry is homogeneous in the longshore direction. We propose an extended EMM to create an incident wave model over the sloping bottom, thereby obtaining the Froude–Krylov (F–K) force and Neumann data on the wet surfaces of the floating body for the diffraction problem. An equivalent depth is introduced to account for the interaction between the sloping bottom and floating bodies when dealing with the diffraction and radiation problems. The accuracy of the present method is validated through a comprehensive comparison with numerical and/or experiment results for a liquefied natural gas (LNG) ship and a floating hemisphere from the literature. Generally, the present, simplified method can give predictions with sufficient accuracy. Full article

In recent decades, there has been a rise in public consciousness of the adverse effects of expanded skin contact with sunlight, particularly the ultraviolet (UV) spectrum. UV radiation causes serious health problems like skin cancer, early aging, erythema, pigmentation, etc., due to contact with the skin. Therefore, the highly efficient UV-protection materials were manufactured using polypropylene and TiO₂ (PPTO) through cost-effective and easy methods. The designated 7.5 PPTO and 15 PPTO were prepared, varying the amount of TiO₂, as well as without using TiO₂ (PPNF), which was also manufactured as a control material. All the as-synthesized nonwoven fibers were carefully characterized employing a variety of microscopic and spectroscopic methods, such as X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, and contact angle measurements. In conclusion, 15 PPTO showed the highest UV-protection ability (87.5%) compared to 7.5 PPTO and PPNF. In addition, 15 PPTO exhibited 1.76 and 1.32 times higher protection than 7.5 PPTO and PPNF, respectively, when exposed to UB-B radiation. The enhanced activity may be due to the amount of TiO₂ because TiO₂ increased the product’s absorption and reflection capability. Overall, the PPTO nonwoven fibers can be applied to block harmful UV radiation. Full article

Inadequate waste management and illegal trash dumping continue to be the leading causes of severe environmental pollution. Human exposure to harmful heavy metals has emerged as a serious health concern on the continent. Some people in Alice, a small town, grow their food in home gardens. They use animal manure and compost derived from soil obtained from landfills to enhance the fertility of the garden soil. Heavy metal heaps in garbage disposals are constantly present, releasing dangerous amounts of metal into the environment. The harmful effects of heavy metals on plants lead to unsanitary conditions and environmental problems. Animals and people who consume these vegetables may also be at risk for health problems. Assessing the soil’s enzyme activity can potentially lessen the negative effects of the accumulated pollutants and improve the soil’s overall health and quality. Soil enzymes are biologically active components that have a catalytic impact and are released from root exudates, crop residues, and animal remains. The activity of enzymes serves as an excellent bioindicator of soil cleanliness and quality because they are sensitive to heavy metals. X-ray diffraction (XRD) was used to quantify the mineral elements in soil using 40 kV parallel beam optics, 30 mA, and CuKα radiation. Meanwhile, the activity of the enzyme was essayed in different coupled substrates. Thirteen (13) clay minerals were found, including Talc 2M, Kaolinite 2M, and Chlorite Lawsonite Muscovite 2M1. The detected trace elements have high concentration levels that exceed the World Health Organization’s (WHO) allowed levels. The identified elements affected the enzyme activity at different levels. The Mn, Al, Si, V, Ti, and Ca negatively affect soil enzyme activity, specifically invertase (INV). However, the amount of Mg, K, Fe, and Zn showed a slightly positive effect on the same enzyme (INV). According to this view, these elements come from several sources, each with a particular impact on soil contamination and enzyme activity. High levels of heavy metals in this study may be due to improper waste disposal, limited recycling opportunities, lack of public awareness, and inadequate enforcement of waste management regulations. It is essential to employ Fourth Industrial Revolution (4IR) technologies, correct disposal techniques, suitable agricultural methods, preventive regulations, and efficient waste management to mitigate the negative effects of heavy metals on the environment. Full article

This study tries to identify the effect of hydrodynamics on the absorbed wave power using a toroidal Oscillating Water Column (OWC) device. To this end, the fundamental hydrodynamic boundary value problem for an arbitrary shaped toroidal OWC device of revolution with vertical axis is solved. The described method is based on the discretization of the flow field around the device by means of ring-shaped macro-elements, in each of which axisymmetric eigenfunction expansions for the velocity potential is made. The solution sought for the corresponding diffraction and radiation velocity potentials is achieved using Galerkin’s method. The applied formulation is generic and can be employed for arbitrary configurations of toroidal OWCs. Therefore, the numerical results shown and discussed in the present paper, in terms of the hydrodynamic loads and the air volume flows inside the OWC chamber, concern different types of OWCs. From the present analysis, it is demonstrated that the absorbed wave power by the examined toroidal devices is strongly affected by the geometrical parameters of the device; thus, these should be properly considered towards the maximization of the device’s wave power efficiency. Full article

One of the most important problems in the plasmonics of the terahertz (THz) range, which is actively developing now, is the efficient generation of surface plasmon polaritons (SPPs). The simplest and most promising technological technique of photon excitation of THz SPPs is through diffraction of radiation on the edge of the conducting surface of the sample (the end-fire coupling technique). In this paper, we experimentally evaluated the efficiency of the generation of monochromatic THz SPPs (λ₀ = 141 μm) by this method with a sample in the form of a cylindrical segment, the convex surface of which has a gold layer coated by zinc sulfide (ZnS) with thickness d = 0–2 µm. Such configuration of the surface supporting the SPPs not only shields the detector from parasitic bulk waves arising during diffraction but also enables one to change the distribution of the SPP field in the air by varying the coating layer thickness d. On an uncoated gold surface, the SPP generation efficiency was η ≈ 20%. In the presence of a ZnS layer on the gold, the SPP generation efficiency gradually increased with d, reached the maximum (η_max ≈ 60%) at d ≈ 1 μm, and then gradually decreased. Theoretical analysis showed that the efficiency of the SPP generation can be raised up to 80% due to the selection of an optimal SPP field profile via variation of the thickness of the dielectric layer on the metal surface, as well as with optimal incidence of the focused radiation on the edge of the sample. Full article

The problem of axially symmetric TM-wave diffraction from a bicone conjoined with an open-ended conical cavity is analysed rigorously. The scatterer is formed by the perfectly conducting semi-infinite and truncated semi-infinite conical surfaces; the spherical termination of an internal area of the truncated cone creates the open-ended cavity. In this paper the certain physical aspects of diffraction which are known to cause mathematical difficulties are considered. It includes an accurate analysis of the wave-mode transformation phenomena at the open end of the cavity, as well as a study of wave radiation from the cavity into the biconical waveguide. The primary outcome of this paper is a precise treatment of the wave diffraction problem mentioned above using new techniques and establishing new properties of resonance modes’ penetration into the biconical waveguide region. Full article

Shot peening is a process wherein the surface of a material is impacted by small, spherical metal shots at high velocity to create residual stresses. Nickel-based superalloy is a material with high strength and hardness along with excellent corrosion and fatigue resistance, and it is therefore used in nuclear power plants and aerospace applications. The application of shot peening to INCONEL, a nickel-based superalloy, has been actively researched, and the measurement of residual stresses has been studied as well. Previous studies have used methods such as perforation strain gauge analysis and X-ray diffraction (XRD) to measure residual stress, which can be evaluated with high accuracy, but doing so damages the specimen and involves critical risks to operator safety due to radiation. On the other hand, ultrasonic testing (UT), which utilizes ultrasonic wave, has the advantage of relatively low unit cost and short test time. One UT method, minimum reflection measurement, uses Rayleigh waves to evaluate the properties of material surfaces. Therefore, the present study utilized ultrasonic minimum reflectivity measurements to evaluate the residual stresses in INCONEL specimens. Specifically, this study utilized ultrasonic minimum reflection measurements to evaluate the residual stress in INCONEL 718 specimens. Moreover, an estimation equation was assumed using exponential functions to estimate the residual stress with depth using the obtained data, and an optimization problem was solved to determine it. Finally, to evaluate the estimated residual stress graph, the residual stress of the specimen was measured and compared using the XRD method. Full article