Laser Radiation Research Articles

The Effect of Supernatant Culture Medium Isolated from 3T3-L1 Cells Subjected to Low Power 980 and 650 nm Laser Radiation on Wound Healing Process

Background: Fibroblasts are the most important cells in the healing process of wounds. The motility activity of low-level laser (light) therapy (LLLT) on fibroblast proliferation has been well-established in vitro. Laser treatment for scar removal increases the number of scars. Objectives: This method uses light therapy to remove the outer layer of the skin surface and produce new skin cells to cover the damaged skin cells. Methods: The present research is from an experimental laboratory. First, tissue fibroblast cells were cultured under appropriate conditions. Then, it was exposed to laser radiation with intensities of 650 and 980 nm, and its supernatant solution was used for wound treatment. Interleukin 2 (IL-2), tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF) levels were used to check the recovery. Results: The results of the MTT assay showed an increase in the viability of the cell line under laser irradiation. In addition, these evaluations showed an increase in IL-2, TNF-α, and VEGF after 650 and 980 nm laser irradiation compared to the control group after 48 hours. Conclusions: According to the present study, laser therapy has potential therapeutic potential for wound healing. However, more studies are suggested to increase the efficiency and speed up the treatment process.

Grain Orientation, Angle of Incidence, and Beam Polarization Effects on Ultraviolet 300 ps‐Laser‐Induced Nanostructures on 316L Stainless Steel

AbstractLaser‐induced periodic surface structures (LIPSS) represent a unique route for functionalizing materials through the fabrication of surface nanostructures. Commercial AISI 316L stainless steel (SS316L) surfaces are laser treated by ultraviolet 300 ps laser pulses in a laser line scanning (LLS) approach. Processing parameters are optimized (pulse energy of 2.08 µJ, pulse repetition frequency of 300 kHz, and suitable laser scan and sample displacement rates) for the generation of low spatial frequency LIPSS over a large 25 × 25 mm2 area. Different angles of incidence of the laser radiation (0°, 30°, and 45°) and different linear laser beam polarizations (s and p) produce a plethora of rippled surface morphologies at distinct grains. Scanning electron microscopy and 2D Fourier transforms, together with calculations of the optical energy deposited at the treated surfaces using Sipe's first‐principles electromagnetic scattering theory, are used to study and analyze in detail these surface morphologies. Combined with electron backscattering diffraction, analyses allow associating site‐selectively various laser‐induced‐surface morphologies with the underlying crystalline grain orientation. Resulting grain orientation maps reveal a strong impact of the grain crystallographic orientation on LIPSS formation and point toward possible strategies, like multi‐step processes, for improving the manufacturing of LIPSS and their areal coverage of polycrystalline technical materials.

Laser-induced Bragg resonances in ferrit/semiconductor heterostructure

The paper reports on laser-induced Bragg resonances in the spectrum of magnetostatic waves in a heterostructure based on a ferrite film [yttrium iron garnet (YIG)] with periodic strips of semiconductor material (Si) on the surface. Laser irradiation of such a structure leads to the formation of Bragg bandgaps due to the modulation of the Si conductivity on the YIG surface, and the magnitude modulation increases with increasing laser radiation intensity. It is shown that an increase in laser radiation intensity also leads to an increase in the depth and frequency shift of the bandgaps.

Evaluation of the Effect of NovaMin and Er,Cr:YSGG Laser on Remineralization of Erosive Lesions of Primary Enamel Teeth: An In Vitro Study.

Introduction: The purpose of this in vitro study is to ascertain how NovaMin and Er,Cr:YSGG laser radiation affect the remineralization of primary tooth enamel lesions. Methods: 40 main teeth served as the study's sample size. These teeth were allocated into five groups at random. The first group served as a negative control (artificial saliva); the second group served as a positive control (APF gel 1.23%); the third group NovaMin, the fourth group Er,Cr:YSGG laser, the fifth group Er,Cr:YSGG laser and finally, the application of NovaMin. For the purpose of measuring microhardness, all samples were submitted to the dental materials laboratory three times. Results: The collected data were compared using the SPSS 28 program between the baseline measurement, after demineralization, and after remineralization. The data were analyzed using ANCOVA and Bonferroni tests. All groups demonstrated a considerable increase in microhardness as compared to the negative control group (P<0.05). With the exception of the third and fourth groups, there was no discernible difference in the rise in microhardness between the other groups. The third and fourth groups were compared, and the results revealed that NovaMin had a greater impact than laser therapy alone (P=0.023). Scanning electron microscopy (SEM) analysis backed up the findings. Conclusion: In comparison to using the Er,Cr:YSGG laser alone, using NovaMin alone can speed up the remineralization of erosion lesions on the surface of primary teeth.

Application of laser radiation for control of RADAN compact pulse generator

This paper presents the results of experimental and theoretical investigations of a plasma jet formed by YAG: Nd3+ laser radiation on an anode in a high-voltage gas gap. Conditions corresponding to the minimal instability of 0.3 ns and delay were experimentally found. The physical mechanisms determining the delay of the gas gap overlap by the plasma jet and the obtained instability level are discussed. A model of processes occurring on the ionization wavefront determined by the absorption/excitation of gas atoms and by the effects of a high-field domain was proposed.

COMPARATIVE ANALYSIS AND SIMULATION OF WELDING MODES DURING THE CONSTRUCTION OF THE MAIN PIPELINE USING AUTOMATED TECHNOLOGIES

In the present work, the technology of laser welding of the circumferential joints of pipes of the main gas pipeline was studied on the basis of the existing certain experience of its application at the facilities of the gas transmission system and an assessment was made of the possibility of using it as an alternative to automatic arc welding during construction and repair and restoration work. An analysis was made of the use of laser radiation for orbital welding of main pipelines, which showed that the use of this technology makes it possible to increase the productivity of the welding process, to obtain more favorable structures in the seam and in the transition zone, and to ensure a high level of mechanical properties and weld density. Temperature and deformation conditions in the zone of the welded joint help to reduce the likelihood of hot and cold cracking.Modeling of a pipeline section with welded joints made by automatic arc welding and laser welding (hereinafter referred to as LS) was carried out. When modeling welded joints, their geometric parameters for the compared welding technologies were taken into account, as well as the area and volume of the deposited metal, which theoretically correspond to natural values. Loads were applied to the pipe section with a welded seam, imitating three types of mechanical tests: tension, compression and bending, which occur in the case of thermal deformations and soil subsidence during pipeline operation.In the course of the study, stresses were determined in the cross section of a welded joint obtained using two welding technologies, which show the level of mechanical properties of the weld. A comparative analysis and evaluation of the operational reliability of the main gas pipeline with welded joints made by modern automated welding technologies has been carried out.

Local measurement of weak stresses on the surface of HgCdTe/CdTe/ZnTe/GaAs structures using the null method

A study of residual mechanical stresses in the surface layer of the HgCdTe/CdTe/ZnTe/GaAs structure based on the registration of the second harmonic signal characteristics of reflected IR laser radiation from the surface of the studied sample passed through a nonlinear crystal was carried out. It is shown that such a sensitive method makes it possible to obtain information about the anisotropy of the polarization of the reflected radiation, caused by the residual deformation. Observations of the fine structure of the angular sweep of the second harmonic signal suggest a complex structure of residual stresses related to the presence of misoriented areas. The results were compared with data obtained from measurements of the azimuthal dependence of the self-reflected second harmonic signal from the sample surface.

Single Pulse Nanosecond Laser-Stimulated Targeted Delivery of Anti-Cancer Drugs from Hybrid Lipid Nanoparticles Containing 5nm Gold Nanoparticles.

Encapsulating chemotherapeutic drugs like doxorubicin (DOX) inside lipid nanoparticles (LNPs) can overcome their acute, systematic toxicity. However, a precise drug release at the tumor microenvironment for improving the maximum tolerated dose and reducing side effects has yet to be well-established by implementing a safe stimuli-responsive strategy. This study proposes an integrated nanoscale perforation to trigger DOX release from hybrid plasmonic multilamellar LNPs composed of 5nm gold (Au) NPs clustered at the internal lamellae interfaces. To promote site-specific DOX release, a single pulse irradiation strategy is developed by taking advantage of the resonant interaction between nanosecond pulsed laser radiation (527nm) and the plasmon mode of the hybrid nanocarriers. This approach enlarges the amount of DOX in the target cells up to 11-fold compared to conventional DOX-loaded LNPs, leading to significant cancer cell death. The simulation of the pulsed laser interactions of the hybrid nanocarriers suggests a release mechanism mediated by either explosive vaporization of thin water layers adjacent to AuNP clusters or thermo-mechanical decomposition of overheated lipid layers. This simulation indicates an intact DOX integrity following irradiation since the temperature distribution is highly localized around AuNP clusters and highlights a controlled light-triggered drug delivery system.

Detection of laser beams based on intensity interferometry

We describe an approach to detecting off-axis radiation of laser beams propagating in scattering media, especially in the atmosphere, in the presence of background (solar) radiation. The method relies on a generalization of the conventional intensity interferometry (II) theory to scenarios involving coexisting sources of relatively long (laser radiation) and much shorter (background) coherence times. In such circumstances, the high coherence of the laser light allows its discrimination against even much stronger, but low-coherence, background. We propose a simple detection system consisting of a small array of photodetectors (e.g. photodiodes) and estimate the ratio of the background-to-laser irradiances at which the laser radiation is expected to be detectable.

Determination of modes for safe application of selective micro-pulse individual retinal therapy of the macular zone using the modeling based on the theory of activated complex

Purpose: to make modeling of various modes of laser radiation, to assess the degree of damage to the retinal pigment epithelium and adjacent structures, and to determine modes and safety conditions of selective micro-pulse individual retinal therapy based on the theory of activated complex. Materials and methods. The authors have modeled the degree of damage to the chorioretinal complex and adjacent structures using the activated complex theory with the Eyring equation. The following definitions were used to determine the regime quality and safety conditions: micro-pulse mode is a mode with fixed values of micro-pulse duration, duty cycle and the number of pulses in the packet; power is a variable parameter. Efficiency is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of protein in it. Selectivity is the ratio of the amount of denatured protein inside the retinal pigment epithelium layer to the total amount of denatured protein. Relative harmfulness is the ratio of denatured protein volume outside the retinal pigment epithelium to the volume of protein in it. Results and discussion. The quality of micro-pulse mode was found as depending on the selectivity value with efficiency equal to 90 %. With the efficiency value less than 50 %, the mode is non-selective, with more than 67 % – selective. Safety conditions for selective micro-pulse modes have been established, taking into account safety of the neurosensory retina and choroid in terms of relative harmfulness which should not exceed 1. Parameters at which micro-pulse modes have high values (more than 90 – 99) of efficiency and selectivity at the same time have been determined as well. It requires single pulse mode, micro pulse duration of 25 microseconds and power from 6 to 8 W. To expand the combination of parameters, it is necessary to be able to freely change them in increments of 1 pulse, 5 microseconds, 100 mW, with long interval and short duty cycle. These technical capabilities can be realized and implemented into clinical practice by manufacturers of laser devices. Conclusion. For selective micro-pulse individual retinal therapy of the macular zone with existing lasers, the following recommendation are to be observed: micro-pulse modes with pulse duration no more than 200 microseconds, short duty cycle less than 5 % and number of pulses in an envelope no more than 5; relative harmfulness less than one, radiation power selection, personalized patient’s characteristics.

Influence of Laser Radiation on the Depth of Hardened Layer of Tool Steel Cutting Dies

Influence of Laser Radiation on the Depth of Hardened Layer of Tool Steel Cutting Dies

THE EFFECT OF ACCELERATED ABSORPTION OF LIQUID IN A TUBE DURING LASER CAVITATION ON A LASER HEATING ELEMENT

The expansion and collapse of a cavitation bubble during laser heating and subcooled boiling of water in the vicinity of the tip of an optical fiber (laser heating element) installed in a water-filled glass tube with two open ends is studied experimentally and numerically. Cavitation, initiated by continuous laser radiation, is accompanied by the pushing and pulling movement of the heated liquid in the tube and outside it. For the first time, it has been shown that in a tube with an installed laser heating element in a liquid flow moving behind the walls of the bubble, when it collapses at the pole of the bubble surface remote from the end, a liquid jet appears, directed through the bubble to the end of the optical fiber. The jet speeds up the process of sucking liquid into the tube.

Synthesis and Properties of Nanosized Germanium Particles Obtained in Acetone under the Influence of Laser Radiation

Stable nanosized germanium particles were synthesized in a liquid medium (acetone) by laser irradiation of single-crystal germanium plates under aerobic and anaerobic conditions at room temperature. Various experimental methods—optical spectrophotometry, atomic force microscopy, and dynamic light scattering—made it possible to detect stable nanosized Ge particles in acetone and record optical absorption and luminescence spectra depending on the time of laser irradiation in the presence and absence of oxygen. Particular attention is paid to the results of the effect of laser irradiation on the physicochemical properties of pure acetone.

Abnormal absorption of extremely intense laser pulses in relativistically underdense plasmas

It is generally believed that relativistically underdense plasmas are transparent for intense laser radiation. However, particle-in-cell simulations reveal abnormal laser field absorption above the intensity threshold of about 3×1024 Wcm−2 for the wavelength of 1 μm. Above the threshold, the further increase in the laser intensity does not lead to an increase in the propagation distance. The simulations take into account emission of hard photons and subsequent pair photoproduction in the laser field. These effects lead to onset of a self-sustained quantum electromagnetic cascade and to formation of dense electron–positron (e+e−) plasma right inside the laser field. The plasma absorbs the laser field efficiently, which ensures the plasma opacity. The role of a weak longitudinal electron–ion electric field in the cascade growth is discussed.

Studying the Composition of Cluster Ions by Matrix- and Surface-Activated Laser Desorption/Ionization in Samples Obtained from Solutions of Sodium Stannate and Tin(II) Chloride

The purpose of this work was to study the composition of cluster ions in samples containing sodium stannate and tin(II) chloride. It has been shown that the composition of mass spectra is influenced by such parameters as the laser radiation energy and the substance content in the sample being studied. Conditions for preparing samples and recording mass spectra using these parameters were optimized. Presumptive identification of peaks in the recorded mass spectra was carried out. It has been shown that many of the ion peaks observed in the mass spectra may correspond to clusters containing tin. In the mass spectra of sodium stannate, ions of the general composition SnxOyNazHm were detected, in which the number of tin atoms reaches eight, and the maximum ion mass-to-charge ratio (m/z) is 1100. In the mass spectra of tin(II) chloride, there are ions of the general composition SnxOyHmClp and SnxCly, where the number of tin atoms reaches 4, and the highest m/z value is 1000.

An acid-engineered sericin nanoplatform enhances photothermal conversion and chemotherapy outcome for inducing immunogenic cell death

Inducing immunogenic cell death (ICD) by external-stimuli therapy holds great promise for cancer immunotherapy, however, hindered by widely-used photodynamic therapy (PDT) and sonodynamic therapy (SDT) due to oxygen depletion that compromises their therapeutic effect. Herein, we report a natural sericin nanoparticle (denoted as SDINPs) as ICD-inducer based on photothermal therapy (PTT) to alleviate immunosuppressive tumor microenvironment. The sericin-based ICD-inducer comprises chemically conjugated pH-responsive chemotherapeutic drugs, doxorubicin (DOX), and a physically loaded photosensitizers, indocyanine green (ICG), the therapeutic ability of which can be specifically activated by non-invasive laser radiation. Compared to free molecules, nanostructured SDINPs exhibit superior photothermal conversion efficiency, prolonged blood circulation time, and enhanced tumor accumulation, retention, and penetration capabilities. As a result of these advantages, they demonstrate potent therapeutic efficacy and PTT-mediated ICD burst induction for antitumor immunity. This study presents a pH/photo-activatable combination strategy that provides a novel perspective for clinical cancer treatment.

Моделирование процесса селективного лазерного плавления в аддитивном производстве

The possibilities of theoretical analysis based on numerical modeling of complex processes of additive manufacturing by selective laser melting method are viewed. Methods of high-precision modeling of the formation of a single melt bath are discussed, taking into account the geometry of the formed powder layer, the energy distribution in the spot, the effects of ray re-reflection, the vapor recoil force, the Marangoni effect and denudation mechanisms. Experimental studies on the cultivation of samples from BrX copper powder with particles of 20...50 microns in size by selective laser melting using continuous fiber laser radiation with a wavelength of 1.064 microns were carried out. In particular, all the experiments were carried out under conditions when growing conditions and modes are completely coincident with the calculated model. To assess the accuracy of the modeling system, the dimensions of the melting region and the morphology of the surface of the melt were compared. The presented computational model was used in the development of technology for growing products from copper alloy powders using selective laser melting method. Research in the field of modeling the stress-strain state in a composite material formed in the SLP process, consisting of an Ak9ch alloy matrix reinforced with titanium carbide particles, is also presented. Calculations were performed to identify the influence of shape (sphere, icosahedron, prism), size (1,0 microns; 5,0 microns; 10 microns) and mass concentration &#x0D; (1,0 %; 3,0 %; 5,0 %; 7,0 %; 10 %; 15 %), taking into account the presence of pores of various shapes. The results of calculations are compared with the results of experiments. Numerical models with subsequent experimental approbation of the optimal variant make it possible to significantly reduce the time spent for the development of new complex and promising additive technologies.

Analyzing Thermal Processes in Laser Welding of Multi- Component Heat-Resistant Alloy Thin-Walled Butt Joints: A Comprehensive Modeling Approach

Niobium-based alloys are vital in high-temperature environments due to their unique chemical composition, phase structure, high density, and oxidation resistance. These alloys find extensive applications in industries such as medicine, engine manufacturing, and space technology. This study delves into the complexities of modeling laser welding processes, necessitated by the multitude of dynamic parameters specific to each surface configuration. Finite element modeling was conducted using COMSOL Multiphysics to analyze the heat transfer in butt joints between Nb-15W-5Mo-1Zr alloy plates under 400 W laser radiation power. The research employed finite element modeling to analyze heat transfer in Nb-15W-5Mo-1Zr alloy plates, considering non-uniform movement at the start and end of the welding process, Gaussian heat flux distribution along the laser spot radius, and temperature-dependent reflection coefficient. The models accounted for non-uniform movement, Gaussian heat flux distribution, and temperature-dependent reflection coefficient. The study demonstrated that thin plates of Nb-15W-5Mo-1Zr alloy can be effectively welded using specific laser processing modes, leveraging their high initial cooling rate of 1.2-1.3 s. Successful welding of Nb-15W-5Mo-1Zr alloy plates requires careful consideration of laser processing parameters. While the alloy's thermodynamic properties allow for effective welding, ensuring weld quality mandates additional production processes aimed at preventing potential part failure.

Efficacy of photodynamic therapy in an experimental mice tuberculosis model

The objective: to study the efficacy of antimicrobial photodynamic therapy (APDT) using hydroxyaluminum phthalocyanine (Photosens) as a photosensitizer in the experimental model of tuberculosis infection in mice.Subjects and Methods. Balb/cmice were infected with the multiple drug resistant (MDR) strain of M. tuberculosis Beijing BO/W148. APDT with hydroxyaluminum phthalocyanine and red laser light exposure were started on Day 45. A total of 4 sessions of APDT on the projection of both lungs, liver and spleen were performed. On Day 60, the therapeutic eff ect of APDTwas assessed by evaluation of severity of mycobacterial load and specific granulomatous infiltration in the lungs, liver and spleen. The absorption of light energy of laser radiation by the chest and abdominal walls, as well as tissues of lungs, liver and spleen was determined by photometry using afluovisor.Results. The tissues of the experimental animal retain a significant amount of light energy, however, the residual value of light transmission is sufficient to provide a pronounced therapeutic effect which manifests itself as a significant decrease of mycobacterial load and specific inflammatory process in all the studied internal organs.Conclusion. APDT may be an effective tool to treat some forms of tuberculous infection including those caused by M. tuberculosis with MDR.

Enhanced Mechanical, Thermal, Surface, Self-Defocusing, Electro-Optic and Photoelastic Characteristics of Doped Potassium Dihydrogen Phosphate Solitary Crystals for Optoelectronic Applications

Potassium dihydrogen phosphate (KDP) is an effective NLO substance. Much research has been concentrated on KDP crystals to increase the effectiveness of KDP's nonlinear optical property. The effectiveness of laser radiation conversion can be increased by altering its expansion. The excellent molecular chirality of organic acids is employed to improve the properties of KDP. Our main objective in this study was to describe the studies on the mechanical, thermal, surface, antibacterial, self-defocusing, and electro-optic properties of doped potassium dihydrogen phosphate solitary crystals for optical, electronic, and biological applications. The effect of itaconic acid (ITA) at concentrations ranging from 1, 3, and 5 mol% on the thermal, SEM, microhardness behaviors, NLO, antibacterial properties, and half-wave voltage of KDP (potassium dihydrogen phosphate) single crystals grown by the slow cooling technique. The existence of dopants was proved with energy-dispersive spectrometry. The mechanical properties of various temperatures for undoped and doped-KDP crystals with rising dopant combinations have been prepared, and the hardness was expanded due to doping. In contrast to several potentially dangerous microorganisms like Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, the produced crystals were exposed to antibiotic activity. The superiority of the fully-fledged crystal is determined by the etching studies. Using the Z-scan method, the good third-order nonlinear response for different planes (2 0 0), (2 1 1), and (1 1 2) of the ITA-doped KDP crystal sample was determined. Half-wave voltage may be discovered in the crystal produced via electro-optic examination. The Z-scan analysis of pure and ITA-doped KDP crystals for different planes reveals good self-defocussing and NLO responses. The electro-optic experiment generated a significant and consistent half-wave voltage. The photoelastic behavior of KDP crystals with ITA as a variable birefringent compensator has been investigated.