Multiple Irradiation Research Articles

Laser power modulation between disturbed and undisturbed material removal regime in laser chemical processing

AbstractLaser chemical machining (LCM) is a method for removing material by thermally induced chemical dissolution of self-passivating metals. However, the process window is limited by disrupted material removal due to gas bubble formation and metallic salts and oxides deposition at higher energy input. Since the temperature increases, and therefore gas bubble growth takes time, it is hypothesized that the temporal modulation of laser power can remove the metal homogeneously, i.e., without disrupted material removal, while achieving a higher removal rate. Based on this, the dynamic process behavior of material removal is investigated for the LCM of titanium in phosphoric acid, using a rectangular modulation of the laser power with varying irradiation durations. As a result, however, high-speed videos show that gas bubbles are consistently generated, regardless of the applied laser power and power modulation, although the quantity of bubbles varies with different parameters. Even with short power durations (10 ms), the material deposition occurs after multiple irradiations. When the duration is longer, the material deposition increases in height along the laser scan direction. For the studied process parameters, a Fourier analysis in the spatial domain further indicates the correlation between the material removal frequencies and the modulation frequencies. In conclusion, the laser power modulation cannot prevent the disturbed material removal at high laser powers. Nevertheless, the material deposition can be utilized to generate periodic surface structures with a depth below and above the initial surface.

Bio-thermal non-equilibrium dynamics and thermal damage in biological tissues induced by multiple time pulse-laser irradiations

BackgroundLaser therapy offers precise medical treatment by directing focused light beams to specific areas without harming surrounding tissue. This precision is particularly valuable in tissue treatment, including cancer therapy, where minimizing collateral damage is critical. The current study focuses on bio-thermal dynamics and thermal damage in biological tissues induced by multiple pulse-laser irradiations. ModelThe Local Thermal Non-Equilibrium (LTNE) bio-heat Transfer model with porosity and dual lag effects is developed to investigate the thermal behavior in tissues. The model contains partial differential equations that is solved through numerical method. ResultsObtained results show temperature variations and thermal damage in tissues, influenced by parameters such as laser intensity, incident duration, and tissue porosity. Higher intensity of laser and extended laser durations increase the temperature distribution and thermal damage. Porosity inversely affects temperature distribution, with large values of porosity leading to decreased distribution. NoveltyThis study introduces the application of multi-time lasers induced on tissue for the therapies, a novel approach that has not been previously explored in the literature.

Efficient extreme ultraviolet emission by multiple laser pulses

We demonstrated an efficient extreme ultraviolet (EUV) source at a wavelength of 13.5 nm using spatially separated multiple solid-state-laser pulse irradiation. The maximum conversion efficiency (CE) achieved was 3.8% for ±30° oblique laser pulse injection, which was about twice as high as that for single laser pulse irradiation of 1.7%, with an EUV source size of about 100 μm for two spatially separated laser pulses with a total laser energy of 500 mJ at a laser intensity of 2×1011 W/cm2. In addition, we achieved an EUV CE of 4.7% for ±60° oblique laser pulse injection, which was one of the highest values ever reported, in the case of a 1-μm solid-state laser-produced planar Sn target plasma by multiple laser pulse irradiation. This result suggests that multiple laser-pulse irradiation at high repetition rate operation could credibly provide the next technology for future high-power EUV sources and exposure tools toward future EUV technology nodes.

High-strength and impermeable sapphire/aluminum joints fabricated by ultrafast laser microwelding: Microstructures and joining mechanism

In this work, robust joints of sapphire and aluminum were successfully achieved by direct ultrafast laser transmission microwelding. Effects of laser parameters on the microstructures and mechanical properties were comprehensively studied. The welding process highly depended on the laser ablated metal nanoparticles within the heterojunction, as well as the thermal accumulation under multiple laser pulses irradiation. It showed that lack of fusion at the sapphire/aluminum interface can occur due to the incomplete melting of ablated nanoparticles at low laser fluence (<0.48 J/cm2). While serious cavities and cracks inside the brittle sapphire were formed with the intensified stress concentration after melting-solidification process at excessive laser fluence (>0.64 J/cm2). A nearly defect-free joint was obtained with max. shear strength of 128.1 ± 8.2 MPa at room temperature, when the laser fluence was 0.56 J/cm2. The high shear strength can be attributed to the tortuous interface with wide elemental transition layer. Meanwhile, the welded sapphire/aluminum joints exhibited high reliability under extreme service temperatures, which the shear strength can reach 159.8 ± 8.96 MPa at −50 °C and 80.6 ± 11.1 MPa at 200 °C. The sealing tests also showed the excellent impermeability of laser welded sapphire/aluminum structure, confirming the micro-crack free joint formation. This work demonstrates the feasibility of using ultrafast laser to achieve high-quality sapphire/aluminum joint, which is promising in heat-dissipation substrate manufacturing in power semiconductor devices.

Molecular Dynamics Analysis of Collison Cascade in Graphite: Insights from Multiple Irradiation Scenarios at Low Temperature

Molecular Dynamics Analysis of Collison Cascade in Graphite: Insights from Multiple Irradiation Scenarios at Low Temperature

Domain shape evolution under multiple IR laser irradiation in lithium niobate

In this work, we have studied the shape evolution of the isolated domains in domain array in congruent lithium niobate crystals under the action of pyroelectric fields arising during multiple irradiation by laser pulses. The loss of the circle shape with the pulse number was obtained in the arrays of isolated domains arising at the edges of the irradiated zone. The simulation of the domain growth under the action of the pyroelectric field allowed revealing two stages of domain shape evolution in the regular domain array. An important role of the neighboring domains was revealed.

Subpicosecond laser ablation behavior of a magnesium target and crater evolution: Molecular dynamics study and experimental validation

Abstract The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics (MD) simulations and experiments. The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms, which has laser-induced high stress. However, under high fluence and short pulse width laser irradiation, the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film. In addition, Mg[0001] has higher pressure sensitivity and is more prone to ablation than Mg [ 10 1 ¯ 0 ] . The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments. The results show that, under multiple pulsed laser irradiation, not only does the crater depth increase linearly with the pulse number, but also the quadratic term and constant term of the fitted crater profile curve increase linearly.

Erythrosine+KI with Multiple Sessions Green LED-mediated Photodynamic Therapy Potentiate Anticandidiasis Effect

SignificanceThe concurrent use of double photosensitizers with multiple irradiation sessions is emerging as a promising modality for photodynamic therapy. ApproachCandida albicans (ATCC10231) biofilm was treated with either erythrosine 220 μM, 100 mM KI, or 220 μM erythrosine+100 mM KI. Control groups were phosphate buffer saline, 1:100,000 U/ml nystatin solution, and Light-only respectively. After 60-secs incubation, experimental groups were irradiated with LED (520-540 nm, 250 mW/cm2, 20 J/cm2/session) for 1 or 3 sessions. The logarithmic transformation of biofilm count was calculated and a comparison at 1, 24 hrs was performed using median±interquartile range. The statistically significant difference was determined using Kruskal Wallis test with post hoc test at p<0.05 Results220 μM Erythrosine+100 mM KI with 60 J/cm2 (20 J/cm2x3 sessions) exerted the most anticandidal effect that comparable to nystatin effect. ConclusionsErythrosine 200 μM+KI 100 mM+3 sessions green LED (total energy 60 J/cm2) effectively reduced C. albicans biofilm.

Aryl Azocyclopropeniums: Minimalist, Visible-Light Photoswitches.

We report convenient syntheses of aryl azocyclopropeniums and a study of their photochemical properties. Incorporation of the smallest arene leads to pronounced redshift of the π-π* absorbance band, compared to azobenzenes. Photoisomerization under purple or green light irradiation affords Z- or E-isomers in ratios up to 94% Z or 90% E, and the switches proved stable over multiple irradiation cycles. Thermal half-lives of metastable Z-isomers range from minutes to hours in acetonitrile and water. These properties together with the concise, versatile syntheses render aryl azocyclopropeniums exciting additions to the tool kit of readily available molecular photoswitches for wide ranging applications.

Morphological study of depth-controlled high quality holes and lines fabricated on a metal substrate with a thin metal film by picosecond laser pulses

Laser micromachining is a convenient technique to structure and/or functionalize the surfaces of various materials. The use of ultrashort laser pulses has an obvious advantage to minimize the heat effect, which results in the formation of a hole without rims. Nevertheless, it is still difficult to fabricate a line without rims even with ultrashort laser pulses, because multiple irradiation of ultrashort laser pulses with a sufficient spatial overlap promotes the formation of rims and undesired structures. In this work we employ a metal substrate with a thin metal film, and demonstrate the fabrication of depth-controlled high quality lines, not to mention holes, through the selective removal of the film by picosecond laser pulses without forming rims and undesired structures. Morphological study of the target surface reveals that the fabricated structures have unprecedentedly flat bottoms with nearly vertical sidewalls to the surface.

Effects of Semiconductor Laser Irradiation on Differentiation of Human Dental Pulp Stem Cells in Co-Culture with Dentin.

This study aimed to determine the effect of photobiomodulation therapy induced by semiconductor laser irradiation on human dental pulp stem cell (hDPSC) proliferation and their differentiation into odontoblast-like cells (OLCs). The effects of various semiconductor laser irradiation conditions on hDPSCs were examined. Three groups were evaluated: a single laser irradiation at 6 h post-seeding, multiple laser irradiations up to four times every 4 days after the first dose, and a control with no laser irradiation. The cells were irradiated at 10, 30, and 150 mW using a semiconductor laser. The effect of laser irradiation on hDPSC differentiation into OLCs was also determined. Four groups were evaluated, including co-culture using basic medium and dentin discs, simple culture using OLC differentiation-inducing medium, co-culture using OLC differentiation-inducing medium and dentin discs, and control culture with basic medium. The expression of the nestin, ALP, DSPP, and DMP-1 genes was measured using real-time PCR. The multiple irradiation group irradiated at 30 mW exhibited significantly more cell proliferation than the control. The expression of nestin associated with differentiation into OLCs during each culture period tended to be lower, whereas DSPP and ALP expression was higher compared with that of the control. Multiple laser irradiations at a low power of 30 mW induced significant hDPSC proliferation and might induce differentiation into OLCs.

Enhanced photodynamic effect of a natural anthraquinone on Candida tropicalis biofilms using a stepwise irradiation strategy

BackgroundAntimicrobial Photodynamic Therapy (aPDT) has demonstrated effectiveness against various Candida biofilms, typical resistant to conventional treatments. Some strategies have shown to enhance the photoactivity of some photosensitizers (PS), such as the use of a multiple irradiation scheme or the combination with drugs that improve the penetration of the PS through the microbial membrane. PurposeHaving demonstrated the photodynamic antibiofilm activity of some natural anthraquinones (AQs), we selected rubiadin 1-methyl ether (R-1ME) that showed a low photo-reduction percentage (%R) on the biofilm mass, with the aim to improve its effect. Study DesignExperimental in vitro photo-stimulation protocols have been developed, which include successive light exposures and the combination of this AQ with a commonly used antifungal such as Amphotericin B (AmB). MethodsThe biofilms reduction was quantified by Crystal Violet staining. Reactive oxygen and nitrosative species were observed as action mechanism, alongside an assessment of antioxidant response through superoxide dismutase enzyme activation and total antioxidant system capacity. ResultsApplying R-1ME to C. tropicalis biofilms with sequential 15-min irradiation sessions at varied incubation intervals (0, 3, 6, 24, 27, and 30 h) yielded a substantial photo-reduction (62.9%R) on biofilm mass, even halving the bioactive concentration of R-1ME. Moreover, combining R-1ME with AmB under this irradiation pattern produced an even greater impact (82%R) at concentrations below the Minimal Inhibitory Concentration. Evident redox imbalances in the biofilm were linked to this photosensitized activity. ConclusionsA new strategy was found to improve the activity of a natural PS on fungal biofilms, by combining it with antifungal drugs, under a staged irradiation scheme, which, in turn, required low doses of the PS and the antifungal to achieve this improved photo-reduction.

Evaluation of in vitro irradiation setup: Designed for the horizontal beamline at the Danish Centre for Particle Therapy.

Radiobiological experimental setups are challenged by precise sample positioning along depth dose profile, scattering conditions, and practical difficulties that must be addressed in individual designs. The aim of this study was to produce cell survival curves with several irradiation modalities, by using a setup designed at the Danish Centre for Particle Therapy (DCPT) for in vitro proton irradiations using a horizontal beam line and thereby evaluating the setups use for in vitro irradiations experiments. The setup is a water phantom suitable for in vitro research with multiple irradiation modalities, in particular the pencil scanning proton beam available from a horizontal experimental beamline. The phantom included a water tank of 39.0 × 17.0 × 20.5 cm. Cell survival-curves were produced using the cell line V79 Chinese hamster lung fibroblast cells (V79s) in biological triplicates of clonogenic assays. Cell survival curves were produced with both a 18 MeV electron beam, 6 MV photon beam, and a Spread-Out Bragg Peak (SOBP) proton beam formed by pristine energies of 85-111 MeV where three positions were examined. Survival curves with uncertainty areas were made for all modalities. Dosimetric uncertainty amounted to, respectively, 4%, 3% and 3% for proton, electron, and high energy photon irradiations. Cell survival fraction uncertainty was depicted as the standard deviation between replications of the experiment. Cell survival curves could be produced with acceptable uncertainties using this novel water phantom and cellular laboratory workflow. The setup is useful for future in vitro irradiation experiments.

Co-Packaged PARP inhibitor and photosensitizer for targeted photo-chemotherapy of 3D ovarian cancer spheroids

BackgroundWithin the last decade, poly(ADP-ribose) polymerase inhibitors (PARPi) have emerged in the clinic as an effective treatment for numerous malignancies. Preclinical data have demonstrated powerful combination effects of PARPi paired with photodynamic therapy (PDT), which involves light-activation of specialized dyes (photosensitizers) to stimulate cancer cell death through reactive oxygen species generation.ResultsIn this report, the most potent clinical PARP inhibitor, talazoparib, is loaded into the core of a polymeric nanoparticle (NP-Tal), which is interfaced with antibody-photosensitizer conjugates (photoimmunoconjugates, PICs) to form PIC-NP-Tal. In parallel, a new 3D fluorescent coculture model is developed using the parental OVCAR-8-DsRed2 and the chemo-resistant subline, NCI/ADR-RES-EGFP. This model enables quantification of trends in the evolutionary dynamics of acquired chemoresistance in response to various treatment regimes. Results reveal that at a low dosage (0.01 μM), NP-Tal kills the parental cells while sparing the chemo-resistant subline, thereby driving chemoresistance. Next, PIC-NP-Tal and relevant controls are evaluated in the 3D coculture model at multiple irradiation doses to characterize effects on total spheroid ablation and relative changes in parental and subline cell population dynamics. Total spheroid ablation data shows potent combination effects when PIC and NP-Tal are co-administered, but decreased efficacy with the conjugated formulation (PIC-NP-Tal). Analysis of cell population dynamics reveals that PIC, BPD + NP-Tal, PIC + NP-Tal, and PIC-NP-Tal demonstrate selection pressures towards chemoresistance.ConclusionsThis study provides key insights into manufacturing parameters for PARPi-loaded nanoparticles, as well as the potential role of PDT-based combination therapies in the context of acquired drug resistance.

A novel simple GMPPT method based on probability distribution of global maximum power point under partial shading conditions

A photovoltaic (PV) array having multiple cells in series with bypass diodes may exhibit multiple power peaks under uneven irradiation, therefore an algorithm is required to reach the global maximum power point (GMPP). While a lot of methods have been proposed in the literature, they are usually quite complex and does not fully utilize the characteristics of the PV array. This paper first highlights a rapid and optimized mathematical simulation of the PV array using MATLAB to find the probability distribution of voltage at GMPP under multiple irradiation conditions and temperatures. The resulting GMPP distribution in 22E6 irradiation and temperature conditions checked for an array of 4 PV modules in series with bypass diodes is presented, as well as the optimizations in MATLAB necessary to keep simulation time in check. From the obtained result, we propose a simple and efficient probability-based algorithm capable of reaching GMPP up to 93.64% of the time.

Влияние ионизирующего излучения на активность антиоксидантных ферментов штамма Escherichia coli «ПЛ-6» при многократном облучении

The article presents the analysis of enzymatic activity of Escherichia coli “PL-6” cells following multiple gamma irradiation with increasing doses. For irradiation the stationary gamma ray unit “Researcher” (Co-60) with the dose rate of 36.7 Gy/min was used. Radiation doses to the bacterial cells increased from 3.5 to 10 kGy in 0.5 kGy increment, and from 10 to 30 kGy in 5 kGy increment. Unirradiated suspended bacterial cells were used as control. The irradiated cells enzymatic activity was estimated with the spectrophotometric method on the "MultiSkan Go" device (Thermo Fisher Scientific, Finland). The results of the study demonstrate the increase in the E. coli ”PL-6” cells radioresistance caused by gamma irradiation of the cells with gradually increased doses. Exposure of the bacteria to a higher gamma radiation dose caused decrease in the number of viable cells from 10Е+9 CFU/ml in the control culture sample to 10Е+2 CFU/ml after irradiation at a dose of 30 kGy. The most radiation-resistant cells were selected from cells undergone successive multiple irradiation with constantly increasing dose of ionizing radiation. The enzymes of the antioxidant system in irradiated cells exhibit increased specific activity as compared to the enzymes in control, unirradiated, cells. The activity of enzymes increases with an increase in the radiation dose. Catalase activity increased after multiple irradiation by 5 times and peroxidase activity increased by 4 times. To compare the results in the groups, the Student's t-test was applied at p&lt;0.05.

Sole brachytherapy for inoperable, recurrent, and irradiated salivary gland cancer

Background and purposeSalivary gland cancers (SGCs) are hard to treat when inoperable, and sole brachytherapy appears to be a promising therapeutic strategy. This study aimed to evaluate the effectiveness, safety, and capability of pain palliation using sole brachytherapy for inoperable, recurrent, and irradiated SGCs. Materials and methodsPatients with inoperable SGCs treated using sole brachytherapy at Peking University School and Hospital of Stomatology were retrospectively included. Patients were divided into primary and recurrent groups and irradiated and non-irradiated groups. Local control (LC), overall survival (OS), radiation-relevant toxicities, and Visual Analogue Scale (VAS) score for pain, were recorded and evaluated. ResultsA total of 176 patients from 2006 to 2020 were included. The 5-year LC rate was 48.6 %; for the primary, recurrent, non-irradiated and irradiated groups, the rates were 72.6 %, 39.5 %, 56.8 %, and 34.5 %, respectively. The 5-year OS rates was 52.6 %; for the primary, recurrent, non-irradiated, and irradiated groups, the rates were 62.9 %, 48.6 %, 58.9 %, and 42.3 %, respectively. The mean ± standard deviation of posttreatment VAS score of pain was 2.154 ± 2.989, which was significantly decreased from the score of 6.923 ± 2.280 prior to brachytherapy. Skin hyperpigmentation, mucositis, and dysphagia were the most frequently reported adverse events. ConclusionsBrachytherapy as a sole modality, was retrospectively proven effective and safe in the management of inoperable SGCs and was beneficial in multiple irradiation and pain control.

Animal Welfare in Radiation Research: The Importance of Animal Monitoring System.

Long-term research into radiation exposure significantly expanded following World War II, driven by the increasing number of individuals falling ill after the detonation of two atomic bombs in Japan. Consequently, researchers intensified their efforts to investigate radiation's effects using animal models and to study disease models that emerged post-catastrophe. As a result, several parameters have been established as essential in these models, encompassing radiation doses, regimens involving single or multiple irradiations, the injection site for transplantation, and the quantity of cells to be injected. Nonetheless, researchers have observed numerous side effects in irradiated animals, prompting the development of scoring systems to monitor these animals' well-being. The aim of this review is to delve into the historical context of using animals in radiation research and explore the ethical considerations related to animal welfare, which has become an increasingly relevant topic in recent years. These concerns have prompted research groups to adopt measures aimed at reducing animal suffering. Consequently, for animal welfare, the implementation of a scoring system for clinical and behavioral monitoring is essential. This represents one of the primary challenges and hurdles in radiation studies. It is concluded that implementing standardized criteria across all institutions is aimed at ensuring result reproducibility and fostering collaboration within the scientific community.

Impact of Dose Perturbations Around Brachytherapy Seeds in External-Beam Radiotherapy Planning: A Fundamental and Clinical Validation Using Treatment Planning System-Based Monte Carlo Simulations.

Background This study evaluates dose perturbations caused by nonradioactive seeds in clinical cases by employing treatment planning system-based Monte Carlo (TPS-MC) simulation. Methodology We investigated dose perturbation using a water-equivalent phantom and 20 clinical cases of prostate cancer (10 cases with seeds and 10 cases without seeds) treated at Fujita Health University Hospital, Japan. First, dose calculations for a simple geometry were performed using the RayStation MC algorithm for a water-equivalent phantom with and without a seed. TPS-independent Monte Carlo (full-MC) simulations and film measurements were conducted to verify the accuracy of TPS-MC simulation. Subsequently, dose calculations using TPS-MC were performed on CT images of clinical cases of prostate cancer with and without seeds, and the dose distributions were compared. Results In clinical cases, dose calculations using MC simulations revealed hotspots around the seeds. However, the size of the hotspot was not correlated with the number of seeds. The maximum difference in dose perturbation between TPS-MC simulations and film measurements was 3.9%, whereas that between TPS-MC simulations and full-MC simulations was 3.7%. The dose error of TPS-MC was negligible for multiple beams or rotational irradiation. Conclusions Hotspots were observed in dose calculations using TPS-MC performed on CT images of clinical cases with seeds. The dose calculation accuracy around the seeds using TPS-MC simulations was comparable to that of film measurements and full-MC simulations, with differences within 3.9%. Although the clinical impact of hotspots occurring around the seeds is minimal, utilizing MC simulations on TPSs can be beneficial to verify their presence.

Antitumor Immunity Mediated by Photodynamic Therapy Using Injectable Chitosan Hydrogels for Intratumoral and Sustained Drug Delivery.

Photodynamic therapy (PDT) is an anticancer therapy with proven efficacy; however, its application is often limited by prolonged skin photosensitivity and solubility issues associated with the phototherapeutic agents. Injectable hydrogels which can effectively provide intratumoral delivery of photosensitizers with sustained release are attracting increased interest for photodynamic cancer therapies. However, most of the hydrogels for PDT applications are based on systems with high complexity, and often, preclinical validation is not provided. Herein, we provide a simple and reliable pH-sensitive hydrogel formulation that presents appropriate rheological properties for intratumoral injection. For this, Temoporfin (m-THPC), which is one of the most potent clinical photosensitizers, was chemically modified to introduce functional groups that act as cross-linkers in the formation of chitosan-based hydrogels. The introduction of -COOH groups resulted in a water-soluble derivative, named PS2, that was the most promising candidate. Although PS2 was not internalized by the target cells, its extracellular activation caused effective damage to the cancer cells, which was likely mediated by lipid peroxidation. The injection of the hydrogel containing PS2 in the tumors was monitored by high-frequency ultrasounds and in vivo fluorescence imaging which confirmed the sustained release of PS2 for at least 72 h. Following local administration, light exposure was conducted one (single irradiation protocol) or three (multiple irradiation protocols) times. The latter delivered the best therapeutic outcomes, which included complete tumor regression and systemic anticancer immune responses. Immunological memory was induced as ∼75% of the mice cured with our strategy rejected a second rechallenge with live cancer cells. Additionally, the failure of PDT to treat immunocompromised mice bearing tumors reinforces the relevance of the host immune system. Finally, our strategy promotes anticancer immune responses that lead to the abscopal protection against distant metastases.