Pulsed Irradiation Research Articles

First in vitro cell co-culture experiments using laser-induced high-energy electron FLASH irradiation for the development of anti-cancer therapeutic strategies

Radiation delivery at ultrahigh dose rates (UHDRs) has potential for use as a new anticancer therapeutic strategy. The FLASH effect induced by UHDR irradiation has been shown to maintain antitumour efficacy with a reduction in normal tissue toxicity; however, the FLASH effect has been difficult to demonstrate in vitro. The objective to demonstrate the FLASH effect in vitro is challenging, aiming to reveal a differential response between cancer and normal cells to further identify cell molecular mechanisms. New high-intensity petawatt laser-driven accelerators can deliver very high-energy electrons (VHEEs) at dose rates as high as 1013 Gy/s in very short pulses (10–13 s). Here, we present the first in vitro experiments carried out on cancer cells and normal non-transformed cells concurrently exposed to laser-plasma accelerated (LPA) electrons. Specifically, melanoma cancer cells and normal melanocyte co-cultures grown on chamber slides were simultaneously irradiated with LPA electrons. A non-uniform dose distribution on the cell cultures was revealed by Gafchromic films placed behind the chamber slide supporting the cells. In parallel experiments, cell co-cultures were exposed to pulsed X-ray irradiation, which served as positive controls for radiation-induced nuclear DNA double-strand breaks. By measuring the impact on discrete areas of the cell monolayers, the greatest proportion of the damaged DNA-containing nuclei was attained by the LPA electrons at a cumulative dose one order of magnitude lower than the dose obtained by pulsed X-ray irradiation. Interestingly, in certain discrete areas, we observed that LPA electron exposure had a different effect on the DNA damage in healthy normal human epidermal melanocyte (NHEM) cells than in A375 melanoma cells; here, the normal cells were less affected by the LPA exposure than cancer cells. This result is the first in vitro demonstration of a differential response of tumour and normal cells exposed to FLASH irradiation and may contribute to the development of new cell culture strategies to explore fundamental understanding of FLASH-induced cell effect.

Raman Spectroscopy Reveals Photobiomodulation-Induced α-Helix to β-Sheet Transition in Tubulins: Potential Implications for Alzheimer's and Other Neurodegenerative Diseases.

In small clinical studies, the application of transcranial photobiomodulation (PBM), which typically delivers low-intensity near-infrared (NIR) to treat the brain, has led to some remarkable results in the treatment of dementia and several neurodegenerative diseases. However, despite the extensive literature detailing the mechanisms of action underlying PBM outcomes, the specific mechanisms affecting neurodegenerative diseases are not entirely clear. While large clinical trials are warranted to validate these findings, evidence of the mechanisms can explain and thus provide credible support for PBM as a potential treatment for these diseases. Tubulin and its polymerized state of microtubules have been known to play important roles in the pathology of Alzheimer's and other neurodegenerative diseases. Thus, we investigated the effects of PBM on these cellular structures in the quest for insights into the underlying therapeutic mechanisms. In this study, we employed a Raman spectroscopic analysis of the amide I band of polymerized samples of tubulin exposed to pulsed low-intensity NIR radiation (810 nm, 10 Hz, 22.5 J/cm2 dose). Peaks in the Raman fingerprint region (300-1900 cm-1)-in particular, in the amide I band (1600-1700 cm-1)-were used to quantify the percentage of protein secondary structures. Under this band, hidden signals of C=O stretching, belonging to different structures, are superimposed, producing a complex signal as a result. An accurate decomposition of the amide I band is therefore required for the reliable analysis of the conformation of proteins, which we achieved through a straightforward method employing a Voigt profile. This approach was validated through secondary structure analyses of unexposed control samples, for which comparisons with other values available in the literature could be conducted. Subsequently, using this validated method, we present novel findings of statistically significant alterations in the secondary structures of polymerized NIR-exposed tubulin, characterized by a notable decrease in α-helix content and a concurrent increase in β-sheets compared to the control samples. This PBM-induced α-helix to β-sheet transition connects to reduced microtubule stability and the introduction of dynamism to allow for the remodeling and, consequently, refreshing of microtubule structures. This newly discovered mechanism could have implications for reducing the risks associated with brain aging, including neurodegenerative diseases like Alzheimer's disease, through the introduction of an intervention following this transition.

OUR EXPERIENCE IN SURGICAL TREATMENT OF MUCOSAL HYPERTROPHY OF TORI TUBARII

Puprose. Evaluation of the effectiveness of surgical treatment of mucous hypertrophy of tori tubarii by submucosal tissue destruction using Ho:YAG laser radiation. Materials and methods. The study involved 48 adult patients with symptoms of Eustachian tube dysfunction. The patency of the auditory tube was assessed by standard tests, the ETDQ 7 questionnaire, tympanometry, pure tone threshold audiometry, and endoscopic video recording of the results were performed. Surgical intervention was carried out by forming under the influence of pulsed radiation from a Ho:YAG laser with a frequency of 10 Hz and a pulse energy of 2 J, 4–6 tunnels with a depth of 5–7 mm in the hypertrophied mucous membrane of the torui tubarii along the posteromedial surface and 2 tunnels up to 3 mm up and down from the pharyngeal mouth of the auditory tube. The control periods after surgery were 1, 3 and 6 months. Results. A significant improvement in the results of the auditory tube according to ETDQ-7 was noted by 3 months after surgery in 71% of patients and in 84% by 6 months. By 6 months after surgery, type C tympanometry and clinically significant conductive hearing loss persisted in 8 and 5% of patients, respectively. The subjective feeling of fully performing the Valsalva test improved in 58% after 3 months and in 82% by the 6th month, and the Toynbee test in 42% and 64% in the 3rd and 6th months, respectively. In 16% of patients, despite a visual decrease in mucosal hypertrophy during endoscopic examination, signs of dysfunction remained according to ETDQ 7. There were no complications after surgical treatment during 6 months of observation. Conclusion. The use of endoscopic diagnosis of the nasopharynx in patients with signs of dysfunction of the auditory tubes in combination with functional tests and the ETDQ-7 questionnaire allows to determine the indications for the surgical treatment of hypertrophy of the mucous membrane of the tori tubarii using the Ho:YAG laser, the effectiveness of which in our study was 84%.

Nongenetic Precise Neuromodulation and Spatiotemporal Neuroprotection for Epilepsy Therapy via Rationally Designed Multifunctional Nanotransducer.

The precise modulation of electrical activity in specific neuronal populations is paramount for rectifying abnormal neurological functions and is a critical element in the therapeutic arsenal for neurological disorders. However, achieving a balance between minimal invasiveness and robust neuroprotection poses a considerable challenge. Herein, we present a nanoneuromodulation strategy integrating neuroprotective features to effectively address epilepsy with minimal invasiveness and enable wireless functionality. Strategically engineered nanotransducer, adorned with platinum (Pt) decoration with titanium disulfide (TiS2) (TiS2/Pt), enables precise modulation of neuronal electrical activity in vitro and in vivo, ensuring exceptional temporal fidelity under millisecond-precision near-infrared (NIR) light pulses irradiation. Concurrently, TiS2/Pt showcase a pronounced enhancement in enzyme-mimicking activity, offering a robust defense against oxidative neurological injury in vitro. Nanotransducer-enabled wireless neuromodulation with biocatalytic neuroprotective capacity is highly effective in alleviating epileptic high-frequency neural activity and diminishing oxidative stress levels, thereby restoring redox equilibrium. This integrated therapeutic approach reduces the severity of epilepsy, demonstrating minimal invasiveness and obviating the requirements for genetic manipulation and optical fiber implantation, while providing an alternative avenue for neurological disorder treatment.

Оценка функционирования дозиметрического оборудования при проведении измерений в полях импульсного микросекундного фотонного излучения с известными характеристиками

This paper continues the series of articles [1,2,3] devoted to the determination of the main dosimetric characteristics of the fields of high-energy pulsed microsecond photon radiation generated by medical linear electron accelerator (LINAC for short) and assessment of the possibility of using LINAC as a source of reference radiation field for calibration of dosimetric equipment. This publication presents the results of evaluation of the portable dosimeter DKSAT1123 and detection unit BDKG-206 when measuring in such fields under different modes of LINAC operation. The possibility of this dosimetric equipment operation in the fields was assessed by comparing dosimeter readings with reference values of dosimetric characteristics of these fields, namely: average ambient dose equivalent rate H*(10), measured with the help of high-precision reference dosimeter DKS-AT5350. It was found that the deviation of H*(10) measurements conducted with the help of the DKS‑AT1123 and BDKG-206 from the reference values strongly depends on the radiation properties, namely the H*(10) value in the pulse. It is shown that at the H*(10) value in the pulse less than 0,2 mSv/s the deviation does not exceed 10%, at the H*(10) value in the pulse 0,2–0,4 mSv/s the deviation does not exceed 33%, and at the H*(10) value in the pulse more than 0,5 mSv/s the deviation can reach 72%.

Massive propagating modes of torsion

The dynamics of the torsion field is analyzed in the framework of the Covariant Canonical Gauge Theory of Gravity (CCGG), a De Donder–Weyl Hamiltonian formulation of gauge gravity. The action is quadratic in both, the torsion and the Riemann–Cartan tensor. Since the latter adds the derivative of torsion to the equations of motion, torsion is no longer identical to spin density, as in the Einstein–Cartan theory, but an additional propagating degree of freedom. As torsion turns out to be totally anti-symmetric, it can be parametrised via a single axial vector. It is shown in this paper that, in the weak torsion limit, the axial vector obeys a wave equation with an effective mass term which is partially dependent on the scalar curvature. The source of torsion is thereby given by the fermion axial current which is the net fermionic spin density of the system. Possible measurable effects and approaches to experimental analysis are addressed. For example, neutron star mergers could act as a dipoles or quadrupoles for torsional radiation, and an analysis of radiation of pulsars could lead to a detection of torsion wave background radiation.

Jaynes-Cummings interaction with a traveling light pulse

The Jaynes-Cummings model provides a simple and accurate description of the interaction between a two-level quantum emitter and a single mode of quantum radiation. Due to the multimode continuum of eigenmodes in free space and in waveguides, the Jaynes-Cummings model should not be expected to properly describe the interaction between an emitter and a traveling pulse of quantum radiation. In this article, we review a cascaded quantum system approach that accurately describes the interaction of a quantum system with an incident quantum pulse of radiation. When applied to the two-level system, different iterations of this approach lead to master equations with different Jaynes-Cummings-like Hamiltonians and damping terms.

Ultrafast opto-magnetic effects in the extreme ultraviolet spectral range

Coherent light-matter interactions mediated by opto-magnetic phenomena like the inverse Faraday effect (IFE) are expected to provide a non-thermal pathway for ultrafast manipulation of magnetism on timescales as short as the excitation pulse itself. As the IFE scales with the spin-orbit coupling strength of the involved electronic states, photo-exciting the strongly spin-orbit coupled core-level electrons in magnetic materials appears as an appealing method to transiently generate large opto-magnetic moments. Here, we investigate this scenario in a ferrimagnetic GdFeCo alloy by using intense and circularly polarized pulses of extreme ultraviolet radiation. Our results reveal ultrafast and strong helicity-dependent magnetic effects which are in line with the characteristic fingerprints of an IFE, corroborated by ab initio opto-magnetic IFE theory and atomistic spin dynamics simulations.

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.Graphical

Transient behaviour analysis in silicon carbide alpha particle detector using TCAD and SRIM simulation

Time response characteristics of α particle detector are crucial for monitoring radiation fields varied with time and its characterization of pulse radiation field. Here, SRIM-informed TCAD simulation is utilized to visually investigate the transient behaviors of carriers and alpha particles in 4H-SiC Schottky barrier detectors for the time response characteristics. We identified external bias voltage and incident particle energy as key factors to influence transient current pulse broadening. Low-energy alpha particles result in low initial kinetic energy of the ionization-generated carriers, leading to transient current broadening and reduced time resolution characteristics. Conversely, high-energy alpha particles ionize carrier with high drift velocity, preventing the broadening effect. Our simulation provides a planform and valuable guidance for optimizing alpha particle detector, selecting appropriate bias voltages, and enhancing time resolution capabilities.

Optical Switchers to Manipulate Intracellular Pathways and Boost Tissue Regeneration

AbstractThe possibility to remotely manipulate intracellular pathways in single cells is among the current goals of regenerative medicine, demanding new strategies to enhance tissue repair and reprogram stem cell activity. Plasmonic nanomaterials are addressing this need, due to improvements in the controlled synthesis allowing convenient regulation and precise thermal positioning. Leveraging on the thermal properties of gold nanoprisms (AuNPs) and on the unparalleled regenerating capabilities of the small invertebrate Hydra vulgaris, here the possibility to activate the molecular machinery underlying the animal regeneration by using AuNPs and applying regular pulses of near infrared irradiation (NIR) is shown. The efficiency of the head regeneration, reproductive capability, and stem cell proliferation rate are boosted by the AuNP photostimulation, indicating NIR triggered hyperthermia as new tool to enhance tissue regeneration. By transcriptional profiling of key developmental genes in animals exposed to external heat or irradiated an estimation of the heat developed in vivo by intracellular nanoheaters is obtained, revealing Hydra as a living thermometer to test performance of plasmonic materials. These results shed light on a novel function of heat emitting nanoparticles to control cell stemness through the activation of molecular pathways that can be targeted for regenerative medicine or wound healing strategies.

Effectiveness of laser pulsed irradiation for antimicrobial photodynamic therapy

The aim of this study was to compare two types of light irradiation devices for antimicrobial photodynamic therapy (aPDT). A 660-nm light-emitting diode (LED) and a 665-nm laser diode (LD) were used for light irradiation, and 0.1 mg/L TONS 504, a cationic chlorin derivative, was used as the photosensitizer. We evaluated the light attenuation along the vertical and horizontal directions, temperature rise following light irradiation, and aPDT efficacy against Staphylococcus aureus under different conditions: TONS 504 only, light irradiation only, and TONS 504 with either LED (30 J/cm2) or LD light irradiation (continuous: 30 J/cm2; pulsed: 20 J/cm2 at 2/3 duty cycle, 10 J/cm2 at 1/3 duty cycle). Both LED and LD light intensities were inversely proportional to the square of the vertical distance from the irradiated area. Along the horizontal distance from the nadir of the light source, the LED light intensity attenuated according to the cosine quadrature law, while the LD light intensity did not attenuate within the measurable range. Following light irradiation, the temperature rise increased as the TONS 504 concentration increased in the order of pulsed LD < continuous LD < LED irradiation. aPDT with light irradiation only or TONS 504 only had no antimicrobial effect, while aPDT with TONS 504 under continuous or pulsed LD light irradiation provided approximately 3 log reduction at 30 J/cm2 and 20 J/cm2 and approximately 2 log reduction at 10 J/cm2. TONS 504-aPDT under pulsed LD light irradiation provided anti-microbial effect without significant temperature rise.

Neck Aging and Rejuvenation: A Balanced Approach to Assessment and Treatment

ABSTRACTIntroductionThe neck is typically the earliest and most visible site of aging‐related esthetic changes; it is an area about which patients frequently express esthetic concerns and seek approaches to rejuvenation. This narrative review examines the current understanding of age‐related structural and cellular changes in the neck and skin, treatment approaches to neck rejuvenation, specifically noninvasive and minimally invasive approaches including skincare, and key patient factors to consider.MethodsA literature search of relevant publications was performed. Experience‐based recommendations for clinical assessment and treatment approach are provided to complement the current literature.ResultsNeck aging results from a combination of intrinsic factors, such as genetic background, and extrinsic factors, primarily ultraviolet light exposure. Positive treatment outcomes begin with thorough patient assessment, including neck aging status, patient‐specific intrinsic and extrinsic factors, and evaluation of skin type, which may help predict positive (e.g., skin tightening) and negative (e.g., dyspigmentation) dermal responses to specific procedures. In addition to skincare, a range of noninvasive, directed‐energy techniques (e.g., chromophore‐based lasers, ablative lasers, intense pulsed light, microfocused ultrasound, cryolipolysis, laser‐assisted lipolysis, and radiofrequency irradiation) and minimally invasive techniques (e.g., neurotoxins, microneedling, and fillers) are currently used for neck rejuvenation. A comprehensive approach to assessment and treatment contributes toward improved patient outcomes.ConclusionsThe neck aging process develops over time, and a prejuvenation strategy, including effective skincare, should be considered. The development of comprehensive noninvasive and minimally invasive techniques geared toward the neck and face as a single entity should provide better outcomes and fulfillment of patient esthetic goals for this critical area.

Formation of high-power microwave dissipative soliton combs based on reactive electron–wave interaction

We theoretically demonstrate the possibility of implementing high-power repetitively pulsed microwave radiation sources based on an analogy with the formation of optical dissipative soliton combs in microresonators with Kerr nonlinearity pumped by laser radiation. A similar mechanism can arise due to electron–wave interaction in a microwave-pumped high-Q resonator when, with near-zero synchronism, detuning, amplification, and absorption are negligible, and the driving electron beam primarily acts as a medium with reactive nonlinearity. The required physical parameters are estimated for observing Ka-band dissipative soliton combs based on an undulator mechanism of electron–wave interaction in a gyrotron-pumped resonator.

Full correction of the self-absorption of laser-induced plasma beryllium emissions via sample preparation

Self-absorption effect is always encountered in laser-induced breakdown spectroscopy (LIBS) and immediately distorts the calibration curves especially for the elemental determination of complex materials. With the aim to provide an expeditious approach for LIBS measurements susceptible to self-absorption effect, an exploratory study for sample preparation by powder mixing is implemented, and the self-absorption of laser-induced plasma beryllium emissions is investigated as a function of the dilution factor. For comparison, boric acid and wax powder are separately used as typical binding agent to mix with beryl powder to produce two sets of pressed pellets with sequential gradient of beryllium content variation. For the resonant lines most prone to self-absorption of Be II emission doublet at 313.042 nm and 313.107 nm, the beryllium spectral line shapes can be directly regulated and improved in the case of both sets of pellets as the dilution factor increases. In addition, the self-absorption effect for the strongly emitting beryllium spectral lines is further assessed by calculating the self-absorption coefficients based on the radiation transport equation. With regard to the both types of binder as diluent, when the dilution factor for beryl increases to 10 with a weight percent of 0.386% for beryllium in the pellet, the SA values may exponentially increase in general to around 0.8 and eventually asymptotically approaches to 1 without exception. Thus the self-absorption effect of laser-induced beryl plasma emissions can be readily overcome with sample preparation by powder mixing. By contrast with laser pulse irradiance in the present work, the dilution factor for powder mixing plays a dominant role in eliminating self-absorption effect. This research proposes a potentially effective approach to reduce self-absorption in laser-induced plasma emissions.

Advancement in embedding Pb quantum dots into a Porous-Si matrix for superior X-ray radiation detection: An extended gate approach

This study reports on the synthesis of porous silicon (PS) and porous silicon doped with lead (PS–Pb) using an electrochemical method with a primary focus on optimizing key synthesis parameters to enhance material properties. During the synthesis, hydrofluoric acid (HF) and ethanol ratios were maintained at 4:1, which was crucial in achieving the desired structural properties. A structural analysis of the synthesized nanocomposites was conducted using Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (FESEM-EDX). This structural analysis validated the successful incorporation of lead (Pb) into the samples. Among the key aspects of this study were the evaluation of the I–V characteristics of the PS-Pb nanocomposites. Based on the findings of I–V measurements, an increase in the bias voltage was observed, which was directly correlated with an increase in measured current, indicating significant changes in electrical properties as a result of Pb doping. Furthermore, the responses of these materials to X-ray pulse irradiation under various conditions were successfully measured and compared, enhancing the understanding of their potential as radiation detectors. The optimal electrochemical conditions for synthesizing PS and Pd-PS were identified as 90 V, 100 mA, 1 s, and 100 V, 100 mA, 0.5 s, respectively. As a result of optimizing electrochemical synthesis parameters, lead-doped porous silicon (Pb-PS) exhibited a marked reduction in pore size, decreasing from an average of 420.88 nm in undoped PS to 244.54 nm in Pb-PS. This structural refinement correlated with improved electrical properties; I–V measurements demonstrated that the current response at a bias voltage of 0.3 V improved from 1.6×10−5 A to 6.23×10−4 An under identical conditions. Furthermore, these materials responded to X-ray radiation and showed enhanced sensitivity, with Pb-PS detectors achieving a lower response time and higher current under X-ray exposure compared to undoped PS. These findings open up new avenues for employing these nanocomposites in advanced applications, particularly in fields that require precise and efficient radiation detection, such as medical imaging and environmental monitoring. This work represents a significant contribution to the field, illustrating the potential of these custom-engineered materials for the advancement of modern healthcare and detection technologies.

Subnanosecond Electromagnetic Pulse Generated by a Long Spark Discharge: Lightning Implication

AbstractThe effects of generating pulsed radiation by a long spark discharge are important for the development of lightning models and applications related to lightning protection. In experiments with a Marx generator simulating a lightning discharge, we detected the radiation in the form of a single ultrawideband electromagnetic pulse (UWB EMP) about 200 ps in duration, and rising time about 100 ps. UWB EMP generation occurs during the breakdown of a “rod–rod” 4 m long gap. Pulses of almost unipolar shape are observed in more than half of all positive discharges. EMP emission occurs before the main stage, and corresponds to the start of the upward leader from a grounded electrode. In negative discharges, pulses are also observed, but less frequently and with a smaller amplitude. The UWB EMPs, given their large amplitude (more than 100 V/m at a distance of 90 m from the discharge), can be considered as possible new lightning damage factors.

Pulse Radiation Characteristics Prediction Method of Vivaldi Antenna based on Dipole Array

This paper presents a theoretical method to estimate the pulse radiation characteristics of Vivaldi antennas. Based on the surface current distribution and the ultra-wideband radiation principle, Vivaldi antenna is equivalently modeled as a dipole array, and the pulse radiation characteristics of a single Vivaldi antenna are brought out utilizing the spatial superposition approach. Then, the influences and results of the Vivaldi antenna pulse characteristics prediction with different construction ways of the dipole array and element numbers are furthermore investigated. Next, a quadratic spatial superposition technique is employed to complete the theoretical prediction for time-domain radiation characteristics of Vivaldi antenna arrays. Experiments and simulations are conducted separately to verify the proposed method for both single Vivaldi antenna and array. The validated results demonstrate that the dipole array-based theoretical prediction method can effectively capture the pulse radiation characteristics for both individual Vivaldi antenna and array operating in different modes, thereby addressing challenges associated with estimating radiation characteristics in ultra-wideband pulse applications.

Demonstration of quantum dot reservoir computing based on spatio-temporal optical processing

A quantum dot network, which consists of coupled structures of randomly dispersed quantum dots, has been studied as a nano-scale optical reservoir for effective machine learning processing. In this study, we defined spatio-temporal fluorescence of a quantum dot network as the reservoir output, which is due to the characteristic dynamics of the excited energy in the network induced by laser pulse irradiation. In order to verify whether a quantum dot reservoir can improve the processing efficiency of advanced machine learning applications, we performed experimental reservoir computing using a numerical model. Several parameters that were required for the construction of the model were defined from the spatio-temporal fluorescence of an experimental quantum dot reservoir. Subsequently, the corresponding reservoir computing based on the model was numerically demonstrated. Reliable performances were successfully demonstrated as sufficient error rates toward the delayed XOR task. Additionally, the dependency on quantum dot compositions of these performances was clarified.

Mechanisms of deformation induced by high-current pulsed electron beam irradiation

AA2024 aluminum alloy was irradiated by a high-current pulsed electron beam with the following parameters: beam energy ∼0.3 MeV, current ∼2000A, pulse duration ∼5·10−6 s, beam diameter ∼3 cm. The thickness of the surface remelted layer reached 100 μm. Dynamic thermal stresses caused by irradiation, induced the development of deformation processes in the irradiated layer. Based on the study of surface morphology and structural state of the remelted layer, it was shown that deformation processes occur in the surface layer by the grain boundary sliding mechanism. The level of residual stresses in the irradiated layer was low and amounted to 34 MPa.