Search Results (38)

For exploration of space, in particular in attempts to find new extra-terrestrial resources, human society has encountered the problem of space pollution with human-made debris, which represents high risks for space missions. This prompted extensive activities for cleaning the space using various techniques, which are briefly overviewed here. But the main focus of this paper is on using lasers for space debris removal. The attention is drawn to laser beam shaping techniques, which are discussed as potential technologies for deorbiting space debris, providing more energetically favorable laser propulsion compared to conventional laser beams. Full article

Ultrahigh dose rate (UHDR) radiotherapy, also known as FLASH radiotherapy (FLASH-RT), has shown potential for increasing tumor control while sparing normal tissue. In parallel, gold nanoparticles (GNPs) have been extensively explored as radiosensitizers due to their high atomic number and ability to enhance the generation of reactive oxygen species (ROS) through water radiolysis. In this study, we investigate the synergistic effects of UHDR electron beams and GNP-mediated radiosensitization using Monte Carlo (MC) simulations based on the Geant4-DNA code. A spherical water phantom with embedded GNPs of varying sizes (5–100 nm) was irradiated using pulsed electron beams (100 keV and 1 MeV) at dose rates of 60, 100, and 150 Gy/s. The chemical yield of ROS near the GNPs was quantified and compared to an equivalent water nanoparticle model, and the yield enhancement factor (YEF) was used to evaluate radiosensitization. Results demonstrated that YEF increased with smaller GNP sizes and at lower UHDR, particularly for 1 MeV electrons. A maximum YEF of 1.25 was observed at 30 nm from the GNP surface for 5 nm particles at 60 Gy/s. The elevated ROS concentration near GNPs under FLASH conditions is expected to intensify DNA damage, especially double-strand breaks, due to increased hydroxyl radical interactions within nanometric distances of critical biomolecular targets. These findings highlight the significance of nanoparticle size and beam parameters in optimizing ROS production for FLASH-RT. The results provide a computational basis for future experimental investigations into the combined use of GNPs and UHDR beams in nanoparticle-enhanced radiotherapy. Full article

Platinum-based radiochemotherapy is associated with hematologic side effects, impacting patient outcomes. However, the clinical mechanisms of cisplatin and its interaction with ionizing radiation (IR), including in biodosimetry for radiotherapy, have not yet been fully clarified. For this purpose, healthy donors’ peripheral blood lymphocytes (PBLs) were pretreated with cisplatin in a pulse (1–4 h) or continuous (24 h) regimen followed by X-rays. DNA damage was assessed as DNA double-strand breaks using repair foci of γH2AX and 53BP1 after 0.5 h and 24 h in G1 PBLs and a proliferation-based cytokinesis-block micronucleus assay. Additionally, cell death and proliferation activity were measured. Unlike a 1 h pulse, a 24 h cisplatin pretreatment caused a concentration-dependent increase in cisplatin-induced foci while decreasing IR-induced foci, especially 24 h after irradiation. This was accompanied by increased apoptosis, with cisplatin and IR having additive effects. Both genotoxins alone caused a dose-dependent increase in micronuclei, while cisplatin significantly reduced binuclear cells, especially after the 24 h treatment, leading to lower micronuclei frequencies post-irradiation. Our results show that prolonged cisplatin exposure, even at low concentrations, impacts the vitality and division activity of PBLs, with significantly stronger effects post-irradiation. This has major implications and must be considered for the detection of DNA damage-associated biomarkers in PBLs used in clinical prediction or biodosimetry during radiotherapy. Full article

Quantum technologies are currently being explored for various applications, including computing, secure communication, and sensor technology. A critical aspect of achieving high-fidelity spin manipulations in quantum devices is the controlled optical initialization of electron spins. This paper introduces a low-cost programming scheme based on a 32-bit STM32F373 microcontroller, aimed at facilitating high-precision measurements of optically active solid-state spin centers within semiconductor crystals (SiC, hBN, and diamond) utilizing a multi-pulse sequence. The effective shaping of short optical pulses across semiconductor and solid-state lasers, covering the visible to near-infrared range (405–1064 nm), has been validated through photoinduced electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopies. The application of pulsed laser irradiation influences the EPR relaxation parameters associated with spin centers, which are crucial for advancements in quantum computing. The presented experimental approach facilitates the investigation of weak electron–nuclear interactions in crystals, a key factor in the development of quantum memory utilizing nuclear qubits. Full article

Pulsed laser ablation in liquids is one of the most versatile and widespread techniques for the easy synthesis of different types of nanoparticles with controllable properties. A huge amount of energy compressed into one pulse that is directed onto a solid target leads to the ejection of materials into surrounding liquid. However, the precision of the focus of laser irradiation can play a crucial role in the synthesis of nanomaterials and, hence, significantly affect their physico-chemical properties. In this paper, we investigated the influence of the focus position of the laser spot on the optical properties of single- and double-element composite silicon/gold nanoparticles, as well as on their structure and chemical composition. Deepening of the focus to 0.5 mm inside the bulk material led to better chemical stability of the colloidal solutions and increased the particle and mass concentrations of the generated nanoparticles. This larger amount of materials led to a stronger absorbance, and resulted in slightly better photoluminescence excitation efficiencies for all nanostructures. Silicon-based nanoparticles had a remarkable photoluminescence peak at ~430 nm upon xenon lamp excitation, which was the most pronounced for pure silicon nanoparticles synthesized at the F+0.5 focus position. This position also led to the best laser-induced heating (~0.85 °C/min) of the colloidal solutions. All nanocomposites revealed amorphous silicon structures with some Si(111) and Au(111), suggesting the formation of gold silicide with different stoichiometries. The observed findings can help in choosing appropriate experimental conditions to achieve the best performance of laser-synthesized colloidal solutions of composite silicon/gold nanostructures. Full article

This paper presents the results of an experimental study of the dynamic characteristics of the process of laser fragmentation/laser-induced fluorescence (LF/LIF) of trinitrotoluene traces on a paper surface under synchronized double-pulse laser irradiation. An Nd:YAG-laser (266 nm) was used for the fragmentation of TNT molecules, while fluorescence excitation of their NO fragments was performed using a KrF laser with a generation line of 247.867 nm in the region of the location of the bandhead of the P₁₂ branch of the γ(0, 2) absorption band of the NO molecule. It was shown that the dissociation process of TNT traces has an inertial character and continues after the cessation of the fragmenting laser pulse. It was found that with the delay values between the fragmenting and probing laser pulses in the region of 200 ns, the efficiency of the LF/LIF method can be increased by 12 times. This paper presents the results of an experimental evaluation of the efficiency of two-pulse LF/LIF compared to single-pulse laser exposure, where the fragmentation of TNT molecules and excitation of their NO fragments were simultaneously performed by KrF laser pulses. The possibility of multiple increases in the efficiency of two-pulse LF/LIF with an increase in the energy density of the fragmenting laser radiation was shown. The obtained results are important in terms of increasing the sensitivity and/or range of the LF/LIF method for remote detection of traces of nitrocompounds. Full article

The rapid detection of the spore form of Clostridioides difficile has remained a challenge for clinicians. To address this, we have developed a novel, precise, microwave-enhanced approach for near-spontaneous release of DNA from C. difficile spores via a bespoke microwave lysis platform. C. difficile spores were microwave-irradiated for 5 s in a pulsed microwave electric field at 2.45 GHz to lyse the spore and bacteria in each sample, which was then added to a screen-printed electrode and electrochemical DNA biosensor assay system to identify presence of the pathogen’s two toxin genes. The microwave lysis method released both single-stranded and double-stranded genome DNA from the bacterium at quantifiable concentrations between 0.02 μg/mL to 250 μg/mL allowing for subsequent downstream detection in the biosensor. The electrochemical bench-top system comprises of oligonucleotide probes specific to conserved regions within tcdA and tcdB toxin genes of C. difficile and was able to detect 800 spores of C. difficile within 300 µL of unprocessed human stool samples in under 10 min. These results demonstrate the feasibility of using a solid-state power generated, pulsed microwave electric field to lyse and release DNA from human stool infected with C. difficile spores. This rapid microwave lysis method enhanced the rapidity of subsequent electrochemical detection in the development of a rapid point-of-care biosensor platform for C. difficile. Full article

This paper aimed to evaluate the performance of a three-phase double-stage photovoltaic water pumping system. Ours is composed of several components. These include a photovoltaic array; a boost DC-DC converter with a maximum power point tracking algorithm based on the Perturb and Observe technique; a three-level neutral-point-clamped inverter, which is controlled using simplified space vector pulse width modulation; and a moto-pump group based on an induction motor and tank. The induction motor is distinguished by its rigidness, reliability and relatively low cost. However, the difficulty of controlling the induction motor is related to the fact that its mathematical model in Park configuration is nonlinear and highly coupled. The regulation of the speed, rotor flux and d-q axis currents of the Field-Oriented Control is achieved through the use of sliding-mode-control-based regulators. To evaluate the performance of the proposed control strategy, simulations were conducted using the Matlab/Simulink platform while considering varying levels of irradiation and temperature. The simulation outcomes conclusively demonstrate that the proposed system control has good performance with regard to dynamic responses, control robustness and power quality, thus affirming its efficacy. A solar water pumping system that uses photovoltaic energy has the potential to be a dependable and effective way to pump water while using sustainable energy sources. Full article

Traditional contact heat flux sensors suffer from a lack of dynamic performance, and existing non-contact optical heat measurement equipment fails to detect convective heat transfer effectively. This limitation precludes the effective testing of composite heat flux in explosive fields. This study introduces an ultra-responsive atomic layer thermopile (ALTP) heat flux sensor, developed and employed for the first time, to evaluate the transient heat flux associated with thermobaric explosions. Measurements reveal that the ALTP sensor’s temporal resolution surpasses that of the thermal resistance thin film heat flux sensor (TFHF), attaining a spectral response time of 10 μs under pulsed laser irradiation. Beyond these radiation-based tests, the present work also conducted novel simulation analyses of high-temperature jet impacts using COMSOL software. Static simulation discovered that fluid velocity significantly influences ALTP’s sensitivity, resulting in an error of 71%. Conversely, dynamic simulation demonstrated that an increase in fluid velocity reduces the ALTP’s time constant, whereas other factors such as fluid temperature exert minimal impact on its dynamic characteristics. This confirms that the simulation model compensates for the cost and accuracy deficiencies of convection heating tests. It also provides a new way to analyze the error of explosive heat flux measurement caused by sensitivity fluctuation and insufficient dynamic performance. In thermobaric explosive trials, the maximum heat fluxes recorded were 202 kW/m² in semi-enclosed environments and 526 kW/m² in open environments. A distinctive double-wave phenomenon was evident in the test curve. By a fast-response thermocouple, the study was able to differentiate between radiation and convective heat flux in the explosion field. The findings substantiate that the ALTP sensor amalgamates the benefits of optical thermal measurement tools with those of traditional contact heat flux sensors, thereby facilitating composite heat flux measurements in the challenging conditions of an explosive field. Full article

Ultra-short 230 fs laser pulses of 515 nm wavelength were tightly focused into 700 nm focal spots and utilised in opening ∼400 nm nano-holes in a Cr etch mask that was tens-of-nm thick. The ablation threshold was found to be 2.3 nJ/pulse, double that of plain silicon. Nano-holes irradiated with pulse energies below this threshold produced nano-disks, while higher energies produced nano-rings. Both these structures were not removed by either Cr or Si etch solutions. Subtle sub-1 nJ pulse energy control was harnessed to pattern large surface areas with controlled nano-alloying of Si and Cr. This work demonstrates vacuum-free large area patterning of nanolayers by alloying them at distinct locations with sub-diffraction resolution. Such metal masks with nano-hole opening can be used for formation of random patterns of nano-needles with sub-100 nm separation when applied to dry etching of Si. Full article

In this study, we fabricated an electric double-layer transistor (EDLT), a synaptic device, by preparing a casein biopolymer electrolyte solution using an efficient microwave-assisted synthesis to replace the conventional heating (heat stirrer) synthesis. Microwave irradiation (MWI) is more efficient in transferring energy to materials than heat stirrer, which significantly reduces the preparation time for casein electrolytes. The capacitance–frequency characteristics of metal–insulator–metal configurations applying the casein electrolyte prepared through MWI or a heat stirrer were measured. The capacitance of the MWI synthetic casein was 3.58 μF/cm² at 1 Hz, which was higher than that of the heat stirrer (1.78 μF/cm²), confirming a stronger EDL gating effect. Electrolyte-gated EDLTs using two different casein electrolytes as gate-insulating films were fabricated. The MWI synthetic casein exhibited superior EDLT electrical characteristics compared to the heat stirrer. Meanwhile, essential synaptic functions, including excitatory post-synaptic current, paired-pulse facilitation, signal filtering, and potentiation/depression, were successfully demonstrated in both EDLTs. However, MWI synthetic casein electrolyte-gated EDLT showed higher synaptic facilitation than the heat stirrer. Furthermore, we performed an MNIST handwritten-digit-recognition task using a multilayer artificial neural network and MWI synthetic casein EDLT achieved a higher recognition rate of 91.24%. The results suggest that microwave-assisted casein solution synthesis is an effective method for realizing biocompatible neuromorphic systems. Full article

In order to improve the ability of the phase-locked loop (PLL) microsystem applied in the aerospace environment to suppress the irradiation effect, this study presents an efficient charge pump hardened scheme by using the radiation-hardened-by-design (RHBD) technology. In this study, the sensitivity analysis of the single-event transient (SET) at different nodes of charge pump and different bombardment energies is carried out. Without changing the original structure and loop parameters, a hardened scheme of phase-locked loop to suppress the single-event effect is proposed. A digital control circuit is added between the charge pump and low-pass filter, which greatly reduces the sensitivity of the charge pump to the SET. The classical double-exponential current pulse model is used to simulate the SET effect on the unreinforced and reinforced phase-locked loops, and the reliability of the proposed reinforcement scheme is verified. The simulation results based on the SMIC 130 nm standard complementary metal–oxide–semiconductor (CMOS) process show that the peak value of the transient response fluctuation of the phase-locked loop using the proposed single-event-hardened scheme decreased by 94.2%, the lock recovery time increased by 75.3%, and the maximum phase shift decreased by 90.8%. This shows that the hardened scheme can effectively reduce the sensitivity of the PLL microsystems to the SET effects. Full article

In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)–triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6–15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm⁻² fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2–7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12–15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760–800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process. Full article

This work investigates spatial and temporal distributions of hydroxyl, OH, in laser-plasma in laboratory air at standard ambient temperature and pressure. Of interest are determination of temperature and density of OH and establishment of a correlation of molecular OH emission spectra with shadow graphs for time delays of 50 to 100 μs, analogous to previous work on shadow graph and emission spectroscopy correlation for cyanide, CN, in gas mixtures and for time delays of the order of 1 μs. Wavelength- and sensitivity-corrected spatiotemporal data analysis focuses on temperature inferences using molecular OH emission spectroscopy. Near-IR radiation from a Q-switched laser device initiates optical breakdown in laboratory air. The laser device provides 6 ns, up to 850 milli Joule, pulses at a wavelength of 1064 nm, and focal irradiance in the range of 1 to 10 terawatt per centimeter-squared. Frequency doubled beams are utilized for capturing shadow graphs for visualization of the breakdown kernel at time delays in the range of 0.1 to 100 μs. OH emission spectra of the laser plasma, spatially resolved along the slit dimension, are recorded in the wavelength range of 298 nm to 321 nm, and with gate widths adjusted to 10 μs for the intensified charge-coupled device that is mounted at the exit plane of a 0.64 m Czerny-Turner configuration spectrometer. Diatomic OH signals occur due to recombination of the plasma and are clearly distinguishable for time delays larger than 50 μs, but are masked by spectra of N₂ early in the plasma decay. Full article

The photoelectrochemical (PEC) activity of metal oxide photoelectrodes for water-splitting applications can be boosted in several different ways. In this study, we showed that PEC activity can be significantly improved with a double-layer (crystalline-amorphous) configuration of WO₃ thin films irradiated with intense pulsed ion beams (IPIB) of a nanosecond duration. It was found that IPIB irradiation promotes the formation of crystalline and sponge-like WO₃ structures on the surface. Due to an increase in the active surface and light scattering in irradiated samples, photocurrent generation increased by ~80% at 1.23 reversible hydrogen electrodes (RHE). Full article