Light Pulses Research Articles

Optical Control of G-Actin with a Photoswitchable Latrunculin.

Actin is one of the most abundant proteins in eukaryotic cells and is a key component of the cytoskeleton. A range of small molecules has emerged that interfere with actin dynamics by either binding to polymeric F-actin or monomeric G-actin to stabilize or destabilize filaments or prevent their formation and growth, respectively. Among these, the latrunculins, which bind to G-actin and affect polymerization, are widely used as tools to investigate actin-dependent cellular processes. Here, we report a photoswitchable version of latrunculin, termed opto-latrunculin (OptoLat), which binds to G-actin in a light-dependent fashion and affords optical control over actin polymerization. OptoLat can be activated with 390-490 nm pulsed light and rapidly relaxes to its inactive form in the dark. Light activated OptoLat induced depolymerization of F-actin networks in oligodendrocytes and budding yeast, as shown by fluorescence microscopy. Subcellular control of actin dynamics in human cancer cell lines was demonstrated via live cell imaging. Light-activated OptoLat also reduced microglia surveillance in organotypic mouse brain slices while ramification was not affected. Incubation in the dark did not alter the structural and functional integrity of the microglia. Together, our data demonstrate that OptoLat is a useful tool for the elucidation of G-actin dependent dynamic processes in cells and tissues.

High-Resolution Printing of Various Electronic Materials by Electrophotography

Electrophotography is a digital, on-demand, dry, and page printing technique that operates based on toner particles of electronic materials using an electrostatic force and generates an electrical circuit via distribution of the toner particles. We developed a 10 μm linewidth resolution with various electronic materials, including conductors, semiconductors, and insulators, without any chemical pretreatments on the substrate films, while a 5 μm resolution was also possible for limited materials. The electrical resistivity of the printed Ag–Ni after an intense pulse light sintering was comparable to that of commercial indium tin oxide transparent films.

Comparing resistance of bacterial spores and fungal conidia to pulsed light and UVC radiation at a wavelength of 254 nm

Pulsed light (PL) inactivates microorganisms by UV-rich, high-irradiance and short time pulses (250 μs) of white light with wavelengths from 200 nm to 1100 nm. PL is applied for disinfection of food packaging material and food-contact equipment. Spores of seven Bacillus ssp. strains and one Geobacillus stearothermophilus strain and conidia of filamentous fungi (One strain of Aspergillus brasiliensis, A. carbonarius and Penicillium rubens) were submitted to PL (fluence from 0.23 J/cm2 to 4.0 J/cm2) and UVC (at λ = 254 nm; fluence from 0.01 J/cm2 to 3.0 J/cm2). One PL flash at 3 J/cm2 allowed at least 3 log-reduction of all tested microorganisms. The emetic B. cereus strain F4810/72 was the most resistant of the tested spore-forming bacteria. The PL fluence to 3 log-reduction (F3 PL) of its spores suspended in water was 2.9 J/cm2 and F3 UVC was 0.21 J/cm2, higher than F3 PL and F3 UVC of spores of B. pumilus SAFR-032 2.0 J/cm2 and 0.15 J/cm2, respectively), yet reported as a highly UV-resistant spore-forming bacterium. PL and UVC sensitivity of bacterial spores was correlated. Aspergillus spp. conidia suspended in water were poorly sensitive to PL. In contrast, PL inactivated Aspergillus spp. conidia spread on a dry surface more efficiently than UVC. The F2 PL of A. brasiliensis DSM1988 was 0.39 J/cm2 and F2 UVC was 0.83 J/cm2. The resistance of spore-forming bacteria to PL could be reasonably predicted from the knowledge of their UVC resistance. In contrast, the sensitivity of fungal conidia to PL must be specifically explored.

Ultra-intense femtosecond laser interactions with aligned nanostructures

The interaction of ultrafast laser pulses of relativistic intensity with high aspect ratio nanostructures can efficiently and volumetrically heat matter to an ultra-high-energy-density regime encountered in the center of stars and within the core of fusion capsules compressed by the world’s largest lasers. It also generates gigantic quasi-static electromagnetic fields that accelerate particles to very high energy. Here, we present an overview of the physics and applications of these dense relativistic plasmas that can be created with pulses of relatively modest energy from lasers that can operate at a high repetition rate. Recent nanowire array experiments produced near-solid density plasmas with an extreme degree of ionization (e.g., Au+72), converted ultrafast pulses of laser light into intense x-ray flashes with record efficiency, and accelerated ions to MeV energies, efficiently driving micro-scale fusion reactions that generate flashes of quasi-monoenergetic neutrons. These plasmas also serve as a platform for advancing the understanding of atomic processes in extreme environments and open a new pathway to laser-driven fusion energy. The irradiation of nanostructures at intensities of >1×1022Wcm−2 is predicted to lead to an extreme ultra-high energy density plasma regime characterized by terabar pressures that is virtually unexplored.

High spatial resolution temperature variation detection in one direction with a fiber solenoid and RDTS system

Limited by the large bottom width of the pulsed light and the large sampling spacing of the data acquisition card in conventional Raman distributed temperature sensing (RDTS) systems, short straight fibers cannot acquire temperature measurements with high spatial resolution and high temperature accuracy in a single temperature variation region (TVR). In contrast, winding sensing fiber on a screwed tube as a fiber solenoid for temperature sensing can indirectly improve the spatial resolution of the system. However, as the radius of the screwed tube decreases, the ability of the screwed tube to improve the spatial resolution of the system will deteriorate. To break this limitation, we innovatively propose a signal processing scheme to first construct a three-dimensional surface of the sensing length of screwed tube-temperature-area value, then obtain the length of the TVR and the area value of the temperature rise curve generated from a single TVR, and finally demodulate the temperature of the TVR in the surface. The experimental results show that the proposed scheme improves the spatial resolution of the conventional screwed tube from 8 cm to 1 cm, and the average temperature accuracy of the three TVRs with the interval and length of the TVRs in the order of centimeters is ± 0.63 °C. The screwed tube can be used for axial temperature distribution measurements of liquids as well as solids, and the proposed method can further expand the application prospects of the RDTS system for continuous measurement of multiple TVRs with lengths and intervals of centimeters in one direction without changing the internal hardware.

Tunable optoelectronic response in van der Waals heterojunction transistors for artificial visual recognition

Optoelectronic synaptic transistors are advantageous in in-memory light sensing for artificial neural networks. Herein, optoelectronic synaptic junction field-effect transistors (JFETs) based on a Ga2O3/MoS2 heterojunction are fabricated. The devices exhibit robust electrical performances, including a high on/off ratio of 108, a low subthreshold swing of 69 mV dec−1, and a high output current of 3.4 μA μm−1. An inverter and a NAND gate are constructed based on the dual-gated configuration, with the inverter showing a high voltage gain of 28 and the near-ideal noise margin of 90.4%. Additionally, the devices demonstrate outstanding optoelectronic performances benefiting from the strong light–matter interactions of MoS2. Typical synaptic plasticities, including short-term plasticity, long-term plasticity, and spiking-rate-dependent plasticity, are simulated by applying the light pulses. Furthermore, metaplastic excitatory postsynaptic current, metaplastic facilitation of long-term potentiation and transition from potentiation to depression are also readily demonstrated. The artificial neural network, in which neurons are interconnected through our proposed optoelectronic synaptic transistors, achieves a high accuracy of 89.8% in recognizing handwritten digits. This work provides insight into the design of an optoelectronic synapse based on JFETs.

Evaluation of thermal shock therapy for reducing pain during intense pulsed light therapy: An intrapatient randomized controlled study.

Intense pulsed light (IPL) is used for the treatment and improvement of various skin issues. However, patients often experience local skin burning and pain after IPL treatment. Cooling and analgesic measures are indispensable. To investigate the clinical effect of thermal shock therapy on pain relief and reduction of adverse reactions during IPL therapy. A total of 60 female patients with facial photoaging who received IPL therapy were enrolled in the study. As a comparative split-face study, one side of the face was randomly selected as the control side. The other side was given thermal shock therapy before and after the IPL treatment immediately as analgesic side. The visual analog scale (VAS) was used to evaluate the pain degree of the patients. The telephone follow-ups regarding the occurrence of adverse reactions were conducted respectively on the 2nd day, 7th day, and 1 month after treatment. The VAS score and skin temperature of analgesia side was lower than that of control side at different stages of treatment. In terms of adverse reactions, the incidence of transient facial redness on the analgesic side was lower than that on the control side. Two patients showed slight secondary pigmentation on the control side, and the other patients showed no other adverse reactions on both sides. Thermal shock therapy assisted IPL therapy can reduce skin temperature during treatment, effectively relieve patients' pain, reduce the occurrence of adverse reactions caused by heat injury, and improve patients' comfort level.

Arabidopsis hypocotyl growth in darkness requires the phosphorylation of a microtubule-associated protein.

Rapid hypocotyl elongation allows buried seedlings to emerge, where light triggers de-etiolation and inhibits hypocotyl growth mainly by photoreceptors. Phosphorylation/dephosphorylation events regulate many aspects of plant development. Only recently we have begun to uncover the earliest phospho-signaling responders to light. Here, we reported a large-scale phosphoproteomic analysis and identified 20 proteins that changed their phosphorylation pattern following a 20 min light pulse compared to darkness. Microtubule-associated proteins were highly overrepresented in this group. Among them, we studied CIP7 (COP1-INTERACTING-PROTEIN 7), which presented microtubule (MT) localization in contrast to the previous description. An isoform of CIP7 phosphorylated at Serine915 was detected in etiolated seedlings but was undetectable after a light pulse in the presence of photoreceptors, while CIP7 transcript expression decays with long light exposure. The short hypocotyl phenotype and rearrangement of MTs in etiolated cip7 mutants are complemented by CIP7-YFP and the phospho-mimetic CIP7S915D-YFP, but not the phospho-null CIP7S915A-YFP suggesting that the phosphorylated S915CIP7 isoform promotes hypocotyl elongation through MT reorganization in darkness. Our evidence on Serine915 of CIP7 unveils phospho-regulation of MT-based processes during skotomorphogenic hypocotyl growth.

Time-delay fourier transform spectrometer for high-speed spectral measurement

In the field of optics, there exist numerous chaotic processes like dissipative soliton dynamics, random laser generation, and laser scattering. It's very challenging to accurately capture the dynamics of these stochastic processes from the wavelength perspective with traditional spectrometers due to their slow signal integration speeds. Here, we propose a new approach, named time-delay Fourier transform spectrometer (TDFTS), to characterize the spectra of laser pulses with durations ranging from fs to ns with high speeds. Based on a fiber array with different lengths to impose frequency-dependent time delay, TDFTS efficiently maps the spectral distribution of light pulses to the temporal domain, and the spectrum can thus be detected with a photodiode and an oscilloscope. In experimental operation, the TDFTS provides spectral acquisition speeds up to 56 MHz frame rates and a bandwidth of tens of nanometers, while keeping comparable fidelity to traditional grating-scan spectrometers. While its spectral resolution of the current configuration is ∼0.1 nm, it can be further improved to 0.001 nm through optimizing the system. Based on its high speed, high spectral resolution, broad-bandwidth coverage, and compact configuration, TDFTS can be used to monitor nanosecond-scale spectral dynamics of non-repetitive optical processes.

The impact of movement path of sesame seeds (Sesamum indicum L.) during treatment with intense pulsed light (IPL) using a continuous pilot-scale device on the reduction of indigenous microorganisms.

The objective of this study was to enhance the microbial inactivation efficacy of sesame seeds through the utilization of a pilot-scale IPL device, while also identifying the process variables that influence the microbial inactivation effect. Three different types of IPL processes were employed, each with a distinct arrangement, to treat sesame seeds. The total fluences applied ranged from 1.33 to 53.94J/cm2. Total aerobic bacteria and fungi exhibited a maximum reduction of 2.27 and 2.77 log, respectively. The curved pathway of the sample flow effectively extended the duration of exposure to the IPL emitted by the lamps. The arrangement of the IPL process using two lamps in parallel but at different locations proved the most efficient for microbial inactivation. The application of IPL was found to be effective in reducing the presence of indigenous microbes in sesame seeds while having no significant impact on the physicochemical properties of the seeds.

Formation of gel and solid phases in acrylic cuvettes upon exposure to DMSO, oxygen and light: implications for fluorescence spectroscopy

We here report the formation of a turbid-gel phase in acrylic cuvettes upon exposure to pure Dimethyl Sulfoxide (DMSO) at room temperature. The observed phenomenon occurred over a 10 h to 14 h incubation in the presence of environmental oxygen. After the turbid gel was removed from the cuvette, it became a white solid exhibiting unique emission behavior. The formation of the turbid-gel phase was accelerated upon exposure to UV 295 LED pulses of light from 6 h to 8 h. Surprisingly, subsequent exposure of the white solid to a few microliters of pure DMSO and vortexing resulted in its transformation into a transparent gel state in just a few minutes, eventually acquiring transparent and liquid properties. Additionally, the white-solid phase can load other molecules, such as Resveratrol and Quercetin, leading to shifts in the respective emission spectra compared with the same molecule in liquid and pure DMSO. These novel findings highlight the interaction between UV photons, oxygen, DMSO and Acrylic, and potentially distort fluorescence spectroscopy experiments.

Modulating antibacterial properties of titanium surface coatings: The role of low intensity pulsed ultrasound and light stimuli

Medical titanium and titanium alloys were susceptible to infection following implantation due to their limited antibacterial properties. One effective approach to mitigate this risk was the application of antibacterial coatings on the medical titanium materials surface. Additionally, there was a pressing need in clinical practice to develop a titanium surface coating that can modulate antibacterial properties in response to external conditions. In this study, a zinc oxide-loaded silver nanorod arrays coating was fabricated on the titanium surface using intensity pulsed ultrasound and light as stimuli, aiming to achieve the desired regulation of antibacterial properties. The coating morphology and the silver distribution within the coating were investigated. The surface roughness and wetting angle were tested. The effect of low intensity pulsed ultrasound and light on the cumulative release of silver ions was studied, and its mechanism was analyzed. The bacteriostasis rate of the polarized ZnO-loaded silver nanorods array coating reached 99.96%. The synergistic bactericidal mechanism of piezoelectric effect, catalysis, silver ion bactericidal effect and nanorod puncture effect on bacteria was expounded. Finally, the ZnO-loaded silver nanorod array coating exhibited non-cytotoxicity and supported full osteoblast adherence morphology. The polarized coating was observed to be coated with abundant granular hydroxyapatite after immersion in simulated body fluids for 7 days. The results provide a possibility for modulating the antibacterial properties of titanium surface coatings in vitro.

Effective Treatment of Rosacea and Other Vascular Lesions Using Intense Pulsed Light System Emitting Vascular Chromophore-Specific Wavelengths: A Clinical and Dermoscopical Analysis.

Background: Facial telangiectasias is a prevalent cosmetic disorder that can be associated with several conditions such as rosacea. IPL (intensity pulsed light) therapy is commonly used for the treatment of vascular lesions. This study tested the efficacy of an IPL system emitting selected vascular chromophore-specific wavelengths in the range of 500-1200 nm for the treatment of vascular lesions. Materials and Methods: A total of 39 patients affected by different vascular lesions on their face were enrolled. The procedure consisted of three treatment sessions, spaced 1 month apart, using the IPL system with a 500-677 and 854-1200 nm filter. Follow-up was performed at 21-90 days (3 weeks-3 months) after the last IPL session. Three-dimensional and dermoscopic clinical photographs were captured and evaluated using a five-point scale. Adverse events were checked. Results: In total, 21 patients achieved excellent improvement, 13 patients achieved good improvement, 3 patients achieved moderate improvement, 2 patients achieved mild improvement, and 0 patients achieved no improvement, with an overall good response to treatment. The photographic evaluation showed good results as soon as 3 days after the last IPL session. Relevant side effects were absent. Conclusions: The study device may represent a successful treatment to improve vascular lesions that are resistant to laser therapy.

Amplified frequency-shifted interferometry fiber loop ringdown glucose sensors using side-polished fiber

An amplified frequency-shifted interferometry fiber loop ringdown (FSI-FLRD) sensor is proposed for the concentration measurement of glucose solutions. It detects glucose concentrations by measuring the ringdown distance of the continuous light in the fiber ringdown loop (RDL) instead of the ringdown time of the pulsed light in the loop as in traditional FLRD glucose sensors. A bidirectional erbium-doped fiber amplifier (Bi-EDFA) and a segment of side-polished fiber (SPF) are respectively inserted into the RDL to compensate the loop attenuation and to act as the sensing probe. The proposed optical sensor was tested with glucose solutions in the concentration range from 0 to 14 % at room temperature, which exhibits a linear response with a sensitivity of 0.0013 km−1/% (4.12x10−4 dB/%) for the 0–8 % glucose solutions. Additionally, it also achieved a system stability of 0.75 %, with a measuring resolution of around 2.63 %. The experimental results show the proposed sensor has simple structure, low cost, robust stability and good resolution, and it is a suitable alternative for the detection of glucose concentrations in biological detection, component analysis and on-line quality control in food industry.

The Nonvolatile Memory and Neuromorphic Simulation of ReS2/h-BN/Graphene Floating Gate Devices Under Photoelectrical Hybrid Modulations.

The floating gate devices, as a kind of nonvolatile memory, obtain great application potential in logic-in-memory chips. The 2D materials have been greatly studied due to atomically flat surfaces, higher carrier mobility, and excellent photoelectrical response. The 2D ReS2 flake is an excellent candidate for channel materials due to thickness-independent direct bandgap and outstanding optoelectronic response. In this paper, the floating gate devices are prepared with the ReS2/h-BN/Gr heterojunction. It obtains superior nonvolatile electrical memory characteristics, including a higher memory window ratio (81.82%), tiny writing/erasing voltage (±8V/2ms), long retention (>1000s), and stable endurance (>1000 times) as well as multiple memory states. Meanwhile, electrical writing and optical erasing are achieved by applying electrical and optical pulses, and multilevel storage can easily be achieved by regulating light pulse parameters. Finally, due to the ideal long-time potentiation/depression synaptic weights regulated by light pulses and electrical pulses, the convolutional neural network (CNN) constructed by ReS2/h-BN/Gr floating gate devices can achieve image recognition with an accuracy of up to 98.15% for MNIST dataset and 91.24% for Fashion-MNIST dataset. The research work adds a powerful option for 2D materials floating gate devices to apply to logic-in-memory chips and neuromorphic computing.

Vortex plate retarder-based approach for the generation of sub-20 fs light pulses carrying orbital angular momentum

We use a vortex retarder-based approach to generate few optical cycles light pulses carrying orbital angular momentum (OAM) (known also as twisted light or optical vortex) from a Yb:KGW oscillator pumping a noncollinear optical parametric amplifier generating sub-10 fs linearly polarized light pulses in the near infrared spectral range (central wavelength 850 nm). We characterize such vortices both spatially and temporally by using astigmatic imaging technique and second harmonic generation-based frequency resolved optical gating, respectively. The generation of optical vortices is analyzed, and its structure reconstructed by estimating the spatio-spectral field and Fourier transforming it into the temporal domain. As a proof of concept, we show that we can also generate sub-20 fs light pulses carrying OAM and with arbitrary polarization on the first-order Poincaré sphere.

Effect of dehydration and pulsed light treatment on decontamination of minced onions: Microbial safety and physicochemical properties.

Microbial contamination of dehydrated onion products is a challenge to the industry. The study focused on opting for a suitable drying condition for minced onion and exploring the decontamination efficacy of pulsed light (PL) treatment conditions for the dehydrated product. The minced onions were hot air dried at 55-75°C for 280min. The drying condition selected was 195min at 75°C with a final water activity of 0.5 and moisture content of 7% (wet basis [w.b.]). The weight losses, browning indexes (BI), shrinkage volumes (%), and thiosulfinate content were considered. The dehydrated product was exposed to PL treatment corresponding to an effective fluence range of 0.007-0.731 J/cm2. A fluence of 0.444 J/cm2 (1.8kV for 150 s) achieved 5.00, 3.14, 2.96, and 2.98 log reduction in total plate count, yeast and mold count, Bacillus cereus 10876, and Escherichia coli ATCC 43888, respectively. The PL-treated sample (0.444 J/cm2) produced a microbially safe product with no significant difference in the moisture contents (%w.b.) and water activity (aw) from the untreated dehydrated sample. Further, a 30.9% increase in the BI and a 4.25% depletion in thiosulfinate content were observed after PL treatment. An optimum drying combination (75°C for 195min) of minced onion followed by decontamination using pulsed light treatment at 0.444 J/cm2 fluence satisfies the microbial safety and quality. PRACTICAL APPLICATION: Dehydrated minced onion can be used for dishes requiring low water content and short cooking time. It is helpful during shortages, high price fluctuations, and famines.

Diamond Bur Microblepharoexfoliation Combined with Intense Pulse Light and Meibomian Gland Expression for Evaporative Dry Eye: A Short-term Controlled Clinical Trial.

To assess the efficacy and safety of the combination of microblepharoexfoliation (MBE), intense pulse light (IPL) and meibomian gland expression (MGX) for treatment of meibomian gland dysfunction (MGD). This was a prospective, parallel-control trial conducted from April 2022 to January 2023. Participants were assigned to receive either three sessions of MBE-IPL-MGX treatment and home-based therapy (treatment group) or home-based therapy alone (control group). Outcome measures were assessed at baseline and after 2-month follow-up. Seventy eyes of 70 patients were enrolled. MBE-IPL-MGX treatment achieved better improvements than home-based therapy in ocular surface disease index (OSDI) and symptom assessment in dry eye (SANDE) scores, noninvasive tear film break-up time (NIBUT), lipid layer grade (LLG), loss area meibomian gland (LAMG) and meibomian gland yielding secretion score (MGYSS). The mean differences between the two groups were as follows: OSDI (- 11.23 ± 4.68 points, P < 0.001), SANDE (- 24.63 ± 13.41 points, P < 0.001), NIBUT (1.3 ± 1.57s, P = 0.033), LLG (0.4 ± 0.04 points, P = 0.003), LAMG (- 2.85 ± 1.69%, P = 0.023) and MGYSS (7.5 ± 2.32 points, P < 0.001). In addition, the increment (Δ) of MGYSS after MBE-IPL-MGX treatment was significantly higher in MGD grades 2 and 3 (all P < 0.001). MBE-IPL-MGX treatment is an effective and well-tolerated procedure that improves dry eye symptoms and signs as well as meibomian gland secretions in patients with MGD. In addition, this treatment is recommended for MGD grades 2 and 3.

Photoacoustic microscopy for real-time monitoring of near-infrared optical absorbers inside biological tissue.

We developed a high-speed optical-resolution photoacoustic microscopy (OR-PAM) system using a high-repetition-rate supercontinuum (SC) light source and a two-axes Galvano scanner. The OR-PAM system enabled real-time imaging of optical absorbers inside biological tissues with excellent excitation wavelength tunability. In the near-infrared (NIR) wavelength range, high-speed OR-PAM faces limitations due to the lack of wavelength-tunable light sources. Our study aimed to enable high-speed OR-PAM imaging of various optical absorbers, including NIR contrast agents, and validate the performance of high-speed OR-PAM in the detection of circulating tumor cells (CTCs). A high-repetition nanosecond pulsed SC light source was used for OR-PAM. The excitation wavelength was adjusted by bandpass filtering of broadband light pulses produced by an SC light source. Phantom and in vivo experiments were performed to detect tumor cells stained with an NIR contrast agent within flowing blood samples. The newly developed high-speed OR-PAM successfully detected stained cells both in the phantom and in vivo. The phantom experiment confirmed the correlation between the tumor cell detection rate and tumor cell concentration in the blood sample. The high-speed OR-PAM effectively detected stained tumor cells. Combining high-speed OR-PAM with molecular probes that stain tumor cells in vivo enables in vivo CTC detection.

An optogenetic method for the controlled release of single molecules

We developed a system for optogenetic release of single molecules in cells. We confined soluble and transmembrane proteins to the Golgi apparatus via a photocleavable protein and released them by short pulses of light. Our method allows for a light dose-dependent delivery of functional proteins to the cytosol and plasma membrane in amounts compatible with single-molecule imaging, greatly simplifying access to single-molecule microscopy of any protein in live cells. We were able to reconstitute ion conductance by delivering BK and LRRC8/volume-regulated anion channels to the plasma membrane. Finally we were able to induce NF-kB signaling in T lymphoblasts stimulated by interleukin-1 by controlled release of a signaling protein that had been knocked out. We observed light-induced formation of functional inflammatory signaling complexes that triggered phosphorylation of the inhibitor of nuclear factor kappa-B kinase only in activated cells. We thus developed an optogenetic method for the reconstitution and investigation of cellular function at the single-molecule level.