Continuous Wave Research Articles

HIFU induces reprogramming of the tumor immune microenvironment in a pancreatic cancer mouse model.

This study evaluates the effects of different high-intensity focused ultrasound irradiation (HIFU) methods on local tumor suppression and systemic antitumor effects, including the abscopal effect, in a mouse model of pancreatic cancer. To ascertain the efficacy of the treatment, pancreatic cancer cells were injected into the thighs of mice and HIFU was applied on one side using continuous waves or trigger pulse waves. Then, tumor volume, tissue changes, and immune marker levels were analyzed. Both the irradiation methods suppressed tumor growth, with the trigger pulse wave showing stronger effects and the difference being significant. Tumor suppression was also observed on the non-irradiated side, suggesting an abscopal effect. These effects vary depending on the irradiation method used. We conclude that HIFU induces both local tumor suppression and a systemic immune response, suggesting its potential for combination with immunotherapy for the treatment of pancreatic cancer.

Role of continuous wave vs pulse wave and color doppler in identifying arterial perforators of lower limb

Role of continuous wave vs pulse wave and color doppler in identifying arterial perforators of lower limb

Continuous-wave and Q-switched Tb:YLF lasers at 587 nm

We report what we believe to be the highest continuous-wave (CW) output power from a Tb:YLF (Tb3+:LiYF4) laser at 587 nm, reaching up to 1 W, and the first actively Q-switched operation in the orange spectral region with output energy of 0.5 mJ in 100 ns pulses at 500 Hz. This represents progress toward a next-generation ozone differential absorption lidar (DIAL) laser source. Unstable behavior in CW operation is observed.

Automatic speech recognition predicts contemporaneous earthquake fault displacement

Significant progress has been made in probing the state of an earthquake fault by applying machine learning to continuous seismic waveforms. The breakthroughs were originally obtained from laboratory shear experiments and numerical simulations of fault shear, then successfully extended to slow-slipping faults. Here we apply the Wav2Vec-2.0 self-supervised framework for automatic speech recognition to continuous seismic signals emanating from a sequence of moderate magnitude earthquakes during the 2018 caldera collapse at the Kīlauea volcano on the island of Hawai’i. We pre-train the Wav2Vec-2.0 model using caldera seismic waveforms and augment the model architecture to predict contemporaneous surface displacement during the caldera collapse sequence, a proxy for fault displacement. We find the model displacement predictions to be excellent. The model is adapted for near-future prediction information and found hints of prediction capability, but the results are not robust. The results demonstrate that earthquake faults emit seismic signatures in a similar manner to laboratory and numerical simulation faults, and artificial intelligence models developed for encoding audio of speech may have important applications in studying active fault zones.

Bleaching effect of radiation-induced darkening in Yb3+-doped large mode area photonic crystal fiber based on deuterium and hydrogen loading.

We report the radiation-induced darkening (RD) effect caused by X-ray radiation and the bleaching effect caused by D2/H2/N2 loading in self-developed Yb3+-doped large mode-area photonic crystal fibers (LMA PCFs). The decrease in the slope efficiency caused by irradiation decays exponentially with an increase in the X-ray radiation doses, and the radiation-induced gain variation (RIGV) showed a linear decay trend with increasing irradiation doses. The slope efficiency of Yb3+-doped LMA PCF, which significantly degraded from 71.00% to 50.42% after 50 Gy irradiation, can be significantly restored after D2 loading to 97.21% of the slope efficiency of pristine fiber. However, the slope efficiency of the PCF loaded by H2 can be recovered to 88.54% that of the pristine. These results suggest that D2 loading has a more pronounced bleaching ability than H2, while N2 does not exhibit any bleaching effect. Based on the all-fiber modular amplification experiment, an average amplified output power of 41.4 W at the pump power of 62.3 W was achieved from Yb3+-doped LMA PCFs irradiated with 50 Gy followed by D2 loading. The slope efficiency (with respect to the pump power) was 69.05%, with the laser beam quality factor M2 of 1.2. No obvious power decaying of the laser output was observed for about 10 h. RD and bleaching effects of the Yb3+-doped LMA PCF core glass have been thoroughly investigated using the absorption, radiation-induced attenuation (RIA), continuous wave electron paramagnetic resonance (CW-EPR), emission, Raman, and Fourier transform infrared (FTIR) spectra.

Challenging the skin pigmentation bias in tissue oximetry via time-domain near-infrared spectroscopy

Recently, skin pigmentation has been shown to affect the performance of pulse oximeters and other light-based techniques like photo-acoustic imaging, tissue oximetry, and continuous wave near-infrared spectroscopy. Evaluating the robustness to changes in skin pigmentation is therefore essential for the proper use of optical technologies in the clinical scenario. We conducted systematic time-domain near-infrared spectroscopy measurements on calibrated tissue phantoms and in vivo on volunteers during static and dynamic (i.e., arterial occlusion) measurements. To simulate varying melanosome volume fractions in the skin, we inserted, between the target sample and the measurement probe, thin tissue phantoms made of silicone and nigrosine (skin phantoms). Additionally, we conducted an extensive measurement campaign on a large cohort of pediatric subjects, covering the full spectrum of skin pigmentation. Our findings consistently demonstrate that skin pigmentation has a negligible effect on time-domain near-infrared spectroscopy results, underscoring the reliability and potential of this emerging technology in diverse clinical settings.

Phosphodiesterase inhibition restoreshypoxia-induced cerebrovascular dysfunction subsequent to improved systemic redox homeostasis: A randomized, double-blind, placebo-controlled crossover study.

To what extent sildenafil, a selective inhibitor of the type-5 phosphodiesterase modulates systemic redox status and cerebrovascular function during acute exposure to hypoxia remains unknown. To address this, 12 healthy males (aged 24 ± 3 y) participated in a randomized, placebo-controlled crossover study involving exposure to both normoxia and acute (60 min) hypoxia (Fi = 0.14), followed by oral administration of 50 mg sildenafil and placebo (double-blinded). Venous blood was sampled for the ascorbate radical (A•-: electron paramagnetic resonance spectroscopy) and nitric oxide metabolites (NO: ozone-based chemiluminescence). Transcranial Doppler ultrasound was employed to determine middle cerebral artery velocity (MCAv), cerebral delivery of oxygen dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity to hypo/hypercapnia (CVRCO2HYPO/HYPER). Cortical oxyhemoglobin (cO2Hb) and oxygenation index (OI) were assessed using pulsed continuous wave near infra-red spectroscopy. Hypoxia decreased total plasma NO (P = 0.008), (P = <0.001) and cO2Hb (P = 0.005). In hypoxia, sildenafil selectively reduced A•- (P = 0.018) and MCAV (P = 0.018), and increased dCA metrics of low-frequency phase (P = 0.029) and CVRCO2HYPER (P = 0.007) compared to hypoxia-placebo. Collectively, these findings provide evidence for a PDE-5 inhibitory pathway that enhances select aspects of cerebrovascular function in hypoxia subsequent to a systemic improvement in redox homeostasis and independent of altered vascular NO bioavailability.

Acoustic lattice resonances and generalised Rayleigh–Bloch waves

The intrigue of waves on periodic lattices and gratings has resonated with physicists and mathematicians alike for decades. In-depth analysis has been devoted to the seemingly simplest array system: a one-dimensionally periodic lattice of two-dimensional scatterers embedded in a dispersionless medium governed by the Helmholtz equation. We investigate such a system and experimentally confirm the existence of a new class of generalised Rayleigh–Bloch waves that have been recently theorised to exist in classical wave regimes, without the need for resonant scatterers. Airborne acoustics serves as such a regime and we experimentally observe the first generalised Rayleigh–Bloch waves above the first cut-off, i.e., in the radiative regime. We consider radiative acoustic lattice resonances along a diffraction grating and connect them to generalised Rayleigh–Bloch waves by considering both short and long arrays of non-resonant 2D cylindrical Neumann scatterers embedded in air. On short arrays, we observe finite lattice resonances under continuous wave excitation, and on long arrays, we observe propagating Rayleigh–Bloch waves under pulsed excitation. We interpret their existence by considering multiple wave scattering theory and, in doing so, unify differing nomenclatures used to describe waves on infinite periodic and finite arrays and the interpretation of their dispersive properties.

In situ Electron Paramagnetic Resonance Investigation of Isotope-selective Breathing in MIL-53 during Dihydrogen Adsorption.

The development of smart materials capable of separating dihydrogen isotopologues has risen recently. Among potential candidates, the flexible MIL-53 (Al) has been gaining attention due to its structural flexibility providing the so-called ''breathing mechanism'' that can be useful to separate hydrogen isotopologues selectively. In the present work, an in situ continuous wave electron paramagnetic resonance investigation has been proven as a sensitive technique to follow the isotopologue-selective adsorption-desorption of dihydrogen species on the paramagnetic metal-doped MIL-53 (Al0.99Cr0.01) and MIL-53 (Al0.99V0.01), respectively. The presence of paramagnetic spin probes such as Cr3+ and V4+ inside the MIL-53 framework allows for monitoring the framework transition including the 2nd transition step that selectively occurs at p > 100 mbar when D2 gas is adsorbed on the pores at 23 K. Furthermore, investigation of D2 desorption from MIL-53 (Al0.99V0.01) by temperature-dependent hyperfine spectroscopy provides a more detailed analysis of the D2 desorption process on a microscopic scale with respect to the embedded spin probe.

Increased sensitivity in electron–nuclear double resonance spectroscopy with chirped radiofrequency pulses

Abstract. Electron–nuclear double resonance (ENDOR) spectroscopy is an EPR technique to detect the nuclear frequency spectra of hyperfine coupled nuclei close to paramagnetic centers, which have interactions that are not resolved in continuous wave EPR spectra and may be fast relaxing on the timescale of NMR. For the common case of non-crystalline solids, such as powders or frozen solutions of transition metal complexes, the anisotropy of the hyperfine and nuclear quadrupole interactions renders ENDOR lines often several megahertz (MHz) broad, thus diminishing intensity. With commonly used ENDOR pulse sequences, only a small fraction of the NMR/ENDOR line is excited with a typical radiofrequency (RF) pulse length of several tens of microseconds (µs), and this limits the sensitivity in conventional ENDOR experiments. In this work, we show the benefit of chirped RF excitation in frequency-domain ENDOR as a simple yet effective way to significantly improve sensitivity. We demonstrate on a frozen solution of Cu(II)-tetraphenylporphyrin that the intensity of broad copper and nitrogen ENDOR lines increases up to 9-fold compared to single-frequency RF excitation, thus making the detection of metal ENDOR spectra more feasible. The tunable bandwidth of the chirp RF pulses allows the operator to optimize for sensitivity and choose a tradeoff with resolution, opening up options previously inaccessible in ENDOR spectroscopy. Also, chirp pulses help to reduce RF amplifier overtones, since lower RF powers suffice to achieve intensities matching conventional ENDOR. In 2D triple resonance experiments (TRIPLE), the signal increase exceeds 10 times for some lines, thus making chirped 2D TRIPLE experiments feasible even for broad peaks in manageable acquisition times.

Low hysteresis and high sensitivity TPU/carbonized wood cellulose sponge sensors for monitoring dynamic pulses.

The importance of continuous and reliable pulse wave monitoring is constantly being increased in health signal monitoring and disease diagnoses. Flexible pressure sensors with high sensitivity, low hysteresis and fast response time are an effective means for monitoring pulses. Herein, a special wave-shaped layered porous structure of carbonized wood cellulose sponge (CWCS) was constructed based on natural wood (NW). Thermoplastic polyurethane (TPU)/CWCS (PCWCS) composite flexible pressure sensitive elements were formed by immersing a TPU solution into the CWCS skeleton. The PCWCS-4 % based sensors exhibited high sensitivity of 164.77 kPa-1 (0.01-0.5 kPa), low hysteresis (0.70 %), short response time (21 ms), low detection limit and good cycling stability. The exceptional sensing performance was attributed to the wave-shaped layered porous structure of the PCWCS, which rapidly established conductive pathways and reduced stress concentrations during compression. Due to the high sensitivity and low hysteresis of sensors, more comprehensive pulse and other physiological signals could be obtained. Therefore, the PCWCS flexible pressure sensor possesses great potential for application in smart wearable and healthcare.

High-Speed Pulsing Circuit for Continuous Wave Laser Beams.

Abstract Tunable continuous wave (CW) lasers produce the highest optical resolution for pumping and&amp;#xD;probing atomic and molecular transitions. These lasers adopt sophisticated electronic control of&amp;#xD;optical components within the cavity to set the wavelength and ensure a narrow bandwidth. The low cost&amp;#xD;circuit described here gates a CW laser beam on and off for high resolution timing experiments,&amp;#xD;using an electro-optic modulator that acts as a switchable waveplate between linear polarizers. The&amp;#xD;switch can operate at rates of up to 100 kHz with a minimum pulse width of 650 ns, or it can be&amp;#xD;configured to deliver laser pulses with widths ≥ 35 ns at lower rates. Multiple laser pulses of equal&amp;#xD;or non-equal widths can also be delivered within each repetition cycle.

Crystal growth, spectral properties, and 2.3 µm continuous-wave laser operation of Tm:YScO3 and Tm:LuScO3 crystals

Crystal growth, spectral properties, and 2.3 µm continuous-wave laser operation of Tm:YScO3 and Tm:LuScO3 crystals

Broadband, multiaxial-mode, passively-stable continuous wave optical parametric oscillator design consideration and dispersion compensation analysis

Broadband, multiaxial-mode, passively-stable continuous wave optical parametric oscillator design consideration and dispersion compensation analysis

FMCW-based contactless heart rate monitoring

Heart disease is a significant global health issue. Traditional methods for heart rate monitoring typically require close physical contact, which limits the continuity and convenience of monitoring. To achieve real-time, non-contact heartbeat monitoring, researchers have introduced millimeter-wave radar technology. The technology’s penetration and privacy offer a potential solution for heart condition monitoring. Therefore, this study utilized frequency-modulated continuous wave (FMCW) radar for heart rate monitoring. Firstly, the collected millimeter-wave radar signals were preprocessed to accurately locate the area of cardiac activity in the human body. Secondly, an adaptive variational mode decomposition (A-VMD) algorithm was designed to extract the heartbeat signal, considering signal variations caused by random body movements and respiration and their harmonics, to obtain an accurate heartbeat signal. Finally, the accurate heart rate is obtained by weighted estimation based on the harmonic relationship of the heartbeat signal. The study invited ten subjects to participate in the experiment to verify the effectiveness of this method. The results show that this method can reduce the influence of and random body movements and respiration and harmonics on heart rate monitoring, the average absolute error of heart rate estimation is less than four bpm.

Single mode, distributed feedback interband cascade lasers grown on Si for gas sensing

A single mode distributed feedback (DFB) interband cascade laser (ICL) grown on a (001) Si substrate has been developed. The designed DFB ICL with a grating on top of the ridge emits at a wavelength near 3.4 μm, suited for methane gas sensing, and operates in continuous wave up to 35 °C, with a maximum output power of 4 mW/facet at 15 °C and a side mode suppression ratio of 20 dB in the whole operating range. Methane detection has been demonstrated by integrating the DFB ICL on Si with a quartz-enhanced photoacoustic spectroscopy setup, a step forward in the development of integrated photonic gas sensors on silicon platforms.

Three-dimensional whole-body imaging of the bioreduction and clearance of nitroxide probes in the thoracic and abdominal regions of mice using a compact and mobile electron paramagnetic resonance imager.

Redox homeostasis plays a key role in regulating the overall health and development of organisms. This study aimed to develop a compact and mobile continuous-wave (CW) electron paramagnetic resonance (EPR) imager to facilitate stable, highly sensitive fast three-dimensional (3D)whole-body imaging of nitroxide-infused mice. A multiturn loop gap resonator with a diameter of 30 mm and length of 35 mm was designed for whole-body EPR imaging. A compact and mobile CW-EPR imager operating at 750 MHz was developed using this resonator. The automatic matching and tuning control systems were also adjusted to compensate for perturbations caused by the movement of the mice. When the mice were inserted into the resonator, the resonant frequency was easily determined for all parts of the mouse, from the head to the lower abdomen. 3D EPR images of the mouse body from the thoracic region to the lower abdomen were obtained following infusion of a nitroxide, 3-carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl (CxP). The EPR images clearly visualized the CxP distribution in various organs at different concentrations. Time-dependent EPR images also revealed that the signal intensities of the CxP decayed over time, and the decay rates for the heart, liver, and kidneys were evaluated. A compact and mobile EPR imager that enables 3D whole-body EPR image of nitroxide in mice was developed. The EPR imager exhibited long-term stability against motion effects caused by respiratory motion and heartbeats in mice. The EPR images clearly visualized the in vivo distribution, clearance, and metabolism of the nitroxide in organs.

Process, dynamics and bioeffects of acoustic droplet vaporization induced by dual-frequency focused ultrasound.

Acoustic droplet vaporization (ADV) plays a crucial role in ultrasound-related biomedical applications. While previous models have examined the stages of nucleation, growth, and oscillation in isolation, which may limit their ability to fully describe the entire ADV process. To address this, our study developed an integrated model that unifies these three stages of ADV, stimulated by a continuous nonlinear dual-frequency ultrasound wave. Using this integrated model, we investigated the influence of nonlinear dual-frequency ultrasound parameters on ADV dynamics and bioeffects by incorporating tissue viscoelasticity through parametric studies. Our results demonstrated that the proposed model accurately captured the entire ADV process, ensuring continuous vapor bubble formation and evolution throughout the phase transition process. Moreover, the applied unified theory for bubble dynamics can simulate intense bubble collapse with high Mach Number as a result of the nonlinear effects of dual-frequency ultrasound. In addition, cavitation-associated mechanical and thermal damage appeared to be more strongly correlated with rapid bubble collapse than with maximum bubble size. Our research also revealed that the mechanical and thermal effects could be regulated independently to some extent by adjusting dual-frequency ultrasound parameters, as they presented differing sensitivities to frequency and acoustic power. Importantly, dual-frequency combinations such as 1.5MHz+3 MHz (fundamental and second harmonic), which exhibit a higher Degree of Nonlinearity (DoN) can extend bubble lifespan, offering a potential pathway to the efficacy of ultrasound treatments.

Ten Years of Perovskite Lasers.

Over the past decade, semiconducting halide perovskite lasers have emerged as a transformative platform in optoelectronics, owing to unique properties such as high photoluminescence quantum yields, tunable bandgaps, and low-cost fabrication processes. This review systematically examines the advancements in halide perovskite lasers, covering diverse laser architectures, such as whispering gallery mode, Fabry-Pérot, plasmonic, bound states in the continuum (BIC), quantum dot, and polariton lasers. The mechanisms of optical gain, the role of material engineering in optimizing lasing performance, and the challenges associated with continuous-wave (CW) pumping and electrically driven lasing are discussed. Furthermore, recent progress in improving the stability and scalability of perovskite lasers, essential for their integration into practical applications in displays, optical communications, sensing, and integrated photonics is highlighted. Finally, future research directions are discussed, emphasizing the potential of perovskite lasers to revolutionize various technological domains by enabling the development of next-generation photonic devices.

Heteroepitaxial (111) Diamond Quantum Sensors with Preferentially Aligned Nitrogen‐Vacancy Centers for an Electric Vehicle Battery Monitor

AbstractA platform for heteroepitaxial (111) chemical vapor deposition (CVD) diamond quantum sensors with preferentially aligned nitrogen vacancy (NV) centers on a large substrate is developed, and its operation as an electric vehicle (EV) battery monitor is demonstrated. A self‐standing heteroepitaxial CVD diamond film with a (111) orientation and a thickness of 150 µm is grown on a non‐diamond substrate and subsequently separated from it. The high uniformity and crystallinity of the (111)‐oriented diamond is confirmed. A 150‐µm thick NV‐diamond layer is then deposited on the heteroepitaxial diamond. The T2 value measured by confocal microscopy is 20 µs, which corresponds to substitutional nitrogen defect concentration of 8 ppm. The nitrogen‐vacancy concentration and T2* are estimated to be 0.05 ppm and 0.05 µs by continuous wave optically detected magnetic resonance (CW‐ODMR) spectroscopy in a fiber‐top sensor configuration. In a gradiometer, where two sensors are placed on both sides of the busbar, the noise floor is 17 nT/Hz0.5 in the frequency range of 10–40 Hz without magnetic shielding. The Allan deviation of the magnetic field noise in the laboratory is below 0.3 µT, which corresponds to a busbar current of 10 mA, in the accumulation time range of 10 ms to 100 s.