A study of direct welding of dissimilar materials of borosilicate glass and 304 stainless steel using a green picosecond laser

Cerebellar focused ultrasound stimulation modulates neural response at hippocampus and suppresses epileptiform activity.

Low-intensity pulsed ultrasound (LIPUS) is approved to promote healing in non-union bone fractures in the UK (NICE) and USA (FDA). Despite extensive in vitro, pre-clinical, and clinical data indicating efficacy, patient outcomes remain inconsistent. A deeper understanding of the mechanisms by which ultrasound vibrations influence cellular behaviour is critical to optimising LIPUS for bone repair and to enable greater patient benefit. The literature offers a broad experimental base, but collective insights are hindered by two key issues: inadequate reporting of ultrasound exposure conditions, often overlooking reflections and standing waves, and reliance on spatial average temporal average intensity (ISATA) as the sole metric of ultrasound dose. While ISATA informs safety thresholds (TI, MI), it fails to describe the specific acoustic stimuli cells experience, masking variations in pressure, pulse repetition, and duty cycle. To identify the ultrasound parameters that are most important for eliciting mechano-sensing responses in osteoblast-like cells, we systematically evaluated a 1MHz pulsed field in a controlled cell culture environment. Immunofluorescence analysis of actin and vinculin were used to assess cytoskeletal changes in response to fully described LIPUS exposures. We identified a pulse repetition frequency (PRF) upper limit of 1kHz, beyond which LIPUS lost efficacy in enhancing mechano-sensing. Optimal response occurred at 20% duty cycle, 160kPa, and 60mW/cm2 ISATA, challenging the currently accepted standard and parameters used to operate existing clinical devices (1MHz, 30mW/cm2 ISATA). Our data demonstrate the necessity to report fully the parameters that describe the ultrasound dose experienced by cells to predict which conditions lead to an upregulation in mechano-sensing and that ISATA alone is not an adequate measure unless all other parameters are known and fixed. Finally, since PRF is determinant of achieving a cellular response, we reaffirm the already accepted understanding that pulsed exposures are critical to a cellular ability to detect and/or respond to ultrasound in a way that is useful for fracture repair.

SuperSTF: A latent diffusion model for cloud-free spatiotemporal remote sensing image fusion

In the ever-evolving landscape of communication technology, the pursuit of faster, more efficient, and more reliable data transmission remains a cornerstone of innovation. In this manuscript, we present a proof-of-concept for what we believe to be a novel, low-cost method of free-space directional spatio-temporal data transmission. The proposed approach utilizes the sensing of speckle patterns generated from the surface of a micro-electromechanical (MEMS) matrix, realized by a piezoelectric micro-speaker array illuminated by a laser beam. Each speaker in the matrix is activated at a predefined frequency, creating a spatial-to-frequency–encoded mapping of the transmitted data. The speckle pattern reflected from the vibrating surface varies temporally according to the spatial data pattern, effectively encoding each pixel with a distinct temporal frequency. By simultaneously utilizing both the temporal and spatial domains, this method offers a framework to considerably increase throughput compared to systems based solely on temporal modulation. Furthermore, this approach enables the recovery of data without the need for high-magnification or high-cost optics; unlike conventional imaging methods, it avoids the impractical focal length requirements typically associated with long-distance communication.

Single-photon lidar (SPL) measures the time delay between a laser pulse emission and a single photon detection. SPL typically uses a periodic sequence of illumination pulses to improve the accuracy of distance estimates, and the radial velocity of a moving target can also be determined from the Doppler shift in the pulse repetition frequency. Although increasing the repetition frequency increases the photon detection rate, it also decreases the unambiguous range. Several alternative pulsing modes have been proposed to break this tradeoff for SPL measurements of static scenes, e.g., using multiple repetition rates or random pulse trains to yield both high count rates and a long unambiguous range. In this work, we show that velocity can still be estimated despite the use of non-periodic range extension pulse patterns. We derive a general model for the photon acquisition process with a moving target and propose maximum likelihood estimators (MLEs) to recover the distance, velocity, and photon flux levels. Each range extension mode requires a tailored initialization scheme in order for our MLE solver to converge to the global optimum. We demonstrate through simulations and experiments that non-periodic SPL can simultaneously achieve long-range, high-accuracy distance and velocity estimates.

Diagnostic test accuracy of the pattern electroretinogram for glaucoma: a systematic review and meta-analysis.

Pulse repetition frequency (PRF) controls pulse off-time and, therefore, the extent of thermal accumulation, melt expulsion, and dielectric recovery in finishing electrical discharge machining (EDM). This study clarifies how PRF modifies crater evolution and surface integrity in finishing EDM of 4Cr13 martensitic stainless steel, a corrosion-resistant mold steel used in precision dies and molds. A 2D axisymmetric electro-thermo-fluid model was established in COMSOL, where Gaussian current density, heat-flux, and plasma pressure were periodically imposed at PRFs of 25–100 kHz, while pulse-on time (6 μs) and peak current (8 A) were kept constant. The simulations tracked the transient pressure, heat-flux, velocity, and temperature fields over a common elapsed time of 25 μs. Finishing experiments were then carried out on flat 4Cr13 coupons at 50, 75, and 100 kHz using a copper electrode and deionized water, followed by characterization by laser confocal microscopy, SEM/EDS, and X-ray diffraction using the cosα method. Increasing PRF localized the coupled pressure-heat-flow fields near the crater rim, but shortened off-time and intensified inter-pulse heat accumulation. Accordingly, the surface roughness decreased from Ra = 1.18 μm at 50 kHz to 0.63 μm at 75 kHz, and then slightly increased to 0.71 μm at 100 kHz because of crater overlap, re-melting, and incomplete gap recovery. SEM observations confirmed large irregular craters with cracks at 50 kHz, more uniform fine craters at 75 kHz, and overlapping re-solidified traces at 100 kHz. The residual stress remained compressive for all tested conditions (−341 to −409 MPa). Overall, 75 kHz offers the best compromise between crater uniformity, roughness, and compressive stress for finishing EDM of 4Cr13 steel.

The organization of the phase of electrical activity in the cortex is critical to inter-site communication, but the balance of this communication across large-scale (>8 cm), macroscopic (>1 cm), and mesoscopic (1 cm to 1 mm) ranges is an open question. The spatial frequencies (i.e. the spatial scales) of cortical waves have been characterized in the gray matter for micro- and mesoscopic scales of cortex and show decreasing spatial power with increasing spatial frequency. This research, however, has been limited by the size of the measurement array, thus excluding large-scale traveling waves. Obversely, poor spatial resolution of extracranial measurements prevents incontrovertible large-scale estimates of spatial power. We estimate the spatial frequency spectrum of phase dynamics in order to quantify the uncertain large-scale range, utilizing stereotactic electroencephalogram to measure local-field potentials within the gray matter. We take advantage of the large extent of spatial coverage of the cortical sheet, and irregular sampling is offset by use of linear algebra techniques. We find the spatial power of the phase is highest at the lowest spatial frequencies (longest wavelengths), consistent with the power spectra ranges for micro- and meso-scale dynamics, but here shown up to the size of the measurement array (up to 8-16 cm). This result arises across a wide range of temporal frequencies, from the delta band (1-3 Hz) through to the high gamma range (60-100 Hz).

Accurate monitoring of water spatiotemporal dynamics is critical for hydrological process analysis and climate impact assessment. While remote sensing enables effective water monitoring, public satellite imagery is limited by mixed-pixel effects that hinder small river detection, and high-resolution commercial data suffers from low temporal frequency and restricted coverage. To address these limitations, this study proposes a deep learning-based super-resolution (SR) framework for multispectral remote sensing imagery. This paper constructs a matched dataset for GF2 and Sentinel-2 imagery and develops an Attention Enhanced Super Resolution Generative Adversarial Network (AESRGAN). By integrating attention mechanisms and a spectral-structural loss design, the network is optimized to adapt to the characteristics of multispectral remote sensing imagery. Experimental results demonstrate that AESRGAN achieves strong reconstruction performance, with a Peak Signal-to-Noise Ratio (PSNR) of 33.83 dB and a Structural Similarity Index Measure (SSIM) of 0.882. Water extraction based on the reconstructed imagery using the U-Net++ model achieved an overall accuracy of 0.97 and a Kappa coefficient of 0.92. In addition, the reconstructed imagery improved the estimation accuracy of river length, width, and area by 0.34%, 3.28%, and 8.51%, respectively. The proposed framework provides an effective solution for multi-source remote sensing data fusion and high-precision surface water monitoring, offering new potential for long-term hydrological observation using medium-resolution satellite imagery.

The photopic negative response (PhNR) is a measure of generalised retinal ganglion cell function. There has been heterogenous methodology to record this, with varied electrode type, stimulus luminance, temporal frequency and measurement approach. This study aimed to empirically explore these features to identify an optimal PhNR luminance-response protocol which produces the lowest variance and maximal efficiency to guide clinical protocols. Twelve healthy participants were recruited (age range 27-51y). Flash ERGs were simultaneously recorded from infraorbital skin and corneal fibre electrodes to a range of red flash stimuli (-0.3-2.4 log cd.s/m2, incremented in 0.3 log units), whilst varying temporal frequency (1-5Hz), background blue luminance (1, 1.5, 2 log cd/m2), and PhNR measurement approach (from baseline or b-wave, as an amplitude or ratio). The luminance-response series data were analysed for changes according to these variables, alongside a calculation of variability. The PhNR luminance-response curves showed few significant differences with increasing temporal frequency, though inter-subject variability was highest for the slowest (1Hz) and highest flash (5Hz) stimulation rates. Background luminance reduced the relative sensitivity (K) but not maximal amplitude of the luminance-response curves (Vmax). With skin electrodes the b-PhNR amplitude and b-PhNR ratio showed the lowest levels of variability compared with other measurement approaches or electrodes. This study demonstrates that temporal frequency can be increased significantly, optimally at 4Hz, without compromising the PhNR. PhNR variance is lower with skin electrode recordings and PhNR amplitude measurements from the b-wave compared to corneal fibre electrodes and baseline-PhNR amplitudes.

Abstract We present a thermal simulation study of the KrF excimer laser doping of Sn into β-Ga 2 O 3 (010) from a SnO 2 top layer. Under various conditions, the laser doping experiments and technology computer-aided design (TCAD) simulations were executed, and their results were comparatively analyzed. The transient temperature-field analysis revealed that each laser pulse induced an intense but transient (~ 100 ns) temperature peak confined to a shallow surface region (sub-μm). At a high repetition frequency of 1000 Hz, the incomplete cooling between pulses causes significant heat accumulation at the surface, resulting in enhanced Sn diffusion at 0.3 J/cm 2 , whereas it was negligible at 100 Hz. The diffusion lengths were estimated from the simulated temperature results, and they showed good agreement with the Sn depth profiles. These results demonstrate that TCAD-based thermal simulation is effective for describing the temperature field and the dopant diffusion in excimer laser doping of β-Ga 2 O 3 .

Abstract We report a compact and narrow spectral linewidth SiN/Si hybrid wavelength-tunable laser for FMCW applications that can generate broadband chirped light at megahertz-order repetition frequency. The hybrid SiN/Si structure enables both narrow linewidth of 2.3 kHz and high-repetition-frequency chirped light generation via the thermo-optic effect. The chirped bandwidth is 0.66 GHz at a repetition frequency of 1 MHz and 2.25 GHz at 100 kHz. In addition, we confirmed that applying an optimized jump to the driving voltage waveform improves the chirp linearity. At a repetition frequency of 100 kHz, a deviation-from-linearity metric of 1-r^2 value of {7.6\times10}^{-4} was achieved without using a linearization algorithm based on a feedback loop. Using this device, short-distance ranging was achieved at a repetition frequency of 1 MHz. Furthermore, long-distance ranging of 50 m was demonstrated at a repetition frequency of 1 kHz.

Abstract We report a dissipative soliton laser utilizing thulium-doped fiber as the saturable absorber. By adjusting the polarization controller and pump power, a stable fundamental dissipative pulse has been successfully achieved, featuring a center wavelength of 1565.88 nm, a 3 dB bandwidth of 1.20 nm, a repetition frequency of 36.9 MHz, and a signal-to-noise ratio of 64 dB. Combined the gradual increase of the pump power with the intracavity polarization optimization, the spectral morphology evolves into a parabolic shape, П-shape and M-shape. Moreover, through increasing the gain, multiple dissipative pulses include dissipative soliton pairs and triples are manifested because of the peak power clamping effect. The repetition frequencies are 73.8 MHz and 110.7 MHz, respectively, with signal-to-noise ratios both more than 60 dB, indicating that the constructed dissipative soliton laser has excellent stability. This study not only enhances the understanding of the nonlinear dynamic process of dissipative soliton generation, but also offers a novel approach for designing ultrafast lasers characterized by high stability and an all-fiber structure.

ABSTRACTUnderstanding the relationship between species occupancy and abundance is a central goal in macroecology. The positive link between species spatial occupancy—the fraction of sites in which a species is present—and mean local abundance has been dubbed a ‘macroecological law’. However, this relationship fails to capture changes in occupancy over time. Temporal occupancy—estimated as the fraction of times a species is recorded in each site—has been used to explore species persistence in local communities but has no clear relationship with mean local abundance. That is, do more persistent species tend to occur at higher abundance? Further, how might species temporal occupancy relate to their spatial occupancy? We explored the relationship between spatial and temporal occupancy, and their respective relationships with mean local abundance using standardized sampling data of small mammal communities from the National Ecological Observatory Network (NEON). These sampling data spanned across the United States from 2014 to 2019. Except for several range‐restricted species, species that occupied a greater fraction of sites also tended to occupy individual sites more frequently. Additionally, species that were more widespread (high spatial occupancy) and/or more persistent (high temporal occupancy) tended to occur with greater local abundance. However, the highest local abundance was observed for geographically restricted but temporally persistent species. This indicates that while there is support for the positive abundance‐spatial occupancy relationship, spatial occupancy alone may underestimate the abundance of range restricted species. In such cases, high local abundance may be better explained by the temporal frequency in which species occupy sites. Taken together, these results demonstrate the positive relationship between spatial and temporal occupancy and highlight the utility of considering temporal occupancy alongside spatial occupancy for understanding abundance patterns.

Nonlinear Response of Phospholipid-Shelled Ultrasound Contrast Agents: Ambient Conditions Affect Temporal Evolution.

The drive to miniaturize optical frequency combs for practical deployment has spotlighted microresonator solitons as a promising chip-scale candidate. However, these soliton microcombs could be very power-hungry when their span increases, especially with fine comb spacings. As a result, realizing an octave-spanning comb at microwave repetition rates for direct optical-microwave linkage is considered not possible for photonic integration due to the high power requirements. Here, we introduce the concept of resonant-coupling to soliton microcombs to reduce pump consumption significantly. Compared to conventional waveguide-coupled designs, we demonstrate (i) a threefold increase in spectral span for high-power combs and (ii) up to a tenfold reduction in repetition frequency for octave-spanning operation. This configuration is compatible with laser integration and yields reliable, turnkey soliton generation. By eliminating the long-standing pump-power bottleneck, microcombs will soon become readily available for portable optical clocks, massively parallel data links, and field-deployable spectrometers.

Organic semiconductors have been widely used to fabricate optoelectronic devices due to their low-cost processing, high mechanical flexibility, high tunable emission wavelength, etc. However, the development of a deep blue organic laser remains constrained, and continuous-wave (CW) operation faces significant challenges due to issues such as singlet-triplet annihilation (STA) and triplet accumulation. In this study, we use two synthesized blue organic molecules, 2-(4-(7-(dibenzo[b,d]furan-3-yl)-9,9-dipropyl-9H-fluoren-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (PWO1) and 2-(4-(7-(dibenzo[b,d]furan-4-yl)-9,9-dipropyl-9H-fluoren-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (PWO2), with a hybridized local and charge-transfer (HLCT) mechanism to study their lasing characteristics. We found that the incorporation of fluorene bridges into molecules significantly enhances the oscillator strength, thus greatly reducing the amplified spontaneous emission (ASE) threshold, which reaches values as low as 1.15 and 0.60 μJ cm-2 for PWO1 and PWO2, respectively, and a long operational lifetime of 105 pump pulses under ambient conditions is observed for PWO2. At a high repetition frequency of 200 kHz, which approximates quasi-continuous-wave (qCW) operation, PWO2 exhibits an invariable ASE threshold, indicating its good photostability. The superior lasing performance is attributed to the negligible overlap between the triplet excited-state absorption and ASE spectra. Furthermore, the external quantum efficiency (EQE) values of the fabricated deep blue organic light-emitting diodes based on PWO1 and PWO2 reach values of 8.22% and 7.26%, respectively, with extremely low efficiency roll-off, which is particularly favorable for the high-current injection required for electrically pumped organic lasers.

Ultrasound offers a noninvasive, clinically relevant means to achieve precise spatiotemporal control of cargo release from ultrasound-responsive drug delivery systems within deep tissues. This approach enables targeted delivery of therapeutic agents, enhancing efficacy while minimizing systemic toxicity. While previous studies show that release from ultrasound-responsive liposomes depends on acoustic parameters, the underlying mechanisms remain unclear. A deeper mechanistic understanding is essential to achieve precision over release and maximize therapeutic outcomes. To address this, we propose a sonoporation-based framework to describe release dynamics across varying frequencies, pressures, duty cycles, and pulse repetition frequencies for ultrasound-responsive poly(ethylene glycol)-functionalized liposomes. Using computational simulations validated by empirical results, our framework identifies a critical pressure threshold for release onset and demonstrates how the time spent above this threshold, modulated by acoustic parameters, governs release efficiency. To elucidate these effects, custom-built ultrasound transducers with different resonance frequencies were fabricated and characterized to ensure precise sample alignment, minimize acoustic distortion, and maintain a controlled focal-volume-to-sample-volume ratio across different frequencies. COMSOL simulations indicated that oscillatory acoustic pressure plays a more dominant role than acoustic radiation force, while coarse-grained molecular dynamics simulations captured pressure-dependent pore formation dynamics within the lipid bilayer. Together, our experiments and simulations highlight mechanical effects-particularly oscillatory acoustic pressure-as the primary driver of sonoporation-facilitated release. Finally, we discuss how optimizing acoustic parameters through this mechanistic framework could facilitate safe and effective clinical translation by considering tissue safety and ultrasound transducer design.

Transcranial focused ultrasound (tFUS) can noninvasively modulate sensory pathways, but the cell-type-specific mechanisms underlying excitatory or inhibitory effects remain unclear. Here, we investigate how tFUS applied to the somatosensory cortex (S1) influences S1 and posterior medial thalamic nucleus (POm) responses to hind paw vibration-tactile stimulation and which neuronal populations mediate these effects. Vibration-tactile stimulation evoked potentials (TEPs) and multi-unit activities (MUA) in S1 and POm were recorded from male rats. Optogenetic tagging was used to identify S1 CaMKII-positive, PV-positive, and SST-positive neurons, while waveform features were used to classify putative excitatory (i.e., regular-spiking units - RSUs) and inhibitory neurons (i.e., fast-spiking units - FSUs) in POm. We found that only S1 CaMKII-positive neurons and POm RSUs responded robustly to tactile stimulation. When tFUS was applied to S1, high pulse repetition frequency (PRF), high duty cycle, and high-pressure stimulation (etFUS) produced excitatory modulation of the sensory pathway, whereas low PRF, low duty cycle, and low-pressure stimulation (itFUS) induced inhibitory effects. Further analyses revealed that excitatory modulation was mediated by activation of S1 CaMKII-positive neurons, while the inhibitory effect arose from their deactivation. These findings demonstrate that tFUS exerts bidirectional, parameter-dependent modulation of a sensory pathway and highlight the critical role of CaMKII-positive neurons in mediating these effects. This study provides mechanistic insight into cell-type-specific neuromodulation by tFUS, particularly in bidirectional modulation of a sensory pathway, and informs the optimization of stimulation parameters for targeted therapeutic interventions.