Synthesis and Unique Behaviors of High-Purity HEA Nanoparticles Using Femtosecond Laser Ablation.

High-entropy alloys (HEAs) are a class of metal alloys consisting of four or more molar equal or near-equal elements. HEA nanomaterials have garnered significant interest due to their wide range of applications, such as electrocatalysis, welding, and brazing. Their unique multi-principle high-entropy effect allows for the tailoring of the alloy composition to facilitate specific electrochemical reactions. This study focuses on the synthesis of high-purity HEA nanoparticles using the method of femtosecond laser ablation synthesis in liquid. The use of ultrashort energy pulses in femtosecond lasers enables uniform ablation of materials at significantly lower power levels compared to longer pulse or continuous pulse lasers. We investigate how various femtosecond laser parameters affect the morphology, phase, and other characteristics of the synthesized nanoparticles. An innovative aspect of our solution is its ability to rapidly generate multi-component nanoparticles with a high fidelity as the input multi-component target material at a significant yielding rate. Our research thus focuses on a novel synthesis of high-entropy alloying CuCoMn1.75NiFe0.25 nanoparticles. We explore the characterization and unique properties of the nanoparticles and consider their electrocatalytic applications, including high power density aluminum air batteries, as well as their efficacy in the oxygen reduction reaction (ORR). Additionally, we report a unique nanowire fabrication phenomenon achieved through nanojoining. The findings from this study shed light on the potential of femtosecond laser ablation synthesis in liquid (FLASiL) as a promising technique for producing high-purity HEA nanoparticles.

Photoplethysmography for Assessing Microcirculation in Hypertensive Patients After Taking Antihypertensive Drugs: A Review.

High blood pressure (BP) is a common disease and is associated with many chronic diseases. Measuring BP is essential for the treatment and management of many diseases, and therefore there is a growing need for a non-invasive, sleeveless and continuous BP monitoring device. With the development of technology, pulse waveform analysis using photoplethysmography (PPG) has become more feasible for evaluating BP. This study aimed to evaluate the changes of vascular elasticity and blood volume over time by using the characteristic parameters extracted by PPG. We reviewed the latest progress and literature on the observation of capillary network characteristics in hypertensive and non-hypertensive patients by PPG, the influence of different drugs on microcirculation characteristics in hypertensive patients with PPG, and further explored the key relationship between microcirculation and hypertension. We found that the PPG waveform produced by the fingertips of hypertensive patients is very different from that of healthy people, and the PPG waveform changes significantly during diastolic period after antihypertensive treatment. With the rapid development of medical technology, people can get more intuitive microcirculation image data, which provides beneficial help for the comprehensive understanding of hypertension.

Effect of repetitive transcranial magnetic stimulation combined with transcranial direct current stimulation on post-stroke dysmnesia: A preliminary study.

OBJECTIVE: This study examined the effect of repetitive transcranial magnetic stimulation (rTMS) combined with transcranial direct current stimulation (tDCS) as a bimodal neuromodulatory approach for post-stroke dysmnesia. METHODS: Thirty-four patients with post-stroke dysmnesia were randomly allocated into a sham group treated with neither rTMS nor tDCS, a group treated with rTMS, and a group treated with a combination of rTMS and tDCS. All three groups received cognitive rehabilitation training for 4 weeks. The memory function of each group before and after the intervention was assessed using the Montreal Cognitive Assessment (MoCA) and Rivermead Behavioral Memory Test (RBMT) scales, as well as in terms of the Mismatch Negativity（MMN）and P300 of event-related potentials. RESULTS: The sham, rTMS, and rTMS-tDCS groups all showed improvement in the total MoCA score after the intervention. Delayed recall, a MoCA item, scored better in the rTMS-tDCS group than in the rTMS and sham groups. Delayed processing, an RBMT item, scored better in the rTMS-tDCS combination group than in the rTMS and sham groups. MMN and P300 latency was significantly shorter in the rTMS-tDCS combination group. CONCLUSION: rTMS-tDCS bimodal stimulation was more effective than cognitive rehabilitation or rTMS alone in treating patients with post-stroke dysmnesia, offering new possibilities for enhancing cognitive function and treating post-stroke dysmnesia.

Femtosecond Laser-Induced Nano-Joining of Volatile Tellurium Nanotube Memristor.

Nanowire/nanotube memristor devices provide great potential for random-access high-density resistance storage. However, fabricating high-quality and stable memristors is still challenging. This paper reports multileveled resistance states of tellurium (Te) nanotube based on the clean-room free femtosecond laser nano-joining method. The temperature for the entire fabrication process was maintained below 190 °C. A femtosecond laser joining technique was used to form nanowire memristor units with enhanced properties. Femtosecond (fs) laser-irradiated silver-tellurium nanotube-silver structures resulted in plasmonic-enhanced optical joining with minimal local thermal effects. This produced a junction between the Te nanotube and the silver film substrate with enhanced electrical contacts. Noticeable changes in memristor behavior were observed after fs laser irradiation. Capacitor-coupled multilevel memristor behavior was observed. Compared to previous metal oxide nanowire-based memristors, the reported Te nanotube memristor system displayed a nearly two-order stronger current response. The research displays that the multileveled resistance state is rewritable with a negative bias.

An Improved Detection Algorithm for Ischemic Stroke NCCT Based on YOLOv5.

Cerebral stroke (CS) is a heterogeneous syndrome caused by multiple disease mechanisms. Ischemic stroke (IS) is a subtype of CS that causes a disruption of cerebral blood flow with subsequent tissue damage. Noncontrast computer tomography (NCCT) is one of the most important IS detection methods. It is difficult to select the features of IS CT within computational image analysis. In this paper, we propose AC-YOLOv5, which is an improved detection algorithm for IS. The algorithm amplifies the features of IS via an NCCT image based on adaptive local region contrast enhancement, which then detects the region of interest via YOLOv5, which is one of the best detection algorithms at present. The proposed algorithm was tested on two datasets, and seven control group experiments were added, including popular detection algorithms at present and other detection algorithms based on image enhancement. The experimental results show that the proposed algorithm has a high accuracy (94.1% and 91.7%) and recall (85.3% and 88.6%) rate; the recall result is especially notable. This proves the excellent performance of the accuracy, robustness, and generalizability of the algorithm.

Association between Changes in White Matter Microstructure and Cognitive Impairment in White Matter Lesions.

This study investigated the characteristics of cognitive impairment in patients with white matter lesions (WMLs) caused by cerebral small vessel disease and the corresponding changes in WM microstructures. Diffusion tensor imaging (DTI) data of 50 patients with WMLs and 37 healthy controls were collected. Patients were divided into vascular cognitive impairment non-dementia and vascular dementia groups. Tract-based spatial statistics showed that patients with WMLs had significantly lower fractional anisotropy (FA) and higher mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values throughout the WM areas but predominately in the forceps minor, forceps major (FMA), bilateral corticospinal tract, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, inferior longitudinal fasciculus (ILF), and anterior thalamic radiation, compared to the control group. These fiber bundles were selected as regions of interest. There were significant differences in the FA, MD, AD, and RD values (p < 0.05) between groups. The DTI metrics of all fiber bundles significantly correlated with the Montreal Cognitive Assessment (p < 0.05), with the exception of the AD values of the FMA and ILF. Patients with WMLs showed changes in diffusion parameters in the main WM fiber bundles. Quantifiable changes in WM microstructure are the main pathological basis of cognitive impairment, and may serve as a biomarker of WMLs.

Comparative study of photoplethysmographic waveforms with application of antihypertensive medication in hypertensive patients.

BACKGROUND: Multiple studies have been published using a pulse oximeter's photoplethysmographic (PPG) capability to detect tissue perfusion. However, the origin of the PPG signal is still debatable. AIM: A comparative study was performed of PPG waveforms in hypertensive patients before and after treatment with antihypertensive medication. The aim of this study was to observe the changes of PPG waveforms before and after lowering blood pressure in hypertensive patients and then to detect the relationship between blood pressure and PPG waveforms. METHODS: The PPG waveforms of 60 patients with hypertension were collected. After administration of the antihypertensive medication nitroglycerin, PPG waveforms were collected again. The changes of the T3 (time3): This phase occurred between Marker 3 and Marker 4 (this phase occurs mid-diastolic) angle, before and after the antihypertensive medication treatment, were compared. The statistical analyses of two related groups were performed using the Paired t-test. RESULTS: The blood perfusion waveforms of hypertensive patients before and after antihypertensive medication administration were differently indicated with the tilt angle T3. The slope angle of the T3 phase waveform increased significantly when the blood pressure dropped to normal (-41.9 ± 16.2° vs. -25.6 ± 21.9°, p < .0001), and the tilt angle of some patients was similar to that of adults with normal blood pressure. CONCLUSION: In patients with hypertension, the tilt angle of the PPG waveform in the T3 phase increased significantly after administration of the antihypertensive medication nitroglycerin. It is worth to conduct deeper research about the relationship between hypertension and the blood perfusion of microcirculation in the diastolic period.

Plasmonic Superstructure Arrays Fabricated by Laser Near-Field Reduction for Wide-Range SERS Analysis of Fluorescent Materials.

Surface-enhanced Raman scattering (SERS) enables trace-detection for biosensing and environmental monitoring. Optimized enhancement of SERS can be achieved when the energy of the localized surface plasmon resonance (LSPR) is close to the energy of the Raman excitation wavelength. The LSPR can be tuned using a plasmonic superstructure array with controlled periods. In this paper, we develop a new technique based on laser near-field reduction to fabricate a superstructure array, which provides distinct features in the formation of periodic structures with hollow nanoclusters and flexible control of the LSPR in fewer steps than current techniques. Fabrication involves irradiation of a continuous wave laser or femtosecond laser onto a monolayer of self-assembled silica microspheres to grow silver nanoparticles along the silica microsphere surfaces by laser near-field reduction. The LSPR of superstructure array can be flexibly tuned to match the Raman excitation wavelengths from the visible to the infrared regions using different diameters of silica microspheres. The unique nanostructure formed can contribute to an increase in the sensitivity of SERS sensing. The fabricated superstructure array thus offers superior characteristics for the quantitative analysis of fluorescent perfluorooctanoic acid with a wide detection range from 11 ppb to 400 ppm.

Phonetic versus spatial processes during motor-oriented imitations of visuo-labial and visuo-lingual speech: A functional near-infrared spectroscopy study.

While a large amount of research has studied the facilitation of visual speech on auditory speech recognition, few have investigated the processing of visual speech gestures in motor-oriented tasks that focus on the spatial and motor features of the articulator actions instead of the phonetic features of auditory and visual speech. The current study examined the engagement of spatial and phonetic processing of visual speech in a motor-oriented speech imitation task. Functional near-infrared spectroscopy (fNIRS) was used to measure the haemodynamic activities related to spatial processing and audiovisual integration in the superior parietal lobe (SPL) and the posterior superior/middle temporal gyrus (pSTG/pMTG) respectively. In addition, visuo-labial and visuo-lingual speech were compared with examine the influence of visual familiarity and audiovisual association on the processes in question. fNIRS revealed significant activations in the SPL but found no supra-additive audiovisual activations in the pSTG/pMTG, suggesting that the processing of audiovisual speech stimuli was primarily focused on spatial processes related to action comprehension and preparation, whereas phonetic processes related to audiovisual integration was minimal. Comparisons between visuo-labial and visuo-lingual speech imitations revealed no significant difference in the activation of the SPL or the pSTG/pMTG, suggesting that a higher degree of visual familiarity and audiovisual association did not significantly influence how visuo-labial speech was processed compared with visuo-lingual speech. The current study offered insights on the pattern of visual-speech processing under a motor-oriented task objective and provided further evidence for the modulation of multimodal speech integration by voluntary selective attention and task objective.

Association between cortical thickness and distinct vascular cognitive impairment and dementia in patients with white matter lesions.

NEW FINDINGS: What is the central question of this study? White matter lesions (WMLs) are a brain disease characterized by altered brain structural and functional connectivity, but findings have shown an inconsistent pattern: are there distinct cortical thickness changes in patients with WMLs subtypes? What is the main finding and its importance? Patients with WMLs with non-dementia vascular cognitive impairment and WMLs with vascular dementia showed distinct pathophysiology in cortical thickness. These neural correlates of WMLs should be considered in future treatment. ABSTRACT: The effect of cortical thickness on white matter lesions (WMLs) in patients with distinct vascular cognitive impairments is relatively unknown. This study investigated the correlation between cortical thickness and vascular cognitive manifestations. WML patients and healthy controls from Beijing Tiantan Hospital between 2014 and 2018 were included. The patients were further divided into two subgroups, namely WMLs with non-dementia vascular cognitive impairment (WML-VCIND) and WMLs with vascular dementia (WML-VaD) according to the Clinical Dementia Rating (CDR) scale and the Beijing version of the Montreal Cognitive Assessment (MoCA). Changes in cortical thickness were calculated using FreeSurfer. Pearson's correlation analysis was performed to explore the relationship between cognitive manifestations and cortical thickness in WML patients. Forty-five WML patients and 23 healthy controls were recruited. The WML group exhibited significant difference in cortical thickness compared to the control group. Significantly decreased cortical thickness in the middle and superior frontal gyri, middle temporal gyrus, angular gyrus and insula was found in the WML-VaD versus WML-VCIND subgroup. Cortical thickness deficits of the left caudal middle frontal gyrus (r = 0.451, P = 0.002), left rostral middle frontal gyrus (r = 0.514, P < 0.001), left superior frontal gyrus (r = 0.410, P = 0.006), right middle temporal gyrus (r = 0.440, P = 0.003), right pars triangularis (r = 0.462, P = 0.002), right superior frontal gyrus (r = 0.434, P = 0.004) and right insula (r = 0.499, P = 0.001) were positively correlated with the MoCA score in WML patients. The specific pattern of cortical thickness deficits in the WML-VaD subgroup revealed the pathophysiology of WMLs, which should be considered in future treatment of WMLs.

Femtosecond laser-induced non-thermal welding for a single Cu nanowire glucose sensor.

Copper nanowires (CuNWs) are a key building block to facilitate carrier conduction across a broad range of nanodevices. For integration into nanoscale devices, manipulation and welding of these nanowires need to be overcome. Based on high energy density laser processing investigation, we report on innovative welding of single CuNWs to a silver film using a tightly focused laser beam combined with manipulation of CuNWs through the dielectrophoresis (DEP) method. Two types of lasers, femtosecond (FS) and continuous-wave (CW), were employed to analyze, improve, and control Cu-NW melting characteristics under high energy density irradiation. The FS laser welding of CuNWs resulted in a metallic joint with a low contact resistance suitable for functional electronic nanodevices. Computational simulations using the 1-D heat diffusion equation and finite difference method (FDM) were performed to gain an insight into metal-laser interactions for high performance welded contact development. Simulation studies on lasers established contrasting melting behavior of metal under laser irradiation. The device feasibility of CuNW based welded contacts was evaluated in terms of the electrical performance of a glucose sensor. It was possible to sense glucose concentration down to 10-6 M, demonstrating a path towards integration of CuNWs into wearable, flexible nanoelectronic devices.

Rapid detection of trace Cu2+ using an l-cysteine based interdigitated electrode sensor integrated with AC electrokinetic enrichment.

Copper is an indispensable trace element for human health. Too much or too little intake of copper ion (Cu2+ ) can lead to its own adverse health conditions. Therefore, detection of Cu2+ is always of vital importance. In this work, a simple sensor was developed for rapid detection of trace Cu2+ in water, in which L-cysteine (Cys) as a molecular probe was self-assembled on a gold interdigital electrode to form a monolayer for specific capture of Cu2+ . The interfacial capacitance of interdigital electrode was detected to indicate the target adsorption level under an AC signal working as the excitation to induce directed movement and enrichment of Cu2+ to the electrode surface. This sensor reached a limit of detection of 4.14 fM and a satisfactory selectivity against eight other ions (Zn2+ , Hg2+ , Pb2+ , Cd2+ , Mg2+ , Fe2+ , As3+ , and As5+ ). Testing of spiked tap water was also performed, demonstrating the sensor's usability. This sensor as well as the detection method shows a great application potential in fields such as environmental monitoring and medical diagnosis.

Fe-based ceramic nanocomposite membranes fabricated via e-spinning and vacuum filtration for Cd2+ ions removal.

In this work, vacuum filtered and polymer mixed e-spinning membranes (ESPMs) made from or doped with Fe-based nanomaterials were successfully fabricated to remove Cd2+ ions from a neutral aqueous solution. The used Fe-based nanomaterials including FeOOH precursor Nanowires (NWs), α-Fe2O3 NWs and Fe3O4 nanoparticles (NPs) were synthesized by elevating the hydrothermal reaction temperature from 250 °C to 500 °C or doing post-heating treatment. The adsorption results showed that vacuum filtered membranes (VFMs) overall performed a better Cd2+ ions removal behavior than e-spinning ones. Among them, VFM made from Fe3O4 NPs has the highest adsorption capacity (qt) with the adsorption amount of Cd2+ ions reaching about 29.3 mg/g within only 2 min due to the high specific surface area of NPs. Models of pseudo-first-order, pseudo-second-order and intraparticle diffusion were used to study the kinetics of Cd2+ ions removal process, and a high correlation coefficient (R2) of 0.99 was obtained when pseudo-second-order model was used. It was calculated that the equilibrium rate constant of VFM made from Fe3O4 NPs has reached about 0.28 g mg-1 min-1, much smaller than those of other membranes, which indicated a high Cd2+ ions removal efficiency.

Laser-Induced Carbon-Based Smart Flexible Sensor Array for Multiflavors Detection.

We report a flexible sensor array electronic tongue system that is fabricated on a polymer substrate by the laser direct writing process for multiflavor detection. Electronic tongue is a sensing system that is applied to detect different elements with the same sensor array. By analyzing responses from different measurement units, it enables a cross-sensitivity, namely, the ability of the system to responding to a range of different analytes in solution without specific functionalization of sensors. In this article, a six-unit sensing array system was fabricated by a laser direct writing process. Sensing units were introduced on a flexible polyamide surface. A high surface-volume ratio porous carbon structure was created by a laser-induced carbonization process, which provides stable conductive carbon electrodes with high sensitivity. Different surface treatments, such as gold plating, reduced-graphene oxide coating, and polyaniline coating, were accomplished for different measurement units. By applying principal component analysis, this sensing system shows a promising result for the detection of multiple flavors. The detection limit for each element is about 0.1 mM for NaCl and sugar solutions. Also, it is able to detect 10-4 times diluted commercial table vinegar solution, which originally contains 5% acetic acid. The detection limit is theoretically lower than the human threshold of 10 mM for NaCl and sugar. Besides, the sensing system shows a high sensitivity and selectivity for mixed elements. By mapping the data points, the sensor system could detect flavor combinations and provide a reliable prediction of analyte concentration ratios.

Laser-Assisted Reduction of Highly Conductive Circuits Based on Copper Nitrate for Flexible Printed Sensors.

Stretchable electronic sensing devices are defining the path toward wearable electronics. High-performance flexible strain sensors attached on clothing or human skin are required for potential applications in the entertainment, health monitoring, and medical care sectors. In this work, conducting copper electrodes were fabricated on polydimethylsiloxane as sensitive stretchable microsensors by integrating laser direct writing and transfer printing approaches. The copper electrode was reduced from copper salt using laser writing rather than the general approach of printing with pre-synthesized copper or copper oxide nanoparticles. An electrical resistivity of 96 µΩ cm was achieved on 40-µm-thick Cu electrodes on flexible substrates. The motion sensing functionality successfully demonstrated a high sensitivity and mechanical robustness. This in situ fabrication method leads to a path toward electronic devices on flexible substrates.

Laser-Direct Writing of Silver Metal Electrodes on Transparent Flexible Substrates with High-Bonding Strength.

We demonstrate a novel approach to rapidly fabricate conductive silver electrodes on transparent flexible substrates with high-bonding strength by laser-direct writing. A new type of silver ink composed of silver nitrate, sodium citrate, and polyvinylpyrrolidone (PVP) was prepared in this work. The role of PVP was elucidated for improving the quality of silver electrodes. Silver nanoparticles and sintered microstructures were simultaneously synthesized and patterned on a substrate using a focused 405 nm continuous wave laser. The writing was completed through the transparent flexible substrate with a programmed 2D scanning sample stage. Silver electrodes fabricated by this approach exhibit a remarkable bonding strength, which can withstand an adhesive tape test at least 50 times. After a 1500 time bending test, the resistance only increased 5.2%. With laser-induced in-situ synthesis, sintering, and simultaneous patterning of silver nanoparticles, this technology is promising for the facile fabrication of conducting electronic devices on flexible substrates.

Bisphenol A Sensors on Polyimide Fabricated by Laser Direct Writing for Onsite River Water Monitoring at Attomolar Concentration.

This work presents an aptamer-based, highly sensitive and specific sensor for atto- to femtomolar level detection of bisphenol A (BPA). Because of its widespread use in numerous products, BPA enters surface water from effluent discharges during its manufacture, use, and from waste landfill sites throughout the world. On-site measurement of BPA concentrations in water is important for evaluating compliance with water quality standards or environmental risk levels of the harmful compound in the environment. The sensor in this work is porous, conducting, interdigitated electrodes that are formed by laser-induced carbonization of flexible polyimide sheets. BPA-specific aptamer is immobilized on the electrodes as the probe, and its binding with BPA at the electrode surface is detected by capacitive sensing. The binding process is aided by ac electroosmotic effect that accelerates the transport of BPA molecules to the nanoporous graphene-like structured electrodes. The sensor achieved a limit of detection of 58.28 aM with a response time of 20 s. The sensor is further applied for recovery analysis of BPA spiked in surface water. This work provides an affordable platform for highly sensitive, real time, and field-deployable BPA surveillance critical to the evaluation of the ecological impact of BPA exposure.

A Facile Method to In-Situ Synthesize Porous Ni2GeO4 Nano-Sheets on Nickel Foam as Advanced Anode Electrodes for Li-Ion Batteries.

A strategy for growth of porous Ni2GeO4 nanosheets on conductive nickel (Ni) foam with robust adhesion as a high-performance electrode for Li-ion batteries is proposed and realized, through a facile two-step method. It involves the low temperature hydro-thermal synthesis of bimetallic (Ni, Ge) hydroxide nanosheets precursor on Ni foam substrates and subsequent thermal transformation to porous Ni2GeO4 nanosheets. The as-prepared Ni2GeO4 nanosheets possess many interparticle mesopores with a size range from 5 to 15 nm. The hierarchical structure of porous Ni2GeO4 nanosheets supported by Ni foam promises fast electron and ion transport, large electroactive surface area, and excellent structural stability. The efficacy of the specially designed structure is demonstrated by the superior electrochemical performance of the generated Ni2GeO4 nanosheets including a high capacity of 1.8 mA·h·cm-2 at a current density of 50 µA·cm-2, good cycle stability, and high power capability at room temperature. Because of simple conditions, this fabrication strategy may be easily extended to other mixed metal oxides (MxGeOy).

Fabrication, characterization, and applications of microlenses.

Microlenses (MLs) and microlens arrays (MLAs) are assuming an increasingly important role in optical devices. In response to this rapid evolution in technology, emphasis is being placed on research into new manufacturing methods for these devices as well as the characterization of their performance. This paper provides an overview of the fabrication of MLs and MLAs by electrical, mechanical, chemical, and optical methods. As each processing method has distinct advantages and limitations, the most significant characteristic parameters and the measurement of these parameters are discussed for each method. These parameters are then used as indices to evaluate and improve each of the processing methods. Some examples of practical applications of MLAs, especially for micromechanical optoelectronic devices, are also given. This paper aims to summarize the present development and the state of the art in processing technology of MLs and MLAs.

Fabrication of embedded microball lens in PMMA with high repetition rate femtosecond fiber laser.

Embedded microball lenses with superior optical properties function as convex microball lens (VMBL) and concave microball lens (CMBL) were fabricated inside a PMMA substrate with a high repetition rate femtosecond fiber laser. The VMBL was created by femtosecond laser-induced refractive index change, while the CMBL was fabricated due to the heat accumulation effect of the successive laser pulses irradiation at a high repetition rate. The processing window for both types of the lenses was studied and optimized, and the optical properties were also tested by imaging a remote object with an inverted microscope. In order to obtain the microball lenses with adjustable focal lengths and suppressed optical aberration, a shape control method was thus proposed and examined with experiments and ZEMAX® simulations. Applying the optimized fabrication conditions, two types of the embedded microball lenses arrays were fabricated and then tested with imaging experiments. This technology allows the direct fabrication of microlens inside transparent bulk polymer material which has great application potential in multi-function integrated microfluidic devices.