Search

Twin graphene can introduce stable and extended defects to energy band engineering, giving unique electron transport properties, which is expected to have potential applications in the fields of magnetism, spin transport or photoluminescence. This study proposes a method of using electric-field-assisted temporally-shaped femtosecond laser ablation liquid (ETLAL) of graphene dispersion to prepare graphene quantum dots (GQDs) with an average particle size of 2–3 nm and oxygen-containing functional groups modified surface, which realizes the controllable preparation of single crystal and twin GQDs (5-fold twin). This method controls the crystallinity of GQDs from two aspects: (1) The intervention of an electric field can rapidly command the directional motion of the cavitation bubbles and the nanoparticles contained therein to collide and crystallize at higher temperatures and pressures, which is the key to the formation of twin GQD; (2) Adjusting temporally-shaped femtosecond laser pulse delay could control the proportion of the Coulomb explosion during the ablation process, which increases the carbon cluster supplied by the cavitation bubble which is the key of polyploid number in twin GQDs. This research provides a fast, green strategy for the preparation of unprecedented twin GQDs, which is of great significance to the applications in the field of 2D material defect engineering.

A one-step method was proposed to prepare a high-performance surface-enhanced Raman scattering (SERS) substrate based on bulk MoS2 via femtosecond laser pulse modification. The Raman spectra of Rho...

Tougher when stressed Hydrogels are typically weak materials because they contain only a small fraction of polymeric material highly swollen with water. Strength can be increased by adding extra cross-linking or interpenetrating networks with some sacrificial bonds to enhance toughness; however, these properties deteriorate upon stretching and may be slow to recover after relaxation. Liu et al. developed polyethylene glycol hydrogels cross-linked with moderate fractions of polymers that form sliding rings. These allow the chain to orient in parallel when stretched, leading to rapid and reversible strain-induced crystallization and thus much tougher hydrogels. Science , aaz6694, this issue p. 1078

Importance. Acupuncture is an effective treatment for stroke, especially in the aspect of motor deficit. Many brain imaging studies of acupuncture have found significant changes in brain function after acupuncture treatment in order to reveal its underlying mechanisms in regulating neural plasticity. However, no definite consensus has been reached. Objective. To analyze the pattern of intrinsic brain activity variability that is altered by acupuncture compared with conventional treatment in stroke patients with motor dysfunction, thus providing the mechanism of stroke treatment by acupuncture. Methods. Chinese and English articles published up to May 2020 were searched in the PubMed, Web of Science, EMBASE, and Cochrane Library databases, China National Knowledge Infrastructure, Chongqing VIP, and Wanfang Database. We only included randomized controlled trials (RCTs) using resting-state fMRI to observe the effect of acupuncture on stroke patients with motor dysfunction. R software was used to analyze the continuous variables, and Seed-based d Mapping with Permutation of Subject Images (SDM-PSI) was used to perform an analysis of fMRI data. Findings. A total of 7 studies comprising 143 patients in the treatment group and 138 in the control group were included in the meta-analysis. The results suggest that acupuncture treatment helps the healing process of motor dysfunction in stroke patients and exhibits hyperactivation in the bilateral basal ganglia and insula and hypoactivation in motor-related areas (especially bilateral BA6 and left BA4). Conclusion. Acupuncture plays a role in promoting neuroplasticity in subcortical regions that are commonly affected by stroke and cortical motor areas that may compensate for motor deficits, which may provide a possible mechanism underlying the therapeutic effect of acupuncture.

Lack of large quantities of annotated data is a major barrier in developing effective text mining models of biomedical literature. In this study, we explored weak supervision to improve the accuracy of text classification models for assessing methodological transparency of randomized controlled trial (RCT) publications. Specifically, we used Snorkel, a framework to programmatically build training sets, and UMLS-EDA, a data augmentation method that leverages a small number of labeled examples to generate new training instances, and assessed their effect on a BioBERT-based text classification model proposed for the task in previous work. Performance improvements due to weak supervision were limited and were surpassed by gains from hyperparameter tuning. Our analysis suggests that refinements to the weak supervision strategies to better deal with multi-label case could be beneficial. Our code and data are available at https://github.com/kilicogluh/CONSORT-TM/tree/master/weakSupervision.

Crystals have been widely used in the pharmaceutical industry, structural elucidation, and other biomedical fields. Different polymorphs of one compound possess distinct physical and chemical prope...

The third-generation semiconductors are the cornerstone of the power semiconductor leap forward and have attracted much attention because of their excellent properties and wide applications. Meanwhile, femtosecond laser processing as a convenient method further improves the performance of the related devices and expands the application prospect. In this work, an approximate 3 times improvement of the internal quantum efficiency (IQE) and a 5.5 times enhancement of the photoluminescence (PL) intensity were achieved in the GaN film prepared using a one-step femtosecond laser fabrication method. Three types of final micro/nanostructures were found with different femtosecond laser fluences, which could be attributed to the decomposition, melting, bubble nucleation, and phase explosion of GaN. The mechanisms of the microbump structure formation and enhancement of IQE were studied experimentally by the time-resolved reflection pump-probe technique, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Simulations for the laser-GaN interaction have also been performed to ascertain the micro/nanostructure formation principle. These results promote the potential applications of femtosecond lasers on GaN and other wide band gap semiconductors, such as UV-light-emitting diodes (LEDs), photodetectors, and random lasers for use in sensing and full-field imaging.

In this study, we report the formation of laser-induced periodic surface nanometric concentric ring structures on silicon surfaces through single-spot irradiation with orthogonally polarized femtosecond laser double-pulse sequences (OP pulses). The period of the ring structures is marginally smaller than the irradiated laser’s wavelength, which indicates that the structures are a type of low-spatial-frequency laser-induced periodic surface structures. Regular nanometric concentric ring structures can be formed when the time delay between two subpulses is approximately 1 ps (roughly from 500 fs to 1.5 ps) and the number of laser bursts is approximately 4. The formation mechanism of the concentric ring structures is attributed to the surface wave (i.e., cylindrical wave) stimulated by OP pulses through single-spot irradiation is radially distributed. Large area of concentric ring structures eliminating anisotropy in the generation of structural colors was shown in this paper.

Omega-3 fatty acids plus vitamin (e.g. vitamin D and E) may be beneficial to treat gestational diabetes mellitus (GDM), and we aimed to study the influence of omega-3 fatty acids plus vitamin versus placebo on the treatment efficacy of GDM.We searched the databases including PubMed, Embase, and the Cochrane Central Register of Controlled Trials, and randomized controlled trials (RCTs) assessing the influence of omega-3 fatty acids and vitamins combination supplementation versus placebo on metabolic status of GDM were included.Five RCTs were included in the meta-analysis. Compared with control intervention for women with GDM or prediabetes, omega-3 fatty acids plus vitamin substantially reduced fasting plasma glucose (FPG, mean difference [MD] = -11.25; 95% confidence intervals [CI] = -13.73 to -8.77;The supplementation of omega-3 fatty acids in combination with vitamin D or E can improve glycemic control, alleviate oxidative stress, and reduce triglycerides, but had no effects on total cholesterol, preterm delivery or macrosomia4000 g in women with GDM or prediabetes.

Proteins with different micropatterns have various applications in biosensing, structural analysis, and other biomedical fields. However, processing of micropatterns on single protein crystals remains a challenge due to the fragility of protein molecules. In this work, we studied femtosecond laser processing on single hen egg white lysozyme protein crystals. Optimized laser parameters were found to achieve micropatterning without cracking of protein crystals. The ablation morphology dependence on the laser fluence and the pulse number was discussed to control the processing results. Under a laser fluence higher than 1 J/cm2, the ablation hole was formed. While multipulses with fluence lower than the ablation threshold were applied, the foaming area was observed due to the denaturation of protein. The numerical simulation shows that the ablation results were influenced by the ionization and energy deposition process. Micropatterns including lines, areas, and microarrays can be processed with a minimum size of 2 μm. Processed patterns on the crystal surface can be used for biosensing microarrays and the enhancement of crystal growth. The microprocessing method proposed in this study has potential applications in different fields including biodevices and biomedicine.

Background An accurate assessment of the severity and prognosis of sepsis, especially septic shock, is vital for the tailored treatment of this condition. miRNA participates in the inflammatory response and cell apoptosis and regulates inflammation-related signaling pathways. Immune disorders often accompany sepsis. Since serum miRNA expression is superior to traditional biological markers in terms of sensitivity and specificity, its role in the assessment of sepsis has increasingly been recognized. Methods Serum miRNAs were extracted from septic patients and healthy individuals by using the ultracentrifugation method. The differential expressions of miRNAs in the serum samples were detected by high-throughput sequencing technology. The differentially expressed miRNAs between the two groups were analyzed by bioinformatics. The quantitative polymerase chain reaction real-time polymerase chain reaction (qRT-PCR) was used to amplify the sample size to verify the results and to screen the highly-expressed miR206 in septic patients. Subsequently, serum samples were collected from 63 septic patients, and 30 patients with septic shock and qRT-PCR were performed to analyze the expression of miR-206. These 93 patients were divided into the miR-206 low-expression group and miR-206 high-expression group according to miR206 expression level. The potential correlations between the miR-206 expression and the clinical data were analyzed by using SPSS 25.0. Results Serum miRNA expression significantly differed between septic patients and healthy individuals. High-throughput sequencing results showed that, compared with those in healthy individuals, 29 miRNA molecules were down-regulated, and 25 molecules were up-regulated in the serum samples of septic patients. qRT-PCR identified the significantly up-regulated miR-206 in septic patients. qRT-PCR also showed significantly higher miR-206 expression levels in patients with septic shock than in septic patients. Furthermore, we observed a significantly longer prothrombin time and activated partial thromboplastin time, and significantly higher SOFA score, APACHE-II score, and in-hospital mortality rate. miR-206 was positively correlated with SOFA sore and APACHE-II score. Conclusions Serum miR-206 expression is positively correlated with the severity and prognosis of sepsis. Thus, it may be a potential biomarker for assessing the severity and prognosis of sepsis, although the specific mechanism warrants further investigations.

To improve the efficiency of femtosecond laser direct writing, holographic femtosecond laser patterning using spatial light modulators has been widely used for the processing of micro/nanopatterns. However, the speckle noise of modulated optical fields severely limits the quality of fabricated patterns. We present a simple and effective method which involves interlacing a target pattern into a series of target subpatterns that consist of spaced spots to solve this problem. The separation of spots weakens the random interference between adjacent spots of optical fields, so the speckle noise reduces effectively, which improves the uniformity of the modulated optical fields and makes the fabricated patterns with high quality. With optimal interlacing numbers, complex micropattern arrays containing curved edges and sophisticated structures can be fabricated with superior quality and high efficiency. Binary holograms with improved optical characterization are realized by using the interlacing-pattern method, revealing the extensive potential of this method in micropattern processing and functional device fabrication with high quality and efficiency.

Numerous valuable studies on electron dynamics have focussed on the extraordinary properties of molybdenum disulfide (MoS2); however, most of them were confined to the level below the damage threshold. Here the electron dynamics of MoS2 under intense ultrafast laser irradiation was investigated by experiments and simulations. Two kinds of ablation mechanisms were revealed, which led to two distinct types of electron dynamics and final ablation morphology. At a higher fluence, the emergence of superheated liquid induced a dramatic change in the transient reflectivity and micro-honeycomb structures. At a lower fluence, the material was just removed by sublimation, and the ablation structure was relatively flat. X-ray photoelectron spectroscopic (XPS) measurements demonstrated that thermal decomposition only occurred at the higher fluence. Furthermore, a theoretical model was developed to deeply reveal the ultrafast dynamics of MoS2 ablation. The simulation results were in good agreement with the temporal and spatial reflectivity distribution obtained from the experiment. The electron and lattice temperature evolution was also obtained to prove the ablation mechanism. Our results revealed ultrafast dynamics of MoS2 above the damage threshold and are helpful for understanding the interaction mechanism between MoS2 and intense ultrafast lasers, as well as for MoS2 processing applications., Optoelectronics: Digging into molybdenum disulfide Ultrafast damage-causing laser pulses affect bulk molybdenum disulfide differently depending on their energy per area, revealing further insight into the ultrafast electron dynamics. The research group of Lan Jiang from Beijing Institute of Technology, in cooperation with Tianhong Cui of University of Minnesota, has predicted and examined what happened to molybdenum disulfide on electron and lattice level when intense femtosecond laser pulses irradiate. Lower damage-causing energies per area, known as fluences, removed material through inducing a solid-to-gas transition. Higher fluences caused superheating, liquidation, and the formation of nanocracks and nanoridges. Tests on electron dynamics obtained by the materials’ reflectivity with different fluences were followed by theoretical simulations, which further helped to reveal the electron and lattice temperature evolution. The findings further understandings for laser processing of molybdenum disulfide and for its use in optoelectronics.

Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics, excellent optical properties, and good biocompatibility and biodegradability. However, nano-processing of the silk fiber is still a challenge limiting its applications in nanoengineering and related fields. Herein, we report localized near-field enhancement-assisted ablation with an ultrafast laser to break this bottleneck. Localized processing of silk fiber, including nano-holing, nano-grooving, and cutting could retain the key molecular structure building blocks and the pristine functionality of the silk fiber. An extremely narrow nanohole with a width of ~64 nm was successfully achieved. The processed silk fiber can be used to transfer micro/nanoparticles and drugs, showing potential for biomedical engineering. The processing strategy developed in this study can also be extended to other materials, paving a new way for fabricating functional nanostructures with precisely controlled size and morphology.

Gold nanoparticles (Au NPs) have a wide range of applications because of their localized surface plasmon resonance properties. Femtosecond laser is considered to be an effective method for preparing Au NPs because of its characteristics of ultrashort irradiation periods and ultrahigh intensities. In this study, a novel method is proposed to produce an Au NP-attached substrate using the spatially and temporally shaped femtosecond laser. Laser-induced periodic surface structures (LIPSS) are designed to obtain the localized optical field enhancement, which leads to the femtosecond laser spatially reshaping, enabling the deposition of Au NPs by photoreduction on silicon substrates. The Au NPs prepared by this method exhibit morphological controllability and chemical stability, especially excellent spatial selectivity and uniformity, resulting in the tunable and stable surface-enhanced Raman scattering (SERS) applications. Also, the temporally shaped femtosecond pulses are introduced to further increase the enhancement factors of the SERS. This method successfully achieves the controllable morphology synthesis and selective deposition of Au NPs on the substrate simultaneously, which provides a promising candidate for SERS substrates fabrication, and holds potential applications in optoelectronics, such as molecular detection and biosensors.

Probiotics, such as Lactobacillus, have been proven to be effective in maintaining intestinal homeostasis. The modulatory effect of Lactobacillus on intestinal epithelial development in early life is still unclear. In this study, Lactobacillus isolates with good probiotic abilities were screened and orally administered to detect their regulatory effect on intestinal development in chickens. L. reuteri 22 was isolated from chickens and chosen for subsequent chicken experiments due to its strong acid and bile salt resistance and ability to adhere to epithelial cells. The 3-day-old chickens were orally administrated with 108 CFU L. reuteri 22 for consecutive 7 days. L. reuteri 22 increased Lgr5 mRNA expression (3.23 ± 0.40, P = 0.001) and activated the Wnt/β-catenin signaling pathway, with increasing expression of proliferating cell nuclear antigen (PCNA) (49.27 ± 9.81, P = 0.021) to support the proliferation of chicken intestinal epithelial cells. Moreover, L. reuteri 22 also inhibited the Notch signaling pathway to induce intestinal stem cell differentiation into goblet cells with increased mucin 2 (Muc-2) expression (1.72 ± 0.34, P = 0.047). L. reuteri 22 significantly enhanced lysozyme mRNA expression (2.32 ± 0.55, P = 0.019) to improve intestinal innate mucosal immunity. This study demonstrated that L. reuteri administration could regulate chicken intestinal epithelium development to ensure the function of the intestinal mucosal barrier, which is beneficial for newborn animals.

In this study, femtosecond laser double pulses were tested to improve their nickel ablation efficiency. The experimental results indicated that compared with single pulses, double pulses with different delay times generated craters with larger diameters and depths. The results obtained for three sets of double pulses with different energy ratios indicated that double pulses with an energy ratio of 1:9 had the highest ablation efficiency, followed by those with energy ratios of 2:8 and 5:5. The double pulses with the aforementioned three energy ratios achieved the maximum ablation efficiency when the delay time was 3–4 ps. Compared with single pulses, double pulses with an energy ratio of 1:9 generated craters with an up to 34% greater depth and up to 14% larger diameter. In addition, an interference effect was observed with a double pulse delay time of 0 ps, which has seldom been reported in the literature. The double pulses were simulated using the two-temperature model. The simulation results indicated that double pulses with an energy ratio of 1:9 with a delay time of 4 ps can perform the strongest ablation. These simulation results are in line with the experimental results.

Optical security involving the use of light to achieve distinctive vision effects has become a widely used approach for anticounterfeiting. Holographic multiplexing has attracted considerable interest in multiplexing security due to its high degree of freedom for manipulating the optical parameters of incident laser beams. However, the complex and time-consuming fabrication process of metasurface-based holograms and the sophisticated nature of holographic imaging systems have hindered the practical application of holographic multiplexing in anticounterfeiting. Combining holography with shape memory polymers to construct reconfigurable holograms provides a simple and efficient way for holographic multiplexing. This paper proposes a reconfigurable four-level amplitude hologram fabricated on a heat-shrinkable shape memory polymer using spatially modulated femtosecond laser pulses. Simply by triggering the shape recovery of the polymer through heating, the amplitude modulation of light by the hologram is reconfigured through the shrinking of processed microcrater pixels with three diameters, which enables variation to be achieved in reconstructed holographic images. Examples of holographic multiplexing and data encryption are used to validate the proposed method. The proposed economic and simple approach for holographic multiplexing provides an integrated and single-material solution to packaging and optical security, which has extensive potential in anticounterfeiting and optical encryption.

Molybdenum disulfide (MoS2) micro/nanostructures are desirable for tuning electronic properties, developing required functionality, and improving the existing performance of multilayer MoS2 devices. This work presents a useful method to flexibly microprocess multilayer MoS2 flakes through femtosecond laser pulse direct writing, which can directly fabricate regular MoS2 nanoribbon arrays with ribbon widths of 179, 152, 116, 98, and 77 nm, and arbitrarily pattern MoS2 flakes to form micro/nanostructures such as single nanoribbon, labyrinth array, and cross structure. This method is mask-free and simple and has high flexibility, strong controllability, and high precision. Moreover, numerous oxygen molecules are chemically and physically adsorbed on laser-processed MoS2, attributed to roughness defect sites and edges of micro/nanostructures that contain numerous unsaturated edge sites and highly active centers. In addition, electrical tests of the field-effect transistor fabricated from the prepared MoS2 nanoribbon arrays reveal new interesting features: output and transfer characteristics exhibit a strong rectification (not going through zero and bipolar conduction) of drain-source current, which is supposedly attributed to the parallel structures with many edge defects and p-type chemical doping of oxygen molecules on MoS2 nanoribbon arrays. This work demonstrates the ability of femtosecond laser pulses to directly induce micro/nanostructures, property changes, and new device properties of two-dimensional materials, which may enable new applications in electronic devices based on MoS2 such as logic circuits, complementary circuits, chemical sensors, and p-n diodes.

A symbiosis-Michelson interferometer (SMI)-based detection scheme is proposed and experimentally demonstrated. The SMI comprises a $3\times 3$ coupler, two FBGs with different center wavelengths, and a common reference arm. Two MIs share a $3\times 3$ coupler and a reference arm. The sensing part is the fiber between the two FBGs. The sensitivity of the sensor is high because of its long sensing fiber. Light beams reflected from two MIs pass the same leading fiber and the reference arm, so the undesirable external perturbation can be removed by calculating the difference of two outputs. Thus, the SMI is insensitive to interfering signals. An SMI-based vibration sensor and an SMI-based acoustic sensor fabricated by a 3D printer are experimentally investigated. For the SMI-based vibration sensor, an OPD sensitivity of 1274 nm/g is obtained. The acceleration resolution of the sensor is

The friction and wear properties of interpenetrating phase composites (IPC) SiC3D/Al sliding against graphite/SiC (G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included a braking pressure of 1.25 MPa and an initial braking speed (IBS) of 200−350 km/h in a braking process of high-speed train according to the scale-conversion rules. The tribo-couple materials were characterized using scanning electron microscopy (SEM), X-ray diffractometry (XRD), and energy-dispersive X-ray spectrometry (EDS). It is found that the matching tribo-couple features low friction surface temperature, reliable friction factor, and high durability. The continuous lubricating mechanically-mixed layer (MML) forms gradually on the worn surfaces of ring in the friction process. The MML is heterogeneous, which greatly controls wear rate and coefficient of friction (COF) of the composites. The wear mechanism of SiC3D/Al is typically abrasive wear at an IBS of 200−300 km/h. When the IBS increases to 350 km/h, oxidation wear and delamination are observed. The friction behavior of the tribo-couple predicted using Solidwork simulation software agrees well with the experimental results. The tribo-couple meets the requirement of emergency braking of high-speed train.

A fiber optic dual-ring Michelson interferometer (DRMI) based detection scheme for the measurement of dynamic signals is proposed and experimentally demonstrated. The fiber optic sensor is a single mode fiber between two broadband fiber Bragg gratings (FBGs) with different center wavelengths. The two FBGs are connected to two output ports of a 3 × 3 coupler to compose a DRMI. High responsivity and wide frequency response range can be achieved at the same time. The scheme has high reliability, in which the undesirable external perturbation applied to interferometric arms is removed. A DRMI-based vibration sensor and a DRMI-based acoustic sensor are fabricated and experimentally investigated. For the DRMI-based vibration sensor, a responsivity of minimum detectable acceleration is 54 μg/√Hz at 300 Hz. The 12.8 rad/g is obtained, and the resonant frequency is 825 Hz. The acoustic sensor is used to detect signals in the frequency range of 0.5-19 kHz. The detection scheme has properties of wide frequency response range, high responsivity, and high reliability.

The fabrication of gold nanostructures on a dielectric substrate with a nanogap between the opposite tips is suitable for the excitation of hot spots. In this study, a novel and efficient one-step ...

Fabry–Perot interference has been employed in optical fibers, sensors, electron optics, and so on. The photoluminescence (PL) spectra of a gallium nitride (GaN)-based light-emitting diode (LED), wh...

As a new type of floor structure, steel vierendeel sandwich plates are widely applied in large-span buildings with multiple storeys. Shear connectors are important stressed members of such plates. To evaluate the seismic performance of the shear connectors, a full-scale test piece in two different connection forms, namely, A and B, is designed and tested under alternating load. Test analysis of the two connection specimens covers the failure modes, hysteresis curves, and main parameters (e.g., bearing capacity, ductility, stiffness degradation, and energy dissipation coefficient). The following results concerning type A connection are obtained: First, it exhibits good ductility and long yielding platform; second, elastoplasticity of steel is fully exerted with it; third, it absorbs and dissipates energy well with strong energy consumption; and fourth, when failure occurs, cracks usually happen in the heat-affected zone of the weld in the core zone. The following conclusions about type B are drawn: first, it has large bearing capacity with high stiffness; also, when failure occurs, the ribbed stiffeners crack and flexion deformity happen.

Femtosecond laser direct writing is widely exploited in surface periodic structures processing. However, this technique still faces challenges in obtaining high surface homogeneity and flexible morphology controllability. In this study, a flexible and efficient approach has been proposed to fabricate highly homogeneous and controllable nanogratings on silicon via chemical etching-assisted femtosecond laser modification. By precisely manipulating the laser-material interaction process, alternating amorphous-crystalline nanofringes are generated when employing femtosecond laser scanning over a Si sample, with almost no material removal. Following auxiliary chemical etching, highly homogeneous nanograting structures are obtained, and the morphology of the nanogratings can be flexibly managed through precisely controlling the duration of the etching process. Complex cross-scale patterns with remarkable structural colors that are visible under indoor light illumination are readily achieved on the sample surfaces exploiting our method. In addition, compared with traditional methods for laser-induced periodic surface structures, the fabrication efficiency is considerably improved. Our processing procedure offers potential applications in the fields of optics, nanoelectronics, and mechatronics.

For fatigue life prediction, the maximum stress calculated by the structural static analysis is used as load calculation in normal continuous operating conditions, which is not valid in time-varyin...

Polymorph-controlled crystallization of acetaminophen was conducted through femtosecond laser double-pulse irradiation. Dependence of the crystal form of acetaminophen on the pulse energy and doubl...

We report the influence of temporally decreasing pulse trains on femtosecond laser-induced chemical etching (FLICE) of fused silica. A systematic comparison of the unshaped pulse and decreasing pulse trains of femtosecond laser for FLICE was conducted, and the differences were interpreted using a plasma model. The results revealed that the decreasing pulse trains not only affected the etching efficiency but also affected the morphology of the etched crater. When an etched crater was pre-irradiated by decreasing pulse trains, it presented a funnel-like shape at the early stage of the etching process, which contrasted with the one pre-irradiated by unshaped pulse. At the later stage of the etching process, the funnel-like shape gradually disappeared, and the crater increased in size. Compared with the unshaped pulse under the same processing conditions, the decreasing pulse trains enhanced the etched crater volume by approximately 18 times. Theoretical calculations based on the plasma model indicated that the free-electron density generated using the unshaped pulse was much higher than that generated by the decreasing pulse trains in skin layer of the sample during the first few hundred femtoseconds. The high free-electron density increased the reflectivity in skin layer of the sample; thus, the tail part of the incident pulse was strongly reflected. Consequently, the laser energy deposition into the fused silica sample decreased, eventually led to a low etching efficiency.

Cephalosporin residues in the environment are a great concern, but bioremediation options do exist. Bacillus clausii T reached a removal rate of 100% within 8 h when challenged with a mixture of cefuroxime (CFX), cefotaxime (CTX), and cefpirome (CPR). The co-culture of B. clausii T and B. clausii O/C displayed a higher removal efficiency for the mixture of CFX, CTX and CPR than a pure culture of B. clausii O/C. B. clausii T alleviated the biotoxicity of CFX and CPR. What's more, the biotoxicity of for CFX and CPR transformation products released by the co-culture of B. clausii T and B. clausii O/C was lower than that in pure cultures. Real-time PCR was applied to detect the changes in the expression levels of the relevant antibiotic-resistance genes of B. clausii T during CFX and CPR degradation. The results indicated that CFX and CPR enhanced the expression of the β-lactamase gene bcl1. Hydrolysis, deacetylation and decarboxylation are likely the major mechanisms of CTX biodegradation by B. clausii. These results demonstrate that B. clausii T is a promising strain for the bioremediation of environmental contamination by CFX, CTX, and CPR.

Low turn-on fields (Eto) and high current emission stabilities are recognized as two crucial factors for the potential applications of field emission (FE) cathodes. In this work, graphene/SiC (G/SiC) heterojunction nanowire arrays were fabricated through catalyst-assisted pyrolysis of polymeric precursors. Aiming to explore advanced field emitters, G/SiC nanoarrays are designed to grow with a desired architecture including sharp tips, rough surface, incorporated dopants, and well-aligned configurations, which could fundamentally increase the effective emission sites, tailor the band gap structure, fully utilize the local field enhancement effect, and limit the shielding effect. The G/SiC emitters established exceptional FE properties with low and stable Eto of 1.10–1.12 V μm−1 when subjected to various anode–cathode distances, as well as a small current emission fluctuation of ∼3.7% over 5 h and high field enhancement factor up to 6383, which were comparable to the state-of-the-art ones previously reported, representing their totally excellent FE performance.

Defect/active site control is crucial for tuning the chemical, optical, and electronic properties of MoS2, which can adjust the performance of MoS2 in application areas such as electronics, optics, catalysis, and molecular sensing. This study presents an effective method of inducing defect/active sites, including micro/nanofractured structures and S atomic vacancies, on monolayer MoS2 flakes by using femtosecond laser pulses, through which physical–chemical adsorption and charge transfer between foreign molecules (O2 or R6G molecules) and MoS2 are enhanced. The enhanced charge transfer between foreign molecules (O2 or R6G) and femtosecond laser-treated MoS2 can enhance the electronic doping effect between them, hence resulting in a photoluminescence photon energy shift (reaching 0.05 eV) of MoS2 and Raman enhancement (reaching 6.4 times) on MoS2 flakes for R6G molecule detection. Finally, photoluminescence control and micropatterns on MoS2 and surface-enhanced-Raman-scattering (SERS) enhancement of MoS2 for organic molecule detection are achieved. The proposed method, which can control the photoluminescence properties and arbitrary micropatterns on MoS2 and enhance its chemicobiological sensing performance for organic/biological molecules, has advantages of simplicity, maskless processing, strong controllability, high precision, and high flexibility, highlighting the superior ability of femtosecond laser pulses to achieve the property control and functionalization of two-dimensional materials.

In this paper, the thermo-optic coefficient of silica fiber is analyzed and measured within a wide temperature range of 0–1200 °C for the first time. To obtain the thermo-optic coefficient, experiments were carried out by using fiber optic extrinsic Fabry–Perot interferometers (EFPIs) embedded in silica fiber. The optical cavity lengths of the EFPIs were measured with white-light interferometry. The experimental results show that the first and second orders of the thermo-optic coefficient are 1.090 × 10−5/°C and 1.611 × 10−9/°C2, respectively. The quadratic model for the temperature dependence of the basic optical parameter, the refractive index, is rigorous within a wide temperature range. Furthermore, this paper also provides a temperature calibration method for extrinsic Fabry–Perot interferometric temperature sensors. The temperatures measured by the sensors are in excellent agreement with those measured by the reference thermocouple. Hence, this calibration method is promising for temperature sensors with a wide working temperature range.

Fiber-optic micro vibration sensors fabricated by a femtosecond laser are proposed and experimentally demonstrated. The proposed sensor is an extrinsic Fabry–Perot interferometer (EFPI), which is the three-section structure sandwiched by a single mode fiber (SMF), a hollow core fiber (HCF) and a coreless silica fiber (CF). A femtosecond laser is employed to fabricate the cantilever beam. The ablation process does not affect reflectivity of the mirrors of the EFPI, resulting in the high visibility of the interferometric fringe. The vibration can be interrogated by using the quadrature passive demodulation. The experimental results show that the sensitivity of 20.678 mV/g@500 Hz is achieved in the acceleration range of 0–10 g. The frequency response of the ANSYS simulation and the experimental results are compared with the frequency range from 100 Hz to 3000 Hz, and the resonant frequency is 1920 Hz.

Background: As one of the important manifestations of neurogenic bowel dysfunction, constipation is characterized by high incidence and harmful effects. It has a negative impact on both physical and psychological health of patients. And there are no effective treatment options for this type of disease clinically. Therefore, this study is designed to examine the effect of the therapy of “combination 3 methods progression” in patients with neurogenic bowel dysfunction (constipated type). Methods: This is a randomized, controlled, parallel-design clinical trial. A total of 60 patients with neurogenic bowel dysfunction (constipated type) will be randomly assigned to intervention group and control group. The control group will receive 4 weeks of usual rehabilitation care, the intervention group will receive 4 weeks of the therapy of “combination 3 methods progression” in addition to usual rehabilitation care. The primary outcome is the number of spontaneous bowel movement per week. Secondary outcomes are stool characteristics, degree of difficulty in defecation, level of anxiety, level of depression, and level of self-efficacy. Discussion: The interventions of this protocol have been programmed to alleviate constipation in patients with neurogenic bowel dysfunction. Findings may provide preliminary evidence for clinical efficacy of the therapy of “combination 3 methods progression.” Trial registration: Chinese Clinical Trial Registry, IDF: ChiCTR2000041463. Registered on December 26, 2020.

Organizational networks are often hierarchical by nature as individuals take on roles or functions at various job levels. Prior studies have used either text-level (e.g., sentiment, affect) or structural-level features (e.g., PageRank, various centrality metrics) to identify influential nodes in networks. In this study, we use a combination of these two levels of information to develop a novel ranking method that combines sentiment analysis and PageRank to infer node-level influence in a real-world organizational network. We detect sentiment scores for all actor pairs based on the content of their email-based communication, and calculate their influence index using an enhanced PageRank method. Finally, we group individual nodes into distinct clusters according to their influence index. Compared to established network metrics designed or used to infer formal and informal influence and ground truth data on job levels, our metric achieves the highest accuracy for inferring formal influence (60.7%) and second highest for inferring informal influence (69.0%). Our approach shows that combining text-level and structural-level information is effective for identifying the job level of nodes in an organizational network.

Introduction: Cesarean section is a common operation in obstetrics, and the incidence of insufficient breast milk is high in parturients undergoing cesarean section. Studies have shown that acupuncture or massage at related acupoints can promote the secretion and excretion of milk. These external treatments are quick, safe, and effective. On the other hand, they can avoid the potential risk of changes in milk composition that may be caused by the use of drugs. Pestle needle therapy is a new branch of traditional acupuncture, and pestle needle operation does not need to break the skin. The pestle needle has good clinical efficacy and safety in cervical spondylosis, insomnia, fatigue, depression, and so on, but few studies have focused on the effect of pestle acupuncture for patients with lactation insufficiency after cesarean section. This study aims to determine whether pestle needle therapy is effective and safe in the treatment of postpartum milk deficiency. Methods: This is a 2 parallel-group, assessor-blinded, randomized controlled trial.128 patients with lactation insufficient after cesarean section will be recruited and randomly divided into control group and the pestle needle group in a 1:1 ratio. The control group will receive routine nursing care of milk deficiency. In the pestle needle group, pestle needles will be used to operate on the acupoints such as bilateral Shao ze (S11), bilateral Ru gen (ST18), Dan zhong (DU14), 8 array acupoints of Shen dao (DU11) and so on. It will be operated once a day for 5 days. The primary outcomes are milk yield, degree of breastfilling, degree of milk siltation and other milk deficiency symptom, and serum prolactin. Secondary outcomes include syndrome of traditional Chinese medicine, such as facial expression, fatigue, loss of appetite, and so on. Discussion: Pestle needle therapy based on acupoint and meridian theory may increase milk secretion and excretion, which will provide a new intervention means to promote breastfeeding and have great significance to guide clinical treatment. Trial registration number: ChiCTR2000039752.

A symmetrical demodulation method is developed for the recovery of dynamic signals. Extrinsic Fabry–Perot interferometers (EFPIs) with different cavity lengths can be interrogated by a same demodulator. In the demodulation technique, three interferometric signals are introduced by selecting three specified laser wavelength, two of the three signals are symmetrical about the third signal. The dynamic signal is recovered by the proposed method from the three interferometric signals. EFPI sensors in a wide cavity length range (>1000 µm) can be demodulated without dead zone. The calculated amplitude error of the demodulated signal is less than 0.25% with the cavity length in the 20-1005 µm range. The proposed demodulation technique is adapted to the measurement of EFPIs with unsteady cavity lengths and unknown cavity lengths.

We have explored an asymmetric optoelectronic response of an FAPb(I0.8Br0.2)3 (FA = formamidine) perovskite device irradiated by a femtosecond (fs) laser at different laser-fluence values. Photoluminescence (PL) spectra indicated a blue shift from 772 nm (1.606 eV) to 745 nm (1.664 eV) and more than 80% quenching of the irradiated perovskite. The blue shift of the PL spectra can be attributed to compositional variation, which was confirmed through elemental analysis and X-ray diffraction. Two distinct characteristic time constants 193-46 ps and 1.9-0.61 ns were obtained by using fs transient absorption spectroscopy. The fast one represents recombination at the interface, whereas the slow one represents band-to-band recombination in the interior of the grain. Interestingly, after the perovskite was irradiated by a femtosecond laser with an appropriate laser fluence (0.135 J/cm2), an asymmetric I-V characteristic was achieved, which should result from irreversible electric domain deflection. Due to the electron-phonon scattering induced by defects, the degree of asymmetry was sensitive to the illumination power. As the photosensitive asymmetric I-V characteristics have a bearing on its photoelectric properties, the findings would be of value in photodiode, memory, and other photoelectric devices.

Micro-supercapacitors are promising miniaturized energy storage devices that have attracted considerable research interest. However, their widespread use is limited by inefficient microfabrication technologies and their low energy density. Here, a flexible, designable micro-supercapacitor can be fabricated by a single pulse laser photonic-reduction stamping. A thousand spatially shaped laser pulses can be generated in one second, and over 30,000 micro-supercapacitors are produced within 10 minutes. The micro-supercapacitor and narrow gaps were dozens of microns and 500 nm, respectively. With the unique three-dimensional structure of laser-induced graphene based electrode, a single micro-supercapacitor exhibits an ultra-high energy density (0.23 Wh cm−3), an ultra-small time constant (0.01 ms), outstanding specific capacitance (128 mF cm−2 and 426.7 F cm−3) and a long-term cyclability. The unique technique is desirable for a broad range of applications, which surmounts current limitations of high-throughput fabrication and low energy density of micro-supercapacitors., Microfabrication for cost-effective miniaturized energy storage devices remains a challenge. Here, the authors propose a spatially shaped femtosecond laser method, which is ultrafast, one-step, high resolution and large-scale, for use in patterning flexible high-performance micro-supercapacitors.

Gels with high mechanical performance have attracted great interest because of their potential biomedical applications. Tough gels reported thus far usually contain sacrificial species to dissipate energy, thus compromising the fatigue resistance. In this study, highly stretchable and recoverable gels can be achieved by cross-linking cyclodextrin (CD)-based polyrotaxane with a low host coverage, synthesized via a one-pot enzymatic end-capping reaction with 90% yield and ∼2% CD coverage (PR02). The low coverage allows the CD cross-links to freely slip on the axis over large distance (∼2/3 of the axis length) and thus allows the PR02 slide-ring network keep intact under large deformation via the pulley effect. The PR02-hydrogel can be stretched up to ∼1600% long, withstand ∼1 MPa stress, and fully recover instantly. PR02-DMSO gels exhibit a shape memory behavior that withstood large deformation. As the first research to control the final property of the network by precisely controlling the slide distance of...

Penetration of lithium metal and uncontrollable growth of lithium dendrites of lithium metal batteries (LMBs) easily induce safety concerns. Herein, we propose a smart lithium-manganite/graphene-oxide/lithium (LMO/GO/Li) battery with rationally designed trilayer films as separator, in which GO film is sandwiched by two pieces of commercial polymer microporous membranes. This unique LMO/GO/Li battery possesses the merits of anti-piercing and eliminating Li dendrites. Once being pierced, the middle GO layer can chemically etch metallic Li based on the spontaneous redox reaction and thus the LMO/GO/Li battery can work normally without short-circuit. Meanwhile, Li dendrites can be efficiently eliminated by GO to avoid internal shorting. Consequently, the LMO/GO/Li battery can reversibly charge/discharge for 6000 cycles that is ca. 48 times longer than that of conventional LMO/Li battery, and still retain a high Coulombic efficiency of 93%. This work not only conceptually provides new opportunities for developing other anti-piercing batteries, but also paves the way for building dendrite-free LMBs.

Ultrafast laser pulse temporal shaping has been widely applied in various important applications such as laser materials processing, coherent control of chemical reactions, and ultrafast imaging. However, temporal pulse shaping has been limited to only-in-lab technique due to the high cost, low damage threshold, and polarization dependence. Herein we propose a novel design of ultrafast laser pulse train generation device, which consists of multiple polarization-independent parallel-aligned thin films. Various pulse trains with controllable temporal profile can be generated flexibly by multi-reflections within the splitting films. Compared with other pulse train generation techniques, this method has advantages of compact structure, low cost, high damage threshold and polarization independence. These advantages endow it with high potential for broad utilization in ultrafast applications.

MoS2-based nanohybrids have garnered extensive research interest for enhancing chemical catalytic performance, application of biochemical sensing, and inducing phase transition of MoS2. This work p...

This study demonstrated that femtosecond-laser-induced ripples on an alumina-doped zinc oxide (AZO) film with space intervals of approximately 340 and 660 nm exhibit modulations of anisotropic optical transmission. At low laser fluence, ripples can not affect the original absorption peak of AZO film, but at higher laser fluence, the absorption peak of AZO film is disappeared due to the modulation by femtosecond laser induced ripples. Moreover, the relationship between the anisotropic optical transmission and the features of nanostructures is discussed. Ripples with a space interval of approximately 660 nm have a higher ability to block light than nanostructures with a space interval of approximately 340 nm. These observations indicate that anisotropic optical transmission has potential applications in the field of optoelectronics.

Water shortage is a serious, long-standing global issue that urgently needs to be solved. Recently, various kinds of techniques have been developed for the treatment of wastewater. Among them, solar thermal conversion of steam generation is a green and sustainable approach for regeneration of clean water. Herein, we develop the solar steam generator based on the defect-abundant graphene sheets for highly efficient production of clean water with high rejection of ions, organic media, and bacteria. The thermal conductivity of defect-abundant graphene aerogel is as low as 0.0075 W m−1 K−1 with a record surface temperature of up to ca 90 °C under only 1 sun, which thus promotes a high water evaporation rate of 1.78 kg m−2 h−1. Efficient production of clean water with high rejection of ions, oil and bacteria is demonstrated, which proved the possibility for a one-step production of drinkable water from the water sources of the sea, lake, and emulsified oil/water mixtures.

Femtosecond laser pulse train induced breakdown of fused silica was studied by investigating its plasma emission and the ablated crater morphology. It was demonstrated that the electron dynamics in the ablated fused silica play a dominant role in the emission intensity of induced plasma and the volume of material removal, corresponding to the evolution of free-electron, self-trapped excitons, and the phase change of the fused silica left over by the first pulse. For a fluence of 11 J/cm2, the maximum plasma intensity of double-pulse irradiation at an interpulse delay of 120 ps was about 35 times stronger than that of a single-pulse, while the ablated crater was reduced by 27% in volume. The ionization of slow plume component generated by the first pulse was found to be the main reason for the extremely high intensity enhancement for an interpulse delay of over 10 ps. The results serve as a route to simultaneously increase the spatial resolution and plasma intensity in laser-induced breakdown spectroscopy of dielectrics.

A compact optical fiber sensor based on a Fabry–Perot interferometer (FPI) with an integrated fiber Bragg grating is proposed to measure pressure and temperature simultaneously. The light reflectors of the proposed FPI comprise a graphene film and a fiber end face. The sensitivities of the FPI sensor for measuring pressure and temperature are 501.4 nm/kPa and 306.2 nm/°C, respectively. Conflicting signals of pressure and temperature can cause cross-impact errors at 610 Pa/°C. The introduction of a fiber Bragg grating can effectively prevent the cross-impact of the FPI sensor. The pressure sensitivity obtained is 7.96 to 12 times higher than the previous study. The proposed fiber sensor can simultaneously measure pressure and temperature using a sensitivity matrix.

Efficient harvesting of solar radiation into exploitable thermal energy for fast generation of clean water has been a recent research focus. However, solar steam generation (SSG) is generally limited to unidirectional evaporation, and the production rate is still low. Herein, we develop three-dimensional water evaporation based on a highly vertically ordered pillar array of graphene-assembled framework (HOPGF) with an enlarged evaporation area and additional free space for fast escape of vapour. As a result, a high water evaporation rate of 2.10 kg m−2 h−1 is achieved under only 1 sun. This efficient SSG system exhibits practical ability to treat sewage by the purification of raw pharmaceutical wastewater. On the other hand, a solar water heater based on HOPGF is conceptually proposed and experimentally designed through 3D printing technology, which presents the potential to heat 30 kg water to ca. 50 °C with only one square meter of HOPGF under 1 sun within hours. Promisingly, a housing self-supply water system was built to verify the effectiveness for high production of clean water. This work develops an efficient HOPGF material platform for construction of fast and scalable solar water-generating and water-heating systems of practical importance.