In vivo biological safety investigation of Yb-CALGO femtosecond laser dental surgery.

While lasers have found their successful applications in various clinical specialties, in clinical dental practice, traditional mechanical drills are still predominantly utilized. Although erbium-doped lasers have been demonstrated for dental therapy, their clinical performance is still not satisfactory due to the long pulse width, low peak power, and small repetition rate. To attain a smaller thermal diffusion thus better biological safety and surgical precision, as well as more rapid ablation, the advancement of femtosecond laser techniques has opened another route of dental surgery; however, no biological safety investigation has been reported. Here, we present a systematic study of dental ablation by a Yb:CaAlGdO4 regenerative amplifier with a central wavelength of 1040 nm and pulse width of 160 fs. The in vivo experiment of dental surgery investigating the inflammatory response has been reported, for the first time to the best of our knowledge. It is demonstrated that dental surgery by Yb:CaAlGdO4 femtosecond laser ablation has better biological safety compared to the turbine drilling, thanks to its non-contact and ultrafast heat dissipation nature.

Wavelength scaling of high harmonic yields and cutoff energies in solids driven by mid-infrared pulses.

The effect of driving wavelengths on high harmonic generation (HHG) have long been a fundamental research topic. However, despite of abundant efforts, the investigation of wavelength scaling of HHG in solids is still confined within the scope of theoretical predictions. In this work, we for the first time to the best of our knowledge, experimentally reveal wavelength scaling of HHG yields and cutoff energy in three typical solid media (namely pristine crystals GaSe, CdTe and polycrystalline ZnSe), driven in a broad mid-infrared (MIR) range from 4.0 to 8.7 µm. It is revealed that when the driving wavelength is shorter than 6.5-7.0 µm, HHG yields decrease monotonously with the MIR driving wavelengths, while they rise abruptly by 1-3 orders of magnitude driven at longer wavelength and exhibit a crest at 7.5 µm. In addition, the cutoff energies are found independent on driving wavelengths across the broad MIR pump spectral range. We propose that the interband mechanism dominates the HHG process when the driving wavelength is shorter than 6.5-7.0 µm, and as the driving wavelength increases, intraband contribution leads to an abrupt rise of the HHG yields, which is verified by the HHG polarization measurement driven at 3.0 and 7.0 µm. This work not only experimentally demonstrate the wavelength scaling of HHG in solids, but more importantly blazes the trail for optimizing the HHG performance by choosing a driving wavelength and provides experimental method to distinguish the interband and intraband dynamics.

Tunable phase-mismatched mid-infrared difference-frequency generation between 6 and 17†µm in CdTe.

In parametric conversion, phase-matching techniques such as birefringence and quasi phase-matching (PM) with the designed crystal angle or periodically poled polarities are employed to fulfill the requirement of momentum conservation. However, directly using phase-mismatched interactions in nonlinear media with large quadratic nonlinear coefficient remains unheeded. Here, for the first time to the best of our knowledge, we study the phase-mismatched difference-frequency generation (DFG) in an isotropic cadmium telluride (CdTe) crystal, with the comparison of other DFG processes based on birefringence-PM, quasi-PM, and random-quasi-PM. Long-wavelength mid-infrared (LWMIR) phase-mismatched DFG with an ultra-broadband spectral tuning range of 6-17 µm based on CdTe is demonstrated. Thanks to the giant quadratic nonlinear coefficient (∼109 pm/V) and good figure of merit in the parametric process, the output power up to 100 µW is obtained, which is comparable to or even better than the DFG output from a polycrystalline ZnSe with the same thickness facilitated by random-quasi-PM. A proof-of-concept demonstration in gas sensing of CH4 and SF6 is conducted based on the phase-mismatched DFG as a typical application. Our results demonstrate the feasibility of phase-mismatched parametric conversion in producing useful LWMIR power and ultra-broadband tunability in a simple and convenient way without the necessity of controlling the polarization, phase-matching angle, or pole periods, which could find applications in the fields of spectroscopy and metrology.

Utilization of two plant polysaccharides to improve fresh goat milk cheese: Texture, rheological properties, and microstructure characterization.

This study aimed to evaluate the effects of added jujube polysaccharide (JP) and Lycium barbarum polysaccharide (LBP) on the texture, rheological properties, and microstructure of goat milk cheese. Seven groups of fresh goat milk cheese were produced with 4 levels (0, 0.2, 0.6, and 1%, wt/wt) of JP and LBP. The goat milk cheese containing 1% JP showed the highest water-holding capacity, hardness, and the strongest rheological properties by creating a denser and more stable casein network structure. In addition, the yield of goat milk cheese was substantially improved as a result of JP incorporation. Cheeses containing LBP expressed lower fat content, higher moisture, and softer texture compared with the control cheese. Fourier-transform infrared spectroscopy and low-field nuclear magnetic resonance analysis demonstrated that the addition of JP improved the stability of the secondary protein structure in cheese and significantly enhanced the binding capacity of the casein matrix to water molecules due to strengthened intermolecular interactions. The current research demonstrated the potential feasibility of modifying the texture of goat milk cheese by JP or LBP, available for developing tunable goat milk cheese to satisfy consumer preferences and production needs.

Multi-color switchable visible light source generated via nonlinear frequency conversion of a random fiber laser.

Nonlinear frequency conversion of random fiber lasers could provide new possibilities to realize visible and mid-infrared light with flexible wavelength and low temporal/spatial coherence. Frequency doubling of random fiber laser is reported to generate visible light with single-color output. Here, we propose a new way to generate multi-color switchable visible light source from a dual-wavelength switchable 1st-order random Raman fiber laser (RRFL) with phosphosilicate fiber. Taking advantage of the existence of the two Raman gain peaks with significant different Raman gain bandwidth at the frequency shifts of 13.2 THz (silica-related one with broad Raman gain bandwidth) and 39.9 THz (phosphorus-related one with narrow Raman gain bandwidth) in phosphosilicate fiber, a dual-wavelength switchable RRFL is developed which can emit 1120 and 1238 nm random Raman lasing individually or simultaneously with 3-watt level output power and sub-1 nm bandwidth by precisely tuning the pump wavelength to manipulate the Raman gain at two fixed Raman Stokes wavelengths. It is expected that the output power can be further increased with a shorter fiber length and more powerful pump, and the spectral bandwidth can be much narrower by adopting a narrowband point reflector in 1st-order RRFL. Based on the dual-wavelength RRFL with a flexible power ratio and a periodically poled lithium niobate (PPLN) crystal array containing three separate poled gratings with different periods, the second-harmonic generation of 1120 nm or 1238 nm random lasing and sum-frequency generation of 1120 nm and 1238 nm random lasing can be performed. As a result, the switchable output of green light at 560 nm, yellow light at 588 nm and red light at 619 nm can be realized with optical power of 22.2 mW, 16.9 mW and 18.5 mW, respectively. Our work demonstrates dual-wavelength RRFL could act as a new platform for generating visible light source with flexible color output which has potential applications in imaging, sensing and visible temporal ghost imaging.

High-power Yb:CALGO regenerative amplifier and 30 fs output via multi-plate compression.

The pulse energy and average power are two long-sought parameters of femtosecond lasers. In the fields of nonlinear-optics and strong-field physics, they respectively play the role to unlock the various nonlinear processes and provide enough photon fluxes. In this paper, a high-energy and high-power Yb:CALGO regenerative amplifier with 120 fs pulse width is reported. This high-performance regenerative amplifier can work with high stability in a large tuning range of repetition rates. Varying the repetition rate from 3 to 180 kHz, the maximum output power of 36 W and the pulse energy up to 4.3 mJ, corresponding to a peak power of more than 20 GW are demonstrated. The output beam is near diffraction limited with M2 = 1.09 and 1.14 on the horizontal and vertical directions, respectively. In addition, multi-plate compression is employed to achieve 30 fs output with 23 W average power which is attractive for applications such as high-harmonic generation.

Ultrabroad (3.7-17†µm) tunable femtosecond optical parametric amplifier based on BaGa4Se7 crystal.

We demonstrate the first (to the best of our knowledge) tunable femtosecond (fs) mid-infrared (MIR) optical parametric amplifier (OPA) based on BaGa4Se7 (BGSe) crystal with an ultra-broadband spectral range. Benefiting from the broad transparency range, high nonlinearity, and relatively large bandgap of BGSe, the MIR OPA pumped at 1030 nm with a repetition of 50 kHz has an output spectrum that is tunable across an extremely wide spectral range spanning from 3.7 to 17 µm. The maximum output power of the MIR laser source is measured as 10 mW at a center wavelength of 16 µm, corresponding to a quantum conversion efficiency of 5%. Power scaling is straightforwardly achieved by using a stronger pump in BGSe with an available large aperture size. A pulse width of 290 fs centered at 16 µm is supported by the BGSe OPA. Our experimental result indicates that BGSe crystal could serve as a promising nonlinear crystal for fs MIR generation with an ultra-broadband tuning spectral range via parametric downconversion for applications such as MIR ultrafast spectroscopy.

Tailoring the efficiency and spectrum of a green random laser generated by frequency doubling of random fiber lasers.

Frequency doubling of random fiber lasers could provide an effective way to realize visible random lasing with the spectrum filled with random frequencies. In this paper, we make a comprehensive study on the efficiency and spectral manipulation of a green random laser generated by frequency doubling of an ytterbium-doped random fiber laser (YRFL). To tailor the efficiency of green random lasing generation, the ytterbium-doped random fiber lasing is filtered at different spectral positions, and then amplified to watt-level to serve as the fundamental laser source for frequency doubling in a periodically poled lithium niobate (PPLN) crystal. We found that by selecting different spectral components of ytterbium-doped random fiber lasing, the temporal intensity fluctuations of the filtered radiations vary dramatically, which plays an important role in enhancing the efficiency of frequency doubling. By fixing the filtering radiation wavelength at 1064.5 nm and tuning the central wavelength of YRFL, we experimentally demonstrate that, compared to the filtered radiation in the center of the spectrum, the efficiency of frequency doubling can be nearly doubled by utilizing the filtered ytterbium-doped random fiber lasing in the wings of the spectrum. As a result, the conversion efficiency of the generated green random laser at 532.25 nm can be more than 11% when the input power of the polarized 1064.5 nm fundamental light is 2.85W. For spectral manipulation, we realize a spectral tunable green random laser in the range of 529.9 nm to 537.3 nm with >100 mW output power for the first time by tuning the wavelength of YRFL and the temperature of PPLN simultaneously. The system can be naturally modified to simultaneously realize the efficiency enhancement and wavelength tuning, thus providing a new route to generate high efficiency and tunable visible random laser via frequency doubling that are potentially useful for imaging, sensing and visible light communication applications.

Large-scale pattern transfer based on non-through-hole AAO self-supporting membranes.

Fabricating large-scale nanoarrays is a significant and challenging work in the field of nanometer devices. Anodic aluminum oxide (AAO) membrane is considered as a promising mask due to its inherent advantages such as low-cost and tunable pore diameter. However, there are few reports on the use of non-through-hole large-area AAO membrane as a mask. Due to its higher mechanical strength, non-through-hole AAO membrane has the advantage of self-supporting for large-area fabrication. Herein, we present a robust approach to transferring nanopattern to substrates with high fidelity by using the non-through-hole AAO membrane as an etching mask. A novel two-step inductively coupled plasma (ICP) etching method is adopted. The morphological evolution of the AAO during ICP etching is systematically investigated. The aspect ratio of the AAO can be quantitatively controlled by adjusting etching time. The AAO nanopore arrays with an area of 7.1 cm2 are successfully transferred to gallium nitride wafer to enhance photoluminescence. The luminous intensity of the nano-array LED with a pore diameter of 400 nm and a depth of 150 nm is improved by 3.4 times compared with the LED without the nano-array. This method extends the opportunities for AAO mask to serve as generic templates for novel applications that are previously impractical due to the difficulty of large-scale nano-pattern transfer.

Cadmium Uptake by Cuttings of Impatiens walleriana in Response to Different Cadmium Concentrations and Growth Periods.

Impatiens walleriana (I. walleriana), a potential cadmium (Cd) hyperaccumulator, can propagate by cuttings, which are less expensive to grow than seedlings. Different growth periods for cuttings, however, may lead to different physiological characteristics. In this study, I. walleriana cuttings were hydroponically grown in Cd-containing solutions (1.0-10.0 µM) for various growth periods (10-60 days). Experimental results showed that the Cd treatments had negative effects on growth compared to the controls that were not spiked with Cd. The extension of the growth period promoted most of the growth exhibitions of I. walleriana, except for SPAD readings for cuttings grown in the 5.0 and 10.0 µM solutions. The accumulation of Cd also increased over time, except in the roots of the cuttings grown in the 5.0 and 10.0 µM solutions. The subcellular distribution and chemical forms of Cd showed that I. walleriana developed better tolerance and detoxification capacities in the cuttings grown in the 5.0 and 10.0 µM solutions than in the cuttings grown in the other two Cd treatments.

Addressing flavor challenges in reduced-fat dairy products: A review from the perspective of flavor compounds and their improvement strategies.

In recent years, the demand for reduced-fat dairy products (RFDPs) has increased rapidly as the health risks associated with high-fat diets have become increasingly apparent. Unfortunately, lowering the fat content in dairy products would reduce the flavor perception of fat. Fat-derived flavor compounds are the main contributor to appealing flavor among dairy products. However, the contribution of fat-derived flavor compounds remains underappreciated among the flavor improvement factors of RFDPs. Therefore, this review aims to summarize the flavor perception mechanism of fat and the profile of fat-derived flavor compounds in dairy products. Furthermore, the characteristics and influencing factors of flavor compound release are discussed. Based on the role of these flavor compounds, this review analyzed the current and potential flavor improvement strategies for RFDPs, including physical processing, lipolysis, microbial applications, and fat replacement. Overall, promoting the synthesis of milk fat characteristic flavor compounds in RFDPs and aligning the release properties of flavor compounds from the RFDPs with those of equivalent full-fat dairy products are two core strategies to improve the flavor of reduced-fat dairy products. In the future, better modulation of the behavior of flavor compounds by various methods is promising to replicate the flavor properties of fat in RFDPs and meet consumer sensory demands.

Characterization of the flavor profile of UHT milk during shelf-life via volatile metabolomics fingerprinting combined with chemometrics.

Ultra-high temperature (UHT) milk is popular among consumers. However, its flavor and texture change in its shelf life. Flavor is highly determinative for the success of dairy products and for consumers' willingness to buy. It is important to milk producers to ensure the optimal flavor of their products in the shelf life. In order to be able to control and predict the flavor quality of UHT milk during the shelf life, this study compared the variations in sensory quality, volatile aroma release and backbone flavor factors and developed a discriminant model to assess flavor quality based on flavouromics data of five competing milk sample during storage. Using partial least squares discriminant analysis (PLS-DA) with Electronic-nose (E-nose) data excellent classification sensitivity and specificity were achieved compared to models based on gas chromatography-mass spectrometry (GC-MS) data. The PLS-DA model using E-nose data exhibited a 100% correct classification rate for the storage period, and a 92% correct rate based on the eight variable importance in the projection (VIP) elements screened for volatile components from different groups. The discriminative model developed herein based on E-nose combined with chemometrics demonstrated advantages such as speed, efficiency, and environmental friendliness. This method shows promise as a precise tool for analyzing aroma changes in UHT milk during its shelf life, and provide support for controlling the flavor substances and milk product development.

A label-free electrochemical aptasensor based on a gold nanoparticle/carbon nanotube/metal-organic framework nanohybrid for ultrasensitive detection of streptomycin in milk samples.

In this work, a novel electrochemical aptasensor was designed for the sensitive and specific detection of STR in milk samples. First, a gold nanoparticle@poly(diallyldimethylammonium chloride) nitrogen-doped carbon nanotube/polyethyleneimine-functionalized metal-organic framework (MOF) (Au@P-N-CNT/PEI-MIL-101(Cr)) composite was synthesized and characterized by various technique. The Au@P-N-CNT/PEI-MIL-101(Cr) composite was then modified on a bare glassy carbon electrode (GCE) surface, providing a favorable platform (Au@P-N-CNT/PEI-MIL-101(Cr)/GCE) for aptamer immobilization and current signal amplification. The STR aptamer was grafted to the Au@P-N-CNT/PEI-MIL-101(Cr)/GCE through the formation of Au-S bonds and π-π stacking interactions. The immobilized STR aptamer binds specifically STR, resulting in an obvious decrease in the current signal. Under the optimal experimental conditions, the linear range of the electrochemical aptasensor for STR detection was 0.01-250 nM which the detection limit (LOD) was calculate as 2.31 nM. This strategy is expected to be a novel platform for the rapid and sensitive detection of STR.

Self-assembly of Au nanocrystals into large-area 3-D ordered flexible superlattice nanostructures arrays for ultrasensitive trace multi-hazard detection.

Plasmonic nanoparticles that self-assemble into highly ordered superlattice nanostructures hold substantial promise for facilitating ultra-trace surface-enhanced Raman scattering (SERS) detection. Herein, we propose a boiling-point evaporation method to synthesize ordered monocrystal-like superlattice Au nanostructures (OML-Au NTs) with a polyhedral morphology. Combined with thermal nanoimprint technology, OML-Au NTs were directly transferred to impact-resistant polystyrene (IPS) flexible SERS substrates, the obtained flexible substrates (donated as OML-Au NTs/IPS) detection limit for R6G molecules as low as 10-13 M. These results were confirmed by simulating the electromagnetic field distribution of ordered/unordered two-dimensional single-layer and three-dimensional aggregated gold nanostructures. The OML-Au NTs/IPS substrates were successfully used to detect and quantify three commonly-used agricultural pesticides, achieving detection limits as low as 10-11 M and 10-12 M, and in situ real-time detection limit reached 0.24 pg/cm2 for thiram on apple peels, which was 3 orders of magnitude lower than the current detection limit. In addition, the Raman intensity from multiple locations showed a relative standard deviation lower than 7 %, exhibiting the reliability necessary for practical applications. As a result, this research demonstrates a highly reproducible method to enable the development of plasmonic nanomaterials with flexible superstructures.

Digital mapping of surface turbulence status and aerodynamic stall on wings of a flying aircraft.

Real-time monitoring of flow turbulence is very difficult but extremely important in fluid dynamics, which plays an important role in flight safety and control. Turbulence can cause airflow to detach at the end of the wings, potentially resulting in the aerodynamic stall of aircraft and causing flight accidents. Here, we developed a lightweight and conformable system on the wing surface of aircraft for stall sensing. Quantitative data about airflow turbulence and the degree of boundary layer separation are provided in situ using conjunct signals provided by both triboelectric and piezoelectric effects. Thus, the system can visualize and directly measure the airflow detaching process on the airfoil, and senses the degree of airflow separation during and after a stall for large aircraft and unmanned aerial vehicles.

Highly efficient octave-spanning long-wavelength infrared generation with a 74% quantum efficiency in a χ(2) waveguide.

The realization of compact and efficient broadband mid-infrared (MIR) lasers has enormous impacts in promoting MIR spectroscopy for various important applications. A number of well-designed waveguide platforms have been demonstrated for MIR supercontinuum and frequency comb generations based on cubic nonlinearities, but unfortunately third-order nonlinear response is inherently weak. Here, we propose and demonstrate for the first time a χ(2) micrometer waveguide platform based on birefringence phase matching for long-wavelength infrared (LWIR) laser generation with a high quantum efficiency. In a ZnGeP2-based waveguide platform, an octave-spanning spectrum covering 5-11 µm is generated through optical parametric generation (OPG). A quantum conversion efficiency of 74% as a new record in LWIR single-pass parametric processes is achieved. The threshold energy is measured as ~616 pJ, reduced by more than 1-order of magnitude as compared to those of MIR OPGs in bulk media. Our prototype micro-waveguide platform could be extended to other χ(2) birefringence crystals and trigger new frontiers of MIR integrated nonlinear photonics.

[Numerical analysis on hemodynamics of cerebral aneurysm clip].

Computational fluid dynamics (CFD) was used to numerically investigate the blood flow in 3-D models of human preoperative and posteroperative of cerebral aneurysm clip, and the feasibility of surgical operation was evaluated by the calculated hemodynamics parameters. Mimics software was used to reconstruct the models from CT angiograms, and numerical simulation of blood flow at different time in a cardiac circle was performed. Comparison analysis of blood flow in three models of human preoperative and posteroperative of cerebral aneurysm clip was conducted in terms of blood velocity distribution, wall shear stress (WSS) distribution and pressure distribution. The results demonstrated that blood velocity and WSS were significantly increased, and pressure was obviously decreased.

A collision-free gallop-based triboelectric-piezoelectric hybrid nanogenerator.

Energy harvesting technologies that convert fluid energy into usable electrical energy are of great significance, especially in long-distance pipeline systems. Here, in order to avoid the collision of conventional galloping triboelectric nanogenerators (GTENGs), and cause material damage or noise, a freestanding gallop-based triboelectric-piezoelectric hybrid nanogenerator (HG P-TENG) is proposed to reduce material wear and improve the reliability of GTENG. Two piezoelectric sheets are attached to the cantilever beam. The root-mean-square (RMS) and peak output power of the HG P-TENG are 68.9 µW and 1.27 mW, respectively. To improve the harvesting efficiency, the fixed copper electrodes are segmented, and experiments indicate that this way of segmenting electrodes can improve the energy harvesting efficiency. Finer electrodes can effectively increase the charging rate of capacitors. A self-powered thermohygrometer and light-emitting diodes (LEDs) are demonstrated in the wind tunnel. It demonstrates that the proposed hybrid nanogenerator will exhibit great potential in pipeline systems.

Preparation of chitosan/sodium alginate conductive hydrogels with high salt contents and their application in flexible supercapacitors.

Conductive hydrogels (CHs) are a potential material for flexible electronics. However, most of CHs display disadvantages of low ionic conductivities and intolerance to low temperatures. Herein, a novel physical CHs with salt contents as high as 30 wt% was prepared with chitosan (CTS) and sodium alginate (SA) by combining the anti-polyelectrolyte effect and semi-dissolution acidification sol-gel transition (SD-A-SGT) method. The obtained hydrogels show extremely high ionic conductivities up to 2.96 × 10-1 S·cm-1 at room temperature and 4.9 × 10-2 S·cm-1 at -20 °C. The effects of different salts on the ion mobility and electrochemical properties of CTS/SA CHs were predicted and analyzed. The flexible supercapacitor assembled using CTS/SA CHs as the electrolyte exhibits the specific capacitance as high as 405 F·g-1 at the current density of 0.25 A·g-1 and satisfying electrochemical stability with 74.91% capacitance retention in 1000 cycles. Our work has provided a new strategy for constructing green CHs with high ionic conductivities.

Unraveling the mechanism of raffinose utilization in Ligilactobacillus salivarius Ren by transcriptomic analysis.

In the gastrointestinal tract, some dietary carbohydrates, such as xylose, raffinose and arabinose, are able to stimulate the growth of Lactobacillus and Bifidobacterium. In this study, the growth rate of Ligilactobacillus salivarius Ren in raffinose was 0.91 ± 0.03 h-1, which was higher than that in glucose (0.83 ± 0.01 h-1). However, limited information is available on specific transporters and glycoside hydrolases responsible for raffinose uptake and catabolism in L. salivarius. Transcriptomic analysis revealed the differential expression of 236 genes (∣log2FoldChange∣ > 0.8) in response to raffinose, which were mainly associated with raffinose transport, raffinose hydrolysis, galactose metabolism and pyruvate metabolism. Notably, gene rafP encoding lactose/raffinose permease was 101.86-fold up-regulated. Two α-galactosidase gene galA1 and galA2 were 117.82-fold and 2.66-fold up-regulated, respectively. To further investigate the role of these genes in raffinose utilization, insertional inactivation was performed using the pORI28-pTRK669 system. The growth assay of these mutants in modified MRS containing 2% (w/v) raffinose indicated that RafP played an important role in raffinose transport and GalA1 was the primary enzyme involved in raffinose hydrolysis. To our knowledge, this is the first report on the molecular mechanism of raffinose utilization in L. salivarius. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03280-6.