Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion.

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500 nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4 °C min-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

A Novel Tensor Ring Sparsity Measurement for Image Completion.

As a promising data analysis technique, sparse modeling has gained widespread traction in the field of image processing, particularly for image recovery. The matrix rank, served as a measure of data sparsity, quantifies the sparsity within the Kronecker basis representation of a given piece of data in the matrix format. Nevertheless, in practical scenarios, much of the data are intrinsically multi-dimensional, and thus, using a matrix format for data representation will inevitably yield sub-optimal outcomes. Tensor decomposition (TD), as a high-order generalization of matrix decomposition, has been widely used to analyze multi-dimensional data. In a direct generalization to the matrix rank, low-rank tensor modeling has been developed for multi-dimensional data analysis and achieved great success. Despite its efficacy, the connection between TD rank and the sparsity of the tensor data is not direct. In this work, we introduce a novel tensor ring sparsity measurement (TRSM) for measuring the sparsity of the tensor. This metric relies on the tensor ring (TR) Kronecker basis representation of the tensor, providing a unified interpretation akin to matrix sparsity measurements, wherein the Kronecker basis serves as the foundational representation component. Moreover, TRSM can be efficiently computed by the product of the ranks of the mode-2 unfolded TR-cores. To enhance the practical performance of TRSM, the folded-concave penalty of the minimax concave penalty is introduced as a nonconvex relaxation. Lastly, we extend the TRSM to the tensor completion problem and use the alternating direction method of the multipliers scheme to solve it. Experiments on image and video data completion demonstrate the effectiveness of the proposed method.

Direct prediction and compensation of atmospheric turbulence for free-space integer and fractional order OAM multiplexed transmission links.

Atmospheric turbulence has an adverse impact on orbital angular momentum (OAM) beam transmission, resulting in power fluctuations and mode crosstalk. These challenges are particularly pronounced in OAM multiplexing links. In this paper, we propose and demonstrate a novel network architecture that integrates convolutional layers and residual structures to address the issue of turbulence phase compensation. By harnessing the local feature learning capability of convolutional layers and the information-preserving function of residual structures, we aim to mitigate the adverse effects of network depth on information loss. By employing the proposed network, we compensate the turbulence phase directly using the received intensity distributions for free space multiplexed integer and fractional order OAM links, respectively. The obtained results show that the received optical power can be improved for more than 10 dB for integer order OAM multiplexed FSO links under weak to strong turbulence conditions, while 9 dB for fractional-order OAM multiplexed FSO links. Moreover, mode crosstalk can be reduced for about 10 dB under 4 OAM modes multiplexed links under turbulence strength D/r0=5. The proposed deep learning based atmospheric turbulence compensation method can predict phase screens rapidly and accurately, thus enhancing the dependability of future OAM multiplexing technology.

Predicting the orbital angular momentum of atmospheric turbulence for OAM-based free-space optical communication.

Spatial modes of light are susceptible to distortion, particularly by the presence of turbulence in atmospheric free-space links. The scattering of one mode to another disrupts the orthogonality among distinct orbital angular momentum (OAM) modes, leading to modal crosstalk between multiple channels. To enhance the performance of OAM-multiplexed free-space optical (FSO) communication, a convolutional neural network (CNN)-based turbulent OAM approach is proposed for compensating turbulence, with a specific focus on predicting the OAM of turbulence itself. An operator approach is utilized to extract the OAM component of atmospheric turbulence and the CNN is trained to predict the turbulent OAM coefficients. By employing the proposed network, the received power of the OAM-based FSO link can be improved by more than 10 dB under weak to strong turbulence conditions. Compared to Zernike modes, the turbulent OAM modes characterize most of the turbulence information using only a small number of orders. After compensation, when the strong turbulence strength D/r0 = 4, the received power of the transmitted beams with turbulent OAM improves by 4 dB over that with Zernike. Additionally, the crosstalk of multiplexed channels with turbulent OAM is reduced by 10 dB over that with Zernike under varying turbulence conditions.

Generation and free-space transmission characterization of bottle vortex beam.

Vortex beams carrying orbital angular momentum (OAM) with the doughnut-shaped intensity distribution can be employed in free-space optical (FSO) communication links to circumvent obstructions. However, the size of the receiver aperture is proportional to the size of obstructions, which seriously constrains the application of OAM beams in this scenario. In this paper, we propose a method to generate bottle vortex beams (BVBs) with a parabolic trajectory by manipulating the radial phase distribution of conventional OAM beams. Meanwhile, the trajectory of BVBs generated are highly compatible with the predesigned trajectory by using this method. Moreover, we evaluate the free-space transmission performance of BVBs under atmospheric turbulence and limited receiving aperture. The results show that BVBs have better OAM FSO communication link performance compared with conventional OAM beams and Bessel beams. In addition, the performance of the BVBs circumventing obstructions is further investigated. The simulation results show that when setting the atmospheric turbulence strength D/r0 = 2 and the obstruction size of 40 mm, the average received optical power of the BVBs captured by a limited receiving aperture diameter (d = 40 mm) is improved about 7 dB and 3 dB compared to conventional OAM beams and Bessel beams, respectively.

Shaping the transmission trajectory of vortex beam by controlling its radial phase.

Vortex beam carrying orbital angular momentum (OAM), which features a helical phase front, has shown its potential applications in diverse areas, especially in free-space optical (FSO) communications. However, when generating vortex beams, the radial phase distribution is usually disregarded in previous reports. In this paper, by controlling the radial phase distribution, we propose a method for the generation of vortex beams with arbitrary convex trajectories. By using this method, we successfully generate vortex beams with different predesigned trajectories with high accuracy. Moreover, we also demonstrate the transmission of the radial phase-controlled vortex beams in FSO links for different scenarios in simulation. Firstly, we generate vortex beams with different OAM states (l=+1, + 3, and +6), which have the same ring diameter at the receiver side. Secondly, we generate three vortex beams (l=+3) with the same ring diameter at different transmission distances (z = 100 m, 200 m, and 300 m). Finally, by carefully controlling the radial phase of the vortex beam, we generate vortex beams that can almost keep the same ring diameter for a long distance. The proposed method for shaping the transmission trajectory of vortex beams may pave the way for more applications in OAM-based FSO communications.

Turbulence-resistant high-capacity free-space optical communications using OAM mode group multiplexing.

Twisted light carrying orbital angular momentum (OAM), which features a helical phase front, has shown its potential applications in diverse areas, especially in free-space optical (FSO) communications. Multiple orthogonal OAM beams can be utilized to enable high-capacity FSO communication systems. However, for practical OAM-based FSO communication links, atmospheric turbulence will cause serious power fluctuations and inter-model crosstalk between the multiplexed OAM channels, impairing link performance. In this paper, we propose and experimentally demonstrate a novel OAM mode-group multiplexing (OAM-MGM) scheme with transmitter mode diversity to increase system reliability under turbulence. Without adding extra system complexity, an FSO system transmitting two OAM groups with a total of 144 Gbit/s discrete multi-tone (DMT) signal is demonstrated under turbulence strength D/r0 of 1, 2, and 4. In our experiments, the proposed OAM-MGM scheme helps to achieve bit-error-rate (BER) mostly less than 3.8 × 10-3 under turbulence strength D/r0 of 1 and 2 with a total transmitted power of 10 dBm. Compared with the conventional OAM mode multiplexed system, the system interruption probability decreases from 28% to 4% under moderate turbulence strength D/r0 of 2.

High-speed spatial light modulation enabling 25-Gbit/s twisted light encoding/decoding and 260-m security free-space data transmission.

Spatial domain of light beam is an important degree of freedom to be extensively explored. As a set of spatial domains, twisted lights have some natural properties such as orthogonality and security, providing great potentials in optical communications especially for data encoding/decoding. However, the speed of traditional spatial light modulators has always been criticized. Here we present a hundred-meter security free-space data transmission based on high-speed spatial light modulation by exploiting temporal-to-spatial domain mapping. We demonstrate 25-Gbit/s twisted light encoding/decoding and 260-m security free-space data transmission in the experiment. The encoding/decoding link will lead to 3-dB improvement in bit error rate (BER) performance compared with a single channel in theory and ∼1-dB optical signal-to-noise ratio (OSNR) penalty at the forward error correction (FEC) threshold of 3.8e-3 in practice. The experiment results also show favorable security performance of the proposed encoding/decoding link system.

Two New Alkaloids from Roots of Zea mays and Their Cytotoxic Activity against Hep3B and SW480 Cells.

Two undescribed alkaloids, along with seven known compounds, were isolated from the roots of Zea mays (RM). Their chemical structures were elucidated based on extensive analyses of HR-ESI-MS, 1D and 2D NMR, and CD spectra. Two new alkaloids exhibited moderate inhibition of Hep3B (IC50 values of 11.7±2.4 and 14.2±3.6 µM) and SW480 cells (IC50 values of 33.4±8.2 and 47.3±5.8 µM) compared to that of the positive control compound, Oxaliplatin, IC50 value of 8.4±1.7 and 45.8±5.6 µM, respectively.

By-Products of Zea mays L.: A Promising Source of Medicinal Properties with Phytochemistry and Pharmacological Activities: A Comprehensive Review.

Zea mays (Z. mays) is one of the main cereal crops in the world, and it's by-products have exhibited medicinal properties to explore. This article intends to review the chemical compositions and pharmacological activities of by-products of Z. mays (corn silks, roots, bract, stems, bran, and leaves) which support the therapeutic potential in the treatment of different diseases, with emphasis on the natural occurring compounds and detailed pharmacological developments. Based on this review, 231 natural compounds are presented. Among them, flavonoids, terpenes, phenylpropanoids, and alkaloids are the most frequently reported. The by-products of Z. mays possess diuretic effects, hepatoprotective, anti-diabetic, antioxidant, neuroprotective, anti-inflammatory, anti-cancer, plant protection activity, and other activities. This article reviewed the phytochemistry and pharmacological activities of Z. mays for comprehensive quality control and the safety and effectiveness to enhance future application.

Citrullus colocynthis (L.) Schrad.: A Promising Pharmaceutical Resource for Multiple Diseases.

Citrullus colocynthis (L.) Schrad. (Cucurbitaceae) is widely distributed in the desert areas of the world. The fruit bodies of C. colocynthis are recognized for their wide range of nutraceutical potential, as well as medicinal and pharmaceutical uses. The plant has been reported for various uses, such as asthma, bronchitis, cancer, colic, common cold, cough, diabetes, dysentery, and jaundice. The fruit has been extensively studied for its biological activities, which include insecticide, antitumor, and antidiabetic effects. Numerous bioactive compounds have been reported in its fruit bodies, such as essential oils, fatty acids, glycosides, alkaloids, and flavonoids. Of these, flavonoids or caffeic acid derivatives are the constituents associated with the inhibition of fungal or bacterial growth, whereas eudesmane sesquiterpenes or sesquiterpene lactones are most active against insects, mites, and nematodes. In this review, the scientific evidence for the biological activity of C. colocynthis against insecticide, cytotoxic, and antidiabetic effects is summarized.

Biotransformation of Ursonic Acid by Aspergillus ochraceus and Aspergillus oryzae to Discover Anti-Neuroinflammatory Derivatives.

Biotransformation of ursonic acid (1) by two fungal strains Aspergillus ochraceus CGMCC 3.5324 and Aspergillus oryzae CGMCC 3.407 yielded thirteen new compounds (4, 5, 7-10, and 13-19), along with five recognized ones. The structural details of new compounds were determined through spectroscopic examination (NMR, IR, and HR-MS) and X-ray crystallography. Various modifications, including hydroxylation, epoxidation, lactonization, oxygen introduction, and transmethylation, were identified on the ursane core. Additionally, the anti-neuroinflammatory efficacy of these derivatives was assessed on BV-2 cells affected by lipopolysaccharides. It was observed that certain methoxylated and epoxylated derivatives (10, 16, and 19) showcased enhanced suppressive capabilities, boasting IC50 values of 8.2, 6.9, and 5.3 µM. Such ursonic acid derivatives might emerge as potential primary molecules in addressing neurodegenerative diseases.

Chemistry and biological activity of resin glycosides from Convolvulaceae species.

Carbohydrate-based drug discovery has gained more and more attention during the last few decades. Resin glycoside is a kind of novel and complex glycolipids mainly distributed in plants of the family Convolvulaceae. Over the last decade, a number of natural resin glycosides and derivatives have been isolated and identified, and exhibited a broad spectrum of biological activities, such as cytotoxic, multidrug-resistant reversal on both microbial pathogens and mammalian cancer cells, antivirus, anticonvulsant, antidepressant, sedative, vasorelaxant, laxative, and α-glucosidase inhibitory effects, indicating their potential as lead compounds for drug discovery. A systematic review of the literature studies was carried out to summarize the chemistry and biological activity of resin glycosides from Convolvulaceae species, based on various data sources such as PubMed, Web of Science, Scopus, and Google scholar. The keyword "Convolvulaceae" was paired with "resin glycoside," "glycosidic acid," "glycolipid," or "oligosaccharide," and the references published between 2009 and June 2021 were covered. In this article, we comprehensively reviewed the structures of 288 natural resin glycoside and derivatives newly reported in the last decade. Moreover, we summarized the biological activities and mechanisms of action of the resin glycosides with pharmaceutical potential. Taken together, great progress has been made on the chemistry and biological activity of resin glycosides from Convolvulaceae species, however, more exploratory research is still needed, especially on the mechanism of action of the biological activities.

Internal structuring of gallium arsenide using short laser pulses.

Laser writing inside semiconductors attracts attention as a possible route for three-dimensional integration in advanced micro technologies. In this context, gallium arsenide (GaAs) is a material for which the best conditions for laser internal modification (LIM) have not been established yet. We address this question by using laser pulses at a fixed wavelength of 1550-nm. A large parameter space is investigated including the response to the applied pulse energy, pulse duration (from femtosecond to nanosecond) and the focusing conditions. We report that well-defined and reproducible internal modifications are achievable with tightly focused nanosecond pulses. The measured writing thresholds are systematically compared to those obtained in silicon (Si), a more extensively studied material. In comparison to Si, we also observe that GaAs is more prone to filamentation effects affecting the modification responses. The reported specific observations for LIM of GaAs should facilitate the future process developments for applications in electronics or photonics.

Ultrafast laser stabilization by nonlinear absorption for enhanced-precision material processing.

Using ultrafast lasers, sub-diffraction features can be produced thanks to the threshold-based response of materials to the local beam fluence. In practice, Gaussian beams with peak fluence near the modification threshold lead to high-resolution. However, this conflicts with reliability as the process becomes increasingly sensitive to pulse-to-pulse energy fluctuations. Using nonlinear absorption in a ZnS crystal, we demonstrate a passive extra-cavity energy stabilization method in a femtosecond laser material machining configuration. Processing precision and repeatability are enhanced as evidenced by highly reliable amorphous features produced on silicon with sizes ten times smaller than the spot size, becoming a practical solution for high-precision manufacturing applications.

Secondary Metabolites from the Fresh Leaves of Pinus yunnanensis Franch.

Fifteen metabolites, including two flavonols (1-2), three lignans (3-5), and ten diterpenoids (6-15), were isolated from the leaves of Pinus yunnanensis. Among them, flavanonol (1) were identified as undescribed flavonol derivative with natural rarely B-ring fission lactone. Massive spectroscopic methods, the DP4+ probabilities and CD/ECD calculations were applied to establish the structure of component 1. Among these compounds, taxifolin (2) showed potent cytotoxicity, having IC50 values from 21.33 to 45.48 µg/mL, it also showed broad antibacterial activity against human pathogens with MIC values from 32 to 64 µg/mL.

Experimental demonstration of OAM-based transmitter mode diversity data transmission under atmosphere turbulence.

Twisted light carrying orbital angular momentum (OAM), which features helical phase front, has shown its potential applications in diverse areas, especially in optical communications. For OAM-based free-space optical (FSO) links, a significant challenge is the power fading induced by atmospheric turbulence. In this paper, we experimentally demonstrate the mitigation of atmospheric turbulence effects with an OAM-based transmitter mode diversity scheme. By designing multi-OAM phase patterns, we successfully generate multiple OAM modes (OAM-1,0,1, OAM+2,+3,+4, OAM+5,+6,+7) carrying the same data stream for transmitter diversity without adding system complexity. An intensity-modulated direct-detection (IM-DD) system with 39.06 Gbit/s discrete multi-tone (DMT) signal is employed to confirm the feasibility of the OAM-based transmitter mode diversity scheme under atmosphere turbulence. The obtained experimental results show that the received power fluctuation and average bit-error rate (BER) are decreased under moderate to strong turbulence compared to the traditional single OAM mode transmission. In addition, the required transmitted power at 10% interruption probability is relaxed by nearly 2 dB under moderate to strong turbulence.

Free-space optical communication with quasi-ring Airy vortex beam under limited-size receiving aperture and atmospheric turbulence.

Vortex beams carrying orbital angular momentum (OAM), which feature helical wavefronts, have been regarded as an alternative degree of freedom for free-space optical (FSO) communication systems. However, in practical applications, atmospheric turbulence and limited-size receiving aperture effects will cause OAM modal degradation and seriously reduce the received power. In this paper, by controlling the radial phase distribution of conventional OAM beams, quasi-ring Airy vortex beams (QRAVBs) are successfully generated in the experiments to increase the received power under the limited-size receiving aperture conditions. By employing 72-Gbit/s 16-ary quadrature amplitude modulation (16-QAM) discrete multi-tone (DMT) signals, we successfully demonstrate free-space data transmission with QRAVBs in the experiments. Moreover, the transmission performance of QRAVBs under atmospheric turbulence is also evaluated. Comparing with conventional OAM beam and Bessel beam, the obtained results show that QRAVBs can achieve higher received power and better BER performance under limited-size receiving aperture and atmospheric turbulence conditions.

Functionalization of freeform curved surfaces by shaped femtosecond laser pulses in the propagation axis.

With ultrashort pulse durations and ultrahigh peak intensities, ultrafast lasers can create different types of micro/nano-structures to functionalize the processed surface with new properties. However, the applications of this method on freeform surfaces are still limited by the short length of a laser focusing spot and complex control of the 3D moving trajectory in the fabrication process. In this paper, we overcome this problem by shaping the on-axis intensity along the propagation axis using the spatial light modulator. By designing the phase mask, we increased the length of the stable-intensity zone (intensity fluctuation < 10%) by more than 3 times compared to that of an unshaped Bessel beam. The energy deposition was also optimized to be less than 2% fluctuation based on simulations. Using this method, we fabricated micro/nano structures on 3D surfaces at different fluences and demonstrated various properties including colorization, anti-reflection, and hydrophobicity in large height range. We demonstrated the applications of the proposed method in creating hydrophobicity on complex freeform syringe tip surfaces. This improved the minimum manipulatable volume of a liquid droplet to 2 times smaller compared with untreated syringe, thus greatly extending its performance for micro-droplet manipulation. This method offers an alternative approach for reliable and affordable freeform curved-surface processing.

Fabrication of microlenses with continuously variable numerical aperture through a temporally shaped femtosecond laser.

We developed a novel method for fabricating microlenses and microlens arrays by controlling numerical aperture (NA) through temporally shaped femtosecond laser on fused silica. The modification area was controlled through the pulse delay of temporally shaped femtosecond laser. The final radius and sag height were obtained through subsequent hydrofluoric acid etching. Electron density was controlled by the temporally shaped femtosecond laser, and the maximum NA value (0.65) of a microlens was obtained in the relevant studies with femtosecond laser fabrication. Furthermore, the NA can be continuously adjusted from 0.1 to 0.65 by this method. Compared with the traditional methods, this method exhibited high flexibility and yielded microlenses with various NAs and microlens arrays to meet the different demands for microlens applications.