Efficient characterizations of multiphoton states with an ultra-thin optical device.

Metasurface enables the generation and manipulation of multiphoton entanglement with flat optics, providing a more efficient platform for large-scale photonic quantum information processing. Here, we show that a single metasurface optical device would allow more efficient characterizations of multiphoton entangled states, such as shadow tomography, which generally requires fast and complicated control of optical setups to perform information-complete measurements, a demanding task using conventional optics. The compact and stable device here allows implementations of general positive operator valued measures with a reduced sample complexity and significantly alleviates the experimental complexity to implement shadow tomography. Integrating self-learning and calibration algorithms, we observe notable advantages in the reconstruction of multiphoton entanglement, including using fewer measurements, having higher accuracy, and being robust against experimental imperfections. Our work unveils the feasibility of metasurface as a favorable integrated optical device for efficient characterization of multiphoton entanglement, and sheds light on scalable photonic quantum technologies with ultra-thin optical devices.

Recognizing the variation of DNA-P during and after the algal bloom in lake Hulun.

Eutrophication has spread from shallow lakes in temperature zones to lakes in cold regions as a result of a continuous warm climate and human activities. Little proof for the importance of dissolved organic phosphorus (DOP) in contributing to phosphorus cycling and algae growth has been generated for aquatic ecosystems, particularly in cold eutrophic lakes. In this study, a comprehensive in situ study was conducted in overlying water, suspended particulate matter, and sediment during and after algal bloom (in July and September, respectively) in Lake Hulun. Multiple methods of 31P NMR, enzymatic hydrolysis, and UV-visible technologies were combined to detect phosphorus occurrence, bioavailability, and molecular structure from a novel angle. The 31P NMR analysis results showed that DNA-P is mainly stored in the dissolved phase and has not been detected in suspended particulate matter or sediment. Enzymatic hydrolysis was used to determine the bioavailability of DOP, which revealed that in July and September, respectively, 85% and 79% of DOP were hydrolyzable. UV-visible analysis represented that the degree of humification and molecular weight of DOP were high during the algal bloom, but these values considerably dropped following the algal bloom. The large amount of DNA-P present in the overlying water is the main reason for the high degree of humification and high molecular weight of the water body. Besides, Lake Hulun's DNA-P remains highly bioavailable during algal blooms, despite its high degree of humification and molecular weight. These findings can serve as a theoretical basis for understanding the migration and transformation of DOP, as well as the persistence of algal blooms in eutrophic lakes located in cold regions.

Response of dissolved organic matter (DOM) and microbial community to submerged macrophytes restoration in lakes: A review.

Microorganisms play a crucial role in the biogeochemical processes of Dissolved Organic Matter (DOM), and the properties of DOM also significantly influence changes in microbial community characteristics. This interdependent relationship is vital for the flow of matter and energy within aquatic ecosystems. The presence, growth state, and community characteristics of submerged macrophytes determine the susceptibility of lakes to eutrophication, and restoring a healthy submerged macrophyte community is an effective way to address this issue. However, the transition from eutrophic lakes dominated by planktic algae to medium or low trophic lakes dominated by submerged macrophytes involves significant changes. Changes in aquatic vegetation have greatly affected the source, composition, and bioavailability of DOM. The adsorption and fixation functions of submerged macrophytes determine the migration and storage of DOM and other substances from water to sediment. Submerged macrophytes regulate the characteristics and distribution of microbial communities by controlling the distribution of carbon sources and nutrients in the lake. They further affect the characteristics of the microbial community in the lake environment through their unique epiphytic microorganisms. The unique process of submerged macrophyte recession or restoration can alter the DOM-microbial interaction pattern in lakes through its dual effects on DOM and microbial commu-----nities, ultimately changing the stability of carbon and mineralization pathways in lakes, such as the release of methane and other greenhouse gases. This review provides a fresh perspective on the dynamic changes of DOM and the role of the microbiome in the future of lake ecosystems.

Improved 31P NMR analysis of phosphorus in highly mineralized lake water using a modified pretreatment procedure with H resin.

31P Nuclear Magnetic Resonance (31P NMR) is an important analytical tool for identifying and quantifying phosphorus-based compounds in aquatic environments. However, the precipitation method typically used for analyzing phosphorus species via 31P NMR has limited application. To expand the scope of the method and apply it to highly mineralized rivers and lakes worldwide, we present an optimization technique that employs H resin to assist phosphorus (P) enrichment in highly mineralized lake water. To explore how to reduce analysis interference from salt in highly mineralized water and improve the accuracy of P analysis using 31P NMR, we conducted case studies on Lake Hulun and Qing River. This study aimed to increase the efficiency of phosphorus extraction in highly mineralized water samples by using H resin and optimizing key parameters. The optimization procedure included determining the enriched water volume, H resin treatment time, AlCl3 addition amount, and precipitation time. The final recommended optimization enrichment procedure involves treating 10 L of filtered water sample with 150 g of Milli-Q water-washed H resin for 30 s, adjusting the pH of the treated sample to 6-7, adding 1.6 g of AlCl3, stirring the mixture, and allowing the solution to settle for 9 h to collect the flocculated precipitate. The precipitate was then extracted with 30 mL of 1 M NaOH +0.05 M DETA extraction solution at 25 °C for 16 h, and the supernatant was separated and lyophilized. The lyophilized sample was redissolved in 1 mL of 1 M NaOH +0.05 M EDTA. This optimized analytical method using 31P NMR effectively identified phosphorus species in highly mineralized natural waters and can be applied to other highly mineralized lake waters globally.

Experimental demonstration of optical trapping and manipulation with multifunctional metasurface.

Chip-scale optical tweezers, which are usually implemented in a planar format without using bulky diffractive optical elements, are recognized as a promising candidate to be integrated with a lab-on-a-chip system. However, traditional chip-scale optical tweezers are often static and allow for only one type of manipulation functionality since the geometrical parameters of the tweezers are fixed. Herein, we introduce a new, to the best of our knowledge, class of on-chip optical tweezers for diverse types of manipulation of micro-particles. Utilizing both the propagation phase and Pancharatnam-Berry phase, we experimentally demonstrate the spin-dependent trapping, moving, and circling of micro-particles with the transfer of optical gradient force and orbital angular momentum to particles. We further show that the spin angular momentum of the output beam provides an additional degree of freedom to control the spinning rotation of particles. This new type of optical tweezers paves the way for multifunctional and dynamical trapping and manipulation of particles with a lab-on-a-chip system.

Compact 2D serpentine optical phased array.

We present a two-dimensional (2D) Si photonics optical phased array (OPA) using a serpentine design which eliminates the long directional couplers used in many 2D OPA designs. It significantly reduces the distance between the antenna benefitting far-field sidelobe reduction while maintaining high optical power use efficiency.

Tailoring PTV expansion to improve the dosimetry of post modified radical mastectomy intensity-modulated radiotherapy for left-sided breast cancer patients by using 4D CT combined with cone beam CT.

PURPOSE: Our study aimed to improve the dosimetry of post modified radical mastectomy intensity-modulated radiotherapy (PMRM-IMRT) for left-sided breast cancer patients by tailoring and minimizing PTV expansion three-dimensionally utilizing 4D CT combined with on-board cone beam CT (CBCT). METHODS: We enrolled a total of 10 consecutive left-sided breast cancer patients to undergo PMRM-IMRT. We measured the intra-fractional CTV displacement attributed to respiratory movement by defining 9 points on the left chest wall and quantifying their displacement by using the 4D CT, and measured the inter-fractional CTV displacement resulting from the integrated effect of respiratory movement, thoracic deformation and set up errors by using CBCT. We created 3 different PMRM-IMRT plans for each of the patients using PTVt (tailored PTV expansion three-dimensionally), PTV0.5 and PTV0.7 (isotropic 0.5- cm and isotropic 0.7- cm expanding margin of CTV), respectively. We performed paired samples t test to establish a hierarchy in terms of plan quality and dosimetric benefits. P < 0.05 was considered statistically significant. RESULTS: The inter-fractional CTV displacement (2.6 ± 2.2 mm vertically, 2.8 ± 2.3 mm longitudinally, and 1.7 ± 1.2 mm laterally) measured by CBCT was much larger than the intra-fractional one (0.5 ± 0.5 mm vertically, 0.5 ± 1.0 mm longitudinally, and 0.3 ± 0.3 mm laterally, respectively) measured by 4D CT. Intensity-modulated radiotherapy with tailored PTV expansion based on inter-fractional CTV displacement had dosimetrical advantages over those with PTV0.5 or those with PTV0.7 owing to its perfect PTV dose coverage and better OARs sparing(especially of heart and left lung). CONCLUSION: The CTV displacement in PMRM-IMRT predominantly arises from inter-fraction rather than from intra-fraction during natural respiration and differs in 3 coordinate axes either inter-fractionally or intra-fractionally. Tailoring and minimizing PTV expansion three-dimensionally significantly improves the dosimetry of PMRM-IMRT for left-sided breast cancer patients.

Preparation of biochar as a coating material for biochar-coated urea.

Biochar was used as a coating material for slow release urea. However, influence of biochar performance on preparing biochar-coated urea (BCU) and nitrogen release characteristics is rarely reported. In this study, total of 24 biochars were prepared and characterized from six biomass residues (rice straw, chicken manure, vinasse, Phyllostachys pubescens, Arundo donax and sugarcane bagasse) at four pyrolysis temperatures (400-700 °C). Grey correlation analysis (GCA) was used to select biochar as a coating material for BCU based on biochar performance indicators. The feasibility (BCU formability) for preparing BCU and characteristics of nitrogen release in BCU based on hydrostatic dissolution test and soil column leaching experiment were evaluated. Biochar prepared at low pyrolysis temperature was not suitable as a coating material for BCU due to low specific surface area. Biochars derived from pyrolysis of Phyllostachys pubescens (BP6), vinasse (BV6) and rice straw (BR6) at 600 °C were selected as coating materials for BCU based on grey correlation analysis (GCA). The adhesion of biochar to urea surface was related to biomass type that preparing biochar. BV6 was recommended for use as coating material for BCU because the feasibility of the biochars followed the order BR6 > BV6 > BP6, and the practicality of the biochars followed the order BP6 > BV6 > BR6. The findings suggest that biochar with a high specific surface area, hydrophilic oxygen-containing functional groups and low pH is a suitable material for BCU.

Impact of third-order dispersion and three-photon absorption on mid-infrared time magnification via four-wave mixing in Si0.8Ge0.2 waveguides.

We investigate the influence of third-order dispersion of dispersive elements, three-photon absorption and free-carrier effects on mid-infrared time magnification via four-wave mixing (FWM) in ${{\rm Si}_{0.8}}{{\rm Ge}_{0.2}}$Si0.8Ge0.2 waveguides. It is found that the magnified waveform is seriously distorted by these factors, and conversion efficiency is decreased, mainly because of nonlinear absorption. A time lens based on FWM in ${{\rm Si}_{0.8}}{{\rm Ge}_{0.2}}$Si0.8Ge0.2 waveguides is proposed for time magnification of mid-infrared ultrashort pulses, in which the low-distortion, high-magnification in the time domain could be obtained by optimizing system parameters. These results make it possible to analyze the transient dynamic process through oscilloscopes and detectors with gigahertz bandwidth and have important applications in ultrafast process analysis, optical pulse sampling, and optical communications.

Mid-infrared dual-comb generation via the cross-phase modulation effect in a normal-dispersion microcavity.

We numerically demonstrate orthogonally polarized dual-comb generation in a single microcavity with normal dispersion assisted by the cross-phase modulation (XPM) effect. It is found that the XPM effect facilitates the emission of a secondary polarized comb with different temporal properties in a wide existence range covering the blue- to red-detuned regime and thus releases the requirements for delicate control on the detuned region of pump frequency. Also, the energy transfer between two polarization components together with the normal-dispersion property contributes to a more balanced intensity difference and significantly increased conversion efficiency from the pump light into the comb operation. This work could provide a route to a low-cost and compact mid-infrared dual-comb system with a lower power requirement as well as an effective approach to higher comb teeth power with improved efficiency for practical applications.

Sulfur controlled cadmium dissolution in pore water of cadmium-contaminated soil as affected by DOC under waterlogging.

Cadmium (Cd) precipitation and dissolution in pore water is associated with dissolved organic carbon (DOC)-induced reduction-oxidation of sulfur (S) under waterlogging and is vital for controlling the bioavailability in paddy soil. A 120-day soil incubation experiment, including application of sulfur (S, 30 mg kg-1) and wheat straw (W, 1.0%) alone or in combination (W + S) into Cd-contaminated paddy soil under waterlogging, was conducted to investigate the dynamic of dissolved Cd and its relationship with DOC, S2-, Fe2+, pH, Eh and pe + pH in soil pore water. The results showed that the lowest dissolved Cd concentration was observed in the W + S-treated soil pore water among all treatments when the soil Eh remained at lower values during the period of 15-60 days of incubation, which could be attributed to CdS precipitation and/or co-precipitation of Cd absorbed by FeS2 because of the reduction in sulfur. The application of S resulted in a Cd rebound in the pore water irrespective of W addition when the Eh began to increase from its lowest values during the period of 45-75 days of incubation, and SOB genera were observed in the S added soil. This could be attributed to re-dissolution of the precipitated Cd in soils under the SOB-driven oxidation of sulfide such as CdS and FeS2. In conclusion, DOC-driven reduction-oxidation of sulfur controls Cd dissolution in the pore water of Cd-contaminated paddy soil under waterlogging conditions. Further studies are required to investigate the interaction of sulfur and SOM-induced DOC on Cd bioavailability in rice-planted paddy soils.

Water-soluble mercury induced by organic amendments affected microbial community assemblage in mercury-polluted paddy soil.

Mercury (Hg) pollution or organic amendments (OA) may individually induce changes in the microbial community of paddy soils. However, little is known regarding the interaction of Hg and OA and the effect of different OA applications on the microbial community assemblage in Hg-polluted paddy soil. A soil incubation experiment was performed by applying three organic amendments (OA), namely a food-waste compost (FC), and its HA and FA, into an Hg-polluted paddy soil to examine the changes in the microbial community and merA/merB gene abundance. The results showed that the OA treatments promoted total (SOC) and dissolved organic carbon (DOC) in soils, which may harbor copiotrophic bacteria. The HA and FA treatments decreased microbial diversity and richness along with an increase of water-soluble Hg (WHg) through the complexation of DOC to Hg, which may be mainly attributed to the enhanced Hg biotoxicity to soil microbiome induced by the increased WHg under these two treatments. Additionally, the WHg enhancement also contributed to the increase of Hg-resistant bacteria and merA/merB gene abundance, and consequently, induced changes in the microbial community. These results indicated the interaction of Hg and different OA induced the variation of WHg fraction in paddy soil, which played a fundamental role in the distinct responses of the microbial community assemblage. Collectively, the application of FA and HA to Hg-polluted soil should be limited considering Hg risk to microbiome, and FC can be an alternative.

Phosphorus Leaching from Soil Profiles in Agricultural and Forest Lands Measured by a Cascade Extraction Method.

The risk of P leaching from topsoil based on the change-point estimated via a split-line model between Olsen P and leachable P extracted by 0.01 M CaCl has been reported. However, little information is available for the assessment of P leaching from soil profiles. In this study, samples were collected at three depth profiles (0-20 cm, topsoil; 20-40 cm, subsoil; 40-60 cm, third-layer soil) at each of 74 sites under agriculture and forest in an agroforestry area. A cascade extraction method was proposed to determine the leachable P in the subsoil, extracted by the topsoil extraction solution; a similar extracted process was followed in the third-layer soil, and in the topsoil, it was still extracted by 0.01 M CaCl. A positive linear correlation was found between the subsoil leachable P extracted by the topsoil extraction solution and the accumulated P obtained from the subsoil leached by topsoil leachates, and so on. Therefore, the cascade extraction method for determining leachable P from topsoils and underlying soils could be valuable for predicting the potential of P leaching from soil profiles. Approximately 81, 73, and 73% of the agricultural sampling sites were at or above the change-points for the soil depths of 0 to 20, 20 to 40, and 40 to 60 cm (30.4, 32.9, and 18.2 mg kg respectively); these values were higher than those for the forest site, implying a high risk of P leaching from agricultural soil profiles in the study area.

Organic amendments affect dissolved organic matter composition and mercury dissolution in pore waters of mercury-polluted paddy soil.

Organic amendments (OA) have been applied in many mercury (Hg)-polluted paddy soils to meet increasing food demands with scarce land resources. However, little is known on the effects of different OAs on Hg dissolution and the composition of dissolved organic matter (DOM) in soil pore waters, both of which may be associated with Hg mobility. Consequently, DOM composition and Hg release levels were investigated in soil pore waters after applying food waste compost (FC), fulvic acids (FA) and humic acids (HA) to Hg-polluted paddy soils. FA and HA treatments promoted increased abundances of humic- and fulvic-like substances in pore water DOM while FC amendment increased soluble microbial by-products. FA amendment and high levels of both HA and FC amendments greatly promoted Hg dissolution in pore waters that could be attributed to the complexation of Hg with different DOM components. However, among all DOM components, only UVA fulvic and visible humic-like substances were positively correlated with Hg release levels and total organic carbon. These results indicate that discrepant DOM compositions are induced by different OA. Further, these differences may be associated with differential Hg dissolution in pore waters. Consequently, FA amendment and high level of FC or HA amendments should be limited to reduce potential Hg release into pore waters.

Optimization of pollutant reduction system for controlling agricultural non-point-source pollution based on grey relational analysis combined with analytic hierarchy process.

Many technologies have been developed to control agricultural non-point-source pollution (ANPSP). However, most reduce pollution from only a single source instead of considering an entire region with multiple pollution sources as a control unit. A pollutant reduction system for controlling ANPSP at a regional scale could be built by integrating technologies and the reuse of treated wastewater (TWR) and nutrients (NR) to protect the environment and achieve agricultural sustainability. The present study proposes four systematic schemes involving TWR for irrigation and NR in a region with three sources of ANPSP (crop farming, livestock and aquaculture). Subsequently, a multi-objective evaluation model is established based on the analytical hierarchy process (AHP) combined with grey relational analysis (GRA) to identify the optimal scheme considering six indices, namely, pollutant reductions (total nitrogen, TN; total phosphorous, TP; ammonium-nitrogen, NH4+-N; and chemical oxygen demand, COD) and costs (construction and operational costs). The Taihu Lake Basin suffers from some of the worst ANPSP in China, and a case study was conducted in a town with three ANPSP sources. Four systems were developed on the basis of suggested technologies and the scenarios of TWR and NR (Scenario I: no reuse, Scenario II: reuse of all livestock wastewater and manure, Scenario III: reuse of some aquaculture wastewater, and Scenario IV: reuse of all livestock wastewater and manure and some aquaculture wastewater). Pollutant reductions were calculated based on removal efficiency and pollutant loads, which were estimated from the local pollutant export coefficients and agricultural information (crop farming, livestock, and aquaculture). The costs were determined on the basis of the total pollutant reductions and unit cost. The results showed that the optimal system was the Scenario IV because it had the highest grey correlation degree among the four proposed systems. The optimal system met the irrigation water demand in Xinjian. In the optimal system, the removal efficiencies of the pollutants TN, TP, NH4+-N, and COD were 84.3%, 94.2%, 89.6% and 94.0%, respectively. In addition, the implementation of NR in the optimal system reduced the use of chemical fertilizers by nearly 81.7 kg N ha-1 and 39.9 kg P ha-1. The proposed methods provide a reference for the construction of a pollutant reduction system for controlling ANPSP in a multi-source region.

Organic Carbon Sequestration in Soil Humic Substances As Affected by Application of Different Nitrogen Fertilizers in a Vegetable-Rotation Cropping System.

Little is known on the effect of application of different nitrogen (N) fertilizers on soil organic carbon (SOC) sequestration in soil humic substances (HS). We investigated HS molecular characteristics in an Orthic Acrisol, southwestern China, under 2-year field fertilization of a urea (U), a polymer-coated urea (PCU) and a biochar-coated urea (BCU) using 13C-CPMAS-NMR spectroscopy. Results showed that N fertilization promoted SOC sequestration into HS and favored alkyl-C and aromatic-C rather than O-alkyl-C and carbonyl-C for humic acids and humin in soil. Application of PCU and BCU may better enhance vegetable yield, SOC sequestration, and HS stability than the U application, which may benefit from longer time of N existence and higher total N in soil. Among the N treatments, BCU application mostly affected the compositions and stability of SOC in the HS for the OC input and prime effect of biochar for SOC transformation.

Influences of high-order dispersion on temporal and spectral properties of microcavity solitons.

We theoretically and numerically investigate the effects of high-order dispersion (HOD) on microcavity solitons, both in time and frequency domain with an extended normalized Lugiato-Lefever equation (LLE). The observed temporal drift of bright and dark solitons is shown to originate from high-odd-order dispersion, while the sign determines the direction of soliton movement and the amplitude decides the drift speed. HOD can also be introduced to stabilize the breathing bright and dark cavity solitons. In spectral domain, the nonlinear symmetry breaking is mainly introduced by third-order dispersion, whereas both third- and fourth-order dispersion can introduce dispersive wave accompanied by soliton tail oscillation. This work could give insight for exploring detailed intracavity pulse dynamics and spectral characteristics of Kerr combs influenced by HOD, as well as provide a viable route to delicate control of Kerr comb generation through tailoring the dispersion parameters.

Low-threshold optical bistability in field-enhanced nonlinear guided-mode resonance grating nanostructure.

We have numerically studied the optical bistability in guided-mode resonance-assisted nonlinear grating nanostructure. A low-index slot is introduced to significantly improve the confinement of light in nonlinear material. In this way, the proposed novel configuration possesses low-threshold optical switching intensity (∼3 MW/cm2), which is about 58 times lower than that of typical nonlinear grating nanostructure without the low-index slot. This bistability study provides an effective method to reduce the threshold of optical switching intensity and thus can be applied in optical logic, optical computation, and all-optical memory.

Robust soliton crystals in a thermally controlled microresonator.

We demonstrate robust soliton crystals generation with a fixed frequency pump laser through a thermoelectric-cooler-based thermal-tuning approach in a butterfly-packaged complementary-metal-oxide-semiconductor-compatible microresonator. Varieties of soliton crystal states, exhibiting "palm-like" optical spectra that result from the strong interactions between the dense soliton ensembles and reflect their temporal distribution directly, are experimentally observed by sweeping one cavity resonance across the pump frequency from the blue-detuned side by reducing the operating temperature of the resonator. Benefitting from the tiny intra-cavity energy change, repeatable interconversion between the chaotic modulation instability and stable soliton crystal states can be successfully achieved via simple tuning of the temperature or pump power, showing the easy accessibility and excellent stability of such soliton crystals. This work could facilitate microresonator-based optical frequency combs towards a portable, adjustable, and low-cost system while avoiding the requirements of delicate frequency-sweeping pump techniques.

Broadband self-collimating phenomenon in a low-loss hybrid plasmonic photonic crystal.

A 2D planar self-collimating photonic crystal, based on a dielectric square lattice and a hexagonal lattice, is proposed. We demonstrate that the proposed structure can support the propagation of a hybrid surface plasmon polarition (SPP) mode with a loss of -0.017 dB/µm, and the mode size is only 0.33 µm. The defined figure of merit is one order of magnitude higher than that of the dielectric-metal structure. In addition, the self-collimating angle of more than 10° can be tuned with a silica index change of 0.08. The proposed structure possesses broad operation bandwidth of 88 nm and 58 nm for a dielectric square lattice and a hexagonal lattice, respectively. These two kinds of photonic crystals promise potential applications in photonic modulators and SPP photonic devices.