Operating point control method for the Mach-Zehnder modulator in a phase-shift laser range finder.

An operating point control method is proposed for the Mach-Zehnder modulator (MZM) based on a dual-cascaded MZM structure. Unlike traditional methods with dither signals, the proposed method is advantageous because the components monitored in the control process are not masked by the spectrum noise floor and the drift direction is clearly determined at the quadrature point, thus imparting greater control stability. Additionally, the proposed control method is suitable for phase-shift laser range finders (PSLRFs). Compared with traditional methods, experimental results reveal that the proposed method increases the operating point stability of MZM from ±0.59° to ±0.36° within 2 h, resulting in better ranging stability than 17 µm in 1 min and 39 µm in 1 h in a PSLRF with a 200 MHz modulation frequency.

High-speed and high-precision measurement of biaxial in-plane displacements: tens of nanometers principle error suppression in microprobe sensors.

When the microprobe sensor is faced with the demand of high-speed biaxial displacement measurement, due to the characteristics of phase generated carrier (PGC) technology, accompanying optical intensity modulation (AOIM) and unfavorable phase modulation depth (PMD) will bring about the tens of nanometer cyclic nonlinear errors, further hindering high-speed and high-precision measurement. Herein, a light source intensity stabilization system based on semiconductor optical amplifier (SOA) feedback control is achieved to eliminate the error caused by AOIM in the presence of high-frequency and large-amplitude laser modulation. Based on this, the reasons for large nonlinear errors in biaxial measurements and the inability to ensure the stability of the accuracy of multiple measurement axes are methodically examined, and an effective nonlinear error elimination methodology based on the normalized amplitude correction of active temperature scanning is proposed. The continuity and linearity of the temperature scanning are also discussed. The performed experiments show that the above approach is capable of reducing the displacement demodulation error from the nanometer scale to the sub-nanometer scale. Further, the nonlinear error is reduced to within 0.1 nm for both measurement axes and the performance becomes consistent. The dual-axis measurement resolution of the microprobe sensor reaches 0.4 nm and the measurement speed is better than 1.2 m/s with the standard deviation of lower than 0.5 nm.

The relationship between refractive error and the risk of diabetic retinopathy: a systematic review and meta-analysis.

Purpose: This meta-analysis was conducted to collect all available data and estimate the relationship between refractive error and the risk of diabetic retinopathy (DR) in patients with diabetes, and to assess whether vision-threatening DR (VTDR) is associated with refractive error. Methods: We systematically searched several literature databases including PubMed, Embase, Cochrane Library, Web of Science, CNKI, CBM, Wan Fang Data, and VIP databases. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using fixed or random effects models. Four models were developed to assess the relationship between refractive error and the risk and DR, VTDR: hyperopia and DR, VTDR; myopia and DR, VTDR; spherical equivalent (SE per D increase) and DR, VTDR; and axial length (AL per mm increase) and DR, VTDR. The included literature was meta-analyzed using Stata 12.0 software, and sensitivity analysis was performed. Publication bias in the literature was evaluated using a funnel plot, Begg's test, and Egger's test. Results: A systematic search identified 3,198 articles, of which 21 (4 cohorts, 17 cross-sectional studies) were included in the meta-analysis. Meta-analysis showed that hyperopia was associated with an increased risk of VTDR (OR: 1.23; 95% CI: 1.08-1.39; P = 0.001), but not with DR (OR: 1.05; 95% CI: 0.94-1.17; P = 0.374). Myopia was associated with a reduced risk of DR (OR: 0.74; 95% CI: 0.61-0.90; P = 0.003), but not with VTDR (OR: 1.08; 95% CI: 0.85-1.38; P = 0.519). Every 1 diopter increase in spherical equivalent, there was a 1.08 increase in the odds ratio of DR (OR: 1.08; 95% CI: 1.05-1.10; P<0.001), but not with VTDR (OR: 1.05; 95% CI: 1.00-1.10; P = 0.06). AL per mm increase was significantly associated with a decreased risk of developing DR (OR: 0.77; 95% CI: 0.71-0.84; P<0.001) and VTDR (OR: 0.63; 95% CI: 0.56-0.72; P<0.001). Analysis of sensitivity confirmed the reliability of the study's findings. Conclusion: This meta-analysis demonstrates hyperopia was associated with an increased risk of VTDR in diabetes patients. Myopia was associated with a reduced risk of DR. AL is an important influencing factor of refractive error. Every 1 mm increase in AL reduces the risk of DR by 23% and the risk of VTDR by 37%. Systematic review registration: identifier: CRD42023413420.

A 23-year bibliometric analysis of the development of global research on hereditary renal carcinoma.

Objectives: Medical research continues to be extensively devoted to investigating the pathogenesis and treatment approaches of hereditary renal cancer. By aspect including researchers, institutions, countries, journals, and keywords, we conduct a bibliometric analysis of the literature pertaining to hereditary renal cancer over the last 23 years. Methods: From the Web of Science Core Collection, we conducted a search for publications published between January 1, 2000 and November 28, 2023. Reviews and original articles were included. Results: A cumulative count of 2,194 publications met the specified criteria for inclusion. The studies of the included articles involved a collective of 2,402 institutions representing 80 countries. Notably, the United States exhibited the highest number of published documents, constituting approximately 45.49% of the total. The preeminent institution in this discipline is the National Cancer Institute (NCI), which maintains a publication volume of 8.98%. In addition to being the most prolific author (125 publications), Linehan WM's works received the highest number of citations (11,985). In a comprehensive count, 803 journals have published related articles. In the top 10 most recent occurrences were the terms "hereditary leiomyomatosis" and "fumarate hydratase." Conclusion: This is the first bibliometric analysis of the literature on hereditary renal cancer. This article offers a thorough examination of the present status of investigations concerning hereditary renal cancer during the previous 23 years.

Low-Density Lipoprotein Cholesterol and Prostate Cancer: A Retrospective Study.

BACKGROUND: This work aimed to investigate the potential role of abnormal lipid metabolism in the development of prostate cancer (PCa). METHODS: A retrospective study design was used. The clinical data of 520 patients who underwent rectal prostate biopsy in our hospital from January 2020 to June 2023 were analysed. The patients were enrolled and divided into the anterior PCa group including 112 patients and benign prostatic hyperplasia (BPH) group including 408 patients. Univariate and multivariate logistic regression analyses were performed for the two patient groups, and further comparisons were made according to the Gleason score and TNM staging. RESULTS: Low-density lipoprotein cholesterol (LDL-C) level may be an independent risk factor for PCa, and it was significantly associated with the risk of PCa (odds ratio (OR) = 1.363, p = 0.030). Patients with PCa were further divided into the low risk group and the high risk group according to the Gleason score. Univariate analysis (p = 0.047) and logistic regression analysis (OR = 2.249, p = 0.036) revealed that LDL-C was a significant factor influencing the Gleason score. Patients with PCa were categorised into four groups based on TNM staging. One-way analysis of variance (ANOVA) analysis (p = 0.015) and ordinal logistic regression analysis (OR = 2.414, p = 0.007) demonstrated that LDL-C was a significant factor influencing TNM staging. CONCLUSIONS: This study revealed the important role of LDL-C in the development of PCa, highlighting its influence as an independent risk factor. Thus, LDL-C may promote the proliferation and invasion of PCa cells.

Differential Sampling of AC Waveforms Based on a Commercial Digital-to-Analog Converter for Reference.

This paper introduces an innovative differential sampling technique for calibrating AC waveforms, leveraging a commercially available 16-bit digital-to-analog converter (DAC) as the reference standard. The novelty of this approach lies in its enhanced stability over traditional direct sampling methods, especially as the frequency of the AC waveform increases. Notably, this technique provides a cost-effective sampler alternative to the differential sampling methods that rely on a programmable Josephson voltage standard (PJVS). A critical aspect of this methodology is the precise measurement of the DAC's output voltage, for which a static measurement strategy is adopted to utilize the exceptional linearity and transfer accuracy of the Keysight 3458A (Santa Rosa, CA, USA) in its standard DCV mode. The differential sampling method has demonstrated good accuracy, achieving a near 1 µV/V agreement with a pulse-driven AC Josephson voltage standard (ACJVS) across a 40 Hz to 200 Hz frequency range. The method attained an expanded uncertainty (k = 2) of 1 part in 106 while measuring a 0.707107 VRMS sine wave at 50 Hz, showcasing its efficacy in precise AC waveform calibration.

Analysis and Design of Fiber Microprobe Displacement Sensors Including Collimated Type and Convergent Type for Ultra-Precision Displacement Measurement.

In this paper, a fiber optic microprobe displacement sensor is proposed considering characteristics of micro-Michelson interference structure and its components. The principal error of micro Fabry-Perot interferometric structure is avoided, and high-precision interferometric displacement measurement is realized. The collimated microprobe and convergent microprobe are analyzed, simulated, and designed for the purposes of measuring long-distance displacement and small spot rough surface, respectively. The core parameters of the probes' internal components are mapped to coupling efficiency and contrast of the sensor measurements, which provides a basis for the probes' design. Finally, simulation and experimental testing of the two probes show that the collimated probe's working distance and converging probe's tolerance angle can reach 40 cm and ±0.5°, respectively. The designed probes are installed in the fiber laser interferometer, and a displacement resolution of 0.4 nm is achieved.

Citric Acid Promotes Immune Function by Modulating the Intestinal Barrier.

Amidst increasing concern about antibiotic resistance resulting from the overuse of antibiotics, there is a growing interest in exploring alternative agents. One such agent is citric acid, an organic compound commonly used for various applications. Our research findings indicate that the inclusion of citric acid can have several beneficial effects on the tight junctions found in the mouse intestine. Firstly, the study suggests that citric acid may contribute to weight gain by stimulating the growth of intestinal epithelial cells (IE-6). Citric acid enhances the small intestinal villus-crypt ratio in mice, thereby promoting intestinal structural morphology. Additionally, citric acid has been found to increase the population of beneficial intestinal microorganisms, including Bifidobacterium and Lactobacillus. It also promotes the expression of important protein genes such as occludin, ZO-1, and claudin-1, which play crucial roles in maintaining the integrity of the tight junction barrier in the intestines. Furthermore, in infected IEC-6 cells with H9N2 avian influenza virus, citric acid augmented the expression of genes closely associated with the influenza virus infection. Moreover, it reduces the inflammatory response caused by the viral infection and thwarted influenza virus replication. These findings suggest that citric acid fortifies the intestinal tight junction barrier, inhibits the replication of influenza viruses targeting the intestinal tract, and boosts intestinal immune function.

Tumor microenvironment-activated theranostic nanozymes for trimodal imaging-guided combined therapy.

Synergistic therapy is expected to be a promising strategy for highly effective cancer treatment. However, the rational design of a simple and multifunctional nanoplatform still remains a grand challenge. Considering the nature of weak acidic, hypoxic, and H2O2 abundant tumor microenvironment, we constructed an indocyanine green (ICG) modified platinum nanoclusters (Pt NCs) decorated gold nanobipyramids (Au NBPs) to form the multifunctional nanocomposites (Au NBPs@Pt NCs-ICG) for multimodal imaging mediated phototherapy and chemodynamic cancer therapy. The photosensitizer ICG was covalently linked to Au NBPs@Pt NCs by bridging molecules of SH-PEG-NH2 for both photodynamic therapy (PDT) and fluorescence imaging. Besides, Au NBPs@Pt NCs-ICG nanocomposites exhibited catalase- and peroxidase-like activities to generate O2 and ·OH, which relieved the tumor hypoxia and upregulated antitumoral ROS level. Moreover, the combination of Au NBPs and ICG endowed the Au NBPs@Pt NCs-ICG with super photothermal conversion for effective photothermal imaging and therapy. In addition, the Au NBPs@Pt NCs-ICG nanoplatform displayed excellent X-ray computed tomography (CT) imaging ability due to the presence of high-Z elements (Au and Pt). Overall, our results demonstrated that Au NBPs@Pt NCs-ICG nanoplatform exhibited a multimodal imaging guided synergistic PTT/PDT/CDT therapeutic manners and held great potential as an efficient treatment for breast cancer.

Climate change enhances stability of wheat-flowering-date.

The stability of winter wheat-flowering-date is crucial for ensuring consistent and robust crop performance across diverse climatic conditions. However, the impact of climate change on wheat-flowering-dates remains uncertain. This study aims to elucidate the influence of climate change on wheat-flowering-dates, predict how projected future climate conditions will affect flowering date stability, and identify the most stable wheat genotypes in the study region. We applied a multi-locus genotype-based (MLG-based) model for simulating wheat-flowering-dates, which we calibrated and evaluated using observed data from the Northern China winter wheat region (NCWWR). This MLG-based model was employed to project flowering dates under different climate scenarios. The simulated flowering dates were then used to assess the stability of flowering dates under varying allelic combinations in projected climatic conditions. Our MLG-based model effectively simulated flowering dates, with a root mean square error (RMSE) of 2.3 days, explaining approximately 88.5 % of the genotypic variation in flowering dates among 100 wheat genotypes. We found that, in comparison to the baseline climate, wheat-flowering-dates are expected to shift earlier within the target sowing window by approximately 11 and 14 days by 2050 under the Representative Concentration Pathways 4.5 (RCP4.5) and RCP8.5 climate scenarios, respectively. Furthermore, our analysis revealed that wheat-flowering-date stability is likely to be further strengthened under projected climate scenarios due to early flowering trends. Ultimately, we demonstrate that the combination of Vrn and Ppd genes, rather than individual Vrn or Ppd genes, plays a critical role in wheat-flowering-date stability. Our results suggest that the combination of Ppd-D1a with winter genotypes carrying the vrn-D1 allele significantly contributes to flowering date stability under current and projected climate scenarios. These findings provide valuable insights for wheat breeders and producers under future climatic conditions.

The Incidence and Effect of Different Organ Metastasis on the Prognosis of NSCLC.

OBJECTIVE: The aim of this study was to explore the effect of different organ metastasis on the prognosis of non-small cell lung cancer (NSCLC). METHODS: Patients with distant metastatic NSCLC were selected from Surveillance, Epidemiology, and End Results database during 2016 to 2019. The incidence of different organ metastasis and their association with clinicopathological factors were explored. Overall survival (OS) and lung cancer-specific survival (LCSS) for metastatic NSCLC were calculated, and multivariate Cox regression analysis was performed with a nomogram for OS being constructed based on Cox regression. RESULTS: Total 26,210 patients with distant metastatic NSCLC were included in this study. Around 48.9% of the metastatic NSCLC were multiple-organ metastasis and bone was the most commonly involved organ (44.4%). For patients with single-organ metastasis, the prognosis for lung or distant lymph nodes (LNs) metastasis was better than others (with median OS of 15 and 16 months for lung and distant LNs metastasis, respectively), and liver metastasis resulted in the worst prognosis with median OS of 8 months. A nomogram was constructed to visualize Cox regression model, along with the receiver operating characteristic (ROC) curve demonstrated good discrimination for the predictive model with 1- and 2-year area under the curve of ROC of 0.687 and 0.702, respectively. CONCLUSION: The prognosis of NSCLC patients with distant metastasis was poor. Liver metastasis results in the worst prognosis among the single-organ metastasis. The nomogram developed based on the Cox regression model has provided a useful tool to estimate the probability of OS of the metastatic NSCLC.

The earliest optimal timing for total-body 68Ga-fibroblast activation protein inhibitor-04 PET scans: an evidence-based single-centre study.

OBJECTIVES: To investigate the earliest optimal timing for positron emission tomography (PET) scans after 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) injection. METHODS: This prospective study enrolled patients who underwent 60-min dynamic 68Ga-FAPI-04 total-body PET/CT scans; the images were reconstructed at 10-min intervals (G0-10, G10-20, G20-30, G30-40, G40-50, and G50-60), and the [68Ga]Ga-FAPI-04 uptake patterns were evaluated. The standardised uptake value (SUV), liver signal-to-noise ratio (SNR), and lesion-to-background ratios (LBRs) for different time windows were calculated to evaluate image quality and lesion detectability. The period from 30 to 40 min was then split into overlapping 5-min intervals starting 1 min apart for further evaluation. G50-60 was considered the reference. RESULTS: A total of 30 patients with suspected malignant tumours were analysed. In the images reconstructed over 10-min intervals, longer acquisition times were associated with lower background uptake and better image quality. Some lesions could not be detected until G30-40. The lesion detection rate, uptake, and LBRs did not differ significantly among G30-40, G40-50, and G50-60 (all p > 0.05). The SUVmean and LBRs of primary tumours in the reconstructed images did not differ significantly among the 5-min intervals between 30 and 40 min; for metastatic and benign lesions, G34-39 and G35-40 showed significantly better SUVmean and LBR values than the other images. The G34-39 and G50-60 scans showed no significant differences in uptake, LBRs, or detection rates (all p > 0.05). CONCLUSION: The earliest optimal time to start acquisition was 34 min after injection of half-dose [68Ga]Ga-FAPI-04. CLINICAL RELEVANCE STATEMENT: This study evaluated 68Ga-fibroblast activation protein inhibitor-04 ([68Ga]Ga-FAPI-04) uptake patterns by comparing the image quality and lesion detection rate with 60-min dynamic [68Ga]Ga-FAPI-04 total-body PET/CT scans and identified the earliest optimal scan time after [68Ga]Ga-FAPI-04 injection. KEY POINTS: • A prospective single-centre study showed that the earliest optimal time point to start acquisition was 34 min after injection of half-dose [68Ga-fibroblast activation protein inhibitor-04 (68Ga]Ga-FAPI-04). • There were statistically significant differences in standardised uptake value, lesion-to-background ratios, and lesion detectability between scans before and after 34 min from the injection of [68Ga]Ga-FAPI-04, but these values did not change further from 34 to 60 min after injection. • With a reasonable acquisition time, the image quality could still meet diagnostic requirements.

Metabolic engineering of Yarrowia lipolytica for high-level production of squalene.

Squalene is an important triterpene with a wide range of applications. Given the growing market demand for squalene, the development of microbial cell factories capable of squalene production is considered a sustainable method. This study aimed to investigate the squalene production potential of Yarrowia lipolytica. First, HMG-CoA reductase from Saccharomyces cerevisiae and squalene synthase from Y. lipolytica was co-overexpressed in Y. lipolytica. Second, by enhancing the supply of NADPH in the squalene synthesis pathway, the production of squalene in Y. lipolytica was effectively increased. Furthermore, by constructing an isoprenol utilization pathway and overexpressing YlDGA1, the strain YLSQ9, capable of producing 868.1 mg/L squalene, was obtained. Finally, by optimizing the fermentation conditions, the highest squalene concentration of 1628.2 mg/L (81.0 mg/g DCW) in Y. lipolytica to date was achieved. This study demonstrated the potential for achieving high squalene production using Y. lipolytica.

Effect of insulin levels and plasma fasting glucose on refractive status in the United States population aged 12-19 years.

Purpose: The causes of myopia are varied, and both genetic and environmental influences play an essential role. The prevalence of myopia is increasing among adolescents and is expected to be more than one-third the global population by 2050. Some animal studies suggest that hyperinsulinemia may be a cause of myopia. In this context, the purpose of this paper is to investigate the potential effects of insulin levels and plasma fasting glucose on the refractive status of adolescents. Methods: Data were collected from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2008. Weighted multivariable linear regression models were used to assess the effect of insulin levels, plasma fasting glucose on refractive status. We used a smooth curve fit to reveal the nonlinear relationship between the variables. Results: In the multivariate regression model, as insulin levels increased, there was a shift towards myopia in refractive status (ß = -0.013, 95% CI: -0.023 to -0.004). This correlation was also evident in the male adolescent subgroup (ß = -0.021, 95% CI: -0.035 to -0.007). Similar findings indicated that in Mexican Americans, there was a myopic shift in refractive status as insulin levels increased (ß = -0.018, 95% CI: -0.033 to -0.002). However, grouping by differences in insulin measurement showed no significant correlation in Mexican-Americans. At the same time, there was no significant correlation between plasma fasting glucose and refractive status (ß = -0.041, 95% CI: -0.174 to 0.091). Conclusion: The present cross-sectional study demonstrated that higher insulin levels may promote the development of myopia in adolescents, but there may be variations across gender and ethnicity. More basic research is needed to reveal the mechanistic reasons for the association.

Development of a 3-DOF Angle Sensor Based on a Single Laser Interference Probe.

The development of high-precision satellites has increased the demand for ultraprecision three-degrees-of-freedom (3-DOF) angle measurements for detecting structural deformation. The required instrument should simultaneously measure pitch, yaw, and roll angles using a single reference point. This paper proposes a 3-DOF angle measurement method based on the wavefront interference principle, and a mathematical model and its decoupling algorithm were built. Then, an angle-sensing probe with an extremely simple structure was designed and constructed. Finally, a series of experiments were performed to verify the method's feasibility. The experiment results showed that the roll, pitch, and yaw measurement resolution of the probe was better than 10, 1, and 1 µrad, respectively, providing a high-performance 3-DOF angle measurement with a single probe. The short-term stabilities of roll, pitch, and yaw were better than 22, 1.7, and 2.0 µrad, respectively.

One-tenth-activity total-body positron emission tomography versus full-activity imaging in patients with a complex of hepatic malignant tumors: a retrospective study.

Background: The value of ultra-low-activity 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET) imaging in patients with hepatic malignancies remains unclear. Methods: A cross-sectional study was conducted from April 2019 to May 2021 in Zhongshan Hospital, Fudan University. A total of 49 patients with hepatic malignancies, including hepatocellular carcinoma (HCC) (n=13) or intrahepatic cholangiocarcinoma (ICC) (n=36), underwent 60-min dynamic PET imaging, with 15 undergoing full-activity 18F-FDG and 34 undergoing ultra-low-activity 18F-FDG. The kinetic metrics (K1-k3, and Ki) of tumors were calculated and compared between the activity groups. Another 54 patients (27 each group) with hepatic malignancies, including HCC (n=9), ICC (n=34), and metastases (n=11), underwent static imaging. Image qualities were compared between the groups in terms of 5-point Likert scores (with a score ≥3 fulfilling the clinical requirement), the mean standardized uptake value (SUVmean), the standard deviation of standardized uptake value (SUVSD), and the signal-to-noise ratio (SNR) of the liver; the SUVmean of blood pool and muscle; and the tumor-to-liver ratio (TLR), tumor-to-blood ratio (TBR), and tumor-to-muscle ratio (TMR) of lesions. Intergroup comparisons were performed using Chi-squared test for categorical variables and the Student's t-test or the Mann-Whitney test for continuous variables depending on the normality of variables. Results: There was a nonsignificant difference in the kinetic metrics (K1-k3 and Ki) of tumors between the activity groups. In static imaging, 1-min full-activity (F1) and 8-min ultra-low-activity (L8) images obtained image-quality scores >3 and were thus selected for intergroup comparisons. Nonsignificant differences in SUVmean of liver, blood pool, and muscle were identified between F1 and L8 images (P=0.641, P=0.542, and P=0.073, respectively) although the liver SNR was slightly higher in F1 (13.10 vs. 11.31; P=0.003). Lesion detectability was 98.5% and 100% for F1 and L8 images, respectively, but there were no significant differences in TLR, TBR, or TMR between the groups. Conclusions: The results of this single-center study indicate that the performance of ultra-low-activity PET imaging is comparable to that of full-activity imaging in patients with hepatic malignancies.

A Two-Dimensional Precision Level for Real-Time Measurement Based on Zoom Fast Fourier Transform.

This paper proposes a two-dimensional precision level for real-time measurement using a zoom fast Fourier transform (zoom FFT)-based decoupling algorithm that was developed and integrated in an FPGA. This algorithm solves the contradiction between obtaining high resolution and obtaining high measurement speed, and achieves both high angle-resolution measurement and real-time measurement. The proposed level adopts a silicone-oil surface as the angle-sensitive interface and combines the principle of homodyne interference. By analyzing the frequency of the interference fringes, the angle variation can be determined. The zoom-FFT-based decoupling algorithm improves the system's frequency resolution of the interference fringes, thereby significantly enhancing the angle resolution. Furthermore, this algorithm improves the efficiency of angle decoupling, while the angle decoupling process can also be transplanted to the board to realize real-time measurement of the level. Finally, a prototype based on the level principle was tested to validate the effectiveness of the proposed method. The principle analysis and test results showed that the angle resolution of the prototype improved from 9 arcsec to about 0.1 arcsec using this angle-solution method. At the same time, the measurement repeatability of the prototype was approximately ±0.2 arcsec. In comparison with a commercial autocollimator, the angle measurement accuracy reached ±0.6 arcsec.

Quantification of the Cumulative Shading Capacity in a Maize-Soybean Intercropping System Using an Unmanned Aerial Vehicle.

In intercropping systems, higher crops block direct radiation, resulting in inevitable shading on the lower crops. Cumulative shading capacity (CSC), defined as the amount of direct radiation shaded by higher crops during a growth period, affects the light interception and radiation use efficiency of crops. Previous studies investigated the light interception and distribution of intercropping. However, how to directly quantify the CSC and its inter-row heterogeneity is still unclear. Considering the canopy height differences (Hms, obtained using an unmanned aerial vehicle) and solar position, we developed a shading capacity model (SCM) to quantify the shading on soybean in maize-soybean intercropping systems. Our results indicated that the southernmost row of soybean had the highest shading proportion, with variations observed among treatments composed of strip configurations and plant densities (ranging from 52.44% to 57.44%). The maximum overall CSC in our treatments reached 123.77 MJ m-2. There was a quantitative relationship between CSC and the soybean canopy height increment (y = 3.61 × 10-2×ln(x)+6.80 × 10-1, P < 0.001). Assuming that the growth status of maize and soybean was consistent under different planting directions and latitudes, we evaluated the effects of factors (i.e., canopy height difference, latitude, and planting direction) on shading to provide insights for optimizing intercropping planting patterns. The simulation showed that increasing canopy height differences and latitude led to increased shading, and the planting direction with the least shading was about 90° to 120° at the experimental site. The newly proposed SCM offers a quantitative approach for better understanding shading in intercropping systems.