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Chlorophyll-a (Chl-a) concentration is a key indicator for assessing the eutrophication level in water bodies. However, accurately inverting Chl-a concentrations in optically complex coastal waters presents a significant challenge for traditional models. To address this, we employed Sentinel-2 MSI sensor data and leveraged the power of five machine learning models, including a convolutional neural network (CNN), to enhance the inversion process in the coastal waters near Hong Kong. The CNN model demonstrated superior performance with on-site data validation, outperforming the other four models (R2 = 0.810, RMSE = 1.165 μg/L, MRE = 35.578%). The CNN model was employed to estimate Chl-a concentrations from images captured over the study area in April and October 2022, resulting in the creation of a thematic map illustrating the spatial distribution of Chl-a levels. The map indicated high Chl-a concentrations in the northeast and southwest areas of Hong Kong Island and low Chl-a concentrations in the southeast facing the open sea. Analysis of patch size effects on CNN model accuracy indicated that 7 × 7 and 9 × 9 patches yielded the most optimal results across the tested sizes. Shapley additive explanations were employed to provide post-hoc interpretations for the best-performing CNN model, highlighting that features B6, B12, and B8 were the most important during the inversion process. This study can serve as a reference for developing machine learning models to invert water quality parameters. [ABSTRACT FROM AUTHOR]

Disulfides, as fundamental scaffolds, are widely present in peptides, natural products, and pharmaceutical molecules. However, traditional synthesis of disulfides often involves the utilization of toxic reagents or environmentally unfriendly reaction conditions. In this work, a green and efficient method was developed for synthesizing pyrrole disulfides using β-ketothioamides and ethyl cyanoacetate as substrates, with lipase serving as a catalyst. Under the optimal conditions (β-Ketothioamides (1 mmol), ethyl cyanoacetate (1 mmol), PPL (200 U), and EtOH (5 mL)), lipase leads to the formation of pyrrole disulfides in yields of up to 88% at 40 °C. The related mechanism is also speculated in this paper. This approach not only presents a new application of lipase in enzyme catalytic promiscuity, but also offers a significant advancement in the synthetic pathway for pyrrole disulfides and aligns with the current mainstream research direction of green chemistry, contributing to the further development of environmentally friendly biocatalytic processes. [ABSTRACT FROM AUTHOR]

A green and efficient method for the construction of functionalized 2,3-dihydrothiophene derivatives in water was reported. In this work, Novozym 435 acted as a remarkable biocatalyst in catalyzing the four-component reaction of aldehydes, malonitrile or ethyl cyanoacetate, 1,3-thiazolidinedione, and amines under mild conditions. Excellent yields (85–95%) of all the corresponding products could be obtained in reasonable reaction time. Moreover, Novozym 435 could be reused for six cycles with a yield of at least 80%. The rationality of this multicomponent reaction mechanism was also verified via control experiments. [ABSTRACT FROM AUTHOR]

The problem of soil fertility imbalance in hilly agriculture is prominent, and accurate estimation of soil potassium balance is key to achieving precision fertilization at the regional level. Crop distribution has a significant impact on potassium balance, but studies on potassium balance with a focus on crop cultivation types are scarce, especially with regard to hilly areas. In this study, the spatial distribution characteristics of soil potassium balance under different cropping conditions and its influencing factors were analyzed for a hilly region. The results showed that (1) the soil rapidly available potassium (RAK) and slowly available potassium (SAK) content in the 0–20 cm soil layer ranged from 29.37 to 122.07 mg kg−1 and from 472.31 to 772.77 mg kg−1, respectively. (2) The soil potassium equilibrium status varied considerably among different cropping systems and the soil potassium deficit was greatest under the rapeseed–maize rotation, reaching −129.50 kg K ha−1 yr−1. The difference in soil potassium deficits between the rice–rapeseed and wheat–maize rotations was not significant, at −46.79 kg K ha−1 yr−1 and −44.07 kg K ha−1 yr−1, respectively, and only the rice–wheat rotation showed a potassium surplus. Due to the low potassium absorption of crops, the equilibrium value of soil potassium is higher than that of crop rotation, and rice and wheat can achieve different degrees of potassium surplus. Rapeseed planting was generally under-applied with potassium, and the potassium deficit could reach −70 kg K ha−1 yr−1. (3) Climate, topography, anthropogenic activity, and soil available potassium explained 20.8% of the variance in soil potassium balance. Anthropogenic activity such as roads and population density had the greatest influence, with 0.797. Topography and average annual precipitation had the weakest influences. These findings emphasize the importance of anthropogenic activity for soil potassium balance, and also provide regional evidence for formulating efficient measures for regional potassium resources management. [ABSTRACT FROM AUTHOR]

Purpose: Heterocyclic compounds are organic compounds with heterocyclic structures, which are common in drug molecules. They include pyrazines with diverse functions, including anti-cancer, antimicrobial, antidiabetic, and anticholinergic activities. In this study a new small molecular compound B7 based on tetrazolium substituted pyrazine was synthesized and its effect on the progression of colorectal cancer (CRC) and its potential mechanism were investigated.Methods: We synthesized a series of tetrazolium-substituted pyrazine compounds by chemoenzymatic method. NCM460 (Human), HCT116 (Human), SW480 (Human) cell lines were selected to analyse the inhibitory effect of B7 on CRC by CCK-8, apoptosis, cell migration and invasion, qPCR, Western blotting, molecular docking, immunofluorescence. Moreover, a CRC xenograft model of mice was used to analyzed the role of B7 in vivo.Results: Among these compounds, 3-methyl-5je-6-bis (1H-tetrazole-5-yl) pyrazine-2-carboxylic acid (B7) inhibited CRC cell proliferation and induced apoptosis. The expression of Caspase-3 was increased after B7 treatment. In addition, the mitochondria abnormalities was observed in B7 group due to decrease the expression of Beclin-1. In addition, B7 inhibited the migration and invasion in CRC cells. Finally, the results showed that B7 had anti-tumor activity in CRC xenograft model of mice.Conclusion: In summary, compound B7 was synthesized efficiently using tetrazolium-substituted pyrazine via a chemoenzymatic method. Moreover, B7 have ability to regulate the expression of Caspase-3 which induced apoptosis in CRC cells. In addition, decreased Beclin-1 expression after B7 treatment, indicating inhibited autophagy. This study showed that B7 effectively induced apoptosis and inhibited autophagy in CRC cells. [ABSTRACT FROM AUTHOR]

Hemoproteins have recently emerged as attractive biocatalysts for catalyzing carbene-mediated cyclopropanation, a synthetically valuable reaction not found in nature. In this study, we present a hemoglobin-catalyzed strategy for the highly stereoselective synthesis of nitrile-substituted cyclopropanes. This method offers efficiency and environmental friendliness by utilizing an asymmetric olefin cyclopropanation reaction catalyzed by wild-type Vitreoscilla hemoglobin in the presence of in situ generated diazoacetonitrile. A diverse range of nitrile-substituted cyclopropanes could be synthesized in water with exceptional stereoselectivity, achieving up to 99.9% de and ee and high turnover numbers of up to 3232. By employing this sustainable approach, not only can various chiral nitrile-substituted cyclopropanes be efficiently obtained, but also the practical application of hemoglobin in organic synthesis can be expanded. [ABSTRACT FROM AUTHOR]

Canopy height is a crucial indicator for assessing the structure and function of the forest ecosystems. It plays a significant role in carbon sequestration, sink enhancement, and promoting green development. This study aimed to evaluate the accuracy of GEDI L2A version 2 data in estimating ground elevation and canopy height by comparing it with airborne laser scanning (ALS) data. Among the six algorithms provided by the GEDI L2A data, algorithm a2 demonstrated higher accuracy than the others in detecting ground elevation and canopy height. Additionally, a relatively strong correlation (R-squared = 0.35) was observed between rh95 for GEDI L2A and RH90 for ALS. To enhance the accuracy of canopy height estimation, this study proposed three backpropagation (BP) neural network inversion models based on GEDI, Landsat 8 OLI, and Landsat 9 OLI-2 data. Multiple sets of relative heights and vegetation indices were extracted from the GEDI and Landsat datasets. The random forest (RF) algorithm was employed to select feature variables with a cumulative importance score of 90% for training the BP neural network inversion models. Validation against RH90 of ALS revealed that the GEDI model outperformed the OLI or OLI-2 data models in terms of accuracy. Moreover, the quality improvement of OLI-2 data relative to OLI data contributed to enhanced inversion accuracy. Overall, the models based on a single dataset exhibited relatively low accuracy. Hence, this study proposed the GEDI and OLI and GEDI and OLI-2 models, which combine the two types of data. The results demonstrated that the combined model integrating GEDI and OLI-2 data exhibited the highest performance. Compared to the weakest OLI data model, the inversion accuracy R-squared improved from 0.38 to 0.74, and the MAE, RMSE, and rRMSE decreased by 1.21 m, 1.81 m, and 8.09%, respectively. These findings offer valuable insights for the remote sensing monitoring of forest sustainability. [ABSTRACT FROM AUTHOR]

As a base structural unit, 1,4-dihydropyridines (DHPs) containing benzosultams widely exist in bioactive molecules and drugs. These compounds are generally synthesized by organic-base catalyzed methods that require specifically functionalized substrates or harsh conditions. Herein, a [3+3] annulation reaction of cyclic N-sulfonyl ketimine with various substituted isatylidene malononitrile or benzylidene malononitriles was documented. This biocatalytic strategy provides a green route for synthesis of 1,4-DHPs containing benzosultams, with good functional groups compatibility and yields. Under optimal conditions, lipase leads to the formation of 1,4-DHPs containing benzosultams in up to 87% yield. [ABSTRACT FROM AUTHOR]

A metal‐free, straightforward, non‐hazardous reagent‐added, one‐pot approach for the efficient synthesis of 2‐arylimino‐2H‐chromenes with high yields was developed for the first time in this report through the coupling of salicylaldehydes with β‐ketothioamides, which was catalyzed by lipase in water. This green strategy provides an efficient method to obtain various 2‐arylimino‐2H‐chromenes and enriches the practical application of biocatalysis. [ABSTRACT FROM AUTHOR]

The development of non-natural enzymatic catalysis is important for multicomponent tandem organic transformations. However, the delicate acting environments of biological enzymes still present some challenges in the synthesis of spirooxindole skeleton via enzymatic catalysis. To address these issues, a lipase-catalyzed method was developed for the synthesis of spirooxindole frameworks. Using easily available isatins, cycloketones, and malononitriles as substrates, mild reaction conditions, and a reasonable reaction time, moderate to good yields (67–92%) and excellent functional group tolerance were accomplished via this protocol. The related mechanism explanation is also speculated in this paper. [ABSTRACT FROM AUTHOR]

Organophosphorus compounds are the core structure of many active natural products. The synthesis of these compounds is generally achieved by metal catalysis requiring specifically functionalized substrates or harsh conditions. Herein, we disclose the phospha-Michael addition reaction of biphenyphosphine oxide with various substituted β-nitrostyrenes or benzylidene malononitriles. This biocatalytic strategy provides a direct route for the synthesis of C-P bonds with good functional group compatibility and simple and practical operation. Under the optimal conditions (styrene (0.5 mmol), biphenyphosphine oxide (0.5 mmol), Novozym 435 (300 U), and EtOH (1 mL)), lipase leads to the formation of organophosphorus compounds in yields up to 94% at room temperature. Furthermore, we confirm the role of the catalytic triad of lipase in this phospha-Michael addition reaction. This new biocatalytic system will have broad applications in organic synthesis. [ABSTRACT FROM AUTHOR]

In this study, supercritical carbon dioxide (ScCO2), which is a sustainable and green solvent, was used as a reaction medium in the lipase‐catalyzed synthesis of anthrone‐functionalized benzylic amines for the first time. We synthesized the target compounds via a lipase‐catalyzed multicomponent cascade reaction of aldehydes, sulfonamides, and anthrones in ScCO2. The reaction can be accomplished in good‐to‐excellent yields (77 %–95 %) and can exhibit good functional group tolerance. In brief, the reaction was characterized by step economy, metal‐free conditions, environmentally friendly solvents, and biocatalysts. [ABSTRACT FROM AUTHOR]

Rapid data processing is crucial for distributed optical fiber vibration sensing systems based on a phase-sensitive optical time domain reflectometer (Φ-OTDR) due to the huge amount of continuously refreshed sensing data. The vibration sensing principle is analyzed to study the data flow of Rayleigh backscattered light among the different processing units. A field-programmable gate array (FPGA) is first chosen to synchronously implement pulse modulation, data acquisition and transmission in parallel. Due to the parallelism characteristics of numerous independent algorithm kernels, graphics processing units (GPU) can be used to execute the same computation instruction by the allocation of multiple threads. As a conventional data processing method for the sensing system, a differential accumulation algorithm using co-processing parallel computation is verified with a time of 1.6 μs spent of the GPU, which is 21,250 times faster than a central processing unit (CPU) for a 2020 m length of optical fiber. Moreover, the cooperation processes of the CPU and GPU are realized for the spectrum analysis, which could shorten substantially the time of fast Fourier transform analysis processing. The combination of FPGA, CPU and GPU can largely enhance the capacity of data acquisition and processing, and improve the real-time performance of distributed optical fiber vibration sensing systems. [ABSTRACT FROM AUTHOR]

A delay line method for a distributed optical fiber vibration sensing system is reported. The sensing system is a combination of non‐balanced Sagnac/Mach‐Zehnder structure and an adjustable optical fiber delay line. The vibration location principle is the expansion of conventional null‐frequencies theory, which needs to adjust the length of delay line, in order to determine a zero point in the amplitude variation curve of detected light intensity for one characteristic frequency appearing in the vibration signal spectrum. Moreover, the location simulation using delay line method for narrowband vibration signals is affected. Finally, the experiment verifies that the location errors of vibration events are within ±70 m. The main advantage of proposed method is that it can locate not only the broadband vibration but also the narrowband vibration. [ABSTRACT FROM AUTHOR]

We have recently reported the creation of the first immortalized cell line derived from human dermal microvascular endothelial cells (HMEC-1). In preliminary studies this line was found to closely resemble microvascular endothelial cells in regard to many phenotypic characteristics. Because two key functional features of endothelial cells are their ability to bind to peripheral blood leukocytes and extracellular matrix proteins via cell adhesion molecules, we have now characterized HMEC-1 in terms of expression and regulation of cell adhesion molecules of the integrin, immunoglobulin gene superfamily, and selectin families. HMEC-1 can either constitutively express or can be induced to express key integrins, including α-1, -2, -3, -4, -5, -6, and -V, as well as β-1, -3, -4, and -5. They also express or are capable of expressing immunoglobulin gene superfamily molecules, such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, and a member of the selectin family, E-selectin. A number of important cell adhesion molecules that are either constitutively expressed or that must be induced are regulated in a time- and dose-dependent fashion by selected cytokines. Experiments comparing the phenotypic characteristics of HMEC-1 with human dermal microvascular endothelial cells or human umbilical vein endothelial cells reveal HMEC- 1 to have features of both small- and large-vessel endothelial cells. [ABSTRACT FROM AUTHOR]

In order to enhance the signal-to-noise ratio (SNR) of a distributed optical fiber vibration sensor based on coherent optical time domain reflectometry (COTDR), a high extinction ratio cascade structure of an acousto-optic modulator and semiconductor optical amplifier is applied. The prior time-frequency analysis and least mean square error algorithm are adopted in the COTDR system for amplitude demodulation and phase demodulation, in order to improve the SNR by noise elimination. The experimental results show that the adaptive filter based on the least mean square error algorithm could realize the extraction of a three-order sinusoidal harmonic signal from strong background noise along the optical fiber and the SNR improvement from 10.4 dB to 42.2 dB. The proposed demodulation algorithm is suitable for the detection of vibration signals with characteristic frequencies in the application of acoustic fault diagnosis for electromechanical devices. [ABSTRACT FROM AUTHOR]

A difference-fitting method is proposed to mitigate the low frequency drift of a phase-sensitive optical time domain reflectometry ( Φ -OTDR) system caused by laser phase noise. The effective difference region for phase demodulation is theoretically analyzed and experimentally verified, which should be greater than the convolution of the spatial resolution and the length of disturbed optical fiber. Then, a median-fitting algorithm is used to obtain the phase noise of the differential region. The vibration signal of 0.2 Hz is first demodulated with the SNR of 41.79 dB on the optical fiber of 11 km. The low-frequency vibration signals of 0.05 Hz and 0.02 Hz are then successfully restored by using the difference-fitting method, which can effectively eliminate the influence of low frequency drift.