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Advancing the PROSPECT-5 Model to Simulate the Spectral Reflectance of Copper-Stressed Leaves
摘要： This paper proposes a modified model based on the PROSPECT-5 model to simulate the spectral reflectance of copper-stressed leaves. Compared with PROSPECT-5, the modified model adds the copper content of leaves as one of input variables, and the specific absorption coefficient related to copper (Kcu) was estimated and fixed in the modified model. The specific absorption coefficients of other biochemical components (chlorophyll, carotenoid, water, dry matter) were the same as those in PROSPECT-5. Firstly, based on PROSPECT-5, we estimated the leaf structure parameters (N), using biochemical contents (chlorophyll, carotenoid, water, and dry matter) and the spectra of all the copper-stressed leaves (samples). Secondly, the specific absorption coefficient related to copper (Kcu) was estimated by fitting the simulated spectra to the measured spectra using 22 samples. Thirdly, other samples were used to verify the effectiveness of the modified model. The spectra with the new model are closer to the measured spectra when compared to that with PROSPECT-5. Moreover, for all the datasets used for validation and calibration, the root mean square errors (RMSEs) from the new model are less than that from PROSPECT-5. The differences between simulated reflectance and measured reflectance at key wavelengths with the new model are nearer to zero than those with the PROSPECT-5 model. This study demonstrated that the modified model could get more accurate spectral reflectance from copper-stressed leaves when compared with PROSPECT-5, and would provide theoretical support for monitoring the vegetation stressed by copper using remote sensing.
关键词： vegetation remote sensing,leaf,PROSPECT,reflectance model,copper,spectra
更新于2025-09-23 15:23:52
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Surface-enhanced Raman scattering (SERS) imaging of bioactive metabolites in mixed bacterial populations
摘要： Bacteria frequently live in mixed multispecies communities, shaped by the action of bioactive metabolites that are secreted by the residing microbial species. The identification and tracking of such chemical exchange processes is fundamental toward understanding how these particular extracellular molecules modulate microbial communities and functions. In this context, most chemical imaging approaches so far have focused on the analysis of metabolic interactions occurring between microbial populations co-cultured separately. We demonstrate here the application of surface-enhanced Raman scattering (SERS) spectroscopy as a valuable imaging tool for the non-invasive detection and visualization of metabolites secreted by Escherichia coli and Pseudomonas aeruginosa bacteria, cultured as mixed populations and thereby mimicking the complexity of natural microbial communities. SERS enabled the simultaneous detection and in situ visualization of indole and pyocyanin, revealing the down-regulation of pyocyanin expression due to indole signaling. The successful detection of chemical interactions in mixed bacterial populations shows the potential of SERS for the investigation of the chemistry underpinning multispecies microbial communities.
关键词： Quorum sensing,Plasmonics,Indole,SERS imaging,Pyocyanin
更新于2025-09-23 15:23:52
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Quasi-one-dimensional silicon nanostructures for gas molecule adsorption: a DFT investigation
摘要： Porous structures offer an enormous surface suitable for gas sensing, however, the effects of their quantum quasi-confinement on their molecular sensing capacities has been seldom studied. In this work the gas-sensing capability of silicon nanopores is investigated by comparing it to silicon nanowires using first principles calculations. In particular, the adsorption of toxic gas molecules CO, NO, SO2 and NO2 on both silicon nanopores and nanowires with the same cross sections was studied. Results show that sensing-related properties of silicon nanopores and nanowires are very similar, suggesting that surface effects are predominant over the confinement. However, there are certain cases where there are remarked differences between the nanowire and porous cases, for instance, CO-adsorbed nanoporous silicon shows a metallic band structure unlike its nanowire counterpart, which remains semiconducting, suggesting that quantum quasi-confinement may be playing an important role in this behaviour. These results are significant in the study of the quantum phenomena behind the adsorption of gas molecules on nanostructure’s surfaces, with possible applications in chemical detectors or catalysts.
关键词： Sensing,Chemical sensors,Silicon nanowires,Density functional theory,Molecule adsorption,Porous silicon
更新于2025-09-23 15:23:52
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Sensing of iron(III)-biomolecules by surfactant-free fluorescent copper nanoclusters
摘要： Surfactant-free copper nanoclusters (sf-CuNCs) synthesized in the absence of external stabilizer, could be promising fluorescence biosensors because of the presence of relatively exposed surfaces that may ease coupling with biomolecules. This article shows that sf-CuNCs are effective fluorescence sensor of iron(III)-biomolecules: hemin, cytochrome C (cyt C), and ferritin. Although, sf-CuNCs are found to be weaker sensor of aqueous Fe3+ (Stern-Volmer constant (KSV) 3.0 × 103 M?1 and limit of detection (LOD) up to 2 μM) compared to other capped CuNCs, however, the sensing ability markedly increases in the presence of Fe(III)-biomolecules. KSV (LOD) are 5.3 × 104 M?1 (0.8 μM), 9.0 × 105 M?1 (68 nM), 1.6 × 106 M?1 (16.50 nM), respectively for cyt C, hemin and ferritin. We carried out detailed mechanistic investigations of the quenching process using time-resolved fluorescence, zeta potential and transmission electron microscopy (TEM) measurements. We found that fluorescence quenching is associated with complexation of Fe3+ with CuNCs which changes zeta potential of the sf-CuNCs and leads to aggregation of CuNCs. Moreover, fluorescence quenching, zeta potential and aggregation of CuNC can be reversed by addition of vitamin C which is a very strong chelator and reducing agent of Fe(III). Vitamin C reduces Fe(III) to Fe(II) and promotes disassembly of CuNCs-aggregates to regenerate fluorescence intensity. Since, the sensing is primarily governed by complex formation with Fe3+, absence of ligands on the surface of sf-CuNCs may be detrimental to quenching to aqueous Fe3+ but favors binding with the biomolecules.
关键词： Iron sensing,Copper nanocluster,Proteins,TEM,Fluorescence
更新于2025-09-23 15:23:52
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Fabrication of 2D thin-film filter-array for compressive sensing spectroscopy
摘要： We demonstrate 2D filter-array compressive sensing spectroscopy based on thin-film technology and a compressive sensing reconstruction algorithm. To obtain different spectral modulations, we fabricate a set of multilayer filters using alternating low- and high-index materials and reconstruct the input spectrum using a small number of measurements. Experimental results show that the fabricated filter-array provides compatible spectral resolution performance with a conventional spectrometer in monochromatic lights and LEDs. In addition, the fabricated filter-array covers a wide range of wavelengths with a single exposure.
关键词： Compressive sensing,Thin films,Spectroscopy,Inverse problems
更新于2025-09-23 15:23:52
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ZnO-enhanced In2O3-based sensors for n-butanol gas
摘要： A series of high-response and fast-response/recovery n-butanol gas sensors was fabricated by adding ZnO to In2O3 in varying molar ratios to form ZnO-In2O3 nanocomposites via a facile co-precipitation hydrothermal method. Morphological characterizations revealed that the shape of pure In2O3 was changed from irregular cubes into irregular nanoparticles, 30-50 nm in size, with the addition of ZnO. Compared with the pure In2O3 gas sensor, the ZnO-In2O3 gas sensor exhibits superior n-butanol sensing performance. With the introduction of ZnO, the response of the sensor to n-butanol was improved from 17 to 99.5 at 180 °C for a [Zn]:[In] molar ratio of 1:1. In addition, the ZnO-In2O3 gas sensors show a reduced optimal working temperature, excellent selectivity to n-butanol, and good repeatability. The response of the ZnO-enhanced In2O3-based sensors showed a strong linear relationship with the n-butanol gas concentration, allowing for the quantitative detection of n-butanol gas.
关键词： ZnO-In2O3,n-Butanol,Gas-sensing property,Selectivity
更新于2025-09-23 15:23:52
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A change detection framework by fusing threshold and clustering methods for optical medium resolution remote sensing images
摘要： In change detection (CD) of medium-resolution remote sensing images, the threshold and clustering methods are two kinds of the most popular ones. It is found that the threshold method of the expectation maximization (EM) algorithm usually generates a CD map including many false alarms but almost detecting all changes, and the fuzzy local information c-means algorithm (FLICM) obtains a homogenous CD map but with some missed detections. Therefore, a framework is designed to improve CD results by fusing the advantages of the threshold and clustering methods. The CD map generated by the clustering method of FLICM is used to remove false alarms in the CD map obtained by EM threshold method by an overlap fusion. Then, the local Markov random field model is implemented to verify the potentially missed detections. Finally, a fused CD map with less false alarms and missed detections is achieved. Two experiments were carried out on two Landsat ETM+ data sets. The proposed method obtained the least errors (1.11% and 3.51%) and the highest kappa coefficient (0.9366 and 0.8834), respectively, when compared with five popular CD methods.
关键词： Change detection,advantage fusion,remote sensing,clustering,threshold
更新于2025-09-23 15:23:52
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Construction of liquid crystal-based sensing platform for sensitive and selective detection of L-phenylalanine based on alkaline phosphatase
摘要： The detection of L-phenylalanine (L-Phe) has become one of most pressing issues concerning diagnosis and treatment of phenylketonuria in neonates, yet a simple and robust methodology has yet to be developed. Here the application of novel liquid crystals (LCs) sensing platform for sensitive, selective, and label-free detection of L-Phe was reported at the first time. We devised a strategy to fabricate the sodium monododecyl phosphate (SMP) decorated LC sensing platform with the appearance of dark. Then, a dark to bright (D-B) optical images alteration of LCs was observed after transferring alkaline phosphatase (ALP) to the interface, owing to cleavage of SMP induced by ALP. LCs remained dark images after the SMP-decorated interface in contact with the pre-incubated ALP and L-Phe. Such optical appearance resulted from the inhibition of ALP by L-Phe, which was further verified by the isothermal titration calorimetry (ITC). The strategy was applied to sensing L-Phe, which have been proven to allow for sensitively and selectively differentiation of L-Phe from interfering compounds with similar aromatic groups, as well as seven other essential amino acids. More importantly, the detection limit of L-Phe reached 1 pg/mL in urine samples, further demonstrated its value in the practical applications. Results obtained in this study clearly demonstrated the superiority of LCs towards the L-Phe detection, which can pave a way for the development of high performance and robust probes for L-Phe detection in clinical applications.
关键词： Sensing platform,Alkaline phosphatase,Surfactant,Liquid crystal,Inhibition,L-phenylalanine
更新于2025-09-23 15:23:52
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Highly Ordered 3D Microstructure Based Electronic Skin Capable of Differentiating Pressure, Temperature, and Proximity
摘要： Electronic skin are devices that mimic the functionalities of human skin, which require high sensitivity, large dynamic range, high spatial uniformity, low-cost and large area processability, and the capacity to differentiate various external inputs. We herein introduce a versatile droplet-based microfluidic-assisted emulsion self-assembly (DMESA) process to generate 3-dimensional microstructure based high-performance capacitive and piezoresistive pressure sensors for electronic skin applications. Our technique can generate uniformly sized micropores that are self-assembled in an orderly close-packed manner over a large area, which results in high spatial uniformity. The size of the micropores can easily be tuned from 100-500 μm, through which sensitivity and dynamic range were controlled to as high as 0.86 kPa-1 and up to 100 kPa. Our device can be printed on curvilinear surfaces and be molded into various shapes. We furthermore demonstrate that by simultaneously utilizing capacitive and piezoresistive pressure sensors, we can distinguish between pressure and temperature, or between pressure and proximity. These demonstrations make our process and sensors highly useful for a wide variety of electronic skin applications.
关键词： multimodal sensation,microporous structure,tactile sensing,decoupled stimuli
更新于2025-09-23 15:23:52
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Fracture behavior of carbon fiber reinforced polymer composites: An optical study of loading rate effects
摘要： Crack initiation and growth in single-edge notched unidirectional T800s/3900-2 CFRP laminates are studied under stress wave and quasi-static loading conditions. An optical technique called reflection-mode Digital Gradient Sensing is also extended to study fracture mechanics of CFRP by using it in conjunction with ultrahigh-speed photography to perform full-field measurement of crack-tip deformations in the pre- and post-crack initiation regimes. DGS is capable of measuring two orthogonal surface slopes in the crack-tip vicinity as angular deflection of light rays. A method for extracting crack-tip parameters - the instantaneous crack speed and stress intensity factor (SIFs) histories - associated with the stationary and propagating cracks using measured surface slopes is presented. The effect of fiber orientation in the range 0°-60° relative to the initial notch and two loading rates are investigated. Nominally mode-I fracture occurs when the fiber orientation is 0° whereas mixed-mode fractures ensue in others. Besides crack initiation occurrence at higher loads as fiber orientation increases, the SIF histories imply strong fiber bridging at low fiber orientations under quasi-static conditions. Furthermore, this CFRP shows significant loading rate dependence during crack growth. Unlike stress wave loading conditions, an increasing crack growth resistance immediately after crack initiation is seen under quasi-static conditions.
关键词： Carbon fiber reinforced plastics,Loading rate effects,Crack growth behavior,Dynamic fracture,Digital Gradient Sensing
更新于2025-09-23 15:23:52