In this paper, we derive the analytical expression for the sensitivity of grating-based surface plasmon resonance (SPR) sensors working in wavelength interrogation. The theoretical analysis shows ...that the sensitivity increases with increasing wavelength and is saturated beyond a certain wavelength for Au and Ag gratings, while it is almost constant for Al gratings in the wavelength range of 500 to 1000 nm. More importantly, the grating period (P) and the diffraction order (m) dominate the value of sensitivity. Higher sensitivity is possible for SPR sensors with a larger grating period and lower diffraction order. At long wavelengths, a simple expression of P/|m| can be used to estimate the sensor sensitivity. Moreover, we perform experimental measurements of the sensitivity of an SPR sensor based on an Al grating to confirm the theoretical calculations.
Topography has an influence on both abiotic (e.g. soil) and biotic (e.g. vegetation) factors influencing soil organic carbon (SOC). In this study, three slope aspects, south-facing, semi-sunny ...(south-west), and semi-shady (north-west) of mountainous grassland in the middle of the Qilian Mountains were sampled to explore the variation in SOC caused by topography. Soil properties were analyzed at different depths (0–10, 10–20, 20–40, and 40–60cm). The results showed that except soil total organic phosphate, SOC, soil water content, soil bulk density, daily soil temperature, biomass, vegetation cover, and species richness on the semi-shady slope aspect were significantly different to those on two other slope aspects. The SOC, vegetation cover, and biomass significantly increased, from the south-facing to semi-shady slope aspect, and their values on the semi-shady slope aspect were around two times greater than on the south-facing slope aspect. The plant community composition also varied by slope aspect, with Agropyron cristatum and Stipa grandis dominant on the south-facing slope aspect, and Agropyron cristatum and Carex aridula dominant on the semi-sunny slope aspect, and Kobresia humilis and Carex crebra dominant on the semi-shady slope aspect. Among all measured abiotic and biotic factors, daily soil temperature, soil bulk density and total soil organic nitrogen could be used to predict SOC, explaining 69.0% of the variation in the data (p<0.001). On all slope aspects, SOC was greatest in the top 20cm of soil, representing around 60.0% of the total SOC to 60cm depth. The results indicated that the distribution of SOC was regulated by slope aspect through its influence on vegetation and soil properties in this region. Therefore, SOC protection measures should be aspect specific.
•High variation in abiotic and biotic factors by slope aspect•The distribution of SOC regulated by both biotic and abiotic factors•The SOC protection measures must be based on aspect specific.
Wavefront manipulations have enabled wide applications across many interdisciplinary fields ranging from optics and microwaves to acoustics. However, the realizations of such functional surfaces ...heavily rely on micro/nanofabrication to define the structured surfaces, which are fixed and only work within a limited spectrum. To address these issues, previous attempts combining tunable materials like liquid crystal or phase-change ones onto the metasurfaces have permitted extra tunability and working spectra, however, these additional layers bring in inevitable loss and complicate the fabrication. Here we demonstrate a fabrication-free tunable flat slab using a nonlinear four-wave mixing process. By wavefront-shaping the pump onto the flat slab, we can successfully tune the effective nonlinear refraction angle of the emitting FWM beams according to the phase-matching condition. In this manner, a focusing and a defocusing nonlinear of FWM beam through the flat slab have been demonstrated with a converging and a diverging pump wavefronts, respectively. Furthermore, a beam steering scheme over a 20° angle has been realized through a non-degenerate four-wave mixing process by introducing a second pump. These features open up a door to manipulating light propagation in an all-optical manner, paving the way to more functional and tunable flat slab devices in the applications of imaging and all-optical information.
Land use and cover change (LUCC) is an important issue affecting the global environment, climate change, and sustainable development. Detecting and predicting LUCC, a dynamic process, and its driving ...factors will help in formulating effective land use and planning policy suitable for local conditions, thus supporting local socioeconomic development and global environmental protection. In this study, taking Gansu Province as a case study example, we explored the LUCC pattern and its driving mechanism from 1980 to 2018, and predicted land use and cover in 2030 using the integrated LCM (Logistic-Cellular Automata-Markov chain) model and data from satellite remote sensing. The results suggest that the LUCC pattern was more reasonable in the second stage (2005 to 2018) compared with that in the first stage (1980 to 2005). This was because a large area of green lands was protected by ecological engineering in the second stage. From 1980 to 2018, in general, natural factors were the main force influencing changes in land use and cover in Gansu, while the effects of socioeconomic factors were not significant because of the slow development of economy. Landscape indices analysis indicated that predicted land use and cover in 2030 under the ecological protection scenario would be more favorable than under the historical trend scenario. Besides, results from the present study suggested that LUCC in arid and semiarid area could be well detected by the LCM model. This study would hopefully provide theoretical instructions for future land use planning and management, as well as a new methodology reference for LUCC analysis in arid and semiarid regions.
The management of small vessels has always been key to maritime administration. This paper presents a novel method for recognizing small fishing vessels based on laser sensors. Using four types of ...small fishing vessels as targets, a recognition method for small fishing vessels based on Markov transition field (MTF) time-series images and VGG-16 transfer learning is proposed. In contrast to conventional methods, this study uses polynomial fitting to obtain the contours of a fishing vessel and transforms one-dimensional vessel contours into two-dimensional time-series images using the MTF coding method. The VGG-16 model is used for the recognition process, and migration learning is applied to improve the results. The UCR time-series public dataset is used as a transfer learning dataset for the MTF time-series image encoding. The experiment demonstrates that the proposed method exhibits higher accuracy and performance than 1D-CNN and other general neural network models, and the highest accuracy rate is 98.92%.
A sandwich-type fluorescent biosensor for the determination of tumor-related exosome was designed. It is based on magnetic nanoparticle (MNP) capture and horseradish peroxidase (HRP) catalysis. MNPs ...were used as the substrate to capture exosomes by modifying the CD63 antibody on MNPs surface. After that, the biotinylated epithelial cell adhesion molecule (EpCAM) antibody was used to capture the tumor-related exosomes, which specifically express EpCAM. A novel method for the fluorescence measurement of tumor-associated exosome was achieved, with a detection limit as low as 200 (± 9) particles mL
−1
. The analytical range of this method is from 576 (± 15) particles mL
−1
to 5.76 × 10
7
(± 5.1 × 10
5
) particles mL
−1
. For the fluorescence measurement, the excitation wavelength was set to 320 nm. Fluorescent spectra were collected at emission wavelength in the range 370 to 550 nm; the data shown in the calibration plot were studied by using the fluorescence intensity at 406 nm. This sensor was also able to successfully detect the exosomes from the plasma of patients with hepatocellular carcinoma (HCC) and healthy humans.
Graphical abstract
Schematic representation of the sensing process of immunoassay-type biosensor based on magnetic nanoparticle capture and the fluorescence signal formed by the horseradish peroxidase (HRP) catalysis for tumor-related exosome determination.
Soils in alpine regions associated with complex topography are characterized by large variability in the spatial distribution of soil organic carbon (SOC). However, the patterns and topographic ...controls on SOC at the hill scale in semiarid alpine regions are not well understood. In this study, the effects of slope aspects and depths on SOC were quantified based on field investigations in a mainly undisturbed region of the Qilian Mountains in northwestern China. Soil samples were collected at 0–10, 10–20, 20–40 and 40–60cm on south-, southwest-, west-, and north-facing slopes of three hills. Results showed that the SOC density at 0–60cm varied from 9.73 to 35.21kgm−2, and increased from the south- to north-facing slopes. The average SOC density on the north-facing slopes was about 3.2, 2.9 and 1.9 times larger than on the south-, southwest- and west-facing slopes. Both the general linear model and mixed linear model suggested that, at the hill scale, the slope aspects and soil depths explained the main variations of SOC concentration in our study. The profile pedotransfer function method indicated that the SOC varied predictably with soil depths and aspects, and the prediction functions well predicted the SOC data from literature. Our results highlight the importance of slope aspect as an indicator of the SOC, and demonstrate that the transformed aspect is a good continuous variable in predicting the SOC in the semiarid alpine region.
•Effects of slope aspects and depths on SOC in a semiarid alpine region were studied.•SOC density ranged from 9.73 to 35.21kgm−2 at 0–60cm at the hill scale.•SOC density on the north aspects was about 3.2, 2.9 and 1.9 times larger than the south, southwest and west aspects.•SOC could be expressed as functions of soil depths and slope aspects.
G protein-coupled receptors (GPCRs) are key regulators of information transmission between cells and organs. Despite this, we have only a limited understanding of the behavior of GPCRs in the apo ...state and the conformational changes upon agonist binding that lead to G protein recruitment and activation. We expressed and purified unmodified apo and peptide-bound calcitonin gene-related peptide (CGRP) receptors from insect cells to determine their cryo-electron microscopy (cryo-EM) structures, and we complemented these with analysis of protein conformational dynamics using hydrogen-deuterium exchange mass spectrometry and three-dimensional variance analysis of the cryo-EM data. Together with our previously published structure of the active, Gs-bound CGRP receptor complex, our work provides insight into the mechanisms of class B1 GPCR activation.
Big data in smart cities Li, DeRen; Cao, JianJun; Yao, Yuan
Science China. Information sciences,
10/2015, Letnik:
58, Številka:
10
Journal Article
Recenzirano
In this paper, we discuss the concept of the smart city, summarize its development, analyze the motivation and goals of building smart cities in China, and illustrate the supporting technologies of ...the smart city. Next, we propose a smart city infrastructure that is based on the concept of the digital city and integrates the Internet of Things and cloud computing technologies, thereby achieving automatic control and intelligence services for people and logistics in physical cities. We analyze the big data of smart cities according to ubiquitous sensor networks. Facing the problems and challenges caused by big data of smart cities, we propose a strategy to handle big data that focuses on cloud computing and data mining. In addition, we present a basic framework for cloud computing platforms and propose the establishment of an operating center for smart cities. In closing, we discuss the bright prospects of smart cities.
Aiming at the problem of permeability enhancement in deep coal roadway strip, it proposed a pressure relief roadway permeability enhancement model, and the model was verified through experiments, ...theoretical calculations, and field tests. The experiment reveals that the unloading of gas-containing coal can achieve the effect of permeability enhancement. Theoretical calculation shows that with the increase of the distance from the coal seam, the overlying coal seam’s permeability enhancement multiple and the width of the significant permeability enhancement zone gradually decrease, and the width of the general permeability enhancement zone gradually increases and then stabilizes. Field tests show that the pressure relief roadway is arranged 9 m directly below the coal seam; the overlying coal strata has a significant pressure relief and permeability enhancement effect. This research can provide reference value for the high-efficiency permeability enhancement in the deep coal roadway strip.
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