Modeling vegetation gross primary productivity (GPP) is crucial to understanding the land–atmosphere interactions and, hence, the global carbon cycle. While studies have demonstrated that ...satellite-based models could well simulate intra-annual variation of vegetation GPP, there is a need to understand our ability to capture interannual GPP variability. This study compares the spatiotemporal performance of six satellite-based models in regional modeling of annual GPP for deciduous broadleaf forests across the eastern United States. The 2001–2012 average annual gross primary productivities (AAGPPs) derived from different models have mismatched spatial patterns with divergent changing trends along both latitude and longitude. Evaluation using flux tower data indicates that some models could have considerable biases on a yearly basis. All tested models, despite performing well on the 8-day basis because of the underlying strong seasonality in vegetation productivity, fail to capture interannual variation of GPP across sites and years. Our study identifies considerable modeling uncertainties on a yearly basis even for an extensively studied biome of deciduous broadleaf forest at both site and large scales. Improvements to the current satellite-based models have to be made to capture interannual GPP variation in addition to intra-annual variation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Multiple cropping, a common practice of intensive agriculture that grows crops multiple times in the agricultural land in one growing season, is an effective way to fulfill the food demand given ...limited cropland areas. Deriving cropping cycles from satellite data provides the spatial distribution of cropping intensities that allows for monitoring of the multiple cropping activities over large areas. Although efforts have been made to map cropping cycles at 500 m or coarser resolution, producing cropping cycle maps at high resolution remain challenging because data from single satellite sensor do not provide sufficient spatiotemporal observations. In this paper, we generate dense time series of satellite data at 30 m resolution by fusion of Landsat and MODIS data, and derive the cropping cycles from the fused time series data. The method achieves overall accuracies of 92.5% and 89.2%, respectively, for two typical regions of multiple cropping in China using samples identified based on satellite time series data, and an overall accuracy of 81.2% for four subregions using all samples identified based on multi-temporal high resolution images. The mapped crop cycles show to be reasonable geographically and agree with the national census data. The fusion approach provides a feasible way to map cropping cycles at 30 m resolution and enables improved depiction of the spatial distribution of multiple cropping.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In Beijing area, the precious stone objects often suffer from the black crusts on the specific parts of the objects, in order to understand the forming mechanism of the black crusts, samples from the ...stone sculptures in Beijing Stone Carving Art Museum, ZHIHUA Temple and Museum of Western Zhou Yandu Relics were taken and studied. Nondestructive measurement was carried out firstly to acquire main elements of the samples by portable X-ray spectrum (pXRF). Morphology and microstructure of typical black crust samples were examined by ultra-depth of field microscope (UDFM) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Compositions of black crusts and body rocks were evaluated with X-ray diffraction (XRD), Raman spectra and mapping. Inductively coupled plasma optical emission spectrometry (ICP-OES) and pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) were used to identify the major pollution sources leading to the black crusts.
Through this study, the composition of the black crusts was revealed. Different gypsum crystals and carbonaceous species were found. Pollutant elements analysis and pyrolysis products provide indicators of the pollution sources. As consequence of strong photochemical oxidation processes and the high temperature from June to September in Beijing, more acid rain precursors can be formed. Frequent sulphation process occurs on the CaCO3/CaMg(CO3)2 surface. Combining morphology results and atmospheric data, the formation of black crusts in Beijing can be deduced.
Black crusts; Gypsum; Pollution sources; Meteorology; Forming mechanism; Marble.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Vertically aligned ZnO nanowire arrays were synthesized by two-step hydrothermal method. ZnO seed layers were prepared on substrate by using anhydrous ethanol and zinc acetate dihydrate ...solution, followed by the generation of ZnO nanowire arrays by low-temperature liquid-phase hydrothermal methods. The ZnO nanowire arrays were prepared under different conditions to compare the effects of growth conditions on the morphology of ZnO nanowires, in order to explore the optimal growth conditions for ZnO nanowire arrays used in semiconductor device. The morphological changes of ZnO nanowire arrays grown under different conditions were systematically analyzed by SEM, XRD and other characterization means. The results show that the seed solution concentration, growth solution concentration, doping concentration and growth time all have certain effects on the morphology of ZnO nanowire arrays. Besides, the Ag/ZnO ohmic contact were investigated, the optimal annealing temperatures of 450 °C was obtained.
Abstract
The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices, which can realize the processing of thick silicon structures. This paper ...proposes that indium tin oxides (ITO) film can serve as a deep silicon etching cut-off layer because ITO is less damaged under the attack of fluoride ions. ITO has good electrical conductivity and can absorb fluoride ions for silicon etching and reduce the reflection of fluoride ions, thus reducing the foot effect. The removal and release of ITO use an acidic solution, which does not damage the silicon structure. Therefore, the selection of the sacrificial layer has an excellent effect in maintaining the shape of the MEMS structure. This method is used in the preparation of MEMS accelerometers with a structure thickness of 100
μ
m and a feature size of 4
μ
m. The over-etching of the bottom of the silicon structure caused by the foot effect is negligible. The difference between the simulated value and the designed value of the device characteristic frequency is less than 5%. This indicates that ITO is an excellent deep silicon etch stopper material.
Self-expansion polymer grouting technology is a new rapid trenchless method for repairing leakage and subsidence of underground concrete structures. The bond between polymer and concrete is critical ...to determine the ultimate conditions of repaired concrete. In this paper, a series of direct shear tests were performed to investigate the influence of normal pressure on the shear bond properties between self-expansion polymer and concrete with different polymer density and concrete strength. Results indicate that failure modes and bond strength are greatly influenced by the normal pressure for specimens with a lower polymer density. For a given normal pressure, the bond strength linearly increases with the increasing polymer density. As the polymer density increased up to 0.43 g/cm3, the increased ratio decreases with the polymer density. Moreover, the displacement at the peak point reduces with an increase in polymer density. Finally, a finite element model is proposed to evaluate the bond strength for specimen failure in concrete and verified with the test results.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Gold nanoparticles (AuNPs) aggregation-based colorimetric biosensing remains a challenge for bacteria due to their large size. Here we propose a novel colorimetric biosensor for rapid detection of ...Escherichia coli O157:H7 (E. coli O157:H7) in milk samples based on pH-regulated transformation of dimer/tetramer of Concanavalin A (Con A) and the Con A-glycosyl recognition. Briefly, antibody-modified magnetic nanoparticles was used to capture and concentrate E. coli O157:H7 and then to label with Con A; pH adjusted to 5 was then applied to dissociate Con A tetramer to release dimer, which was collected and re-formed tetramer at pH of 7 to cause the aggregation of dextran-modified AuNPs. The interesting pH-dependent conformation-transformation behavior of Con A innovated the design of the release from the bacteria surface and then the reconstruction of Con A. Therefore, we realized the sensitive colorimetric biosensing of bacteria, which are much larger than AuNPs that is generally not suitable for this kind of method. The proposed biosensor exhibited a limit of detection down to 41 CFU/mL, short assay time (~95 min) and satisfactory specificity. The biosensor also worked well for the detection in milk sample, and may provide a universal concept for the design of colorimetric biosensors for bacteria and virus.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A horseradish peroxidase (HRP)-Au nanoclusters (AuNCs) bionanocomposite was prepared simply by mixing HRP and NaAuCl4 in an alkaline aqueous solution (pH12) at 37°C for 12h under vigorous stirring. ...Cast-coating the HRP-AuNCs bionanocomposite and then Nafion on a glassy carbon electrode (GCE) yielded a Nafion/HRP-AuNCs/GCE. This electrode exhibited a pair of well-defined cyclic voltammetric peaks of the immobilized HRP with a formal potential of −0.389V vs SCE and an electron transfer rate constant of 3.19s−1 in pH7.0 phosphate buffer. The HRP also exhibits a high bioactivity. This electrode showed high electrocatalytic activity for reduction of both O2 and H2O2, as a result of the synergistic effects of HRP and nearby AuNCs. This electrode gave a linear amperometric response to H2O2 from 0.01 to 3.27mmolL−1 with a sensitivity of 0.86μAmM−1cm−2 and a limit of detection (LOD, S/N=3) of 0.99μM.
•Horseradish peroxidase-Au nanoclusters bionanocomposite•Simultaneous realization of high electroactivity and high bioactivity•Electrocatalyzed reduction of O2 and H2O2•H2O2 biosensing
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A novel label-free electrochemical strategy for monitoring the activity and inhibition of protein kinase is developed, based on the linkage between the phosphorylated peptide and DNA functionalized ...Au nanoparticles (DNA-AuNPs) by Zr(4+) and the chronocoulometric response of Ru(NH(3))(6)(3+) absorbed on the DNA-AuNPs.
High-performance MEMS accelerometers usually use a pendulum structure with a larger mass. Although the performance of the device is guaranteed, the manufacturing cost is high. This paper proposes a ...method of fabricating high-performance MEMS accelerometers with a TGV process, which can reduce the manufacturing cost and ensure the low-noise characteristics of the device. The TGV processing relies on laser drilling, the metal filling in the hole is based on the casting mold and CMP, and the packaging adopts the three-layer anodic bonding process. Moreover, for the first time, the casting mold process is introduced to the preparation of MEMS devices. In terms of structural design, the stopper uses distributed comb electrodes for overload displacement suppression, and the gas released by the packaging method provides excellent mechanical damping characteristics. The prepared accelerometer has an anti-overload capability of 10,000 g, the noise density is less than 0.001°/√Hz, and it has ultra-high performance in tilt measurement.
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