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Open AccessArticle
One-Step Synthesis of Silver Nanoparticles on Polydopamine-Coated Sericin/Polyvinyl Alcohol Composite Films for Potential Antimicrobial Applications
Molecules 2017, 22(5), 721; doi:10.3390/molecules22050721 (registering DOI) -
Abstract
Silk sericin has great potential as a biomaterial for biomedical applications due to its good hydrophilicity, reactivity, and biodegradability. To develop multifunctional sericin materials for potential antibacterial application, a one-step synthesis method for preparing silver nanoparticles (AgNPs) modified on polydopamine-coated sericin/polyvinyl alcohol (PVA)
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Silk sericin has great potential as a biomaterial for biomedical applications due to its good hydrophilicity, reactivity, and biodegradability. To develop multifunctional sericin materials for potential antibacterial application, a one-step synthesis method for preparing silver nanoparticles (AgNPs) modified on polydopamine-coated sericin/polyvinyl alcohol (PVA) composite films was developed. Polydopamine (PDA) acted as both metal ion chelating and reducing agent to synthesize AgNPs in situ on the sericin/PVA composite film. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed that polydopamine could effectively facilitate the high-density growth of AgNPs as a 3-D matrix. X-ray diffractometry studies suggested the synthesized AgNPs formed good face-centered cubic crystalline structures. Contact angle measurement and mechanical test indicated AgNPs modified PDA-sericin/PVA composite film had good hydrophilicity and mechanical property. The bacterial growth curve and inhibition zone assays showed the AgNPs modified PDA-sericin/PVA composite film had long-term antibacterial activities. This work develops a new method for the preparation of AgNPs modified PDA-sericin/PVA film with good hydrophilicity, mechanical performance and antibacterial activities for the potential antimicrobial application in biomedicine. Full article
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Open AccessArticle
A Novel Classification Technique of Landsat-8 OLI Image-Based Data Visualization: The Application of Andrews’ Plots and Fuzzy Evidential Reasoning
Remote Sens. 2017, 9(5), 427; doi:10.3390/rs9050427 (registering DOI) -
Abstract
Andrews first proposed an equation to visualize the structures within data in 1972. Since then, this equation has been used for data transformation and visualization in a wide variety of fields. However, it has yet to be applied to satellite image data. The
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Andrews first proposed an equation to visualize the structures within data in 1972. Since then, this equation has been used for data transformation and visualization in a wide variety of fields. However, it has yet to be applied to satellite image data. The effect of unwanted, or impure, pixels occurring in these data varies with their distribution in the image; the effect is greater if impurity pixels are included in a classifier’s training set. Andrews’ curves enable the interpreter to select outlier or impurity data that can be grouped into a new category for classification. This study overcomes the above-mentioned problem and illustrates the novelty of applying Andrews’ plots to satellite image data, and proposes a robust method for classifying the plots that combines Dempster-Shafer theory with fuzzy set theory. In addition, we present an example, obtained from real satellite images, to demonstrate the application of the proposed classification method. The accuracy and robustness of the proposed method are investigated for different training set sizes and crop types, and are compared with the results of two traditional classification methods. We find that outlier data are easily eliminated by examining Andrews’ curves and that the proposed method significantly outperforms traditional methods when considering the classification accuracy. Full article
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Open AccessFeature PaperArticle
Selenium Speciation in the Fountain Creek Watershed (Colorado, USA) Correlates with Water Hardness, Ca and Mg Levels
Molecules 2017, 22(5), 708; doi:10.3390/molecules22050708 (registering DOI) -
Abstract
The environmental levels of selenium (Se) are regulated and strictly enforced by the Environmental Protection Agency (EPA) because of the toxicity that Se can exert at high levels. However, speciation plays an important role in the overall toxicity of Se, and only when
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The environmental levels of selenium (Se) are regulated and strictly enforced by the Environmental Protection Agency (EPA) because of the toxicity that Se can exert at high levels. However, speciation plays an important role in the overall toxicity of Se, and only when speciation analysis has been conducted will a detailed understanding of the system be possible. In the following, we carried out the speciation analysis of the creek waters in three of the main tributaries—Upper Fountain Creek, Monument Creek and Lower Fountain Creek—located in the Fountain Creek Watershed (Colorado, USA). There are statistically significant differences between the Se, Ca and Mg, levels in each of the tributaries and seasonal swings in Se, Ca and Mg levels have been observed. There are also statistically significant differences between the Se levels when grouped by Pierre Shale type. These factors are considered when determining the forms of Se present and analyzing their chemistry using the reported thermodynamic relationships considering Ca2+, Mg2+, SeO42−, SeO32− and carbonates. This analysis demonstrated that the correlation between Se and water hardness can be explained in terms of formation of soluble CaSeO4. The speciation analysis demonstrated that for the Fountain Creek waters, the Ca2+ ion may be mainly responsible for the observed correlation with the Se level. Considering that the Mg2+ level is also correlating linearly with the Se levels it is important to recognize that without Mg2+ the Ca2+ would be significantly reduced. The major role of Mg2+ is thus to raise the Ca2+ levels despite the equilibria with carbonate and other anions that would otherwise decrease Ca2+ levels. Full article
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Open AccessArticle
Shallow Water Measurements Using a Single Green Laser Corrected by Building a Near Water Surface Penetration Model
Remote Sens. 2017, 9(5), 426; doi:10.3390/rs9050426 (registering DOI) -
Abstract
To reduce the size and cost of an integrated infrared (IR) and green airborne Light Detection And Ranging (LiDAR) bathymetry (ALB) system, and improve the accuracy of the green ALB system, this study proposes a method to accurately determine water surface and water
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To reduce the size and cost of an integrated infrared (IR) and green airborne Light Detection And Ranging (LiDAR) bathymetry (ALB) system, and improve the accuracy of the green ALB system, this study proposes a method to accurately determine water surface and water bottom heights using a single green laser corrected by the near water surface penetration (NWSP) model. The factors that influence the NWSP of green laser are likewise analyzed. In addition, an NWSP modeling method is proposed to determine the relationship between NWSP and the suspended sediment concentration (SSC) of the surface layer, scanning angle of a laser beam and sensor height. The water surface and water bottom height models are deduced by considering NWSP and using only green laser based on the measurement principle of the IR laser and green laser, as well as employing the relationship between NWSP and the time delay of the surface return of the green laser. Lastly, these methods and models are applied to a practical ALB measurement. Standard deviations of 3.0, 5.3, and 1.3 cm are obtained by the NWSP, water-surface height, and water-bottom height models, respectively. Several beneficial conclusions and recommendations are drawn through the experiments and discussions. Full article
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Open AccessArticle
Novel Algorithm for Mining ENSO-Oriented Marine Spatial Association Patterns from Raster-Formatted Datasets
ISPRS Int. J. Geo-Inf. 2017, 6(5), 139; doi:10.3390/ijgi6050139 (registering DOI) -
Abstract
The ENSO (El Niño Southern Oscillation) is the dominant inter-annual climate signal on Earth, and its relationships with marine environments constitute a complex interrelated system. As traditional methods face great challenges in analyzing which, how and where marine parameters change when ENSO events
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The ENSO (El Niño Southern Oscillation) is the dominant inter-annual climate signal on Earth, and its relationships with marine environments constitute a complex interrelated system. As traditional methods face great challenges in analyzing which, how and where marine parameters change when ENSO events occur, we propose an ENSO-oriented marine spatial association pattern (EOMSAP) mining algorithm for dealing with multiple long-term raster-formatted datasets. EOMSAP consists of four key steps. The first quantifies the abnormal variations of marine parameters into three levels using the mean-standard deviation criteria of time series; the second categorizes La Niña events, neutral conditions, or El Niño events using an ENSO index; then, the EOMSAP designs a linking–pruning–generating recursive loop to generate (m + 1)-candidate association patterns from an m-dimensional one by combining a user-specified support with a conditional support; and the fourth generates strong association patterns according to the user-specified evaluation indicators. To demonstrate the feasibility and efficiency of EOMSAP, we present two case studies with real remote sensing datasets from January 1998 to December 2012: one considers performance analysis relative to the ENSO-Apriori and Apriori methods; and the other identifies marine spatial association patterns within the Pacific Ocean. Full article
Open AccessArticle
Hibiscus sabdariffa L. and Its Bioactive Constituents Exhibit Antiviral Activity against HSV-2 and Anti-enzymatic Properties against Urease by an ESI-MS Based Assay
Molecules 2017, 22(5), 722; doi:10.3390/molecules22050722 (registering DOI) -
Abstract
For decades, Hibiscus sabdariffa L. and its phytochemicals have been shown to possess a wide range of pharmacologic properties. In this study, aqueous extract of Hibiscus sabdariffa (AEHS) and its bioactive constituent protocatechuic acid (PCA), have been evaluated in vitro for their antiviral
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For decades, Hibiscus sabdariffa L. and its phytochemicals have been shown to possess a wide range of pharmacologic properties. In this study, aqueous extract of Hibiscus sabdariffa (AEHS) and its bioactive constituent protocatechuic acid (PCA), have been evaluated in vitro for their antiviral activity against HSV-2 clinical isolates and anti-enzymatic activity against urease. Antiherpetic activity was evaluated by the titer reduction assay in infected Vero cells, and cytotoxicity was evaluated by the neutral red dye-uptake method. Anti-urease activity was determined by a developed Electrospray Ionization-Mass Spectrometry (ESI-MS)-based assay. PCA showed potent anti-HSV-2 activity compared with that of acyclovir, with EC50 values of 0.92 and 1.43 µg∙mL−1, respectively, and selectivity indices > 217 and > 140, respectively. For the first time, AEHS was shown to exert anti-urease inhibition activity, with an IC50 value of 82.4 µg∙mL−1. This, combined with its safety, could facilitate its use in practical applications as a natural urease inhibitor. Our results present Hibiscus sabdariffa L. and its bioactive compound PCA as potential therapeutic agents in the treatment of HSV-2 infection and the treatment of diseases caused by urease-producing bacteria. Full article
Open AccessArticle
A Comparison of Terrain Indices toward Their Ability in Assisting Surface Water Mapping from Sentinel-1 Data
ISPRS Int. J. Geo-Inf. 2017, 6(5), 140; doi:10.3390/ijgi6050140 (registering DOI) -
Abstract
The Sentinel-1 mission provides frequent coverage of global land areas and is hence able to monitor surface water dynamics at a fine spatial resolution better than any other Synthetic Aperture Radar (SAR) mission before. However, SAR data acquired by Sentinel-1 also suffer from
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The Sentinel-1 mission provides frequent coverage of global land areas and is hence able to monitor surface water dynamics at a fine spatial resolution better than any other Synthetic Aperture Radar (SAR) mission before. However, SAR data acquired by Sentinel-1 also suffer from terrain effects when being used for mapping surface water, just as other SAR data do. Terrain indices derived from Digital Elevation Models (DEMs) are easy but effective approaches to reduce this kind of interference, considering the close relationship between surface water movement and topography. This study compares two popular terrain indices, namely the Multi-resolution Valley Bottom Flatness (MrVBF) and the Height Above Nearest Drainage (HAND), toward their performance on assisting surface water mapping using Sentinel-1 SAR data. Four study sites with different terrain characteristics were selected to cover a very wide range of topographic conditions. For two of these sites that are floodplain dominated, both normal and flooded scenarios were examined. MrVBF and HAND values for the whole study areas, as well as statistics of these values within water areas were compared. The sensitivity of applying different thresholds for MrVBF and HAND to mask out terrain effect was investigated by adopting quantity disagreement and allocation disagreement as the accuracy indicators. It was found that both indices help improve water mapping, reducing the total disagreement by as much as 1.6%. The HAND index performs slightly better in most of the study cases, with less sensitivity to thresholding. MrVBF classifies low-lying areas with more details, which sometimes makes it more effective in eliminating false water bodies in rugged terrain. It is therefore recommended to use HAND for large scale or global scale water mapping. However, for water detection in complex terrain areas, MrVBF also performs very well. Full article
Open AccessArticle
A Study of Efficiency Droop Phenomenon in GaN-Based Laser Diodes before Lasing
Materials 2017, 10(5), 482; doi:10.3390/ma10050482 (registering DOI) -
Abstract
Carrier recombination behavior in c-plane GaN-based laser diodes (LDs) is numerically investigated by using the commercial software LASTIP. It is found that efficiency droop phenomenon does exist in GaN-based LDs before lasing, which is confirmed by experimental results. However, the current
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Carrier recombination behavior in c-plane GaN-based laser diodes (LDs) is numerically investigated by using the commercial software LASTIP. It is found that efficiency droop phenomenon does exist in GaN-based LDs before lasing, which is confirmed by experimental results. However, the current density corresponding to the peak efficiency of GaN-based LDs before lasing, Jmax, is nearly 40 A/cm2, which is much lower than that reported by other studies. The reported Jmax, measured from the cavity facet side is modulated by the absorption of quantum wells, which shifts the Jmax to a higher value. In addition, the currents due to various recombinations are calculated. It is found that Auger recombination affects the threshold current greatly, but it only plays a small role at high current injection levels. Full article
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Open AccessArticle
Toward Exploring Novel Organic Materials: MP4-DFT Properties of 4-Amino-3-Iminoindene
Molecules 2017, 22(5), 720; doi:10.3390/molecules22050720 (registering DOI) -
Abstract
Tautomerism links with many applications and remains an attracting feature in exploring novel systems. In this regard, properties of indene-based HNCCCN segments have not received any considerable attention. In this computational organic chemistry study, first, to calculate the proton transfer energy barrier at
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Tautomerism links with many applications and remains an attracting feature in exploring novel systems. In this regard, properties of indene-based HNCCCN segments have not received any considerable attention. In this computational organic chemistry study, first, to calculate the proton transfer energy barrier at a reasonable cost, the study identified an accurate forth order Møller–Plesset perturbation theory-density functional theory (MP4-DFT) protocol equivalent to the outstanding pioneering benchmark calculations. The calculations illustrate that the two tautomers of the 4-amino-3-iminoindene nucleus are separated by a considerable energy barrier while featuring different molecular orbital characteristics; frontier orbital distribution, λmax, and energies, which are known basic requirements in molecular switching and logic circuit applications. The N-H/BH2 substitution was found to have significant influence on the electronic structure of the skeleton. Similarities in the two tautomers and the boron derivative to properties of known molecular materials have been found. Full article
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