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Protection mechanisms of periphytic biofilm to photocatalytic nanoparticles (PNPs) exposure
摘要： Researchers are devoting great effort to combine photocatalytic nanoparticles (PNPs) with biological process to create efficient environmental purification technologies (i.e. intimately coupled photobiocatalysis). However, little information is available to illuminate the responses of multispecies microbial aggregates against PNP exposure. Periphytic biofilm, as a model multispecies microbial aggregate, was exposed to three different PNPs (CdS, TiO2, and Fe2O3) under Xenon lamp irradiation. There were no obvious toxic effects of PNP exposure on periphytic biofilm as biomass, chlorophyll content and ATPase activity were not negatively impacted. Enhanced production of extracellular polymetric substances (EPS) is the most important protection mechanism for periphytic biofilm against PNPs exposure. Although PNPs exposure produced extracellular superoxide radicals and caused intracellular reactive oxygen species (ROS) accumulation in periphytic biofilm, the interaction between EPS and PNPs could mitigate production of ROS while superoxide dismutase could alleviate biotic ROS accumulation in periphytic biofilm. The periphytic biofilms changed their community composition in the presence of PNPs by increasing the relative abundance of phototrophic and high nutrient metabolic microorganisms (Families Chlamydomonadaceae, Cyanobacteriacea, Sphingobacteriales and Xanthomonadaceae). This study provides insight into the protection mechanisms of microbial aggregates against simultaneous photogenerated and nanoparticle toxicity from PNPs.
关键词： community composition,EPS,reactive oxygen species,Periphytic biofilm,photocatalyst,nanoparticles
更新于2025-09-23 15:23:52
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Rotationally resolved spectroscopy of (20000) Varuna in the near-infrared
摘要： Context. Models of the escape and retention of volatiles by minor icy objects exclude any presence of volatile ices on the surface of trans-Neptunian objects (TNOs) smaller than ～1000 km in diameter at the typical temperature in this region of the solar system, whereas the same models show that water ice is stable on the surface of objects over a wide range of diameters. Collisions and cometary activity have been used to explain the process of surface refreshing of TNOs and Centaurs. These processes can produce surface heterogeneity that can be studied by collecting information at di?erent rotational phases. Aims. The aims of this work are to study the surface composition of (20000) Varuna, a TNO with a diameter 668+154 ?86 km and to search for indications of rotational variability. Methods. We observed (20000) Varuna during two consecutive nights in January 2011 with the near-infrared camera and spectrometer NICS at the Telescopio Nazionale Galileo, La Palma, Spain. We used the low resolution mode with the AMICI prism to obtain a set of spectra covering the whole rotation period of the Varuna (Pr = 6.34 h). We ?t the resulting relative re?ectance with radiative transfer models of the surface of atmosphereless bodies. Results. After studying the spectra corresponding to di?erent rotational phases of Varuna, we did not ?nd any indication of surface variability at 2σ level. In all the spectra, we detect an absorption at 2.0 μm, suggesting the presence of water ice on the surface. We do not detect any other volatiles on the surface, although the signal-to-noise ratio is not high enough to discard their presence in small quantities. Based on scattering models, we present two possible compositions compatible with our set of data and discuss their implications in the framework of the collisional history of the trans-Neptunian belt. Conclusions. We ?nd that the most probable composition for the surface of Varuna is a mixture of amorphous silicates, complex organics, and water ice. This composition is compatible with all the materials being primordial, so no replenishment mechanism is needed in the equation. However, our data can also be ?tted by models containing up to a 10% of methane ice. For an object with the characteristics of Varuna, this volatile could not be primordial, so an event, such as an energetic impact, would be needed to explain its presence on the surface.
关键词： Kuiper belt objects: individual: (2000) Varuna,planets and satellites: composition,methods: numerical,techniques: spectroscopic,methods: observational
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Investigation of the Phase Composition and Morphology of Silicon Structures by Using the Raman Spectroscopy to Determine the Parameter of Crystallinity
摘要： This work aims to investigate the dependence of the phase composition of thin films of microcrystalline silicon deposition on process parameters. The films of microcrystalline silicon were obtained by plasma-chemical deposition method (PECVD). Phase composition and correlation between degree of crystallinity and structure of the obtained layers were analyzed by Raman Spectroscopy. The results show that the control of several technical parameters, e.g. pressure, discharge power and monosilane flow, allows to reach the crystallinity parameter in the range 50-70 %. Based on the conducted experiments, the recommendations for the control of the crystallinity parameter, which are planned to be implemented when working with silicon-based porous structures, were proposed.
关键词： Morphology,Semiconductors,Silicon,Por-silicon,Phase composition,Raman spectroscopy,Raman Crystallinity
更新于2025-09-23 15:23:52
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Validation of MODIS-Aqua bio-optical algorithms for phytoplankton absorption coefficient measurement in optically complex waters of El Rincón (Argentina)
摘要： El Rincón is a highly productive area in the inner-shelf of the Argentine Sea, southern Buenos Aires Province (39°S–62.5°W; 41.5°S–60°W), regarded as the habitat for commercially valuable ?sh species and important for local artisanal ?sheries. The aims of this work were to characterize for the ?rst time the in situ absorption coe?cient of phytoplankton (aph(λ)) in relation to phytoplankton composition and chlorophyll-a (Chl-a) concentration, and to evaluate the satellite retrieval of aph(443) using two atmospheric correction algorithms and three bio-optical semi-analytical algorithms in order to de?ne which is more suitable for the study area. A total of 28 oceanographic cruises were performed between November 2013 and March 2017 and the sampling included physical variables (temperature, salinity, suspended particulate matter, SPM), Chl-a, phytoplankton absorption and composition. The phytoplankton community was mainly dominated by chain-forming diatoms from the microplankton size class (40–80%), while a single coccolithophore, Gephyrocapsa oceanica (cell diameter < 10 μm) was a key component (up to 40%) of the nanoplankon. In situ Chl-a (mean 1.8 mg m?3) and aph(443) (mean 0.052 m?1) generally covariated with no clear seasonality. Their correlation was rather low (R2 = 0.52) and with high scattering, in agreement with the high interannual variability of phytoplankton composition. Further, the relative low mean speci?c absorption coe?cient of phytoplankton (aph*(443), 0.032 m2 (mg Chl-a)?1) and (aph*(676), 0.014 m2 (mg Chl-a)?1) denoted the presence of big cells and pigment packaging e?ect. Aside from the optical complexity of these waters, reasonable results were found using the Quasi Analytical Algorithm in retrieving aph coe?cient (R2 = 0.55, Bias = 19%) and switching the atmospheric correction algorithm depending on the distance to the coast, the depth and turbidity. The results found in this paper present for the ?rst time the phytoplankton composition and absorption of algal material characteristics and the derived implication on the performance of bio-optical algorithms in the optically complex waters of El Rincon.
关键词： Absorption by phytoplankton,Bio-optical algorithms,Turbid coastal waters,Phytoplankton composition,Validation,MODIS-Aqua
更新于2025-09-23 15:22:29
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Rapid Quantitative Analysis of Forest Biomass Using Fourier Transform Infrared Spectroscopy and Partial Least Squares Regression
摘要： Fourier transform infrared reflectance (FTIR) spectroscopy has been used to predict properties of forest logging residue, a very heterogeneous feedstock material. Properties studied included the chemical composition, thermal reactivity, and energy content. The ability to rapidly determine these properties is vital in the optimization of conversion technologies for the successful commercialization of biobased products. Partial least squares regression of first derivative treated FTIR spectra had good correlations with the conventionally measured properties. For the chemical composition, constructed models generally did a better job of predicting the extractives and lignin content than the carbohydrates. In predicting the thermochemical properties, models for volatile matter and fixed carbon performed very well (i.e., R2 > 0.80, RPD > 2.0). The effect of reducing the wavenumber range to the fingerprint region for PLS modeling and the relationship between the chemical composition and higher heating value of logging residue were also explored. This study is new and different in that it is the first to use FTIR spectroscopy to quantitatively analyze forest logging residue, an abundant resource that can be used as a feedstock in the emerging low carbon economy. Furthermore, it provides a complete and systematic characterization of this heterogeneous raw material.
关键词： FTIR spectroscopy,forest logging residue,energy content,partial least squares regression,thermal reactivity,chemical composition
更新于2025-09-23 15:22:29
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Automatic Pathological Lung Segmentation in Low-dose CT Image using Eigenspace Sparse Shape Composition
摘要： Segmentation of lungs with severe pathology is a nontrivial problem in clinical application. Due to complex structures, pathological changes, individual differences and low image quality, accurate lung segmentation in clinical 3D CT images is still a challenging task. To overcome these problems, a novel dictionary-based approach is introduced to automatically segment pathological lungs in 3D low-dose CT images. Sparse shape composition is integrated with eigenvector space shape prior model, called eigenspace sparse shape composition, to reduce local shape reconstruction error caused by weak and misleading appearance prior information. To initialize the shape model, a landmark recognition method based on discriminative appearance dictionary is introduced to handle lesions and local details. Furthermore, a new vertex search strategy based on gradient vector flow field is also proposed to drive shape deformation to target boundary. The proposed algorithm is tested on 78 3D low-dose CT images with lung tumors. Compared to state-of-the-art methods, the proposed approach can robustly and accurately detect pathological lung surface.
关键词： gradient vector flow,Pathological lung segmentation,discriminative appearance dictionary,eigenspace sparse shape composition
更新于2025-09-23 15:22:29
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A review on smart application of supplemental lighting in greenhouse fruiting vegetable production
摘要： Different spectra of light trigger different plant growth processes. Therefore, the optimum light spectrum for various plant physiological and growth processes may be different. For greenhouse fruiting vegetables, such as tomatoes, it is important to optimize light spectrum to promote canopy growth to increase light interception during the early stage of plant growth. Once the plants reach full canopy, the focus should be moved to optimizing vertical light distribution because most greenhouse fruiting vegetables are tall crops and the growth processes along the vertical profile are different; most of the canopy growth occurs in the top and middle canopy while fruit growth occurs in the middle and bottom canopy. Because the fruit, not the leaf, is the economic product, the optimized light spectral composition should enhance leaf carbon export and translocation to fruit to improve fruit yield and quality. Therefore, a research project was initiated in 2013 to identify proper light spectral composition and vertical distribution regimes for greenhouse fruiting vegetable production. Different overhead light sources (high-pressure sodium light with or without far-red light-emitting diode (LED) light, plasma light and different spectral compositions of LEDs) and several intra-canopy spectral compositions provided by LEDs were evaluated over four winters on tomatoes, mini-cucumbers and sweet peppers. The effects of light spectrum on whole-plant net carbon exchange and leaf carbon export using 14C-isotype tracing were also investigated. The vertical light regimes resulted in significant differences in leaf photosynthetic rate, leaf size, fruit yield and fruit quality in greenhouse tomatoes, mini-cucumbers and sweet peppers. Proper vertical light regimes were identified for hybrid light systems (overhead high intensity discharge light + intra-canopy LEDs) and for pure LED light systems (overhead + intra-canopy LEDs). This review clearly demonstrates that optimized vertical light regimes can be developed for improving both plant growth and fruit yield and quality in year-round greenhouse fruiting vegetable production.
关键词： far-red light,Solanum lycopersicum,Capsicum annuum,Cucumis sativus,light quality,vertical light spectral distribution,temperature,LED,lighting,spectral composition
更新于2025-09-23 15:22:29
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Electro-thermal modeling for InxGa1-xN/GaN based quantum well heterostructures
摘要： The joint effect of the heat transfer and the electronic properties in the InGaN/GaN based quantum well (QW) heterostructures has been investigated theoretically and numerically. One-dimensional Schr?dinger equation solver coupled with Poisson equation solver and Dual-phase-lagging (DPL) heat conduction solver has been developed. The numerical results suggest that the DPL heat conduction equations capture the microscale responses caused by the phonon-electron interaction. Both effects of the polarization charge and conduction band offset between the InGaN/GaN interfaces lead to the creation of the two-dimensional electron gas (2DEG) on the lower interface of the QW. It is found that the 2DEG density at the triangular quantum well increases with increasing Indium (In) composition. This increase is the same for the conduction band offset and the electron density. As a consequence, an increase of the heat dissipation and the temperature is observed at the lower interface of the quantum well.
关键词： Indium composition,Polarization charge,Nanoscale heat transfer,Dual-phase-lagging model,InGaN heterostructure
更新于2025-09-23 15:22:29
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Influence of thickness on the optical properties of Sb doped ZnO thin films
摘要： Sb doped ZnO thin films having various thicknesses have been prepared onto glass substrate by using thermal evaporation method. The atomic compositions of the grown films have been determined by Energy Dispersive Analysis of X-ray (EDAX) method. The optical properties were measured by using a UV-VIS-NIR spectrophotometer (300 to 2500 nm). The EDAX analysis revealed that Sb is doped into the ZnO films. Optical properties showed high absorption coefficient (~105/cm) that direct allowed transition band gap. The optical band gap of the ZnO thin films became reduced due to the doping of Sb.
关键词： Composition,Sb doped ZnO thin films,Optical properties,Thickness
更新于2025-09-23 15:22:29
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The Effect of Precursor Composition on the Structural Properties of Nanocrystalline Diamond Films
摘要： Nanocrystalline diamond (NCD) films were grown by hot filament CVD and the precursor composition dependence of the structural properties was examined. Films grown at 1 and 2 CH4 Vol% were found to be NCD layers with grain sizes of ～23–25 nm while films grown at 3–5 Vol% were identified as the mixtures of microcrystalline diamond and graphitic phase. The sp2/sp3 bonded carbon ratio in the grown films increased as the CH4 content increased up to 3 Vol% and then decreased beyond 4 Vol%. Microstructure and deposition rate were also found to be affected by the precursor composition and the NCD film grown at 1 CH4 Vol% showed a very dense microstructure and the highest deposition rate of ～3 nm/min.
关键词： Precursor Composition,Structural Properties,Nanocrystalline Diamond
更新于2025-09-23 15:22:29