Scanning Electron Microscropy Research Articles

Characterization of rhizosphere Pseudomonas chlororaphis IRHB3 in the reduction of Fusarium root rot and promotion of soybean growth

Rhizosphere beneficial bacteria play an important role in plant health and disease control, and have been widely explored as biocontrol resources and agents for the ecological and sustainable management of soil-borne diseases. In our previous study, a bacterium strain IRHB3 was isolated from soybean rhizosphere under maize-soybean relay strip intercropping. To clarify the characterization of IRHB3 and its biocontrol effects of soybean root rot, we systemically investigated the taxonomy, biological characteristics, bacteriostatic activity, environmental stress tolerance of IRHB3, and also analyzed its effects on the control of root rot as well as growth promotion. Our results showed that IRHB3 as a Gram-negative bacterium was identified as Pseudomonas chlororaphis by multi-locus sequence analysis of 16S rRNA, gyrB, rpoD and gapA. The colony was characterized by yellowish circular and rugby-shaped with rough surface and gullies under scanning electron microscropy.. IRHB3 not only activated kinds of hydrolase such as protease, caseinase, and cellulase, but was also capable of dissolving phosphorus, releasing siderophores and producing IAA. IRHB3 suspension treatment with proper concentration significantly promoted seed germination and seedling growth. Antagonistic assay showed that IRHB3 displayed good inhibition effects on various pathogenic fungi, especially aggressive Fusarium species causing root rot, with the average inhibition rate as high as 69.89%. And meanwhile, introducing IRHB3 into soil effectively alleviated the damage of F. oxysporum to soybean root. Moreover, IRHB3 had strong environmental adaptability of wide pH, low nutrition and salt stress. In conclusion, these results indicate that Pseudomonas chlororaphis IRHB3 from intercropped soybean rhizosphere is one kind of typically plant growth-promoting rhizobacteria (PGPR) and has immense potential and strong environmental adapatability on the control of soil-borne fungal disease.

Rational Design of Mixed Matrix Membranes Modulated by Trisilver Complex for Efficient Propylene/Propane Separation.

The application of membrane-based separation processes for propylene/propane (C3 H6 /C3 H8 ) is extremely promising and attractive as it is poised to reduce the high operation cost of the established low temperature distillation process, but major challenges remain in achieving high gas selectivity/permeability and long-term membrane stability. Herein, a C3 H6 facilitated transport membrane using trisilver pyrazolate (Ag3 pz3 ) as a carrier filler is reported, which is uniformly dispersed in a polymer of intrinsic microporosity (PIM-1) matrix at the molecular level (≈15nm), verified by several analytical techniques, including 3D-reconstructedfocused ion beam scanning electron microscropy (FIB-SEM) tomography. The π-acidic Ag3 pz3 combines preferentially with π-basic C3 H6 , which is confirmed by density functional theory calculations showing that the silver ions in Ag3 pz3 form a reversible π complex with C3 H6 , endowing the membranes with superior C3 H6 affinity. The resulting membranes exhibit superior stability, C3 H6 /C3 H8 selectivity as high as ≈200 and excellent C3 H6 permeability of 306 Barrer, surpassing the upper bound selectivity/permeability performance line of polymeric membranes. This work provides a conceptually new approach of using coordinatively unsaturated 0D complexes as fillers in mixed matrix membranes, which can accomplish olefin/alkane separation with high performance.

StomataCounter: a neural network for automatic stomata identification and counting.

Stomata regulate important physiological processes in plants and are often phenotyped by researchers in diverse fields of plant biology. Currently, there are no user-friendly, fully automated methods to perform the task of identifying and counting stomata, and stomata density is generally estimated by manually counting stomata. We introduce StomataCounter, an automated stomata counting system using a deep convolutional neural network to identify stomata in a variety of different microscopic images. We use a human-in-the-loop approach to train and refine a neural network on a taxonomically diverse collection of microscopic images. Our network achieves 98.1% identification accuracy on Ginkgo scanning electron microscropy micrographs, and 94.2% transfer accuracy when tested on untrained species. To facilitate adoption of the method, we provide the method in a publicly available website at http://www.stomata.science/.

Research on the Rolling and Sliding Behavior of Making Contact and Associated Welding Mechanism for Low-Current Switching Devices

The electrical lifetime of electromechanical device is affected by the contact mechanical rolling and sliding behavior greatly. The sliding distance and broadside lines of contact pair are captured in situ and analyzed by introducing charge-coupled device camera with a high pixel resolution. The variations in sliding distance and electrical performance parameters with operation cycles at each constant contact gap are investigated by using our novel designed test rig. The degradation mechanisms of contact surface are explained with the material transfer resulted by the continuous electric arcing. Combined with the variations in contact resistance, static force, impact force, and the scanning electron microscropy photographs of failure contacts, the degradation process and associated welding mechanisms are proposed.

Geotechnical properties and microstructure of lime-stabilized silt clay

The geotechnical properties and microstructures of lime-stabilized silt clay from Jilin province, China, were studied in detail. Laboratory tests were conducted to evaluate the effects of lime content and curing time on the overall soil properties, including compaction characteristics, Atterberg limits, particle size distribution, pH, stress–strain behavior, peak strength, shear strength parameters, and California bearing ratio (CBR). The stabilized mechanisms of lime in silt clay were examined, and the observed test results were explained based on the results of scanning electron microscropy (SEM) and X-ray diffraction analyses of the specimens. Lime content and curing duration significantly influenced the geotechnical properties and microstructure of the lime-stabilized silt clay specimens. An increase in lime content resulted in increases in compaction water content, liquid limit, plastic limit, sand size-fractions, pH, peak strength, cohesion, internal friction angle, and the CBR, but led to a reduction in the plasticity index, silt fractions, clay fractions, swelling capacity, and water absorption. Also, the addition of lime to silt clay changed this soil type from a ductile to a brittle material. The optimum lime content of the silt clays from Jilin province was determined to be approximately 5–7%. SEM micrographs showed that a white cementitious gel was formed after the addition of lime and that peaks related to smectite, illite, kaolinite, and quartz appeared to be sharper after stabilization with lime and a 90-day period of curing. These results show that the geotechnical properties of lime-stabilized silt clay are affected by the microstructural organization of the silt clay itself.

Promoting Effect of CeO2and MgO for CO2Reforming of Methane over Ni-ZnO Catalyst

The purpose of this study was to find out the effect of CeO2 and MgO (as a promoter) on CO2 reforming of methane or dry reforming of methane (DRM) for the production of synthesis gas. In this aspect, CeO2 and MgO promoted Ni-nanoparticles supported ZnO catalyst was prepared by surfactant induced hydrothermal method, using cetyltrimethylammonium bromide (CTAB) as surfactant, morphology controlling agent and polyvinylpyrrolidone (PVP) as size controlling agent. The prepared catalysts were characterized by BET-Surface area, X-ray diffraction study (XRD), Scanning Electron Microscropy (SEM), Transmission Electron Microscopy (SEM), Inductively coupled plasma atomic emission spectroscopy (ICPAES), Temperature Programmed Reduction (TPR), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA) techniques. Highly basic nature of MgO and excellent redox properties of CeO2 increased nickel dispersion and created strong metal-support interaction, which effectively reduced the coke deposition on the catalyst surface. MgO promoted Ni-ZnO catalyst showed better low temperature activity compared to CeO2 promoted Ni-ZnO catalyst for DRM and Ni-MgO/ZnO catalyst also exhibited better coke resistivity, because of comparatively smaller nickel nanoparticles. Both the promoted catalysts showed more than 24 h of time on stream (TOS) stability at 800 °C without any significant deactivation of the catalysts. The catalysts produced H2/CO ratio 0.99 at 800 °C during the TOS.

Cation Exchange Synthesis and Unusual Resistive Switching Behaviors of Ag2Se Nanobelts

Ag2Se nanobelts are prepared through employing ZnSe nanobelts as templates via a facile cation exchange approach. The templates are derived from precursor ZnSe·0.5N2 H4 nanobelts, which are synthesized by a simple hydrothermal method. As-synthesized precursor nanobelts are with 200 nm in width and several hundreds of micrometers in length. Annealed in N2 , they are transformed into ZnSe nanobelts with preserving their initial morphology. Following with a complete replacement of Zn(2+) by Ag(+), Ag2Se nanobelts with single crystalline are obtained via a cation-exchange reaction. Combined with the Langmuir-Blodgett assembly technique, regular films of ZnSe nanobelts can be achieved on transparent glass substrates and Si wafers with interdigital Au electrode arrays. Further, the optical and electrical evolutions are investigated from ZnSe nanobelts to Ag2 Se nanobelts. Finally, the resistive switching characteristic are carefully explored for Ag2Se nanobelts regularly arranged on interdigital Au microelectrodes. The results indicate that it is analogous to complementary resistive switching behaviors, which is different from that of traditional two terminal devices about previously reported Ag2Se. In order to clarify this phenomenon, a possible mechanism has been proposed and indirectly demonstrated through in situ SEM (scanning electron microscropy) observation.

YSr<sub>2</sub>Fe<sub>3-x</sub>Co<sub>x</sub>O<sub>8</sub> as a Potential Cathode Materials for SOFCs

The composition YSr2Fe3-xCoxO8 (for x = 0.5, 3.0) has been investigated as an alternative cathode material for Solid Oxide Fuel Cells (SOFCs). X-ray diffraction (XRD) pattern shows that the composition YSr2Fe2.5Co0.5O8 crystallizes with cubic symmetry in the space group Pm-3m and YSr2Co3O8 crystallizes with tetragonal symmetry in the space group P4/mmm. Rietveld refinement of XRD data shows the cell parameter of the cubic YSr2Fe2.5Co0.5O8 is a = b = c = 4.1964(2) (Å) and tetragonal YSr2Co3O8 is a = b = 9.8998(9) (Å) and c = 8.9617(6) (Å). Scanning electron microscropy (SEM) images show porous structure for both the samples, which is favourable as a cathode for Solid Oxide Fuel Cells.

Effect of EMA and antioxidants on properties of thermoplastic starch blown films

The objectives of this study were to investigate the effect of poly(ethylene-co-methyl acrylate) (EMA) at 10, 30 and 50 wt% on the morphological properties, moisture sorption, water vapor permeability and biodegradability of thermoplastic starch (TPS). Urea and formamide were used as a mixed plasticizer. In addition, the effect of antioxidants namely, 3,5-di-tert-butyl-4-hydroxyhydrocinnamate (DTBH), butylated hydroxytoluene (BHT) and bis(octadecyl)hydroxylamine (BOH) at 1 wt% on the properties of TPS/EMA film was investigated. TPS/EMA films were produced by a blown film molding machine and characterized by scanning electron microscropy, moisture sorption, water vapor permeability and biodegradability measurement. Results found that the increment of EMA content in the TPS matrix could improve the water sorption, water vapor permeability and biodegradability properties of TPS/EMA films. For biodegradation, the weight loss of the blended films was directly proportional to TPS content. Regarding the antioxidants effect, the water vapor permeability of TPS/EMA films containing DTBH was higher than the one with BOH and BHT. However, the antioxidants contributed little to the biodegradability of TPS/EMA films and had no effect on the moisture sorption of TPS/EMA films.

Titanium Dioxide Nanoparticles Disturb the Fibronectin-Mediated Adhesion and Spreading of Pre-osteoblastic Cells

In the context of rapid development of nanoparticles (NPs) for industrial applications, the question of their toxicity and biological effects must be considered. In this work, we have assessed the influence of titanium dioxide NPs on the adhesion and spreading of MC-3T3 pre-osteoblasts by using a cell subclone that does not produce its own extracellular matrix. Petri dishes were coated with the important adhesion protein fibronectin (Fn). By incubating these Fn-coated surfaces with different amounts of TiO(2) NPs, we have shown that the adhesion of pre-osteoblasts is disturbed, with an important decrease in the number of adherent cells (from 40 to 75% depending upon the concentration and type of NPs). Petri-dish surfaces were analyzed with environmental scanning electron microscropy (ESEM), with images showing that TiO(2) NP aggregates are bound to the layer of adsorbed Fn molecules. The cells cultured on these Fn/NP surfaces adopted an irregular shape and an aberrant organization of actin cytoskeleton, as revealed by fluorescence microscopy. Most importantly, these results, taken together, have revealed that the actin cytoskeleton forms abnormal aggregates, even on top of the nucleus, that coincide with the presence of large aggregates of NPs on top of cells. On the basis of these observations, we propose that some Fn molecules are able to desorb from the Petri dish surface to coat TiO(2) NPs. Fn/NP complexes are not attached firmly enough on the surface to allow for normal cell adhesion/spreading and the development of tense actin fibers. These results stress the paramount need for the assessment of the toxicology of NPs, with special attention to their interactions with biomolecules.

Determination of antibacterial properties and cytocompatibility of silver-loaded coral hydroxyapatite

In this study, silver-loaded coral hydroxyapatites (SLCHAs) were used as scaffolds for bone tissue engineering. The SLCHAs were prepared by surface adsorption process and ion-exchange reaction between Ca(2+) of coral hydroxyapatite (CHA) and Ag(+) of silver nitrate with different concentrations at room temperature. The properties of the composite SLCHAs were investigated by inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscropy (SEM) equipped with backscattered electron detector (BSE), and energy-dispersive X-ray spectrometer (EDS). The SEM images showed that the morphology of the SLCHAs depended on the content of Ag(+), and the silver ions were uniformly distributed on the surface of SLCHAs. The ICP-AES results demonstrated that the silver content of the SLCHAs decreased along with the decrease of the concentration of silver nitrate. The SLCHAs were found effective against Escherichia coli and Staphylococcus aureus by antibacterial test. Mouse embryonic pre-osteoblast cells (MC3T3-E1) were used to test the cytocompatibility of SLCHAs, CHA, and pure coral. Cell morphology and cell proliferation were studied with SEM, laser scanning confocal microscope (LSCM), and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay after 1, 3, and 5 days of culture. The results indicated the cell morphology and proliferation on the scaffolds of Ag(+) (13.6 microg/ml)/CHA and Ag(+) (1.7 microg/ml)/CHA were better than that on Ag(+) (170 microg/ml)/CHA. In addition, adhesion of MC3T3-E1 on the scaffolds showed that the confluent cells showed fusiform shape and arranged tightly on the scaffolds. All the results showed that the antibacterial SLCHAs would have potential clinical application as the scaffolds for bone tissue engineering.

Adherent bacterial colonization in the pathogenesis of osteomyelitis

Osteomyelitic bone can be plagued by extensive bacterial growth in adherent biofilms, which can be observed by direct scanning electron microscropy, and may even obscure the entire infected bone surface. Through synchronized production of exopolysaccharide polymers, microcolony formation and surface adhesion is mediated, and a fibrous matrix is formed which is readily visible by transmission electron microscopy. Multiple bacterial morphotypes may be present simultaneously in these biofilms. The result is an infection that may be very resistant to either antibiotic therapy or host clearance in the damaged tissue or bone, leading to persistent infection unless the compromised material is removed.

Structural properties of molten dilute aluminium–transition metal alloys

The short-range order in liquid binary Al-rich alloys (Al–Fe, Al–Ti) was studied by x-raydiffraction. The measurements were performed using a novel containerless technique whichcombines aerodynamic levitation with inductive heating. The average structure factors,S(Q),have been determined for various temperatures and compositions in the stable liquid state. FromS(Q), the pair correlationfunctions, g(r), have been calculated. The first interatomic distance is nearly temperature-independent,whereas the first-shell coordination number decreases with increasing temperature for allthe alloys investigated. For the Al–Fe alloys, room-temperature scanning electronmicroscropy (SEM) studies show the formation of a microstructure, namely the existence ofAl13Fe4 inclusions in the Al matrix.

Synthesis of hollow ZnO microspheres by an integrated autoclave and pyrolysisprocess

Hollow zinc oxide microspheres have been synthesized from a microZnBr2·2H2O precursor obtained by an autoclave process in bromoform steam at220 °C /2.5 MPa. Field-emission scanning electron microscropy (FE-SEM) andtransmission electron microscopy (TEM) show that the products are about1.0 µm single crystal spherical particles with hollow interiors, partly open surfaces and wallsself-assembled by ZnO nanoparticles. X-ray diffraction (XRD) analysis shows that theas-prepared ZnO hollow spheres are of a hexagonal phase structure. A possible formationmechanism is suggested on the basis of the shape evolution of ZnO nanostructures observedby SEM and TEM. The room-temperature photoluminescence (PL) spectrumshows UV emission around 386 nm and weak green emission peaks indicatingthat there are few defects in the single crystal grains of the ZnO microspheres.

Steps toward a model nanotopography

A natural lithography technique is employed to create an irregular, submonolayer colloidal topography. Epitenon cells were cultured on these colloidal surfaces, and cell morphology investigations using scanning electron microscropy were conducted. Preliminary experiments brought into question the stability of the colloidal nanotopography, and it was unsure if the surface was presented to cells as a static structure. Investigations using secondary electron and backscattered electron imaging, and also X-ray microanalysis, indicated that the colloidal structure was in fact stable, and cells were capable of direct interactions at the peripheral membrane with the colloids.

The preparation and thermal evolution of polymeric gels with garnet stoichiometry in the CaOAl2O3SiO2 and CaOCr2O3SiO2 systems

Abstract The synthesis of gels with garnet stoichiometry in the CaOAl 2 O 3 SiO 2 and CaOCr 2 O 3 SiO 2 systems and their evolution in thermal processing have been studied. Dried gels with the stoichiometry 3CaO.Al 2 O 3 .3SiO 2 show a homogeneous aspect without detectable crystalline phase. The thermal evolution of these gels indicates no formation of grossularite at temperatures up to 1000°C after 12 h. In the uvarovite garnet samples, 3CaO.Cr 2 O 3 .3SiO 2 , a small amount of crystalline phase was detected in the dried gels. The homogeneity of the gels was checked by scanning electron microscropy. The infrared study of these polymeric gels confirmed the presence of SiOMe (MeCr 3+ , Ca 2+ ) bonds. This may facilitate the formation of uvarovite at low temperatures.