Biofilm formation and control in a simulated spacecraft water system - Two-year results

NASA Technical Reports Server (NTRS)

Schultz, John R.; Taylor, Robert D.; Flanagan, David T.; Carr, Sandra E.; Bruce, Rebekah J.; Svoboda, Judy V.; Huls, M. H.; Sauer, Richard L.; Pierson, Duane L.

1991-01-01

The ability of iodine to maintain microbial water quality in a simulated spacecraft water system is being studied. An iodine level of about 2.0 mg/L is maintained by passing ultrapure influent water through an iodinated ion exchange resin. Six liters are withdrawn daily and the chemical and microbial quality of the water is monitored regularly. Stainless steel coupons used to monitor biofilm formation are being analyzed by culture methods, epifluorescence microscopy, and scanning electron microscopy. Results from the first two years of operation show a single episode of high bacterial colony counts in the iodinated system. This growth was apparently controlled by replacing the iodinated ion exchange resin. Scanning electron microscopy indicates that the iodine has limited but not completely eliminated the formation of biofilm during the first two years of operation. Significant microbial contamination has been present continuously in a parallel noniodinated system since the third week of operation.

Pd-Ni-MWCNT nanocomposite thin films: preparation and structure

NASA Astrophysics Data System (ADS)

Kozłowski, Mirosław; Czerwosz, ElŻbieta; Sobczak, Kamil

2017-08-01

The properties of nanocomposite palladium-nickel-multi-walled (Pd-Ni-MWCNT) films deposited on aluminum oxide (Al2O3) substrate have been prepared and investigated. These films were obtained by 3 step process consisted of PVD/CVD/PVD methods. The morphology and structure of the obtained films were characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques at various stages of the film formation. EDX spectrometer was used to measurements of elements segregation in the obtained film. TEM and STEM (Scanning Transmission Electron Microscopy) observations showed MWCNTs decorated with palladium nanoparticles in the film obtained in the last step of film formation (final PVD process). The average size of the palladium nanoparticles observed both on MWCNTs and carbonaceous matrix does not exceed 5 nm. The research was conducted on the use of the obtained films as potential sensors of gases (e.g. H2, NH3, CO2) and bio-sensors or optical sensors.

One-pot template-free synthesis of uniform-sized fullerene-like magnetite hollow spheres

NASA Astrophysics Data System (ADS)

Zhu, Qing; Zhang, Yue; Liu, Zheng; Zhou, Xinrui; Zhang, Xinmei; Zeng, Lintao

2015-11-01

Uniform-sized Fe3O4 hollow spheres with average diameter of 250 nm and shell thickness of ∼50 nm have been successfully synthesized through a simple hydrothermal route with the presence of di-n-propylamine (DPA) as a weak-base. The reaction time and DPA amount play important roles in the formation of the magnetite hollow spheres. The structures of the products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The results show that the single-crystalline Fe3O4 hollow spheres are composed of well-aligned magnetite nanoparticles (NPs). The magnetic property investigation shows that these hollow spheres have a higher saturation magnetization (Ms) than the solid spheres. Furthermore, a possible mechanism for the formation of magnetite hollow spheres is proposed based on the experimental observations.

Zn nanoparticle formation in FIB irradiated single crystal ZnO

NASA Astrophysics Data System (ADS)

Pea, M.; Barucca, G.; Notargiacomo, A.; Di Gaspare, L.; Mussi, V.

2018-03-01

We report on the formation of Zn nanoparticles induced by Ga+ focused ion beam on single crystal ZnO. The irradiated materials have been studied as a function of the ion dose by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy and transmission electron microscopy, evidencing the presence of Zn nanoparticles with size of the order of 5-30 nm. The nanoparticles are found to be embedded in a shallow amorphous ZnO matrix few tens of nanometers thick. Results reveal that ion beam induced Zn clustering occurs producing crystalline particles with the same hexagonal lattice and orientation of the substrate, and could explain the alteration of optical and electrical properties found for FIB fabricated and processed ZnO based devices.

One step synthesis of porous graphene by laser ablation: A new and facile approach

NASA Astrophysics Data System (ADS)

Kazemizadeh, Fatemeh; Malekfar, Rasoul

2018-02-01

Porous graphene (PG) was obtained using one step laser process. Synthesis was carried out by laser ablation of nickel-graphite target under ultra-high flow of argon gas. The field emission scanning electron microscopy (FE-SEM) results showed the formation of a porous structure and the transmission electron microscopy (TEM) revealed that the porosity of PGs increase under intense laser irradiation. Structural characterization study using Raman spectroscopy, X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) technique showed that the obtained PGs display high crystalline structure in the form of few layer rhombohedral graphitic arrangement that can be interpreted as the phase prior to the formation of other carbon nanostructures.

Metallic glass formation at the interface of explosively welded Nb and stainless steel

NASA Astrophysics Data System (ADS)

Bataev, I. A.; Hokamoto, K.; Keno, H.; Bataev, A. A.; Balagansky, I. A.; Vinogradov, A. V.

2015-07-01

The interface between explosively welded niobium and stainless steel SUS 304 was studied using scanning electron microscopy, transmission electron microscopy and energy dispersive X-Ray spectroscopy. The wavy interface along which vortex zones were located was observed. The vortex zones formed due to the mixing of materials typically had amorphous structure. Inoue's criteria of glass formation were used to explain this result. The effect of the composition, cooling rate and pressure on the glass formation are discussed. The conditions of deformation, heating, and cooling as well as shockwaves propagation were numerically simulated. We show that the conditions of vortex zone formation resemble the conditions of rapid solidification processes. In contrast to the "classical" methods of rapid solidification of melt, the conditions of metastable phase formation during explosive welding are significantly complicated by the fluctuations of composition and pressure. Possible metastable structures formation at the interface of some common explosively joined materials is predicted.

Biological applications of phase-contrast electron microscopy.

PubMed

Nagayama, Kuniaki

2014-01-01

Here, I review the principles and applications of phase-contrast electron microscopy using phase plates. First, I develop the principle of phase contrast based on a minimal model of microscopy, introducing a double Fourier-transform process to mathematically formulate the image formation. Next, I explain four phase-contrast (PC) schemes, defocus PC, Zernike PC, Hilbert differential contrast, and schlieren optics, as image-filtering processes in the context of the minimal model, with particular emphases on the Zernike PC and corresponding Zernike phase plates. Finally, I review applications of Zernike PC cryo-electron microscopy to biological systems such as protein molecules, virus particles, and cells, including single-particle analysis to delineate three-dimensional (3D) structures of protein and virus particles and cryo-electron tomography to reconstruct 3D images of complex protein systems and cells.

Catalyst free growth of CNTs by CVD on nanoscale rough surfaces of silicon substrates

NASA Astrophysics Data System (ADS)

Damodar, D.; Sahoo, R. K.; Jacob, C.

2013-06-01

Catalyst free growth of carbon nanotubes (CNT) has been achieved using atmospheric pressure chemical vapor deposition (APCVD) on surface modified Si(111) substrates. The effect of the substrate surface has been observed by partially etching with KOH (potassium hydroxide) solution which is an anisotropic etchant. Scanning electron microscopy (SEM) confirmed the formation of CNTs over most of the area of the substrate where substrates were anisotropically etched. Transmission electron microscopy (TEM) was used to observe the internal structure of the CNTs. Raman spectroscopy further confirmed the formation of the carbon nanostructures and also their graphitic crystallinity.

Nanouric acid or nanocalcium phosphate as central nidus to induce calcium oxalate stone formation: a high-resolution transmission electron microscopy study on urinary nanocrystallites

PubMed Central

Gao, Jie; Xue, Jun-Fa; Xu, Meng; Gui, Bao-Song; Wang, Feng-Xin; Ouyang, Jian-Ming

2014-01-01

Purpose This study aimed to accurately analyze the relationship between calcium oxalate (CaOx) stone formation and the components of urinary nanocrystallites. Method High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction, fast Fourier transformation of HRTEM, and energy dispersive X-ray spectroscopy were performed to analyze the components of these nanocrystallites. Results The main components of CaOx stones are calcium oxalate monohydrate and a small amount of dehydrate, while those of urinary nanocrystallites are calcium oxalate monohydrate, uric acid, and calcium phosphate. The mechanism of formation of CaOx stones was discussed based on the components of urinary nanocrystallites. Conclusion The formation of CaOx stones is closely related both to the properties of urinary nanocrystallites and to the urinary components. The combination of HRTEM, fast Fourier transformation, selected area electron diffraction, and energy dispersive X-ray spectroscopy could be accurately performed to analyze the components of single urinary nanocrystallites. This result provides evidence for nanouric acid and/or nanocalcium phosphate crystallites as the central nidus to induce CaOx stone formation. PMID:25258530

TEM studies of plasma nitrided austenitic stainless steel.

PubMed

Stróz, D; Psoda, M

2010-03-01

Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

Microstructure, texture, and mechanical properties of friction stir welded commercial brass alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heidarzadeh, A., E-mail: ak.hz62@gmail.com

Microstructural evolution during friction stir welding of single-phase brass and corresponding mechanical properties were investigated. For this purpose, 2 mm thick brass plate was friction stir welded at a rotational speed of 450 rpm and traverse speed of 100 mm/min. The microstructure of the joint was studied using optical microscopy, scanning electron microscopy equipped with electron back scattered diffraction system, and scanning transmission electron microscopy. The mechanical properties were measured using hardness and tensile tests. The formation of subgrains and their transformation into new grains in conjunction with existence of A{sub 1}{sup ⁎}, A{sub 2}{sup ⁎} and C texture componentsmore » revealed that the continuous dynamic recrystallization plays a dominant role in the microstructural evolution. However, grain boundary bulging, along with the formation of twin boundaries, and presence of the G texture component showed that the discontinues dynamic recrystallization may participate in the new grain formation. Furthermore, the different strengthening mechanisms, which caused the higher strength of the joint, were discussed. - Highlights: •Microstructural evolution during FSW of a single phase brass was investigated. •CDRX and DDRX were the main mechanisms of the grain structure formation during FSW. •GDRX and SRX were not contributed in grain structure formation. •The lamellas TBs were formed in the SZ of the joints. •Grain boundary, dislocation, and texture effects resulted in higher strength.« less

Transmission electron microscopy study of erbium silicide formation from Ti/Er stack for Schottky contact applications.

PubMed

Ratajczak, J; Łaszcz, A; Czerwinski, A; Katcki, J; Phillipp, F; Van Aken, P A; Reckinger, N; Dubois, E

2010-03-01

In this paper, we present results of transmission electron microscopy studies on erbium silicide structures fabricated under various thermal conditions. A titanium cap has been used as a protective layer against oxidation during rapid thermal annealing of an erbium layer in a temperature range of 300-700 degrees C. Both layers (200 nm Ti and 25 nm Er) were deposited by electron-beam sputtering. The investigations have shown that the transformation of the 25-nm-thick erbium into erbium silicide is completed after annealing at 500 degrees C. At higher temperatures, the formation of a titanium silicide layer above erbium silicide is observed. The lowest Schottky barrier has been measured in the sample annealed at 700 degrees C.

Direct observation of iron-induced conformational changes of mitochondrial DNA by high-resolution field-emission in-lens scanning electron microscopy.

PubMed Central

Yaffee, M; Walter, P; Richter, C; Müller, M

1996-01-01

When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolution field-emission in-lens scanning electron microscopy with backscattered electron detection imaging permits simultaneous detailed visual analysis of DNA topology, iron dose-dependent mtDNA unwinding, and assessment of iron colloid formation on mtDNA strands. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8643576

Correlative cryo-fluorescence light microscopy and cryo-electron tomography of Streptomyces.

PubMed

Koning, Roman I; Celler, Katherine; Willemse, Joost; Bos, Erik; van Wezel, Gilles P; Koster, Abraham J

2014-01-01

Light microscopy and electron microscopy are complementary techniques that in a correlative approach enable identification and targeting of fluorescently labeled structures in situ for three-dimensional imaging at nanometer resolution. Correlative imaging allows electron microscopic images to be positioned in a broader temporal and spatial context. We employed cryo-correlative light and electron microscopy (cryo-CLEM), combining cryo-fluorescence light microscopy and cryo-electron tomography, on vitrified Streptomyces bacteria to study cell division. Streptomycetes are mycelial bacteria that grow as long hyphae and reproduce via sporulation. On solid media, Streptomyces subsequently form distinct aerial mycelia where cell division leads to the formation of unigenomic spores which separate and disperse to form new colonies. In liquid media, only vegetative hyphae are present divided by noncell separating crosswalls. Their multicellular life style makes them exciting model systems for the study of bacterial development and cell division. Complex intracellular structures have been visualized with transmission electron microscopy. Here, we describe the methods for cryo-CLEM that we applied for studying Streptomyces. These methods include cell growth, fluorescent labeling, cryo-fixation by vitrification, cryo-light microscopy using a Linkam cryo-stage, image overlay and relocation, cryo-electron tomography using a Titan Krios, and tomographic reconstruction. Additionally, methods for segmentation, volume rendering, and visualization of the correlative data are described. © 2014 Elsevier Inc. All rights reserved.

Worming Their Way into Shape: Toroidal Formations in Micellar Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardiel Rivera, Joshua J.; Tonggu, Lige; Dohnalkova, Alice

2013-11-01

We report the formation of nanostructured toroidal micellar bundles (nTMB) from a semidilute wormlike micellar solution, evidenced by both cryogenicelectron microscopy and transmission electron microscopy images. Our strategy for creating nTMB involves a two-step protocol consisting of a simple prestraining process followed by flow through a microfluidic device containing an array of microposts, producing strain rates in the wormlike micelles on the order of 105 s^1. In combination with microfluidic confinement, these unusually large strain rates allow for the formation of stable nTMB. Electron microscopy images reveal a variety of nTMB morphologies and provide the size distribution of the nTMB.more » Small-angle neutron scattering indicates the underlying microstructural transition from wormlike micelles to nTMB. We also show that other flow-induced approaches such as sonication can induce and control the emergence of onion-like and nTMB structures, which may provide a useful tool for nanotemplating.« less

Scanning electron microscopy of superficial white onychomycosis*

PubMed Central

de Almeida Jr., Hiram Larangeira; Boabaid, Roberta Oliveira; Timm, Vitor; Silva, Ricardo Marques e; de Castro, Luis Antonio Suita

2015-01-01

Superficial white onychomycosis is characterized by opaque, friable, whitish superficial spots on the nail plate. We examined an affected halux nail of a 20-year-old male patient with scanning electron microscopy. The mycological examination isolated Trichophyton mentagrophytes. Abundant hyphae with the formation of arthrospores were found on the nail's surface, forming small fungal colonies. These findings showed the great capacity for dissemination of this form of onychomycosis. PMID:26560225

Effect of Boron and Titanium Addition on the Hot Ductility of Low-Carbon Nb-Containing Steel

NASA Astrophysics Data System (ADS)

Liu, Wei-Jian; Li, Jing; Shi, Cheng-Bin; Huo, Xiang-Dong

2015-12-01

The effect of boron and titanium addition on the hot ductility of Nb-containing steel was investigated using hot tensile tests. The fracture surface and the quenched longitudinal microstructure were examined by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that both steel samples had the similar change from 1,100°C to 700°C. The hot ductility of Nb-containing steel with boron and titanium addition was higher than the steel without boron and titanium in the temperature range of 900-750°C. Because the formation of intergranular ferrite was inhibited by solute boron segregating on the grain boundary, the formation of TiN changed the distribution of Nb- and boron-containing precipitates and improved the amount of intragranular ferrite.

The application of scanning electron microscopy to fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, C.R.; McGill, B.L.

1994-10-01

Many failures involve fracture, and determination of the fracture process is a key factor in understanding the failure. This is frequently accomplished by characterizing the topography of the fracture surface. Scanning electron microscopy has a prominent role in fractography due to three features of the scanning electron microscope (SEM): high resolution, great depth of field, and the ability to obtain chemical information via analysis of the X-rays generated by the electrons. A qualitative treatment is presented of the interaction of electrons with a sample and the effect of the SEM operating parameters on image formation, quality, and X-ray analysis. Fractographsmore » are presented to illustrate these features of scanning electron microscopy and to illustrate the limitations and precautions in obtaining fractographs and x-ray analyses. The review is concluded with examples of fracture surface features of metallic, ceramic, and polymeric materials.« less

Exopolysaccharide microchannels direct bacterial motility and organize multicellular behavior

DOE PAGES

Berleman, James E.; Zemla, Marcin; Remis, Jonathan P.; ...

2016-05-06

The myxobacteria are a family of soil bacteria that form biofilms of complex architecture, aligned multilayered swarms or fruiting body structures that are simple or branched aggregates containing myxospores. Here, we examined the structural role of matrix exopolysaccharide (EPS) in the organization of these surface-dwelling bacterial cells. Using time-lapse light and fluorescence microscopy, as well as transmission electron microscopy and focused ion beam/scanning electron microscopy (FIB/SEM) electron microscopy, we found that Myxococcus xanthus cell organization in biofilms is dependent on the formation of EPS microchannels. Cells are highly organized within the three-dimensional structure of EPS microchannels that are required formore » cell alignment and advancement on surfaces. Mutants lacking EPS showed a lack of cell orientation and poor colony migration. Purified, cell-free EPS retains a channel-like structure, and can complement EPS - mutant motility defects. In addition, EPS provides the cooperative structure for fruiting body formation in both the simple mounds of M. xanthus and the complex, tree-like structures of Chondromyces crocatus. We furthermore investigated the possibility that EPS impacts community structure as a shared resource facilitating cooperative migration among closely related isolates of M. xanthus.« less

Possible etiology of calculi formation in salivary glands: biophysical analysis of calculus.

PubMed

Mimura, Masafumi; Tanaka, Nobuyuki; Ichinose, Shizuko; Kimijima, Yutaka; Amagasa, Teruo

2005-09-01

Sialolithiasis is one of the common diseases of the salivary glands. It was speculated that, in the process of calculi formation, degenerative substances are emitted by saliva and calcification then occurs around these substances, and finally calculi are formed. However, the exact mechanism of the formation of calculi is still unclear. In this study, we identify some possible etiologies of calculi formation in salivary glands through biophysical analysis. Calculi from 13 patients with submandibular sialolithiasis were investigated by transmission electron microscopy, scanning electron microscopy, X-ray microanalyzer, and electron diffraction. Transmission electron microscopic observation of calculi was performed in the submandibular gland (n = 13). In 3 of the 13 cases, a number of mitochondria-like structures and lysosomes were found near calcified materials. Scanning electron microscopic examination of these materials revealed that there were lamellar and concentric structures and that the degree of calcification was different among the calculi. X-ray microanalysis disclosed the component elements in the calculi to be Ca, P, S, Na, etc., and the main constituents were Ca and P. The calcium-to-phosphorus ratio was 1.60-1.89. Analysis of the area including mitochondria-like structures, lysosomes, and the fibrous structures by electron diffraction revealed the presence of hydroxyapatite and calcified materials. It is speculated that mitochondria and lysosomal bodies from the ductal system of the submandibular gland are an etiological source for calcification in the salivary gland.

Microstructural Evolution of Secondary Phases in the Cast Duplex Stainless Steels CD3MN and CD3MWCuN

NASA Astrophysics Data System (ADS)

Kim, Yoon-Jun; Ugurlu, Ozan; Jiang, Chao; Gleeson, Brian; Chumbley, L. Scott

2007-02-01

The isothermal formation behavior of secondary phases in two types of duplex stainless steels (DSS), CD3MN and CD3MWCuN, was characterized. Samples were heat treated from 1 minute to 30 days at temperatures from 700°C to 900°C. Small carbide (M23C6) and nitride (Cr2N) precipitates, together with the intermetallic phases sigma and chi, were observed using scanning electron microscopy (SEM) and confirmed by transmission electron microscopy (TEM) analyses. Based on SEM analysis, time-temperature-transformation (TTT) curves for the sigma and chi phases were determined by measuring their volume fractions from backscattered electron micrographs of heat-treated and quenched sample cross sections. Resulting TTT curves showed that the maximum formation temperature for chi is lower than that for sigma, while the time to reach 1 vol pct formation is much less for sigma than it is for chi. The thermodynamic driving forces associated with the sigma and chi formation were assessed using Thermo-Calc.

Direct visualization of lithium via annular bright field scanning transmission electron microscopy: a review.

PubMed

Findlay, Scott David; Huang, Rong; Ishikawa, Ryo; Shibata, Naoya; Ikuhara, Yuichi

2017-02-08

Annular bright field (ABF) scanning transmission electron microscopy has proven able to directly image lithium columns within crystalline environments, offering much insight into the structure and properties of lithium-ion battery materials. We summarize the image formation mechanisms underpinning ABF imaging, review the experimental application of this technique to imaging lithium in materials and overview the conditions that help maximize the visibility of lithium columns. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Otoconial formation in the fetal rat

NASA Technical Reports Server (NTRS)

Salamat, M. S.; Ross, M. D.; Peacor, D. R.

1980-01-01

Otoconial formation in the fetal rat is examined by scanning and transmission electron microscopy, and by X-ray elemental analysis. The primitive otoconia appear highly organic, but are trigonal in cross section, indicating that they already possess a three-fold axis of symmetry and a complement of calcite. These otoconia develop into spindle-shaped and, subsequently, dumbbell-shaped units. Transmission electron microscopy of dumbbell-shaped otoconia not exposed to fluids during embedment showed that calcite deposits mimicked the arrangement of the organic material. X-ray elemental analysis demonstrated that calcium was present in lower quantities in the central core than peripherally. It is concluded that organic material is essential to otoconial seeding and directs otoconial growth.

Formation of ZnS nanostructures by a simple way of thermal evaporation

NASA Astrophysics Data System (ADS)

Yuan, H. J.; Xie, S. S.; Liu, D. F.; Yan, X. Q.; Zhou, Z. P.; Ci, L. J.; Wang, J. X.; Gao, Y.; Song, L.; Liu, L. F.; Zhou, W. Y.; Wang, G.

2003-11-01

The mass synthesis of ZnS nanobelts, nanowires, and nanoparticles has been achieved by a simple method of thermal evaporation of ZnS powders onto silicon substrates in the presence of Au catalyst. The temperature of the substrates and the concentration of ZnS vapor were the critical experimental parameters for the formation of different morphologies of ZnS nanostructures. Scanning electron microscopy and transmission electron microscopy show that the diameters of as-prepared nanowires were 30-70 nm. The UV emission at 374 nm is probably related to the exciton emission, while the mechanism of blue emission at 443 nm is probably mainly due to the presence of various surface states.

Understanding the formation and growth of Ag nanoparticles on silver chromate induced by electron irradiation in electron microscope: A combined experimental and theoretical study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fabbro, Maria T.; Department of Inorganic and Organic Chemistry, Universitat Jaume I, Campus del Riu Sec, E-12071 Castellón; Gracia, Lourdes

Ag{sub 2}CrO{sub 4} microcrystals were synthesized using the co-precipitation method. These microcrystals were characterized through X-ray diffraction (XRD) with Rietveld analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS), micro-Raman (MR). XRD patterns and Rietveld refinement data showed that the material exhibits an orthorhombic structure without any deleterious phases. FE-SEM and TEM micrographs revealed the morphology and the growth of Ag nanoparticles on Ag{sub 2}CrO{sub 4} microcrystals during electron beam irradiation. These events were directly monitored in real-time. Their optical properties were investigated using ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy that allowed the calculation of themore » optical band gap energy. Theoretical analyses based on the density functional theory level indicate that the incorporation of electrons is responsible for structural modifications and formation of defects on the [AgO{sub 6}] and [AgO{sub 4}] clusters, generating ideal conditions for the growth of Ag nanoparticles. - Graphical abstract: Theoretical representation of the Ag{sub 2}CrO{sub 4} orthorhombic structure. Display Omitted - Highlights: • The Ag{sub 2}CrO{sub 4} microcrystals indicate an orthorhombic structure. • The formation of Ag{sup 0} promotes Ag-nanoparticle growth on the surface of the Ag{sub 2}CrO{sub 4}. • Electron irradiation of the material induces the formation of Ag vacancies.« less

Low-Cycle Fatigue Properties of P92 Ferritic-Martensitic Steel at Elevated Temperature

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Hu, ZhengFei; Schmauder, Siegfried; Mlikota, Marijo; Fan, KangLe

2016-04-01

The low-cycle fatigue behavior of P92 ferritic-martensitic steel and the corresponding microstructure evolution at 873 K has been extensively studied. The test results of fatigue lifetime are consistent with the Coffin-Manson relationship over a range of controlled total strain amplitudes from 0.15 to 0.6%. The influence of strain amplitude on the fatigue crack initiation and growth has been observed using optical microscopy and scanning electron microscopy. The formation mechanism of secondary cracks is established according to the observation of fracture after fatigue process and there is an intrinsic relationship between striation spacing, current crack length, and strain amplitude. Transmission electron microscopy has been employed to investigate the microstructure evolution after fatigue process. It indicates the interaction between carbides and dislocations together with the formation of cell structure inhibits the cyclic softening. The low-angle sub-boundary elimination in the martensite is mainly caused by the cyclic stress.

The role of an organic matrix during the formation of siliceous scales in the heliozoon Actinophrys sol (actinophryida, protista).

PubMed

Newman, P J; Patterson, D J

1993-07-25

Actinophrys sol is a freshwater heliozoon which has trophic and encysted body forms. During encystment, siliceous scales are laid down in silica deposition vesicles. The scales form one layer of a multi-layered cyst wall. Scale production is described using light microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray microanalysis. Silica is laid down on an organic matrix which is visible prior to silicification and after removal of silica with hydrofluoric acid. Actinophrys sol can be cultured under silica impoverished conditions, with the result that the siliceous plates are absent. The cysts continue to form but are fragile. Silica is not a prerequisite for the processes of encystment and cyst formation. Copyright © 1993 Gustav Fischer Verlag · Stuttgart · Jena · New York. Published by Elsevier GmbH.. All rights reserved.

Contribution of high-resolution correlative imaging techniques in the study of the liver sieve in three-dimensions.

PubMed

Braet, Filip; Wisse, Eddie; Bomans, Paul; Frederik, Peter; Geerts, Willie; Koster, Abraham; Soon, Lilian; Ringer, Simon

2007-03-01

Correlative microscopy has become increasingly important for the analysis of the structure, function, and dynamics of cells. This is largely due to the result of recent advances in light-, probe-, laser- and various electron microscopy techniques that facilitate three-dimensional studies. Furthermore, the improved understanding in the past decade of imaging cell compartments in the third dimension has resulted largely from the availability of powerful computers, fast high-resolution CCD cameras, specifically developed imaging analysis software, and various probes designed for labeling living and or fixed cells. In this paper, we review different correlative high-resolution imaging methodologies and how these microscopy techniques facilitated the accumulation of new insights in the morpho-functional and structural organization of the hepatic sieve. Various aspects of hepatic endothelial fenestrae regarding their structure, origin, dynamics, and formation will be explored throughout this paper by comparing the results of confocal laser scanning-, correlative fluorescence and scanning electron-, atomic force-, and whole-mount electron microscopy. Furthermore, the recent advances of vitrifying cells with the vitrobot in combination with the glove box for the preparation of cells for cryo-electron microscopic investigation will be discussed. Finally, the first transmission electron tomography data of the liver sieve in three-dimensions are presented. The obtained data unambiguously show the involvement of special domains in the de novo formation and disappearance of hepatic fenestrae, and focuses future research into the (supra)molecular structure of the fenestrae-forming center, defenestration center and fenestrae-, and sieve plate cytoskeleton ring by using advanced cryo-electron tomography. (c) 2007 Wiley-Liss, Inc.

Nano-Se: Cheap and easy-to-obtain novel material for all-dielectric nano-photonics

NASA Astrophysics Data System (ADS)

Ivanova, A. K.; Ionin, A. A.; Khmel'nitskii, R. A.; Klevkov, Yu. K.; Kudryashov, S. I.; Levchenko, A. O.; Mel'nik, N. N.; Nastulyavichus, A. A.; Rudenko, A. A.; Saraeva, I. N.; Smirnov, N. A.; Zayarny, D. A.; Gonchukov, S. A.; Tolordava, E. R.; Baranov, A. N.

2017-09-01

Milligram-per-second production of selenium nanoparticles in water sols was realized through few W, kHz-rate nanosecond laser ablation of a solid selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of crater depths and topographies. Deposited particles were inspected by scanning electron microscopy, while optical transmission Raman and dynamic light scattering spectroscopy characterized their hydrosols.

Nanocrystals of [Cu3(btc)2] (HKUST-1): a combined time-resolved light scattering and scanning electron microscopy study.

PubMed

Zacher, Denise; Liu, Jianing; Huber, Klaus; Fischer, Roland A

2009-03-07

The formation of [Cu(3)(btc)(2)] (HKUST-1; btc = 1,3,5-benzenetricarboxylate) nanocrystals from a super-saturated mother solution at room temperature was monitored by time-resolved light scattering (TLS); the system is characterized by a rapid growth up to a size limit of 200 nm within a few minutes, and the size and shape of the crystallites were also determined by scanning electron microscopy (SEM).

Photosynthetic microorganism-mediated synthesis of akaganeite (beta-FeOOH) nanorods.

PubMed

Brayner, Roberta; Yéprémian, Claude; Djediat, Chakib; Coradin, Thibaud; Herbst, Fréderic; Livage, Jacques; Fiévet, Fernand; Couté, Alain

2009-09-01

Common Anabaena and Calothrix cyanobacteria and Klebsormidium green algae are shown to form intracellularly akaganeite beta-FeOOH nanorods of well-controlled size and unusual morphology at room temperature. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy X-ray energy dispersive spectrometry (SEM-EDS) analyses are used to investigate particle structure, size, and morphology. A mechanism involving iron-siderophore complex formation is proposed and compared with iron biomineralization in magnetotactic bacteria.

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

PubMed

Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

2015-06-01

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

Simulation of bone resorption-repair coupling in vitro.

PubMed

Jones, S J; Gray, C; Boyde, A

1994-10-01

In the normal adult human skeleton, new bone formation by osteoblasts restores the contours of bone surfaces following osteoclastic bone resorption, but the evidence for resorption-repair coupling remains circumstantial. To investigate whether sites of prior resorption, more than the surrounding unresorbed surface, attract osteoblasts or stimulate them to proliferate or make new matrix, we developed a simple in vitro system in which resorption-repair coupling occurs. Resorption pits were produced in mammalian dentine or bone slabs by culturing chick bone-derived cells on them for 2-3 days. The chick cells were swept off and the substrata reseeded with rat calvarial osteoblastic cells, which make bone nodules in vitro, for periods of up to 8 weeks. Cell positions and new bone formation were investigated by ordinary light microscopy, fluorescence and reflection confocal laser microscopy, and SEM, in stained and unstained samples. There was no evidence that the osteoblasts were especially attracted to, or influenced by, the sites of resorption in dentine or bone before cell confluence was reached. Bone formation was identified by light microscopy by the accumulation of matrix, staining with alizarin and calcein and by von Kossa's method, and confirmed by scanning electron microscopy (SEM) by using backscattered electron (BSE) and transmitted electron imaging of unembedded samples and BSE imaging of micro-milled embedded material. These new bone patches were located initially in the resorption pits. The model in vitro system may throw new light on the factors that control resorption-repair coupling in the mineralised tissues in vivo.

Deformation localization and dislocation channel dynamics in neutron-irradiated austenitic stainless steels

DOE PAGES

Gussev, Maxim N.; Field, Kevin G.; Busby, Jeremy T.

2015-02-24

We investigated dynamics of deformation localization and dislocation channel formation in situ in a neutron irradiated AISI 304 austenitic stainless steel and a model 304-based austenitic alloy by combining several analytical techniques including optic microscopy and laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. Channel formation was observed at 70% of the formal tensile yield stress for both alloys. It was shown that triple junction points do not always serve as a source of dislocation channels; at stress levels below the yield stress, channels often formed near the middle of the grain boundary. For amore » single grain, the role of elastic stiffness value (Young modulus) in the channel formation was analyzed; it was shown that in the irradiated 304 steels the initial channels appeared in soft grains with a high Schmid factor located near stiff grains with high elastic stiffness. Moreover, the spatial organization of channels in a single grain was analyzed; it was shown that secondary channels operating in the same slip plane as primary channels often appeared at the middle or at one third of the way between primary channels. The twinning nature of dislocation channels was analyzed for grains of different orientation using TEM. Finally, it was shown that in the AISI 304 steel, channels were twin-free in grains oriented close to [001] and [101] of standard unit triangle; [111]-grains and grains oriented close to Schmid factor maximum contained deformation twins.« less

Mechanisms of fine extinction band development in vein quartz: new insights from correlative light and electron microscopy

NASA Astrophysics Data System (ADS)

Derez, Tine; Van Der Donck, Tom; Plümper, Oliver; Muchez, Philippe; Pennock, Gill; Drury, Martyn R.; Sintubin, Manuel

2017-07-01

Fine extinction bands (FEBs) (also known as deformation lamellae) visible with polarized light microscopy in quartz consist of a range of nanostructures, inferring different formation processes. Previous transmission electron microscopy studies have shown that most FEB nanostructures in naturally deformed quartz are elongated subgrains formed by recovery of dislocation slip bands. Here we show that three types of FEB nanostructure occur in naturally deformed vein quartz from the low-grade metamorphic High-Ardenne slate belt (Belgium). Prismatic oriented FEBs are defined by bands of dislocation walls. Dauphiné twin boundaries present along the FEB boundaries probably formed after FEB formation. In an example of two sub-rhombohedral oriented FEBs, developed as two sets in one grain, the finer FEB set consists of elongated subgrains, similar to FEBs described in previous transmission electron microscopy studies. The second wider FEB set consists of bands with different dislocation density and fluid-inclusion content. The wider FEB set is interpreted as bands with different plastic strain associated with the primary growth banding of the vein quartz grain. The nanometre-scale fluid inclusions are interpreted to have formed from structurally bounded hydroxyl groups that moreover facilitated formation of the elongate subgrains. Larger fluid inclusions aligned along FEBs are explained by fluid-inclusion redistribution along dislocation cores. The prismatic FEB nanostructure and the relation between FEBs and growth bands have not been recognized before, although related structures have been reported in experimentally deformed quartz.

Biomineralization of endolithic microbes in rocks from the McMurdo Dry Valleys of Antarctica: implications for microbial fossil formation and their detection.

PubMed

Wierzchos, Jacek; Sancho, Leopoldo García; Ascaso, Carmen

2005-04-01

In some zones of Antarctica's cold and dry desert, the extinction of cryptoendolithic microorganisms leaves behind inorganic traces of microbial life. In this paper, we examine the transition from live microorganisms, through their decay, to microbial fossils using in situ microscopy (transmission electron microscopy, scanning electron microscopy in back-scattered electron mode) and microanalytical (energy dispersive X-ray spectroscopy) techniques. Our results demonstrate that, after their death, endolithic microorganisms inhabiting Commonwealth Glacier sandstone from the Antarctica McMurdo Dry Valleys become mineralized. In some cases, epicellular deposition of minerals and/or simply filling up of empty moulds by minerals leads to the formation of cell-shaped structures that may be considered biomarkers. The continuous deposition of allochthonous clay minerals and sulfate-rich salts fills the sandstone pores. This process can give rise to microbial fossils with distinguishable cell wall structures. Often, fossilized cell interiors were of a different chemical composition to the mineralized cell walls. We propose that the microbial fossil formation observed was induced by mineral precipitation resulting from inorganic processes occurring after the death of cryptoendolithic microorganisms. Nevertheless, it must have been the organic template that provoked the diffusion of mineral elements and gave rise to their characteristic distribution pattern inside the fossilized cells.

3D correlative light and electron microscopy of cultured cells using serial blockface scanning electron microscopy

PubMed Central

Lerner, Thomas R.; Burden, Jemima J.; Nkwe, David O.; Pelchen-Matthews, Annegret; Domart, Marie-Charlotte; Durgan, Joanne; Weston, Anne; Jones, Martin L.; Peddie, Christopher J.; Carzaniga, Raffaella; Florey, Oliver; Marsh, Mark; Gutierrez, Maximiliano G.

2017-01-01

ABSTRACT The processes of life take place in multiple dimensions, but imaging these processes in even three dimensions is challenging. Here, we describe a workflow for 3D correlative light and electron microscopy (CLEM) of cell monolayers using fluorescence microscopy to identify and follow biological events, combined with serial blockface scanning electron microscopy to analyse the underlying ultrastructure. The workflow encompasses all steps from cell culture to sample processing, imaging strategy, and 3D image processing and analysis. We demonstrate successful application of the workflow to three studies, each aiming to better understand complex and dynamic biological processes, including bacterial and viral infections of cultured cells and formation of entotic cell-in-cell structures commonly observed in tumours. Our workflow revealed new insight into the replicative niche of Mycobacterium tuberculosis in primary human lymphatic endothelial cells, HIV-1 in human monocyte-derived macrophages, and the composition of the entotic vacuole. The broad application of this 3D CLEM technique will make it a useful addition to the correlative imaging toolbox for biomedical research. PMID:27445312

Keratitis-associated fungi form biofilms with reduced antifungal drug susceptibility.

PubMed

Zhang, Xiaoyan; Sun, Xuguang; Wang, Zhiqun; Zhang, Yang; Hou, Wenbo

2012-11-21

To investigate the biofilm-forming capacity of Fusarium solani, Cladosporium sphaerospermum, and Acremonium implicatum, and the activities of antifungal agents against the three keratitis-associated fungi. The architecture of biofilms was analyzed using scanning electron microscopy and confocal scanning laser microscopy (CSLM). Susceptibility against six antifungal drugs was measured using the CLSI M38-A method and XTT reduction assay. Time course analyses of CSLM revealed that biofilm formation occurred in an organized fashion through four distinct developmental phases: adhesion, germling formation, microcolony formation, and biofilm maturation. Scanning electron microscopy revealed that mature biofilms displayed a complex three-dimensional structure, consisting of coordinated network of hyphal structures glued by the extracellular matrix (ECM). The antifungal susceptibility testing demonstrated a time-dependent decrease in efficacy for all six antifungal agents as the complexity of fungal hyphal structures developed. Natamycin (NAT), amphotericin B (AMB), and NAT were the most effective against F. solani, C. sphaerospermum, and A. implicatum biofilm, respectively. Corneal isolates of F. solani, C. sphaerospermum, and A. implicatum could produce biofilms that were resistant to antifungal agents in vitro.

Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelic, S.K., E-mail: susanne.michelic@unileoben.ac.at; Loder, D.; Reip, T.

2015-02-15

Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an earlymore » process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information on inclusion formation.« less

Study on biofilm-forming properties of clinical isolates of Staphylococcus aureus.

PubMed

Taj, Yasmeen; Essa, Farhan; Aziz, Faisal; Kazmi, Shahana Urooj

2012-05-14

The purpose of this study was to observe the formation of biofilm, an important virulence factor, by isolates of Staphylococcus aureus (S. aureus) in Pakistan by different conventional methods and through electron microscopy. We screened 115 strains of S. aureus isolated from different clinical specimens by tube method (TM), air-liquid interface coverslip assay method, Congo red agar (CRA) method, and scanning electron microscopy (SEM). Out of 115 S. aureus isolates, 63 (54.78%) showed biofilm formation by tube method. Biofilm forming bacteria were further categorized as high producers (n = 23, 20%) and moderate producers (n = 40, 34.78%). TM coordinated well with the coverslip assay for strong biofilm-producing strains in 19 (16.5%) isolates. By coverslip method, weak producers were difficult to differentiate from biofilm negative isolates. Screening on CRA showed biofilm formation only in four (3.47%) strains. Scanning electron micrographs showed the biofilm-forming strains of S. aureus arranged in a matrix on the propylene surface and correlated well with the TM. Biofilm production is a marker of virulence for clinically relevant staphylococcal infections. It can be studied by various methods but screening on CRA is not recommended for investigation of biofilm formation in Staphylococcus aureus. Electron micrograph images correlate well with the biofilm production as observed by TM.

Synthesis of metal silicide at metal/silicon oxide interface by electronic excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.-G., E-mail: jglee36@kims.re.kr; Nagase, T.; Yasuda, H.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, α-Pt{sub 2}Si, was successfully formed at the platinum/silicon oxide interface under 25–200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation.more » It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation.« less

Formation and anisotropic magnetoresistance of Co/Pt nano-contacts through aluminum oxide barrier

NASA Astrophysics Data System (ADS)

Al-Mahdawi, Muftah; Sahashi, Masashi

2014-01-01

We report on the observation of anisotropic magnetoresistance (AMR) in vertical asymmetric nano-contacts (NCs) made through AlOx nano-oxide layer (NOL) formed by ion-assisted oxidation method in the film stack of Co/AlOx-NOL/Pt. Analysis of NC formation was based on in situ conductive atomic force microscopy and transmission electron microscopy. Depending on the purity of NCs from Al contamination, we observed up to 29% AMR ratio at room temperature.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan Qingtao; Huang Kai; Ni Shibing

Well-crystalline flower- and rod-like NiS nanostructures have been synthesized by an organic-free hydrothermal process at a low temperature of 200 deg. C. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to characterize the as-synthesized NiS nanostructures. The effects of temperature and reaction time on the morphology have been also investigated. The two-step flake-cracking mechanism for the formation of flower- and rod-like NiS nanostructures was discussed. The products were also investigated by photoluminescence (PL) spectroscopy.

Cross section TEM characterization of high-energy-Xe-irradiated U-Mo

DOE PAGES

Ye, B.; Jamison, L.; Miao, Y.; ...

2017-03-09

U-Mo alloys irradiated with 84 MeV Xe ions to various doses were characterized with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. The TEM thin foils were prepared perpendicular to the irradiated surface to allow a direct observation of the entire region modified by ions. Furthermore, depth-selective microstructural information was revealed. Varied irradiation-induced phenomena such as gas bubble formation, phase reversal, and recrystallization were observed at different ion penetration depths in U-Mo.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jana, S.; Devaraj, A.; Kovarik, L.

Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.

Pterygodermatites (Mesopectines) quentini (Nematoda, Rictulariidae), a parasite of Praomys rostratus (Rodentia, Muridae) in Mali: scanning electron and light microscopy

PubMed Central

2013-01-01

Pterygodermatites (Mesopectines) quentini n. sp. (Nematoda, Rictulariidae) is described from the murine host Praomys rostratus in the south of the Republic of Mali. It differs from other species of the subgenus by the morphology of the head, which bears four simple cephalic papillae and a nearly axial oral opening, the number of caudal papillae, the number of precloacal cuticular formations, unequal spicules and the ratio of spicule lengths/body length. The use of scanning electron microscopy in combination with conventional light microscopy enabled us to give a detailed description of the morphological characters of this new species. PMID:24025692

Evaluation of the infection process by Lecanicillium fungicola in Agaricus bisporus by scanning electron microscopy.

PubMed

Santana Nunes, Janaira; Rocha de Brito, Manuela; Cunha Zied, Diego; Aparecida das Graças Leite, Eloisa; Souza Dias, Eustáquio; Alves, Eduardo

Lecanicillium fungicola causes dry bubble disease in Agaricus bisporus mushrooms leading to significant economic losses in commercial production. To monitor the infection process of L. fungicola in Brazilian strains of A. bisporus. The interaction between the mycelium of L. fungicola (LF.1) and three strains of A. bisporus (ABI 7, ABI 11/14 and ABI 11/21) was studied. Electron microscopy and X-ray microanalyses of vegetative growth and basidiocarp infection were evaluated. Micrographs show that the vegetative mycelium of the Brazilian strains of A. bisporus is not infected by the parasite. The images show that the pathogen can interlace the hyphae of A. bisporus without causing damage, which contributes to the presence of L. fungicola during the substrate colonization, allowing their presence during primordial formation of A. bisporus. In the basidiocarp, germ tubes form within 16h of infection with L. fungicola and the beginning of penetration takes place within 18h, both without the formation of specialized structures. Scanning electron microscopy enabled the process of colonization and reproduction to be observed within the formation of phialides, conidiophores and verticils of L. fungicola. The formation of calcium oxalate crystals by the pathogen was also visible using the X-ray microanalysis, both at the hyphae in the Petri plate and at basidiocarp infection site. Copyright © 2016 Asociación Española de Micología. Publicado por Elsevier España, S.L.U. All rights reserved.

Formation of Nanodimensional 3C-SiC Structures from Rice Husks

NASA Astrophysics Data System (ADS)

Gorzkowski, E. P.; Qadri, S. B.; Rath, B. B.; Goswami, R.; Caldwell, J. D.

2013-05-01

We have demonstrated that large quantities of β-SiC nanostructures can be obtained from rice husk agricultural waste by using controlled conditions in a thermogravimetric setup. This simple and inexpensive method of producing these structures on a large scale is critical for applications in nanoelectronics, nanosensors, and biotechnology. The temperature and atmosphere are two critical elements in forming either α-cristobalite (SiO2) or β-SiC. Using different characterization methods (x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy), we have shown that pyrolysis of rice husks in argon atmosphere at 1375°C results in simultaneous formation of carbon nanotubes, β-SiC nanowires/nanorods, and β-SiC powder.

Amyloid Aβ 42, a promoter of magnetite nanoparticle formation in Alzheimer’s disease

NASA Astrophysics Data System (ADS)

Bogachan Tahirbegi, Islam; Pardo, Wilmer Alfonso; Alvira, Margarita; Mir, Mònica; Samitier, Josep

2016-11-01

The accumulation of iron oxides—mainly magnetite—with amyloid peptide is a key process in the development of Alzheimer’s disease (AD). However, the mechanism for biogeneration of magnetite inside the brain of someone with AD is still unclear. The iron-storing protein ferritin has been identified as the main magnetite-storing molecule. However, accumulations of magnetite in AD are not correlated with an increase in ferritin, leaving this question unresolved. Here we demonstrate the key role of amyloid peptide Aβ 42, one of the main hallmarks of AD, in the generation of magnetite nanoparticles in the absence of ferritin. The capacity of amyloid peptide to bind and concentrate iron hydroxides, the basis for the formation of magnetite, benefits the spontaneous synthesis of these nanoparticles, even under unfavorable conditions for their formation. Using scanning and transmission electron microscopy, electron energy loss spectroscopy and magnetic force microscopy we characterized the capacity of amyloid peptide Aβ 42 to promote magnetite formation.

Formation of Porous Germanium Layers by Silver-Ion Implantation

NASA Astrophysics Data System (ADS)

Stepanov, A. L.; Vorob'ev, V. V.; Nuzhdin, V. I.; Valeev, V. F.; Osin, Yu. N.

2018-04-01

We propose a method for the formation of porous germanium ( P-Ge) layers containing silver nanoparticles by means of high-dose implantation of low-energy Ag+ ions into single-crystalline germanium ( c-Ge). This is demonstrated by implantation of 30-keV Ag+ ions into a polished c-Ge plate to a dose of 1.5 × 1017 ion/cm2 at an ion beam-current density of 5 μA/cm2. Examination by high-resolution scanning electron microscopy (SEM), atomic-force microscopy (AFM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) microanalysis, and reflection high-energy electron diffraction (RHEED) showed that the implantation of silver ions into c-Ge surface led to the formation of a P-Ge layer with spongy structure comprising a network of interwoven nanofibers with an average diameter of ˜10-20 nm Ag nanoparticles on the ends of fibers. It is also established that the formation of pores during Ag+ ion implantation is accompanied by effective sputtering of the Ge surface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myllys, Markko; Ruokolainen, Visa; Aho, Vesa

Lytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery. Here, we used three-dimensional soft X-ray tomography, combined with cryogenic fluorescence, confocal and electron microscopy, to analyse the transformation of peripheral chromatin during HSV-1 infection. Our data showed an increased presence of low-density gaps in the marginalized chromatin at late infection. Advanced data analysis indicated the formation of virus-nucleocapsid-sized (or wider) channels extending through the compacted chromatin of the host. Importantly, confocal and electron microscopy analysis showed that these gapsmore » frequently contained viral nucleocapsids. Our results demonstrated that HSV-1 infection induces the formation of channels penetrating the compacted layer of cellular chromatin and allowing for the passage of progeny viruses to the nuclear envelope, their site of nuclear egress.« less

Laser-induced periodic surface structures formation on mesoporous silicon from nanoparticles produced by picosecond and femtosecond laser shots

NASA Astrophysics Data System (ADS)

Talbi, Abderazek; Kaya-Boussougou, Sostaine; Sauldubois, Audrey; Stolz, Arnaud; Boulmer-Leborgne, Chantal; Semmar, Nadjib

2017-07-01

This paper deals with the formation of laser-induced periodic surface structures (LIPSS) on mesoporous silicon thin films induced by two laser regimes in the UV range: picosecond and femtosecond. Different LIPSS formation mechanisms from nanoparticles, mainly coalescence and agglomeration, have been evidenced by scanning electron microscopy analysis. The apparition of a liquid phase during both laser interaction at low fluence (20 mJ/cm2) and after a large number of laser pulses (up to 12,000) has been also shown with 100 nm size through incubation effect. Transmission electron microscopy analyses have been conducted to investigate the molten phase structures below and inside LIPSS. Finally, it has shown that LIPSS are composed of amorphous silicon when mesoporous silicon is irradiated by laser beam in both regimes. Nevertheless, mesoporous silicon located between LIPSS stays crystallized.

Herpes simplex virus 1 induces egress channels through marginalized host chromatin

DOE PAGES

Myllys, Markko; Ruokolainen, Visa; Aho, Vesa; ...

2016-06-28

Lytic infection with herpes simplex virus type 1 (HSV-1) induces profound modification of the cell nucleus including formation of a viral replication compartment and chromatin marginalization into the nuclear periphery. Here, we used three-dimensional soft X-ray tomography, combined with cryogenic fluorescence, confocal and electron microscopy, to analyse the transformation of peripheral chromatin during HSV-1 infection. Our data showed an increased presence of low-density gaps in the marginalized chromatin at late infection. Advanced data analysis indicated the formation of virus-nucleocapsid-sized (or wider) channels extending through the compacted chromatin of the host. Importantly, confocal and electron microscopy analysis showed that these gapsmore » frequently contained viral nucleocapsids. Our results demonstrated that HSV-1 infection induces the formation of channels penetrating the compacted layer of cellular chromatin and allowing for the passage of progeny viruses to the nuclear envelope, their site of nuclear egress.« less

Room Temperature Gas Sensing Properties of Sn-Substituted Nickel Ferrite (NiFe2O4) Thin Film Sensors Prepared by Chemical Co-Precipitation Method

NASA Astrophysics Data System (ADS)

Manikandan, V.; Li, Xiaogan; Mane, R. S.; Chandrasekaran, J.

2018-04-01

Tin (Sn) substituted nickel ferrite (NiFe2O4) thin film sensors were prepared by a simple chemical co-precipitation method, which initially characterized their structure and surface morphology with the help of x-ray diffraction and scanning electron microscopy. Surface morphology of the sensing films reveals particles stick together with nearer particles and this formation leads to a large specific area as a large specific area is very useful for easy adsorption of gas molecules. Transmission electron microscopy and selected area electron diffraction pattern images confirm particle size and nanocrystallnity as due to formation of circular rings. Fourier transform infrared analysis has supported the presence of functional groups. The 3.69 eV optical band gap of the film was found which enabled better gas sensing. Gas sensors demonstrate better response and recovery characteristics, and the maximum response was 68.43%.

Circumventricular mesencephalic trigeminal midline ridge formation in cartilaginous fishes: species variations.

PubMed

MacDonnell, M F

1984-01-01

The midline ridge formation (MRF) of the trigeminal complex in 127 cartilaginous fish of 15 species was examined by scanning electron microscopy or light microscopy. Five distinct species variations of the MRF in sharks are described. The formation has not yet been observed to be present in skates and rays, but its presence in the subclass Holocephali, the sister group to the Elasmobranchii, indicates that this proposed circumventricular organ is an ancient brain characteristic of this line of vertebrates, perhaps predating the emergence of the class Chondrichthyii. The different types of MRF are compared to a current phyletic organization of the elasmobranchs and the possible functional significance of the formation is discussed briefly.

The influence of projectile ion induced chemistry on surface pattern formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karmakar, Prasanta, E-mail: prasantak@vecc.gov.in; Satpati, Biswarup

We report the critical role of projectile induced chemical inhomogeneity on surface nanostructure formation. Experimental inconsistency is common for low energy ion beam induced nanostructure formation in the presence of uncontrolled and complex contamination. To explore the precise role of contamination on such structure formation during low energy ion bombardment, a simple and clean experimental study is performed by selecting mono-element semiconductors as the target and chemically inert or reactive ion beams as the projectile as well as the source of controlled contamination. It is shown by Atomic Force Microscopy, Cross-sectional Transmission Electron Microscopy, and Electron Energy Loss Spectroscopy measurementsmore » that bombardment of nitrogen-like reactive ions on Silicon and Germanium surfaces forms a chemical compound at impact zones. Continuous bombardment of the same ions generates surface instability due to unequal sputtering and non-uniform re-arrangement of the elemental atom and compound. This instability leads to ripple formation during ion bombardment. For Argon-like chemically inert ion bombardment, the chemical inhomogeneity induced boost is absent; as a result, no ripples are observed in the same ion energy and fluence.« less

Note on in situ (scanning) transmission electron microscopy study of liquid samples.

PubMed

Jiang, Nan

2017-08-01

Liquid cell (scanning) transmission electron microscopy has been developed rapidly, using amorphous SiN x membranes as electron transparent windows. The current interpretations of electron beam effects are mainly based on radiolytic processes. In this note, additional effects of the electric field due to electron-beam irradiation are discussed. The electric field can be produced by the charge accumulation due to the emission of secondary and Auger electrons. Besides various beam-induced phenomena, such as nanoparticle precipitation and gas bubble formation and motion, two other effects need to be considered; one is the change of Gibbs free energy of nucleation and the other is the violation of Brownian motion due to ion drifting driven by the electric field. Copyright © 2017 Elsevier B.V. All rights reserved.

Designer amphiphilic proteins as building blocks for the intracellular formation of organelle-like compartments

NASA Astrophysics Data System (ADS)

Huber, Matthias C.; Schreiber, Andreas; von Olshausen, Philipp; Varga, Balázs R.; Kretz, Oliver; Joch, Barbara; Barnert, Sabine; Schubert, Rolf; Eimer, Stefan; Kele, Péter; Schiller, Stefan M.

2015-01-01

Nanoscale biological materials formed by the assembly of defined block-domain proteins control the formation of cellular compartments such as organelles. Here, we introduce an approach to intentionally ‘program’ the de novo synthesis and self-assembly of genetically encoded amphiphilic proteins to form cellular compartments, or organelles, in Escherichia coli. These proteins serve as building blocks for the formation of artificial compartments in vivo in a similar way to lipid-based organelles. We investigated the formation of these organelles using epifluorescence microscopy, total internal reflection fluorescence microscopy and transmission electron microscopy. The in vivo modification of these protein-based de novo organelles, by means of site-specific incorporation of unnatural amino acids, allows the introduction of artificial chemical functionalities. Co-localization of membrane proteins results in the formation of functionalized artificial organelles combining artificial and natural cellular function. Adding these protein structures to the cellular machinery may have consequences in nanobiotechnology, synthetic biology and materials science, including the constitution of artificial cells and bio-based metamaterials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe; Cao, Minhua, E-mail: caomh@bit.edu.cn; Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing Institute of Technology, Beijing 100081

Research highlights: {yields} Novel Bi{sub 2}S{sub 3} hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. {yields} The hierarchical nanostructures exhibit a flower-like shape. {yields} PVP plays an important role for the formation of the hierarchical nanostructures. {yields} Bi{sub 2}S{sub 3} film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties. -- Abstract: Novel Bi{sub 2}S{sub 3} hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. The hierarchical nanostructures exhibit a flower-like shape. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmissionmore » electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were used to characterize the as-synthesized samples. Meanwhile, the effect of various experimental parameters including the concentration of reagents and reaction time on final product has been investigated. In our experiment, PVP plays an important role for the formation of the hierarchical nanostructures and the possible mechanism was proposed. In addition, Bi{sub 2}S{sub 3} film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties, which may bring nontrivial functionalities and may have some promising applications in the future.« less

Environmental scanning electron microscopy analysis of Proteus mirabilis biofilms grown on chitin and stainless steel.

PubMed

Fernández-Delgado, Milagro; Duque, Zoilabet; Rojas, Héctor; Suárez, Paula; Contreras, Monica; García-Amado, María A; Alciaturi, Carlos

Proteus mirabilis is a human pathogen able to form biofilms on the surface of urinary catheters. Little is known about P. mirabilis biofilms on natural or industrial surfaces and the potential consequences for these settings. The main aim of this work was to assess and compare the adhesion and biofilm formation of P. mirabilis strains from different origins on chitin and stainless steel surfaces within 4 to 96 h. Using environmental scanning electron microscopy, the biofilms of a clinical strain grown on chitin at 4 h showed greater adhesion, aggregation, thickness, and extracellular matrix production than those grown on stainless steel, whereas biofilms of an environmental strain had less aggregation on both surfaces. Biofilms of both P. mirabilis strains developed different structures on chitin, such as pillars, mushrooms, channels, and crystalline-like precipitates between 24 and 96 h, in contrast with flat-layer biofilms produced on stainless steel. Significant differences ( p  < 0.05) were found in the frequency of pillars and channels. Images of transmission electron microscopy demonstrated abundant fimbriae in 100 % of cells from both strains, which could be related to surface adherence and biofilm formation. This represents the first study of P. mirabilis showing adhesion, biofilm formation, and development of different structures on surfaces found outside the human host.

Control of Wigner localization and electron cavity effects in near-field emission spectra of In(Ga)P/GaInP quantum-dot structures

NASA Astrophysics Data System (ADS)

Mintairov, A. M.; Kapaldo, J.; Merz, J. L.; Rouvimov, S.; Lebedev, D. V.; Kalyuzhnyy, N. A.; Mintairov, S. A.; Belyaev, K. G.; Rakhlin, M. V.; Toropov, A. A.; Brunkov, P. N.; Vlasov, A. S.; Zadiranov, Yu. M.; Blundell, S. A.; Mozharov, A. M.; Mukhin, I.; Yakimov, M.; Oktyabrsky, S.; Shelaev, A. V.; Bykov, V. A.

2018-05-01

Structural and emission properties of few-electron In(Ga)P/GaInP quantum dots (QDs) representing natural Wigner molecules (WM) and whispering gallery mode (WGM) electron (e ) cavities have been investigated. QD structures were grown using self-organized metal-organic vapor phase epitaxy and deposition from ˜3 to 7 monolayers of InP at 700 °C. Using atomic force microscopy, transmission electron microscopy, near-field scanning optical microscopy (NSOM), and μ -photoluminescence (μ -PL) spectra we obtained In(Ga)P/GaInP QDs having lateral size 80-180 nm, height 5-30 nm, Ga content 0.0-0.4, density 2 -10 μm-2 , and electron population up to 20 and demonstrated control of their density and size distribution. Using high-spatial-resolution low-temperature PL spectra, NSOM imaging, and calculations of charge density distributions we observed Wigner localization and e -cavity effects for a series of dots having quantum confinement ℏ ω0=0.5 -6 meV . We used these data together with time-resolved PL measurements to clarify the effect of Coulomb interaction and WM formation on emission spectra of few-electron QDs. We present direct observation of 2 e , 6 e , and 9 e WMs; 2 e and 4 e WGMs; and Fabry-Perot e modes and establish conditions of e -WGM-cavity formation in these QDs.

Correlated Fluorescence-Atomic Force Microscopy Studies of the Clathrin Mediated Endocytosis in SKMEL Cells

NASA Astrophysics Data System (ADS)

Smith, Steve; Hor, Amy; Luu, Anh; Kang, Lin; Scott, Brandon; Bailey, Elizabeth; Hoppe, Adam

Clathrin-mediated endocytosis is one of the central pathways for cargo transport into cells, and plays a major role in the maintenance of cellular functions, such as intercellular signaling, nutrient intake, and turnover of plasma membrane in cells. The clathrin-mediated endocytosis process involves invagination and formation of clathrin-coated vesicles. However, the biophysical mechanisms of vesicle formation are still debated. We investigate clathrin vesicle formation mechanisms through the utilization of tapping-mode atomic force microscopy for high resolution topographical imaging in neutral buffer solution of unroofed cells exposing the inner membrane, combined with fluorescence imaging to definitively label intracellular constituents with specific fluorescent fusion proteins (actin filaments labeled with green phalloidin-antibody and clathrin coated vesicles with the fusion protein Tq2) in SKMEL (Human Melanoma) cells. Results from our work are compared against dynamical polarized total internal fluorescence (TIRF), super-resolution photo-activated localization microscopy (PALM) and transmission electron microscopy (TEM) to draw conclusions regarding the prominent model of vesicle formation in clathrin-mediated endocytosis. Funding provided by NSF MPS/DMR/BMAT award # 1206908.

Fungi and bacteria involved in desert varnish formation

NASA Technical Reports Server (NTRS)

Taylor-George, S.; Palmer, F.; Staley, J. T.; Curtiss, B.; Adams, J. B.; Borns, D. J.

1983-01-01

Desert varnish is a coating of ferromanganese oxides and clays that develops on rock surfaces in arid to semi-arid regions. Active respiration but not photosynthesis was detected on varnished rock surfaces from the Sonoran Desert. Light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, and cultivation experiments indicate that both fungi, primarily dematiaceous hyphomycetes, and bacteria are found on and within desert varnish coatings from the arid regions studied. Some fungi grow as microcolonial fungi (MCF) on rocks, and microscopic observations suggest MCF become incorporated in the varnish coating. SEM-EDAX (energy dispersive X-ray systems) analyses indicate the MCF contain 3 of the characteristic elements of varnish: iron, aluminum, and silicon. In some locations, MCF are also enriched in manganese relative to the rock substratum. Furthermore, some of the dematiaceous hyphomycetes that have been cultivated are able to oxidize manganese under laboratory conditions. It is possible that manganese-oxidizing bacteria, which are found in varnish, also play an important role in varnish formation.

Spectroscopic study of Pbs nano-structured layer prepared by Pld utilized as a Hall-effect magnetic sensor

NASA Astrophysics Data System (ADS)

Atwa, D. M.; Aboulfotoh, N.; El-magd, A. Abo; Badr, Y.

2013-10-01

Lead sulfide (PbS) nano-structured films have been grown on quartz substrates using PLD technique. The deposited films were characterized by several structural techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Selected-area electron diffraction patterns (SAED). The results prove the formation of cubic phase of PbS nanocrystals. Elemental analysis of the deposited films compared to the bulk target was obtained via laser induced fluorescence of the produced plasma particles and the energy dispersive X-ray "EDX" technique. The Hall coefficient measurements indicate an efficient performance of the deposited films as a magnetic sensor.

Nano-sized graphene flakes: insights from experimental synthesis and first principles calculations.

PubMed

Lin, Pin-Chun; Chen, Yi-Rui; Hsu, Kuei-Ting; Lin, Tzu-Neng; Tung, Kuo-Lun; Shen, Ji-Lin; Liu, Wei-Ren

2017-03-01

In this study, we proposed a cost-effective method for preparing graphene nano-flakes (GNFs) derived from carbon nanotubes (CNTs) via three steps (pressing, homogenization and sonication exfoliation processes). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), laser scattering, as well as ultraviolet-visible and photoluminescence (PL) measurements were carried out. The results indicated that the size of as-synthesized GNFs was approximately 40-50 nm. Furthermore, we also used first principles calculations to understand the transformation from CNTs to GNFs from the viewpoints of the edge formation energies of GNFs in different shapes and sizes. The corresponding photoluminescence measurements of GNFs were carried out in this work.

Singlet oxygen production in Chlamydomonas reinhardtii under heat stress.

PubMed

Prasad, Ankush; Ferretti, Ursula; Sedlářová, Michaela; Pospíšil, Pavel

2016-02-01

In the current study, singlet oxygen formation by lipid peroxidation induced by heat stress (40 °C) was studied in vivo in unicellular green alga Chlamydomonas reinhardtii. Primary and secondary oxidation products of lipid peroxidation, hydroperoxide and malondialdehyde, were generated under heat stress as detected using swallow-tailed perylene derivative fluorescence monitored by confocal laser scanning microscopy and high performance liquid chromatography, respectively. Lipid peroxidation was initiated by enzymatic reaction as inhibition of lipoxygenase by catechol and caffeic acid prevented hydroperoxide formation. Ultra-weak photon emission showed formation of electronically excited species such as triplet excited carbonyl, which, upon transfer of excitation energy, leads to the formation of either singlet excited chlorophyll or singlet oxygen. Alternatively, singlet oxygen is formed by direct decomposition of hydroperoxide via Russell mechanisms. Formation of singlet oxygen was evidenced by the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl detected by electron paramagnetic resonance spin-trapping spectroscopy and the imaging of green fluorescence of singlet oxygen sensor green detected by confocal laser scanning microscopy. Suppression of singlet oxygen formation by lipoxygenase inhibitors indicates that singlet oxygen may be formed via enzymatic lipid peroxidation initiated by lipoxygenase.

Vibrio tapetis, the Causative Agent of Brown Ring Disease, Forms Biofilms with Spherical Components.

PubMed

Rodrigues, Sophie; Paillard, Christine; Le Pennec, Gaël; Dufour, Alain; Bazire, Alexis

2015-01-01

Vibrio tapetis is a marine bacterium causing Brown Ring Disease (BRD) in the Manila clam Ruditapes philippinarum. V. tapetis biofilm formation remains unexplored depite the fact that it might be linked to pathogenicity. Our objectives were to characterize the in vitro biofilm formation of V. tapetis and evaluate the effects of culture conditions. Biofilm structure and its matrix composition were examined by confocal laser scanning microscopy and scanning electron microscopy. V. tapetis was able to form biofilms on a glass substratum within 24 h. Polysaccharides and extracellular DNA of the biofilm matrixes were differently distributed depending on the V. tapetis strains. Spherical components of about 1-2 μm diameter were found at the biofilm surface. They contain DNA, proteins, and seemed to be physically linked to bacteria and of cellular nature. Transmission electron microscopy showed that the spherical components were devoid of internal compartments. Temperatures >21°C inhibit BRD whereas low salinity (2%) favor it, none of the both conditions altered V. tapetis' ability to form biofilms in vitro. We suggest therefore that biofilm formation could play a role in the persistence of the pathogen in clam than in BRD symptoms.

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic-inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm -1 for Pb(II) and ca. 1580 cm -1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. Finally, these complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic–inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm –1 for Pb(II) and ca. 1580 cm –1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. These complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

DOE PAGES

MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.; ...

2016-09-07

To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K +, Zn 2+, Pb 2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic-inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm -1 for Pb(II) and ca. 1580 cm -1 for Zn(II) are consistentmore » with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. Finally, these complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.« less

Focused Ion Beam Microscopy of ALH84001 Carbonate Disks

NASA Technical Reports Server (NTRS)

Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Vali, Hojatollah; Gibson, Everett K., Jr.; Romanek, Christopher S.

2005-01-01

Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. A prerequisite is that a detailed characterization of the chemical and physical properties of the carbonate be established. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB) sectioning and ultramicrotomy. Our results suggest that the formation of ALH84001 carbonate assemblages were produced by considerably more complex process(es) than simple aqueous precipitation followed by partial thermal decomposition as proposed by other investigators [e.g., 1-3].

Time-lapse cinemicrography and scanning electron microscopy of platelet formation by megakaryocytes.

PubMed

Haller, C J; Radley, J M

1983-01-01

The surface architecture of megakaryocytes undergoing platelet formation in vitro has been examined by time-lapse cinemicrography and scanning electron microscopy. Fragments of mouse bone marrow were placed in culture medium and incubated at 37 degrees C. After several hours mature megakaryocytes migrated out of the marrow and some underwent shape changes so that they eventually appeared as a relatively small central body, housing the nucleus, from which emerged a number of thin processes which resembled platelet chains. Scanning electron microscopy showed that initially the megakaryocyte surface was ruffled but with development of processes it became smoother. Circumferential folds of small amplitude were found on the surface of developing constrictions which separated putative platelets. It is thought they may be associated with the mechanism of extension, but could have a role in establishing the topography of membrane components. Rupture of the chains and release of platelets was not observed; this permits the number of putative platelets formed by individual megakaryocytes to be determined. The putative platelets exhibited features common to circulating platelets when exposed to a glass surface including the development of pseudopodia and, eventually, flattening on to the surface.

Electron microscopy characterization of Ni-Cr-B-Si-C laser deposited coatings.

PubMed

Hemmati, I; Rao, J C; Ocelík, V; De Hosson, J Th M

2013-02-01

During laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.

Study of the structure of a thin aluminum layer on the vicinal surface of a gallium arsenide substrate by high-resolution electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lovygin, M. V., E-mail: lemi@miee.ru; Borgardt, N. I.; Seibt, M.

2015-12-15

The results of electron-microscopy studies of a thin epitaxial aluminum layer deposited onto a misoriented gallium-arsenide substrate are reported. It is established that the layer consists of differently oriented grains, whose crystal lattices are coherently conjugated with the substrate with the formation of misfit dislocations, as in the case of a layer on a singular substrate. Atomic steps on the substrate surface are visualized, and their influence on the growth of aluminum crystal grains is discussed.

Structural defects in GaN revealed by Transmission Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liliental-Weber, Zuzanna

This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Lastly, some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

Structural defects in GaN revealed by Transmission Electron Microscopy

DOE PAGES

Liliental-Weber, Zuzanna

2014-09-08

This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Lastly, some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

Synthesis of rose-like boron nitride particles with a high specific surface area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Hongming; Huang, Xiaoxiao; Wen, Guangwu, E-mail: wgw@hitwh.edu.cn

2010-08-15

Novel rose-like BN nanostructures were synthesized on a large scale via a two-step procedure. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer and nitrogen porosimetry. The results show that the obtained rose-like nanostructures are composed of a large amount of h-BN crystalline flakes and have a surface area of 90.31 m{sup 2}/g. A mechanism was proposed to explain the formation process of the rose-like BN nanostructures.

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-04-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

NASA Astrophysics Data System (ADS)

Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

2018-05-01

Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

Revealing 3D Ultrastructure and Morphology of Stem Cell Spheroids by Electron Microscopy.

PubMed

Jaros, Josef; Petrov, Michal; Tesarova, Marketa; Hampl, Ales

2017-01-01

Cell culture methods have been developed in efforts to produce biologically relevant systems for developmental and disease modeling, and appropriate analytical tools are essential. Knowledge of ultrastructural characteristics represents the basis to reveal in situ the cellular morphology, cell-cell interactions, organelle distribution, niches in which cells reside, and many more. The traditional method for 3D visualization of ultrastructural components, serial sectioning using transmission electron microscopy (TEM), is very labor-intensive due to contentious TEM slice preparation and subsequent image processing of the whole collection. In this chapter, we present serial block-face scanning electron microscopy, together with complex methodology for spheroid formation, contrasting of cellular compartments, image processing, and 3D visualization. The described technique is effective for detailed morphological analysis of stem cell spheroids, organoids, as well as organotypic cell cultures.

Histophilus somni biofilm formation in cardiopulmonary tissue of the bovine host following respiratory challenge.

PubMed

Sandal, Indra; Shao, Jian Q; Annadata, Satish; Apicella, Michael A; Boye, Mette; Jensen, Tim K; Saunders, Geoffrey K; Inzana, Thomas J

2009-02-01

Biofilms form in a variety of host sites following infection with many bacterial species. However, the study of biofilms in a host is hindered due to the lack of protocols for the proper experimental investigation of biofilms in vivo. Histophilus somni is an agent of respiratory and systemic diseases in bovines, and readily forms biofilms in vitro. In the present study the capability of H. somni to form biofilms in cardiopulmonary tissue following experimental respiratory infection in the bovine host was examined by light microscopy, transmission electron microscopy, immunoelectron microscopy of ultrathin cryosections, scanning electron microscopy of freeze-fractured samples, and fluorescent in situ hybridization. Biofilms were evident and most prominent in the myocardium, and were associated with a large amount of amorphous extracellular material. Furthermore, Pasteurella multocida was often cultured with H. somni from heart and lung samples. Transposon mutagenesis of H. somni strain 2336 resulted in the generation of mutants that expressed more or less biofilm than the parent strain. Six mutants deficient in biofilm formation had an insertion in the gene encoding for a homolog of filamentous haemagglutinin (FHA), predicted to be involved in attachment. Thus, this investigation demonstrated that H. somni is capable of forming a biofilm in its natural host, that such a biofilm may be capable of harboring other bovine respiratory disease pathogens, and that the genes responsible for biofilm formation can be identified by transposon mutagenesis.

Femtosecond laser surface texturing of titanium as a method to reduce the adhesion of Staphylococcus aureus and biofilm formation

NASA Astrophysics Data System (ADS)

Cunha, Alexandre; Elie, Anne-Marie; Plawinski, Laurent; Serro, Ana Paula; Botelho do Rego, Ana Maria; Almeida, Amélia; Urdaci, Maria C.; Durrieu, Marie-Christine; Vilar, Rui

2016-01-01

The aim of the present work was to investigate the possibility of using femtosecond laser surface texturing as a method to reduce the colonization of Grade 2 Titanium alloy surfaces by Staphylococcus aureus and the subsequent formation of biofilm. The laser treatments were carried out with a Yb:KYW chirped-pulse-regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. Two types of surface textures, consisting of laser-induced periodic surface structures (LIPSS) and nanopillars, were produced. The topography, chemical composition and phase constitution of these surfaces were investigated by atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Surface wettability was assessed by the sessile drop method using water and diiodomethane as testing liquids. The response of S. aureus put into contact with the laser treated surfaces in controlled conditions was investigated by epifluorescence microscopy and scanning electron microscopy 48 h after cell seeding. The results achieved show that the laser treatment reduces significantly the bacterial adhesion to the surface as well as biofilm formation as compared to a reference polished surfaces and suggest that femtosecond laser texturing is a simple and promising method for endowing dental and orthopedic titanium implants with antibacterial properties, reducing the risk of implant-associated infections without requiring immobilized antibacterial substances, nanoparticles or coatings.

Elucidating the real-time Ag nanoparticle growth on α-Ag2WO4 during electron beam irradiation: experimental evidence and theoretical insights.

PubMed

Pereira, Wyllamanney da Silva; Andrés, Juan; Gracia, Lourdes; San-Miguel, Miguel A; da Silva, Edison Z; Longo, Elson; Longo, Valeria M

2015-02-21

Why and how Ag is formed when electron beam irradiation takes place on α-Ag2WO4 in a vacuum transmission electron microscopy chamber? To find an answer, the atomic-scale mechanisms underlying the formation and growth of Ag on α-Ag2WO4 have been investigated by detailed in situ transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) studies, density functional theory based calculations and ab initio molecular dynamics simulations. The growth process at different times, chemical composition, size distribution and element distribution were analyzed in depth at the nanoscale level using FE-SEM, operated at different voltages (5, 10, 15, and 20 kV), and TEM with energy dispersive spectroscopy (EDS) characterization. The size of Ag nanoparticles covers a wide range of values. Most of the Ag particles are in the 20-40 nm range. The nucleation and formation of Ag on α-Ag2WO4 is a result of structural and electronic changes in the AgOx (x = 2,4, 6, and 7) clusters used as constituent building blocks of this material, consistent with metallic Ag formation. First principle calculations point out that Ag-3 and Ag-4-fold coordinated centers, located in the sub-surface of the (100) surface, are the most energetically favorable to undergo the diffusion process to form metallic Ag. Ab initio molecular dynamics simulations and the nudged elastic band (NEB) method were used to investigate the minimum energy pathways of these Ag atoms from positions in the first slab layer to outward sites on the (100) surface of α-Ag2WO4. The results point out that the injection of electrons decreases the activation barrier for this diffusion step and this unusual behavior results from the presence of a lower energy barrier process.

Solid-state nanopores of controlled geometry fabricated in a transmission electron microscope

NASA Astrophysics Data System (ADS)

Qian, Hui; Egerton, Ray F.

2017-11-01

Energy-filtered transmission electron microscopy and electron tomography were applied to in situ studies of the formation, shape, and diameter of nanopores formed in a silicon nitride membrane in a transmission electron microscope. The nanopore geometry was observed in three dimensions by electron tomography. Drilling conditions, such as probe current, beam convergence angle, and probe position, affect the formation rate and the geometry of the pores. With a beam convergence semi-angle of α = 22 mrad, a conical shaped nanopore is formed but at α = 45 mrad, double-cone (hourglass-shaped) nanopores were produced. Nanopores with an effective diameter between 10 nm and 1.8 nm were fabricated by controlling the drilling time.

Electronic structure and fine structural features of the air-grown UNxOy on nitrogen-rich uranium nitride

NASA Astrophysics Data System (ADS)

Long, Zhong; Zeng, Rongguang; Hu, Yin; Liu, Jing; Wang, Wenyuan; Zhao, Yawen; Luo, Zhipeng; Bai, Bin; Wang, Xiaofang; Liu, Kezhao

2018-06-01

Oxide formation on surface of nitrogen-rich uranium nitride film/particles was investigated using X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), aberration-corrected transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) coupled with electron energy-loss spectroscopy (EELS). XPS and AES studies indicated that the oxidized layer on UN2-x film is ternary compound uranium oxynitride (UNxOy) in 5-10 nm thickness. TEM/HAADF-STEM and EELS studies revealed the UNxOy crystallizes in the FCC CaF2-type structure with the lattice parameter close to the CaF2-type UN2-x matrix. The work can provide further information to the oxidation mechanism of uranium nitride.

Green synthesis of BiVO4 nanorods via aqueous extracts of Callistemon viminalis

NASA Astrophysics Data System (ADS)

Mohamed, H. E. A.; Sone, B. T.; Fuku, X. G.; Dhlamini, M. S.; Maaza, M.

2018-05-01

Nowadays, the development of efficient green chemistry methods for synthesis of metal oxides nanoparticles has become a major focus of researchers. These methods are being investigated in order to find an eco-friendly technique for production of well-characterized nanoparticles. In this contribution we report for the first time, the synthesis and structural characterization of n-type Bismuth vanadate (BiVO4) nanoparticles using aqueous extracts of Callistemon viminalis as a chelating agent. To ascertain the formation of BiVO4, X-Ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), Electron Dispersion X-ray Spectroscopy (EDS), Fourier Transform Infra-red Spectroscopy (FTIR), and Photoluminescence spectroscopy (PL) were carried out.

Structure of junctions of multiwalled carbon nanotubes with tetragonal cross section and flattened nanotubes revealed by electron-beam tomography

NASA Astrophysics Data System (ADS)

Nagano, Yuta; Kohno, Hideo

2017-11-01

Multiwalled carbon nanotubes with tetragonal cross section frequently form junctions with flattened multi-walled carbon nanotubes, a kind of carbon nanoribbon. The three-dimensional structure of the junctions is revealed by transmission-electron-microscopy-based tomography. Two types of junction, parallel and diagonal, are found. The formation mechanism of these two types of junction is discussed in terms of the origami mechanism that was previously proposed to explain the formation of carbon nanoribbons and nanotetrahedra.

Phenotypically heterogeneous deletion of the ABH antigen from the transformed bladder urothelium. A scanning electron microscope study.

PubMed

De Harven, E; He, S; Hanna, W; Bootsma, G; Connolly, J G

1987-10-01

The deletion of ABH blood group antigens from the luminal surface of the bladder mucosa in cases of well differentiated transitional cell carcinomata, and the formation of pleomorphic microvilli have both been associated with aggressive biological behaviour and invasiveness of the tumors. We have studied cold cup biopsies from 8 normal mucosae and 17 papillary transitional cell carcinomata of the urinary bladder. The aim of our study was to correlate the formation of uniform or pleomorphic microvilli with the extent of deletion of the ABH blood group antigens on the surface of normal and transformed bladder urothelium. Immunogold scanning electron microscopy (SEM) in the backscattered electron (BE) imaging mode was used for this purpose. In the normal urothelium, uniform labeling of the luminal cells was demonstrated. In well differentiated tumors, the superficial cells exhibited uniform microvilli and a heterogeneous expression of the ABH antigens, giving characteristic 'mosaic' patterns of the antigenic labeling across the mucosal surface. These patterns were sharply delimitated at cell junctions when viewed by SEM; these observations were confirmed by transmission electron microscopy. In higher grade tumors, decreased ABH antigen expression, pleomorphic microvilli and/or featureless luminal cells were observed. In the transformed urothelium, the formation of uniform microvilli appeared to precede the loss of ABH antigen in most cases.

Formation of newly synthesized adeno-associated virus capsids in the cell nucleus.

PubMed

Bell, Peter; Vandenberghe, Luk H; Wilson, James M

2014-06-01

Adeno-associated virus (AAV) particles inside the nucleus of a HEK 293 cell are shown by electron microscopy. Cells have been triple-transfected for vector production and were analyzed for capsid formation three days later. Newly assembled particle are visible as seemingly unstructured conglomerates or crystal-like arrays.

Formation of Worm-Like Micelles in Mixed N-Hexadecyl-N-Methylpyrrolidinium Bromide-Based Cationic Surfactant and Anionic Surfactant Systems

PubMed Central

Dai, Caili; Yan, Zhihu; You, Qing; Du, Mingyong; Zhao, Mingwei

2014-01-01

Through the descriptive and rheological characterization of worm-like micelles formed by N-hexadecyl-N-methylpyrrolidinium bromide and sodium laurate, the formation and properties of the worm-like micelles were affected by the concentrations of sodium laurate and temperature. Additionally, cryogenic transmission electron microscopy images further validated the formation of worm-like micelles. PMID:25019152

Visualization of HIV T Cell Virological Synapses and Virus-Containing Compartments by Three-Dimensional Correlative Light and Electron Microscopy

PubMed Central

Wang, Lili; Eng, Edward T.; Law, Kenneth; Gordon, Ronald E.; Rice, William J.

2016-01-01

ABSTRACT Virological synapses (VS) are adhesive structures that form between infected and uninfected cells to enhance the spread of HIV-1. During T cell VS formation, viral proteins are actively recruited to the site of cell-cell contact where the viral material is efficiently translocated to target cells into heterogeneous, protease-resistant, antibody-inaccessible compartments. Using correlative light and electron microscopy (CLEM), we define the membrane topography of the virus-containing compartments (VCC) where HIV is found following VS-mediated transfer. Focused ion beam scanning electron microscopy (FIB-SEM) and serial sectioning transmission electron microscopy (SS-TEM) were used to better resolve the fluorescent Gag-containing structures within the VCC. We found that small punctate fluorescent signals correlated with single viral particles in enclosed vesicular compartments or surface-localized virus particles and that large fluorescent signals correlated with membranous Gag-containing structures with unknown pathological function. CLEM imaging revealed distinct pools of newly deposited viral proteins within endocytic and nonendocytic compartments in VS target T cells. IMPORTANCE This study directly correlates individual virus-associated objects observed in light microscopy with ultrastructural features seen by electron microscopy in the HIV-1 virological synapse. This approach elucidates which infection-associated ultrastructural features represent bona fide HIV protein complexes. We define the morphology of some HIV cell-to-cell transfer intermediates as true endocytic compartments and resolve unique synapse-associated viral structures created by transfer across virological synapses. PMID:27847357

Assessment and characterization of biofilm formation among human isolates of Streptococcus dysgalactiae subsp. equisimilis.

PubMed

Genteluci, Gabrielle Limeira; Silva, Ligia Guedes; Souza, Maria Clara; Glatthardt, Thaís; de Mattos, Marcos Corrêa; Ejzemberg, Regina; Alviano, Celuta Sales; Figueiredo, Agnes Marie Sá; Ferreira-Carvalho, Bernadete Teixeira

2015-12-01

The capacity to form biofilm is considered a protective mechanism that allows the bacteria to survive and proliferate in hostile environments, facilitating the maintenance of the infectious process. Recently, biofilm has become a topic of interest in the study of the human pathogen group A Streptococcus (GAS). Although GAS has not been associated with infection on medical implants, the presence of microcolonies embedded in an extracellular matrix on infected tissues has been reported. Despite the similarity between GAS and Streptococcus dysgalactiae subspecies equisimilis (SDSE), there are no studies in the literature describing the production of biofilm by SDSE. In this work, we assessed and characterized biofilm development among SDSE human isolates of group C. The in vitro data showed that 59.3% of the 118 isolates tested were able to form acid-induced biofilm on glass, and 28% formed it on polystyrene surfaces. More importantly, biofilm was also formed in a foreign body model in mice. The biofilm structure was analyzed by confocal laser scanning microscopy, transmission electron microscopy, and scanning electron microscopy. Long fibrillar-like structures were observed by scanning electron microscopy. Additionally, the expression of a pilus associated gene of SDSE was increased for in vitro sessile cells compared with planktonics, and when sessile cells were collected from biofilms formed in the animal model compared with that of in vitro model. Results obtained from the immunofluorescence microscopy indicated the biofilm was immunogenic. Our data also suggested a role for proteins, exopolysaccharide and extracellular DNA in the formation and accumulation of biofilm by SDSE. Copyright © 2015 Elsevier GmbH. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bingbing; Knopf, Daniel A.; China, Swarup

Heterogeneous ice nucleation is a physical chemistry process of critical relevance to a range of topics in the fundamental and the applied sciences and technologies. Heterogeneous ice nucleation remains insufficiently understood. This is in part due to the lack of experimental methods capable of in situ visualization of ice formation over nucleating substrates with microscopically characterized morphology and composition. We present development, validation and first applications of a novel electron microscopy platform allowing observation of individual ice nucleation events at temperature and relative humidity (RH) relevant for ice formation in a broad range of environmental and applied technology processes. Themore » approach utilizes a custom-built ice nucleation cell, interfaced with an Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system allows dynamic observations of individual ice formation events over particles of atmospheric relevance and determination of the ice nucleation mechanisms. Additional IN-ESEM experiments allow examination of the location of ice formation on the surface of individual particles and micro-spectroscopy analysis of the ice nucleating particles (INPs). This includes elemental composition detected by the energy dispersed analysis of X-rays (EDX), speciation of the organic content in particles using scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and Helium ion microscopy (HeIM). The capabilities of the IN-ESEM experimental platform are demonstrated first on laboratory standards and then by chemical imaging of INPs using a complex sample of ambient particles.« less

Fourier Transform Infrared (FTIR) Spectroscopy, Ultraviolet Resonance Raman (UVRR) Spectroscopy, and Atomic Force Microscopy (AFM) for Study of the Kinetics of Formation and Structural Characterization of Tau Fibrils.

PubMed

Ramachandran, Gayathri

2017-01-01

Kinetic studies of tau fibril formation in vitro most commonly employ spectroscopic probes such as thioflavinT fluorescence and laser light scattering or negative stain transmission electron microscopy. Here, I describe the use of Fourier transform infrared (FTIR) spectroscopy, ultraviolet resonance Raman (UVRR) spectroscopy, and atomic force microscopy (AFM) as complementary probes for studies of tau aggregation. The sensitivity of vibrational spectroscopic techniques (FTIR and UVRR) to secondary structure content allows for measurement of conformational changes that occur when the intrinsically disordered protein tau transforms into cross-β-core containing fibrils. AFM imaging serves as a gentle probe of structures populated over the time course of tau fibrillization. Together, these assays help further elucidate the structural and mechanistic complexity inherent in tau fibril formation.

Candida tropicalis biofilm and human epithelium invasion is highly influenced by environmental pH.

PubMed

Ferreira, Carina; Gonçalves, Bruna; Vilas Boas, Diana; Oliveira, Hugo; Henriques, Mariana; Azeredo, Joana; Silva, Sónia

2016-11-01

The main goal of this study was to investigate the role of pH on Candida tropicalis virulence determinants, namely the ability to form biofilms and to colonize/invade reconstituted human vaginal epithelia. Biofilm formation was evaluated by enumeration of cultivable cells, total biomass quantification and structural analysis by scanning electron microscopy and confocal laser scanning microscopy. Candida tropicalis human vaginal epithelium colonization and invasiveness were examined qualitatively by epifluorescence microscopy and quantitatively by a novel quantitative real-time PCR protocol for Candida quantification in tissues. The results revealed that environmental pH influences C. tropicalis biofilm formation as well as the colonization and potential to invade human epithelium with intensification at neutral and alkaline conditions compared to acidic conditions. For the first time, we have demonstrated that C. tropicalis biofilm formation and invasion is highly influenced by environmental pH. © Crown copyright 2016.

Prevention of Propionibacterium acnes biofilm formation in prosthetic infections in vitro.

PubMed

Howlin, Robert P; Winnard, Christopher; Angus, Elizabeth M; Frapwell, Connor J; Webb, Jeremy S; Cooper, John J; Aiken, Sean S; Bishop, Julie Y; Stoodley, Paul

2017-04-01

The role of Propionibacterium acnes in shoulder arthroplasty and broadly in orthopedic prosthetic infections has historically been underestimated, with biofilm formation identified as a key virulence factor attributed to invasive isolates. With an often indolent clinical course, P acnes infection can be difficult to detect and treat. This study investigates absorbable cements loaded with a broad-spectrum antibiotic combination as an effective preventive strategy to combat P acnes biofilms. P acnes biofilm formation on an unloaded synthetic calcium sulfate (CaSO 4 ) bone void filler cement bead was evaluated by scanning electron microscopy over a period of 14 days. Beads loaded with tobramycin alone or vancomycin alone (as comparative controls) and beads loaded with a vancomycin-tobramycin dual treatment were assessed for their ability to eradicate planktonic P acnes, prevent biofilm formation, and eradicate preformed biofilms using a combination of viable-cell counts, confocal microscopy, and scanning electron microscopy. P acnes surface colonization and biofilm formation on unloaded CaSO 4 beads was slow. Beads loaded with antibiotics were able to kill planktonic cultures of 10 6  colony-forming units/mL, prevent bacterial colonization, and significantly reduce biofilm formation over periods of weeks. Complete eradication of established biofilms was achieved with a contact time of 1 week. This study demonstrates that antibiotic-loaded CaSO 4 beads may represent an effective antibacterial and antibiofilm strategy to combat prosthetic infections in which P acnes is involved. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Formation mechanism of Ruddlesden-Popper-type antiphase boundaries during the kinetically limited growth of Sr rich SrTiO3 thin films

PubMed Central

Xu, Chencheng; Du, Hongchu; van der Torren, Alexander J. H.; Aarts, Jan; Jia, Chun-Lin; Dittmann, Regina

2016-01-01

We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction. With progressive SrTiO3 growth, islands with thermodynamically stable SrO rock-salt structure are formed, coexisting with TiO2 terminated islands. During the overgrowth of these thermodynamically stable islands, both lateral as well as vertical Ruddlesden-Popper-type anti-phase boundaries are formed, accommodating the Sr excess of the SrTiO3 film. We suggest the formation of thermodynamically stable SrO rock-salt structures as origin for the formation of Ruddlesden-Popper-type antiphase boundaries, which are as a result of kinetic limitations confined to certain regions on the surface. PMID:27922069

Formation mechanism of Ruddlesden-Popper-type antiphase boundaries during the kinetically limited growth of Sr rich SrTiO3 thin films

NASA Astrophysics Data System (ADS)

Xu, Chencheng; Du, Hongchu; van der Torren, Alexander J. H.; Aarts, Jan; Jia, Chun-Lin; Dittmann, Regina

2016-12-01

We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction. With progressive SrTiO3 growth, islands with thermodynamically stable SrO rock-salt structure are formed, coexisting with TiO2 terminated islands. During the overgrowth of these thermodynamically stable islands, both lateral as well as vertical Ruddlesden-Popper-type anti-phase boundaries are formed, accommodating the Sr excess of the SrTiO3 film. We suggest the formation of thermodynamically stable SrO rock-salt structures as origin for the formation of Ruddlesden-Popper-type antiphase boundaries, which are as a result of kinetic limitations confined to certain regions on the surface.

Vertically grown nanowire crystals of dibenzotetrathienocoronene (DBTTC) on large-area graphene

DOE PAGES

Kim, B.; Chiu, C. -Y.; Kang, S. J.; ...

2016-06-01

Here we demonstrate controlled growth of vertical organic crystal nanowires on single layer graphene. Using Scanning Electron Microscopy (SEM), high-resolution transition electron microscopy (TEM), and Grazing Incidence X-ray Diffraction (GIXD), we probe the microstructure and morphology of dibenzotetrathienocoronene (DBTTC) nanowires epitaxially grown on graphene. The investigation is performed at both the ensemble and single nanowire level, and as function of growth parameters, providing insight of and control over the formation mechanism. Finally, the size, density and height of the nanowires can be tuned via growth conditions, opening new avenues for tailoring three-dimensional (3-D) nanostructured architectures for organic electronics with improvedmore » functional performance.« less

Synthesis, Structural Characterization, and Growth Mechanism of Li 1+x V 3 O 8 Submicron Fibers for Lithium-Ion Batteries

DOE PAGES

Yue, Shiyu; Li, Jing; Wang, Lei; ...

2018-03-05

Here, we report on the synthesis of submicron Li 1+xV 3O 8 fibers through a facile mixed ethanol/water solution-mediated solvothermal route in the absence of surfactants. All the raw materials used are commercially available, relatively inexpensive, and low-toxic, and these can be handled in an ambient atmosphere, rendering this synthetic route as reasonably facile and efficient. To ensure a desirable and acceptable sample crystallinity and purity, we introduced a postannealing treatment at 500°C. The monoclinic phase formation of the fiber sample was probed in detail using a series of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-raymore » photoelectron spectroscopy, high resolution transmission electron microscopy, and selected area electron diffraction measurements. Both morphology and chemical composition could be carefully and systematically tuned in terms of generating a class of novel, pure, and well-defined motifs of Li 1+xV 3O 8. A plausible mechanism for the formation of submicron-diameter fibers has been discussed in addition to the expected phase transformation within our Li-V-O materials. Our comprehensive study should provide for needed fundamental insights into putting forth a viable synthesis strategy for the generation of well-defined morphological variants of layered oxide materials for battery applications.« less

Synthesis, Structural Characterization, and Growth Mechanism of Li 1+x V 3 O 8 Submicron Fibers for Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Shiyu; Li, Jing; Wang, Lei

Here, we report on the synthesis of submicron Li 1+xV 3O 8 fibers through a facile mixed ethanol/water solution-mediated solvothermal route in the absence of surfactants. All the raw materials used are commercially available, relatively inexpensive, and low-toxic, and these can be handled in an ambient atmosphere, rendering this synthetic route as reasonably facile and efficient. To ensure a desirable and acceptable sample crystallinity and purity, we introduced a postannealing treatment at 500°C. The monoclinic phase formation of the fiber sample was probed in detail using a series of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-raymore » photoelectron spectroscopy, high resolution transmission electron microscopy, and selected area electron diffraction measurements. Both morphology and chemical composition could be carefully and systematically tuned in terms of generating a class of novel, pure, and well-defined motifs of Li 1+xV 3O 8. A plausible mechanism for the formation of submicron-diameter fibers has been discussed in addition to the expected phase transformation within our Li-V-O materials. Our comprehensive study should provide for needed fundamental insights into putting forth a viable synthesis strategy for the generation of well-defined morphological variants of layered oxide materials for battery applications.« less

Time dependent changes in Schottky barrier mapping of the W/Si(001) interface utilizing ballistic electron emission microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durcan, Chris A.; Balsano, Robert; LaBella, Vincent P., E-mail: vlabella@albany.edu

2015-06-28

The W/Si(001) Schottky barrier height is mapped to nanoscale dimensions using ballistic electron emission microscopy (BEEM) over a period of 21 days to observe changes in the interface electrostatics. Initially, the average spectrum is fit to a Schottky barrier height of 0.71 eV, and the map is uniform with 98% of the spectra able to be fit. After 21 days, the average spectrum is fit to a Schottky barrier height of 0.62 eV, and the spatial map changes dramatically with only 27% of the spectra able to be fit. Transmission electron microscopy shows the formation of an ultra-thin tungsten silicide at themore » interface, which increases in thickness over the 21 days. This increase is attributed to an increase in electron scattering and the changes are observed in the BEEM measurements. Interestingly, little to no change is observed in the I-V measurements throughout the 21 day period.« less

Single shot damage mechanism of Mo/Si multilayer optics under intense pulsed XUV-exposure.

PubMed

Khorsand, A R; Sobierajski, R; Louis, E; Bruijn, S; van Hattum, E D; van de Kruijs, R W E; Jurek, M; Klinger, D; Pelka, J B; Juha, L; Burian, T; Chalupsky, J; Cihelka, J; Hajkova, V; Vysin, L; Jastrow, U; Stojanovic, N; Toleikis, S; Wabnitz, H; Tiedtke, K; Sokolowski-Tinten, K; Shymanovich, U; Krzywinski, J; Hau-Riege, S; London, R; Gleeson, A; Gullikson, E M; Bijkerk, F

2010-01-18

We investigated single shot damage of Mo/Si multilayer coatings exposed to the intense fs XUV radiation at the Free-electron LASer facility in Hamburg - FLASH. The interaction process was studied in situ by XUV reflectometry, time resolved optical microscopy, and "post-mortem" by interference-polarizing optical microscopy (with Nomarski contrast), atomic force microscopy, and scanning transmission electron microcopy. An ultrafast molybdenum silicide formation due to enhanced atomic diffusion in melted silicon has been determined to be the key process in the damage mechanism. The influence of the energy diffusion on the damage process was estimated. The results are of significance for the design of multilayer optics for a new generation of pulsed (from atto- to nanosecond) XUV sources.

Germination and Outgrowth of Single Spores of Saccharomyces cerevisiae Viewed by Scanning Electron and Phase-Contrast Microscopy

PubMed Central

Rousseau, Paul; Halvorson, Harlyn O.; Bulla, Lee A.; Julian, Grant St.

1972-01-01

Single spores of Saccharomyces cerevisiae were examined during germination and outgrowth by scanning electron and phase-contrast microscopy. Also determined were changes in cell weight and light absorbance, trehalose utilization, and synthesis of protein and KOH-soluble carbohydrates. These studies reveal that development of the vegetative cell from a spore follows a definite sequence of events involving dramatic physical and chemical modifications. These changes are: initial rapid loss in cellular absorbance followed later by an abrupt gain in absorbance; reduction in cell weight and a subsequent progressive increase; modification of the spore surface with concomitant diminution in refractility; elongation of the cell and augmentation of surface irregularities; rapid decline in trehalose content of the cell accompanied by extensive formation of KOH-soluble carbohydrates; and bud formation. Images PMID:4551750

Formation of Widmanstätten Austenite in Strip Cast Grain-Oriented Silicon Steel

NASA Astrophysics Data System (ADS)

Song, Hong-Yu; Liu, Hai-Tao; Wang, Guo-Dong; Jonas, John J.

2017-04-01

The formation of Widmanstätten austenite was studied in strip cast grain-oriented silicon steel. The microstructure was investigated by optical microscopy and scanning electron microscopy. The orientations of the ferrite, Widmanstätten austenite, and martensite were determined using electron backscatter diffraction. The Widmanstätten austenite exhibits a lath-like shape and nucleates directly on the ferrite grain boundaries. This differs significantly from earlier work on duplex stainless steels. The orientation relationship between the Widmanstätten austenite and the parent ferrite is closer to Kurdjumov-Sachs than to Nishiyama-Wassermann. The ferrite boundaries migrate so as to accommodate the habit planes of the laths, leading to the presence of zigzag boundaries in the as-cast strip. Carbon partitioning into the Widmanstätten austenite and silicon partitioning into the parent ferrite were observed.

The Antibacterial Polyamide 6-ZnO Hierarchical Nanofibers Fabricated by Atomic Layer Deposition and Hydrothermal Growth

NASA Astrophysics Data System (ADS)

Wang, Zhengduo; Zhang, Li; Liu, Zhongwei; Sang, Lijun; Yang, Lizhen; Chen, Qiang

2017-06-01

In this paper, we report the combination of atomic layer deposition (ALD) with hydrothermal techniques to deposit ZnO on electrospun polyamide 6 (PA 6) nanofiber (NF) surface in the purpose of antibacterial application. The micro- and nanostructures of the hierarchical fibers are characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM). We find that NFs can grow into "water lily"- and "caterpillar"-like shapes, which depend on the number of ALD cycles and the hydrothermal reaction period. It is believed that the thickness of ZnO seed layer by ALD process and the period in hydrothermal reaction have the same importance in crystalline growth and hierarchical fiber formation. The tests of antibacterial activity demonstrate that the ZnO/PA 6 core-shell composite fabricated by the combination of ALD with hydrothermal are markedly efficient in suppressing bacteria survivorship.

Milligram-per-second femtosecond laser production of Se nanoparticle inks and ink-jet printing of nanophotonic 2D-patterns

NASA Astrophysics Data System (ADS)

Ionin, Andrey; Ivanova, Anastasia; Khmel'nitskii, Roman; Klevkov, Yury; Kudryashov, Sergey; Mel'nik, Nikolay; Nastulyavichus, Alena; Rudenko, Andrey; Saraeva, Irina; Smirnov, Nikita; Zayarny, Dmitry; Baranov, Anatoly; Kirilenko, Demid; Brunkov, Pavel; Shakhmin, Alexander

2018-04-01

Milligram-per-second production of selenium nanoparticles in water sols was realized through 7-W, 2 MHz-rate femtosecond laser ablation of a crystalline trigonal selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of the corresponding crater depths and topographies. Deposited selenium particles were inspected by scanning and transmission electron microscopy, while their hydrosols (nanoinks) were characterized by optical transmission, Raman and dynamic light scattering spectroscopy. 2D patterns and coatings were ink-jet printed on thin supported silver films and their bare silica glass substrates, as well as on IR-transparent CaF2 substrates, and characterized by electron microscopy, energy-dispersive x-ray spectroscopy, and broadband (vis-mid IR) transmission spectroscopy, exhibiting crystalline selenium nanoparticles with high refractive index as promising all-dielectric sensing building nanoblocks in nanophotonics.

Electron tomography and cryo-SEM characterization reveals novel ultrastructural features of host-parasite interaction during Chlamydia abortus infection.

PubMed

Wilkat, M; Herdoiza, E; Forsbach-Birk, V; Walther, P; Essig, A

2014-08-01

Chlamydia (C.) abortus is a widely spread pathogen among ruminants that can be transmitted to women during pregnancy leading to severe systemic infection with consecutive abortion. As a member of the Chlamydiaceae, C. abortus shares the characteristic feature of an obligate intracellular biphasic developmental cycle with two morphological forms including elementary bodies (EBs) and reticulate bodies (RBs). In contrast to other chlamydial species, C. abortus ultrastructure has not been investigated yet. To do so, samples were fixed by high-pressure freezing and processed by different electron microscopic methods. Freeze-substituted samples were analysed by transmission electron microscopy, scanning transmission electron microscopical tomography and immuno-electron microscopy, and freeze-fractured samples were analysed by cryo-scanning electron microscopy. Here, we present three ultrastructural features of C. abortus that have not been reported up to now. Firstly, the morphological evidence that C. abortus is equipped with the type three secretion system. Secondly, the accumulation and even coating of whole inclusion bodies by membrane complexes consisting of multiple closely adjacent membranes which seems to be a C. abortus specific feature. Thirdly, the formation of small vesicles in the periplasmic space of RBs in the second half of the developmental cycle. Concerning the time point of their formation and the fact that they harbour chlamydial components, these vesicles might be morphological correlates of an intermediate step during the process of redifferentiation of RBs into EBs. As this feature has also been shown for C. trachomatis and C. pneumoniae, it might be a common characteristic of the family of Chlamydiaceae.

Morphological Effect of the New Antifungal Agent ME1111 on Hyphal Growth of Trichophyton mentagrophytes, Determined by Scanning and Transmission Electron Microscopy.

PubMed

Nishiyama, Yayoi; Takahata, Sho; Abe, Shigeru

2017-01-01

The effects of ME1111, a novel antifungal agent, on the hyphal morphology and ultrastructure of Trichophyton mentagrophytes were investigated by using scanning and transmission electron microscopy. Structural changes, such as pit formation and/or depression of the cell surface, and degeneration of intracellular organelles and plasmolysis were observed after treatment with ME1111. Our results suggest that the inhibition of energy production by ME1111 affects the integrity and function of cellular membranes, leading to fungal cell death. Copyright © 2016 American Society for Microbiology.

Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

NASA Astrophysics Data System (ADS)

Kennedy, S. M.; Zheng, C. X.; Jesson, D. E.

2017-01-01

Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. Cylindrical symmetry of structures grown by droplet epitaxy is assumed in the simulations which reproduce the main features of the experimental MEM image contrast, demonstrating that droplet epitaxy can be studied in real-time. It is therefore confirmed that an inner ring forms at the droplet contact line and an outer ring (or skirt) occurs outside the droplet periphery. We believe that MEM combined with image simulations will be increasingly used to study the formation and growth of quantum structures.

Nanofibers formed through pi...pi stacking of the complexes of glucosyl-C2-salicyl-imine and phenylalanine: characterization by microscopy, modeling by molecular mechanics, and interaction by alpha-helical and beta-sheet proteins.

PubMed

Acharya, Amitabha; Ramanujam, Balaji; Mitra, Atanu; Rao, Chebrolu P

2010-07-27

This paper deals with the self-assembly of the 1:1 complex of two different amphiphiles, namely, a glucosyl-salicyl-imino conjugate (L) and phenylalanine (Phe), forming nanofibers over a period of time through pi...pi interactions. Significant enhancement observed in the fluorescence intensity of L at approximately 423 nm band and the significant decrease observed in the absorbance of the approximately 215 nm band are some characteristics of this self-assembly. Matrix-assisted laser desorption ionization/time of flight titration carried out at different time intervals supports the formation of higher aggregates. Atomic force microscopy (AFM), transmission electron microscopy, and scanning electron miscroscopy results showed the formation of nanofibers for the solutions of L with phenylalanine. In dynamic light scattering measurements, the distribution of the particles extends to a higher diameter range over time, indicating a slow kinetic process of assembly. Similar spectral and microscopy studies carried out with the control molecules support the role of the amino acid moiety over the simple -COOH moiety as well as the side chain phenyl moiety in association with the amino acid, in the formation of these fibers. All these observations support the presence of pi...pi interactions between the initially formed 1:1 complexes leading to the fiber formation. The aggregation of 1:1 complexes leading to fibers followed by the formation of bundles has been modeled by molecular mechanics studies. Thus the fiber formation with L is limited to phenylalanine and not to any other naturally occurring amino acid and hence a polymer composed of two different biocompatible amphiphiles. AFM studies carried out between the fiber forming mixture and proteins resulted in the observation that only BSA selectively adheres to the fiber among the three alpha-helical and two beta-sheet proteins studied and hence may be of use in some medical applications.

Substrate decomposition in galvanic displacement reaction: Contrast between gold and silver nanoparticle formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Tapas; Satpati, Biswarup, E-mail: biswarup.satpati@saha.ac.in; Kabiraj, D.

We have investigated substrate decomposition during formation of silver and gold nanoparticles in galvanic displacement reaction on germanium surfaces. Silver and gold nanoparticles were synthesized by electroless deposition on sputter coated germanium thin film (∼ 200 nm) grown initially on silicon substrate. The nanoparticles formation and the substrate corrosion were studied using scanning transmission electron microscopy (STEM) and the energy dispersive X-ray (EDX) spectroscopy.

Mast Cell Proteases 6 and 7 Stimulate Angiogenesis by Inducing Endothelial Cells to Release Angiogenic Factors

PubMed Central

de Souza, Devandir Antonio; Borges, Antonio Carlos; Santana, Ana Carolina; Oliver, Constance; Jamur, Maria Célia

2015-01-01

Mast cell proteases are thought to be involved with tumor progression and neo-vascularization. However, their exact role is still unclear. The present study was undertaken to further elucidate the function of specific subtypes of recombinant mouse mast cell proteases (rmMCP-6 and 7) in neo-vascularization. SVEC4-10 cells were cultured on Geltrex® with either rmMCP-6 or 7 and tube formation was analyzed by fluorescence microscopy and scanning electron microscopy. Additionally, the capacity of these proteases to induce the release of angiogenic factors and pro and anti-angiogenic proteins was analyzed. Both rmMCP-6 and 7 were able to stimulate tube formation. Scanning electron microscopy showed that incubation with the proteases induced SVEC4-10 cells to invade the gel matrix. However, the expression and activity of metalloproteases were not altered by incubation with the mast cell proteases. Furthermore, rmMCP-6 and rmMCP-7 were able to induce the differential release of angiogenic factors from the SVEC4-10 cells. rmMCP-7 was more efficient in stimulating tube formation and release of angiogenic factors than rmMCP-6. These results suggest that the subtypes of proteases released by mast cells may influence endothelial cells during in vivo neo-vascularization. PMID:26633538

Microscopic analysis of Spodoptera frugiperda (Lepidoptera: Noctuidae) embryonic development before and after treatment with azadirachtin, lufenuron, and deltamethrin.

PubMed

Correia, Alicely A; Wanderley-Teixeira, Valéria; Teixeira, Alvaro A C; Oliveira, José V; Gonçalves, Gabriel G A; Cavalcanti, MaríIia G S; Brayner, Fábio A; Alves, Luiz C

2013-04-01

The botanical insecticides, growth regulators, and pyrethroids have an effect on the biology of Spodoptera frugiperda (Smith). However, no emphasis has been given to the effect of these insecticides on embryonic development of insects, in histological level. Thus, this research aimed to examine by light and scanning electron microscopy S. frugiperda eggs and to describe the embryonic development, before and after immersion treatment, using commercial concentrations and lower concentrations than commercial ones, of the compounds lufenuron (Match), azadirachtin (AzaMax), and deltamethrin (Decis-positive control). For light microscopy semithin sections of eggs were used, and for scanning electron microscopy, images of the surface of eggs, treated and untreated with insecticides. The morphological characteristics of S. frugiperda eggs, in general, were similar to those described in the literature for most of the insects in the order Lepidoptera. Spherical eggs slightly flattened at the poles, with chorion, yolk, vitelline membrane, and embryo formation. In both microscopic analysis, we observed that insecticides acted immediately and independent of concentration, resulting absence, or incomplete embryo, presented yolk granules widely dispersed, without vitellophage formation, chorion disintegration, disorganized blastoderm, presenting vacuoles, yolk region with amorphous cells, and formation of completely uncharacterized appendages. Thus, we conclude that the compounds lufenuron and azadirachtin interfere on S. frugiperda embryonic development.

Scanning tunneling microscopy of the formation, transformation, and property of oligothiophene self-organizations on graphite and gold surfaces.

PubMed

Yang, Zhi-Yong; Zhang, Hui-Min; Yan, Cun-Ji; Li, Shan-Shan; Yan, Hui-Juan; Song, Wei-Guo; Wan, Li-Jun

2007-03-06

Two alkyl-substituted dual oligothiophenes, quarterthiophene (4T)-trimethylene (tm)-octithiophene (8T) and 4T-tm-4T, were used to fabricate molecular structures on highly oriented pyrolytic graphite and Au(111) surfaces. The resulted structures were investigated by scanning tunneling microscopy. The 4T-tm-8T and 4T-tm-4T molecules self-organize into long-range ordered structures with linear and/or quasi-hexagonal patterns on highly oriented pyrolytic graphite at ambient temperature. Thermal annealing induced a phase transformation from quasi-hexagonal to linear in 4T-tm-8T adlayer. The molecules adsorbed on Au(111) surface in randomly folded and linear conformation. Based on scanning tunneling microscopy results, the structural models for different self-organizations were proposed. Scanning tunneling spectroscopy measurement showed the electronic property of individual molecules in the patterns. These results are significant in understanding the chemistry of molecular structure, including its formation, transformation, and electronic properties. They also help to fabricate oligothiophene assemblies with desired structures for future molecular devices.

Microstructural evolution during aging at 800 °C and its effect on the magnetic behavior of UNS S32304 lean duplex stainless steel

NASA Astrophysics Data System (ADS)

Dille, J.; Areiza, M. C. L.; Tavares, S. S. M.; Pereira, G. R.; De Almeida, L. H.; Rebello, J. M. A.

2017-03-01

Duplex stainless steels are high strength and corrosion resistant alloys extensively used in chemical and petrochemical industries. However, exposition to temperatures in the range 300-1000 °C leads to precipitation of different phases having a detrimental effect on the mechanical properties and on the corrosion resistance of the alloy. In this work, the microstructural evolution during aging of a UNS S32304 lean duplex stainless steel was investigated by scanning electron microscopy, transmission electron microscopy and magnetic force microscopy. Formation of secondary austenite as well as Cr2N and Cr23C6 precipitation and, consequently, a decrease of ferrite volume fraction were observed. EDX analysis indicated that secondary austenite is depleted in chromium which is detrimental to the corrosion resistance of the alloy. A variation of magnetic properties and Eddy current measurement parameters during aging was simultaneously detected and can be explained by the decrease of ferrite volume content. Therefore, Eddy current non-destructive testing can be successfully applied to detect the formation of deleterious phases during aging.

Flux Growth of Highly Crystalline Photocatalytic BaTiO3 Particle Layers on Porous Titanium Sponge Substrate and Insights into the Formation Mechanism

NASA Astrophysics Data System (ADS)

Wang, Q.; Li, B.

2017-09-01

A unique architecture of idiomorphic and highly crystalline BaTiO3 particle layers directly grown on a porous titanium sponge substrate was successfully achieved for the first time using a facile molten salt method at a relatively low temperature of 700 °C. Specifically, the low-melting KCl-NaCl eutectic salts and barium hydroxide octahydrate were employed as the reaction medium and barium source, respectively. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectrophotometry were used to characterize the structure, morphology and optical property of the obtained samples. The results revealed that the flux-grown tetragonal BaTiO3 products had well-defined and uniform morphology with an average size of 300 nm and a band gap of ∼3.16 eV. Based on XRD, EDS, SEM, and TEM, the possible formation mechanism responsible for the well-developed architecture of BaTiO3 particle layers was proposed and discussed. Furthermore, the photocatalytic activity of the flux-grown BaTiO3 products for organic pollutant degradation under simulated sunlight irradiation was also investigated.

Evaluation of environmental scanning electron microscopy for analysis of Proteus mirabilis crystalline biofilms in situ on urinary catheters

PubMed Central

Holling, Nina; Dedi, Cinzia; Jones, Caroline E; Hawthorne, Joseph A; Hanlon, Geoffrey W; Salvage, Jonathan P; Patel, Bhavik A; Barnes, Lara M; Jones, Brian V

2014-01-01

Proteus mirabilis is a common cause of catheter-associated urinary tract infections and frequently leads to blockage of catheters due to crystalline biofilm formation. Scanning electron microscopy (SEM) has proven to be a valuable tool in the study of these unusual biofilms, but entails laborious sample preparation that can introduce artefacts, undermining the investigation of biofilm development. In contrast, environmental scanning electron microscopy (ESEM) permits imaging of unprocessed, fully hydrated samples, which may provide much insight into the development of P. mirabilis biofilms. Here, we evaluate the utility of ESEM for the study of P. mirabilis crystalline biofilms in situ, on urinary catheters. In doing so, we compare this to commonly used conventional SEM approaches for sample preparation and imaging. Overall, ESEM provided excellent resolution of biofilms formed on urinary catheters and revealed structures not observed in standard SEM imaging or previously described in other studies of these biofilms. In addition, we show that energy-dispersive X-ray spectroscopy (EDS) may be employed in conjunction with ESEM to provide information regarding the elemental composition of crystalline structures and demonstrate the potential for ESEM in combination with EDS to constitute a useful tool in exploring the mechanisms underpinning crystalline biofilm formation. PMID:24786314

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters.

PubMed

Torre, A La; Åhlgren, E H; Fay, M W; Ben Romdhane, F; Skowron, S T; Parmenter, C; Davies, A J; Jouhannaud, J; Pourroy, G; Khlobystov, A N; Brown, P D; Besley, E; Banhart, F

2016-08-11

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

Self-formation of a nanonet of fluorinated carbon nanowires on the Si surface by combined etching in fluorine-containing plasma

NASA Astrophysics Data System (ADS)

Amirov, I. I.; Gorlachev, E. S.; Mazaletskiy, L. A.; Izyumov, M. O.; Alov, N. V.

2018-03-01

In this work, we report a technique of the self-formation of a nanonet of fluorinated carbon nanowires on the Si surface using a combined etching in fluorine-containing C4F8/Ar and SF6 plasmas. Using scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy, we show that after the etching of Si in the C4F8/Ar plasma, a fluorinated carbon film of nanometer-scale thickness is formed on its surface and its formation accelerates at elevated temperatures. After a subsequent short-term etching in the SF6 plasma, the film is modified into a nanonet of self-formed fluorinated carbon nanowires.

Reactive Brazing of Carbon-Carbon Composites to Titanium

NASA Technical Reports Server (NTRS)

Shpargel, Tarah; Singh, M.; Morscher, Gregory; Asthana, Rajiv

2004-01-01

The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSil. The joint microstructures were examined using optical microscopy, and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint and possible metallurgical bond formation via interdiffusion, which led to good wetting and spreading.

Active Metal Brazing of Carbon-Carbon Composites to Titanium

NASA Technical Reports Server (NTRS)

Singh, M.; Shpargel, T. P.; Morscher, G.; Asthana, R.

2004-01-01

The Ti-metal/C-C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSil. The joint microstructures were examined using optical microscopy, and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results of the microstructure analysis indicate solute redistribution across the joint which led to good wetting, spreading, and metallurgical bond formation via interdiffusion.

Microscopic evolution of dielectric nanoparticles at different calcination temperatures synthesized via sol-gel auto-combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adil, Muhammad, E-mail: muhammadadil86@hotmail.com; Zaid, Hasnah Mohd, E-mail: hasnamz@petronas.com.my; Chuan, Lee Kean, E-mail: lee.kc@petronas.com.my

2015-07-22

Dielectric nano powder synthesis is carried by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders is investigated through the detailed transmission electron microscopy (TEM), revealed the crystallographic alterations and morphological information even at lattice scale. From specific area electron diffraction (SAED) pattern, has specified the d-spacing and corresponding planes supported by the observed lattice fringes. The morphological characterization of nanoparticles is performed through field-emission scanning electron microscopy (FESEM), exhibiting the increment in particle size due to agglomeration with the increase in annealing temperature. Furthermore, EDX pattern has been used to verify themore » formation of nanoparticles by revealing the presence of required elements.« less

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources.

PubMed

Sobierajski, R; Bruijn, S; Khorsand, A R; Louis, E; van de Kruijs, R W E; Burian, T; Chalupsky, J; Cihelka, J; Gleeson, A; Grzonka, J; Gullikson, E M; Hajkova, V; Hau-Riege, S; Juha, L; Jurek, M; Klinger, D; Krzywinski, J; London, R; Pelka, J B; Płociński, T; Rasiński, M; Tiedtke, K; Toleikis, S; Vysin, L; Wabnitz, H; Bijkerk, F

2011-01-03

We investigated the damage mechanism of MoN/SiN multilayer XUV optics under two extreme conditions: thermal annealing and irradiation with single shot intense XUV pulses from the free-electron laser facility in Hamburg - FLASH. The damage was studied "post-mortem" by means of X-ray diffraction, interference-polarizing optical microscopy, atomic force microscopy, and scanning transmission electron microscopy. Although the timescale of the damage processes and the damage threshold temperatures were different (in the case of annealing it was the dissociation temperature of Mo2N and in the case of XUV irradiation it was the melting temperature of MoN) the main damage mechanism is very similar: molecular dissociation and the formation of N2, leading to bubbles inside the multilayer structure.

In Vitro Self-Assembly of the Light Harvesting Pigment-Protein LH2 Revealed by Ultrafast Spectroscopy and Electron Microscopy

PubMed Central

Schubert, Axel; Stenstam, Anna; Beenken, Wichard J. D.; Herek, Jennifer L.; Cogdell, Richard; Pullerits, Tõnu; Sundström, Villy

2004-01-01

Controlled ensemble formation of protein-surfactant systems provides a fundamental concept for the realization of nanoscale devices with self-organizing capability. In this context, spectroscopic monitoring of pigment-containing proteins yields detailed structural information. Here we have studied the association behavior of the bacterial light-harvesting protein LH2 from Rhodobacter spheroides in an n,n-dimethyldodecylamine-n-oxide/water environment. Time-resolved studies of the excitation annihilation yielded information about aggregate sizes and packing of the protein complexes therein. The results are compared to transmission electron microscopy images of instantaneously frozen samples. Our data indicate the manifestation of different phases, which are discussed with respect to the thermodynamic equilibrium in ternary protein-surfactant-water systems. Accordingly, by varying the concentration the formation of different types of aggregates can be controlled. Conditions for the appearance of isolated LH2 complexes are defined. PMID:15041674

Transmission electron microscopy study of the formation of epitaxial CoSi2/Si (111) by a room-temperature codeposition technique

NASA Technical Reports Server (NTRS)

D'Anterroches, Cecile; Yakupoglu, H. Nejat; Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

1988-01-01

Co and Si have been codeposited on Si (111) substrates near room temperature in a stoichiometric 1:2 ratio in a molecular beam epitaxy system. Annealing of these deposits yields high-quality single-crystal CoSi2 layers. Transmission electron microscopy has been used to examine as-deposited layers and layers annealed at 300, 500, and 600 C. Single-crystal epitaxial grains of CoSi2 embedded in a matrix of amorphous Co/Si are observed in as-deposited samples, while the layer is predominantly single-crystal, inhomogeneously strained CoSi2 at 300 C. At 600 C, a homogeneously strained single-crystal layer with a high density of pinholes is observed. In contrast to other solid phase epitaxy techniques used to grow CoSi2 on Si (111), no intermediate silicide phases are observed prior to the formation of CoSi2.

Bio-camouflage of anatase nanoparticles explored by in situ high-resolution electron microscopy.

PubMed

Ribeiro, Ana R; Mukherjee, Arijita; Hu, Xuan; Shafien, Shayan; Ghodsi, Reza; He, Kun; Gemini-Piperni, Sara; Wang, Canhui; Klie, Robert F; Shokuhfar, Tolou; Shahbazian-Yassar, Reza; Borojevic, Radovan; Rocha, Luis A; Granjeiro, José M

2017-08-03

While titanium is the metal of choice for most prosthetics and inner body devices due to its superior biocompatibility, the discovery of Ti-containing species in the adjacent tissue as a result of wear and corrosion has been associated with autoimmune diseases and premature implant failures. Here, we utilize the in situ liquid cell transmission electron microscopy (TEM) in a liquid flow holder and graphene liquid cells (GLCs) to investigate, for the first time, the in situ nano-bio interactions between titanium dioxide nanoparticles and biological medium. This imaging and spectroscopy methodology showed the process of formation of an ionic and proteic bio-camouflage surrounding Ti dioxide (anatase) nanoparticles that facilitates their internalization by bone cells. The in situ understanding of the mechanisms of the formation of the bio-camouflage of anatase nanoparticles may contribute to the definition of strategies aimed at the manipulation of these NPs for bone regenerative purposes.

Strain dynamics during La{sub 2}O{sub 3}/Lu{sub 2}O{sub 3} superlattice and alloy formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Proessdorf, André; Niehle, Michael; Grosse, Frank

The dynamics of strain relaxation and intermixing during molecular beam epitaxy of La{sub 2}O{sub 3} and Lu{sub 2}O{sub 3} superlattices and alloys consisting of both binaries on Si(111) have been studied by real-time in situ grazing incidence x-ray diffraction and high resolution transmission electron microscopy. The presence of both hexagonal and cubic polymorphs of La{sub 2}O{sub 3} influences the epitaxial formation within the superlattice. The process of strain relaxation is closely related to the presence of a (La,Lu){sub 2}O{sub 3} alloy adopting a cubic symmetry. It is formed by interdiffusion of La and Lu atoms reducing internal lattice mismatch withinmore » the superlattice. An interface thickness dominated by interdiffusion regions of about 3 monolayers is determined by high-angle annular dark field scanning transmission electron microscopy.« less

Electron Microscopy Imaging of Zinc Soaps Nucleation in Oil Paint.

PubMed

Hermans, Joen; Osmond, Gillian; van Loon, Annelies; Iedema, Piet; Chapman, Robyn; Drennan, John; Jack, Kevin; Rasch, Ronald; Morgan, Garry; Zhang, Zhi; Monteiro, Michael; Keune, Katrien

2018-06-04

Using the recently developed techniques of electron tomography, we have explored the first stages of disfiguring formation of zinc soaps in modern oil paintings. The formation of complexes of zinc ions with fatty acids in paint layers is a major threat to the stability and appearance of many late 19th and early 20th century oil paintings. Moreover, the occurrence of zinc soaps in oil paintings leading to defects is disturbingly common, but the chemical reactions and migration mechanisms leading to large zinc soap aggregates or zones remain poorly understood. State-of-the-art scanning (SEM) and transmission (TEM) electron microscopy techniques, primarily developed for biological specimens, have enabled us to visualize the earliest stages of crystalline zinc soap growth in a reconstructed zinc white (ZnO) oil paint sample. In situ sectioning techniques and sequential imaging within the SEM allowed three-dimensional tomographic reconstruction of sample morphology. Improvements in the detection and discrimination of backscattered electrons enabled us to identify local precipitation processes with small atomic number contrast. The SEM images were correlated to low-dose and high-sensitivity TEM images, with high-resolution tomography providing unprecedented insight into the structure of nucleating zinc soaps at the molecular level. The correlative approach applied here to study phase separation, and crystallization processes specific to a problem in art conservation creates possibilities for visualization of phase formation in a wide range of soft materials.

Transmission electron microscopy of the preclinical phase of experimental phytophotodermatitis.

PubMed

Almeida, Hiram Larangeira de; Sotto, Miriam Nakagami; Castro, Luis Antonio Suita de; Rocha, Nara Moreira

2008-06-01

To examine the epidermis in induced phytophotodermatitis using transmission electron microscopy in order to detect histologic changes even before lesions are visible by light microscopy. In the first six hours after the experimental induction of phytophotodermatitis, no changes are detectable by light microscopy. Only after 24 hours can keratinocyte necrosis and epidermal vacuolization be detected histologically, and blisters form by 48 hours. The dorsum of four adult rats (Rattus norvegicus) was manually epilated. After painting the right half of the rat with the peel juice of Tahiti lemon, they were exposed to sunlight for eight minutes under general anesthesia. The left side was used as the control and exposed to sunlight only. Biopsies were performed immediately after photoinduction and one and two hours later, and the tissue was analyzed by transmission electron microscopy. No histological changes were seen on the control side. Immediately after induction, vacuolization in keratinocytes was observed. After one hour, desmosomal changes were also observed in addition to vacuolization. Keratin filaments were not attached to the desmosomal plaque. Free desmosomes and membrane ruptures were also seen. At two hours after induction, similar changes were found, and granular degeneration of keratin was also observed. The interaction of sunlight and psoralens generates a photoproduct that damages keratinocyte proteins, leading to keratinocyte necrosis and blister formation. Transmission electron microscopy can detect vacuolization, lesions of the membrane, and desmosomes in the first two hours after experimental induction of phytophotodermatitis.

Shape-controlled synthesis and properties of dandelion-like manganese sulfide hollow spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Wei; State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083; Chen, Gen

2012-09-15

Graphical abstract: Dandelion-like MnS hollow spheres assembled with nanorods could be successfully synthesized in large quantities through a simple and convenient hydrothermal synthetic method under mild conditions using soluble hydrated manganese chloride as Mn source, L-cysteine as both a precipitator and complexing reagent. The dandelion-like MnS hollow spheres might have potential applications in microdevices and magnetic cells. Highlights: ► MnS hollow spheres assembled with nanorods could be synthesized. ► The morphologies and sizes of final products could be controlled. ► Possible formation mechanism of MnS hollow spheres is proposed. -- Abstract: Dandelion-like gamma-manganese (II) sulfide (MnS) hollow spheres assembled withmore » nanorods have been prepared via a hydrothermal process in the presence of L-cysteine and polyvinylpyrrolidone (PVP). L-cysteine was employed as not only sulfur source, but also coordinating reagent for the synthesis of dandelion-like MnS hollow spheres. The morphology, structure and properties of as-prepared products have been investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM) and photoluminescence spectra (PL). The probable formation mechanism of as-prepared MnS hollow spheres was discussed on the basis of the experimental results. This strategy may provide an effective method for the fabrication of other metal sulfides hollow spheres.« less

Spatial Complexity Due to Bulk Electronic Liquid Crystals in Superconducting Dy-Bi2212

NASA Astrophysics Data System (ADS)

Carlson, Erica; Phillabaum, Benjamin; Dahmen, Karin

2012-02-01

Surface probes such as scanning tunneling microscopy (STM) have detected complex electronic patterns at the nanoscale in many high temperature superconductors. In cuprates, the pattern formation is associated with the pseudogap phase, a precursor to the high temperature superconducting state. Rotational symmetry breaking of the host crystal (i.e. from C4 to C2) in the form of electronic nematicity has recently been proposed as a unifying theme of the pseudogap phase [Lawler Nature 2010]. However, the fundamental physics governing the nanoscale pattern formation has not yet been identified. Here we use universal cluster properties extracted from STM studies of cuprate superconductors to identify the funda- mental physics controlling the complex pattern formation. We find that due to a delicate balance between disorder, interactions, and material anisotropy, the rotational symmetry breaking is fractal in nature, and that the electronic liquid crystal extends throughout the bulk of the material.

Phase change in CoTi2 induced by MeV electron irradiation

NASA Astrophysics Data System (ADS)

Zensho, Akihiro; Sato, Kazuhisa; Yasuda, Hidehiro; Mori, Hirotaro

2018-07-01

The phase change induced by MeV electron irradiation in the intermetallic compound E93-CoTi2 was investigated using high-voltage electron microscopy. Under MeV electron irradiation, CoTi2 was first transformed into an amorphous phase and, with continued irradiation, crystallite formation in the amorphous phase (i.e. formation of crystallites of a solid-solution phase within the amorphous phase) was induced. The critical temperature for amorphisation was around 250 K. The total dose (dpa) required for crystallite formation (i.e. that required for partial crystallisation) was high (i.e. 27-80 dpa) and, even after prolonged irradiation, the amorphous phase was retained in the irradiated sample. Such partial crystallisation behaviour of amorphous Co33Ti67 was clearly different from the crystallisation behaviour (i.e. amorphous-to-solid solution, polymorphous transformation) of amorphous Cr67Ti33 reported in the literature. A possible cause of the difference is discussed.

Green synthesis of silver nanoparticles using tannins

NASA Astrophysics Data System (ADS)

Raja, Pandian Bothi; Rahim, Afidah Abdul; Qureshi, Ahmad Kaleem; Awang, Khalijah

2014-09-01

Colloidal silver nanoparticles were prepared by rapid green synthesis using different tannin sources as reducing agent viz. chestnut (CN), mangrove (MG) and quebracho (QB). The aqueous silver ions when exposed to CN, MG and QB tannins were reduced which resulted in formation of silver nanoparticles. The resultant silver nanoparticles were characterized using UV-Visible, X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and transmission electron microscopy (TEM) techniques. Furthermore, the possible mechanism of nanoparticles synthesis was also derived using FT-IR analysis. Spectroscopy analysis revealed that the synthesized nanoparticles were within 30 to 75 nm in size, while XRD results showed that nanoparticles formed were crystalline with face centered cubic geometry.

Polyol-mediated thermolysis process for the synthesis of MgO nanoparticles and nanowires

NASA Astrophysics Data System (ADS)

Subramania, A.; Vijaya Kumar, G.; Sathiya Priya, A. R.; Vasudevan, T.

2007-06-01

The main aim of this work is to prepare MgO nanoparticles and nanowires by a novel polyol-mediated thermolysis (PMT) process. The influence of different mole concentration of magnesium acetate, polyvinyl pyrrolidone (PVP; capping agent) and ethylene glycol (EG; solvent as well as reducing agent) on the formation of nanoparticles and nanowires and the effect of calcination on the crystalline size of the samples were also examined. The resultant oxide structure, thermal behaviour, size and shape have been studied using x-ray diffraction (XRD) studies, thermal (TG/DTA) analysis and scanning electron microscopy (SEM)/transmission electron microscopy (TEM) respectively.

In search of the elusive IrB 2: Can mechanochemistry help?

DOE PAGES

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; ...

2015-10-20

We produced hexagonal ReB 2-type IrB 2 diboride and orthorhombic IrB monoboride phases, that were previously unknown and saw them produced by mechanochemical syntheses. High energy ball milling of elemental Ir and B powder for 30 h, followed by annealing of the powder at 1050 °C for 48 h, resulted in the formation of the desired phases. Both traditional laboratory and high resolution synchrotron X-ray diffraction (XRD) analyses were used for phase identification of the synthesized powder. Additionally, scanning electron microscopy and transmission electron microscopy were employed, along with XRD, to further characterize the microstructure of the phases produced.

Hydrothermal synthesis of uniform WO{sub 3} submicrospheres using thiourea as an assistant agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, X.T.; Xiao, F.; Lin, J.L.

2010-08-15

Nearly monodisperse tungsten trioxide submicrospheres have been synthesized with tungsten acid and HCl as the starting materials and thiourea as a structure-directing agent through a facile hydrothermal method. The obtained products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray, respectively. The results show that the WO{sub 3} submicrospheres are monodisperse with a diameter of about 800-1000 nm. The morphology of the products gradually evolutes from rods to spheres with increase of the reaction time. The formation mechanism of the WO{sub 3} submicrospheres is primarily discussed.

In search of the elusive IrB 2: Can mechanochemistry help?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina

We produced hexagonal ReB 2-type IrB 2 diboride and orthorhombic IrB monoboride phases, that were previously unknown and saw them produced by mechanochemical syntheses. High energy ball milling of elemental Ir and B powder for 30 h, followed by annealing of the powder at 1050 °C for 48 h, resulted in the formation of the desired phases. Both traditional laboratory and high resolution synchrotron X-ray diffraction (XRD) analyses were used for phase identification of the synthesized powder. Additionally, scanning electron microscopy and transmission electron microscopy were employed, along with XRD, to further characterize the microstructure of the phases produced.

Effect of deep cryogenic treatment on the formation of nano-sized carbides and the wear behavior of D2 tool steel

NASA Astrophysics Data System (ADS)

Amini, Kamran; Akhbarizadeh, Amin; Javadpour, Sirus

2012-09-01

The effect of deep cryogenic treatment on the microstructure, hardness, and wear behavior of D2 tool steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), hardness test, pin-on-disk wear test, and the reciprocating pin-on-flat wear test. The results show that deep cryogenic treatment eliminates retained austenite, makes a better carbide distribution, and increases the carbide content. Furthermore, some new nano-sized carbides form during the deep cryogenic treatment, thereby increasing the hardness and improving the wear behavior of the samples.

One-Pot Silver Nanoring Synthesis

NASA Astrophysics Data System (ADS)

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2010-03-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-pot silver nanoring synthesis.

PubMed

Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

2009-12-16

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

One-Pot Silver Nanoring Synthesis

PubMed Central

2010-01-01

Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation. PMID:20672109

Transmission electron microscopy characterization of the erbium silicide formation process using a Pt/Er stack on a silicon-on-insulator substrate.

PubMed

Łaszcz, A; Katcki, J; Ratajczak, J; Tang, Xiaohui; Dubois, E

2006-10-01

Very thin erbium silicide layers have been used as source and drain contacts to n-type Si in low Schottky barrier MOSFETs on silicon-on-insulator substrates. Erbium silicide is formed by a solid-state reaction between the metal and silicon during annealing. The influence of annealing temperature (450 degrees C, 525 degrees C and 600 degrees C) on the formation of an erbium silicide layer in the Pt/Er/Si/SiO(2)/Si structure was analysed by means of cross-sectional transmission electron microscopy. The Si grains/interlayer formed at the interface and the presence of Si grains within the Er-related layer constitute proof that Si reacts with Er in the presence of a Pt top layer in the temperature range 450-600 degrees C. The process of silicide formation in the Pt/Er/Si structure differs from that in the Er/Si structure. At 600 degrees C, the Pt top layer vanishes and a (Pt-Er)Si(x) system is formed.

Formation of insulin amyloid fibrils followed by FTIR simultaneously with CD and electron microscopy.

PubMed Central

Bouchard, M.; Zurdo, J.; Nettleton, E. J.; Dobson, C. M.; Robinson, C. V.

2000-01-01

Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and electron microscopy (EM) have been used simultaneously to follow the temperature-induced formation of amyloid fibrils by bovine insulin at acidic pH. The FTIR and CD data confirm that, before heating, insulin molecules in solution at pH 2.3 have a predominantly native-like alpha-helical structure. On heating to 70 degrees C, partial unfolding occurs and results initially in aggregates that are shown by CD and FT-IR spectra to retain a predominantly helical structure. Following this step, changes in the CD and FTIR spectra occur that are indicative of the extensive conversion of the molecular conformation from alpha-helical to beta-sheet structure. At later stages, EM shows the development of fibrils with well-defined repetitive morphologies including structures with a periodic helical twist of approximately 450 A. The results indicate that formation of fibrils by insulin requires substantial unfolding of the native protein, and that the most highly ordered structures result from a slow evolution of the morphology of the initially formed fibrillar species. PMID:11106169

Silver nanoparticle production by Rhizopus stolonifer and its antibacterial activity against extended spectrum {beta}-lactamase producing (ESBL) strains of Enterobacteriaceae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banu, Afreen; Rathod, Vandana, E-mail: drvandanarathod@rediffmail.com; Ranganath, E.

Highlights: {yields} Silver nanoparticle production by using Rhizopus stolonifer. {yields} Antibacterial activity of silver nanoparticles against extended spectrum {beta}-lactamase producing (ESBL) strains of Enterobacteriaceae. {yields} Synergistic effect of antibiotics with silver nanoparticles towards ESBL-strains. {yields} Characterization of silver nanoparticles made by UV-vis spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectroscopy, atomic force microscopy (AFM). -- Abstract: This report focuses on the synthesis of silver nanoparticles using the fungus, Rhizopus stolonifer and its antimicrobial activity. Research in nanotechnology highlights the possibility of green chemistry pathways to produce technologically important nanomaterials. Characterization of newly synthesized silvermore » nanoparticles was made by UV-visible absorption spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy and atomic force microscope (AFM). TEM micrograph revealed the formation of spherical nanoparticles with size ranging between 3 and 20 nm. The biosynthesized silver nanoparticles (AgNPs) showed excellent antibacterial activity against ESBL-strains which includes E. coli, Proteus. sp. and Klebsiella sp.« less

ELECTRON MICROSCOPY OF HELA CELLS INFECTED WITH ADENOVIRUSES

PubMed Central

Harford, Carl G.; Hamlin, Alice; Parker, Esther; van Ravenswaay, Theodore

1956-01-01

HeLa cells were infected with adenoviruses (types 1–4) and sectioned for electron microscopy after intervals of 20 to 48 hours. Clusters of virus-like particles were found within the nuclei of infected cultures but not in those of uninfected controls. The particles were often arranged in rows as if in crystalline formation. Maximal diameter of particles was approximately 65 mµ, and internal bodies were demonstrated. Lesions of infected cells included target-like structures of the nuclear membrane, large nuclear vacuoles (type 2), and increased numbers of large irregular electron-dense granules in the cytoplasm 48 hours after infection. Examination of infected cultures by light microscopy, using the Feulgen reaction, showed intranuclear inclusion bodies and a cytopathogenic effect consisting of clumping of cells without pyknosis of nuclei. A lipide stain showed numerous cytoplasmic granules that were not identical with the large, irregular, electron-dense granules of the cytoplasm. Practically all the cells showed the viral cytopathogenic effect, but only a minority of cells were found to contain virus-like particles or intranuclear inclusion bodies. PMID:13357696

Initial stem cell adhesion on porous silicon surface: molecular architecture of actin cytoskeleton and filopodial growth

PubMed Central

2014-01-01

The way cells explore their surrounding extracellular matrix (ECM) during development and migration is mediated by lamellipodia at their leading edge, acting as an actual motor pulling the cell forward. Lamellipodia are the primary area within the cell of actin microfilaments (filopodia) formation. In this work, we report on the use of porous silicon (pSi) scaffolds to mimic the ECM of mesenchymal stem cells from the dental pulp (DPSC) and breast cancer (MCF-7) cells. Our atomic force microscopy (AFM), fluorescence microscopy, and scanning electron microscopy (SEM) results show that pSi promoted the appearance of lateral filopodia protruding from the DPSC cell body and not only in the lamellipodia area. The formation of elongated lateral actin filaments suggests that pores provided the necessary anchorage points for protrusion growth. Although MCF-7 cells displayed a lower presence of organized actin network on both pSi and nonporous silicon, pSi stimulated the formation of extended cell protrusions. PMID:25386101

Green synthesis of soya bean sprouts-mediated superparamagnetic Fe 3O 4 nanoparticles

NASA Astrophysics Data System (ADS)

Cai, Yan; Shen, Yuhua; Xie, Anjian; Li, Shikuo; Wang, Xiufang

2010-10-01

Superparamagnetic Fe 3O 4 nanoparticles were first synthesized via soya bean sprouts (SBS) templates under ambient temperature and normal atmosphere. The reaction process was simple, eco-friendly, and convenient to handle. The morphology and crystalline phase of the nanoparticles were determined from scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD) spectra. The effect of SBS template on the formation of Fe 3O 4 nanoparticles was investigated using X-ray photoemission spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). The results indicate that spherical Fe 3O 4 nanoparticles with an average diameter of 8 nm simultaneously formed on the epidermal surface and the interior stem wall of SBS. The SBS are responsible for size and morphology control during the whole formation of Fe 3O 4 nanoparticles. In addition, the superconducting quantum interference device (SQUID) results indicate the products are superparamagnetic at room temperature, with blocking temperature ( TB) of 150 K and saturation magnetization of 37.1 emu/g.

Neutrophil extracellular trap formation is associated with autophagy-related signalling in ANCA-associated vasculitis

PubMed Central

Tang, S; Zhang, Y; Yin, S-W; Gao, X-J; Shi, W-W; Wang, Y; Huang, X; Wang, L; Zou, L-Y; Zhao, J-H; Huang, Y-J; Shan, L-Y; Gounni, A S; Wu, Y-Z; Zhang, J-B

2015-01-01

Increasing evidence indicates that aberrant neutrophil extracellular trap (NET) formation could contribute to the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Recent research has provided evidence that a novel type of ANCA autoantibody, anti-lysosomal membrane protein-2 (LAMP-2) antibody, may have a pathogenic role in AAV. We have shown previously that anti-LAMP-2 antibody-stimulated NET formation contains autoantigens and anti-microbial peptides. The current study sought to determine whether LAMP-2, as a novel antigen of ANCA, was present on NETs in AAV patients, the influence of the anti-LAMP-2 antibody on the neutrophil apoptosis rate and the role of autophagy in anti-LAMP-2 antibody-induced NET formation. NET formation was assessed using immunofluorescence microscopy, scanning electron microscopy or live cell imaging. The neutrophil apoptosis rate was analysed using fluorescence activated cell sorting (FACS). Autophagy was detected using LC3B accumulation and transmission electron microscopy. The results showed that enhanced NET formation, which contains LAMP-2, was observed in kidney biopsies and neutrophils from AAV patients. The apoptosis rate decreased significantly in human neutrophils stimulated with anti-LAMP-2 antibody, and this effect was attenuated by the inhibitors of autophagy 3-methyladenine (3MA) and 2-morpholin-4-yl-8-phenylchromen-4-one (LY294002). The anti-LAMP-2 antibody-stimulated NET formation was unaffected by benzyloxycarbonyl-Val- Ala-Asp (OMe)-fluoromethylketone (zVAD-fmk) and necrostatin-1 (Nec-1), which are inhibitors of apoptosis and necrosis, respectively, but was inhibited by 3MA and LY294002. Moreover, the proportion of LC3BI that was converted to LC3BII increased significantly (P = 0·0057), and massive vacuolizations that exhibited characteristics typical of autophagy were detected in neutrophils stimulated with anti-LAMP-2 antibody. Our results provide further evidence that autophagy is involved in ANCA-induced NET formation in human neutrophils. PMID:25644394

Neutrophil extracellular trap formation is associated with autophagy-related signalling in ANCA-associated vasculitis.

PubMed

Tang, S; Zhang, Y; Yin, S-W; Gao, X-J; Shi, W-W; Wang, Y; Huang, X; Wang, L; Zou, L-Y; Zhao, J-H; Huang, Y-J; Shan, L-Y; Gounni, A S; Wu, Y-Z; Zhang, J-B

2015-06-01

Increasing evidence indicates that aberrant neutrophil extracellular trap (NET) formation could contribute to the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Recent research has provided evidence that a novel type of ANCA autoantibody, anti-lysosomal membrane protein-2 (LAMP-2) antibody, may have a pathogenic role in AAV. We have shown previously that anti-LAMP-2 antibody-stimulated NET formation contains autoantigens and anti-microbial peptides. The current study sought to determine whether LAMP-2, as a novel antigen of ANCA, was present on NETs in AAV patients, the influence of the anti-LAMP-2 antibody on the neutrophil apoptosis rate and the role of autophagy in anti-LAMP-2 antibody-induced NET formation. NET formation was assessed using immunofluorescence microscopy, scanning electron microscopy or live cell imaging. The neutrophil apoptosis rate was analysed using fluorescence activated cell sorting (FACS). Autophagy was detected using LC3B accumulation and transmission electron microscopy. The results showed that enhanced NET formation, which contains LAMP-2, was observed in kidney biopsies and neutrophils from AAV patients. The apoptosis rate decreased significantly in human neutrophils stimulated with anti-LAMP-2 antibody, and this effect was attenuated by the inhibitors of autophagy 3-methyladenine (3MA) and 2-morpholin-4-yl-8-phenylchromen-4-one (LY294002). The anti-LAMP-2 antibody-stimulated NET formation was unaffected by benzyloxycarbonyl-Val- Ala-Asp (OMe)-fluoromethylketone (zVAD-fmk) and necrostatin-1 (Nec-1), which are inhibitors of apoptosis and necrosis, respectively, but was inhibited by 3MA and LY294002. Moreover, the proportion of LC3BI that was converted to LC3BII increased significantly (P=0.0057), and massive vacuolizations that exhibited characteristics typical of autophagy were detected in neutrophils stimulated with anti-LAMP-2 antibody. Our results provide further evidence that autophagy is involved in ANCA-induced NET formation in human neutrophils. © 2015 British Society for Immunology.

Microstructure and Properties of a High-Strength Cu-Ni-Si-Co-Zr Alloy

NASA Astrophysics Data System (ADS)

Chenna Krishna, S.; Srinath, J.; Jha, Abhay K.; Pant, Bhanu; Sharma, S. C.; George, Koshy M.

2013-07-01

A high-strength Cu-Ni-Si alloy was developed with the additions of Co and Zr. The aging curve for the alloy was generated using hardness. Electron microscopy studies were conducted to analyze the phases in the alloy. Two types of phases, one of copper matrix and the other of Ni-Si-Co-Zr intermetallic phase, could be identified using scanning electron microscopy. Transmission electron microscopy studies confirmed the presence of two types of precipitates in solution-treated and aged (STA) condition, i.e., Ni2Si and Co2Si. Mechanical properties and electrical conductivity were evaluated in solution-treated (ST) and STA conditions. Aging of the ST samples at 500 °C for 3 h has shown an increase of 72 and 15% in yield strength (YS) and electrical conductivity, respectively. This increase in YS and conductivity on aging is primarily attributed to the formation of fine Ni2Si and Co2Si precipitates.

Formation of interconnections between carbon nanotubes and copper using tin solder

NASA Astrophysics Data System (ADS)

Mittal, Jagjiwan; Lina, Kwang-Lung

2013-06-01

A process is developed for connecting Multiwalled carbon nanotubes (MWCNTs) between Cu terminals using tin solder. Connections were made on the Cu grid after heating the Sn coated nanotubes above the melting point of tin. High resolution transmission electron microscopy (HRTEM) micrographs demonstrated the joining by CNTs either as straight between two sides or on the one side after bending in the middle. The connections were found to be stable in air and electron beam under TEM observations. Energy dispersive X-ray (EDX) study showed that the formation of intermetallic compound η-C6Sn5 was responsible for the formation and stability of joints between Cu and MWCNT.

Swift heavy ion track formation in Gd2Zr2-xTixO7 pyrochlore: Effect of electronic energy loss

NASA Astrophysics Data System (ADS)

Lang, Maik; Toulemonde, Marcel; Zhang, Jiaming; Zhang, Fuxiang; Tracy, Cameron L.; Lian, Jie; Wang, Zhongwu; Weber, William J.; Severin, Daniel; Bender, Markus; Trautmann, Christina; Ewing, Rodney C.

2014-10-01

The morphology of swift heavy ion tracks in the Gd2Zr2-xTixO7 pyrochlore system has been investigated as a function of the variation in chemical composition and electronic energy loss, dE/dx, over a range of energetic ions: 58Ni, 101Ru, 129Xe, 181Ta, 197Au, 208Pb, and 238U of 11.1 MeV/u specific energy. Bright-field transmission electron microscopy, synchrotron X-ray diffraction, and Raman spectroscopy reveal an increasing degree of amorphization with increasing Ti-content and dE/dx. The size and morphology of individual ion tracks in Gd2Ti2O7 were characterized by high-resolution transmission electron microscopy revealing a core-shell structure with an outer defect-fluorite dominated shell at low dE/dx to predominantly amorphous tracks at high dE/dx. Inelastic thermal-spike calculations have been used together with atomic-scale characterization of ion tracks in Gd2Ti2O7 by high resolution transmission electron microscopy to deduce critical energy densities for the complex core-shell morphologies induced by ions of different dE/dx.

The collection of MicroED data for macromolecular crystallography.

PubMed

Shi, Dan; Nannenga, Brent L; de la Cruz, M Jason; Liu, Jinyang; Sawtelle, Steven; Calero, Guillermo; Reyes, Francis E; Hattne, Johan; Gonen, Tamir

2016-05-01

The formation of large, well-ordered crystals for crystallographic experiments remains a crucial bottleneck to the structural understanding of many important biological systems. To help alleviate this problem in crystallography, we have developed the MicroED method for the collection of electron diffraction data from 3D microcrystals and nanocrystals of radiation-sensitive biological material. In this approach, liquid solutions containing protein microcrystals are deposited on carbon-coated electron microscopy grids and are vitrified by plunging them into liquid ethane. MicroED data are collected for each selected crystal using cryo-electron microscopy, in which the crystal is diffracted using very few electrons as the stage is continuously rotated. This protocol gives advice on how to identify microcrystals by light microscopy or by negative-stain electron microscopy in samples obtained from standard protein crystallization experiments. The protocol also includes information about custom-designed equipment for controlling crystal rotation and software for recording experimental parameters in diffraction image metadata. Identifying microcrystals, preparing samples and setting up the microscope for diffraction data collection take approximately half an hour for each step. Screening microcrystals for quality diffraction takes roughly an hour, and the collection of a single data set is ∼10 min in duration. Complete data sets and resulting high-resolution structures can be obtained from a single crystal or by merging data from multiple crystals.

Advanced electron microscopy methods for the analysis of MgB2 superconductor

NASA Astrophysics Data System (ADS)

Birajdar, B.; Peranio, N.; Eibl, O.

2008-02-01

Advanced electron microscopy methods used for the analysis of superconducting MgB2 wires and tapes are described. The wires and tapes were prepared by the powder in tube method using different processing technologies and thoroughly characterised for their superconducting properties within the HIPERMAG project. Microstructure analysis on μm to nm length scales is necessary to understand the superconducting properties of MgB2. For the MgB2 phase analysis on μm scale an analytical SEM, and for the analysis on nm scale a energy-filtered STEM is used. Both the microscopes were equipped with EDX detector and field emission gun. Electron microscopy and spectroscopy of MgB2 is challenging because of the boron analysis, carbon and oxygen contamination, and the presence of large number of secondary phases. Advanced electron microscopy involves, combined SEM, EPMA and TEM analysis with artefact free sample preparation, elemental mapping and chemical quantification of point spectra. Details of the acquisition conditions and achieved accuracy are presented. Ex-situ wires show oxygen-free MgB2 colonies (a colony is a dense arrangement of several MgB2 grains) embedded in a porous and oxygen-rich matrix, introducing structural granularity. In comparison, in-situ wires are generally more dense, but show inhibited MgB2 phase formation with significantly higher fraction of B-rich secondary phases. SiC additives in the in-situ wires forms Mg2Si secondary phases. The advanced electron microscopy has been used to extract the microstructure parameters like colony size, B-rich secondary phase fraction, O mole fraction and MgB2 grain size, and establish a microstructure-critical current density model [1]. In summary, conventional secondary electron imaging in SEM and diffraction contrast imaging in the TEM are by far not sufficient and advanced electron microscopy methods are essential for the analysis of superconducting MgB2 wires and tapes.

Formation of gallium vacancies and their effects on the nanostructure of Pd/Ir/Au ohmic contact to p-type GaN.

PubMed

Kim, Kyong Nam; Kim, Tae Hyung; Seo, Jin Seok; Kim, Ki Seok; Bae, Jeong Woon; Yeom, Geun Young

2013-12-01

The properties of Pd/Ir/Au ohmic metallization on p-type GaN have been investigated. Contacts annealed at 400 degrees C in O2 atmosphere demonstrated excellent ohmic characteristics with a specific contact resistivity of 1.5 x 10(-5) Omega-cm2. This is attributed to the formation of Ga vacancies at the contact metal-semiconductor interfacial region due to the out-diffusion of Ga atoms. The out-diffusion of Ga atoms was confirmed by X-ray photoelectron spectroscopy depth profiles, high-resolution transmission electron microscopy, and electron energy loss spectroscopy using a scanning transmission electron microscope.

Synergistic effect of polyaniline coverage and surface microstructure on the inhibition of Pseudomonas aeruginosa biofilm formation.

PubMed

Gallarato, L A; Mulko, L E; Dardanelli, M S; Barbero, C A; Acevedo, D F; Yslas, E I

2017-02-01

Biofilm Formation is a survival strategy for microorganisms to adapt to their environment. Microbial cells in biofilm become tolerant and resistant to antibiotics and immune responses, increasing the difficulties for the clinical treatment of microbial infections. The surface chemistry and the micro/nano-topography of solid interfaces play a major role in mediating microorganism activity and adhesion. The effect of the surface chemical composition and topography on the adhesion and viability of Pseudomonas aeruginosa was studied. Polymeric (polyethylene terephthalate) surfaces were covered with a conducting polymer (polyaniline, PANI) film by in-situ polymerization and microstructured by Direct Laser Interference Patterning (DLIP). The viability of Pseudomonas aeruginosa on the different surfaces was investigated. The physicochemical properties of the surfaces were characterized by water contact angle measurements, scanning electron microscopy and atomic force microscopy. Bacterial biofilms were imaged by atomic force and scanning electron microscopies. The bacterial viability decreased on PANI compared with the substrate (polyethylene terephthalate) and it decreased even more upon micro-structuring the PANI films. In addition, the biofilm reduction could be improved using polymers with different chemical composition and/or the same polymer with different topographies. Both methods presented diminish the bacterial attachment and biofilm formation. These findings present a high impact related to materials for biomedical engineer applications regarding medical devices, as prostheses or catheters. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessment of autophagosome formation by transmission electron microscopy

USDA-ARS?s Scientific Manuscript database

Autophagy is a complex degradative process by which cytosolic material, including organelles, is randomly sequestered within double-membrane bound vesicles termed autophagosomes and targeted for degradation. Initially described as a nutrient stress adaptation response, the process of autophagy is n...

High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

PubMed Central

Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

2016-01-01

Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles. PMID:27121137

High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

NASA Astrophysics Data System (ADS)

Plascencia-Villa, Germán; Ponce, Arturo; Collingwood, Joanna F.; Arellano-Jiménez, M. Josefina; Zhu, Xiongwei; Rogers, Jack T.; Betancourt, Israel; José-Yacamán, Miguel; Perry, George

2016-04-01

Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

Anterior lens epithelium in intumescent white cataracts - scanning and transmission electron microscopy study.

PubMed

Andjelic, Sofija; Drašlar, Kazimir; Hvala, Anastazija; Hawlina, Marko

2016-02-01

Our purpose was to study the structure of the lens epithelial cells (LECs) of intumescent white cataracts (IC) in comparison with nuclear cataracts (NC) in order to investigate possible structural reasons for development of IC. The anterior lens capsule (aLC: basement membrane and associated LECs) were obtained from cataract surgery and prepared for scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We observed by SEM that in IC, LEC swelling was pronounced with the clefts surrounding the groups of LECs. Another structural feature was spherical formations, that were observed on the apical side of LEC's, towards the fibre cell layer, both by SEM and TEM. Development of these structures, bulging out from the apical cell membrane of the LEC's and disrupting it, could be followed in steps towards the sphere formation. The degeneration of the lens epithelium and the structures of the aLC in IC similar to Morgagnian globules were also observed. None of these structural changes were observed in NC. We show by SEM and TEM that, in IC, LECs have pronounced structural features not observed in NC. This supports the hypothesis that the disturbed structure of LECs plays a role in water accumulation in the IC lens. We also suggest that, in IC, LECs produce bulging spheres that represent unique structures of degenerated material, extruded from the LEC.

Evaluation of environmental scanning electron microscopy for analysis of Proteus mirabilis crystalline biofilms in situ on urinary catheters.

PubMed

Holling, Nina; Dedi, Cinzia; Jones, Caroline E; Hawthorne, Joseph A; Hanlon, Geoffrey W; Salvage, Jonathan P; Patel, Bhavik A; Barnes, Lara M; Jones, Brian V

2014-06-01

Proteus mirabilis is a common cause of catheter-associated urinary tract infections and frequently leads to blockage of catheters due to crystalline biofilm formation. Scanning electron microscopy (SEM) has proven to be a valuable tool in the study of these unusual biofilms, but entails laborious sample preparation that can introduce artefacts, undermining the investigation of biofilm development. In contrast, environmental scanning electron microscopy (ESEM) permits imaging of unprocessed, fully hydrated samples, which may provide much insight into the development of P. mirabilis biofilms. Here, we evaluate the utility of ESEM for the study of P. mirabilis crystalline biofilms in situ, on urinary catheters. In doing so, we compare this to commonly used conventional SEM approaches for sample preparation and imaging. Overall, ESEM provided excellent resolution of biofilms formed on urinary catheters and revealed structures not observed in standard SEM imaging or previously described in other studies of these biofilms. In addition, we show that energy-dispersive X-ray spectroscopy (EDS) may be employed in conjunction with ESEM to provide information regarding the elemental composition of crystalline structures and demonstrate the potential for ESEM in combination with EDS to constitute a useful tool in exploring the mechanisms underpinning crystalline biofilm formation. © 2014 The Authors. FEMS Microbiology Letters published by John Wiley & Sons Ltd on behalf of Federation of European Microbiological Societies.

Morphology of one-time coated palladium-alumina composite membrane prepared by sol-gel process and electroless plating technique

NASA Astrophysics Data System (ADS)

Sari, R.; Dewi, R.; Pardi; Hakim, L.; Diana, S.

2018-03-01

Palladium coated porous alumina ceramic membrane tube was obtained using a combination of sol-gel process and electroless plating technique. The thickness, structure and composition of palladium-alumina composite membrane were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM). Palladium particle size was 6.18 to 7.64 nm. Palladium membrane with thickness of approximately 301.5 to 815.1 nm was formed at the outer surface of the alumina layer. EDX data confirmed the formation of palladium-alumina membrane containing 45% of palladium. From this research it shows the combination of sol-gel process and electroless plating technique with one-time coating can produce a homogeneous and smoother palladium nano layer film on alumina substrate.

Electron Beam-Induced Writing of Nanoscale Iron Wires on a Functional Metal Oxide

PubMed Central

2013-01-01

Electron beam-induced surface activation (EBISA) has been used to grow wires of iron on rutile TiO2(110)-(1 × 1) in ultrahigh vacuum. The wires have a width down to ∼20 nm and hence have potential utility as interconnects on this dielectric substrate. Wire formation was achieved using an electron beam from a scanning electron microscope to activate the surface, which was subsequently exposed to Fe(CO)5. On the basis of scanning tunneling microscopy and Auger electron spectroscopy measurements, the activation mechanism involves electron beam-induced surface reduction and restructuring. PMID:24159366

Silicifying Biofilm Exopolymers on a Hot-Spring Microstromatolite: Templating Nanometer-Thick Laminae

NASA Astrophysics Data System (ADS)

Handley, Kim M.; Turner, Sue J.; Campbell, Kathleen A.; Mountain, Bruce W.

2008-08-01

Exopolymeric substances (EPS) are an integral component of microbial biofilms; however, few studies have addressed their silicification and preservation in hot-spring deposits. Through comparative analyses with the use of a range of microscopy techniques, we identified abundant EPS significant to the textural development of spicular, microstromatolitic, siliceous sinter at Champagne Pool, Waiotapu, New Zealand. Examination of biofilms coating sinter surfaces by confocal laser scanning microscopy (CLSM), environmental scanning electron microscopy (ESEM), cryo-scanning electron microscopy (cryo-SEM), and transmission electron microscopy (TEM) revealed contraction of the gelatinous EPS matrix into films (approximately 10 nm thick) or fibrillar structures, which is common in conventional SEM analyses and analogous to products of naturally occurring desiccation. Silicification of fibrillar EPS contributed to the formation of filamentous sinter. Matrix surfaces or dehydrated films templated sinter laminae (nanometers to microns thick) that, in places, preserved fenestral voids beneath. Laminae of similar thickness are, in general, common to spicular geyserites. This is the first report to demonstrate EPS templation of siliceous stromatolite laminae. Considering the ubiquity of biofilms on surfaces in hot-spring environments, EPS silicification studies are likely to be important to a better understanding of the origins of laminae in other modern and ancient stromatolitic sinters, and EPS potentially may serve as biosignatures in extraterrestrial rocks.

Shape-controlled solvothermal synthesis of bismuth subcarbonate nanomaterials

NASA Astrophysics Data System (ADS)

Cheng, Gang; Yang, Hanmin; Rong, Kaifeng; Lu, Zhong; Yu, Xianglin; Chen, Rong

2010-08-01

Much effort has been devoted to the synthesis of novel nanostructured materials because of their unique properties and potential applications. Bismuth subcarbonate ((BiO) 2CO 3) is one of commonly used antibacterial agents against Helicobacter pylori ( H. pylori). Different (BiO) 2CO 3 nanostructures such as cube-like nanoparticles, nanobars and nanoplates, were fabricated from bismuth nitrate via a simple solvothermal method. The nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that the solvents and precursors have an influence on the morphologies of (BiO) 2CO 3 nanostructures. The possible formation mechanism of different (BiO) 2CO 3 nanostructures fabricated under different conditions was also discussed.

Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon-germanium nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, Hock-Chun; Gong, Xiao; Yeo, Yee-Chia

Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAsmore » grown and the high growth selectivity of the MEE process.« less

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain

NASA Astrophysics Data System (ADS)

Gussev, M. N.; Field, K. G.; Busby, J. T.

2014-03-01

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ˜1 μm and depths of several microns were observed at channels with heights greater than ˜150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]-[1 1 1] orientation but not in those along the [1 0 1] orientation.

The three dimensionality of cell membranes: lamellar to cubic membrane transition as investigated by electron microscopy.

PubMed

Chong, Ketpin; Deng, Yuru

2012-01-01

Biological membranes are generally perceived as phospholipid bilayer structures that delineate in a lamellar form the cell surface and intracellular organelles. However, much more complex and highly convoluted membrane organizations are ubiquitously present in many cell types under certain types of stress, states of disease, or in the course of viral infections. Their occurrence under pathological conditions make such three-dimensionally (3D) folded and highly ordered membranes attractive biomarkers. They have also stimulated great biomedical interest in understanding the molecular basis of their formation. Currently, the analysis of such membrane arrangements, which include tubulo-reticular structures (TRS) or cubic membranes of various subtypes, is restricted to electron microscopic methods, including tomography. Preservation of membrane structures during sample preparation is the key to understand their true 3D nature. This chapter discusses methods for appropriate sample preparations to successfully examine and analyze well-preserved highly ordered membranes by electron microscopy. Processing methods and analysis conditions for green algae (Zygnema sp.) and amoeba (Chaos carolinense), mammalian cells in culture and primary tissue cells are described. We also discuss methods to identify cubic membranes by transmission electron microscopy (TEM) with the aid of a direct template matching method and by computer simulation. A 3D analysis of cubic cell membrane topology by electron tomography is described as well as scanning electron microscopy (SEM) to investigate surface contours of isolated mitochondria with cubic membrane arrangement. Copyright © 2012 Elsevier Inc. All rights reserved.

Time-resolved measurement of single pulse femtosecond laser-induced periodic surface structure formation induced by a pre-fabricated surface groove.

PubMed

Kafka, K R P; Austin, D R; Li, H; Yi, A Y; Cheng, J; Chowdhury, E A

2015-07-27

Time-resolved diffraction microscopy technique has been used to observe the formation of laser-induced periodic surface structures (LIPSS) from the interaction of a single femtosecond laser pulse (pump) with a nano-scale groove mechanically formed on a single-crystal Cu substrate. The interaction dynamics (0-1200 ps) was captured by diffracting a time-delayed, frequency-doubled pulse (probe) from nascent LIPSS formation induced by the pump with an infinity-conjugate microscopy setup. The LIPSS ripples are observed to form asynchronously, with the first one forming after 50 ps and others forming sequentially outward from the groove edge at larger time delays. A 1-D analytical model of electron heating including both the laser pulse and surface plasmon polariton excitation at the groove edge predicts ripple period, melt spot diameter, and qualitatively explains the asynchronous time-evolution of LIPSS formation.

Formation of multicomponent matrix metal oxide films in anodic alumina matrixes by chemical deposition

NASA Astrophysics Data System (ADS)

Gorokh, G. G.; Zakhlebayeva, A. I.; Metla, A. I.; Zhilinskiy, V. V.; Murashkevich, A. N.; Bogomazova, N. V.

2017-11-01

The metal oxide films of SnxZnyOz and SnxMoyOz systems deposited onto anodic alumina matrixes by chemical and ion layering from an aqueous solutions were characterized by scanning electron microscopy, Raman spectroscopy, electron probe X-ray microanalysis and IR spectroscopy. The obtained matrix films had reproducible composition and structure and possessed certain morphological characteristics and properties.

On-surface formation of one-dimensional polyphenylene through Bergman cyclization.

PubMed

Sun, Qiang; Zhang, Chi; Li, Zhiwen; Kong, Huihui; Tan, Qinggang; Hu, Aiguo; Xu, Wei

2013-06-12

On-surface fabrication of covalently interlinked conjugated nanostructures has attracted significant attention, mainly because of the high stability and efficient electron transport ability of these structures. Here, from the interplay of scanning tunneling microscopy imaging and density functional theory calculations, we report for the first time on-surface formation of one-dimensional polyphenylene chains through Bergman cyclization followed by radical polymerization on Cu(110). The formed surface nanostructures were further corroborated by the results for the ex situ-synthesized molecular product after Bergman cyclization. These findings are of particular interest and importance for the construction of molecular electronic nanodevices on surfaces.

Analysis of Peroxisome Biogenesis in Pollen by Confocal Microscopy and Transmission Electron Microscopy.

PubMed

Jia, Peng-Fei; Li, Hong-Ju; Yang, Wei-Cai

2017-01-01

Peroxisome is an essential single-membrane bound organelle in most eukaryotic cells and functions in diverse cellular processes. De novo formation, division, and turnover of peroxisomes contribute to its biogenesis, morphology, and population regulation. In plants, peroxisome plays multiple roles, including metabolism, development, and stress response. Defective peroxisome biogenesis and development retard plant growth, adaption, and reproduction. Through tracing the subcellular localization of fluorescent reporter tagged matrix protein of peroxisome, fluorescence microscopy is a reliable and fast way to detect peroxisome biogenesis. Further fine-structural observation of peroxisome by TEM enables researchers to observe the detailed ultrastructure of its morphology and spatial contact with other organelles. Pollen grain is a specialized structure where two small sperm cells are enclosed in the cytoplasm of a large vegetative cell. Two features make pollen grain a good system to study peroxisome biogenesis: indispensable requirement of peroxisome for germination on the stigma and homogeneity. Here, we describe the methods of studying peroxisome biogenesis in Arabidopsis pollen grains by fluorescent live-imaging with confocal laser scanning microscopy (CLSM) and by DAB-staining based transmission electron microscopy (TEM).

External cervical resorption: an analysis using cone beam and microfocus computed tomography and scanning electron microscopy.

PubMed

Gunst, V; Mavridou, A; Huybrechts, B; Van Gorp, G; Bergmans, L; Lambrechts, P

2013-09-01

To provide a three-dimensional representation of external cervical resorption (ECR) with microscopy, stereo microscopy, cone beam computed tomography (CT), microfocus CT and scanning electron microscopy (SEM). External cervical resorption is an aggressive form of root resorption, leading to a loss of dental hard tissues. This is due to clastic action, activated by a damage of the covering cementum and stimulated probably by infection. Clinically, it is a challenging situation as it is characterized by a late symptomatology. This is due to the pericanalar protection from a resorption-resistant sheet, composed of pre-dentine and surrounding dentine. The clastic activity is often associated with an attempt to repair, seen by the formation of osteoid tissue. Cone beam CT is extremely useful in the diagnoses and treatment planning of ECR. SEM analyses provide a better insight into the activity of osteoclasts. The root canal is surrounded by a layer of dentine that is resistant to resorption. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Particle formation in SiOx film deposition by low frequency plasma enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Yamaguchi, Tomoyo; Sakamoto, Naoshi; Shimozuma, Mitsuo; Yoshino, Masaki; Tagashira, Hiroaki

1998-01-01

Dust particle formation dynamics in the process of SiOx film deposition from a SiH4 and N2O gas mixture by a low frequency plasma enhanced chemical vapor deposition have been investigated using scanning electron microscopy and laser light scattering. The deposited films are confirmed to be SiOx from the measurements of Auger electron spectroscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. It is observed by scanning electron microscopy that particles are deposited on Si substrate at the plasma power frequency f=5 kHz and above both with and without substrate heating (400 °C), while no particle is deposited below f=1 kHz. Moreover, the laser light scattering indicates that particles are generated at the plasma power frequency of f=3 kHz and above in the gas phase, and that they are not generated in the gas phase at below f=3 kHz. Properties (the refractive index, resistivity, and Vickers hardness) of the films with particles are inferior to those of the films without particles. This article has revealed experimentally the effect of plasma power frequency on SiOx particle formation and makes a contribution to the explication of the particle formation mechanism. We suggest that high-quality film deposition with the low frequency plasma enhanced chemical vapor deposition method is attained at f=1 kHz or less without substrate heating.

Polyethylene nano crystalsomes formed at a curved liquid/liquid interface.

PubMed

Wang, Wenda; Staub, Mark C; Zhou, Tian; Smith, Derrick M; Qi, Hao; Laird, Eric D; Cheng, Shan; Li, Christopher Y

2017-12-21

Crystallization is incommensurate with nanoscale curved space due to the lack of three dimensional translational symmetry of the latter. Herein, we report the formation of single-crystal-like, nanosized polyethylene (PE) capsules using a miniemulsion solution crystallization method. The miniemulsion was formed at elevated temperatures using PE organic solution as the oil phase and sodium dodecyl sulfate as the surfactant. Subsequently, cooling the system stepwisely for controlled crystallization led to the formation of hollow, nanosized PE crystalline capsules, which are named as crystalsomes since they mimic the classical self-assembled structures such as liposome, polymersome and colloidosome. We show that the formation of the nanosized PE crystalsomes is driven by controlled crystallization at the curved liquid/liquid interface of the miniemulson droplet. The morphology, structure and mechanical properties of the PE crystalsomes were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and atomic force spectroscopy. Electron diffraction showed the single-crystal-like nature of the crystalsomes. The incommensurateness between the nanocurved interface and the crystalline packing led to reduced crystallinity and crystallite size of the PE crystalsome, as observed from the X-ray diffraction measurements. Moreover, directly quenching the emulsion below the spinodal line led to the formation of hierarchical porous PE crystalsomes due to the coupling of the PE crystallization and liquid/liquid phase separation. We anticipate that this unique crystalsome represents a new type of nanostructure that might be used as nanodrug carriers and ultrasound contrast agents.

Serial block face-scanning electron microscopy: a tool for studying embryonic development at the cell-matrix interface.

PubMed

Starborg, Tobias; Kadler, Karl E

2015-03-01

Studies of gene regulation, signaling pathways, and stem cell biology are contributing greatly to our understanding of early embryonic vertebrate development. However, much less is known about the events during the latter half of embryonic development, when tissues comprising mostly extracellular matrix (ECM) are formed. The matrix extends far beyond the boundaries of individual cells and is refractory to study by conventional biochemical and molecular techniques; thus major gaps exist in our knowledge of the formation and three-dimensional (3D) organization of the dense tissues that form the bulk of adult vertebrates. Serial block face-scanning electron microscopy (SBF-SEM) has the ability to image volumes of tissue containing numerous cells at a resolution sufficient to study the organization of the ECM. Furthermore, whereas light microscopy was once relatively straightforward and electron microscopy was performed in specialist laboratories, the tables are turned; SBF-SEM is relatively straightforward and is becoming routine in high-end resolution studies of embryonic structures in vivo. In this review, we discuss the emergence of SBF-SEM as a tool for studying embryonic vertebrate development. © 2015 Wiley Periodicals, Inc.

Curcumin Inhibits Tau Aggregation and Disintegrates Preformed Tau Filaments in vitro.

PubMed

Rane, Jitendra Subhash; Bhaumik, Prasenjit; Panda, Dulal

2017-01-01

The pathological aggregation of tau is a common feature of most of the neuronal disorders including frontotemporal dementia, Parkinson's disease, and Alzheimer's disease. The inhibition of tau aggregation is considered to be one of the important strategies for treating these neurodegenerative diseases. Curcumin, a natural polyphenolic molecule, has been reported to have neuroprotective ability. In this work, curcumin was found to bind to adult tau and fetal tau with a dissociation constant of 3.3±0.4 and 8±1 μM, respectively. Molecular docking studies indicated a putative binding site of curcumin in the microtubule-binding region of tau. Using several complementary techniques, including dynamic light scattering, thioflavin S fluorescence, 90° light scattering, electron microscopy, and atomic force microscopy, curcumin was found to inhibit the aggregation of tau. The dynamic light scattering analysis and atomic force microscopic images revealed that curcumin inhibits the oligomerization of tau. Curcumin also disintegrated preformed tau oligomers. Using Far-UV circular dichroism, curcumin was found to inhibit the β-sheets formation in tau indicating that curcumin inhibits an initial step of tau aggregation. In addition, curcumin inhibited tau fibril formation. Furthermore, the effect of curcumin on the preformed tau filaments was analyzed by atomic force microscopy, transmission electron microscopy, and 90° light scattering. Curcumin treatment disintegrated preformed tau filaments. The results indicated that curcumin inhibited the oligomerization of tau and could disaggregate tau filaments.

Standardized Polyalthia longifolia leaf extract (PLME) inhibits cell proliferation and promotes apoptosis: The anti-cancer study with various microscopy methods.

PubMed

Vijayarathna, Soundararajan; Chen, Yeng; Kanwar, Jagat R; Sasidharan, Sreenivasan

2017-07-01

Over the years a number of microscopy methods have been developed to assess the changes in cells. Some non-invasive techniques such as holographic digital microscopy (HDM), which although does not destroy the cells, but helps to monitor the events that leads to initiation of apoptotic cell death. In this study, the apoptogenic property and the cytotoxic effect of P. longifolia leaf methanolic extract (PLME) against the human cervical carcinoma cells (HeLa) was studied using light microscope (LM), holographic digital microscopy (HDM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The average IC 50 value of PLME against HeLa cells obtained by MTT and CyQuant assay was 22.00μg/mL at 24h. However, noncancerous Vero cells tested with PLME exhibited no cytotoxicity with the IC 50 value of 51.07μg/mL at 24h by using MTT assay. Cytological observations showed nuclear condensation, cell shrinkage, multinucleation, abnormalities of mitochondrial cristae, membrane blebbing, disappearance of microvilli and filopodia, narrowing of lamellipodia, holes, formation of numerous smaller vacuoles, cytoplasmic extrusions and formation of apoptotic bodies as confirmed collectively by HDM, LM, SEM and TEM. In conclusion, PLME was able to produce distinctive morphological features of HeLa cell death that corresponds to apoptosis. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Structure Evolution and Distributions of Grain-Boundary Misorientainons in Submicrocrystalline Molybdenum Irradiated with a Pulsed Electron Beam

NASA Astrophysics Data System (ADS)

Stepanova, E. N.; Grabovetskaya, G. P.; Teresov, A. D.; Mishin, I. P.

2018-05-01

Using the methods of electron backscatter diffraction, electron microscopy and X-ray diffraction analysis, it is demonstrated that irradiation of the surface of a submicrocrystalline molybdenum specimen with a pulsed electron beam in a non-melt regime results in the formation of a gradient structure in its bulk. The irradiation temperature is shown to affect the density of defects, the value of stress, and the distributions of grain-boundary misorientations in the surface and bulk of the submicrocrystalline molybdenum specimens.

Tannins Possessing Bacteriostatic Effect Impair Pseudomonas aeruginosa Adhesion and Biofilm Formation

PubMed Central

Trentin, Danielle S.; Silva, Denise B.; Amaral, Matheus W.; Zimmer, Karine R.; Silva, Márcia V.; Lopes, Norberto P.; Giordani, Raquel B.; Macedo, Alexandre J.

2013-01-01

Plants produce many compounds that are biologically active, either as part of their normal program of growth and development or in response to pathogen attack or stress. Traditionally, Anadenanthera colubrina, Commiphora leptophloeos and Myracrodruon urundeuva have been used by communities in the Brazilian Caatinga to treat several infectious diseases. The ability to impair bacterial adhesion represents an ideal strategy to combat bacterial pathogenesis, because of its importance in the early stages of the infectious process; thus, the search for anti-adherent compounds in plants is a very promising alternative. This study investigated the ability of stem-bark extracts from these three species to control the growth and prevent biofilm formation of Pseudomonas aeruginosa, an important opportunistic pathogen that adheres to surfaces and forms protective biofilms. A kinetic study (0–72 h) demonstrated that the growth of extract-treated bacteria was inhibited up to 9 h after incubation, suggesting a bacteriostatic activity. Transmission electron microscopy and fluorescence microscopy showed both viable and nonviable cells, indicating bacterial membrane damage; crystal violet assay and scanning electron microscopy demonstrated that treatment strongly inhibited biofilm formation during 6 and 24 h and that matrix production remained impaired even after growth was restored, at 24 and 48 h of incubation. Herein, we propose that the identified (condensed and hydrolyzable) tannins are able to inhibit biofilm formation via bacteriostatic properties, damaging the bacterial membrane and hindering matrix production. Our findings demonstrate the importance of this abundant class of Natural Products in higher plants against one of the most challenging issues in the hospital setting: biofilm resilience. PMID:23776646

Formation of biogenic sheath-like Fe oxyhydroxides in a near-neutral pH hot spring: Implications for the origin of microfossils in high-temperature, Fe-rich environments

NASA Astrophysics Data System (ADS)

Peng, Xiaotong; Chen, Shun; Xu, Hengchao

2013-12-01

small hot spring that is informally called "Fe-waterfall spring" and is located in the Rehai geothermal area discharges hot (42 to 73°C), near-neutral (pH = 7.65) Fe-rich water. Submerged reddish precipitates are composed largely of ferrihydrite, goethite, lepidocrocite, opal-A, quartz, and anorthite, as revealed by X-ray diffraction (XRD) and Mössbauer spectroscopy. Molecular phylogenetic analysis demonstrates that the bacterial community in these precipitates is mainly composed of Cyanobacteria, Planctomycetes, β-proteobacteria, Deinococci-Thermus, and Chlorobi. Scanning electron microscopy and high-resolution transmission electron microscopy examinations show that abundant sheath-like Fe oxyhydroxides, which exhibit different morphologies and sizes, are present in Fe-rich precipitates. These sheath-like structures are composed of ferrihydrite rather than more crystalline lepidocrocite or goethite. Energy-dispersive X-ray spectrometer, scanning transmission electron microscopy, and nano secondary ion mass spectrometry reveal that they are mainly composed of Fe, Si, and O, together with some trace elements. Most of the sheath-like structures are not morphologically comparable to biogenic Fe oxyhydroxides produced by known chemolithotrophic Fe oxidizers, which is consistent with the fact that no chemolithotrophic Fe oxidizers were identified by molecular analysis in the precipitates. We suggest that the sheath-like Fe oxyhydroxides are formed through passive Fe sorption and nucleation onto the cell walls of various thermophiles rather than by the direct metabolic activities of chemolithotrophic Fe oxidizers. Biogenic sheath-like Fe oxyhydroxides in Fe-waterfall spring have important implications for geochemical cycles driven by microorganisms, the origin of microfossils, and the formation of banded iron formations (BIFs) in the Archean ocean.

Effect of oxygen plasma etching on pore size-controlled 3D polycaprolactone scaffolds for enhancing the early new bone formation in rabbit calvaria.

PubMed

Kook, Min-Suk; Roh, Hee-Sang; Kim, Byung-Hoon

2018-05-02

This study was to investigate the effects of O 2 plasma-etching of the 3D polycaprolactone (PCL) scaffold surface on preosteoblast cell proliferation and differentiation, and early new bone formation. The PCL scaffolds were fabricated by 3D printing technique. After O 2 plasma treatment, surface characterizations were examined by scanning electron microscopy, atomic force microscopy, and contact angle. MTT assay was used to determine cell proliferation. To investigate the early new bone formation, rabbits were sacrificed at 2 weeks for histological analyses. As the O 2 plasma etching time is increased, roughness and hydrophilicity of the PCL scaffold surface increased. The cell proliferation and differentiation on plasma-etched samples was significantly increased than on untreated samples. At 2 weeks, early new bone formation in O 2 plasma-etched PCL scaffolds was the higher than that of untreated scaffolds. The O 2 plasma-etched PCL scaffolds showed increased preosteoblast differentiation as well as increased new bone formation.

Transmission Electron Microscopy of Single Wall Carbon Nanotube/Polymer Nanocomposites: A First-Principles Study

NASA Technical Reports Server (NTRS)

Sola, Francisco; Xia, Zhenhai; Lebrion-Colon, Marisabel; Meador, Michael A.

2012-01-01

The physics of HRTEM image formation and electron diffraction of SWCNT in a polymer matrix were investigated theoretically on the basis of the multislice method, and the optics of a FEG Super TWIN Philips CM 200 TEM operated at 80 kV. The effect of nanocomposite thickness on both image contrast and typical electron diffraction reflections of nanofillers were explored. The implications of the results on the experimental applicability to study dispersion, chirality and diameter of nanofillers are discussed.

Analysis of Carbon/Carbon Fragments From the Columbia Tragedy

NASA Technical Reports Server (NTRS)

Tallant, David R.; Simpson, Regina L.; Jacobson, Nathan S.

2005-01-01

The extensive investigation following the Space Shuttle Orbiter Columbia accident of February 1, 2003 determined that hot gases entered the wing through a breach in the protective reinforced carbon/carbon (RCC) leading edge. In the current study, the exposed edges of the recovered RCC from the vicinity of the breach are examined with scanning electron microscopy and Raman spectroscopy. Electron microscopy of the exposed edges revealed regions of pointed carbon fibers, characteristic of exposure to high temperature oxidizing gases. The Raman technique relates the observed 1350 and 1580 to 1600 cm(-1) bands to graphitic dom ains and their corresponding temperatures of formation. Some of the regions showed evidence of exposure temperatures beyond 2700 ?C during the accident.

Study of environmental biodegradation of LDPE films in soil using optical and scanning electron microscopy.

PubMed

Mumtaz, Tabassum; Khan, M R; Hassan, Mohd Ali

2010-07-01

An outdoor soil burial test was carried out to evaluate the degradation of commercially available LDPE carrier bags in natural soil for up to 2 years. Biodegradability of low density polyethylene films in soil was monitored using both optical and scanning electron microscopy (SEM). After 7-9 months of soil exposure, microbial colonization was evident on the film surface. Exposed LDPE samples exhibit progressive changes towards degradation after 17-22 months. SEM images reveal signs of degradation such as exfoliation and formation of cracks on film leading to disintegration. The possible degradation mode and consequences on the use and disposal of LDPE films is discussed. Copyright 2010 Elsevier Ltd. All rights reserved.

Ehlers-Danlos syndrome associated with fatal spontaneous vascular rupture in a dog.

PubMed

Uri, M; Verin, R; Ressel, L; Buckley, L; McEwan, N

2015-01-01

A 7-month-old male cross breed dog was presented with hyperextensible skin and atrophic scarring. A diagnosis of Ehlers-Danlos syndrome was made based on clinical signs, histopathology and electron microscopy. Two weeks after presentation, the dog died suddenly. Post-mortem examination revealed haemothorax and rupture of the left subclavian artery. Histological findings, including Goldner's modified Masson's trichrome staining and transmission electron microscopy of the subclavian artery, revealed abnormalities in the structure and arrangement of collagen fibrils, suggesting that the defective collagen formation extended to the vasculature. To the authors' knowledge, this is the first report of Ehlers-Danlos syndrome with vascular involvement in animals. Copyright © 2014 Elsevier Ltd. All rights reserved.

Investigation on structural and electrical properties of Fe doped ZnO nanoparticles synthesized by solution combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ram, Mast, E-mail: mastram1999@yahoo.com; Bala, Kanchan; Sharma, Hakikat

In the present study, nanoparticles of Fe doped zinc oxide (ZnO) [Zn{sub 1-x}Fe{sub x}O where x=0.0, 0.01, 0.02, 0.03 and 0.05] were prepared by cost effective solution combustion method. The powder X-ray diffractometry confirms the formation of single phase wurtzite structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the micrsostructure of Fe-doped ZnO nanoparticles. The DC electrical conductivity was found to increase with temperature and measurement was carried out in the temperature range of 300-473K. DC electrical conductivity increases with temperature and decreases with Fe doping concentration.

Connected Au network in annealed Ni/Au thin films on p-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S. P.; Jang, H. W.; Noh, D. Y.

2007-11-12

We report the formation of a connected Au network in annealed Ni/Au thin films on p-GaN, which was studied by scanning electron microscopy, transmission electron microscopy, and synchrotron x-ray diffraction. As the Ni was oxidized into NiO upon annealing at 530 deg. C in air, the Au layer was transformed to an interconnected network with an increased thickness. During annealing, Ni atoms diffuse out onto the Au through defects to form NiO, while Au atoms replace the Ni positions. The Au network grows downward until it reaches the p-GaN substrate, and NiO columns fill the space between the Au network.

Formation of MoS2 inorganic fullerenes (IFs) by the reaction of MoO3 nanobelts and S.

PubMed

Li, Xiao Lin; Li, Ya Dong

2003-06-16

The reaction of MoO3 and S at temperatures higher than 300 degrees C in an argon atmosphere provides a convenient and effective method for the synthesis of MoS2 nanocrystalline substances. MoS2 nanotubes and fullerene-like nanoparticles have been obtained by the reaction at 850 degrees C under well-controlled conditions. The influences of reaction temperature and duration were carefully investigated in this paper. All of the nanostructures were characterized by Xray powder diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). A stepwise reaction model and rolling mechanism were proposed based on the experimental results.

Emodin affects biofilm formation and expression of virulence factors in Streptococcus suis ATCC700794.

PubMed

Yang, Yan-Bei; Wang, Shuai; Wang, Chang; Huang, Quan-Yong; Bai, Jing-Wen; Chen, Jian-Qing; Chen, Xue-Ying; Li, Yan-Hua

2015-12-01

Streptococcus suis (S. suis) is a swine pathogen and also a zoonotic agent. In this study, the effects of subinhibitory concentrations (sub-MICs) of emodin on biofilm formation by S. suis ATCC700794 were evaluated. As quantified by crystal violet staining, biofilm formation by S. suis ATCC700794 was dose-dependently decreased after growth with 1/2 MIC, 1/4 MIC, or 1/8 MIC of emodin. By scanning electron microscopy, the structural architecture of the S. suis ATCC700794 biofilms was examined following growth in culture medium supplemented with 1/2 MIC, 1/4 MIC, 1/8 MIC, or 1/16 MIC of emodin. Scanning electron microscopy analysis revealed the potential effect of emodin on biofilm formation by S. suis ATCC700794. The expression of luxS gene and virulence genes in S. suis ATCC700794 was investigated by quantitative RT-PCR. It was found that sub-MICs of emodin significantly decreased the expression of gapdh, sly, fbps, ef, and luxS. However, it was found that sub-MICs of emodin significantly increased the expression of cps2J, mrp, and gdh. These findings showed that sub-MICs of emodin could cause the difference in the expression level of the virulence genes.

The increase of apatite layer formation by the poly(3-hydroxybutyrate) surface modification of hydroxyapatite and β-tricalcium phosphate.

PubMed

Szubert, M; Adamska, K; Szybowicz, M; Jesionowski, T; Buchwald, T; Voelkel, A

2014-01-01

The aim of this study was the surface modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) grafting and characterization of modificates. The bioactivity examination was carried out by the determination to grow an apatite layer on modified materials during incubation in simulated body fluid at 37°C. The additional issue taken up in this paper was to investigate the influence of fluid replacement. The process of the surface modification of biomaterials was evaluated by means of infrared and Raman spectroscopy. Formation of the apatite layer was assessed by means of scanning electron microscopy and confirmed by energy dispersive, Raman and Fourier transformed infrared spectroscopy. During exposure in simulated body fluid, the variation of the zeta potential, pH measurement and relative weight was monitored. Examination of scanning electron microscopy micrographs suggests that modification of hydroxyapatite and β-tricalcium phosphate by poly(3-hydroxybutyrate) significantly increases apatite layer formation. Raman spectroscopy evaluation revealed that the formation of the apatite layer was more significant in the case of hydroxyapatite modificate, when compared to the β-tricalcium phosphate modificate. Both modificates were characterized by stable pH, close to the natural pH of human body fluids. Furthermore, we have shown that a weekly changed, simulated body fluid solution increases apatite layer formation. © 2013.

Morphological and chemical evolution on InP(1 0 0) surface irradiated with femtosecond laser

NASA Astrophysics Data System (ADS)

Qian, H. X.; Zhou, W.; Zheng, H. Y.; Lim, G. C.

2005-12-01

Single crystalline InP was ablated in air with p-polarized Ti:sapphire femtosecond laser at a fixed laser fluence of 82 mJ/cm 2. Ripples parallel to the laser polarization direction were found by scanning electron microscopy and atomic force microscopy to form for laser pulses ranging from 50 to 1000, whereas flower-like structures appeared for laser pulses of 10 4 and above. Analysis by X-ray photoelectron spectroscopy showed formation of indium and phosphorus oxides on the irradiated surface and the amounts of oxides increased with increasing number of laser pulses. The oxide formation is attributed to chemical reaction between the ultrafast laser ablation plume and oxygen in air, and formation of the flower-like structures is shown to be related to deposition of the oxides on the irradiated surface.

Tin-Assisted Synthesis of ɛ -Ga2O3 by Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Kracht, M.; Karg, A.; Schörmann, J.; Weinhold, M.; Zink, D.; Michel, F.; Rohnke, M.; Schowalter, M.; Gerken, B.; Rosenauer, A.; Klar, P. J.; Janek, J.; Eickhoff, M.

2017-11-01

The synthesis of ɛ -Ga2O3 and β -Ga2O3 by plasma-assisted molecular beam epitaxy on (001 )Al2O3 substrates is studied. The growth window of β -Ga2O3 in the Ga-rich regime, usually limited by the formation of volatile gallium suboxide, is expanded due to the presence of tin during the growth process, which stabilizes the formation of gallium oxides. X-ray diffraction, transmission electron microscopy, time-of-flight secondary-ion mass spectrometry, Raman spectroscopy, and atomic force microscopy are used to analyze the influence of tin on the layer formation. We demonstrate that it allows the synthesis of phase-pure ɛ -Ga2O3 . A growth model based on the oxidation of gallium suboxide by reduction of an intermediate sacrificial tin oxide is suggested.

Alteration of TiC in Supernovae Outflows: Transmission Electron Microscopy Study of TiC Subgrains in Supernovae Graphite

NASA Astrophysics Data System (ADS)

Daulton, T. L.; Bernatowicz, T. J.; Croat, T. K.

2009-03-01

TiC and metal subgrains within supernovae graphites often exhibit rims suggesting alteration prior to encapsulation in the graphite. Detailed TEM microcharacterizations of the rimmed grains are performed to determine the mechanism of rim formation.

Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy

PubMed Central

Cramer, Tobias; Travaglini, Lorenzo; Lai, Stefano; Patruno, Luca; de Miranda, Stefano; Bonfiglio, Annalisa; Cosseddu, Piero; Fraboni, Beatrice

2016-01-01

The development of new materials and devices for flexible electronics depends crucially on the understanding of how strain affects electronic material properties at the nano-scale. Scanning Kelvin-Probe Microscopy (SKPM) is a unique technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM in non-contact mode is feasible on deformed flexible samples and allows to identify strain induced electronic defects. As an example we apply the technique to investigate the strain response of organic thin film transistors containing TIPS-pentacene patterned on polymer foils. Controlled surface strain is induced in the semiconducting layer by bending the transistor substrate. The amount of local strain is quantified by a mathematical model describing the bending mechanics. We find that the step-wise reduction of device performance at critical bending radii is caused by the formation of nano-cracks in the microcrystal morphology of the TIPS-pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects. PMID:27910889

Synthesis of Mn-doped ZnS architectures in ternary solution and their optical properties

NASA Astrophysics Data System (ADS)

Wang, Xinjuan; Zhang, Qinglin; Zou, Bingsuo; Lei, Aihua; Ren, Pinyun

2011-10-01

Mn-doped ZnS sea urchin-like architectures were fabricated by a one-pot solvothermal route in a ternary solution made of ethylenediamine, ethanolamine and distilled water. The as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was demonstrated that the as-prepared sea urchin-like architectures with diameter of 0.5-1.5 μm were composed of nanorods, possessing a wurtzite structures. The preferred growth orientation of nanorods was found to be the [0 0 2] direction. The PL spectra of the Mn-doped ZnS sea urchin-like architectures show a strong orange emission at 587 nm, indicating the successful doping of Mn 2+ ions into ZnS host. Ethanolamine played the role of oriented-assembly agent in the formation of sea urchin-like architectures. A possible growth mechanism was proposed to explain the formation of sea urchin-like architectures.

A general melt-injection-decomposition route to oriented metal oxide nanowire arrays

NASA Astrophysics Data System (ADS)

Han, Dongqiang; Zhang, Xinwei; Hua, Zhenghe; Yang, Shaoguang

2016-12-01

In this manuscript, a general melt-injection-decomposition (MID) route has been proposed and realized for the fabrication of oriented metal oxide nanowire arrays. Nitrate was used as the starting materials, which was injected into the nanopores of the anodic aluminum oxide (AAO) membrane through the capillarity action in its liquid state. At higher temperature, the nitrate decomposed into corresponding metal oxide within the nanopores of the AAO membrane. Oriented metal oxide nanowire arrays were formed within the AAO membrane as a result of the confinement of the nanopores. Four kinds of metal oxide (CuO, Mn2O3, Co3O4 and Cr2O3) nanowire arrays are presented here as examples fabricated by this newly developed process. X-ray diffraction, scanning electron microscopy and transmission electron microscopy studies showed clear evidence of the formations of the oriented metal oxide nanowire arrays. Formation mechanism of the metal oxide nanowire arrays is discussed based on the Thermogravimetry and Differential Thermal Analysis measurement results.

Electron microscopy of iron chalcogenide FeTe(Se) films

NASA Astrophysics Data System (ADS)

Shchichko, I. O.; Presnyakov, M. Yu.; Stepantsov, E. A.; Kazakov, S. M.; Antipov, E. V.; Makarova, I. P.; Vasil'ev, A. L.

2015-05-01

The structure of Fe1 + δTe1 - x Se x films ( x = 0; 0.05) grown on single-crystal MgO and LaAlO3 substrates has been investigated by transmission and scanning transmission electron microscopy. The study of Fe1.11Te/MgO structures has revealed two crystallographic orientation relationships between the film and substrate. It is shown that the lattice mismatch between the film and substrate is compensated for by the formation of misfit dislocations. The Burgers vector projection is determined. The stresses in the film can partially be compensated for due to the formation of an intermediate disordered layer. It is shown that a FeTe0.5Se0.5 film grown on a LaAlO3 substrate is single-crystal and that the FeTe0.5Se0.5/LaAlO3 interface in a selected region is coherent. The orientation relationships between the film and substrate are also determined for this case.

Scanning electron microscopy of heat treated TiO2 nanotubes arrays obtained by anodic oxidation

NASA Astrophysics Data System (ADS)

Naranjo, D. I.; García-Vergara, S. J.; Blanco, S.

2017-12-01

Scanning electron microscopy was used to investigate the anatase-rutile transformation of self-organized TiO2 nanotubes obtained on titanium foil by anodizing and subsequent heat treatment. The anodizing was carried out at 20V in an 1% v/v HF acid and ethylene glycol:water (50:50) electrolyte at room temperature. The anodized samples were initially pre-heat treated at 450°C for 4 hours to modify the amorphous structure of TiO2 nanotubes into anatase structure. Then, the samples were heated between 600 to 800°C for different times, in order to promote the transformation to rutile structure. The formation of TiO2 nanotubes is evident by SEM images. Notably, when the samples are treated at high temperature, the formation of rutile crystals starts to become evident at the nanotubes located on the originally grain boundaries of the titanium. Thus, the anatase - rutile transformation has a close relationship with the microstructure of the titanium, more exactly with grain boundaries.

Mediator structure and rearrangements required for holoenzyme formation.

PubMed

Tsai, Kuang-Lei; Yu, Xiaodi; Gopalan, Sneha; Chao, Ti-Chun; Zhang, Ying; Florens, Laurence; Washburn, Michael P; Murakami, Kenji; Conaway, Ronald C; Conaway, Joan W; Asturias, Francisco J

2017-04-13

The conserved Mediator co-activator complex has an essential role in the regulation of RNA polymerase II transcription in all eukaryotes. Understanding the structure and interactions of Mediator is crucial for determining how the complex influences transcription initiation and conveys regulatory information to the basal transcription machinery. Here we present a 4.4 Å resolution cryo-electron microscopy map of Schizosaccharomyces pombe Mediator in which conserved Mediator subunits are individually resolved. The essential Med14 subunit works as a central backbone that connects the Mediator head, middle and tail modules. Comparison with a 7.8 Å resolution cryo-electron microscopy map of a Mediator-RNA polymerase II holoenzyme reveals that changes in the structure of Med14 facilitate a large-scale Mediator rearrangement that is essential for holoenzyme formation. Our study suggests that access to different conformations and crosstalk between structural elements are essential for the Mediator regulation mechanism, and could explain the capacity of the complex to integrate multiple regulatory signals.

Formation of conductive copper lines by femtosecond laser irradiation of copper nitride film on plastic substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiaodong; Yuan, Ningyi, E-mail: nyyuan@cczu.edu.cn; Center for Low-Dimensional Materials, Micro-Nano Devices and Systems, Changzhou University, Changzhou 213164, Jiangsu

2015-05-15

In this paper, we report a simple method to form conductive copper lines by scanning a single-beam femtosecond pulse laser on a plastic substrate covered with copper nitride (Cu{sub 3}N) film. The Cu{sub 3}N films were prepared by DC magnetron sputtering in the presence of an Ar + N{sub 2} atmosphere at 100 °C. The influence of the laser power and scanning speed on the formed copper line width, surface features, and morphology was analyzed by means of optical microscopy, X-ray diffraction, non-contact 3D profilometer, and scanning electron microscopy. The experimental results demonstrate that low laser power and low scanningmore » speed favor the formation of uniform and flat Cu lines. After process optimization, copper lines with a width less than 5 μm were obtained, which provides an attractive application prospect in the field of flexible electronic devices.« less

Nano-analytical electron microscopy reveals fundamental insights into human cardiovascular tissue calcification

NASA Astrophysics Data System (ADS)

Bertazzo, Sergio; Gentleman, Eileen; Cloyd, Kristy L.; Chester, Adrian H.; Yacoub, Magdi H.; Stevens, Molly M.

2013-06-01

The accumulation of calcified material in cardiovascular tissue is thought to involve cytochemical, extracellular matrix and systemic signals; however, its precise composition and nanoscale architecture remain largely unexplored. Using nano-analytical electron microscopy techniques, we examined valves, aortae and coronary arteries from patients with and without calcific cardiovascular disease and detected spherical calcium phosphate particles, regardless of the presence of calcific lesions. We also examined lesions after sectioning with a focused ion beam and found that the spherical particles are composed of highly crystalline hydroxyapatite that crystallographically and structurally differs from bone mineral. Taken together, these data suggest that mineralized spherical particles may play a fundamental role in calcific lesion formation. Their ubiquitous presence in varied cardiovascular tissues and from patients with a spectrum of diseases further suggests that lesion formation may follow a common process. Indeed, applying materials science techniques to ectopic and orthotopic calcification has great potential to lend critical insights into pathophysiological processes underlying calcific cardiovascular disease.

Fullerenes, PAH, Carbon Nanostructures, and Soot in Low Pressure Diffusion Flames

NASA Technical Reports Server (NTRS)

Grieco, William J.; Lafleur, Arthur L.; Rainey, Lenore C.; Taghizadeh, Koli; VanderSande, John B.; Howard, Jack B.

1997-01-01

The formation of fullerenes C60 and C7O is known to occur in premixed laminar benzene/oxygen/argon flames operated at reduced pressures. High resolution transmission electron microscopy (HRTEM) images of material collected from these flames has identified a variety of multishelled nanotubes and fullerene 'onions' as well as some trigonous structures. These fullerenes and nanostructures resemble the material that results from commercial fullerene production systems using graphite vaporization. As a result, combustion is an interesting method for fullerenes synthesis. If commercial scale operation is to be considered, the use of diffusion flames might be safer and less cumbersome than premixed flames. However, it is not known whether diffusion flames produce the types and yields of fullerenes obtained from premixed benzene/oxygen flames. Therefore, the formation of fullerenes and carbon nanostructures, as well as polycyclic aromatic hydrocarbons (PAH) and soot, in acetylene and benzene diffusion flames is being studied using high performance liquid chromatography (HPLC) and high resolution transmission electron microscopy (HRTEM).

Bombyx mori nucleopolyhedrovirus ORF54, a viral desmoplakin gene, is associated with the infectivity of budded virions.

PubMed

Zhang, Min-Juan; Tian, Cai-Hong; Fan, Xiao-Ying; Lou, Yi-Han; Cheng, Ruo-Lin; Zhang, Chuan-Xi

2012-07-01

Bombyx mori nucleopolyhedrovirus (BmNPV) ORF54 (Bm54), a member of the viral desmoplakin N-terminus superfamily, is homologous to Autographa californica nucleopolyhedrovirus (AcMNPV) ORF66, which is required for the efficient egress of nucleocapsids from the nucleus and occlusion body formation. In this paper, we generated a bacmid with the Bm54 gene deleted via homologous recombination in Escherichia coli and characterized the mutant virus using a transfection-infection assay and transmission electron microscopy analysis. Our results demonstrated that the cells transfected with viral DNA lacking Bm54 produced non-infectious budded viruses (BVs). Electron microscopy showed that although the deletion of Bm54 did not affect assembly and release of nucleocapsids, it severely affected polyhedron formation. In conclusion, deletion of Bm54 resulted in non-infectious BV and defective polyhedra. Although the sequences of Bm54 and Ac66 are very similar, the two genes function quite differently in the regulation of viral life cycle.

Ag(I)-bovine serum albumin hydrosol-mediated formation of Ag3PO4/reduced graphene oxide composites for visible-light degradation of Rhodamine B solution.

PubMed

Ma, Peiyan; Chen, Anliang; Wu, Yan; Fu, Zhengyi; Kong, Wei; Che, Liyuan; Ma, Ruifang

2014-03-01

A cost-effective Ag(I)-bovine serum albumin (BSA) supramolecular hydrosol strategy was utilized to assemble Ag3PO4 nanospheres onto reduced graphene oxide (rGO) sheets. The obtained composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, UV-vis absorption spectroscopy and Fourier transform infrared spectroscopy. Compared with the pure Ag3PO4 crystals and Ag3PO4 particles prepared with Ag(I)-BSA hydrosol as precursor, the Ag3PO4/rGO composites obtained with different content of graphene oxide indicated improved visible-light-driven photocatalysis activity for the decomposition of Rhodamine B aqueous solution. The results pointed to the possibility of synthesizing graphene-based photocatalysts by metal ion-BSA hydrosol. Copyright © 2013 Elsevier Inc. All rights reserved.

Driving force of stacking-fault formation in SiC p-i-n diodes.

PubMed

Ha, S; Skowronski, M; Sumakeris, J J; Paisley, M J; Das, M K

2004-04-30

The driving force of stacking-fault expansion in SiC p-i-n diodes was investigated using optical emission microscopy and transmission electron microscopy. The stacking-fault expansion and properties of the partial dislocations were inconsistent with any stress as the driving force. A thermodynamic free energy difference between the perfect and a faulted structure is suggested as a plausible driving force in the tested diodes, indicating that hexagonal polytypes of silicon carbide are metastable at room temperature.

Scanning electron microscopy of Ancylostoma spp. dog infective larvae captured and destroyed by the nematophagous fungus Duddingtonia flagrans.

PubMed

Maciel, A S; Araújo, J V; Campos, A K; Benjamin, L A; Freitas, L G

2009-06-01

The interaction between the nematode-trapping fungus Duddingtonia flagrans (isolate CG768) against Ancylostoma spp. dog infective larvae (L(3)) was evaluated by means of scanning electron microscopy. Adhesive network trap formation was observed 6h after the beginning of the interaction, and the capture of Ancylostoma spp. L(3) was observed 8h after the inoculation these larvae on the cellulose membranes colonized by the fungus. Scanning electron micrographs were taken at 0, 12, 24, 36 and 48 h, where 0 is the time when Ancylostoma spp. L(3) was first captured by the fungus. Details of the capture structure formed by the fungus were described. Nematophagous Fungus Helper Bacteria (NHB) were found at interactions points between the D. flagrans and Ancylostoma spp. L(3). The cuticle penetration by the differentiated fungal hyphae with the exit of nematode internal contents was observed 36 h after the capture. Ancylostoma spp. L(3) were completely destroyed after 48 h of interaction with the fungus. The scanning electron microscopy technique was efficient on the study of this interaction, showing that the nematode-trapping fungus D. flagrans (isolate CG768) is a potential exterminator of Ancylostoma spp. L(3).

Characterisation of nickel silicide thin films by spectroscopy and microscopy techniques.

PubMed

Bhaskaran, M; Sriram, S; Holland, A S; Evans, P J

2009-01-01

This article discusses the formation and detailed materials characterisation of nickel silicide thin films. Nickel silicide thin films have been formed by thermally reacting electron beam evaporated thin films of nickel with silicon. The nickel silicide thin films have been analysed using Auger electron spectroscopy (AES) depth profiles, secondary ion mass spectrometry (SIMS), and Rutherford backscattering spectroscopy (RBS). The AES depth profile shows a uniform NiSi film, with a composition of 49-50% nickel and 51-50% silicon. No oxygen contamination either on the surface or at the silicide-silicon interface was observed. The SIMS depth profile confirms the existence of a uniform film, with no traces of oxygen contamination. RBS results indicate a nickel silicide layer of 114 nm, with the simulated spectra in close agreement with the experimental data. Atomic force microscopy and transmission electron microscopy have been used to study the morphology of the nickel silicide thin films. The average grain size and average surface roughness of these films was found to be 30-50 and 0.67 nm, respectively. The film surface has also been studied using Kikuchi patterns obtained by electron backscatter detection.

The structure of the desiccated Richtersius coronifer (Richters, 1903).

PubMed

Czerneková, Michaela; Jönsson, K Ingemar; Chajec, Lukasz; Student, Sebastian; Poprawa, Izabela

2017-05-01

Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer.

Formation mechanisms for the dominant kinks with different angles in InP nanowires.

PubMed

Zhang, Minghuan; Wang, Fengyun; Wang, Chao; Wang, Yiqian; Yip, SenPo; Ho, Johnny C

2014-01-01

The morphologies and microstructures of kinked InP nanowires (NWs) prepared by solid-source chemical vapor deposition method were examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Statistical analysis and structural characterization reveal that four different kinds of kinks are dominant in the grown InP NWs with a bending angle of approximately 70°, 90°, 110°, and 170°, respectively. The formation mechanisms of these kinks are discussed. Specifically, the existence of kinks with bending angles of approximately 70° and 110° are mainly attributed to the occurrence of stacking faults and nanotwins in the NWs, which could easily form by the glide of {111} planes, while approximately 90° kinks result from the local amorphorization of InP NWs. Also, approximately 170° kinks are mainly caused by small-angle boundaries, where the insertion of extra atomic planes could make the NWs slightly bent. In addition, multiple kinks with various angles are also observed. Importantly, all these results are beneficial to understand the formation mechanisms of kinks in compound semiconductor NWs, which could guide the design of nanostructured materials, morphologies, microstructures, and/or enhanced mechanical properties.

Formation mechanisms for the dominant kinks with different angles in InP nanowires

PubMed Central

2014-01-01

The morphologies and microstructures of kinked InP nanowires (NWs) prepared by solid-source chemical vapor deposition method were examined using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Statistical analysis and structural characterization reveal that four different kinds of kinks are dominant in the grown InP NWs with a bending angle of approximately 70°, 90°, 110°, and 170°, respectively. The formation mechanisms of these kinks are discussed. Specifically, the existence of kinks with bending angles of approximately 70° and 110° are mainly attributed to the occurrence of stacking faults and nanotwins in the NWs, which could easily form by the glide of {111} planes, while approximately 90° kinks result from the local amorphorization of InP NWs. Also, approximately 170° kinks are mainly caused by small-angle boundaries, where the insertion of extra atomic planes could make the NWs slightly bent. In addition, multiple kinks with various angles are also observed. Importantly, all these results are beneficial to understand the formation mechanisms of kinks in compound semiconductor NWs, which could guide the design of nanostructured materials, morphologies, microstructures, and/or enhanced mechanical properties. PMID:24910572

Porous Si nanowires for highly selective room-temperature NO2 gas sensing

NASA Astrophysics Data System (ADS)

Kwon, Yong Jung; Mirzaei, Ali; Gil Na, Han; Kang, Sung Yong; Choi, Myung Sik; Bang, Jae Hoon; Oum, Wansik; Kim, Sang Sub; Kim, Hyoun Woo

2018-07-01

We report the room-temperature sensing characteristics of Si nanowires (NWs) fabricated from p-Si wafers by a metal-assisted chemical etching method, which is a facile and low-cost method. X-ray diffraction was used to the the study crystallinity and phase formation of Si NWs, and product morphology was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After confirmation of Si NW formation via the SEM and TEM micrographs, sensing tests were carried out at room temperature, and it was found that the Si NW sensor prepared from Si wafers with a resistivity of 0.001–0.003 Ω.cm had the highest response to NO2 gas (Rg/Ra = 1.86 for 50 ppm NO2), with a fast response (15 s) and recovery (30 s) time. Furthermore, the sensor responses to SO2, toluene, benzene, H2, and ethanol were nearly negligible, demonstrating the excellent selectivity to NO2 gas. The gas-sensing mechanism is discussed in detail. The present sensor can operate at room temperature, and is compatible with the microelectronic fabrication process, demonstrating its promise for next-generation Si-based electronics fused with functional chemical sensors.

Porous Si nanowires for highly selective room-temperature NO2 gas sensing.

PubMed

Kwon, Yong Jung; Mirzaei, Ali; Na, Han Gil; Kang, Sung Yong; Choi, Myung Sik; Bang, Jae Hoon; Oum, Wansik; Kim, Sang Sub; Kim, Hyoun Woo

2018-07-20

We report the room-temperature sensing characteristics of Si nanowires (NWs) fabricated from p-Si wafers by a metal-assisted chemical etching method, which is a facile and low-cost method. X-ray diffraction was used to the the study crystallinity and phase formation of Si NWs, and product morphology was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After confirmation of Si NW formation via the SEM and TEM micrographs, sensing tests were carried out at room temperature, and it was found that the Si NW sensor prepared from Si wafers with a resistivity of 0.001-0.003 Ω.cm had the highest response to NO 2 gas (R g /R a  = 1.86 for 50 ppm NO 2 ), with a fast response (15 s) and recovery (30 s) time. Furthermore, the sensor responses to SO 2 , toluene, benzene, H 2 , and ethanol were nearly negligible, demonstrating the excellent selectivity to NO 2 gas. The gas-sensing mechanism is discussed in detail. The present sensor can operate at room temperature, and is compatible with the microelectronic fabrication process, demonstrating its promise for next-generation Si-based electronics fused with functional chemical sensors.

Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique

NASA Astrophysics Data System (ADS)

Geremariam Welearegay, Tesfalem; Cindemir, Umut; Österlund, Lars; Ionescu, Radu

2018-02-01

Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of ∼10 nm (Au), ∼4 nm (Cu) and ∼3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of kΩ and tens of MΩ, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

In situ KPFM imaging of local photovoltaic characteristics of structured organic photovoltaic devices.

PubMed

Watanabe, Satoshi; Fukuchi, Yasumasa; Fukasawa, Masako; Sassa, Takafumi; Kimoto, Atsushi; Tajima, Yusuke; Uchiyama, Masanobu; Yamashita, Takashi; Matsumoto, Mutsuyoshi; Aoyama, Tetsuya

2014-02-12

Here, we discuss the local photovoltaic characteristics of a structured bulk heterojunction, organic photovoltaic devices fabricated with a liquid carbazole, and a fullerene derivative based on analysis by scanning kelvin probe force microscopy (KPFM). Periodic photopolymerization induced by an interference pattern from two laser beams formed surface relief gratings (SRG) in the structured films. The surface potential distribution in the SRGs indicates the formation of donor and acceptor spatial distribution. Under illumination, the surface potential reversibly changed because of the generation of fullerene anions and hole transport from the films to substrates, which indicates that we successfully imaged the local photovoltaic characteristics of the structured photovoltaic devices. Using atomic force microscopy, we confirmed the formation of the SRG because of the material migration to the photopolymerized region of the films, which was induced by light exposure through photomasks. The structuring technique allows for the direct fabrication and the control of donor and acceptor spatial distribution in organic photonic and electronic devices with minimized material consumption. This in situ KPFM technique is indispensable to the fabrication of nanoscale electron donor and electron acceptor spatial distribution in the devices.

Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

2016-04-01

Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

Inhibitory Effect of Sophorolipid on Candida albicans Biofilm Formation and Hyphal Growth

PubMed Central

Haque, Farazul; Alfatah, Md.; Ganesan, K.; Bhattacharyya, Mani Shankar

2016-01-01

Candida albicans causes superficial and life-threatening systemic infections. These are difficult to treat often due to drug resistance, particularly because C. albicans biofilms are inherently resistant to most antifungals. Sophorolipid (SL), a glycolipid biosurfactant, has been shown to have antimicrobial and anticancer properties. In this study, we investigated the effect of SL on C. albicans biofilm formation and preformed biofilms. SL was found to inhibit C. albicans biofilm formation as well as reduce the viability of preformed biofilms. Moreover, SL, when used along with amphotericin B (AmB) or fluconazole (FLZ), was found to act synergistically against biofilm formation and preformed biofilms. Effect of SL on C. albicans biofilm formation was further visualized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), which revealed absence of hyphae, typical biofilm architecture and alteration in the morphology of biofilm cells. We also found that SL downregulates the expression of hypha specific genes HWP1, ALS1, ALS3, ECE1 and SAP4, which possibly explains the inhibitory effect of SL on hyphae and biofilm formation. PMID:27030404

Investigation of the microstructure of metallic droplets on Ga(AsBi)/GaAs

NASA Astrophysics Data System (ADS)

Sterzer, E.; Knaub, N.; Ludewig, P.; Straubinger, R.; Beyer, A.; Volz, K.

2014-12-01

Low Bi content GaAs is a promising material for new optical devices with less heat production. The growth of such devices by metal organic vapor phase epitaxy faces several challenges. This paper summarizes results of the formation of metallic droplets during the epitaxial growth of Ga(AsBi) using all-liquid group III and V precursors. The samples that are grown, investigated by atomic force microscopy and scanning electron microscopy, show a different metal droplet distribution over the surface depending on the growth temperature and the V/III ratio of the precursors. Investigations with energy dispersive X-ray analysis and selective etching prove the appearance of phase separated Ga-Bi and pure Bi droplets at growth temperatures between 375 °C and 425 °C, which is explainable by the phase diagram of Ga-Bi. Since the pure Bi droplets show a preferred orientation on the surface after cool-down, transmission electron microscopy measurements were done by using the dark field imaging mode in addition to electron diffraction and high resolution imaging. These experiments show the single crystalline structure of the Bi droplets. The comparison of experimental diffraction patterns with image simulation shows a preferred alignment of Bi {10-1} lattice planes parallel to GaAs {202} lattice planes with the formation of a coincidence lattice. Thus it is possible to derive a model of how the Bi droplets evolve on the GaAs surface.

A comparative study of the effect of α-, β-, and γ-cyclodextrins as stabilizing agents in the synthesis of silver nanoparticles using a green chemistry method.

PubMed

Suárez-Cerda, Javier; Nuñez, Gabriel Alonso; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

2014-10-01

This paper describes the effect of different types of cyclodextrins (CDs) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with α-, β-, or γ-CDs (aqueous solutions) as stabilizing agents, employing the chemical reduction method with citric acid as a reducing agent. A comparative study was done to determine which cyclodextrin (CD) was the best stabilizing agent, and we found out that β-CD was the best due to the number of glucopyranose units in its structure. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). SEM-EDS showed the formation of a cluster with a significant amount of silver, for β-CD-Ag-NPs, spherical agglomerates can be observed. However, for α-, γ-CD, the agglomerates do not have a specific form, but their appearance is porous. TEM analysis shows spherical nanoparticles in shape and size between ~0.5 to 7 nm. The clear lattice fringes in TEM images and the typical selected area electron diffraction (SAED) pattern, showed that the Ag-NPs obtained were highly crystalline with a face cubic center structure (FCC). Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of bond line discontinuities in a high-Mn TWIP steel pipe welded by HF-ERW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Gitae; Kim, Bongyoon; Kang, Yongjoon

In this work, the microstructure and defects in a high-frequency electrical resistance welded (HF-ERW) pipe of high-Mn twinning-induced plasticity (TWIP) steel were characterized. The microstructure of the base metal and the bond line were examined using both optical microscopy and scanning electron microscopy. The features of the bond line were similar to those of conventional steel. Simultaneously, the circumferential ductility was evaluated via a flaring test. It was concluded that the deterioration of the circumferential ductility in a high-Mn TWIP steel pipe was caused by irregular shaped oxide defects and a penetrator that had been formed during welding. Specifically, themore » penetrator, which is composed of MnO and Mn{sub 2}SiO{sub 4}, was found to be the most influential on the circumferential ductility of the welded pipe. The penetrator was analyzed using both an electron probe micro analyzer and transmission electron microscopy, and the formation sequence of the penetrator was evaluated. - Highlights: •This study focused on applying the HF-ERW process to the seam welding of expandable pipe using TWIP steels. •For improvement of the circumferential ductility, deterioration factors were characterized. •Penetrator which would mainly deteriorate the circumferential ductility consisted of round MnO and Mn{sub 2}SiO{sub 4}. •Metallurgical evidence of existing theory regarding the mechanism of defect formation during the HF-ERW was characterized.« less

Diffuse x-ray scattering and transmission electron microscopy study of defects in antimony-implanted silicon

NASA Astrophysics Data System (ADS)

Takamura, Y.; Marshall, A. F.; Mehta, A.; Arthur, J.; Griffin, P. B.; Plummer, J. D.; Patel, J. R.

2004-04-01

Ion implantation followed by laser annealing has been used to create supersaturated and electrically active concentrations of antimony in silicon. Upon subsequent thermal annealing, however, these metastable dopants deactivate towards the equilibrium solubility limit. In this work, the formation of inactive antimony structures has been studied with grazing incidence diffuse x-ray scattering, and transmission electron microscopy, and the results are correlated to previous high-resolution x-ray diffraction data. We find that at a concentration of 6.0×1020 cm-3, small, incoherent clusters of radius 3-4 Å form during annealing at 900 °C. At a higher concentration of 2.2×1021 cm-3, deactivation at 600 °C occurs through the formation of small, antimony aggregates and antimony precipitates. The size of these precipitates from diffuse x-ray scattering is roughly 15 Å in radius for anneal times from 15 to 180 seconds. This value is consistent with the features observed in high-resolution and mass contrast transmission electron microscopy images. The coherent nature of the aggregates and precipitates causes the expansion of the surrounding silicon matrix as the deactivation progresses. In addition, the sensitivity of the diffuse x-ray scattering technique has allowed us to detect the presence of small clusters of radius ˜2 Å in unprocessed Czochralski silicon wafers. These defects are not observed in floating zone silicon wafers, and are tentatively attributed to thermal donors.

[Biosynthesis of gold nanoparticles by Azospirillum brasilense].

PubMed

Kupriashina, M A; Vetchinkina, E P; Burov, A M; Ponomareva, E G; Nikitina, V E

2014-01-01

Plant-associated nitrogen-fixing soil bacteria Azospirillum brasilense were shown to reduce the gold of chloroauric acid to elemental gold, resulting in formation of gold nanoparicles. Extracellular phenoloxidizing enzymes (laccases and Mn peroxidases) were shown to participate in reduction of Au+3 (HAuCl4) to Au(0). Transmission electron microscopy revealed accumulation of colloidal gold nanoparticles of diverse shape in the culture liquid of A. brasilense strains Sp245 and Sp7. The size of the electron-dense nanospheres was 5 to 50 nm, and the size of nanoprisms varied from 5 to 300 nm. The tentative mechanism responsible for formation of gold nanoparticles is discussed.

Importance of microscopy in durability studies of solidified and stabilized contaminated soils

USGS Publications Warehouse

Klich, I.; Wilding, L.P.; Drees, L.R.; Landa, E.R.

1999-01-01

Solidification/stabilization (S/S) is recognized by the U.S. EPA as a best demonstrated available technology for the containment of contaminated soils and other hazardous wastes that cannot be destroyed by chemical, thermal, or biological means. Despite the increased use of S/S technologies, little research has been conducted on the weathering and degradation of solidified and stabilized wastes once the treated materials have been buried. Published data to verify the performance and durability of landfilled treated wastes over time are rare. In this preliminary study, optical and electron microscopy (scanning electron microscopy [SEM], transmission electron microscopy [TEM] and electron probe microanalyses [EPMA]) were used to evaluate weathering features associated with metal-bearing contaminated soil that had been solidified and stabilized with Portland cement and subsequently buried on site, stored outdoors aboveground, or achieved in a laboratory warehouse for up to 6 yr. Physical and chemical alteration processes identified include: freeze-thaw cracking, cracking caused by the formation of expansive minerals such as ettringite, carbonation, and the movement of metals from waste aggregates into the cement micromass. Although the extent of degradation after 6 yr is considered slight to moderate, results of this study show that the same environmental concerns that affect the durability of concrete must be considered when evaluating the durability and permanence of the solidification and stabilization of contaminated soils with cement. In addition, such evaluations cannot be based on leaching and chemical analyses alone. The use of all levels of microscopic analyses must be incorporated into studies of the long-term performance of S/S technologies.Solidification/stabilization (S/S) is recognized by the U.S. EPA as a best demonstrated available technology for the containment of contaminated soils and other hazardous wastes that cannot be destroyed by chemical, thermal, or biological means. Despite the increased use of S/S technologies, little research has been conducted on the weathering and degradation of solidified and stabilized wastes once the treated materials have been buried. Published data to verify the performance and durability of landfilled treated wastes over time are rare. In this preliminary study, optical and electron microscopy (scanning electron microscopy [SEM], transmission electron microscopy [TEM] and electron probe microanalyses [EPMA]) were used to evaluate weathering features associated with metal-bearing contaminated soil that had been solidified and stabilized with Portland cement and subsequently buried on site, stored outdoors aboveground, or archived in a laboratory, warehouse for up to 6 yr. Physical and chemical alteration processes identified include: freeze-thaw cracking, cracking caused by the formation of expansive minerals such as ettringite, carbonation, and the movement of metals from waste aggregates into the cement micromass. Although the extent of degradation after 6 yr is considered slight to moderate, results of this study show that the same environmental concerns that affect the durability of concrete must be considered when evaluating the durability and permanence of the solidification and stabilization of contaminated soils with cement. In addition, such evaluations cannot be based on leaching and chemical analyses alone. The use of all levels of microscopic analyses must be incorporated into studies of the long-term performance of S/S technologies.

Cryo-electron microscopy study of bacteriophage T4 displaying anthrax toxin proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fokine, Andrei; Bowman, Valorie D.; Battisti, Anthony J.

2007-10-25

The bacteriophage T4 capsid contains two accessory surface proteins, the small outer capsid protein (Soc, 870 copies) and the highly antigenic outer capsid protein (Hoc, 155 copies). As these are dispensable for capsid formation, they can be used for displaying proteins and macromolecular complexes on the T4 capsid surface. Anthrax toxin components were attached to the T4 capsid as a fusion protein of the N-terminal domain of the anthrax lethal factor (LFn) with Soc. The LFn-Soc fusion protein was complexed in vitro with Hoc{sup -}Soc{sup -}T4 phage. Subsequently, cleaved anthrax protective antigen heptamers (PA63){sub 7} were attached to the exposedmore » LFn domains. A cryo-electron microscopy study of the decorated T4 particles shows the complex of PA63 heptamers with LFn-Soc on the phage surface. Although the cryo-electron microscopy reconstruction is unable to differentiate on its own between different proposed models of the anthrax toxin, the density is consistent with a model that had predicted the orientation and position of three LFn molecules bound to one PA63 heptamer.« less

Synthesis and characterization of Ce, Cu co-doped ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Harish, G. S.; Sreedhara Reddy, P.

2015-09-01

Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using a chemical co-precipitation method. The prepared nanoparticles were characterized by X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and high resolution Raman spectroscopic techniques. Transmission electron microscopy (TEM) and X-ray diffraction studies showed that the diameter of the particles was around 2-3 nm. Broadened XRD peaks revealed the formation of nanoparticles with a face centered cubic (fcc) structure. DRS studies confirmed that the band gap increased with an increase in the dopant concentration. The Raman spectra of undoped and Ce, Cu ions co-doped ZnS nanoparticles showed longitudinal optical mode and transverse optical mode. Compared with the Raman modes (276 and 351 cm-1) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co- doped ZnS nanoparticles were slightly shifted towards lower frequency. PL spectra of the samples showed remarkable enhancement in the intensity upon doping.

Characterization of new DOPC/DHPC platform for dermal applications.

PubMed

Rodríguez, Gelen; Rubio, Laia; Barba, Clara; López-Iglesias, Carmen; de la Maza, Alfons; López, Olga; Cócera, Mercedes

2013-05-01

Systems formed by mixtures of the phospholipids dioleoylphosphatidylcholine (DOPC) and dihexanoylphosphatidylcholine (DHPC) were characterized by use of differential scanning calorimetry, small angle X-ray scattering and two electron-microscopy techniques, freeze fracture electron microscopy and cryogenic transmission electron microscopy. These techniques allowed for the determination of the size, morphology, structural topology, self-assembly and thermotropic behavior of the nanostructures present in the mixtures. The interaction between the two phospholipids provides curvatures, irregularities and the increase of thickness and flexibility in the membrane. These effects led to the formation of different aggregates with a differential distribution of both phospholipids. The effect of these systems on the skin in vivo was evaluated by measurement of the biophysical skin parameters. Our results show that the DOPC/DHPC application induces a decrease in the permeability and in the hydration of the tissue. These effects in vivo are related to different microstructural changes promoted by these systems in the skin in vitro, published in a recent work. The fundamental biophysical analyses of DOPC/DHPC systems contribute to our understanding of the mechanisms that govern their interaction with the skin.

Self-assembly approach toward magnetic silica-type nanoparticles of different shapes from reverse block copolymer mesophases.

PubMed

Garcia, Carlos B W; Zhang, Yuanming; Mahajan, Surbhi; DiSalvo, Francis; Wiesner, Ulrich

2003-11-05

In the present study poly(isoprene-block-ethylene oxide), PI-b-PEO, block copolymers are used to structure iron oxide and silica precursors into reverse mesophases, which upon dissolution of the organic matrix lead to well-defined nanoparticles of spheres, cylinders, and plates based on the original structure of the mesophase prepared. The hybrid mesophases with sphere, cylinder, and lamellar morphologies containing the inorganic components in the minority phases are characterized through a combination of small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). After heat treatments the respective nanoparticles on mica surfaces are characterized by scanning force microscopy (SFM). X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometer measurements are performed to demonstrate that the heat treatment leads to the formation of a magnetic gamma-Fe2O3 crystalline phase within the amorphous aluminosilicate. The results pave the way to functional, i.e., magnetic nanoparticles where the size, shape, and iron oxide concentration can be controlled opening a range of possible applications.

Functional biocompatible magnetite-cellulose nanocomposite fibrous networks: Characterization by fourier transformed infrared spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy analysis.

PubMed

Habibi, Neda

2015-02-05

The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the NCH3 functional group about 2850cm(-1) is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field. Copyright © 2014 Elsevier B.V. All rights reserved.

Controlled formation of closed-edge nanopores in graphene

NASA Astrophysics Data System (ADS)

He, Kuang; Robertson, Alex W.; Gong, Chuncheng; Allen, Christopher S.; Xu, Qiang; Zandbergen, Henny; Grossman, Jeffrey C.; Kirkland, Angus I.; Warner, Jamie H.

2015-07-01

Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport.Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport. Electronic supplementary information (ESI) available: Low magnification images, image processing techniques employed, modelling and simulation of closed edge nanoribbon, comprehensive AC-TEM dataset, and supporting analysis. See DOI: 10.1039/c5nr02277k

Laser-Induced Breakdown Spectroscopy (LIBS) for Monitoring the Formation of Hydroxyapatite Porous Layers

PubMed Central

Sola, Daniel; Paulés, Daniel; Grima, Lorena

2017-01-01

Laser-induced breakdown spectroscopy (LIBS) is applied to characterize the formation of porous hydroxyapatite layers on the surface of 0.8CaSiO3-0.2Ca3(PO4)2 biocompatible eutectic glass immersed in simulated body fluid (SBF). Compositional and structural characterization analyses were also conducted by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy. PMID:29211006

Effect of T6 heat treatment on the microstructural and mechanical properties of Al-Si-Cu-Mg alloys

NASA Astrophysics Data System (ADS)

Patel, Dhruv; Davda, Chintan; Solanki, P. S.; Keshvani, M. J.

2016-05-01

In this communication, it is aimed to optimize the conditions for T6 heat treatment of permanent die cast Al-Si-Cu-Mg alloys. Various solutionizing temperatures, aging treatments and soaking times were used to improve / modify the mechanical properties of presently studied alloys. Formation mechanism of the particles was understood by carrying out optical microscopy and energy dispersive X-ray (EDX) spectroscopy measurements. Spherical particles of alloys were studied for their microstructural properties using scanning electron microscopy (SEM). Microhardness test was performed to investigate their mechanical properties. Dependence of cluster formation and microhardness of the alloys on the adequate solutionizing temperature, aging treatment and soaking time has been discussed in detail.

Nanoparticle conversion to biofilms: in vitro demonstration using serum-derived mineralo-organic nanoparticles.

PubMed

Wong, Tsui-Yin; Peng, Hsin-Hsin; Wu, Cheng-Yeu; Martel, Jan; Ojcius, David M; Hsu, Fu-Yung; Young, John D

2015-01-01

Mineralo-organic nanoparticles (NPs) detected in biological fluids have been described as precursors of physiological and pathological calcifications in the body. Our main objective was to examine the early stages of mineral NP formation in body fluids. A nanomaterial approach based on atomic force microscopy, dynamic light scattering, electron microscopy and spectroscopy was used. The mineral particles, which contain the serum proteins albumin and fetuin-A, initially precipitate in the form of round amorphous NPs that gradually grow in size, aggregate and coalesce to form crystalline mineral films similar to the structures observed in calcified human arteries. Our study reveals the early stages of particle formation and provides a platform to analyze the role(s) of mineralo-organic NPs in human tissues.

Understanding of the Formation of Micro/Nanoscale Structures on Metal Surfaces by Ultrafast Pulse Laser Processing

NASA Astrophysics Data System (ADS)

Peng, Edwin

In the recent decades, there has been much interest in functionalized surfaces produced by ultrafast laser processing. Using pulse lasers with nanosecond to femtosecond time scale, a wide range of micro/nanoscale structures can be produced on virtually all metal surfaces. These surface structures create special optoelectronic, wetting, and tribological properties with a diverse range of potential applications. The formation mechanisms of these surface structures, especially microscale, mound-like structures, are not fully understood. There has been wide study of ultrafast laser processing of metals. Yet, the proposed formation models present in current literature often lack sufficient experimental verification. Specifically, many studies are limited to surface characterization, e.g. scanning electron microscopy of the surfaces of these micro/nanoscale structures. Valuable insight into the physical processes responsible for formation can be obtained if standard material science characterization methods are performed across the entire mound. In our study, we examined mound-like structures formed on three metal alloys. Using cross section and 3D slice and view operations by a dual beam scanning electron microscope-focused ion beam, the interior microstructures of these mounds are revealed. Taking advantage of amorphous phase formation during laser processing of Ni60Nb40, we verified the fluence-dependent formation model: mounds formed at low fluence are primarily the result of ablation while mounds formed at high fluence are formed by both ablation and rapid resolidification by hydrodynamical fluid flow. For the first time, we revealed the cross section of a wide variety of mound-like structures on titanium surfaces. The increased contribution to mound formation by fluid flow with increasing fluence was observed. Finally, a 3D scanning electron microscopy technique was applied for mounds produced on silver surface by delayed-pulse laser processing. The interior microstructure demonstrated that most of the volume comprised of resolidified silver grains with 1% porosity.

Kinetic factors determining conducting filament formation in solid polymer electrolyte based planar devices

NASA Astrophysics Data System (ADS)

Krishnan, Karthik; Aono, Masakazu; Tsuruoka, Tohru

2016-07-01

Resistive switching characteristics and conducting filament formation dynamics in solid polymer electrolyte (SPE) based planar-type atomic switches, with opposing active Ag and inert Pt electrodes, have been investigated by optimizing the device configuration and experimental parameters such as the gap distance between the electrodes, the salt inclusion in the polymer matrix, and the compliance current applied in current-voltage measurements. The high ionic conductivities of SPE enabled us to make scanning electron microscopy observations of the filament formation processes in the sub-micrometer to micrometer ranges. It was found that switching behaviour and filament growth morphology depend strongly on several kinetic factors, such as the redox reaction rate at the electrode-polymer interfaces, ion mobility in the polymer matrix, electric field strength, and the reduction sites for precipitation. Different filament formations, resulting from unidirectional and dendritic growth behaviours, can be controlled by tuning specified parameters, which in turn improves the stability and performance of SPE-based devices.Resistive switching characteristics and conducting filament formation dynamics in solid polymer electrolyte (SPE) based planar-type atomic switches, with opposing active Ag and inert Pt electrodes, have been investigated by optimizing the device configuration and experimental parameters such as the gap distance between the electrodes, the salt inclusion in the polymer matrix, and the compliance current applied in current-voltage measurements. The high ionic conductivities of SPE enabled us to make scanning electron microscopy observations of the filament formation processes in the sub-micrometer to micrometer ranges. It was found that switching behaviour and filament growth morphology depend strongly on several kinetic factors, such as the redox reaction rate at the electrode-polymer interfaces, ion mobility in the polymer matrix, electric field strength, and the reduction sites for precipitation. Different filament formations, resulting from unidirectional and dendritic growth behaviours, can be controlled by tuning specified parameters, which in turn improves the stability and performance of SPE-based devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00569a

Damage of Escherichia coli membrane by bactericidal agent polyhexamethylene guanidine hydrochloride: micrographic evidences.

PubMed

Zhou, Z X; Wei, D F; Guan, Y; Zheng, A N; Zhong, J J

2010-03-01

The purpose of this study was to provide micrographic evidences for the damaged membrane structure and intracellular structure change of Escherichia coli strain 8099, induced by polyhexamethylene guanidine hydrochloride (PHMG). The bactericidal effect of PHMG on E. coli was investigated based on beta-galactosidase activity assay, fluorescein-5-isothiocyanate confocal laser scanning microscopy, field emission scanning electron microscopy and transmission electron microscopy. The results revealed that a low dose (13 microg ml(-1)) of PHMG slightly damaged the outer membrane structure of the treated bacteria and increased the permeability of the cytoplasmic membrane, while no significant damage was observed to the morphological structure of the cells. A high dose (23 microg ml(-1)) of PHMG collapsed the outer membrane structure, led to the formation of a local membrane pore across the membrane and badly damaged the internal structure of the cells. Subsequently, intracellular components were leaked followed by cell inactivation. Dose-dependent membrane disruption was the main bactericidal mechanism of PHMG. The formation of the local membrane pores was probable after exposure to a high dose (23 microg ml(-1)) of PHMG. Micrographic evidences were provided about the damaged membrane structure and intracellular structure change of E. coli. The presented information helps understand the bactericidal mechanism of PHMG by membrane damage.

Morphologic study of the effect of iron on pseudocyst formation in Trichomonas vaginalis and its interaction with human epithelial cells.

PubMed

Dias-Lopes, Geovane; Saboia-Vahia, Leonardo; Margotti, Eliane Trindade; Fernandes, Nilma de Souza; Castro, Cássia Luana de Faria; Oliveira, Francisco Odencio; Peixoto, Juliana Figueiredo; Britto, Constança; Silva, Fernando Costa E; Cuervo, Patricia; Jesus, José Batista de

2017-10-01

Trichomonas vaginalis is the aetiological agent of human trichomoniasis, which is one of the most prevalent sexually transmitted diseases in humans. Iron is an important element for the survival of this parasite and the colonisation of the host urogenital tract. In this study, we investigated the effects of iron on parasite proliferation in the dynamics of pseudocyst formation and morphologically characterised iron depletion-induced pseudocysts. We performed structural and ultrastructural analyses using light microscopy, scanning electron microscopy and transmission electron microscopy. It was observed that iron depletion (i) interrupts the proliferation of T. vaginalis, (ii) induces morphological changes in typical multiplicative trophozoites to spherical non-proliferative, non-motile pseudocysts, and (iii) induces the arrest of cell division at different stages of the cell cycle; (iv) iron is the fundamental element for the maintenance of typical trophozoite morphology; (v) pseudocysts induced by iron depletion are viable and reversible forms; and, finally, (vi) we demonstrated that pseudocysts induced by iron depletion are able to interact with human epithelial cells maintaining their spherical forms. Together, these data suggest that pseudocysts could be induced as a response to iron nutritional stress and could have a potential role in the transmission and infection of T. vaginalis.

Microgravity effects during fertilization, cell division, development, and calcium metabolism in sea urchins

NASA Technical Reports Server (NTRS)

Schatten, Heide

1996-01-01

The overall objectives of this project are to explore the role of microgravity during fertilization, early development, cytoskeletal organization, and skeletal calcium deposition in a model development system: the sea urchin eggs and embryos. While pursuing these objectives, we have also helped to develop, test, and fly the Aquatic Research Facility (ARF) system. Cells were fixed at preselected time points to preserve the structures and organelles of interest with regards to cell biology events during development. The protocols used for the analysis of the results had been developed during the earlier part of this research and were applied for post-flight analysis using light and (immuno)fluorescence microscopy, scanning electron microscopy, and transmission electron microscopy. The structures of interest are: microtubules during fertilization, cell division, and cilia movement; microfilaments during cell surface restructuring and cell division; centrosomes and centrioles during cell division, cell differentiation, and cilia formation and movement; membranes, Golgi, endoplasmic reticulum, mitochondria, and chromosomes at all stages of development; and calcium deposits during spicule formation in late-stage embryos. In addition to further explore aspects important or living in space, several aspects of this research are also aimed at understanding diseases that affect humans on Earth which may be accelerated in space.

Morphologic study of the effect of iron on pseudocyst formation in Trichomonas vaginalis and its interaction with human epithelial cells

PubMed Central

Dias-Lopes, Geovane; Saboia-Vahia, Leonardo; Margotti, Eliane Trindade; Fernandes, Nilma de Souza; Castro, Cássia Luana de Faria; Oliveira, Francisco Odencio; Peixoto, Juliana Figueiredo; Britto, Constança; Silva, Fernando Costa e; Cuervo, Patricia; de Jesus, José Batista

2017-01-01

BACKGROUND Trichomonas vaginalis is the aetiological agent of human trichomoniasis, which is one of the most prevalent sexually transmitted diseases in humans. Iron is an important element for the survival of this parasite and the colonisation of the host urogenital tract. OBJECTIVES In this study, we investigated the effects of iron on parasite proliferation in the dynamics of pseudocyst formation and morphologically characterised iron depletion-induced pseudocysts. METHODS We performed structural and ultrastructural analyses using light microscopy, scanning electron microscopy and transmission electron microscopy. FINDINGS It was observed that iron depletion (i) interrupts the proliferation of T. vaginalis, (ii) induces morphological changes in typical multiplicative trophozoites to spherical non-proliferative, non-motile pseudocysts, and (iii) induces the arrest of cell division at different stages of the cell cycle; (iv) iron is the fundamental element for the maintenance of typical trophozoite morphology; (v) pseudocysts induced by iron depletion are viable and reversible forms; and, finally, (vi) we demonstrated that pseudocysts induced by iron depletion are able to interact with human epithelial cells maintaining their spherical forms. MAIN CONCLUSIONS Together, these data suggest that pseudocysts could be induced as a response to iron nutritional stress and could have a potential role in the transmission and infection of T. vaginalis. PMID:28953994

The formation of zona radiata in Pseudosciaena crocea revealed by light and transmission electron microscopy.

PubMed

Ma, Xiao-Xin; Zhu, Jun-Quan; Zhou, Hong; Yang, Wan-Xi

2012-02-01

The egg envelope is an essential structure occurring during oogenesis. It plays an important role during the process of fertilization in the large yellow croaker Pseudosciaena crocea. Elucidation of egg envelope formation helps us to understand fertilization mechanisms in teleosts. In the present work, we studied the formation of egg envelope in P. crocea by light microscopy, as well as by transmission and scanning electron microscopy. Four layers exist outside the oocyte plasmalemma, i.e., theca cell layer, basal membrane, granulosa cell layer and zona radiata. According to our observation, zona radiata is a multilaminar structure just like the same structure reported in teleosts, but the origin of this structure is a little different. Before it is formed, a peripheral space filled with different density of vesicles is the place where zona radiata is formed. Zona radiata (Z1) is secreted only by oocyte itself, it belongs to the primary envelope; zona radiata 2 (Z2) and zona radiata 3 (Z3) belong to the secondary envelope, because the two layers are formed after granulosa cells appear, and microvilli participate this process. It is very interesting that Z2 and Z3 are situated between Z1 and the granulosa cell first, but they translocate to the other side of Z1. This microanatomy difference may due to the participation of microvilli. The new finding about egg envelope formation in P. crocea will help us to do further investigation on fertilization mechanisms and will make artificial breeding possible which may contribute to the resource recovery of this species. Copyright © 2011 Elsevier Ltd. All rights reserved.

Au particle formation on the electron beam induced membrane

NASA Astrophysics Data System (ADS)

Choi, Seong Soo; Park, Myoung Jin; Han, Chul Hee; Oh, Sae-Joong; Kim, Sung-In; Park, Nam Kyou; Park, Doo-Jae; Choi, Soo Bong; Kim, Yong-Sang

2017-02-01

Recently the single molecules such as protein and deoxyribonucleic acid (DNA) have been successfully characterized by using a portable solidstate nanopore (MinION) with an electrical detection technique. However, there have been several reports about the high error rates of the fabricated nanopore device, possibly due to an electrical double layer formed inside the pore channel. The current DNA sequencing technology utilized is based on the optical detection method. In order to utilize the current optical detection technique, we will present the formation of the Au nano-pore with Au particle under the various electron beam irradiations. In order to provide the diffusion of Au atoms, a 2 keV electron beam irradiation has been performed During electron beam irradiations by using field emission scanning electron microscopy (FESEM), Au and C atoms would diffuse together and form the binary mixture membrane. Initially, the Au atoms diffused in the membrane are smaller than 1 nm, below the detection limit of the transmission electron microscopy (TEM), so that we are unable to observe the Au atoms in the formed membrane. However, after several months later, the Au atoms became larger and larger with expense of the smaller particles: Ostwald ripening. Furthermore, we also observe the Au crystalline lattice structure on the binary Au-C membrane. The formed Au crystalline lattice structures were constantly changing during electron beam imaging process due to Spinodal decomposition; the unstable thermodynamic system of Au-C binary membrane. The fabricated Au nanopore with an Au nanoparticle can be utilized as a single molecule nanobio sensor.

Real-space identification of intermolecular bonding with atomic force microscopy.

PubMed

Zhang, Jun; Chen, Pengcheng; Yuan, Bingkai; Ji, Wei; Cheng, Zhihai; Qiu, Xiaohui

2013-11-01

We report a real-space visualization of the formation of hydrogen bonding in 8-hydroxyquinoline (8-hq) molecular assemblies on a Cu(111) substrate, using noncontact atomic force microscopy (NC-AFM). The atomically resolved molecular structures enable a precise determination of the characteristics of hydrogen bonding networks, including the bonding sites, orientations, and lengths. The observation of bond contrast was interpreted by ab initio density functional calculations, which indicated the electron density contribution from the hybridized electronic state of the hydrogen bond. Intermolecular coordination between the dehydrogenated 8-hq and Cu adatoms was also revealed by the submolecular resolution AFM characterization. The direct identification of local bonding configurations by NC-AFM would facilitate detailed investigations of intermolecular interactions in complex molecules with multiple active sites.

Synthesis of TiO2 nanoparticles by hydrolysis and peptization of titanium isopropoxide solution

NASA Astrophysics Data System (ADS)

Mahata, S.; Mahato, S. S.; Nandi, M. M.; Mondal, B.

2012-07-01

Here we report the synthesis and characterization of a stable suspension of modified titania nanoparticles. Phase-pure TiO2 nanocrystallites with narrow particle-size distributions were selectively prepared by hydrolysis-peptization of modified alkoxide followed by hydrothermal treatment. Autoclaving modified TiO2 in the presence of HNO3 as cooperative catalysts led to the formation of crystalline TiO2 with narrow-sized distribution. Following the hydrothermal treatment at 150°C, X-ray diffraction shows the particles to be exclusively anatase. Synthesized powder is characterized by FT-IR, scanning electron microscopy (FESEM) and transmission electron microscopy (HRTEM). The photocatalytic activity in the degradation of orange-II is quite comparable to good anatase and rutile nanocrystallites.

Role of topographical defects in organic film growth of 4,4' -biphenyldicarboxylic acid on graphene: A low-energy electron microscopy study

NASA Astrophysics Data System (ADS)

Khokhar, Fawad S.; van Gastel, Raoul; Poelsema, Bene

2010-11-01

We have used low-energy electron microscopy (LEEM) to study the formation of self-assembled molecular networks on graphene sheets. 4,4' -biphenyldicarboxylic acid (BDA) molecular networks were grown using organic molecular beam epitaxy. LEEM images provide direct insight in the growth dynamics and show that defects in the graphene play a crucial role in the final morphology of the molecular film that forms. BDA is demonstrated to form hydrogen bond-stabilized chains on graphene. Dark-field LEEM images reveal that the same defects that determine the morphology of the film, also direct the orientation of the domains, highlighting the importance of understanding the role of defects in epitaxial processes on graphene.

Precise and economic FIB/SEM for CLEM: with 2 nm voxels through mitosis.

PubMed

Luckner, Manja; Wanner, Gerhard

2018-05-23

A portfolio is presented documenting economic, high-resolution correlative focused ion beam scanning electron microscopy (FIB/SEM) in routine, comprising: (i) the use of custom-labeled slides and coverslips, (ii) embedding of cells in thin, or ultra-thin resin layers for correlative light and electron microscopy (CLEM) and (iii) the claim to reach the highest resolution possible with FIB/SEM in xyz. Regions of interest (ROIs) defined in light microscope (LM), can be relocated quickly and precisely in SEM. As proof of principle, HeLa cells were investigated in 3D context at all stages of the cell cycle, documenting ultrastructural changes during mitosis: nuclear envelope breakdown and reassembly, Golgi degradation and reconstitution and the formation of the midzone and midbody.

Synthesis of noble metal/carbon nanotube composites in supercritical methanol.

PubMed

Sun, Zhenyu; Fu, Lei; Liu, Zhimin; Han, Buxing; Liu, Yunqi; Du, Jimin

2006-03-01

A simple and efficient route has been employed to deposit noble metal nanoparticles (Pt, Ru, Pt-Ru, Rh, Ru-Sn) onto carbon nanotubes (CNTs) in supercritical methanol solution. In this method, the inorganic metallic salts acted as metal precursors, and methanol as solvent as well as reductant for the precursors. The as-prepared nanocomposites were structurally and morphologically characterized by X-ray diffraction spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy, and X-ray photoelectron spectroscopy analyses. It was demonstrated that the CNTs were decorated by crystalline metal nanoparticles with uniform sizes and a narrow particle size distribution. The size and loading content of the nanoparticles on CNTs could be tuned by manipulating reaction parameters. Furthermore, the formation mechanism of the composites was also discussed.

Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

DOE PAGES

Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; ...

2015-12-29

Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke

Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

EPA Science Inventory

The formation of aqueous fullerene suspensions by solvent exchange, sonication, or extended mixing in water is widely reported. Commonly used methods for determining the size of these aggregates rely on static and dynamic light scattering, electron microscopy (EM), or atomic forc...

SURFACE FINISHES ON STAINLESS STEEL REDUCE BACTERIAL ATTACHMENT AND EARLY BIOFILM FORMATION: SCANNING ELECTRON AND ATOMIC FORCE MICROSCOPY STUDY

EPA Science Inventory

Three common finishing treatments of stainless steel that are used for equipment during poultry processing were tested for resistance to bacterial contamination. Methods were developed to measure attached bacteria and to identify factors that make surface finishes susceptible or ...

Antibody localization in the glomerular basement membrane may precede in situ immune deposit formation in rat glomeruli.

PubMed

Agodoa, L Y; Gauthier, V J; Mannik, M

1985-02-01

The administration of cationized antibodies, specific to human serum albumin, into the renal artery of rats caused transient presence of IgG in glomeruli by immunofluorescence microscopy. Intravenous infusion of appropriate doses of antigen after the injection of cationized antibodies resulted in immune deposit formation in glomeruli that persisted through 96 hr. By electron microscopy, these deposits were located in the subepithelial area. The injection of large doses of antigen produced immune deposits which were present in glomeruli for only a few hours, presumably due to formation of only small-latticed immune complexes. The presented data indicate that cationic antibodies bound to the fixed negative charges of the glomerular basement membrane can interact with circulating antigen to form immune deposits in glomeruli. This mechanism may be important because anionic antigens have been shown to induce the synthesis of cationic antibodies.

Fabrication of plasmonic nanopore by using electron beam irradiation for optical bio-sensor

NASA Astrophysics Data System (ADS)

Choi, Seong Soo; Park, Myoung Jin; Han, Chul Hee; Oh, Seh Joong; Park, Nam Kyou; Park, Doo Jae; Choi, Soo Bong; Kim, Yong-Sang

2017-05-01

The Au nano-hole surrounded by the periodic nano-patterns would provide the enhanced optical intensity. Hence, the nano-hole surrounded with periodic groove patterns can be utilized as single molecule nanobio optical sensor device. In this report, the nano-hole on the electron beam induced membrane surrounded by periodic groove patterns were fabricated by focused ion beam technique (FIB), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Initially, the Au films with three different thickness of 40 nm, 60 nm, and 200 nm were deposited on the SiN film by using an electron beam sputter-deposition technique, followed by removal of the supporting SiN film. The nanopore was formed on the electron beam induced membrane under the FESEM electron beam irradiation. Nanopore formation inside the Au aperture was controlled down to a few nanometer, by electron beam irradiations. The optical intensities from the biomolecules on the surfaces including Au coated pyramid with periodic groove patterns were investigated via surface enhanced Raman spectroscopy (SERS). The fabricated nanopore surrounded by periodic patterns can be utilized as a next generation single molecule bio optical sensor.

SEM observation on microbial like structure in the ferromanganese crust from the western Pacific Magellan Seamount

NASA Astrophysics Data System (ADS)

Yang, K.; Park, H.; Baik, H.; Kim, J.; Park, K. R.; Yoon, J.; Kim, J. W.

2016-12-01

Understanding the biogeochemical process in the Fe-Mn crust layer is important to reconstruct the paleo-environment when the Fe-Mn crust layer forms. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Electron Energy Loss Spectroscopy (EELS), and Polymerase Chain Reaction (PCR) were utilized to determine the redox states of Fe/Mn and microbial diversity at each layer. Samples were dredged from the western Pacific Magellan Seamount (OSM11) that consists of five well-defined layers from the rim (L1) to the core (L5). Some microbial like structures of sheath-like with filaments (L1 - L3), capsule-shaped (L2), fossilized coccolith mounds with phosphatized globules (L4), and bean-shaped (L4) were detected in entire layers. The cross sectional observation of bean-shaped microbe like structures encrusted with Fe-vernadite (L3) by Scanning Transmission Electron Microscopy (STEM) and Focused Ion Beam (FIB) technique revealed 1-μm diameter cavity in the center and porous structures of encrusting Fe-vernadite in periphery. Moreover, the organic carbon in the center cavity compared with inorganic C (from carbonate) in periphery was differentiated by C-K edge EELS spectra, suggesting that the microbe used to occupy. Indeed, the PCR analysis indicated the presence of functional gene (cumA; 1056bp & coxC; 810bp) association with Mn & Fe oxidizer that promote the formation of the crust. The cloning and sequencing of DNA PCR fragments revealed the appearance of geobacter species in L3 (G. sulfurreducens and G. lovleyi). The DNA molecular biological analysis and SEM direct observations suggest the evidence of biotic process in the formation of Fe-Mn crust.

Analysis of microstructure in electro-spark deposited IN718 superalloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anisimov, E.; Khan, A.K.; Ojo, O.A., E-mail: olanr

2016-09-15

The microstructure of electro-spark deposited (ESD) superalloy IN718 was studied by the use of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. In converse to general assumption, the extremely high cooling rate involved in the ESD process did not produce partitionless solidification that is devoid of second phase microconstituents in the material, nano-sized Laves phase and MC carbide particles were observed within the deposited layer. Notwithstanding the several thermal cycles involved in the process, the extremely low heat input of the process produced a deposited region that is free ofmore » the main strengthening phase of the alloy, γ″ phase precipitates, which is in contrast to what have been reported on laser deposition. Nevertheless, application of the standard full heat treatment of the alloy resulted in extensive formation of the γ″ phase precipitates and δ phase precipitates, the most stable secondary phase of the alloy, with nearly, if not complete, dissolution of the Laves phase particles. Furthermore, the XPS analysis done in the study revealed the formation of nano-oxides within the deposited layer, which increased the microhardness of the superalloy in the as-deposited condition and inhibited its grain growth during post-process heat treatment. The microstructure analysis done in this work is crucial to the understanding of properties of the superalloy processed by the ESD technique. - Highlights: •Electron microscopy analyses of electro-spark deposited IN 718 superalloy were performed. •Nano-sized secondary phase particles were observed within the deposited layer. •The study shows that the ESD did not produce partitionless solidification of the alloy.« less

Optics in the United kingdom.

PubMed

Ditchburn, R W

1969-10-01

Optics is interpreted to include x-ray optics, electronic optics, and short wave radiooptics as well as the more conventional visible, uv, and ir optics. Recent work in Britain on x-ray optics (applied to molecular biology), on scanning electron microscopy, and in radioastronomy (discovery of pulsars) is mentioned. In the optics of the visible and ir there is an increasing interest in over-all systems design. .The formation of large industrial units capable of carrying through major design program, requiring advanced mechanical and electronic design associated with new lens systems, is welcomed.

Correlative Microscopy of Vitreous Sections Provides Insights into BAR-Domain Organization In Situ.

PubMed

Bharat, Tanmay A M; Hoffmann, Patrick C; Kukulski, Wanda

2018-04-10

Electron microscopy imaging of macromolecular complexes in their native cellular context is limited by the inherent difficulty to acquire high-resolution tomographic data from thick cells and to specifically identify elusive structures within crowded cellular environments. Here, we combined cryo-fluorescence microscopy with electron cryo-tomography of vitreous sections into a coherent correlative microscopy workflow, ideal for detection and structural analysis of elusive protein assemblies in situ. We used this workflow to address an open question on BAR-domain coating of yeast plasma membrane compartments known as eisosomes. BAR domains can sense or induce membrane curvature, and form scaffold-like membrane coats in vitro. Our results demonstrate that in cells, the BAR protein Pil1 localizes to eisosomes of varying membrane curvature. Sub-tomogram analysis revealed a dense protein coat on curved eisosomes, which was not present on shallow eisosomes, indicating that while BAR domains can assemble at shallow membranes in vivo, scaffold formation is tightly coupled to curvature generation. Copyright © 2018 MRC Laboratory of Molecular Biology. Published by Elsevier Ltd.. All rights reserved.

Surface electrical properties of stainless steel fibres: An AFM-based study

NASA Astrophysics Data System (ADS)

Yin, Jun; D'Haese, Cécile; Nysten, Bernard

2015-03-01

Atomic force microscopy (AFM) electrical modes were used to study the surface electrical properties of stainless steel fibres. The surface electrical conductivity was studied by current sensing AFM and I-V spectroscopy. Kelvin probe force microscopy was used to measure the surface contact potential. The oxide film, known as passivation layer, covering the fibre surface gives rise to the observation of an apparently semiconducting behaviour. The passivation layer generally exhibits a p-type semiconducting behaviour, which is attributed to the predominant formation of chromium oxide on the surface of the stainless steel fibres. At the nanoscale, different behaviours are observed from points to points, which may be attributed to local variations of the chemical composition and/or thickness of the passivation layer. I-V curves are well fitted with an electron tunnelling model, indicating that electron tunnelling may be the predominant mechanism for electron transport.

Rare earth ions doped ZnO: Synthesis, characterization and preliminary photoactivity assessment

NASA Astrophysics Data System (ADS)

Cerrato, Erik; Gionco, Chiara; Berruti, Ilaria; Sordello, Fabrizio; Calza, Paola; Paganini, Maria Cristina

2018-08-01

This work reports the effect of doping zinc oxide with lanthanide ions on structural, EPR and UV visible properties. Bare and doped samples were synthesized using the simple and green hydrothermal process. Different rare earth ions (RE = La, Ce, Pr, Er and Yb) with 1% molar ratio RE/Zn were used. The samples have been studied using X Ray Diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and UV visible diffuse reflectance spectroscopy. Finally, electron paramagnetic resonance (EPR) spectroscopy, was used to assess the materials photoactivity under UV irradiation, both in solid state, to see the charge carriers' generation and in solution, evaluating the OH• radical formation using the DMPO (5,5-Dimethyl-1-Pyrroline-N-Oxide) spin trapping technique. The results suggest that the synthesized materials could be interesting systems for the photocatalytic abatement of emerging organic persistent pollutants in wastewater treatment plants.

Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction

PubMed Central

Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

2016-01-01

Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport. PMID:27515115

Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers

PubMed Central

Zhang, Chendong; Chuu, Chih-Piao; Ren, Xibiao; Li, Ming-Yang; Li, Lain-Jong; Jin, Chuanhong; Chou, Mei-Yin; Shih, Chih-Kang

2017-01-01

By using direct growth, we create a rotationally aligned MoS2/WSe2 hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry. We quantitatively determine the influence of interlayer coupling on the electronic structure of the hetero-bilayer at different critical points. We show that the direct gap semiconductor concept is retained in the bilayer although the valence and conduction band edges are located at different layers. We further show that the local bandgap is periodically modulated in the X-Y direction with an amplitude of ~0.15 eV, leading to the formation of a two-dimensional electronic superlattice. PMID:28070558

Characterization of swift heavy ion irradiation damage in ceria

DOE PAGES

Yablinsky, Clarissa A.; Devanathan, Ram; Pakarinen, Janne; ...

2015-03-04

Swift heavy ion induced radiation damage is investigated for ceria (CeO 2), which serves as a UO 2 fuel surrogate. Microstructural changes resulting from an irradiation with 940 MeV gold ions of 42 keV/nm electronic energy loss are investigated by means of electron microscopy accompanied by electron energy loss spectroscopy showing that there exists a small density reduction in the ion track core. While chemical changes in the ion track are not precluded, evidence of them was not observed. Classical molecular dynamics simulations of thermal spikes in CeO 2 with an energy deposition of 12 and 36 keV/nm show damagemore » consisting of isolated point defects at 12 keV/nm, and defect clusters at 36 keV/nm, with no amorphization at either energy. Furthermore, inferences are drawn from modeling about density changes in the ion track and the formation of interstitial loops that shed light on features observed by electron microscopy of swift heavy ion irradiated ceria.« less

Carbon nanotube-like materials in the exhaust from a diesel engine using gas oil/ethanol mixing fuel with catalysts and sulfur.

PubMed

Suzuki, Shunsuke; Mori, Shinsuke

2017-08-01

Particulate matter from a diesel engine, including soot and carbon nanomaterials, was collected on a sampling holder and the structure of the materials was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). As a result of employing gas oil/ethanol mixing fuel with sulfur and ferrocene/molybdenum as catalyst sources, formation of carbon nanotubes (CNT)-like materials in addition to soot was observed in the exhaust gas from a diesel engine. It was revealed that CNT-like materials were included among soot in our system only when the following three conditions were satisfied simultaneously: high ethanol fraction in fuel, high sulfur loading, and presence of catalyst sources in fuel. This study confirmed that if at least one of these three conditions was not satisfied, CNT-like materials were not observed in the exhaust from a diesel engine. These experimental results shown in this work provide insights into understanding CNT-like material formation mechanism in a diesel engine. Recent papers reported that carbon nanotube-like materials were included in the exhaust gas from engines, but conditions for carbon nanotube-like material formation have not been well studied. This work provides the required conditions for carbon nanotube-like material growth in a diesel engine, and this will be helpful for understanding the carbon nanotube-like material formation mechanism and taking countermeasures to preventing carbon nanotube-like material formation in a diesel engine.

Effect of Ag additions on the lengthening rate of Ω plates and formation of σ phase in Al-Cu-Mg alloys during thermal exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yaru; Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.c

Effect of Ag additions on the mechanical properties and microstructures of the peak-aged Al-Cu-Mg alloys during prolonged thermal exposure at 150 °C, was investigated by tensile testing, conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The results showed that after exposure for 500 h, > 85% of the peak strength remained. Microstructure observations indicated that increasing the Ag content from 0.14 to 0.57% promoted the precipitation of a fine and uniform Ω phase and suppressed the formation of the θ′ phase, leading to a notable improvement of the strength properties and thermal stability of the studied alloys.more » Quantitative TEM analysis showed that the coarsening of Ω phase was predominated by plate lengthening rather than thickening, while its lengthening rate was independent of various Ag additions during exposure at 150 °C. In addition, an increase of Ag also facilitated the formation of a cubic σ phase, which was further supported by STEM results. - Highlights: •Increasing Ag improved strength properties and thermal stability of the alloys. •After exposure for 500 h, > 85% of the peak strength remained. •The lengthening rate of Ω plates remained constant as Ag increased at 150 °C. •Increasing Ag content facilitated the formation of σ phase.« less

Viscoelasticity and structure of blood clots generated in-vitro by rheometry: A comparison between human, horse, rat, and camel.

PubMed

Dibiasi, Christoph; Plewka, Jacek; Ploszczanski, Leon; Glanz, Veronika; Lichtenegger, Helga; Windberger, Ursula

2018-04-14

Although the coagulation system is evolutionary well preserved, profound species differences exist in viscoelastic as well as in common laboratory tests of coagulation. Evaluating differences in clot formation and material characterisation of clots of four mammalian species on macro-, micro- and nanoscales by the means of rheometry, scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS). Blood samples were collected from healthy human volunteers, laboratory rats (HL/LE inbred strain), warmblood horses and dromedary camels. Clot formation was observed by oscillating shear rheometry until plateau formation of the shear storage modulus G', at which point selected clots were prepared for scanning electron microscopy. SEM images were analysed for fibre diameter and fractal dimension. Additionally, scattering profiles for plasma and whole blood samples were obtained with SAXS. Viscoelasticity of clots showed great interspecies variation: clots of rats and horses exhibited shorter clotting times and higher G' plateau values, when compared to human clots. Camel clots showed unique clotting characteristics with no G' plateau formation in the timeframe observed. Less differentiating features were found with SEM and SAXS, although the rat fibre network appears to be more convoluted and dense, which resulted in a higher fractal dimension. Clotting kinetic differs between the species, which is not only of clinical interest, but could also be an important finding for animal models of blood coagulation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Sin-Jie; Su, Yen-Hao Frank; Lu, Muh-Jung

In this study, the effect of magnesium addition on the inclusion formation in SS400 steel was investigated. The experimental specimens with and without Mg addition treatment were compared. The microstructure was observed using optical microscopy after etching with 3% nital. The morphology and chemical composition of the inclusions were analyzed via scanning electron microscopy and energy dispersive spectrometry. The lattice structure and orientation of the inclusions were identified by electron backscattering diffraction. The average size of inclusions in SS400 was between 0.67 and 0.75 μm, and between 0.65 and 0.68 μm in SS400 + Mg. The 2 ppm Mg additionmore » resulted in the oxide formation change from Al{sub 2}O{sub 3} to MgO·Al{sub 2}O{sub 3} and in the inclusion formation change from Al{sub 2}O{sub 3}–MnS to MgO·Al{sub 2}O{sub 3}–MnS. Moreover, a simple-phase MnS with an average grain size of 1 μm to 2 μm was observed in rod-like, globular, and polyhedron forms. - Highlights: • The effect of magnesium addition was investigated for SS400 steel. • 2 ppm Mg addition changes the inclusion formation from Al2O3-MnS to MgO·Al2O3-MnS. • MnS observed in inclusions exhibits rod-like, globular, and polyhedron forms.« less

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses.

PubMed

Gräf, Stephan; Kunz, Clemens; Müller, Frank A

2017-08-10

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications.

Formation and Properties of Laser-Induced Periodic Surface Structures on Different Glasses

PubMed Central

Kunz, Clemens; Müller, Frank A.

2017-01-01

The formation and properties of laser-induced periodic surface structures (LIPSS) was investigated on different technically relevant glasses including fused silica, borosilicate glass, and soda-lime-silicate glass under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. For this purpose, LIPSS were fabricated in an air environment at normal incidence with different laser peak fluence, pulse number, and repetition frequency. The generated structures were characterized by using optical microscopy, scanning electron microscopy, focused ion beam preparation and Fast-Fourier transformation. The results reveal the formation of LIPSS on all investigated glasses. LIPSS formation on soda-lime-silicate glass is determined by remarkable melt-formation as an intra-pulse effect. Differences between the different glasses concerning the appearing structures, their spatial period and their morphology were discussed based on the non-linear absorption behavior and the temperature-dependent viscosity. The findings facilitate the fabrication of tailored LIPSS-based surface structures on different technically relevant glasses that could be of particular interest for various applications. PMID:28796180

Amorphous layer formation in Al86.0Co7.6Ce6.4 glass-forming alloy by large-area electron beam irradiation

NASA Astrophysics Data System (ADS)

Li, C. L.; Murray, J. W.; Voisey, K. T.; Clare, A. T.; McCartney, D. G.

2013-09-01

Amorphous Al-Co-Ce alloys are of interest because of their resistance to corrosion, but high cooling rates are generally required to suppress the formation of crystalline phases. In this study, the surface of a bulk crystalline Al-Co-Ce alloy of a glass-forming composition was treated using large area electron beam (LAEB) irradiation. Scanning electron microscopy shows that, compared to the microstructure of the original crystalline material, the treated surface exhibits greatly improved microstructural and compositional uniformity. Glancing angle X-ray diffraction conducted on the surface of treated samples indicates the formation of the amorphous phase following 25 and 50 pulses at 35 kV cathode voltage. However, when the samples are treated with 100 and 150 pulses at 35 kV cathode voltage of electron beam irradiation, the treated layer comprises localised crystalline regions in an amorphous matrix. In addition, the formation of cracks in the treated layer is found to be localised around the Al8Co2Ce phase in the bulk material. Overall, crack length per unit area had no clear change with an increase in the number of pulses.

Electron microscopy study of antioxidant interaction with bacterial cells

NASA Astrophysics Data System (ADS)

Plotnikov, Oleg P.; Novikova, Olga V.; Konnov, Nikolai P.; Korsukov, Vladimir N.; Gunkin, Ivan F.; Volkov, Uryi P.

2000-10-01

To maintain native microorganisms genotype and phenotype features a lyophylization technique is widely used. However in this case cells are affected by influences of vacuum and low temperature that cause a part of the cells population to be destruction. Another factor reduced microorganisms vitality is formation of reactive oxygen forms that damage certain biological targets (such as DNA, membranes etc.) Recently to raise microorganism's resistance against adverse condition natural and synthetic antioxidants are used. Antioxidant- are antagonists of free radicals. Introduction of antioxidants in protective medium for lyophylization increase bacteria storage life about 2,0-4,8 fold in comparison with reference samples. In the article the main results of our investigation of antioxidants interaction with microorganism cells is described. As bacteria cells we use vaccine strain yersinia pestis EV, that were grown for 48 h at 28 degree(s)C on the Hottinger agar (pH 7,2). Antioxidants are inserted on the agar surface in specimen under test. To investigate a localization of antioxidants for electron microscopy investigation, thallium organic antioxidants were used. The thallium organic compounds have an antioxidant features if thallium is in low concentration (about 1(mu) g/ml). The localization of the thallium organic antioxidants on bacteria Y. pestis EV is visible in electron microscopy images, thallium being heavy metal with high electron density. The negatively stained bacteria and bacteria thin sections with thallium organic compounds were investigated by means of transmission electron microscopy. The localization of the thallium organic compounds is clearly visible in electron micrographs as small dark spots with size about 10-80nm. Probably mechanisms of interaction of antioxidants with bacteria cells are discussed.

Thermal evaporation and condensation synthesis of metallic Zn layered polyhedral microparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Waheed S.; Cao, Chuanbao, E-mail: cbcao@bit.edu.cn; Usman, Zahid

2011-12-15

Highlights: Black-Right-Pointing-Pointer Zn polyhedral microparticles prepared by thermal evaporation and condensation route. Black-Right-Pointing-Pointer Vapour-solid process based growth model governs the formation of Zn microparticles. Black-Right-Pointing-Pointer A strong PL emission band is observed at 369 nm in UV region. Black-Right-Pointing-Pointer Radiative recombination of electrons in the s, p conduction band and the holes in the d bands causes this emission. -- Abstract: Metallic zinc layered polyhedral microparticles have been fabricated by thermal evaporation and condensation technique using zinc as precursor at 750 Degree-Sign C for 120 min and NH{sub 3} as a carrier gas. The zinc polyhedral microparticles with oblate sphericalmore » shape are observed to be 2-9 {mu}m in diameter along major axes and 1-7 {mu}m in thickness along minor axes. The structural, compositional and morphological characterizations were performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapour-solid (VS) mechanism based growth model has been proposed for the formation of Zn microparticles. Room temperature photoluminescence (PL) emission spectrum of the product exhibited a strong emission band at 369 nm attributed to the radiative recombination of electrons in the s, p conduction band near Fermi surface and the holes in the d bands generated by the optical excitation.« less

Multi-imaging analysis of nascent surface structures generated during femtosecond laser irradiation of silicon in high vacuum

NASA Astrophysics Data System (ADS)

Gesuele, F.; JJ Nivas, J.; Fittipaldi, R.; Altucci, C.; Bruzzese, R.; Maddalena, P.; Amoruso, S.

2018-02-01

We report a correlative imaging analysis of a crystalline silicon target after irradiation with a low number of 1055 nm, 850 fs laser pulses with several microscopy techniques (e.g., scanning electron microscopy, atomic force microscopy, Raman micro-imaging and confocal optical microscopy). The analysis is carried out on samples irradiated both in high vacuum and at atmospheric pressure conditions, evidencing interesting differences induced by the ambient environment. In high-vacuum conditions, the results evidence the formation of a halo, which is constituted by alternate stripes of amorphous and crystalline silicon, around the nascent ablation crater. In air, such an effect is drastically reduced, due to the significant back-deposition of nanoparticulate material induced by the larger ambient pressure.

Scaffolded DNA origami of a DNA tetrahedron molecular container.

PubMed

Ke, Yonggang; Sharma, Jaswinder; Liu, Minghui; Jahn, Kasper; Liu, Yan; Yan, Hao

2009-06-01

We describe a strategy of scaffolded DNA origami to design and construct 3D molecular cages of tetrahedron geometry with inside volume closed by triangular faces. Each edge of the triangular face is approximately 54 nm in dimension. The estimated total external volume and the internal cavity of the triangular pyramid are about 1.8 x 10(-23) and 1.5 x 10(-23) m(3), respectively. Correct formation of the tetrahedron DNA cage was verified by gel electrophoresis, atomic force microscopy, transmission electron microscopy, and dynamic light scattering techniques.

Analysis of Magnetosome Chains in Magnetotactic Bacteria by Magnetic Measurements and Automated Image Analysis of Electron Micrographs

PubMed Central

Katzmann, E.; Eibauer, M.; Lin, W.; Pan, Y.; Plitzko, J. M.

2013-01-01

Magnetotactic bacteria (MTB) align along the Earth's magnetic field by the activity of intracellular magnetosomes, which are membrane-enveloped magnetite or greigite particles that are assembled into well-ordered chains. Formation of magnetosome chains was found to be controlled by a set of specific proteins in Magnetospirillum gryphiswaldense and other MTB. However, the contribution of abiotic factors on magnetosome chain assembly has not been fully explored. Here, we first analyzed the effect of growth conditions on magnetosome chain formation in M. gryphiswaldense by electron microscopy. Whereas higher temperatures (30 to 35°C) and high oxygen concentrations caused increasingly disordered chains and smaller magnetite crystals, growth at 20°C and anoxic conditions resulted in long chains with mature cuboctahedron-shaped crystals. In order to analyze the magnetosome chain in electron microscopy data sets in a more quantitative and unbiased manner, we developed a computerized image analysis algorithm. The collected data comprised the cell dimensions and particle size and number as well as the intracellular position and extension of the magnetosome chain. The chain analysis program (CHAP) was used to evaluate the effects of the genetic and growth conditions on magnetosome chain formation. This was compared and correlated to data obtained from bulk magnetic measurements of wild-type (WT) and mutant cells displaying different chain configurations. These techniques were used to differentiate mutants due to magnetosome chain defects on a bulk scale. PMID:24096429

Transmission electron microscopy of unstained hybrid Au nanoparticles capped with PPAA (plasma-poly-allylamine): structure and electron irradiation effects.

PubMed

Gontard, Lionel C; Fernández, Asunción; Dunin-Borkowski, Rafal E; Kasama, Takeshi; Lozano-Pérez, Sergio; Lucas, Stéphane

2014-12-01

Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerized-allylamine, an organic compound with the formula C3H5NH2. We discuss the use of energy-filtered TEM in the low-energy-loss range as a contrast enhancement mechanism for imaging the organic shells of such particles. We also study electron-beam-induced crystallization and amorphization of the shells and the formation of graphitic-like layers that contain both C and N. The resistance of the samples to irradiation by high-energy electrons, which is relevant for optical tuning and for understanding the degree to which such hybrid nanostructures are stable in the presence of biomedical radiation, is also discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Direct Investigation of Mg Intercalation into the Orthorhombic V 2O 5 Cathode Using Atomic-Resolution Transmission Electron Microscopy [Direct Investigation of Mg intercalation into orthorhombic V 2O 5 cathode using Atomic Resolution Electron Microscopy Methods

DOE PAGES

Mukherjee, Arijita; Sa, Niya; Phillips, Patrick J.; ...

2017-02-13

Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V 2O 5, combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electronmore » energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V 2O 5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV 2O 5 sample. Results suggest that the electrochemically cycled orthorhombic V 2O 5 cathode shows a local formation of the theoretically predicted ϵ-Mg0.5V2O5 phase; however, the intercalation levels of Mg are lower than predicted. Lastly, this phase is different from the chemically synthesized sample, which is found to represent the δ-MgV 2O 5 phase.« less

Engineered chimeric peptides with antimicrobial and titanium-binding functions to inhibit biofilm formation on Ti implants.

PubMed

Geng, Hongjuan; Yuan, Yang; Adayi, Aidina; Zhang, Xu; Song, Xin; Gong, Lei; Zhang, Xi; Gao, Ping

2018-01-01

Titanium (Ti) implants have been commonly used in oral medicine. However, despite their widespread clinical application, these implants are susceptible to failure induced by microbial infection due to bacterial biofilm formation. Immobilization of chimeric peptides with antibacterial properties on the Ti surface may be a promising antimicrobial approach to inhibit biofilm formation. Here, chimeric peptides were designed by connecting three sequences (hBD-3-1/2/3) derived from human β-defensin-3 (hBD-3) with Ti-binding peptide-l (TBP-l: RKLPDAGPMHTW) via a triple glycine (G) linker to modify Ti surfaces. Using X-ray photoelectron spectroscopy (XPS), the properties of individual domains of the chimeric peptides were evaluated for their binding activity toward the Ti surface. The antimicrobial and anti-biofilm efficacy of the peptides against initial settlers, Streptococcus oralis (S. oralis), Streptococcus gordonii (S. gordonii) and Streptococcus sanguinis (S. sanguinis), was evaluated with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Transmission electron microscopy (TEM) and real-time quantitative PCR (qRT-PCR) were used to study cell membrane changes and the underlying antimicrobial mechanism. Compared with the other two peptides, TBP-1-GGG-hBD3-3 presented stronger antibacterial activity and remained stable in saliva and serum. Therefore, it was chosen as the best candidate to modify Ti surfaces in this study. This peptide inhibited the growth of initial streptococci and biofilm formation on Ti surfaces with no cytotoxicity to MC3T3-E1 cells. Disruption of the integrity of bacterial membranes and decreased expression of adhesion protein genes from S. gordonii revealed aspects of the antibacterial mechanism of TBP-1-GGG-hBD3-3. We conclude that engineered chimeric peptides with antimicrobial activity provide a potential solution for inhibiting biofilm formation on Ti surfaces to reduce or prevent the occurrence of peri-implant diseases. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanoscale imaging of fundamental Li battery chemistry: solid-electrolyte interphase formation and preferential growth of lithium metal nanoclusters

DOE PAGES

Sacci, Robert L; Black, Jennifer M.; Wisinger, Nina; ...

2015-02-23

The performance characteristics of Li-ion batteries are intrinsically linked to evolving nanoscale interfacial electrochemical reactions. To probe the mechanisms of solid electrolyte interphase formation and Li electrodeposition from a standard battery electrolyte, we use in situ electrochemical scanning transmission electron microscopy for controlled potential sweep-hold electrochemical measurements with simultaneous BF and ADF STEM image acquisition. Through a combined quantitative electrochemical measurement and quantitative STEM imaging approach, based upon electron scattering theory, we show that chemically sensitive ADF STEM imaging can be used to estimate the density of evolving SEI constituents and distinguish contrast mechanisms of Li-bearing components in the liquidmore » cell.« less

Synthesis of AlFeCuCrMg{sub x} (x = 0, 0.5, 1, 1.7) alloy powders by mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maulik, Ornov; Kumar, Vinod, E-mail: vkt.meta@mnit.ac.in; Adjunct Faculty, Materials Research Centre, Malaviya National Institute of Technology, Jaipur 302017

2015-12-15

Novel AlFeCuCrMg{sub x} (x = 0, 0.5, 1, 1.7 mol) high-entropy alloys (HEAs) were synthesized by mechanical alloying. The effect of Mg content on the phase evolution of HEAs was investigated using X-Ray diffractometry (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) pattern analysis. The particle morphology and composition of HEAs were investigated by scanning electron microscopy (SEM). Thermodynamic parameters were calculated and analyzed to explain the formation of a solid solution. XRD analysis revealed BCC as major phase and FCC as a minor phase in as-milled AlFeCuCr and AlFeCuCrMg{sub 0.5} HEAs. Also, XRD analysis of as-milledmore » AlFeCuCrMg, AlFeCuCrMg{sub 1.7} confirmed the formation of two BCC phases (BCC 1 and BCC 2). TEM–SAED analysis of AlFeCuCrMg{sub x} HEAs concurred with XRD results. Microstructural features and mechanism for solid solution formation have been conferred in detail. Phase formation of the present HEAs has been correlated with calculated thermodynamic parameters. Differential thermal analysis (TGA-DTA) of these alloys confirmed that there is no substantial phase change up to 500 °C. - Highlights: • Novel AlFeCuCrMg{sub x} (x = 0, 0.5, 1, 1.7) HEAs were prepared by mechanical alloying. • Phase evolution and lattice parameter were studied by X-Ray Diffraction. • Crystallite size and lattice microstrain calculated failed to obey the Williamson–Hall method. • Criterions for formation of simple solid solution were compared to the thermodynamic parameters of the present HEAs. • Increase in the Mg concentration in AlMg{sub x}FeCuCr (x = 0, 0.5, 1, 1.7) HEAs supports the formation of BCC phase.« less

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS2 Films.

PubMed

Precner, M; Polaković, T; Qiao, Qiao; Trainer, D J; Putilov, A V; Di Giorgio, C; Cone, I; Zhu, Y; Xi, X X; Iavarone, M; Karapetrov, G

2018-04-30

We report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the work function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2 . Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2 -based integrated electronics and indicate the importance of defect control and layer passivation.

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS 2 Films

DOE PAGES

Precner, Marian; Polakovic, T.; Qiao, Qiao; ...

2018-04-30

Here, we report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the workmore » function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2. Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2-based integrated electronics and indicate the importance of defect control and layer passivation.« less

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS 2 Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Precner, Marian; Polakovic, T.; Qiao, Qiao

Here, we report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS 2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS 2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the workmore » function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS 2. Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS 2-based integrated electronics and indicate the importance of defect control and layer passivation.« less

Effect of CeLa addition on the microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Jiandi

Development of high strength lithium battery shell alloy is highly desired for new energy automobile industry. The microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy with different CeLa additions were investigated through optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rietveld refinement and tensile testing. Experimental results indicate that Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed due to CeLa addition. Addition of 0.25 wt.% CeLa could promote the formation of denser precipitation of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe) phases, which improved the mechanical properties of the alloy at room temperature.more » However, up to 0.50 wt.% CeLa addition could promote the formation of coarse Al{sub 8}Cu{sub 4}Ce phase, Al{sub 6}Cu{sub 6}La phase and Al{sub 6}(Mn, Fe) phase, which resulted in weakened mechanical properties. - Highlights: •Al-Cu-Mn-Mg-Fe alloys with different CeLa addition were fabricated through casting and rolling. •Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed after CeLa addition. •Addition of 0.25 wt.% CeLa promoted formation of denser precipitates of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe). •Mechanical properties of the alloy was improved after 0.25 wt.% CeLa addition.« less

Transportation of drug-gold nanocomposites by actinomyosin motor system

NASA Astrophysics Data System (ADS)

Kaur, Harsimran; Chaudhary, Archana; Kaur, Inderpreet; Singh, Kashmir; Bharadwaj, Lalit M.

2011-06-01

Nanotechnology is playing an important role in drug delivery to overcome limitations of conventional drug delivery systems in terms of solubility, in vivo stability, pharmacokinetics, and bio-distribution. The controlled transportation of drug into the cell and within the cell is a major challenge to be addressed. Cellular molecular motors have been exploited for their cargo carrying capacity for various applications including engineering and health care. Combination of nanotechnology and biomolecular motors can address some of the challenges in drug delivery. In the present study, transportation of drug nanocomposites has been demonstrated. Nanocomposites of 6-mercaptopurine and levodopa drugs (cancer and Parkinson's disease, respectively) were prepared with gold nanoparticles (GNPs) by covalent attachment and these nanocomposites were attached to actin filaments. These nanocomposites were in-turn transported by actin filaments on myosin tracks. Characterization of drug nanocomposites formation was done by UV-Vis spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and confocal microscopy. GNP composites of 6-mercaptopurine and levodopa were formed by sulfide and amide bond formation, respectively. Average velocity of actin filament attached to nanocomposites was found to be 3.17 and 3.89 μm/s for levodopa and 6-mercaptopurine, respectively, as compared to actin filaments with velocity of 4.0-6.0 μm/s. Three concepts have been proposed for the study of drug transportation into the cell based on polycationic complex formation, interaction of actin with cellular myosin and Biomolecular Adaptor for Retrograde Transport (BART) technology. The aspects of this study heads toward the development of an approach to utilize molecular motors for nanoscale transportation endogenously.

Live-cell Imaging of Platelet Degranulation and Secretion Under Flow.

PubMed

Barendrecht, Arjan D; Verhoef, Johan J F; Pignatelli, Silvia; Pasterkamp, Gerard; Heijnen, Harry F G; Maas, Coen

2017-07-10

Blood platelets are essential players in hemostasis, the formation of thrombi to seal vascular breaches. They are also involved in thrombosis, the formation of thrombi that occlude the vasculature and injure organs, with life-threatening consequences. This motivates scientific research on platelet function and the development of methods to track cell-biological processes as they occur under flow conditions. A variety of flow models are available for the study of platelet adhesion and aggregation, two key phenomena in platelet biology. This work describes a method to study real-time platelet degranulation under flow during activation. The method makes use of a flow chamber coupled to a syringe-pump setup that is placed under a wide-field, inverted, LED-based fluorescence microscope. The setup described here allows for the simultaneous excitation of multiple fluorophores that are delivered by fluorescently labeled antibodies or fluorescent dyes. After live-cell imaging experiments, the cover glasses can be further processed and analyzed using static microscopy (i.e., confocal microscopy or scanning electron microscopy).

Formation of pure Cu nanocrystals upon post-growth annealing of Cu-C material obtained from focused electron beam induced deposition: comparison of different methods.

PubMed

Szkudlarek, Aleksandra; Rodrigues Vaz, Alfredo; Zhang, Yucheng; Rudkowski, Andrzej; Kapusta, Czesław; Erni, Rolf; Moshkalev, Stanislav; Utke, Ivo

2015-01-01

In this paper we study in detail the post-growth annealing of a copper-containing material deposited with focused electron beam induced deposition (FEBID). The organometallic precursor Cu(II)(hfac)2 was used for deposition and the results were compared to that of compared to earlier experiments with (hfac)Cu(I)(VTMS) and (hfac)Cu(I)(DMB). Transmission electron microscopy revealed the deposition of amorphous material from Cu(II)(hfac)2. In contrast, as-deposited material from (hfac)Cu(I)(VTMS) and (hfac)Cu(I)(DMB) was nano-composite with Cu nanocrystals dispersed in a carbonaceous matrix. After annealing at around 150-200 °C all deposits showed the formation of pure Cu nanocrystals at the outer surface of the initial deposit due to the migration of Cu atoms from the carbonaceous matrix containing the elements carbon, oxygen, and fluorine. Post-irradiation of deposits with 200 keV electrons in a transmission electron microscope favored the formation of Cu nanocrystals within the carbonaceous matrix of freestanding rods and suppressed the formation on their surface. Electrical four-point measurements on FEBID lines from Cu(hfac)2 showed five orders of magnitude improvement in conductivity when being annealed conventionally and by laser-induced heating in the scanning electron microscope chamber.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sornadurai, D.; Ravindran, T. R.; Paul, V. Thomas

Synthesis parameters are optimized in order to grow single crystals of multiferroic BiFeO{sub 3}. 2 to 3 mm size pyramid (tetrahedron) shaped single crystals were successfully obtained by solvothermal method. Scanning electron microscopy with EDAX confirmed the phase formation. Raman scattering spectra of bulk BiFeO3 single crystals have been measured which match well with reported spectra.

Raman scattering from rapid thermally annealed tungsten silicide

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Dasgupta, Samhita; Jackson, Howard E.; Boyd, Joseph T.

1987-01-01

Raman scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films have been formed by rapid thermal annealing of thin tungsten films sputter deposited on silicon substrates. The Raman data are interpreted by using data from resistivity measurements, Auger and Rutherford backscattering measurements, and scanning electron microscopy.

Magnetic properties evolution of the CoxFe3-xO4/SiO2 system due to advanced thermal treatment at 700 °C and 1000 °C

NASA Astrophysics Data System (ADS)

Dippong, Thomas; Levei, Erika Andrea; Tanaselia, Claudiu; Gabor, Mihai; Nasui, Mircea; Barbu Tudoran, Lucian; Borodi, Gheorghe

2016-07-01

The CoxFe3-xO4 (x=0.5-2.5) system embedded in the silica matrix was synthesised by sol-gel method using cobalt nitrate, iron nitrate, 1.4-butanediol and tetraethyl orthosilicate. Five different Co/Fe molar ratios in the presence of diol and one without diol were used for the synthesis. The obtained gels were subjected to thermal treatment at 700 °C and 1000 °C. The oxide species formed in the silica matrix, the optimum temperature for the CoFe2O4 phase formation, the evolution of nanocrystallites size and magnetic properties with the calcination temperature were studied. The formed oxide species were studied using X-ray diffraction, Fourier transformed infrared spectrometry, the Co/Fe molar ratio was confirmed using inductively coupled plasma optical emission spectrometry, the nanocrystallites size, shape and clustering was identified by transmission electron microscopy and scanning electron microscopy, while the formation of magnetic phases was investigated by hysteresis and magnetization derivatives measurements.

Advances in Chemical and Structural Characterization of Concretion with Implications for Modeling Marine Corrosion

NASA Astrophysics Data System (ADS)

Johnson, Donald L.; DeAngelis, Robert J.; Medlin, Dana J.; Carr, James D.; Conlin, David L.

2014-05-01

The Weins number model and concretion equivalent corrosion rate methodology were developed as potential minimum-impact, cost-effective techniques to determine corrosion damage on submerged steel structures. To apply the full potential of these technologies, a detailed chemical and structural characterization of the concretion (hard biofouling) that transforms into iron bearing minerals is required. The fractions of existing compounds and the quantitative chemistries are difficult to determine from x-ray diffraction. Environmental scanning electron microscopy was used to present chemical compositions by means of energy-dispersive spectroscopy (EDS). EDS demonstrates the chemical data in mapping format or in point or selected area chemistries. Selected-area EDS data collection at precise locations is presented in terms of atomic percent. The mechanism of formation and distribution of the iron-bearing mineral species at specific locations will be presented. Based on water retention measurements, porosity in terms of void volume varies from 15 v/o to 30 v/o (vol.%). The void path displayed by scanning electron microscopy imaging illustrates the tortuous path by which oxygen migrates in the water phase within the concretion from seaside to metalside.

Direct Observations of the Formation and Redox-Mediator-Assisted Decomposition of Li2 O2 in a Liquid-Cell Li-O2 Microbattery by Scanning Transmission Electron Microscopy.

PubMed

Yang, Chuchu; Han, Jiuhui; Liu, Pan; Hou, Chen; Huang, Gang; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei

2017-11-01

Operando scanning transmission electron microscopy observations of cathodic reactions in a liquid-cell Li-O 2 microbattery in the presence of the redox mediator tetrathiafulvalene (TTF) in 1.0 m LiClO 4 dissolved dimethyl sulfoxide electrolyte are reported. It is found that the TTF addition does not obviously affect the discharge reaction for the formation of a solid Li 2 O 2 phase. The coarsening of Li 2 O 2 nanoparticles occurs via both conventional Ostwald ripening and nonclassical crystallization by particle attachment. During charging, the oxidation reaction at significantly reduced charge potentials mainly takes place at Li 2 O 2 /electrolyte interfaces and has obvious correspondence with the oxidized TTF + distributions in the electric fields of the charged electrode. This study provides direct evidence that TTF truly plays a role in promoting the decomposition of Li 2 O 2 as a soluble charge-transfer agent between the electrode and the Li 2 O 2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation and Characterization of Silver Nanoparticle Composite with Poly(p-Br/F-phenylsilane).

PubMed

Roh, Sung-Hee; Noh, Ji Eun; Woo, Hee-Gweon; Cho, Myong-Shik; Sohn, Honglae

2015-02-01

The one-pot production and structural characterization of composites of silver nanoparticles with poly(p-Br/F-phenylsilane), Br/F-PPS, have been performed. The conversion of Ag+ ions to stable Ag0 nanoparticles is mediated by the copolymer Br/F-PPS having both possibly reactive Si-H bonds in the polymer backbone and C-Br bonds in the substituents along with relatively inert C-F bonds. Transmission electron microscopy and field emission scanning electron microscopy analyses show the formation of the composites where silver nanoparticles (less than 30 nm of size) are well dispersed over the Br/F-PPS matrix. X-ray diffraction patterns are consistent with that for face-centered-cubic typed silver. The polymer solubility in toluene implys that the cleavage of C-Br bond and the Si-F dative bonding may not be occurred appreciably at ambient temperature. Nonetheless, thermogravimetric analysis data suggest that some sort of cross-linking could take place at high temperature. Most of the silver particles undergo macroscopic aggregation without Br/F-PPS, which indicates that the polysilane is necessary for stabilizing the silver nanoparticles.

Hierarchical structured tungsten oxide nanocrystals via hydrothermal route: microstructure, formation mechanism and humidity sensing

NASA Astrophysics Data System (ADS)

Pang, Hua-Feng; Li, Zhi-Jie; Xiang, Xia; Fu, Yong-Qing; Placido, Frank; Zu, Xiao-Tao

2013-09-01

Hierarchical structured tungsten oxide nanocrystals were synthesized via the hydrothermal route assisted by a capping agent of ammonium benzoate (AB). The products were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that the crystal microstructures could be changed from flower-shape to star-shape by changing the mole ratio of ammonium benzoate to sodium tungstate (AB/ST). The crystal phases were changed from orthorhombic WO3ṡ0.33H2O to hexagonal WO3 with the increase in the concentration of AB. Based on the results from Fourier transform infrared spectroscopy and time-dependent growth analysis, a self-assembly growth mechanism has been proposed for the formation of flower, spherical, and star-netted microstructures at different mole ratios of the AB/ST. The star-netted WO3 nanocrystals were applied as a sensitive layer for humidity sensing performed using a Love-mode ZnO/36∘ Y-cut LiTaO3 surface acoustic wave device, and a stable and sensitive response to the change of relative humidity was obtained.

A combined quantitative mass spectrometry and electron microscopy analysis of ribosomal 30S subunit assembly in E. coli

PubMed Central

Sashital, Dipali G; Greeman, Candacia A; Lyumkis, Dmitry; Potter, Clinton S; Carragher, Bridget; Williamson, James R

2014-01-01

Ribosome assembly is a complex process involving the folding and processing of ribosomal RNAs (rRNAs), concomitant binding of ribosomal proteins (r-proteins), and participation of numerous accessory cofactors. Here, we use a quantitative mass spectrometry/electron microscopy hybrid approach to determine the r-protein composition and conformation of 30S ribosome assembly intermediates in Escherichia coli. The relative timing of assembly of the 3′ domain and the formation of the central pseudoknot (PK) structure depends on the presence of the assembly factor RimP. The central PK is unstable in the absence of RimP, resulting in the accumulation of intermediates in which the 3′-domain is unanchored and the 5′-domain is depleted for r-proteins S5 and S12 that contact the central PK. Our results reveal the importance of the cofactor RimP in central PK formation, and introduce a broadly applicable method for characterizing macromolecular assembly in cells. DOI: http://dx.doi.org/10.7554/eLife.04491.001 PMID:25313868

Synthesis of polymer-stabilized monometallic Cu and bimetallic Cu/Ag nanoparticles and their surface-enhanced Raman scattering properties

NASA Astrophysics Data System (ADS)

Zhang, Danhui; Liu, Xiaoheng

2013-03-01

The present study demonstrates a facile process for the production of spherical-shaped Cu and Ag nanoparticles synthesized and stabilized by hydrazine and gelatin, respectively. Advantages of the synthetic method include its production of water dispersible copper and copper/silver nanoparticles at room temperature under no inert atmosphere. The resulting nanoparticles (copper or copper/silver) are investigated by X-ray diffraction (XRD), UV-vis spectroscopy, and transmission electron microscopy (TEM). The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 420 and 572 nm for Ag and Cu nanoparticles, respectively. Transmission electron microscopy showed the formation of nanoparticles in the range of ˜10 nm (silver), and ˜30 nm (copper). The results also demonstrate that the reducing order of Cu2+/Ag+ is important for the formation of the bimetallic nanoparticles. The surface-enhanced Raman scattering effects of copper and copper/silver nanoparticles were also displayed. It was found that the enhancement ability of copper/silver nanoparticles was little higher than the copper nanoparticles.

The interaction of E. coli integration host factor and lambda cos DNA: multiple complex formation and protein-induced bending.

PubMed Central

Kosturko, L D; Daub, E; Murialdo, H

1989-01-01

The interaction of E. coli's integration Host Factor (IHF) with fragments of lambda DNA containing the cos site has been studied by gel-mobility retardation and electron microscopy. The cos fragment used in the mobility assays is 398 bp and spans a region from 48,298 to 194 on the lambda chromosome. Several different complexes of IHF with this fragment can be distinguished by their differential mobility on polyacrylamide gels. Relative band intensities indicate that the formation of a complex between IHF and this DNA fragment has an equilibrium binding constant of the same magnitude as DNA fragments containing lambda's attP site. Gel-mobility retardation and electron microscopy have been employed to show that IHF sharply bends DNA near cos and to map the bending site. The protein-induced bend is near an intrinsic bend due to DNA sequence. The position of the bend suggests that IHF's role in lambda DNA packaging may be the enhancement of terminase binding/cos cutting by manipulating DNA structure. Images PMID:2521383

Transmission electron microscopy investigation of neutron irradiated Si and ZrN coated UMo particles prepared using FIB

NASA Astrophysics Data System (ADS)

Van Renterghem, W.; Miller, B. D.; Leenaers, A.; Van den Berghe, S.; Gan, J.; Madden, J. W.; Keiser, D. D.

2018-01-01

Two fuel plates, containing Si and ZrN coated U-Mo fuel particles dispersed in an Al matrix, were irradiated in the BR2 reactor of SCK•CEN to a burn-up of ∼70% 235U. Five samples were prepared by INL using focused ion beam milling and transported to SCK•CEN for transmission electron microscopy (TEM) investigation. Two samples were taken from the Si coated U-Mo fuel particles at a burn-up of ∼42% and ∼66% 235U and three samples from the ZrN coated U-Mo at a burn-up of ∼42%, ∼52% and ∼66% 235U. The evolution of the coating, fuel structure, fission products and the formation of interaction layers are discussed. Both coatings appear to be an effective barrier against fuel matrix interaction and only on the samples having received the highest burn-up and power, the formation of an interaction between Al and U(Mo) can be observed on those locations where breaches in the coatings were formed during plate fabrication.

Formation of silver nanoparticle at phospholipid template using Langmuir-Blodgett technique and its Surface-enhanced Raman Spectroscopy application

NASA Astrophysics Data System (ADS)

Mahato, M.; Sarkar, R.; Pal, P.; Talapatra, G. B.

2015-10-01

The biosynthesis of metal nanoparticle and their suitable assembly has recently gained tremendous interest for its application in biomedical arena such as substrates for surface-enhanced Raman scattering and others. In this article, an easy, low-cost, fast, bio-friendly and toxic-reducing agent free protocol has been described for the preparation of silver nanoparticle film using biocompatible 1,2-dipalmitoyl-sn-glycero-3-phosphocholine phospholipid Langmuir monolayer template. Interactions, docking and attachment of silver ions to the above-mentioned phospholipid monolayer have been studied by surface pressure-area isotherm and compressibility analysis at the air-water interface. We have deposited the Langmuir-Blodgett monolayer/multilayer containing silver nanoparticle onto glass/SiO2/quartz substrates. The formation of phospholipid-silver nanoparticle complex in Langmuir-Blodgett film has been characterized by field emission-scanning electron microscopy and high-resolution tunneling electron microscopy images. We have applied this deposited film as a substrate for surface-enhanced Raman scattering application using rhodamine 123 to understand the existence of the surface plasmon activity of silver nanoparticle.

The nature and origin of nucleus-like intracellular inclusions in Paleoproterozoic eukaryote microfossils.

PubMed

Pang, K; Tang, Q; Schiffbauer, J D; Yao, J; Yuan, X; Wan, B; Chen, L; Ou, Z; Xiao, S

2013-11-01

The well-known debate on the nature and origin of intracellular inclusions (ICIs) in silicified microfossils from the early Neoproterozoic Bitter Springs Formation has recently been revived by reports of possible fossilized nuclei in phosphatized animal embryo-like fossils from the Ediacaran Doushantuo Formation of South China. The revisitation of this discussion prompted a critical and comprehensive investigation of ICIs in some of the oldest indisputable eukaryote microfossils-the ornamented acritarchs Dictyosphaera delicata and Shuiyousphaeridium macroreticulatum from the Paleoproterozoic Ruyang Group of North China-using a suite of characterization approaches: scanning electron microscopy (SEM), transmission electron microscopy (TEM), and focused ion beam scanning electron microscopy (FIB-SEM). Although the Ruyang acritarchs must have had nuclei when alive, our data suggest that their ICIs represent neither fossilized nuclei nor taphonomically condensed cytoplasm. We instead propose that these ICIs likely represent biologically contracted and consolidated eukaryotic protoplasts (the combination of the nucleus, surrounding cytoplasm, and plasma membrane). As opposed to degradational contraction of prokaryotic cells within a mucoidal sheath-a model proposed to explain the Bitter Springs ICIs-our model implies that protoplast condensation in the Ruyang acritarchs was an in vivo biologically programmed response to adverse conditions in preparation for encystment. While the discovery of bona fide nuclei in Paleoproterozoic acritarchs would be a substantial landmark in our understanding of eukaryote evolution, the various processes (such as degradational and biological condensation of protoplasts) capable of producing nuclei-mimicking structures require that interpretation of ICIs as fossilized nuclei be based on comprehensive investigations. © 2013 John Wiley & Sons Ltd.

Microstructure and mechanical properties of FeCrAl alloys under heavy ion irradiations

NASA Astrophysics Data System (ADS)

Aydogan, E.; Weaver, J. S.; Maloy, S. A.; El-Atwani, O.; Wang, Y. Q.; Mara, N. A.

2018-05-01

FeCrAl ferritic alloys are excellent cladding candidates for accident tolerant fuel systems due to their high resistance to oxidation as a result of formation of a protective Al2O3 scale at high temperatures in steam. In this study, we report the irradiation response of the 10Cr and 13Cr FeCrAl cladding tubes under Fe2+ ion irradiation up to ∼16 dpa at 300 °C. Dislocation loop size, density and characteristics were determined using both two-beam bright field transmission electron microscopy and on-zone scanning transmission electron microscopy techniques. 10Cr (C06M2) tube has a lower dislocation density, larger grain size and a slightly weaker texture compared to the 13Cr (C36M3) tube before irradiation. After irradiation to 0.7 dpa and 16 dpa, the fraction of <100> type sessile dislocations decreases with increasing Cr amount in the alloys. It has been found that there is neither void formation nor α‧ precipitation as a result of ion irradiations in either alloy. Therefore, dislocation loops were determined to be the only irradiation induced defects contributing to the hardening. Nanoindentation testing before the irradiation revealed that the average nanohardness of the C36M3 tube is higher than that of the C06M2 tube. The average nanohardness of irradiated tube samples saturated at 1.6-2.0 GPa hardening for both tubes between ∼3.4 dpa and ∼16 dpa. The hardening calculated based on transmission electron microscopy was found to be consistent with nanohardness measurements.

Identification of Fragile Microscopic Structures during Mineral Transformations in Wet Supercritical CO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arey, Bruce W.; Kovarik, Libor; Qafoku, Odeta

2013-04-01

In this study we examine the nature of highly fragile reaction products that form in low water content super critical carbon dioxide (scCO2) using a combination of scanning electron microscopy/focus ion beam (SEM/FIB), confocal Raman spectroscopy, helium ion microscopy (HeIM), and transmission electron microscopy (TEM). HeIM images show these precipitates to be fragile rosettes that can readily decompose even under slight heating from an electron beam. Using the TEM revealed details on the interfacial structure between the newly formed surface precipitates and the underlying initial solid phases. The detailed microscopic analysis revealed that the growth of the precipitates either followedmore » a tip growth mechanism with precipitates forming directly on the forsterite surface if the initial solid was non-porous (natural forsterite) or growth from the surface of the precipitates where fluid was conducted through the porous (nanoforsterite) agglomerates to the growth center. The mechanism of formation of the hydrated/hydroxylated magnesium carbonate compound (HHMC) phases offers insight into the possible mechanisms of carbonate mineral formation from scCO2 solutions which has recently received a great deal of attention as the result of the potential for CO2 to act as an atmospheric greenhouse gas and impact overall global warming. The techniques used here to examine these fragile structures an also be used to examine a wide range of fragile material surfaces. SEM and FIB technologies have now been brought together in a single instrument, which represents a powerful combination for the studies in biological, geological and materials science.« less

Microstructure and mechanical properties of FeCrAl alloys under heavy ion irradiations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydogan, E.; Weaver, J. S.; Maloy, S. A.

FeCrAl ferritic alloys are excellent cladding candidates for accident tolerant fuel systems due to their high resistance to oxidation as a result of formation of a protective Al 2O 3 scale at high temperatures in steam. In this study, we report the irradiation response of the 10Cr and 13Cr FeCrAl cladding tubes under Fe 2+ ion irradiation up to ~16 dpa at 300 °C. Dislocation loop size, density and characteristics were determined using both two beam bright field transmission electron microscopy and on-zone scanning transmission electron microscopy techniques. 10Cr (C06M2) tube has a lower dislocation density, larger grain size andmore » a slightly weaker texture compared to the 13Cr (C36M3) tube before irradiation. After irradiation to 0.7 dpa and 16 dpa, the fraction of <100> type sessile dislocations decreases with increasing Cr amount in the alloys. It has been found that there is neither void formation nor α' precipitation as a result of ion irradiations in either alloy. Therefore, dislocation loops were determined to be the only irradiation induced defects contributing to the hardening. Nanoindentation testing before the irradiation revealed that the average nanohardness of the C36M3 tube is higher than that of the C06M2 tube. The average nanohardness of irradiated tube samples saturated at 1.6-2.0 GPa hardening for both tubes between ~3.4 dpa and ~16 dpa. The hardening calculated based on transmission electron microscopy was found to be consistent with nanohardness measurements.« less

Microstructure and mechanical properties of FeCrAl alloys under heavy ion irradiations

DOE PAGES

Aydogan, E.; Weaver, J. S.; Maloy, S. A.; ...

2018-03-02

FeCrAl ferritic alloys are excellent cladding candidates for accident tolerant fuel systems due to their high resistance to oxidation as a result of formation of a protective Al 2O 3 scale at high temperatures in steam. In this study, we report the irradiation response of the 10Cr and 13Cr FeCrAl cladding tubes under Fe 2+ ion irradiation up to ~16 dpa at 300 °C. Dislocation loop size, density and characteristics were determined using both two beam bright field transmission electron microscopy and on-zone scanning transmission electron microscopy techniques. 10Cr (C06M2) tube has a lower dislocation density, larger grain size andmore » a slightly weaker texture compared to the 13Cr (C36M3) tube before irradiation. After irradiation to 0.7 dpa and 16 dpa, the fraction of <100> type sessile dislocations decreases with increasing Cr amount in the alloys. It has been found that there is neither void formation nor α' precipitation as a result of ion irradiations in either alloy. Therefore, dislocation loops were determined to be the only irradiation induced defects contributing to the hardening. Nanoindentation testing before the irradiation revealed that the average nanohardness of the C36M3 tube is higher than that of the C06M2 tube. The average nanohardness of irradiated tube samples saturated at 1.6-2.0 GPa hardening for both tubes between ~3.4 dpa and ~16 dpa. The hardening calculated based on transmission electron microscopy was found to be consistent with nanohardness measurements.« less

Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure.

PubMed

Castaneda, Nicholas; Zheng, Tianyu; Rivera-Jacquez, Hector J; Lee, Hyun-Ju; Hyun, Jaekyung; Balaeff, Alexander; Huo, Qun; Kang, Hyeran

2018-04-12

Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.

Effect of γ-PGA on the formation of collagen fibrils in vitro.

PubMed

Ding, Cuicui; Zheng, Zhigong; Liu, Xinzhong; Li, Hengda; Zhang, Min

2016-07-01

The effect of γ-poly(glutamic acid) (γ-PGA) on the self-assembly of collagen was studied. Under physiological conditions, the kinetic curves for fibril formation showed that the turbidity of collagen/γ-PGA blends at 313 nm was increased with the addition of γ-PGA. Furthermore, it was shown using both field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) that fibrils with a larger diameter were obtained following the addition of γ-PGA, probably due to the electrostatic and hydrogen bond interactions between collagen and γ-PGA, which promoted the lateral association of collagen molecules. In addition, both the thermal stability and viscoelastic properties of the hybrid hydrogels, which were evaluated by differential scanning calorimetry and rheological measurements, respectively, were improved by the addition of γ-PGA.

Bacteria interface pickering emulsions stabilized by self-assembled bacteria-chitosan network.

PubMed

Wongkongkatep, Pravit; Manopwisedjaroen, Khajohnpong; Tiposoth, Perapon; Archakunakorn, Somwit; Pongtharangkul, Thunyarat; Suphantharika, Manop; Honda, Kohsuke; Hamachi, Itaru; Wongkongkatep, Jirarut

2012-04-03

An oil-in-water Pickering emulsion stabilized by biobased material based on a bacteria-chitosan network (BCN) was developed for the first time in this study. The formation of self-assembled BCN was possible due to the electrostatic interaction between negatively charged bacterial cells and polycationic chitosan. The BCN was proven to stabilize the tetradecane/water interface, promoting formation of highly stable oil-in-water emulsion (o/w emulsion). We characterized and visualized the BCN stabilized o/w emulsions by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Due to the sustainability and low environmental impact of chitosan, the BCN-based emulsions open up opportunities for the development of an environmental friendly new interface material as well as the novel type of microreactor utilizing bacterial cells network.

Formation of periodic interfacial misfit dislocation array at the InSb/GaAs interface via surface anion exchange

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai

The relationship between growth temperature and the formation of periodic interfacial misfit (IMF) dislocations via the anion exchange process in InSb/GaAs heteroepitaxy was systematically investigated. The microstructural and electrical properties of the epitaxial layer were characterized using atomic force microscope, high-resolution x-ray diffraction, transmission electron microscopy, and Hall resistance measurement. The formation of interfacial misfit (IMF) dislocation arrays depended on growth temperature. A uniformly distributed IMF array was found in a sample grown at 310 °C, which also exhibited the lowest threading dislocation density. The analysis suggested that an incomplete As-for-Sb anion exchange process impeded the formation of IMF on samplemore » grown above 310 °C. At growth temperature below 310 °C, island coalescence led to the formation of 60° dislocations and the disruption of periodic IMF array. All samples showed higher electron mobility at 300 K than at 77 K.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jiaming; Hudak, Bethany M.; Sims, Hunter

One-dimensional (1D) nanostructures are highly sought after, both for their novel electronic properties as well as for their improved functionality. However, due to their nanoscale dimensions, these properties are significantly affected by the environment in which they are embedded. Here in this paper, we report on the creation of 1D homo-endotaxial Si nanostructures, i.e. 1D Si nanostructures with a lattice structure that is uniquely different from the Si diamond lattice in which they are embedded. We use scanning tunneling microscopy and spectroscopy, scanning transmission electron microscopy, density functional theory, and conductive atomic force microscopy to elucidate their formation and properties.more » Depending on kinetic constraints during growth, they can be prepared as endotaxial 1D Si nanostructures completely embedded in crystalline Si, or underneath a stripe of amorphous Si containing a large concentration of Bi atoms. Lastly, these homo-endotaxial 1D Si nanostructures have the potential to be useful components in nanoelectronic devices based on the technologically mature Si platform.« less

Biosynthesis of silver nanoparticles using lemon leaves extract and its application for antimicrobial finish on fabric

NASA Astrophysics Data System (ADS)

Vankar, Padma S.; Shukla, Dhara

2012-06-01

Preparation of silver nanoparticles have been carried out using aqueous extract of lemon leaves ( Citrus limon) which acts as reducing agent and encapsulating cage for the silver nanoparticles. These silver nanoparticles have been used for durable textile finish on cotton and silk fabrics. Remarkable antifungal activity has been observed in the treated fabrics. The antimicrobial activity of silver nanoparticles derived from lemon leaves showed enhancement in activity due to synergistic effect of silver and essential oil components of lemon leaves. The present investigation shows the extracellular synthesis of highly stable silver nanoparticles by biotransformation using the extract of lemon leaves by controlled reduction of the Ag+ ion to Ag0. Further the silver nanoparticles were used for antifungal treatment of fabrics which was tested by antifungal activity assessment of textile material by Agar diffusion method against Fusarium oxysporum and Alternaria brassicicola. Formation of the metallic nanoparticles was established by FT-IR, UV-Visible spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy.

Formation and mechanism of nanocrystalline AZ91 powders during HDDR processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yafen; Fan, Jianfeng, E-mail: fanjianfeng@tyu

2017-03-15

Grain sizes of AZ91 alloy powders were markedly refined to about 15 nm from 100 to 160 μm by an optimized hydrogenation-disproportionation-desorption-recombination (HDDR) process. The effect of temperature, hydrogen pressure and processing time on phase and microstructure evolution of AZ91 alloy powders during HDDR process was investigated systematically by X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy, respectively. The optimal HDDR process for preparing nanocrystalline Mg alloy powders is hydriding at temperature of 350 °C under 4 MPa hydrogen pressure for 12 h and dehydriding at 350 °C for 3 h in vacuum. A modified unreacted coremore » model was introduced to describe the mechanism of grain refinement of during HDDR process. - Highlights: • Grain size of the AZ91 alloy powders was significantly refined from 100 μm to 15 nm. • The optimal HDDR technology for nano Mg alloy powders is obtained. • A modified unreacted core model of grain refinement mechanism was proposed.« less

Homo-endotaxial one-dimensional Si nanostructures

DOE PAGES

Song, Jiaming; Hudak, Bethany M.; Sims, Hunter; ...

2017-11-29

One-dimensional (1D) nanostructures are highly sought after, both for their novel electronic properties as well as for their improved functionality. However, due to their nanoscale dimensions, these properties are significantly affected by the environment in which they are embedded. Here in this paper, we report on the creation of 1D homo-endotaxial Si nanostructures, i.e. 1D Si nanostructures with a lattice structure that is uniquely different from the Si diamond lattice in which they are embedded. We use scanning tunneling microscopy and spectroscopy, scanning transmission electron microscopy, density functional theory, and conductive atomic force microscopy to elucidate their formation and properties.more » Depending on kinetic constraints during growth, they can be prepared as endotaxial 1D Si nanostructures completely embedded in crystalline Si, or underneath a stripe of amorphous Si containing a large concentration of Bi atoms. Lastly, these homo-endotaxial 1D Si nanostructures have the potential to be useful components in nanoelectronic devices based on the technologically mature Si platform.« less

Surfactant-free bio-synthesised Tio2 nanorods from Turbinaria conoides-a study on photocatalytic and anti-bacterial activity

NASA Astrophysics Data System (ADS)

Subhapriya, S.; Gomathipriya, P.

2018-06-01

In this study, Titania nanorods were synthesised from aqueous extract of Turbinaria conoides (brown seaweeds) (TiO2NRs-TC) under surfactant free medium. The photocatalytic activity of the synthesised nanorods was tested towards the photocatalytic decolourization using simulated dye wastewater containing Navy Blue HER (NBHER). The synthesised Titania nanorods were characterized by using x-ray diffraction (XRD), UV–visible spectroscopy (UV–vis), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrophotometer (EDS) and Transmission Electron Microscopy (TEM). XRD pattern confirms the anatase phase formation and HR-SEM micrograph shows the presence of rod like structure with the size of about 50 nm. TEM analysis proves the rod like structure with a size of 45–50 nm which was in agreement with the XRD analysis and HR-SEM images. EDS and XDS confirmed the formation of Titania nanoparticles. The formation of TiO2NRs-TC has a beneficial influence on the dye Navy blue HER photodegradation. TiO2-TC nano rods also show superior photocatalytic ability in hydrogen generation (2.1 mmol/h‑1g‑1). The antibacterial activity of the synthesised nanoparticles was examined using disc diffusion method which showed diverse susceptibility of microorganisms to the Titania nanoparticles.

A Novel Cell Wall Lipopeptide Is Important for Biofilm Formation and Pathogenicity of Mycobacterium avium subspecies paratuberculosis

PubMed Central

Wu, Chia-wei; Schmoller, Shelly K.; Bannantine, John P.; Eckstein, Torsten M.; Inamine, Julie M.; Livesey, Michael; Albrecht, Ralph; Talaat, Adel M.

2009-01-01

Biofilm formation by pathogenic bacteria plays a key role in their pathogenesis. Previously, the pstA gene was shown to be involved in the virulence of Mycobacterium avium subspecies paratuberculosis (M. ap), the causative agent of Johne's disease in cattle and a potential risk factor for Crohn's disease. Scanning electron microscopy and colonization levels of the M. ap mutant indicated that the pstA gene significantly contributes to the ability of M. ap to form biofilms. Digital measurements taken during electron microscopy identified a unique morphology for the ΔpstA mutant, which consisted of significantly shorter bacilli than the wild type. Analysis of the lipid profiles of the mycobacterial strains identified a novel lipopeptide that was present in the cell wall extracts of wild-type M. ap, but missing from the ΔpstA mutant. Interestingly, the calf infection model suggested that pstA contributes to intestinal invasion of M. ap. Furthermore, immunoblot analysis of peptides encoded by pstA identified a specific and significant level of immunogenicity. Taken together, our analysis revealed a novel cell wall component that could contribute to biofilm formation and to the virulence and immunogenicity of M. ap. Molecular tools to better control M. ap infections could be developed utilizing the presented findings. PMID:19490829

Morphology Formation in PC/ABS Blends during Thermal Processing and the Effect of the Viscosity Ratio of Blend Partners

PubMed Central

Bärwinkel, Stefanie; Seidel, Andreas; Hobeika, Sven; Hufen, Ralf; Mörl, Michaela; Altstädt, Volker

2016-01-01

Morphology formation during compounding, as well as injection molding of blends containing 60 wt % polycarbonate (PC) and 40 wt % polybutadiene rubber-modified styrene-acrylonitrile copolymers (ABS), has been investigated by transmission electron microscopy (TEM). Profiles of the blend morphology have been recorded in injection-molded specimens and significant morphology gradients observed between their skin and core. A <10 µm thick surface layer with strongly dispersed and elongated nano-scale (streak-like) styrene acrylonitrile (SAN) phases and well-dispersed, isolated SAN-grafted polybutadiene rubber particles is followed by a 50–150 µm thick skin layer in which polymer morphology is characterized by lamellar SAN/ABS phases. Thickness of these lamellae increases with the distance from the specimen’s surface. In the core of the specimens the SAN-grafted polybutadiene rubber particles are exclusively present within the SAN phases, which exhibit a much coarser and less oriented, dispersed morphology compared to the skin. The effects of the viscosity of the SAN in the PC/ABS blends on phase morphologies and correlations with fracture mechanics in tensile and impact tests were investigated, including scanning electron microscopy (SEM) assessment of the fracture surfaces. A model explaining the mechanisms of morphology formation during injection molding of PC/ABS blends is discussed. PMID:28773780

Risk factors and biofilm detection on central venous catheters of patients attended at tertiary hospital.

PubMed

Pérez-Zárate, Pamela; Aragón-Piña, Antonio; Soria-Guerra, Ruth Elena; González-Amaro, Ana María; Pérez-Urizar, José; Pérez-González, Luis Fernando; Martinez-Gutierrez, Fidel

2015-11-01

To determinate the significance of risk factors with the presence of biofilm on catheters of patients attended at tertiary hospital cares. A total of 126 patients were included, data collection by observing the handling of the CVC, clinical history and microbiological isolation methods of CVCs tips (Roll-plate, sonication and scanning electron microscopy) were evaluated. Certain factors, such as the lack of proper hand washing, the use of primary barriers and preparing medications in the same hospital service, showed an important relationship between biofilm formation in CVCs. The sonication method presented that most of the samples had isolation of multispecies 29 samples (64%); in contrast with the roll-plate method, just one sample (3%) was isolated. The importance of the strict aseptic techniques of insertion and of the handlings of CVC was highlighted, the failure of both techniques was related to the biofilm formation and was evidenced using the scanning electron microscopy. Since this tool is not available in most hospitals, we present the correlation of those evidences with other standard microbiological methods and risk factors, which are necessary for the sensible detection of the different steps of the biofilm formation on CVC and their correct interpretation with clinical evidences. Copyright © 2015 Elsevier Ltd. All rights reserved.

Inter-wall bridging induced peeling of multi-walled carbon nanotubes during tensile failure in aluminum matrix composites.

PubMed

Chen, Biao; Li, Shufeng; Imai, Hisashi; Umeda, Junko; Takahashi, Makoto; Kondoh, Katsuyoshi

2015-02-01

In situ scanning electron microscopy (SEM) observation of a tensile test was performed to investigate the fracturing behavior of multi-walled carbon nanotubes (MWCNTs) in powder metallurgy Al matrix composites. A multiple peeling phenomenon during MWCNT fracturing was clearly observed. Its formation mechanism and resultant effect on the composite strength were examined. Through transition electron microscopy characterizations, it was observed that defective structures like inter-wall bridges cross-linked adjacent walls of MWCNTs. This structure was helpful to improve the inter-wall bonding conditions, leading to the effective load transfer between walls and resultant peeling behaviors of MWCNTs. These results might provide new understandings of the fracturing mechanisms of carbon nanotube reinforcements for designing high-performance nanocomposites. Copyright © 2014 Elsevier Ltd. All rights reserved.

Piper betle-mediated synthesis, characterization, antibacterial and rat splenocyte cytotoxic effects of copper oxide nanoparticles.

PubMed

Praburaman, Loganathan; Jang, Jum-Suk; Muthusamy, Govarthanan; Arumugam, Sengottaiyan; Manoharan, Koildhasan; Cho, Kwang-Min; Min, Cho; Kamala-Kannan, Seralathan; Byung-Taek, Oh

2016-09-01

The study reports a simple, inexpensive, and eco-friendly synthesis of copper oxide nanoparticles (CuONPs) using Piper betle leaf extract. Formation of CuONPs was confirmed by UV-visible spectroscopy at 280 nm. Transmission electron microscopy (TEM) images showed that the CuONPs were spherical, with an average size of 50-100 nm. The scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) peak was observed approximately at 1 and 8 keV. The X-ray diffraction (XRD) studies indicated that the particles were crystalline in nature. CuONPs effectively inhibited the growth of phytopathogens Ralstonia solanacearum and Xanthomonas axonopodis. The cytotoxic effect of the synthesized CuONPs was analyzed using rat splenocytes. The cell viability was decreased to 94% at 300 μg/mL.

Decorating graphene oxide with CuO nanoparticles in a water-isopropanol system.

PubMed

Zhu, Junwu; Zeng, Guiyu; Nie, Fude; Xu, Xiaoming; Chen, Sheng; Han, Qiaofeng; Wang, Xin

2010-06-01

A facile chemical procedure capable of aligning CuO nanoparticles on graphene oxide (GO) in a water-isopropanol system has been described. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate that the exfoliated GO sheets are decorated randomly by spindly or spherical CuO nanoparticle aggregates, forming well-ordered CuO:GO nanocomposites. A formation mechanism of these interesting nanocomposites is proposed as intercalation and adsorption of Cu2+ ions onto the GO sheets, followed by the nucleation and growth of the CuO crystallites, which in return resulted in the exfoliation of GO sheets. Moreover, the obtained nanocomposites exhibit a high catalytic activity for the thermal decomposition of ammonium perchlorate (AP), due to the concerted effect of CuO and GO.

Synthesis of TiO{sub 2} nanoparticles by hydrolysis and peptization of titanium isopropoxide solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahata, S.; Mahato, S. S.; Nandi, M. M.

2012-07-23

Here we report the synthesis and characterization of a stable suspension of modified titania nanoparticles. Phase-pure TiO{sub 2} nanocrystallites with narrow particle-size distributions were selectively prepared by hydrolysis-peptization of modified alkoxide followed by hydrothermal treatment. Autoclaving modified TiO{sub 2} in the presence of HNO3 as cooperative catalysts led to the formation of crystalline TiO{sub 2} with narrow-sized distribution. Following the hydrothermal treatment at 150 Degree-Sign C, X-ray diffraction shows the particles to be exclusively anatase. Synthesized powder is characterized by FT-IR, scanning electron microscopy (FESEM) and transmission electron microscopy (HRTEM). The photocatalytic activity in the degradation of orange-II is quitemore » comparable to good anatase and rutile nanocrystallites.« less

Hydroxyapatite nanocrystals: simple preparation, characterization and formation mechanism.

PubMed

Mohandes, Fatemeh; Salavati-Niasari, Masoud; Fathi, Mohammadhossein; Fereshteh, Zeinab

2014-12-01

Crystalline hydroxyapatite (HAP) nanoparticles and nanorods have been successfully synthesized via a simple precipitation method. To control the shape and particle size of HAP nanocrystals, coordination ligands derived from 2-hydroxy-1-naphthaldehyde were first prepared, characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H-NMR) spectroscopies, and finally applied in the synthesis process of HAP. On the other hand, the HAP nanocrystals were also characterized by several techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to the FE-SEM and TEM micrographs, it was found that the morphology and crystallinity of the HAP powders depended on the coordination mode of the ligands. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanotubes, nanobelts, nanowires, and nanorods of silicon carbide from the wheat husks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.

2015-09-14

Nanotubes, nanowires, nanobelts, and nanorods of SiC were synthesized from the thermal treatment of wheat husks at temperatures in excess of 1450 °C. From the analysis based on x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, it has been found that the processed samples of wheat husk consisted of 2H and 3C polytypes of SiC exhibiting the nanostructure shapes. These nanostructures of silicon carbide formed from wheat husks are of technological importance for designing advance composites, applications in biotechnology, and electro-optics. The thermodynamics of the formation of SiC is discussed in terms of the rapid solid state reactionmore » between hydrocarbons and silica on the molecular scale, which is inherently present in the wheat husks.« less

Catalytic properties of Co3O4 nanoparticles for rechargeable Li/air batteries.

PubMed

Kim, Kwan Su; Park, Yong Joon

2012-01-05

Three types of Co3O4 nanoparticles are synthesized and characterized as a catalyst for the air electrode of a Li/air battery. The shape and size of the nanoparticles are observed using scanning electron microscopy and transmission electron microscopy analyses. The formation of the Co3O4 phase is confirmed by X-ray diffraction. The electrochemical property of the air electrodes containing Co3O4 nanoparticles is significantly associated with the shape and size of the nanoparticles. It appears that the capacity of electrodes containing villiform-type Co3O4 nanoparticles is superior to that of electrodes containing cube- and flower-type Co3O4 nanoparticles. This is probably due to the sufficient pore spaces of the villiform-type Co3O4 nanoparticles.

Structural properties of GaAsN grown on (001) GaAs by metalorganic molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ok, Young-Woo; Choi, Chel-Jong; Seong, Tae-Yeon; Uesugi, K.; Suemune, I.

2001-07-01

Detailed transmission electron microscopy (TEM) and transmission electron diffraction (TED) examination has been made of metalorganic molecular beam epitaxial GaAsN layers grown on (001) GaAs substrates. TEM results show that lateral composition modulation occurs in the GaAs1-xNx layer (x 6.75%). It is shown that increasing N composition and Se (dopant) concentration leads to poor crystallinity. It is also shown that the addition of Se increases N composition. Atomic force microscopy (AFM) results show that the surfaces of the samples experience a morphological change from faceting to islanding, as the N composition and Se concentration increase. Based on the TEM and AFM results, a simple model is given to explain the formation of the lateral composition modulation.

Nanotubes, nanobelts, nanowires, and nanorods of silicon carbide from the wheat husks

NASA Astrophysics Data System (ADS)

Qadri, S. B.; Rath, B. B.; Gorzkowski, E. P.; Feng, J.; Qadri, S. N.; Caldwell, J. D.

2015-09-01

Nanotubes, nanowires, nanobelts, and nanorods of SiC were synthesized from the thermal treatment of wheat husks at temperatures in excess of 1450 °C. From the analysis based on x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy, it has been found that the processed samples of wheat husk consisted of 2H and 3C polytypes of SiC exhibiting the nanostructure shapes. These nanostructures of silicon carbide formed from wheat husks are of technological importance for designing advance composites, applications in biotechnology, and electro-optics. The thermodynamics of the formation of SiC is discussed in terms of the rapid solid state reaction between hydrocarbons and silica on the molecular scale, which is inherently present in the wheat husks.

Willy: A prize noble Ur-Fremdling - Its history and implications for the formation of Fremdlinge and CAI

NASA Technical Reports Server (NTRS)

Armstrong, J. T.; El Goresy, A.; Wasserburg, G. J.

1985-01-01

The structure and composition of Willy, a 150-micron-diameter Fremdling in CAI 5241 from the Allende meteorite, are investigated using optical, secondary-electron, and electron-backscatter microscopy and electron-microprobe analysis. The results are presented in diagrams, maps, tables, graphs, and micrographs and compared with those for other Allende Fremdlinge. Willy is found to have a concentric-zone structure comprising a complex porous core of magnetite, metal, sulfide, scheelite, and other minor phases; a compact magnetite-apatite mantle; a thin (20 microns or less) reaction-assemblage zone; and a dense outer rim of fassaite with minor spinel. A multistage formation sequence involving changes in T and fO2 and preceding the introduction of Willy into the CAI (which itself preceded CAI spinel and silicate formation) is postulated, and it is inferred from the apparent lack of post-capture recrystallization that Willy has not been subjected to temperatures in excess of 600 C and may represent the precursor material for many other Fremdlinge.

Preparation, characterization, physical properties, and photoconducting behaviour of anthracene derivative nanowires

NASA Astrophysics Data System (ADS)

Xiao, Jinchong; Yin, Zongyou; Yang, Bo; Liu, Yi; Ji, Li; Guo, Jun; Huang, Ling; Liu, Xuewei; Yan, Qingyu; Zhang, Hua; Zhang, Qichun

2011-11-01

Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO.Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO. Electronic supplementary information (ESI) available: XRD patterns and simulations, and FT-IR spectra. CCDC reference numbers 840471. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1nr10655d

Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors

PubMed Central

Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; Lupini, Andrew R.; Lee, Jaekwang; Basile, Leonardo; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; Ivanov, Ilia N.; Xiao, Kai; Yoon, Mina; Geohegan, David B.

2015-01-01

The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional crystalline semiconductors as building blocks in next-generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate an approach for the formation of lithographically patterned arrays of lateral semiconducting heterojunctions within a single two-dimensional crystal. Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are studied by Raman and photoluminescence spectroscopy, atomically resolved scanning transmission electron microscopy and device characterization. This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices. PMID:26198727

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikari, R., E-mail: rajdeep.adhikari@jku.at; Capuzzo, G.; Bonanni, A., E-mail: alberta.bonanni@jku.at

Polarization induced degenerate n-type doping with electron concentrations up to ∼10{sup 20 }cm{sup −3} is achieved in graded Al{sub x}Ga{sub 1−x}N layers (x: 0% → 37%) grown on unintentionally doped and on n-doped GaN:Si buffer/reservoir layers by metal organic vapor phase epitaxy. High resolution x-ray diffraction, transmission electron microscopy, and electron dispersive x-ray spectroscopy confirm the gradient in the composition of the Al{sub x}Ga{sub 1−x}N layers, while Hall effect studies reveal the formation of a three dimensional electron slab, whose conductivity can be adjusted through the GaN(:Si) buffer/reservoir.

Scanning electron microscopy, x-ray diffraction, and electron microprobe analysis of calcific deposits on intrauterine contraceptive devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, S.R.; Wilkinson, E.J.

Deposits found on intrauterine contraceptive devices (IUDs) were studied by scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray microanalysis. All seven devices, including five plastic and two copper IUDs, were coated with a crust containing cellular, acellular, and fibrillar material. The cellular material was composed of erythrocytes, leukocytes, cells of epithelial origin, sperm, and bacteria. Some of the bacteria were filamentous, with acute-angle branching. The fibrillar material appeared to be fibrin. Most of the acellular material was amorphous; calcite was identified by x-ray diffraction, and x-ray microanalysis showed only calcium. Some of the acellular material, particularly that on themore » IUD side of the crust, was organized in spherulitic crystals and was identified as calcium phosphate by x-ray microanalysis. The crust was joined to the IUD surface by a layer of fibrillar and amorphous material. It is suggested that the initial event in the formation of calcific deposits on IUD surfaces is the deposition of an amorphous and fibrillar layer. Various types of cells present in the endometrial environment adhere to this layer and then calcify. Thus, the deposition of calcific material on the IUDs is a calcification phenomenon, not unlike the formation of plaque on teeth.« less

Spinel NixZn1-xFe2O4 (0.0 ≤ x ≤ 1.0) nano-photocatalysts: Synthesis, characterization and photocatalytic degradation of methylene blue dye

NASA Astrophysics Data System (ADS)

Padmapriya, G.; Manikandan, A.; Krishnasamy, V.; Jaganathan, Saravana Kumar; Antony, S. Arul

2016-09-01

Spinel NixZn1-xFe2O4 (x = 0.0 to 1.0) nanoparticles were successfully synthesized by a simple microwave combustion method (MCM) using metal nitrates as raw materials and glycine as the fuel. The structural, morphological and opto-magnetic properties of the spinel NixZn1-xFe2O4 ferrites were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern, UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). Powder XRD, and EDX analysis was confirmed the formation of pure phase of spinel ferrites. HR-SEM and HR-TEM analysis was confirmed the formation of sphere like-particle morphology of the samples with smaller agglomeration. VSM analysis clearly showed the superparamagnetic and ferromagnetic nature of the samples. The Ms value is 3.851 emu/g for undoped ZnFe2O4 sample and it increased with increase in Ni content. Photo-catalytic degradation (PCD) of methylene blue (MB) dye using the samples were carried out and observed good PCD results.

Control of biofilm formation by poly-ethylene-co-vinyl acetate films incorporating nisin.

PubMed

Nostro, Antonia; Scaffaro, Roberto; Ginestra, Giovanna; D'Arrigo, Manuela; Botta, Luigi; Marino, Andreana; Bisignano, Giuseppe

2010-06-01

The aim of this study was to evaluate the effect of poly-ethylene-co-vinyl acetate (EVA) films incorporating different concentrations (0.1%, 0.5% and 1%) of nisin on the biofilm-forming ability of Listeria monocytogenes ATCC 7644, Staphylococcus aureus 815 and Staphylococcus epidermidis ATCC 35984. Nisin was incorporated into two grades of EVA (EVA14 and EVA28) in the melt during a common film-blowing operation. The efficacy of EVA/nisin films was evaluated by biofilm biomass measurements and Live/Dead staining in combination with fluorescence microscopy. In order to evaluate whether the nisin incorporation could modify the film surface properties, contact angle measurements and scanning electron microscopy were performed. The results revealed the efficacy of EVA14/nisin films in reducing biofilm formation on their surfaces with more evident effect for S. epidermidis than L. monocytogenes and S. aureus strains. In contrast, EVA28/nisin films showed unsatisfactory activity. Fluorescence microscopy confirmed poor biofilm formation on EVA14/nisin films, also characterised by the presence of dead cells. The data presented in this study offer new potential applications for developing strategies aimed to improve the effect of antimicrobial agents.

Sharing of secondary electrons by in-lens and out-lens detector in low-voltage scanning electron microscope equipped with immersion lens.

PubMed

Kumagai, Kazuhiro; Sekiguchi, Takashi

2009-03-01

To understand secondary electron (SE) image formation with in-lens and out-lens detector in low-voltage scanning electron microscopy (LV-SEM), we have evaluated SE signals of an in-lens and an out-lens detector in LV-SEM. From the energy distribution spectra of SEs with various boosting voltages of the immersion lens system, we revealed that the electrostatic field of the immersion lens mainly collects electrons with energy lower than 40eV, acting as a low-pass filter. This effect is also observed as a contrast change in LV-SEM images taken by in-lens and out-lens detectors.

Formation of Nanostructures on the Nickel Metal Surface in Ionic Liquid under Anodizing

NASA Astrophysics Data System (ADS)

Lebedeva, O. K.; Root, N. V.; Kultin, D. Yu.; Kalmykov, K. B.; Kustov, L. M.

2018-05-01

The formation of nanostructures in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide on the surface of a nickel electrode during anodizing was studied. Hexagonal ordered surface nanostructures were found to form in a narrow range of current densities. The form of the potential transients of the nickel electrode corresponded to the morphology of the nickel surface obtained which was studied by electron microscopy. No other types of nanostructures were found under the electrosynthesis conditions under study.

Formation of nanoparticles from thin silver films irradiated by laser pulses in air

NASA Astrophysics Data System (ADS)

Nastulyavichus, A. A.; Smirnov, N. A.; Kudryashov, S. I.; Ionin, A. A.; Saraeva, I. N.; Busleev, N. I.; Rudenko, A. A.; Khmel'nitskii, R. A.; Zayarnyi, D. A.

2018-03-01

Some specific features of the transport of silver nanoparticles onto a SiO2 substrate under focused nanosecond IR laser pulses is experimentally investigated. A possibility of obtaining silver coatings is demonstrated. The formation of silver nanostructures as a result of pulsed laser ablation in air is studied. Nanoparticles are formed by exposing a silver film to radiation of an HTF MARK (Bulat) laser marker (λ = 1064 nm). The thus prepared nanoparticles are analysed using scanning electron microscopy and optical spectroscopy.

Study of the glass formation of high temperature superconductors

NASA Technical Reports Server (NTRS)

Ethridge, Edwin C.; Kaukler, William F.; Rolin, Terry

1992-01-01

A number of compositions of ceramic oxide high T(sub c) superconductors were elevated for their glass formation ability by means of rapid thermal analysis during quenching, optical, and electron microscopy of the quenched samples, and with subsequent DSC measurements. Correlations between experimental measurements and the methodical composition changes identified the formulations of superconductors that can easily form glass. The superconducting material was first formed as a glass; then, with subsequent devitrification, it was formed into a bulk crystalline superconductor by a series of processing methods.

Electrocrystallization and Properties of Supersaturated Solid Solutions of Copper

NASA Astrophysics Data System (ADS)

Povetkin, V. V.; Ivanova, T. E.; Ismagilova, A. V.

2018-03-01

The role of the alloying element in the formation of the structure and properties of electrolytic copper alloys has been determined. The X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) have shown that electrochemical alloying of copper with low-melting metals leads to the formation of supersaturated solid solutions (SSS) on the cathode, crushing of the crystal structure, smoothing of the surface relief, hardening of the deposits obtained, increasing their solderability and corrosive resistance to acidic media.

Influence of 20 MeV electron irradiation on the optical properties and phase composition of SiOx thin films

NASA Astrophysics Data System (ADS)

Hristova-Vasileva, Temenuga; Petrik, Peter; Nesheva, Diana; Fogarassy, Zsolt; Lábár, János; Kaschieva, Sonia; Dmitriev, Sergei N.; Antonova, Krassimira

2018-05-01

Homogeneous films from SiO1.3 (250 nm thick) were deposited on crystalline Si substrates by thermal evaporation of silicon monoxide. A part of the films was further annealed at 700 °C to grow amorphous Si (a-Si) nanoclusters in an oxide matrix, thus producing composite a-Si-SiO1.8 films. Homogeneous as well as composite films were irradiated by 20-MeV electrons at fluences of 7.2 × 1014 and 1.44 × 1015 el/cm2. The film thicknesses and optical constants were explored by spectroscopic ellipsometry. The development of the phase composition of the films caused by the electron-beam irradiation was studied by transmission electron microscopy. The ellipsometric and electron microscopy results have shown that the SiOx films are optically homogeneous and the electron irradiation with a fluence of 7.2 × 1014 el/cm2 has led to small changes in the optical constants and the formation of very small a-Si nanoclusters. The irradiation of the a-Si-SiOx composite films caused a decrease in the effective refractive index and, at the same time, an increase in the refractive index of the oxide matrix. Irradiation induced increase in the optical band gap and decrease in the absorption coefficient of the thermally grown amorphous Si nanoclusters have also been observed. The obtained results are discussed in terms of the formation of small amorphous silicon nanoclusters in the homogeneous layers and electron irradiation induced reduction in the nanocluster size in the composite films. The conclusion for the nanoparticle size reduction is supported by infrared transmittance results.

The Open Microscopy Environment: open image informatics for the biological sciences

NASA Astrophysics Data System (ADS)

Blackburn, Colin; Allan, Chris; Besson, Sébastien; Burel, Jean-Marie; Carroll, Mark; Ferguson, Richard K.; Flynn, Helen; Gault, David; Gillen, Kenneth; Leigh, Roger; Leo, Simone; Li, Simon; Lindner, Dominik; Linkert, Melissa; Moore, Josh; Moore, William J.; Ramalingam, Balaji; Rozbicki, Emil; Rustici, Gabriella; Tarkowska, Aleksandra; Walczysko, Petr; Williams, Eleanor; Swedlow, Jason R.

2016-07-01

Despite significant advances in biological imaging and analysis, major informatics challenges remain unsolved: file formats are proprietary, storage and analysis facilities are lacking, as are standards for sharing image data and results. While the open FITS file format is ubiquitous in astronomy, astronomical imaging shares many challenges with biological imaging, including the need to share large image sets using secure, cross-platform APIs, and the need for scalable applications for processing and visualization. The Open Microscopy Environment (OME) is an open-source software framework developed to address these challenges. OME tools include: an open data model for multidimensional imaging (OME Data Model); an open file format (OME-TIFF) and library (Bio-Formats) enabling free access to images (5D+) written in more than 145 formats from many imaging domains, including FITS; and a data management server (OMERO). The Java-based OMERO client-server platform comprises an image metadata store, an image repository, visualization and analysis by remote access, allowing sharing and publishing of image data. OMERO provides a means to manage the data through a multi-platform API. OMERO's model-based architecture has enabled its extension into a range of imaging domains, including light and electron microscopy, high content screening, digital pathology and recently into applications using non-image data from clinical and genomic studies. This is made possible using the Bio-Formats library. The current release includes a single mechanism for accessing image data of all types, regardless of original file format, via Java, C/C++ and Python and a variety of applications and environments (e.g. ImageJ, Matlab and R).

Measurement of the Dewetting, Nucleation, and Deactivation Kinetics of Carbon Nanotube Population Growth by Environmental Transmission Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bedewy, Mostafa; Viswanath, B.; Meshot, Eric R.

In order to understand the collective growth of carbon nanotube (CNT) populations tailoring their properties for many applications is key. During the initial stages of CNT growth by chemical vapor deposition, catalyst nanoparticle formation by thin-film dewetting and the subsequent CNT nucleation processes dictate the CNT diameter distribution, areal density, and alignment. We use in situ environmental transmission electron microscopy (E-TEM) to observe the catalyst annealing, growth, and deactivation stages for a population of CNTs grown from a thin-film catalyst. Complementary in situ electron diffraction and TEM imaging show that, during the annealing step in hydrogen, reduction of the ironmore » oxide catalyst is concomitant with changes in the thin-film morphology; complete dewetting and the formation of a population of nanoparticles is only achieved upon the introduction of the carbon source, acetylene. The dewetting kinetics, i.e., the appearance of distinct nanoparticles, exhibits a sigmoidal (autocatalytic) curve with 95% of all nanoparticles appearing within 6 s. After nanoparticles form, they either nucleate CNTs or remain inactive, with incubation times measured to be as small as 3.5 s. Via E-TEM we also directly observe the crowding and self-alignment of CNTs after dewetting and nucleation. Additionally, in situ electron energy loss spectroscopy reveals that the collective rate of carbon accumulation decays exponentially. We conclude that the kinetics of catalyst formation and CNT nucleation must both be addressed in order to achieve uniform and high CNT density, and their transient behavior may be a primary cause of the well-known nonuniform density of CNT forests.« less

Measurement of the Dewetting, Nucleation, and Deactivation Kinetics of Carbon Nanotube Population Growth by Environmental Transmission Electron Microscopy

DOE PAGES

Bedewy, Mostafa; Viswanath, B.; Meshot, Eric R.; ...

2016-05-23

In order to understand the collective growth of carbon nanotube (CNT) populations tailoring their properties for many applications is key. During the initial stages of CNT growth by chemical vapor deposition, catalyst nanoparticle formation by thin-film dewetting and the subsequent CNT nucleation processes dictate the CNT diameter distribution, areal density, and alignment. We use in situ environmental transmission electron microscopy (E-TEM) to observe the catalyst annealing, growth, and deactivation stages for a population of CNTs grown from a thin-film catalyst. Complementary in situ electron diffraction and TEM imaging show that, during the annealing step in hydrogen, reduction of the ironmore » oxide catalyst is concomitant with changes in the thin-film morphology; complete dewetting and the formation of a population of nanoparticles is only achieved upon the introduction of the carbon source, acetylene. The dewetting kinetics, i.e., the appearance of distinct nanoparticles, exhibits a sigmoidal (autocatalytic) curve with 95% of all nanoparticles appearing within 6 s. After nanoparticles form, they either nucleate CNTs or remain inactive, with incubation times measured to be as small as 3.5 s. Via E-TEM we also directly observe the crowding and self-alignment of CNTs after dewetting and nucleation. Additionally, in situ electron energy loss spectroscopy reveals that the collective rate of carbon accumulation decays exponentially. We conclude that the kinetics of catalyst formation and CNT nucleation must both be addressed in order to achieve uniform and high CNT density, and their transient behavior may be a primary cause of the well-known nonuniform density of CNT forests.« less

In situ TEM study of the Li-Au reaction in an electrochemical liquid cell.

PubMed

Zeng, Zhiyuan; Liang, Wen-I; Chu, Ying-Hao; Zheng, Haimei

2014-01-01

We study the lithiation of a Au electrode in an electrochemical liquid cell using transmission electron microscopy (TEM). The commercial liquid electrolyte for lithium ion batteries (1 M lithium hexafluorophosphate LiPF6 dissolved in 1 : 1 (v/v) ethylene carbonate (EC) and diethyl carbonate (DEC)) was used. Three distinct types of morphology change during the reaction, including gradual dissolution, explosive reaction and local expansion/shrinkage, are observed. It is expected that significant stress is generated from lattice expansion during lithium-gold alloy formation. There is vigorous bubble formation from electrolyte decomposition, likely due to the catalytic effect of Au, while the bubble generation is less severe with titanium electrodes. There is an increase of current in response to electron beam irradiation, and electron beam effects on the observed electrochemical reaction are discussed.

Monolayer formation of human osteoblastic cells on vertically aligned multiwalled carbon nanotube scaffolds.

PubMed

Lobo, Anderson O; Antunes, Erica F; Palma, Mariana Bs; Pacheco-Soares, Cristina; Trava-Airoldi, Vladimir J; Corat, Evaldo J

2010-03-12

Monolayer formation of SaOS-2 (human osteoblast-like cells) was observed on VACNT (vertically aligned multiwalled carbon nanotubes) scaffolds without purification or functionalization. The VACNT were produced by a microwave plasma chemical vapour deposition on titanium surfaces with nickel or iron as catalyst. Cell viability and morphology studies were evaluated by LDH (lactate dehydrogenase) release assay and SEM (scanning electron microscopy), respectively. The non-toxicity and the flat spreading with monolayer formation of the SaOs-2 on VACNT scaffolds surface indicate that they can be used for biomedical applications.

Self-assembled formation and transformation of In/CdZnTe(110) nano-rings into camel-humps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen-Taguri, G.; Ruzin, A.; Goldfarb, I.

2012-05-21

We used in situ scanning tunneling microscopy to monitor in real time the formation of nano-rings at the molecular beam epitaxially grown In/CdZnTe(110) surface, and Auger electron spectroscopy to explore the corresponding compositional changes. In-diffusion of In and segregation of Cd to the surface in course of annealing lead to a formation of elliptically distorted nano-rings, elongated along the fast [110] diffusion direction. Exacerbated diffusion anisotropy in the liquid state, at temperatures above the melting point of In, further distorts the nano-rings into a camel-hump shape.

Atomistic modeling and HAADF investigations of misfit and threading dislocations in GaSb/GaAs hetero-structures for applications in high electron mobility transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruterana, Pierre, E-mail: pierre.ruterana@ensicaen.fr; Wang, Yi, E-mail: pierre.ruterana@ensicaen.fr; Chen, Jun, E-mail: pierre.ruterana@ensicaen.fr

A detailed investigation on the misfit and threading dislocations at GaSb/GaAs interface has been carried out using molecular dynamics simulation and quantitative electron microscopy techniques. The sources and propagation of misfit dislocations have been elucidated. The nature and formation mechanisms of the misfit dislocations as well as the role of Sb on the stability of the Lomer configuration have been explained.

Extra and Intracellular Synthesis of Nickel Oxide Nanoparticles Mediated by Dead Fungal Biomass

PubMed Central

Salvadori, Marcia Regina; Ando, Rômulo Augusto; Oller Nascimento, Cláudio Augusto; Corrêa, Benedito

2015-01-01

The use of dead biomass of the fungus Hypocrea lixii as a biological system is a new, effective and environmentally friendly bioprocess for the production and uptake of nickel oxide nanoparticles (NPs), which has become a promising field in nanobiotechnology. Dead biomass of the fungus was successfully used to convert nickel ions into nickel oxide NPs in aqueous solution. These NPs accumulated intracellularly and extracellularly on the cell wall surface through biosorption. The average size, morphology and location of the NPs were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The NPs were mainly spherical and extra and intracellular NPs had an average size of 3.8 nm and 1.25 nm, respectively. X-ray photoelectron spectroscopy analysis confirmed the formation of nickel oxide NPs. Infrared spectroscopy detected the presence of functional amide groups, which are probable involved in particle binding to the biomass. The production of the NPs by dead biomass was analyzed by determining physicochemical parameters and equilibrium concentrations. The present study opens new perspectives for the biosynthesis of nanomaterials, which could become a potential biosorbent for the removal of toxic metals from polluted sites. PMID:26043111

Preparation of electrospun pyrochlore-structure KGdTa2O7:Eu3+ phosphor: the optical and structural properties for white light emitting diode applications.

PubMed

Yim, Chul Jin; Unithrattil, Sanjith; Chung, Woon Jin; Im, Won Bin

2013-12-01

Red emitting nanofibers, KGdTa2O7:Eu3+ were synthesized by electrospinning technique followed by heat treatment. As-prepared uniform fiber precursor with diameter ranging from about 700 nm to about 900 nm were calcined after removing organic species by calcination. The fiber surface become rough and diameter decreased to about 250-340 nm range due to decomposition of organic species and formation of inorganic phase. Morphology, structural and photoluminescent properties of fibers were analyzed using thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL). TG-DTA analysis indicates that KGdTa2O7:Eu3+ began to crystalize at 520 degrees C. Fibers annealed at 900 degrees C formed well crystallized uniform fibers. Under ultraviolet excitation KGdTa2O7:Eu3+ exhibits red emission due to transitions in 4f states of Eu3+. The excitation band is dominated by the Eu(3+)--O2-charge transfer band peaked at 289 nm. The emission peak is in the region that is ideal for red light emission.

Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. II. In situ transmission electron microscopy study of deformation mechanism change of a Zr-2.5Nb alloy upon heavy ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Fei; Daymond, Mark R., E-mail: mark.daymond@queensu.ca; Yao, Zhongwen

2015-03-14

The effect of heavy-ion irradiation on deformation mechanisms of a Zr-2.5Nb alloy was investigated by using the in situ transmission electron microscopy deformation technique. The gliding behavior of prismatic 〈a〉 dislocations has been dynamically observed before and after irradiation at room temperature and 300 °C. Irradiation induced loops were shown to strongly pin the gliding dislocations. Unpinning occurred while loops were incorporated into or eliminated by 〈a〉 dislocations. In the irradiated sample, loop depleted areas with a boundary parallel to the basal plane trace were found by post-mortem observation after room temperature deformation, supporting the possibility of basal channel formation inmore » bulk neutron irradiated samples. Strong activity of pyramidal slip was also observed at both temperatures, which might be another important mechanism to induce plastic instability in irradiated zirconium alloys. Finally, (011{sup ¯}1)〈01{sup ¯}12〉 twinning was identified in the irradiated sample deformed at 300 °C.« less

Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. II. In situ transmission electron microscopy study of deformation mechanism change of a Zr-2.5Nb alloy upon heavy ion irradiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Fei; Daymond, Mark R.; Yao, Zhongwen

2015-03-14

The effect of heavy-ion irradiation on deformation mechanisms of a Zr-2.5Nb alloy was investigated by using the in situ transmission electron microscopy deformation technique. The gliding behavior of prismatic < a > dislocations has been dynamically observed before and after irradiation at room temperature and 300 degrees C. Irradiation induced loops were shown to strongly pin the gliding dislocations. Unpinning occurred while loops were incorporated into or eliminated by < a > dislocations. In the irradiated sample, loop depleted areas with a boundary parallel to the basal plane trace were found by post-mortem observation after room temperature deformation, supporting themore » possibility of basal channel formation in bulk neutron irradiated samples. Strong activity of pyramidal slip was also observed at both temperatures, which might be another important mechanism to induce plastic instability in irradiated zirconium alloys. Finally, {01 (1) over bar1}< 0 (1) over bar 12 > twinning was identified in the irradiated sample deformed at 300 degrees C.« less

Using transmission electron microscopy and 3View® to determine collagen fibril size and three-dimensional organization

PubMed Central

Mironov, Aleksandr; Cootes, Timothy F.; Holmes, David F.; Kadler, Karl E.

2017-01-01

Collagen fibrils are the major tensile element in vertebrate tissues where they occur as ordered bundles in the extracellular matrix. Abnormal fibril assembly and organization results in scarring, fibrosis, poor wound healing and connective tissue diseases. Transmission electron microscopy (TEM) is used to assess formation of the fibrils, predominantly by measuring fibril diameter. Here we describe an enhanced protocol for measuring fibril diameter as well as fibril-volume-fraction, mean fibril length, fibril cross-sectional shape, and fibril 3D organization that are also major determinants of tissue function. Serial section TEM (ssTEM) has been used to visualize fibril 3D-organization in vivo. However, serial block face-scanning electron microscopy (SBF-SEM) has emerged as a time-efficient alternative to ssTEM. The protocol described below is suitable for preparing tissues for TEM and SBF-SEM (by 3View®). We demonstrate the power of 3View® for studying collagen fibril organization in vivo and show how to find and track individual fibrils. Time scale: ~8 days from isolating the tissue to having a 3D image stack. PMID:23807286

Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder

PubMed Central

Shameli, Kamyar; Ahmad, Mansor Bin; Zamanian, Ali; Sangpour, Parvanh; Shabanzadeh, Parvaneh; Abdollahi, Yadollah; Zargar, Mohsen

2012-01-01

Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries. PMID:23341739

Optimizing low-light microscopy with back-illuminated electron multiplying charge-coupled device: enhanced sensitivity, speed, and resolution.

PubMed

Coates, Colin G; Denvir, Donal J; McHale, Noel G; Thornbury, Keith D; Hollywood, Mark A

2004-01-01

The back-illuminated electron multiplying charge-coupled device (EMCCD) camera is having a profound influence on the field of low-light dynamic cellular microscopy, combining highest possible photon collection efficiency with the ability to virtually eliminate the readout noise detection limit. We report here the use of this camera, in 512 x 512 frame-transfer chip format at 10-MHz pixel readout speed, in optimizing a demanding ultra-low-light intracellular calcium flux microscopy setup. The arrangement employed includes a spinning confocal Nipkow disk, which, while facilitating the need to both generate images at very rapid frame rates and minimize background photons, yields very weak signals. The challenge for the camera lies not just in detecting as many of these scarce photons as possible, but also in operating at a frame rate that meets the temporal resolution requirements of many low-light microscopy approaches, a particular demand of smooth muscle calcium flux microscopy. Results presented illustrate both the significant sensitivity improvement offered by this technology over the previous standard in ultra-low-light CCD detection, the GenIII+intensified charge-coupled device (ICCD), and also portray the advanced temporal and spatial resolution capabilities of the EMCCD. Copyright 2004 Society of Photo-Optical Instrumentation Engineers.

Characterization of passive polymer optical waveguides

NASA Astrophysics Data System (ADS)

Joehnck, Matthias; Kalveram, Stefan; Lehmacher, Stefan; Pompe, Guido; Rudolph, Stefan; Neyer, Andreas; Hofstraat, Johannes W.

1999-05-01

The characterization of monomode passive polymer optical devices fabricated according to the POPCORN technology by methods originated from electron, ion and optical spectroscopy is summarized. Impacts of observed waveguide perturbations on the optical characteristics of the waveguide are evaluated. In the POPCORN approach optical components for telecommunication applications are fabricated by photo-curing of liquid halogenated (meth)acrylates which have been applied on moulded thermoplastic substrates. For tuning of waveguide material refractive indices with respect to the substrate refractive index frequently comonomer mixtures are used. The polymerization characteristics, especially the polymerization kinetics of individual monomers, determine the formation of copolymers. Therefore the unsaturation as function of UV-illumination time in the formation of halogenated homo- and copolymers has been examined. From different suitable copolymer system, after characterization of their glass transition temperatures, their curing behavior and their refractive indices as function of the monomer ratios, monomode waveguides applying PMMA substrates have been fabricated. To examine the materials composition also in the 6 X 6 micrometers 2 waveguides they have been visualized by transmission electron microscopy. With this method e.g. segregation phenomena could be observed in the waveguide cross section characterization as well. The optical losses in monomode waveguides caused by segregation and other materials induce defects like micro bubbles formed as a result of shrinkage have been quantized by return loss measurements. Defects causing scattering could be observed by convocal laser scanning microscopy and by conventional light microscopy.

Formation of crystalline heteroepitaxial SiC films on Si by carbonization of polyimide Langmuir-Blodgett films

NASA Astrophysics Data System (ADS)

Luchinin, Viktor V.; Goloudina, Svetlana I.; Pasyuta, Vyacheslav M.; Panov, Mikhail F.; Smirnov, Alexander N.; Kirilenko, Demid A.; Semenova, Tatyana F.; Sklizkova, Valentina P.; Gofman, Iosif V.; Svetlichnyi, Valentin M.; Kudryavtsev, Vladislav V.

2017-06-01

High-quality crystalline nano-thin SiC films on Si substrates were prepared by carbonization of polyimide (PI) Langmuir-Blodgett (LB) films. The obtained films were characterized by Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, Raman spectroscopy, transmission electon microscopy (TEM), transmission electron diffraction (TED), and scanning electron microscopy (SEM). We demonstrated that the carbonization of a PI film on a Si substrate at 1000 °C leads to the formation of a carbon film and SiC nanocrystals on the Si substrate. It was found that five planes in the 3C-SiC(111) film are aligned with four Si(111) planes. As a result of repeated annealing of PI films containing 121 layers at 1200 °C crystalline SiC films were formed on the Si substrate. It was shown that the SiC films (35 nm) grown on Si(111) at 1200 °C have a mainly cubic 3C-SiC structure with small amount of hexagonal polytypes. Only 3C-SiC films (30 nm) were formed on the Si(100) substrate at the same temperature. It was shown that the SiC films (30-35 nm) can cover the voids with size up to 10 µm in the Si substrate. The current-voltage (I-V) characteristics of the n-Si/n-SiC heterostructure were obtained by conductive atomic force microscopy.

Surface-induced polymerization of actin.

PubMed Central

Renault, A; Lenne, P F; Zakri, C; Aradian, A; Vénien-Bryan, C; Amblard, F

1999-01-01

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m. PMID:10049338

Self-assembled indium arsenide quantum dots: Structure, formation dynamics, optical properties

NASA Astrophysics Data System (ADS)

Lee, Hao

1998-12-01

In this dissertation, we investigate the properties of InAs/GaAs quantum dots grown by molecular beam epitaxy. The structure and formation dynamics of InAs quantum dots are studied by a variety of structural characterization techniques. Correlations among the growth conditions, the structural characteristics, and the observed optical properties are explored. The most fundamental structural characteristic of the InAs quantum dots is their shape. Through detailed study of the reflection high energy electron diffraction patterns, we determined that self-assembled InAs islands possess a pyramidal shape with 136 bounding facets. Cross-sectional transmission electron microscopy images and atomic force microscopy images strongly support this model. The 136 model we proposed is the first model that is consistent with all reported shape features determined using different methods. The dynamics of coherent island formation is also studied with the goal of establishing the factors most important in determining the size, density, and the shape of self- organized InAs quantum dots. Our studies clearly demonstrate the roles that indium diffusion and desorption play in InAs island formation. An unexpected finding (from atomic force microscopy images) was that the island size distribution bifurcated during post- growth annealing. Photoluminescence spectra of the samples subjected to in-situ annealing prior to the growth of a capping layer show a distinctive double-peak feature. The power-dependence and temperature-dependence of the photoluminescence spectra reveals that the double- peak emission is associated with the ground-state transition of islands in two different size branches. These results confirm the island size bifurcation observed from atomic force microscopy images. The island size bifurcation provides a new approach to the control and manipulation of the island size distribution. Unexpected dependence of the photoluminescence line-shape on sample temperature and pump intensity was observed for samples grown at relatively high substrate temperatures. The behavior is modeled and explained in terms of competition between two overlapping transitions. The study underscores that the growth conditions can have a dramatic impact on the optical properties of the quantum dots. This dissertation includes both my previously published and unpublished authored materials.

Facile and green synthesis of mesoporous Co3O4 nanocubes and their applications for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Xiangmei; Long, Qing; Jiang, Chunhui; Zhan, Beibei; Li, Chen; Liu, Shujuan; Zhao, Qiang; Huang, Wei; Dong, Xiaochen

2013-06-01

Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer.Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00495c

Quantum dot formation by molecular beam epitaxy of Ge on Si(100)

NASA Astrophysics Data System (ADS)

Chaparro, Sergio Arturo

1999-11-01

A new technique for producing electron systems with quantum confinement in three dimensions, quantum dots, has been studied. These quantum dots are coherent islands spontaneously formed at the early stages of Ge/Si(100) epitaxy due to the misfit of the system. Our goal is to gain understanding and control of the growth process so uniform quantum dot ensembles can be created for possible use in optoelectronic devices. A UHV Molecular Beam Epitaxy (MBE) growth system was built and calibrated to grow our samples. The samples were prepared by depositing Ge onto a Si(100) surface cleaned by flash desorption of the native oxides. Varying the growth rates from 0.6 ML/min to 4.0 ML/min, the substrate temperature from 450°C to 600°C, and the coverage from 3.5 ML to 14 ML produces different sample morphologies. After growth, the samples were analyzed both in situ and ex situ. The in situ analysis consisted of Auger electron spectroscopy for elemental analysis and reflection high energy electron diffraction, for surface structure analysis. The ex situ analysis included atomic force microscopy (AFM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM). Many digital images were obtained from the microscope analysis. A novel, computer based, analysis was developed to extract the islands parameters from the microscope images. This data, which includes island area and average height for each island on every image, was used for a statistical analysis. Also from the data, island size distributions (histograms of island size) were generated. These measurements confirm that islands form after growth of a 3 ML wetting layer and that islands evolve as they grow. As more Ge is deposited these islands grow and as they grow they evolve from huts, square based pyramids, to domes, truncated pyramids, to dislocated domes. Our results show that the substrate temperature, deposition rate, and amount of deposited material are factors that affect the growth evolution. Higher growth temperature affects the size at which islands evolve from one type of island to another, also introduces new strain release mechanisms such as alloying and trench formation that compete with dislocation formation. Finally a detailed morphological characterization of the observed islands was done.

Fayalite Dissolution and Siderite Formation in Water-Saturated Supercritical CO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qafoku, Odeta; Kovarik, Libor; Kukkadapu, Ravi K.

2012-11-25

Olivines, a significant constituent of basaltic rocks, have the potential to immobilize permanently CO2 after it is injected in the deep subsurface, due to carbonation reactions occurring between CO2 and the host rock. To investigate the reactions of fayalitic olivine with supercritical CO2 (scCO2) and formation of mineral carbonates, experiments were conducted at temperatures of 35 °C to 80 °C, 90 atm pressure and anoxic conditions. For every temperature, the dissolution of fayalite was examined both in the presence of liquid water and H2O-saturated scCO2. The experiments were conducted in a high pressure batch reactor at reaction time extending upmore » to 85 days. The newly formed products were characterized using a comprehensive suite of bulk and surface characterization techniques X-ray diffraction, Transmission/Emission Mössbauer Spectroscopy, Scanning Electron Microscopy coupled with Focused Ion Beam, and High Resolution Transmission Electron Microscopy. Siderite with rhombohedral morphology was formed at 35 °C, 50 °C, and 80 °C in the presence of liquid water and scCO2. In H2O-saturated scCO2, the formation of siderite was confirmed only at high temperature (80 °C). Characterization of reacted samples in H2O-saturated scCO2 with high resolution TEM indicated that siderite formation initiated inside voids created during the initial steps of fayalite dissolution. Later stages of fayalite dissolution result in the formation of siderite in layered vertical structures, columns or pyramids with a rhombus base morphology.« less

Meiotic nucleolar cycle and chromatoid body formation during the rat (Rattus novergicus) and mouse (Mus musculus) spermiogenesis.

PubMed

Peruquetti, Rita Luiza; Assis, Isabella Mariana; Taboga, Sebastião Roberto; de Azeredo-Oliveira, Maria Tercília Vilela

2008-06-01

The aims of the present study were to follow the nucleolar cycle in spermiogenesis of the laboratory rodents Rattus novergicus and Mus musculus, to verify the relationship between the nucleolar component and chromatoid body (CB) formation and to investigate the function of this cytoplasmic supramolecular structure in spermatogenic haploid cells. Histological sections of adult seminiferous tubules were analyzed cytochemically by light microscopy and ultrastructural procedures by transmission electron microscopy. The results reveal that in early spermatids, the CB was visualized in association with the Golgi cisterns indicating that this structure may participate in the acrosome formation process. In late spermatids, the CB was observed near the axonema, a fact suggesting that this structure may support the formation of the spermatozoon tail. In conclusion, our data showed that there is disintegration of spermatid nucleoli at the beginning of spermatogenesis and a fraction of this nucleolar material migrates to the cytoplasm, where a specific structure is formed, known as the "chromatoid body", which, apparently, participates in some parts of the rodent spermiogenesis process.

Complete Prevention of Dendrite Formation in Zn Metal Anodes by Means of Pulsed Charging Protocols.

PubMed

Garcia, Grecia; Ventosa, Edgar; Schuhmann, Wolfgang

2017-06-07

Zn metal as anode in rechargeable batteries, such as Zn/air or Zn/Ni, suffers from poor cyclability. The formation of Zn dendrites upon cycling is the key limiting step. We report a systematic study of the influence of pulsed electroplating protocols on the formation of Zn dendrites and in turn on strategies to completely prevent Zn dendrite formation. Because of the large number of variables in electroplating protocols, a scanning droplet cell technique was adapted as a high-throughput methodology in which a descriptor of the surface roughness can be in situ derived by means of electrochemical impedance spectroscopy. Upon optimizing the electroplating protocol by controlling nucleation, zincate ion depletion, and zincate ion diffusion, scanning electron microscopy and atomic force microscopy confirmed the growth of uniform and homogenous Zn deposits with a complete prevention of dendrite growth. The implementation of pulsed electroplating as the charging protocol for commercially available Ni-Zn batteries leads to substantially prolonged cyclability demonstrating the benefits of pulsed charging in Zn metal-based batteries.

The Cording Phenotype of Mycobacterium tuberculosis Induces the Formation of Extracellular Traps in Human Macrophages.

PubMed

Kalsum, Sadaf; Braian, Clara; Koeken, Valerie A C M; Raffetseder, Johanna; Lindroth, Margaretha; van Crevel, Reinout; Lerm, Maria

2017-01-01

The causative agent of tuberculosis, Mycobacterium tuberculosis , shares several characteristics with organisms that produce biofilms during infections. One of these is the ability to form tight bundles also known as cords. However, little is known of the physiological relevance of the cording phenotype. In this study, we investigated whether cord-forming M. tuberculosis induce the formation of macrophage extracellular traps (METs) in human monocyte-derived macrophages. Macrophages have previously been shown to produce extracellular traps in response to various stimuli. We optimized bacterial culturing conditions that favored the formation of the cord-forming phenotype as verified by scanning electron microscopy. Microscopy analysis of METs formation during experimental infection of macrophages with M. tuberculosis revealed that cord-forming M. tuberculosis induced significantly more METs compared to the non-cording phenotype. Deletion of early secreted antigenic target-6 which is an important virulence factor of M. tuberculosis , abrogated the ability of the bacteria to induce METs. The release of extracellular DNA from host cells during infection may represent a defense mechanism against pathogens that are difficult to internalize, including cord-forming M. tuberculosis .

Using micro-patterned surfaces to inhibit settlement and biofilm formation by Bacillus subtilis.

PubMed

Chang, Siyuan; Chen, Xiaodong; Jiang, Shuo; Chen, Jinchun; Shi, Lin

2017-07-01

Biofilm is a biological complex caused by bacteria attachment to the substrates and their subsequent reproduction and secretion. This phenomenon reduces heat transfer efficiency and causes significant losses in treated sewage heat-recovering systems. This paper describes a physical approach to inhibit bacteria settlement and biofilm formation by Bacillus subtilis, which is the dominant species in treated sewage. Here, micro-patterned surfaces with different characteristics (stripe and cube) and dimensions (1-100 μm) were fabricated as surfaces of interest. Model sewage was prepared and a rotating coupon device was used to form the biofilms. Precision balance, scanning electron microscopy, and confocal laser scanning microscopy (CLSM) were employed to investigate the inhibitory effects and the mechanisms of the biofilm-surface interactions. The results have shown that surfaces with small pattern sizes (1 and 2 μm) all reduced biofilm formation significantly. Interestingly, the CLSM images showed that the surfaces do not play a role in "killing" the bacteria. These findings are useful for future development of new process surfaces on which bacteria settlement and biofilm formation can be inhibited or minimized.

Suture-Related Keratitis Caused by Corynebacterium macginleyi▿

PubMed Central

Suzuki, Takashi; Iihara, Hirotoshi; Uno, Toshihiko; Hara, Yuko; Ohkusu, Kiyofumi; Hata, Hiroyuki; Shudo, Masachika; Ohashi, Yuichi

2007-01-01

We report two cases of suture-related keratitis following penetrating keratoplasty. In both cases, Corynebacterium macginleyi was isolated from corneal specimens. Scanning electron microscopy revealed that corynebacteria could aggregate and form a biofilm. The MICs of sulbenicillin and fluoroquinolones were high for both isolates. Our findings show that C. macginleyi can cause keratitis with biofilm formation. PMID:17913935

Impact of nanosecond proton beam processing on nanoblocks of copper

NASA Astrophysics Data System (ADS)

Borodin, Y. V.; Mantina, A. Y.; Pak, V.; Zhang, X. X.

2017-01-01

X-ray studies in conjunction with the method of recoil nuclei and electron microscopy of irradiated plates polycrystalline Cu by nanosecond high power density proton beams (E = 120 keV; I = 80 A/cm2, t = 50 ns) showed nano block nature of the formation of structure in the surface layer target and condensed-formed film.

Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taoufyq, A.; Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc; Département d‘Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache

2013-07-15

The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and directmore » current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.« less

Patterning nanoparticles into rings by "2-D Pickering emulsions".

PubMed

Lee, Cheol Hee; Crosby, Alfred J; Hayward, Ryan C; Emrick, Todd

2014-04-09

We present a simple method for the two-dimensional self-assembly of CdSe/ZnS quantum dots (QDs) into well-defined rings at the air/water interface, through the formation of "2-D Pickering emulsions". Surfactant molecules assemble at the air/water interface into islands that are subsequently surrounded by adsorption of QDs from the aqueous subphase. The QD rings emanating from this process range from ∼100 nm to several micrometers in diameter, as characterized by atomic force microscopy, scanning electron microscopy, and fluorescence microscopy. The deposition and alignment of QD rings onto large areas (cm(2)) were demonstrated by dip-coating onto a substrate. This simple method produces rings of QDs without the need for any templating or fabrication steps.

Reactive Oxygen Species Mediated Bacterial Biofilm Inhibition via Zinc Oxide Nanoparticles and Their Statistical Determination

PubMed Central

Dwivedi, Sourabh; Wahab, Rizwan; Khan, Farheen; Mishra, Yogendra K.; Musarrat, Javed; Al-Khedhairy, Abdulaziz A.

2014-01-01

The formation of bacterial biofilm is a major challenge in clinical applications. The main aim of this study is to describe the synthesis, characterization and biocidal potential of zinc oxide nanoparticles (NPs) against bacterial strain Pseudomonas aeruginosa. These nanoparticles were synthesized via soft chemical solution process in a very short time and their structural properties have been investigated in detail by using X-ray diffraction and transmission electron microscopy measurements. In this work, the potential of synthesized ZnO-NPs (∼10–15 nm) has been assessed in-vitro inhibition of bacteria and the formation of their biofilms was observed using the tissue culture plate assays. The crystal violet staining on biofilm formation and its optical density revealed the effect on biofilm inhibition. The NPs at a concentration of 100 µg/mL significantly inhibited the growth of bacteria and biofilm formation. The biofilm inhibition by ZnO-NPs was also confirmed via bio-transmission electron microscopy (Bio-TEM). The Bio-TEM analysis of ZnO-NPs treated bacteria confirmed the deformation and damage of cells. The bacterial growth in presence of NPs concluded the bactericidal ability of NPs in a concentration dependent manner. It has been speculated that the antibacterial activity of NPs as a surface coating material, could be a feasible approach for controlling the pathogens. Additionally, the obtained bacterial solution data is also in agreement with the results from statistical analytical methods. PMID:25402188

Reactive oxygen species mediated bacterial biofilm inhibition via zinc oxide nanoparticles and their statistical determination.

PubMed

Dwivedi, Sourabh; Wahab, Rizwan; Khan, Farheen; Mishra, Yogendra K; Musarrat, Javed; Al-Khedhairy, Abdulaziz A

2014-01-01

The formation of bacterial biofilm is a major challenge in clinical applications. The main aim of this study is to describe the synthesis, characterization and biocidal potential of zinc oxide nanoparticles (NPs) against bacterial strain Pseudomonas aeruginosa. These nanoparticles were synthesized via soft chemical solution process in a very short time and their structural properties have been investigated in detail by using X-ray diffraction and transmission electron microscopy measurements. In this work, the potential of synthesized ZnO-NPs (∼ 10-15 nm) has been assessed in-vitro inhibition of bacteria and the formation of their biofilms was observed using the tissue culture plate assays. The crystal violet staining on biofilm formation and its optical density revealed the effect on biofilm inhibition. The NPs at a concentration of 100 µg/mL significantly inhibited the growth of bacteria and biofilm formation. The biofilm inhibition by ZnO-NPs was also confirmed via bio-transmission electron microscopy (Bio-TEM). The Bio-TEM analysis of ZnO-NPs treated bacteria confirmed the deformation and damage of cells. The bacterial growth in presence of NPs concluded the bactericidal ability of NPs in a concentration dependent manner. It has been speculated that the antibacterial activity of NPs as a surface coating material, could be a feasible approach for controlling the pathogens. Additionally, the obtained bacterial solution data is also in agreement with the results from statistical analytical methods.

In vitro activity of chlorogenic acid against Aspergillus fumigatus biofilm and gliotoxin production.

PubMed

Kong, Jin-Liang; Luo, Jing; Li, Bing; Dong, Bi-Ying; Huang, Hong; Wang, Ke; Wu, Li-Hong; Chen, Yi-Qiang

2017-06-01

Aspergillus ( A .) fumigatus , one of the most common causes of life-threatening fungal infections in immunocompromised patients, shows resistance to antifungal agents as has a high propensity to forming a biofilm. The present study aimed to investigate the effects of chlorogenic acid (CRA) on A. fumigatus biofilm formation and integrity. Confocal laser scanning microscopy was performed to determine the inhibitory effects of CRA against A. fumigatus biofilm formation. Transmission electron microscopy was performed to investigate the ultrastructural changes of A. fumigatus biofilm after CRA exposure. High-performance liquid chromatography and reverse-transcription quantitative PCR were performed to determine the expression of gliotoxin production in biofilm culture. The results showed that CRA at sub-minimum inhibitory concentrations inhibited A. fumigatus biofilm formation. In addition, CRA could decreased the gliotoxin production in the biofilm culture supernatant through inhibiting the expression of master genes involved in gliotoxin biosynthesis. The present study provided useful information for the development of novel strategies to reduce the incidence of A. fumigatus biofilm-associated diseases.

Biofilm inhibition by an experimental dental resin composite containing octenidine dihydrochloride.

PubMed

Rupf, Stefan; Balkenhol, Markus; Sahrhage, Tim O; Baum, Alexandra; Chromik, Julia N; Ruppert, Klaus; Wissenbach, Dirk K; Maurer, Hans H; Hannig, Matthias

2012-09-01

The aim of the present study was to investigate an antimicrobial additive containing experimental resin composite with regards to its impact on biofilm formation under oral conditions. Biofilms were established in situ on composite specimens (n=192) which contained octenidine dihydrochloride (ODH, 3 wt.% or 6 wt.%). Samples without antimicrobial additive served as control (n=96). Composite specimens were fixed on custom made splints and exposed to the oral cavity of six healthy volunteers for three or seven days. Biofilm formation was assessed by scanning electron microscopy (SEM) and fluorescence microscopy (FM). The biofilm formation was significantly reduced on ODH containing samples compared to controls after three as well as after seven days in situ. FM evaluation additionally showed a lower viability of the reduced biofilms for both ODH concentrations. During this short term investigation, incorporation of ODH into resin based composite materials caused biofilm inhibiting effects in situ. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Jellyfish collagen scaffolds for cartilage tissue engineering.

PubMed

Hoyer, Birgit; Bernhardt, Anne; Lode, Anja; Heinemann, Sascha; Sewing, Judith; Klinger, Matthias; Notbohm, Holger; Gelinsky, Michael

2014-02-01

Porous scaffolds were engineered from refibrillized collagen of the jellyfish Rhopilema esculentum for potential application in cartilage regeneration. The influence of collagen concentration, salinity and temperature on fibril formation was evaluated by turbidity measurements and quantification of fibrillized collagen. The formation of collagen fibrils with a typical banding pattern was confirmed by atomic force microscopy and transmission electron microscopy analysis. Porous scaffolds from jellyfish collagen, refibrillized under optimized conditions, were fabricated by freeze-drying and subsequent chemical cross-linking. Scaffolds possessed an open porosity of 98.2%. The samples were stable under cyclic compression and displayed an elastic behavior. Cytotoxicity tests with human mesenchymal stem cells (hMSCs) did not reveal any cytotoxic effects of the material. Chondrogenic markers SOX9, collagen II and aggrecan were upregulated in direct cultures of hMSCs upon chondrogenic stimulation. The formation of typical extracellular matrix components was further confirmed by quantification of sulfated glycosaminoglycans. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Growth of fullerene-like carbon nitride thin solid films consisting of cross-linked nano-onions

NASA Astrophysics Data System (ADS)

Czigány, Zs.; Brunell, I. F.; Neidhardt, J.; Hultman, L.; Suenaga, K.

2001-10-01

Fullerene-like CNx (x≈0.12) thin solid films were deposited by reactive magnetron sputtering of graphite in a nitrogen and argon discharge on cleaved NaCl and Si(001) substrates at 450 °C. As-deposited films consist of 5 nm diam CNx nano-onions with shell sizes corresponding to Goldberg polyhedra determined by high-resolution transmission electron microscopy. Electron energy loss spectroscopy revealed that N incorporation is higher in the core of the onions than at the perimeter. N incorporation promotes pentagon formation and provides reactive sites for interlinks between shells of the onions. A model is proposed for the formation of CNx nano-onions by continuous surface nucleation and growth of hemispherical shells.

Electron beam induced green luminescence and degradation study of CaS:Ce nanocrystalline phosphors for FED applications

NASA Astrophysics Data System (ADS)

Kumar, Vinay; Mishra, Varun; Biggs, M. M.; Nagpure, I. M.; Ntwaeaborwa, O. M.; Terblans, J. J.; Swart, H. C.

2010-01-01

Green luminescence and degradation of Ce 3+ doped CaS nanocrystalline phosphors were studied with a 2 keV, 10 μA electron beam in an O 2 environment. The nanophosphors were synthesized by the co-precipitation method. The samples were characterized using X-ray diffraction, Transmission electron microscopy, Scanning electron microscopy/electron dispersive X-ray spectroscopy and Photoluminescence (PL) spectroscopy. Cubic CaS with an average particle size of 42 ± 2 nm was obtained. PL emission was observed at 507 nm and a shoulder at 560 nm with an excitation wavelength of 460 nm. Auger electron spectroscopy and Cathodoluminescence (CL) were used to monitor the changes in the surface composition of the CaS:Ce 3+ nanocrystalline phosphors during electron bombardment in an O 2 environment. The effect of different oxygen pressures ranging from 1 × 10 -8 to 1 × 10 -6 Torr on the CL intensity was also investigated. A CaSO 4 layer was observed on the surface after the electron beam degradation. The CL intensity was found to decrease up to 30% of its original intensity at 1 × 10 -6 Torr oxygen pressure after an electron dose of 50 C/cm 2. The formation of oxygen defects during electron bombardment may also be responsible for the decrease in CL intensity.

Toward tunable doping in graphene FETs by molecular self-assembled monolayers

NASA Astrophysics Data System (ADS)

Li, Bing; Klekachev, Alexander V.; Cantoro, Mirco; Huyghebaert, Cedric; Stesmans, André; Asselberghs, Inge; de Gendt, Stefan; de Feyter, Steven

2013-09-01

In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant.In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant. Electronic supplementary information (ESI) available: AFM images of self-assembled monolayers of OA on HOPG; AFM height image of the graphene surface on a SiC substrate; high resolution STM image of a self-assembled monolayer of OA on HOPG; transfer curves of a graphene FET with and without baking steps; transfer curves of a graphene FET under high vacuum conditions; transfer curves of a graphene FET and its Raman response before and after OA treatment; transfer curves of a graphene FET before and after rinsing with n-hexane. See DOI: 10.1039/c3nr01255g

Analytical electron microscopy as a powerful tool in plant cell biology: examples using electron energy loss spectroscopy and X-ray microanalysis.

PubMed

Lichtenberger, O; Neumann, D

1997-08-01

Energy filtering transmission electron microscopy in combination with energy dispersive X-ray analysis (EDX) and quantumchemical calculations opens new possibilities for elemental and bone analysis at the ultrastructural level. The possibilities and limitations of these methods, applied to botanical samples, are discussed and some examples are given. Ca-oxalate crystals in plant cell vacuoles show a specific C K-edge in the electron energy loss spectrum (EELS), which allows a more reliable identification than light microscopical or cytochemical methods. In some dicots crystalline inclusions can be observed in different cell compartments, which are identified as silicon dioxide or calcium silicate by the fine structure of the Si L2,3-edge. Their formation is discussed on the basis of EEL-spectra and quantumchemical calculations. Examples concerning heavy metal detoxification are given for some tolerant plants. In Minuartia Zn is bound as Zn-silicate in cell walls; Armeria accumulates Cu in leaf idioblasts by chelation with phenolic compounds and Cd is precipitated as CdS/phytochelatin-complexes in tomato.

Structure and chemistry of epitaxial ceria thin films on yttria-stabilized zirconia substrates, studied by high resolution electron microscopy

DOE PAGES

Sinclair, Robert; Lee, Sang Chul; Shi, Yezhou; ...

2017-03-18

Here, we have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e-/Å 2s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering. The ordered structure does not appear at lower losemore » rates (ca. 2600 e-/Å 2s) and can be removed by imaging under 1 mbar oxygen gas in an environmental TEM. EELS confirms that there is both oxygen deficiency and the associated increase in Ce 3+ versus Ce 4+ cations in the ordered domains. In situ high resolution TEM recordings show the formation of the ordered domains as well as atomic migration along the ceria thin film (001) surface.« less

Structure and chemistry of epitaxial ceria thin films on yttria-stabilized zirconia substrates, studied by high resolution electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinclair, Robert; Lee, Sang Chul; Shi, Yezhou

Here, we have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e-/Å 2s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering. The ordered structure does not appear at lower losemore » rates (ca. 2600 e-/Å 2s) and can be removed by imaging under 1 mbar oxygen gas in an environmental TEM. EELS confirms that there is both oxygen deficiency and the associated increase in Ce 3+ versus Ce 4+ cations in the ordered domains. In situ high resolution TEM recordings show the formation of the ordered domains as well as atomic migration along the ceria thin film (001) surface.« less

Opal shell structures: direct assembly versus inversion approach.

PubMed

Deng, Tian-Song; Sharifi, Parvin; Marlow, Frank

2013-09-16

Opal shell structures can be fabricated in two ways: By direct assembly from hollow spheres (hs-opal) or by infiltration of precursors into opal templates and inversion. The resulting lattice disturbances were characterized by scanning electron microscopy (SEM), optical microscopy, and transmission spectra. The hs-opal system shows much lower disturbances, for example, a lower number of cracks and lattice deformations. The strong suppression of crack formation in one of these inverse opal structures can be considered as promising candidates for the fabrication of more perfect photonic crystals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Kuan-Kan; Woon, Wei Yen; Chang, Ruey-Dar

We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

NASA Astrophysics Data System (ADS)

Hu, Kuan-Kan; Chang, Ruey-Dar; Woon, Wei Yen

2015-10-01

We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

In vitro Paracoccidioides brasiliensis biofilm and gene expression of adhesins and hydrolytic enzymes.

PubMed

Sardi, Janaina de Cássia Orlandi; Pitangui, Nayla de Souza; Voltan, Aline Raquel; Braz, Jaqueline Derissi; Machado, Marcelo Pelajo; Fusco Almeida, Ana Marisa; Mendes Giannini, Maria Jose Soares

2015-01-01

Paracoccidioides species are dimorphic fungi that initially infect the lungs but can also spread throughout the body. The spreading infection is most likely due to the formation of a biofilm that makes it difficult for the host to eliminate the infection. Biofilm formation is crucial for the development of infections and confines the pathogen to an extracellular matrix. Its presence is associated with antimicrobial resistance and avoidance of host defenses. This current study provides the first description of biofilm formation by Paracoccidioides brasiliensis (Pb18) and an analysis of gene expression, using real-time PCR, associated with 3 adhesins and 2 hydrolytic enzymes that could be associated with the virulence profile. Biofilm formation was analyzed using fluorescence microscopy, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Metabolic activity was determined using the XTT reduction assay. P. brasiliensis was able to form mature biofilm in 144 h with a thickness of 100 μm. The presence of a biofilm was found to be associated with an increase in the expression of adhesins and enzymes. GP43, enolase, GAPDH and aspartyl proteinase genes were over-expressed, whereas phospholipase was down-regulated in biofilm. The characterization of biofilm formed by P. brasiliensis may contribute to a better understanding of the pathogenesis of paracoccidioidomycosis as well as the search for new therapeutic alternatives; while improving the effectiveness of treatment.

On the role of extracellular polymeric substances during early stages of Xylella fastidiosa biofilm formation.

PubMed

Lorite, Gabriela S; de Souza, Alessandra A; Neubauer, Daniel; Mizaikoff, Boris; Kranz, Christine; Cotta, Mônica A

2013-02-01

The structural integrity and protection of bacterial biofilms are intrinsically associated with a matrix of extracellular polymeric substances (EPS) produced by the bacteria cells. However, the role of these substances during biofilm adhesion to a surface remains largely unclear. In this study, the influence of EPS on Xylella fastidiosa biofilm formation was investigated. This bacterium is associated with economically important plant diseases; it presents a slow growth rate and thus allows us to pinpoint more precisely the early stages of cell-surface adhesion. Scanning electron microscopy and atomic force microscopy show evidence of EPS production in such early stages and around individual bacteria cells attached to the substrate surface even a few hours after inoculation. In addition, EPS formation was investigated via attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FTIR). To this end, X. fastidiosa cells were inoculated within an ATR liquid cell assembly. IR-ATR spectra clearly reveal EPS formation already during the early stages of X. fastidiosa biofilm formation, thereby providing supporting evidence for the hypothesis of the relevance of the EPS contribution to the adhesion process. Copyright © 2012 Elsevier B.V. All rights reserved.

Controlled synthesis of magnetic iron oxides@SnO2 quasi-hollow core-shell heterostructures: formation mechanism, and enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Wu, Wei; Zhang, Shaofeng; Ren, Feng; Xiao, Xiangheng; Zhou, Juan; Jiang, Changzhong

2011-11-01

Iron oxide/SnO2 magnetic semiconductor core-shell heterostructures with high purity were synthesized by a low-cost, surfactant-free and environmentally friendly hydrothermal strategy via a seed-mediated method. The morphology and structure of the hybrid nanostructures were characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The morphology evolution investigations reveal that the Kirkendall effect directs the diffusion and causes the formation of iron oxide/SnO2 quasi-hollow particles. Significantly, the as-obtained iron oxides/SnO2 core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to as-used α-Fe2O3 seeds and commercial SnO2 products, mainly owing to the effective electron hole separation at the iron oxides/SnO2 interfaces.Iron oxide/SnO2 magnetic semiconductor core-shell heterostructures with high purity were synthesized by a low-cost, surfactant-free and environmentally friendly hydrothermal strategy via a seed-mediated method. The morphology and structure of the hybrid nanostructures were characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The morphology evolution investigations reveal that the Kirkendall effect directs the diffusion and causes the formation of iron oxide/SnO2 quasi-hollow particles. Significantly, the as-obtained iron oxides/SnO2 core-shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to as-used α-Fe2O3 seeds and commercial SnO2 products, mainly owing to the effective electron hole separation at the iron oxides/SnO2 interfaces. Electronic supplementary information (ESI) available: TEM and HRTEM images of hematite seeds and iron oxide/SnO2 (12 h and 36 h). See DOI: 10.1039/c1nr10728c

Anisotropic Shape Changes of Silica Nanoparticles Induced in Liquid with Scanning Transmission Electron Microscopy.

PubMed

Zečević, Jovana; Hermannsdörfer, Justus; Schuh, Tobias; de Jong, Krijn P; de Jonge, Niels

2017-01-01

Liquid-phase transmission electron microscopy (TEM) is used for in-situ imaging of nanoscale processes taking place in liquid, such as the evolution of nanoparticles during synthesis or structural changes of nanomaterials in liquid environment. Here, it is shown that the focused electron beam of scanning TEM (STEM) brings about the dissolution of silica nanoparticles in water by a gradual reduction of their sizes, and that silica redeposites at the sides of the nanoparticles in the scanning direction of the electron beam, such that elongated nanoparticles are formed. Nanoparticles with an elongation in a different direction are obtained simply by changing the scan direction. Material is expelled from the center of the nanoparticles at higher electron dose, leading to the formation of doughnut-shaped objects. Nanoparticles assembled in an aggregate gradually fuse, and the electron beam exposed section of the aggregate reduces in size and is elongated. Under TEM conditions with a stationary electron beam, the nanoparticles dissolve but do not elongate. The observed phenomena are important to consider when conducting liquid-phase STEM experiments on silica-based materials and may find future application for controlled anisotropic manipulation of the size and the shape of nanoparticles in liquid. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Role of Phase Changes in TiO2/Pt/TiO2 Filaments

NASA Astrophysics Data System (ADS)

Bíró, Ferenc; Hajnal, Zoltán; Dücső, Csaba; Bársony, István

2018-04-01

This work analyses the role of phase changes in TiO2/Pt/TiO2 layer stacks for micro-heater application regarding their stability and reliable operation. The polycrystalline Pt layer wrapped in a TiO2 adhesion layer underwent a continuous recrystallisation in a self-heating operation causing a drift in the resistance ( R) versus temperature ( T) performance. Simultaneously, the TiO2 adhesion layer also deteriorates at high temperature by phase changes from amorphous to anatase and rutile crystallite formation, which not only influences the Pt diffusion in different migration phenomena, but also reduces the cross section of the Pt heater wire. Thorough scanning electron microscopy, energy dispersive spectroscopy, cross-sectional transmission electron microscopy (XTEM) and electron beam diffraction analysis of the structures operated at increasing temperature revealed the elemental structural processes leading to the instabilities and the accelerated degradation, resulting in rapid breakdown of the heater wire. Owing to stability and reliability criteria, the conditions for safe operation of these layer structures could be determined.

Catalytic Graphitization of Coal-Based Carbon Materials with Light Rare Earth Elements.

PubMed

Wang, Rongyan; Lu, Guimin; Qiao, Wenming; Yu, Jianguo

2016-08-30

The catalytic graphitization mechanism of coal-based carbon materials with light rare earth elements was investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, selected-area electron diffraction, and high-resolution transmission electron microscopy. The interface between light rare earth elements and carbon materials was carefully observed, and two routes of rare earth elements catalyzing the carbon materials were found: dissolution-precipitation and carbide formation-decomposition. These two simultaneous processes certainly accelerate the catalytic graphitization of carbon materials, and light rare earth elements exert significant influence on the microstructure and thermal conductivity of graphite. Moreover, by virtue of praseodymium (Pr), it was found that a highly crystallographic orientation of graphite was induced and formed, which was reasonably attributed to the similar arrangements of the planes perpendicular to (001) in both graphite and Pr crystals. The interface between Pr and carbon was found to be an important factor for the orientation of graphite structure.

Coexisting nanoscale inverse spinel and rock salt crystallographic phases in NiCo2O4 epitaxial thin films grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Sharona, H.; Loukya, B.; Bhat, U.; Sahu, R.; Vishal, B.; Silwal, P.; Gupta, A.; Datta, R.

2017-12-01

The origin of alternating wavy dark-bright stripe-like contrast in strain contrast transmission electron microscopy images of NiCo2O4 (NCO) epitaxial thin films grown by pulsed laser deposition has been investigated. The nanoscale stripe-like pattern is determined to be associated with coexisting rock salt (RS) and inverse spinel crystal phases. The presence of two different phases, not addressed in previous reports, is experimentally confirmed by both electron diffraction and high resolution transmission electron microscopy imaging. First principles based calculations, together with compressive strain present in the films, support the formation of such coexisting crystallographic phases in NCO. Similar microstructural patterns and RS structure are not observed in epitaxial films of two other oxides of the spinel family, namely, NiFe2O4 and CoFe2O4. A correlation between the coexisting structures and the macroscopic physical properties of NCO is discussed.

Reversible Cryopreservation of Living Cells Using an Electron Microscopy Cryo-Fixation Method.

PubMed

Huebinger, Jan; Han, Hong-Mei; Grabenbauer, Markus

2016-01-01

Rapid cooling of aqueous solutions is a useful approach for two important biological applications: (I) cryopreservation of cells and tissues for long-term storage, and (II) cryofixation for ultrastructural investigations by electron and cryo-electron microscopy. Usually, both approaches are very different in methodology. Here we show that a novel, fast and easy to use cryofixation technique called self-pressurized rapid freezing (SPRF) is-after some adaptations-also a useful and versatile technique for cryopreservation. Sealed metal tubes with high thermal diffusivity containing the samples are plunged into liquid cryogen. Internal pressure builds up reducing ice crystal formation and therefore supporting reversible cryopreservation through vitrification of cells. After rapid rewarming of pressurized samples, viability rates of > 90% can be reached, comparable to best-performing of the established rapid cooling devices tested. In addition, the small SPRF tubes allow for space-saving sample storage and the sealed containers prevent contamination from or into the cryogen during freezing, storage, or thawing.

Correlation study of nanocrystalline carbon doped thin films prepared by a thermionic vacuum arc deposition technique

NASA Astrophysics Data System (ADS)

Dinca-Balan, Virginia; Vladoiu, Rodica; Mandes, Aurelia; Prodan, Gabriel

2017-11-01

The synthesis of Ag, Mg and Si nanocrystalline, embedded in a hydrogen-free amorphous carbon (a-C) matrix, deposited by a high vacuum and free buffer gas technique, were investigated. The films with compact structures and extremely smooth surfaces were prepared using the thermionic vacuum arc method in one electron gun configuration, on glass and silicon substrates. The surface morphology and wettability of the obtained multifunctional thin films were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and free surface energy (FSE) by See System. The results from the TEM measurements show how the Ag, Mg and Si interacted with carbon and the influence these materials have on the thin film structure formation and the grain size distribution. SEM correlated with EDX results reveal a very precise comparative study, regarding the quantity of the elements that morphed into carbides nanostructures. Also, the FSE results prove how different materials in combination with carbon can make changes to the surface properties.

Effect of replacing Sn4+ ions by Zn2+ ions on structural, optical and magnetic properties of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Selvi, E. Thamarai; Sundar, S. Meenakshi

2017-05-01

This paper highlights on the consequence of replacing tetravalent Sn4+ ions of the SnO2 by divalent Zn2+ ions on their structural, optical, and magnetic properties. Samples of Sn1- x Zn x O2 with x = 0, 0.01, 0.02, 0.03, and 0.04 were synthesized using microwave irradiated solvothermal process. The X-ray powder diffraction patterns reveal the rutile tetragonal phase of all doped SnO2 samples with no secondary phases. The transmission electron microscopy results show the formation of spherical nanoparticles of size 10-30 nm. Morphological changes were observed by scanning electron microscopy. The functional groups were investigated using Fourier transform infrared spectroscopy studies. Optical studies were carried by UV-Vis spectroscopy and fluorescence spectroscopy. Electron paramagnetic resonance was used to calculate the Lande splitting factor ` g'. The magnetic properties using vibrating sample magnetometer exhibit room temperature ferromagnetism for all the samples.

Polarized light and scanning electron microscopic investigation of enamel hypoplasia in primary teeth.

PubMed

Sabel, Nina; Klingberg, Gunilla; Dietz, Wolfram; Nietzsche, Sandor; Norén, Jörgen G

2010-01-01

Enamel hypoplasia is a developmental disturbance during enamel formation, defined as a macroscopic defect in the enamel, with a reduction of the enamel thickness with rounded, smooth borders. Information on the microstructural level is still limited, therefore further studies are of importance to better understand the mechanisms behind enamel hypoplasia. To study enamel hypoplasia in primary teeth by means of polarized light microscopy and scanning electron microscopy. Nineteen primary teeth with enamel hypoplasia were examined in a polarized light microscope and in a scanning electron microscope. The cervical and incisal borders of the enamel hypoplasia had a rounded appearance, as the prisms in the rounded cervical area of the hypoplasia were bent. The rounded borders had a normal surface structure whereas the base of the defects appeared rough and porous. Morphological findings in this study indicate that the aetiological factor has a short duration and affects only certain ameloblasts. The bottom of the enamel hypoplasia is porous and constitutes possible pathways for bacteria into the dentin.

Synthesis of ZnO-CuO/MCM-48 photocatalyst for the degradation of organic pollutions.

PubMed

Duan, Yongzheng; Shen, Yulian

2017-07-01

The photocatalytic properties of ZnO-CuO catalysts supported on siliceous MCM-48 (Mobil Composition of Matter No. 48) for the degradation of organic pollutions such as methylene blue and salicylic acid under UV light irradiation were investigated. These catalysts were prepared by impregnation of MCM-48 with a mixed aqueous solution of copper acetate and zinc acetate. X-ray diffraction, N 2 -physisorption, high resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and photoluminescence were used to characterize these samples. Results from characterizations showed that the addition of ZnO to CuO/MCM-48 could markedly improve the photocatalytic degradation properties. The enhanced photocatalytic behaviors of ZnO-CuO/MCM-48 may be due to the formation of p-n heterojunctions between ZnO and CuO, resulting in the effective separation of photogenerated electron-hole pairs. Moreover, the photocatalysts were easily recovered and reused for five cycles without considerable loss of activity.

Microstructural evolution of NF709 (20Cr–25Ni–1.5MoNbTiN) under neutron irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Byoungkoo; Tan, Lizhen; Xu, C.

In this study, because of its superior creep and corrosion resistance as compared with general austenitic stainless steels, NF709 has emerged as a candidate structural material for advanced nuclear reactors. To obtain fundamental information about the radiation resistance of this material, this study examined the microstructural evolution of NF709 subjected to neutron irradiation to 3 displacements per atom at 500 °C. Transmission electron microscopy, scanning electron microscopy, and high-energy x-ray diffraction were employed to characterize radiation-induced segregation, Frank loops, voids, as well as the formation and reduction of precipitates. Radiation hardening of ~76% was estimated by nanoindentation, approximately consistent withmore » the calculation according to the dispersed barrier-hardening model, suggesting Frank loops as the primary hardening source.« less

Green synthesis of silver nanoparticles using Alternanthera dentata leaf extract at room temperature and their antimicrobial activity

NASA Astrophysics Data System (ADS)

Kumar, Deenadayalan Ashok; Palanichamy, V.; Roopan, Selvaraj Mohana

2014-06-01

A green rapid biogenic synthesis of silver nanoparticles AgNPs using Alternanthera dentata (A. dentata) aqueous extract was demonstrated in this present study. The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance (SPR) at 430 nm using UV-visible spectrophotometer. The reduction of silver ions to silver nanoparticles by A. dentata extract was completed within 10 min. Synthesized nanoparticles were characterized using UV-visible spectroscopy; Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (TEM). The extracellular silver nanoparticles synthesis by aqueous leaf extract demonstrates rapid, simple and inexpensive method comparable to chemical and microbial methods. The colloidal solution of silver nanoparticles were found to exhibit antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia and, Enterococcus faecalis.

Quantitative Description of Crystal Nucleation and Growth from in Situ Liquid Scanning Transmission Electron Microscopy.

PubMed

Ievlev, Anton V; Jesse, Stephen; Cochell, Thomas J; Unocic, Raymond R; Protopopescu, Vladimir A; Kalinin, Sergei V

2015-12-22

Recent advances in liquid cell (scanning) transmission electron microscopy (S)TEM has enabled in situ nanoscale investigations of controlled nanocrystal growth mechanisms. Here, we experimentally and quantitatively investigated the nucleation and growth mechanisms of Pt nanostructures from an aqueous solution of K2PtCl6. Averaged statistical, network, and local approaches have been used for the data analysis and the description of both collective particles dynamics and local growth features. In particular, interaction between neighboring particles has been revealed and attributed to reduction of the platinum concentration in the vicinity of the particle boundary. The local approach for solving the inverse problem showed that particles dynamics can be simulated by a stationary diffusional model. The obtained results are important for understanding nanocrystal formation and growth processes and for optimization of synthesis conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khanal, Suraj P.; Mahfuz, Hassan; Rondinone, Adam Justin

The potential of improving the fracture toughness of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNTs) and polymerized ε-caprolactam (nylon) was researched. A series of HAp samples with CfSWCNTs concentrations varying from 0 to 1.5 wt.%, without, and with nylon addition was prepared. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) were used to characterize the samples. The three point bending test was applied to measure the fracture toughness of the composites. A reproducible value of 3.6 ± 0.3 MPa.√m was found for samples containing 1 wt.% CfSWCNTs and nylon. This valuemore » is in the range of the cortical bone fracture toughness. Lastly, the increase of the CfSWCNTs content results to decrease of the fracture toughness, and formation of secondary phases.« less

RBS/C, HRTEM and HRXRD study of damage accumulation in irradiated SrTiO3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagielski, Jacek; Jozwik, Przemyslaw A.; Jozwik Biala, Iwona

2013-05-14

Damage accumulation in argon-irradiated SrTiO3 single crystals has been studied by using combination of Rutherford Backscattering/Channeling (RBS/C), High Resolution Transmission Electron Microscopy (HRTEM) and High Resolution X-Ray Diffraction (HRXRD) techniques. The RBS/C spectra were fitted using McChasy, a Monte Carlo simulation code allowing the quantitative analysis of amorphous-like and dislocation-like types of defects. The results were interpreted by using a Multi-Step Damage Accumulation model which assumes, that the damage accumulation occurs in a series of structural transformations, the defect transformations are triggered by a stress caused by formation of a free volume in the irradiated crystal. This assumption has beenmore » confirmed by High Resolution Transmission Electron Microscopy and High Resolution X-Ray Diffraction analysis.« less

RBS, TEM and SEM Characterization of Gold Nanoclusters in TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shutthanandan, V; Zhang, Yanwen; Wang, Chong M.

2004-05-01

Nucleation of gold nanoclusters in TiO2(110) single crystal using ion implantation and subsequent annealing were studied by Rutherford backscattering spectrometry /channeling (RBS/C), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Approximately 1000 Au2+/nm2 was implanted at room temperature in TiO2(110) substrates. TEM and SEM measurements revel that rounded nanoclusters were formed during the implantation. In contrast subsequent annealing in air for 10 hours at 1275 K promoted the formation of faceted (rectangular shaped) Au nano structures in TiO2. RBS channeling measurements further reveled that Au atoms randomly occupied in the host TiO2 lattice during the implantation. However, some ofmore » the gold atoms were moved into the Ti lattice position after annealing.« less

Sonochemical fabrication of fluorinated mesoporous titanium dioxide microspheres

NASA Astrophysics Data System (ADS)

Yu, Changlin; Yu, Jimmy C.; Chan, Mui

2009-05-01

A sonochemical-hydrothermal method for preparing fluorinated mesoporous TiO 2 microspheres was developed. Formation of mesoporous TiO 2 and doping of fluorine was achieved by sonication and then hydrothermal treatment of a solution containing titanium isopropoxide, template, and sodium fluoride. The as-synthesized TiO 2 microspheres were characterized by X-ray diffraction (XRD), Fourier translation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, photoluminescence spectroscopy (PL), and BET surface areas. The P123 template was removed completely during the hydrothermal and washing steps, which was different from the conventional calcination treatment. The as- synthesized TiO 2 microspheres had good crystallinity and high stability. Results from the photocatalytic degradation of methylene blue (MB) showed that fluorination could remarkably improve the photocatalytic activity of titanium dioxide.

Processing of Alumina-Toughened Zirconia Composites

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Choi, Sung R.

2003-01-01

Dense and crack-free 10-mol%-yttria-stabilized zirconia (10YSZ)-alumina composites, containing 0 to 30 mol% of alumina, have been fabricated by hot pressing. Release of pressure before onset of cooling was crucial in obtaining crack-free material. Hot pressing at 1600 C resulted in the formation of ZrC by reaction of zirconia with grafoil. However, no such reaction was observed at 1500 C. Cubic zirconia and -alumina were the only phases detected from x-ray diffraction indicating no chemical reaction between the composite constituents during hot pressing. Microstructure of the composites was analyzed by scanning electron microscopy and transmission electron microscopy. Density and elastic modulus of the composites followed the rule-of-mixtures. Addition of alumina to 10YSZ resulted in lighter, stronger, and stiffer composites by decreasing density and increasing strength and elastic modulus.

Size-dependent microstructures in rapidly solidified uranium-niobium powder particles

DOE PAGES

McKeown, Joseph T.; Hsiung, Luke L.; Park, Jong M.; ...

2016-06-14

The microstructures of rapidly solidified U-6wt%Nb powder particles synthesized by centrifugal atomization were characterized using scanning electron microscopy and transmission electron microscopy. Observed variations in microstructure are related to particle sizes. All of the powder particles exhibited a two-zone microstructure. The formation of this two-zone microstructure is described by a transition from solidification controlled by internal heat flow and high solidification rate during recalescence (micro-segregation-free or partitionless growth) to solidification controlled by external heat flow with slower solidification rates (dendritic growth with solute redistribution). The extent of partitionless solidification increased with decreasing particle size due to larger undercoolings in smallermore » particles prior to solidification. The metastable phases that formed are related to variations in Nb concentration across the particles. Lastly, the microstructures of the powders were heavily twinned.« less

Spray pyrolytic deposition of α-MoO3 film and its use in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Tamboli, Parvin S.; Jagtap, Chaitali V.; Kadam, Vishal S.; Ingle, Ravi V.; Vhatkar, Rajiv S.; Mahajan, Smita S.; Pathan, Habib M.

2018-04-01

Thermal decomposition of ammonium para molybdate tetrahydrate precursor has been studied to determine degradation temperatures in air atmosphere. Current work explores the synthesis of α-MoO3 films by an economical spray pyrolysis technique using ammonium para molybdate tetrahydrate precursor in the presence of compressed air. A variety of characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared, and Raman spectroscopy were carried out, and the studies have confirmed that orthorhombic phase formation of MoO3 takes place with spongy mesh-type structure. The study of electro-catalytic activity of α-MoO3 in titania-based dye-sensitized solar cell is also carried out by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel curves to evaluate its performance as a counter electrode.

Microstructural evolution of NF709 (20Cr–25Ni–1.5MoNbTiN) under neutron irradiation

DOE PAGES

Kim, Byoungkoo; Tan, Lizhen; Xu, C.; ...

2015-12-30

In this study, because of its superior creep and corrosion resistance as compared with general austenitic stainless steels, NF709 has emerged as a candidate structural material for advanced nuclear reactors. To obtain fundamental information about the radiation resistance of this material, this study examined the microstructural evolution of NF709 subjected to neutron irradiation to 3 displacements per atom at 500 °C. Transmission electron microscopy, scanning electron microscopy, and high-energy x-ray diffraction were employed to characterize radiation-induced segregation, Frank loops, voids, as well as the formation and reduction of precipitates. Radiation hardening of ~76% was estimated by nanoindentation, approximately consistent withmore » the calculation according to the dispersed barrier-hardening model, suggesting Frank loops as the primary hardening source.« less

Size and morphology controlled NiSe nanoparticles as efficient catalyst for the reduction reactions

NASA Astrophysics Data System (ADS)

Subbarao, Udumula; Marakatti, Vijaykumar S.; Amshumali, Mungalimane K.; Loukya, B.; Singh, Dheeraj Kumar; Datta, Ranjan; Peter, Sebastian C.

2016-12-01

Facile and efficient ball milling and polyol methods were employed for the synthesis of nickel selenide (NiSe) nanoparticle. The particle size of the NiSe nanoparticle has been controlled mechanically by varying the ball size in the milling process. The role of the surfactants in the formation of various morphologies was studied. The compounds were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (EDS). The efficiency of the NiSe nanoparticle as a catalyst was tested for the reduction of para-nitroaniline (PNA) to para-phenyldiamine (PPD) and para-nitrophenol (PNP) to para-aminophenol (PAP) using NaBH4 as the reducing agent. Particle size, morphology and the presence of surfactant played a crucial role in the reduction process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Zhigang, E-mail: xh168688@126.com; State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083; Department of Chemistry and Chemical Engineering, Qiannan Normal College for Nationalities, Duyun 558000

SnO{sub 2} nanorod bundles were synthesized by hydrothermal method. Field-emission scanning electron microscopy and transmission electron microscopy images showed that the as-prepared flowerlike SnO{sub 2} nanorod bundles consist of tetragonal nanorods with size readily tunable. Their electrochemical properties and application as anode for lithium-ion battery were evaluated by galvanostatic discharge–charge testing and cycle voltammetry. SnO{sub 2} nanorod flowers possess improved discharge capacity of 694 mA h g{sup −1} up to 40th cycle at 0.1 C. - Highlights: ► The flowerlike SnO{sub 2} nanorod bundles were synthesized by hydrothermal method. ► SnO{sub 2} nanorod bundles with tunable size by controlling concentrationmore » of SnCl{sub 4}. ► A probable formation mechanism of SnO{sub 2} nanorod bundles has been proposed.« less

Direct Observation of Conducting Filaments in Tungsten Oxide Based Transparent Resistive Switching Memory.

PubMed

Qian, Kai; Cai, Guofa; Nguyen, Viet Cuong; Chen, Tupei; Lee, Pooi See

2016-10-05

Transparent nonvolatile memory has great potential in integrated transparent electronics. Here, we present highly transparent resistive switching memory using stoichiometric WO 3 film produced by cathodic electrodeposition with indium tin oxide electrodes. The memory device demonstrates good optical transmittance, excellent operative uniformity, low operating voltages (+0.25 V/-0.42 V), and long retention time (>10 4 s). Conductive atomic force microscopy, ex situ transmission electron microscopy, and X-ray photoelectron spectroscopy experiments directly confirm that the resistive switching effects occur due to the electric field-induced formation and annihilation of the tungsten-rich conductive channel between two electrodes. Information on the physical and chemical nature of conductive filaments offers insightful design strategies for resistive switching memories with excellent performances. Moreover, we demonstrate the promising applicability of the cathodic electrodeposition method for future resistive memory devices.

Effect of counterpart metals in carbon-supported Pt-based catalysts prepared using radiation chemical method

NASA Astrophysics Data System (ADS)

Okazaki, Tomohisa; Seino, Satoshi; Matsuura, Yoshiyuki; Otake, Hiroaki; Kugai, Junichiro; Ohkubo, Yuji; Nitani, Hiroaki; Nakagawa, Takashi; Yamamoto, Takao A.

2017-04-01

The process of nanoparticle formation by radiation chemical synthesis in a heterogeneous system has been investigated. Carbon-supported Pt-based bimetallic nanoparticles were synthesized using a high-energy electron beam. Rh, Cu, Ru, and Sn were used as counterpart metals. The nanoparticles were characterized by inductively coupled plasma atomic emission spectrometry, transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. PtRh formed a uniform random alloy nanoparticle, while Cu partially formed an alloy with Pt and the remaining Cu existed as CuO. PtRu formed an alloy structure with a composition distribution of a Pt-rich core and Ru-rich shell. No alloying was observed in PtSn, which had a Pt-SnO2 structure. The alloy and oxide formation mechanisms are discussed considering the redox potentials, the standard enthalpy of oxide formation, and the solid solubilities of Pt and the counterpart metals.

In situ monitoring of stacking fault formation and its carrier lifetime mediation in p-type 4H-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Bin, E-mail: chenbinmse@gmail.com; Chen, Jun; Yao, Yuanzhao

Using the fine control of an electron beam (e-beam) in scanning electron microscopy with the capabilities of both electrical and optical imaging, the stacking fault (SF) formation together with its tuning of carrier lifetime was in situ monitored and investigated in p-type 4H-SiC homoepitaxial films. The SFs were formed through engineering basal plane dislocations with the energy supplied by the e-beam. The e-beam intensity required for the SF formation in the p-type films was ∼100 times higher than that in the n-type ones. The SFs reduced the minority-carrier lifetime in the p-type films, which was opposite to that observed inmore » the n-type case. The reason for the peculiar SF behavior in the p-type 4H-SiC is discussed with the cathodoluminescence results.« less

Effect of friction on oxidative graphite intercalation and high-quality graphene formation.

PubMed

Seiler, Steffen; Halbig, Christian E; Grote, Fabian; Rietsch, Philipp; Börrnert, Felix; Kaiser, Ute; Meyer, Bernd; Eigler, Siegfried

2018-02-26

Oxidative wet-chemical delamination of graphene from graphite is expected to become a scalable production method. However, the formation process of the intermediate stage-1 graphite sulfate by sulfuric acid intercalation and its subsequent oxidation are poorly understood and lattice defect formation must be avoided. Here, we demonstrate film formation of micrometer-sized graphene flakes with lattice defects down to 0.02% and visualize the carbon lattice by transmission electron microscopy at atomic resolution. Interestingly, we find that only well-ordered, highly crystalline graphite delaminates into oxo-functionalized graphene, whereas other graphite grades do not form a proper stage-1 intercalate and revert back to graphite upon hydrolysis. Ab initio molecular dynamics simulations show that ideal stacking and electronic oxidation of the graphite layers significantly reduce the friction of the moving sulfuric acid molecules, thereby facilitating intercalation. Furthermore, the evaluation of the stability of oxo-species in graphite sulfate supports an oxidation mechanism that obviates intercalation of the oxidant.

A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers.

PubMed

Reimers, Jeffrey R; Panduwinata, Dwi; Visser, Johan; Chin, Yiing; Tang, Chunguang; Goerigk, Lars; Ford, Michael J; Sintic, Maxine; Sum, Tze-Jing; Coenen, Michiel J J; Hendriksen, Bas L M; Elemans, Johannes A A W; Hush, Noel S; Crossley, Maxwell J

2015-11-10

Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-tetraalkylporphyrin self-assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorph-dependent dispersion-induced substrate-molecule interactions (e.g., -100 kcal mol(-1) to -150 kcal mol(-1) for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70-110 kcal mol(-1)) and entropy effects (25-40 kcal mol(-1) at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion-corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations.

Glass Formation, Phase Equilibria, and Thermodynamic Assessment of the Al-Ce-Co System Assisted by First-Principles Energy Calculations

NASA Astrophysics Data System (ADS)

Gao, Michael C.; Ünlü, Necip; Mihalkovic, Marek; Widom, Michael; Shiflet, G. J.

2007-10-01

This study investigates glass formation, phase equilibria, and thermodynamic descriptions of the Al-rich Al-Ce-Co ternary system using a novel approach that combines critical experiments, CALPHAD modeling, and first-principles (FP) calculations. The glass formation range (GFR) and a partial 500 °C isotherm are determined using a range of experimental techniques including melt spinning, transmission electron microscopy (TEM), electron probe microanalysis (EPMA), X-ray diffraction, and differential thermal analysis (DTA). Three stable ternary phases are confirmed, namely, Al8CeCo2, Al4CeCo, and AlCeCo, while a metastable phase, Al5CeCo2, was discovered. The equilibrium and metastable phases identified by the present and earlier reported experiments, together with many hypothetical ternary compounds, are further studied by FP calculations. Based on new experimental data and FP calculations, the thermodynamics of the Al-rich Al-Co-Ce system is optimized using the CALPHAD method. Application to glass formation is discussed in light of present studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Rabindar K.; Reddy, G. B.

In this work, we have successfully developed plasma assisted paste sublimation route to deposit vertically aligned MoO{sub 3} nanoflakes (NFs) on nickel coated glass substrate in oxygen plasma ambience with the assistant of Ni thin layer as a catalyst. In our case, sublimation source (Mo strip surface) is resistively heated by flowing current across it. The structural, morphological, and optical properties of NFs have been investigated systematically using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), High resolution transmission electron microscopy (HRTEM), micro-Raman spectroscopy, and Photoluminescence (PL) spectroscopy. Studies reveal thatmore » the presence of oxygen plasma and the nickel thin layer are very essential for the growth of vertically aligned NFs. The observed results divulge that α-MoO{sub 3} NFs are deposited uniformly on large scale with very high aspect (height/thickness) ratio more than 30 and well aligned along [0 k 0] crystallographic direction where k is even (2, 4, 6). Raman spectrum shows a significant size effect on the vibrational property of MoO{sub 3} nanoflakes. The PL spectrum of MoO{sub 3} NFs was recorded at room temperature and four prominent peaks at 365 nm, 395 nm, 452 nm, and 465 nm corresponding to UV-visible region were observed. In this paper, a three step growth strategy for the formation of MoO{sub 3} NFs has been proposed in detail.« less

Effects of Nd:YAG laser-heated metal cap on human platelets in vitro

NASA Astrophysics Data System (ADS)

Liu, Xia; Guo, You-chi

1993-03-01

Human platelet-rich plasma (PRP) was irradiated in vitro with a fiberoptic Nd:YAG laser-heated metal cap to study its effects on platelets. The energy of the laser was 5 and 10 watts with an irradiation time of 0, 3, 6, and 9 seconds and 14 watts with an irradiation time of 0, 3, 4, and 5 seconds, respectively. The irradiated PRPs were analyzed for platelet count, aggregation reaction, thromboxane (TX)B2 measurement and electron microscopy. Various degrees of decrease in platelet count were observed in all groups. Except the 5Wx3S group, the other groups showed an increase in the maximum aggregation rate of platelets, which corresponded to the enhancement of TXB2 formation. It was also demonstrated by a transmission electron microscopy in 10Wx3S, 10Wx6S, 10Wx9S, 14Wx3S, 14Wx4S, and 14Wx5S energy groups that alpha- and dense-particles in irradiated platelets became sparse in number or even disappeared, less electron density, irregularity in size and shape, and a tendency for these particles to cluster around platelet membranes and open canalicular systems, which dilated apparently. Furthermore, scanning electron microscopy depicted the appearance of short and thick pseudopods on the surfaces of some irradiated platelets and an increase in the axis rate in most of the irradiated platelets.

Focused electron beam based direct-write fabrication of graphene and amorphous carbon from oxo-functionalized graphene on silicon dioxide.

PubMed

Schindler, Severin; Vollnhals, Florian; Halbig, Christian E; Marbach, Hubertus; Steinrück, Hans-Peter; Papp, Christian; Eigler, Siegfried

2017-01-25

Controlled patterning of graphene is an important task towards device fabrication and thus is the focus of current research activities. Graphene oxide (GO) is a solution-processible precursor of graphene. It can be patterned by thermal processing. However, thermal processing of GO leads to decomposition and CO 2 formation. Alternatively, focused electron beam induced processing (FEBIP) techniques can be used to pattern graphene with high spatial resolution. Based on this approach, we explore FEBIP of GO deposited on SiO 2 . Using oxo-functionalized graphene (oxo-G) with an in-plane lattice defect density of 1% we are able to image the electron beam-induced effects by scanning Raman microscopy for the first time. Depending on electron energy (2-30 keV) and doses (50-800 mC m -2 ) either reduction of GO or formation of permanent lattice defects occurs. This result reflects a step towards controlled FEBIP processing of oxo-G.

Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors

DOE PAGES

Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; ...

2015-07-22

The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe 2 monolayer crystals with SiO 2, and the exposed locations are selectively and totally converted to MoS 2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe 2/MoS 2 heterojunctions in predefinedmore » patterns. The junctions and conversion process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.« less

Supramolecular assemblies of a nitrogen-embedded buckybowl dimer with C60† †Electronic supplementary information (ESI) available. CCDC 1579079 and 1579080. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04453d

PubMed Central

Yokoi, Hiroki; Sakamaki, Daisuke; Seki, Shu

2017-01-01

A directly connected azabuckybowl dimer was synthesized via a palladium-catalysed C–H/C–Br coupling. The electron-donating nature of the pyrrolic nitrogen atoms of the azabuckybowl enabled a strong complexation with pristine C60. In the presence of two equivalents of C60, the azabuckybowl dimer formed crystals with a 1 : 2 stoichiometry. Conversely, in diluted solution, complexes with a 1 : 1 stoichiometry of the dimer and C60 were detected predominantly, and these precipitated upon increasing the concentration of C60. Scanning electron microscopy images of the precipitate showed fibre-like aggregates, indicating the formation of supramolecular assemblies with 1D chain structures. A variable-temperature 1H NMR analysis revealed that the precipitate consists of the dimer and C60 in a 1 : 1 ratio. PMID:29629149

Nanoparticle Immobilization for Controllable Experiments in Liquid-Cell Transmission Electron Microscopy.

PubMed

Robertson, Alex W; Zhu, Guomin; Mehdi, B Layla; Jacobs, Robert M J; De Yoreo, James; Browning, Nigel D

2018-06-22

We demonstrate that silanization can control the adhesion of nanostructures to the SiN windows compatible with liquid-cell transmission electron microscopy (LC-TEM). Formation of an (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayer on a SiN window, producing a surface decorated with amino groups, permits strong adhesion of Au nanoparticles to the window. Many of these nanoparticles remain static, undergoing minimal translation or rotation during LC-TEM up to high electron beam current densities due to the strong interaction between the APTES amino group and Au. We then use this technique to perform a direct comparative LC-TEM study on the behavior of ligand and nonligand-coated Au nanoparticles in a Au growth solution. While the ligand coated nanoparticles remain consistent even under high electron beam current densities, the naked nanoparticles acted as sites for secondary Au nucleation. These nucleated particles decorated the parent nanoparticle surface, forming consecutive monolayer assemblies of ∼2 nm diameter nanoparticles, which sinter into the parent particle when the electron beam was shut off. This method for facile immobilization of nanostructures for LC-TEM study will permit more sophisticated and controlled in situ experiments into the properties of solid-liquid interfaces in the future.

Structural analysis of the PSD-95 cluster by electron tomography and CEMOVIS: a proposal for the application of the genetically encoded metallothionein tag.

PubMed

Hirabayashi, Ai; Fukunaga, Yuko; Miyazawa, Atsuo

2014-06-01

Postsynaptic density-95 (PSD-95) accumulates at excitatory postsynapses and plays important roles in the clustering and anchoring of numerous proteins at the PSD. However, a detailed ultrastructural analysis of clusters exclusively consisting of PSD-95 has never been performed. Here, we employed a genetically encoded tag, three tandem repeats of metallothionein (3MT), to study the structure of PSD-95 clusters in cells by electron tomography and cryo-electron microscopy of vitreous sections. We also performed conventional transmission electron microscopy (TEM). Cultured hippocampal neurons expressing a fusion protein of PSD-95 coupled to 3MT (PDS-95-3MT) were incubated with CdCl2 to result in the formation of Cd-bound PSD-95-3MT. Two types of electron-dense deposits composed of Cd-bound PSD-95-3MT were observed in these cells by TEM, as reported previously. Electron tomography revealed the presence of membrane-shaped structures representing PSD-95 clusters at the PSD and an ellipsoidal structure located in the non-synaptic cytoplasm. By TEM, the PSD-95 clusters appeared to be composed of a number of dense cores. In frozen hydrated sections, these dense cores were also found beneath the postsynaptic membrane. Taken together, our findings suggest that dense cores of PSD-95 aggregate to form the larger clusters present in the PSD and the non-synaptic cytoplasm. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

New developments in electron microscopy for serial image acquisition of neuronal profiles.

PubMed

Kubota, Yoshiyuki

2015-02-01

Recent developments in electron microscopy largely automate the continuous acquisition of serial electron micrographs (EMGs), previously achieved by laborious manual serial ultrathin sectioning using an ultramicrotome and ultrastructural image capture process with transmission electron microscopy. The new systems cut thin sections and capture serial EMGs automatically, allowing for acquisition of large data sets in a reasonably short time. The new methods are focused ion beam/scanning electron microscopy, ultramicrotome/serial block-face scanning electron microscopy, automated tape-collection ultramicrotome/scanning electron microscopy and transmission electron microscope camera array. In this review, their positive and negative aspects are discussed. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Formation of an amorphous phase and its crystallization in the immiscible Nb-Zr system by mechanical alloying

NASA Astrophysics Data System (ADS)

Al-Aqeeli, N.; Suryanarayana, C.; Hussein, M. A.

2013-10-01

Mechanical alloying of binary Nb-Zr powder mixtures was carried out to evaluate the formation of metastable phases in this immiscible system. The milled powders were characterized for their constitution and structure by X-ray diffraction and transmission electron microscopy methods. It was shown that an amorphous phase had formed on milling the binary powder mixture for about 10 h and that it had crystallized on subsequent milling up to 50-70 h, referred to as mechanical crystallization. Thermodynamic and structural arguments have been presented to explain the formation of the amorphous phase and its subsequent crystallization.

Nanometer-scale characterization of exceptionally preserved bacterial fossils in Paleocene phosphorites from Ouled Abdoun (Morocco).

PubMed

Cosmidis, J; Benzerara, K; Gheerbrant, E; Estève, I; Bouya, B; Amaghzaz, M

2013-03-01

Micrometer-sized spherical and rod-shaped forms have been reported in many phosphorites and often interpreted as microbes fossilized by apatite, based on their morphologic resemblance with modern bacteria inferred by scanning electron microscopy (SEM) observations. This interpretation supports models involving bacteria in the formation of phosphorites. Here, we studied a phosphatic coprolite of Paleocene age originating from the Ouled Abdoun phosphate basin (Morocco) down to the nanometer-scale using focused ion beam milling, transmission electron microscopy (TEM), and scanning transmission x-ray microscopy (STXM) coupled with x-ray absorption near-edge structure spectroscopy (XANES). The coprolite, exclusively composed of francolite (a carbonate-fluroapatite), is formed by the accumulation of spherical objects, delimited by a thin envelope, and whose apparent diameters are between 0.5 and 3 μm. The envelope of the spheres is composed of a continuous crown dense to electrons, which measures 20-40 nm in thickness. It is surrounded by two thinner layers that are more porous and transparent to electrons and enriched in organic carbon. The observed spherical objects are very similar with bacteria encrusting in hydroxyapatite as observed in laboratory experiments. We suggest that they are Gram-negative bacteria fossilized by francolite, the precipitation of which started within the periplasm of the cells. We discuss the role of bacteria in the fossilization mechanism and propose that they could have played an active role in the formation of francolite. This study shows that ancient phosphorites can contain fossil biological subcellular structures as fine as a bacterial periplasm. Moreover, we demonstrate that while morphological information provided by SEM analyses is valuable, the use of additional nanoscale analyses is a powerful approach to help inferring the biogenicity of biomorphs found in phosphorites. A more systematic use of this approach could considerably improve our knowledge and understanding of the microfossils present in the geological record. © 2012 Blackwell Publishing Ltd.

Formation of Fluorohydroxyapatite with Silver Diamine Fluoride

PubMed Central

Mei, M.L.; Nudelman, F.; Marzec, B.; Walker, J.M.; Lo, E.C.M.; Walls, A.W.; Chu, C.H.

2017-01-01

Silver diamine fluoride (SDF) is found to promote remineralization and harden the carious lesion. Hydroxyapatite crystallization is a crucial process in remineralization; however, the role of SDF in crystal formation is unknown. We designed an in vitro experiment with calcium phosphate with different SDF concentrations (0.38, 1.52, 2.66, 3.80 mg/mL) to investigate the effect of this additive on the nucleation and growth of apatite crystals. Two control groups were also prepared—calcium phosphate (CaCl2·2H2O + K2HPO4 in buffer solution) and SDF (Ag[NH3]2F in buffer solution). After incubation at 37 oC for 24 h, the shape and organization of the crystals were examined by bright-field transmission electron microscopy and electron diffraction. Unit cell parameters of the obtained crystals were determined with powder X-ray diffraction. The vibrational and rotational modes of phosphate groups were analyzed with Raman microscopy. The transmission electron microscopy and selected-area electron diffraction confirmed that all solids precipitated within the SDF groups were crystalline and that there was a positive correlation between the increased percentage of crystal size and the concentration of SDF. The powder X-ray diffraction patterns indicated that fluorohydroxyapatite and silver chloride were formed in all the SDF groups. Compared with calcium phosphate control, a contraction of the unit cell in the a-direction but not the c-direction in SDF groups was revealed, which suggested that small localized fluoride anions substituted the hydroxyl anions in hydroxyapatite crystals. This was further evidenced by the Raman spectra, which displayed up-field shift of the phosphate band in all the SDF groups and confirmed that the chemical environment of the phosphate functionalities indeed changed. The results suggested that SDF reacted with calcium and phosphate ions and produced fluorohydroxyapatite. This preferential precipitation of fluorohydroxyapatite with reduced solubility could be one of the main factors for arrest of caries lesions treated with SDF. PMID:28521107

Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

DOE PAGES

Han, Binghong; Stoerzinger, Kelsey A.; Tileli, Vasiliki; ...

2016-10-03

Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. In this paper, we report observations of strong structural oscillations of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3$-$δ (BSCF) in the presence of both H 2O vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O 2 formation in these bubbles due to the incorporation of H 2O into BSCF. SrCoO 3$-$δ was found to exhibit small oscillations, while none weremore » observed for La 0.5Sr 0.5CoO 3$-$δ and LaCoO 3. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.« less

Low-pressure clathrate-hydrate formation in amorphous astrophysical ice analogs

NASA Technical Reports Server (NTRS)

Blake, D. F.; Allamandola, L. J.; Sandford, S.; Hudgins, D.; Freund, F.

1991-01-01

In modeling cometary ice, the properties of clathrate hydrates were used to explain anomalous gas release at large radial distances from the Sun, and the retention of particular gas inventories at elevated temperatures. Clathrates may also have been important early in solar system history. However, there has never been a reasonable mechanism proposed for clathrate formation under the low pressures typical of these environments. For the first time, it was shown that clathrate hydrates can be formed by warming and annealing amorphous mixed molecular ices at low pressures. The complex microstructures which occur as a result of clathrate formation from the solid state may provide an explanation for a variety of unexplained phenomena. The vacuum and imaging systems of an Hitachi H-500H Analytical Electron Microscope was modified to study mixed molecular ices at temperatures between 12 and 373 K. The resulting ices are characterized by low-electron dose Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The implications of these results for the mechanical and gas release properties of comets are discussed. Laboratory IR data from similar ices are presented which suggest the possibility of remotely observing and identifying clathrates in astrophysical objects.

Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

PubMed

López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

2017-11-01

Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Huajuan; Zhao, Yanbao, E-mail: zhaoyb902@henu.edu.cn; Sun, Lei

Graphical abstract: A simple method for the synthesis of novel micrometer flower-like Cu/PVP architectures was introduced. Highlights: {yields} Micrometer flower-like copper/polyvinylpyrrolidone architectures were obtained by a simple chemical route. {yields} The amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, the reaction temperature, the molar ratio of CuCl{sub 2} to PVP and different molecular weights of PVP play an important role in the controlling the morphology of the Cu/PVP architectures. {yields} A possible mechanism of the formation of Cu/PVP architectures was discussed. -- Abstract: Micrometer-sized flower-like Cu/polyvinylpyrrolidone (PVP) architectures are synthesized by the reduction of copper (II) salt with hydrazine hydrate in aqueousmore » solution in the presence of PVP capping agent. The resulting Cu/PVP architectures are investigated by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The Cu/PVP flowers have uniform morphologies with an average diameter of 10 {mu}m, made of several intercrossing plates. The formation of Cu/PVP flowers is a new kinetic control process, and the factors such as the amount of N{sub 2}H{sub 4}{center_dot}H{sub 2}O, reaction temperature, molar ratio of CuCl{sub 2} to PVP and molecular weight of PVP have significant effect on the morphology of Cu/PVP architectures. A possible mechanism of the formation of micrometer Cu/PVP architectures was discussed.« less

Polymer Self-Assembly into Unique Fractal Nanostructures in Solution by a One-Shot Synthetic Procedure.

PubMed

Shin, Suyong; Gu, Ming-Long; Yu, Chin-Yang; Jeon, Jongseol; Lee, Eunji; Choi, Tae-Lim

2018-01-10

A fractal nanostructure having a high surface area is potentially useful in sensors, catalysts, functional coatings, and biomedical and electronic applications. Preparation of fractal nanostructures on solid substrates has been reported using various inorganic or organic compounds. However, achieving such a process using polymers in solution has been extremely challenging. Here, we report a simple one-shot preparation of polymer fractal nanostructures in solution via an unprecedented assembly mechanism controlled by polymerization and self-assembly kinetics. This was possible only because one monomer was significantly more reactive than the other, thereby easily forming a diblock copolymer microstructure. Then, the second insoluble block containing poly(p-phenylenevinylene) (PPV) without any side chains spontaneously underwent self-assembly during polymerization by an in situ nanoparticlization of conjugated polymers (INCP) method. The formation of fractal structures in solution was confirmed by various imaging techniques such as atomic force microscopy, transmission electron microscopy (TEM), and cryogenic TEM. The diffusion-limited aggregation theory was adopted to explain the branching patterns of the fractal nanostructures according to the changes in polymerization conditions such as the monomer concentration and the presence of additives. Finally, after detailed kinetic analyses, we proposed a plausible mechanism for the formation of unique fractal nanostructures, where the gradual formation and continuous growth of micelles in a chain-growth-like manner were accounted for.

Mineralogical, micromorphological and geochemical transformations in the initial steps of the weathering process of charnockite from the Caparaó Range, southeastern Brazil

NASA Astrophysics Data System (ADS)

Soares, Caroline Cibele Vieira; Varajão, Angélica Fortes Drummond Chicarino; Varajão, César Augusto Chicarino; Boulangé, Bruno

2014-12-01

X-ray diffraction (XRD), X-ray Fluorescence (XRF), optical microscopy, Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry (SEM-EDS) and Electron Probe micro-analyser (EPMA) and Wavelength-Dispersive Spectroscopy (WDS) were conducted on charnockite from the Caparaó Suite and its alteration cortex to determine the mineralogical, micromorphological and geochemical transformations resulting from the weathering process. The hydrolysis of the charnockite occurred in different stages, in accordance with the order of stability of the minerals with respect to weathering: andesine/orthopyroxene, pargasite and alkali feldspar. The rock modifications had begun with the formation of a layer of incipient alteration due to the percolation of weathering solutions first in the pressure relief fractures and then in cleavage and mineral edges. The iron exuded from ferromagnesian minerals precipitated in the intermineral and intramineral discontinuities. The layer of incipient alteration evolves into an inner cortex where the plagioclase changes into gibbsite by direct alitisation, the ferromagnesian minerals initiate the formation of goethitic boxworks with kaolinitic cores, and the alkali feldspar initiates indirect transformation into gibbsite, forming an intermediate phase of illite and kaolinite. In the outer cortex, mostly traces of alkali feldspar remain, and they are surrounded by goethite and gibbsite as alteromorphics, characterising the formation of the isalteritic horizon that occurs along the slope and explains the bauxitization process at the Caparaó Range, SE Brazil.

Bioinspired synthesis of a soft-nanofilament-based coating consisting of polysilsesquioxanes/polyamine and its divergent surface control.

PubMed

Yuan, Jian-Jun; Kimitsuka, Nobuo; Jin, Ren-Hua

2013-04-24

The synthesis of polysilsesquioxanes coating with controllable one-dimensional nanostructure on substrates remains a major long-term challenge by conventional solution-phase method. The hydrolytic polycondensation of organosilanes in solution normally produces a mixture of incomplete cages, ladderlike, and network structures, resulting in the poor control of the formation of specific nanostructure. This paper describes a simple aqueous process to synthesize nanofilament-based coatings of polysilsesquioxanes possessing various organo-functional groups (for example, thiol, methyl, phenyl, vinyl, and epoxy). We utilized a self-assembled nanostructured polyamine layer as a biomimetically catalytic scaffold/template to direct the formation of one-dimensional nanofilament of polysilsesquioxanes by temporally and spatially controlled hydrolytic polycondensation of organosilane. The surface nanostructure and morphology of polysilsesquioxane coating could be modulated by changing hydrolysis and condensation reaction conditions, and the orientation of nanofilaments of polysilsesquioxanes on substrates could be controlled by simply adjusting the self-assembly conditions of polyamine layer. The nanostructure and polyamine@polysilsesquioxane hybrid composition of nanofilament-based coatings were examined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The template role of nanostructured polyamine layer for the formation of polysilsesquioxane nanofilament was confirmed by combining thin film X-ray diffraction (XRD) and XPS measurements. Moreover, these nanotextured coatings with various organo-functional groups could be changed into superhydrophobic surfaces after surface modification with fluorocarbon molecule.

Synchrotron X-ray imaging of nanomagnetism in meteoritic metal (Invited)

NASA Astrophysics Data System (ADS)

Bryson, J. F.; Herrero Albillos, J.; Kronast, F.; Tyliszczak, T.; Redfern, S. A.; van der Laan, G.; Harrison, R. J.

2013-12-01

It is becoming increasingly apparent that a wealth of paleomagnetic information is stored at the nanoscale within natural samples. To date, this nanopaleomagetism has been investigated using high resolution magnetic microscopies, such as electron holography. Although unparalleled in its spatial resolution, electron holography produces images that are indirectly related to the magnetisation state of the sample, introducing ambiguity when interpreting magnetisation information. Holography also requires extensive off-line processing, making it unsuitable for studying dynamic processes, and the sample preparation negates the study of natural remanences. Here we demonstrate the capabilities of a new generation of nanomagnetic imaging methods using synchrotron X-ray radiation. X-rays tuned to an elemental absorption edge can display differing excitation probabilities depending on the orientation of an electron's magnetic moment relative to that of the X-ray beam. This is achieved by introducing an angular momentum to the photon through circular polarisation, resulting in an absorption signal that is proportional to the projection of the magnetic moment on to the X-ray beam direction. We introduce and compare two experimental set-ups capable of spatially resolving these signals to form a high-resolution magnetisation map: photoemission electron microscopy and scanning transmission electron microscopy. Both techniques provide measurements of magnetisation with 30-50nm resolution and elemental specificity. Photoemission electron microscopy can be used also to create maps of all three of the spatial components of magnetisation and investigate dynamic magnetic switching processes. The full capabilities of X-ray imaging are demonstrated through the application of both of these techniques to meteoritic metal. We show that the 'cloudy zone' within iron meteorites contains nanoscale islands of tetrataenite (FeNi) that are populated equally by all three possible magnetic easy axes, suggesting that there were no stray fields (either magnetic or stress) effecting the magnetisation during cloudy zone formation. This observation allows for dynamo field information to be extracted from X-ray nanomagnetic images of the cloudy zone in metallic inclusions within certain chondritic meteorites, as it implies that any deviation from the randomly populated easy axis distribution can be assigned to an external dynamo field. As the cloudy zone forms over 10-100 Ma, this observation suggests that X-ray imaging of the nanopaleomagentism in these meteorites could provide an elegant and concise relative measure of asteroid dynamo field direction and strength over this entire time period, revolutionising our understanding of dynamo processes and planetary formation.

Origin of Quantum Ring Formation During Droplet Epitaxy

NASA Astrophysics Data System (ADS)

Zhou, Z. Y.; Zheng, C. X.; Tang, W. X.; Tersoff, J.; Jesson, D. E.

2013-07-01

Droplet epitaxy of GaAs is studied in real time using in situ surface electron microscopy. The resulting movies motivate a theoretical model for quantum ring formation which can explain the origin of nanoscale features such as double rings observed under a variety of experimental conditions. Inner rings correspond to GaAs deposition at the droplet edge, while outer rings result from the reaction of Ga and As atoms diffusing along the surface. The observed variety of morphologies primarily reflects relative changes in the outer rings with temperature and As flux.

The microstructure and formation of duplex and black plessite in iron meteorites

NASA Technical Reports Server (NTRS)

Zhang, J.; Williams, D. B.; Goldstein, J. I.

1993-01-01

Two of the most common plessite structures, duplex and black plessite, in the taenite region of the Windmanstatten pattern of two iron meteorites (Grant and Carlton) are characterized using high-resolution electron microscopy and microanalysis techniques. Two types of gamma precipitates, found in the duplex plessite and black plessite regions, respectively, are identified, and their morphologies are described. The formation of the plessite structure is discussed using the information obtained in this study and results of a parallel investigation of decomposed martensitic Fe-Ni laboratory alloys.

Evolution of radiation defect and radiation hardening in heat treated SA508 Gr3 steel

NASA Astrophysics Data System (ADS)

Jin, Hyung-Ha; Kwon, Junhyun; Shin, Chansun

2014-01-01

The formation of radiation defects and corresponding radiation hardening in heat-treated SA508 Gr3 steel after Fe ion irradiation were investigated by means of transmission electron microscopy and a nano-indentation technique. As the residual dislocation density is increased in the matrix, the formation of radiation defects is considerably weakened. Comparison between the characteristics of the radiation defect and an evaluation of radiation hardening indicates that a large dislocation loop contributes little to the radiation hardening in the heat-treated SA508 Gr3 steel.

Bioreduction potentials of dried root of Zingiber officinale for a simple green synthesis of silver nanoparticles: Antibacterial studies.

PubMed

Judith Vijaya, J; Jayaprakash, N; Kombaiah, K; Kaviyarasu, K; John Kennedy, L; Jothi Ramalingam, R; Al-Lohedan, Hamad A; V M, Mansoor-Ali; Maaza, M

2017-12-01

Green synthesis of silver nanoparticles (Ag NPs) using an extract of dried Zingiber officinale (ginger) root as a reducing and capping agent in the presence of microwave irradiation was herein reported for the first time. The formation of symmetrical spheres is confirmed from the UV-Visible spectrum of Ag NPs. Fourier transform infra-red spectroscopy confirms the formation of the Ag NPs. X-ray diffraction analysis was utilized to calculate the crystallite size of Ag NPs and the value was found to be 10nm. High-resolution transmission electron microscopy and high-resolution scanning electron microscopy were used to investigate the morphology and size of the synthesized samples. The sphere like morphology is confirmed from the images. The purity and crystallinity of Ag NPs is confirmed by energy-dispersive X-Ray analysis and selected area electron diffraction respectively. The electrochemical behavior of the synthesized Ag NPs was assessed by cyclic voltammetry (CV) and shows the redox peaks in the potential range of -1.1 to +1.1V. Agar diffusion method is used to examine the antibacterial activity of Ag NPs. For this purpose, two gram positive and two gram negative bacteria were studied. This single step approach was found to be simple, short time, cost-effective, reproducible, and eco-friendly. Copyright © 2017. Published by Elsevier B.V.

Formation of nano-laminated structures in a dry sliding wear-induced layer under different wear mechanisms of 20CrNi2Mo steel

NASA Astrophysics Data System (ADS)

Yin, Cun-hong; Liang, Yi-long; Jiang, Yun; Yang, Ming; Long, Shao-lei

2017-11-01

The microstructures of 20CrNi2Mo steel underneath the contact surface were examined after dry sliding. Scanning Electronic Microscopy (SEM), Transmission Electron Microscopy (TEM), Electron Backscattered Diffraction (EBSD) and an ultra-micro-hardness tester were used to characterize the worn surface and dry sliding wear-induced layer. Martensite laths were ultra-refined due to cumulative strains and a large strain gradient that occurred during cyclic loading in wear near the surface. The microstructure evolution in dominant abrasive wear differs from that in adhesive wear. In dominant abrasive wear, only bent martensite laths with high-density deformation dislocations were observed. In contrast, in dominant adhesive wear, gradient structures were formed along the depth from the wear surface. Cross-sectional TEM foils were prepared in a focused ion beam (FIB) to observe the gradient structures in a dry sliding wear-induced layer at depths of approximately 1-5 μm and 5-20 μm. The gradient structures contained nano-laminated structures with an average thickness of 30-50 nm and bent martensite laths. We found that the original martensite laths coordinated with the strain energy and provided origin boundaries for the formation of gradient structures. Geometrically necessary boundaries (GNBs) and isolated dislocation boundaries (IDBs) play important roles in forming the nano-laminated structures.

Analysis of twin defects in GaAs(111)B molecular beam epitaxy growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Yeonjoon; Cich, Michael J.; Zhao, Rian

2000-05-01

The formation of twin is common during GaAs(111) and GaN(0001) molecular beam epitaxy (MBE) metalorganic chemical vapor deposition growth. A stacking fault in the zinc-blende (ZB)(111) direction can be described as an insertion of one monolayer of wurtzite structure, sandwiched between two ZB structures that have been rotated 60 degree sign along the growth direction. GaAs(111)A/B MBE growth within typical growth temperature regimes is complicated by the formation of pyramidal structures and 60 degree sign rotated twins, which are caused by faceting and stacking fault formation. Although previous studies have revealed much about the structure of these twins, a well-establishedmore » simple nondestructive characterization method which allows the measurement of total aerial density of the twins does not exist at present. In this article, the twin density of AlGaAs layers grown on 1 degree sign miscut GaAs(111)B substrates has been measured using high resolution x-ray diffraction, and characterized with a combination of Nomarski microscopy, atomic force microscopy, and transmission electron microscopy. These comparisons permit the relationship between the aerial twin density and the growth condition to be determined quantitatively. (c) 2000 American Vacuum Society.« less

MBE growth of nanowires using colloidal Ag nanoparticles

NASA Astrophysics Data System (ADS)

Bouravleuv, A. D.; Ilkiv, I. V.; Reznik, R. R.; Shtrom, I. V.; Khrebtov, A. I.; Samsonenko, Yu B.; Soshnikov, I. P.; Cirlin, G. E.; Lipsanen, H.

2017-06-01

Ag colloidal nanoparticles are used as a catalyst for growth of GaAs nanowires by the molecular beam epitaxy on the Si(111) and GaAs(111)B substrate surfaces. The scanning electron microscopy measurements revealed that the nanowire formation occurs in different ways on different substrates, but the parameters of the synthesized nanowires open great prospects for their further use.

Self-organization of the reticular structure of polyurethane

NASA Astrophysics Data System (ADS)

Kiselev, M. R.; Roldugin, V. I.

2010-08-01

The morphology of block samples and coatings of reticular polyurethane were studied by transmission electron microscopy. The morphology was correlated with the internal stresses that appeared in the coatings during their formation. A scenario of the self-assembly of complex structures in reticular polymers was suggested. The boundary between the structural elements of the supermolecular level was found to be strained.

Plasma dynamics and structural modifications induced by femtosecond laser pulses in quartz

NASA Astrophysics Data System (ADS)

Hernandez-Rueda, J.; Puerto, D.; Siegel, J.; Galvan-Sosa, M.; Solis, J.

2012-09-01

We have investigated plasma formation and relaxation dynamics induced by single femtosecond laser pulses at the surface of crystalline SiO2 (quartz) along with the corresponding topography modifications. The use of fs-resolved pump-probe microscopy allows combining spatial and temporal resolution and simultaneous access to phenomena occurring in adjacent regions excited with different local fluences. The results show the formation of a transient free-electron plasma ring surrounding the location of the inner ablation crater. Optical microscopy measurements reveal a 30% reflectivity decrease in this region, consistent with local amorphization. The accompanying weak depression of ≈15 nm in this region is explained by gentle material removal via Coulomb explosion. Finally, we discuss the timescales of the plasma dynamics and its role in the modifications produced, by comparing the results with previous studies obtained in amorphous SiO2 (fused silica). For this purpose, we have conceived a new representation concept of time-resolved microscopy image stacks in a single graph, which allows visualizing quickly suble differences of the overall similar dynamic response of both materials.

Optical spectroscopy and microscopy of radiation-induced light-emitting point defects in lithium fluoride crystals and films

NASA Astrophysics Data System (ADS)

Montereali, R. M.; Bonfigli, F.; Menchini, F.; Vincenti, M. A.

2012-08-01

Broad-band light-emitting radiation-induced F2 and F3+ electronic point defects, which are stable and laser-active at room temperature in lithium fluoride crystals and films, are used in dosimeters, tuneable color-center lasers, broad-band miniaturized light sources and novel radiation imaging detectors. A brief review of their photoemission properties is presented, and their behavior at liquid nitrogen temperatures is discussed. Some experimental data from optical spectroscopy and fluorescence microscopy of these radiation-induced point defects in LiF crystals and thin films are used to obtain information about the coloration curves, the efficiency of point defect formation, the effects of photo-bleaching processes, etc. Control of the local formation, stabilization, and transformation of radiation-induced light-emitting defect centers is crucial for the development of optically active micro-components and nanostructures. Some of the advantages of low temperature measurements for novel confocal laser scanning fluorescence microscopy techniques, widely used for spatial mapping of these point defects through the optical reading of their visible photoluminescence, are highlighted.

Micro-emulsion-assisted synthesis of ZnS nanospheres and their photocatalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Yao; He Xiaoyan; Cao Minhua

2008-11-03

ZnS nanospheres with rough surface were synthesized by using a micro-emulsion-assisted solvothemal process. The molar ratio of [water]/[surfactant] played an important role in controlling the size of the ZnS nanospheres. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscope (FE-SEM), and selected area electron diffraction (SAED) were used for the characterization of the resulting ZnS nanospheres. A possible formation mechanism was proposed. These ZnS nanospheres exhibited a good photocatalytic activity for degradation of an aqueous p-nitrophenol solution and the total organic carbon (TOC) of the degradation product has also been investigated.

Scanning Electron Microscopy and X-Ray Microanalysis

NASA Astrophysics Data System (ADS)

Albee, Arden L.

This outstanding volume has managed the nearly impossible task of combining the expertise of all six authors in a lucid and homogeneous style of writing. Subtitled ‘A Text for Biologists, Material Scientists and Geologists,’ the book has evolved from a short course taught each summer at Lehigh University.The book provides a basic knowledge of (1) the electron optics for these instruments a nd their controls, (2) the characteristics of the electron beam-sample interactions, (3) image formation and interpretation, (4) X ray spectrometry and quantitative X ray microanalysis with separate detailed sections on wavelength dispersive and energy dispersive techniques, and (5) specimen preparation, especially for biological materials.

Lithotrophic iron-oxidizing bacteria produce organic stalks to control mineral growth: implications for biosignature formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, Clara S; Fakra, Sirine C; Emerson, David

Neutrophilic Fe-oxidizing bacteria (FeOB) are often identified by their distinctive morphologies, such as the extracellular twisted ribbon-like stalks formed by Gallionella ferruginea or Mariprofundus ferrooxydans. Similar filaments preserved in silica are often identified as FeOB fossils in rocks. Although it is assumed that twisted iron stalks are indicative of FeOB, the stalk's metabolic role has not been established. To this end, we studied the marine FeOB M. ferrooxydans by light, X-ray and electron microscopy. Using time-lapse light microscopy, we observed cells excreting stalks during growth (averaging 2.2 {micro}m h(-1)). Scanning transmission X-ray microscopy and near-edge X-ray absorption fine structure (NEXAFS)more » spectroscopy show that stalks are Fe(III)-rich, whereas cells are low in Fe. Transmission electron microscopy reveals that stalks are composed of several fibrils, which contain few-nanometer-sized iron oxyhydroxide crystals. Lepidocrocite crystals that nucleated on the fibril surface are much larger ({approx}100 nm), suggesting that mineral growth within fibrils is retarded, relative to sites surrounding fibrils. C and N 1s NEXAFS spectroscopy and fluorescence probing show that stalks primarily contain carboxyl-rich polysaccharides. On the basis of these results, we suggest a physiological model for Fe oxidation in which cells excrete oxidized Fe bound to organic polymers. These organic molecules retard mineral growth, preventing cell encrustation. This model describes an essential role for stalk formation in FeOB growth. We suggest that stalk-like morphologies observed in modern and ancient samples may be correlated confidently with the Fe-oxidizing metabolism as a robust biosignature.« less

High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy

NASA Astrophysics Data System (ADS)

Hihath, Sahar; Santala, Melissa K.; Campbell, Geoffrey; van Benthem, Klaus

2016-08-01

The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO3 substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.

Development of a novel myconanomining approach for the recovery of agriculturally important elements from jarosite waste.

PubMed

Bedi, Ankita; Singh, Braj Raj; Deshmukh, Sunil K; Aggarwal, Nisha; Barrow, Colin J; Adholeya, Alok

2018-05-01

In this study, an ecofriendly and economically viable waste management approach have been attempted towards the biosynthesis of agriculturally important nanoparticles from jarosite waste. Aspergillus terreus strain J4 isolated from jarosite (waste from Debari Zinc Smelter, Udaipur, India), showed good leaching efficiency along with nanoparticles (NPs) formation under ambient conditions. Fourier-transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) confirmed the formation of NPs. Energy dispersive X-ray spectroscopy (EDX analysis) showed strong signals for zinc, iron, calcium and magnesium, with these materials being leached out. TEM analysis and high resolution transmission electron microscopy (HRTEM) showed semi-quasi spherical particles having average size of 10-50nm. Thus, a novel biomethodology was developed using fungal cell-free extract for bioleaching and subsequently nanoconversion of the waste materials into nanostructured form. These biosynthesized nanoparticles were tested for their efficacy on seed emergence activity of wheat (Triticum aestivum) seeds and showed enhanced growth at concentration of 20ppm. These nanomaterials are expected to enhance plant growth properties and being targeted as additives in soil fertility and crop productivity enhancement. Copyright © 2017. Published by Elsevier B.V.

Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles

PubMed Central

Stevanović, Magdalena; Kovačević, Branimir; Petković, Jana; Filipič, Metka; Uskoković, Dragan

2011-01-01

Highly stable dispersions of nanosized silver particles were synthesized using a straightforward, cost-effective, and ecofriendly method. Nontoxic glucose was utilized as a reducing agent and poly-α, γ, L-glutamic acid (PGA), a naturally occurring anionic polymer, was used as a capping agent to protect the silver nanoparticles from agglomeration and render them biocompatible. Use of ammonia during synthesis was avoided. Our study clearly demonstrates how the concentration of the capping agent plays a major role in determining the dimensions, morphology, and stability, as well as toxicity of a silver colloidal solution. Hence, proper optimization is necessary to develop silver colloids of narrow size distribution. The samples were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurement. MTT assay results indicated good biocompatibility of the PGA-capped silver nanoparticles. Formation of intracellular reactive oxygen species was measured spectrophotometrically using 2,7-dichlorofluorescein diacetate as a fluorescent probe, and it was shown that the PGA-capped silver nanoparticles did not induce intracellular formation of reactive oxygen species. PMID:22131829

Preparation and improved photocatalytic activity of mesoporous WS{sub 2} using combined hydrothermal-evaporation induced self-assembly method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vattikuti, S.V. Prabhakar, E-mail: vsvprabu@gmail.com; Byon, Chan, E-mail: cbyon@ynu.ac.kr; Reddy, Ch. Venkata

2016-03-15

Highlights: • One-step method for synthesis of mesoporous WS{sub 2} was proposed. • Role of CTAB surfactant on formation of mesoporous WS{sub 2} was elucidated. • Possible growth mechanism of the mesoporous structure is also reported. • 0.1 wt% mesoporous WS{sub 2} catalyst exhibited high photocatalytic activity under UV light. - Abstract: In this paper, we report mesoporous WS{sub 2} nanosheets with a crystalline network that were synthesized using CTAB as a structure-directing agent via self-assembly induced by hydrothermal and thermal evaporation. Powder X-ray diffraction, Raman spectra, and high-resolution X-ray photoelectron spectroscopy results confirmed the formation of WS{sub 2} structures.more » Scanning electron microscopy and transmission electron microscopy were used to observe the as-prepared mesoporous frameworks. The mesoporous WS{sub 2} nanosheets have a surface area of 197 m{sup 2} g{sup −1}. A possible growth mechanism is reported for these mesoporous WS{sub 2} nanosheets. The mesoporous WS{sub 2} nanosheets demonstrate high photocatalytic activity. Among different concentrations, 0.1 wt% mesoporous WS{sub 2} shows superior catalytic activity compared to pristine WS{sub 2} nanosheets.« less

Stability and Synergistic Effect of Polyaniline/TiO₂ Photocatalysts in Degradation of Azo Dye in Wastewater.

PubMed

Gilja, Vanja; Novaković, Katarina; Travas-Sejdic, Jadranka; Hrnjak-Murgić, Zlata; Roković, Marijana Kraljić; Žic, Mark

2017-11-23

The polyaniline/TiO₂ (PANI/TiO₂) composite photocatalysts were prepared by the in situ chemical oxidation of aniline (An) in the presence of TiO₂ particles. For this purpose, photocatalysts with different amounts of PANI polymer were prepared and analysed. Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis indicated successful synthesis of the PANI polymer and its conductivity was also determined. The micrographs of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to explain the impact of the aniline amount on the aggregation process during the synthesis of the composites. The smallest size of aggregates was obtained for the photocatalysts with 15% of PANI (15PANI/TiO₂) due to the formation of homogenous PANI. The photocatalytic activity of studied PANI/TiO₂ photocatalysts was validated by monitoring the discoloration and mineralization of Reactive Red azo dye (RR45) in wastewater. The 15PANI/TiO₂ sample presented the highest photocatalytic efficiency under ultraviolet A (UVA) irradiation, in comparison to pure TiO₂. This was explained by the formation of uniformly dispersed PANI on the TiO₂ particles, which was responsible for the synergistic PANI-TiO₂ effect.

Synthesis and electrochemical properties of NiO nanospindles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Hai; University of Chinese Academy of Sciences, Beijing 100049; Lv, Baoliang, E-mail: lbl604@sxicc.ac.cn

2014-02-01

Graphical abstract: NiO nanospindles with a different electrochemical activity as compared to those previous reports were synthesized via an agglomeration–dissolution–recrystallization growth process without the addition of any surfactant. - Highlights: • NiO nanospindles were synthesized without the addition of any surfactant. • The agglomeration–dissolution–recrystallization growth process was used to explain the precursors’ formation process of the spindle-like NiO. • As-obtained spindle-like NiO showed a different electrochemical activity as compared to those previous reports. - Abstract: NiO nanospindles were successfully synthesized via a hydrothermal and post-treatment method. The as-synthesized nanospindles were about several hundred nanometers in width and about one micrometermore » in length. X-ray diffraction (XRD) analysis revealed that the spindle-like structure was cubic NiO phase crystalline. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis indicated that these NiO nanospindles were of single crystal nature. On the basis of time-dependent experiments, a possible agglomeration–dissolution–recrystallization growth process was proposed to explain the formation process of the spindle-like precursors. The cyclic voltammetry (CV) measurement showed that the as-prepared spindle-like NiO exhibited a pseudo-capacitance behavior.« less

Catalytic graphitization behavior of phenolic resins by addition of in situ formed nano-Fe particles

NASA Astrophysics Data System (ADS)

Rastegar, H.; Bavand-vandchali, M.; Nemati, A.; Golestani-Fard, F.

2018-07-01

This work presents the catalytic graphitization process of phenolic resins (PR's) by addition of in situ nano-Fe particles as catalyst. Pyrolysis treatments of prepared compositions including various contents of nano-Fe particles were carried out at 600-1200 °C for 3 h under reducing atmosphere and graphitization process were evaluated by different techniques such as X-Ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Simultaneous Thermal Analysis (STA) and Raman spectroscopy that mainly performed to identify the phase and microstructural analysis, oxidation resistance and extend of graphitized carbon formation. Results indicate that, in situ graphitic carbon development were already observed after firing the samples at 800 °C for 3 h under reducing atmosphere, increasing temperature and amount of nano-Fe led to a more effective graphitization level. In addition, the different nano crystalline carbon shapes such as onion and bamboo like and carbon nanotubes (CNTs) were in situ identified during graphitization process of nano-Fe containing samples. It was suggested that formation of these different nano carbon structures related to nano-Fe catalyst behavior and the carbon shell growth.

One-dimensional growth of hexagonal rods of metastable h-MoO3 using one-pot, rapid and environmentally benign supercritical fluid processing

NASA Astrophysics Data System (ADS)

Thangasamy, Pitchai; Shanmugapriya, Vadivel; Sathish, Marappan

2018-05-01

A facile and one-pot supercritical fluid method was demonstrated for the synthesis of phase pure crystalline h-MoO3 microrods within a short reaction time of 5 min at 400 °C. The formation of h-MoO3 was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopic analysis. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images clearly revealed the formation of hexagonal h-MoO3 rods. Further, photoluminescence emission peaks corresponding to band to band transition was observed in the h-MoO3 microrods. It was observed that when increasing the reaction time from 5 min to 30 min at 400 °C, h-MoO3 microrods undergoes disintegration to α-MoO3 thin nanorods. Interestingly, h-MoO3 microrods were also formed in a reaction time of 30 min at 400 °C when reducing the volume of nitric acid from 1 mL to ∼0.5 mL. The short reaction time and simple synthetic strategy makes this method can be suitable for the synthesis of other semiconductor nanomaterials for diverse applications.

Sb surfactant mediated growth of InAs/AlAs{sub 0.56}Sb{sub 0.44} strained quantum well for intersubband absorption at 1.55 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Yu; Bertru, Nicolas; Folliot, Hervé

Surfactant mediated growth of strained InAs/AlAs{sub 0.56}Sb{sub 0.44} quantum wells on InP (001) substrate is investigated. X ray diffraction and transmission electron microscopy analysis reveal that the supply of antimony on InAs surface delays the 2D to 3D growth transition and allows the growth of thick InAs/AlAsSb quantum wells. Quantum well as thick as 7 ML, without defect was achieved by Sb surfactant mediated growth. Further high resolution transmission electron microscopy measurement and geometric phase analysis show that InAs/AlAsSb interfaces are not abrupt. At InAs on AlAsSb interface, the formation of a layer presenting lattice parameter lower than InP leadsmore » to a tensile stress. From energetic consideration, the formation of As rich AlAsSb layer at interface is deduced. At AlAsSb on InAs interface, a compressive layer is formed. The impact on optical properties and the chemical composition of this layer are discussed from microscopic analysis and photoluminescence experiments.« less

The corrosion protection of AA2024-T3 aluminium alloy by leaching of lithium-containing salts from organic coatings.

PubMed

Visser, Peter; Liu, Yanwen; Zhou, Xiaorong; Hashimoto, Teruo; Thompson, George E; Lyon, Stuart B; van der Ven, Leendert G J; Mol, Arjan J M C; Terryn, Herman A

2015-01-01

Lithium carbonate and lithium oxalate were incorporated as leachable corrosion inhibitors in model organic coatings for the protection of AA2024-T3. The coated samples were artificially damaged with a scribe. It was found that the lithium-salts are able to leach from the organic coating and form a protective layer in the scribe on AA2024-T3 under neutral salt spray conditions. The present paper shows the first observation and analysis of these corrosion protective layers, generated from lithium-salt loaded organic coatings. The scribed areas were examined by scanning and transmission electron microscopy before and after neutral salt spray exposure (ASTM-B117). The protective layers typically consist of three different layered regions, including a relatively dense layer near the alloy substrate, a porous middle layer and a flake-shaped outer layer, with lithium uniformly distributed throughout all three layers. Scanning electron microscopy and white light interferometry surface roughness measurements demonstrate that the formation of the layer occurs rapidly and, therefore provides an effective inhibition mechanism. Based on the observation of this work, a mechanism is proposed for the formation of these protective layers.

Biogenic manganese oxide nanoparticle formation by a multimeric multicopper oxidase Mnx.

PubMed

Romano, Christine A; Zhou, Mowei; Song, Yang; Wysocki, Vicki H; Dohnalkova, Alice C; Kovarik, Libor; Paša-Tolić, Ljiljana; Tebo, Bradley M

2017-09-29

Bacteria that produce Mn oxides are extraordinarily skilled engineers of nanomaterials that contribute significantly to global biogeochemical cycles. Their enzyme-based reaction mechanisms may be genetically tailored for environmental remediation applications or bioenergy production. However, significant challenges exist for structural characterization of the enzymes responsible for biomineralization. The active Mn oxidase in Bacillus sp. PL-12, Mnx, is a complex composed of a multicopper oxidase (MCO), MnxG, and two accessory proteins, MnxE and MnxF. MnxG shares sequence similarity with other, structurally characterized MCOs. MnxE and MnxF have no similarity to any characterized proteins. The ~200 kDa complex has been recalcitrant to crystallization, so its structure is unknown. Here, we show that native mass spectrometry defines the subunit topology and copper binding of Mnx, while high-resolution electron microscopy visualizes the protein and nascent Mn oxide minerals. These data provide critical structural information for understanding Mn biomineralization by such unexplored enzymes.Significant challenges exist for structural characterization of enzymes responsible for biomineralization. Here the authors show that native mass spectrometry and high resolution electron microscopy can define the subunit topology and copper binding of a manganese oxidizing complex, and describe early stage formation of its mineral products.

Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel

NASA Astrophysics Data System (ADS)

Huilgol, Prashant; Rajendra Udupa, K.; Udaya Bhat, K.

2018-02-01

Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed.

Characterization of corrosion resistant on NiCoCr coating layer exposed to 5%NaCl

NASA Astrophysics Data System (ADS)

Sugiarti, E.; Sundawa, R.; Desiati, R. D.; Zaini, K. A.

2018-03-01

Highly corrosion resistant of carbon steel coated NiCoCr was applied in corrosive of marine environtment. Carbon steel coated NiCoCr was prepared by a two step technique of NiCo electro-deposition and Cr pack cementation. The samples were exposed to 5 wt.% NaCl for 48 and 168 hours. The microstructure and corrosion product were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The corrosion resistance of carbon steel coated NiCoCr was found to be better than that of carbon steel substrate without coating. The results showed the microstructure of 48 h corroded sample has duplex layer composed of inner α-(Ni,Co), α-Cr and outer Cr2O3, while a quite thin and continues protective oxide of Cr2O3 was observed in outer layer of 168 h corroded sample. The formation of oxide scale rich in Cr2O3 has contributed for the better corrosion resistance of carbon steel coated NiCoCr, whereas the formation of non protective oxide of iron might caused low corrosion resistance of carbon steel substrate.

Pickering emulsions stabilized by a metal-organic framework (MOF) and graphene oxide (GO) for producing MOF/GO composites.

PubMed

Zhang, Fanyu; Liu, Lifei; Tan, Xiuniang; Sang, Xinxin; Zhang, Jianling; Liu, Chengcheng; Zhang, Bingxing; Han, Buxing; Yang, Guanying

2017-10-18

Herein we demonstrate the formation of a novel kind of Pickering emulsion that is stabilized by a Zr-based metal-organic framework (Zr-MOF) and graphene oxide (GO). It was found that the Zr-BDC-NO 2 and GO solids assembling at the oil/water interface can effectively stabilize the oil droplets that are dispersed in the water phase. Such a Pickering emulsion offers a facile route for fabricating Zr-MOF/GO composite materials. After removing water and oil by freeze drying from Pickering emulsions, the Zr-MOF/GO composites were obtained and their morphologies, structures and interaction properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectrometry, respectively. The influences of the concentration of GO and Zr-MOF on the emulsion microstructures and the properties of the MOF/GO composites were studied. Based on experimental results, the mechanisms for the emulsion formation by Zr-MOF and GO and the as-synthesized superstructures of the Zr-MOF/GO composite were proposed. It is expected that this facile and tunable route can be applied to the synthesis of different kinds of MOF-based or GO-based composite materials.

High resolution structural characterisation of laser-induced defect clusters inside diamond

NASA Astrophysics Data System (ADS)

Salter, Patrick S.; Booth, Martin J.; Courvoisier, Arnaud; Moran, David A. J.; MacLaren, Donald A.

2017-08-01

Laser writing with ultrashort pulses provides a potential route for the manufacture of three-dimensional wires, waveguides, and defects within diamond. We present a transmission electron microscopy study of the intrinsic structure of the laser modifications and reveal a complex distribution of defects. Electron energy loss spectroscopy indicates that the majority of the irradiated region remains as sp3 bonded diamond. Electrically conductive paths are attributed to the formation of multiple nano-scale, sp2-bonded graphitic wires and a network of strain-relieving micro-cracks.

Electron microscopic investigation of crystal lattice bending-torsion and internal stresses in deformed polycrystalline alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koneva, N. A., E-mail: koneva@tsuab.ru; Kozlov, E. V.

2016-01-15

Generalization of the results of electron microscopy investigations of the crystal lattice bending-torsion (χ) and the internal stresses (IS) was conducted. The deformed polycrystalline alloys and steels were investigated. The sources of χ and IS origin were established. The regularities of their change with the distance from the sources and the evolution with deformation were revealed. The contribution of IS into the deformation resistance was determined. The nature of formation of two sequences of dislocation substructure transformations during deformation of alloys was established.

Atomic structure and bonding of the interfacial bilayer between Au nanoparticles and epitaxially regrown MgAl{sub 2}O{sub 4} substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Guo-zhen; Canadian Centre of Electron Microscopy and Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1; Majdi, Tahereh

2014-12-08

A unique metal/oxide interfacial bilayer formed between Au nanoparticles and MgAl{sub 2}O{sub 4} substrates following thermal treatment is reported. Associated with the formation of the bilayer was the onset of an abnormal epitaxial growth of the substrate under the nanoparticle. According to the redistribution of atoms and the changes of their electronic structure probed across the interface by a transmission electron microscopy, we suggest two possible atomic models of the interfacial bilayer.

Characterization of Magnetite Scale Formed in Naphthenic Acid Corrosion

NASA Astrophysics Data System (ADS)

Jin, Peng; Robbins, Winston; Bota, Gheorghe; Nesic, Srdjan

2017-02-01

Naphthenic acid corrosion (NAC) is one of the major concerns for corrosion engineers in refineries. Traditionally, the iron sulfide (FeS) scale, formed when sulfur compounds in crudes corrode the metal, is expected to be protective and limit the NAC. Nevertheless, no relationship has been found between protectiveness and the characteristics of FeS scale. In this study, lab scale tests with model sulfur compounds and naphthenic acids replicated corrosive processes of refineries with real crude fractions behavior. The morphology and chemical composition of scales were analyzed with scanning electron microscopy and transmission electron microscopy. These high-resolution microscopy techniques revealed the presence of an iron oxide (Fe3O4 or magnetite) scale and discrete particulates on metal surfaces under FeS scales, especially on a low chrome steel. The presence of the iron oxide was correlated with the naphthenic acid activity during the experiments. It is postulated that the formation of the magnetite scale resulted from the decomposition of iron naphthenates at high temperatures. It is further postulated that a nano-particulate form of magnetite may be providing corrosion resistance.

Preparation and characterization of a novel highly hydrophilic and antifouling polysulfone/nanoporous TiO2 nanocomposite membrane.

PubMed

Bidsorkhi, H Cheraghi; Riazi, H; Emadzadeh, D; Ghanbari, M; Matsuura, T; Lau, W J; Ismail, A F

2016-10-14

In this research, novel ultrafiltration nanocomposite membranes were prepared by incorporating self-synthesized nanoporous titanium dioxide (NTiO2) nanoparticles into polysulfone. The surface of the nanoparticle was treated with a silane-based modifier to improve its distribution in the host polymer. Atomic-force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, transmission electron microscopy, energy-dispersive x-ray spectroscopy, porosity and contact angle tests were conducted to characterize the properties of the particles as well as the fabricated nanocomposite membranes. The effects of the nanoparticle incorporation were evaluated by conducting ultrafiltration experiments. It was reported that the membrane pure water flux was increased with increasing NTiO2 loading owing to the high porosity of the nanoparticles embedded and/or formation of enlarged pores upon addition of them. The antifouling capacity of the membranes was also tested by ultrafiltration of bovine serum albumin fouling solution. It was found that both water flux and antifouling capacity tended to reach desired level if the NTiO2 added was at optimized loading.

Submerged Arc Stainless Steel Strip Cladding—Effect of Post-Weld Heat Treatment on Thermal Fatigue Resistance

NASA Astrophysics Data System (ADS)

Kuo, I. C.; Chou, C. P.; Tseng, C. F.; Lee, I. K.

2009-03-01

Two types of martensitic stainless steel strips, PFB-132 and PFB-131S, were deposited on SS41 carbon steel substrate by a three-pass submerged arc cladding process. The effects of post-weld heat treatment (PWHT) on thermal fatigue resistance and hardness were evaluated by thermal fatigue and hardness testing, respectively. The weld metal microstructure was investigated by utilizing optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results showed that, by increasing the PWHT temperature, hardness decreased but there was a simultaneous improvement in weldment thermal fatigue resistance. During tempering, carbide, such as (Fe, Cr)23C6, precipitated in the weld metals and molybdenum appeared to promote (Fe, Cr, Mo)23C6 formation. The precipitates of (Fe, Cr, Mo)23C6 revealed a face-centered cubic (FCC) structure with fine grains distributed in the microstructure, thereby effectively increasing thermal fatigue resistance. However, by adding nickel, the AC1 temperature decreased, causing a negative effect on thermal fatigue resistance.

Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting

NASA Astrophysics Data System (ADS)

Ahmad, M.; Ali, G.; Ahmed, Ejaz; Haq, M. A.; Akhter, J. I.

2011-06-01

Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

Synergistically-enhanced ion track formation in pre-damaged strontium titanate by energetic heavy ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Haizhou; Zarkadoula, Eva; Sachan, Ritesh

Latent ion tracks created by energetic heavy ions (12 MeV Ti to 946 MeV Au) in single crystal SrTiO 3 are investigated in this paper using Rutherford backscattering spectrometry and scanning transmission electron microscopy. The results demonstrate that pre-existing irradiation damage, introduced via elastic collision processes, interacts synergistically with the electronic energy deposition from energetic heavy ions to enhance formation of latent ion tracks. The average amorphous cross-section increases with the level of pre-damage and is linearly proportional to the electronic energy loss of the ions, with a slope dependent on the pre-damage level. For the highest energy ions (629more » MeV Xe and 946 MeV Au), the tracks are continuous over the pre-damaged depth, but become discontinuous beyond the pre-damaged region. Finally, this work provides new understanding and insights on ion-solid interactions that significantly impact the interpretation of latent track formation processes, models of amorphization, and the fabrication of electro-ceramic devices.« less

Enhanced Photocatalytic Activity of Diamond Thin Films Using Embedded Ag Nanoparticles.

PubMed

Li, Shuo; Bandy, Jason A; Hamers, Robert J

2018-02-14

Silver nanoparticles embedded into the diamond thin films enhance the optical absorption and the photocatalytic activity toward the solvated electron-initiated reduction of N 2 to NH 3 in water. Here, we demonstrate the formation of diamond films with embedded Ag nanoparticles <100 nm in diameter. Cross-sectional scanning electron microscopy (SEM), energy-dependent SEM, and energy-dispersive X-ray analysis demonstrate the formation of encapsulated nanoparticles. Optical absorption measurements in the visible and ultraviolet region show that the resulting films exhibit plasmonic resonances in the visible and near-ultraviolet region. Measurements of photocatalytic activity using supraband gap (λ < 225 nm) and sub-band gap (λ > 225 nm) excitation show significantly enhanced ability to convert N 2 to NH 3 . Incorporation of Ag nanoparticles induces a nearly 5-fold increase in activity using a sub-band gap excitation with λ > 225 nm. Our results suggest that internal photoemission, in which electrons are excited from Ag into diamond's conduction band, is an important process that extends the wavelength region beyond diamond's band gap. Other factors, including Ag-induced optical scattering and formation of graphitic impurities are also discussed.

Synergistically-enhanced ion track formation in pre-damaged strontium titanate by energetic heavy ions

DOE PAGES

Xue, Haizhou; Zarkadoula, Eva; Sachan, Ritesh; ...

2018-03-20

Latent ion tracks created by energetic heavy ions (12 MeV Ti to 946 MeV Au) in single crystal SrTiO 3 are investigated in this paper using Rutherford backscattering spectrometry and scanning transmission electron microscopy. The results demonstrate that pre-existing irradiation damage, introduced via elastic collision processes, interacts synergistically with the electronic energy deposition from energetic heavy ions to enhance formation of latent ion tracks. The average amorphous cross-section increases with the level of pre-damage and is linearly proportional to the electronic energy loss of the ions, with a slope dependent on the pre-damage level. For the highest energy ions (629more » MeV Xe and 946 MeV Au), the tracks are continuous over the pre-damaged depth, but become discontinuous beyond the pre-damaged region. Finally, this work provides new understanding and insights on ion-solid interactions that significantly impact the interpretation of latent track formation processes, models of amorphization, and the fabrication of electro-ceramic devices.« less

Patterned self-assembled monolayers of alkanethiols on copper nanomembranes by submerged laser ablation

NASA Astrophysics Data System (ADS)

Rhinow, Daniel; Hampp, Norbert A.

2012-06-01

Self-assembled monolayers (SAMs) of alkanethiols are major building blocks for nanotechnology. SAMs provide a functional interface between electrodes and biomolecules, which makes them attractive for biochip fabrication. Although gold has emerged as a standard, copper has several advantages, such as compatibility with semiconductors. However, as copper is easily oxidized in air, patterning SAMs on copper is a challenging task. In this work we demonstrate that submerged laser ablation (SLAB) is well-suited for this purpose, as thiols are exchanged in-situ, avoiding air exposition. Using different types of ω-substituted alkanethiols we show that alkanethiol SAMs on copper surfaces can be patterned using SLAB. The resulting patterns were analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Both methods indicate that the intense laser beam promotes the exchange of thiols at the copper surface. Furthermore, we present a procedure for the production of free-standing copper nanomembranes, oxidation-protected by alkanethiol SAMs. Incubation of copper-coated mica in alkanethiol solutions leads to SAM formation on both surfaces of the copper film due to intercalation of the organic molecules. Corrosion-protected copper nanomembranes were floated onto water, transferred to electron microscopy grids, and subsequently analyzed by electron energy loss spectroscopy (EELS).

Synthesis of colloidal silver iron oxide nanoparticles--study of their optical and magnetic behavior.

PubMed

Kumar, Anil; Singhal, Aditi

2009-07-22

Silver iron oxide nanoparticles of fairly small size (average diameter approximately 1 nm) with narrow size distribution have been synthesized by the interaction of colloidal beta- Fe2O3 and silver nanoparticles. The surface morphology and size of these particles have been analyzed by using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Their structural analysis has been carried out by employing x-ray diffraction (XRD), selected-area electron diffraction (SAED), optical and infrared (IR) spectroscopic techniques. The ageing of these particles exhibits the formation of self-assembly, possibly involving weak supramolecular interactions between Ag(I)O4 and Fe(III)O4 species. These particles display the onset of absorption in the near-infrared region and have higher absorption coefficient in the visible range compared to that of its precursors. Magnetic measurements reveal an interesting transition in their magnetic behavior from diamagnetic to superparamagnetic. The magnetic moment of these particles attains a limiting value of about 0.19 emu cm(-2), which is more than two times higher than that of colloidal beta- Fe2O3. With enhanced optical and magnetic properties, this system is suggested to have possible applications in optoelectronic and magnetic devices.

Microwave synthesis of molybdenum doped LiFePO4/C and its electrochemical studies.

PubMed

Naik, Amol; P, Sajan C

2016-05-10

A Mo-doped LiFePO4 composite was prepared successfully from an iron carbonyl complex by adopting a facile and rapid microwave assisted solid state method. The evolution of gases from the iron precursor produces a highly porous product. The formation and substitution of Mo in LiFePO4 were confirmed by X-ray diffraction; surface analysis was carried out by scanning electron microscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the substituted LiFePO4 were examined by cyclic voltammetry, electrochemical impedance spectroscopy and by recording charge-discharge cycles. It was observed that the as prepared composites consisted of a single phase orthorhombic olivine-type structure, where Mo(6+) was successfully introduced into the M2(Fe) sites. Incorporation of supervalent Mo(6+) introduced Li(+) ion vacancies in LiFePO4. The synthesized material facilitated lithium ion diffusion during charging/discharging due to the charge compensation effect and porosity. The battery performance studies showed that LiMo0.05Fe0.095PO4 exhibited a maximum capacity of 169.7 mA h g(-1) at 0.1 C current density, with admirable stability retention. Even at higher current densities, the retention of the specific capacity was exceptional.

Observations and Modeling of the Green Ocean Amazon 2014/15: Transmission Electron Microscopy Analysis of Aerosol Particles Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buseck, Peter

2016-03-01

During two Intensive Operational Periods (IOP), we collected samples at 3-hour intervals for transmission electron microscopy analysis. The resulting transmission electron microscopy images and compositions were analyzed for the samples of interest. Further analysis will be done especially for the plume of interest. We found solid spherical organic particles from rebounded samples collected with Professor Scot Martin’s group (Harvard University). Approximately 30% of the rebounded particles at 95% relative humidity were spherical organic particles. Their sources and formation process are not known, but such spherical particles could be solid and will have heterogeneous chemical reactions. We observed many organic particlesmore » that are internally mixed with inorganic elements such as potassium and nitrogen. They are either homogeneously mixed or have inorganic cores with organic aerosol coatings. Samples collected from the Manaus, Brazil, pollution plume included many nano-size soot particles mixed with organic material and sulfate. Aerosol particles from clean periods included organic aerosol particles, sulfate, sea salt, dust, and primary biogenic aerosol particles. There was more dust, primary biogenic aerosol, and tar balls in samples taken during IOP1 than those taken during IOP2. Many dust particles were found between March 2 and 3.« less

Electrochemical Dissolution of Iridium and Iridium Oxide Particles in Acidic Media: Transmission Electron Microscopy, Electrochemical Flow Cell Coupled to Inductively Coupled Plasma Mass Spectrometry, and X-ray Absorption Spectroscopy Study.

PubMed

Jovanovič, Primož; Hodnik, Nejc; Ruiz-Zepeda, Francisco; Arčon, Iztok; Jozinović, Barbara; Zorko, Milena; Bele, Marjan; Šala, Martin; Šelih, Vid Simon; Hočevar, Samo; Gaberšček, Miran

2017-09-13

Iridium-based particles, regarded as the most promising proton exchange membrane electrolyzer electrocatalysts, were investigated by transmission electron microscopy and by coupling of an electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometry. Additionally, studies using a thin-film rotating disc electrode, identical location transmission and scanning electron microscopy, as well as X-ray absorption spectroscopy have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that Ir particles dissolve well below oxygen evolution reaction (OER) potentials, presumably induced by Ir surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile-type IrO 2 particles are substantially more stable and less active in comparison to as-prepared metallic and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER-relevant conditions, E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism, where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low-temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyzer.

Manipulation of partially oriented hydroxyapatite building blocks to form flowerlike bundles without acid-base regulation.

PubMed

Wen, Zhenliang; Wang, Zihao; Chen, Jingdi; Zhong, Shengnan; Hu, Yimin; Wang, Jianhua; Zhang, Qiqing

2016-06-01

The application of hydroxyapatite (HAP) in different fields depends greatly on its morphology, composition and structure. Besides, the main inorganic building blocks of human bones and teeth are also HAP. Therefore, accurate shape and aggregation control and of hydroxyapatite particles will be of great interest. Herein, oriented bundles of flowerlike HAP nanorods were successfully prepared through hydrothermal treatment without acid-base regulation, with the mono-alkyl phosphate (MAP) and sodium citrate as surfactant and chelating agent, respectively. The prepared samples were characterized by the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and zeta potential, the pH value and conductivity value of suspension were characterized by pH meter and conductivity measurement. The results showed that the MAP and citrate play an important role in assembly of HAP nanorods without acid-base regulation. Citrate calcium complex could decompose slowly and release citrate ions at hydrothermal conditions. Besides, the further decomposition of citrate ions could release aconitic acid as the reaction time prolongs. Moreover, the possible scheme for the formation process was discussed in detail. Copyright © 2016 Elsevier B.V. All rights reserved.

Atomic photoionization processes under magnification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lepine, F.; Bordas, Ch.; Nicole, C.

2004-09-01

Recently, classical simulations of threshold photoionization in the presence of an electric field have shown that a clear distinction between direct and indirect trajectories followed by the outgoing electron can be observed in the patterns of electron impacts on a two-dimensional detector. Subsequently, slow photoelectron imaging experiments have been reported where this distinction could be observed in atomic xenon. Furthermore, using a magnifying electrostatic lens to improve the velocity-map imaging technique, oscillatory patterns were observed modulating the classical envelope that was measured in the experiments of Nicole et al. [Phys. Rev. Lett. 88, 133001 (2002)]. This extension of slow photoelectronmore » imaging, called photoionization microscopy, relies on the existence of interferences between various trajectories by which the electron moves from the atom to the plane of observation. In this article we present the main experimental results obtained both in slow photoelectron imaging and in photoionization microscopy. The formation of the interference pattern is discussed in the framework of a semiclassical model that is described in detail elsewhere. The qualitative information that can be drawn from the experiments is discussed, and the potential applications of photoionization microscopy are considered. Particular attention is paid to the role of continuum Stark resonances that appear between the saddle point in the Coulomb+dc field potential and the field-free ionization limit.« less

Morphological study of the TK cholangiocarcinoma cell line with three-dimensional cell culture.

PubMed

Akiyoshi, Kohei; Kamada, Minori; Akiyama, Nobutake; Suzuki, Masafumi; Watanabe, Michiko; Fujioka, Kouki; Ikeda, Keiichi; Mizuno, Shuichi; Manome, Yoshinobu

2014-04-01

Cholangiocarcinoma is an intractable carcinoma originating from the bile duct epithelium. To gain an understanding of the cell biology of cholangiocarcinoma, in vitro cell culture is valuable. However, well‑characterized cell lines are limited. In the present study, the morphology of the TK cholangiocarcinoma cell line was analyzed by three‑dimensional culture. Dispersed TK cells were injected into a gelatin mesh scaffold and cultivated for 3‑20 days. The morphology of the TK cells was investigated by phase‑contrast microscopy, optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TK cells were observed to proliferate three-dimensionally in the scaffold. The cells exhibited a globoid structure and attached to the scaffold. The SEM observation demonstrated typical microvilli and plicae on the surface of the structure. Light microscopy and TEM confirmed intercellular and cell‑to‑scaffold attachment in the three‑dimensional mesh. The culture also exhibited the formation of a duct-like structure covered by structured microvilli. In conclusion, three‑dimensional culture of TK cells demonstrated the morphological characteristics of cholangiocarcinoma in vitro. Production of high levels of carbohydrate antigen (CA)19‑9, CA50 and carcinoembryonic antigen was previously confirmed in the TK cell line. As a characteristic morphology was demonstrated in the present study, the TK cholangiocarcinoma cell line may be useful as an experimental model for further study of cholangiocarcinoma.

Transformation and motility of human platelets: details of the shape change and release reaction observed by optical and electron microscopy

PubMed Central

1979-01-01

Blood platelets from 10 normal human subjects have been examined with a sensitive differential interference contrast (DIC) microscope. The entire transformation process during adhesion to glass is clearly visible and has been recorded cinematographically, including the disk to sphere change of shape, the formation of sessile protuberances, the extension and retraction of pseudopodia, and the spreading, ruffling, and occasional regression of the hyalomere. The exocytosis of intact dense bodies can be observed either by DIC microscopy, or by epifluorescence microscopy in platelets stained with mepacrine. Details of fluorescent flashes indicate that the dense bodies usually release their contents extracellularly, may do so intracytoplasmically under the influence of strong, short wavelength light on some preparations of mepacrine-stained platelets. The release of one or more dense bodies leaves a crater of variable size on the upper surface of the granulomere. Such craters represent the surface component of the open canalicular system and their formation and disappearance can be directly observed. Because these techniques permit quantitation of several parameters of motility which are not readily observable by other techniques, it is suggested that high extinction DIC microscope examination may become a rapid and useful method of studying congenital and acquired platelet disorders. Many features of platelet transformation have been confirmed and extended by scanning electron micrographs. These can in turn be interpreted by reference to time- lapse films of living platelets. PMID:511936

The first Pan-Podocnemididae turtle egg from the Presidente Prudente Formation (Late Cretaceous, Bauru Group), Brazil.

PubMed

Marsola, Júlio C De A; Grellet-Tinner, Gerald; Montefeltro, Felipe C; Langer, Max C

2014-10-08

Pan-Podocnemididae turtles are ubiquitous in Late Cretaceous rocks of the Bauru Group in southeastern Brazil. This group of side-necked turtles is particularly abundant in a turtle-bearing site of the Presidente Prudente Formation known as Tartaruguito. Here, we describe the first turtle egg (LPRP-USP 0052) from the Tartaruguito site. LPRP-USP 0052 is nearly complete but misses a pole and measures 5,1 and 2,9-2,2 centimeters due to its flattened minor axis. The egg morphology and microstructure were analyzed by observations performed with CT, Optic Microscopy, Scanning Electronic Microscopy and Wave Dispersion Energy analyses. The eggshell ranges from 145 to160 micrometers thick. Considering the matching morphology of the new specimen and its provenance from the stratigraphic horizon that yielded only the podocnemidids Bauruemys and Roxochelys, it is most likely that LPRP-USP 0052 was produced by a podocnemidid turtle. 

Development of photocatalyst coated fluoropolymer based microreactor using ultrasound for water remediation.

PubMed

Colmenares, Juan Carlos; Nair, Vaishakh; Kuna, Ewelina; Łomot, Dariusz

2018-03-01

Formation of thin layers of photocatalyst in photo-microreactor is a challenging work considering the properties of both catalyst and the microchannel material. The deposition of semiconductor materials on fluoropolymer based microcapillary requires the use of economical methods which are also less energy dependent. The current work introduces a new method for depositing nanoparticles of TiO 2 on the inner walls of a hexafluoropropylene tetrafluoroethylene microtube under mild conditions using ultrasound technique. During the ultrasonication process, changes in the polymer surface were observed and characterized using Attenuated Total Reflectance spectroscopy, Scanning Electron Microscopy and Confocal Microscopy. The rough patches form sites for catalyst deposition resulting in the formation of thin layer of TiO 2 nanoparticles in the inner walls of the microtube. The photocatalytic activity of the TiO 2 coated fluoropolymer based microcapillary was evaluated for removal of phenol present in water. Copyright © 2017 Elsevier B.V. All rights reserved.

The oxidation of Inconel-690 alloy at 600 K in air

NASA Astrophysics Data System (ADS)

Allen, G. C.; Dyke, J. M.; Harris, S. J.; Morris, A.

1988-03-01

The alloy Inconel-690 has been oxidised at 600 K in air for periods varying between 30 s and 120 h and the composition of the oxide layer formed examined by scanning Auger microscopy (SAM), scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDAX), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). Analysis of the spectra revealed the formation of a layer of essentially α-Cr 2O 3 at room temperature. Oxidation at 600 K resulted in the formation of a duplex oxide film with a thin outer layer of iron(III) oxide. Beneath this was a mixed chromium, iron, nickel oxide. Following 8 h of oxidation at 600 K the oxide was approximately 10 nm thick but this was found to vary with the physical surface of the underlying alloy which also appeared to affect the relative rates of diffusion of the ionic species during film growth.

Ultrastructural analyses of somatic embryo initiation, development and polarity establishment from mesophyll cells of Dactylis glomerata

NASA Technical Reports Server (NTRS)

Vasilenko, A.; McDaniel, J. K.; Conger, B. V.

2000-01-01

Somatic embryos initiate and develop directly from single mesophyll cells in in vitro-cultured leaf segments of orchardgrass (Dactylis glomerata L.). Embryogenic cells establish themselves in the predivision stage by formation of thicker cell walls and dense cytoplasm. Electron microscopy observations for embryos ranging from the pre-cell-division stage to 20-cell proembryos confirm previous light microscopy studies showing a single cell origin. They also confirm that the first division is predominantly periclinal and that this division plane is important in establishing embryo polarity and in determining the embryo axis. If the first division is anticlinal or if divisions are in random planes after the first division, divisions may not continue to produce an embryo. This result may produce an embryogenic cell mass, callus formation, or no structure at all. Grant numbers: NAGW-3141, NAG10-0221.

Biosynthesis of palladium nanoparticles using Saccharomyces cerevisiae extract and its photocatalytic degradation behaviour

NASA Astrophysics Data System (ADS)

Sriramulu, Mohana; Sumathi, Shanmugam

2018-06-01

In this article, we have discussed the biosynthesis of palladium nanoparticles (PdNPs) using aqueous Saccharomyces cerevisiae extract and its photocatalytic application. The biosynthesised PdNPs were characterised by UV-Vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Atomic force microscopy (AFM). The formation of PdNPs was confirmed from the disappearance of the peak at 405 nm in the UV-Vis spectrum. Agglomerated and hexagonal shaped PdNPs were noted by SEM. FTIR was performed to identify the biomolecules responsible for the synthesis of PdNPs. Bioactive compounds in the yeast extract acted as secondary metabolites which facilitated the formation of PdNPs. The yeast synthesised PdNPs degraded 98% of direct blue 71 dye photochemically within 60 min under UV light.