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Dark field microscopy

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https://www.readbyqxmd.com/read/28432904/optimising-multi-frame-adf-stem-for-high-precision-atomic-resolution-strain-mapping
#1
Lewys Jones, Sigurd Wenner, Magnus Nord, Per Harald Ninive, Ole Martin Løvvik, Randi Holmestad, Peter D Nellist
Annular dark-field scanning transmission electron microscopy is a powerful tool to study crystal defects at the atomic scale but historically single slow-scanned frames have been plagued by low-frequency scanning-distortions prohibiting accurate strain mapping at atomic resolution. Recently, multi-frame acquisition approaches combined with post-processing have demonstrated significant improvements in strain precision, but the optimum number of frames to record has not been explored. Here we use a non-rigid image registration procedure before applying established strain mapping methods...
April 15, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28424663/antimicrobial-photodynamic-therapy-against-endodontic-enterococcus-faecalis-and-candida-albicans-mono-and-mixed-biofilms-in-the-presence-of-photosensitizers-a-comparative-study-with-classical-endodontic-irrigants
#2
Patrícia Diogo, Chantal Fernandes, Francisco Caramelo, Marta Mota, Isabel M Miranda, M A F Faustino, M G P M S Neves, Marciana P Uliana, Kleber T de Oliveira, João M Santos, Teresa Gonçalves
Endodontic biofilms eradication from the infected root canal system remains as the primary focus in endodontic field. In this study, it was assessed the efficacy of antimicrobial Photodynamic Therapy (aPDT) with the Zn(II)chlorin e6 methyl ester (Zn(II)e6Me) activated by red light against monospecies and mixed biofilms of Enterococcus faecalis and Candida albicans. The results were compared with the ones obtained with Rose Bengal (RB), Toluidine Blue-O (TBO), the synthetic tetracationic porphyrin (TMPyP) as well as classical endodontic irrigants (3% NaOCl, 17% EDTA and 2% CHX)...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28418651/electrodeposition-of-highly-porous-pt-nanoparticles-studied-by-quantitative-3d-electron-tomography-influence-of-growth-mechanisms-and-potential-cycling-on-the-active-surface-area
#3
Jon Ustarroz, Bart Geboes, Hans Vanrompay, Kadir Sentosun, Sara Bals, Tom Breugelmans, Annick Hubin
Nanoporous Pt nanoparticles (NPs) are promising fuel cell catalysts due to their large surface area and increased electrocatalytic activity towards the oxygen reduction reaction (ORR). Herein, we report on the influence of the growth mechanisms on the surface properties of electrodeposited Pt dendritic NPs with large surface areas. The electrochemically active surface was studied by hydrogen underpotential deposition (H UPD) and compared for the first time to high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) quantitative 3D electron tomography of individual nanoparticles...
April 18, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28404661/quantitative-assessment-of-fat-levels-in-caenorhabditis-elegans-using-dark-field-microscopy
#4
Anthony D Fouad, Shelly Teng, Shelley H Pu, Julian R Mark, Moyu Fu, Kevin Zhang, Jonathan Huang, David M Raizen, Christopher Fang-Yen
The roundworm Caenorhabditis elegans is widely used as a model for studying conserved pathways for fat storage, aging, and metabolism. The most broadly used methods for imaging fat in C. elegans require fixing and staining the animal. Here, we show that dark field images acquired through an ordinary light microscope can be used to estimate fat levels in worms. We define a metric based on the amount of light scattered per area, and show that this light scattering metric is strongly correlated with worm fat levels as measured by Oil Red O staining across a wide variety of genetic backgrounds and feeding conditions...
April 12, 2017: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/28399709/treponema-pallidum-ssp-pallidum-identification-by-real-time-pcr-targetting-the-pola-gene-in-paraffin-embedded-samples-positive-by-immunohistochemistry
#5
A Gama, E M Carrillo-Casas, R Hernández-Castro, V A Vázquez-Aceituno, S Toussaint-Caire, J Xicohtencatl-Cortes, R Fernández-Martínez, G Moreno-Coutiño
Syphilis is a systemic and sexually transmitted infection caused by Treponema pallidum ssp. pallidum. This spirochete causes different clinical and subclinical stages depending on the duration of infection and immune status of the host. Several tests have been developed for diagnosis, and are classified into direct and indirect methods. The first one includes dark field microscopy, direct fluorescent antibody test in fluids or tissue, and molecular biology techniques. In the indirect method (serologic), the routine tests are used, and are divided in two categories: non-treponemal and treponemal ones...
January 1, 2017: International Journal of STD & AIDS
https://www.readbyqxmd.com/read/28381980/effect-of-screw-threading-dislocations-and-inverse-domain-boundaries-in-gan-on-the-shape-of-reciprocal-space-maps
#6
Mykhailo Barchuk, Mykhaylo Motylenko, Gleb Lukin, Olf Pätzold, David Rafaja
The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature...
April 1, 2017: Journal of Applied Crystallography
https://www.readbyqxmd.com/read/28381030/near-field-spectral-properties-of-coupled-plasmonic-nanoparticle-arrays
#7
Han Yu, Quan Sun, Jinghuan Yang, Kosei Ueno, Tomoya Oshikiri, Atsushi Kubo, Yasutaka Matsuo, Qihuang Gong, Hiroaki Misawa
We investigated the grating effect in complex gold dolmen structures, in which multiple plasmon modes are present due to plasmon hybridization, experimentally from both the far field and the near field. In particular, the near-field properties were investigated using photoemission electron microscopy, and it was demonstrated that two hybridized plasmon modes on the dolmen structures could be influenced by the grating effect. For comparison, we also investigated the grating effect in arrays of simple nanoblocks and heptamer structures, which were supposed to support a strong bright plasmon mode and a strong dark plasmon mode, respectively, in the near field...
March 20, 2017: Optics Express
https://www.readbyqxmd.com/read/28367549/the-effect-of-sb-surfactant-on-gainp-cuptb-type-ordering-assessment-through-dark-field-tem-and-aberration-corrected-haadf-imaging
#8
C Coll, E Barrigón, L López-Conesa, J Rebled, L Barrutia, I Rey-Stolle, S Estradé, C Algora, F Peiró
We report on the effect of Sb on the microstructure of GaInP layers grown by metal organic vapor phase epitaxy (MOVPE). These layers exhibit a CuPtB single variant ordering due to the intentional misorientation of the substrate (Ge(001) substrates with 6° misorientation towards the nearest [111] axis). The use of Sb as a surfactant during the GaInP growth does not modify the type of ordering, but it is found that the order parameter (η) decreases with increasing Sb flux. Dark field microscopy reveals a variation of the angle of the antiphase boundaries (APBs) with Sb amount...
April 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28362786/dark-field-brillouin-microscopy
#9
Giuseppe Antonacci
Brillouin microscopy is a non-contact and label-free technique for mapping fundamental micro-mechanical properties in the volume of biological systems. Specular reflections and elastic scattering easily overwhelm the weak Brillouin spectra due to the limited extinction of virtually imaged phased array spectrometers, thereby affecting the image acquisition. In this Letter, a dark-field method was demonstrated to reject the elastic background light using an annular illumination and a confocal detection. To validate the method, images of polystyrene and liquid samples were obtained using both a confocal and the dark-field system...
April 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28351552/transformation-dynamics-of-ni-clusters-into-nio-rings-under-electron-beam-irradiation
#10
Daniel Knez, Philipp Thaler, Alexander Volk, Gerald Kothleitner, Wolfgang E Ernst, Ferdinand Hofer
We report the transformation of nickel clusters into NiO rings by an electron beam induced nanoscale Kirkendall effect. High-purity nickel clusters consisting of a few thousand atoms have been used as precursors and were synthesized with the superfluid helium droplet technique. Aberration-corrected, analytical scanning transmission electron microscopy was applied to oxidise and simultaneously analyse the nanostructures. The transient dynamics of the oxidation could be documented by time lapse series using high-angle annular dark-field imaging and electron energy-loss spectroscopy...
March 23, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28343390/high-performance-rh2p-electrocatalyst-for-efficient-water-splitting
#11
Haohong Duan, Dongguo Li, Yan Tang, Yang He, Shufang Ji, Rongyue Wang, Haifeng Lv, Pietro P Lopes, Arvydas P Paulikas, Haoyi Li, Scott X Mao, Chongmin Wang, Nenad M Markovic, Jun Li, Vojislav R Stamenkovic, Yadong Li
The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts...
April 5, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28342572/exploring-the-atomic-structure-of-1-8nm-monolayer-protected-gold-clusters-with-aberration-corrected-stem
#12
Jian Liu, Nan Jian, Isabel Ornelas, Alexander J Pattison, Tanja Lahtinen, Kirsi Salorinne, Hannu Häkkinen, Richard E Palmer
Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au144(SCH2CH2Ph)60 provided by two different research groups...
November 22, 2016: Ultramicroscopy
https://www.readbyqxmd.com/read/28322387/color-resolution-improvement-of-the-dark-field-microscopy-imaging-of-single-light-scattering-plasmonic-nanoprobes-for-microrna-visual-detection
#13
Jun Zhou, Peng Fei Gao, Hong Zhi Zhang, Gang Lei, Lin Ling Zheng, Hui Liu, Cheng Zhi Huang
Imaging of light scattering plasmonic nanoparticles (PNPs) with the aid of the dark-field microscopy imaging (iDFM) technique has attracted wide attention owing to its high signal-to-noise ratio, but to improve the color resolution and contrast of dark-field microscopy (DFM) images of single light scattering PNPs in a small spectral variation environment is still a challenge. In this study, a new color analytical method for resolving the resolution and contrast in DFM images has been developed and further applied for colorimetric analysis using the digital image processing technique...
March 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28317997/evidence-of-a-minority-monoclinic-lanio2-5-phase-in-lanthanum-nickelate-thin-films
#14
L López-Conesa, J M Rebled, D Pesquera, N Dix, F Sánchez, G Herranz, J Fontcuberta, C Magén, M J Casanove, S Estradé, F Peiró
LaNiO3 (LNO) thin films of 14 nm and 35 nm thicknesses grown epitaxially on LaAlO3 (LAO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) substrates are studied using High Resolution Transmission Electron Microscopy (HRTEM) and High Angle Annular Dark Field (HAADF) imaging. The strain state of the films is studied using Geometric Phase Analysis (GPA). Results show the successful in-plane adaptation of the films to the substrates, both in the compressive (LAO) and tensile (LSAT) cases. Through the systematic analysis of HRTEM superstructure contrast modulation along different crystal orientations, localized regions of the monoclinic LaNiO2...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28316409/facile-synthesis-of-multifunctional-silver-nanoparticles-using-mangrove-plant-excoecaria-agallocha-l-for-its-antibacterial-antioxidant-and-cytotoxic-effects
#15
R Bhuvaneswari, R John Xavier, M Arumugam
The current study describes a simple, rapid and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Excoecaria agallocha (E. agallocha) leaf extract as stabilizer, bioreductant and capping agent. Synthesized AgNPs were characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Generation of AgNPs was initially confirmed with the color change from yellow to dark brown which produces intense absorbance spectra at 440 nm in UV-Vis spectroscopy without any shifting of peaks...
March 2017: Journal of Parasitic Diseases: Official Organ of the Indian Society for Parasitology
https://www.readbyqxmd.com/read/28292688/hybrid-statistics-simulations-based-method-for-atom-counting-from-adf-stem-images
#16
Annelies De Wael, Annick De Backer, Lewys Jones, Peter D Nellist, Sandra Van Aert
A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions...
January 25, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28282549/atomic-resolution-chemical-mapping-of-ordered-precipitates-in-al-alloys-using-energy-dispersive-x-ray-spectroscopy
#17
Sigurd Wenner, Lewys Jones, Calin D Marioara, Randi Holmestad
Scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDS) is a common technique for chemical mapping in thin samples. Obtaining high-resolution elemental maps in the STEM is jointly dependent on stepping the sharply focused electron probe in a precise raster, on collecting a significant number of characteristic X-rays over time, and on avoiding damage to the sample. In this work, 80kV aberration-corrected STEM-EDS mapping was performed on ordered precipitates in aluminium alloys...
May 2017: Micron: the International Research and Review Journal for Microscopy
https://www.readbyqxmd.com/read/28273523/atomic-structure-and-chemistry-of-a-100-dislocation-cores-in-la2-3sr1-3mno3-films
#18
Kepeng Song, Kui Du, Hengqiang Ye
Oxide thin films with perovskite structures possess multifunctional properties, while defects in the films usually have significant influences on their physical properties. Here, the atomic structure and chemistry of a[100] dislocation cores in epitaxial La2/3Sr1/3MnO3 films were investigated by aberration-corrected scanning transmission electron microscopy combining with atomically resolved electron energy-loss spectroscopy imaging. The results demonstrated an edge dislocation terminated with Mn columns and significant nonstoichiometry at the dislocation core region...
May 2017: Micron: the International Research and Review Journal for Microscopy
https://www.readbyqxmd.com/read/28267641/graphene-supporting-films-and-low-voltage-stem-in-sem-toward-imaging-nanobio-materials-without-staining-observation-of-insulin-amyloid-fibrils
#19
Takashi Ogawa, Geun Won Gang, Minh Thu Thieu, Hyuksang Kwon, Sang Jung Ahn, Tai Hwan Ha, Boklae Cho
Utilization of graphene-supporting films and low-voltage scanning transmission electron microscopy (LV-STEM) in scanning electron microscopy (SEM) is shown to be an effective means of observing unstained nanobio materials. Insulin amyloid fibrils, which are implicated as a cause of type II diabetes, are formed in vitro and observed without staining at room temperature. An in-lens cold field-emission SEM, equipped with an additional homemade STEM detector, provides dark field (DF)-STEM images in the low energy range of 5-30keV, together with secondary electron (SE) images...
May 2017: Micron: the International Research and Review Journal for Microscopy
https://www.readbyqxmd.com/read/28258604/the-effect-of-lunisolar-tidal-acceleration-upon-stem-elongation-growth-nutations-and-leaf-movements-in-peppermint-mentha-%C3%A3-piperita-l
#20
Urszula Zajączkowska, Peter W Barlow
• Orbital movement of the Moon generates a system of gravitational fields which periodically alters the gravitational force on Earth. This lunar tidal acceleration (Etide) is known to act as an external environmental factor affecting many growth and developmental phenomena in plants. Our study has focused on the lunar tidal influence on stem elongation growth, nutations, and leaf movements of peppermint. • Plants were continuously recorded by time-lapse photography under constant illumination as well in constant illumination following five days of alternating dark-light cycles...
March 3, 2017: Plant Biology
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