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Dark field microscopy

Eduardo Ortega, Jesús Cantu-Valle, Germán Plascencia-Villa, Sandra Vergara, Fernando Mendoza-Santoyo, Alejandra Londono-Calderon, Ulises Santiago, Arturo Ponce
In the current work, irregular morphology of Staphylococcus aureus bacteria has been visualized by phase retrieval employing off-axis electron holography (EH) and 3D reconstruction electron tomography using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Bacteria interacting with gold nanoparticles (AuNP) acquired a shrunken or irregular shape due to air dehydration processing. STEM imaging shows the attachment of AuNP on the surface of cells and suggests an irregular 3D morphology of the specimen...
August 11, 2017: Microscopy Research and Technique
Nader Elmelegy, Dalia Mohamed Mofreh El Sakka
BACKGROUND: Hypopigmentation is a troublesome often-permanent sequelae after burn injury, particularly in dark races. A number of methods have been described to treat this phenomenon. In this work, we are going to study the effect of E light (intensive pulsed light+radiofrequency+cooling) in repigmentation of partial thickness and full thickness burn wounds in adult patients and light microscopic changes of biopsy material at various stages of repigmentation. PATIENTS AND METHODS: In this study, 24 patients with postburn hypopigmentation were selected and E light was used, using different filters, according to the skin color...
September 2017: Annals of Plastic Surgery
So Young Lee, Yeji Han, Jong Wook Hong, Ji Won Ha
Plasmonic gold bipyramids (AuBPs) with sharp tips are promising orientation probes in biological studies because of their anisotropic shape, strong electric field enhancement at the tips, and convenient manipulation into other shapes. Herein, we elucidate the optical properties of single AuBPs at their localized surface plasmon resonance (LSPR) wavelengths using dark-field (DF) microscopy and differential interference contrast (DIC) microscopy and test their use as orientation probes in a dynamic biological environment...
August 10, 2017: Nanoscale
Daeseong Jung, Jun-Ho Choi, Soocheol Kim, Suho Ryu, Wonchan Lee, Jong-Seok Lee, Chulmin Joo
We present a portable multi-contrast microscope capable of producing bright-field, dark-field, and differential phase contrast images of thin biological specimens on a smartphone platform. The microscopy method is based on an imaging scheme termed "color-coded light-emitting-diode (LED) microscopy (cLEDscope)," in which a specimen is illuminated with a color-coded LED array and light transmitted through the specimen is recorded by a color image sensor. Decomposition of the image into red, green, and blue colors and subsequent computation enable multi-contrast imaging in a single shot...
August 8, 2017: Scientific Reports
Yifan Sun, Kazunori Fujisawa, Zhong Lin, Yu Lei, Jared S Mondschein, Mauricio Terrones, Raymond E Schaak
Nanostructures of layered transition metal dichalcogenide (TMD) alloys with tunable compositions are promising candidates for a broad scope of applications in electronics, optoelectronics, topological devices, and catalysis. Most TMD alloy nanostructures are synthesized as films on substrates using gas-phase methods at high temperatures. However, lower temperature solution routes present an attractive alternative with the potential for larger-scale, higher-yield syntheses of freestanding, higher surface area materials...
August 16, 2017: Journal of the American Chemical Society
Lian Shen, Huaping Wang, Rujiang Li, Zhiwei Xu, Hongsheng Chen
Sensitive detection of features in a nanostructure may sometimes be puzzled in the presence of significant background noise. In this regard, background suppression and super-resolution are substantively important for detecting weakly scattering nanoscale features. Here, we present a lens design, termed hyperbolic-polaritons-enabled dark-field lens (HPEDL), which has the ability to accomplish straightforward sensitive detection. This HPEDL structure consists of type I and type II hyperbolic media that support high-k field waves via hyperbolic polaritons (HPs)...
August 1, 2017: Scientific Reports
Tianfeng Hua, Xiaobo Wu, Wei Wang, Hao Li, Jennifer Bradley, Mary Ann Peberdy, Joseph P Ornato, Wanchun Tang
Microcirculation is the motor of sepsis. In the present study, we investigated whether microcirculatory alterations occur prior to changes of systemic hemodynamics in a rat model of cecum ligation and puncture (CLP)-induced sepsis. We further investigated renal microcirculatory changes during sepsis and compared those with buccal microcirculation. Twelve male Sprague-Dawley rats were randomized into a sham control group (n = 6) and a CLP group (n = 6). Perfused microvessel density (PVD) and microvascular flow index (MFI) were evaluated using sidestream dark field (SDF) video microscopy at baseline, 60, 120, 180, 240, 300, and 360 minutes following CLP...
July 20, 2017: Shock
Kyung Jin Park, Ji-Hyeok Huh, Dae-Woong Jung, Jin-Sung Park, Gwan H Choi, Gaehang Lee, Pil J Yoo, Hong-Gyu Park, Gi-Ra Yi, Seungwoo Lee
Atomic force microscopy (AFM) nanomanipulation has been viewed as a deterministic method for the assembly of plasmonic metamolecules because it enables unprecedented engineering of clusters with exquisite control over particle number and geometry. Nevertheless, the dimensionality of plasmonic metamolecules via AFM nanomanipulation is limited to 2D, so as to restrict the design space of available artificial electromagnetisms. Here, we show that "2D" nanomanipulation of the AFM tip can be used to assemble "3D" plasmonic metamolecules in a versatile and deterministic way by dribbling highly spherical and smooth gold nanospheres (NSs) on a nanohole template rather than on a flat surface...
July 20, 2017: Scientific Reports
Sk Md Equeenuddin, Binaya Kumar Pattnaik
The Sukinda ultramafic complex in Odisha has the largest chromite reserve in India. Sediment derived from ultramafic rocks has been enriched with various metals. Further, mining activities enhance the influx of metals into sediment by dumping mine overburden and tailings in the open area. Metal concentration in sediment is found in order of CrTotal(Cr) > Mn > Ni > Co > Zn > Cu with average concentration 26,778 mg/kg, 3098 mg/kg, 1813 mg/kg, 184 mg/kg, 116 mg/kg and 44 mg/kg respectively...
October 2017: Chemosphere
J Cui, Y Yao, Y G Wang, X Shen, R C Yu
The effects of the tilt of the crystallographic orientation with respect to an incident electron probe on high-angle annular dark field (HAADF) imaging in aberration-corrected scanning transmission electron microscopy (STEM) have been investigated with experiments and simulations. A small specimen tilt can lead to unequal deviations of different atom species in the HAADF image and result in further relative displacement between anions and cations. Simulated HAADF images also confirm that the crystal tilt causes an artifact in atom polarization as well...
July 3, 2017: Ultramicroscopy
Astrid Avellan, Fabienne Schwab, Armand Masion, Perrine Chaurand, Daniel Borschneck, Vladimir Vidal, Jérôme Rose, Catherine Santaella, Clément Levard
Terrestrial plants can internalize and translocate nanoparticles (NPs). However, direct evidence for the processes driving the NP uptake and distribution in plants is scarce at the cellular level. Here, NP-root interactions were investigated after 10 days of exposure of Arabidopsis thaliana to 10 mg·L(-1) of negatively or positively charged gold NPs (∼12 nm) in gels. Two complementary imaging tools were used: X-ray computed nanotomography (nano-CT) and enhanced dark-field microscopy combined with hyperspectral imaging (DF-HSI)...
July 20, 2017: Environmental Science & Technology
Y Ohno, K Inoue, K Fujiwara, K Kutsukake, M Deura, I Yonenaga, N Ebisawa, Y Shimizu, K Inoue, Y Nagai, H Yoshida, S Takeda, S Tanaka, M Kohyama
We have developed an analytical method to determine the segregation levels on the same tilt boundaries (TBs) at the same nanoscopic location by a joint use of atom probe tomography and scanning transmission electron microscopy, and discussed the mechanism of oxygen segregation at TBs in silicon ingots in terms of bond distortions around the TBs. The three-dimensional distribution of oxygen atoms was determined at the typical small- and large-angle TBs by atom probe tomography with a low impurity detection limit (0...
July 7, 2017: Journal of Microscopy
Louis Kolb, Diego Orbegozo, Jacques Creteur, Jean-Charles Preiser, Jean-Louis Vincent, Daniel De Backer
Nitric oxide (NO) plays an important role in controlling microcirculatory function, but the effects of exogenous administration of nitrate (NO3-) on the microcirculation have not been well studied. We evaluated whether NO3- could influence the microvascular response to hypoxia in 17 healthy volunteers. We used a vascular occlusion test (VOT) to assess the response of near-infrared spectroscopy-derived indexes to hypoxic stress before and 2 h 15 min after oral administration of 800 mg potassium nitrate. We also monitored changes in the sublingual microcirculation using side-stream dark-field (SDF) video microscopy...
July 7, 2017: Journal of Vascular Research
Naoya Shibata, Scott D Findlay, Takao Matsumoto, Yuji Kohno, Takehito Seki, Gabriel Sánchez-Santolino, Yuichi Ikuhara
The functional properties of materials and devices are critically determined by the electromagnetic field structures formed inside them, especially at nanointerface and surface regions, because such structures are strongly associated with the dynamics of electrons, holes and ions. To understand the fundamental origin of many exotic properties in modern materials and devices, it is essential to directly characterize local electromagnetic field structures at such defect regions, even down to atomic dimensions...
July 5, 2017: Accounts of Chemical Research
Ryan J Wu, Anudha Mittal, Michael L Odlyzko, K Andre Mkhoyan
Sub-angstrom scanning transmission electron microscopy (STEM) allows quantitative column-by-column analysis of crystalline specimens via annular dark-field images. The intensity of electrons scattered from a particular location in an atomic column depends on the intensity of the electron probe at that location. Electron beam channeling causes oscillations in the STEM probe intensity during specimen propagation, which leads to differences in the beam intensity incident at different depths. Understanding the parameters that control this complex behavior is critical for interpreting experimental STEM results...
July 4, 2017: Microscopy and Microanalysis
Maryam Vatanparast, Ricardo Egoavil, Turid W Reenaas, Johan Verbeeck, Randi Holmestad, Per Erik Vullum
In the present work Cs aberration corrected and monochromated scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) has been used to explore experimental set-ups that allow bandgaps of high refractive index materials to be determined. Semi-convergence and -collection angles in the µrad range were combined with off-axis or dark field EELS to avoid relativistic losses and guided light modes in the low loss range to contribute to the acquired EEL spectra. Off-axis EELS further supressed the zero loss peak and the tail of the zero loss peak...
June 20, 2017: Ultramicroscopy
Javier Reguera, Dorleta Jiménez de Aberasturi, Malou Henriksen-Lacey, Judith Langer, Ana Espinosa, Boguslaw Szczupak, Claire Wilhelm, Luis M Liz-Marzán
The design of compact nanoprobes for multimodal bioimaging is a current challenge and may have a major impact on diagnostics and therapeutics. Multicomponent gold-iron oxide nanoparticles have shown high potential as contrast agents in numerous imaging techniques due to the complementary features of iron oxide and gold nanomaterials. In this paper we describe novel gold-iron oxide Janus magnetic-plasmonic nanoparticles as versatile nanoprobes for multimodal imaging. The nanoparticles are characterized as contrast agents for different imaging techniques, including X-ray computed tomography (CT), T2-weighted nuclear magnetic resonance imaging (MRI), photoacoustic imaging (PA), dark-field and bright-field optical microscopy, transmission electron microscopy (TEM), and surface enhanced Raman spectroscopy (SERS)...
July 13, 2017: Nanoscale
Jeremy R Poindexter, Robert L Z Hoye, Lea Nienhaus, Rachel C Kurchin, Ashley E Morishige, Erin E Looney, Anna Osherov, Juan-Pablo Correa-Baena, Barry Lai, Vladimir Bulović, Vladan Stevanović, Moungi G Bawendi, Tonio Buonassisi
The relationship between charge-carrier lifetime and the tolerance of lead halide perovskite (LHP) solar cells to intrinsic point defects has drawn much attention by helping to explain rapid improvements in device efficiencies. However, little is known about how charge-carrier lifetime and solar cell performance in LHPs are affected by extrinsic defects (i.e., impurities), including those that are common in manufacturing environments and known to introduce deep levels in other semiconductors. Here, we evaluate the tolerance of LHP solar cells to iron introduced via intentional contamination of the feedstock and examine the root causes of the resulting efficiency losses...
July 25, 2017: ACS Nano
Chenhao Zhang, Junwei Sha, Huilong Fei, Mingjie Liu, Sadegh Yazdi, Jibo Zhang, Qifeng Zhong, Xiaolong Zou, Naiqin Zhao, Haisheng Yu, Zheng Jiang, Emilie Ringe, Boris I Yakobson, Juncai Dong, Dongliang Chen, James M Tour
The cathodic oxygen reduction reaction (ORR) is essential in the electrochemical energy conversion of fuel cells. Here, through the NH3 atmosphere annealing of a graphene oxide (GO) precursor containing trace amounts of Ru, we have synthesized atomically dispersed Ru on nitrogen-doped graphene that performs as an electrocatalyst for the ORR in acidic medium. The Ru/nitrogen-doped GO catalyst exhibits excellent four-electron ORR activity, offering onset and half-wave potentials of 0.89 and 0.75 V, respectively, vs a reversible hydrogen electrode (RHE) in 0...
July 25, 2017: ACS Nano
Jiangkun Fan, Jinshan Li, Yudong Zhang, Hongchao Kou, Jaafar Ghanbaja, Weimin Gan, Lionel Germain, Claude Esling
For the β phase of Ti-5553-type metastable β-Ti alloys, striations in transmission electron microscopy (TEM) bright- and dark-field images have been frequently observed but their origin has not been sufficiently investigated. In the present work, this phenomenon is studied in depth from the macroscopic scale by neutron diffraction to the atomic scale by high-resolution TEM. The results reveal that the β phase contains homogeneously distributed modulated structures, intermediate between that of the β phase (cubic) and that of the α phase or the ω phase (hexagonal), giving rise to the appearance of additional diffraction spots at 1/2, 1/3 and 2/3 β diffraction positions...
June 1, 2017: Journal of Applied Crystallography
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