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Dark field microscopy

Liang Zhu, Guohua Li, Yonghong He, Hui Tan, Shuqing Sun
A highly sensitive homogeneous method for DNA detection has been developed. The system relies on two kinds of gold nanorod (AuNR) probes with complementary DNA sequences to the target DNA. In the presence of the target DNA, two kinds of AuNR probes are assembling into dimers or small aggregates. The target-induced AuNR aggregate has higher scattering intensity than that of a single AuNR because of the plasmonic coupling effect. Dark field microscopy was utilized to image the single particle and measure its scattering intensity...
February 1, 2018: Talanta
Bin Wang, Rongjing Zhang, Junhua Yuan
Rotation of the bacterial flagellar motor is driven by multiple torque-generating units (stator elements). The torque-generating dynamics can be understood in terms of the "duty ratio" of the stator elements, that is, the fraction of time a stator element engages with the rotor during its mechanochemical cycle. The dependence of the limiting speed (zero-load speed) of the motor on the number of stator elements is the determining test of the duty ratio, which has been controversial experimentally and theoretically over the past decade...
November 6, 2017: Proceedings of the National Academy of Sciences of the United States of America
Ibrahim Javed, Yunxiang Sun, Jozef Adamcik, Bo Wang, Aleksandr Kakinen, Emily H Pilkington, Feng Ding, Raffaele Mezzenga, Thomas P Davis, Pu Chun Ke
Biomimetic nanocomposites and scaffolds hold the key to a wide range of biomedical applications. Here we show, for the first time, a facile scheme of cofibrillizing pathogenic and functional amyloid fibrils via gold nanoparticles (AuNPs) and their applications against amyloidogenesis. This scheme was realized by β-sheet stacking between human islet amyloid polypeptide (IAPP) and the β-lactoglobulin "corona" of the AuNPs, as revealed by transmission electron microscopy, 3D atomic force microscopy, circular dichroism spectroscopy, and molecular dynamics simulations...
November 14, 2017: Biomacromolecules
Eduardo Joaquim Lopes Alho, Ana Tereza Di Lorenzo Alho, Lea Grinberg, Edson Amaro, Gláucia Aparecida Bento Dos Santos, Rafael Emídio da Silva, Ricardo Caires Neves, Maryana Alegro, Daniel Boari Coelho, Manoel Jacobsen Teixeira, Erich Talamoni Fonoff, Helmut Heinsen
Stereotaxy is based on the precise image-guided spatial localization of targets within the human brain. Even with the recent advances in MRI technology, histological examination renders different (and complementary) information of the nervous tissue. Although several maps have been selected as a basis for correlating imaging results with the anatomical locations of sub-cortical structures, technical limitations interfere in a point-to-point correlation between imaging and anatomy due to the lack of precise correction for post-mortem tissue deformations caused by tissue fixation and processing...
November 1, 2017: Brain Structure & Function
A A Sheader, A M Varambhia, R A Fleck, S J L Flatters, P D Nellist
The chemotherapeutics cisplatin and oxaliplatin are important tools in the fight against cancer. Both compounds are platinum complexes. Aberration-corrected scanning transmission electron microscopy using the annular dark-field imaging mode now routinely provides single-atom sensitivity with atomic number contrast. Here, this imaging mode is used to directly image the platinum within the two drugs in their dried form on an amorphous carbon support film. The oxaliplatin is found to have wetted the supporting amorphous carbon, forming disordered clusters suggesting that the platinum has remained within the complex...
November 1, 2017: Journal of Microscopy
Tim Grieb, Moritz Tewes, Marco Schowalter, Knut Müller-Caspary, Florian F Krause, Thorsten Mehrtens, Jean-Michel Hartmann, Andreas Rosenauer
The chemical composition of four Si1-xGex layers grown on silicon was determined from quantitative scanning transmission electron microscopy (STEM). The chemical analysis was performed by a comparison of the high-angle annular dark field (HAADF) intensity with multislice simulations. It could be shown that amorphous surface layers originating from the preparation process by focused-ion beam (FIB) at 30 kV have a strong influence on the quantification: the local specimen thickness is overestimated by approximately a factor of two, and the germanium concentration is substantially underestimated...
October 13, 2017: Ultramicroscopy
Ryo Sekine, Katie L Moore, Marianne Matzke, Pascal Vallotton, Haibo Jiang, Gareth M Hughes, Jason K Kirby, Erica Donner, Chris R M Grovenor, Claus Svendsen, Enzo Lombi
Increasing consumer use of engineered nanomaterials has led to significantly increased efforts to understand their potential impact on the environment and living organisms. Currently, no individual technique can provide all the necessary information such as their size, distribution, and chemistry in complex biological systems. Consequently, there is a need to develop complementary instrumental imaging approaches that provide enhanced understanding of these "bio-nano" interactions to overcome the limitations of individual techniques...
November 13, 2017: ACS Nano
Hyung-Jun Kim, Hojoong Kim, Suk Yang, Jang-Yeon Kwon
Transition metal dichalcogenides (TMDCs) have recently been studied using various synthesis methods, such as chemical vapor deposition for large-scale production. Despite the realization of large-scale production with high material quality, a range of approaches have been made to solve the patterning issue of TMDCs focusing on the application of integrated devices; however, patterning is still under study to accurately represent nanoscale-sized patterns, as well as the desired positions and shapes. Here, an insulating substrate is treated selectively with O2 plasma, and MoS2 growth is induced in the superhydrophilic area...
October 23, 2017: Small
Naila A Mugheirbi, Patrick J Marsac, Lynne S Taylor
For amorphous solid dispersions, understanding the phase behavior of a given drug-polymer blend and factors that influence miscibility is crucial to designing an optimally performing formulation. However, it can be challenging to fully map the phase behavior of some systems, especially those produced using a cosolvent system. In this study, a comprehensive investigation of phase separation in itraconazole-hydroxypropylmethylcellulose (ITZ-HPMC) blends fabricated using solvent evaporation processes, including spin coating and spray drying, has been carried out...
November 8, 2017: Molecular Pharmaceutics
Namkje A R Vellinga, E Christiaan Boerma, Matty Koopmans, Abele Donati, Arnaldo Dubin, Nathan I Shapiro, Rupert M Pearse, Peter H J van der Voort, Arjen M Dondorp, Tony Bafi, Michael Fries, Tulin Akarsu-Ayazoglu, Andrius Pranskunas, Steven Hollenberg, Gianmarco Balestra, Mat van Iterson, Farid Sadaka, Gary Minto, Ulku Aypar, F Javier Hurtado, Giampaolo Martinelli, Didier Payen, Frank van Haren, Anthony Holley, Hernando Gomez, Ravindra L Mehta, Alejandro H Rodriguez, Carolina Ruiz, Héctor S Canales, Jacques Duranteau, Peter E Spronk, Shaman Jhanji, Sheena Hubble, Marialuisa Chierego, Christian Jung, Daniel Martin, Carlo Sorbara, Jan Bakker, Can Ince
BACKGROUND: Mildly elevated lactate levels (i.e., 1-2 mmol/L) are increasingly recognized as a prognostic finding in critically ill patients. One of several possible underlying mechanisms, microcirculatory dysfunction, can be assessed at the bedside using sublingual direct in vivo microscopy. We aimed to evaluate the association between relative hyperlactatemia, microcirculatory flow, and outcome. METHODS: This study was a predefined subanalysis of a multicenter international point prevalence study on microcirculatory flow abnormalities, the Microcirculatory Shock Occurrence in Acutely ill Patients (microSOAP)...
October 18, 2017: Critical Care: the Official Journal of the Critical Care Forum
M Lee, R Arras, B Warot-Fonrose, T Hungria, M Lippmaa, H Daimon, M J Casanove
The structure of Ir-doped LaAlO3/SrTiO3(001) interfaces was investigated on the atomic scale using probe-corrected transmission electron microscopy in high-angle annular dark-field scanning mode (HAADF-STEM) and electron energy loss spectroscopy (EELS), combined with first-principles calculations. We report the evolution of the strain state experimentally measured in a 5 unit-cell thick LaAlO3 film as a function of the Ir concentration in the topmost SrTiO3 layer. It is shown that the LaAlO3 layers remain fully elastically strained up to 3% of Ir doping, whereas a higher doping level seems to promote strain relaxation through enhanced cationic interdiffusion...
November 1, 2017: Physical Chemistry Chemical Physics: PCCP
Eileen Otte, Kemal Tekce, Cornelia Denz
Vector beams are of major importance to tailor tightly focused fields by creating an additional z-polarization component. Till now, mainly focusing properties of fundamental vector beams have been investigated, whereas the knowledge of focused higher-order singular vector fields is still missing. We fill this gap by numerical analysis of these fields, applying their attractive characteristics as including a spatially adjustable amount of radial and azimuthal components. We demonstrate the realization of three-dimensional polarization structures whose total intensity resembles dark stars and bright flowers...
August 21, 2017: Optics Express
Nicolas Crespo-Monteiro, Anthony Cazier, Francis Vocanson, Yaya Lefkir, Stéphanie Reynaud, Jean-Yves Michalon, Thomas Kämpfe, Nathalie Destouches, Yves Jourlin
The microstructuring of the distribution of silver nanoparticles (NPs) in mesoporous titania films loaded with silver salts, using two-beam interference lithography leading to 1 Dimension (1D) grating, induces variations in the photocatalytic efficiency. The influence of the structuration was tested on the degradation of methyl blue (MB) under ultraviolet (UV) and visible illumination, giving rise to a significant improvement of the photocatalytic efficiency. The periodic distribution of the NPs was characterized by transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM)...
October 17, 2017: Nanomaterials
Michael Hessler, Philip-Helge Arnemann, Sebastian Rehberg, Christian Ertmer
There is increasing evidence in the literature that preoperative treatment with levosimendan optimizes cardiopulmonary haemodynamics in patients scheduled for the implantation of a Left Ventricular Assist Device (LVAD). The present case report describes changes in sublingual microcirculation using incident dark field video microscopy in a patient, who received a continuous infusion of 0.5 mg/h levosimendan 12 h before LVAD implantation. Despite no evident macrohaemodynamic or metabolic changes, there was a dramatic reduction in total vessel density and perfused vessel density suggesting a deterioration of microcirculation according to the consensus conference criteria in vessels smaller than 20 μm in diameter...
October 7, 2017: Clinical Hemorheology and Microcirculation
Khoa D Tran, Yan Li, Jeffrey D Holiman, Maolong Tang, David Huang, Michael D Straiko, Christopher G Stoeger
Irradiated corneal tissues have been used for a variety of ophthalmic procedures including glaucoma drainage device covers and lamellar grafts. The maintenance of corneal clarity is important, as light obstructions resulting from processing or long-term storage of irradiated corneas may negatively affect vision and postoperative cosmesis. It has been reported that corneal tissues can be preserved in human serum albumin (HSA), however, the clarity of corneas after long-term storage in HSA has not been well described...
October 12, 2017: Cell and Tissue Banking
Fangyao Hu, Hannah Martin, Amy Frees Martinez, Jeffrey Everitt, Alaattin Erkanli, Walter T Lee, Mark W Dewhirst, Nirmala Ramanujam
There remain gaps in knowledge concerning how vascular morphology evolves during carcinogenesis. In this study, we imaged neovascularization by label-free dark field microscopy of a DMBA-induced hamster cheek pouch model of oral squamous cell carcinoma (SCC). Wavelength-dependent imaging revealed distinct vascular features at different imaging depths and vessel sizes. Vascular tortuosity increased significantly in high-risk lesions, while diameter decreased significantly in hyperplastic and SCC lesions. Large vessels preserved the same trends seen in the original images, whereas small vessels displayed different trends, with length and diameter increasing during carcinogenesis...
October 11, 2017: Cancer Research
Nadav Elad, Giuliano Bellapadrona, Lothar Houben, Irit Sagi, Michael Elbaum
Metal ions play essential roles in many aspects of biological chemistry. Detecting their presence and location in proteins and cells is important for understanding biological function. Conventional structural methods such as X-ray crystallography and cryo-transmission electron microscopy can identify metal atoms on protein only if the protein structure is solved to atomic resolution. We demonstrate here the detection of isolated atoms of Zn and Fe on ferritin, using cryogenic annular dark-field scanning transmission electron microscopy (cryo-STEM) coupled with single-particle 3D reconstructions...
October 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
Tzu-Heng Chen, Wei-Lung Tseng
This study describes a bottom-up assembly route for monodisperse carbon dots (CDs) into different sizes of CD aggregates through the control of the concentration of fatty acids. The highly monodisperse CDs were prepared via solvent-thermal treatment of edible soybean oil, which generated glycerol-based polymer as a carbon source and fatty acid as a surface capping in the synthetic process. The as-synthesized CDs exhibited small particle size variation (2.7 ± 0.2 nm) and narrow emission bands (full width at half-maximum <20 nm)...
November 7, 2017: Analytical Chemistry
Deepak Gola, Anushree Malik, Maneesh Namburath, Shaikh Ziauddin Ahammad
Presence of industrial dyes and heavy metal as a contaminant in environment poses a great risk to human health. In order to develop a potential technology for remediation of dyes (Reactive remazol red, Yellow 3RS, Indanthrene blue and Vat novatic grey) and heavy metal [Cu(II), Ni(II), Cd(II), Zn(II), Cr(VI) and Pb(II)] contamination, present study was performed with entomopathogenic fungi, Beauveria bassiana (MTCC no. 4580). High dye removal (88-97%) was observed during the growth of B. bassiana while removal percentage for heavy metals ranged from 58 to 75%...
October 1, 2017: Environmental Science and Pollution Research International
Qieni Lu, Bihua Li, Zhen Li, Baozhen Ge
We report the lifetime enhancement of light-induced refractive index grating by applying a bias field during writing. In comparison with the lifetime of about 10 hours of the photorefractive grating prepared without a bias field, the lifetime of the grating with a 4  kV/cm bias field can be prolonged to 7.5 years, which is obtained from the dynamic behavior of grating visualized and monitored with digital holographic microscopy. The higher the bias field is applied, the longer the dark decay time of grating can be achieved...
July 1, 2017: Optics Letters
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