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Journal of Microscopy

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https://www.readbyqxmd.com/read/30431166/effects-of-object-to-detector-distance-and-beam-energy-on-synchrotron-radiation-phase-contrast-imaging-of-implanted-cochleae
#1
S Alireza Rohani, John E Iyaniwura, Ning Zhu, Sumit K Agrawal, Hanif M Ladak
OBJECTIVES: To demonstrate that synchrotron radiation phase-contrast imaging (SR-PCI) can be used to visualize the intrascalar structures in implanted human cochleae and to find the optimal combination of the parameters object-to-detector distance (ODD) and beam energy (E) for visualization. MATERIALS AND METHODS: Three cadaveric implanted human temporal bones underwent SR-PCI with varying combinations of parameters ODD (3, 2 and 1 m) and E (47, 60 and 72 keV). All images were then reconstructed to a three-dimensional (3D) stack of slices...
November 15, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30417401/open-source-3d-printed-focussing-mechanism-for-cellphone-based-cellular-microscopy
#2
Y K Jawale, U Rapol, C A Athale
The need to improve access to microscopes in low-resource and educational settings coupled with the global proliferation of camera-enabled cellphones has recently led to an explosion in new developments in portable, low-cost microscopy. The availability of accurate ball lenses has resulted in many variants of van Leeuwenhoek-like microscopes. Combined with cellphones, they have the potential for use as portable microscopes in education and clinics. The need for reproducibility in such applications implies that control over focus is critical...
November 12, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30417390/fib-sem-imaging-properties-of-drosophila-melanogaster-tissues-embedded-in-lowicryl-hm20
#3
F Porrati, D Grewe, A Seybert, A S Frangakis, M Eltsov
Lowicryl resins enable processing of biological material for electron microscopy at the lowest temperatures compatible with resin embedding. When combined with high-pressure freezing and freeze-substitution, Lowicryl embedding supports preservation of fine structural details and fluorescent markers. Here, we analysed the applicability of Lowicryl HM20 embedding for focused ion beam (FIB) scanning electron microscopy (SEM) tomography of Drosophila melanogaster embryonic and larval model systems. We show that the freeze-substitution with per-mill concentrations of uranyl acetate provided sufficient contrast and an image quality of SEM imaging in the range of similar samples analysed by transmission electron microscopy (TEM)...
November 12, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30417387/influence-of-the-crosstalk-on-the-intensity-of-haadf-stem-images-of-quaternary-semiconductor-materials
#4
N Baladés, M Herrera, D L Sales, M P Guerrero, E Guerrero, P L Galindo, S I Molina
The influence of the neighbouring atomic-columns in determining the composition at atomic column scale of quaternary semiconductor compounds, using simulated HAADF-STEM images is evaluated. The InAlAsSb alloy, a promising material in the photovoltaic field, is considered. We find that the so called 'crosstalk' effect plays an important role for the aimed compositional determination. The intensity transfer is larger from neighbouring atomic columns with higher average Z, and towards atomic columns with smaller Z...
November 12, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30353546/relationship-between-the-anisotropy-tensor-calculated-through-global-and-object-measurements-in-high-resolution-x-ray-tomography-on-cellular-and-composite-materials
#5
F DE Pascalis, M Nacucchi
Structural anisotropy of two-phase materials can be evaluated through global measurements, as volume orientation or mean-intercept length methods do, or through statistics performed on a set of individual measurements. This last procedure is encouraged by recent improvements in the spatial resolution of conventional X-ray tomography. In this paper, the above-described approaches were compared in three case studies: a foam subjected to an in situ compression test, a second foam with a completely different cell morphology and a plastic material reinforced with short fibres...
October 24, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30320891/exploring-the-potential-of-neutron-imaging-for-life-sciences-on-imat
#6
G Burca, S Nagella, T Clark, D Tasev, I A Rahman, R J Garwood, A R T Spencer, M J Turner, J F Kelleher
Neutron imaging has been employed in life sciences in recent years and has proven to be a viable technique for studying internal features without compromising integrity and internal structure of samples in addition to being complementary to other methods such as X-ray or magnetic resonance imaging. Within the last decade, a neutron imaging beamline, IMAT, was designed and built at the ISIS Neutron and Muon Source, UK, to meet the increasing demand for neutron imaging applications in various fields spanning from materials engineering to biology...
October 15, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30295315/quantitative-colocalization-analysis-of-dna-delivery-by-pei-mediated-cationic-polymers-in-mammalian-cells
#7
I González-Domínguez, L Cervera, F Gòdia, M Roldán
Although cationic polymers are widely used for DNA delivery, the relationship between the properties of the formed complexes and their biological activity is not fully understood. Here, we propose a novel procedure consisting of superresolved images coupled with quantitative colocalization to analyse DNA release in living cells. This work compares the different workflows available in a quantitative colocalization study of DNA delivery using polyethylenimine as transfection reagent. A nimble workflow with deconvolution in three-dimensional images was developed...
October 8, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30252129/removal-of-carbon-contamination-in-etem-by-introducing-ar-during-electron-beam-irradiation
#8
T Tokunaga, K Saito, K Kuno, K Higuchi, Y Yamamoto, T Yamamoto
Organic materials, including carbon, exist inside the transmission electron microscope (TEM) chamber and are adsorbed onto samples under observation during TEM. When these adsorbed organic materials are irradiated by an electron beam, the adsorbed gas is decomposed. Carbon atoms remain on the sample and bond with each other forming a material with an amorphous structure. Due to the carbon deposition on the observation area of the sample, it is contaminated and the TEM image quality is decreased. Ar was introduced into environmental TEM (ETEM) to purge organic material from the sample chamber to reduce contamination growth...
September 25, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30252126/calculations-of-second-harmonic-generation-with-radially-polarized-excitations-by-elliptical-mirror-focusing
#9
W Wang, B Wu, P Liu, J Liu, J Tan
Second harmonic generation (SHG) polarization intensity distribution illuminated with radially polarized beams by lens focusing appears two peaks, when the nonlinear optical coefficients dominate that is relevant to the transverse electric field components. Such two peaks pattern may result in ghosting and the decrement of imaging resolution. In this paper, an elliptical mirror based system is proposed in the case of radially polarized beams illumination for SHG. The calculated predictions and numerical simulations demonstrate that for radially polarized beams, the proportion of transverse field components at the focal plane under the condition of elliptical mirror focusing is 2...
September 25, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30240001/practical-implementation-of-the-planar-and-spatial-rotator-in-a-complex-tissue-the-brain
#10
S Hasselholt, U Hahn, E B Vedel Jensen, J R Nyengaard
In neuroscience, application of widely used stereological local volume estimators, including the planar rotator, is challenged by the combination of a complex tissue organisation and an estimator requirement of either isotropic or vertical sections, i.e. randomly oriented tissue. The spatial rotator is applicable with any tissue orientation but is sensitive to projection artefacts. The challenge is thus to select the most appropriate method for individual analyses. In this study, agreement between estimates of mean cell volume acquired with the vertical planar and the spatial rotator is assessed for two brain regions with different types of cytoarchitecture (motor cortex and hippocampal cornu ammonis 1)...
September 21, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30192016/nonmechanical-and-multiview-3d-measurement-microscope-for-workpiece-with-large-slope-and-complex-geometry
#11
Y Qu, Y Hu, P Zhang
Due to the large slope and complex geometry, it is difficult to measure the three-dimensional parameters of cutting tools and drill bits by using general optical measurement method. A method that combines the multiview rotation scanning and nonmechanical focus variation by using a liquid lens is proposed in this paper. Firstly, the workpiece is rotated by using a rotation unit, and in every rotation position, a sequence of images of the workpiece are captured in the axial direction. Secondly, the relative degree of focus is measured for all pixels by using focus measure operators to obtain the depth value corresponding to each pixel...
September 7, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30191999/photophysical-properties-of-na-indicator-dyes-suitable-for-quantitative-two-photon-fluorescence-lifetime-measurements
#12
G Naumann, K Lippmann, J Eilers
Two-photon microscopy (2PM) offers great potential in fluorescence imaging of intracellular Na+ dynamics of live cells. A severe drawback, however, is that quantitative ratioing of fluorescence intensities at different wavelengths [possible in one-photon imaging with the classical Na+ -indicator dye sodium-binding benzofuran isophtalate (SBFI)] is not practical in 2PM. We aimed at establishing 2PM-based time-correlated fluorescence lifetime measurements as an alternative method for quantifying Na+ dynamics...
September 7, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30153327/signal-noise-and-resolution-in-linear-and-nonlinear-structured-illumination-microscopy
#13
E A Ingerman, R A London, R Heintzmann, M G L Gustafsson
Structured-illumination microscopy allows widefield fluorescence imaging with resolution beyond the classical diffraction limit. Its linear form extends resolution by a factor of two, and its nonlinear form by an in-principle infinite factor, the effective resolution in practice being determined by noise. In this paper, we analyse the noise properties and achievable resolution of linear and nonlinear 1D and 2D patterned SIM from a frequency-space perspective. We develop an analytical theory for a general case of linear or nonlinear fluorescent imaging, and verify the analytical calculations with numerical simulation for a special case where nonlinearity is produced by photoswitching of fluorescent labels...
August 28, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30129975/self-consistent-absorption-correction-for-quantifying-very-noisy-x-ray-maps-group-iii-nitride-nanowires-as-an-example
#14
X Wang, J Bai, T Walther
Energy-dispersive X-ray mapping in a scanning transmission electron microscope is a method to visualize the spatial distribution of chemical elements in a sample. Quantification of the signal intensities depends on proper background elimination and correction of the self-absorption and fluorescence of X-ray lines in the sample. The latter become particularly relevant for slightly thicker and rough samples, small take-off angles and low-energetic X-ray lines, for which we have recently introduced a self-consistent absorption correction based on effective k*-factors selected automatically from curves simulated as function of a K/L line intensity ratio of one of the heavier elements in the sample for ranges of different compositions...
August 21, 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30338534/enhancement-of-fluorescence-emission-difference-microscopy-using-conjugated-vortex-phase-modulation
#15
D Zhu, W Liu, Z Zhang, C Zheng, Y Chen, C Li, C Kuang, J Fan, Y Xu, X Liu, A Hussain
In this paper, we propose and demonstrate an improved fluorescence emission difference microscopy (FED) method, exploiting programmable phase modulation for image enhancement. The main novelty of the proposed approach lies in the matched size and intensity of two excitation spots. The proposed method improves the FED performance on image quality via artefact elimination. We demonstrate the feasibility of this method through theoretical studies and experimental tests. The experimental results of nanobeads and cells validate the practical performance of this method, which can enable reliable observations at superresolution in biomedical studies...
November 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30338530/superior-robustness-of-exem-spfret-to-iiem-spfret-method-in-live-cell-fret-measurement
#16
F Lin, C Zhang, M DU, L Wang, Z Mai, T Chen
We recently developed two quantitative fluorescence resonance energy transfer (FRET) measurement methods based on spectral unmixing of emission spectra (IIem-spFRET) and excitation-emission spectra (ExEm-spFRET), respectively. We here evaluated robustness of the two methods by implementing them on a self-assembled quantitative FRET measurement system using the cells expressing different constructs. For the cells with larger signal-to-noise (S/N) ratio (>9), the two methods obtained consistent FRET efficiency (E) values and total concentration ratio (RC ) values of acceptor to donor for all constructs; for the cells with 3 < S/N < 9, IIem-spFRET obtained bigger RC values than the expected value for VCV construct; for the cells with S/N < 3, although IIem-spFRET method obtained inaccurate E and RC values for VCV construct, the two methods also obtained consistent E and RC values for all other constructs...
November 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/30098210/a-fast-curtain-removal-method-for-3d-fib-sem-images-of-heterogeneous-minerals
#17
S Liu, L Sun, J Gao, K Li
The focused ion beam-scanning electron microscope (FIB-SEM) system plays a crucial role in the research of shale reservoirs. It enables visualise nano-scale pores and helps characterise unconventional reservoirs. In this system, FIB removes a thin layer and SEM generates a high-resolution grey-scale image of this fresh surface. By iteratively using FIB and SEM, we can create a series of 2D images. Through stacking these images, a 3D model of a rock sample is generated. However, curtain noise of varying intensity often appears in FIB-SEM data...
October 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/29999527/automated-noninvasive-epithelial-cell-counting-in-phase-contrast-microscopy-images-with-automated-parameter-selection
#18
R Flight, G Landini, I B Styles, R M Shelton, M R Milward, P R Cooper
Cell counting is commonly used to determine proliferation rates in cell cultures and for adherent cells it is often a 'destructive' process requiring disruption of the cell monolayer resulting in the inability to follow cell growth longitudinally. This process is time consuming and utilises significant resource. In this study a relatively inexpensive, rapid and widely applicable phase contrast microscopy-based technique has been developed that emulates the contrast changes taking place when bright field microscope images of epithelial cell cultures are defocused...
September 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/29953615/an-entirely-enclosed-scanning-tunnelling-microscope-capable-of-being-fully-immersed-in-liquid-helium
#19
Q Feng, W Meng, J Wang, Z Wang, J Zhang, Q Wang, Y Hou, Q Lu
We present an ultrahigh-vacuum (UHV)-sealed high-stability scanning tunnelling microscope (STM) that can be entirely immersed in liquid helium and readily used in a commercial Dewar or superconducting magnet. The STM head features a horizontal microscanner that can become standalone and ultrastable when the coarse approach inertial motor retracts. Low voltage is enough to operate the STM even at low temperature owing to the powerful motor. It is housed in a tubular chamber of 49 mm outer diameter, which can be pumped via a detachable valve (DV), UHV-sealed and remain sealed after the DV is removed...
September 2018: Journal of Microscopy
https://www.readbyqxmd.com/read/29932461/remote-focusing-in-confocal-microscopy-by-means-of-a-modified-alvarez-lens
#20
M Bawart, A Jesacher, S Bernet, M Ritsch-Marte
Alvarez lenses are actuated lens-pairs which allow one to tune the optical power by mechanical displacement of subelements. Here, we show that a recently realized modified Alvarez lens design which does not require mechanical actuation can be integrated into a confocal microscope. Instead of mechanically moving them, the sublenses are imaged onto each other in a 4f-configuration, where the lateral image shift leading to a change in optical power is created by a galvo-mirror. The avoidance of mechanical lens shifts leads to a large speed gain for axial (and hence also 3D) image scans compared to classical Alvarez lenses...
September 2018: Journal of Microscopy
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