WorldWideScience

Sample records for interference contrast microscopy

  1. Wavelength-Dependent Differential Interference Contrast Microscopy: Selectively Imaging Nanoparticle Probes in Live Cells

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Wei; Wang, Gufeng; Fang, Ning; and Yeung, Edward S.

    2009-11-15

    Gold and silver nanoparticles display extraordinarily large apparent refractive indices near their plasmon resonance (PR) wavelengths. These nanoparticles show good contrast in a narrow spectral band but are poorly resolved at other wavelengths in differential interference contrast (DIC) microscopy. The wavelength dependence of DIC contrast of gold/silver nanoparticles is interpreted in terms of Mie's theory and DIC working principles. We further exploit this wavelength dependence by modifying a DIC microscope to enable simultaneous imaging at two wavelengths. We demonstrate that gold/silver nanoparticles immobilized on the same glass slides through hybridization can be differentiated and imaged separately. High-contrast, video-rate images of living cells can be recorded both with and without illuminating the gold nanoparticle probes, providing definitive probe identification. Dual-wavelength DIC microscopy thus presents a new approach to the simultaneous detection of multiple probes of interest for high-speed live-cell imaging.

  2. Cell Membrane Tracking in Living Brain Tissue Using Differential Interference Contrast Microscopy.

    Science.gov (United States)

    Lee, John; Kolb, Ilya; Forest, Craig R; Rozell, Christopher J

    2018-04-01

    Differential interference contrast (DIC) microscopy is widely used for observing unstained biological samples that are otherwise optically transparent. Combining this optical technique with machine vision could enable the automation of many life science experiments; however, identifying relevant features under DIC is challenging. In particular, precise tracking of cell boundaries in a thick ( ) slice of tissue has not previously been accomplished. We present a novel deconvolution algorithm that achieves the state-of-the-art performance at identifying and tracking these membrane locations. Our proposed algorithm is formulated as a regularized least squares optimization that incorporates a filtering mechanism to handle organic tissue interference and a robust edge-sparsity regularizer that integrates dynamic edge tracking capabilities. As a secondary contribution, this paper also describes new community infrastructure in the form of a MATLAB toolbox for accurately simulating DIC microscopy images of in vitro brain slices. Building on existing DIC optics modeling, our simulation framework additionally contributes an accurate representation of interference from organic tissue, neuronal cell-shapes, and tissue motion due to the action of the pipette. This simulator allows us to better understand the image statistics (to improve algorithms), as well as quantitatively test cell segmentation and tracking algorithms in scenarios, where ground truth data is fully known.

  3. Differential-interference-contrast digital in-line holography microscopy based on a single-optical-element.

    Science.gov (United States)

    Zhang, Yuchao; Xie, Changqing

    2015-11-01

    Both digital in-line holography (DIH) and zone plate-based microscopy have received considerable interest as powerful imaging tools. However, the former suffers from a twin-image noise problem. The latter suffers from low efficiency and difficulty in fabrication. Here, we present an effective and efficient phase-contrast imaging approach, named differential-interference-contrast digital in-line holography (DIC-DIH), by using a single optical element to split the incident light into a plane wave and a converging spherical wave and generate a two-dimensional (2D) DIC effect simultaneously. Specifically, to improve image contrast, we present a new single optical element, termed 2D DIC compound photon sieves, by combining two overlaid binary gratings and a compound photon sieve through two logical XOR operations. The proof-of-concept experiments demonstrate that the proposed technique can eliminate the twin-image noise problem and improve image contrast with high efficiency. Additionally, we present an example of the phase-contrast imaging nonuniform thick photoresist development process.

  4. Histological Analysis of the Arabidopsis Gynoecium and Ovules Using Chloral Hydrate Clearing and Differential Interference Contrast Light Microscopy.

    Science.gov (United States)

    Franks, Robert G

    2016-01-01

    The use of chloral hydrate optical clearing paired with differential interference contrast microscopy allows the analysis of internal structures of developing plant organs without the need for paraffin embedding and sectioning. This approach is appropriate for the analysis of the developing gynoecium or seedpod of the flowering plant Arabidopsis thaliana and many other types of fixed plant material. Early stages of ovule development are observable with this approach.

  5. Three-dimensional characterization of extreme ultraviolet mask blank defects by interference contrast photoemission electron microscopy.

    Science.gov (United States)

    Lin, Jingquan; Weber, Nils; Escher, Matthias; Maul, Jochen; Han, Hak-Seung; Merkel, Michael; Wurm, Stefan; Schönhense, Gerd; Kleineberg, Ulf

    2008-09-29

    A photoemission electron microscope based on a new contrast mechanism "interference contrast" is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast photoemission electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

  6. Quantitative DIC microscopy using an off-axis self-interference approach.

    Science.gov (United States)

    Fu, Dan; Oh, Seungeun; Choi, Wonshik; Yamauchi, Toyohiko; Dorn, August; Yaqoob, Zahid; Dasari, Ramachandra R; Feld, Michael S

    2010-07-15

    Traditional Normarski differential interference contrast (DIC) microscopy is a very powerful method for imaging nonstained biological samples. However, one of its major limitations is the nonquantitative nature of the imaging. To overcome this problem, we developed a quantitative DIC microscopy method based on off-axis sample self-interference. The digital holography algorithm is applied to obtain quantitative phase gradients in orthogonal directions, which leads to a quantitative phase image through a spiral integration of the phase gradients. This method is practically simple to implement on any standard microscope without stringent requirements on polarization optics. Optical sectioning can be obtained through enlarged illumination NA.

  7. Quantitative phase imaging and differential interference contrast imaging for biological TEM

    International Nuclear Information System (INIS)

    Allman, B.E.; McMahon, P.J.; Barone-Nugent, E.D.; Nugent, E.D.

    2002-01-01

    Full text: Phase microscopy is a central technique in science. An experienced microscopist uses this effect to visualise (edge) structure within transparent samples by slightly defocusing the microscope. Although widespread in optical microscopy, phase contrast transmission electron microscopy (TEM) has not been widely adopted. TEM for biological specimens has largely relied on staining techniques to yield sufficient contrast. We show here a simple method for quantitative TEM phase microscopy that quantifies this phase contrast effect. Starting with conventional, digital, bright field images of the sample, our algorithm provides quantitative phase information independent of the sample's bright field intensity image. We present TEM phase images of a range of stained and unstained, biological and material science specimens. This independent phase and intensity information is then used to emulate a range of phase visualisation images familiar to optical microscopy, e.g. differential interference contrast. The phase images contain features not visible with the other imaging modalities. Further, if the TEM samples have been prepared on a microtome to a uniform thickness, the phase information can be converted into refractive index structure of the specimen. Copyright (2002) Australian Society for Electron Microscopy Inc

  8. Leakage radiation interference microscopy.

    Science.gov (United States)

    Descrovi, Emiliano; Barakat, Elsie; Angelini, Angelo; Munzert, Peter; De Leo, Natascia; Boarino, Luca; Giorgis, Fabrizio; Herzig, Hans Peter

    2013-09-01

    We present a proof of principle for a new imaging technique combining leakage radiation microscopy with high-resolution interference microscopy. By using oil immersion optics it is demonstrated that amplitude and phase can be retrieved from optical fields, which are evanescent in air. This technique is illustratively applied for mapping a surface mode propagating onto a planar dielectric multilayer on a thin glass substrate. The surface mode propagation constant estimated after Fourier transformation of the measured complex field is well matched with an independent measurement based on back focal plane imaging.

  9. Nanoscale surface characterization using laser interference microscopy

    Science.gov (United States)

    Ignatyev, Pavel S.; Skrynnik, Andrey A.; Melnik, Yury A.

    2018-03-01

    Nanoscale surface characterization is one of the most significant parts of modern materials development and application. The modern microscopes are expensive and complicated tools, and its use for industrial tasks is limited due to laborious sample preparation, measurement procedures, and low operation speed. The laser modulation interference microscopy method (MIM) for real-time quantitative and qualitative analysis of glass, metals, ceramics, and various coatings has a spatial resolution of 0.1 nm for vertical and up to 100 nm for lateral. It is proposed as an alternative to traditional scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. It is demonstrated that in the cases of roughness metrology for super smooth (Ra >1 nm) surfaces the application of a laser interference microscopy techniques is more optimal than conventional SEM and AFM. The comparison of semiconductor test structure for lateral dimensions measurements obtained with SEM and AFM and white light interferometer also demonstrates the advantages of MIM technique.

  10. Visualization of living terminal hypertrophic chondrocytes of growth plate cartilage in situ by differential interference contrast microscopy and time-lapse cinematography.

    Science.gov (United States)

    Farnum, C E; Turgai, J; Wilsman, N J

    1990-09-01

    The functional unit within the growth plate consists of a column of chondrocytes that passes through a sequence of phases including proliferation, hypertrophy, and death. It is important to our understanding of the biology of the growth plate to determine if distal hypertrophic cells are viable, highly differentiated cells with the potential of actively controlling terminal events of endochondral ossification prior to their death at the chondro-osseous junction. This study for the first time reports on the visualization of living hypertrophic chondrocytes in situ, including the terminal hypertrophic chondrocyte. Chondrocytes in growth plate explants are visualized using rectified differential interference contrast microscopy. We record and measure, using time-lapse cinematography, the rate of movement of subcellular organelles at the limit of resolution of this light microscopy system. Control experiments to assess viability of hypertrophic chondrocytes include coincubating organ cultures with the intravital dye fluorescein diacetate to assess the integrity of the plasma membrane and cytoplasmic esterases. In this system, all hypertrophic chondrocytes, including the very terminal chondrocyte, exist as rounded, fully hydrated cells. By the criteria of intravital dye staining and organelle movement, distal hypertrophic chondrocytes are identical to chondrocytes in the proliferative and early hypertrophic cell zones.

  11. Interference of medical contrast media on laboratory testing.

    Science.gov (United States)

    Lippi, Giuseppe; Daves, Massimo; Mattiuzzi, Camilla

    2014-01-01

    The use of contrast media such as organic iodine molecules and gadolinium contrast agents is commonplace in diagnostic imaging. Although there is widespread perception that side effects and drug interactions may be the leading problems caused by these compounds, various degrees of interference with some laboratory tests have been clearly demonstrated. Overall, the described interference for iodinate contrast media include inappropriate gel barrier formation in blood tubes, the appearance of abnormal peaks in capillary zone electrophoresis of serum proteins, and a positive bias in assessment of cardiac troponin I with one immunoassay. The interference for gadolinium contrast agents include negative bias in calcium assessment with ortho-cresolphthalein colorimetric assays and occasional positive bias using some Arsenazo reagents, negative bias in measurement of angiotensin converting enzyme (ACE) and zinc (colorimetric assay), as well as positive bias in creatinine (Jaffe reaction), total iron binding capacity (TIBC, ferrozine method), magnesium (calmagite reagent) and selenium (mass spectrometry) measurement. Interference has also been reported in assessment of serum indices, pulse oximetry and methaemoglobin in samples of patients receiving Patent Blue V. Under several circumstances the interference was absent from manufacturer-supplied information and limited to certain type of reagents and/or analytes, so that local verification may be advisable to establish whether or not the test in use may be biased. Since the elimination half-life of these compounds is typically lower than 2 h, blood collection after this period may be a safer alternative in patients who have received contrast media for diagnostic purposes.

  12. Interference contrast in multi-source few photon optics

    OpenAIRE

    Laskowski, Wieslaw; Wiesniak, Marcin; Zukowski, Marek; Bourennane, Mohamed; Weinfurter, Harald

    2009-01-01

    Many recent experiments employ several parametric down conversion (PDC) sources to get multiphoton interference. Such interference has applications in quantum information. We study here how effects due to photon statistics, misalignment, and partial distinguishability of the PDC pairs originating from different sources may lower the interference contrast in the multiphoton experiments.

  13. Quantitative tracking of tumor cells in phase-contrast microscopy exploiting halo artifact pattern

    Science.gov (United States)

    Kang, Mi-Sun; Song, Soo-Min; Lee, Hana; Kim, Myoung-Hee

    2012-03-01

    Tumor cell morphology is closely related to its invasiveness characteristics and migratory behaviors. An invasive tumor cell has a highly irregular shape, whereas a spherical cell is non-metastatic. Thus, quantitative analysis of cell features is crucial to determine tumor malignancy or to test the efficacy of anticancer treatment. We use phase-contrast microscopy to analyze single cell morphology and to monitor its change because it enables observation of long-term activity of living cells without photobleaching and phototoxicity, which is common in other fluorescence-labeled microscopy. Despite this advantage, there are image-level drawbacks to phase-contrast microscopy, such as local light effect and contrast interference ring, among others. Thus, we first applied a local filter to compensate for non-uniform illumination. Then, we used intensity distribution information to detect the cell boundary. In phase-contrast microscopy images, the cell normally appears as a dark region surrounded by a bright halo. As the halo artifact around the cell body is minimal and has an asymmetric diffusion pattern, we calculated the cross-sectional plane that intersected the center of each cell and was orthogonal to the first principal axis. Then, we extracted the dark cell region by level set. However, a dense population of cultured cells still rendered single-cell analysis difficult. Finally, we measured roundness and size to classify tumor cells into malignant and benign groups. We validated segmentation accuracy by comparing our findings with manually obtained results.

  14. Temporal overlap estimation based on interference spectrum in CARS microscopy

    Science.gov (United States)

    Zhang, Yongning; Jiang, Junfeng; Liu, Kun; Huang, Can; Wang, Shuang; Zhang, Xuezhi; Liu, Tiegen

    2018-01-01

    Coherent Anti-Stokes Raman Scattering (CARS) microscopy has attracted lots of attention because of the advantages, such as noninvasive, label-free, chemical specificity, intrinsic three-dimension spatial resolution and so on. However, the temporal overlap of pump and Stokes has not been solved owing to the ultrafast optical pulse used in CARS microscopy. We combine interference spectrum of residual pump in Stokes path and nonlinear Schrodinger equation (NLSE) to realize the temporal overlap of pump pulse and Stokes pulse. At first, based on the interference spectrum of pump pulse and residual pump in Stokes path, the optical delay is defined when optical path difference between pump path and Stokes path is zero. Then the relative optical delay between Stokes pulse and residual pump in PCF can be calculated by NLSE. According to the spectrum interference and NLSE, temporal overlap of pump pulse and Stokes pulse will be realized easily and the imaging speed will be improved in CARS microscopy.

  15. Phase-Modulation Laser Interference Microscopy

    DEFF Research Database (Denmark)

    Brazhe, Alexey; Brazhe, Nadezda; Maximov, G. V.

    2008-01-01

    We describe how phase-modulation laser interference microscopy and wavelet analysis can be applied to noninvasive nonstained visualization and study of the structural and dynamical properties of living cells. We show how phase images of erythrocytes can reveal the difference between various...... erythrocyte forms and stages of hemolysis and how phase images of neurons reveal their complex intracellular structure. Temporal variations of the refractive index are analyzed to detect cellular rhythmic activity on different time scales as well as to uncover interactions between the cellular processes....

  16. Improved contrast polymer light-emitting diode with optical interference layers

    International Nuclear Information System (INIS)

    Liu, H.Y.; Sun, R.G.; Yang, K.X.; Peng, J.B.; Cao, Y.; Joo, S.K.

    2007-01-01

    An improved contrast polymer light diode based on the destructive optical interference layers deposited between the glass substrate and ITO anode is fabricated. It is unnecessary to be considered that the additional optical interference structure will impede carrier injection from the electrode to the carrier-transporting layer. Due to the quarter-wavelength thickness of medial ITO layer, the reflected light from first Cr layer is inverted 180 o out of phase with the reflected light from second Cr layer, resulting in the destructive interference. It is evident that the contrast ratio of the device with the optical interference structure is about three times higher than that of the conventional device

  17. Biological applications of phase-contrast electron microscopy.

    Science.gov (United States)

    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.

  18. Interference electron microscopy of one-dimensional electron-optical phase objects

    International Nuclear Information System (INIS)

    Fazzini, P.F.; Ortolani, L.; Pozzi, G.; Ubaldi, F.

    2006-01-01

    The application of interference electron microscopy to the investigation of electron optical one-dimensional phase objects like reverse biased p-n junctions and ferromagnetic domain walls is considered. In particular the influence of diffraction from the biprism edges on the interference images is analyzed and the range of applicability of the geometric optical equation for the interpretation of the interference fringe shifts assessed by comparing geometric optical images with full wave-optical simulations. Finally, the inclusion of partial spatial coherence effects are discussed

  19. Contrast Induced by a Static Magnetic Field for Improved Detection in Nanodiamond Fluorescence Microscopy

    Science.gov (United States)

    Singam, Shashi K. R.; Motylewski, Jaroslaw; Monaco, Antonina; Gjorgievska, Elena; Bourgeois, Emilie; Nesládek, Milos; Giugliano, Michele; Goovaerts, Etienne

    2016-12-01

    Diamond nanoparticles with negatively charged nitrogen-vacancy (NV) centers are highly efficient nonblinking emitters that exhibit spin-dependent intensity. An attractive application of these emitters is background-free fluorescence microscopy exploiting the fluorescence quenching induced either by resonant microwaves (RMWs) or by an applied static magnetic field (SMF). Here, we compare RMW- and SMF-induced contrast measurements over a wide range of optical excitation rates for fluorescent nanodiamonds (FNDs) and for NV centers shallowly buried under the (100)-oriented surface of a diamond single crystal (SC). Contrast levels are found to be systematically lower in the FNDs than in the SC. At low excitation rates, the RMW contrast initially rises to a maximum (up to 7% in FNDs and 13% in the SC) but then decreases steadily at higher intensities. Conversely, the SMF contrast increases from approximately 12% at low excitation rates to high values of 20% and 38% for the FNDs and SC, respectively. These observations are well described in a rate-equations model for the charged NV defect using parameters in good agreement with the literature. The SMF approach yields higher induced contrast in image collection under commonly applied optical excitation. Unlike the RMW method, there is no thermal load exerted on the aqueous media in biological samples in the SMF approach. We demonstrate imaging by SMF-induced contrast in neuronal cultures incorporating FNDs (i) in a setup for patch-clamp experiments in parallel with differential-interference-contrast microscopy, (ii) after a commonly used staining procedure as an illustration of the high selectivity against background fluorescence, and (iii) in a confocal fluorescence microscope in combination with bright-field microscopy.

  20. Effects of phase change on reflection in phase-measuring interference microscopy

    OpenAIRE

    Dubois , Arnaud

    2004-01-01

    International audience; We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interference microscope equipped with various numerical-aperture objectives and ar...

  1. Non-Invasive Study of Nerve Fibres using Laser Interference Microscopy

    DEFF Research Database (Denmark)

    Brazhe, A. R.; Brazhe, N. A.; Rodionova, N. N.

    2008-01-01

    This paper presents the results of a laser interference microscopy study of the morphology and dynamical properties of myelinated nerve fibres. We describe the principles of operation of the phase-modulated laser interference microscope and show how this novel technique allows us to obtain...... information non-invasively about the internal structure of different regions of a nerve fibre. We also analyse the temporal variations in the internal optical properties in order to detect the rhythmic activity in the nerve fibre at different time scales and to shed light on the underlying biological...

  2. Reduction of parasitic interferences in digital holographic microscopy by numerically decreased coherence length

    Science.gov (United States)

    Kosmeier, S.; Langehanenberg, P.; von Bally, G.; Kemper, B.

    2012-01-01

    Due to the large coherence length of laser light, optical path length (OPL) resolution in laser based digital holographic microscopy suffers from parasitic interferences caused by multiple reflections within the experimental setup. Use of partially coherent light reduces this drawback but requires precise and stable matching of object and reference arm's OPLs and limits the spatial frequency of the interference pattern in off-axis holography. Here, we investigate if the noise properties of spectrally broadened light sources can be generated numerically. Therefore, holograms are coherently captured at different laser wavelengths and the corresponding reconstructed wave fields are numerically superimposed utilizing variable weightings. Gaussian and rectangular spectral shapes of the so synthesized field are analyzed with respect to the resulting noise level, which is quantified in OPL distributions of a reflective test target. Utilizing a Gaussian weighting, the noise level is found to be similar to the one obtained with the partially coherent light of a superluminescent diode. With a rectangular shaped synthesized spectrum, noise is reduced more efficient than with a Gaussian one. The applicability of the method in label-free cell analysis is demonstrated by quantitative phase contrast images obtained from living cancer cells.

  3. Super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging

    Science.gov (United States)

    Wei, Lu; Zhu, Xinxin; Chen, Zhixing; Min, Wei

    2014-02-01

    Two-photon excited fluorescence microscopy (TPFM) offers the highest penetration depth with subcellular resolution in light microscopy, due to its unique advantage of nonlinear excitation. However, a fundamental imaging-depth limit, accompanied by a vanishing signal-to-background contrast, still exists for TPFM when imaging deep into scattering samples. Formally, the focusing depth, at which the in-focus signal and the out-of-focus background are equal to each other, is defined as the fundamental imaging-depth limit. To go beyond this imaging-depth limit of TPFM, we report a new class of super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging, including multiphoton activation and imaging (MPAI) harnessing novel photo-activatable fluorophores, stimulated emission reduced fluorescence (SERF) microscopy by adding a weak laser beam for stimulated emission, and two-photon induced focal saturation imaging with preferential depletion of ground-state fluorophores at focus. The resulting image contrasts all exhibit a higher-order (third- or fourth- order) nonlinear signal dependence on laser intensity than that in the standard TPFM. Both the physical principles and the imaging demonstrations will be provided for each super-nonlinear microscopy. In all these techniques, the created super-nonlinearity significantly enhances the imaging contrast and concurrently extends the imaging depth-limit of TPFM. Conceptually different from conventional multiphoton processes mediated by virtual states, our strategy constitutes a new class of fluorescence microscopy where high-order nonlinearity is mediated by real population transfer.

  4. Analytical interference by contrast agents in biochemical assays

    DEFF Research Database (Denmark)

    Otnes, Sigrid; Fogh-Andersen, Niels; Rømsing, Janne

    2017-01-01

    Objective. To provide a clinically relevant overview of the analytical interference by contrast agents (CA) in laboratory blood test measurements. Materials and Methods. The effects of five CAs, gadobutrol, gadoterate meglumine, gadoxetate disodium, iodixanol, and iomeprol, were studied on the 29...... most frequently performed biochemical assays. One-day-old plasma, serum, and whole blood were spiked with doses of each agent such that the gadolinium agents and the iodine agents reached concentrations of 0.5mMand 12mg iodine/mL, respectively. Subsequently, 12 assays were reexamined using 1/2 and 1...

  5. Abrasion of 6 dentifrices measured by vertical scanning interference microscopy.

    Science.gov (United States)

    Pascaretti-Grizon, Florence; Mabilleau, Guillaume; Chappard, Daniel

    2013-01-01

    The abrasion of dentifrices is well recognized to eliminate the dental plaque. The aims of this study were to characterize the abrasive powders of 6 dentifrices (3 toothpastes and 3 toothpowders) and to measure the abrasion on a test surface by Vertical Scanning Interference microscopy (VSI). Bright field and polarization microscopy were used to identify the abrasive particles on the crude dentifrices and after prolonged washes. Scanning electron microscopy and microanalysis characterized the shape and nature of the particles. Standardized and polished blocks of poly(methylmethacrylate) were brushed with a commercial electric toothbrush with the dentifrices. VSI quantified the mean roughness (Ra) and illustrated in 3D the abraded areas. Toothpastes induced a limited abrasion. Toothpowders induced a significantly higher roughness linked to the size of the abrasive particles. One powder (Gencix® produced a high abrasion when used with a standard testing weight. However, the powder is based on pumice particles covered by a plant homogenate that readily dissolves in water. When used in the same volume, or after dispersion in water, Ra was markedly reduced. Light and electron microscopy characterize the abrasive particles and VSI is a new tool allowing the analysis of large surface of abraded materials.

  6. Analyzer-based x-ray phase-contrast microscopy combining channel-cut and asymmetrically cut crystals

    International Nuclear Information System (INIS)

    Hoennicke, M. G.; Cusatis, C.

    2007-01-01

    An analyzer-based x-ray phase-contrast microscopy (ABM) setup combining a standard analyzer-based x-ray phase-contrast imaging (ABI) setup [nondispersive 4-crystal setup (Bonse-Hart setup)] and diffraction by asymmetrically cut crystals is presented here. An attenuation-contrast microscopy setup with conventional x-ray source and asymmetrically cut crystals is first analyzed. Edge-enhanced effects attributed to phase jumps or refraction/total external reflection on the fiber borders were detected. However, the long exposure times and the possibility to achieve high contrast microscopies by using extremely low attenuation-contrast samples motivated us to assemble the ABM setup using a synchrotron source. This setup was found to be useful for low contrast attenuation samples due to the low exposure time, high contrast, and spatial resolution found. Moreover, thanks to the combination with the nondispersive ABI setup, the diffraction-enhanced x-ray imaging algorithm could be applied

  7. Isotropic differential phase contrast microscopy for quantitative phase bio-imaging.

    Science.gov (United States)

    Chen, Hsi-Hsun; Lin, Yu-Zi; Luo, Yuan

    2018-05-16

    Quantitative phase imaging (QPI) has been investigated to retrieve optical phase information of an object and applied to biological microscopy and related medical studies. In recent examples, differential phase contrast (DPC) microscopy can recover phase image of thin sample under multi-axis intensity measurements in wide-field scheme. Unlike conventional DPC, based on theoretical approach under partially coherent condition, we propose a new method to achieve isotropic differential phase contrast (iDPC) with high accuracy and stability for phase recovery in simple and high-speed fashion. The iDPC is simply implemented with a partially coherent microscopy and a programmable thin-film transistor (TFT) shield to digitally modulate structured illumination patterns for QPI. In this article, simulation results show consistency of our theoretical approach for iDPC under partial coherence. In addition, we further demonstrate experiments of quantitative phase images of a standard micro-lens array, as well as label-free live human cell samples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Hard X-ray Microscopy with Elemental, Chemical and Structural Contrast

    International Nuclear Information System (INIS)

    Schroer, C.G.; Boye, P.; Feldkamp, J.P.

    2010-01-01

    We review hard X-ray microscopy techniques with a focus on scanning microscopy with synchrotron radiation. Its strength compared to other microscopies is the large penetration depth of hard x rays in matter that allows one to investigate the interior of an object without destructive sample preparation. In combination with tomography, local information from inside of a specimen can be obtained, even from inside special non-ambient sample environments. Different X-ray analytical techniques can be used to produce contrast, such as X-ray absorption, fluorescence, and diffraction, to yield chemical, elemental, and structural information about the sample, respectively. This makes X-ray microscopy attractive to many fields of science, ranging from physics and chemistry to materials, geo-, and environmental science, biomedicine, and nanotechnology. Our scanning microscope based on nanofocusing refractive X-ray lenses has a routine spatial resolution of about 100 nm and supports the contrast mechanisms mentioned above. In combination with coherent X-ray diffraction imaging, the spatial resolution can be improved to the 10 nm range. The current state-of-the-art of this technique is illustrated by several examples, and future prospects of the technique are given. (author)

  9. Height measurement of transparent objects by adopting differential interference contrast technology

    International Nuclear Information System (INIS)

    Yu, Sheng-Kang; Liu, Ting-Kun; Lin, Shih-Chieh

    2010-01-01

    In this study, the differential interference contrast (DIC) approach originally used for image enhancement to increase the contrast between a transparent object and the background is adopted for the dimension measurement of transparent structures. With the phase difference image retrieved using the DIC technique, the phase map of the examined object can be approximated by integrating the phase difference. The need of integration accuracy is much higher for measurement than for image enhancement. In this study, a modified Fourier phase integration is proposed to reduce the effects of noise on surface profile reconstruction. The simulation results show that the proposed approach can effectively reduce the effects of noise. Experimental results are also conducted to study the feasibility of using the transmitted DIC with the proposed integration method for transparent object measurement. The results show that the height of a transparent structure measured using the DIC method is quite close to those measured using an atomic force microscope, while those measured using the white-light interference method result in a much larger measurement than all others.

  10. A numerical analysis of the Born approximation for image formation modeling of differential interference contrast microscopy for human embryos

    Science.gov (United States)

    Trattner, Sigal; Feigin, Micha; Greenspan, Hayit; Sochen, Nir

    2008-03-01

    The differential interference contrast (DIC) microscope is commonly used for the visualization of live biological specimens. It enables the view of the transparent specimens while preserving their viability, being a non-invasive modality. Fertility clinics often use the DIC microscope for evaluation of human embryos quality. Towards quantification and reconstruction of the visualized specimens, an image formation model for DIC imaging is sought and the interaction of light waves with biological matter is examined. In many image formation models the light-matter interaction is expressed via the first Born approximation. The validity region of this approximation is defined in a theoretical bound which limits its use to very small specimens with low dielectric contrast. In this work the Born approximation is investigated via the Helmholtz equation, which describes the interaction between the specimen and light. A solution on the lens field is derived using the Gaussian Legendre quadrature formulation. This numerical scheme is considered both accurate and efficient and has shortened significantly the computation time as compared to integration methods that required a great amount of sampling for satisfying the Whittaker - Shannon sampling theorem. By comparing the numerical results with the theoretical values it is shown that the theoretical bound is not directly relevant to microscopic imaging and is far too limiting. The numerical exhaustive experiments show that the Born approximation is inappropriate for modeling the visualization of thick human embryos.

  11. Longitudinal correlation properties of an optical field with broad angular and frequency spectra and their manifestation in interference microscopy

    International Nuclear Information System (INIS)

    Lyakin, D V; Ryabukho, V P

    2013-01-01

    The results of theoretical and experimental studies of the longitudinal correlation properties of an optical field with broad angular and frequency spectra and manifestations of these properties in interference microscopy are presented. The joint and competitive influence of the angular and frequency spectra of the object-probing field on the longitudinal resolution and on the amplitude of the interference microscope signals from the interfaces between the media inside a multilayer object is demonstrated. The method of compensating the so-called defocusing effect that arises in the interference microscopy using objectives with a large numerical aperture is experimentally demonstrated, which consists in using as a light source in the interference microscope an illuminating interferometer with a frequency-broadband light source. This method of compensation may be used as the basis of simultaneous determination of geometric thickness and refractive index of media forming a multilayer object. (optical fields)

  12. Quantifying the refractive index dispersion of a pigmented biological tissue using Jamin-Lebedeff interference microscopy

    NARCIS (Netherlands)

    Stavenga, Doekele G.; Leertouwer, Hein L.; Wilts, Bodo D.

    Jamin-Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues. Here, we extend the application of this method to pigmented, absorbing biological tissues, based on a theoretical derivation using Jones calculus. This

  13. Single particle analysis based on Zernike phase contrast transmission electron microscopy.

    Science.gov (United States)

    Danev, Radostin; Nagayama, Kuniaki

    2008-02-01

    We present the first application of Zernike phase-contrast transmission electron microscopy to single-particle 3D reconstruction of a protein, using GroEL chaperonin as the test specimen. We evaluated the performance of the technique by comparing 3D models derived from Zernike phase contrast imaging, with models from conventional underfocus phase contrast imaging. The same resolution, about 12A, was achieved by both imaging methods. The reconstruction based on Zernike phase contrast data required about 30% fewer particles. The advantages and prospects of each technique are discussed.

  14. Refractive index and dispersion of butterfly chitin and bird keratin measured by polarizing interference microscopy

    NARCIS (Netherlands)

    Leertouwer, Hein L.; Wilts, Bodo D.; Stavenga, Doekele G.

    2011-01-01

    Using Jamin-Lebedeff interference microscopy, we measured the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600 nm, 1.572, 1.552 and 1.541,

  15. Contrast distortion induced by modulation voltage in scanning capacitance microscopy

    Science.gov (United States)

    Chang, M. N.; Hu, C. W.; Chou, T. H.; Lee, Y. J.

    2012-08-01

    With a dark-mode scanning capacitance microscopy (SCM), we directly observed the influence of SCM modulation voltage (MV) on image contrasts. For electrical junctions, an extensive modulated area induced by MV may lead to noticeable changes in the SCM signal phase and intensity, resulting in a narrowed junction image and a broadened carrier concentration profile. This contrast distortion in SCM images may occur even if the peak-to-peak MV is down to 0.3 V. In addition, MV may shift the measured electrical junction depth. The balance of SCM signals components explain these MV-induced contrast distortions.

  16. Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

    Science.gov (United States)

    Amos, W B; Reichelt, S; Cattermole, D M; Laufer, J

    2003-05-01

    In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

  17. Fluorescence interference contrast based approach to study real time interaction of melittin with plasma membranes

    Science.gov (United States)

    Gupta, Sharad; Gui, Dong; Zandi, Roya; Gill, Sarjeet; Mohideen, Umar

    2014-03-01

    Melittin is an anti-bacterial and hemolytic toxic peptide found in bee venom. Cell lysis behavior of peptides has been widely investigated, but the exact interaction mechanism of lytic peptides with lipid membranes and its constituents has not been understood completely. In this paper we study the melittin interaction with lipid plasma membranes in real time using non-invasive and non-contact fluorescence interference contrast microscopy (FLIC). Particularly the interaction of melittin with plasma membranes was studied in a controlled molecular environment, where these plasma membrane were composed of saturated lipid, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and unsaturated lipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC) with and without cholesterol. We found out that melittin starts to form nanometer size pores in the plasma membranes shortly after interacting with membranes. But the addition of cholesterol in plasma membrane slows down the pore formation process. Our results show that inclusion of cholesterol to the plasma membranes make them more resilient towards pore formation and lysis of membrane.

  18. Topography and refractometry of nanostructures using spatial light interference microscopy.

    Science.gov (United States)

    Wang, Zhuo; Chun, Ik Su; Li, Xiuling; Ong, Zhun-Yong; Pop, Eric; Millet, Larry; Gillette, Martha; Popescu, Gabriel

    2010-01-15

    Spatial light interference microscopy (SLIM) is a novel method developed in our laboratory that provides quantitative phase images of transparent structures with a 0.3 nm spatial and 0.03 nm temporal accuracy owing to the white light illumination and its common path interferometric geometry. We exploit these features and demonstrate SLIM's ability to perform topography at a single atomic layer in graphene. Further, using a decoupling procedure that we developed for cylindrical structures, we extract the axially averaged refractive index of semiconductor nanotubes and a neurite of a live hippocampal neuron in culture. We believe that this study will set the basis for novel high-throughput topography and refractometry of man-made and biological nanostructures.

  19. Anisotropic photoconductivity and current deflection induced in Bi12SiO20 by high contrast interference pattern

    DEFF Research Database (Denmark)

    Kukhtarev, N.V.; Lyuksyutov, S; Buchhave, Preben

    1996-01-01

    We have predicted and observed an anisotropic photocurrent induced in the cubic crystal Bi/sub 12/SiO/sub 20/ by a high-contrast interference pattern. The transverse current detected when the interference pattern is tilted is caused by deflection of the direct current generated by an external...

  20. Dynamic contrast enhancement in widefield microscopy using projector-generated illumination patterns

    International Nuclear Information System (INIS)

    Samson, Edward Carlo; Blanca, Carlo Mar

    2007-01-01

    We present a simple and cost-effective optical protocol to realize contrast-enhancement imaging (such as dark-field, optical-staining and oblique illumination microscopy) of transparent samples on a conventional widefield microscope using commercial multimedia projectors. The projector functions as both light source and mask generator implemented by creating slideshows of the filters projected along the illumination planes of the microscope. The projected optical masks spatially modulate the distribution of the incident light to selectively enhance structures within the sample according to spatial frequency thereby increasing the image contrast of translucent biological specimens. Any amplitude filter can be customized and dynamically controlled so that switching from one imaging modality to another involves a simple slide transition and can be executed at a keystroke with no physical filters and no moving optical parts. The method yields an image contrast of 89-96% comparable with standard enhancement techniques. The polarization properties of the projector are then utilized to discriminate birefringent and non-birefringent sites on the sample using single-shot, simultaneous polarization and optical-staining microscopy. In addition to dynamic pattern generation and polarization, the projector also provides high illumination power and spectral excitation selectivity through its red-green-blue (RGB) channels. We exploit this last property to explore the feasibility of using video projectors to selectively excite stained samples and perform fluorescence imaging in tandem with reflectance and polarization reflectance microscopy

  1. Group velocity measurement using spectral interference in near-field scanning optical microscopy

    International Nuclear Information System (INIS)

    Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

    2006-01-01

    Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

  2. A hybrid scanning force and light microscope for surface imaging and three-dimensional optical sectioning in differential interference contrast.

    Science.gov (United States)

    Stemmer, A

    1995-04-01

    The design of a scanned-cantilever-type force microscope is presented which is fully integrated into an inverted high-resolution video-enhanced light microscope. This set-up allows us to acquire thin optical sections in differential interference contrast (DIC) or polarization while the force microscope is in place. Such a hybrid microscope provides a unique platform to study how cell surface properties determine, or are affected by, the three-dimensional dynamic organization inside the living cell. The hybrid microscope presented in this paper has proven reliable and versatile for biological applications. It is the only instrument that can image a specimen by force microscopy and high-power DIC without having either to translate the specimen or to remove the force microscope. Adaptation of the design features could greatly enhance the suitability of other force microscopes for biological work.

  3. Holography microscopy as an artifact-free alternative to phase-contrast

    Czech Academy of Sciences Publication Activity Database

    Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

    2018-01-01

    Roč. 149, č. 2 (2018), s. 179-186 ISSN 0948-6143 R&D Projects: GA MŠk(CZ) LM2015062 Institutional support: RVO:68378050 Keywords : Holography microscopy * Phase-contrast * Halo effect Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Cell biology Impact factor: 2.553, year: 2016

  4. Channeling contrast microscopy: a new technique for microanalysis of semiconductors

    International Nuclear Information System (INIS)

    McCallum, J.C.

    1985-01-01

    The technique of channeling contrast microscopy has been developed over the past few years for use with the Melbourne microprobe. It has been used for several profitable analyses of small-scale structures in semiconductor materials. This paper outlines the basic features of the technique and examples of its applications are given

  5. Topography and refractometry of nanostructures using spatial light interference microscopy (SLIM)

    Science.gov (United States)

    Wang, Zhuo; Chun, Ik Su; Li, Xiuling; Ong, Zhun-Yong; Pop, Eric; Millet, Larry; Gillette, Martha; Popescu, Gabriel

    2010-01-01

    Spatial Light Interference Microscopy (SLIM) is a novel method developed in our laboratory that provides quantitative phase images of transparent structures with 0.3 nm spatial and 0.03 nm temporal accuracy owing to the white light illumination and its common path interferometric geometry. We exploit these features and demonstrate SLIM's ability to perform topography at a single atomic layer in graphene. Further, using a decoupling procedure that we developed for cylindrical structures, we extract the axially-averaged refractive index of semiconductor nanotubes and a neurite of a live hippocampal neuron in culture. We believe that this study will set the basis for novel high-throughput topography and refractometry of man-made and biological nanostructures. PMID:20081970

  6. Development of microbubble contrast agents for high frequency ultrasound microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jun, Se Jung; Kim, Eun A; Park, Sung Hoon; Lee, Hye Jin; Jun, Hong Young; Byun, Seung Jae; Yoon, Kwon Ha [Wonkwang University School of Medicine, Iksan (Korea, Republic of)

    2007-05-15

    To develop optimal microbubble contrast agents (MBCAs) for performing ultrasound microscopy when examining small animals. We prepared three types of MBCAs. First, a mixture of three parts of 40% dextran and one part of 5% human serum albumin were sonicated with perfluorocarbon (PFC) (MB{sub 1}-D40A5P). Second, three parts of 40% dextran and one part of 1% human serum albumin were sonicated with PFC (MB{sub 2}-D40A1P). Third, all parts of 1% bovine serum albumin were sonicated with PFC (MB{sub 3}-A1P). We measured the microbubbles' sizes and concentrations with using image analysis software. The acoustic properties of the microbubbles were assessed both in vitro and in vivo. The majority of the MB{sub 1}-D40A5Ps had a diameter of 2-5 {mu} m, the mean diameter of the MB{sub 2}-D40A1Ps was 2.5 {mu} m, and the mean diameter of the MB{sub 3}-A1Ps was less than 2.0 {mu} m. Among the microbubbles, the MB{sub 1}-D40A5Ps and MB{sub 2}-D40A1Ps showed increased echogenicity in the abdominal vessels, but the duration of their contrast effect was less than 30 sec. On the contrary, the MB3-A1Ps exhibited strong enhancement in the vessels and their duration was greater than 120 sec. A microbubble contrast agent consisting of all parts of 1% serum albumin sonicated with PFC is an effective contrast agent for ultrasound microscopy.

  7. Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

    Science.gov (United States)

    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.

  8. Contrast-enhanced Spectral Mammography: Modality-Specific Artifacts and Other Factors Which May Interfere with Image Quality.

    Science.gov (United States)

    Bhimani, Chandni; Li, Luna; Liao, Lydia; Roth, Robyn G; Tinney, Elizabeth; Germaine, Pauline

    2017-01-01

    Contrast-enhanced spectral mammography (CESM) uses full field digital mammography with the added benefit of intravenous contrast administration to significantly reduce false-positive and false-negative results and improve specificity while maintaining high sensitivity. For CESM to fulfill its purpose, one should be aware of possible artifacts and other factors which may interfere with image quality, and attention should be taken to minimize these factors. This pictorial demonstration will depict types of artifacts detected and other factors that interfere with image acquisition in our practice since CESM implementation. Many of the artifacts and other factors we have encountered while using CESM have simple solutions to resolve them. The illustrated artifacts and other factors interfering with image quality will serve as a useful reference to anyone using CESM. Copyright © 2017 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

  9. Topographic and electronic contrast of the graphene moir´e on Ir(111) probed by scanning tunneling microscopy and noncontact atomic force microscopy

    NARCIS (Netherlands)

    Sun, Z.; Hämäläinen, K.; Sainio, K.; Lahtinen, J.; Vanmaekelbergh, D.A.M.; Liljeroth, P.

    2011-01-01

    Epitaxial graphene grown on transition-metal surfaces typically exhibits a moir´e pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to probe the electronic and topographic contrast

  10. Holography microscopy as an artifact-free alternative to phase-contrast.

    Science.gov (United States)

    Pastorek, Lukáš; Venit, Tomáš; Hozák, Pavel

    2018-02-01

    Artifact-free microscopic images represent a key requirement of multi-parametric image analysis in modern biomedical research. Holography microscopy (HM) is one of the quantitative phase imaging techniques, which has been finding new applications in life science, especially in morphological screening, cell migration, and cancer research. Rather than the classical imaging of absorbing (typically stained) specimens by bright-field microscopy, the information about the light-wave's phase shifts induced by the biological sample is employed for final image reconstruction. In this comparative study, we investigated the usability and the reported advantage of the holography imaging. The claimed halo-free imaging was analyzed compared to the widely used Zernike phase-contrast microscopy. The intensity and phase cross-membrane profiles at the periphery of the cell were quantified. The intensity profile for cells in the phase-contrast images suffers from the significant increase in intensity values around the cell border. On the contrary, no distorted profile is present outside the cell membrane in holography images. The gradual increase in phase shift values is present in the internal part of the cell body projection in holography image. This increase may be related to the increase in the cell internal material according to the dry mass theory. Our experimental data proved the halo-free nature of the holography imaging, which is an important prerequisite of the correct thresholding and cell segmentation, nowadays frequently required in high-content screening and other image-based analysis. Consequently, HM is a method of choice whenever the image analysis relies on the accurate data on cell boundaries.

  11. Practical aspects of Boersch phase contrast electron microscopy of biological specimens

    Energy Technology Data Exchange (ETDEWEB)

    Walter, Andreas [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, Andre; Goelzhaeuser, Armin [University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Universitaetsstr. 25, D-33615 Bielefeld (Germany); Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter [Caesar Research Center, Ludwig-Erhard-Allee 2, D-53175 Bonn (Germany); Kuehlbrandt, Werner [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany); Rhinow, Daniel, E-mail: daniel.rhinow@biophys.mpg.de [Max-Planck-Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60439 Frankfurt (Germany)

    2012-05-15

    Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90 Degree-Sign achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen-hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: Black-Right-Pointing-Pointer Various obstacles need to be overcome before Boersch phase plates can be used routinely. Black-Right-Pointing-Pointer Technical problems include

  12. Practical aspects of Boersch phase contrast electron microscopy of biological specimens

    International Nuclear Information System (INIS)

    Walter, Andreas; Muzik, Heiko; Vieker, Henning; Turchanin, Andrey; Beyer, André; Gölzhäuser, Armin; Lacher, Manfred; Steltenkamp, Siegfried; Schmitz, Sam; Holik, Peter; Kühlbrandt, Werner; Rhinow, Daniel

    2012-01-01

    Implementation of physical phase plates into transmission electron microscopes to achieve in-focus contrast for ice-embedded biological specimens poses several technological challenges. During the last decade several phase plates designs have been introduced and tested for electron cryo-microscopy (cryoEM), including thin film (Zernike) phase plates and electrostatic devices. Boersch phase plates (BPPs) are electrostatic einzel lenses shifting the phase of the unscattered beam by an arbitrary angle. Adjusting the phase shift to 90° achieves the maximum contrast transfer for phase objects such as biomolecules. Recently, we reported the implementation of a BPP into a dedicated phase contrast aberration-corrected electron microscope (PACEM) and demonstrated its use to generate in-focus contrast of frozen–hydrated specimens. However, a number of obstacles need to be overcome before BPPs can be used routinely, mostly related to the phase plate devices themselves. CryoEM with a physical phase plate is affected by electrostatic charging, obliteration of low spatial frequencies, and mechanical drift. Furthermore, BPPs introduce single sideband contrast (SSB), due to the obstruction of Friedel mates in the diffraction pattern. In this study we address the technical obstacles in detail and show how they may be overcome. We use X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to identify contaminants responsible for electrostatic charging, which occurs with most phase plates. We demonstrate that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope. Finally, we present computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP. -- Highlights: ► Various obstacles need to be overcome before Boersch phase plates can be used routinely. ► Technical problems include electrostatic charging, mechanical drift, and image artefacts.

  13. Photoionization microscopy of Rydberg hydrogen atom in a non-uniform electrical field

    International Nuclear Information System (INIS)

    Cheng Shao-Hao; Wang De-Hua; Chen Zhao-Hang; Chen Qiang

    2016-01-01

    In this paper, we investigate the photoionization microscopy of the Rydberg hydrogen atom in a gradient electric field for the first time. The observed oscillatory patterns in the photoionization microscopy are explained within the framework of the semiclassical theory, which can be considered as a manifestation of interference between various electron trajectories arriving at a given point on the detector plane. In contrast with the photoionization microscopy in the uniform electric field, the trajectories of the ionized electron in the gradient electric field will become chaotic. An infinite set of different electron trajectories can arrive at a given point on the detector plane, which makes the interference pattern of the electron probability density distribution extremely complicated. Our calculation results suggest that the oscillatory pattern in the electron probability density distribution depends sensitively on the electric field gradient, the scaled energy and the position of the detector plane. Through our research, we predict that the interference pattern in the electron probability density distribution can be observed in an actual photoionization microscopy experiment once the external electric field strength and the position of the electron detector plane are reasonable. This study provides some references for the future experimental research on the photoionization microscopy of the Rydberg atom in the non-uniform external fields. (paper)

  14. Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy.

    Science.gov (United States)

    Wang, Zhili; Gao, Kun; Chen, Jian; Hong, Youli; Ge, Xin; Wang, Dajiang; Pan, Zhiyun; Zhu, Peiping; Yun, Wenbing; Jacobsen, Chris; Wu, Ziyu

    2013-01-01

    Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (3D images of cryo-preserved cells. The relatively low X-ray energy (3D imaging (e.g., ~1 μm DoF for 20 nm resolution). An X-ray microscope operating at intermediate energy around 2.5 keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5 keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. Analyzing speckle contrast for HiLo microscopy optimization

    Science.gov (United States)

    Mazzaferri, J.; Kunik, D.; Belisle, J. M.; Singh, K.; Lefrançois, S.; Costantino, S.

    2011-07-01

    HiLo microscopy is a recently developed technique that provides both optical sectioning and fast imaging with a simple implementation and at a very low cost. The methodology combines widefield and speckled illumination images to obtain one optically sectioned image. Hence, the characteristics of such speckle illumination ultimately determine the quality of HiLo images and the overall performance of the method. In this work, we study how speckle contrast influence local variations of fluorescence intensity and brightness profiles of thick samples. We present this article as a guide to adjust the parameters of the system for optimizing the capabilities of this novel technology.

  16. Invited Review Article: Pump-probe microscopy

    Science.gov (United States)

    Wilson, Jesse W.; Robles, Francisco E.; Warren, Warren S.

    2016-01-01

    Multiphoton microscopy has rapidly gained popularity in biomedical imaging and materials science because of its ability to provide three-dimensional images at high spatial and temporal resolution even in optically scattering environments. Currently the majority of commercial and home-built devices are based on two-photon fluorescence and harmonic generation contrast. These two contrast mechanisms are relatively easy to measure but can access only a limited range of endogenous targets. Recent developments in fast laser pulse generation, pulse shaping, and detection technology have made accessible a wide range of optical contrasts that utilize multiple pulses of different colors. Molecular excitation with multiple pulses offers a large number of adjustable parameters. For example, in two-pulse pump-probe microscopy, one can vary the wavelength of each excitation pulse, the detection wavelength, the timing between the excitation pulses, and the detection gating window after excitation. Such a large parameter space can provide much greater molecular specificity than existing single-color techniques and allow for structural and functional imaging without the need for exogenous dyes and labels, which might interfere with the system under study. In this review, we provide a tutorial overview, covering principles of pump-probe microscopy and experimental setup, challenges associated with signal detection and data processing, and an overview of applications. PMID:27036751

  17. Invited Review Article: Pump-probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Martin C., E-mail: Martin.Fischer@duke.edu; Wilson, Jesse W.; Robles, Francisco E. [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Warren, Warren S. [Departments of Chemistry, Biomedical Engineering, Physics, and Radiology, Duke University, Durham, North Carolina 27708 (United States)

    2016-03-15

    Multiphoton microscopy has rapidly gained popularity in biomedical imaging and materials science because of its ability to provide three-dimensional images at high spatial and temporal resolution even in optically scattering environments. Currently the majority of commercial and home-built devices are based on two-photon fluorescence and harmonic generation contrast. These two contrast mechanisms are relatively easy to measure but can access only a limited range of endogenous targets. Recent developments in fast laser pulse generation, pulse shaping, and detection technology have made accessible a wide range of optical contrasts that utilize multiple pulses of different colors. Molecular excitation with multiple pulses offers a large number of adjustable parameters. For example, in two-pulse pump-probe microscopy, one can vary the wavelength of each excitation pulse, the detection wavelength, the timing between the excitation pulses, and the detection gating window after excitation. Such a large parameter space can provide much greater molecular specificity than existing single-color techniques and allow for structural and functional imaging without the need for exogenous dyes and labels, which might interfere with the system under study. In this review, we provide a tutorial overview, covering principles of pump-probe microscopy and experimental setup, challenges associated with signal detection and data processing, and an overview of applications.

  18. Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces

    Czech Academy of Sciences Publication Activity Database

    Ondráček, Martin; González, C.; Jelínek, Pavel

    2012-01-01

    Roč. 24, 08 (2012), 084003/1-084003/7 ISSN 0953-8984 R&D Projects: GA ČR(CZ) GPP204/11/P578; GA ČR GAP204/10/0952; GA ČR GA202/09/0545; GA MŠk(CZ) ME10076 Grant - others:AVČR(CZ) M100100904 Institutional research plan: CEZ:AV0Z10100521 Keywords : atomic force microscopy * metallic surfaces * atomic contrast * scanning tunneling microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.355, year: 2012 http://iopscience.iop.org/0953-8984/24/8/084003

  19. Dual-polarization interference microscopy for advanced quantification of phase associated with the image field.

    Science.gov (United States)

    Bouchal, Petr; Chmelík, Radim; Bouchal, Zdeněk

    2018-02-01

    A new concept of dual-polarization spatial light interference microscopy (DPSLIM) is proposed and demonstrated experimentally. The method works with two orthogonally polarized modes in which signal and reference waves are combined to realize the polarization-sensitive phase-shifting, thus allowing advanced reconstruction of the phase associated with the image field. The image phase is reconstructed directly from four polarization encoded interference records by a single step processing. This is a progress compared with common methods, in which the phase of the image field is reconstructed using the optical path difference and the amplitudes of interfering waves, which are calculated in multiple-step processing of the records. The DPSLIM is implemented in a common-path configuration using a spatial light modulator, which is connected to a commercial microscope Nikon E200. The optical performance of the method is demonstrated in experiments using both polystyrene microspheres and live LW13K2 cells.

  20. Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

    Science.gov (United States)

    Wong, Terence T. W.; Lau, Andy K. S.; Ho, Kenneth K. Y.; Tang, Matthew Y. H.; Robles, Joseph D. F.; Wei, Xiaoming; Chan, Antony C. S.; Tang, Anson H. L.; Lam, Edmund Y.; Wong, Kenneth K. Y.; Chan, Godfrey C. F.; Shum, Ho Cheung; Tsia, Kevin K.

    2014-01-01

    Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity – a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry – permitting high-throughput access to the morphological information of the individual cells simultaneously with a multitude of parameters obtained in the standard assay. PMID:24413677

  1. Correlation of ''twins'' observed by optical microscopy and transmission electron microscopy in YBa2Cu3O7/sub -//sub x/ superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Singh, A.K.; Pande, C.S.

    1988-01-01

    By using transmission electron microscopy and optical microscopy on the same specimens, the patterns of light- and dark-contrast lines seen in reflected polarized light were shown to be an interference pattern due to the variable spacing of suboptical microtwins. These microtwins are mostly [110] reflection twins. The [110] twinning was observed to be cyclic and occasionally pseudotetragonal because of the progressive cycling of contact twin domains. Within a domain, and occasionally in a whole grain, the [110] reflection twins occurred as polysynthetic lamellae. The morphology of the domain structure can be explained from the theory of martensitic transformation

  2. Imaging contrast and tip-sample interaction of non-contact amplitude modulation atomic force microscopy with Q -control

    International Nuclear Information System (INIS)

    Shi, Shuai; Guo, Dan; Luo, Jianbin

    2017-01-01

    Active quality factor ( Q ) exhibits many promising properties in dynamic atomic force microscopy. Energy dissipation and image contrasts are investigated in the non-contact amplitude modulation atomic force microscopy (AM-AFM) with an active Q -control circuit in the ambient air environment. Dissipated power and virial were calculated to compare the highly nonlinear interaction of tip-sample and image contrasts with different Q gain values. Greater free amplitudes and lower effective Q values show better contrasts for the same setpoint ratio. Active quality factor also can be employed to change tip-sample interaction force in non-contact regime. It is meaningful that non-destructive and better contrast images can be realized in non-contact AM-AFM by applying an active Q -control to the dynamic system. (paper)

  3. Application of gold nanoparticles as contrast agents in confocal laser scanning microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lemelle, A; Veksler, B; Piletsky, S A; Meglinski, I [Cranfield Health, Cranfield University, Cranfield, MK43 0AL (United Kingdom); Kozhevnikov, I S; Akchurin, G G, E-mail: a.lemelle.s06@cranfield.ac.uk [Physics Faculty, Saratov State University, Saratov 410012 (Russian Federation)

    2009-01-15

    Confocal laser scanning microscopy (CLSM) is a modern high-resolution optical technique providing detailed image of tissue structure with high (down to microns) spatial resolution. Aiming at a concurrent improvement of imaging depth and image quality the CLSM requires the use of contrast agents. Commonly employed fluorescent contrast agents, such as fluorescent dyes and proteins, suffer from toxicity, photo-bleaching and overlapping with the tissues autofluorescence. Gold nanoparticles are potentially highly attractive to be applied as a contrast agent since they are not subject to photo-bleaching and can target biochemical cells markers associated with the specific diseases. In current report we consider the applicability of gold nano-spheres as a contrast agent to enhance quality of CLSM images of skin tissues in vitro versus the application of optical clearing agent, such as glycerol. The enhancement of CLSM image contrast was observed with an application of gold nano-spheres diffused within the skin tissues. We show that optical clearing agents such as a glycerol provide better CLSM image contrast than gold nano-spheres.

  4. Application of gold nanoparticles as contrast agents in confocal laser scanning microscopy

    International Nuclear Information System (INIS)

    Lemelle, A; Veksler, B; Piletsky, S A; Meglinski, I; Kozhevnikov, I S; Akchurin, G G

    2009-01-01

    Confocal laser scanning microscopy (CLSM) is a modern high-resolution optical technique providing detailed image of tissue structure with high (down to microns) spatial resolution. Aiming at a concurrent improvement of imaging depth and image quality the CLSM requires the use of contrast agents. Commonly employed fluorescent contrast agents, such as fluorescent dyes and proteins, suffer from toxicity, photo-bleaching and overlapping with the tissues autofluorescence. Gold nanoparticles are potentially highly attractive to be applied as a contrast agent since they are not subject to photo-bleaching and can target biochemical cells markers associated with the specific diseases. In current report we consider the applicability of gold nano-spheres as a contrast agent to enhance quality of CLSM images of skin tissues in vitro versus the application of optical clearing agent, such as glycerol. The enhancement of CLSM image contrast was observed with an application of gold nano-spheres diffused within the skin tissues. We show that optical clearing agents such as a glycerol provide better CLSM image contrast than gold nano-spheres

  5. Application of gold nanoparticles as contrast agents in confocal laser scanning microscopy

    Science.gov (United States)

    Lemelle, A.; Veksler, B.; Kozhevnikov, I. S.; Akchurin, G. G.; Piletsky, S. A.; Meglinski, I.

    2009-01-01

    Confocal laser scanning microscopy (CLSM) is a modern high-resolution optical technique providing detailed image of tissue structure with high (down to microns) spatial resolution. Aiming at a concurrent improvement of imaging depth and image quality the CLSM requires the use of contrast agents. Commonly employed fluorescent contrast agents, such as fluorescent dyes and proteins, suffer from toxicity, photo-bleaching and overlapping with the tissues autofluorescence. Gold nanoparticles are potentially highly attractive to be applied as a contrast agent since they are not subject to photo-bleaching and can target biochemical cells markers associated with the specific diseases. In current report we consider the applicability of gold nano-spheres as a contrast agent to enhance quality of CLSM images of skin tissues in vitro versus the application of optical clearing agent, such as glycerol. The enhancement of CLSM image contrast was observed with an application of gold nano-spheres diffused within the skin tissues. We show that optical clearing agents such as a glycerol provide better CLSM image contrast than gold nano-spheres.

  6. Topography and refractometry of sperm cells using spatial light interference microscopy.

    Science.gov (United States)

    Liu, Lina; Kandel, Mikhail E; Rubessa, Marcello; Schreiber, Sierra; Wheeler, Mathew B; Popescu, Gabriel

    2018-02-01

    Characterization of spermatozoon viability is a common test in treating infertility. Recently, it has been shown that label-free, phase-sensitive imaging can provide a valuable alternative for this type of assay. We employ spatial light interference microscopy (SLIM) to perform high-accuracy single-cell phase imaging and decouple the average thickness and refractive index information for the population. This procedure was enabled by quantitative-phase imaging cells on media of two different refractive indices and using a numerical tool to remove the curvature from the cell tails. This way, we achieved ensemble averaging of topography and refractometry of 100 cells in each of the two groups. The results show that the thickness profile of the cell tail goes down to 150 nm and the refractive index can reach values of 1.6 close to the head. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  7. Self-interference fluorescence microscopy with three-phase detection for depth-resolved confocal epi-fluorescence imaging.

    Science.gov (United States)

    Braaf, Boy; de Boer, Johannes F

    2017-03-20

    Three-dimensional confocal fluorescence imaging of in vivo tissues is challenging due to sample motion and limited imaging speeds. In this paper a novel method is therefore presented for scanning confocal epi-fluorescence microscopy with instantaneous depth-sensing based on self-interference fluorescence microscopy (SIFM). A tabletop epi-fluorescence SIFM setup was constructed with an annular phase plate in the emission path to create a spectral self-interference signal that is phase-dependent on the axial position of a fluorescent sample. A Mach-Zehnder interferometer based on a 3 × 3 fiber-coupler was developed for a sensitive phase analysis of the SIFM signal with three photon-counter detectors instead of a spectrometer. The Mach-Zehnder interferometer created three intensity signals that alternately oscillated as a function of the SIFM spectral phase and therefore encoded directly for the axial sample position. Controlled axial translation of fluorescent microsphere layers showed a linear dependence of the SIFM spectral phase with sample depth over axial image ranges of 500 µm and 80 µm (3.9 × Rayleigh range) for 4 × and 10 × microscope objectives respectively. In addition, SIFM was in good agreement with optical coherence tomography depth measurements on a sample with indocyanine green dye filled capillaries placed at multiple depths. High-resolution SIFM imaging applications are demonstrated for fluorescence angiography on a dye-filled capillary blood vessel phantom and for autofluorescence imaging on an ex vivo fly eye.

  8. Line-scanning confocal microscopy for high-resolution imaging of upconverting rare-earth-based contrast agents

    Science.gov (United States)

    Higgins, Laura M.; Zevon, Margot; Ganapathy, Vidya; Sheng, Yang; Tan, Mei Chee; Riman, Richard E.; Roth, Charles M.; Moghe, Prabhas V.; Pierce, Mark C.

    2015-01-01

    Abstract. Rare-earth (RE) doped nanocomposites emit visible luminescence when illuminated with continuous wave near-infrared light, making them appealing candidates for use as contrast agents in biomedical imaging. However, the emission lifetime of these materials is much longer than the pixel dwell times used in scanning intravital microscopy. To overcome this limitation, we have developed a line-scanning confocal microscope for high-resolution, optically sectioned imaging of samples labeled with RE-based nanomaterials. Instrument performance is quantified using calibrated test objects. NaYF4:Er,Yb nanocomposites are imaged in vitro, and in ex vivo tissue specimens, with direct comparison to point-scanning confocal microscopy. We demonstrate that the extended pixel dwell time of line-scanning confocal microscopy enables subcellular-level imaging of these nanomaterials while maintaining optical sectioning. The line-scanning approach thus enables microscopic imaging of this emerging class of contrast agents for preclinical studies, with the potential to be adapted for real-time in vivo imaging in the clinic. PMID:26603495

  9. New generation quantitative x-ray microscopy encompassing phase-contrast

    International Nuclear Information System (INIS)

    Wilkins, S.W.; Mayo, S.C.; Gureyev, T.E.; Miller, P.R.; Pogany, A.; Stevenson, A.W.; Gao, D.; Davis, T.J.; Parry, D.J.; Paganin, D.

    2000-01-01

    Full text: We briefly outline a new approach to X-ray ultramicroscopy using projection imaging in a scanning electron microscope (SEM). Compared to earlier approaches, the new approach offers spatial resolution of ≤0.1 micron and includes novel features such as: i) phase contrast to give additional sample information over a wide energy range, rapid phase/amplitude extraction algorithms to enable new real-time modes of microscopic imaging widespread applications are envisaged to fields such as materials science, biomedical research, and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to X-ray projection microscopy using synchrotron sources

  10. Phase contrast imaging with coherent high energy X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Snigireva, I. [ESRF, Grenoble (France)

    1997-02-01

    X-ray imaging concern high energy domain (>6 keV) like a contact radiography, projection microscopy and tomography is used for many years to discern the features of the internal structure non destructively in material science, medicine and biology. In so doing the main contrast formation is absorption that makes some limitations for imaging of the light density materials and what is more the resolution of these techniques is not better than 10-100 {mu}m. It was turned out that there is now way in which to overcome 1{mu}m or even sub-{mu}m resolution limit except phase contrast imaging. It is well known in optics that the phase contrast is realised when interference between reference wave front and transmitted through the sample take place. Examples of this imaging are: phase contrast microscopy suggested by Zernike and Gabor (in-line) holography. Both of this techniques: phase contrast x-ray microscopy and holography are successfully progressing now in soft x-ray region. For imaging in the hard X-rays to enhance the contrast and to be able to resolve phase variations across the beam the high degree of the time and more importantly spatial coherence is needed. Because of this it was reasonable that the perfect crystal optics was involved like Bonse-Hart interferometry, double-crystal and even triple-crystal set-up using Laue and Bragg geometry with asymmetrically cut crystals.

  11. Electron holography for polymer microscopy

    International Nuclear Information System (INIS)

    Joy, D.C.

    1992-01-01

    Electron holography provides a radically new approach to the problem of imaging objects such as macromolecules, which exhibit little or no contrast when viewed in the conventional transmission electron microscope (TEM). This is overcome in electron holography by using the macromolecule as a phase object. Computer reconstruction of the hologram then allows the phase to be viewed as an image, and amplified. Holography requires a TEM with a field emission gun, and with an electro-static biprism to produce the interference pattern. The hologram requires a similar radiation dose to conventional microscopy but many different images (e.g. a through focal series) can be extracted from the same hologram. Further developments of the technique promise to combine high contrast imaging of the bulk of the macromolecule together with high spatial resolution imaging of surface detail

  12. Teager-Kaiser Energy and Higher-Order Operators in White-Light Interference Microscopy for Surface Shape Measurement

    Directory of Open Access Journals (Sweden)

    Abdel-Ouahab Boudraa

    2005-10-01

    Full Text Available In white-light interference microscopy, measurement of surface shape generally requires peak extraction of the fringe function envelope. In this paper the Teager-Kaiser energy and higher-order energy operators are proposed for efficient extraction of the fringe envelope. These energy operators are compared in terms of precision, robustness to noise, and subsampling. Flexible energy operators, depending on order and lag parameters, can be obtained. Results show that smoothing and interpolation of envelope approximation using spline model performs better than Gaussian-based approach.

  13. High-contrast imaging of mycobacterium tuberculosis using third-harmonic generation microscopy

    Science.gov (United States)

    Kim, Bo Ram; Lee, Eungjang; Park, Seung-Han

    2015-07-01

    Nonlinear optical microcopy has become an important tool in investigating biomaterials due to its various advantages such as label-free imaging capabilities. In particular, it has been shown that third-harmonic generation (THG) signals can be produced at interfaces between an aqueous medium (e.g. cytoplasm, interstitial fluid) and a mineralized lipidic surface. In this work, we have demonstrated that label-free high-contrast THG images of the mycobacterium tuberculosis can be obtained using THG microscopy.

  14. Active voltage contrast imaging of cross-sectional surface of multilayer ceramic capacitor using helium ion microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, C., E-mail: SAKAI.Chikako@nims.go.jp; Ishida, N.; Masuda, H.; Nagano, S.; Kitahara, M.; Fujita, D. [National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Ogata, Y. [TAIYO YUDEN CO., LTD., Takasaki-shi, Gunma 370-3347 (Japan)

    2016-08-01

    We studied active voltage contrast (AVC) imaging using helium ion microscopy (HIM). We observed secondary electron (SE) images of the cross-sectional surface of multilayer ceramic capacitors (MLCCs) with and without a voltage applied to the internal electrodes. When no voltage was applied, we obtained an image reflecting the material contrast between the Ni internal electrode region and the BaTiO{sub 3} dielectric region of the cross-sectional surface of the MLCC. When a voltage was applied, the electrical potential difference between the grounded and the positively biased internal electrodes affected the contrast (voltage contrast). Moreover, attenuation of the SE intensity from the grounded to the positively biased internal electrodes was observed in the dielectric region. Kelvin probe force microscopy (KPFM) measurements of the contact potential difference (CPD) were performed on the same sample. By using the AVC image from the HIM observation and the CPD image from the KPFM measurement, we could quantitatively evaluate the electrical potential. We think that the results of this study will lead to an expansion in the number of applications of HIM.

  15. Single beam Fourier transform digital holographic quantitative phase microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Anand, A., E-mail: arun-nair-in@yahoo.com; Chhaniwal, V. K.; Mahajan, S.; Trivedi, V. [Optics Laboratory, Applied Physics Department, Faculty of Technology and Engineering, M.S. University of Baroda, Vadodara 390001 (India); Faridian, A.; Pedrini, G.; Osten, W. [Institut für Technische Optik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart (Germany); Dubey, S. K. [Siemens Technology and Services Pvt. Ltd, Corporate Technology—Research and Technology Centre, Bangalore 560100 (India); Javidi, B. [Department of Electrical and Computer Engineering, U-4157, University of Connecticut, Storrs, Connecticut 06269-2157 (United States)

    2014-03-10

    Quantitative phase contrast microscopy reveals thickness or height information of a biological or technical micro-object under investigation. The information obtained from this process provides a means to study their dynamics. Digital holographic (DH) microscopy is one of the most used, state of the art single-shot quantitative techniques for three dimensional imaging of living cells. Conventional off axis DH microscopy directly provides phase contrast images of the objects. However, this process requires two separate beams and their ratio adjustment for high contrast interference fringes. Also the use of two separate beams may make the system more vulnerable to vibrations. Single beam techniques can overcome these hurdles while remaining compact as well. Here, we describe the development of a single beam DH microscope providing whole field imaging of micro-objects. A hologram of the magnified object projected on to a diffuser co-located with a pinhole is recorded with the use of a commercially available diode laser and an arrayed sensor. A Fourier transform of the recorded hologram directly yields the complex amplitude at the image plane. The method proposed was investigated using various phase objects. It was also used to image the dynamics of human red blood cells in which sub-micrometer level thickness variation were measurable.

  16. Concomitant use of polarization and positive phase contrast microscopy for the study of microbial cells

    Czech Academy of Sciences Publication Activity Database

    Žižka, Zdeněk; Gabriel, Jiří

    2015-01-01

    Roč. 60, č. 6 (2015), s. 545-550 ISSN 0015-5632 Institutional support: RVO:61388971 Keywords : polarization microscopy * microbial cells * positive phase contrast Subject RIV: EE - Microbiology, Virology Impact factor: 1.335, year: 2015

  17. Application of differential interference contrast with inverted microscopes to the in vitro perfused nephron.

    Science.gov (United States)

    Horster, M; Gundlach, H

    1979-12-01

    The study of in vitro perfused individual nephron segments requires a microscope which provides: (1) easy access to the specimen for measurement of cellular solute flux and voltage; (2) an image with high resolution and contrast; (3) optical sectioning of the object at different levels; and (4) rapid recording of the morphological phenomena. This paper describes an example of commercially available apparatus meeting the above requirements, and illustrates its efficiency. The microscope is of the inverted type (Zeiss IM 35) equipped with differential-interference-contrast (DIC) with a long working distance, and an automatically controlled camera system. The microscopic image exhibits cellular and intercellular details in the unstained transporting mammalian nephron segments despite their tubular structure and great thickness and makes obvious function-structure correlations (e.g. cell volume changes); luminal and contraluminal cell borders are well resolved for controlled microelectrode impalement.

  18. Inducing fluorescence of uranyl acetate as a dual-purpose contrast agent for correlative light-electron microscopy with nanometre precision.

    Science.gov (United States)

    Tuijtel, Maarten W; Mulder, Aat A; Posthuma, Clara C; van der Hoeven, Barbara; Koster, Abraham J; Bárcena, Montserrat; Faas, Frank G A; Sharp, Thomas H

    2017-09-05

    Correlative light-electron microscopy (CLEM) combines the high spatial resolution of transmission electron microscopy (TEM) with the capability of fluorescence light microscopy (FLM) to locate rare or transient cellular events within a large field of view. CLEM is therefore a powerful technique to study cellular processes. Aligning images derived from both imaging modalities is a prerequisite to correlate the two microscopy data sets, and poor alignment can limit interpretability of the data. Here, we describe how uranyl acetate, a commonly-used contrast agent for TEM, can be induced to fluoresce brightly at cryogenic temperatures (-195 °C) and imaged by cryoFLM using standard filter sets. This dual-purpose contrast agent can be used as a general tool for CLEM, whereby the equivalent staining allows direct correlation between fluorescence and TEM images. We demonstrate the potential of this approach by performing multi-colour CLEM of cells containing equine arteritis virus proteins tagged with either green- or red-fluorescent protein, and achieve high-precision localization of virus-induced intracellular membrane modifications. Using uranyl acetate as a dual-purpose contrast agent, we achieve an image alignment precision of ~30 nm, twice as accurate as when using fiducial beads, which will be essential for combining TEM with the evolving field of super-resolution light microscopy.

  19. Single-shot quantitative phase microscopy with color-multiplexed differential phase contrast (cDPC.

    Directory of Open Access Journals (Sweden)

    Zachary F Phillips

    Full Text Available We present a new technique for quantitative phase and amplitude microscopy from a single color image with coded illumination. Our system consists of a commercial brightfield microscope with one hardware modification-an inexpensive 3D printed condenser insert. The method, color-multiplexed Differential Phase Contrast (cDPC, is a single-shot variant of Differential Phase Contrast (DPC, which recovers the phase of a sample from images with asymmetric illumination. We employ partially coherent illumination to achieve resolution corresponding to 2× the objective NA. Quantitative phase can then be used to synthesize DIC and phase contrast images or extract shape and density. We demonstrate amplitude and phase recovery at camera-limited frame rates (50 fps for various in vitro cell samples and c. elegans in a micro-fluidic channel.

  20. Addressing preservation of elastic contrast in energy-filtered transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Brown, H.G.; D' Alfonso, A.J.; Forbes, B.D.; Allen, L.J., E-mail: lja@unimelb.edu.au

    2016-01-15

    Energy-filtered transmission electron microscopy (EFTEM) images with resolutions of the order of an Ångström can be obtained using modern microscopes corrected for chromatic aberration. However, the delocalized nature of the transition potentials for atomic ionization often confounds direct interpretation of EFTEM images, leading to what is known as “preservation of elastic contrast”. In this paper we demonstrate how more interpretable images might be obtained by scanning with a focused coherent probe and incoherently averaging the energy-filtered images over probe position. We dub this new imaging technique energy-filtered imaging scanning transmission electron microscopy (EFISTEM). We develop a theoretical framework for EFISTEM and show that it is in fact equivalent to precession EFTEM, where the plane wave illumination is precessed through a range of tilts spanning the same range of angles as the probe forming aperture in EFISTEM. It is demonstrated that EFISTEM delivers similar results to scanning transmission electron microscopy with an electron energy-loss spectrometer but has the advantage that it is immune to coherent aberrations and spatial incoherence of the probe and is also more resilient to scan distortions. - Highlights: • Interpretation of EFTEM images is complicated by preservation of elastic contrast. • More direct images obtained by scanning with a focused coherent probe and averaging. • This is equivalent to precession EFTEM through the solid angle defined by the probe. • Also yields similar results to energy-loss scanning transmission electron microscopy. • Scanning approach immune to probe aberrations and resilient to scan distortions.

  1. Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

    Science.gov (United States)

    Kazemzadeh, Farnoud; Wong, Alexander

    2016-12-01

    Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

  2. Modeling and analysis of laser active interference optical path

    Science.gov (United States)

    Shan, Cong-miao; Sun, Hua-yan; Zhao, Yan-zhong; Chen, Jian-biao; Ren, Jian-ying

    2017-10-01

    By using the geometrical optics and physical optics method, the models of wedge plate interference optical path, Michelson interferometer and Mach Zehnder interferometer thus three different active interference pattern are built. The optical path difference (OPD) launched by different interference patterns, fringe spacing and contrast expression have been derived. The results show that far field interference peak intensity of the wedge plate interference is small, so the detection distance is limited, Michelson interferometer with low contrast affects the performance of detection system, Mach Zehnder interferometer has greater advantages in peak intensity, the variable range of interference fringe spacing and contrast ratio. The results of this study are useful for the theoretical research and practical application of laser active interference detection.

  3. Automatic tracking of cells for video microscopy in patch clamp experiments.

    Science.gov (United States)

    Peixoto, Helton M; Munguba, Hermany; Cruz, Rossana M S; Guerreiro, Ana M G; Leao, Richardson N

    2014-06-20

    Visualisation of neurons labeled with fluorescent proteins or compounds generally require exposure to intense light for a relatively long period of time, often leading to bleaching of the fluorescent probe and photodamage of the tissue. Here we created a technique to drastically shorten light exposure and improve the targeting of fluorescent labeled cells that is specially useful for patch-clamp recordings. We applied image tracking and mask overlay to reduce the time of fluorescence exposure and minimise mistakes when identifying neurons. Neurons are first identified according to visual criteria (e.g. fluorescence protein expression, shape, viability etc.) and a transmission microscopy image Differential Interference Contrast (DIC) or Dodt contrast containing the cell used as a reference for the tracking algorithm. A fluorescence image can also be acquired later to be used as a mask (that can be overlaid on the target during live transmission video). As patch-clamp experiments require translating the microscope stage, we used pattern matching to track reference neurons in order to move the fluorescence mask to match the new position of the objective in relation to the sample. For the image processing we used the Open Source Computer Vision (OpenCV) library, including the Speeded-Up Robust Features (SURF) for tracking cells. The dataset of images (n = 720) was analyzed under normal conditions of acquisition and with influence of noise (defocusing and brightness). We validated the method in dissociated neuronal cultures and fresh brain slices expressing Enhanced Yellow Fluorescent Protein (eYFP) or Tandem Dimer Tomato (tdTomato) proteins, which considerably decreased the exposure to fluorescence excitation, thereby minimising photodamage. We also show that the neuron tracking can be used in differential interference contrast or Dodt contrast microscopy. The techniques of digital image processing used in this work are an important addition to the set of microscopy

  4. Robust Nucleus/Cell Detection and Segmentation in Digital Pathology and Microscopy Images: A Comprehensive Review.

    Science.gov (United States)

    Xing, Fuyong; Yang, Lin

    2016-01-01

    Digital pathology and microscopy image analysis is widely used for comprehensive studies of cell morphology or tissue structure. Manual assessment is labor intensive and prone to interobserver variations. Computer-aided methods, which can significantly improve the objectivity and reproducibility, have attracted a great deal of interest in recent literature. Among the pipeline of building a computer-aided diagnosis system, nucleus or cell detection and segmentation play a very important role to describe the molecular morphological information. In the past few decades, many efforts have been devoted to automated nucleus/cell detection and segmentation. In this review, we provide a comprehensive summary of the recent state-of-the-art nucleus/cell segmentation approaches on different types of microscopy images including bright-field, phase-contrast, differential interference contrast, fluorescence, and electron microscopies. In addition, we discuss the challenges for the current methods and the potential future work of nucleus/cell detection and segmentation.

  5. Real-time single-molecule imaging of quantum interference.

    Science.gov (United States)

    Juffmann, Thomas; Milic, Adriana; Müllneritsch, Michael; Asenbaum, Peter; Tsukernik, Alexander; Tüxen, Jens; Mayor, Marcel; Cheshnovsky, Ori; Arndt, Markus

    2012-03-25

    The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514 AMU and 1,298 AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics.

  6. Deciphering complex, functional structures with synchrotron-based absorption and phase contrast tomographic microscopy

    Science.gov (United States)

    Stampanoni, M.; Reichold, J.; Weber, B.; Haberthür, D.; Schittny, J.; Eller, J.; Büchi, F. N.; Marone, F.

    2010-09-01

    Nowadays, thanks to the high brilliance available at modern, third generation synchrotron facilities and recent developments in detector technology, it is possible to record volumetric information at the micrometer scale within few minutes. High signal-to-noise ratio, quantitative information on very complex structures like the brain micro vessel architecture, lung airways or fuel cells can be obtained thanks to the combination of dedicated sample preparation protocols, in-situ acquisition schemes and cutting-edge imaging analysis instruments. In this work we report on recent experiments carried out at the TOMCAT beamline of the Swiss Light Source [1] where synchrotron-based tomographic microscopy has been successfully used to obtain fundamental information on preliminary models for cerebral fluid flow [2], to provide an accurate mesh for 3D finite-element simulation of the alveolar structure of the pulmonary acinus [3] and to investigate the complex functional mechanism of fuel cells [4]. Further, we introduce preliminary results on the combination of absorption and phase contrast microscopy for the visualization of high-Z nanoparticles in soft tissues, a fundamental information when designing modern drug delivery systems [5]. As an outlook we briefly discuss the new possibilities offered by high sensitivity, high resolution grating interferomtery as well as Zernike Phase contrast nanotomography [6].

  7. Unraveling cell processes: interference imaging interwoven with data analysis

    DEFF Research Database (Denmark)

    Brazhe, Nadezda; Brazhe, Alexey; Pavlov, A N

    2006-01-01

    The paper presents results on the application of interference microscopy and wavelet-analysis for cell visualization and studies of cell dynamics. We demonstrate that interference imaging of erythrocytes can reveal reorganization of the cytoskeleton and inhomogenity in the distribution of hemoglo......The paper presents results on the application of interference microscopy and wavelet-analysis for cell visualization and studies of cell dynamics. We demonstrate that interference imaging of erythrocytes can reveal reorganization of the cytoskeleton and inhomogenity in the distribution...... properties differ from cell type to cell type and depend on the cellular compartment. Our results suggest that low frequency variations (0.1-0.6 Hz) result from plasma membrane processes and that higher frequency variations (20-26 Hz) are related to the movement of vesicles. Using double-wavelet analysis, we...... study the modulation of the 1 Hz rhythm in neurons and reveal its changes under depolarization and hyperpolarization of the plasma membrane. We conclude that interference microscopy combined with wavelet analysis is a useful technique for non-invasive cell studies, cell visualization, and investigation...

  8. Cell tracking with gadophrin-2: a bifunctional contrast agent for MR imaging, optical imaging, and fluorescence microscopy

    International Nuclear Information System (INIS)

    Daldrup-Link, Heike E.; Rudelius, Martina; Piontek, Guido; Schlegel, Juergen; Metz, Stephan; Settles, Marcus; Rummeny, Ernst J.; Pichler, Bernd; Heinzmann, Ulrich; Oostendorp, Robert A.J.

    2004-01-01

    The purpose of this study was to assess the feasibility of use of gadophrin-2 to trace intravenously injected human hematopoietic cells in athymic mice, employing magnetic resonance (MR) imaging, optical imaging (OI), and fluorescence microscopy. Mononuclear peripheral blood cells from GCSF-primed patients were labeled with gadophrin-2 (Schering AG, Berlin, Germany), a paramagnetic and fluorescent metalloporphyrin, using established transfection techniques with cationic liposomes. The labeled cells were evaluated in vitro with electron microscopy and inductively coupled plasma atomic emission spectrometry. Then, 1 x 10 6 -3 x 10 8 labeled cells were injected into 14 nude Balb/c mice and the in vivo cell distribution was evaluated with MR imaging and OI before and 4, 24, and 48 h after intravenous injection (p.i.). Five additional mice served as controls: three mice were untreated controls and two mice were investigated after injection of unlabeled cells. The contrast agent effect was determined quantitatively for MR imaging by calculating signal-to-noise-ratio (SNR) data. After completion of in vivo imaging studies, fluorescence microscopy of excised organs was performed. Intracellular cytoplasmatic uptake of gadophrin-2 was confirmed by electron microscopy. Spectrometry determined an uptake of 31.56 nmol Gd per 10 6 cells. After intravenous injection, the distribution of gadophrin-2 labeled cells in nude mice could be visualized by MR, OI, and fluorescence microscopy. At 4 h p.i., the transplanted cells mainly distributed to lung, liver, and spleen, and 24 h p.i. they also distributed to the bone marrow. Fluorescence microscopy confirmed the distribution of gadophrin-2 labeled cells to these target organs. Gadophrin-2 is suited as a bifunctional contrast agent for MR imaging, OI, and fluorescence microscopy and may be used to combine the advantages of each individual imaging modality for in vivo tracking of intravenously injected hematopoietic cells. (orig.)

  9. Polarization contrast in photon scanning tunnelling microscopy combined with atomic force microscopy

    NARCIS (Netherlands)

    Propstra, K.; Propstra, K.; van Hulst, N.F.

    1995-01-01

    Photon scanning tunnelling microscopy combined with atomic force microscopy allows simultaneous acquisition and direct comparison of optical and topographical images, both with a lateral resolution of about 30 nm, far beyond the optical diffraction limit. The probe consists of a modified

  10. Robust Nucleus/Cell Detection and Segmentation in Digital Pathology and Microscopy Images: A Comprehensive Review

    Science.gov (United States)

    Xing, Fuyong; Yang, Lin

    2016-01-01

    Digital pathology and microscopy image analysis is widely used for comprehensive studies of cell morphology or tissue structure. Manual assessment is labor intensive and prone to inter-observer variations. Computer-aided methods, which can significantly improve the objectivity and reproducibility, have attracted a great deal of interest in recent literatures. Among the pipeline of building a computer-aided diagnosis system, nucleus or cell detection and segmentation play a very important role to describe the molecular morphological information. In the past few decades, many efforts have been devoted to automated nucleus/cell detection and segmentation. In this review, we provide a comprehensive summary of the recent state-of-the-art nucleus/cell segmentation approaches on different types of microscopy images including bright-field, phase-contrast, differential interference contrast (DIC), fluorescence, and electron microscopies. In addition, we discuss the challenges for the current methods and the potential future work of nucleus/cell detection and segmentation. PMID:26742143

  11. Contrast matching of line gratings obtained with NXE3XXX and EUV- interference lithography

    Science.gov (United States)

    Tasdemir, Zuhal; Mochi, Iacopo; Olvera, Karen Garrido; Meeuwissen, Marieke; Yildirim, Oktay; Custers, Rolf; Hoefnagels, Rik; Rispens, Gijsbert; Fallica, Roberto; Vockenhuber, Michaela; Ekinci, Yasin

    2017-10-01

    Extreme UV lithography (EUVL) has gained considerable attention for several decades as a potential technology for the semiconductor industry and it is now close to being adopted in high-volume manufacturing. At Paul Scherrer Institute (PSI), we have focused our attention on EUV resist performance issues by testing available high-performance EUV resists in the framework of a joint collaboration with ASML. For this purpose, we use the grating-based EUV-IL setup installed at the Swiss Light Source (SLS) at PSI, in which a coherent beam with 13.5 nm wavelength is used to produce a periodic aerial image with virtually 100% contrast and large depth of focus. Interference lithography is a relatively simple technique and it does not require many optical components, therefore the unintended flare is minimized and the aerial image is well-defined sinusoidal pattern. For the collaborative work between PSI and ASML, exposures are being performed on the EUV-IL exposure tool at PSI. For better quantitative comparison to the NXE scanner results, it is targeted to determine the actual NILS of the EUV-IL exposure tool at PSI. Ultimately, any resist-related metrology must be aligned and compared with the performance of EUV scanners. Moreover, EUV-IL is a powerful method for evaluating the resist performance and a resist which performs well with EUV-IL, shows, in general, also good performance with NXE scanners. However, a quantitative prediction of the performance based on EUV-IL measurements has not been possible due to the differences in aerial image formation. In this work, we aim to study the performance of EUV resists with different aerial images. For this purpose, after the real interference pattern exposure, we overlay a flat field exposure to emulate different levels of contrast. Finally, the results are compared with data obtained from EUV scanner. This study will enable not only match the data obtained from EUV- IL at PSI with the performance of NXE scanners, but also a

  12. Microscopy imaging and quantitative phase contrast mapping in turbid microfluidic channels by digital holography.

    Science.gov (United States)

    Paturzo, Melania; Finizio, Andrea; Memmolo, Pasquale; Puglisi, Roberto; Balduzzi, Donatella; Galli, Andrea; Ferraro, Pietro

    2012-09-07

    We show that sharp imaging and quantitative phase-contrast microcopy is possible in microfluidics in flowing turbid media by digital holography. In fact, in flowing liquids with suspended colloidal particles, clear vision is hindered and cannot be recovered by any other microscopic imaging technique. On the contrary, using digital holography, clear imaging is possible thanks to the Doppler frequency shift experienced by the photons scattered by the flowing colloidal particles, which do not contribute to the interference process, i.e. the recorded hologram. The method is illustrated and imaging results are demonstrated for pure phase objects, i.e. biological cells in microfluidic channels.

  13. Stable and simple quantitative phase-contrast imaging by Fresnel biprism

    Science.gov (United States)

    Ebrahimi, Samira; Dashtdar, Masoomeh; Sánchez-Ortiga, Emilio; Martínez-Corral, Manuel; Javidi, Bahram

    2018-03-01

    Digital holographic (DH) microscopy has grown into a powerful nondestructive technique for the real-time study of living cells including dynamic membrane changes and cell fluctuations in nanometer and sub-nanometer scales. The conventional DH microscopy configurations require a separately generated coherent reference wave that results in a low phase stability and a necessity to precisely adjust the intensity ratio between two overlapping beams. In this work, we present a compact, simple, and very stable common-path DH microscope, employing a self-referencing configuration. The microscope is implemented by a diode laser as the source and a Fresnel biprism for splitting and recombining the beams simultaneously. In the overlapping area, linear interference fringes with high contrast are produced. The frequency of the interference pattern could be easily adjusted by displacement of the biprism along the optical axis without a decrease in fringe contrast. To evaluate the validity of the method, the spatial noise and temporal stability of the setup are compared with the common off-axis DH microscope based on a Mach-Zehnder interferometer. It is shown that the proposed technique has low mechanical noise as well as superb temporal stability with sub-nanometer precision without any external vibration isolation. The higher temporal stability improves the capabilities of the microscope for studying micro-object fluctuations, particularly in the case of biological specimens. Experimental results are presented using red blood cells and silica microspheres to demonstrate the system performance.

  14. Mathematical imaging methods for mitosis analysis in live-cell phase contrast microscopy.

    Science.gov (United States)

    Grah, Joana Sarah; Harrington, Jennifer Alison; Koh, Siang Boon; Pike, Jeremy Andrew; Schreiner, Alexander; Burger, Martin; Schönlieb, Carola-Bibiane; Reichelt, Stefanie

    2017-02-15

    In this paper we propose a workflow to detect and track mitotic cells in time-lapse microscopy image sequences. In order to avoid the requirement for cell lines expressing fluorescent markers and the associated phototoxicity, phase contrast microscopy is often preferred over fluorescence microscopy in live-cell imaging. However, common specific image characteristics complicate image processing and impede use of standard methods. Nevertheless, automated analysis is desirable due to manual analysis being subjective, biased and extremely time-consuming for large data sets. Here, we present the following workflow based on mathematical imaging methods. In the first step, mitosis detection is performed by means of the circular Hough transform. The obtained circular contour subsequently serves as an initialisation for the tracking algorithm based on variational methods. It is sub-divided into two parts: in order to determine the beginning of the whole mitosis cycle, a backwards tracking procedure is performed. After that, the cell is tracked forwards in time until the end of mitosis. As a result, the average of mitosis duration and ratios of different cell fates (cell death, no division, division into two or more daughter cells) can be measured and statistics on cell morphologies can be obtained. All of the tools are featured in the user-friendly MATLAB®Graphical User Interface MitosisAnalyser. Copyright © 2017. Published by Elsevier Inc.

  15. Dependency-dependent interference: NPI interference, agreement attraction, and global pragmatic inferences

    Directory of Open Access Journals (Sweden)

    Ming eXiang

    2013-10-01

    Full Text Available Previous psycholinguistics studies have shown that when forming a long distance dependency in online processing, the parser sometimes accepts a sentence even though the required grammatical constraints are only partially met. A mechanistic account of how such errors arise sheds light on both the underlying linguistic representations involved and the processing mechanisms that put such representations together. In the current study, we contrast the NPI (negative polarity items interference effect, as shown by the acceptance of an ungrammatical sentence like The bills that democratic senators have voted for will ever become law, with the well-known phenomenon of agreement attraction (The key to the cabinets are…. On the surface, these two types of errors look alike and thereby can be explained as being driven by the same source: similarity based memory interference. However, we argue that the linguistic representations involved in NPI licensing are substantially different from those of subject-verb agreement, and therefore the interference effects in each domain potentially arise from distinct sources. In particular, we show that NPI interference at least partially arises from pragmatic inferences. In a self-paced reading study with an acceptability judgment task, we showed NPI interference was modulated by participants’ general pragmatic communicative skills, as quantified by the Autism-Spectrum Quotient (Baron-Cohen 2001, especially in offline tasks. Participants with more autistic traits were actually less prone to the NPI interference effect than those with fewer autistic traits. This result contrasted with agreement attraction conditions, which were not influenced by individual pragmatic skill differences. We also show that different NPI licensors have distinct interference profiles. We discuss two kinds of interference effects for NPI licensing: memory-retrieval based and pragmatically triggered.

  16. Wafer defect detection by a polarization-insensitive external differential interference contrast module.

    Science.gov (United States)

    Nativ, Amit; Feldman, Haim; Shaked, Natan T

    2018-05-01

    We present a system that is based on a new external, polarization-insensitive differential interference contrast (DIC) module specifically adapted for detecting defects in semiconductor wafers. We obtained defect signal enhancement relative to the surrounding wafer pattern when compared with bright-field imaging. The new DIC module proposed is based on a shearing interferometer that connects externally at the output port of an optical microscope and enables imaging thin samples, such as wafer defects. This module does not require polarization optics (such as Wollaston or Nomarski prisms) and is insensitive to polarization, unlike traditional DIC techniques. In addition, it provides full control of the DIC shear and orientation, which allows obtaining a differential phase image directly on the camera (with no further digital processing) while enhancing defect detection capabilities, even if the size of the defect is smaller than the resolution limit. Our technique has the potential of future integration into semiconductor production lines.

  17. Interference in the processing of adjunct control

    Directory of Open Access Journals (Sweden)

    Dan eParker

    2015-09-01

    Full Text Available Recent research on the memory operations used in language comprehension has revealed a selective profile of interference effects during memory retrieval. Dependencies such as subject-verb agreement show strong facilitatory interference effects from structurally inappropriate but feature-matching distractors, leading to illusions of grammaticality (Dillon, Mishler, Sloggett, & Phillips, 2013; Pearlmutter, Garnsey, & Bock, 1999; Wagers, Lau, & Phillips, 2009. In contrast, dependencies involving reflexive anaphors are generally immune to interference effects (Dillon et al., 2013; Sturt, 2003; Xiang, Dillon, & Phillips, 2009. This contrast has led to the proposal that all anaphors that are subject to structural constraints are immune to facilitatory interference. Here we use an animacy manipulation to examine whether adjunct control dependencies, which involve an interpreted anaphoric relation between a null subject and its licensor, are also immune to facilitatory interference effects. Our results show reliable facilitatory interference in the processing of adjunct control dependencies, which challenges the generalization that anaphoric dependencies as a class are immune to such effects. To account for the contrast between adjunct control and reflexive dependencies, we suggest that variability within anaphora could reflect either an inherent primacy of animacy cues in retrieval processes, or differential degrees of match between potential licensors and the retrieval probe.

  18. Phase contrast scanning transmission electron microscopy imaging of light and heavy atoms at the limit of contrast and resolution.

    Science.gov (United States)

    Yücelen, Emrah; Lazić, Ivan; Bosch, Eric G T

    2018-02-08

    Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution. We use the technique to resolve both the Gallium and Nitrogen dumbbells in a GaN crystal in [[Formula: see text

  19. Contrast Enhanced Microscopy Digital Image Correlation: A General Method to Contact-Free Coefficient of Thermal Expansion Measurement of Polymer Films

    Science.gov (United States)

    Jairo A. Diaz; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Thermal expansion represents a vital indicator of the processing history and dimensional stability of materials. Solvent-sensitive, thin, and compliant samples are particularly challenging to test. Here we describe how textures highlighted by contrast enhanced optical microscopy modes (i.e., polarized light (PL), phase contrast (PC)) and bright field (BF) can be used...

  20. Automatic neuron segmentation and neural network analysis method for phase contrast microscopy images.

    Science.gov (United States)

    Pang, Jincheng; Özkucur, Nurdan; Ren, Michael; Kaplan, David L; Levin, Michael; Miller, Eric L

    2015-11-01

    Phase Contrast Microscopy (PCM) is an important tool for the long term study of living cells. Unlike fluorescence methods which suffer from photobleaching of fluorophore or dye molecules, PCM image contrast is generated by the natural variations in optical index of refraction. Unfortunately, the same physical principles which allow for these studies give rise to complex artifacts in the raw PCM imagery. Of particular interest in this paper are neuron images where these image imperfections manifest in very different ways for the two structures of specific interest: cell bodies (somas) and dendrites. To address these challenges, we introduce a novel parametric image model using the level set framework and an associated variational approach which simultaneously restores and segments this class of images. Using this technique as the basis for an automated image analysis pipeline, results for both the synthetic and real images validate and demonstrate the advantages of our approach.

  1. Demeclocycline as a contrast agent for detecting brain neoplasms using confocal microscopy

    Science.gov (United States)

    Wirth, Dennis; Smith, Thomas W.; Moser, Richard; Yaroslavsky, Anna N.

    2015-04-01

    Complete resection of brain tumors improves life expectancy and quality. Thus, there is a strong need for high-resolution detection and microscopically controlled removal of brain neoplasms. The goal of this study was to test demeclocycline as a contrast enhancer for the intraoperative detection of brain tumors. We have imaged benign and cancerous brain tumors using multimodal confocal microscopy. The tumors investigated included pituitary adenoma, meningiomas, glioblastomas, and metastatic brain cancers. Freshly excised brain tissues were stained in 0.75 mg ml-1 aqueous solution of demeclocyline. Reflectance images were acquired at 402 nm. Fluorescence signals were excited at 402 nm and registered between 500 and 540 nm. After imaging, histological sections were processed from the imaged specimens and compared to the optical images. Fluorescence images highlighted normal and cancerous brain cells, while reflectance images emphasized the morphology of connective tissue. The optical and histological images were in accordance with each other for all types of tumors investigated. Demeclocyline shows promise as a contrast agent for intraoperative detection of brain tumors.

  2. Demeclocycline as a contrast agent for detecting brain neoplasms using confocal microscopy

    International Nuclear Information System (INIS)

    Wirth, Dennis; Yaroslavsky, Anna N; Smith, Thomas W; Moser, Richard

    2015-01-01

    Complete resection of brain tumors improves life expectancy and quality. Thus, there is a strong need for high-resolution detection and microscopically controlled removal of brain neoplasms. The goal of this study was to test demeclocycline as a contrast enhancer for the intraoperative detection of brain tumors. We have imaged benign and cancerous brain tumors using multimodal confocal microscopy. The tumors investigated included pituitary adenoma, meningiomas, glioblastomas, and metastatic brain cancers. Freshly excised brain tissues were stained in 0.75 mg ml −1 aqueous solution of demeclocyline. Reflectance images were acquired at 402 nm. Fluorescence signals were excited at 402 nm and registered between 500 and 540 nm. After imaging, histological sections were processed from the imaged specimens and compared to the optical images. Fluorescence images highlighted normal and cancerous brain cells, while reflectance images emphasized the morphology of connective tissue. The optical and histological images were in accordance with each other for all types of tumors investigated. Demeclocyline shows promise as a contrast agent for intraoperative detection of brain tumors. (paper)

  3. Creating infinite contrast in fluorescence microscopy by using lanthanide centered emission

    DEFF Research Database (Denmark)

    R. Carro-Temboury, Miguel; Arppe, Riikka Matleena; Hempel, Casper

    2017-01-01

    The popularity of fluorescence microscopy arises from the inherent mode of action, where the fluorescence emission from probes is used to visualize selected features on a presumed dark background. However, the background is rarely truly dark, and image processing and analysis is needed to enhance...... the fluorescent signal that is ascribed to the selected feature. The image acquisition is facilitated by using considerable illumination, bright probes at a relatively high concentration in order to make the fluorescent signal significantly more intense than the background signal. Here, we present two methods......, while method II resolves the fluorescent signal by subtracting a background calculated via the gradient. Both methods improve signal-to-background ratio significantly and we suggest that spectral imaging of lanthanide-centered emission can be used as a tool to obtain absolute contrast in bioimaging....

  4. Focal switching of photochromic fluorescent proteins enables multiphoton microscopy with superior image contrast.

    Science.gov (United States)

    Kao, Ya-Ting; Zhu, Xinxin; Xu, Fang; Min, Wei

    2012-08-01

    Probing biological structures and functions deep inside live organisms with light is highly desirable. Among the current optical imaging modalities, multiphoton fluorescence microscopy exhibits the best contrast for imaging scattering samples by employing a spatially confined nonlinear excitation. However, as the incident laser power drops exponentially with imaging depth into the sample due to the scattering loss, the out-of-focus background eventually overwhelms the in-focus signal, which defines a fundamental imaging-depth limit. Herein we significantly improve the image contrast for deep scattering samples by harnessing reversibly switchable fluorescent proteins (RSFPs) which can be cycled between bright and dark states upon light illumination. Two distinct techniques, multiphoton deactivation and imaging (MPDI) and multiphoton activation and imaging (MPAI), are demonstrated on tissue phantoms labeled with Dronpa protein. Such a focal switch approach can generate pseudo background-free images. Conceptually different from wave-based approaches that try to reduce light scattering in turbid samples, our work represents a molecule-based strategy that focused on imaging probes.

  5. Wave front engineering by means of diffractive optical elements for applications in microscopy

    Science.gov (United States)

    Cojoc, Dan; Ferrari, Enrico; Garbin, Valeria; Cabrini, Stefano; Carpentiero, Alessandro; Prasciolu, Mauro; Businaro, Luca; Kaulich, Burchard; Di Fabrizio, Enzo

    2006-05-01

    We present a unified view regarding the use of diffractive optical elements (DOEs) for microscopy applications a wide range of electromagnetic spectrum. The unified treatment is realized through the design and fabrication of DOE through which wave front beam shaping is obtained. In particular we show applications ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy. We report some details on the design and physical implementation of diffractive elements that beside focusing perform also other optical functions: beam splitting, beam intensity and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of spherical micro beads and for direct trapping and manipulation of biological cells with non-spherical shapes. Another application is the Gauss to Laguerre-Gaussian mode conversion, which allows to trap and transfer orbital angular momentum of light to micro particles with high refractive index and to trap and manipulate low index particles. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for DOEs implementation. High resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in X-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field X-ray microscopy.

  6. Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

    International Nuclear Information System (INIS)

    Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao; Liu Yijin; Yue Zhengbo; Yu Hanqing; Wang Chunru

    2009-01-01

    A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 μm thickness and 4 μm width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

  7. Fresnel zone-plate based X-ray microscopy in Zernike phase contrast with sub-50 nm resolution at NSRL

    Energy Technology Data Exchange (ETDEWEB)

    Chen Jie; Li Wenjie; Tian Jinping; Liu Longhua; Xiong Ying; Liu Gang; Wu Ziyu; Tian Yangchao [National Synchrotron Radiation Laboratory (China); Liu Yijin [School of Physics (China); Yue Zhengbo; Yu Hanqing [Laboratory of Environmental Engineering, School of Chemistry, University of Science and Technology of China, Hefei Anhui 230029 (China); Wang Chunru, E-mail: ychtian@ustc.edu.c [Institute of Chemistry, Chinese Academy of Sciences, Beijing 10060 (China)

    2009-09-01

    A transmission X-ray microscope using Fresnel zone-plates (FZPs) has been installed at U7A beamline of National Synchrotron Radiation Laboratory (NSRL). The objective FZP with 45 nm outermost zone width delivers a sub-50 nm resolution. A gold phase ring with 2.5 {mu}m thickness and 4 {mu}m width was placed at the focal plane of the objective FZP at 8 keV to produce a negative Zernike phase contrast. A series of samples were used to test the performance of the Zernike phase contrast X-ray microscopy.

  8. Fluorescence microscopy.

    Science.gov (United States)

    Sanderson, Michael J; Smith, Ian; Parker, Ian; Bootman, Martin D

    2014-10-01

    Fluorescence microscopy is a major tool with which to monitor cell physiology. Although the concepts of fluorescence and its optical separation using filters remain similar, microscope design varies with the aim of increasing image contrast and spatial resolution. The basics of wide-field microscopy are outlined to emphasize the selection, advantages, and correct use of laser scanning confocal microscopy, two-photon microscopy, scanning disk confocal microscopy, total internal reflection, and super-resolution microscopy. In addition, the principles of how these microscopes form images are reviewed to appreciate their capabilities, limitations, and constraints for operation. © 2014 Cold Spring Harbor Laboratory Press.

  9. Laboratory soft x-ray microscopy and tomography

    International Nuclear Information System (INIS)

    Bertilson, Michael

    2011-01-01

    Soft x-ray microscopy in the water-window (λ = 2.28 nm - 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x-ray facilities, thereby limiting their accessibility for a wider scientific community. This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments

  10. Proactive interference of open field on consummatory successive negative contrast.

    Science.gov (United States)

    Justel, Nadia; Pautassi, Ricardo; Mustaca, Alba

    2014-03-01

    Reactivity to a reward is affected by prior experience with the different reinforcer values of that reward, a phenomenon known as incentive relativity, which can be studied using the consummatory succesive negative contrast (cSNC) paradigm, in which the performance of animals that receive a 4 % sucrose solution after trials on which they were exposed to 32 % sucrose is compared with that of subjects that always receive the 4 % sucrose solution. The exploration of a novel open field can enhance or block the acquisition of associative and nonassociative memories. The effect of open field on cSNC has not yet been explored. The main result of the present study was that open-field exposure significantly modified the expression of cSNC. Exposure to an open field 1 h but not immediately before the downshift interfered with the expression of cSNC. These animals drank more of the downshifted reward than did controls that were not exposed to the apparatus, and this behavior persisted for up to three recovery trials. This phenomenon was observed even when the animals were given a more protracted preshift phase and when the discrepancy between the preshift and shift incentive values of sucrose were increased. An open field also interfered with incentive downshift when open-field exposure occurred 6 h before the downshift, and repeated exposure to the apparatus did not deteriorate this effect. The present study adds to a growing body of literature that indicates that open-field exploration can interfere with memory formation.

  11. High-contrast fluorescence imaging based on the polarization dependence of the fluorescence enhancement using an optical interference mirror slide.

    Science.gov (United States)

    Yasuda, Mitsuru; Akimoto, Takuo

    2015-01-01

    High-contrast fluorescence imaging using an optical interference mirror (OIM) slide that enhances the fluorescence from a fluorophore located on top of the OIM surface is reported. To enhance the fluorescence and reduce the background light of the OIM, transverse-electric-polarized excitation light was used as incident light, and the transverse-magnetic-polarized fluorescence signal was detected. As a result, an approximate 100-fold improvement in the signal-to-noise ratio was achieved through a 13-fold enhancement of the fluorescence signal and an 8-fold reduction of the background light.

  12. Near-field imaging of interference pattern of counterpropagating evanescent waves

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Bozhevolnaya, Elena A.

    1999-01-01

    It is generally accepted that measurement of of the contrast of the intensity interference pattern formed by two counterpropagating evanescent waves can be used to characterize the resolving power of a collection near-field microscope. We argue that, if the light collected by a fiber probe propag...... be equal to the contrast of the interference pattern....

  13. Automated Method for the Rapid and Precise Estimation of Adherent Cell Culture Characteristics from Phase Contrast Microscopy Images

    Science.gov (United States)

    Jaccard, Nicolas; Griffin, Lewis D; Keser, Ana; Macown, Rhys J; Super, Alexandre; Veraitch, Farlan S; Szita, Nicolas

    2014-01-01

    The quantitative determination of key adherent cell culture characteristics such as confluency, morphology, and cell density is necessary for the evaluation of experimental outcomes and to provide a suitable basis for the establishment of robust cell culture protocols. Automated processing of images acquired using phase contrast microscopy (PCM), an imaging modality widely used for the visual inspection of adherent cell cultures, could enable the non-invasive determination of these characteristics. We present an image-processing approach that accurately detects cellular objects in PCM images through a combination of local contrast thresholding and post hoc correction of halo artifacts. The method was thoroughly validated using a variety of cell lines, microscope models and imaging conditions, demonstrating consistently high segmentation performance in all cases and very short processing times (image). Based on the high segmentation performance, it was possible to precisely determine culture confluency, cell density, and the morphology of cellular objects, demonstrating the wide applicability of our algorithm for typical microscopy image processing pipelines. Furthermore, PCM image segmentation was used to facilitate the interpretation and analysis of fluorescence microscopy data, enabling the determination of temporal and spatial expression patterns of a fluorescent reporter. We created a software toolbox (PHANTAST) that bundles all the algorithms and provides an easy to use graphical user interface. Source-code for MATLAB and ImageJ is freely available under a permissive open-source license. Biotechnol. Bioeng. 2014;111: 504–517. © 2013 Wiley Periodicals, Inc. PMID:24037521

  14. Neural mechanisms of interference control in working memory: effects of interference expectancy and fluid intelligence.

    Directory of Open Access Journals (Sweden)

    Gregory C Burgess

    2010-09-01

    Full Text Available A critical aspect of executive control is the ability to limit the adverse effects of interference. Previous studies have shown activation of left ventrolateral prefrontal cortex after the onset of interference, suggesting that interference may be resolved in a reactive manner. However, we suggest that interference control may also operate in a proactive manner to prevent effects of interference. The current study investigated the temporal dynamics of interference control by varying two factors - interference expectancy and fluid intelligence (gF - that could influence whether interference control operates proactively versus reactively.A modified version of the recent negatives task was utilized. Interference expectancy was manipulated across task blocks by changing the proportion of recent negative (interference trials versus recent positive (facilitation trials. Furthermore, we explored whether gF affected the tendency to utilize specific interference control mechanisms. When interference expectancy was low, activity in lateral prefrontal cortex replicated prior results showing a reactive control pattern (i.e., interference-sensitivity during probe period. In contrast, when interference expectancy was high, bilateral prefrontal cortex activation was more indicative of proactive control mechanisms (interference-related effects prior to the probe period. Additional results suggested that the proactive control pattern was more evident in high gF individuals, whereas the reactive control pattern was more evident in low gF individuals.The results suggest the presence of two neural mechanisms of interference control, with the differential expression of these mechanisms modulated by both experimental (e.g., expectancy effects and individual difference (e.g., gF factors.

  15. Interference and Sensitivity Analysis.

    Science.gov (United States)

    VanderWeele, Tyler J; Tchetgen Tchetgen, Eric J; Halloran, M Elizabeth

    2014-11-01

    Causal inference with interference is a rapidly growing area. The literature has begun to relax the "no-interference" assumption that the treatment received by one individual does not affect the outcomes of other individuals. In this paper we briefly review the literature on causal inference in the presence of interference when treatments have been randomized. We then consider settings in which causal effects in the presence of interference are not identified, either because randomization alone does not suffice for identification, or because treatment is not randomized and there may be unmeasured confounders of the treatment-outcome relationship. We develop sensitivity analysis techniques for these settings. We describe several sensitivity analysis techniques for the infectiousness effect which, in a vaccine trial, captures the effect of the vaccine of one person on protecting a second person from infection even if the first is infected. We also develop two sensitivity analysis techniques for causal effects in the presence of unmeasured confounding which generalize analogous techniques when interference is absent. These two techniques for unmeasured confounding are compared and contrasted.

  16. Interference of an array of independent Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Hadzibabic, Zoran; Stock, Sabine; Battelier, Baptiste; Bretin, Vincent; Dalibard, Jean

    2004-01-01

    We have observed high-contrast matter wave interference between 30 Bose-Einstein condensates with uncorrelated phases. Interferences were observed after the independent condensates were released from a one-dimensional optical lattice and allowed to overlap. This phenomenon is explained with a simple theoretical model, which generalizes the analysis of the interference of two condensates

  17. Perspective: Differential dynamic microscopy extracts multi-scale activity in complex fluids and biological systems

    Science.gov (United States)

    Cerbino, Roberto; Cicuta, Pietro

    2017-09-01

    Differential dynamic microscopy (DDM) is a technique that exploits optical microscopy to obtain local, multi-scale quantitative information about dynamic samples, in most cases without user intervention. It is proving extremely useful in understanding dynamics in liquid suspensions, soft materials, cells, and tissues. In DDM, image sequences are analyzed via a combination of image differences and spatial Fourier transforms to obtain information equivalent to that obtained by means of light scattering techniques. Compared to light scattering, DDM offers obvious advantages, principally (a) simplicity of the setup; (b) possibility of removing static contributions along the optical path; (c) power of simultaneous different microscopy contrast mechanisms; and (d) flexibility of choosing an analysis region, analogous to a scattering volume. For many questions, DDM has also advantages compared to segmentation/tracking approaches and to correlation techniques like particle image velocimetry. The very straightforward DDM approach, originally demonstrated with bright field microscopy of aqueous colloids, has lately been used to probe a variety of other complex fluids and biological systems with many different imaging methods, including dark-field, differential interference contrast, wide-field, light-sheet, and confocal microscopy. The number of adopting groups is rapidly increasing and so are the applications. Here, we briefly recall the working principles of DDM, we highlight its advantages and limitations, we outline recent experimental breakthroughs, and we provide a perspective on future challenges and directions. DDM can become a standard primary tool in every laboratory equipped with a microscope, at the very least as a first bias-free automated evaluation of the dynamics in a system.

  18. Adaptive optics in spinning disk microscopy: improved contrast and brightness by a simple and fast method.

    Science.gov (United States)

    Fraisier, V; Clouvel, G; Jasaitis, A; Dimitrov, A; Piolot, T; Salamero, J

    2015-09-01

    Multiconfocal microscopy gives a good compromise between fast imaging and reasonable resolution. However, the low intensity of live fluorescent emitters is a major limitation to this technique. Aberrations induced by the optical setup, especially the mismatch of the refractive index and the biological sample itself, distort the point spread function and further reduce the amount of detected photons. Altogether, this leads to impaired image quality, preventing accurate analysis of molecular processes in biological samples and imaging deep in the sample. The amount of detected fluorescence can be improved with adaptive optics. Here, we used a compact adaptive optics module (adaptive optics box for sectioning optical microscopy), which was specifically designed for spinning disk confocal microscopy. The module overcomes undesired anomalies by correcting for most of the aberrations in confocal imaging. Existing aberration detection methods require prior illumination, which bleaches the sample. To avoid multiple exposures of the sample, we established an experimental model describing the depth dependence of major aberrations. This model allows us to correct for those aberrations when performing a z-stack, gradually increasing the amplitude of the correction with depth. It does not require illumination of the sample for aberration detection, thus minimizing photobleaching and phototoxicity. With this model, we improved both signal-to-background ratio and image contrast. Here, we present comparative studies on a variety of biological samples. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  19. Atomic force microscopy of pea starch: origins of image contrast.

    Science.gov (United States)

    Ridout, Michael J; Parker, Mary L; Hedley, Cliff L; Bogracheva, Tatiana Y; Morris, Victor J

    2004-01-01

    Atomic force microscopy (AFM) has been used to image the internal structure of pea starch granules. Starch granules were encased in a nonpenetrating matrix of rapid-set Araldite. Images were obtained of the internal structure of starch exposed by cutting the face of the block and of starch in sections collected on water. These images have been obtained without staining, or either chemical or enzymatic treatment of the granule. It has been demonstrated that contrast in the AFM images is due to localized absorption of water within specific regions of the exposed fragments of the starch granules. These regions swell, becoming "softer" and higher than surrounding regions. The images obtained confirm the "blocklet model" of starch granule architecture. By using topographic, error signal and force modulation imaging modes on samples of the wild-type pea starch and the high amylose r near-isogenic mutant, it has been possible to demonstrate differing structures within granules of different origin. These architectural changes provide a basis for explaining the changed appearance and functionality of the r mutant. The growth-ring structure of the granule is suggested to arise from localized "defects" in blocklet distribution within the granule. It is proposed that these defects are partially crystalline regions devoid of amylose.

  20. Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

    Science.gov (United States)

    Wang, Dehua

    2014-09-01

    The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

  1. Assessment of occupational exposure to asbestos fibers: Contribution of analytical transmission electron microscopy analysis and comparison with phase-contrast microscopy.

    Science.gov (United States)

    Eypert-Blaison, Céline; Romero-Hariot, Anita; Clerc, Frédéric; Vincent, Raymond

    2018-03-01

    From November 2009 to October 2010, the French general directorate for labor organized a large field-study using analytical transmission electron microscopy (ATEM) to characterize occupational exposure to asbestos fibers during work on asbestos containing materials (ACM). The primary objective of this study was to establish a method and to validate the feasibility of using ATEM for the analysis of airborne asbestos of individual filters sampled in various occupational environments. For each sampling event, ATEM data were compared to those obtained by phase-contrast optical microscopy (PCOM), the WHO-recommended reference technique. A total of 265 results were obtained from 29 construction sites where workers were in contact with ACM. Data were sorted depending on the combination of the ACM type and the removal technique. For each "ACM-removal technique" combination, ATEM data were used to compute statistical indicators on short, fine and WHO asbestos fibers. Moreover, exposure was assessed taking into account the use of respiratory protective devices (RPD). As in previous studies, no simple relationship was found between results by PCOM and ATEM counting methods. Some ACM, such as asbestos-containing plasters, generated very high dust levels, and some techniques generated considerable levels of dust whatever the ACM treated. On the basis of these observations, recommendations were made to measure and control the occupational exposure limit. General prevention measures to be taken during work with ACM are also suggested. Finally, it is necessary to continue acquiring knowledge, in particular regarding RPD and the dust levels measured by ATEM for the activities not evaluated during this study.

  2. Molecular-scale noncontact atomic force microscopy contrasts in topography and energy dissipation on c(4x2) superlattice structures of alkanethiol self-assembled monolayers

    OpenAIRE

    Fukuma, Takeshi; Ichii, Takashi; Kobayashi, Kei; Yamada, Hirofumi; Matsushige, Kazumi

    2004-01-01

    Alkanethiol self-assembledmonolayers formed on Au(111) surfaces were investigated by noncontact atomic force microscopy (NC-AFM). Dodecanethiol monolayers prepared at 78 °C were imaged by NC-AFM, which revealed that the film is composed predominantly of two different phases of c(4×2)superlattice structures. The obtained molecular-scale NC-AFM contrasts are discussed in comparison with previously reported scanning tunneling microscopy images. We found that the energy dissipation image exhibits...

  3. Quantitative optical microscopy: measurement of cellular biophysical features with a standard optical microscope.

    Science.gov (United States)

    Phillips, Kevin G; Baker-Groberg, Sandra M; McCarty, Owen J T

    2014-04-07

    We describe the use of a standard optical microscope to perform quantitative measurements of mass, volume, and density on cellular specimens through a combination of bright field and differential interference contrast imagery. Two primary approaches are presented: noninterferometric quantitative phase microscopy (NIQPM), to perform measurements of total cell mass and subcellular density distribution, and Hilbert transform differential interference contrast microscopy (HTDIC) to determine volume. NIQPM is based on a simplified model of wave propagation, termed the paraxial approximation, with three underlying assumptions: low numerical aperture (NA) illumination, weak scattering, and weak absorption of light by the specimen. Fortunately, unstained cellular specimens satisfy these assumptions and low NA illumination is easily achieved on commercial microscopes. HTDIC is used to obtain volumetric information from through-focus DIC imagery under high NA illumination conditions. High NA illumination enables enhanced sectioning of the specimen along the optical axis. Hilbert transform processing on the DIC image stacks greatly enhances edge detection algorithms for localization of the specimen borders in three dimensions by separating the gray values of the specimen intensity from those of the background. The primary advantages of NIQPM and HTDIC lay in their technological accessibility using "off-the-shelf" microscopes. There are two basic limitations of these methods: slow z-stack acquisition time on commercial scopes currently abrogates the investigation of phenomena faster than 1 frame/minute, and secondly, diffraction effects restrict the utility of NIQPM and HTDIC to objects from 0.2 up to 10 (NIQPM) and 20 (HTDIC) μm in diameter, respectively. Hence, the specimen and its associated time dynamics of interest must meet certain size and temporal constraints to enable the use of these methods. Excitingly, most fixed cellular specimens are readily investigated with

  4. Selective sensitivity in Kerr microscopy.

    Science.gov (United States)

    Soldatov, I V; Schäfer, R

    2017-07-01

    A new technique for contrast separation in wide-field magneto-optical Kerr microscopy is introduced. Utilizing the light from eight light emitting diodes, guided to the microscope by glass fibers and being switched synchronously with the camera exposure, domain images with orthogonal in-plane sensitivity can be displayed simultaneously at real-time, and images with pure in-plane or polar contrast can be obtained. The benefit of this new method of contrast separation is demonstrated for Permalloy films, a NdFeB sinter magnet, and a cobalt crystal. Moreover, the new technique is shown to strongly enhance the sensitivity of Kerr microscopy by eliminating parasitic contrast contributions occurring in conventional setups. A doubling of the in-plane domain contrast and a sensitivity to Kerr rotations as low as 0.6 mdeg is demonstrated.

  5. Selective sensitivity in Kerr microscopy

    Science.gov (United States)

    Soldatov, I. V.; Schäfer, R.

    2017-07-01

    A new technique for contrast separation in wide-field magneto-optical Kerr microscopy is introduced. Utilizing the light from eight light emitting diodes, guided to the microscope by glass fibers and being switched synchronously with the camera exposure, domain images with orthogonal in-plane sensitivity can be displayed simultaneously at real-time, and images with pure in-plane or polar contrast can be obtained. The benefit of this new method of contrast separation is demonstrated for Permalloy films, a NdFeB sinter magnet, and a cobalt crystal. Moreover, the new technique is shown to strongly enhance the sensitivity of Kerr microscopy by eliminating parasitic contrast contributions occurring in conventional setups. A doubling of the in-plane domain contrast and a sensitivity to Kerr rotations as low as 0.6 mdeg is demonstrated.

  6. Fluorescence (Multiwave) Confocal Microscopy.

    Science.gov (United States)

    Welzel, J; Kästle, Raphaela; Sattler, Elke C

    2016-10-01

    In addition to reflectance confocal microscopy, multiwave confocal microscopes with different laser wavelengths in combination with exogenous fluorophores allow fluorescence mode confocal microscopy in vivo and ex vivo. Fluorescence mode confocal microscopy improves the contrast between the epithelium and the surrounding soft tissue and allows the depiction of certain structures, like epithelial tumors, nerves, and glands. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. Enhancing resolution and contrast in second-harmonic generation microscopy using an advanced maximum likelihood estimation restoration method

    Science.gov (United States)

    Sivaguru, Mayandi; Kabir, Mohammad M.; Gartia, Manas Ranjan; Biggs, David S. C.; Sivaguru, Barghav S.; Sivaguru, Vignesh A.; Berent, Zachary T.; Wagoner Johnson, Amy J.; Fried, Glenn A.; Liu, Gang Logan; Sadayappan, Sakthivel; Toussaint, Kimani C.

    2017-02-01

    Second-harmonic generation (SHG) microscopy is a label-free imaging technique to study collagenous materials in extracellular matrix environment with high resolution and contrast. However, like many other microscopy techniques, the actual spatial resolution achievable by SHG microscopy is reduced by out-of-focus blur and optical aberrations that degrade particularly the amplitude of the detectable higher spatial frequencies. Being a two-photon scattering process, it is challenging to define a point spread function (PSF) for the SHG imaging modality. As a result, in comparison with other two-photon imaging systems like two-photon fluorescence, it is difficult to apply any PSF-engineering techniques to enhance the experimental spatial resolution closer to the diffraction limit. Here, we present a method to improve the spatial resolution in SHG microscopy using an advanced maximum likelihood estimation (AdvMLE) algorithm to recover the otherwise degraded higher spatial frequencies in an SHG image. Through adaptation and iteration, the AdvMLE algorithm calculates an improved PSF for an SHG image and enhances the spatial resolution by decreasing the full-width-at-halfmaximum (FWHM) by 20%. Similar results are consistently observed for biological tissues with varying SHG sources, such as gold nanoparticles and collagen in porcine feet tendons. By obtaining an experimental transverse spatial resolution of 400 nm, we show that the AdvMLE algorithm brings the practical spatial resolution closer to the theoretical diffraction limit. Our approach is suitable for adaptation in micro-nano CT and MRI imaging, which has the potential to impact diagnosis and treatment of human diseases.

  8. THE STRUCTURE AND CONCENTRATION OF SOLIDS IN PHOTORECEPTOR CELLS STUDIED BY REFRACTOMETRY AND INTERFERENCE MICROSCOPY

    Science.gov (United States)

    Sidman, Richard L.

    1957-01-01

    Fragments of freshly obtained retinas of several vertebrate species were studied by refractometry, with reference to the structure of the rods and cones. The findings allowed a reassessment of previous descriptions based mainly on fixed material. The refractometric method was used also to measure the refractice indices and to calculate the concentrations of solids and water in the various cell segments. The main quantitative data were confirmed by interference microscopy. When examined by the method of refractometry the outer segments of freshly prepared retinal rods appear homogeneous. Within a few minutes a single eccentric longitudinal fiber appears, and transverse striations may develop. These changes are attributed to imbibition of water and swelling in structures normally too small for detection by light microscopy. The central "core" of outer segments and the chromophobic disc between outer and inner segments appear to be artifacts resulting from shrinkage during dehydration. The fresh outer segments of cones, and the inner segments of rods and cones also are described and illustrated. The volumes, refractive indices, concentrations of solids, and wet and dry weights of various segments of the photoreceptor cells were tabulated. Rod outer segments of the different species vary more than 100-fold in volume and mass but all have concentrations of solids of 40 to 43 per cent. Cone outer segments contain only about 30 per cent solids. The myoids, paraboloids, and ellipsoids of the inner segments likewise have characteristic refractive indices and concentrations of solids. Some of the limitations and particular virtues of refractometry as a method for quantitative analysis of living cells are discussed in comparison with more conventional biochemical techniques. Also the shapes and refractive indices of the various segments of photoreceptor cells are considered in relation to the absorption and transmission of light. The Stiles-Crawford effect can be accounted

  9. Thickness and roughness measurements of nano thin films by interference

    Directory of Open Access Journals (Sweden)

    A Sabzalipour

    2011-06-01

    Full Text Available In the standard optical interference fringes approach, by measuring shift of the interference fringes due to step edge of thin film on substrate, thickness of the layer has already been measured. In order to improve the measurement precision of this popular method, the interference fringes intensity curve was extracted and analyzed before and after the step preparation. By this method, one can measure a few nanometers films thickness. In addition, using the interference fringes intensity curve and its fluctuations, the roughness of surface is measured within a few nanometers accuracy. Comparison of our results with some direct methods of thickness and roughness measurements, i.e. using surface profilemeter and atomic force microscopy confirms the accuracy of the suggested improvements.

  10. Diffraction contrast as a sensitive indicator of femtosecond sub-nanoscale motion in ultrafast transmission electron microscopy

    Science.gov (United States)

    Cremons, Daniel R.; Schliep, Karl B.; Flannigan, David J.

    2013-09-01

    With ultrafast transmission electron microscopy (UTEM), access can be gained to the spatiotemporal scales required to directly visualize rapid, non-equilibrium structural dynamics of materials. This is achieved by operating a transmission electron microscope (TEM) in a stroboscopic pump-probe fashion by photoelectrically generating coherent, well-timed electron packets in the gun region of the TEM. These probe photoelectrons are accelerated down the TEM column where they travel through the specimen before reaching a standard, commercially-available CCD detector. A second laser pulse is used to excite (pump) the specimen in situ. Structural changes are visualized by varying the arrival time of the pump laser pulse relative to the probe electron packet at the specimen. Here, we discuss how ultrafast nanoscale motions of crystalline materials can be visualized and precisely quantified using diffraction contrast in UTEM. Because diffraction contrast sensitively depends upon both crystal lattice orientation as well as incoming electron wavevector, minor spatial/directional variations in either will produce dynamic and often complex patterns in real-space images. This is because sections of the crystalline material that satisfy the Laue conditions may be heterogeneously distributed such that electron scattering vectors vary over nanoscale regions. Thus, minor changes in either crystal grain orientation, as occurs during specimen tilting, warping, or anisotropic expansion, or in the electron wavevector result in dramatic changes in the observed diffraction contrast. In this way, dynamic contrast patterns observed in UTEM images can be used as sensitive indicators of ultrafast specimen motion. Further, these motions can be spatiotemporally mapped such that direction and amplitude can be determined.

  11. Generalised phase contrast: microscopy, manipulation and more

    DEFF Research Database (Denmark)

    Palima, Darwin; Glückstad, Jesper

    2010-01-01

    Generalised phase contrast (GPC) not only leads to more accurate phase imaging beyond thin biological samples, but serves as an enabling framework in developing tools over a wide spectrum of contemporary applications in optics and photonics, including optical trapping and micromanipulation, optic...

  12. Observation of Magnetic Induction Distribution by Scanning Interference Electron Microscopy

    Science.gov (United States)

    Takahashi, Yoshio; Yajima, Yusuke; Ichikawa, Masakazu; Kuroda, Katsuhiro

    1994-09-01

    A scanning interference electron microscope (SIEM) capable of observing magnetic induction distribution with high sensitivity and spatial resolution has been developed. The SIEM uses a pair of fine coherent scanning probes and detects their relative phase change by magnetic induction, giving raster images of microscopic magnetic distributions. Its performance has been demonstrated by observing magnetic induction distributed near the edge of a recorded magnetic storage medium. Obtained images are compared with corresponding images taken in the scanning Lorentz electron microscope mode using the same microscope, and the differences between them are discussed.

  13. Oxygen-free in situ scanning tunnelling microscopy

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Ulstrup, Jens

    2007-01-01

    Scanning tunneling microscopy under full electrochemical potential control (in situ STM) has been used extensively as an efficient method to characterize microstructures at solid/liquid interfaces at the atomic and molecular levels. However, under ambient conditions oxygen may interfere in open i...

  14. CARS microscopy for imaging

    International Nuclear Information System (INIS)

    Arzumanyan Grigory; Voskanyan Karine

    2013-01-01

    Optical microscopy grows in its importance with the development of modern nanotechnology, biotechnology, methods of diagnostics and treatment of most dangerous diseases for mankind. There are several important goals of optical microscopy for biomedical studies among which the next three may be distinguished: fast imaging with high lateral spatial resolution, 3-D sectioning capability and high contrast for chemical selectivity. To meet these specific requirements, various types of both linear and nonlinear optical microscopy were elaborated. (authors)

  15. Combinatorial experiment in Ni-Ti thin films by laser interference structuring

    International Nuclear Information System (INIS)

    Liu, K.W.; Gachot, C.; Leibenguth, P.; Muecklich, F.

    2005-01-01

    Combinatorial experiments are achieved on periodically structured Ni-Ti thin film composition spreads by laser interference irradiation using a Nd:YAG laser. Continuous Ni-Ti compositional spreads covering almost the whole binary system are prepared by combining sputter mask, shutter and movement of substrate. The continuous compositional spread is subsequently micro-structured into a sample library consisting of well-defined lines of individual samples by laser interference irradiation. The composition and microstructure effects in continuous spread and sample libraries after laser structuring are explored by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and white light interferometry (WLI) microscopy. The sample library consists of individual samples with a distance of about 5 μm and a composition resolution as high as 0.1 at.% in between. Although, there are certain difficulties so far in obtaining the optimized laser fluence for the spread, the laser interference irradiation provides an effective way to prepare thin film libraries with around 200 sample lines within 1 mm

  16. Restoration of uneven illumination in light sheet microscopy images.

    Science.gov (United States)

    Uddin, Mohammad Shorif; Lee, Hwee Kuan; Preibisch, Stephan; Tomancak, Pavel

    2011-08-01

    Light microscopy images suffer from poor contrast due to light absorption and scattering by the media. The resulting decay in contrast varies exponentially across the image along the incident light path. Classical space invariant deconvolution approaches, while very effective in deblurring, are not designed for the restoration of uneven illumination in microscopy images. In this article, we present a modified radiative transfer theory approach to solve the contrast degradation problem of light sheet microscopy (LSM) images. We confirmed the effectiveness of our approach through simulation as well as real LSM images.

  17. The Michelson interferometer-how to detect invisible interference patterns

    International Nuclear Information System (INIS)

    Verovnik, Ivo; Likar, Andrej

    2004-01-01

    In a Michelson interferometer, the contrast of the interference pattern fades away due to incoherence of light when the mirrors are not in equidistant positions. We propose an experiment where the distance between the interference fringes can be determined, even when the difference in length of the interferometer arms is far beyond the coherence length of the light, i.e. when the interference pattern disappears completely for the naked eye. We used a semiconductor laser with two photodiodes as sensors, which enabled us to follow the fluctuations of the light intensity on the screen. The distance between invisible interference fringes was determined from periodic changes of the summed fluctuating signal, obtained by changing the distance between the two sensors

  18. Alpha-recoil tracks in natural dark mica: Dating geological samples by optical and scanning force microscopy

    International Nuclear Information System (INIS)

    Glasmacher, U.A.; Lang, M.; Klemme, S.; Moine, B.; Barbero, L.; Neumann, R.; Wagner, G.A.

    2003-01-01

    Alpha-recoil tracks (ART) are lattice defects caused by the α-decay of 238 U, 235 U, 232 Th, and daughter products. Visualization of etched ARTs in dark mica by phase-contrast microscopy allows dating of Quaternary geological as well as archaeological materials. Visualization of etched ARTs by Nomarski-differential-interference-contrast microscopy (NDICM) and scanning force microscopy (SFM) enables the access to areal densities (ρ a ) of ART etch pits beyond 10 4 mm -2 and thus the extension of the new ART-dating technique to an age range >1 Ma. The successful application of SFM as a new tool in geochronology could open the way to a field to be characterized as nanogeochronology. In order to visualize ARTs by NDICM and SFM, dark mica was etched with 4% HF at 21 deg. C for 5-107 min. A linear relationship between ρ a and etching time (t e ) was observed for phlogopites from the Kerguelen Islands (French territory, Indian Ocean), and the Kovdor magmatic complex (Russia). The volume density (ρ v ) of ART is a function of etching speed (v eff ) and slope of the ρ a -growth curve. The ART-age equation allows the calculation of an individual ρ v -growth curve for the phlogopite analysed by us using the uranium and thorium content. The ART-ages were determined by combining the experimentally obtained volume density with the individual ρ v -growth curve

  19. Reconstruction methods for phase-contrast tomography

    Energy Technology Data Exchange (ETDEWEB)

    Raven, C.

    1997-02-01

    Phase contrast imaging with coherent x-rays can be distinguished in outline imaging and holography, depending on the wavelength {lambda}, the object size d and the object-to-detector distance r. When r << d{sup 2}{lambda}, phase contrast occurs only in regions where the refractive index fastly changes, i.e. at interfaces and edges in the sample. With increasing object-to-detector distance we come in the area of holographic imaging. The image contrast outside the shadow region of the object is due to interference of the direct, undiffracted beam and a beam diffracted by the object, or, in terms of holography, the interference of a reference wave with the object wave. Both, outline imaging and holography, offer the possibility to obtain three dimensional information of the sample in conjunction with a tomographic technique. But the data treatment and the kind of information one can obtain from the reconstruction is different.

  20. L'analyse contrastive: histoire et situation actuelle (Contrastive Analysis: History and Current Situation).

    Science.gov (United States)

    Py, Bernard

    1984-01-01

    It is suggested that it is not between two languages that transfers and interference occur, but within the learner. The learner mediates and constructs this relationship according to acquisition operations, processes, strategies, and stages that contrastive analysis, despite its utility, can neither account for nor predict. (MSE)

  1. New microscopy for nanoimaging

    CERN Document Server

    Kinjo, Y; Watanabe, M

    2002-01-01

    Two types of new microscopy, namely, X-ray contact microscopy (XRCM) in combination with atomic force microscopy (AFM) and X-ray projection microscopy (XRPM) using synchrotron radiation and zone plate optics were used to image the fine structures of human chromosomes. In the XRCM plus AFM system, location of X-ray images on a photoresist has become far easier than that with our previous method using transmission electron microscopy coupled with the replica method. In addition, the images obtained suggested that the conformation of chromatin fiber differs from the current textbook model regarding the architecture of a eukaryotic chromosome. X-ray images with high contrast of the specimens could be obtained with XRPM. The resolution of each microscopy was about 30 and 200-300 nm for XRCM plus AFM and XRPM, respectively. (author)

  2. Understanding quantum interference in general nonlocality

    International Nuclear Information System (INIS)

    Wang Haijun

    2011-01-01

    In this paper we attempt to give a new understanding of quantum double-slit interference of fermions in the framework of general nonlocality (GN) [J. Math. Phys. 49, 033513 (2008)] by studying the self-(inter)action of matter wave. From the metric of the GN, we derive a special formalism to interpret the interference contrast when the self-action is perturbative. According to the formalism, the characteristic of interference pattern is in agreement with experiment qualitatively. As examples, we apply the formalism to the cases governed by Schroedinger current and Dirac current, respectively, both of which are relevant to topology. The gap between these two cases corresponds to the fermion magnetic moment, which is possible to test in the near future. In addition, a general interference formalism for both perturbative and nonperturbative self-actions is presented. By analyzing the general formalism we predict that in the nonperturbative limit there is no interference at all. And by comparison with the special formalism of Schroedinger current, the coupling strength of self-action in the limit is found to be ∞. In the perturbative case, the interference from self-action turns out to be the same as that from the standard approach of quantum theory. Then comparing the corresponding coefficients quantitatively we conclude that the coupling strength of self-action in this case falls in the interval [0, 1].

  3. Compressive Phase Contrast Tomography

    International Nuclear Information System (INIS)

    Maia, Filipe; MacDowell, Alastair; Marchesini, Stefano; Padmore, Howard A.; Parkinson, Dula Y.; Pien, Jack; Schirotzek, Andre; Yang, Chao

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

  4. Noninvasive label-free monitoring of cosmetics and pharmaceuticals in human skin using nonlinear optical microscopy (Conference Presentation)

    Science.gov (United States)

    Osseiran, Sam; Wang, Hequn; Evans, Conor L.

    2017-02-01

    Over the past decade, nonlinear optical microscopy has seen a dramatic rise in its use in research settings due to its noninvasiveness, enhanced penetration depth, intrinsic optical sectioning, and the ability to probe chemical compounds with molecular specificity without exogenous contrast agents. Nonlinear optical techniques including two-photon excitation fluorescence (2PEF), fluorescence lifetime imaging microscopy (FLIM), second harmonic generation (SHG), coherent anti-Stokes and stimulated Raman scattering (CARS and SRS, respectively), as well as transient and sum frequency absorption (TA and SFA, respectively), have been widely used to explore the physiology and microanatomy of skin. Recently, these modalities have shed light on dermal processes that could not have otherwise been observed, including the spatiotemporal monitoring of cosmetics and pharmaceuticals. However, a challenge quickly arises when studying such chemicals in a dermatological context: many exogenous compounds have optical signatures that can interfere with the signals that would otherwise be acquired from intact skin. For example, oily solvents exhibit strong signals when probing CH2 vibrations with CARS/SRS; chemical sun filters appear bright in 2PEF microscopy; and darkly colored compounds readily absorb light across a broad spectrum, producing strong TA/SFA signals. Thus, this discussion will first focus on the molecular contrast in skin that can be probed using the aforementioned nonlinear optical techniques. This will be followed by an overview of strategies that take advantage of the exogenous compounds' optical signatures to probe spatiotemporal dynamics while preserving endogenous information from skin.

  5. Performance comparison of optical interference cancellation system architectures.

    Science.gov (United States)

    Lu, Maddie; Chang, Matt; Deng, Yanhua; Prucnal, Paul R

    2013-04-10

    The performance of three optics-based interference cancellation systems are compared and contrasted with each other, and with traditional electronic techniques for interference cancellation. The comparison is based on a set of common performance metrics that we have developed for this purpose. It is shown that thorough evaluation of our optical approaches takes into account the traditional notions of depth of cancellation and dynamic range, along with notions of link loss and uniformity of cancellation. Our evaluation shows that our use of optical components affords performance that surpasses traditional electronic approaches, and that the optimal choice for an optical interference canceller requires taking into account the performance metrics discussed in this paper.

  6. Periodicity in tumor vasculature targeting kinetics of ligand-functionalized nanoparticles studied by dynamic contrast enhanced magnetic resonance imaging and intravital microscopy

    DEFF Research Database (Denmark)

    Hak, Sjoerd; Cebulla, Jana; Huuse, Else Marie

    2014-01-01

    In the past two decades advances in the development of targeted nanoparticles have facilitated their application as molecular imaging agents and targeted drug delivery vehicles. Nanoparticle-enhanced molecular imaging of the angiogenic tumor vasculature has been of particular interest. Not only...... because angiogenesis plays an important role in various pathologies, but also since endothelial cell surface receptors are directly accessible for relatively large circulating nanoparticles. Typically, nanoparticle targeting towards these receptors is studied by analyzing the contrast distribution...... kinetics. These kinetics will not only depend on nanoparticle characteristics, but also on receptor binding and recycling. In this study, we monitored the in vivo targeting kinetics of αvβ3-integrin specific nanoparticles with intravital microscopy and dynamic contrast enhanced magnetic resonance imaging...

  7. Distinction of heterogeneity on Au nanostructured surface based on phase contrast imaging of atomic force microscopy

    International Nuclear Information System (INIS)

    Jung, Mi; Choi, Jeong-Woo

    2010-01-01

    The discrimination of the heterogeneity of different materials on nanostructured surfaces has attracted a great deal of interest in biotechnology as well as nanotechnology. Phase imaging through tapping mode of atomic force microscopy (TMAFM) can be used to distinguish the heterogeneity on a nanostructured surface. Nanostructures were fabricated using anodic aluminum oxide (AAO). An 11-mercaptoundecanoic acid (11-MUA) layer adsorbed onto the Au nanodots through self-assembly to improve the bio-compatibility. The Au nanostructures that were modified with 11-MUA and the concave surfaces were investigated using the TMAFM phase images to compare the heterogeneous and homogeneous nanostructured surfaces. Although the topography and phase images were taken simultaneously, the images were different. Therefore, the contrast in the TMAFM phase images revealed the different compositional materials on the heterogeneous nanostructure surface.

  8. Microscopy of biological sample through advanced diffractive optics from visible to X-ray wavelength regime.

    Science.gov (United States)

    Di Fabrizio, Enzo; Cojoc, Dan; Emiliani, Valentina; Cabrini, Stefano; Coppey-Moisan, Maite; Ferrari, Enrico; Garbin, Valeria; Altissimo, Matteo

    2004-11-01

    The aim of this report is to demonstrate a unified version of microscopy through the use of advanced diffractive optics. The unified scheme derives from the technical possibility of realizing front wave engineering in a wide range of electromagnetic spectrum. The unified treatment is realized through the design and nanofabrication of phase diffractive elements (PDE) through which wave front beam shaping is obtained. In particular, we will show applications, by using biological samples, ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy combined with X-ray fluorescence. We report some details on the design and physical implementation of diffractive elements that besides focusing also perform other optical functions: beam splitting, beam intensity, and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of micro-beads surrounding a cell as an array of tweezers and for arraying and sorting microscopic size biological samples. Another application is the Gauss to Laguerre-Gauss mode conversion, which allows for trapping and transfering orbital angular momentum of light to micro-particles immersed in a fluid. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for diffractive optics implementation. High-resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in x-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field x-ray microscopy. Besides the topographic information, fluorescence allows detection of certain chemical elements (Cl, P, Sc, K) in the same setup, by changing the photon energy of the x-ray beam. (c) 2005 Wiley-Liss, Inc.

  9. Optimum angle of incidence for monochromatic interference in transparent films on absorbing substrates

    International Nuclear Information System (INIS)

    Muller, R.H.; Sand, M.L.

    1980-01-01

    Angles of incidence for s- and p-polarized light have been computed and confirmed experimentally for which monochromatic interference in transparent thin films on absorbing substrates results in optimum interference fringe contrast (visibility=1). Under these angles of incidence and with polarized light, film thickness determinations which are not possible at normal incidence or with unpolarized light can be carried out by use of thin-film interference

  10. The mathematical cell model reconstructed from interference microscopy data

    Science.gov (United States)

    Rogotnev, A. A.; Nikitiuk, A. S.; Naimark, O. B.; Nebogatikov, V. O.; Grishko, V. V.

    2017-09-01

    The mathematical model of cell dynamics is developed to link the dynamics of the phase cell thickness with the signs of the oncological pathology. The measurements of irregular oscillations of cancer cells phase thickness were made with laser interference microscope MIM-340 in order to substantiate this model. These data related to the dynamics of phase thickness for different cross-sections of cells (nuclei, nucleolus, and cytoplasm) allow the reconstruction of the attractor of dynamic system. The attractor can be associated with specific types of collective modes of phase thickness responsible for the normal and cancerous cell dynamics. Specific type of evolution operator was determined using an algorithm of designing of the mathematical cell model and temporal phase thickness data for cancerous and normal cells. Qualitative correspondence of attractor types to the cell states was analyzed in terms of morphological signs associated with maximum value of mean square irregular oscillations of phase thickness dynamics.

  11. Coherent imaging with incoherent light in digital holographic microscopy

    Science.gov (United States)

    Chmelik, Radim

    2012-01-01

    Digital holographic microscope (DHM) allows for imaging with a quantitative phase contrast. In this way it becomes an important instrument, a completely non-invasive tool for a contrast intravital observation of living cells and a cell drymass density distribution measurement. A serious drawback of current DHMs is highly coherent illumination which makes the lateral resolution worse and impairs the image quality by a coherence noise and a parasitic interference. An uncompromising solution to this problem can be found in the Leith concept of incoherent holography. An off-axis hologram can be formed with arbitrary degree of light coherence in systems equipped with an achromatic interferometer and thus the resolution and the image quality typical for an incoherent-light wide-field microscopy can be achieved. In addition, advanced imaging modes based on limited coherence can be utilized. The typical example is a coherence-gating effect which provides a finite axial resolution and makes DHM image similar to that of a confocal microscope. These possibilities were described theoretically using the formalism of three-dimensional coherent transfer functions and proved experimentally by the coherence-controlled holographic microscope which is DHM based on the Leith achromatic interferometer. Quantitative-phase-contrast imaging is demonstrated with incoherent light by the living cancer cells observation and their motility evaluation. The coherence-gating effect was proved by imaging of model samples through a scattering layer and living cells inside an opalescent medium.

  12. Study of the structure of the particles of channel black of phase-contrasting electron microscopy of high resolution

    Energy Technology Data Exchange (ETDEWEB)

    Varlakov, V.P.; Fialkov, A.S.; Smirnov, B.N.

    1981-01-01

    The structure of channel black, DG-100, in the initial and graphitized states has been studied by phase-contrasting electron microscopy with a direct resolution of the carbon layers. An individual carbon layer is the main structural element of carbon black. The structure of channel black in the graphitized state looks like a hollow closed polyhedron made up of bundles of continuous carbon layers which can bend and become deformed to a great extent, testifying to the polymeric nature of the structure of channel black. The authors give an interpretation of the roentgen values of the 'dimensions of crystallites' in channel black.

  13. Interference from previous distraction disrupts older adults' memory.

    Science.gov (United States)

    Biss, Renée K; Campbell, Karen L; Hasher, Lynn

    2013-07-01

    Previously relevant information can disrupt the ability of older adults to remember new information. Here, the researchers examined whether prior irrelevant information, or distraction, can also interfere with older adults' memory for new information. Younger and older adults first completed a 1-back task on pictures that were superimposed with distracting words. After a delay, participants learned picture-word paired associates and memory was tested using picture-cued recall. In 1 condition (high interference), some pairs included pictures from the 1-back task now paired with new words. In a low-interference condition, the transfer list used all new items. Older adults had substantially lower cued-recall performance in the high- compared with the low-interference condition. In contrast, younger adults' performance did not vary across conditions. These findings suggest that even never-relevant information from the past can disrupt older adults' memory for new associations.

  14. DNA conformation on surfaces measured by fluorescence self-interference.

    Science.gov (United States)

    Moiseev, Lev; Unlü, M Selim; Swan, Anna K; Goldberg, Bennett B; Cantor, Charles R

    2006-02-21

    The conformation of DNA molecules tethered to the surface of a microarray may significantly affect the efficiency of hybridization. Although a number of methods have been applied to determine the structure of the DNA layer, they are not very sensitive to variations in the shape of DNA molecules. Here we describe the application of an interferometric technique called spectral self-interference fluorescence microscopy to the precise measurement of the average location of a fluorescent label in a DNA layer relative to the surface and thus determine specific information on the conformation of the surface-bound DNA molecules. Using spectral self-interference fluorescence microscopy, we have estimated the shape of coiled single-stranded DNA, the average tilt of double-stranded DNA of different lengths, and the amount of hybridization. The data provide important proofs of concept for the capabilities of novel optical surface analytical methods of the molecular disposition of DNA on surfaces. The determination of DNA conformations on surfaces and hybridization behavior provide information required to move DNA interfacial applications forward and thus impact emerging clinical and biotechnological fields.

  15. Semantic Interference in Immediate and Delayed Naming and Reading: Attention and Task Decisions

    Science.gov (United States)

    Piai, Vitoria; Roelofs, Ardi; Schriefers, Herbert

    2011-01-01

    Disagreement exists about whether lexical selection in word production is a competitive process. Competition predicts semantic interference from distractor words in immediate but not in delayed picture naming. In contrast, Janssen, Schirm, Mahon, and Caramazza (2008) obtained semantic interference in delayed picture naming when participants had to…

  16. Fluorescence lifetime imaging microscopy using near-infrared contrast agents.

    Science.gov (United States)

    Nothdurft, R; Sarder, P; Bloch, S; Culver, J; Achilefu, S

    2012-08-01

    Although single-photon fluorescence lifetime imaging microscopy (FLIM) is widely used to image molecular processes using a wide range of excitation wavelengths, the captured emission of this technique is confined to the visible spectrum. Here, we explore the feasibility of utilizing near-infrared (NIR) fluorescent molecular probes with emission >700 nm for FLIM of live cells. The confocal microscope is equipped with a 785 nm laser diode, a red-enhanced photomultiplier tube, and a time-correlated single photon counting card. We demonstrate that our system reports the lifetime distributions of NIR fluorescent dyes, cypate and DTTCI, in cells. In cells labelled separately or jointly with these dyes, NIR FLIM successfully distinguishes their lifetimes, providing a method to sort different cell populations. In addition, lifetime distributions of cells co-incubated with these dyes allow estimate of the dyes' relative concentrations in complex cellular microenvironments. With the heightened interest in fluorescence lifetime-based small animal imaging using NIR fluorophores, this technique further serves as a bridge between in vitro spectroscopic characterization of new fluorophore lifetimes and in vivo tissue imaging. © 2012 The Author Journal of Microscopy © 2012 Royal Microscopical Society.

  17. Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.

    Science.gov (United States)

    Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro

    2017-08-25

    We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.

  18. Resistance to Interference of Olfactory Perceptual Learning

    Science.gov (United States)

    Stevenson, Richard J.; Case, Trevor I.; Tomiczek, Caroline

    2007-01-01

    Olfactory memory is especially persistent. The current study explored whether this applies to a form of perceptual learning, in which experience of an odor mixture results in greater judged similarity between its elements. Experiment 1A contrasted 2 forms of interference procedure, "compound" (mixture AW, followed by presentation of new mixtures…

  19. Fluorescence confocal microscopy for pathologists.

    Science.gov (United States)

    Ragazzi, Moira; Piana, Simonetta; Longo, Caterina; Castagnetti, Fabio; Foroni, Monica; Ferrari, Guglielmo; Gardini, Giorgio; Pellacani, Giovanni

    2014-03-01

    Confocal microscopy is a non-invasive method of optical imaging that may provide microscopic images of untreated tissue that correspond almost perfectly to hematoxylin- and eosin-stained slides. Nowadays, following two confocal imaging systems are available: (1) reflectance confocal microscopy, based on the natural differences in refractive indices of subcellular structures within the tissues; (2) fluorescence confocal microscopy, based on the use of fluorochromes, such as acridine orange, to increase the contrast epithelium-stroma. In clinical practice to date, confocal microscopy has been used with the goal of obviating the need for excision biopsies, thereby reducing the need for pathological examination. The aim of our study was to test fluorescence confocal microscopy on different types of surgical specimens, specifically breast, lymph node, thyroid, and colon. The confocal images were correlated to the corresponding histological sections in order to provide a morphologic parallel and to highlight current limitations and possible applications of this technology for surgical pathology practice. As a result, neoplastic tissues were easily distinguishable from normal structures and reactive processes such as fibrosis; the use of fluorescence enhanced contrast and image quality in confocal microscopy without compromising final histologic evaluation. Finally, the fluorescence confocal microscopy images of the adipose tissue were as accurate as those of conventional histology and were devoid of the frozen-section-related artefacts that can compromise intraoperative evaluation. Despite some limitations mainly related to black/white images, which require training in imaging interpretation, this study confirms that fluorescence confocal microscopy may represent an alternative to frozen sections in the assessment of margin status in selected settings or when the conservation of the specimen is crucial. This is the first study to employ fluorescent confocal microscopy on

  20. High-Throughput Light Sheet Microscopy for the Automated Live Imaging of Larval Zebrafish

    Science.gov (United States)

    Baker, Ryan; Logan, Savannah; Dudley, Christopher; Parthasarathy, Raghuveer

    The zebrafish is a model organism with a variety of useful properties; it is small and optically transparent, it reproduces quickly, it is a vertebrate, and there are a large variety of transgenic animals available. Because of these properties, the zebrafish is well suited to study using a variety of optical technologies including light sheet fluorescence microscopy (LSFM), which provides high-resolution three-dimensional imaging over large fields of view. Research progress, however, is often not limited by optical techniques but instead by the number of samples one can examine over the course of an experiment, which in the case of light sheet imaging has so far been severely limited. Here we present an integrated fluidic circuit and microscope which provides rapid, automated imaging of zebrafish using several imaging modes, including LSFM, Hyperspectral Imaging, and Differential Interference Contrast Microscopy. Using this system, we show that we can increase our imaging throughput by a factor of 10 compared to previous techniques. We also show preliminary results visualizing zebrafish immune response, which is sensitive to gut microbiota composition, and which shows a strong variability between individuals that highlights the utility of high throughput imaging. National Science Foundation, Award No. DBI-1427957.

  1. Quantitative surface topography determination by Nomarski reflection microscopy. 2: Microscope modification, calibration, and planar sample experiments

    International Nuclear Information System (INIS)

    Hartman, J.S.; Gordon, R.L.; Lessor, D.L.

    1980-01-01

    The application of reflective Nomarski differential interference contrast microscopy for the determination of quantitative sample topography data is presented. The discussion includes a review of key theoretical results presented previously plus the experimental implementation of the concepts using a commercial Momarski microscope. The experimental work included the modification and characterization of a commercial microscope to allow its use for obtaining quantitative sample topography data. System usage for the measurement of slopes on flat planar samples is also discussed. The discussion has been designed to provide the theoretical basis, a physical insight, and a cookbook procedure for implementation to allow these results to be of value to both those interested in the microscope theory and its practical usage in the metallography laboratory

  2. Newly designed, simple relief phase contrast for microscopy of microorganisms

    Czech Academy of Sciences Publication Activity Database

    Žižka, Zdeněk

    2010-01-01

    Roč. 55, č. 6 (2010), s. 662-665 ISSN 0015-5632 R&D Projects: GA MŠk LC06066 Institutional research plan: CEZ:AV0Z50200510 Keywords : optical microscopy * Zeiss NG 10/1 * microphotography Subject RIV: EE - Microbiology, Virology Impact factor: 0.977, year: 2010

  3. Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

    Science.gov (United States)

    Mehta, Shalin B.; Sheppard, Colin J. R.

    2010-05-01

    Various methods that use large illumination aperture (i.e. partially coherent illumination) have been developed for making transparent (i.e. phase) specimens visible. These methods were developed to provide qualitative contrast rather than quantitative measurement-coherent illumination has been relied upon for quantitative phase analysis. Partially coherent illumination has some important advantages over coherent illumination and can be used for measurement of the specimen's phase distribution. However, quantitative analysis and image computation in partially coherent systems have not been explored fully due to the lack of a general, physically insightful and computationally efficient model of image formation. We have developed a phase-space model that satisfies these requirements. In this paper, we employ this model (called the phase-space imager) to elucidate five different partially coherent systems mentioned in the title. We compute images of an optical fiber under these systems and verify some of them with experimental images. These results and simulated images of a general phase profile are used to compare the contrast and the resolution of the imaging systems. We show that, for quantitative phase imaging of a thin specimen with matched illumination, differential phase contrast offers linear transfer of specimen information to the image. We also show that the edge enhancement properties of spiral phase contrast are compromised significantly as the coherence of illumination is reduced. The results demonstrate that the phase-space imager model provides a useful framework for analysis, calibration, and design of partially coherent imaging methods.

  4. Live cell refractometry based on non-SPR microparticle sensor.

    Science.gov (United States)

    Liu, Chang; Chen, David D Y; Yu, Lirong; Luo, Yong

    2013-06-01

    Unlike the nanoparticles with surface plasmon resonance, the optical response of polystyrene microparticles (PSMPs) is insensitive to the chemical components of the surrounding medium under the wavelength-dependent differential interference contrast microscopy. This fact is exploited for the measurement of the refractive index of cytoplasm in this study. PSMPs of 400 nm in diameter were loaded into the cell to contact cytoplasm seamlessly, and the refractive index information of cytoplasm could be extracted by differential interference contrast microscopy operated at 420 nm illumination wavelength through the contrast analysis of PSMPs images. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Quasiparticle Interference Studies of Quantum Materials.

    Science.gov (United States)

    Avraham, Nurit; Reiner, Jonathan; Kumar-Nayak, Abhay; Morali, Noam; Batabyal, Rajib; Yan, Binghai; Beidenkopf, Haim

    2018-06-03

    Exotic electronic states are realized in novel quantum materials. This field is revolutionized by the topological classification of materials. Such compounds necessarily host unique states on their boundaries. Scanning tunneling microscopy studies of these surface states have provided a wealth of spectroscopic characterization, with the successful cooperation of ab initio calculations. The method of quasiparticle interference imaging proves to be particularly useful for probing the dispersion relation of the surface bands. Herein, how a variety of additional fundamental electronic properties can be probed via this method is reviewed. It is demonstrated how quasiparticle interference measurements entail mesoscopic size quantization and the electronic phase coherence in semiconducting nanowires; helical spin protection and energy-momentum fluctuations in a topological insulator; and the structure of the Bloch wave function and the relative insusceptibility of topological electronic states to surface potential in a topological Weyl semimetal. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Compact diffraction phase microscopy for quantitative visualization of cells in biomedical applications

    International Nuclear Information System (INIS)

    Talaikova, N A; Ryabukho, V P

    2016-01-01

    We consider a simplified and compact scheme of interference phase microscopy using a diffraction grating and spatial filtering of the diffracted field, i.e., diffraction phase microscopy. The scheme and the parameters of the device with the possibility of using the optical system of a smartphone and its software are analysed. The results of experimental determination of the spatial structure parameters of erythrocytes are presented. (paper)

  7. Photoionization microscopy of hydrogen atom near a metal surface

    International Nuclear Information System (INIS)

    Yang Hai-Feng; Wang Lei; Liu Xiao-Jun; Liu Hong-Ping

    2011-01-01

    We have studied the ionization of Rydberg hydrogen atom near a metal surface with a semiclassical analysis of photoionization microscopy. Interference patterns of the electron radial distribution are calculated at different scaled energies above the classical saddle point and at various atom—surface distances. We find that different types of trajectories contribute predominantly to different manifolds in a certain interference pattern. As the scaled energy increases, the structure of the interference pattern evolves smoothly and more types of trajectories emerge. As the atom approaches the metal surface closer, there are more types of trajectories contributing to the interference pattern as well. When the Rydberg atom comes very close to the metal surface or the scaled energy approaches the zero field ionization energy, the potential induced by the metal surface will make atomic system chaotic. The results also show that atoms near a metal surface exhibit similar properties like the atoms in the parallel electric and magnetic fields. (atomic and molecular physics)

  8. The path of chewing movement before and after experimental occlusal interference.

    Science.gov (United States)

    Kobayashi, Y; Shiga, H

    1991-01-01

    To understand functions of the masticatory system accurate recording and analysis of mandibular movement are indispensable. The purpose of this experiment was to find functional differences in the path of masticatory movement due to experimental occlusal interference. Occlusal interference was placed on the mandibular first molar or cuspid of the habitual chewing side in seven normal subjects. While subjects were asked to masticate gum on one side at a time, jaw movements were recorded and analyzed using an automatic masticatory movement analysis system previously developed. Standard deviations (SD) of the vertical and lateral elements in the opening and closing phases were calculated and compared before and after the occlusal interference. In the opening phase the SDs increased significantly with either the interference placed on the cuspid or molar tooth. In the closing phase it generally increased with either the interference. The effect was significantly more with the cuspid interference than that of the molar tooth. The SD of the vertical element is also generally increased with either interference. However, in contrast to the lateral element, the effect of the molar interference on the vertical element was significantly more than that of the cuspid.

  9. Ti-catalyzed HfSiO4 formation in HfTiO4 films on SiO2 studied by Z-contrast scanning electron microscopy

    Directory of Open Access Journals (Sweden)

    Elizabeth Ellen Hoppe

    2013-08-01

    Full Text Available Hafnon (HfSiO4 as it is initially formed in a partially demixed film of hafnium titanate (HfTiO4 on fused SiO2 is studied by atomic number (Z contrast high resolution scanning electron microscopy, x-ray diffraction, and Raman spectroscopy and microscopy. The results show exsoluted Ti is the catalyst for hafnon formation by a two-step reaction. Ti first reacts with SiO2 to produce a glassy Ti-silicate. Ti is then replaced by Hf in the silicate to produce HfSiO4. The results suggest this behavior is prototypical of other Ti-bearing ternary or higher order oxide films on SiO2 when film thermal instability involves Ti exsolution.

  10. Interference and memory capacity limitations.

    Science.gov (United States)

    Endress, Ansgar D; Szabó, Szilárd

    2017-10-01

    Working memory (WM) is thought to have a fixed and limited capacity. However, the origins of these capacity limitations are debated, and generally attributed to active, attentional processes. Here, we show that the existence of interference among items in memory mathematically guarantees fixed and limited capacity limits under very general conditions, irrespective of any processing assumptions. Assuming that interference (a) increases with the number of interfering items and (b) brings memory performance to chance levels for large numbers of interfering items, capacity limits are a simple function of the relative influence of memorization and interference. In contrast, we show that time-based memory limitations do not lead to fixed memory capacity limitations that are independent of the timing properties of an experiment. We show that interference can mimic both slot-like and continuous resource-like memory limitations, suggesting that these types of memory performance might not be as different as commonly believed. We speculate that slot-like WM limitations might arise from crowding-like phenomena in memory when participants have to retrieve items. Further, based on earlier research on parallel attention and enumeration, we suggest that crowding-like phenomena might be a common reason for the 3 major cognitive capacity limitations. As suggested by Miller (1956) and Cowan (2001), these capacity limitations might arise because of a common reason, even though they likely rely on distinct processes. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  11. Comparison between diffraction contrast tomography and high-energy diffraction microscopy on a slightly deformed aluminium alloy

    Directory of Open Access Journals (Sweden)

    Loïc Renversade

    2016-01-01

    Full Text Available The grain structure of an Al–0.3 wt%Mn alloy deformed to 1% strain was reconstructed using diffraction contrast tomography (DCT and high-energy diffraction microscopy (HEDM. 14 equally spaced HEDM layers were acquired and their exact location within the DCT volume was determined using a generic algorithm minimizing a function of the local disorientations between the two data sets. The microstructures were then compared in terms of the mean crystal orientations and shapes of the grains. The comparison shows that DCT can detect subgrain boundaries with disorientations as low as 1° and that HEDM and DCT grain boundaries are on average 4 µm apart from each other. The results are important for studies targeting the determination of grain volume. For the case of a polycrystal with an average grain size of about 100 µm, a relative deviation of about ≤10% was found between the two techniques.

  12. Paleomagnetic Analysis Using SQUID Microscopy

    Science.gov (United States)

    Weiss, Benjamin P.; Lima, Eduardo A.; Fong, Luis E.; Baudenbacher, Franz J.

    2007-01-01

    Superconducting quantum interference device (SQUID) microscopes are a new generation of instruments that map magnetic fields with unprecedented spatial resolution and moment sensitivity. Unlike standard rock magnetometers, SQUID microscopes map magnetic fields rather than measuring magnetic moments such that the sample magnetization pattern must be retrieved from source model fits to the measured field data. In this paper, we presented the first direct comparison between paleomagnetic analyses on natural samples using joint measurements from SQUID microscopy and moment magnetometry. We demonstrated that in combination with apriori geologic and petrographic data, SQUID microscopy can accurately characterize the magnetization of lunar glass spherules and Hawaiian basalt. The bulk moment magnitude and direction of these samples inferred from inversions of SQUID microscopy data match direct measurements on the same samples using moment magnetometry. In addition, these inversions provide unique constraints on the magnetization distribution within the sample. These measurements are among the most sensitive and highest resolution quantitative paleomagnetic studies of natural remanent magnetization to date. We expect that this technique will be able to extend many other standard paleomagnetic techniques to previously inaccessible microscale samples.

  13. Optofluidic time-stretch quantitative phase microscopy.

    Science.gov (United States)

    Guo, Baoshan; Lei, Cheng; Wu, Yi; Kobayashi, Hirofumi; Ito, Takuro; Yalikun, Yaxiaer; Lee, Sangwook; Isozaki, Akihiro; Li, Ming; Jiang, Yiyue; Yasumoto, Atsushi; Di Carlo, Dino; Tanaka, Yo; Yatomi, Yutaka; Ozeki, Yasuyuki; Goda, Keisuke

    2018-03-01

    Innovations in optical microscopy have opened new windows onto scientific research, industrial quality control, and medical practice over the last few decades. One of such innovations is optofluidic time-stretch quantitative phase microscopy - an emerging method for high-throughput quantitative phase imaging that builds on the interference between temporally stretched signal and reference pulses by using dispersive properties of light in both spatial and temporal domains in an interferometric configuration on a microfluidic platform. It achieves the continuous acquisition of both intensity and phase images with a high throughput of more than 10,000 particles or cells per second by overcoming speed limitations that exist in conventional quantitative phase imaging methods. Applications enabled by such capabilities are versatile and include characterization of cancer cells and microalgal cultures. In this paper, we review the principles and applications of optofluidic time-stretch quantitative phase microscopy and discuss its future perspective. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Frequent video game players resist perceptual interference.

    Directory of Open Access Journals (Sweden)

    Aaron V Berard

    Full Text Available Playing certain types of video games for a long time can improve a wide range of mental processes, from visual acuity to cognitive control. Frequent gamers have also displayed generalized improvements in perceptual learning. In the Texture Discrimination Task (TDT, a widely used perceptual learning paradigm, participants report the orientation of a target embedded in a field of lines and demonstrate robust over-night improvement. However, changing the orientation of the background lines midway through TDT training interferes with overnight improvements in overall performance on TDT. Interestingly, prior research has suggested that this effect will not occur if a one-hour break is allowed in between the changes. These results have suggested that after training is over, it may take some time for learning to become stabilized and resilient against interference. Here, we tested whether frequent gamers have faster stabilization of perceptual learning compared to non-gamers and examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed overnight performance improvement only on one background orientation, replicating previous results with the interference in TDT. In contrast, frequent gamers demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning.

  15. Frequent video game players resist perceptual interference.

    Science.gov (United States)

    Berard, Aaron V; Cain, Matthew S; Watanabe, Takeo; Sasaki, Yuka

    2015-01-01

    Playing certain types of video games for a long time can improve a wide range of mental processes, from visual acuity to cognitive control. Frequent gamers have also displayed generalized improvements in perceptual learning. In the Texture Discrimination Task (TDT), a widely used perceptual learning paradigm, participants report the orientation of a target embedded in a field of lines and demonstrate robust over-night improvement. However, changing the orientation of the background lines midway through TDT training interferes with overnight improvements in overall performance on TDT. Interestingly, prior research has suggested that this effect will not occur if a one-hour break is allowed in between the changes. These results have suggested that after training is over, it may take some time for learning to become stabilized and resilient against interference. Here, we tested whether frequent gamers have faster stabilization of perceptual learning compared to non-gamers and examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed overnight performance improvement only on one background orientation, replicating previous results with the interference in TDT. In contrast, frequent gamers demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning.

  16. The development of optical microscopy techniques for the advancement of single-particle studies

    Science.gov (United States)

    Marchuk, Kyle

    find the 3D orientation of stationary metallic anisotropic nanoparticles utilizing only long-axis SPR enhancement. The polarization direction of the illuminating light was rotated causing the relative intensity of p-polarized and s-polarized light within the evanescent field to change. The interaction of the evanescent field with the particles is dependent on the orientation of the particle producing an intensity curve. This curve and the in-plane angle can be compared with simulations to accurately determine the 3D orientation. Differential interference contrast (DIC) microscopy is another non-invasive far-field technique based upon interferometry that does not rely on staining or other contrast enhancing techniques. In addition, high numerical aperture condensers and objectives can be used to give a very narrow depth of field allowing for the optical tomography of samples, which makes it an ideal candidate to study biological systems. DIC microscopy has also proven itself in determining the orientation of gold nanorods in both engineered environments and within cells. Many types of nanoparticles and nanostructures have been synthesized using lithographic techniques on silicon wafer substrates. Traditionally, reflective mode DIC microscopes have been developed and applied to the topographical study of reflective substrates and the imaging of chips on silicon wafers. Herein, a laser-illuminated reflected-mode DIC was developed for studying nanoparticles on reflective surfaces.

  17. The development of optical microscopy techniques for the advancement of single-particle studies

    Energy Technology Data Exchange (ETDEWEB)

    Marchuk, Kyle [Iowa State Univ., Ames, IA (United States)

    2013-05-15

    find the 3D orientation of stationary metallic anisotropic nanoparticles utilizing only long-axis SPR enhancement. The polarization direction of the illuminating light was rotated causing the relative intensity of p-polarized and s-polarized light within the evanescent field to change. The interaction of the evanescent field with the particles is dependent on the orientation of the particle producing an intensity curve. This curve and the in-plane angle can be compared with simulations to accurately determine the 3D orientation. Differential interference contrast (DIC) microscopy is another non-invasive far-field technique based upon interferometry that does not rely on staining or other contrast enhancing techniques. In addition, high numerical aperture condensers and objectives can be used to give a very narrow depth of field allowing for the optical tomography of samples, which makes it an ideal candidate to study biological systems. DIC microscopy has also proven itself in determining the orientation of gold nanorods in both engineered environments and within cells. Many types of nanoparticles and nanostructures have been synthesized using lithographic techniques on silicon wafer substrates. Traditionally, reflective mode DIC microscopes have been developed and applied to the topographical study of reflective substrates and the imaging of chips on silicon wafers. Herein, a laser-illuminated reflected-mode DIC was developed for studying nanoparticles on reflective surfaces.

  18. Comparison of contrast-enhanced T1-weighted and 3D constructive interference in steady state images for predicting outcome after hearing-preservation surgery for vestibular schwannoma

    Energy Technology Data Exchange (ETDEWEB)

    Kocaoglu, M.; Bulakbasi, N.; Ucoz, T.; Ustunsoz, B.; Tayfun, C.; Somuncu, I. [GATA Department of Radiology, 06018, Etlik, Ankara (Turkey); Pabuscu, Y. [Department of Radiology, Celal Bayar University, Manisa (Turkey)

    2003-07-01

    We compared contrast-enhanced T1-weighted and 3D constructive interference in steady state (CISS) sequences for demonstrating possible prognostic factors in hearing-preservation surgery for vestibular schwannoma. We studied 22 patients with vestibular schwannomas having hearing-preservation surgery. Postoperatively six (27%) had a facial palsy and eight (36%) had hearing loss. There was a significant correlation between the size of the tumour and facial palsy (r=-0.72). Both techniques adequately demonstrated all tumours. Involvement of the fundus of the internal auditory canal (IAC) and a small distance between the lateral border of the tumour and the fundus were correlated significantly with hearing loss (r=-0.81 and -0.75, respectively). The 3D-CISS sequence, by virtue of its high contrast resolution was superior to T1-weighted images (P<0.05) for detection of the fundal involvement. The direction of displacement of the facial nerve did not correlate with facial palsy or hearing loss. We think that 3D-CISS images better show the features influencing surgical outcome, but that contrast-enhanced T1-weighted images are required for diagnosis. (orig.)

  19. Comparison of contrast-enhanced T1-weighted and 3D constructive interference in steady state images for predicting outcome after hearing-preservation surgery for vestibular schwannoma

    International Nuclear Information System (INIS)

    Kocaoglu, M.; Bulakbasi, N.; Ucoz, T.; Ustunsoz, B.; Tayfun, C.; Somuncu, I.; Pabuscu, Y.

    2003-01-01

    We compared contrast-enhanced T1-weighted and 3D constructive interference in steady state (CISS) sequences for demonstrating possible prognostic factors in hearing-preservation surgery for vestibular schwannoma. We studied 22 patients with vestibular schwannomas having hearing-preservation surgery. Postoperatively six (27%) had a facial palsy and eight (36%) had hearing loss. There was a significant correlation between the size of the tumour and facial palsy (r=-0.72). Both techniques adequately demonstrated all tumours. Involvement of the fundus of the internal auditory canal (IAC) and a small distance between the lateral border of the tumour and the fundus were correlated significantly with hearing loss (r=-0.81 and -0.75, respectively). The 3D-CISS sequence, by virtue of its high contrast resolution was superior to T1-weighted images (P<0.05) for detection of the fundal involvement. The direction of displacement of the facial nerve did not correlate with facial palsy or hearing loss. We think that 3D-CISS images better show the features influencing surgical outcome, but that contrast-enhanced T1-weighted images are required for diagnosis. (orig.)

  20. Transmission Electron Microscopy Physics of Image Formation

    CERN Document Server

    Kohl, Helmut

    2008-01-01

    Transmission Electron Microscopy: Physics of Image Formation presents the theory of image and contrast formation, and the analytical modes in transmission electron microscopy. The principles of particle and wave optics of electrons are described. Electron-specimen interactions are discussed for evaluating the theory of scattering and phase contrast. Also discussed are the kinematical and dynamical theories of electron diffraction and their applications for crystal-structure analysis and imaging of lattices and their defects. X-ray microanalysis and electron energy-loss spectroscopy are treated as analytical methods. Specimen damage and contamination by electron irradiation limits the resolution for biological and some inorganic specimens. This fifth edition includes discussion of recent progress, especially in the area of aberration correction and energy filtering; moreover, the topics introduced in the fourth edition have been updated. Transmission Electron Microscopy: Physics of Image Formation is written f...

  1. Automated microscopy for high-content RNAi screening

    Science.gov (United States)

    2010-01-01

    Fluorescence microscopy is one of the most powerful tools to investigate complex cellular processes such as cell division, cell motility, or intracellular trafficking. The availability of RNA interference (RNAi) technology and automated microscopy has opened the possibility to perform cellular imaging in functional genomics and other large-scale applications. Although imaging often dramatically increases the content of a screening assay, it poses new challenges to achieve accurate quantitative annotation and therefore needs to be carefully adjusted to the specific needs of individual screening applications. In this review, we discuss principles of assay design, large-scale RNAi, microscope automation, and computational data analysis. We highlight strategies for imaging-based RNAi screening adapted to different library and assay designs. PMID:20176920

  2. Integrated Photoacoustic and Fluorescence Confocal Microscopy

    OpenAIRE

    Wang, Yu; Maslov, Konstantin; Kim, Chulhong; Hu, Song; Wang, Lihong V.

    2010-01-01

    We have developed a dual-modality imaging system by integrating optical-resolution photoacoustic microscopy and fluorescence confocal microscopy to provide optical absorption and fluorescence contrasts simultaneously. By sharing the same laser source and objective lens, intrinsically registered photoacoustic and fluorescence images are acquired in a single scan. The micrometer resolution allows imaging of both blood and lymphatic vessels down to the capillary level. Simultaneous photoacoustic...

  3. Thin dielectric film thickness determination by advanced transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, A.C.; Foran, B.; Kisielowski, C.; Muller, D.; Pennycook, S.; Principe, E.; Stemmer, S.

    2003-09-01

    High Resolution Transmission Electron Microscopy (HR-TEM) has been used as the ultimate method of thickness measurement for thin films. The appearance of phase contrast interference patterns in HR-TEM images has long been confused as the appearance of a crystal lattice by non-specialists. Relatively easy to interpret crystal lattice images are now directly observed with the introduction of annular dark field detectors for scanning TEM (STEM). With the recent development of reliable lattice image processing software that creates crystal structure images from phase contrast data, HR-TEM can also provide crystal lattice images. The resolution of both methods was steadily improved reaching now into the sub Angstrom region. Improvements in electron lens and image analysis software are increasing the spatial resolution of both methods. Optimum resolution for STEM requires that the probe beam be highly localized. In STEM, beam localization is enhanced by selection of the correct aperture. When STEM measurement is done using a highly localized probe beam, HR-TEM and STEM measurement of the thickness of silicon oxynitride films agree within experimental error. In this paper, the optimum conditions for HR-TEM and STEM measurement are discussed along with a method for repeatable film thickness determination. The impact of sample thickness is also discussed. The key result in this paper is the proposal of a reproducible method for film thickness determination.

  4. Quantum interference experiments with complex organic molecules

    International Nuclear Information System (INIS)

    Eibenberger, S. I.

    2015-01-01

    Matter-wave interference with complex particles is a thriving field in experimental quantum physics. The quest for testing the quantum superposition principle with highly complex molecules has motivated the development of the Kapitza-Dirac-Talbot-Lau interferometer (KDTLI). This interferometer has enabled quantum interference with large organic molecules in an unprecedented mass regime. In this doctoral thesis I describe quantum superposition experiments which we were able to successfully realize with molecules of masses beyond 10 000 amu and consisting of more than 800 atoms. The typical de Broglie wavelengths of all particles in this thesis are in the order of 0.3-5 pm. This is significantly smaller than any molecular extension (nanometers) or the delocalization length in our interferometer (hundreds of nanometers). Many vibrational and rotational states are populated since the molecules are thermally highly excited (300-1000 K). And yet, high-contrast quantum interference patterns could be observed. The visibility and position of these matter-wave interference patterns is highly sensitive to external perturbations. This sensitivity has opened the path to extensive studies of the influence of internal molecular properties on the coherence of their associated matter waves. In addition, it enables a new approach to quantum-assisted metrology. Quantum interference imprints a high-contrast nano-structured density pattern onto the molecular beam which allows us to resolve tiny shifts and dephasing of the molecular beam. I describe how KDTL interferometry can be used to investigate a number of different molecular properties. We have studied vibrationally-induced conformational changes of floppy molecules and permanent electric dipole moments using matter-wave deflectometry in an external electric field. We have developed a new method for optical absorption spectroscopy which uses the recoil of the molecules upon absorption of individual photons. This allows us to

  5. Stronger interference from distractors in the right hemifield during visual search.

    Science.gov (United States)

    Carlei, Christophe; Kerzel, Dirk

    2018-03-01

    The orientation-bias hypothesis states that there is a bias to attend to the right visual hemifield (RVF) when there is spatial competition between stimuli in the left and right hemifield [Pollmann, S. (1996). A pop-out induced extinction-like phenomenon in neurologically intact subjects. Neuropsychologia, 34(5), 413-425. doi: 10.1016/0028-3932(95)00125-5 ]. In support of this hypothesis, stronger interference was reported for RVF distractors with contralateral targets. In contrast, previous studies using rapid serial visual presentation (RSVP) found stronger interference from distractors in the left visual hemifield (LVF). We used the additional singleton paradigm to test whether this discrepancy was due to the different distractor features that were employed (colour vs. orientation). Interference from the colour distractor with contralateral targets was larger in the RVF than in the LVF. However, the asymmetrical interference disappeared when observers had to search for an inconspicuous colour target instead of the inconspicuous shape target. We suggest that the LVF orienting-bias is limited to situations where search is driven by bottom-up saliency (singleton search) instead of top-down search goals (feature search). In contrast, analysis of the literature suggests the opposite for the LVF bias in RSVP tasks. Thus, the attentional asymmetry may depend on whether the task involves temporal or spatial competition, and whether search is based on bottom-up or top-down signals.

  6. The effects of trait impulsivity on proactive and reactive interference control.

    Science.gov (United States)

    Xiang, Ling; Chen, Yan; Chen, Antao; Zhang, Fenghua; Xu, Fuming; Wang, Baoxi

    2018-02-01

    The current study used event-related brain potentials (ERPs) to explore whether self-reported trait impulsivity in healthy individuals might be differentially related to proactive and reactive interference control. Participants with high and low impulsivity (HI and LI, respectively) performed a modified version of the prime-target interference task. Proactive interference control was induced in the mostly incongruent (MI) context and reactive interference control was induced in the mostly congruent (MC) context. Although the behavioral data revealed no difference between HI and LI individuals in terms of the interference effects (incongruent - congruent) under both contexts, the ERP results showed that impulsivity has a different influence on the interference effects under different task contexts. In the MC context, the interference effects on the medial frontal negativity (MFN) and the negative sustained potential (N-SP) were greater, while that on the positive sustained potential (P-SP) were smaller in the HI compared to those in the LI group. This suggests that high levels of impulsivity might be associated with a reduced efficiency of the processes supporting reactive control to resolve interference when interference is not expected. In contrast, the three ERP indices (MFN, P-SP, and N-SP) of interference processing in the MI context were insensitive to variations in impulsivity. This suggests that HI individuals might be as effective as LI individuals in recruiting proactive control for sustained active maintenance of task goals to anticipate and prevent interference throughout the experimental blocks where interference occurs frequently. In conclusion, these results indicate that impulsivity has a more negative influence on reactive interference control than on proactive interference control. Copyright © 2017. Published by Elsevier B.V.

  7. Cooperation for Interference Management: A GDoF Perspective

    KAUST Repository

    Gherekhloo, Soheil

    2016-10-13

    The impact of cooperation on interference management is investigated by studying an elemental wireless network, the so-called symmetric interference relay channel (IRC), from a generalized degrees of freedom (GDoF) perspective. This is motivated by the fact that the deployment of relays is considered as a remedy to overcome the bottleneck of current systems in terms of achievable rates. The focus of this paper is on the regime in which the interference link is weaker than the source-relay link in the IRC. Our approach toward studying the GDoF goes through the capacity analysis of the linear deterministic IRC (LD-IRC). New upper bounds on the sum capacity of the LD-IRC based on genie-aided approaches are established. These upper bounds together with some existing upper bounds are achieved by using four novel transmission schemes. Extending the upper bounds and the transmission schemes to the Gaussian case, the GDoF of the Gaussian IRC is characterized for the aforementioned regime. This completes the GDoF results available in the literature for the symmetric GDoF. It turns out that even if the incoming and outgoing links of the relay are both weaker than the desired channel, involving a relay can increase the GDoF. Interestingly, utilizing the relay in this case can increase the slope of the GDoF from -2 [in the interference channel (IC)] to -1 or 0. This shrinks the regime where ignoring the interference by treating it as noise is optimal. Furthermore, the analysis shows that if the relay ingoing and outgoing links are sufficiently strong, the relay is able to neutralize the interference completely. In this case, the bottleneck of the transmission will be the interference links, and hence, the GDoF increases if the interference link gets stronger. It is shown that in the strong interference regime, in contrast to the IC, the GDoF can be a monotonically decreasing function of the interference level. © 1963-2012 IEEE.

  8. Creating infinite contrast in fluorescence microscopy by using lanthanide centered emission

    DEFF Research Database (Denmark)

    R. Carro-Temboury, Miguel; Arppe, Riikka Matleena; Hempel, Casper

    2017-01-01

    The popularity of fluorescence microscopy arises from the inherent mode of action, where the fluorescence emission from probes is used to visualize selected features on a presumed dark background. However, the background is rarely truly dark, and image processing and analysis is needed to enhance...

  9. Cell reactions with biomaterials: the microscopies

    Directory of Open Access Journals (Sweden)

    Curtis A. S.G.

    2001-01-01

    Full Text Available The methods and results of optical microscopy that can be used to observe cell reactions to biomaterials are Interference Reflection Microscopy (IRM, Total Internal Reflection Fluorescence Microscopy (TIRFM, Surface Plasmon Resonance Microscopy (SPRM and Forster Resonance Energy Transfer Microscopy (FRETM and Standing Wave Fluorescence Microscopy. The last three are new developments, which have not yet been fully perfected. TIRFM and SPRM are evanescent wave methods. The physics of these methods depend upon optical phenomena at interfaces. All these methods give information on the dimensions of the gap between cell and the substratum to which it is adhering and thus are especially suited to work with biomaterials. IRM and FRETM can be used on opaque surfaces though image interpretation is especially difficult for IRM on a reflecting opaque surface. These methods are compared with several electron microscopical methods for studying cell adhesion to substrata. These methods all yield fairly consistent results and show that the cell to substratum distance on many materials is in the range 5 to 30 nm. The area of contact relative to the total projected area of the cell may vary from a few per cent to close to 100% depending on the cell type and substratum. These methods show that those discrete contact areas well known as focal contacts are frequently present. The results of FRETM suggest that the separation from the substratum even in a focal contact is about 5 nm.

  10. Nano-contact microscopy of supracrystals

    Directory of Open Access Journals (Sweden)

    Adam Sweetman

    2015-05-01

    Full Text Available Background: Highly ordered three-dimensional colloidal crystals (supracrystals comprised of 7.4 nm diameter Au nanocrystals (with a 5% size dispersion have been imaged and analysed using a combination of scanning tunnelling microscopy and dynamic force microscopy.Results: By exploring the evolution of both the force and tunnel current with respect to tip–sample separation, we arrive at the surprising finding that single nanocrystal resolution is readily obtained in tunnelling microscopy images acquired more than 1 nm into the repulsive (i.e., positive force regime of the probe–nanocrystal interaction potential. Constant height force microscopy has been used to map tip–sample interactions in this regime, revealing inhomogeneities which arise from the convolution of the tip structure with the ligand distribution at the nanocrystal surface.Conclusion: Our combined STM–AFM measurements show that the contrast mechanism underpinning high resolution imaging of nanoparticle supracrystals involves a form of nanoscale contact imaging, rather than the through-vacuum tunnelling which underpins traditional tunnelling microscopy and spectroscopy.

  11. Coherent double-color interference microscope for traceable optical surface metrology

    Science.gov (United States)

    Malinovski, I.; França, R. S.; Bessa, M. S.; Silva, C. R.; Couceiro, I. B.

    2016-06-01

    Interference microscopy is an important field of dimensional surface metrology because it provides direct traceability of the measurements to the SI base unit definition of the metre. With a typical measurement range from micrometres to nanometres interference microscopy (IM) covers the gap between classic metrology and nanometrology, providing continuous transfer of dimensional metrology into new areas of nanoscience and nanotechnology. Therefore IM is considered to be an indispensable tool for traceable transfer of the metre unit to different instruments. We report here the metrological study of an absolute Linnik interference microscope (IM) based on two frequency stabilized lasers. The design permits the flexible use of both lasers for measurements depending on the demand of the concrete measurement task. By principle of operation IM is combination of imaging and phase-shifting interferometry (PSI). The traceability is provided by the wavelength reference, that is, a He-Ne 633 nm stabilized laser. The second laser source, that is, a Blue-Green 488 nm grating stabilized laser diode, is used for improvements of resolution, and also for resolving integer fringe discontinuities on sharp features of the surface. The IM was optimized for surface height metrology. We have performed the study of the systematic effects of the measurements. This study allowed us to improve the hardware and software of IM and to find corrections for main systematic errors. The IM is purposed for 1D to 3D height metrology and surface topography in an extended range from nanometres to micrometres. The advantages and disadvantages of the design and developed methods are discussed.

  12. Coherent double-color interference microscope for traceable optical surface metrology

    International Nuclear Information System (INIS)

    Malinovski, I; França, R S; Bessa, M S; Silva, C R; Couceiro, I B

    2016-01-01

    Interference microscopy is an important field of dimensional surface metrology because it provides direct traceability of the measurements to the SI base unit definition of the metre. With a typical measurement range from micrometres to nanometres interference microscopy (IM) covers the gap between classic metrology and nanometrology, providing continuous transfer of dimensional metrology into new areas of nanoscience and nanotechnology. Therefore IM is considered to be an indispensable tool for traceable transfer of the metre unit to different instruments. We report here the metrological study of an absolute Linnik interference microscope (IM) based on two frequency stabilized lasers. The design permits the flexible use of both lasers for measurements depending on the demand of the concrete measurement task. By principle of operation IM is combination of imaging and phase-shifting interferometry (PSI). The traceability is provided by the wavelength reference, that is, a He-Ne 633 nm stabilized laser. The second laser source, that is, a Blue-Green 488 nm grating stabilized laser diode, is used for improvements of resolution, and also for resolving integer fringe discontinuities on sharp features of the surface. The IM was optimized for surface height metrology. We have performed the study of the systematic effects of the measurements. This study allowed us to improve the hardware and software of IM and to find corrections for main systematic errors. The IM is purposed for 1D to 3D height metrology and surface topography in an extended range from nanometres to micrometres. The advantages and disadvantages of the design and developed methods are discussed. (paper)

  13. Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Salgado, J. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Domínguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Castro-Domínguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113–8656 (Japan); Hernández-Hernández, P. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)

    2013-12-15

    The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.

  14. Efficient phase contrast imaging in STEM using a pixelated detector. Part 1: Experimental demonstration at atomic resolution

    Energy Technology Data Exchange (ETDEWEB)

    Pennycook, Timothy J., E-mail: tpennycook@gmail.com [EPSRC SuperSTEM Facility, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Lupini, Andrew R. [Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN 37830 (United States); Yang, Hao [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Murfitt, Matthew F. [Nion Co., 1102 8th St., Kirkland, WA 98033 (United States); Jones, Lewys [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Nellist, Peter D. [EPSRC SuperSTEM Facility, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-04-15

    We demonstrate a method to achieve high efficiency phase contrast imaging in aberration corrected scanning transmission electron microscopy (STEM) with a pixelated detector. The pixelated detector is used to record the Ronchigram as a function of probe position which is then analyzed with ptychography. Ptychography has previously been used to provide super-resolution beyond the diffraction limit of the optics, alongside numerically correcting for spherical aberration. Here we rely on a hardware aberration corrector to eliminate aberrations, but use the pixelated detector data set to utilize the largest possible volume of Fourier space to create high efficiency phase contrast images. The use of ptychography to diagnose the effects of chromatic aberration is also demonstrated. Finally, the four dimensional dataset is used to compare different bright field detector configurations from the same scan for a sample of bilayer graphene. Our method of high efficiency ptychography produces the clearest images, while annular bright field produces almost no contrast for an in-focus aberration-corrected probe. - Highlights: • Ptychographic high efficiency phase contrast imaging is demonstrated in STEM. • We rely on a hardware aberration corrector to eliminate aberrations. • High efficiency is achieved by collecting all the relevant interference. • Use of a pixelated detector allows comparison of bright field modes post acquisition. • Ptychography provides the clearest images among the STEM bright field modes tested.

  15. Influence of chronic stress and oclusal interference on masseter muscle pain in rat.

    Science.gov (United States)

    Simonić-Kocijan, Suncana; Uhac, Ivone; Braut, Vedrana; Kovac, Zoran; Pavicić, Daniela Kovacević; Fugosić, Vesna; Urek, Miranda Muhvić

    2009-09-01

    This study aimed to investigate the individual effects of chronic stress and occlusal interference, as well as their combined influence on masseter muscle pain. Experiments were performed on 28 male Wistar rats. Animals were submitted to chronic stress procedure, exposed to occlusal interference, or exposed to both mantioned procedures. At the end of the procedure animals were submitted to orofacial formalin test, and nociceptive behavioral response was evaluated. Statisticaly significant difference of nociceptive behavioral response in chronicaly stressed rats and in the animals with occlusal interference in comparation to the control group were not obtained (p > 0.05). In contrast, nociceptive behavioral response was significantly increased in rats submitted to both of experimental procedures (p occlusal interference and chronic stress influence masseter muscle pain.

  16. Rapid sensing of melamine in milk by interference green synthesis of silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Varun, S.; Kiruba Daniel, S.C.G.; Gorthi, Sai Siva, E-mail: saisiva.gorthi@iap.iisc.ernet.in

    2017-05-01

    A highly sensitive, selective, and rapid interference green synthesis based determination of potential milk adulterant melamine has been reported here. Melamine is a nitrogenous compound added to milk for mimicking proteins, consumption of which leads to kidney stones and renal failures. Melamine interacts with ascorbic acid (AA) through strong hydrogen-bonding interactions, thus resulting in an interference/interruption in the formation of silver (Ag) nanoparticles which was confirmed by UV–Vis spectroscopy and Transmission Electron Microscopy (TEM). The corresponding benchmark validations for melamine spiked milk samples were performed using High Performance Liquid Chromatography (HPLC). This interference in the formation of Ag nanoparticles resulted in color change that varies with concentration of melamine, thereby enabling in-situ rapid sensing of melamine from milk to a lower limit of 0.1 ppm with a linear correlation coefficient of 0.9908. - Highlights: • Rapid detection of milk adulterant melamine based on interference green synthesis. • Green chemical ascorbic acid used as the reducing agent for interference sensing. • Enabling in-situ sensing of melamine from milk with a limit of detection of 0.1 ppm. • Presence of analyte inhibits the nanoparticle formation.

  17. High-contrast 3D image acquisition using HiLo microscopy with an electrically tunable lens

    Science.gov (United States)

    Philipp, Katrin; Smolarski, André; Fischer, Andreas; Koukourakis, Nektarios; Stürmer, Moritz; Wallrabe, Ulricke; Czarske, Jürgen

    2016-04-01

    We present a HiLo microscope with an electrically tunable lens for high-contrast three-dimensional image acquisition. HiLo microscopy combines wide field and speckled illumination images to create optically sectioned images. Additionally, the depth-of-field is not fixed, but can be adjusted between wide field and confocal-like axial resolution. We incorporate an electrically tunable lens in the HiLo microscope for axial scanning, to obtain three-dimensional data without the need of moving neither the sample nor the objective. The used adaptive lens consists of a transparent polydimethylsiloxane (PDMS) membrane into which an annular piezo bending actuator is embedded. A transparent fluid is filled between the membrane and the glass substrate. When actuated, the piezo generates a pressure in the lens which deflects the membrane and thus changes the refractive power. This technique enables a large tuning range of the refractive power between 1/f = (-24 . . . 25) 1/m. As the NA of the adaptive lens is only about 0.05, a fixed high-NA lens is included in the setup to provide high resolution. In this contribution, the scan properties and capabilities of the tunable lens in the HiLo microscope are analyzed. Eventually, exemplary measurements are presented and discussed.

  18. Vibrational Imaging with High Sensitivity via Epidetected Coherent Anti-Stokes Raman Scattering Microscopy

    International Nuclear Information System (INIS)

    Volkmer, Andreas; Cheng, Ji-Xin; Sunney Xie, X.

    2001-01-01

    We demonstrate theoretically and experimentally a novel epidetection scheme for coherent anti-Stokes Raman scattering (CARS) microscopy that significantly improves the detection sensitivity. Calculations show that epidetected CARS (E-CARS) signals are present for scatterers smaller than the wavelength of light, whereas the large background signals from the surrounding bulk solvent are suppressed by destructive interference. E-CARS microscopy is capable of revealing small intracellular features that are otherwise buried by the strong water CARS signal

  19. Visualizing Escherichia coli sub-cellular structure using sparse deconvolution Spatial Light Interference Tomography.

    Directory of Open Access Journals (Sweden)

    Mustafa Mir

    Full Text Available Studying the 3D sub-cellular structure of living cells is essential to our understanding of biological function. However, tomographic imaging of live cells is challenging mainly because they are transparent, i.e., weakly scattering structures. Therefore, this type of imaging has been implemented largely using fluorescence techniques. While confocal fluorescence imaging is a common approach to achieve sectioning, it requires fluorescence probes that are often harmful to the living specimen. On the other hand, by using the intrinsic contrast of the structures it is possible to study living cells in a non-invasive manner. One method that provides high-resolution quantitative information about nanoscale structures is a broadband interferometric technique known as Spatial Light Interference Microscopy (SLIM. In addition to rendering quantitative phase information, when combined with a high numerical aperture objective, SLIM also provides excellent depth sectioning capabilities. However, like in all linear optical systems, SLIM's resolution is limited by diffraction. Here we present a novel 3D field deconvolution algorithm that exploits the sparsity of phase images and renders images with resolution beyond the diffraction limit. We employ this label-free method, called deconvolution Spatial Light Interference Tomography (dSLIT, to visualize coiled sub-cellular structures in E. coli cells which are most likely the cytoskeletal MreB protein and the division site regulating MinCDE proteins. Previously these structures have only been observed using specialized strains and plasmids and fluorescence techniques. Our results indicate that dSLIT can be employed to study such structures in a practical and non-invasive manner.

  20. Determining oxygen relaxations at an interface: A comparative study between transmission electron microscopy techniques.

    Science.gov (United States)

    Gauquelin, N; van den Bos, K H W; Béché, A; Krause, F F; Lobato, I; Lazar, S; Rosenauer, A; Van Aert, S; Verbeeck, J

    2017-10-01

    Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO 3 -La 0.67 Sr 0.33 MnO 3 (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. The relationship between target quality and interference in sound zones

    DEFF Research Database (Denmark)

    Baykaner, Khan; Coleman, Phillip; Mason, Russell

    2015-01-01

    Sound zone systems aim to control sound fields in such a way that multiple listeners can enjoy different audio programs within the same room with minimal acoustic interference. Often, there is a trade-off between the acoustic contrast achieved between the zones and the fidelity of the reproduced...... audio program in the target zone. A listening test was conducted to obtain subjective measures of distraction, target quality, and overall quality of listening experience for ecologically valid programs within a sound zoning system. Sound zones were reproduced using acoustic contrast control, planarity...

  2. Interference of Multiple Surface Plasmon Polaritons

    International Nuclear Information System (INIS)

    Wang, Dapeng; Yuan, Xiaocong; Lin, Jiao

    2017-01-01

    Benefiting from strongly electromagnetic confinement and enhancement effects, surface plasmon polaritons (SPPs) hold great promises for tailoring light on micro and nanoscale. By contrast with previous efforts which massively concentrate on localized SPP mode, we investigated the propagating SPPs in this paper. A number of symmetrical gratings on metal surface are employed to excite multiple SPPs. Interestingly, the exotic interfering phenomena have been observed. They show good agreement with free-space interferences and take advantage of precise controllability. These findings will be promising in the applications of optical tweezers and SPP lithography. (paper)

  3. Beamforming design with proactive interference cancelation in MISO interference channels

    Science.gov (United States)

    Li, Yang; Tian, Yafei; Yang, Chenyang

    2015-12-01

    In this paper, we design coordinated beamforming at base stations (BSs) to facilitate interference cancelation at users in interference networks, where each BS is equipped with multiple antennas and each user is with a single antenna. By assuming that each user can select the best decoding strategy to mitigate the interference, either canceling the interference after decoding when it is strong or treating it as noise when it is weak, we optimize the beamforming vectors that maximize the sum rate for the networks under different interference scenarios and find the solutions of beamforming with closed-form expressions. The inherent design principles are then analyzed, and the performance gain over passive interference cancelation is demonstrated through simulations in heterogeneous cellular networks.

  4. Electrochemical gating in scanning electrochemical microscopy

    NARCIS (Netherlands)

    Ahonen, P.; Ruiz, V.; Kontturi, K.; Liljeroth, P.; Quinn, B.M.

    2008-01-01

    We demonstrate that scanning electrochemical microscopy (SECM) can be used to determine the conductivity of nanoparticle assemblies as a function of assembly potential. In contrast to conventional electron transport measurements, this method is unique in that electrical connection to the film is not

  5. Very low energy scanning electron microscopy in nanotechnology

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Hovorka, Miloš; Mika, Filip; Mikmeková, Eliška; Mikmeková, Šárka; Pokorná, Zuzana; Frank, Luděk

    2012-01-01

    Roč. 9, 8/9 (2012), s. 695-716 ISSN 1475-7435 R&D Projects: GA MŠk OE08012; GA MŠk ED0017/01/01; GA AV ČR IAA100650902 Institutional research plan: CEZ:AV0Z20650511 Keywords : scanning electron microscopy * very low energy electrons * cathode lens * grain contrast * strain contrast * imaging of participates * dopant contrast * very low energy STEM * graphene Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.087, year: 2012

  6. Distractor interference during a choice limb reaching task.

    Directory of Open Access Journals (Sweden)

    Matthew Ray

    Full Text Available According to action-centered models of attention, the patterns of distractor interference that emerge in selective reaching tasks are related to the time and effort required to resolve a race for activation between competing target and non-target response producing processes. Previous studies have only used unimanual aiming tasks and, as such, only examined the effects of competition that occurs within a limb. The results of studies using unimanual aiming movements often reveal an "ipsilateral effect"--distractors on the same side of space as the effector cause greater interference than distractors on the opposite side of space. The cost of the competition when response selection is between the limbs has yet to be addressed. Participants in the present study executed reaching movements to 1 of 4 (2 left, 2 right possible target locations with and without a distractor. Participants made ipsilateral reaches (left hand to left targets, right hand to right targets. In contrast to studies using unimanual aiming movements, a "contralateral effect" was observed; distractors affording responses for the other hand (in contralateral space caused more interference than distractors affording responses for the same hand. The findings from the present research demonstrate that when certain portions of response planning must be resolved prior to response initiation, distractors that code for that dimension cause the greatest interference.

  7. Escaping the recent past: which stimulus dimensions influence proactive interference?

    Science.gov (United States)

    Craig, Kimberly S; Berman, Marc G; Jonides, John; Lustig, Cindy

    2013-07-01

    Proactive interference occurs when information from the past disrupts current processing and is a major source of confusion and errors in short-term memory (STM; Wickens, Born, & Allen, Journal of Verbal Learning and Verbal Behavior, 2:440-445, 1963). The present investigation examines potential boundary conditions for interference, testing the hypothesis that potential competitors must be similar along task-relevant dimensions to influence proactive interference effects. We manipulated both the type of task being completed (Experiments 1, 2, and 3) and dimensions of similarity irrelevant to the current task (Experiments 4 and 5) to determine how the recent presentation of a probe item would affect the speed with which participants could reject that item. Experiments 1, 2, and 3 contrasted STM judgments, which require temporal information, with semantic and perceptual judgments, for which temporal information is irrelevant. In Experiments 4 and 5, task-irrelevant information (perceptual similarity) was manipulated within the recent probes task. We found that interference from past items affected STM task performance but did not affect performance in semantic or perceptual judgment tasks. Conversely, similarity along a nominally irrelevant perceptual dimension did not affect the magnitude of interference in STM tasks. Results are consistent with the view that items in STM are represented by noisy codes consisting of multiple dimensions and that interference occurs when items are similar to each other and, thus, compete along the dimensions relevant to target selection.

  8. Imaging bacterial spores by soft-x-ray microscopy

    International Nuclear Information System (INIS)

    Stead, A.D.; Ford, T.W.; Judge, J.

    1997-01-01

    Bacterial spores are able to survive dehydration, but neither the physiological nor structural basis of this have been fully elucidated. Furthermore, once hydrated, spores often require activation before they will germinate. Several treatments can be used to activate spores, but in the case of Bacillus subtlis the most effective is heat treatment. The physiological mechanism associated with activation is also not understood, but some workers suggest that the loss of calcium from the spores may be critical. However, just prior to germination, the spores change from being phase bright to phase dark when viewed by light microscopy. Imaging spores by soft x-ray microscopy is possible without fixation. Thus, in contrast to electron microscopy, it is possible to compare the structure of dehydrated and hydrated spores in a manner not possible previously. A further advantage is that it is possible to monitor individual spores by phase contrast light microscopy immediately prior to imaging with soft x-rays; whereas, with both electron microscopy and biochemical studies, it is a population of spores being studied without knowledge of the phase characteristics of individual spores. This study has therefore tried to compare dehydrated and hydrated spores and to determine if there is a mass loss from individual spores as they pass the transition from being phase bright to phase dark

  9. Imaging bacterial spores by soft-x-ray microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stead, A.D.; Ford, T.W. [Univ. of London, Surrey (United Kingdom); Judge, J. [Unilever plc, Sharnbrook (United Kingdom)] [and others

    1997-04-01

    Bacterial spores are able to survive dehydration, but neither the physiological nor structural basis of this have been fully elucidated. Furthermore, once hydrated, spores often require activation before they will germinate. Several treatments can be used to activate spores, but in the case of Bacillus subtlis the most effective is heat treatment. The physiological mechanism associated with activation is also not understood, but some workers suggest that the loss of calcium from the spores may be critical. However, just prior to germination, the spores change from being phase bright to phase dark when viewed by light microscopy. Imaging spores by soft x-ray microscopy is possible without fixation. Thus, in contrast to electron microscopy, it is possible to compare the structure of dehydrated and hydrated spores in a manner not possible previously. A further advantage is that it is possible to monitor individual spores by phase contrast light microscopy immediately prior to imaging with soft x-rays; whereas, with both electron microscopy and biochemical studies, it is a population of spores being studied without knowledge of the phase characteristics of individual spores. This study has therefore tried to compare dehydrated and hydrated spores and to determine if there is a mass loss from individual spores as they pass the transition from being phase bright to phase dark.

  10. Distracted and down: neural mechanisms of affective interference in subclinical depression.

    Science.gov (United States)

    Kaiser, Roselinde H; Andrews-Hanna, Jessica R; Spielberg, Jeffrey M; Warren, Stacie L; Sutton, Bradley P; Miller, Gregory A; Heller, Wendy; Banich, Marie T

    2015-05-01

    Previous studies have shown that depressed individuals have difficulty directing attention away from negative distractors, a phenomenon known as affective interference. However, findings are mixed regarding the neural mechanisms and network dynamics of affective interference. The present study addressed these issues by comparing neural activation during emotion-word and color-word Stroop tasks in participants with varying levels of (primarily subclinical) depression. Depressive symptoms predicted increased activation to negative distractors in areas of dorsal anterior cingulate cortex (dACC) and posterior cingulate cortex (PCC), regions implicated in cognitive control and internally directed attention, respectively. Increased dACC activity was also observed in the group-average response to incongruent distractors, suggesting that dACC activity during affective interference is related to overtaxed cognitive control. In contrast, regions of PCC were deactivated across the group in response to incongruent distractors, suggesting that PCC activity during affective interference represents task-independent processing. A psychophysiological interaction emerged in which higher depression predicted more positively correlated activity between dACC and PCC during affective interference, i.e. greater connectivity between cognitive control and internal-attention systems. These findings suggest that, when individuals high in depression are confronted by negative material, increased attention to internal thoughts and difficulty shifting resources to the external world interfere with goal-directed behavior. © The Author (2014). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  11. X-ray Phase Contrast analysis - Digital wavefront development

    International Nuclear Information System (INIS)

    Idir, Mourad; Potier, Jonathan; Fricker, Sebastien; Snigirev, Anatoly; Snigireva, Irina; Modi, M. H.

    2010-01-01

    Optical schemes that enable imaging of the phase shift produced by an object have become popular in the x-ray region, where phase can be the dominant contrast mechanism. The propagation-based technique consists of recording the interference pattern produced by choosing one or several sample-to-detector distances. Pioneering studies, carried out making use of synchrotron radiation, demonstrated that this technique results in a dramatic increase of image contrast and detail visibility, allowing the detection of structures invisible with conventional techniques. An experimental and theoretical study of in-line hard x-ray phase-contrast imaging had been performed. The theoretical description of the technique is based on Fresnel diffraction. As an illustration of the potential of this quantitative imaging technique, high-resolution x-ray phase contrast images of simple objects will be presented.

  12. Are precues effective in proactively controlling taboo interference during speech production?

    Science.gov (United States)

    White, Katherine K; Abrams, Lise; Hsi, Lisa R; Watkins, Emily C

    2018-02-07

    This research investigated whether precues engage proactive control to reduce emotional interference during speech production. A picture-word interference task required participants to name target pictures accompanied by taboo, negative, or neutral distractors. Proactive control was manipulated by presenting precues that signalled the type of distractor that would appear on the next trial. Experiment 1 included one block of trials with precues and one without, whereas Experiment 2 mixed precued and uncued trials. Consistent with previous research, picture naming was slowed in both experiments when distractors were taboo or negative compared to neutral, with the greatest slowing effect when distractors were taboo. Evidence that precues engaged proactive control to reduce interference from taboo (but not negative) distractors was found in Experiment 1. In contrast, mixing precued trials in Experiment 2 resulted in no taboo cueing benefit. These results suggest that item-level proactive control can be engaged under certain conditions to reduce taboo interference during speech production, findings that help to refine a role for cognitive control of distraction during speech production.

  13. The time-course of feature interference in agreement comprehension: Multiple mechanisms and asymmetrical attraction.

    Science.gov (United States)

    Tanner, Darren; Nicol, Janet; Brehm, Laurel

    2014-10-01

    Attraction interference in language comprehension and production may be as a result of common or different processes. In the present paper, we investigate attraction interference during language comprehension, focusing on the contexts in which interference arises and the time-course of these effects. Using evidence from event-related brain potentials (ERPs) and sentence judgment times, we show that agreement attraction in comprehension is best explained as morphosyntactic interference during memory retrieval. This stands in contrast to attraction as a message-level process involving the representation of the subject NP's number features, which is a strong contributor to attraction in production. We thus argue that the cognitive antecedents of agreement attraction in comprehension are non-identical with those of attraction in production, and moreover, that attraction in comprehension is primarily a consequence of similarity-based interference in cue-based memory retrieval processes. We suggest that mechanisms responsible for attraction during language comprehension are a subset of those involved in language production.

  14. Dual-wavelength recording, a simple algorithm to eliminate interferences due to UV-absorbing substances in capillary electrophoresis.

    Science.gov (United States)

    Seaux, Liesbeth; Van Houcke, Sofie; Dumoulin, Els; Fiers, Tom; Lecocq, Elke; Delanghe, Joris R

    2014-08-01

    Analytical interferences have been described due to the presence of various exogenous UV-absorbing substances in serum. Iodine-based X-ray contrast agents and various antibiotics have been reported to interfere with interpretation of serum protein pherograms, resulting in false diagnosis of paraproteinemia. In the present study, we have explored the possibility of measuring UV absorbance at two distinct wavelengths (210 and 246 nm) to distinguish between true and false paraproteins on a Helena V8 clinical electrophoresis instrument. This study demonstrates that most substances potentially interfering with serum protein electrophoresis show UV-absorption spectra that are distinct from those of serum proteins. Scanning at 246 nm allows detection of all described interfering agents. Comparing pherograms recorded at both wavelengths (210 and 246 nm) enables to distinguish paraproteins from UV-absorbing substances. In case of a true paraprotein, the peak with an electrophoretic mobility in the gamma-region decreases, whereas the X-ray contrast media and antibiotics show an increased absorption when compared to the basic setting (210 nm). The finding of iodine-containing contrast media interfering with serum protein electrophoresis is not uncommon. In a clinical series, interference induced by contrast media was reported in 54 cases (of 13 237 analyses), corresponding with a prevalence of 0.4%. In the same series, 1631 true paraproteins (12.3%) were detected. Implementation of the proposed algorithm may significantly improve the interpretation of routine electrophoresis results. However, attention should still be paid to possible interference due to presence of atypical proteins fractions (e.g., tumor markers, C3). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Fluorescence microscopy for the characterization of structural integrity

    Science.gov (United States)

    Street, Kenneth W.; Leonhardt, Todd A.

    1991-01-01

    The absorption characteristics of light and the optical technique of fluorescence microscopy for enhancing metallographic interpretation are presented. Characterization of thermally sprayed coatings by optical microscopy suffers because of the tendency for misidentification of the microstructure produced by metallographic preparation. Gray scale, in bright field microscopy, is frequently the only means of differentiating the actual structural details of porosity, cracking, and debonding of coatings. Fluorescence microscopy is a technique that helps to distinguish the artifacts of metallographic preparation (pullout, cracking, debonding) from the microstructure of the specimen by color contrasting structural differences. Alternative instrumentation and the use of other dye systems are also discussed. The combination of epoxy vacuum infiltration with fluorescence microscopy to verify microstructural defects is an effective means to characterize advanced materials and to assess structural integrity.

  16. Developments in Scanning Hall Probe Microscopy

    Science.gov (United States)

    Chouinard, Taras; Chu, Ricky; David, Nigel; Broun, David

    2009-05-01

    Low temperature scanning Hall probe microscopy is a sensitive means of imaging magnetic structures with high spatial resolution and magnetic flux sensitivity approaching that of a Superconducting Quantum Interference Device. We have developed a scanning Hall probe microscope with novel features, including highly reliable coarse positioning, in situ optimization of sensor-sample alignment and capacitive transducers for linear, long range positioning measurement. This has been motivated by the need to reposition accurately above fabricated nanostructures such as small superconducting rings. Details of the design and performance will be presented as well as recent progress towards time-resolved measurements with sub nanosecond resolution.

  17. Virtual Hematoxylin and Eosin Transillumination Microscopy Using Epi-Fluorescence Imaging.

    Science.gov (United States)

    Giacomelli, Michael G; Husvogt, Lennart; Vardeh, Hilde; Faulkner-Jones, Beverly E; Hornegger, Joachim; Connolly, James L; Fujimoto, James G

    2016-01-01

    We derive a physically realistic model for the generation of virtual transillumination, white light microscopy images using epi-fluorescence measurements from thick, unsectioned tissue. We demonstrate this technique by generating virtual transillumination H&E images of unsectioned human breast tissue from epi-fluorescence multiphoton microscopy data. The virtual transillumination algorithm is shown to enable improved contrast and color accuracy compared with previous color mapping methods. Finally, we present an open source implementation of the algorithm in OpenGL, enabling real-time GPU-based generation of virtual transillumination microscopy images using conventional fluorescence microscopy systems.

  18. Microfabricated high-bandpass foucault aperture for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Glaeser, Robert; Cambie, Rossana; Jin, Jian

    2014-08-26

    A variant of the Foucault (knife-edge) aperture is disclosed that is designed to provide single-sideband (SSB) contrast at low spatial frequencies but retain conventional double-sideband (DSB) contrast at high spatial frequencies in transmission electron microscopy. The aperture includes a plate with an inner open area, a support extending from the plate at an edge of the open area, a half-circle feature mounted on the support and located at the center of the aperture open area. The radius of the half-circle portion of reciprocal space that is blocked by the aperture can be varied to suit the needs of electron microscopy investigation. The aperture is fabricated from conductive material which is preferably non-oxidizing, such as gold, for example.

  19. Selective interference with pacemaker activity by electrical dental devices.

    Science.gov (United States)

    Miller, C S; Leonelli, F M; Latham, E

    1998-01-01

    We sought to determine whether electromagnetic interference with cardiac pacemakers occurs during the operation of contemporary electrical dental equipment. Fourteen electrical dental devices were tested in vitro for their ability to interfere with the function of two Medtronics cardiac pacemakers (one a dual-chamber, bipolar Thera 7942 pacemaker, the other a single-chamber, unipolar Minix 8340 pacemaker). Atrial and ventricular pacemaker output and electrocardiographic activity were monitored by means of telemetry with the use of a Medtronics 9760/90 programmer. Atrial and ventricular pacing were inhibited by electromagnetic interference produced by the electrosurgical unit up to a distance of 10 cm, by the ultrasonic bath cleaner up to 30 cm, and by the magnetorestrictive ultrasonic scalers up to 37.5 cm. In contrast, operation of the amalgamator, electric pulp tester, composite curing light, dental handpieces, electric toothbrush, microwave oven, dental chair and light, ENAC ultrasonic instrument, radiography unit, and sonic scaler did not alter pacing rate or rhythm. These results suggest that certain electrosurgical and ultrasonic instruments may produce deleterious effects in medically fragile patients with cardiac pacemakers.

  20. Application of Hoffman modulation contrast microscopy coupled with three-wavelength two-beam interferometry to the in situ direct observation of the growth process of a crystal in microgravity

    Science.gov (United States)

    Tsukamoto, Katsuo

    1988-01-01

    Direct visualization of three dimensional transfer process of both heat and mass around a growing crystal and mono-molecular growth layers on the surface is possible in situ by means of high resolution Hoffman modulation contrast microscopy coupled with three wavelength two beam Mach-Zehnder interferometry. This in situ observation is very suitable for the verification of the growth mechanism of a crystal in a solution or a melt in microgravity.

  1. High efficiency and flexible working distance digital in-line holographic microscopy based on Fresnel zone plate

    International Nuclear Information System (INIS)

    Tian, Peng; Yang, Fan; Li, Fanxing; Hu, Song; Yan, Wei; Hua, Yilei

    2017-01-01

    Traditional digital in-line holography suffers from twin-image noise problems and extremely short working distances between the object and light source. Here, we propose lensless Fourier transform digital in-line holographic microscopy based on a single optical element. A Fresnel zone plate is used to split the incident light into two parts: one is scattered along the original direction, the other is gathered at a focal point and the sample is put behind the focus. The interference fringe pattern, formed by the two beams, is recorded digitally by a CCD camera. A novel reconstruction algorithm is proposed to present the object image. The proof-of-concept experiments demonstrate that the proposed technique can eliminate the twin-image noise problem, improving the image contrast with high efficiency, and increasing the flexibility of the working distance. Furthermore, a wide field of view and no contact make it a promising tool for the study of materials science, biology and microelectronics. (paper)

  2. Phase-contrast tomographic imaging using an X-ray interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Momose, A. [Hitachi Ltd, Advanced Research Lab., Saitama (Japan); Takeda, T.; Itai, Y. [Univ. of Tsukuba, Inst. of Clinical Medicine, Ibaraki (Japan); Yoneyama, A. [Hitachi Ltd, Central Resarch Lab., Tokyo (Japan); Hirano, K. [High Energy Accelerator Research Organization, Inst. of Materials Structure Science, Ibaraki (Japan)

    1998-05-01

    Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays. 35 refs.

  3. Phase-contrast tomographic imaging using an X-ray interferometer

    International Nuclear Information System (INIS)

    Momose, A.; Takeda, T.; Itai, Y.; Yoneyama, A.; Hirano, K.

    1998-01-01

    Apparatus for phase-contrast X-ray computed tomography using a monolithic X-ray interferometer is presented with some observational results for human breast tissues. Structures characteristic of the tissues were revealed in the phase-contrast tomograms. The procedure of image analysis consists of phase retrieval from X-ray interference patterns and tomographic image reconstruction from the retrieved phase shift. Next, feasibility of phase-contrast imaging using a two-crystal X-ray interferometer was studied aiming at in vivo observation in the future. In a preliminary study, the two-crystal X-ray interferometer was capable of generating fringes of 70% visibility using synchrotron X-rays

  4. Effective segmentation of fresh post-mortem murine lung parenchyma in phase contrast X-ray tomographic microscopy images

    International Nuclear Information System (INIS)

    Oikonomidis, Ioannis Vogiatzis; Cremona, Tiziana P; Schittny, Johannes C; Lovric, Goran; Arcadu, Filippo; Stampanoni, Marco

    2017-01-01

    The acinus represents the functional unit of the mammalian lung. It is defined as the small tree of gas-exchanging airways, which is fed by the most distal purely conducting airway. Different hypotheses exist on how the fine structure of the acinus changes during ventilation and development. Since in classical 2-dimensional (2D) sections of the lung the borders of the acini are not detectable, every study of acini requires 3-dimensional (3D) datasets. As a basis for further studies of pulmonary acini we imaged rodent lungs as close to life as possible using phase contrast synchrotron radiation-based X-ray tomographic microscopy (SRXTM), and developed a protocol for the segmentation of the alveolar septa. The method is based on a combined multilevel filtering approach. Seeds are automatically defined for separate regions of tissue and airspace during each 2D filtering level and then given as input to a 3D random walk segmentation. Thus, the different types of artifacts present in the images are treated separately, taking into account the sample’s structural complexity. The proposed procedure yields high-quality 3D segmentations of acinar microstructure that can be used for a reliable morphological analysis. (paper)

  5. Phase-contrast X-ray CT

    Energy Technology Data Exchange (ETDEWEB)

    Momose, Atsushi [Hitachi Ltd., Saitama (Japan). Advanced Research Laboratory; Takeda, Tohoru; Itai, Yuji

    1995-12-01

    Phase-contrast X-ray computed tomography (CT) enabling the observation of biological soft tissues without contrast enhancement has been developed. The X-ray phase shift caused by an object is measured and input to a standard CT reconstruction algorithm. A thousand times increase in the image sensitivity to soft tissues is achieved compared with the conventional CT using absorption contrast. This is because the X-ray phase shift cross section of light elements is about a thousand times larger than the absorption cross section. The phase shift is detected using an X-ray interferometer and computer analyses of interference patterns. Experiments were performed using a synchrotron X-ray source. Excellent image sensitivity is demonstrated in the observation of cancerous rabbit liver. The CT images distinguish cancer lesion from normal liver tissue and, moreover, visualize the pathological condition in the lesion. Although the X-ray energy employed and the present observation area size are not suitable for medical applications as they are, phase-contrast X-ray CT is promising for investigating the internal structure of soft tissue which is almost transparent for X-rays. The high sensitivity also provides the advantage of reducing X-ray doses. (author).

  6. Anisotropic contrast optical microscope.

    Science.gov (United States)

    Peev, D; Hofmann, T; Kananizadeh, N; Beeram, S; Rodriguez, E; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M

    2016-11-01

    An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent, or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. These images are obtained from sets of multiple images obtained under various polarizer, analyzer, and compensator settings. Up to 16 independent Mueller matrix images can be obtained, while our current setup is limited to 11 images normalized by the unpolarized intensity. We demonstrate the anisotropic contrast optical microscope by measuring lithographically defined micro-patterned anisotropic filters, and we quantify the adsorption of an organic self-assembled monolayer film onto the anisotropic filter. Comparison with an isotropic glass slide demonstrates the image enhancement obtained by our method over microscopy without the use of an anisotropic filter. In our current instrument, we estimate the limit of detection for organic volumetric mass within the object plane of ≈49 fg within ≈7 × 7 μm 2 object surface area. Compared to a quartz crystal microbalance with dissipation instrumentation, where contemporary limits require a total load of ≈500 pg for detection, the instrumentation demonstrated here improves

  7. Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference.

    Science.gov (United States)

    Jolie, Wouter; Lux, Jonathan; Pörtner, Mathias; Dombrowski, Daniela; Herbig, Charlotte; Knispel, Timo; Simon, Sabina; Michely, Thomas; Rosch, Achim; Busse, Carsten

    2018-03-09

    We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n-band material.

  8. Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference

    Science.gov (United States)

    Jolie, Wouter; Lux, Jonathan; Pörtner, Mathias; Dombrowski, Daniela; Herbig, Charlotte; Knispel, Timo; Simon, Sabina; Michely, Thomas; Rosch, Achim; Busse, Carsten

    2018-03-01

    We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n -band material.

  9. Noninvasive 3D Structural Analysis of Arthropod by Synchrotron X-Ray Phase Contrast Tomography

    International Nuclear Information System (INIS)

    Yao, S.; Zong, Y.; Fan, J.; Sun, Z.; Jiang, H.

    2015-01-01

    X-ray imaging techniques significantly advanced our understanding of materials and biology, among which phase contrast X-ray microscopy has obvious advantages in imaging biological specimens which have low contrast by conventional absorption contrast microscopy. In this paper, three-dimensional microstructure of arthropod with high contrast has been demonstrated by synchrotron X-ray in-line phase contrast tomography. The external morphology and internal structures of an earthworm were analyzed based upon tomographic reconstructions with and without phase retrieval. We also identified and characterized various fine structural details such as the musculature system, the digestive system, the nervous system, and the circulatory system. This work exhibited the high efficiency, high precision, and wide potential applications of synchrotron X-ray phase contrast tomography in nondestructive investigation of low-density materials and biology.

  10. Quantitative transmission electron microscopy at atomic resolution

    International Nuclear Information System (INIS)

    Allen, L J; D'Alfonso, A J; Forbes, B D; Findlay, S D; LeBeau, J M; Stemmer, S

    2012-01-01

    In scanning transmission electron microscopy (STEM) it is possible to operate the microscope in bright-field mode under conditions which, by the quantum mechanical principle of reciprocity, are equivalent to those in conventional transmission electron microscopy (CTEM). The results of such an experiment will be presented which are in excellent quantitative agreement with theory for specimens up to 25 nm thick. This is at variance with the large contrast mismatch (typically between two and five) noted in equivalent CTEM experiments. The implications of this will be discussed.

  11. Comparable mechanisms of working memory interference by auditory and visual motion in youth and aging.

    Science.gov (United States)

    Mishra, Jyoti; Zanto, Theodore; Nilakantan, Aneesha; Gazzaley, Adam

    2013-08-01

    Intrasensory interference during visual working memory (WM) maintenance by object stimuli (such as faces and scenes), has been shown to negatively impact WM performance, with greater detrimental impacts of interference observed in aging. Here we assessed age-related impacts by intrasensory WM interference from lower-level stimulus features such as visual and auditory motion stimuli. We consistently found that interference in the form of ignored distractions and secondary task interruptions presented during a WM maintenance period, degraded memory accuracy in both the visual and auditory domain. However, in contrast to prior studies assessing WM for visual object stimuli, feature-based interference effects were not observed to be significantly greater in older adults. Analyses of neural oscillations in the alpha frequency band further revealed preserved mechanisms of interference processing in terms of post-stimulus alpha suppression, which was observed maximally for secondary task interruptions in visual and auditory modalities in both younger and older adults. These results suggest that age-related sensitivity of WM to interference may be limited to complex object stimuli, at least at low WM loads. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Integration of multiple theories for the simulation of laser interference lithography processes.

    Science.gov (United States)

    Lin, Te-Hsun; Yang, Yin-Kuang; Fu, Chien-Chung

    2017-11-24

    The periodic structure of laser interference lithography (LIL) fabrication is superior to other lithography technologies. In contrast to traditional lithography, LIL has the advantages of being a simple optical system with no mask requirements, low cost, high depth of focus, and large patterning area in a single exposure. Generally, a simulation pattern for the periodic structure is obtained through optical interference prior to its fabrication through LIL. However, the LIL process is complex and combines the fields of optical and polymer materials; thus, a single simulation theory cannot reflect the real situation. Therefore, this research integrates multiple theories, including those of optical interference, standing waves, and photoresist characteristics, to create a mathematical model for the LIL process. The mathematical model can accurately estimate the exposure time and reduce the LIL process duration through trial and error.

  13. Integration of multiple theories for the simulation of laser interference lithography processes

    Science.gov (United States)

    Lin, Te-Hsun; Yang, Yin-Kuang; Fu, Chien-Chung

    2017-11-01

    The periodic structure of laser interference lithography (LIL) fabrication is superior to other lithography technologies. In contrast to traditional lithography, LIL has the advantages of being a simple optical system with no mask requirements, low cost, high depth of focus, and large patterning area in a single exposure. Generally, a simulation pattern for the periodic structure is obtained through optical interference prior to its fabrication through LIL. However, the LIL process is complex and combines the fields of optical and polymer materials; thus, a single simulation theory cannot reflect the real situation. Therefore, this research integrates multiple theories, including those of optical interference, standing waves, and photoresist characteristics, to create a mathematical model for the LIL process. The mathematical model can accurately estimate the exposure time and reduce the LIL process duration through trial and error.

  14. Nonlinear multicontrast microscopy of hematoxylin-and-eosin-stained histological sections

    Science.gov (United States)

    Tuer, Adam; Tokarz, Danielle; Prent, Nicole; Cisek, Richard; Alami, Jennifer; Dumont, Daniel J.; Bakueva, Ludmila; Rowlands, John; Barzda, Virginijus

    2010-03-01

    Imaging hematoxylin-and-eosin-stained cancerous histological sections with multicontrast nonlinear excitation fluorescence, second- and third-harmonic generation (THG) microscopy reveals cellular structures with extremely high image contrast. Absorption and fluorescence spectroscopy together with second hyperpolarizability measurements of the dyes shows that strong THG appears due to neutral hemalum aggregation and is subsequently enhanced by interaction with eosin. Additionally, fluorescence lifetime imaging microscopy reveals eosin fluorescence quenching by hemalums, showing better suitability of only eosin staining for fluorescence microscopy. Multicontrast nonlinear microscopy has the potential to differentiate between cancerous and healthy tissue at a single cell level.

  15. Virtual Hematoxylin and Eosin Transillumination Microscopy Using Epi-Fluorescence Imaging.

    Directory of Open Access Journals (Sweden)

    Michael G Giacomelli

    Full Text Available We derive a physically realistic model for the generation of virtual transillumination, white light microscopy images using epi-fluorescence measurements from thick, unsectioned tissue. We demonstrate this technique by generating virtual transillumination H&E images of unsectioned human breast tissue from epi-fluorescence multiphoton microscopy data. The virtual transillumination algorithm is shown to enable improved contrast and color accuracy compared with previous color mapping methods. Finally, we present an open source implementation of the algorithm in OpenGL, enabling real-time GPU-based generation of virtual transillumination microscopy images using conventional fluorescence microscopy systems.

  16. ERP evidence of distinct processes underlying semantic facilitation and interference in word production.

    Science.gov (United States)

    Python, Grégoire; Fargier, Raphaël; Laganaro, Marina

    2018-02-01

    In everyday conversations, we take advantage of lexical-semantic contexts to facilitate speech production, but at the same time, we also have to reduce interference and inhibit semantic competitors. The blocked cyclic naming paradigm (BCNP) has been used to investigate such context effects. Typical results on production latencies showed semantic facilitation (or no effect) during the first presentation cycle, and interference emerging in subsequent cycles. Even if semantic contexts might be just as facilitative as interfering, previous BCNP studies focused on interference, which was interpreted as reflecting lemma selection and self-monitoring processes. Facilitation in the first cycle was rarely considered/analysed, although it potentially informs on word production to the same extent as interference. Here we contrasted the event-related potential (ERP) signatures of both semantic facilitation and interference in a BCNP. ERPs differed between homogeneous and heterogeneous blocks from about 365 msec post picture onset in the first cycle (facilitation) and in an earlier time-window (270 msec post picture onset) in the third cycle (interference). Three different analyses of the ERPs converge towards distinct processes underlying semantic facilitation and interference (post-lexical vs lexical respectively). The loci of semantic facilitation and interference are interpreted in the context of different theoretical frameworks of language production: the post-lexical locus of semantic facilitation involves interactive phonological-semantic processes and/or self-monitoring, whereas the lexical locus of semantic interference is in line with selection through increased lexical competition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Measures of extents of laterality for high-frequency ``transposed'' stimuli under conditions of binaural interference

    Science.gov (United States)

    Bernstein, Leslie R.; Trahiotis, Constantine

    2005-09-01

    Our purpose in this study was to determine whether across-frequency binaural interference would occur if ITD-based extents of laterality were measured using high-frequency transposed stimuli as targets. The results of an earlier study [L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 116, 3062-3069 (2004)], which focused on threshold-ITDs, rather than extents of laterality, suggested that high-frequency transposed stimuli might be ``immune'' to binaural interference effects resulting from the addition of a spectrally remote, low-frequency interferer. In contrast to the earlier findings, the data from this study indicate that high-frequency transposed targets are susceptible to binaural interference. Nevertheless, high-frequency transposed targets, even when presented along with an interferer, yielded greater extents of ITD-based laterality than did high-frequency Gaussian noise targets presented in isolation. That is, the ``enhanced potency'' of ITDs conveyed by transposed stimuli persisted, even in the presence of a low-frequency interferer. Predictions made using an extension of the model of Heller and Trahiotis [L. M. Heller and C. Trahiotis, J. Acoust. Soc. Am. 99, 3632-3637 (1996)] accounted well for across-frequency binaural interference obtained with conventional Gaussian noise targets but, in all but one case, overpredicted the amounts of interference found with the transposed targets.

  18. Software for imaging phase-shift interference microscope

    Science.gov (United States)

    Malinovski, I.; França, R. S.; Couceiro, I. B.

    2018-03-01

    In recent years absolute interference microscope was created at National Metrology Institute of Brazil (INMETRO). The instrument by principle of operation is imaging phase-shifting interferometer (PSI) equipped with two stabilized lasers of different colour as traceable reference wavelength sources. We report here some progress in development of the software for this instrument. The status of undergoing internal validation and verification of the software is also reported. In contrast with standard PSI method, different methodology of phase evaluation is applied. Therefore, instrument specific procedures for software validation and verification are adapted and discussed.

  19. Experimental occlusal interferences. Part III. Mandibular rotations induced by a rigid interference.

    Science.gov (United States)

    Rassouli, N M; Christensen, L V

    1995-10-01

    A rigid intercuspal interference (minimum mean height of 0.24 mm) was placed on either the right or left mandibular second premolar and first molar of 12 subjects. During brisk and forceful biting on the interference, rotational electrognathography measured maximum torque of the right and left mandibular condyles in the frontal and horizontal planes of orientation. All subjects showed frontal plan upward rotation (mean of 0.7 degrees) of the mandibular condyle contralateral to the interference. In 33% of the subjects there was no horizontal plane backward rotation. In 58% of the subjects there was horizontal plane backward rotation (mean of 0.5 degrees) of the mandibular condyle ipsilateral to the interference, and in one subject (8%) there was backward horizontal plane rotation (0.1 degree) of the mandibular condyle contralateral to the interference. It was inferred that the masseter muscle, ipsilateral to the interference, generated negative work in order to decelerate frontal plane 'unseating' of the mandibular condyle ipsilateral to the interference. It was inferred that the masseter muscle, contralateral to the interference, produced positive work in order to accelerate frontal plane 'seating' of the mandibular condyle contralateral to the interference. Finally, it was speculated that the impact forces of frontal plane 'seating' of the mandibular condyle, contralateral to the interference, might lead to 'vacuum sticking' of the temporomandibular joint disc because of the formation of negative hydrostatic pressures.

  20. Experimental occlusal interferences. Part II. Masseteric EMG responses to an intercuspal interference.

    Science.gov (United States)

    Christensen, L V; Rassouli, N M

    1995-07-01

    In 12 subjects, a rigid unilateral intercuspal interference (minimum mean height of 0.24 mm) was placed on either the right or left mandibular second premolar and first molar (sagittal physiological equilibrium point of the hemimandibular dental arch). During brisk and forceful clenching on the interference, bipolar surface electromyograms were obtained from the right and left masseter muscles. On the side opposite the interference, myoelectric clenching activity was significantly reduced. Correlation analyses showed that the interference elicited a non-linear (complex) co-ordination of the amplitude, but not the duration, of bilateral masseteric clenching activity, i.e. frequently there was significant motor facilitation on the side of the interference, and significant motor inhibition on the side opposite the interference. Theoretical considerations predicted that brief clenching on the interference would easily lead to frontal plane rotatory motions of the mandible which, indeed, occurred clinically.

  1. Three-Dimensional Constructive Interference in Steady State Sequences and Phase-Contrast Magnetic Resonance Imaging of Arrested Hydrocephalus.

    Science.gov (United States)

    Elkafrawy, Fatma; Reda, Ihab; Elsirafy, Mohamed; Gawad, Mohamed Saied Abdel; Elnaggar, Alaa; Khalek Abdel Razek, Ahmed Abdel

    2017-02-01

    To evaluate the role of three-dimensional constructive interference in steady state (3D-CISS) sequences and phase-contrast magnetic resonance imaging (PC-MRI) in patients with arrested hydrocephalus. A prospective study of 20 patients with arrested hydrocephalus was carried out. All patients underwent PC-MRI and 3D-CISS for assessment of the aqueduct. Axial (through-plane), sagittal (in-plane) PC-MRI, and sagittal 3D-CISS were applied to assess the cerebral aqueduct and the spontaneous third ventriculostomy if present. Aqueductal patency was graded using 3D-CISS and PC-MRI. Quantitative analysis of flow through the aqueduct was performed using PC-MRI. The causes of obstruction were aqueductal obstruction in 75% (n = 15), third ventricular obstruction in 5% (n = 1), and fourth ventricular obstruction in 20% (n = 4). The cause of arrest of hydrocephalus was spontaneous third ventriculostomy in 65% (n = 13), endoscopic third ventriculostomy in 10% (n = 2), and ventriculoperitoneal shunt in 5% (n = 1), and no cause could be detected in 20% of patients (n = 4). There is a positive correlation (r = 0.80) and moderate agreement (κ = 0.509) of grading with PC-MRI and 3D-CISS sequences. The mean peak systolic velocity of cerebrospinal fluid was 1.86 ± 2.48 cm/second, the stroke volume was 6.43 ± 13.81 μL/cycle, and the mean flow was 0.21 ± 0.32 mL/minute. We concluded that 3D-CISS and PC-MRI are noninvasive sequences for diagnosis of the level and cause of arrested hydrocephalus. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Contrast media: interactions with other drugs and clinical tests

    International Nuclear Information System (INIS)

    Morcos, Sameh K.; Exley, C.M.; Thomsen, Henrik S.

    2005-01-01

    Many patients with multiple medical problems who are receiving a variety of drugs are investigated with imaging techniques which require intravascular contrast media. The Contrast Media Safety Committee of the European Society of Urogenital Radiology therefore decided to review the literature and to draw up simple guidelines on interactions between contrast media and other drugs. An extensive literature search was carried out and summarized in a report. Based on the available information, simple guidelines have been drawn up. The report and guidelines were discussed at the 11th European Symposium on Urogenital Radiology in Santiago de Compostela. Contrast media may interact with other drugs, and may interfere with isotope studies and biochemical measurements. Awareness of the patient drug history is important to avoid potential hazards. Simple guidelines are presented. (orig.)

  3. IETS and quantum interference

    DEFF Research Database (Denmark)

    Jørgensen, Jacob Lykkebo; Gagliardi, Alessio; Pecchia, Alessandro

    2014-01-01

    Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low...... suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference....

  4. Thermal diffuse scattering in transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Forbes, B.D.; D' Alfonso, A.J. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Findlay, S.D. [School of Physics, Monash University, Victoria 3800 (Australia); Van Dyck, D. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); LeBeau, J.M. [North Carolina State University, Raleigh, NC 27695-7907 (United States); Stemmer, S. [Materials Department, University of California, Santa Barbara, CA 93106-5050 (United States); Allen, L.J., E-mail: lja@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia)

    2011-12-15

    In conventional transmission electron microscopy, thermal scattering significantly affects the image contrast. It has been suggested that not accounting for this correctly is the main cause of the Stobbs factor, the ubiquitous, large contrast mismatch found between theory and experiment. In the case where a hard aperture is applied, we show that previous conclusions drawn from work using bright field scanning transmission electron microscopy and invoking the principle of reciprocity are reliable in the presence of thermal scattering. In the aperture-free case it has been suggested that even the most sophisticated mathematical models for thermal diffuse scattering lack in their numerical implementation, specifically that there may be issues in sampling, including that of the contrast transfer function of the objective lens. We show that these concerns can be satisfactorily overcome with modest computing resources; thermal scattering can be modelled accurately enough for the purpose of making quantitative comparison between simulation and experiment. Spatial incoherence of the source is also investigated. Neglect or inadequate handling of thermal scattering in simulation can have an appreciable effect on the predicted contrast and can be a significant contribution to the Stobbs factor problem. -- Highlights: Black-Right-Pointing-Pointer We determine the numerical requirements for accurate simulation of TDS in CTEM. Black-Right-Pointing-Pointer TDS can be simulated to high precision using the Born-Oppenheimer model. Black-Right-Pointing-Pointer Such calculations establish the contribution of TDS to the Stobbs factor problem. Black-Right-Pointing-Pointer Treating spatial incoherence using envelope functions increases image contrast. Black-Right-Pointing-Pointer Rigorous treatment of spatial incoherence significantly reduces image contrast.

  5. In-phase and anti-phase interference fringes in rocking curves of resonant X-ray dynamical diffraction

    International Nuclear Information System (INIS)

    Negishi, Riichirou; Fukamachi, Tomoe; Yoshizawa, Masami; Hirano, Kenji; Hirano, Keiichi; Kawamura, Takaaki

    2008-01-01

    We have observed the interference fringes that are in phase with each other in the diffracted and transmitted rocking curves of GaAs 200 reflection near the K-absorption edge of As. The fringes are in contrast with the well-known Pendelloesung fringes that are anti-phase with each other in the diffracted and transmitted waves. The origin of the in-phase interference fringe is analyzed to be due to the diffraction only by the imaginary part of the atomic scattering factor. It is also shown that the interference fringes become typical Pendelloesung fringes when the diffraction is caused only by the real part. (author)

  6. Quantitative contrast-enhanced optical coherence tomography

    Energy Technology Data Exchange (ETDEWEB)

    Winetraub, Yonatan; SoRelle, Elliott D. [Molecular Imaging Program at Stanford, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Bio-X Program, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Biophysics Program, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Department of Structural Biology, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Liba, Orly [Molecular Imaging Program at Stanford, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Bio-X Program, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Department of Structural Biology, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Department of Electrical Engineering, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Zerda, Adam de la [Molecular Imaging Program at Stanford, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Bio-X Program, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Biophysics Program, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Department of Structural Biology, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States); Department of Electrical Engineering, Stanford University, 299 Campus Drive, Stanford, California 94305 (United States)

    2016-01-11

    We have developed a model to accurately quantify the signals produced by exogenous scattering agents used for contrast-enhanced Optical Coherence Tomography (OCT). This model predicts distinct concentration-dependent signal trends that arise from the underlying physics of OCT detection. Accordingly, we show that real scattering particles can be described as simplified ideal scatterers with modified scattering intensity and concentration. The relation between OCT signal and particle concentration is approximately linear at concentrations lower than 0.8 particle per imaging voxel. However, at higher concentrations, interference effects cause signal to increase with a square root dependence on the number of particles within a voxel. Finally, high particle concentrations cause enough light attenuation to saturate the detected signal. Predictions were validated by comparison with measured OCT signals from gold nanorods (GNRs) prepared in water at concentrations ranging over five orders of magnitude (50 fM to 5 nM). In addition, we validated that our model accurately predicts the signal responses of GNRs in highly heterogeneous scattering environments including whole blood and living animals. By enabling particle quantification, this work provides a valuable tool for current and future contrast-enhanced in vivo OCT studies. More generally, the model described herein may inform the interpretation of detected signals in modalities that rely on coherence-based detection or are susceptible to interference effects.

  7. Use of atomic force microscopy and transmission electron microscopy for correlative studies of bacterial capsules.

    Science.gov (United States)

    Stukalov, Oleg; Korenevsky, Anton; Beveridge, Terry J; Dutcher, John R

    2008-09-01

    Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of four different gram-negative bacterial strains: Escherichia coli K30, Pseudomonas aeruginosa FRD1, Shewanella oneidensis MR-4, and Geobacter sulfurreducens PCA. TEM analysis of bacterial cells using different preparative techniques (whole-cell mounts, conventional embeddings, and freeze-substitution) revealed capsules for some but not all of the strains. In contrast, the use of AFM allowed the unambiguous identification of the presence of capsules on all strains used in the present study, including those that were shown by TEM to be not encapsulated. In addition, the use of AFM phase imaging allowed the visualization of the bacterial cell within the capsule, with a depth sensitivity that decreased with increasing tapping frequency.

  8. Codebook-based interference alignment for uplink MIMO interference channels

    KAUST Repository

    Lee, Hyun Ho; Park, Kihong; Ko, Youngchai; Alouini, Mohamed-Slim

    2014-01-01

    In this paper, we propose a codebook-based interference alignment (IA) scheme in the constant multiple-input multipleoutput (MIMO) interference channel especially for the uplink scenario. In our proposed scheme, we assume cooperation among base

  9. Combining scanning tunneling microscopy and synchrotron radiation for high-resolution imaging and spectroscopy with chemical, electronic, and magnetic contrast

    International Nuclear Information System (INIS)

    Cummings, M.L.; Chien, T.Y.; Preissner, C.; Madhavan, V.; Diesing, D.; Bode, M.; Freeland, J.W.; Rose, V.

    2012-01-01

    The combination of high-brilliance synchrotron radiation with scanning tunneling microscopy opens the path to high-resolution imaging with chemical, electronic, and magnetic contrast. Here, the design and experimental results of an in-situ synchrotron enhanced x-ray scanning tunneling microscope (SXSTM) system are presented. The system is designed to allow monochromatic synchrotron radiation to enter the chamber, illuminating the sample with x-ray radiation, while an insulator-coated tip (metallic tip apex open for tunneling, electron collection) is scanned over the surface. A unique feature of the SXSTM is the STM mount assembly, designed with a two free-flex pivot, providing an angular degree of freedom for the alignment of the tip and sample with respect to the incoming x-ray beam. The system designed successfully demonstrates the ability to resolve atomic-scale corrugations. In addition, experiments with synchrotron x-ray radiation validate the SXSTM system as an accurate analysis technique for the study of local magnetic and chemical properties on sample surfaces. The SXSTM system's capabilities have the potential to broaden and deepen the general understanding of surface phenomena by adding elemental contrast to the high-resolution of STM. -- Highlights: ► Synchrotron enhanced x-ray scanning tunneling microscope (SXSTM) system designed. ► Unique STM mount design allows angular DOF for tip alignment with x-ray beam. ► System demonstrates ability to resolve atomic corrugations on HOPG. ► Studies show chemical sensitivity with STM tip from photocurrent and tunneling. ► Results show system's ability to study local magnetic (XMCD) properties on Fe films.

  10. Biological applications of near-field scanning optical microscopy

    NARCIS (Netherlands)

    Moers, M.H.P.; Moers, Marco H.P.; Ruiter, A.G.T.; Jalocha, A.; Jalocha, Alain; van Hulst, N.F.

    1995-01-01

    Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on

  11. Microscopy imaging system and method employing stimulated raman spectroscopy as a contrast mechanism

    Science.gov (United States)

    Xie, Xiaoliang Sunney [Lexington, MA; Freudiger, Christian [Boston, MA; Min, Wei [Cambridge, MA

    2011-09-27

    A microscopy imaging system includes a first light source for providing a first train of pulses at a first center optical frequency .omega..sub.1, a second light source for providing a second train of pulses at a second center optical frequency .omega..sub.2, a modulator system, an optical detector, and a processor. The modulator system is for modulating a beam property of the second train of pulses at a modulation frequency f of at least 100 kHz. The optical detector is for detecting an integrated intensity of substantially all optical frequency components of the first train of pulses from the common focal volume by blocking the second train of pulses being modulated. The processor is for detecting, a modulation at the modulation frequency f, of the integrated intensity of the optical frequency components of the first train of pulses to provide a pixel of an image for the microscopy imaging system.

  12. Motion contrast using optical coherence tomography

    Science.gov (United States)

    Fingler, Jeffrey Paul

    Diagnosis of ophthalmic diseases like age-related macular degeneration is very important for treatment of the disease as well as the development of future treatments. Optical coherence tomography (OCT) is an optical interference technique which can measure the three-dimensional structural information of the reflecting layers within a sample. In retinal imaging, OCT is used as the primary diagnostic tool for structural abnormalities such as retinal holes and detachments. The contrast within the images of this technique is based upon reflectivity changes from different regions of the retina. This thesis demonstrates the developments of methods used to produce additional contrast to the structural OCT images based on the tiny fluctuations of motion experienced by the mobile scatterers within a sample. Motion contrast was observed for motions smaller than 50 nm in images of a variety of samples. Initial contrast method demonstrations used Brownian motion differences to separate regions of a mobile Intralipid solution from a static agarose gel, chosen in concentration to minimize reflectivity contrast. Zebrafish embryos in the range of 3-4 days post fertilization were imaged using several motion contrast methods to determine the capabilities of identifying regions of vascular flow. Vasculature identification was demonstrated in zebrafish for blood vessels of all orientations as small as 10 microns in diameter. Mouse retinal imaging utilized the same motion contrast methods to determine the contrast capabilities for motions associated with vasculature within the retina. Improved contrast imaging techniques demonstrated comparable images to fluorescein angiography, the gold standard of retinal vascular imaging. Future studies can improve the demonstrated contrast analysis techniques and apply them towards human retinal motion contrast imaging for ophthalmic diagnostic purposes.

  13. High resolution electron microscopy of the triply incommensurate phase of 2H-TaSe2

    Science.gov (United States)

    Onozuka, Takashi; Otsuka, Nobuo; Sato, Hiroshi

    1986-09-01

    The triply incommensurate phase of 2H-TaSe2 obtained by cooling from the normal phase was investigated by transmission electron microscopy between 87 and 113 K with the resolution of 3 Å, one order of magnitude better than earlier experiments. Moirélike patterns observed in this phase were confirmed to be interference fringes due to the first- and second-order diffraction beams (with small separation and possibly with higher-order diffraction beams) from the incommensurate structure and were not due to the dark-field diffraction contrast of domains of the commensurate structure as interpreted earlier. Lattice fringes (~9 Å) of this modulated phase do not show any discontinuity across the boundaries of regions of different contrasts of the moirélike fringes which is expected from domain boundaries. Instead, a periodic change in the spacing of the lattice fringes (phase-slip region) expected from the superposition of split superlattice spots in forming the lattice image is observed. This is what is believed to be the first direct observation of the existence of the phase-slip region which is also expected from the discommensuration theory. A series of observations presented here thus shows that the triply incommensurate phase is intrinsically incommensurate and suggests the need for a modification of interpretations of this phase in terms of the double honeycomb discommensuration model.

  14. Characterization of interference thin films grown on stainless steel surface by alternate pulse current in a sulphochromic solution

    Directory of Open Access Journals (Sweden)

    Rosa Maria Rabelo Junqueira

    2008-12-01

    Full Text Available The aim of this work was to characterize thin interference films grown on the surface of AISI 304 stainless steel for decorative purposes. Films were grown in a sulphochromic solution at room temperature by an alternating pulse current method. The morphology and chemical state of the elements in the films were investigated by field emission scanning electron microscopy (FESEM, atomic force microscopy (AFM, glow discharge optical emission spectrometry (GDOES, and infrared Fourier transform spectroscopy (FTIR. Depth-sensing indentation (DSI experiments and wear abrasion tests were employed to assess the mechanical resistance of the films. The coloration process resulted in porous thin films which increased the surface roughness of the substrate. The interference films mainly consisted of hydrated chromium oxide containing iron. Increasing film thickness produced different colors and affected the mechanical properties of the coating-substrate system. Thicker films, such as those producing gold and green colors, were softer but more abrasion resistant.

  15. Contrast enhancement of microsphere-assisted super-resolution imaging in dark-field microscopy

    Science.gov (United States)

    Zhou, Yi; Tang, Yan; Deng, Qinyuan; Zhao, Lixin; Hu, Song

    2017-08-01

    We report a method of boosting the imaging contrast of microsphere-assisted super-resolution visualization by utilizing dark-field illumination (DFI). We conducted experiments on both 10-µm-diameter silica (SiO2) microspheres with refractive index n ∼ 1.46 under no and partial immersion in ethyl alcohol (n ∼ 1.36) and 20-µm-diameter barium titanate glass (BTG, n ∼ 1.9) microspheres with full immersion to show the super-resolution capability. We experimentally demonstrated that the imaging contrast and uniformity were extraordinarily improved in the DFI mode. The intensity profiles in the visualization also numerically confirm the enhanced sharpness for a better imaging quality when applying DFI.

  16. Iterative Soft Decision Interference Cancellation for DS-CDMA Employing the Distribution of Interference

    Directory of Open Access Journals (Sweden)

    Gerstacker WolfgangH

    2010-01-01

    Full Text Available A well-known receiver strategy for direct-sequence code-division multiple-access (DS-CDMA transmission is iterative soft decision interference cancellation. For calculation of soft estimates used for cancellation, the distribution of residual interference is commonly assumed to be Gaussian. In this paper, we analyze matched filter-based iterative soft decision interference cancellation (MF ISDIC when utilizing an approximation of the actual probability density function (pdf of residual interference. In addition, a hybrid scheme is proposed, which reduces computational complexity by considering the strongest residual interferers according to their pdf while the Gaussian assumption is applied to the weak residual interferers. It turns out that the bit error ratio decreases already noticeably when only a small number of residual interferers is regarded according to their pdf. For the considered DS-CDMA transmission the bit error ratio decreases by 80% for high signal-to-noise ratios when modeling all residual interferers but the strongest three to be Gaussian distributed.

  17. Handheld Fluorescence Microscopy based Flow Analyzer.

    Science.gov (United States)

    Saxena, Manish; Jayakumar, Nitin; Gorthi, Sai Siva

    2016-03-01

    Fluorescence microscopy has the intrinsic advantages of favourable contrast characteristics and high degree of specificity. Consequently, it has been a mainstay in modern biological inquiry and clinical diagnostics. Despite its reliable nature, fluorescence based clinical microscopy and diagnostics is a manual, labour intensive and time consuming procedure. The article outlines a cost-effective, high throughput alternative to conventional fluorescence imaging techniques. With system level integration of custom-designed microfluidics and optics, we demonstrate fluorescence microscopy based imaging flow analyzer. Using this system we have imaged more than 2900 FITC labeled fluorescent beads per minute. This demonstrates high-throughput characteristics of our flow analyzer in comparison to conventional fluorescence microscopy. The issue of motion blur at high flow rates limits the achievable throughput in image based flow analyzers. Here we address the issue by computationally deblurring the images and show that this restores the morphological features otherwise affected by motion blur. By further optimizing concentration of the sample solution and flow speeds, along with imaging multiple channels simultaneously, the system is capable of providing throughput of about 480 beads per second.

  18. Near-infrared branding efficiently correlates light and electron microscopy.

    Science.gov (United States)

    Bishop, Derron; Nikić, Ivana; Brinkoetter, Mary; Knecht, Sharmon; Potz, Stephanie; Kerschensteiner, Martin; Misgeld, Thomas

    2011-06-05

    The correlation of light and electron microscopy of complex tissues remains a major challenge. Here we report near-infrared branding (NIRB), which facilitates such correlation by using a pulsed, near-infrared laser to create defined fiducial marks in three dimensions in fixed tissue. As these marks are fluorescent and can be photo-oxidized to generate electron contrast, they can guide re-identification of previously imaged structures as small as dendritic spines by electron microscopy.

  19. Probing graphene defects and estimating graphene quality with optical microscopy

    International Nuclear Information System (INIS)

    Lai, Shen; Kyu Jang, Sung; Jae Song, Young; Lee, Sungjoo

    2014-01-01

    We report a simple and accurate method for detecting graphene defects that utilizes the mild, dry annealing of graphene/Cu films in air. In contrast to previously reported techniques, our simple approach with optical microscopy can determine the density and degree of dislocation of defects in a graphene film without inducing water-related damage or functionalization. Scanning electron microscopy, confocal Raman and atomic force microscopy, and X-ray photoelectron spectroscopy analysis were performed to demonstrate that our nondestructive approach to characterizing graphene defects with optimized thermal annealing provides rapid and comprehensive determinations of graphene quality

  20. Mitigation of MIMO Co-Channel Interference using robust interference cancellation receiver

    DEFF Research Database (Denmark)

    Rahman, Muhammad Imadur; De Carvalho, Elisabeth; Prasad, Ramjee

    2007-01-01

    (STBC) link may become equivalent to an interfering Spatial Multiplexing (SM) link. Using this knowledge and understanding, we propose an interference cancellation receiver robust to different types of MIMO interferers at cell edge for the Downlink (DL) of cellular systems. The receiver systematically...... performs a multiple symbol processing: this is the appropriate processing when the signal of interest or the signal of interferer is correlated across symbols, which is the case for STBC transmission. We evaluated different link combinations in terms of Signal to Interference and Noise Ratio (SINR......) statistics and Bit Error Rate (BER) performance in cellular Orthogonal Frequency Division Multiple Access (OFDMA) systems. We have found that the proposed multiple-symbol linear interference cancellation receiver performs satisfactorily when any kind of single 'logical' stream MIMO scheme is present...

  1. Experimental occlusal interferences. Part IV. Mandibular rotations induced by a pliable interference.

    Science.gov (United States)

    Christensen, L V; Rassouli, N M

    1995-11-01

    In 12 subjects, a pliable, yet unbreakable, intercuspal interference (aluminum shim onlay splint; uniform height of 0.25 mm) was placed between either the right or left maxillary and mandibular second premolars and first molars. During brief and forceful biting (dynamic chewing stroke of about 20 kg force) the interference emulated a semisoft food bolus, and at the end of biting (subsequent static clenching stroke of about 20 kg force) it emulated a rigid metal interference. During dynamic/static biting, rotational electrognathography measured maximum frontal and horizontal plane torque of the right and left mandibular condyles. Eleven subjects (92%) showed frontal plane upward rotation (mean of 1.0 degree) of the condyle contralateral to the interference, and one subject (8%) showed frontal plane upward rotation (0.4 degree) of the condyle ipsilateral to the interference. Two subjects (17%) showed no horizontal plane rotation; seven subjects (58%) showed backward rotation (mean of 0.4 degree) of the condyle contralateral to the interference; and three subjects (25%) showed backward rotation (mean of 0.3 degree) of the condyle ipsilateral to the interference. It is suggested that, in the presence of an occlusal interference, mastication may have both short- and long-term detrimental effects.

  2. Investigation of graphite composite anodes surfaces by atomic force microscopy and related techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hirasawa, Karen Akemi; Nishioka, Keiko; Sato, Tomohiro; Yamaguchi, Shoji; Mori, Shoichiro [Mitsubishi Chemical Corp., Tsukuba Research Center, Ibaraki (Japan)

    1997-11-01

    The surface of a synthetic graphite (KS-44) and polyvinylidene difluoride binder (PVDF) anode for lithium-ion secondary batteries is imaged using atomic force microscopy (AFM) and several related scanning probe microscope (SPM) instruments including: dynamic force microscopy (DFM), friction force microscopy (FFM), laterally-modulated friction force microscopy (LM-FFM), visco-elasticity atomic force microscopy (VE-AFM), and AFM/simultaneous current measurement mode (SCM). DFM is found to be an exceptional mode for topographic imaging while FFM results in the clearest contrast distinction between PVDF binder and KS-44 graphite regions. (orig.)

  3. Morfologia do Mycobacterium leprae hominis e do M. leprae muris: estudo baseado na microscopia electrônica e de contraste de fases Morphology of Mycobacterium leprae hominis and M. leprae muris based on electron and phases contrast microscopy

    Directory of Open Access Journals (Sweden)

    H. C. de Souza-Araújo

    1955-12-01

    Full Text Available Hansen's Bacillus: By electron microscopy this bacillus shows membrane and halo, this being more visible when sorrounding the globi or bundles of bacilli; shows, also, free granules of various sizes which were before considered as dust of the dyes; shows external granules bound with the membrane and some times branching. By phases contrast microscopy examining leproma suspensions and subcataneous lymph at 400 x we saw many free granules with intense rotatory movement; granulated bacilli with screw, skip or stroke motion, producing slow progressive motion. All such elementes are surrounded by a halo, corresponding to the classical gloea. By a patient and delayed examination we were able to see that the internal granules are motile and help the progression of the bacilli, giving the impression that the cytoplasm is liquid. By a lasting observation we could see the larger granules form prolapse, like a pseudopode and abandon the bacilli and going in very rapid rotatory movement. There are branched bacilli; there are pedunculated fred granules like comets. The addition of a drop of formol at the preparation stops all movements. Stefansky's Bacillus: Repeated examination by RCA electron microscope, type EMU-25 of fresh suspensions of rat lepromas, led us to confirm the close relationship between human and murine leprosy agents. We examined also material from carabo (Lepra bubalorum from Java, but due to fixation, the material was unsuitable for comparative studies. The Stefansky's bacilli showed also emmbranes and halos, internal or external granules (smaller than those of Hansen's bacillus. The bacilli shaded by chromium look thicker and shorter than those of Hansen. Due to electron bombardment both, Hansen's and Stefansky's baccilli suffer considerable alterations in their structure, showing black barrs of chromatin condensation at their extremities as also in their centers. By phase microscopy the Stefansky's bacilli showed elements with 1, 2

  4. Transmission electron microscopy physics of image formation and microanalysis

    CERN Document Server

    Reimer, Ludwig

    1997-01-01

    Transmission Electron Microscopy presents the theory of image and contrast formation, and the analytical modes in transmission electron microscopy. The principles of particle and wave optics of electrons are described. Electron-specimen interactions are discussed for evaluating the theory of scattering and phase contrast. Also discussed are the kinematical and dynamical theories of electron diffraction and their applications for crystal-structure analysis and imaging of lattices and their defects. X-ray micronanalysis and electron energy-loss spectroscopy are treated as analytical methods. Specimen damage and contamination by electron irradiation limits the resolution for biological and some inorganic specimens. This fourth edition includes discussion of recent progress, especially in the area of Schottky emission guns, convergent-beam electron diffraction, electron tomography, holography and the high resolution of crystal lattices.

  5. Helium ion microscopy of graphene: beam damage, image quality and edge contrast

    International Nuclear Information System (INIS)

    Fox, D; Zhou, Y B; O’Neill, A; Wang, J J; Coleman, J N; Donegan, J F; Zhang, H Z; Kumar, S; Duesberg, G S

    2013-01-01

    A study to analyse beam damage, image quality and edge contrast in the helium ion microscope (HIM) has been undertaken. The sample investigated was graphene. Raman spectroscopy was used to quantify the disorder that can be introduced into the graphene as a function of helium ion dose. The effects of the dose on both freestanding and supported graphene were compared. These doses were then correlated directly to image quality by imaging graphene flakes at high magnification. It was found that a high magnification image with a good signal to noise ratio will introduce very significant sample damage. A safe imaging dose of the order of 10 13 He + cm −2 was established, with both graphene samples becoming highly defective at doses over 5 × 10 14 He + cm −2 . The edge contrast of a freestanding graphene flake imaged in the HIM was then compared with the contrast of the same flake observed in a scanning electron microscope and a transmission electron microscope. Very strong edge sensitivity was observed in the HIM. This enhanced edge sensitivity over the other techniques investigated makes the HIM a powerful nanoscale dimensional metrology tool, with the capability of both fabricating and imaging features with sub-nanometre resolution. (paper)

  6. Does Proactive Interference Play a Significant Role in Visual Working Memory Tasks?

    Science.gov (United States)

    Makovski, Tal

    2016-01-01

    Visual working memory (VWM) is an online memory buffer that is typically assumed to be immune to source memory confusions. Accordingly, the few studies that have investigated the role of proactive interference (PI) in VWM tasks found only a modest PI effect at best. In contrast, a recent study has found a substantial PI effect in that performance…

  7. UV Direct Laser Interference Patterning of polyurethane substrates as tool for tuning its surface wettability

    Energy Technology Data Exchange (ETDEWEB)

    Estevam-Alves, Regina [Instituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos (Brazil); Günther, Denise; Dani, Sophie; Eckhardt, Sebastian; Roch, Teja [Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden 01277 (Germany); Chair for Large Area Laser Based Surface Micro/Nano-Structuring, Institute for Manufacturing Technology, Technische Universität Dresden, George-Bähr-Str. 3c, 01069 Dresden (Germany); Mendonca, Cleber R., E-mail: crmendon@ifsc.usp.br [Instituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos (Brazil); Cestari, Ismar N. [Heart Institute (InCOr), University of São Paulo Medical School, São Paulo 05403-000 (Brazil); Lasagni, Andrés F., E-mail: andres_fabian.lasagni@tu-dresden.de [Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstr. 28, Dresden 01277 (Germany); Chair for Large Area Laser Based Surface Micro/Nano-Structuring, Institute for Manufacturing Technology, Technische Universität Dresden, George-Bähr-Str. 3c, 01069 Dresden (Germany)

    2016-06-30

    Highlights: • First reported experiments on Direct Laser Interference Patterning of polyurethane. • First reported sub-micrometer structures (feature size ∼250 nm) fabricated in polyurethane materials using laser processing technologies. • Anisotropic wetting behavior of structured surfaces and possibility to tune the contact angle as function of surface structure parameters. - Abstract: Direct Laser Interference Patterning (DLIP) is a versatile tool for the fabrication of micro and sub-micropatterns on different materials. In this work, DLIP was used to produce periodic surface structures on polyurethane (PU) substrates with spatial periods ranging from 0.5 to 5.0 μm. The influence of the laser energy density on the quality and topographical characteristics of the produced micropatterns was investigated. To characterize the surface topography of the produced structures, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Confocal Microscopy (CFM) were utilized. It was found that high quality and defect free periodic line-like patterns with spatial periods down to 500 nm could be fabricated, with structure depths between 0.88 up to 1.25 μm for spatial periods larger than 2.0 μm and up to 270 nm for spatial periods between 500 nm and 1.0 μm. Measurements of the contact angle of water on the treated surface allowed to identify an anisotropic wetting behavior depending mainly on the spatial period and filling factor of the structured surfaces.

  8. Investigation of the AZ 5214E photoresist by the laser interference, EBDW and NSOM lithographies

    Energy Technology Data Exchange (ETDEWEB)

    Škriniarová, J., E-mail: jaroslava.skriniarova@stuba.sk [Institute of Electronics and Photonics, Slovak University of Technology, Bratislava (Slovakia); Pudiš, D. [Department of Physics, University of Žilina, Žilina (Slovakia); Andok, R. [Department of E-Beam Lithography, Institute of Informatics, Slovak Academy of Sciences, Bratislava (Slovakia); Lettrichová, I. [Department of Physics, University of Žilina, Žilina (Slovakia); Uherek, F. [Institute of Electronics and Photonics, Slovak University of Technology, Bratislava (Slovakia)

    2017-02-15

    Highlights: • Applicability of the AZ 5214E photoresist for three different lithographies. • Useful for the fabrication of 1D and 2D periodic and irregular structures. • 2D structures with 260 nm period achieved by the laser interference lithography. • Structures with period below 500 nm achieved with the e-beam direct-write lithography. • Holes of 270 nm diameter made by the near-field scanning optical microscopy lithography. - Abstract: In this paper we show a comparison of chosen lithographies used for the AZ 5214E photoresist, which is normally UV sensitive but has also been investigated for its sensitivity to e-beam exposure. Three lithographies, the E-Beam Direct Write lithography (EBDW), laser Interference Lithography (IL) and the non-contact Near-field Scanning Optical Microscopy (NSOM) lithography, are discussed here and the results on exposed arrays of simple patterns are shown. With the EBDW and IL we achieved periods of the structures around half-micron, and we demonstrate attainability of dimensions smaller or comparable than usually achieved by a standard optical photolithography with the investigated photoresist. With the non-contact NSOM lithography structures with periods slightly above a micron were achieved.

  9. X-ray microscopy of human malaria

    International Nuclear Information System (INIS)

    Magowan, C.; Brown, J.T.; Mohandas, N.; Meyer-Ilse, W.

    1997-01-01

    Associations between intracellular organisms and host cells are complex and particularly difficult to examine. X-ray microscopy provides transmission images of subcellular structures in intact cells at resolutions superior to available methodologies. The spatial resolution is 50-60nm with a 1 micron depth of focus, superior to anything achievable with light microscopy. Image contrast is generated by differences in photoelectric absorption by the atoms in different areas (i.e. subcellular structures) throughout the full thickness of the sample. Absorption due to carbon dominates among all the elements in the sample at 2.4 nm x-ray wavelength. Thus images show features or structures, in a way not usually seen by other types of microscopy. The authors used soft x-ray microscopy to investigate structural development of Plasmodium falciparum malaria parasites in normal and genetically abnormal erythrocytes, and in infected erythrocytes treated with compounds that have anti-malarial effects. X-ray microscopy showed newly elaborated structures in the cytosol of unstained, intact erythrocytes, redistribution of mass (carbon) in infected erythrocytes, and aberrant parasite morphology. Better understanding of the process of intracellular parasite maturation and the interactions between the parasite and its host erythrocyte can help define new approaches to the control of this deadly disease

  10. X-ray microscopy of human malaria

    Energy Technology Data Exchange (ETDEWEB)

    Magowan, C.; Brown, J.T.; Mohandas, N.; Meyer-Ilse, W. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    Associations between intracellular organisms and host cells are complex and particularly difficult to examine. X-ray microscopy provides transmission images of subcellular structures in intact cells at resolutions superior to available methodologies. The spatial resolution is 50-60nm with a 1 micron depth of focus, superior to anything achievable with light microscopy. Image contrast is generated by differences in photoelectric absorption by the atoms in different areas (i.e. subcellular structures) throughout the full thickness of the sample. Absorption due to carbon dominates among all the elements in the sample at 2.4 nm x-ray wavelength. Thus images show features or structures, in a way not usually seen by other types of microscopy. The authors used soft x-ray microscopy to investigate structural development of Plasmodium falciparum malaria parasites in normal and genetically abnormal erythrocytes, and in infected erythrocytes treated with compounds that have anti-malarial effects. X-ray microscopy showed newly elaborated structures in the cytosol of unstained, intact erythrocytes, redistribution of mass (carbon) in infected erythrocytes, and aberrant parasite morphology. Better understanding of the process of intracellular parasite maturation and the interactions between the parasite and its host erythrocyte can help define new approaches to the control of this deadly disease.

  11. Quasiparticle interference in the heavy-fermion superconductor CeCoIn5

    Science.gov (United States)

    Akbari, Alireza; Thalmeier, Peter; Eremin, Ilya

    2011-10-01

    We investigate the quasiparticle interference in the heavy fermion superconductor CeCoIn5 as a direct method to confirm the d-wave gap symmetry. The ambiguity between dxy and dx2-y2 symmetry remaining from earlier specific heat and thermal transport investigations has been resolved in favor of the latter by the observation of a spin resonance that can occur only in dx2-y2 symmetry. However, these methods are all indirect and depend considerably on theoretical interpretation. Here we propose that quasiparticle interference (QPI) spectroscopy by scanning tunneling microscopy (STM) can give a direct fingerprint of the superconducting gap in real space that may lead to a definite conclusion on its symmetry for CeCoIn5 and related 115 compounds. The QPI pattern for both magnetic and nonmagnetic impurities is calculated for the possible d-wave symmetries and characteristic differences are found that may be identified by use of the STM method.

  12. Interference control in working memory: comparing groups of children with atypical development.

    Science.gov (United States)

    Palladino, Paola; Ferrari, Marcella

    2013-01-01

    The study aimed to test whether working memory deficits in children at risk of Learning Disabilities (LD) and/or attention deficit/hyperactivity disorder (ADHD) can be attributed to deficits in interference control, thereby implicating prefrontal systems. Two groups of children known for showing poor working memory (i.e., children with poor comprehension and children with ADHD) were compared to a group of children with specific reading decoding problems (i.e., having severe problems in phonological rather than working memory) and to a control group. All children were tested with a verbal working memory task. Interference control of irrelevant items was examined by a lexical decision task presented immediately after the final recall in about half the trials, selected at random. The interference control measure was therefore directly related to working memory performance. Results confirmed deficient working memory performance in poor comprehenders and children at risk of ADHD + LD. More interestingly, this working memory deficit was associated with greater activation of irrelevant information than in the control group. Poor decoders showed more efficient interference control, in contrast to poor comprehenders and ADHD + LD children. These results indicated that interfering items were still highly accessible to working memory in children who fail the working memory task. In turn, these findings strengthen and clarify the role of interference control, one of the most critical prefrontal functions, in working memory.

  13. Imaging of phase change materials below a capping layer using correlative infrared near-field microscopy and electron microscopy

    Science.gov (United States)

    Lewin, M.; Hauer, B.; Bornhöfft, M.; Jung, L.; Benke, J.; Michel, A.-K. U.; Mayer, J.; Wuttig, M.; Taubner, T.

    2015-10-01

    Phase Change Materials (PCM) show two stable states in the solid phase with significantly different optical and electronic properties. They can be switched reversibly between those two states and are promising candidates for future non-volatile memory applications. The development of phase change devices demands characterization tools, yielding information about the switching process at high spatial resolution. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows for spectroscopic analyses of the different optical properties of the PCMs on the nm-scale. By correlating the optical s-SNOM images with transmission electron microscopy images of the same sample, we unambiguously demonstrate the correlation of the infrared optical contrast with the structural state of the phase change material. The investigated sample consists of sandwiched amorphous and crystalline regions of Ag 4 In 3 Sb 67 Te 26 below a 100 nm thick ( ZnS ) 80 - ( SiO2 ) 20 capping layer. Our results demonstrate the sensitivity of s-SNOM to small dielectric near-field contrasts even below a comparably thick capping layer ( 100 nm ).

  14. CRISPR/Cas9-Mediated Immunity to Geminiviruses: Differential Interference and Evasion

    KAUST Repository

    Ali, Zahir; Ali, Shawkat; Tashkandi, Manal; Zaidi, Syed Shan-e-Ali; Mahfouz, Magdy M.

    2016-01-01

    The CRISPR/Cas9 system has recently been used to confer molecular immunity against several eukaryotic viruses, including plant DNA geminiviruses. Here, we provide a detailed analysis of the efficiencies of targeting different coding and non-coding sequences in the genomes of multiple geminiviruses. Moreover, we analyze the ability of geminiviruses to evade the CRISPR/Cas9 machinery. Our results demonstrate that the CRISPR/Cas9 machinery can efficiently target coding and non-coding sequences and interfere with various geminiviruses. Furthermore, targeting the coding sequences of different geminiviruses resulted in the generation of viral variants capable of replication and systemic movement. By contrast, targeting the noncoding intergenic region sequences of geminiviruses resulted in interference, but with inefficient recovery of mutated viral variants, which thus limited the generation of variants capable of replication and movement. Taken together, our results indicate that targeting noncoding, intergenic sequences provides viral interference activity and significantly limits the generation of viral variants capable of replication and systemic infection, which is essential for developing durable resistance strategies for long-term virus control.

  15. CRISPR/Cas9-Mediated Immunity to Geminiviruses: Differential Interference and Evasion

    KAUST Repository

    Ali, Zahir

    2016-05-26

    The CRISPR/Cas9 system has recently been used to confer molecular immunity against several eukaryotic viruses, including plant DNA geminiviruses. Here, we provide a detailed analysis of the efficiencies of targeting different coding and non-coding sequences in the genomes of multiple geminiviruses. Moreover, we analyze the ability of geminiviruses to evade the CRISPR/Cas9 machinery. Our results demonstrate that the CRISPR/Cas9 machinery can efficiently target coding and non-coding sequences and interfere with various geminiviruses. Furthermore, targeting the coding sequences of different geminiviruses resulted in the generation of viral variants capable of replication and systemic movement. By contrast, targeting the noncoding intergenic region sequences of geminiviruses resulted in interference, but with inefficient recovery of mutated viral variants, which thus limited the generation of variants capable of replication and movement. Taken together, our results indicate that targeting noncoding, intergenic sequences provides viral interference activity and significantly limits the generation of viral variants capable of replication and systemic infection, which is essential for developing durable resistance strategies for long-term virus control.

  16. Event-related potential evidence for separable automatic and controlled retrieval processes in proactive interference.

    Science.gov (United States)

    Bergström, Zara M; O'Connor, Richard J; Li, Martin K-H; Simons, Jon S

    2012-05-21

    Interference between competing memories is a major source of retrieval failure, yet, surprisingly little is known about how competitive memory activation arises in the brain. One possibility is that interference during episodic retrieval might be produced by relatively automatic conceptual priming mechanisms that are independent of strategic retrieval processes. Such priming-driven interference might occur when the competing memories have strong pre-existing associations to the retrieval cue. We used ERPs to measure the neural dynamics of retrieval competition, and investigated whether the ERP correlates of interference were affected by varying task demands for selective retrieval. Participants encoded cue words that were presented either two or four times, paired either with the same or different strongly associated words across repetitions. In a subsequent test, participants either selectively recalled each cue's most recent associate, or simply judged how many times a cue had been presented, without requiring selective recall. Interference effects on test performance were only seen in the recall task. In contrast, ERPs during test revealed an early posterior positivity for high interference items that was present in both retrieval tasks. This early ERP effect likely reflects a conceptual priming-related N400 reduction when many associations to a cue were pre-activated. A later parietal positivity resembling the ERP correlate of conscious recollection was found only in the recall task. The results suggest that early effects of proactive interference are relatively automatic and independent of intentional retrieval processes, consistent with suggestions that interference can arise through conceptual priming. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Interference of identical particles from entanglement to boson-sampling

    International Nuclear Information System (INIS)

    Tichy, Malte C

    2014-01-01

    Progress in the reliable preparation, coherent propagation and efficient detection of many-body states has recently brought collective quantum phenomena of many identical particles into the spotlight. This tutorial introduces the physics of many-boson and many-fermion interference required for the description of current experiments and for the understanding of novel approaches to quantum computing. The field is motivated via the two-particle case, for which the uncorrelated, classical dynamics of distinguishable particles is compared to the quantum behaviour of identical bosons and fermions. Bunching of bosons is opposed to anti-bunching of fermions, while both species constitute equivalent sources of bipartite two-level entanglement. The realms of indistinguishable and distinguishable particles are connected by a monotonic transition, on a scale defined by the coherence length of the interfering particles. As we move to larger systems, any attempt to understand many particles via the two-particle paradigm fails: in contrast to two-particle bunching and anti-bunching, the very same signatures can be exhibited by bosons and fermions, and coherent effects dominate over statistical behaviour. The simulation of many-boson interference, termed boson-sampling, entails a qualitatively superior computational complexity when compared to fermions. The problem can be tamed by an artificially designed symmetric instance, which allows a systematic understanding of coherent bosonic and fermionic signatures for arbitrarily large particle numbers, and a means to stringently assess many-particle interference. The hierarchy between bosons and fermions also characterizes multipartite entanglement generation, for which bosons again clearly outmatch fermions. Finally, the quantum-to-classical transition between many indistinguishable and many distinguishable particles features non-monotonic structures, which dismisses the single-particle coherence length as unique indicator for

  18. The difficult relationship between occlusal interferences and temporomandibular disorder - insights from animal and human experimental studies.

    Science.gov (United States)

    Xie, Q; Li, X; Xu, X

    2013-04-01

    The aetiology of temporomandibular disorder (TMD) is multifactorial, and numerous studies have addressed that occlusion may be of great importance. However, whether occlusion plays a crucial role in the pathogenesis of TMD remains controversial. Study designs utilising animal models have been used to study the effects of artificial occlusal alterations. Experimental traumatic occlusion affects blood flow in the temporomandibular joint and results in changes in the condylar cartilage, and artificial occlusal interference induces masticatory muscle nociceptive responses that are associated with peripheral sensitisation and lead to central sensitisation, which maintains masticatory muscle hyperalgesia. The possibility that occlusal interference results in TMD has been investigated in humans using a double-blind randomised design. Subjects without a history of TMD show fairly good adaptation to interferences. In contrast, subjects with a history of TMD develop a significant increase in clinical signs and self-report stronger symptoms (occlusal discomfort and chewing difficulties) in response to interferences. Meanwhile, psychological factors appear meaningful for symptomatic responses to artificial interferences in subjects with a history of TMD. Thus, individual differences in vulnerability to occlusal interferences do exist. Although there are advantages and disadvantages to using human and animal occlusal interference models, these approaches are indispensable for discovering the role of occlusion in TMD pathogenesis. © 2013 Blackwell Publishing Ltd.

  19. Color-word matching stroop task: separating interference and response conflict.

    Science.gov (United States)

    Zysset, S; Müller, K; Lohmann, G; von Cramon , D Y

    2001-01-01

    The Stroop interference task requires a person to respond to a specific dimension of a stimulus while suppressing a competing stimulus dimension. Previous PET and fMRI studies using the Color Stroop paradigm have shown increased activity in the "cognitive division" of the cingulate cortex. In our fMRI study with nine subjects, we used a Color-Word Matching Stroop task. A frontoparietal network, including structures in the lateral prefrontal cortex, the frontopolar region, the intraparietal sulcus, as well as the lateral occipitotemporal gyrus, was activated when contrasting the incongruent vs the neutral condition. However, no substantial activation in either the right or left hemisphere of the anterior cingulate cortex (ACC) was detected. In accordance with a series of recent articles, we argue that the ACC is not specifically involved in interference processes. The ACC seems rather involved in motor preparation processes which were controlled in the present Color-Word Matching Stroop task. We argue that the region around the banks of the inferior frontal sulcus is required to solve interference problems, a concept which can also be seen as a component of task set management. Copyright 2001 Academic Press.

  20. Primary Salvage Survey of the Interference of Radiowaves Emitted by Smartphones on Medical Equipment.

    Science.gov (United States)

    Takao, Hiroyuki; Yeh, Yu Chih; Arita, Hiroyuki; Obatake, Takumi; Sakano, Teppei; Kurihara, Minoru; Matsuki, Akira; Ishibashi, Toshihiro; Murayama, Yuichi

    2016-10-01

    Use of mobile phones has become a standard reality of everyday living for many people worldwide, including medical professionals, as data sharing has drastically helped to improve quality of care. This increase in the use of mobile phones within hospitals and medical facilities has raised concern regarding the influence of radio waves on medical equipment. Although comprehensive studies have examined the effects of electromagnetic interference from 2G wireless communication and personal digital cellular systems on medical equipment, similar studies on more recent wireless technologies such as Long Term Evolution, wideband code division multiple access, and high-speed uplink access have yet to be published. Numerous tests targeting current wireless technologies were conducted between December 2012 and March 2013 in an anechoic chamber, shielded from external radio signals, with a dipole antenna to assess the effects of smartphone interference on several types of medical equipment. The interference produced by electromagnetic waves across five frequency bands from four telecommunication standards was assessed on 49 components from 22 pieces of medical equipment. Of the 22 pieces of medical equipment tested, 13 experienced interference at maximum transmission power. In contrast, at minimum transmission power, the maximum interference distance varied from 2 to 5 cm for different wireless devices. Four machines were affected at the minimum transmission power, and the maximum interference distance at the maximum transmission power was 38 cm. Results show that the interference from smartphones on medical equipment is very controllable.

  1. Recent observations with phase-contrast x-ray computed tomography

    Science.gov (United States)

    Momose, Atsushi; Takeda, Tohoru; Itai, Yuji; Tu, Jinhong; Hirano, Keiichi

    1999-09-01

    Recent development in phase-contrast X-ray computed tomography using an X-ray interferometer is reported. To observe larger samples than is possible with our previous X-ray interferometer, a large monolithic X-ray interferometer and a separated-type X-ray interferometer were studied. At the present time, 2.5 cm X 1.5 cm interference patterns have been generated with the X-ray interferometers using synchrotron X-rays. The large monolithic X-ray interferometer has produced interference fringes with 80% visibility, and has been used to measure various tissues. To produce images with higher spatial resolution, we fabricated another X-ray interferometer whose wafer was partially thinned by chemical etching. A preliminary test suggested that the spatial resolution has been improved.

  2. Serum sample containing endogenous antibodies interfering with multiple hormone immunoassays. Laboratory strategies to detect interference

    Directory of Open Access Journals (Sweden)

    Elena García-González

    2016-04-01

    Full Text Available Objectives: Endogenous antibodies (EA may interfere with immunoassays, causing erroneous results for hormone analyses. As (in most cases this interference arises from the assay format and most immunoassays, even from different manufacturers, are constructed in a similar way, it is possible for a single type of EA to interfere with different immunoassays. Here we describe the case of a patient whose serum sample contains EA that interfere several hormones tests. We also discuss the strategies deployed to detect interference. Subjects and methods: Over a period of four years, a 30-year-old man was subjected to a plethora of laboratory and imaging diagnostic procedures as a consequence of elevated hormone results, mainly of pituitary origin, which did not correlate with the overall clinical picture. Results: Once analytical interference was suspected, the best laboratory approaches to investigate it were sample reanalysis on an alternative platform and sample incubation with antibody blocking tubes. Construction of an in-house ‘nonsense’ sandwich assay was also a valuable strategy to confirm interference. In contrast, serial sample dilutions were of no value in our case, while polyethylene glycol (PEG precipitation gave inconclusive results, probably due to the use of inappropriate PEG concentrations for several of the tests assayed. Conclusions: Clinicians and laboratorians must be aware of the drawbacks of immunometric assays, and alert to the possibility of EA interference when results do not fit the clinical pattern. Keywords: Endogenous antibodies, Immunoassay, Interference, Pituitary hormones, Case report

  3. Localization of proteins and nucleic acids using soft x-ray microscopy

    International Nuclear Information System (INIS)

    Larabell, Carolyn A.; Yager, Deborah; Meyer-Ilse, Werner

    2000-01-01

    The high-resolution soft x-ray microscope (XM-1) at the Advanced Light Source was used to examine whole, hydrated mammalian cells, both chemically fixed and rapidly frozen and viewed in a cryostage. Using x-ray microscopy, high contrast information about the organization of the cytoplasm and nucleus of these cells was revealed at unsurpassed resolution. It is important to note that cryo-fixed cells have been examined in a state that most closely resembles their natural environment in that the cells were not exposed to chemical fixatives or chemical contrast enhancement reagents. We also used the power of soft x-ray microscopy to examine the localization of proteins and nucleic acids in whole, hydrated cells using silver-enhanced, immunogold labeling techniques. With this approach, we have obtained information about the distribution of such molecules with respect to cellular ultrastructure at five times better resolution than light microscopy. The power of soft x-ray microscopy to provide superb resolution information about the subcellular localization of proteins and nucleic acids places it in a commanding position to contribute to our understanding of the numerous molecules being identified through modern molecular biology techniques

  4. Three-dimensional constructive interference in steady-state magnetic resonance imaging in syringomyelia: advantages over conventional imaging.

    Science.gov (United States)

    Roser, Florian; Ebner, Florian H; Danz, Søren; Riether, Felix; Ritz, Rainer; Dietz, Klaus; Naegele, Thomas; Tatagiba, Marcos S

    2008-05-01

    Neuroradiology has become indispensable in detecting the pathophysiology in syringomyelia. Constructive interference in steady-state (CISS) magnetic resonance (MR) imaging can provide superior contrast at the sub-arachnoid tissue borders. As this region is critical in preoperative evaluation, the authors hypothesized that CISS imaging would provide superior assessment of syrinx pathology and surgical planning. Based on records collected from a database of 130 patients with syringomyelia treated at the authors' institution, 59 patients were prospectively evaluated with complete neuroradiological examinations. In addition to routine acquisitions with FLAIR, T1- and T2-weighted, and contrast-enhanced MR imaging series, the authors obtained sagittal cardiac-gated sequences to visualize cerebrospinal fluid (CSF) pulsations and axial 3D CISS MR sequences to detect focal arachnoid webs. Statistical qualitative and quantitative evaluations of spinal cord/CSF contrast, spinal cord/CSF delineation, motion artifacts, and artifacts induced by pulsatile CSF flow were performed. The 3D CISS MR sequences demonstrated a contrast-to-noise ratio significantly better than any other routine imaging sequence (p CSF flow voids. Constructive interference in steady-state MR imaging enables the neurosurgeon to accurately identify cases requiring decompression for obstructed CSF. Motion artifacts can be eliminated with technical variations.

  5. X-ray Tomographic Microscopy at TOMCAT

    Energy Technology Data Exchange (ETDEWEB)

    Marone, F; Hintermueller, C; McDonald, S; Abela, R; Mikuljan, G; Isenegger, A; Stampanoni, M, E-mail: federica.marone@psi.c [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen (Switzerland)

    2009-09-01

    Synchrotron-based X-ray Tomographic Microscopy is a powerful technique for fast non-destructive, high resolution quantitative volumetric investigations on diverse samples. At the TOMCAT (TOmographic Microscopy and Coherent rAdiology experimenTs) beamline at the Swiss Light Source, synchrotron light is delivered by a 2.9 T superbend. The main optical component, a Double Crystal Multilayer Monochromator, covers an energy range between 8 and 45 keV. The standard TOMCAT detector offers field of views ranging from 0.75x0.75 mm{sup 2} up to 12.1x12.1 mm{sup 2} with a pixel size of 0.37 {mu}m and 5.92 {mu}m, respectively. In addition to routine measurements, which exploit the absorption contrast, the high coherence of the source also enables phase contrast tomography, implemented with two complementary techniques (Modified Transport of Intensity approach and Grating Interferometry). Typical acquisition times for a tomogram are in the order of few minutes, ensuring high throughput and allowing for semi-dynamical investigations. Raw data are automatically post-processed online and full reconstructed volumes are available shortly after a scan with minimal user intervention.

  6. Examining Thermally Sprayed Coats By Fluorescence Microscopy

    Science.gov (United States)

    Street, Kenneth W., Jr.; Leonhardt, Todd A.

    1994-01-01

    True flaws distinquished from those induced by preparation of specimens. Fluorescence microscopy reveals debonding, porosity, cracks, and other flaws in specimens of thermally sprayed coating materials. Specimen illuminated, and dye it contains fluoresces, emitting light at different wavelength. Filters emphasize contrast between excitation light and emission light. Specimen viewed directly or photographed on color film.

  7. Absence of auditory 'global interference' in autism.

    Science.gov (United States)

    Foxton, Jessica M; Stewart, Mary E; Barnard, Louise; Rodgers, Jacqui; Young, Allan H; O'Brien, Gregory; Griffiths, Timothy D

    2003-12-01

    There has been considerable recent interest in the cognitive style of individuals with Autism Spectrum Disorder (ASD). One theory, that of weak central coherence, concerns an inability to combine stimulus details into a coherent whole. Here we test this theory in the case of sound patterns, using a new definition of the details (local structure) and the coherent whole (global structure). Thirteen individuals with a diagnosis of autism or Asperger's syndrome and 15 control participants were administered auditory tests, where they were required to match local pitch direction changes between two auditory sequences. When the other local features of the sequence pairs were altered (the actual pitches and relative time points of pitch direction change), the control participants obtained lower scores compared with when these details were left unchanged. This can be attributed to interference from the global structure, defined as the combination of the local auditory details. In contrast, the participants with ASD did not obtain lower scores in the presence of such mismatches. This was attributed to the absence of interference from an auditory coherent whole. The results are consistent with the presence of abnormal interactions between local and global auditory perception in ASD.

  8. Does selection against transcriptional interference shape retroelement-free regions in mammalian genomes?

    DEFF Research Database (Denmark)

    Mourier, Tobias; Willerslev, Eske

    2008-01-01

    in generating and maintaining retroelement-free regions in the human genome. METHODOLOGY/PRINCIPAL FINDINGS: Based on the known transcriptional properties of retroelements, we expect long interspersed elements (LINEs) to be able to display a high degree of transcriptional interference. In contrast, we expect......BACKGROUND: Eukaryotic genomes are scattered with retroelements that proliferate through retrotransposition. Although retroelements make up around 40 percent of the human genome, large regions are found to be completely devoid of retroelements. This has been hypothesised to be a result of genomic...... activity of LINEs has been identified previously. CONCLUSIONS/SIGNIFICANCE: Our observations are consistent with the notion that selection against transcriptional interference has contributed to the maintenance and/or generation of retroelement-free regions in the human genome....

  9. Emotional prosody of task-irrelevant speech interferes with the retention of serial order.

    Science.gov (United States)

    Kattner, Florian; Ellermeier, Wolfgang

    2018-04-09

    Task-irrelevant speech and other temporally changing sounds are known to interfere with the short-term memorization of ordered verbal materials, as compared to silence or stationary sounds. It has been argued that this disruption of short-term memory (STM) may be due to (a) interference of automatically encoded acoustical fluctuations with the process of serial rehearsal or (b) attentional capture by salient task-irrelevant information. To disentangle the contributions of these 2 processes, the authors investigated whether the disruption of serial recall is due to the semantic or acoustical properties of task-irrelevant speech (Experiment 1). They found that performance was affected by the prosody (emotional intonation), but not by the semantics (word meaning), of irrelevant speech, suggesting that the disruption of serial recall is due to interference of precategorically encoded changing-state sound (with higher fluctuation strength of emotionally intonated speech). The authors further demonstrated a functional distinction between this form of distraction and attentional capture by contrasting the effect of (a) speech prosody and (b) sudden prosody deviations on both serial and nonserial STM tasks (Experiment 2). Although serial recall was again sensitive to the emotional prosody of irrelevant speech, performance on a nonserial missing-item task was unaffected by the presence of neutral or emotionally intonated speech sounds. In contrast, sudden prosody changes tended to impair performance on both tasks, suggesting an independent effect of attentional capture. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  10. Origins of phase contrast in the atomic force microscope in liquids

    OpenAIRE

    Melcher, John; Carrasco, Carolina; Xu, Xianfan; Carrascosa, Jose L; Gomez-Herrero, Julio; Jose de Pablo, Pedro; Raman, Arvind

    2009-01-01

    We study the physical origins of phase contrast in dynamic atomic force microscopy (dAFM) in liquids where low-stiffness microcantilever probes are often used for nanoscale imaging of soft biological samples with gentle forces. Under these conditions, we show that the phase contrast derives primarily from a unique energy flow channel that opens up in liquids due to the momentary excitation of higher eigenmodes. Contrary to the common assumption, phase-contrast images in liquids using soft mic...

  11. Preparation and characterization of PVPI-coated Fe3O4 nanoparticles as an MRI contrast agent

    International Nuclear Information System (INIS)

    Wang, Guangshuo; Chang, Ying; Wang, Ling; Wei, Zhiyong; Kang, Jianyun; Sang, Lin; Dong, Xufeng; Chen, Guangyi; Wang, Hong; Qi, Min

    2013-01-01

    Polyvinylpyrrolidone-iodine (PVPI)-coated Fe 3 O 4 nanoparticles were prepared by using inverse chemical co-precipitation method, in which the PVPI serves as a stabilizer and dispersant. The wide angle X-ray diffraction (WAXD) and selected area electron diffraction (SAED) results showed that the inverse spinel structure pure phase polycrystalline Fe 3 O 4 was obtained. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results exhibited that the resulted Fe 3 O 4 nanoparticles were roughly spherical in shape with narrow size distribution and homogenous shape. Fourier transform infrared spectroscopy (FTIR) results suggested that PVPI interacted with Fe 3 O 4 via its carbonyl groups. Results of superconducting quantum interference device (SQUID) indicated prepared Fe 3 O 4 nanoparticles exhibited superparamagnetic behavior and high saturation magnetization. T 2 -weighted MRI images of PVPI-coated Fe 3 O 4 nanoparticles showed that the magnetic resonance signal was enhanced significantly with increasing nanoparticles concentration in water at room temperature. These results indicated that the PVPI-coated Fe 3 O 4 nanoparticles had great potential for application in MRI as a T 2 contrast agent. - Highlights: • PVPI-coated Fe 3 O 4 nanoparticles were prepared using inverse co-precipitation method. • Resulted Fe 3 O 4 nanoparticles were roughly spherical in shape with narrow size distribution and homogenous shape. • Prepared Fe 3 O 4 nanoparticles exhibited superparamagnetic behavior. • T 2 -weighted MRI images of PVPI-coated Fe 3 O 4 nanoparticles were obtained

  12. Humidity effects on scanning polarization force microscopy imaging

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yue, E-mail: shenyue@isl.ac.cn [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); Key Laboratory of Interfacial Physics and Technology of Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, Yuan, E-mail: zhouy@isl.ac.cn [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); Sun, Yanxia; Zhang, Lijuan [Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai 810008 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Ying; Hu, Jun; Zhang, Yi [Key Laboratory of Interfacial Physics and Technology of Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2017-08-01

    Highlights: • The humidity dramatically affects the contrast of scanning polarization force microscopy (SPFM) imaging on mica surface. • This influence roots in the sensitive dielectric constant of mica surface to the humidity change. • A strategy of controllable and repeatable imaging the local dielectric properties of nanomaterials with SPFM is proposed. - Abstract: Scanning polarization force microscopy (SPFM) is a useful surface characterization technique to visually characterize and distinguish nanomaterial with different local dielectric properties at nanometer scale. In this paper, taking the individual one-atom-thick graphene oxide (GO) and reduced graphene oxide (rGO) sheets on mica as examples, we described the influences of environmental humidity on SPFM imaging. We found that the apparent heights (AHs) or contrast of SPFM imaging was influenced significantly by relative humidity (RH) at a response time of a few seconds. And this influence rooted in the sensitive dielectric constant of mica surface to the RH change. While dielectric properties of GO and rGO sheets were almost immune to the humidity change. In addition, we gave the method to determine the critical humidity at which the contrast conversion happened under different conditions. And this is important to the contrast control and repeatable imaging of SPFM through RH adjusting. These findings suggest a strategy of controllable and repeatable imaging the local dielectric properties of nanomaterials with SPFM, which is critically important for further distinguishment, manipulation, electronic applications, etc.

  13. Between-Trial Forgetting Due to Interference and Time in Motor Adaptation.

    Directory of Open Access Journals (Sweden)

    Sungshin Kim

    Full Text Available Learning a motor task with temporally spaced presentations or with other tasks intermixed between presentations reduces performance during training, but can enhance retention post training. These two effects are known as the spacing and contextual interference effect, respectively. Here, we aimed at testing a unifying hypothesis of the spacing and contextual interference effects in visuomotor adaptation, according to which forgetting between trials due to either spaced presentations or interference by another task will promote between-trial forgetting, which will depress performance during acquisition, but will promote retention. We first performed an experiment with three visuomotor adaptation conditions: a short inter-trial-interval (ITI condition (SHORT-ITI; a long ITI condition (LONG-ITI; and an alternating condition with two alternated opposite tasks (ALT, with the same single-task ITI as in LONG-ITI. In the SHORT-ITI condition, there was fastest increase in performance during training and largest immediate forgetting in the retention tests. In contrast, in the ALT condition, there was slowest increase in performance during training and little immediate forgetting in the retention tests. Compared to these two conditions, in the LONG-ITI, we found intermediate increase in performance during training and intermediate immediate forgetting. To account for these results, we fitted to the data six possible adaptation models with one or two time scales, and with interference in the fast, or in the slow, or in both time scales. Model comparison confirmed that two time scales and some degree of interferences in either time scale are needed to account for our experimental results. In summary, our results suggest that retention following adaptation is modulated by the degree of between-trial forgetting, which is due to time-based decay in single adaptation task and interferences in multiple adaptation tasks.

  14. Interference Calculus A General Framework for Interference Management and Network Utility Optimization

    CERN Document Server

    Schubert, Martin

    2012-01-01

    This book develops a mathematical framework for modeling and optimizing interference-coupled multiuser systems. At the core of this framework is the concept of general interference functions, which provides a simple means of characterizing interdependencies between users. The entire analysis builds on the two core axioms scale-invariance and monotonicity. The proposed network calculus has its roots in power control theory and wireless communications. It adds theoretical tools for analyzing the typical behavior of interference-coupled networks. In this way it complements existing game-theoretic approaches. The framework should also be viewed in conjunction with optimization theory. There is a fruitful interplay between the theory of interference functions and convex optimization theory. By jointly exploiting the properties of interference functions, it is possible to design algorithms that outperform general-purpose techniques that only exploit convexity. The title “network calculus” refers to the fact tha...

  15. Relevance of Bose-Einstein condensation to the interference of two independent Bose gases

    International Nuclear Information System (INIS)

    Iazzi, Mauro; Yuasa, Kazuya

    2011-01-01

    Interference of two independently prepared ideal Bose gases is discussed, on the basis of the idea of measurement-induced interference. It is known that, even if the number of atoms in each gas is individually fixed finite and the symmetry of the system is not broken, an interference pattern is observed on each single snapshot. The key role is played by the Hanbury Brown and Twiss effect, which leads to an oscillating pattern of the cloud of identical atoms. Then, how essential is the Bose-Einstein condensation to the interference? In this work, we describe two ideal Bose gases trapped in two separate three-dimensional harmonic traps at a finite temperature T, using the canonical ensembles (with fixed numbers of atoms). We compute the full statistics of the snapshot profiles of the expanding and overlapping gases released from the traps. We obtain a simple formula valid for finite T, which shows that the average fringe spectrum (average fringe contrast) is given by the purity of each gas. The purity is known to be a good measure of condensation, and the formula clarifies the relevance of the condensation to the interference. The results for T=0, previously known in the literature, can be recovered from our analysis. The fluctuation of the interference spectrum is also studied, and it is shown that the fluctuation is vanishingly small only below the critical temperature T c , meaning that interference pattern is certainly observed on every snapshot below T c . The fact that the number of atoms is fixed in the canonical ensemble is crucial to this vanishing fluctuation.

  16. Examination of the foreign body response to biomaterials by nonlinear intravital microscopy

    OpenAIRE

    Dondossola, Eleonora; Holzapfel, Boris M.; Alexander, Stephanie; Filippini, Stefano; Hutmacher, Dietmar W.; Friedl, Peter

    2016-01-01

    Implanted biomaterials often fail because they elicit a foreign body response (FBR) and concomitant fibrotic encapsulation. To design clinically relevant interference approaches, it is crucial to first examine the FBR mechanisms. Here, we report the development and validation of infrared-excited nonlinear microscopy to resolve the three-dimensional (3D) organization and fate of 3D-electrospun scaffolds implanted deep into the skin of mice, and the following step-wise FBR process. We observed ...

  17. High-resolution intravital microscopy.

    Directory of Open Access Journals (Sweden)

    Volker Andresen

    Full Text Available Cellular communication constitutes a fundamental mechanism of life, for instance by permitting transfer of information through synapses in the nervous system and by leading to activation of cells during the course of immune responses. Monitoring cell-cell interactions within living adult organisms is crucial in order to draw conclusions on their behavior with respect to the fate of cells, tissues and organs. Until now, there is no technology available that enables dynamic imaging deep within the tissue of living adult organisms at sub-cellular resolution, i.e. detection at the level of few protein molecules. Here we present a novel approach called multi-beam striped-illumination which applies for the first time the principle and advantages of structured-illumination, spatial modulation of the excitation pattern, to laser-scanning-microscopy. We use this approach in two-photon-microscopy--the most adequate optical deep-tissue imaging-technique. As compared to standard two-photon-microscopy, it achieves significant contrast enhancement and up to 3-fold improved axial resolution (optical sectioning while photobleaching, photodamage and acquisition speed are similar. Its imaging depth is comparable to multifocal two-photon-microscopy and only slightly less than in standard single-beam two-photon-microscopy. Precisely, our studies within mouse lymph nodes demonstrated 216% improved axial and 23% improved lateral resolutions at a depth of 80 µm below the surface. Thus, we are for the first time able to visualize the dynamic interactions between B cells and immune complex deposits on follicular dendritic cells within germinal centers (GCs of live mice. These interactions play a decisive role in the process of clonal selection, leading to affinity maturation of the humoral immune response. This novel high-resolution intravital microscopy method has a huge potential for numerous applications in neurosciences, immunology, cancer research and

  18. High-Resolution Intravital Microscopy

    Science.gov (United States)

    Andresen, Volker; Pollok, Karolin; Rinnenthal, Jan-Leo; Oehme, Laura; Günther, Robert; Spiecker, Heinrich; Radbruch, Helena; Gerhard, Jenny; Sporbert, Anje; Cseresnyes, Zoltan; Hauser, Anja E.; Niesner, Raluca

    2012-01-01

    Cellular communication constitutes a fundamental mechanism of life, for instance by permitting transfer of information through synapses in the nervous system and by leading to activation of cells during the course of immune responses. Monitoring cell-cell interactions within living adult organisms is crucial in order to draw conclusions on their behavior with respect to the fate of cells, tissues and organs. Until now, there is no technology available that enables dynamic imaging deep within the tissue of living adult organisms at sub-cellular resolution, i.e. detection at the level of few protein molecules. Here we present a novel approach called multi-beam striped-illumination which applies for the first time the principle and advantages of structured-illumination, spatial modulation of the excitation pattern, to laser-scanning-microscopy. We use this approach in two-photon-microscopy - the most adequate optical deep-tissue imaging-technique. As compared to standard two-photon-microscopy, it achieves significant contrast enhancement and up to 3-fold improved axial resolution (optical sectioning) while photobleaching, photodamage and acquisition speed are similar. Its imaging depth is comparable to multifocal two-photon-microscopy and only slightly less than in standard single-beam two-photon-microscopy. Precisely, our studies within mouse lymph nodes demonstrated 216% improved axial and 23% improved lateral resolutions at a depth of 80 µm below the surface. Thus, we are for the first time able to visualize the dynamic interactions between B cells and immune complex deposits on follicular dendritic cells within germinal centers (GCs) of live mice. These interactions play a decisive role in the process of clonal selection, leading to affinity maturation of the humoral immune response. This novel high-resolution intravital microscopy method has a huge potential for numerous applications in neurosciences, immunology, cancer research and developmental biology

  19. Flipping interferometry and its application for quantitative phase microscopy in a micro-channel.

    Science.gov (United States)

    Roitshtain, Darina; Turko, Nir A; Javidi, Bahram; Shaked, Natan T

    2016-05-15

    We present a portable, off-axis interferometric module for quantitative phase microscopy of live cells, positioned at the exit port of a coherently illuminated inverted microscope. The module creates on the digital camera an interference pattern between the image of the sample and its flipped version. The proposed simplified module is based on a retro-reflector modification in an external Michelson interferometer. The module does not contain any lenses, pinholes, or gratings and its alignment is straightforward. Still, it allows full control of the off-axis angle and does not suffer from ghost images. As experimentally demonstrated, the module is useful for quantitative phase microscopy of live cells rapidly flowing in a micro-channel.

  20. Subsurface measurement of nanostructures on GaAs by electrostatic force microscopy

    International Nuclear Information System (INIS)

    Yamada, Fumihiko; Kamiya, Itaru

    2013-01-01

    The size of surface buried oxide nanostructures are measured by electrostatic force microscopy (EFM). In contrast to atomic force microscopy that cannot probe subsurface structures and thickness, we show that EFM data include information about the thickness of individual nanostructures, consequently allowing us to determine the thickness of buried nanostructures on semiconductor substrates. We further show that this measurement can be performed simultaneously with AFM using EFM modulation spectroscopy.

  1. Concomitant use of polarization and positive phase contrast microscopy for the study of microbial cells

    Czech Academy of Sciences Publication Activity Database

    Žižka, Zdeněk; Gabriel, Jiří

    2014-01-01

    Roč. 60, č. 6 (2014), s. 545-550 ISSN 0015-5632 Institutional support: RVO:61388971 Keywords : microbial cells * microscopy * microorganism Subject RIV: EE - Microbiology, Virology Impact factor: 1.000, year: 2014

  2. Characteristic contrast in Deltafmin maps of organic molecules using atomic force microscopy

    Czech Academy of Sciences Publication Activity Database

    van der Heijden, N.J.; Hapala, Prokop; Rombouts, J.A.; van der Lit, J.; Smith, D.; Mutombo, Pingo; Švec, Martin; Jelínek, Pavel; Swart, I.

    2016-01-01

    Roč. 10, č. 9 (2016), 8517-8525 ISSN 1936-0851 R&D Projects: GA ČR(CZ) GC14-16963J Institutional support: RVO:68378271 Keywords : nc AFM * chemical contrast * DFT * molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 13.942, year: 2016

  3. Scanning tunneling microscopy II further applications and related scanning techniques

    CERN Document Server

    Güntherodt, Hans-Joachim

    1992-01-01

    Scanning Tunneling Microscopy II, like its predecessor, presents detailed and comprehensive accounts of the basic principles and broad range of applications of STM and related scanning probe techniques. The applications discussed in this volume come predominantly from the fields of electrochemistry and biology. In contrast to those described in Vol. I, these sudies may be performed in air and in liquids. The extensions of the basic technique to map other interactions are described inchapters on scanning force microscopy, magnetic force microscopy, scanning near-field optical microscopy, together with a survey of other related techniques. Also described here is the use of a scanning proximal probe for surface modification. Togehter, the two volumes give a comprehensive account of experimental aspcets of STM. They provide essentialreading and reference material for all students and researchers involvedin this field.

  4. REM sleep rescues learning from interference

    Science.gov (United States)

    McDevitt, Elizabeth A.; Duggan, Katherine A.; Mednick, Sara C.

    2015-01-01

    Classical human memory studies investigating the acquisition of temporally-linked events have found that the memories for two events will interfere with each other and cause forgetting (i.e., interference; Wixted, 2004). Importantly, sleep helps consolidate memories and protect them from subsequent interference (Ellenbogen, Hulbert, Stickgold, Dinges, & Thompson-Schill, 2006). We asked whether sleep can also repair memories that have already been damaged by interference. Using a perceptual learning paradigm, we induced interference either before or after a consolidation period. We varied brain states during consolidation by comparing active wake, quiet wake, and naps with either non-rapid eye movement sleep (NREM), or both NREM and REM sleep. When interference occurred after consolidation, sleep and wake both produced learning. However, interference prior to consolidation impaired memory, with retroactive interference showing more disruption than proactive interference. Sleep rescued learning damaged by interference. Critically, only naps that contained REM sleep were able to rescue learning that was highly disrupted by retroactive interference. Furthermore, the magnitude of rescued learning was correlated with the amount of REM sleep. We demonstrate the first evidence of a process by which the brain can rescue and consolidate memories damaged by interference, and that this process requires REM sleep. We explain these results within a theoretical model that considers how interference during encoding interacts with consolidation processes to predict which memories are retained or lost. PMID:25498222

  5. Developments in contact X-ray microscopy in biomedical research

    International Nuclear Information System (INIS)

    Davies, R.L.; Flores, N.A.; Pye, J.K.

    1985-01-01

    Contact X-ray microscopy (microradiography) is a method of studying the microstructure of biological tissue. These techniques have been used to study the historadiological details of human breast tissue and sections of human ear ossicles. X-ray microscopy can also be used to demonstrate variations in structural densities seen in histological specimens including the detection of microcalcification. A modification of existing apparatus is described which has resulted in improved image-contrast and detail. The ability of X-rays to penetrate relatively thick sections of tissue makes it an ideal method for studying the morphology of biological structures, particularly in calcified tissue. The tissues may be further examined by conventional histology, elemental analysis, etc. The technique has a complementary role to alternative methods of tissue microscopy. (author)

  6. New directions in scanning-tunneling microscopy

    International Nuclear Information System (INIS)

    Ferrell, T.L.; Warmack, R.J.; Reddick, R.C.

    1989-01-01

    The tunneling of electrons in scanning-tunneling microscopy (STM) has permitted imaging of the electronic distribution about individual atoms on surfaces. The need for use of conducting surfaces in STM limits its applicability, and new forms of scanning microscopy have emerged as a result of interest in poorly conducting samples. Atomic force microscopy has demonstrated that the force between a surface and a probe tip can be used to image selected materials. Now being developed are magnetic probe STM's and photon tunneling microscopes in which the probe is a sharpened optical fiber. Also of great interest presently is the measurement of differential conductance of surfaces using electron STM's. This method supplies spectral information and contrast enhancement in images. At present there remains much theoretical work to be carried out in order to better characterize related data on inelastic electron tunneling, and valuable insight may be gained from data being gathered on the local work function of materials. As matters stand today, the key problems lie in determining tip and contamination effects, preparation of samples, and understanding conductivity mechanisms in very thin materials on conducting substrates. Resolution of these problems and introduction of new forms of scanning microscopy may permit novel and important applications in biology as well as surface science

  7. High-throughput, high-resolution X-ray phase contrast tomographic microscopy for visualisation of soft tissue

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, S A; Marone, F; Hintermueller, C; Stampanoni, M [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Bensadoun, J-C; Aebischer, P, E-mail: samuel.mcdonald@psi.c [EPFL, School of Life Sciences, Station 15, 1015 Lausanne (Switzerland)

    2009-09-01

    The use of conventional absorption based X-ray microtomography can become limited for samples showing only very weak absorption contrast. However, a wide range of samples studied in biology and materials science can produce significant phase shifts of the X-ray beam, and thus the use of the phase signal can provide substantially increased contrast and therefore new and otherwise inaccessible information. The application of two approaches for high-throughput, high-resolution X-ray phase contrast tomography, both available on the TOMCAT beamline of the SLS, is illustrated. Differential Phase Contrast (DPC) imaging uses a grating interferometer and a phase-stepping technique. It has been integrated into the beamline environment on TOMCAT in terms of the fast acquisition and reconstruction of data and the availability to scan samples within an aqueous environment. The second phase contrast approach is a modified transfer of intensity approach that can yield the 3D distribution of the phase (refractive index) of a weakly absorbing object from a single tomographic dataset. These methods are being used for the evaluation of cell integrity in 3D, with the specific aim of following and analyzing progressive cell degeneration to increase knowledge of the mechanistic events of neurodegenerative disorders such as Parkinson's disease.

  8. Fluctuation microscopy: a probe of medium range order

    International Nuclear Information System (INIS)

    Treacy, M M J; Gibson, J M; Fan, L; Paterson, D J; McNulty, I

    2005-01-01

    Fluctuation microscopy is a hybrid diffraction-imaging technique that detects medium range order in amorphous materials by examining spatial fluctuations in coherent scattering. These fluctuations appear as speckle in images and diffraction patterns. The volume of material contributing to the speckle is determined by the point-spread function (the resolution) of the imaging optics and the sample thickness. The spatial periodicities being probed are related to the diffraction vector. Statistical analysis of the speckle allows the random and non-random (ordered) contributions to be discriminated. The image resolution that gives the maximum speckle contrast, as determined by the normalized variance of the image intensity, is determined by the characteristic length scale of the ordering. Because medium range ordering length scales can extend out to about the tenth coordination shell, fluctuation microscopy tends to be a low image resolution technique. This review presents the kinematical scattering theory underpinning fluctuation microscopy and a description of fluctuation electron microscopy as it has been employed in the transmission electron microscope for studying amorphous materials. Recent results using soft x-rays for studying nanoscale materials are also presented. We summarize outstanding issues and point to possible future directions for fluctuation microscopy as a technique

  9. Simultaneous topographic and elemental chemical and magnetic contrast in scanning tunneling microscopy

    Science.gov (United States)

    Rose, Volker; Preissner, Curt A; Hla, Saw-Wai; Wang, Kangkang; Rosenmann, Daniel

    2014-09-30

    A method and system for performing simultaneous topographic and elemental chemical and magnetic contrast analysis in a scanning, tunneling microscope. The method and system also includes nanofabricated coaxial multilayer tips with a nanoscale conducting apex and a programmable in-situ nanomanipulator to fabricate these tips and also to rotate tips controllably.

  10. Recent achievements in multi-keV x-ray microscopy

    International Nuclear Information System (INIS)

    Susini, J.; Barrett, R.; Salome, M.; Kaulich, B.

    2002-01-01

    X-ray microscopy (XRM) techniques are emerging as powerful and complementary tools for sub-micron investigations. Soft XRM traditionally offers the possibility to form direct images of thick hydrated biological material in near-native environments, at a spatial resolution well beyond that achievable with visible light microscopy. Natural contrast is available in the soft X-ray region, in the so-called 'water-window', due to the presence of absorption edges of the major constituents (C,N,O). Recent advances in manufacturing techniques have enlarged the accessible energy range of micro-focusing optics and offer new applications in a broad range of disciplines. XRM in the 1-20 keV energy range is better suited to map trace elements in fluorescence yield, 3-D tomographic imaging and in micro-diffraction. After a brief introduction to the principles and methods, the main attributes of X-ray microscopy will be presented. This presentation will be biased towards sub-micron microscopy developed at the ESRF in the 2-10 keV energy. Strengths and weaknesses of X-ray microscopy and spectro-microscopy techniques will be discussed and illustrated by examples in biology, materials sciences and geology. (authors)

  11. Contact microscopy with synchrotron radiation

    International Nuclear Information System (INIS)

    Panessa-Warren, B.J.

    1985-10-01

    Soft x-ray contact microscopy with synchrotron radiation offers the biologist and especially the microscopist, a way to morphologically study specimens that could not be imaged by conventional TEM, STEM or SEM methods (i.e. hydrated samples, samples easily damaged by an electron beam, electron dense samples, thick specimens, unstained low contrast specimens) at spatial resolutions approaching those of the TEM, with the additional possibility to obtain compositional (elemental) information about the sample as well. Although flash x-ray sources offer faster exposure times, synchrotron radiation provides a highly collimated, intense radiation that can be tuned to select specific discrete ranges of x-ray wavelengths or specific individual wavelengths which optimize imaging or microanalysis of a specific sample. This paper presents an overview of the applications of x-ray contact microscopy to biological research and some current research results using monochromatic synchrotron radiation to image biological samples. 24 refs., 10 figs

  12. High contrast laser marking of alumina

    International Nuclear Information System (INIS)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; Val, J. del; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-01-01

    Highlights: • Laser marking of alumina using near infrared (NIR) lasers was experimentally analyzed. • Color change produced by NIR lasers is due to thermally induced oxygen vacancies. • Laser marking results obtained using NIR lasers and green laser are compared. • High contrast marks on alumina were achieved. - Abstract: Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks

  13. Hybrid Imaging for Extended Depth of Field Microscopy

    Science.gov (United States)

    Zahreddine, Ramzi Nicholas

    An inverse relationship exists in optical systems between the depth of field (DOF) and the minimum resolvable feature size. This trade-off is especially detrimental in high numerical aperture microscopy systems where resolution is pushed to the diffraction limit resulting in a DOF on the order of 500 nm. Many biological structures and processes of interest span over micron scales resulting in significant blurring during imaging. This thesis explores a two-step computational imaging technique known as hybrid imaging to create extended DOF (EDF) microscopy systems with minimal sacrifice in resolution. In the first step a mask is inserted at the pupil plane of the microscope to create a focus invariant system over 10 times the traditional DOF, albeit with reduced contrast. In the second step the contrast is restored via deconvolution. Several EDF pupil masks from the literature are quantitatively compared in the context of biological microscopy. From this analysis a new mask is proposed, the incoherently partitioned pupil with binary phase modulation (IPP-BPM), that combines the most advantageous properties from the literature. Total variation regularized deconvolution models are derived for the various noise conditions and detectors commonly used in biological microscopy. State of the art algorithms for efficiently solving the deconvolution problem are analyzed for speed, accuracy, and ease of use. The IPP-BPM mask is compared with the literature and shown to have the highest signal-to-noise ratio and lowest mean square error post-processing. A prototype of the IPP-BPM mask is fabricated using a combination of 3D femtosecond glass etching and standard lithography techniques. The mask is compared against theory and demonstrated in biological imaging applications.

  14. Interfering with theories of sleep and memory: sleep, declarative memory, and associative interference.

    Science.gov (United States)

    Ellenbogen, Jeffrey M; Hulbert, Justin C; Stickgold, Robert; Dinges, David F; Thompson-Schill, Sharon L

    2006-07-11

    Mounting behavioral evidence in humans supports the claim that sleep leads to improvements in recently acquired, nondeclarative memories. Examples include motor-sequence learning; visual-discrimination learning; and perceptual learning of a synthetic language. In contrast, there are limited human data supporting a benefit of sleep for declarative (hippocampus-mediated) memory in humans (for review, see). This is particularly surprising given that animal models (e.g.,) and neuroimaging studies (e.g.,) predict that sleep facilitates hippocampus-based memory consolidation. We hypothesized that we could unmask the benefits of sleep by challenging the declarative memory system with competing information (interference). This is the first study to demonstrate that sleep protects declarative memories from subsequent associative interference, and it has important implications for understanding the neurobiology of memory consolidation.

  15. Interference in motor learning - is motor interference sensory?

    DEFF Research Database (Denmark)

    Jensen, Jesper Lundbye; Petersen, Tue Hvass; Rothwell, John C

    mechanisms determine whether or not interference occurs. We hypothesised that interference requires the same neural circuits to be engaged in the two tasks and provoke competing processes of synaptic plasticity. To test this, subjects learned a ballistic ankle plantarflexion task. Early motor memory...... was disrupted by subsequent learning of a precision tracking task with the same agonist muscle group, but not by learning involving antagonist muscles or by voluntary agonist contractions that did not require learning. If the competing task was learned with the same agonist muscle group 4 hours following...

  16. Elemental mapping in scanning transmission electron microscopy

    International Nuclear Information System (INIS)

    Allen, L J; D'Alfonso, A J; Lugg, N R; Findlay, S D; LeBeau, J M; Stemmer, S

    2010-01-01

    We discuss atomic resolution chemical mapping in scanning transmission electron microscopy (STEM) based on core-loss electron energy loss spectroscopy (EELS) and also on energy dispersive X-ray (EDX) imaging. Chemical mapping using EELS can yield counterintuitive results which, however, can be understood using first principles calculations. Experimental chemical maps based on EDX bear out the thesis that such maps are always likely to be directly interpretable. This can be explained in terms of the local nature of the effective optical potential for ionization under those imaging conditions. This is followed by an excursion into the complementary technique of elemental mapping using energy-filtered transmission electron microscopy (EFTEM) in a conventional transmission electron microscope. We will then consider the widely used technique of Z-contrast or high-angle annular dark field (HAADF) imaging, which is based on phonon excitation, where it has recently been shown that intensity variations can be placed on an absolute scale by normalizing the measured intensities to the incident beam. Results, showing excellent agreement between theory and experiment to within a few percent, are shown for Z-contrast imaging from a sample of PbWO 4 .

  17. Does selection against transcriptional interference shape retroelement-free regions in mammalian genomes?

    Directory of Open Access Journals (Sweden)

    Tobias Mourier

    Full Text Available BACKGROUND: Eukaryotic genomes are scattered with retroelements that proliferate through retrotransposition. Although retroelements make up around 40 percent of the human genome, large regions are found to be completely devoid of retroelements. This has been hypothesised to be a result of genomic regions being intolerant to insertions of retroelements. The inadvertent transcriptional activity of retroelements may affect neighbouring genes, which in turn could be detrimental to an organism. We speculate that such retroelement transcription, or transcriptional interference, is a contributing factor in generating and maintaining retroelement-free regions in the human genome. METHODOLOGY/PRINCIPAL FINDINGS: Based on the known transcriptional properties of retroelements, we expect long interspersed elements (LINEs to be able to display a high degree of transcriptional interference. In contrast, we expect short interspersed elements (SINEs to display very low levels of transcriptional interference. We find that genomic regions devoid of long interspersed elements (LINEs are enriched for protein-coding genes, but that this is not the case for regions devoid of short interspersed elements (SINEs. This is expected if genes are subject to selection against transcriptional interference. We do not find microRNAs to be associated with genomic regions devoid of either SINEs or LINEs. We further observe an increased relative activity of genes overlapping LINE-free regions during early embryogenesis, where activity of LINEs has been identified previously. CONCLUSIONS/SIGNIFICANCE: Our observations are consistent with the notion that selection against transcriptional interference has contributed to the maintenance and/or generation of retroelement-free regions in the human genome.

  18. Comparison of confocal microscopy and two-photon microscopy in mouse cornea in vivo.

    Science.gov (United States)

    Lee, Jun Ho; Lee, Seunghun; Gho, Yong Song; Song, In Seok; Tchah, Hungwon; Kim, Myoung Joon; Kim, Ki Hean

    2015-03-01

    High-resolution imaging of the cornea is important for studying corneal diseases at cellular levels. Confocal microscopy (CM) has been widely used in the clinic, and two-photon microscopy (TPM) has recently been introduced in various pre-clinical studies. We compared the performance of CM and TPM in normal mouse corneas and neovascularized mouse corneas induced by suturing. Balb/C mice and C57BL/6 mice expressing green fluorescent protein (GFP) were used to compare modalities based on intrinsic contrast and extrinsic fluorescence contrast. CM based on reflection (CMR), CM based on fluorescence (CMF), and TPM based on intrinsic/extrinsic fluorescence and second harmonic generation (SHG) were compared by imaging the same sections of mouse corneas sequentially in vivo. In normal mouse corneas, CMR visualized corneal cell morphologies with some background noise, and CMF visualized GFP expressing corneal cells clearly. TPM visualized corneal cells and collagen in the stroma based on fluorescence and SHG, respectively. However, in neovascularized mouse corneas, CMR could not resolve cells deep inside the cornea due to high background noise from the effects of increased structural irregularity induced by suturing. CMF and TPM visualized cells and induced vasculature better than CMR because both collect signals from fluorescent cells only. Both CMF and TPM had signal decays with depth due to the structural irregularity, with CMF having faster signal decay than TPM. CMR, CMF, and TPM showed different degrees of image degradation in neovascularized mouse corneas. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. High-resolution electron microscopy and its applications.

    Science.gov (United States)

    Li, F H

    1987-12-01

    A review of research on high-resolution electron microscopy (HREM) carried out at the Institute of Physics, the Chinese Academy of Sciences, is presented. Apart from the direct observation of crystal and quasicrystal defects for some alloys, oxides, minerals, etc., and the structure determination for some minute crystals, an approximate image-contrast theory named pseudo-weak-phase object approximation (PWPOA), which shows the image contrast change with crystal thickness, is described. Within the framework of PWPOA, the image contrast of lithium ions in the crystal of R-Li2Ti3O7 has been observed. The usefulness of diffraction analysis techniques such as the direct method and Patterson method in HREM is discussed. Image deconvolution and resolution enhancement for weak-phase objects by use of the direct method are illustrated. In addition, preliminary results of image restoration for thick crystals are given.

  20. High contrast laser marking of alumina

    Science.gov (United States)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-05-01

    Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.

  1. Sleep can reduce proactive interference.

    Science.gov (United States)

    Abel, Magdalena; Bäuml, Karl-Heinz T

    2014-01-01

    Sleep has repeatedly been connected to processes of memory consolidation. While extensive research indeed documents beneficial effects of sleep on memory, little is yet known about the role of sleep for interference effects in episodic memory. Although two prior studies reported sleep to reduce retroactive interference, no sleep effect has previously been found for proactive interference. Here we applied a study format differing from that employed by the prior studies to induce a high degree of proactive interference, and asked participants to encode a single list or two interfering lists of paired associates via pure study cycles. Testing occurred after 12 hours of diurnal wakefulness or nocturnal sleep. Consistent with the prior work, we found sleep in comparison to wake did not affect memory for the single list, but reduced retroactive interference. In addition we found sleep reduced proactive interference, and reduced retroactive and proactive interference to the same extent. The finding is consistent with the view that arising benefits of sleep are caused by the reactivation of memory contents during sleep, which has been suggested to strengthen and stabilise memories. Such stabilisation may make memories less susceptible to competition from interfering memories at test and thus reduce interference effects.

  2. Interference experiment with asymmetric double slit by using 1.2-MV field emission transmission electron microscope.

    Science.gov (United States)

    Harada, Ken; Akashi, Tetsuya; Niitsu, Kodai; Shimada, Keiko; Ono, Yoshimasa A; Shindo, Daisuke; Shinada, Hiroyuki; Mori, Shigeo

    2018-01-17

    Advanced electron microscopy technologies have made it possible to perform precise double-slit interference experiments. We used a 1.2-MV field emission electron microscope providing coherent electron waves and a direct detection camera system enabling single-electron detections at a sub-second exposure time. We developed a method to perform the interference experiment by using an asymmetric double-slit fabricated by a focused ion beam instrument and by operating the microscope under a "pre-Fraunhofer" condition, different from the Fraunhofer condition of conventional double-slit experiments. Here, pre-Fraunhofer condition means that each single-slit observation was performed under the Fraunhofer condition, while the double-slit observations were performed under the Fresnel condition. The interference experiments with each single slit and with the asymmetric double slit were carried out under two different electron dose conditions: high-dose for calculation of electron probability distribution and low-dose for each single electron distribution. Finally, we exemplified the distribution of single electrons by color-coding according to the above three types of experiments as a composite image.

  3. Application of multiphoton microscopy in dermatological studies: A mini-review

    Directory of Open Access Journals (Sweden)

    Elijah Yew

    2014-09-01

    Full Text Available This review summarizes the historical and more recent developments of multiphoton microscopy, as applied to dermatology. Multiphoton microscopy offers several advantages over competing microscopy techniques: there is an inherent axial sectioning, penetration depths that compete well with confocal microscopy on account of the use of near-infrared light, and many two-photon contrast mechanisms, such as second-harmonic generation, have no analogue in one-photon microscopy. While the penetration depths of photons into tissue are typically limited on the order of hundreds of microns, this is of less concern in dermatology, as the skin is thin and readily accessible. As a result, multiphoton microscopy in dermatology has generated a great deal of interest, much of which is summarized here. The review covers the interaction of light and tissue, as well as the various considerations that must be made when designing an instrument. The state of multiphoton microscopy in imaging skin cancer and various other diseases is also discussed, along with the investigation of aging and regeneration phenomena, and finally, the use of multiphoton microscopy to analyze the transdermal transport of drugs, cosmetics and other agents is summarized. The review concludes with a look at potential future research directions, especially those that are necessary to push these techniques into widespread clinical acceptance.

  4. Dark Matter Interference

    DEFF Research Database (Denmark)

    Del Nobile, Eugenio; Kouvaris, Christoforos; Sannino, Francesco

    2012-01-01

    We study different patterns of interference in WIMP-nuclei elastic scattering that can accommodate the DAMA and CoGeNT experiments via an isospin violating ratio $f_n/f_p=-0.71$. We study interference between the following pairs of mediators: Z and Z', Z' and Higgs, and two Higgs fields. We show ...

  5. Second-Harmonic Generation Scanning Microscopy on Domains in Al Surfaces

    DEFF Research Database (Denmark)

    Pedersen, Kjeld; Bozhevolnyi, Sergey I.

    1999-01-01

    Scanning optical second-harmonic generation microscopy has been used to investigate domains in the surface of polycrystaline Al. Strong contrast among the crystalline grains is obtained due to variations in their crystallographic orientations and thus also nonlinear response. The origin of the co...

  6. Medipix 2 detector applied to low energy electron microscopy

    International Nuclear Information System (INIS)

    Gastel, R. van; Sikharulidze, I.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, S.J. van der

    2009-01-01

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy. Here, we report on a successful test series using a solid state hybrid pixel detector, Medipix 2, in LEEM and PEEM. Medipix 2 is a background-free detector with an infinite dynamic range, making it very promising for both real-space imaging and spectroscopy. We demonstrate a significant enhancement of both image contrast and resolution, as compared to MCPs. Since aging of the Medipix 2 detector is negligible for the electron energies used in LEEM/PEEM, we expect Medipix to become the detector of choice for a new generation of systems.

  7. Medipix 2 detector applied to low energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gastel, R. van, E-mail: R.vanGastel@utwente.nl [University of Twente, MESA Institute for Nanotechnology, P.O. Box 217, NL-7500 AE Enschede (Netherlands); Sikharulidze, I. [Leiden University, Leiden Institute of Chemistry, P.O. Box 9502, NL-2300 RA Leiden (Netherlands); Schramm, S. [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); Abrahams, J.P. [Leiden University, Leiden Institute of Chemistry, P.O. Box 9502, NL-2300 RA Leiden (Netherlands); Poelsema, B. [University of Twente, MESA Institute for Nanotechnology, P.O. Box 217, NL-7500 AE Enschede (Netherlands); Tromp, R.M. [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Molen, S.J. van der [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands)

    2009-12-15

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy. Here, we report on a successful test series using a solid state hybrid pixel detector, Medipix 2, in LEEM and PEEM. Medipix 2 is a background-free detector with an infinite dynamic range, making it very promising for both real-space imaging and spectroscopy. We demonstrate a significant enhancement of both image contrast and resolution, as compared to MCPs. Since aging of the Medipix 2 detector is negligible for the electron energies used in LEEM/PEEM, we expect Medipix to become the detector of choice for a new generation of systems.

  8. Transmission electron microscopy physics of image formation and microanalysis

    CERN Document Server

    Reimer, Ludwig

    1993-01-01

    "Transmission Electron Microscopy" presents the theory of image and contrastformation, and the analytical modes in transmission electron microscopy Theprinciples of particle and wave optics of electrons are described Electron-specimen interactions are discussed for evaluating the theory of scattering and phase contrast Also analysed are the kinetical and dynamical theories of electron diffraction and their applications for crystal-structure determination and imaging of lattices and their defects X-ray microanalysis and electron energy-loss spectroscopy are treated as analytical methods The third edition includes a brief discussionof Schottky emission guns, some clarification of minor details, and references to the recent literature

  9. Phase Contrast Imaging

    DEFF Research Database (Denmark)

    1996-01-01

    The invention relates to a method and a system for synthesizing a prescribed intensity pattern based on phase contrast imaging that is not based on the assumption of prior art methods that the pahase shift phi is less than 1 radian. An improved method based on a simple imaging operation...... phasors attain predetermined values for predetermined spatial frequencies, and the phasor value of the specific resolution element of the spatial phase mask corresponds to a distinct intensity level of the image of the resolution element in the intensity pattern, and a spatial phase filter for phase...... shifting of a part of the electromagntic radiation, in combination with an imaging system for generation of the intensity pattern by interference in the image plane of the imaging system between the part of the electromagnetic raidation that has been phase shifted by the phase filter and the remaining part...

  10. X-ray phase-contrast CT of a pancreatic ductal adenocarcinoma mouse model.

    Directory of Open Access Journals (Sweden)

    Arne Tapfer

    Full Text Available To explore the potential of grating-based x-ray phase-contrast computed tomography (CT for preclinical research, a genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC was investigated. One ex-vivo mouse specimen was scanned with different grating-based phase-contrast CT imaging setups covering two different settings: i high-resolution synchrotron radiation (SR imaging and ii dose-reduced imaging using either synchrotron radiation or a conventional x-ray tube source. These experimental settings were chosen to assess the potential of phase-contrast imaging for two different types of application: i high-performance imaging for virtual microscopy applications and ii biomedical imaging with increased soft-tissue contrast for in-vivo applications. For validation and as a reference, histological slicing and magnetic resonance imaging (MRI were performed on the same mouse specimen. For each x-ray imaging setup, attenuation and phase-contrast images were compared visually with regard to contrast in general, and specifically concerning the recognizability of lesions and cancerous tissue. To quantitatively assess contrast, the contrast-to-noise ratios (CNR of selected regions of interest (ROI in the attenuation images and the phase images were analyzed and compared. It was found that both for virtual microscopy and for in-vivo applications, there is great potential for phase-contrast imaging: in the SR-based benchmarking data, fine details about tissue composition are accessible in the phase images and the visibility of solid tumor tissue under dose-reduced conditions is markedly superior in the phase images. The present study hence demonstrates improved diagnostic value with phase-contrast CT in a mouse model of a complex endogenous cancer, promoting the use and further development of grating-based phase-contrast CT for biomedical imaging applications.

  11. Image contrast enhancement of Ni/YSZ anode during the slice-and-view process in FIB-SEM.

    Science.gov (United States)

    Liu, Shu-Sheng; Takayama, Akiko; Matsumura, Syo; Koyama, Michihisa

    2016-03-01

    Focused ion beam-scanning electron microscopy (FIB-SEM) is a widely used and easily operational equipment for three-dimensional reconstruction with flexible analysis volume. It has been using successfully and increasingly in the field of solid oxide fuel cell. However, the phase contrast of the SEM images is indistinct in many cases, which will bring difficulties to the image processing. Herein, the phase contrast of a conventional Ni/yttria stabilized zirconia anode is tuned in an FIB-SEM with In-Lens secondary electron (SE) and backscattered electron detectors. Two accessories, tungsten probe and carbon nozzle, are inserted during the observation. The former has no influence on the contrast. When the carbon nozzle is inserted, best and distinct contrast can be obtained by In-Lens SE detector. This method is novel for contrast enhancement. Phase segmentation of the image can be automatically performed. The related mechanism for different images is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  12. Temporary interference over the posterior parietal cortices disrupts thermoregulatory control in humans.

    Directory of Open Access Journals (Sweden)

    Alberto Gallace

    Full Text Available The suggestion has recently been made that certain higher-order cortical areas involved in supporting multisensory representations of the body, and of the space around it, might also play a role in controlling thermoregulatory functions. Here we demonstrate that temporary interference with the function of one of these areas, the posterior parietal cortex, by repetitive transcranial magnetic stimulation, results in a decrease in limb temperature. By contrast, interference with the activity of a sensory-specific area (the primary somatosensory cortex had no effect on temperature. The results of this experiment suggest that associative multisensory brain areas might exert a top-down modulation over basic physiological control. Such a function might be part of a larger neural circuit responsible for maintaining the integrity of the body at both a homeostatic and a psychological level.

  13. Depiction of blood vessels by x-ray phase contrast

    Energy Technology Data Exchange (ETDEWEB)

    Momose, Atsushi [School of Engineering, University of Tokyo, Tokyo (Japan); Takeda, Tohoru; Itai, Yuji [Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki (Japan)

    2001-04-01

    Blood vessels in livers of a mouse and a rat were depicted by phase-contrast x-ray imaging with an x-ray interferometer without using contrast agents. X-ray interference patterns were converted to image mapping x-ray phase shift caused by the livers using the technique of phase-shifting x-ray interferometry. The arteries and veins to and from the livers were tied before excision in order to prevent blood from flowing out of the liver. The x-ray phase shift caused by blood was substantially different from that caused by other soft sues, and consequently trees of blood vessels were revealed in the images. Vessels of diameter smaller than 0.1 mm were detected. This result suggests new possibilities for investigating vascular systems. (author)

  14. Operation of a separated-type x-ray interferometer for phase-contrast x-ray imaging

    Science.gov (United States)

    Yoneyama, Akio; Momose, Atsushi; Seya, Eiichi; Hirano, Keiichi; Takeda, Tohoru; Itai, Yuji

    1999-12-01

    Aiming at large-area phase-contrast x-ray imaging, a separated-type x-ray interferometer system was designed and developed to produce 25×20 mm interference patterns. The skew-symmetric optical system was adopted because of the feasibility of alignment. The rotation between the separated crystal blocks was controlled within a drift of 0.06 nrad using a feedback positioning system. This interferometer generated a 25×15 mm interference pattern with 0.07 nm synchrotron x-rays. A slice of a rabbit's kidney was observed, and its tubular structure could be revealed in a measured phase map.

  15. Multiple-Antenna Interference Cancellation for WLAN with MAC Interference Avoidance in Open Access Networks

    Directory of Open Access Journals (Sweden)

    Alexandr M. Kuzminskiy

    2007-10-01

    Full Text Available The potential of multiantenna interference cancellation receiver algorithms for increasing the uplink throughput in WLAN systems such as 802.11 is investigated. The medium access control (MAC in such systems is based on carrier sensing multiple-access with collision avoidance (CSMA/CA, which itself is a powerful tool for the mitigation of intrasystem interference. However, due to the spatial dependence of received signal strengths, it is possible for the collision avoidance mechanism to fail, resulting in packet collisions at the receiver and a reduction in system throughput. The CSMA/CA MAC protocol can be complemented in such scenarios by interference cancellation (IC algorithms at the physical (PHY layer. The corresponding gains in throughput are a result of the complex interplay between the PHY and MAC layers. It is shown that semiblind interference cancellation techniques are essential for mitigating the impact of interference bursts, in particular since these are typically asynchronous with respect to the desired signal burst. Semiblind IC algorithms based on second- and higher-order statistics are compared to the conventional no-IC and training-based IC techniques in an open access network (OAN scenario involving home and visiting users. It is found that the semiblind IC algorithms significantly outperform the other techniques due to the bursty and asynchronous nature of the interference caused by the MAC interference avoidance scheme.

  16. Multiple-Antenna Interference Cancellation for WLAN with MAC Interference Avoidance in Open Access Networks

    Directory of Open Access Journals (Sweden)

    Kuzminskiy Alexandr M

    2007-01-01

    Full Text Available The potential of multiantenna interference cancellation receiver algorithms for increasing the uplink throughput in WLAN systems such as 802.11 is investigated. The medium access control (MAC in such systems is based on carrier sensing multiple-access with collision avoidance (CSMA/CA, which itself is a powerful tool for the mitigation of intrasystem interference. However, due to the spatial dependence of received signal strengths, it is possible for the collision avoidance mechanism to fail, resulting in packet collisions at the receiver and a reduction in system throughput. The CSMA/CA MAC protocol can be complemented in such scenarios by interference cancellation (IC algorithms at the physical (PHY layer. The corresponding gains in throughput are a result of the complex interplay between the PHY and MAC layers. It is shown that semiblind interference cancellation techniques are essential for mitigating the impact of interference bursts, in particular since these are typically asynchronous with respect to the desired signal burst. Semiblind IC algorithms based on second- and higher-order statistics are compared to the conventional no-IC and training-based IC techniques in an open access network (OAN scenario involving home and visiting users. It is found that the semiblind IC algorithms significantly outperform the other techniques due to the bursty and asynchronous nature of the interference caused by the MAC interference avoidance scheme.

  17. Collision-induced destructive quantum interference

    International Nuclear Information System (INIS)

    Yang Xihua; Sun Zhenrong; Zhang Shi'an; Ding Liang'en; Wang Zugeng

    2005-01-01

    We conduct theoretical studies on the collision-induced destructive quantum interference of two-colour two-photon transitions in an open rhomb-type five-level system with a widely separated doublet by the density matrix approach. The effects of the collision-induced decay rates, the ratio of the transition dipole moments and the energy separation of the doublet on the interference are analysed. It is shown that a narrow dip appears in the excitation spectrum due to the collision-induced destructive interference, and that the narrow interference dip still exists even when the collision broadening is comparable to the energy separation of the doublet. The physical origin of the collision-induced destructive quantum interference is analysed in the dressed-atom picture

  18. Microsphere imaging with confocal microscopy and two photon microscopy

    International Nuclear Information System (INIS)

    Chun, Hyung Su; An, Kyung Won; Lee, Jai Hyung

    2002-01-01

    We have acquired images of polystyrene and fused-silica microsphere by using conventional optical microscopy, confocal microscopy and two-photon microscopy, and performed comparative analysis of these images. Different from conventional optical microscopy, confocal and two-photon microscopy had good optical sectioning capability. In addition, confocal microscopy and two-photon microscopy had better lateral resolution than conventional optical microscopy. These results are attributed to confocality and nonlinearity of confocal microscopy and two photon microscopy, respectively.

  19. Mechanism of ascorbic acid interference in biochemical tests that use peroxide and peroxidase to generate chromophore.

    Science.gov (United States)

    Martinello, Flávia; Luiz da Silva, Edson

    2006-11-01

    Ascorbic acid interferes negatively in peroxidase-based tests (Trinder method). However, the precise mechanism remains unclear for tests that use peroxide, a phenolic compound and 4-aminophenazone (4-AP). We determined the chemical mechanism of this interference, by examining the effects of ascorbic acid in the reaction kinetics of the production and reduction of the oxidized chromophore in urate, cholesterol, triglyceride and glucose tests. Reaction of ascorbic acid with the Trinder method constituents was also verified. Ascorbic acid interfered stoichiometrically with all tests studied. However, it had two distinct effects on the reaction rate. In the urate test, ascorbic acid decreased the chromophore formation with no change in its production kinetics. In contrast, in cholesterol, triglyceride and glucose tests, an increase in the lag phase of color development occurred. Of all the Trinder constituents, only peroxide reverted the interference. In addition, ascorbic acid did not interfere with oxidase activity nor reduce significantly the chromophore formed. Peroxide depletion was the predominant chemical mechanism of ascorbic acid interference in the Trinder method with phenolics and 4-AP. Distinctive effects of ascorbic acid on the reaction kinetics of urate, cholesterol, glucose and triglyceride might be due to the rate of peroxide production by oxidases.

  20. Biological applications of near-field scanning optical microscopy

    Science.gov (United States)

    Moers, Marco H. P.; Ruiter, A. G. T.; Jalocha, Alain; van Hulst, Niko F.; Kalle, W. H. J.; Wiegant, J. C. A. G.; Raap, A. K.

    1995-09-01

    Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on metal coated adiabatically tapered fibers, combined with shear force feedback and operated in illumination mode, has proven to be the most powerful NSOM arrangement, because of its true localization of the optical interaction, its various optical contrast possibilities and its sensitivity down to the single molecular level. In this paper applications of `aperture' NSOM to Fluorescence In Situ Hybridization of human metaphase chromosomes are presented, where the localized fluorescence allows to identify specific DNA sequences. All images are accompanied by the simultaneously acquired force image, enabling direct comparison of the optical contrast with the sample topography on nanometer scale, far beyond the diffraction limit. Thus the unique combination of high resolution, specific optical contrast and ambient operation offers many new direction possibilities in biological studies.

  1. Studies on the biological effects of deuteriated organic compounds

    International Nuclear Information System (INIS)

    Hellgren, L.; Liljemark, A.; Vincent, J.

    1976-01-01

    In order to visualise the morphological changes of Epidermophyton floccosum associated with exposure to perdeuteriated n-hendecanoic acid, the architecture of the dermatophyte was investigated by means of interference contrast and scanning electron microscopy. The mortphology of mycelia grown on substrate containing perdeuteriated n-hendecnoic acid, or the unlabelled analogue, was compared. The perdeuteriated n-hendecanoic acid produced a characteristic undulant effect of the hyphae. The characteristic wave-lake appearance of the mycelia looked similar to the curling effect occurring after treatment of dermatophytes with griseofulvin, but was not so pronounced. Perdeuteriated n-hendecanoic acid, unlike the unlabelled analogue, also seems to cause a reduction of the number of chlamydospores perforations of the macroconidia. The changes in the morphological structure of Epidermophyton floccosum exposed to perdeuteriated n-hendecanoic acid have been investigated. Morphological examination of mycelia exposed to this substance by interference contrast microscopy demonstrated a picture of defect hyphae and macroconidia. By the aid of scanning electron microscopy an attempt was made to obtain a better visualization of these changes at ultrastructural level

  2. Enhancement of the optical image with a DC blocked spiral holographic pattern

    International Nuclear Information System (INIS)

    Hwang, Sung-In; Lee, Jung-Kyun; Song, Dong-Hoon; Choi, Dae-Sik; Ko, Do-Kyeong

    2011-01-01

    A modification of microscopy using a spiral phase plate, which enhanced the optical image by blocking the DC part of the object spectrum is presented. In conventional differential-interference-contrast microscopy, enhancement of optical images is achieved by interference of mutual coherent beams which experience different optical phases. This method increases the contrast of the optical image compared to normal microscopy, but the image still has some blurring around the edge of the sample. Our modification consists of placing a DC blocking region on an optical spatial filter, which allows us to achieve a sharp edge compared to the conventional one. By patterning the grating of the circular area in the center with a different direction (π/4 in our case), we could redirect the DC part of the Fourier component that passed through the center of the phase plate. By eliminating the DC part of the object spectrum, we could get a highly enhanced image and clearly observed the inside of the cheek cell, which was invisible otherwise.

  3. Electron microscopy of intermediate filaments: teaming up with atomic force and confocal laser scanning microscopy.

    Science.gov (United States)

    Kreplak, Laurent; Richter, Karsten; Aebi, Ueli; Herrmann, Harald

    2008-01-01

    Intermediate filaments (IFs) were originally discovered and defined by electron microscopy in myoblasts. In the following it was demonstrated and confirmed that they constitute, in addition to microtubules and microfilaments, a third independent, general filament system in the cytoplasm of most metazoan cells. In contrast to the other two systems, IFs are present in cells in two principally distinct cytoskeletal forms: (i) extended and free-running filament arrays in the cytoplasm that are integrated into the cytoskeleton by associated proteins of the plakin type; and (ii) a membrane- and chromatin-bound thin 'lamina' of a more or less regular network of interconnected filaments made from nuclear IF proteins, the lamins, which differ in several important structural aspects from cytoplasmic IF proteins. In man, more than 65 genes code for distinct IF proteins that are expressed during embryogenesis in various routes of differentiation in a tightly controlled manner. IF proteins exhibit rather limited sequence identity implying that the different types of IFs have distinct biochemical properties. Hence, to characterize the structural properties of the various IFs, in vitro assembly regimes have been developed in combination with different visualization methods such as transmission electron microscopy of fixed and negatively stained samples as well as methods that do not use staining such as scanning transmission electron microscopy (STEM) and cryoelectron microscopy as well as atomic force microscopy. Moreover, with the generation of both IF-type specific antibodies and chimeras of fluorescent proteins and IF proteins, it has become possible to investigate the subcellular organization of IFs by correlative fluorescence and electron microscopic methods. The combination of these powerful methods should help to further develop our understanding of nuclear architecture, in particular how nuclear subcompartments are organized and in which way lamins are involved.

  4. Stroop interference and reverse Stroop interference as potential measures of cognitive ability during exposure to stress

    OpenAIRE

    景山, 望; 箱田, 裕司; Kageyama, Nozomu; Hakoda, Yuji

    2011-01-01

    Stroop interference and reverse-Stroop interference are one of the easiest and most powerful effects to demonstrate in a classroom. Therefore, they have been studied not only through basic research in the laboratory but also through applied research in extreme environments. First, we reviewed studies tha investigated Stroop interference and reverse-Stroop interference as hallmark measures of selective at attention and conflict resolution. Second, we reviewed studies that examined the effects ...

  5. Influence of contrast agent dose and ultrasound exposure on cardiomyocyte injury induced by myocardial contrast echocardiography in rats.

    Science.gov (United States)

    Miller, Douglas L; Li, Peng; Dou, Chunyan; Gordon, David; Edwards, Chris A; Armstrong, William F

    2005-10-01

    To detect specific cardiomyocyte injury induced by myocardial contrast material-enhanced echocardiography (ie, myocardial contrast echocardiography) in rats and to ascertain the influences of contrast material dose and ultrasound exposure on this injury. All animal procedures were approved by the university committee for the use and care of animals. Myocardial contrast echocardiography with 1:4 electrocardiographic (ECG) triggering was performed at 1.5 MHz in 61 anesthetized rats. Evans blue (EB) dye was injected as the vital stain for cardiomyocyte injury. At the start of myocardial contrast echocardiography, which lasted 10 minutes, perflutren lipid microsphere-based contrast material was infused through the tail vein for 5 minutes. Premature heartbeats were counted from the ECG record. The numbers of EB-stained cells counted on sections of heart specimens obtained 24 hours after myocardial contrast echocardiography and then either fresh frozen or embedded in paraffin were determined by using fluorescence microscopy. Results were compared statistically by using t tests and Mann-Whitney rank sum tests. EB-stained cells were concentrated in the anterior region of the myocardium. In the paraffin-embedded specimens, EB-stained cells were often accompanied by but largely separate from areas of inflammatory cell infiltration. At end-systolic triggering with a 50 microL/kg dose of microsphere contrast material, the EB-stained cell count increased with increasing peak rarefactional pressure amplitude, with significantly increased cell counts at 1.6 MPa (P .1). EB-stained cell counts increased with increasing contrast material dose, from 10 to 50 microL/kg, at 2.0 MPa. Cardiomyocyte injury was induced by the interaction of ultrasound pulses with contrast agent microbubbles during myocardial contrast echocardiography in rats, and the numbers of injured cells increased with increasing contrast agent dose and ultrasound exposure. RSNA, 2005

  6. Sub-Angstrom microscopy through incoherent imaging and image reconstruction

    International Nuclear Information System (INIS)

    Pennycook, S.J.; Jesson, D.E.; Chisholm, M.F.; Ferridge, A.G.; Seddon, M.J.

    1992-03-01

    Z-contrast scanning transmission electron microscopy (STEM) with a high-angle annular detector breaks the coherence of the imaging process, and provides an incoherent image of a crystal projection. Even in the presence of strong dynamical diffraction, the image can be accurately described as a convolution between an object function, sharply peaked at the projected atomic sites, and the probe intensity profile. Such an image can be inverted intuitively without the need for model structures, and therefore provides the important capability to reveal unanticipated interfacial arrangements. It represents a direct image of the crystal projection, revealing the location of the atomic columns and their relative high-angle scattering power. Since no phase is associated with a peak in the object function or the contrast transfer function, extension to higher resolution is also straightforward. Image restoration techniques such as maximum entropy, in conjunction with the 1.3 Angstrom probe anticipated for a 300 kV STEM, appear to provide a simple and robust route to the achievement of sub-Angstrom resolution electron microscopy

  7. Quantitative phase imaging with scanning holographic microscopy: an experimental assesment

    Directory of Open Access Journals (Sweden)

    Tada Yoshitaka

    2006-11-01

    Full Text Available Abstract This paper demonstrates experimentally how quantitative phase information can be obtained in scanning holographic microscopy. Scanning holography can operate in both coherent and incoherent modes, simultaneously if desired, with different detector geometries. A spatially integrating detector provides an incoherent hologram of the object's intensity distribution (absorption and/or fluorescence, for example, while a point detector in a conjugate plane of the pupil provides a coherent hologram of the object's complex amplitude, from which a quantitative measure of its phase distribution can be extracted. The possibility of capturing simultaneously holograms of three-dimensional specimens, leading to three-dimensional reconstructions with absorption contrast, reflectance contrast, fluorescence contrast, as was previously demonstrated, and quantitative phase contrast, as shown here for the first time, opens up new avenues for multimodal imaging in biological studies.

  8. Visualization of single-wall carbon nanotube (SWNT) networks in conductive polystyrene nanocomposites by charge contrast imaging

    International Nuclear Information System (INIS)

    Loos, Joachim; Alexeev, Alexander; Grossiord, Nadia; Koning, Cor E.; Regev, Oren

    2005-01-01

    The morphology of conductive nanocomposites consisting of low concentration of single-wall carbon nanotubes (SWNT) and polystyrene (PS) has been studied using atomic force microscopy (AFM), transmission electron microscopy (TEM) and, in particular, scanning electron microscopy (SEM). Application of charge contrast imaging in SEM allows visualization of the overall SWNT dispersion within the polymer matrix as well as the identification of individual or bundled SWNTs at high resolution. The contrast mechanism involved will be discussed. In conductive nanocomposites the SWNTs are homogeneously dispersed within the polymer matrix and form a network. Beside fairly straight SWNTs, strongly bended SWNTs have been observed. However, for samples with SWNT concentrations below the percolation threshold, the common overall charging behavior of an insulating material is observed preventing the detailed morphological investigation of the sample

  9. Contrasting behavior of covalent and molecular carbon allotropes exposed to extreme ultraviolet and soft x-ray free-electron laser radiation

    Science.gov (United States)

    Toufarová, M.; Hájková, V.; Chalupský, J.; Burian, T.; Vacík, J.; Vorlíček, V.; Vyšín, L.; Gaudin, J.; Medvedev, N.; Ziaja, B.; Nagasono, M.; Yabashi, M.; Sobierajski, R.; Krzywinski, J.; Sinn, H.; Störmer, M.; Koláček, K.; Tiedtke, K.; Toleikis, S.; Juha, L.

    2017-12-01

    All carbon materials, e.g., amorphous carbon (a-C) coatings and C60 fullerene thin films, play an important role in short-wavelength free-electron laser (FEL) research motivated by FEL optics development and prospective nanotechnology applications. Responses of a-C and C60 layers to the extreme ultraviolet (SPring-8 Compact SASE Source in Japan) and soft x-ray (free-electron laser in Hamburg) free-electron laser radiation are investigated by Raman spectroscopy, differential interference contrast, and atomic force microscopy. A remarkable difference in the behavior of covalent (a-C) and molecular (C60) carbonaceous solids is demonstrated under these irradiation conditions. Low thresholds for ablation of a fullerene crystal (estimated to be around 0.15 eV/atom for C60 vs 0.9 eV/atom for a-C in terms of the absorbed dose) are caused by a low cohesive energy of fullerene crystals. An efficient mechanism of the removal of intact C60 molecules from the irradiated crystal due to Coulomb repulsion of fullerene-cage cation radicals formed by the ionizing radiation is revealed by a detailed modeling.

  10. Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure.

    Science.gov (United States)

    Kowoll, Thomas; Müller, Erich; Fritsch-Decker, Susanne; Hettler, Simon; Störmer, Heike; Weiss, Carsten; Gerthsen, Dagmar

    2017-01-01

    This study is concerned with backscattered electron scanning electron microscopy (BSE SEM) contrast of complex nanoscaled samples which consist of SiO 2 nanoparticles (NPs) deposited on indium-tin-oxide covered bulk SiO 2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC-) simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

  11. Lensfree microscopy on a cellphone

    Science.gov (United States)

    Tseng, Derek; Mudanyali, Onur; Oztoprak, Cetin; Isikman, Serhan O.; Sencan, Ikbal; Yaglidere, Oguzhan; Ozcan, Aydogan

    2010-01-01

    We demonstrate lensfree digital microscopy on a cellphone. This compact and light-weight holographic microscope installed on a cellphone does not utilize any lenses, lasers or other bulky optical components and it may offer a cost-effective tool for telemedicine applications to address various global health challenges. Weighing ~38 grams (cellphone where the samples are loaded from the side, and are vertically illuminated by a simple light-emitting diode (LED). This incoherent LED light is then scattered from each micro-object to coherently interfere with the background light, creating the lensfree hologram of each object on the detector array of the cellphone. These holographic signatures captured by the cellphone permit reconstruction of microscopic images of the objects through rapid digital processing. We report the performance of this lensfree cellphone microscope by imaging various sized micro-particles, as well as red blood cells, white blood cells, platelets and a waterborne parasite (Giardia lamblia). PMID:20445943

  12. Scanning tunneling microscopy II further applications and related scanning techniques

    CERN Document Server

    Güntherodt, Hans-Joachim

    1995-01-01

    Scanning Tunneling Microscopy II, like its predecessor, presents detailed and comprehensive accounts of the basic principles and broad range of applications of STM and related scanning probe techniques. The applications discussed in this volume come predominantly from the fields of electrochemistry and biology. In contrast to those described in STM I, these studies may be performed in air and in liquids. The extensions of the basic technique to map other interactions are described in chapters on scanning force microscopy, magnetic force microscopy, and scanning near-field optical microscopy, together with a survey of other related techniques. Also described here is the use of a scanning proximal probe for surface modification. Together, the two volumes give a comprehensive account of experimental aspects of STM. They provide essential reading and reference material for all students and researchers involved in this field. In this second edition the text has been updated and new methods are discussed.

  13. DMD-based LED-illumination super-resolution and optical sectioning microscopy.

    Science.gov (United States)

    Dan, Dan; Lei, Ming; Yao, Baoli; Wang, Wen; Winterhalder, Martin; Zumbusch, Andreas; Qi, Yujiao; Xia, Liang; Yan, Shaohui; Yang, Yanlong; Gao, Peng; Ye, Tong; Zhao, Wei

    2013-01-01

    Super-resolution three-dimensional (3D) optical microscopy has incomparable advantages over other high-resolution microscopic technologies, such as electron microscopy and atomic force microscopy, in the study of biological molecules, pathways and events in live cells and tissues. We present a novel approach of structured illumination microscopy (SIM) by using a digital micromirror device (DMD) for fringe projection and a low-coherence LED light for illumination. The lateral resolution of 90 nm and the optical sectioning depth of 120 μm were achieved. The maximum acquisition speed for 3D imaging in the optical sectioning mode was 1.6×10(7) pixels/second, which was mainly limited by the sensitivity and speed of the CCD camera. In contrast to other SIM techniques, the DMD-based LED-illumination SIM is cost-effective, ease of multi-wavelength switchable and speckle-noise-free. The 2D super-resolution and 3D optical sectioning modalities can be easily switched and applied to either fluorescent or non-fluorescent specimens.

  14. Ultrafast ultrasound localization microscopy for deep super-resolution vascular imaging

    Science.gov (United States)

    Errico, Claudia; Pierre, Juliette; Pezet, Sophie; Desailly, Yann; Lenkei, Zsolt; Couture, Olivier; Tanter, Mickael

    2015-11-01

    Non-invasive imaging deep into organs at microscopic scales remains an open quest in biomedical imaging. Although optical microscopy is still limited to surface imaging owing to optical wave diffusion and fast decorrelation in tissue, revolutionary approaches such as fluorescence photo-activated localization microscopy led to a striking increase in resolution by more than an order of magnitude in the last decade. In contrast with optics, ultrasonic waves propagate deep into organs without losing their coherence and are much less affected by in vivo decorrelation processes. However, their resolution is impeded by the fundamental limits of diffraction, which impose a long-standing trade-off between resolution and penetration. This limits clinical and preclinical ultrasound imaging to a sub-millimetre scale. Here we demonstrate in vivo that ultrasound imaging at ultrafast frame rates (more than 500 frames per second) provides an analogue to optical localization microscopy by capturing the transient signal decorrelation of contrast agents—inert gas microbubbles. Ultrafast ultrasound localization microscopy allowed both non-invasive sub-wavelength structural imaging and haemodynamic quantification of rodent cerebral microvessels (less than ten micrometres in diameter) more than ten millimetres below the tissue surface, leading to transcranial whole-brain imaging within short acquisition times (tens of seconds). After intravenous injection, single echoes from individual microbubbles were detected through ultrafast imaging. Their localization, not limited by diffraction, was accumulated over 75,000 images, yielding 1,000,000 events per coronal plane and statistically independent pixels of ten micrometres in size. Precise temporal tracking of microbubble positions allowed us to extract accurately in-plane velocities of the blood flow with a large dynamic range (from one millimetre per second to several centimetres per second). These results pave the way for deep non

  15. Dark-field image contrast in transmission scanning electron microscopy: Effects of substrate thickness and detector collection angle

    Energy Technology Data Exchange (ETDEWEB)

    Woehl, Taylor, E-mail: tjwoehl@umd.edu; Keller, Robert

    2016-12-15

    An annular dark field (ADF) detector was placed beneath a specimen in a field emission scanning electron microscope operated at 30 kV to calibrate detector response to incident beam current, and to create transmission images of gold nanoparticles on silicon nitride (SiN) substrates of various thicknesses. Based on the linear response of the ADF detector diodes to beam current, we developed a method that allowed for direct determination of the percentage of that beam current forward scattered to the ADF detector from the sample, i.e. the transmitted electron (TE) yield. Collection angles for the ADF detector region were defined using a masking aperture above the detector and were systematically varied by changing the sample to detector distance. We found the contrast of the nanoparticles, relative to the SiN substrate, decreased monotonically with decreasing inner exclusion angle and increasing substrate thickness. We also performed Monte Carlo electron scattering simulations, which showed quantitative agreement with experimental contrast associated with the nanoparticles. Together, the experiments and Monte Carlo simulations revealed that the decrease in contrast with decreasing inner exclusion angle was due to a rapid increase in the TE yield of the low atomic number substrate. Nanoparticles imaged at low inner exclusion angles (<150 mrad) and on thick substrates (>50 nm) showed low image contrast in their centers surrounded by a bright high-contrast halo on their edges. This complex image contrast was predicted by Monte Carlo simulations, which we interpreted in terms of mixing of the nominally bright field (BF) and ADF electron signals. Our systematic investigation of inner exclusion angle and substrate thickness effects on ADF t-SEM imaging provides fundamental understanding of the contrast mechanisms for image formation, which in turn suggest practical limitations and optimal imaging conditions for different substrate thicknesses. - Highlights: • Developed a

  16. Red blood cell labeling with technetium-99m. Effect of radiopaque contrast agents

    International Nuclear Information System (INIS)

    Finkel, J.; Chervu, L.R.; Bernstein, R.G.; Srivastava, S.C.

    1988-01-01

    Radiographic contrast agents have been reported in the literature to interfere significantly with red blood cell (RBC) labeling in vivo by Tc-99m. Moreover, in the presence of contrast agents, red cells have been known to undergo significant morphologic changes. These observations led to the current RBC labeling study in patients (N = 25) undergoing procedures with the administration of contrast media. Before and after contrast administration, blood samples were drawn from each patient into vacutainer tubes containing heparin and RBC labeling was performed using 1-ml aliquots of these samples following the Brookhaven National Laboratory protocol. The differences in average percentage labeling yield with and without contrast media were not significant. In vivo labeling in hypertensive rats with administration of contrast media up to 600 mg likewise consistently gave high labeling yields at all concentrations. Purported alterations in cell labeling attributed to contrast agents are not reflected in these studies, and other pathophysiologic factors need to be identified to substantiate the previous reports. In vitro study offers a potentially useful and simple method to delineate effects of various agents on cell labeling

  17. Communications in interference limited networks

    CERN Document Server

    2016-01-01

    This book offers means to handle interference as a central problem of operating wireless networks. It investigates centralized and decentralized methods to avoid and handle interference as well as approaches that resolve interference constructively. The latter type of approach tries to solve the joint detection and estimation problem of several data streams that share a common medium. In fact, an exciting insight into the operation of networks is that it may be beneficial, in terms of an overall throughput, to actively create and manage interference. Thus, when handled properly, "mixing" of data in networks becomes a useful tool of operation rather than the nuisance as which it has been treated traditionally. With the development of mobile, robust, ubiquitous, reliable and instantaneous communication being a driving and enabling factor of an information centric economy, the understanding, mitigation and exploitation of interference in networks must be seen as a centrally important task.

  18. Stereo soft x-ray microscopy and elemental mapping of hematite and clay suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Gleber, S.-C.; Thieme, J.; Chao, W.; Fischer, P.

    2008-09-01

    The spatial arrangements of hematite particles within aqueous soil and clay samples are investigated with soft X-ray microscopy, taking advantage of the elemental contrast at the Fe-L edge around E = 707 eV. In combination with stereo microscopy, information about spatial arrangements are revealed and correlated to electrostatic interactions of the different mixtures. Manipulation of a sample mounted to the microscope is possible and particles added while imaging can be detected.

  19. In Situ Scanning Probe Microscopy and New Perspectives in Analytical Chemistry

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Zhang, Jingdong; Chi, Qijin

    1999-01-01

    The resolution of scanning probe microscopies is unpresedented but the techniques are fraught with limitations as analytical tools. These limitations and their relationship to the physical mechanisms of image contrast are first discussed. Some new options based on in situ STM, which hold prospect...

  20. Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

    International Nuclear Information System (INIS)

    Glaeser, Robert M.

    2013-01-01

    Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics

  1. The Approximate Capacity Region of the Symmetric $K$-user Gaussian Interference Channel with Strong Interference

    KAUST Repository

    Chaaban, Anas

    2016-03-01

    The symmetric K-user interference channel is studied with the goal of characterizing its capacity region in the strong interference regime within a constant gap. The achievable rate region of a scheme combining rate-splitting at the transmitters and interference alignment and successive decoding/computation at the receivers is derived. Next it is shown that this scheme achieves the so-called greedy-max corner points of the capacity region within a constant gap. By combining this result with previous results by Ordentlich et al. on the sum-capacity of the symmetric interference channel, a constant gap characterization of the capacity region for the strong interference regime is obtained. This leads to the first approximate characterization of the capacity region of the symmetric K-user IC. Furthermore, a new scheme that achieves the sum-capacity of the channel in the strong interference regime within a constant gap is also proposed, and the corresponding gap is calculated. The advantage of the new scheme is that it leads to a characterization within a constant gap without leaving an outage set contrary to the scheme by Ordentlich et al..

  2. The Approximate Capacity Region of the Symmetric $K$-user Gaussian Interference Channel with Strong Interference

    KAUST Repository

    Chaaban, Anas; Sezgin, Aydin

    2016-01-01

    The symmetric K-user interference channel is studied with the goal of characterizing its capacity region in the strong interference regime within a constant gap. The achievable rate region of a scheme combining rate-splitting at the transmitters and interference alignment and successive decoding/computation at the receivers is derived. Next it is shown that this scheme achieves the so-called greedy-max corner points of the capacity region within a constant gap. By combining this result with previous results by Ordentlich et al. on the sum-capacity of the symmetric interference channel, a constant gap characterization of the capacity region for the strong interference regime is obtained. This leads to the first approximate characterization of the capacity region of the symmetric K-user IC. Furthermore, a new scheme that achieves the sum-capacity of the channel in the strong interference regime within a constant gap is also proposed, and the corresponding gap is calculated. The advantage of the new scheme is that it leads to a characterization within a constant gap without leaving an outage set contrary to the scheme by Ordentlich et al..

  3. Contributed review: Review of integrated correlative light and electron microscopy.

    Science.gov (United States)

    Timmermans, F J; Otto, C

    2015-01-01

    New developments in the field of microscopy enable to acquire increasing amounts of information from large sample areas and at an increased resolution. Depending on the nature of the technique, the information may reveal morphological, structural, chemical, and still other sample characteristics. In research fields, such as cell biology and materials science, there is an increasing demand to correlate these individual levels of information and in this way to obtain a better understanding of sample preparation and specific sample properties. To address this need, integrated systems were developed that combine nanometer resolution electron microscopes with optical microscopes, which produce chemically or label specific information through spectroscopy. The complementary information from electron microscopy and light microscopy presents an opportunity to investigate a broad range of sample properties in a correlated fashion. An important part of correlating the differences in information lies in bridging the different resolution and image contrast features. The trend to analyse samples using multiple correlated microscopes has resulted in a new research field. Current research is focused, for instance, on (a) the investigation of samples with nanometer scale distribution of inorganic and organic materials, (b) live cell analysis combined with electron microscopy, and (c) in situ spectroscopic and electron microscopy analysis of catalytic materials, but more areas will benefit from integrated correlative microscopy.

  4. Contributed Review: Review of integrated correlative light and electron microscopy

    International Nuclear Information System (INIS)

    Timmermans, F. J.; Otto, C.

    2015-01-01

    New developments in the field of microscopy enable to acquire increasing amounts of information from large sample areas and at an increased resolution. Depending on the nature of the technique, the information may reveal morphological, structural, chemical, and still other sample characteristics. In research fields, such as cell biology and materials science, there is an increasing demand to correlate these individual levels of information and in this way to obtain a better understanding of sample preparation and specific sample properties. To address this need, integrated systems were developed that combine nanometer resolution electron microscopes with optical microscopes, which produce chemically or label specific information through spectroscopy. The complementary information from electron microscopy and light microscopy presents an opportunity to investigate a broad range of sample properties in a correlated fashion. An important part of correlating the differences in information lies in bridging the different resolution and image contrast features. The trend to analyse samples using multiple correlated microscopes has resulted in a new research field. Current research is focused, for instance, on (a) the investigation of samples with nanometer scale distribution of inorganic and organic materials, (b) live cell analysis combined with electron microscopy, and (c) in situ spectroscopic and electron microscopy analysis of catalytic materials, but more areas will benefit from integrated correlative microscopy

  5. Applications of phase-contrast x-ray imaging to medicine using an x-ray interferometer

    Science.gov (United States)

    Momose, Atsushi; Yoneyama, Akio; Takeda, Tohoru; Itai, Yuji; Tu, Jinhong; Hirano, Keiichi

    1999-10-01

    We are investigating possible medical applications of phase- contrast X-ray imaging using an X-ray interferometer. This paper introduces the strategy of the research project and the present status. The main subject is to broaden the observation area to enable in vivo observation. For this purpose, large X-ray interferometers were developed, and 2.5 cm X 1.5 cm interference patterns were generated using synchrotron X-rays. An improvement of the spatial resolution is also included in the project, and an X-ray interferometer designed for high-resolution phase-contrast X-ray imaging was fabricated and tested. In parallel with the instrumental developments, various soft tissues are observed by phase- contrast X-ray CT to find correspondence between the generated contrast and our histological knowledge. The observation done so far suggests that cancerous tissues are differentiated from normal tissues and that blood can produce phase contrast. Furthermore, this project includes exploring materials that modulate phase contrast for selective imaging.

  6. The componential processing of fractions in adults and children: effects of stimuli variability and contextual interference.

    Science.gov (United States)

    Zhang, Li; Fang, Qiaochu; Gabriel, Florence C; Szücs, Dénes

    2014-01-01

    Recent studies have indicated that people have a strong tendency to compare fractions based on constituent numerators or denominators. This is called componential processing. This study explored whether componential processing was preferred in tasks involving high stimuli variability and high contextual interference, when fractions could be compared based either on the holistic values of fractions or on their denominators. Here, stimuli variability referred to the fact that fractions were not monotonous but diversiform. Contextual interference referred to the fact that the processing of fractions was interfered by other stimuli. To our ends, three tasks were used. In Task 1, participants compared a standard fraction 1/5 to unit fractions. This task was used as a low stimuli variability and low contextual interference task. In Task 2 stimuli variability was increased by mixing unit and non-unit fractions. In Task 3, high contextual interference was created by incorporating decimals into fractions. The RT results showed that the processing patterns of fractions were very similar for adults and children. In task 1 and task 3, only componential processing was utilzied. In contrast, both holistic processing and componential processing were utilized in task 2. These results suggest that, if individuals are presented with the opportunity to perform componential processing, both adults and children will tend to do so, even if they are faced with high variability of fractions or high contextual interference.

  7. Origins of phase contrast in the atomic force microscope in liquids.

    Science.gov (United States)

    Melcher, John; Carrasco, Carolina; Xu, Xin; Carrascosa, José L; Gómez-Herrero, Julio; José de Pablo, Pedro; Raman, Arvind

    2009-08-18

    We study the physical origins of phase contrast in dynamic atomic force microscopy (dAFM) in liquids where low-stiffness microcantilever probes are often used for nanoscale imaging of soft biological samples with gentle forces. Under these conditions, we show that the phase contrast derives primarily from a unique energy flow channel that opens up in liquids due to the momentary excitation of higher eigenmodes. Contrary to the common assumption, phase-contrast images in liquids using soft microcantilevers are often maps of short-range conservative interactions, such as local elastic response, rather than tip-sample dissipation. The theory is used to demonstrate variations in local elasticity of purple membrane and bacteriophage 29 virions in buffer solutions using the phase-contrast images.

  8. Contrast of Backscattered Electron SEM Images of Nanoparticles on Substrates with Complex Structure

    Directory of Open Access Journals (Sweden)

    Thomas Kowoll

    2017-01-01

    Full Text Available This study is concerned with backscattered electron scanning electron microscopy (BSE SEM contrast of complex nanoscaled samples which consist of SiO2 nanoparticles (NPs deposited on indium-tin-oxide covered bulk SiO2 and glassy carbon substrates. BSE SEM contrast of NPs is studied as function of the primary electron energy and working distance. Contrast inversions are observed which prevent intuitive interpretation of NP contrast in terms of material contrast. Experimental data is quantitatively compared with Monte-Carlo- (MC- simulations. Quantitative agreement between experimental data and MC-simulations is obtained if the transmission characteristics of the annular semiconductor detector are taken into account. MC-simulations facilitate the understanding of NP contrast inversions and are helpful to derive conditions for optimum material and topography contrast.

  9. Interference-exact radiative transfer equation

    DEFF Research Database (Denmark)

    Partanen, Mikko; Haÿrynen, Teppo; Oksanen, Jani

    2017-01-01

    Maxwell's equations with stochastic or quantum optical source terms accounting for the quantum nature of light. We show that both the nonlocal wave and local particle features associated with interference and emission of propagating fields in stratified geometries can be fully captured by local damping...... and scattering coefficients derived from the recently introduced quantized fluctuational electrodynamics (QFED) framework. In addition to describing the nonlocal optical interference processes as local directionally resolved effects, this allows reformulating the well known and widely used radiative transfer...... equation (RTE) as a physically transparent interference-exact model that extends the useful range of computationally efficient and quantum optically accurate interference-aware optical models from simple structures to full optical devices....

  10. Labeling Human Mesenchymal Stem Cells with Gold Nanocages for in vitro and in vivo Tracking by Two-Photon Microscopy and Photoacoustic Microscopy

    Science.gov (United States)

    Zhang, Yu Shrike; Wang, Yu; Wang, Lidai; Wang, Yucai; Cai, Xin; Zhang, Chi; Wang, Lihong V.; Xia, Younan

    2013-01-01

    Stem cell tracking is a highly important subject. Current techniques based on nanoparticle-labeling, such as magnetic resonance imaging, fluorescence microscopy, and micro-computed tomography, are plagued by limitations including relatively low sensitivity or penetration depth, involvement of ionizing irradiation, and potential cytotoxicity of the nanoparticles. Here we introduce a new class of contrast agents based on gold nanocages (AuNCs) with hollow interiors and porous walls to label human mesenchymal stem cells (hMSCs) for both in vitro and in vivo tracking using two-photon microscopy and photoacoustic microscopy. As demonstrated by the viability assay, the AuNCs showed negligible cytotoxicity under a reasonable dose, and did not alter the differentiation potential of the hMSCs into desired lineages. We were able to image the cells labeled with AuNCs in vitro for at least 28 days in culture, as well as to track the cells that homed to the tumor region in nude mice in vivo. PMID:23946820

  11. Torsional resonance mode magnetic force microscopy: enabling higher lateral resolution magnetic imaging without topography-related effects

    International Nuclear Information System (INIS)

    Kaidatzis, A; García-Martín, J M

    2013-01-01

    We present experimental work that reveals the benefits of performing magnetic force microscopy measurements employing the torsional resonance mode of cantilever oscillation. This approach provides two clear advantages: the ability of performing magnetic imaging without topography-related interference and the significant lateral resolution improvement (approximately 15%). We believe that this work demonstrates a significant improvement to a versatile magnetic imaging technique widely used in academia and in industry. (paper)

  12. Laser self-mixing interference fibre sensor

    International Nuclear Information System (INIS)

    Zhu Jun; Zhao Yan; Jin Guofan

    2008-01-01

    Fibre sensors exhibit a number of advantages over other sensors such as high sensitivity, electric insulation, corrosion resistance, interference rejection and so on. And laser self-mixing interference can accurately detect the phase difference of feedback light. In this paper, a novel laser self-mixing interference fibre sensor that combines the advantages of fibre sensors with those of laser self-mixing interference is presented. Experimental configurations are set up to study the relationship between laser power output and phase of laser feedback light when the fibre trembles or when the fibre is stretched or pressed. The theoretical analysis of pressure sensors based on laser self-mixing interference is indicated to accord with the experimental results. (classical areas of phenomenology)

  13. 47 CFR 27.1221 - Interference protection.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Interference protection. 27.1221 Section 27... Technical Standards § 27.1221 Interference protection. (a) Interference protection will be afforded to BRS... height benchmark (hbm). (c) Protection for Receiving Antennas not Exceeding the Height Benchmark. Absent...

  14. Binaural Interference: Quo Vadis?

    Science.gov (United States)

    Jerger, James; Silman, Shlomo; Silverman, Carol; Emmer, Michele

    2017-04-01

    The reality of the phenomenon of binaural interference with speech recognition has been debated for two decades. Research has taken one of two avenues; group studies or case reports. In group studies, a sample of the elderly population is tested on speech recognition under three conditions; binaural, monaural right and monaural left. The aim is to determine the percent of the sample in which the expected outcome (binaural score-better-than-either-monaural score) is reversed (i.e., one of the monaural scores is better than the binaural score). This outcome has been commonly used to define binaural interference. The object of group studies is to answer the "how many" question, what is the prevalence of binaural interference in the sample. In case reports the binaural interference conclusion suggested by the speech recognition tests is not accepted until it has been corroborated by other independent diagnostic audiological measures. The aim is to attempt to determine the basis for the findings, to answer the "why" question. This article is at once tutorial, editorial and a case report. We argue that it is time to accept the reality of the phenomenon of binaural interference, to eschew group statistical approaches in search of an answer to the "how many" question, and to focus on individual case reports in search of an answer to the "why" question. American Academy of Audiology.

  15. Scanning electron microscopy of semiconductor materials

    International Nuclear Information System (INIS)

    Bresse, J.F.; Dupuy, M.

    1978-01-01

    The use of scanning electron microscopy in semiconductors opens up a large field of use. The operating modes lending themselves to the study of semiconductors are the induced current, cathodoluminescence and the use of the potential contrast which can also be applied very effectively to the study of the devices (planar in particular). However, a thorough knowledge of the mechanisms of the penetration of electrons, generation and recombination of generated carriers in a semiconductor is necessary in order to attain a better understanding of the operating modes peculiar to semiconductors [fr

  16. Transmission electron microscope examination of rare-gas bubbles in metals: analysis of observed contrast effects

    International Nuclear Information System (INIS)

    Levy, V.

    1964-01-01

    Metallic samples containing rare gas bubbles have been examined by transmission electron microscopy. The different features of the contrast patterns of the bubbles have been explained by the dynamical theory of contrast, assuming that the bubble behaves as a hole in the metal. Experimental results are in good agreement with the theory. (author) [fr

  17. On the Progress of Scanning Transmission Electron Microscopy (STEM) Imaging in a Scanning Electron Microscope.

    Science.gov (United States)

    Sun, Cheng; Müller, Erich; Meffert, Matthias; Gerthsen, Dagmar

    2018-04-01

    Transmission electron microscopy (TEM) with low-energy electrons has been recognized as an important addition to the family of electron microscopies as it may avoid knock-on damage and increase the contrast of weakly scattering objects. Scanning electron microscopes (SEMs) are well suited for low-energy electron microscopy with maximum electron energies of 30 keV, but they are mainly used for topography imaging of bulk samples. Implementation of a scanning transmission electron microscopy (STEM) detector and a charge-coupled-device camera for the acquisition of on-axis transmission electron diffraction (TED) patterns, in combination with recent resolution improvements, make SEMs highly interesting for structure analysis of some electron-transparent specimens which are traditionally investigated by TEM. A new aspect is correlative SEM, STEM, and TED imaging from the same specimen region in a SEM which leads to a wealth of information. Simultaneous image acquisition gives information on surface topography, inner structure including crystal defects and qualitative material contrast. Lattice-fringe resolution is obtained in bright-field STEM imaging. The benefits of correlative SEM/STEM/TED imaging in a SEM are exemplified by structure analyses from representative sample classes such as nanoparticulates and bulk materials.

  18. Correlative Stochastic Optical Reconstruction Microscopy and Electron Microscopy

    Science.gov (United States)

    Kim, Doory; Deerinck, Thomas J.; Sigal, Yaron M.; Babcock, Hazen P.; Ellisman, Mark H.; Zhuang, Xiaowei

    2015-01-01

    Correlative fluorescence light microscopy and electron microscopy allows the imaging of spatial distributions of specific biomolecules in the context of cellular ultrastructure. Recent development of super-resolution fluorescence microscopy allows the location of molecules to be determined with nanometer-scale spatial resolution. However, correlative super-resolution fluorescence microscopy and electron microscopy (EM) still remains challenging because the optimal specimen preparation and imaging conditions for super-resolution fluorescence microscopy and EM are often not compatible. Here, we have developed several experiment protocols for correlative stochastic optical reconstruction microscopy (STORM) and EM methods, both for un-embedded samples by applying EM-specific sample preparations after STORM imaging and for embedded and sectioned samples by optimizing the fluorescence under EM fixation, staining and embedding conditions. We demonstrated these methods using a variety of cellular targets. PMID:25874453

  19. An accumulator model of semantic interference

    NARCIS (Netherlands)

    van Maanen, Leendert; van Rijn, Hedderik

    To explain latency effects in picture-word interference tasks, cognitive models need to account for both interference and stimulus onset asynchrony (SOA) effects. As opposed to most models of picture-word interference, which model the time course during the task in a ballistic manner, the RACE model

  20. (Sub-)Optimality of Treating Interference as Noise in the Cellular Uplink With Weak Interference

    KAUST Repository

    Gherekhloo, Soheil; Chaaban, Anas; Di, Chen; Sezgin, Aydin

    2015-01-01

    Despite the simplicity of the scheme of treating interference as noise (TIN), it was shown to be sum-capacity optimal in the Gaussian interference channel (IC) with very-weak (noisy) interference. In this paper, the two-user IC is altered by introducing an additional transmitter that wants to communicate with one of the receivers of the IC. The resulting network thus consists of a point-to-point channel interfering with a multiple access channel (MAC) and is denoted by PIMAC. The sum-capacity of the PIMAC is studied with main focus on the optimality of TIN. It turns out that TIN in its naive variant, where all transmitters are active and both receivers use TIN for decoding, is not the best choice for the PIMAC. In fact, a scheme that combines both time division multiple access and TIN (TDMA-TIN) strictly outperforms the naive-TIN scheme. Furthermore, it is shown that in some regimes, TDMA-TIN achieves the sum-capacity for the deterministic PIMAC and the sum-capacity within a constant gap for the Gaussian PIMAC. In addition, it is shown that, even for very-weak interference, there are some regimes where a combination of interference alignment with power control and TIN at the receiver side outperforms TDMA-TIN. As a consequence, on the one hand, TIN in a cellular uplink is approximately optimal in certain regimes. On the other hand, those regimes cannot be simply described by the strength of interference.

  1. (Sub-)Optimality of Treating Interference as Noise in the Cellular Uplink With Weak Interference

    KAUST Repository

    Gherekhloo, Soheil

    2015-11-09

    Despite the simplicity of the scheme of treating interference as noise (TIN), it was shown to be sum-capacity optimal in the Gaussian interference channel (IC) with very-weak (noisy) interference. In this paper, the two-user IC is altered by introducing an additional transmitter that wants to communicate with one of the receivers of the IC. The resulting network thus consists of a point-to-point channel interfering with a multiple access channel (MAC) and is denoted by PIMAC. The sum-capacity of the PIMAC is studied with main focus on the optimality of TIN. It turns out that TIN in its naive variant, where all transmitters are active and both receivers use TIN for decoding, is not the best choice for the PIMAC. In fact, a scheme that combines both time division multiple access and TIN (TDMA-TIN) strictly outperforms the naive-TIN scheme. Furthermore, it is shown that in some regimes, TDMA-TIN achieves the sum-capacity for the deterministic PIMAC and the sum-capacity within a constant gap for the Gaussian PIMAC. In addition, it is shown that, even for very-weak interference, there are some regimes where a combination of interference alignment with power control and TIN at the receiver side outperforms TDMA-TIN. As a consequence, on the one hand, TIN in a cellular uplink is approximately optimal in certain regimes. On the other hand, those regimes cannot be simply described by the strength of interference.

  2. Polarization contrast in reflection near-field optical microscopy with uncoated fibre tips

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Langbein, Wolfgang; Hvam, Jørn Märcher

    1999-01-01

    Using cross-hatched, patterned semiconductor surfaces and round 20-nm-thick gold pads on semiconductor wafers, we investigate the imaging characteristics of a reflection near-field optical microscope with an uncoated fibre tip for different polarization configurations and light wavelengths....... Is is shown that cross-polarized detection allows one to effectively suppress far-field components in the detected signal and to realise imaging of optical contrast on the sub-wavelength scale. The sensitivity window of our microscope, i.e. the scale on which near-field optical images represent mainly optical...

  3. B-Spline potential function for maximum a-posteriori image reconstruction in fluorescence microscopy

    Directory of Open Access Journals (Sweden)

    Shilpa Dilipkumar

    2015-03-01

    Full Text Available An iterative image reconstruction technique employing B-Spline potential function in a Bayesian framework is proposed for fluorescence microscopy images. B-splines are piecewise polynomials with smooth transition, compact support and are the shortest polynomial splines. Incorporation of the B-spline potential function in the maximum-a-posteriori reconstruction technique resulted in improved contrast, enhanced resolution and substantial background reduction. The proposed technique is validated on simulated data as well as on the images acquired from fluorescence microscopes (widefield, confocal laser scanning fluorescence and super-resolution 4Pi microscopy. A comparative study of the proposed technique with the state-of-art maximum likelihood (ML and maximum-a-posteriori (MAP with quadratic potential function shows its superiority over the others. B-Spline MAP technique can find applications in several imaging modalities of fluorescence microscopy like selective plane illumination microscopy, localization microscopy and STED.

  4. Explicit attention interferes with selective emotion processing in human extrastriate cortex

    Directory of Open Access Journals (Sweden)

    Junghöfer Markus

    2007-02-01

    Full Text Available Abstract Background Brain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN for pleasant and unpleasant compared to neutral images (~150–300 ms poststimulus. The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands. Results Participants successfully performed the primary visual attention task as revealed by behavioral performance and selected event-related potential components (Selection Negativity and P3b. Replicating previous results, emotional modulation of the EPN was observed in a task condition with low processing demands. In contrast, pleasant and unpleasant pictures failed to elicit increased EPN amplitudes compared to neutral images in more difficult explicit attention task conditions. Further analyses determined that even the processing of pleasant and unpleasant pictures high in emotional arousal is subject to interference in experimental conditions with high task demand. Taken together, performing demanding feature-based counting tasks interfered with differential emotion processing indexed by the EPN. Conclusion The present findings demonstrate that taxing processing resources by a competing primary visual attention task markedly attenuated the early discrimination of emotional from neutral picture contents. Thus, these results provide further empirical support for an interference account of the emotion-attention interaction under conditions of competition. Previous studies revealed the interference of selective emotion processing when attentional resources were directed to locations of explicitly task

  5. Explicit attention interferes with selective emotion processing in human extrastriate cortex.

    Science.gov (United States)

    Schupp, Harald T; Stockburger, Jessica; Bublatzky, Florian; Junghöfer, Markus; Weike, Almut I; Hamm, Alfons O

    2007-02-22

    Brain imaging and event-related potential studies provide strong evidence that emotional stimuli guide selective attention in visual processing. A reflection of the emotional attention capture is the increased Early Posterior Negativity (EPN) for pleasant and unpleasant compared to neutral images (approximately 150-300 ms poststimulus). The present study explored whether this early emotion discrimination reflects an automatic phenomenon or is subject to interference by competing processing demands. Thus, emotional processing was assessed while participants performed a concurrent feature-based attention task varying in processing demands. Participants successfully performed the primary visual attention task as revealed by behavioral performance and selected event-related potential components (Selection Negativity and P3b). Replicating previous results, emotional modulation of the EPN was observed in a task condition with low processing demands. In contrast, pleasant and unpleasant pictures failed to elicit increased EPN amplitudes compared to neutral images in more difficult explicit attention task conditions. Further analyses determined that even the processing of pleasant and unpleasant pictures high in emotional arousal is subject to interference in experimental conditions with high task demand. Taken together, performing demanding feature-based counting tasks interfered with differential emotion processing indexed by the EPN. The present findings demonstrate that taxing processing resources by a competing primary visual attention task markedly attenuated the early discrimination of emotional from neutral picture contents. Thus, these results provide further empirical support for an interference account of the emotion-attention interaction under conditions of competition. Previous studies revealed the interference of selective emotion processing when attentional resources were directed to locations of explicitly task-relevant stimuli. The present data suggest

  6. Bright-field scanning confocal electron microscopy using a double aberration-corrected transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Peng; Behan, Gavin; Kirkland, Angus I. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Nellist, Peter D., E-mail: peter.nellist@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Cosgriff, Eireann C.; D' Alfonso, Adrian J.; Morgan, Andrew J.; Allen, Leslie J. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Hashimoto, Ayako [Advanced Nano-characterization Center, National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba 305-0003 (Japan); Takeguchi, Masaki [Advanced Nano-characterization Center, National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba 305-0003 (Japan); High Voltage Electron Microscopy Station, NIMS, 3-13 Sakura, Tsukuba 305-0003 (Japan); Mitsuishi, Kazutaka [Advanced Nano-characterization Center, National Institute for Materials Science (NIMS), 3-13 Sakura, Tsukuba 305-0003 (Japan); Quantum Dot Research Center, NIMS, 3-13 Sakura, Tsukuba 305-0003 (Japan); Shimojo, Masayuki [High Voltage Electron Microscopy Station, NIMS, 3-13 Sakura, Tsukuba 305-0003 (Japan); Advanced Science Research Laboratory, Saitama Institute of Technology, 1690 Fusaiji, Fukaya 369-0293 (Japan)

    2011-06-15

    Scanning confocal electron microscopy (SCEM) offers a mechanism for three-dimensional imaging of materials, which makes use of the reduced depth of field in an aberration-corrected transmission electron microscope. The simplest configuration of SCEM is the bright-field mode. In this paper we present experimental data and simulations showing the form of bright-field SCEM images. We show that the depth dependence of the three-dimensional image can be explained in terms of two-dimensional images formed in the detector plane. For a crystalline sample, this so-called probe image is shown to be similar to a conventional diffraction pattern. Experimental results and simulations show how the diffracted probes in this image are elongated in thicker crystals and the use of this elongation to estimate sample thickness is explored. -- Research Highlights: {yields} The confocal probe image in a scanning confocal electron microscopy image reveals information about the thickness and height of the crystalline layer. {yields} The form of the contrast in a three-dimensional bright-field scanning confocal electron microscopy image can be explained in terms of the confocal probe image. {yields} Despite the complicated form of the contrast in bright-field scanning confocal electron microscopy, we see that depth information is transferred on a 10 nm scale.

  7. X-ray microscopy study of track membranes and biological objects

    International Nuclear Information System (INIS)

    Artioukov, I.A.; Levashov, V.E.; Struk, I.I.; Vinogradov, A.V.; Asadchikov, V.E.; Mchedlishvili, B.V.; Postnov, A.A.; Vilensky, A.I.; Zagorsky, D.L.; Gulimova, V.I.; Saveliev, S.V.; Kurohtin, A.N.; Popov, A.V.

    2000-01-01

    The development of two types of X-ray microscopy applying to the organic objects investigation (biological samples and polymer matrix) is reported. Polymer track membranes were investigated using Schwarzchild X-ray microscope with 20 nm wavelength. Pore diameters down to 0.2 μm were clearly imaged. Contact X-ray microscopy at 0.229 nm wavelength was used to obtain clear images of inner structure of native biological samples. High contrast together with the high resolution (about 2-3 μm) allowed us to use this method for quantitative analysis of demineralization process taking place in the skeleton of amphibious after several weeks of weightlessness on biosputnik board

  8. Correlative Analysis of Immunoreactivity in Confocal Laser-Scanning Microscopy and Scanning Electron Microscopy with Focused Ion Beam Milling

    Directory of Open Access Journals (Sweden)

    Takahiro eSonomura

    2013-02-01

    Full Text Available Three-dimensional reconstruction of ultrastructure of rat brain with minimal effort has recently been realized by scanning electron microscopy combined with focused ion beam milling (FIB-SEM. Because application of immunohistochemical staining to electron microscopy has a great advantage in that molecules of interest are specifically localized in ultrastructures, we here tried to apply immunocytochemistry to FIB-SEM and correlate immunoreactivity in confocal laser-scanning microcopy (CF-LSM with that in FIB-SEM. The dendrites of medium-sized spiny neurons in rat neostriatum were visualized with a recombinant viral vector, which labeled the infected neurons with membrane-targeted GFP in a Golgi stain-like fashion, and thalamostriatal afferent terminals were immunolabeled with Cy5 fluorescence for vesicular glutamate transporter 2 (VGluT2. After detecting the sites of terminals apposed to the dendrites in CF-LSM, GFP and VGluT2 immunoreactivities were further developed for electron microscopy by the immunogold/silver enhancement and immunoperoxidase/diaminobenzidine (DAB methods, respectively. In the contrast-inverted FIB-SEM images, silver precipitation and DAB deposits were observed as fine dark grains and diffuse dense profiles, respectively, indicating that these immunoreactivities were easily recognizable as in the images of transmission electron microscopy. In the sites of interest, some appositions were revealed to display synaptic specialization of asymmetric type. The present method is thus useful in the three-dimensional analysis of immunocytochemically differentiated synaptic connection in the central neural circuit.

  9. Using Interference to Block RFID Tags

    DEFF Research Database (Denmark)

    Krigslund, Rasmus; Popovski, Petar; Pedersen, Gert Frølund

    We propose a novel method to block RFID tags from responding, using intentional interference. We focus on the experimental evaluation, where we impose interference on the download and uplink, respectively. The results are positive, where modulated CCI shows most effective to block a tag.......We propose a novel method to block RFID tags from responding, using intentional interference. We focus on the experimental evaluation, where we impose interference on the download and uplink, respectively. The results are positive, where modulated CCI shows most effective to block a tag....

  10. Use of hydrogen-deuterium exchange for contrast in {sup 1}H NMR microscopy investigations of an operating PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Feindel, Kirk W.; Bergens, Steven H.; Wasylishen, Roderick E. [Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alta. T6G 2G2 (Canada)

    2007-11-08

    The use of hydrogen-deuterium (H-D) exchange as a method to introduce contrast in {sup 1}H NMR microscopy images and to investigate the dynamic distribution of water throughout an operating H{sub 2}/O{sub 2} polymer electrolyte membrane fuel cell, PEMFC, is demonstrated. Cycling D{sub 2}O(l) through the flow channels of a PEMFC causes H-D exchange with water in the PEM to result in a D{sub 2}O-saturated PEM and thus concomitant removal of the {sup 1}H NMR signal. Subsequent operation of the PEMFC with H{sub 2}(g) enables visualization of the redistribution of water from wet or flooded conditions as H-D exchange occurs with D{sub 2}O in the PEM and results in recovery of the {sup 1}H NMR signal. Alternating between H{sub 2}(g) and D{sub 2}(g) as fuel allows observation of water distributions in the PEM while the cell is operating at a steady-state under low relative humidity. At similar currents, the rate of observable H-D exchange in the PEM during fuel cell operation was faster when the PEM was saturated with water than when under low relative humidity. These results are consistent with the known proportions of the conductive hydrophilic and nonconductive hydrophobic domains of Nafion when exposed to different relative humidities. (author)

  11. US patent interferences vs. international first-to-file patent systems, and current GATT problems

    International Nuclear Information System (INIS)

    Parkhurst, R.W.; Serbinowski, P.A.

    1991-01-01

    Simultaneous superconductivity research activities by different entities have resulted in numerous US patent applications, some of which may claim identical inventions and thus likely will be involved in interference proceedings in the US Patent and Trademark Office to determine which inventors are entitled to priority of invention and the resulting US patent. The determination in an interference proceeding of what inventors were the first-to-invent a patentable invention is contrasted with the patent systems in the rest of the world where the first inventor to file his patent application automatically gains priority. This issue and other aspects of US patent law are the subjects of criticism of US patent law and practice in the current Uruguay round of talks on the General Agreement on Trade and Tariffs (GATT). Interesting aspects of each of these subjects will be discussed

  12. Optical interference with noncoherent states

    International Nuclear Information System (INIS)

    Sagi, Yoav; Firstenberg, Ofer; Fisher, Amnon; Ron, Amiram

    2003-01-01

    We examine a typical two-source optical interference apparatus consisting of two cavities, a beam splitter, and two detectors. We show that field-field interference occurs even when the cavities are not initially in coherent states but rather in other nonclassical states. However, we find that the visibility of the second-order interference, that is, the expectation values of the detectors' readings, changes from 100%, when the cavities are prepared in coherent states, to zero visibility when they are initially in single Fock states. We calculate the fourth-order interference, and for the latter case find that it corresponds to a case where the currents oscillate with 100% visibility, but with a random phase for every experiment. Finally, we suggest an experimental realization of the apparatus with nonclassical sources

  13. Interference management using direct sequence spread spectrum ...

    African Journals Online (AJOL)

    Interference management using direct sequence spread spectrum (DSSS) technique ... Journal of Fundamental and Applied Sciences ... Keywords: DSSS, LTE network; Wi-Fi network; SINR; interference management and interference power.

  14. The feasibility of a targeted ultrasound contrast agent carrying genes and cell-penetrating peptides to hypoxic HUVEC

    International Nuclear Information System (INIS)

    Tian Ju; Wang Zhigang; Ren Jianli; Zhang Qingfeng; Liu Li

    2012-01-01

    Objective: To prepare an anti-P-selectin targeted ultrasound contrast agent carrying genes and cell-penetrating peptides (CPP) and to investigate its feasibility of delivery to hypoxic human umbilical vein endothelial cells (HUVEC). Methods: Anti-P-selectin targeted ultrasound contrast agent carrying a green fluorescent protein gene (pEGFP-N1) and CPP was prepared by mechanical vibration and carbodiimide techniques. The appearance, distribution, concentration and diameter of the ultrasound contrast agent were measured. The gene and CPP distribution on the agent was investigated using confocal laser scanning microscopy (CLSM). The efficiency of the ultrasound contrast agent to carry the gene and CPP was investigated by fluorospectrophotometry. HUVEC were cultured in vitro and hypoxic HUVEC were prepared using hydrogen peroxide (H 2 O 2 ). Hypoxic HUVEC were randomly assigned targeted ultrasound contrast agents and non-targeted ultrasound contrast agents for transfection. The transfection effect of green fluorescent protein in the two groups was observed using fluorescence microscopy and flow cytometry. T-test and linear correlation analysis were used for statistical analysis. Results: The average diameter of anti-P-selectin targeted ultrasound contrast agents carrying gene and CPP was (2.15 ±0.36) μm and the concentration was (1.58 ± 0.23) × 10 7 /ml.The results of CLSM showed that gene and CPP were distributed on the shell of the agent. The gene encapsulation efficiency was 28% (y=0.932x-0.09, r=0.993, P<0.05), and the CPP encapsulation efficiency was 25% (y=5.875x-0.81, r=0.987, P<0.05). EGFP expression was observed using fluorescence microscopy in targeted ultrasound contrast agents and non-targeted ultrasound contrast agents. The average transfection efficiencies of targeted ultrasound contrast agents and non-targeted ultrasound contrast agents were (18.74 ± 0.47) % and (15.34 ± 0.22) % after 24 h (t=10.923, P<0.001). Conclusions: The in vitro studies

  15. Exploring semiconductor quantum dots and wires by high resolution electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Molina, S I [Departamento de Ciencia de los Materiales e Ing Metalurgica y Q. Inorganica, F. de Ciencias, Universidad de Cadiz, Campus Rio San Pedro. 11510 Puerto Real (Cadiz) (Spain); Galindo, P L [Departamento de Lenguajes y Sistemas Informaticos, CASEM, Universidad de Cadiz, Campus Rio San Pedro. 11510 Puerto Real (Cadiz) (Spain); Gonzalez, L; Ripalda, J M [Instituto de Microelectronica de Madrid (CNM, CSIC), Isaac Newton 8, 28760 Tres Cantos, Madrid (Spain); Varela, M; Pennycook, S J, E-mail: sergio.molina@uca.e [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 (United States)

    2010-02-01

    We review in this communication our contribution to the structural characterisation of semiconductor quantum dots and wires by high resolution electron microscopy, both in phase-contrast and Z-contrast modes. We show how these techniques contribute to predict the preferential sites of nucleation of these nanostructures, and also determine the compositional distribution in 1D and 0D nanostructures. The results presented here were produced in the framework of the European Network of Excellence entitled {sup S}elf-Assembled semiconductor Nanostructures for new Devices in photonics and Electronics (SANDiE){sup .}

  16. Cell motility dynamics: a novel segmentation algorithm to quantify multi-cellular bright field microscopy images.

    Directory of Open Access Journals (Sweden)

    Assaf Zaritsky

    Full Text Available Confocal microscopy analysis of fluorescence and morphology is becoming the standard tool in cell biology and molecular imaging. Accurate quantification algorithms are required to enhance the understanding of different biological phenomena. We present a novel approach based on image-segmentation of multi-cellular regions in bright field images demonstrating enhanced quantitative analyses and better understanding of cell motility. We present MultiCellSeg, a segmentation algorithm to separate between multi-cellular and background regions for bright field images, which is based on classification of local patches within an image: a cascade of Support Vector Machines (SVMs is applied using basic image features. Post processing includes additional classification and graph-cut segmentation to reclassify erroneous regions and refine the segmentation. This approach leads to a parameter-free and robust algorithm. Comparison to an alternative algorithm on wound healing assay images demonstrates its superiority. The proposed approach was used to evaluate common cell migration models such as wound healing and scatter assay. It was applied to quantify the acceleration effect of Hepatocyte growth factor/scatter factor (HGF/SF on healing rate in a time lapse confocal microscopy wound healing assay and demonstrated that the healing rate is linear in both treated and untreated cells, and that HGF/SF accelerates the healing rate by approximately two-fold. A novel fully automated, accurate, zero-parameters method to classify and score scatter-assay images was developed and demonstrated that multi-cellular texture is an excellent descriptor to measure HGF/SF-induced cell scattering. We show that exploitation of textural information from differential interference contrast (DIC images on the multi-cellular level can prove beneficial for the analyses of wound healing and scatter assays. The proposed approach is generic and can be used alone or alongside traditional

  17. Cell motility dynamics: a novel segmentation algorithm to quantify multi-cellular bright field microscopy images.

    Science.gov (United States)

    Zaritsky, Assaf; Natan, Sari; Horev, Judith; Hecht, Inbal; Wolf, Lior; Ben-Jacob, Eshel; Tsarfaty, Ilan

    2011-01-01

    Confocal microscopy analysis of fluorescence and morphology is becoming the standard tool in cell biology and molecular imaging. Accurate quantification algorithms are required to enhance the understanding of different biological phenomena. We present a novel approach based on image-segmentation of multi-cellular regions in bright field images demonstrating enhanced quantitative analyses and better understanding of cell motility. We present MultiCellSeg, a segmentation algorithm to separate between multi-cellular and background regions for bright field images, which is based on classification of local patches within an image: a cascade of Support Vector Machines (SVMs) is applied using basic image features. Post processing includes additional classification and graph-cut segmentation to reclassify erroneous regions and refine the segmentation. This approach leads to a parameter-free and robust algorithm. Comparison to an alternative algorithm on wound healing assay images demonstrates its superiority. The proposed approach was used to evaluate common cell migration models such as wound healing and scatter assay. It was applied to quantify the acceleration effect of Hepatocyte growth factor/scatter factor (HGF/SF) on healing rate in a time lapse confocal microscopy wound healing assay and demonstrated that the healing rate is linear in both treated and untreated cells, and that HGF/SF accelerates the healing rate by approximately two-fold. A novel fully automated, accurate, zero-parameters method to classify and score scatter-assay images was developed and demonstrated that multi-cellular texture is an excellent descriptor to measure HGF/SF-induced cell scattering. We show that exploitation of textural information from differential interference contrast (DIC) images on the multi-cellular level can prove beneficial for the analyses of wound healing and scatter assays. The proposed approach is generic and can be used alone or alongside traditional fluorescence single

  18. Applying tattoo dye as a third-harmonic generation contrast agent for in vivo optical virtual biopsy of human skin

    Science.gov (United States)

    Tsai, Ming-Rung; Lin, Chen-Yu; Liao, Yi-Hua; Sun, Chi-Kuang

    2013-02-01

    Third-harmonic generation (THG) microscopy has been reported to provide intrinsic contrast in elastic fibers, cytoplasmic membrane, nucleus, actin filaments, lipid bodies, hemoglobin, and melanin in human skin. For advanced molecular imaging, exogenous contrast agents are developed for a higher structural or molecular specificity. We demonstrate the potential of the commonly adopted tattoo dye as a THG contrast agent for in vivo optical biopsy of human skin. Spectroscopy and microscopy experiments were performed on cultured cells with tattoo dyes, in tattooed mouse skin, and in tattooed human skin to demonstrate the THG enhancement effect. Compared with other absorbing dyes or nanoparticles used as exogenous THG contrast agents, tattoo dyes are widely adopted in human skin so that future clinical biocompatibility evaluation is relatively achievable. Combined with the demonstrated THG enhancement effect, tattoo dyes show their promise for future clinical imaging applications.

  19. Polydimethylsiloxane: a new contrast material for localization of occult breast lesions

    International Nuclear Information System (INIS)

    Vitral, Geraldo Sérgio Farinazzo; Raposo, Nádia Rezende Barbosa

    2011-01-01

    The radioguided localization of occult breast lesions (ROLL) technique often utilizes iodinated radiographic contrast to assure that the local injection of 99m Tc-MAA corresponds to the location of the lesion under investigation. However, for this application, this contrast has several shortcomings. The objective of this study was to evaluate the safety, effectiveness and technical feasibility of the use of polydimethylsiloxane (PDMS) as radiological contrast and tissue marker in ROLL. The safety assessment was performed by the acute toxicity study in Wistar rats (n = 50). The radiological analysis of breast tissue (n = 32) from patients undergoing reductive mammoplasty was used to verify the effectiveness of PDMS as contrast media. The technical feasibility was evaluated through the scintigraphic and histologic analysis. We found no toxic effects of PDMS for this use during the observational period. It has been demonstrated in human breast tissue that the average diameter of the tissue marked by PDMS was lower than when marked by the contrast medium (p <0.001). PDMS did not interfere with the scintigraphic uptake (p = 0.528) and there was no injury in histological processing of samples. This study demonstrated not only the superiority of PDMS as radiological contrast in relation to the iodinated contrast, but also the technical feasibility for the same applicability in the ROLL

  20. Quantum eraser for three-slit interference

    Indian Academy of Sciences (India)

    Naveed Ahmad Shah

    2017-11-09

    Nov 9, 2017 ... Abstract. It is well known that in a two-slit interference experiment, if the information, on which of the two paths the particle followed, is stored in a quantum path detector, the interference is destroyed. However, in a set-up where this path information is 'erased', the interference can reappear. Such a set-up is ...

  1. Magnetic anisotropy considerations in magnetic force microscopy studies of single superparamagnetic nanoparticles

    International Nuclear Information System (INIS)

    Nocera, Tanya M; Agarwal, Gunjan; Chen Jun; Murray, Christopher B

    2012-01-01

    In recent years, superparamagnetic nanoparticles (SPNs) have become increasingly important in applications ranging from solid state memory devices to biomedical diagnostic and therapeutic tools. However, detection and characterization of the small and unstable magnetic moment of an SPN at the single particle level remains a challenge. Further, depending on their physical shape, crystalline structure or orientation, SPNs may also possess magnetic anisotropy, which can govern the extent to which their magnetic moments can align with an externally applied magnetic field. Here, we demonstrate how we can exploit the magnetic anisotropy of SPNs to enable uniform, highly-sensitive detection of single SPNs using magnetic force microscopy (MFM) in ambient air. Superconducting quantum interference device magnetometry and analytical transmission electron microscopy techniques are utilized to characterize the collective magnetic behavior, morphology and composition of the SPNs. Our results show how the consideration of magnetic anisotropy can enhance the ability of MFM to detect single SPNs at ambient room temperature with high force sensitivity and spatial resolution. (paper)

  2. X-ray microscopy resource center at the Advanced Light Source

    International Nuclear Information System (INIS)

    Meyer-Ilse, W.; Koike, M.; Beguiristain, R.; Maser, J.; Attwood, D.

    1992-07-01

    An x-ray microscopy resource center for biological x-ray imaging vvill be built at the Advanced Light Source (ALS) in Berkeley. The unique high brightness of the ALS allows short exposure times and high image quality. Two microscopes, an x-ray microscope (XM) and a scanning x-ray microscope (SXM) are planned. These microscopes serve complementary needs. The XM gives images in parallel at comparable short exposure times, and the SXM is optimized for low radiation doses applied to the sample. The microscopes extend visible light microscopy towards significantly higher resolution and permit images of objects in an aqueous medium. High resolution is accomplished by the use of Fresnel zone plates. Design considerations to serve the needs of biological x-ray microscopy are given. Also the preliminary design of the microscopes is presented. Multiple wavelength and multiple view images will provide elemental contrast and some degree of 3D information

  3. Electromagnetic interference: a radiant future!

    NARCIS (Netherlands)

    Leferink, Frank Bernardus Johannes

    2015-01-01

    Although Electromagnetic Interference and Electromagnetic Compatibility are well established domains, the introduction of new technologies results in new challenges. Changes in both measurement techniques, and technological trends resulting in new types of interference are described. These are the

  4. Atomic force microscopy applied to the quantification of nano-precipitates in thermo-mechanically treated microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Renteria-Borja, Luciano [Instituto Tecnologico de Morelia, Av. Tecnologico No. 1500, Lomas de Santiaguito, 58120 Morelia (Mexico); Hurtado-Delgado, Eduardo, E-mail: hurtado@itmorelia.edu.mx [Instituto Tecnologico de Morelia, Av. Tecnologico No. 1500, Lomas de Santiaguito, 58120 Morelia (Mexico); Garnica-Gonzalez, Pedro [Instituto Tecnologico de Morelia, Av. Tecnologico No. 1500, Lomas de Santiaguito, 58120 Morelia (Mexico); Dominguez-Lopez, Ivan; Garcia-Garcia, Adrian Luis [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada-IPN Unidad Queretaro, Cerro Blanco No. 141, Colinas del Cimatario, 76090 Queretaro (Mexico)

    2012-07-15

    Quantification of nanometer-size precipitates in microalloyed steels has been traditionally performed using transmission electron microscopy (TEM), in spite of its complicated sample preparation procedures, prone to preparation errors and sample perturbation. In contrast to TEM procedures, atomic force microscopy (AFM) is performed on the as-prepared specimen, with sample preparation requirements similar to those for optical microscopy (OM), rendering three-dimensional representations of the sample surface with vertical resolution of a fraction of a nanometer. In AFM, contrast mechanisms are directly related to surface properties such as topography, adhesion, and stiffness, among others. Chemical etching was performed using 0.5% nital, at time intervals between 4 and 20 s, in 4 s steps, until reaching the desired surface finish. For the present application, an average surface-roughness peak-height below 200 nm was sought. Quantification results of nanometric precipitates were obtained from the statistical analysis of AFM images of the microstructure developed by microalloyed Nb and V-Mo steels. Topography and phase contrast AFM images were used for quantification. The results obtained using AFM are consistent with similar TEM reports. - Highlights: Black-Right-Pointing-Pointer We quantified nanometric precipitates in Nb and V-Mo microalloyed steels using AFM. Black-Right-Pointing-Pointer Microstructures of the thermo-mechanically treated microalloyed steels were used. Black-Right-Pointing-Pointer Topography and phase contrast AFM images were used for quantification. Black-Right-Pointing-Pointer AFM results are comparable with traditionally obtained TEM measurements.

  5. Applications of energy loss contrast STIM

    International Nuclear Information System (INIS)

    Bench, G.; Saint, A.; Legge, G.J.F.; Cholewa, M.

    1992-01-01

    Scanning Transmission Ion Microscopy (STIM) with energy loss contrast is a quantitative imaging technique. A focussed MeV ion microbeam is scanned over the sample and measured energy losses of residual ions at each beam location are used to provide the contrast in the image. The technique is highly efficient as almost every ion carries useful information from which quantitative data can be obtained. The high efficiency of data collection at present necessitates the use of small beam currents. Therefore small apertures can be used and fine spatial resolution can be achieved. High efficiency also makes it possible to collect large data sets for high definition imaging with a small radiation dose. Owing to the simple relationship between energy loss and areal density, STIM with energy loss contrast can provide a quantitative image that can be used to obtain areal density information on the sample. These areal density maps can be used not only to provide a high resolution image of the sample but also to normalise Particle Induced Xray Emission (PIXE) data. The small radiation dose required to form these areal density maps also allows one to use STIM with energy loss contrast to quantitatively monitor ion beam induced specimen changes caused by higher doses and dose rates used in other microanalytical techniques. STIM with energy loss contrast also provides the possibility of stereo imaging and ion microtomography. STIM has also been used in conjunction with channeling to explore transmission channeling in thin crystals. This paper will discuss these applications of STIM with energy loss contrast and look at further developments from them

  6. Complete staining of human spermatozoa and immature germ cells combined with phase contrast microscopy

    DEFF Research Database (Denmark)

    Michael, A Y; Drejer, J O; Bagger, P V

    1987-01-01

    A method combining Janus green B and Thymol blue stains the anterior part of the head, the nuclear membrane, middle piece, and tail of spermatozoa light green and the nucleus deep purple. The method provides excellent stained preparations for the evaluation of sperm morphology by phase contrast...

  7. Nephrotoxicity of cyclosporin A and contrast media

    International Nuclear Information System (INIS)

    Thomsen, H.S.; Larsen, S.; Skaarup, P.; Hemmingsen, L.; Dieperink, H.; Golman, K.; Herlev Hospital; Herlev Hospital; Centralsygehuset, Nykoebing Falster; Odense Sygehus; Malmoe Allmaenna Sjukhus

    1989-01-01

    Urine profiles (albumin, glucose, NAG, LDH, GGT and sodium) were followed for 22 h or 8 days after intravenous injection of diatrizoate, iohexol or saline in 30 adult Wistar rats in which nephrotoxicity was induced by daily peroral administration of 25 mg/kg body weight cyclosporin A over a 14-day period. Another 10 rats which had the vehicle of the cyclosporin A solution (placebo) and saline injected intravenously served as controls. The effect of iohexol and saline on the albumin excretion was similar, whereas diatrizoate increased it significantly. Both contrast media caused significantly increased excretion of all three enzymes. The contrast media had no effect on the excretion of glucose and sodium. Except for the fact that the excretion of NAG was significantly higher following iohexol than following diatrizoate 24 to 46 h after injection no significant differences between the two media were found from 24 h after injection among the rats given cyclosporin A. No contrast medium related changes were found by light microscopy of the kidneys. Neither iohexol nor diatrizoate potentiate acute cyclosporin A nephrotoxicity. (orig.)

  8. Analysis of low-field isotropic vortex glass containing vortex groups in YBa2Cu3O7-x thin films visualized by scanning SQUID microscopy

    NARCIS (Netherlands)

    Wells, Frederick S.; Pan, Alexey V.; Wang, X.; Fedoseev, Sergey A.; Hilgenkamp, Hans

    2015-01-01

    The glass-like vortex distribution in pulsed laser deposited YBa2Cu3O7-x thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth's field. Autocorrelation calculations on

  9. An Interference-Aware Traffic-Priority-Based Link Scheduling Algorithm for Interference Mitigation in Multiple Wireless Body Area Networks

    Directory of Open Access Journals (Sweden)

    Thien T. T. Le

    2016-12-01

    Full Text Available Currently, wireless body area networks (WBANs are effectively used for health monitoring services. However, in cases where WBANs are densely deployed, interference among WBANs can cause serious degradation of network performance and reliability. Inter-WBAN interference can be reduced by scheduling the communication links of interfering WBANs. In this paper, we propose an interference-aware traffic-priority-based link scheduling (ITLS algorithm to overcome inter-WBAN interference in densely deployed WBANs. First, we model a network with multiple WBANs as an interference graph where node-level interference and traffic priority are taken into account. Second, we formulate link scheduling for multiple WBANs as an optimization model where the objective is to maximize the throughput of the entire network while ensuring the traffic priority of sensor nodes. Finally, we propose the ITLS algorithm for multiple WBANs on the basis of the optimization model. High spatial reuse is also achieved in the proposed ITLS algorithm. The proposed ITLS achieves high spatial reuse while considering traffic priority, packet length, and the number of interfered sensor nodes. Our simulation results show that the proposed ITLS significantly increases spatial reuse and network throughput with lower delay by mitigating inter-WBAN interference.

  10. Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

    International Nuclear Information System (INIS)

    Kun-Yu, Zhao; Hua-Rong, Zeng; Hong-Zhang, Song; Sen-Xing, Hui; Guo-Rong, Li; Qing-Rui, Yin; Shimamura, Kiyoshi; Kannan, Chinna Venkadasamy; Villora, Encarnacion Antonia Garcia; Takekawa, Shunji; Kitamura, Kenji

    2008-01-01

    We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.5 kHz by AFM-based acoustic microscopy The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10kHz, and reached maximum at 8.1kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. [The possibility for using the phenomenon of polarized light interference in treating amblyopia].

    Science.gov (United States)

    Abramov, V G; Vakurina, A E; Kashchenko, T P; Pargina, N M

    1996-01-01

    A new method for treating amblyopia is proposed, making use of the phenomenon of polarized light interference. It helps act simultaneously on the brightness, contrast frequency, and color sensitivity in response to patterns. The method was used in the treatment of 36 children. In group 1 (n = 20) it was combined with the traditional methods. Such treatment was more effective than in controls treated routinely. Group 2 consisted of 16 children in whom previous therapy was of no avail. Visual function was improved in 7 of them.

  12. Quantum Interference and Coherence Theory and Experiments

    CERN Document Server

    Ficek, Zbigniew; Rhodes, William T; Asakura, Toshimitsu; Brenner, Karl-Heinz; Hänsch, Theodor W; Kamiya, Takeshi; Krausz, Ferenc; Monemar, Bo; Venghaus, Herbert; Weber, Horst; Weinfurter, Harald

    2005-01-01

    For the first time, this book assembles in a single volume accounts of many phenomena involving quantum interference in optical fields and atomic systems. It provides detailed theoretical treatments and experimental analyses of such phenomena as quantum erasure, quantum lithography, multi-atom entanglement, quantum beats, control of decoherence, phase control of quantum interference, coherent population trapping, electromagnetically induced transparency and absorption, lasing without inversion, subluminal and superluminal light propagation, storage of photons, quantum interference in phase space, interference and diffraction of cold atoms, and interference between Bose-Einstein condensates. This book fills a gap in the literature and will be useful to both experimentalists and theoreticians.

  13. Rank-Constrained Beamforming for MIMO Cognitive Interference Channel

    Directory of Open Access Journals (Sweden)

    Duoying Zhang

    2016-01-01

    Full Text Available This paper considers the spectrum sharing multiple-input multiple-output (MIMO cognitive interference channel, in which multiple primary users (PUs coexist with multiple secondary users (SUs. Interference alignment (IA approach is introduced that guarantees that secondary users access the licensed spectrum without causing harmful interference to the PUs. A rank-constrained beamforming design is proposed where the rank of the interferences and the desired signals is concerned. The standard interferences metric for the primary link, that is, interference temperature, is investigated and redesigned. The work provides a further improvement that optimizes the dimension of the interferences in the cognitive interference channel, instead of the power of the interference leakage. Due to the nonconvexity of the rank, the developed optimization problems are further approximated as convex form and are solved via choosing the transmitter precoder and receiver subspace iteratively. Numerical results show that the proposed designs can improve the achievable degree of freedom (DoF of the primary links and provide the considerable sum rate for both secondary and primary transmissions under the rank constraints.

  14. Automated quantitative cytological analysis using portable microfluidic microscopy.

    Science.gov (United States)

    Jagannadh, Veerendra Kalyan; Murthy, Rashmi Sreeramachandra; Srinivasan, Rajesh; Gorthi, Sai Siva

    2016-06-01

    In this article, a portable microfluidic microscopy based approach for automated cytological investigations is presented. Inexpensive optical and electronic components have been used to construct a simple microfluidic microscopy system. In contrast to the conventional slide-based methods, the presented method employs microfluidics to enable automated sample handling and image acquisition. The approach involves the use of simple in-suspension staining and automated image acquisition to enable quantitative cytological analysis of samples. The applicability of the presented approach to research in cellular biology is shown by performing an automated cell viability assessment on a given population of yeast cells. Further, the relevance of the presented approach to clinical diagnosis and prognosis has been demonstrated by performing detection and differential assessment of malaria infection in a given sample. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Interference in immunoassay

    International Nuclear Information System (INIS)

    Chapman, R.S.

    1998-01-01

    Interfering factors are evident in both limited reagent (radioimmunoassay) and excess reagent (immunometric assay) technologies and should be suspected whenever there is a discrepancy between analytical results and clinical findings in the investigation of particular diseases. The overall effect of interference in immunoassay is analytical bias in result, either positive or negative of variable magnitude. The interference maybe caused by a wide spectrum of factors from poor sample collection and handling to physiological factors e.g. lipaemia, heparin treatment, binding protein abnormalities, autoimmunity and drug treatments. The range of interfering factors is extensive and difficult to discuss effectively in a short review

  16. Crystals seen on CSF microscopy in a case of suspected subarachnoid haemorrhage

    Science.gov (United States)

    Weiand, Daniel; Hanning, Ian; Mouhamadou, Moussa; Wearmouth, Debbie

    2015-01-01

    Although crystals are rarely identified on cerebrospinal fluid (CSF) microscopy, their presence can be of significant diagnostic value. We report a case of oxalate crystals seen on CSF microscopy of a 43-year-old woman. The patient presented with headaches, nausea and vomiting. CT of the head showed a small focus of hyper-density, suspicious of haemorrhage, in the right side of the pontine cistern. CSF cell count was within the normal range. Although no organisms were seen on microscopy, copious oxalate crystals were seen. The same crystals were seen on microscopy of CSF collected in a fluoride oxalate container used for glucose analysis. A follow-up contrast-enhanced CT angiogram did not demonstrate any abnormalities. It transpired that excess CSF had been collected into a fluoride oxalate container. This had subsequently been decanted into a plain container for microbiological analysis. Correct specimen collection should be emphasised when teaching lumbar puncture technique. PMID:26139652

  17. Top predators, mesopredators and their prey: interference ecosystems along bioclimatic productivity gradients.

    Science.gov (United States)

    Elmhagen, B; Ludwig, G; Rushton, S P; Helle, P; Lindén, H

    2010-07-01

    1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems. 2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels. 3. We use the recolonization of a top predator in a three-level boreal ecosystem as a natural experiment to test if large-scale biomass distributions and population trends support MRH. Inspired by EEH, we also test if top-down interference and bottom-up productivity impact regional ecosystem structures. 4. We use data from the Finnish Wildlife Triangle Scheme which has monitored top predator (lynx, Lynx lynx), mesopredator (red fox, Vulpes vulpes) and prey (mountain hare, Lepus timidus) abundance for 17 years in a 200 000 km(2) study area which covers a distinct productivity gradient. 5. Fox biomass was lower than expected from productivity where lynx biomass was high, whilst hare biomass was lower than expected from productivity where fox biomass was high. Hence, where interference controlled fox abundance, lynx had an indirect positive impact on hare abundance as predicted by MRH. The rates of change indicated that lynx expansion gradually suppressed fox biomass. 6. Lynx status caused shifts between ecosystem structures. In the 'interference ecosystem', lynx and hare biomass increased with productivity whilst fox biomass did not. In the 'mesopredator release ecosystem', fox biomass increased with productivity but hare biomass did not. Thus, biomass controlled top-down did not respond to changes in productivity. This fulfils a critical prediction of EEH. 7. We conclude that the cascade

  18. Correlated Light Microscopy and Electron Microscopy

    NARCIS (Netherlands)

    Sjollema, Klaas A.; Schnell, Ulrike; Kuipers, Jeroen; Kalicharan, Ruby; Giepmans, Ben N. G.; MullerReichert, T; Verkade, P

    2012-01-01

    Understanding where, when, and how biomolecules (inter)act is crucial to uncover fundamental mechanisms in cell biology. Recent developments in fluorescence light microscopy (FLM) allow protein imaging in living cells and at the near molecular level. However, fluorescence microscopy only reveals

  19. Scanning near-field infrared microscopy on semiconductor structures

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, Rainer

    2011-01-15

    Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from

  20. Scanning near-field infrared microscopy on semiconductor structures

    International Nuclear Information System (INIS)

    Jacob, Rainer

    2011-01-01

    Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from

  1. Interference and problem size effect in multiplication fact solving: Individual differences in brain activations and arithmetic performance.

    Science.gov (United States)

    De Visscher, Alice; Vogel, Stephan E; Reishofer, Gernot; Hassler, Eva; Koschutnig, Karl; De Smedt, Bert; Grabner, Roland H

    2018-05-15

    In the development of math ability, a large variability of performance in solving simple arithmetic problems is observed and has not found a compelling explanation yet. One robust effect in simple multiplication facts is the problem size effect, indicating better performance for small problems compared to large ones. Recently, behavioral studies brought to light another effect in multiplication facts, the interference effect. That is, high interfering problems (receiving more proactive interference from previously learned problems) are more difficult to retrieve than low interfering problems (in terms of physical feature overlap, namely the digits, De Visscher and Noël, 2014). At the behavioral level, the sensitivity to the interference effect is shown to explain individual differences in the performance of solving multiplications in children as well as in adults. The aim of the present study was to investigate the individual differences in multiplication ability in relation to the neural interference effect and the neural problem size effect. To that end, we used a paradigm developed by De Visscher, Berens, et al. (2015) that contrasts the interference effect and the problem size effect in a multiplication verification task, during functional magnetic resonance imaging (fMRI) acquisition. Forty-two healthy adults, who showed high variability in an arithmetic fluency test, participated in our fMRI study. In order to control for the general reasoning level, the IQ was taken into account in the individual differences analyses. Our findings revealed a neural interference effect linked to individual differences in multiplication in the left inferior frontal gyrus, while controlling for the IQ. This interference effect in the left inferior frontal gyrus showed a negative relation with individual differences in arithmetic fluency, indicating a higher interference effect for low performers compared to high performers. This region is suggested in the literature to be

  2. Effects of prestudy and poststudy rest on memory: Support for temporal interference accounts of forgetting.

    Science.gov (United States)

    Ecker, Ullrich K H; Tay, Jia-Xin; Brown, Gordon D A

    2015-06-01

    According to interference-based theories of memory, including temporal-distinctiveness theory, both prestudy and poststudy rest should have beneficial impacts on memory performance. Specifically, higher temporal isolation of a memorandum should reduce proactive and/or retroactive interference, and thus should result in better recall. In the present study, we investigated the effects of prestudy and poststudy rest in a free recall paradigm. Participants studied three lists of words, separated by either a short or a long period of low mental activity (a tone-detection task). Recall targeted the second list; this list was studied in one of four conditions, defined by the fully crossed factors of prestudy and poststudy rest duration. Two experiments revealed a beneficial effect of prestudy rest (and, to a lesser extent, of poststudy rest) on list recall. This result is in line with interference-based theories of memory. By contrast, a beneficial effect of prestudy rest is not predicted by consolidation accounts of memory and forgetting; our results thus require additional assumptions and/or a better specification of the consolidation process and its time course in order to be reconciled with consolidation theory.

  3. Quasiparticle interference in unconventional 2D systems.

    Science.gov (United States)

    Chen, Lan; Cheng, Peng; Wu, Kehui

    2017-03-15

    At present, research of 2D systems mainly focuses on two kinds of materials: graphene-like materials and transition-metal dichalcogenides (TMDs). Both of them host unconventional 2D electronic properties: pseudospin and the associated chirality of electrons in graphene-like materials, and spin-valley-coupled electronic structures in the TMDs. These exotic electronic properties have attracted tremendous interest for possible applications in nanodevices in the future. Investigation on the quasiparticle interference (QPI) in 2D systems is an effective way to uncover these properties. In this review, we will begin with a brief introduction to 2D systems, including their atomic structures and electronic bands. Then, we will discuss the formation of Friedel oscillation due to QPI in constant energy contours of electron bands, and show the basic concept of Fourier-transform scanning tunneling microscopy/spectroscopy (FT-STM/STS), which can resolve Friedel oscillation patterns in real space and consequently obtain the QPI patterns in reciprocal space. In the next two parts, we will summarize some pivotal results in the investigation of QPI in graphene and silicene, in which systems the low-energy quasiparticles are described by the massless Dirac equation. The FT-STM experiments show there are two different interference channels (intervalley and intravalley scattering) and backscattering suppression, which associate with the Dirac cones and the chirality of quasiparticles. The monolayer and bilayer graphene on different substrates (SiC and metal surfaces), and the monolayer and multilayer silicene on a Ag(1 1 1) surface will be addressed. The fifth part will introduce the FT-STM research on QPI in TMDs (monolayer and bilayer of WSe 2 ), which allow us to infer the spin texture of both conduction and valence bands, and present spin-valley coupling by tracking allowed and forbidden scattering channels.

  4. The effects of water soluble contrast agents on the respiratory tract

    International Nuclear Information System (INIS)

    Lovett, I.; Donchey, S.; Doust, B.; Branson, J.; Munro, V.

    1989-01-01

    The water soluble contrast agents Gastrografin R (Sodium diatrizoate and meglumine diatrizoate, Schering, Berlin), Iopamiro 300 R (Iopamidol, Schering, Berlin), and Dionosil Aqueous R (propyliodone BP, Glaxo, England) were instilled into the tracheobronchial tree of rats in doses of either 0.1 ml and 0.25 ml. Rats being used as controls, underwent sham operations with the instillation of air instead of contrast agent. In all, 85 rats were used. All rats that had not already died from the effects of contrast agent were sacrificed 30 minutes after instillation. The relative effects of the contrast agents were measured by comparing: survival time; radiographic effects of the contrast agents on the lungs; and pathological changes as estimated by post mortem lung section and microscopy. The least toxic agent was the one with the lowest osmotic activity, namely Aqueous Dionosil. It is therefore recommended that Aqueous Dionosil be used in preference to Gastrografin or Iopamidol for studies of the oesophagus whenever there is a danger of aspiration of contrast agent into the tracheobronchial tree. 11 refs., 3 figs., 5 tabs

  5. Automated seeding-based nuclei segmentation in nonlinear optical microscopy.

    Science.gov (United States)

    Medyukhina, Anna; Meyer, Tobias; Heuke, Sandro; Vogler, Nadine; Dietzek, Benjamin; Popp, Jürgen

    2013-10-01

    Nonlinear optical (NLO) microscopy based, e.g., on coherent anti-Stokes Raman scattering (CARS) or two-photon-excited fluorescence (TPEF) is a fast label-free imaging technique, with a great potential for biomedical applications. However, NLO microscopy as a diagnostic tool is still in its infancy; there is a lack of robust and durable nuclei segmentation methods capable of accurate image processing in cases of variable image contrast, nuclear density, and type of investigated tissue. Nonetheless, such algorithms specifically adapted to NLO microscopy present one prerequisite for the technology to be routinely used, e.g., in pathology or intraoperatively for surgical guidance. In this paper, we compare the applicability of different seeding and boundary detection methods to NLO microscopic images in order to develop an optimal seeding-based approach capable of accurate segmentation of both TPEF and CARS images. Among different methods, the Laplacian of Gaussian filter showed the best accuracy for the seeding of the image, while a modified seeded watershed segmentation was the most accurate in the task of boundary detection. The resulting combination of these methods followed by the verification of the detected nuclei performs high average sensitivity and specificity when applied to various types of NLO microscopy images.

  6. Enhanced light microscopy visualization of virus particles from Zika virus to filamentous ebolaviruses.

    Directory of Open Access Journals (Sweden)

    George G Daaboul

    Full Text Available Light microscopy is a powerful tool in the detection and analysis of parasites, fungi, and prokaryotes, but has been challenging to use for the detection of individual virus particles. Unlabeled virus particles are too small to be visualized using standard visible light microscopy. Characterization of virus particles is typically performed using higher resolution approaches such as electron microscopy or atomic force microscopy. These approaches require purification of virions away from their normal millieu, requiring significant levels of expertise, and can only enumerate small numbers of particles per field of view. Here, we utilize a visible light imaging approach called Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS that allows automated counting and sizing of thousands of individual virions. Virions are captured directly from complex solutions onto a silicon chip and then detected using a reflectance interference imaging modality. We show that the use of different imaging wavelengths allows the visualization of a multitude of virus particles. Using Violet/UV illumination, the SP-IRIS technique is able to detect individual flavivirus particles (~40 nm, while green light illumination is capable of identifying and discriminating between vesicular stomatitis virus and vaccinia virus (~360 nm. Strikingly, the technology allows the clear identification of filamentous infectious ebolavirus particles and virus-like particles. The ability to differentiate and quantify unlabeled virus particles extends the usefulness of traditional light microscopy and can be embodied in a straightforward benchtop approach allowing widespread applications ranging from rapid detection in biological fluids to analysis of virus-like particles for vaccine development and production.

  7. In vivo imaging of cell nuclei by photoacoustic microscopy without staining

    Science.gov (United States)

    Yao, Da-Kang; Chen, Ruimin; Maslov, Konstantin; Zhou, Qifa; Wang, Lihong V.

    2012-02-01

    Ultraviolet photoacoustic microscopy (UVPAM) can image cell nuclei in vivo with high contrast and resolution noninvasively without staining. Here, we used UV light at wavelengths of 210-310 nm for excitation of DNA and RNA to produce photoacoustic waves. We applied the UVPAM to in vivo imaging of cell nuclei in mouse skin, and obtained UVPAM images of the unstained cell nuclei at wavelengths of 245-282 nm as ultrasound gel was used for acoustic coupling. The largest ratio of contrast to noise was found for the images of cell nuclei at a 250 nm wavelength.

  8. Single-molecule fluorescence microscopy review: shedding new light on old problems.

    Science.gov (United States)

    Shashkova, Sviatlana; Leake, Mark C

    2017-08-31

    Fluorescence microscopy is an invaluable tool in the biosciences, a genuine workhorse technique offering exceptional contrast in conjunction with high specificity of labelling with relatively minimal perturbation to biological samples compared with many competing biophysical techniques. Improvements in detector and dye technologies coupled to advances in image analysis methods have fuelled recent development towards single-molecule fluorescence microscopy, which can utilize light microscopy tools to enable the faithful detection and analysis of single fluorescent molecules used as reporter tags in biological samples. For example, the discovery of GFP, initiating the so-called 'green revolution', has pushed experimental tools in the biosciences to a completely new level of functional imaging of living samples, culminating in single fluorescent protein molecule detection. Today, fluorescence microscopy is an indispensable tool in single-molecule investigations, providing a high signal-to-noise ratio for visualization while still retaining the key features in the physiological context of native biological systems. In this review, we discuss some of the recent discoveries in the life sciences which have been enabled using single-molecule fluorescence microscopy, paying particular attention to the so-called 'super-resolution' fluorescence microscopy techniques in live cells, which are at the cutting-edge of these methods. In particular, how these tools can reveal new insights into long-standing puzzles in biology: old problems, which have been impossible to tackle using other more traditional tools until the emergence of new single-molecule fluorescence microscopy techniques. © 2017 The Author(s).

  9. Proactive Interference in Human Predictive Learning

    OpenAIRE

    Castro, Leyre; Ortega, Nuria; Matute, Helena

    2002-01-01

    The impairment in responding to a secondly trained association because of the prior training of another (i.e., proactive interference) is a well-established effect in human and animal research, and it has been demonstrated in many paradigms. However, learning theories have been concerned with proactive interference only when the competing stimuli have been presented in compound at some moment of the training phase. In this experiment we investigated the possibility of proactive interference b...

  10. Microstructural and micromechanical characterisation of TiAl alloys using atomic force microscopy and nanoindentation

    International Nuclear Information System (INIS)

    Gebhard, S.; Pyczak, F.; Goeken, M.

    2009-01-01

    Different microstructures were generated in the Ti-45Al-4.6Nb-0.2B-0.2C and Ti-45Al-1Cr alloys (at.%) by heat treatment. The microstructures were investigated using nanoindentation and atomic force microscopy which was compared with transmission electron microscopy. Topographic contrast is usually used for phase identification in the atomic force microscope. However, it was found that the topographic order of the phases changes with different microstructures and specimen preparations. Nanoindentation measurements provided local hardness values not obtainable by other methods and enabled clear distinction of the phases. The hardness values can give information on surrounding microstructure and solid solution hardening. The mean lamellar spacing of the colonies was measured using both atomic force microscopy and transmission electron microscopy. Atomic force microscopy was found to be suitable to determine the spacing between α 2 /γ-interfaces offering the advantages of easier sample preparation and fewer specimens compared to evaluation by TEM analysis.

  11. Exogenous sample contamination. Sources and interference.

    Science.gov (United States)

    Cornes, Michael P

    2016-12-01

    Clinical laboratory medicine is involved in the vast majority of patient care pathways. It has been estimated that pathology results inform 60-70% of critical patient care decisions. The primary goal of the laboratory is to produce precise and accurate results which reflect the true situation in vivo. It is not surprising that interference occurs in laboratory analysis given the complexity of some of the assays used to perform them. Interference is defined as "the effect of a substance upon any step in the determination of the concentration or catalytic activity of the metabolite". Exogenous interferences are defined as those that derive from outside of the body and are therefore not normally found in a specimen and can cause either a positive or negative bias in analytical results. Interferences in analysis can come from various sources and can be classified as endogenous or exogenous. Exogenous substances could be introduced at any point in the sample journey. The laboratory must take responsibility for the quality of results produced. It has a responsibility to have processes in place to identify and minimise the occurrence and effect contamination and interference. To do this well the laboratory needs to work with clinicians and manufacturers. Failure to identify an erroneous result could have an impact on patient care, patient safety and also on hospital budgets. However it is not always easy to recognise interferences. This review summarises the types and sources of exogenous interference and some steps to minimise the impact they have. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.

  12. Investigation of Interference Models for RFID Systems

    Directory of Open Access Journals (Sweden)

    Linchao Zhang

    2016-02-01

    Full Text Available The reader-to-reader collision in an RFID system is a challenging problem for communications technology. In order to model the interference between RFID readers, different interference models have been proposed, mainly based on two approaches: single and additive interference. The former only considers the interference from one reader within a certain range, whereas the latter takes into account the sum of all of the simultaneous interferences in order to emulate a more realistic behavior. Although the difference between the two approaches has been theoretically analyzed in previous research, their effects on the estimated performance of the reader-to-reader anti-collision protocols have not yet been investigated. In this paper, the influence of the interference model on the anti-collision protocols is studied by simulating a representative state-of-the-art protocol. The results presented in this paper highlight that the use of additive models, although more computationally intensive, is mandatory to improve the performance of anti-collision protocols.

  13. Major and minor crRNA annealing sites facilitate low stringency DNA protospacer binding prior to Type I-A CRISPR-Cas interference in Sulfolobus

    DEFF Research Database (Denmark)

    Mousaei, Marzieh; Deng, Ling; She, Qunxin

    2016-01-01

    The stringency of crRNA-protospacer DNA base pair matching required for effective CRISPR-Cas interference is relatively low in crenarchaeal Sulfolobus species in contrast to that required in some bacteria. To understand its biological significance we studied crRNA-protospacer interactions...... in Sulfolobus islandicus REY15A which carries multiple, and functionally diverse, interference complexes. A range of mismatches were introduced into a vector-borne protospacer that was identical to spacer 1 of CRISPR locus 2, with a cognate CCN PAM sequence. Two important crRNA annealing regions were identified...

  14. UV Fluorescence Photography of Works of Art : Replacing the Traditional UV Cut Filters with Interference Filters

    Directory of Open Access Journals (Sweden)

    Luís BRAVO PEREIRA

    2010-09-01

    Full Text Available For many years filters like the Kodak Wratten E series, or the equivalent Schneider B+W 415, were used as standard UV cut filters, necessary to obtain good quality on UV Fluorescence photography. The only problem with the use of these filters is that, when they receive the UV radiation that they should remove, they present themselves an internal fluorescence as side effect, that usually reduce contrast and quality on the final image. This article presents the results of our experiences on using some innovative filters, that appeared available on the market in recent years, projected to adsorb UV radiation even more efficiently than with the mentioned above pigment based standard filters: the interference filters for UV rejection (and, usually, for IR rejection too manufactured using interference layers, that present better results than the pigment based filters. The only problem with interference filters type is that they are sensitive to the rays direction and, because of that, they are not adequate to wide-angle lenses. The internal fluorescence for three filters: the B+W 415 UV cut (equivalent to the Kodak Wratten 2E, pigment based, the B+W 486 UV IR cut (an interference type filter, used frequently on digital cameras to remove IR or UV and the Baader UVIR rejection filter (two versions of this interference filter were used had been tested and compared. The final quality of the UV fluorescence images seems to be of a superior quality when compared to the images obtained with classic filters.

  15. Distributed interference alignment iterative algorithms in symmetric wireless network

    Directory of Open Access Journals (Sweden)

    YANG Jingwen

    2015-02-01

    Full Text Available Interference alignment is a novel interference alignment way,which is widely noted all of the world.Interference alignment overlaps interference in the same signal space at receiving terminal by precoding so as to thoroughly eliminate the influence of interference impacted on expected signals,thus making the desire user achieve the maximum degree of freedom.In this paper we research three typical algorithms for realizing interference alignment,including minimizing the leakage interference,maximizing Signal to Interference plus Noise Ratio (SINR and minimizing mean square error(MSE.All of these algorithms utilize the reciprocity of wireless network,and iterate the precoders between original network and the reverse network so as to achieve interference alignment.We use the uplink transmit rate to analyze the performance of these three algorithms.Numerical simulation results show the advantages of these algorithms.which is the foundation for the further study in the future.The feasibility and future of interference alignment are also discussed at last.

  16. All-optical universal logic gates on nonlinear multimode interference coupler using tunable input intensity

    Science.gov (United States)

    Tajaldini, Mehdi; Jafri, Mohd Zubir Mat

    2015-04-01

    The theory of Nonlinear Modal Propagation Analysis Method (NMPA) have shown significant features of nonlinear multimode interference (MMI) coupler with compact dimension and when launched near the threshold of nonlinearity. Moreover, NMPA have the potential to allow studying the nonlinear MMI based the modal interference to explorer the phenomenon that what happen due to the natural of multimode region. Proposal of all-optical switch based NMPA has approved its capability to achieving the all-optical gates. All-optical gates have attracted increasing attention due to their practical utility in all-optical signal processing networks and systems. Nonlinear multimode interference devices could apply as universal all-optical gates due to significant features that NMPA introduce them. In this Paper, we present a novel Ultra-compact MMI coupler based on NMPA method in low intensity compared to last reports either as a novel design method and potential application for optical NAND, NOR as universal gates on single structure for Boolean logic signal processing devices and optimize their application via studding the contrast ratio between ON and OFF as a function of output width. We have applied NMPA for several applications so that the miniaturization in low nonlinear intensities is their main purpose.

  17. Cognitive interference management in heterogeneous networks

    CERN Document Server

    Marabissi, Dania

    2015-01-01

    This brief investigates the role of interference management in Heterogeneous Networks (Het Nets), focusing on cognitive approaches and the use of beamforming. Key concepts of Het Nets are introduced and different deployment strategies are examined, such as sharing the same frequency band of the macro cells or using new high frequency bands. Particular attention is devoted to co-channel deployment and to the problem of interference management, addressing various strategies that can be adopted to handle the interference between the cells. In addition, the brief explores cognitive small cells which are able to avoid or limit interference by using suitable beamforming and resource allocation schemes. The suggested solutions are supported by numerical results in terms of performance evaluations and comparisons.

  18. Viewing individual cells and ambient microvasculature using two molecular contrasts

    Science.gov (United States)

    Xie, Zhixing; Chen, Sung-Liang; Fabiilli, Mario L.; Fowlkes, J. Brian; Shung, K. Kirk; Zhou, Qifa; Wei, Xunbin; Carson, Paul L.; Wang, Xueding

    2013-03-01

    To view the individual cells and ambient microvasculature simultaneously will be helpful to study tumor angiogenesis and microenvironments. To achieve this, two molecular contrast mechanisms were exploited simultaneously by integrating two imaging modalities, confocal fluorescence microscopy (CFM) and photoacoustic microscopy (PAM). These share the same scanning optical path and laser source. The induced photoacoustic (PA) signal was detected by a highly sensitive needle hydrophone; while the back-traveling fluorescent photons emitted from the same sample were collected by an avalanche photodetector. Experiments on ex vivo rat bladders were conducted. The CFM image depicted the shape and size of the individual cells successfully. Besides large polygonal umbrella cells, some intracellular components can also be discerned. With the CFM image presenting morphologic cellular information in the bladder wall, the PAM image provides the complementary information, based on the endogenous optical absorption contrast, of the microvascular distribution inside the bladder wall, from large vessels to capillaries. Such multimodal imaging provides the opportunity to realize both histological assay and characterization of microvasculature using one imaging setup. This approach offers the possibility of comprehensive diagnosis of cancer in vivo.

  19. Dual-detection confocal fluorescence microscopy: fluorescence axial imaging without axial scanning.

    Science.gov (United States)

    Lee, Dong-Ryoung; Kim, Young-Duk; Gweon, Dae-Gab; Yoo, Hongki

    2013-07-29

    We propose a new method for high-speed, three-dimensional (3-D) fluorescence imaging, which we refer to as dual-detection confocal fluorescence microscopy (DDCFM). In contrast to conventional beam-scanning confocal fluorescence microscopy, where the focal spot must be scanned either optically or mechanically over a sample volume to reconstruct a 3-D image, DDCFM can obtain the depth of a fluorescent emitter without depth scanning. DDCFM comprises two photodetectors, each with a pinhole of different size, in the confocal detection system. Axial information on fluorescent emitters can be measured by the axial response curve through the ratio of intensity signals. DDCFM can rapidly acquire a 3-D fluorescent image from a single two-dimensional scan with less phototoxicity and photobleaching than confocal fluorescence microscopy because no mechanical depth scans are needed. We demonstrated the feasibility of the proposed method by phantom studies.

  20. Direct imaging of phase objects enables conventional deconvolution in bright field light microscopy.

    Directory of Open Access Journals (Sweden)

    Carmen Noemí Hernández Candia

    Full Text Available In transmitted optical microscopy, absorption structure and phase structure of the specimen determine the three-dimensional intensity distribution of the image. The elementary impulse responses of the bright field microscope therefore consist of separate absorptive and phase components, precluding general application of linear, conventional deconvolution processing methods to improve image contrast and resolution. However, conventional deconvolution can be applied in the case of pure phase (or pure absorptive objects if the corresponding phase (or absorptive impulse responses of the microscope are known. In this work, we present direct measurements of the phase point- and line-spread functions of a high-aperture microscope operating in transmitted bright field. Polystyrene nanoparticles and microtubules (biological polymer filaments serve as the pure phase point and line objects, respectively, that are imaged with high contrast and low noise using standard microscopy plus digital image processing. Our experimental results agree with a proposed model for the response functions, and confirm previous theoretical predictions. Finally, we use the measured phase point-spread function to apply conventional deconvolution on the bright field images of living, unstained bacteria, resulting in improved definition of cell boundaries and sub-cellular features. These developments demonstrate practical application of standard restoration methods to improve imaging of phase objects such as cells in transmitted light microscopy.

  1. Laser reflector with an interference coating

    International Nuclear Information System (INIS)

    Vol'pyan, O D; Semenov, A A; Yakovlev, P P

    1998-01-01

    An analysis was made of the reflectivity of interference coatings intended for the use in optical pumping of solid-state lasers. Ruby and Nd 3+ :YAG lasers were used as models in comparative pumping efficiency measurements, carried out employing reflectors with interference and silver coatings. Estimates of the service life of reflectors with interference coatings were obtained. The power of a thermo-optical lens was reduced by the use of such coatings in cw lasers. (laser system components)

  2. The development of the spatially correlated adjustment wavelet filter for atomic force microscopy data

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Andrzej, E-mail: sikora@iel.wroc.pl [Electrotechnical Institute, Division of Electrotechnology and Materials Science, M. Skłodowskiej-Curie 55/61, 50-369 Wrocław (Poland); Rodak, Aleksander [Faculty of Electronics, Wrocław University of Technology, Janiszewskiego 11/17, 50-372 Wrocław (Poland); Unold, Olgierd [Institute of Computer Engineering, Control and Robotics, Faculty of Electronics, Wrocław University of Technology, Janiszewskiego 11/17, 50-372 Wrocław (Poland); Klapetek, Petr [Czech Metrology Institute, Okružní 31, 638 00 Brno (Czech Republic)

    2016-12-15

    In this paper a novel approach for the practical utilization of the 2D wavelet filter in terms of the artifacts removal from atomic force microscopy measurements results is presented. The utilization of additional data such as summary photodiode signal map is implemented in terms of the identification of the areas requiring the data processing, filtering settings optimization and the verification of the process performance. Such an approach allows to perform the filtering parameters adjustment by average user, while the straightforward method requires an expertise in this field. The procedure was developed as the function of the Gwyddion software. The examples of filtering the phase imaging and Electrostatic Force Microscopy measurement result are presented. As the wavelet filtering feature may remove a local artifacts, its superior efficiency over similar approach with 2D Fast Fourier Transformate based filter (2D FFT) can be noticed. - Highlights: • A novel approach to 2D wavelet-based filter for atomic force microscopy is shown. • The additional AFM measurement signal is used to adjust the filter. • Efficient removal of the local interference phenomena caused artifacts is presented.

  3. The development of the spatially correlated adjustment wavelet filter for atomic force microscopy data

    International Nuclear Information System (INIS)

    Sikora, Andrzej; Rodak, Aleksander; Unold, Olgierd; Klapetek, Petr

    2016-01-01

    In this paper a novel approach for the practical utilization of the 2D wavelet filter in terms of the artifacts removal from atomic force microscopy measurements results is presented. The utilization of additional data such as summary photodiode signal map is implemented in terms of the identification of the areas requiring the data processing, filtering settings optimization and the verification of the process performance. Such an approach allows to perform the filtering parameters adjustment by average user, while the straightforward method requires an expertise in this field. The procedure was developed as the function of the Gwyddion software. The examples of filtering the phase imaging and Electrostatic Force Microscopy measurement result are presented. As the wavelet filtering feature may remove a local artifacts, its superior efficiency over similar approach with 2D Fast Fourier Transformate based filter (2D FFT) can be noticed. - Highlights: • A novel approach to 2D wavelet-based filter for atomic force microscopy is shown. • The additional AFM measurement signal is used to adjust the filter. • Efficient removal of the local interference phenomena caused artifacts is presented.

  4. Applications of focused MeV light ion beams for high resolution channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson, D N; Breese, M B.H.; Prawer, S; Dooley, S P; Allen, M G; Bettiol, A A; Saint, A [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Ryan, C G [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1994-12-31

    The technique of Nuclear Microscopy, utilizing a focused ion probe of typically MeV H{sup +} or He{sup +} ions, can produce images where the contrast depends on typical Ion Beam Analysis (lBA) processes. The probe forming lens system usually utilizes strong focusing, precision magnetic quadrupole lenses and the probe is scanned over the target to produce images. Originally, this imaging technique was developed to utilize backscattered particles with incident beam currents typically of a few nA, and the technique became known as Channeling Contrast Microscopy (CCM). Recently, the technique has been developed further to utilize the forward scattering of ions incident along a major crystal axis in thin crystals. This technique is known as Channeling Scanning Transmission Ion Microscopy (CSTIM). Since nearly all incident ions are detected, CSTIM is highly efficient and very low beam currents are sufficient for imaging, typically as low as a few fA. This allows probes as small as 50 nm to be used. In this paper we briefly review the recent applications of these emerging techniques to a variety of single crystal materials (authors). 13 refs., 5 figs.

  5. Applications of focused MeV light ion beams for high resolution channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson, D.N.; Breese, M.B.H.; Prawer, S.; Dooley, S.P.; Allen, M.G.; Bettiol, A.A.; Saint, A. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Ryan, C.G. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    The technique of Nuclear Microscopy, utilizing a focused ion probe of typically MeV H{sup +} or He{sup +} ions, can produce images where the contrast depends on typical Ion Beam Analysis (lBA) processes. The probe forming lens system usually utilizes strong focusing, precision magnetic quadrupole lenses and the probe is scanned over the target to produce images. Originally, this imaging technique was developed to utilize backscattered particles with incident beam currents typically of a few nA, and the technique became known as Channeling Contrast Microscopy (CCM). Recently, the technique has been developed further to utilize the forward scattering of ions incident along a major crystal axis in thin crystals. This technique is known as Channeling Scanning Transmission Ion Microscopy (CSTIM). Since nearly all incident ions are detected, CSTIM is highly efficient and very low beam currents are sufficient for imaging, typically as low as a few fA. This allows probes as small as 50 nm to be used. In this paper we briefly review the recent applications of these emerging techniques to a variety of single crystal materials (authors). 13 refs., 5 figs.

  6. Nanometric locking of the tight focus for optical microscopy and tip-enhanced microscopy

    International Nuclear Information System (INIS)

    Hayazawa, N; Furusawa, K; Kawata, S

    2012-01-01

    We have successfully stabilized the tight focus onto the sample surface of an optical microscope within ±1.0 nm for a virtually unlimited time duration. The time-dependent thermal drift of the tight focus and the mechanical tilt of the sample surface were simultaneously sensed by a non-optical means based on a capacitive sensor and were compensated for in real-time. This non-optical scheme is promising for the suppression of background light sources for optical microscopy. The focus stabilization is crucial for microscopic measurement at an interface, particularly when scanning a large surface area, because there is always a certain amount of mechanical tilt of the sample substrate, which degrades the contrast of the image. When imaging nanoscopic materials such as carbon nanotubes or silicon nanowires, more stringent nanometric stabilization of the focus position relative to such samples is required, otherwise it is often difficult to interpret the results from the observations. Moreover, the smaller the sample volume is, the smaller the signal becomes, resulting in a long exposure time at each position. In this sense, long-term stability of the tight focus is essential for both microscopic large area scanning and nanosized sample scanning (high-resolution/large-area imaging). In addition, the recently developed tip-enhanced microscopy requires long-term stability of the relative position of the tip, sample and focus position. We were able to successfully demonstrate a stability improvement for tip-enhanced microscopy in the same manner. The stabilization of the tight focus enables us to perform long-term and robust measurements without any degradation of optical signal, resulting in the capability of true nanometric optical imaging with good reproducibility and high precision. The technique presented is a simple add-on for any kind of optical microscope. (paper)

  7. Developmental Change in Proactive Interference.

    Science.gov (United States)

    Kail, Robert

    2002-01-01

    Two studies examined age-related change in proactive interference from previously learned material. The meta-analysis of 26 studies indicated that proactive interference decreased with age. The cross-sectional study found that third through sixth graders' and college students' recall was accurate on Trial 1, but became less so over Trials 2…

  8. Interference Phenomenon with Mobile Displays

    Science.gov (United States)

    Trantham, Kenneth

    2015-01-01

    A simple experiment is presented in which the spacing and geometric pattern of pixels in mobile displays is measured. The technique is based on optical constructive interference. While the experiment is another opportunity to demonstrate wave interference from a grating-like structure, this can also be used to demonstrate concepts of solid state…

  9. Neural mechanisms of proactive interference-resolution.

    Science.gov (United States)

    Nee, Derek Evan; Jonides, John; Berman, Marc G

    2007-12-01

    The ability to mitigate interference from information that was previously relevant, but is no longer relevant, is central to successful cognition. Several studies have implicated left ventrolateral prefrontal cortex (VLPFC) as a region tied to this ability, but it is unclear whether this result generalizes across different tasks. In addition, it has been suggested that left anterior prefrontal cortex (APFC) also plays a role in proactive interference-resolution although support for this claim has been limited. The present study used event-related functional magnetic resonance imaging (fMRI) to investigate the role of these regions in resolving proactive-interference across two different tasks performed on the same subjects. Results indicate that both left VLPFC and left APFC are involved in the resolution of proactive interference across tasks. However, different functional networks related to each region suggest dissociable roles for the two regions. Additionally, regions of the posterior cingulate gyrus demonstrated unique involvement in facilitation when short- and long-term memory converged. This pattern of results serves to further specify models of proactive interference-resolution.

  10. Human response to interference with TV picture quality

    Energy Technology Data Exchange (ETDEWEB)

    Janischewskyj, W.; Harvey, E.B.

    1980-10-01

    Corona on transmission line conductors and spark gaps on loose or defective transmission line hardware can give rise to visual interference to television interference. The extent to which the interference is a concern (i.e., annoying) depends on the intensity of the interference as well as the strength of the television signal and can best be expressed as a function of the signal-to-noise ratio (SNR), the decibel difference between the wanted signal and the unwanted noise (interference). The study documented in this report has assessed, through subjective testing involving over 500 subjects, the interference level, as a function of SNR, of three different sources of interference: wet-weather conductor corona, a large spark gap (5 mm), and a small spark gap (0.8 mm). The results of the study should be particularly useful to the utility industry in assessing the environmental impact of high-voltage transmission lines.

  11. Dictionary of Microscopy

    Science.gov (United States)

    Heath, Julian

    2005-10-01

    The past decade has seen huge advances in the application of microscopy in all areas of science. This welcome development in microscopy has been paralleled by an expansion of the vocabulary of technical terms used in microscopy: terms have been coined for new instruments and techniques and, as microscopes reach even higher resolution, the use of terms that relate to the optical and physical principles underpinning microscopy is now commonplace. The Dictionary of Microscopy was compiled to meet this challenge and provides concise definitions of over 2,500 terms used in the fields of light microscopy, electron microscopy, scanning probe microscopy, x-ray microscopy and related techniques. Written by Dr Julian P. Heath, Editor of Microscopy and Analysis, the dictionary is intended to provide easy navigation through the microscopy terminology and to be a first point of reference for definitions of new and established terms. The Dictionary of Microscopy is an essential, accessible resource for: students who are new to the field and are learning about microscopes equipment purchasers who want an explanation of the terms used in manufacturers' literature scientists who are considering using a new microscopical technique experienced microscopists as an aide mémoire or quick source of reference librarians, the press and marketing personnel who require definitions for technical reports.

  12. Carbon nanostructure composite for electromagnetic interference

    Indian Academy of Sciences (India)

    2015-05-30

    based composite materials for electromagnetic interference (EMI) shielding. With more and more electronic gadgets being used at different frequencies, there is a need for shielding them from one another to avoid interference.

  13. Vibrational imaging and microspectroscopies based on coherent anti-Stokes Raman scattering microscopy

    International Nuclear Information System (INIS)

    Volkmer, Andreas

    2005-01-01

    For noninvasive characterization of chemical species or biological components within a complex heterogeneous system, their intrinsic molecular vibrational properties can be used in contrast mechanisms in optical microscopy. A series of recent advances have made coherent anti-Stokes Raman scattering (CARS) microscopy a powerful technique that allows vibrational imaging with high sensitivity, high spectral resolution and three-dimensional sectioning capability. In this review, we discuss theoretical and experimental aspects of CARS microscopy in a collinear excitation beam geometry. Particular attention is given to the underlying physical principles behind the new features of CARS signal generation under tight focusing conditions. We provide a brief overview of the instrumentation of CARS microscopy and its experimental characterization by means of imaging of model systems and live unstained cells. CARS microscopy offers the possibility of spatially resolved vibrational spectroscopy, providing chemical and physical structure information of molecular specimens on the sub-micrometre length scale. We review multiplex CARS microspectroscopy allowing fast acquisition of frequency-resolved CARS spectra, time-resolved CARS microspectroscopy recording ultrafast Raman free induction decays and CARS correlation spectroscopy probing dynamical processes with chemical selectivity. (topical review)

  14. The structure of dodecagonal (Ta,V){sub 1.6}Te imaged by phase-contrast scanning transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Krumeich, F., E-mail: krumeich@inorg.chem.ethz.ch [Laboratory of Inorganic Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Mueller, E.; Wepf, R.A. [Electron Microscopy ETH Zurich (EMEZ), Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland); Conrad, M.; Reich, C.; Harbrecht, B. [Department of Chemistry and Centre of Materials Science, Philipps-Universitaet, Hans-Meerwein-Strasse, 35032 Marburg (Germany); Nesper, R. [Laboratory of Inorganic Chemistry, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)

    2012-10-15

    While HRTEM is the well-established method to characterize the structure of dodecagonal tantalum (vanadium) telluride quasicrystals and their periodic approximants, phase-contrast imaging performed on an aberration-corrected scanning transmission electron microscope (STEM) represents a favorable alternative. The (Ta,V){sub 151}Te{sub 74} clusters, the basic structural unit in all these phases, can be visualized with high resolution. A dependence of the image contrast on defocus and specimen thickness has been observed. In thin areas, the projected crystal potential is basically imaged with either dark or bright contrast at two defocus values close to Scherzer defocus as confirmed by image simulations utilizing the principle of reciprocity. Models for square-triangle tilings describing the arrangement of the basic clusters can be derived from such images. - Graphical abstract: PC-STEM image of a (Ta,V){sub 151}Te{sub 74} cluster. Highlights: Black-Right-Pointing-Pointer C{sub s}-corrected STEM is applied for the characterization of dodecagonal quasicrystals. Black-Right-Pointing-Pointer The projected potential of the structure is mirrored in the images. Black-Right-Pointing-Pointer Phase-contrast STEM imaging depends on defocus and thickness. Black-Right-Pointing-Pointer For simulations of phase-contrast STEM images, the reciprocity theorem is applicable.

  15. Helium ion microscopy based wall thickness and surface roughness analysis of polymer foams obtained from high internal phase emulsion

    International Nuclear Information System (INIS)

    Rodenburg, C.; Viswanathan, P.; Jepson, M.A.E.; Liu, X.; Battaglia, G.

    2014-01-01

    Due to their wide range of applications, porous polymers obtained from high internal phase emulsions have been widely studied using scanning electron microscopy. However, due to their lack of electrical conductivity, quantitative information of wall thicknesses and surface roughness, which are of particular interest to tissue engineering, has not been obtained. Here, Helium Ion Microscopy is used to examine uncoated polymer foams and some very strong but unexpected contrast is observed, the origin of which is established here. Based on this analysis, a method for the measurement of wall thickness variations and wall roughness measurements has been developed, based on the modeling of Helium ion transmission. The results presented here indicate that within the walls of the void structure there exist small features with height variations of ∼30 nm and wall thickness variations from ∼100 nm to larger 340 nm in regions surrounding interconnecting windows within the structure. The suggested imaging method is applicable to other porous carbon based structures with wall thicknesses in the range of 40–340 nm. - Highlights: • The first helium ion microscopy image of uncoated structures formed from HIPEs is presented. • Unusually high contrast features that change with accelerating voltage are observed. • The origin of the observed contrast is determined to be mass thickness contrast. • A new method for quantitative wall thickness variation/roughness measurements is demonstrated

  16. Helium ion microscopy based wall thickness and surface roughness analysis of polymer foams obtained from high internal phase emulsion

    Energy Technology Data Exchange (ETDEWEB)

    Rodenburg, C., E-mail: c.rodenburg@sheffield.ac.uk [Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Viswanathan, P. [Department of Biomedical Sciences, University of Sheffield, Firth Court, Western Bank Sheffield, Sheffield S10 2 TN (United Kingdom); Jepson, M.A.E. [Department of Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom); Liu, X. [Carl Zeiss Microscopy GmbH, Carl-Zeiss-Strasse 22, 73447 Oberkochen (Germany); Battaglia, G. [Department of Chemistry University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); The MRC/UCL Centre for Medical Molecular Virology, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2014-04-01

    Due to their wide range of applications, porous polymers obtained from high internal phase emulsions have been widely studied using scanning electron microscopy. However, due to their lack of electrical conductivity, quantitative information of wall thicknesses and surface roughness, which are of particular interest to tissue engineering, has not been obtained. Here, Helium Ion Microscopy is used to examine uncoated polymer foams and some very strong but unexpected contrast is observed, the origin of which is established here. Based on this analysis, a method for the measurement of wall thickness variations and wall roughness measurements has been developed, based on the modeling of Helium ion transmission. The results presented here indicate that within the walls of the void structure there exist small features with height variations of ∼30 nm and wall thickness variations from ∼100 nm to larger 340 nm in regions surrounding interconnecting windows within the structure. The suggested imaging method is applicable to other porous carbon based structures with wall thicknesses in the range of 40–340 nm. - Highlights: • The first helium ion microscopy image of uncoated structures formed from HIPEs is presented. • Unusually high contrast features that change with accelerating voltage are observed. • The origin of the observed contrast is determined to be mass thickness contrast. • A new method for quantitative wall thickness variation/roughness measurements is demonstrated.

  17. Atomic Force Microscope Image Contrast Mechanisms on Supported Lipid Bilayers

    OpenAIRE

    Schneider, James; Dufrêne, Yves F.; Barger Jr., William R.; Lee, Gil U.

    2000-01-01

    This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures o...

  18. Methylene blue microbubbles as a model dual-modality contrast agent for ultrasound and activatable photoacoustic imaging

    Science.gov (United States)

    Jeon, Mansik; Song, Wentao; Huynh, Elizabeth; Kim, Jungho; Kim, Jeesu; Helfield, Brandon L.; Leung, Ben Y. C.; Goertz, David E.; Zheng, Gang; Oh, Jungtaek; Lovell, Jonathan F.; Kim, Chulhong

    2014-01-01

    Ultrasound and photoacoustic imaging are highly complementary modalities since both use ultrasonic detection for operation. Increasingly, photoacoustic and ultrasound have been integrated in terms of hardware instrumentation. To generate a broadly accessible dual-modality contrast agent, we generated microbubbles (a standard ultrasound contrast agent) in a solution of methylene blue (a standard photoacoustic dye). This MB2 solution was formed effectively and was optimized as a dual-modality contrast solution. As microbubble concentration increased (with methylene blue concentration constant), photoacoustic signal was attenuated in the MB2 solution. When methylene blue concentration increased (with microbubble concentration held constant), no ultrasonic interference was observed. Using an MB2 solution that strongly attenuated all photoacoustic signal, high powered ultrasound could be used to burst the microbubbles and dramatically enhance photoacoustic contrast (>800-fold increase), providing a new method for spatiotemporal control of photoacoustic signal generation.

  19. Waveguide evanescent field fluorescence microscopy & its application in cell biology

    Science.gov (United States)

    Hassanzadeh, Abdollah

    There are many powerful microscopy technologies available for the investigation of bulk materials as well as for thin film samples. Nevertheless, for imaging an interface, especially live cells on a substrate and ultra thin-films, only Total Internal Reflection Fluorescence (TIRF) microscopy is available. This TIRF microscopy allows imaging without interference of the bulk. Various approaches are employed in fluorescence microscopy applications to restrict the excitation and detection of fluorophores to a thin region of the specimen. Elimination of background fluorescence from outside the focal plane can dramatically improve the signal-to-noise ratio, and consequently, the spatial resolution of the features or events of interest. TIRF microscopy is an evanescent field based microscopy. In this method, fluorescent dyes are only excited within an evanescent field: roughly within 100 nm above a glass coverslip. This will allow imaging surface and interfacial issues of the glass coverslip and an adjacent material. Waveguide evanescent field fluorescence (WEFF) microscopy is a new development for imaging cell-substrate interactions in real time and in vitro. It is an alternative to TIRF microscopy. In this method the light is coupled into a waveguide via an optical grating. The coupled light propagates as a waveguide mode and exhibits an evanescent field on top of the waveguide. This can be used as a surface-bound illumination source to excite fluorophores. This evanescent field serves as an extremely powerful tool for quality control of thin films, to study cell-substrate contacts, and investigating the effect of external agents and drugs on the cell-substrate interaction in real time and in vitro. This new method has been established and optimized to minimize non-uniformity, scattering and photo bleaching issues. Visualizing and quantifying of the cell-substrates and solid thin films have been carried out by WEFF microscopy. The images of the cell-substrate interface

  20. Clinical experience with a commercially available negative oral contrast medium in PET/CT

    International Nuclear Information System (INIS)

    Hausegger, K.; Reinprecht, P.; Kau, T.; Igerc, I.; Lind, P.

    2005-01-01

    Purpose: to evaluate a commercially available negative oral contrast material for PET/CT. Material and methods: in a prospective series of 49 patients, Mukofalk registered , which is a vegetarian-based substance, was used as a negative oral contrast medium in whole body PET/CT studies. Mukofalk was administered during a time period of 1.5 hours before the examination. Quality of small bowl distension and eventual pathological tracer uptake in the intestine were evaluated. Results: distension of the small bowel was excellent or good in 41 (85%) and poor in 8 (15%) patients. Mild tracer uptake in the small bowel was observed in 5 patients (10.2%) and moderate uptake in another 2 patients (4%). In none of these patients did the F-18 FDG uptake interfere with image interpretation. Conclusion: Mukofalk registered can be used as a negative oral contrast medium in PET/CT studies. (orig.)

  1. Clinical experience with a commercially available negative oral contrast medium in PET/CT

    Energy Technology Data Exchange (ETDEWEB)

    Hausegger, K.; Reinprecht, P. [Roentgendiagnostisches Zentralinstitut, LKH Klagenfurt (Austria); Kau, T. [Roentgendiagnostisches Zentral Inst., Klagenfurt (Austria); Igerc, I.; Lind, P. [Abt. fuer Nuklearmedizin und Spezielle Endokrinologie, LKH Klagenfurt (Austria)

    2005-06-01

    Purpose: to evaluate a commercially available negative oral contrast material for PET/CT. Material and methods: in a prospective series of 49 patients, Mukofalk {sup registered}, which is a vegetarian-based substance, was used as a negative oral contrast medium in whole body PET/CT studies. Mukofalk was administered during a time period of 1.5 hours before the examination. Quality of small bowl distension and eventual pathological tracer uptake in the intestine were evaluated. Results: distension of the small bowel was excellent or good in 41 (85%) and poor in 8 (15%) patients. Mild tracer uptake in the small bowel was observed in 5 patients (10.2%) and moderate uptake in another 2 patients (4%). In none of these patients did the F-18 FDG uptake interfere with image interpretation. Conclusion: Mukofalk {sup registered} can be used as a negative oral contrast medium in PET/CT studies. (orig.)

  2. Preclinical Studies of a Kidney Safe Iodinated Contrast Agent.

    Science.gov (United States)

    Rowe, Elizabeth S; Rowe, Vernon D; Biswas, Sangita; Mosher, Gerold; Insisienmay, Lovella; Ozias, Marlies K; Gralinski, Michael R; Hunter, John; Barnett, James S

    2016-09-01

    Contrast-induced acute kidney injury (CI-AKI) is a serious complication of the use of iodinated contrast agents. This problem is particularly acute in interventional neurology and interventional cardiology, probably due to the intra-arterial route of injection, high contrast volumes, and preexisting risk factors of these patients. In an attempt to develop a contrast agent that is less damaging to the kidneys, we have studied the effects of adding a small amount of the substituted cyclodextrin, sulfobutyl-ether-β-cyclodextrin (SBECD), to iohexol in rodent models of renal toxicity. Renally compromised mice and rats were injected with iohexol and iohexol-SBECD via the tail vein. The renal pathology, creatinine clearance, and survival benefits of iohexol-SBECD were studied. The safety of direct intra-arterial injection of the iohexol-SBECD formulation was studied in a dog heart model system. Mechanism of action studies in cell culture model using a human kidney cell line was performed using flow cytometry. Nephrotoxicity was significantly reduced using iohexol-SBECD compared to iohexol alone, at mole ratios of iohexol:SBECD of 1:0.025. SBECD increased survival from 50% to 88% in a rat survival study. In the dog heart model, iohexol-SBECD was safe. Cell culture studies suggest that SBECD interferes with the early stages of contrast-induced apoptosis in a human renal cell line. We have shown that the addition of a small amount of SBECD (one molecule of SBECD per 40 iohexol molecules) significantly protects rodent kidneys from CI-AKI. Further development of this new formulation of iodinated contrast is warranted. © 2016 The Authors. Journal of Neuroimaging published by Wiley Periodicals, Inc. on behalf of American Society of Neuroimaging.

  3. Heavy-ion microscopy

    International Nuclear Information System (INIS)

    Kraft, G.; Yang, T.C.H.; Richards, T.; Tobias, C.A.

    1980-01-01

    This chapter briefly describes the techniques of optical microscopy, scanning and transmission electron microscopy, soft x-ray microscopy and compares these latter techniques with heavy-ion microscopy. The resolution obtained with these various types of microscopy are compared and the influence of the etching procedure on total resolution is discussed. Several micrographs of mammalian cells are included

  4. Interference impacts working memory in mild cognitive impairment

    Directory of Open Access Journals (Sweden)

    Sara Aurtenetxe

    2016-10-01

    Full Text Available Mild cognitive impairment (MCI is considered a transitional stage between healthy aging and dementia, specifically Alzheimer’s disease (AD. The most common cognitive impairment of MCI includes episodic memory loss and difficulties in working memory (WM. Interference can deplete WM, and an optimal WM performance requires an effective control of attentional resources between the memoranda and the incoming stimuli. Difficulties in handling interference lead to forgetting. However, the interplay between interference and WM in MCI is not well understood and needs further investigation. The current study investigated the effect of interference during a WM task in 20 MCIs and 20 healthy elder volunteers. Participants performed a delayed match-to-sample paradigm which consisted in two interference conditions, distraction and interruption, and one control condition without any interference. Results evidenced a disproportionate impact of interference on the WM performance of MCIs, mainly in the presence of interruption. These findings demonstrate that interference, and more precisely interruption, is an important proxy for memory-related deficits in MCI. Thus the current findings reveal novel evidence regarding the causes of WM forgetting in MCI patients, associated with difficulties in the mechanisms of attentional control.

  5. Output Interference in Recognition Memory

    Science.gov (United States)

    Criss, Amy H.; Malmberg, Kenneth J.; Shiffrin, Richard M.

    2011-01-01

    Dennis and Humphreys (2001) proposed that interference in recognition memory arises solely from the prior contexts of the test word: Interference does not arise from memory traces of other words (from events prior to the study list or on the study list, and regardless of similarity to the test item). We evaluate this model using output…

  6. Direct observation of Young’s double-slit interferences in vibrationally resolved photoionization of diatomic molecules

    Science.gov (United States)

    Canton, Sophie E.; Plésiat, Etienne; Bozek, John D.; Rude, Bruce S.; Decleva, Piero; Martín, Fernando

    2011-01-01

    Vibrationally resolved valence-shell photoionization spectra of H2, N2 and CO have been measured in the photon energy range 20–300 eV using third-generation synchrotron radiation. Young’s double-slit interferences lead to oscillations in the corresponding vibrational ratios, showing that the molecules behave as two-center electron-wave emitters and that the associated interferences leave their trace in the angle-integrated photoionization cross section. In contrast to previous work, the oscillations are directly observable in the experiment, thereby removing any possible ambiguity related to the introduction of external parameters or fitting functions. A straightforward extension of an original idea proposed by Cohen and Fano [Cohen HD, Fano U (1966) Phys Rev 150:30] confirms this interpretation and shows that it is also valid for diatomic heteronuclear molecules. Results of accurate theoretical calculations are in excellent agreement with the experimental findings.

  7. Nanoshells for in vivo imaging using two-photon excitation microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gao Liang; Nammalvar, Vengadesan [Department of Bioengineering, Rice University, Houston, TX 77005 (United States); Vadakkan, Tegy J, E-mail: lg3@rice.edu, E-mail: venkyn@rice.edu [Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030 (United States)

    2011-09-07

    Gold nanoshells have been intensively investigated and applied to various biomedical fields because of their flexible optical tunability and biological compatibility. They hold great potential to serve as luminescent contrast agents excitable with near-infrared (NIR) lasers. In this paper, we describe the development of nanoshells with a peak of plasmon resonance at 800 nm and their subsequent use for in vivo blood vessel imaging using two-photon excitation microscopy at an excitation wavelength of 750 nm. We were able to image single nanoshell particles in blood vessels and generate optical contrast for blood vessel structure using luminescent signals. These results confirm the feasibility of engineering nanoshells with controlled optical properties for single-particle-based in vivo imaging.

  8. Optimal interference code based on machine learning

    Science.gov (United States)

    Qian, Ye; Chen, Qian; Hu, Xiaobo; Cao, Ercong; Qian, Weixian; Gu, Guohua

    2016-10-01

    In this paper, we analyze the characteristics of pseudo-random code, by the case of m sequence. Depending on the description of coding theory, we introduce the jamming methods. We simulate the interference effect or probability model by the means of MATLAB to consolidate. In accordance with the length of decoding time the adversary spends, we find out the optimal formula and optimal coefficients based on machine learning, then we get the new optimal interference code. First, when it comes to the phase of recognition, this study judges the effect of interference by the way of simulating the length of time over the decoding period of laser seeker. Then, we use laser active deception jamming simulate interference process in the tracking phase in the next block. In this study we choose the method of laser active deception jamming. In order to improve the performance of the interference, this paper simulates the model by MATLAB software. We find out the least number of pulse intervals which must be received, then we can make the conclusion that the precise interval number of the laser pointer for m sequence encoding. In order to find the shortest space, we make the choice of the greatest common divisor method. Then, combining with the coding regularity that has been found before, we restore pulse interval of pseudo-random code, which has been already received. Finally, we can control the time period of laser interference, get the optimal interference code, and also increase the probability of interference as well.

  9. Coherent interference effects in SIEM and CBED

    International Nuclear Information System (INIS)

    Cowley, J.M.

    1981-01-01

    The coherent convergent incident beam produced by the field emission gun of a STEM instrument allows the observation of a number of unusual interference effects in the shadow images (SIEM) and convergent beam diffraction (CBED) patterns visible on the detector plane. Shadow images of thin crystals display the electron Ronchigrams having a form sensitive to the defocus and aberrations of the objective lens. For large crystal lattice spacings the Ronchigrams show characteristic ellipses of low contrast. CBED patterns of thin crystal show symmetries and intensities which vary with the position of the incident beam within the unit cell. Discontinuities in the specimen such as the edges of crystals show striking Fresnel diffraction effects in SIEM. In CBED patterns they give rise to the splitting of diffraction spots. If the incident beam is parallel to a smooth face of a small crystal the potential field outside the crystal gives rise to strong refraction effects. (orig.)

  10. Diffraction contrast STEM of dislocations: Imaging and simulations

    International Nuclear Information System (INIS)

    Phillips, P.J.; Brandes, M.C.; Mills, M.J.; De Graef, M.

    2011-01-01

    The application of scanning transmission electron microscopy (STEM) to crystalline defect analysis has been extended to dislocations. The present contribution highlights the use of STEM on two oppositely signed sets of near-screw dislocations in hcp α-Ti with 6 wt% Al in solid solution. In addition to common systematic row diffraction conditions, other configurations such as zone axis and 3g imaging are explored, and appear to be very useful not only for defect analysis, but for general defect observation. It is demonstrated that conventional TEM rules for diffraction contrast such as g.b and g.R are applicable in STEM. Experimental and computational micrographs of dislocations imaged in the aforementioned modes are presented. -- Highlights: → STEM defect analysis has been extended to include dislocations. → Systematic row, zone axis and 3g diffraction conditions are all found to be useful for general defect observations in STEM mode. → Conventional contrast visibility rules for diffraction contrast are found to remain valid for STEM observations. → Multi-beam dynamical scattering matrix simulations provide excellent agreement with experimental images.

  11. A PHONETIC CONTRASTIVE ANALYSIS OF ENGLISH WORDS IN THREE JAPANESE SONGS BY AKB48

    OpenAIRE

    Harwintha Y. Anjarningsih; Anisa Saraayu

    2015-01-01

    Many studies have revealed how Japanese speakers pronounce English words differently. However, not much research has explained the causes of the difference, let alone relating such difference with native language interference. By drawing a comparison between the sound structures of the English and Japanese languages using Contrastive Analysis Hypothesis (CAH), we will see how native language may influence foreign language USAge and cause pronunciation differences in popular songs. Transcripti...

  12. WEED INTERFERENCE IN EGGPLANT CROPS

    Directory of Open Access Journals (Sweden)

    LUIZ JUNIOR PEREIRA MARQUES

    2017-01-01

    Full Text Available Uncontrolled weed growth interferes with the growth eggplants and crop yields. To control weeds, the main weed species must be identified in crop growing areas and during weed control periods, as weed species might vary in relation to management practices. Therefore, this study aimed to identify the main weed species and determine the periods of weed interference in the eggplant cultivar Nápoli when grown under certain cultural practices, including plant staking and sprout thinning. The experiment was carried out in 2014 using a randomized complete block design, with 3 replications. The treatments consisted of 11 periods of (1 increasing weed control and (2 increasing coexistence of eggplant with weeds from the first day of transplanting (0-14, 0-28, 0-42, 0-56, 0-70, 0-84, 0-98, 0-112, 0-126, 0-140, and up do day 154. Eggplant staking and sprout thinning were performed 42 days after transplanting (DAT. Weed identification and crop yield assessments were performed to determine the Period Before Interference (PBI, Total Period of Interference Prevention (TPIP, and the Critical Period of Interference Prevention (CPIP. The major weeds found in the eggplant cultivar Nápoli were Eleusine indica, Portulaca oleracea, and Cyperus rotundus. Coexistence between the weed community and the eggplant throughout the entire crop production cycle reduced eggplant fruit yield by 78%. The PBI was 29 DAT and the TPIP was 48 DAT, resulting in 19 days of CPIP.

  13. Effects of intraarticular contrast media on synovial membrane and cartilage: An electron microscopic evaluation in rabbit knees

    International Nuclear Information System (INIS)

    Kose, N.; Inan, U.; Omeroglu, H.; Seber, S.; Baycu, C.; Omeroglu, H.

    2007-01-01

    To evaluate the histological and ultrastructural alterations in rabbit knee joint cartilage and synovia induced by intraarticular injections of 2 water soluble contrast agents. The study was conducted at the Department of Orthopedics and Traumatology, Medical Faculty, Osmangazi University, Eskisehir, Turkey in January 2002. To examine the effect of contrast agents on articular cartilage and synovial membrane, rabbit model was used. Specimens from 62 knee joints were examined by light microscopy and transmission electron microscopy one hour, one day, one week and 2 weeks after intraarticular administration of gadolinium-diethylenetriamine pentaacetic acid, iopromide or saline. In the knees injected with saline, light microscopic changes of the synovium consisted of edema only. Edema and hyperemia were seen in contrast agent injected knees. Ultrastructurally, numerous and large pinocytotic vesicles in A cells of the synovial membrane were seen in contrast agent injected groups. In the knees injected with saline the cartilage were ultrastructurally normal but contrast agent injected knees showed increased activation of chondrocytes with increase of dense glycogen accumulation, large lipid vacuoles and matrix material. There were very rare pycnotic cells in these samples. The rating scale has been used and the means of the total scores were determined for the groups. The effects of contrast agents reduced gradually on the cartilage and synovium in general but did not become completely normal in the observation period. (author)

  14. Analysing Self Interference Cancellation in Full Duplex Radios

    DEFF Research Database (Denmark)

    Mahmood, Nurul Huda; Shafique Ansari, Imran; Berardinelli, Gilberto

    2016-01-01

    Full duplex communication promises a theoretical $100\\%$ throughput gain by doubling the number of simultaneous transmissions. Such compelling gains are conditioned on perfect cancellation of the self interference power resulting from simultaneous transmission and reception. Generally, self...... interference power is modelled as a noise-like constant level interference floor. However, experimental validations have shown that the self interference power is in practice a random variable depending on a number of factors such as the surrounding wireless environment and the degree of interference...... cancellation. In this study, we derive an analytical model for the residual self interference power, and demonstrate various applications of the derived model in analysing the performance of a Full Duplex radio. In general, full duplex communication is found to provide only modest throughput gains over half...

  15. Comparison of mounting methods for the evaluation of fibers by phase contrast microscopy.

    Science.gov (United States)

    Lee, Eun Gyung; Pang, Thomas W S; Nelson, John; Andrew, Mike; Harper, Martin

    2011-07-01

    The objectives of this study were to evaluate mounting methods for fiber examination of air sample filters by phase contrast microscopy (PCM) and to evaluate differences in fiber counts that might be due to fiber movement. Acetone/triacetin (AT) with various amounts of triacetin and acetone/Euparal (AE) where the mounting medium was placed between the cleared filter wedge and the coverslip were tested as a function of time. Field sample slides collected from a taconite iron-ore processing mill, a tremolitic talc-ore processing mill, and from around a crusher in a meta-basalt stone quarry were prepared with relocatable coverslips to revisit the same field areas on the slides. For each slide, three or four field areas were randomly selected and pictures were taken every 2 weeks to determine any sign of fiber movement over time. For 11 AT slides (named as AT-3.5) prepared with 3.5 μl of the mounting medium according to the NIOSH 7400 method, no fiber movements were detected over 59 weeks. On the other hand, AT slides prepared with larger quantities (10, 15, and 20 μl) of the mounting medium (named as AT-10) and AE slides prepared with ∼10 μl mounting medium showed fiber movement from the eighth day at the earliest. Fiber movement began earlier for the slides mounted with excess triacetin than for those mounted with Euparal. The sample slide storage method, either vertically or horizontally, did not seem to accelerate fiber movement. Additionally, two other modified methods, dimethylformamide solution/Euparal (mDE) and dimethylformamide solution/triacetin (mDT), were also prepared where the mounting medium was placed between the cleared filter wedge and the glass slide. The findings of fiber movements were similar; when 3.5 μl of triacetin was used for the mDT slides, fiber movements were not detected, while fibers on slides prepared with 10 μl triacetin (mDT-10) moved around. No fiber movements were observed for the mDE slides at any time during 59 weeks. Once

  16. Mechanisms of decoherence in electron microscopy.

    Science.gov (United States)

    Howie, A

    2011-06-01

    The understanding and where possible the minimisation of decoherence mechanisms in electron microscopy were first studied in plasmon loss, diffraction contrast images but are of even more acute relevance in high resolution TEM phase contrast imaging and electron holography. With the development of phase retrieval techniques they merit further attention particularly when their effect cannot be eliminated by currently available energy filters. The roles of electronic excitation, thermal diffuse scattering, transition radiation and bremsstrahlung are examined here not only in the specimen but also in the electron optical column. Terahertz-range aloof beam electronic excitation appears to account satisfactorily for recent observations of decoherence in electron holography. An apparent low frequency divergence can emerge for the calculated classical bremsstrahlung event probability but can be ignored for photon wavelengths exceeding the required coherence distance or path lengths in the equipment. Most bremsstrahlung event probabilities are negligibly important except possibly in large-angle bending magnets or mandolin systems. A more reliable procedure for subtracting thermal diffuse scattering from diffraction pattern intensities is proposed. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Mechanisms of decoherence in electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Howie, A., E-mail: ah30@cam.ac.uk [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2011-06-15

    The understanding and where possible the minimisation of decoherence mechanisms in electron microscopy were first studied in plasmon loss, diffraction contrast images but are of even more acute relevance in high resolution TEM phase contrast imaging and electron holography. With the development of phase retrieval techniques they merit further attention particularly when their effect cannot be eliminated by currently available energy filters. The roles of electronic excitation, thermal diffuse scattering, transition radiation and bremsstrahlung are examined here not only in the specimen but also in the electron optical column. Terahertz-range aloof beam electronic excitation appears to account satisfactorily for recent observations of decoherence in electron holography. An apparent low frequency divergence can emerge for the calculated classical bremsstrahlung event probability but can be ignored for photon wavelengths exceeding the required coherence distance or path lengths in the equipment. Most bremsstrahlung event probabilities are negligibly important except possibly in large-angle bending magnets or mandolin systems. A more reliable procedure for subtracting thermal diffuse scattering from diffraction pattern intensities is proposed.

  18. Mechanisms of decoherence in electron microscopy

    International Nuclear Information System (INIS)

    Howie, A.

    2011-01-01

    The understanding and where possible the minimisation of decoherence mechanisms in electron microscopy were first studied in plasmon loss, diffraction contrast images but are of even more acute relevance in high resolution TEM phase contrast imaging and electron holography. With the development of phase retrieval techniques they merit further attention particularly when their effect cannot be eliminated by currently available energy filters. The roles of electronic excitation, thermal diffuse scattering, transition radiation and bremsstrahlung are examined here not only in the specimen but also in the electron optical column. Terahertz-range aloof beam electronic excitation appears to account satisfactorily for recent observations of decoherence in electron holography. An apparent low frequency divergence can emerge for the calculated classical bremsstrahlung event probability but can be ignored for photon wavelengths exceeding the required coherence distance or path lengths in the equipment. Most bremsstrahlung event probabilities are negligibly important except possibly in large-angle bending magnets or mandolin systems. A more reliable procedure for subtracting thermal diffuse scattering from diffraction pattern intensities is proposed.

  19. Cross-limb interference during motor learning.

    Directory of Open Access Journals (Sweden)

    Benedikt Lauber

    Full Text Available It is well known that following skill learning, improvements in motor performance may transfer to the untrained contralateral limb. It is also well known that retention of a newly learned task A can be degraded when learning a competing task B that takes place directly after learning A. Here we investigate if this interference effect can also be observed in the limb contralateral to the trained one. Therefore, five different groups practiced a ballistic finger flexion task followed by an interfering visuomotor accuracy task with the same limb. Performance in the ballistic task was tested before the training, after the training and in an immediate retention test after the practice of the interference task for both the trained and the untrained hand. After training, subjects showed not only significant learning and interference effects for the trained limb but also for the contralateral untrained limb. Importantly, the interference effect in the untrained limb was dependent on the level of skill acquisition in the interfering motor task. These behavioural results of the untrained limb were accompanied by training specific changes in corticospinal excitability, which increased for the hemisphere ipsilateral to the trained hand following ballistic training and decreased during accuracy training of the ipsilateral hand. The results demonstrate that contralateral interference effects may occur, and that interference depends on the level of skill acquisition in the interfering motor task. This finding might be particularly relevant for rehabilitation.

  20. Optimization and stability of the contrast transfer function in aberration-corrected electron microscopy

    International Nuclear Information System (INIS)

    Tromp, R.M.; Schramm, S.M.

    2013-01-01

    The Contrast Transfer Function (CTF) describes the manner in which the electron microscope modifies the object exit wave function as a result of objective lens aberrations. For optimum resolution in C 3 -corrected microscopes it is well established that a small negative value of C 3 , offset by positive values of C 5 and defocus C 1 results in the most optimal instrument resolution, and optimization of the CTF has been the subject of several studies. Here we describe a simple design procedure for the CTF that results in a most even transfer of information below the resolution limit. We address not only the resolution of the instrument, but also the stability of the CTF in the presence of small disturbances in C 1 and C 3 . We show that resolution can be traded for stability in a rational and transparent fashion. These topics are discussed quantitatively for both weak-phase and strong-phase (or amplitude) objects. The results apply equally to instruments at high electron energy (TEM) and at very low electron energy (LEEM), as the basic optical properties of the imaging lenses are essentially identical. - Highlights: ► An optimized Contrast Transfer Function for aberration corrected electron microscopes is proposed. ► Based on the properties of the CTF near optimum settings, we address its stability. ► Over some range of parameters resolution can be traded for stability. ► These issues are addressed for weak-phase objects, as well as strong-phase and amplitude object. ► We compare our results with CTF settings previously proposed

  1. Detection device for control rod interference

    International Nuclear Information System (INIS)

    Saito, Noboru.

    1984-01-01

    Purpose: To enable to detect the mechanical interference or friction between a control rod and a channel box automatically, simply and rapidly. Constitution: A signal from a gate circuit and a signal from a comparison mechanism are inputted into an AND circuit if a control rod has not been displaced by a predetermined distance within a prescribed time Δt after the output of an insertion or withdrawal signal for the control rod, by which a control-rod-interference signal is outputted from the AND circuit. Accordingly, the interference between the control rod and the channel box can be detected automatically, easily and rapidly. Furthermore, by properly adjusting the prescribed time Δt set by the gate circuit, the degree of the interference can also be detected, whereby the safety and the reliability of the reactor can be improved significantly. (Horiuchi, T.)

  2. Interference Coordination for Dense Wireless Networks

    DEFF Research Database (Denmark)

    Soret, Beatriz; Pedersen, Klaus I.; Jørgensen, Niels T.K.

    2015-01-01

    and dense deployment in Tokyo are compared. Evolution to DenseNets offers new opportunities for further development of downlink interference cooperation techniques. Various mechanisms in LTE and LTE-Advanced are revisited. Some techniques try to anticipate the future in a proactive way, whereas others......The promise of ubiquitous and super-fast connectivity for the upcoming years will be in large part fulfilled by the addition of base stations and spectral aggregation. The resulting very dense networks (DenseNets) will face a number of technical challenges. Among others, the interference emerges...... as an old acquaintance with new significance. As a matter of fact, the interference conditions and the role of aggressor and victim depend to a large extent on the density and the scenario. To illustrate this, downlink interference statistics for different 3GPP simulation scenarios and a more irregular...

  3. Phase Contrast Imaging

    International Nuclear Information System (INIS)

    Menk, Ralf Hendrik

    2008-01-01

    All standard (medical) x-ray imaging technologies, rely primarily on the amplitude properties of the incident radiation, and do not depend on its phase. This is unchanged since the discovery by Roentgen that the intensity of an x-ray beam, as measured by the exposure on a film, was related to the relative transmission properties of an object. However, recently various imaging techniques have emerged which depend on the phase of the x-rays as well as the amplitude. Phase becomes important when the beam is coherent and the imaging system is sensitive to interference phenomena. Significant new advances have been made in coherent optic theory and techniques, which now promise phase information in medical imaging. The development of perfect crystal optics and the increasing availability of synchrotron radiation facilities have contributed to a significant increase in the application of phase based imaging in materials and life sciences. Unique source characteristics such as high intensity, monochromaticity, coherence and high collimating provide an ideal source for advanced imaging. Phase contrast imaging has been applied in both projection and computed tomography modes, and recent applications have been made in the field of medical imaging. Due to the underlying principle of X-ray detection conventional image receptors register only intensities of wave fields and not their phases. During the last decade basically five different methods were developed that translate the phase information into intensity variations. These methods are based on measuring the phase shift φ directly (using interference phenomena), the gradient ∇ φ , or the Laplacian ∇ 2 φ. All three methods can be applied to polychromatic X-ray sources keeping in mind that the native source is synchrotron radiation, featuring monochromatic and reasonable coherent X-ray beams. Due to the vast difference in the coefficients that are driven absorption and phase effects (factor 1,000-10,000 in the energy

  4. Neurogenesis-mediated forgetting minimizes proactive interference.

    Science.gov (United States)

    Epp, Jonathan R; Silva Mera, Rudy; Köhler, Stefan; Josselyn, Sheena A; Frankland, Paul W

    2016-02-26

    Established memories may interfere with the encoding of new memories, particularly when existing and new memories overlap in content. By manipulating levels of hippocampal neurogenesis, here we show that neurogenesis regulates this form of proactive interference. Increasing hippocampal neurogenesis weakens existing memories and, in doing so, facilitates the encoding of new, conflicting (but not non-conflicting) information in mice. Conversely, decreasing neurogenesis stabilizes existing memories, and impedes the encoding of new, conflicting information. These results suggest that reduced proactive interference is an adaptive benefit of neurogenesis-induced forgetting.

  5. Exploitation of Contrasts in Low Energy SEM to Reveal True Microstructure

    Czech Academy of Sciences Publication Activity Database

    Müllerová, Ilona; Mikmeková, Šárka; Mikmeková, Eliška; Pokorná, Zuzana; Frank, Luděk

    2014-01-01

    Roč. 20, S3 (2014), s. 858-859 ISSN 1431-9276 R&D Projects: GA TA ČR TE01020118; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : scanning low energy electron microscopy * contrast * cathode lens Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.877, year: 2014

  6. Innovative Strategies for Clinical Microscopy Instruction: Virtual Versus Light Microscopy.

    Science.gov (United States)

    McDaniel, M Jane; Russell, Gregory B; Crandall, Sonia J

    2018-06-01

    The purpose of the study was to compare virtual microscopy with light microscopy to determine differences in learning outcomes and learner attitudes in teaching clinical microscopy to physician assistant (PA) students. A prospective, randomized, crossover design study was conducted with a convenience sample of 67 first-year PA students randomized to 2 groups. One group used light microscopes to find microscopic structures, whereas the other group used instructor-directed video streaming of microscopic elements. At the midpoint of the study, the groups switched instructional strategies. Learning outcomes were assessed via posttest after each section of the study, with comparison of final practical examination results to previous cohorts. Attitudes about the 2 educational strategies were assessed through a postcourse questionnaire with a Likert scale. Analysis of the first posttest demonstrated that students in the video-streamed group had significantly better learning outcomes than those in the light microscopy group (P = .004; Cohen's d = 0.74). Analysis of the posttest after crossover showed no differences between the 2 groups (P = .48). Between the 2 posttests, students first assigned to the light microscopy group scored a 6.6 mean point increase (±10.4 SD; p = .0011), whereas students first assigned to the virtual microscopy group scored a 1.3 mean point increase (±7.1 SD; p = .29). The light microscopy group improved more than the virtual microscopy group (P = .019). Analysis of practical examination data revealed higher scores for the study group compared with 5 previous cohorts of first-year students (P virtual microscopy to traditional light microscopy. Virtual microscopy is an effective educational strategy, and students prefer this method when learning to interpret images of clinical specimens.

  7. Naming and categorizing objects: task differences modulate the polarity of semantic effects in the picture-word interference paradigm.

    Science.gov (United States)

    Hantsch, Ansgar; Jescheniak, Jörg D; Mädebach, Andreas

    2012-07-01

    The picture-word interference paradigm is a prominent tool for studying lexical retrieval during speech production. When participants name the pictures, interference from semantically related distractor words has regularly been shown. By contrast, when participants categorize the pictures, facilitation from semantically related distractors has typically been found. In the extant studies, however, differences in the task instructions (naming vs. categorizing) were confounded with the response level: While responses in naming were typically located at the basic level (e.g., "dog"), responses were located at the superordinate level in categorization (e.g., "animal"). The present study avoided this confound by having participants respond at the basic level in both naming and categorization, using the same pictures, distractors, and verbal responses. Our findings confirm the polarity reversal of the semantic effects--that is, semantic interference in naming, and semantic facilitation in categorization. These findings show that the polarity reversal of the semantic effect is indeed due to the different tasks and is not an artifact of the different response levels used in previous studies. Implications for current models of language production are discussed.

  8. Ultrasonic force microscopy on poly(vinyl alcohol)/SrTiO3 nano-perovskites hybrid films

    International Nuclear Information System (INIS)

    Marino, Salvatore; Joshi, Girish M.; Lusuardi, Angelo; Cuberes, M. Teresa

    2014-01-01

    Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM) have been applied to the characterization of composite samples formed by SrTiO 3 (STO) nanoparticles (NPs) and polyvinyl alcohol (PVA). The morphological features of the STO NPs were much better resolved using UFM than contact-mode AFM topography. For high STO concentrations the individual STO NPs formed nanoclusters, which gathered in microaggregates. The STO aggregates, covered by PVA, exhibited no AFM frictional contrast, but were clearly distinguished from the PVA matrix using UFM. Similar aggregation was observed for NPs in the composite samples and for NPs deposited on top of a flat silicon substrate from milliQ water solution in the absence of polymer. In the hybrid films, most STO nanoparticles typically presented a lower UFM contrast than the PVA matrix, even though stiffer sample regions such as STO should give rise to a higher UFM contrast. STO NPs with intermediate contrast were characterized by an UFM halo of lower contrast at the PVA/STO interface. The results may be explained by considering that ultrasound is effectively damped on the nanometer scale at PVA/STO interfaces. According to our data, the nanoscale ultrasonic response at the PVA/STO interface plays a fundamental role in the UFM image contrast. - Highlights: • Hybrid films of SrTiO 3 nanoparticles and PVA have been studied using AFM, FFM and UFM. • The SrTiO 3 nanoparticles form nano-clusters from 3 to 5 individuals, which for high concentrations gather in micro-aggregates. • Most SrTiO 3 nanoparticles in the composite samples exhibited a lower (softer) UFM contrast than the PVA matrix. • In the UFM images, SrTiO 3 nanoparticles with intermediate contrast are delimited by a lower-contrast halo at the PVA boundary. • The nanoscale ultrasonic response at the PVA/SrTiO 3 interface plays a fundamental role in the UFM image contrast

  9. Heteroepitaxial Patterned Growth of Vertically Aligned and Periodically Distributed ZnO Nanowires on GaN Using Laser Interference Ablation

    KAUST Repository

    Yuan, Dajun

    2010-08-23

    A simple two-step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm2, with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA-patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site-selective growth of the ZnO nanowires. The method demonstrates high application potential for wafer-scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Atomic force microscope image contrast mechanisms on supported lipid bilayers.

    Science.gov (United States)

    Schneider, J; Dufrêne, Y F; Barger, W R; Lee, G U

    2000-08-01

    This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures onto a monolayer of DSPE show an abrupt breakthrough event at a repeatable, material-dependent force. The breakthrough force for DSPE and MGDG is sizable, whereas the breakthrough force for DOPE is too small to measure accurately. Contact-mode AFM images on 1:1 mixed monolayers of DSPE/DOPE and MGDG/DOPE have a high topographic contrast at loads between the breakthrough force of each phase, and a low topographic contrast at loads above the breakthrough force of both phases. Frictional contrast is inverted and magnified at loads above the breakthrough force of both phases. These results emphasize the important role that surface forces and mechanics can play in imaging multicomponent biomembranes with AFM.

  11. High-resolution photoluminescence electro-modulation microscopy by scanning lock-in

    Science.gov (United States)

    Koopman, W.; Muccini, M.; Toffanin, S.

    2018-04-01

    Morphological inhomogeneities and structural defects in organic semiconductors crucially determine the charge accumulation and lateral transport in organic thin-film transistors. Photoluminescence Electro-Modulation (PLEM) microscopy is a laser-scanning microscopy technique that relies on the modulation of the thin-film fluorescence in the presence of charge-carriers to image the spatial distribution of charges within the active organic semiconductor. Here, we present a lock-in scheme based on a scanning beam approach for increasing the PLEM microscopy resolution and contrast. The charge density in the device is modulated by a sinusoidal electrical signal, phase-locked to the scanning beam of the excitation laser. The lock-in detection scheme is achieved by acquiring a series of images with different phases between the beam scan and the electrical modulation. Application of high resolution PLEM to an organic transistor in accumulation mode demonstrates its potential to image local variations in the charge accumulation. A diffraction-limited precision of sub-300 nm and a signal to noise ratio of 21.4 dB could be achieved.

  12. Transmission electron microscopy a textbook for materials science

    CERN Document Server

    Williams, David B

    1996-01-01

    Electron microscopy has revolutionized our understanding the extraordinary intellectual demands required of the mi­ of materials by completing the processing-structure-prop­ croscopist in order to do the job properly: crystallography, erties links down to atomistic levels. It now is even possible diffraction, image contrast, inelastic scattering events, and to tailor the microstructure (and meso structure ) of materials spectroscopy. Remember, these used to be fields in them­ to achieve specific sets of properties; the extraordinary abili­ selves. Today, one has to understand the fundamentals ties of modem transmission electron microscopy-TEM­ of all of these areas before one can hope to tackle signifi­ instruments to provide almost all of the structural, phase, cant problems in materials science. TEM is a technique of and crystallographic data allow us to accomplish this feat. characterizing materials down to the atomic limits. It must Therefore, it is obvious that any curriculum in modem mate­ be use...

  13. The Cost of Learning: Interference Effects in Memory Development

    Science.gov (United States)

    Darby, Kevin P.; Sloutsky, Vladimir M.

    2015-01-01

    Learning often affects future learning and memory for previously learned information by exerting either facilitation or interference effects. Several theoretical accounts of interference effects have been proposed, each making different developmental predictions. This research examines interference effects across development, with the goal of better understanding mechanisms of interference and of memory development. Preschool-aged children and adults participated in a three-phased associative learning paradigm containing stimuli that were either unique or repeated across phases. Both age groups demonstrated interference effects, but only for repeated items. Whereas proactive interference effects were comparable across age groups, retroactive interference reached catastrophic-like levels in children. Additionally, retroactive interference increased in adults when contextual differences between phases were minimized (Experiment 2), and decreased in adults who were more successful at encoding repeated pairs of stimuli during a training phase (Experiment 3). These results are discussed with respect to theories of memory and memory development. PMID:25688907

  14. Superresolution upgrade for confocal spinning disk systems using image scanning microscopy (Conference Presentation)

    Science.gov (United States)

    Isbaner, Sebastian; Hähnel, Dirk; Gregor, Ingo; Enderlein, Jörg

    2017-02-01

    Confocal Spinning Disk Systems are widely used for 3D cell imaging because they offer the advantage of optical sectioning at high framerates and are easy to use. However, as in confocal microscopy, the imaging resolution is diffraction limited, which can be theoretically improved by a factor of 2 using the principle of Image Scanning Microscopy (ISM) [1]. ISM with a Confocal Spinning Disk setup (CSDISM) has been shown to improve contrast as well as lateral resolution (FWHM) from 201 +/- 20 nm to 130 +/- 10 nm at 488 nm excitation. A minimum total acquisition time of one second per ISM image makes this method highly suitable for 3D live cell imaging [2]. Here, we present a multicolor implementation of CSDISM for the popular Micro-Manager Open Source Microscopy platform. Since changes in the optical path are not necessary, this will allow any researcher to easily upgrade their standard Confocal Spinning Disk system at remarkable low cost ( 5000 USD) with an ISM superresolution option. [1]. Müller, C.B. and Enderlein, J. Image Scanning Microscopy. Physical Review Letters 104, (2010). [2]. Schulz, O. et al. Resolution doubling in fluorescence microscopy with confocal spinning-disk image scanning microscopy. Proceedings of the National Academy of Sciences of the United States of America 110, 21000-5 (2013).

  15. Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyacrylate composite films

    International Nuclear Information System (INIS)

    Li Yong; Chen Changxin; Zhang Song; Ni Yuwei; Huang Jie

    2008-01-01

    Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in pure acrylic emulsion by ultrasonication to prepare MWCNT/polyacrylate composites applied on building interior wall for electromagnetic interference (EMI) shielding applications. The structure and surface morphology of the MWCNTs and MWCNT/polyacrylate composites were studied by field emission scanning microscopy (FESEM) and transmission electron microscopy (TEM). The electrical conductivity at room temperature and EMI shielding effectiveness (SE) of the composite films on concrete substrate with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in two different frequency ranges of 100-1000 MHz (radio frequency range) and 8.2-12.4 GHz (X-band). The experimental results show that a low mass concentration of MWCNTs could achieve a high conductivity and the EMI SE of the MWCNT/polyacrylate composite films has a strong dependence on MWCNTs content in both two frequency ranges. The SE is higher in X-band than that in radio frequency range. For the composite films with 10 wt.% MWCNTs, the EMI SE of experiment agrees well with that of theoretical prediction in far field

  16. Disorganized collagen scaffold interferes with fibroblast mediated deposition of organized extracellular matrix in vitro.

    Science.gov (United States)

    Saeidi, Nima; Guo, Xiaoqing; Hutcheon, Audrey E K; Sander, Edward A; Bale, Shyam Sundar; Melotti, Suzanna A; Zieske, James D; Trinkaus-Randall, Vickery; Ruberti, Jeffrey W

    2012-10-01

    Many tissue engineering applications require the remodeling of a degradable scaffold either in vitro or in situ. Although inefficient remodeling or failure to fully remodel the temporary matrix can result in a poor clinical outcome, very few investigations have examined in detail, the interaction of regenerative cells with temporary scaffoldings. In a recent series of investigations, randomly oriented collagen gels were directly implanted into human corneal pockets and followed for 24 months. The resulting remodeling response exhibited a high degree of variability which likely reflects differing regenerative/synthetic capacity across patients. Given this variability, we hypothesize that a disorganized, degradable provisional scaffold could be disruptive to a uniform, organized reconstruction of stromal matrix. In this investigation, two established corneal stroma tissue engineering culture systems (collagen scaffold-based and scaffold-free) were compared to determine if the presence of the disorganized collagen gel influenced matrix production and organizational control exerted by primary human corneal fibroblast cells (PHCFCs). PHCFCs were cultured on thin disorganized reconstituted collagen substrate (RCS--five donors: average age 34.4) or on a bare polycarbonate membrane (five donors: average age 32.4 controls). The organization and morphology of the two culture systems were compared over the long-term at 4, 8, and 11/12 weeks. Construct thickness and extracellular matrix organization/alignment was tracked optically with bright field and differential interference contrast (DIC) microscopy. The details of cell/matrix morphology and cell/matrix interaction were examined with standard transmission, cuprolinic blue and quick-freeze/deep-etch electron microscopy. Both the scaffold-free and the collagen-based scaffold cultures produced organized arrays of collagen fibrils. However, at all time points, the amount of organized cell-derived matrix in the scaffold

  17. Two-photon quantum interference in a Michelson interferometer

    International Nuclear Information System (INIS)

    Odate, Satoru; Wang Haibo; Kobayashi, Takayoshi

    2005-01-01

    We have observed two-photon quantum interference in a Michelson interferometer. For the first time, we experimentally demonstrated two-photon quantum interference patterns, which show the transition from nonsubwavelength interference fringes to the general subwavelength interference. At the same time, a photon bunching effect was also shown by a postselection. The |1, 1> state with a single photon in a mode corresponding to each arm of the interferometer was exclusively postselected by using path difference between two arms

  18. Prefrontal inhibition of threat processing protects working memory from interference.

    Directory of Open Access Journals (Sweden)

    Robert James Clarke

    2013-05-01

    Full Text Available Bottom-up processes can interrupt ongoing cognitive processing in order to adaptively respond to emotional stimuli of high potential significance, such as those that threaten wellbeing. However it is vital that this interference can be modulated in certain contexts to focus on current tasks. Deficits in the ability to maintain the appropriate balance between cognitive and emotional demands can severely impact on day-to-day activities. This fMRI study examined this interaction between threat processing and cognition; 18 adult participants performed a visuospatial working memory (WM task with two load conditions, in the presence and absence of anxiety induction by threat of electric shock. Threat of shock interfered with performance in the low cognitive load condition; however interference was eradicated under high load, consistent with engagement of emotion regulation mechanisms. Under low load the amygdala showed significant activation to threat of shock that was modulated by high cognitive load. A directed top-down control contrast identified two regions associated with top-down control; ventrolateral PFC and dorsal ACC. Dynamic causal modelling provided further evidence that under high cognitive load, top-down inhibition is exerted on the amygdala and its outputs to prefrontal regions. Additionally, we hypothesised that individual differences in a separate, non-emotional top-down control task would predict the recruitment of dorsal ACC and ventrolateral PFC during top-down control of threat. Consistent with this, performance on a separate dichotic listening task predicted dorsal ACC and ventrolateral PFC activation during high WM load under threat of shock, though activation in these regions did not directly correlate with WM performance. Together, the findings suggest that under high cognitive load and threat, top-down control is exerted by dACC and vlPFC to inhibit threat processing, thus enabling WM performance without threat

  19. Cognitive Aware Interference Mitigation Scheme for LTE Femtocells

    KAUST Repository

    Alqerm, Ismail

    2015-04-21

    Femto-cells deployment in today’s cellular networks came into practice to fulfill the increasing demand for data services. However, interference to other femto and macro-cells users remains an unresolved challenge. In this paper, we propose an interference mitigation scheme to control the cross-tier interference caused by femto-cells to the macro users and the co-tier interference among femtocells. Cognitive radio spectrum sensing capability is utilized to determine the non-occupied channels or the ones that cause minimal interference to the macro users. An awareness based channel allocation scheme is developed with the assistance of the graph-coloring algorithm to assign channels to the femto-cells base stations with power optimization, minimal interference, maximum throughput, and maximum spectrum efficiency. In addition, the scheme exploits negotiation capability to match traffic load and QoS with the channel capacity, and to maintain efficient utilization of the available channels.

  20. Imaging latex–carbon nanotube composites by subsurface electrostatic force microscopy

    International Nuclear Information System (INIS)

    Patel, Sajan; Petty, Clayton W.; Krafcik, Karen Lee

    2016-01-01

    Electrostatic modes of atomic force microscopy have shown to be non-destructive and relatively simple methods for imaging conductors embedded in insulating polymers. Here we use electrostatic force microscopy to image the dispersion of carbon nanotubes in a latex-based conductive composite, which brings forth features not observed in previously studied systems employing linear polymer films. A fixed-potential model of the probe-nanotube electrostatics is presented which in principle gives access to the conductive nanoparticle's depth and radius, and the polymer film dielectric constant. Comparing this model to the data results in nanotube depths that appear to be slightly above the film–air interface. Furthermore, this result suggests that water-mediated charge build-up at the film–air interface may be the source of electrostatic phase contrast in ambient conditions.