WorldWideScience

Sample records for atom probe tomography

  1. Atom Probe Tomography of Geomaterials

    Science.gov (United States)

    Parman, S. W.; Diercks, D.; Gorman, B.; Cooper, R. F.

    2013-12-01

    From the electron microprobe to the secondary ion microprobe to laser-ablation ICP-MS, steady improvements in the spatial resolution and detection limits of geochemical micro-analysis have been central to generating new discoveries. Atom probe tomography (APT) is a relatively new technology that promises nm-scale spatial resolution (in three dimensions) with ppm level detection limits. The method is substantially different from traditional beam-based (electron, ion, laser) methods. In APT, the sample is shaped (usually with a dual-beam FIB) into a needle with typical dimensions of 1-2 μm height and 100-200 nm diameter. Within the atom probe, the needle is evaporated one atom (ideally) at a time by a high electric field (ten's of V per square nm at the needle tip). A femtosecond laser (12 ps pulse width) is used to assist in evaporating non-conducting samples. The two-dimensional detector locates where the atom was released from the needle's surface and so can reconstruct the positions of all detected atoms in three dimensions. It also records the time of flight of the ion, which is used to calculate the mass/charge ratio of the ion. We will discuss our results analyzing a range of geologic materials. In one case, naturally occurring platinum group alloys (PGA) from the Josephine Ophiolite have been imaged. Such alloys are of interest as recorders of the Os heterogeneity of the mantle [1,2]. Optimal ablation was achieved with a laser power of 120-240 pJ and laser pulse rates 500 kHz. Runs were stopped after 10 million atoms were imaged. An example analysis is: Pt 61(1), Fe 26.1(9), Rh 1.20(4), Ir 7.0(7), Ni 2.65(8), Ru 0.20(9), Cu 1.22(8), Co 0.00029(5). Values are in atomic %; values in parentheses are one-sigma standard deviations on five separate needles from the same FIB lift-out, which was 30 μm long. Assuming the sample is homogenous over the 30 μm from which the needle was extracted, the analyses suggest relative errors for major elements below 5% and for

  2. Modeling Atom Probe Tomography: A review

    Energy Technology Data Exchange (ETDEWEB)

    Vurpillot, F., E-mail: francois.vurpillot@univ-rouen.fr [Groupe de Physique des Matériaux, UMR CNRS 6634, Université de Rouen, Saint Etienne du Rouvray 76801 (France); Oberdorfer, C. [Institut für Materialwissenschaft, Lehrstuhl für Materialphysik, Universität Stuttgart, Heisenbergstr. 3, 70569 Stuttgart (Germany)

    2015-12-15

    Improving both the precision and the accuracy of Atom Probe Tomography reconstruction requires a correct understanding of the imaging process. In this aim, numerical modeling approaches have been developed for 15 years. The injected ingredients of these modeling tools are related to the basic physic of the field evaporation mechanism. The interplay between the sample nature and structure of the analyzed sample and the reconstructed image artefacts have pushed to gradually improve and make the model more and more sophisticated. This paper reviews the evolution of the modeling approach in Atom Probe Tomography and presents some future potential directions in order to improve the method. - Highlights: • The basics of field evaporation. • The main aspects of Atom Probe Tomography modeling. • The intrinsic limitations of the current method and future potential directions to improve the understanding of tip to image ion projection.

  3. Atom Probe Tomography and Its Application to Refractory Metal Nuggets

    Science.gov (United States)

    Daly, L.; Bland, P. A.; Forman, L. V.; Reddy, S. M.; Rickard, W. D. A.; Saxey, D. W.; La Fontaine, A.; Yang, L.; Trimby, P. W.; Cairney, J.; Ringer, S.; Schaefer, B. F.

    2016-08-01

    Atom probe tomography is capable of achieving atomic resolution. This allows us to accurately measure the chemistry of refractory metal nuggets in situ, revealing nanometre scale variations in their chemistry and the presence of sulphur in the alloy.

  4. HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

    Science.gov (United States)

    Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

    2015-12-01

    The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. An environmental transfer hub for multimodal atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Perea, Daniel E.; Gerstl, Stephan S. A.; Chin, Jackson; Hirschi, Blake; Evans, James. E.

    2017-05-02

    Environmental control during transfer between instruments is required for specimens sensitive to air or thermal exposure to prevent morphological or chemical changes. Atom Probe Tomography is an expanding technique but commercial instruments remain limited to loading under ambient conditions. Here we describe a multifunctional environmental transfer hub allowing controlled cryogenic, atmospheric and vacuum transfer between an Atom Probe and other instruments containing separate chambers to allow downstream time-resolved in-situ studies.

  6. An environmental transfer hub for multimodal atom probe tomography.

    Science.gov (United States)

    Perea, Daniel E; Gerstl, Stephan S A; Chin, Jackson; Hirschi, Blake; Evans, James E

    2017-01-01

    Environmental control during transfer between instruments is required for samples sensitive to air or thermal exposure to prevent morphological or chemical changes prior to analysis. Atom probe tomography is a rapidly expanding technique for three-dimensional structural and chemical analysis, but commercial instruments remain limited to loading specimens under ambient conditions. In this study, we describe a multifunctional environmental transfer hub allowing controlled cryogenic or room-temperature transfer of specimens under atmospheric or vacuum pressure conditions between an atom probe and other instruments or reaction chambers. The utility of the environmental transfer hub is demonstrated through the acquisition of previously unavailable mass spectral analysis of an intact organic molecule made possible via controlled cryogenic transfer into the atom probe using the hub. The ability to prepare and transfer specimens in precise environments promises a means to access new science across many disciplines from untainted samples and allow downstream time-resolved in situ atom probe studies.

  7. Encapsulation method for atom probe tomography analysis of nanoparticles

    NARCIS (Netherlands)

    Larson, D.J.; Giddings, A.D.; Wub, Y.; Verheijen, M.A.; Prosa, T.J.; Roozeboom, F.; Rice, K.P.; Kessels, W.M.M.; Geiser, B.P.; Kelly, T.F.

    2015-01-01

    Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact

  8. Data mining for isotope discrimination in atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Broderick, Scott R. [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States); Bryden, Aaron [Ames National Laboratory, Ames, IA 50011-2230 (United States); Suram, Santosh K. [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States); Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, Ames, IA 50011-2230 (United States)

    2013-09-15

    Ions with similar time-of-flights (TOF) can be discriminated by mapping their kinetic energy. While current generation position-sensitive detectors have been considered insufficient for capturing the isotope kinetic energy, we demonstrate in this paper that statistical learning methodologies can be used to capture the kinetic energy from all of the parameters currently measured by mathematically transforming the signal. This approach works because the kinetic energy is sufficiently described by the descriptors on the potential, the material, and the evaporation process within atom probe tomography (APT). We discriminate the isotopes for Mg and Al by capturing the kinetic energy, and then decompose the TOF spectrum into its isotope components and identify the isotope for each individual atom measured. This work demonstrates the value of advanced data mining methods to help enhance the information resolution of the atom probe. - Highlights: ► Atom probe tomography and statistical learning were combined for data enhancement. ► Multiple eigenvalue decompositions decomposed a spectrum with overlapping peaks. ► The isotope of each atom was determined by kinetic energy discrimination. ► Eigenspectra were identified and new chemical information was identified.

  9. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota

    2012-12-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  10. Implementing Transmission Electron Backscatter Diffraction for Atom Probe Tomography.

    Science.gov (United States)

    Rice, Katherine P; Chen, Yimeng; Prosa, Ty J; Larson, David J

    2016-06-01

    There are advantages to performing transmission electron backscattering diffraction (tEBSD) in conjunction with focused ion beam-based specimen preparation for atom probe tomography (APT). Although tEBSD allows users to identify the position and character of grain boundaries, which can then be combined with APT to provide full chemical and orientation characterization of grain boundaries, tEBSD can also provide imaging information that improves the APT specimen preparation process by insuring proper placement of the targeted grain boundary within an APT specimen. In this report we discuss sample tilt angles, ion beam milling energies, and other considerations to optimize Kikuchi diffraction pattern quality for the APT specimen geometry. Coordinated specimen preparation and analysis of a grain boundary in a Ni-based Inconel 600 alloy is used to illustrate the approach revealing a 50° misorientation and trace element segregation to the grain boundary.

  11. Multivariate statistical analysis of atom probe tomography data.

    Science.gov (United States)

    Parish, Chad M; Miller, Michael K

    2010-10-01

    The application of spectrum imaging multivariate statistical analysis methods, specifically principal component analysis (PCA), to atom probe tomography (APT) data has been investigated. The mathematical method of analysis is described and the results for two example datasets are analyzed and presented. The first dataset is from the analysis of a PM 2000 Fe-Cr-Al-Ti steel containing two different ultrafine precipitate populations. PCA properly describes the matrix and precipitate phases in a simple and intuitive manner. A second APT example is from the analysis of an irradiated reactor pressure vessel steel. Fine, nm-scale Cu-enriched precipitates having a core-shell structure were identified and qualitatively described by PCA. Advantages, disadvantages, and future prospects for implementing these data analysis methodologies for APT datasets, particularly with regard to quantitative analysis, are also discussed. Copyright 2010 Elsevier B.V. All rights reserved.

  12. Nanometer-scale isotope analysis of bulk diamond by atom probe tomography

    NARCIS (Netherlands)

    Schirhagl, R.; Raatz, N.; Meijer, J.; Markham, M.; Gerstl, S. S. A.; Degen, C. L.

    2015-01-01

    Atom-probe tomography (APT) combines field emission of atoms with mass spectrometry to reconstruct three-dimensional tomograms of materials with atomic resolution and isotope specificity. Despite significant recent progress in APT technology, application to wide-bandgap materials with strong

  13. C12/C13-ratio determination in nanodiamonds by atom-probe tomography.

    Science.gov (United States)

    Lewis, Josiah B; Isheim, Dieter; Floss, Christine; Seidman, David N

    2015-12-01

    The astrophysical origins of ∼ 3 nm-diameter meteoritic nanodiamonds can be inferred from the ratio of C12/C13. It is essential to achieve high spatial and mass resolving power and minimize all sources of signal loss in order to obtain statistically significant measurements. We conducted atom-probe tomography on meteoritic nanodiamonds embedded between layers of Pt. We describe sample preparation, atom-probe tomography analysis, 3D reconstruction, and bias correction. We present new data from meteoritic nanodiamonds and terrestrial standards and discuss methods to correct isotopic measurements made with the atom-probe tomograph. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Nanoscale photoconductive switching effect applied to atom probe tomography

    Science.gov (United States)

    Zhao, L.; Normand, A.; Houard, J.; Blum, I.; Delaroche, F.; Vurpillot, F.

    2016-10-01

    By combining a laser pulse and a high-voltage (HV) pulse on the same sample, field evaporation of materials with poor electrical conductivity using ultra-short HV pulses is reported. Using a pump-probe setup, the shape of HV pulses experienced by surface atoms of the sample apex is experimentally observed. These results are in good agreement with classical models considering the temperature and free carriers produced by a laser pulse giving rise to local photoconduction.

  15. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    Science.gov (United States)

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M

    2017-04-01

    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  16. Dopant distributions in n-MOSFET structure observed by atom probe tomography.

    Science.gov (United States)

    Inoue, K; Yano, F; Nishida, A; Takamizawa, H; Tsunomura, T; Nagai, Y; Hasegawa, M

    2009-11-01

    The dopant distributions in an n-type metal-oxide-semiconductor field effect transistor (MOSFET) structure were analyzed by atom probe tomography. The dopant distributions of As, P, and B atoms in a MOSFET structure (gate, gate oxide, channel, source/drain extension, and halo) were obtained. P atoms were segregated at the interface between the poly-Si gate and the gate oxide, and on the grain boundaries of the poly-Si gate, which had an elongated grain structure along the gate height direction. The concentration of B atoms was enriched near the edge of the source/drain extension where the As atoms were implanted.

  17. Local electrode atom probe tomography a user's guide

    CERN Document Server

    Larson, David J; Ulfig, Robert M; Geiser, Brian P; Kelly, Thomas F; Humphreys, Professor Sir Colin J

    2014-01-01

    The first single-source reference to all the major features of LEAP tomography, this volume includes a wealth of practical tips and covers all four core aspects of a LEAP tomography experiment from start to finish, as well as the software methods employed.

  18. Preparation of nanowire specimens for laser-assisted atom probe tomography.

    Science.gov (United States)

    Blumtritt, H; Isheim, D; Senz, S; Seidman, D N; Moutanabbir, O

    2014-10-31

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  19. Modern Focused-Ion-Beam-Based Site-Specific Specimen Preparation for Atom Probe Tomography.

    Science.gov (United States)

    Prosa, Ty J; Larson, David J

    2017-04-01

    Approximately 30 years after the first use of focused ion beam (FIB) instruments to prepare atom probe tomography specimens, this technique has grown to be used by hundreds of researchers around the world. This past decade has seen tremendous advances in atom probe applications, enabled by the continued development of FIB-based specimen preparation methodologies. In this work, we provide a short review of the origin of the FIB method and the standard methods used today for lift-out and sharpening, using the annular milling method as applied to atom probe tomography specimens. Key steps for enabling correlative analysis with transmission electron-beam backscatter diffraction, transmission electron microscopy, and atom probe tomography are presented, and strategies for preparing specimens for modern microelectronic device structures are reviewed and discussed in detail. Examples are used for discussion of the steps for each of these methods. We conclude with examples of the challenges presented by complex topologies such as nanowires, nanoparticles, and organic materials.

  20. Point-by-point compositional analysis for atom probe tomography.

    Science.gov (United States)

    Stephenson, Leigh T; Ceguerra, Anna V; Li, Tong; Rojhirunsakool, Tanaporn; Nag, Soumya; Banerjee, Rajarshi; Cairney, Julie M; Ringer, Simon P

    2014-01-01

    This new alternate approach to data processing for analyses that traditionally employed grid-based counting methods is necessary because it removes a user-imposed coordinate system that not only limits an analysis but also may introduce errors. We have modified the widely used "binomial" analysis for APT data by replacing grid-based counting with coordinate-independent nearest neighbour identification, improving the measurements and the statistics obtained, allowing quantitative analysis of smaller datasets, and datasets from non-dilute solid solutions. It also allows better visualisation of compositional fluctuations in the data. Our modifications include:.•using spherical k-atom blocks identified by each detected atom's first k nearest neighbours.•3D data visualisation of block composition and nearest neighbour anisotropy.•using z-statistics to directly compare experimental and expected composition curves. Similar modifications may be made to other grid-based counting analyses (contingency table, Langer-Bar-on-Miller, sinusoidal model) and could be instrumental in developing novel data visualisation options.

  1. Atom-probe tomography of tribological boundary films resulting from boron-based oil additives

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon-Jun; Baik, Sung-Il; Bertolucci-Coelho, Leonardo; Mazzaferro, Lucca; Ramirez, Giovanni; Erdemir, Ali; Seidman, D K

    2016-01-15

    Correlative characterization using atom-probe tomography (APT) and transmission electron microscopy (TEM) was performed on a tribofilm formed during sliding frictional testing with a fully formulated engine oil, which also contains a boron-based additive. The tribofilm formed is ~15 nm thick and consists of oxides of iron and compounds of B, Ca, P, and S, which are present in the additive. This study provides strong evidence for boron being embedded in the tribofilm, which effectively reduces friction and wear losses.

  2. Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

    KAUST Repository

    Boll, Torben

    2012-10-01

    In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations are based on the Müller-Schottky equation, which is modified to include different atomic neighborhoods and their characteristic bonds. The local environment is considered up to the fifth next nearest neighbors. To compare the experimental with simulated APT data, the AtomVicinity algorithm, which provides statistical information about the positions of the neighboring atoms, is applied. The quality of this information is influenced by the field evaporation behavior of the different species, which is connected to the bonding energies. © Microscopy Society of America 2012.

  3. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. The mystery of missing species in atom probe tomography of composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Karahka, M.; Xia, Y.; Kreuzer, H. J. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada)

    2015-08-10

    There is a serious problem in atom probe tomography of composite materials such as oxides that even from stoichiometric samples one observes non-stoichiometric ion yields. We present a quantitative model that explains the non-stoichiometry allowing a fit to experimental data of ion yields as a function of applied field to extract activation barriers and prefactors. The numbers are confirmed by density functional theory. We also show that for oxides the missing oxygen is thermally desorbed as neutral O{sub 2}, either directly or associatively. Finally, we suggest methods to improve the experimental setup.

  5. Controlling residual hydrogen gas in mass spectra during pulsed laser atom probe tomography.

    Science.gov (United States)

    Kolli, R Prakash

    2017-01-01

    Residual hydrogen (H2) gas in the analysis chamber of an atom probe instrument limits the ability to measure H concentration in metals and alloys. Measuring H concentration would permit quantification of important physical phenomena, such as hydrogen embrittlement, corrosion, hydrogen trapping, and grain boundary segregation. Increased insight into the behavior of residual H2 gas on the specimen tip surface in atom probe instruments could help reduce these limitations. The influence of user-selected experimental parameters on the field adsorption and desorption of residual H2 gas on nominally pure copper (Cu) was studied during ultraviolet pulsed laser atom probe tomography. The results indicate that the total residual hydrogen concentration, HTOT, in the mass spectra exhibits a generally decreasing trend with increasing laser pulse energy and increasing laser pulse frequency. Second-order interaction effects are also important. The pulse energy has the greatest influence on the quantity HTOT, which is consistently less than 0.1 at.% at a value of 80 pJ.

  6. Atom probe tomography studies of Al₂O₃ gate dielectrics on GaN

    Energy Technology Data Exchange (ETDEWEB)

    Mazumder, Baishakhi, E-mail: bmazumder@engineering.ucsb.edu; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Liu, Xiang; Yeluri, Ramya; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07

    Atom probe tomography was used to achieve three-dimensional characterization of in situ Al₂O₃/GaN structures grown by metal organic chemical vapor deposition (MOCVD). Al₂O₃ dielectrics grown at three different temperatures of 700, 900, and 1000 °C were analyzed and compared. A low temperature GaN cap layer grown atop Al₂O₃ enabled a high success rate in the atom probe experiments. The Al₂O₃/GaN interfaces were found to be intermixed with Ga, N, and O over the distance of a few nm. Impurity measurements data showed that the 1000 °C sample contains higher amounts of C (4 × 10¹⁹/cm³) and lower amounts of H (7 × 10¹⁹/cm³), whereas the 700 °C sample exhibits lower C impurities (<10¹⁷/cm³) and higher H incorporation (2.2 × 10²⁰/cm³). On comparing with Al₂O₃ grown by atomic layer deposition (ALD), it was found that the MOCVD Al₂O₃/GaN interface is comparatively abrupt. Scanning transmission electron microscopy data showed that the 900 °C and 1000 °C MOCVD films exhibit polycrystalline nature, while the ALD films were found to be amorphous.

  7. Blind deconvolution of time-of-flight mass spectra from atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, L.J.S., E-mail: larsj@ifm.liu.se [Linköping University, Department of Physics, Chemistry, and Biology (IFM), Linköping SE-581 83 (Sweden); Thuvander, M.; Stiller, K. [Chalmers University of Technology, Department of Applied Physics, Gothenburg, SE-412 96 (Sweden); Odén, M.; Hultman, L. [Linköping University, Department of Physics, Chemistry, and Biology (IFM), Linköping SE-581 83 (Sweden)

    2013-09-15

    A major source of uncertainty in compositional measurements in atom probe tomography stems from the uncertainties of assigning peaks or parts of peaks in the mass spectrum to their correct identities. In particular, peak overlap is a limiting factor, whereas an ideal mass spectrum would have peaks at their correct positions with zero broadening. Here, we report a method to deconvolute the experimental mass spectrum into such an ideal spectrum and a system function describing the peak broadening introduced by the field evaporation and detection of each ion. By making the assumption of a linear and time-invariant behavior, a system of equations is derived that describes the peak shape and peak intensities. The model is fitted to the observed spectrum by minimizing the squared residuals, regularized by the maximum entropy method. For synthetic data perfectly obeying the assumptions, the method recovered peak intensities to within ±0.33at%. The application of this model to experimental APT data is exemplified with Fe–Cr data. Knowledge of the peak shape opens up several new possibilities, not just for better overall compositional determination, but, e.g., for the estimation of errors of ranging due to peak overlap or peak separation constrained by isotope abundances. - Highlights: • A method for the deconvolution of atom probe mass spectra is proposed. • Applied to synthetic randomly generated spectra the accuracy was ±0.33 at. • Application of the method to an experimental Fe–Cr spectrum is demonstrated.

  8. Evaporation mechanisms of MgO in laser assisted atom probe tomography

    KAUST Repository

    Mazumder, Baishakhi

    2011-05-01

    In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO. It is also shown that as long as the MgO layer is buried in Fe, the evaporation is dominated by the photon absorption in Fe layer at the tip apex. Eventually the evaporation process of MgO is discussed based on the difference between the bulk materials and the multilayer samples. © 2010 Elsevier B.V.

  9. Analysis of deuterium in V-Fe5at.% film by atom probe tomography (APT)

    KAUST Repository

    Gemma, Ryota

    2011-09-01

    V-Fe5at.% 2 and 10-nm thick single layered films were prepared by ion beam sputtering on W substrate. They were loaded with D from gas phase at 0.2 Pa and at 1 Pa, respectively. Both lateral and depth D distribution of these films was investigated in detail by atom probe tomography. The results of analysis are in good agreement between the average deuterium concentration and the value, expected from electromotive force measurement on a similar flat film. An enrichment of deuterium at the V/W interface was observed for both films. The origin of this D-accumulation was discussed in respect to electron transfer, mechanical stress and misfit dislocations. © 2010 Elsevier B.V. All rights reserved.

  10. Atom probe tomography of thermally grown oxide scale on FeCrAl

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang, E-mail: fang.liu@chalmers.se [Department of Applied Physics, Chalmers University of Technology, 41296 Gothenburg (Sweden); Stiller, Krystyna [Department of Applied Physics, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2013-09-15

    Thermally grown Al{sub 2}O{sub 3} scales formed on a FeCrAl alloy were successfully analyzed using pulsed green laser atom probe tomography. Two types of atom probe tomography specimens, the “thin oxide” type: a thin Al{sub 2}O{sub 3} layer (<100 nm) with underlying metal (1 μm), and the “thick oxide” type: only with Al{sub 2}O{sub 3} (1 μm), were prepared and analyzed. It was found that the thin oxide type yields poorer mass resolution due to a combined effect of laser absorption and thermal conduction effects. Application of a relatively low laser energy yields a better mass resolution and increased multiple events, however, more accurate quantification results. Although no other oxide phase than Al{sub 2}O{sub 3} is expected to form, some iron–oxygen and chromium–oxygen molecular ions were recorded at the Al{sub 2}O{sub 3}/metal interface due to the large change in evaporation field over this zone. - Highlights: ► Thermally grown Al{sub 2}O{sub 3} scales formed on a FeCrAl alloy were successfully analyzed. ► Specimens with a thin oxide and underlying metal yield poorer mass resolution. ► Low laser energy yields a better mass resolution. ► Fe–O, Cr–O molecular ions were found at Al{sub 2}O{sub 3}/metal interface; this is an ion evaporation effect.

  11. Coke Formation in a Zeolite Crystal During the Methanol-to- Hydrocarbons Reaction as Studied with Atom Probe Tomography

    NARCIS (Netherlands)

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; Winter, D A Matthijs De; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-01-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new,superior materials for various applications,including oil and gas conversion pro- cesses.Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub- nm length

  12. Effects of Optical Dopants and Laser Wavelength on Atom Probe Tomography Analyses of Borosilicate Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xiaonan; Schreiber, Daniel K.; Neeway, James J.; Ryan, Joseph V.; Du, Jincheng

    2017-10-02

    Atom probe tomography (APT) is a novel analytical microscopy method that provides three dimensional elemental mapping with sub-nanometer spatial resolution and has only recently been applied to insulating glass and ceramic samples. In this paper, we have studied the influence of the optical absorption in glass samples on APT characterization by introducing different transition metal optical dopants to a model borosilicate nuclear waste glass (international simple glass). A systematic comparison is presented of the glass optical properties and the resulting APT data quality in terms of compositional accuracy and the mass spectra quality for two APT systems: one with a green laser (532 nm, LEAP 3000X HR) and one with a UV laser (355 nm, LEAP 4000X HR). These data were also compared to the study of a more complex borosilicate glass (SON68). The results show that the analysis data quality such as compositional accuracy and total ions collected, was clearly linked to optical absorption when using a green laser, while for the UV laser optical doping aided in improving data yield but did not have a significant effect on compositional accuracy. Comparisons of data between the LEAP systems suggest that the smaller laser spot size of the LEAP 4000X HR played a more critical role for optimum performance than the optical dopants themselves. The smaller spot size resulted in more accurate composition measurements due to a reduced background level independent of the material’s optical properties.

  13. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Laboratory; Miller, Michael K. [ORNL; Alexander, David J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Clarke, Kester D. [Los Alamos National Laboratory

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  14. Nanoscale Stoichiometric Analysis of a High-Temperature Superconductor by Atom Probe Tomography.

    Science.gov (United States)

    Pedrazzini, Stella; London, Andrew J; Gault, Baptiste; Saxey, David; Speller, Susannah; Grovenor, Chris R M; Danaie, Mohsen; Moody, Michael P; Edmondson, Philip D; Bagot, Paul A J

    2017-04-01

    The functional properties of the high-temperature superconductor Y1Ba2Cu3O7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y7.7Ba15.3Cu23O54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of the experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y7.9Ba10.4Cu24.4O57.2.

  15. Characterization of nano-sized precipitates in a Mn-based lean maraging steel by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Millan, J.; Ponge, D.; Raabe, D.; Choi, P.; Dmitrieva, O. [Max-Planck-Institut fuer Eisenforschung, Duesseldorf (Germany)

    2011-02-15

    We present atom probe tomography results of a precipitation-hardened Mn-based maraging steel (9 Mn, 1.9 Ni, 0.6 Mo, 1.1 Ti, 0.33 Al; in at.%). The alloy is characterized by the surprising effect that both, strength and total elongation increase upon aging. The material reveals a high ultimate tensile strength (UTS) up to 1 GPa and good ductility (total elongation (TE) of up to 15% in a tensile test) depending on aging conditions. We map the evolution of the precipitates after 450 C aging treatment using atom probe tomography in terms of chemical composition and size distribution. (Copyright copyright 2011 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Atom probe tomography investigation of lath boundary segregation and precipitation in a maraging stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Thuvander, Mattias, E-mail: mattias.thuvander@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Andersson, Marcus [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); R and D Centre, Sandvik Materials Technology, SE-811 81 Sandviken (Sweden); Stiller, Krystyna [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2013-09-15

    Lath boundaries in a maraging stainless steel of composition 13Cr–8Ni–2Mo–2Cu–1Ti–0.7Al–0.3Mn–0.2Si–0.03C (at%) have been investigated using atom probe tomography following aging at 475 °C for up to 100 h. Segregation of Mo, Si and P to the lath boundaries was observed already after 5 min of aging, and the amount of segregation increases with aging time. At lath boundaries also precipitation of η-Ni{sub 3}(Ti, Al) and Cu-rich 9R, in contact with each other, takes place. These co-precipitates grow with time and because of coarsening the area number density decreases. After 100 h of aging a ∼5 nm thick film-like precipitation of a Mo-rich phase was observed at the lath boundaries. From the composition of the film it is suggested that the phase in question is the quasicrystalline R′ phase. The film is perforated with Cu-rich 9R and η-Ni{sub 3}(Ti, Al) co-precipitates. Not all precipitate types present in the matrix do precipitate at the lath boundaries; the Si-containing G phase and γ′-Ni{sub 3}(Ti, Al, Si) and the Cr-rich α′ phase were not observed at the lath boundaries. - Highlights: ► Lath boundaries in a maraging steel were analyzed by APT. ► Segregation of Mo, Si and P was measured. ► Precipitation of η-Ni{sub 3}(Ti, Al) and Cu-rich 9R was observed. ► After 100 h of aging a quasicrystalline Mo-rich film was observed.

  17. Interpretation of atom probe tomography data for the intermetallic TiAl+Nb by means of field evaporation simulation

    KAUST Repository

    Boll, Torben

    2013-01-01

    In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model [1] was extended to include the local atomic arrangement on the evaporation process of atoms. This arrangement was described by the sum of the next-neighbor-binding-energies, which differ for an atom of type A, depending on how many A-A, B-B or A-B bonds are present. Thus simulations of APT-data of intermetallic phases become feasible. In this study simulations of L10-TiAl with additions of Nb are compared with experimental data. Certain artifacts, which appear for experimental data are treated as well. © 2012 Elsevier B.V.

  18. Interpretation of atom probe tomography data for the intermetallic TiAl+Nb by means of field evaporation simulation.

    Science.gov (United States)

    Boll, T; Al-Kassab, T

    2013-01-01

    In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model was extended to include the local atomic arrangement on the evaporation process of atoms. This arrangement was described by the sum of the next-neighbor-binding-energies, which differ for an atom of type A, depending on how many A-A, B-B or A-B bonds are present. Thus simulations of APT-data of intermetallic phases become feasible. In this study simulations of L1(0)-TiAl with additions of Nb are compared with experimental data. Certain artifacts, which appear for experimental data are treated as well. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Investigation of olivine and orthopyroxene grain boundaries by atom probe tomography

    Science.gov (United States)

    Krawczynski, M.; Skemer, P. A.; Bachhav, M.; Dong, Y.; Marquis, E. A.

    2016-12-01

    Accurate chemical analysis at grain boundaries is challenging by traditional microscopic techniques, especially for poor conducting geological samples. Atom probe tomography (APT) is a unique technique that can elucidate chemistry and 3-D distribution of elements within a sample volume at the sub-nanometer length scale. With advances in laser and sample preparation techniques in the last decade, APT is now successfully applied to a wide range of poor conducting materials like metal oxides, ceramics, and biological minerals. In this study, we apply the APT technique to investigate the grain boundary chemistry of orthopyroxene (opx) and olivine. These minerals are the most abundant in the upper mantle and their grain boundaries may be important geochemical reservoirs in Earth. Moreover, physical properties such as grain boundary diffusivity, conductivity, and mobility, are likely influenced by the presence or absence of impurities. Single crystals of opx and olivine grains, separated from a San Carlos xenolith, were deformed at 1 GPa and 1500 K. Plastic deformation promoted dynamic recrystallization, creating new grain boundaries within a chemically homogeneous medium. Needle shaped specimens of opx-opx and olivine-olivine grain boundaries were prepared using standard lift out techniques and a dual beam focused ion beam (FIB). APT analyses were performed in laser mode with laser energy of 50 pJ/pulse, repetition rate of 200 kHz, and detection rate of 1%. A 3-D distribution of elements was reconstructed and 1-D profiles across the grain boundary have been calculated. Fe, Al, and Ca show enrichments at the grain boundaries for both phases, consistent with previous studies that used STEM/EDX or EPMA techniques. Although qualitatively similar, the spatial resolution of the APT method is significantly better than other methods, and our data show that the grain-boundary enrichment of minor elements in both olivine and pyroxene compositions is limited to a region no greater

  20. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography

    KAUST Repository

    Al-Kassab, Talaat

    2014-09-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3at.% Ti were investigated, the states selected from the decomposition path were the metastable γ″ and γ\\' states introduced on the basis of small-angle neutron scattering (SANS) and the two-phase model for evaluation. The composition values of the precipitates in these states could not be confirmed by APT data as the interface of the ordered precipitates may not be neglected. The present results rather suggest to apply a three-phase model for the interpretation of SANS measurements, in which the width of the interface remains nearly unchanged and the L12 structure close to 3:1 stoichiometry is maintained in the core of the precipitates from the γ″ to the γ\\' state. © 2014 Elsevier Ltd.

  1. Long-term thermal stability of nanoclusters in ODS-Eurofer steel: An atom probe tomography study

    Science.gov (United States)

    Zilnyk, K. D.; Pradeep, K. G.; Choi, P.; Sandim, H. R. Z.; Raabe, D.

    2017-08-01

    Oxide-dispersion strengthened materials are important candidates for several high-temperature structural applications in advanced nuclear power plants. Most of the desirable mechanical properties presented by these materials are due to the dispersion of stable nanoparticles in the matrix. Samples of ODS-Eurofer steel were annealed for 4320 h (6 months) at 800 °C. The material was characterized using atom probe tomography in both conditions (prior and after heat treatment). The particles number density, size distribution, and chemical compositions were determined. No significant changes were observed between the two conditions indicating a high thermal stability of the Y-rich nanoparticles at 800 °C.

  2. Atom probe tomography study of alloying element distributions in Zr alloys and their oxides

    Science.gov (United States)

    Dong, Yan; Motta, Arthur T.; Marquis, Emmanuelle A.

    2013-11-01

    A detailed study of alloying element distributions in the metal and oxygen rich regions of corroded Zr alloys and of the phases formed ahead of the oxide front was conducted using atom probe tomography (APT). A consistent sequence of sub-oxide phases is observed ahead of the ZrO2 oxide front, consisting of (i) a thin layer of equiatomic ZrO (occasionally slightly over and under stoichiometric) (ii) saturated solid solution Zr(O)sat, and (iii) a slowly decreasing oxygen profile into the metal. The results also show that the distribution of the alloying elements in the metal is more inhomogeneous than previously thought and that in the oxygen-rich phases enhanced segregation is observed, compared to the metal. the stable oxide ZrO2 (which is in contact with water), the equiatomic suboxide ZrO (both slightly sub and superstoichiometric, denoted here ZrO1+x and ZrO1-x), a saturated solution of constant oxygen content at about 30% O, denoted Zr(O)sat, and an undersaturated solid solution of O in Zr, denoted Zr(O), the oxygen content of which decreases with distance from the oxide-metal interface. As stated above, the field evaporation behavior of these phases is drastically different, resulting in characteristic ions being evaporated from each phase. As a result, the phases can be identified both by atomic concentrations and by the nature of the ionic species evaporating from each phase. The latter method was also used to visualize the distribution of phases within needles. For example, it was found in the present study that oxygen was evaporated as O+, O2+, ZrO2+, ZrO3+, ZrO2+,ZrO22+,ZrO3+ with occasional instances of ZrO23+ and ZrO33+ observed. Zr ions (Zr2+, Zr3+) become significant in the Zr(O)sat phase. O2+ is only observed in the oxide (ZrO2) phase, so it is considered a marker for that phase. ZrO2+ and ZrO22+ are present both in the ZrO2 and ZrO1+x phases but absent in the ZrO1-x, Zr(O)sat and Zr(O) phase. the equiatomic ZrO phase (observed as both ZrO1+x and Zr

  3. Complementary use of transmission electron microscopy and atom probe tomography for the examination of plastic accommodation in nanocrystalline bainitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Caballero, F.G., E-mail: fgc@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas (CENIM-CSIC), Avda Gregorio del Amo 8, Madrid E-28040 (Spain); Yen, Hung-Wei [Department of Materials Science and Engineering, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Miller, M.K. [Oak Ridge National Laboratory (ORNL), Materials Science and Technology Division, Oak Ridge, TN 37831-6136 (United States); Yang, Jer-Ren [Department of Materials Science and Engineering, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Cornide, J.; Garcia-Mateo, C. [Centro Nacional de Investigaciones Metalurgicas (CENIM-CSIC), Avda Gregorio del Amo 8, Madrid E-28040 (Spain)

    2011-09-15

    A displacive transformation involves the motion of a glissile interface. As in work hardening, its motion can be halted by defects such as dislocations, stacking faults or twins in the austenite. The defects are created when the shape deformation accompanying bainite growth is accommodated by plastic relaxation of the surrounding austenite. The growing plate stops when it collides with the austenite grain boundary. Because transformation from strong austenite leads to fine plates, alloys can be designed such that the bainite transformation is suppressed to low temperatures (125-350 deg. C), leading to a nanoscale bainitic microstructure. Complementary high-resolution transmission electron microscopy and atom probe tomography have provided new experimental evidence on the accommodation of transformation strain, a subject critically relevant to understanding the atomic mechanisms controlling bainitic ferrite growth.

  4. Fundamental insights into the radium uptake into barite by atom probe tomography and electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Juliane

    2017-10-01

    -of-the-art high-resolution microscopy techniques was used to answer the questions regarding (1) the internal microstructure of the initial barite (2) the role of this internal microstructure during the Ra uptake and (3) t he changes in the Ra distribution within the barite. This study comprises the first characterization of barite by atom probe tomography (APT). By combining APT and transmission electron microscopy (TEM) methods, pores covering the size range from a few nanometers to a few micrometers were identified in the SL barite. The pores were organized in layers parallel to the outer crystal faces. High resolution chemical analysis indicated that the pores contain a solution of water and sodium chloride. By focused ion beam (FIB) tomography, it was revealed that open macropores of several micrometers size are present as well within the SL barite. These partially connected macropores are distributed within the complete barite particles. Therefore, the macropores provide a direct pathway for Ra-containing aqueous fluid to enter the SL barite particles by diffusion within the aqueous solution. In addition, pores were also identified in the AL barite by TEM characterization. The entrapment of solution during mineral precipitation is known for several minerals at high supersaturation. As barite only precipitates at high supersaturation, nanoscale fluid inclusions as well as macropores probably were entrapped during the particle growth by precipitation. A microstructure similar to the one of the barite type used in this study was previously reported for other barites. In Ra-free reference experiment, no microstructural changes were noted over recrystallization times of up to 898 days. In prior studies, three different stages of Ra uptake were described based on macroscopic results. Ra-containing barite samples from all three stages were characterized to understand the role of the internal barite microstructure. At the beginning, the nano-scale fluid inclusions disappeared

  5. 3D Atom Probe Tomography Analysis of Neutron-irradiated SA508 Gr.4N

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sang Yeob; Kwon, Jun Hyun; Lee, Gyeong Geun; Jin, Hyung Ha; Chang, Kun Ok [KAERI, Daejeon (Korea, Republic of); Shin, Chan Sun [Myongi University, Yongin (Korea, Republic of)

    2016-05-15

    The embrittlement is induced by the formation of radiation defects (so-called 'matrix damage') and/or of radiation induced precipitates. Cu-rich precipitates (CRP) have been observed in Cu-bearing RPV steels. In case of Cu free, high Mn (and Ni and Si) containing RPV steels such as SA508 Gr.3 (1.4Mn-0.9Ni-0.15Cr-0.2C-0.002P in wt.%), Mn-Ni-rich precipitates (MNP) are reported to form at low temperature and high neutron fluence. These MNPs are believed to have long incubation time. But once nucleated, they rapidly grow to large volume fractions and mechanical properties deteriorate abruptly, e.g., increase in ductile-to-brittle transition temperature. For such reasons, MNPs are denoted as late blooming phases (LBP). MNPs are often observed in RPV steels with Mn content of -1 wt.% and similar or lower Ni content. Atom probe experiments of neutron irradiated SA508 Gr.3, which has a composition of, showed Mn, Ni, Si, and P atoms are formed MNPs and segregated at dislocation lines.

  6. Experimental Investigation Of Segregation Of Carbon Atoms Due To Sub-Zero Cryogenic Treatment In Cold Work Tool Steel By Mechanical Spectroscopy And Atom Probe Tomography

    Directory of Open Access Journals (Sweden)

    Min N.

    2015-06-01

    Full Text Available In this work, we present mechanical spectroscopy of cold work tool steel subjected to sub-zero cryogenic soaking treatment to reveal the carbon segregation and the subsequent carbides refinement. The maximum of Snoek-Köster (SK peak height was obtained in the sample subjected to soaking 1h at −130°C cryogenic treatment. The SK peak height is reduced with prolonging the soaking time. The results indicate that an increase in the height of SK peak is connected with an increase in dislocation density and the number of segregated carbon atoms in the vicinity of dislocations or twin planes after martensite transformation at −130°C which is confirmed by corresponding TEM and atom probe tomography measurement. Hence, it is suggested that the isothermal martensite, formed during the cryogenic soaking treatment decreases (APT the height of SK peak.

  7. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  8. Isotopic analysis of individual refractory metal nuggets using atom probe tomography

    Science.gov (United States)

    Daly, L.; Bland, P.; Schaefer, B. F.; Saxey, D. W.; Reddy, S.; Fougerouse, D.; William, R. D. A.; Forman, L. V.; Trimby, P.; La Fontaine, A.; Yang, L.; Cairney, J.; Ringer, S.

    2016-12-01

    Sub-micrometre metallic alloys of the highly siderophile elements, known as refractory metal nuggets (RMNs), can be found in primitive carbonaceous chondrites. There has been some suggestion that these grains may have a pre-solar origin, however their <1 µm size has meant that isotopic analysis of individual grains has not previously been possible. Atom probe microscopy has sufficient spatial resolution to quantify the isotopic compositions, across the entire mass range, of small sample volumes (<0.02 µm3) with high sensitivity and precision. We present analyses of four individual RMNs from the same refractory inclusion within the ALH 77307 meteorite. The results indicate that these RMNs have significant isotopic deviations from solar relative isotope abundances and therefore preserve a pre-solar isotopic signature. All RMNs exhibit large p-process enrichments in 98Ru and depletions in s-process 186Os. Two RMNs have a similar isotopic signature, suggesting formation in the same stellar environment. This similarity between two RMNs indicates that there may be a significant contribution of material to our solar system from a single source. The other two RMNs are isotopically dissimilar. Finally, three of the RMNs plot on a 187Re -187Os isochron from which we can derive a galactic age of 12.5 Ga ±1.8. To the best of our knowledge this is the first direct determination of the age of the Milky Way through physical analysis of non-solar material.

  9. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  10. Atom probe tomography study on Ge{sub 1−x−y}Sn{sub x}C{sub y} hetero-epitaxial film on Ge substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, Eiji, E-mail: ejkamiyama@aol.com [Technology, GlobalWafers Japan Corp. Ltd., 6-861-5 Higashiko, Seiro, Niigata 957-0197 (Japan); Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan); Terasawa, Kengo; Yamaha, Takashi; Nakatsuka, Osamu [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Izunome, Koji; Kashima, Kazuhiko [Technology, GlobalWafers Japan Corp. Ltd., 6-861-5 Higashiko, Seiro, Niigata 957-0197 (Japan); Uchida, Hiroshi [Physical Analysis Technology Center, Toshiba Nanoanalysis Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama 235-8522 (Japan)

    2015-10-01

    We analyzed the incorporation of C atoms into a ternary alloy Ge{sub 1−x−y}Sn{sub x}C{sub y} epitaxial film on Ge substrates on a sub-nanometer scale by using atom probe tomography. Periodic atom distributions from individual (111) atomic planes were observed both in the Ge{sub 1−x−y}Sn{sub x}C{sub y} film and at the Ge substrates. Sn/C atoms had non-uniform distributions in the film. They also demonstrated a clear positive correlation in their distributions. Substitutional C atoms were only incorporated into the film when an Sn atom beam was applied onto the substrates under film growth conditions. - Highlights: • Incorporation of C atoms into epitaxial Ge{sub 1−x−y}Sn{sub x}C{sub y} film was studied. • Individual (111) atomic planes were observed by atom probe tomography. • Sn/C atoms had non-uniform distributions in the film. • Clear positive correlation in Sn/C atoms distributions was obtained.

  11. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Gnaser, Hubert, E-mail: gnaser@rhrk.uni-kl.de [Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, D-67663 Kaiserslautern (Germany); Institut für Oberflächen- und Schichtanalytik GmbH (IFOS), Trippstadter Strasse 120, D-67663 Kaiserslautern (Germany); Radny, Tobias [Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, D-67663 Kaiserslautern (Germany)

    2015-12-15

    Surfaces of InP were bombarded by 1.9 keV Ar{sup +} ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1×10{sup 17} cm{sup −2} to 3×10{sup 18} cm{sup −2} and ion flux densities f of (0.4−2)×10{sup 14} cm{sup −2} s{sup −1} were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3–1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of P{sub n} cluster ions was observed, with n≤11. - Highlights: • Nanodot formation on InP surfaces under Ar{sup +} ion irradiation. • Atom probe tomography of InP: influence of laser pulse energy. • Compositional analysis of individual nanodots with nm spatial resolution. • Abundant emission of P{sub n} cluster ions (n≤11).

  12. Analysis of atomic distribution in as-fabricated Zircaloy-2 claddings by atom probe tomography under high-energy pulsed laser

    Energy Technology Data Exchange (ETDEWEB)

    Sawabe, T., E-mail: sawabe@criepi.denken.or.jp [Central Research Institute of Electric Power Industry (CRIEPI), Iwado Kita 2-11-1, Komae, Tokyo 201-8511 (Japan); Sonoda, T.; Kitajima, S. [Central Research Institute of Electric Power Industry (CRIEPI), Iwado Kita 2-11-1, Komae, Tokyo 201-8511 (Japan); Kameyama, T. [Tokai University, Department of Nuclear Engineering, Kitakaname 4-1-1, Hiratsuka, Kanagawa 259-1292 (Japan)

    2013-11-15

    The properties of second-phase particles (SPPs) in Zircaloy-2 claddings are key factors influencing the corrosion resistance of the alloy. The chemical compositions of Zr (Fe, Cr){sub 2} and Zr{sub 2}(Fe, Ni) SPPs were investigated by means of pulsed laser atom probe tomography. In order to prevent specimen fracture and to analyse wide regions of the specimen, the pulsed laser energy was increased to 2.0 nJ. This gave a high yield of average of 3 × 10{sup 7} ions per specimen. The Zr (Fe, Cr){sub 2} SPPs contained small amounts of Ni and Si atoms, while in Zr{sub 2}(Fe, Ni) SPPs almost all the Si was concentrated and the ratio of Zr: (Fe + Ni + Si) was 2:1. Atomic concentrations of the Zr-matrix and the SPPs were identified by two approaches: the first by using all the visible peaks of the mass spectrum and the second using the representative peaks with the natural abundance of the corresponding atoms. It was found that the change in the concentration between the Zr-matrix and the SPPs can be estimated more accurately by the second method, although Sn concentration in the Zr{sub 2}(Fe, Ni) SPPs is slightly overestimated.

  13. Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

    Science.gov (United States)

    Valderrama, B.; Henderson, H. B.; Gan, J.; Manuel, M. V.

    2015-04-01

    Atom probe tomography (APT) provides the ability to detect subnanometer chemical variations spatially, with high accuracy. However, it is known that compositional accuracy can be affected by experimental conditions. A study of the effect of laser energy, specimen base temperature, and detection rate is performed on the evaporation behavior of uranium dioxide (UO2). In laser-assisted mode, tip geometry and standing voltage also contribute to the evaporation behavior. In this investigation, it was determined that modifying the detection rate and temperature did not affect the evaporation behavior as significantly as laser energy. It was also determined that three laser evaporation regimes are present in UO2. Very low laser energy produces a behavior similar to DC-field evaporation, moderate laser energy produces the desired laser-assisted field evaporation characteristic and high laser energy induces thermal effects, negatively altering the evaporation behavior. The need for UO2 to be analyzed under moderate laser energies to produce accurate stoichiometry distinguishes it from other oxides. The following experimental conditions providing the best combination of mass resolving power, accurate stoichiometry, and uniform evaporation behavior: 50 K, 10 pJ laser energy, a detection rate of 0.003 atoms per pulse, and a 100 kHz repetition rate.

  14. Atom Probe Tomography Unveils Formation Mechanisms of Wear-Protective Tribofilms by ZDDP, Ionic Liquid, and Their Combination.

    Science.gov (United States)

    Guo, Wei; Zhou, Yan; Sang, Xiahan; Leonard, Donovan N; Qu, Jun; Poplawsky, Jonathan D

    2017-07-12

    The development of advanced lubricant additives has been a critical component in paving the way for increasing energy efficiency and durability for numerous industry applications. However, the formation mechanisms of additive-induced protective tribofilms are not yet fully understood because of the complex chemomechanical interactions at the contact interface and the limited spatial resolution of many characterizing techniques currently used. Here, the tribofilms on a gray cast iron surface formed by three antiwear additives are systematically studied; a phosphonium-phosphate ionic liquid (IL), a zinc dialkyldithiophosphate (ZDDP), and an IL+ZDDP combination. All three additives provide excellent wear protection, with the IL+ZDDP combination exhibiting a synergetic effect, resulting in further reduced friction and wear. Atom probe tomography (APT) and scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) were used to interrogate the subnm chemistry and bonding states for each of the tribofilms of interest. The IL tribofilm appeared amorphous and was Fe, P, and O rich. Wear debris particles having an Fe-rich core and an oxide shell were present in this tribofilm and a transitional oxide (Fe2O3)-containing layer was identified at the interface between the tribofilm and the cast iron substrate. The ZDDP+IL tribofilm shared some of the characteristics found in the IL and ZDDP tribofilms. Tribofilm formation mechanisms are proposed on the basis of the observations made at the atomic level.

  15. Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Fengzai; Zhu, Tongtong; Oehler, Fabrice; Fu, Wai Yuen; Griffiths, James T.; Massabuau, Fabien C.-P.; Kappers, Menno J.; Oliver, Rachel A., E-mail: rao28@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Martin, Tomas L.; Bagot, Paul A. J.; Moody, Michael P., E-mail: michael.moody@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-02-16

    Atom probe tomography (APT) has been used to characterize the distribution of In atoms within non-polar a-plane InGaN quantum wells (QWs) grown on a GaN pseudo-substrate produced using epitaxial lateral overgrowth. Application of the focused ion beam microscope enabled APT needles to be prepared from the low defect density regions of the grown sample. A complementary analysis was also undertaken on QWs having comparable In contents grown on polar c-plane sample pseudo-substrates. Both frequency distribution and modified nearest neighbor analyses indicate a statistically non-randomized In distribution in the a-plane QWs, but a random distribution in the c-plane QWs. This work not only provides insights into the structure of non-polar a-plane QWs but also shows that APT is capable of detecting as-grown nanoscale clustering in InGaN and thus validates the reliability of earlier APT analyses of the In distribution in c-plane InGaN QWs which show no such clustering.

  16. Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

    KAUST Repository

    Khushaim, Muna

    2015-05-19

    The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shaped T 1 Al 2 CuLi / θ ′ Al 2 Cu precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The θ ′ platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al 2 Cu equilibrium composition. Additionally, the Li distribution inside the θ ′ platelets was found to equal the same value as in the matrix. The equally thin T 1 platelet deviates from the formula (Al 2 CuLi) in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al 2 CuLi) stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the T 1 platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thin T 1 platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

  17. Characterization of Precipitation in Al-Li Alloy AA2195 by means of Atom Probe Tomography and Transmission Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Muna Khushaim

    2015-01-01

    Full Text Available The microstructure of the commercial alloy AA2195 was investigated on the nanoscale after conducting T8 tempering. This particular thermomechanical treatment of the specimen resulted in the formation of platelet-shaped T1Al2CuLi/θ′Al2Cu precipitates within the Al matrix. The electrochemically prepared samples were analyzed by scanning transmission electron microscopy and atom probe tomography for chemical mapping. The θ′ platelets, which are less than 2 nm thick, have the stoichiometric composition consistent with the expected Al2Cu equilibrium composition. Additionally, the Li distribution inside the θ′ platelets was found to equal the same value as in the matrix. The equally thin T1 platelet deviates from the formula (Al2CuLi in its stoichiometry and shows Mg enrichment inside the platelet without any indication of a higher segregation level at the precipitate/matrix interface. The deviation from the (Al2CuLi stoichiometry cannot be simply interpreted as a consequence of artifacts when measuring the Cu and Li concentrations inside the T1 platelet. The results show rather a strong hint for a true lower Li and Cu contents, hence supporting reasonably the hypothesis that the real chemical composition for the thin T1 platelet in the T8 tempering condition differs from the equilibrium composition of the thermodynamic stable bulk phase.

  18. Influence of the Electronic Structure and Optical Properties of CeO2 and UO2 for Characterization with UV-Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Billy Valderrama; H.B. Henderson; C. Yablinsky; J. Gan; T.R. Allen; M.V. Manuel

    2015-09-01

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO2) and uranium oxide (UO2) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

  19. Determination of Gamma-Prime Site Occupancies in Nickel Superalloys Using Atom Probe Tomography and X-Ray Diffraction (Preprint)

    Science.gov (United States)

    2012-08-01

    atom probe results from the same alloy that indicate that chromium prefers the aluminum sublattice sites. Modeling studies indicate cobalt has no...sublattice sites while cobalt is likely to occupy both the aluminum and nickel sublattice sites. The x-ray results on the chromium occupancy disagree with...experimental results also indicate that chromium prefers the nickel sublattice sites while cobalt is likely to occupy both the aluminum and nickel

  20. Ordering and site occupancy of D03 ordered Fe3Al-5 at%Cr evaluated by means of atom probe tomography

    KAUST Repository

    Rademacher, Thomas W.

    2011-05-01

    Addition of ternary elements to the D03 ordered Fe3Al intermetallic phase is a general approach to optimise its mechanical properties. To understand the physical influences of such additions the determination of the probability of site occupancies of these additions on the lattice site and ordering parameters is of high interest. Some common experimental techniques such as X-ray diffraction or Atom Location by Channelling Enhanced Microanalysis (ALCHEMI) are usually applied to explore this interplay. Unfortunately, certain published results are partly inconsistent, imprecise or even contradictory. In this study, these aspects are evaluated systematically by atom probe tomography (APT) and a special data analysis method. Additionally, to account for possible field evaporation effects that can falsify the estimation of site occupancy and induce misinterpretations, APT evaporation sequences were also simulated. As a result, chromium occupies most frequently the next nearest neighbour sites of Al atoms and local ordering parameters could be achieved. © 2010 Elsevier B.V.

  1. Studying nearest neighbor correlations by atom probe tomography (APT) in metallic glasses as exemplified for Fe40Ni40B20 glassy ribbons

    KAUST Repository

    Shariq, Ahmed

    2012-01-01

    A next nearest neighbor evaluation procedure of atom probe tomography data provides distributions of the distances between atoms. The width of these distributions for metallic glasses studied so far is a few Angstrom reflecting the spatial resolution of the analytical technique. However, fitting Gaussian distributions to the distribution of atomic distances yields average distances with statistical uncertainties of 2 to 3 hundredth of an Angstrom. Fe 40Ni40B20 metallic glass ribbons are characterized this way in the as quenched state and for a state heat treated at 350 °C for 1 h revealing a change in the structure on the sub-nanometer scale. By applying the statistical tool of the χ2 test a slight deviation from a random distribution of B-atoms in the as quenched sample is perceived, whereas a pronounced elemental inhomogeneity of boron is detected for the annealed state. In addition, the distance distribution of the first fifteen atomic neighbors is determined by using this algorithm for both annealed and as quenched states. The next neighbor evaluation algorithm evinces a steric periodicity of the atoms when the next neighbor distances are normalized by the first next neighbor distance. A comparison of the nearest neighbor atomic distribution for as quenched and annealed state shows accumulation of Ni and B. Moreover, it also reveals the tendency of Fe and B to move slightly away from each other, an incipient step to Ni rich boride formation. © 2011 Elsevier B.V.

  2. Pulsed-voltage atom probe tomography of low conductivity and insulator materials by application of ultrathin metallic coating on nanoscale specimen geometry.

    Science.gov (United States)

    Adineh, Vahid R; Marceau, Ross K W; Chen, Yu; Si, Kae J; Velkov, Tony; Cheng, Wenlong; Li, Jian; Fu, Jing

    2017-10-01

    We present a novel approach for analysis of low-conductivity and insulating materials with conventional pulsed-voltage atom probe tomography (APT), by incorporating an ultrathin metallic coating on focused ion beam prepared needle-shaped specimens. Finite element electrostatic simulations of coated atom probe specimens were performed, which suggest remarkable improvement in uniform voltage distribution and subsequent field evaporation of the insulated samples with a metallic coating of approximately 10nm thickness. Using design of experiment technique, an experimental investigation was performed to study physical vapor deposition coating of needle specimens with end tip radii less than 100nm. The final geometries of the coated APT specimens were characterized with high-resolution scanning electron microscopy and transmission electron microscopy, and an empirical model was proposed to determine the optimal coating thickness for a given specimen size. The optimal coating strategy was applied to APT specimens of resin embedded Au nanospheres. Results demonstrate that the optimal coating strategy allows unique pulsed-voltage atom probe analysis and 3D imaging of biological and insulated samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Atomic scale chemical tomography of human bone

    Science.gov (United States)

    Langelier, Brian; Wang, Xiaoyue; Grandfield, Kathryn

    2017-01-01

    Human bone is a complex hierarchical material. Understanding bone structure and its corresponding composition at the nanometer scale is critical for elucidating mechanisms of biomineralization under healthy and pathological states. However, the three-dimensional structure and chemical nature of bone remains largely unexplored at the nanometer scale due to the challenges associated with characterizing both the structural and chemical integrity of bone simultaneously. Here, we use correlative transmission electron microscopy and atom probe tomography for the first time, to our knowledge, to reveal structures in human bone at the atomic level. This approach provides an overlaying chemical map of the organic and inorganic constituents of bone on its structure. This first use of atom probe tomography on human bone reveals local gradients, trace element detection of Mg, and the co-localization of Na with the inorganic-organic interface of bone mineral and collagen fibrils, suggesting the important role of Na-rich organics in the structural connection between mineral and collagen. Our findings provide the first insights into the hierarchical organization and chemical heterogeneity in human bone in three-dimensions at its smallest length scale - the atomic level. We demonstrate that atom probe tomography shows potential for new insights in biomineralization research on bone.

  4. Analysis of compositional uniformity in Al{sub x}Ga{sub 1−x}N thin films using atom probe tomography and electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Huang, Li; Porter, Lisa M.; Davis, Robert F., E-mail: rfd@andrew.cmu.edu [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States); Schreiber, Daniel K. [Energy and Environment Directorate, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)

    2016-07-15

    Calculated frequency distributions of atom probe tomography reconstructions (∼80 nm field of view) of very thin Al{sub x}Ga{sub 1−x}N (0.18 ≤ x ≤ 0.51) films grown via metalorganic vapor phase epitaxy on both (0001) GaN/AlN/SiC and (0001) GaN/sapphire heterostructures revealed homogeneous concentrations of Al and chemically abrupt Al{sub x}Ga{sub 1−x}N/GaN interfaces. The results of scanning transmission electron microscopy and selected area diffraction corroborated these results and revealed that neither superlattice ordering nor phase separation was present at nanometer length scales.

  5. Characterization of electrical properties in axial Si-Ge nanowire heterojunctions using off-axis electron holography and atom-probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Zhaofeng [Department of Physics, Arizona State University, Tempe, Arizona 85287, USA; Perea, Daniel E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Yoo, Jinkyoung [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA; He, Yang [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pennsylvania 15261, USA; Colby, Robert J. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Barker, Josh E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Gu, Meng [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Mao, Scott X. [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pennsylvania 15261, USA; Wang, Chongmin [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Picraux, S. T. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287, USA; McCartney, Martha R. [Department of Physics, Arizona State University, Tempe, Arizona 85287, USA

    2016-09-13

    Doped Si-Ge nanowire (NW) heterojunctions were grown using the vapor-liquid-solid method with AuGa and Au catalyst particles. Transmission electron microscopy and off-axis electron holography (EH) were used to characterize the nanostructure and to measure the electrostatic potential profile across the junction resulting from electrically active dopants, while atom-probe tomography (APT) was used to determine the Si, Ge and total (active and inactive) dopant concentration profiles. A comparison of the measured potential profile with simulations indicated that Ga dopants unintentionally introduced during AuGa catalyst growth were electronically inactive despite APT results that showed considerable amounts of Ga in the Si region. 10% P in Ge and 100% B in Si were estimated to be activated, which was corroborated by in situ electron-holography biasing experiments. This combination of EH, APT, in situ biasing and simulations allows a better knowledge and understanding of the electrically active dopant distributions in NWs.

  6. A model for oxidation-driven surface segregation and transport on Pt-alloys studied by atom probe tomography

    Science.gov (United States)

    Bagot, P. A. J.; Kreuzer, H. J.; Cerezo, A.; Smith, G. D. W.

    2011-08-01

    Using a purpose-built 3D atom probe, we have previously shown that exposure to oxidising gases (NO, N2O, O2) induces Rh surface segregation in Pt-Rh alloys, the extent of which is strongly dependent on treatment temperature, crystallographic plane and the presence of ternary alloy additions. In this paper, the segregation trends identified on three different crystallographic surfaces of Pt-Rh are analysed using thermodynamic and kinetic arguments. The segregation model we present is generic for diffusion on alloy surfaces in the presence of active gases. From it we obtain activation energies and diffusion coefficients for the processes of metal-oxide species diffusion both perpendicular to and laterally across the surface. Using these we propose a simple model for the interaction of chemically active gases with the surfaces of such alloys. Applying this understanding to sequential oxidation/reduction treatments would in principle allow improved control of the surface composition of alloy catalysts. Related applications of this model include optimisation of core-shell catalyst nanoparticles.

  7. Mining information from atom probe data

    Energy Technology Data Exchange (ETDEWEB)

    Cairney, Julie M., E-mail: julie.cairney@sydney.edu.au [School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Rajan, Krishna [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Haley, Daniel [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Max Planck Institut für Eisenforschung GmbH, Max-Planck Straße 1, 40237 Düsseldorf (Germany); Gault, Baptiste; Bagot, Paul A.J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Choi, Pyuck-Pa [Max Planck Institut für Eisenforschung GmbH, Max-Planck Straße 1, 40237 Düsseldorf (Germany); Felfer, Peter J.; Ringer, Simon P. [School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Marceau, Ross K.W. [Institute for Frontier Materials, Deakin University, Geelong Technology Precinct, 75 Pigdons Road, Waurn Ponds, Victoria 3216 (Australia); Moody, Michael P. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-12-15

    Whilst atom probe tomography (APT) is a powerful technique with the capacity to gather information containing hundreds of millions of atoms from a single specimen, the ability to effectively use this information creates significant challenges. The main technological bottleneck lies in handling the extremely large amounts of data on spatial–chemical correlations, as well as developing new quantitative computational foundations for image reconstruction that target critical and transformative problems in materials science. The power to explore materials at the atomic scale with the extraordinary level of sensitivity of detection offered by atom probe tomography has not been not fully harnessed due to the challenges of dealing with missing, sparse and often noisy data. Hence there is a profound need to couple the analytical tools to deal with the data challenges with the experimental issues associated with this instrument. In this paper we provide a summary of some key issues associated with the challenges, and solutions to extract or “mine” fundamental materials science information from that data. - Highlights: • Overview of the newest developments in techniques to extract information from atom probe data. • As well as reviewing existing approaches, improvements and new approaches are presented. • Techniques covered include tests for randomness, short range order and crystallography. • Methods for interfacial excess mapping and spectral decomposition are also covered.

  8. Characterization of electrical properties in axial Si-Ge nanowire heterojunctions using off-axis electron holography and atom-probe tomography

    Science.gov (United States)

    Gan, Zhaofeng; Perea, Daniel E.; Yoo, Jinkyoung; He, Yang; Colby, Robert J.; Barker, Josh E.; Gu, Meng; Mao, Scott X.; Wang, Chongmin; Picraux, S. T.; Smith, David J.; McCartney, Martha R.

    2016-09-01

    Nanowires (NWs) consisting of P-doped Si/B-doped Ge axial heterojunctions were grown via vapor-liquid-solid synthesis using a combination of Au and AuGa catalyst particles. Off-axis electron holography (EH) was used to measure the electrostatic potential profile across the junction resulting from electrically active dopants, and atom-probe tomography (APT) was used to map total dopant concentration profiles. A comparison of the electrostatic potential profile measured from EH with simulations that were based on the APT results indicates that Ga atoms unintentionally introduced during AuGa catalyst growth were mostly electronically inactive. This finding was also corroborated by in situ electron-holography biasing experiments. Electronic band structure simulations guided by the experimental results helped to provide a much better explanation of the NW electrical behavior. Overall, this work demonstrates that the combination of EH, APT, in situ biasing, and simulations allows a more complete understanding of NW electrical properties to be developed.

  9. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    Science.gov (United States)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-04-01

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  10. Systematic approaches for targeting an atom-probe tomography sample fabricated in a thin TEM specimen: Correlative structural, chemical and 3-D reconstruction analyses.

    Science.gov (United States)

    Baik, Sung-Il; Isheim, Dieter; Seidman, David N

    2018-01-01

    Atom-probe tomography (APT) is a unique analysis tool that enables true three-dimensional (3-D) analyses with sub-nano scale spatial resolution. Recent implementations of the local-electrode atom-probe (LEAP) tomograph with ultraviolet laser pulsing have significantly expanded the research applications of APT. The small field-of-view of a needle-shaped specimen with a less than 100 nm diam. is, however, a major limitation for analyzing materials. The systematic approaches for site-specific targeting of an APT nanotip in a transmission electron microscope (TEM) of a thin sample are introduced to solve the geometrical limitations of a sharpened APT nanotip. In addition to "coupling APT to TEM", the technique presented here allows for targeting the preparation of an APT tip based on TEM observation of a much larger area than what is captured in the APT tip. The correlative methods have synergies for not only high-resolution structural analyses but also for obtaining chemical information. Chemical analyses in a TEM, both energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS), are performed and compared with the APT chemical analyses of a carbide phase (M 7 C 3 ) precipitate at a grain boundary in a Ni-based alloy. Additionally, a TEM image of a sharpened APT nanotip is utilized for calculation of the detection area ratio of an APT nanotip by comparison with a TEM image for precise tomographic reconstructions. A grain-boundary/carbide precipitate triple junction is used to attain precise positioning of an APT nanotip in an analyzed TEM specimen. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Fe-implanted 6H-SiC: Direct evidence of Fe{sub 3}Si nanoparticles observed by atom probe tomography and {sup 57}Fe Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Diallo, M. L.; Fnidiki, A., E-mail: abdeslem.fnidiki@univ-rouen.fr; Lardé, R.; Cuvilly, F.; Blum, I. [Groupe de Physique des Matériaux, Université et INSA de Rouen - UMR CNRS 6634 - Normandie Université. F-76801 Saint Etienne du Rouvray (France); Lechevallier, L. [Groupe de Physique des Matériaux, Université et INSA de Rouen - UMR CNRS 6634 - Normandie Université. F-76801 Saint Etienne du Rouvray (France); Département de GEII, Université de Cergy-Pontoise, rue d' Eragny, Neuville sur Oise, 95031 Cergy-Pontoise (France); Debelle, A.; Thomé, L. [Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), CNRS-IN2P3-Univ. Paris-Sud 11, Bât. 108, 91405 Orsay (France); Viret, M. [Service de Physique de l' Etat Condensé (DSM/IRAMIS/SPEC), UMR 3680 CNRS, Bât. 772, Orme des Merisiers, CEA Saclay 91191 Gif sur Yvette (France); Marteau, M.; Eyidi, D.; Declémy, A. [Institut PPRIME, UPR 3346 CNRS, Université de Poitiers, ENSMA, SP2MI, téléport 2, 11 Bvd M. et P. Curie 86962 Futuroscope, Chasseneuil (France)

    2015-05-14

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, {sup 57}Fe Mössbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe{sub 3}Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  12. Carbon Redistribution and Carbide Precipitation in a High-Strength Low-Carbon HSLA-115 Steel Studied on a Nanoscale by Atom Probe Tomography

    Science.gov (United States)

    Jain, Divya; Isheim, Dieter; Seidman, David N.

    2017-07-01

    HSLA-115 is a newly developed Cu-bearing high-strength low-carbon martensitic steel for use in Naval structural applications. This research provides, for the first time, a comprehensive compositional analysis of carbon redistribution and associated complex phase transformations in an isothermal aging study of HSLA-115 at 823 K (550 °C). Specifically, we characterize carbon segregation at lath boundaries, grain-refining niobium carbonitrides, cementite, and secondary hardening M2C carbides, in addition to copper precipitation, by 3D atom probe tomography (APT). Segregation of carbon (3 to 6 at. pct C) is observed at martensitic lath boundaries in the as-quenched and 0.12-hour aged microstructures. On further aging, carbon redistributes itself forming cementite and M2C carbides. Niobium carbonitride precipitates do not dissolve during the austenitizing treatment and are inherited in the as-quenched and aged microstructures; these are characterized along with cementite by synchrotron X-ray diffraction and APT. Sub-nanometer-sized M2C carbide precipitates are observed after the formation of Cu precipitates, co-located with the latter, indicating heterogeneous nucleation of M2C. The temporal evolution of the composition and morphology of M2C carbides at 823 K (550 °C) is described using APT; their precipitation kinetics is intertwined with Cu precipitates, affecting the bulk mechanical properties of HSLA-115. Phase compositions determined by APT are compared with computed compositions at thermodynamic equilibrium using ThermoCalc.

  13. Investigation of modulus hardening of various co-clusters in aged Al-Cu-Mg-Ag alloy by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Song [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Ying, Puyou; Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

    2016-06-21

    The modulus hardening capability of various co-clusters in a low Cu/Mg ratio Al-Cu-Mg-Ag alloy aged at 165 °C is investigated by quantitative atom probe tomography analysis. Prolonged aging from 5 min to 2 h leads to the simultaneous increase in the critical shear stress of both Mg-Ag and Cu-Mg co-clusters. Regardless of the higher shear modulus of Cu-Mg co-clusters, calculation results show that Mg-Ag co-clusters possess a greater modulus hardening capability than Cu-Mg co-clusters, suggesting its primary contribution to the rapid hardening at the early aging stage. As aging extends from 30 min to 2 h, the increment in the critical shear stress of Mg-Ag co-clusters is lower than that of Cu-Mg co-clusters due to the precipitation of high density Ω phase. In addition, the shear modulus of Mg-Ag co-clusters is generally independent on its size at each investigated condition.

  14. Carbon Redistribution and Carbide Precipitation in a High-Strength Low-Carbon HSLA-115 Steel Studied on a Nanoscale by Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Divya; Isheim, Dieter; Seidman, David N. (NWU)

    2017-05-09

    HSLA-115 is a newly developed Cu-bearing high-strength low-carbon martensitic steel for use in Naval structural applications. This research provides, for the first time, a comprehensive compositional analysis of carbon redistribution and associated complex phase transformations in an isothermal aging study of HSLA-115 at 823 K (550 °C). Specifically, we characterize carbon segregation at lath boundaries, grain-refining niobium carbonitrides, cementite, and secondary hardening M2C carbides, in addition to copper precipitation, by 3D atom probe tomography (APT). Segregation of carbon (3 to 6 at. pct C) is observed at martensitic lath boundaries in the as-quenched and 0.12-hour aged microstructures. On further aging, carbon redistributes itself forming cementite and M2C carbides. Niobium carbonitride precipitates do not dissolve during the austenitizing treatment and are inherited in the as-quenched and aged microstructures; these are characterized along with cementite by synchrotron X-ray diffraction and APT. Sub-nanometer-sized M2C carbide precipitates are observed after the formation of Cu precipitates, co-located with the latter, indicating heterogeneous nucleation of M2C. The temporal evolution of the composition and morphology of M2C carbides at 823 K (550 °C) is described using APT; their precipitation kinetics is intertwined with Cu precipitates, affecting the bulk mechanical properties of HSLA-115. Phase compositions determined by APT are compared with computed compositions at thermodynamic equilibrium using ThermoCalc.

  15. Ultra-reduced phases in Apollo 16 regolith: Combined field emission electron probe microanalysis and atom probe tomography of submicron Fe-Si grains in Apollo 16 sample 61500

    Science.gov (United States)

    Gopon, Phillip; Spicuzza, Michael J.; Kelly, Thomas F.; Reinhard, David; Prosa, Ty J.; Fournelle, John

    2017-09-01

    The lunar regolith contains a variety of chemically reduced phases of interest to planetary scientists and the most common, metallic iron, is generally ascribed to space weathering processes (Lucey et al. ). Reports of silicon metal and iron silicides, phases indicative of extremely reducing conditions, in lunar samples are rare (Anand et al. ; Spicuzza et al. ). Additional examples of Fe-silicides have been identified in a survey of particles from Apollo 16 sample 61501,22. Herein is demonstrated the utility of low keV electron probe microanalysis (EPMA), using the Fe Ll X-ray line, to analyze these submicron phases, and the necessity of accounting for carbon contamination. We document four Fe-Si and Si0 minerals in lunar regolith return material. The new Fe-Si samples have a composition close to (Fe,Ni)3Si, whereas those associated with Si0 are close to FeSi2 and Fe3Si7. Atom probe tomography of (Fe,Ni)3Si shows trace levels of C (60 ppma and nanodomains enriched in C, Ni, P, Cr, and Sr). These reduced minerals require orders of magnitude lower oxygen fugacity and more reducing conditions than required to form Fe0. Documenting the similarities and differences in these samples is important to constrain their formation processes. These phases potentially formed at high temperatures resulting from a meteorite impact. Whether carbon played a role in achieving the lower oxygen fugacities—and there is evidence of nearby carbonaceous chondritic material—it remains to be proven that carbon was the necessary component for the unique existence of these Si0 and iron silicide minerals.

  16. Correlating Atom Probe Crystallographic Measurements with Transmission Kikuchi Diffraction Data.

    Science.gov (United States)

    Breen, Andrew J; Babinsky, Katharina; Day, Alec C; Eder, K; Oakman, Connor J; Trimby, Patrick W; Primig, Sophie; Cairney, Julie M; Ringer, Simon P

    2017-04-01

    Correlative microscopy approaches offer synergistic solutions to many research problems. One such combination, that has been studied in limited detail, is the use of atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) on the same tip specimen. By combining these two powerful microscopy techniques, the microstructure of important engineering alloys can be studied in greater detail. For the first time, the accuracy of crystallographic measurements made using APT will be independently verified using TKD. Experimental data from two atom probe tips, one a nanocrystalline Al-0.5Ag alloy specimen collected on a straight flight-path atom probe and the other a high purity Mo specimen collected on a reflectron-fitted instrument, will be compared. We find that the average minimum misorientation angle, calculated from calibrated atom probe reconstructions with two different pole combinations, deviate 0.7° and 1.4°, respectively, from the TKD results. The type of atom probe and experimental conditions appear to have some impact on this accuracy and the reconstruction and measurement procedures are likely to contribute further to degradation in angular resolution. The challenges and implications of this correlative approach will also be discussed.

  17. Atom-probe tomography the local electrode atom probe

    CERN Document Server

    Miller, Michael K

    2014-01-01

    In this comprehensive introduction to the use of APT in nanocharacterization, readers will find everything they need to get up to speed on the technique, from the core physics to state-of-the-art instrumentation and revised methods of data analysis.

  18. On the Stability of Reversely Formed Austenite and Related Mechanism of Transformation in an Fe-Ni-Mn Martensitic Steel Aided by Electron Backscattering Diffraction and Atom Probe Tomography

    Science.gov (United States)

    Koohdar, Hamidreza; Nili-Ahmadabadi, Mahmoud; Habibi-Parsa, Mohammad; Jafarian, Hamid Reza; Bhattacharjee, Tilak; Tsuji, Nobuhiro

    2017-08-01

    The stability of reversely formed austenite and related mechanism of transformation were investigated against temperature and time in an Fe-9.6Ni-7.1Mn (at. pct) martensitic steel during intercritical annealing at a dual-phase (α + γ) region. Dilatometry, electron backscattering diffraction (EBSD), atom probe tomography (APT), and X-ray diffraction (XRD) were used to characterize the mechanism of reverse transformation. It was found that under intercritical annealing at 853 K (580 °C), when the heating rate is 20 K/s (20 °C/s), reverse transformation takes place through a mixed diffusion control mechanism, i.e., controlled by bulk diffusion and diffusion along the interface, where Ni controls the diffusion as its diffusivity is lower than that of Mn in the martensite and austenite. Increasing the intercritical annealing to 873 K (600 °C) at an identical heating rate of 20 K/s (20 °C/s) showed that reverse transformation occurs through a sequential combination of both martensitic and diffusional mechanisms. The transition temperature from diffusional to martensitic transformation was obtained close to 858 K (585 °C). Experimental results revealed that the austenite formed by the diffusional mechanism at 853 K (580 °C) mainly remains untransformed after cooling to ambient temperature due to the enrichment with Ni and Mn. It was also found that the stability of the reversely formed austenite by martensitic mechanism at 873 K (600 °C) is related to grain refinement.

  19. On the Stability of Reversely Formed Austenite and Related Mechanism of Transformation in an Fe-Ni-Mn Martensitic Steel Aided by Electron Backscattering Diffraction and Atom Probe Tomography

    Science.gov (United States)

    Koohdar, Hamidreza; Nili-Ahmadabadi, Mahmoud; Habibi-Parsa, Mohammad; Jafarian, Hamid Reza; Bhattacharjee, Tilak; Tsuji, Nobuhiro

    2017-11-01

    The stability of reversely formed austenite and related mechanism of transformation were investigated against temperature and time in an Fe-9.6Ni-7.1Mn (at. pct) martensitic steel during intercritical annealing at a dual-phase ( α + γ) region. Dilatometry, electron backscattering diffraction (EBSD), atom probe tomography (APT), and X-ray diffraction (XRD) were used to characterize the mechanism of reverse transformation. It was found that under intercritical annealing at 853 K (580 °C), when the heating rate is 20 K/s (20 °C/s), reverse transformation takes place through a mixed diffusion control mechanism, i.e., controlled by bulk diffusion and diffusion along the interface, where Ni controls the diffusion as its diffusivity is lower than that of Mn in the martensite and austenite. Increasing the intercritical annealing to 873 K (600 °C) at an identical heating rate of 20 K/s (20 °C/s) showed that reverse transformation occurs through a sequential combination of both martensitic and diffusional mechanisms. The transition temperature from diffusional to martensitic transformation was obtained close to 858 K (585 °C). Experimental results revealed that the austenite formed by the diffusional mechanism at 853 K (580 °C) mainly remains untransformed after cooling to ambient temperature due to the enrichment with Ni and Mn. It was also found that the stability of the reversely formed austenite by martensitic mechanism at 873 K (600 °C) is related to grain refinement.

  20. Probing the structure of heterogeneous diluted materials by diffraction tomography.

    Science.gov (United States)

    Bleuet, Pierre; Welcomme, Eléonore; Dooryhée, Eric; Susini, Jean; Hodeau, Jean-Louis; Walter, Philippe

    2008-06-01

    The advent of nanosciences calls for the development of local structural probes, in particular to characterize ill-ordered or heterogeneous materials. Furthermore, because materials properties are often related to their heterogeneity and the hierarchical arrangement of their structure, different structural probes covering a wide range of scales are required. X-ray diffraction is one of the prime structural methods but suffers from a relatively poor detection limit, whereas transmission electron analysis involves destructive sample preparation. Here we show the potential of coupling pencil-beam tomography with X-ray diffraction to examine unidentified phases in nanomaterials and polycrystalline materials. The demonstration is carried out on a high-pressure pellet containing several carbon phases and on a heterogeneous powder containing chalcedony and iron pigments. The present method enables a non-invasive structural refinement with a weight sensitivity of one part per thousand. It enables the extraction of the scattering patterns of amorphous and crystalline compounds with similar atomic densities and compositions. Furthermore, such a diffraction-tomography experiment can be carried out simultaneously with X-ray fluorescence, Compton and absorption tomographies, enabling a multimodal analysis of prime importance in materials science, chemistry, geology, environmental science, medical science, palaeontology and cultural heritage.

  1. Interpreting atom probe data from chromium oxide scales

    Energy Technology Data Exchange (ETDEWEB)

    La Fontaine, Alexandre [School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Gault, Baptiste [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Breen, Andrew; Stephenson, Leigh; Ceguerra, Anna V.; Yang, Limei [School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Dinh Nguyen, Thuan; Zhang, Jianqiang; Young, David J. [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Cairney, Julie M., E-mail: julie.cairney@sydney.edu.au [School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2015-12-15

    Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed “laser sensitivity factor” is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite samples. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia. - Highlights: • Chromium oxide scales are analyzed by picosecond-pulsed ultraviolet-laser assisted atom probe tomography. • The influence of laser energy, pulse frequency and temperature on thermal tail and composition is reported. • “Laser sensitivity factor”, a new thermal tail quantification parameter was introduced. • Ions dissociations in chromia during the analysis are discussed.

  2. Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

    Science.gov (United States)

    Haley, Daniel; Bagot, Paul A J; Moody, Michael P

    2017-04-01

    In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

  3. Atom-Probe Tomography, TEM and ToF-SIMS study of borosilicate glass alteration rim: A multiscale approach to investigating rate-limiting mechanisms

    Science.gov (United States)

    Gin, S.; Jollivet, P.; Barba Rossa, G.; Tribet, M.; Mougnaud, S.; Collin, M.; Fournier, M.; Cadel, E.; Cabie, M.; Dupuy, L.

    2017-04-01

    Significant efforts have been made into understanding the dissolution of silicate glasses and minerals, but there is still debate about the formation processes and the properties of surface layers. Here, we investigate glass coupons of ISG glass - a 6 oxide borosilicate glass of nuclear interest - altered at 90 °C in conditions close to saturation and for durations ranging from 1 to 875 days. Altered glass coupons were characterized from atomic to macroscopic levels to better understand how surface layers become protective. With this approach, it was shown that a rough interface, whose physical characteristics have been modeled, formed in a few days and then propagated into the pristine material at a rate controlled by the reactive transport of water within the growing alteration layer. Several observations such as stiff interfacial B, Na, and Ca profiles and damped profiles within the rest of the alteration layer are not consistent with the classical inter-diffusion model, or with the interfacial dissolution-precipitation model. A new paradigm is proposed to explain these features. Inter-diffusion, a process based on water ingress into the glass and ion-exchange, may only explain the formation of the rough interface in the early stage of glass corrosion. A thin layer of altered glass is formed by this process, and as the layer grows, the accessibility of water to the reactive interface becomes rate-limiting. As a consequence, only the most easily accessible species are dissolved. The others remain undissolved in the alteration layer, probably fixed in highly hydrolysis resistant clusters. A new estimation of water diffusivity in the glass when covered by the passivating layer was determined from the shift between B and H profiles, and was 10-23 m2.s-1, i.e. approximately 3 orders of magnitude lower than water diffusivity in the pristine material. Overall, in the absence of secondary crystalline phases that could consume the major components of the alteration

  4. Microfluidics for Positron Emission Tomography Probe Development

    Directory of Open Access Journals (Sweden)

    Ming-Wei Wang

    2010-07-01

    Full Text Available Owing to increased needs for positron emission tomography (PET, high demands for a wide variety of radiolabeled compounds will have to be met by exploiting novel radiochemistry and engineering technologies to improve the production and development of PET probes. The application of microfluidic reactors to perform radiosyntheses is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional labeling systems. Microfluidics-based radiochemistry can lead to the use of smaller quantities of precursors, accelerated reaction rates, and easier purification processes with greater yield and higher specific activity of desired probes. Several proof-of-principle examples along with the basics of device architecture and operation and the potential limitations of each design are discussed. Along with the concept of radioisotope distribution from centralized cyclotron facilities to individual imaging centers and laboratories (“decentralized model”, an easy-to-use, stand-alone, flexible, fully automated, radiochemical microfluidic platform can provide simpler and more cost-effective procedures for molecular imaging using PET.

  5. Materials applications of an advanced 3-dimensional atom probe

    NARCIS (Netherlands)

    Cerezo, A; Gibuoin, D; Sijbrandij, SJ; Venker, FM; Warren, PJ; Wilde, J; Smith, GDW

    An advanced 3-dimensional atom probe system has been constructed, based on an optical position-sensitive atom probe (OPoSAP) detector with energy compensation using a reflectron lens. The multi-hit detection capability of the OPoSAP lends to significant improvements in the efficiency of the

  6. Comparison of the quantitative analysis performance between pulsed voltage atom probe and pulsed laser atom probe.

    Science.gov (United States)

    Takahashi, J; Kawakami, K; Raabe, D

    2017-04-01

    The difference in quantitative analysis performance between the voltage-mode and laser-mode of a local electrode atom probe (LEAP3000X HR) was investigated using a Fe-Cu binary model alloy. Solute copper atoms in ferritic iron preferentially field evaporate because of their significantly lower evaporation field than the matrix iron, and thus, the apparent concentration of solute copper tends to be lower than the actual concentration. However, in voltage-mode, the apparent concentration was higher than the actual concentration at 40K or less due to a detection loss of matrix iron, and the concentration decreased with increasing specimen temperature due to the preferential evaporation of solute copper. On the other hand, in laser-mode, the apparent concentration never exceeded the actual concentration, even at lower temperatures (20K), and this mode showed better quantitative performance over a wide range of specimen temperatures. These results indicate that the pulsed laser atom probe prevents both detection loss and preferential evaporation under a wide range of measurement conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Two-probe STM experiments at the atomic level.

    Science.gov (United States)

    Kolmer, Marek; Olszowski, Piotr; Zuzak, Rafal; Godlewski, Szymon; Joachim, Christian; Szymonski, Marek

    2017-11-08

    Direct characterization of planar atomic or molecular scale devices and circuits on a supporting surface by multi-probe measurements requires unprecedented stability of single atom contacts and manipulation of scanning probes over large, nanometer scale area with atomic precision. In this work, we describe the full methodology behind atomically defined two-probe scanning tunneling microscopy (STM) experiments performed on a model system: dangling bond dimer wire supported on a hydrogenated germanium (0 0 1) surface. We show that 70 nm long atomic wire can be simultaneously approached by two independent STM scanners with exact probe to probe distance reaching down to 30 nm. This allows direct wire characterization by two-probe I-V characteristics at distances below 50 nm. Our technical results presented in this work open a new area for multi-probe research, which can be now performed with precision so far accessible only by single-probe scanning probe microscopy (SPM) experiments.

  8. Two-probe STM experiments at the atomic level

    Science.gov (United States)

    Kolmer, Marek; Olszowski, Piotr; Zuzak, Rafal; Godlewski, Szymon; Joachim, Christian; Szymonski, Marek

    2017-11-01

    Direct characterization of planar atomic or molecular scale devices and circuits on a supporting surface by multi-probe measurements requires unprecedented stability of single atom contacts and manipulation of scanning probes over large, nanometer scale area with atomic precision. In this work, we describe the full methodology behind atomically defined two-probe scanning tunneling microscopy (STM) experiments performed on a model system: dangling bond dimer wire supported on a hydrogenated germanium (0 0 1) surface. We show that 70 nm long atomic wire can be simultaneously approached by two independent STM scanners with exact probe to probe distance reaching down to 30 nm. This allows direct wire characterization by two-probe I-V characteristics at distances below 50 nm. Our technical results presented in this work open a new area for multi-probe research, which can be now performed with precision so far accessible only by single-probe scanning probe microscopy (SPM) experiments.

  9. Manipulating collective quantum states of ultracold atoms by probing

    DEFF Research Database (Denmark)

    Wade, Andrew Christopher James

    2015-01-01

    nature of the measurement interaction and backaction is yet to be realised. This dissertation is concerned with ultracold atoms and their control via fully quantum mechanical probes. Nonclassical, squeezed and entangled states of matter and single photon sources are important for fundamental studies...... and quantum technologies. By probing, the production of squeezed and entangled states of collective variables in a Bose-Einstein condensate is investigated. Thereafter, an atomic probe using the strong interactions between highly excited atomic states, manipulates the light-matter dynamics of an ultracold gas...

  10. An update in proton probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sakellariou, A.; Cholewa, M.; Saint, A.; Legge, G.L.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Howard, J. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1996-12-31

    The analysis of scanning transmission ion microscopy (STIM) tomography data is improved. The volumetric density information is obtained directly from an iterative convolution and back-projection (BFP) reconstruction method. The iterative method allows the effects of stopping-power to be incorporated easily. One draw back is that a priori constituency information is required for the iterative method to work However, this is of no concern because the iterative method was designed with PIXE tomography in mind. In this light, the a priori information will be obtained as the zeroth iteration of a PIXE tomography iterative reconstruction method. 4 refs., 1 tab., 4 figs.

  11. A miniature forward-imaging optical coherence tomography (OCT) probe

    Science.gov (United States)

    Joos, Karen M.; Shen, Jin-Hui

    2012-03-01

    Optical coherence tomography (OCT) has had a tremendous global health impact upon the current ability to diagnose, treat, and monitor multiple eye diseases. We propose that a miniature forward-imaging OCT probe can be developed for real-time ocular imaging. A miniature 25-gauge forward-imaging probe was designed and developed to use with an 850 nm spectral-domain optical coherence tomography (SDOCT) system (Bioptigen, Inc. Durham, NC). Imaging parameters were determined. Ocular tissues were examined with the miniature OCT probe. A miniature SDOCT probe was developed with the scanning driver within the hand piece. The SDOCT fiber-scanning probe maximally transmitted power of 800 μW. The scanning range was 3 mm when the probe tip was held 3 to 5 mm from the tissue surface. The axial resolution was 6 μm and the lateral resolution was 30-35 μm. The 25-gauge forward-imaging probe was used to image cellophane tape, eyelid skin, cornea, conjunctiva, sclera, iris, anterior lens, anterior chamber angle, retina, retinal tear, retinal detachment, optic nerve head, and optic nerve sheath. Images obtained from the miniature probe appeared similar to images from a 3 mm scanning range of a commercial large handheld OCT probe (Bioptigen, Inc. Durham, NC).

  12. Fabrication of an all-metal atomic force microscope probe

    DEFF Research Database (Denmark)

    Rasmussen, Jan Pihl; Tang, Peter Torben; Hansen, Ole

    1997-01-01

    This paper presents a method for fabrication of an all-metal atomic force microscope probe (tip, cantilever and support) for optical read-out, using a combination of silicon micro-machining and electroforming. The paper describes the entire fabrication process for a nickel AFM-probe. In addition...

  13. Improvements in three-dimensional atom probe design

    Science.gov (United States)

    Cerezo, A.; Godfrey, T. J.; Hyde, J. M.; Sijbrandij, S. J.; Smith, G. D. W.

    1994-03-01

    An improved position-sensitive atom probe has been designed which uses a combination of a parallel timing system and a silicon photodiode array camera. The use of two separate data acquisition systems allows the two functions of accurate positioning and flight time determination to be divorced, thus removing the compromises which must be made when these functions are carried out with only a single detector. The resulting instrument is able to determine flight times and positions of impacts straightforwardly, even when multiple ions are evaporated on a single pulse, and should be capable of operating at evaporation rates close to that of a conventional probe-hole atom probe.

  14. Prospects of linear reconstruction in atomic resolution electron holographic tomography

    Energy Technology Data Exchange (ETDEWEB)

    Krehl, Jonas, E-mail: Jonas.Krehl@triebenberg.de; Lubk, Axel

    2015-03-15

    Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak. - Highlights: • We simulate a holographic tilt series of a nanocrystal with atomic resolution. • Using PGA-based Holographic Tomography we reconstruct the atomic structure. • The reconstruction shows characteristic artefacts, chiefly caused by defocus. • Changing one atom's Z produces a well localised in the reconstruction.

  15. Nanoparticle Probes for Structural and Functional Photoacoustic Molecular Tomography

    Directory of Open Access Journals (Sweden)

    Haobin Chen

    2015-01-01

    Full Text Available Nowadays, nanoparticle probes have received extensive attention largely due to its potential biomedical applications in structural, functional, and molecular imaging. In addition, photoacoustic tomography (PAT, a method based on the photoacoustic effect, is widely recognized as a robust modality to evaluate the structure and function of biological tissues with high optical contrast and high acoustic resolution. The combination of PAT with nanoparticle probes holds promises for detecting and imaging diseased tissues or monitoring their treatments with high sensitivity. This review will introduce the recent advances in the emerging field of nanoparticle probes and their preclinical applications in PAT, as well as relevant perspectives on future development.

  16. Quantum metrology to probe atomic parity violation

    OpenAIRE

    Mukherjee, M.

    2009-01-01

    An entangled state prepared in the decoherence free sub-space together with a Ramsey type measurement can probe parity violation in heavy alkali ions like Ba+ or Ra+. Here we propose an experiment with Ba+ ions as an example to measure the small parity violating effect in this system.

  17. Probing dark energy with atom interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Burrage, Clare; Copeland, Edmund J. [School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD (United Kingdom); Hinds, E.A., E-mail: Clare.Burrage@nottingham.ac.uk, E-mail: Edmund.Copeland@nottingham.ac.uk, E-mail: Ed.Hinds@imperial.ac.uk [Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom)

    2015-03-01

    Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too small to screen the chameleon field inside a large high-vacuum chamber, and therefore can detect the field with high sensitivity. We derive new limits on the chameleon parameters from existing experiments, and show that most of the remaining chameleon parameter space is readily accessible using atom interferometry.

  18. Surface Plasmon Polaritons Probed with Cold Atoms

    DEFF Research Database (Denmark)

    Kawalec, Tomasz; Sierant, Aleksandra; Panas, Roman

    2017-01-01

    We report on an optical mirror for cold rubidium atoms based on a repulsive dipole potential created by means of a modified recordable digital versatile disc. Using the mirror, we have determined the absolute value of the surface plasmon polariton (SPP) intensity, reaching 90 times the intensity...

  19. Cadherin interaction probed by atomic force microscopy

    OpenAIRE

    Baumgartner, W.; Hinterdorfer, P.; Ness, W.; Raab, A.; Vestweber, D; Schindler, H; Drenckhahn, D

    2000-01-01

    Single molecule atomic force microscopy was used to characterize structure, binding strength (unbinding force), and binding kinetics of a classical cadherin, vascular endothelial (VE)-cadherin, secreted by transfected Chinese hamster ovary cells as cis-dimerized full-length external domain fused to Fc-portion of human IgG. In physiological buffer, the external domain of VE-cadherin dimers is a ≈20-nm-long rod-shaped molecule that collapses and dissociates into monomers (V-shaped structures) i...

  20. Dynamical symmetry reduction and discrete tomography of a {Xi} atom

    Energy Technology Data Exchange (ETDEWEB)

    Mahler, Dylan; De Guise, Hubert [Department of Physics, Lakehead University, Thunder Bay (Canada); Klimov, Andrei B, E-mail: dmahler@physics.utoronto.c [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410 Guadalajara, Jalisco (Mexico)

    2010-09-01

    When implemented using a reasonable Hamiltonian, the tomography of a three-level {Xi} atom is complicated by the equidistant energy levels of the atom. This restricts the possible transformations to those in the SO(3) subgroup of SU(3). Although complete reconstruction is possible for a single {Xi} atom using a continuous set of tomograms, the discrete optimal set of tomograms, related to mutually unbiased bases in dimension 3, are not accessible by time evolution. We discuss here the search for an optimal set of discrete basis states compatible with the reduced SO(3) symmetry of the system.

  1. Cadherin interaction probed by atomic force microscopy

    Science.gov (United States)

    Baumgartner, W.; Hinterdorfer, P.; Ness, W.; Raab, A.; Vestweber, D.; Schindler, H.; Drenckhahn, D.

    2000-04-01

    Single molecule atomic force microscopy was used to characterize structure, binding strength (unbinding force), and binding kinetics of a classical cadherin, vascular endothelial (VE)-cadherin, secreted by transfected Chinese hamster ovary cells as cis-dimerized full-length external domain fused to Fc-portion of human IgG. In physiological buffer, the external domain of VE-cadherin dimers is a 20-nm-long rod-shaped molecule that collapses and dissociates into monomers (V-shaped structures) in the absence of Ca2+. Trans-interaction of dimers is a low-affinity reaction (KD = 10-3-10-5 M, koff = 1.8 s-1, kon = 103-105 M-1·s-1) with relatively low unbinding force (35-55 pN at retrace velocities of 200-4,000 nm·s-1). Higher order unbinding forces, that increase with interaction time, indicate association of cadherins into complexes with cumulative binding strength. These observations favor a model by which the inherently weak unit binding strength and affinity of cadherin trans-interaction requires clustering and cytoskeletal immobilization for amplification. Binding is regulated by low-affinity Ca2+ binding sites (KD = 1.15 mM) with high cooperativity (Hill coefficient of 5.04). Local changes of free extracellular Ca2+ in the narrow intercellular space may be of physiological importance to facilitate rapid remodeling of intercellular adhesion and communication.

  2. Tomography vs quantum control for a three-level atom

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar, O. [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44420 Guadalajara, Jalisco (Mexico)]. E-mail: caronte30@yahoo.com; Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44420 Guadalajara, Jalisco (Mexico); Guise, Hubert de [Department of Physics, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada)

    2006-12-04

    We investigate the possibilities of controlling and reconstructing the state of a single three-level atom. We propose a physical scheme where information about the atomic state is extracted by measuring the total number of excitations after successive application of electromagnetic field pulses. We show that, in the non-degenerate case (different transition frequencies for different atomic transitions), a three-level atom is completely controllable and its state can be completely reconstructed. In the degenerate case (when both atomic transitions are identical), we consider two dynamically inequivalent configurations, {lambda} and {xi}. In this case, we show that the density matrix can always be completely reconstructed whereas their respective system cannot be completely controlled. We explain why this last incompatibility between control and tomography arises.

  3. Astigmatism corrected common path probe for optical coherence tomography.

    Science.gov (United States)

    Singh, Kanwarpal; Yamada, Daisuke; Tearney, Guillermo

    2017-03-01

    Optical coherence tomography (OCT) catheters for intraluminal imaging are subject to various artifacts due to reference-sample arm dispersion imbalances and sample arm beam astigmatism. The goal of this work was to develop a probe that minimizes such artifacts. Our probe was fabricated using a single mode fiber at the tip of which a glass spacer and graded index objective lens were spliced to achieve the desired focal distance. The signal was reflected using a curved reflector to correct for astigmatism caused by the thin, protective, transparent sheath that surrounds the optics. The probe design was optimized using Zemax, a commercially available optical design software. Common path interferometric operation was achieved using Fresnel reflection from the tip of the focusing graded index objective lens. The performance of the probe was tested using a custom designed spectrometer-based OCT system. The probe achieved an axial resolution of 15.6 μm in air, a lateral resolution 33 μm, and a sensitivity of 103 dB. A scattering tissue phantom was imaged to test the performance of the probe for astigmatism correction. Images of the phantom confirmed that this common-path, astigmatism-corrected OCT imaging probe had minimal artifacts in the axial, and lateral dimensions. In this work, we developed an astigmatism-corrected, common path probe that minimizes artifacts associated with standard OCT probes. This design may be useful for OCT applications that require high axial and lateral resolutions. Lasers Surg. Med. 49:312-318, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  4. Toward the Atomic-Level Mass Analysis of Biomolecules by the Scanning Atom Probe.

    Science.gov (United States)

    Nishikawa, Osamu; Taniguchi, Masahiro

    2017-04-01

    In 1994, a new type of atom probe instrument, named the scanning atom probe (SAP), was proposed. The unique feature of the SAP is the introduction of a small extraction electrode, which scans over a specimen surface and confines the high field, required for field evaporation of surface atoms in a small space, between the specimen and the electrode. Thus, the SAP does not require a sharp specimen tip. This indicates that the SAP can mass analyze the specimens which are difficult to form in a sharp tip, such as organic materials and biomolecules. Clean single wall carbon nanotubes (CNT), made by high-pressure carbon monoxide process are found to be the best substrates for biomolecules. Various amino acids and dipeptide biomolecules were successfully mass analyzed, revealing characteristic clusters formed by strongly bound atoms in the specimens. The mass analysis indicates that SAP analysis of biomolecules is not only qualitative, but also quantitative.

  5. Probing stem cell differentiation using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xiaobin [Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8550 (Japan); Shi, Xuetao, E-mail: mrshixuetao@gmail.com [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Ostrovidov, Serge [WPI-Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); Wu, Hongkai, E-mail: chhkwu@ust.hk [Department of Chemistry & Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Nakajima, Ken [Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo 152-8550 (Japan)

    2016-03-15

    Graphical abstract: - Highlights: • Atomic force microscopy (AFM) was developed to probe stem cell differentiation. • The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. • AFM is a facile and useful tool for monitoring stem cell differentiation in a non-invasive manner. - Abstract: A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.

  6. Atomic force microscopy probing in the measurement of cell mechanics

    OpenAIRE

    Kirmizis, Dimitrios

    2010-01-01

    Dimitrios Kirmizis, Stergios LogothetidisDepartment of Physics, Laboratory for Thin Films-Nanosystems and Nanometrology, Aristotle University, Thessaloniki, GreeceAbstract: Atomic force microscope (AFM) has been used incrementally over the last decade in cell biology. Beyond its usefulness in high resolution imaging, AFM also has unique capabilities for probing the viscoelastic properties of living cells in culture and, even more, mapping the spatial distribution of cell mechanical properties...

  7. Design of cantilever probes for Atomic Force Microscopy (AFM)

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2000-01-01

    A cantilever beam used in an Atomic Force Microscope is optimized with respect to two different objectives. The first goal is to maximize the first eigenfrequency while keeping the stiffness of the probe constant. The second goal is to maximize the tip angle of the first eigenmode while again kee...... beam finite elements and the optimizations are carried through with either SLP (Sequential Linear Programming) or MMA (Method of Moving Asymptotes) and similar results are obtained....

  8. Multispectral optoacoustic tomography resolves smart probe activation in vulnerable plaques

    Science.gov (United States)

    Razansky, Daniel; Harlaar, Niels J.; Hillebrands, Jan-Luuk; Taruttis, Adrian; Herzog, Eva; Zeebregts, Clark; van Dam, Goitzen; Ntziachristos, Vasilis

    2011-03-01

    In this work, we show, for the first time to our knowledge, that multispectral optoacoustic tomography (MSOT) can deliver high resolution images of activatable molecular probe's distribution, sensitive to matrix metalloproteinases (MMP), deep within optically scattering human carotid specimen. It is further demonstrated that this method can be used in order to provide accurate maps of vulnerable plaque formations in atherosclerotic disease. Moreover, optoacoustic images can simultaneously show the underlining plaque morphology for accurate localization of MMP activity in three dimensions. This performance directly relates to small animal screening applications and to clinical potential as well.

  9. Handheld probes and galvanometer scanning for optical coherence tomography

    Science.gov (United States)

    Duma, V.-F.; Dobre, G.; Demian, D.; Cernat, R.; Sinescu, C.; Topala, F. I.; Negrutiu, M. L.; Hutiu, Gh.; Bradu, A.; Rolland, J. P.; Podoleanu, A. G.

    2015-09-01

    As part of the ongoing effort of the biomedical imaging community to move Optical Coherence Tomography (OCT) systems from the lab to the clinical environment and produce OCT systems appropriate for multiple types of investigations in a medical department, handheld probes equipped with different types of scanners need to be developed. These allow different areas of a patient's body to be investigated using OCT with the same system and even without changing the patient's position. This paper reviews first the state of the art regarding OCT handheld probes. Novel probes with a uni-dimensional (1D) galvanometer-based scanner (GS) developed in our groups are presented. Their advantages and limitations are discussed. Aspects regarding the use of galvoscanners with regard to Micro-Electro- Mechanical Systems (MEMS) are pointed out, in relationship with our studies on optimal scanning functions of galvanometer devices in OCT. These scanning functions are briefly discussed with regard to their main parameters: profile, theoretical duty cycle, scan frequency, and scan amplitude. The optical design of the galvoscanner and refractive optics combination in the probe head, optimized for various applications, is considered. Perspectives of the field are pointed out in the final part of the paper.

  10. Gold-coated conducting-atomic force microscopy probes.

    Science.gov (United States)

    John, Neena Susan; Kulkarni, G U

    2005-04-01

    Some aspects of the performance of gold-coated conductive probes used in conducting atomic force microscopy (C-AFM) technique are discussed. The resistance of the nanocontact between the gold-coated AFM tip and the graphite substrate has been monitored at various applied forces. For small forces (forces in the range 100-150 nN, beyond which the tip seems to undergo plastic deformation. The resistance of the nanocontact increased when current on the order of 100 microA was allowed to pass through, finally resulting in melting of the gold coating.

  11. Probing an atomic gas confined in a nanocell

    Energy Technology Data Exchange (ETDEWEB)

    Maurin, I; Todorov, P; Hamdi, I; Yarovitski, A; Dutier, G; Sarkisyan, D; Saltiel, S; Gorza, M-P; Fichet, M; Bloch, D; Ducloy, M [Laboratoire de Physique des Lasers, UMR 7538 du CNRS et de l' Universite Paris 13, 99 Av JB Clement, F-93430 Villetaneuse (France)

    2005-01-01

    Since the recent realization of extremely thin vapour cells (local thickness: 20-1000 nm), we investigate the optical properties of these 1-D confined vapours. Aside from their interest for Doppler-free spectroscopy, nanocells offer a new tool to evaluate collisional shift and broadening, yielding an access to the open problem of collisions under confinement. It also allows probing of the atom-surface interaction in a range of unusual short distances. The experimental exploration of the distance dependence, normally evolving according to the z{sup -3} van der Waals (vW) dependence (z : the atom-surface distance), is worth doing because it could be affected by imperfections of the real surface, such as roughness, adsorbed impurities or charges. A detailed lineshape analysis is now under progress, with tight constraints imposed to the fitting by the twin information brought by simultaneous reflection and transmission spectra. Another issue is a possible resonant enhancement, susceptible to induce a repulsive vW, due to the coupling between atom excitation and a surface mode.

  12. The effect orientation of features in reconstructed atom probe data on the resolution and measured composition of T1 plates in an A2198 aluminium alloy.

    Science.gov (United States)

    Mullin, Maria A; Araullo-Peters, Vicente J; Gault, Baptiste; Cairney, Julie M

    2015-12-01

    Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Mapping energetics of atom probe evaporation events through first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Peralta, Joaquín, E-mail: jperaltac@gmail.com [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, 2220 Hoover Hall, Iowa State University, Ames, IA 50011-2230 (United States); Broderick, Scott R., E-mail: sbroderick@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, 2220 Hoover Hall, Iowa State University, Ames, IA 50011-2230 (United States); Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, 2220 Hoover Hall, Iowa State University, Ames, IA 50011-2230 (United States)

    2013-09-15

    The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al–Al and Al–Sc dimers from an L1{sub 2}-Al{sub 3}Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al–Al dimer, Al ion, Sc ion, and Al–Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1{sub 2}-Al{sub 3}Sc, we extract relative evaporation fields and identify that an Al–Al dimer has a lower evaporation field than an Al–Sc dimer. Additionally, comparatively an Al–Al surface dimer is more likely to evaporate as a dimer, while an Al–Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics. - Highlights: ► Calculated evaporation field of monomer and dimer atom probe evaporations. ► Determined relative evaporation fields using ion evaporation maps. ► Compared the experimental and calculated results and found that they agreed.

  14. A Filtering Method to Reveal Crystalline Patterns from Atom Probe Microscopy Desorption Maps

    Science.gov (United States)

    2016-03-26

    reveal crystalline patterns from atom probe microscopy desorption maps Lan Yao Department of Materials Science and Engineering, University of Michigan, Ann...reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. Themethod filters atoms based on the time difference...between their evaporation and the evaporation of the previous atom . Since this time difference correlates with the location and the local structure of

  15. Probing atomic Higgs-like forces at the precision frontier

    Science.gov (United States)

    Delaunay, Cédric; Ozeri, Roee; Perez, Gilad; Soreq, Yotam

    2017-11-01

    We propose a novel approach to probe new fundamental interactions using isotope shift spectroscopy in atomic clock transitions. As a concrete toy example we focus on the Higgs boson couplings to the building blocks of matter: the electron and the up and down quarks. We show that the attractive Higgs force between nuclei and their bound electrons, which is poorly constrained, might induce effects that are larger than the current experimental sensitivities. More generically, we discuss how new interactions between the electron and the neutrons, mediated via light new degrees of freedom, may lead to measurable nonlinearities in a King plot comparison between isotope shifts of two different transitions. Given state-of-the-art accuracy in frequency comparison, isotope shifts have the potential to be measured with sub-Hz accuracy, thus potentially enabling the improvement of current limits on new fundamental interactions. A candidate atomic system for this measurement requires two different clock transitions and four zero nuclear spin isotopes. We identify several systems that satisfy this requirement and also briefly discuss existing measurements. We consider the size of the effect related to the Higgs force and the requirements for it to produce an observable signal.

  16. Time-of-flight atom probe measurements on Ni3Al and Co3W

    NARCIS (Netherlands)

    Soer, W.A.; Bronsveld, P.M.; Hosson, J.Th.M. De

    2003-01-01

    In this study, a VG FIM100 was taken into operation, consisting of a field-ion microscope (FIM), a time-of-flight atom probe (TOFAP) and an imaging atom probe. A tungsten specimen was used to calibrate the conversion of flight times to m/n values. The resulting relative mass resolution of the TOFAP

  17. Dynamics of trapped atoms around an optical nanofiber probed through polarimetry.

    Science.gov (United States)

    Solano, Pablo; Fatemi, Fredrik K; Orozco, Luis A; Rolston, S L

    2017-06-15

    The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies.

  18. Dynamics of trapped atoms around an optical nanofiber probed through polarimetry

    Science.gov (United States)

    Solano, Pablo; Fatemi, Fredrik K.; Orozco, Luis A.; Rolston, S. L.

    2017-06-01

    The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies.

  19. Probe Knots and Hopf Insulators with Ultracold Atoms

    Science.gov (United States)

    Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, L.-M.

    2018-01-01

    Knots and links are fascinating and intricate topological objects. Their influence spans from DNA and molecular chemistry to vortices in superfluid helium, defects in liquid crystals and cosmic strings in the early universe. Here we find that knotted structures also exist in a peculiar class of three-dimensional topological insulators—the Hopf insulators. In particular, we demonstrate that the momentum-space spin textures of Hopf insulators are twisted in a nontrivial way, which implies the presence of various knot and link structures. We further illustrate that the knots and nontrivial spin textures can be probed via standard time-of-flight images in cold atoms as preimage contours of spin orientations in stereographic coordinates. The extracted Hopf invariants, knots, and links are validated to be robust to typical experimental imperfections. Our work establishes the existence of knotted structures in Hopf insulators, which may have potential applications in spintronics and quantum information processing. D.L.D., S.T.W. and L.M.D. are supported by the ARL, the IARPA LogiQ program, and the AFOSR MURI program, and supported by Tsinghua University for their visits. K.S. acknowledges the support from NSF under Grant No. PHY1402971. D.L.D. is also supported by JQI-NSF-PFC and LPS-MPO-CMTC at the final stage of this paper.

  20. Conductive-probe atomic force microscopy characterization of silicon nanowire

    Directory of Open Access Journals (Sweden)

    Yu Linwei

    2011-01-01

    Full Text Available Abstract The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs were investigated using a conductive-probe atomic force microscopy (AFM. Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V. Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.

  1. Sodium distribution in solar-grade Cu2ZnSnS4 layers using atom-probe tomographic technique

    Science.gov (United States)

    Tajima, Shin; Asahi, Ryoji; Isheim, Dieter; Seidman, David N.; Itoh, Tadayoshi; Ohishi, Kei-ichiro

    2015-11-01

    To investigate the effect of alkali doping on Cu2ZnSnS4 (CZTS) photovoltaic cells, we studied compositional distributions in CZTS layers using three-dimensional atom-probe tomography. The segregation of Na at a concentration of approximately 1 at. % was observed predominantly at CZTS grain boundaries. The concentration of Na in the interior of the CZTS grains was below the detection limit (approximately 40 ppm). Na ions may exist as sulfide compounds at CZTS grain boundaries, independent of the presence of oxygen.

  2. Novel dual-probes atomic force microscope for line width measurements

    Science.gov (United States)

    Wang, Hequn; Gao, Sitian; Li, Wei; Shi, Yushu; Li, Qi; Li, Shi

    2017-11-01

    Dual-probe Atomic Force Microscope (AFM) can effectively eliminate the influence of the probe size on measurement of the line width, and realize true three-dimensional measurement. Novel dual-probe AFM consists of probe system, scanning system, alignment system and displacement measurement system. As displacement measurement system, the interferometers are added to the novel dual-probes AFM. In order to simplify the dual-probe AFM structure, self-sensing tuning fork probe is used. Measurement method has two steps: the first step is to align two probes and obtain the reference point; the second step is to scan two sides of measured line by two probes separately, and calculate the line width value according to the reference point. In the alignment of two probes, the alignment method is improved by using the edge alignment and the feedback scanning alignment.

  3. Atom probe field ion microscopy and related topics: A bibliography 1991

    Energy Technology Data Exchange (ETDEWEB)

    Russell, K.F.; Miller, M.K.

    1993-01-01

    This report contains a bibliography for 1991 on the following topics: Atom probe field ion microscopy; field desorption mass spectrometry; field emission; field ion microscopy; and field emission theory.

  4. Atomic quantum superposition state generation via optical probing

    DEFF Research Database (Denmark)

    Nielsen, Anne Ersbak Bang; Poulsen, Uffe Vestergaard; Negretti, Antonio

    2009-01-01

    We analyze the performance of a protocol to prepare an atomic ensemble in a superposition of two macroscopically distinguishable states. The protocol relies on conditional measurements performed on a light field, which interacts with the atoms inside an optical cavity prior to detection, and we...

  5. Gain and Absorption of a Probe Light in an Open Tripod Atomic System

    Science.gov (United States)

    Hu, Zheng-Feng; Lin, Jin-Da; Deng, Jian-Liao; He, Hui-Juan; Wang, Yu-Zhu

    2012-05-01

    We theoretically investigate an open four-level atomic system interacting with control, probe and microwave fields. When there is no repumping light and a microwave field is applied, the probe light can be absorbed or amplified, which has different features than those of a system whose populations are pumped into only one ground state. In this system the microwave field and the population distributions of the ground states can be used as switches to control the propagation of the probe light.

  6. Fast-ion-beam laser probing of ion-source energy distributions and atomic structure

    Energy Technology Data Exchange (ETDEWEB)

    Holt, Richard A., E-mail: rholt@uwo.ca; Rosner, S. David [University of Western Ontario, Physics and Astronomy Department (Canada)

    2013-04-15

    Collinear fast-ion-beam laser spectroscopy is a very high resolution probe for measuring ion-beam energy distributions and atomic structure parameters of interest in nuclear physics, atomic physics, and astrophysics. We have used offline 10-keV beams of atomic ions and a CW laser system to study the behavior of a Penning ion source and to measure hyperfine structure, isotope shifts, atomic lifetimes, spontaneous-emission branching fractions, oscillator strengths, and absolute wavelengths of a variety of atomic species from the lanthanide and transition-metal groups.

  7. Understanding the Atomic-Scale Contrast in Kelvin Probe Force Microscopy

    OpenAIRE

    Nony, Laurent; Foster, Adam; Bocquet, Franck; Loppacher, Christian

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a noncontact atomic force microscope simulator including a Kelvin module. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and contact potential difference contrasts were reported. The local...

  8. Double common-path interferometer for flexible optical probe of optical coherence tomography

    OpenAIRE

    Park, Jae Seok; Chen, Zhongping; Jeong, Myung Yung; Kim, Chang-Seok

    2012-01-01

    A flexible curled optical cord is useful for a common-path optical coherence tomography (OCT) system because a bending-insensitive arbitrary length can be chosen for the endoscopic imaging probe. However, there has been a critical problem that the partial reflector needs to be placed in between the sample and the objective lens. It limits the structure design of optical probe and leads to a low transverse resolution OCT imaging. Instead of a conventional single common-path interferometer, we ...

  9. Restoring the lattice of Si-based atom probe reconstructions for enhanced information on dopant positioning.

    Science.gov (United States)

    Breen, Andrew J; Moody, Michael P; Ceguerra, Anna V; Gault, Baptiste; Araullo-Peters, Vicente J; Ringer, Simon P

    2015-12-01

    The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Amyloid-β positron emission tomography imaging probes

    DEFF Research Database (Denmark)

    Kepe, Vladimir; Moghbel, Mateen C; Långström, Bengt

    2013-01-01

    The rapidly rising prevalence and cost of Alzheimer's disease in recent decades has made the imaging of amyloid-β deposits the focus of intense research. Several amyloid imaging probes with purported specificity for amyloid-β plaques are currently at various stages of FDA approval. However...

  11. Atomic Resolution Imaging with a sub-50 pm Electron Probe

    Energy Technology Data Exchange (ETDEWEB)

    Erni, Rolf P.; Rossell, Marta D.; Kisielowski, Christian; Dahmen, Ulrich

    2009-03-02

    Using a highly coherent focused electron probe in a 5th order aberration-corrected transmission electron microscope, we report on resolving a crystal spacing less than 50 pm. Based on the geometrical source size and residual coherent and incoherent axial lens aberrations, an electron probe is calculated, which is theoretically capable of resolving an ideal 47 pm spacing with 29percent contrast. Our experimental data show the 47 pm spacing of a Ge 114 crystal imaged with 11-18percent contrast at a 60-95percent confidence level, providing the first direct evidence for sub 50-pm resolution in ADF STEM imaging.

  12. Toward quantum state tomography of a single polariton state of an atomic ensemble

    DEFF Research Database (Denmark)

    Christensen, S.L.; Béguin, J.B.; Sørensen, H.L.

    2013-01-01

    We present a proposal and a feasibility study for the creation and quantum state tomography of a single polariton state of an atomic ensemble. The collective non-classical and non-Gaussian state of the ensemble is generated by detection of a single forward-scattered photon. The state is subsequen...... the feasibility of the proposed method for the detection of a non-classical and non-Gaussian state of the mesoscopic atomic ensemble. This work represents the first attempt at hybrid discrete-continuous variable quantum state processing with atomic memories....... is subsequently characterized by atomic state tomography performed using strong dispersive light-atom interaction followed by a homodyne measurement on the transmitted light. The proposal is backed by preliminary experimental results showing projection noise limited sensitivity and a simulation demonstrating...

  13. Two-probe atomic-force microscope manipulator and its applications.

    Science.gov (United States)

    Zhukov, A A; Stolyarov, V S; Kononenko, O V

    2017-06-01

    We report on a manipulator based on a two-probe atomic force microscope (AFM) with an individual feedback system for each probe. This manipulator works under an upright optical microscope with 3 mm focal distance. The design of the microscope helps us tomanipulate nanowires using the microscope probes as a two-prong fork. The AFM feedback is realized based on the dynamic full-time contact mode. The applications of the manipulator and advantages of its two-probe design are presented.

  14. A computational geometry framework for the optimisation of atom probe reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, Peter [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Institute for General Materials Properties, Department of Materials Science, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen (Germany); Cairney, Julie [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2016-10-15

    In this paper, we present pathways for improving the reconstruction of atom probe data on a coarse (>10 nm) scale, based on computational geometry. We introduce a way to iteratively improve an atom probe reconstruction by adjusting it, so that certain known shape criteria are fulfilled. This is achieved by creating an implicit approximation of the reconstruction through a barycentric coordinate transform. We demonstrate the application of these techniques to the compensation of trajectory aberrations and the iterative improvement of the reconstruction of a dataset containing a grain boundary. We also present a method for obtaining a hull of the dataset in both detector and reconstruction space. This maximises data utilisation, and can be used to compensate for ion trajectory aberrations caused by residual fields in the ion flight path through a ‘master curve’ and correct for overall shape deviations in the data. - Highlights: • An atom probe reconstruction can be iteratively improved by using shape constraints. • An atom probe reconstruction can be inverted using barycentric coordinate transforms. • Hulls for atom probe datasets can be obtained from 2D detector outlines that are co-reconstructed with the data. • Ion trajectory compressions caused by instrument-specific residual fields in the drift tube can be corrected.

  15. Control of the millisecond spin lifetime of an electrically probed atom

    Science.gov (United States)

    Paul, William; Yang, Kai; Baumann, Susanne; Romming, Niklas; Choi, Taeyoung; Lutz, Christopher P.; Heinrich, Andreas J.

    2017-04-01

    Electrical control and readout of magnetic states is an important goal in spintronics. But electrical access to quantum spin systems comes at the cost of coupling to electrodes, which reduces the spin lifetimes through relaxation to electron-hole pairs. Here we report an electrically probed single-atom spin that is long-lived thanks to engineering the coupling of individual iron atoms to the nearby metallic electrodes. Using spin-polarized scanning tunnelling microscopy, we show that the excited spin state of these atoms persists for more than ten milliseconds. The lifetime can be tuned by varying the distance to the microscope probe tip--acting as one electrode--and by changing the thickness of the insulating film which separates the atom from the underlying electrode. The cross-section for spin-flip scattering is so small that many thousands of electrons can probe the spin state projectively before it relaxes. Using all-electrical pump-probe spectroscopy, we measure the lifetime of the atom for different tip-atom distances and determine the intrinsic lifetime as a function of the insulator thickness. We explain the tuning of the spin lifetime in terms of the conductance to each of the electrodes, which provides a method to maximize the electrical readout signal for a given lifetime.

  16. Advances in tomography: probing the molecular architecture of cells.

    Science.gov (United States)

    Fridman, Karen; Mader, Asaf; Zwerger, Monika; Elia, Natalie; Medalia, Ohad

    2012-11-01

    Visualizing the dynamic molecular architecture of cells is instrumental for answering fundamental questions in cellular and structural biology. Although modern microscopy techniques, including fluorescence and conventional electron microscopy, have allowed us to gain insights into the molecular organization of cells, they are limited in their ability to visualize multicomponent complexes in their native environment. Cryo-electron tomography (cryo-ET) allows cells, and the macromolecular assemblies contained within, to be reconstructed in situ, at a resolution of 2-6 nm. By combining cryo-ET with super-resolution fluorescence microscopy approaches, it should be possible to localize proteins with high precision inside cells and so elucidate a more realistic view of cellular processes. Thus, cryo-ET may bridge the resolution gap between cellular and structural biology.

  17. Atomic-scale investigations of grain boundary segregation in astrology with a three dimensional atom-probe

    Energy Technology Data Exchange (ETDEWEB)

    Blavette, D. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut Universitaire de France (France); Letellier, L. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Duval, P. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Guttmann, M. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut de Recherches de la Siderurgie Francaise (IRSID), 57 - Maizieres-les-Metz (France)

    1996-08-01

    Both conventional and 3D atom-probes were applied to the investigation of grain-boundary (GB) segregation phenomena in two-phase nickel base superalloys Astroloy. 3D images as provided by the tomographic atom-probe reveal the presence of a strong segregation of both boron and molybdenum at grain-boundaries. Slight carbon enrichment is also detected. Considerable chromium segregation is exhibited at {gamma}`-{gamma}` grain-boundaries. All these segregants are distributed in a continuous manner along the boundary over a width close to 0.5 nm. Experiments show that segregation occurs during cooling and more probably between 1000 C and 800 C. Boron and molybdenum GB enrichments are interpreted as due to an equilibrium type-segregation while chromium segregation is thought to be induced by {gamma}` precipitation at GB`s and stabilised by the presence of boron. No segregation of zirconium is detected. (orig.)

  18. Design and testing of prototype handheld scanning probes for optical coherence tomography.

    Science.gov (United States)

    Demian, Dorin; Duma, Virgil-Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-08-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic-for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat-in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated. © IMechE 2014.

  19. Single molecule probing of SNARE proteins by Atomic Force Microscopy

    Science.gov (United States)

    Liu, Wei; Parpura, Vladimir

    2009-01-01

    Atomic Force Microscopy (AFM) in force spectroscopy mode has recently emerged as a technique of choice for studying mechanical interactions between the proteins of the core Soluble N-ethylmalmeimide-sensitive fusion protein Attachment protein REceptor (SNARE) complex. In these experiments, the rupture force, extension, spontaneous dissociation times and interaction energy for SNARE protein-protein interactions can be obtained at the single molecule level. These measurements, which are complementary to results and conclusions drawn from other techniques, improve our understanding of the role of the SNARE complex in exocytosis. PMID:19161382

  20. Design of functionalized gold nanoparticle probes for computed tomography imaging.

    Science.gov (United States)

    Silvestri, Alessandro; Zambelli, Vanessa; Ferretti, Anna M; Salerno, Domenico; Bellani, Giacomo; Polito, Laura

    2016-09-01

    The development of new molecules able to efficiently act as long-circulating computed tomography (CT) contrast agents is one of the most crucial topics in the biomedical field. In the last years, the chance to manipulate materials at the nano-size level gave new boost to this research, with the specific aim to design innovative nanoprobes. Gold nanoparticles (AuNPs) have showed unique X-rays attenuation properties which, combined with their easy surface functionalization, makes them ideal candidates for the next generation of contrast agents. In this paper, we present a rational and facile approach to synthesize engineered and water-stable AuNPs, achieving concentrated colloidal solution with high Hounsfield Units (HU). An accurate control of reagents ratio allowed us to design AuNPs with different shapes, from symmetrical to anisotropic morphology, in a convenient 'one-pot' fashion. Their activity as efficient and reliable CT contrast agents has been evaluated and compared. Moreover, glucosamine-functionalized gold nanoparticles have been developed ([Au] = 31.20 mg/mL; HU = 2453), in order to obtain a CT contrast agent able to combine spatial resolution with metabolic information. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  1. Neurosurgical hand-held optical coherence tomography (OCT) forward-viewing probe

    Science.gov (United States)

    Sun, Cuiru; Lee, Kenneth K. C.; Vuong, Barry; Cusimano, Michael; Brukson, Alexander; Mariampillai, Adrian; Standish, Beau A.; Yang, Victor X. D.

    2012-02-01

    A prototype neurosurgical hand-held optical coherence tomography (OCT) imaging probe has been developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic hand-held probe has been designed based on our group's previous work on electrostatically driven optical fibers. It has been packaged into a catheter probe in the familiar form factor of the clinically accepted Bayonet shaped neurosurgical non-imaging Doppler ultrasound probes. The optical design was optimized using ZEMAX simulation. Optical properties of the probe were tested to yield an ~20 um spot size, 5 mm working distance and a 3.5 mm field of view. The scan frequency can be increased or decreased by changing the applied voltage. Typically a scan frequency of less than 60Hz is chosen to keep the applied voltage to less than 2000V. The axial resolution of the probe was ~15 um (in air) as determined by the OCT system. A custom-triggering methodology has been developed to provide continuous stable imaging, which is crucial for clinical utility. Feasibility of this probe, in combination with a 1310 nm swept source OCT system was tested and images are presented to highlight the usefulness of such a forward viewing handheld OCT imaging probe. Knowledge gained from this research will lay the foundation for developing new OCT technologies for endovascular management of cerebral aneurysms and transsphenoidal neuroendoscopic treatment of pituitary tumors.

  2. Note: Production of stable colloidal probes for high-temperature atomic force microscopy applications.

    Science.gov (United States)

    Ditscherlein, L; Peuker, U A

    2017-04-01

    For the application of colloidal probe atomic force microscopy at high temperatures (>500 K), stable colloidal probe cantilevers are essential. In this study, two new methods for gluing alumina particles onto temperature stable cantilevers are presented and compared with an existing method for borosilicate particles at elevated temperatures as well as with cp-cantilevers prepared with epoxy resin at room temperature. The durability of the fixing of the particle is quantified with a test method applying high shear forces. The force is calculated with a mechanical model considering both the bending as well as the torsion on the colloidal probe.

  3. Adhesive properties of Staphylococcus epidermidis probed by atomic force microscopy

    DEFF Research Database (Denmark)

    Hu, Yifan; Ulstrup, Jens; Zhang, Jingdong

    2011-01-01

    Mapping of the surface properties of Staphylococcus epidermidis and of biofilm forming bacteria in general is a key to understand their functions, particularly their adhesive properties. To gain a comprehensive view of the structural and chemical properties of S. epidermidis, four different strains...... (biofilm positive and biofilm negative strains) were analyzed using in situ atomic force microscopy (AFM). Force measurements performed using bare hydrophilic silicon nitride tips disclosed similar adhesive properties for each strain. However, use of hydrophobic tips showed that hydrophobic forces...... are not the driving forces for adhesion of the four strains. Rather, the observation of sawtooth force–distance patterns on the surface of biofilm positive strains documents the presence of modular proteins such as Aap that may mediate cell adhesion. Treatment of two biofilm positive strains with two chemical...

  4. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Science.gov (United States)

    Cai, Jiandong; Wang, Michael Yu; Zhang, Li

    2015-12-01

    In multifrequency atomic force microscopy (AFM), probe's characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude's sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  5. Probing atomic structure and Majorana wavefunctions in mono-atomic Fe chains on superconducting Pb surface

    Science.gov (United States)

    Pawlak, Rémy; Kisiel, Marcin; Klinovaja, Jelena; Meier, Tobias; Kawai, Shigeki; Glatzel, Thilo; Loss, Daniel; Meyer, Ernst

    2016-11-01

    Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localisation of MBSs is a key feature and is crucial for their future implementation as qubits. Here we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunnelling microscopy and atomic force microscopy. We demonstrate that the Fe chains are mono-atomic, structured in a linear manner and exhibit zero-bias conductance peaks at their ends, which we interpret as signature for a MBS. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localised at the chain ends (≲25 nm), with two localisation lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum-computing devices.

  6. Adaptive optical probe design for optical coherence tomography and microscopy using tunable optics.

    Science.gov (United States)

    Choi, Minseog; Lee, Seungwan; Chang, Jong-Hyeon; Lee, Eunsung; Jung, Kyu-Dong; Kim, Woonbae

    2013-01-28

    We present a tunable, adaptive optical imaging probe for multimodal imaging such as optical coherence tomography and microscopy. The probe is compatible with forward-looking scanning laser imaging devices such as an endoscope. The lens configuration includes a tunable iris and two varifocal lenses, both driven by microelectrofluidics, as well as several conventional fixed focus lenses. The modulation transfer function and spot size in the focal plane is evaluated, and we show using optical simulations that there are three possible imaging modes with different transverse resolutions and focal depths.

  7. Probing electronic state at atomic scale on the surface of SrVO3 film

    Science.gov (United States)

    Okada, Yoshinori; Shimizu, Ryota; Shiraki, Susumu; Hitosugi, Taro

    2014-03-01

    Probing electronic structure of atomically well controlled surface of Perovskite-type 3d transition-metal oxides have been attracting much interest because of their intriguing emergent physical properties by heterostructure engineering. In this study, we have especially focused on SrVO3, where importance of correlation effects has been considered. We successfully obtained atomically flat surfaces of SrVO3, which gave us the great opportunity to visualize correlated electronic state at atomic scale by means of spectroscopic imaging scanning tunneling spectroscopy. Based on the experimental data, we discuss spectroscopic signature of many body effects on the surface of SrVO3 system.

  8. Probe for an atomic force microscope and method for making such a probe

    NARCIS (Netherlands)

    van den Bos, A.G.; Abelmann, Leon; Lodder, J.C.

    2005-01-01

    De uitvinding heeft betrekking op een probe voor een magnetische kracht-microscoop, omvattende een in een wafervlak geplaatste beweegbare cantilever en een in hoofdzaak loodrecht op de cantilever geplaatste tip, waarbij de cantilever beweegbaar is en een trillingsrichting heeft in het wafervlak, en

  9. Probing the conformal Calabrese-Cardy scaling with cold atoms

    CERN Document Server

    Unmuth-Yockey, J; Preiss, P M; Yang, Li-Ping; Tsai, S -W; Meurice, Y

    2016-01-01

    We demonstrate that current experiments using cold bosonic atoms trapped in one-dimensional optical lattices and designed to measure the second-order Renyi entanglement entropy S_2, can be used to verify detailed predictions of conformal field theory (CFT) and estimate the central charge c. We discuss the adiabatic preparation of the ground state at half-filling where we expect a CFT with c=1. This can be accomplished with a very small hoping parameter J, in contrast to existing studies with density one where a much larger J is needed. We provide two complementary methods to estimate and subtract the classical entropy generated by the experimental preparation and imaging processes. We compare numerical calculations for the classical O(2) model with a chemical potential on a 1+1 dimensional lattice, and the quantum Bose-Hubbard Hamiltonian implemented in the experiments. S_2 is very similar for the two models and follows closely the Calabrese-Cardy scaling, (c/8)\\ln(N_s), for N_s sites with open boundary condi...

  10. Probing Single Membrane Proteins by Atomic Force Microscopy

    Science.gov (United States)

    Scheuring, S.; Sapra, K. Tanuj; Müller, Daniel J.

    In this book chapter, we describe the working principle of the atomic force microscope (AFM), followed by the applications of AFM in high-resolution imaging and single-molecule force spectroscopy of membrane proteins. In the imaging mode, AFM allows observing the assembly of membrane proteins directly in native membranes approaching a resolution of ~0.5 nm with an outstanding signal-to-noise ratio. Conformational deviations of individual membrane proteins can be observed and their functional states directly imaged. Time-lapse AFM can image membrane proteins at work. In conjunction with high- resolution imaging, the use of the AFM as a single-molecule force spectroscope (SMFS) has gained tremendous importance in recent years. This combination allows to locate the inter- and intramolecular interactions of single membrane proteins. SMFS allows characterization of interactions that guide the folding of proteins and describe the parameters that lead to their destabilization, malfunction and misfolding. Moreover, it enables to measure the interactions established by ligand- and inhibitor-binding and in membrane protein assemblies. Because of its practical use in characterizing various parameters of membrane proteins in their native environment, AFM can be aptly described as a `lab on a tip' device.

  11. Handheld scanning probes for optical coherence tomography: developments, applications, and perspectives

    Science.gov (United States)

    Duma, V.-F.; Demian, D.; Sinescu, C.; Cernat, R.; Dobre, G.; Negrutiu, M. L.; Topala, F. I.; Hutiu, Gh.; Bradu, A.; Podoleanu, A. G.

    2016-03-01

    We present the handheld scanning probes that we have recently developed in our current project for biomedical imaging in general and for Optical Coherence Tomography (OCT) in particular. OCT is an established, but dynamic imagistic technique based on laser interferometry, which offers micrometer resolutions and millimeters penetration depths. With regard to existing devices, the newly developed handheld probes are simple, light and relatively low cost. Their design is described in detail to allow for the reproduction in any lab, including for educational purposes. Two probes are constructed almost entirely from off-the-shelf components, while a third, final variant is constructed with dedicated components, in an ergonomic design. The handheld probes have uni-dimensional (1D) galvanometer scanners therefore they achieve transversal sections through the biological sample investigated - in contrast to handheld probes equipped with bi-dimensional (2D) scanners that can also achieve volumetric (3D) reconstructions of the samples. These latter handheld probes are therefore also discussed, as well as the possibility to equip them with galvanometer 2D scanners or with Risley prisms. For galvanometer scanners the optimal scanning functions studied in a series of previous works are pointed out; these functions offer a higher temporal efficiency/duty cycle of the scanning process, as well as artifact-free OCT images. The testing of the handheld scanning probes in dental applications is presented, for metal ceramic prosthesis and for teeth.

  12. Noncontact atomic force microscopy in liquid environment with quartz tuning fork and carbon nanotube probe

    DEFF Research Database (Denmark)

    Kageshima, M.; Jensenius, Henriette; Dienwiebel, M.

    2002-01-01

    A force sensor for noncontact atomic force microscopy in liquid environment was developed by combining a multiwalled carbon nanotube (MWNT) probe with a quartz tuning fork. Solvation shells of octamethylcyclotetrasiloxane surface were detected both in the frequency shift and dissipation. Due...

  13. Probing parity nonconservation effects with laser cooled and trapped francium atoms

    Science.gov (United States)

    Kalita, Mukut; Aubin, Seth; Behr, John; Collister, Robert; Dehart, Austin; Gorelov, Alexandre; Garcia, Eduardo; Gwinner, Gerald; Kossin, Michael; Livermore, David; Orozco, Luis; Pearson, Matt; FrPNC Collaboration

    2016-09-01

    Measurements of parity nonconservation (PNC) effects in atomic systems test the Standard Model at low energies. We are developing an experiment to probe PNC effect in neutral francium atoms. Francium ions produced at the ISAC radioactive beam facility at TRIUMF are neutralized using a zirconium foil. The foil is momentarily heated and the released atoms are first trapped in a capture magneto optical trap (MOT). Then, the atoms are transported with about 50% efficiency to another MOT in a science chamber. In this chamber, in one experiment the 7S to 8S atomic transition will be probed using a laser beam, and in another experiment the ground state hyperfine transition will be probed using a microwave beam. In this talk I will report on recent developments towards the measurements. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This work is also supported by NSERC from Canada, the DOE and NSF from the USA and CONACYT from Mexico.

  14. Three-dimensional atomic models from a single projection using Z-contrast imaging: verification by electron tomography and opportunities.

    Science.gov (United States)

    De Backer, A; Jones, L; Lobato, I; Altantzis, T; Goris, B; Nellist, P D; Bals, S; Van Aert, S

    2017-06-29

    In order to fully exploit structure-property relations of nanomaterials, three-dimensional (3D) characterization at the atomic scale is often required. In recent years, the resolution of electron tomography has reached the atomic scale. However, such tomography typically requires several projection images demanding substantial electron dose. A newly developed alternative circumvents this by counting the number of atoms across a single projection. These atom counts can be used to create an initial atomic model with which an energy minimization can be applied to obtain a relaxed 3D reconstruction of the nanoparticle. Here, we compare, at the atomic scale, this single projection reconstruction approach with tomography and find an excellent agreement. This new approach allows for the characterization of beam-sensitive materials or where the acquisition of a tilt series is impossible. As an example, the utility is illustrated by the 3D atomic scale characterization of a nanodumbbell on an in situ heating holder of limited tilt range.

  15. X-ray phase computed tomography for nanoparticulated imaging probes and therapeutics: preliminary feasibility study

    Science.gov (United States)

    Tang, Xiangyang; Yang, Yi; Tang, Shaojie

    2011-03-01

    With the scientific progress in cancer biology, pharmacology and biomedical engineering, the nano-biotechnology based imaging probes and therapeutical agents (namely probes/agents) - a form of theranostics - are among the strategic solutions bearing the hope for the cure of cancer. The key feature distinguishing the nanoparticulated probes/agents from their conventional counterparts is their targeting capability. A large surface-to-volume ratio in nanoparticulated probes/agents enables the accommodation of multiple targeting, imaging and therapeutic components to cope with the intra- and inter-tumor heterogeneity. Most nanoparticulated probes/agents are synthesized with low atomic number materials and thus their x-ray attenuation are very similar to biological tissues. However, their microscopic structures are very different, which may result in significant differences in their refractive properties. Recently, the investigation in the x-ray grating-based differential phase contrast (DPC) CT has demonstrated its advantages in differentiating low-atomic materials over the conventional attenuation-based CT. We believe that a synergy of x-ray grating-based DPC CT and nanoparticulated imaging probes and therapeutic agents may play a significant role in extensive preclinical and clinical applications, or even become a modality for molecular imaging. Hence, we propose to image the refractive property of nanoparticulated imaging probes and therapeutical agents using x-ray grating-based DPC CT. In this work, we conduct a preliminary feasibility study with a focus to characterize the contrast-to-noise ratio (CNR) and contrast-detail behavior of the x-ray grating-based DPC CT. The obtained data may be instructive to the architecture design and performance optimization of the x-ray grating-based DPC CT for imaging biomarker-targeted imaging probes and therapeutic agents, and even informative to the translation of preclinical research in theranostics into clinical applications.

  16. Design and optimization of a miniaturized imaging probe for simultaneous endomicroscopy and optical coherence tomography

    Science.gov (United States)

    Kretschmer, Simon; Vilches, Sergio; Blattmann, Marc; Ataman, Caglar; Zappe, Hans

    2017-02-01

    A highly-integrated MEMS-based bimodal probe design with integrated piezoelectric fiber scanner for simul- taneous endomicroscopy and optical coherence tomography (OCT) is presented. The two modalities rely on spectrally-separated optical paths that run partially in parallel through a micro-optical bench system, which has dimensions of only 13 x 2 x 3mm3 (l x w x h). An integrated tubular piezoelectric fiber scanner is used to perform en face scanning required for three dimensional OCT measurements. This scanning engine has an outer diameter of 0.9mm and a length of 9mm, and features custom fabricated 10 μm thick polyimide flexible interconnect lines to address the four piezoelectric electrodes. As a platform combining a full-field and a scanning imaging modality, the developed probe design constitutes a blue print for a wide range of multi-modal endoscopic imaging probes.

  17. Specialized probes based on hydroxyapatite calcium for heart tissues research by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhukov, Mikhail, E-mail: cloudjyk@yandex.ru; Golubok, Alexander [St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University), Kronverkskii pr. 49, St. Petersburg, 197101 (Russian Federation); Institute for Analytical Instrumentation, Russian Academy of Sciences (RAS), Rizhskii pr. 26, St. Petersburg, 190103 (Russian Federation); Gulyaev, Nikolai [Military Medical Academy named after S.M. Kirov, Academic Lebedev str. 6, St. Petersburg, 194044 (Russian Federation)

    2016-06-17

    The new specialized AFM-probes with hydroxyapatite structures for atomic force microscopy of heart tissues calcification were created and studied. A process of probe fabrication is demonstrated. The adhesive forces between specialized hydroxyapatite probe and endothelium/subendothelial layers were investigated. It was found that the adhesion forces are significantly higher for the subendothelial layers. We consider that it is connected with the formation and localization of hydroxyapatite in the area of subendothelial layers of heart tissues. In addition, the roughness analysis and structure visualization of the endothelial surface of the heart tissue were carried out. The results show high efficiency of created specialized probes at study a calcinations process of the aortic heart tissues.

  18. Application of atomic force microscopy in morphological observation of antisense probe labeled with magnetism

    Science.gov (United States)

    Wen, Ming; Bai, Wei; Yang, Xueheng

    2008-01-01

    Purpose To explore the possibility of the c-erbB2 oncogene antisense probe labeled with superparamagnetic iron oxide (SPIO) nanoparticles as a target contrast agent for magnetic resonance (MR) imaging whose morphology was observed with atomic force microscopy (AFM), and its efficiency was examined by MR imaging. Methods The c-erbB2 oncogene antisense probe labeled with SPIO was synthesized by a chemical cross-linking approach. Its morphology was observed with AFM. Results The chemical constitution of c-erbB2 oncogene antisense probes can be observed with AFM. The molecular structure of probes is easily visualized under AFM. Probes with diameters of 25–40 nm are in order, follow uniformity and the arrangement rule, can be separated from each other, and appear as cubes with a rugged surface morphology. Strong, low signals of the probes in transfected cells were observed by MR cellular imaging. Conclusions AFM is ideal for morphological observation and for analyzing the molecular structure of synthesized c-erbB2 oncogene antisense probes. PMID:18253092

  19. Dynamics of hollow atom formation in intense x-ray pulses probed by partial covariance mapping.

    Science.gov (United States)

    Frasinski, L J; Zhaunerchyk, V; Mucke, M; Squibb, R J; Siano, M; Eland, J H D; Linusson, P; v d Meulen, P; Salén, P; Thomas, R D; Larsson, M; Foucar, L; Ullrich, J; Motomura, K; Mondal, S; Ueda, K; Osipov, T; Fang, L; Murphy, B F; Berrah, N; Bostedt, C; Bozek, J D; Schorb, S; Messerschmidt, M; Glownia, J M; Cryan, J P; Coffee, R N; Takahashi, O; Wada, S; Piancastelli, M N; Richter, R; Prince, K C; Feifel, R

    2013-08-16

    When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called "partial covariance mapping" to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

  20. Proposal for efficient two-dimensional atom localization using probe absorption in a microwave-driven four-level atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Ding Chunling; Li Jiahua; Yang Xiaoxue; Xiong Hao [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang Duo [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Mathematics and Physics, Wuhan Polytechnic University, Wuhan 430023 (China)

    2011-10-15

    The behavior of two-dimensional (2D) atom localization is explored by monitoring the probe absorption in a microwave-driven four-level atomic medium under the action of two orthogonal standing-wave fields. Because of the position-dependent atom-field interaction, the information about the position of the atom can be obtained via the absorption measurement of the weak probe field. It is found that the localization behavior is significantly improved due to the joint quantum interference induced by the standing-wave and microwave-driven fields. Most importantly, the atom can be localized at a particular position and the maximal probability of finding the atom in one period of the standing-wave fields reaches unity by properly adjusting the system parameters. The proposed scheme may provide a promising way to achieve high-precision and high-resolution 2D atom localization.

  1. Probing double Rydberg wave packets in a helium atom with fast single-cycle pulses

    Science.gov (United States)

    Wang, Xiao; Robicheaux, F.

    2017-10-01

    Fully quantum and classical calculations on a helium atom with two excited, radially localized Rydberg wave packets are performed. The differences between classical and quantum methods are compared for a wide range of principal quantum numbers to study the validity of the classical method for low-lying states. The effects of fast terahertz single-cycle pulses on an atomic system with one or two Rydberg wave packets are also studied using classical equations of motion. These results suggest that single-cycle pulses can be used as time-resolved probes to detect motion of the wave packets and to investigate autoionization properties.

  2. Atom probe microscopy of zinc isotopic enrichment in ZnO nanorods

    Directory of Open Access Journals (Sweden)

    C. N. Ironside

    2017-02-01

    Full Text Available We report on atomic probe microscopy (APM of isotopically enriched ZnO nanorods that measures the spatial distribution of zinc isotopes in sections of ZnO nanorods for natural abundance natZnO and 64Zn and 66Zn enriched ZnO nanorods. The results demonstrate that APM can accurately quantify isotopic abundances within these nanoscale structures. Therefore the atom probe microscope is a useful tool for characterizing Zn isotopic heterostructures in ZnO. Isotopic heterostructures have been proposed for controlling thermal conductivity and also, combined with neutron transmutation doping, they could be key to a novel technology for producing p-n junctions in ZnO thin films and nanorods.

  3. Train of high-power femtosecond pulses: Probe wave in a gas of prepared atoms

    Science.gov (United States)

    Muradyan, Gevorg; Muradyan, Atom Zh.

    2009-09-01

    We present a method for generating a regular train of ultrashort optical pulses in a prepared two-level medium. The train develops from incident monochromatic probe radiation traveling in a medium of atoms, which are in a quantum mechanical superposition of dressed internal states. In the frame of linear theory for the probe radiation, the energy of individual pulses is an exponentially growing function of atom density and of interaction cross section. Pulse repetition rate is determined by the pump field’s generalized Rabi frequency and can be around 1 THz and greater. We also show that the terms, extra to the dipole approximation, endow the gas by a new property: nonsaturating dependence of refractive index on dressing monochromatic field intensity. Contribution of these nonsaturating terms can be compatible with the main dipole approximation term contribution in the wavelength region of about ten micrometers (the range of CO2 laser) or larger.

  4. 'Big Bang' tomography as a new route to atomic-resolution electron tomography.

    Science.gov (United States)

    Van Dyck, Dirk; Jinschek, Joerg R; Chen, Fu-Rong

    2012-06-13

    Until now it has not been possible to image at atomic resolution using classical electron tomographic methods, except when the target is a perfectly crystalline nano-object imaged along a few zone axes. The main reasons are that mechanical tilting in an electron microscope with sub-ångström precision over a very large angular range is difficult, that many real-life objects such as dielectric layers in microelectronic devices impose geometrical constraints and that many radiation-sensitive objects such as proteins limit the total electron dose. Hence, there is a need for a new tomographic scheme that is able to deduce three-dimensional information from only one or a few projections. Here we present an electron tomographic method that can be used to determine, from only one viewing direction and with sub-ångström precision, both the position of individual atoms in the plane of observation and their vertical position. The concept is based on the fact that an experimentally reconstructed exit wave consists of the superposition of the spherical waves that have been scattered by the individual atoms of the object. Furthermore, the phase of a Fourier component of a spherical wave increases with the distance of propagation at a known 'phase speed'. If we assume that an atom is a point-like object, the relationship between the phase and the phase speed of each Fourier component is linear, and the distance between the atom and the plane of observation can therefore be determined by linear fitting. This picture has similarities with Big Bang cosmology, in which the Universe expands from a point-like origin such that the distance of any galaxy from the origin is linearly proportional to the speed at which it moves away from the origin (Hubble expansion). The proof of concept of the method has been demonstrated experimentally for graphene with a two-layer structure and it will work optimally for similar layered materials, such as boron nitride and molybdenum disulphide.

  5. Atom probe field ion microscopy and related topics: A bibliography 1989

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.; Hawkins, A.R.; Russell, K.F.

    1990-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion spectroscopy (FIM), field emission microscopy (FEM), liquid metal ion sources (LMIS), scanning tunneling microscopy (STM), and theory. Technique-orientated studies and applications are included. This bibliography covers the period 1989. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications.

  6. Atom probe field-ion microscopy and related topics: A bibliography, 1988

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.; Hawkins, A.R.

    1989-10-01

    This bibliography includes references related to the following topics: field-ion microscopy (FIM), field emission microscopy (FEM), atom probe field-ion microscopy (APFIM), and liquid metal ion sources (LMIS). Technique-orientated studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles.

  7. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O., E-mail: o.dmitrieva@mpie.de [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Choi, P., E-mail: p.choi@mpie.de [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Gerstl, S.S.A. [Imago Scientific Instruments, Madison, WI 53711 (United States); Ponge, D.; Raabe, D. [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-05-15

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. -- Research highlights: {yields} Changing the laser pulse energy in pulsed-laser atom probe could induce some changes in the analysis results of complex steels. {yields} Decreases in the evaporation fields and the ++/+ charge state ratios were detected with raising laser energy. {yields} Chemical composition of the intermetallic precipitates and the interface sharpness were not influenced by changing the laser energy.

  8. Polarisation response of delay dependent absorption modulation in strong field dressed helium atoms probed near threshold

    Science.gov (United States)

    Simpson, E. R.; Sanchez-Gonzalez, A.; Austin, D. R.; Diveki, Z.; Hutchinson, S. E. E.; Siegel, T.; Ruberti, M.; Averbukh, V.; Miseikis, L.; Strüber, C. S.; Chipperfield, L.; Marangos, J. P.

    2016-08-01

    We present the first measurement of the vectorial response of strongly dressed helium atoms probed by an attosecond pulse train (APT) polarised either parallel or perpendicular to the dressing field polarisation. The transient absorption is probed as a function of delay between the APT and the linearly polarised 800 nm field of peak intensity 1.3× {10}14 {{W}} {{cm}}-2. The APT spans the photon energy range 16-42 eV, covering the first ionisation energy of helium (24.59 eV). With parallel polarised dressing and probing fields, we observe modulations with periods of one half and one quarter of the dressing field period. When the polarisation of the dressing field is altered from parallel to perpendicular with respect to the APT polarisation we observe a large suppression in the modulation depth of the above ionisation threshold absorption. In addition to this we present the intensity dependence of the harmonic modulation depth as a function of delay between the dressing and probe fields, with dressing field peak intensities ranging from 2 × 1012 to 2 × 1014 {{W}} {{cm}}-2. We compare our experimental results with a full-dimensional solution of the single-atom time-dependent (TD) Schrödinger equation obtained using the recently developed abinitio TD B-spline ADC method and find good qualitative agreement for the above threshold harmonics.

  9. Monochromated STEM with a 30 meV-wide, atom-sized electron probe.

    Science.gov (United States)

    Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Carpenter, R W

    2013-02-01

    The origins and the recent accomplishments of aberration correction in scanning transmission electron microscopy (STEM) are reviewed. It is remembered that the successful correction of imaging aberrations of round lenses owes much to the successful correction of spectrum aberrations achieved in electron energy loss spectrometers 2-3 decades earlier. Two noteworthy examples of the types of STEM investigation that aberration correction has made possible are shown: imaging of single-atom impurities in graphene and analyzing atomic bonding of single atoms by electron energy loss spectroscopy (EELS). Looking towards the future, a new all-magnetic monochromator is described. The monochromator uses several of the principles pioneered in round lens aberration correction, and it employs stabilization schemes that make it immune to variations in the high voltage of the microscope and in the monochromator main prism current. Tests of the monochromator carried out at 60 keV have demonstrated energy resolution as good as 12 meV and monochromated probe size of ∼1.2 Å. These results were obtained in separate experiments, but they indicate that the instrument can perform imaging and EELS with an atom-sized probe <30 meV wide in energy, and that an improvement in energy resolution to 10 meV and beyond should be possible in the future.

  10. Understanding the atomic-scale contrast in Kelvin probe force microscopy.

    Science.gov (United States)

    Nony, Laurent; Foster, Adam S; Bocquet, Franck; Loppacher, Christian

    2009-07-17

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a noncontact atomic force microscope simulator including a Kelvin module. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and contact potential difference contrasts were reported. The local contact potential difference does reflect the periodicity of the ionic crystal, but not the magnitude of its Madelung surface potential. The imaging mechanism relies on the induced polarization of the ions at the tip-surface interface owing to the modulation of the applied bias voltage. Our findings are in excellent agreement with previous theoretical expectations and experimental observations.

  11. Role of geometry on the frequency spectra of U-shaped atomic force microscope probes

    Science.gov (United States)

    Rezaei, E.; Turner, J. A.

    2017-02-01

    Contact resonance atomic force microscopy (CR-AFM) is a specific technique that is used to determine elastic or viscoelastic properties of materials. The success of this technique is highly dependent on the accuracy of frequency spectra that must be measured for both noncontact and the case in which the tip is in contact with the sample of interest. Thus, choosing the right probe is crucial for accurate experiments. U-shaped probes also offer new opportunities for CR-AFM measurements because of certain specific modes that have tip motion parallel to the sample surface such that these resonances can access in-plane sample properties. However, analysis of the spectra from U-shaped probes is much more challenging due to these modes. The geometry of these probes is the main driver for the spectral response. Here, this influence on the resonance frequencies of the commercially fabricated U-shaped probe AN2-300 is evaluated with respect to geometry in terms of leg width, crossbeam width, and crossbeam length. Both noncontact and contact cases are examined with respect to variations of the nominal geometry. An energy distribution approach is also presented to assist with the identification of modes that have close resonances. Finally, this analysis allows recommendations to be made in order to minimize the convergence of multiple resonances for a specific range of measurement parameters.

  12. Double common-path interferometer for flexible optical probe of optical coherence tomography.

    Science.gov (United States)

    Park, Jae Seok; Chen, Zhongping; Jeong, Myung Yung; Kim, Chang-Seok

    2012-01-16

    A flexible curled optical cord is useful for a common-path optical coherence tomography (OCT) system because a bending-insensitive arbitrary length can be chosen for the endoscopic imaging probe. However, there has been a critical problem that the partial reflector needs to be placed in between the sample and the objective lens. It limits the structure design of optical probe and leads to a low transverse resolution OCT imaging. Instead of a conventional single common-path interferometer, we propose a novel double common-path interferometer configuration in order to generate an interference signal that is independent of the optical distance between the partial reflector and sample. Due to the limitless tuning of the objective distance, an objective lens with a high numerical aperture (NA) up to 0.85 can be successfully used for phase-sensitive optical coherence tomography to achieve a 3-dimensional profile image of a transverse resolution of 0.7 μm. The intensity and phase terms of the interference signal can be obtained simultaneously from a Fourier-domain mode locked swept laser source for fast data acquisition with a phase stability of 979 pm.

  13. Atomic Force Microscope nanolithography on chromosomes to generate single-cell genetic probes

    Directory of Open Access Journals (Sweden)

    Valle Francesco

    2011-06-01

    Full Text Available Abstract Background Chromosomal dissection provides a direct advance for isolating DNA from cytogenetically recognizable region to generate genetic probes for fluorescence in situ hybridization, a technique that became very common in cyto and molecular genetics research and diagnostics. Several reports describing microdissection methods (glass needle or a laser beam to obtain specific probes from metaphase chromosomes are available. Several limitations are imposed by the traditional methods of dissection as the need for a large number of chromosomes for the production of a probe. In addition, the conventional methods are not suitable for single chromosome analysis, because of the relatively big size of the microneedles. Consequently new dissection techniques are essential for advanced research on chromosomes at the nanoscale level. Results We report the use of Atomic Force Microscope (AFM as a tool for nanomanipulation of single chromosomes to generate individual cell specific genetic probes. Besides new methods towards a better nanodissection, this work is focused on the combination of molecular and nanomanipulation techniques which enable both nanodissection and amplification of chromosomal and chromatidic DNA. Cross-sectional analysis of the dissected chromosomes reveals 20 nm and 40 nm deep cuts. Isolated single chromosomal regions can be directly amplified and labeled by the Degenerate Oligonucleotide-Primed Polymerase Chain Reaction (DOP-PCR and subsequently hybridized to chromosomes and interphasic nuclei. Conclusions Atomic force microscope can be easily used to visualize and to manipulate biological material with high resolution and accuracy. The fluorescence in situ hybridization (FISH performed with the DOP-PCR products as test probes has been tested succesfully in avian microchromosomes and interphasic nuclei. Chromosome nanolithography, with a resolution beyond the resolution limit of light microscopy, could be useful to the

  14. Molecular Imaging Probes for Positron Emission Tomography and Optical Imaging of Sentinel Lymph Node and Tumor

    Science.gov (United States)

    Qin, Zhengtao

    Molecular imaging is visualizations and measurements of in vivo biological processes at the molecular or cellular level using specific imaging probes. As an emerging technology, biocompatible macromolecular or nanoparticle based targeted imaging probes have gained increasing popularities. Those complexes consist of a carrier, an imaging reporter, and a targeting ligand. The active targeting ability dramatically increases the specificity. And the multivalency effect may further reduce the dose while providing a decent signal. In this thesis, sentinel lymph node (SLN) mapping and cancer imaging are two research topics. The focus is to develop molecular imaging probes with high specificity and sensitivity, for Positron Emission Tomography (PET) and optical imaging. The objective of this thesis is to explore dextran radiopharmaceuticals and porous silicon nanoparticles based molecular imaging agents. Dextran polymers are excellent carriers to deliver imaging reporters or therapeutic agents due to its well established safety profile and oligosaccharide conjugation chemistry. There is also a wide selection of dextran polymers with different lengths. On the other hand, Silicon nanoparticles represent another class of biodegradable materials for imaging and drug delivery. The success in fluorescence lifetime imaging and enhancements of the immune activation potency was briefly discussed. Chapter 1 begins with an overview on current molecular imaging techniques and imaging probes. Chapter 2 presents a near-IR dye conjugated probe, IRDye 800CW-tilmanocept. Fluorophore density was optimized to generate the maximum brightness. It was labeled with 68Ga and 99mTc and in vivo SLN mapping was successfully performed in different animals, such as mice, rabbits, dogs and pigs. With 99mTc labeled IRDye 800CW-tilmanocept, chapter 3 introduces a two-day imaging protocol with a hand-held imager. Chapter 4 proposed a method to dual radiolabel the IRDye 800CW-tilmanocept with both 68Ga and

  15. Large-Scale Fabrication of Carbon Nanotube Probe Tips For Atomic Force Microscopy Critical Dimension Imaging Applications

    Science.gov (United States)

    Ye, Qi Laura; Cassell, Alan M.; Stevens, Ramsey M.; Meyyappan, Meyya; Li, Jun; Han, Jie; Liu, Hongbing; Chao, Gordon

    2004-01-01

    Carbon nanotube (CNT) probe tips for atomic force microscopy (AFM) offer several advantages over Si/Si3N4 probe tips, including improved resolution, shape, and mechanical properties. This viewgraph presentation discusses these advantages, and the drawbacks of existing methods for fabricating CNT probe tips for AFM. The presentation introduces a bottom up wafer scale fabrication method for CNT probe tips which integrates catalyst nanopatterning and nanomaterials synthesis with traditional silicon cantilever microfabrication technology. This method makes mass production of CNT AFM probe tips feasible, and can be applied to the fabrication of other nanodevices with CNT elements.

  16. Accuracy of cone beam computed tomography, intraoral radiography, and periodontal probing for periodontal bone defects measurement

    Directory of Open Access Journals (Sweden)

    Eskandarlo A

    2011-02-01

    Full Text Available "nBackground and Aims: Cone beam computed tomography (CBCT produces high-quality data about diagnosis and periodontal treatment. To date, there is not enough research regarding periodontal bone measurement using CBCT. The aim of this study was to compare the accuracy of CBCT in measuring periodontal defects to that of intraoral radiography and probing methods."nMaterials and Methods: Two-hundred and eighteen artificial osseous defects (buccal and lingual infrabony, interproximal, horizontal, crater, dehiscence and fenestration defects were created on 13 mandibles of dry skulls. The mandibles were put into a plexiglass box full of water to simulate soft tissue. CBCT images, radiographic images taken with parallel technique and direct measurements using a WHO periodontal probe were recorded and compared to a standard reference (digital caliper. Inter and intra observe consistencies were assessed using Intra class correlation coefficient and pearson correlation."nResults: Inter and intra observer consistencies were high for CBCT and probing methods (ICC- Intra class correlation coefficient>88%, but moderate for intraoral radiography (ICC-Intra class correlation coefficient > 54%. There were not any significant differences between observers for all techniques (P>0/05. According to paired T-test analysis, mean difference for CBCT technique (0.01 mm was lower than that for probing (0.04 mm and radiography (0.62 mm. CBCT was able to measure all kinds of lesions, but radiography could not measure defects in the buccal and lingual sites."nConclusion: All three modalities are useful for identifying periodontal defects. Compared to probing and radiography, the CBCT technique has the most accuracy in measuring periodontal defects.

  17. Improved in situ spring constant calibration for colloidal probe atomic force microscopy

    Science.gov (United States)

    McBride, Sean P.; Law, Bruce M.

    2010-11-01

    In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (V-theory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper, a new in situ spring constant calibration method based upon the residuals, namely, the difference between experimental force-distance data and V-theory is presented and contrasted with two other popular spring constant determination methods. In this residuals calibration method, V-theory is fitted to the experimental force-distance data for a range of systematically varied spring constants where the only adjustable parameter in V-theory is the slip length b. The optimal spring constant k is that value where the residuals are symmetrically displaced about zero for all colloidal probe separations. This residual spring constant calibration method is demonstrated by studying three different liquids (n-decanol, n-hexadecane, and n-octane) and two different silane coated colloidal probe-silicon wafer systems (n-hexadecyltrichlorosilane and n-dodecyltrichlorosilane).

  18. Improved in situ spring constant calibration for colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McBride, Sean P.; Law, Bruce M. [Department of Physics, Cardwell Hall, Kansas State University, Manhattan, Kansas 66506-2601 (United States)

    2010-11-15

    In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (V-theory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper, a new in situ spring constant calibration method based upon the residuals, namely, the difference between experimental force-distance data and V-theory is presented and contrasted with two other popular spring constant determination methods. In this residuals calibration method, V-theory is fitted to the experimental force-distance data for a range of systematically varied spring constants where the only adjustable parameter in V-theory is the slip length b. The optimal spring constant k is that value where the residuals are symmetrically displaced about zero for all colloidal probe separations. This residual spring constant calibration method is demonstrated by studying three different liquids (n-decanol, n-hexadecane, and n-octane) and two different silane coated colloidal probe-silicon wafer systems (n-hexadecyltrichlorosilane and n-dodecyltrichlorosilane).

  19. An Atom Probe Study of κ-carbide Precipitation in Austenitic Lightweight Steel and the Effect of Phosphorus

    Science.gov (United States)

    Bartlett, L. N.; Van Aken, D. C.; Medvedeva, J.; Isheim, D.; Medvedeva, N.; Song, K.

    2017-11-01

    The influence of phosphorus on κ-carbide precipitation and alloy partitioning in an austenitic Fe-30Mn-9Al-1Si-0.9C-0.5Mo cast steel was studied utilizing a combination of transmission electron microscopy, 3D atom probe tomography, X-ray diffraction, and first-principles atomistic modeling. Increasing the amount of phosphorus from 0.006 to 0.043 wt pct P increased the kinetics of the initial ordering reaction. Specimens from the high-phosphorus steel showed some degree of short-range ordering of Fe-Al-C that took place during the quench. It was shown that phosphorus increases both the size and volume fraction of κ-carbide during aging. However, the distribution of phosphorus appears to be homogeneous, and thus long-range diffusion of phosphorus was not responsible for the observed increase in hardening. It is shown that phosphorus encourages the initial short-range ordering into the E21 structure of κ-carbide and also accelerates spinodal decomposition associated with carbon and aluminum diffusions.

  20. Atom probe field ion microscopy and related topics: A bibliography 1993

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included.

  1. Probing the atomic structure of amorphous Ta2O5 coatings

    Science.gov (United States)

    Bassiri, R.; Borisenko, K. B.; Cockayne, D. J. H.; Hough, J.; MacLaren, I.; Rowan, S.

    2011-01-01

    Low optical and mechanical loss Ta2O5 amorphous coatings have a growing number of applications in precision optical measurements systems. Transmission electron microscopy is a promising way to probe the atomic structure of these coatings in an effort to better understand the causes of the observed mechanical and optical losses. Analysis of the experimental reduced density functions using a combination of reverse Monte Carlo refinements and density functional theory molecular dynamics simulations reveals that the structure of amorphous Ta2O5 consists of clusters with increased contribution from a Ta2O2 ring fragment.

  2. Analytic treatment of charge cloud overlaps: an improvement of the tomographic atom probe efficiency

    Science.gov (United States)

    Bas, P.; Bostel, A.; Grancher, G.; Deconihout, B.; Blavette, D.

    1996-03-01

    Although reliable position and composition data are obtained with the Tomographic Atom Probe, the procedure of position calculation by charge centroiding fails when the detector receives two or more ions with close spaced positions and the same mass-to-charge ratio. As the charge clouds of the ions overlap, they form a unique charge pattern on the multianode detector. Only one atom is represented and its position is biased. In order to estimate real positions, we have developed a correction method. The spatial distribution of charges inside a cloud issued from one impact is modelled by a Gaussian law. The particular properties of the Gaussian enable the calculation of exact positions of the two impacts of the overlapped charge patterns and charges of corresponding clouds. The calculation may be generalized for more than two overlapped clouds. The method was tested on a plane-by-plane analysis of a fully ordered Cu 3Au alloy performed on a (100) pole.

  3. Speckle reduction in optical coherence tomography images based on wave atoms

    Science.gov (United States)

    Du, Yongzhao; Liu, Gangjun; Feng, Guoying; Chen, Zhongping

    2014-01-01

    Abstract. Optical coherence tomography (OCT) is an emerging noninvasive imaging technique, which is based on low-coherence interferometry. OCT images suffer from speckle noise, which reduces image contrast. A shrinkage filter based on wave atoms transform is proposed for speckle reduction in OCT images. Wave atoms transform is a new multiscale geometric analysis tool that offers sparser expansion and better representation for images containing oscillatory patterns and textures than other traditional transforms, such as wavelet and curvelet transforms. Cycle spinning-based technology is introduced to avoid visual artifacts, such as Gibbs-like phenomenon, and to develop a translation invariant wave atoms denoising scheme. The speckle suppression degree in the denoised images is controlled by an adjustable parameter that determines the threshold in the wave atoms domain. The experimental results show that the proposed method can effectively remove the speckle noise and improve the OCT image quality. The signal-to-noise ratio, contrast-to-noise ratio, average equivalent number of looks, and cross-correlation (XCOR) values are obtained, and the results are also compared with the wavelet and curvelet thresholding techniques. PMID:24825507

  4. Probing poly(N-isopropylacrylamide-co-butylacrylate)/cell interactions by atomic force microscopy.

    Science.gov (United States)

    Natalia, Becerra; Henry, Andrade; Betty, López; Marina, Restrepo Luz; Roberto, Raiteri

    2015-01-01

    Poly(N-isopropylacrylamide) based hydrogels have been proposed as cell culture supports in cell sheet engineering. Toward this goal, we characterized the poly(N-isopropylacrylamide-co-butylacrylate) copolymer thermo-sensitivity and the cell/copolymer interactions above and below the copolymer lower critical solution temperature. We did that by direct force measurements at different temperatures using an atomic force microscope with either a polystyrene or a glass microbead as probes. We used a copolymer-coated microbead to measure adhesion after a short contact time with a single fibroblast in culture. Statistical analysis of the maximum adhesion force and the mechanical work necessary to separate the probe from the cell surface confirmed the hydrophilic/hydrophobic behavior of poly(N-isopropylacrylamide-co-butylacrylate) as a function of temperature in the range 20-37°C and, consequently, a reversible increase/decrease in cell adhesion with the copolymer. As control experiments we measured interactions between uncoated microbeads with the copolymer hydrogel or cells as well as interaction of the Poly(N-isopropylacrylamide) homopolymer with cells. These results show the potential of an assay based on atomic force microscopy for an in situ and quantitative assessment of cell/substrate interactions and support the use of poly(N-isopropylacrylamide-co-butylacrylate) copolymer as an efficient culture substrate in cell sheet engineering. © 2014 Wiley Periodicals, Inc.

  5. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A.

    1978-08-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min/sup -1/ can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected.

  6. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Andrew; Butte, Manish J., E-mail: manish.butte@stanford.edu [Department of Pediatrics, Division of Immunology, Allergy and Rheumatology, Stanford University, Stanford, California 94305 (United States)

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  7. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes

    Directory of Open Access Journals (Sweden)

    Gemma Rius

    2015-01-01

    Full Text Available Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  8. Probing resonant energy transfer in collisions of ammonia with Rydberg helium atoms by microwave spectroscopy

    Science.gov (United States)

    Zhelyazkova, V.; Hogan, S. D.

    2017-12-01

    We present the results of experiments demonstrating the spectroscopic detection of Förster resonance energy transfer from NH3 in the X1A1 ground electronic state to helium atoms in 1sns 3S1 Rydberg levels, where n = 37 and n = 40. For these values of n, the 1sns 3S1 → 1snp 3PJ transitions in helium lie close to resonance with the ground-state inversion transitions in NH3 and can be tuned through resonance using electric fields of less than 10 V/cm. In the experiments, energy transfer was detected by direct state-selective electric field ionization of the 3S1 and 3PJ Rydberg levels and by monitoring the population of the 3DJ levels following pulsed microwave transfer from the 3PJ levels. Detection by microwave spectroscopic methods represents a highly state selective, low-background approach to probing the collisional energy transfer process and the environment in which the atom-molecule interactions occur. The experimentally observed electric-field dependence of the resonant energy transfer process, probed both by direct electric field ionization and by microwave transfer, agrees well with the results of calculations performed using a simple theoretical model of the energy transfer process. For measurements performed in zero electric field with atoms prepared in the 1s40s 3S1 level, the transition from a regime in which a single energy transfer channel can be isolated for detection to one in which multiple collision channels begin to play a role has been identified as the NH3 density was increased.

  9. Probe alignment and design issues of microelectromechanical system based optical coherence tomography endoscopic imaging.

    Science.gov (United States)

    Duan, Can; Sun, Jingjing; Samuelson, Sean; Xie, Huikai

    2013-09-10

    Endoscopic optical coherence tomography (OCT) imaging has been demonstrated using microelectromechanical system (MEMS) technology by several research groups. The focus of this work is to study how the OCT imaging performance is affected by the radius of curvature of MEMS mirrors as well as the optical alignment accuracy inside small imaging probes. The goal of this study is to provide guidance for assembly tolerance and design optimization of OCT endoscopic probes. Gaussian beam propagation is used for theoretical analysis which is confirmed by optical simulation and verified experimentally with a time-domain OCT system as well. It has been found that the OCT imaging is very sensitive to the distance from the fiber end to the gradient-index (GRIN) lens, which needs to be controlled within 0.1 mm to achieve working distance (WD) longer than 3.5 mm and lateral resolution around 25 μm. The impact on image quality of the MEMS mirror is negligible if the radius of curvature of the mirror surface is greater than 200 mm. In addition, we studied the astigmatism introduced by cylindrical plastic tubing; the maximum astigmatism ratio is 1.1 when the WD is around 2.5 mm.

  10. Miniature endoscopic optical coherence tomography probe employing a two-axis microelectromechanical scanning mirror with through-silicon vias.

    Science.gov (United States)

    Liu, Lin; Wu, Lei; Sun, Jingjing; Lin, Elaine; Xie, Huikai

    2011-02-01

    We present the design and experimental results of a new MEMS-based endoscopic optical coherence tomography (OCT) probe. The uniqueness of this miniature OCT imaging probe is a two-axis MEMS mirror with through-silicon vias (TSVs) for interconnecting. The TSV interconnection enables ultracompact probe design, successfully reducing the probe size to only 2.6 mm in diameter. The MEMS mirror is actuated by an electrothermal actuator that is capable of scanning ± 16° at only 3.6 V DC. Two-dimensional and three-dimensional OCT images of microspheres embedded in PDMS and acute rat brain tissue have been obtained with this miniature probe in a time-domain OCT system.

  11. Concept of effective atomic number and effective mass density in dual-energy X-ray computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Bonnin, Anne, E-mail: annebonnin@free.fr [ESRF, 6 Jules Horowitz, F-38073 Grenoble Cedex (France); LVA, Vibrations and Acoustic Laboratory, INSA-Lyon, Université de Lyon, F-69621 Villeurbanne Cedex (France); Duvauchelle, Philippe, E-mail: philippe.duvauchelle@insa-lyon.fr [LVA, Vibrations and Acoustic Laboratory, INSA-Lyon, Université de Lyon, F-69621 Villeurbanne Cedex (France); Kaftandjian, Valérie [LVA, Vibrations and Acoustic Laboratory, INSA-Lyon, Université de Lyon, F-69621 Villeurbanne Cedex (France); Ponard, Pascal [Thales Electron Devices SAS, 2 Rue Marcel Dassault, BP23 78141 Vélizy, Villacoublay Cedex (France)

    2014-01-01

    This paper focuses on dual-energy X-ray computed tomography and especially the decomposition of the measured attenuation coefficient in a mass density and atomic number basis. In particular, the concept of effective atomic number is discussed. Although the atomic number is well defined for chemical elements, the definition of an effective atomic number for any compound is not an easy task. After reviewing different definitions available in literature, a definition related to the method of measurement and X-ray energy, is suggested. A new concept of effective mass density is then introduced in order to characterize material from dual-energy computed tomography. Finally, this new concept and definition are applied on a simulated case, focusing on explosives identification in luggage.

  12. A highly selective and ratiometric fluorescent probe for cyanide by rationally altering the susceptible H-atom.

    Science.gov (United States)

    Hao, Yuanqiang; Nguyen, Khac Hong; Zhang, Yintang; Zhang, Guan; Fan, Shengnan; Li, Fen; Guo, Chao; Lu, Yuanyuan; Song, Xiaoqing; Qu, Peng; Liu, You-Nian; Xu, Maotian

    2018-01-01

    A highly selective and ratiometric fluorescent probe for cyanide was rationally designed and synthesized. The probe comprises a fluorophore unit of naphthalimide and a CN- acceptor of methylated trifluoroacetamide group. For these previous reported trifluoroacetamide derivative-based cyanide chemosensors, the H-atom of amide adjacent to trifluoroacetyl group is susceptible to be attacked by various anions (CN- itself, F-, AcO-, et al.) and even the solvent molecule, which resulted in the bewildered reaction mechanism and poor selectivity of the assay. In this work, the susceptible H-atom of trifluoroacetamide was artfully substituted by alkyl group. Thus a highly specific fluorescent probe was developed for cyanide sensing. Upon the nucleophilic addition of cyanide anion to the carbonyl of trifluoroacetamide moiety of the probe, the ICT process of the probe was significantly enhanced and leading to a remarkable red shift in both absorption and emission spectra of the probe. This fluorescent assay showed a linear range of 1.0-80.0µM and a LOD (limit of detection) of 0.23µM. All the investigated interference have no influence on the sensing behavior of the probe toward cyanide. Moreover, by coating on TLC plate, the probe can be utilized for practical detection of trace cyanide in water samples. Copyright © 2017. Published by Elsevier B.V.

  13. Atomic scale properties of magnetic Mn-based alloys probed by emission Mössbauer spectroscopy

    CERN Multimedia

    Mn-based alloys are characterized by a wealth of properties, which are of interest both from fundamental physics point of view and particularly attractive for different applications in modern technology: from magnetic storage to sensing and spin-based electronics. The possibility to tune their magnetic properties through post-growth thermal processes and/or stoichiometry engineering is highly important in order to target different applications (i.e. Mn$_{x}$Ga) or to increase their Curie temperature above room temperature (i.e. off-stoichiometric MnSi). In this project, the Mössbauer effect will be applied at $^{57}$Fe sites following implantation of radioactive $^{57}$Mn, to probe the micro-structure and magnetism of Mn-based alloys on the atomic-scale. The proposed experimental plan is devoted to establish a direct correlation between the local structure and bulk magnetism (and other physical properties) of Mn-based alloys.

  14. Imaging collector channel entrance with a new intraocular micro-probe swept-source optical coherence tomography.

    Science.gov (United States)

    Xin, Chen; Chen, Xiaoya; Li, Meng; Shi, Yan; Wang, Huaizhou; Wang, Ruikang; Wang, Ningli

    2017-09-01

    To describe the use of a newly developed side-viewing catheter probe to provide the cross-sectional images of collector channel entrance (CCE), achieved by swept-source optical coherence tomography (SS-OCT). A side-viewing SS-OCT catheter probe was developed that has a core probe diameter of 0.15 mm and an outer diameter of 0.25 mm, for the purpose of imaging CCEs within eye globe. Cadaver eyes harvested from swine and human were used to demonstrate its feasibility. For porcine eyes, the probe imaged the CCE by accessing the region of the aqueous plexus (AP) as well as along the inner wall (IW) of the trabecular meshwork (TM). For human eyes, the CCE images were captured by placing the probe within the lumen of the Schlemm's canal (SC) and along its IW. With the optical coherence tomography (OCT) catheter probe, the CCE is well delineated as optically empty areas within the highly scattering sclera. In porcine eyes, images captured in the region of the AP demonstrate a large cavity with delicate tissue strands around the probe. The CCE can be identified at the outer margin of the AP. When imaged along the IW, the TM is discernable but difficult to be distinguished from the AP. In the human limbal regions, when placed within the lumen of the SC, the catheter probe fully occupies the potential space. TM is highly compact. The CCE can be identified at the outer wall of the SC. When imaged along the IW of TM, the SC and CCE can be identified. The intraocular SS-OCT catheter probe is feasible to provide the CCE images, indicating useful clinical applications to assist glaucoma surgery. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  15. Implementation and characterization of a quartz tuning fork based probe consisted of discrete resonators for dynamic mode atomic force microscopy.

    Science.gov (United States)

    Akiyama, Terunobu; de Rooij, Nicolaas F; Staufer, Urs; Detterbeck, Manfred; Braendlin, Dominik; Waldmeier, Simon; Scheidiger, Martin

    2010-06-01

    The quartz tuning fork based probe {e.g., Akiyama et al. [Appl. Surf. Sci. 210, 18 (2003)]}, termed "A-Probe," is a self-sensing and self-actuating (exciting) probe for dynamic mode atomic force microscope (AFM) operation. It is an oscillatory force sensor consisting of the two discrete resonators. This paper presents the investigations on an improved A-Probe: its batch fabrication and assembly, mounting on an AFM head, electrical setup, characterization, and AFM imaging. The fundamental features of the A-Probe are electrically and optically characterized in "approach-withdraw" experiments. Further investigations include the frequency response of an A-Probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. Imaging of an electronic chip, a compact disk stamper, carbon nanotubes, and Si beads is demonstrated with this probe at ambient conditions in the so-called frequency modulation mode. A special probe substrate, which can snap on a receptacle fixed on an AFM head, and a special holder including a preamplifier electronic are introduced. We hope that the implementation and characterization of the A-Probe described in this paper will provide hints for new scanning probe techniques.

  16. Nanogeochronology of discordant zircon measured by atom probe microscopy of Pb-enriched dislocation loops

    Science.gov (United States)

    Peterman, Emily M.; Reddy, Steven M.; Saxey, David W.; Snoeyenbos, David R.; Rickard, William D. A.; Fougerouse, Denis; Kylander-Clark, Andrew R. C.

    2016-01-01

    Isotopic discordance is a common feature in zircon that can lead to an erroneous age determination, and it is attributed to the mobilization and escape of radiogenic Pb during its post-crystallization geological evolution. The degree of isotopic discordance measured at analytical scales of ~10 μm often differs among adjacent analysis locations, indicating heterogeneous distributions of Pb at shorter length scales. We use atom probe microscopy to establish the nature of these sites and the mechanisms by which they form. We show that the nanoscale distribution of Pb in a ~2.1 billion year old discordant zircon that was metamorphosed c. 150 million years ago is defined by two distinct Pb reservoirs. Despite overall Pb loss during peak metamorphic conditions, the atom probe data indicate that a component of radiogenic Pb was trapped in 10-nm dislocation loops that formed during the annealing of radiation damage associated with the metamorphic event. A second Pb component, found outside the dislocation loops, represents homogeneous accumulation of radiogenic Pb in the zircon matrix after metamorphism. The 207Pb/206Pb ratios measured from eight dislocation loops are equivalent within uncertainty and yield an age consistent with the original crystallization age of the zircon, as determined by laser ablation spot analysis. Our results provide a specific mechanism for the trapping and retention of radiogenic Pb during metamorphism and confirm that isotopic discordance in this zircon is characterized by discrete nanoscale reservoirs of Pb that record different isotopic compositions and yield age data consistent with distinct geological events. These data may provide a framework for interpreting discordance in zircon as the heterogeneous distribution of discrete radiogenic Pb populations, each yielding geologically meaningful ages. PMID:27617295

  17. Quantitative imaging of electrospun fibers by PeakForce Quantitative NanoMechanics atomic force microscopy using etched scanning probes.

    Science.gov (United States)

    Chlanda, Adrian; Rebis, Janusz; Kijeńska, Ewa; Wozniak, Michal J; Rozniatowski, Krzysztof; Swieszkowski, Wojciech; Kurzydlowski, Krzysztof J

    2015-05-01

    Electrospun polymeric submicron and nanofibers can be used as tissue engineering scaffolds in regenerative medicine. In physiological conditions fibers are subjected to stresses and strains from the surrounding biological environment. Such stresses can cause permanent deformation or even failure to their structure. Therefore, there is a growing necessity to characterize their mechanical properties, especially at the nanoscale. Atomic force microscopy is a powerful tool for the visualization and probing of selected mechanical properties of materials in biomedical sciences. Image resolution of atomic force microscopy techniques depends on the equipment quality and shape of the scanning probe. The probe radius and aspect ratio has huge impact on the quality of measurement. In the presented work the nanomechanical properties of four different polymer based electrospun fibers were tested using PeakForce Quantitative NanoMechanics atomic force microscopy, with standard and modified scanning probes. Standard, commercially available probes have been modified by etching using focused ion beam (FIB). Results have shown that modified probes can be used for mechanical properties mapping of biomaterial in the nanoscale, and generate nanomechanical information where conventional tips fail. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Probing the interaction between air bubble and sphalerite mineral surface using atomic force microscope.

    Science.gov (United States)

    Xie, Lei; Shi, Chen; Wang, Jingyi; Huang, Jun; Lu, Qiuyi; Liu, Qingxia; Zeng, Hongbo

    2015-03-03

    The interaction between air bubbles and solid surfaces plays important roles in many engineering processes, such as mineral froth flotation. In this work, an atomic force microscope (AFM) bubble probe technique was employed, for the first time, to directly measure the interaction forces between an air bubble and sphalerite mineral surfaces of different hydrophobicity (i.e., sphalerite before/after conditioning treatment) under various hydrodynamic conditions. The direct force measurements demonstrate the critical role of the hydrodynamic force and surface forces in bubble-mineral interaction and attachment, which agree well with the theoretical calculations based on Reynolds lubrication theory and augmented Young-Laplace equation by including the effect of disjoining pressure. The hydrophobic disjoining pressure was found to be stronger for the bubble-water-conditioned sphalerite interaction with a larger hydrophobic decay length, which enables the bubble attachment on conditioned sphalerite at relatively higher bubble approaching velocities than that of unconditioned sphalerite. Increasing the salt concentration (i.e., NaCl, CaCl2) leads to weakened electrical double layer force and thereby facilitates the bubble-mineral attachment, which follows the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory by including the effects of hydrophobic interaction. The results provide insights into the basic understanding of the interaction mechanism between bubbles and minerals at nanoscale in froth flotation processes, and the methodology on probing the interaction forces of air bubble and sphalerite surfaces in this work can be extended to many other mineral and particle systems.

  19. Nanomechanical and topographical imaging of living cells by atomic force microscopy with colloidal probes

    Energy Technology Data Exchange (ETDEWEB)

    Puricelli, Luca; Galluzzi, Massimiliano; Schulte, Carsten; Podestà, Alessandro, E-mail: alessandro.podesta@mi.infn.it; Milani, Paolo [CIMaINa and Department of Physics, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

    2015-03-15

    Atomic Force Microscopy (AFM) has a great potential as a tool to characterize mechanical and morphological properties of living cells; these properties have been shown to correlate with cells’ fate and patho-physiological state in view of the development of novel early-diagnostic strategies. Although several reports have described experimental and technical approaches for the characterization of cellular elasticity by means of AFM, a robust and commonly accepted methodology is still lacking. Here, we show that micrometric spherical probes (also known as colloidal probes) are well suited for performing a combined topographic and mechanical analysis of living cells, with spatial resolution suitable for a complete and accurate mapping of cell morphological and elastic properties, and superior reliability and accuracy in the mechanical measurements with respect to conventional and widely used sharp AFM tips. We address a number of issues concerning the nanomechanical analysis, including the applicability of contact mechanical models and the impact of a constrained contact geometry on the measured Young’s modulus (the finite-thickness effect). We have tested our protocol by imaging living PC12 and MDA-MB-231 cells, in order to demonstrate the importance of the correction of the finite-thickness effect and the change in Young’s modulus induced by the action of a cytoskeleton-targeting drug.

  20. Probing new spin-independent interactions through precision spectroscopy in atoms with few electrons

    Science.gov (United States)

    Delaunay, Cédric; Frugiuele, Claudia; Fuchs, Elina; Soreq, Yotam

    2017-12-01

    The very high precision of current measurements and theory predictions of spectral lines in few-electron atoms allows us to efficiently probe the existence of exotic forces between electrons, neutrons and protons. We investigate the sensitivity to new spin-independent interactions in transition frequencies (and their isotopic shifts) of hydrogen, helium and some heliumlike ions. We find that present data probe new regions of the force-carrier couplings to electrons and neutrons around the MeV mass range. We also find that, below few keV, the sensitivity to the electron coupling in precision spectroscopy of helium and positronium is comparable to that of the anomalous magnetic moment of the electron. Finally, we interpret our results in the dark-photon model where a new gauge boson is kinetically mixed with the photon. There, we show that helium transitions, combined with the anomalous magnetic moment of the electron, provide the strongest indirect bound from laboratory experiments above 100 keV.

  1. Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons

    Science.gov (United States)

    Zhou, You; Scuri, Giovanni; Wild, Dominik S.; High, Alexander A.; Dibos, Alan; Jauregui, Luis A.; Shu, Chi; de Greve, Kristiaan; Pistunova, Kateryna; Joe, Andrew Y.; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip; Lukin, Mikhail D.; Park, Hongkun

    2017-09-01

    Transition metal dichalcogenide (TMD) monolayers with a direct bandgap feature tightly bound excitons, strong spin-orbit coupling and spin-valley degrees of freedom. Depending on the spin configuration of the electron-hole pairs, intra-valley excitons of TMD monolayers can be either optically bright or dark. Dark excitons involve nominally spin-forbidden optical transitions with a zero in-plane transition dipole moment, making their detection with conventional far-field optical techniques challenging. Here, we introduce a method for probing the optical properties of two-dimensional materials via near-field coupling to surface plasmon polaritons (SPPs). This coupling selectively enhances optical transitions with dipole moments normal to the two-dimensional plane, enabling direct detection of dark excitons in TMD monolayers. When a WSe2 monolayer is placed on top of a single-crystal silver film, its emission into near-field-coupled SPPs displays new spectral features whose energies and dipole orientations are consistent with dark neutral and charged excitons. The SPP-based near-field spectroscopy significantly improves experimental capabilities for probing and manipulating exciton dynamics of atomically thin materials, thus opening up new avenues for realizing active metasurfaces and robust optoelectronic systems, with potential applications in information processing and communication.

  2. Probing the interactions between lignin and inorganic oxides using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingyu; Qian, Yong, E-mail: qianyong86@163.com; Deng, Yonghong; Liu, Di; Li, Hao; Qiu, Xueqing, E-mail: xueqingqiu66@163.com

    2016-12-30

    Graphical abstract: The interactions between lignin and inorganic oxides are quantitatively probed by atomic force microscopy, which is fundamental but beneficial for understanding and optimizing the absorption-dispersion and catalytic degradation processes of lignin. - Highlights: • The interactions between lignin and inorganic oxides are measured using AFM. • The adhesion forces between lignin and metal oxides are larger than that in nonmetal systems. • Hydrogen bond plays an important role in lignin-inorganic oxides system. - Abstract: Understanding the interactions between lignin and inorganic oxides has both fundamental and practical importance in industrial and energy fields. In this work, the specific interactions between alkali lignin (AL) and three inorganic oxide substrates in aqueous environment are quantitatively measured using atomic force microscopy (AFM). The results show that the average adhesion force between AL and metal oxide such as Al{sub 2}O{sub 3} or MgO is nearly two times bigger than that between AL and nonmetal oxide such as SiO{sub 2} due to the electrostatic difference and cation-π interaction. When 83% hydroxyl groups of AL is blocked by acetylation, the adhesion forces between AL and Al{sub 2}O{sub 3}, MgO and SiO{sub 2} decrease 43, 35 and 75% respectively, which indicate hydrogen bonds play an important role between AL and inorganic oxides, especially in AL-silica system.

  3. Imaging the distribution of photoswitchable probes with temporally-unmixed multispectral optoacoustic tomography

    Science.gov (United States)

    Deán-Ben, X. Luís.; Stiel, Andre C.; Jiang, Yuanyuan; Ntziachristos, Vasilis; Westmeyer, Gil G.; Razansky, Daniel

    2016-03-01

    Synthetic and genetically encoded chromo- and fluorophores have become indispensable tools for biomedical research enabling a myriad of applications in imaging modalities based on biomedical optics. The versatility offered by the optoacoustic (photoacoustic) contrast mechanism enables to detect signals from any substance absorbing light, and hence these probes can be used as optoacoustic contrast agents. While contrast versatility generally represents an advantage of optoacoustics, the strong background signal generated by light absorption in endogeneous chromophores hampers the optoacoustic capacity to detect a photo-absorbing agent of interest. Increasing the optoacoustic sensitivity is then determined by the capability to differentiate specific features of such agent. For example, multispectral optoacoustic tomography (MSOT) exploits illuminating the tissue at multiple optical wavelengths to spectrally resolve (unmix) the contribution of different chromophores. Herein, we present an alternative approach to enhance the sensitivity and specificity in the detection of optoacoustic contrast agents. This is achieved with photoswitchable probes that change optical absorption upon illumination with specific optical wavelengths. Thereby, temporally unmixed MSOT (tuMSOT) is based on photoswitching the compounds according to defined schedules to elicit specific time-varying optoacoustic signals, and then use temporal unmixing algorithms to locate the contrast agent based on their particular temporal profile. The photoswitching kinetics is further affected by light intensity, so that tuMSOT can be employed to estimate the light fluence distribution in a biological sample. The performance of the method is demonstrated herein with the reversibly switchable fluorescent protein Dronpa and its fast-switching fatigue resistant variant Dronpa-M159T.

  4. Nanoparticle imaging probes for molecular imaging with computed tomography and application to cancer imaging

    Science.gov (United States)

    Roeder, Ryan K.; Curtis, Tyler E.; Nallathamby, Prakash D.; Irimata, Lisa E.; McGinnity, Tracie L.; Cole, Lisa E.; Vargo-Gogola, Tracy; Cowden Dahl, Karen D.

    2017-03-01

    Precision imaging is needed to realize precision medicine in cancer detection and treatment. Molecular imaging offers the ability to target and identify tumors, associated abnormalities, and specific cell populations with overexpressed receptors. Nuclear imaging and radionuclide probes provide high sensitivity but subject the patient to a high radiation dose and provide limited spatiotemporal information, requiring combined computed tomography (CT) for anatomic imaging. Therefore, nanoparticle contrast agents have been designed to enable molecular imaging and improve detection in CT alone. Core-shell nanoparticles provide a powerful platform for designing tailored imaging probes. The composition of the core is chosen for enabling strong X-ray contrast, multi-agent imaging with photon-counting spectral CT, and multimodal imaging. A silica shell is used for protective, biocompatible encapsulation of the core composition, volume-loading fluorophores or radionuclides for multimodal imaging, and facile surface functionalization with antibodies or small molecules for targeted delivery. Multi-agent (k-edge) imaging and quantitative molecular imaging with spectral CT was demonstrated using current clinical agents (iodine and BaSO4) and a proposed spectral library of contrast agents (Gd2O3, HfO2, and Au). Bisphosphonate-functionalized Au nanoparticles were demonstrated to enhance sensitivity and specificity for the detection of breast microcalcifications by conventional radiography and CT in both normal and dense mammary tissue using murine models. Moreover, photon-counting spectral CT enabled quantitative material decomposition of the Au and calcium signals. Immunoconjugated Au@SiO2 nanoparticles enabled highly-specific targeting of CD133+ ovarian cancer stem cells for contrast-enhanced detection in model tumors.

  5. Probing the accuracy and precision of Hirshfeld atom refinement withHARtinterfaced withOlex2.

    Science.gov (United States)

    Fugel, Malte; Jayatilaka, Dylan; Hupf, Emanuel; Overgaard, Jacob; Hathwar, Venkatesha R; Macchi, Piero; Turner, Michael J; Howard, Judith A K; Dolomanov, Oleg V; Puschmann, Horst; Iversen, Bo B; Bürgi, Hans-Beat; Grabowsky, Simon

    2018-01-01

    Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element-hydrogen distances, r ( X -H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r ( X -H) values obtained from HAR. These quantities are compared and found to agree with those obtained from (i) accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii) multipole modelling (MM), an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydro-carbon rubrene (orthorhombic 5,6,11,12-tetra-phenyl-tetracene), a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa), and the salt potassium hydrogen oxalate (KHOx). The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element-hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily launched

  6. Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2

    Directory of Open Access Journals (Sweden)

    Malte Fugel

    2018-01-01

    Full Text Available Hirshfeld atom refinement (HAR is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM, such as too short element–hydrogen distances, r(X—H, or too large atomic displacement parameters (ADPs. This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r(X—H values obtained from HAR. These quantities are compared and found to agree with those obtained from (i accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii multipole modelling (MM, an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydrocarbon rubrene (orthorhombic 5,6,11,12-tetraphenyltetracene, a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa, and the salt potassium hydrogen oxalate (KHOx. The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element–hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily

  7. The Model Analysis of a Complex Tuning Fork Probe and Its Application in Bimodal Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Zhichao Wu

    2017-01-01

    Full Text Available A new electromechanical coupling model was built to quantitatively analyze the tuning fork probes, especially the complex ones. A special feature of a novel, soft tuning fork probe, that the second eigenfrequency of the probe was insensitive to the effective force gradient, was found and used in a homemade bimodal atomic force microscopy to measure power dissipation quantitatively. By transforming the mechanical parameters to the electrical parameters, a monotonous and concise method without using phase to calculate the power dissipation was proposed.

  8. Electrical tomography using atomic force microscopy and its application towards carbon nanotube-based interconnects.

    Science.gov (United States)

    Schulze, A; Hantschel, T; Dathe, A; Eyben, P; Ke, X; Vandervorst, W

    2012-08-03

    The fabrication and integration of low-resistance carbon nanotubes (CNTs) for interconnects in future integrated circuits requires characterization techniques providing structural and electrical information at the nanometer scale. In this paper we present a slice-and-view approach based on electrical atomic force microscopy. Material removal achieved by successive scanning using doped ultra-sharp full-diamond probes, manufactured in-house, enables us to acquire two-dimensional (2D) resistance maps originating from different depths (equivalently different CNT lengths) on CNT-based interconnects. Stacking and interpolating these 2D resistance maps results in a three-dimensional (3D) representation (tomogram). This allows insight from a structural (e.g. size, density, distribution, straightness) and electrical point of view simultaneously. By extracting the resistance evolution over the length of an individual CNT we derive quantitative information about the resistivity and the contact resistance between the CNT and bottom electrode.

  9. Atomic XAFS as a Tool To Probe the Reactivity of Metal Oxide Catalysts: Quantifying Metal Oxide Support Effects

    NARCIS (Netherlands)

    Keller, D.E.; Airaksinen, S.M.K.; Krause, A.O.I.; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397; Koningsberger, D.C.|info:eu-repo/dai/nl/073704342

    2007-01-01

    The potential of atomic XAFS (AXAFS) to directly probe the catalytic performances of a set of supported metal oxide catalysts has been explored for the first time. For this purpose, a series of 1 wt % supported vanadium oxide catalysts have been prepared differing in their oxidic support material

  10. Quantification of aortic valve calcification using multislice spiral computed tomography: comparison with atomic absorption spectroscopy.

    Science.gov (United States)

    Koos, Ralf; Mahnken, Andreas Horst; Kühl, Harald Peter; Mühlenbruch, Georg; Mevissen, Vera; Stork, Ludwig; Dronskowski, Richard; Langebartels, Georg; Autschbach, Rüdiger; Ortlepp, Jan R

    2006-05-01

    Multislice spiral computed tomography (MSCT) allows the in vivo detection of valvular calcification. The aim of this study was to validate the quantification of aortic valve calcification (AVC) by MSCT with in vitro measurements by atomic absorption spectroscopy. In 18 patients with severe aortic stenosis, 16 detector row MSCT (SOMATOM Sensation 16, Siemens, Forchheim, Germany with scan parameters as follows: 420 milliseconds tube rotation time, 12 x 0.75 mm collimation, tube voltage 120 KV) was performed before aortic valve replacement. Images were reconstructed at 60% of the RR interval with an effective slice thickness of 3 mm and a reconstruction increment of 2 mm. AVC was assessed using Agatston AVC score, mass AVC score, and volumetric AVC score. After valve replacement, the calcium content of the excised human stenotic aortic valves was determined in vitro using atomic absorption spectroscopy. The mean Agatston AVC score was 3,842 +/- 1,790, the mean volumetric AVC score was 3,061 +/- 1,406, and mass AVC score was 888 +/- 492 as quantified by MSCT. Atomic absorption spectroscopy showed a mean true calcification mass (Ca5(PO4)3OH) of 19 +/- 8 mass%. There was a significant correlation between in vivo AVC scores determined by MSCT and in vitro mean true calcification mass (r = 0.74, P = 0.0004 for mass AVC score, r = 0.79, P = 0.0001 for volumetric AVC score and r = 0.80, P = 0.0001 for Agatston AVC score) determined by atomic absorption spectroscopy. Linear regression analysis showed a significant association between the degree of hydroxyapatite (given in mass%) in the aortic valve and the degree of AVC (R = 0.74, F = 19.6, P = 0.0004 for mass AVC score, R = 0.80, F = 29.3, P = 0.0001 for Agatston AVC score and R = 0.79, F = 27.3, P = 0.0001 for volumetric AVC score) assessed by MSCT. MSCT allows accurate in vivo quantification of aortic valve calcifications.

  11. Miniature optical coherence tomography-ultrasound probe for automatically coregistered three-dimensional intracoronary imaging with real-time display.

    Science.gov (United States)

    Li, Jiawen; Ma, Teng; Jing, Joseph; Zhang, Jun; Patel, Pranav M; Kirk Shung, K; Zhou, Qifa; Chen, Zhongping

    2013-10-01

    We have developed a novel miniature integrated optical coherence tomography (OCT)-intravascular ultrasound (IVUS) probe, with a 1.5-mm-long rigid part and 0.9-mm outer diameter, for real-time intracoronary imaging of atherosclerotic plaques and guiding of interventional procedures. By placing the OCT ball lens and IVUS transducer back-to-back at the same axial position, this probe can provide automatically coregistered, coaxial OCT-IVUS imaging. To demonstrate its real-time capability, three-dimensional OCT-IVUS imaging of a pig's coronary artery displaying in polar coordinates, as well as images of three major types of atherosclerotic plaques in human cadaver coronary segments, were obtained using this probe and our upgraded system. Histology validation is also presented.

  12. Non-invasive diagnostic system and its opto-mechanical probe for combining confocal Raman spectroscopy and optical coherence tomography.

    Science.gov (United States)

    Klemes, Jan; Kotzianova, Adela; Pokorny, Marek; Mojzes, Peter; Novak, Jindrich; Sukova, Lada; Demuth, Jaroslav; Vesely, Jaroslav; Sasek, Ladislav; Velebny, Vladimir

    2017-11-01

    Non-invasive optical diagnostic methods allow important information about studied systems to be obtained in a non-destructive way. Complete diagnosis requires information about the chemical composition as well as the morphological structure of a sample. We report on the development of an opto-mechanical probe that combines Raman spectroscopy (RS) and optical coherence tomography (OCT), two methods that provide all the crucial information needed for a non-invasive diagnosis. The aim of this paper is to introduce the technical design, construction and optimization of a dual opto-mechanical probe combining two in-house developed devices for confocal RS and OCT. The unique benefit of the probe is a gradual acquisition of OCT and RS data, which allows to use the acquired OCT images to pinpoint locations of interest for RS measurements. The parameters and the correct functioning of the probe were verified by RS scanning of various samples (silicon wafer and ex vivo tissue) based on their OCT images - lateral as well as depth scanning was performed. Both the OCT and RS systems were developed, optimized and tested with the ultimate aim of verifying the functionality of the probe. Picture: Schematic illustration and visualization of the developed RS-OCT probe. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Detection and characterization of atherosclerotic plaques by Raman probe spectroscopy and optical coherence tomography (Conference Presentation)

    Science.gov (United States)

    Matthäus, Christian; Dochow, Sebastian; Egodage, Kokila D.; Schie, Iwan; Romeike, Bernd F.; Brehm, Bernhard R.; Popp, Jürgen

    2017-02-01

    Visualization and characterization of inner arterial plaque depositions is of vital diagnostic interest. Established intravascular imaging techniques provide valuable morphological information, but cannot deliver information about the chemical composition of individual plaques. Probe based Raman spectroscopy offers the possibility for a biochemical characterization of atherosclerotic plaque formations during an intravascular intervention. From post mortem studies it is well known that the severity of a plaque and its stability are strongly correlated with its biochemical composition. Especially the identification of vulnerable plaques remains one of the most important and challenging aspects in cardiology. Thus, specific information about the composition of a plaque would greatly improve the risk assessment and management. Furthermore, knowledge about the composition can offer new therapeutic and medication strategies. Plaque calcifications as well as major lipid components such as cholesterol, cholesterol esters and triglycerides can be spectroscopically easily differentiated. Intravascular optical coherence tomography (OCT) is currently a prominent catheter based imaging technique for the localization and visualization of atherosclerotic plaque depositions. The high resolution of OCT with 10 to 15 µm allows for very detailed characterization of morphological features such as different plaque formations, thin fibrous caps and accurate measurements of lesion lengths. In combination with OCT imaging the obtained spectral information can provide substantial information supporting on on-site diagnosis of various plaque types and therefor an improved risk assessment. The potential and feasibility of combining OCT with Raman spectroscopy is demonstrated on excised plaque samples, as well as under in vivo conditions. Acknowledgements: Financial support from the Carl Zeiss Foundation is greatly acknowledged.

  14. Effects of methotrexate on the viscoelastic properties of single cells probed by atomic force microscopy.

    Science.gov (United States)

    Li, Mi; Liu, Lianqing; Xiao, Xiubin; Xi, Ning; Wang, Yuechao

    2016-10-01

    Methotrexate is a commonly used anti-cancer chemotherapy drug. Cellular mechanical properties are fundamental parameters that reflect the physiological state of a cell. However, so far the role of cellular mechanical properties in the actions of methotrexate is still unclear. In recent years, probing the behaviors of single cells with the use of atomic force microscopy (AFM) has contributed much to the field of cell biomechanics. In this work, with the use of AFM, the effects of methotrexate on the viscoelastic properties of four types of cells were quantitatively investigated. The inhibitory and cytotoxic effects of methotrexate on the proliferation of cells were observed by optical and fluorescence microscopy. AFM indenting was used to measure the changes of cellular viscoelastic properties (Young's modulus and relaxation time) by using both conical tip and spherical tip, quantitatively showing that the stimulation of methotrexate resulted in a significant decrease of both cellular Young's modulus and relaxation times. The morphological changes of cells induced by methotrexate were visualized by AFM imaging. The study improves our understanding of methotrexate action and offers a novel way to quantify drug actions at the single-cell level by measuring cellular viscoelastic properties, which may have potential impacts on developing label-free methods for drug evaluation.

  15. Compact metal probes: a solution for atomic force microscopy based tip-enhanced Raman spectroscopy.

    Science.gov (United States)

    Rodriguez, R D; Sheremet, E; Müller, S; Gordan, O D; Villabona, A; Schulze, S; Hietschold, M; Zahn, D R T

    2012-12-01

    There are many challenges in accomplishing tip-enhanced Raman spectroscopy (TERS) and obtaining a proper tip is probably the greatest one. Since tip size, composition, and geometry are the ultimate parameters that determine enhancement of intensity and lateral resolution, the tip becomes the most critical component in a TERS experiment. However, since the discovery of TERS the cantilevers used in atomic force microscopy (AFM) have remained basically the same: commercial silicon (or silicon nitride) tips covered by a metallic coating. The main issues of using metal-coated silicon cantilevers, such as wearing off of the metal layer or increased tip radius, can be completely overcome by using all-metal cantilevers. Until now in TERS experiments such probes have only been used in a scanning tunneling microscope or in a tuning fork-based shear force microscope but not in AFM. In this work for the first time, we show the use of compact silver cantilevers that are fully compatible with contact and tapping modes in AFM demonstrating their superb performance in TERS experiments.

  16. Probing the local structure of doped manganites using the atomic pair distribution function

    Science.gov (United States)

    Proffen, T.; Billinge, S. J. L.

    We have used atomic pair distribution function (PDF) analysis based on neutron powder diffraction data to investigate the local structure of the colossal magnetoresistant manganite La0.75Ca0.25MnO3 as a function of temperature. In the doping range 0.17materials show a metal-to-insulator transition, transforming from a ferromagnetic metal (FM) at low temperature to a paramagnetic insulator (PI). We can probe the charge distribution of the sample using the PDF by searching for evidence of Jahn-Teller (JT) distorted octahedra, implying the presence of Mn3+ ions. A two-phase model based on the local structures of the FM and PI phases was used to refine the experimental PDFs quantitatively. We observe the co-existence of both phases over a wide temperature range: approximately 10% of the localized JT phase (PI) is present even at the lowest temperature (T=20K), whereas at room temperature nearly half of the sample remains in the delocalized (FM) phase.

  17. Roles of Atomic Injection Rate and External Magnetic Field on Optical Properties of Elliptical Polarized Probe Light

    Science.gov (United States)

    Karimi, R.; Asadpour, S. H.; Batebi, S.; Rahimpour Soleimani, H.

    2016-01-01

    In this paper we investigate the optical properties of an open four-level tripod atomic system driven by an elliptically polarized probe field in the presence of the external magnetic field and compare its properties with the corresponding closed system. Our result reveals that absorption, dispersion and group velocity of probe field can be manipulated by adjusting the phase difference between the two circularly polarized components of a single coherent field, magnetic field and cavity parameters i.e. the atomic exit rate from cavity and atomic injection rates. We show that the system can exhibit multiple electromagnetically induced transparency windows in the presence of the external magnetic field. The numerical result shows that the probe field in the open system can be amplified by appropriate choice of cavity parameters, while in the closed system with introduce appropriate phase difference between fields the probe field can be enhanced. Also it is shown that the group velocity of light pulse can be controlled by external magnetic field, relative phase of applied fields and cavity parameters. By changing the parameters the group velocity of light pulse changes from subluminal to superluminal light propagation and vice versa.

  18. Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

    Science.gov (United States)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam

  19. Hidden Markov Model of atomic quantum jump dynamics in an optically probed cavity

    DEFF Research Database (Denmark)

    Gammelmark, S.; Molmer, K.; Alt, W.

    2014-01-01

    We analyze the quantum jumps of an atom interacting with a cavity field. The strong atom- field interaction makes the cavity transmission depend on the time dependent atomic state, and we present a Hidden Markov Model description of the atomic state dynamics which is conditioned in a Bayesian......, the atomic state is determined in a Bayesian manner from the measurement data, and we present an iterative protocol, which determines both the atomic state and the model parameters. As a new element in the treatment of observed quantum systems, we employ a Bayesian approach that conditions the atomic state...... manner on the detected signal. We suggest that small variations in the observed signal may be due to spatial motion of the atom within the cavity, and we represent the atomic system by a number of hidden states to account for both the small variations and the internal state jump dynamics. In our theory...

  20. Probing Deviations From Traditional Colloid Filtration Theory by Atomic Force Microscopy

    Science.gov (United States)

    Bowman, R. S.; Reno, M. D.; Altman, S. J.

    2006-12-01

    Understanding colloid transport through saturated media is an integral component of predicting the fate and transport of groundwater contaminants. Developing sound predictive capabilities and establishing effective methodologies for remediation relies heavily on our ability to understand the physical and chemical mechanisms controlling colloid attachment and detachment. Colloid filtration theory (CFT) has been ubiquitously employed to describe particle advection, dispersion, and deposition in saturated media and predicts an exponential decrease in colloid concentration with travel distance from the source. Colloid depositional behavior can be further understood through consideration of Derjaguin Landau Verwey Overbeek (DLVO) interactions. Recent studies give evidence for significant deviations from traditional CFT in the presence of repulsive DLVO interactions. Deposition in the secondary energy minimum has been suggested as a mechanism to explain the observed deviations. This work reports on attempts to quantify the secondary energy minimum as predicted by DLVO theory using direct measurements obtained by atomic force microscopy. The colloid probe technique is used to directly measure the force of interaction between a single carboxylate modified polystyrene latex microsphere and a model collector surface in electrolyte solutions of varying ionic strength. Systematic variations in the size of the microsphere and the ionic strength of the electrolyte solutions yield force measurements that are compared to theoretical predictions and the experimental results of others. The importance of proper sample characterization and cleaning in obtaining meaningful measurements is emphasized. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04- 94AL85000.

  1. Power-Law Stress and Creep Relaxations of Single Cells Measured by Colloidal Probe Atomic Force Microscopy

    OpenAIRE

    Hiratsuka, Shinichiro; Mizutani, Yusuke; Toda, Akitoshi; Fukushima, Norichika; Kawahara, Koichi; Tokumoto, Hiroshi; Okajima, Takaharu

    2009-01-01

    We measured stress and creep relaxations of mouse fibroblast cells arranged and cultured on a microarray, by colloidal probe atomic force microscopy (AFM). A hydrophobic monolayer coating of perfluorodecyltrichlorosilane (FDTS) on the surface of colloidal silica beads significantly reduced the adhesion force of live cells, compared with untreated beads. The rheological behaviors of cells were estimated by averaging several relaxation curves of cells measured by the AFM. Longer-time tailing of...

  2. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy

    NARCIS (Netherlands)

    Sîretanu, Igor; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther

    2016-01-01

    Atomic scale details of surface structure play a crucial role for solid–liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to

  3. Piezoelectric tuning fork probe for atomic force microscopy imaging and specific recognition force spectroscopy of an enzyme and its ligand.

    Science.gov (United States)

    Makky, Ali; Viel, Pascal; Chen, Shu-wen Wendy; Berthelot, Thomas; Pellequer, Jean-Luc; Polesel-Maris, Jérôme

    2013-11-01

    Piezoelectric quartz tuning fork has drawn the attention of many researchers for the development of new atomic force microscopy (AFM) self-sensing probes. However, only few works have been done for soft biological materials imaging in air or aqueous conditions. The aim of this work was to demonstrate the efficiency of the AFM tuning fork probe to perform high-resolution imaging of proteins and to study the specific interaction between a ligand and its receptor in aqueous media. Thus, a new kind of self-sensing AFM sensor was introduced to realize imaging and biochemical specific recognition spectroscopy of glucose oxidase enzyme using a new chemical functionalization procedure of the metallic tips based on the electrochemical reduction of diazonium salt. This scanning probe as well as the functionalization strategy proved to be efficient respectively for the topography and force spectroscopy of soft biological materials in buffer conditions. Copyright © 2013 John Wiley & Sons, Ltd.

  4. Probing the properties of quantum matter; an experimental study in three parts using ultracold atoms

    NARCIS (Netherlands)

    Bons, P.C.

    2015-01-01

    The three experiments described in this thesis investigate fundamental properties of ultracold atoms. Using laser cooling and evaporative cooling, a dilute gas of sodium atoms is cooled to ~100 nK. Under these circumstances a Bose-Einstein condensate (BEC) forms, where millions of atoms collapse

  5. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    Science.gov (United States)

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are

  6. Transverse Micro-structuring of Photonic Crystal Fibers for Industrial Sensors and Side Viewing Probes for Optical Coherence Tomography Applications

    Directory of Open Access Journals (Sweden)

    Sanjay KHER

    2010-05-01

    Full Text Available In this work, we report a simple and easily adaptable technique of lateral micro-machining of Photonic Crystal fibers (PCFs using modulated CO2-laser in conjunction with electrical arc system. The technique is controlled, convenient and precise over wide dimensions (50-250 mm. Lateral access to the holes of PCF provides additional flexibility for sensitive real time detection of gases such as green-house gases. Long period gratings are made in PCF through inscription of micro-grooves for sensitive detection of longitudinal strain. A unique and versatile PCF based probe for possible endoscopic Optical Coherence Tomography (OCT applications is reported.

  7. Positron emission tomography probe to monitor selected sugar metabolism in vivo

    Science.gov (United States)

    Witte, Owen; Clark, Peter M.; Castillo, Blanca Graciela Flores; Jung, Michael E.; Evdokimov, Nikolai M.

    2017-03-14

    The invention disclosed herein discloses selected ribose isomers that are useful as PET probes (e.g. [18F]-2-fluoro-2-deoxy-arabinose). These PET probes are useful, for example, in methods designed to monitor physiological processes including ribose metabolism and/or to selectively observe certain tissue/organs in vivo. The invention disclosed herein further provides methods for making and using such probes.

  8. Ultra-compact swept-source optical coherence tomography handheld probe with motorized focus adjustment (Conference Presentation)

    Science.gov (United States)

    LaRocca, Francesco; Nankivil, Derek; Keller, Brenton; Farsiu, Sina; Izatt, Joseph A.

    2017-02-01

    Handheld optical coherence tomography (OCT) systems facilitate imaging of young children, bedridden subjects, and those with less stable fixation. Smaller and lighter OCT probes allow for more efficient imaging and reduced operator fatigue, which is critical for prolonged use in either the operating room or neonatal intensive care unit. In addition to size and weight, the imaging speed, image quality, field of view, resolution, and focus correction capability are critical parameters that determine the clinical utility of a handheld probe. Here, we describe an ultra-compact swept source (SS) OCT handheld probe weighing only 211 g (half the weight of the next lightest handheld SSOCT probe in the literature) with 20.1 µm lateral resolution, 7 µm axial resolution, 102 dB peak sensitivity, a 27° x 23° field of view, and motorized focus adjustment for refraction correction between -10 to +16 D. A 2D microelectromechanical systems (MEMS) scanner, a converging beam-at-scanner telescope configuration, and an optical design employing 6 different custom optics were used to minimize device size and weight while achieving diffraction limited performance throughout the system's field of view. Custom graphics processing unit (GPU)-accelerated software was used to provide real-time display of OCT B-scans and volumes. Retinal images were acquired from adult volunteers to demonstrate imaging performance.

  9. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  10. Application of colloid probe atomic force microscopy to the adhesion of thin films of viscous and viscoelastic silicone fluids.

    Science.gov (United States)

    Bowen, James; Cheneler, David; Andrews, James W; Avery, Andrew R; Zhang, Zhibing; Ward, Michael C L; Adams, Michael J

    2011-09-20

    The adhesive characteristics of thin films (0.2-2 μm) of linear poly(dimethylsiloxane) (PDMS) liquids with a wide range of molecular weights have been measured using an atomic force microscope with a colloid probe (diameters 5 and 12 μm) for different separation velocities. The data were consistent with a residual film in the contact region having a thickness of ∼6 nm following an extended dwell time before separation of the probe. It was possible to estimate the maximum adhesive force as a function of the capillary number, Ca, by applying existing theoretical models based on capillary interactions and viscous flow except at large values of Ca in the case of viscoelastic fluids, for which it was necessary to develop a nonlinear viscoelastic model. The compliance of the atomic force microscope colloid beam was an important factor in governing the retraction velocity of the probe and therefore the value of the adhesive force, but the inertia of the beam and viscoelastic stress overshoot effects were not significant in the range of separation velocities investigated. © 2011 American Chemical Society

  11. Effect of the tip state during qPlus noncontact atomic force microscopy of Si(100) at 5 K: Probing the probe.

    Science.gov (United States)

    Sweetman, Adam; Jarvis, Sam; Danza, Rosanna; Moriarty, Philip

    2012-01-01

    Noncontact atomic force microscopy (NC-AFM) now regularly produces atomic-resolution images on a wide range of surfaces, and has demonstrated the capability for atomic manipulation solely using chemical forces. Nonetheless, the role of the tip apex in both imaging and manipulation remains poorly understood and is an active area of research both experimentally and theoretically. Recent work employing specially functionalised tips has provided additional impetus to elucidating the role of the tip apex in the observed contrast. We present an analysis of the influence of the tip apex during imaging of the Si(100) substrate in ultra-high vacuum (UHV) at 5 K using a qPlus sensor for noncontact atomic force microscopy (NC-AFM). Data demonstrating stable imaging with a range of tip apexes, each with a characteristic imaging signature, have been acquired. By imaging at close to zero applied bias we eliminate the influence of tunnel current on the force between tip and surface, and also the tunnel-current-induced excitation of silicon dimers, which is a key issue in scanning probe studies of Si(100). A wide range of novel imaging mechanisms are demonstrated on the Si(100) surface, which can only be explained by variations in the precise structural configuration at the apex of the tip. Such images provide a valuable resource for theoreticians working on the development of realistic tip structures for NC-AFM simulations. Force spectroscopy measurements show that the tip termination critically affects both the short-range force and dissipated energy.

  12. Handheld optical coherence tomography-reflectance confocal microscopy probe for detection of basal cell carcinoma and delineation of margins

    Science.gov (United States)

    Iftimia, Nicusor; Yélamos, Oriol; Chen, Chih-Shan J.; Maguluri, Gopi; Cordova, Miguel A.; Sahu, Aditi; Park, Jesung; Fox, William; Alessi-Fox, Christi; Rajadhyaksha, Milind

    2017-07-01

    We present a hand-held implementation and preliminary evaluation of a combined optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) probe for detecting and delineating the margins of basal cell carcinomas (BCCs) in human skin in vivo. A standard OCT approach (spectrometer-based) with a central wavelength of 1310 nm and 0.11 numerical aperture (NA) was combined with a standard RCM approach (830-nm wavelength and 0.9 NA) into a common path hand-held probe. Cross-sectional OCT images and enface RCM images are simultaneously displayed, allowing for three-dimensional microscopic assessment of tumor morphology in real time. Depending on the subtype and depth of the BCC tumor and surrounding skin conditions, OCT and RCM imaging are able to complement each other, the strengths of each helping overcome the limitations of the other. Four representative cases are summarized, out of the 15 investigated in a preliminary pilot study, demonstrating how OCT and RCM imaging may be synergistically combined to more accurately detect BCCs and more completely delineate margins. Our preliminary results highlight the potential benefits of combining the two technologies within a single probe to potentially guide diagnosis as well as treatment of BCCs.

  13. Plasma-deposited fluorocarbon films: insulation material for microelectrodes and combined atomic force microscopy-scanning electrochemical microscopy probes.

    Science.gov (United States)

    Wiedemair, Justyna; Balu, Balamurali; Moon, Jong-Seok; Hess, Dennis W; Mizaikoff, Boris; Kranz, Christine

    2008-07-01

    Pinhole-free insulation of micro- and nanoelectrodes is the key to successful microelectrochemical experiments performed in vivo or in combination with scanning probe experiments. A novel insulation technique based on fluorocarbon insulation layers deposited from pentafluoroethane (PFE, CF3CHF2) plasmas is presented as a promising electrical insulation approach for microelectrodes and combined atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) probes. The deposition allows reproducible and uniform coating, which is essential for many analytical applications of micro- and nanoelectrodes such as, e.g., in vivo experiments and SECM experiments. Disk-shaped microelectrodes and frame-shaped AFM tip-integrated electrodes have been fabricated by postinsulation focused ion beam (FIB) milling. The thin insulation layer for combined AFM-SECM probes renders this fabrication technique particularly useful for submicro insulation providing radius ratios of the outer insulation versus the disk electrode (RG values) suitable for SECM experiments. Characterization of PFE-insulated AFM-SECM probes will be presented along with combined AFM-SECM approach curves and imaging.

  14. Mg I as a probe of the solar chromosphere - The atomic model

    Science.gov (United States)

    Mauas, Pablo J.; Avrett, Eugene H.; Loeser, Rudolf

    1988-01-01

    This paper presents a complete atomic model for Mg I line synthesis, where all the atomic parameters are based on recent experimental and theoretical data. It is shown how the computed profiles at 4571 A and 5173 A are influenced by the choice of these parameters and the number of levels included in the model atom. In addition, observed profiles of the 5173 A b2 line and theoretical profiles for comparison (based on a recent atmospheric model for the average quiet sun) are presented.

  15. Nanofabrication technique based on localized photocatalytic reactions using a TiO2-coated atomic force microscopy probe

    Science.gov (United States)

    Shibata, Takayuki; Iio, Naohiro; Furukawa, Hiromi; Nagai, Moeto

    2017-02-01

    We performed a fundamental study on the photocatalytic degradation of fluorescently labeled DNA molecules immobilized on titanium dioxide (TiO2) thin films under ultraviolet irradiation. The films were prepared by the electrochemical anodization of Ti thin films sputtered on silicon substrates. We also confirmed that the photocurrent arising from the photocatalytic oxidation of DNA molecules can be detected during this process. We then demonstrated an atomic force microscopy (AFM)-based nanofabrication technique by employing TiO2-coated AFM probes to penetrate living cell membranes under near-physiological conditions for minimally invasive intracellular delivery.

  16. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: probing atomic structure in situ.

    Science.gov (United States)

    Wang, Hsiu-Wen; Fanelli, Victor R; Reiche, Helmut M; Larson, Eric; Taylor, Mark A; Xu, Hongwu; Zhu, Jinlong; Siewenie, Joan; Page, Katharine

    2014-12-01

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO2 measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO2 sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H2 and natural gas uptake/storage.

  17. Atomic probe microscopy of 3C SiC films grown on 6H SiC substrates

    Science.gov (United States)

    Steckl, A. J.; Roth, M. D.; Powell, J. A.; Larkin, D. J.

    1993-01-01

    The surface of 3C SiC films grown on 6H SiC substrates has been studied by atomic probe microscopy in air. Atomic-scale images of the 3C SiC surface have been obtained by STM which confirm the 111 line type orientation of the cubic 3C layer grown on the 0001 plane type surface of the hexagonal 6H substrate. The nearest-neighbor atomic spacing for the 3C layer has been measured to be 3.29 +/- 0.2 A, which is within 7 percent of the bulk value. Shallow terraces in the 3C layer have been observed by STM to separate regions of very smooth growth in the vicinity of the 3C nucleation point from considerably rougher 3C surface regions. These terraces are oriented at right angles to the growth direction. Atomic force microscopy has been used to study etch pits present on the 6H substrate due to high temperature HCl cleaning prior to CVD growth of the 3C layer. The etch pits have hexagonal symmetry and vary in depth from 50 nm to 1 micron.

  18. Miniature forward-imaging B-scan optical coherence tomography probe to guide real-time laser ablation.

    Science.gov (United States)

    Li, Zhuoyan; Shen, Jin H; Kozub, John A; Prasad, Ratna; Lu, Pengcheng; Joos, Karen M

    2014-03-01

    Investigations have shown that pulsed lasers tuned to 6.1 µm in wavelength are capable of ablating ocular and neural tissue with minimal collateral damage. This study investigated whether a miniature B-scan forward-imaging optical coherence tomography (OCT) probe can be combined with the laser to provide real-time visual feedback during laser incisions. A miniature 25-gauge B-scan forward-imaging OCT probe was developed and combined with a 250 µm hollow-glass waveguide to permit delivery of 6.1 µm laser energy. A gelatin mixture and both porcine corneal and retinal tissues were simultaneously imaged and lased (6.1 µm, 10 Hz, 0.4-0.7 mJ) through air. The ablation studies were observed and recorded in real time. The crater dimensions were measured using OCT imaging software (Bioptigen, Durham, NC). Histological analysis was performed on the ocular tissues. The combined miniature forward-imaging OCT and mid-infrared laser-delivery probe successfully imaged real-time tissue ablation in gelatin, corneal tissue, and retinal tissue. Application of a constant number of 60 pulses at 0.5 mJ/pulse to the gelatin resulted in a mean crater depth of 123 ± 15 µm. For the corneal tissue, there was a significant correlation between the number of pulses used and depth of the lased hole (Pearson correlation coefficient = 0.82; P = 0.0002). Histological analysis of the cornea and retina tissues showed discrete holes with minimal thermal damage. A combined miniature OCT and laser-delivery probe can monitor real-time tissue laser ablation. With additional testing and improvements, this novel instrument has the future possibility of effectively guiding surgeries by simultaneously imaging and ablating tissue. © 2013 Wiley Periodicals, Inc.

  19. A Miniature Forward-imaging B-scan Optical Coherence Tomography Probe to Guide Real-time Laser Ablation

    Science.gov (United States)

    Li, Zhuoyan; Shen, Jin H.; Kozub, John A.; Prasad, Ratna; Lu, Pengcheng; Joos, Karen M.

    2014-01-01

    Background and Objective Investigations have shown that pulsed lasers tuned to 6.1 μm in wavelength are capable of ablating ocular and neural tissue with minimal collateral damage. This study investigated whether a miniature B-scan forward-imaging optical coherence tomography (OCT) probe can be combined with the laser to provide real-time visual feedback during laser incisions. Study Design/Methods and Materials A miniature 25-gauge B-scan forward-imaging OCT probe was developed and combined with a 250 μm hollow-glass waveguide to permit delivery of 6.1 μm laser energy. A gelatin mixture and both porcine corneal and retinal tissues were simultaneously imaged and lased (6.1 μm, 10 Hz, 0.4-0.7 mJ) through air. The ablation studies were observed and recorded in real time. The crater dimensions were measured using OCT imaging software (Bioptigen, Durham, NC). Histological analysis was performed on the ocular tissues. Results The combined miniature forward-imaging OCT and mid-infrared laser-delivery probe successfully imaged real-time tissue ablation in gelatin, corneal tissue, and retinal tissue. Application of a constant number of 60 pulses at 0.5 mJ/pulse to the gelatin resulted in a mean crater depth of 123 ± 15 μm. For the corneal tissue, there was a significant correlation between the number of pulses used and depth of the lased hole (Pearson correlation coefficient = 0.82; P = 0.0002). Histological analysis of the cornea and retina tissues showed discrete holes with minimal thermal damage. Conclusions A combined miniature OCT and laser -delivery probe can monitor real-time tissue laser ablation. With additional testing and improvements, this novel instrument has the future possibility of effectively guiding surgeries by simultaneously imaging and ablating tissue. PMID:24648326

  20. [Connection of magnetic antisense probe with SK-Br-3 oncocyte mRNA nucleotide detected by high resolution atomic force microscope].

    Science.gov (United States)

    Tan, Shude; Ouyang, Yu; Li, Xinyou; Wen, Ming; Li, Shaolin

    2011-06-01

    The present paper is aimed to detect superparamagnetic iron oxide labeled c-erbB2 oncogene antisense oligonucleotide probe (magnetic antisense probe) connected with SK-Br-3 oncocyte mRNA nucleotide by high resolution atomic force microscope (AFM). We transfected SK-Br-3 oncocyte with magnetic antisense probe, then observed the cells by AFM with high resolution and detected protein expression and magnetic resonance imagine (MRI). The high resolution AFM clearly showed the connection of the oligonucleotide remote end of magnetic antisense probe with the mRNA nucleotide of oncocyte. The expression of e-erbB2 protein in SK-Br3 cells were highly inhibited by using magnetic antisense probe. We then obtained the lowest signal to noise ratio (SNR) of SK-Br-3 oncocyte transfected with magnetic antisense probe by MRI (Pmagnetic antisense probe and SK-Br-3 mRNA of tumor cell nuclear.

  1. Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies.

    Science.gov (United States)

    Tettamanzi, Giuseppe Carlo; Hile, Samuel James; House, Matthew Gregory; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y

    2017-03-28

    The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

  2. Probing Magnetism in 2D Molecular Networks after in Situ Metalation by Transition Metal Atoms.

    Science.gov (United States)

    Schouteden, K; Ivanova, Ts; Li, Z; Iancu, V; Janssens, E; Van Haesendonck, C

    2015-03-19

    Metalated molecules are the ideal building blocks for the bottom-up fabrication of, e.g., two-dimensional arrays of magnetic particles for spintronics applications. Compared to chemical synthesis, metalation after network formation by an atom beam can yield a higher degree of control and flexibility and allows for mixing of different types of magnetic atoms. We report on successful metalation of tetrapyridyl-porphyrins (TPyP) by Co and Cr atoms, as demonstrated by scanning tunneling microscopy experiments. For the metalation, large periodic networks formed by the TPyP molecules on a Ag(111) substrate are exposed in situ to an atom beam. Voltage-induced dehydrogenation experiments support the conclusion that the porphyrin macrocycle of the TPyP molecule incorporates one transition metal atom. The newly synthesized Co-TPyP and Cr-TPyP complexes exhibit striking differences in their electronic behavior, leading to a magnetic character for Cr-TPyP only as evidenced by Kondo resonance measurements.

  3. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Science.gov (United States)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio

    2017-02-01

    Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO2 probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  4. Probing buried carbon nanotubes within polymer-nanotube composite matrices by Atomic Force Microscopy

    NARCIS (Netherlands)

    Phang, In Yee; Liu, Tianxi; Zhang, Wei-De; Schönherr, Holger; Vancso, Gyula J.

    2007-01-01

    Multi-walled carbon nanotubes (MW-CNT) inside a polyamide-6 (PA6)–MW-CNT composite were visualized by atomic force microscopy (i) in a field-assisted intermittent contact and (ii) in the tunneling (TUNA) mode. Individual buried MW-CNTs were clearly discerned within the PA6 matrix. An average

  5. Shot noise as a probe of spin-polarized transport through single atoms

    DEFF Research Database (Denmark)

    Burtzlaff, Andreas; Weismann, Alexander; Brandbyge, Mads

    2015-01-01

    Single atoms on Au(111) surfaces have been contacted with the Au tip of a low temperature scanning tunneling microscope. The shot noise of the current through these contacts has been measured up to frequencies of 120 kHz and Fano factors have been determined to characterize the transport channels...

  6. Atomic and Electronic Structure of Quantum Dots Measured with Scanning Probe Techniques

    NARCIS (Netherlands)

    Sun, Z.|info:eu-repo/dai/nl/314075674

    2012-01-01

    This thesis deals with low temperature scanning tunneling microscopy/spectroscopy and atomic force microscopy (LT-STM/STS and AFM) studies on colloidal semiconductor and graphene quantum dots (g-QDs). These nanostructures are interesting because they show tunable electrical and optical properties

  7. The extended wedge method: Atomic force microscope friction calibration for improved tolerance to instrument misalignments, tip offset, and blunt probes

    Science.gov (United States)

    Khare, H. S.; Burris, D. L.

    2013-05-01

    One of the major challenges in understanding and controlling friction is the difficulty in bridging the length and time scales of macroscale contacts and those of the single asperity interactions they comprise. While the atomic force microscope (AFM) offers a unique ability to probe tribological surfaces in a wear-free single-asperity contact, instrument calibration challenges have limited the usefulness of this technique for quantitative nanotribological studies. A number of lateral force calibration techniques have been proposed and used, but none has gained universal acceptance due to practical considerations, configuration limitations, or sensitivities to unknowable error sources. This paper describes a simple extension of the classic wedge method of AFM lateral force calibration which: (1) allows simultaneous calibration and measurement on any substrate, thus eliminating prior tip damage and confounding effects of instrument setup adjustments; (2) is insensitive to adhesion, PSD cross-talk, transducer/piezo-tube axis misalignment, and shear-center offset; (3) is applicable to integrated tips and colloidal probes; and (4) is generally applicable to any reciprocating friction coefficient measurement. The method was applied to AFM measurements of polished carbon (99.999% graphite) and single crystal MoS2 to demonstrate the technique. Carbon and single crystal MoS2 had friction coefficients of μ = 0.20 ± 0.04 and μ = 0.006 ± 0.001, respectively, against an integrated Si probe. Against a glass colloidal sphere, MoS2 had a friction coefficient of μ = 0.005 ± 0.001. Generally, the measurement uncertainties ranged from 10%-20% and were driven by the effect of actual frictional variation on the calibration rather than calibration error itself (i.e., due to misalignment, tip-offset, or probe radius).

  8. Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

    CERN Document Server

    Wade, Christopher G; Keaveney, James; Adams, Charles S; Weatherill, Kevin J

    2014-01-01

    We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

  9. Nonlocal Response of Metallic Nanospheres Probed by Light, Electrons, and Atoms

    DEFF Research Database (Denmark)

    Christensen, Thomas; Yan, Wei; Raza, Søren

    2014-01-01

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss...... spectroscopy, and light scattering. These constitute two near-field and one far-field measurements, with zero-, one-, and two-dimensional excitation sources, respectively. We search for the clearest signatures of hydrodynamic pressure waves in nanospheres. We employ a linearized hydrodynamic model, and Mie...

  10. Graphene Coatings: Probing the Limits of the One Atom Thick Protection Layer

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Balog, Richard

    2012-01-01

    The limitations of graphene as an effective corrosion-inhibiting coating on metal surfaces, here exemplified by the hex-reconstructed Pt(100) surface, are probed by scanning tunneling microscopy measurements and density functional theory calculations. While exposure of small molecules directly onto...... the Pt(100) surface will lift the reconstruction, a single graphene layer is observed to act as an effective coating, protecting the reactive surface from O2 exposure and thus preserving the reconstruction underneath the graphene layer in O2 pressures as high as 104 mbar. A similar protective effect...

  11. Global measurements of coarse-mode aerosol size distributions - first results from the Atmospheric Tomography Mission (ATom)

    Science.gov (United States)

    Weinzierl, B.; Dollner, M.; Schuh, H.; Brock, C. A.; Bui, T. V.; Gasteiger, J.; Froyd, K. D.; Schwarz, J. P.; Spanu, A.; Murphy, D. M.; Katich, J. M.; Kupc, A.; Williamson, C.

    2016-12-01

    Although coarse-mode aerosol (>1 µm diameter), composed mainly of mineral dust and sea-salt, is highly abundant over large regions of the world, these particles form a particularly poorly understood and characterized subset of atmospheric aerosol constituents. The NASA-sponsored Atmospheric Tomography Mission (ATom) is an unprecedented field program that investigates how human emissions affect air quality and climate change. ATom provides a singular opportunity to characterize the global coarse-mode size distribution by continuously profiling between 0.2 and 13 km with the NASA DC-8 research aircraft while traveling from the high Arctic down south the middle of the Pacific Ocean, to the Southern Ocean and back north over the Atlantic Ocean basin in four seasons. For ATom, the DC-8 aircraft has been equipped with multiple instruments to observe the composition of the air. The coarse mode and cloud particle size distribution is measured in-situ with a Cloud, Aerosol, and Precipitation Spectrometer (CAPS) mounted under the wing of the DC-8 research aircraft. The CAPS consists of an optical spectrometer providing size distributions in the size range between 0.5 and 50 µm and an imager detecting number concentration, size and shape of particles between 15 and 930 µm diameter. Early ATom flights indicated complicated vertical layering: over the sea, we regularly observed sea salt aerosol which extended from the ground up to 0.6-1 km altitude. In addition - depending on the location of the measurements - we frequently found layers with coarse mode aerosol originating from deserts and biomass burning aerosol aloft. In this study, we will present first results of coarse mode aerosol observations from the entire first ATom deployment in summer 2016. We will show vertical profiles of coarse mode aerosol number concentration, discuss their interhemispheric differences, and look into the question how frequently coarse-mode aerosol is externally mixed with submicron black

  12. Structure and orbital ordering of ultrathin LaVO{sub 3} probed by atomic resolution electron microscopy and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors-Vrejoiu, Ionela; Engelmayer, Johannes; Loosdrecht, Paul H.M. van [II. Physikalisches Institut, Koeln Univ. (Germany); Jin, Lei; Jia, Chun-Lin [Peter Gruenberg Institut (PGI-5) and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH (Germany); Himcinschi, Cameliu [Institut fuer Theoretische Physik, TU Bergakademie Freiberg (Germany); Hensling, Felix; Waser, Rainer; Dittmann, Regina [Peter Gruenberg Institut (PGI-7), Forschungszentrum Juelich GmbH (Germany)

    2017-03-15

    Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO{sub 3} films. The transition to orbital ordering of epitaxial layers as thin as ∼4 nm was probed by temperature-dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm{sup -1} Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO{sub 3} films at about 130 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. The limit of time resolution in frequency modulation atomic force microscopy by a pump-probe approach

    Science.gov (United States)

    Schumacher, Zeno; Spielhofer, Andreas; Miyahara, Yoichi; Grutter, Peter

    2017-01-01

    Atomic force microscopy (AFM) routinely achieves structural information in the sub-nm length scale. Measuring time resolved properties on this length scale to understand kinetics at the nm scale remains an elusive goal. We present a general analysis of the lower limit for time resolution in AFM. Our finding suggests that the time resolution in AFM is ultimately limited by the well-known thermal limit of AFM and not as often proposed by the mechanical response time of the force sensing cantilever. We demonstrate a general pump-probe approach using the cantilever as a detector responding to the averaged signal. This method can be applied to any excitation signal such as electrical, thermal, magnetic or optical. Experimental implementation of this method allows us to measure a photocarrier decay time of ˜1 ps in low temperature grown GaAs using a cantilever with a resonant frequency of 280 kHz.

  14. Indirect modulation of nonmagnetic probes for force modulation atomic force microscopy.

    Science.gov (United States)

    Li, Jie-Ren; Garno, Jayne C

    2009-02-15

    Frequency-dependent changes for phase and amplitude images are demonstrated with test platforms of organosilane ring patterns, using force modulation atomic force microscopy (FM-AFM) with an alternate instrument configuration. The imaging setup using indirect magnetic modulation (IMM) is based on indirect oscillation of soft, nonmagnetic cantilevers, with spring constants coating is not required to drive the periodic oscillation of the tip. The instrument configuration for IMM may not be practical for intermittent imaging modes, which often work best with stiff cantilevers. However, indirect actuation provides an effective approach for imaging with low force setpoints and is well-suited for dynamic AFM modes using continuous contact imaging.

  15. Applications of a versatile modelling approach to 3D atom probe simulations.

    Science.gov (United States)

    Oberdorfer, Christian; Eich, Sebastian Manuel; Lütkemeyer, Martin; Schmitz, Guido

    2015-12-01

    The article addresses application examples of a flexible simulation approach, which is based on an irregular mesh of Voronoi cells. The detailed atomic structure of APT field emitters is represented by Wigner-Seitz cells. In this way, arbitrary crystal structures can be modelled. The electric field results from the solution of the Poisson equation. The evaporation sequence of atoms from the emitter surface is enabled by calculation of the field-induced force, which acts on the surface cells. Presented examples show simulated field desorption maps of a cubic fcc structure in comparison to the close-packed hcp structure. Additionally, the desorption maps of the cubic sc, bcc, and fcc lattices in orientation are presented. The effect of inhomogeneous evaporation conditions on the emitter apex curvature is demonstrated. Reconstructions derived from the simulation of Σ5 GBs differently inclined with respect to the emitter axis are analyzed. Finally, the stress exerted on an embedded nano-particle during the simulated evaporation with inhomogeneous evaporation thresholds is estimated. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Probing many-body dynamics on a 51-atom quantum simulator.

    Science.gov (United States)

    Bernien, Hannes; Schwartz, Sylvain; Keesling, Alexander; Levine, Harry; Omran, Ahmed; Pichler, Hannes; Choi, Soonwon; Zibrov, Alexander S; Endres, Manuel; Greiner, Markus; Vuletić, Vladan; Lukin, Mikhail D

    2017-11-29

    Controllable, coherent many-body systems can provide insights into the fundamental properties of quantum matter, enable the realization of new quantum phases and could ultimately lead to computational systems that outperform existing computers based on classical approaches. Here we demonstrate a method for creating controlled many-body quantum matter that combines deterministically prepared, reconfigurable arrays of individually trapped cold atoms with strong, coherent interactions enabled by excitation to Rydberg states. We realize a programmable Ising-type quantum spin model with tunable interactions and system sizes of up to 51 qubits. Within this model, we observe phase transitions into spatially ordered states that break various discrete symmetries, verify the high-fidelity preparation of these states and investigate the dynamics across the phase transition in large arrays of atoms. In particular, we observe robust many-body dynamics corresponding to persistent oscillations of the order after a rapid quantum quench that results from a sudden transition across the phase boundary. Our method provides a way of exploring many-body phenomena on a programmable quantum simulator and could enable realizations of new quantum algorithms.

  17. Probing deviations from traditional colloid filtration theory by atomic forces microscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Reno, Marissa Devan

    2005-12-01

    Colloid transport through saturated media is an integral component of predicting the fate and transport of groundwater contaminants. Developing sound predictive capabilities and establishing effective methodologies for remediation relies heavily on our ability to understand the pertinent physical and chemical mechanisms. Traditionally, colloid transport through saturated media has been described by classical colloid filtration theory (CFT), which predicts an exponential decrease in colloid concentration with travel distance. Furthermore, colloid stability as determined by Derjaguin-Landau-Veney-Overbeek (DLVO) theory predicts permanent attachment of unstable particles in a primary energy minimum. However, recent studies show significant deviations from these traditional theories. Deposition in the secondary energy minimum has been suggested as a mechanism by which observed deviations can occur. This work investigates the existence of the secondary energy minimum as predicted by DLVO theory using direct force measurements obtained by Atomic Forces Microscopy. Interaction energy as a function of separation distance between a colloid and a quartz surface in electrolyte solutions of varying ionic strength are obtained. Preliminary force measurements show promise and necessary modifications to the current experimental methodology have been identified. Stringent surface cleaning procedures and the use of high-purity water for all injectant solutions is necessary for the most accurate and precise measurements. Comparisons between direct physical measurements by Atomic Forces Microscopy with theoretical calculations and existing experimental findings will allow the evaluation of the existence or absence of a secondary energy minimum.

  18. Precipitates in Al-Cu alloys revisited: Atom-probe tomographic experiments and first-principles calculations of compositional evolution and interfacial segregation

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Aniruddha [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 (United States); Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Siegel, Donald J., E-mail: djsiege@umich.edu [Mechanical Engineering Department, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109-2125 (United States); Applied Physics Program, University of Michigan, 2350 Hayward St., Ann Arbor, MI 48109-2125 (United States); Wolverton, C. [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 (United States); Seidman, David N. [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 (United States); Northwestern University Center for Atom-Probe Tomography, Northwestern University, Evanston, IL 60208 (United States)

    2011-09-15

    Atom-probe tomography, transmission electron microscopy, X-ray diffraction and first-principles calculations are employed to study: (i) compositional evolution of GPII zones and {theta}' precipitates; and (ii) solute segregation at {alpha}-Al/{theta}' interfaces in Al-1.7 at.% Cu (Al-4 wt.% Cu) alloys. GPII zones are observed after aging at 438 K for 8 h, whereas higher aging temperatures, 463 K for 8 h and 533 K for 4 h, reveal only {theta}' precipitates. Most GPII zones and {theta}' precipitates are demonstrated to be Cu-deficient at the lower two aging temperatures; only the 533 K treatment resulted in {theta}' stoichiometries consistent with the expected Al{sub 2}Cu equilibrium composition. For alloys containing {approx}200 at. ppm Si we find evidence of Si partitioning to GPII zones and {theta}' precipitates. Significant Si segregation is observed at the coherent {alpha}-Al/{theta}' interface for aging at 533 K, resulting in an interfacial Si concentration more than 11 times greater than in the {alpha}-Al matrix. Importantly, the Si interfacial concentration undergoes a transition from a non-equilibrium delocalized profile to an equilibrium localized profile as the aging temperature is increased from 463 to 533 K. Consistent with these measurements, first-principles calculations predict a strong thermodynamic driving force favoring Si partitioning to Cu sites in {theta}'. Silicon segregation at, and partitioning to, {theta}' precipitates results in a decrease in interfacial free energy, and concomitantly an increase in the nucleation current. Our results suggest that Si catalyzes the early stages of precipitation in these alloys, consistent with the higher precipitate number densities observed in commercial Al-Cu-Si alloys.

  19. Atom-Probe Tomographic Investigation of Austenite Stability and Carbide Precipitation in a TRIP-Assisted 10 Wt Pct Ni Steel and Its Weld Heat-Affected Zones

    Science.gov (United States)

    Jain, Divya; Seidman, David N.; Barrick, Erin J.; DuPont, John N.

    2018-01-01

    Newly developed low-carbon 10 wt pct Ni-Mo-Cr-V martensitic steels rely on the Ni-enriched, thermally stable austenite [formed via multistep intercritical Quench-Lamellarization-Tempering (QLT)-treatment] for their superior mechanical properties, specifically ballistic resistance. Critical to the thermal stability of austenite is its composition, which can be severely affected in the weld heat-affected zones (HAZs) and thus needs investigations. This article represents the first study of the nanoscale redistributions of C, Ni, and Mn in single-pass HAZ microstructures of QLT-treated 10 wt pct Ni steels. Local compositions of Ni-rich regions (representative of austenite compositions) in the HAZs are determined using site-specific 3-D atom-probe tomography (APT). Martensite-start temperatures are then calculated for these compositions, employing the Ghosh-Olson thermodynamic and kinetics approach. These calculations predict that austenite (present at high temperatures) in the HAZs is susceptible to a martensitic transformation upon cooling to room temperature, unlike the austenite in the QLT-treated base-metal. While C in the QLT-treated base-metal is consumed primarily in MC and M2C-type carbide precipitates (M is Mo, Cr, V), its higher concentration in the Ni-rich regions in the HAZs indicates the dissolution of carbide precipitates, particularly M2C carbide precipitates. The role of M2C carbide precipitates and austenite stability is discussed in relation to the increase in microhardness values observed in the HAZs, relative to the QLT-treated base-metal. Insights gained from this research on austenite stability and carbide precipitation in the single-pass HAZ microstructures will assist in designing multiple weld cycles for these novel 10 wt pct Ni steels.

  20. Pyrenyl Derivative with a Four-Atom Linker That Can Probe the Local Polarity of Pyrene-Labeled Macromolecules.

    Science.gov (United States)

    Farhangi, Shiva; Duhamel, Jean

    2016-02-04

    The fluorescent probe 1-pyrenemethoxyethanol (PyMeEGOH) was designed to replace commercially available 1-pyrenebutanol (PyButOH) as an alternative fluorescent label to probe the internal dynamics and interior polarity of macromolecules by steady-state and time-resolved fluorescence. While excimer formation and sensitivity to solvent polarity are two well-recognized properties of pyrene, much less known is that these properties are often mutually exclusive when a 1-pyrenebutyl derivative is used to prepare pyrene-labeled macromolecules (PyLMs). As the sensitivity of pyrene to solvent polarity is a result of its symmetry, attaching a butyl group to pyrene breaks the symmetry of pyrene, so that the 1-pyrenebutyl derivatives are much less sensitive to the polarity of their environment compared to unmodified pyrene. This report demonstrates that replacement of a methylene group in the β-position of PyButOH by an oxygen atom, such as in PyMeEGOH, restores the sensitivity of this pyrene derivative to the polarity of its local environment to the same level as that of molecular pyrene without impeding pyrene excimer formation upon incorporation into PyLMs.

  1. Lyman-tomography of cosmic infrared background fluctuations with euclid : probing emissions and baryonic acoustic oscillations at z ≳ 1

    Energy Technology Data Exchange (ETDEWEB)

    Kashlinsky, A.; Arendt, R. G. [Observational Cosmology Lab, NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Atrio-Barandela, F. [Department of Theoretical Physics, University of Salamanca (Spain); Helgason, K., E-mail: Alexander.Kashlinsky@nasa.gov [MPA, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)

    2015-11-01

    The Euclid space mission, designed to probe evolution of the Dark Energy (DE), will map a large area of the sky at three adjacent near-IR filters, Y, J, and H. This coverage will also enable mapping source-subtracted cosmic infrared background (CIB) fluctuations with unprecedented accuracy on sub-degree angular scales. Here, we propose methodology, using the Lyman-break tomography applied to the Euclid -based CIB maps, to accurately isolate the history of CIB emissions as a function of redshift from 10 ≲ z ≲ 20 and to identify the baryonic acoustic oscillations (BAOs) at those epochs. To identify the BAO signature, we would assemble individual CIB maps over conservatively large contiguous areas of ≳400 deg{sup 2}. The method can isolate the CIB spatial spectrum by z to sub-percent statistical accuracy. We illustrate this with a specific model of CIB production at high z normalized to reproduce the measured Spitzer -based CIB fluctuation. We show that even if the latter contains only a small component from high- z sources, the amplitude of that component can be accurately isolated with the methodology proposed here and the BAO signatures at z ≳ 10 are recovered well from the CIB fluctuation spatial spectrum. Probing the BAO at those redshifts will be an important test of the underlying cosmological paradigm and would narrow the overall uncertainties on the evolution of cosmological parameters, including the DE. Similar methodology is applicable to the planned WFIRST mission, where we show that a possible fourth near-IR channel at ≥2 μ m would be beneficial.

  2. High sensitivity detection of protein molecules picked up on a probe of atomic force microscope based on the fluorescence detection by a total internal reflection fluorescence microscope.

    Science.gov (United States)

    Yamada, Takafumi; Afrin, Rehana; Arakawa, Hideo; Ikai, Atsushi

    2004-07-02

    We developed a method to detect and identify proteins on a probe of the atomic force microscope (AFM) with a high sensitivity. Due to a low background noise of the total internal reflection fluorescence microscope employed as a detecting system, we were able to achieve a high enough sensitivity to detect zeptomole orders of protein molecules immobilized on the tip. Several different methods to immobilize protein molecules to AFM-probes were tested, meant for a wide range of applications of this method. Furthermore, we demonstrated that different proteins were clearly distinguished by immunofluorescence microscopy on the probe using their specific antibodies.

  3. Atomic force microscopy and spectroscopy to probe single membrane proteins in lipid bilayers.

    Science.gov (United States)

    Sapra, K Tanuj

    2013-01-01

    The atomic force microscope (AFM) has opened vast avenues hitherto inaccessible to the biological scientist. The high temporal (millisecond) and spatial (nanometer) resolutions of the AFM are suited for studying many biological processes in their native conditions. The AFM cantilever stylus is aptly termed as a "lab on a tip" owing to its versatility as an imaging tool as well as a handle to manipulate single bonds and proteins. Recent examples assert that the AFM can be used to study the mechanical properties and monitor processes of single proteins and single cells, thus affording insight into important mechanistic details. This chapter specifically focuses on practical and analytical protocols of single-molecule AFM methodologies related to high-resolution imaging and single-molecule force spectroscopy of membrane proteins. Both these techniques are operator oriented, and require specialized working knowledge of the instrument, theoretical, and practical skills.

  4. Probing nucleic acid-ion interactions with buffer exchange-atomic emission spectroscopy.

    Science.gov (United States)

    Greenfeld, Max; Herschlag, Daniel

    2009-01-01

    The ion atmosphere of nucleic acids directly affects measured biochemical and biophysical properties. However, study of the ion atmosphere is difficult due to its diffuse and dynamic nature. Standard techniques available have significant limitations in sensitivity, specificity, and directness of the assays. Buffer exchange-atomic emission spectroscopy (BE-AES) was developed to overcome many of the limitations of previously available techniques. This technique can provide a complete accounting of all ions constituting the ionic atmosphere of a nucleic acid at thermodynamic equilibrium. Although initially developed for the study of the ion atmosphere of nucleic acids, BE-AES has also been applied to study site-bound ions in RNA and protein. Copyright © 2009 Elsevier Inc. All rights reserved.

  5. FIB-SEM Tomography Probes the Mesoscale Pore Space of an Individual Catalytic Cracking Particle.

    Science.gov (United States)

    de Winter, D A Matthijs; Meirer, Florian; Weckhuysen, Bert M

    2016-05-06

    The overall performance of a catalyst particle strongly depends on the ability of mass transport through its pore space. Characterizing the three-dimensional structure of the macro- and mesopore space of a catalyst particle and establishing a correlation with transport efficiency is an essential step toward designing highly effective catalyst particles. In this work, a generally applicable workflow is presented to characterize the transport efficiency of individual catalyst particles. The developed workflow involves a multiscale characterization approach making use of a focused ion beam-scanning electron microscope (FIB-SEM). SEM imaging is performed on cross sections of 10.000 μm2, visualizing a set of catalyst particles, while FIB-SEM tomography visualized the pore space of a large number of 8 μm3 cubes (subvolumes) of individual catalyst particles. Geometrical parameters (porosity, pore connectivity, and heterogeneity) of the material were used to generate large numbers of virtual 3D volumes resembling the sample's pore space characteristics, while being suitable for computationally demanding transport simulations. The transport ability, defined as the ratio of unhindered flow over hindered flow, is then determined via transport simulations through the virtual volumes. The simulation results are used as input for an upscaling routine based on an analogy with electrical networks, taking into account the spatial heterogeneity of the pore space over greater length scales. This novel approach is demonstrated for two distinct types of industrially manufactured fluid catalytic cracking (FCC) particles with zeolite Y as the active cracking component. Differences in physicochemical and catalytic properties were found to relate to differences in heterogeneities in the spatial porosity distribution. In addition to the characterization of existing FCC particles, our method of correlating pore space with transport efficiency does also allow for an up-front evaluation of

  6. Fluorescence-Guided Probes of Aptamer-Targeted Gold Nanoparticles with Computed Tomography Imaging Accesses for in Vivo Tumor Resection

    Science.gov (United States)

    Li, Cheng-Hung; Kuo, Tsung-Rong; Su, Hsin-Jan; Lai, Wei-Yun; Yang, Pan-Chyr; Chen, Jinn-Shiun; Wang, Di-Yan; Wu, Yi-Chun; Chen, Chia-Chun

    2015-01-01

    Recent development of molecular imaging probes for fluorescence-guided surgery has shown great progresses for determining tumor margin to execute the tissue resection. Here we synthesize the fluorescent gold nanoparticles conjugated with diatrizoic acid and nucleolin-targeted AS1411 aptamer. The nanoparticle conjugates exhibit high water-solubility, good biocompatibility, visible fluorescence and strong X-ray attenuation for computed tomography (CT) contrast enhancement. The fluorescent nanoparticle conjugates are applied as a molecular contrast agent to reveal the tumor location in CL1-5 tumor-bearing mice by CT imaging. Furthermore, the orange-red fluorescence emitting from the conjugates in the CL1-5 tumor can be easily visualized by the naked eyes. After the resection, the IVIS measurements show that the fluorescence signal of the nanoparticle conjugates in the tumor is greatly enhanced in comparison to that in the controlled experiment. Our work has shown potential application of functionalized nanoparticles as a dual-function imaging agent in clinical fluorescence-guided surgery. PMID:26507179

  7. Multimodality Imaging Probe for Positron Emission Tomography and Fluorescence Imaging Studies

    Directory of Open Access Journals (Sweden)

    Suresh K. Pandey

    2014-05-01

    Full Text Available Our goal is to develop multimodality imaging agents for use in cell tracking studies by positron emission tomography (PET and optical imaging (OI. For this purpose, bovine serum albumin (BSA was complexed with biotin (histologic studies, 5(6- carboxyfluorescein, succinimidyl ester (FAM SE (OI studies, and diethylenetriamine pentaacetic acid (DTPA for chelating gallium 68 (PET studies. For synthesis of BSA-biotin-FAM-DTPA, BSA was coupled to (+-biotin N-hydroxysuccinimide ester (biotin-NHSI. BSA- biotin was treated with DTPA-anhydride and biotin-BSA-DTPA was reacted with FAM. The biotin-BSA-DTPA-FAM was reacted with gallium chloride 3 to 5 mCi eluted from the generator using 0.1 N HCl and was passed through basic resin (AG 11 A8 and 150 mCi (100 μL, pH 7–8 was incubated with 0.1 mg of FAM conjugate (100 μL at room temperature for 15 minutes to give 66Ga-BSA-biotin-DTPA-FAM. A shaved C57 black mouse was injected with FAM conjugate (50 μL at one flank and FAM-68Ga (50 μL, 30 mCi at the other. Immediately after injection, the mouse was placed in a fluorescence imaging system (Kodak In-Vivo F, Bruker Biospin Co., Woodbridge, CT and imaged (Λex: 465 nm, Λem: 535 nm, time: 8 seconds, Xenon Light Source, Kodak. The same mouse was then placed under an Inveon microPET scanner (Siemens Medical Solutions, Knoxville, TN injected (intravenously with 25 μCi of 18F and after a half-hour (to allow sufficient bone uptake was imaged for 30 minutes. Molecular weight determined using matrix-associated laser desorption ionization (MALDI for the BSA sample was 66,485 Da and for biotin-BSA was 67,116 Da, indicating two biotin moieties per BSA molecule; for biotin-BSA-DTPA was 81,584 Da, indicating an average of 30 DTPA moieties per BSA molecule; and for FAM conjugate was 82,383 Da, indicating an average of 1.7 fluorescent moieties per BSA molecule. Fluorescence imaging clearly showed localization of FAM conjugate and FAM-68Ga at respective flanks of the mouse

  8. Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy.

    Science.gov (United States)

    Zorba, S; Le, Q T; Watkins, N J; Yan, L; Gao, Y

    2001-09-01

    Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.

  9. Probing tethered targets of a single biomolecular complex with atomic force microscopy.

    Science.gov (United States)

    Wu, Na; Wang, Qi; Zhou, Xingfei; Jia, Si Si; Fan, Youjie; Hu, Jun; Li, Bin

    2013-12-01

    DNA origami shows tremendous promise as templates for the assembly of nano-components and detection of molecular recognition events. So far, the method of choice for evaluating these structures has been atomic force microscopy (AFM), a powerful tool for imaging nanoscale objects. In most cases, tethered targets on DNA origami have proven to be highly effective samples for investigation. Still, while maximal assembly of the nanostructures might benefit from the greatest flexibility in the tether, AFM imaging requires a sufficient stability of the adsorbed components. The balance between the tether flexibility and sample stability is a major, poorly understood, concern in such studies. Here, we investigated the dependence of the tethering length on molecular capture events monitored by AFM. In our experiments, single biotin molecules were attached to DNA origami templates with various linker lengths of thymidine nucleotides, and their interaction with streptavidin was observed with AFM. Our results show that the streptavidin-biotin complexes are easily detected with short tethered lengths, and that their morphological features clearly change with the tethering length. We identify the functionally useful tether lengths for these investigations, which are also expected to prove useful in the construction and further application of DNA origami in bio-nanotechnology studies. Copyright © 2013 John Wiley & Sons, Ltd.

  10. Perfect/complete scattering experiments probing quantum mechanics on atomic and molecular collisions and coincidences

    CERN Document Server

    Kleinpoppen, Hans; Grum-Grzhimailo, Alexei N

    2013-01-01

    The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter.  The feasibility of such perfect' and-or `complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory.  It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment `complete'.  The language of the related theory is the language of quantum mechanical amplitudes and their relative phases.  This book captures the spi...

  11. Nanostructural evolution of Cr-rich precipitates in a Cu-Cr-Zr alloy during heat treatment studied by 3 dimensional atom probe

    DEFF Research Database (Denmark)

    Hatakeyama, Masahiko; Toyama, Takeshi; Nagai, Yasuyoshi

    2008-01-01

    Nanostructural evolution of Cr (Cr-rich) precipitates in a Cu-0.78%Cr-0.13%Zr alloy has been studied after aging and overaging (reaging) by laser assisted local electrode 3 dimensional atom probe (Laser-LEAP). This material is a candidate for the first wall and divertor components of future fusion...

  12. Probing the nanoadhesion of Streptococcus sanguinis to titanium implant surfaces by atomic force microscopy.

    Science.gov (United States)

    Aguayo, Sebastian; Donos, Nikolaos; Spratt, Dave; Bozec, Laurent

    2016-01-01

    As titanium (Ti) continues to be utilized in great extent for the fabrication of artificial implants, it is important to understand the crucial bacterium-Ti interaction occurring during the initial phases of biofilm formation. By employing a single-cell force spectroscopy technique, the nanoadhesive interactions between the early-colonizing Streptococcus sanguinis and a clinically analogous smooth Ti substrate were explored. Mean adhesion forces between S. sanguinis and Ti were found to be 0.32±0.00, 1.07±0.06, and 4.85±0.56 nN for 0, 1, and 60 seconds contact times, respectively; while adhesion work values were reported at 19.28±2.38, 104.60±7.02, and 1,317.26±197.69 aJ for 0, 1, and 60 seconds, respectively. At 60 seconds surface delays, minor-rupture events were modeled with the worm-like chain model yielding an average contour length of 668±12 nm. The mean force for S. sanguinis minor-detachment events was 1.84±0.64 nN, and Poisson analysis decoupled this value into a short-range force component of -1.60±0.34 nN and a long-range force component of -0.55±0.47 nN. Furthermore, a solution of 2 mg/mL chlorhexidine was found to increase adhesion between the bacterial probe and substrate. Overall, single-cell force spectroscopy of living S. sanguinis cells proved to be a reliable way to characterize early-bacterial adhesion onto machined Ti implant surfaces at the nanoscale.

  13. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    Science.gov (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  14. Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

    Science.gov (United States)

    Choi, Jinho; Park, Byong Chon; Ahn, Sang Jung; Kim, Dal-Hyun; Lyou, Joon; Dixson, Ronald G.; Orji, Ndubuisi G.; Fu, Joseph; Vorburger, Theodore V.

    2016-07-01

    The decreasing size of semiconductor features and the increasing structural complexity of advanced devices have placed continuously greater demands on manufacturing metrology, arising both from the measurement challenges of smaller feature sizes and the growing requirement to characterize structures in more than just a single critical dimension. For scanning electron microscopy, this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFMs), this has resulted in the need for smaller and more complex tips. Carbon nanotube (CNT) tips have thus been the focus of much interest and effort by a number of researchers. However, there have been significant issues surrounding both the manufacture and use of CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to the fabrication of CNT tips, and the flexibility and resultant bending artifacts have presented challenges to using CNT tips. The Korea Research Institute for Standards and Science (KRISS) has invested considerable effort in the controlled fabrication of CNT tips and is collaborating with the National Institute of Standards and Technology on the application of CNT tips for CD-AFM. Progress by KRISS on the precise control of CNT orientation, length, and end modification, using manipulation and focused ion beam processes, has allowed us to implement ball-capped CNT tips and bent CNT tips for CD-AFM. Using two different generations of CD-AFM instruments, we have evaluated these tip types by imaging a line/space grating and a programmed line edge roughness specimen. We concluded that these CNTs are capable of scanning the profiles of these structures, including re-entrant sidewalls, but there remain important challenges to address. These challenges include tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.

  15. Probed adhesion force of living lung cells with a tip-modified atomic force microscope.

    Science.gov (United States)

    Fu, Wei-En; Sivashanmugan, Kundan; Liao, Jiunn-Der; Lin, Ying-Yi; Cheng, Kai-Hung; Liu, Bernard Haochih; Yan, Jun-Jer; Yeh, Ming-Hong

    2016-12-19

    The mechanical properties of the extracellular matrix play an important role in bio-microenvironment activities. Herein, atomic force microscope (AFM) was used to measure the interaction between Au and Ag nanoparticle (NP) clusters on the surface of human fetal lung cells. Using (3-mercapto-propyl) triethoxysilane (MPTMS), NP clusters were grafted onto the apex of AFM tip, and then, the adhesion force between the tip and the cell was analyzed. The measured adhesion force increased from 92 pN for AFM tip to 332 pN for that modified with MPTMS. The increase is most probably contributed by the nonspecific interactions between the apex of the modified AFM tip and the surface of the cells. The adhesion forces between the surface of NPs clusters grafted AFM tip and that of lung cells were dramatically reduced as NPs clusters were replaced by MPTMS. For the former, as the Au NPs cluster was applied, the adhesion force reached to 122 pN, whereas it significantly augmented with the addition of the cluster's size and dimension on the AFM tip. For the case of Ag cluster grafted on AFM tip, its adhesion force with the surface of the cells significantly lowered and reduced to 56 pN. Presumably, the electrostatic or van der Waals force between the two surfaces results in the variation of measurements. It is also very likely that the cell-surface interactions are probably varied by the nature of the contact surfaces, like the force-distance of attraction. The result is significant for understanding the the nature of the interactions between the surface of NPs and the membrane of lung cells.

  16. High Atomic Number Contrast Media Offer Potential for Radiation Dose Reduction in Contrast-Enhanced Computed Tomography.

    Science.gov (United States)

    Roessler, Ann-Christin; Hupfer, Martin; Kolditz, Daniel; Jost, Gregor; Pietsch, Hubertus; Kalender, Willi A

    2016-04-01

    Spectral optimization of x-ray computed tomography (CT) has led to substantial radiation dose reduction in contrast-enhanced CT studies using standard iodinated contrast media. The purpose of this study was to analyze the potential for further dose reduction using high-atomic-number elements such as hafnium and tungsten. As in previous studies, spectra were determined for which the patient dose necessary to provide a given contrast-to-noise ratio (CNR) is minimized. We used 2 different quasi-anthropomorphic phantoms representing the liver cross-section of a normal adult and an obese adult patient with the lateral widths of 360 and 460 mm and anterior-posterior heights of 200 and 300 mm, respectively. We simulated and measured on 2 different scanners with x-ray spectra from 80 to 140 kV and from 70 to 150 kV, respectively. We determined the contrast for iodine-, hafnium-, and tungsten-based contrast media, the noise, and 3-dimensional dose distributions at all available tube voltages by measurements and by simulations. The dose-weighted CNR was determined as optimization parameter. Simulations and measurements were in good agreement regarding their dependence on energy for all parameters investigated. Hafnium provided the best performance for normal and for obese patient phantoms, indicating a dose reduction potential of 30% for normal and 50% for obese patients at 120 kV compared with iodine; this advantage increased further with higher kV values. Dose-weighted CNR values for tungsten were always slightly below the hafnium results. Iodine proved to be the superior choice at voltage values of 80 kV and below. Hafnium and tungsten both seem to be candidates for contrast-medium-enhanced CT of normal and obese adult patients with strongly reduced radiation dose at unimpaired image quality. Computed tomography examinations of obese patients will decrease in dose for higher kV values.

  17. Gold-decorated highly ordered self-organized grating-like nanostructures on Ge surface: Kelvin probe force microscopy and conductive atomic force microscopy studies.

    Science.gov (United States)

    Mollick, Safiul Alam; Kumar, Mohit; Singh, Ranveer; Satpati, Biswarup; Ghose, Debabrata; Som, Tapobrata

    2016-10-28

    Nanoarchitecture by atomic manipulation is considered to be one of the emerging trends in advanced functional materials. It has a gamut of applications to offer in nanoelectronics, chemical sensing, and nanobiological science. In particular, highly ordered one-dimensional semiconductor nanostructures fabricated by self-organization methods are in high demand for their high aspect ratios and large number of applications. An efficient way of fabricating semiconductor nanostructures is by molecular beam epitaxy, where atoms are added to a crystalline surface at an elevated temperature during growth, yielding the desired structures in a self-assembled manner. In this article, we offer a room temperature process, in which atoms are sputtered away by ion impacts. Using gold ion implantation, the present study reports on the formation of highly ordered self-organized long grating-like nanostructures, with grooves between them, on a germanium surface. The ridges of the patterns are shown to have flower-like protruding nanostructures, which are mostly decorated by gold atoms. By employing local probe microscopic techniques like Kelvin probe force microscopy and conductive atomic force microscopy, we observe a spatial variation in the work function and different nanoscale electrical conductivity on the ridges of the patterns and the grooves between them, which can be attributed to gold atom decorated ridges. Thus, the architecture  presented offers the advantage of using the patterned germanium substrates as periodic arrays of conducting ridges and poorly conducting grooves between them.

  18. Back-to-back optical coherence tomography-ultrasound probe for co-registered three-dimensional intravascular imaging with real-time display

    Science.gov (United States)

    Li, Jiawen; Ma, Teng; Jing, Joseph; Zhang, Jun; Patel, Pranav M.; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

    2014-03-01

    We have developed a novel integrated optical coherence tomography (OCT)-intravascular ultrasound (IVUS) probe, with a 1.5 mm-long rigid-part and 0.9 mm outer diameter, for real-time intracoronary imaging of atherosclerotic plaques and guiding interventional procedures. By placing the OCT ball lens and IVUS 45MHz single element transducer back-to-back at the same axial position, this probe can provide automatically co-registered, co-axial OCT-IVUS imaging. To demonstrate its capability, 3D OCT-IVUS imaging of a pig's coronary artery in real-time displayed in polar coordinates, as well as images of two major types of advanced plaques in human cadaver coronary segments, was obtained using this probe and our upgraded system. Histology validation is also presented.

  19. Performance of a Multispectral Optoacoustic Tomography (MSOT System equipped with 2D vs. 3D Handheld Probes for Potential Clinical Translation

    Directory of Open Access Journals (Sweden)

    Volker Neuschmelting

    2016-03-01

    Full Text Available A handheld approach to optoacoustic imaging is essential for the clinical translation. The first 2- and 3-dimensional handheld multispectral optoacoustic tomography (MSOT probes featuring real-time unmixing have recently been developed. Imaging performance of both probes was determined in vitro and in a brain melanoma metastasis mouse model in vivo. T1-weighted MR images were acquired for anatomical reference. The limit of detection of melanoma cells in vitro was significantly lower using the 2D than the 3D probe. The signal decrease was more profound in relation to depth with the 3D versus the 2D probe. Both approaches were capable of imaging the melanoma tumors qualitatively at all time points. Quantitatively, the 2D approach enabled closer anatomical resemblance of the tumor compared to the 3D probe, particularly at depths beyond 3 mm. The 3D probe was shown to be superior for rapid 3D imaging and, thus, holds promise for more superficial target structures.

  20. Reconstructing virus structures from nanometer to near-atomic resolutions with cryo-electron microscopy and tomography

    Science.gov (United States)

    Chang, Juan; Liu, Xiangan; Rochat, Ryan H.; Baker, Matthew L.; Chiu, Wah

    2014-01-01

    The past few decades have seen tremendous advances in single particle electron cryo-microscopy (cryo-EM). The field has matured to the point that near-atomic resolution density maps can be generated for icosahedral viruses without the need for crystallization. In parallel, substantial progress has been made in determining the structures of non-icosahedrally arranged proteins in viruses by employing either single particle cryo-EM or cryo-electron tomography (cryo-ET). Implicit in this course has been the availability of a new generation of electron cryo-microscopes and the development of the computational tools that are essential for generating these maps and models. This methodology has enabled structural biologists to analyze structures in increasing detail for virus particles that are in different morphogenetic and biochemical states. Furthermore, electron imaging of frozen, hydrated cells, in the process of being infected by viruses, has also opened up a new avenue for studying virus structures “in situ”. Here we present the common techniques used to acquire and process cryo-EM and cryo-ET data and discuss their implications for structural virology both now and in the future. PMID:22297510

  1. Reconstructing virus structures from nanometer to near-atomic resolutions with cryo-electron microscopy and tomography.

    Science.gov (United States)

    Chang, Juan; Liu, Xiangan; Rochat, Ryan H; Baker, Matthew L; Chiu, Wah

    2012-01-01

    The past few decades have seen tremendous advances in single-particle electron -cryo-microscopy (cryo-EM). The field has matured to the point that near-atomic resolution density maps can be generated for icosahedral viruses without the need for crystallization. In parallel, substantial progress has been made in determining the structures of nonicosahedrally arranged proteins in viruses by employing either single-particle cryo-EM or cryo-electron tomography (cryo-ET). Implicit in this course have been the availability of a new generation of electron cryo-microscopes and the development of the computational tools that are essential for generating these maps and models. This methodology has enabled structural biologists to analyze structures in increasing detail for virus particles that are in different morphogenetic states. Furthermore, electron imaging of frozen, hydrated cells, in the process of being infected by viruses, has also opened up a new avenue for studying virus structures "in situ". Here we present the common techniques used to acquire and process cryo-EM and cryo-ET data and discuss their implications for structural virology both now and in the future.

  2. Measurement and deposition of nanometer-scale Cu dot using an atomic force microscope with a nanopipette probe in liquid condition

    Science.gov (United States)

    Ito, So; Yamazaki, Koji; Iwata, Futoshi

    2011-12-01

    In this study, we developed novel techniques of nanometer-scale measurement and deposition using an atomic force microscope (AFM) with a nanopipette in liquid condition. The nanopipette, filled with CuSO4 electrolyte solution, was employed as the AFM probe. Observation and deposition of nanometer-scale Cu dots were carried out using the nanopipette probe. In order to avoid drying of the nanopipette solution and clogging of the probe-edge aperture, Cu dots were deposited and measured in liquid condition. As for the measurement of the surface, the nanopipette probe was glued on a tuning fork quartz crystal resonator (TF-QCR) to detect a probe oscillation and vertically oscillated to use a method of frequency modulation in tapping-mode AFM. With regard to the deposition of nanometer-scale Cu dot, an electrode wire inside the electrolyte-filled nanopipette and conductive surface of Au coated glass slide were employed as the anode and cathode, respectively. By utilizing the probe-surface distance control during the deposition, nanometerscale Cu dot were successfully deposited on Au surface without the diffusion. Then, the deposited dots were observed by using the nanopipette probe. This technique of the local deposition in the liquid would be applicable for various fields such as fabrication of micro/nanometer-scale devices and arrangement of biological samples.

  3. Study on probe field propagation in the presence of control and coupling fields through a four-level N-type atomic system

    Science.gov (United States)

    Islam, Khairul; Bhattacharyya, Dipankar; Ghosh, Arindam; Biswas, Debasish; Bandyopadhyay, Amitava

    2017-11-01

    The absorption features of a probe field propagating through a four-level N-type atomic system in the presence of two coherent radiation fields is studied analytically by using a density matrix formulation. The system has two ground levels and two excited levels. A weak probe laser couples the upper ground level to the lower excited level whereas a strong control field connects the lower ground level to the lower excited level. The coupling field acts between the upper ground level and the upper excited level. The transition parameters of the 87Rb D1 line have been used to simulate the probe response. The simulated probe absorption shows a gain-like structure depending on the relative field intensities. The spectral features of the probe response exhibit substantial differences under thermal averaging as compared to a Doppler-free condition. The splitting of simulated probe absorption can be explained by the dressed state model. Electromagnetically induced absorption (EIA) is observed in the simulated probe response curve when the spontaneous decay of the population from the uppermost excited state to the lower ground state is absent.

  4. Probing the atomic structure of amorphous Ta2O5 mirror coatings for advanced gravitational wave detectors using transmission electron microscopy

    Science.gov (United States)

    Bassiri, R.; Borisenko, K. B.; Cockayne, D. J. H.; Hough, J.; MacLaren, I.; Rowan, S.

    2010-07-01

    Advanced generations of ground-based gravitational wave detectors will use ultra-low-loss amorphous dielectric multilayer mirror coatings in order to minimise thermal noise, a limiting factor in detector sensitivity. Transmission electron microscopy is a promising way to probe the atomic structure of these coatings in an effort to better understand the causes of the observed mechanical loss (internal friction) and hence thermal noise.

  5. Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ageev, O. A., E-mail: ageev@sfedu.ru [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation); Bykov, Al. V. [NT-MDT (Russian Federation); Kolomiitsev, A. S.; Konoplev, B. G.; Rubashkina, M. V.; Smirnov, V. A.; Tsukanova, O. G. [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation)

    2015-12-15

    The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering.

  6. Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction

    Directory of Open Access Journals (Sweden)

    Shi H.

    2016-01-01

    Full Text Available In the exotic atoms where one atomic 1s electron is replaced by a K−, the strong interaction between the K− and the nucleus introduces an energy shift and broadening of the low-lying kaonic atomic levels which are determined by only the electromagnetic interaction. By performing X-ray spectroscopy for Z = 1,2 kaonic atoms, the SIDDHARTA experiment determined with high precision the shift and width for the 1s state of K− p and the 2p state of kaonic helium-3 and kaonic helium-4. These results provided unique information of the kaon-nucleus interaction in the low energy limit.

  7. Photoelectron imaging, probe of the dynamics: from atoms... to clusters; Imagerie de photoelectrons, sonde de la dynamique: des atomes... aux agregats

    Energy Technology Data Exchange (ETDEWEB)

    Lepine, F

    2003-06-15

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W{sub n}{sup -}, C{sub n}{sup -}, C{sub 60}). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  8. Electrochemically assisted localized etching of ZnO single crystals in water using a catalytically active Pt-coated atomic force microscopy probe

    Science.gov (United States)

    Shibata, Takayuki; Yamamoto, Kota; Sasano, Junji; Nagai, Moeto

    2017-09-01

    This paper presents a nanofabrication technique based on the electrochemically assisted chemical dissolution of zinc oxide (ZnO) single crystals in water at room temperature using a catalytically active Pt-coated atomic force microscopy (AFM) probe. Fabricated grooves featured depths and widths of several tens and several hundreds of nanometers, respectively. The material removal rate of ZnO was dramatically improved by controlling the formation of hydrogen ions (H+) on the surface of the catalytic Pt-coated probe via oxidation of H2O molecules; this reaction can be enhanced by applying a cathodic potential to an additional Pt-wire working electrode in a three-electrode configuration. Consequently, ZnO can be dissolved chemically in water as a soluble Zn2+ species via a reaction with H+ species present in high concentrations in the immediate vicinity of the AFM tip apex.

  9. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  10. XUV Transient Absorption Spectroscopy: Probing Laser-Perturbed Dipole Polarization in Single Atom, Macroscopic, and Molecular Regimes

    OpenAIRE

    Chen-Ting Liao; Arvinder Sandhu

    2017-01-01

    We employ an extreme ultraviolet (XUV) pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR) pulse then perturbs the fast evolving polarization, and the resultant absorbance change is monitored in dilute helium, dense helium, and sulfur hexafluoride (SF6) molecules. We observe and quantify the time-dependence of various transient phenomena in helium atoms,includinglaser-indu...

  11. Charge-coupled-device based scanner for tomography of fluorescent near-infrared probes in turbid media.

    Science.gov (United States)

    Ntziachristos, Vasilis; Weissleder, Ralph

    2002-05-01

    We present a novel tomographer for three-dimensional reconstructions of fluorochromes in diffuse media. Photon detection is based on charge-coupled device technology that allows the implementation of a large parallel array of detection channels with high sensitivity. Using this instrument we studied the response and detection limits of near-infrared fluorochromes in diffuse media as a function of light intensity and for a wide range of biologically relevant concentrations. We further examined the resolution of the scanner and the reconstruction linearity achieved. We demonstrate that the instrument attains better than 3 mm resolution, is linear within more than two orders of magnitude of fluorochrome concentration, and can detect fluorescent objects at femto-mole quantities in small animal-like geometries. These measurements delineate detection and reconstruction characteristics associated with imaging of novel classes of fluorescent probes developed for in vivo molecular and functional probing of tissues.

  12. Probing/Manipulating the Interfacial Atomic Bonding between High k Dielectrics and InGaAs for Ultimate CMOS

    Science.gov (United States)

    2015-04-24

    10.1039/C4CE00734D 2014 3. “III-V Compound Semiconductor Transistors – From Planar to Nanowire Structures”, H. Riel, L.-E. Wernersson, M. Hong, J...extract interface state densities at atomic-layer-deposited high-k dielectric/III-V heterostructures ”, Y. T. Fanchiang, Y. K. Su, K. S. Chen, Y. C

  13. In Vivo Molecular Imaging of Thrombosis and Thrombolysis Using a Fibrin-binding Positron Emission Tomography Probe

    Science.gov (United States)

    Ay, Ilknur; Blasi, Francesco; Rietz, Tyson A.; Rotile, Nicholas J.; Kura, Sreekanth; Brownell, Anna Liisa; Day, Helen; Oliveira, Bruno L.; Looby, Richard J.; Caravan, Peter

    2014-01-01

    Background Fibrin is a major component of arterial and venous thrombi and represents an ideal candidate for molecular imaging of thrombosis. Here, we describe imaging properties and target uptake of a new fibrin-specific PET probe for thrombus detection and therapy monitoring in two rat thrombosis models. Methods and Results The fibrin-binding probe FBP7 was synthesized by conjugation of a known short cyclic peptide to a cross-bridged chelator (CB-TE2A), followed by labeling with copper-64. Adult male Wistar rats (n=26) underwent either carotid crush injury (mural thrombosis model) or embolic stroke (occlusive thrombosis model) followed by rtPA treatment (10 mg/kg, i.v.). FBP7 detected thrombus location in both animal models with a high PET target-to-background ratio that increased over time (>5-fold at 30–90 min, >15-fold at 240–285 min). In the carotid crush injury animals, biodistribution analysis confirmed high probe uptake in the thrombotic artery (~0.5 %ID/g; >5-fold greater than blood and other tissues of the head and thorax). Similar results were obtained from ex vivo autoradiography of the ipsilateral vs. contralateral carotid arteries. In embolic stroke animals, PET-CT imaging localized the clot in the internal carotid/middle cerebral artery segment of all rats. Time-dependent reduction of activity at the level of the thrombus was detected in rtPA-treated rats but not in vehicle-injected animals. Brain autoradiography confirmed clot dissolution in rtPA-treated animals, but enduring high thrombus activity in control rats. Conclusions We demonstrated that FBP7 is suitable for molecular imaging of thrombosis and thrombolysis in vivo, and represents a very promising candidate for bench-to-bedside translation. PMID:24777937

  14. Creating a Multi-material Probing Error Test for the Acceptance Testing of Dimensional Computed Tomography Systems

    DEFF Research Database (Denmark)

    Borges de Oliveira, Fabrício; Stolfi, Alessandro; Bartscher, Markus

    2017-01-01

    -material scenarios and the appropriate parameters for surface determination in a multi-surface setting. Thus, this paper presents – as part of a multi-material acceptance test and to create trust in multi-material CT measurement – a new concept for multi-material probing error testing (P-test) and discusses the test...... design and the first experimental results. This paper also attempts to perform a critical analysis of this new concept ̶ featuring a compound sphere made of two half spheres of different materials ̶ and tries to perform analyses of geometrical features of the new standard....

  15. XUV Transient Absorption Spectroscopy: Probing Laser-Perturbed Dipole Polarization in Single Atom, Macroscopic, and Molecular Regimes

    Directory of Open Access Journals (Sweden)

    Chen-Ting Liao

    2017-03-01

    Full Text Available We employ an extreme ultraviolet (XUV pulse to impulsively excite dipole polarization in atoms or molecules, which corresponds to coherently prepared superposition of excited states. A delayed near infrared (NIR pulse then perturbs the fast evolving polarization, and the resultant absorbance change is monitored in dilute helium, dense helium, and sulfur hexafluoride (SF6 molecules. We observe and quantify the time-dependence of various transient phenomena in helium atoms,includinglaser-inducedphase(LIP,time-varying(ACStarkshift,quantumpathinterference, and laser-induced continuum structure. In the case of dense helium targets, we discuss nonlinear macroscopic propagation effects pertaining to LIP and resonant pulse propagation, which accoun tfor the appearance of new spectral features in transient lineshapes. We then use tunable NIR photons to demonstrate the wavelength dependence of the transient laser induced effects. In the case of molecular polarization experiment in SF6, we show suppression of XUV photoabsorption corresponding to inter-valence transitions in the presence of a strong NIR field. In each case, the temporal evolution of transient absorption spectra allows us to observe and understand the transient laser induced modifications of the electronic structure of atoms and molecules.

  16. Diffractive molecular-orbital tomography

    Science.gov (United States)

    Zhai, Chunyang; Zhu, Xiaosong; Lan, Pengfei; Wang, Feng; He, Lixin; Shi, Wenjing; Li, Yang; Li, Min; Zhang, Qingbin; Lu, Peixiang

    2017-03-01

    High-order-harmonic generation in the interaction of femtosecond lasers with atoms and molecules opens the path to molecular-orbital tomography and to probe the electronic dynamics with attosecond-Ångström resolutions. Molecular-orbital tomography requires both the amplitude and phase of the high-order harmonics. Yet the measurement of phases requires sophisticated techniques and represents formidable challenges at present. Here we report a scheme, called diffractive molecular-orbital tomography, to retrieve the molecular orbital solely from the amplitude of high-order harmonics without measuring any phase information. We have applied this method to image the molecular orbitals of N2, CO2, and C2H2 . The retrieved orbital is further improved by taking account the correction of Coulomb potential. The diffractive molecular-orbital tomography scheme, removing the roadblock of phase measurement, significantly simplifies the molecular-orbital tomography procedure and paves an efficient and robust way to the imaging of more complex molecules.

  17. Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Hanaul Noh

    2017-03-01

    Full Text Available Organic photovoltaic systems comprising donor polymers and acceptor fullerene derivatives are attractive for inexpensive energy harvesting. Extensive research on polymer solar cells has provided insight into the factors governing device-level efficiency and stability. However, the detailed investigation of nanoscale structures is still challenging. Here we demonstrate the analysis and modification of unidentified surface aggregates. The aggregates are characterized electrically by Kelvin probe force microscopy and conductive atomic force microscopy (C-AFM, whereby the correlation between local electrical potential and current confirms a defective charge transport. Bimodal AFM modification confirms that the aggregates exist on top of the solar cell structure, and is used to remove them and to reveal the underlying active layer. The systematic analysis of the surface aggregates suggests that the structure consists of PCBM molecules.

  18. Observation of silicon carbide Schottky barrier diode under applied reverse bias using atomic force microscopy/Kelvin probe force microscopy/scanning capacitance force microscopy

    Science.gov (United States)

    Uruma, Takeshi; Satoh, Nobuo; Yamamoto, Hidekazu

    2017-08-01

    We have observed a commercial silicon-carbide Schottky barrier diode (SiC-SBD) using our novel analysis system, in which atomic force microscopy (AFM) is combined with both Kelvin probe force microscopy (KFM; for surface-potential measurement) and scanning capacitance force microscopy (SCFM; for differential-capacitance measurement). The results obtained for the SiC-SBD under an applied reverse bias indicate both the scan area in the sample and a peak value of the SCFM signal in the region where the existence of trapped electrons is deduced from the KFM analysis. Thus, our measurement system can be used to examine commercial power devices; however, novel polishing procedures are required in order to investigate the Schottky contact region.

  19. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    Science.gov (United States)

    Warren, K. M.; Mpagazehe, J. N.; LeDuc, P. R.; Higgs, C. F.

    2014-10-01

    With the re-emergence of microalgae as a replacement feedstock for petroleum-derived oils, researchers are working to understand its chemical and mechanical behavior. In this work, the mechanical properties of microalgae, Scenedesmus dimorphus, were investigated at the subcellular level to determine the elastic response of cells that were in an aqueous and dried state using nano-scale indentation through atomic force microscopy. The elastic modulus of single-celled S. dimorphus cells increased over tenfold from an aqueous state to a dried state, which allows us to better understand the biophysical response of microalgae to stress.

  20. Probing the elastic response of microalga Scenedesmus dimorphus in dry and aqueous environments through atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Warren, K. M.; Mpagazehe, J. N.; Higgs, C. F., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); LeDuc, P. R., E-mail: prl@andrew.cmu.edu, E-mail: higgs@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania 15213 (United States); Departments of Biomedical Engineering and Biological Sciences, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States)

    2014-10-20

    With the re-emergence of microalgae as a replacement feedstock for petroleum-derived oils, researchers are working to understand its chemical and mechanical behavior. In this work, the mechanical properties of microalgae, Scenedesmus dimorphus, were investigated at the subcellular level to determine the elastic response of cells that were in an aqueous and dried state using nano-scale indentation through atomic force microscopy. The elastic modulus of single-celled S. dimorphus cells increased over tenfold from an aqueous state to a dried state, which allows us to better understand the biophysical response of microalgae to stress.

  1. Towards non-invasive high-resolution 3D nano-tomography by ultrasonic scanning probe microscopy

    Science.gov (United States)

    Sharahi, Hossein J.; Shekhawat, Gajendra; Dravid, Vinayak; Egberts, Philip; Kim, Seonghwan

    2017-07-01

    Nanoscale imaging techniques that can be used to visualize and characterize local aggregations of the embedded nanoparticulates with sufficient resolution have attracted a great deal of interest. Ultrasonic scanning probe microscopy (SPM) and its derivatives are nondestructive techniques that can be used to elucidate subsurface nanoscale features and mechanical properties. Although many different ultrasonic methods have been used for subsurface imaging, the mechanisms and crucial parameters associated with the contrast formation in subsurface imaging are still unclear. Here, the impact of mechanical properties of the nanoparticulates/matrix, size of the nanoparticulates, buried depth of the nanoparticulates, and the ultrasonic excitation frequency on the developed ultrasonic SPM images have been investigated. To verify our theoretical model, experimental measurements of scanning near-field ultrasound holography (SNFUH) have been recreated in our theoretical analysis to reveal comparable variations in phase contrast measured in SNFUH while scanning over the nanoparticulates embedded in bacteria.

  2. Note: A silicon-on-insulator microelectromechanical systems probe scanner for on-chip atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, Anthony G.; Maroufi, Mohammad; Moheimani, S. O. Reza, E-mail: Reza.Moheimani@newcastle.edu.au [School of Electrical Engineering and Computer Science, University of Newcastle, Callaghan, NSW 2308 (Australia)

    2015-04-15

    A new microelectromechanical systems-based 2-degree-of-freedom (DoF) scanner with an integrated cantilever for on-chip atomic force microscopy (AFM) is presented. The silicon cantilever features a layer of piezoelectric material to facilitate its use for tapping mode AFM and enable simultaneous deflection sensing. Electrostatic actuators and electrothermal sensors are used to accurately position the cantilever within the x-y plane. Experimental testing shows that the cantilever is able to be scanned over a 10 μm × 10 μm window and that the cantilever achieves a peak-to-peak deflection greater than 400 nm when excited at its resonance frequency of approximately 62 kHz.

  3. Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography

    Science.gov (United States)

    Naha, Pratap C.; Lau, Kristen C.; Hsu, Jessica C.; Hajfathalian, Maryam; Mian, Shaameen; Chhour, Peter; Uppuluri, Lahari; McDonald, Elizabeth S.; Maidment, Andrew D. A.; Cormode, David P.

    2016-07-01

    Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various

  4. Immobilisation of oligo-peptidic probes for microarray implementation: characterisation by FTIR, atomic force microscopy and 2D fluorescence.

    Science.gov (United States)

    Soultani-Vigneron, S; Dugas, V; Rouillat, M H; Fédollière, J; Duclos, M C; Vnuk, E; Phaner-Goutorbe, M; Bulone, V; Martin, J R; Wallach, J; Cloarec, J P

    2005-08-05

    Proteomic microarrays show a wide range of applications for the investigation of DNA-protein, enzyme-substrate as well as protein-protein interactions. Among many challenges to build a viable "protein microarray", the surface chemistry that will allow to immobilised various proteins to retain their biological activity is of paramount importance. Here we report a chemical functionalisation method allowing immobilisation of oligo-peptides onto silica surface (porous silica, glass, thermal silicon dioxide). Substrates were first derivatised with a monofunctional silane allowing the elaboration of dense and uniform monolayers in highly reproducible way. Prior to the oligo-peptides grafting, this organic layer was functionalised with an amino-polyethyleneglycol. The coupling step of oligo-peptides onto functionalised supports is achieved through activation of the C-terminal function of the oligo-peptides. Chemical surface modifications were followed by FTIR spectroscopy, AFM measurements and fluorescence scanning microscopy. A systematic study of the oligo-peptide grafting conditions (time, concentration, solvent) was carried out to optimise this step. The oligo-peptides grafting strategy implemented in this work ensure a covalent and oriented grafting of the oligo-peptides. This orientation is ensured through the use of fully protected peptide except the terminal primary amine. The immobilized peptides will be then deprotected before biological recognition. This strategy is crucial to retain the biological activity of thousands of oligo-probes assessed on a microarray.

  5. Multi-Electrode Resistivity Probe for Investigation of Local Temperature Inside Metal Shell Battery Cells via Resistivity: Experiments and Evaluation of Electrical Resistance Tomography

    Directory of Open Access Journals (Sweden)

    Xiaobin Hong

    2015-01-01

    Full Text Available Direct Current (DC electrical resistivity is a material property that is sensitive to temperature changes. In this paper, the relationship between resistivity and local temperature inside steel shell battery cells (two commercial 10 Ah and 4.5 Ah lithium-ion cells is innovatively studied by Electrical Resistance Tomography (ERT. The Schlumberger configuration in ERT is applied to divide the cell body into several blocks distributed in different levels, where the apparent resistivities are measured by multi-electrode surface probes. The investigated temperature ranges from −20 to 80 °C. Experimental results have shown that the resistivities mainly depend on temperature changes in each block of the two cells used and the function of the resistivity and temperature can be fitted to the ERT-measurement results in the logistical-plot. Subsequently, the dependence of resistivity on the state of charge (SOC is investigated, and the SOC range of 70%–100% has a remarkable impact on the resistivity at low temperatures. The proposed approach under a thermal cool down regime is demonstrated to monitor the local transient temperature.

  6. Receptor binding characterization of the benzodiazepine radioligand sup 125 I-Ro16-0154: Potential probe for SPECT (Single Photon Emission Computed Tomography) brain imaging

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, E.W.; Woods, S.W.; Zoghbi, S.; Baldwin, R.M.; Innis, R.B. (Yale Univ., West Haven, CT (USA)); McBride, B.J. (Medi-Physics, Inc., Emeryville, CA (USA))

    1990-01-01

    The binding of an iodinated benzodiazepine (BZ) radioligand has been characterized, particularly in regard to its potential use as a neuroreceptor brain imaging agent with SPECT (Single Photon Emission Computed Tomography). Ro16-0154 is an iodine-containing BZ antagonist and a close analog of Ro15-1788. In tissue homogenates prepared from human and monkey brain, the binding of {sup 125}I-labeled Ro16-0154 was saturable, of high affinity, and had high ratios of specific to non-specific binding. Physiological concentrations of NaCl enhanced specific binding approximately 15% compared to buffer without this salt. Kinetic studies of association and dissociation demonstrated a temperature dependent decrease in affinity with increasing temperature. Drug displacement studies confirmed that {sup 125}I-Ro16-0154 binds to the central type BZ receptor: binding is virtually identical to that of {sup 3}H-Ro15-1788 except that {sup 125}I-Ro16-0154 shows an almost 10 fold higher affinity at 37{degree}C. These in vitro results suggest that {sup 123}I-labeled Ro16-0154 shows promise as a selective, high affinity SPECT probe of the brain's BZ receptor.

  7. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    Science.gov (United States)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  8. Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

    Energy Technology Data Exchange (ETDEWEB)

    Vecchiola, Aymeric [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis (France); Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Chrétien, Pascal; Schneegans, Olivier; Mencaraglia, Denis; Houzé, Frédéric, E-mail: frederic.houze@geeps.centralesupelec.fr [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Delprat, Sophie [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); UPMC, Université Paris 06, 4 place Jussieu, 75005 Paris (France); Bouzehouane, Karim; Seneor, Pierre; Mattana, Richard [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Tatay, Sergio [Molecular Science Institute, University of Valencia, 46980 Paterna (Spain); Geffroy, Bernard [Lab. Physique des Interfaces et Couches minces (PICM), UMR 7647 CNRS-École polytechnique, 91128 Palaiseau (France); Lab. d' Innovation en Chimie des Surfaces et Nanosciences (LICSEN), NIMBE UMR 3685 CNRS-CEA Saclay, 91191 Gif-sur-Yvette (France); and others

    2016-06-13

    An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10 decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes.

  9. In-Situ Probing of Coupled Atomic Restructuring and Metallicity of Oxide Heterointerfaces Induced by Polar Adsorbates.

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, S.; Zhou, H.; Paudel, T. R.; Irwin, J.; Podkaminer, J. P.; Bark, C. W.; Lee, D.; Kim, T. H.; Fong, D. D.; Rzchowski, M. S.; Tsymbal, E. Y.; Eom, C. B.

    2017-10-02

    Microscopic understanding of the surface-controlled conductivity of the two dimensional electron gas at complex oxide interfaces is crucial for developing functional interfaces. We observe conductivity and structural modification using in-situ synchrotron surface x-ray diffraction as the surface of a model LaAlO3/SrTiO3 (001) heterostructure is changed by polar adsorbates. We find that polar adsorbate-induced interfacial metallicity reduces polar distortions in the LaAlO3 layer. First-principles density functional theory calculations show that surface dipoles introduced by polar adsorbates lead to additional charge transfer and the reduction of polar displacements in the LaAlO3 layer, consistent with the experimental observations. Our study supports that internal structural deformations controlling functionalities can be driven without the application of direct electrical or thermal bias and offers a route to tuning interfacial properties. These results also highlight the important role of in-situ x-ray scattering with atomic resolution in capturing and exploring structural distortions and charge density changes caused by external perturbations such as chemical adsorption, redox reaction, and generation and/or annihilation of surface defects.

  10. Applications of nucleoside-based molecular probes for the in vivo assessment of tumour biochemistry using positron emission tomography (PET

    Directory of Open Access Journals (Sweden)

    Leonard I. Wiebe

    2007-05-01

    Full Text Available Positron emission tomography (PET is a non-invasive nuclear imaging technique. In PET, radiolabelled molecules decay by positron emission. The gamma rays resulting from positron annihilation are detected in coincidence and mapped to produce three dimensional images of radiotracer distribution in the body. Molecular imaging with PET refers to the use of positron-emitting biomolecules that are highly specific substrates for target enzymes, transport proteins or receptor proteins. Molecular imaging with PET produces spatial and temporal maps of the target-related processes. Molecular imaging is an important analytical tool in diagnostic medical imaging, therapy monitoring and the development of new drugs. Molecular imaging has its roots in molecular biology. Originally, molecular biology meant the biology of gene expression, but now molecular biology broadly encompasses the macromolecular biology and biochemistry of proteins, complex carbohydrates and nucleic acids. To date, molecular imaging has focused primarily on proteins, with emphasis on monoclonal antibodies and their derivative forms, small-molecule enzyme substrates and components of cell membranes, including transporters and transmembrane signalling elements. This overview provides an introduction to nucleosides, nucleotides and nucleic acids in the context of molecular imaging.A tomografia por emissão de pósitrons (TEP é uma técnica de imagem não invasiva da medicina nuclear. A TEP utiliza moléculas marcadas com emissores de radiação beta positiva (pósitrons. As radiações gama medidas que resultam do aniquilamento dos pósitrons são detectadas por um sistema de coincidência e mapeadas para produzir uma imagem tridimensional da distribuição do radiotraçador no corpo. A imagem molecular com TEP refere-se ao uso de biomoléculas marcadas com emissor de pósitron que são substratos altamente específicos para alvos como enzimas, proteínas transportadoras ou receptores prot

  11. Microscopic techniques bridging between nanoscale and microscale with an atomically sharpened tip - field ion microscopy/scanning probe microscopy/ scanning electron microscopy.

    Science.gov (United States)

    Tomitori, Masahiko; Sasahara, Akira

    2014-11-01

    Over a hundred years an atomistic point of view has been indispensable to explore fascinating properties of various materials and to develop novel functional materials. High-resolution microscopies, rapidly developed during the period, have taken central roles in promoting materials science and related techniques to observe and analyze the materials. As microscopies with the capability of atom-imaging, field ion microscopy (FIM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) can be cited, which have been highly evaluated as methods to ultimately bring forward the viewpoint of reductionism in materials science. On one hand, there have been difficulties to derive useful and practical information on large (micro) scale unique properties of materials using these excellent microscopies and to directly advance the engineering for practical materials. To make bridges over the gap between an atomic scale and an industrial engineering scale, we have to develop emergence science step-by-step as a discipline having hierarchical structures for future prospects by combining nanoscale and microscale techniques; as promising ways, the combined microscopic instruments covering the scale gap and the extremely sophisticated methods for sample preparation seem to be required. In addition, it is noted that spectroscopic and theoretical methods should implement the emergence science.Fundamentally, the function of microscope is to determine the spatial positions of a finite piece of material, that is, ultimately individual atoms, at an extremely high resolution with a high stability. To define and control the atomic positions, the STM and AFM as scanning probe microscopy (SPM) have successfully demonstrated their power; the technological heart of SPM lies in an atomically sharpened tip, which can be observed by FIM and TEM. For emergence science we would like to set sail using the tip as a base. Meanwhile, it is significant

  12. Evaluation of (89Zr-labeled human anti-CD147 monoclonal antibody as a positron emission tomography probe in a mouse model of pancreatic cancer.

    Directory of Open Access Journals (Sweden)

    Aya Sugyo

    Full Text Available INTRODUCTION: Pancreatic cancer is an aggressive cancer and its prognosis remains poor. Therefore, additional effective therapy is required to augment and/or complement current therapy. CD147, high expression in pancreatic cancer, is involved in the metastatic process and is considered a good candidate for targeted therapy. CD147-specfic imaging could be useful for selection of appropriate patients. Therefore, we evaluated the potential of a fully human anti-CD147 monoclonal antibody 059-053 as a new positron emission tomography (PET probe for pancreatic cancer. METHODS: CD147 expression was evaluated in four pancreatic cancer cell lines (MIA Paca-2, PANC-1, BxPC-3, and AsPC-1 and a mouse cell line A4 as a negative control. Cell binding, competitive inhibition and internalization assays were conducted with (125I-, (67Ga-, or (89Zr-labeled 059-053. In vivo biodistribution of (125I- or (89Zr-labeled 059-053 was conducted in mice bearing MIA Paca-2 and A4 tumors. PET imaging with [(89Zr]059-053 was conducted in subcutaneous and orthotopic tumor mouse models. RESULTS: Among four pancreatic cancer cell lines, MIA Paca-2 cells showed the highest expression of CD147, while A4 cells had no expression. Immunohistochemical staining showed that MIA Paca-2 xenografts also highly expressed CD147 in vivo. Radiolabeled 059-053 specifically bound to MIA Paca-2 cells with high affinity, but not to A4. [(89Zr]059-053 uptake in MIA Paca-2 tumors increased with time from 11.0±1.3% injected dose per gram (ID/g at day 1 to 16.9±3.2% ID/g at day 6, while [(125I]059-053 uptake was relatively low and decreased with time, suggesting that 059-053 was internalized into tumor cells in vivo and (125I was released from the cells. PET with [(89Zr]059-053 clearly visualized subcutaneous and orthotopic tumors. CONCLUSION: [(89Zr]059-053 is a promising PET probe for imaging CD147 expression in pancreatic cancer and has the potential to select appropriate patients with CD147

  13. Investigation of droplet distribution in electrohydrodynamic atomization (EHDA) using an ac-based electrical capacitance tomography (ECT) system with an internal-external electrode sensor

    Science.gov (United States)

    Rezvanpour, Alireza; Wang, Chi-Hwa; Liang, Yung C.; Yang, Wuqiang

    2012-01-01

    Electrohydrodynamic atomization (EHDA) has recently been applied to the fabrication of polymeric micro- or nano-particles or fibres for drug encapsulation. For in situ monitoring of pharmaceutical particle fabrication in an EHDA encapsulation chamber, electrical capacitance tomography (ECT) has been used as a non-invasive measurement technique. The key achievements made during this study include the successful monitoring of very dilute droplet and particle trajectories in different regions of the EHDA encapsulation chamber. The results of both a charge/discharge ECT system and an ac-based ECT system are compared. A new type of ECT sensor with internal and external electrodes is used to improve the sensitivity of ECT measurement for detection of the objects in the central area of the EHDA encapsulation chamber. The water-air and dicholoromethane (DCM)-air systems in the dripping and spray modes have been investigated to determine the feasibility of imaging water and DCM droplets of low concentration in the encapsulation chamber using ECT.

  14. Atomic Layer Deposition of Hafnium(IV) Oxide on Graphene Oxide: Probing Interfacial Chemistry and Nucleation by using X-ray Absorption and Photoelectron Spectroscopies.

    Science.gov (United States)

    Alivio, Theodore E G; De Jesus, Luis R; Dennis, Robert V; Jia, Ye; Jaye, Cherno; Fischer, Daniel A; Singisetti, Uttam; Banerjee, Sarbajit

    2015-07-27

    Interfacing graphene with metal oxides is of considerable technological importance for modulating carrier density through electrostatic gating as well as for the design of earth-abundant electrocatalysts. Herein, we probe the early stages of the atomic layer deposition (ALD) of HfO2 on graphene oxide using a combination of C and O K-edge near-edge X-ray absorption fine structure spectroscopies and X-ray photoelectron spectroscopy. Dosing with water is observed to promote defunctionalization of graphene oxide as a result of the reaction between water and hydroxyl/epoxide species, which yields carbonyl groups that further react with migratory epoxide species to release CO2 . The carboxylates formed by the reaction of carbonyl and epoxide species facilitate binding of Hf precursors to graphene oxide surfaces. The ALD process is accompanied by recovery of the π-conjugated framework of graphene. The delineation of binding modes provides a means to rationally assemble 2D heterostructures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, V., E-mail: v.migunov@fz-juelich.de; Dunin-Borkowski, R. E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute (PGI), Forschungszentrum Jülich, D-52425 Jülich (Germany); London, A. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Farle, M. [Fakultät für Physik and Center of Nanointegration (CeNIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2015-04-07

    The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with ∼10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.

  16. Laser-induced reversion of δ′ precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe

    KAUST Repository

    Khushaim, Muna Saeed Amin

    2016-06-14

    The influence of tuning the laser pulse energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction, and composition of δ\\' precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser pulse energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser pulse energy of 100 pJ was in fairly good agreement with reported range of δ\\' solvus temperature, suggesting a result of reversion upon heating due to laser pulsing. © 2016 Wiley Periodicals, Inc.

  17. Using the atomic pair distribution function (PDF) to probe the local structural aspects of charge-density-wave (CDW) state in complex materials.

    Science.gov (United States)

    Kim, Hyunjeong; Bozin, Emil; Malliakas, Christos; Kanatzidis, Mercouri; Billinge, Simon; Dabrowski, Bogdan; Gutmann, Matthias

    2007-03-01

    The atomic pair distribution function (PDF) analysis [1], based on total scattering approach, is used to study the CDW state, one of the fundamental broken-symmetry ground-states of metals, commonly found in complex materials. Incommensurate CDW (IC-CDW) found in 2-D tellurium square-net in CeTe3 is a simple single-q CDW driven by Fermi-surface nesting. Our recent PDF study on local distortions in CeTe3 suggests that the IC-CDW in CeTe3 at 300K consists of commensurate CDW domains separated by discommensurations, rather than being a uniform incommensurate CDW as seen crystallographically [2]. Recent PDF results of a study of the local Peierls distortions in isostructural compounds SmTe3 and HoTe3 will be presented. The PDF analysis has also been extended to probe the CDW state in K doped BaBiO3, and a report on the current state of this study will be provided. [1] T. Egami & S. J. L. Billinge, Underneath the Bragg Peaks: Structural Analysis of Complex Materials, Pergamon Press Elsevier, Oxford, England, 2003 [2] H. J. Kim et al., Phys. Rev. Lett. 96, 226401 (2006)

  18. Toward Comprehensive Physical/Chemical Understanding of the Circumstellar Environments - Simultaneous Probing of Each of the Ionized/Atomic/Molecular Gas and Dust Components

    Science.gov (United States)

    Ueta, Toshiya

    We propose to continue our successful investigations into simultaneous probing of each of the ionized/atomic/molecular gas and dust components in planetary nebulae using primarily far-IR broadband images and spatially-resolved spectroscopic data cubes obtained with the Herschel Space Observatory to enhance our understanding of the circumstellar environments. This research originally started as the Herschel Planetary Nebula Survey (HerPlaNS) - an open time 1 program of the Herschel Space Observatory - in which 11 high-excitation PNs were observed to study the nebular energetics that involves very hot X-ray emitting plasma to very cold dust grains, whose density ranges over 3 to 4 orders of magnitude and temperature ranges over 7 orders of magnitude. The HerPlaNS data include broadband maps, IFU spectral data cubes, and bolometer array spectral data cubes covering 50 to 670 microns. Because of the sheer volume and complexity of the data set, the original funding was exhausted almost exclusively to the initial data reduction and not much to the subsequent science analysis. However, we managed to perform a nearly full science analysis for one target, NGC 6781, for which the broadband maps confirm the nearly pole-on barrel structure of the amorphous carbonrich dust shell and the surrounding halo having temperatures of 26-40 K. We also demonstrated that spatially resolved far-IR line diagnostics would yield the (Te, ne) profiles, from which distributions of ionized, atomic, and molecular gases can be determined. Direct comparison of the dust and gas column mass maps constrained by the HerPlaNS data allowed to construct an empirical gas-to-dust mass ratio map, which shows a range of ratios with the median of 195 with a standard deviation of 110. The analysis also yielded estimates of the total mass of the shell to be 0.86 M_sun, consisting of 0.54 M_sun of ionized gas, 0.12 M_sun of atomic gas, 0.2 M_sun of molecular gas, and 0.004 M_sun of dust grains. These estimates

  19. Comparison of soil thickness in a zero-order basin in the Oregon Coast Range using a soil probe and electrical resistivity tomography

    Science.gov (United States)

    Morse, Michael S.; Lu, Ning; Godt, Jonathan W.; Revil, André; Coe, Jeffrey A.

    2012-01-01

    Accurate estimation of the soil thickness distribution in steepland drainage basins is essential for understanding ecosystem and subsurface response to infiltration. One important aspect of this characterization is assessing the heavy and antecedent rainfall conditions that lead to shallow landsliding. In this paper, we investigate the direct current (DC) resistivity method as a tool for quickly estimating soil thickness over a steep (33–40°) zero-order basin in the Oregon Coast Range, a landslide prone region. Point measurements throughout the basin showed bedrock depths between 0.55 and 3.2 m. Resistivity of soil and bedrock samples collected from the site was measured for degrees of saturation between 40 and 92%. Resistivity of the soil was typically higher than that of the bedrock for degrees of saturation lower than 70%. Results from the laboratory measurements and point-depth measurements were used in a numerical model to evaluate the resistivity contrast at the soil-bedrock interface. A decreasing-with-depth resistivity contrast was apparent at the interface in the modeling results. At the field site, three transects were surveyed where coincident ground truth measurements of bedrock depth were available, to test the accuracy of the method. The same decreasing-with-depth resistivity trend that was apparent in the model was also present in the survey data. The resistivity contour of between 1,000 and 2,000 Ωm that marked the top of the contrast was our interpreted bedrock depth in the survey data. Kriged depth-to-bedrock maps were created from both the field-measured ground truth obtained with a soil probe and interpreted depths from the resistivity tomography, and these were compared for accuracy graphically. Depths were interpolated as far as 16.5 m laterally from the resistivity survey lines with root mean squared error (RMSE) = 27 cm between the measured and interpreted depth at those locations. Using several transects and analysis of the subsurface

  20. Determination of hydrogen sulfide and volatile thiols in air samples by mercury probe derivatization coupled with liquid chromatography-atomic fluorescence spectrometry.

    Science.gov (United States)

    Bramanti, Emilia; D'Ulivo, Lucia; Lomonte, Cristina; Onor, Massimo; Zamboni, Roberto; Raspi, Giorgio; D'Ulivo, Alessandro

    2006-10-02

    A new procedure is proposed for the sampling and storage of hydrogen sulphide (H2S) and volatile thiols (methanethiol or methyl mercaptan, ethanethiol and propanethiol) for their determination by liquid chromatography. The sampling procedure is based on the trapping/pre-concentration of the analytes in alkaline aqueous solution containing an organic mercurial probe p-hydroxymercurybenzoate, HO-Hg-C6H4-COO- (PHMB), where they are derivatized to stable PHMB complexes based on mercury-sulfur covalent bonds. PHMB complexes are separated on a C18 reverse phase column, allowing their determination by liquid chromatography coupled with sequential non-selective UV-vis (DAD) and mercury specific (chemical vapor generation atomic fluorescence spectrometry, CVGAFS) on-line detectors. PHMB complexes, S(PHMB)2CH3S-PHMB, C2H5S-PHMB and C3H7S-PHMB, are stable alt least for 12 h at room temperature and for 3 months if stored frozen (-20 degrees C). The best analytical figures of merits in the optimized conditions were obtained by CVGAFS detection, with detection limits (LODc) of 9.7 microg L(-1) for H2S, 13.7 microg L(-1) for CH(3)SH, 17.7 microg L(-1) for C2H5SH and 21.7 microg L(-1) for C3H7SH in the trapping solution in form of RS-PHMB complexes, the relative standard deviation (R.S.D.) ranging between 1.0 and 1.5%, and a linear dynamic range (LDR) between 10 and 9700 microg L(-1). Conventional UV absorbance detectors tuned at 254 nm can be employed as well with comparable R.S.D. and LDR, but with LODc one order of magnitude higher than AFS detector and lower specificity. The sampling procedure followed by LC-DAD-CVGAFS analysis has been validated, as example, for H2S determination by a certified gas permeation tube as a source of 3.071+/-0.154 microg min(-1) of H2S, giving a recovery of 99.8+/-7% and it has been applied to the determination of sulfur compounds in real gas samples (biogas and the air of a plant for fractional distillation of crude oil).

  1. EDITORIAL: Probing the nanoworld Probing the nanoworld

    Science.gov (United States)

    Miles, Mervyn

    2009-10-01

    In nanotechnology, it is the unique properties arising from nanometre-scale structures that lead not only to their technological importance but also to a better understanding of the underlying science. Over the last twenty years, material properties at the nanoscale have been dominated by the properties of carbon in the form of the C60 molecule, single- and multi-wall carbon nanotubes, nanodiamonds, and recently graphene. During this period, research published in the journal Nanotechnology has revealed the amazing mechanical properties of such materials as well as their remarkable electronic properties with the promise of new devices. Furthermore, nanoparticles, nanotubes, nanorods, and nanowires from metals and dielectrics have been characterized for their electronic, mechanical, optical, chemical and catalytic properties. Scanning probe microscopy (SPM) has become the main characterization technique and atomic force microscopy (AFM) the most frequently used SPM. Over the past twenty years, SPM techniques that were previously experimental in nature have become routine. At the same time, investigations using AFM continue to yield impressive results that demonstrate the great potential of this powerful imaging tool, particularly in close to physiological conditions. In this special issue a collaboration of researchers in Europe report the use of AFM to provide high-resolution topographical images of individual carbon nanotubes immobilized on various biological membranes, including a nuclear membrane for the first time (Lamprecht C et al 2009 Nanotechnology 20 434001). Other SPM developments such as high-speed AFM appear to be making a transition from specialist laboratories to the mainstream, and perhaps the same may be said for non-contact AFM. Looking to the future, characterisation techniques involving SPM and spectroscopy, such as tip-enhanced Raman spectroscopy, could emerge as everyday methods. In all these advanced techniques, routinely available probes will

  2. Examination of biogenic selenium-containing nanosystems based on polyelectrolyte complexes by atomic force, Kelvin probe force and electron microscopy methods

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanova, T. E., E-mail: tat-sukhanova@mail.ru; Vylegzhanina, M. E.; Valueva, S. V.; Volkov, A. Ya.; Kutin, A. A. [Institute of Macromolecular Compounds RAS, 199004 Bolshoy Pr., 31, St.-Petersburg (Russian Federation); Temiryazeva, M. P.; Temiryazev, A. G. [Kotel’nikov Institute of Radio Engineering and Electronics (Fryazino Branch) Russian Academy of Sciences, Fryazino, Moscow region, 141190 (Russian Federation)

    2016-06-17

    The morphology and electrical properties of biogenic selenium-containing nanosystems based on polyelectrolyte complexes (PECs) were examined using AFM, Kelvin Probe Force and electron microscopy methods. It has been found, that prepared nanostructures significantly differed in their morphological types and parameters. In particular, multilayers capsules can be produced via varying synthesis conditions, especially, the selenium–PEC mass ratio ν. At the “special point” (ν = 0.1), filled and hollow nano- and microcapsules are formed in the system. The multilayer character of the capsules walls is visible in the phase images. Kelvin Probe Force images showed the inhomogeneity of potential distribution in capsules and outside them.

  3. Formation of field induced absorption in the probe response signal of a four-level V type atomic system a theoretical study

    CERN Document Server

    Islam, Khairul; Bhattacharyya, Dipankar; Bandyopadhyay, Amitava

    2016-01-01

    A density matrix based analytical model is developed to study the coherent probe field propagation through a four-level V type system in presence of a coherent control field. The model allows coupling of the probe field from the upper ground level to both of the excited levels keeping the control field locked to a particular transition. The addition of an extra ground level to a conventional three-level V type system creates extra decay paths to the ground levels for the upper level population. A set of sixteen density matrix based equations are formed and then solved analytically under rotating wave approximation to study the probe response under steady state condition. The simulated probe absorption spectra shows absorption dip at the centre of a transparency window only under Doppler broadened condition although the conventional EIT window appears under Doppler free condition. The dependence of the field induced absorption signal on the Rabi frequency of the control field, population transfer rate among th...

  4. RADMAP: Simple probes for rapid assessment of complex reactivity: A method and case studies on the reaction of hydrogen atoms with unsaturated organic molecules.

    Science.gov (United States)

    Long, Andrew K; Fawcett, Jason A; Clyburne, Jason A C; Pye, Cory C

    2016-03-01

    RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H(+), H(-), Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Quantum tomography of an electron

    Science.gov (United States)

    Jullien, T.; Roulleau, P.; Roche, B.; Cavanna, A.; Jin, Y.; Glattli, D. C.

    2014-10-01

    The complete knowledge of a quantum state allows the prediction of the probability of all possible measurement outcomes, a crucial step in quantum mechanics. It can be provided by tomographic methods which have been applied to atomic, molecular, spin and photonic states. For optical or microwave photons, standard tomography is obtained by mixing the unknown state with a large-amplitude coherent photon field. However, for fermions such as electrons in condensed matter, this approach is not applicable because fermionic fields are limited to small amplitudes (at most one particle per state), and so far no determination of an electron wavefunction has been made. Recent proposals involving quantum conductors suggest that the wavefunction can be obtained by measuring the time-dependent current of electronic wave interferometers or the current noise of electronic Hanbury-Brown/Twiss interferometers. Here we show that such measurements are possible despite the extreme noise sensitivity required, and present the reconstructed wavefunction quasi-probability, or Wigner distribution function, of single electrons injected into a ballistic conductor. Many identical electrons are prepared in well-controlled quantum states called levitons by repeatedly applying Lorentzian voltage pulses to a contact on the conductor. After passing through an electron beam splitter, the levitons are mixed with a weak-amplitude fermionic field formed by a coherent superposition of electron-hole pairs generated by a small alternating current with a frequency that is a multiple of the voltage pulse frequency. Antibunching of the electrons and holes with the levitons at the beam splitter changes the leviton partition statistics, and the noise variations provide the energy density matrix elements of the levitons. This demonstration of quantum tomography makes the developing field of electron quantum optics with ballistic conductors a new test-bed for quantum information with fermions. These results may

  6. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff Mathiasen, Anne-Gitte

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings point...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  7. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff, Anne-Gitte

    2012-01-01

    and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings......Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  8. Analyzing the effect of the forces exerted on cantilever probe tip of atomic force microscope with tapering-shaped geometry and double piezoelectric extended layers in the air and liquid environments

    Science.gov (United States)

    Korayem, Moharam Habibnejad; Nahavandi, Amir

    2017-01-01

    The aim of the present study is to assess the force vibrational performance of tapering-shaped cantilevers, using Euler-Bernoulli theory. Tapering-shaped cantilevers have plan-view geometry consisting of a rectangular section at the clamped end and a triangular section at the tip. Hamilton's principle is utilized to obtain the partial differential equations governing the nonlinear vibration of the system as well as the corresponding boundary conditions. In this model, a micro cantilever, which is covered by two piezoelectric layers at the top and the bottom, is modeled at angle α. Both of these layers are subjected to similar AC and DC voltages. This paper attempts to determine the effect of the capillary force exerted on the cantilever probe tip of an atomic force microscope. The capillary force emerges due to the contact between thin water films with a thickness of hc which have accumulated on the sample and the probe. In addition, an attempt is made to develop the capillary force between the tip and the sample surface with respect to the geometry obtained. The smoothness or the roughness of the surfaces as well as the geometry of the cantilever tip have significant effects on the modeling of forces applied to the probe tip. In this article, the Van der Waals and the repulsive forces are considered to be the same in all of the simulations, and only is the capillary force altered in order to evaluate the role of this force in the atomic force microscope based modeling. We also indicate that the tip shape and the radial distance of the meniscus greatly influence the capillary force. The other objective of our study is to draw a comparison between tapering-and rectangular-shaped cantilevers. Furthermore, the equation for converting the tip of a tapering-shaped cantilever into a rectangular cantilever is provided. Moreover, the modal analysis method is employed to solve the motion equation. The mode shape function for the two tapering-shaped sections of the first

  9. Neuronavigation using an articulated arm with a bayonet probe on a computer graphic composite of magnetic resonance and computerized tomography images.

    Science.gov (United States)

    Hayashi, N; Endo, S; Ikeda, H; Takaku, A

    1998-09-01

    This report describes a neurosurgical navigational system using a newly-designed articulated arm with an interchangeable probe shaped like a bayonet, which can be used in deep structures through narrow openings. This system enables three-dimensional integration of magnetic resonance and computed tomographical images, and thereby yields computer graphic composites of the scalp, brain, skull, and vessels. The arm was used in 15 patients during open brain surgery, including 5 skull base procedures. This system was useful for comprehension of skull base anatomy and could conveniently be used in microscopic neurosurgical procedures without limiting the operative field.

  10. Three-dimensional atomic-scale investigation of ZnO-MgxZn1-xO m-plane heterostructures

    Science.gov (United States)

    Di Russo, E.; Mancini, L.; Moyon, F.; Moldovan, S.; Houard, J.; Julien, F. H.; Tchernycheva, M.; Chauveau, J. M.; Hugues, M.; Da Costa, G.; Blum, I.; Lefebvre, W.; Blavette, D.; Rigutti, L.

    2017-07-01

    The structural, compositional, and optical properties of ZnO/MgxZn1-xO m-plane heterostructures are investigated using scanning transmission electron microscopy, laser-assisted atom probe tomography, and micro-photoluminescence. Coupled with electron tomography, atom probe tomography is currently the only technique providing a 3D reconstruction of the position of the atoms of a nanoscale specimen with their chemical nature. The multi-quantum well system investigated exhibits a V-groove grating profile along the a-axis accompanied by the formation of Zn- and Mg-enriched regions corresponding to the edges pointing towards the substrate and towards the upper surface, respectively. The optical signature of these heterostructures has been investigated by performing micro-photoluminescence on atom probe tip specimens. Effective mass calculations based on the 3D microscopy data indicate that the quantum well geometry and barrier composition yield a localization of hole states at the bottom of the V-groove.

  11. Reduced hydrophobic interaction of polystyrene surfaces by spontaneous segregation of block copolymers with oligo (ethylene glycol) methyl ether methacrylate blocks: force measurements in water using atomic force microscope with hydrophobic probes.

    Science.gov (United States)

    Zhang, Rui; Seki, Akiko; Ishizone, Takashi; Yokoyama, Hideaki

    2008-05-20

    Reduction of hydrophobic interaction in water is important in biological interfaces. In our previous work, we have found that poly(styrene- b-triethylene glycol methyl ether methacrylate) (PS-PME3MA) segregates the PME3MA block to the surface in hydrophobic environment, such as in air or in a vacuum, and shows remarkable resistance against adsorption or adhesion of proteins, platelets, and cells in water. In this paper, we report that atomic force microscopy (AFM) with hydrophobic probes can directly monitor the reduced hydrophobic interaction of the PS surfaces modified by poly(styrene- b-origoethylene glycol methyl ether methacrylate) (PS-PME NMA), where N is the number of ethylene glycol units. The pull-off forces between the hydrophobic probes that are coated with octyltrichlorosilane (OLTS) and the PS-PME NMA modified polystyrene (PS) surfaces in water were measured. The absolute spring constants and tip-curvatures of the AFM cantilevers were measured to compute the work of adhesion by the Johnson, Kendall, and Roberts (JKR) theory, which relates the pull-off force at which the separation occurs between a hemisphere and a plane to the work of adhesion. The hydrophobic interactions between the hydrophobic tip and polymer surfaces in water were greatly reduced with the segregated PME NMA blocks. The hydrophobic interactions decrease with increasing N of the series of PS-PME NMA and show a correlation with the amount of protein adsorbed.

  12. O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

    Directory of Open Access Journals (Sweden)

    Roman Sommer

    2016-12-01

    Full Text Available Selenoglycosides are used as reactive glycosyl donors in the syntheses of oligosaccharides. In addition, such heavy atom analogs of natural glycosides are useful tools for structure determination of their lectin receptors using X-ray crystallography. Some lectins, e.g., members of the tectonin family, only bind to carbohydrate epitopes with O-alkylated ring hydroxy groups. In this context, we report the first synthesis of an O-methylated selenoglycoside, specifically methyl 2-O-methyl-L-selenofucopyranoside, a ligand of the lectin tectonin-2 from the mushroom Laccaria bicolor. The synthetic route required a strategic revision and further optimization due to the intrinsic lability of alkyl selenoglycosides, in particular for the labile fucose. Here, we describe a successful synthetic access to methyl 2-O-methyl-L-selenofucopyranoside in 9 linear steps and 26% overall yield starting from allyl L-fucopyranoside.

  13. Probing viscoelastic surfaces with bimodal tapping-mode atomic force microscopy: Underlying physics and observables for a standard linear solid model.

    Science.gov (United States)

    Solares, Santiago D

    2014-01-01

    This paper presents computational simulations of single-mode and bimodal atomic force microscopy (AFM) with particular focus on the viscoelastic interactions occurring during tip-sample impact. The surface is modeled by using a standard linear solid model, which is the simplest system that can reproduce creep compliance and stress relaxation, which are fundamental behaviors exhibited by viscoelastic surfaces. The relaxation of the surface in combination with the complexities of bimodal tip-sample impacts gives rise to unique dynamic behaviors that have important consequences with regards to the acquisition of quantitative relationships between the sample properties and the AFM observables. The physics of the tip-sample interactions and its effect on the observables are illustrated and discussed, and a brief research outlook on viscoelasticity measurement with intermittent-contact AFM is provided.

  14. Single atom microscopy.

    Science.gov (United States)

    Zhou, Wu; Oxley, Mark P; Lupini, Andrew R; Krivanek, Ondrej L; Pennycook, Stephen J; Idrobo, Juan-Carlos

    2012-12-01

    We show that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene. Sequential fast-scan annular dark-field (ADF) imaging provides direct visualization of point defect diffusion within the graphene lattice, with all atoms clearly resolved and identified via quantitative image analysis. Summing multiple ADF frames of stationary defects produce images with minimized statistical noise and reduced distortions of atomic positions. Electron energy-loss spectrum imaging of single atoms allows the delocalization of inelastic scattering to be quantified, and full quantum mechanical calculations are able to describe the delocalization effect with good accuracy. These capabilities open new opportunities to probe the defect structure, defect dynamics, and local optical properties in 2D materials with single atom sensitivity.

  15. Synthesis and in vitro and in vivo evaluation of SiFA-tagged bombesin and RGD peptides as tumor imaging probes for positron emission tomography.

    Science.gov (United States)

    Lindner, Simon; Michler, Christina; Leidner, Stephanie; Rensch, Christian; Wängler, Carmen; Schirrmacher, Ralf; Bartenstein, Peter; Wängler, Björn

    2014-04-16

    Gastrin-releasing-peptide (GRP)-receptors and αvβ3-integrins are widely discussed as potential target structures for oncological imaging with positron emission tomography (PET). Favored by the overexpression of receptors on the surface of tumor cells good imaging characteristics can be achieved with highly specific radiolabeled receptor ligands. PEGylated bombesin (PESIN) derivatives as specific GRP receptor ligands and RGD (one-letter codes for arginine-glycine-aspartic acid) peptides as specific αvβ3 binders were synthesized and tagged with a silicon-fluorine-acceptor (SiFA) moiety. The SiFA synthon allows for a fast and highly efficient isotopic exchange reaction at room temperature giving the [(18)F]fluoride labeled peptides in up to 62% radiochemical yields (d.c.) and ≥99% radiochemical purity in a total synthesis time of less than 20 min. Using nanomolar quantities of precursor high specific activities of up to 60 GBq μmol(-1) were obtained. To compensate the high lipophilicity of the SiFA moiety various hydrophilic structure modifications were introduced leading to significantly reduced logD values. Competitive displacement experiments with the PESIN derivatives showed a 32 to 6 nM affinity to the GRP receptor on PC3 cells, and with the RGD peptides a 7 to 3 μM affinity to the αvβ3 integrins on U87MG cells. All derivatives proved to be stable in human plasma over at least 120 min. Small animal PET measurements and biodistribution studies revealed an enhanced and specific accumulation of the RGD peptide (18)F-SiFA-LysMe3-γ-carboxy-d-Glu-RGD (17) in the tumor tissue of U87MG tumor-bearing mice of 5.3% ID/g whereas the PESIN derivatives showed a high liver uptake and only a low accumulation in the tumor tissue of PC3 xenografts. Stability studies with compound 17 provided further information on its metabolism in vivo. These results altogether demonstrate that the reduction of the overall lipophilicity of SiFA tagged RGD peptides is a promising

  16. Atomic force microscopy analysis of IgG films at hydrophobic surfaces: a promising method to probe IgG orientations and optimize ELISA tests performance.

    Science.gov (United States)

    de Thier, Pierre; Bacharouche, Jalal; Duval, Jérôme F L; Skali-Lami, Salaheddine; Francius, Grégory

    2015-02-01

    IgG films are widely used in the field of immunoassays, especially in (double) antibody-sandwich ELISA tests where capture antibodies are coated on surfaces like polystyrene or hydrophobic self-assembled monolayers (h-SAMs). It is critical to analyze-at a molecular scale and under liquid conditions-the structure of the deposited IgG film in order to quantitatively address the efficiency of the ELISA test in terms of antigen detection. In this communication, we report an atomic force microscopy (AFM) analysis evidencing a strong relationship between immunological activities of mouse monoclonal anti-human interleukin-2 (IL-2) and 6 (IL-6) antibodies, thickness and roughness of the IgG monolayer adsorbed onto h-SAMs, and surface concentration of IgG molecules. Indirect information may be further obtained on antibody orientation. Collating the results obtained by AFM and those from ELISA tests leads us to conclude that antibodies like anti-IL-6 forming flat monolayers should be more efficient under ELISA detection conditions. In addition, the concentration of IgG in the coating suspension should be optimized to obtain a monolayer heavily populated by "end-on" adsorbed molecules, an orientation that is desirable for enhancing ELISA tests performance. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. 5-[{sup 18}F]Fluoroalkyl pyrimidine nucleosides: probes for positron emission tomography imaging of herpes simplex virus type 1 thymidine kinase gene expression

    Energy Technology Data Exchange (ETDEWEB)

    Chacko, Ann-Marie [Institute for Environmental Medicine, Targeted Therapeutics Program, University of Pennsylvania, Philadelphia, PA 19104 (United States); Blankemeyer, Eric; Lieberman, Brian P.; Qu, Wenchao [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kung, Hank F. [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104 (United States)], E-mail: kunghf@gmail.com

    2009-01-15

    Introduction: The preliminary in vivo evaluation of novel 5-[{sup 18}F]fluoroalkyl-2'-deoxyuridines ([{sup 18}F]FPrDU, [{sup 18}F]FBuDU, [{sup 18}F]FPeDU; [{sup 18}F]1a-c, respectively) and 2'-fluoro-2'-deoxy-5-[{sup 18}F]fluoroalkyl-1-{beta}-D-arabinofuranosyl uracils ([{sup 18}F]FFPrAU, [{sup 18}F]FFBuAU, [{sup 18}F]FFPeAU; [{sup 18}F]1d-f, respectively) as probes for imaging herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene expression is described. Methods: [{sup 18}F]1a-f were successfully synthesized by a rapid and efficient two-step one-pot nucleophilic fluorination reaction using 5-O-mesylate precursors and [{sup 18}F]F{sup -}. For in vivo studies, tumor xenografts were grown in nude mice by implanting RG2 cells stably expressing HSV1-tk (RG2TK+) and wild-type cells (RG2). Results: Biodistribution studies at 2 h pi revealed that the uptake of [{sup 18}F]1a-b and [{sup 18}F]1d-e in RG2TK+ tumors was not significantly different from control tumors. However, [{sup 18}F]1c and [{sup 18}F]1f had an average 1.6- and 1.7-fold higher uptake in RG2TK+ tumors than control RG2 tumors. Blood activity curves for [{sup 18}F]1c and [{sup 18}F]1f highlight rapid clearance of radioactivity in the blood. Dynamic small animal PET (A-PET) imaging studies of tumor-bearing mice with [{sup 18}F]1c and [{sup 18}F]1f showed higher initial uptake (3.5- and 1.4-fold, respectively) in RG2TK+ tumors than in control tumors, with continued washout of activity from both tumors over time. Conclusions: Biological evaluations suggest that [{sup 18}F]1c and [{sup 18}F]1f may have limited potential for imaging HSV1-tk gene expression due to fast washout of activity from the blood, thus significantly decreasing sensitivity and specificity of tracer accumulation in HSV1-tk-expressing tumors.

  18. Analysis of the effect of LRP-1 silencing on the invasive potential of cancer cells by nanomechanical probing and adhesion force measurements using atomic force microscopy

    Science.gov (United States)

    Le Cigne, A.; Chièze, L.; Beaussart, A.; El-Kirat-Chatel, S.; Dufrêne, Y. F.; Dedieu, S.; Schneider, C.; Martiny, L.; Devy, J.; Molinari, M.

    2016-03-01

    Low-density lipoprotein receptor-related protein 1 (LRP-1) can internalize proteases involved in cancer progression and is thus considered a promising therapeutic target. However, it has been demonstrated that LRP-1 is also able to regulate the endocytosis of membrane-anchored proteins. Thus, strategies that target LRP-1 to modulate proteolysis could also affect adhesion and cytoskeleton dynamics. Here, we investigated the effect of LRP-1 silencing on parameters reflecting cancer cells' invasiveness by atomic force microscopy (AFM). The results show that LRP-1 silencing induces changes in the cells' adhesion behavior, particularly the dynamics of cell attachment. Clear alterations in morphology, such as more pronounced stress fibers and increased spreading, leading to increased area and circularity, were also observed. The determination of the cells' mechanical properties by AFM showed that these differences are correlated with an increase in Young's modulus. Moreover, the measurements show an overall decrease in cell motility and modifications of directional persistence. An overall increase in the adhesion force between the LRP-1-silenced cells and a gelatin-coated bead was also observed. Ultimately, our AFM-based force spectroscopy data, recorded using an antibody directed against the β1 integrin subunit, provide evidence that LRP-1 silencing modifies the rupture force distribution. Together, our results show that techniques traditionally used for the investigation of cancer cells can be coupled with AFM to gain access to complementary phenotypic parameters that can help discriminate between specific phenotypes associated with different degrees of invasiveness.Low-density lipoprotein receptor-related protein 1 (LRP-1) can internalize proteases involved in cancer progression and is thus considered a promising therapeutic target. However, it has been demonstrated that LRP-1 is also able to regulate the endocytosis of membrane-anchored proteins. Thus, strategies

  19. Putting zircon surface geochronology and geochemistry in textural context using 3D Xray tomography: Probing the magmatic history of Mount St. Helens

    Science.gov (United States)

    Claiborne, L. L.; Wooden, J. L.; Miller, C. F.; Gualda, G. A.; Clynne, M. A.; Flanagan, D. M.

    2010-12-01

    -ray tomography to create 3D Zr maps for pumices for which we have surface compositional and age data. We located and characterized the zircons in a given sample, described their textural relations, and identified multiple populations of zircons in individual samples. Preliminary results for the 3 imaged samples show zircons as both phenocrysts in glass and inclusions in other minerals, clearly explaining the variations in zircon surfaces. Careful characterization of these relationships may allow us to determine magma composition and timing of episodes of major phase mineral growth that incorporates certain populations of zircons, possibly corresponding to cooling, depressurization, or recharge events. This, combined with our existing ‘conventional’ zircon age and compositional data, allows us to characterize MSH magmas as they undergo crystallization, fractionation, rejuvenation and mixing and to constrain the timing of these processes.

  20. Talin-driven inside-out activation mechanism of platelet αIIbβ3 integrin probed by multimicrosecond, all-atom molecular dynamics simulations.

    Science.gov (United States)

    Provasi, Davide; Negri, Ana; Coller, Barry S; Filizola, Marta

    2014-12-01

    Platelet aggregation is the consequence of the binding of extracellular bivalent ligands such as fibrinogen and von Willebrand factor to the high affinity, active state of integrin αIIbβ3. This state is achieved through a so-called "inside-out" mechanism characterized by the membrane-assisted formation of a complex between the F2 and F3 subdomains of intracellular protein talin and the integrin β3 tail. Here, we present the results of multi-microsecond, all-atom molecular dynamics simulations carried on the complete transmembrane (TM) and C-terminal (CT) domains of αIIbβ3 integrin in an explicit lipid-water environment, and in the presence or absence of the talin-1 F2 and F3 subdomains. These large-scale simulations provide unprecedented molecular-level insights into the talin-driven inside-out activation of αIIbβ3 integrin. Specifically, they suggest a preferred conformation of the complete αIIbβ3 TM/CT domains in a lipid-water environment, and testable hypotheses of key intermolecular interactions between αIIbβ3 integrin and the F2/F3 domains of talin-1. Notably, not only do these simulations give support to a stable left-handed reverse turn conformation of the αIIb juxtamembrane motif rather than a helical turn, but they raise the question as to whether TM helix separation is required for talin-driven integrin activation. © 2014 Wiley Periodicals, Inc.

  1. Radioactive Probes on Ferromagnetic Surfaces

    CERN Document Server

    2002-01-01

    On the (broad) basis of our studies of nonmagnetic radioactive probe atoms on magnetic surfaces and at interfaces, we propose to investigate the magnetic interaction of magnetic probe atoms with their immediate environment, in particular of rare earth (RE) elements positioned on and in ferromagnetic surfaces. The preparation and analysis of the structural properties of such samples will be performed in the UHV chamber HYDRA at the HMI/Berlin. For the investigations of the magnetic properties of RE atoms on surfaces Perturbed Angular Correlation (PAC) measurements and Mössbauer Spectroscopy (MS) in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN) are proposed.

  2. Probing the Dielectric Properties of Ultrathin Al/Al2O3/Al Trilayers Fabricated Using in Situ Sputtering and Atomic Layer Deposition.

    Science.gov (United States)

    Acharya, Jagaran; Wilt, Jamie; Liu, Bo; Wu, Judy

    2018-01-12

    Dielectric properties of ultrathin Al2O3 (1.1-4.4 nm) in metal-insulator-metal (M-I-M) Al/Al2O3/Al trilayers fabricated in situ using an integrated sputtering and atomic layer deposition (ALD) system were investigated. An M-I interfacial layer (IL) formed during the pre-ALD sample transfer even under high vacuum has a profound effect on the dielectric properties of the Al2O3 with a significantly reduced dielectric constant (εr) of 0.5-3.3 as compared to the bulk εr ∼ 9.2. Moreover, the observed soft-type electric breakdown suggests defects in both the M-I interface and the Al2O3 film. By controlling the pre-ALD exposure to reduce the IL to a negligible level, a high εr up to 8.9 was obtained on the ALD Al2O3 films with thicknesses from 3.3 to 4.4 nm, corresponding to an effective oxide thickness (EOT) of ∼1.4-1.9 nm, respectively, which are comparable to the EOTs found in high-K dielectrics like HfO2 at 3-4 nm in thickness and further suggest that the ultrathin ALD Al2O3 produced in optimal conditions may provide a low-cost alternative gate dielectric for CMOS. While εr decreases at a smaller Al2O3 thickness, the hard-type dielectric breakdown at 32 MV/cm and in situ scanning tunneling spectroscopy revealed band gap ∼2.63 eV comparable to that of an epitaxial Al2O3 film. This suggests that the IL is unlikely a dominant reason for the reduced εr at the Al2O3 thickness of 1.1-2.2 nm but rather a consequence of the electron tunneling as confirmed in the transport measurement. This result demonstrates the critical importance in controlling the IL to achieving high-performance ultrathin dielectric in MIM structures.

  3. Atomic Force Microscopy and Real Atomic Resolution. Simple Computer Simulations

    NARCIS (Netherlands)

    Koutsos, V.; Manias, E.; Brinke, G. ten; Hadziioannou, G.

    1994-01-01

    Using a simple computer simulation for AFM imaging in the contact mode, pictures with true and false atomic resolution are demonstrated. The surface probed consists of two f.c.c. (111) planes and an atomic vacancy is introduced in the upper layer. Changing the size of the effective tip and its

  4. Evaluation of F-18-labeled 5-iodocytidine ({sup 18}F-FIAC) as a new potential positron emission tomography probe for herpes simplex virus type 1 thymidine kinase imaging

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Pei-Chia; Wu, Chun-Yi; Chang, Wen-Yi; Chang, Wei-Ting [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, 11221, Taiwan (China); Alauddin, Mian [Department of Experimental Diagnostic Imaging, MD Anderson Cancer Center, University of Texas, TX, 77054 (United States); Liu, Ren-Shan [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, 11221, Taiwan (China); Department of Nuclear Medicine, Faculty of Medicine, National Yang-Ming University, Taipei, 11221, Taiwan (China); Department of Nuclear Medicine and National PET/Cyclotron Center, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Lin, Wuu-Jyh [Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan, 32546, Taiwan (China); Chen, Fu-Du [College of Health and Leisure Science, TransWorld University, Yunlin, 64063, Taiwan (China); Chen, Chuan-Lin, E-mail: clchen2@ym.edu.tw [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, 11221, Taiwan (China); Wang, Hsin-Ell, E-mail: hewang@ym.edu.tw [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, 11221, Taiwan (China)

    2011-10-15

    Objective: Herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene in combination with radiolabeled nucleoside substrates is the most widely used reporter system. This study characterized 1-(2'-deoxy-2'-[{sup 18}F]fluoro-{beta}-D-arabinofuranosyl)-5-iodocytosine ({sup 18}F-FIAC) as a new potential positron emission tomography (PET) probe for HSV1-tk gene imaging and compared it with 2'-deoxy-2'-[{sup 18}F]fluoro-5-iodo-1-{beta}-D-arabinofuranosyluracil ({sup 18}F-FIAU) and 2'-deoxy-2'-[{sup 18}F]fluoro-5-ethyl-1-{beta}-D-arabinofuranosyluracil({sup 18}F-FEAU) (thymidine analogues) in an NG4TL4-WT/STK sarcoma-bearing mouse model. Methods: A cellular uptake assay, biodistribution study, radioactive metabolites assay and microPET imaging of NG4TL4-WT/STK tumor-bearing mice post administration of {sup 18}F-FIAC, {sup 18}F-FIAU and {sup 18}F-FEAU were conducted to characterize the biological properties of these tracers. Results: Highly specific uptake of {sup 18}F-FIAC, {sup 18}F-FIAU and {sup 18}F-FEAU in tk-transfected [tk(+)] cells was observed. The tk(+)-to-tk(-) cellular uptake ratio after a 2-h incubation was 66.6{+-}25.1, 76.3{+-}18.2 and 247.2{+-}37.2, respectively. In biodistribution studies, {sup 18}F-FIAC showed significant tk(+) tumor specificity (12.6; expressed as the tk(+)-to-tk(-) tumor uptake ratio at 2 h postinjection) comparable with {sup 18}F-FIAU (15.8) but lower than {sup 18}F-FEAU (48.0). The results of microPET imaging also revealed the highly specific accumulation of these three radioprobes in the NG4TL4-tk(+) tumor. Conclusion: Our findings suggested that the cytidine analogue {sup 18}F-FIAC is a new potential PET probe for the imaging of HSV1-tk gene expression. {sup 18}F-FIAC may be regarded as the prodrug of {sup 18}F-FIAU in vivo.

  5. Optical nanofibres and neutral atoms

    CERN Document Server

    Nieddu, Thomas; Chormaic, Sile Nic

    2015-01-01

    Optical nanofibres are increasingly being used in cold atom experiments due to their versatility and the clear advantages they have when developing all-fibred systems for quantum technologies. They provide researchers with a method of overcoming the Rayleigh range for achieving high intensities in a focussed beam over a relatively long distance, and can act as a noninvasive tool for probing cold atoms. In this review article, we will briefly introduce the theory of mode propagation in an ultrathin optical fibre and highlight some of the more significant theoretical and experimental progresses to date, including the early work on atom probing, manipulation and trapping, the study of atom-dielectric surface interactions, and the more recent observation of nanofibre-mediated nonlinear optics phenomena in atomic media. The functionality of optical nanofibres in relation to the realisation of atom-photon hybrid quantum systems is also becoming more evident as some of the earlier technical challenges are surpassed ...

  6. Electric field imaging of single atoms

    Science.gov (United States)

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-05-01

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.

  7. Electric field imaging of single atoms

    Science.gov (United States)

    Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

    2017-01-01

    In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

  8. Single atom electrochemical and atomic analytics

    Science.gov (United States)

    Vasudevan, Rama

    In the past decade, advances in electron and scanning-probe based microscopies have led to a wealth of imaging and spectroscopic data with atomic resolution, yielding substantial insight into local physics and chemistry in a diverse range of systems such as oxide catalysts, multiferroics, manganites, and 2D materials. However, typical analysis of atomically resolved images is limited, despite the fact that image intensities and distortions of the atoms from their idealized positions contain unique information on the physical and chemical properties inherent to the system. Here, we present approaches to data mine atomically resolved images in oxides, specifically in the hole-doped manganite La5/8Ca3/8MnO3, on epitaxial films studied by in-situ scanning tunnelling microscopy (STM). Through application of bias to the STM tip, atomic-scale electrochemistry is demonstrated on the manganite surface. STM images are then further analyzed through a suite of algorithms including 2D autocorrelations, sliding window Fourier transforms, and others, and can be combined with basic thermodynamic modelling to reveal relevant physical and chemical descriptors including segregation energies, existence and strength of atomic-scale diffusion barriers, surface energies and sub-surface chemical species identification. These approaches promise to provide tremendous insights from atomically resolved functional imaging, can provide relevant thermodynamic parameters, and auger well for use with first-principles calculations to yield quantitative atomic-level chemical identification and structure-property relations. This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE. Research was conducted at the Center for Nanophase Materials Sciences, which also provided support and is a DOE Office of Science User Facility.

  9. Development of atomic beam probe for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Berta, M., E-mail: bertam@sze.hu [Széchenyi István University, EURATOM Association, Győr (Hungary); Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Anda, G.; Aradi, M.; Bencze, A.; Buday, Cs.; Kiss, I.G.; Tulipán, Sz.; Veres, G.; Zoletnik, S. [Wigner – RCP, HAS, EURATOM Association, Budapest (Hungary); Havlícek, J.; Háček, P. [Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Charles University in Prague, Faculty of Mathematics and Physics (Czech Republic)

    2013-11-15

    Highlights: • ABP is newly developed diagnostic. • Unique measurement method for the determination of plasma edge current variations caused by different transient events such as ELMs. • The design process has been fruitfully supported by the physically motivated computer simulations. • Li-BES system has been modified accordingly to the needs of the ABP. -- Abstract: The concept and development of a new detection method for light alkali ions stemming from diagnostic beams installed on medium size tokamak is described. The method allows us the simultaneous measurement of plasma density fluctuations and fast variations in poloidal magnetic field, therefore one can infer the fast changes in edge plasma current. The concept has been worked out and the whole design process has been done at Wigner RCP. The test detector with appropriate mechanics and electronics is already installed on COMPASS tokamak. General ion trajectory calculation code (ABPIons) has also been developed. Detailed calculations show the possibility of reconstruction of edge plasma current density profile changes with high temporal resolution, and the possibility of density profile reconstruction with better spatial resolution compared to standard Li-BES measurement, this is important for pedestal studies.

  10. Noninvasive visualization and quantification of tumor {alpha}{sub V{beta}3} integrin expression using a novel positron emission tomography probe, {sup 64}Cu-cyclam-RAFT-c(-RGDfK-){sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Zhao-Hui [Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Furukawa, Takako, E-mail: tfuru@nirs.go.j [Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Biomedical Imaging Research Center, University of Fukui, Fukui 910-1193 (Japan); Galibert, Mathieu; Boturyn, Didier [Departement de Chimie Moleculaire, UMR 5250, CNRS-Universite Joseph Fourier, 38041 Grenoble Cedex 9 (France); Coll, Jean-Luc [INSERM U823, Institut Albert Bonniot and Universite Joseph Fourier, 38706 La Tronche Cedex, Grenoble (France); Fukumura, Toshimitsu; Saga, Tsuneo [Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Dumy, Pascal [Departement de Chimie Moleculaire, UMR 5250, CNRS-Universite Joseph Fourier, 38041 Grenoble Cedex 9 (France); Fujibayashi, Yasuhisa [Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555 (Japan); Biomedical Imaging Research Center, University of Fukui, Fukui 910-1193 (Japan)

    2011-05-15

    Introduction: The {alpha}{sub V{beta}3} integrin is a well-known transmembrane receptor involved in tumor invasion, angiogenesis and metastasis. Our aim was to evaluate a novel positron emission tomography (PET) probe, {sup 64}Cu-cyclam-RAFT-c(-RGDfK-){sub 4}, for noninvasive visualization and quantification of {alpha}{sub V{beta}3} integrin expression. Methods: RAFT-c(-RGDfK-){sub 4}, a tetrameric cyclic Arg-Gly-Asp (RGD)-based peptide, was conjugated with a bifunctional chelator, 1,4,8,11-tetraazacyclotetradecane (cyclam), radiolabeled with the positron emitter {sup 64}Cu and evaluated in vitro by cell binding and competitive inhibition assays and in vivo by biodistribution and receptor blocking studies, and PET imaging. The following cell lines, human embryonic kidney HEK293({beta}{sub 1}) [{alpha}{sub V{beta}3}-negative] and HEK293({beta}{sub 3}) [{alpha}{sub V{beta}3}-overexpressing] and human glioblastoma U87MG [naturally expressing {alpha}{sub V{beta}3}], together with their subcutaneous xenografts in athymic nude mice, were used for the present study. The expression levels of {alpha}{sub V{beta}3} on these cell lines and tumor xenografts were analyzed by flow cytometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis/autoradiography, respectively. Results: {sup 64}Cu-cyclam-RAFT-c(-RGDfK-){sub 4} demonstrated the in vitro and in vivo specificity for the {alpha}{sub V{beta}3} integrin and displayed rapid blood clearance, predominantly renal excretion and low uptake in nontumor tissues. Tumor uptake of {sup 64}Cu-cyclam-RAFT-c(-RGDfK-){sub 4} (3 h postinjection) in HEK293({beta}{sub 3}) (high levels of {alpha}{sub V{beta}3}), U87MG (moderate levels of {alpha}{sub V{beta}3}) and HEK293({beta}{sub 1}) (undetectable levels of {alpha}{sub V{beta}3}) tumors was 9.35%{+-}1.19%, 3.46%{+-}0.45% and 1.18%{+-}0.30% injected dose per gram, respectively, with a strong and positive correlation with the tumor {alpha}{sub V{beta}3} expression levels

  11. Catheters for optical coherence tomography

    Science.gov (United States)

    Atif, M.; Ullah, H.; Hamza, M. Y.; Ikram, M.

    2011-09-01

    The objective of this review article is to overview technology, clinical evidence, and future applications to date optical coherence tomography (OCT) probes to yield the diagnostic purpose. We have reviewed the designing, construction and working of different categories of OCT probes developed for optical diagnostics having a potential for non invasive and improved detection of different types of cancer as well as other neoplasm. Rotational and balloon catheters, imaging needles and hand-held, linear scanning, multichannel, micro electro mechanical systems (MEMS) technology based, dynamic focusing, forward view imaging, and common path interferometer based probes have been discussed in details. The fiber probes have shown excellent performance for two dimensional and three dimensional higher resolution, cross-sectional imaging of interior and exterior body tissues that can be compared with histopathology to provide the information about the angiogenesis and other lesions in the tissue. The MEMS-technology based probes are found to be more suitable for three dimensional morphological imaging.

  12. Cavity electromagnetically induced transparency with Rydberg atoms

    Science.gov (United States)

    Bakar Ali, Abu; Ziauddin

    2018-02-01

    Cavity electromagnetically induced transparency (EIT) is revisited via the input probe field intensity. A strongly interacting Rydberg atomic medium ensemble is considered in a cavity, where atoms behave as superatoms (SAs) under the dipole blockade mechanism. Each atom in the strongly interacting Rydberg atomic medium (87 Rb) follows a three-level cascade atomic configuration. A strong control and weak probe field are employed in the cavity with the ensemble of Rydberg atoms. The features of the reflected and transmitted probe light are studied under the influence of the input probe field intensity. A transparency peak (cavity EIT) is revealed at a resonance condition for small values of input probe field intensity. The manipulation of the cavity EIT is reported by tuning the strength of the input probe field intensity. Further, the phase and group delay of the transmitted and reflected probe light are studied. It is found that group delay and phase in the reflected light are negative, while for the transmitted light they are positive. The magnitude control of group delay in the transmitted and reflected light is investigated via the input probe field intensity.

  13. Cultural probes

    DEFF Research Database (Denmark)

    Madsen, Jacob Østergaard

    The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation.......The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation....

  14. Atom-by-Atom Construction of a Quantum Device.

    Science.gov (United States)

    Petta, Jason R

    2017-03-28

    Scanning tunneling microscopes (STMs) are conventionally used to probe surfaces with atomic resolution. Recent advances in STM include tunneling from spin-polarized and superconducting tips, time-domain spectroscopy, and the fabrication of atomically precise Si nanoelectronics. In this issue of ACS Nano, Tettamanzi et al. probe a single-atom transistor in silicon, fabricated using the precision of a STM, at microwave frequencies. While previous studies have probed such devices in the MHz regime, Tettamanzi et al. probe a STM-fabricated device at GHz frequencies, which enables excited-state spectroscopy and measurements of the excited-state lifetime. The success of this experiment will enable future work on quantum control, where the wave function must be controlled on a time scale that is much shorter than the decoherence time. We review two major approaches that are being pursued to develop spin-based quantum computers and highlight some recent progress in the atom-by-atom fabrication of donor-based devices in silicon. Recent advances in STM lithography may enable practical bottom-up construction of large-scale quantum devices.

  15. Atom probe analysis and magnetic properties of nanocrystalline Fe{sub 84.3}Si{sub 4}B{sub 8}P{sub 3}Cu{sub 0.7}

    Energy Technology Data Exchange (ETDEWEB)

    Jafari, S., E-mail: sahar_jafari@iust.ac.ir [Magnetic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047 (Japan); Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114 (Iran, Islamic Republic of); Beitollahi, A., E-mail: beitolla@iust.ac.ir [Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114 (Iran, Islamic Republic of); Yekta, B. Eftekhari [Center of Excellence for Ceramics in Energy and Environment, School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114 (Iran, Islamic Republic of); Ohkubo, T. [Magnetic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047 (Japan); Budinsky, Viktoria; Marsilius, Mie; Herzer, Giselher [Vacuumschmelze GmbH & Co. KG, D-63450, Hanau (Germany); Hono, K. [Magnetic Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047 (Japan)

    2016-07-25

    We have investigated the microstructure and the magnetic properties of as-cast and flash annealed (4 s at 420 °C–560 °C) Fe{sub 84.3}Si{sub 4}B{sub 8}P{sub 3}Cu{sub 0.7} melt-spun ribbons. The scanning electron microscopy-electron backscattered diffraction (SEM-EBSD) analyses proved the existence of crystalline layer with the thickness of 1 μm in the as-cast state on both the wheel-contacted and the free surfaces of ribbons. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) patterns showed that the crystalline surfaces were textured. Moreover, the microstructure, composition and phase evolution of surface crystallization were studied using TEM and 3DAP which the spherulitic microstructure on the surface was demonstrated. Flash annealing above 420 °C led to a nanocrystalline microstructure of containing 10–15 nm α-Fe (Si) crystallites embedded in a residual amorphous matrix containing Fe, Si, B and P. Three-dimensional atom probe (3DAP) and high resolution transmission electron microscopy (HRTEM) analysis revealed that boron and phosphorous were rejected from α-Fe (Si) phase and enriched in the residual amorphous phase. The nucleation of the nanocrystals occurs heterogeneously from the 3–5 nm α-Fe crystals that were present in the as-cast state. The saturation magnetic induction (B{sub s}) increases from B{sub s} = 1.55 T in the amorphous state to B{sub s} = 1.76 T after the crystallization. The saturation magnetostriction constant, λ{sub s}, decreased from originally 35 ppm in the as-cast state to about 14 ppm with coercive fields in the range of H{sub c} = 20–30 A/m. - Highlights: • We studied microstructure and magnetic properties of Fe{sub 84.3}Si{sub 4}B{sub 8}P{sub 3}Cu{sub 0.7} alloys. • The crystalline layer with spherulitic microstructure in as-cast state was shown. • In as-cast sample, nano clusters of α-Fe were detected within amorphous matrix. • B and P partitioned in amorphous phase that led to the grain growth

  16. Quantum state atomic force microscopy

    OpenAIRE

    Passian, Ali; Siopsis, George

    2017-01-01

    New classical modalities of atomic force microscopy continue to emerge to achieve higher spatial, spectral, and temporal resolution for nanometrology of materials. Here, we introduce the concept of a quantum mechanical modality that capitalizes on squeezed states of probe displacement. We show that such squeezing is enabled nanomechanically when the probe enters the van der Waals regime of interaction with a sample. The effect is studied in the non-contact mode, where we consider the paramete...

  17. Optical angular momentum and atoms.

    Science.gov (United States)

    Franke-Arnold, Sonja

    2017-02-28

    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  18. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  19. Atomic Physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  20. The bone-implant interface of dental implants in humans on the atomic scale.

    Science.gov (United States)

    Sundell, Gustav; Dahlin, Christer; Andersson, Martin; Thuvander, Mattias

    2017-01-15

    Osseointegration of dental implants occurs on a hierarchy of length scales down to the atomic level. A deeper understanding of the complex processes that take place at the surface of an implant on the smallest scale is of interest for the development of improved biomaterials. To date, transmission electron microscopy (TEM) has been utilized for examination of the bone-implant interface, providing details on the nanometer level. In this study we show that TEM imaging can be complemented with atom probe tomography (APT) to reveal the chemical composition of a Ti-based dental implant in a human jaw on the atomic level of resolution. As the atom probe technique has equal sensitivity for all elements, it allows for 3 dimensional characterizations of osseointegrated interfaces with unprecedented resolution. The APT reconstructions reveal a Ca-enriched zone in the immediate vicinity of the implant surface. A surface oxide of some 5nm thickness was measured on the titanium implant, with a sub-stoichiometric composition with respect to TiO2. Minor incorporation of Ca into the thin oxide film was also evident. We conclude that the APT technique is capable of revealing chemical information from the bone-implant interface in 3D with unprecedented resolution, thus providing important insights into the mechanisms behind osseointegration. Osseointegration of dental implants occurs on a hierarchy of length scales down to the atomic level. A deeper understanding of the complex processes that take place at the surface of an implant on the smallest scale is of interest for the development of improved biomaterials. To date, transmission electron microscopy (TEM) has been utilized for examination of the bone-implant interface, providing details on the nanometer level. In this study we show that TEM imaging can be complemented with atom probe tomography (APT) to reveal the chemical composition of a Ti-based dental implant in a human jaw on the atomic level of resolution. Correlative

  1. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.

    2005-01-01

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  2. Physical probing of cells

    Science.gov (United States)

    Rehfeldt, Florian; Schmidt, Christoph F.

    2017-11-01

    In the last two decades, it has become evident that the mechanical properties of the microenvironment of biological cells are as important as traditional biochemical cues for the control of cellular behavior and fate. The field of cell and matrix mechanics is quickly growing and so is the development of the experimental approaches used to study active and passive mechanical properties of cells and their surroundings. Within this topical review we will provide a brief overview, on the one hand, over how cellular mechanics can be probed physically, how different geometries allow access to different cellular properties, and, on the other hand, how forces are generated in cells and transmitted to the extracellular environment. We will describe the following experimental techniques: atomic force microscopy, traction force microscopy, magnetic tweezers, optical stretcher and optical tweezers pointing out both their advantages and limitations. Finally, we give an outlook on the future of the physical probing of cells.

  3. Final Technical Report for Award DESC0011912, "Trimodal Tapping Mode Atomic Force Microscopy: Simultaneous 4D Mapping of Conservative and Dissipative Probe-Sample Interactions of Energy-Relevant Materials”

    Energy Technology Data Exchange (ETDEWEB)

    Solares, Santiago D. [George Washington Univ., Washington, DC (United States)

    2017-09-22

    The final project report covering the period 7/1/14-6/30/17 provides an overview of the technical accomplishments in the areas of (i) fundamental viscoelasticity, (ii) multifrequency atomic force microscopy, and (iii) characterization of energy-relevant materials with atomic force microscopy. A list of publications supported by the project is also provided.

  4. Three-dimensional atom localization via electromagnetically induced transparency in a three-level atomic system.

    Science.gov (United States)

    Wang, Zhiping; Cao, Dewei; Yu, Benli

    2016-05-01

    We present a new scheme for three-dimensional (3D) atom localization in a three-level atomic system via measuring the absorption of a weak probe field. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the probe absorption. It is found that, by properly varying the parameters of the system, the probability of finding the atom in 3D space can be almost 100%. Our scheme opens a promising way to achieve high-precision and high-efficiency 3D atom localization, which provides some potential applications in laser cooling or atom nano-lithography via atom localization.

  5. Innovation and optimization of a method of pump-probe polarimetry with pulsed laser beams in view of a precise measurement of parity violation in atomic cesium; Innovation et optimisation d'une methode de polarimetrie pompe-sonde avec des faisceaux laser impulsionnels en vue d'une mesure precise de violation de la parite dans l'atome de cesium

    Energy Technology Data Exchange (ETDEWEB)

    Chauvat, D

    1997-10-15

    While Parity Violation (PV) experiments on highly forbidden transitions have been using detection of fluorescence signals; our experiment uses a pump-probe scheme to detect the PV signal directly on a transmitted probe beam. A pulsed laser beam of linear polarisation {epsilon}{sub 1} excites the atoms on the 6S-7S cesium transition in a colinear electric field E || k(ex). The probe beam (k(pr) || k(ex)) of linear polarisation {epsilon}{sub 2} tuned to the transition 7S-6P(3/2) is amplified. The small asymmetry ({approx} 10{sup -6}) in the gain that depends on the handedness of the tri-hedron (E, {epsilon}{sub 1}, {epsilon}{sub 2}) is the manifestation of the PV effect. This is measured as an E-odd apparent rotation of the plane of polarization of the probe beam; using balanced mode polarimetry. New criteria of selection have been devised, that allow us to distinguish the true PV-signal against fake rotations due to electromagnetic interferences, geometrical effects, polarization imperfections, or stray transverse electric and magnetic fields. These selection criteria exploit the symmetry of the PV-rotation - linear dichroism - and the revolution symmetry of the experiment. Using these criteria it is not only possible to reject fake signals, but also to elucidate the underlying physical mechanisms and to measure the relevant defects of the apparatus. The present signal-to-noise ratio allows embarking in PV measurements to reach the 10% statistical accuracy. A 1% measurement still requires improvements. Two methods have been demonstrated. The first one exploits the amplification of the asymmetry at high gain - one major advantage provided by our detection method based on stimulated emission. The second method uses both a much higher incident intensity and a special dichroic component which magnifies tiny polarization rotations. (author)

  6. Conductivity Probe

    Science.gov (United States)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air. The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air. The needles on the probe are 15 millimeters (0.6 inch) long. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  7. An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene.

    Science.gov (United States)

    Baik, Sung-Il; Ma, Lulu; Kim, Yoon-Jun; Li, Bo; Liu, Mingjie; Isheim, Dieter; Yakobson, Boris I; Ajayan, Pulickel M; Seidman, David N

    2015-11-25

    The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO2 ) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part-per-million (atomic ppm) detection level, employing laser assisted atom-probe tomography. The atomistic plan and cross-sectional views of graphene indicate that oxygen, hydrogen, and their co-functionalities, OH, CO, and CO2 , which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density-functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Broadband X-ray Imaging in the Near-Field Region of an Airblast Atomizer

    Science.gov (United States)

    Li, Danyu; Bothell, Julie; Morgan, Timothy; Heindel, Theodore

    2017-11-01

    The atomization process has a close connection to the efficiency of many spray applications. Examples include improved fuel atomization increasing the combustion efficiency of aircraft engines, or controlled droplet size and spray angle enhancing the quality and speed of the painting process. Therefore, it is vital to understand the physics of the atomization process, but the near-field region is typically optically dense and difficult to probe with laser-based or intrusive measurement techniques. In this project, broadband X-ray radiography and X-ray computed tomography (CT) imaging were performed in the near-field region of a canonical coaxial airblast atomizer. The X-ray absorption rate was enhanced by adding 20% by weight of Potassium Iodide to the liquid phase to increase image contrast. The radiographs provided an estimate of the liquid effective mean path length and spray angle at the nozzle exit for different flow conditions. The reconstructed CT images provided a 3D map of the time-average liquid spray distribution. X-ray imaging was used to quantify the changes in the near-field spray characteristics for various coaxial airblast atomizer flow conditions. Office of Naval Research.

  9. Atomic physics

    CERN Document Server

    Born, Max

    1969-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  10. Early Atomism

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  11. Quantum-Non-Demolition Endoscopic Tomography

    OpenAIRE

    Fortunato, Mauro; Tombesi, Paolo; Schleich, Wolfgang P.

    1998-01-01

    We present a new indirect method to measure the quantum state of a single mode of the electromagnetic field in a cavity. Our proposal combines the idea of (endoscopic) probing and that of tomography in the sense that the signal field is coupled via a quantum-non-demolition Hamiltonian to a meter field on which then quantum state tomography is performed using balanced homodyne detection. This technique provides full information about the signal state. We also discuss the influence of the measu...

  12. Pollution Probe.

    Science.gov (United States)

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…

  13. Mobile probes

    DEFF Research Database (Denmark)

    Ørngreen, Rikke; Jørgensen, Anna Neustrup; Noesgaard, Signe Schack

    2016-01-01

    to in an interview. This method provided valuable insight into the contextual use, i.e. how did the online resource transfer to the work practice. However, the research team also found that mobile probes may provide the scaffolding necessary for individual and peer learning at a very local (intra-school) community...

  14. Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation

    Energy Technology Data Exchange (ETDEWEB)

    Yamanaka, N. [RIKEN, Wako, iTHES Research Group, Saitama (Japan); Far Eastern Federal University, Complex Simulation Group, School of Biomedicine, Vladivostok (Russian Federation); Sahoo, B.K. [Physical Research Laboratory, Atomic, Molecular and Optical Physics Division, Ahmedabad (India); Yoshinaga, N. [Graduate School of Science and Engineering, Saitama (Japan); Sato, T. [RIKEN, Nishina Center, Saitama (Japan); Asahi, K. [RIKEN, Nishina Center, Saitama (Japan); Tokyo Institute of Technology, Department of Physics and International Education and Research Center of Science, Tokyo (Japan); Das, B.P. [Tokyo Institute of Technology, Department of Physics and International Education and Research Center of Science, Tokyo (Japan)

    2017-03-15

    The current status of electric dipole moments of diamagnetic atoms which involves the synergy between atomic experiments and three different theoretical areas, i.e. particle, nuclear and atomic, is reviewed. Various models of particle physics that predict CP violation, which is necessary for the existence of such electric dipole moments, are presented. These include the standard model of particle physics and various extensions of it. Effective hadron level combined charge conjugation (C) and parity (P) symmetry violating interactions are derived taking into consideration different ways in which a nucleon interacts with other nucleons as well as with electrons. Nuclear structure calculations of the CP-odd nuclear Schiff moment are discussed using the shell model and other theoretical approaches. Results of the calculations of atomic electric dipole moments due to the interaction of the nuclear Schiff moment with the electrons and the P and time-reversal (T) symmetry violating tensor-pseudotensor electron-nucleus are elucidated using different relativistic many-body theories. The principles of the measurement of the electric dipole moments of diamagnetic atoms are outlined. Upper limits for the nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained combining the results of atomic experiments and relativistic many-body theories. The coefficients for the different sources of CP violation have been estimated at the elementary particle level for all the diamagnetic atoms of current experimental interest and their implications for physics beyond the standard model is discussed. Possible improvements of the current results of the measurements as well as quantum chromodynamics, nuclear and atomic calculations are suggested. (orig.)

  15. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Computed Tomography (CT) - Sinuses Computed tomography (CT) of the sinuses ... of CT of the Sinuses? What is CT (Computed Tomography) of the Sinuses? Computed tomography, more commonly known ...

  16. Perfect Precision Detecting Probability Of An Atom Via Sgc Mechanism

    Science.gov (United States)

    Hamedi, H. R.

    2015-06-01

    This letter investigates a scheme of high efficient two-dimensional (2D) atom localization via scanning probe absorption in a Y-type four-level atomic scheme with two orthogonal standing waves. It is shown that because of the position dependent atom-field interaction, the spatial probability distribution of the atom can be directly determined via monitoring the probe absorption and gain spectra. The impact of different controlling parameters of the system on 2D localization is studied. We find that owning the effect of spontaneously generated coherence (SGC), the atom can be localized at a particular position and the maximal probability of detecting the atom within the sub-wavelength domain of the two orthogonal standing waves reaches to hundred percent. Phase controlling of position dependent probe absorption is then discussed. The presented scheme may be helpful in laser cooling or atom nanolithography via high precision and high resolution atom localization.

  17. Chameleon Induced Atomic Afterglow

    CERN Document Server

    Brax, Philippe

    2010-01-01

    The chameleon is a scalar field whose mass depends on the density of its environment. Chameleons are necessarily coupled to matter particles and will excite transitions between atomic energy levels in an analogous manner to photons. When created inside an optical cavity by passing a laser beam through a constant magnetic field, chameleons are trapped between the cavity walls and form a standing wave. This effect will lead to an afterglow phenomenon even when the laser beam and the magnetic field have been turned off, and could be used to probe the interactions of the chameleon field with matter.

  18. Pyramidal nanowire tip for atomic force microscopy and thermal imaging

    NARCIS (Netherlands)

    Burouni, N.; Sarajlic, Edin; Siekman, Martin Herman; Abelmann, Leon; Tas, Niels Roelof

    2012-01-01

    We present a novel 3D nanowire pyramid as scanning microscopy probe for thermal imaging and atomic force microscopy. This probe is fabricated by standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four

  19. Internet tomography an introduction to concepts, techniques, tools and applications

    CERN Document Server

    Moloisane, Abia; O’Droma, Máirtín

    2013-01-01

    Internet tomography, introduced from basic principles through to techniques, tools and applications, is the subject of this book. The design of Internet Tomography Measurement Systems (ITMS) aimed at mapping the Internet performance profile spatially and temporally over paths between probing stations is a particular focus.The Internet Tomography Measurement System design criteria addressed include:Minimally-invasive, independent and autonomous, active or passive measurement;Flexibility and scalability;Capability of targeting local, regional and global Internet paths and underlying IP networks;

  20. Development of the Atomic-Resolution Environmental Transmission Electron Microscope

    DEFF Research Database (Denmark)

    Gai, Pratibha L.; Boyes, Edward D.; Yoshida, Kenta

    2016-01-01

    The development of the novel atomic-resolution environmental transmission electron microscope (atomic-resolution ETEM) for directly probing dynamic gas–solid reactions in situ at the atomic level under controlled reaction conditions consisting of gas environment and elevated temperatures...... is used to study steels, graphene, nanowires, etc. In this chapter, the experimental setup of the microscope column and its peripherals are described....

  1. Verification of CTDI and Dlp values for a head tomography reported by the manufacturers of the CT scanners, using a CT dose profiler probe, a head phantom and a piranha electrometer

    Energy Technology Data Exchange (ETDEWEB)

    Castillo C, E.; Garcia F, I. B.; Garcia H, J.; Roman L, S. [Servicios de Salud de Michoacan, Centro Estatal de Atencion Oncologica, Gertrudis Bocanegra No. 300, Col. Cuauhtemoc, 58020 Morelia, Michoacan (Mexico); Salmeron C, O., E-mail: edithcastillocorona@gmail.com [Servicios de Salud de Michoacan, Hospital General Dr. Miguel Silva, Isidro Huarte s/n, Centro Historico, 58000 Morelia, Michoacan (Mexico)

    2015-10-15

    The extensive use of Computed Tomography (CT) and the associated increase in patient dose calls for an accurate dose evaluation technique. The CT contributes up to 70% of the total dose given to patients during X-ray examinations. The rapid advancements in CT technology are placing new demands on the methods and equipment that are used for quality assurance. The wide beam widths found in CT scanners with multiple beam apertures make it impossible to use existing CT ionization chambers to measure the total dose given to the patient. Using a standard 10 cm CT ionization chamber may result in inaccurate measurements due to underestimation of the dose profile for wide beams. The use a CT dose profiler based on solid-state technology and the Piranha electrometer from RTI electronics provides a potential solution to the arising concerns over patient dose. This study intend to evaluate the feasibility and accuracy of CT Dose Index (CTDI) and Dose Length Product (Dlp) values for a head tomography reported by the manufacturers of the CT scanners at each study. (Author)

  2. Deep atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, H.; Drake, B.; Randall, C.; Hansma, P. K. [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

    2013-12-15

    The Atomic Force Microscope (AFM) possesses several desirable imaging features including the ability to produce height profiles as well as two-dimensional images, in fluid or air, at high resolution. AFM has been used to study a vast selection of samples on the scale of angstroms to micrometers. However, current AFMs cannot access samples with vertical topography of the order of 100 μm or greater. Research efforts have produced AFM scanners capable of vertical motion greater than 100 μm, but commercially available probe tip lengths are still typically less than 10 μm high. Even the longest probe tips are below 100 μm and even at this range are problematic. In this paper, we present a method to hand-fabricate “Deep AFM” probes with tips of the order of 100 μm and longer so that AFM can be used to image samples with large scale vertical topography, such as fractured bone samples.

  3. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  4. Quantum Process Tomography of an Optically-Controlled Kerr Non-linearity

    Science.gov (United States)

    Kupchak, Connor; Rind, Samuel; Jordaan, Bertus; Figueroa, Eden

    2015-11-01

    Any optical quantum information processing machine would be comprised of fully-characterized constituent devices for both single state manipulations and tasks involving the interaction between multiple quantum optical states. Ideally for the latter, would be an apparatus capable of deterministic optical phase shifts that operate on input quantum states with the action mediated solely by auxiliary signal fields. Here we present the complete experimental characterization of a system designed for optically controlled phase shifts acting on single-photon level probe coherent states. Our setup is based on a warm vapor of rubidium atoms under the conditions of electromagnetically induced transparency with its dispersion properties modified through the use of an optically triggered N-type Kerr non-linearity. We fully characterize the performance of our device by sending in a set of input probe states and measuring the corresponding output via time-domain homodyne tomography and subsequently performing the technique of coherent state quantum process tomography. This method provides us with the precise knowledge of how our optical phase shift will modify any arbitrary input quantum state engineered in the mode of the reconstruction.

  5. Advances in atomic, molecular, and optical physics

    CERN Document Server

    Berman, Paul R; Arimondo, Ennio

    2006-01-01

    Volume 54 of the Advances Series contains ten contributions, covering a diversity of subject areas in atomic, molecular and optical physics. The article by Regal and Jin reviews the properties of a Fermi degenerate gas of cold potassium atoms in the crossover regime between the Bose-Einstein condensation of molecules and the condensation of fermionic atom pairs. The transition between the two regions can be probed by varying an external magnetic field. Sherson, Julsgaard and Polzik explore the manner in which light and atoms can be entangled, with applications to quantum information processing

  6. Atomic Power

    African Journals Online (AJOL)

    Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of ... method of producing radioactive isotopes, which are materials .... the sealing and the pressure balancing, all can be carried out ...

  7. Computed Tomography (CT) - Spine

    Science.gov (United States)

    ... Professions Site Index A-Z Computed Tomography (CT) - Spine Computed tomography (CT) of the spine is a ... the Spine? What is CT Scanning of the Spine? Computed tomography, more commonly known as a CT ...

  8. A Scanning Quantum Cryogenic Atom Microscope

    CERN Document Server

    Yang, Fan; Taylor, Stephen F; Turner, Richard W; Lev, Benjamin L

    2016-01-01

    Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity, high-resolution scanning probe magnetometers. We introduce a quantum-noise-limited scanning probe magnetometer that can operate from room-to-cryogenic temperatures with unprecedented DC-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. The SQCRAMscope has a noise floor of 300 pT and provides a 100x improvement in magnetic flux sensitivity over previous atomic scanning probe magnetometers. These capabilities are carefully benchmarked by imaging magnet...

  9. z calibration of the atomic force microscope by means of a pyramidal tip

    DEFF Research Database (Denmark)

    Jensen, Flemming

    1993-01-01

    A new method for imaging the probe tip of an atomic force microscope cantilever by the atomic force microscope itself (self-imaging) is presented. The self-imaging is accomplished by scanning the probe tip across a sharper tip on the surface. By using a pyramidal probe tip with a very well......-defined aspect ratio, this technique provides an excellent z-calibration standard for the atomic force microscope....

  10. Atomic arias

    Science.gov (United States)

    Crease, Robert P.

    2009-01-01

    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  11. Atomic rivals

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, B.

    1990-01-01

    This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.

  12. Application of spectral computed tomography in diagnosis of liver and gallbladder diseases

    Directory of Open Access Journals (Sweden)

    LI Bolong

    2017-03-01

    Full Text Available Spectral computed tomography (CT is a perfect combination of diamond probe and strong computer processing technology and a technological revolution of traditional CT. This article reviews the application of spectral CT in the diagnosis of liver and gallbladder diseases. It summarizes the application value of monochromatic spectral CT imaging, spectral curve, material separation and quantitation, and effective atomic number in the diagnosis and differentiation of liver and gallbladder diseases and analyze the advantages of energy spectrum in identification of small lesions, low dose, and judgment of homology. It is pointed out that the application of spectral CT can be further explored in the aspects of early identification, differentiation, and prognosis of tumors.

  13. NEUTRON IMAGING, RADIOGRAPHY AND TOMOGRAPHY.

    Energy Technology Data Exchange (ETDEWEB)

    SMITH,G.C.

    2002-03-01

    Neutrons are an invaluable probe in a wide range of scientific, medical and commercial endeavors. Many of these applications require the recording of an image of the neutron signal, either in one-dimension or in two-dimensions. We summarize the reactions of neutrons with the most important elements that are used for their detection. A description is then given of the major techniques used in neutron imaging, with emphasis on the detection media and position readout principle. Important characteristics such as position resolution, linearity, counting rate capability and sensitivity to gamma-background are discussed. Finally, the application of a subset of these instruments in radiology and tomography is described.

  14. Synthesis, structure activity relationship, radiolabeling and preclinical evaluation of high affinity ligands for the ion channel of the N-methyl-d-aspartate receptor as potential imaging probes for positron emission tomography.

    Science.gov (United States)

    Klein, Pieter J; Christiaans, Johannes A M; Metaxas, Athanasios; Schuit, Robert C; Lammertsma, Adriaan A; van Berckel, Bart N M; Windhorst, Albert D

    2015-03-01

    The N-methyl-d-aspartate receptor (NMDAr) is involved in many neurological and psychiatric disorders including Alzheimer's disease and schizophrenia. Currently, it is not possible to assess NMDAr availability in vivo. The purpose of this study was to develop a positron emission tomography (PET) ligand for the NMDAr ion channel. A series of di- and tri-N-substituted diarylguanidines was synthesized. In addition, in vitro binding affinity for the NMDAr ion channel in rat forebrain membrane fractions was assessed. Compounds 10, 11 and 32 were radiolabeled with either carbon-11 or fluorine-18. Ligands [(11)C]10 and [(18)F]32 were evaluated ex vivo in B6C3 mice. Biodistribution studies showed higher uptake of [(11)C]10 and [(18)F]32 in forebrain regions compared with cerebellum. In addition, for [(11)C]10 54% and for [(18)F]32 70% of activity in the brain at 60min was due to intact tracer. Pre-treatment with MK-801 (0.6mg·kg(-1), ip) slightly decreased uptake in NMDAr-specific regions for [(18)F]32, but not for [(11)C]10. As such [(18)F]32 has the best characteristics as a PET tracer for the ion channel of the NMDAr. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Imaging DNA Structure by Atomic Force Microscopy.

    Science.gov (United States)

    Pyne, Alice L B; Hoogenboom, Bart W

    2016-01-01

    Atomic force microscopy (AFM) is a microscopy technique that uses a sharp probe to trace a sample surface at nanometre resolution. For biological applications, one of its key advantages is its ability to visualize substructure of single molecules and molecular complexes in an aqueous environment. Here, we describe the application of AFM to determine superstructure and secondary structure of surface-bound DNA. The method is also readily applicable to probe DNA-DNA interactions and DNA-protein complexes.

  16. Atom-specific surface magnetometry

    Science.gov (United States)

    Sirotti, Fausto; Panaccione, Giancarlo; Rossi, Giorgio

    1995-12-01

    A powerful atom-specific surface magnetometry can be based on efficient measurements of magnetic dichroism in l>~0 core level photoemission. The temperature dependence M(T) of the Fe(100) surface magnetization was obtained from the photoemission magnetic asymmetry of 3p core levels, providing the measure of the surface exchange coupling via the spin-wave stiffness and of the surface critical exponent. Beyond the magnetic order the photoemission dichroism allows us to derive the energy splitting of the magnetic sublevels of the photoexcited core hole. Fe 3p photoemission dichroism probes directly the magnetic moment changes of iron atoms at Fe(100) surfaces as a function of structural disorder or sulfur segregation. The appearance of dichroism in the 2p photoemission of segregated sulfur atoms in the c(2×2)S/Fe(100) superstructure measures the magnetic-moment transfer and shows the possibility of investigating surface magnetochemistry in a very direct way.

  17. Trapping cold ground state argon atoms.

    Science.gov (United States)

    Edmunds, P D; Barker, P F

    2014-10-31

    We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39)  C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10)  cm(3) s(-1).

  18. Nanobits - exchangable and customisable scanning probe tips

    DEFF Research Database (Denmark)

    Yildiz, Izzet

    Invention of atomic force microscopy (AFM) pioneered a novel aspect for the surface metrology concept. A range of scanning probe methods have been developed over the years based on different sorts of tip-surface interaction: electrical, optical, thermal, force. Reproducible and fast fabrication...

  19. Piezoresistive Probe Array for High Throughput Applications

    NARCIS (Netherlands)

    Gaitas, A.; French, P.

    2011-01-01

    Microcantilevers are used in a number of applications including atomic-force microscopy (AFM). In this work, piezoresistive deflection-sensing elements are integrated onto micromachined cantilevers to increase sensitivity, and reduce complexity and cost. An array of probes with 5 nm gold ultrathin

  20. Proximal Probes Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Proximal Probes Facility consists of laboratories for microscopy, spectroscopy, and probing of nanostructured materials and their functional properties. At the...

  1. Helium ion beam induced growth of hammerhead AFM probes

    NARCIS (Netherlands)

    Nanda, G.; Van Veldhoven, E.; Maas, D.; Sadeghian, H.; Alkemade, P.F.A.

    2015-01-01

    The authors report the direct-write growth of hammerhead atomic force microscope(AFM) probes by He+beam induced deposition of platinum-carbon. In order to grow a thin nanoneedle on top of a conventional AFM probe, the authors move a focused He+beam during exposure to a PtC precursor gas. In the

  2. Helium ion beam induced growth of hammerhead AFM probes

    NARCIS (Netherlands)

    Nanda, G.; Veldhoven, E. van; Maas, D.J.; Sadeghian Marnani, H.; Alkemade, P.F.A.

    2015-01-01

    The authors report the direct-write growth of hammerhead atomic force microscope (AFM) probes by He+ beam induced deposition of platinum-carbon. In order to grow a thin nanoneedle on top of a conventional AFM probe, the authors move a focused He+ beam during exposure to a PtC precursor gas. In the

  3. Design of a High-Perveance Electron Gun for Electron Cooling in the Low Energy Ion Ring (LEIR) at CERN and Non-Interceptive Proton Beam Profile Monitors using Ion or Atomic Probe Beams

    CERN Document Server

    Dimopoulou, Christina

    2002-01-01

    For an efficient electron cooling of the low-energy Pb54+ ions in LEIR a high-perveance (at least 3.6microperv) electron gun had to be designed. The theoretical study of electron guns has shown that the required perveance can be achieved by using a convex cathode. The gun should be immersed in a strong magnetic field (B=2-6kG) in order to obtain a parallel beam with very low transverse energy (typically 0.1 eV). This idea was confirmed by experimental tests at Fermilab. An adiabatic magnetic expansion is foreseen after the gun in order to reduce the magnetic field to accpetable values (0.6-1 kG) in the cooling section. The internal geometry of a convex cathode gun for the LEIR electron cooler together with the parameters of the magnetic expansion are proposed. The scheme fulfils the requirements. In addition, the author has made an important contribution in the field of beam instrumentation for the LHC and other accelerators at CERN. A profile monitor has been developed that uses a Xe ion probe beam that inte...

  4. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  5. Comparison of the cohesion-adhesion balance approach to colloidal probe atomic force microscopy and the measurement of Hansen partial solubility parameters by inverse gas chromatography for the prediction of dry powder inhalation performance.

    Science.gov (United States)

    Jones, Matthew D; Buckton, Graham

    2016-07-25

    The abilities of the cohesive-adhesive balance approach to atomic force microscopy (AFM) and the measurement of Hansen partial solubility parameters by inverse gas chromatography (IGC) to predict the performance of carrier-based dry powder inhaler (DPI) formulations were compared. Five model drugs (beclometasone dipropionate, budesonide, salbutamol sulphate, terbutaline sulphate and triamcinolone acetonide) and three model carriers (erythritol, α-lactose monohydrate and d-mannitol) were chosen, giving fifteen drug-carrier combinations. Comparison of the AFM and IGC interparticulate adhesion data suggested that they did not produce equivalent results. Comparison of the AFM data with the in vitro fine particle delivery of appropriate DPI formulations normalised to account for particle size differences revealed a previously observed pattern for the AFM measurements, with a slightly cohesive AFM CAB ratio being associated with the highest fine particle fraction. However, no consistent relationship between formulation performance and the IGC data was observed. The results as a whole highlight the complexity of the many interacting variables that can affect the behaviour of DPIs and suggest that the prediction of their performance from a single measurement is unlikely to be successful in every case. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Probing cis-trans isomerization in the S1 state of C2H2 via H-atom action and hot band-pumped IR-UV double resonance spectroscopies

    Science.gov (United States)

    Changala, P. Bryan; Baraban, Joshua H.; Merer, Anthony J.; Field, Robert W.

    2015-08-01

    We report novel experimental strategies that should prove instrumental in extending the vibrational and rotational assignments of the S1 state of acetylene, C2H2, in the region of the cis-trans isomerization barrier. At present, the assignments are essentially complete up to ˜500 cm-1 below the barrier. Two difficulties arise when the assignments are continued to higher energies. One is that predissociation into C2H + H sets in roughly 1100 cm-1 below the barrier; the resulting quenching of laser-induced fluorescence (LIF) reduces its value for recording spectra in this region. The other difficulty is that tunneling through the barrier causes a staggering in the K-rotational structure of isomerizing vibrational levels. The assignment of these levels requires data for K values up to at least 3. Given the rotational selection rule K' - ℓ'' = ± 1, such data must be obtained via excited vibrational levels of the ground state with ℓ'' > 0. In this paper, high resolution H-atom resonance-enhanced multiphoton ionization spectra are demonstrated to contain predissociated bands which are almost invisible in LIF spectra, while preliminary data using a hyperthermal pulsed nozzle show that ℓ'' = 2 states can be selectively populated in a jet, giving access to K' = 3 states in IR-UV double resonance.

  7. High sensitivity probe absorption technique for time-of-flight ...

    Indian Academy of Sciences (India)

    We report on a phase-sensitive probe absorption technique with high sensitivity, capable of detecting a few hundred ultra-cold atoms in flight in an observation time of a few milliseconds. The large signal-to-noise ratio achieved is sufficient for reliable measurements on low intensity beams of cold atoms. We demonstrate the ...

  8. High sensitivity probe absorption technique for time-of-flight ...

    Indian Academy of Sciences (India)

    Absorption imaging using a high sensitivity CCD camera gives the size of the expanding cloud and hence ... (LVIS) [2], the peak signal in a 1 mm thick resonant probe beam corresponds to the absorption by 3 × 105 ... used in our atom optics experiments on the reflection of atoms from magnetic thin films [13]. The sensitivity ...

  9. The Galaxy Evolution Probe

    Science.gov (United States)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

    The Galaxy Evolution Probe (GEP) is a concept for a far-infrared observatory to survey large regions of sky for star-forming galaxies from z = 0 to beyond z = 3. Our knowledge of galaxy formation is incomplete and requires uniform surveys over a large range of redshifts and environments to accurately describe mass assembly, star formation, supermassive black hole growth, interactions between these processes, and what led to their decline from z ~ 2 to the present day. Infrared observations are sensitive to dusty, star-forming galaxies, which have bright polycyclic aromatic hydrocarbon (PAH) emission features and warm dust continuum in the rest-frame mid infrared and cooler thermal dust emission in the far infrared. Unlike previous far-infrared continuum surveys, the GEP will measure photometric redshifts commensurate with galaxy detections from PAH emission and Si absorption features, without the need for obtaining spectroscopic redshifts of faint counterparts at other wavelengths.The GEP design includes a 2 m diameter telescope actively cooled to 4 K and two instruments: (1) An imager covering 10 to 300 um with 25 spectral resolution R ~ 8 bands (with lower R at the longest wavelengths) to detect star-forming galaxies and measure their redshifts photometrically. (2) A 23 – 190 um, R ~ 250 dispersive spectrometer for redshift confirmation and identification of obscured AGN using atomic fine-structure lines. Lines including [Ne V], [O IV], [O III], [O I], and [C II] will probe gas physical conditions, radiation field hardness, and metallicity. Notionally, the GEP will have a two-year mission: galaxy surveys with photometric redshifts in the first year and a second year devoted to follow-up spectroscopy. A comprehensive picture of star formation in galaxies over the last 10 billion years will be assembled from cosmologically relevant volumes, spanning environments from field galaxies and groups, to protoclusters, to dense galaxy clusters.Commissioned by NASA, the

  10. Hydrodynamic ultrasonic probe

    Science.gov (United States)

    Day, Robert A.; Conti, Armond E.

    1980-01-01

    An improved probe for in-service ultrasonic inspection of long lengths of a workpiece, such as small diameter tubing from the interior. The improved probe utilizes a conventional transducer or transducers configured to inspect the tubing for flaws and/or wall thickness variations. The probe utilizes a hydraulic technique, in place of the conventional mechanical guides or bushings, which allows the probe to move rectilinearly or rotationally while preventing cocking thereof in the tube and provides damping vibration of the probe. The probe thus has lower friction and higher inspection speed than presently known probes.

  11. High Atom Number in Microsized Atom Traps

    Science.gov (United States)

    2015-12-14

    Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce

  12. Electrochemical current-sensing atomic force microscopy in conductive solutions

    OpenAIRE

    Pobelov, Ilya; Mohos, Miklos; Yoshida, Koji; Kolivoska, Viliam; Avdic, Amra; Lugstein, Alois; Bertagnolli, Emmerich; Leonhardt, Kelly; Guy, Denuault; Gollas, Bernhard; Wandlowski, Thomas

    2013-01-01

    Insulated atomic force microscopy probes carrying gold conductive tips were fabricated and employed as bifunctional force and current sensors in electrolyte solutions under electrochemical potential control. The application of the probes for current-sensing imaging, force and current–distance spectroscopy as well as scanning electrochemical microscopy experiments was demonstrated.

  13. Electrochemical current-sensing atomic force microscopy in conductive solutions.

    Science.gov (United States)

    Pobelov, Ilya V; Mohos, Miklós; Yoshida, Koji; Kolivoska, Viliam; Avdic, Amra; Lugstein, Alois; Bertagnolli, Emmerich; Leonhardt, Kelly; Denuault, Guy; Gollas, Bernhard; Wandlowski, Thomas

    2013-03-22

    Insulated atomic force microscopy probes carrying gold conductive tips were fabricated and employed as bifunctional force and current sensors in electrolyte solutions under electrochemical potential control. The application of the probes for current-sensing imaging, force and current-distance spectroscopy as well as scanning electrochemical microscopy experiments was demonstrated.

  14. Multipartite entanglement detection with nonsymmetric probing

    DEFF Research Database (Denmark)

    Dellantonio, Luca; Das, Sumanta; Appel, Jürgen

    2017-01-01

    We show that spin-squeezing criteria commonly used for entanglement detection can be erroneous if the probe is not symmetric. We then derive a lower bound on squeezing for separable states in spin systems probed asymmetrically. Using this we further develop a procedure that allows us to verify th...... the degree of entanglement of a quantum state in the spin system. Finally, we apply our method for entanglement verification to existing experimental data, and use it to prove the existence of tripartite entanglement in a spin-squeezed atomic ensemble.......We show that spin-squeezing criteria commonly used for entanglement detection can be erroneous if the probe is not symmetric. We then derive a lower bound on squeezing for separable states in spin systems probed asymmetrically. Using this we further develop a procedure that allows us to verify...

  15. Transforming a Targeted Porphyrin Theranostic Agent into a PET Imaging Probe for Cancer

    National Research Council Canada - National Science Library

    Shi, Jiyun; Liu, Tracy W B; Chen, Juan; Green, David; Jaffray, David; Wilson, Brian C; Wang, Fan; Zheng, Gang

    2011-01-01

    ...)Cu-PPF into a positron emission tomography (PET) probe for cancer imaging. Noninvasive PET imaging followed by radioassay evaluated the tumor accumulation, pharmacokinetics and biodistribution of (64)Cu-PPF. (64...

  16. Spectroscopic Photoacoustic Tomography of Prostate Cancer

    Science.gov (United States)

    2009-03-01

    tomography, ultrasonography 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON USAMRMC...will continue the validation and development of this novel technique through the study on living animals . Moreover, feasibility of SPAT aided by a...transducer probe and the preamplifier board have been delivered to our group in Dec. 2008. We are now conducting the proposed experiments on animals and

  17. A Network Coding Approach to Loss Tomography

    DEFF Research Database (Denmark)

    Sattari, Pegah; Markopoulou, Athina; Fragouli, Christina

    2013-01-01

    multicast and/or unicast end-to-end probes. Independently, recent advances in network coding have shown that there are several advantages from allowing intermediate nodes to process and combine, in addition to just forward, packets. In this paper, we pose the problem of loss tomography in networks that have...... network coding capabilities. We design a framework for estimating link loss rates, which leverages network coding capabilities and we show that it improves several aspects of tomography, including the identifiability of links, the tradeoff between estimation accuracy and bandwidth efficiency...... and multiple paths between sources and receivers. This work was the first to make the connection between active network tomography and network coding, and thus opened a new research direction....

  18. Scattering of Slow Metastable Argon Atoms by Dielectric Nanospheres

    Science.gov (United States)

    Baudon, J.; Hamamda, M.; Grucker, J.; Perales, F.; Dutier, G.; Ducloy, M.; Bocvarski, V.

    2009-11-01

    The elastic scattering at low energy of metastable argon atoms with internal angular momentum J = 0 and 2 by dielectric nanospheres is investigated. The differential cross sections are calculated for both isotropic and anisotropic interactions. A polarization effect is clearly evidenced. The possible use of a metastable atom beam as a probe of an ensemble of nanospheres deposited on a passive substrate is examined.

  19. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... the Sinuses? What is CT (Computed Tomography) of the Sinuses? Computed tomography, more commonly known as a ... of page What are some common uses of the procedure? CT of the sinuses is primarily used ...

  20. Scanning Quantum Cryogenic Atom Microscope

    Science.gov (United States)

    Yang, Fan; Kollár, Alicia J.; Taylor, Stephen F.; Turner, Richard W.; Lev, Benjamin L.

    2017-03-01

    Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed-matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity high-resolution scanning probe magnetometers. We introduce a quantum-noise-limited scanning probe magnetometer that can operate from room-to-cryogenic temperatures with unprecedented dc-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. The SQCRAMscope has a field sensitivity of 1.4 nT per resolution-limited point (approximately 2 μ m ) or 6 nT /√{Hz } per point at its duty cycle. Compared to point-by-point sensors, the long length of the BEC provides a naturally parallel measurement, allowing one to measure nearly 100 points with an effective field sensitivity of 600 pT /√{Hz } for each point during the same time as a point-by-point scanner measures these points sequentially. Moreover, it has a noise floor of 300 pT and provides nearly 2 orders of magnitude improvement in magnetic flux sensitivity (down to 10-6 Φ0/√{Hz } ) over previous atomic probe magnetometers capable of scanning near samples. These capabilities are carefully benchmarked by imaging magnetic fields arising from microfabricated wire patterns in a system where samples may be scanned, cryogenically cooled, and easily exchanged. We anticipate the SQCRAMscope will provide charge-transport images at temperatures from room temperature to 4 K in unconventional superconductors and topologically nontrivial materials.

  1. Mobile Game Probes

    DEFF Research Database (Denmark)

    Borup Lynggaard, Aviaja

    2006-01-01

    This paper will examine how probes can be useful for game designers in the preliminary phases of a design process. The work is based upon a case study concerning pervasive mobile phone games where Mobile Game Probes have emerged from the project. The new probes are aimed towards a specific target...... group and the goal is to specify the probes so they will cover the most relevant areas for our project. The Mobile Game Probes generated many interesting results and new issues occurred, since the probes came to be dynamic and favorable for the process in new ways....

  2. "Bohr's Atomic Model."

    Science.gov (United States)

    Willden, Jeff

    2001-01-01

    "Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

  3. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Computed Tomography (CT) - Head Computed tomography (CT) of the head uses special x-ray ... Head? What is CT Scanning of the Head? Computed tomography, more commonly known as a CT or CAT ...

  4. A macrophage uptaking near-infrared chemical probe CDnir7 for in vivo imaging of inflammation.

    Science.gov (United States)

    Kang, Nam-Young; Park, Sung-Jin; Ang, Xiao Wei Emmiline; Samanta, Animesh; Driessen, Wouter H P; Ntziachristos, Vasilis; Vasquez, Kristine O; Peterson, Jeffrey D; Yun, Seong-Wook; Chang, Young-Tae

    2014-06-25

    Visualization of macrophages in live animals has been of great interest for a better understanding of inflammation. We developed a near infrared (NIR) probe that can selectively detect macrophages and visualize inflammation in vivo using the IVIS spectrum, Fluorescence Molecular Tomography (FMT) and Multi-Spectral Optoacoustic Tomography (MSOT).

  5. Angle Statistics Reconstruction: a robust reconstruction algorithm for Muon Scattering Tomography

    Science.gov (United States)

    Stapleton, M.; Burns, J.; Quillin, S.; Steer, C.

    2014-11-01

    Muon Scattering Tomography (MST) is a technique for using the scattering of cosmic ray muons to probe the contents of enclosed volumes. As a muon passes through material it undergoes multiple Coulomb scattering, where the amount of scattering is dependent on the density and atomic number of the material as well as the path length. Hence, MST has been proposed as a means of imaging dense materials, for instance to detect special nuclear material in cargo containers. Algorithms are required to generate an accurate reconstruction of the material density inside the volume from the muon scattering information and some have already been proposed, most notably the Point of Closest Approach (PoCA) and Maximum Likelihood/Expectation Maximisation (MLEM) algorithms. However, whilst PoCA-based algorithms are easy to implement, they perform rather poorly in practice. Conversely, MLEM is a complicated algorithm to implement and computationally intensive and there is currently no published, fast and easily-implementable algorithm that performs well in practice. In this paper, we first provide a detailed analysis of the source of inaccuracy in PoCA-based algorithms. We then motivate an alternative method, based on ideas first laid out by Morris et al, presenting and fully specifying an algorithm that performs well against simulations of realistic scenarios. We argue this new algorithm should be adopted by developers of Muon Scattering Tomography as an alternative to PoCA.

  6. Meaning of Interior Tomography

    CERN Document Server

    Wang, Ge

    2013-01-01

    The classic imaging geometry for computed tomography is for collection of un-truncated projections and reconstruction of a global image, with the Fourier transform as the theoretical foundation that is intrinsically non-local. Recently, interior tomography research has led to theoretically exact relationships between localities in the projection and image spaces and practically promising reconstruction algorithms. Initially, interior tomography was developed for x-ray computed tomography. Then, it has been elevated as a general imaging principle. Finally, a novel framework known as omni-tomography is being developed for grand fusion of multiple imaging modalities, allowing tomographic synchrony of diversified features.

  7. Teach us atom structure

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Suh Yeon

    2006-08-15

    This book is written to teach atom structure in very easy way. It is divided into nine chapters, which indicates what is the components of matter? when we divide matter continuously, it becomes atom, what did atom look like? particles comprised of matter is not only atom, discover of particles comprised of atom, symbol of element, various radiation, form alchemy to nuclear transmutation, shape of atom is evolving. It also has various pictures in each chapters to explain easily.

  8. Playing pinball with atoms.

    Science.gov (United States)

    Saedi, Amirmehdi; van Houselt, Arie; van Gastel, Raoul; Poelsema, Bene; Zandvliet, Harold J W

    2009-05-01

    We demonstrate the feasibility of controlling an atomic scale mechanical device by an external electrical signal. On a germanium substrate, a switching motion of pairs of atoms is induced by electrons that are directly injected into the atoms with a scanning tunneling microscope tip. By precisely controlling the tip current and distance we make two atom pairs behave like the flippers of an atomic-sized pinball machine. This atomic scale mechanical device exhibits six different configurations.

  9. Parallel Probe Readout

    NARCIS (Netherlands)

    Koelmans, W.W.

    2011-01-01

    In this thesis techniques are developed to read out nanoscale probes and arrays of probes.The main targeted application area is probe-based data storage.The work also contributes to other areas, such as metrology, biological sensing, materials research and nano-electro-mechanical switches. First, an

  10. Micro-modulated luminescence tomography

    CERN Document Server

    Cong, Wenxiang; Wang, Chao; Wang, Ge

    2013-01-01

    Imaging depth of optical microscopy has been fundamentally limited to millimeter or sub-millimeter due to light scattering. X-ray microscopy can resolve spatial details of few microns deeply inside a sample but the contrast resolution is still inadequate to depict heterogeneous features at cellular or sub-cellular levels. To enhance and enrich biological contrast at large imaging depth, various nanoparticles are introduced and become essential to basic research and molecular medicine. Nanoparticles can be functionalized as imaging probes, similar to fluorescent and bioluminescent proteins. LiGa5O8:Cr3+ nanoparticles were recently synthesized to facilitate luminescence energy storage with x-ray pre-excitation and the subsequently stimulated luminescence emission by visible/near-infrared (NIR) light. In this paper, we suggest a micro-modulated luminescence tomography (MLT) approach to quantify a nanophosphor distribution in a thick biological sample with high resolution. Our numerical simulation studies demonst...

  11. Gravitational Wave Detection with Atom Interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Dimopoulos, Savas; /Stanford U., Phys. Dept.; Graham, Peter W.; /SLAC /Stanford U., Phys. Dept.; Hogan, Jason M.; Kasevich, Mark A.; /Stanford U., Phys. Dept.; Rajendran, Surjeet; /SLAC /Stanford U., Phys. Dept.

    2008-01-23

    We propose two distinct atom interferometer gravitational wave detectors, one terrestrial and another satellite-based, utilizing the core technology of the Stanford 10m atom interferometer presently under construction. The terrestrial experiment can operate with strain sensitivity {approx} 10{sup -19}/{radical}Hz in the 1 Hz-10 Hz band, inaccessible to LIGO, and can detect gravitational waves from solar mass binaries out to megaparsec distances. The satellite experiment probes the same frequency spectrum as LISA with better strain sensitivity {approx} 10{sup -20}/{radical}Hz. Each configuration compares two widely separated atom interferometers run using common lasers. The effect of the gravitational waves on the propagating laser field produces the main effect in this configuration and enables a large enhancement in the gravitational wave signal while significantly suppressing many backgrounds. The use of ballistic atoms (instead of mirrors) as inertial test masses improves systematics coming from vibrations and acceleration noise, and reduces spacecraft control requirements.

  12. Nanoscale tomography reveals the deactivation of automotive copper-exchanged zeolite catalysts.

    Science.gov (United States)

    Schmidt, Joel E; Oord, Ramon; Guo, Wei; Poplawsky, Jonathan D; Weckhuysen, Bert M

    2017-11-21

    Copper-exchanged zeolite chabazite (Cu-SSZ-13) was recently commercialized for the selective catalytic reduction of NO X with ammonia in vehicle emissions as it exhibits superior reaction performance and stability compared to all other catalysts, notably Cu-ZSM-5. Herein, the 3D distributions of Cu as well as framework elements (Al, O, Si) in both fresh and aged Cu-SSZ-13 and Cu-ZSM-5 are determined with nanometer resolution using atom probe tomography (APT), and correlated with catalytic activity and other characterizations. Both fresh catalysts contain a heterogeneous Cu distribution, which is only identified due to the single atom sensitivity of APT. After the industry standard 135,000 mile simulation, Cu-SSZ-13 shows Cu and Al clustering, whereas Cu-ZSM-5 is characterized by severe Cu and Al aggregation into a copper aluminate phase (CuAl 2 O 4 spinel). The application of APT as a sensitive and local characterization method provides identification of nanometer scale heterogeneities that lead to catalytic activity and material deactivation.

  13. A Compact Microchip-Based Atomic Clock Based on Ultracold Trapped Rb Atoms

    CERN Document Server

    Farkas, Daniel M; Anderson, Dana Z

    2009-01-01

    We propose a compact atomic clock based on ultracold Rb atoms that are magnetically trapped near the surface of an atom microchip. An interrogation scheme that combines electromagnetically-induced transparency (EIT) with Ramsey's method of separated oscillatory fields can achieve atomic shot-noise level performance of 10^{-13}/sqrt(tau) for 10^6 atoms. The EIT signal can be detected with a heterodyne technique that provides noiseless gain; with this technique the optical phase shift of a 100 pW probe beam can be detected at the photon shot-noise level. Numerical calculations of the density matrix equations are used to identify realistic operating parameters at which AC Stark shifts are eliminated. By considering fluctuations in these parameters, we estimate that AC Stark shifts can be canceled to a level better than 2*10^{-14}. An overview of the apparatus is presented with estimates of duty cycle and power consumption.

  14. Turbocharging Quantum Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Blume-Kohout, Robin J. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Gamble, John King [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Nielsen, Erik [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Maunz, Peter Lukas Wilhelm [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Scholten, Travis L. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Rudinger, Kenneth Michael [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Quantum tomography is used to characterize quantum operations implemented in quantum information processing (QIP) hardware. Traditionally, state tomography has been used to characterize the quantum state prepared in an initialization procedure, while quantum process tomography is used to characterize dynamical operations on a QIP system. As such, tomography is critical to the development of QIP hardware (since it is necessary both for debugging and validating as-built devices, and its results are used to influence the next generation of devices). But tomography suffers from several critical drawbacks. In this report, we present new research that resolves several of these flaws. We describe a new form of tomography called gate set tomography (GST), which unifies state and process tomography, avoids prior methods critical reliance on precalibrated operations that are not generally available, and can achieve unprecedented accuracies. We report on theory and experimental development of adaptive tomography protocols that achieve far higher fidelity in state reconstruction than non-adaptive methods. Finally, we present a new theoretical and experimental analysis of process tomography on multispin systems, and demonstrate how to more effectively detect and characterize quantum noise using carefully tailored ensembles of input states.

  15. High-precision three-dimensional atom localization via phase-sensitive absorption spectra in a four-level atomic system

    Science.gov (United States)

    Zhang, Duo; Yu, Rong; Sun, Zhaoyu; Ding, Chunling; Zubairy, M. Suhail

    2018-01-01

    We propose a new scheme for highly efficient three-dimensional (3D) atom localization in a coherently driven closed-loop four-level atomic system via measuring the probe absorption of the weak field. Due to the spatially dependent atom–field interaction, the absorption spectra of the weak probe laser field carry the information about the atomic position. By solving the density-matrix equations of motion and properly modulating the system parameters such as the probe detuning, the relative phase of three driving fields, and the intensity of the control and microwave fields, we can realize high-precision and high-resolution 3D atom localization. Furthermore, we can find the atom at a certain position with 100% probability under appropriate conditions, and then we employ the dressed-state analysis to explain qualitatively the reason of high-precision 3D atom localization.

  16. Photonic probing of radio waves for k-space tomography.

    Science.gov (United States)

    Murakowski, Janusz; Schneider, Garrett J; Shi, Shouyuan; Schuetz, Christopher A; Prather, Dennis W

    2017-07-10

    We harness coherent optical processing to simultaneously sense the angle of arrival and the frequency of radio waves. Signals captured by a distributed antenna array are up-converted to optical domain using electro-optic modulators coupled to individual antennas. Employing a common laser source to feed all the modulators ensures spatially coherent up-conversion of radio-frequency (RF) waves to optical beams carried by optical fibers. Fiber-length dispersion extends the spatial aperture of the distributed antenna array into the temporal dimension. The interference of beams emanating from the fibers is captured by a CCD and used to computationally reconstruct RF waves in k-space.

  17. Atomic-scale compositional mapping reveals Mg-rich amorphous calcium phosphate in human dental enamel.

    Science.gov (United States)

    La Fontaine, Alexandre; Zavgorodniy, Alexander; Liu, Howgwei; Zheng, Rongkun; Swain, Michael; Cairney, Julie

    2016-09-01

    Human dental enamel, the hardest tissue in the body, plays a vital role in protecting teeth from wear as a result of daily grinding and chewing as well as from chemical attack. It is well established that the mechanical strength and fatigue resistance of dental enamel are derived from its hierarchical structure, which consists of periodically arranged bundles of hydroxyapatite (HAP) nanowires. However, we do not yet have a full understanding of the in vivo HAP crystallization process that leads to this structure. Mg(2+) ions, which are present in many biological systems, regulate HAP crystallization by stabilizing its precursor, amorphous calcium phosphate (ACP), but their atomic-scale distribution within HAP is unknown. We use atom probe tomography to provide the first direct observations of an intergranular Mg-rich ACP phase between the HAP nanowires in mature human dental enamel. We also observe Mg-rich elongated precipitates and pockets of organic material among the HAP nanowires. These observations support the postclassical theory of amelogenesis (that is, enamel formation) and suggest that decay occurs via dissolution of the intergranular phase. This information is also useful for the development of more accurate models to describe the mechanical behavior of teeth.

  18. Control the fear atomic

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Gwan [I and Book, Seoul (Korea, Republic of)

    2003-04-15

    This book has a lot of explanation of nuclear energy with articles. Their titles are the bad man likes atomic, the secret of atom, nuclear explosion, NPT?, the secret of uranium fuel rod, nuclear power plant vs nuclear bomb, I hate atomic, keep plutonium in control, atomic in peace and find out alternative energy.

  19. Laser Cooling and Trapping of Neutral Atoms

    Science.gov (United States)

    1992-07-01

    Weiner, Dept of Chemistry, University of Maryland.) Studies of ultra cold collisions in traps can probe the lowest energy interactions of atoms but are...Ramsey resonance. The experimental set up is shown in fig. 10. VL.-Abt) T ~5cm :- TE, avity 9.2GH,7input/ =. molasses VL molasses fluorecence " TOF~~ sinl...implies that there is a rich resonant structure to be probed by superimposing a separately tunable laser on the trap laser. Unfortunately, we cannot tune

  20. Use of a new intra-ocular spectral domain optical coherence tomography in vitreoretinal surgery

    NARCIS (Netherlands)

    Mura, Marco; Iannetta, Danilo; Nasini, Francesco; Barca, Francesco; Peiretti, Enrico; Engelbrecht, Leonore; de Smet, Marc D.; Verbraak, Frank

    2016-01-01

    To describe the use of a novel intra-ocular side-scanning probe enabling the acquisition of spectral-domain optical coherence tomography (SD-OCT) images during surgery in a series of patients with complex forms of retinal detachment. A 23-gauge, side-scanning SD-OCT probe (C7 System; LightLab

  1. Microanalysis of welds using field ion microscope/atom probe

    NARCIS (Netherlands)

    Gadgil, V.J.; Kolster, B.H.; Kolster, B.H.

    1994-01-01

    Since transmission electron microscopy (TEM) was first applied to study metals and alloys, an extensive amount of knowledge has been obtained on microstructures that govern the strength, ductility toughness, workability, and other properties of materials. Particularly analytical transmission

  2. Pair distribution function computed tomography.

    Science.gov (United States)

    Jacques, Simon D M; Di Michiel, Marco; Kimber, Simon A J; Yang, Xiaohao; Cernik, Robert J; Beale, Andrew M; Billinge, Simon J L

    2013-01-01

    An emerging theme of modern composites and devices is the coupling of nanostructural properties of materials with their targeted arrangement at the microscale. Of the imaging techniques developed that provide insight into such designer materials and devices, those based on diffraction are particularly useful. However, to date, these have been heavily restrictive, providing information only on materials that exhibit high crystallographic ordering. Here we describe a method that uses a combination of X-ray atomic pair distribution function analysis and computed tomography to overcome this limitation. It allows the structure of nanocrystalline and amorphous materials to be identified, quantified and mapped. We demonstrate the method with a phantom object and subsequently apply it to resolving, in situ, the physicochemical states of a heterogeneous catalyst system. The method may have potential impact across a range of disciplines from materials science, biomaterials, geology, environmental science, palaeontology and cultural heritage to health.

  3. Atom probe study of the microstructural evolution induced by irradiation in Fe-Cu ferritic alloys and pressure vessel steels; Etude a la sonde atomique de l`evolution microstructurale sous irradiation d`alliages ferritiques Fe-Cu et d`aciers de cuve REP

    Energy Technology Data Exchange (ETDEWEB)

    Pareige, P.

    1996-04-01

    Pressure vessel steels used in pressurized water reactors are low alloyed ferritic steels. They may be prone to hardening and embrittlement under neutron irradiation. The changes in mechanical properties are generally supposed to result from the formation of point defects, dislocation loops, voids and/or copper rich clusters. However, the real nature of the irradiation induced-damage in these steels has not been clearly identified yet. In order to improve our vision of this damage, we have characterized the microstructure of several steels and model alloys irradiated with electrons and neutrons. The study was performed with conventional and tomographic atom probes. The well known importance of the effects of copper upon pressure vessel steel embrittlement has led us to study Fe-Cu binary alloys. We have considered chemical aging as well as aging under electron and neutron irradiations. The resulting effects depend on whether electron or neutron irradiations ar used for thus. We carried out both kinds of irradiation concurrently so as to compare their effects. We have more particularly considered alloys with a low copper supersaturation representative of that met with the French vessel alloys (0.1% Cu). Then, we have examined steels used on French nuclear reactor pressure vessels. To characterize the microstructure of CHOOZ A steel and its evolution when exposed to neutrons, we have studied samples from the reactor surveillance program. The results achieved, especially the characterization of neutron-induced defects have been compared with those for another steel from the surveillance program of Dampierre 2. All the experiment results obtained on model and industrial steels have allowed us to consider an explanation of the way how the defects appear and grow, and to propose reasons for their influence upon steel embrittlement. (author). 3 appends.

  4. Towards Atomic Column-by-Column Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pennycook, S.J.; Rafferty, B.

    1998-09-06

    The optical arrangement of the scanning transmission electron microscope (STEM) is ideally suited for performing analysis of individual atomic columns in materials. Using the incoherent Z-contrast image as a reference, and arranging incoherent conditions also for the spectroscopy, a precise correspondence is ensured between features in the inelastic image and elastic signals. In this way the exact probe position needed to maximise the inelastic signal from a selected column can be located and monitored during the analysis using the much higher intensity elastic signal. Although object functions for EELS are typically less than 1 {Angstrom} full width at half maximum, this is still an order of magnitude larger than the corresponding object functions for elastic (or diffuse) scattering used to form the Z-contrast image. Therefore the analysis is performed with an effective probe that is significantly broader than that used for the reference Z-contrast image. For a 2.2 {Angstrom} probe the effective probe is of the order of 2.5 {Angstrom}, while for a 1.3 {Angstrom} probe the effective probe is 1.6 {Angstrom}. Such increases in effective probe size can significantly reduce or even eliminate contrast between atomic columns that are visible in the image. However, this is only true if we consider circular collector apertures. Calculations based upon the theory of Maslen and Rossouw (Maslen and Rossouw 1984; Rossouw and Maslen 1984) show that employing an annular aperture can reduce the FWHM of the inelastic object function down to values close 0.1 {Angstrom}. With practical aperture sizes it should be possible to achieve this increased spatial resolution without loosing too much signal.

  5. Meaning of Interior Tomography

    Science.gov (United States)

    Wang, Ge; Yu, Hengyong

    2013-01-01

    The classic imaging geometry for computed tomography is for collection of un-truncated projections and reconstruction of a global image, with the Fourier transform as the theoretical foundation that is intrinsically non-local. Recently, interior tomography research has led to theoretically exact relationships between localities in the projection and image spaces and practically promising reconstruction algorithms. Initially, interior tomography was developed for x-ray computed tomography. Then, it has been elevated as a general imaging principle. Finally, a novel framework known as “omni-tomography” is being developed for grand fusion of multiple imaging modalities, allowing tomographic synchrony of diversified features. PMID:23912256

  6. Diffusion tensor optical coherence tomography

    Science.gov (United States)

    Marks, Daniel L.; Blackmon, Richard L.; Oldenburg, Amy L.

    2018-01-01

    In situ measurements of diffusive particle transport provide insight into tissue architecture, drug delivery, and cellular function. Analogous to diffusion-tensor magnetic resonance imaging (DT-MRI), where the anisotropic diffusion of water molecules is mapped on the millimeter scale to elucidate the fibrous structure of tissue, here we propose diffusion-tensor optical coherence tomography (DT-OCT) for measuring directional diffusivity and flow of optically scattering particles within tissue. Because DT-OCT is sensitive to the sub-resolution motion of Brownian particles as they are constrained by tissue macromolecules, it has the potential to quantify nanoporous anisotropic tissue structure at micrometer resolution as relevant to extracellular matrices, neurons, and capillaries. Here we derive the principles of DT-OCT, relating the detected optical signal from a minimum of six probe beams with the six unique diffusion tensor and three flow vector components. The optimal geometry of the probe beams is determined given a finite numerical aperture, and a high-speed hardware implementation is proposed. Finally, Monte Carlo simulations are employed to assess the ability of the proposed DT-OCT system to quantify anisotropic diffusion of nanoparticles in a collagen matrix, an extracellular constituent that is known to become highly aligned during tumor development.

  7. Preparation of Ultracold Atom Clouds at the Shot Noise Level

    DEFF Research Database (Denmark)

    Gajdacz, M.; Hilliard, A. J.; Kristensen, Mick

    2016-01-01

    We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^6 is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔN... on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level....

  8. Atom-specific surface magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Sirotti, F.; Panaccione, G. [Laboratoire pour l`Utilisation du Rayonnement Electromagnetique, Centre National de la Recherche Scientifique, Commissariat a l`Energie Atomique, MESR, F-91405 Orsay (France); Rossi, G. [Laboratorium fuer Festkoerperphysik, Eidgenossische Technische Hochschule-Zuerich, Zuerich CH-8093 (Switzerland)

    1995-12-15

    A powerful atom-specific surface magnetometry can be based on efficient measurements of magnetic dichroism in {ital l}{gt}0 core level photoemission. The temperature dependence M({ital T}) of the Fe(100) surface magnetization was obtained from the photoemission magnetic asymmetry of 3{ital p} core levels, providing the measure of the surface exchange coupling via the spin-wave stiffness and of the surface critical exponent. Beyond the magnetic order {l_angle}M{r_angle} the photoemission dichroism allows us to derive the energy splitting of the magnetic sublevels of the photoexcited core hole. Fe 3{ital p} photoemission dichroism probes directly the magnetic moment changes of iron atoms at Fe(100) surfaces as a function of structural disorder or sulfur segregation. The appearance of dichroism in the 2{ital p} photoemission of segregated sulfur atoms in the {ital c}(2{times}2)S/Fe(100) superstructure measures the magnetic-moment transfer and shows the possibility of investigating surface magnetochemistry in a very direct way.

  9. Directly measuring the concurrence of two-atom state via detecting coherent lights

    Science.gov (United States)

    Chen, Li; Yang, Ming; Zhang, Li-Hua; Cao, Zhuo-Liang

    2017-11-01

    Concurrence is an important parameter for quantifying quantum entanglement, but usually the state tomography must be determined before quantification. In this paper we propose a scheme, based on cavity-assisted atom–light interaction, to measure the concurrence of two-atom pure states and the Collins–Gisin state directly, without tomography. The concurrence of atomic states is encoded in the output coherent optical beams after interacting with cavities and the atoms therein, so the results of detection applied to the output coherent optical beams provide the concurrence data of the atomic states. This scheme provides an alternative method for directly measuring atomic entanglement by detecting coherent light, rather than measuring the atomic systems, which thus greatly simplifies the realization complexity of the direct measurement of atomic entanglement. In addition, as the cavity-assisted atom–light interaction used here is robust and scalable in realistic applications, the current scheme may be realized in the near future.

  10. Scanned probe microscopy for thin film superconductor development

    Energy Technology Data Exchange (ETDEWEB)

    Moreland, J. [National Institute of Standards and Technology, Boulder, CO (United States)

    1996-12-31

    Scanned probe microscopy is a general term encompassing the science of imaging based on piezoelectric driven probes for measuring local changes in nanoscale properties of materials and devices. Techniques like scanning tunneling microscopy, atomic force microscopy, and scanning potentiometry are becoming common tools in the production and development labs in the semiconductor industry. The author presents several examples of applications specific to the development of high temperature superconducting thin films and thin-film devices.

  11. Microfabricated Waveguide Atom Traps.

    Energy Technology Data Exchange (ETDEWEB)

    Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading cold atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.

  12. Atomic and molecular manipulation

    CERN Document Server

    Mayne, Andrew J

    2011-01-01

    Work with individual atoms and molecules aims to demonstrate that miniaturized electronic, optical, magnetic, and mechanical devices can operate ultimately even at the level of a single atom or molecule. As such, atomic and molecular manipulation has played an emblematic role in the development of the field of nanoscience. New methods based on the use of the scanning tunnelling microscope (STM) have been developed to characterize and manipulate all the degrees of freedom of individual atoms and molecules with an unprecedented precision. In the meantime, new concepts have emerged to design molecules and substrates having specific optical, mechanical and electronic functions, thus opening the way to the fabrication of real nano-machines. Manipulation of individual atoms and molecules has also opened up completely new areas of research and knowledge, raising fundamental questions of "Optics at the atomic scale", "Mechanics at the atomic scale", Electronics at the atomic scale", "Quantum physics at the atomic sca...

  13. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    2000-01-01

    This fifth volume of the successful series Advances in Atomic Spectroscopy continues to discuss and investigate the area of atomic spectroscopy.It begins with a description of the use of various atomic spectroscopic methods and applications of speciation studies in atomic spectroscopy. The emphasis is on combining atomic spectroscopy with gas and liquid chromatography. In chapter two the authors describe new developments in tunable lasers and the impact they will have on atomic spectroscopy. The traditional methods of detection, such as photography and the photomultiplier, and how they are being replaced by new detectors is discussed in chapter three. The very active area of glow discharge atomic spectrometry is presented in chapter four where, after a brief introduction and historical review, the use of glow discharge lamps for atomic spectroscopy and mass spectrometry are discussed. Included in this discussion is geometry and radiofrequency power. The future of this source in atomic spectroscopy is also dis...

  14. Pump-probe optical coherence microscopy

    Science.gov (United States)

    Wan, Qiujie; Applegate, Brian E.

    2010-02-01

    High-resolution optical molecular imaging has become a vital tool for understanding and measuring physiologically important biometrics on the cellular and subcellular level. In spite of significant recent advances in microscopy, molecular imaging of most endogenous biomolecular species remains elusive. Directly imaging endogenous biomolecules without the aid of exogenous tags is highly desirable. We developed pump-probe optical coherence microscopy (PPOCM) based on our previous success in integrating pump-probe absorption spectroscopy with optical coherence tomography. A fixed human skin tissue with melanoma was imaged by the PPOCM system. The preliminary results show that PPOCM can provide better can clear contrast between normal tissue and melanoma than OCM. This system also can be used to image other chromophores.

  15. Children's (Pediatric) CT (Computed Tomography)

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Children's (Pediatric) CT (Computed Tomography) Pediatric computed tomography (CT) ... are the limitations of Children's CT? What is Children's CT? Computed tomography, more commonly known as a ...

  16. Atomic Force Microscope for Imaging and Spectroscopy

    Science.gov (United States)

    Pike, W. T.; Hecht, M. H.; Anderson, M. S.; Akiyama, T.; Gautsch, S.; deRooij, N. F.; Staufer, U.; Niedermann, Ph.; Howald, L.; Mueller, D.

    2000-01-01

    We have developed, built, and tested an atomic force microscope (AFM) for extraterrestrial applications incorporating a micromachined tip array to allow for probe replacement. It is part of a microscopy station originally intended for NASA's 2001 Mars lander to identify the size, distribution, and shape of Martian dust and soil particles. As well as imaging topographically down to nanometer resolution, this instrument can be used to reveal chemical information and perform infrared and Raman spectroscopy at unprecedented resolution.

  17. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... are the limitations of CT of the Sinuses? What is CT (Computed Tomography) of the Sinuses? Computed tomography, more commonly known as a CT or CAT scan, is a diagnostic medical test that, like traditional x-rays, produces multiple images or pictures of the inside of ...

  18. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... the limitations of CT of the Sinuses? What is CT (Computed Tomography) of the Sinuses? Computed tomography, more commonly known as a ... top of page What are some common uses of the procedure? CT of the sinuses is primarily ...

  19. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... Computed tomography (CT) of the head uses special x-ray equipment to help assess head injuries, severe headaches, dizziness, and other symptoms of ... content. Related Articles and Media Radiation Dose in X-Ray and CT ... Perfusion of the Head CT Angiography (CTA) Stroke Brain Tumors Computer Tomography ( ...

  20. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... Videos About Us News Physician Resources Professions Site Index A-Z Computed Tomography (CT) - Sinuses Computed tomography (CT) of the sinuses uses special x-ray equipment to evaluate the paranasal sinus cavities – hollow, air-filled spaces within the bones of ...

  1. Tomography of nonclassical states

    NARCIS (Netherlands)

    Bazrafkan, MR; Man'ko, [No Value

    2003-01-01

    A review of the symplectic tomography method is presented. Superpositions of different types of photon states are considered within the framework of the tomography approach. Such nonclassical photon states as even and odd coherent states, crystallized Schrodinger cat states, and other superposition

  2. Formative Assessment Probes

    Science.gov (United States)

    Eberle, Francis; Keeley, Page

    2008-01-01

    Formative assessment probes can be effective tools to help teachers build a bridge between students' initial ideas and scientific ones. In this article, the authors describe how using two formative assessment probes can help teachers determine the extent to which students make similar connections between developing a concept of matter and a…

  3. Atomic White-Out: Enabling Atomic Circuitry through Mechanically Induced Bonding of Single Hydrogen Atoms to a Silicon Surface.

    Science.gov (United States)

    Huff, Taleana R; Labidi, Hatem; Rashidi, Mohammad; Koleini, Mohammad; Achal, Roshan; Salomons, Mark H; Wolkow, Robert A

    2017-09-26

    We report the mechanically induced formation of a silicon-hydrogen covalent bond and its application in engineering nanoelectronic devices. We show that using the tip of a noncontact atomic force microscope (NC-AFM), a single hydrogen atom could be vertically manipulated. When applying a localized electronic excitation, a single hydrogen atom is desorbed from the hydrogen-passivated surface and can be transferred to the tip apex, as evidenced from a unique signature in frequency shift curves. In the absence of tunnel electrons and electric field in the scanning probe microscope junction at 0 V, the hydrogen atom at the tip apex is brought very close to a silicon dangling bond, inducing the mechanical formation of a silicon-hydrogen covalent bond and the passivation of the dangling bond. The functionalized tip was used to characterize silicon dangling bonds on the hydrogen-silicon surface, which was shown to enhance the scanning tunneling microscope contrast, and allowed NC-AFM imaging with atomic and chemical bond contrasts. Through examples, we show the importance of this atomic-scale mechanical manipulation technique in the engineering of the emerging technology of on-surface dangling bond based nanoelectronic devices.

  4. Atomic vapor density monitor

    Energy Technology Data Exchange (ETDEWEB)

    Sewall, N.; Harris, W.; Beeler, R.; Wooldridge, J.; Chen, H.L.

    1986-09-01

    This report presents information on the Atomic Vapor Density Monitor (AVDM) system that measures the density of a vapor by measuring the absorption of light from a swept-wavelength laser that passes through an atomic vapor stream.

  5. Inflatable traversing probe seal

    Science.gov (United States)

    Trimarchi, Paul A.

    1991-01-01

    An inflatable seal acts as a pressure-tight zipper to provide traversing capability for instrumentation rakes and probes. A specially designed probe segment with a teardrop cross-section in the vicinity of the inflatable seal minimizes leakage at the interface. The probe is able to travel through a lengthwise slot in a pressure vessel or wind tunnel section, while still maintaining pressure integrity. The design uses two commercially available inflatable seals, opposing each other, to cover the probe slot in a wind tunnel wall. Proof-of-concept tests were conducted at vessel pressures up to 30 psig, with seals inflated to 50 psig, showing no measurable leakage along the seal's length or around the probe teardrop cross-section. This seal concept can replace the existing technology of sliding face plate/O-ring systems in applications where lengthwise space is limited.

  6. Atomic Spectra Database (ASD)

    Science.gov (United States)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  7. Playing Pinball with Atoms

    NARCIS (Netherlands)

    Saedi, A.; van Houselt, Arie; van Gastel, Raoul; Poelsema, Bene; Zandvliet, Henricus J.W.

    2009-01-01

    We demonstrate the feasibility of controlling an atomic scale mechanical device by an external electrical signal. On a germanium substrate, a switching motion of pairs of atoms is induced by electrons that are directly injected into the atoms with a scanning tunneling microscope tip. By precisely

  8. Scanning probe and micropatterning approaches for biomolecular screening applications

    CERN Document Server

    Wilde, L M

    2002-01-01

    Force mapping using atomic force microscopy (AFM) allows for the simultaneous acquisition of topography and probe-sample interaction data. For example, AFM probes functionalised with an antigen can be employed to map the spatial distribution of recognition events on a substrate functionalised with the complementary specific antibody. However, this technique is currently limited to the detection of a single receptor-ligand species. Were the detection of multiple receptor-ligand interactions possible, AFM force mapping would offer greater scope as a sensitive tool for bioassay and screening applications. This thesis outlines developments in probe and substrate immobilisation methods to facilitate this process. We have developed an immobilisation strategy, which allows two antigen species, human serum albumin (HSA) and the beta subunit of human chorionic gonadotropin (beta hCG) to be simultaneously present on an AFM probe. Single point force spectroscopy results have revealed the ability of such probes to discri...

  9. Collecting optical coherence elastography depth profiles with a micromachined cantilever probe

    NARCIS (Netherlands)

    Chavan, D.C.; Mo, J.; de Groot, M.; Meijering, A.E.C.; de Boer, J.F.; Iannuzzi, D.

    2013-01-01

    We present an experimental setup that combines optical coherence elastography depth sensing with atomic force microscope indentation. The instrument relies on a miniaturized cantilever probe that compresses a sample with a small footprint force and simultaneously collects an optical coherence

  10. Light assisted collisions with cold metastable neon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Glover, R D; Laban, D E; Sang, R T, E-mail: R.Sang@griffith.edu.a [Centre for Quantum Dynamics, Griffith University, Brisbane, QLD 4111 (Australia)

    2009-11-01

    Control of the combined Penning and associative ionization cross section is demonstrated with cold ({approx}1mK) metastable Ne (3s{sup 3}P{sub 2}) atoms in a magneto-optical trap (MOT). By illuminating the trapped atoms with a near resonant probe laser beam, increased ionization rates are observed at several detunings. The probe beam is swept through a region from +500MHz to -500MHz. The increase in the Penning and associative ionization cross section is observed in both the red and blue regions of the spectrum.

  11. Ultrafast Rabi oscillation of a Gaussian atom ensemble

    CERN Document Server

    Lee, Han-gyeol; Ahn, Jaewook

    2014-01-01

    We investigate Rabi oscillation of an atom ensemble in Gaussian spatial distribution. By using the ultrafast laser interaction with the cold atomic rubidium vapor spatially confined in a magneto-optical trap, the oscillatory behavior of the atom excitation is probed as a function of the laser pulse power. Theoretical model calculation predicts that the oscillation peaks of the ensemble-atom Rabi flopping fall on the simple Rabi oscillation curve of a single atom and the experimental result shows good agreement with the prediction. We also test the the three-pulse composite interaction $R_x(\\pi/2)R_y(\\pi)R_x(\\pi/2)$ to develop a robust method to achieve a higher fidelity population inversion of the atom ensemble.

  12. Dynamic of cold-atom tips in anharmonic potentials

    Science.gov (United States)

    Menold, Tobias; Federsel, Peter; Rogulj, Carola; Hölscher, Hendrik; Fortágh, József

    2016-01-01

    Background: Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion. Results: Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time. In agreement with theory, the first measurements show that particle interactions and anharmonic motion have a significant impact on the tip dynamics. Conclusion: Our findings will be crucial for the realization of high-sensitivity force spectroscopy with cold-atom tips and could possibly allow for the development of advanced spectroscopic techniques such as Q-control. PMID:28144505

  13. Atomization characteristics of a prefilming airblast atomizer

    Science.gov (United States)

    Hayashi, Shigeru; Koito, Atsushi; Hishiki, Manabu

    1992-01-01

    The size distribution of water test sprays generated by a prefilming airblast atomizer used for aeroengines was measured in swirling and non-swirling flows with the well established laser scattering particle sizing technique. Atomizing air velocity (or pressure difference) was varied in a range wider than the conditions of actual engines. The Sauter Mean Diameter (SMD) decreased at approximately a 1.5 power of the atomizing air velocity, being a higher velocity index than the previously reported values of 1 to 1.2. It was unexpectedly found that the effect of the liquid/air flow ratio was small. Since swirling flow increased the SMD at lower air velocities yet decreased it at higher ones, it is suggested that the reverse flow near the nozzle pintle adversely affects atomization.

  14. Multilevel Atomic Coherent States and Atomic Holomorphic Representation

    Science.gov (United States)

    Cao, Chang-Qi; Haake, Fritz

    1996-01-01

    The notion of atomic coherent states is extended to the case of multilevel atom collective. Based on atomic coherent states, a holomorphic representation for atom collective states and operators is defined. An example is given to illustrate its application.

  15. Universal aspects of adhesion and atomic force microscopy

    Science.gov (United States)

    Banerjea, Amitava; Smith, John R.; Ferrante, John

    1990-01-01

    Adhesive energies are computed for flat and atomically sharp tips as a function of the normal distance to the substrate. The dependence of binding energies on tip shape is investigated. The magnitudes of the binding energies for the atomic force microscope are found to depend sensitively on tip material, tip shape and the sample site being probed. The form of the energy-distance curve, however, is universal and independent of these variables, including tip shape.

  16. Foldable polymers as probes

    Science.gov (United States)

    Li, Alexander D. Q.; Wang, Wei

    2007-07-03

    Disclosed herein are novel probes, which can be used to detect and identify target molecules of interest in a sample. The disclosed probes can be used to monitor conformational changes induced by molecular recognition events in addition to providing signaling the presence and/or identity of a target molecule. Methods, including solid phase synthesis techniques, for making probe molecules that exhibit changes in their optical properties upon target molecule binding are described in the disclosure. Also disclosed herein are novel chromophore moieties, which have tailored fluorescent emission spectra.

  17. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... Tomography (CT) Safety During Pregnancy Head and Neck Cancer X-ray, Interventional Radiology and Nuclear ... or other physician. To locate a medical imaging or radiation oncology provider in your community, you can search the ...

  18. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... Computed tomography (CT) of the sinuses uses special x-ray equipment to evaluate the paranasal sinus cavities – hollow, air-filled spaces within the bones of the face surrounding the ...

  19. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... tomography (CT) scan. View full size with caption Pediatric Content Some imaging tests and treatments have special pediatric considerations. The teddy bear denotes child-specific content. ...

  20. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... tomography, more commonly known as a CT or CAT scan, is a diagnostic medical test that, like ... imaging provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as ...

  1. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... tissue, such as organs like the heart or liver, shows up in shades of gray, and air ... Neck Cancer X-ray, Interventional Radiology and Nuclear Medicine Radiation Safety Images related to Computed Tomography (CT) - ...

  2. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... tissue, such as organs like the heart or liver, shows up in shades of gray, and air ... Neck Cancer X-ray, Interventional Radiology and Nuclear Medicine Radiation Safety Images related to Computed Tomography (CT) - ...

  3. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... tomography (CT) scan. View full size with caption Pediatric Content Some imaging tests and treatments have special pediatric considerations. The teddy bear denotes child-specific content. ...

  4. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... the limitations of CT Scanning of the Head? What is CT Scanning of the Head? Computed tomography, ... than regular radiographs (x-rays). top of page What are some common uses of the procedure? CT ...

  5. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... are the limitations of CT of the Sinuses? What is CT (Computed Tomography) of the Sinuses? Computed ... nasal cavity by small openings. top of page What are some common uses of the procedure? CT ...

  6. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... story about radiology? Share your patient story here Images × Image Gallery Patient undergoing computed tomography (CT) scan. View ... possible charges you will incur. Web page review process: This Web page is reviewed regularly by a ...

  7. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... for Brain Tumors Radiation Therapy for Head and Neck Cancer Others American Stroke Association National Stroke Association ... Computer Tomography (CT) Safety During Pregnancy Head and Neck Cancer X-ray, Interventional Radiology and Nuclear Medicine ...

  8. Computed Tomography (CT) -- Sinuses

    Medline Plus

    Full Text Available ... other medical conditions and whether you have a history of heart disease, asthma, diabetes, kidney disease or ... Neck Cancer X-ray, Interventional Radiology and Nuclear Medicine Radiation Safety Images related to Computed Tomography (CT) - ...

  9. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... other medical conditions and whether you have a history of heart disease, asthma, diabetes, kidney disease or ... Neck Cancer X-ray, Interventional Radiology and Nuclear Medicine Radiation Safety Images related to Computed Tomography (CT) - ...

  10. Computed Tomography (CT) -- Head

    Medline Plus

    Full Text Available ... of the Head? What is CT Scanning of the Head? Computed tomography, more commonly known as a ... of page What are some common uses of the procedure? CT scanning of the head is typically ...

  11. The atomic structure of polar and non-polar InGaN quantum wells and the green gap problem

    Energy Technology Data Exchange (ETDEWEB)

    Humphreys, C.J., E-mail: colin.humphreys@msm.cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Griffiths, J.T., E-mail: jg641@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Tang, F., E-mail: ft274@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Oehler, F., E-mail: fabrice.oehler@lpn.cnrs.fr [CNRS/C2N, Paris Sud University, Route de Nozay, 91460 Marcoussis (France); Findlay, S.D., E-mail: scott.findlay@monash.edu [School of Physics and Astronomy, Monash University, Victoria 3800 (Australia); Zheng, C., E-mail: changlin.zheng@monash.edu [Monash Centre for Electron Microscopy, Monash University, Victoria 3800 (Australia); Etheridge, J., E-mail: joanne.etheridge@mcem.monash.edu [Department of Materials Science and Engineering, Monash University, Victoria 3800 (Australia); Martin, T.L., E-mail: tomas.martin@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Bagot, P.A.J., E-mail: paul.bagot@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Moody, M.P., E-mail: michael.moody@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Sutherland, D., E-mail: danny.sutherland@manchester.ac.uk [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Dawson, P., E-mail: philip.dawson@manchester.ac.uk [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Schulz, S., E-mail: stefan.schulz@tyndall.ie [Tyndall National Institute, Lee Maltings Complex, Dyke Parade, Cork (Ireland); and others

    2017-05-15

    Highlights: • We have studied the atomic structure of polar and non-polar InGaN quantum wells. • The non-polar (11-20) InGaN quantum wells contain indium-rich clusters, unlike the polar (0001) quantum wells. • The electrons and holes in the quantum wells are localised by different mechanisms. - Abstract: We have used high resolution transmission electron microscopy (HRTEM), aberration-corrected quantitative scanning transmission electron microscopy (Q-STEM), atom probe tomography (APT) and X-ray diffraction (XRD) to study the atomic structure of (0001) polar and (11-20) non-polar InGaN quantum wells (QWs). This paper provides an overview of the results. Polar (0001) InGaN in QWs is a random alloy, with In replacing Ga randomly. The InGaN QWs have atomic height interface steps, resulting in QW width fluctuations. The electrons are localised at the top QW interface by the built-in electric field and the well-width fluctuations, with a localisation energy of typically 20 meV. The holes are localised near the bottom QW interface, by indium fluctuations in the random alloy, with a localisation energy of typically 60 meV. On the other hand, the non-polar (11-20) InGaN QWs contain nanometre-scale indium-rich clusters which we suggest localise the carriers and produce longer wavelength (lower energy) emission than from random alloy non-polar InGaN QWs of the same average composition. The reason for the indium-rich clusters in non-polar (11-20) InGaN QWs is not yet clear, but may be connected to the lower QW growth temperature for the (11-20) InGaN QWs compared to the (0001) polar InGaN QWs.

  12. Impedimentric and microscopic probes of the integrities of ...

    African Journals Online (AJOL)

    Electrical and structural integrities of Self-assembled Monolayers (SAMs) of some organosulphur-metal complexes, formed on polycrystalline gold disc electrode, were probed, using Electrochemical Impedance Spectroscopy (EIS) and Atomic Force Microscopy (AFM) respectively. Values of relevant circuit elements in the ...

  13. Electrospray deposition from AFM probes with nanoscale apertures

    NARCIS (Netherlands)

    Geerlings, J.; Sarajlic, Edin; Berenschot, Johan W.; Sanders, Remco G.P.; Abelmann, Leon; Tas, Niels Roelof

    2014-01-01

    Electrospray deposition utilizes a high electric field to extract liquid droplets from a capillary nozzle. In this contribution we demonstrate non-contact droplet deposition by electrospray from atomic force microscopy (AFM) probes with a fully integrated microfluidic system, so called FluidFM

  14. Hard probes 2006 Asilomar

    CERN Multimedia

    2006-01-01

    "The second international conference on hard and electromagnetic probes of high-energy nuclear collisions was held June 9 to 16, 2006 at the Asilomar Conference grounds in Pacific Grove, California" (photo and 1/2 page)

  15. Introduction to Seismic Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, Charlotte Anne [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-21

    Tomography is a method of obtaining an image of a 3d object by observing the behavior of energy transmissions through the object. The image is obtained by Interrogating the object with Energy sources at a variety of Locations and observing the Object’s effects on the energy at a Variety of sensors. Tomography was first Used to build 3-dimensional Scans through Human bodies. These Are called computed Tomographic (ct) scans.

  16. Transient-absorption phases with strong probe and pump pulses

    Science.gov (United States)

    Becquet, Vadim; Cavaletto, Stefano M.

    2018-02-01

    The quantum dynamics of a system of Rb atoms, modeled by a V-type three-level system interacting with intense probe and pump pulses, are studied. The time-delay-dependent transient-absorption spectrum of an intense probe pulse is thus predicted, simulating pump-probe experiments in which this is preceded or followed by a strong pump pulse. Numerical results are interpreted in terms of an analytical model based on interaction operators, which quantify the transformation undergone by the system under the action of an intense pulse. The oscillating features of the resulting transient-absorption spectra, due to the coupling of several excited states, are thus interpreted in terms of the atomic population and phase changes imposed by the pump and probe pulses. Strong-field-induced phases and their influence on the resulting transient-absorption spectra are thereby investigated for different values of pump and probe intensities and frequencies, focusing on the atomic properties which are encoded in the absorption line shapes for positive and negative time delays.

  17. Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

    OpenAIRE

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.

    2005-01-01

    The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...

  18. Muon Tomography for Geological Repositories.

    Science.gov (United States)

    Woodward, D.; Kudryavtsev, V.; Gluyas, J.; Clark, S. J.; Thompson, L. F.; Klinger, J.; Spooner, N. J.; Blackwell, T. B.; Pal, S.; Lincoln, D. L.; Paling, S. M.; Mitchell, C. N.; Benton, C.; Coleman, M. L.; Telfer, S.; Cole, A.; Nolan, S.; Chadwick, P.

    2015-12-01

    Cosmic-ray muons are subatomic particles produced in the upper atmosphere in collisions of primary cosmic rays with atoms in air. Due to their high penetrating power these muons can be used to image the content (primarily density) of matter they pass through. They have already been used to image the structure of pyramids, volcanoes and other objects. Their applications can be extended to investigating the structure of, and monitoring changes in geological formations and repositories, in particular deep subsurface sites with stored CO2. Current methods of monitoring subsurface CO2, such as repeat seismic surveys, are episodic and require highly skilled personnel to operate. Our simulations based on simplified models have previously shown that muon tomography could be used to continuously monitor CO2 injection and migration and complement existing technologies. Here we present a simulation of the monitoring of CO2 plume evolution in a geological reservoir using muon tomography. The stratigraphy in the vicinity of the reservoir is modelled using geological data, and a numerical fluid flow model is used to describe the time evolution of the CO2 plume. A planar detection region with a surface area of 1000 m2 is considered, at a vertical depth of 776 m below the seabed. We find that one year of constant CO2 injection leads to changes in the column density of about 1%, and that the CO2 plume is already resolvable with an exposure time of less than 50 days. The attached figure show a map of CO2 plume in angular coordinates as reconstructed from observed muons. In parallel with simulation efforts, a small prototype muon detector has been designed, built and tested in a deep subsurface laboratory. Initial calibrations of the detector have shown that it can reach the required angular resolution for muon detection. Stable operation in a small borehole within a few months has been demonstrated.

  19. An All-Fiber-Optic Combined System of Noncontact Photoacoustic Tomography and Optical Coherence Tomography

    Directory of Open Access Journals (Sweden)

    Jonghyun Eom

    2016-05-01

    Full Text Available We propose an all-fiber-based dual-modal imaging system that combines noncontact photoacoustic tomography (PAT and optical coherence tomography (OCT. The PAT remotely measures photoacoustic (PA signals with a 1550-nm laser on the surface of a sample by utilizing a fiber interferometer as an ultrasound detector. The fiber-based OCT, employing a swept-source laser centered at 1310 nm, shares the sample arm of the PAT system. The fiber-optic probe for the combined system was homemade with a lensed single-mode fiber (SMF and a large-core multimode fiber (MMF. The compact and robust common probe is capable of obtaining both the PA and the OCT signals at the same position without any physical contact. Additionally, the MMF of the probe delivers the short pulses of a Nd:YAG laser to efficiently excite the PA signals. We experimentally demonstrate the feasibility of the proposed dual-modal system with a phantom made of a fishing line and a black polyethylene terephthalate fiber in a tissue mimicking solution. The all-fiber-optic system, capable of providing complementary information about absorption and scattering, has a promising potential in minimally invasive and endoscopic imaging.

  20. Development of a combined OCT-Raman probe for the prospective in vivo clinical melanoma skin cancer screening

    Science.gov (United States)

    Mazurenka, M.; Behrendt, L.; Meinhardt-Wollweber, M.; Morgner, U.; Roth, B.

    2017-10-01

    A combined optical coherence tomography (OCT)-Raman probe was designed and built into a spectral domain OCT head, and its performance was evaluated and compared to the most common Raman probe setups, based on a fiber bundle and confocal free space optics. Due to the use of the full field of view of an OCT scanning lens, the combined probe has a superior performance within maximum permissible exposure limits, compared to the other two probes. Skin Raman spectra, recorded in vivo, further prove the feasibility of the OCT-Raman probe for the future in vivo clinical applications in skin cancer screening.