Science.gov

Sample records for reveal in-situ time-resolved

  1. In situ time-resolved FRET reveals effects of sarcomere length on cardiac thin-filament activation.

    PubMed

    Li, King-Lun; Rieck, Daniel; Solaro, R John; Dong, Wenji

    2014-08-05

    During cardiac thin-filament activation, the N-domain of cardiac troponin C (N-cTnC) binds to Ca(2+) and interacts with the actomyosin inhibitory troponin I (cTnI). The interaction between N-cTnC and cTnI stabilizes the Ca(2+)-induced opening of N-cTnC and is presumed to also destabilize cTnI-actin interactions that work together with steric effects of tropomyosin to inhibit force generation. Recently, our in situ steady-state FRET measurements based on N-cTnC opening suggested that at long sarcomere length, strongly bound cross-bridges indirectly stabilize this Ca(2+)-sensitizing N-cTnC-cTnI interaction through structural effects on tropomyosin and cTnI. However, the method previously used was unable to determine whether N-cTnC opening depends on sarcomere length. In this study, we used time-resolved FRET to monitor the effects of cross-bridge state and sarcomere length on the Ca(2+)-dependent conformational behavior of N-cTnC in skinned cardiac muscle fibers. FRET donor (AEDANS) and acceptor (DDPM)-labeled double-cysteine mutant cTnC(T13C/N51C)AEDANS-DDPM was incorporated into skinned muscle fibers to monitor N-cTnC opening. To study the structural effects of sarcomere length on N-cTnC, we monitored N-cTnC opening at relaxing and saturating levels of Ca(2+) and 1.80 and 2.2-μm sarcomere length. Mg(2+)-ADP and orthovanadate were used to examine the structural effects of noncycling strong-binding and weak-binding cross-bridges, respectively. We found that the stabilizing effect of strongly bound cross-bridges on N-cTnC opening (which we interpret as transmitted through related changes in cTnI and tropomyosin) become diminished by decreases in sarcomere length. Additionally, orthovanadate blunted the effect of sarcomere length on N-cTnC conformational behavior such that weak-binding cross-bridges had no effect on N-cTnC opening at any tested [Ca(2+)] or sarcomere length. Based on our findings, we conclude that the observed sarcomere length-dependent positive

  2. Time-resolved in situ powder X-ray diffraction reveals the mechanisms of molten salt synthesis.

    PubMed

    Moorhouse, Saul J; Wu, Yue; Buckley, Hannah C; O'Hare, Dermot

    2016-11-24

    We report the first use of high-energy monochromatic in situ X-ray powder diffraction to gain unprecedented insights into the chemical processes occurring during high temperature, lab-scale metal oxide syntheses. During the flux synthesis of the n = 4 Aurivillius phase, Bi5Ti3Fe0.5Cr0.5O15 at 950 °C in molten Na2SO4 we observe the progression of numerous metastable phases. Using sequential multiphase Rietveld refinement of the time-dependent in situ XRD data, we are able to obtain mechanistic understanding of this reaction under a range of conditions.

  3. Time-resolved Raman spectroscopy for in situ planetary mineralogy.

    PubMed

    Blacksberg, Jordana; Rossman, George R; Gleckler, Anthony

    2010-09-10

    Planetary mineralogy can be revealed through a variety of remote sensing and in situ investigations that precede any plans for eventual sample return. We briefly review those techniques and focus on the capabilities for on-surface in situ examination of Mars, Venus, the Moon, asteroids, and other bodies. Over the past decade, Raman spectroscopy has continued to develop as a prime candidate for the next generation of in situ planetary instruments, as it provides definitive structural and compositional information of minerals in their natural geological context. Traditional continuous-wave Raman spectroscopy using a green laser suffers from fluorescence interference, which can be large (sometimes saturating the detector), particularly in altered minerals, which are of the greatest geophysical interest. Taking advantage of the fact that fluorescence occurs at a later time than the instantaneous Raman signal, we have developed a time-resolved Raman spectrometer that uses a streak camera and pulsed miniature microchip laser to provide picosecond time resolution. Our ability to observe the complete time evolution of Raman and fluorescence spectra in minerals makes this technique ideal for exploration of diverse planetary environments, some of which are expected to contain strong, if not overwhelming, fluorescence signatures. We discuss performance capability and present time-resolved pulsed Raman spectra collected from several highly fluorescent and Mars-relevant minerals. In particular, we have found that conventional Raman spectra from fine grained clays, sulfates, and phosphates exhibited large fluorescent signatures, but high quality spectra could be obtained using our time-resolved approach.

  4. In Situ Time-Resolved FRET Reveals Effects of Sarcomere Length on Cardiac Thin-Filament Activation

    PubMed Central

    Li, King-Lun; Rieck, Daniel; Solaro, R. John; Dong, Wenji

    2014-01-01

    During cardiac thin-filament activation, the N-domain of cardiac troponin C (N-cTnC) binds to Ca2+ and interacts with the actomyosin inhibitory troponin I (cTnI). The interaction between N-cTnC and cTnI stabilizes the Ca2+-induced opening of N-cTnC and is presumed to also destabilize cTnI–actin interactions that work together with steric effects of tropomyosin to inhibit force generation. Recently, our in situ steady-state FRET measurements based on N-cTnC opening suggested that at long sarcomere length, strongly bound cross-bridges indirectly stabilize this Ca2+-sensitizing N-cTnC–cTnI interaction through structural effects on tropomyosin and cTnI. However, the method previously used was unable to determine whether N-cTnC opening depends on sarcomere length. In this study, we used time-resolved FRET to monitor the effects of cross-bridge state and sarcomere length on the Ca2+-dependent conformational behavior of N-cTnC in skinned cardiac muscle fibers. FRET donor (AEDANS) and acceptor (DDPM)-labeled double-cysteine mutant cTnC(T13C/N51C)AEDANS-DDPM was incorporated into skinned muscle fibers to monitor N-cTnC opening. To study the structural effects of sarcomere length on N-cTnC, we monitored N-cTnC opening at relaxing and saturating levels of Ca2+ and 1.80 and 2.2-μm sarcomere length. Mg2+-ADP and orthovanadate were used to examine the structural effects of noncycling strong-binding and weak-binding cross-bridges, respectively. We found that the stabilizing effect of strongly bound cross-bridges on N-cTnC opening (which we interpret as transmitted through related changes in cTnI and tropomyosin) become diminished by decreases in sarcomere length. Additionally, orthovanadate blunted the effect of sarcomere length on N-cTnC conformational behavior such that weak-binding cross-bridges had no effect on N-cTnC opening at any tested [Ca2+] or sarcomere length. Based on our findings, we conclude that the observed sarcomere length-dependent positive feedback

  5. Evolution of polytypism in GaAs nanowires during growth revealed by time-resolved in situ x-ray diffraction.

    PubMed

    Schroth, Philipp; Köhl, Martin; Hornung, Jean-Wolfgang; Dimakis, Emmanouil; Somaschini, Claudio; Geelhaar, Lutz; Biermanns, Andreas; Bauer, Sondes; Lazarev, Sergey; Pietsch, Ullrich; Baumbach, Tilo

    2015-02-06

    In III-V nanowires the energetic barriers for nucleation in the zinc blende or wurtzite arrangement are typically of a similar order of magnitude. As a result, both arrangements can occur in a single wire. Here, we investigate the evolution of this polytypism in self-catalyzed GaAs nanowires on Si(111) grown by molecular beam epitaxy with time-resolved in situ x-ray diffraction. We interpret our data in the framework of a height dependent Markov model for the stacking in the nanowires. In this way, we extract the mean sizes of faultless wurtzite and zinc blende segments-a key parameter of polytypic nanowires-and their temporal evolution during growth. Thereby, we infer quantitative information on the differences of the nucleation barriers including their evolution without requiring a model of the nucleus.

  6. ED-XAS Data Reveal In-situ Time-Resolved Adsorbate Coverage on Supported Molybdenum Oxide Catalysts during Propane Dehydrogenation

    NASA Astrophysics Data System (ADS)

    Ramaker, David; Gatewood, Daniel; Beale, Andrew M.; Weckhuysen, Bert M.

    2007-02-01

    Energy-Dispersive X-ray Absorption Spectroscopy (ED-XAS) data combined with UV/Vis, Raman, and mass spectrometry data on alumina- and silica-supported molybdenum oxide catalysts under propane dehydrogenation conditions have been previously reported. A novel Δμ adsorbate isolation technique was applied here to the time-resolved (0.1 min) Mo K-edge ED-XAS data by taking the difference of absorption, μ, at t>1 against the initial time, t=0. Further, full multiple scattering calculations using the FEFF 8.0 code are performed to interpret the Δμ signatures. The resulting difference spectra and interpretation provide real time propane coverage and O depletion at the MoOn surface. The propane coverage is seen to correlate with the propene and/or coke production, with the maximum coke formation occurring when the propane coverage is the largest. Combined, these data give unprecedented insight into the complicated dynamics for propane dehydrogenation.

  7. ED-XAS Data Reveal In-situ Time-Resolved Adsorbate Coverage on Supported Molybdenum Oxide Catalysts during Propane Dehydrogenation

    SciTech Connect

    Ramaker, David; Gatewood, Daniel; Beale, Andrew M.; Weckhuysen, Bert M.

    2007-02-02

    Energy-Dispersive X-ray Absorption Spectroscopy (ED-XAS) data combined with UV/Vis, Raman, and mass spectrometry data on alumina- and silica-supported molybdenum oxide catalysts under propane dehydrogenation conditions have been previously reported. A novel {delta}{mu} adsorbate isolation technique was applied here to the time-resolved (0.1 min) Mo K-edge ED-XAS data by taking the difference of absorption, {mu}, at t>1 against the initial time, t=0. Further, full multiple scattering calculations using the FEFF 8.0 code are performed to interpret the {delta}{mu} signatures. The resulting difference spectra and interpretation provide real time propane coverage and O depletion at the MoOn surface. The propane coverage is seen to correlate with the propene and/or coke production, with the maximum coke formation occurring when the propane coverage is the largest. Combined, these data give unprecedented insight into the complicated dynamics for propane dehydrogenation.

  8. Time resolved electron microscopy for in situ experiments

    SciTech Connect

    Campbell, Geoffrey H. McKeown, Joseph T.; Santala, Melissa K.

    2014-12-15

    Transmission electron microscopy has functioned for decades as a platform for in situ observation of materials and processes with high spatial resolution. Yet, the dynamics often remain elusive, as they unfold too fast to discern at these small spatial scales under traditional imaging conditions. Simply shortening the exposure time in hopes of capturing the action has limitations, as the number of electrons will eventually be reduced to the point where noise overtakes the signal in the image. Pulsed electron sources with high instantaneous current have successfully shortened exposure times (thus increasing the temporal resolution) by about six orders of magnitude over conventional sources while providing the necessary signal-to-noise ratio for dynamic imaging. We describe here the development of this new class of microscope and the principles of its operation, with examples of its application to problems in materials science.

  9. Time-Resolved In Situ Measurements During Rapid Alloy Solidification: Experimental Insight for Additive Manufacturing

    DOE PAGES

    McKeown, Joseph T.; Zweiacker, Kai; Liu, Can; ...

    2016-01-27

    In research and industrial environments, additive manufacturing (AM) of metals and alloys is becoming a pervasive technology, though significant challenges remain before widespread implementation of AM can be realized. In situ investigations of rapid alloy solidification with high spatial and temporal resolutions can provide unique experimental insight into microstructure evolution and kinetics that are relevant for AM processing. Hypoeutectic thin-film Al–Cu and Al–Si alloys were investigated using dynamic transmission electron microscopy to monitor pulsed-laser-induced rapid solidification across microsecond timescales. Solid–liquid interface velocities measured from time-resolved images revealed accelerating solidification fronts in both alloys. We observed microstructure evolution, solidification product, andmore » presence of a morphological instability at the solid–liquid interface in the Al–4 at.%Cu alloy are related to the measured interface velocities and small differences in composition that affect the thermophysical properties of the alloys. These time-resolved in situ measurements can inform and validate predictive modeling efforts for AM.« less

  10. Time-Resolved In Situ Measurements During Rapid Alloy Solidification: Experimental Insight for Additive Manufacturing

    SciTech Connect

    McKeown, Joseph T.; Zweiacker, Kai; Liu, Can; Coughlin, Daniel R.; Clarke, Amy J.; Baldwin, J. Kevin; Gibbs, John W.; Roehling, John D.; Imhoff, Seth D.; Gibbs, Paul J.; Tourret, Damien; Wiezorek, Jörg M. K.; Campbell, Geoffrey H.

    2016-01-27

    In research and industrial environments, additive manufacturing (AM) of metals and alloys is becoming a pervasive technology, though significant challenges remain before widespread implementation of AM can be realized. In situ investigations of rapid alloy solidification with high spatial and temporal resolutions can provide unique experimental insight into microstructure evolution and kinetics that are relevant for AM processing. Hypoeutectic thin-film Al–Cu and Al–Si alloys were investigated using dynamic transmission electron microscopy to monitor pulsed-laser-induced rapid solidification across microsecond timescales. Solid–liquid interface velocities measured from time-resolved images revealed accelerating solidification fronts in both alloys. We observed microstructure evolution, solidification product, and presence of a morphological instability at the solid–liquid interface in the Al–4 at.%Cu alloy are related to the measured interface velocities and small differences in composition that affect the thermophysical properties of the alloys. These time-resolved in situ measurements can inform and validate predictive modeling efforts for AM.

  11. The molecular pathway to ZIF-7 microrods revealed by in situ time-resolved small- and wide-angle X-ray scattering, quick-scanning extended X-ray absorption spectroscopy, and DFT calculations.

    PubMed

    Goesten, Maarten; Stavitski, Eli; Pidko, Evgeny A; Gücüyener, Canan; Boshuizen, Bart; Ehrlich, Steven N; Hensen, Emiel J M; Kapteijn, Freek; Gascon, Jorge

    2013-06-10

    We present an in situ small- and wide-angle X-ray scattering (SAXS/WAXS) and quick-scanning extended X-ray absorption fine-structure (QEXAFS) spectroscopy study on the crystallization of the metal-organic framework ZIF-7. In combination with DFT calculations, the self-assembly and growth of ZIF-7 microrods together with the chemical function of the crystal growth modulator (diethylamine) are revealed at all relevant length scales, from the atomic to the full crystal size.

  12. Fixed target matrix for femtosecond time-resolved and in situ serial micro-crystallography

    PubMed Central

    Mueller, C.; Marx, A.; Epp, S. W.; Zhong, Y.; Kuo, A.; Balo, A. R.; Soman, J.; Schotte, F.; Lemke, H. T.; Owen, R. L.; Pai, E. F.; Pearson, A. R.; Olson, J. S.; Anfinrud, P. A.; Ernst, O. P.; Dwayne Miller, R. J.

    2015-01-01

    We present a crystallography chip enabling in situ room temperature crystallography at microfocus synchrotron beamlines and X-ray free-electron laser (X-FEL) sources. Compared to other in situ approaches, we observe extremely low background and high diffraction data quality. The chip design is robust and allows fast and efficient loading of thousands of small crystals. The ability to load a large number of protein crystals, at room temperature and with high efficiency, into prescribed positions enables high throughput automated serial crystallography with microfocus synchrotron beamlines. In addition, we demonstrate the application of this chip for femtosecond time-resolved serial crystallography at the Linac Coherent Light Source (LCLS, Menlo Park, California, USA). The chip concept enables multiple images to be acquired from each crystal, allowing differential detection of changes in diffraction intensities in order to obtain high signal-to-noise and fully exploit the time resolution capabilities of XFELs. PMID:26798825

  13. In Situ, Time-Resolved Accelerator Grid Erosion Measurements in the NSTAR 8000 Hour Ion Engine Wear Test

    NASA Technical Reports Server (NTRS)

    Sovey, J.

    1997-01-01

    Time-resolved, in situ measurements of the charge exchange ion erosion pattern on the downstream face of the accelerator grid have been made during an ongoin wear test of the NSTAR 30 cm ion thruster.

  14. Fixed target matrix for femtosecond time-resolved and in situ serial micro-crystallography

    DOE PAGES

    Mueller, C.; Marx, A.; Epp, S. W.; ...

    2015-08-18

    We present a crystallography chip enabling in situ room temperature crystallography at microfocus synchrotron beamlines and X-ray free-electron laser (X-FEL) sources. Compared to other in situ approaches, we observe extremely low background and high diffraction data quality. The chip design is robust and allows fast and efficient loading of thousands of small crystals. The ability to load a large number of protein crystals, at room temperature and with high efficiency, into prescribed positions enables high throughput automated serial crystallography with microfocus synchrotron beamlines. In addition, we demonstrate the application of this chip for femtosecond time-resolved serial crystallography at the Linacmore » Coherent Light Source (LCLS, Menlo Park, California, USA). As a result, the chip concept enables multiple images to be acquired from each crystal, allowing differential detection of changes in diffraction intensities in order to obtain high signal-to-noise and fully exploit the time resolution capabilities of XFELs.« less

  15. Assessment of In Situ Time Resolved Shock Experiments at Synchrotron Light Sources*

    NASA Astrophysics Data System (ADS)

    Belak, J.; Ilavsky, J.; Hessler, J. P.

    2005-07-01

    Prior to fielding in situ time resolved experiments of shock wave loading at the Advanced Photon Source, we have performed feasibility experiments assessing a single photon bunch. Using single and poly-crystal Al, Ti, V and Cu shock to incipient spallation on the gas gun, samples were prepared from slices normal to the spall plane of thickness 100-500 microns. In addition, single crystal Al of thickness 500 microns was shocked to incipient spallation and soft recovered using the LLNL e-gun mini-flyer system. The e-gun mini-flyer impacts the sample target producing a 10's ns flat-top shock transient. Here, we present results for imaging, small-angle scattering (SAS), and diffraction. In particular, there is little SAS away from the spall plane and significant SAS at the spall plane, demonstrating the presence of sub-micron voids. * Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38 and work performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  16. Revealing Deactivation Pathways Hidden in Time-Resolved Photoelectron Spectra

    PubMed Central

    Ruckenbauer, Matthias; Mai, Sebastian; Marquetand, Philipp; González, Leticia

    2016-01-01

    Time-resolved photoelectron spectroscopy is commonly employed with the intention to monitor electronic excited-state dynamics occurring in a neutral molecule. With the help of theory, we show that when excited-state processes occur on similar time scales the different relaxation pathways are completely obscured in the total photoionization signal recorded in the experiment. Using non-adiabatic molecular dynamics and Dyson norms, we calculate the photoionization signal of cytosine and disentangle the transient contributions originating from the different deactivation pathways of its tautomers. In the simulations, the total signal from the relevant keto and enol tautomers can be decomposed into contributions either from the neutral electronic state populations or from the distinct mechanistic pathways across the multiple potential surfaces. The lifetimes corresponding to these contributions cannot be extracted from the experiment, thereby illustrating that new experimental setups are necessary to unravel the intricate non-adiabatic pathways occurring in polyatomic molecules after irradiation by light. PMID:27762396

  17. Revealing Deactivation Pathways Hidden in Time-Resolved Photoelectron Spectra

    NASA Astrophysics Data System (ADS)

    Ruckenbauer, Matthias; Mai, Sebastian; Marquetand, Philipp; González, Leticia

    2016-10-01

    Time-resolved photoelectron spectroscopy is commonly employed with the intention to monitor electronic excited-state dynamics occurring in a neutral molecule. With the help of theory, we show that when excited-state processes occur on similar time scales the different relaxation pathways are completely obscured in the total photoionization signal recorded in the experiment. Using non-adiabatic molecular dynamics and Dyson norms, we calculate the photoionization signal of cytosine and disentangle the transient contributions originating from the different deactivation pathways of its tautomers. In the simulations, the total signal from the relevant keto and enol tautomers can be decomposed into contributions either from the neutral electronic state populations or from the distinct mechanistic pathways across the multiple potential surfaces. The lifetimes corresponding to these contributions cannot be extracted from the experiment, thereby illustrating that new experimental setups are necessary to unravel the intricate non-adiabatic pathways occurring in polyatomic molecules after irradiation by light.

  18. The Oxford-Diamond In Situ Cell for studying chemical reactions using time-resolved X-ray diffraction.

    PubMed

    Moorhouse, Saul J; Vranješ, Nenad; Jupe, Andrew; Drakopoulos, Michael; O'Hare, Dermot

    2012-08-01

    A versatile, infrared-heated, chemical reaction cell has been assembled and commissioned for the in situ study of a range of chemical syntheses using time-resolved energy-dispersive X-ray diffraction (EDXRD) on Beamline I12 at the Diamond Light Source. Specialized reactor configurations have been constructed to enable in situ EDXRD investigation of samples under non-ambient conditions. Chemical reactions can be studied using a range of sample vessels such as alumina crucibles, steel hydrothermal autoclaves, and glassy carbon tubes, at temperatures up to 1200 °C.

  19. The Oxford-Diamond In Situ Cell for studying chemical reactions using time-resolved X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Moorhouse, Saul J.; Vranješ, Nenad; Jupe, Andrew; Drakopoulos, Michael; O'Hare, Dermot

    2012-08-01

    A versatile, infrared-heated, chemical reaction cell has been assembled and commissioned for the in situ study of a range of chemical syntheses using time-resolved energy-dispersive X-ray diffraction (EDXRD) on Beamline I12 at the Diamond Light Source. Specialized reactor configurations have been constructed to enable in situ EDXRD investigation of samples under non-ambient conditions. Chemical reactions can be studied using a range of sample vessels such as alumina crucibles, steel hydrothermal autoclaves, and glassy carbon tubes, at temperatures up to 1200 °C.

  20. Detection of rhodopsin dimerization in situ by PIE-FCCS, a time-resolved fluorescence spectroscopy.

    PubMed

    Smith, Adam W

    2015-01-01

    Rhodopsin self-associates in the plasma membrane. At low concentrations, the interactions are consistent with a monomer-dimer equilibrium (Comar et al., J Am Chem Soc 136(23):8342-8349, 2014). At high concentrations in native tissue, higher-order clusters have been observed (Fotiadis et al., Nature 421:127-128, 2003). The physiological role of rhodopsin dimerization is still being investigated, but it is clear that a quantitative assessment is essential to determining the function of rhodopsin clusters in vision. To quantify rhodopsin interactions, I will outline the theory and methodology of a specialized time-resolved fluorescence spectroscopy for measuring membrane protein-protein interactions called pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS). The strength of this technique is its ability to quantify rhodopsin interactions in situ (i.e., a live cell plasma membrane). There are two reasons for restricting the scope to live cell membranes. First, the compositional heterogeneity of the plasma membrane creates a complex milieu with thousands of lipid, protein, and carbohydrate species. This makes it difficult to infer quaternary interactions from detergent solubilized samples or construct a model phospholipid bilayer that recapitulates all of the interactions present in native membranes. Second, organizational structure and dynamics is a key feature of the plasma membrane, and fixation techniques like formaldehyde cross-linking and vitrification will modulate the interactions. PIE-FCCS is based on two-color fluorescence imaging with time-correlated single-photon counting (TCSPC) (Becker et al., Rev Sci Instrum 70:1835-1841, 1999). By time-tagging every detected photon, the data can be analyzed as a fluorescence intensity distribution, fluorescence lifetime histogram, or fluorescence (cross-)correlation spectra (FCS/FCCS) (Becker, Advanced time-correlated single-photon counting techniques, Springer, Berlin, 2005). These

  1. Time-resolved metabolomics reveals metabolic modulation in rice foliage

    PubMed Central

    Sato, Shigeru; Arita, Masanori; Soga, Tomoyoshi; Nishioka, Takaaki; Tomita, Masaru

    2008-01-01

    Background To elucidate the interaction of dynamics among modules that constitute biological systems, comprehensive datasets obtained from "omics" technologies have been used. In recent plant metabolomics approaches, the reconstruction of metabolic correlation networks has been attempted using statistical techniques. However, the results were unsatisfactory and effective data-mining techniques that apply appropriate comprehensive datasets are needed. Results Using capillary electrophoresis mass spectrometry (CE-MS) and capillary electrophoresis diode-array detection (CE-DAD), we analyzed the dynamic changes in the level of 56 basic metabolites in plant foliage (Oryza sativa L. ssp. japonica) at hourly intervals over a 24-hr period. Unsupervised clustering of comprehensive metabolic profiles using Kohonen's self-organizing map (SOM) allowed classification of the biochemical pathways activated by the light and dark cycle. The carbon and nitrogen (C/N) metabolism in both periods was also visualized as a phenotypic linkage map that connects network modules on the basis of traditional metabolic pathways rather than pairwise correlations among metabolites. The regulatory networks of C/N assimilation/dissimilation at each time point were consistent with previous works on plant metabolism. In response to environmental stress, glutathione and spermidine fluctuated synchronously with their regulatory targets. Adenine nucleosides and nicotinamide coenzymes were regulated by phosphorylation and dephosphorylation. We also demonstrated that SOM analysis was applicable to the estimation of unidentifiable metabolites in metabolome analysis. Hierarchical clustering of a correlation coefficient matrix could help identify the bottleneck enzymes that regulate metabolic networks. Conclusion Our results showed that our SOM analysis with appropriate metabolic time-courses effectively revealed the synchronous dynamics among metabolic modules and elucidated the underlying biochemical

  2. In situ multipurpose time-resolved spectrometer for monitoring nanoparticle generation in a high-pressure fluid

    SciTech Connect

    Wei, Shaoyu; Saitow, Ken-ichi

    2012-07-15

    We developed a multipurpose time-resolved spectrometer for studying the dynamics of nanoparticles generated by pulsed-laser ablation (PLA) in a high-pressure fluid. The apparatus consists of a high-pressure optical cell and three spectrometers for in situ measurements. The optical cell was designed for experiments at temperatures up to 400 K and pressures up to 30 MPa with fluctuations within {+-}0.1% h{sup -1}. The three spectrometers were used for the following in situ measurements at high pressures: (i) transient absorption spectrum measurements from 350 to 850 nm to investigate the dynamics of nanoparticle generation from nanoseconds to milliseconds after laser irradiation, (ii) absorption spectrum measurements from 220 to 900 nm to observe the time evolution of nanoparticles from seconds to hours after laser ablation, and (iii) dynamic light scattering measurements to track nanoparticles with sizes from 10 nm to 10 {mu}m in the time range from seconds to hours after laser ablation. By combining these three spectrometers, we demonstrate in situ measurements of gold nanoparticles generated by PLA in supercritical fluids. This is the first report of in situ time-resolved measurements of the dynamics of nanoparticles generated in a supercritical fluid.

  3. Structural kinetics of a Pt/C cathode catalyst with practical catalyst loading in an MEA for PEFC operating conditions studied by in situ time-resolved XAFS.

    PubMed

    Ishiguro, Nozomu; Saida, Takahiro; Uruga, Tomoya; Sekizawa, Oki; Nagasawa, Kensaku; Nitta, Kiyofumi; Yamamoto, Takashi; Ohkoshi, Shin-ichi; Yokoyama, Toshihiko; Tada, Mizuki

    2013-11-21

    The structural kinetics of surface events on a Pt/C cathode catalyst in a membrane electrode assembly (MEA) with a practical catalyst loading (0.5 mgPt cm(-2)) for a polymer electrolyte fuel cell were investigated by in situ time-resolved X-ray absorption fine structure analysis (XAFS; time resolution: 100 ms) for the first time. The rate constants of structural changes in the Pt/C cathode catalyst in the MEA during voltage cycling were successfully estimated. For voltage-cycling processes, all reactions (electrochemical reactions and structural changes in the Pt catalyst) in the MEA were found to be much faster than those in an MEA with a thick cathode catalyst layer, but the in situ time-resolved XAFS analysis revealed that significant time lags similarly existed between the electrochemical reactions and the structural changes in the Pt cathode catalyst. The time-resolved XAFS also revealed differences in the structural kinetics of the Pt/C cathode catalyst for the voltage-cycling processes under N2 and air flows at the cathode.

  4. In-situ straining and time-resolved electron tomography data acquisition in a transmission electron microscope.

    PubMed

    Hata, S; Miyazaki, S; Gondo, T; Kawamoto, K; Horii, N; Sato, K; Furukawa, H; Kudo, H; Miyazaki, H; Murayama, M

    2016-12-18

    This paper reports the preliminary results of a new in-situ three-dimensional (3D) imaging system for observing plastic deformation behavior in a transmission electron microscope (TEM) as a directly relevant development of the recently reported straining-and-tomography holder [Sato K et al (2015) Development of a novel straining holder for transmission electron microscopy compatible with single tilt-axis electron tomography. Microsc. 64: 369-375]. We designed an integrated system using the holder and newly developed straining and image-acquisition software and then developed an experimental procedure for in-situ straining and time-resolved electron tomography (ET) data acquisition. The software for image acquisition and 3D visualization was developed based on the commercially available ET software TEMography(TM) We achieved time-resolved 3D visualization of nanometer-scale plastic deformation behavior in a Pb-Sn alloy sample, thus demonstrating the capability of this system for potential applications in materials science.

  5. In-situ Characterization of Water-Gas Shift Catalysts using Time-Resolved X-ray Diffraction

    SciTech Connect

    Rodriguez, J.; Hanson, J; Wen, W; Wang, X; Brito, J; Martnez-Arias, A; Fernandez-Garca, M

    2009-01-01

    Time-resolved X-ray diffraction (XRD) has emerged as a powerful technique for studying the behavior of heterogeneous catalysts (metal oxides, sulfides, carbides, phosphides, zeolites, etc.) in-situ during reaction conditions. The technique can identify the active phase of a heterogeneous catalyst and how its structure changes after interacting with the reactants and products (80 K < T < 1200 K; P < 50 atm). In this article, we review a series of recent works that use in-situ time-resolved XRD for studying the water-gas shift reaction (WGS, CO + H2O ? H2 + CO2) over several mixed-metal oxides: CuMoO4, NiMoO4, Ce1-xCuxO2-d and CuFe2O4. Under reaction conditions the oxides undergo partial reduction. Neutral Cu0 (i.e. no Cu1+ or Cu2+ cations) and Ni0 are the active species in the catalysts, but interactions with the oxide support are necessary in order to obtain high catalytic activity. These studies illustrate the important role played by O vacancies in the mechanism for the WGS. In the case of Ce1-xCuxO2-d, Rietveld refinement shows expansions/contractions in the oxide lattice which track steps within the WGS process: CO(gas) + O(oxi) ? CO2(gas) + O(vac); H2O(gas) + O(vac) ? O(oxi) + H2(gas).

  6. In Situ Planetary Mineralogy Using Simultaneous Time Resolved Fluorescence and Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Blacksberg, J.; Rossman , G.R.

    2011-01-01

    Micro-Raman spectroscopy is one of the primary methods of mineralogical analysis in the laboratory, and more recently in the field. Because of its versatility and ability to interrogate rocks in their natural form it is one of the front runners for the next generation of in situ instruments designed to explore adverse set of solar system bodies (e.g. Mars, Venus, the Moon, and other primitive bodies such as asteroids and the Martian moons Phobos and Deimos), as well as for pre-selection of rock and soil samples for potential cache and return missions.

  7. Development of customised environmental chambers for time-resolved in situ diffraction studies

    NASA Astrophysics Data System (ADS)

    Styles, M. J.; Riley, D. P.

    2010-11-01

    In an effort to mitigate the expense and broaden the applicability of customised environment chambers, researchers at the University of Melbourne and the Australian Nuclear Science and Technology Organisation (ANSTO) have designed and are currently commissioning a modular reaction chamber, capable of separating the necessities of diffraction methodologies from those of the desired sample environment. The In Situ Reaction Chamber (ISRC) abstracts many of the details intrinsic to the diffractometer, allowing users to design inexpensive environmental inserts that may be readily customised to their individual needs. The first insert to be developed for use with the ISRC is a high temperature furnace capable of providing an oxidising sample environment up to 1600°C.

  8. Time-resolved in-situ measurement of mitochondrial malfunction by energy transfer spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Gschwend, Michael H.; Strauss, Wolfgang S. L.; Sailer, Reinhard; Schoch, Lars; Schuh, Alexander; Stock, Karl; Steiner, Rudolf W.; Zipfl, Peter

    1999-07-01

    To establish optical in situ detection of mitochondrial malfunction, non-radiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. An experimental setup was developed, where these signals are detected simultaneously using a time-gated technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the apparatus are described, and preliminary result of cultivated endothelial cells are reported. Results are compared with those obtained from a previously established microscopic system and discussed in view of potential applications.

  9. Time-resolved in situ measurement of mitochondrial malfunction by energy transfer spectroscopy

    NASA Astrophysics Data System (ADS)

    Schneckenburger, Herbert; Sailer, Reinhard; Strauss, Wolfgang S.; Lyttek, Marco; Stock, Karl; Zipfl, Peter

    2000-10-01

    To establish optical in situ detection of mitochondrial malfunction, nonradiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. A screening system was developed in which these signals are detected simultaneously using a time-gated (nanosecond) technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the apparatus are described, and results obtained from cultivated endothelial cells are reported. The ratio of fluorescence intensities excited in the near ultraviolet and blue-green spectral ranges increased by a factor 1.5 or 1.35 after inhibition of the mitochondrial respiratory chain by rotenone at cytotoxic or noncytotoxic concentrations, respectively. Concomitantly the amount of mitochondrial NADH increased. Excellent linearity between the number of cells incubated with R123 and fluorescence intensity was found in suspension.

  10. Time-resolved in situ measurement of mitochondrial malfunction by energy transfer spectroscopy.

    PubMed

    Schneckenburger, H; Gschwend, M H; Sailer, R; Strauss, W S; Lyttek, M; Stock, K; Zipfl, P

    2000-10-01

    To establish optical in situ detection of mitochondrial malfunction, nonradiative energy transfer from the coenzyme NADH to the mitochondrial marker rhodamine 123 (R123) was examined. Dual excitation of R123 via energy transfer from excited NADH molecules as well as by direct absorption of light results in two fluorescence signals whose ratio is a measure of mitochondrial NADH. A screening system was developed in which these signals are detected simultaneously using a time-gated (nanosecond) technique for energy transfer measurements and a frequency selective technique for direct excitation and fluorescence monitoring of R123. Optical and electronic components of the apparatus are described, and results obtained from cultivated endothelial cells are reported. The ratio of fluorescence intensities excited in the near ultraviolet and blue-green spectral ranges increased by a factor 1.5 or 1.35 after inhibition of the mitochondrial respiratory chain by rotenone at cytotoxic or noncytotoxic concentrations, respectively. Concomitantly the amount of mitochondrial NADH increased. Excellent linearity between the number of cells incubated with R123 and fluorescence intensity was found in suspension.

  11. Time-resolved Neutron-gamma-ray Data Acquisition for in Situ Subsurface Planetary Geochemistry

    NASA Technical Reports Server (NTRS)

    Bodnarik, Julie G.; Burger, Dan Michael; Burger, A.; Evans, L. G.; Parsons, A. M.; Schweitzer, J. S.; Starr R. D.; Stassun, K. G.

    2013-01-01

    The current gamma-ray/neutron instrumentation development effort at NASA Goddard Space Flight Center aims to extend the use of active pulsed neutron interrogation techniques to probe the subsurface elemental composition of planetary bodies in situ. Previous NASA planetary science missions, that used neutron and/or gamma-ray spectroscopy instruments, have relied on neutrons produced from galactic cosmic rays. One of the distinguishing features of this effort is the inclusion of a high intensity 14.1 MeV pulsed neutron generator synchronized with a custom data acquisition system to time each event relative to the pulse. With usually only one opportunity to collect data, it is difficult to set a priori time-gating windows to obtain the best possible results. Acquiring time-tagged, event-by-event data from nuclear induced reactions provides raw data sets containing channel/energy, and event time for each gamma ray or neutron detected. The resulting data set can be plotted as a function of time or energy using optimized analysis windows after the data are acquired. Time windows can now be chosen to produce energy spectra that yield the most statistically significant and accurate elemental composition results that can be derived from the complete data set. The advantages of post-processing gamma-ray time-tagged event-by-event data in experimental tests using our prototype instrument will be demonstrated.

  12. Time-Resolved Data Acquisition for In Situ Subsurface Planetary Geochemistry

    NASA Technical Reports Server (NTRS)

    Bodnarik, Julia Gates; Burger, Dan M.; Burger, Arnold; Evans, Larry G.; Parsons, Ann M.; Starr, Richard D.; Stassun, Keivan G.

    2012-01-01

    The current gamma-ray/neutron instrumentation development effort at NASA Goddard Space Flight Center aims to extend the use of active pulsed neutron interrogation techniques to probe the subsurface geochemistry of planetary bodies in situ. All previous NASA planetary science missions, that used neutron and/or gamma-ray spectroscopy instruments, have relied on a constant neutron source produced from galactic cosmic rays. One of the distinguishing features of this effort is the inclusion of a high intensity 14.1 MeV pulsed neutron generator synchronized with a custom data acquisition system to time each event relative to the pulse. With usually only one opportunity to collect data, it is difficult to set a priori time-gating windows to obtain the best possible results. Acquiring time-tagged, event-by-event data from nuclear induced reactions provides raw data sets containing channel/energy, and event time for each gamma ray or neutron detected. The resulting data set can be plotted as a function of time or energy using optimized analysis windows after the data are acquired. Time windows can now be chosen to produce energy spectra that yield the most statistically significant and accurate elemental composition results that can be derived from the complete data set. The advantages of post-processing gamma-ray time-tagged event-by-event data in experimental tests using our prototype instrument will be demonstrated.

  13. In situ and time resolved nucleation and growth of silica nanoparticles forming under simulated geothermal conditions

    NASA Astrophysics Data System (ADS)

    Tobler, Dominique J.; Benning, Liane G.

    2013-08-01

    Detailed knowledge of the reaction kinetics of silica nanoparticle formation in cooling supersaturated waters is fundamental to the understanding of many natural processes including biosilicifcation, sinter formation, and silica diagenesis. Here, we quantified the formation of silica nanoparticles from solution as it would occur in geothermal waters. We used an in situ and real-time approach with silica polymerisation being induced by fast cooling of a 230 °C hot and supersaturated silica solution. Experiments were carried out using a novel flow-through geothermal simulator system that was designed to work on-line with either a synchrotron-based small angle X-ray scattering (SAXS) or a conventional dynamic light scattering (DLS) detector system. Our results show that the rate of silica nanoparticle formation is proportional to the silica concentration (640 vs. 960 ppm SiO2), and the first detected particles form spheres of approximately 3 nm in diameter. These initial nanoparticles grow and reach a final particle diameter of approximately 7 nm. Interestingly, neither variations in ionic strength (0.02 vs. 0.06) nor temperature (reactions at 30 to 60 °C, mimicking Earth surface values) seem to affect the formation kinetics or the final size of the silica nanoparticles formed. Comparing these results with our previous data from experiments where silica polymerisation and nanoparticle formation was induced by a drop in pH from 12 to near neutral (pH-induced, Tobler et al., 2009) showed that (a) the mechanisms and kinetics of silica nanoparticle nucleation and growth were unaffected by the means to induce silica polymerisation (T drop or pH drop), both following first order reactions kinetics coupled with a surface controlled reaction mechanism. However, the rates of the formation of silica nanoparticles were substantially (around 50%) slower when polymerisation was induced by fast cooling as opposed to pH change. This was evidenced by the occurrence of an induction

  14. In-SITU, Time-resolved Raman Spectro-micro-topography of an Operating Lithium Ion Battery

    NASA Technical Reports Server (NTRS)

    Luo, Yu; Cai, Wen-Bin; Xing, Xue-Kun; Scherson, Daniel A.

    2003-01-01

    A Raman microscope has been coupled to a computer-controlled, two-dimensional linear translator attached to a custom-designed, sealed optical chamber to allow in situ acquisition of space-, and time-resolved spectra of an operating thin graphite/LiCoO2 Li-ion battery. This unique arrangement made it possible to collect continuously series of Raman spectra from a sharply defined edge of the battery exposing the anode (A), separator (S), and cathode (C), during charge and discharge, while the device was moved back and forth under the fixed focused laser beam along an axis normal to the layered A/S/C plane. Clear spectral evidence was obtained for changes in the amount of Li(+) within particles of graphite in the anode, and, to a lesser extent, of LiCoO2 in the cathode, during battery discharge both as a function of position and time. Analysis of time-resolved Raman spectro-micro-topography (SMT) measurements of the type described in this work are expected to open new prospects for assessing the validity of theoretical models aimed at simulating the flow of Li(+) within Li-ion batteries under operating conditions.

  15. Sol-to-Gel Transition in Fast Evaporating Systems Observed by in Situ Time-Resolved Infrared Spectroscopy.

    PubMed

    Innocenzi, Plinio; Malfatti, Luca; Carboni, Davide; Takahashi, Masahide

    2015-06-22

    The in situ observation of a sol-to-gel transition in fast evaporating systems is a challenging task and the lack of a suitable experimental design, which includes the chemistry and the analytical method, has limited the observations. We synthesise an acidic sol, employing only tetraethylorthosilicate, SiCl4 as catalyst and deuterated water; the absence of water added to the sol allows us to follow the absorption from the external environment and the evaporation of deuterated water. The time-resolved data, obtained by attenuated total reflection infrared spectroscopy on an evaporating droplet, enables us to identify four different stages during evaporation. They are linked to specific hydrolysis and condensation rates that affect the uptake of water from external environment. The second stage is characterized by a decrease in hydroxyl content, a fast rise of condensation rate and an almost stationary absorption of water. This stage has been associated with the sol-to-gel transition.

  16. Fixed target matrix for femtosecond time-resolved and in situ serial micro-crystallography

    SciTech Connect

    Mueller, C.; Marx, A.; Epp, S. W.; Zhong, Y.; Kuo, A.; Balo, A. R.; Soman, J.; Schotte, F.; Lemke, H. T.; Owen, R. L.; Pai, E. F.; Pearson, A. R.; Olson, J. S.; Anfinrud, P. A.; Ernst, O. P.; Miller, R. J. Dwayne

    2015-08-18

    We present a crystallography chip enabling in situ room temperature crystallography at microfocus synchrotron beamlines and X-ray free-electron laser (X-FEL) sources. Compared to other in situ approaches, we observe extremely low background and high diffraction data quality. The chip design is robust and allows fast and efficient loading of thousands of small crystals. The ability to load a large number of protein crystals, at room temperature and with high efficiency, into prescribed positions enables high throughput automated serial crystallography with microfocus synchrotron beamlines. In addition, we demonstrate the application of this chip for femtosecond time-resolved serial crystallography at the Linac Coherent Light Source (LCLS, Menlo Park, California, USA). As a result, the chip concept enables multiple images to be acquired from each crystal, allowing differential detection of changes in diffraction intensities in order to obtain high signal-to-noise and fully exploit the time resolution capabilities of XFELs.

  17. In situ and time-resolved infrared detection of the reactivity induced by electrons in polymer films

    NASA Astrophysics Data System (ADS)

    Bouhier, M.; Vigneron, G.; Ngono-Ravache, Y.; Shirdhonkar, M.; Renault, J. P.; Le Caër, S.

    2017-03-01

    The real time and in situ analysis of chemical reactions such as polymerization reactions, polymer degradation, and oxidation of polymers is of utmost importance. Surprisingly, only few experimental tools allowing this are available. To bridge this gap, we have developed a new experimental setup coupling a 60 keV electron gun with an infrared spectrometer operating in the mid-IR region (800-4000 cm-1) and associated with the rapid scan mode. The measurements are performed using the infrared reflection absorption spectroscopy approach. We worked here with 0.5-25 ms pulses for which the dose per pulse ranges from 4 to 200 kGy. Combining pulse electrons with rapid scan analysis enables performing experiments with a time resolution of 80 ms (and above). Therefore, this new platform can, for instance, give direct insights into reaction mechanisms at stake during the degradation of polymers. First results on a bisphenol A polycarbonate irradiated under vacuum enabling the validation of this new setup and also the recording of time-resolved spectra are presented. Reaction mechanisms are then proposed.

  18. Structural evolution during evaporation of a 3-glycidoxypropyltrimethoxysilane film studied in situ by time resolved infrared spectroscopy.

    PubMed

    Innocenzi, Plinio; Figus, Cristiana; Takahashi, Masahide; Piccinini, Massimo; Malfatti, Luca

    2011-09-29

    Time resolved infrared spectroscopy has been applied to study in situ the evaporation process of a 3-glycidoxypropyltrimethoxysilane hybrid sol by casting a droplet on a ZnSe substrate; the analysis has been performed in the middle-infrared range and in the near-infrared range. The experiment has allowed following the structural changes induced by water evaporation and the formation of ordered structures within the cast film; the CH(2) scissoring bands have been used as a fingerprint for the disorder to order transition of the hybrid. The experiment has been done using both a fresh sol and an aged sol which produce respectively an amorphous material and a crystalline hybrid material. The analysis has shown that the epoxy groups do not react during the evaporation while the silica structure shows only a slight condensation and an increase in open cage-like species. At the end of evaporation the hybrid has a "soft-like" state which allows structural rearrangements to self-order.

  19. In situ and time resolved quantification of the kinetics and mechanisms of CaCO3 nucleation and growth

    NASA Astrophysics Data System (ADS)

    Rodriguez-Blanco, J. D.; Shaw, S.; Benning, L. G.

    2009-04-01

    The crystal chemistry, occurrence and relevance of amorphous CaCO3 and its crystalline polymorphs in inorganic and organic environments have been studied for decades and are nowadays relatively well known [1]. However, due to the fast kinetics of the reactions that take place in solution [2], there is virtually no quantitative data available about the kinetics and mechanisms of the nucleation, growth and transformation of these phases in aqueous solutions. In this study we demonstrate that in situ and time resolved synchrotron-based Energy Dispersive X-Ray Diffraction combined with the corresponding solution chemistry and imaging can be successfully applied to evaluate quantitatively kinetic rates and mechanisms of the crystallization and transformation of CaCO3 phases in solution. The precipitation of amorphous calcium carbonate (ACC) and its crystallization to vaterite and calcite was followed in closed thermostated reactors at temperatures between 7.5 and 40˚ C with the time-resolved data collected every 15 secs. The growth/decay of vaterite and calcite diffraction peaks was fitted using a Johnson-Mehl-Avrami-Kolmogorov model [3] to evaluate the kinetics and mechanisms of crystallization [4]. The results show that vaterite grows fast via a 3D growth process following a first order reaction and the subsequent transformation to calcite takes place slower, being controlled by the dissolution of the vaterite precursor. From the temperature dependent data apparent activation energies of nucleation and crystallization for both crystalline CaCO3 polymorphs have been calculated. In addition, wet chemical data and imaging also confirm these findings. Finally, this approach was applied also to other carbonate systems (i.e., dolomite , Ca/Mg carbonates). [1] Reeder R. (1983) Rev. Mineral, 11. [2] Ogino et al. (1987) Geochim. Cosmochim. Acta 51, 2757-2767. [3] Johnson, P.F. and Mehl, R.F. (1939) Reaction kinetics in processes of nucleation and growth. American Institute

  20. Fragmentation process during Ho:YAG laser lithotripsy revealed by time-resolved imaging

    NASA Astrophysics Data System (ADS)

    Beghuin, Didier; Delacretaz, Guy P.; Schmidlin, Franz R.; Rink, Klaus

    1998-01-01

    The stone fragmentation process induced during Ho:YAG laser lithotripsy was observed by time-resolved flash video imaging. Possible acoustic transient occurrence was simultaneously monitored with a PVDF needle hydrophone. We used artificial and cystine kidney stones. We observed that, although the fragmentation process is accompanied with the formation of a cavitation bubble, cavitation has a minimal incidence on stone fragmentation. Fragment ejection is mainly due to a direct laser stone heating and vaporization of stone organic constituents and interstitial water. The minimal effect of the cavitation bubble for fragmentation is confirmed by acoustic transients measurements, which reveal weak pressure transients. This is in contrast with the fragmentation mechanisms induced by laser of shorter pulse duration.

  1. Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects.

    PubMed

    Pham, Van Thi Bich; Hoang, Hao Minh; Grampp, Günter; Kattnig, Daniel Rudolf

    2017-03-06

    External magnetic fields can impact recombination yields of photo-induced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor-acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in micro-heterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore) / N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using Time-Correlated Single Photon Counting (TCSPC). In micro-heterogeneous environments, the MFE of the exciplex emission occurs on a faster timescale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in micro-heterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar micro-domains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in micro-heterogeneous binary solvents.

  2. Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects

    PubMed Central

    2017-01-01

    External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor–acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents. PMID:28263599

  3. Time-Resolved Soft X-ray Diffraction Reveals Transient Structural Distortions of Ternary Liquid Crystals

    PubMed Central

    Quevedo, Wilson; Peth, Christian; Busse, Gerhard; Scholz, Mirko; Mann, Klaus; Techert, Simone

    2009-01-01

    Home-based soft X-ray time-resolved scattering experiments with nanosecond time resolution (10 ns) and nanometer spatial resolution were carried out at a table top soft X-ray plasma source (2.2–5.2 nm). The investigated system was the lyotropic liquid crystal C16E7/paraffin/glycerol/formamide/IR 5. Usually, major changes in physical, chemical, and/or optical properties of the sample occur as a result of structural changes and shrinking morphology. Here, these effects occur as a consequence of the energy absorption in the sample upon optical laser excitation in the IR regime. The liquid crystal shows changes in the structural response within few hundred nanoseconds showing a time decay of 182 ns. A decrease of the Bragg peak diffracted intensity of 30% and a coherent macroscopic movement of the Bragg reflection are found as a response to the optical pump. The Bragg reflection movement is established to be isotropic and diffusion controlled (1 μs). Structural processes are analyzed in the Patterson analysis framework of the time-varying diffraction peaks revealing that the inter-lamellar distance increases by 2.7 Å resulting in an elongation of the coherently expanding lamella crystallite. The present studies emphasize the possibility of applying TR-SXRD techniques for studying the mechanical dynamics of nanosystems. PMID:20087463

  4. Wall current probe: A non-invasive in situ plasma diagnostic for space and time resolved current density distribution measurement

    SciTech Connect

    Baude, R.; Gaboriau, F.; Hagelaar, G. J. M.

    2013-08-15

    In the context of low temperature plasma research, we propose a wall current probe to determine the local charged particle fluxes flowing to the chamber walls. This non-intrusive planar probe consists of an array of electrode elements which can be individually biased and for which the current can be measured separately. We detail the probe properties and present the ability of the diagnostic to be used as a space and time resolved measurement of the ion and electron current density at the chamber walls. This diagnostic will be relevant to study the electron transport in magnetized low-pressure plasmas.

  5. Wall current probe: a non-invasive in situ plasma diagnostic for space and time resolved current density distribution measurement.

    PubMed

    Baude, R; Gaboriau, F; Hagelaar, G J M

    2013-08-01

    In the context of low temperature plasma research, we propose a wall current probe to determine the local charged particle fluxes flowing to the chamber walls. This non-intrusive planar probe consists of an array of electrode elements which can be individually biased and for which the current can be measured separately. We detail the probe properties and present the ability of the diagnostic to be used as a space and time resolved measurement of the ion and electron current density at the chamber walls. This diagnostic will be relevant to study the electron transport in magnetized low-pressure plasmas.

  6. Laser lithotripsy with the Ho:YAG laser: fragmentation process revealed by time-resolved imaging

    NASA Astrophysics Data System (ADS)

    Schmidlin, Franz R.; Beghuin, Didier; Delacretaz, Guy P.; Venzi, Giordano; Jichlinski, Patrice; Rink, Klaus; Leisinger, Hans-Juerg; Graber, Peter

    1998-07-01

    Improvements of endoscopic techniques have renewed the interest of urologists in laser lithotripsy in recent years. Laser energy can be easily transmitted through flexible fibers thereby enabling different surgical procedures such as cutting, coagulating and lithotripsy. The Ho:YAG laser offers multiple medical applications in Urology, among them stone fragmentation. However, the present knowledge of its fragmentation mechanism is incomplete. The objective was therefore to analyze the fragmentation process and to discuss the clinical implications related to the underlying fragmentation mechanism. The stone fragmentation process during Ho:YAG laser lithotripsy was observed by time resolved flash video imaging. Possible acoustic transient occurrence was simultaneously monitored with a PVDF-needle hydrophone. Fragmentation was performed on artificial and cystine kidney stones in water. We observed that though the fragmentation process is accompanied with the formation of a cavitation bubble, cavitation has only a minimal effect on stone fragmentation. Fragment ejection is mainly due to direct laser stone heating leading to vaporization of organic stone constituents and interstitial water. The minimal effect of the cavitation bubble is confirmed by acoustic transients measurements, which reveal weak pressure transients. Stone fragmentation with the Holmium laser is the result of vaporization of interstitial (stone) water and organic stone constituents. It is not due to the acoustic effects of a cavitation bubble or plasma formation. The fragmentation process is strongly related with heat production thereby harboring the risk of undesired thermal damage. Therefore, a solid comprehension of the fragmentation process is needed when using the different clinically available laser types of lithotripsy.

  7. In Vivo Time-Resolved Microtomography Reveals the Mechanics of the Blowfly Flight Motor

    PubMed Central

    Mokso, Rajmund; Wicklein, Martina; Müller, Tonya; Doube, Michael; Stampanoni, Marco; Krapp, Holger G.; Taylor, Graham K.

    2014-01-01

    Dipteran flies are amongst the smallest and most agile of flying animals. Their wings are driven indirectly by large power muscles, which cause cyclical deformations of the thorax that are amplified through the intricate wing hinge. Asymmetric flight manoeuvres are controlled by 13 pairs of steering muscles acting directly on the wing articulations. Collectively the steering muscles account for <3% of total flight muscle mass, raising the question of how they can modulate the vastly greater output of the power muscles during manoeuvres. Here we present the results of a synchrotron-based study performing micrometre-resolution, time-resolved microtomography on the 145 Hz wingbeat of blowflies. These data represent the first four-dimensional visualizations of an organism's internal movements on sub-millisecond and micrometre scales. This technique allows us to visualize and measure the three-dimensional movements of five of the largest steering muscles, and to place these in the context of the deforming thoracic mechanism that the muscles actuate. Our visualizations show that the steering muscles operate through a diverse range of nonlinear mechanisms, revealing several unexpected features that could not have been identified using any other technique. The tendons of some steering muscles buckle on every wingbeat to accommodate high amplitude movements of the wing hinge. Other steering muscles absorb kinetic energy from an oscillating control linkage, which rotates at low wingbeat amplitude but translates at high wingbeat amplitude. Kinetic energy is distributed differently in these two modes of oscillation, which may play a role in asymmetric power management during flight control. Structural flexibility is known to be important to the aerodynamic efficiency of insect wings, and to the function of their indirect power muscles. We show that it is integral also to the operation of the steering muscles, and so to the functional flexibility of the insect flight motor

  8. Ordering of PCDTBT revealed by time-resolved electron paramagnetic resonance spectroscopy of its triplet excitons.

    PubMed

    Biskup, Till; Sommer, Michael; Rein, Stephan; Meyer, Deborah L; Kohlstädt, Markus; Würfel, Uli; Weber, Stefan

    2015-06-22

    Time-resolved electron paramagnetic resonance (TREPR) spectroscopy is shown to be a powerful tool to characterize triplet excitons of conjugated polymers. The resulting spectra are highly sensitive to the orientation of the molecule. In thin films cast on PET film, the molecules' orientation with respect to the surface plane can be determined, providing access to sample morphology on a microscopic scale. Surprisingly, the conjugated polymer investigated here, a promising material for organic photovoltaics, exhibits ordering even in bulk samples. Orientation effects may significantly influence the efficiency of solar cells, thus rendering proper control of sample morphology highly important.

  9. Intercalation chemistry in a LDH system: anion exchange process and staging phenomenon investigated by means of time-resolved, in situ X-ray diffraction.

    PubMed

    Taviot-Guého, Christine; Feng, Yongjun; Faour, Azzam; Leroux, Fabrice

    2010-07-14

    Using time-resolved, in situ energy-dispersive X-ray diffraction (EDXRD), the formation of interstratified LDH structures, with alternate interlayer spaces occupied by different anions, have been demonstrated during anion exchange reactions. Novel hybrid LDH nanostructures can thus be prepared, combining the physicochemical properties of two intercalated anions plus those of the LDH host. A general trend is that inorganic-inorganic anion exchange reactions occur in a one-step process while inorganic-organic exchanges may proceed via a second-stage intermediate, suggesting that staging occurs partly as a result of organic-inorganic separation. Yet, other influencing parameters must be considered such as LDH host composition, LDH affinity for different anions and LDH particle size as well as extrinsic parameters like the reaction temperature. Hence, a correlation between the occurrence of staging phenomenon and the difficulty of the exchange of the initial anion is observed, suggesting that staging is needed to overcome the energy barrier in the case of the exchange by organic anions. Notwithstanding the LiAl(2) system, staging has mainly been observed with Zn(2)Cr LDH host so far, a peculiar LDH composition with a unique Zn/Cr ratio of two and a local order of the cations within the hydroxide layers. The formation of a higher order-staged intermediate than stage two, observed during the exchange reaction of CO(3)(2-) or SO(4)(2-) anions with Zn(2)Cr-tartrate, is in favour of a Daumas-Herold model although this model implies a bending of LDH layers. The analysis of the X-ray powder diffraction pattern of Zn(2)Cr-Cl/tartrate second-stage intermediate, isolated almost as a pure phase during the exchange of Cl(-) with tartrate anions in Zn(2)Cr LDH, indicates a disorder in the stacking sequence and a relative proportion of the two kinds of interlayers slightly different from 50/50. Besides, the microstructural analysis of the XRD pattern reveals a great reduction of the

  10. Isothermal nucleation and growth kinetics of Pd/Ag alloy phase via in-situ time-resolved high-temperature x-ray diffraction (HTXRD) analysis

    SciTech Connect

    Ayturk, Mahmut Engin; Payzant, E Andrew; Speakman, Scott A; Ma, Yi Hua

    2008-01-01

    Among several different approaches to form Pd/Ag alloys for hydrogen separation applications, ex-situ studies carried by conventional X-ray point scanning detectors might fail to reveal the key aspects of the phase transformation between Pd and Ag metals. In this respect, in-situ time-resolved high temperature X-ray diffraction (HTXRD) was employed to study the Pd/Ag alloy phase nucleation and growth kinetics. By the use of linear position sensitive detectors, advanced optics and profile fitting with the use of JADE-6.5 software, isothermal phase evolution of the Pd/Ag alloy at 500 C, 550 C and 600 C under hydrogen atmosphere were quantified to elucidate the mechanistic details of the Pd/Ag alloy phase nucleation and growth pattern. Analysis of the HTXRD data by the Avrami model indicated that the nucleation of the Pd/Ag alloy phase was instantaneous where the growth mechanism was through diffusion-controlled one-dimensional thickening of the Pd/Ag alloy layer. The value of the Avrami exponent, n, was found to increase with temperature with the values of 0.34, 0.39 and 0.67 at 500oC, 550oC and 600oC, respectively. In addition, parabolic rate law analysis suggested that the nucleation of the Pd/Ag alloy phase was through a heterogeneous nucleation mode, in which the nucleation sites were defined as the non-equilibrium defects. The cross-sectional SEI micrographs indicated that the Pd/Ag alloy phase growth was strongly dependent upon the deposition morphology of the as-synthesized Pd and Ag layers formed by the electroless plating. Based on the Avrami model and the parabolic rate law, the estimated activation energies for the phase transformation were 236.5 and 185.6 kJ/mol and in excellent agreement with the literature values (183-239.5 kJ/mol).

  11. Structural changes and thermal stability of charged LiNixMnyCozO2 cathode materials studied by combined in situ time-resolved XRD and mass spectroscopy

    DOE PAGES

    Bak, Seong -Min; Hu, Enyuan; Zhou, Yongning; ...

    2014-11-24

    Thermal stability of charged LiNixMnyCozO2 (NMC, with x + y + z = 1, x:y:z = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined in situ time- resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and the larger amount of oxygenmore » release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3a octahedral sites of a layered structure (R3¯m) but Co ions prefer to migrate to the 8a tetrahedral sites of a spinel structure (Fd3¯m) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. As a result, this systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density.« less

  12. Cooperative macromolecular device revealed by meta-analysis of static and time-resolved structures

    SciTech Connect

    Ren, Zhong; Šrajer, Vukica; Knapp, James E.; Royer, Jr., William E.

    2013-04-08

    Here we present a meta-analysis of a large collection of static structures of a protein in the Protein Data Bank in order to extract the progression of structural events during protein function. We apply this strategy to the homodimeric hemoglobin HbI from Scapharca inaequivalvis. We derive a simple dynamic model describing how binding of the first ligand in one of the two chemically identical subunits facilitates a second binding event in the other partner subunit. The results of our ultrafast time-resolved crystallographic studies support this model. We demonstrate that HbI functions like a homodimeric mechanical device, such as pliers or scissors. Ligand-induced motion originating in one subunit is transmitted to the other via conserved pivot points, where the E and F' helices from two partner subunits are 'bolted' together to form a stable dimer interface permitting slight relative rotation but preventing sliding.

  13. Revisited: Decomposition or melting? Formation mechanism investigation of LiCoO2 via in-situ time-resolved X-ray diffraction.

    PubMed

    Wicker, Scott A; Walker, Edwin H

    2013-02-18

    We report the first in-situ time-resolved X-ray diffraction investigation in conjunction with a non-isothermal kinetic study using the model-free isoconversional kinetic method to determine the formation mechanism for the solid-state synthesis of electrochemically active LiCoO(2) from Li(2)CO(3) and Co(3)O(4). Detailed information on the phase evolution as well as thermal events during the heating process was clearly observed, explained, and supported. This investigation provides structural as well as kinetic evidence for a multistep reaction and proposes the first plausible formation mechanism for the solid-state synthesis of LiCoO(2).

  14. New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I.; Chowdhury, Mohammed; Fikremariam, Hanna

    2010-12-01

    The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO2 (Anatase) in supercritical D2O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

  15. New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction.

    PubMed

    Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I; Chowdhury, Mohammed; Fikremariam, Hanna

    2010-12-01

    The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

  16. Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolved in situ Laue diffraction

    DOE PAGES

    Wehrenberg, C. E.; Comley, A. J.; Barton, N. R.; ...

    2015-09-29

    We report direct lattice level measurements of plastic relaxation kinetics through time-resolved, in-situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27-210 GPa. For a 50 GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points (<0.6 ns) and the average shear strain relaxes to a near steady state over ~1 ns. For 80 and 125 GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure ~65 GPa.more » The relaxation rate and shear stresses are used to estimate the dislocation density and these quantities are compared to the Livermore Multiscale Strength model as well as various molecular dynamics simulations.« less

  17. In-situ characterization of femtosecond laser-induced crystallization in borosilicate glass using time-resolved surface third-harmonic generation

    SciTech Connect

    Liu, Weimin; Wang, Liang; Han, Fangyuan; Fang, Chong

    2013-11-11

    Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF{sub 2} and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free, high-sensitivity third harmonic generation (THG) signal in between the two crossing near-IR pulses. Pronounced intensity quantum beats reveal the impulsively excited low-frequency Raman mode evolution on the femtosecond to picosecond timescale. After amplified laser irradiation, danburite-crystal-like structure units form at the glass surface. This versatile TRSTHG setup paves the way to mechanistically study and design advanced thermoelectrics and photovoltaics.

  18. The CO oxidation kinetics on supported Pd model catalysts: A molecular beam/in situ time-resolved infrared reflection absorption spectroscopy study

    NASA Astrophysics Data System (ADS)

    Libuda, J.; Meusel, I.; Hoffmann, J.; Hartmann, J.; Piccolo, L.; Henry, C. R.; Freund, H.-J.

    2001-03-01

    Combining molecular beam techniques and time-resolved infrared reflection absorption spectroscopy (TR-IRAS) we have studied the kinetics of the CO oxidation reaction on an alumina-supported Pd model catalyst. The Pd particles are deposited by metal evaporation under ultrahigh vacuum (UHV) conditions onto a well-ordered alumina film, prepared on a NiAl(110) single crystal. Particle size, density and structure of the Pd deposits have been characterized in previous studies. In the low temperature region, transient and steady-state experiments have been performed over a wide range of CO and oxygen fluxes by crossing two effusive molecular beams on the sample surface. We determine the steady-state CO2 production rate as a function of the CO fraction in the impinging gas flux. Simultaneously, the occupation of CO adsorption sites under steady-state conditions is monitored by in situ IR spectroscopy. The origin of different types of CO2 transients is discussed. In particular we focus on the transient CO2 production after switching off the CO beam. For the model catalyst investigated, detailed reaction rate measurements in combination with time-resolved IRAS show that the origin of the particular transient behavior of the supported model system is not due to the presence of specific adsorption sites on small particles, as has been proposed previously. Instead, we show that the transient behavior can be semiquantitatively simulated on the basis of a simple kinetic model considering a homogeneous surface, and accounting for the inhibition of the dissociative adsorption of O2 at high CO coverage. Moreover, it is discussed how the inherent heterogeneity of the supported particle system can additionally enhance the observed effect.

  19. In-Situ Observations of Phase Transformations During Welding of 1045 Steel using Spatially Resolved and Time Resolved X-Ray Diffraction

    SciTech Connect

    Elmer, J; Palmer, T; DebRoy, T

    2005-10-28

    Synchrotron-based methods have been developed at Lawrence Livermore National Laboratory (LLNL) for the direct observation of microstructure evolution during welding. These techniques, known as spatially resolved (SRXRD) and time resolved (TRXRD) x-ray diffraction, allow in-situ experiments to be performed during welding and provide direct observations of high temperature phases that form under the intense thermal cycles that occur. This paper presents observations of microstructural evolution that occur during the welding of a medium carbon AISI 1045 steel, using SRXRD to map the phases that are present during welding, and TRXRD to dynamically observe transformations during rapid heating and cooling. SRXRD was further used to determine the influence of welding heat input on the size of the high temperature austenite region, and the time required to completely homogenize this region during welding. These data can be used to determine the kinetics of phase transformations under the steep thermal gradients of welds, as well as benchmark and verify phase transformation models.

  20. In-situ Time-Resolved Neutron Diffraction Measurements of Microstructure Variations during Friction Stir Welding in a 6061-T6 Aluminum Alloy

    SciTech Connect

    Woo, Wan Chuck; Wang, Xun-Li; Ungar, Prof Tomas; Feng, Zhili; David, Stan A; Clausen, B; Hubbard, Camden R

    2008-01-01

    The microstructure change is one of the most important research areas in the friction stir welding (FSW). However, direct observation of microstructure changes during FSW has been extremely challenging because many measurement techniques are inapplicable. Recently developed in-situ time-resolved neutron diffraction methodology, which drastically improves the temporal resolution of neutron diffraction, enables to observe the transient microstructure changes during FSW. We installed a portable FSW system in the Spectrometer for MAterials Research at Temperature and Stress (SMARTS) at Los Alamos Neutron Science Center and the FSW was made on 6.35mm-thickness 6061-T6 Al alloy plate. At the same time, the neutron beam was centered on the mid-plane of the Al plate at 8 mm from the tool center (underneath the tool shoulder) and the diffraction peak was continuously measured during welding. The peak broadening analysis has been performed using the Williamson-Hall Method. The result shows that the dislocation density of about 3.2 x 10^15 m-2 duing FSW, which is the significant increse compared to the before (4.5 x 10^14 m-2) and after (4.0 x 10^14 m-2) the FSW. The quantitatively analysis of the grain structure can provide an insight to understand the transient variation of the microstructure during FSW.

  1. Time-Resolved, In Situ DRIFTS/EDE/MS Studies on Alumina-Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions**

    PubMed Central

    Kroner, Anna B; Newton, Mark A; Tromp, Moniek; Roscioni, Otello M; Russell, Andrea E; Dent, Andrew J; Prestipino, Carmelo; Evans, John

    2014-01-01

    The effects of ceria and zirconia on the structure–function properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ-Al2O3) during CO exposure are described. Ceria and zirconia are introduced through two preparation methods: 1) ceria is deposited on γ-Al2O3 from [Ce(acac)3] and rhodium metal is subsequently added, and 2) through the controlled surface modification (CSM) technique, which involves the decomposition of [M(acac)x] (M=Ce, x=3; M=Zr, x=4) on Rh/γ-Al2O3. The structure–function correlations of ceria and/or zirconia-doped rhodium catalysts are investigated by diffuse reflectance infrared Fourier-transform spectroscopy/energy-dispersive extended X-ray absorption spectroscopy/mass spectrometry (DRIFTS/EDE/MS) under time-resolved, in situ conditions. CeOx and ZrO2 facilitate the protection of Rh particles against extensive oxidation in air and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts prepared by CSM are observed and compared with Rh/γ-Al2O3 samples, whereas supported Rh particles are easily disrupted by CO forming mononuclear Rh geminal dicarbonyl species. DRIFTS results indicate that, through the interaction of CO with ceriated Rh particles, a significantly larger amount of linear CO species form; this suggests the predominance of a metallic Rh phase. PMID:25044889

  2. Skyrmion Hall effect revealed by direct time-resolved X-ray microscopy

    NASA Astrophysics Data System (ADS)

    Litzius, Kai; Lemesh, Ivan; Krüger, Benjamin; Bassirian, Pedram; Caretta, Lucas; Richter, Kornel; Büttner, Felix; Sato, Koji; Tretiakov, Oleg A.; Förster, Johannes; Reeve, Robert M.; Weigand, Markus; Bykova, Iuliia; Stoll, Hermann; Schütz, Gisela; Beach, Geoffrey S. D.; Kläui, Mathias

    2016-12-01

    Magnetic skyrmions are promising candidates for future spintronic applications such as skyrmion racetrack memories and logic devices. They exhibit exotic and complex dynamics governed by topology and are less influenced by defects, such as edge roughness, than conventionally used domain walls. In particular, their non-zero topological charge leads to a predicted `skyrmion Hall effect', in which current-driven skyrmions acquire a transverse velocity component analogous to charged particles in the conventional Hall effect. Here, we use nanoscale pump-probe imaging to reveal the real-time dynamics of skyrmions driven by current-induced spin-orbit torques. We find that skyrmions move at a well-defined angle ΘSkH that can exceed 30° with respect to the current flow, but in contrast to conventional theoretical expectations, ΘSkH increases linearly with velocity up to at least 100 ms-1. We qualitatively explain our observation based on internal mode excitations in combination with a field-like spin-orbit torque, showing that one must go beyond the usual rigid skyrmion description to understand the dynamics.

  3. Cation Movements during Dehydration and NO2 Desorption in a Ba-Y,FAU zeolite: an in situ Time-resolved X-ray Diffraction Study

    SciTech Connect

    Wang, Xianqin; Hanson, Jonathan C.; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-02-28

    Synchrotron-based in situ time-resolved X-ray diffraction and Rietveld analysis were used to probe the interactions between BaY, FAU zeolite frameworks and H2O or NO2 molecules. These results provided information about the migration of the Ba2+ cations in the zeolite framework during dehydration and during NO2 adsorption/desorption processes in a water free zeolite. In the hydrated structure water molecules form four double rings of hexagonal ice-like clusters [(H2O)6] in the 12-ring openings of the super-cage. These water rings interacted with the cations and the zeolite framework through four cation/water clusters centered over the four 6-membered rings of the super-cage (site II). Interpenetrating tetrahedral water clusters [(H2O)4] and tetrahedral Ba+2 cation clusters were observed in the sodalite cage. Consistent with the reported FT-IR results, three different ionic NOx species (NO+, NO+-NO2, and NO3-) were observed following NO2 adsorption by the dehydrated Ba-Y,FAU zeolite. The structure of the water and the NOx species were correlated with the interactions between the adsorbates, the cations, and the framework. The population of Ba2+ ions at different cationic positions strongly depended on the amount of bound water or NOx species. Both dehydration and NO2 adsorption/desorption resulted in facile migration of Ba2+ ions among the different cationic positions. Data obtained in this work have provided direct evidence for the Ba2+ cation migration to accommodate the binding of gas molecules. This important feature may play a pivotal role in the strong binding of NO2 to Ba-Y,FAU zeolite, a prerequisite for high catalytic activity in lean NOx reduction catalysis.

  4. Charge separation in subcells of triple-junction solar cells revealed by time-resolved photoluminescence spectroscopy.

    PubMed

    Tex, David M; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-11-30

    We measure the excitation-wavelength and power dependence of time-resolved photoluminescence (PL) from the top InGaP subcell in a InGaP/GaAs/Ge triple-junction solar cell. The wavelength-dependent data reveals that the PL decays are governed by charge separation. A fast single-exponential PL decay is observed at low excitation power densities, which is the charge separation under short-circuit condition. Under strong excitation a bi-exponential PL decay is observed. Its slow component appears at early times, followed by a faster component at late times. The slow decay is the carrier recombination of the subcell. The following fast component is the charge separation process under reduced built-in potential near the operating point. The subcells electrical conversion efficiency close to the operating point is evaluated using this decay time constant.

  5. Bright and dark triplet states of the negatively charged magnetoexcitons revealed in photoluminescence and time-resolved measurements

    NASA Astrophysics Data System (ADS)

    Munteanu, F. M.; Rickel, D. G.; Perry, C. H.; Kim, Yongmin; Simmons, J. A.; Reno, J. L.

    2000-12-01

    Continuous and time-resolved magnetophotoluminescence measurements of three GaAs/AlxGa1-xAs heterostructures have been made in high magnetic fields. The spectra revealed the presence of a singlet and two triplet states (the so-called ``bright'' and ``dark'' states) of the negatively charged magnetoexciton, in addition to the neutral exciton. For an asymmetrically doped single quantum well sample, the singlet and the dark triplet states converge (and possibly cross) at a field of about 40 T. The two single heterojunction samples on the other hand show no such convergence, and the singlet remains the fundamental state at least in fields to 60 T. The lifetimes of the charged magnetoexcitons increased linearly with field, whereas the neutral exciton was essentially field independent. The results clarify earlier experimental studies, and provide a confirmation of a recent theory of the behavior of charged magnetoexcitons in magnetic fields by Wojs et al. [Phys Rev. B 62, 4630 (2000)].

  6. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    PubMed Central

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-01-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases. PMID:27357449

  7. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample.

    PubMed

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-30

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  8. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    NASA Astrophysics Data System (ADS)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  9. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-02-01

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

  10. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    PubMed Central

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-01-01

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems. PMID:26915398

  11. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    DOE PAGES

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; ...

    2016-02-26

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase seperated regions. The ability to simultanousely track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of- the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiatedmore » at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, which is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. Lastly, the direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.« less

  12. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy.

    PubMed

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J; Jung, Il Woong; Walko, Donald A; Dufresne, Eric M; Jeong, Jaewoo; Samant, Mahesh G; Parkin, Stuart S P; Freeland, John W; Evans, Paul G; Wen, Haidan

    2016-02-26

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

  13. Time-resolved diffraction and interference: Young's interference with photons of different energy as revealed by time resolution.

    PubMed

    Garcia, N; Saveliev, I G; Sharonov, M

    2002-05-15

    We present time-resolved diffraction and two-slit interference experiments using a streak camera as a detector for femtosecond pulses of photons. These experiments show how the diffraction pattern is built by adding frames of a few photons to each frame. It is estimated that after 300 photons the diffraction pattern emerges. With time resolution we can check the speed of light and put an upper limit of 2 ps at our resolution to the time for wave function collapse in the quantum measurement process. We then produce interference experiments with photons of different energies impinging on the slits, i.e. we know which photon impinges on each slit. We show that for poor time resolution, no interference is observed, but for high time resolution, we have interference that is revealed as beats of 100 GHz frequency. The condition for interference is that the two pulses should overlap spatially at the detector, even if the pulses have different energies but are generated from the same pulse of the laser. The interference seems to be in agreement with classical theory at first sight. However, closer study and analysis of the data show deviations in the visibility of the interference fringes and of their phase. These experiments are discussed in connection with quantum mechanics and it may be concluded that the time resolution provides new data for understanding the longstanding and continuing arguments on wave-particle duality initiated by Newton, Young, Fresnel, Planck and others. A thought experiment is presented in the appendix to try to distinguish the photons at the detector by making it sensitive to colour.

  14. Direct Observation of Phase Transformations in Austenitic Stainless Steel Welds Using In-situ Spatially Resolved and Time-resolved X-ray Diffraction

    SciTech Connect

    Elmer, J.; Wong, J.; Ressler, T.

    1999-09-23

    Spatially resolved x-ray diffraction (SRXRD) and time resolved x-ray diffraction (TRXRD) were used to investigate real time solid state phase transformations and solidification in AISI type 304 stainless steel gas tungsten arc (GTA) welds. These experiments were conducted at Stanford Synchrotron Radiation Laboratory (SSRL) using a high flux beam line. Spatially resolved observations of {gamma} {leftrightarrow} {delta} solid state phase transformations were performed in the heat affected zone (HAZ) of moving welds and time-resolved observations of the solidification sequence were performed in the fusion zone (FZ) of stationary welds after the arc had been terminated. Results of the moving weld experiments showed that the kinetics of the {gamma}{yields}{delta} phase transformation on heating in the HAZ were sufficiently rapid to transform a narrow region surrounding the liquid weld pool to the {delta} ferrite phase. Results of the stationary weld experiments showed, for the first time, that solidification can occur directly to the {delta} ferrite phase, which persisted as a single phase for 0.5s. Upon solidification to {delta}, the {delta} {yields} {gamma} phase transformation followed and completed in 0.2s as the weld cooled further to room temperature.

  15. Site-specific structural dynamics of α-Synuclein revealed by time-resolved fluorescence spectroscopy: a review.

    PubMed

    Sahay, Shruti; Krishnamoorthy, G; Maji, Samir K

    2016-10-11

    Aggregation of α-Synuclein (α-Syn) into amyloid fibrils is known to be associated with the pathogenesis of Parkinson's disease (PD). Several missense mutations of the α-Syn gene have been associated with rare, early onset familial forms of PD. Despite several studies done so far, the local/residue-level structure and dynamics of α-Syn in its soluble and aggregated fibril form and how these are affected by the familial PD associated mutations are still not clearly understood. Here, we review studies performed by our group as well as other research groups, where time-resolved fluorescence spectroscopy has been used to understand the site-specific structure and dynamics of α-Syn under physiological conditions as well as under conditions that alter the aggregation properties of the protein such as low pH, high temperature, presence of membrane mimics and familial PD associated mutations. These studies have provided important insights into the critical structural properties of α-Syn that may govern its aggregation. The review also highlights time-resolved fluorescence as a promising tool to study the critical conformational transitions associated with early oligomerization of α-Syn, which are otherwise not accessible using other commonly used techniques such as thioflavin T (ThT) binding assay.

  16. Functional Stability of the Human Kappa Opioid Receptor Reconstituted in Nanodiscs Revealed by a Time-Resolved Scintillation Proximity Assay

    PubMed Central

    Hansen, Randi Westh; Wang, Xiaole; Golab, Agnieszka; Bornert, Olivier; Oswald, Christine; Wagner, Renaud; Martinez, Karen Laurence

    2016-01-01

    Long-term functional stability of isolated membrane proteins is crucial for many in vitro applications used to elucidate molecular mechanisms, and used for drug screening platforms in modern pharmaceutical industry. Compared to soluble proteins, the understanding at the molecular level of membrane proteins remains a challenge. This is partly due to the difficulty to isolate and simultaneously maintain their structural and functional stability, because of their hydrophobic nature. Here we show, how scintillation proximity assay can be used to analyze time-resolved high-affinity ligand binding to membrane proteins solubilized in various environments. The assay was used to establish conditions that preserved the biological function of isolated human kappa opioid receptor. In detergent solution the receptor lost high-affinity ligand binding to a radiolabelled ligand within minutes at room temperature. After reconstitution in Nanodiscs made of phospholipid bilayer the half-life of high-affinity ligand binding to the majority of receptors increased 70-fold compared to detergent solubilized receptors—a level of stability that is appropriate for further downstream applications. Time-resolved scintillation proximity assay has the potential to screen numerous conditions in parallel to obtain high levels of stable and active membrane proteins, which are intrinsically unstable in detergent solution, and with minimum material consumption. PMID:27035823

  17. Site-specific structural dynamics of α-Synuclein revealed by time-resolved fluorescence spectroscopy: a review

    NASA Astrophysics Data System (ADS)

    Sahay, Shruti; Krishnamoorthy, G.; Maji, Samir K.

    2016-12-01

    Aggregation of α-Synuclein (α-Syn) into amyloid fibrils is known to be associated with the pathogenesis of Parkinson’s disease (PD). Several missense mutations of the α-Syn gene have been associated with rare, early onset familial forms of PD. Despite several studies done so far, the local/residue-level structure and dynamics of α-Syn in its soluble and aggregated fibril form and how these are affected by the familial PD associated mutations are still not clearly understood. Here, we review studies performed by our group as well as other research groups, where time-resolved fluorescence spectroscopy has been used to understand the site-specific structure and dynamics of α-Syn under physiological conditions as well as under conditions that alter the aggregation properties of the protein such as low pH, high temperature, presence of membrane mimics and familial PD associated mutations. These studies have provided important insights into the critical structural properties of α-Syn that may govern its aggregation. The review also highlights time-resolved fluorescence as a promising tool to study the critical conformational transitions associated with early oligomerization of α-Syn, which are otherwise not accessible using other commonly used techniques such as thioflavin T (ThT) binding assay.

  18. Network theory inspired analysis of time-resolved expression data reveals key players guiding P. patens stem cell development.

    PubMed

    Busch, Hauke; Boerries, Melanie; Bao, Jie; Hanke, Sebastian T; Hiss, Manuel; Tiko, Theodhor; Rensing, Stefan A

    2013-01-01

    Transcription factors (TFs) often trigger developmental decisions, yet, their transcripts are often only moderately regulated and thus not easily detected by conventional statistics on expression data. Here we present a method that allows to determine such genes based on trajectory analysis of time-resolved transcriptome data. As a proof of principle, we have analysed apical stem cells of filamentous moss (P. patens) protonemata that develop from leaflets upon their detachment from the plant. By our novel correlation analysis of the post detachment transcriptome kinetics we predict five out of 1,058 TFs to be involved in the signaling leading to the establishment of pluripotency. Among the predicted regulators is the basic helix loop helix TF PpRSL1, which we show to be involved in the establishment of apical stem cells in P. patens. Our methodology is expected to aid analysis of key players of developmental decisions in complex plant and animal systems.

  19. Ultrafast terahertz modulation characteristic of tungsten doped vanadium dioxide nanogranular film revealed by time-resolved terahertz spectroscopy

    SciTech Connect

    Xiao, Yang; Zhai, Zhao-Hui; Zhu, Li-Guo E-mail: huangwanxia@scu.edu.cn; Li, Jun; Peng, Qi-Xian; Li, Ze-Ren; Shi, Qi-Wu; Huang, Wan-Xia E-mail: huangwanxia@scu.edu.cn; Yue, Fang; Hu, Yan-Yan

    2015-07-20

    The ultrafast terahertz (THz) modulation characteristic during photo-induced insulator-to-metal transition (IMT) of undoped and tungsten (W)-doped VO{sub 2} film was investigated at picoseconds time scale using time-resolved THz spectroscopy. W-doping slows down the photo-induced IMT dynamic processes (both the fast non-thermal process and the slow metallic phase propagation process) in VO{sub 2} film and also reduces the pump fluence threshold of photo-induced IMT in VO{sub 2} film. Along with the observed broadening of phase transition temperature window of IMT in W-doped VO{sub 2}, we conclude that W-doping prevents metallic phase domains from percolation. By further extracting carrier properties from photo-induced THz conductivity at several phase transition times, we found that the electron-electron correlation during IMT is enhanced in W-doped VO{sub 2}.

  20. Ultrafast potential energy surface softening of one-dimensional organic conductors revealed by picosecond time-resolved Laue crystallography.

    PubMed

    Messerschmidt, Marc; Tschentscher, Thomas; Cammarata, Marco; Meents, Alke; Sager, Christian; Davaasambuu, Jav; Busse, Gerhard; Techert, Simone

    2010-07-29

    Time-resolved Laue crystallography has been employed to study the structural dynamics of a one-dimensional organic conductor (tetrathiafulvalene-p-chloranil) during photoexcitation in the regime of the neutral to ionic phase transition. Exciting this crystalline system with 800 nm 100 fs long optical pulses leads to ultrafast population of a structural intermediate as early as 50 ps after excitation with a lifetime of at least 10 ns. Starting from the neutral phase, this intermediate has been assigned as a precursor state toward the photoinduced population of the ionic phase. The observed intensity changes are significantly different from comparable equilibrium structures. The interpretation of this structural data is that the potential of this intermediate is being softened during its population in a dynamical process. The depopulation proceeds through thermal processes.

  1. Dislocation-mediated relaxation in nanograined columnar palladium films revealed by on-chip time-resolved HRTEM testing

    PubMed Central

    Colla, M. -S.; Amin-Ahmadi, B.; Idrissi, H.; Malet, L.; Godet, S.; Raskin, J. -P.; Schryvers, D.; Pardoen, T.

    2015-01-01

    The high-rate sensitivity of nanostructured metallic materials demonstrated in the recent literature is related to the predominance of thermally activated deformation mechanisms favoured by a large density of internal interfaces. Here we report time-resolved high-resolution electron transmission microscopy creep tests on thin nanograined films using on-chip nanomechanical testing. Tests are performed on palladium, which exhibited unexpectedly large creep rates at room temperature. Despite the small 30-nm grain size, relaxation is found to be mediated by dislocation mechanisms. The dislocations interact with the growth nanotwins present in the grains, leading to a loss of coherency of twin boundaries. The density of stored dislocations first increases with applied deformation, and then decreases with time to drive additional deformation while no grain boundary mechanism is observed. This fast relaxation constitutes a key issue in the development of various micro- and nanotechnologies such as palladium membranes for hydrogen applications. PMID:25557273

  2. In situ radiolysis time-resolved ESR studies of spin trapping by DMPO: Re-evalution of hydroxyl radical and hydrated electron trapping rates and spin adduct yields

    SciTech Connect

    Madden, K.P.; Taniguchi, Hitoshi

    1996-05-02

    The second-order rate constants for the reaction of 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) with radiolytically produced hydroxyl radicals and hydrated electrons have been measured in aqueous solution by direct observation of spin adduct initial yield using time-resolved electron spin resonance. The rate constants are 2.8 x 10{sup 9} mol{sup -1} dm{sup 3} S{sup -1} for the DMPO-hydroxyl radical reaction and 3.2 x 10{sup 9} mol{sup -1} dm{sup 3} s{sup -1} for the reaction of DMPO and hydrated electron, using sodium formate and chloroacetic acid as competitive scavengers of the hydroxyl radical and hydrated electron, respectively. The hydrated electron-DMPO competition study determined the fraction of DMPO-H produced directly from radiolytically produced hydrogen atoms as 0.082 of the total DMPO-H yield, indicating that approximately half of the hydrogen atoms react with DMPO to produce non-aminoxyl products. The fraction of the total hydroxyl radical yield leading to DMPO-OH spin adduct was determined to be 0.94, using the bleach of 2,2,6,6-tetramethylpiperidone-N-oxyl by carbon dioxide radical anion as a reference standard. 36 refs., 8 figs., 1 tab.

  3. Kinetics of copper growth on graphene revealed by time-resolved small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Hodas, M.; Siffalovic, P.; Jergel, M.; Pelletta, M.; Halahovets, Y.; Vegso, K.; Kotlar, M.; Majkova, E.

    2017-01-01

    Metal growth on graphene has many applications. Transition metals are known to favor three-dimensional (3D) cluster growth on graphene. Copper is of particular interest for cost-effective surface-supported catalysis applications and as a contact material in electronics. This paper presents an in situ real-time study of Cu growth kinetics on graphene covering all stages preceding formation of a continuous film performed by laboratory-based grazing-incidence small-angle x-ray scattering (GISAXS) technique. In particular, nucleation and 3D cluster growth, coalescence, and percolation stages were identified. The cluster nucleation saturates after reaching a density of 1012c m-2 at ≈1 monolayer thickness. A Kratky plot and a paracrystal model with cumulative structural disorder were necessary to evaluate properly cluster growth and coalescence, respectively. The power law scaling constants 0.27 ±0.05 and 0.81 ±0.02 of the temporal evolution of Cu cluster size suggest the growth of isolated clusters and dynamic cluster coalescence keeping the cluster shape, respectively. Coalescence and percolation thresholds occur at Cu thicknesses of 2 ±0.4 and 8.8 ±0.7 nm , respectively. This paper demonstrates the potential of laboratory-based in situ GISAXS as a vital diagnostic tool for tailoring a large variety of Cu nanostructures on graphene based on an in situ Cu growth monitoring which is applicable in a broad range of deposition times.

  4. In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

    SciTech Connect

    Matsui, Kunio; Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Sato, Masugu

    2011-05-15

    The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

  5. Time-Resolved Transcriptomics and Bioinformatic Analyses Reveal Intrinsic Stress Responses during Batch Culture of Bacillus subtilis

    PubMed Central

    Blom, Evert-Jan; Ridder, Anja N. J. A.; Lulko, Andrzej T.; Roerdink, Jos B. T. M.; Kuipers, Oscar P.

    2011-01-01

    We have determined the time-resolved transcriptome of the model gram-positive organism B. subtilis during growth in a batch fermentor on rich medium. DNA microarrays were used to monitor gene transcription using 10-minute intervals at 40 consecutive time points. From the growth curve and analysis of all gene expression levels, we identified 4 distinct growth phases and one clear transition point: a lag phase, an exponential growth phase, the transition point and the very clearly separated early and late stationary growth phases. The gene expression profiles suggest the occurrence of stress responses at specific times although no external stresses were applied. The first one is a small induction of the SigB regulon that occurs at the transition point. Remarkably, a very strong response is observed for the SigW regulon, which is highly upregulated at the onset of the late stationary phase. Bioinformatic analyses that were performed on our data set suggest several novel putative motifs for regulator binding. In addition, the expression profiles of several genes appeared to correlate with the oxygen concentration. This data set of the expression profiles of all B. subtilis genes during the entire growth curve on rich medium constitutes a rich repository that can be further mined by the scientific community. PMID:22087258

  6. Mechanism for formation of the lightstruck flavor in beer revealed by time-resolved electron paramagnetic resonance.

    PubMed

    Burns, C S; Heyerick, A; De Keukeleire, D; Forbes, M D

    2001-11-05

    Time-resolved electron paramagnetic resonance (TREPR) data collected during the photodegradation of iso-a-acids (isohumulones), the principal bittering agents from hops in beer, are presented and discussed, and, from the data, the photophysics leading to free-radical production as the primary step in the photodecomposition of iso-alpha-acids towards the development of "skunky" beer are explained. During laser flash photolysis of iso-alpha-acids at 308 nm in toluene/methylcyclohexane (1:1), TREPR spectra exhibit net emissive signals that are strongly spin polarized by the triplet mechanism of chemically induced electron spin polarization. From two potential photochemically active sites, the TREPR data show that although the first site, an enolized beta-triketone, is the primary light-absorbing chromophore, an uphill intramolecular triplet energy transfer process leads to Norrish type I alpha-cleavage at a second site, an alpha-hydroxycarbonyl. The energy transfer mechanism is supported by additional TREPR experiments with chemically modified hop compounds. Structural parameters (hyperfine coupling constants, g factors, line widths) for the observed free radicals, obtained from computer simulations, are presented and discussed.

  7. In situ time-resolved XAFS study on the structural transformation and phase separation of Pt3Sn and PtSn alloy nanoparticles on carbon in the oxidation process.

    PubMed

    Uemura, Y; Inada, Y; Bando, K K; Sasaki, T; Kamiuchi, N; Eguchi, K; Yagishita, A; Nomura, M; Tada, M; Iwasawa, Y

    2011-09-21

    The dynamic behavior and kinetics of the structural transformation of supported bimetallic nanoparticle catalysts with synergistic functions in the oxidation process are fundamental issues to understand their unique catalytic properties as well as to regulate the catalytic capability of alloy nanoparticles. The phase separation and structural transformation of Pt(3)Sn/C and PtSn/C catalysts during the oxidation process were characterized by in situ time-resolved energy-dispersive XAFS (DXAFS) and quick XAFS (QXAFS) techniques, which are element-selective spectroscopies, at the Pt L(III)-edge and the Sn K-edge. The time-resolved XAFS techniques provided the kinetics of the change in structures and oxidation states of the bimetallic nanoparticles on carbon surfaces. The kinetic parameters and mechanisms for the oxidation of the Pt(3)Sn/C and PtSn/C catalysts were determined by time-resolved XAFS techniques. The oxidation of Pt to PtO in Pt(3)Sn/C proceeded via two successive processes, while the oxidation of Sn to SnO(2) in Pt(3)Sn/C proceeded as a one step process. The rate constant for the fast Pt oxidation, which was completed in 3 s at 573 K, was the same as that for the Sn oxidation, and the following slow Pt oxidation rate was one fifth of that for the first Pt oxidation process. The rate constant and activation energy for the Sn oxidation in PtSn/C were similar to those for the Sn oxidation in Pt(3)Sn/C. In the PtSn/C, however, it was hard for Pt oxidation to PtO to proceed at 573 K, where Pt oxidation was strongly affected by the quantity of Sn in the alloy nanoparticles due to swift segregation of SnO(2) nanoparticles/layers on the Pt nanoparticles. The mechanisms for the phase separation and structure transformation in the Pt(3)Sn/C and PtSn/C catalysts are also discussed on the basis of the structural kinetics of the catalysts themselves determined by the in situ time-resolved DXAFS and QXAFS.

  8. Lattice-level observation of the elastic-to-plastic relaxation process with subnanosecond resolution in shock-compressed Ta using time-resolved in situ Laue diffraction

    SciTech Connect

    Wehrenberg, C. E.; Comley, A. J.; Barton, N. R.; Coppari, F.; Fratanduono, D.; Huntington, C. M.; Maddox, B. R.; Park, H. -S.; Plechaty, C.; Prisbrey, S. T.; Remington, B. A.; Rudd, R. E.

    2015-09-29

    We report direct lattice level measurements of plastic relaxation kinetics through time-resolved, in-situ Laue diffraction of shock-compressed single-crystal [001] Ta at pressures of 27-210 GPa. For a 50 GPa shock, a range of shear strains is observed extending up to the uniaxial limit for early data points (<0.6 ns) and the average shear strain relaxes to a near steady state over ~1 ns. For 80 and 125 GPa shocks, the measured shear strains are fully relaxed already at 200 ps, consistent with rapid relaxation associated with the predicted threshold for homogeneous nucleation of dislocations occurring at shock pressure ~65 GPa. The relaxation rate and shear stresses are used to estimate the dislocation density and these quantities are compared to the Livermore Multiscale Strength model as well as various molecular dynamics simulations.

  9. Time-resolved in situ detection of CO in a shock tube using cavity-enhanced absorption spectroscopy with a quantum-cascade laser near 4.6 µm.

    PubMed

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-10-06

    Cavity-enhanced absorption spectroscopy (CEAS) using a mid-infrared DFB quantum-cascade laser is reported for sensitive time-resolved (10 μs) in situ CO measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 91 was demonstrated, which enabled sub-ppm detection sensitivity for gas temperatures of 1000-2100K in a 15 cm diameter shock tube. This substantial improvement in detection sensitivity compared to conventional single-pass absorption measurements, shows great potential for the study of reaction pathways of high-temperature combustion kinetics mechanisms in shock tubes.

  10. Time-resolved and in-situ X-ray scattering methods beyond photoactivation: Utilizing high-flux X-ray sources for the study of ubiquitous non-photoactive proteins.

    PubMed

    Jain, Rohit; Techert, Simone

    2016-01-01

    X-ray scattering technique, comprising of small-angle/wide-angle X-ray scattering (SAXS/WAXS) techniques is increasingly used to characterize the structure and interactions of biological macromolecules and their complexes in solution. It is a method of choice to characterize the flexible, partially folded and unfolded protein systems. X-ray scattering is the last resort for proteins that cannot be investigated by crystallography or NMR and acts as a complementary technique with different biophysical techniques to answer challenging scientific questions. The marriage of the X-ray scattering technique with the fourth dimension "time" yields structural dynamics and kinetics information for protein motions in hierarchical timescales from picoseconds to days. The arrival of the high-flux X-ray beam at third generation synchrotron sources, exceptional X-ray optics, state-of-the-art detectors, upgradation of X-ray scattering beamlines with microfluidics devices and advanced X-ray scattering data analysis procedures are the important reasons behind the shining years of X-ray scattering technique. The best days of the X-ray scattering technique are on the horizon with the advent of the nanofocus X-ray scattering beamlines and fourth generation X-ray lightsources, i.e., free electron lasers (XFELs). Complementary to the photon-triggered time-resolved X-ray scattering techniques, we will present an overview of the time-resolved and in-situ X-ray scattering techniques for structural dynamics of ubiquitous non-photoactive proteins.

  11. Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

    SciTech Connect

    Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; Yang, Xiao-Qing; Nam, Kyung-Wan; Zhang, Lulu; Shao, Minhua

    2015-03-01

    Thermal stabilities of a series of blended LiMn2O4(LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25°C-580°C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250°C. Formation of MnO with rocksalt structure started at 520°C. This observation is in contrast to the previous report for chemically delithiate LMO in air, in which a process of λ-MnO2 transforming to β-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumption by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.

  12. Thermal stability in the blended lithium manganese oxide – Lithium nickel cobalt manganese oxide cathode materials: An in situ time-resolved X-Ray diffraction and mass spectroscopy study

    DOE PAGES

    Hu, Enyuan; Bak, Seong Min; Senanayake, Sanjaya D.; ...

    2015-03-01

    Thermal stabilities of a series of blended LiMn2O4(LMO)-LiNi1/3Co1/3Mn1/3O2 (NCM) cathode materials with different weight ratios were studied by in situ time-resolved X-ray diffraction (XRD) combined with mass spectroscopy in the temperature range of 25°C-580°C under helium atmosphere. Upon heating, the electrochemically delithiated LMO changed into Mn3O4 phase at around 250°C. Formation of MnO with rocksalt structure started at 520°C. This observation is in contrast to the previous report for chemically delithiate LMO in air, in which a process of λ-MnO2 transforming to β-MnO2 was observed. Oxygen peak was not observed in all cases, presumably as a result of either consumptionmore » by the carbon or detection limit. CO2 profile correlates well with the phase transition and indirectly suggests the oxygen release of the cathode. Introducing NCM into LMO has two effects: first, it makes the high temperature rock-salt phase formation more complicated with more peaks in CO2 profile due to different MO (M = Ni, Mn, Co) phases; secondly, the onset temperature of CO2 release is lowered, implying lowered oxygen release temperature. Upon heating, XRD patterns indicate the NCM part reacts first, followed by the LMO part. This confirms the better thermal stability of LMO over NCM.« less

  13. Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

    SciTech Connect

    Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, II Woong; Walko, Donald A.; Dufresne, Eric M.; Jaewoo, Jeong; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

    2016-02-26

    Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase seperated regions. The ability to simultanousely track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of- the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, which is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. Lastly, the direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

  14. Anomalous lattice expansion in yttria stabilized zirconia under simultaneous applied electric and thermal fields: A time-resolved in situ energy dispersive x-ray diffractometry study with an ultrahigh energy synchrotron probe

    SciTech Connect

    Akdogan, E. K.; Savkl Latin-Small-Letter-Dotless-I y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I z, I.; Bicer, H.; Paxton, W.; Toksoy, F.; Tsakalakos, T.; Zhong, Z.

    2013-06-21

    Nonisothermal densification in 8% yttria doped zirconia (8YSZ) particulate matter of 250 nm median particle size was studied under 215 V/cm dc electric field and 9 Degree-Sign C/min heating rate, using time-resolved in-situ high temperature energy dispersive x-ray diffractometry with a polychromatic 200 keV synchrotron probe. Densification occurred in the 876-905 Degree-Sign C range, which resulted in 97% of the theoretical density. No local melting at particle-particle contacts was observed in scanning electron micrographs, implying densification was due to solid state mass transport processes. The maximum current draw at 905 Degree-Sign C was 3 A, corresponding to instantaneous absorbed power density of 570 W/cm{sup 3}. Densification of 8YSZ was accompanied by anomalous elastic volume expansions of the unit cell by 0.45% and 2.80% at 847 Degree-Sign C and 905 Degree-Sign C, respectively. The anomalous expansion at 905 Degree-Sign C at which maximum densification was observed is characterized by three stages: (I) linear stage, (II) anomalous stage, and (III) anelastic recovery stage. The densification in stage I (184 s) and II (15 s) was completed in 199 s, while anelastic relaxation in stage III lasted 130 s. The residual strains ({epsilon}) at room temperature, as computed from tetragonal (112) and (211) reflections, are {epsilon}{sub (112)} = 0.05% and {epsilon}{sub (211)} = 0.13%, respectively. Time dependence of (211) and (112) peak widths ({beta}) show a decrease with both exhibiting a singularity at 905 Degree-Sign C. An anisotropy in (112) and (211) peak widths of {l_brace} {beta}{sub (112)}/{beta}{sub (211)}{r_brace} = (3:1) magnitude was observed. No phase transformation occurred at 905 Degree-Sign C as verified from diffraction spectra on both sides of the singularity, i.e., the unit cell symmetry remains tetragonal. We attribute the reduction in densification temperature and time to ultrafast ambipolar diffusion of species arising from the

  15. Cooperative protein structural dynamics of homodimeric hemoglobin linked to water cluster at subunit interface revealed by time-resolved X-ray solution scattering

    PubMed Central

    Kim, Jong Goo; Muniyappan, Srinivasan; Oang, Key Young; Kim, Tae Wu; Yang, Cheolhee; Kim, Kyung Hwan; Kim, Jeongho; Ihee, Hyotcherl

    2016-01-01

    Homodimeric hemoglobin (HbI) consisting of two subunits is a good model system for investigating the allosteric structural transition as it exhibits cooperativity in ligand binding. In this work, as an effort to extend our previous study on wild-type and F97Y mutant HbI, we investigate structural dynamics of a mutant HbI in solution to examine the role of well-organized interfacial water cluster, which has been known to mediate intersubunit communication in HbI. In the T72V mutant of HbI, the interfacial water cluster in the T state is perturbed due to the lack of Thr72, resulting in two less interfacial water molecules than in wild-type HbI. By performing picosecond time-resolved X-ray solution scattering experiment and kinetic analysis on the T72V mutant, we identify three structurally distinct intermediates (I1, I2, and I3) and show that the kinetics of the T72V mutant are well described by the same kinetic model used for wild-type and F97Y HbI, which involves biphasic kinetics, geminate recombination, and bimolecular CO recombination. The optimized kinetic model shows that the R-T transition and bimolecular CO recombination are faster in the T72V mutant than in the wild type. From structural analysis using species-associated difference scattering curves for the intermediates, we find that the T-like deoxy I3 intermediate in solution has a different structure from deoxy HbI in crystal. In addition, we extract detailed structural parameters of the intermediates such as E-F distance, intersubunit rotation angle, and heme-heme distance. By comparing the structures of protein intermediates in wild-type HbI and the T72V mutant, we reveal how the perturbation in the interfacial water cluster affects the kinetics and structures of reaction intermediates of HbI. PMID:27158635

  16. Photon Emission and Reabsorption Processes in CH3NH3PbBr3 Single Crystals Revealed by Time-Resolved Two-Photon-Excitation Photoluminescence Microscopy

    NASA Astrophysics Data System (ADS)

    Yamada, Takumi; Yamada, Yasuhiro; Nakaike, Yumi; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2017-01-01

    The dynamical processes of radiative recombination of photocarriers and reabsorption of emitted photons in CH3NH3PbBr3 single crystals are studied using time-resolved two-photon-excitation photoluminescence (PL) microscopy. We find that the PL spectrum and its decay dynamics depend on the excitation-depth profile. As the excitation depth increases, the PL spectrum becomes asymmetric, the peak energy redshifts, and the PL decay time becomes longer. These observations can be well explained by a simple model including photon recycling (photon emission and reabsorption) in thick samples with strong band-to-band transitions and high radiative recombination efficiencies.

  17. Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory.

    PubMed

    Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P

    2015-07-01

    In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles.

  18. Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P.

    2015-07-01

    In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles.

  19. Spatial density profile of electrons near the LaAlO{sub 3}/SrTiO{sub 3} heterointerface revealed by time-resolved photoluminescence spectroscopy

    SciTech Connect

    Yamada, Yasuhiro Kanemitsu, Yoshihiko; Sato, Hiroki K.; Hikita, Yasuyuki; Hwang, Harold Y.

    2014-04-14

    The depth profile of the electron density near the LaAlO{sub 3}/SrTiO{sub 3} heterointerface has been studied by means of time-resolved photoluminescence (PL) spectroscopy. A broad blue PL band is observed at 2.9 eV, originating from the two-carrier radiative recombination of interface-induced electrons and photoexcited holes. The PL lifetime of LaAlO{sub 3}/SrTiO{sub 3} heterointerface is dominated by the three-carrier Auger recombination of electrons and holes and is sensitive to electron density. We tuned the probing depth by changing the excitation photon energy and evaluated the carrier-density profile using the relation between the carrier density and the PL lifetime. Our non-contact probe method based on PL spectroscopy indicates that the carriers are confined within several nanometers in depth near the LaAlO{sub 3}/SrTiO{sub 3} heterostructures.

  20. Ultrafast time-resolved electron diffraction revealing the nonthermal dynamics of near-UV photoexcitation-induced amorphization in Ge2Sb2Te5

    PubMed Central

    Hada, Masaki; Oba, Wataru; Kuwahara, Masashi; Katayama, Ikufumi; Saiki, Toshiharu; Takeda, Jun; Nakamura, Kazutaka G.

    2015-01-01

    Because of their robust switching capability, chalcogenide glass materials have been used for a wide range of applications, including optical storages devices. These phase transitions are achieved by laser irradiation via thermal processes. Recent studies have suggested the potential of nonthermal phase transitions in the chalcogenide glass material Ge2Sb2Te5 triggered by ultrashort optical pulses; however, a detailed understanding of the amorphization and damage mechanisms governed by nonthermal processes is still lacking. Here we performed ultrafast time-resolved electron diffraction and single-shot optical pump-probe measurements followed by femtosecond near-ultraviolet pulse irradiation to study the structural dynamics of polycrystalline Ge2Sb2Te5. The experimental results present a nonthermal crystal-to-amorphous phase transition of Ge2Sb2Te5 initiated by the displacements of Ge atoms. Above the fluence threshold, we found that the permanent amorphization caused by multi-displacement effects is accompanied by a partial hexagonal crystallization. PMID:26314613

  1. Millifluidics for Chemical Synthesis and Time-resolved Mechanistic Studies

    PubMed Central

    Krishna, Katla Sai; Biswas, Sanchita; Navin, Chelliah V.; Yamane, Dawit G.; Miller, Jeffrey T.; Kumar, Challa S.S.R.

    2013-01-01

    Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the first, synthesis of ultra-small copper nanoclusters is described. The second example provides their utility for investigating time resolved kinetics of chemical reactions by analyzing gold nanoparticle formation using in situ X-ray absorption spectroscopy. The final example demonstrates continuous flow catalysis of reactions inside millifluidic channel coated with nanostructured catalyst. PMID:24327099

  2. Time-resolved vibrational spectroscopy

    SciTech Connect

    Tokmakoff, Andrei; Champion, Paul; Heilweil, Edwin J.; Nelson, Keith A.; Ziegler, Larry

    2009-05-14

    This document contains the Proceedings from the 14th International Conference on Time-Resolved Vibrational Spectroscopy, which was held in Meredith, NH from May 9-14, 2009. The study of molecular dynamics in chemical reaction and biological processes using time-resolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE's Office of Science because of their role in the development of alternative energy sources, the understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time-resolved spectroscopy is central to all fiveof DOE's grand challenges for fundamental energy science. The Time-Resolved Vibrational Spectroscopy conference is organized biennially to bring the leaders in this field from around the globe together with young scientists to discuss the most recent scientific and technological advances. The latest technology in ultrafast infrared, Raman, and terahertz spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.

  3. Redefining the Speed Limit of Phase Change Memory Revealed by Time-resolved Steep Threshold-Switching Dynamics of AgInSbTe Devices

    PubMed Central

    Shukla, Krishna Dayal; Saxena, Nishant; Durai, Suresh; Manivannan, Anbarasu

    2016-01-01

    Although phase-change memory (PCM) offers promising features for a ‘universal memory’ owing to high-speed and non-volatility, achieving fast electrical switching remains a key challenge. In this work, a correlation between the rate of applied voltage and the dynamics of threshold-switching is investigated at picosecond-timescale. A distinct characteristic feature of enabling a rapid threshold-switching at a critical voltage known as the threshold voltage as validated by an instantaneous response of steep current rise from an amorphous off to on state is achieved within 250 picoseconds and this is followed by a slower current rise leading to crystallization. Also, we demonstrate that the extraordinary nature of threshold-switching dynamics in AgInSbTe cells is independent to the rate of applied voltage unlike other chalcogenide-based phase change materials exhibiting the voltage dependent transient switching characteristics. Furthermore, numerical solutions of time-dependent conduction process validate the experimental results, which reveal the electronic nature of threshold-switching. These findings of steep threshold-switching of ‘sub-50 ps delay time’, opens up a new way for achieving high-speed non-volatile memory for mainstream computing. PMID:27886266

  4. Complexity of Lipid Domains and Rafts in Giant Unilamellar Vesicles Revealed by Combining Imaging and Microscopic and Macroscopic Time-Resolved Fluorescence

    PubMed Central

    de Almeida, Rodrigo F. M.; Borst, JanWillem; Fedorov, Alexander; Prieto, Manuel; Visser, Antonie J. W. G.

    2007-01-01

    The application of fluorescence lifetime imaging microscopy to study gel/fluid and raftlike lipid domains in giant unilamellar vesicles (GUVs) is demonstrated here. Different regions of the ternary dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine/cholesterol phase diagram were studied. The head-labeled phospholipid Rhodamine-dioleoylphosphatidylethanolamine (Rhod-DOPE) was used as a fluorescent probe. Gel/fluid and liquid-ordered (lo)/liquid-disordered (ld) phase separation were clearly visualized upon two-photon excitation. Fluorescence intensity decays in different regions of a GUV were also obtained with the microscope in fixed laser-beam configuration. The ensemble behavior of the system was studied by obtaining fluorescence intensity decays of Rhod-DOPE in nongiant vesicle suspensions. The fingerprints for gel/fluid coexistence and for the presence of lo raftlike phase, based on fluorescence lifetime imaging microscopy histograms and images, and on the fluorescence intensity decay parameters of Rhod-DOPE, are presented. The presence of three lipid phases in one single GUV is detected unequivocally. From the comparison of lifetime parameters, it can be concluded that the lo phase is formed in the binary dipalmitoylphosphatidylcholine/cholesterol but not in the dioleoylphosphatidylcholine/cholesterol mixture. The domains apparent in fluorescence intensity images have a more complex substructure revealed by analysis of the lifetime data. The potential applications of this combined imaging/microscopic/macroscopic methodology are discussed. PMID:17449668

  5. Structural changes and thermal stability of charged LiNixMnyCozO2 cathode materials studied by combined in situ time-resolved XRD and mass spectroscopy

    SciTech Connect

    Bak, Seong -Min; Hu, Enyuan; Zhou, Yongning; Yu, Xiqian; Senanayake, Sanjaya D.; Cho, Sung -Jin; Kim, Kwang -Bum; Chung, Kyung Yoon; Yang, Xiao -Qing; Nam, Kyung -Wan

    2014-11-24

    Thermal stability of charged LiNixMnyCozO2 (NMC, with x + y + z = 1, x:y:z = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined in situ time- resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and the larger amount of oxygen release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3a octahedral sites of a layered structure (R3¯m) but Co ions prefer to migrate to the 8a tetrahedral sites of a spinel structure (Fd3¯m) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. As a result, this systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density.

  6. Revealing the radiative and non-radiative relaxation rates of the fluorescent dye Atto488 in a λ/2 Fabry-Pérot-resonator by spectral and time resolved measurements

    NASA Astrophysics Data System (ADS)

    Konrad, Alexander; Metzger, Michael; Kern, Andreas M.; Brecht, Marc; Meixner, Alfred J.

    2016-07-01

    Using a Fabry-Pérot-microresonator with controllable cavity lengths in the λ/2-regime, we show the controlled modification of the vibronic relaxation dynamics of a fluorescent dye molecule in the spectral and time domain. By altering the photonic mode density around the fluorophores we are able to shape the fluorescence spectrum and enhance specifically the probability of the radiative transitions from the electronic excited state to distinct vibronic excited states of the electronic ground state. Analysis and correlation of the spectral and time resolved measurements by a theoretical model and a global fitting procedure allows us to reveal quantitatively the spectrally distributed radiative and non-radiative relaxation dynamics of the respective dye molecule under ambient conditions at the ensemble level.Using a Fabry-Pérot-microresonator with controllable cavity lengths in the λ/2-regime, we show the controlled modification of the vibronic relaxation dynamics of a fluorescent dye molecule in the spectral and time domain. By altering the photonic mode density around the fluorophores we are able to shape the fluorescence spectrum and enhance specifically the probability of the radiative transitions from the electronic excited state to distinct vibronic excited states of the electronic ground state. Analysis and correlation of the spectral and time resolved measurements by a theoretical model and a global fitting procedure allows us to reveal quantitatively the spectrally distributed radiative and non-radiative relaxation dynamics of the respective dye molecule under ambient conditions at the ensemble level. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR02380K

  7. Structural and Electronic Transformations of Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C Cathode Catalysts in Polymer Electrolyte Fuel Cells during Potential-step Operating Processes Characterized by In-situ Time-resolved XAFS

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Shin-ichi; Takao, Shinobu; Samjeské, Gabor; Nagasawa, Kensaku; Sekizawa, Oki; Kaneko, Takuma; Higashi, Kotaro; Uruga, Tomoya; Gayen, Sirshendu; Velaga, Srihari; Saniyal, Milan K.; Iwasawa, Yasuhiro

    2016-06-01

    The dynamic structural and electronic transformations of Pt/C, Pd@Pt(1 ML)/C, Pd@Pt(2 ML)/C cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the potential-step operating processes between 0.4 and 1.4 VRHE (potential vs RHE) were characterized by in-situ (operando) time-resolved Pt LIII-edge quick-XAFS at 100 ms time-resolution. Potential-dependent surface structures and oxidation states of Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticles on carbon at 0.4 and 1.4 VRHE were also analyzed by in-situ Pt LIII-edge and Pd K-edge quick-XAFS. The Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticle surfaces were restructured and disordered at 1.4 VRHE, which were induced by strong Pt-O bonds as well as alloying effects. The rate constants for the changes of Pt valence, CN(Pt-Pt), CN(Pt-Pd) and CN(Pt-O) (CN: coordination number) in the potential-step operating processes were also determined and discussed in relation to the origin of oxygen reduction reaction (ORR) activities of the Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C cathode catalysts.

  8. Revealing anelasticity and structural rearrangements in nanoscale metallic glass films using in situ TEM diffraction

    PubMed Central

    Sarkar, Rohit; Ebner, Christian; Izadi, Ehsan; Rentenberger, Christian; Rajagopalan, Jagannathan

    2017-01-01

    ABSTRACT We used a novel diffraction-based method to extract the local, atomic-level elastic strain in nanoscale amorphous TiAl films during in situ transmission electron microscopy deformation, while simultaneously measuring the macroscopic strain. The complementary strain measurements revealed significant anelastic deformation, which was independently confirmed by strain rate experiments. Furthermore, the distribution of first nearest-neighbor distances became narrower during loading and permanent changes were observed in the atomic structure upon unloading, even in the absence of macroscopic plasticity. The results demonstrate the capability of in situ electron diffraction to probe structural rearrangements and decouple elastic and anelastic deformation in metallic glasses. PMID:28382229

  9. Surface phenomena revealed by in situ imaging: studies from adhesion, wear and cutting

    NASA Astrophysics Data System (ADS)

    Viswanathan, Koushik; Mahato, Anirban; Yeung, Ho; Chandrasekar, Srinivasan

    2017-03-01

    Surface deformation and flow phenomena are ubiquitous in mechanical processes. In this work we present an in situ imaging framework for studying a range of surface mechanical phenomena at high spatial resolution and across a range of time scales. The in situ framework is capable of resolving deformation and flow fields quantitatively in terms of surface displacements, velocities, strains and strain rates. Three case studies are presented demonstrating the power of this framework for studying surface deformation. In the first, the origin of stick-slip motion in adhesive polymer interfaces is investigated, revealing a intimate link between stick-slip and surface wave propagation. Second, the role of flow in mediating formation of surface defects and wear particles in metals is analyzed using a prototypical sliding process. It is shown that conventional post-mortem observation and inference can lead to erroneous conclusions with regard to formation of surface cracks and wear particles. The in situ framework is shown to unambiguously capture delamination wear in sliding. Third, material flow and surface deformation in a typical cutting process is analyzed. It is shown that a long-standing problem in the cutting of annealed metals is resolved by the imaging, with other benefits such as estimation of energy dissipation and power from the flow fields. In closure, guidelines are provided for profitably exploiting in situ observations to study large-strain deformation, flow and friction phenomena at surfaces that display a variety of time-scales.

  10. Revealing cyclic hardening mechanism of a TRIP steel by real-time in situ neutron diffraction

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Yan; Chen, Xu

    2014-01-01

    Real-time in situ neutron diffraction was performed on a transformation-induced plasticity (TRIP) steel under cyclic loading at room temperature. By Rietveld refinement and single peak analysis, the volume fraction and average stress estimates as well as dislocation density of individual phases (austenite and martensite phase) were derived. The results reveal that the volume fraction of martensite phase, instead of individual phase strengthening, should be accounted for the remarkable secondary cyclic hardening.

  11. Time-Resolved Photoluminescence and Photovoltaics

    SciTech Connect

    Metzger, W. K.; Ahrenkiel, R. K.; Dippo, P.; Geisz, J.; Wanlass, M. W.; Kurtz, S.

    2005-01-01

    The time-resolved photoluminescence (TRPL) technique and its ability to characterize recombination in bulk photovoltaic semiconductor materials are reviewed. Results from a variety of materials and a few recent studies are summarized and compared.

  12. Time-resolved transillumination and optical tomography

    NASA Astrophysics Data System (ADS)

    de Haller, Emmanuel B.

    1996-01-01

    In response to an invitation by the editor-in-chief, I would like to present the current status of time-domain imaging. With exciting new photon diffusion techniques being developed in the frequency domain and promising optical coherence tomography, time-resolved transillumination is in constant evolution and the subject of passionate discussions during the numerous conferences dedicated to this subject. The purpose of time-resolved optical tomography is to provide noninvasive, high-resolution imaging of the interior of living bodies by the use of nonionizing radiation. Moreover, the use of visible to near-infrared wavelength yields metabolic information. Breast cancer screening is the primary potential application for time-resolved imaging. Neurology and tissue characterization are also possible fields of applications. Time- resolved transillumination and optical tomography should not only improve diagnoses, but the welfare of the patient. As no overview of this technique has yet been presented to my knowledge, this paper briefly describes the various methods enabling time-resolved transillumination and optical tomography. The advantages and disadvantages of these methods, as well as the clinical challenges they face are discussed. Although an analytic and computable model of light transport through tissues is essential for a meaningful interpretation of the transillumination process, this paper will not dwell on the mathematics of photon propagation.

  13. Stacking sequence and interlayer coupling in few-layer graphene revealed by in situ imaging

    SciTech Connect

    Wang, Zhu-Jun; Dong, Jichen; Cui, Yi; Eres, Gyula; Timpe, Olaf; Fu, Qiang; Ding, Feng; Willinger, Marc-Georg; Schloegl, R.

    2016-10-19

    In the transition from graphene to graphite, the addition of each individual graphene layer modifies the electronic structure and produces a different material with unique properties. Controlled growth of few-layer graphene is therefore of fundamental interest and will provide access to materials with engineered electronic structure. Here we combine isothermal growth and etching experiments with in situ scanning electron microscopy to reveal the stacking sequence and interlayer coupling strength in few-layer graphene. The observed layer-dependent etching rates reveal the relative strength of the graphene graphene and graphene substrate interaction and the resulting mode of adlayer growth. Scanning tunnelling microscopy and density functional theory calculations confirm a strong coupling between graphene edge atoms and platinum. Simulated etching confirms that etching can be viewed as reversed growth. This work demonstrates that real-time imaging under controlled atmosphere is a powerful method for designing synthesis protocols for sp2 carbon nanostructures in between graphene and graphite.

  14. Revealing the anomalous tensile properties of WS2 nanotubes by in situ transmission electron microscopy.

    PubMed

    Tang, Dai-Ming; Wei, Xianlong; Wang, Ming-Sheng; Kawamoto, Naoyuki; Bando, Yoshio; Zhi, Chunyi; Mitome, Masanori; Zak, Alla; Tenne, Reshef; Golberg, Dmitri

    2013-03-13

    Mechanical properties and fracture behaviors of multiwalled WS2 nanotubes produced by large scale fluidized bed method were investigated under uniaxial tension using in situ transmission electron microscopy probing; these were directly correlated to the nanotube atomic structures. The tubes with the average outer diameter ∼40 nm sustained tensile force of ∼2949 nN and revealed fracture strength of ∼11.8 GPa. Surprisingly, these rather thick WS2 nanotubes could bear much higher loadings than the thin WS2 nanotubes with almost "defect-free" structures studied previously. In addition, the fracture strength of the "thick" nanotubes did not show common size dependent degradation when the tube diameters increased from ∼20 to ∼60 nm. HRTEM characterizations and real time observations revealed that the anomalous tensile properties are related to the intershell cross-linking and geometric constraints from the inverted cone-shaped tube cap structures, which resulted in the multishell loading and fracturing.

  15. Stacking sequence and interlayer coupling in few-layer graphene revealed by in situ imaging

    NASA Astrophysics Data System (ADS)

    Wang, Zhu-Jun; Dong, Jichen; Cui, Yi; Eres, Gyula; Timpe, Olaf; Fu, Qiang; Ding, Feng; Schloegl, R.; Willinger, Marc-Georg

    2016-10-01

    In the transition from graphene to graphite, the addition of each individual graphene layer modifies the electronic structure and produces a different material with unique properties. Controlled growth of few-layer graphene is therefore of fundamental interest and will provide access to materials with engineered electronic structure. Here we combine isothermal growth and etching experiments with in situ scanning electron microscopy to reveal the stacking sequence and interlayer coupling strength in few-layer graphene. The observed layer-dependent etching rates reveal the relative strength of the graphene-graphene and graphene-substrate interaction and the resulting mode of adlayer growth. Scanning tunnelling microscopy and density functional theory calculations confirm a strong coupling between graphene edge atoms and platinum. Simulated etching confirms that etching can be viewed as reversed growth. This work demonstrates that real-time imaging under controlled atmosphere is a powerful method for designing synthesis protocols for sp2 carbon nanostructures in between graphene and graphite.

  16. Metatranscriptomics reveal differences in in situ energy and nitrogen metabolism among hydrothermal vent snail symbionts

    PubMed Central

    Sanders, J G; Beinart, R A; Stewart, F J; Delong, E F; Girguis, P R

    2013-01-01

    Despite the ubiquity of chemoautotrophic symbioses at hydrothermal vents, our understanding of the influence of environmental chemistry on symbiont metabolism is limited. Transcriptomic analyses are useful for linking physiological poise to environmental conditions, but recovering samples from the deep sea is challenging, as the long recovery times can change expression profiles before preservation. Here, we present a novel, in situ RNA sampling and preservation device, which we used to compare the symbiont metatranscriptomes associated with Alviniconcha, a genus of vent snail, in which specific host–symbiont combinations are predictably distributed across a regional geochemical gradient. Metatranscriptomes of these symbionts reveal key differences in energy and nitrogen metabolism relating to both environmental chemistry (that is, the relative expression of genes) and symbiont phylogeny (that is, the specific pathways employed). Unexpectedly, dramatic differences in expression of transposases and flagellar genes suggest that different symbiont types may also have distinct life histories. These data further our understanding of these symbionts' metabolic capabilities and their expression in situ, and suggest an important role for symbionts in mediating their hosts' interaction with regional-scale differences in geochemistry. PMID:23619306

  17. Time resolved astronomy with the SALT

    NASA Astrophysics Data System (ADS)

    Buckley, D. A. H.; Crawford, S.; Gulbis, A. A. S.; McPhate, J.; Nordsieck, K. H.; Potter, S. B.; O'Donoghue, D.; Siegmund, O. H. W.; Schellart, P.; Spark, M.; Welsh, B. Y.; Zietsman, E.

    2010-07-01

    While time resolved astronomical observations are not new, the extension of such studies to sub-second time resolution is and has resulted in the opening of a new observational frontier, High Time Resolution Astronomy (HTRA). HTRA studies are well suited to objects like compact binary stars (CVs and X-ray binaries) and pulsars, while asteroseismology of pulsating stars, occultations, transits and the study of transients, will all benefit from such HTRA studies. HTRA has been a SALT science driver from the outset and the first-light instruments, namely the UV-VIS imager, SALTICAM, and the multi-purpose Robert Stobie Spectrograph (RSS), both have high time resolution modes. These are described, together with some observational examples. We also discuss the commissioning observations with the photon counting Berkeley Visible Image Tube camera (BVIT) on SALT. Finally we describe the software tools, developed in Python, to reduce SALT time resolved observations.

  18. Time-resolved photoemission using attosecond streaking

    NASA Astrophysics Data System (ADS)

    Nagele, S.; Pazourek, R.; Wais, M.; Wachter, G.; Burgdörfer, J.

    2014-04-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric efect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the feld-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for efective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes A@C60 and discuss how streaking time shifts are modifed due to the interaction of the C60 cage with the probing infrared streaking field.

  19. Time-Resolved Measurements in Optoelectronic Microbioanalysis

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory; Kossakovski, Dmitri

    2003-01-01

    A report presents discussion of time-resolved measurements in optoelectronic microbioanalysis. Proposed microbioanalytical laboratory-on-a-chip devices for detection of microbes and toxic chemicals would include optoelectronic sensors and associated electronic circuits that would look for fluorescence or phosphorescence signatures of multiple hazardous biomolecules in order to detect which ones were present in a given situation. The emphasis in the instant report is on gating an active-pixel sensor in the time domain, instead of filtering light in the wavelength domain, to prevent the sensor from responding to a laser pulse used to excite fluorescence or phosphorescence while enabling the sensor to respond to the decaying fluorescence or phosphorescence signal that follows the laser pulse. The active-pixel sensor would be turned on after the laser pulse and would be used to either integrate the fluorescence or phosphorescence signal over several lifetimes and many excitation pulses or else take time-resolved measurements of the fluorescence or phosphorescence. The report also discusses issues of multiplexing and of using time-resolved measurements of fluorophores with known different fluorescence lifetimes to distinguish among them.

  20. Growth mechanism of microporous zincophosphate sodalite revealed by in situ atomic force microscopy.

    PubMed

    Holden, Mark A; Cubillas, Pablo; Attfield, Martin P; Gebbie, James T; Anderson, Michael W

    2012-08-08

    Microporous zincophosphate sodalite crystal growth has been studied in situ by atomic force microscopy. This simple model system permits an in depth investigation of some of the axioms governing crystal growth of nanoporous framework solids in general. In particular, this work reveals the importance of considering the growth of a framework material as the growth of a dense phase material where the framework structure, nonframework cations, and hydrogen-bonded water must all be considered. The roles of the different components of the structure, including the role of strict framework ordering, are disentangled, and all of the growth features, both crystal habit and nanoscopic surface structure, are explained according to a simple set of rules. The work describes, for the first time, both ideal growth and growth leading to defect structures on all of the principal facets of the sodalite structure. Also, the discovery of the presence of anisotropic friction on a framework material is described.

  1. Time resolved optical tomography of the human forearm

    NASA Astrophysics Data System (ADS)

    Hillman, Elizabeth M. C.; Hebden, Jeremy C.; Schweiger, Martin; Dehghani, Hamid; Schmidt, Florian E. W.; Delpy, David T.; Arridge, Simon R.

    2001-04-01

    A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise.

  2. Time resolved optical tomography of the human forearm.

    PubMed

    Hillman, E M; Hebden, J C; Schweiger, M; Dehghani, H; Schmidt, F E; Delpy, D T; Arridge, S R

    2001-04-01

    A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise.

  3. Time Resolved Studies Of Adsorbed Species

    NASA Astrophysics Data System (ADS)

    Howard, J.; Nicol, J. M.

    1985-12-01

    A time-resolved Fourier transform IR study of ethyne adsorbed on ZnNaA zeolite yields results very different from those reported for related systems. Initially two species (A and B) are formed by the interaction of C2H2 with the cations. Whereas species A (π-bonded C2H2) was found to be removed immediately on evacuation, species B (probably Zn-acetylide) was not fully removed after 60 mins evacuation. In the presence of the gas phase, bands due to Species A decreased slowly in intensity as new bands due to adsorbed ethanal were observed.

  4. Time Resolved Raman and Fluorescence Spectrometer for Planetary Mineralogy

    NASA Astrophysics Data System (ADS)

    Blacksberg, Jordana; Rossman, George

    2010-05-01

    Raman spectroscopy is a prime candidate for the next generation of planetary instruments, as it addresses the primary goal of mineralogical analysis which is structure and composition. It does not require sample preparation and provides unique mineral fingerprints, even for mixed phase samples. However, large fluorescence return from many mineral samples under visible light excitation can seriously compromise the quality of the spectra or even render Raman spectra unattainable. Fluorescence interference is likely to be a problem on Mars and is evident in Raman spectra of Martian Meteorites[1]. Our approach uses time resolution for elimination of fluorescence from Raman spectra, allowing for traditional visible laser excitation (532 nm). Since Raman occurs instantaneously with the laser pulse and fluorescence lifetimes vary from nsec to msec depending on the mineral, it is possible to separate them out in time. Complementary information can also be obtained simultaneously using the time resolved fluorescence data. The Simultaneous Spectral Temporal Adaptive Raman Spectrometer (SSTARS) is a planetary instrument under development at the Jet Propulsion Laboratory, capable of time-resolved in situ Raman and fluorescence spectroscopy. A streak camera and pulsed miniature microchip laser provide psec scale time resolution. Our ability to observe the complete time evolution of Raman and fluorescence in minerals provides a foundation for design of pulsed Raman and fluorescence spectrometers in diverse planetary environments. We will discuss the SSTARS instrument design and performance capability. We will also present time-resolved pulsed Raman spectra collected from a relevant set of minerals selected using available data on Mars mineralogy[2]. Of particular interest are minerals resulting from aqueous alteration on Mars. For comparison, we will present Raman spectra obtained using a commercial continuous wave (CW) green (514 nm) Raman system. In many cases using a CW laser

  5. Stacking sequence and interlayer coupling in few-layer graphene revealed by in situ imaging

    PubMed Central

    Wang, Zhu-Jun; Dong, Jichen; Cui, Yi; Eres, Gyula; Timpe, Olaf; Fu, Qiang; Ding, Feng; Schloegl, R.; Willinger, Marc-Georg

    2016-01-01

    In the transition from graphene to graphite, the addition of each individual graphene layer modifies the electronic structure and produces a different material with unique properties. Controlled growth of few-layer graphene is therefore of fundamental interest and will provide access to materials with engineered electronic structure. Here we combine isothermal growth and etching experiments with in situ scanning electron microscopy to reveal the stacking sequence and interlayer coupling strength in few-layer graphene. The observed layer-dependent etching rates reveal the relative strength of the graphene–graphene and graphene–substrate interaction and the resulting mode of adlayer growth. Scanning tunnelling microscopy and density functional theory calculations confirm a strong coupling between graphene edge atoms and platinum. Simulated etching confirms that etching can be viewed as reversed growth. This work demonstrates that real-time imaging under controlled atmosphere is a powerful method for designing synthesis protocols for sp2 carbon nanostructures in between graphene and graphite. PMID:27759024

  6. Stacking sequence and interlayer coupling in few-layer graphene revealed by in situ imaging

    DOE PAGES

    Wang, Zhu-Jun; Dong, Jichen; Cui, Yi; ...

    2016-10-19

    In the transition from graphene to graphite, the addition of each individual graphene layer modifies the electronic structure and produces a different material with unique properties. Controlled growth of few-layer graphene is therefore of fundamental interest and will provide access to materials with engineered electronic structure. Here we combine isothermal growth and etching experiments with in situ scanning electron microscopy to reveal the stacking sequence and interlayer coupling strength in few-layer graphene. The observed layer-dependent etching rates reveal the relative strength of the graphene graphene and graphene substrate interaction and the resulting mode of adlayer growth. Scanning tunnelling microscopy andmore » density functional theory calculations confirm a strong coupling between graphene edge atoms and platinum. Simulated etching confirms that etching can be viewed as reversed growth. This work demonstrates that real-time imaging under controlled atmosphere is a powerful method for designing synthesis protocols for sp2 carbon nanostructures in between graphene and graphite.« less

  7. In situ Expression of Functional Genes Reveals Nitrogen Cycling at High Temperatures in Terrestrial Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Loiacono, S. T.; Meyer-Dombard, D. R.

    2011-12-01

    An essential element for life, nitrogen occurs in all living organisms and is critical for the synthesis of amino acids, proteins, nucleic acids, and other forms of biomass. Thus, nitrogen cycling likely plays a vital role in microbial metabolic processes as well as nutrient availability. For microorganisms in "extreme" environments, this means developing adaptations that allow them to survive in harsh conditions and still perform the metabolisms essential to sustain life. Recent studies have screened biofilms and thermal sediments of Yellowstone National Park (YNP) thermal features for the presence of nifH genes, which code for a key enzyme in the nitrogen fixation process [1-4]. Furthermore, analysis of nitrogen isotopes in biofilms across a temperature and chemical gradient revealed that nitrogen fixation likely varies across the chemosynthetic/photosynthetic ecotone [5]. Although research has evaluated and confirmed the presence of nifH genes in various thermophilic microbial communities, the existence of a gene in the DNA of an organism does not verify its use. Instead, other methods, such as culturing, isotope tracer assays, and gene expression studies are required to provide direct evidence of biological nitrogen fixation. Culturing and isotope tracer approaches have successfully revealed high-temperature biological nitrogen fixation in both marine hydrothermal vent microbial communities [6] and in acidic, terrestrial hydrothermal sediment [3]. Transcriptomics-based techniques (using mRNA extracted from samples to confirm in situ expression of targeted genes) have been much more limited in number, and only a few studies have, to date, investigated in situ expression of the nifH gene in thermophilic microbial communities [2, 7]. This study explores the presence and expression of nifH genes in several features of the Lower Geyser Basin (LGB) of YNP. Nucleic acids from chemosynthetic and photosynthetic microbial communities were extracted and then amplified

  8. Time-resolved RNA SHAPE chemistry.

    PubMed

    Mortimer, Stefanie A; Weeks, Kevin M

    2008-12-03

    Selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry yields quantitative RNA secondary and tertiary structure information at single nucleotide resolution. SHAPE takes advantage of the discovery that the nucleophilic reactivity of the ribose 2'-hydroxyl group is modulated by local nucleotide flexibility in the RNA backbone. Flexible nucleotides are reactive toward hydroxyl-selective electrophiles, whereas constrained nucleotides are unreactive. Initial versions of SHAPE chemistry, which employ isatoic anhydride derivatives that react on the minute time scale, are emerging as the ideal technology for monitoring equilibrium structures of RNA in a wide variety of biological environments. Here, we extend SHAPE chemistry to a benzoyl cyanide scaffold to make possible facile time-resolved kinetic studies of RNA in approximately 1 s snapshots. We then use SHAPE chemistry to follow the time-dependent folding of an RNase P specificity domain RNA. Tertiary interactions form in two distinct steps with local tertiary contacts forming an order of magnitude faster than long-range interactions. Rate-determining tertiary folding requires minutes despite that no non-native interactions must be disrupted to form the native structure. Instead, overall folding is limited by simultaneous formation of interactions approximately 55 A distant in the RNA. Time-resolved SHAPE holds broad potential for understanding structural biogenesis and the conformational interconversions essential to the functions of complex RNA molecules at single nucleotide resolution.

  9. Time Resolved Deposition Measurements in NSTX

    SciTech Connect

    C.H. Skinner; H. Kugel; A.L. Roquemore; J. Hogan; W.R. Wampler; the NSTX team

    2004-08-03

    Time-resolved measurements of deposition in current tokamaks are crucial to gain a predictive understanding of deposition with a view to mitigating tritium retention and deposition on diagnostic mirrors expected in next-step devices. Two quartz crystal microbalances have been installed on NSTX at a location 0.77m outside the last closed flux surface. This configuration mimics a typical diagnostic window or mirror. The deposits were analyzed ex-situ and found to be dominantly carbon, oxygen, and deuterium. A rear facing quartz crystal recorded deposition of lower sticking probability molecules at 10% of the rate of the front facing one. Time resolved measurements over a 4-week period with 497 discharges, recorded 29.2 {micro}g/cm{sup 2} of deposition, however surprisingly, 15.9 {micro}g/cm{sup 2} of material loss occurred at 7 discharges. The net deposited mass of 13.3 {micro}g/cm{sup 2} matched the mass of 13.5 {micro}g/cm{sup 2} measured independently by ion beam analysis. Monte Carlo modeling suggests that transient processes are likely to dominate the deposition.

  10. Sequential and Coupled Proton and Electron Transfer Events in the S2 → S3 Transition of Photosynthetic Water Oxidation Revealed by Time-Resolved X-ray Absorption Spectroscopy.

    PubMed

    Zaharieva, Ivelina; Dau, Holger; Haumann, Michael

    2016-12-20

    The choreography of electron transfer (ET) and proton transfer (PT) in the S-state cycle at the manganese-calcium (Mn4Ca) complex of photosystem II (PSII) is pivotal for the mechanism of photosynthetic water oxidation. Time-resolved room-temperature X-ray absorption spectroscopy (XAS) at the Mn K-edge was employed to determine the kinetic isotope effect (KIE = τD2O/τH2O) of the four S transitions in a PSII membrane particle preparation in H2O and D2O buffers. We found a small KIE (1.2-1.4) for manganese oxidation by ET from Mn4Ca to the tyrosine radical (YZ(•+)) in the S0(n) → S1(+) and S1(n) → S2(+) transitions and for manganese reduction by ET from substrate water to manganese ions in the O2-evolving S3(n) → S0(n) step, but a larger KIE (∼1.8) for manganese oxidation in the S2(n) → S3(+) step (subscript, number of accumulated oxidizing equivalents; superscript, charge of Mn4Ca). Kinetic lag phases detected in the XAS transients prior to the respective ET steps were assigned to S3(+) → S3(n) (∼150 μs, H2O; ∼380 μs, D2O) and S2(+) → S2(n) (∼25 μs, H2O; ∼120 μs, D2O) steps and attributed to PT events according to their comparatively large KIE (∼2.4, ∼4.5). Our results suggest that proton movements and molecular rearrangements within the hydrogen-bonded network involving Mn4Ca and its bound (substrate) water ligands and the surrounding amino acid/water matrix govern to different extents the rates of all ET steps but affect particularly strongly the S2(n) → S3(+) transition, assigned as proton-coupled electron transfer. Observation of a lag phase in the classical S2 → S3 transition verifies that the associated PT is a prerequisite for subsequent ET, which completes Mn4Ca oxidation to the all-Mn(IV) level.

  11. In situ structure of trypanosomal ATP synthase dimer reveals a unique arrangement of catalytic subunits

    PubMed Central

    Mühleip, Alexander W.; Dewar, Caroline E.; Schnaufer, Achim; Kühlbrandt, Werner; Davies, Karen M.

    2017-01-01

    We used electron cryotomography and subtomogram averaging to determine the in situ structures of mitochondrial ATP synthase dimers from two organisms belonging to the phylum euglenozoa: Trypanosoma brucei, a lethal human parasite, and Euglena gracilis, a photosynthetic protist. At a resolution of 32.5 Å and 27.5 Å, respectively, the two structures clearly exhibit a noncanonical F1 head, in which the catalytic (αβ)3 assembly forms a triangular pyramid rather than the pseudo-sixfold ring arrangement typical of all other ATP synthases investigated so far. Fitting of known X-ray structures reveals that this unusual geometry results from a phylum-specific cleavage of the α subunit, in which the C-terminal αC fragments are displaced by ∼20 Å and rotated by ∼30° from their expected positions. In this location, the αC fragment is unable to form the conserved catalytic interface that was thought to be essential for ATP synthesis, and cannot convert γ-subunit rotation into the conformational changes implicit in rotary catalysis. The new arrangement of catalytic subunits suggests that the mechanism of ATP generation by rotary ATPases is less strictly conserved than has been generally assumed. The ATP synthases of these organisms present a unique model system for discerning the individual contributions of the α and β subunits to the fundamental process of ATP synthesis. PMID:28096380

  12. Submicroscopic deletions at the WAGR locus, revealed by nonradioactive in situ hybridization

    SciTech Connect

    Fantes, J.A.; Bickmore, W.A.; Fletcher, J.M.; Hanson, I.M.; Heyningen, V. van ); Ballesta, F. )

    1992-12-01

    Fluorescence in situ hybridization (FISH) with biotin-labeled probes mapping to 11p13 has been used for the molecular analysis of deletions of the WAGR (Wilms tumor, aniridia, genitourinary abnormalities, and mental retardation) locus. They have detected a submicroscopic 11p13 deletion in a child with inherited aniridia who subsequently presented with Wilms tumor in a horseshoe kidney, only revealed at surgery. The mother, who has aniridia, was also found to carry a deletion including both the aniridia candidate gene (AN2) and the Wilms tumor predisposition gene (WT1). This is therefore a rare case of an inherited WAGR deletion. Wilms tumor has so far only been associated with sporadic de novo aniridia cases. The authors have shown that a cosmid probe for a candidate aniridia gene, homologous to the mouse Pax-6 gene, is deleted in cell lines from aniridia patients with previously characterized deletions at 11p13, while another cosmid marker mapping between two aniridia-associated translocation breakpoints (and hence a second candidate marker) is present on both chromosomes. These results support the Pax-6 homologue as a strong candidate for the AN2 gene. FISH with cosmid probes has proved to be a fast and reliable technique for the molecular analysis of deletions. It can be used with limited amounts of material and has strong potential for clinical applications. 41 refs., 1 figs., 3 tabs.

  13. In situ structure of trypanosomal ATP synthase dimer reveals a unique arrangement of catalytic subunits.

    PubMed

    Mühleip, Alexander W; Dewar, Caroline E; Schnaufer, Achim; Kühlbrandt, Werner; Davies, Karen M

    2017-01-31

    We used electron cryotomography and subtomogram averaging to determine the in situ structures of mitochondrial ATP synthase dimers from two organisms belonging to the phylum euglenozoa: Trypanosoma brucei, a lethal human parasite, and Euglena gracilis, a photosynthetic protist. At a resolution of 32.5 Å and 27.5 Å, respectively, the two structures clearly exhibit a noncanonical F1 head, in which the catalytic (αβ)3 assembly forms a triangular pyramid rather than the pseudo-sixfold ring arrangement typical of all other ATP synthases investigated so far. Fitting of known X-ray structures reveals that this unusual geometry results from a phylum-specific cleavage of the α subunit, in which the C-terminal αC fragments are displaced by ∼20 Å and rotated by ∼30° from their expected positions. In this location, the αC fragment is unable to form the conserved catalytic interface that was thought to be essential for ATP synthesis, and cannot convert γ-subunit rotation into the conformational changes implicit in rotary catalysis. The new arrangement of catalytic subunits suggests that the mechanism of ATP generation by rotary ATPases is less strictly conserved than has been generally assumed. The ATP synthases of these organisms present a unique model system for discerning the individual contributions of the α and β subunits to the fundamental process of ATP synthesis.

  14. Time-Resolved Conformational Dynamics in Hydrocarbon Chains

    SciTech Connect

    Minitti, Michael P.; Weber, Peter M.

    2007-06-22

    Internal rotation about carbon-carbon bonds allows N,N-dimethyl-2-butanamine (DM2BA) and N,N-dimethyl-3-hexanamine (DM3HA) to assume multiple conformeric structures. We explore the equilibrium composition and dynamics between such conformeric structures using Rydberg fingerprint spectroscopy. Time constants for conformeric interconversion of DM2BA (at 1.79 eV of internal energy) are 19 and 66 ps, and for DM3HA (1.78 eV) 23 and 41 ps. For the first time, a time-resolved and quantitative view of conformational dynamics of flexible hydrocarbon molecules at high temperatures is revealed.

  15. Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Kang, Zhitao; Banishev, Alexandr A.; Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Xiao, Pan; Christensen, James; Zhou, Min; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.

    2016-07-01

    The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

  16. Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

    DOE PAGES

    Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; ...

    2015-09-21

    Ruddlesden-Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2), and LaSr3Co1.5Fe1.5O10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10-1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7-δ > LaSr3Co1.5Fe1.5O10-δmore » > LaSrCo0.5Fe0.5O4-δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.« less

  17. Time-Resolved Measurements of Carbon Nanotube and Nanohorn Growth

    NASA Astrophysics Data System (ADS)

    Geohegan, David

    2005-11-01

    Mechanisms for carbon nanotube growth have been investigated for both laser vaporization (LV) and chemical vapor deposition (CVD) synthesis techniques through the use of time-resolved, in situ laser-based diagnostics for the measurement of absolute growth rates. Optimization of both the production of loose single-wall carbon nanotubes (SWNTs) by LV and the sustained growth of mm-long, vertically-aligned carbon nanotube arrays (VANTAs) by CVD are described. For SWNT growth by laser co-vaporization of carbon and trace metal catalysts at high (1200 C) temperatures, nanotubes are found to grow at ˜ 1--5 microns/second to lengths of only several microns, as determined by gated-ICCD imaging and laser spectroscopy of the plume of ejected material. Efforts to scale the LV production of SWNTs utilizing an industrial Nd:YAG laser (600 W average power, 1-500 Hz repetition rate, 0.5-10ms pulse width) are described. In addition to vaporizing material at much higher rates, the high-power laser irradiation provides sufficient plasma plume density and temperature to enable the growth of novel single-wall carbon nanohorn (SWNH) structures without the need for metal catalysts in the target. Applications of these SWNH structures as metal catalyst supports will be discussed. Through the application of time-resolved reflectivity and direct imaging, CVD growth of VANTAs from hydrocarbon gases at sustained rates of 0.2 -- 0.5 microns/second have been directly measured over millimeters of length at lower (˜ 700 C) temperatures. Now, through a new laser-CVD setup at the ALPS (Advanced Laser Processing and Synthesis) facility at ORNL, high-power laser heating is being employed for the fast and position-controlled growth of carbon nanotubes on substrates. In situ fast optical pyrometry is employed to record the rapid thermal processing of metal-catalyst-prepared substrates to investigate the nucleation and early growth behavior of CVD-grown nanotubes. New nanotube growth and tunable Raman

  18. Time resolved ion beam induced charge collection

    SciTech Connect

    SEXTON,FREDERICK W.; WALSH,DAVID S.; DOYLE,BARNEY L.; DODD,PAUL E.

    2000-04-01

    Under this effort, a new method for studying the single event upset (SEU) in microelectronics has been developed and demonstrated. Called TRIBICC, for Time Resolved Ion Beam Induced Charge Collection, this technique measures the transient charge-collection waveform from a single heavy-ion strike with a {minus}.03db bandwidth of 5 GHz. Bandwidth can be expanded up to 15 GHz (with 5 ps sampling windows) by using an FFT-based off-line waveform renormalization technique developed at Sandia. The theoretical time resolution of the digitized waveform is 24 ps with data re-normalization and 70 ps without re-normalization. To preserve the high bandwidth from IC to the digitizing oscilloscope, individual test structures are assembled in custom high-frequency fixtures. A leading-edge digitized waveform is stored with the corresponding ion beam position at each point in a two-dimensional raster scan. The resulting data cube contains a spatial charge distribution map of up to 4,096 traces of charge (Q) collected as a function of time. These two dimensional traces of Q(t) can cover a period as short as 5 ns with up to 1,024 points per trace. This tool overcomes limitations observed in previous multi-shot techniques due to the displacement damage effects of multiple ion strikes that changed the signal of interest during its measurement. This system is the first demonstration of a single-ion transient measurement capability coupled with spatial mapping of fast transients.

  19. Time-resolved Temperature Measurements in SSPX

    SciTech Connect

    Ludington, A R; Hill, D N; McLean, H S; Moller, J; Wood, R D

    2006-08-14

    We seek to measure time-resolved electron temperatures in the SSPX plasma using soft X-rays from free-free Bremsstrahlung radiation. To increase sensitivity to changes in temperature over the range 100-300 eV, we use two photodiode detectors sensitive to different soft X-ray energies. The detectors, one with a Zr/C coating and the other with a Ti/Pd coating, view the plasma along a common line of sight tangential to the magnetic axis of the spheromak, where the electron temperature is a maximum. The comparison of the signals, over a similar volume of plasma, should be a stronger function of temperature than a single detector in the range of Te< 300 eV. The success of using photodiodes to detect changing temperatures along a chord will make the case for designing an array of the detectors, which could provide a time changing temperature profile over a larger portion of the plasma.

  20. Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

    SciTech Connect

    Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; McIntosh, Steven

    2015-09-21

    Ruddlesden-Popper structured oxides, general form An+1BnO3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2), and LaSr3Co1.5Fe1.5O10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO2 of 10-1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, and were found to have increased total oxygen vacancy concentration in the order La0.3Sr2.7CoFeO7-δ > LaSr3Co1.5Fe1.5O10-δ > LaSrCo0.5Fe0.5O4-δ, following the trend predicted for charge compensation upon increasing Sr2+/La3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.

  1. Time resolved strain dependent morphological study of electrically conducting nanocomposites

    NASA Astrophysics Data System (ADS)

    Khan, Imran; Mitchell, Geoffrey; Mateus, Artur; Kamma-Lorger, Christina S.

    2015-10-01

    An efficient and reliable method is introduced to understand the network behaviour of nano-fillers in a polymeric matrix under uniaxial strain coupled with small angle x-ray scattering measurements. The nanoparticles (carbon nanotubes) are conductive and the particles form a percolating network that becomes apparent source of electrical conduction and consequently the samples behave as a bulk conductor. Polyurethane based nanocomposites containing 2% w/w multiwall carbon nanotubes are studied. The electrical conductivity of the nanocomposite was (3.28×10-5s/m).The sample was able to be extended to an extension ratio of 1.7 before fracture. A slight variation in the electrical conductivity is observed under uniaxial strain which we attribute to the disturbance of conductive pathways. Further, this work is coupled with in- situ time resolved small angle x-ray scattering measurements using a synchrotron beam line to enable its measurements to be made during the deformation cycle. We use a multiscale structure to model the small angle x-ray data. The results of the analysis are interpreted as the presence of aggregates which would also go some way towards understanding why there is no alignment of the carbon nanotubes.

  2. Time Resolved FTIR Analysis of Combustion of Ethanol and Gasoline Combustion in AN Internal Combustion Engine

    NASA Astrophysics Data System (ADS)

    White, Allen R.; Sakai, Stephen; Devasher, Rebecca B.

    2011-06-01

    In order to pursue In Situ measurements in an internal combustion engine, a MegaTech Mark III transparent spark ignition engine was modified with a sapphire combustion chamber. This modification will allow the transmission of infrared radiation for time-resolved spectroscopic measurements by an infrared spectrometer. By using a Step-scan equipped Fourier transform spectrometer, temporally resolved infrared spectral data were acquired and compared for combustion in the modified Mark III engine. Measurements performed with the FTIR system provide insight into the energy transfer vectors that precede combustion and also provides an in situ measurement of the progress of combustion. Measurements were performed using ethanol and gasoline.

  3. CCD time-resolved photometry of faint cataclysmic variables. II

    SciTech Connect

    Szkody, P.; Howell, S.B.; Mateo, M.; Kreidl, T.J. Planetary Science Institute, Tucson, AZ Mount Wilson and Las Campanas Observatories, Pasadena, CA Lowell Observatory, Flagstaff, AZ )

    1989-10-01

    Time-resolved optical broad-band light curves obtained from differential photometry on sequential CCD frames of the known or suspected cataclysmic variable FO And, EH Aqr, WX Cet, XX Cet, AL Com, V503 Cyg, AH Eri, CP Eri, IR Gem, RW UMi, PG0134+070, and US 3215 are presented. The analysis of the light curves with coverage of greater than 2 hrs shows repeatable periodicity in five objects. PG0134+070 exhibits eclipses of 1.3-1.8 mag depth with a period of 313 min. V503 Cyg has a 0.7-1.0 mag peak-to-peak modulation with a period of 109 min. IR Gem shows a large modulation at the orbital period of 99 min, and comparison with previous data indicates that this modulation may have an amplitude dependent on outburst phase. AH Eri reveals a 0.1-0.3 mag modulation, at a period of 42 min. Better time-resolved data on AL Com confirm the 0.4-mag variation reported by Howell and Szkody (1988) at a period of 42 min. These latter two short periods likely indicate magnetic systems. There is also some evidence of periodicity in RW UMi and WX Cet which must be confirmed with further data. 25 refs.

  4. Formulation for Time-resolved Aerodynamic Damping in Dynamic Stall

    NASA Astrophysics Data System (ADS)

    Corke, Thomas; Bowles, Patrick; Coleman, Dusty; Thomas, Flint

    2012-11-01

    A new Hilbert transform formulation of the equation of motion for a pitching airfoil in a uniform stream yields a time resolved aerodynamic damping factor, Ξ (t) = (√{ (Cm2 (t) +C m2 } /αmax) sinψ (t) , where Cm (t) is the instantaneous pitch moment coefficient, and C m (t) is the Hilbert transform of Cm (t) , αmax is the pitching amplitude, and ψ (t) is the time-resolved phase difference between the aerodynamic pitch moment and the instantaneous angle of attack. A Ξ (t) < 0 indicates unstable pressure loading that can be considered a necessary condition to excite stall flutter in an elastic airfoil. This will be illustrated in experiments with conditions producing ``light'' dynamic stall for a range of Mach numbers from 0.3-0.6. These reveal large negative excursions of Ξ (t) during the pitch-up portion of the cycle that correlates with the formation and convection of the dynamic stall vortex. The fact that the cycle-integrated damping coefficient is positive in all these cases underscores how the traditional diagnostic masks much of the physics that underlies the destabilizing effect of the dynamic stall process. This new insight can explain instances of transient limit-cycle growth of helicopter rotor vibrations. Supported by Bell Helicopter.

  5. Portable optical oxygen sensor based on time-resolved fluorescence.

    PubMed

    Chu, Cheng-Shane; Chu, Ssu-Wei

    2014-11-10

    A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The ratio τ0100 measures sensitivity of the sensing film, where τ0 and τ100 represent the detected fluorescence lifetimes from the sensing film exposed to 100% nitrogen and 100% oxygen, respectively. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0%-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors.

  6. Insights into reaction mechanisms in heterogeneous catalysis revealed by in situ NMR spectroscopy.

    PubMed

    Blasco, Teresa

    2010-12-01

    This tutorial review intends to show the possibilities of in situ solid state NMR spectroscopy in the elucidation of reaction mechanisms and the nature of the active sites in heterogeneous catalysis. After a brief overview of the more usual experimental devices used for in situ solid state NMR spectroscopy measurements, some examples of applications taken from the recent literature will be presented. It will be shown that in situ NMR spectroscopy allows: (i) the identification of stable intermediates and transient species using indirect methods, (ii) to prove shape selectivity in zeolites, (iii) the study of reaction kinetics, and (iv) the determination of the nature and the role played by the active sites in a catalytic reaction. The approaches and methodology used to get this information will be illustrated here summarizing the most relevant contributions on the investigation of the mechanisms of a series of reactions of industrial interest: aromatization of alkanes on bifunctional catalysts, carbonylation reaction of methanol with carbon monoxide, ethylbenzene disproportionation, and the Beckmann rearrangement reaction. Special attention is paid to the research carried out on the role played by carbenium ions and alkoxy as intermediate species in the transformation of hydrocarbon molecules on solid acid catalysts.

  7. Epithelial cells captured from ductal carcinoma in situ reveal a gene expression signature associated with progression to invasive breast cancer

    PubMed Central

    Abuázar, Carolina Sens; de Toledo Osorio, Cynthia Aparecida Bueno; Pinilla, Mabel Gigliola; da Silva, Sabrina Daniela; Camargo, Anamaria Aranha; Silva, Wilson Araujo; e Ferreira, Elisa Napolitano; Brentani, Helena Paula; Carraro, Dirce Maria

    2016-01-01

    Breast cancer biomarkers that can precisely predict the risk of progression of non-invasive ductal carcinoma in situ (DCIS) lesions to invasive disease are lacking. The identification of molecular alterations that occur during the invasion process is crucial for the discovery of drivers of transition to invasive disease and, consequently, biomarkers with clinical utility. In this study, we explored differences in gene expression in mammary epithelial cells before and after the morphological manifestation of invasion, i.e., early and late stages, respectively. In the early stage, epithelial cells were captured from both pre-invasive lesions with distinct malignant potential [pure DCIS as well as the in situ component that co-exists with invasive breast carcinoma lesions (DCIS-IBC)]; in the late stage, epithelial cells were captured from the two distinct morphological components of the same sample (in situ and invasive components). Candidate genes were identified using cDNA microarray and rapid subtractive hybridization (RaSH) cDNA libraries and validated by RT-qPCR assay using new samples from each group. These analyses revealed 26 genes, including 20 from the early and 6 from the late stage. The expression profile based on the 20 genes, marked by a preferential decrease in expression level towards invasive phenotype, discriminated the majority of DCIS samples. Thus, this study revealed a gene expression signature with the potential to predict DCIS progression and, consequently, provides opportunities to tailor treatments for DCIS patients. PMID:27708222

  8. Time-resolved spin-dependent processes in magnetic field effects in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Peng, Qiming; Li, Xianjie; Li, Feng

    2012-12-01

    We investigated the time-resolved magnetic field effects (MFEs) in tri-(8-hydroxyquinoline)-aluminum (Alq3) based organic light-emitting diodes (OLEDs) through the transient electroluminescence (EL) method. The values of magneto-electroluminescence (MEL) decrease with the time, and the decreasing slope is proportional to the driving voltage. Specifically, negative MELs are seen when the driving voltage is high enough (V > 11 V). We propose a model to elucidate the spin-dependent processes and theoretically simulate the time-resolved MELs. In particular, this dynamic analysis of time-resolved MELs reveals that the intersystem crossing between singlet and triplet electron-hole pairs and the triplet-triplet annihilation are responsible for the time-resolved MELs at the beginning and enduring periods of the pulse, respectively.

  9. Photosensing performance of branched CdS/ZnO heterostructures as revealed by in situ TEM and photodetector tests.

    PubMed

    Zhang, Chao; Tian, Wei; Xu, Zhi; Wang, Xi; Liu, Jiangwei; Li, Song-Lin; Tang, Dai-Ming; Liu, Dequan; Liao, Meiyong; Bando, Yoshio; Golberg, Dmitri

    2014-07-21

    CdS/ZnO branched heterostructures have been successfully synthesized by combining thermal vapour deposition and a hydrothermal method. Drastic optoelectronic performance enhancement of such heterostructures was revealed, compared to plain CdS nanobelts, as documented by comparative in situ optoelectronic studies on corresponding individual nanostructures using an originally designed laser-compatible transmission electron microscopy (TEM) technique. Furthermore, flexible thin-film based photodetectors based on standard CdS nanobelts and newly prepared CdS/ZnO heterostructures were fabricated on PET substrates, and comparative photocurrent and photo-responsivity measurements thoroughly verified the in situ TEM results. The CdS/ZnO branched heterostructures were found to have better performance than standard CdS nanobelts for optoelectronic applications with respect to the photocurrent to dark current ratio and responsivity.

  10. In situ X-ray diffraction monitoring of a mechanochemical reaction reveals a unique topology metal-organic framework

    NASA Astrophysics Data System (ADS)

    Katsenis, Athanassios D.; Puškarić, Andreas; Štrukil, Vjekoslav; Mottillo, Cristina; Julien, Patrick A.; Užarević, Krunoslav; Pham, Minh-Hao; Do, Trong-On; Kimber, Simon A. J.; Lazić, Predrag; Magdysyuk, Oxana; Dinnebier, Robert E.; Halasz, Ivan; Friščić, Tomislav

    2015-03-01

    Chemical and physical transformations by milling are attracting enormous interest for their ability to access new materials and clean reactivity, and are central to a number of core industries, from mineral processing to pharmaceutical manufacturing. While continuous mechanical stress during milling is thought to create an environment supporting nonconventional reactivity and exotic intermediates, such speculations have remained without proof. Here we use in situ, real-time powder X-ray diffraction monitoring to discover and capture a metastable, novel-topology intermediate of a mechanochemical transformation. Monitoring the mechanochemical synthesis of an archetypal metal-organic framework ZIF-8 by in situ powder X-ray diffraction reveals unexpected amorphization, and on further milling recrystallization into a non-porous material via a metastable intermediate based on a previously unreported topology, herein named katsenite (kat). The discovery of this phase and topology provides direct evidence that milling transformations can involve short-lived, structurally unusual phases not yet accessed by conventional chemistry.

  11. The origin of molecular mobility during biomass pyrolysis as revealed by in situ (1)H NMR spectroscopy.

    PubMed

    Dufour, Anthony; Castro-Diaz, Miguel; Brosse, Nicolas; Bouroukba, Mohamed; Snape, Colin

    2012-07-01

    The thermochemical conversion of lignocellulosic biomass feedstocks offers an important potential route for the production of biofuels and value-added green chemicals. Pyrolysis is the first phenomenon involved in all biomass thermochemical processes and it controls to a major extent the product composition. The composition of pyrolysis products can be affected markedly by the extent of softening that occurs. In spite of extensive work on biomass pyrolysis, the development of fluidity during the pyrolysis of biomass has not been quantified. This paper provides the first experimental investigation of proton mobility during biomass pyrolysis by in situ (1)H NMR spectroscopy. The origin of mobility is discussed for cellulose, lignin and xylan. The effect of minerals on cellulose mobility is also investigated. Interactions between polymers in the native biomass network are revealed by in situ (1)H NMR analysis.

  12. Photosensing performance of branched CdS/ZnO heterostructures as revealed by in situ TEM and photodetector tests

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Tian, Wei; Xu, Zhi; Wang, Xi; Liu, Jiangwei; Li, Song-Lin; Tang, Dai-Ming; Liu, Dequan; Liao, Meiyong; Bando, Yoshio; Golberg, Dmitri

    2014-06-01

    CdS/ZnO branched heterostructures have been successfully synthesized by combining thermal vapour deposition and a hydrothermal method. Drastic optoelectronic performance enhancement of such heterostructures was revealed, compared to plain CdS nanobelts, as documented by comparative in situ optoelectronic studies on corresponding individual nanostructures using an originally designed laser-compatible transmission electron microscopy (TEM) technique. Furthermore, flexible thin-film based photodetectors based on standard CdS nanobelts and newly prepared CdS/ZnO heterostructures were fabricated on PET substrates, and comparative photocurrent and photo-responsivity measurements thoroughly verified the in situ TEM results. The CdS/ZnO branched heterostructures were found to have better performance than standard CdS nanobelts for optoelectronic applications with respect to the photocurrent to dark current ratio and responsivity.CdS/ZnO branched heterostructures have been successfully synthesized by combining thermal vapour deposition and a hydrothermal method. Drastic optoelectronic performance enhancement of such heterostructures was revealed, compared to plain CdS nanobelts, as documented by comparative in situ optoelectronic studies on corresponding individual nanostructures using an originally designed laser-compatible transmission electron microscopy (TEM) technique. Furthermore, flexible thin-film based photodetectors based on standard CdS nanobelts and newly prepared CdS/ZnO heterostructures were fabricated on PET substrates, and comparative photocurrent and photo-responsivity measurements thoroughly verified the in situ TEM results. The CdS/ZnO branched heterostructures were found to have better performance than standard CdS nanobelts for optoelectronic applications with respect to the photocurrent to dark current ratio and responsivity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00963k

  13. Millifluidics for time-resolved mapping of the growth of gold nanostructures

    SciTech Connect

    Sai Krishna, Katla; Navin, Chelliah; Biswas, Sanchita; Singh, Varshni; Ham, Kyungmin; Bovencamp, L. S.; Theegala, Chandra; Miller, Jeffrey T; Spivey, James J.; Kumar, Challa S.S.R.

    2013-04-10

    Innovative in situ characterization tools are essential for understanding the reaction mechanisms leading to the growth of nanoscale materials. Though techniques, such as in situ transmission X-ray microscopy, fast single-particle spectroscopy, small-angle X-ray scattering, etc., are currently being developed, these tools are complex, not easily accessible, and do not necessarily provide the temporal resolution required to follow the formation of nanomaterials in real time. Here, we demonstrate for the first time the utility of a simple millifluidic chip for an in situ real time analysis of morphology and dimension-controlled growth of gold nano- and microstructures with a time resolution of 5 ms. The structures formed were characterized using synchrotron radiation-based in situ X-ray absorption spectroscopy, 3-D X-ray tomography, and high-resolution electron microscopy. These gold nanostructures were found to be catalytically active for conversion of 4-nitrophenol into 4-aminophenol, providing an example of the potential opportunities for time-resolved analysis of catalytic reactions. While the investigations reported here are focused on gold nanostructures, the technique can be applied to analyze the time-resolved growth of other types of nanostructured metals and metal oxides. With the ability to probe at least a 10-fold higher concentrations, in comparison with traditional microfluidics, the tool has potential to revolutionize a broad range of fields from catalysis, molecular analysis, biodefense, and molecular biology.

  14. Patterns of gene expression in the murine brain revealed by in situ hybridization of brain-specific mRNAs.

    PubMed

    Branks, P L; Wilson, M C

    1986-07-01

    Biochemical differences between neuronal cell populations of the mammalian brain, including selection of neurotransmitters and distinct neural antigens, suggest that the regulation of gene expression plays an important role in defining brain function. Here we describe the use of in situ hybridization to identify cDNA clones of highly regulated mRNA species and to define directly their pattern of gene expression in brain at both gross morphological and cellular levels. One of the selected cDNA clones, pMuBr2, detected a single 3.0 kb mRNA species, which from in situ hybridization appears specific to oligodendroglia cells. Three other cDNA clones, pMuBr3, 8 and 85, identified polyadenylated mRNA transcripts expressed by neuronal cells of the murine brain. Viewed at the gross morphological level, the mRNAs hybridizing to these cDNA sequences exhibit different patterns of abundance distinguishing such brain structures as pons, anterior thalamus, hippocampus, basal ganglia and anterior lobe of the neuroendocrine pituitary gland. At the cellular level, in situ hybridization revealed that these mRNAs are differentially expressed by morphologically and functionally distinct neurons of the cerebellum and hippocampal formation. When examined in the context of known brain function, however, the regulated expression of the neuron-specific mRNAs does not correlate simply with known cellular morphology or previously demonstrated neuronal relationships suggesting novel patterns of gene expression which may contribute to brain function.

  15. In Situ X-Ray Probing Reveals Fingerprints of Surface Platinum Oxide

    SciTech Connect

    Friebel, Daniel

    2011-08-24

    In situ x-ray absorption spectroscopy (XAS) at the Pt L{sub 3} edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard x-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF8 code and complementary extended x-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.

  16. Tribology. Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts.

    PubMed

    Gosvami, N N; Bares, J A; Mangolini, F; Konicek, A R; Yablon, D G; Carpick, R W

    2015-04-03

    Zinc dialkyldithiophosphates (ZDDPs) form antiwear tribofilms at sliding interfaces and are widely used as additives in automotive lubricants. The mechanisms governing the tribofilm growth are not well understood, which limits the development of replacements that offer better performance and are less likely to degrade automobile catalytic converters over time. Using atomic force microscopy in ZDDP-containing lubricant base stock at elevated temperatures, we monitored the growth and properties of the tribofilms in situ in well-defined single-asperity sliding nanocontacts. Surface-based nucleation, growth, and thickness saturation of patchy tribofilms were observed. The growth rate increased exponentially with either applied compressive stress or temperature, consistent with a thermally activated, stress-assisted reaction rate model. Although some models rely on the presence of iron to catalyze tribofilm growth, the films grew regardless of the presence of iron on either the tip or substrate, highlighting the critical role of stress and thermal activation.

  17. In Situ Tagged nsp15 Reveals Interactions with Coronavirus Replication/Transcription Complex-Associated Proteins

    PubMed Central

    Athmer, Jeremiah; Fehr, Anthony R.; Grunewald, Matthew; Smith, Everett Clinton; Denison, Mark R.

    2017-01-01

    ABSTRACT Coronavirus (CoV) replication and transcription are carried out in close proximity to restructured endoplasmic reticulum (ER) membranes in replication/transcription complexes (RTC). Many of the CoV nonstructural proteins (nsps) are required for RTC function; however, not all of their functions are known. nsp15 contains an endoribonuclease domain that is conserved in the CoV family. While the enzymatic activity and crystal structure of nsp15 are well defined, its role in replication remains elusive. nsp15 localizes to sites of RNA replication, but whether it acts independently or requires additional interactions for its function remains unknown. To begin to address these questions, we created an in situ tagged form of nsp15 using the prototypic CoV, mouse hepatitis virus (MHV). In MHV, nsp15 contains the genomic RNA packaging signal (P/S), a 95-bp RNA stem-loop structure that is not required for viral replication or nsp15 function. Utilizing this knowledge, we constructed an internal hemagglutinin (HA) tag that replaced the P/S. We found that nsp15-HA was localized to discrete perinuclear puncta and strongly colocalized with nsp8 and nsp12, both well-defined members of the RTC, but not the membrane (M) protein, involved in virus assembly. Finally, we found that nsp15 interacted with RTC-associated proteins nsp8 and nsp12 during infection, and this interaction was RNA independent. From this, we conclude that nsp15 localizes and interacts with CoV proteins in the RTC, suggesting it plays a direct or indirect role in virus replication. Furthermore, the use of in situ epitope tags could be used to determine novel nsp-nsp interactions in coronaviruses. PMID:28143984

  18. Laser capture microdissection reveals dose-response of gene expression in situ consequent to asbestos exposure.

    PubMed

    Yin, Qi; Brody, Arnold R; Sullivan, Deborah E

    2007-12-01

    The genes that mediate fibroproliferative lung disease remain to be defined. Prior studies from our laboratory showed by in situ hybridization and immunohistochemistry that the genes coding for tumour necrosis factor alpha, transforming growth factor beta, the platelet-derived growth factor A and B isoforms, and alpha-1 pro-collagen are expressed in fibroproliferative lesions that develop quickly after asbestos inhalation. These five genes, along with matrix metalloproteinase 9, a collagenase found to be increased in several lung diseases, are known to control matrix production and cell proliferation in humans and animals. Here we show by laser capture microdissection that (i) The six genes are expressed at significantly higher levels in the asbestos-exposed mice when comparing the same anatomic regions 'captured' in unexposed mice. (ii) The bronchiolar-alveolar duct (BAD) junctions, where the greatest number of fibres initially deposit, were always significantly higher than the other anatomic regions for each gene. The first alveolar duct bifurcation (ADB) generally was higher than the second ADB, the ADBs were always significantly higher than the airway walls and pleura, and the airway walls and pleura were generally higher than the unexposed tissues. (iii) Animals exposed for 3 days always exhibited significantly higher levels of gene expression at the BAD junctions and ADBs than animals exposed for 2 days. To our knowledge, this is the first demonstration of a dose-response to a toxic particle in situ, and this response appears to be dependent on the number of fibres that deposits at the individual anatomic site.

  19. Ultrafast time-resolved vibrational spectroscopies of carotenoids in photosynthesis.

    PubMed

    Hashimoto, Hideki; Sugisaki, Mitsuru; Yoshizawa, Masayuki

    2015-01-01

    This review discusses the application of time-resolved vibrational spectroscopies to the studies of carotenoids in photosynthesis. The focus is on the ultrafast time regime and the study of photophysics and photochemistry of carotenoids by femtosecond time-resolved stimulated Raman and four-wave mixing spectroscopies. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

  20. Time-resolved pulsed EPR: microwave and optical detection

    SciTech Connect

    Trifunac, A.D.; Smith, J.P.

    1981-01-01

    Time-resolved pulsed EPR spectrometers are described. EPR spectra, kinetic profiles, and relaxation studies are used to illustrate some capabilities of the pulsed EPR experiment. Optical detection of time-resolved EPR spectra of radical ion pairs is used to study radical-ion recombination kinetics, recombination pathways, and the structure of radical anions and cations. 17 figures.

  1. Excitation emission and time-resolved fluorescence spectroscopy of selected varnishes used in historical musical instruments.

    PubMed

    Nevin, Austin; Echard, Jean-Philippe; Thoury, Mathieu; Comelli, Daniela; Valentini, Gianluca; Cubeddu, Rinaldo

    2009-11-15

    The analysis of various varnishes from different origins, which are commonly found on historical musical instruments was carried out for the first time with both fluorescence excitation emission spectroscopy and laser-induced time-resolved fluorescence spectroscopy. Samples studied include varnishes prepared using shellac, and selected diterpenoid and triterpenoid resins from plants, and mixtures of these materials. Fluorescence excitation emission spectra have been collected from films of naturally aged varnishes. In parallel, time-resolved fluorescence spectroscopy of varnishes provides means for discriminating between short- (less than 2.0 ns) and long-lived (greater than 7.5 ns) fluorescence emissions in each of these complex materials. Results suggest that complementary use of the two non destructive techniques allows a better understanding of the main fluorophores responsible for the emission in shellac, and further provides means for distinguishing the main classes of other varnishes based on differences in fluorescence lifetime behaviour. Spectrofluorimetric data and time resolved spectra presented here may form the basis for the interpretation of results from future in situ fluorescence examination and time resolved fluorescence imaging of varnished musical instruments.

  2. Electron-beam irradiation induced conductivity in ZnS nanowires as revealed by in situ transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Wang, Mingsheng; Zhi, Chunyi; Fang, Xiaosheng; Tang, Chengchun; Mitome, Masanori; Golberg, Dmitri

    2009-08-01

    Electron transport variations in individual ZnS nanowires synthesized through a chemical vapor deposition process were in situ studied in transmission electron microscope under convergent electron-beam irradiation (EBI). It was found that the transport can dramatically be enhanced using proper irradiation conditions. The conductivity mechanism was revealed based on a detailed study of microstructure and composition evolutions under irradiation. EBI-induced Zn-rich domains' appearance and related O doping were mainly responsible for the conductivity improvements. First-principles theoretical calculations additionally indicated that the generation of midbands within a ZnS band gap might also contribute to the improved conductivity.

  3. Attosecond Time-Resolved Autoionization of Argon

    SciTech Connect

    Wang He; Chini, Michael; Chen Shouyuan; Zhang Changhua; Cheng Yan; Wu Yi; Thumm, Uwe; He Feng; Chang Zenghu

    2010-10-01

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p{sup 6}np {sup 1}P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p{sup 6}4p {sup 1}P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  4. Environmental controls of frost cracking revealed through in situ acoustic emission measurements in steep bedrock

    NASA Astrophysics Data System (ADS)

    Girard, Lucas; Gruber, Stephan; Weber, Samuel; Beutel, Jan

    2013-05-01

    Frost cracking, the breakdown of rock by freezing, is one of the most important mechanical weathering processes acting on Earth's surface. Insights on the mechanisms driving frost cracking stem mainly from laboratory and theoretical studies. Transferring insights from such studies to natural conditions, involving jointed bedrock and heterogeneous thermal and hydrological properties, is a major challenge. We address this problem with simultaneous in situ measurements of acoustic emissions, used as proxy of rock damage, and rock temperature/moisture content. The 1 year data set acquired in an Alpine rock wall shows that (1) liquid water content has an important impact on freezing-induced rock damage, (2) sustained freezing can yield much stronger damage than repeated freeze-thaw cycling, and (3) that frost cracking occurs over the full range of temperatures measured extending from 0 down to -15°C. These new measurements yield a slightly different picture than previous field studies where ice segregation appears to play an important role.

  5. Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Fan; Kooyman, Patricia J.; Koper, Marc T. M.

    2016-08-01

    Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of Pt(111) and Pt(100) single crystals in perchloric acid. Density functional theory calculations were carried out to assist in assigning the experimental Raman bands by simulating the vibrational frequencies of possible intermediates and products. The perchlorate anion is suggested to interact with hydroxyl phase formed on the surface. Peroxo-like and superoxo-like two-dimensional (2D) surface oxides and amorphous 3D α-PtO2 are sequentially formed during the anodic polarization. Our measurements elucidate the process of the electrochemical oxidation of platinum single crystals by providing evidence for the structure-sensitive formation of a 2D platinum-(su)peroxide phase. These results may contribute towards a fundamental understanding of the mechanism of degradation of platinum electrocatalysts.

  6. Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

    PubMed Central

    Huang, Yi-Fan; Kooyman, Patricia J.; Koper, Marc T. M.

    2016-01-01

    Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of Pt(111) and Pt(100) single crystals in perchloric acid. Density functional theory calculations were carried out to assist in assigning the experimental Raman bands by simulating the vibrational frequencies of possible intermediates and products. The perchlorate anion is suggested to interact with hydroxyl phase formed on the surface. Peroxo-like and superoxo-like two-dimensional (2D) surface oxides and amorphous 3D α-PtO2 are sequentially formed during the anodic polarization. Our measurements elucidate the process of the electrochemical oxidation of platinum single crystals by providing evidence for the structure-sensitive formation of a 2D platinum-(su)peroxide phase. These results may contribute towards a fundamental understanding of the mechanism of degradation of platinum electrocatalysts. PMID:27514695

  7. In situ imaging reveals the biomass of giant protists in the global ocean.

    PubMed

    Biard, Tristan; Stemmann, Lars; Picheral, Marc; Mayot, Nicolas; Vandromme, Pieter; Hauss, Helena; Gorsky, Gabriel; Guidi, Lionel; Kiko, Rainer; Not, Fabrice

    2016-04-28

    Planktonic organisms play crucial roles in oceanic food webs and global biogeochemical cycles. Most of our knowledge about the ecological impact of large zooplankton stems from research on abundant and robust crustaceans, and in particular copepods. A number of the other organisms that comprise planktonic communities are fragile, and therefore hard to sample and quantify, meaning that their abundances and effects on oceanic ecosystems are poorly understood. Here, using data from a worldwide in situ imaging survey of plankton larger than 600 μm, we show that a substantial part of the biomass of this size fraction consists of giant protists belonging to the Rhizaria, a super-group of mostly fragile unicellular marine organisms that includes the taxa Phaeodaria and Radiolaria (for example, orders Collodaria and Acantharia). Globally, we estimate that rhizarians in the top 200 m of world oceans represent a standing stock of 0.089 Pg carbon, equivalent to 5.2% of the total oceanic biota carbon reservoir. In the vast oligotrophic intertropical open oceans, rhizarian biomass is estimated to be equivalent to that of all other mesozooplankton (plankton in the size range 0.2-20 mm). The photosymbiotic association of many rhizarians with microalgae may be an important factor in explaining their distribution. The previously overlooked importance of these giant protists across the widest ecosystem on the planet changes our understanding of marine planktonic ecosystems.

  8. Proteome-wide analysis reveals an age-associated cellular phenotype of in situ aged human fibroblasts

    PubMed Central

    Waldera-Lupa, Daniel M.; Kalfalah, Faiza; Florea, Ana-Maria; Sass, Steffen; Kruse, Fabian; Rieder, Vera; Tigges, Julia; Fritsche, Ellen; Krutmann, Jean; Busch, Hauke; Boerries, Melanie; Meyer, Helmut E.; Boege, Fritz; Theis, Fabian

    2014-01-01

    We analyzed an ex vivo model of in situ aged human dermal fibroblasts, obtained from 15 adult healthy donors from three different age groups using an unbiased quantitative proteome-wide approach applying label-free mass spectrometry. Thereby, we identified 2409 proteins, including 43 proteins with an age-associated abundance change. Most of the differentially abundant proteins have not been described in the context of fibroblasts’ aging before, but the deduced biological processes confirmed known hallmarks of aging and led to a consistent picture of eight biological categories involved in fibroblast aging, namely proteostasis, cell cycle and proliferation, development and differentiation, cell death, cell organization and cytoskeleton, response to stress, cell communication and signal transduction, as well as RNA metabolism and translation. The exhaustive analysis of protein and mRNA data revealed that 77% of the age-associated proteins were not linked to expression changes of the corresponding transcripts. This is in line with an associated miRNA study and led us to the conclusion that most of the age-associated alterations detected at the proteome level are likely caused post-transcriptionally rather than by differential gene expression. In summary, our findings led to the characterization of novel proteins potentially associated with fibroblast aging and revealed that primary cultures of in situ aged fibroblasts are characterized by moderate age-related proteomic changes comprising the multifactorial process of aging. PMID:25411231

  9. Interactions of arsenic with calcite surfaces revealed by in-situ nanoscale imaging

    NASA Astrophysics Data System (ADS)

    Renard, Francois; Putnis, Christine; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hövelmann, Jörn; Sarret, Géraldine

    2015-04-01

    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in-situ study of calcite dissolution and growth in the presence of solutions with various amounts of As(III) or As(V). This was performed at room temperature and pH range 6-9 using a flow through cell connected to an atomic force microscope (AFM), to study the evolution of the (10-14) calcite cleavage surface morphology. Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  10. Interactions of arsenic with calcite surfaces revealed by in situ nanoscale imaging

    NASA Astrophysics Data System (ADS)

    Renard, François; Putnis, Christine V.; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion; Hovelmann, Jörn; Sarret, Géraldine

    2015-06-01

    Arsenic dissolved in water represents a key environmental and health challenge because several million people are under the threat of contamination. In calcareous environments calcite may play an important role in arsenic solubility and transfer in water. Arsenic-calcite interactions remain controversial, especially for As(III) which was proposed to be either incorporated as such, or as As(V) after oxidation. Here, we provide the first time-lapse in situ study of the evolution of the (10-14) calcite cleavage surface morphology during dissolution and growth in the presence of solutions with various amounts of As(III) or As(V) at room temperature and pH range 6-11 using a flow-through cell connected to an atomic force microscope (AFM). Reaction products were then characterized by Raman spectroscopy. In parallel, co-precipitation experiments with either As(III) or As(V) were performed in batch reactors, and the speciation of arsenic in the resulting solids was studied by X-ray absorption spectroscopy (XAS). For As(V), AFM results showed that it interacts strongly with the calcite surface, and XAS results showed that As(V) was mostly incorporated in the calcite structure. For As(III), AFM results showed much less impact on calcite growth and dissolution and less incorporation was observed. This was confirmed by XAS results that indicate that As(III) was partly oxidized into As(V) before being incorporated into calcite and the resulting calcite contained 36% As(III) and 64% As(V). All these experimental results confirm that As(V) has a much stronger interaction with calcite than As(III) and that calcite may represent an important reservoir for arsenic in various geological environments.

  11. Hydration effects on gypsum dissolution revealed by in situ nanoscale atomic force microscopy observations

    NASA Astrophysics Data System (ADS)

    Burgos-Cara, A.; Putnis, C. V.; Rodriguez-Navarro, C.; Ruiz-Agudo, E.

    2016-04-01

    Recent work has suggested that the rates of mineral dissolution in aqueous solutions are dependent on the kinetics of dehydration of the ions building the crystal. Dehydration kinetics will be ultimately determined by the competition between ion-water and water-water interactions, which can be significantly modified by the presence of background ions in solution. At low ionic strength, the effect of electrolytes on ion-water (electrostatic) interactions will dominate (Kowacz et al., 2007). By performing macroscopic and in situ, microscopic (atomic force microscopy) dissolution experiments, the effect of background electrolytes on the dissolution kinetics of gypsum (CaSO4·2H2O) {0 1 0} cleavage surfaces is tested at constant, low ionic strength (IS = 0.05) and undersaturation (saturation index, SI = -0.045). Dissolution rates are systematically lower in the presence of 1:1 background electrolytes than in an electrolyte-free solution, regardless of the nature of the electrolyte tested. We hypothesize that stabilization of the hydration shell of calcium by the presence of background ions can explain this result, based on the observed correlations in dissolution rates with the ionic surface tension increment of the background ion in solution. Stabilization of the cation hydration shell should favor dissolution. However, in the case of strongly hydrated ions such as Ca2+, this has a direct entropic effect that reduces the overall ΔG of the system, so that dissolution is energetically less favorable. Overall, these results provide new evidence that supports cation dehydration being the rate-controlling step for gypsum dissolution, as proposed for other minerals such as barite, dolomite and calcite.

  12. In situ cardiac perfusion reveals interspecific variation of intraventricular flow separation in reptiles.

    PubMed

    Joyce, William; Axelsson, Michael; Altimiras, Jordi; Wang, Tobias

    2016-07-15

    The ventricles of non-crocodilian reptiles are incompletely divided and provide an opportunity for mixing of oxygen-poor blood and oxygen-rich blood (intracardiac shunting). However, both cardiac morphology and in vivo shunting patterns exhibit considerable interspecific variation within reptiles. In the present study, we develop an in situ double-perfused heart approach to characterise the propensity and capacity for shunting in five reptile species: the turtle Trachemys scripta, the rock python Python sebae, the yellow anaconda Eunectes notaeus, the varanid lizard Varanus exanthematicus and the bearded dragon Pogona vitticeps To simulate changes in vascular bed resistance, pulmonary and systemic afterloads were independently manipulated and changes in blood flow distribution amongst the central outflow tracts were monitored. As previously demonstrated in Burmese pythons, rock pythons and varanid lizards exhibited pronounced intraventricular flow separation. As pulmonary or systemic afterload was raised, flow in the respective circulation decreased. However, flow in the other circulation, where afterload was constant, remained stable. This correlates with the convergent evolution of intraventricular pressure separation and the large intraventricular muscular ridge, which compartmentalises the ventricle, in these species. Conversely, in the three other species, the pulmonary and systemic flows were strongly mutually dependent, such that the decrease in pulmonary flow in response to elevated pulmonary afterload resulted in redistribution of perfusate to the systemic circuit (and vice versa). Thus, in these species, the muscular ridge appeared labile and blood could readily transverse the intraventricular cava. We conclude that relatively minor structural differences between non-crocodilian reptiles result in the fundamental changes in cardiac function. Further, our study emphasises that functionally similar intracardiac flow separation evolved independently in

  13. Time Resolved Imaging of Longitudinal Modulations in Intense Beams

    NASA Astrophysics Data System (ADS)

    Tian, Kai

    2007-11-01

    The longitudinal evolution of high intensity beams is not well understood despite its importance to the success of such applications as free electron lasers and light sources, heavy ion inertial fusion, and high energy colliders. For example any amplification of current modulations in an FEL photoinjector can lead to unwanted coherent synchrotron radiation further downstream in compression chicanes or bends. A significant factor usually neglected is the coupling to the transverse dynamics which can strongly affect the longitudinal evolution. Previous experiments at the University of Maryland have revealed much about the longitudinal physics of space-charge dominated beams by monitoring the evolution of longitudinal perturbations. For the first time, experimental results are presented here which reveal the effect of longitudinal perturbations on the transverse beam distribution, with the aid of several new diagnostics that capture detailed time-resolved density images. A longitudinal modulation of the particle density is deliberately generated at the source, and its evolution is tracked downstream using a number of diagnostics such as current monitors, high-resolution energy analyzers, as well as the transverse imaging devices. The latter consist of a high-resolution 16-bit gated camera coupled with very fast emitters such as prompt optical transition radiation (OTR) from an alumina screen, or fast Phosphor screens with 3-ns time resolution. Simulations using the particle-in-cell code WARP are applied to cross-check the experimental results. These experiments and especially the comparisons to simulation represent significant progress towards understanding the longitudinal physics of intense beams.

  14. PREFACE: Time-resolved scanning tunnelling microscopy Time-resolved scanning tunnelling microscopy

    NASA Astrophysics Data System (ADS)

    Zandvliet, Harold J. W.; Lin, Nian

    2010-07-01

    out the potential landscape of the system (often a molecule or an atom) under study [4, 5]. However, the dynamical processes might also be induced by the tunnelling process itself [6, 7]. In the field of molecular science, excited single molecule experiments have been especially performed [8]. As a nice example, we refer to the work of Sykes' group [9] on thioether molecular rotors. In addition, several groups explore the possibility of combining time-resolved scanning tunnelling microscopy with optical techniques [10, 11]. Although the majority of studies that have been performed so far focus on rather simple systems under nearly ideal and well-defined conditions, we anticipate that time-resolved scanning tunnelling microscopy can also be applied in other research areas, such as biology and soft condensed matter, where the experimental conditions are often less ideal. We hope that readers will enjoy this collection of papers and that it will trigger them to further explore the possibilities of this simple, but powerful technique. References [1] Besenbacher F, Laegsgaard E and Stengaard I 2005 Mater. Today 8 26 [2] van Houselt A and Zandvliet H J W 2010 Rev. Mod. Phys. 82 1593 [3] Tringides M C and Hupalo M 2010 J. Phys.: Condens. Matter 22 264002 [4] Ronci F, Colonna S, Cricenti A and Le Lay G 2010 J. Phys.: Condens. Matter 22 264003 [5] van Houselt A, Poelsema B and Zandvliet H J W 2010 J. Phys.: Condens. Matter 22 264004 [6] Sprodowski C, Mehlhorn M and Morgenstern K 2010 J. Phys.: Condens. Matter 22 264005 [7] Saedi A, Poelsema B and Zandvliet H J W 2010 J. Phys.: Condens. Matter 22 264007 [8] Sloan P A 2010 J. Phys.: Condens. Matter 22 264001 [9] Jewell A D, Tierney H L, Baber A E, Iski E V, Laha M M and Sykes E C H 2010 J. Phys.: Condens. Matter 22 264006 [10] Riedel D 2010 J. Phys.: Condens. Matter 22 264009 [11] Terada Y, Yoshida S, Takeuchi O and Shigekawa H 2010 J. Phys.: Condens. Matter 22 264008

  15. Time resolved fluorescence of naproxen in organogel medium

    NASA Astrophysics Data System (ADS)

    Burguete, M. Isabel; Izquierdo, M. Angeles; Galindo, Francisco; Luis, Santiago V.

    2008-07-01

    The interaction between non-steroidal anti-inflammatory drug naproxen and the self assembled fibrillar network created by a low molecular weight organogelator has been probed by means of time resolved fluorescence spectroscopy.

  16. In situ proteo-metabolomics reveals metabolite secretion by the acid mine drainage bio-indicator, Euglena mutabilis.

    PubMed

    Halter, David; Goulhen-Chollet, Florence; Gallien, Sébastien; Casiot, Corinne; Hamelin, Jérôme; Gilard, Françoise; Heintz, Dimitri; Schaeffer, Christine; Carapito, Christine; Van Dorsselaer, Alain; Tcherkez, Guillaume; Arsène-Ploetze, Florence; Bertin, Philippe N

    2012-07-01

    Euglena mutabilis is a photosynthetic protist found in acidic aquatic environments such as peat bogs, volcanic lakes and acid mine drainages (AMDs). Through its photosynthetic metabolism, this protist is supposed to have an important role in primary production in such oligotrophic ecosystems. Nevertheless, the exact contribution of E. mutabilis in organic matter synthesis remains unclear and no evidence of metabolite secretion by this protist has been established so far. Here we combined in situ proteo-metabolomic approaches to determine the nature of the metabolites accumulated by this protist or potentially secreted into an AMD. Our results revealed that the secreted metabolites are represented by a large number of amino acids, polyamine compounds, urea and some sugars but no fatty acids, suggesting a selective organic matter contribution in this ecosystem. Such a production may have a crucial impact on the bacterial community present on the study site, as it has been suggested previously that prokaryotes transport and recycle in situ most of the metabolites secreted by E. mutabilis. Consequently, this protist may have an indirect but important role in AMD ecosystems but also in other ecological niches often described as nitrogen-limited.

  17. A versatile apparatus for time-resolved photoemission spectroscopy via femtosecond pump-probe experiments.

    PubMed

    Carpene, E; Mancini, E; Dallera, C; Ghiringhelli, G; Manzoni, C; Cerullo, G; De Silvestri, S

    2009-05-01

    A laser-based system for time-resolved photoemission spectroscopy using up to 6.2 eV photons is presented. The versatility of the laser source permits several combinations of pump and probe photon energies with pulse durations of 50-100 fs. The ultrahigh vacuum system, equipped with evaporators, a low energy electron diffraction system and an Auger spectrometer, grants the possibility to grow and characterize thin films in situ. The electron energy analyzer is a time-of-flight spectrometer with a multianode detector allowing high count rates. The performance of the whole experimental setup is investigated on Cu(100), Cu(111), and Ag(111) single crystals.

  18. Seventh international conference on time-resolved vibrational spectroscopy

    SciTech Connect

    Dyer, R.B.; Martinez, M.A.D.; Shreve, A.; Woodruff, W.H.

    1997-04-01

    The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities for time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.

  19. Time-resolved neutron imaging at ANTARES cold neutron beamline

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Dangendorf, V.; Tittelmeier, K.; Schillinger, B.; Schulz, M.; Lerche, M.; Feller, W. B.

    2015-07-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and integrated over multiple cycles. A fast MCP/Timepix neutron counting detector was used to image the water distribution within a model steam engine operating at 10 Hz frequency. Within <10 minutes integration the amount of water was measured as a function of cycle time with a sub-mm spatial resolution, thereby demonstrating the capabilities of time-resolved neutron radiography for the future applications. The neutron spectrum of the ANTARES beamline as well as transmission spectra of a Fe sample were also measured with the Time Of Flight (TOF) technique in combination with a high resolution beam chopper. The energy resolution of our setup was found to be ~ 0.8% at 5 meV and ~ 1.7% at 25 meV. The background level (most likely gammas and epithermal/fast neutrons) of the ANTARES beamline was also measured in our experiments and found to be on the scale of 3% when no filters are installed in the beam. Online supplementary data available from stacks.iop.org/jinst/10

  20. Electron-transfer acceleration investigated by time resolved infrared spectroscopy.

    PubMed

    Vlček, Antonín; Kvapilová, Hana; Towrie, Michael; Záliš, Stanislav

    2015-03-17

    Ultrafast electron transfer (ET) processes are important primary steps in natural and artificial photosynthesis, as well as in molecular electronic/photonic devices. In biological systems, ET often occurs surprisingly fast over long distances of several tens of angströms. Laser-pulse irradiation is conveniently used to generate strongly oxidizing (or reducing) excited states whose reactions are then studied by time-resolved spectroscopic techniques. While photoluminescence decay and UV-vis absorption supply precise kinetics data, time-resolved infrared absorption (TRIR) and Raman-based spectroscopies have the advantage of providing additional structural information and monitoring vibrational energy flows and dissipation, as well as medium relaxation, that accompany ultrafast ET. We will discuss three cases of photoinduced ET involving the Re(I)(CO)3(N,N) moiety (N,N = polypyridine) that occur much faster than would be expected from ET theories. [Re(4-N-methylpyridinium-pyridine)(CO)3(N,N)](2+) represents a case of excited-state picosecond ET between two different ligands that remains ultrafast even in slow-relaxing solvents, beating the adiabatic limit. This is caused by vibrational/solvational excitation of the precursor state and participation of high-frequency quantum modes in barrier crossing. The case of Re-tryptophan assemblies demonstrates that excited-state Trp → *Re(II) ET is accelerated from nanoseconds to picoseconds when the Re(I)(CO)3(N,N) chromophore is appended to a protein, close to a tryptophan residue. TRIR in combination with DFT calculations and structural studies reveals an interaction between the N,N ligand and the tryptophan indole. It results in partial electronic delocalization in the precursor excited state and likely contributes to the ultrafast ET rate. Long-lived vibrational/solvational excitation of the protein Re(I)(CO)3(N,N)···Trp moiety, documented by dynamic IR band shifts, could be another accelerating factor. The last

  1. Time-resolved neurite mechanics by thermal fluctuation assessments.

    PubMed

    Gárate, Fernanda; Betz, Timo; Pertusa, María; Bernal, Roberto

    2015-12-30

    In the absence of simple noninvasive measurements, the knowledge of temporal and spatial variations of axons mechanics remains scarce. By extending thermal fluctuation spectroscopy (TFS) to long protrusions, we determine the transverse amplitude thermal fluctuation spectra that allow direct and simultaneous access to three key mechanics parameters: axial tension, bending flexural rigidity and plasma membrane tension. To test our model, we use PC12 cell protrusions-a well-know biophysical model of axons-in order to simplify the biological system under scope. For instance, axial and plasma membrane tension are found in the range of nano Newton and tens of pico Newtons per micron respectively. Furthermore, our results shows that the TFS technique is capable to distinguish quasi-identical protrusions. Another advantage of our approach is the time resolved nature of the measurements. Indeed, in the case of long term experiments on PC12 protrusions, TFS has revealed large temporal, correlated variations of the protrusion mechanics, displaying extraordinary feedback control over the axial tension in order to maintain a constant tension value.

  2. Mechanical properties of Si nanowires as revealed by in situ transmission electron microscopy and molecular dynamics simulations.

    PubMed

    Tang, Dai-Ming; Ren, Cui-Lan; Wang, Ming-Sheng; Wei, Xianlong; Kawamoto, Naoyuki; Liu, Chang; Bando, Yoshio; Mitome, Masanori; Fukata, Naoki; Golberg, Dmitri

    2012-04-11

    Deformation and fracture mechanisms of ultrathin Si nanowires (NWs), with diameters of down to ~9 nm, under uniaxial tension and bending were investigated by using in situ transmission electron microscopy and molecular dynamics simulations. It was revealed that the mechanical behavior of Si NWs had been closely related to the wire diameter, loading conditions, and stress states. Under tension, Si NWs deformed elastically until abrupt brittle fracture. The tensile strength showed a clear size dependence, and the greatest strength was up to 11.3 GPa. In contrast, under bending, the Si NWs demonstrated considerable plasticity. Under a bending strain of <14%, they could repeatedly be bent without cracking along with a crystalline-to-amorphous phase transition. Under a larger strain of >20%, the cracks nucleated on the tensed side and propagated from the wire surface, whereas on the compressed side a plastic deformation took place because of dislocation activities and an amorphous transition.

  3. The asymmetrical structure of Golgi apparatus membranes revealed by in situ atomic force microscope.

    PubMed

    Xu, Haijiao; Su, Weiheng; Cai, Mingjun; Jiang, Junguang; Zeng, Xianlu; Wang, Hongda

    2013-01-01

    The Golgi apparatus has attracted intense attentions due to its fascinating morphology and vital role as the pivot of cellular secretory pathway since its discovery. However, its complex structure at the molecular level remains elusive due to limited approaches. In this study, the structure of Golgi apparatus, including the Golgi stack, cisternal structure, relevant tubules and vesicles, were directly visualized by high-resolution atomic force microscope. We imaged both sides of Golgi apparatus membranes and revealed that the outer leaflet of Golgi membranes is relatively smooth while the inner membrane leaflet is rough and covered by dense proteins. With the treatment of methyl-β-cyclodextrin and Triton X-100, we confirmed the existence of lipid rafts in Golgi apparatus membrane, which are mostly in the size of 20 nm -200 nm and appear irregular in shape. Our results may be of significance to reveal the structure-function relationship of the Golgi complex and pave the way for visualizing the endomembrane system in mammalian cells at the molecular level.

  4. Identifying Fossil Biosignatures and Minerals in Mars Analog Materials Using Time-Resolved Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shkolyar, S.; Farmer, J.; Alerstam, E.; Maruyama, Y.; Blacksberg, J.

    2013-12-01

    Mars sample return has been identified as a top priority in the planetary science decadal survey. A Mars sample selection and caching mission would be the likely first step in this endeavor. Such a mission would aim to select and prioritize for return to Earth aqueously formed geological samples present at a selected site on Mars, based upon their potential for biosignature capture and preservation. If evidence of past life exists and is found, it is likely to come via the identification of fossilized carbonaceous matter of biological origin (kerogen) found in the selected samples analyzed in laboratories after return to Earth. Raman spectroscopy is considered one of the primary techniques for analyzing materials in situ and selecting the most promising samples for Earth return. We have previously performed a pilot study to better understand the complexities of identifying kerogen using Raman spectroscopy. For the study, we examined a variety of Mars analog materials representing a broad range of mineral compositions and kerogen maturities. The study revealed that kerogen identification in many of the most promising lithologies is often impeded by background fluorescence that originates from long (>10 ns to ms) and short (<1 ns) lifetime fluorophores in both the mineral matrixes and preserved organic matter in the samples. This work explores the potential for time-gated Raman spectroscopy to enable clear kerogen and mineral identifications in such samples. The JPL time-resolved Raman system uses time gating to reduce background fluorescence. It uses a custom-built SPAD (single photon avalanche diode) detector, featuring a 1-ns time-gate, and electronically variable gate delay. Results for a range of fluorescent samples show that the JPL system reduces fluorescence, allowing the identification of both kerogen and mineral components more successfully than with conventional Raman systems. In some of the most challenging samples, the detection of organic matter is

  5. Native architecture of the Chlamydomonas chloroplast revealed by in situ cryo-electron tomography

    PubMed Central

    Engel, Benjamin D; Schaffer, Miroslava; Kuhn Cuellar, Luis; Villa, Elizabeth; Plitzko, Jürgen M; Baumeister, Wolfgang

    2015-01-01

    Chloroplast function is orchestrated by the organelle's intricate architecture. By combining cryo-focused ion beam milling of vitreous Chlamydomonas cells with cryo-electron tomography, we acquired three-dimensional structures of the chloroplast in its native state within the cell. Chloroplast envelope inner membrane invaginations were frequently found in close association with thylakoid tips, and the tips of multiple thylakoid stacks converged at dynamic sites on the chloroplast envelope, implicating lipid transport in thylakoid biogenesis. Subtomogram averaging and nearest neighbor analysis revealed that RuBisCO complexes were hexagonally packed within the pyrenoid, with ∼15 nm between their centers. Thylakoid stacks and the pyrenoid were connected by cylindrical pyrenoid tubules, physically bridging the sites of light-dependent photosynthesis and light-independent carbon fixation. Multiple parallel minitubules were bundled within each pyrenoid tubule, possibly serving as conduits for the targeted one-dimensional diffusion of small molecules such as ATP and sugars between the chloroplast stroma and the pyrenoid matrix. DOI: http://dx.doi.org/10.7554/eLife.04889.001 PMID:25584625

  6. Apoptotic DNA fragmentation can be revealed in situ: an ultrastructural approach.

    PubMed

    Burattini, Sabrina; Ferri, Paola; Battistelli, Michela; D'Emilio, Alessandra; Biagiotti, Laura; Sestili, Piero; Rocchi, Marco B L; Falcieri, Elisabetta

    2009-12-01

    A common pattern of apoptotic death is DNA cleavage, initially producing large fragments (50 kbp), followed by the production of nucleosomic/oligonucleosomic fragments. Nevertheless, apoptosis without DNA fragmentation, at least of the nucleosomic type, has been reported. To investigate the spatial relationship between DNA cleavage and chromatin condensation, we applied the TUNEL technique to the ultrastructural analysis of apoptotic cells. A modified method, utilizing a gold-conjugated antidigoxigenin antibody, was carried out on U937 versus Molt-4 cells, both exposed to UVB radiation or staurosporine treatment. Gold particle density in the different domains of apoptotic cells was evaluated by a four-way ANOVA test. Gold labelling was more strongly localised in condensed chromatin than in the diffuse chromatin. U937 cells, which evidenced in vitro oligonucleosomic fragmentation after both UVB and staurosporine treatments, revealed a significantly higher gold particle density, when compared with Molt-4, which did not show, on the other hand, oligonucleosomic cleavage even in the presence of < or = 50 kbp cleavage. Thus, a correlation between DNA fragment sizes and gold particle density appears. TUNEL applied to electron microscopy is an effective approach to study the relationship between apoptotic chromatin condensation and DNA cleavage. Both these events indeed appear in the apoptotic nucleus, but their reciprocal correlation is still greatly unknown. Microsc. Res. Tech. 2009. (c) 2009 Wiley-Liss, Inc.

  7. In-situ time resolved synchrotron powder diffraction studies of synthesis and chemical reactions

    SciTech Connect

    Norby, P.

    1995-09-01

    Equipment for time and temperature dependent powder diffraction has been developed, especially in order to be able to study hydrothermal syntheses of zeolites. The system is very versatile and has so far been used to study e.g. hydrothermal syntheses of zeolites and aluminophosphates, syntheses of layered phosphates, formation of Sorel cements, dehydration and phase transformations of zeolites, solid state synthesis of lanthanum manganites, ion exchange of zeolites using molten salt, and oxidation/reduction of lanthanum manganites at high temperatures. The sample is contained in quartz capillaries and is heated using a stream of hot air. External pressure can be applied allowing hydrothermal syntheses at temperatures up to 200 C to be performed. Controlled atmosphere is obtained by flowing gas or a mixture of gases through the capillary.

  8. Revealing the surface and bulk regimes of isothermal graphene growth on Ni with in situ kinetic measurements and modeling

    SciTech Connect

    Puretzky, Alexander A; Merkulov, Igor A; Rouleau, Christopher M; Eres, Gyula; Geohegan, David B

    2014-01-01

    In situ optical diagnostics are used to reveal the isothermal nucleation and growth mechanisms of graphene on Ni across a wide temperature range (560 C < T < 840 C) by chemical vapor deposition from single, sub-second pulses of acetylene. An abrupt, two-orders of magnitude change in growth times (~ 100s to 1s) is revealed at T = 680 C. Below and above this temperature, similar sigmoidal kinetics are measured and attributed to autocatalytic growth reactions but by two different mechanisms, surface assembly and dissolution/precipitation, respectively. These data are used to develop a simple and general kinetic model for graphene growth that includes the nucleation phase and includes the effects of carbon solubility in metals, describes delayed nucleation, and allows the interpretation of the competition between surface and bulk growth modes. The sharp transition in growth kinetics at T = 680 C is explained by a change in defect site density required for nucleation due to a transition in the carbon-induced mobility of the Ni surface. The easily-implemented optical reflectivity diagnostics and the simple kinetic model described here allow a pathway to optimize the growth of graphene on metals with arbitrary carbon solubility.

  9. Similarities and differences in the nuclear genome organization within Pooideae species revealed by comparative genomic in situ hybridization (GISH).

    PubMed

    Majka, Joanna; Majka, Maciej; Kwiatek, Michał; Wiśniewska, Halina

    2016-10-14

    In this paper, we highlight the affinity between the genomes of key representatives of the Pooideae subfamily, revealed at the chromosomal level by genomic in situ hybridization (GISH). The analyses were conducted using labeled probes from each species to hybridize with chromosomes of every species used in this study based on a "round robin" rule. As a result, the whole chromosomes or chromosome regions were distinguished or variable types of signals were visualized to prove the different levels of the relationships between genomes used in this study. We observed the unexpected lack of signals in secondary constrictions of rye (RR) chromosomes probed by triticale (AABBRR) genomic DNA. We have also identified unlabeled chromosome regions, which point to species-specific sequences connected with disparate pathways of chromosome differentiation. Our results revealed a conservative character of coding sequence of 35S rDNA among selected species of the genera Aegilops, Brachypodium, Festuca, Hordeum, Lolium, Secale, and Triticum. In summary, we showed strong relationships in genomic DNA sequences between species which have been previously reported to be phylogenetically distant.

  10. Time-resolved x-ray crystallography of heme proteins

    PubMed Central

    Royer, William E.

    2012-01-01

    Heme proteins, with their natural photosensitivity, are excellent systems for the application of time-resolved crystallographic methods. Ligand dissociation can be readily initiated by a short laser pulse with global structural changes probed at the atomic level by X-rays in real time. Third generation synchrotrons provide 100ps X-ray pulses of sufficient intensity for monitoring very fast processes. Successful application of such time-resolved crystallographic experiments requires that the structural changes being monitored are compatible with the crystal lattice. These techniques have permitted observing allosteric transitions in real time for a cooperative dimeric hemoglobin. PMID:18433638

  11. Time-Resolved X-Ray Crystallography of Heme Proteins

    SciTech Connect

    Srajer, Vukica; Royer, Jr., William E.

    2008-04-29

    Heme proteins, with their natural photosensitivity, are excellent systems for the application of time-resolved crystallographic methods. Ligand dissociation can be readily initiated by a short laser pulse with global structural changes probed at the atomic level by X-rays in real time. Third-generation synchrotrons provide 100-ps X-ray pulses of sufficient intensity for monitoring very fast processes. Successful application of such time-resolved crystallographic experiments requires that the structural changes being monitored are compatible with the crystal lattice. These techniques have recently permitted observing for the first time allosteric transitions in real time for a cooperative dimeric hemoglobin.

  12. Time-resolved photon emission from layered turbid media

    SciTech Connect

    Hielscher, A.H.; Liu, H.; Chance, B.; Tittel, F.K.; Jacques, S.L.

    1996-02-01

    We present numerical and experimental results of time-resolved emission profiles from various layered turbid media. Numerical solutions determined by time-resolved Monte Carlo simulations are compared with measurements on layered-tissue phantoms made from gelatin. In particular, we show that in certain cases the effects of the upper layers can be eliminated. As a practical example, these results are used to analyze {ital in} {ital vivo} measurements on the human head. This demonstrates the influence of skin, skull, and meninges on the determination of the blood oxygenation in the brain. {copyright} {ital 1996 Optical Society of America.}

  13. Mid-infrared time-resolved photoconduction in black phosphorus

    NASA Astrophysics Data System (ADS)

    Suess, Ryan J.; Leong, Edward; Garrett, Joseph L.; Zhou, Tong; Salem, Reza; Munday, Jeremy N.; Murphy, Thomas E.; Mittendorff, Martin

    2016-12-01

    Black phosphorus has attracted interest as a material for use in optoelectronic devices due to many favorable properties such as a high carrier mobility, field-effect, and a direct bandgap that can range from 0.3 eV in its bulk crystalline form to 1.7-2.0 eV for a single atomic layer. The low bandgap energy for multilayer black phosphorus consisting of more than approximately five atomic layers allows for direct transition photoabsorption that enables detection of light out to mid-infrared frequencies. In this work, we characterize the room temperature optical response of a black phosphorus photoconductive detector at wavelengths ranging from 1.56 to 3.75 μm. Pulsed autocorrelation measurements in the near-infrared regime reveal a strong, sub-linear photocurrent nonlinearity with a response time of 1 ns, indicating that gigahertz electrical bandwidth is feasible. Time resolved photoconduction measurements covering near- and mid-infrared frequencies show a fast 65 ps rise time, followed by a carrier relaxation with a time scale that matches the intrinsic limit determined by autocorrelation. The sublinear photoresponse is shown to be caused by a reduction in the carrier relaxation time as more energy is absorbed in the black phosphorus flake and is well described by a carrier recombination model that is nonlinear with excess carrier density. The device exhibits a measured noise-equivalent power of 530 pW Hz-1/2, which is the value expected for Johnson noise limited performance. The fast and sensitive room temperature photoresponse demonstrates that black phosphorus is a promising new material for mid-infrared optoelectronics.

  14. Time-resolved imaging of cavitation effects during laser lithotripsy

    NASA Astrophysics Data System (ADS)

    Siano, Salvatore; Pini, Roberto; Salimbeni, Renzo; Vannini, Matteo

    1995-01-01

    We devised a diagnostic technique based on a pump-and-probe scheme that provided time- resolved imaging of photofragmentation effects during laser lithotripsy. The evolution of the cavitation bubble induced on kidney stone samples by underwater irradiation with a XeCl excimer laser is presented and analyzed.

  15. Germanium as a Sodium Ion Battery Material: In Situ TEM Reveals Fast Sodiation Kinetics with High Capacity

    SciTech Connect

    Lu, Xiaotang; Adkins, Emily R.; He, Yang; Zhong, Li; Luo, Langli; Mao, Scott X.; Wang, Chong M.; Korgel, Brian A.

    2016-01-29

    Amorphous germanium (a-Ge) nanowires have great potential for application as anodes in Na-ion batteries. However, the Na-Ge reaction is much less studied and understood compared with other metal alloy anodes. Here, in situ transmission electron microscopy (TEM) is used to study the sodiation/desodiation behavior of a-Ge nanowires. Unexpectedly, our experiments revealed that a-Ge nanowires can be charged at a very fast rate and the final sodiation product, with over 300% volume expansion, is close to Na3Ge instead of NaGe which was considered as the ultimate sodiation state that Ge could achieve. Porous structure was observed in desodiation and, in contrast to delithiation, Na extraction is more likely to create pores in the nanowires due to the much larger radius of the Na ion. This porous structure has demonstrated excellent robustness upon cycling: it could recover flawlessly from the giant pores that were created during experimentation. These results show that the potential of a-Ge for Na-ion battery applications may have been previously underestimated.

  16. In situ hybridization and sequence analysis reveal an association of Plasmodium spp. with mortalities in wild passerine birds in Austria.

    PubMed

    Dinhopl, Nora; Nedorost, Nora; Mostegl, Meike M; Weissenbacher-Lang, Christiane; Weissenböck, Herbert

    2015-04-01

    Native European passerine birds are frequently clinically inapparent carriers of haemosporidian parasites of the genus Plasmodium. Clinical disease and death are only exceptionally reported. In the present study, tissue samples of 233 wild passerine birds found dead in Eastern Austria were examined by in situ hybridization (ISH) and partial cytochrome B gene sequence analysis for the presence, abundance and taxonomic assignment of Plasmodium spp. In 34 cases (14.6%), ISH yielded a positive result with large numbers of developmental stages in different cell types of the spleen, liver, brain and lung. The abundance of the tissue stages, which was comparable to fatal cases of avian malaria in penguins, suggested a major contribution to the cause of death. Genetic analysis revealed infections with representatives of three different valid species of Plasmodium, Plasmodium elongatum, Plasmodium lutzi and Plasmodium vaughani. Genetically identical parasite lineages had been found in a previous study in penguins kept in the Vienna zoo, providing evidence for the role of wild birds as reservoir hosts. Further, this study provides evidence that several species of Plasmodium are able to abundantly proliferate in endemic wild birds ultimately resulting in mortalities.

  17. Fluorescent in situ hybridization (FISH) and high resolution karyotype analysis reveal a novel inversion duplication of 10q

    SciTech Connect

    Czarnecki, P.; Dyke, D.L. Van; Dowling, P.K.

    1994-09-01

    A white male born with dysmorphic features, including upslanting palpebral fissures, bilateral simian creases, posteriorly rotated ears, bitemporal narrowing, frontal bossing, camptodactyly and head circumference and weight less than the 5th percentile was found to have a de novo add(10)(q26.1). High resolution karyotype analysis revealed a novel chromosomal abnormality: 46,XY,inv dup(10)(q26.3-q25.1). Fluorescent in situ hybridization using a chromosome 10-specific painting probe (Oncor, Inc.) confirmed that the extra material was derived from chromosome 10. Duplication of 10q24 or 10q25 is associated with characteristic craniofacial malformations, minor malformations of the hands and feet, major malformations of the heart, skeleton, and kidneys and severe mental retardation. Our patient, currently 7 months old, has many of the skeletal and craniofacial manifestations of other patients, but is developmentally normal at this early age. This is the first FISH confirmation of a 10q duplication and demonstrates the utility of this technology in addition to karyotype analysis. Molecular studies to determine the parental origin and extent of the duplication are in progress, since the apparent lack of developmental delay was unexpected. Identification of the origin of duplicated material will help assist in genetic counseling by further delineating new genetic syndromes.

  18. Atomic-Scale Mechanism on Nucleation and Growth of Mo2C Nanoparticles Revealed by in Situ Transmission Electron Microscopy.

    PubMed

    Fei, Linfeng; Ng, Sheung Mei; Lu, Wei; Xu, Ming; Shu, Longlong; Zhang, Wei-Bing; Yong, Zehui; Sun, Tieyu; Lam, Chi Hang; Leung, Chi Wah; Mak, Chee Leung; Wang, Yu

    2016-12-14

    With a similar electronic structure as that of platinum, molybdenum carbide (Mo2C) holds significant potential as a high performance catalyst across many chemical reactions. Empirically, the precise control of particle size, shape, and surface nature during synthesis largely determines the catalytic performance of nanoparticles, giving rise to the need of clarifying the underlying growth characteristics in the nucleation and growth of Mo2C. However, the high-temperature annealing involved during the growth of carbides makes it difficult to directly observe and understand the nucleation and growth processes. Here, we report on the use of advanced in situ transmission electron microscopy with atomic resolution to reveal a three-stage mechanism during the growth of Mo2C nanoparticles over a wide temperature range: initial nucleation via a mechanism consistent with spinodal decomposition, subsequent particle coalescence and monomer attachment, and final surface faceting to well-defined particles with minimum surface energy. These microscopic observations made under a heating atmosphere offer new perspectives toward the design of carbide-based catalysts, as well as the tuning of their catalytic performances.

  19. Kinetic and Conformational Insights of Protein Adsorption onto Montmorillonite Revealed Using in Situ ATR-FTIR/2D-COS.

    PubMed

    Schmidt, Michael P; Martínez, Carmen Enid

    2016-08-09

    Protein adsorption onto clay minerals is a process with wide-ranging impacts on the environmental cycling of nutrients and contaminants. This process is influenced by kinetic and conformational factors that are often challenging to probe in situ. This study represents an in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopic investigation of the adsorption of a model protein (bovine serum albumin (BSA)) onto a clay mineral (montmorillonite) at four concentrations (1.50, 3.75, 7.50, and 15.0 μM) under environmentally relevant conditions. At all concentrations probed, FTIR spectra show that BSA readily adsorbs onto montmorillonite. Adsorption kinetics follow an Elovich model, suggesting that primary limitations on adsorption rates are surface-related heterogeneous energetic restrictions associated with protein rearrangement and lateral protein-protein interaction. BSA adsorption onto montmorillonite fits the Langmuir model, yielding K = 5.97 × 10(5) M(-1). Deconvolution and curve fitting of the amide I band at the end of the adsorption process (∼120 min) shows a large extent of BSA unfolding upon adsorption at 1.50 μM, with extended chains and turns increasing at the expense of α-helices. At higher concentrations/surface coverages, BSA unfolding is less pronounced and a more compact structure is assumed. Two-dimensional correlation spectroscopic (2D-COS) analysis reveals three different pathways corresponding to adsorbed conformations. At 1.50 μM, adsorption increases extended chains, followed by a loss in α-helices and a subsequent increase in turns. At 3.75 μM, extended chains decrease and then aggregated strands increase and side chains decrease, followed by a decrease in turns. With 7.50 and 15.0 μM BSA, the loss of side-chain vibrations is followed by an increase in aggregated strands and a subsequent decrease in turns and extended chains. Overall, the BSA concentration and resultant surface coverage have a profound

  20. Elucidating low-frequency vibrational dynamics in calcite and water with time-resolved third-harmonic generation spectroscopy.

    PubMed

    Wang, Liang; Liu, Weimin; Fang, Chong

    2015-07-14

    Low-frequency vibrations are foundational for material properties including thermal conductivity and chemical reactivity. To resolve the intrinsic molecular conformational dynamics in condensed phase, we implement time-resolved third-harmonic generation (TRTHG) spectroscopy to unravel collective skeletal motions in calcite, water, and aqueous salt solution in situ. The lifetime of three Raman-active modes in polycrystalline calcite at 155, 282 and 703 cm(-1) is found to be ca. 1.6 ps, 1.3 ps and 250 fs, respectively. The lifetime difference is due to crystallographic defects and anharmonic effects. By incorporating a home-built wire-guided liquid jet, we apply TRTHG to investigate pure water and ZnCl2 aqueous solution, revealing ultrafast dynamics of water intermolecular stretching and librational bands below 500 cm(-1) and a characteristic 280 cm(-1) vibrational mode in the ZnCl4(H2O)2(2-) complex. TRTHG proves to be a compact and versatile technique that directly uses the 800 nm fundamental laser pulse output to capture ultrafast low-frequency vibrational motion snapshots in condensed-phase materials including the omnipresent water, which provides the important time dimension to spectral characterization of molecular structure-function relationships.

  1. Plasticity mechanisms in ultrafine grained freestanding aluminum thin films revealed by in-situ transmission electron microscopy nanomechanical testing

    SciTech Connect

    Idrissi, Hosni; Kobler, Aaron; Amin-Ahmadi, Behnam; Schryvers, Dominique; Coulombier, Michael; Pardoen, Thomas; Galceran, Montserrat; Godet, Stéphane; Kübel, Christian

    2014-03-10

    In-situ bright field transmission electron microscopy (TEM) nanomechanical tensile testing and in-situ automated crystallographic orientation mapping in TEM were combined to unravel the elementary mechanisms controlling the plasticity of ultrafine grained Aluminum freestanding thin films. The characterizations demonstrate that deformation proceeds with a transition from grain rotation to intragranular dislocation glide and starvation plasticity mechanism at about 1% deformation. The grain rotation is not affected by the character of the grain boundaries. No grain growth or twinning is detected.

  2. Benchtop time-resolved magneto-optical Kerr magnetometer.

    PubMed

    Barman, Anjan; Kimura, T; Otani, Y; Fukuma, Y; Akahane, K; Meguro, S

    2008-12-01

    We present here the construction and application of a compact benchtop time-resolved Kerr magnetometer to measure the magnetization precession in magnetic thin films and lithographically patterned elements. As opposed to very expensive femtosecond lasers this system is built upon a picosecond pulsed injection diode laser and electronic pulse and delay generators. The precession is triggered by the electronic pulses of controlled duration and shape, which is launched onto the sample by a microstrip line. We used polarized optical pulses synchronous to the electronic pulses to measure the magneto-optical Kerr rotation. The system is integrated in a conventional upright microscope configuration with separate illumination, imaging, and magneto-optical probe paths. The system offers high stability, relative ease of alignment, sample changing, and a long range of time delay. We demonstrate the measurements of time-resolved dynamics of a Permalloy microwire and microdot using this system, which showed dynamics at two different time scales.

  3. Time-Resolved Rayleigh Scattering Measurements in Hot Gas Flows

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.; Sung, Chih-Jen

    2008-01-01

    A molecular Rayleigh scattering technique is developed to measure time-resolved gas velocity, temperature, and density in unseeded gas flows at sampling rates up to 32 kHz. A high power continuous-wave laser beam is focused at a point in an air flow field and Rayleigh scattered light is collected and fiber-optically transmitted to the spectral analysis and detection equipment. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. Photomultipler tubes operated in the photon counting mode allow high frequency sampling of the circular interference pattern to provide time-resolved flow property measurements. Mean and rms velocity and temperature fluctuation measurements in both an electrically-heated jet facility with a 10-mm diameter nozzle and also in a hydrogen-combustor heated jet facility with a 50.8-mm diameter nozzle at NASA Glenn Research Center are presented.

  4. The RATIO method for time-resolved Laue crystallography

    PubMed Central

    Coppens, Philip; Pitak, Mateusz; Gembicky, Milan; Messerschmidt, Marc; Scheins, Stephan; Benedict, Jason; Adachi, Shin-ichi; Sato, Tokushi; Nozawa, Shunsuke; Ichiyanagi, Kohei; Chollet, Matthieu; Koshihara, Shin-ya

    2009-01-01

    A RATIO method for analysis of intensity changes in time-resolved pump–probe Laue diffraction experiments is described. The method eliminates the need for scaling the data with a wavelength curve representing the spectral distribution of the source and removes the effect of possible anisotropic absorption. It does not require relative scaling of series of frames and removes errors due to all but very short term fluctuations in the synchrotron beam. PMID:19240334

  5. Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

    SciTech Connect

    Hastings, J.B.; Rudakov, F.M.; Dowell, D.H.; Schmerge, J.F.; Cardoza, J.D.; Castro, J.M.; Gierman, S.M.; Loos, H.; Weber, P.M.; /Brown U.

    2006-10-24

    An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.

  6. Time Resolved Measurements and Reactive Pathways of Hypergolic Bipropellant Combustion

    DTIC Science & Technology

    2006-03-31

    estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the...0704-0188,) Washington, DC 20503. 1 . AGENCY USE ONLY ( Leave Blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED 4. TITLE AND SUBTITLE 5...Standard Form 298 (Rev.2-89) Prescribed by ANSI Std. 239-18 298-102 Enclosure 1 03/31/06 Final Report 01 Aug 02 - 31 Dec 05 TIME RESOLVED

  7. Time-resolved WAXD studies on the crystallization of semicrystalline/graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Endoh, Maya; Nishitsuji, Shotaro; Koga, Tad; Rafailovich, Mirian

    Graphene is one layer of carbon atoms, which has good electronic, thermal conductivity, and mechanical properties. By adding graphene to semicrystalline polymers such as polyethylene (PE) and isotactic polypropylene (iPP), the mechanical and electrical properties of the polymers are significantly improved. To further achieve high performance of semicrystalline polymer/graphene nanocomposites, it is important to investigate the relationship between the crystalline structure of the polymer and the mechanical property of the nanocomposites. In this study, the effect of graphene on the crystallization behavior of PE and iPP was investigated by using time-resolved wide angle X-ray diffraction (WAXD). The in situ WAXD results on the melt-crystallization process showed that the crystalline structures of all the samples remained the same as the pure bulk, while both the rate and degree of the crystallinity increased. We will discuss the detailed structure information along with DSC and mechanical test results.

  8. Space and time-resolved probing of heterogeneous catalysis reactions using lab-on-a-chip.

    PubMed

    Navin, Chelliah V; Krishna, Katla Sai; Theegala, Chandra S; Kumar, Challa S S R

    2016-03-14

    Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors.

  9. Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging

    PubMed Central

    Zheng, Kaiyu; Jensen, Thomas P.; Savtchenko, Leonid P.; Levitt, James A.; Suhling, Klaus; Rusakov, Dmitri A.

    2017-01-01

    Neural activity relies on molecular diffusion within nanoscopic spaces outside and inside nerve cells, such as synaptic clefts or dendritic spines. Measuring diffusion on this small scale in situ has not hitherto been possible, yet this knowledge is critical for understanding the dynamics of molecular events and electric currents that shape physiological signals throughout the brain. Here we advance time-resolved fluorescence anisotropy imaging combined with two-photon excitation microscopy to map nanoscale diffusivity in ex vivo brain slices. We find that in the brain interstitial gaps small molecules move on average ~30% slower than in a free medium whereas inside neuronal dendrites this retardation is ~70%. In the synaptic cleft free nanodiffusion is decelerated by ~46%. These quantities provide previously unattainable basic constrains for the receptor actions of released neurotransmitters, the electrical conductance of the brain interstitial space and the limiting rate of molecular interactions or conformational changes in the synaptic microenvironment. PMID:28181535

  10. Thin film growth studies using time-resolved x-ray scattering

    NASA Astrophysics Data System (ADS)

    Kowarik, Stefan

    2017-02-01

    Thin-film growth is important for novel functional materials and new generations of devices. The non-equilibrium growth physics involved is very challenging, because the energy landscape for atomic scale processes is determined by many parameters, such as the diffusion and Ehrlich-Schwoebel barriers. We review the in situ real-time techniques of x-ray diffraction (XRD), x-ray growth oscillations and diffuse x-ray scattering (GISAXS) for the determination of structure and morphology on length scales from Å to µm. We give examples of time resolved growth experiments mainly from molecular thin film growth, but also highlight growth of inorganic materials using molecular beam epitaxy (MBE) and electrochemical deposition from liquids. We discuss how scaling parameters of rate equation models and fundamental energy barriers in kinetic Monte Carlo methods can be determined from fits of the real-time x-ray data.

  11. Relationship between time-resolved and non-time-resolved Beer-Lambert law in turbid media.

    PubMed

    Nomura, Y; Hazeki, O; Tamura, M

    1997-06-01

    The time-resolved Beer-Lambert law proposed for oxygen monitoring using pulsed light was extended to the non-time-resolved case in a scattered medium such as living tissues with continuous illumination. The time-resolved Beer-Lambert law was valid for the phantom model and living tissues in the visible and near-infrared regions. The absolute concentration and oxygen saturation of haemoglobin in rat brain and thigh muscle could be determined. The temporal profile of rat brain was reproduced by Monte Carlo simulation. When the temporal profiles of rat brain under different oxygenation states were integrated with time, the absorbance difference was linearly related to changes in the absorption coefficient. When the simulated profiles were integrated, there was a linear relationship within the absorption coefficient which was predicted for fractional inspiratory oxygen concentration from 10 to 100% and, in the case beyond the range of the absorption coefficient, the deviation from linearity was slight. We concluded that an optical pathlength which is independent of changes in the absorption coefficient is a good approximation for near-infrared oxygen monitoring.

  12. Watching a protein as it functions with 150-ps time-resolved x-ray crystallography.

    PubMed

    Schotte, Friedrich; Lim, Manho; Jackson, Timothy A; Smirnov, Aleksandr V; Soman, Jayashree; Olson, John S; Phillips, George N; Wulff, Michael; Anfinrud, Philip A

    2003-06-20

    We report picosecond time-resolved x-ray diffraction from the myoglobin (Mb) mutant in which Leu29 is replaced by Phe (L29Fmutant). The frame-by-frame structural evolution, resolved to 1.8 angstroms, allows one to literally "watch" the protein as it executes its function. Time-resolved mid-infrared spectroscopy of flash-photolyzed L29F MbCO revealed a short-lived CO intermediate whose 140-ps lifetime is shorter than that found in wild-type protein by a factor of 1000. The electron density maps of the protein unveil transient conformational changes far more dramatic than the structural differences between the carboxy and deoxy states and depict the correlated side-chain motion responsible for rapidly sweeping CO away from its primary docking site.

  13. Lucas-Kanade fluid trajectories for time-resolved PIV

    NASA Astrophysics Data System (ADS)

    Yegavian, Robin; Leclaire, Benjamin; Champagnat, Frédéric; Illoul, Cédric; Losfeld, Gilles

    2016-08-01

    We introduce a new method for estimating fluid trajectories in time-resolved PIV. It relies on a Lucas-Kanade paradigm and consists in a simple and direct extension of a two-frame estimation with FOLKI-PIV (Champagnat et al 2011 Exp. Fluids 50 1169-82). The so-called Lucas-Kanade Fluid Trajectories (LKFT) are assumed to be polynomial in time, and are found as the minimizer of a global functional, in which displacements are sought so as to match the intensities of a series of images pairs in the sequence, in the least-squares sense. All pairs involve the central image, similar to other recent time-resolved approaches (FTC (Lynch and Scarano 2013 Meas. Sci. Technol. 24 035305) and FTEE (Jeon et al 2014 Exp. Fluids 55 1-16)). As switching from a two-frame to a time-resolved objective simply amounts to adding terms in a functional, no significant additional algorithmic element is required. Similar to FOLKI-PIV the method is very well suited for GPU acceleration, which is an important feature as computational complexity increases with the image sequence size. Tests on synthetic data exhibiting peak-locking show that increasing the image sequence size strongly reduces both associated bias and random error, and that LKFT has a remaining total error comparable to that of FTEE on this case. Results on case B of the third PIV challenge (Stanislas et al 2008 Exp. Fluids 45 27-71) also show its ability to drastically reduce the error in situations with low signal-to-noise ratio. These results are finally confirmed on experimental images acquired in the near-field of a low Reynolds number jet. Strong reductions in peak-locking, spatial and temporal noise compared to two-frame estimation are also observed, on the displacement components themselves, as well as on spatial or temporal derivatives, such as vorticity and material acceleration.

  14. Time resolved spectral behavior of bright BATSE precursors

    NASA Astrophysics Data System (ADS)

    Burlon, D.; Ghirlanda, G.; Ghisellini, G.; Greiner, J.; Celotti, A.

    2009-10-01

    Aims: Gamma ray bursts (GRBs) are sometimes preceded by dimmer emission episodes, called “precursors”, whose nature is still a puzzle: they could either have the same origin as the main emission episode or they could be due to another mechanism. We investigate if precursors have some spectral distinctive feature with respect to the main GRB episodes. Methods: To this aim we compare the spectral evolution of the precursor with that of the main GRB event. We also study if and how the spectral parameters, and in particular the peak of the ν Fν spectrum of time resolved spectra, correlates with the flux. This allows us to test if the spectra of the precursor and of the main event belong to the same correlation (if any). We searched GRBs with precursor activity in the complete sample of 2704 bursts detected by BATSE finding that 12% of GRBs have one or more precursors. Among these we considered the bursts with time resolved spectral analysis performed by Kaneko et al. ( 2006, ApJS, 166, 298), selecting those having at least two time resolved spectra for the precursor. Results: We find that precursors and main events have very similar spectral properties. The spectral evolution within precursors has similar trends as the spectral evolution observed in the subsequent peaks. Also the typical spectral parameters of the precursors are similar to those of the main GRB events. Moreover, in several cases we find that within the precursors the peak energy of the spectrum is correlated with the flux similarly to what happens in the main GRB event. This strongly favors models in which the precursor is due to the same fireball physics of the main emission episodes. Figures 8 to 41 are only available in electronic form at http://www.aanda.org

  15. Time Resolved Phonon Spectroscopy, Version 1.0

    SciTech Connect

    Goett, Johnny; Zhu, Brian

    2016-12-22

    TRPS code was developed for the project "Time Resolved Phonon Spectroscopy". Routines contained in this piece of software were specially created to model phonon generation and tracking within materials that interact with ionizing radiation, particularly applicable to the modeling of cryogenic radiation detectors for dark matter and neutrino research. These routines were created to link seamlessly with the open source Geant4 framework for the modeling of radiation transport in matter, with the explicit intent of open sourcing them for eventual integration into that code base.

  16. A compact electron gun for time-resolved electron diffraction

    SciTech Connect

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A.

    2015-01-15

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern.

  17. Time-resolved Hyperspectral Fluorescence Spectroscopy using Frequency Modulated Excitation

    SciTech Connect

    ,; Neill, M

    2012-07-01

    An intensity-modulated excitation light source is used together with a micro channel plate intensified CCD (ICCD) detector gated at a slightly different frequency to generate a beat frequency from a fluorescent sample. The addition of a spectrograph produces a hyperspectral time-resolved data product where the resulting beat frequency is detected with a low frame rate camera. Measuring the beat frequency of the spectrum as a function of time allows separation of the excited fluorescence from ambient constant light sources. The excitation and detector repetition rates are varied over a range of discrete frequencies, and the phase shift of the beat wave maps out the emission decay rate(s).

  18. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, Chiranjit; Steinkamp, John A.

    1999-01-01

    Time-resolved fluorescence decay measurements for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated cw laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes.

  19. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, C.; Steinkamp, J.A.

    1999-06-01

    Time-resolved fluorescence decay measurements are disclosed for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated CW laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes. 12 figs.

  20. Femtosecond time-resolved electronic relaxation dynamics in tetrathiafulvalene

    SciTech Connect

    Staedter, D.; Polizzi, L.; Thiré, N.; Mairesse, Y.; Mayer, P.; Blanchet, V.

    2015-05-21

    In the present paper, the ultrafast electronic relaxation of tetrathiafulvalene (TTF) initiated around 4 eV is studied by femtosecond time-resolved velocity-map imaging. The goal is to investigate the broad double structure observed in the absorption spectrum at this energy. By monitoring the transients of the parent cation and its fragments and by varying the pump and the probe wavelengths, two internal conversions and intramolecular vibrational relaxation are detected both on the order of a few hundred of femtoseconds. Photoelectron images permit the assignment of a dark electronic state involved in the relaxation. In addition, the formation of the dimer of TTF has been observed.

  1. Sensitive, time-resolved, broadband spectroscopy of single transient processes

    NASA Astrophysics Data System (ADS)

    Fjodorow, Peter; Baev, Ivan; Hellmig, Ortwin; Sengstock, Klaus; Baev, Valery M.

    2015-09-01

    Intracavity absorption spectroscopy with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of transient gain and absorption in electrically excited Xe and Kr plasmas. The achieved time resolution for broadband spectral recording of a single process is 25 µs. For pulsed-periodic processes, the time resolution is limited by the laser pulse duration, which is set here to 3 µs. This pulse duration also predefines the effective absorption path length, which amounts to 900 m. The presented technique can be applied to multicomponent analysis of single transient processes such as shock tube experiments, pulse detonation engines, or explosives.

  2. Revealing Chemical Processes Involved in Electrochemical (De)Lithiation of Al with in Situ Neutron Depth Profiling and X-ray Diffraction.

    PubMed

    Liu, Danny X; Co, Anne C

    2016-01-13

    Herein we report a direct measurement of Li transport in real-time during charge and discharge process within an Al matrix using neutron depth profiling (NDP). In situ NDP was used to reveal and quantify parasitic losses during the first 25 mAhr/g of lithiation, followed by the formation of LiAl protrusions from the surface of pristine Al. Evidence of Li entrapment is also reported during delithiation. Subsequent lithiation and delithiation showed electrochemical charge passed to be equivalent to the amount of lithium incorporated into the Al matrix with negligible difference, suggesting that the parasitic losses including the formation of the solid electrolyte layer may be confined to the first lithiation. Parallel in situ XRD measurements also confirm the transformation of β-LiAl from a solid solution of α-LiAl, revealing solid solution-mediated crystallization of β-LiAl.

  3. Miniaturized time-resolved Raman spectrometer for planetary science based on a fast single photon avalanche diode detector array.

    PubMed

    Blacksberg, Jordana; Alerstam, Erik; Maruyama, Yuki; Cochrane, Corey J; Rossman, George R

    2016-02-01

    We present recent developments in time-resolved Raman spectroscopy instrumentation and measurement techniques for in situ planetary surface exploration, leading to improved performance and identification of minerals and organics. The time-resolved Raman spectrometer uses a 532 nm pulsed microchip laser source synchronized with a single photon avalanche diode array to achieve sub-nanosecond time resolution. This instrument can detect Raman spectral signatures from a wide variety of minerals and organics relevant to planetary science while eliminating pervasive background interference caused by fluorescence. We present an overview of the instrument design and operation and demonstrate high signal-to-noise ratio Raman spectra for several relevant samples of sulfates, clays, and polycyclic aromatic hydrocarbons. Finally, we present an instrument design suitable for operation on a rover or lander and discuss future directions that promise great advancement in capability.

  4. Motor Oil Classification Based on Time-Resolved Fluorescence

    PubMed Central

    Mu, Taotao; Chen, Siying; Zhang, Yinchao; Guo, Pan; Chen, He; Meng, Fandong

    2014-01-01

    A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils. PMID:24988439

  5. Nonadiabatic and Time-Resolved Photoelectron Spectroscopy for Molecular Systems.

    PubMed

    Flick, Johannes; Appel, Heiko; Rubio, Angel

    2014-04-08

    We quantify the nonadiabatic contributions to the vibronic sidebands of equilibrium and explicitly time-resolved nonequilibrium photoelectron spectra for a vibronic model system of trans-polyacetylene. Using exact diagonalization, we directly evaluate the sum-over-states expressions for the linear-response photocurrent. We show that spurious peaks appear in the Born-Oppenheimer approximation for the vibronic spectral function, which are not present in the exact spectral function of the system. The effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states and also persists when either only initial or final states are replaced by correlated vibronic states. Only when correlated initial and final vibronic states are taken into account are the spurious spectral weights of the Born-Oppenheimer approximation suppressed. In the nonequilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic wavepacket motion of the system can be traced in the time-resolved photoelectron spectra as a function of the pump-probe delay.

  6. Time-resolved luminescent lateral flow assay technology.

    PubMed

    Song, Xuedong; Knotts, Michael

    2008-09-26

    We here report a detection technology that integrates highly sensitive time-resolved luminescence technique into lateral flow assay platform to achieve excellent detection performance with low cost. We have developed very bright, surface-functionalized and mono-dispersed phosphorescent nanoparticles of long lifetime under ambient conditions. The phosphorescent nanoparticles have been used to conjugate with monoclonal antibody for C-reactive protein (CRP), an inflammatory biomarker. Lateral flow immunoassay devices have been developed using the conjugate for highly sensitive detection of CRP. The CRP assay can achieve a detection sensitivity of <0.2 ngmL(-1) in serum with a linear response from 0.2 to 200 ngmL(-1) CRP. We have also developed a low cost time-resolved luminescence reader for the lateral flow immunoassay (LFIA) devices. The reader does not use expensive band pass filter and still provide very low detection background and high detection sensitivity on solid substrates such as nitrocellulose membranes. The reader can detect less than 2.5 ng phosphorescent particles captured on a nitrocellulose membrane strip with more than three orders of magnitude linear detection dynamic range. The technology should find a number of applications, ranging from clinical diagnostics, detection of chemical and biological warfare agents, to food and environmental monitoring.

  7. Time-resolved quasielastic neutron scattering studies of native photosystems.

    PubMed

    Pieper, Jörg

    2010-01-01

    The internal molecular dynamics of proteins plays an important role in a number of functional processes in native photosystems. Prominent examples include the photocycle of bacteriorhodopsin and electron transfer in the reaction center of plant photosystem II. In this regard, the recently developed technique of time-resolved quasielastic neutron scattering with laser excitation opens up new perspectives for the study of protein/membrane dynamics in specific functional states of even complex systems. The first direct observation of a functionally modulated protein dynamics has just recently been reported for the model system bacteriorhodopsin (Pieper et al., Phys. Rev. Lett. 100, 2008, 228103.), where a transient softening of the protein was observed on a timescale of approximately 1 ms along with the large-scale structural change in the M-intermediate of bacteriorhodopsin. In contrast, photosystem II membrane fragments with inhibited electron transfer show a suppression of protein dynamics approximately 160 mus after the actinic laser flash (Pieper and Renger, Biochemistry 48, 2009, 6111). This effect may reflect aggregation-like conformational changes capable of dissipation of excess excitation energy to prevent photodamage in the absence of Q(A)-->Q(B) electron transfer. These findings indicate that proteins exhibit a remarkable flexibility to accommodate different functional processes. This contribution will discuss methodical aspects, challenges, and recent applications of laser-excited, time-resolved quasielastic neutron scattering.

  8. Time Resolved FTIR Analysis of Tailpipe Exhaust for Several Automobiles

    NASA Astrophysics Data System (ADS)

    White, Allen R.; Allen, James; Devasher, Rebecca B.

    2011-06-01

    The automotive catalytic converter reduces or eliminates the emission of various chemical species (e.g. CO, hydrocarbons, etc.) that are the products of combustion from automobile exhaust. However, these units are only effective once they have reached operating temperature. The design and placement of catalytic converters has changed in order to reduce both the quantity of emissions and the time that is required for the converter to be effective. In order to compare the effectiveness of catalytic converters, time-resolved measurements were performed on several vehicles, including a 2010 Toyota Prius, a 2010 Honda Fit, a 1994 Honda Civic, and a 1967 Oldsmobile 442 (which is not equipped with a catalytic converter but is used as a baseline). The newer vehicles demonstrate bot a reduced overall level of CO and hydrocarbon emissions but are also effective more quickly than older units. The time-resolved emissions will be discussed along with the impact of catalytic converter design and location on the measured emissions.

  9. Time resolved imaging microscopy. Phosphorescence and delayed fluorescence imaging.

    PubMed Central

    Marriott, G; Clegg, R M; Arndt-Jovin, D J; Jovin, T M

    1991-01-01

    An optical microscope capable of measuring time resolved luminescence (phosphorescence and delayed fluorescence) images has been developed. The technique employs two phase-locked mechanical choppers and a slow-scan scientific CCD camera attached to a normal fluorescence microscope. The sample is illuminated by a periodic train of light pulses and the image is recorded within a defined time interval after the end of each excitation period. The time resolution discriminates completely against light scattering, reflection, autofluorescence, and extraneous prompt fluorescence, which ordinarily decrease contrast in normal fluorescence microscopy measurements. Time resolved image microscopy produces a high contrast image and particular structures can be emphasized by displaying a new parameter, the ratio of the phosphorescence to fluorescence. Objects differing in luminescence decay rates are easily resolved. The lifetime of the long lived luminescence can be measured at each pixel of the microscope image by analyzing a series of images that differ by a variable time delay. The distribution of luminescence decay rates is displayed directly as an image. Several examples demonstrate the utility of the instrument and the complementarity it offers to conventional fluorescence microscopy. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:1723311

  10. Time-resolved single dopant charge dynamics in silicon

    PubMed Central

    Rashidi, Mohammad; Burgess, Jacob A. J.; Taucer, Marco; Achal, Roshan; Pitters, Jason L.; Loth, Sebastian; Wolkow, Robert A.

    2016-01-01

    As the ultimate miniaturization of semiconductor devices approaches, it is imperative that the effects of single dopants be clarified. Beyond providing insight into functions and limitations of conventional devices, such information enables identification of new device concepts. Investigating single dopants requires sub-nanometre spatial resolution, making scanning tunnelling microscopy an ideal tool. However, dopant dynamics involve processes occurring at nanosecond timescales, posing a significant challenge to experiment. Here we use time-resolved scanning tunnelling microscopy and spectroscopy to probe and study transport through a dangling bond on silicon before the system relaxes or adjusts to accommodate an applied electric field. Atomically resolved, electronic pump-probe scanning tunnelling microscopy permits unprecedented, quantitative measurement of time-resolved single dopant ionization dynamics. Tunnelling through the surface dangling bond makes measurement of a signal that would otherwise be too weak to detect feasible. Distinct ionization and neutralization rates of a single dopant are measured and the physical process controlling those are identified. PMID:27782125

  11. Time resolved fluorescence of cow and goat milk powder

    NASA Astrophysics Data System (ADS)

    Brandao, Mariana P.; de Carvalho dos Anjos, Virgílio; Bell., Maria José V.

    2017-01-01

    Milk powder is an international dairy commodity. Goat and cow milk powders are significant sources of nutrients and the investigation of the authenticity and classification of milk powder is particularly important. The use of time-resolved fluorescence techniques to distinguish chemical composition and structure modifications could assist develop a portable and non-destructive methodology to perform milk powder classification and determine composition. This study goal is to differentiate milk powder samples from cows and goats using fluorescence lifetimes. The samples were excited at 315 nm and the fluorescence intensity decay registered at 468 nm. We observed fluorescence lifetimes of 1.5 ± 0.3, 6.4 ± 0.4 and 18.7 ± 2.5 ns for goat milk powder; and 1.7 ± 0.3, 6.9 ± 0.2 and 29.9 ± 1.6 ns for cow's milk powder. We discriminate goat and cow powder milk by analysis of variance using Fisher's method. In addition, we employed quadratic discriminant analysis to differentiate the milk samples with accuracy of 100%. Our results suggest that time-resolved fluorescence can provide a new method to the analysis of powder milk and its composition.

  12. Time-resolved multispectral imaging of combustion reaction

    NASA Astrophysics Data System (ADS)

    Huot, Alexandrine; Gagnon, Marc-André; Jahjah, Karl-Alexandre; Tremblay, Pierre; Savary, Simon; Farley, Vincent; Lagueux, Philippe; Guyot, Éric; Chamberland, Martin; Marcotte, Fréderick

    2015-05-01

    Thermal infrared imaging is a field of science that evolves rapidly. Scientists have used for years the simplest tool: thermal broadband cameras. This allows to perform target characterization in both the longwave (LWIR) and midwave (MWIR) infrared spectral range. Infrared thermal imaging is used for a wide range of applications, especially in the combustion domain. For example, it can be used to follow combustion reactions, in order to characterize the injection and the ignition in a combustion chamber or even to observe gases produced by a flare or smokestack. Most combustion gases such as carbon dioxide (CO2) selectively absorb/emit infrared radiation at discrete energies, i.e. over a very narrow spectral range. Therefore, temperatures derived from broadband imaging are not reliable without prior knowledge about spectral emissivity. This information is not directly available from broadband images. However, spectral information is available using spectral filters. In this work, combustion analysis was carried out using Telops MS-IR MW camera which allows multispectral imaging at a high frame rate. A motorized filter wheel allowing synchronized acquisitions on eight (8) different channels was used to provide time-resolved multispectral imaging of combustion products of a candle in which black powder has been burnt to create a burst. It was then possible to estimate the temperature by modeling spectral profile derived from information obtained with the different spectral filters. Comparison with temperatures obtained using conventional broadband imaging illustrates the benefits of time-resolved multispectral imaging for the characterization of combustion processes.

  13. Time-resolved multispectral imaging of combustion reactions

    NASA Astrophysics Data System (ADS)

    Huot, Alexandrine; Gagnon, Marc-André; Jahjah, Karl-Alexandre; Tremblay, Pierre; Savary, Simon; Farley, Vincent; Lagueux, Philippe; Guyot, Éric; Chamberland, Martin; Marcotte, Frédérick

    2015-10-01

    Thermal infrared imaging is a field of science that evolves rapidly. Scientists have used for years the simplest tool: thermal broadband cameras. These allow to perform target characterization in both the longwave (LWIR) and midwave (MWIR) infrared spectral range. Infrared thermal imaging is used for a wide range of applications, especially in the combustion domain. For example, it can be used to follow combustion reactions, in order to characterize the injection and the ignition in a combustion chamber or even to observe gases produced by a flare or smokestack. Most combustion gases, such as carbon dioxide (CO2), selectively absorb/emit infrared radiation at discrete energies, i.e. over a very narrow spectral range. Therefore, temperatures derived from broadband imaging are not reliable without prior knowledge of spectral emissivity. This information is not directly available from broadband images. However, spectral information is available using spectral filters. In this work, combustion analysis was carried out using a Telops MS-IR MW camera, which allows multispectral imaging at a high frame rate. A motorized filter wheel allowing synchronized acquisitions on eight (8) different channels was used to provide time-resolved multispectral imaging of combustion products of a candle in which black powder has been burnt to create a burst. It was then possible to estimate the temperature by modeling spectral profiles derived from information obtained with the different spectral filters. Comparison with temperatures obtained using conventional broadband imaging illustrates the benefits of time-resolved multispectral imaging for the characterization of combustion processes.

  14. Experimental Time Resolved Electron Beam Temperature Measurements Using Bremsstrahlung Diagnostics

    SciTech Connect

    Menge, P.R.; Maenchen, J.E.; Mazarakis, M.G.; Rosenthal, S.E.

    1999-06-25

    Electron beam temperature, {beta}{perpendicular} (= v{perpendicular}/v), is important to control for the development of high dose flash radiographic bremsstrahlung sources. At high voltage (> 5 MV) increasing electron beam temperature has a serious deleterious effect on dose production. The average and time resolved behavior of beam temperature was measured during radiographic experiments on the HERMES III accelerator (10 MV, 50 kA, 70 ns). A linear array of thermoluminescent dosimeters (TLDs) were used to estimate the time integrated average of beam temperature. On and off-axis photoconducting diamond (PCD) detectors were used to measure the time resolved bremsstrahlung dose rate, which is dependent on beam energy and temperature. The beam temperature can be determined by correlating PCD response with accelerator voltage and current and also by analyzing the ratio of PCD amplitudes on and off axis. This ratio is insensitive to voltage and current and thus, is more reliable than utilizing absolute dose rate. The data is unfolded using comparisons with Monte Carlo simulations to obtain absolute beam temperatures. The data taken on HERMES III show abrupt increases in {beta}{perpendicular} midway through the pulse indicating rapid onset of beam instability.

  15. Dynamic structural evolution of supported palladium-ceria core-shell catalysts revealed by in situ electron microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Shuyi; Chen, Chen; Cargnello, Matteo; Fornasiero, Paolo; Gorte, Raymond J.; Graham, George W.; Pan, Xiaoqing

    2015-07-01

    The exceptional activity for methane combustion of modular palladium-ceria core-shell subunits on silicon-functionalized alumina that was recently reported has created renewed interest in the potential of core-shell structures as catalysts. Here we report on our use of advanced ex situ and in situ electron microscopy with atomic resolution to show that the modular palladium-ceria core-shell subunits undergo structural evolution over a wide temperature range. In situ observations performed in an atmospheric gas cell within this temperature range provide real-time evidence that the palladium and ceria nanoparticle constituents of the palladium-ceria core-shell participate in a dynamical process that leads to the formation of an unanticipated structure comprised of an intimate mixture of palladium, cerium, silicon and oxygen, with very high dispersion. This finding may open new perspectives about the origin of the activity of this catalyst.

  16. Dynamic structural evolution of supported palladium-ceria core-shell catalysts revealed by in situ electron microscopy.

    PubMed

    Zhang, Shuyi; Chen, Chen; Cargnello, Matteo; Fornasiero, Paolo; Gorte, Raymond J; Graham, George W; Pan, Xiaoqing

    2015-07-10

    The exceptional activity for methane combustion of modular palladium-ceria core-shell subunits on silicon-functionalized alumina that was recently reported has created renewed interest in the potential of core-shell structures as catalysts. Here we report on our use of advanced ex situ and in situ electron microscopy with atomic resolution to show that the modular palladium-ceria core-shell subunits undergo structural evolution over a wide temperature range. In situ observations performed in an atmospheric gas cell within this temperature range provide real-time evidence that the palladium and ceria nanoparticle constituents of the palladium-ceria core-shell participate in a dynamical process that leads to the formation of an unanticipated structure comprised of an intimate mixture of palladium, cerium, silicon and oxygen, with very high dispersion. This finding may open new perspectives about the origin of the activity of this catalyst.

  17. Distinct charge dynamics in battery electrodes revealed by in situ and operando soft X-ray spectroscopy

    PubMed Central

    Liu, Xiaosong; Wang, Dongdong; Liu, Gao; Srinivasan, Venkat; Liu, Zhi; Hussain, Zahid; Yang, Wanli

    2013-01-01

    Developing high-performance batteries relies on material breakthroughs. During the past few years, various in situ characterization tools have been developed and have become indispensible in studying and the eventual optimization of battery materials. However, soft X-ray spectroscopy, one of the most sensitive probes of electronic states, has been mainly limited to ex situ experiments for battery research. Here we achieve in situ and operando soft X-ray absorption spectroscopy of lithium-ion battery cathodes. Taking advantage of the elemental, chemical and surface sensitivities of soft X-rays, we discover distinct lithium-ion and electron dynamics in Li(Co1/3Ni1/3Mn1/3)O2 and LiFePO4 cathodes in polymer electrolytes. The contrast between the two systems and the relaxation effect in LiFePO4 is attributed to a phase transformation mechanism, and the mesoscale morphology and charge conductivity of the electrodes. These discoveries demonstrate feasibility and power of in situ soft X-ray spectroscopy for studying integrated and dynamic effects in batteries. PMID:24100759

  18. Distinct charge dynamics in battery electrodes revealed by in situ and operando soft X-ray spectroscopy.

    PubMed

    Liu, Xiaosong; Wang, Dongdong; Liu, Gao; Srinivasan, Venkat; Liu, Zhi; Hussain, Zahid; Yang, Wanli

    2013-01-01

    Developing high-performance batteries relies on material breakthroughs. During the past few years, various in situ characterization tools have been developed and have become indispensible in studying and the eventual optimization of battery materials. However, soft X-ray spectroscopy, one of the most sensitive probes of electronic states, has been mainly limited to ex situ experiments for battery research. Here we achieve in situ and operando soft X-ray absorption spectroscopy of lithium-ion battery cathodes. Taking advantage of the elemental, chemical and surface sensitivities of soft X-rays, we discover distinct lithium-ion and electron dynamics in Li(Co(¹/₃)Ni(¹/₃)Mn(¹/₃))O₂ and LiFePO₄ cathodes in polymer electrolytes. The contrast between the two systems and the relaxation effect in LiFePO₄ is attributed to a phase transformation mechanism, and the mesoscale morphology and charge conductivity of the electrodes. These discoveries demonstrate feasibility and power of in situ soft X-ray spectroscopy for studying integrated and dynamic effects in batteries.

  19. Synthesis and time-resolved structural characterization of framework and mineral sulfides

    NASA Astrophysics Data System (ADS)

    Cahill, Christopher Langley

    A new class of open-framework organic/inorganic hybrid materials based on In-S chemistry has been discovered. The compounds therein exhibit unprecedented structural diversity compared to known porous sulfides, primarily due to variation in framework building units. Further, large increases in pore dimensions (vs. zeolites, for example) are observed as these materials consist of comer and edge linked clusters, e.g. In10S20, In9S17, In4S10 and In6S 15. Choice of organic structure directing agents (templates) and careful control of reaction conditions (temperature, pH) both in the In-S and Ge-S systems is shown not only to dictate which building unit will form, but also to direct the resulting framework topology. Several of the compounds described herein crystallize either as powders, or as crystals too small for standard in-house X-ray structural analysis. Diffraction experiments have thus required synchrotron based single crystal techniques for structure determination. Further, certain reaction mixture compositions result in multi-phase end products, the formation pathways of which have been studied with time resolved, in situ synchrotron powder diffraction. An extension of the applicability of the in situ techniques investigated the role of oxygen in hydrothermal systems. Oxidation state is proposed to dictate speciation in the Ni-Ge-S system and to promote phase transformations in the Fe-S mineral system.

  20. Time-Resolved Chemical Mapping in Light-Emitting Electrochemical Cells.

    PubMed

    Jafari, Mohammad Javad; Liu, Jiang; Engquist, Isak; Ederth, Thomas

    2017-01-25

    An understanding of the doping and ion distributions in light-emitting electrochemical cells (LECs) is required to approach a realistic conduction model which can precisely explain the electrochemical reactions, p-n junction formation, and ion dynamics in the active layer and to provide relevant information about LECs for systematic improvement of function and manufacture. Here, Fourier-transform infrared (FTIR) microscopy is used to monitor anion density profile and polymer structure in situ and for time-resolved mapping of electrochemical doping in an LEC under bias. The results are in very good agreement with the electrochemical doping model with respect to ion redistribution and formation of a dynamic p-n junction in the active layer. We also physically slow ions by decreasing the working temperature and study frozen-junction formation and immobilization of ions in a fixed-junction LEC device by FTIR imaging. The obtained results show irreversibility of the ion redistribution and polymer doping in a fixed-junction device. In addition, we demonstrate that infrared microscopy is a useful tool for in situ characterization of electroactive organic materials.

  1. Highly sensitive detection of human papillomavirus type 16 DNA using time-resolved fluorescence microscopy and long lifetime probes

    NASA Astrophysics Data System (ADS)

    Wang, Xue F.; Periasamy, Ammasi; Wodnicki, Pawel; Siadat-Pajouh, M.; Herman, Brian

    1995-04-01

    We have been interested in the role of Human Papillomavirus (HPV) in cervical cancer and its diagnosis; to that end we have been developing microscopic imaging and fluorescent in situ hybridization (FISH) techniques to genotype and quantitate the amount of HPV present at a single cell level in cervical PAP smears. However, we have found that low levels of HPV DNA are difficult to detect accurately because theoretically obtainable sensitivity is never achieved due to nonspecific autofluorescence, fixative induced fluorescence of cells and tissues, and autofluorescence of the optical components in the microscopic system. In addition, the absorption stains used for PAP smears are intensely autofluorescent. Autofluorescence is a rapidly decaying process with lifetimes in the range of 1-100 nsec, whereas phosphorescence and delayed fluorescence have lifetimes in the range of 1 microsecond(s) ec-10 msec. The ability to discriminate between specific fluorescence and autofluorescence in the time-domain has improved the sensitivity of diagnostic test such that they perform comparably to, or even more sensitive than radioisotopic assays. We have developed a novel time-resolved fluorescence microscope to improve the sensitivity of detection of specific molecules of interest in slide based specimens. This time-resolved fluorescence microscope is based on our recently developed fluorescence lifetime imaging microscopy (FILM) in conjunction with the use of long lifetime fluorescent labels. By using fluorescence in situ hybridization and the long lifetime probe (europium), we have demonstrated the utility of this technique for detection of HPV DNA in cervicovaginal cells. Our results indicate that the use of time-resolved fluorescence microscopy and long lifetime probes increases the sensitivity of detection by removing autofluorescence and will thus lead to improved early diagnosis of cervical cancer. Since the highly sensitive detection of DNA in clinical samples using

  2. Singlet internal conversion processes in the order of 1Bu+→3Ag-→1Bu-→2Ag-→1Ag- in all- trans-spheroidene and lycopene as revealed by subpicosecond time-resolved Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Rondonuwu, Ferdy S.; Kakitani, Yoshinori; Tamura, Hiroshi; Koyama, Yasushi

    2006-09-01

    Key Raman lines ascribable to the 1Bu+, 3Ag-, 1Bu- and 2Ag- states were identified in the subpicosecond time-resolved Raman spectra of spheroidene and lycopene having 10 and 11 conjugated double bonds, respectively. The sequential rise-and-decay of the key Raman lines showed the internal conversion processes of 1Bu+→3Ag-→1Bu-→2Ag-→1Ag- (ground). The time constant in each step of internal conversion reflects the energy gap between the relevant states that had been determined by measurement of resonance - Raman excitation profiles [K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 (2002) 547].

  3. Time-resolved measurements of equilibrium profiles in MST

    NASA Astrophysics Data System (ADS)

    Deng, B. H.; Brower, D. L.; Ding, W. X.; Yates, T. F.; Anderson, J. K.; Caspary, K.; McCollam, K. J.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Craig, D.

    2007-11-01

    Based on the high-speed, three-wave, far-infrared polarimeter-interferometer measurement of Bpol profiles and external coil measurements of Btave and Btw, a new method is developed to derive Btor and other equilibrium profiles (J// and q) with high time resolution. Using Faraday's law, the inductive electric field (E//) profile is also deduced from the temporal derivatives of the time-resolved magnetic field profiles. The derived B(0) values have excellent agreement with direct measurements using a Motional Stark Effect (MSE) diagnostic. Evolution of equilibrium profiles during single sawtooth events in MST, both the slow linear ramp and crash phases, are presented. Profile scaling with plasma current Ip and reversal parameter F is also explored. MHD stability is tested from the spatial gradients of the J// and q profiles, and correlation with fluctuation mode amplitude is investigated. Future improvements to equilibrium reconstruction are expected by measuring Btor(r,t) directly via Cotton-Mouton interferometry.

  4. Time-resolved spectroscopy of low-dimensional semiconductor structures

    NASA Astrophysics Data System (ADS)

    Murphy, Joseph R.

    This dissertation is a survey of ultrafast time-resolved optical measurements conducted on a variety of low-dimensional semiconductor systems to further the understanding of the dynamic behavior in the following systems: ZnMnTe/ZnSe quantum dots, ZnTe/ZnMnSe quantum dots, InGaAs quantum wells, CdMnSe colloidal quantum dots, multi-shell CdSe/CdMnS/CdS colloidal nanoplatelets, and graphene and graphene-related solutions and films. Using time-resolved photoluminescence to study epitaxially-grown ZnTe and ZnMnTe quantum dots in corresponding ZnMnSe and ZnSe matrices, the location dependence of manganese ions in respect to magnetic polaron formation is shown. The structure with manganese ions located in the matrix exhibited magnetic polaron behavior consistent with previous literature, whereas the structure with the magnetic ions located within the quantum dots exhibited unconventional magnetic polaron properties. These properties, including temperature and magnetic field insensitivity, were explained through the use of a model that predicted an increased internal magnetic field due to a decreased effective volume of the magnetic polaron and a higher effective temperature due to laser heating. Magneto-time-resolved photoluminescence measurements on a system of colloidal CdMnSe quantum dots show that the magnetic polaron properties differ significantly from the epitaxially grown quantum dots. First the timescales at which the magnetic polaron forms and the polarization saturates are different by more than an order of magnitude, and second, the magnetic polaron energy exhibited step-like behavior as the strength of the externally applied magnetic field is increased. The field dependent MP formation energy that is observed experimentally is explained as due to the breaking of the antiferromagnetic coupling of Mn dimers within the QDs. This model is further verified by the observation of quantized behavior in the Zeeman energy splitting. Through the use of magneto

  5. Examining Electron-Boson Coupling Using Time-Resolved Spectroscopy

    SciTech Connect

    Sentef, Michael; Kemper, Alexander F.; Moritz, Brian; Freericks, James K.; Shen, Zhi-Xun; Devereaux, Thomas P.

    2013-12-26

    Nonequilibrium pump-probe time-domain spectroscopies can become an important tool to disentangle degrees of freedom whose coupling leads to broad structures in the frequency domain. Here, using the time-resolved solution of a model photoexcited electron-phonon system, we show that the relaxational dynamics are directly governed by the equilibrium self-energy so that the phonon frequency sets a window for “slow” versus “fast” recovery. The overall temporal structure of this relaxation spectroscopy allows for a reliable and quantitative extraction of the electron-phonon coupling strength without requiring an effective temperature model or making strong assumptions about the underlying bare electronic band dispersion.

  6. Towards time-resolved serial crystallography in a microfluidic device.

    PubMed

    Pawate, Ashtamurthy S; Šrajer, Vukica; Schieferstein, Jeremy; Guha, Sudipto; Henning, Robert; Kosheleva, Irina; Schmidt, Marius; Ren, Zhong; Kenis, Paul J A; Perry, Sarah L

    2015-07-01

    Serial methods for crystallography have the potential to enable dynamic structural studies of protein targets that have been resistant to single-crystal strategies. The use of serial data-collection strategies can circumvent challenges associated with radiation damage and repeated reaction initiation. This work utilizes a microfluidic crystallization platform for the serial time-resolved Laue diffraction analysis of macroscopic crystals of photoactive yellow protein (PYP). Reaction initiation was achieved via pulsed laser illumination, and the resultant electron-density difference maps clearly depict the expected pR(1)/pR(E46Q) and pR(2)/pR(CW) states at 10 µs and the pB1 intermediate at 1 ms. The strategies presented here have tremendous potential for extension to chemical triggering methods for reaction initiation and for extension to dynamic, multivariable analyses.

  7. Nonselective and polarization effects in time-resolved optogalvanic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhechev, D.; Steflekova, V.

    2016-02-01

    Three interfering effects in optogalvanic (OG) spectroscopy are identified in a hollow cathode discharge (HCD) - OG detector. The laser beam is found to generate two nonselective processes, namely photoelectron emission (PE) from the cathode surface with a sub-breakdown bias applied, and nonresonant space ionization. The convolution of these galvanic contributions was determined experimentally as an instrumental function and a deconvolution procedure to determine the actual OG signal was developed. Specific plasma conductance is detected dependent on the polarization of the laser beam irradiating. Linearly/circularly polarized light beam is found to induce OG signals differ in amplitude (and their shape parameters in the time-resolved OG signals (TROGS)). The phenomena coherence and specific conductance are found to be in causal relationship. The additional conductance due to coherent states of atoms manifests itself as an intrinsic instrumental property of OG detector.

  8. Time-resolve study of the photooxygenation of 3-hydroxyflavone

    SciTech Connect

    Studer, S.L.; Brewer, W.E.; Martinez, M.L.; Chou, Pi-Tai )

    1989-09-13

    3-hydroxyflavones are prototype molecules for studying the dynamics of the proton-transfer reaction in the excited state as well as in the ground state. Their lasing action has been reported with a high efficiency of laser gain. Unfortunately, a major obstruction to the practical application of 3-hydroxy-flavones as laser dyes is due to a photochemical reaction possibly involving molecular oxygen. In this communication we report a direct time-resolved study of the photooxygenation of 3-hydroxyflavone (3HF) in the normal state as well as in the tau-tomer state. Our results not only provide a detailed mechanism of the photooxygenation reaction but also give indirect evidence to support the role of the triplet state in the reverse proton-transfer reaction.

  9. Multidimensional Time-Resolved Spectroscopy of Vibrational Coherence in Biopolyenes

    NASA Astrophysics Data System (ADS)

    Buckup, Tiago; Motzkus, Marcus

    2014-04-01

    Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm-1 to over 2,000 cm-1 and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as β-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence.

  10. Towards time-resolved serial crystallography in a microfluidic device

    PubMed Central

    Pawate, Ashtamurthy S.; Šrajer, Vukica; Schieferstein, Jeremy; Guha, Sudipto; Henning, Robert; Kosheleva, Irina; Schmidt, Marius; Ren, Zhong; Kenis, Paul J. A.; Perry, Sarah L.

    2015-01-01

    Serial methods for crystallography have the potential to enable dynamic structural studies of protein targets that have been resistant to single-crystal strategies. The use of serial data-collection strategies can circumvent challenges associated with radiation damage and repeated reaction initiation. This work utilizes a microfluidic crystallization platform for the serial time-resolved Laue diffraction analysis of macroscopic crystals of photoactive yellow protein (PYP). Reaction initiation was achieved via pulsed laser illumination, and the resultant electron-density difference maps clearly depict the expected pR1/pRE46Q and pR2/pRCW states at 10 µs and the pB1 intermediate at 1 ms. The strategies presented here have tremendous potential for extension to chemical triggering methods for reaction initiation and for extension to dynamic, multivariable analyses. PMID:26144226

  11. Time-resolved phase-sensitive second harmonic generation spectroscopy

    NASA Astrophysics Data System (ADS)

    Nowakowski, Paweł J.; Woods, David A.; Bain, Colin D.; Verlet, Jan R. R.

    2015-02-01

    A methodology based on time-resolved, phase-sensitive second harmonic generation (SHG) for probing the excited state dynamics of species at interfaces is presented. It is based on an interference measurement between the SHG from the sample and a local oscillator generated at a reference together with a lock-in measurement to remove the large constant offset from the interference. The technique is characterized by measuring the phase and excited state dynamics of the dye malachite green at the water/air interface. The key attributes of the technique are that the observed signal is directly proportional to sample concentration, in contrast to the quadratic dependence from non-phase sensitive SHG, and that the real and imaginary parts of the 2nd order non-linear susceptibility can be determined independently. We show that the method is highly sensitive and can provide high quality excited state dynamics in short data acquisition times.

  12. Spectral characteristics of time resolved magnonic spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Etesami, S. R.; Chotorlishvili, L.; Berakdar, J.

    2015-09-01

    Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans [Phys. Rev. B 90, 064421 (2014)]. Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics.

  13. Photon-Counting Arrays for Time-Resolved Imaging

    PubMed Central

    Antolovic, I. Michel; Burri, Samuel; Hoebe, Ron A.; Maruyama, Yuki; Bruschini, Claudio; Charbon, Edoardo

    2016-01-01

    The paper presents a camera comprising 512 × 128 pixels capable of single-photon detection and gating with a maximum frame rate of 156 kfps. The photon capture is performed through a gated single-photon avalanche diode that generates a digital pulse upon photon detection and through a digital one-bit counter. Gray levels are obtained through multiple counting and accumulation, while time-resolved imaging is achieved through a 4-ns gating window controlled with subnanosecond accuracy by a field-programmable gate array. The sensor, which is equipped with microlenses to enhance its effective fill factor, was electro-optically characterized in terms of sensitivity and uniformity. Several examples of capture of fast events are shown to demonstrate the suitability of the approach. PMID:27367697

  14. Spectral characteristics of time resolved magnonic spin Seebeck effect

    SciTech Connect

    Etesami, S. R.; Chotorlishvili, L.; Berakdar, J.

    2015-09-28

    Spin Seebeck effect (SSE) holds promise for new spintronic devices with low-energy consumption. The underlying physics, essential for a further progress, is yet to be fully clarified. This study of the time resolved longitudinal SSE in the magnetic insulator yttrium iron garnet concludes that a substantial contribution to the spin current stems from small wave-vector subthermal exchange magnons. Our finding is in line with the recent experiment by S. R. Boona and J. P. Heremans [Phys. Rev. B 90, 064421 (2014)]. Technically, the spin-current dynamics is treated based on the Landau-Lifshitz-Gilbert equation also including magnons back-action on thermal bath, while the formation of the time dependent thermal gradient is described self-consistently via the heat equation coupled to the magnetization dynamics.

  15. Attosecond time-resolved imaging of molecular structure by photoelectron holography.

    PubMed

    Bian, Xue-Bin; Bandrauk, André D

    2012-06-29

    Dynamic imaging of the molecular structure of H(2)(+) is investigated by attosecond photoelectron holography. The interference between direct (reference) and backward rescattered (signal) photoelectrons in attosecond photoelectron holography reveals the birth time of both channels and the spatial information of molecular structure. This is confirmed by simulations with a semiclassical model and numerical solutions of the corresponding time-dependent Schrödinger equation, suggesting an attosecond time-resolved way of imaging molecular structure obtained from laser induced rescattering of ionized electrons. It is shown that both short and long rescattered electron trajectories can be imaged from the momentum distribution.

  16. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    SciTech Connect

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko

    2015-11-16

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼10{sup 4} times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si−O−Si angles bridging rigid SiO{sub 4} tetrahedra, which efficiently transduce electric energy into elastic energy.

  17. Time-resolved pump-probe spectroscopy of intraband absorption by a semiconductor nanorod

    NASA Astrophysics Data System (ADS)

    Leonov, Mikhail Y.; Rukhlenko, Ivan D.; Baranov, Alexander V.; Fedorov, Anatoly V.

    2013-09-01

    We develop a theory of time-resolved pump-probe optical spectroscopy of intraband absorption of a probe pulse inside an anisotropic semiconductor nanorod. The absorption is preceded by the absorption of the pump pulse resonant to an interband transition. It is assumed that the resonantly exited states of the nanorod are interrelated via the relaxation induced by their interaction with a bath. We reveal the conditions for which the absorption of the probe's pulse is governed by a simple formula regardless of the pulse's shape. This formula is useful for the analysis of the experimental data containing information on the relaxation parameters of the nanorod's electronic subsystem.

  18. In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors.

    PubMed

    Griffin, John M; Forse, Alexander C; Tsai, Wan-Yu; Taberna, Pierre-Louis; Simon, Patrice; Grey, Clare P

    2015-08-01

    Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results show that charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

  19. Time Resolved Phase Transitions via Dynamic Transmission Electron Microscopy

    SciTech Connect

    Reed, B W; Armstrong, M R; Blobaum, K J; Browning, N D; Burnham, A K; Campbell, G H; Gee, R; Kim, J S; King, W E; Maiti, A; Piggott, W T; Torralva, B R

    2007-02-22

    The Dynamic Transmission Electron Microscope (DTEM) project is developing an in situ electron microscope with nanometer- and nanosecond-scale resolution for the study of rapid laser-driven processes in materials. We report on the results obtained in a year-long LDRD-supported effort to develop DTEM techniques and results for phase transitions in molecular crystals, reactive multilayer foils, and melting and resolidification of bismuth. We report the first in situ TEM observation of the HMX {beta}-{delta} phase transformation in sub-{micro}m crystals, computational results suggesting the importance of voids and free surfaces in the HMX transformation kinetics, and the first electron diffraction patterns of intermediate states in fast multilayer foil reactions. This project developed techniques which are applicable to many materials systems and will continue to be employed within the larger DTEM effort.

  20. Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation

    PubMed Central

    Nevin, Austin; Cesaratto, Anna; Bellei, Sara; D'Andrea, Cosimo; Toniolo, Lucia; Valentini, Gianluca; Comelli, Daniela

    2014-01-01

    Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested. PMID:24699285

  1. Calcium carbonate nucleation driven by ion binding in a biomimetic matrix revealed by in situ electron microscopy.

    PubMed

    Smeets, Paul J M; Cho, Kang Rae; Kempen, Ralph G E; Sommerdijk, Nico A J M; De Yoreo, James J

    2015-04-01

    The characteristic shapes, structures and properties of biominerals arise from their interplay with a macromolecular matrix. The developing mineral interacts with acidic macromolecules, which are either dissolved in the crystallization medium or associated with insoluble matrix polymers, that affect growth habits and phase selection or completely inhibit precipitation in solution. Yet little is known about the role of matrix-immobilized acidic macromolecules in directing mineralization. Here, by using in situ liquid-phase electron microscopy to visualize the nucleation and growth of CaCO3 in a matrix of polystyrene sulphonate (PSS), we show that the binding of calcium ions to form Ca-PSS globules is a key step in the formation of metastable amorphous calcium carbonate (ACC), an important precursor phase in many biomineralization systems. Our findings demonstrate that ion binding can play a significant role in directing nucleation, independently of any control over the free-energy barrier to nucleation.

  2. Molecular orientation of molybdate ions adsorbed on goethite nanoparticles revealed by polarized in situ ATR-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Davantès, Athénaïs; Lefèvre, Grégory

    2016-11-01

    The speciation of species adsorbed on nanoparticles is a major concern for several fields, as environmental pollution and remediation, surface functionalization, or catalysis. Attenuated total reflectance infrared spectroscopy (ATR-IR) was amongst the rare methods able to give in situ information about the geometry of surface complexes on nanoparticles. A new possibility using this technique is illustrated here with the MoO42 -/goethite system. Using deuterated goethite to avoid spectral interferences, adsorption of molybdate ions on a spontaneous oriented film of nanoparticles has been followed using a polarized infrared beam. From the decomposition of spectra in the x, y and z directions, a monodentate surface complex on the {101} faces has been found as the most probable geometry. This result demonstrates that polarized ATR-IR allows to characterize in more details adsorption mode at the atomic scale, in comparison with usual ATR-IR spectroscopy.

  3. In-Situ Incubation of Iron-Sulfide Mineral in Seawater Reveals Colonization by Iron-Oxidizing Gammaproteobacteria and Zetaproteobacteria.

    NASA Astrophysics Data System (ADS)

    Barco, R. A.; Ramírez, G. A.; Sylvan, J. B.; Edwards, K. J.

    2015-12-01

    Sulfide mineral precipitation occurs at mid-ocean ridge (MOR) spreading centers, both in the form of plume particles and massive sulfide structures. A common constituent of MOR sulfide mineral is pyrrhotite (Fe1-xS). This mineral was chosen as a substrate for in-situ incubation studies in the shallow waters of Catalina Islands, CA to investigate the colonization of iron-oxidizing bacteria. Gammaproteobacteria and Alphaproteobacteria largely dominated the bacterial community on pyrrhotite samples incubated in the water column. Pyrrhotite samples incubated at the sediment/water column interface showed more even dominance by Gammaproteobacteria, Alphaproteobacteria, Deltaproteobacteria and Bacteroidetes. Cultivations that originated from these pyrrhotite samples resulted in the enrichment of Zetaproteobacteria with either twisted-stalks (Mariprofundus) or sheath structures. Additionally, a candidate novel Gammaproteobacterium was isolated and shown to grow autotrophically via the oxidation of iron.

  4. Segmental duplications within the Glycine max genome revealed by fluorescence in situ hybridization of bacterial artificial chromosomes.

    PubMed

    Pagel, Janice; Walling, Jason G; Young, Nevin D; Shoemaker, Randy C; Jackson, Scott A

    2004-08-01

    Soybean (Glycine max L. Merr.) is presumed to be an ancient polyploid based on chromosome number and multiple RFLP fragments in genetic mapping. Direct cytogenetic observation of duplicated regions within the soybean genome has not heretofore been reported. Employing fluorescence in situ hybridization (FISH) of genetically anchored bacterial artificial chromosomes (BACs) in soybean, we were able to observe that the distal ends of molecular linkage group E had duplicated regions on linkage groups A2 and B2. Further, using fiber-FISH, it was possible to measure the molecular size and organization of one of the duplicated regions. As FISH did not require repetitive DNA for blocking fluorescence signals, we assume that the 200-kb genome region is relatively low in repetitive sequences. This observation, along with the observation that the BACs are located in distal euchromatin regions, has implications for genome structure/evolution and the approach used to sequence the soybean genome.

  5. In situ SUMOylation analysis reveals a modulatory role of RanBP2 in the nuclear rim and PML bodies

    SciTech Connect

    Saitoh, Noriko . E-mail: hisa@gpo.kumamoto-u.ac.jp; Uchimura, Yasuhiro; Tachibana, Taro; Sugahara, Satoko; Saitoh, Hisato; Nakao, Mitsuyoshi . E-mail: mnakao@gpo.kumamoto-u.ac.jp

    2006-05-01

    SUMO modification plays a critical role in a number of cellular functions including nucleocytoplasmic transport, gene expression, cell cycle and formation of subnuclear structures such as promyelocytic leukemia (PML) bodies. In order to identify the sites where SUMOylation takes place in the cell, we developed an in situ SUMOylation assay using a semi-intact cell system and subsequently combined it with siRNA-based knockdown of nucleoporin RanBP2, also known as Nup358, which is one of the known SUMO E3 proteins. With the in situ SUMOylation assay, we found that both nuclear rim and PML bodies, besides mitotic apparatuses, are major targets for active SUMOylation. The ability to analyze possible SUMO conjugation sites would be a valuable tool to investigate where SUMO E3-like activities and/or SUMO substrates exist in the cell. Specific knockdown of RanBP2 completely abolished SUMOylation along the nuclear rim and dislocated RanGAP1 from the nuclear pore complexes. Interestingly, the loss of RanBP2 markedly reduced the number of PML bodies, in contrast to other, normal-appearing nuclear compartments including the nuclear lamina, nucleolus and chromatin, suggesting a novel link between RanBP2 and PML bodies. SUMOylation facilitated by RanBP2 at the nuclear rim may be a key step for the formation of a particular subnuclear organization. Our data imply that SUMO E3 proteins like RanBP2 facilitate spatio-temporal SUMOylation for certain nuclear structure and function.

  6. Time-resolved spectral imaging: better photon economy, higher accuracy

    NASA Astrophysics Data System (ADS)

    Fereidouni, Farzad; Reitsma, Keimpe; Blab, Gerhard A.; Gerritsen, Hans C.

    2015-03-01

    Lifetime and spectral imaging are complementary techniques that offer a non-invasive solution for monitoring metabolic processes, identifying biochemical compounds, and characterizing their interactions in biological tissues, among other tasks. Newly developed instruments that perform time-resolved spectral imaging can provide even more information and reach higher sensitivity than either modality alone. Here we report a multispectral lifetime imaging system based on a field-programmable gate array (FPGA), capable of operating at high photon count rates (12 MHz) per spectral detection channel, and with time resolution of 200 ps. We performed error analyses to investigate the effect of gate width and spectral-channel width on the accuracy of estimated lifetimes and spectral widths. Temporal and spectral phasors were used for analysis of recorded data, and we demonstrated blind un-mixing of the fluorescent components using information from both modalities. Fractional intensities, spectra, and decay curves of components were extracted without need for prior information. We further tested this approach with fluorescently doubly-labeled DNA, and demonstrated its suitability for accurately estimating FRET efficiency in the presence of either non-interacting or interacting donor molecules.

  7. Time-resolved pump-probe experiments at the LCLS

    SciTech Connect

    Glownia, James; Cryan, J.; Andreasson, J.; Belkacem, A.; Berrah, N.; Blaga, C.L.; Bostedt, C.; Bozek, J.; DiMauro, L.F.; Fang, L.; Frisch, J.; Gessner, O.; Guhr, M.; Hajdu, J.; Hertlein, M.P.; Hoener, M.; Huang, G.; Kornilov, O.; Marangos, J.P.; March, A.M.; McFarland, B.K.; /SLAC /Stanford U., Phys. Dept. /SLAC /IRAMIS, Saclay /Stanford U., Phys. Dept. /Georgia Tech /Argonne /Kansas State U. /SLAC /Stanford U., Phys. Dept. /SLAC /Stanford U., Appl. Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC /LBNL /Argonne /SLAC /SLAC /Stanford U., Appl. Phys. Dept. /Stanford U., Phys. Dept.

    2011-08-12

    The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

  8. Time-resolved pump-probe experiments at the LCLS.

    PubMed

    Glownia, James M; Cryan, J; Andreasson, J; Belkacem, A; Berrah, N; Blaga, C I; Bostedt, C; Bozek, J; DiMauro, L F; Fang, L; Frisch, J; Gessner, O; Gühr, M; Hajdu, J; Hertlein, M P; Hoener, M; Huang, G; Kornilov, O; Marangos, J P; March, A M; McFarland, B K; Merdji, H; Petrovic, V S; Raman, C; Ray, D; Reis, D A; Trigo, M; White, J L; White, W; Wilcox, R; Young, L; Coffee, R N; Bucksbaum, P H

    2010-08-16

    The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.

  9. Development of ultrafast time-resolved dual-comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Asahara, Akifumi; Minoshima, Kaoru

    2017-04-01

    Ultrafast time-resolved dual-comb spectroscopy (TR-DCS) has been demonstrated, which enables direct observations of transient responses of complex optical spectra by combining dual-comb spectroscopy with the pump-probe method. TR-DCS achieves two-dimensional spectroscopy with a wide dynamic range for both the temporal and frequency axes. As a demonstration, we investigated the femtosecond relaxation dynamics of a photo-excited InGaAs saturable absorber in the near-infrared frequency region. The transient response of the interferogram was successfully obtained, and both the amplitude and phase spectra of the dynamic complex transmittance were independently deduced without using the Kramers-Kronig relations. A high phase resolution in the order of milliradian was achieved by suppressing the effect from the slow phase drift caused in the experimental system. Our proof-of-principle experiment promotes a pathway to coherent, highly accurate, and multi-dimensional pump-probe spectroscopy using the optical frequency comb technology.

  10. A Multi-Enzyme Bioluminescent Time-Resolved Pyrophosphate Assay

    PubMed Central

    Sun, Ye; Jacobson, K. Bruce; Golovlev, Val

    2009-01-01

    We have developed a high-sensitivity assay for measurement of inorganic pyrophosphate (PPi) in adenosine 5′-triphosphate (ATP) contaminated samples. The assay is based on time-resolved measurements of the luminescence kinetics and implements multiple enzymes to convert PPi to ATP that is, in turn, utilized to produce light; and to hydrolyze PPi for measurement of the steady-state background luminescence. A theoretical model for describing luminescence kinetics and optimizing composition of the assay detection mixture is presented. We found the model is in excellent agreement with the experimental results. We have developed and evaluated two algorithms for PPi measurement from luminescence kinetics acquired from ATP-contaminated samples. The first algorithm is considered to be the method of choice for analysis of long, i.e., 3-5 min, kinetics. The activity of enzymes is controlled during the experiment; the sensitivity of PPi detection is about 7 pg/ml or 15 pM of PPi in ATP-contaminated samples. The second algorithm is designed for analysis of short, i.e., less than 1-min luminescence kinetics. It has about 20 pM PPi detection sensitivity and may be the better choice for assays in microplate format, where a short measurement time is required. The PPi assay is primarily developed for RNA expression analysis, but it also can be used in various applications, which require high sensitivity PPi detection in ATP-contaminated samples. PMID:17540325

  11. Time-Resolved Hard X-Ray Spectrometer

    SciTech Connect

    Kenneth Moya; Ian McKennaa; Thomas Keenana; Michael Cuneob

    2007-03-01

    Wired array studies are being conducted at the SNL Z accelerator to maximize the x-ray generation for inertial confinement fusion targets and high energy density physics experiments. An integral component of these studies is the characterization of the time-resolved spectral content of the x-rays. Due to potential spatial anisotropy in the emitted radiation, it is also critical to diagnose the time-evolved spectral content in a space-resolved manner. To accomplish these two measurement goals, we developed an x-ray spectrometer using a set of high-speed detectors (silicon PIN diodes) with a collimated field-of-view that converged on a 1-cm-diameter spot at the pinch axis. Spectral discrimination is achieved by placing high Z absorbers in front of these detectors. We built two spectrometers to permit simultaneous different angular views of the emitted radiation. Spectral data have been acquired from recent Z shots for the radial and polar views. UNSPEC1 has been adapted to analyze and unfold the measured data to reconstruct the x-ray spectrum. The unfold operator code, UFO2, is being adapted for a more comprehensive spectral unfolding treatment.

  12. Time resolved spectroscopic NMR imaging using hyperpolarized 129Xe

    NASA Astrophysics Data System (ADS)

    Han, S.; Kühn, H.; Häsing, F. W.; Münnemann, K.; Blümich, B.; Appelt, S.

    2004-04-01

    We have visualized the melting and dissolution processes of xenon (Xe) ice into different solvents using the methods of nuclear magnetic resonance (NMR) spectroscopy, imaging, and time resolved spectroscopic imaging by means of hyperpolarized 129Xe. Starting from the initial condition of a hyperpolarized solid Xe layer frozen on top of an ethanol (ethanol/water) ice block we measured the Xe phase transitions as a function of time and temperature. In the pure ethanol sample, pieces of Xe ice first fall through the viscous ethanol to the bottom of the sample tube and then form a thin layer of liquid Xe/ethanol. The xenon atoms are trapped in this liquid layer up to room temperature and keep their magnetization over a time period of 11 min. In the ethanol/water mixture (80 vol%/20%), most of the polarized Xe liquid first stays on top of the ethanol/water ice block and then starts to penetrate into the pores and cracks of the ethanol/water ice block. In the final stage, nearly all the Xe polarization is in the gas phase above the liquid and trapped inside the pores. NMR spectra of homogeneous samples of pure ethanol containing thermally polarized Xe and the spectroscopic images of the melting process show that very high concentrations of hyperpolarized Xe (about half of the density of liquid Xe) can be stored or delivered in pure ethanol.

  13. Fielding of a time-resolved tomographic diagnostic

    SciTech Connect

    Daniel Frayer, Brian Cox, Wendi Dreesen, Douglas Johnson, Morris Kaufman

    2008-03-01

    A diagnostic instrument has been developed for the acquisition of high-speed time-resolved images at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The instrument was developed in order to create time histories of the electron beam. Four discrete optical subsystems view Cerenkov light generated at an X-ray target inside of a vacuum envelope. Each system employs cylindrical optics to image light in one direction and collapse light in the orthogonal direction. Each of the four systems images and collapses in unique axes, thereby capturing unique information. Light along the imaging axis is relayed via optical fiber to streak cameras. A computer is used to reconstruct the original image from the four optically collapsed images. Due to DARHT’s adverse environment, the instrument can be operated remotely to adjust optical parameters and contains a subsystem for remote calibration. The instrument was deployed and calibrated, and has been used to capture and reconstruct images. Matters of alignment, calibration, control, resolution, adverse conditions and maintenance will be discussed.

  14. Time resolved EUV spectra from Zpinching capillary discharge plasma

    NASA Astrophysics Data System (ADS)

    Jancarek, Alexandr; Nevrkla, Michal; Nawaz, Fahad

    2015-09-01

    We developed symmetrically charged driver to obtain high voltage, high current Z-pinching capillary discharge. Plasma is created by up to 70 kA, 29 ns risetime current pulse passing through a 5 mm inner diameter, 224 mm long capillary filled with gas to initial pressure in the range of 1 kPa. Due to the low inductance design of the driver, the pinch is observable directly from the measured current curve. Time-integrated and time-resolved spectra of discharge plasma radiation are recorded together with the capillary current and analyzed. The most encouraging spectra were captured in the wavelength range 8.3 ÷ 14 nm. This spectral region contains nitrogen Balmer series lines including potentially lasing NVII 2 - 3 transition. Spectral lines are identified in the NIST database using the FLY kinetic code. The line of 13.38 nm wavelength, transition NVII 2 - 3, was observed in gated, and also in time-integrated spectra for currents >60 kA. This work has been supported by the Ministry of Education, Youth and Sports of the Czech Republic grants LG13029.

  15. Chopper system for time resolved experiments with synchrotron radiation.

    PubMed

    Cammarata, Marco; Eybert, Laurent; Ewald, Friederike; Reichenbach, Wolfgang; Wulff, Michael; Anfinrud, Philip; Schotte, Friedrich; Plech, Anton; Kong, Qingyu; Lorenc, Maciej; Lindenau, Bernd; Räbiger, Jürgen; Polachowski, Stephan

    2009-01-01

    A chopper system for time resolved pump-probe experiments with x-ray beams from a synchrotron is described. The system has three parts: a water-cooled heatload chopper, a high-speed chopper, and a millisecond shutter. The chopper system, which is installed in beamline ID09B at the European Synchrotron Radiation Facility, provides short x-ray pulses for pump-probe experiments with ultrafast lasers. The chopper system can produce x-ray pulses as short as 200 ns in a continuous beam and repeat at frequencies from 0 to 3 kHz. For bunch filling patterns of the synchrotron with pulse separations greater than 100 ns, the high-speed chopper can isolate single 100 ps x-ray pulses that are used for the highest time resolution. A new rotor in the high-speed chopper is presented with a single pulse (100 ps) and long pulse (10 micros) option. In white beam experiments, the heatload of the (noncooled) high-speed chopper is lowered by a heatload chopper, which absorbs 95% of the incoming power without affecting the pulses selected by the high speed chopper.

  16. Fielding of a Time-Resolved Tomographic Diagnostic

    SciTech Connect

    Daniel Frayer, Brian Cox, Wendi Dreesen, Douglas Johnson, Mike Jones, Morris Kaufman

    2008-09-11

    A diagnostic instrument has been developed for the acquisition of high-speed time-resolved images at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The instrument was developed in order to create time histories of the electron beam. Four discrete optical subsystems view Cerenkov light generated at an x-ray target inside of a vacuum envelope. Each system employs cylindrical optics to image light in one direction and collapse light in the orthogonal direction. Each of the four systems images and collapses in unique axes, thereby capturing unique information. Light along the imaging axis is relayed via optical fiber to streak cameras. A computer is used to reconstruct the original image from the four optically collapsed images. Due to DARHT’s adverse environment, the instrument can be operated remotely to adjust optical parameters and contains a subsystem for remote calibration. The instrument was deployed and calibrated, and has been used to capture and reconstruct images. Matters of alignment, calibration, control, resolution, and adverse conditions will be discussed.

  17. Picosecond time-resolved fluorescence spectroscopy of phytochrome and stentorin

    NASA Astrophysics Data System (ADS)

    Song, Pill-Soon

    1991-05-01

    Phytochrome is a tetrapyrrole chromoprotein. It serves as a sensitive photosensor for red lightmediated gene expression and other developmental/morphological responses in plants. In this paper photochemical dynamics of the phytochrome molecule have been described in terms of photoisomerization of the tetrapyrrole chromophore in its singlet excited state and subsequent thermal processes in the Pr Pfr phototransformation of phytochrome. Stentorin acts as the photosensor molecule in the ciliate Stentor coeruleus. This unicellular protozoan is most sensitive to red light (610-620 urn). Stentor also senses the direction of light propagation as evidenced by their light-avoiding and negative phototactic swimming behaviors. This aneural photosensory phenomenon is triggered by the photoreceptor stentorin. The possible involvement of a light-induced transient proton release from the photoreceptor as the primary mechanism of light-signal processing has been discussed on the basis of picosecond fluorescence decays and time-resolved fluorescence spectra of stentorin in solution. An initial sensory signal generated by the primary photoprocess of stentorin then triggers subsequent transduction steps that include calcium ion influx from the extracellular medium. Calcium ion influx from the extracellular medium to the cytosol causes the Stentor cell to reverse its ciliary beating and subsequently steer away from the light trap. II.

  18. Femtosecond time-resolved MeV electron diffraction

    DOE PAGES

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; ...

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing themore » evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.« less

  19. Femtosecond time-resolved MeV electron diffraction

    SciTech Connect

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; Tobey, R. I.; Hill, J. P.; Wang, X. J.

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.

  20. Monitoring tissue metabolism via time-resolved laser fluorescence

    NASA Astrophysics Data System (ADS)

    Maerz, Holger K.; Buchholz, Rainer; Emmrich, Frank; Fink, Frank; Geddes, Clive L.; Pfeifer, Lutz; Raabe, Ferdinand; Marx, Uwe

    1999-05-01

    Most assays for drug screening are monitoring the metabolism of cells by detecting the NADH content, which symbolize its metabolic activity, indirectly. Nowadays, the performance of a LASER enables us to monitor the metabolic state of mammalian cells directly and on-line by using time-resolved autofluorescence detection. Therefore, we developed in combination with tissue engineering, an assay for monitoring minor toxic effects of volatile organic compounds (VOC), which are accused of inducing Sick Building Syndrome (SBS). Furthermore, we used the Laserfluoroscope (LF) for pharmacological studies on human bone marrow in vitro with special interest in chemotherapy simulation. In cancer research and therapy, the effect of chemostatica in vitro in the so-called oncobiogram is being tested; up to now without great success. However, it showed among other things that tissue structure plays a vital role. Consequently, we succeeded in simulating a chemotherapy in vitro on human bone marrow. Furthermore, after tumor ektomy we were able to distinguish between tumoric and its surrounding healthy tissue by using the LF. With its sensitive detection of metabolic changes in tissues the LF enables a wide range of applications in biotechnology, e.g. for quality control in artificial organ engineering or biocompatability testing.

  1. Time-resolved shadowgraphy of optical breakdown in fused silica

    NASA Astrophysics Data System (ADS)

    Tran, K. A.; Grigorov, Y. V.; Nguyen, V. H.; Rehman, Z. U.; Le, N. T.; Janulewicz, K. A.

    2015-07-01

    Dynamics of a laser-induced optical breakdown in the bulk of fused silica initiated by a sub-nanosecond laser pulse of an energy fluence as high as 8.7 kJ/cm2 was investigated by using femtosecond time-resolved shadowgraphy. Plasma ignition, growth of the damaged region and accompanying hydrodynamic motion were recorded from the moment directly before the arrival of the driving laser pulse, in the time steps adapted to the rate of the occurring processes. The growth rate of the plasma channel, curvature radii and velocities of the wave fronts were extracted from the shadowgrams. It was found that the plasma channel develops with a supersonic velocity and the first observed shock front tends to transform itself from the initial bowl-like shape to the final spherical one characterising an acoustic wave. Appearance of multiple fronts accompanying the main shock front was registered and used in more detailed analysis of the optical breakdown dynamics in the transparent dielectrics.

  2. Time-resolved local strain tracking microscopy for cell mechanics

    NASA Astrophysics Data System (ADS)

    Aydin, O.; Aksoy, B.; Akalin, O. B.; Bayraktar, H.; Alaca, B. E.

    2016-02-01

    A uniaxial cell stretching technique to measure time-resolved local substrate strain while simultaneously imaging adherent cells is presented. The experimental setup comprises a uniaxial stretcher platform compatible with inverted microscopy and transparent elastomer samples with embedded fluorescent beads. This integration enables the acquisition of real-time spatiotemporal data, which is then processed using a single-particle tracking algorithm to track the positions of fluorescent beads for the subsequent computation of local strain. The present local strain tracking method is demonstrated using polydimethylsiloxane (PDMS) samples of rectangular and dogbone geometries. The comparison of experimental results and finite element simulations for the two sample geometries illustrates the capability of the present system to accurately quantify local deformation even when the strain distribution is non-uniform over the sample. For a regular dogbone sample, the experimentally obtained value of local strain at the center of the sample is 77%, while the average strain calculated using the applied cross-head displacement is 48%. This observation indicates that considerable errors may arise when cross-head measurement is utilized to estimate strain in the case of non-uniform sample geometry. Finally, the compatibility of the proposed platform with biological samples is tested using a unibody PDMS sample with a well to contain cells and culture media. HeLa S3 cells are plated on collagen-coated samples and cell adhesion and proliferation are observed. Samples with adherent cells are then stretched to demonstrate simultaneous cell imaging and tracking of embedded fluorescent beads.

  3. Time-resolved hard x-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Moy, Kenneth; Cuneo, Michael; McKenna, Ian; Keenan, Thomas; Sanford, Thomas; Mock, Ray

    2006-08-01

    Wired array studies are being conducted at the SNL Z accelerator to maximize the x-ray generation for inertial confinement fusion targets and high energy density physics experiments. An integral component of these studies is the characterization of the time-resolved spectral content of the x-rays. Due to potential spatial anisotropy in the emitted radiation, it is also critical to diagnose the time-evolved spectral content in a space-resolved manner. To accomplish these two measurement goals, we developed an x-ray spectrometer using a set of high-speed detectors (silicon PIN diodes) with a collimated field-of-view that converged on a 1-cm-diameter spot at the pinch axis. Spectral discrimination is achieved by placing high Z absorbers in front of these detectors. We built two spectrometers to permit simultaneous different angular views of the emitted radiation. Spectral data have been acquired from recent Z shots for the radial and axial (polar) views. UNSPEC 1 has been adapted to analyze and unfold the measured data to reconstruct the x-ray spectrum. The unfold operator code, UFO2, is being adapted for a more comprehensive spectral unfolding treatment.

  4. Static and time-resolved spectroscopic studies of low-symmetry Ru(II) polypyridyl complexes

    SciTech Connect

    Curtright, A.E.; McCusker, J.K.

    1999-09-02

    The spectroscopic and electrochemical properties of a series of four Ru{sup II} polypyridyl complexes are reported. Compounds of the form [Ru(dmb){sub x}(dea){sub 3{minus}x}]{sup 2+} (x = 0--3), where dmb is 4,4{prime}-dimethyl-2,2{prime}-bipyridine and dea is 4,4{prime}-bis(diethylamino)-2,2{prime}-bipyridine, have been prepared and studied using static and time-resolved electronic and vibrational spectroscopies as a prelude to femtosecond spectroscopic studies of excited-state dynamics. Static electronic spectra in CH{sub 3}CN solution reveal a systematic shift of the MLCT absorption envelope from a maximum of 458 nm in the case of [Ru(dmb){sub 3}]{sup 2+} to 518 nm for [Ru(dea){sub 3}]{sup 2+} with successive substitutions of dea for dmb, suggesting a dea-based chromophore as the lowest-energy species. However, analysis of static and time-resolved emission data indicates an energy gap ordering of [Ru(dmb){sub 3}]{sup 2+} > [Ru(dmb){sub 2}(dea)]{sup 2+} > [Ru(dea){sub 3}]{sup 2+} > [Ru(dmb)(DEA){sub 2}]{sup 2+}, at variance with the electronic structures inferred from the absorption spectra. Nanosecond time-resolved electronic absorption and time-resolved step-scan infrared data are used to resolve this apparent conflict and confirm localization of the long-lived {sup 3}MLCT state on dmb in all three complexes where this ligand is present, thus making the dea-based excited state unique to [Ru(dea){sub 3}]{sup 2+}. Electrochemical studies further reveal the origin of this result, where a strong influence of the dea ligand on the oxidative Ru{sup II/III} couple, due to {pi} donation from the diethylamino substituent, is observed. The electronic absorption spectra are then reexamined in light of the now well-determined excited-state electronic structure. The results serve to underscore the importance of complete characterization of the electronic structures of transition metal complexes before embarking on ultrafast studies of their excited-state properties.

  5. Persistent luminescence nanoprobe for biosensing and lifetime imaging of cell apoptosis via time-resolved fluorescence resonance energy transfer.

    PubMed

    Zhang, Lei; Lei, Jianping; Liu, Jintong; Ma, Fengjiao; Ju, Huangxian

    2015-10-01

    Time-resolved fluorescence technique can reduce the short-lived background luminescence and auto-fluorescence interference from cells and tissues by exerting the delay time between pulsed excitation light and signal acquisition. Here, we prepared persistent luminescence nanoparticles (PLNPs) to design a universal time-resolved fluorescence resonance energy transfer (TR-FRET) platform for biosensing, lifetime imaging of cell apoptosis and in situ lifetime quantification of intracellular caspase-3. Three kinds of PLNPs-based nanoprobes are assembled by covalently binding dye-labeled peptides or DNA to carboxyl-functionalized PLNPs for the efficient detection of caspase-3, microRNA and protein. The peptides-functionalized nanoprobe is also employed for fluorescence lifetime imaging to monitor cell apoptosis, which shows a dependence of cellular fluorescence lifetime on caspase-3 activity and thus leads to an in situ quantification method. This work provides a proof-of-concept for PLNPs-based TR-FRET analysis and demonstrates its potential in exploring dynamical information of life process.

  6. New Pathways and Time-resolved Vibrational Dynamics of Surface Reactions

    NASA Astrophysics Data System (ADS)

    Wolf, Martin

    2000-03-01

    We discuss recent results of femtosecond laser-induced reactions and time-resolved vibrational spectroscopy at metal surfaces which provide detailed insights into the microscopic reaction mechanism and the rate of energy flow between the adsorbate and the underlying substrate. We demonstrate that fs laser excitation allows to access new reaction pathways which cannot be induced with conventional thermal activation: Heating of a Ru(001) surface on which CO and atomic oxygen are co-adsorbed leads exclusively to desorption of CO. In contrast, excitation with intense fs laser pulses enables also the formation of CO_2, in addition to CO desorption. Thus a new reaction path is opened upon fs laser excitation. Time-resolved two-pulse-correlation and isotope substitution experiments as well as density functional calculations reveal that this novel reaction pathway is initiated by laser heated hot substrate electrons which populate an antibonding unoccupied state of the O-Ru bond. The vibrationally activated oxygen reacts with co-adsorbed CO on an ultrashort time scale. On the other hand, desorption of CO molecules is caused by coupling of the adsorbate to the phonon bath of the substrate, which occurs much slower than the hot electron driven CO2 formation. Thus under fs excitation the process of CO desorption is outpaced, but prevails for conventional thermal heating due to a lower activation energy. In a further set of experiments the technique of fs infrared-visible sum-frequency generation (SFG) has been used as a time-resolved molecule specific 'probe' to analyze the transient changes of the CO stretching mode on Ru(001) after excitation with an intense fs 'pump' pulse. At low CO coverages the broadband infrared laser pulses also allow to excite the overtones of the CO stretch.

  7. Taking the pulse of snowmelt: in situ sensors reveal seasonal, event and diurnal patterns of nitrate and dissolved organic matter variability in an upland forest stream

    USGS Publications Warehouse

    Pellerin, Brian A.; Saraceno, John Franco; Shanley, James B.; Sebestyen, Stephen D.; Aiken, George R.; Wollheim, Wilfred M.; Bergamaschi, Brian A.

    2011-01-01

    Highly resolved time series data are useful to accurately identify the timing, rate, and magnitude of solute transport in streams during hydrologically dynamic periods such as snowmelt. We used in situ optical sensors for nitrate (NO3-) and chromophoric dissolved organic matter fluorescence (FDOM) to measure surface water concentrations at 30 min intervals over the snowmelt period (March 21–May 13, 2009) at a 40.5 hectare forested watershed at Sleepers River, Vermont. We also collected discrete samples for laboratory absorbance and fluorescence as well as δ18O–NO3- isotopes to help interpret the drivers of variable NO3- and FDOM concentrations measured in situ. In situ data revealed seasonal, event and diurnal patterns associated with hydrological and biogeochemical processes regulating stream NO3- and FDOM concentrations. An observed decrease in NO3- concentrations after peak snowmelt runoff and muted response to spring rainfall was consistent with the flushing of a limited supply of NO3- (mainly from nitrification) from source areas in surficial soils. Stream FDOM concentrations were coupled with flow throughout the study period, suggesting a strong hydrologic control on DOM concentrations in the stream. However, higher FDOM concentrations per unit streamflow after snowmelt likely reflected a greater hydraulic connectivity of the stream to leachable DOM sources in upland soils. We also observed diurnal NO3- variability of 1–2 μmol l-1 after snowpack ablation, presumably due to in-stream uptake prior to leafout. A comparison of NO3- and dissolved organic carbon yields (DOC, measured by FDOM proxy) calculated from weekly discrete samples and in situ data sub-sampled daily resulted in small to moderate differences over the entire study period (-4 to 1% for NO3- and -3 to -14% for DOC), but resulted in much larger differences for daily yields (-66 to +27% for NO3- and -88 to +47% for DOC, respectively). Despite challenges inherent in in situ sensor

  8. Concerted growth and ordering of cobalt nanorod arrays as revealed by tandem in situ SAXS-XAS studies

    SciTech Connect

    Cormary, Benoit; Li, Tao; Liakakos, Nikos; Peres, Laurent; Fazzini, Pier -Francesco; Blon, Thomas; Respaud, Marc; Kropf, A. Jeremy; Chaudret, Bruno; Miller, Jeffrey T.; Mader, Elizabeth A.; Soulantica, Katerina

    2016-06-14

    The molecular and ensemble dynamics for the growth of hierarchical supercrystals of cobalt nanorods have been studied by in situ tandem X-ray Absorption Spectroscopy – Small Angle X-ray Scattering (XAS - SAXS). The super-crystals were obtained by reducing a Co(II) precursor under H2 in the presence of a long chain amine and a long chain carboxylic acid. Complementary time-dependent ex situ TEM studies were also performed. The experimental data provide critical insights into the nanorod growth mechanism, and unequivocal evidence for a concerted growth-organization process. Nanorod formation involves cobalt nucleation, a fast atom by atom anisotropic growth and a slower oriented attach-ment process that continues well after cobalt reduction is complete. As a result, smectic-like ordering of the nanorods appears very early in the process, as soon as nanoparticle elongation appears, and nanorod growth takes place inside organized super-lattices, which can be regarded as mesocrystals.

  9. Homoeologous chromosome pairing between the A and B genomes of Musa spp. revealed by genomic in situ hybridization

    PubMed Central

    Jeridi, Mouna; Bakry, Frédéric; Escoute, Jacques; Fondi, Emmanuel; Carreel, Françoise; Ferchichi, Ali; D'Hont, Angélique; Rodier-Goud, Marguerite

    2011-01-01

    Background and Aims Most cooking banana and several desert bananas are interspecific triploid hybrids between Musa acuminata (A genome) and Musa balbisiana (B genome). In addition, M. balbisiana has agronomical characteristics such as resistance to biotic and abiotic stresses that could be useful to improve monospecific acuminata cultivars. To develop efficient breeding strategies for improving Musa cultivars, it is therefore important to understand the possibility of chromosome exchange between these two species. Methods A protocol was developed to prepare chromosome at meiosis metaphase I suitable for genomic in situ hybridization. A series of technical challenges were encountered, the main ones being the hardness of the cell wall and the density of the microsporocyte's cytoplasm, which hampers accessibility of the probes to the chromosomes. Key parameters in solving these problems were addition of macerozyme in the enzyme mix, the duration of digestion and temperature during the spreading phase. Results and Conclusions This method was applied to analyse chromosome pairing in metaphase from triploid interspecific cultivars, and it was clearly demonstrated that interspecific recombinations between M. acuminata and M. balbisiana chromosomes do occur and may be frequent in triploid hybrids. These results provide new insight into Musa cultivar evolution and have important implications for breeding. PMID:21835815

  10. Deep-sea in situ observations of gonatid squid and their prey reveal high occurrence of cannibalism

    NASA Astrophysics Data System (ADS)

    Hoving, H. J. T.; Robison, B. H.

    2016-10-01

    In situ observations are rarely applied in food web studies of deep-sea organisms. Using deep-sea observations obtained by remotely operated vehicles in the Monterey Submarine Canyon, we examined the prey choices of more than 100 individual squids of the genus Gonatus. Off the California coast, these squids are abundant, semelparous (one reproductive cycle) oceanic predators but their diet has remained virtually unknown. Gonatus onyx and Gonatus berryi were observed to feed on mesopelagic fishes (in particular the myctophid Stenobrachius leucopsarus) as often as on squids but inter-specific differences in feeding were apparent. Gonatids were the most common squid prey and while cannibalism occurred in both species it was particularly high in Gonatus onyx (42% of all prey items). Typically, the size of prey was similar to the size of the predator but the squids were also seen to take much larger prey. Postjuvenile gonatids are opportunistic predators that consume nektonic members of the meso-and bathypelagic communities, including their own species. Such voracious feeding is likely necessary to support the high energetic demands associated with the single reproductive event; and for females the long brooding period during which they must depend on stored resources.

  11. In situ observations of the basal angiosperm Amborella trichopoda reveal a long fruiting cycle overlapping two annual flowering periods.

    PubMed

    Fourcade, Fanny; Pouteau, Robin; Jaffré, Tanguy; Marmey, Philippe

    2015-09-01

    Amborella trichopoda is the sole living angiosperm species belonging to the sister lineage of all other extant flowering plants. In the last decade, the species has been the focus of many phylogenetic, genomic and reproductive biology studies, bringing new highlights regarding the evolution of flowering plants. However, little attention has been paid to in situ A. trichopoda populations, particularly to their fruiting cycle. In this study, an A. trichopoda population was observed during three annual flowering cycles. Individuals and branches were labeled in order to monitor the fruiting cycle precisely, from the flowering stage until the abscission of the fruit. Fruit exocarp was green during the first 9 months following flowering, turned red when the next flowering started a year later then remained on the branch during another year, between fruit ripping and abscission. Presence of fruits with two stages of maturity on shrubs was always noticed. Germination tests showed that seeds acquired their germination capacity 1 year after flowering, when fruits changed color. A. trichopoda's fruiting cycle is a long process overlapping two annual flowering periods. These results introduce a new model for flowering and fruiting cycles. The availability of mature seeds on shrubs for more than 1 year is likely to maximize opportunities to be dispersed, thus promoting the survival of this basal angiosperm.

  12. In Situ Experiments To Reveal the Role of Surface Feature Sidewalls in the Cassie–Wenzel Transition

    PubMed Central

    2014-01-01

    Waterproof and self-cleaning surfaces continue to attract much attention as they can be instrumental in various different technologies. Such surfaces are typically rough, allowing liquids to contact only the outermost tops of their asperities, with air being entrapped underneath. The formed solid–liquid–air interface is metastable and, hence, can be forced into a completely wetted solid surface. A detailed understanding of the wetting barrier and the dynamics of this transition is critically important for the practical use of the related surfaces. Toward this aim, wetting transitions were studied in situ at a set of patterned perfluoropolyether dimethacrylate (PFPEdma) polymer surfaces exhibiting surface features with different types of sidewall profiles. PFPEdma is intrinsically hydrophobic and exhibits a refractive index very similar to water. Upon immersion of the patterned surfaces into water, incident light was differently scattered at the solid–liquid–air and solid–liquid interface, which allows for distinguishing between both wetting states by dark-field microscopy. The wetting transition observed with this methodology was found to be determined by the sidewall profiles of the patterned structures. Partial recovery of the wetting was demonstrated to be induced by abrupt and continuous pressure reductions. A theoretical model based on Laplace’s law was developed and applied, allowing for the analytical calculation of the transition barrier and the potential to revert the wetting upon pressure reduction. PMID:25496232

  13. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Wu, Wei; Teng, Zhenke; Liaw, Peter K

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  14. Concerted growth and ordering of cobalt nanorod arrays as revealed by tandem in situ SAXS-XAS studies

    DOE PAGES

    Cormary, Benoit; Li, Tao; Liakakos, Nikos; ...

    2016-06-14

    The molecular and ensemble dynamics for the growth of hierarchical supercrystals of cobalt nanorods have been studied by in situ tandem X-ray Absorption Spectroscopy – Small Angle X-ray Scattering (XAS - SAXS). The super-crystals were obtained by reducing a Co(II) precursor under H2 in the presence of a long chain amine and a long chain carboxylic acid. Complementary time-dependent ex situ TEM studies were also performed. The experimental data provide critical insights into the nanorod growth mechanism, and unequivocal evidence for a concerted growth-organization process. Nanorod formation involves cobalt nucleation, a fast atom by atom anisotropic growth and a slowermore » oriented attach-ment process that continues well after cobalt reduction is complete. As a result, smectic-like ordering of the nanorods appears very early in the process, as soon as nanoparticle elongation appears, and nanorod growth takes place inside organized super-lattices, which can be regarded as mesocrystals.« less

  15. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    DOE PAGES

    Huang, Shenyan; Gao, Yanfei; An, Ke; ...

    2014-10-22

    In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

  16. Deformation mechanisms in a precipitation-strengthened ferritic super alloy revealed by in situ neutron dffraction studies at elevated temperatures

    SciTech Connect

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Teng, Zhenke; Wu, Wei; Liaw, Peter K.

    2015-01-01

    The ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)AlB2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

  17. Time-resolved study of Higgs mode in superconductors

    NASA Astrophysics Data System (ADS)

    Shimano, Ryo

    The behavior of superconductors far from equilibrium has been intensively studied over decades. Goals of these studies are the elucidation of bosonic fluctuations essential for the pairing mechanisms, the manifestation of competing orders or hidden phases, and the optical manipulation of superconductivity. The study of collective modes is crucially important for these perspectives as it provides the information on the dynamics of order parameters in non-equilibirium states. Generally, collective modes in ordered phases associated with spontaneous symmetry breaking are classified into 1) gapless phase modes and 2) gapped amplitude modes. In superconductors, the phase mode is eaten by gauge field, according to the Anderson-Higgs mechanism. The remaining amplitude mode is recently termed as Higgs mode from its analogy to the Higgs boson in particle physics. Despite its long history of investigation, unambiguous observation of Higgs mode has remained elusive. This is because the Higgs mode does not have a charge nor electric dipole and therefore it does not couple directly to the electromagnetic field. Here we report on our recent observation of Higgs mode in s-wave superconductors by using THz-pump and THz-probe spectroscopy technique. After nonadiabatic excitation near the superconducting gap energy with monocycle THz pulses, Higgs mode was observed as oscillations in the transmission of THz probe pulse. The resonant nonlinear coupling between the Higgs mode and coherent radiation field was also discovered, resulting in an efficient third order harmonic generation of the incident THz radiation. The extension of experiments to multiband superconductors and unconventional superconductors will be discussed. Time-resolved study of Higgs mode in superconductors.

  18. Time-resolved diagnostics for concrete target response

    SciTech Connect

    Baum, D.W.; Kuklo, R.M.; Reaugh, J.E.; Simonson, S.C.

    1996-05-01

    In order to facilitate the design of advanced penetrating weapons for defeating land targets, the interaction of concrete with high-velocity penetrators needs to be better characterized. To aid in this effort, three new types of time-resolved diagnostics are being developed and have been used in two experiments and one demonstration: fiber optic arrays to localize penetrators in space and time, Fabry-Perot velocimetry to record the concrete particle velocity, which is related to the pressure, at specific locations within concrete targets, and micropower impulse radar to provide a non-intrusive measure of the penetrator position-time history in a target. The two experiments used the fiber optic array and the Fabry-Perot velocimeter to diagnose the response of concrete to penetration by a Viper shaped charge jet. The results were analyzed using the CALE continuum mechanics simulation program, for which a preliminary model of the material properties of concrete was developed. The fiber optic arrays recorded the bow shock at locations 6.4 and 16.9 cm from the front surfaces. The Fabry-Perot velocimeter measured a free-surface velocity of 0.13 km/s at a distance of 3 cm and obliquity 70{degree} from the jet, which was moving at an interface velocity of 4.0 km/s at a depth of 29 cm. These values imply a pressure of about 6.6 kbar at that location. The demonstration used micropower impulse radar with a pulse repetition frequency of 0.25 MHz and a cell size of 30 ps to detect and record the motion of a metal penetrator simulant moving inside a cylindrical concrete target.

  19. Time resolved studies of bond activation by organometallic complexes

    SciTech Connect

    Wilkens, Matthew J.

    1998-05-01

    In 1971, Jetz and Graham discovered that the silicon-hydrogen bond in silanes could be broken under mild photochemical conditions in the presence of certain transition metal carbonyls. Such reactions fall within the class of oxidative addition. A decade later, similar reactivity was discovered in alkanes. In these cases a C-H bond in non-functionalized alkanes was broken through the oxidative addition of Cp*Ir(H)2L (Cp* = (CH3)5C5, L = PPh3, Ph = C6H5) to form Cp*ML(R)(H) or of Cp*Ir(CO)2 to form Cp*Ir(CO)(R)(H). These discoveries opened an entirely new field of research, one which naturally included mechanistic studies aimed at elucidating the various paths involved in these and related reactions. Much was learned from these experiments but they shared the disadvantage of studying under highly non-standard conditions a system which is of interest largely because of its characteristics under standard conditions. Ultrafast time-resolved IR spectroscopy provides an ideal solution to this problem; because it allows the resolution of chemical events taking place on the femto-through picosecond time scale, it is possible to study this important class of reactions under the ambient conditions which are most of interest to the practicing synthetic chemist. Certain of the molecules in question are particularly well-suited to study using the ultrafast IR spectrophotometer described in the experimental section because they contain one or more carbonyl ligands.

  20. Time-Resolved Bandgap Reflectivity of Photoexcited Cadmium-Selenium

    NASA Astrophysics Data System (ADS)

    Frigo, Nicholas John

    The first time-resolved bandgap reflectivity measurements of CdSe are presented. The time resolution was in the ten picosecond range and was attained by using a two-pulse pump-probe technique. Carriers were created by the absorption of the pump pulse and the reflectivity of the probe pulse was measured as a function of the probe's wavelength and its time delay relative to the pump. Specifically, the excitonic reflectivity was the feature monitored in these experiments. In order to perform the experiments, a new type of two-wavelength picosecond dye laser was developed. Its novel intersecting cavity configuration permitted the high flux levels, wide tuning range, spectral location, and pulse synchronization needed for creating high electron -hole densities and measuring the reflectivity near the bandgap of CdSe. The reflectivity results were surprising. A rapid recovery of the screened excitonic reflectivity was seen that was unanticipated by earlier experimental results and theoretical estimates. Attempts to explain the data by electron-hole liquid formation, surface recombination, or bimolecular recombination were unable to agree with the data. To explain the unusual speed of the recovery a model was developed which emphasized carrier diffusion against impurity scattering. The carrier diffusion model gave estimates of the recovery time in substantial agreement with the reflectivity measurements. In addition, the model's predictions agreed well with a wide range of other reported experiments ranging from picosecond to nanosecond time scales in CdS, CdSe, and GaAs using gain and luminescence measurements. Approximate solutions in closed form were presented that duplicated the major features of the model. Preliminary evidence against electron-hole liquid formation was presented; a low power experiment failed to give the expected signature. This result is unexpected since the temperature of these experiments is estimated to be lower than the temperature of the

  1. On-chip time resolved detection of quantum dot emission using integrated superconducting single photon detectors.

    PubMed

    Reithmaier, G; Lichtmannecker, S; Reichert, T; Hasch, P; Müller, K; Bichler, M; Gross, R; Finley, J J

    2013-01-01

    We report the routing of quantum light emitted by self-assembled InGaAs quantum dots (QDs) into the optical modes of a GaAs ridge waveguide and its efficient detection on-chip via evanescent coupling to NbN superconducting nanowire single photon detectors (SSPDs). The waveguide coupled SSPDs primarily detect QD luminescence, with scattered photons from the excitation laser onto the proximal detector being negligible by comparison. The SSPD detection efficiency from the evanescently coupled waveguide modes is shown to be two orders of magnitude larger when compared with operation under normal incidence illumination, due to the much longer optical interaction length. Furthermore, in-situ time resolved measurements performed using the integrated detector show an average QD spontaneous emission lifetime of 0.95 ns, measured with a timing jitter of only 72 ps. The performance metrics of the SSPD integrated directly onto GaAs nano-photonic hardware confirms the strong potential for on-chip few-photon quantum optics using such semiconductor-superconductor hybrid systems.

  2. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    PubMed Central

    Lambert, P. K.; Hustedt, C. J.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Woll, A. R.; Purohit, P.; Weiss, J. T.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.

    2014-01-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼103–104 s−1 in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation. PMID:25273733

  3. Time-resolved WAXD studies on the crystallization of isotactic polypropylene/graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Nishitsuji, Shotaro; Endoh, Maya; Guo, Yichen; Rafailovich, Miriam; Koga, Tadanori

    2015-03-01

    Graphene is one layer of carbon atoms, which has good electronic, thermal conductivity and mechanical properties. By adding graphene to isotactic polypropylene (iPP), the mechanical and electrical properties of the polymer are significantly improved. To further achieve high performance of iPP/graphene nanocomposites (``NCs''), it is important to investigate the relationship between the crystalline structure of iPP and the mechanical property of the iPP/graphene NCs. In this study, the effect of the graphene on the crystallization behavior of the polymer was investigated by using time-resolved wide angle X-ray diffraction (WAXD). The iPP/graphene NCs with different weight ratios of graphene were prepared by using a twin screw extruder. After temperature jump from 210 °C (>Tm) to 170 °C, the melt-crystallization process was observed by in situ WAXD. The results showed that the crystalline structure of all the samples was still α-form that is the same as the neat PP, while the ratios of the diffraction peaks are quite different from those of the neat PP. We will discuss the detailed structure in this presentation.

  4. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

    SciTech Connect

    Lambert, P. K.; Hustedt, C. J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C.; Vecchio, K. S.; Huskins, E. L.; Casem, D. T.; Gruner, S. M.; Tate, M. W.; Philipp, H. T.; Purohit, P.; Weiss, J. T.; Woll, A. R.; Kannan, V.; Ramesh, K. T.; Kenesei, P.; Okasinski, J. S.; Almer, J.

    2014-09-15

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼10{sup 3}–10{sup 4} s{sup −1} in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

  5. Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading.

    PubMed

    Lambert, P K; Hustedt, C J; Vecchio, K S; Huskins, E L; Casem, D T; Gruner, S M; Tate, M W; Philipp, H T; Woll, A R; Purohit, P; Weiss, J T; Kannan, V; Ramesh, K T; Kenesei, P; Okasinski, J S; Almer, J; Zhao, M; Ananiadis, A G; Hufnagel, T C

    2014-09-01

    We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ~10(3)-10(4) s(-1) in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10-20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (~40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

  6. Time-resolved monitoring of biofouling development on a flat sheet membrane using optical coherence tomography.

    PubMed

    Fortunato, Luca; Jeong, Sanghyun; Leiknes, TorOve

    2017-12-01

    Biofouling on a membrane leads to significant performance decrease in filtration processes. In this study, an optical coherence tomography (OCT) was used to perform a time-resolved analysis of dynamic biofouling development on a submerged membrane under continuous operation. A real-time change in the biofouling morphology was calculated through the image analysis of OCT scans. Three videos were generated through the acquisition of serial static images. This is the first study that displays the dynamic biofouling formation process as a video. The acquisition of OCT cross-sectional scans of the biofouling allowed to evaluate the time-lapsed evolution for three different time periods (early stage, double layers and long-term). Firstly, at the early filtration stage, membrane coverage and average biofouling layer thickness were found to be linearly correlated with the permeate flux pattern. Secondly, after 3 d of operation, an anomalous morphology was observed, constituted by a double-layered biofouling structure: denser on the bottom and looser on the top. In a long-term operation, the biofouling structure underwent a dynamic evolution over time, resulting in a multi-layered structure. The biofouling formation information was closely associated with filtration performance (i.e. flux) indicating the suitability of OCT as real-time and in-situ biofouling monitoring technique.

  7. Applications of time-resolved laser fluorescence spectroscopy to the environmental biogeochemistry of actinides.

    PubMed

    Collins, Richard N; Saito, Takumi; Aoyagi, Noboru; Payne, Timothy E; Kimura, Takaumi; Waite, T David

    2011-01-01

    Time-resolved laser fluorescence spectroscopy (TRLFS) is a useful means of identifying certain actinide species resulting from various biogeochemical processes. In general, TRLFS differentiates chemical species of a fluorescent metal ion through analysis of different excitation and emission spectra and decay lifetimes. Although this spectroscopic technique has largely been applied to the analysis of actinide and lanthanide ions having fluorescence decay lifetimes on the order of microseconds, such as UO , Cm, and Eu, continuing development of ultra-fast and cryogenic TRLFS systems offers the possibility to obtain speciation information on metal ions having room-temperature fluorescence decay lifetimes on the order of nanoseconds to picoseconds. The main advantage of TRLFS over other advanced spectroscopic techniques is the ability to determine in situ metal speciation at environmentally relevant micromolar to picomolar concentrations. In the context of environmental biogeochemistry, TRLFS has principally been applied to studies of (i) metal speciation in aqueous and solid phases and (ii) the coordination environment of metal ions sorbed to mineral and bacterial surfaces. In this review, the principles of TRLFS are described, and the literature reporting the application of this methodology to the speciation of actinides in systems of biogeochemical interest is assessed. Significant developments in TRLFS methodology and advanced data analysis are highlighted, and we outline how these developments have the potential to further our mechanistic understanding of actinide biogeochemistry.

  8. Time resolved studies on pulsed fluorocarbon plasmas using chirped quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Welzel, S.; Stepanov, S.; Meichsner, J.; Röpcke, J.

    2010-03-01

    The kinetics of stable species has been studied in situ in pulsed CF4/H2 radio frequency discharges by means of time resolved quantum cascade laser absorption spectroscopy. The absorption spectra were usually recorded with a time resolution of 5 ms and required a multi-species analysis, because of interfering complex absorption features of CF4 and C3F8. For this reason, measurements were carried out at two different spectral positions. High resolution spectroscopic data were established by calibrating effective absorption cross sections and their relative temperature dependences for the relevant low pressure conditions (10 Pa). During the discharge a decrease in the CF4 density by ~12% was observed. The off-phase was characterized mainly by the gas exchange. The C3F8 density in the off-phase was found to be of the order of the detection limit (3 × 1013 cm-3). Spectra acquired during the plasma-on phase showed a rapid temperature-induced increase in the absorption signal and, additionally, suggested the influence of a short-lived broadband absorbing species. The reasonable assumption of the presence of CF4 hotbands has not yet enabled a further quantification.

  9. Time-resolved characterization of laser-induced plasma from fresh potatoes

    NASA Astrophysics Data System (ADS)

    Lei, Wenqi; Motto-Ros, Vincent; Boueri, Myriam; Ma, Qianli; Zhang, Dacheng; Zheng, Lijuan; Zeng, Heping; Yu, Jin

    2009-09-01

    Optical emission of laser-induced plasma on the surface of fresh vegetables provides sensitive analysis of trace elements for in situ or online detection of these materials. This emergent technique promises applications with expected outcomes in food security or nutrition quality, as well as environment pollution detection. Characterization of the plasma induced on such soft and humid materials represents the first step towards quantitative measurement using this technique. In this paper, we present the experimental setup and protocol that optimize the plasma generation on fresh vegetables, potatoes for instance. The temporal evolution of the plasma properties are investigated using time-resolved laser-induced breakdown spectroscopy (LIBS). In particular, the electron density and the temperatures of the plasma are reported as functions of its decay time. The temperatures are evaluated from the well known Boltzmann and Saha-Boltzmann plot methods. These temperatures are further compared to that of the typical molecular species, CN, for laser-induced plasma from plant materials. This comparison validates the local thermodynamic equilibrium (LTE) in the specific case of fresh vegetables ablated in the typical LIBS conditions. A study of the temporal evolution of the signal to noise ratio also provides practical indications for an optimized detection of trace elements. We demonstrate finally that, under certain conditions, the calibration-free LIBS procedure can be applied to determine the concentrations of trace elements in fresh vegetables.

  10. Microbial diversity in an in situ reactor system treating monochlorobenzene contaminated groundwater as revealed by 16S ribosomal DNA analysis.

    PubMed

    Alfreider, Albin; Vogt, Carsten; Babel, Wolfgang

    2002-08-01

    A molecular approach based on the construction of 16S ribosomal DNA clone libraries was used to investigate the microbial diversity of an underground in situ reactor system filled with the original aquifer sediments. After chemical steady state was reached in the monochlorobenzene concentration between the original inflowing groundwater and the reactor outflow, samples from different reactor locations and from inflowing and outflowing groundwater were taken for DNA extraction. Small-subunit rRNA genes were PCR-amplified with primers specific for Bacteria, subsequently cloned and screened for variation by restriction fragment length polymorphism (RFLP). A total of 87 bacterial 16S rDNA genes were sequenced and subjected to phylogenetic analysis. The original groundwater was found to be dominated by a bacterial consortium affiliated with various members of the class of Proteobacteria, by phylotypes not affiliated with currently recognized bacterial phyla, and also by sporulating and non-sporulating sulfate-reducing bacteria. The most occurring clone types obtained from the sediment samples of the reactor were related to the beta-Proteobacteria, dominated by sequences almost identical to the widespread bacterium Alcaligenes faecalis, to low G+C gram-positive bacteria and to Acidithiobacillus ferrooxidans (formerly Thiobacillus ferrooxidans) within the gamma subclass of Proteobacteria in the upper reactor sector. Although bacterial phylotypes originating from the groundwater outflow of the reactors also grouped within different subdivisions of Proteobacteria and low G+C gram-positive bacteria, most of the 16S rDNA sequences were not associated with the sequence types observed in the reactor samples. Our results suggest that the different environments were inhabited by distinct microbial communities in respect to their taxonomic diversity, particular pronounced between sediment attached microbial communities from the reactor samples and free-living bacteria from the

  11. High frequency measurements using in situ sensors in a coupled watershed-estuary reveal factors driving DOC variability

    NASA Astrophysics Data System (ADS)

    Mulukutla, G. K.; Carey, R. O.; Wollheim, W. M.; Salisbury, J.

    2012-12-01

    Estuaries are recipients of large inputs of organic matter and nutrients from coastal river systems and together form a vital link between two of the largest pools of carbon, the terrestrial and ocean environment, at the same time actively cycling carbon. The Great Bay situated in New Hampshire/Maine is a nitrogen(N)-impaired estuary with a suburbanizing watershed of the Lamprey River its largest source of DOC. Long term deployment of continuously monitoring sensors are changing the way biogeochemical studies of rivers, streams and estuaries are conducted. We linked simultaneous and continuous in situ measurements of CDOM and associated measures of DOC quality (e.g. absorption coefficient, spectral slope ) in both the Great Bay estuary and its largest source of DOC the Lamprey River between April and December 2011. These sensors allowed us to examine the continuous dynamics of CDOM from inland to the coastal waters not only in short-term hydrologically varying (storm pulses) conditions, but also the longer term seasonal variability. We also collected a suite of other relevant parameters in both the watershed and estuary, including NO3, PO4, Turbidity, Chlorophyll, Conductivity/Salinity to help understand the dynamics of DOC in the river and estuary. Preliminary time series analysis indicates that DOC in the Great Bay estuary co-varies with discharge of the Lamprey River, especially in spring and fall. Freshwater discharges and its variations explained the variability in estuarine DOC. UV- absorbance at 254 nm (the precursor to SUVA) co-varies in periods of high flow during spring and fall, consistent with the bulk DOC results This suggests that hydrology is the more important driver of variability of coastal CDOM. In light of climate change, suburbanization and changing land use patterns this emphasizes the need to examine continuous measurements of DOC quantity and quality in coupled watershed-estuarine systems.

  12. In situ Spectroscopy Reveals that Microorganisms in Different Phyla Use Different Electron Transfer Biomolecules to Respire Aerobically on Soluble Iron

    PubMed Central

    Blake II, Robert C.; Anthony, Micah D.; Bates, Jordan D.; Hudson, Theresa; Hunter, Kamilya M.; King, Brionna J.; Landry, Bria L.; Lewis, Megan L.; Painter, Richard G.

    2016-01-01

    Absorbance spectra were collected on 12 different live microorganisms, representing six phyla, as they respired aerobically on soluble iron at pH 1.5. A novel integrating cavity absorption meter was employed that permitted accurate absorbance measurements in turbid suspensions that scattered light. Illumination of each microorganism yielded a characteristic spectrum of electrochemically reduced colored prosthetic groups. A total of six different patterns of reduced-minus-oxidized difference spectra were observed. Three different spectra were obtained with members of the Gram-negative eubacteria. Acidithiobacillus, representing Proteobacteria, yielded a spectrum in which cytochromes a and c and a blue copper protein were all prominent. Acidihalobacter, also representing the Proteobacteria, yielded a spectrum in which both cytochrome b and a long-wavelength cytochrome a were clearly visible. Two species of Leptospirillum, representing the Nitrospirae, both yielded spectra that were dominated by a cytochrome with a reduced peak at 579 nm. Sulfobacillus and Alicyclobacillus, representing the Gram-positive Firmicutes, both yielded spectra dominated by a-type cytochromes. Acidimicrobium and Ferrimicrobium, representing the Gram-positive Actinobacteria, also yielded spectra dominated by a-type cytochromes. Acidiplasma and Ferroplasma, representing the Euryarchaeota, both yielded spectra dominated by a ba3-type of cytochrome. Metallosphaera and Sulfolobus, representing the Crenarchaeota, both yielded spectra dominated by the same novel cytochrome as that observed in the Nitrospirae and a new, heretofore unrecognized redox-active prosthetic group with a reduced peak at around 485 nm. These observations are consistent with the hypothesis that individual acidophilic microorganisms that respire aerobically on iron utilize one of at least six different types of electron transfer pathways that are characterized by different redox-active prosthetic groups. In situ absorbance

  13. The Time-Resolved Flow Field of a Spatially Oscillating Jet in Crossflow

    NASA Astrophysics Data System (ADS)

    Ostermann, F.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

    2016-11-01

    Spatially oscillating jets in crossflow emitted by fluidic oscillators have been proven beneficial for flow control applications in recent studies. However, the driving mechanism behind the efficacy remains unknown. The presented study examines the fundamental, time-resolved flow field of a spatially oscillating jet in crossflow. The inclination angle between oscillation plane and crossflow is 90°. The underlying experimental dataset is acquired plane-by-plane by a traversable stereoscopic particle image velocimetry system. Phase-averaging reduces stochastic noise, compensates low sampling rates, and allows combining the individual planes to a time-resolved three-dimensional flow field. The trajectory of the oscillating jet is much shallower than a steady jet. Two counter-rotating streamwise vortices are revealed. The sense of rotation is opposite to that of the counter-rotating vortex pair of steady jets in crossflow. This sense of rotation enables the vortices to prevail far downstream because they push each other toward the wall. The strength of the vortices is alternating. This vortex pair is a promising candidate to be the driving mechanism behind the high efficacy in separation control. PhD Student.

  14. Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

    2016-06-01

    An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform’s size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke’s brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

  15. The time-resolved natural flow field of a fluidic oscillator

    NASA Astrophysics Data System (ADS)

    Woszidlo, Rene; Ostermann, Florian; Nayeri, C. N.; Paschereit, C. O.

    2015-06-01

    The internal and external flow field of a fluidic oscillator with two feedback channels are examined experimentally within the incompressible flow regime. A scaled-up device with a square outlet nozzle is supplied with pressurized air and emits a spatially oscillating jet into quiescent environment. Time-resolved information are obtained by phase-averaging pressure and PIV data based on an internal reference signal. The temporal resolution is better than a phase angle of 3°. A detailed analysis of the internal dynamics reveals that the oscillation mechanism is based on fluid feeding into a separation bubble between the jet and mixing chamber wall which pushes the jet to the opposite side. The total volume of fluid transported through one feedback channel during one oscillation cycle matches the total growth of the separation bubble from its initial size to its maximum extent. Although the oscillation frequency increases linearly with supply rate, sudden changes in the internal dynamics are observed. These changes are caused by a growth in reversed flow through the feedback channels. The time-resolved properties of the emitted jet such as instantaneous jet width and exit velocity are found to oscillate substantially during one oscillation cycle. Furthermore, the results infer that the jet's oscillation pattern is approximately sinusoidal with comparable residence and switching times.

  16. Time-resolved luminescence detection of spleen tyrosine kinase activity through terbium sensitization.

    PubMed

    Lipchik, Andrew M; Parker, Laurie L

    2013-03-05

    Disruption of regulatory protein phosphorylation can lead to disease and is particularly prevalent in cancers. Inhibitors that target deregulated kinases are therefore a major focus of chemotherapeutic development. Achieving sensitivity and specificity in high-throughput compatible kinase assays is key to successful inhibitor development. Here, we describe the application of time-resolved luminescence detection to the direct sensing of spleen tyrosine kinase (Syk) activity and inhibition using a novel peptide substrate. Chelation and luminescence sensitization of Tb(3+) allowed the direct detection of peptide phosphorylation without any antibodies or other labeling reagents. Characterizing the Tb(3+) coordination properties of the phosphorylated vs unphosphorylated form of the peptide revealed that an inner-sphere water was displaced upon phosphorylation, which likely was responsible for both enhancing the luminescence intensity and also extending the lifetime, which enabled gating of the luminescence signal to improve the dynamic range. Furthermore, a shift in the optimal absorbance maximum for excitation was observed, from 275 nm (for the unphosphorylated tyrosine peptide) to 266 nm (for the phosphorylated tyrosine peptide). Accordingly, time-resolved measurements with excitation at 266 nm via a monochromator enabled a 16-fold improvement in base signal-to-noise for distinguishing phosphopeptide from unphosphorylated peptide. This led to a high degree of sensitivity and quantitative reproducibility, demonstrating the amenability of this method to both research laboratory and high-throughput applications.

  17. Time-resolved studies of impact-initiated combustion in aluminum powder compacts

    NASA Astrophysics Data System (ADS)

    Breidenich, Jennifer; Dixon, Sean; Aydelotte, Brady; Thadhani, Naresh

    2011-06-01

    The mechanisms of combustion reaction occurring under impact loading of aluminum powder compacts are studied using UV/Vis spectroscopy to gain time-resolved chemical information. Impact experiments performed on aluminum powder compacts reveal light emission due to reaction at velocities greater than 400m/s in air, while no reaction is observed in a vacuum (50mTorr). Light emission and reaction occurrence is also sensitive to the density of the Al powder compacts. Upon combustion, wavelengths indicative of the well-known reaction Al +O2 --> AlO + O , a sharp doublet at 398 nm and multiple broad peaks between 420 and 500 nm, are observed. Microsecond time-resolved chemical information is gained through analysis of these wavelengths using a spectrometer coupled with an electron multiplier CCD camera. The impact initiated reaction is also monitored by high speed imaging of transient deformation profiles which are compared to those predicted using numerical simulations employing ANSYS-AUTODYN-3D computer code. The insight obtained from the combination of these analyses of impact-initiated combustion reaction in aluminum powder compacts will be presented. Funded by DTRA, Grant No. HDTRA1-10-1-0038

  18. Time-Resolved Photoluminescence Studies of InGaN/AlGaN Multiple Quantum Wells

    NASA Astrophysics Data System (ADS)

    Zeng, K. C.; Smith, M.; Lin, J. Y.; Jiang, H. X.; Robert, J. C.; Piner, E. L.; McIntosh, F. G.; Bahbahani, M.; Bedair, S. M.; Zavada, J.

    1997-03-01

    Picosecond time-resolved photoluminescence (PL) spectroscopy has been employed to study the dynamic processes of optical transitions in InGaN/AlGaN multiple quantum wells (MQW) grown by metal-organic chemical vapor deposition (MOCVD). The dynamical behavior of the PL emission reveals that the main emission line in these MQW is the combination of the localized exciton and a band-to-impurity emission lines. The spectral lineshape and the recombination dynamics of the localized exciton and of the band-to-impurity transitions have been systematically investigated at different temperatures and excitation intensities and for MQW with different structures and growth conditions. From these studies, important parameters, including the localization energy and the recombination lifetimes of the localized excitons in InGaN/AlGaN quantum wells, the well width fluctuation, alloy compositions in the well and the barrier materials, and the band offset between InGaN and AlGaN can be deduced. Comparing with time-resolved PL results of InGaN/GaN and GaN/AlGaN MQW, important effects of interface on the optical properties of the III-nitride MQW have been evaluated. Implications of our results to device applications will be discussed.

  19. Time-resolved Optical Spectroscopy of the Cataclysmic Variable PG 0859+415

    NASA Astrophysics Data System (ADS)

    Hoard, D. W.; Szkody, Paula

    1996-10-01

    We present time-resolved, high-resolution (2 Å) spectra of the nova-like cataclysmic variable (CV) PG 0859+415. The average optical spectrum of this star displays a continuum slope that is steeper than expected for a steady state accretion disk this is attributed to the presence of a hot spot with T ˜ 12,000 K at the impact site of the accretion stream. As first observed by Grauer et al., the time- resolved spectra exhibit a transient central absorption feature in the Balmer lines that appears near φ = 0.6 and lasts into the (partial) eclipse, and the radial velocity solution of the Balmer lines shows a phase offset of Δφ = -0.1 from the photometric phasing. System parameters are estimated from the radial velocity solution to the He II lines (which is consistent with an origin close to the white dwarf primary star). Doppler tomograms constructed from the Balmer emission lines reveal the presence of a region of enhanced emission at a location consistent with the expected impact site of the accretion stream with the edge of the disk. Finally, the similarities between PG 0859+415 and the recently identified SW Sextantis subclass of CV is discussed, and a qualitative model for the system is proposed to explain the observational results.

  20. Time-Resolved Spectroscopy of Active Binary Stars

    NASA Technical Reports Server (NTRS)

    Brown, Alexander

    2000-01-01

    This NASA grant covered EUVE observing and data analysis programs during EUVE Cycle 5 GO observing. The research involved a single Guest Observer project 97-EUVE-061 "Time-Resolved Spectroscopy of Active Binary Stars". The grant provided funding that covered 1.25 months of the PI's salary. The activities undertaken included observation planning and data analysis (both temporal and spectral). This project was awarded 910 ksec of observing time to study seven active binary stars, all but one of which were actually observed. Lambda-And was observed on 1997 Jul 30 - Aug 3 and Aug 7-14 for a total of 297 ksec; these observations showed two large complex flares that were analyzed by Osten & Brown (1999). AR Psc, observed for 350 ksec on 1997 Aug 27 - Sep 13, showed only relatively small flares that were also discussed by Osten & Brown (1999). EUVE observations of El Eri were obtained on 1994 August 24-28, simultaneous with ASCA X-ray spectra. Four flares were detected by EUVE with one of these also observed simultaneously, by ASCA. The other three EUVE observations were of the stars BY Dra (1997 Sep 22-28), V478 Lyr (1998 May 18-27), and sigma Gem (1998 Dec 10-22). The first two stars showed a few small flares. The sigma Gem data shows a beautiful complete flare with a factor of ten peak brightness compared to quiescence. The flare rise and almost all the decay phase are observed. Unfortunately no observations in other spectral regions were obtained for these stars. Analysis of the lambda-And and AR Psc observations is complete and the results were published in Osten & Brown (1999). Analysis of the BY Dra, V478 Lyr and sigma Gem EUVE data is complete and will be published in Osten (2000, in prep.). The El Eri EUV analysis is also completed and the simultaneous EUV/X-ray study will be published in Osten et al. (2000, in prep.). Both these latter papers will be submitted in summer 2000. All these results will form part of Rachel Osten's PhD thesis.

  1. Time-resolved optical spectroscopy measurements of shocked liquid deuterium

    NASA Astrophysics Data System (ADS)

    Bailey, J. E.; Knudson, M. D.; Carlson, A. L.; Dunham, G. S.; Desjarlais, M. P.; Hanson, D. L.; Asay, J. R.

    2008-10-01

    Time-resolved optical spectroscopy has been used to measure the shock pressure steadiness, emissivity, and temperature of liquid deuterium shocked to 22-90 GPa. The shock was produced using magnetically accelerated flyer plate impact, and spectra were acquired with a suite of four fiber-optic-coupled spectrometers with streak camera detectors. The shock pressure changes by an average of -1.2% over the 10-30 ns cell transit time, determined from the relative changes in the shock front self-emission with time. The shock front reflectivity was measured from 5140Å and 5320Å laser light reflected from the D2 shock. The emissivity inferred from the reflectivity measurements was in reasonably good agreement with quantum molecular dynamics simulation predictions. The spectral radiance wavelength dependence was found to agree well (average normalized χ2=1.6 ) with a Planckian multiplied by the emissivity. The shock front temperature was determined from the emissivity and the wavelength-dependent shock self-emission. Thirty-seven temperature measurements spanning the 22-90 GPa range were accumulated. The large number of temperature measurements enables a comparison of the scatter in the data with expectations for a Gaussian distribution. This facilitates determination of uncertainties that incorporate both apparatus contributions and otherwise unquantified systematic effects that cause self-emission variations from one experiment to another. Agreement between temperatures determined from the absolute spectral radiance and from the relative shape of the spectrum further substantiates the absence of systematic biases. The weighted mean temperature uncertainties were as low as ±3-4% , enabling the discrimination between competing models for the D2 equation of state (EOS). The temperature results agree well with models that predict a maximum compression of ˜4.4 . Softer models that predict approximately sixfold compression are inconsistent with the data to a very high

  2. Immunotoxicity risks associated with land-treatment of petrochemical wastes revealed using an in situ rodent model.

    PubMed

    Rafferty, D P; Lochmiller, R L; McBee, K; Qualls, C W; Basta, N T

    2001-01-01

    Land-treatment of petrochemical wastes is a widely used method to dispose of hazardous and non-hazardous waste by biodegradation. However, no comprehensive assessment of the impact of such disposal techniques on terrestrial ecosystems has been conducted. Despite the presence of suspected immunotoxicants in the soil, wild rodents frequently reside on these waste sites after closure or abandonment. We explored the seasonal sensitivity of the immune system of the hispid cotton rat (Sigmodon hispidus) to in situ exposures on sites land-treated with petrochemical wastes. Animals were monitored on five contaminated land-treatment sites and five ecologically matched-reference sites in Oklahoma, USA, over two seasons (summer and winter). Most hematological parameters were not adversely affected by land-treatment; however, platelet counts were 26% greater in cotton rats from land-treatment sites compared to reference sites in winter. Significant treatment-related differences were observed in total serum protein concentrations, organ mass and organ cellularity, but these differences were not consistent across the five land-treatment units. Lymphoproliferative responses of cotton rat splenocytes stimulated in vitro were elevated for a T-cell mitogen and depressed for a B-cell mitogen in animals from land-treatment compared to reference sites. The ability of splenocytes to proliferate in response to interleukin-2 receptor-binding was not influenced by treatment. Total yields of peritoneal cells, yield of peritoneal macrophages, and yield of peritoneal lymphocytes were influenced to varying degrees by land-treatment. Functionally, in vitro metabolic activity of peritoneal macrophages was 114% greater in cotton rats from land-treatment sites compared to reference sites during summer. These results indicate that petrochemical wastes applied to soils on these five land-treatment sites had variable immunomodulatory effects in resident cotton rats. Immune alterations for some assays

  3. Time-Resolved Fluorescent Immunochromatography of Aflatoxin B1 in Soybean Sauce: A Rapid and Sensitive Quantitative Analysis

    PubMed Central

    Wang, Du; Zhang, Zhaowei; Li, Peiwu; Zhang, Qi; Zhang, Wen

    2016-01-01

    Rapid and quantitative sensing of aflatoxin B1 with high sensitivity and specificity has drawn increased attention of studies investigating soybean sauce. A sensitive and rapid quantitative immunochromatographic sensing method was developed for the detection of aflatoxin B1 based on time-resolved fluorescence. It combines the advantages of time-resolved fluorescent sensing and immunochromatography. The dynamic range of a competitive and portable immunoassay was 0.3–10.0 µg·kg−1, with a limit of detection (LOD) of 0.1 µg·kg−1 and recoveries of 87.2%–114.3%, within 10 min. The results showed good correlation (R2 > 0.99) between time-resolved fluorescent immunochromatographic strip test and high performance liquid chromatography (HPLC). Soybean sauce samples analyzed using time-resolved fluorescent immunochromatographic strip test revealed that 64.2% of samples contained aflatoxin B1 at levels ranging from 0.31 to 12.5 µg·kg−1. The strip test is a rapid, sensitive, quantitative, and cost-effective on-site screening technique in food safety analysis. PMID:27428975

  4. Resistive switching mechanism in the one diode-one resistor memory based on p+-Si/n-ZnO heterostructure revealed by in-situ TEM

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhu, Liang; Li, Xiaomei; Xu, Zhi; Wang, Wenlong; Bai, Xuedong

    2017-03-01

    One diode-one resistor (1D1R) memory is an effective architecture to suppress the crosstalk interference, realizing the crossbar network integration of resistive random access memory (RRAM). Herein, we designed a p+-Si/n-ZnO heterostructure with 1D1R function. Compared with the conventional multilayer 1D1R devices, the structure and fabrication technique can be largely simplified. The real-time imaging of formation/rupture process of conductive filament (CF) process demonstrated the RS mechanism by in-situ transmission electron microscopy (TEM). Meanwhile, we observed that the formed CF is only confined to the outside of depletion region of Si/ZnO pn junction, and the formation of CF does not degrade the diode performance, which allows the coexistence of RS and rectifying behaviors, revealing the 1D1R switching model. Furthermore, it has been confirmed that the CF is consisting of the oxygen vacancy by in-situ TEM characterization.

  5. Resistive switching mechanism in the one diode-one resistor memory based on p(+)-Si/n-ZnO heterostructure revealed by in-situ TEM.

    PubMed

    Zhang, Lei; Zhu, Liang; Li, Xiaomei; Xu, Zhi; Wang, Wenlong; Bai, Xuedong

    2017-03-21

    One diode-one resistor (1D1R) memory is an effective architecture to suppress the crosstalk interference, realizing the crossbar network integration of resistive random access memory (RRAM). Herein, we designed a p(+)-Si/n-ZnO heterostructure with 1D1R function. Compared with the conventional multilayer 1D1R devices, the structure and fabrication technique can be largely simplified. The real-time imaging of formation/rupture process of conductive filament (CF) process demonstrated the RS mechanism by in-situ transmission electron microscopy (TEM). Meanwhile, we observed that the formed CF is only confined to the outside of depletion region of Si/ZnO pn junction, and the formation of CF does not degrade the diode performance, which allows the coexistence of RS and rectifying behaviors, revealing the 1D1R switching model. Furthermore, it has been confirmed that the CF is consisting of the oxygen vacancy by in-situ TEM characterization.

  6. Resistive switching mechanism in the one diode-one resistor memory based on p+-Si/n-ZnO heterostructure revealed by in-situ TEM

    PubMed Central

    Zhang, Lei; Zhu, Liang; Li, Xiaomei; Xu, Zhi; Wang, Wenlong; Bai, Xuedong

    2017-01-01

    One diode-one resistor (1D1R) memory is an effective architecture to suppress the crosstalk interference, realizing the crossbar network integration of resistive random access memory (RRAM). Herein, we designed a p+-Si/n-ZnO heterostructure with 1D1R function. Compared with the conventional multilayer 1D1R devices, the structure and fabrication technique can be largely simplified. The real-time imaging of formation/rupture process of conductive filament (CF) process demonstrated the RS mechanism by in-situ transmission electron microscopy (TEM). Meanwhile, we observed that the formed CF is only confined to the outside of depletion region of Si/ZnO pn junction, and the formation of CF does not degrade the diode performance, which allows the coexistence of RS and rectifying behaviors, revealing the 1D1R switching model. Furthermore, it has been confirmed that the CF is consisting of the oxygen vacancy by in-situ TEM characterization. PMID:28322336

  7. Laser scanning confocal microscopy and quantitative microscopy with a charge coupled device camera improve detection of human papillomavirus DNA revealed by fluorescence in situ hybridization.

    PubMed

    Lizard, G; Chignol, M C; Souchier, C; Schmitt, D; Chardonnet, Y

    1994-04-01

    Epithelial cervical CaSki, SiHa and HeLa cells containing respectively 600 copies of human papillomavirus (HPV) DNA type 16, 1-2 copies of HPV DNA type 16 and 10-50 copies of HPV DNA type 18 were used as model to detect different quantities of integrated HPV genome. The HPV DNA was identified on cell deposits with specific biotinylated DNA probes either by enzymatic in situ hybridization (EISH) or fluorescence in situ hybridization (FISH) involving successively a rabbit anti-biotin antibody, a biotinylated goat anti-rabbit antibody and streptavidin-alkaline phosphatase complex or streptavidin-fluorescein isothiocyanate complex. With brightfield microscopy and EISH, hybridization spots were observed in CaSki and HeLa cells but hardly any in SiHa cells. With fluorescence microscopy and FISH, hybridization spots were clearly seen only on CaSki cell nuclei. In an attempt to improve the detection of low quantities of HPV DNA signals revealed by FISH, laser scanning confocal microscopy (LSCM) and quantitative microscopy with an intensified charge coupled device (CCD) camera were used. With both LSCM and quantitative microscopy, as few as 1-2 copies of HPV DNA were detected and found to be confined to cell nuclei counterstained with propidium iodide. Under Nomarski phase contrast, a good preservation of the cell structure was observed. With quantitative microscopy, differences in the number, size, total area and integrated fluorescence intensity of hybridization spots per nucleus were revealed between CaSki, SiHa and HeLa cells.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Time-resolved scanning Kerr microscopy of flux beam formation in hard disk write heads

    NASA Astrophysics Data System (ADS)

    Valkass, Robert A. J.; Spicer, Timothy M.; Burgos Parra, Erick; Hicken, Robert J.; Bashir, Muhammad A.; Gubbins, Mark A.; Czoschke, Peter J.; Lopusnik, Radek

    2016-06-01

    To meet growing data storage needs, the density of data stored on hard disk drives must increase. In pursuit of this aim, the magnetodynamics of the hard disk write head must be characterized and understood, particularly the process of "flux beaming." In this study, seven different configurations of perpendicular magnetic recording (PMR) write heads were imaged using time-resolved scanning Kerr microscopy, revealing their detailed dynamic magnetic state during the write process. It was found that the precise position and number of driving coils can significantly alter the formation of flux beams during the write process. These results are applicable to the design and understanding of current PMR and next-generation heat-assisted magnetic recording devices, as well as being relevant to other magnetic devices.

  9. Protein analysis by time-resolved measurements with an electro-switchable DNA chip

    PubMed Central

    Langer, Andreas; Hampel, Paul A.; Kaiser, Wolfgang; Knezevic, Jelena; Welte, Thomas; Villa, Valentina; Maruyama, Makiko; Svejda, Matej; Jähner, Simone; Fischer, Frank; Strasser, Ralf; Rant, Ulrich

    2013-01-01

    Measurements in stationary or mobile phases are fundamental principles in protein analysis. Although the immobilization of molecules on solid supports allows for the parallel analysis of interactions, properties like size or shape are usually inferred from the molecular mobility under the influence of external forces. However, as these principles are mutually exclusive, a comprehensive characterization of proteins usually involves a multi-step workflow. Here we show how these measurement modalities can be reconciled by tethering proteins to a surface via dynamically actuated nanolevers. Short DNA strands, which are switched by alternating electric fields, are employed as capture probes to bind target proteins. By swaying the proteins over nanometre amplitudes and comparing their motional dynamics to a theoretical model, the protein diameter can be quantified with Angström accuracy. Alterations in the tertiary protein structure (folding) and conformational changes are readily detected, and even post-translational modifications are revealed by time-resolved molecular dynamics measurements. PMID:23839273

  10. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    SciTech Connect

    Walsh, D. A. Snedden, E. W.; Jamison, S. P.

    2015-05-04

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  11. Cluster-surface interaction studied by time-resolved two-photon photoemission

    NASA Astrophysics Data System (ADS)

    Busolt, U.; Cottancin, E.; Röhr, H.; Socaciu, L.; Leisner, T.; Wöste, L.

    We use time-resolved two-photon photoemission to study the stability of size selected Agn+ clusters (n=2-9)deposited onto highly oriented pyrolytic graphite (HOPG) substrates at liquid nitrogen temperatures. The deposition was carried out with variable kinetic energies of the clusters. Clusters deposited with high kinetic energy (up to 60 eV/cluster) become fragmented upon impact. For low deposition energies (1-4 eV/cluster) the size dependence of the photoelectron spectra reveals a pronounced odd/even effect, which is well known for gas phase silver clusters. This indicates that the soft deposited clusters retain their size and identity on the sample. The phase of the odd/even effect suggests that transient negatively charged cluster ions serve as an intermediate step in the two-photon photoemission process. The lifetime of the anions rises with cluster size. This is attributed to an increasing electronic density of states for larger clusters.

  12. Time-resolved transmittance: a comparison of the diffusion model approach with Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Rothfischer, Ramona; Grosenick, Dirk; Macdonald, Rainer

    2015-07-01

    We discuss the determination of optical properties of thick scattering media from measurements of time-resolved transmittance by diffusion theory using Monte Carlo simulations as a gold standard to model photon migration. Our theoretical and experimental investigations reveal differences between calculated distributions of times of flight (DTOFs) of photons from both models which result in an overestimation of the absorption and the reduced scattering coefficient by diffusion theory which becomes larger for small scattering coefficients. By introducing a temporal shift in the DTOFs obtained with the diffusion model as additional fit parameter, the deviation in the absorption coefficient can be compensated almost completely. If the scattering medium is additionally covered by transparent layers (e.g. glass plates) the deviation between the DTOFs from both models is even larger which mainly effects the determination of the reduced scattering coefficient by diffusion theory. A temporal shift improves the accuracy of the optical properties derived by diffusion theory in this case as well.

  13. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    NASA Astrophysics Data System (ADS)

    Walsh, D. A.; Snedden, E. W.; Jamison, S. P.

    2015-05-01

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  14. In-situ atomic force microscopy observation revealing gel-like plasticity on a metallic glass surface

    NASA Astrophysics Data System (ADS)

    Lu, Y. M.; Zeng, J. F.; Huang, J. C.; Kuan, S. Y.; Nieh, T. G.; Wang, W. H.; Pan, M. X.; Liu, C. T.; Yang, Y.

    2017-03-01

    It has been decade-long and enduring efforts to decipher the structural mechanism of plasticity in metallic glasses; however, it still remains a challenge to directly reveal the structural change, if any, that precedes; and dominant plastics flow in them. Here, by using the dynamic atomic force microscope as an "imaging" as well as a "forcing" tool, we unfold a real-time sequence of structural evolution occurring on the surface of an Au-Si thin film metallic glass. In sharp contrast to the common notion that plasticity comes along with mechanical softening in bulk metallic glasses, our experimental results directly reveal three types of nano-sized surface regions, which undergo plasticity but exhibit different characters of structural evolution following the local plasticity events, including stochastic structural rearrangement, unusual local relaxation and rejuvenation. As such, yielding on the metallic-glass surface manifests as a dynamic equilibrium between local relaxation and rejuvenation as opposed to shear instability in bulk metallic-glasses. Our finding demonstrates that plasticity on the metallic glass surface of Au-Si metallic glass bears much resemblance to that of the colloidal gels, of which nonlinear rheology rather than shear instability governs the constitutive behavior of plasticity.

  15. In situ microscopy analysis reveals local innate immune response developed around Brucella infected cells in resistant and susceptible mice.

    PubMed

    Copin, Richard; Vitry, Marie-Alice; Hanot Mambres, Delphine; Machelart, Arnaud; De Trez, Carl; Vanderwinden, Jean-Marie; Magez, Stefan; Akira, Shizuo; Ryffel, Bernhard; Carlier, Yves; Letesson, Jean-Jacques; Muraille, Eric

    2012-01-01

    Brucella are facultative intracellular bacteria that chronically infect humans and animals causing brucellosis. Brucella are able to invade and replicate in a broad range of cell lines in vitro, however the cells supporting bacterial growth in vivo are largely unknown. In order to identify these, we used a Brucella melitensis strain stably expressing mCherry fluorescent protein to determine the phenotype of infected cells in spleen and liver, two major sites of B. melitensis growth in mice. In both tissues, the majority of primary infected cells expressed the F4/80 myeloid marker. The peak of infection correlated with granuloma development. These structures were mainly composed of CD11b⁺ F4/80⁺ MHC-II⁺ cells expressing iNOS/NOS2 enzyme. A fraction of these cells also expressed CD11c marker and appeared similar to inflammatory dendritic cells (DCs). Analysis of genetically deficient mice revealed that differentiation of iNOS⁺ inflammatory DC, granuloma formation and control of bacterial growth were deeply affected by the absence of MyD88, IL-12p35 and IFN-γ molecules. During chronic phase of infection in susceptible mice, we identified a particular subset of DC expressing both CD11c and CD205, serving as a reservoir for the bacteria. Taken together, our results describe the cellular nature of immune effectors involved during Brucella infection and reveal a previously unappreciated role for DC subsets, both as effectors and reservoir cells, in the pathogenesis of brucellosis.

  16. Calcium Triggered Lα-H2 Phase Transition Monitored by Combined Rapid Mixing and Time-Resolved Synchrotron SAXS

    PubMed Central

    Yaghmur, Anan; Laggner, Peter; Sartori, Barbara; Rappolt, Michael

    2008-01-01

    Background Awad et al. [1] reported on the Ca2+-induced transitions of dioleoyl-phosphatidylglycerol (DOPG)/monoolein (MO) vesicles to bicontinuous cubic phases at equilibrium conditions. In the present study, the combination of rapid mixing and time-resolved synchrotron small-angle X-ray scattering (SAXS) was applied for the in-situ investigations of fast structural transitions of diluted DOPG/MO vesicles into well-ordered nanostructures by the addition of low concentrated Ca2+ solutions. Methodology/Principal Findings Under static conditions and the in absence of the divalent cations, the DOPG/MO system forms large vesicles composed of weakly correlated bilayers with a d-spacing of ∼140 Å (Lα-phase). The utilization of a stopped-flow apparatus allowed mixing these DOPG/MO vesicles with a solution of Ca2+ ions within 10 milliseconds (ms). In such a way the dynamics of negatively charged PG to divalent cation interactions, and the kinetics of the induced structural transitions were studied. Ca2+ ions have a very strong impact on the lipidic nanostructures. Intriguingly, already at low salt concentrations (DOPG/Ca2+>2), Ca2+ ions trigger the transformation from bilayers to monolayer nanotubes (inverted hexagonal phase, H2). Our results reveal that a binding ratio of 1 Ca2+ per 8 DOPG is sufficient for the formation of the H2 phase. At 50°C a direct transition from the vesicles to the H2 phase was observed, whereas at ambient temperature (20°C) a short lived intermediate phase (possibly the cubic Pn3m phase) coexisting with the H2 phase was detected. Conclusions/Significance The strong binding of the divalent cations to the negatively charged DOPG molecules enhances the negative spontaneous curvature of the monolayers and causes a rapid collapsing of the vesicles. The rapid loss of the bilayer stability and the reorganization of the lipid molecules within ms support the argument that the transition mechanism is based on a leaky fusion of the vesicles. PMID

  17. Zoo-fluorescence in situ hybridization analysis of human and Indian muntjac karyotypes (Muntiacus muntjak vaginalis) reveals satellite DNA clusters at the margins of conserved syntenic segments.

    PubMed

    Frönicke, L; Scherthan, H

    1997-06-01

    Zoo-fluorescence in situ hybridization (FISH) with human whole chromosome-specific paint probes revealed extensive homoeologies between Indian muntjac (2n=6, 7 female, male) and human karyotypes (2n=46). Forty-two conserved syntenic segments, corresponding to all human chromosomes except the Y chromosome, produced a near-complete coverage of the muntjac complement and revealed margins of interspecific segmental homoeology. To test the hypothesis that interstitial satellite DNA loci, illuminated by a Chinese muntjac C5-satellite probe in Indian muntjac chromosome arms, mark ancestral fusion points (Lin CC, Sasi R, Fan YS, Chen Z-Q (1991) New evidence for tandem chromosome fusions in the karyotypic evolution of the Asian muntjacs. Chromosoma 101: 19-24), we combined Zoo-FISH with C5 satellite mapping. Twenty-six interstitial satellite DNA loci were detected in the haploid Indian muntjac genome and were found to co-localize with the margins of conserved human/Indian muntjac syntenic segments. These results were confirmed by two-colour FISH and are in accordance with the tandem fusion hypothesis for Indian muntjac chromosomes. Furthermore, conserved syntenic segment combinations detected in pig, cattle and Indian muntjac Zoo-FISH maps reveal ancestral artiodactyl chromosomes.

  18. Pyrosequencing reveals high-temperature cellulolytic microbial consortia in Great Boiling Spring after in situ lignocellulose enrichment.

    PubMed

    Peacock, Joseph P; Cole, Jessica K; Murugapiran, Senthil K; Dodsworth, Jeremy A; Fisher, Jenny C; Moser, Duane P; Hedlund, Brian P

    2013-01-01

    To characterize high-temperature cellulolytic microbial communities, two lignocellulosic substrates, ammonia fiber-explosion-treated corn stover and aspen shavings, were incubated at average temperatures of 77 and 85°C in the sediment and water column of Great Boiling Spring, Nevada. Comparison of 109,941 quality-filtered 16S rRNA gene pyrosequences (pyrotags) from eight enrichments to 37,057 quality-filtered pyrotags from corresponding natural samples revealed distinct enriched communities dominated by phylotypes related to cellulolytic and hemicellulolytic Thermotoga and Dictyoglomus, cellulolytic and sugar-fermenting Desulfurococcales, and sugar-fermenting and hydrogenotrophic Archaeoglobales. Minor enriched populations included close relatives of hydrogenotrophic Thermodesulfobacteria, the candidate bacterial phylum OP9, and candidate archaeal groups C2 and DHVE3. Enrichment temperature was the major factor influencing community composition, with a negative correlation between temperature and richness, followed by lignocellulosic substrate composition. This study establishes the importance of these groups in the natural degradation of lignocellulose at high temperatures and suggests that a substantial portion of the diversity of thermophiles contributing to consortial cellulolysis may be contained within lineages that have representatives in pure culture.

  19. Pyrosequencing Reveals High-Temperature Cellulolytic Microbial Consortia in Great Boiling Spring after In Situ Lignocellulose Enrichment

    PubMed Central

    Peacock, Joseph P.; Cole, Jessica K.; Murugapiran, Senthil K.; Dodsworth, Jeremy A.; Fisher, Jenny C.; Moser, Duane P.; Hedlund, Brian P.

    2013-01-01

    To characterize high-temperature cellulolytic microbial communities, two lignocellulosic substrates, ammonia fiber-explosion-treated corn stover and aspen shavings, were incubated at average temperatures of 77 and 85°C in the sediment and water column of Great Boiling Spring, Nevada. Comparison of 109,941 quality-filtered 16S rRNA gene pyrosequences (pyrotags) from eight enrichments to 37,057 quality-filtered pyrotags from corresponding natural samples revealed distinct enriched communities dominated by phylotypes related to cellulolytic and hemicellulolytic Thermotoga and Dictyoglomus, cellulolytic and sugar-fermenting Desulfurococcales, and sugar-fermenting and hydrogenotrophic Archaeoglobales. Minor enriched populations included close relatives of hydrogenotrophic Thermodesulfobacteria, the candidate bacterial phylum OP9, and candidate archaeal groups C2 and DHVE3. Enrichment temperature was the major factor influencing community composition, with a negative correlation between temperature and richness, followed by lignocellulosic substrate composition. This study establishes the importance of these groups in the natural degradation of lignocellulose at high temperatures and suggests that a substantial portion of the diversity of thermophiles contributing to consortial cellulolysis may be contained within lineages that have representatives in pure culture. PMID:23555835

  20. Dynamic changes in the higher-level chromatin organization of specific sequences revealed by in situ hybridization to nuclear halos

    PubMed Central

    1994-01-01

    A novel approach to study the higher level packaging of specific DNA sequences has been developed by coupling high-resolution fluorescence hybridization with biochemical fractionation to remove histones and distend DNA loops to form morphologically reproducible nuclear "halos." Results demonstrate consistent differences in the organization of specific sequences, and further suggest a relationship to functional activity. Pulse-incorporated bromodeoxyuridine representing nascent replicating DNA localized with the base of the chromatin loops in discrete clustered patterns characteristic of intact cells, whereas at increasing chase times, the replicated DNA was consistently found further out on the extended region of the halo. Fluorescence hybridization to unique loci for four transcriptionally inactive sequences produced long strings of signal extending out onto the DNA halo or "loop," whereas four transcriptionally active sequences remained tightly condensed as single spots within the residual nucleus. In contrast, in non-extracted cells, all sequences studied typically remained condensed as single spots of fluorescence signal. Interestingly, two transcriptionally active, tandemly repeated gene clusters exhibited strikingly different packaging by this assay. Analysis of specific genes in single cells during the cell cycle revealed changes in packaging between S-phase and non S-phase cells, and further suggested a dramatic difference in the structural associations in mitotic and interphase chromatin. These results are consistent with and suggestive of a loop domain organization of chromatin packaging involving both stable and transient structural associations, and provide precedent for an approach whereby different biochemical fractionation methods may be used to unravel various aspects of the complex higher-level organization of the genome. PMID:8034736

  1. Time-resolved x-ray diffraction and electrical resistance measurements of structural phase transitions in zirconium

    SciTech Connect

    Velisavljevic, N.; Sinogeikin, S.; Saavedra, R.; Chellappa, R. S.; Rothkirch, A.; Dattelbaum, D. M.; Konopkova, Z.; Liermann, H. -P.; Bishop, M.; Tsoi, G. M.; Vohra, Y. K.

    2014-05-07

    Here, we have designed a portable pressure controller module to tune compression rates and maximum pressures attainable in a standard gas-membrane diamond anvil cell (DAC). During preliminary experiments, performed on zirconium (Zr) metal sample, pressure jumps of up to 80 GPa were systematically obtained in less than 0.2s (resulting in compression rate of few GPa/s up to more than 400 GPa/s). In-situ x-ray diffraction and electrical resistance measurements were performed simultaneously during this rapid pressure increase to provide the first time resolved data on α → ω → β structural evolution in Zr at high pressures. Direct control of compression rates and peak pressures, which can be held for prolonged time, allows for investigation of structural evolution and kinetics of structural phase transitions of materials under previously unexplored compression rate-pressure conditions that bridge traditional static and shock/dynamic experimental platforms.

  2. Time-resolved x-ray diffraction and electrical resistance measurements of structural phase transitions in zirconium

    DOE PAGES

    Velisavljevic, N.; Sinogeikin, S.; Saavedra, R.; ...

    2014-05-07

    Here, we have designed a portable pressure controller module to tune compression rates and maximum pressures attainable in a standard gas-membrane diamond anvil cell (DAC). During preliminary experiments, performed on zirconium (Zr) metal sample, pressure jumps of up to 80 GPa were systematically obtained in less than 0.2s (resulting in compression rate of few GPa/s up to more than 400 GPa/s). In-situ x-ray diffraction and electrical resistance measurements were performed simultaneously during this rapid pressure increase to provide the first time resolved data on α → ω → β structural evolution in Zr at high pressures. Direct control of compressionmore » rates and peak pressures, which can be held for prolonged time, allows for investigation of structural evolution and kinetics of structural phase transitions of materials under previously unexplored compression rate-pressure conditions that bridge traditional static and shock/dynamic experimental platforms.« less

  3. Lateral association and elongation of vimentin intermediate filament proteins: A time-resolved light-scattering study

    PubMed Central

    Saldanha, Oliva; Huber, Klaus; Köster, Sarah

    2016-01-01

    Vimentin intermediate filaments (IFs) are part of a family of proteins that constitute one of the three filament systems in the cytoskeleton, a major contributor to cell mechanics. One property that distinguishes IFs from the other cytoskeletal filament types, actin filaments and microtubules, is their highly hierarchical assembly pathway, where a lateral association step is followed by elongation. Here we present an innovative technique to follow the elongation reaction in solution and in situ by time-resolved static and dynamic light scattering, thereby precisely capturing the relevant time and length scales of seconds to minutes and 60–600 nm, respectively. We apply a quantitative model to our data and succeed in consistently describing the entire set of data, including particle mass, radius of gyration, and hydrodynamic radius during longitudinal association. PMID:27655889

  4. Spatially complex distribution of dissolved manganese in a fjord as revealed by high-resolution in situ sensing using the autonomous underwater vehicle Autosub.

    PubMed

    Statham, P J; Connelly, D P; German, C R; Brand, T; Overnell, J O; Bulukin, E; Millard, N; McPhail, S; Pebody, M; Perrett, J; Squire, M; Stevenson, P; Webb, A

    2005-12-15

    Loch Etive is a fjordic system on the west coast of Scotland. The deep waters of the upper basin are periodically isolated, and during these periods oxygen is lost through benthic respiration and concentrations of dissolved manganese increase. In April 2000 the autonomous underwater vehicle (AUV) Autosub was fitted with an in situ dissolved manganese analyzer and was used to study the spatial variability of this element together with oxygen, salinity, and temperature throughout the basin. Six along-loch transects were completed at either constant height above the seafloor or at constant depth below the surface. The ca. 4000 in situ 10-s-average dissolved Mn (Mnd) data points obtained provide a new quasi-synoptic and highly detailed view of the distribution of manganese in this fjordic environment not possible using conventional (water bottle) sampling. There is substantial variability in concentrations (<25 to >600 nM) and distributions of Mnd. Surface waters are characteristically low in Mnd reflecting mixing of riverine and marine end-member waters, both of which are low in Mnd. The deeper waters are enriched in Mnd, and as the water column always contains some oxygen, this must reflect primarily benthic inputs of reduced dissolved Mn. However, this enrichment of Mnd is spatially very variable, presumably as a result of variability in release of Mn coupled with mixing of water in the loch and removal processes. This work demonstrates how AUVs coupled with chemical sensors can reveal substantial small-scale variability of distributions of chemical species in coastal environments that would not be resolved by conventional sampling approaches. Such information is essential if we are to improve our understanding of the nature and significance of the underlying processes leading to this variability.

  5. Individual boron nanowire has ultra-high specific Young's modulus and fracture strength as revealed by in situ transmission electron microscopy.

    PubMed

    Liu, Fei; Tang, Dai-Ming; Gan, Haibo; Mo, Xiaoshu; Chen, Jun; Deng, Shaozhi; Xu, Ningsheng; Bando, Yoshio; Golberg, Dmitri

    2013-11-26

    Boron nanowires (BNWs) may have potential applications as reinforcing materials because B fibers are widely known for their excellent mechanical performance. However until now, there have been only few reports on the mechanical properties of individual BNW, and in situ transmission electron microscopy (TEM) investigations shining a light on their fracture mechanism have not been performed. In this paper, we applied in situ high-resolution TEM (HRTEM) technique to study the mechanical properties of individual BNWs using three loading schemes. The mean fracture strength and the maximum strain of individual BNWs were measured to be 10.4 GPa and 4.1%, respectively, during the tensile tests. And the averaged Young's modulus was calculated to be 308.2 GPa under tensile and compression tests. Bending experiments for the first time performed on individual BNWs revealed that their maximum bending strain could reach 9.9% and their ultimate bending stress arrived at 36.2 GPa. These figures are much higher than those of Si and ZnO nanowires known for their high bending strength. Moreover, the BNWs exhibited very high specific fracture strength (3.9 (GPa·cm(3))/g) and specific elastic modulus (130.6 (GPa·cm(3))/g), which are several dozens of times larger compared to many nanostructures known for their superb mechanical behaviors. At last, the effect of surface oxide layer on the Young's modulus, fracture strength and maximum bending strength of individual BNWs was elucidated to extract their intrinsic mechanical parameters using calculated corrections. All experimental results suggest that the present BNW are a bright promise as lightweight reinforcing fillers.

  6. In-situ analysis of fruit anthocyanins by means of total internal reflectance, continuous wave and time-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Zude, Manuela; Spinelli, Lorenzo; Dosche, Carsten; Torricelli, Alessandro

    2009-08-01

    In sweet cherry (Prunus avium), the red pigmentation is correlated with the fruit maturity stage and can be measured by non-invasive spectroscopy. In the present study, the influence of varying fruit scattering coefficients on the fruit remittance spectrum (cw) were corrected with the effective pathlength and refractive index in the fruit tissue obtained with distribution of time-of-flight (DTOF) readings and total internal reflection fluorescence (TIRF) analysis, respectively. The approach was validated on fruits providing variation in the scattering coefficient outside the calibration sample set. In the validation, the measuring uncertainty when non-invasively analyzing fruits with cw method in comparison with combined application of cw, DTOF, and TIRF measurements showed an increase in r2 up to 22.7 % with, however, high errors in all approaches.

  7. Standoff Time-Resolved Laser-Based Spectroscopy Tools for Sample Characterization and Biosignature Detection

    NASA Astrophysics Data System (ADS)

    Gasda, P. J.; Acosta-Maeda, T.; Lucey, P. G.; Misra, A. K.; Sharma, S. K.; Taylor, J.

    2014-12-01

    The NASA Mars2020 rover will be searching for signs of past habitability and past life on Mars. Additionally, the rover mission will prepare a cache of highly significant samples for a future sample return mission. NASA requires these samples to be well characterized; the instruments on the rover must be capable of fine-scale in situ mineralogical or elemental analysis with emphasis on biosignature detection or characterization. We have been developing multiple standoff laser-based instruments at the University of Hawaii, Manoa that are capable of fine-scale in situ chemical analysis and biosignatures detection. By employing a time-resolved spectroscopy, we can perform elemental analysis with Laser-Induced Breakdown Spectroscopy (LIBS), mineral and organic analysis with Raman spectroscopy, and biosignature detection with Laser-Induced Fluorescence (LIF). Each of these techniques share the same optics and detection equipment, allowing us to integrate them into a single, compact instrument. High time-resolution (~100 ns/pulse) is the key to this instrument; with it, the detector only records data when the signal is the brightest. Spectra can be taken during the day, LIBS can be measured without a plasma light background, and the Raman signal can be separated from the mineral fluorescence signal. Since bio-organics have very short fluorescence lifetimes, the new instrument can be used to unambiguously detect bio-organics. The prototype uses a low power (0.5 mJ/pulse) 532 nm laser with a detection limit of < 30 ppm of organics in a sample of Antarctica Dry Valley soil measured from 8 m. Another LIF instrument under development in our lab, called the Biofinder, takes advantage of the extremely intense fluorescence signal produced by organics by using a wide laser spot and a camera to produce LIF images of wide area (25 cm area from 2 m distance with 2 mm/pixel resolution). The Biofinder can quickly assess the area around the rover (at 10 frames/s) by imaging sample

  8. Intraoperative imaging of cortical perfusion by time-resolved thermography using cold bolus approach

    NASA Astrophysics Data System (ADS)

    Hollmach, Julia; Schnabel, Christian; Hoffmann, Nico; Radev, Yordan; Sobottka, Stephan; Kirsch, Matthias; Schackert, Gabriele; Koch, Edmund; Steiner, Gerald

    2014-03-01

    During the past decade, thermographic cameras with high thermal and temporal resolution of up to 30 mK and 50 Hz, respectively, have been developed. These camera systems can be used to reveal thermal variations and heterogeneities of tissue and blood. Thus, they provide a fast, sensitive, noninvasive, and label-free application to investigate blood perfusion and to detect perfusion disorders. Therefore, time-resolved thermography is evaluated and tested for intraoperative imaging of the cerebral cortex during neurosurgeries. The motivation of this study is the intraoperative evaluation of the cortical perfusion by observing the temporal temperature curve of the cortex during and after the intravenous application of a cold bolus. The temperature curve caused by a cold bolus is influenced by thermodilution, depending on the temperature difference to the patient's circulation, and the pattern of mixing with the patient's blood. In this initial study, a flow phantom was used in order to determine the temperature variations of cold boli under stable conditions in a vascular system. The typical temperature profile of cold water passing by can be approximated by a bi- Gaussian function involving a set of four parameters. These parameters can be used to assess the cold bolus, since they provide information about its intensity, duration and arrival time. The findings of the flow phantom can be applied to thermographic measurements of the human cortex. The results demonstrate that time-resolved thermographic imaging is a suitable method to detect cold boli not only at a flow phantom but also at the human cortex.

  9. Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani

    2009-01-01

    A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.

  10. Optimization and comprehensive characterization of metal hydride based hydrogen storage systems using in-situ Neutron Radiography

    NASA Astrophysics Data System (ADS)

    Börries, S.; Metz, O.; Pranzas, P. K.; Bellosta von Colbe, J. M.; Bücherl, T.; Dornheim, M.; Klassen, T.; Schreyer, A.

    2016-10-01

    For the storage of hydrogen, complex metal hydrides are considered as highly promising with respect to capacity, reversibility and safety. The optimization of corresponding storage tanks demands a precise and time-resolved investigation of the hydrogen distribution in scaled-up metal hydride beds. In this study it is shown that in situ fission Neutron Radiography provides unique insights into the spatial distribution of hydrogen even for scaled-up compacts and therewith enables a direct study of hydrogen storage tanks. A technique is introduced for the precise quantification of both time-resolved data and a priori material distribution, allowing inter alia for an optimization of compacts manufacturing process. For the first time, several macroscopic fields are combined which elucidates the great potential of Neutron Imaging for investigations of metal hydrides by going further than solely 'imaging' the system: A combination of in-situ Neutron Radiography, IR-Thermography and thermodynamic quantities can reveal the interdependency of different driving forces for a scaled-up sodium alanate pellet by means of a multi-correlation analysis. A decisive and time-resolved, complex influence of material packing density is derived. The results of this study enable a variety of new investigation possibilities that provide essential information on the optimization of future hydrogen storage tanks.

  11. Micromechanics of ultra-toughened electrospun PMMA/PEO fibres as revealed by in-situ tensile testing in an electron microscope

    NASA Astrophysics Data System (ADS)

    Andersson, Richard L.; Ström, Valter; Gedde, Ulf W.; Mallon, Peter E.; Hedenqvist, Mikael S.; Olsson, Richard T.

    2014-09-01

    A missing cornerstone in the development of tough micro/nano fibre systems is an understanding of the fibre failure mechanisms, which stems from the limitation in observing the fracture of objects with dimensions one hundredth of the width of a hair strand. Tensile testing in the electron microscope is herein adopted to reveal the fracture behaviour of a novel type of toughened electrospun poly(methyl methacrylate)/poly(ethylene oxide) fibre mats for biomedical applications. These fibres showed a toughness more than two orders of magnitude greater than that of pristine PMMA fibres. The in-situ microscopy revealed that the toughness were not only dependent on the initial molecular alignment after spinning, but also on the polymer formulation that could promote further molecular orientation during the formation of micro/nano-necking. The true fibre strength was greater than 150 MPa, which was considerably higher than that of the unmodified PMMA (17 MPa). This necking phenomenon was prohibited by high aspect ratio cellulose nanocrystal fillers in the ultra-tough fibres, leading to a decrease in toughness by more than one order of magnitude. The reported necking mechanism may have broad implications also within more traditional melt-spinning research.

  12. The time-resolved transcriptome of C. elegans

    PubMed Central

    Boeck, Max E.; Huynh, Chau; Gevirtzman, Lou; Thompson, Owen A.; Wang, Guilin; Kasper, Dionna M.; Reinke, Valerie; Hillier, LaDeana W.; Waterston, Robert H.

    2016-01-01

    We generated detailed RNA-seq data for the nematode Caenorhabditis elegans with high temporal resolution in the embryo as well as representative samples from post-embryonic stages across the life cycle. The data reveal that early and late embryogenesis is accompanied by large numbers of genes changing expression, whereas fewer genes are changing in mid-embryogenesis. This lull in genes changing expression correlates with a period during which histone mRNAs produce almost 40% of the RNA-seq reads. We find evidence for many more splice junctions than are annotated in WormBase, with many of these suggesting alternative splice forms, often with differential usage over the life cycle. We annotated internal promoter usage in operons using SL1 and SL2 data. We also uncovered correlated transcriptional programs that span >80 kb. These data provide detailed annotation of the C. elegans transcriptome. PMID:27531719

  13. Attosecond Time-Resolved Photoelectron Dispersion and Photoemission Time Delays

    NASA Astrophysics Data System (ADS)

    Liao, Q.; Thumm, U.

    2014-01-01

    We compute spectrograms and relative time delays for laser-assisted photoemission by single attosecond extreme ultraviolet pulses from valence band (VB) and 2p core levels (CLs) of a Mg(0001) surface within a quantum-mechanical model. Comparing the time-dependent dispersion of photoelectron (PE) wave packets for VB and CL emission, we find striking differences in their dependence on the (i) electron mean free path (MFP) in the solid, (ii) screening of the streaking laser field, and (iii) chirp of the attosecond pulse. The relative photoemission delay between VB and 2p PEs is shown to be sensitive to the electron MFP and screening of the streaking laser field inside the solid. Our model is able to reproduce a recent attosecond-streaking experiment [S. Neppl et al., Phys. Rev. Lett. 109, 087401 (2012)], which reveals no relative streaking time delay between VB and 2p PEs.

  14. Time-Resolved Imaging of Single HIV-1 Uncoating In Vitro and in Living Cells

    PubMed Central

    Francis, Ashwanth C.; Marin, Mariana; Shi, Jiong; Aiken, Christopher; Melikyan, Gregory B.

    2016-01-01

    Disassembly of the cone-shaped HIV-1 capsid in target cells is a prerequisite for establishing a life-long infection. This step in HIV-1 entry, referred to as uncoating, is critical yet poorly understood. Here we report a novel strategy to visualize HIV-1 uncoating using a fluorescently tagged oligomeric form of a capsid-binding host protein cyclophilin A (CypA-DsRed), which is specifically packaged into virions through the high-avidity binding to capsid (CA). Single virus imaging reveals that CypA-DsRed remains associated with cores after permeabilization/removal of the viral membrane and that CypA-DsRed and CA are lost concomitantly from the cores in vitro and in living cells. The rate of loss is modulated by the core stability and is accelerated upon the initiation of reverse transcription. We show that the majority of single cores lose CypA-DsRed shortly after viral fusion, while a small fraction remains intact for several hours. Single particle tracking at late times post-infection reveals a gradual loss of CypA-DsRed which is dependent on reverse transcription. Uncoating occurs both in the cytoplasm and at the nuclear membrane. Our novel imaging assay thus enables time-resolved visualization of single HIV-1 uncoating in living cells, and reveals the previously unappreciated spatio-temporal features of this incompletely understood process. PMID:27322072

  15. Time-Resolved Spectral Analysis of Blazar 0716+714

    NASA Astrophysics Data System (ADS)

    Diaz, Rosamaria; Harp, Gerald

    2016-01-01

    As electromagnetic (EM) waves from sources such as blazars travel through the intergalactic medium (IGM), they are slowed by electrons; a phenomenon called dispersion delay [2]. We study the propagation effects in emissions of EM waves from blazar source BL 0716+714 by estimating the average electron density, or dispersion measure (DM), of the IGM on a line of sight to the blazar. Measuring the variations in these effects with time allow us to understand the properties of the intervening material. Toward this goal we analyzed months of archived observations of BL 0716+714 taken by the Allen Telescope Array (ATA). The ATA's correlator produces cross-power vs. frequency spectra for every baseline (distance between a pair of antennas) in ten-second intervals. To reduce this immense load of data we used a technique based on interferometry called bispectrum, which does not depend on complicated array calibration and simplifies our work. The bispectrum multiplies baselines, three at a time, so that they form a closed loop, then the cube root of spectra are averaged [1]. This technique is independent of phase errors associated with any individual antenna and has a better SNR ratio than simply taking the average of all the baselines. We developed a numerical analysis program that takes in archived blazar files containing correlation data, computes the bispectrum, and outputs FITS images for each day of observations. The results show that our observations do not have sufficient sensitivity to reveal blazar variations in the frequency ranges that were studied. It is suggested that future observations at higher frequencies and/or with another telescope having greater sensitivity would reveal the time/frequency dependence of emission structure that would allow measurements of electron content. This work shows that but bispectrum is a useful tool for rapid characterization of interferometer data that does not require interferometer caclibration which could introduce artifacts

  16. Time-resolved study on dynamic chemical state conversion of SiO2-supported Co species by means of dispersive XAFS technique

    NASA Astrophysics Data System (ADS)

    Chotiwan, S.; Tomiga, H.; Yamashita, S.; Katayama, M.; Inada, Y.

    2016-05-01

    The chemical state conversion of the Co species supported on SiO2 was investigated using the in-situ and the time-resolved XAFS techniques. The supported Co3O4 species was finally reduced to metallic Co with the stable intermediate state of CoO for both the temperature-programmed and time-course processes. The oxidation of Co0 traced the reverse route to Co3O4, whereas the relative stability of the Co3O4 species to the CoO intermediate under the oxidative environment diminished the composition of CoO. The time-resolved measurement for the oxidation reaction showed an additional intermediate at the early stage of the CoO intermediate formation suggesting the Co0 particle dispersion.

  17. Polar plot representation of time-resolved fluorescence.

    PubMed

    Eichorst, John Paul; Wen Teng, Kai; Clegg, Robert M

    2014-01-01

    Measuring changes in a molecule's fluorescence emission is a common technique to study complex biological systems such as cells and tissues. Although the steady-state fluorescence intensity is frequently used, measuring the average amount of time that a molecule spends in the excited state (the fluorescence lifetime) reveals more detailed information about its local environment. The lifetime is measured in the time domain by detecting directly the decay of fluorescence following excitation by short pulse of light. The lifetime can also be measured in the frequency domain by recording the phase and amplitude of oscillation in the emitted fluorescence of the sample in response to repetitively modulated excitation light. In either the time or frequency domain, the analysis of data to extract lifetimes can be computationally intensive. For example, a variety of iterative fitting algorithms already exist to determine lifetimes from samples that contain multiple fluorescing species. However, recently a method of analysis referred to as the polar plot (or phasor plot) is a graphical tool that projects the time-dependent features of the sample's fluorescence in either the time or frequency domain into the Cartesian plane to characterize the sample's lifetime. The coordinate transformations of the polar plot require only the raw data, and hence, there are no uncertainties from extensive corrections or time-consuming fitting in this analysis. In this chapter, the history and mathematical background of the polar plot will be presented along with examples that highlight how it can be used in both cuvette-based and imaging applications.

  18. Characterization of type I, II, III, IV, and V collagens by time-resolved laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Marcu, Laura; Cohen, David; Maarek, Jean-Michel I.; Grundfest, Warren S.

    2000-04-01

    The relative proportions of genetically distinct collagen types in connective tissues vary with tissue type and change during disease progression, development, wound healing, aging. This study aims to 1) characterize the spectro- temporal fluorescence emission of fiber different types of collagen and 2) assess the ability of time-resolved laser- induced fluorescence spectroscopy to distinguish between collagen types. Fluorescence emission of commercially available purified samples was induced with nitrogen laser excitation pulses and detected with a MCP-PMT connected to a digital storage oscilloscope. The recorded time-resolved emission spectra displayed distinct fluorescence emission characteristics for each collagen type. The time domain information complemented the spectral domain intensity data for improved discrimination between different collagen types. Our results reveal that analysis of the fluorescence emission can be used to characterize different species of collagen. Also, the results suggest that time-resolved spectroscopy can be used for monitoring of connective tissue matrix composition changes due to various pathological and non-pathological conditions.

  19. Steady state and time resolved optical characterization studies of Zn2SnO4 nanowires for solar cell applications

    NASA Astrophysics Data System (ADS)

    Yakami, Baichhabi R.; Poudyal, Uma; Nandyala, Shashank R.; Rimal, Gaurab; Cooper, Jason K.; Zhang, Xuejie; Wang, Jing; Wang, Wenyong; Pikal, Jon M.

    2016-10-01

    Nanowires are a promising option for sensitized solar cells, sensors, and display technology. Most of the work thus far has focused on binary oxides for these nanowires, but ternary oxides have advantages in additional control of optical and electronic properties. Here, we report on the diffuse reflectance, Low Temperature and Room Temperature Photoluminescence (PL), PL excitation spectrum, and Time Resolved PL (TRPL) of Zinc Tin Oxide (ZTO) nanowires grown by Chemical Vapor Deposition. The PL from the ZTO nanowires does not exhibit any band gap or near gap emission, and the diffuse reflectance measurement confirms that these ZTO nanowires have a direct forbidden transition. The broad PL spectrum reveals two Gaussian peaks centered at 1.86 eV (red) and 2.81 eV (blue), representing two distinct defect states or complexes. The PL spectra were further studied by the Time Resolved Emission Spectrum and intensity dependent PL and TRPL. The time resolved measurements show complex non-exponential decays at all wavelengths, indicative of defect to defect transitions, and the red emissive states decay much slower than the blue emissive states. The effects of annealing in air and vacuum are studied to investigate the origin of the defect states in the nanowires, showing that the blue states are related to oxygen vacancies. We propose an energy band model for the nanowires containing defect states within the band gap and the associated transitions between these states that are consistent with our measurements.

  20. Mass gain of glaciers in Lahaul and Spiti region (North India) during the nineties revealed by in-situ and satellite geodetic measurements

    NASA Astrophysics Data System (ADS)

    Vincent, C.; Ramanathan, A.; Wagnon, P.; Dobhal, D. P.; Linda, A.; Berthier, E.; Sharma, P.; Arnaud, Y.; Azam, M. F.; Jose, P. G.; Gardelle, J.

    2012-09-01

    The volume change of Chhota Shigri Glacier (India, 32° N) between 1988 and 2010 has been determined using in-situ geodetic measurements. This glacier has experienced only a slight mass loss over the last 22 yr (-3.8 ± 1.8 m w.e.). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2011 (-4.7 ± 1.8 m w.e.). Thus, we deduce a positive MB between 1988 and 1999 (+1.0 ± 2.5 m w.e.). Furthermore, satellite DEM differencing reveals a good correspondence between the MB of Chhota Shigri Glacier and the MB of an over 2000 km2 glaciarized area in the Lahaul and Spiti region during 1999-2011. We conclude that there has been no large ice wastage in this region over the last 22 yr, ice mass loss being limited to the last decade. This contrasts to the most recent compilation of MB data in the Himalayan range that indicates ice wastage since 1975, accelerating after 1990. For the rest of western Himalaya, available observations of glacier MBs are too sparse and discontinuous to provide a clear and relevant regional pattern of glacier volume change over the last two decades.

  1. Fluorescence In Situ Hybridization (FISH)-Based Karyotyping Reveals Rapid Evolution of Centromeric and Subtelomeric Repeats in Common Bean (Phaseolus vulgaris) and Relatives

    PubMed Central

    Iwata-Otsubo, Aiko; Radke, Brittany; Findley, Seth; Abernathy, Brian; Vallejos, C. Eduardo; Jackson, Scott A.

    2016-01-01

    Fluorescence in situ hybridization (FISH)-based karyotyping is a powerful cytogenetics tool to study chromosome organization, behavior, and chromosome evolution. Here, we developed a FISH-based karyotyping system using a probe mixture comprised of centromeric and subtelomeric satellite repeats, 5S rDNA, and chromosome-specific BAC clones in common bean, which enables one to unambiguously distinguish all 11 chromosome pairs. Furthermore, we applied the karyotyping system to several wild relatives and landraces of common bean from two distinct gene pools, as well as other related Phaseolus species, to investigate repeat evolution in the genus Phaseolus. Comparison of karyotype maps within common bean indicates that chromosomal distribution of the centromeric and subtelomeric satellite repeats is stable, whereas the copy number of the repeats was variable, indicating rapid amplification/reduction of the repeats in specific genomic regions. In Phaseolus species that diverged approximately 2–4 million yr ago, copy numbers of centromeric repeats were largely reduced or diverged, and chromosomal distributions have changed, suggesting rapid evolution of centromeric repeats. We also detected variation in the distribution pattern of subtelomeric repeats in Phaseolus species. The FISH-based karyotyping system revealed that satellite repeats are actively and rapidly evolving, forming genomic features unique to individual common bean accessions and Phaseolus species. PMID:26865698

  2. Time-resolved spectroscopy of the fluorescence quenching of a donor — acceptor pair by halothane

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Draxler, S.; Lippitsch, M. E.

    1992-04-01

    Donor (anthracene) sensitized acceptor (perylene) fluorescence is quenched more efficiently by halothane than is intrinsic perylene fluorescence. The underlying process of dynamic fluorescence quenching is investigated by time-resolved fluorescence spectroscopy.

  3. Radical ions and excited states in radiolysis. Optically detected time resolved EPR

    SciTech Connect

    Trifunac, A.D.; Smith, J.P.

    1981-01-01

    Excited-state production and radical-ion recombination kinetics in pulse-irradiated solutions of aromatic solutes in cyclohexane are studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra. 7 figures.

  4. Time Resolved Studies of Bright Short Gamma Ray Bursts in the Fermi Gamma Ray Burst Monitor

    NASA Astrophysics Data System (ADS)

    Burns, E.; Connaughton, V.; Preece, R.; Goldstein, A.

    2016-10-01

    We present preliminary results on using a Bayesian Block representation of Fermi GBM data to select intervals for time resolved analysis of short GRBs. Additionally, we search for possible precursor and extended emission in short GRBs.

  5. Jasmonate-mediated stomatal closure under elevated CO2 revealed by time-resolved metabolomics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foliar stomatal movements are critical for regulating plant water status and gas exchange. Elevated carbon dioxide (CO2) concentrations are known to induce stomatal closure. However, current knowledge on CO2 signal transduction in stomatal guard cells is limited. Here we report the metabolomic respo...

  6. Quantitative time-resolved analysis reveals intricate, differential regulation of standard- and immuno-proteasomes.

    PubMed

    Liepe, Juliane; Holzhütter, Hermann-Georg; Bellavista, Elena; Kloetzel, Peter M; Stumpf, Michael P H; Mishto, Michele

    2015-09-22

    Proteasomal protein degradation is a key determinant of protein half-life and hence of cellular processes ranging from basic metabolism to a host of immunological processes. Despite its importance the mechanisms regulating proteasome activity are only incompletely understood. Here we use an iterative and tightly integrated experimental and modelling approach to develop, explore and validate mechanistic models of proteasomal peptide-hydrolysis dynamics. The 20S proteasome is a dynamic enzyme and its activity varies over time because of interactions between substrates and products and the proteolytic and regulatory sites; the locations of these sites and the interactions between them are predicted by the model, and experimentally supported. The analysis suggests that the rate-limiting step of hydrolysis is the transport of the substrates into the proteasome. The transport efficiency varies between human standard- and immuno-proteasomes thereby impinging upon total degradation rate and substrate cleavage-site usage.

  7. Phase-locked 10 MHz reference signal for frequency domain time-resolved fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Smith, Trevor A.; Bird, Damian K.; Nuske, John W.

    2007-05-01

    A complete electronic system that is suitable for use in megahertz frequency domain time-resolved fluorescence instruments based on mode-locked lasers is described. The circuit produces a 10MHz signal, phase locked to the mode-locked laser pulse frequency, which is required by many commercial frequency synthesizers as the external reference signal. This device is particularly useful in conjunction with ultrafast gated intensified charge coupled device cameras capable of being frequency modulated for time-resolved fluorescence imaging.

  8. A time-resolved single-pass technique for measuring optical absorption coefficients of window materials under 100 GPa shock pressures.

    PubMed

    Li, Jun; Zhou, Xianming; Li, Jiabo

    2008-12-01

    An experimental method was developed to perform time-resolved, single-pass optical absorption measurements and to determine absorption coefficients of window materials under strong shock compression up to approximately 200 GPa. Experimental details are described of (i) a configuration to generate an in situ dynamic, bright, optical source and (ii) a sample assembly with a lithium fluoride plate to essentially eliminate heat transfer from the hot radiator into the specimen and to maintain a constant optical source within the duration of the experiment. Examples of measurements of optical absorption coefficients of several initially transparent single crystal materials at high shock pressures are presented.

  9. [A method for time-resolved laser-induced breakdown spectroscopy measurement].

    PubMed

    Pan, Cong-Yuan; Han, Zhen-Yu; Li, Chao-Yang; Yu, Yun-Si; Wang, Sheng-Bo; Wang, Qiu-Ping

    2014-04-01

    Laser-Induced Breakdown Spectroscopy (LIBS) is strongly time related. Time-resolved LIBS measurement is an important technique for the research on laser induced plasma evolution and self-absorption of the emission lines. Concerning the temporal characteristics of LIBS spectrum, a method is proposed in the present paper which can achieve micros-scale time-resolved LIBS measurement by using general ms-scale detector. By setting different integration delay time of the ms-scale spectrum detector, a series of spectrum are recorded. And the integration delay time interval should be longer than the worst temporal precision. After baseline correction and spectrum fitting, the intensity of the character line was obtained. Calculating this intensity with differential method at a certain time interval and then the difference value is the time-resolved line intensity. Setting the plasma duration time as X-axis and the time-resolved line intensity as Y-axis, the evolution curve of the character line intensity can be plotted. Character line with overlap-free and smooth background should be a priority to be chosen for analysis. Using spectrometer with ms-scale integration time and a control system with temporal accuracy is 0.021 micros, experiments carried out. The results validate that this method can be used to characterize the evolution of LIBS characteristic lines and can reduce the cost of the time-resolved LIBS measurement system. This method makes high time-resolved LIBS spectrum measurement possible with cheaper system.

  10. Time-resolved and continuous wave spectroscopic imaging of biological media

    NASA Astrophysics Data System (ADS)

    Al-Rubaiee, Mohammad

    Time-resolved and spectroscopic imaging approaches were developed and adapted and developed to detect and localize tumors in ex vivo breast tissue samples and tumorlike inhomogeneities breastlike phantoms. The experimental arrangement for time-sliced optical imaging used 120 fs, 1 kHz repetition-rate, 800 nm light pulses from a Ti:sapphire laser system for sample illumination and a 80 ps resolution ultrafast gated intensified camera system for recording 2-D time-sliced images. The spectroscopic imaging arrangement used 1225-1300 nm tunable output of a Cr: forsterite laser for sample illumination, a Fourier space gate to discriminate against multiple-scattered light and a near-infrared area camera to record 2-D images. Results of these direct time-resolved imaging measurements on thin (5 mm--10 mm) breast tissue specimens revealed that early-light images highlight cancerous regions of the specimens, while late arriving light accentuates the normal fibroglandular tissues. These differences are attributed to the difference in light scattering characteristics of normal and cancerous tissues. In direct spectroscopic imaging measurements, when light was tuned closer to the 1203 nm absorption resonance of adipose tissues, a marked enhancement in contrast between the images of adipose and fibro-glandular tissues was observed. A similar wavelength-dependent difference between normal and cancerous tissues was observed. These results correlate well with pathology and nuclear magnetic resonance based analyses of the samples, and indicate the diagnostic potential of optical imaging approaches. Detection and localization of targets in thick breast tissue specimens and phantoms was accomplished using independent component analysis (ICA) from information theory. The approach known as Optical Tomography using Independent Component Analysis (OPTICA) made use of multi-source probing of the samples, multi-detector transillumination signal acquisition, and analysis of resulting data

  11. A novel setup for time-resolved X-ray diffraction on gas gun experiments

    NASA Astrophysics Data System (ADS)

    Zucchini, Frédéric; Chauvin, Camille; Loyen, Arnaud; Combes, Philippe; Petit, Jacques; Bland, Simon

    2017-01-01

    Polymorphic phase transitions in metals have been investigated for a long time under dynamic loadings through usual dynamic compression diagnostics such as velocity and temperature measurements. Such measurements were valuable for revealing the key role of kinetic effects in most phase transition mechanisms. However, the information extracted was mostly macroscopic. Obtaining direct insight about the crystallographic structure under dynamic loadings is critical for understanding mechanisms governing shock-induced structural changes. For example, in order to evidence a mixture phase or to determine the time scale of a transition, structural information may be extremely valuable. Over the last 20 years a significant number of X-ray diffraction experiments were carried under dynamic loading, either using laboratory X-ray sources or synchrotron radiation. We are developing a novel experimental setup based on a compact High Pulsed Power generator capable of producing intense X radiation through an X-pinch X-ray source. This source is specifically designed for time-resolved X-ray diffraction in Bragg geometry on gas gun experiments. Promising preliminary diffraction data obtained under static conditions are presented.

  12. Nonadiabatic Dynamics May Be Probed through Electronic Coherence in Time-Resolved Photoelectron Spectroscopy.

    PubMed

    Bennett, Kochise; Kowalewski, Markus; Mukamel, Shaul

    2016-02-09

    We present a hierarchy of Fermi golden rules (FGRs) that incorporate strongly coupled electronic/nuclear dynamics in time-resolved photoelectron spectroscopy (TRPES) signals at different levels of theory. Expansion in the joint electronic and nuclear eigenbasis yields the numerically most challenging exact FGR (eFGR). The quasistatic Fermi Golden Rule (qsFGR) neglects nuclear motion during the photoionization process but takes into account electronic coherences as well as populations initially present in the pumped matter as well as those generated internally by coupling between electronic surfaces. The standard semiclassical Fermi Golden Rule (scFGR) neglects the electronic coherences and the nuclear kinetic energy during the ionizing pulse altogether, yielding the classical Condon approximation. The coherence contributions depend on the phase-profile of the ionizing field, allowing coherent control of TRPES signals. The photoelectron spectrum from model systems is simulated using these three levels of theory. The eFGR and the qsFGR show temporal oscillations originating from the electronic or vibrational coherences generated as the nuclear wave packet traverses a conical intersection. These oscillations, which are missed by the scFGR, directly reveal the time-evolving splitting between electronic states of the neutral molecule in the curve-crossing regime.

  13. Initial processes of proton transfer in salicylideneaniline studied by time-resolved photoelectron spectroscopy.

    PubMed

    Sekikawa, Taro; Schalk, Oliver; Wu, Guorong; Boguslavskiy, Andrey E; Stolow, Albert

    2013-04-11

    Excited-state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in the para position of the anilino group have been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). SA has a twisted structure at the energetic minimum of the ground state, but ESIPT is assumed to take place through a planar structure, although this has not been fully established. The TRPES studies revealed that the excited-state dynamics within the S1 band varied significantly with excitation wavelength. At finite temperatures, the ground state was found to sample a broad range of torsional angles, from planar to twisted. At lower photon energies (370 nm), only the planar ground-state molecules were excited, and the excited-state reaction took place within 50 fs. At higher energies (350 and 330 nm), predominantly twisted ground-state molecules were excited: they had to planarize before ESIPT could occur. This process was found to be slower in methylated SA but did not change significantly in the brominated and nitrated SAs. These substitution effects on the decay dynamics can be explained by modifications of the potential barriers, as predicted by the TDDFT calculations, and support the mechanism of a twisting motion of the anilino ring prior to ESIPT. The contribution of another pathway leading to internal conversion within the enol form was found to be minor at the excitation wavelengths considered here.

  14. Theoretical study of time-resolved luminescence in semiconductors. III. Trap states in the band gap

    SciTech Connect

    Maiberg, Matthias Hölscher, Torsten; Zahedi-Azad, Setareh; Scheer, Roland

    2015-09-14

    In the third part of this series, we study the influence of trap states in the band gap of semiconductors on the time-resolved luminescence decay (TRL) after a pulsed excitation. The results based on simulations with Synopsys TCAD{sup ®} and analytical approximations are given for p-doped Cu(In,Ga)Se{sub 2} as a working example. We show that a single trap can be mostly described by two parameters which are assigned to minority carrier capture and emission. We analyze their influence on the luminescence decay and study the difference between a single trap and an energetic Gaussian trap distribution. It is found that trap states artificially increase the TRL decay and obscure the recombination dynamics. Thus, there is a demand for experimental methods which can reveal the recombination of minority carriers in a TRL experiment without trapping effect. In this regard, a variation of the device temperature, the excitation frequency, the injection level, as well as a bias illumination may be promising approaches. We study these methods, discuss advantages and disadvantages, and show experimental TRL for prove of concept. At the end, we validate our approach of simulating only band-to-band radiative recombination although photoluminescence spectra often exhibit free-to-bound radiative recombination of charge carriers.

  15. Observing molecular dynamics with time-resolved 3D momentum imaging

    NASA Astrophysics Data System (ADS)

    Sturm, F. P.; Wright, T.; Bocharova, I.; Ray, D.; Shivaram, N.; Cryan, J.; Belkacem, A.; Weber, T.; Dörner, R.

    2014-05-01

    Photo-excitation and ionization trigger rich dynamics in molecular systems which play a key role in many important processes in nature such as vision, photosynthesis or photoprotection. Observing those reactions in real-time without significantly disturbing the molecules by a strong electric field has been a great challenge. Recent experiments using Time-of-Flight and Velocity Map Imaging techniques have revealed important information on the dynamics of small molecular systems upon photo-excitation. We have developed an apparatus for time-resolved momentum imaging of electrons and ions in all three spatial dimensions that employs two-color femtosecond laser pulses in the vacuum and extreme ultraviolet (VUV, XUV) for probing molecular dynamics. Our COLTRIMS style reaction microscope can measure electrons and ions in coincidence and reconstruct the momenta of the reaction fragments in 3D. We use a high power 800 nm laser in a loose focusing geometry gas cell to efficinetly drive High Harmonic Generation. The resulting photon flux is sufficient to perform 2-photon pump-probe experiments using VUV and XUV pulses for both pump and probe. With this setup we investigate non-Born-Oppenheimer dynamics in small molecules such as C2H4 and CO2 on a femtosecond time scale. Supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.

  16. Time-resolved Analysis of the Matrix Metalloproteinase 10 Substrate Degradome*

    PubMed Central

    Schlage, Pascal; Egli, Fabian E.; Nanni, Paolo; Wang, Lauren W.; Kizhakkedathu, Jayachandran N.; Apte, Suneel S.; Keller, Ulrich auf dem

    2014-01-01

    Proteolysis is an irreversible post-translational modification that affects intra- and intercellular communication by modulating the activity of bioactive mediators. Key to understanding protease function is the system-wide identification of cleavage events and their dynamics in physiological contexts. Despite recent advances in mass spectrometry-based proteomics for high-throughput substrate screening, current approaches suffer from high false positive rates and only capture single states of protease activity. Here, we present a workflow based on multiplexed terminal amine isotopic labeling of substrates for time-resolved substrate degradomics in complex proteomes. This approach significantly enhances confidence in substrate identification and categorizes cleavage events by specificity and structural accessibility of the cleavage site. We demonstrate concomitant quantification of cleavage site spanning peptides and neo-N and/or neo-C termini to estimate relative ratios of noncleaved and cleaved forms of substrate proteins. By applying this strategy to dissect the matrix metalloproteinase 10 (MMP10) substrate degradome in fibroblast secretomes, we identified the extracellular matrix protein ADAMTS-like protein 1 (ADAMTSL1) as a direct MMP10 substrate and revealed MMP10-dependent ectodomain shedding of platelet-derived growth factor receptor alpha (PDGFRα) as well as sequential processing of type I collagen. The data have been deposited to the ProteomeXchange Consortium with identifier PXD000503. PMID:24281761

  17. Defect characterization in ZnGeP2 by time-resolved photoluminescence

    NASA Technical Reports Server (NTRS)

    Dietz, N.; Wood, G.; Bachmann, K. J.; Busse, W.; Gumlich, H. E.; Ruderman, W.; Tsveybak, I.

    1995-01-01

    The native defect-related optical properties of ZnGeP2 are studied by steady-state and time-resolved photoluminescence. ZnGeP2 crystals grown from the vapor phase by high pressure physical vapor transport (HPVT) and from the melt by gradient freezing (GF) show a broad infrared emission with peak position at 1.2 eV with a decay time constant of a few micro-s and a faster recombination center peaked at 1.68 eV. The decay transient for the emission at 1.2 eV exhibits features of classical donor-acceptor recombination and is linked to close-pairs that are tentatively associated with germanium-on-zinc antisite donors and zinc vacancy acceptors. Higher energetic luminescence structures at 1.6eV and 1.7eV are revealed after annealing of the ZnGeP2 crystals and are associated with the formation zinc and phosphorous vacancies in the near surface region. ZnGeP2 crystals grown by HPVT from zinc and phosphorus supersaturated vapor compositions show additional emission structure at 1.8 eV and a sharp donor-acceptor emission at 1.778 eV that is related to the presence of additional donor states.

  18. Time-resolved electron kinetics in swift heavy ion irradiated solids

    NASA Astrophysics Data System (ADS)

    Medvedev, N. A.; Rymzhanov, R. A.; Volkov, A. E.

    2015-09-01

    The event-by-event Monte Carlo model, TREKIS, was developed to describe the excitation of the electron subsystems of various solids by a penetrating swift heavy ion (SHI), the spatial spreading of generated fast electrons, and secondary electron and hole cascades. Complex dielectric function formalism is used to obtain relevant cross sections. This allows the recognition of fundamental effects resulting from the collective response of the electron subsystem of a target for excitation that is not possible within the binary collision approximation of these cross sections, e.g. the differences in the electronic stopping of an ion and in the electron mean free paths for different structures (phases) of a material. A systematic study performed with this model for different materials (insulators, semiconductors and metals) revealed effects which may be important for an ion track: e.g. the appearance of a second front of excess electronic energy propagation outwards from the track core following the primary front of spreading of generated electrons. We also analyze how the initial ballistic spatial spreading of fast electrons generated in a track turns to the diffusion ~10 fs after ion passage. Detailed time-resolved simulations of electronic subsystem kinetics helped in understanding the reasons behind enhanced silicon resistance to SHI irradiation in contrast to easily produced damage in this material by femtosecond laser pulses. We demonstrate that the fast spreading of excited electrons from the track core on a sub-100 fs timescale prevents the Si lattice from nonthermal melting in a relaxing SHI track.

  19. In vivo time-resolved spectroscopy of the human bronchial early cancer autofluorescence

    NASA Astrophysics Data System (ADS)

    Uehlinger, Pascal; Gabrecht, Tanja; Glanzmann, Thomas; Ballini, Jean-Pierre; Radu, Alexandre; Andrejevic, Snezana; Monnier, Philippe; Wagnières, Georges

    2009-03-01

    Time-resolved measurements of tissue autofluorescence (AF) excited at 405 nm were carried out with an optical-fiber-based spectrometer in the bronchi of 11 patients. The objectives consisted of assessing the lifetime as a new tumor/normal (T/N) tissue contrast parameter and trying to explain the origin of the contrasts observed when using AF-based cancer detection imaging systems. No significant change in the AF lifetimes was found. AF bronchoscopy performed in parallel with an imaging device revealed both intensity and spectral contrasts. Our results suggest that the spectral contrast might be due to an enhanced blood concentration just below the epithelial layers of the lesion. The intensity contrast probably results from the thickening of the epithelium in the lesions. The absence of T/N lifetime contrast indicates that the quenching is not at the origin of the fluorescence intensity and spectral contrasts. These lifetimes (6.9 ns, 2.0 ns, and 0.2 ns) were consistent for all the examined sites. The fact that these lifetimes are the same for different emission domains ranging between 430 and 680 nm indicates that there is probably only one dominant fluorophore involved. The measured lifetimes suggest that this fluorophore is elastin.

  20. Investigation of Prolactin Receptor Activation and Blockade Using Time-Resolved Fluorescence Resonance Energy Transfer

    PubMed Central

    Tallet, Estelle; Fernandez, Isabelle; Zhang, Chi; Salsac, Marion; Gregor, Nathalie; Ayoub, Mohammed Akli; Pin, Jean Philippe; Trinquet, Eric; Goffin, Vincent

    2011-01-01

    The prolactin receptor (PRLR) is emerging as a therapeutic target in oncology. Knowledge-based drug design led to the development of a pure PRLR antagonist (Del1-9-G129R-hPRL) that was recently shown to prevent PRL-induced mouse prostate tumorogenesis. In humans, the first gain-of-function mutation of the PRLR (PRLRI146L) was recently identified in breast tumor patients. At the molecular level, the actual mechanism of action of these two novel players in the PRL system remains elusive. In this study, we addressed whether constitutive PRLR activation (PRLRI146L) or PRLR blockade (antagonist) involved alteration of receptor oligomerization and/or of inter-chain distances compared to unstimulated and PRL-stimulated PRLR. Using a combination of various biochemical and spectroscopic approaches (co-IP, blue native electrophoresis, BRET1), we demonstrated that preformed PRLR homodimers are altered neither by PRL- or I146L-induced receptor triggering, nor by antagonist-mediated blockade. These findings were confirmed using a novel time-resolved fluorescence resonance energy transfer (TR-FRET) technology that allows monitoring distance changes between cell surface tagged receptors. This technology revealed that PRLR blockade or activation did not involve detectable distance changes between extracellular domains of receptor chains within the dimer. This study merges with our previous structural investigations suggesting that the mechanism of PRLR activation solely involves intermolecular contact adaptations leading to subtle intramolecular rearrangements. PMID:22649370

  1. Time-resolved vortex wake of a common swift flying over a range of flight speeds

    PubMed Central

    Henningsson, P.; Muijres, F. T.; Hedenström, A.

    2011-01-01

    The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s−1. The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of ‘wing root vortices’ are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings. PMID:21131333

  2. Time-resolved vortex wake of a common swift flying over a range of flight speeds.

    PubMed

    Henningsson, P; Muijres, F T; Hedenström, A

    2011-06-06

    The wake of a freely flying common swift (Apus apus L.) is examined in a wind tunnel at three different flight speeds, 5.7, 7.7 and 9.9 m s(-1). The wake of the bird is visualized using high-speed stereo digital particle image velocimetry (DPIV). Wake images are recorded in the transverse plane, perpendicular to the airflow. The wake of a swift has been studied previously using DPIV and recording wake images in the longitudinal plane, parallel to the airflow. The high-speed DPIV system allows for time-resolved wake sampling and the result shows features that were not discovered in the previous study, but there was approximately a 40 per cent vertical force deficit. As the earlier study also revealed, a pair of wingtip vortices are trailing behind the wingtips, but in addition, a pair of tail vortices and a pair of 'wing root vortices' are found that appear to originate from the wing/body junction. The existence of wing root vortices suggests that the two wings are not acting as a single wing, but are to some extent aerodynamically detached from each other. It is proposed that this is due to the body disrupting the lift distribution over the wing by generating less lift than the wings.

  3. Femtosecond time-resolved energy transfer from CdSe nanoparticles to phthalocyanines

    NASA Astrophysics Data System (ADS)

    Dayal, S.; Królicki, R.; Lou, Y.; Qiu, X.; Berlin, J. C.; Kenney, M. E.; Burda, C.

    2006-07-01

    The first real-time observation of the early events during energy transfer from a photoexcited CdSe nanoparticle to an attached phthalocyanine molecule are presented in terms of a femtosecond spectroscopic pump-probe study of the energy transfer in conjugates of CdSe nanoparticles (NPs) and silicon phthalocyanines (Pcs) with 120 fs time resolution. Four different silicon phthalocyanines have been conjugated to CdSe NPs. All of these have proven potential for photodynamic therapy (PDT). In such NP-Pc conjugates efficient energy transfer (ET) from CdSe NPs to Pcs occurs upon selective photoexcitation of the NP moiety. Spectral analysis as well as time-resolved fluorescence up-conversion measurements revealed the structure and dynamics of the investigated conjugates. Femtosecond transient differential absorption (TDA) spectroscopy was used for the investigation of the non-radiative carrier and ET dynamics. The formation of excitons, trapped carriers states, as well as stimulated emission was monitored in the TDA spectra and the corresponding lifetimes of these states were recorded. The time component for energy transfer was found to be between 15 and 35 ps. The ET efficiencies are found to be 20-70% for the four Pc conjugates, according to fluorescence quenching experiments. Moreover, as a result of the conjugation between NP and the Pcs the photoluminescence efficiency of the Pc moieties in the conjugates do not strictly follow the quantum yields of the bare phthalocyanines.

  4. Automated design of probes for rRNA-targeted fluorescence in situ hybridization reveals the advantages of using dual probes for accurate identification.

    PubMed

    Wright, Erik S; Yilmaz, L Safak; Corcoran, Andrew M; Ökten, Hatice E; Noguera, Daniel R

    2014-08-01

    Fluorescence in situ hybridization (FISH) is a common technique for identifying cells in their natural environment and is often used to complement next-generation sequencing approaches as an integral part of the full-cycle rRNA approach. A major challenge in FISH is the design of oligonucleotide probes with high sensitivity and specificity to their target group. The rapidly expanding number of rRNA sequences has increased awareness of the number of potential nontargets for every FISH probe, making the design of new FISH probes challenging using traditional methods. In this study, we conducted a systematic analysis of published probes that revealed that many have insufficient coverage or specificity for their intended target group. Therefore, we developed an improved thermodynamic model of FISH that can be applied at any taxonomic level, used the model to systematically design probes for all recognized genera of bacteria and archaea, and identified potential cross-hybridizations for the selected probes. This analysis resulted in high-specificity probes for 35.6% of the genera when a single probe was used in the absence of competitor probes and for 60.9% when up to two competitor probes were used. Requiring the hybridization of two independent probes for positive identification further increased specificity. In this case, we could design highly specific probe sets for up to 68.5% of the genera without the use of competitor probes and 87.7% when up to two competitor probes were used. The probes designed in this study, as well as tools for designing new probes, are available online (http://DECIPHER.cee.wisc.edu).

  5. Human milk fat globules: polar lipid composition and in situ structural investigations revealing the heterogeneous distribution of proteins and the lateral segregation of sphingomyelin in the biological membrane.

    PubMed

    Lopez, Christelle; Ménard, Olivia

    2011-03-01

    Although human milk fat globules (MFG) are of primary importance since they are the exclusive lipid delivery carriers in the gastrointestinal tract of breast-fed infants, they remain the poorly understood aspect of milk. The objectives of this study were to investigate these unique colloidal assemblies and their interfacial properties, i.e. composition and structure of their biological membrane. In mature breast milk, MFG have a mean diameter of 4-5 microm, a surface area of about 2m(2)/g fat and an apparent zeta potential ζ=-6.7 ± 0.5 mV at 37°C. Human MFG contain 3-4mg polar lipids/g fat as quantified by HPLC/ELSD. The main polar lipids are sphingomyelin (SM; 36-45%, w/w), phosphatidylcholine (19-23%, w/w) and phosphatidylethanolamine (10-15%, w/w). In situ structural investigations of human MFG have been performed using light and confocal microscopy with adapted fluorescent probes, i.e. Nile Red, the extrinsic phospholipid Rh-DOPE, Fast Green and the lectin WGA-488. This study revealed a spatial heterogeneity in the human milk fat globule membrane (MFGM), with the lateral segregation of SM in liquid-ordered phase domains of various shapes and sizes surrounded by a liquid-disordered phase composed of the glycerophospholipids in which the proteins are dispersed. The glycocalyx formed by glycoproteins and cytoplasmic remnents have also been characterised around human MFG. A new model for the structure of the human MFGM is proposed and discussed. The unique composition and lateral organisation of the human MFGM components could be of metabolic significance and have health impact for the infants that need to be further explored.

  6. SVD-aided pseudo principal-component analysis: A new method to speed up and improve determination of the optimum kinetic model from time-resolved data

    PubMed Central

    Oang, Key Young; Yang, Cheolhee; Muniyappan, Srinivasan; Kim, Jeongho; Ihee, Hyotcherl

    2017-01-01

    Determination of the optimum kinetic model is an essential prerequisite for characterizing dynamics and mechanism of a reaction. Here, we propose a simple method, termed as singular value decomposition-aided pseudo principal-component analysis (SAPPA), to facilitate determination of the optimum kinetic model from time-resolved data by bypassing any need to examine candidate kinetic models. We demonstrate the wide applicability of SAPPA by examining three different sets of experimental time-resolved data and show that SAPPA can efficiently determine the optimum kinetic model. In addition, the results of SAPPA for both time-resolved X-ray solution scattering (TRXSS) and transient absorption (TA) data of the same protein reveal that global structural changes of protein, which is probed by TRXSS, may occur more slowly than local structural changes around the chromophore, which is probed by TA spectroscopy.

  7. Time-resolved study of the mechanical response of tissue phantoms to nanosecond laser pulses.

    PubMed

    Pérez-Gutiérrez, Francisco G; Camacho-López, Santiago; Aguilar, Guillermo

    2011-11-01

    We present a time-resolved study of the interaction of nanosecond laser pulses with tissue phantoms. When a laser pulse interacts with a material, optical energy is absorbed by a combination of linear (heat generation and thermoelastic expansion) and nonlinear absorption (expanding plasma), according to both the laser light irradiance and material properties. The objective is to elucidate the contribution of linear and nonlinear optical absorption to bubble formation. Depending on the local temperatures and pressures reached, both interactions may lead to the formation of bubbles. We discuss three experimental approaches: piezoelectric sensors, time-resolved shadowgraphy, and time-resolved interferometry, to follow the formation of bubbles and measure the pressure originated by 6 ns laser pulses interacting with tissue phantoms. We studied the bubble formation and pressure transients for varying linear optical absorption and for radiant exposures above and below threshold for bubble formation. We report a rapid decay (of 2 orders of magnitude) of the laser-induced mechanical pressure measured (by time-resolved shadowgraphy) very close to the irradiation spot and beyond 1 mm from the irradiation site (by the piezoelectric sensor). Through time-resolved interferometry measurements, we determined that bubble formation can occur at marginal temperature increments as low as 3°C.

  8. Nitrate and Nitrite Variability at the Seafloor of an Oxygen Minimum Zone Revealed by a Novel Microfluidic In-Situ Chemical Sensor

    PubMed Central

    Yücel, Mustafa; Beaton, Alexander D.; Dengler, Marcus; Mowlem, Matthew C.; Sohl, Frank; Sommer, Stefan

    2015-01-01

    Microfluidics, or lab-on-a-chip (LOC) is a promising technology that allows the development of miniaturized chemical sensors. In contrast to the surging interest in biomedical sciences, the utilization of LOC sensors in aquatic sciences is still in infancy but a wider use of such sensors could mitigate the undersampling problem of ocean biogeochemical processes. Here we describe the first underwater test of a novel LOC sensor to obtain in situ calibrated time-series (up to 40 h) of nitrate+nitrite (ΣNOx) and nitrite on the seafloor of the Mauritanian oxygen minimum zone, offshore Western Africa. Initial tests showed that the sensor successfully reproduced water column (160 m) nutrient profiles. Lander deployments at 50, 100 and 170 m depth indicated that the biogeochemical variability was high over the Mauritanian shelf: The 50 m site had the lowest ΣNOx concentration, with 15.2 to 23.4 μM (median=18.3 μM); while at the 100 site ΣNOx varied between 21.0 and 30.1 μM over 40 hours (median = 25.1μM). The 170 m site had the highest median ΣNOx level (25.8 μM) with less variability (22.8 to 27.7 μM). At the 50 m site, nitrite concentration decreased fivefold from 1 to 0.2 μM in just 30 hours accompanied by decreasing oxygen and increasing nitrate concentrations. Taken together with the time series of oxygen, temperature, pressure and current velocities, we propose that the episodic intrusion of deeper waters via cross-shelf transport leads to intrusion of nitrate-rich, but oxygen-poor waters to shallower locations, with consequences for benthic nitrogen cycling. This first validation of an LOC sensor at elevated water depths revealed that when deployed for longer periods and as a part of a sensor network, LOC technology has the potential to contribute to the understanding of the benthic biogeochemical dynamics. PMID:26161958

  9. Nitrate and Nitrite Variability at the Seafloor of an Oxygen Minimum Zone Revealed by a Novel Microfluidic In-Situ Chemical Sensor.

    PubMed

    Yücel, Mustafa; Beaton, Alexander D; Dengler, Marcus; Mowlem, Matthew C; Sohl, Frank; Sommer, Stefan

    2015-01-01

    Microfluidics, or lab-on-a-chip (LOC) is a promising technology that allows the development of miniaturized chemical sensors. In contrast to the surging interest in biomedical sciences, the utilization of LOC sensors in aquatic sciences is still in infancy but a wider use of such sensors could mitigate the undersampling problem of ocean biogeochemical processes. Here we describe the first underwater test of a novel LOC sensor to obtain in situ calibrated time-series (up to 40 h) of nitrate+nitrite (ΣNOx) and nitrite on the seafloor of the Mauritanian oxygen minimum zone, offshore Western Africa. Initial tests showed that the sensor successfully reproduced water column (160 m) nutrient profiles. Lander deployments at 50, 100 and 170 m depth indicated that the biogeochemical variability was high over the Mauritanian shelf: The 50 m site had the lowest ΣNOx concentration, with 15.2 to 23.4 μM (median=18.3 μM); while at the 100 site ΣNOx varied between 21.0 and 30.1 μM over 40 hours (median = 25.1 μM). The 170 m site had the highest median ΣNOx level (25.8 μM) with less variability (22.8 to 27.7 μM). At the 50 m site, nitrite concentration decreased fivefold from 1 to 0.2 μM in just 30 hours accompanied by decreasing oxygen and increasing nitrate concentrations. Taken together with the time series of oxygen, temperature, pressure and current velocities, we propose that the episodic intrusion of deeper waters via cross-shelf transport leads to intrusion of nitrate-rich, but oxygen-poor waters to shallower locations, with consequences for benthic nitrogen cycling. This first validation of an LOC sensor at elevated water depths revealed that when deployed for longer periods and as a part of a sensor network, LOC technology has the potential to contribute to the understanding of the benthic biogeochemical dynamics.

  10. Femtosecond Time-Resolved Resonance-Enhanced CARS of Gaseous Iodine at Room Temperature

    NASA Astrophysics Data System (ADS)

    He, Ping; Fan, Rong-Wei; Xia, Yuan-Qin; Yu, Xin; Yao, Yong; Chen, De-Ying

    2011-04-01

    Time-resolved resonance-enhanced coherent anti-Stokes Raman scattering (CARS) is applied to investigate molecular dynamics in gaseous iodine. 40 fs laser pulses are applied to create and monitor the high vibrational states of iodine at room temperature (corresponding to a vapor pressure as low as about 35 Pa) by femtosecond time-resolved CARS. Depending on the time delay between the probe pulse and the pump/Stokes pulse pairs, the high vibrational states both on the electronically ground states and the excited states can be detected as oscillations in the CARS transient signal. It is proved that the femtosecond time-resolved CARS technique is a promising candidate for investigating the molecular dynamics of a low concentration system and can be applied to environmental and atmospheric monitoring measurements.

  11. The kinetic dose limit in room-temperature time-resolved macromolecular crystallography

    PubMed Central

    Schmidt, M.; Šrajer, V.; Purwar, N.; Tripathi, S.

    2012-01-01

    Protein X-ray structures are determined with ionizing radiation that damages the protein at high X-ray doses. As a result, diffraction patterns deteriorate with the increased absorbed dose. Several strategies such as sample freezing or scavenging of X-ray-generated free radicals are currently employed to minimize this damage. However, little is known about how the absorbed X-ray dose affects time-resolved Laue data collected at physiological temperatures where the protein is fully functional in the crystal, and how the kinetic analysis of such data depends on the absorbed dose. Here, direct evidence for the impact of radiation damage on the function of a protein is presented using time-resolved macromolecular crystallography. The effect of radiation damage on the kinetic analysis of time-resolved X-ray data is also explored. PMID:22338689

  12. Cluster mass fraction and size distribution determined by fs-time-resolved measurements

    NASA Astrophysics Data System (ADS)

    Gao, Xiaohui; Wang, Xiaoming; Shim, Bonggu; Arefiev, Alexey; Tushentsov, Mikhail; Breizman, Boris; Downer, Mike

    2009-11-01

    Characterization of supersonic gas jets is important for accurate interpretation and control of laser-cluster experiments. While average size and total atomic density can be found by standard Rayleigh scatter and interferometry, cluster mass fraction and size distribution are usually difficult to measure. Here we determine the cluster fraction and the size distribution with fs-time-resolved refractive index and absorption measurements in cluster gas jets after ionization and heating by an intense pump pulse. The fs-time-resolved refractive index measured with frequency domain interferometer (FDI) shows different contributions from monomer plasma and cluster plasma in the time domain, enabling us to determine the cluster fraction. The fs-time-resolved absorption measured by a delayed probe shows the contribution from clusters of various sizes, allowing us to find the size distribution.

  13. Solving the Structure of Reaction Intermediates by Time-Resolved Synchrotron X-ray Absorption Spectroscopy

    SciTech Connect

    Wang, Q.; Hanson, J; Frenkel, A

    2008-01-01

    We present a robust data analysis method of time-resolved x-ray absorption spectroscopy experiments suitable for chemical speciation and structure determination of reaction intermediates. Chemical speciation is done by principal component analysis (PCA) of the time-resolved x-ray absorption near-edge structure data. Structural analysis of intermediate phases is done by theoretical modeling of their extended x-ray absorption fine-structure data isolated by PCA. The method is demonstrated using reduction and reoxidation of Cu-doped ceria catalysts where we detected reaction intermediates and measured fine details of the reaction kinetics. This approach can be directly adapted to many time-resolved x-ray spectroscopy experiments where new rapid throughput data collection and analysis methods are needed.

  14. Recent Advances in 3D Time-Resolved Contrast-Enhanced MR Angiography

    PubMed Central

    Riederer, Stephen J.; Haider, Clifton R.; Borisch, Eric A.; Weavers, Paul T.; Young, Phillip M.

    2015-01-01

    Contrast-enhanced MR angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3 to 4 mm spatial resolution with acquisition times in the 30 sec range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution three-dimensional (3D) time-resolved studies. The purpose of this work is to describe how this has been accomplished. Specific technical enablers have been: improved gradients allowing reduced repetition times, improved k-space sampling and reconstruction methods, parallel acquisition particularly in two directions, and improved and higher count receiver coil arrays. These have collectively made high resolution time-resolved studies readily available for many anatomic regions. Depending on the application, approximate 1 mm isotropic resolution is now possible with frame times of several seconds. Clinical applications of time-resolved CE-MRA are briefly reviewed. PMID:26032598

  15. Feasibility experiments on time-resolved fluorosensing applied to oil slicks

    NASA Technical Reports Server (NTRS)

    Camagni, P.; Colombo, G.; Koechler, C.; Pedrini, A.; Omenetto, N.; Rossi, G.

    1986-01-01

    The introduction of time resolved observations can provide a very penetrating tool in the practice of laser fluorosensing. The investigations have demonstrated a relevance of multispectral, time resolved analysis for oil fingerprinting. By comparative studies on a variety of crude oils and their most significant fractions, it was found that the process of time decay in a composite oil is characterized by a few steps, which are associated with specific components in the medium light range. The average decay times of these pure fractions are markedly differentiated as to absolute values and spectral spread; as a consequence, the corresponding parameters in the resultant crude are quite sensitive to the particular mixture of these components. Measurements of the time response give then a finer discrimination between oil classes, depending on the relative content of certain fractions. Experiments were pursued with an improved fluorosensor facility, in order to test the application of time resolved fluorosensing to remote samples on water.

  16. Apparatus and Techniques for Time-resolved Synchrotron X-ray Diffraction using Diamond Anvil Cells

    NASA Astrophysics Data System (ADS)

    Smith, J.; Sinogeikin, S. V.; Lin, C.; Rod, E.; Bai, L.; Shen, G.

    2015-12-01

    Complementary advances in synchrotron sources, x-ray optics, area detectors, and sample environment control have recently made possible many time-resolved experimental techniques for studying materials at extreme pressure and temperature conditions. The High Pressure Collaborative Access Team (HPCAT) at the Advanced Photon Source has made a sustained effort to assemble a powerful collection of high-pressure apparatus for time-resolved research, and considerable time has been invested in developing techniques for collecting high-quality time-resolved x-ray scattering data. Herein we present key aspects of the synchrotron beamline and ancillary equipment, including source considerations, rapid (de)compression apparatus, high frequency imaging detectors, and software suitable for processing large volumes of data. A number of examples are presented, including fast equation of state measurements, compression rate dependent synthesis of metastable states in silicon and germanium, and ultrahigh compression rates using a piezoelectric driven diamond anvil cell.

  17. Combined single-pulse holography and time-resolved laser schlieren for flow visualization

    NASA Astrophysics Data System (ADS)

    Burner, A. W.; Goad, W. K.

    1981-06-01

    A pulsed ruby laser and continuous-wave argon ion laser were used in a combined setup at the Langley Expansion Tube for single pulse holography and time resolved laser schlieren with a common optical axis. The systems can be operated simultaneously for a single run. For a single frame, the pulsed holographic setup offers the options of shadowgraph, Schlieren, and interferometry from the reconstructed hologram as well as the advantage of post-run sensitivity adjustments. For flow establishment studies the time resolved laser Schlieren provides visualization of the flow field every 12.5 microns for up to 80 frames with an exposure time per frame of 5.4 microns.

  18. TRIASSIC: the Time-Resolved Industrial Alpha-Source Scanning Induced Current microscope

    NASA Astrophysics Data System (ADS)

    Pallone, Arthur

    Time-resolved ion beam induced current (TRIBIC) microscopy yields useful information such as carrier mobility and lifetimes in semiconductors and defect locations in devices; however, traditional TRIBIC uses large, expensive particle accelerators that require specialized training to operate and maintain. The time-resolved industrial alpha-source scanning induced current (TRIASSIC) microscope transforms TRIBIC by replacing the particle accelerator facility with an affordable, tabletop instrument suitable for use in research and education at smaller colleges and universities. I will discuss the development of, successes with, setbacks to and future directions for TRIASSIC.

  19. A time-resolved infrared vibrational spectroscopic study of the photo-dynamics of crystalline materials.

    PubMed

    Towrie, Mike; Parker, Anthony W; Ronayne, Kate L; Bowes, Katharine F; Cole, Jacqueline M; Raithby, Paul R; Warren, John E

    2009-01-01

    Time-resolved infrared vibrational spectroscopy is a structurally sensitive probe of the excited-state properties of matter. The technique has found many applications in the study of molecules in dilute solution phase but has rarely been applied to crystalline samples. We report on the use of a sensitive pump-probe time-resolved infrared spectrometer and sample handling techniques for studies of the ultrafast excited-state dynamics of crystalline materials. The charge transfer excited states of crystalline metal carbonyls and the proton transfer of dihydroxyquinones are presented and compared with the solution phase.

  20. Probing ultrafast internal conversion of o-xylene via femtosecond time-resolved photoelectron imaging.

    PubMed

    Liu, Yuzhu; Tang, Bifeng; Shen, Huan; Zhang, Song; Zhang, Bing

    2010-03-15

    The dynamics of excited states in o-xylene molecules has been studied by femtosecond time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. The ultrafast internal conversion from the S(2) state to the vibrationally hot S(1) state on timescale of 60 fs is observed on real time. The secondarily populated high vibronic S(1) state deactivates further to the S(0) state on timescale of 9.85 ps. Interestingly, the lifetime of the low vibronic S(1) state is much longer, extrapolated to ~12.7 ns. The great differences of lifetime of different vibronic S(1) state are due to their different radiationless dynamics.

  1. Monte Carlo algorithm for efficient simulation of time-resolved fluorescence in layered turbid media.

    PubMed

    Liebert, A; Wabnitz, H; Zołek, N; Macdonald, R

    2008-08-18

    We present an efficient Monte Carlo algorithm for simulation of time-resolved fluorescence in a layered turbid medium. It is based on the propagation of excitation and fluorescence photon bundles and the assumption of equal reduced scattering coefficients at the excitation and emission wavelengths. In addition to distributions of times of arrival of fluorescence photons at the detector, 3-D spatial generation probabilities were calculated. The algorithm was validated by comparison with the analytical solution of the diffusion equation for time-resolved fluorescence from a homogeneous semi-infinite turbid medium. It was applied to a two-layered model mimicking intra- and extracerebral compartments of the adult human head.

  2. High time-resolved measurements of organic air toxics in different source regimes

    NASA Astrophysics Data System (ADS)

    Logue, J. M.; Huff-Hartz, K. E.; Lambe, A. T.; Donahue, N. M.; Robinson, A. L.

    2009-12-01

    High time-resolved (HTR) measurements can provide significant insight into sources and exposures of air pollution. In this study, an automated instrument was developed and deployed to measure hourly concentrations of 18 gas-phase organic air toxics and 6 volatile organic compounds (VOCs) at three sites in and around Pittsburgh, Pennsylvania. The sites represent different source regimes: a site with substantial mobile-source emissions; a residential site adjacent to a heavily industrialized zone; and an urban background site. Despite the close proximity of the sites (less than 13 km apart), the temporal characteristic of outdoor concentrations varied widely. Most of the compounds measured were characterized by short periods of elevated concentrations or plume events, but the duration, magnitude and composition of these events varied from site to site. The HTR data underscored the strong role of emissions from local sources on exposure to most air toxics. Plume events contributed more than 50% of the study average concentrations for all pollutants except chloroform, 1,2-dichloroethane, and carbon tetrachloride. Wind directional dependence of air toxic concentrations revealed that emissions from large industrial facilities affected concentrations at all of the sites. Diurnal patterns and weekend/weekday variations indicated the effects of the mixing layer, point source emissions patterns, and mobile source air toxics (MSATs) on concentrations. Concentrations of many air toxics were temporally correlated, especially MSATs, indicating that they are likely co-emitted. It was also shown that correlations of the HTR data were greater than lower time resolution data (24-h measurements). This difference was most pronounced for the chlorinated pollutants. The stronger correlations in HTR measurements underscore their value for source apportionment studies.

  3. Rotational diffusion of receptors for epidermal growth factor measured by time-resolved phosphorescence depolarization

    NASA Astrophysics Data System (ADS)

    Zidovetzki, Raphael; Johnson, David A.; Arndt-Jovin, Donna J.; Jovin, Thomas M.

    1991-06-01

    The cell surface receptor for epidermal growth factor (EGFR) is one of the most studied integral membrane proteins. The receptor is widely distributed in cells and tissues of mammalian and avian tissues and plays an important role in growth control. Binding of the epidermal growth factor (EGF) to EGFR initiates a complex biological response, which includes self-phosphorylation of the receptor due to an intrinsic tyrosine kinase activity, phosphorylation of other membrane proteins, increased intake of metabolites, and increased proliferation. Complete amino acid sequence of EGFR revealed a high degree of homology with viral oncogenes and allowed tentative identification of an external hormone binding domain, a transmembrane domain, and a cytoplasmic domain that includes tyrosine kinase activity. EGF binding induces rapid aggregation of EGFR, a process which was also observed on other receptor systems. These and other observations led to a hypothesis that microaggregation of EGFR is a necessary prerequisite for the biological response of EGF. A direct approach to study the processes of oligomerization of cell membrane proteins is to measure their mobility under various conditions. The lateral mobility of the EGFR was studied on mouse 3T3 fibroblasts and on A431 cells. However, an examination of the equations for the lateral and rotational diffusion in membranes shows that only rotational diffusion is strongly dependent on the size of the diffusing entity. A method of measuring protein rotational diffusion by time-resolved phosphorescence has proved to be very useful in the analysis of both in vivo and in vitro systems. The authors apply this method to study the mobility of EGFR on living A431 cells and membrane preparations.

  4. Time-Resolved Studies of Molecular Dynamics Using - and Femto-Second Laser Pulses

    NASA Astrophysics Data System (ADS)

    Deliwala, Shrenik Mahendra

    1995-01-01

    This thesis presents the results of two experiments that measure the evolution of laser excited molecules. The experiment performed with 0.1-ps laser pulses elucidates the dynamics of desorption of O_2 and formation of CO_2 on a platinum surface. The experiment performed with nanosecond time resolution reveals the inter- and intra-molecular vibrational dynamics of infrared laser pumped molecules. Desorption of O_2 and formation of CO_2 were induced with subpicosecond laser pulses on a Pt(111) surface dosed with coadsorbed O_2 and CO. Fluence dependent yields obtained over a range of laser wavelengths from 267 to 800 nm, and pulse durations from 80 fs to 3.6 ps are presented. We observe a dependence of the nonlinear desorption yield on wavelength. Two-pulse correlation measurements show two different time-scales relevant to the desorption. The results show that nonthermal electrons play a role in the surface chemistry, and that an equilibrated pre-heating of the surface modes leads to enhanced desorption. In the second set of experiments reported in this thesis, time-resolved coherent anti-Stokes Raman spectroscopy was used to obtain the rovibrational energy distributions in polyatomic molecules following infrared multiphoton excitation. In addition to presenting new results on SF _6, we review previously obtained data on SO_2 and OCS. The data yield new details about infrared multiphoton excitation and intramolecular vibrational energy relaxation. In particular they show the significance of collisions in redistributing vibrational energy following excitation. The results also clearly show stronger inter-mode coupling and higher excitation in systems with increasing numbers of atoms per molecule. In addition, a detailed description is provided of the Ti:Sapphire based ultrashort pulsed amplified laser system. Both, the principles and the design of the laser system are discussed to serve as a manual for the femtosecond laser system constructed for the study of

  5. New portable instrument for combined reflectance, time-resolved and steady-state luminescence measurements on works of art

    NASA Astrophysics Data System (ADS)

    Romani, Aldo; Grazia, Chiara; Anselmi, Chiara; Miliani, Costanza; Brunetti, Brunetto Giovanni

    2011-06-01

    In this paper a new compact and portable instrument for combined reflectance, time-resolved and steady-state fluorescence is presented. All the optical parts of the apparatus, carefully described in the text, were chosen after an extensive market survey in order to obtain the best performances coupled with the smallest dimensions. This instrument through the use of a dedicated multiple fiber optic probe, allows the complete photophysical behaviors of investigated materials to be collected from the same point of the analyzed surface. In this way, the resultant instrumental setup is a portable device, usable in situ for non destructive and non invasive diagnostic purposes in the field of cultural heritage. Preliminary results concerning organic dyes characterization, which is the main application of luminescence-based diagnostic techniques in artworks, are presented and compared with those previously obtained using separate devices. Concerning reflectance data, improvements in the deep detectable UV spectral range have been achieved switching from the integrating sphere of the old instrument to bifurcated optical fibers used as probe in the new one. Special attention was devoted to test the instrument capability in order to obtain the true emission spectrum, corrected for the selfabsorption effect, for which good results were found. This particular experimental procedure is strongly recommended, by a diagnostic point of view, to avoid distortions in the instrumental responses, namely the spectral shape and emission maximum wavelength of a fluorophore as function of the color saturation.

  6. In vivo and in situ synchrotron radiation-based μ-XRF reveals elemental distributions during the early attachment phase of barnacle larvae and juvenile barnacles.

    PubMed

    Senkbeil, Tobias; Mohamed, Tawheed; Simon, Rolf; Batchelor, David; Di Fino, Alessio; Aldred, Nick; Clare, Anthony S; Rosenhahn, Axel

    2016-02-01

    Barnacles are able to establish stable surface contacts and adhere underwater. While the composition of adult barnacle cement has been intensively studied, far less is known about the composition of the cement of the settlement-stage cypris larva. The main challenge in studying the adhesives used by these larvae is the small quantity of material available for analysis, being on the order of nanograms. In this work, we applied, for the first time, synchrotron radiation-based μ-X-ray fluorescence analysis (SR-μ-XRF) for in vivo and in situ analysis of young barnacles and barnacle cyprids. To obtain biologically relevant information relating to the body tissues, adhesives, and shell of the organisms, an in situ sample environment was developed to allow direct microprobe investigation of hydrated specimens without pretreatment of the samples. In 8-day-old juvenile barnacles (Balanus improvisus), the junctions between the six plates forming the shell wall showed elevated concentrations of calcium, potassium, bromine, strontium, and manganese. Confocal measurements allowed elemental characterization of the adhesive interface of recently attached cyprids (Balanus amphitrite), and substantiated the accumulation of bromine both at the point of initial attachment as well as within the cyprid carapace. In situ measurements of the cyprid cement established the presence of bromine, chlorine, iodine, sulfur, copper, iron, zinc, selenium, and nickel for both species. The previously unrecognized presence of bromine, iron, and selenium in the cyprid permanent adhesive will hopefully inspire further biochemical investigations of the function of these substances.

  7. X-ray induced chemical reaction revealed by in-situ X-ray diffraction and scanning X-ray microscopy in 15 nm resolution (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ge, Mingyuan; Liu, Wenjun; Bock, David; De Andrade, Vincent; Yan, Hanfei; Huang, Xiaojing; Marschilok, Amy; Takeuchi, Esther; Xin, Huolin; Chu, Yong S.

    2016-09-01

    The detection sensitivity of synchrotron-based X-ray techniques has been largely improved due to the ever increasing source brightness, which have significantly advanced ex-situ and in-situ research for energy materials, such as lithium-ion batteries. However, the strong beam-matter interaction arisen from the high beam flux can significantly modify the material structure. The parasitic beam-induced effect inevitably interferes with the intrinsic material property, which brings difficulties in interpreting experimental results, and therefore requires comprehensive evaluation. Here we present a quantitative in-situ study of the beam-effect on one electrode material Ag2VO2PO4 using four different X-ray probes with different radiation dose rate. The material system we reported exhibits interesting and reversible radiation-induced thermal and chemical reactions, which was further evaluated under electron microscopy to illustrate the underlying mechanism. The work we presented here will provide a guideline in using synchrotron X-rays to distinguish the materials' intrinsic behavior from extrinsic structure changed induced by X-rays, especially in the case of in-situ and operando study where the materials are under external field of either temperature or electric field.

  8. Time-resolved luminescence from Jahn-Teller split states of self-trapped excitons in PbWO4

    NASA Astrophysics Data System (ADS)

    Itoh, Minoru; Sakurai, Takaaki

    2006-06-01

    This paper reports the observation of time-resolved luminescence from a self-trapped exciton (STE) localized at tetrahedral (WO4)2- complex anion in PbWO4 . The results clearly reveal that the STE luminescence is composed of three emission bands peaking at 407, 425, and 450nm . Such a composite nature is explained well by assuming that the lowest triplet states of the STE split into three sublevels owing to the symmetry lowering from Td to C3v due to the Jahn-Teller effect. This assumption is in accordance with the theoretical prediction of Bacci [M. Bacci, S. Porcinai, E. Mihóková, M. Nikl, and K. Polák, Phys. Rev. B 64, 104302 (2001); M. Bacci, E. Mihóková, and L. S. Schulman, ibid. 66, 132301 (2002)]. The decay curve of each component and its temperature dependence are investigated in the range of 77to300K . These results are discussed on the basis of an adiabatic potential energy diagram of the triplet STE state. Time-resolved luminescence spectra are also measured for Mo-doped PbWO4 crystals. From a comparison with the spectra of undoped PbWO4 crystals, the Mo-related luminescence is clearly separated from the intrinsic luminescence due to STEs.

  9. Comparison of time-resolved and continuous-wave near-infrared techniques for measuring cerebral blood flow in piglets

    NASA Astrophysics Data System (ADS)

    Diop, Mamadou; Tichauer, Kenneth M.; Elliott, Jonathan T.; Migueis, Mark; Lee, Ting-Yim; Lawrence, Keith St.

    2010-09-01

    A primary focus of neurointensive care is monitoring the injured brain to detect harmful events that can impair cerebral blood flow (CBF), resulting in further injury. Since current noninvasive methods used in the clinic can only assess blood flow indirectly, the goal of this research is to develop an optical technique for measuring absolute CBF. A time-resolved near-infrared (TR-NIR) apparatus is built and CBF is determined by a bolus-tracking method using indocyanine green as an intravascular flow tracer. As a first step in the validation of this technique, CBF is measured in newborn piglets to avoid signal contamination from extracerebral tissue. Measurements are acquired under three conditions: normocapnia, hypercapnia, and following carotid occlusion. For comparison, CBF is concurrently measured by a previously developed continuous-wave NIR method. A strong correlation between CBF measurements from the two techniques is revealed with a slope of 0.79+/-0.06, an intercept of -2.2+/-2.5 ml/100 g/min, and an R2 of 0.810+/-0.088. Results demonstrate that TR-NIR can measure CBF with reasonable accuracy and is sensitive to flow changes. The discrepancy between the two methods at higher CBF could be caused by differences in depth sensitivities between continuous-wave and time-resolved measurements.

  10. Time Resolved Shadowgraph Images of Silicon during Laser Ablation:Shockwaves and Particle Generation

    SciTech Connect

    Liu, C.Y.; Mao, X.L.; Greif, R.; Russo, R.E.

    2006-05-06

    Time resolved shadowgraph images were recorded of shockwaves and particle ejection from silicon during laser ablation. Particle ejection and expansion were correlated to an internal shockwave resonating between the shockwave front and the target surface. The number of particles ablated increased with laser energy and was related to the crater volume.

  11. Expected resolution and detectability of adenocarcinoma tumors within human breast in time-resolved images

    NASA Astrophysics Data System (ADS)

    Gandjbakhche, Amir H.; Nossal, Ralph J.; Dadmarz, Roya; Schwartzentruber, Douglas; Bonner, Robert F.

    1995-04-01

    The prospects for time-resolved optical mammography rests on the ability to detect adenocarcinoma within the breast with sufficient resolution and specificity to compete with X-ray mammography. We characterized the optical properties of an unusually large (6 cm diameter) fresh adenocarcinoma and normal breast tissue (determined by histology to be predominantly adipose tissue) obtained from a patient undergoing mastectomy. Large specimens (5 mm thick and 3 cm wide) allowed the determination of absorption and scattering coefficients and their spatial heterogeneity as probed with a 1 mm diameter laser beam at 633 nm and 800 nm utilizing total reflectance and transmittance measure with integrating spheres. The difference between scattering coefficients of the malignant tumor and those of normal (principally adipose) breast tissue at 633 nm was much greater than the heterogeneity within each sample. This scattering difference is the principal source of contrast, particularly in time-resolved images. However, the high scattering coefficient of normal breast tissue at 633 nm limits the practicality of time-resolved mammography of a human breast compressed to 5 cm. Although the scattering coefficient of the normal breast tissue decreases at 800 nm, the differences between the optical properties of normal and abnormal breast tissue also are reduced. We used these empirical results in theoretical expressions obtained from random walk theory to quantify the expected resolution, contrast, and the detected intensity of 3, 6, and 9 mm tumors within otherwise homogeneous human breasts as a function of the gating-time of time-resolved optical mammography.

  12. Latent fingerprint and trace explosives detection by photoluminescence and time-resolved imaging

    NASA Astrophysics Data System (ADS)

    Bouldin, Kimberly Kay

    Latent fingerprint detection by photoluminescence is a well-developed field. Many development techniques exist and are currently being employed in forensic laboratories to detect fingerprints by making them luminescent. However, in forensic science, time-resolved imaging techniques, designed to suppress background fluorescence that interferes with fingerprint detectability, are to date not used outside of the research laboratory, and the chemistry necessary to use time-resolved imaging for fingerprint detection is somewhat limited. For this reason, the first section of this dissertation deals with fingerprint detection methods that have direct application to time-resolved imaging techniques. Trace explosive detection field methods based on chemical reactions have until recently utilized only colorimetric products. To increase the sensitivity of such detection, a field explosive test kit which produces a product that is both colorimetric and luminescent is studied. Detection sensitivity can be gained by taking advantage of the luminescence of these products, something that has not been done to date. When the appropriate chemistry is chosen for explosive detection, time-resolved imaging techniques may again be applicable. This dissertation thus looks at possibilities of taking trace explosives detection to this next level.

  13. Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

    NASA Astrophysics Data System (ADS)

    Hedqvist, Anders; Rachlew-Källne, Elisabeth

    1998-09-01

    Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.

  14. Time-resolved fluorescence spectroscopy of oil spill detected by ocean lidar

    NASA Astrophysics Data System (ADS)

    Li, Xiao-long; Chen, Yong-hua; Li, Jie; Jiang, Jingbo; Ni, Zuotao; Liu, Zhi-shen

    2016-10-01

    Based on time-resolved fluorescence of oils, an oceanographic fluorescence Lidar was designed to identify oil pollutions. A third harmonic (at 355nm) of Nd:YAG laser is used as the excitation source, and the fluorescence intensities and lifetimes of oil fluorescence at wavelength from 380 nm to 580 nm are measured by an intensified CCD (ICCD). In the experiments, time-resolved fluorescence spectra of 20 oil samples, including crude oils, fuel oils, lubricating oil, diesel oils and gasoline, are analyzed to discuss fluorescence spectral characteristics of samples for oil classification. The spectral characteristics of oil fluorescence obtained by ICCD with delay time of 2 ns, 4 ns, and 6 ns were studied by using the principal component analysis (PCA) method. Moreover, an efficient method is used to improve the recognition rate of the oil spill types, through enlarging spectral differences of oil fluorescence at different delay times. Experimental analysis shows that the optimization method can discriminate between crude oil and fuel oil, and a more accurate classification of oils is obtained by time-resolved fluorescence spectroscopy. As the result, comparing to traditional fluorescence spectroscopy, a higher recognition rate of oil spill types is achieved by time-resolved fluorescence spectroscopy which is also a feasibility technology for Ocean Lidar.

  15. Ultrafast Time Resolved X-ray Diffraction Studies of Laser Heated Metals and Semiconductors

    NASA Astrophysics Data System (ADS)

    Chen, Peilin; Tomov, I. V.; Rentzepis, P. M.

    1998-03-01

    Time resolved hard x-ray diffraction has been employed to study the dynamics of lattice structure deformation. When laser pulse energy is deposited in a material it generates a non uniform transient temperature distribution, which alters the lattice structure of the crystal. The deformed crystal lattice will change the angle of diffraction for a monochromatic x-ray beam. We report picosecond and nanosecond time resolved x-ray diffraction measurements of the lattice temperature distribution, transient structure and stress, in Pt (111) and GaAs (111) crystals, caused by pulsed UV laser irradiation. An ArF excimer laser operated at 300 Hz was used, both, to drive an x-ray diode with copper anode and heat the crystal. Bragg diffracted x-ray radiation was recorded by a direct imaging x-ray CCD. Changes in the diffraction patterns induced by a few millijouls pulse energy were observed at different time delays between the laser heating pulse and the x-ray probing pulse. A kinematical model for time resolved x-ray diffraction was used to analyze the experimental data. Good agreement between the measured and calculated scattered x-ray intensities profiles was achieved, indicating that detailed time resolved x-ray diffraction measurements can be made with nanosecond and picosecond resolution for small temperature changes. Our system can detect changes in the lattice spacing of about 10-3 A.

  16. Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain

    NASA Astrophysics Data System (ADS)

    De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.

    1991-06-01

    PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.

  17. Two-dimensional time resolved measurements of toroidal velocity correlated with density blobs in magnetized plasmas

    SciTech Connect

    Labit, B.; Furno, I.; Fasoli, A.; Podesta, M.

    2008-08-15

    A new method for toroidal velocity measurements with Mach probes is presented. This technique is based on the conditional sampling technique, the triggering events being density blobs. A reconstruction of the time resolved two-dimensional profile of electron density, electron temperature, plasma potential, and toroidal velocity is possible with a single point measurement on a shot-to-shot basis.

  18. Experimental results on time-resolved reflectance diffuse optical tomography with fast-gated SPADs

    NASA Astrophysics Data System (ADS)

    Puszka, Agathe; Di Sieno, Laura; Dalla Mora, Alberto; Pifferi, Antonio; Contini, Davide; Boso, Gianluca; Tosi, Alberto; Planat-Chrétien, Anne; Hervé, Lionel; Koenig, Anne; Dinten, Jean-Marc

    2013-06-01

    We present experimental results of time-resolved reflectance diffuse optical tomography performed with fast-gated single-photon avalanche diodes (SPADs) and show an increased imaged depth range for a given acquisition time compared to the non gated mode.

  19. Exploratory study on a statistical method to analyse time resolved data obtained during nanomaterial exposure measurements

    NASA Astrophysics Data System (ADS)

    Clerc, F.; Njiki-Menga, G.-H.; Witschger, O.

    2013-04-01

    Most of the measurement strategies that are suggested at the international level to assess workplace exposure to nanomaterials rely on devices measuring, in real time, airborne particles concentrations (according different metrics). Since none of the instruments to measure aerosols can distinguish a particle of interest to the background aerosol, the statistical analysis of time resolved data requires special attention. So far, very few approaches have been used for statistical analysis in the literature. This ranges from simple qualitative analysis of graphs to the implementation of more complex statistical models. To date, there is still no consensus on a particular approach and the current period is always looking for an appropriate and robust method. In this context, this exploratory study investigates a statistical method to analyse time resolved data based on a Bayesian probabilistic approach. To investigate and illustrate the use of the this statistical method, particle number concentration data from a workplace study that investigated the potential for exposure via inhalation from cleanout operations by sandpapering of a reactor producing nanocomposite thin films have been used. In this workplace study, the background issue has been addressed through the near-field and far-field approaches and several size integrated and time resolved devices have been used. The analysis of the results presented here focuses only on data obtained with two handheld condensation particle counters. While one was measuring at the source of the released particles, the other one was measuring in parallel far-field. The Bayesian probabilistic approach allows a probabilistic modelling of data series, and the observed task is modelled in the form of probability distributions. The probability distributions issuing from time resolved data obtained at the source can be compared with the probability distributions issuing from the time resolved data obtained far-field, leading in a

  20. In-situ incubation of iron-sulfur mineral reveals a diverse chemolithoautotrophic community and a new biogeochemical role for Thiomicrospira.

    PubMed

    Barco, Roman A; Hoffman, Colleen L; Ramírez, Gustavo A; Toner, Brandy M; Edwards, Katrina J; Sylvan, Jason B

    2017-03-01

    Sulfide mineral precipitation occurs at mid-ocean ridge (MOR) spreading centers, both in the form of plume particles and seafloor massive sulfide structures. A common constituent of MOR is the iron-bearing sulfide mineral pyrrhotite, which was chosen as a substrate for in-situ incubation studies in shallow waters of Catalina Island, CA to investigate the colonization of iron-oxidizing bacteria. Microbial community datasets were obtained from in-situ incubated pyrrhotite, allowing for direct comparison to microbial communities of iron-sulfides from active and inactive chimneys in deep-sea environments. Unclassified Gammaproteobacteria and Alphaproteobacteria (Magnetovibrio) largely dominated the bacterial community on pyrrhotite samples incubated in the water column while samples incubated at the surface sediment showed more even dominance by Deltaproteobacteria (Desulfobulbus), Gammaproteobacteria (Piscirickettsiaceae), Alphaproteobacteria (Rhodobacteraceae), and Bacteroidetes (Flavobacteriia). Cultivations that originated from pyrrhotite samples resulted in the enrichment of both, sheath-forming and stalk-forming Zetaproteobacteria. Additionally, a putative novel species of Thiomicrospira was isolated and shown to grow autotrophically with iron, indicating a new biogeochemical role for this ubiquitous microorganism.

  1. Time-resolved magnetization dynamics in crystalline ferromagnets and exchange-biased systems

    NASA Astrophysics Data System (ADS)

    Engebretson, David Michael

    Time-resolved ferromagnetic resonance (FMR) measurements are performed using a pump-probe technique with a non-optical pump to observe precession and relaxation of the magnetization in epitaxial magnetic thin films at temperatures down to 5 K. Spatial localization achieved through use of an optical probe allows a direct measurement of spin relaxation, reducing the effects of inhomogeneous dephasing relative to probes of larger areas, while the use of low fields allows a study of dynamics throughout the entire magnetization reversal process. The reversal mechanism of FexCo1-x is probed as a function of cubic and uniaxial anisotropy strengths, using FMR as a direct probe of the free energy surface. A coherent rotation model describes the reversal for fields up through 700 Oe, failing only for fields near 105 Oe applied along the GaAs [01 1¯] direction where nucleation of nearly perpendicular domains is observed. Measurements of the Gilbert damping parameter alpha indicate that it is smaller for fields applied along the [01 1¯] direction than for fields along [011] or [010]. Dynamic interactions between local moments and itinerant carriers are examined in the diluted magnetic semiconductor Ga1-xMn xAs. Holes and local moments are found to precess together on timescales greater than 50 ps. Although previous experiments by other groups have observed a change in the magnetization due to introduction of photoexcited carriers, our measurements indicate no dynamical change in magnetization due to additional optically pumped carriers. The Gilbert damping parameter alpha is observed to increase more than twofold as temperature is raised from 20 K to the Curie temperature, although the decay time remains nearly independent of temperature over this range. Exchange-biased Fe/FeF2 is found to exhibit temperature-dependent anisotropy above its Neel temperature (78 K), while the anisotropy of structurally similar Fe/MnF2 remains independent of temperature above TN = 67 K. Dynamic

  2. Time resolved single molecule spectroscopy of semiconductor quantum dot/conjugated organic hybrid nanostructures

    NASA Astrophysics Data System (ADS)

    Odoi, Michael Yemoh

    Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport between the OPV ligands and the CdSe quantum dot core. This electronic interaction greatly modify, the photoluminescence properties of both bulk and single CdSe-OPV nanostructure thin film samples. Size-correlated wide-field fluorescence imaging show that blinking suppression in single CdSe-OPV is linked to the degree of OPV coverage (inferred from AFM height scans) on the quantum dot surface. The effect of the complex electronic environment presented by photoexcited OPV ligands on the excited state property of CdSe-OPV is measured with single photon counting and photon-pair correlation spectroscopy techniques. Time-tagged-time-resolved (TTTR) single photon counting measurements from individual CdSe-OPV nanostructures, show excited state lifetimes an order of magnitude shorter relative to conventional ZnS/CdSe quantum dots. Second-order intensity correlation measurements g(2)(tau) from individual CdSe-OPV nanostructures point to a weak multi-excitonic character with a strong wavelength dependent modulation depth. By tuning in and out of the absorption of the OPV ligands we observe changes in modulation depth from g(2) (0) ≈ 0.2 to 0.05 under 405 and 514 nm excitation respectively. Defocused images and polarization anisotropy measurements also reveal a well-defined linear dipole emission pattern in single CdSe-OPV nanostructures. These results provide new insights into to the mechanism behind the electronic interactions in composite quantum dot/conjugated organic composite systems at the single molecule level. The observed intensity flickering , blinking suppression and associated lifetime/count rate and antibunching behaviour is well explained by a Stark interaction model. Charge transfer from photo-excitation of the OPV ligands to the surface of the Cd

  3. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    NASA Astrophysics Data System (ADS)

    Al-Rubaiey, Najem A.; Walsh, Robin

    2017-03-01

    Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann

  4. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector.

    PubMed

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J; Yliperttula, Marjo

    2016-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is possible to overcome the strong fluorescence background that usually interferes with the much weaker Raman spectra. Second, using the high photon energy excitation light source, we are able to generate a stronger Raman signal compared to traditional instruments. In addition, observations in the time domain can be performed, thus enabling new capabilities in the field of Raman and fluorescence spectroscopy. With this system, we demonstrate for the first time the possibility of recording fluorescence-suppressed Raman spectra of solid, amorphous and crystalline, and non-photoluminescent and photoluminescent drugs such as caffeine, ranitidine hydrochloride, and indomethacin (amorphous and crystalline forms). The raw data acquired by utilizing only the picosecond pulsed laser and a CMOS SPAD detector could be used for identifying the compounds directly without any data processing. Moreover, to validate the accuracy of this time-resolved technique, we present density functional theory (DFT) calculations for a widely used gastric acid inhibitor, ranitidine hydrochloride. The obtained time-resolved Raman peaks were identified based on the calculations and existing literature. Raman spectra using non-time-resolved setups with continuous-wave 785- and 532-nm excitation lasers were used as reference data. Overall, this demonstration of time-resolved Raman and fluorescence measurements with a CMOS SPAD detector shows promise in diverse areas, including fundamental chemical research, the

  5. Wide-field time-resolved luminescence imaging and spectroscopy to decipher obliterated documents in forensic science

    NASA Astrophysics Data System (ADS)

    Suzuki, Mototsugu; Akiba, Norimitsu; Kurosawa, Kenji; Kuroki, Kenro; Akao, Yoshinori; Higashikawa, Yoshiyasu

    2016-01-01

    We applied a wide-field time-resolved luminescence (TRL) method with a pulsed laser and a gated intensified charge coupled device (ICCD) for deciphering obliterated documents for use in forensic science. The TRL method can nondestructively measure the dynamics of luminescence, including fluorescence and phosphorescence lifetimes, which prove to be useful parameters for image detection. First, we measured the TRL spectra of four brands of black porous-tip pen inks on paper to estimate their luminescence lifetimes. Next, we acquired the TRL images of 12 obliterated documents at various delay times and gate times of the ICCD. The obliterated contents were revealed in the TRL images because of the difference in the luminescence lifetimes of the inks. This method requires no pretreatment, is nondestructive, and has the advantage of wide-field imaging, which makes it is easy to control the gate timing. This demonstration proves that TRL imaging and spectroscopy are powerful tools for forensic document examination.

  6. Relaxation Dynamics in Photoexcited Chiral Molecules Studied by Time-Resolved Photoelectron Circular Dichroism: Toward Chiral Femtochemistry

    PubMed Central

    2016-01-01

    Unravelling the main initial dynamics responsible for chiral recognition is a key step in the understanding of many biological processes. However, this challenging task requires a sensitive enantiospecific probe to investigate molecular dynamics on their natural femtosecond time scale. Here we show that, in the gas phase, the ultrafast relaxation dynamics of photoexcited chiral molecules can be tracked by recording time-resolved photoelectron circular dichroism (TR-PECD) resulting from the photoionization by a circularly polarized probe pulse. A large forward–backward asymmetry along the probe propagation axis is observed in the photoelectron angular distribution. Its evolution with pump–probe delay reveals ultrafast dynamics that are inaccessible in the angle-integrated photoelectron spectrum or via the usual electron emission anisotropy parameter (β). PECD, which originates from the electron scattering in the chiral molecular potential, appears as a new sensitive observable for ultrafast molecular dynamics in chiral systems. PMID:27786493

  7. Time-resolved 3D contrast-enhanced MRA of an extended FOV using continuous table motion.

    PubMed

    Madhuranthakam, Ananth J; Kruger, David G; Riederer, Stephen J; Glockner, James F; Hu, Houchun H

    2004-03-01

    A method is presented for acquiring 3D time-resolved MR images of an extended (>100 cm) longitudinal field of view (FOV), as used for peripheral MR angiographic runoff studies. Previous techniques for long-FOV peripheral MRA have generally provided a single image (i.e., with no time resolution). The technique presented here generates a time series of 3D images of the FOV that lies within the homogeneous volume of the magnet. This is achieved by differential sampling of 3D k-space during continuous motion of the patient table. Each point in the object is interrogated in five consecutive 3D image sets generated at 2.5-s intervals. The method was tested experimentally in eight human subjects, and the leading edge of the bolus was observed in real time and maintained within the imaging FOV. The data revealed differential bolus velocities along the vasculature of the legs.

  8. Early nucleation events in the polymerization of actin, probed by time-resolved small-angle x-ray scattering

    PubMed Central

    Oda, Toshiro; Aihara, Tomoki; Wakabayashi, Katsuzo

    2016-01-01

    Nucleators generating new F-actin filaments play important roles in cell activities. Detailed information concerning the events involved in nucleation of actin alone in vitro is fundamental to understanding these processes, but such information has been hard to come by. We addressed the early process of salt-induced polymerization of actin using the time-resolved synchrotron small-angle X-ray scattering (SAXS). Actin molecules in low salt solution maintain a monomeric state by an electrostatic repulsive force between molecules. On mixing with salts, the repulsive force was rapidly screened, causing an immediate formation of many of non-polymerizable dimers. SAXS kinetic analysis revealed that tetramerization gives the highest energetic barrier to further polymerization, and the major nucleation is the formation of helical tetramers. Filaments start to grow rapidly with the formation of pentamers. These findings suggest an acceleration mechanism of actin assembly by a variety of nucleators in cells. PMID:27775032

  9. Gauge invariance in the theoretical description of time-resolved angle-resolved pump/probe photoemission spectroscopy

    SciTech Connect

    Freericks, J. K.; Krishnamurthy, H. R.; Sentef, M. A.; Devereaux, T. P.

    2015-10-01

    Nonequilibrium calculations in the presence of an electric field are usually performed in a gauge, and need to be transformed to reveal the gauge-invariant observables. In this work, we discuss the issue of gauge invariance in the context of time-resolved angle-resolved pump/probe photoemission. If the probe is applied while the pump is still on, one must ensure that the calculations of the observed photocurrent are gauge invariant. We also discuss the requirement of the photoemission signal to be positive and the relationship of this constraint to gauge invariance. We end by discussing some technical details related to the perturbative derivation of the photoemission spectra, which involve processes where the pump pulse photoexcites electrons due to nonequilibrium effects.

  10. A fluorescence LIDAR sensor for hyper-spectral time-resolved remote sensing and mapping.

    PubMed

    Palombi, Lorenzo; Alderighi, Daniele; Cecchi, Giovanna; Raimondi, Valentina; Toci, Guido; Lognoli, David

    2013-06-17

    In this work we present a LIDAR sensor devised for the acquisition of time resolved laser induced fluorescence spectra. The gating time for the acquisition of the fluorescence spectra can be sequentially delayed in order to achieve fluorescence data that are resolved both in the spectral and temporal domains. The sensor can provide sub-nanometric spectral resolution and nanosecond time resolution. The sensor has also imaging capabilities by means of a computer-controlled motorized steering mirror featuring a biaxial angular scanning with 200 μradiant angular resolution. The measurement can be repeated for each point of a geometric grid in order to collect a hyper-spectral time-resolved map of an extended target.

  11. A direct electron detector for time-resolved MeV electron microscopy

    NASA Astrophysics Data System (ADS)

    Vecchione, T.; Denes, P.; Jobe, R. K.; Johnson, I. J.; Joseph, J. M.; Li, R. K.; Perazzo, A.; Shen, X.; Wang, X. J.; Weathersby, S. P.; Yang, J.; Zhang, D.

    2017-03-01

    The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μ m spatial resolution and less than 20 analogue-to-digital converter count RMS pixel noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.

  12. Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

    PubMed

    Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

    2015-02-01

    We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of <100 nm. In order to demonstrate the spatiotemporal magnetic imaging capability of this microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

  13. Detecting functional interactions in a gene and signaling network by time-resolved somatic complementation analysis.

    PubMed

    Marwan, Wolfgang

    2003-10-01

    Somatic complementation by fusion of two mutant cells and mixing of their cytoplasms occurs when the genetic defect of one fusion partner is cured by the functional gene product provided by the other. We have found that complementation of mutational defects in the network mediating stimulus-induced commitment and sporulation of Physarum polycephalum may reflect time-dependent changes in the signaling state of its molecular building blocks. Network perturbation by fusion of mutant plasmodial cells in different states of activation, and the time-resolved analysis of somatic complementation effects can be used to systematically probe network structure and dynamics. Time-resolved somatic complementation quantitatively detects regulatory interactions between the functional modules of a network, independent of their biochemical composition or subcellular localization, and without being limited to direct physical interactions.

  14. Developments in time-resolved high pressure x-ray diffraction using rapid compression and decompression

    SciTech Connect

    Smith, Jesse S.; Sinogeikin, Stanislav V.; Lin, Chuanlong; Rod, Eric; Bai, Ligang; Shen, Guoyin

    2015-07-15

    Complementary advances in high pressure research apparatus and techniques make it possible to carry out time-resolved high pressure research using what would customarily be considered static high pressure apparatus. This work specifically explores time-resolved high pressure x-ray diffraction with rapid compression and/or decompression of a sample in a diamond anvil cell. Key aspects of the synchrotron beamline and ancillary equipment are presented, including source considerations, rapid (de)compression apparatus, high frequency imaging detectors, and software suitable for processing large volumes of data. A number of examples are presented, including fast equation of state measurements, compression rate dependent synthesis of metastable states in silicon and germanium, and ultrahigh compression rates using a piezoelectric driven diamond anvil cell.

  15. Noninvasive assessment of breast cancer risk using time-resolved diffuse optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Spinelli, Lorenzo; Torricelli, Alessandro; Abbate, Francesca; Villa, Anna; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

    2010-11-01

    Breast density is a recognized strong and independent risk factor for breast cancer. We propose the use of time-resolved transmittance spectroscopy to estimate breast tissue density and potentially provide even more direct information on breast cancer risk. Time-resolved optical mammography at seven wavelengths (635 to 1060 nm) is performed on 49 subjects. Average information on breast tissue of each subject is obtained on oxy- and deoxyhemoglobin, water, lipids, and collagen content, as well as scattering amplitude and power. All parameters, except for blood volume and oxygenation, correlate with mammographic breast density, even if not to the same extent. A synthetic optical index proves to be quite effective in separating different breast density categories. Finally, the estimate of collagen content as a more direct means for the assessment of breast cancer risk is discussed.

  16. Time-resolved wave profile measurements in copper to Megabar pressures

    SciTech Connect

    Chhabildas, L C; Asay, J R

    1981-01-01

    Many time-resolved techniques have been developed which have greatly aided in the understanding of dynamic material behavior such as the high pressure-dynamic strength of materials. In the paper, time-resolved measurements of copper (at shock-induced high pressures and temperatures) are used to illustrate the capability of using such techniques to investigate high pressure strength. Continuous shock loading and release wave profiles have been made in copper to 93 GPa using velocity interferometric techniques. Fine structure in the release wave profiles from the shocked state indicates an increase in shear strength of copper to 1.5 GPa at 93 GPa from its ambient value of 0.08 GPa.

  17. Phosphorescent nanoparticles and their applications for time-resolved luminescent biological assays

    NASA Astrophysics Data System (ADS)

    Song, Xuedong; Huang, Lei; Knotts, Mike; Wu, Bin

    2009-02-01

    A new class of phosphorescent nanoparticles has been developed that use halogen-containing polymers and copolymers to encapsulate phosphorescent molecules. Their strong phosphorescence of long lifetime and large Stoke shift are not subject to oxygen quenching under ambient conditions due to the low oxygen permeability of the encapsulation matrix. The cross-linked phosphorescent particles are very stable and easily re-suspendable in aqueous media with surface functional groups to allow covalent tagging of biological recognition molecules such as antibodies. The conjugates can be used to provide very sensitive detection of analytes through time-resolved phosphorescence measurements. In addition to their applications for solution-based biological assays, those particles have also been demonstrated to be very useful for dry-chemistry-based time-resolved luminescent lateral flow assays.

  18. Recent applications of multiwire proportional chambers for time resolved studies on muscle

    NASA Astrophysics Data System (ADS)

    Faruqi, A. R.; Huxley, H. E.; Kress, M.

    1986-12-01

    The use of multiwire proportional chambers has played an important role in recording time resolved data from vertebrate muscle under various physiological conditions from which we have selected two examples from recent work. The first example describes the measurement of the equatorial pattern along with measurements of the muscle sarcomere length showing that the delay in tension development relative to changes in the X-ray intensity are not due to "internal" shortening in the muscle. The second example describes time-resolved measurements on the thin filament activation process, studied with both a linear and an area detector. The results show clearly that changes in thin filament structure precede cross-bridge formation producing further strong evidence for the "steric blocking model" for muscle contraction.

  19. Isotope identification capabilities using time resolved prompt gamma emission from epithermal neutrons

    NASA Astrophysics Data System (ADS)

    Festa, G.; Arcidiacono, L.; Pappalardo, A.; Minniti, T.; Cazzaniga, C.; Scherillo, A.; Andreani, C.; Senesi, R.

    2016-03-01

    We present a concept of integrated measurements for isotope identification which takes advantage of the time structure of spallation neutron sources for time resolved γ spectroscopy. Time resolved Prompt Gamma Activation Analysis (T-PGAA) consists in the measurement of gamma energy spectrum induced by the radioactive capture as a function of incident neutron Time Of Flight (TOF), directly related with the energy of incident neutrons. The potential of the proposed concept was explored on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (U.K.). Through this new technique we show an increase in the sensitivity to specific elements of archaeometric relevance, through incident neutron energy selection in prompt γ spectra for multicomponent samples. Results on a standard bronze sample are presented.

  20. Towards Measurement of the Time-resolved Heat Release of Protein Conformation Dynamics

    NASA Technical Reports Server (NTRS)

    Puchalla, Jason; Adamek, Daniel; Austin, Robert

    2004-01-01

    We present a way to observe time-resolved heat release using a laminar flow diffusional mixer coupled with a highly sensitive infrared camera which measures the temperature change of the solvent. There are significant benefits to the use of laminar flow mixers for time-resolved calorimetry: (1) The thermal signal can be made position and time- stationary to allow for signal integration; (2) Extremely small volumes (nl/s) of sample are required for a measurement; (3) The same mixing environment can be observed spectroscopically to obtain state occupation information; (4) The mixer allows one to do out of equilibrium dynamic studies. The hope is that these measurements will allow us probe the non-equilibrium thermodynamics as a protein moves along a free energy trajectory from one state to another.

  1. Time-resolved and polarised microspectroscopy of thin films of bio- and nanomaterials

    NASA Astrophysics Data System (ADS)

    Soleimaninejad, Hamid; Hong, Yuning; Smith, Trevor A.

    2016-09-01

    We report on the use of time-resolved and polarised evanescent wave-induced fluorescence anisotropy measurements to probe molecular photophysics, motion and energy migration of fluorescent species in close proximity to a silica/film interface. In particular we show that the fluorescence decay and anisotropy of common fluorophores varies as a function of the plane of the fluorophore with respect to the interface, the distance from the interface, and as a function of position (using polarised EW imaging). We have applied time-resolved and polarised EW-induced fluorescence microspectroscopic measurements to dyes, thin polymer nanoparticle films and cells on silica surfaces, probing the variation in the photophysical dynamics within the films.

  2. Time-resolved photoluminescence studies of InGaN epilayers

    NASA Astrophysics Data System (ADS)

    Smith, M.; Chen, G. D.; Lin, J. Y.; Jiang, H. X.; Asif Khan, M.; Chen, Q.

    1996-11-01

    Time-resolved photoluminescence (PL) has been employed to study the optical transitions and their dynamic processes and to evaluate materials quality of InGaN epilayers grown by metalorganic chemical vapor deposition. Our results suggest that the PL emissions in InGaN epilayers result primarily from localized exciton recombination. The localization energies of these localized excitons have been obtained. In relatively lower quality epilayers, the localized exciton recombination lifetime τ, decreases monotonically with an increase of temperature. In high quality epilayers, τ increases with temperature at low temperatures, which is a well-known indication of radiative exciton recombination. Our results demonstrate that time-resolved PL measurements uniquely provide opportunities for the understanding of basic optical processes as well as for identifying high quality materials.

  3. Subtraction-based approach for enhancing the depth sensitivity of time-resolved NIRS

    PubMed Central

    Milej, Daniel; Abdalmalak, Androu; McLachlan, Peter; Diop, Mamadou; Liebert, Adam; St. Lawrence, Keith.

    2016-01-01

    The aim of this study was to evaluate enhancing of the depth sensitivity of time-resolved near-infrared spectroscopy with a subtraction-based approach. Due to the complexity of light propagation in a heterogeneous media, and to prove the validity of the proposed method in a heterogeneous turbid media we conducted a broad analysis taking into account a number of parameters related to the method as well as various parameters of this media. The results of these experiments confirm that the depth sensitivity of the subtraction-based approach is better than classical approaches using continuous-wave or time-resolved methods. Furthermore, the results showed that the subtraction-based approach has a unique, selective sensitivity to a layer at a specific depth. In vivo application of the proposed method resulted in a greater magnitude of the hemodynamic changes during functional activation than with the standard approach. PMID:27895992

  4. Alteration of time-resolved autofluorescence properties of rat aorta, induced by diabetes mellitus

    NASA Astrophysics Data System (ADS)

    Uherek, M.; Uličná, O.; Vančová, O.; Muchová, J.; Ďuračková, Z.; Šikurová, L.; Chorvát, D.

    2016-10-01

    Changes in autofluorescence properties of isolated rat aorta, induced by diabetes mellitus, were detected using time-resolved fluorescence spectroscopy with pulsed ultraviolet (UV) laser excitation. We demonstrated that time-resolved spectroscopy was able to detect changes in aorta tissues related to diabetes and unambiguously discriminate diabetic (τ 1 0.63  ±  0.05 ns, τ 2 3.66  ±  0.10 ns) samples from the control (τ 1 0.76  ±  0.03 ns, τ 2 4.48  ±  0.15 ns) group. We also report changes in the ratio of relative amplitudes of the two lifetime component in aorta tissue during diabetes, most likely related to the pseudohypoxic state with altered NADH homeostasis.

  5. Time-resolved diffuse optical tomography using fast-gated single-photon avalanche diodes

    PubMed Central

    Puszka, Agathe; Di Sieno, Laura; Mora, Alberto Dalla; Pifferi, Antonio; Contini, Davide; Boso, Gianluca; Tosi, Alberto; Hervé, Lionel; Planat-Chrétien, Anne; Koenig, Anne; Dinten, Jean-Marc

    2013-01-01

    We present the first experimental results of reflectance Diffuse Optical Tomography (DOT) performed with a fast-gated single-photon avalanche diode (SPAD) coupled to a time-correlated single-photon counting system. The Mellin-Laplace transform was employed to process time-resolved data. We compare the performances of the SPAD operated in the gated mode vs. the non-gated mode for the detection and localization of an absorbing inclusion deeply embedded in a turbid medium for 5 and 15 mm interfiber distances. We demonstrate that, for a given acquisition time, the gated mode enables the detection and better localization of deeper absorbing inclusions than the non-gated mode. These results obtained on phantoms demonstrate the efficacy of time-resolved DOT at small interfiber distances. By achieving depth sensitivity with limited acquisition times, the gated mode increases the relevance of reflectance DOT at small interfiber distance for clinical applications. PMID:24009998

  6. Time-resolved X-ray scattering program at the Advanced Photon Source

    SciTech Connect

    Rodricks, B.

    1994-08-01

    The Time-Resolved Scattering Program`s goal is the development of instruments and techniques for time-resolved studies. This entails the development of wide bandpass and focusing optics, high-speed detectors, mechanical choppers, and components for the measurement and creation of changes in samples. Techniques being developed are pump-probe experiments, single-bunch scattering experiments, high-speed white and pink beam Laue scattering, and nanosecond to microsecond synchronization of instruments. This program will be carried out primarily from a white-beam, bend-magnet source, experimental station, 1-BM-B, that immediately follows the first optics enclosure (1-BM-A). This paper will describe the experimental station and instruments under development to carry out the program.

  7. Biochemical Applications Of Frequency-Domain Fluorometry; Determination Of Time-Resolved Anisotropies And Emission Spectra

    NASA Astrophysics Data System (ADS)

    Lakowicz, Joseph R.; Gryczynski, Ignazy; Cherek, Henryh; Laczko, Gabor; Joshi, Nanda

    1987-01-01

    Measurements of time-resolved fluorescence are often used for studies of biological macromolecules. Such measurements are usually performed in the time-domain, by measurement of the time-dependent emission following pulsed excitation. It has recently become possible to measure the frequency-response of the emission to intensity modulated light, over a wide range of modulation frequencies. We used frequency-domain fluorometers which operates from 1 to 220 MHz, and more recently to 2000 MHz. The frequency-domain data provide excellent resolution of time-dependent spectral parameters. It is now possible to resolve closely spaced fluorescence lifetimes, to determine multi-exponential decays of anisotropy and to determine time-resolved emission spectra of samples which display time-dependent spectral shifts. In this article we show representative results on tryptophan fluorescence from proteins and for protein-bound fluorophores.

  8. Time-Resolved Emission Spectra Of Tryptophan And Proteins From Frequency-Domain Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Szmacineki, Henryk; Lakowicz, Joseph R.; Johnson, Michael L.

    1988-06-01

    We report measurements of time-resolved emission spectra of N-acetyl-L-tryptophanamide (NATA), adrenocorticotropic hormone (ACTH, residues 1-24), and of S. Nuclease. These spectra were calculated from the frequency-response of the emission, measured at several wavelengths across the emission spectra. Measurements were performed on samples not quenched and quenched by acrylamide, the latter providing additional information on the short time events. The time-resolved center-of-gravity does not decay as a single exponential. At least two spectral relaxation times are needed to account for the present data. NATA and ACTH each display relaxation times near 50 and 800 ps, which may be characteristic of exposed tryptophan residues. S. nuclease displayed slower relaxation times near 0.5 and 10 ns, which probably reflect the dynamic protein matrix which surrounds the residue.

  9. Theory and experiments on time-resolved reflectance from adult heads for functional tomographic imaging of brain activities

    NASA Astrophysics Data System (ADS)

    Tanifuji, T.; Suzuki, M.

    2014-02-01

    Finite difference time domain (FDTD) analysis has been formulated for predicting time-resolved reflectance from an adult head model with brain grooves containing a non-scattering layer. Mean delay (MD) dependences on source detector separation (d) and time-resolved reflectance calculated using the FDTD analysis were compared with in vivo experiments of human heads. It is shown that the theoretical and experimental MD dependences on d and the time-resolved reflectance are well predicted by FDTD analysis. These results have shown that tomographic imaging of brain activities is promising, which improves depth sensitivities by enhancing the contribution of late photons in time-resolved systems.

  10. Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films.

    PubMed

    Bel Haj Mohamed, N; Haouari, M; Zaaboub, Z; Nafoutti, M; Hassen, F; Maaref, H; Ben Ouada, H

    2014-01-01

    In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a time τ1 in the range 0.5-0.8 ns, whereas the other decays much more slowly, with a time τ2 in the range 1-3 ns. The weak activation energy (32-37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals.

  11. Dating chert using in-situ produced 10Be: Possible complications revealed on landslide scarps through a comparison with 36Cl applied to coexisting limestone.

    NASA Astrophysics Data System (ADS)

    Zerathe, Swann; Braucher, Régis; Lebourg, Thomas; Leani, Leatitia; Manetti, Michel; Bourles, Didier

    2013-04-01

    This abstract and presentation highlights potential complications that may arise while using in situ produced 10Be to date diagenetic silica (chert)exposure or burial event. The initiation and evolution of large gravitational collapses in sedimentary rocks were constrained using cosmic ray exposure dating. Because these collapses occurred in a stratigraphic level composed of chert (diagenetic silica) concretions interbedded in limestone layers, their development was studied by performing in situ-produced 36Cl and 10Be concentration measurements in both the limestone and coexisting diagenetic silica (chert), respectively. Following the routinely used decontamination and preparation protocols for 10Be produced in diagenetic silica, large discrepancies were observed with exposure ages determined by 36Cl within carbonate for samples originating from the same scarp. While 36Cl exposure ages were clustered as expected for a unique single gravitational event, 10Be exposure ages were scattered along the same studied scarps. To determine the origin of such a bias, petrological investigations were carried out for chert (diagenetic silica). Thin sections highlighted a complex mineralogical texture characterized by remnant silicified ooids showing calcitic cores, calcite inclusions and a dominant amorphous hydrated silica (grain > 20 μm). To decipher and characterize the potential origins of the excess measured 10Be within diagenetic silica, all samples were first reprocessed following the routine decontamination protocol (HCL-H2SiF6 leachings and three partial HF dissolutions) but starting from three different grain size fractions (GS1: 1000-500, GS2: 500-250 and GS3: 250-50 μm). The resulting concentrations clearly showed a decreasing 10Be content as a function of the grain size, but still yielded 10Be exposure ages significantly higher than 36Cl counterparts. Because potential adsorption of 10Be at the surface of amorphous silica grains was suspected, partial dissolution

  12. Time-resolved Langmuir Probing of a New Lanthanum Hexaboride (LaB6) Hollow Cathode

    DTIC Science & Technology

    2011-09-01

    like texture and is easily machineable with standard tooling. Competing thermally conductive but electrically insulating ceramics such as aluminum...The 32nd International Electric Propulsion Conference, Wiesbaden, Germany September 11 – 15, 2011 1 Time-resolved Langmuir Probing of a New...Lanthanum Hexaboride (LaB6) Hollow Cathode IEPC-2011-245 Presented at the 32nd International Electric Propulsion Conference, Wiesbaden

  13. Time resolved analysis of water drainage in porous asphalt concrete using neutron radiography.

    PubMed

    Poulikakos, L D; Sedighi Gilani, M; Derome, D; Jerjen, I; Vontobel, P

    2013-07-01

    Porous asphalt as a road surface layer controls aquaplaning as rain water can drain through its highly porous structure. The process of water drainage through this permeable layer is studied using neutron radiography. Time-resolved water configuration and distribution within the porous structure are reported. It is shown that radiography depicts the process of liquid water transport within the complex geometry of porous asphalt, capturing water films, filled dead end pores and water islands.

  14. Accelerating calculations of ultrafast time-resolved electronic spectra with efficient quantum dynamics methods.

    PubMed

    Wehrle, Marius; Sulc, Miroslav; Vanícek, Jirí

    2011-01-01

    We explore three specific approaches for speeding up the calculation of quantum time correlation functions needed for time-resolved electronic spectra. The first relies on finding a minimum set of sufficiently accurate electronic surfaces. The second increases the time step required for convergence of exact quantum simulations by using different split-step algorithms to solve the time-dependent Schrödinger equation. The third approach lowers the number of trajectories needed for convergence of approximate semiclassical dynamics methods.

  15. Time-resolved circular dichroism in carbonmonoxy-myoglobin: the central role of the proximal histidine.

    PubMed

    Dartigalongue, Thibault; Hache, François

    2006-05-05

    A calculation of the circular dichroism (CD) spectra of carbonmonoxy- and deoxy-myoglobin is carried out in relation to a time-resolved CD experiment. This calculation allows us to assign a dominant role to the proximal histidine in the definition of the electronic normal modes and to interpret the transient CD structure observed in a strain of the proximal histidine. This strain builds up in 10 ps and relaxes in 50 ps as the protein evolves towards its deoxy form.

  16. A quantitative ratiometric sensor for time-resolved analysis of auxin dynamics

    PubMed Central

    Wend, Sabrina; Bosco, Cristina Dal; Kämpf, Michael M.; Ren, Fugang; Palme, Klaus; Weber, Wilfried; Dovzhenko, Alexander; Zurbriggen, Matias D.

    2013-01-01

    Time-resolved quantitative analysis of auxin-mediated processes in plant cells is as of yet limited. By applying a synergistic mammalian and plant synthetic biology approach, we have developed a novel ratiometric luminescent biosensor with wide applicability in the study of auxin metabolism, transport, and signalling. The sensitivity and kinetic properties of our genetically encoded biosensor open new perspectives for the analysis of highly complex auxin dynamics in plant growth and development. PMID:23787479

  17. Time-resolved phase measurement of a self-amplified free-electron laser.

    PubMed

    Li, Yuelin; Lewellen, John; Huang, Zhirong; Sajaev, Vadim; Milton, Stephen V

    2002-12-02

    We report on the first time-resolved phase measurement on self-amplified spontaneous emission (SASE) free-electron laser (FEL) pulses. We observed that the spikes in the output of such free-electron laser pulses have an intrinsic positive chirp. We also observed that the energy chirp in the electron bunch mapped directly into the FEL output. Under certain conditions, the two chirps cancel each other. The experimental result was compared with simulations and interpreted with SASE theory.

  18. Structural determination of a photochemically active diplatinum molecule by time-resolved EXAFS spectroscopy.

    PubMed

    van der Veen, Renske M; Milne, Chris J; El Nahhas, Amal; Lima, Frederico A; Pham, Van-Thai; Best, Jonathan; Weinstein, Julia A; Borca, Camelia N; Abela, Rafael; Bressler, Christian; Chergui, Majed

    2009-01-01

    Metallica: A large contraction of the Pt-Pt bond in the triplet excited state of the photoreactive [Pt(2)(P(2)O(5)H(2))(4)](4-) ion is determined by time-resolved X-ray absorption spectroscopy (see picture). The strengthening of the Pt-Pt interaction is accompanied by a weakening of the ligand coordination bonds, resulting in an elongation of the platinum-ligand bond that is determined for the first time.

  19. [Progress in research and application of time-resolved optoacoustic method in biomedicine].

    PubMed

    Li, Fenlan; Xu, Kexin; Wang, Ruikang

    2006-12-01

    Based on optoacoustic effect, time-resolved optoacoustic technique effectively combines optical technology with acoustic technology and partly overcomes the biological tissue's scatter characteristics which might influence the results of measurement. Optoacoustic technique has the advantages of high sensitivity and high resolution and has been widely applied in biomedicine field. In this paper, the measuring principles, the key technique, application and future direction of this technique are synthetically reviewed to promote the research in theory and application in the future.

  20. Functional muscle studies by dual-wavelength eight-channel time-resolved oximetry

    NASA Astrophysics Data System (ADS)

    Cubeddu, Rinaldo; Biscotti, Giovanni; Pifferi, Antonio; Taroni, Paola; Torricelli, Alessandro; Ferrari, Marco; Quaresima, Valentina

    2003-10-01

    A portable instrument for tissue oximetry based on time-resolved reflectance spectroscopy was developed. The performances of the system were tested on phantoms in terms of stability, reproducibility among channels, and accuracy in the determination of the optical properties. Preliminary in vivo measurements were performed on healthy volunteers to monitor spatial changes in calf (medial and lateral gastrocnemius) oxygen hemoglobin saturation and blood volume during dynamic plantar flexion exercise.

  1. Spectroscopic analysis of time-resolved emission from detonating thin film explosive samples

    NASA Astrophysics Data System (ADS)

    Kay, Jeffrey J.; Wixom, Ryan R.; Jilek, Brook A.; Knepper, Robert; Tappan, Alexander S.; Damm, David L.

    2017-01-01

    We report a series of time-resolved spectroscopic measurements that aim to characterize the reactions that occur during shock initiation of high explosives. The experiments employ time- and wavelength-resolved emission spectroscopy to analyze light emitted from detonating thin explosive films. This paper presents analysis of optical emission spectra from hexanitrostilbene (HNS) and pentaerythritol tetranitrate (PETN) thin film samples. Both vibrationally resolved and broadband emission features are observed in the spectra and area as electronic transitions of intermediate species.

  2. Visualizing a protein quake with time resolved X-ray scattering at a free electron laser

    PubMed Central

    Arnlund, David; Johansson, Linda C.; Wickstrand, Cecilia; Barty, Anton; Williams, Garth J.; Malmerberg, Erik; Davidsson, Jan; Milathianaki, Despina; DePonte, Daniel P.; Shoeman, Robert L.; Wang, Dingjie; James, Daniel; Katona, Gergely; Westenhoff, Sebastian; White, Thomas A.; Aquila, Andrew; Bari, Sadia; Berntsen, Peter; Bogan, Mike; van Driel, Tim Brandt; Doak, R. Bruce; Kjær, Kasper Skov; Frank, Matthias; Fromme, Raimund; Grotjohann, Ingo; Henning, Robert; Hunter, Mark S.; Kirian, Richard A.; Kosheleva, Irina; Kupitz, Christopher; Liang, Mengning; Martin, Andrew V.; Nielsen, Martin Meedom; Messerschmidt, Marc; Seibert, M. Marvin; Sjöhamn, Jennie; Stellato, Francesco; Weierstall, Uwe; Zatsepin, Nadia A.; Spence, John C. H.; Fromme, Petra; Schlichting, Ilme; Boutet, Sébastien; Groenhof, Gerrit; Chapman, Henry N.; Neutze, Richard

    2014-01-01

    A ‘protein quake’ describes the hypothesis that proteins rapidly dissipate energy through quake like structural motions. Here we measure ultrafast structural changes in the Blastochloris viridis photosynthetic reaction center following multi-photon excitation using time-resolved wide angle X-ray scattering at an X-ray free electron laser. A global conformational change arises within picoseconds, which precedes the propagation of heat through the protein. This motion is damped within a hundred picoseconds. PMID:25108686

  3. Semiconductors Investigated by Time Resolved Raman Absorption and Photoluminescence Spectroscopy Using Femtosecond and Picosecond Laser Techniques.

    DTIC Science & Technology

    1983-05-05

    if necessary and identify by block number) Picosecond Lasers, Femtosecond Lasers, Ring Cavity, Mode Locked Dye and Glass Lasers, Time-resolved...conductor processes. In addition, we have improved the stabil ity and shortened the pulse duration emitted from a mode - locked glass laser by at...pulse duration emitted from a mode -locked glass laser by at least a factor of two, by using heptamethine pyrylium #5 - a new saturable absorber. In the

  4. Time-resolved photoemission electron microscopy imaging of mode coupling between three interacting magnetic vortices

    SciTech Connect

    Wang, Xiao; Cheng, X. M.; Keavney, D. J.; Asmat-Uceda, M.; Buchanan, K. S.; Melikyan, A.

    2014-09-08

    The interactions between three magnetic vortices in a planar equilateral triangular arrangement were studied by time-resolved photoemission electron microscopy. The gyrotropic resonance frequencies of the three individual vortices in the tri-disk system are different from one another and also shifted from that of an isolated vortex by as much as 12%. A comparison with analytical calculations and numerical simulations shows that the observed frequency shifts result from the dipolar interaction between the vortices.

  5. Elasticity and Anelasticity of Materials from Time-Resolved X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Sinogeikin, S. V.; Smith, J.; Lin, C.; Bai, L.; Rod, E.; Shen, G.

    2014-12-01

    Recent advances in synchrotron sources, x-ray optics, area detectors, and sample environment control have enabled many time-resolved experimental techniques for studying materials at extreme pressure and temperature conditions. The High Pressure Collaborative Access Team (HPCAT) at the Advanced Photon Source has made a sustained effort to develop and assemble a powerful collection of high-pressure apparatus for time-resolved research, and considerable time has been invested in developing techniques for collecting high-quality time-resolved x-ray scattering data. In this talk we will outline recently developed capabilities at HPCAT for studying elasticity and anelasticity of minerals using fast compression and cyclic compression-decompression. A few recent studies will be highlighted. For example, with fast x-ray area detectors having millisecond time resolution, accurate thermal equations of state of materials at temperatures up to 1000K and megabar pressures can be collected in a matter of seconds using membrane-driven diamond anvil cells (DAC), yielding unprecedented time and pressure resolution of true isotherms. Short duration of the experiments eliminates temperature variation during the experiments and in general allows volume measurements at higher pressures and temperatures. Alternatively, high-frequency (kilohertz range) radial diffraction measurements in a panoramic DAC combined with fast, precise cyclic loading/unloading by piezo drive could provide the short time scale necessary for studying rheology of minerals from the elastic response and lattice relaxation as a function of pressure, temperature and strain rate. Finally, we consider some possible future applications for time-resolved high-pressure, high-temperature research of mantle minerals.

  6. New time-resolved micro-photoluminescence spectroscopy of natural and synthetic analogue minerals

    NASA Astrophysics Data System (ADS)

    Panczer, G.; Ollier, N.; Champagnon, B.; Gaft, M.

    2003-04-01

    Minerals as well as geomaterials often present light emissions under UV or visible excitations. This property called photoluminescence is due to low concentration impurities such as the rare earths, the transition elements and the lanthanides. The induced color is used for ore prospection but only spectroscopic analyses indicate the nature of the emitted centers. However natural samples contained numerous luminescent centers simultaneously and with regular steady-state measurements (such as in cathodoluminescence) all the emissions are often over lapping. In order to record the contributions of each separate center, it is possible to use time-resolved measurements based on the decay time of the emissions and using pulsed laser excitation. Some characteristic examples will be presented on apatites, zircons as well as gemstones. Geomaterials present as well micro scale heterogeneities (growth zoning, inclusions, devitrification, microphases...). Precise identification and optical effects of such heterogeneities have to be taken into account. To reach the microscale using photo luminescence studies, a microscope has be modified to allowed pulsed laser injection (from UV to visible), beam focus with micro scale resolution on the sample (<10 μm), as well as time resolved collection of micro fluorescence. Such equipment allows now undertaking time-resolved measurements of microphases. Applications on geomaterials will be presented.

  7. Time-resolved rotational spectroscopy of para-difluorobenzene·Ar

    NASA Astrophysics Data System (ADS)

    Weichert, A.; Riehn, C.; Matylitsky, V. V.; Jarzeba, W.; Brutschy, B.

    2002-07-01

    We report on time-resolved rotational spectroscopy experiments of the cluster para-difluorobenzene·Ar ( pDFB·Ar) by picosecond laser pulses in a supersonic expansion. Rotational coherences of pDFB·Ar are generated by resonant electronic excitation and probed by time-resolved fluorescence depletion spectroscopy and time-resolved photoionization ((1+1') PPI) spectroscopy. The former allows the determination of both ground and excited state rotational constants, whereas the latter technique enables the separate study of the excited state with the benefit of mass-selective detection. Since pDFB·Ar represents a near symmetric oblate rotor, persistent J-type transients with tJ≈ n/2( A+ B) could be measured. From their analysis, (A″+B″)=2234.9±2 MHz and (A'+B')=2237.9±2 MHz were obtained. A structural investigation, based on data of the pDFB monomer, is presented resulting in a pDFB·Ar center-of-mass distance of both moieties of R z=3.543±0.017 Å with a change of ΔR z=-0.057±0.009 Å upon electronic excitation. These results are compared to data of former frequency-resolved experiments and ab initio computations.

  8. Time-resolved Spectroscopy of a Sheared Flow Stabilized Z-pinch Plasma

    NASA Astrophysics Data System (ADS)

    Forbes, Eleanor

    2016-10-01

    The ZaP Flow Z-pinch Project investigates the use of sheared-axial flows to stabilize an otherwise unstable plasma configuration. Diagnostics with sub-microsecond resolution are required to obtain accurate time-resolved data since the plasma pulse is approximately 100 μs. Analyzing the Doppler shift of impurity line radiation from the pinch provides a measure of the velocity profile and is a reliable method of determining the plasma sheared flow. The velocity profile is spatially resolved through the use of a 20-chord fiber bundle. The ZaP-HD experiment has used a PI-MAX intensified CCD array to record a single time-resolved spectrum per plasma pulse. Obtaining the evolution of the velocity profile using this method required spectra acquired over hundreds of pulses with identical initial parameters and varying acquisition times. The use of a Kirana 05M ultra-fast framing camera is investigated for recording time-resolved velocity profiles during a single pulse. The Kirana utilizes an ultraviolet intensifier to record 180 frames of UV light at up to 2 million frames per second. An ultraviolet optics system is designed to couple the exit port of an Acton SP-500i spectrometer to the Kirana UV intensifier and focus spectra at the camera detector plane. This work is supported by US DoE FES, NNSA, and ARPA-E ALPHA.

  9. Bypassing the energy-time uncertainty in time-resolved photoemission

    NASA Astrophysics Data System (ADS)

    Randi, Francesco; Fausti, Daniele; Eckstein, Martin

    2017-03-01

    The energy-time uncertainty is an intrinsic limit for time-resolved experiments imposing a tradeoff between the duration of the light pulses used in experiments and their frequency content. In standard time-resolved photoemission, this limitation maps directly onto a tradeoff between the time resolution of the experiment and the energy resolution that can be achieved on the electronic spectral function. Here we propose a protocol to disentangle the energy and time resolutions in photoemission. We demonstrate that dynamical information on all time scales can be retrieved from time-resolved photoemission experiments using suitably shaped light pulses of quantum or classical nature. As a paradigmatic example, we study the dynamical buildup of the Kondo peak, a narrow feature in the electronic response function arising from the screening of a magnetic impurity by the conduction electrons. After a quench, the electronic screening builds up on timescales shorter than the inverse width of the Kondo peak and we demonstrate that the proposed experimental scheme could be used to measure the intrinsic time scales of such electronic screening. The proposed approach provides an experimental framework to access the nonequilibrium response of collective electronic properties beyond the spectral uncertainty limit and will enable the direct measurement of phenomena such as excited Higgs modes and, possibly, the retarded interactions in superconducting systems.

  10. Fast single photon avalanche photodiode-based time-resolved diffuse optical tomography scanner

    PubMed Central

    Mu, Ying; Niedre, Mark

    2015-01-01

    Resolution in diffuse optical tomography (DOT) is a persistent problem and is primarily limited by high degree of light scatter in biological tissue. We showed previously that the reduction in photon scatter between a source and detector pair at early time points following a laser pulse in time-resolved DOT is highly dependent on the temporal response of the instrument. To this end, we developed a new single-photon avalanche photodiode (SPAD) based time-resolved DOT scanner. This instrument uses an array of fast SPADs, a femto-second Titanium Sapphire laser and single photon counting electronics. In combination, the overall instrument temporal impulse response function width was 59 ps. In this paper, we report the design of this instrument and validate its operation in symmetrical and irregularly shaped optical phantoms of approximately small animal size. We were able to accurately reconstruct the size and position of up to 4 absorbing inclusions, with increasing image quality at earlier time windows. We attribute these results primarily to the rapid response time of our instrument. These data illustrate the potential utility of fast SPAD detectors in time-resolved DOT. PMID:26417526

  11. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs.

    PubMed

    Lemos, M Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-06-26

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein.

  12. Recombination of photodissociated iodine: A time-resolved x-ray-diffraction study

    SciTech Connect

    Wulff, M.; Bratos, S.; Plech, A.; Vuilleumier, R.; Mirloup, F.; Lorenc, M.; Kong, Q.; Ihee, H.

    2006-01-21

    A time-resolved x-ray-diffraction experiment is presented that aims to study the recombination of laser-dissociated iodine molecules dissolved in CCl{sub 4}. This process is monitored over an extended time interval from pico- to microseconds. The variations of atom-atom distances are probed with a milliangstrom resolution. A recent theory of time-resolved x-ray diffraction is used to analyze the experimental data; it employs the correlation function approach of statistical mechanics. The most striking outcome of this study is the experimental determination of time-dependent I-I atom-atom distribution functions. The structure of the CCl{sub 4} solvent changes simultaneously; the solvent thus appears as a reaction partner rather than an inert medium hosting it. Thermal expansion of the system is nonuniform in time, an effect due to the presence of the acoustic horizon. One concludes that a time-resolved x-ray diffraction permits real-time visualization of solvent and solute motions during a chemical reaction.

  13. Time-Resolved Optical Measurements of Fuel-Air Mixedness in Windowless High Speed Research Combustors

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    1998-01-01

    Fuel distribution measurements in gas turbine combustors are needed from both pollution and fuel-efficiency standpoints. In addition to providing valuable data for performance testing and engine development, measurements of fuel distributions uniquely complement predictive numerical simulations. Although equally important as spatial distribution, the temporal distribution of the fuel is an often overlooked aspect of combustor design and development. This is due partly to the difficulties in applying time-resolved diagnostic techniques to the high-pressure, high-temperature environments inside gas turbine engines. Time-resolved measurements of the fuel-to-air ratio (F/A) can give researchers critical insights into combustor dynamics and acoustics. Beginning in early 1998, a windowless technique that uses fiber-optic, line-of-sight, infrared laser light absorption to measure the time-resolved fluctuations of the F/A (refs. 1 and 2) will be used within the premixer section of a lean-premixed, prevaporized (LPP) combustor in NASA Lewis Research Center's CE-5 facility. The fiber-optic F/A sensor will permit optical access while eliminating the need for film-cooled windows, which perturb the flow. More importantly, the real-time data from the fiber-optic F/A sensor will provide unique information for the active feedback control of combustor dynamics. This will be a prototype for an airborne sensor control system.

  14. Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes

    NASA Astrophysics Data System (ADS)

    Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng

    2016-09-01

    Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.

  15. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

    SciTech Connect

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; Coe, Jesse; Bean, Richard; Zhao, Yun; Bath, Petra; Dods, Robert; Harimoorthy, Rajiv; Beyerlein, Kenneth R.; Rheinberger, Jan; James, Daniel; DePonte, Daniel; Li, Chufeng; Sala, Leonardo; Williams, Garth J.; Hunter, Mark S.; Koglin, Jason E.; Berntsen, Peter; Nango, Eriko; Chapman, Henry N.; Fromme, Petra; Frank, Matthias; Abela, Rafael; Boutet, Sebastien; Barty, Anton; White, Thomas A.; Weierstall, Uwe; Spence, John; Neutze, Richard; Schertler, Gebhard; Standfuss, Jorg

    2016-08-22

    Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. Furthermore, this study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.

  16. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

    DOE PAGES

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; ...

    2016-08-22

    Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within themore » crystal lattice is confirmed by time-resolved visible absorption spectroscopy. Furthermore, this study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.« less

  17. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

    PubMed Central

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; Coe, Jesse; Bean, Richard; Zhao, Yun; Båth, Petra; Dods, Robert; Harimoorthy, Rajiv; Beyerlein, Kenneth R.; Rheinberger, Jan; James, Daniel; DePonte, Daniel; Li, Chufeng; Sala, Leonardo; Williams, Garth J.; Hunter, Mark S.; Koglin, Jason E.; Berntsen, Peter; Nango, Eriko; Iwata, So; Chapman, Henry N.; Fromme, Petra; Frank, Matthias; Abela, Rafael; Boutet, Sébastien; Barty, Anton; White, Thomas A.; Weierstall, Uwe; Spence, John; Neutze, Richard; Schertler, Gebhard; Standfuss, Jörg

    2016-01-01

    Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. This study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX. PMID:27545823

  18. Particle tracking during Ostwald ripening using time-resolved laboratory X-ray microtomography

    SciTech Connect

    Werz, T.; Baumann, M.; Wolfram, U.; Krill, C.E.

    2014-04-01

    Laboratory X-ray microtomography is investigated as a method for obtaining time-resolved images of microstructural coarsening of the semisolid state of Al–5 wt.% Cu samples during Ostwald ripening. Owing to the 3D imaging capability of tomography, this technique uniquely provides access to the growth rates of individual particles, thereby not only allowing a statistical characterization of coarsening—as has long been possible by conventional metallography—but also enabling quantification of the influence of local environment on particle boundary migration. The latter information is crucial to understanding growth kinetics during Ostwald ripening at high volume fractions of the coarsening phase. Automated image processing and segmentation routines were developed to close gaps in the network of particle boundaries and to track individual particles from one annealing step to the next. The particle tracking success rate places an upper bound of only a few percent on the likelihood of segmentation errors for any given particle. The accuracy of particle size trajectories extracted from the time-resolved tomographic reconstructions is correspondingly high. Statistically averaged coarsening data and individual particle growth rates are in excellent agreement with the results of prior experimental studies and with computer simulations of Ostwald ripening. - Highlights: • Ostwald ripening in Al–5 wt.% Cu measured by laboratory X-ray microtomography • Time-resolved measurement of individual particle growth • Automated segmentation routines developed to close gaps in particle boundary network • Particle growth/shrinkage rates deviate from LSW model prediction.

  19. Probing interfacial electron dynamics with time-resolved X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Neppl, Stefan

    2015-05-01

    Time-resolved core-level spectroscopy techniques using laser pulses to initiate and short X-ray pulses to probe photo-induced processes have the potential to provide electronic state- and atomic site-specific insight into fundamental electron dynamics at complex interfaces. We describe the implementation of femto- and picosecond time-resolved photoelectron spectroscopy at the Linac Coherent Light Source (LCLS) and at the Advanced Light Source (ALS) in order to follow light-driven electron dynamics at dye-semiconductor interfaces on femto- to nanosecond timescales, and from the perspective of individual atomic sites. A distinct transient binding-energy shift of the Ru3d photoemission lines originating from the metal centers of N3 dye-molecules adsorbed on nanoporous ZnO is observed 500 fs after resonant HOMO-LUMO excitation with a visible laser pulse. This dynamical chemical shift is accompanied by a characteristic surface photo-voltage response of the semiconductor substrate. The two phenomena and their correlation will be discussed in the context of electronic bottlenecks for efficient interfacial charge-transfer and possible charge recombination and relaxation pathways leading to the neutralization of the transiently oxidized dye following ultrafast electron injection. First steps towards in operando time-resolved X-ray absorption spectroscopy techniques to monitor interfacial chemical dynamics will be presented.

  20. Time-resolved High Spectral Resolution Observation of 2MASSW J0746425+200032AB

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Prato, Lisa; Mawet, Dimitri

    2017-03-01

    Many brown dwarfs (BDs) exhibit photometric variability at levels from tenths to tens of percents. The photometric variability is related to magnetic activity or patchy cloud coverage, characteristic of BDs near the L–T transition. Time-resolved spectral monitoring of BDs provides diagnostics of cloud distribution and condensate properties. However, current time-resolved spectral studies of BDs are limited to low spectral resolution (R ∼ 100) with the exception of the study of Luhman 16 AB at a resolution of 100,000 using the VLT+CRIRES. This work yielded the first map of BD surface inhomogeneity, highlighting the importance and unique contribution of high spectral resolution observations. Here, we report on the time-resolved high spectral resolution observations of a nearby BD binary, 2MASSW J0746425+200032AB. We find no coherent spectral variability that is modulated with rotation. Based on simulations, we conclude that the coverage of a single spot on 2MASSW J0746425+200032AB is smaller than 1% or 6.25% if spot contrast is 50% or 80% of its surrounding flux, respectively. Future high spectral resolution observations aided by adaptive optics systems can put tighter constraints on the spectral variability of 2MASSW J0746425+200032AB and other nearby BDs.

  1. The analysis of time-resolved optical waveguide absorption spectroscopy based on positive matrix factorization.

    PubMed

    Liu, Ping; Li, Zhu; Li, Bo; Shi, Guolong; Li, Minqiang; Yu, Daoyang; Liu, Jinhuai

    2013-08-01

    Time-resolved optical waveguide absorption spectroscopy (OWAS) makes use of an evanescent field to detect the polarized absorption spectra of sub-monomolecular adlayers. This technique is suitable for the investigation of kinetics at the solid/liquid interface of dyes, pigments, fluorescent molecules, quantum dots, metallic nanoparticles, and proteins with chromophores. In this work, we demonstrate the application of positive matrix factorization (PMF) to analyze time-resolved OWAS for the first time. Meanwhile, PCA is researched to compare with PMF. The absorption/desorption kinetics of Rhodamine 6G (R6G) onto a hydrophilic glass surface and the dynamic process of Meisenheimer complex between Cysteine and TNT are selected as samples to verify experimental system and analytical methods. The results are shown that time-resolved OWAS can well record the absorption/desorption of R6G onto a hydrophilic glass surface and the dynamic formation process of Meisenheimer complexes. The feature of OWAS extracted by PMF is dynamic and consistent with the results analyzed by the traditional function of time/wavelength-absorbance. Moreover, PMF prevents the negative factors from occurring, avoids contradicting physical reality, and makes factors more easily interpretable. Therefore, we believe that PMF will provide a valuable analysis route to allow processing of increasingly large and complex data sets.

  2. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

    PubMed Central

    Rutherford, Michael E.; Chapman, David J.; White, Thomas G.; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E.

    2016-01-01

    The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits). PMID:27140147

  3. Combined continuous and time-resolved CL to study semiconductor structure and defects (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sonderegger, Samuel; Gachet, David; Berney, Jean

    2016-09-01

    Spectroscopic information may be acquired using an electron beam in a modern scanning electron microscope (SEM), exploiting the cathodoluminescence (CL) signal. CL offers several advantages over the usual optical spectroscopy. The multimode imaging capabilities of the SEM enable the correlation of optical properties (via CL) with surface morphology (secondary electron mode) at the nanometer scale and the large energy of the electrons allows the excitation of wide-bandgap materials. Here, we present results obtained on a field emission time-resolved and continuous (CW) cathodoluminescence scanning electron microscope. The microscope can either be operated in CW mode by heating up the emitter (Schottky emission), or in time-resolved mode by illuminating the field emission gun with a femtosecond UV laser, so that ultrafast electron pulses are emitted through the photoelectric effect. In both modes, a spacial resolution around 10 nm is demonstrated. The collected cathodoluminescence signal is dispersed in a spectrometer and analyzed with a CCD camera (CW mode) or an ultrafast STREAK camera to obtain <10 ps time resolution (TR mode). Quantitative CW cathodoluminescence was first used to quickly map defects in III-V semiconductor structures. Then, time-resolved cathodoluminescence measurements were carried out on specific regions in order to measure local lifetimes and carrier diffusion within the structures. We will also discuss the advantages of combining CL with a scanning transmission electron microscope (STEM) and introduce Attolight's most recent developments in this field.

  4. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs

    PubMed Central

    Lemos, M. Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-01-01

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein. PMID:26132136

  5. Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources.

    PubMed

    Rutherford, Michael E; Chapman, David J; White, Thomas G; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E

    2016-05-01

    The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).

  6. Hyperfast time-resolved spectroscopy of electron correlation in excited states

    NASA Astrophysics Data System (ADS)

    Nicolaides, Cleanthes A.

    2007-06-01

    As a consequence of continuing developments in the science and technology of techniques that produce and control electromagnetic pulses with frequencies that are found in a broad part of the spectrum, from the ir to the soft X-rays, it is possible to have hyperfast pump-probe time delay spectroscopic techniques capable of time resolving the dynamics of various atomic and molecular systems involving excited states. In this context, it has been demonstrated via first principles solution of the time-dependent Schr"odinger equation (TDSE), that effects which are caused by strong electron correlations in excited states, including the process of autoionization and the formation of resonances, can be time-resolved on a time scale of attoseconds [1-3]. By extending the investigations to polyelectronic atoms, we have obtained new results for various time resolved processes associated with the photo-ejection of inner (2s) electrons and of two electrons (LM) from the thirteen electron atom of Aluminum and with the electron correlation beats in bound and autoionizind states of N^+3 and Al. The theory and computations account for the interference of direct double ionization, inner hole states and Auger decay [4]. [1] C. A. Nicolaides et al, J. Phys. B 35, L271 (2002). [2] Th. Mercouris et al, Phys. Rev. A 69, 032502 (2004). [3] Th. Mercouris, et al, Phys. Rev. A 75, 013407 (2007). [4] Th. Mercouris, Y. Komninos and C. A. Nicolaides, unpublished.

  7. Novel laser gain and time-resolved FTIR studies of photochemistry

    NASA Technical Reports Server (NTRS)

    Leone, Stephen R.

    1990-01-01

    Several techniques are discussed which can be used to explore laboratory photochemical processes and kinetics relevant to planetary atmospheres; these include time-resolved laser gain-versus-absorption spectroscopy and time-resolved Fourier transform infrared (FTIR) emission studies. The laser gain-versus-absorption method employed tunable diode and F-center lasers to determine the yields of excited photofragments and their kinetics. The time-resolved FTIR technique synchronizes the sweep of a commercial FTIR with a pulsed source of light to obtain emission spectra of novel transient species in the infrared. These methods are presently being employed to investigate molecular photodissociation, the yields of excited states of fragments, their subsequent reaction kinetics, Doppler velocity distributions, and velocity-changing collisions of translationally fast atoms. Such techniques may be employed in future investigations of planetary atmospheres, for example to study polycyclic aromatic hydrocarbons related to cometary emissions, to analyze acetylene decomposition products and reactions, and to determine spectral features in the near infrared and infrared wavelength regions for planetary molecules and clusters.

  8. Comparative time-resolved photoemission from the Cu(100) and Cu(111) surfaces

    NASA Astrophysics Data System (ADS)

    Ambrosio, Marcelo J.; Thumm, Uwe

    2016-12-01

    Motivated by the striking dependence of the valence electronic structure of transition metal surfaces on their crystallographic orientation, and by emerging experiments on laser-assisted extended ultraviolet (XUV) photoemission from solid surfaces, we calculate photoemission spectra from Cu(100) and Cu(111) surfaces as a function of the photoelectron final kinetic energy and the delay between the ionizing attosecond XUV pulse train and assisting infrared (IR) laser pulse. Our numerical simulations predict distinct differences in delay-dependent photoelectron energy distributions and photoemission time delays for Cu(100) and Cu(111) surfaces. These differences can be scrutinized experimentally with existing technology in a suggested in situ comparative RABBITT (reconstruction of attosecond beating by interference of two-photon transitions) configuration by placing the two surfaces on a sliding platform while keeping all optical components and pathlengths fixed. Our calculations also show that the inclusion of the Fresnel-reflected incident IR pulse at the metal-vacuum interface modifies photoelectron spectra and photoemission time delays in a characteristic way that reveals the degree of spatial location of the initial electronic states.

  9. Time-resolved measurements of the hot-electron population in ignition-scale experiments on the National Ignition Facility (invited).

    PubMed

    Hohenberger, M; Albert, F; Palmer, N E; Lee, J J; Döppner, T; Divol, L; Dewald, E L; Bachmann, B; MacPhee, A G; LaCaille, G; Bradley, D K; Stoeckl, C

    2014-11-01

    In laser-driven inertial confinement fusion, hot electrons can preheat the fuel and prevent fusion-pellet compression to ignition conditions. Measuring the hot-electron population is key to designing an optimized ignition platform. The hot electrons in these high-intensity, laser-driven experiments, created via laser-plasma interactions, can be inferred from the bremsstrahlung generated by hot electrons interacting with the target. At the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)], the filter-fluorescer x-ray (FFLEX) diagnostic-a multichannel, hard x-ray spectrometer operating in the 20-500 keV range-has been upgraded to provide fully time-resolved, absolute measurements of the bremsstrahlung spectrum with ∼300 ps resolution. Initial time-resolved data exhibited significant background and low signal-to-noise ratio, leading to a redesign of the FFLEX housing and enhanced shielding around the detector. The FFLEX x-ray sensitivity was characterized with an absolutely calibrated, energy-dispersive high-purity germanium detector using the high-energy x-ray source at NSTec Livermore Operations over a range of K-shell fluorescence energies up to 111 keV (U Kβ). The detectors impulse response function was measured in situ on NIF short-pulse (∼90 ps) experiments, and in off-line tests.

  10. Time-resolved measurements of the hot-electron population in ignition-scale experiments on the National Ignition Facility (invited)

    NASA Astrophysics Data System (ADS)

    Hohenberger, M.; Albert, F.; Palmer, N. E.; Lee, J. J.; Döppner, T.; Divol, L.; Dewald, E. L.; Bachmann, B.; MacPhee, A. G.; LaCaille, G.; Bradley, D. K.; Stoeckl, C.

    2014-11-01

    In laser-driven inertial confinement fusion, hot electrons can preheat the fuel and prevent fusion-pellet compression to ignition conditions. Measuring the hot-electron population is key to designing an optimized ignition platform. The hot electrons in these high-intensity, laser-driven experiments, created via laser-plasma interactions, can be inferred from the bremsstrahlung generated by hot electrons interacting with the target. At the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)], the filter-fluorescer x-ray (FFLEX) diagnostic-a multichannel, hard x-ray spectrometer operating in the 20-500 keV range-has been upgraded to provide fully time-resolved, absolute measurements of the bremsstrahlung spectrum with ˜300 ps resolution. Initial time-resolved data exhibited significant background and low signal-to-noise ratio, leading to a redesign of the FFLEX housing and enhanced shielding around the detector. The FFLEX x-ray sensitivity was characterized with an absolutely calibrated, energy-dispersive high-purity germanium detector using the high-energy x-ray source at NSTec Livermore Operations over a range of K-shell fluorescence energies up to 111 keV (U Kβ). The detectors impulse response function was measured in situ on NIF short-pulse (˜90 ps) experiments, and in off-line tests.

  11. Time-resolved functional analysis of acute impairment of frataxin expression in an inducible cell model of Friedreich ataxia

    PubMed Central

    Poburski, Dörte; Boerner, Josefine Barbara; Koenig, Michel; Ristow, Michael

    2016-01-01

    ABSTRACT Friedreich ataxia is a neurodegenerative disease caused by a GAA triplet repeat expansion in the first intron of the frataxin gene, which results in reduced expression levels of the corresponding protein. Despite numerous animal and cellular models, therapeutic options that mechanistically address impaired frataxin expression are lacking. Here, we have developed a new mammalian cell model employing the Cre/loxP recombination system to induce a homozygous or heterozygous frataxin knockout in mouse embryonic fibroblasts. Induction of Cre-mediated disruption by tamoxifen was successfully tested on RNA and protein levels. After loss of frataxin protein, cell division, aconitase activity and oxygen consumption rates were found to be decreased, while ROS production was increased in the homozygous state. By contrast, in the heterozygous state no such changes were observed. A time-resolved analysis revealed the loss of aconitase activity as an initial event after induction of complete frataxin deficiency, followed by secondarily elevated ROS production and a late increase in iron content. Initial impairments of oxygen consumption and ATP production were found to be compensated in the late state and seemed to play a minor role in Friedreich ataxia pathophysiology. In conclusion and as predicted from its proposed role in iron sulfur cluster (ISC) biosynthesis, disruption of frataxin primarily causes impaired function of ISC-containing enzymes, whereas other consequences, including elevated ROS production and iron accumulation, appear secondary. These parameters and the robustness of the newly established system may additionally be used for a time-resolved study of pharmacological candidates in a HTS manner. PMID:27106929

  12. Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin

    SciTech Connect

    Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T.

    2004-12-13

    The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

  13. Kinetics of methane-ethane gas replacement in clathrate-hydrates studied by time-resolved neutron diffraction and Raman spectroscopy.

    PubMed

    Murshed, M Mangir; Schmidt, Burkhard C; Kuhs, Werner F

    2010-01-14

    The kinetics of CH(4)-C(2)H(6) replacement in gas hydrates has been studied by in situ neutron diffraction and Raman spectroscopy. Deuterated ethane structure type I (C(2)H(6) sI) hydrates were transformed in a closed volume into methane-ethane mixed structure type II (CH(4)-C(2)H(6) sII) hydrates at 5 MPa and various temperatures in the vicinity of 0 degrees C while followed by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. The role of available surface area of the sI starting material on the formation kinetics of sII hydrates was studied. Ex situ Raman spectroscopic investigations were carried out to crosscheck the gas composition and the distribution of the gas species over the cages as a function of structure type and compared to the in situ neutron results. Raman micromapping on single hydrate grains showed compositional and structural gradients between the surface and core of the transformed hydrates. Moreover, the observed methane-ethane ratio is very far from the one expected for a formation from a constantly equilibrated gas phase. The results also prove that gas replacement in CH(4)-C(2)H(6) hydrates is a regrowth process involving the nucleation of new crystallites commencing at the surface of the parent C(2)H(6) sI hydrate with a progressively shrinking core of unreacted material. The time-resolved neutron diffraction results clearly indicate an increasing diffusion limitation of the exchange process. This diffusion limitation leads to a progressive slowing down of the exchange reaction and is likely to be responsible for the incomplete exchange of the gases.

  14. In situ hybridization reveals that type I and III collagens are produced by pericytes in the anterior pituitary gland of rats.

    PubMed

    Fujiwara, Ken; Jindatip, Depicha; Kikuchi, Motoshi; Yashiro, Takashi

    2010-12-01

    Type I and III collagens widely occur in the rat anterior pituitary gland and are the main components of the extracellular matrix (ECM). Although ECM components possibly play an important role in the function of the anterior pituitary gland, little is known about collagen-producing cells. Type I collagen is a heterotrimer of two α1(I) chains (the product of the col1a1 gene) and one α2(I) chain (the product of the col1a2 gene). Type III collagen is a homotrimer of α1(III) chains (the product of the col3a1 gene). We used in situ hybridization with digoxigenin-labeled cRNA probes to examine the expression of col1a1, col1a2, and col3a1 mRNAs in the pituitary gland of adult rats. mRNA expression for these collagen genes was clearly observed, and cells expressing col1a1, col1a2, and col3a1 mRNA were located around capillaries in the gland. We also investigated the possible double-staining of collagen mRNA and pituitary hormones, S-100 protein (a marker of folliculo-stellate cells), or desmin (a marker of pericytes). Col1a1 and col3a1 mRNA were identified in desmin-immunopositive cells. Thus, only pericytes produce type I and III collagens in the rat anterior pituitary gland.

  15. XY sex reversal in the wood lemming is associated with deletion of Xp21-23 as revealed by chromosome microdissection and fluorescence in situ hybridization.

    PubMed

    Liu, W S; Eriksson, L; Fredga, K

    1998-08-01

    In the wood lemming (Myopus schisticolor), XY sex reversal occurs naturally because of the presence of an X chromosome variant designated X*. The two types of X chromosome, X and X*, can be distinguished by G-banding, and analyses have demonstrated complex rearrangements of the short arm of X*. Here, chromosomal microdissection, degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR) and fluorescence in situ hybridization (FISH) techniques have been used to generate and map DNA probes for different parts of the X and X* chromosomes. The results showed that the region of Xp21-23 is deleted from the X* and some of the deleted DNA sequences are homologous to the mouse gamma-satellite. The deletion must be associated with the sex reversal in this species. FISH experiments with dissected probes of X and distal half of Xq provided evidence for presence of homologous sequences between large regions of the X and Y chromosomes, including euchromatic and heterochromatic parts of the sex chromosomes. The findings of this study will be of significance for further cloning of important candidate gene(s) responsible for the XY sex reversal.

  16. In Silico and Fluorescence In Situ Hybridization Mapping Reveals Collinearity between the Pennisetum squamulatum Apomixis Carrier-Chromosome and Chromosome 2 of Sorghum and Foxtail Millet

    PubMed Central

    Sapkota, Sirjan; Conner, Joann A.; Hanna, Wayne W.; Simon, Bindu; Fengler, Kevin; Deschamps, Stéphane; Cigan, Mark; Ozias-Akins, Peggy

    2016-01-01

    Apomixis, or clonal propagation through seed, is a trait identified within multiple species of the grass family (Poaceae). The genetic locus controlling apomixis in Pennisetum squamulatum (syn Cenchrus squamulatus) and Cenchrus ciliaris (syn Pennisetum ciliare, buffelgrass) is the apospory-specific genomic region (ASGR). Previously, the ASGR was shown to be highly conserved but inverted in marker order between P. squamulatum and C. ciliaris based on fluorescence in situ hybridization (FISH) and varied in both karyotype and position of the ASGR on the ASGR-carrier chromosome among other apomictic Cenchrus/Pennisetum species. Using in silico transcript mapping and verification of physical positions of some of the transcripts via FISH, we discovered that the ASGR-carrier chromosome from P. squamulatum is collinear with chromosome 2 of foxtail millet and sorghum outside of the ASGR. The in silico ordering of the ASGR-carrier chromosome markers, previously unmapped in P. squamulatum, allowed for the identification of a backcross line with structural changes to the P. squamulatum ASGR-carrier chromosome derived from gamma irradiated pollen. PMID:27031857

  17. In Silico and Fluorescence In Situ Hybridization Mapping Reveals Collinearity between the Pennisetum squamulatum Apomixis Carrier-Chromosome and Chromosome 2 of Sorghum and Foxtail Millet.

    PubMed

    Sapkota, Sirjan; Conner, Joann A; Hanna, Wayne W; Simon, Bindu; Fengler, Kevin; Deschamps, Stéphane; Cigan, Mark; Ozias-Akins, Peggy

    2016-01-01

    Apomixis, or clonal propagation through seed, is a trait identified within multiple species of the grass family (Poaceae). The genetic locus controlling apomixis in Pennisetum squamulatum (syn Cenchrus squamulatus) and Cenchrus ciliaris (syn Pennisetum ciliare, buffelgrass) is the apospory-specific genomic region (ASGR). Previously, the ASGR was shown to be highly conserved but inverted in marker order between P. squamulatum and C. ciliaris based on fluorescence in situ hybridization (FISH) and varied in both karyotype and position of the ASGR on the ASGR-carrier chromosome among other apomictic Cenchrus/Pennisetum species. Using in silico transcript mapping and verification of physical positions of some of the transcripts via FISH, we discovered that the ASGR-carrier chromosome from P. squamulatum is collinear with chromosome 2 of foxtail millet and sorghum outside of the ASGR. The in silico ordering of the ASGR-carrier chromosome markers, previously unmapped in P. squamulatum, allowed for the identification of a backcross line with structural changes to the P. squamulatum ASGR-carrier chromosome derived from gamma irradiated pollen.

  18. In situ electrophysiological examination of pancreatic α cells in the streptozotocin-induced diabetes model, revealing the cellular basis of glucagon hypersecretion.

    PubMed

    Huang, Ya-Chi; Rupnik, Marjan S; Karimian, Negar; Herrera, Pedro L; Gilon, Patrick; Feng, Zhong-Ping; Gaisano, Herbert Y

    2013-02-01

    Early-stage type 1 diabetes (T1D) exhibits hyperglucagonemia by undefined cellular mechanisms. Here we characterized α-cell voltage-gated ion channels in a streptozotocin (STZ)-induced diabetes model that lead to increased glucagon secretion mimicking T1D. GYY mice expressing enhanced yellow fluorescence protein in α cells were used to identify α cells within pancreas slices. Mice treated with low-dose STZ exhibited hyperglucagonemia, hyperglycemia, and glucose intolerance, with 71% reduction of β-cell mass. Although α-cell mass of STZ-treated mice remained unchanged, total pancreatic glucagon content was elevated, coinciding with increase in size of glucagon granules. Pancreas tissue slices enabled in situ examination of α-cell electrophysiology. α cells of STZ-treated mice exhibited the following: 1) increased exocytosis (serial depolarization-induced capacitance), 2) enhanced voltage-gated Na(+) current density, 3) reduced voltage-gated K(+) current density, and 4) increased action potential (AP) amplitude and firing frequency. Hyperglucagonemia in STZ-induced diabetes is thus likely due to increased glucagon content arising from enlarged glucagon granules and increased AP firing frequency and amplitude coinciding with enhanced Na(+) and reduced K(+) currents. These alterations may prime α cells in STZ-treated mice for more glucagon release per cell in response to low glucose stimulation. Thus, our study provides the first insight that STZ treatment sensitizes release mechanisms of α cells.

  19. Distribution of 45S rDNA in Modern Rose Cultivars (Rosa hybrida), Rosa rugosa, and Their Interspecific Hybrids Revealed by Fluorescence in situ Hybridization.

    PubMed

    Ding, Xiao-Liu; Xu, Ting-Liang; Wang, Jing; Luo, Le; Yu, Chao; Dong, Gui-Min; Pan, Hui-Tang; Zhang, Qi-Xiang

    2016-01-01

    To elucidate the evolutionary dynamics of the location and number of rDNA loci in the process of polyploidization in the genus Rosa, we examined 45S rDNA sites in the chromosomes of 6 modern rose cultivars (R. hybrida), 5 R. rugosa cultivars, and 20 hybrid progenies by fluorescence in situ hybridization. Variation in the number of rDNA sites in parents and their interspecific hybrids was detected. As expected, 4 rDNA sites were observed in the genomes of 4 modern rose cultivars, while 3 hybridization sites were observed in the 2 others. Two expected rDNA sites were found in 2 R. rugosa cultivars, while in the other 3 R. rugosa cultivars 4 sites were present. Among the 20 R. hybrida × R. rugosa offspring, 13 carried the expected number of rDNA sites, and 1 had 6 hybridization sites, which exceeded the expected number by far. The other 6 offspring had either 2 or 3 hybridization sites, which was less than expected. Differences in the number of rDNA loci were observed in interspecific offspring, indicating that rDNA loci exhibit instability after distant hybridization events. Abnormal chromosome pairing may be the main factor explaining the variation in rDNA sites during polyploidization.

  20. Dynamical vertical structure of the tropical upper troposphere and stratosphere revealed by CH4:N2O correlations derived from in situ measurements

    NASA Astrophysics Data System (ADS)

    Catoire, Valery; Berthet, Gwenael; Huret, Nathalie

    Within the frame of an ENVISAT satellite validation campaign operated by CNES, the SPI- RALE balloon-borne absorption spectrometer using six infrared diode lasers was flown in the Tropics (Teresina, Brazil, 5.1° S-42.9° W) in June 2005. In situ vertical profiles of O3, CO, CH4, HCHO, N2O, NO, NO2, HNO3, and HCl were obtained between 12 and 34 km height at a very high vertical resolution ( 5 m). In the present paper, emphasis is put on the dynamics. CH4:N2O tracer correlations are used to characterize the air mass origin and possible mixing processes. The results are compared to the well-established correlations from Michelsen et al. (J. Geophys. Res., 1998), and possibly to a new SPIRALE dataset collected during the May 2008 planned flight. Previous SPIRALE measurements at midand high-latitudes have shown their relevance for studying detailed dynamical vertical structure from the upper troposphere to the middle stratosphere (Huret et al., J. Geophys. Res., 2006). They will therefore help for the interpretation of the tropical profile together with the use of outputs from potential vorticity maps.