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Sample records for resolution time resolved

  1. Fast time-resolved electrostatic force microscopy: Achieving sub-cycle time resolution.

    PubMed

    Karatay, Durmus U; Harrison, Jeffrey S; Glaz, Micah S; Giridharagopal, Rajiv; Ginger, David S

    2016-05-01

    The ability to measure microsecond- and nanosecond-scale local dynamics below the diffraction limit with widely available atomic force microscopy hardware would enable new scientific studies in fields ranging from biology to semiconductor physics. However, commercially available scanning-probe instruments typically offer the ability to measure dynamics only on time scales of milliseconds to seconds. Here, we describe in detail the implementation of fast time-resolved electrostatic force microscopy using an oscillating cantilever as a means to measure fast local dynamics following a perturbation to a sample. We show how the phase of the oscillating cantilever relative to the perturbation event is critical to achieving reliable sub-cycle time resolution. We explore how noise affects the achievable time resolution and present empirical guidelines for reducing noise and optimizing experimental parameters. Specifically, we show that reducing the noise on the cantilever by using photothermal excitation instead of piezoacoustic excitation further improves time resolution. We demonstrate the discrimination of signal rise times with time constants as fast as 10 ns, and simultaneous data acquisition and analysis for dramatically improved image acquisition times. PMID:27250430

  2. Fast time-resolved electrostatic force microscopy: Achieving sub-cycle time resolution

    NASA Astrophysics Data System (ADS)

    Karatay, Durmus U.; Harrison, Jeffrey S.; Glaz, Micah S.; Giridharagopal, Rajiv; Ginger, David S.

    2016-05-01

    The ability to measure microsecond- and nanosecond-scale local dynamics below the diffraction limit with widely available atomic force microscopy hardware would enable new scientific studies in fields ranging from biology to semiconductor physics. However, commercially available scanning-probe instruments typically offer the ability to measure dynamics only on time scales of milliseconds to seconds. Here, we describe in detail the implementation of fast time-resolved electrostatic force microscopy using an oscillating cantilever as a means to measure fast local dynamics following a perturbation to a sample. We show how the phase of the oscillating cantilever relative to the perturbation event is critical to achieving reliable sub-cycle time resolution. We explore how noise affects the achievable time resolution and present empirical guidelines for reducing noise and optimizing experimental parameters. Specifically, we show that reducing the noise on the cantilever by using photothermal excitation instead of piezoacoustic excitation further improves time resolution. We demonstrate the discrimination of signal rise times with time constants as fast as 10 ns, and simultaneous data acquisition and analysis for dramatically improved image acquisition times.

  3. Time-resolved serial crystallography captures high-resolution intermediates of photoactive yellow protein

    DOE PAGESBeta

    Tenboer, Jason; Basu, Shibom; Zatsepin, Nadia; Pande, Kanupriya; Milathianaki, Despina; Frank, Matthias; Hunter, Mark; Boutet, Sebastien; Williams, Garth J.; Koglin, Jason E.; et al

    2014-12-05

    We report that serial femtosecond crystallography using ultrashort pulses from X-ray Free Electron Lasers (XFELs) offers the possibility to study light-triggered dynamics of biomolecules. Using microcrystals of the blue light photoreceptor, photoactive yellow protein, as a model system, we present high resolution, time-resolved difference electron density maps of excellent quality with strong features, which allow the determination of structures of reaction intermediates to 1.6 Å resolution. These results open the way to the study of reversible and non-reversible biological reactions on time scales as short as femtoseconds under conditions which maximize the extent of reaction initiation throughout the crystal.

  4. Time-resolved high-resolution electron microscopy of structural stability in MgO clusters

    SciTech Connect

    Kizuka, T.; Tanaka, N.

    1996-12-31

    Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science. In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.

  5. Parameters affecting temporal resolution of Time Resolved Integrative Optical Neutron Detector (TRION)

    NASA Astrophysics Data System (ADS)

    Mor, I.; Vartsky, D.; Dangendorf, V.; Bar, D.; Feldman, G.; Goldberg, M. B.; Tittelmeier, K.; Bromberger, B.; Brandis, M.; Weierganz, M.

    2013-11-01

    The Time-Resolved Integrative Optical Neutron (TRION) detector was developed for Fast Neutron Resonance Radiography (FNRR), a fast-neutron transmission imaging method that exploits characteristic energy-variations of the total scattering cross-section in the En = 1-10 MeV range to detect specific elements within a radiographed object. As opposed to classical event-counting time of flight (ECTOF), it integrates the detector signal during a well-defined neutron Time of Flight window corresponding to a pre-selected energy bin, e.g., the energy-interval spanning a cross-section resonance of an element such as C, O and N. The integrative characteristic of the detector permits loss-free operation at very intense, pulsed neutron fluxes, at a cost however, of recorded temporal resolution degradation This work presents a theoretical and experimental evaluation of detector related parameters which affect temporal resolution of the TRION system.

  6. Simulations of the temporal and spatial resolution for a compact time-resolved electron diffractometer

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    A novel compact electron gun for use in time-resolved gas electron diffraction experiments has recently been designed and commissioned. In this paper we present and discuss the extensive simulations that were performed to underpin the design in terms of the spatial and temporal qualities of the pulsed electron beam created by the ionisation of a gold photocathode using a femtosecond laser. The response of the electron pulses to a solenoid lens used to focus the electron beam has also been studied. The simulated results show that focussing the electron beam affects the overall spatial and temporal resolution of the experiment in a variety of ways, and that factors that improve the resolution of one parameter can often have a negative effect on the other. A balance must, therefore, be achieved between spatial and temporal resolution. The optimal experimental time resolution for the apparatus is predicted to be 416 fs for studies of gas-phase species, while the predicted spatial resolution of better than 2 nm-1 compares well with traditional time-averaged electron diffraction set-ups.

  7. Time-resolved photoemission apparatus achieving sub-20-meV energy resolution and high stability

    SciTech Connect

    Ishida, Y.; Togashi, T.; Yamamoto, K.; Tanaka, M.; Kiss, T.; Otsu, T.; Kobayashi, Y.; Shin, S.

    2014-12-15

    The paper describes a time- and angle-resolved photoemission apparatus consisting of a hemispherical analyzer and a pulsed laser source. We demonstrate 1.48-eV pump and 5.92-eV probe measurements at the ⩾10.5-meV and ⩾240-fs resolutions by use of fairly monochromatic 170-fs pulses delivered from a regeneratively amplified Ti:sapphire laser system operating typically at 250 kHz. The apparatus is capable to resolve the optically filled superconducting peak in the unoccupied states of a cuprate superconductor, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ}. A dataset recorded on Bi(111) surface is also presented. Technical descriptions include the followings: A simple procedure to fine-tune the spatio-temporal overlap of the pump-and-probe beams and their diameters; achieving a long-term stability of the system that enables a normalization-free dataset acquisition; changing the repetition rate by utilizing acoustic optical modulator and frequency-division circuit.

  8. XNAP: a hybrid pixel detector with nanosecond resolution for time resolved synchrotron radiation studies

    NASA Astrophysics Data System (ADS)

    Fajardo, P.; Baron, A. Q. R.; Dautet, H.; Davies, M.; Fischer, P.; Göttlicher, P.; Graafsma, H.; Hervé, C.; Rüffer, R.; Thil, C.

    2013-03-01

    The XNAP collaboration is constructing a hybrid pixel X-ray detector based on a monolithic silicon avalanche photodiode (APD) sensor array aiming at applications in synchrotron radiation facilities. The 2D detector is capable of identifying which individual electron bunch produces each detected X-ray photon, even when the storage ring operates in multibunch filling modes. This instrument is intended to be used in X-ray Photon Correlation Spectroscopy and Nuclear Resonance experiments and serve as a demonstrator for various kind of time resolved diffraction and scattering applications as well as a very high count rate device. The detector is a 1 kilopixel device with 280 μm pitch that implements both counting mode up to MHz frame rates and event-by-event readout with sub-nanosecond time resolution. The paper describes the detector design and some results obtained with small 4×4 pixel prototypes that have been built and measured to make and validate the most critical choices for the final detector.

  9. Sub-100ps single photoelectron time resolution of a strip silicon photomultiplier for time-resolved optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Shenyuan; Liu, Rongdan; Liang, Kun; Yang, Ru; Han, Dejun

    2015-10-01

    SiPM with epitaxial quenching resistors developed at NDL (Novel Device Laboratory, Beijing) could alleviate the conflict between large dynamic range and high photon detection efficiency (PDE). It can be used as low light level detector in various applications with excellent single photoelectron time resolution (SPTR) and photon counting capacity. SPTR is mainly determined by the intrinsic structure parameters of the SiPM. However, it is also limited to measurement setup, electronics readout and the ultra-small signal of single photoelectron level. In this work, we designed and fabricated a 1 mm × 1 mm strip SiPM array for possible applications in time-resolved optical spectroscopy. The SiPM array consists of sixteen 50 μm × 1 mm strip SiPM elements. Each element contains five hundred 6.5 μm × 6.5 μm micro avalanche photodiode (APD) cells with 10μm pitch. The strip SiPM demonstrated SPTR of 68 ps (FWHM), peak PDE of 17% around 450 nm and high photon number resolving and photon counting capability.

  10. Time-Resolved, Atomic-Resolution Imaging of Metastable Atom Configurations

    NASA Astrophysics Data System (ADS)

    Kisielowski, Christian

    2013-03-01

    In the recent past significant initiatives are dedicated to the exploration of sustainable energy solutions. Certainly, related research must address a rich diversity of challenges because it is not only the static arrangement of matter that must be understood at a single atom level but also the collective behavior of molecular assemblies that leads to functionality. Moreover, hybrid materials are commonly employed that contain hard and soft matter components to artificially stimulate complex behavior. Electron microscopy is often considered a method of choice that may address these challenges if further improved. This paper reports on the development of in-line holography for atomic-resolution electron microscopy, which makes use of dose rates as low as a few atto Amperes per square Ångstrom and of variable acceleration voltages between 20 kV and 300 kV. The approach allows for enhancing resolution in radiation sensitive materials and is especially well suited to study the time evolution of nanoscale objects with single atom sensitivity. For the first time temporary displacements of single atoms from their equilibrium lattice sites into metastable sites across a projected distance of only 0.07 nm and 0.10 nm are directly captured in images with a time resolution around one second. These temporary excitations seem relevant to the irreversible transformation of graphene into carbene and to self-diffusion in catalysts. In suitable experimental conditions, however, atom displacements of 0.05 - 0.1 nm are entirely reversible. Exploiting the reversible nature of such excitations, it may become feasible to probe for conformational object changes in beam sensitive materials at improved spatial resolution. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231

  11. Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging

    NASA Astrophysics Data System (ADS)

    Namboodiri, Mahesh; Khan, Tahirzeb; Karki, Khadga; Kazemi, Mehdi Mohammad; Bom, Sidhant; Flachenecker, Günter; Namboodiri, Vinu; Materny, Arnulf

    2014-04-01

    The combination of near-field microscopy along with nonlinear optical spectroscopic techniques is presented here. The scanning near-field imaging technique can be integrated with nonlinear spectroscopic techniques to improve spatial and axial resolution of the images. Additionally, ultrafast dynamics can be probed down to nano-scale dimension. The review shows some examples for this combination, which resulted in an exciton map and vibrational contrast images with sub-wavelength resolution. Results of two-color femtosecond time-resolved pump-probe experiments using scanning near-field optical microscopy (SNOM) on thin films of the organic semiconductor 3,4,9,10 Perylenetetracarboxylic dianhydride (PTCDA) are presented. While nonlinear Raman techniques have been used to obtain highly resolved images in combination with near-field microscopy, the use of femtosecond laser pulses in electronic resonance still constitutes a big challenge. Here, we present our first results on coherent anti-Stokes Raman scattering (fs-CARS) with femtosecond laser pulses detected in the near-field using SNOM. We demonstrate that highly spatially resolved images can be obtained from poly(3-hexylthiophene) (P3HT) nano-structures where the fs-CARS process was in resonance with the P3HT absorption and with characteristic P3HT vibrational modes without destruction of the samples. Sub-diffraction limited lateral resolution is achieved. Especially the height resolution clearly surpasses that obtained with standard microCARS. These results will be the basis for future investigations of mode-selective dynamics in the near-field.

  12. High Resolution Time-resolved UCLES Spectroscopy of AE Aqr: I. The Secondary Star Revealed

    NASA Astrophysics Data System (ADS)

    Echevarria, J.; Diego, F.; Mills, D.; Connon Smith, R.

    2006-06-01

    High-dispersion time-resolved spectroscopy of the cataclysmic variable AE Aqr has been obtained. The emission lines have a complex structure that make difficult to measure the motion of the white dwarf. The cross correlation for the absorption lines shows a clear asymmetric profile as expected from a heated side of the red star. The spectral type for the secondary star varies from K2 to K5; there are clear indications that the temperature varies as a function of star longitude. The radial velocity analysis yield Kab = 165.2 ± 0.6 Km s-1 for the cross-correlated secondary star. The rotational velocity of the red star has been measured as a function of orbital period. It shows ellipsoidal variations with a period half the orbital period. The rotational velocities vary within the range Vrot sin i = 105 ± 3 Km s-1 and Vrot sin i = 130 ± 3 Km s-1. The former can be used to constrain the white dwarf semi-amplitude value to yield Kem = 139 ± 4 Km s-1 consistent with derived values from published radial velocity measurements. From a variation in the absorption line strength of 30%, we constrain the inclination angle to i = 58° ± 3. The estimated masses of the binary are: Mw = 1.07 ± 0.07 M? and Mr = 0.90 ± 0.05 M?. If this is correct we should expect a spectral type of G5 if the secondary star is a main sequence star. We suggest that the discrepancy is explained if the star has a radius 40% greater than a main sequence star for a mass of 0.90 M?.

  13. Time-resolved RNA SHAPE chemistry: quantitative RNA structure analysis in one second snapshots and at single nucleotide resolution

    PubMed Central

    Mortimer, Stefanie A.; Weeks, Kevin M.

    2016-01-01

    RNA SHAPE chemistry exploits the discovery that conformationally dynamic nucleotides preferentially adopt conformations that facilitate reaction between the 2′-OH group and a hydroxyl-selective electrophile, such as benzoyl cyanide (BzCN), to form a 2′-O-adduct. BzCN is ideally suited for quantitative, time-resolved analysis of RNA folding and RNP assembly mechanisms because this reagent both reacts with flexible RNA nucleotides and also undergoes auto-inactivating hydrolysis with a half-life of 0.25 s at 37 °C. RNA folding is initiated by addition of Mg2+ or protein, or other change in solution conditions, and nucleotide resolution structural images are obtained by adding aliquots of the evolving reaction to BzCN and then “waiting” for 1 sec. Sites of 2′-O-adduct formation are subsequently scored as stops to primer extension using reverse transcriptase. This time resolved SHAPE protocol makes it possible to obtain 1 sec snapshots in time-resolved kinetic studies for RNAs of arbitrary length and complexity in a straightforward and concise experiment. PMID:19745823

  14. Far-field infrared super-resolution microscopy using picosecond time-resolved transient fluorescence detected IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakai, Makoto; Kawashima, Yasutake; Takeda, Akihiro; Ohmori, Tsutomu; Fujii, Masaaki

    2007-05-01

    A new far-field infrared super-resolution microscopy combining laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy is proposed. TFD-IR spectroscopy is a kind of IR-visible/UV double resonance spectroscopy, and detects IR transitions by the transient fluorescence due to electronic transition originating from vibrationally excited level populated by IR light. IR images of rhodamine-6G solution and of fluorescent beads were clearly observed by monitoring the transient fluorescence. Super-resolution twice higher than the diffraction limit for IR light was achieved. The IR spectrum due to the transient fluorescence was also measured from spatial domains smaller than the diffraction limit.

  15. High Temporal and Spatial Resolution 3D Time-Resolved Contrast-Enhanced MR Angiography of the Hands and Feet

    PubMed Central

    Haider, Clifton R.; Riederer, Stephen J.; Borisch, Eric A.; Glockner, James F.; Grimm, Roger C.; Hulshizer, Thomas C.; Macedo, Thanila A.; Mostardi, Petrice M.; Rossman, Phillip J.; Vrtiska, Terri J.; Young, Phillip M.

    2010-01-01

    Methods are described for generating 3D time-resolved contrast-enhanced MR angiograms of the hands and feet. Given targeted spatial resolution and frame times, it is shown that acceleration of about one order of magnitude or more is necessary. This is obtained by a combination of 2D Sensitivity Encoding (SENSE) and homodyne (HD) acceleration methods. Image update times from 3.4 to 6.8 sec are provided in conjunction with view sharing. Modular receiver coil arrays are described which can be designed to the targeted vascular region. Images representative of the technique are generated in the vasculature of the hands and feet in volunteers and in patient studies. PMID:21698702

  16. Time-Resolved Molecular Characterization of Limonene/Ozone Aerosol using High-Resolution Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Bateman, Adam P.; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2009-09-09

    Molecular composition of limonene/O3 secondary organic aerosol (SOA) was investigated using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) as a function of reaction time. SOA was generated by ozonation of D-limonene in a reaction chamber and sampled at different time intervals using a cascade impactor. The SOA samples were extracted into acetonitrile and analyzed using a HR-ESI-MS instrument with a resolving power of 100,000 (m/Δm). The resulting mass spectra provided detailed information about the extent of oxidation inferred from the O:C ratios, double bond equivalency (DBE) factors, and aromaticity indexes (AI) in hundreds of identified individual SOA species.

  17. Magnetic dynamics studied by high-resolution electron spectroscopy and time-resolved electron microscopy

    NASA Astrophysics Data System (ADS)

    Jayaraman, Rajeswari

    Future information technology requires an increased magnetically encoded data density and novel electromagnetic modes of data transfer. While to date magnetic properties are observed and characterized mostly statically, the need emerges to monitor and capture their fast dynamics. In this talk, I will focus on the spin dynamics i.e. spin wave excitations and the dynamics of a new topological distribution of spins termed ``skyrmions''. Wave packets of spin waves offer the unique capability to transport a quantum bit, the spin, without the transport of charge or mass. Here, large wave-vector spin waves are of particular interest as they admit spin localization within a few nanometers. By using our recently developed electron energy loss spectrometer, we could study such spin waves in ultrathin films with an unprecedented energy resolution of 4 meV. By virtue of the finite penetration depth of low energy electrons, spin waves localized at interfaces between a substrate and a thin capping layer can be been studied yielding information about the exchange coupling between atoms at the interface. The quantization of spin waves with wave vectors perpendicular to the film gives rise to standing modes to which EELS has likewise access. Such studies when carried out as function of the film thickness again yield information on the layer dependence of the exchange coupling. Magnetic skyrmions are promising candidates as information carriers in logic or storage devices. Currently, little is known about the influence of disorder, defects, or external stimuli on the spatial distribution and temporal evolution of the skyrmion lattice. In this talk, I will describe the dynamical role of disorder in a large and flat thin film of Cu2OSeO3, exhibiting a skyrmion phase in an insulating material. We image up to 70,000 skyrmions by means of cryo-Lorentz Transmission Electron Microscopy as a function of the applied magnetic field. In the skyrmion phase, dislocations are shown to cause the

  18. Resolution of Two Sub-Populations of Conformers and Their Individual Dynamics by Time Resolved Ensemble Level FRET Measurements

    PubMed Central

    Rahamim, Gil; Chemerovski-Glikman, Marina; Rahimipour, Shai; Amir, Dan; Haas, Elisha

    2015-01-01

    Most active biopolymers are dynamic structures; thus, ensembles of such molecules should be characterized by distributions of intra- or intermolecular distances and their fast fluctuations. A method of choice to determine intramolecular distances is based on Förster resonance energy transfer (FRET) measurements. Major advances in such measurements were achieved by single molecule FRET measurements. Here, we show that by global analysis of the decay of the emission of both the donor and the acceptor it is also possible to resolve two sub-populations in a mixture of two ensembles of biopolymers by time resolved FRET (trFRET) measurements at the ensemble level. We show that two individual intramolecular distance distributions can be determined and characterized in terms of their individual means, full width at half maximum (FWHM), and two corresponding diffusion coefficients which reflect the rates of fast ns fluctuations within each sub-population. An important advantage of the ensemble level trFRET measurements is the ability to use low molecular weight small-sized probes and to determine nanosecond fluctuations of the distance between the probes. The limits of the possible resolution were first tested by simulation and then by preparation of mixtures of two model peptides. The first labeled polypeptide was a relatively rigid Pro7 and the second polypeptide was a flexible molecule consisting of (Gly-Ser)7 repeats. The end to end distance distributions and the diffusion coefficients of each peptide were determined. Global analysis of trFRET measurements of a series of mixtures of polypeptides recovered two end-to-end distance distributions and associated intramolecular diffusion coefficients, which were very close to those determined from each of the pure samples. This study is a proof of concept study demonstrating the power of ensemble level trFRET based methods in resolution of subpopulations in ensembles of flexible macromolecules. PMID:26699718

  19. Time-Resolved O3 Chemical Chain Reaction Kinetics Via High-Resolution IR Laser Absorption Methods

    NASA Technical Reports Server (NTRS)

    Kulcke, Axel; Blackmon, Brad; Chapman, William B.; Kim, In Koo; Nesbitt, David J.

    1998-01-01

    Excimer laser photolysis in combination with time-resolved IR laser absorption detection of OH radicals has been used to study O3/OH(v = 0)/HO2 chain reaction kinetics at 298 K, (i.e.,(k(sub 1) is OH + 03 yields H02 + 02 and (k(sub 2) is H02 + 03 yields OH + 202). From time-resolved detection of OH radicals with high-resolution near IR laser absorption methods, the chain induction kinetics have been measured at up to an order of magnitude higher ozone concentrations ([03] less than or equal to 10(exp 17) molecules/cu cm) than accessible in previous studies. This greater dynamic range permits the full evolution of the chain induction, propagation, and termination process to be temporally isolated and measured in real time. An exact solution for time-dependent OH evolution under pseudo- first-order chain reaction conditions is presented, which correctly predicts new kinetic signatures not included in previous OH + 03 kinetic analyses. Specifically, the solutions predict an initial exponential loss (chain "induction") of the OH radical to a steady-state level ([OH](sub ss)), with this fast initial decay determined by the sum of both chain rate constants, k(sub ind) = k(sub 1) + k(sub 2). By monitoring the chain induction feature, this sum of the rate constants is determined to be k(sub ind) = 8.4(8) x 10(exp -14) cu cm/molecule/s for room temperature reagents. This is significantly higher than the values currently recommended for use in atmospheric models, but in excellent agreement with previous results from Ravishankara et al.

  20. High harmonic generation based time resolved ARPES at 30 eV with 50 meV energy resolution

    NASA Astrophysics Data System (ADS)

    Rohwer, Timm; Sie, Edbert J.; Mahmood, Fahad; Gedik, Nuh

    Angle-resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in identifying equilibrium properties of complex electronic systems as well as their correlated dynamics. By using femtosecond high harmonic generation (HHG) pulses, this technique can be extended to monitor ultrafast changes in the electronic structure in response to an optical excitation. However, the broad bandwidth of the HHG pulses has been a major experimental limitation. In this contribution, we combine the HHG source with an off-axis Czerny-Turner XUV monochromator and a three-dimensional ``ARTOF'' photoelectron detector to achieve an unrivaled overall energy resolution of 50 meV in multiple harmonic energies. Moreover, the use of a stack of different gratings enables us to fine control both the photon energy and time vs. energy resolution to its particular needs. The performance of our setup is demonstrated by studies on the transition metal dichalcogenide IrTe2 which undergoes a first-order structural transition and accompanied reconstruction of the band structure upon cooling without the characteristic opening of an energy gap.

  1. Rapid high-resolution spin- and angle-resolved photoemission spectroscopy with pulsed laser source and time-of-flight spectrometer

    SciTech Connect

    Gotlieb, K.; Hussain, Z.; Bostwick, A.; Jozwiak, C.; Lanzara, A.

    2013-09-15

    A high-efficiency spin- and angle-resolved photoemission spectroscopy (spin-ARPES) spectrometer is coupled with a laboratory-based laser for rapid high-resolution measurements. The spectrometer combines time-of-flight (TOF) energy measurements with low-energy exchange scattering spin polarimetry for high detection efficiencies. Samples are irradiated with fourth harmonic photons generated from a cavity-dumped Ti:sapphire laser that provides high photon flux in a narrow bandwidth, with a pulse timing structure ideally matched to the needs of the TOF spectrometer. The overall efficiency of the combined system results in near-E{sub F} spin-resolved ARPES measurements with an unprecedented combination of energy resolution and acquisition speed. This allows high-resolution spin measurements with a large number of data points spanning multiple dimensions of interest (energy, momentum, photon polarization, etc.) and thus enables experiments not otherwise possible. The system is demonstrated with spin-resolved energy and momentum mapping of the L-gap Au(111) surface states, a prototypical Rashba system. The successful integration of the spectrometer with the pulsed laser system demonstrates its potential for simultaneous spin- and time-resolved ARPES with pump-probe based measurements.

  2. Time-resolved holography

    NASA Astrophysics Data System (ADS)

    Rebane, A.; Feinberg, Jack

    1991-05-01

    IN a conventional hologram, a photographic film records the interference pattern of monochromatic light, scattered from the object to be imaged, with a reference beam of unscattered light. Illumination of the developed film with a replica of the reference beam then creates a virtual image of the original object. Here we show how a molecular resonance can be used to record an interference pattern between light signals that arrive at different times, and with this technique create a hologram with time resolution. Using a timed reference pulse as a Might shutter', we can record holographic images selectively, according to the time taken by light travelling from the object to the hologram. We use this method to image an object behind a semi-opaque screen, and indicate how a similar method could be used to inspect objects embedded in a dense scattering medium. Ultimately, this technique might be applied to the medical imaging of tumours.

  3. A photoelectron-photoion coincidence imaging apparatus for femtosecond time-resolved molecular dynamics with electron time-of-flight resolution of {sigma}=18 ps and energy resolution {delta}E/E=3.5%

    SciTech Connect

    Vredenborg, Arno; Roeterdink, Wim G.; Janssen, Maurice H. M.

    2008-06-15

    We report on the construction and performance of a novel photoelectron-photoion coincidence machine in our laboratory in Amsterdam to measure the full three-dimensional momentum distribution of correlated electrons and ions in femtosecond time-resolved molecular beam experiments. We implemented sets of open electron and ion lenses to time stretch and velocity map the charged particles. Time switched voltages are operated on the particle lenses to enable optimal electric field strengths for velocity map focusing conditions of electrons and ions separately. The position and time sensitive detectors employ microchannel plates (MCPs) in front of delay line detectors. A special effort was made to obtain the time-of-flight (TOF) of the electrons at high temporal resolution using small pore (5 {mu}m) MCPs and implementing fast timing electronics. We measured the TOF distribution of the electrons under our typical coincidence field strengths with a temporal resolution down to {sigma}=18 ps. We observed that our electron coincidence detector has a timing resolution better than {sigma}=16 ps, which is mainly determined by the residual transit time spread of the MCPs. The typical electron energy resolution appears to be nearly laser bandwidth limited with a relative resolution of {delta}E{sub FWHM}/E=3.5% for electrons with kinetic energy near 2 eV. The mass resolution of the ion detector for ions measured in coincidence with electrons is about {delta}m{sub FWHM}/m=1/4150. The velocity map focusing of our extended source volume of particles, due to the overlap of the molecular beam with the laser beams, results in a parent ion spot on our detector focused down to {sigma}=115 {mu}m.

  4. Invited Article: Micron resolution spatially resolved measurement of heat capacity using dual-frequency time-domain thermoreflectance

    NASA Astrophysics Data System (ADS)

    Wei, Changdong; Zheng, Xuan; Cahill, David G.; Zhao, Ji-Cheng

    2013-07-01

    A pump-probe photothermal technique - dual-frequency time-domain thermoreflectance - was developed for measuring heat capacity with a spatial resolution on the order of 10 μm. The method was validated by measuring several common materials with known heat capacity. Rapid measurement of composition-phase-property relationships was demonstrated on Ti-TiSi2 and Ni-Zr diffusion couples; experimental values of heat capacity of the intermetallic compounds in these diffusion couples were compared with literature values and CALPHAD (CALculation of PHAse Diagram) calculations. The combination of this method and diffusion multiples provides an efficient way to generate thermodynamic data for CALPHAD modeling and database construction. The limitation of this method in measuring low thermal diffusivity materials is also discussed.

  5. Invited article: micron resolution spatially resolved measurement of heat capacity using dual-frequency time-domain thermoreflectance.

    PubMed

    Wei, Changdong; Zheng, Xuan; Cahill, David G; Zhao, Ji-Cheng

    2013-07-01

    A pump-probe photothermal technique - dual-frequency time-domain thermoreflectance - was developed for measuring heat capacity with a spatial resolution on the order of 10 μm. The method was validated by measuring several common materials with known heat capacity. Rapid measurement of composition-phase-property relationships was demonstrated on Ti-TiSi2 and Ni-Zr diffusion couples; experimental values of heat capacity of the intermetallic compounds in these diffusion couples were compared with literature values and CALPHAD (CALculation of PHAse Diagram) calculations. The combination of this method and diffusion multiples provides an efficient way to generate thermodynamic data for CALPHAD modeling and database construction. The limitation of this method in measuring low thermal diffusivity materials is also discussed. PMID:23902037

  6. High temporal and spatial resolution 3D time-resolved contrast-enhanced magnetic resonance angiography of the hands and feet.

    PubMed

    Haider, Clifton R; Riederer, Stephen J; Borisch, Eric A; Glockner, James F; Grimm, Roger C; Hulshizer, Thomas C; Macedo, Thanila A; Mostardi, Petrice M; Rossman, Phillip J; Vrtiska, Terri J; Young, Phillip M

    2011-07-01

    Methods are described for generating 3D time-resolved contrast-enhanced magnetic resonance (MR) angiograms of the hands and feet. Given targeted spatial resolution and frame times, it is shown that acceleration of about one order of magnitude or more is necessary. This is obtained by a combination of 2D sensitivity encoding (SENSE) and homodyne (HD) acceleration methods. Image update times from 3.4-6.8 seconds are provided in conjunction with view sharing. Modular receiver coil arrays are described which can be designed to the targeted vascular region. Images representative of the technique are generated in the vasculature of the hands and feet in volunteers and in patient studies. PMID:21698702

  7. 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.

  8. TIME-RESOLVED VIBRATIONAL SPECTROSCOPY

    SciTech Connect

    Andrei Tokmakoff, MIT; Paul Champion, Northeastern University; Edwin J. Heilweil, NIST; Keith A. Nelson, MIT; Larry Ziegler, Boston University

    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 five of 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.

  9. 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.

  10. Time-resolved molecular imaging

    NASA Astrophysics Data System (ADS)

    Xu, Junliang; Blaga, Cosmin I.; Agostini, Pierre; DiMauro, Louis F.

    2016-06-01

    Time-resolved molecular imaging is a frontier of ultrafast optical science and physical chemistry. In this article, we review present and future key spectroscopic and microscopic techniques for ultrafast imaging of molecular dynamics and show their differences and connections. The advent of femtosecond lasers and free electron x-ray lasers bring us closer to this goal, which eventually will extend our knowledge about molecular dynamics to the attosecond time domain.

  11. Characterization of plant materials by pyrolysis-field ionization mass spectrometry: high-resolution mass spectrometry, time-resolved high-resolution mass spectrometry, and Curie-point pyrolysis-gas chromatography/mass spectrometry of spruce needles

    SciTech Connect

    Schulten, H.F.; Simmleit, N.; Mueller, R.

    1989-02-01

    In the course of a forest damage research project spruce needles are analyzed, without pretreatment except drying and milling, by in-source pyrolysis-field ionization mass spectrometry. The mass signals are assigned by using high-resolution mass measurements and thermal degradation products identified by Curie-point pyrolysis-gas chromatography. It is demonstrated that the thermal degradation products characterize the main chemical constituents of spruce needs such as polysaccharides and lignin. Furthermore, thermostable constituents such as lipids, steroids, and flavons are detected. The thermal degradation process is studied by temperature-programmed microfurnace pyrolysis in combination with time-resolved high-resolution mass spectrometry. The integrated interpretation of results achieved by the presented methods can be applied for the universal characterization of complex and in particular nonsoluble, polydisperse biological and geochemical materials.

  12. Ultrafast Time-Resolved Photoelectric Emission.

    PubMed

    Juffmann, Thomas; Klopfer, Brannon B; Skulason, Gunnar E; Kealhofer, Catherine; Xiao, Fan; Foreman, Seth M; Kasevich, Mark A

    2015-12-31

    The emission times of laser-triggered electrons from a sharp tungsten tip are directly characterized under ultrafast, near-infrared laser excitation at Keldysh parameters of 6.6<γ<19.1. Emission delays up to 10 fs are observed, which are inferred from the energy gain of photoelectrons emitted into a synchronously driven microwave cavity. Few femtosecond timing resolution is achieved in a configuration capable of measuring timing shifts up to 55 ps. The technique can also be used to measure the microwave phase inside the cavity with a precision below 70 fs upon the energy resolved detection of a single electron. PMID:26764997

  13. Resolution-Tunable Angle-Resolved X-ray Imaging

    SciTech Connect

    Hirano, Keiichi

    2004-05-12

    A resolution-tunable double-crystal device was successfully applied to angle-resolved x-ray imaging. The angular resolution of a Si (220) double-crystal analyzer was tuned between 0.5'' and 2.3'' through the offset angle at {lambda} = 0.0733nm. The throughput of the analyzer was higher than 90%. The angle-resolved images of a spider were recorded on nuclear emulsion plates at various angular resolutions. It was clearly observed that the quality of the angle-resolved image varies with the angular resolution of the analyzer.

  14. Flip-flop resolving time test circuit

    NASA Technical Reports Server (NTRS)

    Rosenberger, F.; Chaney, T. J.

    1982-01-01

    Integrated circuit (IC) flip-flop resolving time parameters are measured by wafer probing, without need of dicing or bonding, throught the incorporation of test structures on an IC together with the flip-flop to be measured. Several delays that are fabricated as part of the test circuit, including a voltage-controlled delay with a resolution of a few picosecs, are calibrated as part of the test procedure by integrating them into, and out of, the delay path of a ring oscillator. Each of the delay values is calculated by subtracting the period of the ring oscillator with the delay omitted from the period with the delay included. The delay measurement technique is sufficiently general for other applications. The technique is illustrated for the case of the flip-flop parameters of a 5-micron feature size NMOS circuit.

  15. Atomic Resolution Mapping of the Excited-State Electronic Structure of Cu2O with Time-Resolved X-Ray Absorption Spectroscopy

    SciTech Connect

    Hillyard, Patrick B.; Kuchibhatla, Satyanarayana V N T; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, Ponnusamy; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Gaffney, Kelly J.

    2009-09-29

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that that the conduction band and valence band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  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 PAGESBeta

    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.; et al

    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. Atomic resolution mapping of the excited-state electronic structure of Cu2O with time-resolved x-ray absorption spectroscopy

    SciTech Connect

    Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, Nils; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.

    2010-05-02

    We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.

  18. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array

    NASA Astrophysics Data System (ADS)

    King, R. B.; Agnew, C. E.; O’Connell, B. F.; Prise, K. M.; Hounsell, A. R.; McGarry, C. K.

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS® SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5 mm were

  19. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array.

    PubMed

    King, R B; Agnew, C E; O'Connell, B F; Prise, K M; Hounsell, A R; McGarry, C K

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS(®) SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5

  20. Pro-resolving lipid mediators are leads for resolution physiology.

    PubMed

    Serhan, Charles N

    2014-06-01

    Advances in our understanding of the mechanisms that bring about the resolution of acute inflammation have uncovered a new genus of pro-resolving lipid mediators that include the lipoxin, resolvin, protectin and maresin families, collectively called specialized pro-resolving mediators. Synthetic versions of these mediators have potent bioactions when administered in vivo. In animal experiments, the mediators evoke anti-inflammatory and novel pro-resolving mechanisms, and enhance microbial clearance. Although they have been identified in inflammation resolution, specialized pro-resolving mediators are conserved structures that also function in host defence, pain, organ protection and tissue remodelling. This Review covers the mechanisms of specialized pro-resolving mediators and omega-3 essential fatty acid pathways that could help us to understand their physiological functions. PMID:24899309

  1. Time-Resolved Quantitative Measurement of OH HO2 and CH2O in Fuel Oxidation Reactions by High Resolution IR Absorption Spectroscopy.

    SciTech Connect

    Huang, Haifeng; Rotavera, Brandon; Taatjes, Craig A.

    2014-08-01

    Combined with a Herriott-type multi-pass slow flow reactor, high-resolution differential direct absorption spectroscopy has been used to probe, in situ and quantitatively, hydroxyl (OH), hydroperoxy (HO 2 ) and formaldehyde (CH 2 O) molecules in fuel oxidation reactions in the reactor, with a time resolution of about 1 micro-second. While OH and CH 2 O are probed in the mid-infrared (MIR) region near 2870nm and 3574nm respectively, HO 2 can be probed in both regions: near-infrared (NIR) at 1509nm and MIR at 2870nm. Typical sensitivities are on the order of 10 10 - 10 11 molecule cm -3 for OH at 2870nm, 10 11 molecule cm -3 for HO 2 at 1509nm, and 10 11 molecule cm -3 for CH 2 O at 3574nm. Measurements of multiple important intermediates (OH and HO 2 ) and product (CH 2 O) facilitate to understand and further validate chemical mechanisms of fuel oxidation chemistry.

  2. Protein-ligand interactions probed by time-resolved crystallography

    SciTech Connect

    Schmidt, M.; Ihee, H.; Pahl, R.; Srajer, V.

    2005-03-09

    Time-resolved (TR) crystallography is a unique method for determining the structures of intermediates in biomolecular reactions. The technique reached its mature stage with the development of the powerful third-generation synchrotron X-ray sources, and the advances in data processing and analysis of time-resolved Laue crystallographic data. A time resolution of 100 ps has been achieved and relatively small structural changes can be detected even from only partial reaction initiation. The remaining challenge facing the application of this technique to a broad range of biological systems is to find an efficient and rapid, system-specific method for the reaction initiation in the crystal. Other frontiers for the technique involve the continued improvement in time resolution and further advances in methods for determining intermediate structures and reaction mechanisms. The time-resolved technique, combined with trapping methods and computational approaches, holds the promise for a complete structure-based description of biomolecular reactions.

  3. 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.

  4. 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.

  5. Time-resolved protein crystallography.

    PubMed Central

    Johnson, L. N.

    1992-01-01

    Advances in synchrotron radiation technology have allowed exposure times from protein crystals of the order of milliseconds to be used routinely, and in exceptional circumstances exposure times of 100 ps have been obtained. However, many data sets take seconds to record because of the slow time scale of film change or crystal reorientation or translation when more than one exposure is required. This problem has been addressed by Amemiya et al. (1989). There has been considerable progress in methods to initiate reactions in protein crystals, especially the development of photolabile caged compounds but also temperature jump, pH jump, and diffusion. Although flash lamps deliver pulses of 100 mJ/ms, often several pulses are required to release sufficient product, and reaction initiation can take several seconds. Laser illumination can provide more powerful input, but the laser must be accommodated within the restricted space at the synchrotron station. The requirement to maintain synchrony among the molecules in the crystal lattice as the reaction proceeds and to ensure that the lifetime of intermediates is longer than data collection rates emphasizes the need for chemical characterization of the reaction under study. As Ringe advocated in the studies with chymotrypsin, it may be more profitable to devise conditions under which certain intermediates along the reaction pathway accumulate in the crystal and to record these in a series of discrete steps rather than continuous monitoring of the reaction. The Laue method is limited to those proteins that give well-ordered crystals and problems of transient disorder on initiation of reaction and problems of radiation damage need to be overcome or avoided by suitable experimental protocols.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1303743

  6. Complete momentum and energy resolved TOF electron spectrometerfor time-resolved photoemission spectroscopy

    SciTech Connect

    Hussain, Zahid; Lebedev, G.; Tremsin, A.; Siegmund, O.; Chen, Y.; Shen, Z.X.; Hussain, Z.

    2007-08-12

    Over the last decade, high-resolution Angle-Resolved Photoemission Spectroscopy (ARPES) has emerged as a tool of choice for studying the electronic structure of solids, in particular, strongly correlated complex materials such as cuprate superconductors. In this paper we present the design of a novel time-of-flight based electron analyzer with capability of 2D in momentum space (kx and ky) and all energies (calculated from time of flight) in the third dimension. This analyzer will utilize an improved version of a 2D delay linedetector capable of imaging with<35 mm (700x700 pixels) spatial resolution and better than 120 ps FWHM timing resolution. Electron optics concepts and optimization procedure are considered for achieving an energy resolution less than 1 meV and an angular resolution better than 0.11.

  7. Time-resolved spectroscopic techniques in laser medicine

    NASA Astrophysics Data System (ADS)

    Ortega-Martínez, Roberto; Román-Moreno, Carlos J.; Rodríguez-Rosales, Antonio A.

    2000-10-01

    Spectroscopic lasers techniques are very useful for the detection and treatment of cancer and removing atherosclerotic plaque. Photobiology and photochemical studies, with the new generation of lasers high resolution time-resolved optical tomography is mentioned. A brief review of some of these applications is discussed and a partial list of recent references is given.

  8. Time-resolved photoelectron spectroscopy of liquids

    NASA Astrophysics Data System (ADS)

    Buchner, Franziska; Lübcke, Andrea; Heine, Nadja; Schultz, Thomas

    2010-11-01

    We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 μm thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition making femtosecond time-resolved experiments feasible. We describe the experimental setup, a detailed spectrometer characterization based on the spectroscopy of nitric oxide in the gas phase, and results from femtosecond time-resolved experiments on sodium iodide solutions. The latter experiments reveal the formation and evolution of the solvated electron and we characterize two distinct spectral components corresponding to initially thermalized and unthermalized solvated electrons. The absence of dark states in photoionization, the direct measurement of electron binding energies, and the ability to resolve dynamic processes on the femtosecond time scale make time-resolved photoelectron spectroscopy from the liquid jet a very promising method for the characterization of photochemical processes in liquids.

  9. Time-resolved photoelectron spectroscopy of liquids.

    PubMed

    Buchner, Franziska; Lübcke, Andrea; Heine, Nadja; Schultz, Thomas

    2010-11-01

    We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 μm thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition making femtosecond time-resolved experiments feasible. We describe the experimental setup, a detailed spectrometer characterization based on the spectroscopy of nitric oxide in the gas phase, and results from femtosecond time-resolved experiments on sodium iodide solutions. The latter experiments reveal the formation and evolution of the solvated electron and we characterize two distinct spectral components corresponding to initially thermalized and unthermalized solvated electrons. The absence of dark states in photoionization, the direct measurement of electron binding energies, and the ability to resolve dynamic processes on the femtosecond time scale make time-resolved photoelectron spectroscopy from the liquid jet a very promising method for the characterization of photochemical processes in liquids. PMID:21133461

  10. Photon-number-resolving detector with 10 bits of resolution

    SciTech Connect

    Jiang, Leaf A.; Dauler, Eric A.; Chang, Joshua T

    2007-06-15

    A photon-number-resolving detector with single-photon resolution is described and demonstrated. It has 10 bits of resolution, does not require cryogenic cooling, and is sensitive to near ir wavelengths. This performance is achieved by flood illuminating a 32x32 element In{sub x}Ga{sub 1-x}AsP Geiger-mode avalanche photodiode array that has an integrated counter and digital readout circuit behind each pixel.

  11. Photon-number-resolving detector with 10bits of resolution

    NASA Astrophysics Data System (ADS)

    Jiang, Leaf A.; Dauler, Eric A.; Chang, Joshua T.

    2007-06-01

    A photon-number-resolving detector with single-photon resolution is described and demonstrated. It has 10bits of resolution, does not require cryogenic cooling, and is sensitive to near ir wavelengths. This performance is achieved by flood illuminating a 32×32 element InxGa1-xAsP Geiger-mode avalanche photodiode array that has an integrated counter and digital readout circuit behind each pixel.

  12. Time resolved thermal lens in edible oils

    NASA Astrophysics Data System (ADS)

    Albuquerque, T. A. S.; Pedreira, P. R. B.; Medina, A. N.; Pereira, J. R. D.; Bento, A. C.; Baesso, M. L.

    2003-01-01

    In this work time resolved thermal lens spectrometry is applied to investigate the optical properties of the following edible oils: soya, sunflower, canola, and corn oils. The experiments were performed at room temperature using the mode mismatched thermal lens configuration. The results showed that when the time resolved procedure is adopted the technique can be applied to investigate the photosensitivity of edible oils. Soya oil presented a stronger photochemical reaction as compared to the other investigated samples. This observation may be relevant for future studies evaluating edible oils storage conditions and also may contribute to a better understanding of the physical and chemical properties of this important foodstuff.

  13. A time-resolved image sensor for tubeless streak cameras

    NASA Astrophysics Data System (ADS)

    Yasutomi, Keita; Han, SangMan; Seo, Min-Woong; Takasawa, Taishi; Kagawa, Keiichiro; Kawahito, Shoji

    2014-03-01

    This paper presents a time-resolved CMOS image sensor with draining-only modulation (DOM) pixels for tube-less streak cameras. Although the conventional streak camera has high time resolution, the device requires high voltage and bulky system due to the structure with a vacuum tube. The proposed time-resolved imager with a simple optics realize a streak camera without any vacuum tubes. The proposed image sensor has DOM pixels, a delay-based pulse generator, and a readout circuitry. The delay-based pulse generator in combination with an in-pixel logic allows us to create and to provide a short gating clock to the pixel array. A prototype time-resolved CMOS image sensor with the proposed pixel is designed and implemented using 0.11um CMOS image sensor technology. The image array has 30(Vertical) x 128(Memory length) pixels with the pixel pitch of 22.4um. .

  14. 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.

  15. Deflection evaluation using time-resolved radiography

    SciTech Connect

    Fry, D.A.; Lucero, J.P.

    1990-01-01

    Time-resolved radiography is the creation of an x-ray image for which both the start-exposure and stop-exposure times are known with respect to the event under study. The combination of image and timing are used to derive information about the event. We have applied time-resolved radiography to evaluate motions of explosive-driven events. In the particular application discussed here, our intent is to measure maximum deflections of the components involved. Exposures are made during the time just before to just after the event of interest occurs. A smear or blur of motion out to its furthest extent is recorded on the image. Comparison of the dynamic images with static images allows deflection measurements to be made. 2 figs.

  16. Time-resolved crystallography using the Hadamard Transform

    PubMed Central

    Yorke, Briony A.; Beddard, Godfrey S.; Owen, Robin L.; Pearson, Arwen R.

    2014-01-01

    A new method for performing time-resolved X-ray crystallographic experiments based on the Hadamard Transform is proposed and demonstrated. The time-resolution is defined by the underlying periodicity of the probe pulse sequence and the signal to noise is greatly improved compared to the fastest experiments depending on a single pulse. This approach is general and equally applicable to any spectroscopic or imaging measurement where the probe can be encoded. PMID:25282611

  17. 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.

  18. Optimal arrangements of fiber optic probes to enhance the spatial resolution in depth for 3D reflectance diffuse optical tomography with time-resolved measurements performed with fast-gated single-photon avalanche diodes

    NASA Astrophysics Data System (ADS)

    Puszka, Agathe; Di Sieno, Laura; Dalla Mora, Alberto; Pifferi, Antonio; Contini, Davide; Boso, Gianluca; Tosi, Alberto; Hervé, Lionel; Planat-Chrétien, Anne; Koenig, Anne; Dinten, Jean-Marc

    2014-02-01

    Fiber optic probes with a width limited to a few centimeters can enable diffuse optical tomography (DOT) in intern organs like the prostate or facilitate the measurements on extern organs like the breast or the brain. We have recently shown on 2D tomographic images that time-resolved measurements with a large dynamic range obtained with fast-gated single-photon avalanche diodes (SPADs) could push forward the imaged depth range in a diffusive medium at short source-detector separation compared with conventional non-gated approaches. In this work, we confirm these performances with the first 3D tomographic images reconstructed with such a setup and processed with the Mellin- Laplace transform. More precisely, we investigate the performance of hand-held probes with short interfiber distances in terms of spatial resolution and specifically demonstrate the interest of having a compact probe design featuring small source-detector separations. We compare the spatial resolution obtained with two probes having the same design but different scale factors, the first one featuring only interfiber distances of 15 mm and the second one, 10 mm. We evaluate experimentally the spatial resolution obtained with each probe on the setup with fast-gated SPADs for optical phantoms featuring two absorbing inclusions positioned at different depths and conclude on the potential of short source-detector separations for DOT.

  19. Baltimore Supersite: Highly time- and size-resolved concentrations of urban PM 2.5 and its constituents for resolution of sources and immune responses

    NASA Astrophysics Data System (ADS)

    Ondov, J. M.; Buckley, T. J.; Hopke, P. K.; Ogulei, D.; Parlange, M. B.; Rogge, W. F.; Squibb, K. S.; Johnston, M. V.; Wexler, A. S.

    Protection of public health from the effects of air particulate matter (PM) requires measurements and methods that assess the PM chemical constituents, physical properties, and their sources. Sampling was conducted at three sites in the Baltimore area: a source-oriented (industrial) area in south Baltimore (FMC site), and two receptor area sites (Clifton Park and Ponca Street). FMC measurements were made for the initial 1-month of the project; Clifton measurements lasted for about 2 months, while measurements at Ponca Street lasted for about 9.5 months. Pollutant samples were collected at intervals ranging from 5 min to 1 h using semi-continuous monitors for PM 2.5 mass, sulfate, nitrate, elemental and organic carbon, particle number size distributions (10-20,000 nm), CO, NO x, O 3, 11 metals, and mass spectra of individual particles, throughout the project. In addition to standard meteorological measurements, a 3D-sonic anemometer and a LIDAR system were operated during selected periods as were a rotating drum impactor with 3- to 6-h resolution and a filter/PUF sampler for 3-h measurements of organic compounds. Standard speciation and FRM mass measurements were also made. This report describes the types of measurements that were made at the various sites of the Baltimore Supersite program as well as presents the summary statistics for some of the PM measurements that have been made. The measurements of aerosol mass, major components, and size distribution data for the three sites are compared. Results show comparable PM concentrations at Ponca Street and Clifton Park. Increased variability was observed at Ponca Street.

  20. Time-resolved multiple probe spectroscopy

    SciTech Connect

    Greetham, G. M.; Sole, D.; Clark, I. P.; Parker, A. W.; Pollard, M. R.; Towrie, M.

    2012-10-15

    Time-resolved multiple probe spectroscopy combines optical, electronic, and data acquisition capabilities to enable measurement of picosecond to millisecond time-resolved spectra within a single experiment, using a single activation pulse. This technology enables a wide range of dynamic processes to be studied on a single laser and sample system. The technique includes a 1 kHz pump, 10 kHz probe flash photolysis-like mode of acquisition (pump-probe-probe-probe, etc.), increasing the amount of information from each experiment. We demonstrate the capability of the instrument by measuring the photolysis of tungsten hexacarbonyl (W(CO){sub 6}) monitored by IR absorption spectroscopy, following picosecond vibrational cooling of product formation through to slower bimolecular diffusion reactions on the microsecond time scale.

  1. Time-resolved circularly polarized protein phosphorescence.

    PubMed Central

    Schauerte, J A; Steel, D G; Gafni, A

    1992-01-01

    The existence of circular polarization in room-temperature protein phosphorescence is demonstrated, and time-resolved circularly polarized phosphorescence (TR-CPP) is used to characterize unique tryptophan environments in multitryptophan proteins. Circularly polarized luminescence studies provide information regarding the excited state chirality of a lumiphore which can be used to extract sensitive structural information. It is shown by time resolving the circular polarization that it is possible to correlate the excited state chirality with unique decay components in a multiexponential phosphorescence decay profile. The present study presents a concurrent analysis of room-temperature time-resolved phosphorescence and TR-CPP of bacterial glucose-6-phosphate dehydrogenase as well as those of horse liver alcohol dehydrogenase. Only one of the two tryptophan residues per subunit of dimeric alcohol dehydrogenase is believed to phosphorescence, while the dimeric glucose-6-phosphate dehydrogenase has eight tryptophan residues per subunit and shows a corresponding complexity in its phosphorescence decay profile. The anisotropy factor [g(em) = delta I/(Itotal/2); delta I = Ileft circular-Iright circular] for alcohol dehydrogenase is time independent, suggesting a unique excited state chirality. The phosphorescence decay of glucose-6-phosphate dehydrogenase can be well fitted with four exponential terms of 4, 23, 76, and 142 msec, and the TR-CPP of this enzyme shows a strong time dependence that can be resolved into four individual time-independent anisotropy factors of -4.0, -2.1, +6.5, and +6.9 (x10(-3)), each respectively associated with one of the four lifetime components. These results demonstrate how the use of TR-CPP can facilitate the study of proteins with multiple lumiphores. PMID:1438204

  2. The Resolution Code of Acute Inflammation: Novel Pro-Resolving Lipid Mediators in Resolution

    PubMed Central

    Serhan, Charles N.; Chiang, Nan; Dalli, Jesmond

    2015-01-01

    Studies into the mechanisms in resolution of self-limited inflammation and acute reperfusion injury have uncovered a new genus of pro-resolving lipid mediators coined specialized pro-resolving mediators (SPM) including lipoxins, resolvins, protectins and maresins that are each temporally produced by resolving-exudates with distinct actions for return to homeostasis. SPM evoke potent anti-inflammatory and novel pro-resolving mechanisms as well as enhance microbial clearance. While born in inflammation-resolution, SPM are conserved structures with functions discovered in microbial defense, pain, organ protection and tissue regeneration, wound healing, cancer, reproduction, and neurobiology-cognition. This review covers these SPM mechanisms and other new omega-3 PUFA pathways that open their path for functions in resolution physiology. PMID:25857211

  3. Time-resolved air monitoring using Fourier absorption spectroscopy

    SciTech Connect

    Biermann, H.W.

    1995-12-31

    Two categories where spectroscopic techniques excel are the capabilities to perform air analyses in situ and to obtain data at very high time resolutions. Because of these features, the Department of Pesticide Regulation augmented its extensive air monitoring capabilities with a Fourier transform infrared (FTIR) spectrometer using open-path optical systems for time resolved ambient air monitoring. A description of the instrumentation and the data analysis procedures will be presented based on two data sets obtained with this FTIR system. In one case, a 100 m folded optical path was used to measure methyl bromide concentrations after fumigation in a warehouse with a time resolution of 15 min and a detection limit of 0.2 ppm. And trying to assess the capability of this FTIR spectrometer to determine flux, water vapor concentrations were measured with a four-meter path length at a time resolution of 0.6 seconds.

  4. 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

    Scanning tunnelling microscopy has revolutionized our ability to image, manipulate, and investigate solid surfaces on the length scale of individual atoms and molecules. The strength of this technique lies in its imaging capabilities, since for many scientists 'seeing is believing'. However, scanning tunnelling microscopy also suffers from a severe limitation, namely its poor time resolution. Recording a scanning tunnelling microscopy image typically requires a few tens of seconds for a conventional scanning tunnelling microscope to a fraction of a second for a specially designed fast scanning tunnelling microscope. Designing and building such a fast scanning tunnelling microscope is a formidable task in itself and therefore, only a limited number of these microscopes have been built [1]. There is, however, another alternative route to significantly enhance the time resolution of a scanning tunnelling microscope. In this alternative method, the tunnelling current is measured as a function of time with the feedback loop switched off. The time resolution is determined by the bandwidth of the IV converter rather than the cut-off frequency of the feedback electronics. Such an approach requires a stable microscope and goes, of course, at the expense of spatial information. In this issue, we have collected a set of papers that gives an impression of the current status of this rapidly emerging field [2]. One of the very first attempts to extract information from tunnel current fluctuations was reported by Tringides' group in the mid-1990s [3]. They showed that the collective diffusion coefficient can be extracted from the autocorrelation of the time-dependent tunnelling current fluctuations produced by atom motion in and out of the tunnelling junction. In general, current-time traces provide direct information on switching/conformation rates and distributions of residence times. In the case where these processes are thermally induced it is rather straightforward to map

  5. High resolution time interval meter

    DOEpatents

    Martin, A.D.

    1986-05-09

    Method and apparatus are provided for measuring the time interval between two events to a higher resolution than reliability available from conventional circuits and component. An internal clock pulse is provided at a frequency compatible with conventional component operating frequencies for reliable operation. Lumped constant delay circuits are provided for generating outputs at delay intervals corresponding to the desired high resolution. An initiation START pulse is input to generate first high resolution data. A termination STOP pulse is input to generate second high resolution data. Internal counters count at the low frequency internal clock pulse rate between the START and STOP pulses. The first and second high resolution data are logically combined to directly provide high resolution data to one counter and correct the count in the low resolution counter to obtain a high resolution time interval measurement.

  6. Ocean wavenumber estimation from wave-resolving time series imagery

    USGS Publications Warehouse

    Plant, N.G.; Holland, K.T.; Haller, M.C.

    2008-01-01

    We review several approaches that have been used to estimate ocean surface gravity wavenumbers from wave-resolving remotely sensed image sequences. Two fundamentally different approaches that utilize these data exist. A power spectral density approach identifies wavenumbers where image intensity variance is maximized. Alternatively, a cross-spectral correlation approach identifies wavenumbers where intensity coherence is maximized. We develop a solution to the latter approach based on a tomographic analysis that utilizes a nonlinear inverse method. The solution is tolerant to noise and other forms of sampling deficiency and can be applied to arbitrary sampling patterns, as well as to full-frame imagery. The solution includes error predictions that can be used for data retrieval quality control and for evaluating sample designs. A quantitative analysis of the intrinsic resolution of the method indicates that the cross-spectral correlation fitting improves resolution by a factor of about ten times as compared to the power spectral density fitting approach. The resolution analysis also provides a rule of thumb for nearshore bathymetry retrievals-short-scale cross-shore patterns may be resolved if they are about ten times longer than the average water depth over the pattern. This guidance can be applied to sample design to constrain both the sensor array (image resolution) and the analysis array (tomographic resolution). ?? 2008 IEEE.

  7. 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.

  8. Recent advances in 3D time-resolved contrast-enhanced MR angiography.

    PubMed

    Riederer, Stephen J; Haider, Clifton R; Borisch, Eric A; Weavers, Paul T; Young, Phillip M

    2015-07-01

    Contrast-enhanced magnetic resonance angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3-4 mm spatial resolution with acquisition times in the 30-second range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution 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, ∼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

  9. 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

  10. Time-resolved orbital angular momentum spectroscopy

    SciTech Connect

    Noyan, Mehmet A.; Kikkawa, James M.

    2015-07-20

    We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

  11. 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

  12. Time-Resolved Imaging Of Transient Plasma

    SciTech Connect

    Chan, L. S.; Wong, C. S.; Yap, S. L.; Singh, J.; Ahmad, Z.

    2009-07-07

    Pulsed capillary discharge is a compact device that is used to perform fast electrical discharge that is used to produce transient plasma. In this work, a more economical imaging technique is developed in order to study the dynamics of the plasma that is formed in a capillary tube. The imaging system consists of two main devices, a four-frame gated micro-channel plate and a Nikon Coolpix5000 camera. The time-resolved imaging that we have performed in order to study the dynamics of the plasma that is formed in a 10 mm long and 1 mm diameter low pressure capillary tube is reported. The images obtained portrayed that the plasma is heated up when the magnitude of the current is around the maximum and cools down when the current magnitude is around the minimum.

  13. Receptor modeling for multiple time resolved species: The Baltimore supersite

    NASA Astrophysics Data System (ADS)

    Ogulei, David; Hopke, Philip K.; Zhou, Liming; Paatero, Pentti; Park, Seung Shik; Ondov, John M.

    A number of advances have been made toward solving receptor modeling problems using advanced factor analysis methods. Most recently, a factor analysis method has been developed for source apportionment utilizing aerosol compositional data with varying temporal resolution. The data used in that study had time resolutions ranged from 10 min to 1 h. In this work, this expanded model is tested using a data set from the Ponca Street site of the Baltimore supersite with time resolutions ranging from 30 min to 24 h. The nature of this data set implies that traditional eigenvalue-based methods cannot adequately resolve source factors for the atmospheric situation under consideration. Also, valuable temporal information is lost if one averaged or interpolated data in an attempt to produce a data set of the identical time resolution. Each data point has been used in its original time schedule and the source contributions were averaged to correspond to the specific sampling time interval. A weighting coefficient, w24, was incorporated in the modeling equations in order to improve data fitting for the 24-h data in the model. A total of nine sources were resolved: oil-fired power plant (2%), diesel emissions (1%), secondary sulfate (23%), coal-fired power plant (3%), incinerator (9%), steel plant (12%), aged sea salt (1%), secondary nitrate (23%), and spark-ignition emissions (26%). The results showed the very strong influence of the adjacent interstate highways I-95 and I-895 as well as the tunnel toll booths located to the south of the sampling site. Most of the sulfate observed was found to be associated with distant coal-fired power plants situated in the heavily industrialized midwestern parts of the United States. The contribution of the steel plant (<10 miles, 141°SE) to the observed PM concentrations (12%) was also significant.

  14. Time-resolved doubly bent crystal x-ray spectrometer

    SciTech Connect

    Hockaday, M.P.; Wilke, M.D.; Blake, R.L.; Vaninetti, J.; Gray, N.T.; Nedrow, P.T.

    1988-08-01

    X-ray spectroscopy is an essential tool in high-temperature plasma research. We describe a time-resolved x-ray spectrometer suitable for measuring spectra in harsh environments common to many very high-energy density laboratory plasma sources. The spectrometer consisted of a doubly curved Si(111) crystal diffraction element, a WL-1201 (ZnO:Ga) phosphor, a coherent fiber-optic array, and two visible streak cameras. The spectrometer design described here has a minimum time resolution of 1.3 ns with 2.8-eV spectral resolution over a 200-eV-wide bandpass in the 6--7-keV region of the spectrum. Complete system spectral throughput calibrations were done at the Cornell High Energy Synchrotron (CHESS). Details of the design and calibration results are presented.

  15. Time-resolved doubly bent crystal x-ray spectrometer

    SciTech Connect

    Hockaday, M.P.; Wilke, M.D.; Blake, R.L.; Vaninetti, J.; Gray, N.T.; Nedrow, P.T.

    1988-01-01

    X-ray spectroscopy is an essential tool in high temperature plasma research. We describe a time-resolved x-ray spectrometer suitable for measuring spectra in harsh environments common to many very high energy density laboratory plasma sources. The spectrometer consisted of a doubly curved Si(111) crystal diffraction element, a WL-1201 (ZnO:Ga) phosphor, a coherent fiber optic array, and two visible streak cameras. The spectrometer design described here has a minimum time resolution of 1.3 ns with 2.8 eV spectral resolution over a 200 eV wide bandpass in the 6-7 keV region of the spectrum. Complete system spectral throughput calibrations were done at the Cornell High Energy Synchrotron (CHESS). Details of the design and calibration results are presented. 5 refs., 5 figs.

  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. A compact electron gun for time-resolved electron diffraction

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  18. Resolving the percentage of component terrains within single resolution elements

    NASA Technical Reports Server (NTRS)

    Marsh, S. E.; Switzer, P.; Kowalik, W. S.; Lyon, R. J. P.

    1980-01-01

    An approximate maximum likelihood technique employing a widely available discriminant analysis program is discussed that has been developed for resolving the percentage of component terrains within single resolution elements. The method uses all four channels of Landsat data simultaneously and does not require prior knowledge of the percentage of components in mixed pixels. It was tested in five cases that were chosen to represent mixtures of outcrop, soil and vegetation which would typically be encountered in geologic studies with Landsat data. For all five cases, the method proved to be superior to single band weighted average and linear regression techniques and permitted an estimate of the total area occupied by component terrains to within plus or minus 6% of the true area covered. Its major drawback is a consistent overestimation of the pixel component percent of the darker materials (vegetation) and an underestimation of the pixel component percent of the brighter materials (sand).

  19. Time-resolved digital holographic microscopy of laser-induced forward transfer process

    PubMed Central

    Ma, H.; Venugopalan, V.

    2014-01-01

    We develop a method for time-resolved digital holographic microscopy to obtain time-resolved 3-D deformation measurements of laser induced forward transfer (LIFT) processes. We demonstrate nanometer axial resolution and nanosecond temporal resolution of our method which is suitable for measuring dynamic morphological changes in LIFT target materials. Such measurements provide insight into the early dynamics of the LIFT process and a means to examine the effect of laser and material parameters on LIFT process dynamics. PMID:24748724

  20. Time-resolved digital holographic microscopy of laser-induced forward transfer process.

    PubMed

    Ma, H; Venugopalan, V

    2014-03-01

    We develop a method for time-resolved digital holographic microscopy to obtain time-resolved 3-D deformation measurements of laser induced forward transfer (LIFT) processes. We demonstrate nanometer axial resolution and nanosecond temporal resolution of our method which is suitable for measuring dynamic morphological changes in LIFT target materials. Such measurements provide insight into the early dynamics of the LIFT process and a means to examine the effect of laser and material parameters on LIFT process dynamics. PMID:24748724

  1. 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

  2. Time resolved x-ray detection

    NASA Astrophysics Data System (ADS)

    Rentzepis, Peter M.

    1994-04-01

    The goal of the project was to design, develop and construct an x-ray detector with high sensitivity and picosecond time resolution. This was achieved. A Ford Aerospace Charged Coupled Device, CCD, was utilized as the x-ray sensitive material around which the design and construction of the picosecond x-ray detector was built. This device has now become a commercial product sold, among other companies, by Photometrics Inc., and Princeton Research Inc. In addition we designed and built the first picosecond x-ray system. This system was utilized for the first ever picosecond x-ray diffraction experiments. The picosecond x-ray system was utilized in the oxidative fuel cell project to measure the decomposition of methanol and the change of the structure of its platinum catalyst. Another direct product of the work is the publication of 36 papers, in major scientific journals, and two patents.

  3. Diagnosis of meningioma by time-resolved fluorescence spectroscopy.

    PubMed

    Butte, Pramod V; Pikul, Brian K; Hever, Aviv; Yong, William H; Black, Keith L; Marcu, Laura

    2005-01-01

    We investigate the use of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) as an adjunctive tool for the intraoperative rapid evaluation of tumor specimens and delineation of tumor from surrounding normal tissue. Tissue autofluorescence is induced with a pulsed nitrogen laser (337 nm, 1.2 ns) and the intensity decay profiles are recorded in the 370 to 500 nm spectral range with a fast digitizer (0.2 ns resolution). Experiments are conducted on excised specimens (meningioma, dura mater, cerebral cortex) from 26 patients (97 sites). Spectral intensities and time-dependent parameters derived from the time-resolved spectra of each site are used for tissue characterization. A linear discriminant analysis algorithm is used for tissue classification. Our results reveal that meningioma is characterized by unique fluorescence characteristics that enable discrimination of tumor from normal tissue with high sensitivity (>89%) and specificity (100%). The accuracy of classification is found to increase (92.8% cases in the training set and 91.8% in the cross-validated set correctly classified) when parameters from both the spectral and the time domain are used for discrimination. Our findings establish the feasibility of using TR-LIFS as a tool for the identification of meningiomas and enables further development of real-time diagnostic tools for analyzing surgical tissue specimens of meningioma or other brain tumors. PMID:16409091

  4. Time-resolved NMR studies of RNA folding.

    PubMed

    Fürtig, Boris; Buck, Janina; Manoharan, Vijayalaxmi; Bermel, Wolfgang; Jäschke, Andres; Wenter, Philipp; Pitsch, Stefan; Schwalbe, Harald

    The application of real-time NMR experiments to the study of RNA folding, as reviewed in this article, is relatively new. For many RNA folding events, current investigations suggest that the time scales are in the second to minute regime. In addition, the initial investigations suggest that different folding rates are observed for one structural transition may be due to the hierarchical folding units of RNA. Many of the experiments developed in the field of NMR of protein folding cannot directly be transferred to RNA: hydrogen exchange experiments outside the spectrometer cannot be applied since the intrinsic exchange rates are too fast in RNA, relaxation dispersion experiments on the other require faster structural transitions than those observed in RNA. On the other hand, information derived from time-resolved NMR experiments, namely the acquisition of native chemical shifts, can be readily interpreted in light of formation of a single long-range hydrogen bonding interaction. Together with mutational data that can readily be obtained for RNA and new ligation technologies that enhance site resolution even further, time-resolved NMR may become a powerful tool to decipher RNA folding. Such understanding will be of importance to understand the functions of coding and non-coding RNAs in cells. PMID:17595685

  5. Photo-magnetic imaging: resolving optical contrast at MRI resolution

    NASA Astrophysics Data System (ADS)

    Lin, Yuting; Gao, Hao; Thayer, David; Luk, Alex L.; Gulsen, Gultekin

    2013-06-01

    In this paper, we establish the mathematical framework of a novel imaging technique, namely photo-magnetic imaging (PMI). PMI uses a laser to illuminate biological tissues and measure the induced temperature variations using magnetic resonance imaging (MRI). PMI overcomes the limitation of conventional optical imaging and allows imaging of the optical contrast at MRI spatial resolution. The image reconstruction for PMI, using a finite-element-based algorithm with an iterative approach, is presented in this paper. The quantitative accuracy of PMI is investigated for various inclusion sizes, depths and absorption values. Then, a comparison between conventional diffuse optical tomography (DOT) and PMI is carried out to illustrate the superior performance of PMI. An example is presented showing that two 2 mm diameter inclusions embedded 4.5 mm deep and located side by side in a 25 mm diameter circular geometry medium are recovered as a single 6 mm diameter object with DOT. However, these two objects are not only effectively resolved with PMI, but their true concentrations are also recovered successfully.

  6. High resolution time interval counter

    DOEpatents

    Condreva, Kenneth J.

    1994-01-01

    A high resolution counter circuit measures the time interval between the occurrence of an initial and a subsequent electrical pulse to two nanoseconds resolution using an eight megahertz clock. The circuit includes a main counter for receiving electrical pulses and generating a binary word--a measure of the number of eight megahertz clock pulses occurring between the signals. A pair of first and second pulse stretchers receive the signal and generate a pair of output signals whose widths are approximately sixty-four times the time between the receipt of the signals by the respective pulse stretchers and the receipt by the respective pulse stretchers of a second subsequent clock pulse. Output signals are thereafter supplied to a pair of start and stop counters operable to generate a pair of binary output words representative of the measure of the width of the pulses to a resolution of two nanoseconds. Errors associated with the pulse stretchers are corrected by providing calibration data to both stretcher circuits, and recording start and stop counter values. Stretched initial and subsequent signals are combined with autocalibration data and supplied to an arithmetic logic unit to determine the time interval in nanoseconds between the pair of electrical pulses being measured.

  7. High resolution time interval counter

    DOEpatents

    Condreva, K.J.

    1994-07-26

    A high resolution counter circuit measures the time interval between the occurrence of an initial and a subsequent electrical pulse to two nanoseconds resolution using an eight megahertz clock. The circuit includes a main counter for receiving electrical pulses and generating a binary word--a measure of the number of eight megahertz clock pulses occurring between the signals. A pair of first and second pulse stretchers receive the signal and generate a pair of output signals whose widths are approximately sixty-four times the time between the receipt of the signals by the respective pulse stretchers and the receipt by the respective pulse stretchers of a second subsequent clock pulse. Output signals are thereafter supplied to a pair of start and stop counters operable to generate a pair of binary output words representative of the measure of the width of the pulses to a resolution of two nanoseconds. Errors associated with the pulse stretchers are corrected by providing calibration data to both stretcher circuits, and recording start and stop counter values. Stretched initial and subsequent signals are combined with autocalibration data and supplied to an arithmetic logic unit to determine the time interval in nanoseconds between the pair of electrical pulses being measured. 3 figs.

  8. Modern electron microscopy resolved in space, energy and time

    NASA Astrophysics Data System (ADS)

    Carbone, F.

    2011-06-01

    Recent pioneering experiments combining ultrafast lasers with electron-based technology demonstrated the possibility to obtain real-time information about chemical bonds and their dynamics during reactions and phase transformation. These techniques have been successfully applied to several states of matter including gases, liquids, solids and biological samples showing a unique versatility thanks to the high sensitivity of electrons to tiny amounts of material and their low radiation damage. A very powerful tool, the time-resolved Transmission Electron Microscope (TEM), is capable of delivering information on the structure of ordered and disordered matter through diffraction and imaging, with a spatial resolution down to the atomic limit (10-10 m); the same apparatus can distinguish dynamical phenomena happening on the time-scales between fs and ms, with a dynamic range of 12 orders of magnitude. At the same time, spectroscopic information can be obtained from the loss of kinetic energy of electrons interacting with specimens in the range of interband transitions and plasmons in solids, or charge transfers in molecules, all the way up to the atomic core levels with the same time-resolution. In this contribution, we focus on the recent advances in fs Electron Energy Loss Spectroscopy (FEELS), discussing the main results and their implications for future studies.

  9. Analytical model of coincidence resolving time in TOF-PET.

    PubMed

    Wieczorek, H; Thon, A; Dey, T; Khanin, V; Rodnyi, P

    2016-06-21

    The coincidence resolving time (CRT) of scintillation detectors is the parameter determining noise reduction in time-of-flight PET. We derive an analytical CRT model based on the statistical distribution of photons for two different prototype scintillators. For the first one, characterized by single exponential decay, CRT is proportional to the decay time and inversely proportional to the number of photons, with a square root dependence on the trigger level. For the second scintillator prototype, characterized by exponential rise and decay, CRT is proportional to the square root of the product of rise time and decay time divided by the doubled number of photons, and it is nearly independent of the trigger level. This theory is verified by measurements of scintillation time constants, light yield and CRT on scintillator sticks. Trapping effects are taken into account by defining an effective decay time. We show that in terms of signal-to-noise ratio, CRT is as important as patient dose, imaging time or PET system sensitivity. The noise reduction effect of better timing resolution is verified and visualized by Monte Carlo simulation of a NEMA image quality phantom. PMID:27245232

  10. Analytical model of coincidence resolving time in TOF-PET

    NASA Astrophysics Data System (ADS)

    Wieczorek, H.; Thon, A.; Dey, T.; Khanin, V.; Rodnyi, P.

    2016-06-01

    The coincidence resolving time (CRT) of scintillation detectors is the parameter determining noise reduction in time-of-flight PET. We derive an analytical CRT model based on the statistical distribution of photons for two different prototype scintillators. For the first one, characterized by single exponential decay, CRT is proportional to the decay time and inversely proportional to the number of photons, with a square root dependence on the trigger level. For the second scintillator prototype, characterized by exponential rise and decay, CRT is proportional to the square root of the product of rise time and decay time divided by the doubled number of photons, and it is nearly independent of the trigger level. This theory is verified by measurements of scintillation time constants, light yield and CRT on scintillator sticks. Trapping effects are taken into account by defining an effective decay time. We show that in terms of signal-to-noise ratio, CRT is as important as patient dose, imaging time or PET system sensitivity. The noise reduction effect of better timing resolution is verified and visualized by Monte Carlo simulation of a NEMA image quality phantom.

  11. Time-resolved photoelectron spectroscopy using synchrotron radiation time structure.

    PubMed

    Bergeard, N; Silly, M G; Krizmancic, D; Chauvet, C; Guzzo, M; Ricaud, J P; Izquierdo, M; Stebel, L; Pittana, P; Sergo, R; Cautero, G; Dufour, G; Rochet, F; Sirotti, F

    2011-03-01

    Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station. PMID:21335912

  12. FXR LIA Optimization - Time-resolved OTR Emittance Measurement

    SciTech Connect

    Jacob, J; Ong, M; Wargo, P; LeSage, G

    2005-07-21

    The Flash X-Ray Radiography (FXR) facility at Lawrence Livermore National Laboratory utilizes a high current, long pulse linear induction accelerator to produce high doses of x-ray radiation. Accurate characterization of the transverse beam emittance is required in order to facilitate accelerator modeling and tuning efforts and, ultimately, to optimize the final focus spot size, yielding higher resolution radiographs. In addition to conventional magnet scan, pepper-pot, and multiple screen techniques, optical transition radiation (OTR) has been proven as a useful emittance measurement diagnostic and is particularly well suited to the FXR accelerator. We shall discuss the time-resolved emittance characterization of an induction linac electron beam using OTR, and we will present our experimental apparatus and analysis software. We shall also develop the theoretical background of beam emittance and transition radiation.

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

    PubMed

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

    2015-01-01

    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. PMID:25638074

  14. 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

  15. 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. PMID:23787661

  16. The High Time Resolution Universe

    NASA Astrophysics Data System (ADS)

    Bailes, Matthew; Possenti, Andrea; Johnston, Simon; Kramer, Michael; Burgay, Marta; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; van Straten, Willem; Stappers, Benjamin; Bates, Samuel

    2008-04-01

    The Parkes multibeam surveys heralded a new era in pulsar surveys, more than doubling the number of pulsars known. However, at high time resolution, they were severely limited by the analogue backend system, which limited the volume of sky they could effectively survey to just the local 2-3 kpc. Here we propose to use a new digital backend coupled with Australia's most powerful (16 Tflop) supercomputing cluster to conduct three ambitious surveys for millisecond and relativistic pulsars with the Parkes telescope. We hope to discover over 200 new millisecond and relativistic pulsars that will define the recycled pulsar period distribution, supply pulsars for the timing array and aid in our understanding of binary evolution.

  17. Versatile portable fluorometer for time-resolved luminescence analysis

    NASA Astrophysics Data System (ADS)

    Chen, Guoying

    2005-06-01

    A robust, filter-based portable fluorometer was designed, prototyped, and tested for time-resolved luminescence (TRL) analysis. Its flexible optical design allows interchangeable configurations to support three measurement modes: liquid-phase TRL using a sample cuvette, solid-matrix TRL using a sorbent strip, and evanescent-field TRL using a quartz-rod waveguide. A xenon flashlamp is used as the light source and a photomultiplier tube (PMT) as the photodetector. A gating technique was implemented to overcome PMT saturation by the intense xenon lamp flash, therefore higher gains can be set to measure weak luminescence signals. The TRL signal is digitized at a 4μs time resolution and a 12bit amplitude resolution. Individual flashes were monitored by a photodiode and its current was integrated to compensate for source light fluctuation. Using tetracycline as a model analyte, a 0.025ppb limit of detection (LOD) with a typical 2% relative standard deviation, and a 3 orders of magnitude (0.5-300ppb) linear dynamic range (r2=0.9996) were achieved.

  18. Time Resolved Spectroscopy of Eclipsing Polars

    NASA Astrophysics Data System (ADS)

    Barrett, Paul

    2005-09-01

    No changes have been made since the last annual progress report was submitted in conjunction with a unilateral NCX. Dr. Barrett was affected by an STScI Reduction in Force (RIF). He is now employed by the Johns Hopkins University and plans to continue his research there. No expenses have been charged to this grant, however the FUSE data for the eclipsing polar V1432 Aql has been received and processed using CALFWSE v3.0.6. The resulting summed spectrum has been used for a preliminary analysis of the interstellar absorption towards V1432 Aql. We find a hydrogen column density of less than 1.5e21 cm^-2. We have used this result in the paper "X-Ray Emission and Optical Polarization of V1432 Aquilae: An Asynchronous Polar" to fix the hydrogen column density in the soft (<0.5 keV) X-ray band when analyzing the XMM-Newton spectra of this polar. This has enabled us to find an accurate temperature for the blackbody component of 88+/-2 eV, which is significantly higher than that of other polars (20 - 40 eV). We hope to complete our analysis of the phase-resolved emission line spectra of V1432 Aql and to prepare the results for publication in a refereed journal. We hope to begin work on this star within the next few months.

  19. Time Resolved Spectroscopy of Eclipsing Polars

    NASA Technical Reports Server (NTRS)

    Barrett, Paul

    2005-01-01

    No changes have been made since the last annual progress report was submitted in conjunction with a unilateral NCX. Dr. Barrett was affected by an STScI Reduction in Force (RIF). He is now employed by the Johns Hopkins University and plans to continue his research there. No expenses have been charged to this grant, however the FUSE data for the eclipsing polar V1432 Aql has been received and processed using CALFWSE v3.0.6. The resulting summed spectrum has been used for a preliminary analysis of the interstellar absorption towards V1432 Aql. We find a hydrogen column density of less than 1.5e21 cm^-2. We have used this result in the paper "X-Ray Emission and Optical Polarization of V1432 Aquilae: An Asynchronous Polar" to fix the hydrogen column density in the soft (<0.5 keV) X-ray band when analyzing the XMM-Newton spectra of this polar. This has enabled us to find an accurate temperature for the blackbody component of 88+/-2 eV, which is significantly higher than that of other polars (20 - 40 eV). We hope to complete our analysis of the phase-resolved emission line spectra of V1432 Aql and to prepare the results for publication in a refereed journal. We hope to begin work on this star within the next few months.

  20. Tunneling Ionization Time Resolved by Backpropagation

    NASA Astrophysics Data System (ADS)

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan-Michael

    2016-07-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular, the fraction of electrons that has tunneled out. We find that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion.

  1. Tunneling Ionization Time Resolved by Backpropagation.

    PubMed

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan-Michael

    2016-07-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular, the fraction of electrons that has tunneled out. We find that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion. PMID:27447504

  2. Tunneling ionization time-resolved by backpropagation

    NASA Astrophysics Data System (ADS)

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan M.; Max-Planck-Institut für Physik komplexer Systeme Team

    2016-05-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular the fraction of electrons that has tunneled out. We find, that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion. This work was supported by Alexander von Humboldt Foundation.

  3. 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. PMID:25725848

  4. TRIPP: Time Resolved Imaging Photometry Package

    NASA Astrophysics Data System (ADS)

    Geckeler, Ralf D.; Schuh, Sonja; Dreizler, Stefan; Deetjen, Jochen; Gleissner, Thomas; Risse, Patrick; Rauch, Thomas; Göhler, Eckart; Hügelmeyer, Simon; Husser, Tim-Oliver; Israel, Holger; Benlloch-Garcia, Sara; Pottschmidt, Katja; Wilms, Jörn

    2014-05-01

    Written in IDL, TRIPP performs CCD time series reduction and analysis. It provides an on-line check of the incoming frames, performs relative aperture photometry and provides a set of time series tools, such as calculation of periodograms including false alarm probability determination, epoc folding, sinus fitting, and light curve simulations.

  5. Kerr and Faraday microscope for space- and time-resolved studies

    NASA Astrophysics Data System (ADS)

    Schmitt, Oliver; Steil, Daniel; Alebrand, Sabine; Ganss, Fabian; Hehn, Michel; Mangin, Stéphane; Albrecht, Manfred; Mathias, Stefan; Cinchetti, Mirko; Aeschlimann, Martin

    2014-09-01

    We present a multi-purpose scanning magneto-optical microscope for the investigation of magnetic thin films. The setup can be used for both static and time-resolved (pump-probe) measurements. It is moreover compatible with samples with arbitrary magnetic anisotropy, as it allows Kerr measurements in polar and longitudinal geometry as well as in transmission (Faraday geometry). We demonstrate that the microscope can be used in the following modi: (i) static imaging mode (in polar Kerr and Faraday geometry) with a spatial resolution of 1.7 μm; (ii) time-resolved mode (polar Kerr geometry) with a temporal resolution of 300 femtoseconds.

  6. 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.

  7. Time-resolved and spectral-resolved optical imaging to study brain hemodynamics in songbirds

    NASA Astrophysics Data System (ADS)

    Mottin, Stéphane; Montcel, Bruno; Guillet de Chatellus, Hugues; Ramstein, Stéphane; Vignal, Clémentine; Mathevon, Nicolas

    2011-07-01

    Contrary to the intense debate about brain oxygen dynamics and its uncoupling in mammals, very little is known in birds. In zebra finches, picosecond optical tomography (POT) with a white laser and a streak camera can measure in vivo oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb) concentration changes following physiological stimulation (familiar calls and songs). POT demonstrated sufficient sub-micromolar sensitivity to resolve the fast changes in hippocampus and auditory forebrain areas with 250 μm resolution. The time-course is composed of (i) an early 2s-long event with a significant decrease in Hb and HbO2, respectively -0.7 μMoles/L and -0.9 μMoles/L (ii) a subsequent increase in blood oxygen availability with a plateau of HbO2 (+0.3μMoles/L) and (iii) pronounced vasodilatation events immediately following the end of the stimulus. One of the findings of our work is the direct link between the blood oxygen level-dependent (BOLD) signals previously published in birds and our results. Furthermore, the early vasoconstriction event and post-stimulus ringing seem to be more pronounced in birds than in mammals. These results in bird, a tachymetabolic vertebrate with a long lifespan, can potentially yield new insights for example in brain aging.

  8. Sensing cell metabolism by time-resolved autofluorescence.

    PubMed

    Wu, Yicong; Zheng, Wei; Qu, Jianan Y

    2006-11-01

    We built a time-resolved confocal fluorescence spectroscopy system equipped with the multichannel time-correlated single-photon-counting technique. The instrument provides a unique approach to study the fluorescence sensing of cell metabolism via analysis of the wavelength- and time-resolved intracellular autofluorescence. The experiments on monolayered cell cultures show that with UV excitation at 365 nm the time-resolved autofluorescence decays, dominated by free-bound reduced nicotinamide adenine dinucleotide signals, are sensitive indicators for cell metabolism. However, the sensitivity decreases with the increase of excitation wavelength possibly due to the interference from free-bound flavin adenine dinucleotide fluorescence. The results demonstrate that time-resolved autofluorescence can be potentially used as an important contrast mechanism to detect epithelial precancer. PMID:17041655

  9. Sensing cell metabolism by time-resolved autofluorescence

    NASA Astrophysics Data System (ADS)

    Wu, Yicong; Zheng, Wei; Qu, Jianan Y.

    2006-11-01

    We built a time-resolved confocal fluorescence spectroscopy system equipped with the multichannel time-correlated single-photon-counting technique. The instrument provides a unique approach to study the fluorescence sensing of cell metabolism via analysis of the wavelength- and time-resolved intracellular autofluorescence. The experiments on monolayered cell cultures show that with UV excitation at 365 nm the time-resolved autofluorescence decays, dominated by free-bound reduced nicotinamide adenine dinucleotide signals, are sensitive indicators for cell metabolism. However, the sensitivity decreases with the increase of excitation wavelength possibly due to the interference from free-bound flavin adenine dinucleotide fluorescence. The results demonstrate that time-resolved autofluorescence can be potentially used as an important contrast mechanism to detect epithelial precancer.

  10. Thymine Dimer Formation probed by Time-Resolved Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Schreier, Wolfgang J.; Schrader, Tobias E.; Roller, Florian O.; Gilch, Peter; Zinth, Wolfgang; Kohler, Bern

    Cyclobutane pyrimidine dimers are the major photoproducts formed when DNA is exposed to UV light. Femtosecond time-resolved vibrational spectroscopy reveals that thymine dimers are formed in thymidine oligonucleotides in an ultrafast photoreaction.

  11. Time resolved spin Seebeck effect experiments

    SciTech Connect

    Roschewsky, Niklas Schreier, Michael; Schade, Felix; Ganzhorn, Kathrin; Meyer, Sibylle; Geprägs, Stephan; Kamra, Akashdeep; Huebl, Hans; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2014-05-19

    In this Letter, we present the results of transient thermopower experiments, performed at room temperature on yttrium iron garnet/platinum bilayers. Upon application of a time-varying thermal gradient, we observe a characteristic low-pass frequency response of the ensuing thermopower voltage with cutoff frequencies of up to 37 MHz. We interpret our results in terms of the spin Seebeck effect, and argue that small wavevector magnons are of minor importance for the spin Seebeck effect in our thin film hybrid structures.

  12. Time-resolved structural studies of protein reaction dynamics: a smorgasbord of X-ray approaches

    SciTech Connect

    Westenhoff, Sebastian; Nazarenko, Elena; Malmerberg, Erik; Davidsson, Jan; Katona, Gergely; Neutze, Richard

    2010-03-01

    Time-resolved structural studies of proteins have undergone several significant developments during the last decade. Recent developments using time-resolved X-ray methods, such as time-resolved Laue diffraction, low-temperature intermediate trapping, time-resolved wide-angle X-ray scattering and time-resolved X-ray absorption spectroscopy, are reviewed. Proteins undergo conformational changes during their biological function. As such, a high-resolution structure of a protein’s resting conformation provides a starting point for elucidating its reaction mechanism, but provides no direct information concerning the protein’s conformational dynamics. Several X-ray methods have been developed to elucidate those conformational changes that occur during a protein’s reaction, including time-resolved Laue diffraction and intermediate trapping studies on three-dimensional protein crystals, and time-resolved wide-angle X-ray scattering and X-ray absorption studies on proteins in the solution phase. This review emphasizes the scope and limitations of these complementary experimental approaches when seeking to understand protein conformational dynamics. These methods are illustrated using a limited set of examples including myoglobin and haemoglobin in complex with carbon monoxide, the simple light-driven proton pump bacteriorhodopsin, and the superoxide scavenger superoxide reductase. In conclusion, likely future developments of these methods at synchrotron X-ray sources and the potential impact of emerging X-ray free-electron laser facilities are speculated upon.

  13. 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

  14. Millifluidics for chemical synthesis and time-resolved mechanistic studies.

    PubMed

    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

  15. Pro-Resolving Lipid Mediators (SPMs) and Their Actions in Regulating miRNA in Novel Resolution Circuits in Inflammation

    PubMed Central

    Recchiuti, Antonio; Serhan, Charles N.

    2012-01-01

    Unresolved inflammation is associated with several widely occurring diseases such as arthritis, periodontal diseases, cancer, and atherosclerosis. Endogenous mechanisms that curtail excessive inflammation and prompt its timely resolution are of considerable interest. In recent years, previously unrecognized chemical mediators derived from polyunsaturated fatty acids were identified that control the acute inflammatory response by activating local resolution programs. Among these are the so-called specialized pro-resolving lipid mediators (SPMs) that include lipoxins (LX), resolvins (Rv), protectins (PD), and maresins (MaR), because they are enzymatically biosynthesized during resolution of self-limited inflammation. They each possess distinct chemical structures and regulate cellular pathways by their ability to activate pro-resolving G-protein coupled receptors (GPCRs) in a stereospecific manner. For instance, RvD1 controls several miRNAs of interest in self-limited acute inflammation that counter-regulate the mediators and proteins that are involved in inflammation. Here, we overview some of the biosynthesis and mechanisms of SPM actions with focus on the recently reported miR involved in their pro-resolving responses that underscore their beneficial actions in the regulation of acute inflammation and its timely resolution. The elucidation of these mechanisms operating in vivo to keep acute inflammation within physiologic boundaries as well as stimulate resolution have opened resolution pharmacology and many new opportunities to target inflammation-related human pathologies via activating resolution mechanisms. PMID:23093949

  16. 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.

  17. 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.

  18. 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.

  19. Chopper system for time resolved experiments with synchrotron radiation

    SciTech Connect

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

    2009-01-15

    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 {mu}s) 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.

  20. Femtosecond time-resolved MeV electron diffraction

    DOE PAGESBeta

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; et al

    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

  1. Fielding of a time-resolved tomographic diagnostic

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

    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, and adverse conditions will be discussed.

  2. 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.

  3. 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.

  4. Time-to-digital converter card for multichannel time-resolved single-photon counting applications

    NASA Astrophysics Data System (ADS)

    Tamborini, Davide; Portaluppi, Davide; Tisa, Simone; Tosi, Alberto

    2015-03-01

    We present a high performance Time-to-Digital Converter (TDC) card that provides 10 ps timing resolution and 20 ps (rms) timing precision with a programmable full-scale-range from 160 ns to 10 μs. Differential Non-Linearity (DNL) is better than 1.3% LSB (rms) and Integral Non-Linearity (INL) is 5 ps rms. Thanks to the low power consumption (400 mW) and the compact size (78 mm x 28 mm x 10 mm), this card is the building block for developing compact multichannel time-resolved instrumentation for Time-Correlated Single-Photon Counting (TCSPC). The TDC-card outputs the time measurement results together with the rates of START and STOP signals and the number of valid TDC conversions. These additional information are needed by many TCSPC-based applications, such as: Fluorescence Lifetime Imaging (FLIM), Time-of-Flight (TOF) ranging measurements, time-resolved Positron Emission Tomography (PET), single-molecule spectroscopy, Fluorescence Correlation Spectroscopy (FCS), Diffuse Optical Tomography (DOT), Optical Time-Domain Reflectometry (OTDR), quantum optics, etc.

  5. Time-resolved heme protein intermediates

    NASA Astrophysics Data System (ADS)

    Rousseau, Denis

    2005-03-01

    To determine the enzymatic mechanisms of heme proteins, it is necessary to identify the intermediates along the catalytic pathway and measure the times of their formation and decay. Resonance Raman scattering spectra are especially powerful for obtaining such information as the electronic structure of the heme group and the nature of the ligand coordinated to the heme iron atom may be monitored. The oxygen intermediates of two physiologically important enzymes will be presented. Nitric oxide synthase (NOS) uses oxygen to convert arginine to NO and citrulline; and cytochrome c oxidase (CcO) reduces oxygen to water to support oxidative phosphorylation. The fate or the oxygen in each of these enzymes has been followed by resonance Raman scattering. In NOS the oxygen is slowly converted to an activated species that then reacts fast, whereas in CcO the oxygen is rapidly converted to a reactive species that subsequently reacts slowly. The properties of the intermediates and the origin of the differences between these enzymes will be discussed.

  6. 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.

  7. Time-Resolved X-Ray Triple-Crystal Diffractometry Probing Dynamic Strain in Semiconductors

    SciTech Connect

    Hayashi, Yujiro; Tanaka, Yoshihito; Kirimura, Tomoyuki; Ishikawa, Tetsuya; Tsukuda, Noboru; Kuramoto, Eiichi

    2007-01-19

    Intense synchrotron radiation sources have enabled us to combine time-resolved measurements and triple-crystal diffractometry. The time-resolved triple-crystal diffractometry (TRTCD) determines the time-dependent dilational and shear components of deformation tensor, separately. The TRTCD experiments have been performed at a long undulator beamline of SPring-8. The time-resolved measurement system using pump-probe technique and a fast multi-channel scaler covers a full range of milliseconds with a time-resolution of several tens of picoseconds. The TRTCD with wide time range was applied to the dynamic strain measurement for semiconductor wafers irradiated by a femtosecond pulse laser. We observed a dilational component of acoustic echo pulses to analyze the time-varying pulse shape due to propagation. The lattice motion in the successively induced flexural standing wave has also been observed through a shear component.

  8. Time-resolved far-infrared experiments at the National Synchrotron Light Source. Final report

    SciTech Connect

    Tanner, D.B.; Reitze, D.H.; Carr, G.L.

    1999-10-12

    A facility for time-resolved infrared and far-infrared spectroscopy has been built and commissioned at the National Synchrotron Light Source. This facility permits the study of time dependent phenomena over a frequency range from 2-8000cm{sup {minus}1} (0.25 meV-1 eV). Temporal resolution is approximately 200 psec and time dependent phenomena in the time range out to 100 nsec can be investigated.

  9. Nodal Quasiparticle Meltdown in Ultra-High Resolution Pump-Probe Angle-Resolved Photoemission

    SciTech Connect

    Graf, Jeff; Jozwiak, Chris; Smallwood, Chris L.; Eisaki, H.; Kaindl, Robert A.; Lee, Dung-Hai; Lanzara, Alessandra

    2011-06-03

    High-T{sub c} cuprate superconductors are characterized by a strong momentum-dependent anisotropy between the low energy excitations along the Brillouin zone diagonal (nodal direction) and those along the Brillouin zone face (antinodal direction). Most obvious is the d-wave superconducting gap, with the largest magnitude found in the antinodal direction and no gap in the nodal direction. Additionally, while antin- odal quasiparticle excitations appear only below T{sub c}, superconductivity is thought to be indifferent to nodal excitations as they are regarded robust and insensitive to T{sub c}. Here we reveal an unexpected tie between nodal quasiparticles and superconductivity using high resolution time- and angle-resolved photoemission on optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} . We observe a suppression of the nodal quasiparticle spectral weight following pump laser excitation and measure its recovery dynamics. This suppression is dramatically enhanced in the superconducting state. These results reduce the nodal-antinodal dichotomy and challenge the conventional view of nodal excitation neutrality in superconductivity. The electronic structures of high-Tc cuprates are strongly momentum-dependent. This is one reason why the momentum-resolved technique of angle-resolved photoemission spectroscopy (ARPES) has been a central tool in the field of high-temperature superconductivity. For example, coherent low energy excitations with momenta near the Brillouin zone face, or antinodal quasiparticles (QPs), are only observed below T{sub c} and have been linked to superfluid density. They have therefore been the primary focus of ARPES studies. In contrast, nodal QPs, with momenta along the Brillouin zone diagonal, have received less attention and are usually regarded as largely immune to the superconducting transition because they seem insensitive to perturbations such as disorder, doping, isotope exchange, charge ordering, and temperature. Clearly

  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. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector

    SciTech Connect

    Souma, S.; Sugawara, K.; Takayama, A.; Sato, T.; Takahashi, T.

    2010-09-15

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90 deg. electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states.

  12. Novel Pro-Resolving Lipid Mediators in Inflammation Are Leads for Resolution Physiology

    PubMed Central

    Serhan, Charles N.

    2014-01-01

    Preface Advances on mechanisms in resolution of acute inflammation uncovered a new genus of pro-resolving lipid mediators that include separate families of molecules: lipoxins, resolvins, protectins and maresins, collectively coined specialized pro-resolving mediators (SPM). Synthetic SPM possess potent bioactions when administered in vivo. In animal experiments, SPM evoke anti-inflammatory and novel pro-resolving mechanisms as well as enhance microbial clearance. While identified in inflammation-resolution, SPM are conserved structures with functions also in host defense, pain, organ protection and tissue remodeling. This review covers SPM mechanisms and new omega-3 essential fatty acid pathways that open a path for physiologic functions. PMID:24899309

  13. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector.

    PubMed

    Souma, S; Takayama, A; Sugawara, K; Sato, T; Takahashi, T

    2010-09-01

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90° electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states. PMID:20887002

  14. The 7BM beamline at the APS: a facility for time-resolved fluid dynamics measurements

    PubMed Central

    Kastengren, Alan; Powell, Christopher F.; Arms, Dohn; Dufresne, Eric M.; Gibson, Harold; Wang, Jin

    2012-01-01

    In recent years, X-ray radiography has been used to probe the internal structure of dense sprays with microsecond time resolution and a spatial resolution of 15 µm even in high-pressure environments. Recently, the 7BM beamline at the Advanced Photon Source (APS) has been commissioned to focus on the needs of X-ray spray radiography measurements. The spatial resolution and X-ray intensity at this beamline represent a significant improvement over previous time-resolved X-ray radiography measurements at the APS. PMID:22713903

  15. Spatially resolved and observer-free experimental quantification of spatial resolution in tomographic images

    SciTech Connect

    Tsekenis, S. A.; McCann, H.; Tait, N.

    2015-03-15

    We present a novel framework and experimental method for the quantification of spatial resolution of a tomography system. The framework adopts the “black box” view of an imaging system, considering only its input and output. The tomography system is locally stimulated with a step input, viz., a sharp edge. The output, viz., the reconstructed images, is analysed by Fourier decomposition of their spatial frequency components, and the local limiting spatial resolution is determined using a cut-off threshold. At no point is an observer involved in the process. The framework also includes a means of translating the quantification region in the imaging space, thus creating a spatially resolved map of objectively quantified spatial resolution. As a case-study, the framework is experimentally applied using a gaseous propane phantom measured by a well-established chemical species tomography system. A spatial resolution map consisting of 28 regions is produced. In isolated regions, the indicated performance is 4-times better than that suggested in the literature and varies by 57% across the imaging space. A mechanism based on adjacent but non-interacting beams is hypothesised to explain the observed behaviour. The mechanism suggests that, as also independently concluded by other methods, a geometrically regular beam array maintains maximum objectivity in reconstructions. We believe that the proposed framework, methodology, and findings will be of value in the design and performance evaluation of tomographic imaging arrays and systems.

  16. Observation of light diffraction by time-resolved femtosecond correlation interferometry.

    PubMed

    Zeylikovich, I; Bai, G; Alfano, R R

    1995-07-15

    We demonstrate time development of the diffraction of light waves from objects for what is to our knowledge the f irst time by using a new femtosecond correlation interferometry. This new dynamical optics method allows for the conversion of temporal information to space information with femtosecond resolution and has the potential to produce a time-resolved femtosecond movie for the visualization of light-wave propagation in space for scientific, biological, and medical applications. PMID:19862089

  17. An optimized protocol for the analysis of time-resolved elastic scattering experiments.

    PubMed

    Calabrese, Michelle A; Wagner, Norman J; Rogers, Simon A

    2016-02-28

    A deconvolution protocol is developed for obtaining material responses from time-resolved small-angle scattering data from light (SALS), X-rays (SAXS), or neutrons (SANS). Previously used methods convolve material responses with information from the procedure used to group data into discrete time intervals, known as binning. We demonstrate that enhanced signal resolution can be obtained by using methods of signal processing to analyze time-resolved scattering data. The method is illustrated for a time-resolved rheo-SANS measurement of a complex, structured surfactant solution under oscillatory shear flow. We show how the underlying material response can be clearly decoupled from the binning procedure. This method greatly reduces the experimental acquisition time, by approximately one-third for the aforementioned rheo-SANS experiment. PMID:26781708

  18. Numerical simulations of time-resolved quantum electronics

    NASA Astrophysics Data System (ADS)

    Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier

    2014-01-01

    Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects-mathematical and numerical-associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation capabilities

  19. Time resolved studies of bond activation by organometallic complexes

    SciTech Connect

    Wilkens, M 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){sub 2}L (Cp* = (CH{sub 3}){sub 5}C{sub 5}, L = PPh{sub 3}, Ph = C{sub 6}H{sub 5}) to form Cp*ML(R)(H) or of Cp*Ir(CO){sub 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. Traumatic Lateral Plantar Artery Pseudoaneurysm and the Use of Time-Resolved MR Angiography

    PubMed Central

    Chang, Anthony; Foo, Li Foong

    2010-01-01

    Vascular injury resulting in pseudoaneurysm formation in the plantar aspect of the foot is an uncommon injury after trauma. Such injuries are more often reported in the lateral plantar artery rather than the medial plantar artery, most likely because of its more superficial location. Traditional modalities in diagnosis have included ultrasound and digital subtraction angiography. We present a case of traumatic pseudoaneurysm of the lateral plantar artery following a foot laceration. Diagnosis was made by the use of high-resolution, time-resolved contrast-enhanced 3D magnetic resonance angiography, also referred to as “TRICKS” (time-resolved imaging of contrast kinetics). This technique provided high spatial resolution for the arterial anatomy as well as temporal resolution which allowed better delineation of the hemodynamic characteristics of the pseudoaneurysm. Electronic supplementary material The online version of this article (doi:10.1007/s11420-010-9170-3) contains supplementary material, which is available to authorized users. PMID:21886538

  1. An innovative Yb-based ultrafast deep ultraviolet source for time-resolved photoemission experiments

    SciTech Connect

    Boschini, F.; Hedayat, H.; Dallera, C.; Cerullo, G.; Farinello, P.; Manzoni, C.; Carpene, E.; Magrez, A.; Berger, H.

    2014-12-15

    Time- and angle-resolved photoemission spectroscopy is a powerful technique to study ultrafast electronic dynamics in solids. Here, an innovative optical setup based on a 100-kHz Yb laser source is presented. Exploiting non-collinear optical parametric amplification and sum-frequency generation, ultrashort pump (hν = 1.82 eV) and ultraviolet probe (hν = 6.05 eV) pulses are generated. Overall temporal and instrumental energy resolutions of, respectively, 85 fs and 50 meV are obtained. Time- and angle-resolved measurements on BiTeI semiconductor are presented to show the capabilities of the setup.

  2. Coherence time measurements using a single detector with variable time resolution.

    PubMed

    Assmann, Marc; Bayer, Manfred

    2012-07-15

    We present a simple technique for measuring coherence times for stationary light fields using a single detector with tunable time resolution. By measuring the equal-time second-order correlation function at varying instrument response functions it is possible to determine the coherence time and also the shape of the temporal decay without the need to record time-resolved data. The technique is demonstrated for pseudothermal light. Possible applications for dynamic light scattering and photon statistics measurements are discussed. PMID:22825142

  3. Optoacoustic tomography using time-resolved interferometric detection of surface displacement.

    PubMed

    Payne, Barry P; Venugopalan, Vasan; Mikić, Bora B; Nishioka, Norman S

    2003-04-01

    We introduce a minimally invasive technique for optoacoustic imaging of turbid media using optical interferometric detection of surface displacement produced by thermoelastic stress transients. The technique exploits endogenous or exogenous optical contrast of heterogeneous tissues and the low attenuation of stress wave propagation to localize and image subsurface absorbers in optically turbid media. We present a system that utilizes a time-resolved high-resolution interferometer capable of angstrom-level displacement resolution and nanosecond temporal resolution to detect subsurface blood vessels within model tissue phantoms and a human forearm in vivo. PMID:12683854

  4. Thermalization of positronium atoms studied with time-resolved angular correlation of annihilation radiation

    NASA Astrophysics Data System (ADS)

    Takada, S.; Iwata, T.; Kawashima, K.; Saito, H.; Nagashima, Y.; Hyodo, T.

    2000-06-01

    Time dependence of the kinetic energy of positronium atoms in the free space between the grains of a pressed tablet (1 g/cm 3) of ultrafine silica powder (Cab-O-Sil EH-5) has been measured with time-resolved angular correlation of annihilation radiation (ACAR) apparatus. The apparatus has a momentum resolution of 1.29×10 -3 mc in full width at half maximum and a time resolution of 2.7 ns in full width at half maximum. It is found that the energy of positronium falls below 0.1e V in ˜10 ns after the formation.

  5. High-harmonic XUV source for time- and angle-resolved photoemission spectroscopy

    SciTech Connect

    Dakovski, Georgi L; Li, Yinwan; Durakiewicz, Tomasz; Rodriguez, George

    2009-01-01

    We present a laser-based apparatus for visible pump/XUV probe time- and angle-resolved photoemission spectroscopy (TRARPES) utilizing high-harmonic generation from a noble gas. Femtosecond temporal resolution for each selected harmonic is achieved by using a time-delay-compensated monochromator (TCM). The source has been used to obtain photoemission spectra from insulators (UO{sub 2}) and ultrafast pump/probe processes in semiconductors (GaAs).

  6. Ultrahigh-throughput single-molecule spectroscopy and spectrally resolved super-resolution microscopy.

    PubMed

    Zhang, Zhengyang; Kenny, Samuel J; Hauser, Margaret; Li, Wan; Xu, Ke

    2015-10-01

    By developing a wide-field scheme for spectral measurement and implementing photoswitching, we synchronously obtained the fluorescence spectra and positions of ∼10(6) single molecules in labeled cells in minutes, which consequently enabled spectrally resolved, 'true-color' super-resolution microscopy. The method, called spectrally resolved stochastic optical reconstruction microscopy (SR-STORM), achieved cross-talk-free three-dimensional (3D) imaging for four dyes 10 nm apart in emission spectrum. Excellent resolution was obtained for every channel, and 3D localizations of all molecules were automatically aligned within one imaging path. PMID:26280329

  7. 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. PMID:19123577

  8. Time and spectrum-resolving multiphoton correlator for 300–900 nm

    SciTech Connect

    Johnsen, Kelsey D.; Thibault, Marilyne; Jennewein, Thomas; Kolenderski, Piotr; Scarcella, Carmelo; Tosi, Alberto

    2014-10-14

    We demonstrate a single-photon sensitive spectrometer in the visible range, which allows us to perform time-resolved and multi-photon spectral correlation measurements at room temperature. It is based on a monochromator composed of two gratings, collimation optics, and an array of single photon avalanche diodes. The time resolution can reach 110 ps and the spectral resolution is 2 nm/pixel, limited by the design of the monochromator. This technique can easily be combined with commercial monochromators and can be useful for joint spectrum measurements of two photons emitted in the process of parametric down conversion, as well as time-resolved spectrum measurements in optical coherence tomography or medical physics applications.

  9. Extreme Precipitation: Resolving the Added Value of High-Resolution Physical and Statistical Modeling

    NASA Astrophysics Data System (ADS)

    Hayhoe, K.; Stoner, A. M. K.; Wang, J.; Scott-Fleming, I.; Abeysundara, S.; Kotamarthi, V. R.

    2014-12-01

    Human-induced climate change is altering the risk of many types of weather extremes, including the frequency and/or severity of heavy precipitation events. The basic science connecting global warming to more frequent heavy precipitation is relative straightforward. It is far more challenging, however, to predict how climate change will affect the magnitude and frequency of these events at the relatively fine spatial scales at which the impacts of extreme rainfall, snow storms, and flooding are typically characterized. Using a case study based on a set of geographically distributed long-term weather stations located at Dept. of Defense installations across the U.S., we explore the individual and combined contributions of high-resolution regional climate modeling (WRF), station-based statistical downscaling (ARRM), extreme value distributions (GEV), and the use of global mean temperature-based thresholds rather than time slices (an approach that is illustrated Figure 1) to resolve observed trends and narrow the envelope of projected future change. All projections and analyses are based on the CESM1-MOAR simulation driven by the higher RCP 8.5 scenario, a consistency specifically introduced into the experiment in order to better resolve the strengths and limitations of each method in understanding extreme precipitation trends. Each of these approaches provides clear added value when compared to direct output from the global climate model. We also find that the ability to refine global model output using high-resolution physical modeling, statistics, and observations can all prove useful at different geographic locations and for different parts of the distribution. However, the primary conclusion of this analysis is the utility of combining multiple physical and statistical modeling and analysis approaches when addressing issues such as extreme precipitation that occur at the tails of the distribution.

  10. Transmission mode time-reversal super-resolution imaging.

    PubMed

    Lehman, Sean K; Devaney, Anthony J

    2003-05-01

    The theory of time-reversal super-resolution imaging of point targets embedded in a reciprocal background medium [A. J. Devaney, "Super-resolution imaging using time-reversal and MUSIC," J. Acoust. Soc. Am. (to be published)] is generalized to the case where the transmitter and receiver sensor arrays need not be coincident and for cases where the background medium can be nonreciprocal. The new theory developed herein is based on the singular value decomposition of the generalized multistatic data matrix of the sensor system rather than the standard eigenvector/eigenvalue decomposition of the time-reversal matrix as was employed in the above-mentioned work and other treatments of time-reversal imaging [Prada, Thomas, and Fink, "The iterative time reversal process: Analysis of the convergence," J. Acoust. Soc. Am. 97, 62 (1995); Prada et al., "Decomposition of the time reversal operator: Detection and selective focusing on two scatterers," J. Acoust. Soc. Am. 99, 2067 (1996)]. A generalized multiple signal classification (MUSIC) algorithm is derived that allows super-resolution imaging of both well-resolved and non-well-resolved point targets from arbitrary sensor array geometries. MUSIC exploits the orthogonal nature of the scatterer and noise subspaces defined by the singular vectors of the multistatic data matrix to form scatterer images. The time-reversal/MUSIC algorithm is tested and validated in two computer simulations of offset vertical seismic profiling where the sensor sources are aligned along the earth's surface and the receiver array is aligned along a subsurface borehole. All results demonstrate the high contrast, high resolution imaging capabilities of this new algorithm combination when compared with "classical" backpropagation or field focusing. Above and beyond the application of seismo-acoustic imaging, the time-reversal super-resolution theory has applications in ocean acoustics for target location, and ultrasonic nondestructive evaluation of

  11. Watching a signaling protein function in real time via 100-ps time-resolved Laue crystallography

    SciTech Connect

    Schotte, Friedrich; Cho, Hyun Sun; Kaila, Ville R.I.; Kamikubo, Hironari; Dashdorj, Naranbaatar; Henry, Eric R.; Graber, Timothy J.; Henning, Robert; Wulff, Michael; Hummer, Gerhard; Kataoka, Mikio; Anfinrud, Philip A.

    2012-11-06

    To understand how signaling proteins function, it is necessary to know the time-ordered sequence of events that lead to the signaling state. We recently developed on the BioCARS 14-IDB beamline at the Advanced Photon Source the infrastructure required to characterize structural changes in protein crystals with near-atomic spatial resolution and 150-ps time resolution, and have used this capability to track the reversible photocycle of photoactive yellow protein (PYP) following trans-to-cis photoisomerization of its p-coumaric acid (pCA) chromophore over 10 decades of time. The first of four major intermediates characterized in this study is highly contorted, with the pCA carbonyl rotated nearly 90° out of the plane of the phenolate. A hydrogen bond between the pCA carbonyl and the Cys69 backbone constrains the chromophore in this unusual twisted conformation. Density functional theory calculations confirm that this structure is chemically plausible and corresponds to a strained cis intermediate. This unique structure is short-lived (~600 ps), has not been observed in prior cryocrystallography experiments, and is the progenitor of intermediates characterized in previous nanosecond time-resolved Laue crystallography studies. The structural transitions unveiled during the PYP photocycle include trans/cis isomerization, the breaking and making of hydrogen bonds, formation/relaxation of strain, and gated water penetration into the interior of the protein. This mechanistically detailed, near-atomic resolution description of the complete PYP photocycle provides a framework for understanding signal transduction in proteins, and for assessing and validating theoretical/computational approaches in protein biophysics.

  12. Watching a signaling protein function in real time via 100-ps time-resolved Laue crystallography

    PubMed Central

    Schotte, Friedrich; Cho, Hyun Sun; Kaila, Ville R. I.; Kamikubo, Hironari; Dashdorj, Naranbaatar; Henry, Eric R.; Graber, Timothy J.; Henning, Robert; Wulff, Michael; Hummer, Gerhard; Kataoka, Mikio; Anfinrud, Philip A.

    2012-01-01

    To understand how signaling proteins function, it is crucial to know the time-ordered sequence of events that lead to the signaling state. We recently developed on the BioCARS 14-IDB beamline at the Advanced Photon Source the infrastructure required to characterize structural changes in protein crystals with near-atomic spatial resolution and 150-ps time resolution, and have used this capability to track the reversible photocycle of photoactive yellow protein (PYP) following trans-to-cis photoisomerization of its p-coumaric acid (pCA) chromophore over 10 decades of time. The first of four major intermediates characterized in this study is highly contorted, with the pCA carbonyl rotated nearly 90° out of the plane of the phenolate. A hydrogen bond between the pCA carbonyl and the Cys69 backbone constrains the chromophore in this unusual twisted conformation. Density functional theory calculations confirm that this structure is chemically plausible and corresponds to a strained cis intermediate. This unique structure is short-lived (∼600 ps), has not been observed in prior cryocrystallography experiments, and is the progenitor of intermediates characterized in previous nanosecond time-resolved Laue crystallography studies. The structural transitions unveiled during the PYP photocycle include trans/cis isomerization, the breaking and making of hydrogen bonds, formation/relaxation of strain, and gated water penetration into the interior of the protein. This mechanistically detailed, near-atomic resolution description of the complete PYP photocycle provides a framework for understanding signal transduction in proteins, and for assessing and validating theoretical/computational approaches in protein biophysics. PMID:23132943

  13. Time-resolved x-ray transmission grating spectrometer for studying laser-produced plasmas.

    PubMed

    Ceglio, N M; Kauffman, R L; Hawryluk, A M; Medecki, H

    1983-01-15

    The development of a new time-resolved x-ray spectrometer is reported in which a free-standing x-ray transmission grating is coupled to a soft x-ray streak camera. The instrument measures continuous x-ray spectra with 20-psec temporal resolution and moderate spectral resolution (deltalambda >/= 1 A) over a broad spectral range (0.1-5 keV) with high sensitivity and large information recording capacity. Its capabilities are well suited to investigation of laser-generated plasmas, and they nicely complement the characteristics of other time-resolved spectroscopic techniques presently in use. The transmission grating spectrometer has been used on a variety of laser-plasma experiments. We report the first measurements of the temporal variation of continuous low-energy x-ray spectra from laser-irradiated disk targets. PMID:18195786

  14. Time-resolved crystallography and protein design: signalling photoreceptors and optogenetics.

    PubMed

    Moffat, Keith

    2014-07-17

    Time-resolved X-ray crystallography and solution scattering have been successfully conducted on proteins on time-scales down to around 100 ps, set by the duration of the hard X-ray pulses emitted by synchrotron sources. The advent of hard X-ray free-electron lasers (FELs), which emit extremely intense, very brief, coherent X-ray pulses, opens the exciting possibility of time-resolved experiments with femtosecond time resolution on macromolecular structure, in both single crystals and solution. The X-ray pulses emitted by an FEL differ greatly in many properties from those emitted by a synchrotron, in ways that at first glance make time-resolved measurements of X-ray scattering with the required accuracy extremely challenging. This opens up several questions which I consider in this brief overview. Are there likely to be chemically and biologically interesting structural changes to be revealed on the femtosecond time-scale? How shall time-resolved experiments best be designed and conducted to exploit the properties of FELs and overcome challenges that they pose? To date, fast time-resolved reactions have been initiated by a brief laser pulse, which obviously requires that the system under study be light-sensitive. Although this is true for proteins of the visual system and for signalling photoreceptors, it is not naturally the case for most interesting biological systems. To generate more biological targets for time-resolved study, can this limitation be overcome by optogenetic, chemical or other means? PMID:24914168

  15. Time-resolved crystallography and protein design: signalling photoreceptors and optogenetics

    PubMed Central

    Moffat, Keith

    2014-01-01

    Time-resolved X-ray crystallography and solution scattering have been successfully conducted on proteins on time-scales down to around 100 ps, set by the duration of the hard X-ray pulses emitted by synchrotron sources. The advent of hard X-ray free-electron lasers (FELs), which emit extremely intense, very brief, coherent X-ray pulses, opens the exciting possibility of time-resolved experiments with femtosecond time resolution on macromolecular structure, in both single crystals and solution. The X-ray pulses emitted by an FEL differ greatly in many properties from those emitted by a synchrotron, in ways that at first glance make time-resolved measurements of X-ray scattering with the required accuracy extremely challenging. This opens up several questions which I consider in this brief overview. Are there likely to be chemically and biologically interesting structural changes to be revealed on the femtosecond time-scale? How shall time-resolved experiments best be designed and conducted to exploit the properties of FELs and overcome challenges that they pose? To date, fast time-resolved reactions have been initiated by a brief laser pulse, which obviously requires that the system under study be light-sensitive. Although this is true for proteins of the visual system and for signalling photoreceptors, it is not naturally the case for most interesting biological systems. To generate more biological targets for time-resolved study, can this limitation be overcome by optogenetic, chemical or other means? PMID:24914168

  16. 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.

  17. 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.

  18. Time-resolved x-ray diffraction study of photostimulated purple membrane.

    PubMed Central

    Frankel, R D; Forsyth, J M

    1985-01-01

    A nanosecond resolution laser-driven x-ray source has been used to perform a time-resolved, x-ray diffraction study of the purple membrane of the Halobacterium halobium. Alterations in diffraction patterns have been observed 1 ms after photostimulation, and are interpreted to show disorder of bacteriorhodopsin packing in the plane of the membrane with little bacteriorhodopsin structural change. PMID:3978209

  19. 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

  20. Probing Kinetic Mechanisms of Protein Function and Folding with Time-Resolved Natural and Magnetic Chiroptical Spectroscopies

    PubMed Central

    Kliger, David S.; Chen, Eefei; Goldbeck, Robert A.

    2012-01-01

    Recent and ongoing developments in time-resolved spectroscopy have made it possible to monitor circular dichroism, magnetic circular dichroism, optical rotatory dispersion, and magnetic optical rotatory dispersion with nanosecond time resolution. These techniques have been applied to determine structural changes associated with the function of several proteins as well as to determine the nature of early events in protein folding. These studies have required new approaches in triggering protein reactions as well as the development of time-resolved techniques for polarization spectroscopies with sufficient time resolution and sensitivity to probe protein structural changes. PMID:22312279

  1. Time-resolved measurement of quadrupole wakefields in corrugated structures

    NASA Astrophysics Data System (ADS)

    Lu, Chao; Fu, Feichao; Jiang, Tao; Liu, Shengguang; Shi, Libin; Wang, Rui; Zhao, Lingrong; Zhu, Pengfei; Zhang, Zhen; Xiang, Dao

    2016-02-01

    Corrugated structures have recently been widely used for manipulating electron beam longitudinal phase space and for producing THz radiation. Here we report on time-resolved measurements of the quadrupole wakefields in planar corrugated structures. It is shown that while the time-dependent quadrupole wakefield produced by a planar corrugated structure causes significant growth in beam transverse emittance, it can be effectively canceled with a second corrugated structure with orthogonal orientation. The strengths of the time-dependent quadrupole wakefields for various corrugated structure gaps are also measured and found to be in good agreement with theories. Our work should forward the applications of corrugated structures in many accelerator based scientific facilities.

  2. 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.

  3. [System of ns time-resolved spectroscopy diagnosis and radioprotection].

    PubMed

    Yao, Wei-Bo; Guo, Jian-Ming; Zhang, Yong-min; Tang, Jun-Ping; Cheng, Liang; Xu, Qi-fuo

    2014-06-01

    Cathode plasma of high current electron beam diode is an important research on high power microwave and strong pulsed radio accelerator. It is a reliable method to study cathode plasma by diagnosing the cathode plasma parameters with non-contact spectroscopy measurement system. The present paper introduced the work principle, system composition and performance of the nanosecond (ns) time-resolved spectroscopy diagnosis system. Furthermore, it introduced the implementing method and the temporal relation of lower jitter synchronous trigger system. Simultaneously, the authors designed electromagnetic and radio shield room to protect the diagnosis system due to the high electromagnetic and high X-ray and γ-ray radiation, which seriously interferes with the system. Time-resolved spectroscopy experiment on brass (H62) cathode shows that, the element and matter composition of cathode plasma is clearly increase with the increase in the diode pulsed voltage and current magnitude. The spectroscopy diagnosis system could be of up to 10 ns time resolve capability. It's least is 2 ns. Synchronous trigger system's jitter is less than 4 ns. The spectroscopy diagnosis system will open a new way to study the cathode emission mechanism in depth. PMID:25358142

  4. Time-resolved lidar fluorosensor for sea pollution detection

    NASA Technical Reports Server (NTRS)

    Ferrario, A.; Pizzolati, P. L.; Zanzottera, E.

    1986-01-01

    A contemporary time and spectral analysis of oil fluorescence is useful for the detection and the characterization of oil spills on the sea surface. Nevertheless the fluorosensor lidars, which were realized up to now, have only partial capability to perform this double analysis. The main difficulties are the high resolution required (of the order of 1 nanosecond) and the complexity of the detection system for the recording of a two-dimensional matrix of data for each laser pulse. An airborne system whose major specifications were: time range, 30 to 75 ns; time resolution, 1 ns; spectral range, 350 to 700 nm; and spectral resolution, 10 nm was designed and constructed. The designed system of a short pulse ultraviolet laser source and a streak camera based detector are described.

  5. Simultaneous time and frequency resolved fluorescence microscopy of single molecules.

    SciTech Connect

    Hayden, Carl C.; Gradinaru, Claudiu C.; Chandler, David W.; Luong, A. Khai

    2005-01-01

    Single molecule fluorophores were studied for the first time with a new confocal fluorescence microscope that allows the wavelength and emission time to be simultaneously measured with single molecule sensitivity. In this apparatus, the photons collected from the sample are imaged through a dispersive optical system onto a time and position sensitive detector. This detector records the wavelength and emission time of each detected photon relative to an excitation laser pulse. A histogram of many events for any selected spatial region or time interval can generate a full fluorescence spectrum and correlated decay plot for the given selection. At the single molecule level, this approach makes entirely new types of temporal and spectral correlation spectroscopy of possible. This report presents the results of simultaneous time- and frequency-resolved fluorescence measurements of single rhodamine 6G (R6G), tetramethylrhodamine (TMR), and Cy3 embedded in thin films of polymethylmethacrylate (PMMA).

  6. Time-Resolved Microdialysis for In Vivo Neurochemical Measurements and Other Applications

    NASA Astrophysics Data System (ADS)

    Schultz, Kristin N.; Kennedy, Robert T.

    2008-07-01

    Monitoring changes in chemical concentrations over time in complex environments is typically performed using sensors and spectroscopic techniques. Another approach is to couple sampling methods, such as microdialysis, with chromatographic, electrophoretic, or enzymatic assays. Recent advances of such coupling have enabled improvements in temporal resolution, multianalyte capability, and automation. In a sampling and analysis method, the temporal resolution is set by the mass sensitivity of the analytical method, analysis time, and zone dispersion during sampling. Coupling methods with high speed and mass sensitivity to microdialysis sampling help to reduce some of these contributions to yield methods with temporal resolution of seconds. These advances have been primarily used in monitoring neurotransmitters in vivo. This review covers the problems associated with chemical monitoring in the brain, recent advances in using microdialysis for time-resolved in vivo measurements, sample applications, and other potential applications of the technology such as determining reaction kinetics and process monitoring.

  7. 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.

  8. 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.

  9. 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).

  10. A 3-dimensional time-resolved photothermal deflection ``Mirage'' method

    NASA Astrophysics Data System (ADS)

    Astrath, N. G. C.; Malacarne, L. C.; Lukasievicz, G. V. B.; Bernabe, H. S.; Rohling, J. H.; Baesso, M. L.; Shen, J.; Bialkowski, S. E.

    2012-02-01

    A three-dimensional time-resolved theory and experiment for photothermal deflection spectroscopy is developed. The heat conduction equations for two semi-infinite media consisting of an opaque sample and a fluid are solved considering temperature and energy flux balance conditions for a Gaussian heat source. The time dependent perpendicular deflection signal is calculated and compared to experimental measurements on glassy carbon and copper samples. Excellent agreement with literature values for thermal diffusivity of the samples is found. The transient behavior is analyzed for different coupling fluids.

  11. Lateral-Looking Time-Resolved Thermal Wave Microscopy

    SciTech Connect

    David H Hurley; Subhash Shinde; Vitalyi Gusev

    2010-08-01

    Time-resolved thermal wave microscopy was used to measure lateral thermal transport in a thin metallic film on an insulating substrate. The basis of this approach is to decompose the reflectivity signal into a component that varies with delay time and a steady state component that varies with pump modulation frequency. The transient component is a summation of thermal waves at integral multiples of the pulse repetition frequency (76 MHz). The steady state component depends only on thermal waves at the pump chopping frequency (10-100 kHz). It is shown that for long delays, the steady state component is dominant and can be used to measure the thermal diffusivity.

  12. Distributed vibration sensing with time-resolved optical frequency-domain reflectometry.

    PubMed

    Zhou, Da-Peng; Qin, Zengguang; Li, Wenhai; Chen, Liang; Bao, Xiaoyi

    2012-06-01

    The distributed vibration or dynamic strain information can be obtained using time-resolved optical frequency-domain reflectometry. Time-domain information is resolved by measuring Rayleigh backscatter spectrum in different wavelength ranges which fall in successive time sequence due to the linear wavelength sweep of the tunable laser source with a constant sweeping rate. The local Rayleigh backscatter spectrum shift of the vibrated state with respect to that of the non-vibrated state in time sequence can be used to determine dynamic strain information at a specific position along the fiber length. Standard single-mode fibers can be used as sensing head, while the measurable frequency range of 0-32 Hz with the spatial resolution of 10 cm can be achieved up to the total length of 17 m. PMID:22714342

  13. Time-resolved studies of dynamic biomolecules using small angle X-ray scattering.

    PubMed

    Kirby, Nigel M; Cowieson, Nathan P

    2014-10-01

    Small angle X-ray scattering (SAXS) of biomacromolecules in solution has become a prominent technique in structural biology. Whilst the majority of current use is for static measurements, the field is also advancing for measurements where the sample at the beam position changes with time, using high throughput systems, chromatography, high speed mixing and pump-probe techniques in particular. Time resolved work is greatly aided by increasingly sophisticated software for acquiring and analysing data, together with developments in X-ray sources, beamline optics and detectors. The exploitation of spatial coherence is under development, with X-ray free electron lasers aiming to provide major advances in single molecule structure reconstruction and time resolution. Here we provide an overview of current developments advancing time resolved solution SAXS. PMID:25108308

  14. A method for coincidence timing resolution enhancement

    NASA Astrophysics Data System (ADS)

    Ermis, E. E.; Celiktas, C.; Pilicer, E.

    2016-05-01

    A method including the coincidence time resolution improvement for a TOF/positron emission tomography system was suggested. The spectrometer for this aim was composed of two NaI(Tl) and two plastic scintillation detectors. Experimental results were supported by FLUKA Monte Carlo simulation program by constructing the detector setup in software medium. Present experimental results verified our previous results and conclusions obtained from the suggested method. It was concluded that better resolutions would help the improvement not only on the TOF gain but also on the spatial resolution, leading to better images and helping the Physician in his/her diagnosis and treatment.

  15. 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.

  16. Simple photomultiplier tube internal-gating method for use in subnanosecond time-resolved spectroscopy.

    PubMed

    Iwata, Tetsuo; Takasu, Tsuyoshi; Araki, Tsutomu

    2003-09-01

    We propose a simple photomultiplier tube (PMT) internal-gating method for use in the field of subnanosecond time-resolved spectroscopy. In the proposed method, we control two dynodes in the PMT by applying a gate signal whose pulse width is Tg. When controlling the mth and the n(> m)th dynodes, a resolution time delta t is approximately given by delta t = Tg-(n-m) tau, where tau is a transit time of a lump of secondary electrons traveling between the two dynodes in the PMT. In principle, the resolution time delta t shorter than the pulse width Tg of the gate signal can be easily obtained. From a fundamental performance test, we found that a subnanosecond resolution time delta t = 0.31 ns was obtained for the case of m = 2 and n = 5. To demonstrate the effectiveness of the proposed method, we carried out a time-resolved spectroscopic measurement of emission obtained from a white-light-emitting diode (LED) driven by a nanosecond current pulse. PMID:14611045

  17. Reduction of reconstruction time for time-resolved spiral 3D contrast-enhanced magnetic resonance angiography using parallel computing.

    PubMed

    Kressler, Bryan; Spincemaille, Pascal; Prince, Martin R; Wang, Yi

    2006-09-01

    Time-resolved 3D MRI with high spatial and temporal resolution can be achieved using spiral sampling and sliding-window reconstruction. Image reconstruction is computationally intensive because of the need for data regridding, a large number of temporal phases, and multiple RF receiver coils. Inhomogeneity blurring correction for spiral sampling further increases the computational work load by an order of magnitude, hindering the clinical utility of spiral trajectories. In this work the reconstruction time is reduced by a factor of >40 compared to reconstruction using a single processor. This is achieved by using a cluster of 32 commercial off-the-shelf computers, commodity networking hardware, and readily available software. The reconstruction system is demonstrated for time-resolved spiral contrast-enhanced (CE) peripheral MR angiography (MRA), and a reduction of reconstruction time from 80 min to 1.8 min is achieved. PMID:16892189

  18. 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.

  19. Femtosecond time-resolved dynamical Franz-Keldysh effect

    NASA Astrophysics Data System (ADS)

    Otobe, T.; Shinohara, Y.; Sato, S. A.; Yabana, K.

    2016-01-01

    We theoretically investigate the dynamical Franz-Keldysh effect in femtosecond time resolution, that is, the time-dependent modulation of a dielectric function at around the band gap under an irradiation of an intense laser field. We develop a pump-probe formalism in two distinct approaches: first-principles simulation based on real-time time-dependent density functional theory and analytic consideration of a simple two-band model. We find that, while time-average modulation can be reasonably described by the static Franz-Keldysh theory, a remarkable phase shift is found to appear between the dielectric response and the applied electric field.

  20. 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.

  1. Approaches to time-resolved diffraction using an XFEL.

    PubMed

    Spence, John C H

    2014-01-01

    We describe several schemes for time-resolved imaging of molecular motion using a free-electron laser (XFEL), in response to the many challenges and opportunities which XFEL radiation has created for accurate time-resolved measurement of structure. For pump-probe experiments using crystals, the problem of recording full Bragg reflections (not partials) in each shot arises. Two solutions, the use of the large bandwith which necesarily results from using attosecond pulses, and the use the coherent convergent beam mode are suggested. We also show that with attosecond recording times shorter than the temporal coherence time, Bragg reflections excited by different wavelengths from different reflections can interfere, providing structure factor phase information. For slower processes, a mixing jet sample-delivery device is described to allow snapshot solution scattering during molecular reactions on the microsecond scale. For optically excited membrane proteins, we suggest the use of the lipid cubic phase sample delivery device operating at atmospheric pressure. The use of two-color and split-and-delay schemes is suggested for improved accuracy in the Monte-Carlo method of serial femtosecond crystallography (SFX). PMID:25415269

  2. Watching proteins function with 150-ps time-resolved X-ray crystallography

    NASA Astrophysics Data System (ADS)

    Anfinrud, Philip

    2007-03-01

    We have used time-resolved Laue crystallography to characterize ligand migration pathways and dynamics in wild-type and several mutant forms of myoglobin (Mb), a ligand-binding heme protein found in muscle tissue. In these pump-probe experiments, which were conducted on the ID09B time-resolved beamline at the European Synchrotron and Radiation Facility, a laser pulse photodissociates CO from an MbCO crystal and a suitably delayed X-ray pulse probes its structure via Laue diffraction. Single-site mutations in the vicinity of the heme pocket docking site were found to have a dramatic effect on ligand migration. To visualize this process, time-resolved electron density maps were stitched together into movies that unveil with <2-å spatial resolution and 150-ps time-resolution the correlated protein motions that accompany and/or mediate ligand migration. These studies help to illustrate at an atomic level relationships between protein structure, dynamics, and function.

  3. A CAMAC system controlled by an IBM AT computer for time-resolved spectroscopy

    SciTech Connect

    Lindquist, L.O.; Moss, C.E.

    1987-01-01

    An IBM AT computer interfaced to a small CAMAC system offers considerable power without the complexity and expense of a large general-purpose system. Our system for time-resolved spectroscopy features menu-driven FORTRAN-based software; high-resolution and high-speed (8K channels, 5-..mu..s fixed dead time) ADCs; segmentable histogram memories (24-bit counts) with large memory space for many histogram segments; independently variable separate histogram dwell times; remote control via a CAMAC serial highway; and ground isolation between the data acquisition equipment and control computer by means of fiber optics.

  4. A CAMAC system controlled by an IBM AT computer for time-resolved spectroscopy

    SciTech Connect

    Lindquist, L.O.; Moss, C.E.

    1987-08-01

    An IBM AT computer interfaced to a small CAMAC system offers considerable power without the complexity and expense of a large general-purpose system. The authors' system for time-resolved spectroscopy features menu-driven FORTRAN-based software; high-resolution and high-speed 98K channels, 5-..mu..s fixed dead time) ADCs; segmentable histogram memories (24-bit counts) with large memory space for many histogram segments; independently variable separate histogram dwell times; remote control via a CAMAC serial highway; and ground isolation between the data acquisition equipment and control computer by means of fiber optics.

  5. Time-resolved temperature measurements in hypervelocity dust impact

    NASA Astrophysics Data System (ADS)

    Collette, A.; Drake, K.; Mocker, A.; Sternovsky, Z.; Munsat, T.; Horanyi, M.

    2013-12-01

    We present time-resolved temperature measurements of the debris cloud generated by hypervelocity dust impact. Micron- and submicron-sized iron grains were accelerated to speeds of 1-32 km/s using the 3 MV electrostatic dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies, and impacted on a tungsten target. The resulting light flashes were analyzed by an array of photomultiplier tubes equipped with narrowband interference filters to determine the blackbody temperature and radiant power of the impact-generated cloud as a function of time. We find time-averaged temperatures in the range of 2500-5000 K, increasing with velocity over the range studied; initial temperatures up to approximately twice the time averaged temperature persisting on short timescales (<1μs) compared to the 20μs duration of the flash; and that the temperature falls in a manner consistent with radiative cooling.

  6. Nonequilibrium Green's Function approach to time-resolved photoabsorption

    NASA Astrophysics Data System (ADS)

    Stefanucci, Gianluca; Perfetto, Enrico; Uimonen, Anna-Maija; van Leeuwen, Robert

    We propose a nonequilibrium Green's function (NEGF) approach to calculate the time-resolved absorption spectrum of nanoscale systems. We can deal with arbitrary shape, intensity, duration and relative delay of the pump and probe fields and include ionization processes as well as hybridization effects due to surfaces. We present numerical simulations of atomic systems using different approximate self-energies and show that electron correlations are pivotal to reproduce important qualitative features. E.P. and G.S. acknowledge funding by MIUR FIRB Grant No. RBFR12SW0J. R.v.L. thanks the Academy of Finland for support.

  7. Ultrafast time-resolved spectroscopy of lead halide perovskite films

    NASA Astrophysics Data System (ADS)

    Idowu, Mopelola A.; Yau, Sung H.; Varnavski, Oleg; Goodson, Theodore

    2015-09-01

    Recently, lead halide perovskites which are organic-inorganic hybrid structures, have been discovered to be highly efficient as light absorbers. Herein, we show the investigation of the excited state dynamics and emission properties of non-stoichiometric precursor formed lead halide perovskites grown by interdiffusion method using steady-state and time-resolved spectroscopic measurements. The influence of the different ratios of the non-stoichiometric precursor solution was examined. The observed photoluminescence properties were correlated with the femtosecond transient absorption measurements.

  8. Time resolved structural dynamics of butadiyne-linked porphyrin dimers

    PubMed Central

    Camargo, Franco V. A.; Hall, Christopher R.; Anderson, Harry L.; Meech, Stephen R.; Heisler, Ismael A.

    2016-01-01

    In this work, the timescales and mechanisms associated with the structural dynamics of butadiyne-linked porphyrin dimers are investigated through time resolved narrowband pump/broadband probe transient absorption spectroscopy. Our results confirm previous findings that the broadening is partly due to a distribution of structures with different (dihedral) angular conformations. Comparison of measurements with excitations on the red and blue sides of the Q-band unravel the ground and excited state conformational re-equilibration timescales. Further comparison to a planarized dimer, through the addition of a ligand, provides conclusive evidence for the twisting motion performed by the porphyrin dimer in solution. PMID:26798839

  9. CCD time-resolved photometry of faint cataclysmic variables. III

    NASA Technical Reports Server (NTRS)

    Howell, Steve B.; Szkody, Paula; Kreidl, Tobias J.; Mason, Keith O.; Puchnarewicz, E. M.

    1990-01-01

    CCD time-resolved photometry in V, B, and near-IR for 17 faint cataclysmic variables (CVs) is presented and analyzed. The data are obtained at Kitt Peak National Observatory, the Perkins reflector, Lowell Observatory, and the Observatorio del Roque de los Muchachos from April-June 1989. The degree of variability and periodicities for the CVs are examined. It is observed that the variability of most of the stars is consistent with CV class behavior. Orbital periods for five CVs are determined, and three potential eclipsing systems are detected.

  10. 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.

  11. Capturing molecular structural dynamics by 100 ps time-resolved X-ray absorption spectroscopy.

    PubMed

    Sato, Tokushi; Nozawa, Shunsuke; Ichiyanagi, Kohei; Tomita, Ayana; Chollet, Matthieu; Ichikawa, Hirohiko; Fujii, Hiroshi; Adachi, Shin Ichi; Koshihara, Shin Ya

    2009-01-01

    An experimental set-up for time-resolved X-ray absorption spectroscopy with 100 ps time resolution at beamline NW14A at the Photon Factory Advanced Ring is presented. The X-ray positional active feedback to crystals in a monochromator combined with a figure-of-merit scan of the laser beam position has been utilized as an essential tool to stabilize the spatial overlap of the X-ray and laser beams at the sample position. As a typical example, a time-resolved XAFS measurement of a photo-induced spin crossover reaction of the tris(1,10-phenanthrorine)iron(II) complex in water is presented. PMID:19096182

  12. 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.

  13. Time-resolved photoluminescence of undoped InP

    SciTech Connect

    Keyes, B.M.; Dunlavy, D.J.; Ahrenkiel, R.K. ); Shaw, G.; Summers, G.P. ); Tzafaras, N.; Lentz, C. )

    1994-04-15

    Energy and time-resolved photoluminescence data have been obtained for nominally undoped ([ital n] 4.5[times]10[sup 15] cm[sup [minus]3]) bulk InP grown by the vertical-gradient freeze method. The data were taken as a function of temperature, from 80 to 290 K, and analyzed using a solution to the continuity equation. The resulting lifetime values range from 300 ns to 3.2 [mu]s, and surface recombination velocities were fund to be on the order of 10[sup 3] cm/s. The temperature dependence can be explained by assuming a radiatively limited recombination with a resulting [ital B] coefficient [ge]5.9[times]10[sup [minus]11] cm[sup 3]/s at 300 K.

  14. Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Kentarou; Hama, Yoichi; Nishida, Shigeki

    2005-07-01

    Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H 2 mixture to observe time profiles of ArH + and ArH emission spectra. Electronic transitions of He 2 have been observed in the infrared region with this method, and from the time profiles, He 2 in Rydberg states with higher energy than the b3Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm -1 region have been assigned by using previously reported data from the optical region. A new band from the 5 f state has been assigned for the first time through the 5 f-4 d band in the 2600 cm -1 region.

  15. A high-order harmonic generation apparatus for time- and angle-resolved photoelectron spectroscopy

    SciTech Connect

    Frietsch, B.; Gahl, C.; Teichmann, M.; Weinelt, M.; Carley, R.; Döbrich, K.; Schwarzkopf, O.; Wernet, Ph.

    2013-07-15

    We present a table top setup for time- and angle-resolved photoelectron spectroscopy to investigate band structure dynamics of correlated materials driven far from equilibrium by femtosecond laser pulse excitation. With the electron-phonon equilibration time being in the order of 1–2 ps it is necessary to achieve sub-picosecond time resolution. Few techniques provide both the necessary time and energy resolution to map non-equilibrium states of the band structure. Laser-driven high-order harmonic generation is such a technique. In our experiment, a grating monochromator delivers tunable photon energies up to 40 eV. A photon energy bandwidth of 150 meV and a pulse duration of 100 fs FWHM allow us to cover the k-space necessary to map valence bands at different k{sub z} and detect outer core states.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Time-resolved scanning electron microscopy with polarization analysis

    NASA Astrophysics Data System (ADS)

    Frömter, Robert; Kloodt, Fabian; Rößler, Stefan; Frauen, Axel; Staeck, Philipp; Cavicchia, Demetrio R.; Bocklage, Lars; Röbisch, Volker; Quandt, Eckhard; Oepen, Hans Peter

    2016-04-01

    We demonstrate the feasibility of investigating periodically driven magnetization dynamics in a scanning electron microscope with polarization analysis based on spin-polarized low-energy electron diffraction. With the present setup, analyzing the time structure of the scattering events, we obtain a temporal resolution of 700 ps, which is demonstrated by means of imaging the field-driven 100 MHz gyration of the vortex in a soft-magnetic FeCoSiB square. Owing to the efficient intrinsic timing scheme, high-quality movies, giving two components of the magnetization simultaneously, can be recorded on the time scale of hours.

  1. Time-resolved photoinduced thermoelectric and transport currents in GaAs nanowires.

    PubMed

    Prechtel, Leonhard; Padilla, Milan; Erhard, Nadine; Karl, Helmut; Abstreiter, Gerhard; Fontcuberta I Morral, Anna; Holleitner, Alexander W

    2012-05-01

    In order to clarify the temporal interplay of the different photocurrent mechanisms occurring in single GaAs nanowire based circuits, we introduce an on-chip photocurrent pump-probe spectroscopy with a picosecond time resolution. We identify photoinduced thermoelectric, displacement, and carrier lifetime limited currents as well as the transport of photogenerated holes to the electrodes. Moreover, we show that the time-resolved photocurrent spectroscopy can be used to investigate the drift velocity of photogenerated carriers in semiconducting nanowires. Hereby, our results are relevant for nanowire-based optoelectronic and photovoltaic applications. PMID:22494021

  2. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

    PubMed Central

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J. R.; Krenner, Hubert J.; Wixforth, Achim; Salditt, Tim

    2014-01-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length). PMID:25294979

  3. Time-resolved quantitative-phase microscopy of laser-material interactions using a wavefront sensor.

    PubMed

    Gallais, Laurent; Monneret, Serge

    2016-07-15

    We report on a simple and efficient technique based on a wavefront sensor to obtain time-resolved amplitude and phase images of laser-material interactions. The main interest of the technique is to obtain quantitative self-calibrated phase measurements in one shot at the femtosecond time-scale, with high spatial resolution. The technique is used for direct observation and quantitative measurement of the Kerr effect in a fused silica substrate and free electron generation by photo-ionization processes in an optical coating. PMID:27420506

  4. 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.

  5. Time-resolved aluminium laser-induced plasma temperature measurements

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2014-11-01

    We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 ± 270 to 3862 ± 46 Kelvin from 10 to 100 μs time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened Hβ spectra.

  6. 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.

  7. 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.

  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 spectroscopy using a chopper wheel as a fast shutter

    NASA Astrophysics Data System (ADS)

    Wang, Shicong; Wendt, Amy E.; Boffard, John B.; Lin, Chun C.

    2015-01-01

    Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a "fast" electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a "fast" mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas.

  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. Time-resolved spectroscopy using a chopper wheel as a fast shutter

    SciTech Connect

    Wang, Shicong; Wendt, Amy E.; Boffard, John B.; Lin, Chun C.

    2015-01-15

    Widely available, small form-factor, fiber-coupled spectrometers typically have a minimum exposure time measured in milliseconds, and thus cannot be used directly for time-resolved measurements at the microsecond level. Spectroscopy at these faster time scales is typically done with an intensified charge coupled device (CCD) system where the image intensifier acts as a “fast” electronic shutter for the slower CCD array. In this paper, we describe simple modifications to a commercially available chopper wheel system to allow it to be used as a “fast” mechanical shutter for gating a fiber-coupled spectrometer to achieve microsecond-scale time-resolved optical measurements of a periodically pulsed light source. With the chopper wheel synchronized to the pulsing of the light source, the time resolution can be set to a small fraction of the pulse period by using a chopper wheel with narrow slots separated by wide spokes. Different methods of synchronizing the chopper wheel and pulsing of the light sources are explored. The capability of the chopper wheel system is illustrated with time-resolved measurements of pulsed plasmas.

  12. Antimicrobial aspects of inflammatory resolution in the mucosa: A role for pro-resolving mediators1

    PubMed Central

    Campbell, Eric L.; Serhan, Charles N.; Colgan, Sean P.

    2011-01-01

    Mucosal surfaces function as selectively permeable barriers between the host and the outside world. Given their close proximity to microbial antigens, mucosal surfaces have evolved sophisticated mechanisms for maintaining homeostasis and preventing excessive acute inflammatory reactions. The role attributed to epithelial cells was historically limited to serving as a selective barrier, in recent years numerous findings implicate an active role of the epithelium with pro-resolving mediators in the maintenance of immunological equilibrium. In this brief review, we highlight new evidence that the epithelium actively contributes to coordination and resolution of inflammation, principally through the generation of anti-inflammatory and pro-resolution lipid mediators. These autacoids, derived from ω-6 and ω-3 polyunsaturated fatty acids, are implicated in the initiation, progression and resolution of acute inflammation and display specific, epithelial-directed actions focused on mucosalhomeostasis. We also summarize present knowledge of mechanisms for resolution via regulation of epithelial-derived antimicrobial peptides in response to pro-resolving lipid mediators. PMID:21934099

  13. Protectins and maresins: New pro-resolving families of mediators in acute inflammation and resolution bioactive metabolome.

    PubMed

    Serhan, Charles N; Dalli, Jesmond; Colas, Romain A; Winkler, Jeremy W; Chiang, Nan

    2015-04-01

    Acute inflammatory responses are protective, yet without timely resolution can lead to chronic inflammation and organ fibrosis. A systems approach to investigate self-limited (self-resolving) inflammatory exudates in mice and structural elucidation uncovered novel resolution phase mediators in vivo that stimulate endogenous resolution mechanisms in inflammation. Resolving inflammatory exudates and human leukocytes utilize DHA and other n-3 EFA to produce three structurally distinct families of potent di- and trihydroxy-containing products, with several stereospecific potent mediators in each family. Given their potent and stereoselective picogram actions, specific members of these new families of mediators from the DHA metabolome were named D-series resolvins (Resolvin D1 to Resolvin D6), protectins (including protectin D1-neuroprotectin D1), and maresins (MaR1 and MaR2). In this review, we focus on a) biosynthesis of protectins and maresins as anti-inflammatory-pro-resolving mediators; b) their complete stereochemical assignments and actions in vivo in disease models. Each pathway involves the biosynthesis of epoxide-containing intermediates produced from hydroperoxy-containing precursors from human leukocytes and within exudates. Also, aspirin triggers an endogenous DHA metabolome that biosynthesizes potent products in inflammatory exudates and human leukocytes, namely aspirin-triggered Neuroprotectin D1/Protectin D1 [AT-(NPD1/PD1)]. Identification and structural elucidation of these new families of bioactive mediators in resolution has opened the possibility of diverse patho-physiologic actions in several processes including infection, inflammatory pain, tissue regeneration, neuroprotection-neurodegenerative disorders, wound healing, and others. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance". PMID:25139562

  14. Evidencing the need for high spatial resolution in angle-resolved photoemission experiments

    NASA Astrophysics Data System (ADS)

    Joucken, Frédéric; Reckinger, Nicolas; Lorcy, Stéphane; Avila, José; Chen, Chaoyu; Lagoute, Jérôme; Colomer, Jean-François; Ghijsen, Jacques; Asensio, Maria Carmen; Sporken, Robert

    2016-06-01

    Angle-resolved photoemission spectroscopy (ARPES) is the most direct tool to measure the electronic structure of materials. In particular, fine features of the spectra can be analyzed for evaluating the electron self-energy. Owing to a setup allowing ARPES investigation with submicron resolution and state-of-the-art energy and momentum resolution, we show here first that ARPES spectra of pristine and virtually undoped monolayer graphene acquired on a small spot do not display manifestations of self-energy. We next demonstrate that, although the region of the sample investigated is a unique graphene domain, it displays faint spatial inhomogeneity, both in its crystallographic orientation and its thickness, which is undetectable with conventional ARPES but renders the spectra improper for self-energy extraction. These results indicate that care should be taken when analyzing ARPES spectra obtained with poor spatial resolution.

  15. Protein chip analysis by probing time-resolved UV fluorescence

    NASA Astrophysics Data System (ADS)

    Grigaravicius, Paulius; Dietrich, Rüdiger; Fritzsche, Wolfgang; Greulich, Karl Otto; Horn, Uwe; Knoll, Dietmar; Peters, Sven; Striebel, Hans-Martin; Schellenberg, Peter

    2007-07-01

    We describe a novel label-free method to analyse protein interactions on microarrays as well as in solution. By this technique the time resolved native protein fluorescence in the UV is probed. The method is based on alterations of the protein upon ligand binding, and, as a consequence, of alterations of the environment of the proteins' aromatic amino acids. These amino acids act as internal probes, and as a result, the fluorescence lifetime of the proteins change due to binding to a ligand partner such as another protein. We were able to demonstrate the feasibility of the method with many compounds, including protein-protein, protein-antibody, protein-nucleic acid and protein-small ligand pairs. Unlike to many other label-free techniques, the sensitivity of the method does not depend on the size of the counterbinding ligand and therefore is particularly suitable for drug monitoring, when small molecules are involved.

  16. Time-resolved tomographic images of a relativistic electron beam

    SciTech Connect

    Koehler, H.A.; Jacoby, B.A.; Nelson, M.

    1984-07-01

    We obtained a sequential series of time-resolved tomographic two-dimensional images of a 4.5-MeV, 6-kA, 30-ns electron beam. Three linear fiber-optic arrays of 30 or 60 fibers each were positioned around the beam axis at 0/sup 0/, 61/sup 0/, and 117/sup 0/. The beam interacting with nitrogen at 20 Torr emitted light that was focused onto the fiber arrays and transmitted to a streak camera where the data were recorded on film. The film was digitized, and two-dimensional images were reconstructed using the maximum-entropy tomographic technique. These images were then combined to produce an ultra-high-speed movie of the electron-beam pulse.

  17. 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

  18. Photon-Counting Arrays for Time-Resolved Imaging.

    PubMed

    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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 30 CFR 291.103 - May I use alternative dispute resolution to informally resolve an allegation that open and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false May I use alternative dispute resolution to... SHELF LANDS ACT § 291.103 May I use alternative dispute resolution to informally resolve an allegation... Action and Dispute Resolution (CADR); or (3) MMS staff trained in ADR and certified by the CADR. (b)...

  4. 30 CFR 291.103 - May I use alternative dispute resolution to informally resolve an allegation that open and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false May I use alternative dispute resolution to... alternative dispute resolution to informally resolve an allegation that open and nondiscriminatory access was... parties; (2) The Department's Office of Collaborative Action and Dispute Resolution (CADR); or (3)...

  5. Time-resolved infrared spectroscopic techniques as applied to channelrhodopsin

    PubMed Central

    Ritter, Eglof; Puskar, Ljiljana; Bartl, Franz J.; Aziz, Emad F.; Hegemann, Peter; Schade, Ulrich

    2015-01-01

    Among optogenetic tools, channelrhodopsins, the light gated ion channels of the plasma membrane from green algae, play the most important role. Properties like channel selectivity, timing parameters or color can be influenced by the exchange of selected amino acids. Although widely used, in the field of neurosciences for example, there is still little known about their photocycles and the mechanism of ion channel gating and conductance. One of the preferred methods for these studies is infrared spectroscopy since it allows observation of proteins and their function at a molecular level and in near-native environment. The absorption of a photon in channelrhodopsin leads to retinal isomerization within femtoseconds, the conductive states are reached in the microsecond time scale and the return into the fully dark-adapted state may take more than minutes. To be able to cover all these time regimes, a range of different spectroscopical approaches are necessary. This mini-review focuses on time-resolved applications of the infrared technique to study channelrhodopsins and other light triggered proteins. We will discuss the approaches with respect to their suitability to the investigation of channelrhodopsin and related proteins. PMID:26217670

  6. Time-resolved CIDNP: applications to radical and biradical chemistry

    SciTech Connect

    Closs, G.L.; Miller, R.J.; Redwine, O.D.

    1985-07-01

    Nuclear magnetic resonance has long been one of the most useful tools for investigating reaction kinetics. The direct method follows resonance intensities as a function of time and correlates them with reactant or product concentrations. This approach can be applied only to slow reactions, although flow and stopped-flow techniques can reduce the time scale to approximately 10/sup -2/s. With use of line-shape analysis, kinetic measurements can be carried out under dynamic equilibrium conditions. With modern high-field spectrometers rates up to 10/sup 4/ s/sup -1/ can be measured in diamagnetic molecules. The fundamental limit for the time resolution is imposed by the weakness of the interactions of the nuclear spins with the molecular environment or the lattice. In systems containing unpaired electrons the strong hyperfine (hf) interactions allow measurements of diamagnetic-paramagnetic exchange rates up to 10/sup 10/ s/sup -1/. In this Account a new NMR method for measuring rates of irreversible reactions with a time resolution approaching 10/sup -8/ s is reviewed. This extends the previous limit for irreversible reactions by 5-6 orders of magnitude. The method is an extension of chemically induced dynamic nuclear polarization (CI-DNP) originating from radical pair chemistry via the hyperfine interaction. 25 references, 8 figures, 1 table.

  7. 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). PMID:27140147

  8. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

    DOE PAGESBeta

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; et al

    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

  9. 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

  10. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography.

    PubMed

    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

  11. Time-resolved FRET fluorescence spectroscopy of visible fluorescent protein pairs.

    PubMed

    Visser, A J W G; Laptenok, S P; Visser, N V; van Hoek, A; Birch, D J S; Brochon, J-C; Borst, J W

    2010-01-01

    Förster resonance energy transfer (FRET) is a powerful method for obtaining information about small-scale lengths between biomacromolecules. Visible fluorescent proteins (VFPs) are widely used as spectrally different FRET pairs, where one VFP acts as a donor and another VFP as an acceptor. The VFPs are usually fused to the proteins of interest, and this fusion product is genetically encoded in cells. FRET between VFPs can be determined by analysis of either the fluorescence decay properties of the donor molecule or the rise time of acceptor fluorescence. Time-resolved fluorescence spectroscopy is the technique of choice to perform these measurements. FRET can be measured not only in solution, but also in living cells by the technique of fluorescence lifetime imaging microscopy (FLIM), where fluorescence lifetimes are determined with the spatial resolution of an optical microscope. Here we focus attention on time-resolved fluorescence spectroscopy of purified, selected VFPs (both single VFPs and FRET pairs of VFPs) in cuvette-type experiments. For quantitative interpretation of FRET-FLIM experiments in cellular systems, details of the molecular fluorescence are needed that can be obtained from experiments with isolated VFPs. For analysis of the time-resolved fluorescence experiments of VFPs, we have utilised the maximum entropy method procedure to obtain a distribution of fluorescence lifetimes. Distributed lifetime patterns turn out to have diagnostic value, for instance, in observing populations of VFP pairs that are FRET-inactive. PMID:19693494

  12. 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.

  13. 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

  14. Method of ultrafast beam rotation for single-shot, time-resolved measurements.

    PubMed

    Spiro, Alex; Lowe, Mary

    2014-09-15

    Ultrafast optical beam rotation is proposed for single-shot, time-resolved measurements. A pump-probe configuration is considered using a diffraction grating and focusing optics to create angular encoding of the time delay between the pump and probe pulses. The characteristic time t(ap) of the grating-lens system is derived as a function of dispersion, NA, and time window T. An analytical equation for time resolution is obtained that incorporates t(ap)laser pulse width, and beam crossing, enabling optimum selection of optical components. For commercial standard gratings with width W≤50 mm, laser λ=800 nm, and NA=.05, a 160 ps time window can be achieved, and t(ap)=23 fs for T=1 ps. PMID:26466272

  15. Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Yerramilli, Vamsee K.; Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

  16. Time resolution of a scintillating fiber detector

    NASA Astrophysics Data System (ADS)

    Horikawa, S.; Toeda, T.; Daito, I.; Doushita, N.; Hasegawa, T.; Horikawa, N.; Iwata, T.; Kibe, Y.; Matsuda, T.; Miyachi, Y.; Noboriguchi, K.; Takabayashi, N.; Tohyama, T.; Wakai, A.

    1999-07-01

    The performance of scintillating fiber detectors with 2 m long light guides was investigated for COMPASS experiment, using a 450 MeV/ c electron beam.Prototypes consisting of 0.5 mm diameter fibers (Kuraray SCSF-38 single-cladding) with the position-sensitive photomultipliers H6568 (Hamamatsu) were constructed for the test. The time resolution of σ˜430 ps was obtained with about 10 photoelectrons for the prototype of 10-layers structure.

  17. Evaluation of thermally driven flows and orographic convection at cloud-resolving resolutions

    NASA Astrophysics Data System (ADS)

    Schmidli, J.; Langhans, W.; Fuhrer, O.; Bieri, S.; Schar, C.

    2013-12-01

    The purpose of this contribution is to evaluate the representation of thermally driven flows and moist convection over the European Alps at cloud-resolving resolutions (CRM; 1.1 and 2.2 km). The two simulations and further sensitivity experiments are validated against a large set of observations for an 18-day fair-weather summer period. The episode considered is characterized by pronounced plain-valley pressure gradients, strong daytime upvalley flows, and weak nighttime down-valley flows. In addition, convective precipitation is recorded during the late afternoon and is preceded by a phase of shallow convection. The observed transition from shallow to deep convection occurs within a 3-h period. The results indicate generally good agreement between both CRMs and the observed diurnal evolution in terms of near-surface winds, cloud formation, and precipitation. The differences between the 1.1 and 2.2 km resolution runs are surprisingly small. In contrast, a convection-parameterizing simulation with 6.6 km resolution (CPM) produces too-early peaks of cloud cover and precipitation that are due to a too-early activation of deep convection. Detailed sensitivity experiments show that the convection scheme, rather than the under-resolved small-scale topography, is responsible for the poor performance of the CPM.

  18. Spatially resolved high resolution x-ray spectroscopy for magnetically confined fusion plasmas (invited)

    SciTech Connect

    Ince-Cushman, A.; Rice, J. E.; Reinke, M. L.; Podpaly, Y.; Marmar, E. S.; Bitter, M.; Hill, K. W.; Scott, S.; Gu, M. F.; Eikenberry, E.; Broennimann, Ch.; Lee, S. G.

    2008-10-15

    The use of high resolution x-ray crystal spectrometers to diagnose fusion plasmas has been limited by the poor spatial localization associated with chord integrated measurements. Taking advantage of a new x-ray imaging spectrometer concept [M. Bitter et al., Rev. Sci. Instrum. 75, 3660 (2004)], and improvements in x-ray detector technology [Ch. Broennimann et al., J. Synchrotron Radiat. 13, 120 (2006)], a spatially resolving high resolution x-ray spectrometer has been built and installed on the Alcator C-Mod tokamak. This instrument utilizes a spherically bent quartz crystal and a set of two dimensional x-ray detectors arranged in the Johann configuration [H. H. Johann, Z. Phys. 69, 185 (1931)] to image the entire plasma cross section with a spatial resolution of about 1 cm. The spectrometer was designed to measure line emission from H-like and He-like argon in the wavelength range 3.7 and 4.0 A with a resolving power of approximately 10 000 at frame rates up to 200 Hz. Using spectral tomographic techniques [I. Condrea, Phys. Plasmas 11, 2427 (2004)] the line integrated spectra can be inverted to infer profiles of impurity emissivity, velocity, and temperature. From these quantities it is then possible to calculate impurity density and electron temperature profiles. An overview of the instrument, analysis techniques, and example profiles are presented.

  19. CMOS Time-Resolved, Contact, and Multispectral Fluorescence Imaging for DNA Molecular Diagnostics

    PubMed Central

    Guo, Nan; Cheung, Ka Wai; Wong, Hiu Tung; Ho, Derek

    2014-01-01

    Instrumental limitations such as bulkiness and high cost prevent the fluorescence technique from becoming ubiquitous for point-of-care deoxyribonucleic acid (DNA) detection and other in-field molecular diagnostics applications. The complimentary metal-oxide-semiconductor (CMOS) technology, as benefited from process scaling, provides several advanced capabilities such as high integration density, high-resolution signal processing, and low power consumption, enabling sensitive, integrated, and low-cost fluorescence analytical platforms. In this paper, CMOS time-resolved, contact, and multispectral imaging are reviewed. Recently reported CMOS fluorescence analysis microsystem prototypes are surveyed to highlight the present state of the art. PMID:25365460

  20. Time-Resolved Imaging and Manipulation of H{sub 2} Fragmentation in Intense Laser Fields

    SciTech Connect

    Ergler, Th.; Rudenko, A.; Feuerstein, B.; Zrost, K.; Schroeter, C.D.; Moshammer, R.; Ullrich, J.

    2005-08-26

    We report on the experimental realization of time-resolved coincident Coulomb explosion imaging of H{sub 2} fragmentation in 10{sup 14} W/cm{sup 2} laser fields. Combining a high-resolution 'reaction microscope' and a fs pump-probe setup, we map the motion of wave packets dissociating via one- or two-photon channels, respectively, and observe a new region of enhanced ionization. The long-term interferometric stability of our system allows us to extend pump-probe experiments into the region of overlapping pulses, which offers new possibilities for the manipulation of ultrafast molecular fragmentation dynamics.

  1. Time-resolved experiments in the frequency domain using synchrotron radiation (invited)

    SciTech Connect

    De Stasio, G. ); Giusti, A.M.; Parasassi, T.; Ravagnan, G. ); Sapora, O. )

    1992-01-01

    PLASTIQUE is the only synchrotron radiation beam line in the world that performs time-resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and the dynamics of molecules. This technique measures fluorescence lifetimes with picosecond resolution in the near UV spectral range. Such accurate measurements are rendered possible by taking phase and modulation data, and by the advantages of the cross-correlation technique. A successful experiment demonstrated the radiation damage induced by low doses of radiation on rabbit blood cell membranes.

  2. Time resolved spectroscopic NMR imaging using hyperpolarized 129Xe.

    PubMed

    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. PMID:15040986

  3. A Clinical Tissue Oximeter Using NIR Time-Resolved Spectroscopy.

    PubMed

    Fujisaka, Shin-ichi; Ozaki, Takeo; Suzuki, Tsuyoshi; Kamada, Tsuyoshi; Kitazawa, Ken; Nishizawa, Mitsunori; Takahashi, Akira; Suzuki, Susumu

    2016-01-01

    The tNIRS-1, a new clinical tissue oximeter using NIR time-resolved spectroscopy (TRS), has been developed. The tNIRS-1 measures oxygenated, deoxygenated and total hemoglobin and oxygen saturation in living tissues. Two-channel TRS measurements are obtained using pulsed laser diodes (LD) at three wavelengths, multi-pixel photon counters (MPPC) for light detection, and time-to-digital converters (TDC) for time-of-flight photon measurements. Incorporating advanced semiconductor devices helped to make the design of this small-size, low-cost and low-power TRS instrument possible. In order to evaluate the correctness and reproducibility of measurement data obtained with the tNIRS-1, a study using blood phantoms and healthy volunteers was conducted to compare data obtained from a conventional SRS device and data from an earlier TRS system designed for research purposes. The results of the study confirmed the correctness and reproducibility of measurement data obtained with the tNIRS-1. Clinical evaluations conducted in several hospitals demonstrated a high level of usability in clinical situations and confirmed the efficacy of measurement data obtained with the tNIRS-1. PMID:26782242

  4. Time-resolved photoluminescence of SiOx encapsulated Si

    NASA Astrophysics Data System (ADS)

    Kalem, Seref; Hannas, Amal; Österman, Tomas; Sundström, Villy

    Silicon and its oxide SiOx offer a number of exciting electrical and optical properties originating from defects and size reduction enabling engineering new electronic devices including resistive switching memories. Here we present the results of photoluminescence dynamics relevant to defects and quantum confinement effects. Time-resolved luminescence at room temperature exhibits an ultrafast decay component of less than 10 ps at around 480 nm and a slower component of around 60 ps as measured by streak camera. Red shift at the initial stages of the blue luminescence decay confirms the presence of a charge transfer to long lived states. Time-correlated single photon counting measurements revealed a life-time of about 5 ns for these states. The same quantum structures emit in near infrared close to optical communication wavelengths. Nature of the emission is described and modeling is provided for the luminescence dynamics. The electrical characteristics of metal-oxide-semiconductor devices were correlated with the optical and vibrational measurement results in order to have better insight into the switching mechanisms in such resistive devices as possible next generation RAM memory elements. ``This work was supported by ENIAC Joint Undertaking and Laser-Lab Europe''.

  5. [Laser-time-resolved fluorescence spectroscopy in immunoassays].

    PubMed

    Pan, L; Du, J; Xie, W; Du, Q; Yun, Q

    2000-06-01

    This paper described a laser-excited time-resolved fluoroimmunoassay set. It made lanthanide ion to couple the anhydrde of diethylenetriaminepentaacetic acid (DTPAA) for labeling antibodies. The experiment used polystyrene tap coated with HCV antigen as the solid phase and a chelate of the rare earth metal europium as fluorescent label. A nitrogen laser beam was used to excite the Eu3- chelates and after 60 microseconds delay time, the emission fluorescence was measured. Background fluorescence of short lifetimes caused by serum components and Raman scattering can be eliminated by set the delay time. In the system condition, fluorescent spectra and fluorescent lifetimes of Eu3+ beta-naphthoyltrifluroacetone (NTA) chelates were measured. The fluorescent lifetime value is 650 microseconds. The maximum emission wavelength is 613 nm. The linear range of europium ion concentration is 1 x 10(-7)-1 x 10(-11) g.mL-1 and the detection limit is 1 x 10(-13) g.mL-1. The relative standard deviation of determination (n = 12) for samples at 0.01 ng.mL-1 magnitude is 6.4%. Laser-TRFIA was also found to be suitable for diagnosis of HCV. The sensitivity and specificity were comparable to enzyme immunoassay. The result was obtained with laser-TRFIA for 29 human correlated well with enzyme immunoassay. PMID:12958930

  6. 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.

  7. Phase-resolved time-domain nonlinear optical signals

    NASA Astrophysics Data System (ADS)

    Gallagher Faeder, Sarah M.; Jonas, David M.

    2000-09-01

    A systematic theoretical and computational investigation of the microscopic factors which determine the phase of the signal field in time-resolved quasidegenerate three-pulse scattering experiments is presented. The third-order phase-matched response is obtained by density-matrix perturbation theory using a Green-function formalism for a system composed of two well-separated sets of closely spaced energy levels. Equations for calculating the electric field of four-wave-mixing signals generated by path-length delayed pulses are given. It is found that the phase of the signal field is determined by the excitation pulse phases, the dynamics of the nonlinear polarization decay, the product of four transition dipole matrix elements, and by a pulse-delay-dependent phase modulation at the frequency of the first dipole oscillation in the four-wave-mixing process. Analytic results for a two-level Bloch model show the phase shift from rapid nonlinear polarization decay. The product of dipole matrix elements is real and positive for three-level processes (bleached ground-state absorption and excited-state emission), but can be real and negative for some four-level Raman processes. The pulse-delay-dependent phase modulation treated here is closely related to the interferometric pulse-delay-dependent amplitude modulation observed in some collinear experiments, and plays a role in producing photon echos in inhomogeneously broadened samples. Numerical calculations of phase-resolved electric fields for finite duration pulses using a Brownian oscillator model appropriate for condensed-phase dynamics are presented. The ability of pulse-delay-dependent phase modulation to encode the frequency of the initially excited dipole onto the phase of the signal field can be exploited to examine energy-level connectivity, reveal correlations hidden under the inhomogeneous lineshape, and probe relaxation pathways in multilevel systems.

  8. Resolving Intralocus Sexual Conflict: Genetic Mechanisms and Time Frame

    PubMed Central

    Pischedda, Alison; Rice, William R.

    2010-01-01

    Intralocus sexual conflict occurs due to the expression of sexually antagonistic alleles: those that increase fitness when expressed in one sex but decrease fitness when expressed in the other sex. This genetic conflict is expected whenever the sexes are selected toward differing phenotypic optima for a trait that has a positive genetic correlation between the sexes. Here we synthesize recent developments in the areas of genomics, microarray analysis, and developmental and molecular genetics to establish feasible mechanisms by which the intersexual genetic correlation can be reduced, as well as the time course over which conflict resolution is expected to evolve. PMID:20421329

  9. DSCOVR High Time Resolution Solar Wind Measurements

    NASA Technical Reports Server (NTRS)

    Szabo, Adam

    2012-01-01

    The Deep Space Climate Observatory (DSCOVR), previously known as Triana, spacecraft is expected to be launched in late 2014. It will carry a fluxgate magnetometer, Faraday Cup solar wind detector and a top-hat electron electrostatic analyzer. The Faraday Cup will provide an unprecedented 10 vectors/sec time resolution measurement of the solar wind proton and alpha reduced distribution functions. Coupled with the 40 vector/sec vector magnetometer measurements, the identification of specific wave modes in the solar wind will be possible for the first time. The science objectives and data products of the mission will be discussed.

  10. High-accuracy time- and space-resolved Stark shift measurements

    SciTech Connect

    Bailey, J.E.; Adams, R.; Carlson, A.L.; Ching, C.H.; Filuk, A.B.; Lake, P.

    1996-07-01

    Stark-shift measurements using emission spectroscopy are a powerful tool for advancing understanding in many plasma physics experiments. The authors use simultaneous 2-D-spatial and time-resolved spectra to study the electric field evolution in the 20 TW Particle Beam Fusion Accelerator II ion diode acceleration gap. Fiber optic arrays transport light from the gap to remote streaked spectrographs operated in a multiplexed mode that enables recording time-resolved spectra from eight spatial locations on a single instrument. Design optimization and characterization measurements of the multiplexed spectrograph properties include the astigmatism, resolution, dispersion variation, and sensitivity. A semi-automated line-fitting procedure determines the Stark shift and the related uncertainties. Fields up to 10 MV/cm are measured with an accuracy {+-}2--4%. Detailed tests of the fitting procedure confirm that the wavelength shift uncertainties are accurate to better than {+-}20%. Development of an active spectroscopy probe technique that uses laser-induced fluorescence from an injected atomic beam to obtain 3-D space- and time-resolved measurements of the electric and magnetic fields is in progress.

  11. 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.

  12. Time-resolved electric-field-induced second harmonic

    NASA Astrophysics Data System (ADS)

    Meshulam, Guilia; Berkovic, Garry; Kotler, Zvi

    2001-12-01

    One limitation of using electric field induced second harmonic (EFISH) to determine the molecular first hyperpolarizability (beta) of nonlinear optical molecules lies in the fact that part of the second harmonic signal comes from the second hyperpolarizability (gamma) produced by mixing two optical fields with the DC field. In analyzing EFISH results, the second hyperpolarizability contribution of the studied molecules is generally neglected. We present a modified time resolved EFISH technique that allows us, in a single experiment, to determine separately the beta and the gamma contributions. We study para-nitro aniline dissolved in Glycerol, a highly viscous solvent, and apply the DC field via a high voltage pulse with a fast rise time of approximately 40 nsec. As a result, the orientation of the molecules under the applied electric field is slow relative to the build-up of the field, enabling us to directly measure only the DC induced second harmonic (gamma contribution), at the beginning of the HV pulse. The pure beta contribution is determined from the difference between this signal and the conventional EFISH signal at the plateau of the HV pulse. Our result confirm that the gamma contribution is indeed less than 10% of the total.

  13. 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.

  14. 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

  15. Phase-ambiguity resolution for QPSK modulation systems. Part 2: A method to resolve offset QPSK

    NASA Technical Reports Server (NTRS)

    Nguyen, Tien Manh

    1989-01-01

    Part 2 presents a new method to resolve the phase-ambiguity for Offset QPSK modulation systems. When an Offset Quaternary Phase-Shift-Keyed (OQPSK) communications link is utilized, the phase ambiguity of the reference carrier must be resolved. At the transmitter, two different unique words are separately modulated onto the quadrature carriers. At the receiver, the recovered carrier may have one of four possible phases, 0, 90, 180, or 270 degrees, referenced to the nominally correct phase. The IF portion of the channel may cause a phase-sense reversal, i.e., a reversal in the direction of phase rotation for a specified bit pattern. Hence, eight possible phase relationships (the so-called eight ambiguous phase conditions) between input and output of the demodulator must be resolved. Using the In-phase (I)/Quadrature (Q) channel reversal correcting property of an OQPSK Costas loop with integrated symbol synchronization, four ambiguous phase conditions are eliminated. Thus, only four possible ambiguous phase conditions remain. The errors caused by the remaining ambiguous phase conditions can be corrected by monitoring and detecting the polarity of the two unique words. The correction of the unique word polarities results in the complete phase-ambiguity resolution for the OQPSK system.

  16. Time-resolved microrheology of actively remodeling actomyosin networks

    NASA Astrophysics Data System (ADS)

    Silva, Marina Soares e.; Stuhrmann, Björn; Betz, Timo; Koenderink, Gijsje H.

    2014-07-01

    Living cells constitute an extraordinary state of matter since they are inherently out of thermal equilibrium due to internal metabolic processes. Indeed, measurements of particle motion in the cytoplasm of animal cells have revealed clear signatures of nonthermal fluctuations superposed on passive thermal motion. However, it has been difficult to pinpoint the exact molecular origin of this activity. Here, we employ time-resolved microrheology based on particle tracking to measure nonequilibrium fluctuations produced by myosin motor proteins in a minimal model system composed of purified actin filaments and myosin motors. We show that the motors generate spatially heterogeneous contractile fluctuations, which become less frequent with time as a consequence of motor-driven network remodeling. We analyze the particle tracking data on different length scales, combining particle image velocimetry, an ensemble analysis of the particle trajectories, and finally a kymograph analysis of individual particle trajectories to quantify the length and time scales associated with active particle displacements. All analyses show clear signatures of nonequilibrium activity: the particles exhibit random motion with an enhanced amplitude compared to passive samples, and they exhibit sporadic contractile fluctuations with ballistic motion over large (up to 30 μm) distances. This nonequilibrium activity diminishes with sample age, even though the adenosine triphosphate level is held constant. We propose that network coarsening concentrates motors in large clusters and depletes them from the network, thus reducing the occurrence of contractile fluctuations. Our data provide valuable insight into the physical processes underlying stress generation within motor-driven actin networks and the analysis framework may prove useful for future microrheology studies in cells and model organisms.

  17. Calibrated time-resolved transmission grating spectrometer for the study of ultrafast x-ray sources.

    PubMed

    Pelletier, J F; Chaker, M; Kieffer, J C

    1996-01-01

    A transmission grating spectrometer has been coupled to a high-temporal-resolution soft x-ray streak camera for the study of picosecond laser-plasma x-ray sources. A procedure to deconvolve the overlapping contributions of diffraction orders and to calibrate the instrument has been established in order to obtain absolute time-resolved x-ray emission spectra in the 0.1-1.2 keV spectral region. The deconvolution and calibration techniques are presented along with measurements establishing the temporal resolution of this diagnostic at ~2 ps. Examples of calibrated spectra of laser-plasma x-ray sources created by 400 fs laser pulses at intensities of 1018 W/cm2 are also shown. PMID:21307534

  18. Time-resolved neurite mechanics by thermal fluctuation assessments

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  19. Space-time resolved kinetics of low-pressure breakdown

    NASA Astrophysics Data System (ADS)

    Marić, D.; Malović, G.; Radmilović-Radenović, M.; Petrović, Z. L.

    2008-05-01

    A review of diagnostics of low-current low-pressure discharges is given with an aim to illustrate how such discharges are used to determine swarm parameters and also how such data may be applied to model and understand the discharges. We have revised how comprehensive modelling of breakdown has led to agreement between binary collision data and the data that may be inferred from the breakdown (Paschen) curves by including processes such as space charge (current) effect on the local field in front of the cathode, photoemission, heavy particle gas phase ionization and backdiffusion. It is also discussed how modelling of Volt-Ampere characteristics in addition to Paschen curves is necessary to establish models of secondary electron emission and how these models may be applied in high current discharges. Finally we show how space time resolved anatomy of the breakdown can lead to understanding of the physics of the initial stages of gas breakdown and formation of Townsend regime, glow and abnormal glow discharges.

  20. Time-resolved multiphoton imaging of basal cell carcinoma

    NASA Astrophysics Data System (ADS)

    Cicchi, R.; Sestini, S.; De Giorgi, V.; Stambouli, D.; Carli, P.; Massi, D.; Pavone, F. S.

    2007-02-01

    We investigated human cutaneous basal cell carcinoma ex-vivo samples by combined time resolved two photon intrinsic fluorescence and second harmonic generation microscopy. Morphological and spectroscopic differences were found between malignant skin and corresponding healthy skin tissues. In comparison with normal healthy skin, cancer tissue showed a different morphology and a mean fluorescence lifetime distribution slightly shifted towards higher values. Topical application of delta-aminolevulinic acid to the lesion four hours before excision resulted in an enhancement of the fluorescence signal arising from malignant tissue, due to the accumulation of protoporphyrines inside tumor cells. Contrast enhancement was prevalent at tumor borders by both two photon fluorescence microscopy and fluorescence lifetime imaging. Fluorescence-based images showed a good correlation with conventional histopathological analysis, thereby supporting the diagnostic accuracy of this novel method. Combined morphological and lifetime analysis in the study of ex-vivo skin samples discriminated benign from malignant tissues, thus offering a reliable, non-invasive tool for the in-vivo analysis of inflammatory and neoplastic skin lesions.

  1. 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.

  2. Sea Butterfly Swimming: Time-resolved Tomographic PIV measurements

    NASA Astrophysics Data System (ADS)

    Murphy, David; Zheng, Lingxiao; Mittal, Rajat; Webster, Donald; Yen, Jeannette

    2011-11-01

    The planktonic sea butterfly Limacina helicina swims by flapping its flexible, wing-like parapodia. The appendage stroke kinematics of this shell-bearing pteropod are three-dimensional and likely contain elements of both drag-based (rowing) and lift-based (flapping) propulsion. Unsteady lift-generating mechanisms such as clap-and-fling may also be present. Upstroke and downstroke motions both propel the animal upward and roll it forwards and backwards, resulting in a sawtooth trajectory. We present time-resolved, tomographic PIV measurements of flow generated by free-swimming pteropods (Limacina helicina) moving upwards with average swimming speeds of 5 - 17 mm/s. The pteropods beat their appendages with a stroke frequency of 4 - 5 Hz. With a size range of 1 - 2 mm, the animals filmed in this study operate in a viscous environment with a Reynolds number of 5 to 20. The volumetric flow measurements provide insight into the three dimensional nature of the flow and into the relative importance of drag- and lift-based propulsion at this low Reynolds number. Preliminary results from Navier-Stokes simulations of the flow associated with the swimming of this organism will also be presented.

  3. Time-Resolved Synchronous Fluorescence for Biomedical Diagnosis

    PubMed Central

    Zhang, Xiaofeng; Fales, Andrew; Vo-Dinh, Tuan

    2015-01-01

    This article presents our most recent advances in synchronous fluorescence (SF) methodology for biomedical diagnostics. The SF method is characterized by simultaneously scanning both the excitation and emission wavelengths while keeping a constant wavelength interval between them. Compared to conventional fluorescence spectroscopy, the SF method simplifies the emission spectrum while enabling greater selectivity, and has been successfully used to detect subtle differences in the fluorescence emission signatures of biochemical species in cells and tissues. The SF method can be used in imaging to analyze dysplastic cells in vitro and tissue in vivo. Based on the SF method, here we demonstrate the feasibility of a time-resolved synchronous fluorescence (TRSF) method, which incorporates the intrinsic fluorescent decay characteristics of the fluorophores. Our prototype TRSF system has clearly shown its advantage in spectro-temporal separation of the fluorophores that were otherwise difficult to spectrally separate in SF spectroscopy. We envision that our previously-tested SF imaging and the newly-developed TRSF methods will combine their proven diagnostic potentials in cancer diagnosis to further improve the efficacy of SF-based biomedical diagnostics. PMID:26404289

  4. Conditions for reliable time-resolved dosimetry of electronic portal imaging devices for fixed-gantry IMRT and VMAT

    SciTech Connect

    Yeo, Inhwan Jason; Patyal, Baldev; Mandapaka, Anant; Jung, Jae Won; Yi, Byong Yong; Kim, Jong Oh

    2013-07-15

    Purpose: The continuous scanning mode of electronic portal imaging devices (EPID) that offers time-resolved information has been newly explored for verifying dynamic radiation deliveries. This study seeks to determine operating conditions (dose rate stability and time resolution) under which that mode can be used accurately for the time-resolved dosimetry of intensity-modulated radiation therapy (IMRT) beams.Methods: The authors have designed the following test beams with variable beam holdoffs and dose rate regulations: a 10 Multiplication-Sign 10 cm open beam to serve as a reference beam; a sliding window (SW) beam utilizing the motion of a pair of multileaf collimator (MLC) leaves outside the 10 Multiplication-Sign 10 cm jaw; a step and shoot (SS) beam to move the pair in step; a volumetric modulated arc therapy (VMAT) beam. The beams were designed in such a way that they all produce the same open beam output of 10 Multiplication-Sign 10 cm. Time-resolved ion chamber measurements at isocenter and time-resolved and integrating EPID measurements were performed for all beams. The time-resolved EPID measurements were evaluated through comparison with the ion chamber and integrating EPID measurements, as the latter are accepted procedures. For two-dimensional, time-resolved evaluation, a VMAT beam with an infield MLC travel was designed. Time-resolved EPID measurements and Monte Carlo calculations of such EPID dose images for this beam were performed and intercompared.Results: For IMRT beams (SW and SS), the authors found disagreement greater than 2%, caused by frame missing of the time-resolved mode. However, frame missing disappeared, yielding agreement better than 2%, when the dose rate of irradiation (and thus the frame acquisition rates) reached a stable and planned rate as the dose of irradiation was raised past certain thresholds (a minimum 12 s of irradiation per shoot used for SS IMRT). For VMAT, the authors found that dose rate does not affect the frame

  5. Conditions for reliable time-resolved dosimetry of electronic portal imaging devices for fixed-gantry IMRT and VMAT

    PubMed Central

    Yeo, Inhwan Jason; Jung, Jae Won; Patyal, Baldev; Mandapaka, Anant; Yong Yi, Byong; Oh Kim, Jong

    2013-01-01

    Purpose: The continuous scanning mode of electronic portal imaging devices (EPID) that offers time-resolved information has been newly explored for verifying dynamic radiation deliveries. This study seeks to determine operating conditions (dose rate stability and time resolution) under which that mode can be used accurately for the time-resolved dosimetry of intensity-modulated radiation therapy (IMRT) beams. Methods: The authors have designed the following test beams with variable beam holdoffs and dose rate regulations: a 10 × 10 cm open beam to serve as a reference beam; a sliding window (SW) beam utilizing the motion of a pair of multileaf collimator (MLC) leaves outside the 10 × 10 cm jaw; a step and shoot (SS) beam to move the pair in step; a volumetric modulated arc therapy (VMAT) beam. The beams were designed in such a way that they all produce the same open beam output of 10 × 10 cm. Time-resolved ion chamber measurements at isocenter and time-resolved and integrating EPID measurements were performed for all beams. The time-resolved EPID measurements were evaluated through comparison with the ion chamber and integrating EPID measurements, as the latter are accepted procedures. For two-dimensional, time-resolved evaluation, a VMAT beam with an infield MLC travel was designed. Time-resolved EPID measurements and Monte Carlo calculations of such EPID dose images for this beam were performed and intercompared. Results: For IMRT beams (SW and SS), the authors found disagreement greater than 2%, caused by frame missing of the time-resolved mode. However, frame missing disappeared, yielding agreement better than 2%, when the dose rate of irradiation (and thus the frame acquisition rates) reached a stable and planned rate as the dose of irradiation was raised past certain thresholds (a minimum 12 s of irradiation per shoot used for SS IMRT). For VMAT, the authors found that dose rate does not affect the frame acquisition rate, thereby causing no frame missing

  6. Evaluation of Tomographic Inverse Models Resolved from Various Travel- time Theories and Parameterizations

    NASA Astrophysics Data System (ADS)

    Chang, Y.; Hung, S.; Chiao, L.; Yang, H.

    2010-12-01

    Whether different forward theories or parameterization methods employed in seismic tomographic imaging lead to the improvement of the resulting Earth structures has been a focus of attention in the seismological community. Recent advance in tomographic theory has gone beyond classical ray theory and incorporated the 3-D sensitivity kernels of frequency-dependent travel-time data into probing the mantle velocity heterogeneity with unprecedented resolution. On the other hand, the conception of multi-scale parameterization has been introduced to deal with naturally uneven data distribution and spatially-varying model resolution for the tomographic inverse problems. The multi-resolution model automatically built through the wavelet decomposition and synthesis results in the non-stationary spatial resolution and data-adaptive resolvable scales. Because the Gram matrix of Frechét derivatives that relates observed data to seismic velocity variations is usually too large to be practically inverted by singular value decomposition (SVD), the iterative LSQR algorithm is instead employed in the inversion which inhibits the direct calculation of resolution matrix to assess the model performance. Recently, with the increasing computing power, we are now able to calculate the SVD of the Gram matrix more efficiently using the parallel PROPACK solver. In this study, we compute the ground-truth pseudo-spectral seismograms in random media with certain heterogeneity strengths and scale lengths. The finite-frequency travel-time residuals measured from waveform cross correlation are then used to invert for the implanted random structure based on different forward theory and model parameterization. For each inversion approach, the trade-off between model covariance and model spread is utilized to determine the optimal solution, showing that the multi-scale model yields a much lower model covariance and remains better spectral resolution for longer-wavelength velocity structures than the

  7. Modeling and optimization of a time-resolved proton radiographic imaging system for proton cancer treatment

    NASA Astrophysics Data System (ADS)

    Han, Bin

    This dissertation describes a research project to test the clinical utility of a time-resolved proton radiographic (TRPR) imaging system by performing comprehensive Monte Carlo simulations of a physical device coupled with realistic lung cancer patient anatomy defined by 4DCT for proton therapy. A time-resolved proton radiographic imaging system was modeled through Monte Carlo simulations. A particle-tracking feature was employed to evaluate the performance of the proton imaging system, especially in its ability to visualize and quantify proton range variations during respiration. The Most Likely Path (MLP) algorithm was developed to approximate the multiple Coulomb scattering paths of protons for the purpose of image reconstruction. Spatial resolution of ˜ 1 mm and range resolution of 1.3% of the total range were achieved using the MLP algorithm. Time-resolved proton radiographs of five patient cases were reconstructed to track tumor motion and to calculate water equivalent length variations. By comparing with direct 4DCT measurement, the accuracy of tumor tracking was found to be better than 2 mm in five patient cases. Utilizing tumor tracking information to reduce margins to the planning target volume, a gated treatment plan was compared with un-gated treatment plan. The equivalent uniform dose (EUD) and the normal tissue complication probability (NTCP) were used to quantify the gain in the quality of treatments. The EUD of the OARs was found to be reduced up to 11% and the corresponding NTCP of organs at risk (OARs) was found to be reduced up to 16.5%. These results suggest that, with image guidance by proton radiography, dose to OARs can be reduced and the corresponding NTCPs can be significantly reduced. The study concludes that the proton imaging system can accurately track the motion of the tumor and detect the WEL variations, leading to potential gains in using image-guided proton radiography for lung cancer treatments.

  8. Development of dispersive XAFS system for analysis of time-resolved spatial distribution of electrode reaction.

    PubMed

    Katayama, Misaki; Miyahara, Ryota; Watanabe, Toshiki; Yamagishi, Hirona; Yamashita, Shohei; Kizaki, Terue; Sugawara, Yoshimi; Inada, Yasuhiro

    2015-09-01

    Apparatus for a technique based on the dispersive optics of X-ray absorption fine structure (XAFS) has been developed at beamline BL-5 of the Synchrotron Radiation Center of Ritsumeikan University. The vertical axis of the cross section of the synchrotron light is used to disperse the X-ray energy using a cylindrical polychromator and the horizontal axis is used for the spatially resolved analysis with a pixel array detector. The vertically dispersive XAFS (VDXAFS) instrument was designed to analyze the dynamic changeover of the inhomogeneous electrode reaction of secondary batteries. The line-shaped X-ray beam is transmitted through the electrode sample, and then the dispersed transmitted X-rays are detected by a two-dimensional detector. An array of XAFS spectra in the linear footprint of the transmitted X-ray on the sample is obtained with the time resolution of the repetition frequency of the detector. Sequential measurements of the space-resolved XAFS data are possible with the VDXAFS instrument. The time and spatial resolutions of the VDXAFS instrument depend on the flux density of the available X-ray beam and the size of the light source, and they were estimated as 1 s and 100 µm, respectively. The electrode reaction of the LiFePO4 lithium ion battery was analyzed during the constant current charging process and during the charging process after potential jumping. PMID:26289274

  9. Time-resolved spectroscopy of nucleic acid systems using synchrotron radiation from 230 nm to 354 nm

    NASA Astrophysics Data System (ADS)

    Daniels, Malcolm; Ballini, Jean-Pierre; Vigny, Paul

    1992-07-01

    The excited states of nucleic acids are complex, both at the individual chromophore level and because of the effect of stacking interactions on the electronic states. Considerable progress has been made recently by studying the lifetimes of the stacked states and by utilizing the technique of time-resolved spectroscopy. Experimental results obtained using the ACO synchrotron at LURE, Orsay, will be presented. Resolution of the decay data gives a model-based estimate of the number of emitting species and their lifetimes, and this information is then used to deconvolate experimental time-windowed spectra (time-delayed spectra) to give true time-resolved spectra. It is a unique feature of the synchrotron, compared with the laser, that the combination of delayed detection (photon counting) with the continuous wavelength distribution of the synchrotron allows the acquisition of excitation spectra by uninterrupted repetitive scanning over a wide range of UV exciting wavelengths, in the present work from 230 nm to 354 nm. Such time-delayed excitation spectra can also be deconvoluted into components corresponding to the various time-resolved emission spectra. In this way we are able to demonstrate for the first time that ground state stacking interactions are directly responsible for excimer-like emissions. Time-resolved emission spectra and time-resolved excitation spectra will be presented for the dinucleoside phosphate d(CG) and the synthetic alternating polynucleotide poly d(GC), a `B-type' DNA structure.

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

    PubMed

    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. PMID:26931864

  11. Time-resolved binding of azithromycin to Escherichia coli ribosomes.

    PubMed

    Petropoulos, Alexandros D; Kouvela, Ekaterini C; Starosta, Agata L; Wilson, Daniel N; Dinos, George P; Kalpaxis, Dimitrios L

    2009-01-30

    Azithromycin is a semisynthetic derivative of erythromycin that inhibits bacterial protein synthesis by binding within the peptide exit tunnel of the 50S ribosomal subunit. Nevertheless, there is still debate over what localization is primarily responsible for azithromycin binding and as to how many molecules of the drug actually bind per ribosome. In the present study, kinetic methods and footprinting analysis are coupled together to provide time-resolved details of the azithromycin binding process. It is shown that azithromycin binds to Escherichia coli ribosomes in a two-step process: The first-step involves recognition of azithromycin by the ribosomal machinery and places the drug in a low-affinity site located in the upper part of the exit tunnel. The second step corresponds to the slow formation of a final complex that is both much tighter and more potent in hindering the progression of the nascent peptide through the exit tunnel. Substitution of uracil by cytosine at nucleoside 2609 of 23S rRNA, a base implicated in the high-affinity site, facilitates the shift of azithromycin to this site. In contrast, mutation U754A hardly affects the binding process. Binding of azithromycin to both sites is hindered by high concentrations of Mg(2+) ions. Unlike Mg(2+) ions, polyamines do not significantly affect drug binding to the low-affinity site but attenuate the formation of the final complex. The low- and high-affinity sites of azithromycin binding are mutually exclusive, which means that one molecule of the drug binds per E. coli ribosome at a time. In contrast, kinetic and binding data indicate that in Deinococcus radiodurans, two molecules of azithromycin bind cooperatively to the ribosome. This finding confirms previous crystallographic results and supports the notion that species-specific structural differences may primarily account for the apparent discrepancies between the antibiotic binding modes obtained for different organisms. PMID:19071138

  12. Role of electron-electron interference in ultrafast time-resolved imaging of electronic wavepackets

    SciTech Connect

    Dixit, Gopal; Santra, Robin

    2013-04-07

    Ultrafast time-resolved x-ray scattering is an emerging approach to image the dynamical evolution of the electronic charge distribution during complex chemical and biological processes in real-space and real-time. Recently, the differences between semiclassical and quantum-electrodynamical (QED) theory of light-matter interaction for scattering of ultrashort x-ray pulses from the electronic wavepacket were formally demonstrated and visually illustrated by scattering patterns calculated for an electronic wavepacket in atomic hydrogen [G. Dixit, O. Vendrell, and R. Santra, Proc. Natl. Acad. Sci. U.S.A. 109, 11636 (2012)]. In this work, we present a detailed analysis of time-resolved x-ray scattering from a sample containing a mixture of non-stationary and stationary electrons within both the theories. In a many-electron system, the role of scattering interference between a non-stationary and several stationary electrons to the total scattering signal is investigated. In general, QED and semiclassical theory provide different results for the contribution from the scattering interference, which depends on the energy resolution of the detector and the x-ray pulse duration. The present findings are demonstrated by means of a numerical example of x-ray time-resolved imaging for an electronic wavepacket in helium. It is shown that the time-dependent scattering interference vanishes within semiclassical theory and the corresponding patterns are dominated by the scattering contribution from the time-independent interference, whereas the time-dependent scattering interference contribution do not vanish in the QED theory and the patterns are dominated by the scattering contribution from the non-stationary electron scattering.

  13. Advances in coincidence time resolution for PET.

    PubMed

    Cates, Joshua W; Levin, Craig S

    2016-03-21

    Coincidence time resolution (CTR), an important parameter for time-of-flight (TOF) PET performance, is determined mainly by properties of the scintillation crystal and photodetector used. Stable production techniques for LGSO:Ce (Lu1.8Gd0.2SiO5:Ce) with decay times varying from ∼ 30-40 ns have been established over the past decade, and the decay time can be accurately controlled with varying cerium concentration (0.025-0.075 mol%). This material is promising for TOF-PET, as it has similar light output and equivalent stopping power for 511 keV annihilation photons compared to industry standard LSO:Ce and LYSO:Ce, and the decay time is improved by more than 30% with proper Ce concentration. This work investigates the achievable CTR with LGSO:Ce (0.025 mol%) when coupled to new silicon photomultipliers. Crystal element dimension is another important parameter for achieving fast timing. 20 mm length crystal elements achieve higher 511 keV photon detection efficiency, but also introduce higher scintillation photon transit time variance. 3 mm length crystals are not practical for PET, but have reduced scintillation transit time spread. The CTR between pairs of 2.9 × 2.9 × 3 mm(3) and 2.9 × 2.9 × 20 mm(3) LGSO:Ce crystals was measured to be 80 ± 4 and 122 ± 4 ps FWHM, respectively. Measurements of light yield and intrinsic decay time are also presented for a thorough investigation into the timing performance with LGSO:Ce (0.025 mol%). PMID:26914187

  14. Time-resolved spectroscopy of the intrinsic fluorescence of nucleic acid species

    NASA Astrophysics Data System (ADS)

    Daniels, Malcolm; Hart, Lucas P.; Ho, Paul S.; Ballini, Jean-Pierre; Vigny, Paul

    1990-05-01

    Polarization and lifetime studies have shown that the fluorescence from nucleic acid species is complex, both at the individual chromophore level and because of the effect of stacking interactions on the electronic states. Recent work aimed at elucidating some aspects of this behavior by decay analysis and time-resolved spectroscopy is surveyed. Experimental work has been carried out using the ACO synchrotron at LURE, France) with time-correlated single photon counting, or a frequency-doubled N2-pumped dye laser, pulse width 700 ps, with fast-gated (100 ps width) analog detection and signal averaging. Decay curves are treated by global analysis using the Marquardt non-linear least-squares algorithm (synchrotron data) or the SPLMOD program (EMBO), which carries out a non-linear leastsquares minimization using cubic splines, for the laser data. Resolution of the decay data gives a model-based estimate of the number of components and their lifetimes. This information is then used to deconvolute timewindowed spectra (time-delayed spectra) into the time-resolved spectra. It is a particular feature of the combination of delayed photon counting with the continuous wavelength distribution of pulsed synchrotron radiation that excitation spectra correlating with emissions of different lifetimes can be obtained by uninterrupted repetitive scanning over a wide range of exciting wavelengths, in the present work from 230 nm to 354 urn. Such time-delayed excitation spectra can also be deconvoluted into components corresponding to the various time-resolved emission spectra. Examples of these three types of information viz resolved lifetimes, time-resolved emission spectra and their excitation spectra are presented and discussed for the following systems. I. adenosine; 6N, 6N-dimethyladenosine; protonated adenosine; this work shows the role of rotamers in the excited state behavior of this chromophore and demonstrates the forbidden nature of the lowest excited state. II. d(AT); d

  15. Compact 32-channel time-resolved single-photon detection system

    NASA Astrophysics Data System (ADS)

    Cuccato, A.; Antonioli, S.; Gulinatti, A.; Labanca, I.; Rech, I.; Ghioni, M.

    2013-05-01

    Nowadays, many research fields like biology, chemistry, medicine and space technology rely on high sensitivity imaging instruments that allow to exploit modern measurement techniques; among these, Time-Correlated Single-Photon Counting (TCSPC) provides extremely high time resolution. Single-photon detectors play a key role in these advanced imaging systems, and in recent years Single-Photon Avalanche Diodes (SPADs) have become a valid alternative to Photo Multiplier Tubes (PMTs). Moreover scientific research has recently focused on single photon detector arrays, pushed by a growing demand for multichannel systems. In this scenario, we developed a compact, stand-alone, 32-channel system for time-resolved single-photon counting applications. The system core is represented by a 32×1 SPAD array built in custom technology, featuring high time resolution, high photon detection efficiency (> 45%) and low dark count rate. The SPAD avalanche signal is exported through an integrated inverter which is placed close to the photo detector, this way the avalanche event is detected with high time resolution while achieving negligible crosstalk between adjacent pixels. SPAD proper operation is guaranteed by a 32×1 mixed passive-active quenching circuit (AQC) array built in 0.18 μm HV-CMOS technology; its digital outputs are fed to an FPGA that performs on-board processing of photon counting information. On the contrary, photon timing information is directly extracted from the pixel array and exported in Current Mode Logic (CML) standard. Preliminary experiments have been carried out on the developed system, resulting in a high time resolution (< 60 ps FWHM) and mean dark count rate lower than 8500 counts/s at 25°C.

  16. Time Resolved Detection of Infrared Synchrotron Radiation at DA{phi}NE

    SciTech Connect

    Bocci, A.; Marcelli, A.; Drago, A.; Guidi, M. Cestelli; Pace, E.; Piccinini, M.; Sali, D.; Morini, P.

    2007-01-19

    Synchrotron radiation is characterized by a very wide spectral emission from IR to X-ray wavelengths and a pulsed structure that is a function of the source time structure. In a storage ring, the typical temporal distance between two bunches, whose duration is a few hundreds of picoseconds, is on the nanosecond scale. Therefore, synchrotron radiation sources are a very powerful tools to perform time-resolved experiments that however need extremely fast detectors. Uncooled IR devices optimized for the mid-IR range with sub-nanosecond response time, are now available and can be used for fast detection of intense IR sources such as synchrotron radiation storage rings. We present here different measurements of the pulsed synchrotron radiation emission at DA{phi}NE (Double Annular {phi}-factory for Nice Experiments), the collider of the Laboratori Nazionali of Frascati (LNF) of the Istituto Nazionale di Fisica Nucleare (INFN), performed with very fast uncooled infrared detectors with a time resolution of a few hundreds of picoseconds. We resolved the emission time structure of the electron bunches of the DA{phi}NE collider when it works in a normal condition for high energy physics experiments with both photovoltaic and photoconductive detectors. Such a technology should pave the way to new diagnostic methods in storage rings, monitoring also source instabilities and bunch dynamics.

  17. Instrumentation for time-resolved dispersive studies at Advanced Photon Source beamline 1-BM

    SciTech Connect

    Brauer, S.; Rodricks, B.

    1996-07-01

    We describe progress in optics and instrumentation at beamline 1-BM, designed in part for time-resolved dispersive x-ray absorption fine structure (XAFS) measurements. The key optical element is a horizontally focusing curved-crystal monochromator that invokes a 4-point bending scheme and a liquid-metal cooling bath. The device has been designed for dispersive studies in the 5-24 keV range, with a horizontal focal spot size of {le}100 micrometers FWHM. To minimize thermal distortions and thermal equilibration time, the 355 {times} 32 {times} 0.8 mm crystal is nearly half submerged in a bath of Ga-In-Sn-Zn alloy, which thermally couples the crystal to the water-cooled Cu frame, while permitting the required crystal bending. Harmonic rejection, focusing schemes and the novel spectrometer positioning system will be described. For microsecond-resolution time-resolved studies, a fast CCD streak camera detector has been developed. Results from commissioning tests of the instrumentation are described. 11 refs., 4 figs.

  18. MONSTIR II: A 32-channel, multispectral, time-resolved optical tomography system for neonatal brain imaging

    SciTech Connect

    Cooper, Robert J. Magee, Elliott; Everdell, Nick; Magazov, Salavat; Varela, Marta; Airantzis, Dimitrios; Gibson, Adam P.; Hebden, Jeremy C.

    2014-05-15

    We detail the design, construction and performance of the second generation UCL time-resolved optical tomography system, known as MONSTIR II. Intended primarily for the study of the newborn brain, the system employs 32 source fibres that sequentially transmit picosecond pulses of light at any four wavelengths between 650 and 900 nm. The 32 detector channels each contain an independent photo-multiplier tube and temporally correlated photon-counting electronics that allow the photon transit time between each source and each detector position to be measured with high temporal resolution. The system's response time, temporal stability, cross-talk, and spectral characteristics are reported. The efficacy of MONSTIR II is demonstrated by performing multi-spectral imaging of a simple phantom.

  19. MONSTIR II: a 32-channel, multispectral, time-resolved optical tomography system for neonatal brain imaging.

    PubMed

    Cooper, Robert J; Magee, Elliott; Everdell, Nick; Magazov, Salavat; Varela, Marta; Airantzis, Dimitrios; Gibson, Adam P; Hebden, Jeremy C

    2014-05-01

    We detail the design, construction and performance of the second generation UCL time-resolved optical tomography system, known as MONSTIR II. Intended primarily for the study of the newborn brain, the system employs 32 source fibres that sequentially transmit picosecond pulses of light at any four wavelengths between 650 and 900 nm. The 32 detector channels each contain an independent photo-multiplier tube and temporally correlated photon-counting electronics that allow the photon transit time between each source and each detector position to be measured with high temporal resolution. The system's response time, temporal stability, cross-talk, and spectral characteristics are reported. The efficacy of MONSTIR II is demonstrated by performing multi-spectral imaging of a simple phantom. PMID:24880351

  20. Time-resolved and time-integrated radiography of fast reactor fuel elements

    SciTech Connect

    De Volpi, A.

    1981-01-01

    The fast-reactor safety program has some unusual requirements in radiography. Applications may be divided into two areas: time-resolved or time-integrated radiography. The fast-neutron hodoscope has supplied all recent time-resolved cineradiographic in-pile fuel-motion data, and various x-ray and photographic techniques have been used for out-of-pile experiments. Thick containers and the large number of radioactive fuel pins involved in safety research have been responsible for some nonconventional applications of time-integrated radiography of stationary objects. Hodoscopes record fuel-motion during transient experiments at the TREAT reactor in the United States and CABRI in France. Other special techniques have been under development for out-of-pile nondestructive radiography of fuel element subassemblies, including fast-neutron and gamma-ray tomographic methods.

  1. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

    DOE PAGESBeta

    Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.; Bell, P.; Bionta, R.; Cerjan, C.; Gatu Johnson, M.; Kilkenny, J. D.; Li, C. K.; Séguin, F. H.; et al

    2016-08-02

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (Ti), yield (Yn), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with amore » time resolution of ~20 ps and energy resolution of ~100 keV for total neutron yields above ~1016. Lastly, at lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ~20 ps.« less

  2. 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.

  3. Time-resolved fluoroimmunoassay of plasma daidzein and genistein.

    PubMed

    Wang, G J; Lapcík, O; Hampl, R; Uehara, M; Al-Maharik, N; Stumpf, K; Mikola, H; Wähälä, K; Adlercreutz, H

    2000-06-01

    We present a method for the determination of the phytoestrogens daidzein and genistein in plasma (serum). These weakly estrogenic isoflavones occur in soybeans and in smaller amounts in some other beans and plants. It has been suggested that they may afford protection against prostate and breast cancer. The method is based on time-resolved fluoroimmunoassay (TR-FIA) using a europium chelate as a label. After synthesis of 4'-O-carboxymethyl-daidzein and 4'-O-carboxymethyl-genistein the compounds are coupled to bovine serum albumin (BSA), then used as antigens to immunize rabbits. The tracers with the europium chelate are synthesized using the same 4'-O-derivative of the isoflavones. After enzymatic hydrolysis and ether extraction the immunoassay is carried out using the VICTOR 1420 multilabel counter (Wallac Oy, Turku, Finland). The antisera cross-reacted to some extent with some isoflavonoids but not with flavonoids. The cross-reactivity seems not to influence the results, which were highly specific for both compounds. The correlation coefficients between the TR-FIA methods and the reference method based on isotope dilution gas chromatography-mass spectrometry were high; r-values were about 0.95-0.99 depending on concentration. The intra-assay coefficients of variation (CV%) for daidzein and genistein at three different concentrations vary 3.2-4.5 and 3.2-4.1, respectively. The inter-assay CVs vary 5.0-6.3 and 4.5-5.3, respectively. The working ranges of the daidzein and genistein assays are 1.0-216 and 1.7-370 nmol/l, respectively. The plasma values (n = 80) of daidzein and genistein are very low in Finnish subjects (mean for daidzein, 3.8+/-6.8 and for genistein, 3.2+/-7.6 nmol/l; median value for daidzein 1.5 and for genistein 1.4 nmol/l). PMID:10802284

  4. Length of Time to Resolve Criminal Charges of Child Sexual Abuse: A Three-County Case Study.

    PubMed

    Walsh, Wendy A; Lippert, Tonya; Edelson, Meredyth Goldberg; Jones, Lisa M

    2015-08-01

    The present study sought to examine the court culture of three Oregon counties and their timelines for resolving felony child sexual abuse cases. Specifically, we examined (a) case outcomes, churning (i.e., the extent to which four court events were rescheduled), the length of time to reach a criminal case resolution, and how this length of time compared to that for felonies generally; (b) whether mandatory minimum sentences affected resolution timeliness; and (c) key stakeholders' perceptions about their local court culture. Data included retrospective case-file abstraction (N = 532) on all felony child sex crimes for a 2-year period and interviews with legal professionals (N = 23). Across all three counties, a minority of child sexual abuse cases (18% to 47%) were resolved within the target timeframe of 4 months. In contrast, most felonies (65% to 77%) were resolved within this timeframe. The rescheduling of trials and the requirement of mandatory minimum sentences for some felony child sexual abuse crimes increased the time until case resolution. Results suggest that court cultures that are hierarchical and cooperative may lead to longer case resolution times than court cultures that are self-managing or autonomous. Implications of these results and other results are discussed. PMID:26206709

  5. Time-resolved measurements of aerosol elemental concentrations in indoor working environments

    NASA Astrophysics Data System (ADS)

    Žitnik, M.; Kastelic, A.; Rupnik, Z.; Pelicon, P.; Vaupetič, P.; Bučar, K.; Novak, S.; Samardžija, Z.; Matsuyama, S.; Catella, G.; Ishii, K.

    2010-12-01

    We have measured the elemental concentrations in aerosols with a 2-h time resolution in two different types of working environment: a chemistry laboratory dealing with the processing of advanced nanoparticulate materials and a medium-sized machine workshop. Non-stop 10-day and 12-day samplings were performed at each location in order to determine the concentration trends during the non-working/working and weekday/weekend periods. Supplementary measurements of PM10 aerosols with a 2-day sample collection time were performed with a standard Gent PM10 sampler to compare the elemental concentrations with the time-averaged concentrations detected by the 2D step-sampler. The concentrations were determined a posteriori by analyzing the x-ray spectra of aerosol samples emitted after 3-MeV proton bombardment. The PM10 samples collected in the chemistry laboratory were additionally inspected by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to determine the chemical compositions of the individual particles. In the workshop, a total PM10 mass sampling was performed simultaneously with a minute resolution to compare the signal with typical outdoor PM10 concentration levels. A factor analysis of the time-resolved dataset points to six and eight factors in the chemistry laboratory and the machine workshop, respectively. These factors describe most of the data variance, and their composition in terms of different elements can be related to specific indoor activities and conditions. We were able to demonstrate that the elemental concentration sampling with hourly resolution is an excellent tool for studying the indoor air pollution. While sampling the total PM10 mass concentration with a minute resolution may lack the potential to identify the emission sources in a "noisy" environment, the time averaging on a day time scale is too coarse to cope with the working dynamics, even if elemental sensitivity is an option.

  6. The Fermi GBM gamma-ray burst time-resolved spectral catalog: brightest bursts in the first four years

    NASA Astrophysics Data System (ADS)

    Yu, Hoi-Fung; Preece, Robert D.; Greiner, Jochen; Narayana Bhat, P.; Bissaldi, Elisabetta; Briggs, Michael S.; Cleveland, William H.; Connaughton, Valerie; Goldstein, Adam; von Kienlin, Andreas; Kouveliotou, Chryssa; Mailyan, Bagrat; Meegan, Charles A.; Paciesas, William S.; Rau, Arne; Roberts, Oliver J.; Veres, Péter; Wilson-Hodge, Colleen; Zhang, Bin-Bin; van Eerten, Hendrik J.

    2016-04-01

    Aims: We aim to obtain high-quality time-resolved spectral fits of gamma-ray bursts observed by the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. Methods: We performed time-resolved spectral analysis with high temporal and spectral resolution of the brightest bursts observed by Fermi GBM in its first four years of mission. Results: We present the complete catalog containing 1491 spectra from 81 bursts with high spectral and temporal resolution. Distributions of parameters, statistics of the parameter populations, parameter-parameter and parameter-uncertainty correlations, and their exact values are obtained and presented as main results in this catalog. We report a criterion that is robust enough to automatically distinguish between different spectral evolutionary trends between bursts. We also search for plausible blackbody emission components and find that only three bursts (36 spectra in total) show evidence of a pure Planck function. It is observed that peak energy and the averaged, time-resolved power-law index at low energy are slightly harder than the time-integrated values. Time-resolved spectroscopic results should be used instead of time-integrated results when interpreting physics from the observed spectra. Tables A.1 and B.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A135

  7. Distinction of brain tissue, low grade and high grade glioma with time-resolved fluorescence spectroscopy.

    PubMed

    Yong, William H; Butte, Pramod V; Pikul, Brian K; Jo, Javier A; Fang, Qiyin; Papaioannou, Thanassis; Black, Keith; Marcu, Laura

    2006-01-01

    Neuropathology frozen section diagnoses are difficult in part because of the small tissue samples and the paucity of adjunctive rapid intraoperative stains. This study aims to explore the use of time-resolved laser-induced fluorescence spectroscopy as a rapid adjunctive tool for the diagnosis of glioma specimens and for distinction of glioma from normal tissues intraoperatively. Ten low grade gliomas, 15 high grade gliomas without necrosis, 6 high grade gliomas with necrosis and/or radiation effect, and 14 histologically uninvolved "normal" brain specimens are spectroscopicaly analyzed and contrasted. Tissue autofluorescence was induced with a pulsed Nitrogen laser (337 nm, 1.2 ns) and the transient intensity decay profiles were recorded in the 370-500 nm spectral range with a fast digitized (0.2 ns time resolution). Spectral intensities and time-dependent parameters derived from the time-resolved spectra of each site were used for tissue characterization. A linear discriminant analysis diagnostic algorithm was used for tissue classification. Both low and high grade gliomas can be distinguished from histologically uninvolved cerebral cortex and white matter with high accuracy (above 90%). In addition, the presence or absence of treatment effect and/or necrosis can be identified in high grade gliomas. Taking advantage of tissue autofluorescence, this technique facilitates a direct and rapid investigation of surgically obtained tissue. PMID:16368511

  8. Microcontroller based resonance tracking unit for time resolved continuous wave cavity-ringdown spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Votava, Ondrej; Mašát, Milan; Parker, Alexander E.; Jain, Chaithania; Fittschen, Christa

    2012-04-01

    We present in this work a new tracking servoloop electronics for continuous wave cavity-ringdown absorption spectroscopy (cw-CRDS) and its application to time resolved cw-CRDS measurements by coupling the system with a pulsed laser photolysis set-up. The tracking unit significantly increases the repetition rate of the CRDS events and thus improves effective time resolution (and/or the signal-to-noise ratio) in kinetics studies with cw-CRDS in given data acquisition time. The tracking servoloop uses novel strategy to track the cavity resonances that result in a fast relocking (few ms) after the loss of tracking due to an external disturbance. The microcontroller based design is highly flexible and thus advanced tracking strategies are easy to implement by the firmware modification without the need to modify the hardware. We believe that the performance of many existing cw-CRDS experiments, not only time-resolved, can be improved with such tracking unit without any additional modification to the experiment.

  9. Time-Resolved Single-State Measurements of the Electronic Structure of Isochoric Heated Copper

    SciTech Connect

    Nelson, A J; Dunn, J; Widmann, K; Ao, T; Ping, Y; Hunter, J; Ng, A

    2004-10-22

    Time-resolved x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) Cu. Single-shot x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution is used in conjunction with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated Cu foils persisting 4-5 ps. This metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.1-2.5 mJ laser energy focused in a large 500 x 700 {micro}m{sup 2} spot to create heated conditions of 0.07-1.8 x 10{sup 12} W cm{sup -2} intensity. Valence band photoemission spectra showing the changing occupancy of the Cu 3d level with heating are presented. These are the first picosecond x-ray laser time-resolved photoemission spectra of laser-heated ultra-thin Cu foil showing changes in electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials.

  10. Frequency- and time-resolved coherence transfer spectroscopy.

    PubMed

    Rickard, Mark A; Pakoulev, Andrei V; Mathew, Nathan A; Kornau, Kathryn M; Wright, John C

    2007-02-22

    Frequency-domain two-color triply vibrational enhanced four-wave mixing using a new phase-matching geometry discriminates against coherent multidimensional spectral features created solely by radiative transitions, spectrally resolves pathways with different numbers of coherence transfer steps, and temporally resolves modulations created by interference between coherence transfer pathways. Coherence transfer is a nonradiative transition where a superposition of quantum states evolves to a different superposition. The asymmetric and symmetric C[triple bond]O stretching modes of rhodium(I) dicarbonyl acetylacetonate are used as a model system for coherence transfer. A simplified theoretical model based on Redfield theory is used to describe the experimental results. PMID:17300169

  11. 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.

  12. Using time-frequency analysis to determine time-resolved detonation velocity with microwave interferometry.

    PubMed

    Kittell, David E; Mares, Jesus O; Son, Steven F

    2015-04-01

    Two time-frequency analysis methods based on the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) were used to determine time-resolved detonation velocities with microwave interferometry (MI). The results were directly compared to well-established analysis techniques consisting of a peak-picking routine as well as a phase unwrapping method (i.e., quadrature analysis). The comparison is conducted on experimental data consisting of transient detonation phenomena observed in triaminotrinitrobenzene and ammonium nitrate-urea explosives, representing high and low quality MI signals, respectively. Time-frequency analysis proved much more capable of extracting useful and highly resolved velocity information from low quality signals than the phase unwrapping and peak-picking methods. Additionally, control of the time-frequency methods is mainly constrained to a single parameter which allows for a highly unbiased analysis method to extract velocity information. In contrast, the phase unwrapping technique introduces user based variability while the peak-picking technique does not achieve a highly resolved velocity result. Both STFT and CWT methods are proposed as improved additions to the analysis methods applied to MI detonation experiments, and may be useful in similar applications. PMID:25933878

  13. Ultra-high resolution Fourier domain optical coherence tomography for resolving thin layers in painted works of art

    NASA Astrophysics Data System (ADS)

    Cheung, C. S.; Liang, Haida

    2013-05-01

    While OCT has been applied to the non-invasive examination of the stratigraphy of paint layers in recent years, it has been recognized that the resolutions of commercially available OCT cannot compete in depth resolution with conventional microscopic examination of cross-sections of paint samples. It is necessary to achieve resolutions better than 3 microns to resolve the thinnest layers of paint and varnish. In this paper, we demonstrate a Fourier domain ultrahigh resolution OCT at 810nm with depth resolution of 1.8 μm in air (or 1.2μm in varnish or paint).

  14. A tunable low-energy photon source for high-resolution angle-resolved photoemission spectroscopy

    SciTech Connect

    Harter, John W.; Monkman, Eric J.; Shai, Daniel E.; Nie Yuefeng; Uchida, Masaki; Burganov, Bulat; Chatterjee, Shouvik; King, Philip D. C.; Shen, Kyle M.

    2012-11-15

    We describe a tunable low-energy photon source consisting of a laser-driven xenon plasma lamp coupled to a Czerny-Turner monochromator. The combined tunability, brightness, and narrow spectral bandwidth make this light source useful in laboratory-based high-resolution photoemission spectroscopy experiments. The source supplies photons with energies up to {approx}7 eV, delivering under typical conditions >10{sup 12} ph/s within a 10 meV spectral bandwidth, which is comparable to helium plasma lamps and many synchrotron beamlines. We first describe the lamp and monochromator system and then characterize its output, with attention to those parameters which are of interest for photoemission experiments. Finally, we present angle-resolved photoemission spectroscopy data using the light source and compare its performance to a conventional helium plasma lamp.

  15. High Resolution Angle Resolved Photoemission Studies on Quasi-Particle Dynamics in Graphite

    SciTech Connect

    Leem, C.S.

    2010-06-02

    We obtained the spectral function of the graphite H point using high resolution angle resolved photoelectron spectroscopy (ARPES). The extracted width of the spectral function (inverse of the photo-hole lifetime) near the H point is approximately proportional to the energy as expected from the linearly increasing density of states (DOS) near the Fermi energy. This is well accounted by our electron-phonon coupling theory considering the peculiar electronic DOS near the Fermi level. And we also investigated the temperature dependence of the peak widths both experimentally and theoretically. The upper bound for the electron-phonon coupling parameter is 0.23, nearly the same value as previously reported at the K point. Our analysis of temperature dependent ARPES data at K shows that the energy of phonon mode of graphite has much higher energy scale than 125K which is dominant in electron-phonon coupling.

  16. Hyperspectral waveband group optimization for time-resolved human sensing

    NASA Astrophysics Data System (ADS)

    Kaur, Balvinder; Hodgkin, Van A.; Nelson, Jill K.; Ikonomidou, Vasiliki N.; Hutchinson, J. Andrew

    2013-05-01

    Pulse and respiration rates provide vital information for evaluating the physiological state of an individual during triage. Traditionally, pulse and respiration have been tracked by means of contact sensors. Recent work has shown that visible cameras can passively and remotely obtain pulse signals under controlled environmental conditions [2] [5] [14] [27]. This paper introduces methods for extracting and characterizing pulse and respiration signals from skin reflectivity data captured in peak sensitivity range for silicon detector (400nm-1100nm). Based on the physiological understanding [12] [13] [15] of human skin and reflectivity at various skin depths, we optimize a group of spectral bands to determine pulse and respiration with high Peak Signal-to-Noise Ratio (PSNR) and correlation values [27] [30]. Our preliminary results indicate top six optimal waveband groups in about 100nm - 200nm resolution in each, with rank-ordered peaks at 409nm, 512nm, 584nm, 667nm, 885nm and 772nm. This work, collected under an approved IRB protocol enhances non-contact, remote, passive, and real-time measurement of pulse and respiration for security and medical applications.

  17. Time resolved optical methods for investigation of phase transformations in materials exposed to nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Martan, J.; Semmar, N.; Cibulka, O.

    2011-06-01

    Infrared (IR) radiometry and time resolved reflectivity (TRR) methods can be used for investigation of laser pulse effects on materials in nanosecond time scale. The methods in combination are capable to quantify object temperature and detect phase transformations in the solid state, melting and plasma formation from vapour. Measurements with different laser pulse energy densities provide threshold of the transformation. The melt duration can be also determined. The experimental system is described. It contains KrF excimer laser with homogenizer and variable attenuator, fast IR detector for radiometry, continuous probing laser with Si photodiode for reflectivity measurement and UV detector for pump laser pulse reflection measurement. The system was applied to investigation of responses to laser light of silicon and different pure metals and alloys. The range of energy densities used was 1-5500 mJ.cm-2 and measurements were done with temporal resolution of 6 ns for radiometry and 1 ns for reflectivity.

  18. Glucose sensing by time-resolved fluorescence of sol-gel immobilized glucose oxidase.

    PubMed

    Esposito, Rosario; Della Ventura, Bartolomeo; De Nicola, Sergio; Altucci, Carlo; Velotta, Raffaele; Mita, Damiano Gustavo; Lepore, Maria

    2011-01-01

    A monolithic silica gel matrix with entrapped glucose oxidase (GOD) was constructed as a bioactive element in an optical biosensor for glucose determination. Intrinsic fluorescence of free and immobilised GOD was investigated in the visible range in presence of different glucose concentrations by time-resolved spectroscopy with time-correlated single-photon counting detector. A three-exponential model was used for analysing the fluorescence transients. Fractional intensities and mean lifetime were shown to be sensitive to the enzymatic reaction and were used for obtaining calibration curve for glucose concentration determination. The sensing system proposed achieved high resolution (up to 0.17 mM) glucose determination with a detection range from 0.4 mM to 5 mM. PMID:22163807

  19. A 32-channel time-resolved instrument for medical optical tomography

    NASA Astrophysics Data System (ADS)

    Schmidt, Florian E. W.; Fry, Martin E.; Hillman, Elizabeth M. C.; Hebden, Jeremy C.; Delpy, David T.

    2000-01-01

    A prototype multichannel time-resolved medical optical tomography system is presented, and various instrumental aspects and performance issues are discussed. The instrument has been designed primarily as a continuous bedside monitor for obtaining functional images of premature infants' brains that are at an increased risk of injury due to dysfunction in cerebral oxygenation or hemodynamics. Separate maps of the internal absorption and scattering properties can be reconstructed from purely temporal measurements of photons transmitted diffusely through the tissue, and without recourse to reference or baseline measurements. The instrument employs 32 source fibers that sequentially deliver near-infrared pulsed laser radiation of picosecond duration. Transit time measurements of very high temporal resolution and stability are made between these sources and 32 detector optodes that are located on the surface. The effectiveness of this instrument is demonstrated by successfully imaging a tissue-equivalent phantom.

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

    PubMed

    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

    2015-09-01

    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

  1. A time resolved microfocus XEOL facility at the Diamond Light Source

    NASA Astrophysics Data System (ADS)

    Mosselmans, J. F. W.; Taylor, R. P.; Quinn, P. D.; Finch, A. A.; Cibin, G.; Gianolio, D.; Sapelkin, A. V.

    2013-03-01

    We have constructed a Time-Resolved X-ray Excited Optical Luminescence (TR-XEOL) detection system at the Microfocus Spectroscopy beamline I18 at the Diamond Light Source. Using the synchrotron in "hybrid bunch mode", the data collection is triggered by the RF clock, and we are able to record XEOL photons with a time resolution of 6.1 ps during the 230 ns gap between the hybrid bunch and the main train of electron bunches. We can detect photons over the range 180-850 nm using a bespoke optical fibre, with X-ray excitation energies between 2 and 20 keV. We have used the system to study a range of feldspars. The detector is portable and has also been used on beamline B18 to collect Optically Determined X-ray Absorption Spectroscopy (OD-XAS) in QEXAFS mode.

  2. 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

  3. Few-femtosecond sensitivity of ultrafast molecular dynamics with time-resolved photoelectron spectra

    NASA Astrophysics Data System (ADS)

    Champenois, Elio G.; Cryan, James P.; Larsen, Kirk; Shivaram, Niranjan H.; Belkacem, Ali

    2016-05-01

    We explore ultrafast dynamics involving non-adiabatic couplings following valence electronic excitation of small molecular systems. By measuring the time-resolved photoelectron spectra (TRPES) resulting from ionization with ultraviolet light, the excited wave packet can be tracked with state specificity. If the nuclear motion is dominated by a limited number of degrees of freedom, the TRPES also yields information about the molecular geometry. Even with limited temporal resolution, the onset times of the signal at different photoelectron energies can lead to few-femtosecond sensitivity. Applying this technique to ethylene (C2 H4) excited to the ππ* state, ultrafast motion along the twist coordinate is observed along with transient population to the π 3 s state through non-adiabatic coupling. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Divison under Contract No. DE-AC02-05CH11231.

  4. Ultrafast time-resolved spectroscopy of xanthophylls at low temperature.

    PubMed

    Cong, Hong; Niedzwiedzki, Dariusz M; Gibson, George N; Frank, Harry A

    2008-03-20

    Many of the spectroscopic features and photophysical properties of xanthophylls and their role in energy transfer to chlorophyll can be accounted for on the basis of a three-state model. The characteristically strong visible absorption of xanthophylls is associated with a transition from the ground state S0 (1(1)Ag-) to the S2 (1(1)Bu+) excited state. The lowest lying singlet state denoted S1 (2(1)Ag-), is a state into which absorption from the ground state is symmetry forbidden. Ultrafast optical spectroscopic studies and quantum computations have suggested the presence of additional excited singlet states in the vicinity of S1 (2(1)Ag-) and S2 (1(1)Bu+). One of these is denoted S* and has been suggested in previous work to be associated with a twisted molecular conformation of the molecule in the S1 (2(1)Ag-) state. In this work, we present the results of a spectroscopic investigation of three major xanthophylls from higher plants: violaxanthin, lutein, and zeaxanthin. These molecules have systematically increasing extents of pi-electron conjugation from nine to eleven conjugated carbon-carbon double bonds. All-trans isomers of the molecules were purified by high-performance liquid chromatography (HPLC) and studied by steady-state and ultrafast time-resolved optical spectroscopy at 77 K. Analysis of the data using global fitting techniques has revealed the inherent spectral properties and ultrafast dynamics of the excited singlet states of each of the molecules. Five different global fitting models were tested, and it was found that the data are best explained using a kinetic model whereby photoexcitation results in the promotion of the molecule into the S2 (1(1)Bu+) state that subsequently undergoes decay to a vibrationally hot S1 (1(1)Ag-) state and with the exception of violaxanthin also to the S* state. The vibrationally hot S1 (1(1)Ag-) state then cools to a vibrationally relaxed S1 (2(1)Ag-) state in less than a picosecond. It was also found that a portion

  5. Time-resolved emission of dye probes in a shock-compressed polymer

    NASA Astrophysics Data System (ADS)

    Brown, Kathryn E.; Fu, Yuanxi; Shaw, William L.; Dlott, Dana D.

    2012-11-01

    Simultaneous impact velocity and time-resolved emission measurements are made on shocked poly-methylmethacryalate doped with rhodamine 640 (R640) dye. Planar single-stage shocks in the 0-16 GPa range are produced using a laser-driven flyer plate apparatus. This method allows for reproducible measurements of the time-resolved dye emission intensity, redshift, and spectral width monitored with 1 ns time resolution. The redshift is used to probe the shock front, which has a two-part viscoelastic structure. The maximum dye emission redshift under shock loading stops increasing above ˜6 GPa. In static high-pressure measurements, the redshift continues to increase up to at least 10 GPa. The smaller redshift seen in shock experiments is not an effect of the shock temperature increase, and it is attributed to incomplete polymer configurational relaxation frustrated by the short duration (<15 ns) of the shock. The viscous relaxation behind the shock front has a part whose rate increases with increasing shock pressure and a part that does not. It is this latter part that causes the shock-induced emission redshift to stop increasing above 6 GPa, and the differences between the two types of relaxation are explained in the context of the free-energy needed to surmount configurational barriers.

  6. Probing ultrafast valley dynamics in 2D semiconductors via time-resolved Kerr rotation

    NASA Astrophysics Data System (ADS)

    Huang, Jiani; Hoang, Thang; Ming, Tian; Kong, Jing; Mikkelsen, Maiken

    Monolayer transition metal dichalcogenides (TMDCs) offer a tantalizing platform for controlling spin and valley degrees of freedom, enabling future optoelectronic devices with enhanced and novel functionalities. Here, we experimentally probe the valley dynamics in monolayer MoS2 and WSe2 using time-resolved Kerr rotation (TRKR) from T = 10 K to 300 K . This pump-probe technique offers sub-picosecond temporal resolution, providing insight into ultrafast valley dynamics inaccessible by polarized and time-resolved photoluminescence spectroscopy. Bi-exponential decay dynamics were observed for both materials at low temperatures. Strong long-range exchange interactions between the K valleys led to a rapid exciton valley depolarization time (< 10 ps), while the valley polarization of the trion and defect states decays within several tens of ps. Moreover, spatial distributions of the TRKR amplitude across monolayer flakes indicated weaker valley polarizations near the edges of MoS2, which is likely associated with the Mo- or S-zigzag terminations at the boundaries. These temporal and spatial TRKR measurements reveal insight into the complex dynamics of valley excitonic states in monolayer TMDCs.

  7. A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

    SciTech Connect

    Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E.; Leone, Stephen R.

    2008-05-21

    A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a home-built soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray CCD camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterization of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.

  8. 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.

  9. Satellite Remote Sensing for Developing Time and Space Resolved Estimates of Ambient Particulate in Cleveland, OH

    PubMed Central

    Kumar, Naresh; Chu, Allen D.; Foster, Andrew D.; Peters, Thomas; Willis, Robert

    2011-01-01

    This article empirically demonstrates the use of fine resolution satellite-based aerosol optical depth (AOD) to develop time and space resolved estimates of ambient particulate matter (PM) ≤2.5 µm and ≤10 µm in aerodynamic diameters (PM2.5 and PM10, respectively). AOD was computed at three different spatial resolutions, i.e., 2 km (means 2 km × 2 km area at nadir), 5 km, and 10 km, by using the data from MODerate Resolution Imaging Spectroradiometer (MODIS), aboard the Terra and Aqua satellites. Multiresolution AOD from MODIS (AODMODIS) was compared with the in situ measurements of AOD by NASA’s AErosol RObotic NETwork (AERONET) sunphotometer (AODAERONET) at Bondville, IL, to demonstrate the advantages of the fine resolution AODMODIS over the 10-km AODMODIS, especially for air quality prediction. An instrumental regression that corrects AODMODIS for meteorological conditions was used for developing a PM predictive model. The 2-km AODMODIS aggregated within 0.025° and 15-min intervals shows the best association with the in situ measurements of AODAERONET. The 2-km AODMODIS seems more promising to estimate time and space resolved estimates of ambient PM than the 10-km AODMODIS, because of better location precision and a significantly greater number of data points across geographic space and time. Utilizing the collocated AODMODIS and PM data in Cleveland, OH, a regression model was developed for predicting PM for all AODMODIS data points. Our analysis suggests that the slope of the 2-km AODMODIS (instrumented on meteorological conditions) is close to unity with the PM monitored on the ground. These results should be interpreted with caution, because the slope of AODMODIS ranges from 0.52 to 1.72 in the site-specific models. In the cross validation of the overall model, the root mean square error (RMSE) of PM10 was smaller (2.04 µg/m3 in overall model) than that of PM2.5 (2.5 µg/m3). The predicted PM in the AODMODIS data (∼2.34 million data points) was

  10. 100-picosecond time-resolved X-ray absorption fine structure of FeII(1,10-phenanthroline)3

    NASA Astrophysics Data System (ADS)

    Sato, Tokushi; Nozawa, Shunsuke; Ichiyanagi, Kouhei; Tomita, Ayana; Ichikawa, Hirohiko; Chollet, Matthieu; Fujii, Hiroshi; Adachi, Shin-ichi; Koshihara, Shin-ya

    2009-02-01

    Studying photo-induced molecular dynamics in liquid with sub-nanosecond time-resolution and sub-Angstrom spatial resolution gives information for understanding fundamental chemical process in the photo-induced cooperative phenomena of molecular systems and also for developing new materials and devices. Here, we present time-resolved X-ray absorption fine structure on the spin-crossover complex FeII tris-(1,10-phenanthroline) dissolved in aqueous solution. We utilized femtosecond laser at 400nm pulse for excitation and 100ps X-ray pulse for probe.

  11. Deconvolution method for recovering the photon time-of-flight distribution from time-resolved measurements.

    PubMed

    Diop, Mamadou; St Lawrence, Keith

    2012-06-15

    A nonparametric deconvolution algorithm for recovering the photon time-of-flight distribution (TOFD) from time-resolved (TR) measurements is described. The algorithm combines wavelet denoising and a two-stage deconvolution method based on generalized singular value decomposition and Tikhonov regularization. The efficacy of the algorithm was tested on simulated and experimental TR data and the results show that it can recover the photon TOFD with high fidelity. Combined with the microscopic Beer-Lambert law, the algorithm enables accurate quantification of absorption changes from arbitrary time-of-flight windows, thereby optimizing the depth sensitivity provided by TR measurements. PMID:22739907

  12. Monitoring antibacterial permeabilization in real time using time-resolved flow cytometry.

    PubMed

    Freire, João Miguel; Gaspar, Diana; de la Torre, Beatriz Garcia; Veiga, Ana Salomé; Andreu, David; Castanho, Miguel A R B

    2015-02-01

    Despite the intensive study of antibiotic-induced bacterial permeabilization, its kinetics and molecular mechanism remain largely elusive. A new methodology that extends the concept of the live-dead assay in flow cytometry to real time-resolved detection was used to overcome these limitations. The antimicrobial activity of pepR was monitored in time-resolved flow cytometry for three bacterial strains: Escherichia coli (ATCC 25922), E. coli K-12 (CGSC Strain 4401) and E. coli JW3596-1 (CGSC Strain 11805). The latter strain has truncated lipopolysaccharides (LPS) in the outer membrane. This new methodology provided information on the efficacy of the antibiotics and sheds light on their mode of action at membrane-level. Kinetic data regarding antibiotic binding and lytic action were retrieved. Membrane interaction and permeabilization events differ significantly among strains. The truncation of LPS moieties does not hamper AMP binding but compromises membrane disruption and bacterial killing. We demonstrated the usefulness of time-resolved flow cytometry to study antimicrobial-induced permeabilization by collecting kinetic data that contribute to characterize the action of antibiotics directly on bacteria. PMID:25445678

  13. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser.

    PubMed

    He, Yu; Vishik, Inna M; Yi, Ming; Yang, Shuolong; Liu, Zhongkai; Lee, James J; Chen, Sudi; Rebec, Slavko N; Leuenberger, Dominik; Zong, Alfred; Jefferson, C Michael; Moore, Robert G; Kirchmann, Patrick S; Merriam, Andrew J; Shen, Zhi-Xun

    2016-01-01

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10(12) photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å(-1), respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å(-1), granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors. PMID:26827301

  14. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

    NASA Astrophysics Data System (ADS)

    He, Yu; Vishik, Inna M.; Yi, Ming; Yang, Shuolong; Liu, Zhongkai; Lee, James J.; Chen, Sudi; Rebec, Slavko N.; Leuenberger, Dominik; Zong, Alfred; Jefferson, C. Michael; Moore, Robert G.; Kirchmann, Patrick S.; Merriam, Andrew J.; Shen, Zhi-Xun

    2016-01-01

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 1012 photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å-1, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å-1, granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.

  15. Complete time-resolved polarimetry of scattered light at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Turnbull, David; Ayers, Shannon; Bell, Perry; Chow, Robert; Frieders, Gene; Hibbard, Robin L.; Michel, Pierre; Ralph, Joseph E.; Ross, James S.; Stanley, Joel R.; Vickers, James L.; Zeid, Ziad M.; Moody, John D.

    2015-08-01

    The 3ω scattered light polarimetry diagnostic in the 30° incidence cone backscatter diagnostic at the National Ignition Facility (NIF) is being upgraded to measure the full time-resolved Stokes vector. Previously, the diagnostic had a single channel capable of diagnosing the time-integrated balance of the horizontal and vertical polarizations. Two additional channels were added - one that measures the balance of the 45° and 135° projections, and another that measures the right- and left-circular polarizations - and together the three complete the Stokes vector measurement. A division-of-aperture scheme is employed in which three nearby portions of the near field are sampled simultaneously. Time resolution is obtained by relaying an image of the measured regions onto a set of fibers coupled to diodes. The new diagnostic will be capable of measuring scattered light signals <≍ .1GW with ≍ 120ps time resolution. This will allow more rigorous evaluation of earlier indications that backscatter polarization can serve as a quantitative diagnostic of crossed-beam energy transfer in indirect-drive inertial confinement fusion experiments. It will also be used to diagnose Faraday rotation induced by magnetic fields in collisionless shock and turbulent dynamo experiments later this year.

  16. Adaptive Decomposition of Highly Resolved Time Series into Local and Non‐local Components

    EPA Science Inventory

    Highly time-resolved air monitoring data are widely being collected over long time horizons in order to characterizeambient and near-source air quality trends. In many applications, it is desirable to split the time-resolved data into two ormore components (e.g., local and region...

  17. Time Resolved Thermal Diffusivity of Seasonal Snow Determined from Inexpensive, Easily-Implemented Temperature Measurements

    NASA Astrophysics Data System (ADS)

    Oldroyd, H. J.; Higgins, C. W.; Huwald, H.; Selker, J. S.; Parlange, M. B.

    2011-12-01

    Thermal diffusivity of snow is an important physical property associated with key hydrological phenomena such as snow melt and heat and water vapor exchange with the atmosphere. These phenomena have broad implications in studies of climate and heat and water budgets on many scales. However, direct measurements of snow thermal diffusivity require coupled point measurements of thermal conductivity and density, which are nonstationary due to snow metamorphism. Furthermore, thermal conductivity measurements are typically obtained with specialized heating probes or plates and snow density measurements require digging snow pits. Therefore, direct measurements are difficult to obtain with high enough temporal resolution such that direct comparisons with atmospheric conditions can be made. This study uses highly resolved (7.5 to 10 cm for depth and 1min for time) temperature measurements from the Plaine Morte glacier in Switzerland as initial and boundary conditions to numerically solve the 1D heat equation and iteratively optimize for thermal diffusivity. The method uses flux boundary conditions to constrain thermal diffusivity such that spuriously high values in thermal diffusivity are eliminated. Additionally, a t-test ensuring statistical significance between solutions of varied thermal diffusivity result in further constraints on thermal diffusivity that eliminate spuriously low values. The results show that time resolved (1 minute) thermal diffusivity can be determined from easily implemented and inexpensive temperature measurements of seasonal snow with good agreement to widely used parameterizations based on snow density. This high time resolution further affords the ability to explore possible turbulence-induced enhancements to heat and mass transfer in the snow.

  18. Frequency domain approach for time-resolved pump-probe microscopy using intensity modulated laser diodes

    NASA Astrophysics Data System (ADS)

    Miyazaki, J.; Kawasumi, K.; Kobayashi, T.

    2014-09-01

    We present a scheme for time-resolved pump-probe microscopy using intensity modulated laser diodes. The modulation frequencies of the pump and probe beams are varied up to 500 MHz with fixed frequency detuning typically set at 15 kHz. The frequency response of the pump-probe signal is detected using a lock-in amplifier referenced at the beat frequency. This frequency domain method is capable of characterizing the nanosecond to picosecond relaxation dynamics of sample species without the use of a high speed detector or a high frequency lock-in amplifier. Furthermore, as the pump-probe signal is based on the nonlinear interaction between the two laser beams and the sample, our scheme provides better spatial resolution than the conventional diffraction-limited optical microscopes. Time-resolved pump-probe imaging of fluorescence beads and aggregates of quantum dots demonstrates that this method is useful for the microscopic analysis of optoelectronic devices. The system is implemented using compact and low-cost laser diodes, and thus has a broad range of applications in the fields of photochemistry, optical physics, and biological imaging.

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-03-01

    Additive manufacturing (AM) of metals and alloys is becoming a pervasive technology in both research and industrial environments, 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. The 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.

  20. Time-resolved X-ray PIV measurements of hemodynamic information of real pulsatile blood flows

    NASA Astrophysics Data System (ADS)

    Park, Hanwook; Yeom, Eunseop; Lee, Sang Joon

    2015-11-01

    X-ray imaging technique has been used to visualize various bio-fluid flow phenomena as a nondestructive manner. To obtain hemodynamic information related with circulatory vascular diseases, a time-resolved X-ray PIV technique with high temporal resolution was developed. In this study, to embody actual pulsatile blood flows in a circular conduit without changes in hemorheological properties, a bypass loop is established by connecting a microtube between the jugular vein and femoral artery of a rat. Biocompatible CO2 microbubbles are used as tracer particles. After mixing with whole blood, CO2 microbubbles are injected into the bypass loop. Particle images of the pulsatile blood flows in the bypass loop are consecutively captured by the time-resolved X-ray PIV system. The velocity field information are obtained with varying flow rate and pulsataility. To verify the feasibility of the use of CO2 microbubbles under in vivo conditions, the effects of the surrounding-tissues are also investigated, because these effects are crucial for deteriorating the image contrast of CO2 microbubbles. Therefore, the velocity information of blood flows in the abdominal aorta are obtained to demonstrate the visibility and usefulness of CO2 microbubbles under ex vivo conditions. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2008-0061991).

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

    DOE PAGESBeta

    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.; et al

    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

  2. Time-Resolved Research at the Advanced Photon Source Beamline 7-ID

    SciTech Connect

    Dufresne, Eric M.; Adams, Bernhard; Arms, Dohn A.; Chollet, Matthieu; Li, Yuelin; Walko, Donald A.; Wang Jin; Landahl, Eric C.

    2010-06-23

    The Sector 7 undulator beamline (7-ID) of the Advanced Photon Source (APS) is dedicated to time-resolved x-ray research and is capable of ultrafast measurements on the order of 100 ps. Beamline 7-ID has a laser laboratory featuring a Ti:Sapphire system (average power of 2.5 W, pulse duration <50 fs, repetition rate 1-5 kHz) that can be synchronized to the bunch pattern of the storage ring. The laser is deliverable to x-ray enclosures, which contain diffractometers, as well as motorized optical tables for table-top experiments. Beamline 7-ID has a single APS Undulator A and uses a diamond (111) double-crystal monochromator, providing good energy resolution over a range of 6-24 keV. Available optics include Kirkpatrick-Baez (KB) mirrors to microfocus the x-ray beam. A variety of time-resolved diffraction and spectroscopy research is available at 7-ID, with experiments being done in the atomic, molecular, optical, chemistry, and solid state (bulk and surface) fields.

  3. Time-Resolved Research at the Advanced Photon Source Beamline 7-ID

    SciTech Connect

    Dufresne, Eric M.; Adams, Bernhard; Arms, Dohn A.; Chollet, Matthieu; Landahl, Eric C.; Li, Yuelin; Walko, Donald A.; Wang, Jin

    2010-08-02

    The Sector 7 undulator beamline (7-ID) of the Advanced Photon Source (APS) is dedicated to time-resolved x-ray research and is capable of ultrafast measurements on the order of 100 ps. Beamline 7-ID has a laser laboratory featuring a Ti:Sapphire system (average power of 2.5W, pulse duration <50 fs, repetition rate 1-5 kHz) that can be synchronized to the bunch pattern of the storage ring. The laser is deliverable to x-ray enclosures, which contain diffractometers, as well as motorized optical tables for table-top experiments. Beamline 7-ID has a single APS Undulator A and uses a diamond (111) double-crystal monochromator, providing good energy resolution over a range of 6-24 keV. Available optics include Kirkpatrick-Baez (KB) mirrors to microfocus the x-ray beam. A variety of time-resolved diffraction and spectroscopy research is available at 7-ID, with experiments being done in the atomic, molecular, optical, chemistry, and solid state (bulk and surface) fields.

  4. The High Time Resolution Radio Sky

    NASA Astrophysics Data System (ADS)

    Thornton, D.

    2013-11-01

    Pulsars are laboratories for extreme physics unachievable on Earth. As individual sources and possible orbital companions can be used to study magnetospheric, emission, and superfluid physics, general relativistic effects, and stellar and binary evolution. As populations they exhibit a wide range of sub-types, with parameters varying by many orders of magnitude signifying fundamental differences in their evolutionary history and potential uses. There are currently around 2200 known pulsars in the Milky Way, the Magellanic clouds, and globular clusters, most of which have been discovered with radio survey observations. These observations, as well as being suitable for detecting the repeating signals from pulsars, are well suited for identifying other transient astronomical radio bursts that last just a few milliseconds that either singular in nature, or rarely repeating. Prior to the work of this thesis non-repeating radio transients at extragalactic distances had possibly been discovered, however with just one example status a real astronomical sources was in doubt. Finding more of these sources was a vital to proving they were real and to open up the universe for millisecond-duration radio astronomy. The High Time Resolution Universe survey uses the multibeam receiver on the 64-m Parkes radio telescope to search the whole visible sky for pulsars and transients. The temporal and spectral resolution of the receiver and the digital back-end enable the detection of relatively faint, and distant radio sources. From the Parkes telescope a large portion of the Galactic plane can be seen, a rich hunting ground for radio pulsars of all types, while previously poorly surveyed regions away from the Galactic plane are also covered. I have made a number of pulsar discoveries in the survey, including some rare systems. These include PSR J1226-6208, a possible double neutron star system in a remarkably circular orbit, PSR J1431-471 which is being eclipsed by its companion with

  5. Planetary Surface Exploration Using Time-Resolved Laser Spectroscopy on Rovers and Landers

    NASA Astrophysics Data System (ADS)

    Blacksberg, Jordana; Alerstam, Erik; Maruyama, Yuki; Charbon, Edoardo; Rossman, George

    2013-04-01

    Planetary surface exploration using laser spectroscopy has become increasingly relevant as these techniques become a reality on Mars surface missions. The ChemCam instrument onboard the Curiosity rover is currently using laser induced breakdown spectroscopy (LIBS) on a mast-mounted platform to measure elemental composition of target rocks. The RLS Raman Spectrometer is included on the payload for the ExoMars mission to be launched in 2018 and will identify minerals and organics on the Martian surface. We present a next-generation instrument that builds on these widely used techniques to provide a means for performing both Raman spectroscopy and LIBS in conjunction with microscopic imaging. Microscopic Raman spectroscopy with a laser spot size smaller than the grains of interest can provide surface mapping of mineralogy while preserving morphology. A very small laser spot size (~ 1 µm) is often necessary to identify minor phases that are often of greater interest than the matrix phases. In addition to the difficulties that can be posed by fine-grained material, fluorescence interference from the very same material is often problematic. This is particularly true for many of the minerals of interest that form in environments of aqueous alteration and can be highly fluorescent. We use time-resolved laser spectroscopy to eliminate fluorescence interference that can often make it difficult or impossible to obtain Raman spectra. As an added benefit, we have found that with small changes in operating parameters we can include microscopic LIBS using the same hardware. This new technique relies on sub-ns, high rep-rate lasers with relatively low pulse energy and compact solid state detectors with sub-ns time resolution. The detector technology that makes this instrument possible is a newly developed Single-Photon Avalanche Diode (SPAD) sensor array based on Complementary Metal-Oxide Semiconductor (CMOS) technology. The use of this solid state time-resolved detector offers a

  6. Molecular component distribution imaging of living cells by multivariate curve resolution analysis of space-resolved Raman spectra.

    PubMed

    Ando, Masahiro; Hamaguchi, Hiro-o

    2014-01-01

    Label-free Raman microspectroscopy combined with a multivariate curve resolution (MCR) analysis can be a powerful tool for studying a wide range of biomedical molecular systems. The MCR with the alternating least squares (MCR-ALS) technique, which retrieves the pure component spectra from complicatedly overlapped spectra, has been successfully applied to in vivo and molecular-level analysis of living cells. The principles of the MCR-ALS analysis are reviewed with a model system of titanium oxide crystal polymorphs, followed by two examples of in vivo Raman imaging studies of living yeast cells, fission yeast, and budding yeast. Due to the non-negative matrix factorization algorithm used in the MCR-ALS analysis, the spectral information derived from this technique is just ready for physical and/or chemical interpretations. The corresponding concentration profiles provide the molecular component distribution images (MCDIs) that are vitally important for elucidating life at the molecular level, as stated by Schroedinger in his famous book, "What is life?" Without any a priori knowledge about spectral profiles, time- and space-resolved Raman measurements of a dividing fission yeast cell with the MCR-ALS elucidate the dynamic changes of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle. The MCR-ALS technique also resolves broadly overlapped OH stretch Raman bands of water, clearly indicating the existence of organelle-specific water structures in a living budding yeast cell. PMID:24108582

  7. Molecular component distribution imaging of living cells by multivariate curve resolution analysis of space-resolved Raman spectra

    NASA Astrophysics Data System (ADS)

    Ando, Masahiro; Hamaguchi, Hiro-o.

    2014-01-01

    Label-free Raman microspectroscopy combined with a multivariate curve resolution (MCR) analysis can be a powerful tool for studying a wide range of biomedical molecular systems. The MCR with the alternating least squares (MCR-ALS) technique, which retrieves the pure component spectra from complicatedly overlapped spectra, has been successfully applied to in vivo and molecular-level analysis of living cells. The principles of the MCR-ALS analysis are reviewed with a model system of titanium oxide crystal polymorphs, followed by two examples of in vivo Raman imaging studies of living yeast cells, fission yeast, and budding yeast. Due to the non-negative matrix factorization algorithm used in the MCR-ALS analysis, the spectral information derived from this technique is just ready for physical and/or chemical interpretations. The corresponding concentration profiles provide the molecular component distribution images (MCDIs) that are vitally important for elucidating life at the molecular level, as stated by Schroedinger in his famous book, "What is life?" Without any a priori knowledge about spectral profiles, time- and space-resolved Raman measurements of a dividing fission yeast cell with the MCR-ALS elucidate the dynamic changes of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle. The MCR-ALS technique also resolves broadly overlapped OH stretch Raman bands of water, clearly indicating the existence of organelle-specific water structures in a living budding yeast cell.

  8. A fast 1-D detector for imaging and time resolved SAXS experiments

    NASA Astrophysics Data System (ADS)

    Menk, R. H.; Arfelli, F.; Bernstorff, S.; Pontoni, D.; Sarvestani, A.; Besch, H. J.; Walenta, A. H.

    1999-02-01

    A one-dimensional test detector on the principle of a highly segmented ionization chamber with shielding grid (Frisch grid) was developed to evaluate if this kind of detector is suitable for advanced small-angle X-ray scattering (SAXS) experiments. At present it consists of 128 pixels which can be read out within 0.2 ms with a noise floor of 2000 e-ENC. A quantum efficiency of 80% for a photon energy of 8 keV was achieved. This leads to DQE values of 80% for photon fluxes above 1000 photons/pixel and integration time. The shielding grid is based on the principles of the recently invented MCAT structure and the GEM structure which also allows electron amplification in the gas. In the case of the MCAT structure, an energy resolution of 20% at 5.9 keV was observed. The gas amplification mode enables imaging with this integrating detector on a subphoton noise level with respect to the integration time. Preliminary experiments of saturation behavior show that this kind of detector digests a photon flux density up to 10 12 photons/mm 2 s and operates linearly. A spatial resolution of at least three line pairs/mm was obtained. All these features show that this type of detector is well suited for time-resolved SAXS experiments as well as high flux imaging applications.

  9. A low-dimensional, time-resolved and adapting model neuron.

    PubMed

    Cartling, B

    1996-07-01

    A low-dimensional, time-resolved and adapting model neuron is formulated and evaluated. The model is an extension of the integrate-and-fire type of model with respect to adaptation and of a recent adapting firing-rate model with respect to time-resolution. It is obtained from detailed conductance-based models by a separation of fast and slow ionic processes of action potential generation. The model explicitly includes firing-rate regulation via the slow afterhyperpolarization phase of action potentials, which is controlled by calcium-sensitive potassium channels. It is demonstrated that the model closely reproduces the firing pattern and excitability behaviour of a detailed multicompartment conductance-based model of a neocortical pyramidal cell. The inclusion of adaptation in a model neuron is important for its capability to generate complex dynamics of networks of interconnected neurons. The time-resolution is required for studies of systems in which the temporal aspects of neural coding are important. The simplicity of the model facilitates analytical studies, insight into neurocomputational mechanisms and simulations of large-scale systems. The capability to generate complex network computations may also make the model useful in practical applications of artificial neural networks. PMID:8891839

  10. Time, Energy, and Spatially Resolved TEM Investigations of Defectsin InGaN

    SciTech Connect

    Jinschek, J.R.; Kisielowski, C.

    2005-10-01

    A novel sample preparation technique is reported to fabricate electron transparent samples from devices utilizing a FIB process with a successive wet etching step. The high quality of the obtained samples allows for band gap--and chemical composition measurements of In{sub x}Ga{sub 1-x}N quantum wells where electron beam induced damage can be controlled and shown to be negligible. The results reveal indium enrichment in nanoclusters and defects that cause fluctuations of the band gap energy and can be measured by low loss Electron Energy Spectroscopy with nm resolution. Comparing our time, energy, and spatially resolved measurements of band gap energies, chemical composition, and their related fluctuations with literature data, we find quantitative agreement if the band gap energy of InN is 1.5-2 eV.

  11. Microbeam, timing and signal-resolved studies of nuclear materials with synchrotron X-ray sources

    SciTech Connect

    Ice, Gene E; Specht, Eliot D

    2012-01-01

    The development of ultra-brilliant synchrotron X-ray sources enables characterization methods that are particularly important for nuclear materials. Here we discuss emerging synchrotron methods with unprecedented signal-to-noise, spatial and time resolution. Microprobe methods are discussed that extend virtually any X-ray characterization measurement to ultra-small sample volumes. This ability is critical to resolve heterogeneities in nuclear materials and for studies on volumes with vastly lower activity than are needed for traditional X-ray characterization. Specific methods discussed include microdiffraction for the characterization of local crystal structure and micro-spectroscopy techniques that allow for characterization of elemental distributions with sensitivity for daughter products, oxidation states and diffusion through buffer layers. Opportunities are also discussed that exploit the high brilliance and pulsed nature of synchrotron radiation to reduce backgrounds from sample radiation and to study materials dynamics.

  12. Time-resolved chirp measurement for 100GBaud test systems using an ideal frequency discriminator

    NASA Astrophysics Data System (ADS)

    Watts, Regan T.; Shi, Kai; Barry, Liam P.

    2012-04-01

    In this paper we present multi-channel chirp measurements of wide-band sources, using a programmable Fourier-domain optical processor (FDOP) as a near-perfect linear frequency discriminator element followed by a fast photodiode and electrical sampling oscilloscope. The electric field of a 10.7 Gbit/s phase-encoded data source and a directly modulated laser diode are simultaneously interrogated with this measurement system. The constellation diagram of the phase-encoded data source is demonstrated, and a comparison with another phase-sensitive measurement technique is performed. Additionally, an extension to this technique is demonstrated in which the time-resolved chirp of a picosecond-duration mode-locked laser diode with a 260 GHz spectral bandwidth is characterised using the FDOP and a high-bandwidth optical sampling oscilloscope. This measurement ensemble has sufficient temporal resolution to characterise random or repetitive data signals up to 100GBaud.

  13. Time-Resolved Imaging Reveals Heterogeneous Landscapes of Nanomolar Ca(2+) in Neurons and Astroglia.

    PubMed

    Zheng, Kaiyu; Bard, Lucie; Reynolds, James P; King, Claire; Jensen, Thomas P; Gourine, Alexander V; Rusakov, Dmitri A

    2015-10-21

    Maintaining low intracellular calcium is essential to the functioning of brain cells, yet the phenomenology and mechanisms involved remain an enigma. We have advanced a two-photon excitation time-resolved imaging technique, which exploits high sensitivity of the OGB-1 fluorescence lifetime to nanomolar Ca(2+) concentration ([Ca(2+)]) and enables a high data acquisition rate in situ. The [Ca(2+)] readout is not affected by dye concentration, light scattering, photobleaching, micro-viscosity, temperature, or the main known concomitants of cellular activity. In quiescent tissue, standard whole-cell configuration has little effect on resting [Ca(2+)] inside neuronal dendrites or inside astroglia dye-filled via gap junctions. Mapping basal [Ca(2+)] in neurons and astrocytes with submicron resolution unveils heterogeneous concentration landscapes that depend on age and preceding activity. The rich information content represented by such landscapes in acute slices and in vivo promises to unveil the hitherto unexplored, potentially fundamental aspects of brain cell physiology. PMID:26494277

  14. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    DOE PAGESBeta

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlationmore » between spatial maps of the lifetime, dark current, and relative response.« less

  15. Towards on-chip time-resolved thermal mapping with micro-/nanosensor arrays

    PubMed Central

    2012-01-01

    In recent years, thin-film thermocouple (TFTC) array emerged as a versatile candidate in micro-/nanoscale local temperature sensing for its high resolution, passive working mode, and easy fabrication. However, some key issues need to be taken into consideration before real instrumentation and industrial applications of TFTC array. In this work, we will demonstrate that TFTC array can be highly scalable from micrometers to nanometers and that there are potential applications of TFTC array in integrated circuits, including time-resolvable two-dimensional thermal mapping and tracing the heat source of a device. Some potential problems and relevant solutions from a view of industrial applications will be discussed in terms of material selection, multiplexer reading, pattern designing, and cold-junction compensation. We show that the TFTC array is a powerful tool for research fields such as chip thermal management, lab-on-a-chip, and other novel electrical, optical, or thermal devices. PMID:22931306

  16. Time-resolved luminescent biosensing based on inorganic lanthanide-doped nanoprobes.

    PubMed

    Zheng, Wei; Tu, Datao; Huang, Ping; Zhou, Shanyong; Chen, Zhuo; Chen, Xueyuan

    2015-03-11

    Time-resolved (TR) photoluminescence (PL) biosensing has been widely adopted in many research and medical institutions. However, commercial molecular TRPL bioprobes like lanthanide (Ln(3+))-chelates suffer from poor photochemical stability and long-term toxicity. Inorganic Ln(3+)-doped nanocrystals (NCs), owing to their superior physicochemical properties over Ln(3+)-chelates, are regarded as a new generation of luminescent nanoprobes for TRPL biosensing. The long-lived PL of Ln(3+)-doped NCs combined with the TRPL technique is able to completely suppress the interference of the short-lived background, resulting in a background-free signal and therefore a remarkable sensitivity for biosensing. In this feature article, we summarize the latest advancements in inorganic Ln(3+)-doped NCs as TRPL nano-bioprobes from their fundamental optical properties to their potential applications for ultrasensitive biodetection and high-resolution bioimaging. Future efforts towards the commercialization of these nanoprobes are also proposed. PMID:25633111

  17. Time-Resolved Vibrational and Electronic Spectroscopy in Shocked Ammonium Perchlorate Single Crystals

    NASA Astrophysics Data System (ADS)

    Gruzdkov, Yuri; Winey, Michael; Feng, Ruqiang

    1997-07-01

    Experimental methods to obtain time-resolved Raman and absorption spectroscopy data on shocked ammonium perchlorate (AP) single crystals were developed. These included: (a) target designs for thin sample shock wave reverberation experiments; (b) techniques to perform Raman measurements with non-transparent flyers; and (c) adaptation of a high-velocity, 20 mm powder gun for optical spectroscopy. Good quality Raman and absorption spectra, with 50 ns resolution, have been obtained for shock compression along the [210] and [001] directions. Results for peak pressures up to 18 GPa and calculated temperatures up to 600 K are presented. Pressure/temperature-induced frequency hardening and broadening of the different AP Raman modes is observed. Evidence for shock-induced chemical decomposition is discussed.

  18. Time resolved photo-luminescent decay characterization of mercury cadmium telluride focal plane arrays

    SciTech Connect

    Soehnel, Grant

    2015-01-20

    The minority carrier lifetime is a measurable material property that is an indication of infrared detector device performance. To study the utility of measuring the carrier lifetime, an experiment has been constructed that can time resolve the photo-luminescent decay of a detector or wafer sample housed inside a liquid nitrogen cooled Dewar. Motorized stages allow the measurement to be scanned over the sample surface, and spatial resolutions as low as 50µm have been demonstrated. A carrier recombination simulation was developed to analyze the experimental data. Results from measurements performed on 4 mercury cadmium telluride focal plane arrays show strong correlation between spatial maps of the lifetime, dark current, and relative response.

  19. Analytical model of SiPM time resolution and order statistics with crosstalk

    NASA Astrophysics Data System (ADS)

    Vinogradov, S.

    2015-07-01

    Time resolution is the most important parameter of photon detectors in a wide range of time-of-flight and time correlation applications within the areas of high energy physics, medical imaging, and others. Silicon photomultipliers (SiPM) have been initially recognized as perfect photon-number-resolving detectors; now they also provide outstanding results in the scintillator timing resolution. However, crosstalk and afterpulsing introduce false secondary non-Poissonian events, and SiPM time resolution models are experiencing significant difficulties with that. This study presents an attempt to develop an analytical model of the timing resolution of an SiPM taking into account statistics of secondary events resulting from a crosstalk. Two approaches have been utilized to derive an analytical expression for time resolution: the first one based on statistics of independent identically distributed detection event times and the second one based on order statistics of these times. The first approach is found to be more straightforward and "analytical-friendly" to model analog SiPMs. Comparisons of coincidence resolving times predicted by the model with the known experimental results from a LYSO:Ce scintillator and a Hamamatsu MPPC are presented.

  20. High-resolution dust emission and the resolved star formation law in the z~4 submillimeter galaxy GN20

    NASA Astrophysics Data System (ADS)

    Hodge, Jacqueline; Riechers, Dominik A.; Decarli, Roberto; Walter, Fabian; Carilli, Chris Luke; Daddi, Emanuele; Dannerbauer, Helmut

    2015-01-01

    We present high-resolution observations of the 880μm (rest-frame far-infrared) continuum emission in the z=4.05 submillimeter galaxy GN20. These data, taken with the IRAM Plateau de Bure Interferometer (PdBI), allow us to resolve the obscured star formation on scales of 0.3'×0.2' (~2.1×1.3 kpc). The observations reveal a bright (16±1 mJy) dusty starburst centered on the cold molecular gas reservoir as traced by previous high-fidelity CO(2-1) imaging and showing a bar-like extension along the galaxy's major axis. The striking anti-correlation with the HST/WFC3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical light in all but one small region several kpc from the nucleus. A comparison with 1.2 mm PdBI data reveals no evidence for variations in the dust continuum slope across the source. A detailed star formation rate surface density map reveals values that peak at 119±8 M⊙ yr-1 kpc-2 in the galaxy's center, showing that the star formation in GN20 remains sub-Eddington on scales down to 3 kpc2. Lastly, we examine the resolved star formation law on the same scales, deriving a power law slope of ΣSFR ~ ΣH_22.1±1.0 and a mean depletion time of 130 Myr. Despite its disk-like morphology and the use of custom-derived CO-to-H2 conversion factors, GN20 lies roughly in-line with the other existing resolved starbursts and above the sequence of star forming disks, implying that the offset is not due solely to choice of conversion factor.

  1. The excited-state chemistry of protochlorophyllide a: a time-resolved fluorescence study.

    PubMed

    Dietzek, Benjamin; Kiefer, Wolfgang; Yartsev, Arkady; Sundström, Villy; Schellenberg, Peter; Grigaravicius, Paulius; Hermann, Gudrun; Popp, Jürgen; Schmitt, Michael

    2006-08-11

    The excited-state processes of protochlorophyllide a, the precursor of chlorophyll a in chlorophyll biosynthesis, are studied using picosecond time-resolved fluorescence spectroscopy. Following excitation into the Soret band, two distinct fluorescence components, with emission maxima at 640 and 647 nm, are observed. The 640 nm emitting component appears within the time resolution of the experiment and then decays with a time constant of 27 ps. In contrast, the 647 nm emitting component is built up with a 3.5 ps rise time and undergoes a subsequent decay with a time constant of 3.5 ns. The 3.5 ps rise kinetics are attributed to relaxations in the electronically excited state preceding the nanosecond fluorescence, which is ascribed to emission out of the thermally equilibrated S(1) state. The 27 ps fluorescence, which appears within the experimental response of the streak camera, is suggested to originate from a second minimum on the excited-state potential-energy surface. The population of the secondary excited state is suggested to reflect a very fast motion out of the Franck-Condon region along a reaction coordinate different from the one connecting the Franck-Condon region with the S(1) potential-energy minimum. The 27 ps-component is an emissive intermediate on the reactive excited-state pathway, as its decay yields the intermediate photoproduct, which has been identified previously (J. Phys. Chem. B 2006, 110, 4399-4406). No emission of the photoproduct is observed. The results of the time-resolved fluorescence study allow a detailed spectral characterization of the emission of the excited states in protochlorophyllide a, and the refinement of the kinetic model deduced from ultrafast absorption measurements. PMID:16841352

  2. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

    SciTech Connect

    Jozwiak, Chris M.; Graff, Jeff; Lebedev, Gennadi; Andresen, Nord; Schmid, Andreas; Fedorov, Alexei; El Gabaly, Farid; Wan, Weishi; Lanzara, Alessandra; Hussain, Zahid

    2010-04-13

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

  3. Design of a High Resolution and High Flux Beam line for VUV Angle-Resolved Photoemission at UVSOR-II

    SciTech Connect

    Kimura, Shin-ichi; Ito, Takahiro; Nakamura, Eiken; Hosaka, Masahito; Katoh, Masahiro

    2007-01-19

    A high-energy-resolution angle-resolved photoemission beamline in the vacuum-ultraviolet (VUV) region has been designed for a 750 MeV synchrotron light source UVSOR-II. The beamline equips an APPLE-II-type undulator with the horizontally/vertically linear and right/left circular polarizations, a modified Wadsworth-type monochromator and a high-resolution photoelectron analyzer. The monochromator covers the photon energy range of 6 - 40 eV. The energy resolution (hv/{delta}hv) and the photon flux on samples are expected to be 2 x 104 and 1012 photons/sec at 10 eV, 4 x 104 and 5 x 1011 photons/sec at 20 eV, and 6 x 104 and 1011 photons/sec at 40 eV, respectively. The beamline provides the high-resolution angle-resolved photoemission spectroscopy less than 1 meV in the whole VUV energy range.

  4. An inexpensive technique for the time resolved laser induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmed, Rizwan; Ahmed, Nasar; Iqbal, J.; Aslam Baig, M.

    2016-08-01

    We present an efficient and inexpensive method for calculating the time resolved emission spectrum from the time integrated spectrum by monitoring the time evolution of neutral and singly ionized species in the laser produced plasma. To validate our assertion of extracting time resolved information from the time integrated spectrum, the time evolution data of the Cu II line at 481.29 nm and the molecular bands of AlO in the wavelength region (450-550 nm) have been studied. The plasma parameters were also estimated from the time resolved and time integrated spectra. A comparison of the results clearly reveals that the time resolved information about the plasma parameters can be extracted from the spectra registered with a time integrated spectrograph. Our proposed method will make the laser induced plasma spectroscopy robust and a low cost technique which is attractive for industry and environmental monitoring.

  5. Experimental and theoretical studies of time-averaged and time resolved rotor heat transfer

    NASA Astrophysics Data System (ADS)

    Dunn, M. G.; Rae, W. J.; Rigby, D. L.

    Efforts in support of the Space Shuttle Main Engine (SSME) structural durability program have concentrated on obtaining detailed time-averaged and time-resolved (or phase-locked) measurements on a full-scale rotating turbine both with and without cold gas injection and on theoretical studies designed to improve the prediction capability for these turbine flows. The experimental efforts have concentrated on use of the Garrett TFE 731-2 hp turbine. However, it has been possible to apply the theoretical efforts to predicting heat-flux distributions obtained for two additional turbines - i.e., (1) the Garrett low aspect ratio turbine (LART) and (2) the Teledyne 702 turbine. The experimental technique is the short duration, shock-tunnel approach, in which fast-response, thin-film resistance thermometers are used to measure surface temperature histories at prescribed locations on the turbine component parts. Heat-flux values are then inferred from the temperature histories by using standard data reduction procedures. The turbine being used is the Garrett TFE 731-2 hp stage, and both the nozzle guide vanes and the rotor blades are heavily instrumented with thin-film heat-flux gauges. Depending on how the data from a particular heat-flux gauge are recorded, one can get either time-resolved (or phase-locked) or time-averaged results. Both types of data are illustrated.

  6. Experimental and theoretical studies of time-averaged and time resolved rotor heat transfer

    NASA Technical Reports Server (NTRS)

    Dunn, M. G.; Rae, W. J.; Rigby, D. L.

    1987-01-01

    Efforts in support of the Space Shuttle Main Engine (SSME) structural durability program have concentrated on obtaining detailed time-averaged and time-resolved (or phase-locked) measurements on a full-scale rotating turbine both with and without cold gas injection and on theoretical studies designed to improve the prediction capability for these turbine flows. The experimental efforts have concentrated on use of the Garrett TFE 731-2 hp turbine. However, it has been possible to apply the theoretical efforts to predicting heat-flux distributions obtained for two additional turbines - i.e., (1) the Garrett low aspect ratio turbine (LART) and (2) the Teledyne 702 turbine. The experimental technique is the short duration, shock-tunnel approach, in which fast-response, thin-film resistance thermometers are used to measure surface temperature histories at prescribed locations on the turbine component parts. Heat-flux values are then inferred from the temperature histories by using standard data reduction procedures. The turbine being used is the Garrett TFE 731-2 hp stage, and both the nozzle guide vanes and the rotor blades are heavily instrumented with thin-film heat-flux gauges. Depending on how the data from a particular heat-flux gauge are recorded, one can get either time-resolved (or phase-locked) or time-averaged results. Both types of data are illustrated.

  7. Real-time digital signal processing in multiphoton and time-resolved microscopy

    NASA Astrophysics Data System (ADS)

    Wilson, Jesse W.; Warren, Warren S.; Fischer, Martin C.

    2016-03-01

    The use of multiphoton interactions in biological tissue for imaging contrast requires highly sensitive optical measurements. These often involve signal processing and filtering steps between the photodetector and the data acquisition device, such as photon counting and lock-in amplification. These steps can be implemented as real-time digital signal processing (DSP) elements on field-programmable gate array (FPGA) devices, an approach that affords much greater flexibility than commercial photon counting or lock-in devices. We will present progress toward developing two new FPGA-based DSP devices for multiphoton and time-resolved microscopy applications. The first is a high-speed multiharmonic lock-in amplifier for transient absorption microscopy, which is being developed for real-time analysis of the intensity-dependence of melanin, with applications in vivo and ex vivo (noninvasive histopathology of melanoma and pigmented lesions). The second device is a kHz lock-in amplifier running on a low cost (50-200) development platform. It is our hope that these FPGA-based DSP devices will enable new, high-speed, low-cost applications in multiphoton and time-resolved microscopy.

  8. X-ray studies and time-resolved photoluminescence on optically pumped antimonide-based midinfrared type-II lasers.

    PubMed

    Schwender, Carsten; Drumm, Jan Oliver; Hoffmann, Goetz; Vogelgesang, Birgit; Fouckhardt, Henning

    2004-12-01

    We report on high-resolution X-ray diffraction and time-resolved photoluminescence (TR-PL) studies of antimonide-based midinfrared (MIR) type-II laser samples. A structural characterization taking into account asymmetrical strain, layer tilting, and relaxation enables an accurate determination of the average lattice constant of the active region and the composition of the cladding layers. By designing the antimonide-to-arsenide interfaces, we achieve exact lattice matching of the active region to the substrate. Non-radiative recombination processes are investigated with time-resolved photoluminescence. The samples are also characterized under optically pumped laser operation. By an examination of the time-integrated and time-resolved amplified spontaneous emission (TR-ASE), we investigate the modal gain and gain dynamics. The variable stripe length method is combined with the TR-PL approach. Compared to the time-integrated gain spectra the spectral dependence of the maximum and minimum time-resolved gain shows a broad plateau. The full width half maximum (FWHM) of the TR-ASE pulse is 5.5 +/- 0.5 ps. Thus, short pulses in this range should be achievable upon laser operation. The active regions of the laser structures investigated here are promising subunits of type-II quantum cascade lasers. PMID:15561624

  9. Protein structural dynamics in solution unveiled via 100-ps time-resolved x-ray scattering

    PubMed Central

    Anfinrud, Philip

    2010-01-01

    We have developed a time-resolved x-ray scattering diffractometer capable of probing structural dynamics of proteins in solution with 100-ps time resolution. This diffractometer, developed on the ID14B BioCARS (Consortium for Advanced Radiation Sources) beamline at the Advanced Photon Source, records x-ray scattering snapshots over a broad range of q spanning 0.02–2.5 Å-1, thereby providing simultaneous coverage of the small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) regions. To demonstrate its capabilities, we have tracked structural changes in myoglobin as it undergoes a photolysis-induced transition from its carbon monoxy form (MbCO) to its deoxy form (Mb). Though the differences between the MbCO and Mb crystal structures are small (rmsd < 0.2 Å), time-resolved x-ray scattering differences recorded over 8 decades of time from 100 ps to 10 ms are rich in structure, illustrating the sensitivity of this technique. A strong, negative-going feature in the SAXS region appears promptly and corresponds to a sudden > 22 Å3 volume expansion of the protein. The ensuing conformational relaxation causes the protein to contract to a volume ∼2 Å3 larger than MbCO within ∼10 ns. On the timescale for CO escape from the primary docking site, another change in the SAXS/WAXS fingerprint appears, demonstrating sensitivity to the location of the dissociated CO. Global analysis of the SAXS/WAXS patterns recovered time-independent scattering fingerprints for four intermediate states of Mb. These SAXS/WAXS fingerprints provide stringent constraints for putative models of conformational states and structural transitions between them. PMID:20406909

  10. Protein structural dynamics in solution unveiled via 100-ps time-resolved x-ray scattering

    SciTech Connect

    Cho, Hyun Sun; Dashdorj, Naranbaatar; Schotte, Friedrich; Graber, Timothy; Henning, Robert; Anfinruda, Philip

    2010-04-21

    We have developed a time-resolved x-ray scattering diffractometer capable of probing structural dynamics of proteins in solution with 100-ps time resolution. This diffractometer, developed on the ID14B BioCARS (Consortium for Advanced Radiation Sources) beamline at the Advanced Photon Source, records x-ray scattering snapshots over a broad range of q spanning 0.02-2.5 {angstrom}{sup -1}, thereby providing simultaneous coverage of the small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) regions. To demonstrate its capabilities, we have tracked structural changes in myoglobin as it undergoes a photolysis-induced transition from its carbon monoxy form (MbCO) to its deoxy form (Mb). Though the differences between the MbCO and Mb crystal structures are small (rmsd < 0.2 {angstrom}), time-resolved x-ray scattering differences recorded over 8 decades of time from 100 ps to 10 ms are rich in structure, illustrating the sensitivity of this technique. A strong, negative-going feature in the SAXS region appears promptly and corresponds to a sudden > 22 {angstrom}{sup 3} volume expansion of the protein. The ensuing conformational relaxation causes the protein to contract to a volume {approx}2 {angstrom}{sup 3} larger than MbCO within {approx}10 ns. On the timescale for CO escape from the primary docking site, another change in the SAXS/WAXS fingerprint appears, demonstrating sensitivity to the location of the dissociated CO. Global analysis of the SAXS/WAXS patterns recovered time-independent scattering fingerprints for four intermediate states of Mb. These SAXS/WAXS fingerprints provide stringent constraints for putative models of conformational states and structural transitions between them.

  11. A resource conflict resolution problem formulated in continuous time

    NASA Astrophysics Data System (ADS)

    Gaver, D. P.; Fayolle, G.; Weiss, A.

    1985-08-01

    In many situations involving data transmission from diverse sources there can be conflict for a limited number of channels or other facilities. Uncoordinated attempts by several sources to use a single facility can result in collision, the destruction of all participants in the collision, meaning the loss of the transmission, and hence the need for re-transmission. An important problem concerns the development of workable procedures for alleviating the conflict and corresponding message delay problems. Often such problems are viewed as occurring in discrete time: slots of equal length occur in temporal succession, and each slot can handle just one packet of data at a time, if two or more packets try to use the same slot simultaneously, a collision occurs that somehow must be resolved. A recent paper analyzed a stack protocol for handling such a situation, but there are many other proposals. This report is concerned with some simple models for a single facility (channel), and for contention or conflict resolution. The models are formulated in a continuous-time manner: messages, or numbers of packets constituting messages, are long, meaning that they occupy many consecutive slots on the average if a single transmission is occurring.

  12. Time and Space Resolved Wall Temperature Measurements during Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Yerramilli, Vamsee K.; Kim, Jungho

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work is to acquire time and space resolved temperature distributions under nucleate bubbles on a constant heat flux surface. This was performed using a microheater array with 100 micron resolution that allowed effectively simultaneous measurements of surface temperature while supplying a constant dissipative heat flux. This data is then correlated with high speed (> 1000Hz) visual recordings of the bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that a significant source of energy during bubble nucleation and initial growth is the superheated layer around the bubble. Bubble coalescence was not observed to decrease surface temperature as significantly as bubble departure from the surface. Since bubble departure is typically followed by a sharp increase in the heater surface temperature, it is surmised that the departing bubble effectively removes the superheated layer, allowing a high local heat transfer rate with the bulk fluid through transient conduction/micro-convection during rewetting.

  13. A synchronized emissive probe for time-resolved plasma potential measurements of pulsed discharges

    SciTech Connect

    Sanders, Jason M.; Rauch, Albert; Mendelsberg, Rueben J.; Anders, Andre

    2011-09-15

    A pulsed emissive probe technique is presented for measuring the plasma potential of pulsed plasma discharges. The technique provides time-resolved data and features minimal disturbance of the plasma achieved by alternating probe heating with the generation of plasma. Time resolution of about 20 ns is demonstrated for high power impulse magnetron sputtering (HIPIMS) plasma of niobium in argon. Spatial resolution of about 1 mm is achieved by using a miniature tungsten filament mounted on a precision translational stage. Repeated measurements for the same discharge conditions show that the standard deviation of the measurements is about 1-2 V, corresponding to 4%-8% of the maximum plasma potential relative to ground. The principle is demonstrated for measurements at a distance of 30 mm from the target, for different radial positions, at an argon pressure of 0.3 Pa, a cathode voltage of -420 V, and a discharge current of about 60 A in the steady-state phase of the HIPIMS pulse.

  14. Laser microfabrication of biomedical devices: time-resolved microscopy of the printing process

    NASA Astrophysics Data System (ADS)

    Serra, P.; Patrascioiu, A.; Fernández-Pradas, J. M.; Morenza, J. L.

    2013-04-01

    Laser printing constitutes an interesting alternative to more conventional printing techniques in the microfabrication of biomedical devices. The principle of operation of most laser printing techniques relies on the highly localized absorption of strongly focused laser pulses in the close proximity of the free surface of the liquid to be printed. This leads to the generation of a cavitation bubble which further expansion results in the ejection of a small fraction of the liquid, giving place to the deposition of a well-defined droplet onto a collector substrate. Laser printing has proved feasible for printing biological materials, from single-stranded DNA to proteins, and even living cells and microorganisms, with high degrees of resolution and reproducibility. In consequence, laser printing appears to be an excellent candidate for the fabrication of biological microdevices, such as DNA and protein microarrays, or miniaturized biosensors. The optimization of the performances of laser printing techniques requires a detailed knowledge of the dynamics of liquid transfer. Time-resolved microscopy techniques play a crucial role in this concern, since they allow tracking the evolution of the ejected material with excellent time and spatial resolution. Investigations carried out up to date have shown that liquid ejection proceeds through the formation of long, thin and stable liquid jets. In this work the different approaches used so far for monitoring liquid ejection during laser printing are considered, and it is shown how these techniques make possible to understand the complex dynamics involved in the process.

  15. Design of a portable fluorometer capable of time-resolved luminescence measurements

    NASA Astrophysics Data System (ADS)

    Chen, Guoying

    2004-11-01

    A rugged, filter-based fluorometer capable of time-resolved luminescence (TRL) measurements was designed, prototyped and tested for field applications. The instrument operation and data processing were controlled by a laptop computer running a custom LabVIEW program. A xenon flashlamp was used as the light source and a photomultiplier tube (PMT) as the photodetector. A gating technique was implemented to effectively overcome PMT saturation by intense xenon lamp flash so signal integrity was maintained even at very high gains, leading to improved sensitivity and reproducibility. The instrument was tested by TRL using tetracycline as a model analyte; and the signal was digitized at a 2-μs time resolution and a 12-bit amplitude resolution. Its performance was similar to or slightly better than that of a commercial fluorescence spectrophotometer. A 0-300 ppb linear dynamic range (r2 = 0.9996) and a 0.025-ppb limit of detection (LOD) were achieved with a <=5% relative standard deviation.

  16. Time-Resolved Luminescence Nanothermometry with Nitrogen-Vacancy Centers in Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Tsai, Pei-Chang; Chen, Oliver Y.; Tzeng, Yan-Kai; Liu, Hsiou-Yuan; Hsu, Hsiang; Huang, Shaio-Chih; Chen, Jeson; Yee, Fu-Ghoul; Chang, Huan-Cheng; Chang, Ming-Shien

    2016-05-01

    Measuring thermal properties with nanoscale spatial resolution either at or far from equilibrium is gaining importance in many scientific and engineering applications. Although negatively charged nitrogen-vacancy (NV-) centers in diamond have recently emerged as promising nanometric temperature sensors, most previous measurements were performed under steady state conditions. Here we employ a three-point sampling method which not only enables real-time detection of temperature changes over +/-100 K with a sensitivity of 2 K/(Hz)1/2, but also allows the study of nanometer scale heat transfer with a temporal resolution of better than 1 μs with the use of a pump-probe-type experiment. In addition to temperature sensing, we further show that nanodiamonds conjugated with gold nanorods, as optically-activated dual-functional nanoheaters and nanothermometers, are useful for highly localized hyperthermia treatment. We experimentally demonstrated time-resolved fluorescence nanothermometry, and the validity of the measurements was verified with finite-element numerical simulations. The approaches provided here will be useful for probing dynamical thermal properties on nanodevices in operation.

  17. Phylogenomics resolves the timing and pattern of insect evolution.

    PubMed

    Misof, Bernhard; Liu, Shanlin; Meusemann, Karen; Peters, Ralph S; Donath, Alexander; Mayer, Christoph; Frandsen, Paul B; Ware, Jessica; Flouri, Tomáš; Beutel, Rolf G; Niehuis, Oliver; Petersen, Malte; Izquierdo-Carrasco, Fernando; Wappler, Torsten; Rust, Jes; Aberer, Andre J; Aspöck, Ulrike; Aspöck, Horst; Bartel, Daniela; Blanke, Alexander; Berger, Simon; Böhm, Alexander; Buckley, Thomas R; Calcott, Brett; Chen, Junqing; Friedrich, Frank; Fukui, Makiko; Fujita, Mari; Greve, Carola; Grobe, Peter; Gu, Shengchang; Huang, Ying; Jermiin, Lars S; Kawahara, Akito Y; Krogmann, Lars; Kubiak, Martin; Lanfear, Robert; Letsch, Harald; Li, Yiyuan; Li, Zhenyu; Li, Jiguang; Lu, Haorong; Machida, Ryuichiro; Mashimo, Yuta; Kapli, Pashalia; McKenna, Duane D; Meng, Guanliang; Nakagaki, Yasutaka; Navarrete-Heredia, José Luis; Ott, Michael; Ou, Yanxiang; Pass, Günther; Podsiadlowski, Lars; Pohl, Hans; von Reumont, Björn M; Schütte, Kai; Sekiya, Kaoru; Shimizu, Shota; Slipinski, Adam; Stamatakis, Alexandros; Song, Wenhui; Su, Xu; Szucsich, Nikolaus U; Tan, Meihua; Tan, Xuemei; Tang, Min; Tang, Jingbo; Timelthaler, Gerald; Tomizuka, Shigekazu; Trautwein, Michelle; Tong, Xiaoli; Uchifune, Toshiki; Walzl, Manfred G; Wiegmann, Brian M; Wilbrandt, Jeanne; Wipfler, Benjamin; Wong, Thomas K F; Wu, Qiong; Wu, Gengxiong; Xie, Yinlong; Yang, Shenzhou; Yang, Qing; Yeates, David K; Yoshizawa, Kazunori; Zhang, Qing; Zhang, Rui; Zhang, Wenwei; Zhang, Yunhui; Zhao, Jing; Zhou, Chengran; Zhou, Lili; Ziesmann, Tanja; Zou, Shijie; Li, Yingrui; Xu, Xun; Zhang, Yong; Yang, Huanming; Wang, Jian; Wang, Jun; Kjer, Karl M; Zhou, Xin

    2014-11-01

    Insects are the most speciose group of animals, but the phylogenetic relationships of many major lineages remain unresolved. We inferred the phylogeny of insects from 1478 protein-coding genes. Phylogenomic analyses of nucleotide and amino acid sequences, with site-specific nucleotide or domain-specific amino acid substitution models, produced statistically robust and congruent results resolving previously controversial phylogenetic relations hips. We dated the origin of insects to the Early Ordovician [~479 million years ago (Ma)], of insect flight to the Early Devonian (~406 Ma), of major extant lineages to the Mississippian (~345 Ma), and the major diversification of holometabolous insects to the Early Cretaceous. Our phylogenomic study provides a comprehensive reliable scaffold for future comparative analyses of evolutionary innovations among insects. PMID:25378627

  18. A time-resolved x-ray scattering experiment for the study of phase transitions and crystallization processes in metallic alloys

    SciTech Connect

    Pelletier, J. F.; Sutton, M.; Altounian, Z.; Saini, S.; Luriom L. B.; Sandy, A. R.; Lumma, D.; Borthwick, M. A.; Falus, P.; Mochrie, S. G. J.; Stephenson, G. B.

    1999-10-29

    An experimental setup to perform high-resolution time-resolved X-ray scattering has been commissioned on the side station of beamline 8-ID at the Advanced Photon Source. A Peltier-cooled diode detector array covering an angle range of 20 degrees is mounted on a 4-circle goniometer and is used to temporally resolve X-ray scattering patterns with a resolution up to 10 ms. Metallic ribbon samples can be quickly heated and cooled from temperatures up to 500 C inside a furnace with controllable atmosphere and equipped with a beryllium window. A description of the setup is presented along with actual results showing time-resolved phase transitions and crystallization processes in AlYNi metallic alloys. These results demonstrate the power of this technique to investigate complex crystallization processes as well as the versatility of this time-resolved X-ray scattering spectrometer.

  19. High-resolution isotope measurements resolve rapid ecohydrological dynamics at the soil-plant interface.

    PubMed

    Volkmann, Till H M; Haberer, Kristine; Gessler, Arthur; Weiler, Markus

    2016-05-01

    Plants rely primarily on rainfall infiltrating their root zones - a supply that is inherently variable, and fluctuations are predicted to increase on most of the Earth's surface. Yet, interrelationships between water availability and plant use on short timescales are difficult to quantify and remain poorly understood. To overcome previous methodological limitations, we coupled high-resolution in situ observations of stable isotopes in soil and transpiration water. We applied the approach along with Bayesian mixing modeling to track the fate of (2) H-labeled rain pulses following drought through soil and plants of deciduous tree ecosystems. We resolve how rainwater infiltrates the root zones in a nonequilibrium process and show that tree species differ in their ability to quickly acquire the newly available source. Sessile oak (Quercus petraea) adjusted root uptake to vertical water availability patterns under drought, but readjustment toward the rewetted topsoil was delayed. By contrast, European beech (Fagus sylvatica) readily utilized water from all soil depths independent of water depletion, enabling faster uptake of rainwater. Our results demonstrate that species-specific plasticity and responses to water supply fluctuations on short timescales can now be identified and must be considered to predict vegetation functional dynamics and water cycling under current and future climatic conditions. PMID:26864434

  20. Vibrationally resolved high-resolution NEXAFS and XPS spectra of phenanthrene and coronene

    SciTech Connect

    Fronzoni, Giovanna; Baseggio, Oscar; Stener, Mauro; Hua, Weijie; Tian, Guangjun; Luo, Yi; Apicella, Barbara; Alfé, Michela; Simone, Monica de; Kivimäki, Antti; Coreno, Marcello

    2014-07-28

    We performed a combined experimental and theoretical study of the C1s Near-Edge X-ray Absorption Fine-Structure (NEXAFS) spectroscopy and X-ray Photoelectron Spectroscopy in the gas phase of two polycyclic aromatic hydrocarbons (phenanthrene and coronene), typically formed in combustion reactions. In the NEXAFS of both molecules, a double-peak structure appears in the C1s → LUMO region, which differ by less than 1 eV in transition energies. The vibronic coupling is found to play an important role in such systems. It leads to weakening of the lower-energy peak and strengthening of the higher-energy one because the 0 − n (n > 0) vibrational progressions of the lower-energy peak appear in nearly the same region of the higher-energy peak. Vibrationally resolved theoretical spectra computed within the Frank-Condon (FC) approximation and linear coupling model agree well with the high-resolution experimental results. We find that FC-active normal modes all correspond to in-plane vibrations.

  1. Time-resolved optical studies of wide-gap II-VI semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Hong

    ZnSe and ZnSe-based quantum well and superlattice structures are potential candidates for light emitting devices and other optical devices such as switches and modulators working in the blue-green wavelength range. Carrier dynamics studies of these structures are important in evaluating device performance as well as understanding the underlying physical processes. In this thesis, a carrier dynamics investigation is conducted for temperature from 77K to 295K on CdZnSSe/ZnSSe single quantum well structure (SQW) and ZnSe/ZnSTe superlattice fabricated by molecular beam epitaxy (MBE). Two experimental techniques with femtosecond time resolution are used in this work: up-conversion technique for time- resolved photoluminescence (PL) and pump-probe technique for time-resolved differential absorption studies. For both heterostructures, the radiative recombination is dominated by exciton transition due to the large exciton binding energy as a result of quantum confinement effect. The measured decay time of free exciton PL in CdZnSSe/ZnSSe SQW increases linearly with increasing temperature which agrees with the theoretical prediction by considering the conservation of momentum requirement for radiative recombination. However, the recombination of free carriers is also observed in CdZnSSe/ZnSSe SQW for the whole temperature range studied. On the other hand, in ZnSe/ZnSTe superlattice structures, the non- radiative recombination processes are non-negligible even at 77K and become more important in higher temperature range. The relaxation processes such as spectral hole burning, carrier thermalization and hot-carrier cooling are observed in ZnSe/ZnSTe superlattices at room temperature (295K) by the femtosecond pump-probe measurements. A rapid cooling of the thermalized hot- carrier from 763K to 450K within 4ps is deduced. A large optical nonlinearity (i.e., the induced absorption change) around the heavy-hole exciton energy is also obtained.

  2. 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.

  3. The time resolution of the St Petersburg paradox

    PubMed Central

    Peters, Ole

    2011-01-01

    A resolution of the St Petersburg paradox is presented. In contrast to the standard resolution, utility is not required. Instead, the time-average performance of the lottery is computed. The final result can be phrased mathematically identically to Daniel Bernoulli's resolution, which uses logarithmic utility, but is derived using a conceptually different argument. The advantage of the time resolution is the elimination of arbitrary utility functions. PMID:22042904

  4. ASIC-enabled High Resolution Optical Time Domain Reflectometer

    NASA Astrophysics Data System (ADS)

    Skendzic, Sandra

    Fiber optics has become the preferred technology in communication systems because of what it has to offer: high data transmission rates, immunity to electromagnetic interference, and lightweight, flexible cables. An optical time domain reflectometer (OTDR) provides a convenient method of locating and diagnosing faults (e.g. break in a fiber) along a fiber that can obstruct crucial optical pathways. Both the ability to resolve the precise location of the fault and distinguish between two discrete, closely spaced faults are figures of merit. This thesis presents an implementation of a high resolution OTDR through the use of a compact and programmable ASIC (application specific integrated circuit). The integration of many essential OTDR functions on a single chip is advantageous over existing commercial instruments because it enables small, lightweight packaging, and offers low power and cost efficiency. Furthermore, its compactness presents the option of placing multiple ASICs in parallel, which can conceivably ease the characterization of densely populated fiber optic networks. The OTDR ASIC consists of a tunable clock, pattern generator, precise timer, electrical receiver, and signal sampling circuit. During OTDR operation, the chip generates narrow electrical pulse, which can then be converted to optical format when coupled with an external laser diode driver. The ASIC also works with an external photodetector to measure the timing and amplitude of optical reflections in a fiber. It has a 1 cm sampling resolution, which allows for a 2 cm spatial resolution. While this OTDR ASIC has been previously demonstrated for multimode fiber fault diagnostics, this thesis focuses on extending its functionality to single mode fiber. To validate this novel approach to OTDR, this thesis is divided into five chapters: (1) introduction, (2) implementation, (3), performance of ASIC-based OTDR, (4) exploration in optical pre-amplification with a semiconductor optical amplifier, and

  5. Characterization of spatially resolved high resolution x-ray spectrometers for high energy density physics and light source experiments

    SciTech Connect

    Hill, K. W. Bitter, M.; Delgado-Aparacio, L.; Efthimion, P.; Pablant, N. A.; Lu, J.; Beiersdorfer, P.; Chen, H.; Magee, E.

    2014-11-15

    A high resolution 1D imaging x-ray spectrometer concept comprising a spherically bent crystal and a 2D pixelated detector is being optimized for diagnostics of small sources such as high energy density physics (HEDP) and synchrotron radiation or x-ray free electron laser experiments. This instrument is used on tokamak experiments for Doppler measurements of ion temperature and plasma flow velocity profiles. Laboratory measurements demonstrate a resolving power, E/ΔE of order 10 000 and spatial resolution better than 10 μm. Initial tests of the high resolution instrument on HEDP plasmas are being performed.

  6. Interfacing a transient digitizer to a step-scan Fourier transform spectrometer for nanosecond time resolved spectroscopy

    SciTech Connect

    Letendre, L.T.; Dai, H.; McLaren, I.A.; Johnson, T.J.

    1999-01-01

    A new signal processing and data acquisition system has been developed that allows a Fourier transform spectrometer to be interfaced to external transient digitizers for time-resolved spectroscopy. Time resolution is limited only by the transient digitizer and detection system response time. For the present system it is about 1 ns. The capabilities of this system are demonstrated with visible Fourier transform spectra of both scattered laser light and fluorescence from electronically excited NO{sub 2} gas. {copyright} {ital 1999 American Institute of Physics.}

  7. LDS-750 as a probe of solvation dynamics: a femtosecond time-resolved fluorescence study in liquid aniline

    NASA Astrophysics Data System (ADS)

    Smith, Neil A.; Meech, Stephen R.; Rubtsov, Igor V.; Yoshihara, Keitaro

    1999-04-01

    The dynamics of the fluorescence Stokes shift of the styryl dye LDS-750 have been measured in liquid aniline with sub-100 fs time resolution. The shape of the time-resolved spectra are time dependent, which is not consistent with the predictions of a solvation dynamics mechanism. However, the measured spectral shift correlation function is reasonably well described by the dynamical mean spherical approximation model of solvation dynamics. It is suggested that these observations are consistent if solvent dynamics is the rate controlling process in both solvation of the increased dipole moment of the excited state of LDS-750 and the stabilisation of a distribution of solute conformers in the excited state.

  8. Time Resolved Studies of Carrier Dynamics in III -v Heterojunction Semiconductors.

    NASA Astrophysics Data System (ADS)

    Westland, Duncan James

    Available from UMI in association with The British Library. Requires signed TDF. Picosecond time-resolution photoluminescence spectroscopy has been used to study transient processes in Ga _{.47}In_{.53 }As/InP multiple quantum wells (MQWs), and in bulk Ga_{.47}In _{.53}As and GaSb. To facilitate the experimental studies, apparatus was constructed to allow the detection of transient luminescence with 3ps time resolution. A frequency upconversion technique was employed. Relaxation of energetic carriers in bulk Ga _{.47}In_{.53 }As by optic phonons has been investigated, and, at carrier densities ~3 times 10^{18}cm ^{-3} is found to be a considerably slower process than simple theory predicts. The discrepancy is resolved by the inclusion of a non-equilibrium population of longitudinal optic phonons in the theoretical description. Slow energy loss is also observed in a 154A MQW under similar conditions, but carriers are found to relax more quickly in a 14A MQW with a comparable repeat period. The theory of non-equilibrium mode occupation is modified to describe the case of a MQW and is found to agree with experiment. Carrier relaxation in GaSb is studied and the importance of occupation of the L _6 conduction band valley in this material is demonstrated. The ambipolar diffusion of a photoexcited carrier plasma through an InP capping layer was investigated using an optical time-of-flight technique. This experiment also enables the efficiency of carrier capture by a Ga _{.47}In_{.53 }As quantum well to be determined. A capture time of 4ps was found.

  9. Time-Resolved PIV for Space-Time Correlations in Hot Jets

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.

    2007-01-01

    Temporally Resolved Particle Image Velocimetry (TR-PIV) is being used to characterize the decay of turbulence in jet flows a critical element for understanding the acoustic properties of the flow. A TR-PIV system, developed in-house at the NASA Glenn Research Center, is capable of acquiring planar PIV image frame pairs at up to 10 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number.

  10. High-resolution spectrally-resolved fiber optic sensor interrogation system based on a standard DWDM laser module.

    PubMed

    Njegovec, Matej; Donlagic, Denis

    2010-11-01

    This paper presents a spectrally-resolved integration system suitable for the reading of Bragg grating, all-fiber Fabry-Perot, and similar spectrally-resolved fiber-optic sensors. This system is based on a standard telecommunication dense wavelength division multiplexing transmission module that contains a distributed feedback laser diode and a wavelength locker. Besides the transmission module, only a few additional opto-electronic components were needed to build an experimental interrogation system that demonstrated over a 2 nm wide wavelength interrogation range, and a 1 pm wavelength resolution. When the system was combined with a typical Bragg grating sensor, a strain resolution of 1 με and temperature resolution of 0.1 °C were demonstrated experimentally. The proposed interrogation system relies entirely on Telecordia standard compliant photonic components and can thus be straightforwardly qualified for use within the range of demanding applications. PMID:21164765

  11. 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.

  12. Vacuum ultraviolet luminescence of wide band-gap solids studied using time-resolved spectroscopy with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Makhov, V. N.

    2014-04-01

    Some highlights of the time-resolved vacuum ultraviolet (VUV) luminescence spectroscopy of solids using synchrotron radiation (SR) are outlined, including studies of the unique phenomenon crossluminescence (CL) and the contribution of time-resolved VUV spectroscopy to the understanding of 5d-4f transitions of rare earth ions in solids. The main properties of CL studied at different SR sources are described and some unclear aspects of CL are pointed out. The results of recent studies of some CL-active nanosize materials are presented. We describe the time-resolved experiments which led to the discovery of 5d-4f luminescence in the deep VUV region (near 10 eV) of Gd3+ and Lu3+ ions incorporated into some wide band-gap fluoride hosts. The results of high-resolution (Δλ ˜ 0.5 Å) studies of 5d-4f emission and 4f-5d excitation spectra of Gd3+ and Lu3+, which allowed the detailed analysis of electron-lattice coupling in these systems, are presented. Possible new developments in the femtosecond time-resolved spectroscopy of solids with a free electron laser are discussed.

  13. EMCCD-Based Detector for Time-Resolved X-Ray Diffraction and Scattering Studies of Biological Specimens

    SciTech Connect

    Nagarkar, Vivek V.; Singh, Bipin; Guo, Liang; Gore, David; Irving, Thomas C.

    2007-11-26

    Third generation synchrotron sources such as the Advanced Photon Source (APS), Argonne, IL, are outstanding tools for X-ray diffraction and scattering studies of non-crystalline biological materials. However, these studies are hindered by the lack of detectors that provide multiple frames of detailed structural information on the millisecond time scale at the required high spatial resolution, and large active areas. Here we report the development of a cost effective detector for time-resolved small angle X-ray scattering (SAXS) using a cooled, fiberoptically coupled electron multiplying CCD (EMCCD), whose internal gain is selectable in real-time. The performance of the detector was evaluated using a Gd{sub 2}O{sub 2}S:Tb scintillator and was compared to a current state-of-the-art SAXS detector developed at Brandeis University. We also report our first results on the fabrication of a novel, microcolumnar, ZnSe(Te) scintillator that has a promise to provide very high emission efficiency of over 100,000 photons/MeV, high spatial resolution in excess of 10 lp/mm, and a fast decay time with virtually absent afterglow. Development of this scintillator will complement the EMCCD design, permitting the advances of a high spatial and temporal resolution, large area detector for time resolved applications.

  14. Time-resolved homo-FRET studies of biotin-streptavidin complexes.

    PubMed

    Andreoni, Alessandra; Nardo, Luca; Rigler, Rudolf

    2016-09-01

    Förster resonance energy transfer is a mechanism of fluorescence quenching that is notably useful for characterizing properties of biomolecules and/or their interactions. Here we study water-solutions of Biotin-Streptavidin complexes, in which Biotin is labeled with a rigidly-bound fluorophore that can interact by Förster resonance energy transfer with the fluorophores labeling the other, up to three, Biotins of the same complex. The fluorophore, Atto550, is a Rhodamine analogue. We detect the time-resolved fluorescence decay of the fluorophores with an apparatus endowed with single-photon sensitivity and temporal resolution of ~30ps. The decay profiles we observe for samples containing constant Biotin-Atto550 conjugates and varying Streptavidin concentrations are multi-exponential. Each decay component can be associated with the rate of quenching exerted on each donor by each of the acceptors that label the other Biotin molecules, depending on the binding site they occupy. The main features that lead to this result are that (i) the transition dipole moments of the up-to-four Atto550 fluorophores that label the complexes are fixed as to both relative positions and mutual orientations; (ii) the fluorophores are identical and the role of donor in each Biotin-Streptavidin complex is randomly attributed to the one that has absorbed the excitation light (homo-FRET). Obviously the high-temporal resolution of the excitation-detection apparatus is necessary to discriminate among the fluorescence decay components. PMID:27494295

  15. Ultrabroadband Relay Imaged GRENOUILLE as a Time-Resolved Diagnostic for Relativistic Hole Boring

    NASA Astrophysics Data System (ADS)

    Wagner, Craig; Bernstein, Aaron; Dyer, Gilliss; Ditmire, Todd

    2015-11-01

    In a highly intense laser-solid interaction, the surface of the resultant plasma is pushed into the interior of the target at a significant fraction of the speed of light as a result of the intense radiation pressure from the focused laser beam. This is known as hole boring. During the hole boring process laser interactions with electrons at the receding target surface generate light at frequency harmonics of the incident laser. The frequency shift of these harmonics is proportional to the velocity of the target surface. In previous experiments at the Texas Petawatt we observed red-shifts in the 351nm harmonic up to 513nm, corresponding to a recession velocity of 0.18c. We designed an ultra-broadband GRENOUILLE to conduct time resolved measurements of spectral shifting of second harmonic light over the duration of the incident laser pulse. This GRENOUILLE is relay imaged from the target plane to prevent spectral splitting, and is an all reflective design to reduce pulse broadening and chromatic aberrations. With an f/3.15 optic focusing into a thick BBO crystal, the system accepts wavelengths from 526nm to 766nm with 4.8nm spectral resolution and 5.6fs temporal resolution. This work was supported by NNSA cooperative agreement DE-NA0002008.

  16. Compact SPAD-Based Pixel Architectures for Time-Resolved Image Sensors.

    PubMed

    Perenzoni, Matteo; Pancheri, Lucio; Stoppa, David

    2016-01-01

    This paper reviews the state of the art of single-photon avalanche diode (SPAD) image sensors for time-resolved imaging. The focus of the paper is on pixel architectures featuring small pixel size (<25 μm) and high fill factor (>20%) as a key enabling technology for the successful implementation of high spatial resolution SPAD-based image sensors. A summary of the main CMOS SPAD implementations, their characteristics and integration challenges, is provided from the perspective of targeting large pixel arrays, where one of the key drivers is the spatial uniformity. The main analog techniques aimed at time-gated photon counting and photon timestamping suitable for compact and low-power pixels are critically discussed. The main features of these solutions are the adoption of analog counting techniques and time-to-analog conversion, in NMOS-only pixels. Reliable quantum-limited single-photon counting, self-referenced analog-to-digital conversion, time gating down to 0.75 ns and timestamping with 368 ps jitter are achieved. PMID:27223284

  17. Compact SPAD-Based Pixel Architectures for Time-Resolved Image Sensors

    PubMed Central

    Perenzoni, Matteo; Pancheri, Lucio; Stoppa, David

    2016-01-01

    This paper reviews the state of the art of single-photon avalanche diode (SPAD) image sensors for time-resolved imaging. The focus of the paper is on pixel architectures featuring small pixel size (<25 μm) and high fill factor (>20%) as a key enabling technology for the successful implementation of high spatial resolution SPAD-based image sensors. A summary of the main CMOS SPAD implementations, their characteristics and integration challenges, is provided from the perspective of targeting large pixel arrays, where one of the key drivers is the spatial uniformity. The main analog techniques aimed at time-gated photon counting and photon timestamping suitable for compact and low-power pixels are critically discussed. The main features of these solutions are the adoption of analog counting techniques and time-to-analog conversion, in NMOS-only pixels. Reliable quantum-limited single-photon counting, self-referenced analog-to-digital conversion, time gating down to 0.75 ns and timestamping with 368 ps jitter are achieved. PMID:27223284

  18. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    SciTech Connect

    Dorchies, F. Fedorov, N.; Lecherbourg, L.

    2015-07-15

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%–20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ∼1 mn and ∼100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  19. Direct Imaging of Transient Fano Resonances in N2 Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J. J.; Kornilov, Oleg

    2016-04-01

    Autoionizing Rydberg states of molecular N2 are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14 ±1 fs , while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance.

  20. Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy

    NASA Astrophysics Data System (ADS)

    Dorchies, F.; Fedorov, N.; Lecherbourg, L.

    2015-07-01

    We present an experimental station designed for time-resolved X-ray Absorption Near-Edge Spectroscopy (XANES). It is based on ultrashort laser-plasma x-ray pulses generated from a table-top 100 mJ-class laser at 10 Hz repetition rate. A high transmission (10%-20%) x-ray beam line transport using polycapillary optics allows us to set the sample in an independent vacuum chamber, providing high flexibility over a wide spectral range from 0.5 up to 4 keV. Some XANES spectra are presented, demonstrating 1% noise level in only ˜1 mn and ˜100 cumulated laser shots. Time-resolved measurements are reported, indicating that the time resolution of the entire experimental station is 3.3 ± 0.6 ps rms.

  1. 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. PMID:26836075

  2. Direct Imaging of Transient Fano Resonances in N_{2} Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy.

    PubMed

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J J; Kornilov, Oleg

    2016-04-22

    Autoionizing Rydberg states of molecular N_{2} are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14±1  fs, while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance. PMID:27152799

  3. 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.

  4. Integrated Tree-Ring-Radiocarbon High-Resolution Timeframe to Resolve Earlier Second Millennium BCE Mesopotamian Chronology.

    PubMed

    Manning, Sturt W; Griggs, Carol B; Lorentzen, Brita; Barjamovic, Gojko; Ramsey, Christopher Bronk; Kromer, Bernd; Wild, Eva Maria

    2016-01-01

    500 years of ancient Near Eastern history from the earlier second millennium BCE, including such pivotal figures as Hammurabi of Babylon, Šamši-Adad I (who conquered Aššur) and Zimrilim of Mari, has long floated in calendar time subject to rival chronological schemes up to 150+ years apart. Texts preserved on clay tablets provide much information, including some astronomical references, but despite 100+ years of scholarly effort, chronological resolution has proved impossible. Documents linked with specific Assyrian officials and rulers have been found and associated with archaeological wood samples at Kültepe and Acemhöyük in Turkey, and offer the potential to resolve this long-running problem. Here we show that previous work using tree-ring dating to place these timbers in absolute time has fundamental problems with key dendrochronological crossdates due to small sample numbers in overlapping years and insufficient critical assessment. To address, we have integrated secure dendrochronological sequences directly with radiocarbon (14C) measurements to achieve tightly resolved absolute (calendar) chronological associations and identify the secure links of this tree-ring chronology with the archaeological-historical evidence. The revised tree-ring-sequenced 14C time-series for Kültepe and Acemhöyük is compatible only with the so-called Middle Chronology and not with the rival High, Low or New Chronologies. This finding provides a robust resolution to a century of uncertainty in Mesopotamian chronology and scholarship, and a secure basis for construction of a coherent timeframe and history across the Near East and East Mediterranean in the earlier second millennium BCE. Our re-dating also affects an unusual tree-ring growth anomaly in wood from Porsuk, Turkey, previously tentatively associated with the Minoan eruption of the Santorini volcano. This tree-ring growth anomaly is now directly dated ~1681-1673 BCE (68.2% highest posterior density range), ~20

  5. Integrated Tree-Ring-Radiocarbon High-Resolution Timeframe to Resolve Earlier Second Millennium BCE Mesopotamian Chronology

    PubMed Central

    Griggs, Carol B.; Lorentzen, Brita; Barjamovic, Gojko; Ramsey, Christopher Bronk; Kromer, Bernd; Wild, Eva Maria

    2016-01-01

    500 years of ancient Near Eastern history from the earlier second millennium BCE, including such pivotal figures as Hammurabi of Babylon, Šamši-Adad I (who conquered Aššur) and Zimrilim of Mari, has long floated in calendar time subject to rival chronological schemes up to 150+ years apart. Texts preserved on clay tablets provide much information, including some astronomical references, but despite 100+ years of scholarly effort, chronological resolution has proved impossible. Documents linked with specific Assyrian officials and rulers have been found and associated with archaeological wood samples at Kültepe and Acemhöyük in Turkey, and offer the potential to resolve this long-running problem. Here we show that previous work using tree-ring dating to place these timbers in absolute time has fundamental problems with key dendrochronological crossdates due to small sample numbers in overlapping years and insufficient critical assessment. To address, we have integrated secure dendrochronological sequences directly with radiocarbon (14C) measurements to achieve tightly resolved absolute (calendar) chronological associations and identify the secure links of this tree-ring chronology with the archaeological-historical evidence. The revised tree-ring-sequenced 14C time-series for Kültepe and Acemhöyük is compatible only with the so-called Middle Chronology and not with the rival High, Low or New Chronologies. This finding provides a robust resolution to a century of uncertainty in Mesopotamian chronology and scholarship, and a secure basis for construction of a coherent timeframe and history across the Near East and East Mediterranean in the earlier second millennium BCE. Our re-dating also affects an unusual tree-ring growth anomaly in wood from Porsuk, Turkey, previously tentatively associated with the Minoan eruption of the Santorini volcano. This tree-ring growth anomaly is now directly dated ~1681–1673 BCE (68.2% highest posterior density range), ~20

  6. A method for generating high resolution satellite image time series

    NASA Astrophysics Data System (ADS)

    Guo, Tao

    2014-10-01

    There is an increasing demand for satellite remote sensing data with both high spatial and temporal resolution in many applications. But it still is a challenge to simultaneously improve spatial resolution and temporal frequency due to the technical limits of current satellite observation systems. To this end, much R&D efforts have been ongoing for years and lead to some successes roughly in two aspects, one includes super resolution, pan-sharpen etc. methods which can effectively enhance the spatial resolution and generate good visual effects, but hardly preserve spectral signatures and result in inadequate analytical value, on the other hand, time interpolation is a straight forward method to increase temporal frequency, however it increase little informative contents in fact. In this paper we presented a novel method to simulate high resolution time series data by combing low resolution time series data and a very small number of high resolution data only. Our method starts with a pair of high and low resolution data set, and then a spatial registration is done by introducing LDA model to map high and low resolution pixels correspondingly. Afterwards, temporal change information is captured through a comparison of low resolution time series data, and then projected onto the high resolution data plane and assigned to each high resolution pixel according to the predefined temporal change patterns of each type of ground objects. Finally the simulated high resolution data is generated. A preliminary experiment shows that our method can simulate a high resolution data with a reasonable accuracy. The contribution of our method is to enable timely monitoring of temporal changes through analysis of time sequence of low resolution images only, and usage of costly high resolution data can be reduces as much as possible, and it presents a highly effective way to build up an economically operational monitoring solution for agriculture, forest, land use investigation

  7. [Time-Resolved XEOL Experiment System on BL14W1 at SSRF].

    PubMed

    Zhang, Zhao-hong; Jiang, Zheng; Xue, Song; Zheng, Li-fang

    2015-08-01

    A novel time-resolved X-ray excited optical luminescence (TRXEOL) experiment system was developed for X ray absorption fine structure spectroscopy(XAFS) beamline at Shanghai Synchrotron Radiation Facility (SSRF). The TRXEOL system is composed of three parts: timing system, spectrometer system and nuclear instrument module (NIM) system. These three systems were integrated to measure and record the optical luminescence from the sample excited by the synchrotron X-ray pulses, according to the time-correlated single photon counting methodology. It's the first time in the domestic synchrotron radiation facilities to achieve TRXEOL experiment using the synchrotron X-ray pulses and the time structure of the storage ring. In this work, a SSRF-self-developed timing system was used, which is based on the Field programmable Gate Array and the high-speed serial communication technology. The timing system can provide trigger pulse synchronized with the X-ray pulse. The timing jitter is about 6 ps, and the timing delay resolution is 5 ps. The NIM system is the core of the TRXEOL experiment system, it has three main modules: the Constant Fraction Discriminator (CFD), the Time to Amplitude Converter (TAC) and the Multi-Channel Analyzer (MCA). During one excitation circle, the spectrometer and the Photomultiplier Tube detector translate the induced luminescence of the sample excited by a single X-ray pulse into electrical pulse. The CFD module eliminates the timing walk larger than 50 ps induced by the amplitude of the electrical pulse. The TAC module calculates the time interval between the timing trigger pulse and the luminescence electrical pulse, and converts the interval into proportional amplitude of voltage. After plenty of circles, the MCA module gets the luminescence decay curve by recording and analyzing the voltage signals. And the data acquisition system gets the TRXEOL spectra by scanning the spectrometer and acquiring the frequency of the voltage pulses from the TAC

  8. Broadband time-resolved elliptical crystal spectrometer for X-ray spectroscopic measurements in laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Wang, Rui-Rong; Jia, Guo; Fang, Zhi-Heng; Wang, Wei; Meng, Xiang-Fu; Xie, Zhi-Yong; Zhang, Fan

    2014-11-01

    The X-ray spectrometer used in high-energy-density plasma experiments generally requires both broad X-ray energy coverage and high temporal, spatial, and spectral resolutions for overcoming the difficulties imposed by the X-ray background, debris, and mechanical shocks. By using an elliptical crystal together with a streak camera, we resolve this issue at the SG-II laser facility. The carefully designed elliptical crystal has a broad spectral coverage with high resolution, strong rejection of the diffuse and/or fluorescent background radiation, and negligible source broadening for extended sources. The spectra that are Bragg reflected (23° < θ < 38°) from the crystal are focused onto a streak camera slit 18 mm long and about 80 μm wide, to obtain a time-resolved spectrum. With experimental measurements, we demonstrate that the quartz(1011) elliptical analyzer at the SG-II laser facility has a single-shot spectral range of (4.64-6.45) keV, a typical spectral resolution of E/ΔE = 560, and an enhanced focusing power in the spectral dimension. For titanium (Ti) data, the lines of interest show a distribution as a function of time and the temporal variations of the He-α and Li-like Ti satellite lines and their spatial profiles show intensity peak red shifts. The spectrometer sensitivity is illustrated with a temporal resolution of better than 25 ps, which satisfies the near-term requirements of high-energy-density physics experiments.

  9. The beauty of resolution: The SN Ib factory NGC 2770 spatially resolved

    NASA Astrophysics Data System (ADS)

    Thöne, C. C.; Christensen, L.; Gorosabel, J.; de Ugarte Postigo, A.

    2015-02-01

    The late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.

  10. Time resolved diagnostics of ions in colliding carbon plasmas

    SciTech Connect

    Singh, Ravi Pratap; Gupta, Shyam L.; Thareja, Raj K.

    2014-11-14

    We report a comparative study of the dynamic behaviour of ions at different pressures in laser ablated colliding and single plasma plumes using 2D imaging, optical emission spectroscopy (OES) and a retarding field analyser (RFA). 2D imaging shows the splitting of plasma plumes due to different velocities of various plasma species. OES shows enhancement in abundance of ionic species with their presence for a longer time in colliding plume. C{sub 2} molecular formation is seen at later time in colliding plume compared to single plume and is attributed to dominating collisional processes in the colliding region of the plumes. The time of flight distribution of ions traced by the RFA shows the variation with change in fluence as well as ambient pressure for both colliding and single plume. Time of flight analysis of ions also shows the appearance of a fast peak in ion signal due to acceleration of ions at larger fluence.

  11. Serial time-resolved crystallography of photosystem II using a femtosecond X-ray laser.

    PubMed

    Kupitz, Christopher; Basu, Shibom; Grotjohann, Ingo; Fromme, Raimund; Zatsepin, Nadia A; Rendek, Kimberly N; Hunter, Mark S; Shoeman, Robert L; White, Thomas A; Wang, Dingjie; James, Daniel; Yang, Jay-How; Cobb, Danielle E; Reeder, Brenda; Sierra, Raymond G; Liu, Haiguang; Barty, Anton; Aquila, Andrew L; Deponte, Daniel; Kirian, Richard A; Bari, Sadia; Bergkamp, Jesse J; Beyerlein, Kenneth R; Bogan, Michael J; Caleman, Carl; Chao, Tzu-Chiao; Conrad, Chelsie E; Davis, Katherine M; Fleckenstein, Holger; Galli, Lorenzo; Hau-Riege, Stefan P; Kassemeyer, Stephan; Laksmono, Hartawan; Liang, Mengning; Lomb, Lukas; Marchesini, Stefano; Martin, Andrew V; Messerschmidt, Marc; Milathianaki, Despina; Nass, Karol; Ros, Alexandra; Roy-Chowdhury, Shatabdi; Schmidt, Kevin; Seibert, Marvin; Steinbrener, Jan; Stellato, Francesco; Yan, Lifen; Yoon, Chunhong; Moore, Thomas A; Moore, Ana L; Pushkar, Yulia; Williams, Garth J; Boutet, Sébastien; Doak, R Bruce; Weierstall, Uwe; Frank, Matthias; Chapman, Henry N; Spence, John C H; Fromme, Petra

    2014-09-11

    Photosynthesis, a process catalysed by plants, algae and cyanobacteria converts sunlight to energy thus sustaining all higher life on Earth. Two large membrane protein complexes, photosystem I and II (PSI and PSII), act in series to catalyse the light-driven reactions in photosynthesis. PSII catalyses the light-driven water splitting process, which maintains the Earth's oxygenic atmosphere. In this process, the oxygen-evolving complex (OEC) of PSII cycles through five states, S0 to S4, in which four electrons are sequentially extracted from the OEC in four light-driven charge-separation events. Here we describe time resolved experiments on PSII nano/microcrystals from Thermosynechococcus elongatus performed with the recently developed technique of serial femtosecond crystallography. Structures have been determined from PSII in the dark S1 state and after double laser excitation (putative S3 state) at 5 and 5.5 Å resolution, respectively. The results provide evidence that PSII undergoes significant conformational changes at the electron acceptor side and at the Mn4CaO5 core of the OEC. These include an elongation of the metal cluster, accompanied by changes in the protein environment, which could allow for binding of the second substrate water molecule between the more distant protruding Mn (referred to as the 'dangler' Mn) and the Mn3CaOx cubane in the S2 to S3 transition, as predicted by spectroscopic and computational studies. This work shows the great potential for time-resolved serial femtosecond crystallography for investigation of catalytic processes in biomolecules. PMID:25043005

  12. Serial time-resolved crystallography of photosystem II using a femtosecond X-ray laser

    PubMed Central

    Kupitz, Christopher; Basu, Shibom; Grotjohann, Ingo; Fromme, Raimund; Zatsepin, Nadia A.; Rendek, Kimberly N.; Hunter, Mark S.; Shoeman, Robert L.; White, Thomas A.; Wang, Dingjie; James, Daniel; Yang, Jay-How; Cobb, Danielle E.; Reeder, Brenda; Sierra, Raymond G.; Liu, Haiguang; Barty, Anton; Aquila, Andrew L.; Deponte, Daniel; Kirian, Richard A.; Bari, Sadia; Bergkamp, Jesse J.; Beyerlein, Kenneth R.; Bogan, Michael J.; Caleman, Carl; Chao, Tzu-Chiao; Conrad, Chelsie E.; Davis, Katherine M.; Fleckenstein, Holger; Galli, Lorenzo; Hau-Riege, Stefan P.; Kassemeyer, Stephan; Laksmono, Hartawan; Liang, Mengning; Lomb, Lukas; Marchesini, Stefano; Martin, Andrew V.; Messerschmidt, Marc; Milathianaki, Despina; Nass, Karol; Ros, Alexandra; Roy-Chowdhury, Shatabdi; Schmidt, Kevin; Seibert, Marvin; Steinbrener, Jan; Stellato, Francesco; Yan, Lifen; Yoon, Chunhong; Moore, Thomas A.; Moore, Ana L.; Pushkar, Yulia; Williams, Garth J.; Boutet, Sébastien; Doak, R. Bruce; Weierstall, Uwe; Frank, Matthias; Chapman, Henry N.; Spence, John C. H.; Fromme, Petra

    2015-01-01

    Photosynthesis, a process catalysed by plants, algae and cyanobacteria converts sunlight to energy thus sustaining all higher life on Earth. Two large membrane protein complexes, photosystem I and II (PSI and PSII), act in series to catalyse the light-driven reactions in photosynthesis. PSII catalyses the light-driven water splitting process, which maintains the Earth’s oxygenic atmosphere1. In this process, the oxygen-evolving complex (OEC) of PSII cycles through five states, S0 to S4, in which four electrons are sequentially extracted from the OEC in four light-driven charge-separation events. Here we describe time resolved experiments on PSII nano/microcrystals from Thermosynechococcus elongatus performed with the recently developed2 technique of serial femtosecond crystallography. Structures have been determined from PSII in the dark S1 state and after double laser excitation (putative S3 state) at 5 and 5.5 Å resolution, respectively. The results provide evidence that PSII undergoes significant conformational changes at the electron acceptor side and at the Mn4CaO5 core of the OEC. These include an elongation of the metal cluster, accompanied by changes in the protein environment, which could allow for binding of the second substrate water molecule between the more distant protruding Mn (referred to as the ‘dangler’ Mn) and the Mn3CaOx cubane in the S2 to S3 transition, as predicted by spectroscopic and computational studies3,4. This work shows the great potential for time-resolved serial femtosecond crystallography for investigation of catalytic processes in biomolecules. PMID:25043005

  13. Time- and polarization-resolved cellular autofluorescence towards quantitative biochemistry on living cells

    NASA Astrophysics Data System (ADS)

    Alfveby, John; TImerman, Randi; Soto Velasquez, Monica P.; Wickramasinghe, Dhanushka W. P. M.; Bartusek, Jillian; Heikal, Ahmed A.

    2014-09-01

    Native coenzymes such as the reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavin adenine dinucleotide play pivotal roles in energy metabolism and a myriad of biochemical reactions in living cells/tissues. These coenzymes are naturally fluorescent and, therefore, have the potential to serve as intrinsic biomarkers for mitochondrial activities, programmed cell death (apoptosis), oxidative stress, aging, and neurodegenerative disease. In this contribution, we employ two-photon fluorescence lifetime imaging microscopy (FLIM) and time-resolved anisotropy imaging of intracellular NADH for quantitative, non-invasive biochemistry on living cells in response to hydrogenperoxide- induced oxidative stress. In contrast with steady-state one-photon, UV-excited autofluorescence, two-photon FLIM is sensitive to both molecular conformation and stimuli-induced changes in the local environment in living cells with minimum photodamage and inherently enhanced spatial resolution. On the other hand, time-resolved, two-photon anisotropy imaging of cellular autofluorescence allows for quantitative assessment of binding state and environmental restrictions on the tumbling mobility of intrinsic NADH. Our measurements reveal that free and enzyme-bound NADH exist at equilibrium, with a dominant autofluorescence contribution of the bound fraction in living cells. Parallel studies on NADH-enzyme binding in controlled environments serve as a point of reference in analyzing autofluorescence in living cells. These autofluorescence-based approaches complement the conventional analytical biochemistry methods that require the destruction of cells/tissues, while serving as an important step towards establishing intracellular NADH as a natural biomarker for monitoring changes in energy metabolism and redox state of living cells in response to environmental hazards.

  14. Time-Resolved Photoelectron Spectroscopy of Dissociating 1,2-Butadiene Molecules by High Harmonic Pulses.

    PubMed

    Iikubo, Ryo; Fujiwara, Takehisa; Sekikawa, Taro; Harabuchi, Yu; Satoh, Sota; Taketsugu, Tetsuya; Kayanuma, Yosuke

    2015-07-01

    Using 42 nm high harmonic pulses, the dissociation dynamics of 1,2-butadiene was investigated by time-resolved photoelectron spectroscopy (TRPES), enabling us to observe dynamical changes of multiple molecular orbitals (MOs) with higher temporal resolution than conventional light sources. Because each lower-lying occupied MO has particular spatial electron distribution, the structural dynamics of photochemical reaction can be revealed. On the femtosecond time scale, a short-lived excited state with a lifetime of 37 ± 15 fs and the coherent oscillation of the photoelectron yield stimulated by Hertzberg-Teller coupling were observed. Ab initio molecular dynamics simulations in the electronically excited state find three relaxation pathways from the vertically excited structure in S1 to the ground state, and one of them is the dominant relaxation pathway, observed as the short-lived excited state. On the picosecond time scale, the photoelectron yields related to the C-C bond decreased upon photoexcitation, indicating C-C bond cleavage. PMID:26266720

  15. Anisotropic time-resolved solution X-ray scattering patterns from explicit-solvent molecular dynamics

    NASA Astrophysics Data System (ADS)

    Brinkmann, Levin U. L.; Hub, Jochen S.

    2015-09-01

    Time-resolved wide-angle X-ray scattering (TR-WAXS) is an emerging experimental technique used to track chemical reactions and conformational transitions of proteins in real time. Thanks to increased time resolution of the method, anisotropic TR-WAXS patterns were recently reported, which contain more structural information than isotropic patterns. So far, however, no method has been available to compute anisotropic WAXS patterns of biomolecules, thus limiting the structural interpretation. Here, we present a method to compute anisotropic TR-WAXS patterns from molecular dynamics simulations. The calculations accurately account for scattering of the hydration layer and for thermal fluctuations. For many photo-excitable proteins, given a low intensity of the excitation laser, the anisotropic pattern is described by two independent components: (i) an isotropic component, corresponding to common isotropic WAXS experiments and (ii) an anisotropic component depending on the orientation of the excitation dipole of the solute. We present a set of relations for the calculation of these two components from experimental scattering patterns. Notably, the isotropic component is not obtained by a uniform azimuthal average on the detector. The calculations are illustrated and validated by computing anisotropic WAXS patterns of a spheroidal protein model and of photoactive yellow protein. Effects due to saturated excitation at high intensities of the excitation laser are discussed, including opportunities to extract additional structural information by modulating the laser intensity.

  16. Toward Femtosecond Time-Resolved Studies of Solvent-Solute Energy Transfer in Doped Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Bacellar, C.; Ziemkiewicz, M. P.; Leone, S. R.; Neumark, D. M.; Gessner, O.

    2015-05-01

    Superfluid helium nanodroplets provide a unique cryogenic matrix for high resolution spectroscopy and ultracold chemistry applications. With increasing photon energy and, in particular, in the increasingly important Extreme Ultraviolet (EUV) regime, the droplets become optically dense and, therefore, participate in the EUV-induced dynamics. Energy- and charge-transfer mechanisms between the host droplets and dopant atoms, however, are poorly understood. Static energy domain measurements of helium droplets doped with noble gas atoms (Xe, Kr) indicate that Penning ionization due to energy transfer from the excited droplet to dopant atoms may be a significant relaxation channel. We have set up a femtosecond time-resolved photoelectron imaging experiment to probe these dynamics directly in the time-domain. Droplets containing 104 to 106 helium atoms and a small percentage (<10-4) of dopant atoms (Xe, Kr, Ne) are excited to the 1s2p Rydberg band by 21.6 eV photons produced by high harmonic generation (HHG). Transiently populated states are probed by 1.6 eV photons, generating time-dependent photoelectron kinetic energy distributions, which are monitored by velocity map imaging (VMI). The results will provide new information about the dynamic timescales and the different relaxation channels, giving access to a more complete physical picture of solvent-solute interactions in the superfluid environment. Prospects and challenges of the novel experiment as well as preliminary experimental results will be discussed.

  17. Full-field pressure from snapshot and time-resolved volumetric PIV

    NASA Astrophysics Data System (ADS)

    Laskari, A.; de Kat, R.; Ganapathisubramani, B.

    2016-03-01

    This paper deals with pressure estimation from snapshot and time-resolved three-component (3C) volumetric PIV data using Taylor's hypothesis, an Eulerian and a pseudo-Lagrangian approach. The Taylor's hypothesis approach has been shown to provide accurate results for pressure in the case of 3C planar PIV data with an appropriate choice of convection velocity (de Kat and Ganapathisubramani 2013), and here we extend its use on 3C volumetric velocity snapshots. Application of the techniques to synthetic data shows that the Taylor's hypothesis approach performs best using the streamwise mean as the convection velocity and is affected the least by noise, while the Eulerian approach suffers the most. In terms of resolution, the pseudo-Lagrangian approach is the most sensitive. Its accuracy can be improved by increasing the frame time-separation when computing the material derivative, at the expense of volume loss from fluid parcels leaving the FOV. Comparison of the techniques on turbulent boundary layer data with DNS supports these observations and shows that the Taylor's hypothesis approach is the only way we can get pressure when time information is not present.

  18. Anisotropic time-resolved solution X-ray scattering patterns from explicit-solvent molecular dynamics.

    PubMed

    Brinkmann, Levin U L; Hub, Jochen S

    2015-09-14

    Time-resolved wide-angle X-ray scattering (TR-WAXS) is an emerging experimental technique used to track chemical reactions and conformational transitions of proteins in real time. Thanks to increased time resolution of the method, anisotropic TR-WAXS patterns were recently reported, which contain more structural information than isotropic patterns. So far, however, no method has been available to compute anisotropic WAXS patterns of biomolecules, thus limiting the structural interpretation. Here, we present a method to compute anisotropic TR-WAXS patterns from molecular dynamics simulations. The calculations accurately account for scattering of the hydration layer and for thermal fluctuations. For many photo-excitable proteins, given a low intensity of the excitation laser, the anisotropic pattern is described by two independent components: (i) an isotropic component, corresponding to common isotropic WAXS experiments and (ii) an anisotropic component depending on the orientation of the excitation dipole of the solute. We present a set of relations for the calculation of these two components from experimental scattering patterns. Notably, the isotropic component is not obtained by a uniform azimuthal average on the detector. The calculations are illustrated and validated by computing anisotropic WAXS patterns of a spheroidal protein model and of photoactive yellow protein. Effects due to saturated excitation at high intensities of the excitation laser are discussed, including opportunities to extract additional structural information by modulating the laser intensity. PMID:26374019

  19. In vivo flow cytometry and time-resolved near-IR angiography and lymphography

    NASA Astrophysics Data System (ADS)

    Galanzha, Ekaterina I.; Tuchin, Valery V.; Brock, Robert W.; Zharov, Vladimir P.

    2007-05-01

    Integration of photoacoustic and photothermal techniques with high-speed, high-resolution transmission and fluorescence microscopy shows great potential for in vivo flow cytometry and indocyanine green (ICG) near-infrared (IR) angiography of blood and lymph microvessels. In particular, the capabilities of in vivo flow cytometry using rat mesentery and nude mouse ear models are demonstrated for real-time quantitative detection of circulating and migrating individual blood and cancer cells in skin, mesentery, lymph nodes, liver, kidney; studying vascular dynamics with a focus on lymphatics; monitoring cell traffic between blood and lymph systems; high-speed imaging of cell deformability in flow; and label-free real-time monitoring of single cell extravasation from blood vessel lumen into tissue. As presented, the advantages of ICG IR-angiography include estimation of time resolved dye dynamics (appearance and clearance) in blood and lymph microvessels using fluorescent and photoacoustic modules of the integrated technique. These new approaches are important for monitoring and quantifying metastatic and apoptotic cells; comparative measurements of plasma and cell velocities; analysis of immune responses; monitoring of circulating macromolecules, chylomicrons, bacteria, viruses and nanoparticles; molecular imaging. In the future, we believe that the integrated technique presented will have great potential for translation to early disease diagnoses (e.g. cancer) or assessment of innovative therapeutic interventions in humans.

  20. 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.

  1. Time Resolved Atmospheric Carbon Satellite Observations from Geostationary Orbit

    NASA Astrophysics Data System (ADS)

    Edwards, David; Worden, Helen

    This presentation describes proposed satellite carbon measurements from CHRONOS (Commercially Hosted spectroRadiometer Observations and New Opportunities for Science). The primary goal of this mission is to measure the atmospheric pollutants carbon monoxide (CO) and methane (CH4) from geostationary orbit, with hourly observations of North America at high spatial resolution. Carbon monoxide is produced by combustion processes such as urban activity and wildfires, and serves as a proxy for other combustion pollutants that are not easily measured. Both CO and CH4 are chemical precursors of tropospheric ozone pollution. Methane has diverse anthropogenic sources ranging from fossil fuel production, animal husbandry, agriculture and waste management. The impact of gas exploration in the Western States of the USA and oil extraction from the Canadian tar sands will be particular foci of the mission, as will the poorly-quantified natural CH4 emissions from wetlands and thawing permafrost. In addition to characterizing pollutant sources, improved understanding of the domestic CH4 budget is a priority for policy decisions related to short-lived climate forcers. A primary motivation for targeting CO is its value as a tracer of atmospheric pollution. The CHRONOS measurements will provide insight into local and long-range transport across the North American continent, as well as the processes governing the entrainment and venting of pollution in and out of the planetary boundary layer. As a result of significantly improved characterization of diurnal changes in atmospheric composition, CHRONOS observations will find direct societal applications for air quality regulation and forecasting. We present a quantification of this expected improvement in the prediction of near-surface concentrations when CHRONOS measurements are used in Observation System Simulation Experiments (OSSEs). If CHRONOS and the planned NASA Earth Venture TEMPO (Tropospheric Emissions: Monitoring of Pollution

  2. Time Resolved Atmospheric Carbon Satellite Observations from Geostationary Orbit

    NASA Astrophysics Data System (ADS)

    Edwards, D. P.; Worden, H. M.; Deeter, M. N.; Worden, H. M.

    2013-12-01

    This presentation describes proposed satellite carbon measurements from CHRONOS (Commercially Hosted spectroRadiometer Observations and New Opportunities for Science). The primary goal of this mission is to measure the atmospheric pollutants carbon monoxide (CO) and methane (CH4) from geostationary orbit, with hourly observations of North America at high spatial resolution. Carbon monoxide is produced by combustion processes such as urban activity and wildfires, and serves as a proxy for other combustion pollutants that are not easily measured. Both CO and CH4 are chemical precursors of tropospheric ozone pollution. Methane has diverse anthropogenic sources ranging from fossil fuel production, animal husbandry, agriculture and waste management. The impact of gas exploration in the Western States of the USA and oil extraction from the Canadian tar sands will be particular foci of the mission, as will the poorly-quantified natural CH4 emissions from wetlands and thawing permafrost. In addition to characterizing pollutant sources, improved understanding of the domestic CH4 budget is a priority for policy decisions related to short-lived climate forcers. A primary motivation for targeting CO is its value as a tracer of atmospheric pollution. The CHRONOS measurements will provide insight into local and long-range transport across the North American continent, as well as the processes governing the entrainment and venting of pollution in and out of the planetary boundary layer. As a result of significantly improved characterization of diurnal changes in atmospheric composition, CHRONOS observations will find direct societal applications for air quality regulation and forecasting. We present a quantification of this expected improvement in the prediction of near-surface concentrations when CHRONOS measurements are used in Observation System Simulation Experiments (OSSEs). If CHRONOS and the planned NASA Earth Venture TEMPO (Tropospheric Emissions: Monitoring of Pollution

  3. Time-resolved x-ray scattering instrumentation

    DOEpatents

    Borso, C.S.

    1985-11-21

    An apparatus and method for increased speed and efficiency of data compilation and analysis in real time is presented in this disclosure. Data is sensed and grouped in combinations in accordance with predetermined logic. The combinations are grouped so that a simplified reduced signal results, such as pairwise summing of data values having offsetting algebraic signs, thereby reducing the magnitude of the net pair sum. Bit storage requirements are reduced and speed of data compilation and analysis is increased by manipulation of shorter bit length data values, making real time evaluation possible.

  4. Time Resolved PIV for Space-Time Correlations in Hot Jets

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.

    2007-01-01

    Temporally Resolved Particle Image Velocimetry (TR-PIV) is the newest and most exciting tool recently developed to support our continuing efforts to characterize and improve our understanding of the decay of turbulence in jet flows -- a critical element for understanding the acoustic properties of the flow. A new TR-PIV system has been developed at the NASA Glenn Research Center which is capable of acquiring planar PIV image frame pairs at up to 25 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number

  5. Time-resolved fluorescence spectroscopy for chemical sensors

    NASA Astrophysics Data System (ADS)

    Draxler, Sonja; Lippitsch, Max E.

    1996-07-01

    A family of sensors is presented with fluorescence decay-time measurements used as the sensing technique. The concept is to take a single fluorophore with a suitably long fluorescence decay time as the basic building block for numerous different sensors. Analyte recognition can be performed by different functional groups that are necessary for selective interaction with the analyte. To achieve this, the principle of excited-state electron transfer is applied with pyrene as the fluorophore. Therefore the same instrumentation based on a small, ambient air-nitrogen laser and solid-state electronics can be used to measure different analytes, for example, oxygen, pH, carbon dioxide, potassium, ammonium, lead, cadmium, zinc, and phosphate.

  6. Space-time resolved wave turbulence in a vibrating plate.

    PubMed

    Cobelli, Pablo; Petitjeans, Philippe; Maurel, Agnès; Pagneux, Vincent; Mordant, Nicolas

    2009-11-13

    Wave turbulence in a thin elastic plate is experimentally investigated. By using a Fourier transform profilometry technique, the deformation field of the plate surface is measured simultaneously in time and space. This enables us to compute the wave-vector-frequency (k, omega) Fourier spectrum of the full space-time deformation velocity. In the 3D (k, omega) space, we show that the energy of the motion is concentrated on a 2D surface that represents a nonlinear dispersion relation. This nonlinear dispersion relation is close to the linear dispersion relation. This validates the usual wave-number-frequency change of variables used in many experimental studies of wave turbulence. The deviation from the linear dispersion, which increases with the input power of the forcing, is attributed to weak nonlinear effects. Our technique opens the way for many new extensive quantitative comparisons between theory and experiments of wave turbulence. PMID:20365984

  7. Time-Resolved Electron Diffraction from Selectively Aligned Molecules

    SciTech Connect

    Reckenthaeler, Peter; Krausz, Ferenc; Centurion, Martin; Fuss, Werner; Trushin, Sergei A.; Fill, Ernst E.

    2009-05-29

    We experimentally demonstrate ultrafast electron diffraction from transiently aligned molecules in the absence of external (aligning) fields. A sample of aligned molecules is generated through photodissociation with femtosecond laser pulses, and the diffraction pattern is captured by probing the sample with picosecond electron pulses shortly after dissociation - before molecular rotation causes the alignment to vanish. In our experiments the alignment decays with a time constant of 2.6{+-}1.2 ps.

  8. Evolutionary dynamics of time-resolved social interactions

    NASA Astrophysics Data System (ADS)

    Cardillo, Alessio; Petri, Giovanni; Nicosia, Vincenzo; Sinatra, Roberta; Gómez-Gardeñes, Jesús; Latora, Vito

    2014-11-01

    Cooperation among unrelated individuals is frequently observed in social groups when their members combine efforts and resources to obtain a shared benefit that is unachievable by an individual alone. However, understanding why cooperation arises despite the natural tendency of individuals toward selfish behavior is still an open problem and represents one of the most fascinating challenges in evolutionary dynamics. Recently, the structural characterization of the networks in which social interactions take place has shed some light on the mechanisms by which cooperative behavior emerges and eventually overcomes the natural temptation to defect. In particular, it has been found that the heterogeneity in the number of social ties and the presence of tightly knit communities lead to a significant increase in cooperation as compared with the unstructured and homogeneous connection patterns considered in classical evolutionary dynamics. Here, we investigate the role of social-ties dynamics for the emergence of cooperation in a family of social dilemmas. Social interactions are in fact intrinsically dynamic, fluctuating, and intermittent over time, and they can be represented by time-varying networks. By considering two experimental data sets of human interactions with detailed time information, we show that the temporal dynamics of social ties has a dramatic impact on the evolution of cooperation: the dynamics of pairwise interactions favors selfish behavior.

  9. Evolutionary dynamics of time-resolved social interactions.

    PubMed

    Cardillo, Alessio; Petri, Giovanni; Nicosia, Vincenzo; Sinatra, Roberta; Gómez-Gardeñes, Jesús; Latora, Vito

    2014-11-01

    Cooperation among unrelated individuals is frequently observed in social groups when their members combine efforts and resources to obtain a shared benefit that is unachievable by an individual alone. However, understanding why cooperation arises despite the natural tendency of individuals toward selfish behavior is still an open problem and represents one of the most fascinating challenges in evolutionary dynamics. Recently, the structural characterization of the networks in which social interactions take place has shed some light on the mechanisms by which cooperative behavior emerges and eventually overcomes the natural temptation to defect. In particular, it has been found that the heterogeneity in the number of social ties and the presence of tightly knit communities lead to a significant increase in cooperation as compared with the unstructured and homogeneous connection patterns considered in classical evolutionary dynamics. Here, we investigate the role of social-ties dynamics for the emergence of cooperation in a family of social dilemmas. Social interactions are in fact intrinsically dynamic, fluctuating, and intermittent over time, and they can be represented by time-varying networks. By considering two experimental data sets of human interactions with detailed time information, we show that the temporal dynamics of social ties has a dramatic impact on the evolution of cooperation: the dynamics of pairwise interactions favors selfish behavior. PMID:25493851

  10. Flow cytometry using Brillouin imaging and sensing via time-resolved optical (BISTRO) measurements.

    PubMed

    Meng, Zhaokai; Petrov, Georgi I; Yakovlev, Vladislav V

    2015-11-01

    A novel concept of Brillouin imaging and sensing via time-resolved optical (BISTRO) measurements is introduced for flow cytometry applications. The system affords robust, maintenance-free and high-speed elasticity-sensitive measurements. PMID:26347908

  11. Wavelet-based fast time-resolved magnetic sensing with electronic spins in diamond

    NASA Astrophysics Data System (ADS)

    Xu, Nanyang; Jiang, Fengjian; Tian, Yu; Ye, Jianfeng; Shi, Fazhan; Lv, Haijiang; Wang, Ya; Wrachtrup, Jörg; Du, Jiangfeng

    2016-04-01

    Time-resolved magnetic sensing is of great importance from fundamental studies to applications in physical and biological sciences. Recently, the nitrogen-vacancy defect center in diamond has been developed as a promising sensor of magnetic fields under ambient conditions. However, methods to reconstruct time-resolved magnetic fields with high sensitivity are not yet fully developed. Here, we propose and demonstrate a sensing method based on spin echo and Haar wavelet transformation. Our method is exponentially faster in reconstructing time-resolved magnetic fields with comparable sensitivity than existing methods. It is also easier to implement in experiments. Furthermore, the wavelet's unique features enable our method to extract information from the whole signal with only part of the measuring sequences. We then explore this feature for a fast detection of simulated nerve impulses. These results will be useful to time-resolved magnetic sensing with quantum probes at nanoscale.

  12. Time-resolved resonance Raman spectroscopy of radiation-chemical processes. [Pulsed irradiation

    SciTech Connect

    Tripathi, G.N.R.

    1983-01-01

    A tunable pulsed laser Raman spectrometer for time resolved Raman studies of radiation-chemical processes is described. This apparatus utilizes the state of art optical multichannel detection and analysis techniques for data acquisition and electron pulse radiolysis for initiating the reactions. By using this technique the resonance Raman spectra of intermediates with absorption spectra in the 248-900 nm region, and mean lifetimes > 30 ns can be examined. This apparatus can be used to time resolve the vibrational spectral overlap between transients absorbing in the same region, and to follow their decay kinetics by monitoring the well resolved Raman peaks. For kinetic measurements at millisecond time scale, the Raman technique is preferable over optical absorption method where low frequency noise is quite bothersome. A time resolved Raman study of the pulse radiolytic oxidation of aqueous tetrafluorohydroquinone and p-methoxyphenol is briefly discussed. 15 references, 5 figures.

  13. Time-of-flight mass spectrometry for time-resolved measurements

    SciTech Connect

    Blitz, Mark A.; Goddard, Andrew; Ingham, Trevor; Pilling, Michael J.

    2007-03-15

    A time-resolved time-of-flight mass spectrometer (TOF-MS) that can simultaneously monitor multiple species on the millisecond time scale has been constructed. A pulsed photolysis laser is used to initiate reaction, and then via a pinhole the reaction mixture is sampled by the TOF-MS. The ions are created by photoionization via either a discharge lamp or a pulsed laser. Comparison between the two ionization sources showed that the laser is at least an order of magnitude more efficient, based on the time to accumulate the data. Also, unlike the continuous lamp the pulsed laser is not mass limited. Frequency tripling the 355 nm output of a Nd:YAG laser provided a convenient laser ionization source. However, using a dye laser provided an equally intense laser ionization source with the ability to tune the vacuum ultraviolet (vuv) light. To show the versatility of the system the kinetics of the reaction of SO and ClSO radicals with NO{sub 2} were simultaneously measured, and using the dye laser the vuv light was tuned to 114 nm in order to observe H{sub 2}CO being formed from the reaction between CH{sub 3}CO and O{sub 2}.

  14. Time resolved imaging of carrier and thermal transport in silicon

    SciTech Connect

    D. H. Hurley; O. B. Wright; O. Matsuda; S. L. Shinde

    2010-01-01

    We use ultrashort optical pulses to microscopically image carrier and thermal diffusion in two spatial dimensions in pristine and mechanically polished surfaces of crystalline silicon. By decomposing changes in reflectivity in the latter sample into a transient component that varies with delay time and a steady state component that varies with pump chopping frequency, the influence of thermal diffusion is isolated from that of carrier diffusion and recombination. Additionally, studies using carrier injection density as a parameter are used to clearly identify the carrier recombination pathway.

  15. Resonant and time-resolved spin noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Pursley, Brennan C.; Song, X.; Sih, V.

    2015-11-01

    We demonstrate a method to extend the range of pulsed laser spin noise measurements to long spin lifetimes. We use an analog detection scheme with a bandwidth limited only by laser pulse duration. Our model uses statistics and Bloch-Torrey equations to extract the Lande g-factor, Faraday cross-section σ F , and spin lifetime τ s , while accounting for finite detector response. Varying the magnetic field with a fixed probe-probe delay yields τ s when it is longer than the laser repetition period. Varying the probe-probe delay with a fixed field produces a time-domain measurement of the correlation function.

  16. Time-resolved diffused optical characterization of key tissue constituents of human bony prominence locations

    NASA Astrophysics Data System (ADS)

    Konugolu Venkata Sekar, Sanathana; Farina, Andrea; Martinenghi, Edoardo; Dalla Mora, Alberto; Taroni, Paola; Pifferi, Antonio; Negredo, Eugènia; Puig, Jordi; Escrig, Roser; Rosales, Quim; Lindner, Claus; Pagliazzi, Marco; Durduran, Turgut

    2015-07-01

    We report a broadband time-resolved characterization of selected bony prominence locations of the human body. A clinical study was performed at six different bony prominence locations of 53 subjects. A portable broadband time-resolved system equipped with pulse drift and distortion compensation strategy was used for absorption and scattering measurements. Key tissue constituents were quantified as a pilot step towards non-invasive optical assessment of bone pathologies.

  17. Attosecond time-resolved streaked photoemission from solids

    NASA Astrophysics Data System (ADS)

    Liao, Qing; Thumm, Uwe

    2015-05-01

    We established a quantum-mechanical model for infrared (IR) laser streaked photoelectron (PE) emission from metal solids by an ultrashort extreme ultraviolet (XUV) pulse. Special emphasis was laid on the influence of the energy dispersion of PEs inside the solids on the photoemission time delay. We first applied this model to Mg(0001) surfaces, assuming free-electron dispersion and found good agreement with measured streaked PE spectra and streaking time delays. Next, we investigate W(110) surfaces for which non-free PE dispersion must be included in order to reproduce the measured photoemission delays at different XUV central photon energies. Our model reproduces a series of measured streaked spectrograms and photoemission delays for different metal solids, including clean Mg(0001) and W(110) surfaces and Mg-covered W(110) surfaces. It incorporates modeling of the target band structure, electron mean free paths, energy dispersion, and screening of the IR laser field on the surface. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy under Grant No. DE-FG02-86ER13491 and NSF Grant PHY-1068752.

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

    DOE PAGESBeta

    Mueller, C.; Marx, A.; Epp, S. W.; Zhong, Y.; Kuo, A.; Balo, A. R.; Soman, J.; Schotte, F.; Lemke, H. T.; Owen, R. L.; et al

    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

  19. Particulate PAH emissions from residential biomass combustion: time-resolved analysis with aerosol mass spectrometry.

    PubMed

    Eriksson, A C; Nordin, E Z; Nyström, R; Pettersson, E; Swietlicki, E; Bergvall, C; Westerholm, R; Boman, C; Pagels, J H

    2014-06-17

    Time-resolved emissions of particulate polycyclic aromatic hydrocarbons (PAHs) and total organic particulate matter (OA) from a wood log stove and an adjusted pellet stove were investigated with high-resolution time-of-flight aerosol mass spectrometry (AMS). The highest OA emissions were found during the addition of log wood on glowing embers, that is, slow burning pyrolysis conditions. These emissions contained about 1% PAHs (of OA). The highest PAH emissions were found during fast burning under hot air starved combustion conditions, in both stoves. In the latter case, PAHs contributed up to 40% of OA, likely due to thermal degradation of other condensable species. The distribution of PAHs was also shifted toward larger molecules in these emissions. AMS signals attributed to PAHs were found at molecular weights up to 600 Da. The vacuum aerodynamic size distribution was found to be bimodal with a smaller mode (Dva ∼ 200 nm) dominating under hot air starved combustion and a larger sized mode dominating under slow burning pyrolysis (Dva ∼ 600 nm). Simultaneous reduction of PAHs, OA and total particulate matter from residential biomass combustion may prove to be a challenge for environmental legislation efforts as these classes of emissions are elevated at different combustion conditions. PMID:24866381

  20. Time-Resolved Photoelectron Studies of IBr^-: a Classical and Quantum Tug-Of

    NASA Astrophysics Data System (ADS)

    Horvath, Samantha; McCoy, Anne B.

    2010-06-01

    To understand the dynamics of molecular species, especially those involved in photochemistry, we often turn to classical mechanics, which, despite the assumed quantum nature of small, light particles, has been extremely helpful in describing the underlying photophysics and can often explain the big picture of the dynamics. One such example is the recent duel experimental and theoretical study on the photodissociation of IBr^- performed by Sanov and co-workers. Of greater interest, though, is when does classical mechanics break down? More generally, when is a quantum approach needed to fully describe the system at the resolution of the experiment? In this work, we address these questions by investigating quantum interference effects on the time-resolved spectra of IBr^- where we look at how pulse width affects the overall signal. In the limit of an infinitely narrow pulse, we regain the Franck-Condon picture and the classical limit because all transitions are energetically allowed. In the limit of an infinitely wide pulse width, quantum interference effects become important and give rise to the bimodal character of the spectrum at short delay times (Δ t < 350 fs). Results of the calculated IBr^- spectra are in good agreement with experiment and serve to illustrate how varying the pulse widths can shift the description of the dynamics from a classical picture to a quantum one. R. Mabbs, K. Pichugin, and A. Sanov, J. Chem. Phys., 2005, 122, 174305.

  1. Time-Resolved Dispersive XAFS Instrument at NW2A Beamline of PF-AR

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Suzuki, A.; Niwa, Y.; Nomura, M.

    2007-01-01

    The configuration and performance of the time-resolved dispersive XAFS (DXAFS) instrument, which has been constructed at the NW2A beamline of PF-AR (KEK), are presented. The DXAFS instrument is mainly composed of a polychromator part, a position control part for sample, and a linear detector part. The Bragg- and Laue-type polychromator crystal (Si(111) or Si(311)) is bent using the holder with fixed bending radius, in which the thermostated water is circulated to prevent the temperature change of crystal due to the heat load. The photodiode array (PDA) with and without phosphor screen is used as the linear X-ray detector, and the minimum exposure time is 2 ms for the 1024-element PDA. The phosphor screen on the PDA detector prevents the damage of the chip especially for high energy X-rays but the existence reduces the energy resolution because of the scattering of the visible light converted on the phosphor. The DXAFS instrument was applied to the mechanistic study of the reduction processes of Cu supported on MFI zeolite, and the intermediate Cu(I) states have been successfully observed during the reduction from Cu(II) to Cu(0).

  2. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  3. Time-resolved measurement of pressure evolution in underwater nanosecond discharge

    NASA Astrophysics Data System (ADS)

    Marinov, Ilya; Guaitella, Olivier; Starikovskaia, Svetlana; Rousseau, Antoine

    2012-10-01

    Electrical discharges in water and other dielectric liquids have been extensively studied since almost fifty years, however reliable data on plasma parameters within the propagation phase is still missing. We report on shadowgraphic imaging and optical emission spectroscopy (OES) both with nanosecond time resolution of pulsed nanosecond discharge generated with point to wire electrode configuration. High voltage pulses of 10 kV and 30 ns duration (FWHM) are delivered by commercial pulse generator FPG 10 (FIG GmbH). Sub-millimeter discharge with filamentary structure develops at 50 km/s in axial direction of pin electrode. Using Hugoniot equations maximal discharge pressure at ignition can be obtained from shock wave front velocity. Analytical model of supersonic cavity expansion based on Kirkwood-Bethe approximation gives discharge pressure evolution from experimentally measured discharge channel expansion velocity profile. Thus, the pressure of 5 GPa is measured at the discharge ignition and drops drastically by the end of voltage pulse. Time-resolved OES spectrum shows a strong broadening of atomic Hydrogen (Balmer series) and oxygen (OI 777 nm) lines with almost continuum emission in the region 300-700 nm. Complex Hα and OI 777 profiles are due to combined contribution of Van Der Waals and Stark broadening. Electronic density can be deduced from lorentzian fit of Stark broadening and gives for electronic density 10^24 - 10^25 m-3.

  4. Nanosecond Time-Resolved Polarization Spectroscopies: Tools for Probing Protein Reaction Mechanisms

    PubMed Central

    Chen, Eefei; Goldbeck, Robert A.; Kliger, David S.

    2010-01-01

    Polarization methods, introduced in the 1800’s, offered one of the earliest ways to examine protein structure. Since then, many other structure-sensitive probes have been developed, but circular dichroism (CD) remains a powerful technique because of its versatility and the specificity of protein structural information that can be explored. With improvements in time-resolution, from millisecond to picosecond CD measurements, it has proven to be an important tool for studying the mechanism of folding and function in many biomolecules. For example, nanosecond time-resolved CD (TRCD) studies of the sub-microsecond events of reduced cytochrome c folding have provided direct experimental evidence of kinetic heterogeneity, which is an inherent property of the diffusional nature of early folding dynamics on the energy landscape. In addition, TRCD has been applied to the study of many biochemical processes, such as ligand rebinding in hemoglobin and myoglobin and signaling state formation in photoactive yellow protein and prototropin 1 LOV2. The basic approach to TRCD has also been extended to include a repertoire of nanosecond polarization spectroscopies: optical rotatory dispersion (ORD), magnetic CD and ORD, and linear dichroism. This article will discuss the details of the polarization methods used in this laboratory, as well as the coupling of timeresolved ORD with the temperature-jump trigger so that protein folding can be studied in a larger number of proteins. PMID:20438842

  5. 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

  6. Energy- and time-resolved detection of prompt gamma-rays for proton range verification

    NASA Astrophysics Data System (ADS)

    Verburg, Joost M.; Riley, Kent; Bortfeld, Thomas; Seco, Joao

    2013-10-01

    In this work, we present experimental results of a novel prompt gamma-ray detector for proton beam range verification. The detection system features an actively shielded cerium-doped lanthanum(III) bromide scintillator, coupled to a digital data acquisition system. The acquisition was synchronized to the cyclotron radio frequency to separate the prompt gamma-ray signals from the later-arriving neutron-induced background. We designed the detector to provide a high energy resolution and an effective reduction of background events, enabling discrete proton-induced prompt gamma lines to be resolved. Measuring discrete prompt gamma lines has several benefits for range verification. As the discrete energies correspond to specific nuclear transitions, the magnitudes of the different gamma lines have unique correlations with the proton energy and can be directly related to nuclear reaction cross sections. The quantification of discrete gamma lines also enables elemental analysis of tissue in the beam path, providing a better prediction of prompt gamma-ray yields. We present the results of experiments in which a water phantom was irradiated with proton pencil-beams in a clinical proton therapy gantry. A slit collimator was used to collimate the prompt gamma-rays, and measurements were performed at 27 positions along the path of proton beams with ranges of 9, 16 and 23 g cm-2 in water. The magnitudes of discrete gamma lines at 4.44, 5.2 and 6.13 MeV were quantified. The prompt gamma lines were found to be clearly resolved in dimensions of energy and time, and had a reproducible correlation with the proton depth-dose curve. We conclude that the measurement of discrete prompt gamma-rays for in vivo range verification of clinical proton beams is feasible, and plan to further study methods and detector designs for clinical use.

  7. Time Resolved X-ray Imaging of a Detonation Front

    NASA Astrophysics Data System (ADS)

    Vantine, Harry; Aufderheide, Maurice; Egan, Patrick; Morgan, David

    1998-03-01

    A one inch diameter cylinder of LX-14 was detonated at one end. The detonation was then made to propagate around an obstacle, in this case a one-half inch diameter lucite sphere. The detonation front was imaged at three times per shot with an array of three Scandiflash-450 Flash X-ray heads, spaced 2.1m from the explosive. The spectrum was 450 keV brehmstrahlung with a strong contribution from W K-radiation. The x-ray pulse width was approximately 20ns, and the tme between pulses was adjustable (typically 1-2 μs). Data were recorded on screened film (LANEX-fine and TMAT H) located 0.6m from the explosive. The film was digitized on a PDS microdensitometer for subsequent analysis. Tomagraphic reconstruction and comparison with CALE numerical simulations will be shown.

  8. Femtosecond time-resolved photoemission electron microscopy for spatiotemporal imaging of photogenerated carrier dynamics in semiconductors.

    PubMed

    Fukumoto, Keiki; Onda, Ken; Yamada, Yuki; Matsuki, Takashi; Mukuta, Tatsuhiko; Tanaka, Sei-ichi; Koshihara, Shin-ya

    2014-08-01

    We constructed an instrument for time-resolved photoemission electron microscopy (TR-PEEM) utilizing femtosecond (fs) laser pulses to visualize the dynamics of photogenerated electrons in semiconductors on ultrasmall and ultrafast scales. The spatial distribution of the excited electrons and their relaxation and/or recombination processes were imaged by the proposed TR-PEEM method with a spatial resolution about 100 nm and an ultrafast temporal resolution defined by the cross-correlation of the fs laser pulses (240 fs). A direct observation of the dynamical behavior of electrons on higher resistivity samples, such as semiconductors, by TR-PEEM has still been facing difficulties because of space and/or sample charging effects originating from the high photon flux of the ultrashort pulsed laser utilized for the photoemission process. Here, a regenerative amplified fs laser with a widely tunable repetition rate has been utilized, and with careful optimization of laser parameters, such as fluence and repetition rate, and consideration for carrier lifetimes, the electron dynamics in semiconductors were visualized. For demonstrating our newly developed TR-PEEM method, the photogenerated carrier lifetimes around a nanoscale defect on a GaAs surface were observed. The obtained lifetimes were on a sub-picosecond time scale, which is much shorter than the lifetimes of carriers observed in the non-defective surrounding regions. Our findings are consistent with the fact that structural defects induce mid-gap states in the forbidden band, and that the electrons captured in these states promptly relax into the ground state. PMID:25173274

  9. Femtosecond time-resolved photoemission electron microscopy for spatiotemporal imaging of photogenerated carrier dynamics in semiconductors

    SciTech Connect

    Fukumoto, Keiki Yamada, Yuki; Matsuki, Takashi; Koshihara, Shin-ya; Onda, Ken; Mukuta, Tatsuhiko; Tanaka, Sei-ichi

    2014-08-15

    We constructed an instrument for time-resolved photoemission electron microscopy (TR-PEEM) utilizing femtosecond (fs) laser pulses to visualize the dynamics of photogenerated electrons in semiconductors on ultrasmall and ultrafast scales. The spatial distribution of the excited electrons and their relaxation and/or recombination processes were imaged by the proposed TR-PEEM method with a spatial resolution about 100 nm and an ultrafast temporal resolution defined by the cross-correlation of the fs laser pulses (240 fs). A direct observation of the dynamical behavior of electrons on higher resistivity samples, such as semiconductors, by TR-PEEM has still been facing difficulties because of space and/or sample charging effects originating from the high photon flux of the ultrashort pulsed laser utilized for the photoemission process. Here, a regenerative amplified fs laser with a widely tunable repetition rate has been utilized, and with careful optimization of laser parameters, such as fluence and repetition rate, and consideration for carrier lifetimes, the electron dynamics in semiconductors were visualized. For demonstrating our newly developed TR-PEEM method, the photogenerated carrier lifetimes around a nanoscale defect on a GaAs surface were observed. The obtained lifetimes were on a sub-picosecond time scale, which is much shorter than the lifetimes of carriers observed in the non-defective surrounding regions. Our findings are consistent with the fact that structural defects induce mid-gap states in the forbidden band, and that the electrons captured in these states promptly relax into the ground state.

  10. Allosteric action in real time: Time-resolved crystallographic studies of a cooperative dimeric hemoglobin

    PubMed Central

    Knapp, James E.; Pahl, Reinhard; Šrajer, Vukica; Royer, William E.

    2006-01-01

    Protein allostery provides mechanisms for regulation of biological function at the molecular level. We present here an investigation of global, ligand-induced allosteric transition in a protein by time-resolved x-ray diffraction. The study provides a view of structural changes in single crystals of Scapharca dimeric hemoglobin as they proceed in real time, from 5 ns to 80 μs after ligand photodissociation. A tertiary intermediate structure forms rapidly (<5 ns) as the protein responds to the presence of an unliganded heme within each R-state protein subunit, with key structural changes observed in the heme groups, neighboring residues, and interface water molecules. This intermediate lays a foundation for the concerted tertiary and quaternary structural changes that occur on a microsecond time scale and are associated with the transition to a low-affinity T-state structure. Reversal of these changes shows a considerable lag as a T-like structure persists well after ligand rebinding, suggesting a slow T-to-R transition. PMID:16684887

  11. Time Resolved Measurements of Primary Biogenic Aerosol Particles in Amazonia

    NASA Astrophysics Data System (ADS)

    Wollny, A. G.; Garland, R.; Pöschl, U.

    2009-04-01

    Biogenic aerosols are ubiquitous in the Earth's atmosphere and they influence atmospheric chemistry and physics, the biosphere, climate, and public health. They play an important role in the spread of biological organisms and reproductive materials, and they can cause or enhance human, animal, and plant diseases. Moreover, they influence the Earth's energy budget by scattering and absorbing radiation, and they can initiate the formation of clouds and precipitation as cloud condensation and ice nuclei. The composition, abundance, and origin of biogenic aerosol particles and components are, however, still not well understood and poorly quantified. Prominent examples of primary biogenic aerosol particles, which are directly emitted from the biosphere to the atmosphere, are pollen, bacteria, fungal spores, viruses, and fragments of animals and plants. During the Amazonian Aerosol Characterization Experiment (AMAZE-08) a large number of aerosol and gas-phase measurements were taken on a remote site close to Manaus, Brazil, during a period of five weeks in February and March 2008. This presented study is focused on data from an ultraviolet aerodynamic particle sizer (UVAPS, TSI inc.) that has been deployed for the first time in Amazonia. In this instrument, particle counting and aerodynamic sizing over the range of 0.5-20 µm are complemented by the measurement of UV fluorescence at 355 nm (excitation) and 420-575 nm (emission), respectively. Fluorescence at these wavelengths is characteristic for reduced pyridine nucleotides (e.g., NAD(P)H) and for riboflavin, which are specific for living cells. Thus particles exhibiting fluorescence signals can be regarded as "viable aerosols" or "fluorescent bioparticles" (FBAP), and their concentration can be considered as lower limit for the actual abundance of primary biogenic aerosol particles. Data from the UVAPS were averaged over 5 minute time intervals. The presence of bioparticles in the observed size range has been

  12. Exploiting Molecular Biology by Time-Resolved Fluorescence Imaging

    NASA Astrophysics Data System (ADS)

    Müller, Francis; Fattinger, Christof

    Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal fluorophore. With fluorescence lifetimes in the microsecond range and fluorescence quantum yield of 0.4 some water soluble complexes of Ruthenium like modified Ru(sulfobathophenanthroline) complexes fulfill these properties. They are outstanding fluorescent labels for ultrasensitive assays as illustrated in two examples, in drug discovery and in point of care testing.We discuss the fundamentals and the state-of-the-art of the most sensitive time-gated fluorescence assays. We reflect on how the imaging devices currently employed for readout of these assays might evolve in the future. Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal

  13. Ultrafast Space-time and Spectrum-time Resolved Diagnostics of Multicharged Femtosecond Laser Microplasma

    NASA Astrophysics Data System (ADS)

    Garnov, S. V.; Bukin, V. V.; Malyutin, A. A.; Strelkov, V. V.

    2009-07-01

    We present the review of the recent experimental studies of fundamental mechanisms of femtosecond laser plasma formation and evolution performed in A. M. Prokhorov General Physics Institute of Russian Academy of Sciences. The main object we dealt with was the micro-sized plasma produced in gases with high intensity (up to 5×1017 W/cm2), tightly focused (to a few microns in diameter) IR and UV femtosecond laser pulses. The main attention in the experiments was paid to the initial stage of microplasma formation and evolution characterized by strong laser-plasma coupling resulting in efficient ionization and heating of the medium, distortion of laser beam, and nonlinear spectral conversion of laser radiation to the continuum and laser harmonics. Using a precise pump-probe micro-interferometric technique the dynamics of plasma was studied with femtosecond time-resolution in a wide density range—from a minimal detectable electron concentration (1019 cm-3) to the almost total (down to nuclei) ionization of ions occurred under femtosecond excitation. The obtained time-dependences of plasma density were analyzed. It was observed, for the first time, that a characteristic time of femtosecond laser plasma formation in gases considerably (in times) exceeds the duration of the pump laser pulse. This postionization process is attributed to impact ionization of plasma by hot electrons. We compare the results of the experiments with what the developed theory predicts. Using an ultrafast streak-camera-based spectroscopy technique the temporal evolution of microplasma emission and the dynamics of spectral lines formation in UV-visible range were studied with picosecond time-resolution.

  14. Combined time- and depth-resolved autofluorescence spectroscopy for tissue diagnosis

    NASA Astrophysics Data System (ADS)

    Wu, Yicong; Qu, Jianan Y.

    2006-02-01

    A fluorescence spectroscopy system combining depth- and time-resolved measurements is developed to investigate the layered fluorescence temporal characteristics of epithelial tissue. It is found that esophageal tissue structure can be resolved well by means of the autofluorescence time-resolved decay process with 375-, 405- and 435- nm excitation. The decay of the autofluorescence signals can be accurately fitted with a dual-exponential function consisting of a short lifetime (0.4 ~ 0.6 ns) and a long lifetime (3 ~ 4 ns) components. The short lifetime component dominates the decay of normal epithelial fluorescence while the decay of the signals from keratinized epithelium and stroma are mainly determined by the long lifetime component. The ratio of the amplitudes of two components provides the information of fine structure of epithelial tissue. This study demonstrates that the combined depth- and time-resolved measurements can potentially provide accurate information for the diagnosis of tissue pathology.

  15. Time-resolved proper orthogonal decomposition of liquid jet dynamics

    NASA Astrophysics Data System (ADS)

    Arienti, Marco; Soteriou, Marios C.

    2009-11-01

    New insight into the mechanism of liquid jet in crossflow atomization is provided by an analysis technique based on proper orthogonal decomposition and spectral analysis. Data are provided in the form of high-speed videos of the jet near field from experiments over a broad range of injection conditions. For each condition, proper orthogonal modes (POMs) are generated and ordered by intensity variation relative to the time average. The feasibility of jet dynamics reduction by truncation of the POM series to the first few modes is then examined as a function of crossflow velocity for laminar and turbulent liquid injection. At conditions where the jet breaks up into large chunks of liquid, the superposition of specific orthogonal modes is observed to track long waves traveling along the liquid column. The temporal coefficients of these modes can be described as a bandpass spectrum that shifts toward higher frequencies as the crossflow velocity is increased. The dynamic correlation of these modes is quantified by their cross-power spectrum density. Based on the frequency and wavelength extracted from the videos, the observed traveling waves are linked to the linearly fastest growing wave of Kelvin-Helmholtz instability. The gas boundary layer thickness at the gas-liquid shear layer emerges at the end of this study as the dominant length scale of jet dynamics at moderate Weber numbers.

  16. Quantum beats in attosecond time-resolved autoionization of krypton

    NASA Astrophysics Data System (ADS)

    Cheng, Yan; Chini, Michael; Tong, Xiao-Min; Chew, Andrew; Biedermann, Julius; Wu, Yi; Cunningham, Eric; Chang, Zenghu

    2015-05-01

    The recent development of attosecond transient absorption spectroscopy (ATAS) has allowed probing of electron dynamics in atoms with few-femtosecond to sub-cycle time scales. Recently, the contribution of quantum beating to the two-color multi-photon excitation process has been proposed and demonstrated in the attosecond transient absorption experiment in the bound state of atoms. Here we performed an attosecond transient absorption experiment with krypton atoms, the attosecond pulse launched electronic wave packets composed of multiple bound excited states and spin-orbit coupling induced autoionization states of krypton atoms. Quantum beats were observed in the autoionizing states near the ionization threshold. Recurrences were observed in the 4s24p5(2 P° 1/2) 6d, 4s24p5(2 P°1/2) 7d, 4s24p5(2 P° 1/2) 8d states with periods of 5-10 fs. The relative phase among these autoionizing states can be retrieved from such measurement, thus allowed the reconstruction of the valence state wave packets. This material is based upon work supported by Army Research Office, Air Force Office of Scientific Research, the National Science Foundation, and the DARPA PULSE program by a grant from AMRDEC.

  17. Ultimate sensitivity of time-resolved optoacoustic detection

    NASA Astrophysics Data System (ADS)

    Oraevsky, Alexander A.; Karabutov, Alexander A.

    2000-05-01

    The major limitation in sensitivity of the optical tomography is associated with strong optical attenuation in human tissues. Opto-acoustic tomography overcomes this limitation utilizing detection of acoustic waves instead of detection of transmitted photons. Exceptional sensitivity of the opto-acoustic tomography allows early detection of small tumors located dep in human tissues, such as breast. This paper demonstrates that an optimally designed opto-acoustic imaging system can detect early 1-mm tumors with minimal blood content of only 7 percent at the depth of up to 7-cm within the breast attenuating laser irradiation 3.3 times per each 1-cm of its depth. A theoretical consideration of the ultimate sensitivity of piezo-detection in a wide ultrasonic frequency band is developed. The detection sensitivity is presented as a function of the ultrasonic frequency, tumor dimensions and optical absorption coefficient. Comparative analysis of piezo and optical interferometric detection of opto-acoustic transients is presented. The theoretical models of piezo detection were developed for the open-circuit and short-circuit schemes of operation. The ultimate sensitivity limited by thermal noise of electric capacitor of the piezo-element was estimated. It was shown that the limit of detection depends on the frequency band, the electric capacity of the transducer and the sped of sound in the piezo-element. Comparative analysis of various piezo-materials was made from the point of view of their utility for sensitive opto-acoustic detection.

  18. In vivo time-resolved autofluorescence measurements on human skin

    NASA Astrophysics Data System (ADS)

    Katika, Kamal M.; Pilon, Laurent; Dipple, Katrina; Levin, Seymour; Blackwell, Jennifer; Berberoglu, Halil

    2006-02-01

    In this paper we present preliminary results obtained from fluorescence lifetime measurements on human skin using time-correlated single photon counting (TCSPC) techniques. Human skin was exposed to light from a pulsed LED of 700 ps pulse width at a wavelength of 375 nm and fluorescence decays were recorded at four different emission wavelengths (442, 460, 478 and 496 nm) using a photomultiplier tube (PMT) coupled to a monochromator. Measurements were carried out on the left and right palms of subjects recruited for the study after obtaining consent using a UCLA IRB approved consent form. The subjects recruited consisted of 18 males and 17 females with different skin complexions and ages ranging from 10 to 70 years. In addition, a set of experiments were also performed on various locations including the palm, the arm and the cheek of a Caucasian subject. The fluorescence decays thus obtained were fit to a three-exponential decay model in all cases and were approximately 0.4, 2.7 and 9.4 ns, respectively. The variations in these lifetimes with location, gender, skin complexion and age are studied. It is speculated that the shorter lifetimes correspond to free and bound NADH while the longer lifetime is due to AGE crosslinks.

  19. High resolution geodetic techniques for monitoring fluid levels over time

    NASA Astrophysics Data System (ADS)

    Hare, Jennifer Thompson

    1998-11-01

    lineation for elevation measurement is complicated by erosional degradation, and the fact that the terraces were irregular at the time of formation. In order to address this problem, local high resolution Digital Elevation Models (DEMs) are generated at six sample terrace sites using a variety of survey techniques, including conventional total station, rapid static GPS, and new real-time kinematic GPS methods. The data are tied to a regional framework of absolute geodetic control. A signal processing method is developed that uses derivative filters for geomorphic feature recognition and averaging for noise reduction. Propagation of errors related to surveying, geoid estimation, and terrace feature estimation indicates that tectonic displacements on the order of one-half meter should be resolvable. This work establishes the foundation for analysis of the terraces on a regional scale by using a high resolution DEM of the entire shoreline trace around the perimeter of Lake Lahontan. (Abstract shortened by UMI.)

  20. High time-resolution photodetectors for PET applications

    SciTech Connect

    Ronzhin, Anatoly

    2015-11-27

    This paper describes recent developments aiming at the improvement of the time resolution of photodetectors used in positron emission tomography (PET). Promising photodetector candidates for future PET-time-of-flight (TOF) applications are also discussed.

  1. High time-resolution photodetectors for PET applications

    DOE PAGESBeta

    Ronzhin, Anatoly

    2016-02-01

    This paper describes recent developments aiming at the improvement of the time resolution of photodetectors used in positron emission tomography (PET). Promising photodetector candidates for future PET-time-of-flight (TOF) applications are also discussed.

  2. Image-domain motion compensated time resolved 4D cardiac CT

    NASA Astrophysics Data System (ADS)

    Taguchi, Katsuyuki; Sun, Zhihui; Segars, W. Paul; Fishman, Elliot K.; Tsui, Benjamin M. W.

    2007-03-01

    Two major problems with the current electrocardiogram-gated cardiac computed tomography (CT) imaging technique are a large patient radiation dose (10-15 mSv) and insufficient temporal resolution (83-165 ms). Our long-term goal is to develop new time resolved and low dose cardiac CT imaging techniques that consist of image reconstruction algorithms and estimation methods of the time-dependent motion vector field (MVF) of the heart from the acquired CT data. Toward this goal, we developed a method that estimates the 2D components of the MVF from a sequence of cardiac CT images and used it to "reconstruct" cardiac images at rapidly moving phases. First, two sharp image frames per heart beat (cycle) obtained at slow motion phases (i.e., mid-diastole and end-systole) were chosen. Nodes were coarsely placed among images; and the temporal motion of each node was modeled by B-splines. Our cost function consisted of 3 terms: mean-squared-error with the block-matching, and smoothness constraints in space and time. The time-dependent MVF was estimated by minimizing the cost function. We then warped images at slow motion phases using the estimated vector fields to "reconstruct" images at rapidly moving phase. The warping algorithm was evaluated using true time-dependent motion vector fields and images both provided by the NCAT phantom program. Preliminary results from ongoing quantitative and qualitative evaluation using the 4D NCAT phantom and patient data are encouraging. Major motion artifact is much reduced. We conclude the new image-based motion estimation technique is an important step toward the development of the new cardiac CT imaging techniques.

  3. 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.

  4. Resolving inflammation: dual anti-inflammatory and pro-resolution lipid mediators

    PubMed Central

    Serhan, Charles N.; Chiang, Nan; Van Dyke, Thomas E.

    2009-01-01

    Preface Active resolution of acute inflammation is a previously unrecognized interface between innate and adaptive immunity. Once thought to be a passive process, the resolution of inflammation is now shown to involve active biochemical programmes that enable inflamed tissues to return to homeostasis. This Review presents newly uncovered cellular and molecular mechanisms for the resolution of inflammation, revealing key roles for eicosanoids, such as lipoxins, and new families of endogenous chemical mediators, termed resolvins and protectins. These mediators carry antiinflammatory and pro-resolution properties with leukocytes, protect organs and stimulate mucosal antimicrobial defence and clearance. Together, they control local inflammatory responses at multiple levels to stimulate resolution. PMID:18437155

  5. Multispectral scanning time-resolved fluorescence spectroscopy (TRFS) technique for intravascular diagnosis

    PubMed Central

    Xie, Hongtao; Bec, Julien; Liu, Jing; Sun, Yang; Lam, Matthew; Yankelevich, Diego R.; Marcu, Laura

    2012-01-01

    This study describes a scanning time-resolved fluorescence spectroscopy (TRFS) system designed to continuously acquire fluorescence emission and to reconstruct fluorescence lifetime images (FLIM) from a luminal surface by using a catheter-based optical probe with rotary joint and pull-back device. The ability of the system to temporally and spectrally resolve the fluorescence emission from tissue was validated using standard dyes and tissue phantoms (e.g., ex vivo pig aorta phantom). Current results demonstrate that this system is capable to reliably resolve the fluorescence emission of multiple fluorophores located in the lumen; and suggest its potential for intravascular detection of distinct biochemical features of atherosclerotic plaques. PMID:22808425

  6. Time- and spatial-resolved XAFS spectroscopy in a single shot: new analytical possibilities for in situ material characterization.

    PubMed

    Buzanich, Ana Guilherme; Radtke, Martin; Reinholz, Uwe; Riesemeier, Heinrich; Emmerling, Franziska

    2016-05-01

    A new concept that comprises both time- and lateral-resolved X-ray absorption fine-structure information simultaneously in a single shot is presented. This uncomplicated set-up was tested at the BAMline at BESSY-II (Berlin, Germany). The primary broadband beam was generated by a double multilayer monochromator. The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by either an energy-sensitive area detector, the so-called color X-ray camera, or by an area-sensitive detector based on a CCD camera, in θ-2θ geometry. The first tests were performed with thin metal foils and some iron oxide mixtures. A time resolution of lower than 1 s together with a spatial resolution in one dimension of at least 50 µm is achieved. PMID:27140157

  7. Measuring Exciton Migration in Conjugated Polymer Films with Ultrafast Time Resolved Stimulated Emission Depletion Microscopy

    NASA Astrophysics Data System (ADS)

    Penwell, Samuel

    Conjugated polymers are highly tunable organic semiconductors, which can be solution processed to form thin films, making them prime candidates for organic photovoltaic devices. One of the most important parameters in a conjugated polymer solar cell is the exciton diffusion length, which depends on intermolecular couplings, and is typically on the order of 10 nm. This mean exciton migration can vary dramatically between films and within a single film due to heterogeneities in morphology on length scales of 10's to 100's nm. To study the variability of exciton diffusion and morphology within individual conjugated polymer films, we are adapting stimulated emission depletion (STED) microscopy. STED is typically used in biology with sparse well-engineered fluorescent labels or on NV-centers in diamond. I will, however, describe how we have demonstrated the extension of STED to conjugated polymer films and nanoparticles of MEH-PPV and CN-PPV, despite the presence of two photon absorption, by taking care to first understand the material's photophysical properties. We then further adapt this approach, by introducing a second ultrafast STED pulse at a variable delay. Excitons that migrate away from the initial subdiffraction excitation volume during the ps-ns time delay, are preferentially quenched by the second STED pulse, while those that remain in the initial volume survive. The resulting effect of the second STED pulse is modulated by the degree of migration over the ultrafast time delay, thus providing a new method to study exciton migration. Since this technique utilizes subdiffraction optical excitation and detection volumes with ultrafast time resolution, it provides a means of spatially and temporally resolving measurements of exciton migration on the native length and time scales. In this way, we will obtain a spatiotemporal map of exciton distributions and migration that will help to correlate the energetic landscape to film morphology at the nanoscale.

  8. Probing Anisotropic Structure Changes in Proteins with Picosecond Time-Resolved Small Angle X-ray Scattering

    PubMed Central

    Cho, Hyun Sun; Schotte, Friedrich; Dashdorj, Naranbaatar; Kyndt, John; Anfinrud, Philip A.

    2014-01-01

    We have exploited the principle of photoselection and the method of time-resolved Small Angle X-ray Scattering (SAXS) to investigate protein size and shape changes following photoactivation of photoactive yellow protein (PYP) in solution with ~150 ps time resolution. This study partially overcomes the orientational average intrinsic to solution scattering methods, and provides structural information at a higher level of detail. Photoactivation of the p-coumaric acid (pCA) chromophore in PYP produces a highly-contorted, short-lived, red shifted intermediate (pR0), and triggers prompt, protein compaction of approximately 0.3% along the direction defined by the electronic transition dipole moment of the chromophore. Contraction along this dimension is accompanied by expansion along the orthogonal directions, with the net protein volume change being approximately -0.25%. More than half the strain arising from formation of pR0 is relieved by the pR0 to pR1 structure transition (1.8 ± 0.2 ns), with the persistent strain presumably contributing to the driving force needed to generate the spectroscopically blue-shifted pB signaling state. The results reported here are consistent with the near-atomic resolution structural dynamics reported in a recent time-resolved Laue crystallography study of PYP crystals, and suggest that the early-time structural dynamics in the crystalline state carry over to proteins in solution. PMID:24125473

  9. Time-resolved spectroscopic studies of detonating heterogeneous explosives. [HMX and HNS

    SciTech Connect

    Trott, W.M.; Renlund, A.M.

    1985-01-01

    Emission spectroscopy and pulsed-laser-excited Raman scattering methods have been applied to the study of detonating heterogeneous explosives, including PETN, HMX and HNS. Time-resolved spectra of emission from detonating HNS show the evolution of features due to electronically-excited radical species. For HNS, the CN(B-X) system near 388 nm has been studied at a wavelength resolution of 0.5 A. Boltzmann vibrational temperatures have been calculated by comparing the experimental data with computer-simulated spectra. These temperatures are consistent with the expected trend of detonation temperature as a function of charge density. Using 532-nm laser excitation, single-pulse Raman scattering measurements have been made at the free surface of detonating HMX and PETN samples. Monotonic attenuation of Raman scattering intensity over a 100-ns interval is observed after detonation front arrival at the free surface. Depletion of the Raman signal occurs prior to significant loss of the scattered laser light. The significance of the Raman measurements as a possible probe of reaction zone length in detonating explosives is discussed. 21 refs., 11 figs.

  10. Time Resolved 2D X-Ray Densitometry of a Ventilated Partial Cavity Closure

    NASA Astrophysics Data System (ADS)

    Makiharju, Simo; Ceccio, Steven

    2011-11-01

    A time resolved x-ray densitometry system was developed to measure the spatial distribution of void fraction for nominally two-dimensional flows. The system can image a region of (15 cm)2 at a frame rate of up to 4000 fps. The source was a rotating anode type normally used for cineradiography and angiography. Supplied by a 65 kW high frequency generator with a high speed starter, it could be operated at up to 433 mA at 150 kV. The imager subsystem comprised of a high speed camera coupled with a high resolution image intensifier. The range of measured void fraction can be changed to span a desired range yielding an uncertainty on the order of 1% of the measurement range. The system is used to examine the void fraction field in the closure region of a ventilated partial cavity behind a backward facing step. The cavity has Reynolds number of O(105) based on the cavity length, and a non-dimensional gas flux of Q* = 0.0048. The bubbly flow created in the cavity wake is examined using the x-ray densitometry system, duel fiber optical probes, and high speed cinematography. The local void fraction and bubble size distributions in the cavity wake are determined, and the measurements methods are compared. The research was sponsored by ONR under grant N00014-08-1-0215, program manager Dr. L. Patrick Purtell.

  11. Space-time resolved measurements of spontaneous magnetic fields in laser-produced plasma

    SciTech Connect

    Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Borodziuk, S.; Gus'kov, S. Yu.; Dudzak, R.; Dostal, J.; Krousky, E.; Ullschmied, J.; Hrebicek, J.; Medrik, T.; Golasowski, J.; Pfeifer, M.; Skala, J.; Demchenko, N. N.; Korneev, Ph.; Kalal, M.; Renner, O.; Smid, M.; Pisarczyk, P.

    2015-10-15

    The first space-time resolved spontaneous magnetic field (SMF) measurements realized on Prague Asterix Laser System are presented. The SMF was generated as a result of single laser beam (1.315 μm) interaction with massive planar targets made of materials with various atomic numbers (plastic and Cu). Measured SMF confirmed azimuthal geometry and their maximum amplitude reached the value of 10 MG at the laser energy of 250 J for both target materials. It was demonstrated that spatial distributions of these fields are associated with the character of the ablative plasma expansion which clearly depends on the target material. To measure the SMF, the Faraday effect was employed causing rotation of the vector of polarization of the linearly polarized diagnostic beam. The rotation angle was determined together with the phase shift using a novel design of a two-channel polaro-interferometer. To obtain sufficiently high temporal resolution, the polaro-interferometer was irradiated by Ti:Sa laser pulse with the wavelength of 808 nm and the pulse duration of 40 fs. The results of measurements were compared with theoretical analysis.

  12. Time- and space-resolved spectroscopic characterization of laser-induced swine muscle tissue plasma

    NASA Astrophysics Data System (ADS)

    Camacho, J. J.; Diaz, L.; Martinez-Ramirez, S.; Caceres, J. O.

    2015-09-01

    The spatial-temporal evolution of muscle tissue sample plasma induced by a high-power transversely excited atmospheric (TEA) CO2 pulsed laser at vacuum conditions (0.1-0.01 Pa) has been investigated using high-resolution optical emission spectroscopy (OES) and imaging methods. The induced plasma shows mainly electronically excited neutral Na, K, C, Mg, H, Ca, N and O atoms, ionized C+, C2 +, C3 +, Mg+, Mg2 +, N+, N2 +, Ca+, O+ and O2 + species and molecular band systems of CN(B2Σ+-X2Σ+), C2(d3Πg-a3Πu), CH(B2Σ--X2Π; A2Δ-X2Π), NH(A3Π-X3Σ-), OH(A2Σ+-X2 Σ+), and CaOH(B2Σ+-X2Σ+; A2Π-X2Σ+). Time-resolved two-dimensional emission spectroscopy is used to study the expanded distribution of different species ejected during ablation. Spatial and temporal variations of different atoms and ionic excited species are reported. Plasma parameters such as electron density and temperature were measured from the spatio-temporal analysis of different species. Average velocities of some plasma species were estimated.

  13. Space-time resolved measurements of spontaneous magnetic fields in laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Pisarczyk, T.; Gus'kov, S. Yu.; Dudzak, R.; Chodukowski, T.; Dostal, J.; Demchenko, N. N.; Korneev, Ph.; Kalinowska, Z.; Kalal, M.; Renner, O.; Smid, M.; Borodziuk, S.; Krousky, E.; Ullschmied, J.; Hrebicek, J.; Medrik, T.; Golasowski, J.; Pfeifer, M.; Skala, J.; Pisarczyk, P.

    2015-10-01

    The first space-time resolved spontaneous magnetic field (SMF) measurements realized on Prague Asterix Laser System are presented. The SMF was generated as a result of single laser beam (1.315 μm) interaction with massive planar targets made of materials with various atomic numbers (plastic and Cu). Measured SMF confirmed azimuthal geometry and their maximum amplitude reached the value of 10 MG at the laser energy of 250 J for both target materials. It was demonstrated that spatial distributions of these fields are associated with the character of the ablative plasma expansion which clearly depends on the target material. To measure the SMF, the Faraday effect was employed causing rotation of the vector of polarization of the linearly polarized diagnostic beam. The rotation angle was determined together with the phase shift using a novel design of a two-channel polaro-interferometer. To obtain sufficiently high temporal resolution, the polaro-interferometer was irradiated by Ti:Sa laser pulse with the wavelength of 808 nm and the pulse duration of 40 fs. The results of measurements were compared with theoretical analysis.

  14. Time-Resolved Imaging Reveals Heterogeneous Landscapes of Nanomolar Ca2+ in Neurons and Astroglia

    PubMed Central

    Zheng, Kaiyu; Bard, Lucie; Reynolds, James P.; King, Claire; Jensen, Thomas P.; Gourine, Alexander V.; Rusakov, Dmitri A.

    2015-01-01

    Summary Maintaining low intracellular calcium is essential to the functioning of brain cells, yet the phenomenology and mechanisms involved remain an enigma. We have advanced a two-photon excitation time-resolved imaging technique, which exploits high sensitivity of the OGB-1 fluorescence lifetime to nanomolar Ca2+ concentration ([Ca2+]) and enables a high data acquisition rate in situ. The [Ca2+] readout is not affected by dye concentration, light scattering, photobleaching, micro-viscosity, temperature, or the main known concomitants of cellular activity. In quiescent tissue, standard whole-cell configuration has little effect on resting [Ca2+] inside neuronal dendrites or inside astroglia dye-filled via gap junctions. Mapping basal [Ca2+] in neurons and astrocytes with submicron resolution unveils heterogeneous concentration landscapes that depend on age and preceding activity. The rich information content represented by such landscapes in acute slices and in vivo promises to unveil the hitherto unexplored, potentially fundamental aspects of brain cell physiology. Video Abstract PMID:26494277

  15. Total variation based reconstruction of scattering inhomogeneities in tissue from time-resolved optical projections

    NASA Astrophysics Data System (ADS)

    Konovalov, Alexander B.; Vlasov, Vitaly V.

    2016-04-01

    The important advantage of diffuse optical tomography (DOT) is the possibility of tissue functional diagnosis. However the possibility implements if only we separately reconstruct the spatial distributions of optical parameters, specifically the absorption and scattering coefficients. We have recently demonstrated that time-domain DOT based on the perturbation model by Lyubimov is capable of reconstructing absorbing inhomogeneities in tissue with a DOT high spatial resolution (better than 3 mm at a depth of 4 cm). This paper continues our research and focuses on the reconstruction of scattering inhomogeneities. We consider the flat layer transmission geometry which is traditional for optical mammography, and use diffusion approximation to derive analytical expressions for weight functions responsible for the reconstruction of scattering inhomogeneities. To confirm that our calculations are correct we perform a numerical experiment where we reconstruct a rectangular scattering object 10×8 cm in size with 4 circular scattering macroinhomogeneities 4 mm in diameter each, and a randomly inhomogeneous scattering structure. The inverse DOT problem is solved with a multiplicative algebraic reconstruction technique where interim iterations are processed through total variation norm minimization. The results suggest that our DOT method reliably resolves the scattering macroinhomogeneities of mentioned size against a randomly inhomogeneous structure.

  16. Spatiotemporally resolved electrodynamic properties of a Sun-aligned arc over Resolute Bay

    NASA Astrophysics Data System (ADS)

    Perry, G. W.; Dahlgren, H.; Nicolls, M. J.; Zettergren, M.; St.-Maurice, J.-P.; Semeter, J. L.; Sundberg, T.; Hosokawa, K.; Shiokawa, K.; Chen, S.

    2015-11-01

    Common volume measurements by the Resolute Bay Incoherent Scatter Radar-North (RISR-N) and Optical Mesosphere and Thermosphere Imagers (OMTI) have been used to clarify the electrodynamic structure of a Sun-aligned arc in the polar cap. The plasma parameters of the dusk-to-dawn drifting arc and surrounding ionosphere are extracted using the volumetric imaging capabilities of RISR-N. Multipoint line-of-sight RISR-N measurements of the plasma drift are inverted to construct a time sequence of the electric field and field-aligned current system of the arc. Evidence of dramatic electrodynamic and plasma structuring of the polar cap ionosphere due to the arc is described. One notable feature of the arc is a meridionally extended plasma density depletion on its leading edge, located partially within a downward field-aligned current region. The depletion is determined to be a by-product of enhanced chemical recombination operating on a time scale of 15 min. A similarly shaped electric field structure of over 100 mV/m and line-of-sight ion temperatures nearing 3000 K were collocated with the depletion.

  17. Time-resolved fluorescence and photon migration studies in biomedical and model random media

    NASA Astrophysics Data System (ADS)

    Das, B. B.; Liu, Feng; Alfano, R. R.

    1997-02-01

    This review highlights time-resolved fluorescence kinetics and photon transport in tissues and other biomedical media with a special emphasis on ultrafast measurements of key optical parameters. Measurements of fluorescence decay lifetimes from human breast and atherosclerotic artery tissues in the uv and visible region are described after a brief description of fundamentals of fluorescence kinetics. A time-dependent diffusion model for photon migration and various ultrafast methods for time-resolved light scattering measurements to obtain key optical parameters of tissues and other model turbid media are presented. The usefulness of optical parameters as markers in optical diagnostics and imaging is considered. Time-gated measurements of ballistic and snake photons to obtain shadowgrams and an inverse numerical reconstruction of the interior map of a turbid medium from time-resolved data in the context of optical tomography are presented.

  18. Time-resolved materials science opportunities using synchrotron x-ray sources

    SciTech Connect

    Larson, B.C.; Tischler, J.Z.

    1995-06-01

    The high brightness, high intensity, and pulsed time-structure of synchrotron sources provide new opportunities for time-resolved x-ray diffraction investigations. With third generation synchrotron sources coming on line, high brilliance and high brightness are now available in x-ray beams with the highest flux. In addition to the high average flux, the instantaneous flux available in synchrotron beams is greatly enhanced by the pulsed time structure, which consists of short bursts of x-rays that are separated by {approximately}tens to hundreds of nanoseconds. Time-resolved one- and two-dimensional position sensitive detection techniques that take advantage of synchrotron radiation for materials science x-ray diffraction investigations are presented, and time resolved materials science applications are discussed in terms of recent diffraction and spectroscopy results and materials research opportunities.

  19. Characteristics and sensitivity analysis of multiple-time-resolved source patterns of PM2.5 with real time data using Multilinear Engine 2

    NASA Astrophysics Data System (ADS)

    Peng, Xing; Shi, Guo-Liang; Gao, Jian; Liu, Jia-Yuan; HuangFu, Yan-Qi; Ma, Tong; Wang, Hai-Ting; Zhang, Yue-Chong; Wang, Han; Li, Hui; Ivey, Cesunica E.; Feng, Yin-Chang

    2016-08-01

    With real time resolved data of Particulate matter (PM) and chemical species, understanding the source patterns and chemical characteristics is critical to establish controlling of PM. In this work, PM2.5 and chemical species were measured by corresponding online instruments with 1-h time resolution in Beijing. Multilinear Engine 2 (ME2) model was applied to explore the sources, and four sources (vehicle emission, crustal dust, secondary formation and coal combustion) were identified. To investigate the sensitivity of time resolution on the source contributions and chemical characteristics, ME2 was conducted with four time resolution runs (1-h, 2-h, 4-h, and 8-h). Crustal dust and coal combustion display large variation in the four time resolutions runs, with their contributions ranging from 6.7 to 10.4 μg m-3 and from 6.4 to 12.2 μg m-3, respectively. The contributions of vehicle emission and secondary formation range from 7.5 to 10.5 and from 14.7 to 16.7 μg m-3, respectively. The sensitivity analyses were conducted by principal component analysis-plot (PCA-plot), coefficient of divergence (CD), average absolute error (AAE) and correlation coefficients. For the four time resolution runs, the source contributions and profiles of crustal dust and coal combustion were more unstable than other source categories, possibly due to the lack of key markers of crustal dust and coal combustion (e.g. Si, Al). On the other hand, vehicle emission and crustal dust were more sensitive to time series of source contributions at different time resolutions. Findings in this study can improve our knowledge of source contributions and chemical characteristics at different time solutions.

  20. Determining Chemically and Spatially Resolved Atomic Profile of Low Contrast Interface Structure with High Resolution

    PubMed Central

    Nayak, Maheswar; Pradhan, P. C.; Lodha, G. S.

    2015-01-01

    We present precise measurements of atomic distributions of low electron density contrast at a buried interface using soft x-ray resonant scattering. This approach allows one to construct chemically and spatially highly resolved atomic distribution profile upto several tens of nanometer in a non-destructive and quantitative manner. We demonstrate that the method is sensitive enough to resolve compositional differences of few atomic percent in nano-scaled layered structures of elements with poor electron density differences (0.05%). The present study near the edge of potential impurities in soft x-ray range for low-Z system will stimulate the activity in that field. PMID:25726866

  1. Determining chemically and spatially resolved atomic profile of low contrast interface structure with high resolution.

    PubMed

    Nayak, Maheswar; Pradhan, P C; Lodha, G S

    2015-01-01

    We present precise measurements of atomic distributions of low electron density contrast at a buried interface using soft x-ray resonant scattering. This approach allows one to construct chemically and spatially highly resolved atomic distribution profile upto several tens of nanometer in a non-destructive and quantitative manner. We demonstrate that the method is sensitive enough to resolve compositional differences of few atomic percent in nano-scaled layered structures of elements with poor electron density differences (0.05%). The present study near the edge of potential impurities in soft x-ray range for low-Z system will stimulate the activity in that field. PMID:25726866

  2. High Resolution Imaging of Very Low Mass Spectral Binaries: Three Resolved Systems and Detection of Orbital Motion in an L/T Transition Binary

    NASA Astrophysics Data System (ADS)

    Bardalez Gagliuffi, Daniella C.; Gelino, Christopher R.; Burgasser, Adam J.

    2015-11-01

    We present high resolution Laser Guide Star Adaptive Optics imaging of 43 late-M, L and T dwarf systems with Keck/NIRC2. These include 17 spectral binary candidates, systems whose spectra suggest the presence of a T dwarf secondary. We resolve three systems: 2MASS J1341-3052, SDSS J1511+0607 and SDSS J2052-1609 the first two are resolved for the first time. All three have projected separations <8 AU and estimated periods of 14-80 years. We also report a preliminary orbit determination for SDSS J2052-1609 based on six epochs of resolved astrometry between 2005 and 2010. Among the 14 unresolved spectral binaries, 5 systems were confirmed binaries but remained unresolved, implying a minimum binary fraction of {47}-11+12% for this sample. Our inability to resolve most of the spectral binaries, including the confirmed binaries, supports the hypothesis that a large fraction of very low mass systems have relatively small separations and are missed with direct imaging. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  3. Time-resolved molecular characterization of organic aerosols by PILS + UPLC/ESI-Q-TOFMS

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Dalleska, N. F.; Huang, D. D.; Bates, K. H.; Sorooshian, A.; Flagan, R. C.; Seinfeld, J. H.

    2016-04-01

    Real-time and quantitative measurement of particulate matter chemical composition represents one of the most challenging problems in the field of atmospheric chemistry. In the present study, we integrate the Particle-into-Liquid Sampler (PILS) with Ultra Performance Liquid Chromatography/Electrospray ionization Quadrupole Time-of-Flight High-Resolution/Mass Spectrometry (UPLC/ESI-Q-TOFMS) for the time-resolved molecular speciation of chamber-derived secondary organic aerosol (SOA). The unique aspect of the combination of these two well-proven techniques is to provide quantifiable molecular-level information of particle-phase organic compounds on timescales of minutes. We demonstrate that the application of the PILS + UPLC/ESI-Q-TOFMS method is not limited to water-soluble inorganic ions and organic carbon, but is extended to slightly water-soluble species through collection efficiency calibration together with sensitivity and linearity tests. By correlating the water solubility of individual species with their O:C ratio, a parameter that is available for aerosol ensembles as well, we define an average aerosol O:C ratio threshold of 0.3, above which the PILS overall particulate mass collection efficiency approaches ∼0.7. The PILS + UPLC/ESI-Q-TOFMS method can be potentially applied to probe the formation and evolution mechanism of a variety of biogenic and anthropogenic SOA systems in laboratory chamber experiments. We illustrate the application of this method to the reactive uptake of isoprene epoxydiols (IEPOX) on hydrated and acidic ammonium sulfate aerosols.

  4. A time-resolved imaging and electrical study on a high current atmospheric pressure spark discharge

    NASA Astrophysics Data System (ADS)

    Palomares, J. M.; Kohut, A.; Galbács, G.; Engeln, R.; Geretovszky, Zs.

    2015-12-01

    We present a time-resolved imaging and electrical study of an atmospheric pressure spark discharge. The conditions of the present study are those used for nanoparticle generation in spark discharge generator setups. The oscillatory bipolar spark discharge was generated between two identical Cu electrodes in different configurations (cylindrical flat-end or tipped-end geometries, electrode gap from 0.5 to 4 mm), in a controlled co-axial N2 flow, and was supplied by a high voltage capacitor. Imaging data with nanosecond time resolution were collected using an intensified CCD camera. This data were used to study the time evolution of plasma morphology, total light emission intensity, and the rate of plasma expansion. High voltage and high current probes were employed to collect electrical data about the discharge. The electrical data recorded allowed, among others, the calculation of the equivalent resistance and inductance of the circuit, estimations for the energy dissipated in the spark gap. By combining imaging and electrical data, observations could be made about the correlation of the evolution of total emitted light and the dissipated power. It was also observed that the distribution of light emission of the plasma in the spark gap is uneven, as it exhibits a "hot spot" with an oscillating position in the axial direction, in correlation with the high voltage waveform. The initial expansion rate of the cylindrical plasma front was found to be supersonic; thus, the discharge releases a strong shockwave. Finally, the results on equivalent resistance and channel expansion are comparable to those of unipolar arcs. This shows the spark discharge has a similar behavior to the arc regime during the conductive phase and until the current oscillations stop.

  5. BioCARS: a synchrotron resource for time-resolved X-ray science

    PubMed Central

    Graber, T.; Anderson, S.; Brewer, H.; Chen, Y.-S.; Cho, H. S.; Dashdorj, N.; Henning, R. W.; Kosheleva, I.; Macha, G.; Meron, M.; Pahl, R.; Ren, Z.; Ruan, S.; Schotte, F.; Šrajer, V.; Viccaro, P. J.; Westferro, F.; Anfinrud, P.; Moffat, K.

    2011-01-01

    BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick–Baez mirror system capable of focusing the X-ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high-speed chopper isolates single X-ray pulses at 1 kHz in both hybrid and 24-bunch modes of the APS storage ring. In hybrid mode each isolated X-ray pulse delivers up to ∼4 × 1010 photons to the sample, thereby achieving a time-averaged flux approaching that of fourth-generation X-FEL sources. A new high-power picosecond laser system delivers pulses tunable over the wavelength range 450–2000 nm. These pulses are synchronized to the storage-ring RF clock with long-term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained. PMID:21685684

  6. BioCARS: a synchrotron resource for time-resolved X-ray science

    SciTech Connect

    Graber, T.; Anderson, S.; Brewer, H.; Chen, Y.-S.; Cho, H.; Dashdorj, N.; Henning, R.W.; Kosheleva, I.; Macha, G.; Meron, M.; Pahl, R.; Ren, Z.; Ruan, S.; Schotte, F.; Srajer, V.; Viccaro, P.J.; Westferro, F.; Anfinrud, P.; Moffat, K.

    2011-08-16

    BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick-Baez mirror system capable of focusing the X-ray beam to a spot size of 90 {micro}m horizontal by 20 {micro}m vertical. A high-speed chopper isolates single X-ray pulses at 1 kHz in both hybrid and 24-bunch modes of the APS storage ring. In hybrid mode each isolated X-ray pulse delivers up to {approx}4 x 10{sup 10} photons to the sample, thereby achieving a time-averaged flux approaching that of fourth-generation X-FEL sources. A new high-power picosecond laser system delivers pulses tunable over the wavelength range 450-2000 nm. These pulses are synchronized to the storage-ring RF clock with long-term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained.

  7. BioCARS: a synchrotron resource for time-resolved X-ray science.

    PubMed

    Graber, T; Anderson, S; Brewer, H; Chen, Y S; Cho, H S; Dashdorj, N; Henning, R W; Kosheleva, I; Macha, G; Meron, M; Pahl, R; Ren, Z; Ruan, S; Schotte, F; Srajer, V; Viccaro, P J; Westferro, F; Anfinrud, P; Moffat, K

    2011-07-01

    BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick-Baez mirror system capable of focusing the X-ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high-speed chopper isolates single X-ray pulses at 1 kHz in both hybrid and 24-bunch modes of the APS storage ring. In hybrid mode each isolated X-ray pulse delivers up to ~4 × 10(10) photons to the sample, thereby achieving a time-averaged flux approaching that of fourth-generation X-FEL sources. A new high-power picosecond laser system delivers pulses tunable over the wavelength range 450-2000 nm. These pulses are synchronized to the storage-ring RF clock with long-term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained. PMID:21685684

  8. 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.

  9. 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.

  10. Time-resolved imaging of material response during laser-induced bulk damage in SiO2

    SciTech Connect

    Demos, S G; Negres, R A

    2008-10-24

    We report on time resolved imaging of the dynamic events taking place during laser-induced damage in the bulk of fused silica samples with nanosecond temporal resolution and one micron spatial resolution. These events include: shock/pressure wave formation and propagation, transient absorption, crack propagation and formation of residual stress fields. The work has been performed using a time-resolved microscope system that utilizes a probe pulse to acquire images at delay times covering the entire timeline of a damage event. Image information is enhanced using polarized illumination and simultaneously recording the two orthogonal polarization image components. For the case of fused silica, an electronic excitation is first observed accompanied by the onset of a pressure wave generation and propagation. Cracks are seen to form early in the process and reach their final size at about 25 ns into the damage event. In addition, changes that in part are attributed to transient absorption in the modified material are observed for delays up to about 200 microseconds.

  11. Time-resolved two-photon excitation of dark states in quantum dots

    SciTech Connect

    Gautham, C. Snoke, D. W.; Rastelli, A.; Schmidt, O. G.

    2014-04-07

    We have performed time-resolved measurements of the time scale for conversion of excitons in dark states to bright (light-emitting) states in GaAs quantum dots. The dark states are pumped using two-photon absorption, while the bright state emission is observed in single-photon emission. This conversion time is connected to the spin flip time for carriers in the quantum dots. The time scale is found to be of the order of several hundred picoseconds.

  12. Four-wavelength time-resolved optical mammography in the 680-980-nm range

    NASA Astrophysics Data System (ADS)

    Pifferi, Antonio; Taroni, Paola; Torricelli, Alessandro; Messina, Fabrizio; Cubeddu, Rinaldo; Danesini, Gianmaria

    2003-07-01

    What is to our knowledge the first instrument for time-resolved optical mammography operating at wavelengths longer than 900 nm has been developed. It is a scanning system that relies on the acquisition of time-resolved transmittance curves at 683, 785, 912, and 975 nm, with a total measurement time of ~5 min for an entire image. Breast structures and lesions can be discriminated based on the different absorption and scattering properties at the four wavelengths, which reflect different contributions of oxyhemoglobin, deoxyhemoglobin, water, and lipids, as well as distinct structures. The system is currently used in a European clinical trial.

  13. Remote time-resolved filament-induced breakdown spectroscopy of biological materials

    NASA Astrophysics Data System (ADS)

    Xu, H. L.; Liu, W.; Chin, S. L.

    2006-05-01

    We report, for what we believe to be the first time, on the feasibility of remote time-resolved filament-induced breakdown spectroscopy (FIBS) of biological materials. The fluorescence from egg white and yeast powder, induced by femtosecond laser pulse filamentation in air, was detected in the backward direction with targets located 3.5 m away from the detection system. The remarkably distinct spectra of egg white and yeast allow us to propose that this technique, time-resolved FIBS, could be potentially useful for remote detection and identification of harmful biological agents.

  14. Combined single-pulse holography and time-resolved laser schlieren for flow visualization

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Goad, W. K.

    1981-01-01

    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.

  15. Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry

    SciTech Connect

    Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

    2007-11-13

    Time resolved signals in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are studied to determine the influence of experimental parameters on ICP-induced fractionation effects. Differences in sample composition and morphology, i.e., ablating brass, glass, or dust pellets, have a profound effect on the time resolved signal. Helium transport gas significantly decreases large positive signal spikes arising from large particles in the ICP. A binder for pellets also reduces the abundance and amplitude of spikes in the signal. MO{sup +} ions also yield signal spikes, but these MO{sup +} spikes generally occur at different times from their atomic ion counterparts.

  16. Time-Resolved Measurement of Landau-Zener Tunneling in Periodic Potentials

    SciTech Connect

    Zenesini, A.; Radogostowicz, J.; Ciampini, D.; Mannella, R.; Arimondo, E.; Lignier, H.; Morsch, O.; Tayebirad, G.; Wimberger, S.

    2009-08-28

    We report time-resolved measurements of Landau-Zener tunneling of Bose-Einstein condensates in accelerated optical lattices, clearly resolving the steplike time dependence of the band populations. Using different experimental protocols we were able to measure the tunneling probability both in the adiabatic and in the diabatic bases of the system. We also experimentally determine the contribution of the momentum width of the Bose condensates to the temporal width of the tunneling steps and discuss the implications for measuring the jump time in the Landau-Zener problem.

  17. Prospects for Electron Imaging with Ultrafast Time Resolution

    SciTech Connect

    Armstrong, M R; Reed, B W; Torralva, B R; Browning, N D

    2007-01-26

    Many pivotal aspects of material science, biomechanics, and chemistry would benefit from nanometer imaging with ultrafast time resolution. Here we demonstrate the feasibility of short-pulse electron imaging with t10 nanometer/10 picosecond spatio-temporal resolution, sufficient to characterize phenomena that propagate at the speed of sound in materials (1-10 kilometer/second) without smearing. We outline resolution-degrading effects that occur at high current density followed by strategies to mitigate these effects. Finally, we present a model electron imaging system that achieves 10 nanometer/10 picosecond spatio-temporal resolution.

  18. The uses of alternative dispute resolution to resolve genetic disputes. Final report

    SciTech Connect

    Stein, Robert E.

    2003-01-01

    The report sets out lessons learned while carrying out the study. It concludes that genetic disputes will increase in number and that ADR processes including mediation, arbitration, the use of independent experts and court-appointed masters can be helpful in resolving them. It suggests additional effort on bioremediation, and workplace disputes and training for ADR neutrals.

  19. A Resolution in Service: SFX Usage Logs as a Basis for Link Resolver Menu Redesign

    ERIC Educational Resources Information Center

    Highsmith, Anne L.; Ponsford, Bennett Claire

    2011-01-01

    In this study, three years of SFX usage logs at Texas A&M University were analyzed to determine how patrons use link resolver services. The study contrasts the actions taken by users when full text is and is not available and compares public versus staff usage. The results confirmed users' preference for full-text services but also provided…

  20. Proton uptake mechanism of bacteriorhodopsin as determined by time-resolved stroboscopic-FTIR-spectroscopy.

    PubMed

    Souvignier, G; Gerwert, K

    1992-11-01

    Bacteriorhodopsin's proton uptake reaction mechanism in the M to BR reaction pathway was investigated by time-resolved FTIR spectroscopy under physiological conditions (293 K, pH 6.5, 1 M KCl). The time resolution of a conventional fast-scan FTIR spectrometer was improved from 10 ms to 100 mus, using the stroboscopic FTIR technique. Simultaneously, absorbance changes at 11 wavelengths in the visible between 410 and 680 nm were recorded. Global fit analysis with sums of exponentials of both the infrared and visible absorbance changes yields four apparent rate constants, k(7) = 0.3 ms, k(4) = 2.3 ms, k(3) = 6.9 ms, k(6) = 30 ms, for the M to BR reaction pathway. Although the rise of the N and O intermediates is dominated by the same apparent rate constant (k(4)), protein reactions can be attributed to either the N or the O intermediate by comparison of data sets taken at 273 and 293 K. Conceptionally, the Schiff base has to be oriented in its deprotonated state from the proton donor (asp 85) to the proton acceptor (asp 96) in the M(1) to M(2) transition. However, experimentally two different M intermediates are not resolved, and M(2) and N are merged. From the results the following conclusions are drawn: (a) the main structural change of the protein backbone, indicated by amide I, amide II difference bands, takes place in the M to N (conceptionally M(2)) transition. This reaction is proposed to be involved in the "reset switch" of the pump, (b) In the M to N (conceptionally M(2)) transition, most likely, asp-85's carbonyl frequency shifts from 1,762 to 1,753 cm(-1) and persists in O. Protonation of asp-85 explains the red-shift of the absorbance maximum in O. (c) The catalytic proton uptake binding site asp-96 is deprotonated in the M to N transition and is reprotonated in O. PMID:19431858

  1. A time-resolved fluorescence study of matrix-isolated Ag 2

    NASA Astrophysics Data System (ADS)

    Hebert, T.; Kolb, D. M.; Rotermund, H. H.; Schriever, U.; Wiggenhauser, H.

    1990-02-01

    The nanosecond lifetimes of the A, B and C states of Ag 2 in Ar, Kr and Xe matrices were determined by time-resolved emission spectroscopy. From an analysis of the rise and decay times after pulsed optical excitation, the non-radiative relaxation channel between the B and A states was quantitatively established.

  2. Magnetic relaxation studies on a single-molecule magnet by time-resolved inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Waldmann, O.; Carver, G.; Dobe, C.; Biner, D.; Sieber, A.; Güdel, H. U.; Mutka, H.; Ollivier, J.; Chakov, N. E.

    2006-01-01

    Time-resolved inelastic neutron scattering measurements on an array of single-crystals of the single-molecule magnet Mn12ac are presented. The data facilitate a spectroscopic investigation of the slow relaxation of the magnetization in this compound in the time domain.

  3. Fiber-coupled high-speed asynchronous optical sampling with sub-50 fs time resolution.

    PubMed

    Krauss, N; Nast, A; Heinecke, D C; Kölbl, C; Barros, H G; Dekorsy, T

    2015-02-01

    We present a fiber-coupled pump-probe system with a sub-50 fs time resolution and a nanosecond time window, based on high-speed asynchronous optical sampling. By use of a transmission grism pulse compressor, we achieve pump pulses with a pulse duration of 42 fs, an average power of 300 mW and a peak power exceeding 5 kW at a pulse repetition rate of 1 GHz after 6 m of optical fiber. With this system we demonstrate thickness mapping of soft X-ray mirrors at a sub-nm thickness resolution on a cm(2) scan area. In addition, terahertz field generation with resolved spectral components of up to 3.5 THz at a GHz frequency resolution is demonstrated. PMID:25836085

  4. 20 CFR 670.991 - How does Job Corps ensure that complaints or disputes are resolved in a timely fashion?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... provider may be appealed to the DOL Office of Administrative Law Judges under 20 CFR 667.800 or 667.840. ... disputes are resolved in a timely fashion? 670.991 Section 670.991 Employees' Benefits EMPLOYMENT AND... resolved in a timely fashion? (a) If a complaint is not resolved by the center operator or service...

  5. 20 CFR 670.991 - How does Job Corps ensure that complaints or disputes are resolved in a timely fashion?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... provider may be appealed to the DOL Office of Administrative Law Judges under 20 CFR 667.800 or 667.840. ... disputes are resolved in a timely fashion? 670.991 Section 670.991 Employees' Benefits EMPLOYMENT AND... resolved in a timely fashion? (a) If a complaint is not resolved by the center operator or service...

  6. Determination of the optical properties of multilayered phantoms by time-resolved reflectance measurements

    NASA Astrophysics Data System (ADS)

    García, H.; Iriarte, D.; Pomarico, J.; Grosenick, D.; Macdonald, R.

    2015-07-01

    Diffuse optical imaging of the human brain requires methods to account for the layered structure of the head. In this work we present results of experiments performed on layered phantoms in reflection geometry by a time-resolved technique. We investigate structures with two and three layers with the goal to retrieve the optical properties of the deepest one. Data analysis is based on an existing solution of the time-resolved diffusion equation for a multilayer cylinder. Using a sufficiently large source-detector separation the absorption and reduced scattering coefficients of the deepest layer can be derived from time-resolved reflectance with a deviation of typically not more than 10% from the known values.

  7. 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

  8. A high-resolution 2D J-resolved NMR detection technique for metabolite analyses of biological samples

    PubMed Central

    Huang, Yuqing; Zhang, Zhiyong; Chen, Hao; Feng, Jianghua; Cai, Shuhui; Chen, Zhong

    2015-01-01

    NMR spectroscopy is a commonly used technique for metabolite analyses. Due to the observed macroscopic magnetic susceptibility in biological tissues, current NMR acquisitions in measurements of biological tissues are generally performed on tissue extracts using liquid NMR or on tissues using magic-angle spinning techniques. In this study, we propose an NMR method to achieve high-resolution J-resolved information for metabolite analyses directly from intact biological samples. A dramatic improvement in spectral resolution is evident in our contrastive demonstrations on a sample of pig brain tissue. Metabolite analyses for a postmortem fish from fresh to decayed statuses are presented to further reveal the capability of the proposed method. This method is a previously-unreported high-resolution 2D J-resolved spectroscopy for biological applications without specialised hardware requirements or complicated sample pretreatments. It provides a significant contribution to metabolite analyses of biological samples, and may be potentially applicable to in vivo samples. Furthermore, this method also can be applied to measurements of semisolid and viscous samples. PMID:25670027

  9. High-resolution nuclear magnetic resonance measurements in inhomogeneous magnetic fields: A fast two-dimensional J-resolved experiment

    NASA Astrophysics Data System (ADS)

    Huang, Yuqing; Lin, Yung-Ya; Cai, Shuhui; Yang, Yu; Sun, Huijun; Lin, Yanqin; Chen, Zhong

    2016-03-01

    High spectral resolution in nuclear magnetic resonance (NMR) is a prerequisite for achieving accurate information relevant to molecular structures and composition assignments. The continuous development of superconducting magnets guarantees strong and homogeneous static magnetic fields for satisfactory spectral resolution. However, there exist circumstances, such as measurements on biological tissues and heterogeneous chemical samples, where the field homogeneity is degraded and spectral line broadening seems inevitable. Here we propose an NMR method, named intermolecular zero-quantum coherence J-resolved spectroscopy (iZQC-JRES), to face the challenge of field inhomogeneity and obtain desired high-resolution two-dimensional J-resolved spectra with fast acquisition. Theoretical analyses for this method are given according to the intermolecular multiple-quantum coherence treatment. Experiments on (a) a simple chemical solution and (b) an aqueous solution of mixed metabolites under externally deshimmed fields, and on (c) a table grape sample with intrinsic field inhomogeneity from magnetic susceptibility variations demonstrate the feasibility and applicability of the iZQC-JRES method. The application of this method to inhomogeneous chemical and biological samples, maybe in vivo samples, appears promising.

  10. High-resolution nuclear magnetic resonance measurements in inhomogeneous magnetic fields: A fast two-dimensional J-resolved experiment.

    PubMed

    Huang, Yuqing; Lin, Yung-Ya; Cai, Shuhui; Yang, Yu; Sun, Huijun; Lin, Yanqin; Chen, Zhong

    2016-03-14

    High spectral resolution in nuclear magnetic resonance (NMR) is a prerequisite for achieving accurate information relevant to molecular structures and composition assignments. The continuous development of superconducting magnets guarantees strong and homogeneous static magnetic fields for satisfactory spectral resolution. However, there exist circumstances, such as measurements on biological tissues and heterogeneous chemical samples, where the field homogeneity is degraded and spectral line broadening seems inevitable. Here we propose an NMR method, named intermolecular zero-quantum coherence J-resolved spectroscopy (iZQC-JRES), to face the challenge of field inhomogeneity and obtain desired high-resolution two-dimensional J-resolved spectra with fast acquisition. Theoretical analyses for this method are given according to the intermolecular multiple-quantum coherence treatment. Experiments on (a) a simple chemical solution and (b) an aqueous solution of mixed metabolites under externally deshimmed fields, and on (c) a table grape sample with intrinsic field inhomogeneity from magnetic susceptibility variations demonstrate the feasibility and applicability of the iZQC-JRES method. The application of this method to inhomogeneous chemical and biological samples, maybe in vivo samples, appears promising. PMID:26979686

  11. A high-resolution 2D J-resolved NMR detection technique for metabolite analyses of biological samples.

    PubMed

    Huang, Yuqing; Zhang, Zhiyong; Chen, Hao; Feng, Jianghua; Cai, Shuhui; Chen, Zhong

    2015-01-01

    NMR spectroscopy is a commonly used technique for metabolite analyses. Due to the observed macroscopic magnetic susceptibility in biological tissues, current NMR acquisitions in measurements of biological tissues are generally performed on tissue extracts using liquid NMR or on tissues using magic-angle spinning techniques. In this study, we propose an NMR method to achieve high-resolution J-resolved information for metabolite analyses directly from intact biological samples. A dramatic improvement in spectral resolution is evident in our contrastive demonstrations on a sample of pig brain tissue. Metabolite analyses for a postmortem fish from fresh to decayed statuses are presented to further reveal the capability of the proposed method. This method is a previously-unreported high-resolution 2D J-resolved spectroscopy for biological applications without specialised hardware requirements or complicated sample pretreatments. It provides a significant contribution to metabolite analyses of biological samples, and may be potentially applicable to in vivo samples. Furthermore, this method also can be applied to measurements of semisolid and viscous samples. PMID:25670027

  12. Overpressure wave interaction with droplets: time resolved measurements by laser shadowscopy

    NASA Astrophysics Data System (ADS)

    Slangen, Pierre; Aprin, Laurent; Heymes, Frédéric; Munier, Laurent; Lapébie, Emmanuel; Dusserre, Gilles

    2012-10-01

    Risk sciences involve increasingly optics applications to perform accurate analysis of critical behavior such as failures, explosions, fires. In this particular context, different area sizes are investigated under high temporal sampling rate up to 10000fps. With the improvement of light sources and optical sensors, it is now possible to cope with high spatial resolution even for time resolved measurement. The paper deals with the study of the interaction between overpressure waves, occurring in case of explosion for example, with a liquid droplet present in the vicinity of the overpressure wave. This is a typical scenario encountered in case of industrial breakdown including liquid leakage and explosions. We designed an experimental setup for the evaluation of the interaction between the overpressure wave and falling liquid droplets. A gas chamber is filled with nitrogen until breakage of the outlet rupture disk at about 4 bar. The droplets fall is controlled by an automatic syringe injector placed in the overpressure wave. The imaging system is based on laser shadowscopy. The laser source is a double cavity 15mJ- 1000Hz Nd YLF laser emitting double pulses of about 10ns at 527nm. To record the double pulse after crossing the falling droplets, the transmitted light is captured by a lasersynchronized double frame camera. Since these measurements are time-synchronized, it is then possible to know accurately the different parameters of the phenomenon, such as overpressure wave velocity, droplets diameter, and Reynolds number. Different experiments have been carried out at about 4000 doubleframe/s. The paper presents the whole experiment, the enhancements of the setup and the results for different liquid products from water to acetone.

  13. Time-resolved holography for the microscopic study of crack-tip motion in dynamic fracture

    NASA Astrophysics Data System (ADS)

    Steckenrider, John Scott

    A novel laser system has been designed and developed for the time-resolved holographic analysis of dynamic crack propagation with a frame-to-frame resolution of from 28.3 to 161.6 ns. Average velocities of approximately 1300 m/s were measured in macroscopic (1.2 mm thick) glass specimens, and velocities of 1200 m/s were measured in microscopic (0.15 mm thick) glass specimens. Holographic analyses were conducted using both diffuse and direct laser illumination, demonstrating a broad range of applicability for this method. Normalized crack length versus time plots were generated for a series of specimens with pre-crack lengths of from 3.5 to 10.5 mm wing various pre-load levels and initiating explosive sizes. All specimens exhibited similar dynamic fracture behavior, particularly those outside of the region of shock of the initiating explosive (those of the longer pre-crack set). A best-fit to the theoretical prediction for mode I crack growth revealed a good match to the case for a specimen overloaded by 64 percent. However, no variation with applied load was evident, indicating that an immediate acceleration to a velocity of approximately 1200 m/s (near the empirically determined terminal velocity) was the more plausible fit. Since the terminal velocity was approximately the same for all specimens, this investigation also demonstrated that the terminal velocity is independent of crack-tip stresses, even for the most extreme explosive pulses. In addition, a different loading configuration was attempted in which the specimen was shielded from the explosive shock. The resulting crack growth behavior displayed a velocity well below the aforementioned terminal velocity, indicating an acceleration was present. However, owing to the lack of reproducibility in this method of loading, repeated experiments were not possible. Finally, applications of the described laser system for use in laser ultrasonics were investigated, and these results are included.

  14. A high-resolution time-to-digital converter using a three-level resolution

    NASA Astrophysics Data System (ADS)

    Dehghani, Asma; Saneei, Mohsen; Mahani, Ali

    2016-08-01

    In this article, a three-level resolution Vernier delay line time-to-digital converter (TDC) was proposed. The proposed TDC core was based on the pseudo-differential digital architecture that made it insensitive to nMOS and pMOS transistor mismatches. It also employed a Vernier delay line (VDL) in conjunction with an asynchronous read-out circuitry. The time interval resolution was equal to the difference of delay between buffers of upper and lower chains. Then, via the extra chain included in the lower delay line, resolution was controlled and power consumption was reduced. This method led to high resolution and low power consumption. The measurement results of TDC showed a resolution of 4.5 ps, 12-bit output dynamic range, and integral nonlinearity of 1.5 least significant bits. This TDC achieved the consumption of 68.43 µW from 1.1-V supply.

  15. Mapping atomic motions with ultrabright electrons: towards fundamental limits in space-time resolution.

    PubMed

    Manz, Stephanie; Casandruc, Albert; Zhang, Dongfang; Zhong, Yinpeng; Loch, Rolf A; Marx, Alexander; Hasegawa, Taisuke; Liu, Lai Chung; Bayesteh, Shima; Delsim-Hashemi, Hossein; Hoffmann, Matthias; Felber, Matthias; Hachmann, Max; Mayet, Frank; Hirscht, Julian; Keskin, Sercan; Hada, Masaki; Epp, Sascha W; Flöttmann, Klaus; Miller, R J Dwayne

    2015-01-01

    The long held objective of directly observing atomic motions during the defining moments of chemistry has been achieved based on ultrabright electron sources that have given rise to a new field of atomically resolved structural dynamics. This class of experiments requires not only simultaneous sub-atomic spatial resolution with temporal resolution on the 100 femtosecond time scale but also has brightness requirements approaching single shot atomic resolution conditions. The brightness condition is in recognition that chemistry leads generally to irreversible changes in structure during the experimental conditions and that the nanoscale thin samples needed for electron structural probes pose upper limits to the available sample or "film" for atomic movies. Even in the case of reversible systems, the degree of excitation and thermal effects require the brightest sources possible for a given space-time resolution to observe the structural changes above background. Further progress in the field, particularly to the study of biological systems and solution reaction chemistry, requires increased brightness and spatial coherence, as well as an ability to tune the electron scattering cross-section to meet sample constraints. The electron bunch density or intensity depends directly on the magnitude of the extraction field for photoemitted electron sources and electron energy distribution in the transverse and longitudinal planes of electron propagation. This work examines the fundamental limits to optimizing these parameters based on relativistic electron sources using re-bunching cavity concepts that are now capable of achieving 10 femtosecond time scale resolution to capture the fastest nuclear motions. This analysis is given for both diffraction and real space imaging of structural dynamics in which there are several orders of magnitude higher space-time resolution with diffraction methods. The first experimental results from the Relativistic Electron Gun for Atomic

  16. Development and characterization of a time-, position- and energy-resolved x-ray diagnostic for PBFA II target experiments

    SciTech Connect

    Derzon, M.S.; Filuk, A.B.; Pantuso, J.; Dukart, R.J.; Olsen, R.; Barber, T.; Bernard, M.

    1992-12-31

    A time-, position- and energy-resolved soft x-ray (100--500 eV) diagnostic is being developed for PBFA II target experiments. The diagnostic provides measurements of hydrodynamic motion and thermal gradients in light-ion fusion targets. A slit-image of the source is imprinted onto thin sheets (20{mu}m) of organic scintillator to create a one-dimensional image. The scintillator light is then proximity-coupled to a linear array of fiber-optics that transports the light to a streak camera that is operated without an intensifier. The streak camera output is recorded on a charge-coupled-device (CCD) camera. We are characterizing the spatial and temporal resolutions of the systems. This is done by collecting data from as many as 90 individual fibers and correcting for variations in throughput and the effects of spatial resolution to roughly 5% standard deviation in their relative throughput. Spatial resolution of these systems at the source is approximately 0.4 mm. Timing resolution is nominally 2 ns and it is limited primarily by the scintillator response and dispersion in the 50-m-long fiber array. We describe the measurement techniques and the results of the characterization.

  17. High-resolution J-resolved NMR spectra of dilute spins in solids

    NASA Astrophysics Data System (ADS)

    Terao, T.; Miura, H.; Saika, A.

    1981-08-01

    A technique for obtaining J-resolved NMR spectra of dilute spins in solids has been developed. It is based on the observation that a combination of magic-angle irradiation and magic-angle spinning removes dipolar broadening, but leaves indirect spin-spin coupling. A preliminary application of this technique to adamantane clearly reveals the AX (J = 121 Hz) and AX (J = 135 Hz) multiplets in the methylene and methyne 13C spectrum, respectively.

  18. Advances in ultrafast time resolved fluorescence physics for cancer detection in optical biopsy

    NASA Astrophysics Data System (ADS)

    Alfano, R. R.

    2012-03-01

    We discuss the use of time resolved fluorescence spectroscopy to extract fundamental kinetic information on molecular species in tissues. The temporal profiles reveal the lifetime and amplitudes associated with key active molecules distinguishing the local spectral environment of tissues. The femtosecond laser pulses at 310 nm excite the tissue. The emission profile at 340 nm from tryptophan is non-exponential due to the micro-environment. The slow and fast amplitudes and lifetimes of emission profiles reveal that cancer and normal states can be distinguished. Time resolved optical methods offer a new cancer diagnostic modality for the medical community.

  19. 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.

  20. Ultrasensitive time-resolved linear dichroism spectral measurements using near-crossed linear polarizers

    NASA Astrophysics Data System (ADS)

    Che, Diping; Shapiro, Daniel B.; Esquerra, Raymond M.; Kliger, David S.

    1994-07-01

    A simple and sensitive technique is introduced to measure time-resolved linear dichroism of spectral transitions. This technique uses the fact that a linear dichroic sample rotates the polarization plane of linearly polarized light. The theoretical basis of the technique is presented using Mueller calculus and a detailed signal analysis is given to account for the effects of various optical imperfections. The results of this analysis are confirmed with the application of the technique to the time-resolved linear dichroism of bacteriorhodopsin in membrane patches (purple membrane) during its photocycle. These experimental results demonstrate the sentivity of the technique.