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Sample records for resolving nonstationary spectral

  1. On Holo-Hilbert spectral analysis: a full informational spectral representation for nonlinear and non-stationary data.

    PubMed

    Huang, Norden E; Hu, Kun; Yang, Albert C C; Chang, Hsing-Chih; Jia, Deng; Liang, Wei-Kuang; Yeh, Jia Rong; Kao, Chu-Lan; Juan, Chi-Hung; Peng, Chung Kang; Meijer, Johanna H; Wang, Yung-Hung; Long, Steven R; Wu, Zhauhua

    2016-04-13

    The Holo-Hilbert spectral analysis (HHSA) method is introduced to cure the deficiencies of traditional spectral analysis and to give a full informational representation of nonlinear and non-stationary data. It uses a nested empirical mode decomposition and Hilbert-Huang transform (HHT) approach to identify intrinsic amplitude and frequency modulations often present in nonlinear systems. Comparisons are first made with traditional spectrum analysis, which usually achieved its results through convolutional integral transforms based on additive expansions of an a priori determined basis, mostly under linear and stationary assumptions. Thus, for non-stationary processes, the best one could do historically was to use the time-frequency representations, in which the amplitude (or energy density) variation is still represented in terms of time. For nonlinear processes, the data can have both amplitude and frequency modulations (intra-mode and inter-mode) generated by two different mechanisms: linear additive or nonlinear multiplicative processes. As all existing spectral analysis methods are based on additive expansions, either a priori or adaptive, none of them could possibly represent the multiplicative processes. While the earlier adaptive HHT spectral analysis approach could accommodate the intra-wave nonlinearity quite remarkably, it remained that any inter-wave nonlinear multiplicative mechanisms that include cross-scale coupling and phase-lock modulations were left untreated. To resolve the multiplicative processes issue, additional dimensions in the spectrum result are needed to account for the variations in both the amplitude and frequency modulations simultaneously. HHSA accommodates all the processes: additive and multiplicative, intra-mode and inter-mode, stationary and non-stationary, linear and nonlinear interactions. The Holo prefix in HHSA denotes a multiple dimensional representation with both additive and multiplicative capabilities. PMID:26953180

  2. On Holo-Hilbert spectral analysis: a full informational spectral representation for nonlinear and non-stationary data

    PubMed Central

    Huang, Norden E.; Hu, Kun; Yang, Albert C. C.; Chang, Hsing-Chih; Jia, Deng; Liang, Wei-Kuang; Yeh, Jia Rong; Kao, Chu-Lan; Juan, Chi-Hung; Peng, Chung Kang; Meijer, Johanna H.; Wang, Yung-Hung; Long, Steven R.; Wu, Zhauhua

    2016-01-01

    The Holo-Hilbert spectral analysis (HHSA) method is introduced to cure the deficiencies of traditional spectral analysis and to give a full informational representation of nonlinear and non-stationary data. It uses a nested empirical mode decomposition and Hilbert–Huang transform (HHT) approach to identify intrinsic amplitude and frequency modulations often present in nonlinear systems. Comparisons are first made with traditional spectrum analysis, which usually achieved its results through convolutional integral transforms based on additive expansions of an a priori determined basis, mostly under linear and stationary assumptions. Thus, for non-stationary processes, the best one could do historically was to use the time–frequency representations, in which the amplitude (or energy density) variation is still represented in terms of time. For nonlinear processes, the data can have both amplitude and frequency modulations (intra-mode and inter-mode) generated by two different mechanisms: linear additive or nonlinear multiplicative processes. As all existing spectral analysis methods are based on additive expansions, either a priori or adaptive, none of them could possibly represent the multiplicative processes. While the earlier adaptive HHT spectral analysis approach could accommodate the intra-wave nonlinearity quite remarkably, it remained that any inter-wave nonlinear multiplicative mechanisms that include cross-scale coupling and phase-lock modulations were left untreated. To resolve the multiplicative processes issue, additional dimensions in the spectrum result are needed to account for the variations in both the amplitude and frequency modulations simultaneously. HHSA accommodates all the processes: additive and multiplicative, intra-mode and inter-mode, stationary and non-stationary, linear and nonlinear interactions. The Holo prefix in HHSA denotes a multiple dimensional representation with both additive and multiplicative capabilities. PMID:26953180

  3. Spectral resolvability of iterated rippled noise

    NASA Astrophysics Data System (ADS)

    Yost, William A.

    2005-04-01

    A forward-masking experiment was used to estimate the spectral ripple of iterated rippled noise (IRN) that is possibly resolved by the auditory system. Tonal signals were placed at spectral peaks and valleys of IRN maskers for a wide variety of IRN conditions that included different delays, number of iterations, and stimulus durations. The differences in the forward-masked thresholds of tones at spectral peaks and valleys were used to estimate spectral resolvability, and these results were compared to estimates obtained from a gamma-tone filter bank. The IRN spectrum has spectral peaks that are harmonics of the reciprocal of the delay used to generate IRN stimuli. As the number of iterations in the generation of IRN stimuli increases so does the difference in the spectral peak-to-valley ratio. For high number of iterations, long delays, and long durations evidence for spectral resolvability existed up to the 6th harmonic. For all other conditions spectral resolvability appeared to disappear at harmonics lower than the 6th, or was not measurable at all. These data will be discussed in terms of the role spectral resolvability might play in processing the pitch, pitch strength, and timbre of IRN stimuli. [Work supported by a grant from NIDCD.

  4. A two dimensional power spectral estimate for some nonstationary processes. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Smith, Gregory L.

    1989-01-01

    A two dimensional estimate for the power spectral density of a nonstationary process is being developed. The estimate will be applied to helicopter noise data which is clearly nonstationary. The acoustic pressure from the isolated main rotor and isolated tail rotor is known to be periodically correlated (PC) and the combined noise from the main and tail rotors is assumed to be correlation autoregressive (CAR). The results of this nonstationary analysis will be compared with the current method of assuming that the data is stationary and analyzing it as such. Another method of analysis is to introduce a random phase shift into the data as shown by Papoulis to produce a time history which can then be accurately modeled as stationary. This method will also be investigated for the helicopter data. A method used to determine the period of a PC process when the period is not know is discussed. The period of a PC process must be known in order to produce an accurate spectral representation for the process. The spectral estimate is developed. The bias and variability of the estimate are also discussed. Finally, the current method for analyzing nonstationary data is compared to that of using a two dimensional spectral representation. In addition, the method of phase shifting the data is examined.

  5. Resolvent approach for two-dimensional scattering problems. Application to the nonstationary Schrödinger problem and the KPI equation

    NASA Astrophysics Data System (ADS)

    Boiti, M.; Pempinelli, F.; Pogrebkov, A. K.; Polivanov, M. C.

    1992-11-01

    The resolvent operator of the linear problem is determined as the full Green function continued in the complex domain in two variables. An analog of the known Hilbert identity is derived. We demonstrate the role of this identity in the study of two-dimensional scattering. Considering the nonstationary Schrödinger equation as an example, we show that all types of solutions of the linear problems, as well as spectral data known in the literature, are given as specific values of this unique function — the resolvent function. A new form of the inverse problem is formulated.

  6. Using the nonstationary spectral method to analyze asymptotic macrodispersion in uniformly recharged heterogeneous aquifers

    NASA Astrophysics Data System (ADS)

    Chang, Ching-Min; Yeh, Hund-Der

    2008-02-01

    SummaryThis paper describes an investigation of the influence of uniformly distributed groundwater recharge on asymptotic macrodispersion in two-dimensional heterogeneous media. This is performed using a nonstationary spectral approach [Li, S.-G., McLaughlin, D., 1991. A nonstationary spectral method for solving stochastic groundwater problems: unconditional analysis. Water Resour. Res. 27 (7), 1589-1605; Li, S.-G., McLaughlin, D., 1995. Using the nonstationary spectral method to analyze flow through heterogeneous trending media. Water Resour. Res. 31 (3), 541-551] based on Fourier-Stieltjes representations for the perturbed quantities. To solve the problem analytically, focus is placed on the case where the local longitudinal dispersivity αL is much smaller than the integral scale of log transmissivity λ (i.e., αL/ λ ≪ 1). The closed-form expressions are obtained for describing the spectrum of flow velocity, the variability of flow velocity and asymptotic macrodispersion, in terms of the statistical properties and the integral scale of log transmissivity, local transport parameters and a parameter β [Rubin, Y., Bellin, A., 1994. The effects of recharge on flow nonuniformity and macrodispersion. Water Resour. Res. 30 (4), 939-948] used to characterize the degree of flow nonuniformity due to the groundwater recharge. The impact of β on these results is examined.

  7. Enhancing the resolution of non-stationary seismic data using improved time-frequency spectral modelling

    NASA Astrophysics Data System (ADS)

    Zhou, Huai-lai; Wang, Chang-cheng; Marfurt, Kurt J.; Jiang, Yi-wei; Bi, Jian-xia

    2016-04-01

    Maximizing vertical resolution is a key objective in seismic data processing. Early deconvolution and spectral balancing algorithms assumed that the seismic source wavelet was temporally invariant, or stationary. In practice, seismic scattering and attenuation give rise to non-stationary seismic source wavelets. To address this issue, most conventional time-varying deconvolution wavelet shaping and spectral modelling techniques using the stationary polynomial fitting assume the wavelet to be locally stationary within a small number of overlapping analysis windows while the fitting coefficients are invariant with all the frequencies. In this paper, we show an improvement obtained by modelling smoothly varying spectra of the seismic wavelet using non-stationary polynomial fitting in the time-frequency domain. We first decompose each seismic trace using a generalized S-transform that provides a good time-frequency distribution for the estimation of the time-varying wavelet spectra. We then model the slowly varying source wavelet spectrum at each time sample by a smooth low-order polynomial. Finally, we spectrally balance the modelled wavelet to flatten the seismic response, thereby increasing vertical resolution. We calibrate the algorithm on a simple synthetic and then apply it to a 3-D land survey acquired in western China, showing the value on both vertical slices through seismic amplitude and attribute time slices. Our new algorithm significantly improves the vertical resolution of the seismic signal, while not increasing the noise.

  8. Spatially resolved spectral-imaging device

    DOEpatents

    Bloom, Joshua Simon; Tyson, John Anthony

    2016-02-09

    A spatially resolved spectral device comprising a dispersive array to receive an incident light comprising a principal ray. The dispersive array comprising a plurality of dichroic layers, each of the plurality of dichroic layers disposed in a path of a direction of the principal ray. Each of the plurality of dichroic layers configured to at least one of reflect or transmit a different wavelength range of the incident light. The device further comprising a detection array operatively coupled with the dispersive array. The detection array comprising a photosensitive component including a plurality of detection pixels, each of the plurality of detection pixels having a light-receiving surface disposed parallel to the direction of the principal ray to detect a respective one of the different wavelength ranges of incident light reflected from a corresponding one of the plurality of dichroic layers.

  9. Theoretical study of multispectral structured illumination for depth resolved imaging of non-stationary objects: focus on retinal imaging

    PubMed Central

    Gruppetta, Steve; Chetty, Sabah

    2011-01-01

    Current implementations of structured illumination microscopy for depth-resolved (three-dimensional) imaging have limitations that restrict its use; specifically, they are not applicable to non-stationary objects imaged with relatively poor condenser optics and in non-fluorescent mode. This includes in-vivo retinal imaging. A novel implementation of structured illumination microscopy is presented that overcomes these issues. A three-wavelength illumination technique is used to obtain the three sub-images required for structured illumination simultaneously rather than sequentially, enabling use on non-stationary objects. An illumination method is presented that produces an incoherent pattern through interference, bypassing the limitations imposed by the aberrations of the condenser lens and thus enabling axial sectioning in non-fluorescent imaging. The application to retinal imaging can lead to a device with similar sectioning capabilities to confocal microscopy without the optical complexity (and cost) required for scanning systems. PMID:21339871

  10. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

    NASA Astrophysics Data System (ADS)

    Kumar, Ajitesh; Karthick Kumar, S. K.; Gupta, Aditya; Goswami, Debabrata

    2010-12-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  11. Spectrally resolved femtosecond photon echo spectroscopy of astaxanthin

    NASA Astrophysics Data System (ADS)

    Kumar, Ajitesh; Karthick Kumar, S. K.; Gupta, Aditya; Goswami, Debabrata

    2011-08-01

    We have studied the coherence and population dynamics of Astaxanthin solution in methanol and acetonitrile by spectrally resolving their photon echo signals. Our experiments indicate that methanol has a much stronger interaction with the ultrafast dynamics of Astaxanthin in comparison to that of acetonitrile.

  12. Modeling and image reconstruction in spectrally resolved bioluminescence tomography

    NASA Astrophysics Data System (ADS)

    Dehghani, Hamid; Pogue, Brian W.; Davis, Scott C.; Patterson, Michael S.

    2007-02-01

    Recent interest in modeling and reconstruction algorithms for Bioluminescence Tomography (BLT) has increased and led to the general consensus that non-spectrally resolved intensity-based BLT results in a non-unique problem. However, the light emitted from, for example firefly Luciferase, is widely distributed over the band of wavelengths from 500 nm to 650 nm and above, with the dominant fraction emitted from tissue being above 550 nm. This paper demonstrates the development of an algorithm used for multi-wavelength 3D spectrally resolved BLT image reconstruction in a mouse model. It is shown that using a single view data, bioluminescence sources of up to 15 mm deep can be successfully recovered given correct information about the underlying tissue absorption and scatter.

  13. Spectral-resolved multifocal multiphoton microscopy with multianode photomultiplier tubes

    PubMed Central

    Cha, Jae Won; Tzeranis, Dimitrios; Subramanian, Jaichandar; Yannas, Ioannis V.; Nedivi, Elly; So, Peter T. C.

    2014-01-01

    Multiphoton excitation fluorescence microscopy is the preferred method for in vivo deep tissue imaging. Many biological applications demand both high imaging speed and the ability to resolve multiple fluorophores. One of the successful methods to improve imaging speed in a highly turbid specimen is multifocal multiphoton microscopy (MMM) based on use of multi-anode photomultiplier tubes (MAPMT). This approach improves imaging speed by using multiple foci for parallelized excitation without sacrificing signal to noise ratio (SNR) due to the scattering of emission photons. In this work, we demonstrate that the MAPMT based MMM can be extended with spectral resolved imaging capability. Instead of generating multiple excitation foci in a 2D grid pattern, a linear array of foci is generated. This leaves one axis of the 2D MAPMT available for spectral dispersion and detection. The spectral-resolved MMM can detect several emission signals simultaneously with high imaging speed optimized for high-throughput, high-contents applications. The new procedure is illustrated using imaging data from the kidney, peripheral nerve regeneration and dendritic morphological data from the brain. PMID:25321515

  14. 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.

  15. The Sun's spectrally resolved center-to-limb variation

    NASA Astrophysics Data System (ADS)

    Stenflo, Jan Olof

    2016-05-01

    The center-to-limb variation (CLV) of the Sun's continuous spectrum is well known and has served as a major observational constraint on models of the solar atmosphere. The CLV however also varies dramatically with wavelength inside each spectral line. Here we report on two new atlases that show the properties of the CLV with high spectral resolution. One is a fully resolved spectral atlas from 4084 to 9950 Å of the ratio between the near limb spectrum, at 10 arcsec inside the limb, and the disk center spectrum, both recorded with the FTS at NSO/Kitt Peak. The other atlas gives the same kind of information but covers the whole range of limb distances by giving the ratio spectra for the nine μ positions 0.1, 0.2, …, 0.9. This set of nine atlases for different μ have been recorded over the last couple of years with the solar facility at IRSOL (Istituto Ricerche Solari Locarno) in Switzerland. We find that the CLV is spectrally as richly structured as the ordinary intensity spectrum, but the structuring is different and contains diagnostic information that is not contained in the intensity spectrum. Here we illustrate the properties of the new spectral structures and discuss what they mean.

  16. Phase Resolved X-ray Spectral Analysis of Soft IPs

    NASA Astrophysics Data System (ADS)

    Pekon, Yakup

    2016-07-01

    As a subclass of Cataclysmic Variables, Intermediate Polars (IPs) are magnetic systems which mainly show hard X-ray emission. However, there have been an increasing number of systems that also show a soft emission component arising from reprocessed X-rays from the white dwarf limbs. Due to their relatively short periods, they pose as good canditates to perform phase resolved analysis. In this work, X-ray phase resolved spectral analysis of selected IPs with soft X-ray emission components (such as PQ Gem, V2069 Cyg etc.) over the orbital and/or spin periods will be presented. The analyses will help a better understanding of the complex absorption mechanisms and the nature of the soft X-ray emissions in soft IPs.

  17. Spectrally resolved photon-echo spectroscopy of Rhodamine-6G

    PubMed Central

    Kumar, Ajitesh; Karthick, S. K.; Goswami, D.

    2013-01-01

    Wavelength dependent study of a laser dye: Rhodamine-6G (Rh6G) by using spectrally resolved photon-echo spectroscopy is presented. The coherence and population dynamics of Rh6G solution in methanol changes as the excitation wavelength is tuned near its absorption maxima of 528 nm. Specifically, the central wavelength of the femtosecond laser pulse was set to 535 nm and to 560 nm while the respective spectra of the photon-echo signals were collected. This gives information on how the ultrafast dynamics of the Rh6G molecule changes with a change in the excitation wavelength. PMID:24098869

  18. Spectrally resolved laser-induced fluorescence for bioaerosols standoff detection

    NASA Astrophysics Data System (ADS)

    Buteau, Sylvie; Stadnyk, Laurie; Rowsell, Susan; Simard, Jean-Robert; Ho, Jim; Déry, Bernard; McFee, John

    2007-09-01

    An efficient standoff biological warfare detection capability could become an important asset for both defence and security communities based on the increasing biological threat and the limits of the presently existing protection systems. Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF). This LIDAR system named SINBAHD monitors the spectrally resolved LIF originating from inelastic interactions with bioaerosols present in atmospheric cells customizable in size and in range. SINBAHD has demonstrated the capability of near real-time detection and classification of bioaerosolized threats at multi-kilometre ranges. In spring 2005, DRDC has initiated the BioSense demonstration project, which combines the SINBAHD technology with a geo-referenced Near InfraRed (NIR) LIDAR cloud mapper. SINBAHD is now being used to acquire more signatures to add in the spectral library and also to optimize and test the new BioSense algorithm strategy. In September 2006, SINBAHD has participated in a two-week trial held at DRDC-Suffield where different open-air wet releases of live and killed bioagent simulants, growth media and obscurants were performed. An autoclave killing procedure was performed on two biological materials (Bacillus subtilis var globigii or BG, and Bacillus thuringiensis or Bt) before being aerosolized, disseminated and spectrally characterized with SINBAHD. The obtained results showed no significant impact of this killing process on their normalised spectral signature in comparison with their live counterparts. Correlation between the detection signals from SINBAHD, an array of slit samplers and a FLuorescent Aerosol Particle Sensor (C-FLAPS) was obtained and SINBAHD's sensitivity could then be estimated. At the 2006 trial, a detection limit of a few tens of Agent Containing Particles per Liter of Air (ACPLA) was obtained

  19. Spectrally resolved motional Stark effect measurements on ASDEX Upgrade

    SciTech Connect

    Reimer, R.; Dinklage, A.; Wolf, R.; Fischer, R.; Hobirk, J.; Löbhard, T.; Mlynek, A.; Reich, M.; Sawyer, L.; Collaboration: ASDEX Upgrade

    2013-11-15

    A spectrally resolved Motional Stark Effect (MSE) diagnostic has been installed at ASDEX Upgrade. The MSE data have been fitted by a forward model providing access to information about the magnetic field in the plasma interior [R. Reimer, A. Dinklage, J. Geiger et al., Contrib. Plasma Phys. 50, 731–735 (2010)]. The forward model for the beam emission spectra comprises also the fast ion D{sub α} signal [W. W. Heidbrink and G. J. Sadler, Nucl. Fusion 34, 535–615 (1994)] and the smearing on the CCD-chip. The calculated magnetic field data as well as the revealed (dia)magnetic effects are consistent with the results from equilibrium reconstruction solver. Measurements of the direction of the magnetic field are affected by unknown and varying polarization effects in the observation.

  20. Spectrally resolved white light interferometry to measure material dispersion over a wide spectral band in a single acquisition.

    PubMed

    Arosa, Yago; Lago, Elena López; Varela, Luis Miguel; de la Fuente, Raúl

    2016-07-25

    In this paper we apply spectrally resolved white light interferometry to measure refractive and group index over a wide spectral band from 400 to 1000 nm. The output of a Michelson interferometer is spectrally decomposed by a homemade prism spectrometer with a high resolution camera. The group index is determined directly from the phase extracted from the spectral interferogram while the refractive index is estimated once its value at a given wavelength is known. PMID:27464179

  1. Structural investigations of human hairs by spectrally resolved ellipsometry

    NASA Astrophysics Data System (ADS)

    Schulz, Benjamin; Chan, D.; Ruebhausen, M.; Wessel, S.; Wepf, R.

    2006-03-01

    Human hair is a biological layered system composed of two major layers, the cortex and the cuticle. We show spectrally resolved ellipsometry measurements of the ellipsometric parameters ψ and δ of single human hairs. The spectra reflect the layered nature of hair and the optical anisotropy of the hair’s structure. In addition, measurements on strands of human hair show a high reproducibility of the ellipsometric parameters for different hair fiber bundles from the same person. Based on the measurements, we develop a model of the dielectric function of hair that explains the spectra. This model includes the dielectric properties of the cuticle and cortex as well as their associated layer thicknesses. In addition, surface roughness effects modelled by a roughness layer with an complex refractive index given by an effective medium approach can have a significant effect on the measurements. We derive values for the parameters of the cuticle surface roughness layer of the thickness dACu= 273-360 nm and the air inclusion fA= 0.6 -5.7%. [1] accepted for publication in J. Biomed Opt., 2005

  2. Spectrally Resolved Magnetic Resonance Imaging of the XenonBiosensor

    SciTech Connect

    Hilty, Christian; Lowery, Thomas; Wemmer, David; Pines, Alexander

    2005-07-15

    Due to its ability to non-invasively record images, as well as elucidate molecular structure, nuclear magnetic resonance is the method of choice for applications as widespread as chemical analysis and medical diagnostics. Its detection threshold is, however, limited by the small polarization of nuclear spins in even the highest available magnetic fields. This limitation can, under certain circumstances, be alleviated by using hyper-polarized substances. Xenon biosensors make use of the sensitivity gain of hyperpolarized xenon to provide magnetic resonance detection capability for a specific low-concentration target. They consist of a cryptophane cage, which binds one xenon atom, and which has been connected via a linker to a targeting moiety such as a ligand or antibody. Recent work has shown the possibility of using the xenon biosensor to detect small amounts of a substance in a heterogeneous environment by NMR. Here, we demonstrate that magnetic resonance (MR) provides the capability to obtain spectrally and spatially resolved images of the distribution of immobilized biosensor, opening the possibility for using the xenon biosensor for targeted imaging.

  3. Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

    DOE PAGESBeta

    Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Los Alamos National Lab.; Smith, Darryl L.; Los Alamos National Lab.

    2014-12-22

    The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solutionmore » using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. In order to validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. Furthermore, these observations are consistent with the model.« less

  4. Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

    SciTech Connect

    Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Smith, Darryl L.

    2014-12-22

    The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solution using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. In order to validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. Furthermore, these observations are consistent with the model.

  5. Data Inversion for Over-Resolved Spectral Imaging in Astronomy

    NASA Astrophysics Data System (ADS)

    Rodet, Thomas; Orieux, François; Giovannelli, Jean-François; Abergel, Alain

    2008-11-01

    We present an original method for reconstructing a 3-D object having two spatial dimensions and one spectral dimension from data provided by the infrared slit spectrograph on board the Spitzer Space Telescope. During acquisition, the light flux is deformed by a complex process comprising four main elements (the telescope aperture, the slit, the diffraction grating, and optical distortion) before it reaches the 2-D sensor. The originality of this work lies in the physical modeling, in integral form, of this process of data formation in continuous variables. The inversion is also approached with continuous variables in a semi-parametric format decomposing the object into a family of Gaussian functions. The estimate is built in a deterministic regularization framework as the minimizer of a quadratic criterion. These specificities give our method the power to over-resolve. Its performance is illustrated using real and simulated data. We also present a study of the resolution showing a 1.5-fold improvement relative to conventional methods.

  6. Spectrally Resolved Maker Fringes in High-Order Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Heyl, C. M.; Güdde, J.; Höfer, U.; L'Huillier, A.

    2011-07-01

    We investigate macroscopic interference effects in high-order harmonic generation using a Ti:sapphire laser operating at a 100 kHz repetition rate. The structure and behavior of spectral and spatial interference fringes are explained and analytically described by transient phase matching of the long electron trajectory contribution. Time-frequency mapping due to the temporal chirp of the harmonic emission allows us to observe Maker fringes directly in the spectral domain.

  7. Improved optical profiling using the spectral phase in spectrally resolved white-light interferometry

    SciTech Connect

    Debnath, Sanjit Kumar; Kothiyal, Mahendra Prasad

    2006-09-20

    In spectrally resolved white-light interferometry (SRWLI), the white-light interferogram is decomposed into its monochromatic constituent. The phase of the monochromatic constituents can be determined using a phase-shifting technique over a range of wavelengths. These phase value shave fringe order ambiguity. However, the variation of the phase with respect to the wavenumber is linear and its slope gives the absolute value of the optical-path difference. Since the path difference is related to the height of the test object at a point, a line profile can be determined without ambiguity. The slope value, though less precise helps us determine the fringe order. The fringe order combined with the monochromatic phase value gives the absolute profile, which has the precision of phase-shifting interferometry. The presence of noise in the phase may lead to the misidentification of fringe order, which in turn gives unnecessary jumps in the precise profile. The experimental details of measurement on standard samples with SRWLI are discussed in this paper.

  8. Spectrally resolved fluorescence imaging of human colonic adenomas.

    PubMed

    Chwirot, B W; Kowalska, M; Sypniewska, N; Michniewicz, Z; Gradziel, M

    1999-06-01

    Native fluorescence (autofluorescence) of human tissues can be a valuable source of diagnostic information for detecting premalignant and malignant lesions in the human body. Digital imaging of autofluorescence may be useful for localization of such lesions during endoscopic examinations. Tissue fluorescence of 31 adenomatous polyps obtained from 16 patients has been excited in vitro using the 325 nm line of a He-Cd laser. Digital images of the autofluorescence are recorded in six spectral bands. This study provides new data about the spatial distributions of autofluorescence intensities emitted in different spectral bands by colonic adenomatous lesions and normal colonic mucosa. Areas characterized by autofluorescence intensity lower than in normal mucosa are found for a majority of the polyps under study. The observed patterns of spatial distribution differ for the different spectral bands and for different polypoid lesions. No inverse correlation is found between the emission intensity and the thickness of colonic mucosa. The results indicate the spectral bands most useful for diagnostic applications and demonstrate the complexity of the optical processes involved in shaping both the spectra and intensities of the autofluorescence. PMID:10515079

  9. 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

  10. Time-resolved spectral investigations of laser light induced microplasma

    NASA Astrophysics Data System (ADS)

    Nánai, L.; Hevesi, I.

    1992-01-01

    The dynamical and spectral properties of an optical breakdown microplasma created by pulses of different lasers on surfaces of insulators (KCI), metals (Cu) and semiconductors (V 2O 5), have been investigated. Experiments were carried out in air and vacuum using different wavelengths (λ = 0.694μm, type OGM-20,λ = 1.06μm with a home-made laser based on neodymium glass crystal, and λ = 10.6μm, similarly home-made) and pulse durations (Q-switched and free-running regimes). To follow the integral, dynamical and spectral characteristics of the luminous spot of microplasma we have used fast cameras (SFR-2M, IMACON-HADLAND), a high speed spectral camera (AGAT-2) and a spectrograph (STE-1). It has been shown that the microplasma consists of two parts: fast front (peak) with τ≈100 ns and slow front (tail) with τ≈1μs durations. The detonation front speed is of the order of ≈10 5 cm s -1 and follows the temporal dependence of to t0.4. It depends on the composition of the surrounding gas and its pressure and could be connected with quick evaporation of the material investigated (peak) and optical breakdown of the ambient gaseous atmosphere (tail). From the delay in appearance of different characteristic spectral lines of the target material and its gaseous surrounding we have shown that the evolution of the microplasma involves evaporation and ionization of the atoms of the parent material followed by optical breakdown due to the incident and absorbed laser light, together with microplasma expansion.

  11. Spectrally resolved fast transient brain states in electrophysiological data.

    PubMed

    Vidaurre, Diego; Quinn, Andrew J; Baker, Adam P; Dupret, David; Tejero-Cantero, Alvaro; Woolrich, Mark W

    2016-02-01

    The brain is capable of producing coordinated fast changing neural dynamics across multiple brain regions in order to adapt to rapidly changing environments. However, it is non-trivial to identify multiregion dynamics at fast sub-second time-scales in electrophysiological data. We propose a method that, with no knowledge of any task timings, can simultaneously identify and describe fast transient multiregion dynamics in terms of their temporal, spectral and spatial properties. The approach models brain activity using a discrete set of sequential states, with each state distinguished by its own multiregion spectral properties. This can identify potentially very short-lived visits to a brain state, at the same time as inferring the state's properties, by pooling over many repeated visits to that state. We show how this can be used to compute state-specific measures such as power spectra and coherence. We demonstrate that this can be used to identify short-lived transient brain states with distinct power and functional connectivity (e.g., coherence) properties in an MEG data set collected during a volitional motor task. PMID:26631815

  12. Spectrally resolved fast transient brain states in electrophysiological data

    PubMed Central

    Vidaurre, Diego; Quinn, Andrew J.; Baker, Adam P.; Dupret, David; Tejero-Cantero, Alvaro; Woolrich, Mark W.

    2016-01-01

    The brain is capable of producing coordinated fast changing neural dynamics across multiple brain regions in order to adapt to rapidly changing environments. However, it is non-trivial to identify multiregion dynamics at fast sub-second time-scales in electrophysiological data. We propose a method that, with no knowledge of any task timings, can simultaneously identify and describe fast transient multiregion dynamics in terms of their temporal, spectral and spatial properties. The approach models brain activity using a discrete set of sequential states, with each state distinguished by its own multiregion spectral properties. This can identify potentially very short-lived visits to a brain state, at the same time as inferring the state's properties, by pooling over many repeated visits to that state. We show how this can be used to compute state-specific measures such as power spectra and coherence. We demonstrate that this can be used to identify short-lived transient brain states with distinct power and functional connectivity (e.g., coherence) properties in an MEG data set collected during a volitional motor task. PMID:26631815

  13. 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.

  14. Spectral characteristics of time resolved magnonic spin Seebeck effect

    SciTech Connect

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

    2015-09-28

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

  15. 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. Marine fluorescence from high spectrally resolved satellite measurements

    NASA Astrophysics Data System (ADS)

    Wolanin, Aleksandra; Dinter, Tilman; Rozanov, Vladimir; Noël, Stefan; Vountas, Marco; Burrows, John P.; Bracher, Astrid

    2014-05-01

    When chlorophyll molecules absorb light, most of this energy is transformed into chemical energy in a process of photosynthesis. However, a fraction of the energy absorbed is reemitted as fluorescence. As a result of its relationship to photosynthetic e?ciency, information about chlorophyll fluorescence can be used to assess the physiological state of phytoplankton (Falkowski and Kolber,1995). In-situ measurements of chlorophyll fluorescence are widespread in physiological and ecophysiological studies. When retrieved from space, chlorophyll fluorescence can improve our knowledge of global biogeochemical cycles and phytoplankton productivity (Behrenfeld et al., 2009; Huot et al., 2013) by providing high coverage and periodicity. So far, the only satellite retrieval of sun-induced marine fluorescence, Fluorescence Line Height (FLH), was designed for MODIS (Abbott and Letelier, 1999), and later also applied to the similar sensor MERIS (Gower et al., 2004). However, it could so far not be evaluated on global scale. Here, we present a different approach to observe marine chlorophyll fluorescence, based on the Differential Optical Absorption Spectroscopy (DOAS) technique (Perner and Platt, 1979) applied to the hyperspectral data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Global Ozone Monitoring Experiment-2 (GOME-2). Since fluorescence, as a trans-spectral process, leads to the shift of the wavelength of the radiation, it can be observed in the filling-in of Fraunhofer lines. In our retrieval, we evaluate the filling-in of the Zeeman triplet Fraunhofer line FeI at 684.3 nm, which is located very close to the emission peak of marine fluorescence (~685 nm). In order to conduct the chlorophyll fluorescence retrieval with the DOAS method, we calculated the reference spectra for chlorophyll fluorescence, based on simulations performed with the coupled ocean-atmosphere radiative transfer model SCIATRAN (Rozanov et al., 2014

  17. Angular and spectrally resolved investigations of yeast cells by light scattering microscopy and goniometric measurements

    NASA Astrophysics Data System (ADS)

    Stark, Julian; Müller, Dennis; Nothelfer, Steffen; Kienle, Alwin

    2015-07-01

    Spectrally and angular resolved light scattering from yeast cells was studied with a scattering microscope and a goniometer. Different cell models were investigated with help of analytical solutions of Maxwell's equations. It was found that extraction of precise morphological and optical cellular properties from the measured scattering patterns and phase functions requires more sophisticated cell models than standard Mie theory.

  18. Comparing spectral resolvability in chinchillas and human listeners using phase discrimination

    NASA Astrophysics Data System (ADS)

    Shofner, William P.; Sparks, Kathryn; Wu, Yuanxing Esther; Pham, Ellen

    2001-05-01

    A tone complex made of harmonic components that are added in cosine-starting phase can be discriminated from complexes comprised of identical harmonics that are added with random-starting phases. Phase discrimination occurs when unresolved harmonics interact within a single auditory channel. When harmonics are resolved, there is less interaction among components resulting in poorer phase discrimination performance. Thus, phase discrimination indirectly reflects spectral resolvability. Performance in a phase discrimination task was measured in chinchillas and human listeners to compare spectral resolvability between the two groups. Subjects discriminated a cosine-phase tone complex from random-phase tone complexes in a go/no-go behavioral paradigm. Tone complexes were comprised of a 250-Hz fundamental frequency and N consecutive higher harmonics, where N was 5, 10, 20, and 40. Performance was evaluated in terms of d'. The results show that the measured d' increased as N increased, and values of d' for each N condition were similar between chinchillas and human listeners. Values of the criterion for each N condition were also similar between chinchillas and humans. The results do not support the hypothesis that spectral resolvability is poorer in chinchillas, but suggest that resolvability is similar between the two groups. [Work supported by NIH/NIDCD.

  19. 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.

  20. An empirical method for correcting the detector spectral response in energy-resolved CT

    NASA Astrophysics Data System (ADS)

    Schmidt, Taly Gilat

    2012-03-01

    Energy-resolving photon-counting detectors have the potential for improved material decomposition compared to dual-kVp approaches. However, material decomposition accuracy is limited by the nonideal spectral response of the detectors. This work proposes an empirical method for correcting the nonideal spectral response, including spectrum-tailing effects. Unlike previous correction methods which relied on synchrotron measurements, the proposed method can be performed on the scanner. The proposed method estimates a spectral-response matrix by performing x-ray projection measurements through a range of known thicknesses of two or more calibration materials. Once estimated, the spectral-response matrix is incorporated into conventional material decomposition algorithms. A simulation study investigated preliminary feasibility of the proposed method. The spectral-response matrix was estimated using simulated projection measurements through PMMA, aluminum, and gadolinium. An energy-resolved acquisition of a thorax phantom with gadolinium in the blood pool was simulated assuming a five-bin detector with realistic spectral response. Energy-bin data was decomposed into Compton, photoelectric, and gadolinium basis projections with and without the proposed correction method. Basis images were reconstructed by filtered backprojection. Results demonstrated that the nonideal spectral response reduced the ability to distinguish gadolinium from materials such as bone, while images reconstructed with the proposed correction method successfully depicted the contrast agent. The proposed correction method reduced errors from 9% to 0.6% in the Compton image, 90% to 0.6% in the photoelectric image and from 40% to 6% in the gadolinium image when using a three-material calibration. Overall, results support feasibility of the proposed spectral-response correction method.

  1. 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.

  2. Spectrally resolved detection in transient-reflectivity measurements of coherent optical phonons in diamond

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazutaka G.; Ohya, Kazuma; Takahashi, Hiroshi; Tsuruta, Tetsuya; Sasaki, Hiroya; Uozumi, Shin-ichi; Norimatsu, Katsura; Kitajima, Masahiro; Shikano, Yutaka; Kayanuma, Yosuke

    2016-07-01

    Coherent optical phonons in bulk solid systems play a crucial role in understanding and designing light-matter interactions and can be detected by the transient-reflectivity measurement. In this paper, we demonstrate spectrally resolved detection of coherent optical phonons in diamond from ultrashort infrared pump-probe measurements using optical bandpass filters. We show that this enhances the sensitivity approximately 35 times in measuring the coherent oscillations in the transient reflectivity compared with the commonly used spectrally integrated measurement. To explain this observation, we discuss its mechanism.

  3. Nonstationary gasdynamics

    NASA Astrophysics Data System (ADS)

    Gottlieb, J. J.; Groth, C. P. T.; Hawboldt, R. J.; Hawken, D. F.; Lock, G. D.; Wong, C. H.; Chan, Y. S.; Maillette, J.; Petrini, G. L.; Picket, J. S.

    A review is provided of nonstationary gas dynamic investigations carried out at the University of Toronto Institute for Aerospace Studies. Numerical studies aimed at predicting the operation and performance of two stage light-gas guns and selecting optimum gas operating conditions are ongoing. Preliminary internal ballistics work on modelling the motions of propellant gases and projectiles in an experimental gun with a high pressure combustion section and a low pressure launch tube has been completed. The study of propellant combustion in a closed vessel to obtain propellant burning rates and combustion gas properties for use in modelling of gas guns is now underway. The nonequilibrium structure of a shock front in a dusty gas is being studied in a dusty shock tube facility to determine particle drag and heat transfer coefficients. Studies undertaken to provide data for the design of a large air-blast and thermal simulation facility include: investigation of the reflection eliminator, the venting from the test section of combustion products from thermal radiation sources, and the prediction of unsteady flow. A high pressure reservoir with an exit nozzle containing a slot has been constructed to obtain experimental data on discharge coefficients of orifices and slots in high-low pressure guns and on blast simulators.

  4. Spectrally resolved optical probing of laser induced magnetization dynamics in bismuth iron garnet.

    PubMed

    Koene, Benny; Deb, Marwan; Popova, Elena; Keller, Niels; Rasing, Theo; Kirilyuk, Andrei

    2016-07-13

    The spectrally resolved magnetization dynamics in bismuth iron garnet shows a fluence dependent light induced modification of the magneto-optical Faraday spectrum. It is demonstrated that the relative contributions from the tetrahedral and octahedral iron sites to the Faraday spectrum change due to the impact of the pump pulse. This change explains the observed deviation from a linear dependence of the amplitude of the oscillations on the fluence, as expected for the inverse Faraday effect. PMID:27213266

  5. DISPERSION ANALYSIS OF RADIATION/THERMAL FRONTS WITH FULL RESOLVED SPECTRAL OPACITY VARIATION.

    SciTech Connect

    L. AUER; R. LOWRIE

    2000-12-01

    The radiation transport and linearized thermal energy equations have been analyzed to find the temporal dependence of the component modes in a radiation/thermal front. The fully resolved spectral variation of the opacity as a function of energy, as well as the exact time and angular dependence, is treated in this work. As we are able to study arbitrarily complicated opacity spectra, we stress the importance of the new results as a check on the effect of using opacity averages.

  6. Spectrally resolved optical probing of laser induced magnetization dynamics in bismuth iron garnet

    NASA Astrophysics Data System (ADS)

    Koene, Benny; Deb, Marwan; Popova, Elena; Keller, Niels; Rasing, Theo; Kirilyuk, Andrei

    2016-07-01

    The spectrally resolved magnetization dynamics in bismuth iron garnet shows a fluence dependent light induced modification of the magneto-optical Faraday spectrum. It is demonstrated that the relative contributions from the tetrahedral and octahedral iron sites to the Faraday spectrum change due to the impact of the pump pulse. This change explains the observed deviation from a linear dependence of the amplitude of the oscillations on the fluence, as expected for the inverse Faraday effect.

  7. Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

    NASA Astrophysics Data System (ADS)

    Lunt, Richard R.; Giebink, Noel C.; Belak, Anna A.; Benziger, Jay B.; Forrest, Stephen R.

    2009-03-01

    We demonstrate spectrally resolved photoluminescence quenching as a means to determine the exciton diffusion length of several archetype organic semiconductors used in thin film devices. We show that aggregation and crystal orientation influence the anisotropy of the diffusion length for vacuum-deposited polycrystalline films. The measurement of the singlet diffusion lengths is found to be in agreement with diffusion by Förster transfer, whereas triplet diffusion occurs primarily via Dexter transfer.

  8. Time- and spectrally resolved characteristics of flavin fluorescence in U87MG cancer cells in culture

    NASA Astrophysics Data System (ADS)

    Horilova, Julia; Cunderlikova, Beata; Marcek Chorvatova, Alzbeta

    2015-05-01

    Early detection of cancer is crucial for the successful diagnostics of its presence and its subsequent treatment. To improve cancer detection, we tested the progressive multimodal optical imaging of U87MG cells in culture. A combination of steady-state spectroscopic methods with the time-resolved approach provides a new insight into the native metabolism when focused on endogenous tissue fluorescence. In this contribution, we evaluated the metabolic state of living U87MG cancer cells in culture by means of endogenous flavin fluorescence. Confocal microscopy and time-resolved fluorescence imaging were employed to gather spectrally and time-resolved images of the flavin fluorescence. We observed that flavin fluorescence in U87MG cells was predominantly localized outside the cell nucleus in mitochondria, while exhibiting a spectral maximum under 500 nm and fluorescence lifetimes under 1.4 ns, suggesting the presence of bound flavins. In some cells, flavin fluorescence was also detected inside the cell nuclei in the nucleoli, exhibiting longer fluorescence lifetimes and a red-shifted spectral maximum, pointing to the presence of free flavin. Extra-nuclear flavin fluorescence was diminished by 2-deoxyglucose, but failed to increase with 2,4-dinitrophenol, the uncoupler of oxidative phosphorylation, indicating that the cells use glycolysis, rather than oxidative phosphorylation for functioning. These gathered data are the first step toward monitoring the metabolic state of U87MG cancer cells.

  9. Spectrally-resolved measurement of concentrated light distributions for Fresnel lens concentrators.

    PubMed

    Besson, P; White, P McVey; Dominguez, C; Voarino, P; Garcia-Linares, P; Lemiti, M; Schriemer, H; Hinzer, K; Baudrit, M

    2016-01-25

    A test method that measures spectrally resolved irradiance distribution for a concentrator photovoltaic (CPV) optical system is presented. In conjunction with electrical I-V curves, it is a means to visualize and characterize the effects of chromatic aberration and nonuniform flux profiles under controllable testing conditions. The indoor characterization test bench, METHOD (Measurement of Electrical, Thermal and Optical Devices), decouples the temperatures of the primary optical element (POE) and the cell allowing their respective effects on optical and electrical performance to be analysed. In varying the temperature of the POE, the effects on electrical efficiency, focal distance, spectral sensitivity, acceptance angle and multi-junction current matching profiles can be quantified. This work presents the calibration procedures to accurately image the spectral irradiance distribution of a CPV system and a study of system behavior over lens temperature. PMID:26832591

  10. Transit spectroscopy of exoplanets from space: how to optimize the wavelength coverage and spectral resolving power

    NASA Astrophysics Data System (ADS)

    Encrenaz, T.; Tinetti, G.; Tessenyi, M.; Drossart, P.; Hartogh, P.; Coustenis, A.

    2015-12-01

    The study of exoplanets is an exploding field in astronomy. Recent discoveries have made possible the development of a new research field, the spectroscopic characterization of the exoplanetary atmospheres, using both primary and eclipse transits. A dedicated space mission will make possible the characterization of many classes of exoplanets, from the hot Jupiters to the temperate super-Earths. In this paper, we discuss how the spectral range and the spectral resolving power can be optimized for identifying a maximum number of candidate atmospheric species. Spectral modeling shows that the simultaneous observation of the whole spectral range, from 0.55 to 16 μm is ideal for (1) capturing all types of planets at different temperatures, (2) detecting the variety of chemical atmospheric compounds with some redundancy, and (3) enabling an optimal retrieval of the chemical abundances and thermal profile. Limiting the spectral interval to 11 μm would make the retrieval more difficult in the case of cold exoplanets. In the visible range, the extension down to 0.4 s at different temperatures, (2) detecting the variety of chemical atmospheric compounds with some redundancy, and (3) enabling an optimal retrieval of the chemical abundances andst candidate molecules.

  11. Distribution of ALA metabolic products in esophageal carcinoma cells using spectrally resolved confocal laser microscopy

    NASA Astrophysics Data System (ADS)

    Smolka, Jozef; Mateasik, Anton

    2006-08-01

    Aminolevulinic acid (ALA) is an efficient substance used in photodynamic therapy (PDT). It is a precursor of light-sensitive products that can selectively accumulate in malignant cells following the altered activity of the heme biosynthetic pathway enzymes in such cells. These products are synthesized in mitochondria and distributed to various cellular structures [1]. The localization of ALA products in subcellular structures depends on their chemical characteristics as well as on the properties of the intracellular environment [2]. Characterization of such properties is possible by means of fluorescent probes like JC-1 and carboxy SNARF-1. However, the emission spectra of these probes are overlapped with spectral pattern of typical ALA product -protoporphyrin IX (PpIX). Spectral overlap of fluorescence signals prevents to clearly separate a distribution of probes from PpIX distribution what can completely mess the applicability of these probes in characterization of cell properties. The spectrally resolved confocal laser microscopy can be used to overcome this problem. In this study, a distribution of ALA metabolic products in relation to the mitochondrial membrane potential and intracellular pH was examined. Human cell lines (KYSE-450, KYSE-70) from esophageal squamous cell carcinoma were used. Cells were incubated with 1mM solution of ALA for four hours. Two fluorescent probes, carboxy SNARF-1 and JC-1 , were used to monitor intracellular pH levels and to determine membrane potential changes, respectively. The samples were scanned by spectrally resolved laser scanning microscope. Spectral linear unmixing method was used to discriminate and separate regions of accumulation of ALA metabolic products of JC-1 and carboxy SNARF-1.

  12. Yukawas, G-flux, and spectral covers from resolved Calabi-Yau's

    NASA Astrophysics Data System (ADS)

    Marsano, Joseph; Schäfer-Nameki, Sakura

    2011-11-01

    We use the resolution procedure of Esole and Yau [1] to study Yukawa couplings, G-flux, and the emergence of spectral covers from elliptically fibered Calabi-Yau's with a surface of A 4 singularities. We provide a global description of the Esole-Yau resolution and use it to explicitly compute Chern classes of the resolved 4-fold, proving the conjecture of [2] for the Euler character in the process. We comment on the physical implications of the surprising singular fibers in codimension 2 and 3 in [1] and emphasize a group theoretic interpretation based on the A 4 weight lattice. We then construct explicit G-fluxes by brute force in one of the 6 birationally equivalent Esole-Yau resolutions, quantize them explicitly using our result for the second Chern class, and compute the spectrum and flux-induced 3-brane charges, finding agreement with results and conjectures of local models in all cases. Finally, we provide a precise description of the spectral divisor formalism in this setting and sharpen the procedure described in [3] in order to explicitly demonstrate how the Higgs bundle spectral cover of the local model emerges from the resolved Calabi-Yau geometry. Along the way, we demonstrate explicitly how the quantization rules for fluxes in the local and global models are related.

  13. Velocity and Temperature Measurement in Supersonic Free Jets Using Spectrally Resolved Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Panda, J.; Seasholtz, R. G.

    2004-01-01

    The flow fields of unheated, supersonic free jets from convergent and convergent-divergent nozzles operating at M = 0.99, 1.4, and 1.6 were measured using spectrally resolved Rayleigh scattering technique. The axial component of velocity and temperature data as well as density data obtained from a previous experiment are presented in a systematic way with the goal of producing a database useful for validating computational fluid dynamics codes. The Rayleigh scattering process from air molecules provides a fundamental means of measuring flow properties in a non-intrusive, particle free manner. In the spectrally resolved application, laser light scattered by the air molecules is collected and analyzed using a Fabry-Perot interferometer (FPI). The difference between the incident laser frequency and the peak of the Rayleigh spectrum provides a measure of gas velocity. The temperature is measured from the spectral broadening caused by the random thermal motion and density is measured from the total light intensity. The present point measurement technique uses a CW laser, a scanning FPI and photon counting electronics. The 1 mm long probe volume is moved from point to point to survey the flow fields. Additional arrangements were made to remove particles from the main as well as the entrained flow and to isolate FPI from the high sound and vibration levels produced by the supersonic jets. In general, velocity is measured within +/- 10 m/s accuracy and temperature within +/- 10 K accuracy.

  14. Photophysical properties of DASPMI as revealed by spectrally resolved fluorescence decays.

    PubMed

    Ramadass, Radhan; Bereiter-Hahn, Jürgen

    2007-07-01

    Photophysical properties of 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide (DASPMI) in various solvents were investigated using time- and space-correlated single photon counting. DASPMI is known to selectively stain mitochondria in living cells.1,2 The uptake and fluorescence intensity of DASPMI in mitochondria is a dynamic measure of membrane potential. Hence, an endeavor has been made to elucidate the mechanism of DASPMI fluorescence by obtaining spectrally resolved fluorescence decays in different solvents. A biexponential decay model was sufficient to globally describe the wavelength-dependent fluorescence in ethanol and chloroform. While in glycerol, a three-exponential decay model was necessary for global analysis. In the polar low-viscous solvent water, a monoexponential decay model fitted the decay data. The sensitivity of DASPMI to solvent viscosity was analyzed using various proportions of glycerol-ethanol mixtures. The lifetimes were found to increase with increasing solvent viscosity. The negative amplitudes of the short lifetime component found in chloroform and glycerol at the longer wavelengths validated the formation of new excited-state species from the initially excited state. Time-resolved emission spectra in chloroform and glycerol showed a biphasic increase of spectral width and emission maxima. The spectral width had an initial fast increase within 150 ps and a near constant thereafter. A three-state model of generalized scheme, on the basis of successive formation of locally excited state (LE), intramolecular charge transfer state (ICT), and twisted intramolecular charge transfer (TICT) state, has been proposed to explain the excited-state kinetics. The presumed role of solvation dynamics of ICT and TICT states leading to the asymmetrical broadening and structureless fluorescence has been substantiated by the decomposition of time-resolved emission spectra in chloroform, glycerol, and ethanol/glycerol mixtures. PMID:17559255

  15. Time-resolved spectral measurements for the boeing free-electron laser experiments

    SciTech Connect

    Lumpkin, A.H.; King, N.S.P.; Wilke, M.D.; Wei, S.P.; Davis, K.J.

    1988-01-01

    A time-resolved optical spectrometer based on the integration of a Jarrell-Ash 1/4-m spectrometer and a streak camera has been used to evaluate the Boeing Burst Mode Oscillator experiment. The system provides information on spectral evolution on both the micropulse (10 ps) and macropulse (50-100..mu..s) time scales. We have measured the micropulse duration, a wavelength shift within a micropulse and the development of a discrete second wavelength during a macropulse. 4 refs., 9 figs., 1 tab.

  16. Spectrally resolved four-wave mixing experiments on bulk GaAs with 14-fs pulses

    SciTech Connect

    Wehner, M.U.; Steinbach, D.; Wegener, M.; Marschner, T.; Stolz, W.

    1996-05-01

    We investigate the coherent dynamics at the band edge of GaAs at low temperatures for carrier densities ranging from 4.3{times}10{sup 14} cm{sup {minus}3} to 4.4{times}10{sup 17} cm{sup {minus}3} by means of spectrally resolved transient four-wave mixing with 14-fs pulses. At large nonequilibrium carrier densities we observe oscillations with an energy-dependent oscillation period related to interference among continuum states. The experimental findings are compared with a simple model. This comparison delivers a weak energy dependence of dephasing in the initial buildup phase of screening. {copyright} {ital 1996 Optical Society of America.}

  17. Spectrally resolved fluorescence cross sections of BG and BT with a 266-nm pump wavelength

    NASA Astrophysics Data System (ADS)

    Atkins, Joshua; Thomas, Michael E.; Joseph, Richard I.

    2007-04-01

    The spectrally resolved absolute fluorescence cross sections of Bacillus globigii (BG) and Bacillus thuringiensis (BT) were measured with a 266nm Nd:YAG laser source. The aerosol samples were prepared in dilute aqueous suspensions for measurement and the absolute cross section was found by use of the Raman scattering line from water. Integrated cross sections for BT and BG were found to be 1.1864 × 10 -12 cm2(spore sr) and 3.251 × 10 -13 cm2/ (spore sr) respectively.

  18. Spectrally resolved analysis of fluorescence blinking of single dye molecules in polymers at low temperatures

    NASA Astrophysics Data System (ADS)

    Orlov, S. V.; Naumov, A. V.; Vainer, Yu. G.; Kador, Lothar

    2012-11-01

    We present a method for the spectrally resolved analysis of fluorescence blinking of single quantum emitters. It is based on the well-known technique of repeated recording of single-molecule (SM) fluorescence excitation spectra. The potential of our approach is presented for the example of single tetra-tert-butylterrylene molecules in an amorphous polymer matrix (polyisobutylene), which exhibit fluorescence blinking at cryogenic temperatures. Measuring the spectral dependence of the blinking statistics improves the possibility to clarify the microscopic nature of the dark state(s) of the emitters. We demonstrate how the blinking statistics can be definitely attributed to conformational changes in the local environment of a SM and how the parameters of the corresponding elementary excitations can be measured. The analysis of the blinking statistics as a function of the optical excitation frequency allows us to discriminate between photo-induced and spontaneous transitions into a dark state.

  19. Extended resolvent and inverse scattering with an application to KPI

    NASA Astrophysics Data System (ADS)

    Boiti, M.; Pempinelli, F.; Pogrebkov, A. K.; Prinari, B.

    2003-08-01

    We present in detail an extended resolvent approach for investigating linear problems associated to 2+1 dimensional integrable equations. Our presentation is based as an example on the nonstationary Schrödinger equation with potential being a perturbation of the one-soliton potential by means of a decaying two-dimensional function. Modification of the inverse scattering theory as well as properties of the Jost solutions and spectral data as follows from the resolvent approach are given.

  20. Spectrally resolved fluorescence lifetime imaging of Nile red for measurements of intracellular polarity

    NASA Astrophysics Data System (ADS)

    Levitt, James A.; Chung, Pei-Hua; Suhling, Klaus

    2015-09-01

    Spectrally resolved confocal microscopy and fluorescence lifetime imaging have been used to measure the polarity of lipid-rich regions in living HeLa cells stained with Nile red. The emission peak from the solvatochromic dye in lipid droplets is at a shorter wavelength than other, more polar, stained internal membranes, and this is indicative of a low polarity environment. We estimate that the dielectric constant, ɛ, is around 5 in lipid droplets and 25<ɛ<40 in other lipid-rich regions. Our spectrally resolved fluorescence lifetime imaging microscopy (FLIM) data show that intracellular Nile red exhibits complex, multiexponential fluorescence decays due to emission from a short lifetime locally excited state and a longer lifetime intramolecular charge transfer state. We measure an increase in the average fluorescence lifetime of the dye with increasing emission wavelength, as shown using phasor plots of the FLIM data. We also show using these phasor plots that the shortest lifetime decay components arise from lipid droplets. Thus, fluorescence lifetime is a viable contrast parameter for distinguishing lipid droplets from other stained lipid-rich regions. Finally, we discuss the FLIM of Nile red as a method for simultaneously mapping both polarity and relative viscosity based on fluorescence lifetime measurements.

  1. The complex ion structure of warm dense carbon measured by spectrally resolved x-ray scattering

    SciTech Connect

    Kraus, D.; Barbrel, B.; Falcone, R. W.; Vorberger, J.; Helfrich, J.; Frydrych, S.; Ortner, A.; Otten, A.; Roth, F.; Schaumann, G.; Schumacher, D.; Siegenthaler, K.; Wagner, F.; Roth, M.; Gericke, D. O.; Wünsch, K.; Bachmann, B.; Döppner, T.; Bagnoud, V.; Blažević, A.; and others

    2015-05-15

    We present measurements of the complex ion structure of warm dense carbon close to the melting line at pressures around 100 GPa. High-pressure samples were created by laser-driven shock compression of graphite and probed by intense laser-generated x-ray sources with photon energies of 4.75 keV and 4.95 keV. High-efficiency crystal spectrometers allow for spectrally resolving the scattered radiation. Comparing the ratio of elastically and inelastically scattered radiation, we find evidence for a complex bonded liquid that is predicted by ab-initio quantum simulations showing the influence of chemical bonds under these conditions. Using graphite samples of different initial densities we demonstrate the capability of spectrally resolved x-ray scattering to monitor the carbon solid-liquid transition at relatively constant pressure of 150 GPa. Showing first single-pulse scattering spectra from cold graphite of unprecedented quality recorded at the Linac Coherent Light Source, we demonstrate the outstanding possibilities for future high-precision measurements at 4th Generation Light Sources.

  2. Spectrally resolved fluorescence lifetime imaging to investigate cell metabolism in malignant and nonmalignant oral mucosa cells

    NASA Astrophysics Data System (ADS)

    Rück, Angelika; Hauser, Carmen; Mosch, Simone; Kalinina, Sviatlana

    2014-09-01

    Fluorescence-guided diagnosis of tumor tissue is in many cases insufficient, because false positive results interfere with the outcome. Improvement through observation of cell metabolism might offer the solution, but needs a detailed understanding of the origin of autofluorescence. With respect to this, spectrally resolved multiphoton fluorescence lifetime imaging was investigated to analyze cell metabolism in metabolic phenotypes of malignant and nonmalignant oral mucosa cells. The time-resolved fluorescence characteristics of NADH were measured in cells of different origins. The fluorescence lifetime of bound and free NADH was calculated from biexponential fitting of the fluorescence intensity decay within different spectral regions. The mean lifetime was increased from nonmalignant oral mucosa cells to different squamous carcinoma cells, where the most aggressive cells showed the longest lifetime. In correlation with reports in the literature, the total amount of NADH seemed to be less for the carcinoma cells and the ratio of free/bound NADH was decreased from nonmalignant to squamous carcinoma cells. Moreover for squamous carcinoma cells a high concentration of bound NADH was found in cytoplasmic organelles (mainly mitochondria). This all together indicates that oxidative phosphorylation and a high redox potential play an important role in the energy metabolism of these cells.

  3. Spectrally resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography

    PubMed Central

    Cong, Wenxiang; Shen, Haiou; Wang, Ge

    2011-01-01

    The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach. PMID:21721815

  4. Spectrally resolved microprobe cathodoluminescence of intergrowth Bi5-xLaxTiNbWO15 ferroelectrics

    NASA Astrophysics Data System (ADS)

    Ge, Wanyin; Zhu, Wenliang; Higashino, Masayuki; Li, Yongxiang; Yi, Zhiguo; Pezzotti, Giuseppe

    2007-10-01

    Spectrally resolved cathodoluminescence measurements of Bi5-xLaxTiNbWO15 (x=0-1.50) ceramics at room temperature showed three distinct luminescence bands located at about 380, 502, and 660nm, respectively, which were tentatively assigned to F+ center, oxygen vacancy-related defect and octahedron structure-related luminescence center, respectively. These assignments could be made in light of electron irradiation experiments with different exposure times. Bands related to oxygen vacancies were clearly enhanced by lanthanum doping, indicating that charge compensation occurred by the substitution of Bi for La3+ in perovskitelike structured intergrowth ferroelectrics. We observed that, for contents of La3+ x >0.75, La3+ ions entered the [Bi2O2]2+ layer according to a doping mechanism which is briefly discussed in this letter.

  5. Novel characterization of the nonlinear refractive response of materials using spatially and spectrally resolved interferometry

    NASA Astrophysics Data System (ADS)

    Meier, Amanda; Adams, Daniel; Squier, Jeff; Durfee, Charles

    2010-10-01

    Characterization of the nonlinear refractive index of a material is important in order to fully understand the nonlinear propagation of femtosecond laser pulses. The most common method to obtaining the nonlinear refractive index is Z-scan. However, since it averages over pulse duration and beam profile, Z-scan is not reliable when there is time- and intensity-dependence of the nonlinear response. The new method we are exploring to make these nonlinear refractive index measurements is spatially and spectrally resolved interferometry (SSRI). SSRI is a method that can give a simultaneous measurement of the spatial wave-front across the frequency or temporal profile of the pulse. The SSRI method proves better in measuring response at specific y and t, allowing it to measure both delayed response and saturation effects. The ability to make a measurement in both dimensions enables understanding of spatiotemporal dynamics in other experiments as cross-wave polarization and filamentation.

  6. Platform for spectrally resolved x-ray scattering from imploding capsules at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Kraus, D.; Döppner, T.; Kritcher, A. L.; Yi, A.; Boehm, K.; Bachmann, B.; Divol, L.; Fletcher, L. B.; Glenzer, S. H.; Landen, O. L.; Masters, N.; Saunders, A. M.; Weber, C.; Falcone, R. W.; Neumayer, P.

    2016-05-01

    We present a new experimental platform to perform spectrally resolved x-ray scattering measurements of ionization, density and temperature in imploding CH or beryllium capsules at the National Ignition Facility. Scattered x-rays at 9 keV from a zinc He-alpha plasma source at a scattering angle of 120 degrees are highly sensitive to K-shell ionization, while at the same time constraining density and temperature. This platform will allow for x-ray scattering studies of dense plasmas with free electron densities up to 1025 cm-3 giving the possibility to investigate effects of pressure ionization and Pauli blocking on the ablator ionization state right before or shortly after stagnation of the implosion.

  7. Field-resolved measurement of reaction-induced spectral densities by polarizability response spectroscopy

    NASA Astrophysics Data System (ADS)

    Moran, Andrew M.; Nome, Rene A.; Scherer, Norbert F.

    2007-11-01

    The experimental design and theoretical description of a novel five-pulse laser spectroscopy is presented with an application to a pyridinium charge transfer complex in acetonitrile and methanol. In field-resolved polarizability response spectroscopy (PORS), an electronically resonant laser pulse first excites a solvated chromophore (reactant) and off-resonant Raman spectra of the resulting nuclear motions are measured as a function of the reaction time. The present apparatus differs from our earlier design by performing the Raman probe measurement (with fixed pulse delays) in the frequency domain. In addition, the full electric fields of the signals are measured by spectral interferometry to separate nonresonant and Raman responses. Our theoretical model shows how the PORS signal arises from nuclear motions that are displaced/driven by the photoinduced reaction. The field-resolved off-resonant (of the solute's electronic transitions) probing favors detection of solvent (as opposed to solute) dynamics coupled to the reaction. The sign of the signal represents the relative strengths of polarization responses associated with the ground and photoexcited solutions. Signatures of nonresonant and PORS signal contributions to the experimental results are analyzed with numerical calculations based on a theoretical model we have developed for reaction-induced PORS. Our model identifies two mechanisms of PORS signal generation: (i) structural relaxation induced resonance; (ii) dephasing induced resonance. In the charge transfer reaction investigated, the solvent-dependent and time-evolving (solvent) polarizability spectral density (PSD) is readily obtained. The general trend of an initial broadband inertial nuclear response followed by a decrease in the linewidth of the PSD establishes that the measured PSD is inconsistent with the approximation of a linear response. Furthermore, the explicit time evolution of the PSD is important for properly describing solvent control of

  8. Field-resolved measurement of reaction-induced spectral densities by polarizability response spectroscopy

    SciTech Connect

    Moran, Andrew M.; Nome, Rene A.; Scherer, Norbert F.

    2007-11-14

    The experimental design and theoretical description of a novel five-pulse laser spectroscopy is presented with an application to a pyridinium charge transfer complex in acetonitrile and methanol. In field-resolved polarizability response spectroscopy (PORS), an electronically resonant laser pulse first excites a solvated chromophore (reactant) and off-resonant Raman spectra of the resulting nuclear motions are measured as a function of the reaction time. The present apparatus differs from our earlier design by performing the Raman probe measurement (with fixed pulse delays) in the frequency domain. In addition, the full electric fields of the signals are measured by spectral interferometry to separate nonresonant and Raman responses. Our theoretical model shows how the PORS signal arises from nuclear motions that are displaced/driven by the photoinduced reaction. The field-resolved off-resonant (of the solute's electronic transitions) probing favors detection of solvent (as opposed to solute) dynamics coupled to the reaction. The sign of the signal represents the relative strengths of polarization responses associated with the ground and photoexcited solutions. Signatures of nonresonant and PORS signal contributions to the experimental results are analyzed with numerical calculations based on a theoretical model we have developed for reaction-induced PORS. Our model identifies two mechanisms of PORS signal generation: (i) structural relaxation induced resonance; (ii) dephasing induced resonance. In the charge transfer reaction investigated, the solvent-dependent and time-evolving (solvent) polarizability spectral density (PSD) is readily obtained. The general trend of an initial broadband inertial nuclear response followed by a decrease in the linewidth of the PSD establishes that the measured PSD is inconsistent with the approximation of a linear response. Furthermore, the explicit time evolution of the PSD is important for properly describing solvent control of

  9. Spectrally-resolved Soft X-ray Observations and the Temperature Structure of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Caspi, Amir; Warren, Harry; McTiernan, James; Woods, Thomas N.

    2015-04-01

    Solar X-ray observations provide important diagnostics of plasma heating and particle acceleration, during solar flares and quiescent periods. How the corona is heated to its ~1-3 MK nominal temperature remains one of the fundamental unanswered questions of solar physics; heating of plasma to tens of MK during solar flares -- particularly to the hottest observed temperatures of up to ~50 MK -- is also still poorly understood. Soft X-ray emission (~0.1-10 keV; or ~0.1-10 nm) is particularly sensitive to hot coronal plasma and serves as a probe of the thermal processes driving coronal plasma heating. Spectrally- and temporally-resolved measurements are crucial for understanding these energetic processes, but there have historically been very few such observations. We present new solar soft X-ray spectra from the Amptek X123-SDD, measuring quiescent solar X-ray emission from ~0.5 to ~30 keV with ~0.15 keV FWHM resolution from two SDO/EVE calibration sounding rocket underflights in 2012 and 2013. Combined with observations from RHESSI, GOES/XRS, SDO/EVE, and SDO/AIA, the temperature distribution derived from these data suggest significant hot (5-10 MK) emission from active regions, and the 2013 spectra suggest a low-FIP enhancement of only ~1.6 relative to the photosphere, 40% of the usually-observed value from quiescent coronal plasma. We explore the implications of these findings on coronal heating. We discuss future missions for spectrally-resolved soft X-ray observations using the X123-SDD, including the upcoming MinXSS 3U CubeSat using the X123-SDD and scheduled for deployment in mid-2015, and the CubIXSS 6U CubeSat mission concept.

  10. High Broadband Spectral Resolving Transition-Edge Sensors for High Count-Rate Astrophysical Applications

    NASA Technical Reports Server (NTRS)

    Smith, Stephen

    2011-01-01

    We are developing arrays of transition-edge sensor (TES) X-ray detectors optimized for high count-rate solar astronomy applications where characterizing the high velocity motions of X-ray jets in solar flares is of particular interest. These devices are fabricated on thick Si substrates and consist of 35x35micron^2 TESs with 4.5micron thick, 60micron pitch, electroplated absorbers. We have tested devices fabricated with different geometric stem contact areas with the TES and surrounding substrate area, which allows us to investigate the loss of athermal phonons to the substrate. Results show a correlation between the stem contact area and a non-Gaussian broadening in the spectral line shape consistent with athermal phonon loss. When the contact area is minimized we have obtained remarkable board-band spectral resolving capabilities of 1.3 plus or minus 0.leV at an energy of 1.5 keV, 1.6 plus or minus 0.1 eV at 5.9 keV and 2.0 plus or minus 0.1 eV at 8 keV. This, coupled with a capability of accommodating 100's of counts per second per pixel makes these devices an exciting prospect of future x-ray astronomy applications.

  11. 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

  12. In vivo stoichiometry monitoring of G protein coupled receptor oligomers using spectrally resolved two-photon microscopy

    NASA Astrophysics Data System (ADS)

    Stoneman, M. R.; Singh, D. R.; Raicu, V.

    2010-02-01

    Resonance Energy Transfer (RET) between a donor molecule in an electronically excited state and an acceptor molecule in close proximity has been frequently utilized for studies of protein-protein interactions in living cells. Typically, the cell under study is scanned a number of times in order to accumulate enough spectral information to accurately determine the RET efficiency for each region of interest within the cell. However, the composition of these regions may change during the course of the acquisition period, limiting the spatial determination of the RET efficiency to an average over entire cells. By means of a novel spectrally resolved two-photon microscope, we were able to obtain a full set of spectrally resolved images after only one complete excitation scan of the sample of interest. From this pixel-level spectral data, a map of RET efficiencies throughout the cell is calculated. By applying a simple theory of RET in oligomeric complexes to the experimentally obtained distribution of RET efficiencies throughout the cell, a single spectrally resolved scan reveals stoichiometric and structural information about the oligomer complex under study. This presentation will describe our experimental setup and data analysis procedure, as well as an application of the method to the determination of RET efficiencies throughout yeast cells (S. cerevisiae) expressing a G-protein-coupled receptor, Sterile 2 α factor protein (Ste2p), in the presence and absence of α-factor - a yeast mating pheromone.

  13. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector

    NASA Astrophysics Data System (ADS)

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-09-01

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97-1.01 and NRMSEs of 0.20-4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17-0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  14. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector.

    PubMed

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-09-21

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97-1.01 and NRMSEs of 0.20-4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17-0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  15. Spectrally and spatially resolved cathodoluminescence of nanodiamonds: local variations of the NV(0) emission properties.

    PubMed

    Tizei, L H G; Kociak, M

    2012-05-01

    Here we report the spectrally and spatially resolved cathodoluminescence of diamond nanoparticles using focused fast electron beams in a transmission electron microscope. We demonstrate the possibility of quickly detecting various individual colour centres of different kinds on wide areas (several micrometres square) contained in nanoparticles separated by subwavelength distances. Among them, nanoparticles containing one or more neutral nitrogen-vacancy (NV(0)) intensity maxima have been seen, attributable to individual emitters. Thanks to a spatial resolution which is solely limited by charge carrier diffusion in the case of a fast electron (80 keV) setup, the spectra of two individual NV(0) emitters separated by 80 nm inside a nanoparticle have been spatially discerned. A shift of the zero phonon line (ZPL) between the two emitters, which we attribute to internal stress, is shown to arise even within the same nanoparticle. Detailed emission spectra (ZPL, phonon lines and Huang-Rhys factor, directly linked to the relaxation energy of the colour centre) in 51 individual NV(0) centres have been measured in 39 particles. The ZPL and Huang-Rhys factor are found to be measurably dispersed, while the phonon energies keep constant. PMID:22481219

  16. Application of a Phase-resolving, Directional Nonlinear Spectral Wave Model

    NASA Astrophysics Data System (ADS)

    Davis, J. R.; Sheremet, A.; Tian, M.; Hanson, J. L.

    2014-12-01

    We describe several applications of a phase-resolving, directional nonlinear spectral wave model. The model describes a 2D surface gravity wave field approaching a mildly sloping beach with parallel depth contours at an arbitrary angle accounting for nonlinear, quadratic triad interactions. The model is hyperbolic, with the initial wave spectrum specified in deep water. Complex amplitudes are generated based on the random phase approximation. The numerical implementation includes unidirectional propagation as a special case. In directional mode, it solves the system of equations in the frequency-alongshore wave number space. Recent enhancements of the model include the incorporation of dissipation caused by breaking and propagation over a viscous mud layer and the calculation of wave induced setup. Applications presented include: a JONSWAP spectrum with a cos2s directional distribution, for shore-perpendicular and oblique propagation, a study of the evolution of a single directional triad, and several preliminary comparisons to wave spectra collected at the USACE-FRF in Duck, NC which show encouraging results although further validation with a wider range of beach slopes and wave conditions is needed.

  17. Source Reconstruction for Spectrally-resolved Bioluminescence Tomography with Sparse A priori Information

    PubMed Central

    Lu, Yujie; Zhang, Xiaoqun; Douraghy, Ali; Stout, David; Tian, Jie; Chan, Tony F.; Chatziioannou, Arion F.

    2009-01-01

    Through restoration of the light source information in small animals in vivo, optical molecular imaging, such as fluorescence molecular tomography (FMT) and bioluminescence tomography (BLT), can depict biological and physiological changes observed using molecular probes. A priori information plays an indispensable role in tomographic reconstruction. As a type of a priori information, the sparsity characteristic of the light source has not been sufficiently considered to date. In this paper, we introduce a compressed sensing method to develop a new tomographic algorithm for spectrally-resolved bioluminescence tomography. This method uses the nature of the source sparsity to improve the reconstruction quality with a regularization implementation. Based on verification of the inverse crime, the proposed algorithm is validated with Monte Carlo-based synthetic data and the popular Tikhonov regularization method. Testing with different noise levels and single/multiple source settings at different depths demonstrates the improved performance of this algorithm. Experimental reconstruction with a mouse-shaped phantom further shows the potential of the proposed algorithm. PMID:19434138

  18. Application and development of a spectrally-resolved confocal microscope: A study of lipofuscin emission properties

    NASA Astrophysics Data System (ADS)

    Haralampus-Grynaviski, Nicole Marie

    A unique spectrally-resolved confocal microscope is developed for use in biophysical applications. This microscope enables the rapid collection of the complete emission spectra for every pixel in a fluorescence image. The basic optical design and function of the device are assessed through examination of fluorescently labeled beads, using both one- and two-photon excitation. The spatial resolution of the device is found to approach the diffraction limit in the lateral plane and ˜2 mum in the axial plane. This device can readily distinguish between overlapping emissions which are not easily differentiated using standard filter techniques. The potential of this device to be used as a detection method in DNA sequence experiments is demonstrated. Images of a human skin tissue section and a mouse kidney section are presented which demonstrate the structure and spectra of biologic samples can be resolved. The emission properties of human ocular lipofuscin, LF, a heterogeneous auto-fluorescent material associated with age-related macular degeneration is investigated in detail. Isolated LF granules show substantial variation in emission spectra. Near-field scanning microscopy experiments find the emissive regions on a single LF granule are homogeneous on the ˜150 nm scale and confirm results obtained on the microscope developed here. For ˜100 studied LF deposits, the histogram of the measured peak emission is centered around 18,000 cm-1 (555 nm). The average emission spectra for large LF aggregates (peak 17,150 cm-1) is red-shifted compared to the average emission from small individual granules (peak 17,600 cm-1). The average LF granule emission observed here is similar to previously reported bulk LF emission and the emission of a previously identified LF chromophore, A2E. Individual LF granules show a broad range in emission maximum whether the LF is isolated from multiple donors or examined within the cells of a single donor. Multiple as yet unidentified chromophores

  19. Spectral data of specular reflectance, narrow-angle transmittance and angle-resolved surface scattering of materials for solar concentrators

    PubMed Central

    Good, Philipp; Cooper, Thomas; Querci, Marco; Wiik, Nicolay; Ambrosetti, Gianluca; Steinfeld, Aldo

    2015-01-01

    The spectral specular reflectance of conventional and novel reflective materials for solar concentrators is measured with an acceptance angle of 17.5 mrad over the wavelength range 300−2500 nm at incidence angles 15–60° using a spectroscopic goniometry system. The same experimental setup is used to determine the spectral narrow-angle transmittance of semi-transparent materials for solar collector covers at incidence angles 0–60°. In addition, the angle-resolved surface scattering of reflective materials is recorded by an area-scan CCD detector over the spectral range 350–1050 nm. A comprehensive summary, discussion, and interpretation of the results are included in the associated research article “Spectral reflectance, transmittance, and angular scattering of materials for solar concentrators” in Solar Energy Materials and Solar Cells. PMID:26862556

  20. 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

  1. New Instruments for Spectrally-Resolved Solar Soft X-ray Observations from CubeSats, and Larger Missions

    NASA Astrophysics Data System (ADS)

    Caspi, A.; Shih, A.; Warren, H. P.; DeForest, C. E.; Woods, T. N.

    2015-12-01

    Solar soft X-ray (SXR) observations provide important diagnostics of plasma heating, during solar flares and quiescent times. Spectrally- and temporally-resolved measurements are crucial for understanding the dynamics and evolution of these energetic processes; spatially-resolved measurements are critical for understanding energy transport. A better understanding of the thermal plasma informs our interpretation of hard X-ray (HXR) observations of nonthermal particles, improving our understanding of the relationships between particle acceleration, plasma heating, and the underlying release of magnetic energy during reconnection. We introduce a new proposed mission, the CubeSat Imaging X-ray Solar Spectrometer (CubIXSS), to measure spectrally- and spatially-resolved SXRs from the quiescent and flaring Sun from a 6U CubeSat platform in low-Earth orbit during a nominal 1-year mission. CubIXSS includes the Amptek X123-SDD silicon drift detector, a low-noise, commercial off-the-shelf (COTS) instrument enabling solar SXR spectroscopy from ~0.5 to ~30 keV with ~0.15 keV FWHM spectral resolution with low power, mass, and volume requirements. An X123-CdTe cadmium-telluride detector is also included for ~5-100 keV HXR spectroscopy with ~0.5-1 keV FWHM resolution. CubIXSS also includes a novel spectro-spatial imager -- the first ever solar imager on a CubeSat -- utilizing a pinhole aperture and X-ray transmission diffraction grating to provide full-Sun imaging from ~0.1 to ~10 keV, with ~25 arcsec and ~0.1 Å FWHM spatial and spectral resolutions, respectively. We discuss scaled versions of these instruments, with greater sensitivity and dynamic range, and significantly improved spectral and spatial resolutions for the imager, for deployment on larger platforms such as Small Explorer missions.

  2. Modeling spatially and spectrally resolved observations to diagnose the formation of elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Snyder, Gregory Frantz

    2013-03-01

    In extragalactic astronomy, a central challenge is that we cannot directly watch what happens to galaxies before and after they are observed. This dissertation focuses on linking predictions of galaxy time-evolution directly with observations, evaluating how interactions, mergers, and other processes affect the appearance of elliptical galaxies. The primary approach is to combine hydrodynamical simulations of galaxy formation, including all major components, with dust radiative transfer to predict their observational signatures The current paradigm implies that a quiescent elliptical emerges following a formative starburst event. These trigger accretion onto the central supermassive black hole (SMBH), which then radiates as an active galactic nucleus (AGN). However, it is not clear the extent to which SMBH growth is fueled by these events nor how important is their energy input at setting the appearance of the remnant. This thesis presents results drawing from three phases in the formation of a typical elliptical: 1) I evaluate how to disentangle AGN from star formation signatures in mid-infrared spectra during a dust-enshrouded starburst, making testable predictions for robustly tracing SMBH growth with the James Webb Space Telescope; 2) I develop a model for the rate of merger-induced post-starburst galaxies selected from optical spectra, resolving tension between their observed rarity and merger rates from other estimates; and 3) I present results from Hubble Space Telescope imaging of elliptical galaxies in galaxy clusters at 1 < z < 2, the precursors of present-day massive clusters with M ~ 1015 solar masses, demonstrating that their stars formed over an extended period and ruling out the simplest model for their formation history. These results lend support to a stochastic formation history for ellipticals driven by mergers or interactions. However, significant uncertainties remain in how to evaluate the implications of galaxy appearance, in particular their

  3. A Comparison of PSD Enveloping Methods for Nonstationary Vibration

    NASA Technical Reports Server (NTRS)

    Irvine, Tom

    2015-01-01

    There is a need to derive a power spectral density (PSD) envelope for nonstationary acceleration time histories, including launch vehicle data, so that components can be designed and tested accordingly. This paper presents the results of the three methods for an actual flight accelerometer record. Guidelines are given for the application of each method to nonstationary data. The method can be extended to other scenarios, including transportation vibration.

  4. Magnetic field effects on spectrally resolved lifetime of on-line oxygen monitoring using magneto-optic probes

    NASA Astrophysics Data System (ADS)

    Mermut, O.; Gallant, P.; Le Bouch, N.; Leclair, S.; Noiseux, I.; Vernon, M.; Morin, J.-F.; Diamond, K.; Patterson, M. S.; Samkoe, K.; Pogue, B.

    2009-02-01

    Multimodal agents that serve as both probes for contrast and light-activated effectors of cellular processes in diseased tissue were developed. These agents were introduced into multicellular tumor spheroids (3D tissue models) and in the chorioallantoic membrane (CAM) of a chicken embryo. The luminescence decay was examined using a novel technique involving a spectrally-resolved fluorescence lifetime apparatus integrated with a weak electromagnet. A spectrallyresolved lifetime setup was used to identify magneto-optic species sensitive to magnetic field effects and distinguish from background emissions. We demonstrate that the applied magnetic fields can alter reaction rates and product distribution of some dyes detected by time- and spectrally-resolved luminescence changes. We will discuss the use of exogenous magneto-optical probes taken up in tumors to both induce phototoxicity, a process that is governed by complex and dynamically evolving mechanisms involving reactive oxygen species, and monitor treatment progress. The magnetic field enhancement, measured over a range of weak fields (0-300 mT) is correlated to oxygenation and may be used to monitor dynamic changes occurring due to oxygen consumption over the course of photodynamic therapy. Such online measurements provide the possibility to derive real-time information about response to treatment via monitoring magnetic field enhancement/suppression of the time-resolved, spectrally-resolved luminescence of the probe at the site of the treatment directly. Magnetic perturbation of lifetime can serve as a status reporter, providing optical feedback of oxygen-mediated treatments in situ and allowing for real-time adjustment of a phototherapy treatment plan.

  5. Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs

    PubMed Central

    Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi

    2014-01-01

    Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10−7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy. PMID:24448604

  6. Simultaneous recovery of chromophore concentrations and ultrasound velocity by spectrally resolved photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Yuan, Zhen; Zhang, Qizhi; Grobmyer, Stephen; Jiang, Huabei

    2009-02-01

    We describe a new spectral approach for inversion of photoacoustic data with multi-wavelength pulsed laser illumination. Multi-spectral PAT provides a means of recovery of different chromophore concentrations and ultrasound velocity simultaneously and directly by incorporating prior spectral information into the image reconstruction process. It is demonstrated from simulation tests and small animal experiments that the multi-parameter recovery based on multispectral PAT is reliable and accurate. The reconstructed multiple parameter images may provide us a key tool to quantify physiological function, disease progression, or response to intervention.

  7. Spectrally resolved eclipse maps of the accretion disk in UX Ursae Majoris

    NASA Technical Reports Server (NTRS)

    Rutten, Rene G. M.; Dhillon, V. S.; Horne, Keith; Kuulkers, E.; Van Paradijs, J.

    1993-01-01

    An effort is made to observationally constrain accretion disks on the basis of light curves from the eclipsing cataclysmic variable UX Ursae Majoris, reconstructing the spectral energy distribution across the face of an accretion disk. The spectral resolution obtained suffices to reveal not only the radial dependence of absorption and emission line features within the disk, but also the spectral details of the bright spot that is formed where the accretion stream from the secondary star collides with the disk. The importance of such constraints for theoretical models is noted.

  8. Spectrally resolved time-correlated single photon counting: a novel approach for characterization of endogenous fluorescence in isolated cardiac myocytes.

    PubMed

    Chorvat, D; Chorvatova, A

    2006-12-01

    A new setup for time-resolved fluorescence micro-spectroscopy of cells, based on multi-dimensional time-correlated single photon counting, was designed and tested. Here we demonstrate that the spectrometer allows fast and reproducible measurements of endogenous flavin fluorescence measured directly in living cardiac cells after excitation with visible picosecond laser diodes. Two complementary approaches for the analysis of spectrally- and time-resolved autofluorescence data are presented, comprising the fluorescence decay fitting by exponential series and the time-resolved emission spectroscopy analysis. In isolated cardiac myocytes, we observed three distinct lifetime pools with characteristic lifetime values spanning from picosecond to nanosecond range and the time-dependent red shift of the autofluorescence emission spectra. We compared obtained results to in vitro recordings of free flavin adenine dinucleotide (FAD) and FAD in lipoamide dehydrogenase (LipDH). The developed setup combines the strength of both spectral and fluorescence lifetime analysis and provides a solid base for the study of complex systems with intrinsic fluorescence, such as identification of the individual flavinoprotein components in living cardiac cells. This approach therefore constitutes an important instrumental advancement towards redox fluorimetry of living cardiomyocytes, with the perspective of its applications in the investigation of oxidative metabolic state under pathophysiological conditions, such as ischemia and/or metabolic disorders. PMID:17033778

  9. Areal-averaged and Spectrally-resolved Surface Albedo from Ground-based Transmission Data Alone: Toward an Operational Retrieval

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Michalsky, Joseph; Hodges, G. B.

    2014-08-22

    We present here a simple retrieval of the areal-averaged and spectrally resolved surface albedo using only ground-based measurements of atmospheric transmission under fully overcast conditions. Our retrieval is based on a one-line equation and widely accepted assumptions regarding the weak spectral dependence of cloud optical properties in the visible and near-infrared spectral range. The feasibility of our approach for the routine determinations of albedo is demonstrated for different landscapes with various degrees of heterogeneity using three sets of measurements:(1) spectrally resolved atmospheric transmission from Multi-Filter Rotating Shadowband Radiometer (MFRSR) at wavelength 415, 500, 615, 673, and 870 nm, (2) tower-based measurements of local surface albedo at the same wavelengths, and (3) areal-averaged surface albedo at four wavelengths (470, 560, 670 and 860 nm) from collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) observations. These integrated datasets cover both long (2008-2013) and short (April-May, 2010) periods at the ARM Southern Great Plains (SGP) site and the NOAA Table Mountain site, respectively. The calculated root mean square error (RMSE), which is defined here as the root mean squared difference between the MODIS-derived surface albedo and the retrieved area-averaged albedo, is quite small (RMSE≤0.01) and comparable with that obtained previously by other investigators for the shortwave broadband albedo. Good agreement between the tower-based daily averages of surface albedo for the completely overcast and non-overcast conditions is also demonstrated. This agreement suggests that our retrieval originally developed for the overcast conditions likely will work for non-overcast conditions as well.

  10. Chromatic-aberration diagnostic based on a spectrally resolved lateral-shearing interferometer

    DOE PAGESBeta

    Bahk, Seung -Whan; Dorrer, Christopher; Roides, Rick G.; Bromage, Jake

    2016-03-18

    Here, a simple diagnostic characterizing one-dimensional chromatic aberrations in a broadband beam is introduced. A Ronchi grating placed in front of a spectrometer entrance slit provides spectrally coupled spatial phase information. The radial-group delay of a refractive system and the pulse-front delay of a wedged glass plate have been characterized accurately in a demonstration experiment.

  11. Spectral Characterization of A Resolved M dwarf-M dwarf Binary

    NASA Astrophysics Data System (ADS)

    Tamiya, Tomoki; Burgasser, Adam J.; Aganze, Christian; Mercado, Gretel; Suarez, Adrian

    2016-06-01

    We report characterization of the resolved binary M dwarf SDSS J155526.53+095409.5AB through spectroscopic and imaging analysis. Classification of resolved near-infrared spectra with IRTF/SpeX and tools in the SpeX Prism Library Analysis Toolkit (SPLAT) indicate component types of M3.5 and M8, separated by about 4''. We match the data to atmosphere models using an Monte Carlo Markov Chain routine to determine preliminary physical properties for each component (temperature, surface gravity and metallicity), and obtain estimates for the distance (106±11 pc) and projected separation (419±45 AU).Funding acknowledgement: This project is supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G.

  12. SPATIALLY AND SPECTRALLY RESOLVED HYDROGEN GAS WITHIN 0.1 AU OF T TAURI AND HERBIG Ae/Be STARS

    SciTech Connect

    Eisner, J. A.; Monnier, J. D.; Woillez, J.; Ragland, S.; Wizinowich, P.; Akeson, R. L.; Millan-Gabet, R.; Graham, J. R.; Hillenbrand, L. A.; Pott, J.-U.

    2010-08-01

    We present near-infrared observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milliarcseconds and a spectral resolution of {approx}2000. Our observations spatially resolve gas and dust in the inner regions of protoplanetary disks, and spectrally resolve broad-linewidth emission from the Br{gamma} transition of hydrogen gas. We use the technique of spectro-astrometry to determine centroids of different velocity components of this gaseous emission at a precision orders of magnitude better than the angular resolution. In all sources, we find the gaseous emission to be more compact than or distributed on similar spatial scales to the dust emission. We attempt to fit the data with models including both dust and Br{gamma}-emitting gas, and we consider both disk and infall/outflow morphologies for the gaseous matter. In most cases where we can distinguish between these two models, the data show a preference for infall/outflow models. In all cases, our data appear consistent with the presence of some gas at stellocentric radii of {approx}0.01 AU. Our findings support the hypothesis that Br{gamma} emission generally traces magnetospherically driven accretion and/or outflows in young star/disk systems.

  13. Time-resolved optically stimulated luminescence and spectral emission features of α-Al2O3:C

    NASA Astrophysics Data System (ADS)

    Chithambo, M. L.; Nyirenda, A. N.; Finch, A. A.; Rawat, N. S.

    2015-09-01

    This report is concerned with the influence of measurement temperature on luminescence lifetime and on the spectral emission features of luminescence from α-Al2O3:C. The lifetimes were determined from time-resolved luminescence spectra. Spectral measurements were done using thermoluminescence and X-ray excited optical luminescence. The emission spectra of α-Al2O3:C studied in this work shows prominent bands at 330, 380 and 420 nm associated with vacancies in the oxygen sub-lattice in α-Al2O3:C and an additional band at 695 nm due to Cr substitution for Al. Emission bands below 500 nm are independent of temperature below 125 °C but widen with temperature. Direct evidence of thermal quenching of the 420 nm emission band is provided. Beyond 200 °C, the 380 and 420 nm bands merge and widen, with the 420 nm emission dominant. Before the onset of thermal quenching, luminescence lifetimes are affected by retrapping both in the shallow- and in the main electron trap. This was deduced from features of time-resolved luminescence spectra measured from samples with and without the shallow trap. Additional measurements with temperature decreasing from 160 to 20 °C, after phototransfer as well as after a considerable delay between irradiation and measurement, suggest that the change in lifetimes could also be related to other factors including slight shifts in emission wavelength for the 380 and 420 nm emissions.

  14. Near-infrared optical mammography with broadband spectral imaging for spatially resolved oximetry

    NASA Astrophysics Data System (ADS)

    Yu, Yang; Sassaroli, Angelo; Homer, Marc J.; Graham, Roger A.; Fantini, Sergio

    2011-02-01

    We report the development of an instrument for diffuse spectral imaging of the human breast operating over the wavelength range 650-900 nm. This instrument images the slightly compressed human breast in a planar geometry by performing a tandem scan, over the x-y plane, of a 3 mm illumination optical fiber and a 5 mm collection optical fiber that are collinear and located on opposite sides of the breast. An edge-correction algorithm accounts for breast thickness variability over the x-y plane, a second-derivative imaging algorithm enhances the display of optical inhomogeneities, and a paired-wavelength spectral method yields oxygenation maps. We report our results of oxygenation mapping in eighteen human subjects, two of which are breast cancer patients, one with a ductal carcinoma in situ, the other with an invasive ductal carcinoma.

  15. Time-resolved spatial phase measurements with 2-dimensional spectral interferometry

    NASA Astrophysics Data System (ADS)

    Childress, Colby; Planchon, Thomas; Amir, Wafa; Squier, Jeff A.; Durfee, Charles G.

    2007-03-01

    We are using 2-dimensional spectral interferometry for sensitive measurements of spatial phase distortions. The reference pulse and the time-delayed probe pulse are coincident on an imaging spectrometer, yielding spectral and spatial phase information. This technique offers the potential of higher sensitivity than traditional spatial interferometry since there are many fringes of data for each spatial point. We illustrate this technique with measurements of the thermal lensing profile in a cryogenically cooled Ti:sapphire amplifier crystal that is pumped by tens of watts of power from four frequency-doubled Nd:YLF lasers running at 1 kHz. By adjusting the relative delay of the probe and reference pulses, we characterize the thermal transients during and after the pump pulses. We compare the measured transient thermal profiles with those calculated with a finite-element model.

  16. Spectrally-resolved measurements of aerosol extinction at ultraviolet and visible wavelengths

    NASA Astrophysics Data System (ADS)

    Flores, M.; Washenfelder, R. A.; Brock, C. A.; Brown, S. S.; Rudich, Y.

    2012-12-01

    Aerosols play an important role in the Earth's radiative budget. Aerosol extinction includes both the scattering and absorption of light, and these vary with wavelength, aerosol diameter, and aerosol composition. Historically, aerosol absorption has been measured using filter-based or extraction methods that are prone to artifacts. There have been few investigations of ambient aerosol optical properties at the blue end of the visible spectrum and into the ultraviolet. Brown carbon is particularly important in this spectral region, because it both absorbs and scatters light, and encompasses a large and variable group of organic compounds from biomass burning and secondary organic aerosol. We have developed a laboratory instrument that combines new, high-power LED light sources with high-finesse optical cavities to achieve sensitive measurements of aerosol optical extinction. This instrument contains two broadband channels, with spectral coverage from 360 - 390 nm and 385 - 420 nm. Using this instrument, we report aerosol extinction in the ultraviolet and near-visible spectral region as a function of chemical composition and structure. We have measured the extinction cross-sections between 360 - 420 nm with 0.5 nm resolution using different sizes and concentrations of polystyrene latex spheres, ammonium sulfate, and Suwannee River fulvic acid. Fitting the real and imaginary part of the refractive index allows the absorption and scattering to be determined.

  17. Corneal birefringence measured by spectrally resolved Mueller matrix ellipsometry and implications for non-invasive glucose monitoring

    PubMed Central

    Westphal, Peter; Kaltenbach, Johannes-Maria; Wicker, Kai

    2016-01-01

    A good understanding of the corneal birefringence properties is essential for polarimetric glucose monitoring in the aqueous humor of the eye. Therefore, we have measured complete 16-element Mueller matrices of single-pass transitions through nine porcine corneas in-vitro, spectrally resolved in the range 300…1000 nm. These ellipsometric measurements have been performed at several angles of incidence at the apex and partially at the periphery of the corneas. The Mueller matrices have been decomposed into linear birefringence, circular birefringence (i.e. optical rotation), depolarization, and diattenuation. We found considerable circular birefringence, strongly increasing with decreasing wavelength, for most corneas. Furthermore, the decomposition revealed significant dependence of the linear retardance (in nm) on the wavelength below 500 nm. These findings suggest that uniaxial and biaxial crystals are insufficient models for a general description of the corneal birefringence, especially in the blue and in the UV spectral range. The implications on spectral-polarimetric approaches for glucose monitoring in the eye (for diabetics) are discussed. PMID:27446644

  18. Corneal birefringence measured by spectrally resolved Mueller matrix ellipsometry and implications for non-invasive glucose monitoring.

    PubMed

    Westphal, Peter; Kaltenbach, Johannes-Maria; Wicker, Kai

    2016-04-01

    A good understanding of the corneal birefringence properties is essential for polarimetric glucose monitoring in the aqueous humor of the eye. Therefore, we have measured complete 16-element Mueller matrices of single-pass transitions through nine porcine corneas in-vitro, spectrally resolved in the range 300…1000 nm. These ellipsometric measurements have been performed at several angles of incidence at the apex and partially at the periphery of the corneas. The Mueller matrices have been decomposed into linear birefringence, circular birefringence (i.e. optical rotation), depolarization, and diattenuation. We found considerable circular birefringence, strongly increasing with decreasing wavelength, for most corneas. Furthermore, the decomposition revealed significant dependence of the linear retardance (in nm) on the wavelength below 500 nm. These findings suggest that uniaxial and biaxial crystals are insufficient models for a general description of the corneal birefringence, especially in the blue and in the UV spectral range. The implications on spectral-polarimetric approaches for glucose monitoring in the eye (for diabetics) are discussed. PMID:27446644

  19. Probing Gamma-ray Emission of Geminga and Vela with Non-stationary Models

    NASA Astrophysics Data System (ADS)

    Chai, Yating; Cheng, Kwong-Sang; Takata, Jumpei

    2016-06-01

    It is generally believed that the high energy emissions from isolated pulsars are emitted from relativistic electrons/positrons accelerated in outer magnetospheric accelerators (outergaps) via a curvature radiation mechanism, which has a simple exponential cut-off spectrum. However, many gamma-ray pulsars detected by the Fermi LAT (Large Area Telescope) cannot be fitted by simple exponential cut-off spectrum, and instead a sub-exponential is more appropriate. It is proposed that the realistic outergaps are non-stationary, and that the observed spectrum is a superposition of different stationary states that are controlled by the currents injected from the inner and outer boundaries. The Vela and Geminga pulsars have the largest fluxes among all targets observed, which allows us to carry out very detailed phase-resolved spectral analysis. We have divided the Vela and Geminga pulsars into 19 (the off pulse of Vela was not included) and 33 phase bins, respectively. We find that most phase resolved spectra still cannot be fitted by a simple exponential spectrum: in fact, a sub-exponential spectrum is necessary. We conclude that non-stationary states exist even down to the very fine phase bins.

  20. Two-photon spectral amplitude of entangled states resolved in separable Schmidt modes

    NASA Astrophysics Data System (ADS)

    Avella, A.; Brida, G.; Chekhova, M.; Gramegna, M.; Shurupov, A.; Genovese, M.

    2015-10-01

    The ability to access high dimensionality in Hilbert spaces represents a demanding key-stone for state-of-the-art quantum information. The manipulation of entangled states in continuous variables, wavevector as well frequency, represents a powerful resource in this sense. The number of dimensions of the Hilbert space that can be used in practical information protocols can be determined by the number of Schmidt modes that it is possible to address one by one. In the case of wavevector variables, the Schmidt modes can be losslessly selected using single-mode fibre and a spatial light modulator, but no similar procedure exists for the frequency space. The aim of this work is to present a technique to engineer the spectral properties of biphoton light, emitted via ultrafast spontaneous parametric down conversion, in such a way that the two-photon spectral amplitude (TPSA) contains several non-overlapping Schmidt modes, each of which can be filtered losslessly in frequency variables. Such TPSA manipulation is operated by a fine balancing of parameters like the pump frequency, the shaping of pump pulse spectrum, the dispersion dependence of spontaneous parametric down-conversion crystals as well as their length. Measurements have been performed exploiting the group velocity dispersion induced by the passage of optical fields through dispersive media, operating a frequency-to-time two-dimensional Fourier transform of the TPSA. Exploiting this kind of measurement we experimentally demonstrate the ability to control the Schmidt modes structure in TPSA through the pump spectrum manipulation.

  1. Resolving the xi Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "Fip Effect"

    NASA Technical Reports Server (NTRS)

    Wood, Brian E.; Linsky, Jeffrey L.

    2010-01-01

    On 2008 May 2, Chandra observed the X-ray spectrum of xi Boo (G8 V+K4 V), resolving the binary for the first time in X-rays and allowing the coronae of the two stars to be studied separately. With the contributions of ξ Boo A and B to the system's total X-ray emission now observationally established (88.5% and 11.5% respectively), consideration of mass loss measurements for GK dwarfs of various activity levels (including one for xi Boo) leads to the surprising conclusion that xi Boo B may dominate the wind from the binary, with xi Boo A's wind being very weak despite its active corona. Emission measure (EM) distributions and coronal abundances are computed for both stars and compared with Chandra measurements of other moderately active stars with G8-K5 spectral types, all of which exhibit a narrow peak in EM near log T = 6.6, indicating that the coronal heating process in these stars has a strong preference for this temperature. As is the case for the Sun and many other stars, our sample of stars shows coronal abundance anomalies dependent on the first ionization potential (FIP) of the element. We see no dependence of the degree of FIP effect on activity, but there is a dependence on spectral type, a correlation that becomes more convincing when moderately active main-sequence stars with a broader range of spectral types are considered. This clear dependence of coronal abundances on spectral type weakens if the stellar sample is allowed to be contaminated by evolved stars, interacting binaries or extremely active stars with logLX 29, explaining why this correlation has not been recognized in the past.

  2. Resolving the ξ Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "FIP Effect"

    NASA Astrophysics Data System (ADS)

    Wood, Brian E.; Linsky, Jeffrey L.

    2010-07-01

    On 2008 May 2, Chandra observed the X-ray spectrum of ξ Boo (G8 V+K4 V), resolving the binary for the first time in X-rays and allowing the coronae of the two stars to be studied separately. With the contributions of ξ Boo A and B to the system's total X-ray emission now observationally established (88.5% and 11.5%, respectively), consideration of mass loss measurements for GK dwarfs of various activity levels (including one for ξ Boo) leads to the surprising conclusion that ξ Boo B may dominate the wind from the binary, with ξ Boo A's wind being very weak despite its active corona. Emission measure (EM) distributions and coronal abundances are computed for both stars and compared with Chandra measurements of other moderately active stars with G8-K5 spectral types, all of which exhibit a narrow peak in EM near log T = 6.6, indicating that the coronal heating process in these stars has a strong preference for this temperature. As is the case for the Sun and many other stars, our sample of stars shows coronal abundance anomalies dependent on the first ionization potential (FIP) of the element. We see no dependence of the degree of "FIP effect" on activity, but there is a dependence on spectral type, a correlation that becomes more convincing when moderately active main-sequence stars with a broader range of spectral types are considered. This clear dependence of coronal abundances on spectral type weakens if the stellar sample is allowed to be contaminated by evolved stars, interacting binaries, or extremely active stars with log LX >29, explaining why this correlation has not been recognized in the past.

  3. RESOLVING THE {xi} BOO BINARY WITH CHANDRA, AND REVEALING THE SPECTRAL TYPE DEPENDENCE OF THE CORONAL 'FIP EFFECT'

    SciTech Connect

    Wood, Brian E.; Linsky, Jeffrey L. E-mail: jlinsky@jila.colorado.ed

    2010-07-10

    On 2008 May 2, Chandra observed the X-ray spectrum of {xi} Boo (G8 V+K4 V), resolving the binary for the first time in X-rays and allowing the coronae of the two stars to be studied separately. With the contributions of {xi} Boo A and B to the system's total X-ray emission now observationally established (88.5% and 11.5%, respectively), consideration of mass loss measurements for GK dwarfs of various activity levels (including one for {xi} Boo) leads to the surprising conclusion that {xi} Boo B may dominate the wind from the binary, with {xi} Boo A's wind being very weak despite its active corona. Emission measure (EM) distributions and coronal abundances are computed for both stars and compared with Chandra measurements of other moderately active stars with G8-K5 spectral types, all of which exhibit a narrow peak in EM near log T = 6.6, indicating that the coronal heating process in these stars has a strong preference for this temperature. As is the case for the Sun and many other stars, our sample of stars shows coronal abundance anomalies dependent on the first ionization potential (FIP) of the element. We see no dependence of the degree of 'FIP effect' on activity, but there is a dependence on spectral type, a correlation that becomes more convincing when moderately active main-sequence stars with a broader range of spectral types are considered. This clear dependence of coronal abundances on spectral type weakens if the stellar sample is allowed to be contaminated by evolved stars, interacting binaries, or extremely active stars with log L{sub X} >29, explaining why this correlation has not been recognized in the past.

  4. Time- and spectrally resolved measurements of laser-driven hohlraum radiation

    SciTech Connect

    Hessling, T.; Blazevic, A.; Stoehlker, T.; Frank, A.; Kraus, D.; Roth, M.; Schaumann, G.; Schumacher, D.; Hoffmann, D. H. H.

    2011-07-15

    At the GSI Helmholtz center for heavy-ion research combined experiments with heavy ions and laser-produced plasmas are investigated. As a preparation to utilize indirectly heated targets, where a converter hohlraum provides thermal radiation to create a more homogeneous plasma, this converter target has to be characterized. In this paper the latest results of these measurements are presented. Small spherical cavities with diameters between 600 and 750 {mu}m were heated with laser energies up to 30 J at 532-nm wavelength. Radiation temperatures could be determined by time-resolved as well as time-integrated diagnostics, and maximum values of up to 35 eV were achieved.

  5. Time- and spectrally resolved measurements of laser-driven hohlraum radiation.

    PubMed

    Hessling, T; Blažević, A; Frank, A; Kraus, D; Roth, M; Schaumann, G; Schumacher, D; Stöhlker, T; Hoffmann, D H H

    2011-07-01

    At the GSI Helmholtz center for heavy-ion research combined experiments with heavy ions and laser-produced plasmas are investigated. As a preparation to utilize indirectly heated targets, where a converter hohlraum provides thermal radiation to create a more homogeneous plasma, this converter target has to be characterized. In this paper the latest results of these measurements are presented. Small spherical cavities with diameters between 600 and 750 μm were heated with laser energies up to 30 J at 532-nm wavelength. Radiation temperatures could be determined by time-resolved as well as time-integrated diagnostics, and maximum values of up to 35 eV were achieved. PMID:21867327

  6. Measurement of depth-resolved thermal deformation distribution using phase-contrast spectral optical coherence tomography.

    PubMed

    Zhang, Yun; Dong, Bo; Bai, Yulei; Ye, Shuangli; Lei, Zhenkun; Zhou, Yanzhou

    2015-10-19

    An updated B-scan method is proposed for measuring the evolution of thermal deformation fields in polymers. In order to measure the distributions of out-of-plane deformation and normal strain field, phase-contrast spectral optical coherence tomography (PC-SOCT) was performed with the depth range and resolution of 4.3 mm and 10.7 μm, respectively, as thermal loads were applied to three different multilayer samples. The relation between temperature and material refractive index was predetermined before the measurement. After accounting for the refractive index, the thermal deformation fields in the polymer were obtained. The measured thermal expansion coefficient of silicone sealant was approximately equal to its reference value. This method allows correctly assessing the mechanical properties in semitransparent polymers. PMID:26480464

  7. Peak Flux Distributions of Solar Radio Type-i Bursts from Highly Resolved Spectral Observations

    NASA Astrophysics Data System (ADS)

    Iwai, K.; Masuda, S.; Miyoshi, Y.; Tsuchiya, F.; Morioka, A.; Misawa, H.

    2013-05-01

    Solar radio type-I bursts were observed on 2011 January 26 by high resolution observations with the radio telescope AMATERAS in order to derive their peak flux distributions. We have developed a two-dimensional auto burst detection algorithm that can distinguish each type-I burst element from complex noise storm spectra that include numerous instances of radio frequency interference (RFI). This algorithm removes RFI from the observed radio spectra by applying a moving median filter along the frequency axis. Burst and continuum components are distinguished by a two-dimensional maximum and minimum search of the radio dynamic spectra. The analysis result shows that each type-I burst element has one peak flux without double counts or missed counts. The peak flux distribution of type-I bursts derived using this algorithm follows a power law with a spectral index between 4 and 5.

  8. Gas temperature and density measurements based on spectrally resolved Rayleigh-Brillouin scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Lock, James A.

    1992-01-01

    The use of molecular Rayleigh scattering for measurements of gas density and temperature is evaluated. The technique used is based on the measurement of the spectrum of the scattered light, where both temperature and density are determined from the spectral shape. Planar imaging of Rayleigh scattering from air using a laser light sheet is evaluated for ambient conditions. The Cramer-Rao lower bounds for the shot-noise limited density and temperature measurement uncertainties are calculated for an ideal optical spectrum analyzer and for a planar mirror Fabry-Perot interferometer used in a static, imaging mode. With this technique, a single image of the Rayleigh scattered light can be analyzed to obtain density (or pressure) and temperature. Experimental results are presented for planar measurements taken in a heated air stream.

  9. Advanced microscopy :time-resolved multi-spectral imaging of single biomolecules.

    SciTech Connect

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

    2005-12-01

    Over the past few years we have developed the ability to acquire images through a confocal microscope that contain, for each pixel, the simultaneous fluorescence lifetime and spectra of multiple fluorophores within that pixel. We have demonstrated that our system has the sensitivity to make these measurements on single molecules. The spectra and lifetimes of fluorophores bound to complex molecules contain a wealth of information on the conformational dynamics and local chemical environments of the molecules. However, the detailed record of spectral and temporal information our system provides from fluorophores in single molecules has not been previously available. Therefore, we have studied several fluorophores and simple fluorophore-molecule systems that are representative of the use of fluorophores in biological systems. Experiments include studies of a simple fluorescence resonance energy transfer (FRET) system, green fluorescent probe variants and quantum dots. This work is intended to provide a basis for understanding how fluorophores report on the chemistry of more complex biological molecules.

  10. Spectrally resolved multi-channel contributions to the harmonic emission in N2

    NASA Astrophysics Data System (ADS)

    Diveki, Z.; Camper, A.; Haessler, S.; Auguste, T.; Ruchon, T.; Carré, B.; Salières, P.; Guichard, R.; Caillat, J.; Maquet, A.; Taïeb, R.

    2012-02-01

    When generated in molecules, high-order harmonics can be emitted through different ionization channels. The coherent and ultrafast electron dynamics occurring in the ion during the generation process is directly imprinted in the harmonic signal, i.e. in its amplitude and spectral phase. In aligned N2 molecules, we find evidence for a fast variation of this phase as a function of the harmonic order when varying the driving laser intensity. Basing our analysis on a three-step model, we find that this phase variation is a signature of transitions from a single- to a multi-channel regime. In particular, we show that significant nuclear dynamics may occur in the ionization channels on the attosecond timescale, affecting both the amplitude and the phase of the harmonic signal.

  11. PEAK FLUX DISTRIBUTIONS OF SOLAR RADIO TYPE-I BURSTS FROM HIGHLY RESOLVED SPECTRAL OBSERVATIONS

    SciTech Connect

    Iwai, K.; Masuda, S.; Miyoshi, Y.; Tsuchiya, F.; Morioka, A.; Misawa, H.

    2013-05-01

    Solar radio type-I bursts were observed on 2011 January 26 by high resolution observations with the radio telescope AMATERAS in order to derive their peak flux distributions. We have developed a two-dimensional auto burst detection algorithm that can distinguish each type-I burst element from complex noise storm spectra that include numerous instances of radio frequency interference (RFI). This algorithm removes RFI from the observed radio spectra by applying a moving median filter along the frequency axis. Burst and continuum components are distinguished by a two-dimensional maximum and minimum search of the radio dynamic spectra. The analysis result shows that each type-I burst element has one peak flux without double counts or missed counts. The peak flux distribution of type-I bursts derived using this algorithm follows a power law with a spectral index between 4 and 5.

  12. Identification of key aerosol populations through their size and composition resolved spectral scattering and absorption

    NASA Astrophysics Data System (ADS)

    Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.

    2013-03-01

    Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.

  13. Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

    NASA Astrophysics Data System (ADS)

    Crooker, S. A.; Liu, F.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Ruden, P. P.

    2014-10-01

    We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ˜ 11%) than at the low-energy red end (˜4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

  14. Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

    SciTech Connect

    Crooker, S. A.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Liu, F.; Ruden, P. P.

    2014-10-13

    We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ∼ 11%) than at the low-energy red end (∼4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

  15. Spatial resolving power and spectral sensitivity of the saltwater crocodile, Crocodylus porosus, and the freshwater crocodile, Crocodylus johnstoni.

    PubMed

    Nagloo, Nicolas; Collin, Shaun P; Hemmi, Jan M; Hart, Nathan S

    2016-05-01

    Crocodilians are apex amphibious predators that occupy a range of tropical habitats. In this study, we examined whether their semi-aquatic lifestyle and ambush hunting mode are reflected in specific adaptations in the peripheral visual system. Design-based stereology and microspectrophotometry were used to assess spatial resolving power and spectral sensitivity of saltwater (Crocodylus porosus) and freshwater crocodiles (Crocodylus johnstoni). Both species possess a foveal streak that spans the naso-temporal axis and mediates high spatial acuity across the central visual field. The saltwater crocodile and freshwater crocodile have a peak spatial resolving power of 8.8 and 8.0 cycles deg(-1), respectively. Measurement of the outer segment dimensions and spectral absorbance revealed five distinct photoreceptor types consisting of three single cones, one twin cone and a rod. The three single cones (saltwater/freshwater crocodile) are violet (424/426 nm λmax), green (502/510 nm λmax) and red (546/554 nm λmax) sensitive, indicating the potential for trichromatic colour vision. The visual pigments of both members of the twin cones have the same λmax as the red-sensitive single cone and the rod has a λmax at 503/510 nm (saltwater/freshwater). The λmax values of all types of visual pigment occur at longer wavelengths in the freshwater crocodile compared with the saltwater crocodile. Given that there is a greater abundance of long wavelength light in freshwater compared with a saltwater environment, the photoreceptors would be more effective at detecting light in their respective habitats. This suggests that the visual systems of both species are adapted to the photic conditions of their respective ecological niche. PMID:27208035

  16. Spectral mapping of 3D multi-cellular tumor spheroids: time-resolved confocal microscopy.

    PubMed

    Mohapatra, Saswat; Nandi, Somen; Chowdhury, Rajdeep; Das, Gaurav; Ghosh, Surajit; Bhattacharyya, Kankan

    2016-07-21

    A tumor-like multi-cellular spheroid (3D) differs from a 2D cell in a number of ways. This is demonstrated using time resolved confocal microscopy. Two different tumor spheroids - HeLa (cervical cancer) and A549 (lung cancer) - are studied using 3 different fluorescent dyes - C153 (non-covalent), CPM (covalent) and doxorubicin (non-covalent, anti-cancer drug). The pattern of localization of these three fluorescent probes in the 3D tumor cell exhibits significant differences from that in the conventional 2D cells. For both the cells (HeLa and A549), the total uptake of doxorubicin in the 3D cell is much lower than that in the 2D cell. The uptake of doxorubicin molecules in the A549 spheroid is significantly different compared to the HeLa spheroid. The local polarity (i.e. emission maxima) and solvation dynamics in the 3D tumor cell differ from those in 2D cells. The covalent probe CPM exhibits intermittent fluorescence oscillations in the 1-2 s time scale. This is attributed to redox processes. These results may provide new insights into 3D tumors. PMID:27336201

  17. Novel instrumentation for spectrally resolved soft x-ray plasma tomography: Development and pilot results on TEXTOR

    NASA Astrophysics Data System (ADS)

    Shmaenok, L. A.; Golovkin, S. V.; Govorun, V. N.; Ekimov, A. V.; Salashchenko, N. N.; Pickalov, V. V.; Belik, V. P.; Schüller, F. C.; Donné, A. J. H.; Oomens, A. A. M.; Prokhorov, K. A.; Andreev, S. S.; Sorokin, A. A.; Podlaskin, B. G.; Khasanov, L. V.

    2001-02-01

    A novel instrumentation for wavelength- and time-resolved plasma emission tomography in the range 0.1-4 keV has been demonstrated on the Torus Experiment for Technology Oriented Research (TEXTOR). The technique is intended for reconstruction of distributions of local emission coefficients (LEC) for selected spectral lines of impurity ions. Further determination (with additional data on electron density and temperature) of spatial distributions of impurity ions at particular ionization stages will become feasible. Spectrally selective plasma images at several viewpoints around plasma are obtained with miniature pinhole cameras supplemented with multilayer mirrors as dispersion elements. The x-ray image is converted to a visible image and transported by a fiber bundle to a gain enhanced recording camera with an electron bombarded charge coupled device tube. A part of the system has been installed on temporary TEXTOR ports. First demonstration results have been obtained on plasma imaging and on subsequent LEC reconstruction using a modified iterative sinogram restoration tomography algorithm. The complete diagnostics will be operational after the TEXTOR shutdown in 2001.

  18. Phenomenology of spectrally and temporally resolved infrared emissions from bomb detonations

    NASA Astrophysics Data System (ADS)

    Gross, Kevin; Dills, Anthony; Tuttle, Ron; Perram, Glen

    2002-10-01

    The remote sensing of infrared signatures from exothermic reactions during military operations, including missile launches, muzzle flashes, and bomb detonations has been studied using fast FTIR techniques. Battle space characterization includes the ability to classify the munitions type, size, and other characteristics. One possible approach to munitions classification is to understand the spectral and temporal signatures from explosive ordinance. To investigate this possibility, experimental data has been collected remotely from ground-based sensors, processed, and analyzed for several conventional munitions. Field observations of 56 detonation events included a set of aircraft delivered ordnance and a series of static ground detonations for a variety of bomb sizes, types and environmental conditions. The emission is well represented by a gray body with continuously decreasing temperature and characteristic decay times of 1-4 s, providing only limited variability with detonation conditions. However, the fireball size times the emissivity as a function of time can be determined from the spectra without imaging and provides a more sensitive signature. The degree of temporal overlap as a function of frequency for a pair of detonation events provides a very sensitive discriminator for explosion conditions. The temporal overlap decreases with increasing emission frequency for all the observed events, indicating more information content at higher frequencies. Finally, the temporal nature of the emissions has been analyzed, providing a significant reduction in the dimensionality of the data.

  19. SPATIALLY AND SPECTRALLY RESOLVED OBSERVATIONS OF A ZEBRA PATTERN IN A SOLAR DECIMETRIC RADIO BURST

    SciTech Connect

    Chen Bin; Bastian, T. S.; Gary, D. E.; Jing Ju

    2011-07-20

    We present the first interferometric observation of a zebra-pattern radio burst with simultaneous high spectral ({approx}1 MHz) and high time (20 ms) resolution. The Frequency-Agile Solar Radiotelescope Subsystem Testbed (FST) and the Owens Valley Solar Array (OVSA) were used in parallel to observe the X1.5 flare on 2006 December 14. By using OVSA to calibrate the FST, the source position of the zebra pattern can be located on the solar disk. With the help of multi-wavelength observations and a nonlinear force-free field extrapolation, the zebra source is explored in relation to the magnetic field configuration. New constraints are placed on the source size and position as a function of frequency and time. We conclude that the zebra burst is consistent with a double-plasma resonance model in which the radio emission occurs in resonance layers where the upper-hybrid frequency is harmonically related to the electron cyclotron frequency in a coronal magnetic loop.

  20. "Cat"-ology: Spectrally resolved neurophotonics in the mammalian brain and phantom studies

    NASA Astrophysics Data System (ADS)

    Tanner, Kandice

    Physicists provide significant contributions to the field of Biology and Medical Sciences by applying basic physics principles to the field. Specifically, in this work, we probed the light-matter interactions in the NIR region to understand physiological processes in the mammalian brain. We sought to improve on existing principles and propose a new technique by which we can decipher these processes spectrally. This technique touted to be independent of the light transport regime allowed us to examine the hemodynamics and neuronal activity. The aim was then to test this technique and see if it produces results that were comparable to the well established Fd-NIRS in distinguishing physiological processes. Secondly, we wanted to prove that this technique was light transport regime independent which is not the case for the Fd-NIRS. The cat was chosen as an ideal test subject as its anatomy is such that photons are not fully diffusive before being detected as the total size of the grey matter in the cat is roughly 3mm thick. Additionally, we had a priori information about the activation of the visual cortex as a response to specific stimuli.

  1. Coherent photon interference elimination and spectral correction in femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

    NASA Astrophysics Data System (ADS)

    Dang, Wei; Mao, Pengcheng; Weng, Yuxiang

    2013-07-01

    We report an improved setup of femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) with a 210 fs temporal response. The system employs a Cassegrain objective to collect and focus fluorescence photons, which eliminates the interference from the coherent photons in the fluorescence amplification by temporal separation of the coherent photons and the fluorescence photons. The gain factor of the Cassegrain objective-assisted FNOPAS is characterized as 1.24 × 105 for Rhodamine 6G. Spectral corrections have been performed on the transient fluorescence spectra of Rhodamine 6G and Rhodamine 640 in ethanol by using an intrinsic calibration curve derived from the spectrum of superfluorescence, which is generated from the amplification of the vacuum quantum noise. The validity of spectral correction is illustrated by comparisons of spectral shape and peak wavelength between the corrected transient fluorescence spectra of these two dyes acquired by FNOPAS and their corresponding standard reference spectra collected by the commercial streak camera. The transient fluorescence spectra of the Rhodamine 6G were acquired in an optimized phase match condition, which gives a deviation in the peak wavelength between the retrieved spectrum and the reference spectrum of 1.0 nm, while those of Rhodamine 640 were collected in a non-optimized phase match condition, leading to a deviation in a range of 1.0-3.0 nm. Our results indicate that the improved FNOPAS can be a reliable tool in the measurement of transient fluorescence spectrum for its high temporal resolution and faithfully corrected spectrum.

  2. Spatially Resolved WFC3/Grism Spectral Line Imaging of Gravitational Lensed Herschel-selected Luminous Dusty Starbursts

    NASA Astrophysics Data System (ADS)

    Cooray, Asantha

    2013-10-01

    We propose WFC3 G102 and G141 grism spectral imaging of two gravitationally lensed dusty, starburst galaxies found with the 600 square degree Herschel-ATLAS survey. One galaxy is the brightest {both in far-IR at 250 micron and in near-IR in J/K-band}, while the second is the largest {11 arcsec on the sky} of the lensed sub-mm galaxies in a sample of 200 imaged with WFC3/F110W. The two galaxies are at redshifts that are optimal for grism observations with HST/WFC3. The lensing flux magnification and spatial enhancement makes them very unique for the study proposed hereand will increase the number of lensed galaxies imaged in spectral lines with WFC3 grisms to three from existing single serendipitous lens studied in HST-3D survey. With WFC3 grism spectra taken in a specific orientation to minimize foreground and lensing galaxy confusion we can map each of these galaxies in a variety of spatially-resolved spectral lines in the rest-frame optical, including impostant Balmer lines for studies on the interstellar medium. The grism spectra will allow us to determine the gas-phase metallicities of these two galaxies and to study the extinction of optically-thin regions compared to direct sub-mm emission seen in interferometric continuum images of optically thick dust in starbursting knots and clumps. With spatial resolution provided by gravitational lensing combined with HST/WFC3 resolution, we will be able to study the dependence of line ratios in high density/SFR regions to low dense diffuse environments.

  3. Protein interaction quantified in vivo by spectrally resolved fluorescence resonance energy transfer

    PubMed Central

    2004-01-01

    We describe a fluorescence resonance energy transfer (FRET)-based method for finding in living cells the fraction of a protein population (αT) forming complexes, and the average number (n) of those protein molecules in each complex. The method relies both on sensitized acceptor emission and on donor de-quenching (by photobleaching of the acceptor molecules), coupled with full spectral analysis of the differential fluorescence signature, in order to quantify the donor/acceptor energy transfer. The approach and sensitivity limits are well suited for in vivo microscopic investigations. This is demonstrated using a scanning laser confocal microscope to study complex formation of the sterile 2 α-factor receptor protein (Ste2p), labelled with green, cyan, and yellow fluorescent proteins (GFP, CFP, and YFP respectively), in budding yeast Saccharomyces cerevisiae. A theoretical model is presented that relates the efficiency of energy transfer in protein populations (the apparent FRET efficiency, Eapp) to the energy transferred in a single donor/acceptor pair (E, the true FRET efficiency). We determined E by using a new method that relies on Eapp measurements for two donor/acceptor pairs, Ste2p–CFP/Ste2p–YFP and Ste2p–GFP/Ste2p–YFP. From Eapp and E we determined αT≈1 and n≈2 for Ste2 proteins. Since the Ste2p complexes are formed in the absence of the ligand in our experiments, we conclude that the α-factor pheromone is not necessary for dimerization. PMID:15352875

  4. Spatially resolved Spitzer-IRS spectral maps of the superwind in M82

    NASA Astrophysics Data System (ADS)

    Beirão, P.; Armus, L.; Lehnert, M. D.; Guillard, P.; Heckman, T.; Draine, B.; Hollenbach, D.; Walter, F.; Sheth, K.; Smith, J. D.; Shopbell, P.; Boulanger, F.; Surace, J.; Hoopes, C.; Engelbracht, C.

    2015-08-01

    We have mapped the superwind/halo region of the nearby starburst galaxy M82 in the mid-infrared with Spitzer - IRS. The spectral regions covered include the H2 S(1)-S(3), [Ne II], [Ne III] emission lines and polycyclic aromatic hydrocarbon (PAH) features. We estimate the total warm H2 mass and the kinetic energy of the outflowing warm molecular gas to be between Mwarm ˜ 5 and 17 × 106 M⊙ and EK ˜ 6 and 20 × 1053 erg. Using the ratios of the 6.2, 7.7 and 11.3 μm PAH features in the IRS spectra, we are able to estimate the average size and ionization state of the small grains in the superwind. There are large variations in the PAH flux ratios throughout the outflow. The 11.3/7.7 and the 6.2/7.7 PAH ratios both vary by more than a factor of 5 across the wind region. The northern part of the wind has a significant population of PAH's with smaller 6.2/7.7 ratios than either the starburst disc or the southern wind, indicating that on average, PAH emitters are larger and more ionized. The warm molecular gas to PAH flux ratios (H2/PAH) are enhanced in the outflow by factors of 10-100 as compared to the starburst disc. This enhancement in the H2/PAH ratio does not seem to follow the ionization of the atomic gas (as measured with the [Ne III]/[Ne II] line flux ratio) in the outflow. This suggests that much of the warm H2 in the outflow is excited by shocks. The observed H2 line intensities can be reproduced with low-velocity shocks (v < 40 km s-1) driven into moderately dense molecular gas (102 < nH < 104 cm-3) entrained in the outflow.

  5. The stellar populations of low-luminosity active galactic nuclei - III. Spatially resolved spectral properties

    NASA Astrophysics Data System (ADS)

    Cid Fernandes, R.; González Delgado, R. M.; Storchi-Bergmann, T.; Martins, L. Pires; Schmitt, H.

    2005-01-01

    In a recently completed survey of the stellar population properties of low-ionization nuclear emission-line regions (LINERs) and LINER/HII transition objects (TOs), we have identified a numerous class of galactic nuclei which stand out because of their conspicuous 108-9 yr populations, traced by high-order Balmer absorption lines and other stellar indices. These objects are called `young-TOs', because they all have TO-like emission-line ratios. In this paper we extend this previous work, which concentrated on the nuclear properties, by investigating the radial variations of spectral properties in low-luminosity active galactic nuclei (LLAGNs). Our analysis is based on high signal-to-noise ratio (S/N) long-slit spectra in the 3500-5500 Å interval for a sample of 47 galaxies. The data probe distances of typically up to 850 pc from the nucleus with a resolution of ~100 pc (~1 arcsec) and S/N ~ 30. Stellar population gradients are mapped by the radial profiles of absorption-line equivalent widths and continuum colours along the slit. These variations are further analysed by means of a decomposition of each spectrum in terms of template galaxies representative of very young (<=107 yr), intermediate age (108-9 yr) and old (1010 yr) stellar populations. This study reveals that young-TOs also differ from old-TOs and old-LINERs in terms of the spatial distributions of their stellar populations and dust. Specifically, our main findings are as follows. (i) Significant stellar population gradients are found almost exclusively in young-TOs. (ii) The intermediate age population of young-TOs, although heavily concentrated in the nucleus, reaches distances of up to a few hundred pc from the nucleus. Nevertheless, the half width at half-maximum of its brightness profile is more typically 100 pc or less. (iii) Objects with predominantly old stellar populations present spatially homogeneous spectra, be they LINERs or TOs. (iv) Young-TOs have much more dust in their central regions

  6. First spectrally-resolved H2 observations towards HH 54 . Low H2O abundance in shocks

    NASA Astrophysics Data System (ADS)

    Santangelo, G.; Antoniucci, S.; Nisini, B.; Codella, C.; Bjerkeli, P.; Giannini, T.; Lorenzani, A.; Lundin, L. K.; Cabrit, S.; Calzoletti, L.; Liseau, R.; Neufeld, D.; Tafalla, M.; van Dishoeck, E. F.

    2014-09-01

    Context. Herschel observations suggest that the H2O distribution in outflows from low-mass stars resembles the H2 emission. It is still unclear which of the different excitation components that characterise the mid- and near-IR H2 distribution is associated with H2O. Aims: The aim is to spectrally resolve the different excitation components observed in the H2 emission. This will allow us to identify the H2 counterpart associated with H2O and finally derive directly an H2O abundance estimate with respect to H2. Methods: We present new high spectral resolution observations of H2 0-0 S(4), 0-0 S(9), and 1-0 S(1) towards HH 54, a bright nearby shock region in the southern sky. In addition, new Herschel/HIFI H2O (212 - 101) observations at 1670 GHz are presented. Results: Our observations show for the first time a clear separation in velocity of the different H2 lines: the 0-0 S(4) line at the lowest excitation peaks at -7 km s-1, while the more excited 0-0 S(9) and 1-0 S(1) lines peak at -15 km s-1. H2O and high-J CO appear to be associated with the H2 0-0 S(4) emission, which traces a gas component with a temperature of 700-1000 K. The H2O abundance with respect to H2 0-0 S(4) is estimated to be X(H2O) < 1.4 × 10-5 in the shocked gas over an area of 13''. Conclusions: We resolve two distinct gas components associated with the HH 54 shock region at different velocities and excitations. This allows us to constrain the temperature of the H2O emitting gas (≤1000 K) and to derive correct estimates of H2O abundance in the shocked gas, which is lower than what is expected from shock model predictions. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs: 089.C-0772, 292.C-5025.

  7. Using Analytic Techniques to Resolve Numerical Issues in a Pseudo Spectral Solver for a Black Hole Scalar Field

    NASA Astrophysics Data System (ADS)

    Munro, Eugene

    2013-12-01

    In this paper, we will solve the Hamiltonian constraint describing a curved general relativistic spacetime to find initial data describing how a black hole exists in vacuum. This has been done before by other researchers [Ansorg, 2004], and we will be adapting our own methods to an existing pseudo spectral Poisson solver [Gourgoulhon, 2001]. The need for this adaptation arises from improper numerical handling, done by pseudo spectral-methods, of a large part the Hamiltonian constraint equation due to the presence of the black hole singularity. To resolve a portion of this issue up to a given order, we will determine irregularities by executing a polynomial expansion on the Hamiltonian constraint, analytically solving the troublesome components of the equation and subtracting those out of the numerical process. This technique will increase the equation's differentiability and allow the numerical solver to run more efficiently. We will cover all the calculations needed to describe one black hole with arbitrary spin and linear momentum. Our process is easily expanded into cases with n black holes [Brandt, 1997], which we will show in chapter 2. We will implement a spherical harmonic decomposition of the black hole conformal factor, using them as basis functions by which to further expand and dissect the Hamiltonian Constraint equation. In the end, the expansion and subtraction method will be done out to the order of r4, where r is the spherical radius assuming the black hole is at the coordinate origin, making the Hamiltonian equation, which, unaltered, is a C 2 equation, become a C7 equation. Smoothing the Hamiltonian improves numerical precision, especially near the BH where the most interesting physics occurs. The method used in this paper can be further implemented to higher orders of r to yield even smoother conditions. We will test the numerical results of using this method against the existing solver that uses the publicly available Lorene numerical libraries

  8. Spectrally Resolved Flux Derived from Collocated AIRS and CERES Observations and its Application in Model Validation. Part I; Clear-Sky Over the Tropic Oceans

    NASA Technical Reports Server (NTRS)

    Huang, Xianglei; Yang, Wenze; Loeb, Norman G.; Ramaswamy, V.

    2008-01-01

    Spectrally resolved outgoing IR flux, the integrand of the outgoing longwave radiation (OLR), has its unique value in evaluating model simulations. Here we describe an algorithm of deriving such clear-sky outgoing spectral flux through the whole IR region from the collocated Atmospheric Infrared Sounder (AIRS) and the Clouds & the Earth's Radiant Energy System (CERES) measurements over the tropical oceans. Based on the scene types and corresponding angular distribution models (ADMs) used in the CERES Single Satellite Footprint (SSF) dataset, spectrally-dependent ADMs are developed and used to estimate the spectral flux at each AIRS channel. A multivariate linear prediction scheme is then used to estimate spectral fluxes at frequencies not covered by the AIRS instrument. The whole algorithm is validated using synthetic spectra as well as the CERES OLR measurements. Using the GFDL AM2 model simulation as a case study, the application of the derived clear-sky outgoing spectral flux in model evaluation is illustrated. By comparing the observed and simulated spectral flux in 2004, compensating errors in the simulated OLR from different absorption bands can be revealed, so does the errors from frequencies within a given absorption band. Discrepancies between the simulated and observed spatial distributions and seasonal evolutions of the spectral fluxes at different spectral ranges are further discussed. The methodology described in this study can be applied to other surface types as well as cloudy-sky observations and corresponding model evaluations.

  9. Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA

    SciTech Connect

    Mancini, R. C.; Johns, H. M.; Joshi, T.; Mayes, D.; Nagayama, T.; Hsu, S. C.; Baumgaertel, J. A.; Cobble, J.; Krasheninnikova, N. S.; Bradley, P. A.; Hakel, P.; Murphy, T. J.; Schmitt, M. J.; Shah, R. C.; Tregillis, I. L.; Wysocki, F. J.

    2014-12-15

    We present spatially, temporally, and spectrally resolved narrow- and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight, including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to laser imprinting and zero-order hydrodynamics. Equatorial-view images show a “double bun” structure that is consistent with synthetic images obtained from post-processing 2D and 3D radiation-hydrodynamic simulations of the experiment. Polar-view images show a pentagonal, petal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of PDD OMEGA implosions not previously observed. Differences are noted with respect to a PDD experiment performed at National Ignition Facility.

  10. Spectral dependence of direct and trap-mediated recombination processes in lead halide perovskites using time resolved microwave conductivity.

    PubMed

    Guse, Joanna A; Soufiani, Arman M; Jiang, Liangcong; Kim, Jincheol; Cheng, Yi-Bing; Schmidt, Timothy W; Ho-Baillie, Anita; McCamey, Dane R

    2016-04-28

    Elucidating the decay mechanisms of photoexcited charge carriers is key to improving the efficiency of solar cells based on organo-lead halide perovskites. Here we investigate the spectral dependence (via above-, inter- and sub-bandgap optical excitations) of direct and trap-mediated decay processes in CH3NH3PbI3 using time resolved microwave conductivity (TRMC). We find that the total end-of-pulse mobility is excitation wavelength dependent - the mobility is maximized (172 cm(2) V(-1) s(-1)) when charge carriers are excited by near bandgap light (780 nm) in the low charge carrier density regime (10(9) photons per cm(2)), and is lower for above- and sub-bandgap excitations. Direct recombination is found to occur on the 100-400 ns timescale across excitation wavelengths near and above the bandgap, whereas indirect recombination processes displayed distinct behaviour following above- and sub-bandgap excitations, suggesting the influence of different trap distributions on recombination dynamics. PMID:27067120

  11. Nonstationary oscillation of gyrotron backward wave oscillators with cylindrical interaction structure

    SciTech Connect

    Chen, Shih-Hung; Chen, Liu

    2013-12-15

    The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) with cylindrical interaction structure was studied utilizing both steady-state analyses and time-dependent simulations. Comparisons of the numerical results reveal that the gyro-BWO becomes nonstationary when the trailing field structure completely forms due to the dephasing energetic electrons. The backward propagation of radiated waves with a lower resonant frequency from the trailing field structure interferes with the main internal feedback loop, thereby inducing the nonstationary oscillation of the gyro-BWO. The nonstationary gyro-BWO exhibits the same spectral pattern of modulated oscillations with a constant frequency separation between the central frequency and sidebands throughout the whole system. The frequency separation is found to be scaled with the square root of the maximum field amplitude, thus further demonstrating that the nonstationary oscillation of the gyro-BWO is associated with the beam-wave resonance detuning.

  12. 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.

  13. Scale Dependency of Convective Momentum Transport as Diagnosed from Cloud-Resolving Model Simulation with Spectral-bin Microphysics

    NASA Astrophysics Data System (ADS)

    Liu, Y. C.; Fan, J.; Zhang, G. J.; Xu, K. M.; Ghan, S. J.

    2014-12-01

    Convective momentum transport (CMT) has been demonstrated to have a large impact on global atmospheric circulation in both observational and numerical studies. In General Circulation Models (GCMs) CMT is often parameterized in a simple way by assuming that in-cloud horizontal momentum depends only on lateral entrainment and detrainment rates [Schneider and Lindzen, 1976]. In addition to lateral entrainment and detrainment rates the effect of perturbation pressure gradient force induced by convection (Pc) on momentum transport is significant. Because it is the most complicated term to be parameterized, a very simple form of products among a constant coefficient, mass flux, and environment vertical wind shear was employed to parameterize it [Gregory et al., 1997]. In addition, none of these CMT parameterizations deal with the scale problems. Thus, the goal of this study is to evaluate the past CMT parameterizations and explore the scale dependencies of Pc and CMT using Cloud Resolving Model (CRM) simulations from the Weather Research and Forecasting (WRF) coupled with the most sophisticated spectral-bin microphysics. Our preliminary results show that the parameterized CMT from the top-hat approach is underestimated especially at the gray zone scale (~4-50 km); using the simplified 3-updraft and 1-downdraft formulation proposed in our previous study for eddy transport of moisture, the CMT can be represented well. The formulation also produced a more accurate mass flux compared to the top-hat approach, which can potentially improve the parameterization of Pc. We investigate the relative contributions from linear and nonlinear forcing to Pc at different model grid spacing (dx). Our results show that the assumption that non-linear forcing is much smaller than linear force is valid only at dx > 128 km and dx < 8 km. At the dx = 32~16 km, linear and nonlinear forcings become compatible, suggesting a more sophisticated formula for Pc might be needed.

  14. Information retrieval for nonstationary data records

    NASA Technical Reports Server (NTRS)

    Su, M. Y.

    1971-01-01

    A review and a critical discussion are made on the existing methods for analysis of nonstationary time series, and a new algorithm for splitting nonstationary time series, is applied to the analysis of sunspot data.

  15. A BOINC based, citizen-science project for pixel spectral energy distribution fitting of resolved galaxies in multi-wavelength surveys

    NASA Astrophysics Data System (ADS)

    Vinsen, Kevin; Thilker, David

    2013-11-01

    In this work we present our experience from the first year of theSkyNet Pan-STARRS1 Optical Galaxy Survey (POGS) project. This citizen-scientist driven research project uses the Berkeley Open Infrastructure for Network Computing (BOINC) middleware and thousands of Internet-connected computers to measure the resolved galactic structural properties of ˜100,000 low redshift galaxies. We are combining the spectral coverage of GALEX, Pan-STARRS1, SDSS, and WISE to generate a value-added, multi-wavelength UV-optical-NIR galaxy atlas for the nearby Universe. Specifically, we are measuring physical parameters (such as local stellar mass, star formation rate, and first-order star formation history) on a resolved pixel-by-pixel basis using spectral energy distribution (SED) fitting techniques in a distributed computing mode. Berkeley Open Infrastructure for Network Computing.

  16. Nonstationary statistical theory for multipactor

    SciTech Connect

    Anza, S.; Vicente, C.; Gil, J.

    2010-06-15

    This work presents a new and general approach to the real dynamics of the multipactor process: the nonstationary statistical multipactor theory. The nonstationary theory removes the stationarity assumption of the classical theory and, as a consequence, it is able to adequately model electron exponential growth as well as absorption processes, above and below the multipactor breakdown level. In addition, it considers both double-surface and single-surface interactions constituting a full framework for nonresonant polyphase multipactor analysis. This work formulates the new theory and validates it with numerical and experimental results with excellent agreement.

  17. Linear dispersion-diffusion analysis and its application to under-resolved turbulence simulations using discontinuous Galerkin spectral/hp methods

    NASA Astrophysics Data System (ADS)

    Moura, R. C.; Sherwin, S. J.; Peiró, J.

    2015-10-01

    We investigate the potential of linear dispersion-diffusion analysis in providing direct guidelines for turbulence simulations through the under-resolved DNS (sometimes called implicit LES) approach via spectral/hp methods. The discontinuous Galerkin (DG) formulation is assessed in particular as a representative of these methods. We revisit the eigensolutions technique as applied to linear advection and suggest a new perspective to the role of multiple numerical modes, peculiar to spectral/hp methods. From this new perspective, "secondary" eigenmodes are seen to replicate the propagation behaviour of a "primary" mode, so that DG's propagation characteristics can be obtained directly from the dispersion-diffusion curves of the primary mode. Numerical dissipation is then appraised from these primary eigencurves and its effect over poorly-resolved scales is quantified. Within this scenario, a simple criterion is proposed to estimate DG's effective resolution in terms of the largest wavenumber it can accurately resolve in a given hp approximation space, also allowing us to present points per wavelength estimates typically used in spectral and finite difference methods. Although strictly valid for linear advection, the devised criterion is tested against (1D) Burgers turbulence and found to predict with good accuracy the beginning of the dissipation range on the energy spectra of under-resolved simulations. The analysis of these test cases through the proposed methodology clarifies why and how the DG formulation can be used for under-resolved turbulence simulations without explicit subgrid-scale modelling. In particular, when dealing with communication limited hardware which forces one to consider the performance for a fixed number of degrees of freedom, the use of higher polynomial orders along with moderately coarser meshes is shown to be the best way to translate available degrees of freedom into resolution power.

  18. Resolving the shocked gas in HH 54 with Herschel. CO line mapping at high spatial and spectral resolution

    NASA Astrophysics Data System (ADS)

    Bjerkeli, P.; Liseau, R.; Brinch, C.; Olofsson, G.; Santangelo, G.; Cabrit, S.; Benedettini, M.; Black, J. H.; Herczeg, G.; Justtanont, , K.; Kristensen, L. E.; Larsson, B.; Nisini, B.; Tafalla, M.

    2014-11-01

    Context. The HH 54 shock is a Herbig-Haro object, located in the nearby Chamaeleon II cloud. Observed CO line profiles are due to a complex distribution in density, temperature, velocity, and geometry. Aims: Resolving the HH 54 shock wave in the far-infrared (FIR) cooling lines of CO constrain the kinematics, morphology, and physical conditions of the shocked region. Methods: We used the PACS and SPIRE instruments on board the Herschel space observatory to map the full FIR spectrum in a region covering the HH 54 shock wave. Complementary Herschel-HIFI, APEX, and Spitzer data are used in the analysis as well. The observed features in the line profiles are reproduced using a 3D radiative transfer model of a bow-shock, constructed with the Line Modeling Engine code (LIME). Results: The FIR emission is confined to the HH 54 region and a coherent displacement of the location of the emission maximum of CO with increasing J is observed. The peak positions of the high-J CO lines are shifted upstream from the lower J CO lines and coincide with the position of the spectral feature identified previously in CO (10-9) profiles with HIFI. This indicates a hotter molecular component in the upstream gas with distinct dynamics. The coherent displacement with increasing J for CO is consistent with a scenario where IRAS12500 - 7658 is the exciting source of the flow, and the 180 K bow-shock is accompanied by a hot (800 K) molecular component located upstream from the apex of the shock and blueshifted by -7 km s-1. The spatial proximity of this knot to the peaks of the atomic fine-structure emission lines observed with Spitzer and PACS ([O i]63, 145 μm) suggests that it may be associated with the dissociative shock as the jet impacts slower moving gas in the HH 54 bow-shock. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  19. Confirmation of spectral jitter: a measured shift in the spectral distribution of intense pulsed light systems using a time-resolved spectrometer during exposure and increased fluence.

    PubMed

    Ash, C; Town, G; Clement, M

    2010-02-01

    High quality intense pulsed light (IPL) systems can offer simple, safe and effective treatments for long-term hair reduction, skin rejuvenation and removal of benign vascular and pigmented lesions. Considerable differences in clinical efficacy and adverse effects have been recorded amongst different IPL systems despite comparable display settings. This study examines the variation in pulse structures exhibited by several popular professional IPL systems that can cause a spectral change within the broadband output depending on the pulse structure chosen by the system designers. A fast spectrometer was used to capture IPL spectral outputs. A spectral distribution shift that occurs both within a pulse and between pulses is clearly demonstrated and is more prominent with uncontrolled free discharge systems than with square pulsed technology, which provides a constant spectral distribution throughout the pulse duration. PMID:20017711

  20. Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

    NASA Astrophysics Data System (ADS)

    Johns, H. M.; Mancini, R. C.; Nagayama, T.; Mayes, D. C.; Tommasini, R.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J. A.

    2016-01-01

    In warm target direct-drive inertial confinement fusion implosion experiments performed at the OMEGA laser facility, plastic micro-balloons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. These 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400 ± 28 eV, electron number density (Ne) = 8.5 × 1024 ± 2.5 × 1024 cm-3, and average areal density <ρR> = 86 ± 7 mg/cm2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2-9, dominated by l = 2. We extract a target breakup fraction of 7.1 ± 1.5% from our Fourier analysis. A new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5 ± 1 μm.

  1. Spectrally resolved modulated infrared radiometry of photothermal, photocarrier, and photoluminescence response of CdSe crystals: Determination of optical, thermal, and electronic transport parameters

    NASA Astrophysics Data System (ADS)

    Pawlak, M.; Chirtoc, M.; Horny, N.; Pelzl, J.

    2016-03-01

    Spectrally resolved modulated infrared radiometry (SR-MIRR) with super-band gap photoexcitation is introduced as a self-consistent method for semiconductor characterization (CdSe crystals grown under different conditions). Starting from a theoretical model combining the contributions of the photothermal (PT) and photocarrier (PC) signal components, an expression is derived for the thermal-to-plasma wave transition frequency ftc which is found to be wavelength-independent. The deviation of the PC component from the model at high frequency is quantitatively explained by a quasi-continuous distribution of carrier recombination lifetimes. The integral, broad frequency band (0.1 Hz-1 MHz) MIRR measurements simultaneously yielded the thermal diffusivity a, the effective IR optical absorption coefficient βeff, and the bulk carrier lifetime τc. Spectrally resolved frequency scans were conducted with interchangeable IR bandpass filters (2.2-11.3 μm) in front of the detector. The perfect spectral match of the PT and PC components is the direct experimental evidence of the key assumption in MIRR that de-exciting carriers are equivalent to blackbody (Planck) radiators. The exploitation of the β spectrum measured by MIRR allowed determining the background (equilibrium) free carrier concentration n0. At the shortest wavelength (3.3 μm), the photoluminescence (PL) component supersedes the PC one and has distinct features. The average sample temperature influences the PC component but not the PT one.

  2. Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

    DOE PAGESBeta

    Johns, H. M.; Mancini, R. C.; Nagayama, T.; Mayes, D. C.; Tommasini, R.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J. A.

    2016-01-25

    In warm target direct-drive ICF implosion experiments performed at the OMEGA laser facility, plastic microballoons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. These 2-D space-resolvedmore » titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400±28eV, electron number density (Ne) = 8.5x1024±2.5x1024 cm-3, and average areal density <ρR> = 86±7mg/cm2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2-9, dominated by l = 2. We extract a target breakup fraction of 7.1±1.5% from our Fourier analysis. A new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5±1μm.« less

  3. Retrieval of atomic oxygen and temperature in the thermosphere. Part 1: Feasibility of an experiment based on the spectrally resolved 147 micrometer limb emission

    NASA Astrophysics Data System (ADS)

    Zachor, A. S.; Sharma, R. D.; Yap, B. K.; Riehl, J. P.

    1989-04-01

    The importance of atomic oxygen and translational temperature in mesospheric/thermospheric processes is the motivation to study the feasibility of recovering vertical profiles of the temperature and O-atom density from limb scan data obtained near 147 micrometer and/or 63 micrometer wavelength, corresponding to the oxygen atom ground electronic state (OI) transitions. The limb radiance data must be spectrally resolved to recover both temperature and atomic oxygen density if only one of the OI lines is used, which is the approach investigated in this report. We show how the two vertical profiles can be recovered by applying an onion-peeling method to synthetic data. The temperature and O-atom density in each peeled layer are obtained simultaneously by nonlinear least-squares spectrum fitting. Spectral data in the 147 micrometer line was found to yield reasonably accurate and stable profiles from 300 km down to an altitude between 130 and 90 km, depending on the noise level and spectral resolution, and gave better results than the stronger 63 micrometer data below 140 km. We estimate that the S/N and spectral resolution required for successful retrievals could be provided by a confocal Fabry-Perot system operating near 147 micrometer although retrievals down to 90 km from data obtained at orbital altitude would require cooled foreoptics roughly a meter in diameter.

  4. Spectrally-resolved fluorescence cross sections of aerosolized biological live agents and simulants using five excitation wavelengths in a BSL-3 laboratory.

    PubMed

    Pan, Yong-Le; Hill, Steven C; Santarpia, Joshua L; Brinkley, Kelly; Sickler, Todd; Coleman, Mark; Williamson, Chatt; Gurton, Kris; Felton, Melvin; Pinnick, Ronald G; Baker, Neal; Eshbaugh, Jonathan; Hahn, Jerry; Smith, Emily; Alvarez, Ben; Prugh, Amber; Gardner, Warren

    2014-04-01

    A system for measuring spectrally-resolved fluorescence cross sections of single bioaerosol particles has been developed and employed in a biological safety level 3 (BSL-3) facility at Edgewood Chemical and Biological Center (ECBC). It is used to aerosolize the slurry or solution of live agents and surrogates into dried micron-size particles, and to measure the fluorescence spectra and sizes of the particles one at a time. Spectrally-resolved fluorescence cross sections were measured for (1) bacterial spores: Bacillus anthracis Ames (BaA), B. atrophaeus var. globigii (BG) (formerly known as Bacillus globigii), B. thuringiensis israelensis (Bti), B. thuringiensis kurstaki (Btk), B. anthracis Sterne (BaS); (2) vegetative bacteria: Escherichia coli (E. coli), Pantoea agglomerans (Eh) (formerly known as Erwinia herbicola), Yersinia rohdei (Yr), Yersinia pestis CO92 (Yp); and (3) virus preparations: Venezuelan equine encephalitis TC83 (VEE) and the bacteriophage MS2. The excitation wavelengths were 266 nm, 273 nm, 280 nm, 365 nm and 405 nm. PMID:24718194

  5. Using 2D correlation analysis to enhance spectral information available from highly spatially resolved AFM-IR spectra

    NASA Astrophysics Data System (ADS)

    Marcott, Curtis; Lo, Michael; Hu, Qichi; Kjoller, Kevin; Boskey, Adele; Noda, Isao

    2014-07-01

    The recent combination of atomic force microscopy and infrared spectroscopy (AFM-IR) has led to the ability to obtain IR spectra with nanoscale spatial resolution, nearly two orders-of-magnitude better than conventional Fourier transform infrared (FT-IR) microspectroscopy. This advanced methodology can lead to significantly sharper spectral features than are typically seen in conventional IR spectra of inhomogeneous materials, where a wider range of molecular environments are coaveraged by the larger sample cross section being probed. In this work, two-dimensional (2D) correlation analysis is used to examine position sensitive spectral variations in datasets of closely spaced AFM-IR spectra. This analysis can reveal new key insights, providing a better understanding of the new spectral information that was previously hidden under broader overlapped spectral features. Two examples of the utility of this new approach are presented. Two-dimensional correlation analysis of a set of AFM-IR spectra were collected at 200-nm increments along a line through a nucleation site generated by remelting a small spot on a thin film of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). There are two different crystalline carbonyl band components near 1720 cm-1 that sequentially disappear before a band at 1740 cm-1 due to more disordered material appears. In the second example, 2D correlation analysis of a series of AFM-IR spectra spaced every 1 μm of a thin cross section of a bone sample measured outward from an osteon center of bone growth. There are many changes in the amide I and phosphate band contours, suggesting changes in the bone structure are occurring as the bone matures.

  6. A spectral-timing analysis of the kHz QPOs in 4U 1636-53: the frequency-energy resolved RMS spectrum

    NASA Astrophysics Data System (ADS)

    Ribeiro, Evandro M.; Mendez, Mariano; Zhang, Guo-Bao; De Avellar, Márcio G. B.

    2016-07-01

    Our understanding of quasi-periodic oscillations (QPO) has been further advanced in the last few years by the use of combined spectral and timing techniques, and it is now clear that QPO properties are closely related to the spectral state of the source in which they appear. In this work we used all the available RXTE observations of the neutron-star low-mass X-ray binary 4U~1636-53 to study the properties of the kilohertz QPO as a function of energy and frequency. By following the frequency evolution of the kHz QPOs we created frequency-resolved fractional RMS spectra. We also studied the connection between the frequency of the kHz QPOs and the parameters of the model that fits the X-ray energy spectrum. We show the dependence of the QPO properties in a multi-parameter space, and we discuss the implication of our results to the mechanism that produces the QPOs. Our results provide input to the next generation of spectral-timing models, which will help us understand the variability and the environment around the neutron star in these systems.

  7. Spectral properties of transition metal pnictides and chalcogenides: Angle-resolved photoemission spectroscopy and dynamical mean-field theory

    NASA Astrophysics Data System (ADS)

    van Roekeghem, Ambroise; Richard, Pierre; Ding, Hong; Biermann, Silke

    2016-01-01

    Electronic Coulomb correlations lead to characteristic signatures in the spectroscopy of transition metal pnictides and chalcogenides: quasi-particle renormalizations, lifetime effects or incoherent badly metallic behavior above relatively low coherence temperatures are measures of many-body effects due to local Hubbard and Hund's couplings. We review and compare the results of angle-resolved photoemission spectroscopy experiments (ARPES) and of combined density functional/dynamical mean-field theory (DFT+DMFT) calculations. We emphasize the doping-dependence of the quasi-particle mass renormalization and coherence properties.

  8. Noise-Robust Spectral Signature Classification in Non-resolved Object Detection using Feedback Controlled Adaptive Learning

    NASA Astrophysics Data System (ADS)

    Schmalz, M.; Key, G.

    2012-09-01

    Accurate spectral signature classification is key to reliable nonresolved detection and recognition of spaceborne objects. In classical signature-based recognition applications, classification accuracy has been shown to depend on accurate spectral endmember discrimination. Unfortunately, signatures are corrupted by noise and clutter that can be nonergodic in astronomical imaging practice. In previous work, we have shown that object class separation and classifier refinement results can be severely corrupted by input noise, leading to suboptimal classification. We have also shown that computed pattern recognition, like its human counterpart, can benefit from processes such as learning or forgetting, which in spectral signature classification can support adaptive tracking of input nonergodicities. In this paper, we model learning as the acquisition or insertion of a new pattern into a classifier's knowledge base. For example, in neural nets (NNs), this insertion process could correspond to the superposition of a new pattern onto the NN weight matrix. Similarly, we model forgetting as the deletion of a pattern currently stored in the classifier knowledge base, for example, as a pattern deletion operation on the NN weight matrix, which is a difficult goal with classical neural nets (CNNs). In particular, this paper discusses the implementation of feedback control for pattern insertion and deletion in lattice associative memories (LAMs) and dynamically adaptive statistical data fusion (DASDAF) paradigms, in support of signature classification. It is shown that adaptive classifiers based on LNN or DASDAF technology can achieve accurate signature classification in the presence of nonergodic Gaussian and non-Gaussian noise, at low signal-to-noise ratio (SNR). Demonstration involves classification of multiple closely spaced, noise corrupted signatures from a NASA database of space material signatures at SNR > 0.1:1.

  9. The MUSCLES Treasury Survey: Temporally- and Spectrally-Resolved Irradiance from Low-mass Exoplanet Host Stars

    NASA Astrophysics Data System (ADS)

    France, Kevin; Parke Loyd, R. O.; Youngblood, Allison; Linsky, Jeffrey; MUSCLES Treasury Survey Team

    2016-01-01

    The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to near-UV; 5 - 3200 Ang) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential "biomarker" gases. It has been shown that the atmospheric signatures of potentially habitable planets around low-mass stars may be significantly different from planets orbiting Sun-like stars owing to the different UV spectral energy distribution. I will present results from a panchromatic survey (Hubble/Chandra/XMM/optical) of M and K dwarf exoplanet hosts, the MUSCLES Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems). We reconstruct the Lyman-alpha and extreme-UV (100-900 Ang) radiation lost to interstellar attenuation and create 5 Angstrom to 5 micron stellar irradiance spectra; these data will be publically available as a High-Level Science Product on MAST. We find that all low-mass exoplanet host stars exhibit significant chromospheric/transition region/coronal emission -- no "UV inactive" M dwarfs are observed. The F(far-UV)/F(near-UV) flux ratio, a driver for possible abiotic production of the suggested biomarkers O2 and O3, increases by ~3 orders of magnitude as the habitable zone moves inward from 1 to 0.1 AU, while the incident far-UV (912 - 1700 Ang) and XUV (5 - 900 Ang) radiation field strengths decrease by factors of a few across this range. Far-UV flare activity is common in 'optically inactive' M dwarfs; statistics from the entire sample indicate that large UV flares (E(300 - 1700 Ang) >= 10^31 erg) occur several times per day on typical M dwarf exoplanet hosts.

  10. Non-Markovian dynamics of an open quantum system with nonstationary coupling

    SciTech Connect

    Kalandarov, S. A.; Adamian, G. G.; Kanokov, Z.; Antonenko, N. V.; Scheid, W.

    2011-04-15

    The spectral, dissipative, and statistical properties of the damped quantum oscillator are studied in the case of non-Markovian and nonstationary system-heat bath coupling. The dissipation of collective energy is shown to be slowed down, and the decoherence rate and entropy grow with modulation frequency.

  11. Non-Markovian dynamics of an open quantum system with nonstationary coupling.

    PubMed

    Kalandarov, S A; Kanokov, Z; Adamian, G G; Antonenko, N V; Scheid, W

    2011-04-01

    The spectral, dissipative, and statistical properties of the damped quantum oscillator are studied in the case of non-Markovian and nonstationary system-heat bath coupling. The dissipation of collective energy is shown to be slowed down, and the decoherence rate and entropy grow with modulation frequency. PMID:21599112

  12. Model of non-stationary, inhomogeneous turbulence

    NASA Astrophysics Data System (ADS)

    Bragg, Andrew D.; Kurien, Susan; Clark, Timothy T.

    2016-07-01

    We compare results from a spectral model for non-stationary, inhomogeneous turbulence (Besnard et al. in Theor Comp Fluid Dyn 8:1-35, 1996) with direct numerical simulation (DNS) data of a shear-free mixing layer (SFML) (Tordella et al. in Phys Rev E 77:016309, 2008). The SFML is used as a test case in which the efficacy of the model closure for the physical-space transport of the fluid velocity field can be tested in a flow with inhomogeneity, without the additional complexity of mean-flow coupling. The model is able to capture certain features of the SFML quite well for intermediate to long times, including the evolution of the mixing-layer width and turbulent kinetic energy. At short-times, and for more sensitive statistics such as the generation of the velocity field anisotropy, the model is less accurate. We propose two possible causes for the discrepancies. The first is the local approximation to the pressure-transport and the second is the a priori spherical averaging used to reduce the dimensionality of the solution space of the model, from wavevector to wavenumber space. DNS data are then used to gauge the relative importance of both possible deficiencies in the model.

  13. Evidence of non-LTE Effects in Mesospheric Water Vapor from Spectrally-Resolved Emissions Observed by CIRRIS-1A

    NASA Technical Reports Server (NTRS)

    Zhou, D. K.; Mlynczak, M. G.; Lopez-Puertas, M.; Zaragoza, G.

    1999-01-01

    Evidence of non-LTE effects in mesospheric water vapor as determined by infrared spectral emission measurements taken from the space shuttle is reported. A cryogenic Michelson interferometer in the CIRRIS-1A shuttle payload yielded high quality, atmospheric infrared spectra. These measurements demonstrate the enhanced daytime emissions of H2O (020-010) which are the result of non-LTE processes and in agreement with non-LTE models. The radiance ratios of H2O (010 to 000) and (020 to 010) Q(1) transitions during daytime are compared with non-LTE model calculations to assess the vibration-to-vibration exchange rate between H2O and O2 in the mesosphere. An exchange rate of 1.2 x 10(exp -12)cc/s is derived.

  14. Spectral and spatial resolving of photoelectric property of femtosecond laser drilled holes of GaSb(1-x)Bi(x).

    PubMed

    Pan, C B; Zha, F X; Song, Y X; Shao, J; Dai, Y; Chen, X R; Ye, J Y; Wang, S M

    2015-07-15

    Femtosecond laser drilled holes of GaSbBi were characterized by the joint measurements of photoconductivity (PC) spectroscopy and laser-beam-induced current (LBIC) mapping. The excitation light in PC was focused down to 60 μm presenting the spectral information of local electronic property of individual holes. A redshift of energy band edge of about 6-8 meV was observed by the PC measurement when the excitation light irradiated on the laser drilled holes. The spatial resolving of photoelectric property was achieved by the LBIC mapping which shows "pseudo-holes" with much larger dimensions than the geometric sizes of the holes. The reduced LBIC current with the pseudo-holes is associated with the redshift effect indicating that the electronic property of the rim areas of the holes is modified by the femtosecond laser drilling. PMID:26176477

  15. Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.

    PubMed

    Zhao, Weixiong; Dong, Meili; Chen, Weidong; Gu, Xuejun; Hu, Changjin; Gao, Xiaoming; Huang, Wei; Zhang, Weijun

    2013-02-19

    Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days. PMID:23320530

  16. Efficient Spectral Diffusion at the Air/Water Interface Revealed by Femtosecond Time-Resolved Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy.

    PubMed

    Inoue, Ken-Ichi; Ishiyama, Tatsuya; Nihonyanagi, Satoshi; Yamaguchi, Shoichi; Morita, Akihiro; Tahara, Tahei

    2016-05-19

    Femtosecond vibrational dynamics at the air/water interface is investigated by time-resolved heterodyne-detected vibrational sum frequency generation (TR-HD-VSFG) spectroscopy and molecular dynamics (MD) simulation. The low- and high-frequency sides of the hydrogen-bonded (HB) OH stretch band at the interface are selectively excited with special attention to the bandwidth and energy of the pump pulses. Narrow bleach is observed immediately after excitation of the high-frequency side of the HB OH band at ∼3500 cm(-1), compared to the broad bleach observed with excitation of the low-frequency side at ∼3300 cm(-1). However, the time-resolved spectra observed with the two different excitations become very similar at 0.5 ps and almost indistinguishable by 1.0 ps. This reveals that efficient spectral diffusion occurs regardless of the difference of the pump frequency. The experimental observations are well-reproduced by complementary MD simulation. There is no experimental and theoretical evidence that supports extraordinary slow dynamics in the high-frequency side of the HB OH band, which was reported before. PMID:27120559

  17. Spatial methods for nonstationary fields

    NASA Astrophysics Data System (ADS)

    Nychka, D. W.

    2012-12-01

    Kriging is a non-parametric regression method used in geostatistics for estimating curves and surfaces and forms the core of most statistical methods for spatial data. In climate science these methods are very useful for estimating how climate varies over a geographic region when the observational data is sparse or the computer model runs are limited. A statistical challenge is to implement spatial methods for large sample sizes and also the heterogenity in the physical fields. Both common features of many geophysical problems. Equally important is to provide companion measures of uncertainty so that the estimated surfaces can be compared and interpreted in an objective way. Here we present a new statistical method that can represent nonstationary structure in a field and also scale to large numbers of spatial locations. A practical example is also presented for a subset of the North American Regional Climate Change and Assessment Program model data.

  18. Nonstationary oscillations in gyrotrons revisited

    SciTech Connect

    Dumbrajs, O.; Kalis, H.

    2015-05-15

    Development of gyrotrons requires careful understanding of different regimes of gyrotron oscillations. It is known that in the planes of the generalized gyrotron variables: cyclotron resonance mismatch and dimensionless current or cyclotron resonance mismatch and dimensionless interaction length complicated alternating sequences of regions of stationary, periodic, automodulation, and chaotic oscillations exist. In the past, these regions were investigated on the supposition that the transit time of electrons through the interaction space is much shorter than the cavity decay time. This assumption is valid for short and/or high diffraction quality resonators. However, in the case of long and/or low diffraction quality resonators, which are often utilized, this assumption is no longer valid. In such a case, a different mathematical formalism has to be used for studying nonstationary oscillations. One example of such a formalism is described in the present paper.

  19. Resolving the Large Scale Spectral Variability of the Luminous Seyfert 1 Galaxy 1H 0419-577

    NASA Technical Reports Server (NTRS)

    Pounds, K. A.; Reeves, J. N.; Page, K. L.; OBrien, P. T.

    2004-01-01

    An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 in September 2002, when the source was in an extreme low-flux state, found a very hard X-ray spectrum at 1-10 keV with a strong soft excess below approximately 1 keV. Comparison with an earlier XMM-Newton observation when 1H 0419-577 was X-ray bright indicated the dominant spectral variability was due to a steep power law or cool Comptonized thermal emission. Four further XMM-Newton observations, with 1H 0419-577 in intermediate flux states, now support that conclusion, while we also find the variable emission component in intermediate state difference spectra to be strongly modified by absorption in low ionisation matter. The variable soft excess is seen to be an artefact of absorption of the underlying continuum while the core soft emission is attributed to recombination in an extended region of more highly ionised gas. This new analysis underlines the importance of fully accounting for absorption in characterizing AGN X-ray spectra.

  20. Spatially-resolved spectral image of a microwave-induced plasma with Okamoto-cavity for nitridation of steel substrate.

    PubMed

    Sato, Shigeo; Arai, Yuuki; Wagatsuma, Kazuaki

    2014-01-01

    When a nitrogen microwave-induced plasma produced with an Okamoto-cavity was employed as a source for the nitridation of steel samples, the characteristics of the plasma were investigated by analyzing a spatially-resolved emission image of nitrogen excited species obtained with a two-dimensionally imaging spectrograph. Our previous study had reported on an excellent performance of the Okamoto-cavity microwave-induced plasma (MIP), enabling a nitrided layer having a several-micrometer-thickness to form on an iron substrate, even if the treatment is completed within 1 min, which is superior to a conventional plasma nitriding using low-pressure glow discharges requiring a prolonged treatment time. In this paper, the reason for this is discussed based on a spectrometric investigation. The emission images of band heads of nitrogen molecule and nitrogen molecule ion extended toward the axial/radial directions of the plasma at larger microwave powers supplied to the MIP, thus elevating the number density of the excited species of nitrogen, which would activate any chemical reaction on the iron substrate. However, a drastic increase in the growth rate of the nitrided layer when increasing the microwave power from 600 to 700 W, which had been observed in our previous study, could not be explained only from such a variation in the excited species of nitrogen. This result is probably because the growth process is dominantly controlled by thermal diffusion of nitrogen atom after it enters into the iron substrate, where the substrate temperature is the most important parameter concerning the mobility in the iron lattice. Therefore, the Okamoto-cavity MIP could contribute to a thermal source through radiative heating as well as a source of nitrogen excited species, especially in the growth process of the nitrided layer. PMID:24521910

  1. Non-Stationary Signals: Phase-Energy APPROACH—THEORY and Simulations

    NASA Astrophysics Data System (ADS)

    Klein, R.; Ingman, D.; Braun, S.

    2001-11-01

    Modern time-frequency methods are intended to deal with a variety of non-stationary signals. One specific class, prevalent in the area of rotating machines, is that of harmonic signals of varying frequencies and amplitude. This paper presents a new adaptive phase-energy (APE) approach for time-frequency representation of varying harmonic signals. It is based on the concept of phase (frequency) paths and the instantaneous power spectral density (PSD). It is this path which represents the dynamic behaviour of the system generating the observed signal. The proposed method utilises dynamic filters based on an extended Nyquist theorem, enabling to extract signal components with optimal signal-to-noise ratio. The APE detects the most energetic harmonic components (frequency paths) in the analysed signal. Tests on simulated signals show the superiority of the APE in resolution and resolving power as compared to STFT and wavelets wave-packet decomposition. The dynamic filters also enable the reconstruction of the signal components (paths) from the noisy signal. A quantitative comparison was performed both for the detected path in the time-frequency plane as well as for the reconstructed signal, demonstrating the performance of the APE.

  2. Tissue photosensitizer dosimetry using spectrally-resolved fluorescence for pre-clinical and clinical verteporfin-PDT of pancreatic cancer

    NASA Astrophysics Data System (ADS)

    Isabelle, Martin; Davis, Scott; Li, Zan; Gunn, Jason; Hoopes, P. J.; Pereira, S.; Mosse, C. A.; Hasan, T.; Pogue, B. W.

    2012-02-01

    Photodynamic therapy (PDT) mediated with verteporfin is currently being investigated to treat pancreatic cancer in patients who are not surgical candidates. Clinically, interstitial light delivery is administered through a fiber, via percutaneous needle implantation guided by ultrasound and/or verified by CT. Tumor response to PDT is based on photosensitizer (PS) dose, light dose, light dose rate and the timing of light application following PS injection. However, studies have shown that even when matching administered PDT treatment parameters such as drug dose and light level, there can be significant inter-patient variation in tissue damage post-PDT, and this has been primarily attributed to imprecise PS concentration at the target tissue site. In order to achieve optimal tumor response from PDT without causing major damage to surrounding tissue, it would be advantageous to measure the PS concentration in the target tissue just prior to light application. From these measurements, the clinician can adapt the light application dose to the measured target tissue PS concentration (i.e. insufficient target tissue PS concentrations compensated by higher light doses and vice versa.) in order to provide an optimal light dose for each patient. In animal studies, a spectrometer-based in-vivo fluorescence dosimetry system has been used to assess accumulated PS levels (verteporfin) in situ. Measurements are taken from skin, leg muscle, buccal mucosa and tumor tissue locations one hour after injection of the photosensitizer. Real-time spectral fitting, subtraction of background autofluorescence and ratiometric analysis is performed on the raw data to extract out only the photosensitizer fluorescence and therefore concentration. Using a pre-measured calibration data set of varying concentrations for verteporfin in tissue phantoms composed of intralipid and whole blood, it was possible detect concentrations of the photosensitizer below 0.5nM. In the clinical studies being

  3. Determination of the PSI/PSII ratio in living plant cells at room temperature by spectrally resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Elgass, Kirstin; Zell, Martina; Maurino, Veronica G.; Schleifenbaum, Frank

    2011-02-01

    Leaf cells of living plants exhibit strong fluorescence from chloroplasts, the reaction centers of photosynthesis. Mutations in the photosystems change their structure and can, thus, be monitored by recording the fluorescence spectra of the emitted chlorophyll light. These measurements have, up to now, mostly been carried out at low temperatures (77 K), as these conditions enable the differentiation between the fluorescence of Photosystem I (PSI) and Photosystem II (PSII). In contrast, at room temperature, energy transfer processes between the various photosynthetic complexes result in very similar fluorescence emissions, which mainly consist of fluorescence photons emitted by PSII hindering a discrimination based on spectral ROIs (regions of interest). However, by statistical analysis of high resolution fluorescence spectra recorded at room temperature, it is possible to draw conclusions about the relative PSI/PSII ratio. Here, the possibility of determining the relative PSI/PSII ratio by fluorescence spectroscopy is demonstrated in living maize plants. Bundle-sheath chloroplasts of mature maize plants have a special morphologic characteristic; they are agranal, or exhibit only rudimentary grana, respectively. These chloroplasts are depleted in PSII activity and it could be shown that PSII is progressively reduced during leaf differentiation. A direct comparison of PSII activity in isolated chloroplasts is nearly impossible, since the activity of PSII in both mesophyll- and bundle-sheath chloroplasts decays with time after isolation and it takes significantly longer to isolate bundle-sheath chloroplasts. Considering this fact the measurement of PSI/PSII ratios with the 77K method, which includes taking fluorescence spectra from a diluted suspension of isolated chloroplasts at 77K, is questionable. These spectra are then used to analyze the distribution of energy between PSI and PSII. After rapid cooling to 77K secondary biochemical influences, which attenuate the

  4. Quantum radiation of general nonstationary black holes

    NASA Astrophysics Data System (ADS)

    Hua, Jia-Chen; Huang, Yong-Chang

    2009-02-01

    Quantum radiation of general nonstationary black holes is investigated by using the method of generalized tortoise-coordinate transformation (GTT). It is shown in general that the temperature and the shape of the event horizon of this kind of black holes depend on time and angle. Further, we find that the chemical potential in the thermal-radiation spectrum is equal to the highest energy of the negative-energy state of particles in nonthermal radiation for general nonstationary black holes.

  5. Effects of oxygen background pressure on the stoichiometry of a LaGaO3 laser ablation plume investigated by time and spectrally resolved two-dimensional imaging

    NASA Astrophysics Data System (ADS)

    Sambri, A.; Aruta, C.; Di Gennaro, E.; Wang, X.; Scotti di Uccio, U.; Miletto Granozio, F.; Amoruso, S.

    2016-03-01

    The plume expansion dynamics strongly affects the growth and the chemistry of pulsed laser deposited thin films. The interaction with the background gas determines the kinetic energy of the species impinging on the substrate, their angular broadening, the plasma chemistry, and eventually the cations stoichiometric ratio in oxide films. Here, we exploit two-dimensional, spectrally resolved plume imaging to characterize the diverse effects of the oxygen background pressure on the expansion dynamics of La, Ga, and LaO species during pulsed laser deposition of LaGaO3. The propagation of the ablated species towards the substrate is studied for background oxygen pressures ranging from high vacuum up to ≈10-1 mbar. Our experimental results show specie-dependent effects of the background gas on the angular distribution of the precursors within the plume. These findings suggest that even in the presence of a stoichiometric ablation and of a globally stoichiometric plume, cations off-stoichiometry can take place in the forefront portion of the plume impinging on the substrate. We show that such effect can be compensated by a proper choice of process parameters.

  6. Spectrally resolved intraband transitions on two-step photon absorption in InGaAs/GaAs quantum dot solar cell

    SciTech Connect

    Tamaki, Ryo Shoji, Yasushi; Okada, Yoshitaka; Miyano, Kenjiro

    2014-08-18

    Two-step photon absorption processes in a self-organized In{sub 0.4}Ga{sub 0.6}As/GaAs quantum dot (QD) solar cell have been investigated by monitoring the mid-infrared (IR) photoinduced modulation of the external quantum efficiency (ΔEQE) at low temperature. The first step interband and the second step intraband transitions were both spectrally resolved by scanning photon energies of visible to near-IR CW light and mid-IR pulse lasers, respectively. A peak centered at 0.20 eV corresponding to the transition to virtual bound states and a band above 0.42 eV probably due to photoexcitation to GaAs continuum states were observed in ΔEQE spectra, when the interband transition was above 1.4 eV, directly exciting wetting layers or GaAs spacer layers. On the other hand, resonant excitation of the ground state of QDs at 1.35 eV resulted in a reduction of EQE. The sign of ΔEQE below 1.40 eV changed from negative to positive by increasing the excitation intensity of the interband transition. We ascribe this to the filling of higher energy trap states.

  7. Spectrally resolved multidepth fluorescence imaging

    PubMed Central

    Luo, Yuan; Zervantonakis, Ioannis K.; Oh, Se Baek; Kamm, Roger D.; Barbastathis, George

    2011-01-01

    We present a multicolor fluorescence imaging modality to visualize in real-time tissue structures emitting multispectral fluorescent light from different focal depths. Each designated spectrum of fluorescent emission from a specific depth within a volumetric tissue is probed by a depth-spectrum selective holographic grating. The grating for each fluorescent color are multiplexed within a volume hologram, which enables simultaneously obtaining multicolored fluorescent information at different depths within a biological tissue sample. We demonstrate the imaging modality's ability to obtain laser-induced multicolored fluorescence images of a biological sample from different depths without scanning. We also experimentally demonstrate that the imaging modality can be simultaneously operated at both fluorescent and bright field modes to provide complementary information of volumetric tissue structures at different depths in real-time. PMID:21950929

  8. Spectrally resolved multidepth fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Luo, Yuan; Zervantonakis, Ioannis K.; Oh, Se Baek; Kamm, Roger D.; Barbastathis, George

    2011-09-01

    We present a multicolor fluorescence imaging modality to visualize in real-time tissue structures emitting multispectral fluorescent light from different focal depths. Each designated spectrum of fluorescent emission from a specific depth within a volumetric tissue is probed by a depth-spectrum selective holographic grating. The grating for each fluorescent color are multiplexed within a volume hologram, which enables simultaneously obtaining multicolored fluorescent information at different depths within a biological tissue sample. We demonstrate the imaging modality's ability to obtain laser-induced multicolored fluorescence images of a biological sample from different depths without scanning. We also experimentally demonstrate that the imaging modality can be simultaneously operated at both fluorescent and bright field modes to provide complementary information of volumetric tissue structures at different depths in real-time.

  9. Wavelet analysis as a nonstationary plasma fluctuation diagnostic tool

    SciTech Connect

    Santoso, S.; Powers, E.J.; Ouroua, A.; Heard, J.W.; Bengtson, R.D.

    1996-12-31

    Analysis of nonstationary plasma fluctuation data has been a long-time challenge for the plasma diagnostic community. For this reason, in this paper the authors present and apply wavelet transforms as a new diagnostic tool to analyze nonstationary plasma fluctuation data. Unlike the Fourier transform, which represents a given signal globally without temporal resolution, the wavelet transform provides a local representation of the given signal in the time-scale domain. The fundamental concepts and multiresolution properties of wavelet transforms, along with a brief comparison with the short-time Fourier transform, are presented in this paper. The selection of a prototype wavelet or a mother wavelet is also discussed. Digital implementation of wavelet spectral analysis, which include time-scale power spectra and scale power spectra are described. The efficacy of the wavelet approach is demonstrated by analyzing transient broadband electrostatic potential fluctuations inside the inversion radius of sawtoothing TEXT-U plasmas during electron cyclotron resonance heating. The potential signals are collected using a 2 MeV heavy ion beam probe.

  10. Axisymmetric, Nonstationary Black Hole Magnetospheres: Revisited

    NASA Astrophysics Data System (ADS)

    Song, Yoo Geun; Park, Seok Jae

    2015-10-01

    An axisymmetric, stationary, general-relativistic, electrodynamic engine model of an active galactic nucleus was formulated by Macdonald and Thorne that consisted of a supermassive black hole surrounded by a plasma magnetosphere and a magnetized accretion disk. Based on this initial formulation, a nonstationary, force-free version of their model was constructed by Park & Vishniac (PV), with the simplifying assumption that the poloidal component of the magnetic field line velocity be confined along the radial direction in cylindrical polar coordinates. In this paper, we derive the new, nonstationary “Transfield Equation,” which was not specified in PV. If we can solve this “Transfield Equation” numerically, then we will understand the axisymmetric, nonstationary black hole magnetosphere in more rigorous ways.

  11. Heuristic segmentation of a nonstationary time series

    NASA Astrophysics Data System (ADS)

    Fukuda, Kensuke; Eugene Stanley, H.; Nunes Amaral, Luís A.

    2004-02-01

    Many phenomena, both natural and human influenced, give rise to signals whose statistical properties change under time translation, i.e., are nonstationary. For some practical purposes, a nonstationary time series can be seen as a concatenation of stationary segments. However, the exact segmentation of a nonstationary time series is a hard computational problem which cannot be solved exactly by existing methods. For this reason, heuristic methods have been proposed. Using one such method, it has been reported that for several cases of interest—e.g., heart beat data and Internet traffic fluctuations—the distribution of durations of these stationary segments decays with a power-law tail. A potential technical difficulty that has not been thoroughly investigated is that a nonstationary time series with a (scalefree) power-law distribution of stationary segments is harder to segment than other nonstationary time series because of the wider range of possible segment lengths. Here, we investigate the validity of a heuristic segmentation algorithm recently proposed by Bernaola-Galván et al. [Phys. Rev. Lett. 87, 168105 (2001)] by systematically analyzing surrogate time series with different statistical properties. We find that if a given nonstationary time series has stationary periods whose length is distributed as a power law, the algorithm can split the time series into a set of stationary segments with the correct statistical properties. We also find that the estimated power-law exponent of the distribution of stationary-segment lengths is affected by (i) the minimum segment length and (ii) the ratio R≡σɛ/σx¯, where σx¯ is the standard deviation of the mean values of the segments and σɛ is the standard deviation of the fluctuations within a segment. Furthermore, we determine that the performance of the algorithm is generally not affected by uncorrelated noise spikes or by weak long-range temporal correlations of the fluctuations within segments.

  12. Testing climate models with space-borne spectrally resolved observations of outgoing terrestrial long-wave radiation. Part I: optimum choice for cloud screening.

    NASA Astrophysics Data System (ADS)

    Fiorenza, C.; Coppola, E.; Cimini, D.; Marzano, F. S.; Visconti, G.

    2003-04-01

    Testing Numerical Prediction Models (NPM) is a major issue for climate studies. Different approaches are possible, based on comparison between numerical output and atmospheric and oceanic measurements, such as air temperature, humidity, sea surface temperature. More recently, another approach has been proposed [Haskins et al, 1995; 1997; 1998; Goody et al., 1998], which make use of direct observations, such as outgoing long-wave radiance, instead of retrieved products. In order to accomplish this goal, it?'s necessary to obtain an equivalent set of data from numerical models and observations. Spectrally resolved outgoing long-wave radiance from the Earth-Atmosphere system has been measured by the IRIS and IMG [Hanel et al., 1972; Kobayashi et al., 1999; Cimini et al., 2002] interferometers. On the other hand, NPM do not provide this information directly. However, by processing the thermodynamical and chemical information from the NPM about the Earth-Atmosphere system with a Radiative Tranfer Model (RTM) code, we are able to produce this quantity. Although, since NPM do not provide detailed information about the microphysics of hydrometeors, which is necessary to compute exactly the radiation extinction by clouds, we are forced to reduced our analysis to clear-sky cases [Huang et al., 2002]. Thus, from the simulation point of view, we simply don?t input clouds in the RTM, while for the observations we need to detect and remove cloud-contaminated cases from the entire dataset. Several screening techniques are available in the open literature, each one using a different approach to detect cloud contamination, which forces us to make a choice. Thus, we take in account four different techniques, and apply each one independently to the observations data set. Finally, we discuss the results, motivating our choice of the optimum? " screening technique.

  13. Whole-body multicolor spectrally resolved fluorescence imaging for development of target-specific optical contrast agents using genetically engineered probes

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hisataka; Hama, Yukihiro; Koyama, Yoshinori; Barrett, Tristan; Urano, Yasuteru; Choyke, Peter L.

    2007-02-01

    Target-specific contrast agents are being developed for the molecular imaging of cancer. Optically detectable target-specific agents are promising for clinical applications because of their high sensitivity and specificity. Pre clinical testing is needed, however, to validate the actual sensitivity and specificity of these agents in animal models, and involves both conventional histology and immunohistochemistry, which requires large numbers of animals and samples with costly handling. However, a superior validation tool takes advantage of genetic engineering technology whereby cell lines are transfected with genes that induce the target cell to produce fluorescent proteins with characteristic emission spectra thus, identifying them as cancer cells. Multicolor fluorescence imaging of these genetically engineered probes can provide rapid validation of newly developed exogenous probes that fluoresce at different wavelengths. For example, the plasmid containing the gene encoding red fluorescent protein (RFP) was transfected into cell lines previously developed to either express or not-express specific cell surface receptors. Various antibody-based or receptor ligand-based optical contrast agents with either green or near infrared fluorophores were developed to concurrently target and validate cancer cells and their positive and negative controls, such as β-D-galactose receptor, HER1 and HER2 in a single animal/organ. Spectrally resolved fluorescence multicolor imaging was used to detect separate fluorescent emission spectra from the exogenous agents and RFP. Therefore, using this in vivo imaging technique, we were able to demonstrate the sensitivity and specificity of the target-specific optical contrast agents, thus reducing the number of animals needed to conduct these experiments.

  14. Nonstationary Transient Vibroacoustic Response of a Beam Structure

    NASA Technical Reports Server (NTRS)

    Caimi, R. E.; Margasahayam, R. N.; Nayfeh, Jamal F.

    1997-01-01

    This study consists of an investigation into the nonstationary transient response of the Verification Test Article (VETA) when subjected to random acoustic excitation. The goal is to assess excitation models that can be used in the design of structures and equipment when knowledge of the structure and the excitation is limited. The VETA is an instrumented cantilever beam that was exposed to acoustic loading during five Space Shuttle launches. The VETA analytical structural model response is estimated using the direct averaged power spectral density and the normalized pressure spectra methods. The estimated responses are compared to the measured response of the VETA. These comparisons are discussed with a focus on prediction conservatism and current design practice.

  15. EDITORIAL: CAMOP: Quantum Non-Stationary Systems CAMOP: Quantum Non-Stationary Systems

    NASA Astrophysics Data System (ADS)

    Dodonov, Victor V.; Man'ko, Margarita A.

    2010-09-01

    Although time-dependent quantum systems have been studied since the very beginning of quantum mechanics, they continue to attract the attention of many researchers, and almost every decade new important discoveries or new fields of application are made. Among the impressive results or by-products of these studies, one should note the discovery of the path integral method in the 1940s, coherent and squeezed states in the 1960-70s, quantum tunneling in Josephson contacts and SQUIDs in the 1960s, the theory of time-dependent quantum invariants in the 1960-70s, different forms of quantum master equations in the 1960-70s, the Zeno effect in the 1970s, the concept of geometric phase in the 1980s, decoherence of macroscopic superpositions in the 1980s, quantum non-demolition measurements in the 1980s, dynamics of particles in quantum traps and cavity QED in the 1980-90s, and time-dependent processes in mesoscopic quantum devices in the 1990s. All these topics continue to be the subject of many publications. Now we are witnessing a new wave of interest in quantum non-stationary systems in different areas, from cosmology (the very first moments of the Universe) and quantum field theory (particle pair creation in ultra-strong fields) to elementary particle physics (neutrino oscillations). A rapid increase in the number of theoretical and experimental works on time-dependent phenomena is also observed in quantum optics, quantum information theory and condensed matter physics. Time-dependent tunneling and time-dependent transport in nano-structures are examples of such phenomena. Another emerging direction of study, stimulated by impressive progress in experimental techniques, is related to attempts to observe the quantum behavior of macroscopic objects, such as mirrors interacting with quantum fields in nano-resonators. Quantum effects manifest themselves in the dynamics of nano-electromechanical systems; they are dominant in the quite new and very promising field of circuit

  16. Inflammatory Acne in the Asian Skin Type III Treated with a Square Pulse, Time Resolved Spectral Distribution IPL System: A Preliminary Study

    PubMed Central

    2012-01-01

    Background and aims: Acne remains a severe problem for both patients and clinicians. Various approaches using photosurgery and phototherapy have been reported with varying degrees of success and robustness of results. An improved intense pulsed light (IPL) system has become available with interesting beam characteristic which might improve IPL treatment of inflammatory acne in the Asian skin, Fitzpatrick type III/IV. Subjects and Methods: The 18 study subjects comprised 15 females and 3 males with active mild to moderately severe inflammatory acne (mean age 25.3 ± 7.70 yr, range 17–47 yr, Burton scale 1-4, all Fitzpatrick type III Asian skin). They were treated once (8 subjects) or twice (10 subjects) with an IPL system offering both square pulse and time resolved spectral distribution technologies (420 nm cut-off filter, 30 ms pulse, 8 – 12 J/cm2, 2–3 passes). Clinical photography was taken at baseline and at 4 weeks after the final treatment. Percentage of acne clearance was assessed by an independent dermatological panel and graded from zero to 5, 5 being total clearance. Results: All subjects completed the study. Post-treatment side effects were mild and transient, with virtually no downtime or postinflammatory hyperpigmentation (PIH) experienced by any subject. All subjects had some improvement and no exacerbation was seen in any subject. Clearance was evaluated by the panel as grade 4 in 5 subjects, grade 3 in 8, grade 2 in 4 and grade 1 in 1, so that 14 of 18 subjects (78%) had clearance of at least 60%. Patient evaluation was in general slightly better than that of the panel. Conclusions: The special beam characteristics of the IPL system used in the present preliminary study achieved good to very good results in the treatment of acne in the Fitzpatrick type III Asian skin without PIH induction. The results suggested that acne treatment in the Asian skin using this system is both safe and effective, and merits larger population studies to further

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  18. Resolution enhancement of non-stationary seismic data using amplitude-frequency partition

    NASA Astrophysics Data System (ADS)

    Xie, Yujiang; Liu, Gao

    2015-02-01

    As the Earth's inhomogeneous and viscoelastic properties, seismic signal attenuation we are trying to mitigate is a long-standing problem facing with high-resolution techniques. For addressing such a problem in the fields of time-frequency transform, Gabor transform methods such as atom-window method (AWM) and molecular window method (MWM) have been reported recently. However, we observed that these methods might be much better if we partition the non-stationary seismic data into adaptive stationary segments based on the amplitude and frequency information of the seismic signal. In this study, we present a new method called amplitude-frequency partition (AFP) to implement this process in the time-frequency domain. Cases of a synthetic and field seismic data indicated that the AFP method could partition the non-stationary seismic data into stationary segments approximately, and significantly, a high-resolution result would be achieved by combining the AFP method with conventional spectral-whitening method, which could be considered superior to previous resolution-enhancement methods like time-variant spectral whitening method, the AWM and the MWM as well. This AFP method presented in this study would be an effective resolution-enhancement tool for the non-stationary seismic data in the fields of an adaptive time-frequency transform.

  19. New wave effects in nonstationary plasma

    SciTech Connect

    Schmit, P. F.; Fisch, N. J.

    2013-05-15

    Through particle-in-cell simulations and analytics, a host of interesting and novel wave effects in nonstationary plasma are examined. In particular, Langmuir waves serve as a model system to explore wave dynamics in plasmas undergoing compression, expansion, and charge recombination. The entire wave life-cycle is explored, including wave excitation, adiabatic evolution and action conservation, nonadiabatic evolution and resonant wave-particle effects, collisional dissipation, and potential laboratory applications of the aforementioned phenomenology.

  20. Sequential decision analysis for nonstationary stochastic processes

    NASA Technical Reports Server (NTRS)

    Schaefer, B.

    1974-01-01

    A formulation of the problem of making decisions concerning the state of nonstationary stochastic processes is given. An optimal decision rule, for the case in which the stochastic process is independent of the decisions made, is derived. It is shown that this rule is a generalization of the Bayesian likelihood ratio test; and an analog to Wald's sequential likelihood ratio test is given, in which the optimal thresholds may vary with time.

  1. Hazard function theory for nonstationary natural hazards

    NASA Astrophysics Data System (ADS)

    Read, L.; Vogel, R. M.

    2015-12-01

    Studies from the natural hazards literature indicate that many natural processes, including wind speeds, landslides, wildfires, precipitation, streamflow and earthquakes, show evidence of nonstationary behavior such as trends in magnitudes through time. Traditional probabilistic analysis of natural hazards based on partial duration series (PDS) generally assumes stationarity in the magnitudes and arrivals of events, i.e. that the probability of exceedance is constant through time. Given evidence of trends and the consequent expected growth in devastating impacts from natural hazards across the world, new methods are needed to characterize their probabilistic behavior. The field of hazard function analysis (HFA) is ideally suited to this problem because its primary goal is to describe changes in the exceedance probability of an event over time. HFA is widely used in medicine, manufacturing, actuarial statistics, reliability engineering, economics, and elsewhere. HFA provides a rich theory to relate the natural hazard event series (x) with its failure time series (t), enabling computation of corresponding average return periods and reliabilities associated with nonstationary event series. This work investigates the suitability of HFA to characterize nonstationary natural hazards whose PDS magnitudes are assumed to follow the widely applied Poisson-GP model. We derive a 2-parameter Generalized Pareto hazard model and demonstrate how metrics such as reliability and average return period are impacted by nonstationarity and discuss the implications for planning and design. Our theoretical analysis linking hazard event series x, with corresponding failure time series t, should have application to a wide class of natural hazards.

  2. Time-frequency filtering for classifying targets in nonstationary clutter

    NASA Astrophysics Data System (ADS)

    Gomatam, Vikram Thiruneermalai; Loughlin, Patrick

    2014-06-01

    Classifying underwater targets from their sonar backscatter is often complicated by induced or self-noise (i.e. clutter, reverberation) arising from the scattering of the sonar pulse from non-target objects. Because clutter is inherently nonstationary, and because the propagation environment can induce nonstationarities as well, in addition to any nonstationarities / time-varying spectral components of the target echo itself, a joint phase space approach to target classification has been explored. In this paper, we apply a previously developed minimum mean square time-frequency spectral estimation method to design a bank of time-frequency filters from training data to distinguish targets from clutter. The method is implemented in the ambiguity domain in order to reduce computational requirements. In this domain, the optimal filter (more commonly called a "kernel" in the time-frequency literature) multiples the ambiguity function of the received signal, and then the mean squared distance to each target class is computed. Simulations demonstrate that the class-specific optimal kernel better separates each target from the clutter and other targets, compared to a simple mean-squared distance measure with no kernel processing.

  3. First-excursion probability in non-stationary random vibration.

    NASA Technical Reports Server (NTRS)

    Yang, J.-N.

    1973-01-01

    The first-excursion probability of a non-stationary Gaussian process with zero mean has been studied. Within the framework of the point process approach, a variety of analytical approximations applicable to stationary random processes is extended herein to non-stationary random processes. The extension is possible owing to a recent definition of non-stationary envelope processes proposed by the author. With the aid of numerical examples, merits of each approximation are examined by comparing with the results of simulation. It is found that under non-stationary excitations with short duration, the Markov approximation is the best among all the approximations discussed in this paper.

  4. Unified treatment and measurement of the spectral resolution and temporal effects in frequency-resolved sum-frequency generation vibrational spectroscopy (SFG-VS)

    SciTech Connect

    Velarde Ruiz Esparza, Luis A.; Wang, Hongfei

    2013-12-14

    The emergence of sub-wavenumber high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BBSFG-VS) [Velarde et al., J. Chem. Phys., 2011, 135, 241102] has offered new opportunities in obtaining and understanding the spectral lineshape and temporal effects on the surface vibrational spectroscopy. Particularly, the high accuracy in the HR-BBSFG-VS spectral lineshape measurement provides detailed information on the complex coherent vibrational dynamics through spectral measurement. Here we present a unified formalism of the theoretical and experimental approaches for obtaining the accurate lineshape of the SFG response, and then present a analysis on the higher and lower spectral resolution SFG spectra as well as their temporal effects of the cholesterol molecules at the air/water interface. With the high spectral resolution and accurate lineshape, it is shown that the parameters from the sub-wavenumber resolution SFG spectra can be used not only to understand but also to quantitatively reproduce the temporal effects in the lower resolution SFG measurement. These not only provide a unified picture in understanding both the frequency-domain and the time-domain SFG response of the complex molecular interface, but also provide novel experimental approaches that can directly measure them.

  5. The influence of non-stationary ENSO teleconnections on reconstructions of paleoclimate using a pseudoproxy framework

    NASA Astrophysics Data System (ADS)

    Batehup, R.; McGregor, S.; Gallant, A. J. E.

    2015-08-01

    Reconstructions of the El Niño-Southern Oscillation (ENSO) ideally require high-quality, annually-resolved and long-running paleoclimate proxy records in the eastern tropical Pacific Ocean, located in ENSO's centre-of-action. However, to date, the paleoclimate records that have been extracted in the region are short or temporally and spatially sporadic, limiting the information that can be provided by these reconstructions. Consequently, most ENSO reconstructions exploit the downstream influences of ENSO on remote locations, known as teleconnections, where longer records from paleoclimate proxies exist. However, using teleconnections to reconstruct ENSO relies on the assumption that the relationship between ENSO and the remote location is stationary in time. Increasing evidence from observations and climate models suggests that some teleconnections are, in fact, non-stationary, potentially threatening the validity of those paleoclimate reconstructions that exploit teleconnections. This study examines the implications of non-stationary teleconnections on modern multi-proxy reconstructions of ENSO. The sensitivity of the reconstructions to non-stationary teleconnections were tested using a suite of idealized pseudoproxy experiments that employed output from a fully coupled global climate model. Reconstructions of the variance in the Niño 3.4 index, representing ENSO variability, were generated using four different methods to which surface temperature data from the GFDL CM2.1 was applied as a pseudoproxy. As well as sensitivity of the reconstruction to the method, the experiments tested the sensitivity of the reconstruction to the number of non-stationary pseudoproxies and the location of these proxies. ENSO reconstructions in the pseudoproxy experiments were not sensitive to non-stationary teleconnections when global, uniformly-spaced networks of a minimum of approximately 20 proxies were employed. Neglecting proxies from ENSO's center-of-action still produced

  6. Stationary versus non-stationary (13)C-MFA: a comparison using a consistent dataset.

    PubMed

    Noack, Stephan; Nöh, Katharina; Moch, Matthias; Oldiges, Marco; Wiechert, Wolfgang

    2011-07-10

    Besides the well-established (13)C-metabolic flux analysis ((13)C-MFA) which characterizes a cell's fluxome in a metabolic and isotopic stationary state a current area of research is isotopically non-stationary MFA. Non-stationary (13)C-MFA uses short-time isotopic transient data instead of long-time isotopic equilibrium data and thus is capable to resolve fluxes within much shorter labeling experiments. However, a comparison of both methods with data from one single experiment has not been made so far. In order to create a consistent database for directly comparing both methods a (13)C-labeling experiment in a fed-batch cultivation with a Corynebacterium glutamicum lysine producer was carried out. During the experiment the substrate glucose was switched from unlabeled to a specifically labeled glucose mixture which was immediately traced by fast sampling and metabolite quenching. The time course of labeling enrichments in intracellular metabolites until isotopic stationarity was monitored by LC-MS/MS. The resulting dataset was evaluated using the classical as well as the isotopic non-stationary MFA approach. The results show that not only the obtained relative data, i.e. intracellular flux distributions, but also the more informative quantitative fluxome data significantly depend on the combination of the measurements and the underlying modeling approach used for data integration. Taking further criteria on the experimental and computational part into consideration, the current limitations of both methods are demonstrated and possible pitfalls are concluded. PMID:20638432

  7. Hazard function theory for nonstationary natural hazards

    NASA Astrophysics Data System (ADS)

    Read, Laura K.; Vogel, Richard M.

    2016-04-01

    Impact from natural hazards is a shared global problem that causes tremendous loss of life and property, economic cost, and damage to the environment. Increasingly, many natural processes show evidence of nonstationary behavior including wind speeds, landslides, wildfires, precipitation, streamflow, sea levels, and earthquakes. Traditional probabilistic analysis of natural hazards based on peaks over threshold (POT) generally assumes stationarity in the magnitudes and arrivals of events, i.e., that the probability of exceedance of some critical event is constant through time. Given increasing evidence of trends in natural hazards, new methods are needed to characterize their probabilistic behavior. The well-developed field of hazard function analysis (HFA) is ideally suited to this problem because its primary goal is to describe changes in the exceedance probability of an event over time. HFA is widely used in medicine, manufacturing, actuarial statistics, reliability engineering, economics, and elsewhere. HFA provides a rich theory to relate the natural hazard event series (X) with its failure time series (T), enabling computation of corresponding average return periods, risk, and reliabilities associated with nonstationary event series. This work investigates the suitability of HFA to characterize nonstationary natural hazards whose POT magnitudes are assumed to follow the widely applied generalized Pareto model. We derive the hazard function for this case and demonstrate how metrics such as reliability and average return period are impacted by nonstationarity and discuss the implications for planning and design. Our theoretical analysis linking hazard random variable X with corresponding failure time series T should have application to a wide class of natural hazards with opportunities for future extensions.

  8. Hazard function theory for nonstationary natural hazards

    NASA Astrophysics Data System (ADS)

    Read, L. K.; Vogel, R. M.

    2015-11-01

    Impact from natural hazards is a shared global problem that causes tremendous loss of life and property, economic cost, and damage to the environment. Increasingly, many natural processes show evidence of nonstationary behavior including wind speeds, landslides, wildfires, precipitation, streamflow, sea levels, and earthquakes. Traditional probabilistic analysis of natural hazards based on peaks over threshold (POT) generally assumes stationarity in the magnitudes and arrivals of events, i.e. that the probability of exceedance of some critical event is constant through time. Given increasing evidence of trends in natural hazards, new methods are needed to characterize their probabilistic behavior. The well-developed field of hazard function analysis (HFA) is ideally suited to this problem because its primary goal is to describe changes in the exceedance probability of an event over time. HFA is widely used in medicine, manufacturing, actuarial statistics, reliability engineering, economics, and elsewhere. HFA provides a rich theory to relate the natural hazard event series (X) with its failure time series (T), enabling computation of corresponding average return periods, risk and reliabilities associated with nonstationary event series. This work investigates the suitability of HFA to characterize nonstationary natural hazards whose POT magnitudes are assumed to follow the widely applied Generalized Pareto (GP) model. We derive the hazard function for this case and demonstrate how metrics such as reliability and average return period are impacted by nonstationarity and discuss the implications for planning and design. Our theoretical analysis linking hazard event series X, with corresponding failure time series T, should have application to a wide class of natural hazards with rich opportunities for future extensions.

  9. Hazard function theory for nonstationary natural hazards

    DOE PAGESBeta

    Read, Laura K.; Vogel, Richard M.

    2016-04-11

    Impact from natural hazards is a shared global problem that causes tremendous loss of life and property, economic cost, and damage to the environment. Increasingly, many natural processes show evidence of nonstationary behavior including wind speeds, landslides, wildfires, precipitation, streamflow, sea levels, and earthquakes. Traditional probabilistic analysis of natural hazards based on peaks over threshold (POT) generally assumes stationarity in the magnitudes and arrivals of events, i.e., that the probability of exceedance of some critical event is constant through time. Given increasing evidence of trends in natural hazards, new methods are needed to characterize their probabilistic behavior. The well-developed field ofmore » hazard function analysis (HFA) is ideally suited to this problem because its primary goal is to describe changes in the exceedance probability of an event over time. HFA is widely used in medicine, manufacturing, actuarial statistics, reliability engineering, economics, and elsewhere. HFA provides a rich theory to relate the natural hazard event series (X) with its failure time series (T), enabling computation of corresponding average return periods, risk, and reliabilities associated with nonstationary event series. This work investigates the suitability of HFA to characterize nonstationary natural hazards whose POT magnitudes are assumed to follow the widely applied generalized Pareto model. We derive the hazard function for this case and demonstrate how metrics such as reliability and average return period are impacted by nonstationarity and discuss the implications for planning and design. As a result, our theoretical analysis linking hazard random variable X with corresponding failure time series T should have application to a wide class of natural hazards with opportunities for future extensions.« less

  10. Multiaxis Rainflow Fatigue Methods for Nonstationary Vibration

    NASA Technical Reports Server (NTRS)

    Irvine, T.

    2016-01-01

    Mechanical structures and components may be subjected to cyclical loading conditions, including sine and random vibration. Such systems must be designed and tested accordingly. Rainflow cycle counting is the standard method for reducing a stress time history to a table of amplitude-cycle pairings prior to the Palmgren-Miner cumulative damage calculation. The damage calculation is straightforward for sinusoidal stress but very complicated for random stress, particularly for nonstationary vibration. This paper evaluates candidate methods and makes a recommendation for further study of a hybrid technique.

  11. Harmonic demodulation of nonstationary shot noise.

    PubMed

    Gray, M B; Stevenson, A J; Bachor, H A; McClelland, D E

    1993-05-15

    We report on experimental demodulation of nonstationary shot noise, which is associated with strongly modulated light. For sinusoidal modulation and demodulation, measurements confirm theoretical predictions of 1.8-dB excess noise in the modulation quadrature and 3-dB noise reduction in the opposite quadrature, relative to the standard quantum limit. Demodulation with a third harmonic produces noise correlated with that which is due to the fundamental. Reducing excess noise by 0.8 dB in the modulation quadrature, by combining the fundamental and third harmonics in a 2:1 ratio, is shown to be feasible. PMID:19802263

  12. The Stokes phenomenon and quantum tunneling for de Sitter radiation in nonstationary coordinates

    NASA Astrophysics Data System (ADS)

    Kim, Sang Pyo

    2010-09-01

    We study quantum tunneling for the de Sitter radiation in the planar coordinates and global coordinates, which are nonstationary coordinates and describe the expanding geometry. Using the phase-integral approximation for the Hamilton-Jacobi action in the complex plane of time, we obtain the particle-production rate in both coordinates and derive the additional sinusoidal factor depending on the dimensionality of spacetime and the quantum number for spherical harmonics in the global coordinates. This approach resolves the factor of two problem in the tunneling method.

  13. Decoupled tracking and thermal monitoring of non-stationary targets.

    PubMed

    Tan, Kok Kiong; Zhang, Yi; Huang, Sunan; Wong, Yoke San; Lee, Tong Heng

    2009-10-01

    Fault diagnosis and predictive maintenance address pertinent economic issues relating to production systems as an efficient technique can continuously monitor key health parameters and trigger alerts when critical changes in these variables are detected, before they lead to system failures and production shutdowns. In this paper, we present a decoupled tracking and thermal monitoring system which can be used on non-stationary targets of closed systems such as machine tools. There are three main contributions from the paper. First, a vision component is developed to track moving targets under a monitor. Image processing techniques are used to resolve the target location to be tracked. Thus, the system is decoupled and applicable to closed systems without the need for a physical integration. Second, an infrared temperature sensor with a built-in laser for locating the measurement spot is deployed for non-contact temperature measurement of the moving target. Third, a predictive motion control system holds the thermal sensor and follows the moving target efficiently to enable continuous temperature measurement and monitoring. PMID:19539922

  14. Simultaneous depth-resolved imaging of sub-nanometer scale ossicular vibrations and morphological features of the human-cadaver middle ear with spectral-domain phase-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Subhash, Hrebesh M.; Nguyen-Huynh, Anh; Wang, Ruikang K.; Jacques, Steven L.; Nuttall, Alfred L.

    2012-02-01

    We describe a novel method for the detection of the tiny motions of the middle ear (ME) ossicles and their morphological features with a spectral-domain phase sensitive optical coherence tomography (PS-OCT). Laser Doppler Vibrometry (LDV) and its variations are the most extensively used methods for studding the vibrational modes of the ME. However, most techniques are limited to single point analysis methods, and do not have the ability to provide depth resolved simultaneous imaging of multiple points on the ossicles especially with the intact eardrum. Consequently, the methods have the limited ability to provide relative vibration information at these points. In this study, we demonstrated the feasibility of using PS-OCT for simultaneous depth resolved imaging of both vibration information and morphological features in a cadaver human middle ear with high sensitivity and resolution. This technique has the potential to provide meaningful vibration of ossicles with a vibration sensitivity of ~0.5nm at 1kHz acoustic stimulation. To the best of our knowledge, this is the first demonstration of depth-resolved vibration imaging of ossicles with a PS-OCT system at sub-nanometer scale.

  15. Waves, shocks and non-stationary phenomena in the outer solar atmosphere

    NASA Technical Reports Server (NTRS)

    Hansteen, V. H.

    1997-01-01

    The dynamics of the solar chromosphere, transition region and corona were investigated. The consequences of the solar dynamics on the formation of spectral features in solar atmosphere regions are discussed. Data mainly from the solar ultraviolet measurement of emitted radiation (SUMER) instrument, showing signatures of non-stationary processes, are presented. These data are compared to the predictions of numerical models of the chromosphere and transition region. The observations seem to support the importance of upwardly propagating acoustic shocks in the heating of the chromosphere.

  16. Analysis of the Spectral Function of Nd1.85Ce0.15CuO4, Obtained by Angle Resolved Photoemission Spectroscopy

    SciTech Connect

    Schmitt, F.

    2010-05-03

    Samples of Nd{sub 2-x}Ce{sub x}CuO{sub 4}, an electron-doped high temperature superconducting cuprate (HTSC), near optimal doping at x = 0.155 were measured via angle resolved photoemission (ARPES). We report a renormalization feature in the self energy ('kink') in the band dispersion at {approx} 50-60 meV present in nodal and antinodal cuts across the Fermi surface. Specifically, while the kink had been seen in the antinodal region, it is now observed also in the nodal region, reminiscent of what has been observed in hole-doped cuprates.

  17. Broadband time-resolved diffuse optical spectrometer for clinical diagnostics: characterization and in-vivo measurements in the 600-1350 nm spectral range

    NASA Astrophysics Data System (ADS)

    Konugolu Venkata Sekar, Sanathana; Farina, Andrea; Martinenghi, Edoardo; Dalla Mora, Alberto; Taroni, Paola; Pifferi, Antonio; Durduran, Turgut; Pagliazzi, Marco; Lindner, Claus; Farzam, Parisa; Mora, Mireia; Squarcia, Mattia; Urbano-Ispizua, A.

    2015-07-01

    We report on the design, performance assessment, and first in vivo measurement of a Time-Resolved Diffuse Optical system for broadband (600-1350 nm) nm measurement of absorption and scattering spectra of biological tissues for non-invasive clinical diagnostics. Two strategies to reduce drift and enhance responsivity are adopted. The system was enrolled in a first in vivo test phase on healthy volunteers, carrying out non-invasive, in vivo quantification of key tissue constituents (oxy- and deoxy-hemoglobin, water, lipids, collagen) and tissue micro-structure (scatterer size and density).

  18. Performance and Prospects of Khayyam, A Tunable Spatial Heterodyne Spectrometer (SHS) for High Spectral Resolving Power Observation of Extended Planetary Targets in Optical Wavelengths

    NASA Astrophysics Data System (ADS)

    Hosseini, S.; Harris, W.

    2014-12-01

    We present initial results, calibration and data reduction process from observations of wide-field targets using Khayyam at Mt. Hamilton, a new instrument based on a reflective spatial heterodyne spectrometer (SHS) at the focus of the Coudé Auxiliary Telescope (CAT). SHS instruments are common path two-beam Fourier transform spectrometers that produce 2-D spatial interference patterns without the requirement for moving parts. The utility of SHS comes from its combination of a wide input acceptance angle (0.5-1°), high resolving power (of order ~105), compact format, high dynamic range, and relaxed optical tolerances compared with other interferometer designs. This combination makes them extremely useful for velocity resolved for observations of wide field targets from both small and large telescopes. This report focuses on the tunable instrument at Mt Hamilton, The CAT provides a test case for on-axis use of SHS, and the impact of the resulting field non-uniformity caused by the spider pattern will be discussed. Observations of several targets will be presented that demonstrate the capabilities of SHS, including comet C/2014 E2 (Jacques), Jupiter, and both the day sky and night glow. Raw interferometric data and transformed power spectra will be shown and evaluated in terms of instrumental stability.

  19. Stochastic Analysis of Spatial Variability in Two-Dimensional Steady Groundwater Flow Assuming Stationary and Nonstationary Heads

    NASA Astrophysics Data System (ADS)

    Mizell, Steve A.; Gutjahr, Allan L.; Gelhar, Lynn W.

    1982-08-01

    Two-dimensional steady groundwater flow in a confined aquifer with spatially variable transmissivity T is analyzed stochastically using spectral analysis and the theory of intrinsic random functions. Conditions that ensure a stationary (statistically homogeneous) head process are derived, and using two convenient forms for the covariance function of the ln T process, the head covariance function is studied. In addition, the head variogram is obtained for a particular nonstationary case, and the asymptotic head variogram is derived under very general conditions. Results are compared to those obtained by Gelhar (1976) for one- and two-dimensional phreatic flow and Bakr et al. (1978) for one- and three-dimensional confined flow. Multidimensional flow analysis results in a significantly reduced head variance. The head correlation remains high over much greater distances than the ln T correlation. The variogram obtained when stationary heads are assumed is identical to that obtained for nonstationary heads for dimensionless lag distances up to 2½ times the correlation scale of the log transmissivity. The variogram for nonstationary heads continues to grow logarithmically as lag distance increases, independent of the form of the input covariance in the nonstationary case. The conditions for stationarity are contrasted with the corresponding results obtained for the one- and three-dimensional cases of Gutjahr and Gelhar (1981). The head variance calculated from the stationary theory is found to agree with that of previous Monte Carlo simulations.

  20. Numerical and Experimental Aspects of Data Acquisition and Processing in Application to Temperature Resolved 3-D Sub-Millimeter Spectroscopy for Astrophysics and Spectral Assignment.

    NASA Astrophysics Data System (ADS)

    Medvedev, Ivan R.; Fortman, Sarah M.; Neese, Christopher F.; De Lucia, Frank C.

    2009-06-01

    Experimental determination of the lower state energy for every transition in molecular spectra, made possible by temperature resolved 3-D spectroscopy, opens new frontiers in our ability to predict molecular spectra over a wide range of temperatures and to assign rotational spectra in many vibrational states. Our improved collisional cooling cell design extends temperature coverage of this technique to 77 K. This enhances our ability to simulate molecular spectra at temperatures of astronomical relevance. We are reporting on experimental and numerical aspects of dealing with exceptionally high information content of these spectra. New data reduction algorithms allow us to process this data in timely fashion in an attempt to make them available to astronomical community.

  1. Linear response to nonstationary random excitation.

    NASA Technical Reports Server (NTRS)

    Hasselman, T.

    1972-01-01

    Development of a method for computing the mean-square response of linear systems to nonstationary random excitation of the form given by y(t) = f(t) x(t), in which x(t) = a stationary process and f(t) is deterministic. The method is suitable for application to multidegree-of-freedom systems when the mean-square response at a point due to excitation applied at another point is desired. Both the stationary process, x(t), and the modulating function, f(t), may be arbitrary. The method utilizes a fundamental component of transient response dependent only on x(t) and the system, and independent of f(t) to synthesize the total response. The role played by this component is analogous to that played by the Green's function or impulse response function in the convolution integral.

  2. Credibility of statistical downscaling under nonstationary climate

    NASA Astrophysics Data System (ADS)

    Salvi, Kaustubh; Ghosh, Subimal; Ganguly, Auroop R.

    2016-03-01

    Statistical downscaling (SD) establishes empirical relationships between coarse-resolution climate model simulations with higher-resolution climate variables of interest to stakeholders. These statistical relations are estimated based on historical observations at the finer resolutions and used for future projections. The implicit assumption is that the SD relations, extracted from data are stationary or remain unaltered, despite non-stationary change in climate. The validity of this assumption relates directly to the credibility of SD. Falsifiability of climate projections is a challenging proposition. Calibration and verification, while necessary for SD, are unlikely to be able to reproduce the full range of behavior that could manifest at decadal to century scale lead times. We propose a design-of-experiments (DOE) strategy to assess SD performance under nonstationary climate and evaluate the strategy via a transfer-function based SD approach. The strategy relies on selection of calibration and validation periods such that they represent contrasting climatic conditions like hot-versus-cold and ENSO-versus-non-ENSO years. The underlying assumption is that conditions such as warming or predominance of El Niño may be more prevalent under climate change. In addition, two different historical time periods are identified, which resemble pre-industrial and the most severe future emissions scenarios. The ability of the empirical relations to generalize under these proxy conditions is considered an indicator of their performance under future nonstationarity. Case studies over two climatologically disjoint study regions, specifically India and Northeast United States, reveal robustness of DOE in identifying the locations where nonstationarity prevails as well as the role of effective predictor selection under nonstationarity.

  3. Online updating and uncertainty quantification using nonstationary output-only measurement

    NASA Astrophysics Data System (ADS)

    Yuen, Ka-Veng; Kuok, Sin-Chi

    2016-01-01

    Extended Kalman filter (EKF) is widely adopted for state estimation and parametric identification of dynamical systems. In this algorithm, it is required to specify the covariance matrices of the process noise and measurement noise based on prior knowledge. However, improper assignment of these noise covariance matrices leads to unreliable estimation and misleading uncertainty estimation on the system state and model parameters. Furthermore, it may induce diverging estimation. To resolve these problems, we propose a Bayesian probabilistic algorithm for online estimation of the noise parameters which are used to characterize the noise covariance matrices. There are three major appealing features of the proposed approach. First, it resolves the divergence problem in the conventional usage of EKF due to improper choice of the noise covariance matrices. Second, the proposed approach ensures the reliability of the uncertainty quantification. Finally, since the noise parameters are allowed to be time-varying, nonstationary process noise and/or measurement noise are explicitly taken into account. Examples using stationary/nonstationary response of linear/nonlinear time-varying dynamical systems are presented to demonstrate the efficacy of the proposed approach. Furthermore, comparison with the conventional usage of EKF will be provided to reveal the necessity of the proposed approach for reliable model updating and uncertainty quantification.

  4. Evaluation of a novel noncontact spectrally and spatially resolved reflectance setup with continuously variable source-detector separation using silicone phantoms.

    PubMed

    Andree, Stefan; Reble, Carina; Helfmann, Jurgen; Gersonde, Ingo; Illing, Gerd

    2010-01-01

    We present a new variant of a noncontact, oblique incidence spatially resolved reflectance setup. The continuously variable source detector separation enables adaptation to high and low albedo samples. Absorption (μ(a)) and reduced scattering coefficients (μ(') (s)) are determined in the wavelength range of 400-1000 nm using a lookup table, calculated by a Monte Carlo simulation of the light transport. The method is characterized by an silicone phantom study covering a wide parameter range 0.01 mm(-1) ≤ μ(a) ≤ 2.5 mm(-1) and 0.2 mm(-1) ≤ μ(') (s) ≤ 10 mm(-1), which includes the optical parameters of tissue in the visible and near infrared. The influence of the incident angle and the detection aperture on the simulated remission was examined. Using perpendicular incidence and 90-deg detection aperture in the Monte Carlo simulation in contrast to the experimental situation with 30-deg incidence and 4.6-deg detection aperture is shown to be valid for the parameter range μ(') (s) > 1 mm(-1) and μ(a) < 1.2 mm(-1). A Mie calculation is presented, showing that a decreasing reduced scattering coefficient for increasing absorption can be the consequence of real physics instead of cross talk. PMID:21198213

  5. On the nonstationary Stokes system in a cone

    NASA Astrophysics Data System (ADS)

    Kozlov, Vladimir; Rossmann, Jürgen

    2016-06-01

    The authors consider the Dirichlet problem for the nonstationary Stokes system in a threedimensional cone. They obtain existence and uniqueness results for solutions in weighted Sobolev spaces and prove a regularity assertion for the solutions.

  6. Phase unwrapping in spectral X-ray differential phase-contrast imaging with an energy-resolving photon-counting pixel detector.

    PubMed

    Epple, Franz M; Ehn, Sebastian; Thibault, Pierre; Koehler, Thomas; Potdevin, Guillaume; Herzen, Julia; Pennicard, David; Graafsma, Heinz; Noël, Peter B; Pfeiffer, Franz

    2015-03-01

    Grating-based differential phase-contrast imaging has proven to be feasible with conventional X-ray sources. The polychromatic spectrum generally limits the performance of the interferometer but benefit can be gained with an energy-sensitive detector. In the presented work, we employ the energy-discrimination capability to correct for phase-wrapping artefacts. We propose to use the phase shifts, which are measured in distinct energy bins, to estimate the optimal phase shift in the sense of maximum likelihood. We demonstrate that our method is able to correct for phase-wrapping artefacts, to improve the contrast-to-noise ratio and to reduce beam hardening due to the modelled energy dependency. The method is evaluated on experimental data which are measured with a laboratory Talbot-Lau interferometer equipped with a conventional polychromatic X-ray source and an energy-sensitive photon-counting pixel detector. Our work shows, that spectral imaging is an important step to move differential phase-contrast imaging closer to pre-clinical and clinical applications, where phase wrapping is particularly problematic. PMID:25163054

  7. Temporally and spectrally resolved subpicosecond energy transfer within the peripheral antenna complex (LH2) and from LH2 to the core antenna complex in photosynthetic purple bacteria.

    PubMed Central

    Hess, S; Chachisvilis, M; Timpmann, K; Jones, M R; Fowler, G J; Hunter, C N; Sundström, V

    1995-01-01

    We report studies of energy transfer from the 800-nm absorbing pigment (B800) to the 850-nm absorbing pigment (B850) of the LH2 peripheral antenna complex and from LH2 to the core antenna complex (LH1) in Rhodobacter (Rb.) sphaeroides. The B800 to B850 process was studied in membranes from a LH2-reaction center (no LH1) mutant of Rb. sphaeroides and the LH2 to LH1 transfer was studied in both the wild-type species and in LH2 mutants with blue-shifted B850. The measurements were performed by using approximately 100-fs pulses to probe the formation of acceptor excitations in a two-color pump-probe measurement. Our experiments reveal a B800 to B850 transfer time of approximately 0.7 ps at 296 K and energy transfer from LH2 to LH1 is characterized by a time constant of approximately 3 ps at 296 K and approximately 5 ps at 77 K. In the blue-shifted B850 mutants, the transfer time from B850 to LH1 becomes gradually longer with increasing blue-shift of the B850 band as a result of the decreasing spectral overlap between the antennae. The results have been used to produce a model for the association between the ring-like structures that are characteristic of both the LH2 and LH1 antennae. PMID:11607622

  8. Measuring correlations between non-stationary series with DCCA coefficient

    NASA Astrophysics Data System (ADS)

    Kristoufek, Ladislav

    2014-05-01

    In this short report, we investigate the ability of the DCCA coefficient to measure correlation level between non-stationary series. Based on a wide Monte Carlo simulation study, we show that the DCCA coefficient can estimate the correlation coefficient accurately regardless the strength of non-stationarity (measured by the fractional differencing parameter d). For a comparison, we also report the results for the standard Pearson correlation coefficient. The DCCA coefficient dominates the Pearson coefficient for non-stationary series.

  9. Tunnelling effect of the non-stationary Kerr black hole

    NASA Astrophysics Data System (ADS)

    Yang, Shu-Zheng; Chen, De-You

    2008-03-01

    Extending Parikh and Wilczek's work to the non-stationary black hole, we study the Hawking radiation of the non-stationary Kerr black hole by the Hamilton-Jacobi method. The result shows that the radiation spectrum is not purely thermal and the tunnelling probability is related to the change of Bekenstein-Hawking entropy, which gives a correction to the Hawking thermal radiation of the black hole.

  10. Performance evaluation of a sub-millimetre spectrally resolved CT system on high- and low-frequency imaging tasks: a simulation.

    PubMed

    Yveborg, Moa; Danielsson, Mats; Bornefalk, Hans

    2012-04-21

    We are developing a photon-counting silicon strip detector with 0.4 × 0.5 mm² detector elements for clinical CT applications. Except for the limited detection efficiency of approximately 0.8 for a spectrum of 80 kVp, the largest discrepancies from ideal spectral behaviour have been shown to be Compton interactions in the detector and electronic noise. Using the framework of cascaded system analysis, we reconstruct the 3D MTF and NPS of a silicon strip detector including the influence of scatter and charge sharing inside the detector. We compare the reconstructed noise and signal characteristics with a reconstructed 3D MTF and NPS of an ideal energy-integrating detector system with unity detection efficiency, no scatter or charge sharing inside the detector, unity presampling MTF and 1 × 1 mm² detector elements. The comparison is done by calculating the dose-normalized detectability index for some clinically relevant imaging tasks and spectra. This work demonstrates that although the detection efficiency of the silicon detector rapidly drops for the acceleration voltages encountered in clinical computed tomography practice, and despite the high fraction of Compton interactions due to the low atomic number, silicon detectors can perform on a par with ideal energy-integrating detectors for routine imaging tasks containing low-frequency components. For imaging tasks containing high-frequency components, the proposed silicon detector system can perform approximately 1.1-1.3 times better than a fully ideal energy-integrating system. PMID:22469924

  11. Time-frequency analysis of non-stationary fusion plasma signals using an improved Hilbert-Huang transform

    SciTech Connect

    Liu, Yangqing Tan, Yi; Xie, Huiqiao; Wang, Wenhao; Gao, Zhe

    2014-07-15

    An improved Hilbert-Huang transform method is developed to the time-frequency analysis of non-stationary signals in tokamak plasmas. Maximal overlap discrete wavelet packet transform rather than wavelet packet transform is proposed as a preprocessor to decompose a signal into various narrow-band components. Then, a correlation coefficient based selection method is utilized to eliminate the irrelevant intrinsic mode functions obtained from empirical mode decomposition of those narrow-band components. Subsequently, a time varying vector autoregressive moving average model instead of Hilbert spectral analysis is performed to compute the Hilbert spectrum, i.e., a three-dimensional time-frequency distribution of the signal. The feasibility and effectiveness of the improved Hilbert-Huang transform method is demonstrated by analyzing a non-stationary simulated signal and actual experimental signals in fusion plasmas.

  12. Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC 6334I

    NASA Astrophysics Data System (ADS)

    van der Wiel, M. H. D.; van der Tak, F. F. S.; Lis, D. C.; Bell, T.; Bergin, E. A.; Comito, C.; Emprechtinger, M.; Schilke, P.; Caux, E.; Ceccarelli, C.; Baudry, A.; Goldsmith, P. F.; Herbst, E.; Langer, W.; Lord, S.; Neufeld, D.; Pearson, J.; Phillips, T.; Rolffs, R.; Yorke, H.; Bacmann, A.; Benedettini, M.; Blake, G. A.; Boogert, A.; Bottinelli, S.; Cabrit, S.; Caselli, P.; Castets, A.; Cernicharo, J.; Codella, C.; Coutens, A.; Crimier, N.; Demyk, K.; Dominik, C.; Encrenaz, P.; Falgarone, E.; Fuente, A.; Gerin, M.; Helmich, F.; Hennebelle, P.; Henning, T.; Hily-Blant, P.; Jacq, T.; Kahane, C.; Kama, M.; Klotz, A.; Lefloch, B.; Lorenzani, A.; Maret, S.; Melnick, G.; Nisini, B.; Pacheco, S.; Pagani, L.; Parise, B.; Salez, M.; Saraceno, P.; Schuster, K.; Tielens, A. G. G. M.; Vastel, C.; Viti, S.; Wakelam, V.; Walters, A.; Wyrowski, F.; Edwards, K.; Zmuidzinas, J.; Morris, P.; Samoska, L. A.; Teyssier, D.

    2010-10-01

    Context. In contrast to the more extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. Aims: We study the molecular gas in the Galactic high-mass star-forming region NGC 6334I, which contains diffuse, quiescent components that are inconspicuous in widely used molecular tracers such as CO. Methods: We present Herschel/HIFI observations of methylidyne (CH) toward NGC 6334I observed as part of the “Chemical HErschel Survey of Star forming regions” (CHESS) key program. HIFI resolves each of the six hyperfine components of the lowest rotational transition (J = 3/2 - 1/2) of CH, observed in both emission and absorption. Results: The CH emission features appear close to the systemic velocity of NGC 6334I, while its measured FWHM linewidth of 3 km s-1 is smaller than previously observed in dense gas tracers such as NH3 and SiO. The CH abundance in the hot core is ~7 × 10-11, two to three orders of magnitude lower than in diffuse clouds. While other studies find distinct outflows in, e.g., CO and H2O toward NGC 6334I, we do not detect any outflow signatures in CH. At least two redshifted components of cold absorbing material must be present at -3.0 and +6.5 km s-1 to explain the absorption signatures. We derive a CH column density (NCH) of 7 × 1013 and 3 × 1013 cm-2 for these two absorbing clouds. We find evidence of two additional absorbing clouds at +8.0 and 0.0 km s-1, both with NCH ≈ 2 × 1013 cm-2. Turbulent linewidths for the four absorption components vary between 1.5 and 5.0 km s-1 in FWHM. We constrain the physical properties and locations of the clouds by matching our CH absorbers with the absorption signatures seen in other molecular tracers. Conclusions: In the hot core, molecules such as H2O and CO trace gas that is heated and dynamically influenced by outflow activity, whereas the CH molecule traces more quiescent material. The four CH absorbing clouds have column densities and turbulent

  13. Nonstationary Analysis of Annual Maximum Streamflow of Canada

    NASA Astrophysics Data System (ADS)

    Yew Gan, Thian; Tan, Xuezhi

    2016-04-01

    Both natural climate change and anthropogenic impacts may cause nonstationarities in hydrological ex-tremes. In this study, long-term annual maximum streamflow (AMS) records from 145 stations over Canada were used to investigate the nonstationary characteristics of AMS, which include abrupt changes and monotonic temporal trends. The nonparameteric Pettitt test was applied to detect abrupt changes, while temporal monotonic trend analysis in AMS series was conducted using the nonparameteric Mann-Kendall and Spearman tests, as well as a parametric Pearson test. Nonstationary frequency analysis of the AMS series was done using a group of nonstationary probability distributions. The nonstationary characteristics of Ca-nadian AMS were further investigated in terms of the Hurst exponent (H), which represents the long-term persistence (LTP) of streamflow data. The results presented here indicate that for Canadian AMS data, abrupt changes are detected more frequently than monotonic trends, partly because many rivers began to be regulated in the twentieth century. Drainage basins that have experienced significant land-use changes are more likely to show temporal trends in AMS, compared to pristine basins with stable land-use conditions. The nonstationary characteristics of AMS were accounted for by fitting the data with probability distributions with time-varying parameters. Large H found in almost 2/ 3 of the Canadian AMS dataset indicates strong LTP, which may partly represent the presence of long-term memories in many Canadian river basins. Furthermore, H values of AMS data are positively correlated with the basin area of Canadian rivers. It seems that non-stationary frequency analysis, instead of the traditional stationary hydrologic frequency analysis, should be employed in the future. Reference: Tan, X., and Gan, T. Y., 2015, Nonstationary analysis of annual maximum streamflow of Canada, Journal of Climate, DOI: 10.1175/JCLI-D-14-00538.1

  14. Bayesian soft X-ray tomography using non-stationary Gaussian Processes

    SciTech Connect

    Li, Dong; Svensson, J.; Thomsen, H.; Werner, A.; Wolf, R.; Medina, F.

    2013-08-15

    In this study, a Bayesian based non-stationary Gaussian Process (GP) method for the inference of soft X-ray emissivity distribution along with its associated uncertainties has been developed. For the investigation of equilibrium condition and fast magnetohydrodynamic behaviors in nuclear fusion plasmas, it is of importance to infer, especially in the plasma center, spatially resolved soft X-ray profiles from a limited number of noisy line integral measurements. For this ill-posed inversion problem, Bayesian probability theory can provide a posterior probability distribution over all possible solutions under given model assumptions. Specifically, the use of a non-stationary GP to model the emission allows the model to adapt to the varying length scales of the underlying diffusion process. In contrast to other conventional methods, the prior regularization is realized in a probability form which enhances the capability of uncertainty analysis, in consequence, scientists who concern the reliability of their results will benefit from it. Under the assumption of normally distributed noise, the posterior distribution evaluated at a discrete number of points becomes a multivariate normal distribution whose mean and covariance are analytically available, making inversions and calculation of uncertainty fast. Additionally, the hyper-parameters embedded in the model assumption can be optimized through a Bayesian Occam's Razor formalism and thereby automatically adjust the model complexity. This method is shown to produce convincing reconstructions and good agreements with independently calculated results from the Maximum Entropy and Equilibrium-Based Iterative Tomography Algorithm methods.

  15. Bayesian soft X-ray tomography using non-stationary Gaussian Processes

    NASA Astrophysics Data System (ADS)

    Li, Dong; Svensson, J.; Thomsen, H.; Medina, F.; Werner, A.; Wolf, R.

    2013-08-01

    In this study, a Bayesian based non-stationary Gaussian Process (GP) method for the inference of soft X-ray emissivity distribution along with its associated uncertainties has been developed. For the investigation of equilibrium condition and fast magnetohydrodynamic behaviors in nuclear fusion plasmas, it is of importance to infer, especially in the plasma center, spatially resolved soft X-ray profiles from a limited number of noisy line integral measurements. For this ill-posed inversion problem, Bayesian probability theory can provide a posterior probability distribution over all possible solutions under given model assumptions. Specifically, the use of a non-stationary GP to model the emission allows the model to adapt to the varying length scales of the underlying diffusion process. In contrast to other conventional methods, the prior regularization is realized in a probability form which enhances the capability of uncertainty analysis, in consequence, scientists who concern the reliability of their results will benefit from it. Under the assumption of normally distributed noise, the posterior distribution evaluated at a discrete number of points becomes a multivariate normal distribution whose mean and covariance are analytically available, making inversions and calculation of uncertainty fast. Additionally, the hyper-parameters embedded in the model assumption can be optimized through a Bayesian Occam's Razor formalism and thereby automatically adjust the model complexity. This method is shown to produce convincing reconstructions and good agreements with independently calculated results from the Maximum Entropy and Equilibrium-Based Iterative Tomography Algorithm methods.

  16. The influence of non-stationary teleconnections on palaeoclimate reconstructions of ENSO variance using a pseudoproxy framework

    NASA Astrophysics Data System (ADS)

    Batehup, R.; McGregor, S.; Gallant, A. J. E.

    2015-12-01

    Reconstructions of the El Niño-Southern Oscillation (ENSO) ideally require high-quality, annually resolved and long-running palaeoclimate proxy records in the eastern tropical Pacific Ocean, located in ENSO's centre of action. However, to date, the palaeoclimate records that have been extracted in the region are short or temporally and spatially sporadic, limiting the information that can be provided by these reconstructions. Consequently, most ENSO reconstructions exploit the downstream influences of ENSO on remote locations, known as teleconnections, where longer records from palaeoclimate proxies exist. However, using teleconnections to reconstruct ENSO relies on the assumption that the relationship between ENSO and the remote location is stationary in time. Increasing evidence from observations and climate models suggests that some teleconnections are, in fact, non-stationary, potentially threatening the validity of those palaeoclimate reconstructions that exploit teleconnections. This study examines the implications of non-stationary teleconnections on modern multi-proxy reconstructions of ENSO variance. The sensitivity of the reconstructions to non-stationary teleconnections were tested using a suite of idealised pseudoproxy experiments that employed output from a fully coupled global climate model. Reconstructions of the variance in the Niño 3.4 index representing ENSO variability were generated using four different methods. Surface temperature data from the GFDL CM2.1 were used as pseudoproxies for these reconstruction methods. As well as sensitivity of the reconstruction to the method, the experiments tested the sensitivity of the reconstruction to the number of non-stationary pseudoproxies and the location of these proxies. We find that non-stationarities can act to degrade the skill of ENSO variance reconstructions. However, when global, randomly spaced networks (assuming a minimum of approximately 20 proxies) were employed, the resulting pseudoproxy

  17. Non-stationary random ground vibration due to loads moving along a railway track

    NASA Astrophysics Data System (ADS)

    Lu, Feng; Gao, Qiang; Lin, J. H.; Williams, F. W.

    2006-11-01

    The pseudo-excitation method (PEM) and the precise integration algorithm are combined to compute the non-stationary random ground vibration caused by loads moving along a railway track at constant speed. The rails are modeled as a single infinite Euler beam connected to sleepers and hence to ballast. This ballast rests on the ground, which is assumed to consist of layered transversely isotropic soil. The equations of motion of the system are established in a Cartesian coordinate system which moves with the loads. The non-stationary power spectral density and the time-dependent standard deviation can be derived conveniently by means of PEM, while the precise integration algorithm for two-point boundary value problems is applied to the solution of the equations of motion in the frequency/wavenumber domain. By virtue of the transverse isotropic property of the layered soils, the threefold iteration process in the frequency/wavenumber domain is reduced into a twofold iteration process. Hence the computational efficiency is improved considerably.

  18. Non-stationary resonance dynamics of weakly coupled pendula

    NASA Astrophysics Data System (ADS)

    Manevitch, L. I.; Romeo, F.

    2015-11-01

    In this letter we fill the gap in understanding the non-stationary Hamiltonian dynamics of the weakly coupled pendula model having significant applications in numerous fields of physics. While common knowledge of this model is predominantly based on the stationary theory and quasi-linear approach to non-stationary dynamics, we consider a strongly nonlinear system without any polynomial approximation of the anharmonic potential. In the adopted asymptotics only closeness to any inter-pendulum resonance frequency is assumed. Being able to explore the whole diapason of initial conditions, two key nonlinear features are revealed by means of the Limiting Phase Trajectories concept: the conditions of intense energy exchange between the pendula and transition to energy localization. The roots and the domain of chaotic behavior are clarified as they are associated with the latter, purely non-stationary, topological transition.

  19. Non-Stationary Internal Tides Observed with Satellite Altimetry

    NASA Technical Reports Server (NTRS)

    Ray, Richard D.; Zaron, E. D.

    2011-01-01

    Temporal variability of the internal tide is inferred from a 17-year combined record of Topex/Poseidon and Jason satellite altimeters. A global sampling of along-track sea-surface height wavenumber spectra finds that non-stationary variance is generally 25% or less of the average variance at wavenumbers characteristic of mode-l tidal internal waves. With some exceptions the non-stationary variance does not exceed 0.25 sq cm. The mode-2 signal, where detectable, contains a larger fraction of non-stationary variance, typically 50% or more. Temporal subsetting of the data reveals interannual variability barely significant compared with tidal estimation error from 3-year records. Comparison of summer vs. winter conditions shows only one region of noteworthy seasonal changes, the northern South China Sea. Implications for the anticipated SWOT altimeter mission are briefly discussed.

  20. Theory, implementation and applications of nonstationary Gabor frames

    PubMed Central

    Balazs, P.; Dörfler, M.; Jaillet, F.; Holighaus, N.; Velasco, G.

    2011-01-01

    Signal analysis with classical Gabor frames leads to a fixed time–frequency resolution over the whole time–frequency plane. To overcome the limitations imposed by this rigidity, we propose an extension of Gabor theory that leads to the construction of frames with time–frequency resolution changing over time or frequency. We describe the construction of the resulting nonstationary Gabor frames and give the explicit formula for the canonical dual frame for a particular case, the painless case. We show that wavelet transforms, constant-Q transforms and more general filter banks may be modeled in the framework of nonstationary Gabor frames. Further, we present the results in the finite-dimensional case, which provides a method for implementing the above-mentioned transforms with perfect reconstruction. Finally, we elaborate on two applications of nonstationary Gabor frames in audio signal processing, namely a method for automatic adaptation to transients and an algorithm for an invertible constant-Q transform. PMID:22267893

  1. Distribution of a nonstationary electron beam in a dense gas

    SciTech Connect

    Sklyarov, Y.M.; Shelepin, L.A.; Syts'ko, Y.L.

    1986-11-01

    The problem of the temporal and spatial dependences of the parameters of the action of a modulated fast-electron beam on a dense gas is posed on the basis of the transport equation. The problem is simplified by making it nondimensional and by transforming to the Fokker-Planck approximation. A Green's function formalism is developed for this problem and is used to express the solution of the general nonstationary problem in the form of a convolution of a nonstationary boundary flow with a stationary Green's function. The use of the derived equation is illustrated using as an example the solution of a problem with the simplest stationary Green's function corresponding to the ''straight-ahead'' approximation. This approximation is used to consider a general relativistic case with model scattering cross sections. The methods and results of a numerical computer solution of the nonstationary problem of electron retardation in the upper layer of the atmosphere are surveyed.

  2. DIFFEOMORPHIC POINT SET REGISTRATION USING NON-STATIONARY MIXTURE MODELS

    PubMed Central

    Wassermann, D.; Ross, J.; Washko, G.; Westin, C-F; Estépar, R. San José

    2013-01-01

    This paper investigates a diffeomorphic point-set registration based on non-stationary mixture models. The goal is to improve the non-linear registration of anatomical structures by representing each point as a general non-stationary kernel that provides information about the shape of that point. Our framework generalizes work done by others that use stationary models. We achieve this by integrating the shape at each point when calculating the point-set similarity and transforming it according to the calculated deformation. We also restrict the non-rigid transform to the space of symmetric diffeomorphisms. Our algorithm is validated in synthetic and human datasets in two different applications: fiber bundle and lung airways registration. Our results shows that non-stationary mixture models are superior to Gaussian mixture models and methods that do not take into account the shape of each point. PMID:24419463

  3. The Effect of White Nonstationary and Colored Nonstationary Noise on Signal Detection

    NASA Astrophysics Data System (ADS)

    Flores, Mauricio; Benacquista, Matthew; Stroeer, Alexander

    2012-02-01

    We analyze the effect of non-stationary noise on the detection of signals on unevenly sampled data. Initial frequency estimation is obtained from a Lomb-Scargle periodogram; which is followed by a global multi-start optimization, as working on a dense local Nelder-Mead iterator for parameter estimates. It has been found that a varying white noise level has no effect on the required relative signal-to-noise ratio for detection in the proposed algorithm, though affecting the absolute amplitude strength of the signal recording. Further analysis has been done on realistic colored noise. Different whitening routines have been incorporated to the proposed algorithm. Detection efficiency is compared for these different routines.

  4. Nonstationary Analysis of Annual Maximum Streamflow of Canada

    NASA Astrophysics Data System (ADS)

    Gan, T. Y.; Tan, X.

    2015-12-01

    Both natural climate change and anthropogenic impacts may cause nonstationarities in hydrological ex-tremes. In this study, long-term annual maximum streamflow (AMS) records from 145 stations over Canada were used to investigate the nonstationary characteristics of AMS, which include abrupt changes and monotonic temporal trends. The nonparameteric Pettitt test was applied to detect abrupt changes, while temporal monotonic trend analysis in AMS series was conducted using the nonparameteric Mann-Kendall and Spearman tests, as well as a parametric Pearson test. Nonstationary frequency analysis of the AMS series was done using a group of nonstationary probability distributions. The nonstationary characteristics of Ca-nadian AMS were further investigated in terms of the Hurst exponent (H), which represents the long-term persistence (LTP) of streamflow data. The results presented here indicate that for Canadian AMS data, abrupt changes are detected more frequently than monotonic trends, partly because many rivers began to be regulated in the twentieth century. Drainage basins that have experienced significant land-use changes are more likely to show temporal trends in AMS, compared to pristine basins with stable land-use conditions. The nonstationary characteristics of AMS were accounted for by fitting the data with probability distributions with time-varying parameters. Large H found in almost 2/ 3 of the Canadian AMS dataset indicates strong LTP, which may partly represent the presence of long-term memories in many Canadian river basins. Furthermore, H values of AMS data are positively correlated with the basin area of Canadian rivers. It seems that non-stationary frequency analysis, instead of the traditional stationary hydrologic frequency analysis, should be employed in the future.

  5. Learning geotemporal nonstationary failure and recovery of power distribution.

    PubMed

    Wei, Yun; Ji, Chuanyi; Galvan, Floyd; Couvillon, Stephen; Orellana, George; Momoh, James

    2014-01-01

    Smart energy grid is an emerging area for new applications of machine learning in a nonstationary environment. Such a nonstationary environment emerges when large-scale failures occur at power networks because of external disruptions such as hurricanes and severe storms. Power distribution networks lie at the edge of the grid, and are especially vulnerable to external disruptions. Quantifiable approaches are lacking and needed to learn nonstationary behaviors of large-scale failure and recovery of power distribution. This paper studies such nonstationary behaviors in three aspects. First, a novel formulation is derived for an entire life cycle of large-scale failure and recovery of power distribution. Second, spatial-temporal models of failure and recovery of power distribution are developed as geolocation-based multivariate nonstationary GI(t)/G(t)/∞ queues. Third, the nonstationary spatial-temporal models identify a small number of parameters to be learned. Learning is applied to two real-life examples of large-scale disruptions. One is from Hurricane Ike, where data from an operational network is exact on failures and recoveries. The other is from Hurricane Sandy, where aggregated data is used for inferring failure and recovery processes at one of the impacted areas. Model parameters are learned using real data. Two findings emerge as results of learning: 1) failure rates behave similarly at the two different provider networks for two different hurricanes but differently at the geographical regions and 2) both the rapid and slow-recovery are present for Hurricane Ike but only slow recovery is shown for a regional distribution network from Hurricane Sandy. PMID:24806656

  6. Characterization of stationary and nonstationary behavior in gyrotron oscillators.

    PubMed

    Chang, T H; Chen, S H; Barnett, L R; Chu, K R

    2001-08-01

    The transition from the stationary state to a sequence of nonstationary states in the gyromonotron oscillator is experimentally characterized for the first time. We have also demonstrated the stationary operation of a gyrotron backward-wave oscillator at a beam current far in excess of the generally predicted nonstationary threshold. This difference in nonlinear behavior has been investigated and shown to be fundamental with a comparative analysis of the feedback mechanisms, energy deposition profiles, and field shaping processes involved in these two types of oscillations. PMID:11497832

  7. On the temporal variability of the surface solar radiation by means of spectral representations

    NASA Astrophysics Data System (ADS)

    Bengulescu, Marc; Blanc, Philippe; Wald, Lucien

    2016-07-01

    This work deals with the temporal variability of daily means of the global broadband surface solar irradiance (SSI) impinging on a horizontal plane by studying a decennial time-series of high-quality measurements recorded at a BSRN ground station. Since the data have a non-linear and non-stationary character, two time-frequency-energy representations of signal processing are compared in their ability to resolve the temporal variability of the pyranometric signal. First, the continuous wavelet transform is used to construct the wavelet power spectrum of the data. Second, the adaptive, noise-assisted empirical mode decomposition is employed to extract the intrinsic mode functions of the signal, followed by Hilbert spectral analysis. In both spectral representations, the temporal variability of the SSI is portrayed having clearly distinguishable features: a plateau between scales of two days and two-three months that has decreasing power with increasing scale, a large spectral peak corresponding to the annual variability cycle, and a low power regime in between the previous two. It is shown that the data-driven, noise-assisted method yields a somewhat more sparse representation and that it is a suitable tool for inspecting the temporal variability of SSI measurements.

  8. The Spectral Shift Function and Spectral Flow

    NASA Astrophysics Data System (ADS)

    Azamov, N. A.; Carey, A. L.; Sukochev, F. A.

    2007-11-01

    At the 1974 International Congress, I. M. Singer proposed that eta invariants and hence spectral flow should be thought of as the integral of a one form. In the intervening years this idea has lead to many interesting developments in the study of both eta invariants and spectral flow. Using ideas of [24] Singer’s proposal was brought to an advanced level in [16] where a very general formula for spectral flow as the integral of a one form was produced in the framework of noncommutative geometry. This formula can be used for computing spectral flow in a general semifinite von Neumann algebra as described and reviewed in [5]. In the present paper we take the analytic approach to spectral flow much further by giving a large family of formulae for spectral flow between a pair of unbounded self-adjoint operators D and D + V with D having compact resolvent belonging to a general semifinite von Neumann algebra {mathcal{N}} and the perturbation V in {mathcal{N}} . In noncommutative geometry terms we remove summability hypotheses. This level of generality is made possible by introducing a new idea from [3]. There it was observed that M. G. Krein’s spectral shift function (in certain restricted cases with V trace class) computes spectral flow. The present paper extends Krein’s theory to the setting of semifinite spectral triples where D has compact resolvent belonging to {mathcal{N}} and V is any bounded self-adjoint operator in {mathcal{N}} . We give a definition of the spectral shift function under these hypotheses and show that it computes spectral flow. This is made possible by the understanding discovered in the present paper of the interplay between spectral shift function theory and the analytic theory of spectral flow. It is this interplay that enables us to take Singer’s idea much further to create a large class of one forms whose integrals calculate spectral flow. These advances depend critically on a new approach to the calculus of functions of non

  9. Diagnosing non-stationary behaviour in a hydrological model

    NASA Astrophysics Data System (ADS)

    Thyer, Mark; Westra, Seth; Leonard, Michael; Kavetski, Dmitri; Lambert, Martin

    2013-04-01

    The stationarity of hydrological models is increasingly being called into question, due partly to changes in land cover as well as natural and anthropogenic climate change. This issue is manifest in model parameters which change over time, creating challenges in calibration and validation (as the joint distribution of model parameters is conditional to the period used for model calibration), and in prediction when one wishes to investigate runoff properties in the future. This paper describes the incorporation of non-stationary parameters into a well established rainfall-runoff model - GR4J - using a Bayesian framework for calibration and prediction, and the use of an information theoretic approach to evaluate whether the inclusion of non-stationary parameters was justified. A subcatchment of the Onkaparinga river in South Australia was used as a case study, and it was found that GR4J parameter 'x1' varied significantly seasonally and also exhibited a longer-term increasing trend over the calibration period from 1974 to 1999. The inclusion of this non-stationary parameter in the model reduced the over-prediction in the drier validation period from 2000 to 2010 from 25% to 1.5%. Whilst including non-stationarity parameters provided substantial improvements in prediction, it is advocated that this non-stationary parameters be used as a diagnostic tool to identify model deficiencies, rather than for prediction. Techniques to reduce the non-stationarity by enhancing the model structure will to include one or more missing processes will be discussed.

  10. Nonstationary Gas Flow in Thin Pipes of Variable Cross Section

    NASA Technical Reports Server (NTRS)

    Guderley, G.

    1948-01-01

    Characteristic methods for nonstationary flows have been published only for the special case of the isentropic flow up until the present, althought they are applicable in various places to more difficult questions too. This report derives the characteristic method for the flows which depend only on the position coordinates and time. At the same time the treatment of compression shocks is shown.

  11. Time reversibility from visibility graphs of nonstationary processes

    NASA Astrophysics Data System (ADS)

    Lacasa, Lucas; Flanagan, Ryan

    2015-08-01

    Visibility algorithms are a family of methods to map time series into networks, with the aim of describing the structure of time series and their underlying dynamical properties in graph-theoretical terms. Here we explore some properties of both natural and horizontal visibility graphs associated to several nonstationary processes, and we pay particular attention to their capacity to assess time irreversibility. Nonstationary signals are (infinitely) irreversible by definition (independently of whether the process is Markovian or producing entropy at a positive rate), and thus the link between entropy production and time series irreversibility has only been explored in nonequilibrium stationary states. Here we show that the visibility formalism naturally induces a new working definition of time irreversibility, which allows us to quantify several degrees of irreversibility for stationary and nonstationary series, yielding finite values that can be used to efficiently assess the presence of memory and off-equilibrium dynamics in nonstationary processes without the need to differentiate or detrend them. We provide rigorous results complemented by extensive numerical simulations on several classes of stochastic processes.

  12. Redefine Water Infrastructure Adaptation to a Nonstationary Climate (Editorial)

    EPA Science Inventory

    The statement “Climate Stationarity is Dead” by Milly et al. (2008) stresses the need to evaluate and when necessary, incorporate non-stationary hydroclimatic changes into water resources and infrastructure planning and engineering. Variations of this theme echo in several other ...

  13. Ultrafast CARS with Improved Spectral Resolution

    NASA Astrophysics Data System (ADS)

    Lütgens, M.; Chatzipapadopoulos, S.; Lochbrunner, S.

    2013-03-01

    Molecular vibrations are investigated by time and frequency resolved CARS applying ultrafast excitation and picosecond probing for high spectral resolution. Enhanced spectral structure and beating phenomena are demonstrated for coalescing Raman bands.

  14. Spectral correlations of fractional Brownian motion

    SciTech Connect

    Oigaard, Tor Arne; Hanssen, Alfred; Scharf, Louis L.

    2006-09-15

    Fractional Brownian motion (fBm) is a ubiquitous nonstationary model for many physical processes with power-law time-averaged spectra. In this paper, we exploit the nonstationarity to derive the full spectral correlation structure of fBm. Starting from the time-varying correlation function, we derive two different time-frequency spectral correlation functions (the ambiguity function and the Kirkwood-Rihaczek spectrum), and one dual-frequency spectral correlation function. The dual-frequency spectral correlation has a surprisingly simple structure, with spectral support on three discrete lines. The theoretical predictions are verified by spectrum estimates of Monte Carlo simulations and of a time series of earthquakes with a magnitude of 7 and higher.

  15. Energy expectation values of a particle in nonstationary fields

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.

    2015-01-01

    We show that the origin of the nonequivalence of Hamiltonians in different representations is a change of the form of the time-derivative operator at a time-dependent unitary transformation. This nonequivalence does not lead to an ambiguity of the energy expectation values of a particle in nonstationary fields but assigns the basic representation. It has been explicitly or implicitly supposed in previous investigations that this representation is the Dirac one. We prove the alternative assertion about the basic role of the Foldy-Wouthuysen representation. We also derive the general equation for the energy expectation values in the Dirac representation. As an example, we consider a spin-1/2 particle with anomalous magnetic and electric dipole moments in strong time-dependent electromagnetic fields. We apply the obtained results to a spin-1/2 particle in a plane monochromatic electromagnetic wave and give an example of the exact Foldy-Wouthuysen transformation in the nonstationary case.

  16. Compounding approach for univariate time series with nonstationary variances

    NASA Astrophysics Data System (ADS)

    Schäfer, Rudi; Barkhofen, Sonja; Guhr, Thomas; Stöckmann, Hans-Jürgen; Kuhl, Ulrich

    2015-12-01

    A defining feature of nonstationary systems is the time dependence of their statistical parameters. Measured time series may exhibit Gaussian statistics on short time horizons, due to the central limit theorem. The sample statistics for long time horizons, however, averages over the time-dependent variances. To model the long-term statistical behavior, we compound the local distribution with the distribution of its parameters. Here, we consider two concrete, but diverse, examples of such nonstationary systems: the turbulent air flow of a fan and a time series of foreign exchange rates. Our main focus is to empirically determine the appropriate parameter distribution for the compounding approach. To this end, we extract the relevant time scales by decomposing the time signals into windows and determine the distribution function of the thus obtained local variances.

  17. The evaluation of regional frequency analyses methods for nonstationary data

    NASA Astrophysics Data System (ADS)

    Nam, W.; Kim, S.; Kim, H.; Joo, K.; Heo, J.-H.

    2015-06-01

    Regional frequency analysis is widely used to estimate more reliable quantiles of extreme hydro-meteorological events. The stationarity of data is required for its application. This assumption tends to be violated due to climate change. In this paper, four nonstationary index flood models were used to analyze the nonstationary regional data. Monte Carlo simulation was used to evaluate the performances of these models for the generalized extreme value distribution with linearly time varying location parameter and constant scale and shape parameters. As a results, it was found that the index flood model with time-invariant index flood and time-variant growth curve could yield more statistically efficient quantile when record is long enough to show significant nonstationarity.

  18. Deviations from uniform power law scaling in nonstationary time series

    NASA Technical Reports Server (NTRS)

    Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

    1997-01-01

    A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

  19. Compounding approach for univariate time series with nonstationary variances.

    PubMed

    Schäfer, Rudi; Barkhofen, Sonja; Guhr, Thomas; Stöckmann, Hans-Jürgen; Kuhl, Ulrich

    2015-12-01

    A defining feature of nonstationary systems is the time dependence of their statistical parameters. Measured time series may exhibit Gaussian statistics on short time horizons, due to the central limit theorem. The sample statistics for long time horizons, however, averages over the time-dependent variances. To model the long-term statistical behavior, we compound the local distribution with the distribution of its parameters. Here, we consider two concrete, but diverse, examples of such nonstationary systems: the turbulent air flow of a fan and a time series of foreign exchange rates. Our main focus is to empirically determine the appropriate parameter distribution for the compounding approach. To this end, we extract the relevant time scales by decomposing the time signals into windows and determine the distribution function of the thus obtained local variances. PMID:26764768

  20. Hawking's radiation in non-stationary rotating de Sitter background

    NASA Astrophysics Data System (ADS)

    Ibohal, N.; Ibungochouba, T.

    2011-05-01

    Hawking's radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell's electromagnetic field in the non-stationary rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation. The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived. It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics and the calculated stress-energy tensor contains the thermal radiation effect.

  1. Quantum tunneling of the non-stationary BTZ black hole

    NASA Astrophysics Data System (ADS)

    Yang, Juan; Yang, Shu Zheng

    2009-07-01

    The semi-classical tunneling method is extended to study the Hawking tunneling radiation from the non-stationary BTZ black hole via general tortoise coordination transformation and WKB approximation. In this paper, we simplify the spin-0 scalar field equation and the spin-1/2 Dirac equation at the event horizon of this black hole, and then the quantum tunneling probability and Hawking temperature are obtained. Finally, the correctional tunneling rate is researched, and the results show that after considering the changed background space-time of the non-stationary BTZ black hole, the tunneling rate depends not only on the entropy change but also on the integral about {\\dot r}_H .

  2. Non-stationary frequency domain system identification using time-frequency representations

    NASA Astrophysics Data System (ADS)

    Guo, Yanlin; Kareem, Ahsan

    2016-05-01

    System properties of buildings and bridges may vary with time due to temperature changes, aging or extreme loadings. To identify these time-varying system properties, this study proposes a new output-only non-stationary system identification (SI) framework based on instantaneous or marginal spectra derived from the time-frequency representation, e.g., short time Fourier or wavelet transform. Spectra derived from these time-frequency representations are very popular in tracking time-varying frequencies; however, they have seldom been used to identify the time-varying damping ratio because a short window needed to capture the time-varying information amplifies the bandwidth significantly, which may lead to considerably overestimating the damping ratio. To overcome this shortcoming, this study modifies the theoretical frequency response function (FRF) to explicitly account for the windowing effect, and therefore enables SI directly using instantaneous or marginal spectra derived from the wavelet or short time Fourier transform. The response spectrum estimated using the short time window and the modified FRF are both influenced by the same time window, thus the instantaneous or time-localized marginal spectrum of response can be fitted to the modified FRF to identify frequency and damping ratio at each time instant. This spectral-based SI framework can reliably identify damping in time-varying systems under non-stationary excitations. The efficacy of the proposed framework is demonstrated by both numerical and full-scale examples, and also compared to the time-domain SI method, stochastic subspace identification (SSI), since the time-domain SI approaches and their extensions are popular in identifying time-varying systems utilizing recursive algorithms or moving windows.

  3. Wave Propagation in Non-Stationary Statistical Mantle Models at the Global Scale

    NASA Astrophysics Data System (ADS)

    Meschede, M.; Romanowicz, B. A.

    2014-12-01

    We study the effect of statistically distributed heterogeneities that are smaller than the resolution of current tomographic models on seismic waves that propagate through the Earth's mantle at teleseismic distances. Current global tomographic models are missing small-scale structure as evidenced by the failure of even accurate numerical synthetics to explain enhanced coda in observed body and surface waveforms. One way to characterize small scale heterogeneity is to construct random models and confront observed coda waveforms with predictions from these models. Statistical studies of the coda typically rely on models with simplified isotropic and stationary correlation functions in Cartesian geometries. We show how to construct more complex random models for the mantle that can account for arbitrary non-stationary and anisotropic correlation functions as well as for complex geometries. Although this method is computationally heavy, model characteristics such as translational, cylindrical or spherical symmetries can be used to greatly reduce the complexity such that this method becomes practical. With this approach, we can create 3D models of the full spherical Earth that can be radially anisotropic, i.e. with different horizontal and radial correlation functions, and radially non-stationary, i.e. with radially varying model power and correlation functions. Both of these features are crucial for a statistical description of the mantle in which structure depends to first order on the spherical geometry of the Earth. We combine different random model realizations of S velocity with current global tomographic models that are robust at long wavelengths (e.g. Meschede and Romanowicz, 2014, GJI submitted), and compute the effects of these hybrid models on the wavefield with a spectral element code (SPECFEM3D_GLOBE). We finally analyze the resulting coda waves for our model selection and compare our computations with observations. Based on these observations, we make

  4. Estimation of Parameters from Discrete Random Nonstationary Time Series

    NASA Astrophysics Data System (ADS)

    Takayasu, H.; Nakamura, T.

    For the analysis of nonstationary stochastic time series we introduce a formulation to estimate the underlying time-dependent parameters. This method is designed for random events with small numbers that are out of the applicability range of the normal distribution. The method is demonstrated for numerical data generated by a known system, and applied to time series of traffic accidents, batting average of a baseball player and sales volume of home electronics.

  5. Effect of water compressibility on nonstationary characteristics of hydraulic turbines

    NASA Astrophysics Data System (ADS)

    Kurzin, V. B.

    2013-09-01

    We have investigated the effect of water compressibility on the nonstationary characteristics of turbines connected with the ability of the liquid to execute natural hydroacoustic vibrations in the setting of hydroelectric units. We have constructed a model of the setting up of forced hydroacoustic vibrations in the water conduit due to the precession of the vortex core running off the turbine. The conditions for the possibility that low-frequency hydroacoustic natural vibrations will arise have been considered.

  6. Nonstationary Mass Transfer Near the Surface of a Cylindrical Body

    NASA Astrophysics Data System (ADS)

    Rudobashta, S. P.; Kosheleva, M. K.; Kartashov, É. M.

    2015-11-01

    The problem of nonstationary diffusion of the target component to a phase that is external relative to the surface of a cylindrical body has been formulated and solved analytically. From the found solution the dependences have been obtained for calculating the instantaneous mass transfer coefficient and the phase-contact-time mean mass transfer coefficient, on the basis of which the process of extraction of technological pollutants from fibrous materials has been analyzed.

  7. Macroscopic vacuum effects in an inhomogeneous and nonstationary electromagnetic field

    SciTech Connect

    Gal'tsov, D.V.; Nikitina, N.S.

    1983-04-01

    Macroscopic effects of vacuum polarization by a strong nonuniform and nonstationary fields, which are kinematically forbidden in the case of a uniform magnetic field, are considered. Calculations are perfomed for the deflection of a light beam in the field of a magnetic dipole, for the production of photon pairs by an inclined rotator, and for doubling and modulation of the frequency in scattering of low-frequency electromagnetic waves by the magnetic field of an inclined rotator.

  8. Response of laminated plates to non-stationary random excitation

    NASA Technical Reports Server (NTRS)

    Cederbaum, Gabriel; Librescu, Liviu; Elishakoff, Isaac

    1989-01-01

    The response of composite laminated plates subjected to nonstationary random excitation is determined. First-order shear deformation theory is used for the analysis of symmetric cross-ply and antisymmetric angle-ply plates. The time-dependent component of the forcing function is taken as a product of a well-defined, slowly varying envelope function, and a noise function, assumed to be white or narrow-band random excitation.

  9. Application of nonstationary generalized logistic models for analyzing the annual maximum rainfall data in Korea

    NASA Astrophysics Data System (ADS)

    Kim, S.; Joo, K.; Kim, H.; Heo, J. H.

    2014-12-01

    Recently, the various approaches for the nonstationary frequency analysis have been studied since the effect of climate change was widely recognized for hydrologic data. Most nonstationary studies proposed the nonstationary general extreme value (GEV) and generalized Pareto models for the annual maximum and POT (peak-over-threshold) data, respectively. However, various alternatives is needed to analyze the nonstationary hydrologic data because of the complicated influence of climate change. This study proposed the nonstationary generalized logistic models containing time-dependent location and scale parameters. These models contain only or both nonstationary location and scale parameters that change linearly over time. The parameters are estimated using the method of maximum likelihood based on the Newton-Raphson method. In addition, the proposed models apply to the annual maximum rainfall data of Korea in order to evaluate the applicability of the proposed models.

  10. RESOLVE Project

    NASA Technical Reports Server (NTRS)

    Parker, Ray; Coan, Mary; Cryderman, Kate; Captain, Janine

    2013-01-01

    The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis conducted include: pneumatic analysis to calculate the WDD's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. Since LAVA is a scientific subsystem, the near-infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.