Domains of Pyrococcus furiosus L-asparaginase fold sequentially and assemble through strong intersubunit associative forces.

PubMed

Garg, Dushyant K; Tomar, Rachana; Dhoke, Reema R; Srivastava, Ankit; Kundu, Bishwajit

2015-05-01

Here, we report the folding and assembly of a Pyrococcus furiosus-derived protein, L-asparaginase (PfA). PfA functions as a homodimer, with each monomer made of distinct N- and C-terminal domains. The purified individual domains as well as single Trp mutant of each domain were subjected to chemical denaturation/renaturation and probed by combination of spectroscopic, chromatographic, quenching and scattering techniques. We found that the N-domain acts like a folding scaffold and assists the folding of remaining polypeptide. The domains displayed sequential folding with the N-domain having higher thermodynamic stability. We report that the extreme thermal stability of PfA is due to the presence of high intersubunit associative forces supported by extensive H-bonding and ionic interactions network. Our results proved that folding cooperativity in a thermophilic, multisubunit protein is dictated by concomitant folding and association of constituent domains directly into a native quaternary structure. This report gives an account of the factors responsible for folding and stability of a therapeutically and industrially important protein.

Spectral element method for elastic and acoustic waves in frequency domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Linlin; Zhou, Yuanguo; Wang, Jia-Min

Numerical techniques in time domain are widespread in seismic and acoustic modeling. In some applications, however, frequency-domain techniques can be advantageous over the time-domain approach when narrow band results are desired, especially if multiple sources can be handled more conveniently in the frequency domain. Moreover, the medium attenuation effects can be more accurately and conveniently modeled in the frequency domain. In this paper, we present a spectral-element method (SEM) in frequency domain to simulate elastic and acoustic waves in anisotropic, heterogeneous, and lossy media. The SEM is based upon the finite-element framework and has exponential convergence because of the usemore » of GLL basis functions. The anisotropic perfectly matched layer is employed to truncate the boundary for unbounded problems. Compared with the conventional finite-element method, the number of unknowns in the SEM is significantly reduced, and higher order accuracy is obtained due to its spectral accuracy. To account for the acoustic-solid interaction, the domain decomposition method (DDM) based upon the discontinuous Galerkin spectral-element method is proposed. Numerical experiments show the proposed method can be an efficient alternative for accurate calculation of elastic and acoustic waves in frequency domain.« less

SSME propellant path leak detection real-time

NASA Technical Reports Server (NTRS)

Crawford, R. A.; Smith, L. M.

1994-01-01

Included are four documents that outline the technical aspects of the research performed on NASA Grant NAG8-140: 'A System for Sequential Step Detection with Application to Video Image Processing'; 'Leak Detection from the SSME Using Sequential Image Processing'; 'Digital Image Processor Specifications for Real-Time SSME Leak Detection'; and 'A Color Change Detection System for Video Signals with Applications to Spectral Analysis of Rocket Engine Plumes'.

Random Initialisation of the Spectral Variables: an Alternate Approach for Initiating Multivariate Curve Resolution Alternating Least Square (MCR-ALS) Analysis.

PubMed

Kumar, Keshav

2017-11-01

Multivariate curve resolution alternating least square (MCR-ALS) analysis is the most commonly used curve resolution technique. The MCR-ALS model is fitted using the alternate least square (ALS) algorithm that needs initialisation of either contribution profiles or spectral profiles of each of the factor. The contribution profiles can be initialised using the evolve factor analysis; however, in principle, this approach requires that data must belong to the sequential process. The initialisation of the spectral profiles are usually carried out using the pure variable approach such as SIMPLISMA algorithm, this approach demands that each factor must have the pure variables in the data sets. Despite these limitations, the existing approaches have been quite a successful for initiating the MCR-ALS analysis. However, the present work proposes an alternate approach for the initialisation of the spectral variables by generating the random variables in the limits spanned by the maxima and minima of each spectral variable of the data set. The proposed approach does not require that there must be pure variables for each component of the multicomponent system or the concentration direction must follow the sequential process. The proposed approach is successfully validated using the excitation-emission matrix fluorescence data sets acquired for certain fluorophores with significant spectral overlap. The calculated contribution and spectral profiles of these fluorophores are found to correlate well with the experimental results. In summary, the present work proposes an alternate way to initiate the MCR-ALS analysis.

A wavelet and least square filter based spatial-spectral denoising approach of hyperspectral imagery

NASA Astrophysics Data System (ADS)

Li, Ting; Chen, Xiao-Mei; Chen, Gang; Xue, Bo; Ni, Guo-Qiang

2009-11-01

Noise reduction is a crucial step in hyperspectral imagery pre-processing. Based on sensor characteristics, the noise of hyperspectral imagery represents in both spatial and spectral domain. However, most prevailing denosing techniques process the imagery in only one specific domain, which have not utilized multi-domain nature of hyperspectral imagery. In this paper, a new spatial-spectral noise reduction algorithm is proposed, which is based on wavelet analysis and least squares filtering techniques. First, in the spatial domain, a new stationary wavelet shrinking algorithm with improved threshold function is utilized to adjust the noise level band-by-band. This new algorithm uses BayesShrink for threshold estimation, and amends the traditional soft-threshold function by adding shape tuning parameters. Comparing with soft or hard threshold function, the improved one, which is first-order derivable and has a smooth transitional region between noise and signal, could save more details of image edge and weaken Pseudo-Gibbs. Then, in the spectral domain, cubic Savitzky-Golay filter based on least squares method is used to remove spectral noise and artificial noise that may have been introduced in during the spatial denoising. Appropriately selecting the filter window width according to prior knowledge, this algorithm has effective performance in smoothing the spectral curve. The performance of the new algorithm is experimented on a set of Hyperion imageries acquired in 2007. The result shows that the new spatial-spectral denoising algorithm provides more significant signal-to-noise-ratio improvement than traditional spatial or spectral method, while saves the local spectral absorption features better.

The Application of Deterministic Spectral Domain Method to the Analysis of Planar Circuit Discontinuities on Open Substrates

DTIC Science & Technology

1990-08-01

the spectral domain is extended to include the effects of two-dimensional, two-component current flow in planar transmission line discontinuities 6n...PROFESSOR: Tatsuo Itoh A deterministic formulation of the method of moments carried out in the spectral domain is extended to include the effects of...two-dimensional, two- component current flow in planar transmission line discontinuities on open substrates. The method includes the effects of space

Dynamic anticipatory processing of hierarchical sequential events: a common role for Broca's area and ventral premotor cortex across domains?

PubMed

Fiebach, Christian J; Schubotz, Ricarda I

2006-05-01

This paper proposes a domain-general model for the functional contribution of ventral premotor cortex (PMv) and adjacent Broca's area to perceptual, cognitive, and motor processing. We propose to understand this frontal region as a highly flexible sequence processor, with the PMv mapping sequential events onto stored structural templates and Broca's Area involved in more complex, hierarchical or hypersequential processing. This proposal is supported by reference to previous functional neuroimaging studies investigating abstract sequence processing and syntactic processing.

Multi-channel imaging cytometry with a single detector

NASA Astrophysics Data System (ADS)

Locknar, Sarah; Barton, John; Entwistle, Mark; Carver, Gary; Johnson, Robert

2018-02-01

Multi-channel microscopy and multi-channel flow cytometry generate high bit data streams. Multiple channels (both spectral and spatial) are important in diagnosing diseased tissue and identifying individual cells. Omega Optical has developed techniques for mapping multiple channels into the time domain for detection by a single high gain, high bandwidth detector. This approach is based on pulsed laser excitation and a serial array of optical fibers coated with spectral reflectors such that up to 15 wavelength bins are sequentially detected by a single-element detector within 2.5 μs. Our multichannel microscopy system uses firmware running on dedicated DSP and FPGA chips to synchronize the laser, scanning mirrors, and sampling clock. The signals are digitized by an NI board into 14 bits at 60MHz - allowing for 232 by 174 pixel fields in up to 15 channels with 10x over sampling. Our multi-channel imaging cytometry design adds channels for forward scattering and back scattering to the fluorescence spectral channels. All channels are detected within the 2.5 μs - which is compatible with fast cytometry. Going forward, we plan to digitize at 16 bits with an A-toD chip attached to a custom board. Processing these digital signals in custom firmware would allow an on-board graphics processing unit to display imaging flow cytometry data over configurable scanning line lengths. The scatter channels can be used to trigger data buffering when a cell is present in the beam. This approach enables a low cost mechanically robust imaging cytometer.

Broadband Structural Dynamics: Understanding the Impulse-Response of Structures Across Multiple Length and Time Scales

DTIC Science & Technology

2010-08-18

Spectral domain response calculated • Time domain response obtained through inverse transform Approach 4: WASABI Wavelet Analysis of Structural Anomalies...differences at unity scale! Time Function Transform Apply Spectral Domain Transfer Function Time Function Inverse Transform Transform Transform  mtP

Solution of electromagnetic scattering and radiation problems using a spectral domain approach - A review

NASA Technical Reports Server (NTRS)

Mittra, R.; Ko, W. L.; Rahmat-Samii, Y.

1979-01-01

This paper presents a brief review of some recent developments on the use of the spectral-domain approach for deriving high-frequency solutions to electromagnetics scattering and radiation problems. The spectral approach is not only useful for interpreting the well-known Keller formulas based on the geometrical theory of diffraction (GTD), it can also be employed for verifying the accuracy of GTD and other asymptotic solutions and systematically improving the results when such improvements are needed. The problem of plane wave diffraction by a finite screen or a strip is presented as an example of the application of the spectral-domain approach.

Combined Parameter and State Estimation Problem in a Complex Domain: RF Hyperthermia Treatment Using Nanoparticles

NASA Astrophysics Data System (ADS)

Bermeo Varon, L. A.; Orlande, H. R. B.; Eliçabe, G. E.

2016-09-01

The particle filter methods have been widely used to solve inverse problems with sequential Bayesian inference in dynamic models, simultaneously estimating sequential state variables and fixed model parameters. This methods are an approximation of sequences of probability distributions of interest, that using a large set of random samples, with presence uncertainties in the model, measurements and parameters. In this paper the main focus is the solution combined parameters and state estimation in the radiofrequency hyperthermia with nanoparticles in a complex domain. This domain contains different tissues like muscle, pancreas, lungs, small intestine and a tumor which is loaded iron oxide nanoparticles. The results indicated that excellent agreements between estimated and exact value are obtained.

The p2 domain of human immunodeficiency virus type 1 Gag regulates sequential proteolytic processing and is required to produce fully infectious virions.

PubMed

Pettit, S C; Moody, M D; Wehbie, R S; Kaplan, A H; Nantermet, P V; Klein, C A; Swanstrom, R

1994-12-01

The proteolytic processing sites of the human immunodeficiency virus type 1 (HIV-1) Gag precursor are cleaved in a sequential manner by the viral protease. We investigated the factors that regulate sequential processing. When full-length Gag protein was digested with recombinant HIV-1 protease in vitro, four of the five major processing sites in Gag were cleaved at rates that differ by as much as 400-fold. Three of these four processing sites were cleaved independently of the others. The CA/p2 site, however, was cleaved approximately 20-fold faster when the adjacent downstream p2/NC site was blocked from cleavage or when the p2 domain of Gag was deleted. These results suggest that the presence of a C-terminal p2 tail on processing intermediates slows cleavage at the upstream CA/p2 site. We also found that lower pH selectively accelerated cleavage of the CA/p2 processing site in the full-length precursor and as a peptide primarily by a sequence-based mechanism rather than by a change in protein conformation. Deletion of the p2 domain of Gag results in released virions that are less infectious despite the presence of the processed final products of Gag. These findings suggest that the p2 domain of HIV-1 Gag regulates the rate of cleavage at the CA/p2 processing site during sequential processing in vitro and in infected cells and that p2 may function in the proper assembly of virions.

Episodic Contributions to Sequential Control: Learning from a Typist's Touch

ERIC Educational Resources Information Center

Crump, Matthew J. C.; Logan, Gordon D.

2010-01-01

Sequential control over routine action is widely assumed to be controlled by stable, highly practiced representations. Our findings demonstrate that the processes controlling routine actions in the domain of skilled typing can be flexibly manipulated by memory processes coding recent experience with typing particular words and letters. In two…

Accounting for Test Variability through Sizing Local Domains in Sequential Design Optimization with Concurrent Calibration-Based Model Validation

DTIC Science & Technology

2013-08-01

in Sequential Design Optimization with Concurrent Calibration-Based Model Validation Dorin Drignei 1 Mathematics and Statistics Department...Validation 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Dorin Drignei; Zissimos Mourelatos; Vijitashwa Pandey

On the modeling of hyperspectral remote-sensing reflectance of high-sediment-load waters in the visible to shortwave-infrared domain.

PubMed

Lee, Zhongping; Shang, Shaoling; Lin, Gong; Chen, Jun; Doxaran, David

2016-03-01

We evaluated three key components in modeling hyperspectral remote-sensing reflectance in the visible to shortwave-infrared (Vis-SWIR) domain of high-sediment-load (HSL) waters, which are the relationship between remote-sensing reflectance (R(rs)) and inherent optical properties (IOPs), the absorption coefficient spectrum of pure water (a(w)) in the IR-SWIR region, and the spectral variation of sediment absorption coefficient (a(sed)). Results from this study indicate that it is necessary to use a more generalized R(rs)-IOP model to describe the spectral variation of R(rs) of HSL waters from Vis to SWIR; otherwise it may result in a spectrally distorted R(rs) spectrum if a constant model parameter is used. For hyperspectral a(w) in the IR-SWIR domain, the values reported in Kou et al. (1993) provided a much better match with the spectral variation of R(rs) in this spectral range compared to that of Segelstein (1981). For a(sed) spectrum, an empirical a(sed) spectral shape derived from sample measurements is found working much better than the traditional exponential-decay function of wavelength in modeling the spectral variation of R(rs) in the visible domain. These results would improve our understanding of the spectral signatures of R(rs) of HSL waters in the Vis-SWIR domain and subsequently improve the retrieval of IOPs from ocean color remote sensing, which could further help the estimation of sediment loading of such waters. Limitations in estimating chlorophyll concentration in such waters are also discussed.

New spectral imaging techniques for blood oximetry in the retina

NASA Astrophysics Data System (ADS)

Alabboud, Ied; Muyo, Gonzalo; Gorman, Alistair; Mordant, David; McNaught, Andrew; Petres, Clement; Petillot, Yvan R.; Harvey, Andrew R.

2007-07-01

Hyperspectral imaging of the retina presents a unique opportunity for direct and quantitative mapping of retinal biochemistry - particularly of the vasculature where blood oximetry is enabled by the strong variation of absorption spectra with oxygenation. This is particularly pertinent both to research and to clinical investigation and diagnosis of retinal diseases such as diabetes, glaucoma and age-related macular degeneration. The optimal exploitation of hyperspectral imaging however, presents a set of challenging problems, including; the poorly characterised and controlled optical environment of structures within the retina to be imaged; the erratic motion of the eye ball; and the compounding effects of the optical sensitivity of the retina and the low numerical aperture of the eye. We have developed two spectral imaging techniques to address these issues. We describe first a system in which a liquid crystal tuneable filter is integrated into the illumination system of a conventional fundus camera to enable time-sequential, random access recording of narrow-band spectral images. Image processing techniques are described to eradicate the artefacts that may be introduced by time-sequential imaging. In addition we describe a unique snapshot spectral imaging technique dubbed IRIS that employs polarising interferometry and Wollaston prism beam splitters to simultaneously replicate and spectrally filter images of the retina into multiple spectral bands onto a single detector array. Results of early clinical trials acquired with these two techniques together with a physical model which enables oximetry map are reported.

Field-scale comparison of frequency- and time-domain spectral induced polarization

NASA Astrophysics Data System (ADS)

Maurya, P. K.; Fiandaca, G.; Christiansen, A. V.; Auken, E.

2018-05-01

In this paper we present a comparison study of the time-domain (TD) and frequency-domain (FD) spectral induced polarization (IP) methods in terms of acquisition time, data quality, and spectral information retrieved from inversion. We collected TDIP and FDIP surface measurements on three profiles with identical electrode setups, at two different field sites with different lithology. In addition, TDIP data were collected in two boreholes using the El-Log drilling technique, in which apparent formation resistivity and chargeability values are measured during drilling using electrodes integrated within the stem auger.

Deposition and growth of domains in one dimension

NASA Astrophysics Data System (ADS)

Rodgers, G. J.; Tavassoli, Z.

1998-09-01

A model of deposition and growth in one dimension is studied in which finite sized domains are deposited by the random sequential adsorption process. The domains then grow with a time dependent growth rate. When the initial deposited domains are monomers and dimers the coverage is found exactly for a number of different growth rates. A continuum version of this model is also considered.

Digital coding of Shuttle TV

NASA Technical Reports Server (NTRS)

Habibi, A.; Batson, B.

1976-01-01

Space Shuttle will be using a field-sequential color television system for the first few missions, but the present plans are to switch to a NTSC color TV system for future missions. The field-sequential color TV system uses a modified black and white camera, producing a TV signal with a digital bandwidth of about 60 Mbps. This article discusses the characteristics of the Shuttle TV systems and proposes a bandwidth-compression technique for the field-sequential color TV system that could operate at 13 Mbps to produce a high-fidelity signal. The proposed bandwidth-compression technique is based on a two-dimensional DPCM system that utilizes temporal, spectral, and spatial correlation inherent in the field-sequential color TV imagery. The proposed system requires about 60 watts and less than 200 integrated circuits.

Fundus autofluorescence and optical coherence tomography findings in thiamine responsive megaloblastic anemia.

PubMed

Ach, Thomas; Kardorff, Rüdiger; Rohrschneider, Klaus

2015-01-01

To report ophthalmologic fundus autofluorescence and spectral domain optical coherence tomography findings in a patient with thiamine responsive megaloblastic anemia (TRMA). A 13-year-old girl with genetically proven TRMA was ophthalmologically (visual acuity, funduscopy, perimetry, electroretinogram) followed up over >5 years. Fundus imaging also included autofluorescence and spectral domain optical coherence tomography. During a 5-year follow-up, visual acuity and visual field decreased, despite a special TRMA diet. Funduscopy revealed bull's eye appearance, whereas fundus autofluorescence showed central and peripheral hyperfluorescence and perifoveal hypofluorescence. Spectral domain optical coherence tomography revealed affected inner segment ellipsoid band and irregularities in the retinal pigment epithelium and choroidea. Autofluorescence and spectral domain optical coherence tomography findings in a patient with TRMA show retinitis pigmentosa-like retina, retinal pigment epithelium, and choroid alterations. These findings might progress even under special TRMA diet, indispensable to life. Ophthalmologist should consider TRMA in patients with deafness and ophthalmologic disorders.

Combined spectral-domain optical coherence tomography and hyperspectral imaging applied for tissue analysis: Preliminary results

NASA Astrophysics Data System (ADS)

Dontu, S.; Miclos, S.; Savastru, D.; Tautan, M.

2017-09-01

In recent years many optoelectronic techniques have been developed for improvement and the development of devices for tissue analysis. Spectral-Domain Optical Coherence Tomography (SD-OCT) is a new medical interferometric imaging modality that provides depth resolved tissue structure information with resolution in the μm range. However, SD-OCT has its own limitations and cannot offer the biochemical information of the tissue. These data can be obtained with hyperspectral imaging, a non-invasive, sensitive and real time technique. In the present study we have combined Spectral-Domain Optical Coherence Tomography (SD-OCT) with Hyperspectral imaging (HSI) for tissue analysis. The Spectral-Domain Optical Coherence Tomography (SD-OCT) and Hyperspectral imaging (HSI) are two methods that have demonstrated significant potential in this context. Preliminary results using different tissue have highlighted the capabilities of this technique of combinations.

Binary Coded Web Access Pattern Tree in Education Domain

ERIC Educational Resources Information Center

Gomathi, C.; Moorthi, M.; Duraiswamy, K.

2008-01-01

Web Access Pattern (WAP), which is the sequence of accesses pursued by users frequently, is a kind of interesting and useful knowledge in practice. Sequential Pattern mining is the process of applying data mining techniques to a sequential database for the purposes of discovering the correlation relationships that exist among an ordered list of…

Paracentral acute middle maculopathy in nonischemic central retinal vein occlusion.

PubMed

Rahimy, Ehsan; Sarraf, David; Dollin, Michael L; Pitcher, John D; Ho, Allen C

2014-08-01

To better characterize a novel spectral-domain optical coherence tomography (OCT) presentation, termed paracentral acute middle maculopathy, to describe this finding in patients with nonischemic central retinal vein occlusion (CRVO), and to support a proposed pathogenesis of intermediate and deep retinal capillary ischemia. Retrospective observational case series. Clinical histories, high-resolution digital color imaging, red-free photography, fluorescein angiography, near-infrared reflectance, and spectral-domain OCT images of 484 patients with acute CRVO from 2 centers were evaluated for the presence of coexisting paracentral acute middle maculopathy. Of 484 patients diagnosed with CRVO, 25 (5.2%) demonstrated evidence of concurrent paracentral acute middle maculopathy. Patients averaged 51 years of age and presented with complaints of paracentral scotomas. All patients demonstrated hyper-reflective plaquelike lesions at the level of the inner nuclear layer by spectral-domain OCT and showed corresponding dark-gray lesions on near-infrared reflectance and perivenular deep retinal whitening on color fundus photography. There was no fluorescein angiographic correlate to these lesions. On follow-up spectral-domain OCT imaging, the lesions had resolved into areas of inner nuclear layer atrophy with persistence of scotomas. Paracentral acute middle maculopathy refers to characteristic hyper-reflective spectral-domain OCT lesions involving the middle layers of the retina at the level of the inner nuclear layer that may develop in response to ischemia of the intermediate and deep capillary plexuses. This series is the largest to describe this spectral-domain OCT finding to date, and it is the first to associate it with nonischemic CRVO. Copyright © 2014 Elsevier Inc. All rights reserved.

Preclinical evaluation and intraoperative human retinal imaging with a high-resolution microscope-integrated spectral domain optical coherence tomography device.

PubMed

Hahn, Paul; Migacz, Justin; O'Donnell, Rachelle; Day, Shelley; Lee, Annie; Lin, Phoebe; Vann, Robin; Kuo, Anthony; Fekrat, Sharon; Mruthyunjaya, Prithvi; Postel, Eric A; Izatt, Joseph A; Toth, Cynthia A

2013-01-01

The authors have recently developed a high-resolution microscope-integrated spectral domain optical coherence tomography (MIOCT) device designed to enable OCT acquisition simultaneous with surgical maneuvers. The purpose of this report is to describe translation of this device from preclinical testing into human intraoperative imaging. Before human imaging, surgical conditions were fully simulated for extensive preclinical MIOCT evaluation in a custom model eye system. Microscope-integrated spectral domain OCT images were then acquired in normal human volunteers and during vitreoretinal surgery in patients who consented to participate in a prospective institutional review board-approved study. Microscope-integrated spectral domain OCT images were obtained before and at pauses in surgical maneuvers and were compared based on predetermined diagnostic criteria to images obtained with a high-resolution spectral domain research handheld OCT system (HHOCT; Bioptigen, Inc) at the same time point. Cohorts of five consecutive patients were imaged. Successful end points were predefined, including ≥80% correlation in identification of pathology between MIOCT and HHOCT in ≥80% of the patients. Microscope-integrated spectral domain OCT was favorably evaluated by study surgeons and scrub nurses, all of whom responded that they would consider participating in human intraoperative imaging trials. The preclinical evaluation identified significant improvements that were made before MIOCT use during human surgery. The MIOCT transition into clinical human research was smooth. Microscope-integrated spectral domain OCT imaging in normal human volunteers demonstrated high resolution comparable to tabletop scanners. In the operating room, after an initial learning curve, surgeons successfully acquired human macular MIOCT images before and after surgical maneuvers. Microscope-integrated spectral domain OCT imaging confirmed preoperative diagnoses, such as full-thickness macular hole and vitreomacular traction, and demonstrated postsurgical changes in retinal morphology. Two cohorts of five patients were imaged. In the second cohort, the predefined end points were exceeded with ≥80% correlation between microscope-mounted OCT and HHOCT imaging in 100% of the patients. This report describes high-resolution MIOCT imaging using the prototype device in human eyes during vitreoretinal surgery, with successful achievement of predefined end points for imaging. Further refinements and investigations will be directed toward fully integrating MIOCT with vitreoretinal and other ocular surgery to image surgical maneuvers in real time.

Single-pixel imaging based on compressive sensing with spectral-domain optical mixing

NASA Astrophysics Data System (ADS)

Zhu, Zhijing; Chi, Hao; Jin, Tao; Zheng, Shilie; Jin, Xiaofeng; Zhang, Xianmin

2017-11-01

In this letter a single-pixel imaging structure is proposed based on compressive sensing using a spatial light modulator (SLM)-based spectrum shaper. In the approach, an SLM-based spectrum shaper, the pattern of which is a predetermined pseudorandom bit sequence (PRBS), spectrally codes the optical pulse carrying image information. The energy of the spectrally mixed pulse is detected by a single-pixel photodiode and the measurement results are used to reconstruct the image via a sparse recovery algorithm. As the mixing of the image signal and the PRBS is performed in the spectral domain, optical pulse stretching, modulation, compression and synchronization in the time domain are avoided. Experiments are implemented to verify the feasibility of the approach.

High speed parallel spectral-domain OCT using spectrally encoded line-field illumination

NASA Astrophysics Data System (ADS)

Lee, Kye-Sung; Hur, Hwan; Bae, Ji Yong; Kim, I. Jong; Kim, Dong Uk; Nam, Ki-Hwan; Kim, Geon-Hee; Chang, Ki Soo

2018-01-01

We report parallel spectral-domain optical coherence tomography (OCT) at 500 000 A-scan/s. This is the highest-speed spectral-domain (SD) OCT system using a single line camera. Spectrally encoded line-field scanning is proposed to increase the imaging speed in SD-OCT effectively, and the tradeoff between speed, depth range, and sensitivity is demonstrated. We show that three imaging modes of 125k, 250k, and 500k A-scan/s can be simply switched according to the sample to be imaged considering the depth range and sensitivity. To demonstrate the biological imaging performance of the high-speed imaging modes of the spectrally encoded line-field OCT system, human skin and a whole leaf were imaged at the speed of 250k and 500k A-scan/s, respectively. In addition, there is no sensitivity dependence in the B-scan direction, which is implicit in line-field parallel OCT using line focusing of a Gaussian beam with a cylindrical lens.

Doppler flow imaging of cytoplasmic streaming using spectral domain phase microscopy

NASA Astrophysics Data System (ADS)

Choma, Michael A.; Ellerbee, Audrey K.; Yazdanfar, Siavash; Izatt, Joseph A.

2006-03-01

Spectral domain phase microscopy (SDPM) is a function extension of spectral domain optical coherence tomography. SDPM achieves exquisite levels of phase stability by employing common-path interferometry. We discuss the theory and limitations of Doppler flow imaging using SDPM, demonstrate monitoring the thermal contraction of a glass sample with nanometer per second velocity sensitivity, and apply this technique to measurement of cytoplasmic streaming in an Amoeba proteus pseudopod. We observe reversal of cytoplasmic flow induced by extracellular CaCl2, and report results that suggest parabolic flow of cytoplasm in the A. proteus pseudopod.

Imaging Polarimetry in Age-Related Macular Degeneration

PubMed Central

Miura, Masahiro; Yamanari, Masahiro; Iwasaki, Takuya; Elsner, Ann E.; Makita, Shuichi; Yatagai, Toyohiko; Yasuno, Yoshiaki

2010-01-01

PURPOSE To evaluate the birefringence properties of eyes with age-related macular degeneration (AMD). To compare the information from two techniques—scanning laser polarimetry (GDx) and polarization-sensitive spectral-domain optical coherence tomography (OCT)—and investigate how they complement each other. METHODS The authors prospectively examined the eyes of two healthy subjects and 13 patients with exudative AMD. Using scanning laser polarimetry, they computed phase-retardation maps, average reflectance images, and depolarized light images. To obtain polarimetry information with improved axial resolution, they developed a fiber-based, polarization-sensitive, spectral-domain OCT system and measured the phase retardation associated with birefringence in the same eyes. RESULTS Both GDx and polarization-sensitive spectral-domain optical coherence tomography detected abnormal birefringence at the locus of exudative lesions. Polarization-sensitive, spectral-domain OCT showed that in the old lesions with fibrosis, phase-retardation values were significantly larger than in the new lesions (P = 0.020). Increased scattered light and altered polarization scramble were associated with portions of the lesions. CONCLUSIONS GDx and polarization-sensitive spectral-domain OCT are complementary in probing birefringence properties in exudative AMD. Polarimetry findings in exudative AMD emphasized different features and were related to the progression of the disease, potentially providing a noninvasive tool for microstructure in exudative AMD. PMID:18515594

Toward More Accurate Iris Recognition Using Cross-Spectral Matching.

PubMed

Nalla, Pattabhi Ramaiah; Kumar, Ajay

2017-01-01

Iris recognition systems are increasingly deployed for large-scale applications such as national ID programs, which continue to acquire millions of iris images to establish identity among billions. However, with the availability of variety of iris sensors that are deployed for the iris imaging under different illumination/environment, significant performance degradation is expected while matching such iris images acquired under two different domains (either sensor-specific or wavelength-specific). This paper develops a domain adaptation framework to address this problem and introduces a new algorithm using Markov random fields model to significantly improve cross-domain iris recognition. The proposed domain adaptation framework based on the naive Bayes nearest neighbor classification uses a real-valued feature representation, which is capable of learning domain knowledge. Our approach to estimate corresponding visible iris patterns from the synthesis of iris patches in the near infrared iris images achieves outperforming results for the cross-spectral iris recognition. In this paper, a new class of bi-spectral iris recognition system that can simultaneously acquire visible and near infra-red images with pixel-to-pixel correspondences is proposed and evaluated. This paper presents experimental results from three publicly available databases; PolyU cross-spectral iris image database, IIITD CLI and UND database, and achieve outperforming results for the cross-sensor and cross-spectral iris matching.

A hybrid spatial-spectral denoising method for infrared hyperspectral images using 2DPCA

NASA Astrophysics Data System (ADS)

Huang, Jun; Ma, Yong; Mei, Xiaoguang; Fan, Fan

2016-11-01

The traditional noise reduction methods for 3-D infrared hyperspectral images typically operate independently in either the spatial or spectral domain, and such methods overlook the relationship between the two domains. To address this issue, we propose a hybrid spatial-spectral method in this paper to link both domains. First, principal component analysis and bivariate wavelet shrinkage are performed in the 2-D spatial domain. Second, 2-D principal component analysis transformation is conducted in the 1-D spectral domain to separate the basic components from detail ones. The energy distribution of noise is unaffected by orthogonal transformation; therefore, the signal-to-noise ratio of each component is used as a criterion to determine whether a component should be protected from over-denoising or denoised with certain 1-D denoising methods. This study implements the 1-D wavelet shrinking threshold method based on Stein's unbiased risk estimator, and the quantitative results on publicly available datasets demonstrate that our method can improve denoising performance more effectively than other state-of-the-art methods can.

Documentation and user's guide for interactive spectral analysis and filter program package useful in the processing of seismic reflection data

USGS Publications Warehouse

Miller, J.J.

1982-01-01

The spectral analysis and filter program package is written in the BASIC language for the HP-9845T desktop computer. The program's main purpose is to perform spectral analyses on digitized time-domain data. In addition, band-pass filtering of the data can be performed in the time domain. Various other processes such as autocorrelation can be performed to the time domain data in order to precondition them for spectral analyses. The frequency domain data can also be transformed back into the time domain if desired. Any data can be displayed on the CRT in graphic form using a variety of plot routines. A hard copy can be obtained immediately using the internal thermal printer. Data can also be displayed in tabular form on the CRT or internal thermal printer or it can be stored permanently on a mass storage device like a tape or disk. A list of the processes performed in the order in which they occurred can be displayed at any time.

Contribution of Implicit Sequence Learning to Spoken Language Processing: Some Preliminary Findings with Hearing Adults

ERIC Educational Resources Information Center

Conway, Christopher M.; Karpicke, Jennifer; Pisoni, David B.

2007-01-01

Spoken language consists of a complex, sequentially arrayed signal that contains patterns that can be described in terms of statistical relations among language units. Previous research has suggested that a domain-general ability to learn structured sequential patterns may underlie language acquisition. To test this prediction, we examined the…

Lexical and Grammatical Associations in Sequential Bilingual Preschoolers

ERIC Educational Resources Information Center

Kohnert, Kathryn; Kan, Pui Fong; Conboy, Barbara T.

2010-01-01

Purpose: The authors investigated potential relationships between traditional linguistic domains (words, grammar) in the first (L1) and second (L2) languages of young sequential bilingual preschool children. Method: Participants were 19 children, ages 2;11 (years;months) to 5;2 (M = 4;3) who began learning Hmong as the L1 from birth and English as…

Power spectral ensity of markov texture fields

NASA Technical Reports Server (NTRS)

Shanmugan, K. S.; Holtzman, J. C.

1984-01-01

Texture is an important image characteristic. A variety of spatial domain techniques were proposed for extracting and utilizing textural features for segmenting and classifying images. for the most part, these spatial domain techniques are ad hos in nature. A markov random field model for image texture is discussed. A frequency domain description of image texture is derived in terms of the power spectral density. This model is used for designing optimum frequency domain filters for enhancing, restoring and segmenting images based on their textural properties.

Cotranslational structure acquisition of nascent polypeptides monitored by NMR spectroscopy.

PubMed

Eichmann, Cédric; Preissler, Steffen; Riek, Roland; Deuerling, Elke

2010-05-18

The folding of proteins in living cells may start during their synthesis when the polypeptides emerge gradually at the ribosomal exit tunnel. However, our current understanding of cotranslational folding processes at the atomic level is limited. We employed NMR spectroscopy to monitor the conformation of the SH3 domain from alpha-spectrin at sequential stages of elongation via in vivo ribosome-arrested (15)N,(13)C-labeled nascent polypeptides. These nascent chains exposed either the entire SH3 domain or C-terminally truncated segments thereof, thus providing snapshots of the translation process. We show that nascent SH3 polypeptides remain unstructured during elongation but fold into a compact, native-like beta-sheet assembly when the entire sequence information is available. Moreover, the ribosome neither imposes major conformational constraints nor significantly interacts with exposed unfolded nascent SH3 domain moieties. Our data provide evidence for a domainwise folding of the SH3 domain on ribosomes without significant population of folding intermediates. The domain follows a thermodynamically favorable pathway in which sequential folding units are stabilized, thus avoiding kinetic traps during the process of cotranslational folding.

Optimizing spectral wave estimates with adjoint-based sensitivity maps

NASA Astrophysics Data System (ADS)

Orzech, Mark; Veeramony, Jay; Flampouris, Stylianos

2014-04-01

A discrete numerical adjoint has recently been developed for the stochastic wave model SWAN. In the present study, this adjoint code is used to construct spectral sensitivity maps for two nearshore domains. The maps display the correlations of spectral energy levels throughout the domain with the observed energy levels at a selected location or region of interest (LOI/ROI), providing a full spectrum of values at all locations in the domain. We investigate the effectiveness of sensitivity maps based on significant wave height ( H s ) in determining alternate offshore instrument deployment sites when a chosen nearshore location or region is inaccessible. Wave and bathymetry datasets are employed from one shallower, small-scale domain (Duck, NC) and one deeper, larger-scale domain (San Diego, CA). The effects of seasonal changes in wave climate, errors in bathymetry, and multiple assimilation points on sensitivity map shapes and model performance are investigated. Model accuracy is evaluated by comparing spectral statistics as well as with an RMS skill score, which estimates a mean model-data error across all spectral bins. Results indicate that data assimilation from identified high-sensitivity alternate locations consistently improves model performance at nearshore LOIs, while assimilation from low-sensitivity locations results in lesser or no improvement. Use of sub-sampled or alongshore-averaged bathymetry has a domain-specific effect on model performance when assimilating from a high-sensitivity alternate location. When multiple alternate assimilation locations are used from areas of lower sensitivity, model performance may be worse than with a single, high-sensitivity assimilation point.

Spectrometer calibration for spectroscopic Fourier domain optical coherence tomography

PubMed Central

Szkulmowski, Maciej; Tamborski, Szymon; Wojtkowski, Maciej

2016-01-01

We propose a simple and robust procedure for Fourier domain optical coherence tomography (FdOCT) that allows to linearize the detected FdOCT spectra to wavenumber domain and, at the same time, to determine the wavelength of light for each point of detected spectrum. We show that in this approach it is possible to use any measurable physical quantity that has linear dependency on wavenumber and can be extracted from spectral fringes. The actual values of the measured quantity have no importance for the algorithm and do not need to be known at any stage of the procedure. As example we calibrate a spectral OCT spectrometer using Doppler frequency. The technique of spectral calibration can be in principle adapted to of all kind of Fourier domain OCT devices. PMID:28018723

Stable multi-domain spectral penalty methods for fractional partial differential equations

NASA Astrophysics Data System (ADS)

Xu, Qinwu; Hesthaven, Jan S.

2014-01-01

We propose stable multi-domain spectral penalty methods suitable for solving fractional partial differential equations with fractional derivatives of any order. First, a high order discretization is proposed to approximate fractional derivatives of any order on any given grids based on orthogonal polynomials. The approximation order is analyzed and verified through numerical examples. Based on the discrete fractional derivative, we introduce stable multi-domain spectral penalty methods for solving fractional advection and diffusion equations. The equations are discretized in each sub-domain separately and the global schemes are obtained by weakly imposed boundary and interface conditions through a penalty term. Stability of the schemes are analyzed and numerical examples based on both uniform and nonuniform grids are considered to highlight the flexibility and high accuracy of the proposed schemes.

Spectral domain optical coherence tomography imaging in optic disk pit associated with outer retinal dehiscence

PubMed Central

Wong, Chee Wai; Wong, Doric; Mathur, Ranjana

2014-01-01

A 37-year-old Bangladeshi male presented with an inferotemporal optic disk pit and serous macular detachment in the left eye. Imaging with spectral domain optical coherence tomography (OCT) revealed a multilayer macular schisis pattern with a small subfoveal outer retinal dehiscence. This case illustrates a rare phenotype of optic disk maculopathy with macular schisis and a small outer retinal layer dehiscence. Spectral domain OCT was a useful adjunct in delineating the retinal layers in optic disk pit maculopathy, and revealed a small area of outer retinal layer dehiscence that could only have been detected on high-resolution OCT. PMID:25349471

Effect of Sequential Exposition to Short- and Long-Wavelength Radiation on the Optical Absorption in the Bismuth Titanium Oxide Crystal Doped by Aluminum

NASA Astrophysics Data System (ADS)

Dyu, V. G.; Kisteneva, M. G.; Shandarov, S. M.; Khudyakova, E. S.; Smirnov, S. V.; Kargin, Yu. F.

Changes in the spectral dependences of the optical absorption induced in the bismuth titanium oxide crystal doped by aluminum as a result of sequential exposition to cw laser radiation first with the wavelength λi = 532 nm and then with the longer wavelength λn = 633, 655, 663, 780, 871, or 1064 nm are investigated. Our experiments show that after the short-wavelength exposition to radiation with λi = 532 nm, the optical absorption in the crystal increases, and in the range 470-1000 nm, yields the spectrum whose form is independent of the initial crystal state. The subsequent exposition to longer-wavelength radiation leads to enhanced transmittance of the crystal in the examined spectral range. A maximum decrease of the optical absorption in the crystal is observed upon exposure to radiation with the wavelength λn = 663 nm.

Characterization of cancer and normal tissue fluorescence through wavelet transform and singular value decomposition

NASA Astrophysics Data System (ADS)

Gharekhan, Anita H.; Biswal, Nrusingh C.; Gupta, Sharad; Pradhan, Asima; Sureshkumar, M. B.; Panigrahi, Prasanta K.

2008-02-01

The statistical and characteristic features of the polarized fluorescence spectra from cancer, normal and benign human breast tissues are studied through wavelet transform and singular value decomposition. The discrete wavelets enabled one to isolate high and low frequency spectral fluctuations, which revealed substantial randomization in the cancerous tissues, not present in the normal cases. In particular, the fluctuations fitted well with a Gaussian distribution for the cancerous tissues in the perpendicular component. One finds non-Gaussian behavior for normal and benign tissues' spectral variations. The study of the difference of intensities in parallel and perpendicular channels, which is free from the diffusive component, revealed weak fluorescence activity in the 630nm domain, for the cancerous tissues. This may be ascribable to porphyrin emission. The role of both scatterers and fluorophores in the observed minor intensity peak for the cancer case is experimentally confirmed through tissue-phantom experiments. Continuous Morlet wavelet also highlighted this domain for the cancerous tissue fluorescence spectra. Correlation in the spectral fluctuation is further studied in different tissue types through singular value decomposition. Apart from identifying different domains of spectral activity for diseased and non-diseased tissues, we found random matrix support for the spectral fluctuations. The small eigenvalues of the perpendicular polarized fluorescence spectra of cancerous tissues fitted remarkably well with random matrix prediction for Gaussian random variables, confirming our observations about spectral fluctuations in the wavelet domain.

Application of the sequential quadratic programming algorithm for reconstructing the distribution of optical parameters based on the time-domain radiative transfer equation.

PubMed

Qi, Hong; Qiao, Yao-Bin; Ren, Ya-Tao; Shi, Jing-Wen; Zhang, Ze-Yu; Ruan, Li-Ming

2016-10-17

Sequential quadratic programming (SQP) is used as an optimization algorithm to reconstruct the optical parameters based on the time-domain radiative transfer equation (TD-RTE). Numerous time-resolved measurement signals are obtained using the TD-RTE as forward model. For a high computational efficiency, the gradient of objective function is calculated using an adjoint equation technique. SQP algorithm is employed to solve the inverse problem and the regularization term based on the generalized Gaussian Markov random field (GGMRF) model is used to overcome the ill-posed problem. Simulated results show that the proposed reconstruction scheme performs efficiently and accurately.

Velocity measurement using frequency domain interferometer and chirped pulse laser

NASA Astrophysics Data System (ADS)

Ishii, K.; Nishimura, Y.; Mori, Y.; Hanayama, R.; Kitagawa, Y.; Sekine, T.; Sato, N.; Kurita, T.; Kawashima, T.; Sunahara, A.; Sentoku, Y.; Miura, E.; Iwamoto, A.; Sakagami, H.

2017-02-01

An ultra-intense short pulse laser induces a shock wave in material. The pressure of shock compression is stronger than a few tens GPa. To characterize shock waves, time-resolved velocity measurement in nano- or pico-second time scale is needed. Frequency domain interferometer and chirped pulse laser provide single-shot time-resolved measurement. We have developed a laser-driven shock compression system and frequency domain interferometer with CPA laser. In this paper, we show the principle of velocity measurement using a frequency domain interferometer and a chirped pulse laser. Next, we numerically calculated spectral interferograms and show the time-resolved velocity measurement can be done from the phase analysis of spectral interferograms. Moreover we conduct the laser driven shock generation and shock velocity measurement. From the spectral fringes, we analyze the velocities of the sample and shockwaves.

Ventilatory thresholds determined from HRV: comparison of 2 methods in obese adolescents.

PubMed

Quinart, S; Mourot, L; Nègre, V; Simon-Rigaud, M-L; Nicolet-Guénat, M; Bertrand, A-M; Meneveau, N; Mougin, F

2014-03-01

The development of personalised training programmes is crucial in the management of obesity. We evaluated the ability of 2 heart rate variability analyses to determine ventilatory thresholds (VT) in obese adolescents. 20 adolescents (mean age 14.3±1.6 years and body mass index z-score 4.2±0.1) performed an incremental test to exhaustion before and after a 9-month multidisciplinary management programme. The first (VT1) and second (VT2) ventilatory thresholds were identified by the reference method (gas exchanges). We recorded RR intervals to estimate VT1 and VT2 from heart rate variability using time-domain analysis and time-varying spectral-domain analysis. The coefficient correlations between thresholds were higher with spectral-domain analysis compared to time-domain analysis: Heart rate at VT1: r=0.91 vs. =0.66 and VT2: r=0.91 vs. =0.66; power at VT1: r=0.91 vs. =0.74 and VT2: r=0.93 vs. =0.78; spectral-domain vs. time-domain analysis respectively). No systematic bias in heart rate at VT1 and VT2 with standard deviations <6 bpm were found, confirming that spectral-domain analysis could replace the reference method for the detection of ventilatory thresholds. Furthermore, this technique is sensitive to rehabilitation and re-training, which underlines its utility in clinical practice. This inexpensive and non-invasive tool is promising for prescribing physical activity programs in obese adolescents. © Georg Thieme Verlag KG Stuttgart · New York.

A spectral analysis of the domain decomposed Monte Carlo method for linear systems

DOE PAGES

Slattery, Stuart R.; Evans, Thomas M.; Wilson, Paul P. H.

2015-09-08

The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear oper- ator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approxi- mation and the mean chord approximation are applied to estimate the leakagemore » frac- tion of random walks from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem in numerical experiments to test the models for symmetric operators with spectral qualities similar to light water reactor problems. We find, in general, the derived approximations show good agreement with random walk lengths and leakage fractions computed by the numerical experiments.« less

Spectral domain phase microscopy: a new tool for measuring cellular dynamics and cytoplasmic flow

NASA Astrophysics Data System (ADS)

McDowell, Emily J.; Choma, Michael A.; Ellerbee, Audrey K.; Izatt, Joseph A.

2005-03-01

Broadband interferometry is an attractive technique for the detection of cellular motions because it provides depth-resolved interferometric phase information via coherence gating. Here a phase sensitive technique called spectral domain phase microscopy (SDPM) is presented. SDPM is a functional extension of spectral domain optical coherence tomography that allows for the detection of cellular motions and dynamics with nanometer-scale sensitivity. This sensitivity is made possible by the inherent phase stability of spectral domain OCT combined with common-path interferometry. The theory that underlies this technique is presented, the sensitivity of the technique is demonstrated by the measurement of the thermal expansion coefficient of borosilicate glass, and the response of an Amoeba proteus to puncture of its cell membrane is measured. We also exploit the phase stability of SDPM to perform Doppler flow imaging of cytoplasmic streaming in A. proteus. We show reversal of cytoplasmic flow in response to stimuli, and we show that the cytoplasmic flow is laminar (i.e. parabolic) in nature. We are currently investigating the use of SDPM in a variety of different cell types.

A spectral multi-domain technique applied to high-speed chemically reacting flows

NASA Technical Reports Server (NTRS)

Macaraeg, Michele G.; Streett, Craig L.; Hussaini, M. Yousuff

1989-01-01

The first applications of a spectral multidomain method for viscous compressible flow is presented. The method imposes a global flux balance condition at the interface so that high-order continuity of the solution is preserved. The global flux balance is imposed in terms of a spectral integral of the discrete equations across adjoining domains. Since the discretized equations interior to each domain solved are uncoupled from each other, and since the interface relation has a block structure, the solution scheme can be adapted to the particular requirements of each subdomain. The spectral multidomain technique presented is well-suited for the multiple scales associated with the chemically reacting and transition flows in hypersonic research. A nonstaggered multidomain discretization is used for the chemically reacting flow calculation, and the first implementation of a staggered multidomain mesh is presented for accurately solving the stability equation for a viscous compressible fluid.

Immunoreceptor Tyrosine-based Inhibitory Motif (ITIM)-mediated Inhibitory Signaling is Regulated by Sequential Phosphorylation Mediated by Distinct Nonreceptor Tyrosine Kinases: A Case Study Involving PECAM-1

PubMed Central

Tourdot, Benjamin E.; Brenner, Michelle K.; Keough, Kathleen C.; Holyst, Trudy; Newman, Peter J.; Newman, Debra K.

2013-01-01

The activation state of many blood and vascular cells is tightly controlled by a delicate balance between receptors that contain immunoreceptor tyrosine-based activation motifs (ITAMs) and those that contain immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Precisely how the timing of cellular activation by ITAM-coupled receptors is regulated by ITIM-containing receptors is, however, poorly understood. Using platelet endothelial cell adhesion molecule 1 (PECAM-1) as a prototypical ITIM-bearing receptor, we demonstrate that initiation of inhibitory signaling occurs via a novel, sequential process in which Src family kinases phosphorylate the C-terminal ITIM, thereby enabling phosphorylation of the N-terminal ITIM of PECAM-1 by other Src homology 2 domain-containing non-receptor tyrosine kinases (NRTKs). NRTKs capable of mediating the second phosphorylation event include C-terminal Src kinase (Csk) and Bruton’s tyrosine kinase (Btk). Btk and Csk function downstream of phosphatidylinositol 3-kinase (PI3K) activation during ITAM-dependent platelet activation. In ITAM-activated platelets that were treated with a PI3K inhibitor, PECAM-1 was phosphorylated but did not bind the tandem SH2 domain-containing tyrosine phosphatase SHP-2, indicating that it was not phosphorylated on its N-terminal ITIM. Csk bound to and phosphorylated PECAM-1 more efficiently than did Btk, and required its SH2 domain to perform these functions. Additionally, the phosphorylation of the N-terminal ITIM of Siglec-9 by Csk is enhanced by the prior phosphorylation of its C-terminal ITIM, providing evidence that the ITIMs of other dual ITIM-containing receptors are also sequentially phosphorylated. On the basis of these findings, we propose that sequential ITIM phosphorylation provides a general mechanism for precise temporal control over the recruitment and activation of tandem SH2 domain-containing tyrosine phosphatases that dampen ITAM-dependent signals. PMID:23418871

Spectral analysis of point-vortex dynamics: first application to vortex polygons in a circular domain

NASA Astrophysics Data System (ADS)

Speetjens, M. F. M.; Meleshko, V. V.; van Heijst, G. J. F.

2014-06-01

The present study addresses the classical problem of the dynamics and stability of a cluster of N-point vortices of equal strength arranged in a polygonal configuration (‘N-vortex polygons’). In unbounded domains, such N-vortex polygons are unconditionally stable for N\\leqslant 7. Confinement in a circular domain tightens the stability conditions to N\\leqslant 6 and a maximum polygon size relative to the domain radius. This work expands on existing studies on stability and integrability by a first giving an exploratory spectral analysis of the dynamics of N vortex polygons in circular domains. Key to this is that the spectral signature of the time evolution of vortex positions reflects their qualitative behaviour. Expressing vortex motion by a generic evolution operator (the so-called Koopman operator) provides a rigorous framework for such spectral analyses. This paves the way to further differentiation and classification of point-vortex behaviour beyond stability and integrability. The concept of Koopman-based spectral analysis is demonstrated for N-vortex polygons. This reveals that conditional stability can be seen as a local form of integrability and confirms an important generic link between spectrum and dynamics: discrete spectra imply regular (quasi-periodic) motion; continuous (sub-)spectra imply chaotic motion. Moreover, this exposes rich nonlinear dynamics as intermittency between regular and chaotic motion and quasi-coherent structures formed by chaotic vortices. Dedicated to the memory of Slava Meleshko, a dear friend and inspiring colleague.

Spectral analysis of variable-length coded digital signals

NASA Astrophysics Data System (ADS)

Cariolaro, G. L.; Pierobon, G. L.; Pupolin, S. G.

1982-05-01

A spectral analysis is conducted for a variable-length word sequence by an encoder driven by a stationary memoryless source. A finite-state sequential machine is considered as a model of the line encoder, and the spectral analysis of the encoded message is performed under the assumption that the sourceword sequence is composed of independent identically distributed words. Closed form expressions for both the continuous and discrete parts of the spectral density are derived in terms of the encoder law and sourceword statistics. The jump part exhibits jumps at multiple integers of per lambda(sub 0)T, where lambda(sub 0) is the greatest common divisor of the possible codeword lengths, and T is the symbol period. The derivation of the continuous part can be conveniently factorized, and the theory is applied to the spectral analysis of BnZS and HDBn codes.

Dynamics of modulated beams in spectral domain

DOE PAGES

Yampolsky, Nikolai A.

2017-07-16

General formalism for describing dynamics of modulated beams along linear beamlines is developed. We describe modulated beams with spectral distribution function which represents Fourier transform of the conventional beam distribution function in the 6-dimensional phase space. The introduced spectral distribution function is localized in some region of the spectral domain for nearly monochromatic modulations. It can be characterized with a small number of typical parameters such as the lowest order moments of the spectral distribution. We study evolution of the modulated beams in linear beamlines and find that characteristic spectral parameters transform linearly. The developed approach significantly simplifies analysis ofmore » various schemes proposed for seeding X-ray free electron lasers. We use this approach to study several recently proposed schemes and find the bandwidth of the output bunching in each case.« less

CONNJUR Workflow Builder: A software integration environment for spectral reconstruction

PubMed Central

Fenwick, Matthew; Weatherby, Gerard; Vyas, Jay; Sesanker, Colbert; Martyn, Timothy O.; Ellis, Heidi J.C.; Gryk, Michael R.

2015-01-01

CONNJUR Workflow Builder (WB) is an open-source software integration environment that leverages existing spectral reconstruction tools to create a synergistic, coherent platform for converting biomolecular NMR data from the time domain to the frequency domain. WB provides data integration of primary data and metadata using a relational database, and includes a library of pre-built workflows for processing time domain data. WB simplifies maximum entropy reconstruction, facilitating the processing of non-uniformly sampled time domain data. As will be shown in the paper, the unique features of WB provide it with novel abilities to enhance the quality, accuracy, and fidelity of the spectral reconstruction process. WB also provides features which promote collaboration, education, parameterization, and non-uniform data sets along with processing integrated with the Rowland NMR Toolkit (RNMRTK) and NMRPipe software packages. WB is available free of charge in perpetuity, dual-licensed under the MIT and GPL open source licenses. PMID:26066803

CONNJUR Workflow Builder: a software integration environment for spectral reconstruction.

PubMed

Fenwick, Matthew; Weatherby, Gerard; Vyas, Jay; Sesanker, Colbert; Martyn, Timothy O; Ellis, Heidi J C; Gryk, Michael R

2015-07-01

CONNJUR Workflow Builder (WB) is an open-source software integration environment that leverages existing spectral reconstruction tools to create a synergistic, coherent platform for converting biomolecular NMR data from the time domain to the frequency domain. WB provides data integration of primary data and metadata using a relational database, and includes a library of pre-built workflows for processing time domain data. WB simplifies maximum entropy reconstruction, facilitating the processing of non-uniformly sampled time domain data. As will be shown in the paper, the unique features of WB provide it with novel abilities to enhance the quality, accuracy, and fidelity of the spectral reconstruction process. WB also provides features which promote collaboration, education, parameterization, and non-uniform data sets along with processing integrated with the Rowland NMR Toolkit (RNMRTK) and NMRPipe software packages. WB is available free of charge in perpetuity, dual-licensed under the MIT and GPL open source licenses.

Isothermal crystallization of poly(3-hydroxybutyrate) studied by terahertz two-dimensional correlation spectroscopy

NASA Astrophysics Data System (ADS)

Hoshina, Hiromichi; Ishii, Shinya; Morisawa, Yusuke; Sato, Harumi; Noda, Isao; Ozaki, Yukihiro; Otani, Chiko

2012-01-01

The isothermal crystallization of poly(3-hydroxybutylate) (PHB) was studied by monitoring the temporal evolution of terahertz absorption spectra in conjunction with spectral analysis using two-dimensional correlation spectroscopy. Correlation between the absorption peaks and the sequential order of the changes in spectral intensity extracted from synchronous and asynchronous plots indicated that crystallization of PHB at 90 °C is a two step process, in which C-H...O=C hydrogen bonds are initially formed before well-defined crystal structures are established.

Quality monitoring of extra-virgin olive oil using an optical sensor

NASA Astrophysics Data System (ADS)

Mignani, A. G.; Ciaccheri, L.; Mencaglia, A. A.; Paolesse, R.; Di Natale, C.; Del Nobile, A.; Benedetto, A.; Mentana, A.

2006-04-01

An optical sensor for the detection of olive oil aroma is presented. It is capable of distinguishing different ageing levels of extra-virgin olive oils, and shows effective potential for achieving a non destructive olfactory perception of oil ageing. The sensor is an optical scanner, fitted with an array of metalloporphyrin-based sensors. The scanner provides exposure of the sensors to the flow of the oil vapor being tested, and their sequential spectral interrogation. Spectral data are then processed using chemometric methodologies.

Coupling finite element and spectral methods: First results

NASA Technical Reports Server (NTRS)

Bernardi, Christine; Debit, Naima; Maday, Yvon

1987-01-01

A Poisson equation on a rectangular domain is solved by coupling two methods: the domain is divided in two squares, a finite element approximation is used on the first square and a spectral discretization is used on the second one. Two kinds of matching conditions on the interface are presented and compared. In both cases, error estimates are proved.

Sequentially Executed Model Evaluation Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

2015-10-20

Provides a message passing framework between generic input, model and output drivers, and specifies an API for developing such drivers. Also provides batch and real-time controllers which step the model and I/O through the time domain (or other discrete domain), and sample I/O drivers. This is a library framework, and does not, itself, solve any problems or execute any modeling. The SeMe framework aids in development of models which operate on sequential information, such as time-series, where evaluation is based on prior results combined with new data for this iteration. Has applications in quality monitoring, and was developed as partmore » of the CANARY-EDS software, where real-time water quality data is being analyzed for anomalies.« less

From moonlight to movement and synchronized randomness: Fourier and wavelet analyses of animal location time series data

PubMed Central

Polansky, Leo; Wittemyer, George; Cross, Paul C.; Tambling, Craig J.; Getz, Wayne M.

2011-01-01

High-resolution animal location data are increasingly available, requiring analytical approaches and statistical tools that can accommodate the temporal structure and transient dynamics (non-stationarity) inherent in natural systems. Traditional analyses often assume uncorrelated or weakly correlated temporal structure in the velocity (net displacement) time series constructed using sequential location data. We propose that frequency and time–frequency domain methods, embodied by Fourier and wavelet transforms, can serve as useful probes in early investigations of animal movement data, stimulating new ecological insight and questions. We introduce a novel movement model with time-varying parameters to study these methods in an animal movement context. Simulation studies show that the spectral signature given by these methods provides a useful approach for statistically detecting and characterizing temporal dependency in animal movement data. In addition, our simulations provide a connection between the spectral signatures observed in empirical data with null hypotheses about expected animal activity. Our analyses also show that there is not a specific one-to-one relationship between the spectral signatures and behavior type and that departures from the anticipated signatures are also informative. Box plots of net displacement arranged by time of day and conditioned on common spectral properties can help interpret the spectral signatures of empirical data. The first case study is based on the movement trajectory of a lion (Panthera leo) that shows several characteristic daily activity sequences, including an active–rest cycle that is correlated with moonlight brightness. A second example based on six pairs of African buffalo (Syncerus caffer) illustrates the use of wavelet coherency to show that their movements synchronize when they are within ∼1 km of each other, even when individual movement was best described as an uncorrelated random walk, providing an important spatial baseline of movement synchrony and suggesting that local behavioral cues play a strong role in driving movement patterns. We conclude with a discussion about the role these methods may have in guiding appropriately flexible probabilistic models connecting movement with biotic and abiotic covariates. PMID:20503882

Extension of the Time-Spectral Approach to Overset Solvers for Arbitrary Motion

NASA Technical Reports Server (NTRS)

Leffell, Joshua Isaac; Murman, Scott M.; Pulliam, Thomas H.

2012-01-01

Forced periodic flows arise in a broad range of aerodynamic applications such as rotorcraft, turbomachinery, and flapping wing configurations. Standard practice involves solving the unsteady flow equations forward in time until the initial transient exits the domain and a statistically stationary flow is achieved. It is often required to simulate through several periods to remove the initial transient making unsteady design optimization prohibitively expensive for most realistic problems. An effort to reduce the computational cost of these calculations led to the development of the Harmonic Balance method [1, 2] which capitalizes on the periodic nature of the solution. The approach exploits the fact that forced temporally periodic flow, while varying in the time domain, is invariant in the frequency domain. Expanding the temporal variation at each spatial node into a Fourier series transforms the unsteady governing equations into a steady set of equations in integer harmonics that can be tackled with the acceleration techniques afforded to steady-state flow solvers. Other similar approaches, such as the Nonlinear Frequency Domain [3,4,5], Reduced Frequency [6] and Time-Spectral [7, 8, 9] methods, were developed shortly thereafter. Additionally, adjoint-based optimization techniques can be applied [10, 11] as well as frequency-adaptive methods [12, 13, 14] to provide even more flexibility to the method. The Fourier temporal basis functions imply spectral convergence as the number of harmonic modes, and correspondingly number of time samples, N, is increased. Some elect to solve the equations in the frequency domain directly, while others choose to transform the equations back into the time domain to simplify the process of adding this capability to existing solvers, but each harnesses the underlying steady solution in the frequency domain. These temporal projection methods will herein be collectively referred to as Time-Spectral methods. Time-Spectral methods have demonstrated marked success in reducing the computational costs associated with simulating periodic forced flows, but have yet to be fully applied to overset or Cartesian solvers for arbitrary motion with dynamic hole-cutting. Overset and Cartesian grid methodologies are versatile techniques capable of handling complex geometry configurations in practical engineering applications, and the combination of the Time-Spectral approach with this general capability potentially provides an enabling new design and analysis tool. In an arbitrary moving-body scenario for these approaches, a Lagrangian body moves through a fixed Eulerian mesh and mesh points in the Eulerian mesh interior to the solid body are removed (cut or blanked), leaving a hole in the Eulerian mesh. During the dynamic motion some gridpoints in the domain are blanked and do not have a complete set of time-samples preventing a direct implementation of the Time-Spectral method. Murman[6] demonstrated the Time-Spectral approach for a Cartesian solver with a rigid domain motion, wherein the hole cutting remains constant. Similarly, Custer et al. [15, 16] used the NASA overset OVERFLOW solver and limited the amount of relative motion to ensure static hole-cutting and interpolation. Recently, Mavriplis and Mundis[17] demonstrated a qualitative method for applying the Time-Spectral approach to an unstructured overset solver for arbitrary motion. The goal of the current work is to develop a robust and general method for handling arbitrary motion with the Time-Spectral approach within an overset or Cartesian mesh method, while still approaching the spectral convergence rate of the original Time-Spectral approach. The viscous OVERFLOW solver will be augmented with the new Time-Spectral algorithm and the capability of the method for benchmark problems in rotorcraft and turbomachinery will be demonstrated. This abstract begins with a brief synopsis of the Time-Spectral approach for overset grids and provides details of e current approach to allow for arbitrary motion. Model problem results in one and two dimensions are included to demonstrate the viability of the method and the convergence properties. Section IV briefly outlines the implementation into the OVERFLOW solver, and the abstract closes with a description of the benchmark test cases which will be included in the final paper.

On the detection and monitoring of reduced water content in plants using spectral responses in the visible domain

NASA Astrophysics Data System (ADS)

Baranoski, Gladimir V. G.; Van Leeuwen, Spencer; Chen, Tenn F.

2016-05-01

The water status of cultivated plants can have a significant impact not only on food production, but also on the appropriate usage of increasingly scarce freshwater supplies. Accordingly, the cost-effective detection and monitoring of changes in their water content are longstanding remote sensing goals. Existing procedures employed to achieve these goals are largely based on the spectral responses of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. Recently, it has been suggested that such procedures could be implemented using spectral responses, more specifically spectral subsurface reflectance to transmittance ratios, obtained in the visible domain. The basis for this proposition resides on the premise that a reduced water content (RWC) can result in histological changes whose effects on the foliar optical properties may not be limited to the infrared domain. However, the experiments leading to this proposition were performed on detached leaves, which were not influenced by the whole plant's adaptation mechanisms to water stress. In this work, we investigate whether the spectral responses of living plant leaves in the visible domain can lead to reliable RWC estimations. We employ measured biophysical data and predictive light transport simulations in order to extend qualitatively and quantitatively the scope of previous studies in this area. Our findings indicate that the living specimens' physiological responses to water stress should be taken into account in the design of new procedures for the cost-effective RWC estimation using visible subsurface reflectance to transmittance ratios.

Modified Spectral Fatigue Methods for S-N Curves With MIL-HDBK-5J Coefficients

NASA Technical Reports Server (NTRS)

Irvine, Tom; Larsen, Curtis

2016-01-01

The rainflow method is used for counting fatigue cycles from a stress response time history, where the fatigue cycles are stress-reversals. The rainflow method allows the application of Palmgren-Miner's rule in order to assess the fatigue life of a structure subject to complex loading. The fatigue damage may also be calculated from a stress response power spectral density (PSD) using the semi-empirical Dirlik, Single Moment, Zhao-Baker and other spectral methods. These methods effectively assume that the PSD has a corresponding time history which is stationary with a normal distribution. This paper shows how the probability density function for rainflow stress cycles can be extracted from each of the spectral methods. This extraction allows for the application of the MIL-HDBK-5J fatigue coefficients in the cumulative damage summation. A numerical example is given in this paper for the stress response of a beam undergoing random base excitation, where the excitation is applied separately by a time history and by its corresponding PSD. The fatigue calculation is performed in the time domain, as well as in the frequency domain via the modified spectral methods. The result comparison shows that the modified spectral methods give comparable results to the time domain rainflow counting method.

[Spatial domain display for interference image dataset].

PubMed

Wang, Cai-Ling; Li, Yu-Shan; Liu, Xue-Bin; Hu, Bing-Liang; Jing, Juan-Juan; Wen, Jia

2011-11-01

The requirements of imaging interferometer visualization is imminent for the user of image interpretation and information extraction. However, the conventional researches on visualization only focus on the spectral image dataset in spectral domain. Hence, the quick show of interference spectral image dataset display is one of the nodes in interference image processing. The conventional visualization of interference dataset chooses classical spectral image dataset display method after Fourier transformation. In the present paper, the problem of quick view of interferometer imager in image domain is addressed and the algorithm is proposed which simplifies the matter. The Fourier transformation is an obstacle since its computation time is very large and the complexion would be even deteriorated with the size of dataset increasing. The algorithm proposed, named interference weighted envelopes, makes the dataset divorced from transformation. The authors choose three interference weighted envelopes respectively based on the Fourier transformation, features of interference data and human visual system. After comparing the proposed with the conventional methods, the results show the huge difference in display time.

DigiLens color sequential filtering for microdisplay-based projection applications

NASA Astrophysics Data System (ADS)

Sagan, Stephen F.; Smith, Ronald T.; Popovich, Milan M.

2000-10-01

Application Specific Integrated Filters (ASIFs), based on a unique holographic polymer dispersed liquid crystal (H-PDLC) material system offering high efficiency, fast switching and low power, are being developed for microdisplay based projection applications. A new photonics technology based H-PDLC materials combined with the ability to be electrically switched on and off offers a new approach to color sequential filtering of a white light source for microdisplay-based front and rear projection display applications. Switchable Bragg gratings created in the PDLC are fundamental building blocks. Combined with the well- defined spectral and angular characteristics of Bragg gratings, these selectable filters can provide a large color gamut and a dynamically adjustable white balance. These switchable Bragg gratings can be reflective or transmissive and in each case can be designed to operate in either additive or subtractive mode. The spectral characteristics of filters made from a stack of these Bragg gratings can be configured for a specific lamp spectrum to give high diffractive efficiency over the broad bandwidths required for an illumination system. When it is necessary to reduce the spectral bandwidth, it is possible to use the properties of reflection Bragg holograms to construct very narrow band high efficiency filters. The basic properties and key benefits of ASIFs in projection displays are reviewed.

Deblurring sequential ocular images from multi-spectral imaging (MSI) via mutual information.

PubMed

Lian, Jian; Zheng, Yuanjie; Jiao, Wanzhen; Yan, Fang; Zhao, Bojun

2018-06-01

Multi-spectral imaging (MSI) produces a sequence of spectral images to capture the inner structure of different species, which was recently introduced into ocular disease diagnosis. However, the quality of MSI images can be significantly degraded by motion blur caused by the inevitable saccades and exposure time required for maintaining a sufficiently high signal-to-noise ratio. This degradation may confuse an ophthalmologist, reduce the examination quality, or defeat various image analysis algorithms. We propose an early work specially on deblurring sequential MSI images, which is distinguished from many of the current image deblurring techniques by resolving the blur kernel simultaneously for all the images in an MSI sequence. It is accomplished by incorporating several a priori constraints including the sharpness of the latent clear image, the spatial and temporal smoothness of the blur kernel and the similarity between temporally-neighboring images in MSI sequence. Specifically, we model the similarity between MSI images with mutual information considering the different wavelengths used for capturing different images in MSI sequence. The optimization of the proposed approach is based on a multi-scale framework and stepwise optimization strategy. Experimental results from 22 MSI sequences validate that our approach outperforms several state-of-the-art techniques in natural image deblurring.

Sensitivity study of heavy precipitation in Limited Area Model climate simulations: influence of the size of the domain and the use of the spectral nudging technique

NASA Astrophysics Data System (ADS)

Colin, Jeanne; Déqué, Michel; Radu, Raluca; Somot, Samuel

2010-10-01

We assess the impact of two sources of uncertainties in a limited area model (LAM) on the representation of intense precipitation: the size of the domain of integration and the use of the spectral nudging technique (driving of the large-scale within the domain of integration). We work in a perfect-model approach where the LAM is driven by a general circulation model (GCM) run at the same resolution and sharing the same physics and dynamics as the LAM. A set of three 50 km resolution simulations run over Western Europe with the LAM ALADIN-Climate and the GCM ARPEGE-Climate are performed to address this issue. Results are consistent with previous studies regarding the seasonal-mean fields. Furthermore, they show that neither the use of the spectral nudging nor the choice of a small domain are detrimental to the modelling of heavy precipitation in the present experiment.

Simulation of ultrasonic wave propagation in anisotropic poroelastic bone plate using hybrid spectral/finite element method.

PubMed

Nguyen, Vu-Hieu; Naili, Salah

2012-08-01

This paper deals with the modeling of guided waves propagation in in vivo cortical long bone, which is known to be anisotropic medium with functionally graded porosity. The bone is modeled as an anisotropic poroelastic material by using Biot's theory formulated in high frequency domain. A hybrid spectral/finite element formulation has been developed to find the time-domain solution of ultrasonic waves propagating in a poroelastic plate immersed in two fluid halfspaces. The numerical technique is based on a combined Laplace-Fourier transform, which allows to obtain a reduced dimension problem in the frequency-wavenumber domain. In the spectral domain, as radiation conditions representing infinite fluid halfspaces may be exactly introduced, only the heterogeneous solid layer needs to be analyzed by using finite element method. Several numerical tests are presented showing very good performance of the proposed procedure. A preliminary study on the first arrived signal velocities computed by using equivalent elastic and poroelastic models will be presented. Copyright © 2012 John Wiley & Sons, Ltd.

The magnifying glass - A feature space local expansion for visual analysis. [and image enhancement

NASA Technical Reports Server (NTRS)

Juday, R. D.

1981-01-01

The Magnifying Glass Transformation (MGT) technique is proposed, as a multichannel spectral operation yielding visual imagery which is enhanced in a specified spectral vicinity, guided by the statistics of training samples. An application example is that in which the discrimination among spectral neighbors within an interactive display may be increased without altering distant object appearances or overall interpretation. A direct histogram specification technique is applied to the channels within the multispectral image so that a subset of the spectral domain occupies an increased fraction of the domain. The transformation is carried out by obtaining the training information, establishing the condition of the covariance matrix, determining the influenced solid, and initializing the lookup table. Finally, the image is transformed.

Spectral Collocation Time-Domain Modeling of Diffractive Optical Elements

NASA Astrophysics Data System (ADS)

Hesthaven, J. S.; Dinesen, P. G.; Lynov, J. P.

1999-11-01

A spectral collocation multi-domain scheme is developed for the accurate and efficient time-domain solution of Maxwell's equations within multi-layered diffractive optical elements. Special attention is being paid to the modeling of out-of-plane waveguide couplers. Emphasis is given to the proper construction of high-order schemes with the ability to handle very general problems of considerable geometric and material complexity. Central questions regarding efficient absorbing boundary conditions and time-stepping issues are also addressed. The efficacy of the overall scheme for the time-domain modeling of electrically large, and computationally challenging, problems is illustrated by solving a number of plane as well as non-plane waveguide problems.

Sequential Classifier Training for Rice Mapping with Multitemporal Remote Sensing Imagery

NASA Astrophysics Data System (ADS)

Guo, Y.; Jia, X.; Paull, D.

2017-10-01

Most traditional methods for rice mapping with remote sensing data are effective when they are applied to the initial growing stage of rice, as the practice of flooding during this period makes the spectral characteristics of rice fields more distinguishable. In this study, we propose a sequential classifier training approach for rice mapping that can be used over the whole growing period of rice for monitoring various growth stages. Rice fields are firstly identified during the initial flooding period. The identified rice fields are used as training data to train a classifier that separates rice and non-rice pixels. The classifier is then used as a priori knowledge to assist the training of classifiers for later rice growing stages. This approach can be applied progressively to sequential image data, with only a small amount of training samples being required from each image. In order to demonstrate the effectiveness of the proposed approach, experiments were conducted at one of the major rice-growing areas in Australia. The proposed approach was applied to a set of multitemporal remote sensing images acquired by the Sentinel-2A satellite. Experimental results show that, compared with traditional spectral-indexbased algorithms, the proposed method is able to achieve more stable and consistent rice mapping accuracies and it reaches higher than 80% during the whole rice growing period.

Investigation of Retinal Morphology Alterations Using Spectral Domain Optical Coherence Tomography in a Mouse Model of Retinal Branch and Central Retinal Vein Occlusion

PubMed Central

Ebneter, Andreas; Agca, Cavit; Dysli, Chantal; Zinkernagel, Martin S.

2015-01-01

Retinal vein occlusion is a leading cause of visual impairment. Experimental models of this condition based on laser photocoagulation of retinal veins have been described and extensively exploited in mammals and larger rodents such as the rat. However, few reports exist on the use of this paradigm in the mouse. The objective of this study was to investigate a model of branch and central retinal vein occlusion in the mouse and characterize in vivo longitudinal retinal morphology alterations using spectral domain optical coherence tomography. Retinal veins were experimentally occluded using laser photocoagulation after intravenous application of Rose Bengal, a photo-activator dye enhancing thrombus formation. Depending on the number of veins occluded, variable amounts of capillary dropout were seen on fluorescein angiography. Vascular endothelial growth factor levels were markedly elevated early and peaked at day one. Retinal thickness measurements with spectral domain optical coherence tomography showed significant swelling (p<0.001) compared to baseline, followed by gradual thinning plateauing two weeks after the experimental intervention (p<0.001). Histological findings at day seven correlated with spectral domain optical coherence tomography imaging. The inner layers were predominantly affected by degeneration with the outer nuclear layer and the photoreceptor outer segments largely preserved. The application of this retinal vein occlusion model in the mouse carries several advantages over its use in other larger species, such as access to a vast range of genetically modified animals. Retinal changes after experimental retinal vein occlusion in this mouse model can be non-invasively quantified by spectral domain optical coherence tomography, and may be used to monitor effects of potential therapeutic interventions. PMID:25775456

SPECTRAL DOMAIN VERSUS SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF THE RETINAL CAPILLARY PLEXUSES IN SICKLE CELL MACULOPATHY.

PubMed

Jung, Jesse J; Chen, Michael H; Frambach, Caroline R; Rofagha, Soraya; Lee, Scott S

2018-01-01

To compare the spectral domain and swept source optical coherence tomography angiography findings in two cases of sickle cell maculopathy. A 53-year-old man and a 24-year-old man both with sickle cell disease (hemoglobin SS) presented with no visual complaints; Humphrey visual field testing demonstrated asymptomatic paracentral scotomas that extended nasally in the involved eyes. Clinical examination and multimodal imaging including spectral domain and swept source optical coherence tomography, and spectral domain optical coherence tomography angiography and swept source optical coherence tomography angiography (Carl Zeiss Meditec Inc, Dublin, CA) were performed. Fundus examination of both patients revealed subtle thinning of the macula. En-face swept source optical coherence tomography confirmed the extent of the thinning correlating with the functional paracentral scotomas on Humphrey visual field. Swept source optical coherence tomography B-scan revealed multiple confluent areas of inner nuclear thinning and significant temporal retinal atrophy. En-face 6 × 6-mm spectral domain optical coherence tomography angiography of the macula demonstrated greater loss of the deep capillary plexus compared with the superficial capillary plexus. Swept source optical coherence tomography angiography 12 × 12-mm imaging captured the same macular findings and loss of both plexuses temporally outside the macula. In these two cases of sickle cell maculopathy, deep capillary plexus ischemia is more extensive within the macula, whereas both the superficial capillary plexus and deep capillary plexus are involved outside the macula likely due to the greater oxygen demands and watershed nature of these areas. Swept source optical coherence tomography angiography clearly demonstrates the angiographic extent of the disease correlating with the Humphrey visual field scotomas and confluent areas of inner nuclear atrophy.

Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

PubMed Central

Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

2014-01-01

Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

A path-level exact parallelization strategy for sequential simulation

NASA Astrophysics Data System (ADS)

Peredo, Oscar F.; Baeza, Daniel; Ortiz, Julián M.; Herrero, José R.

2018-01-01

Sequential Simulation is a well known method in geostatistical modelling. Following the Bayesian approach for simulation of conditionally dependent random events, Sequential Indicator Simulation (SIS) method draws simulated values for K categories (categorical case) or classes defined by K different thresholds (continuous case). Similarly, Sequential Gaussian Simulation (SGS) method draws simulated values from a multivariate Gaussian field. In this work, a path-level approach to parallelize SIS and SGS methods is presented. A first stage of re-arrangement of the simulation path is performed, followed by a second stage of parallel simulation for non-conflicting nodes. A key advantage of the proposed parallelization method is to generate identical realizations as with the original non-parallelized methods. Case studies are presented using two sequential simulation codes from GSLIB: SISIM and SGSIM. Execution time and speedup results are shown for large-scale domains, with many categories and maximum kriging neighbours in each case, achieving high speedup results in the best scenarios using 16 threads of execution in a single machine.

Transient spectral domain optical coherence tomography findings in classic MEWDS: a case report.

PubMed

Lavigne, Luciana Castro; Isaac, David Leonardo Cruvinel; Duarte Júnior, José Osório; Avila, Marcos Pereira de

2014-01-01

The purpose of this study was to describe a patient with multiple evanescent white dot syndrome (MEWDS) who presented with classic retinal findings and transient changes in outer retinal anatomy. A 20-year-old man presented with mild blurred vision in the left eye, reporting flu-like symptoms 1 week before the visual symptoms started. Fundus examination of the left eye revealed foveal granularity and multiple scattered spots deep to the retina in the posterior pole. Fluorescein angiography and indocyanine green angiography showed typical MEWDS findings. Spectral Domain Optical Coherence Tomography has shown transient changes in outer retinal anatomy with disappearance of inner segment-outer segment junction and mild attenuation of external limiting membrane. Six months later, Spectral Domain Optical Coherence Tomography has shown complete resolution with recovery of normal outer retinal aspect.

Convergence of Spectral Discretizations of the Vlasov--Poisson System

DOE PAGES

Manzini, G.; Funaro, D.; Delzanno, G. L.

2017-09-26

Here we prove the convergence of a spectral discretization of the Vlasov-Poisson system. The velocity term of the Vlasov equation is discretized using either Hermite functions on the infinite domain or Legendre polynomials on a bounded domain. The spatial term of the Vlasov and Poisson equations is discretized using periodic Fourier expansions. Boundary conditions are treated in weak form through a penalty type term that can be applied also in the Hermite case. As a matter of fact, stability properties of the approximated scheme descend from this added term. The convergence analysis is carried out in detail for the 1D-1Vmore » case, but results can be generalized to multidimensional domains, obtained as Cartesian product, in both space and velocity. The error estimates show the spectral convergence under suitable regularity assumptions on the exact solution.« less

Endoscopic spectral-domain polarization-sensitive optical coherence tomography system

NASA Astrophysics Data System (ADS)

Wang, Yi; Chen, Xiaodong; Hu, Zhiqiang; Li, Qiao; Yu, Daoyin

2008-02-01

In this paper, we introduced a fiber-based endoscopic Spectral-domain Polarization-sensitive OCT (SD-PS-OCT) experimental scheme for detecting the internal organ disease, which is based on low-coherence interferometer and two spectrometers. The SD-PS-OCT has the advantages of both Spectral-domain OCT (SD-OCT) and Polarization-sensitive OCT (PS-OCT). It is able to get the real-time image of reflectivity and birefringence distribution of tissue at the same time. The usage of SD-PS-OCT in endoscopic diagnosing system provides it the possibility to detect the internal organ disease. Since SD-PS-OCT can image the pathological changes of biological tissue below surface (1-3mm) with high resolution (1-15μm), it is able to help diagnosing early diseases of internal organs, which makes it a biomedical technology with bright future.

Impacts of spectral nudging on the simulated surface air temperature in summer compared with the selection of shortwave radiation and land surface model physics parameterization in a high-resolution regional atmospheric model

NASA Astrophysics Data System (ADS)

Park, Jun; Hwang, Seung-On

2017-11-01

The impact of a spectral nudging technique for the dynamical downscaling of the summer surface air temperature in a high-resolution regional atmospheric model is assessed. The performance of this technique is measured by comparing 16 analysis-driven simulation sets of physical parameterization combinations of two shortwave radiation and four land surface model schemes of the model, which are known to be crucial for the simulation of the surface air temperature. It is found that the application of spectral nudging to the outermost domain has a greater impact on the regional climate than any combination of shortwave radiation and land surface model physics schemes. The optimal choice of two model physics parameterizations is helpful for obtaining more realistic spatiotemporal distributions of land surface variables such as the surface air temperature, precipitation, and surface fluxes. However, employing spectral nudging adds more value to the results; the improvement is greater than using sophisticated shortwave radiation and land surface model physical parameterizations. This result indicates that spectral nudging applied to the outermost domain provides a more accurate lateral boundary condition to the innermost domain when forced by analysis data by securing the consistency with large-scale forcing over a regional domain. This consequently indirectly helps two physical parameterizations to produce small-scale features closer to the observed values, leading to a better representation of the surface air temperature in a high-resolution downscaled climate.

Spectral identification of topological domains

PubMed Central

Chen, Jie; Hero, Alfred O.; Rajapakse, Indika

2016-01-01

Motivation: Topological domains have been proposed as the backbone of interphase chromosome structure. They are regions of high local contact frequency separated by sharp boundaries. Genes within a domain often have correlated transcription. In this paper, we present a computational efficient spectral algorithm to identify topological domains from chromosome conformation data (Hi-C data). We consider the genome as a weighted graph with vertices defined by loci on a chromosome and the edge weights given by interaction frequency between two loci. Laplacian-based graph segmentation is then applied iteratively to obtain the domains at the given compactness level. Comparison with algorithms in the literature shows the advantage of the proposed strategy. Results: An efficient algorithm is presented to identify topological domains from the Hi-C matrix. Availability and Implementation: The Matlab source code and illustrative examples are available at http://bionetworks.ccmb.med.umich.edu/ Contact: indikar@med.umich.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27153657

Spectral reconstruction analysis for enhancing signal-to-noise in time-resolved spectroscopies

NASA Astrophysics Data System (ADS)

Wilhelm, Michael J.; Smith, Jonathan M.; Dai, Hai-Lung

2015-09-01

We demonstrate a new spectral analysis for the enhancement of the signal-to-noise ratio (SNR) in time-resolved spectroscopies. Unlike the simple linear average which produces a single representative spectrum with enhanced SNR, this Spectral Reconstruction analysis (SRa) improves the SNR (by a factor of ca. 0 . 6 √{ n } ) for all n experimentally recorded time-resolved spectra. SRa operates by eliminating noise in the temporal domain, thereby attenuating noise in the spectral domain, as follows: Temporal profiles at each measured frequency are fit to a generic mathematical function that best represents the temporal evolution; spectra at each time are then reconstructed with data points from the fitted profiles. The SRa method is validated with simulated control spectral data sets. Finally, we apply SRa to two distinct experimentally measured sets of time-resolved IR emission spectra: (1) UV photolysis of carbonyl cyanide and (2) UV photolysis of vinyl cyanide.

Low complexity feature extraction for classification of harmonic signals

NASA Astrophysics Data System (ADS)

William, Peter E.

In this dissertation, feature extraction algorithms have been developed for extraction of characteristic features from harmonic signals. The common theme for all developed algorithms is the simplicity in generating a significant set of features directly from the time domain harmonic signal. The features are a time domain representation of the composite, yet sparse, harmonic signature in the spectral domain. The algorithms are adequate for low-power unattended sensors which perform sensing, feature extraction, and classification in a standalone scenario. The first algorithm generates the characteristic features using only the duration between successive zero-crossing intervals. The second algorithm estimates the harmonics' amplitudes of the harmonic structure employing a simplified least squares method without the need to estimate the true harmonic parameters of the source signal. The third algorithm, resulting from a collaborative effort with Daniel White at the DSP Lab, University of Nebraska-Lincoln, presents an analog front end approach that utilizes a multichannel analog projection and integration to extract the sparse spectral features from the analog time domain signal. Classification is performed using a multilayer feedforward neural network. Evaluation of the proposed feature extraction algorithms for classification through the processing of several acoustic and vibration data sets (including military vehicles and rotating electric machines) with comparison to spectral features shows that, for harmonic signals, time domain features are simpler to extract and provide equivalent or improved reliability over the spectral features in both the detection probabilities and false alarm rate.

Highly sensitive index of sympathetic activity based on time-frequency spectral analysis of electrodermal activity.

PubMed

Posada-Quintero, Hugo F; Florian, John P; Orjuela-Cañón, Álvaro D; Chon, Ki H

2016-09-01

Time-domain indices of electrodermal activity (EDA) have been used as a marker of sympathetic tone. However, they often show high variation between subjects and low consistency, which has precluded their general use as a marker of sympathetic tone. To examine whether power spectral density analysis of EDA can provide more consistent results, we recently performed a variety of sympathetic tone-evoking experiments (43). We found significant increase in the spectral power in the frequency range of 0.045 to 0.25 Hz when sympathetic tone-evoking stimuli were induced. The sympathetic tone assessed by the power spectral density of EDA was found to have lower variation and more sensitivity for certain, but not all, stimuli compared with the time-domain analysis of EDA. We surmise that this lack of sensitivity in certain sympathetic tone-inducing conditions with time-invariant spectral analysis of EDA may lie in its inability to characterize time-varying dynamics of the sympathetic tone. To overcome the disadvantages of time-domain and time-invariant power spectral indices of EDA, we developed a highly sensitive index of sympathetic tone, based on time-frequency analysis of EDA signals. Its efficacy was tested using experiments designed to elicit sympathetic dynamics. Twelve subjects underwent four tests known to elicit sympathetic tone arousal: cold pressor, tilt table, stand test, and the Stroop task. We hypothesize that a more sensitive measure of sympathetic control can be developed using time-varying spectral analysis. Variable frequency complex demodulation, a recently developed technique for time-frequency analysis, was used to obtain spectral amplitudes associated with EDA. We found that the time-varying spectral frequency band 0.08-0.24 Hz was most responsive to stimulation. Spectral power for frequencies higher than 0.24 Hz were determined to be not related to the sympathetic dynamics because they comprised less than 5% of the total power. The mean value of time-varying spectral amplitudes in the frequency band 0.08-0.24 Hz were used as the index of sympathetic tone, termed TVSymp. TVSymp was found to be overall the most sensitive to the stimuli, as evidenced by a low coefficient of variation (0.54), and higher consistency (intra-class correlation, 0.96) and sensitivity (Youden's index > 0.75), area under the receiver operating characteristic (ROC) curve (>0.8, accuracy > 0.88) compared with time-domain and time-invariant spectral indices, including heart rate variability. Copyright © 2016 the American Physiological Society.

FSCS Reveals the Complexity of Lipid Domain Dynamics in the Plasma Membrane of Live Cells.

PubMed

Nicovich, Philip R; Kwiatek, Joanna M; Ma, Yuanqing; Benda, Aleš; Gaus, Katharina

2018-06-19

The coexistence of lipid domains with different degrees of lipid packing in the plasma membrane of mammalian cells has been postulated, but direct evidence has so far been challenging to obtain because of the small size and short lifetime of these domains in live cells. Here, we use fluorescence spectral correlation spectroscopy in conjunction with a probe sensitive to the membrane environment to quantify spectral fluctuations associated with dynamics of membrane domains in live cells. With this method, we show that membrane domains are present in live COS-7 cells and have a lifetime lower bound of 5.90 and 14.69 ms for the ordered and disordered phases, respectively. Comparisons to simulations indicate that the underlying mechanism of these fluctuations is complex but qualitatively described by a combination of dye diffusion between membrane domains as well as the motion of domains within the membrane. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Broadband CARS spectral phase retrieval using a time-domain Kramers–Kronig transform

PubMed Central

Liu, Yuexin; Lee, Young Jong; Cicerone, Marcus T.

2014-01-01

We describe a closed-form approach for performing a Kramers–Kronig (KK) transform that can be used to rapidly and reliably retrieve the phase, and thus the resonant imaginary component, from a broadband coherent anti-Stokes Raman scattering (CARS) spectrum with a nonflat background. In this approach we transform the frequency-domain data to the time domain, perform an operation that ensures a causality criterion is met, then transform back to the frequency domain. The fact that this method handles causality in the time domain allows us to conveniently account for spectrally varying nonresonant background from CARS as a response function with a finite rise time. A phase error accompanies KK transform of data with finite frequency range. In examples shown here, that phase error leads to small (<1%) errors in the retrieved resonant spectra. PMID:19412273

Fourier/Chebyshev methods for the incompressible Navier-Stokes equations in finite domains

NASA Technical Reports Server (NTRS)

Corral, Roque; Jimenez, Javier

1992-01-01

A fully spectral numerical scheme for the incompressible Navier-Stokes equations in domains which are infinite or semi-infinite in one dimension. The domain is not mapped, and standard Fourier or Chebyshev expansions can be used. The handling of the infinite domain does not introduce any significant overhead. The scheme assumes that the vorticity in the flow is essentially concentrated in a finite region, which is represented numerically by standard spectral collocation methods. To accomodate the slow exponential decay of the velocities at infinity, extra expansion functions are introduced, which are handled analytically. A detailed error analysis is presented, and two applications to Direct Numerical Simulation of turbulent flows are discussed in relation with the numerical performance of the scheme.

EDDIE Seismology: Introductory spectral analysis for undergraduates

NASA Astrophysics Data System (ADS)

Soule, D. C.; Gougis, R.; O'Reilly, C.

2016-12-01

We present a spectral seismology lesson in which students use spectral analysis to describe the frequency of seismic arrivals based on a conceptual presentation of waveforms and filters. The goal is for students to surpass basic waveform terminology and relate a time domain signals to their conjugates in the frequency domain. Although seismology instruction commonly engages students in analysis of authentic seismological data, this is less true for lower-level undergraduate seismology instruction due to coding barriers to many seismological analysis tasks. To address this, our module uses Seismic Canvas (Kroeger, 2015; https://seiscode.iris.washington.edu/projects/seismiccanvas), a graphically interactive application for accessing, viewing and analyzing waveform data, which we use to plot earthquake data in the time domain. Once students are familiarized with the general components of the waveform (i.e. frequency, wavelength, amplitude and period), they use Seismic Canvas to transform the data into the frequency domain. Bypassing the mathematics of Fourier Series allows focus on conceptual understanding by plotting and manipulating seismic data in both time and frequency domains. Pre/post-tests showed significant improvements in students' use of seismograms and spectrograms to estimate the frequency content of the primary wave, which demonstrated students' understanding of frequency and how data on the spectrogram and seismogram are related. Students were also able to identify the time and frequency of the largest amplitude arrival, indicating understanding of amplitude and use of a spectrogram as an analysis tool. Students were also asked to compare plots of raw data and the same data filtered with a high-pass filter, and identify the filter used to create the second plot. Students demonstrated an improved understanding of how frequency content can be removed from a signal in the spectral domain.

Generalized analytical solutions to sequentially coupled multi-species advective-dispersive transport equations in a finite domain subject to an arbitrary time-dependent source boundary condition

NASA Astrophysics Data System (ADS)

Chen, Jui-Sheng; Liu, Chen-Wuing; Liang, Ching-Ping; Lai, Keng-Hsin

2012-08-01

SummaryMulti-species advective-dispersive transport equations sequentially coupled with first-order decay reactions are widely used to describe the transport and fate of the decay chain contaminants such as radionuclide, chlorinated solvents, and nitrogen. Although researchers attempted to present various types of methods for analytically solving this transport equation system, the currently available solutions are mostly limited to an infinite or a semi-infinite domain. A generalized analytical solution for the coupled multi-species transport problem in a finite domain associated with an arbitrary time-dependent source boundary is not available in the published literature. In this study, we first derive generalized analytical solutions for this transport problem in a finite domain involving arbitrary number of species subject to an arbitrary time-dependent source boundary. Subsequently, we adopt these derived generalized analytical solutions to obtain explicit analytical solutions for a special-case transport scenario involving an exponentially decaying Bateman type time-dependent source boundary. We test the derived special-case solutions against the previously published coupled 4-species transport solution and the corresponding numerical solution with coupled 10-species transport to conduct the solution verification. Finally, we compare the new analytical solutions derived for a finite domain against the published analytical solutions derived for a semi-infinite domain to illustrate the effect of the exit boundary condition on coupled multi-species transport with an exponential decaying source boundary. The results show noticeable discrepancies between the breakthrough curves of all the species in the immediate vicinity of the exit boundary obtained from the analytical solutions for a finite domain and a semi-infinite domain for the dispersion-dominated condition.

Privacy protection in surveillance systems based on JPEG DCT baseline compression and spectral domain watermarking

NASA Astrophysics Data System (ADS)

Sablik, Thomas; Velten, Jörg; Kummert, Anton

2015-03-01

An novel system for automatic privacy protection in digital media based on spectral domain watermarking and JPEG compression is described in the present paper. In a first step private areas are detected. Therefore a detection method is presented. The implemented method uses Haar cascades to detects faces. Integral images are used to speed up calculations and the detection. Multiple detections of one face are combined. Succeeding steps comprise embedding the data into the image as part of JPEG compression using spectral domain methods and protecting the area of privacy. The embedding process is integrated into and adapted to JPEG compression. A Spread Spectrum Watermarking method is used to embed the size and position of the private areas into the cover image. Different methods for embedding regarding their robustness are compared. Moreover the performance of the method concerning tampered images is presented.

Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Zorgani, Ali; Lescanne, Maxime; Boccara, Claude; Fink, Mathias; Catheline, Stefan

2016-12-01

Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

Wavelet-based spectral finite element dynamic analysis for an axially moving Timoshenko beam

NASA Astrophysics Data System (ADS)

Mokhtari, Ali; Mirdamadi, Hamid Reza; Ghayour, Mostafa

2017-08-01

In this article, wavelet-based spectral finite element (WSFE) model is formulated for time domain and wave domain dynamic analysis of an axially moving Timoshenko beam subjected to axial pretension. The formulation is similar to conventional FFT-based spectral finite element (SFE) model except that Daubechies wavelet basis functions are used for temporal discretization of the governing partial differential equations into a set of ordinary differential equations. The localized nature of Daubechies wavelet basis functions helps to rule out problems of SFE model due to periodicity assumption, especially during inverse Fourier transformation and back to time domain. The high accuracy of WSFE model is then evaluated by comparing its results with those of conventional finite element and SFE results. The effects of moving beam speed and axial tensile force on vibration and wave characteristics, and static and dynamic stabilities of moving beam are investigated.

Diffuse shear wave imaging: toward passive elastography using low-frame rate spectral-domain optical coherence tomography.

PubMed

Nguyen, Thu-Mai; Zorgani, Ali; Lescanne, Maxime; Boccara, Claude; Fink, Mathias; Catheline, Stefan

2016-12-01

Optical coherence tomography (OCT) can map the stiffness of biological tissue by imaging mechanical perturbations (shear waves) propagating in the tissue. Most shear wave elastography (SWE) techniques rely on active shear sources to generate controlled displacements that are tracked at ultrafast imaging rates. Here, we propose a noise-correlation approach to retrieve stiffness information from the imaging of diffuse displacement fields using low-frame rate spectral-domain OCT. We demonstrated the method on tissue-mimicking phantoms and validated the results by comparison with classic ultrafast SWE. Then we investigated the in vivo feasibility on the eye of an anesthetized rat by applying noise correlation to naturally occurring displacements. The results suggest a great potential for passive elastography based on the detection of natural pulsatile motions using conventional spectral-domain OCT systems. This would facilitate the transfer of OCT-elastography to clinical practice, in particular, in ophthalmology or dermatology.

Partially coherent isodiffracting pulsed beams

NASA Astrophysics Data System (ADS)

Koivurova, Matias; Ding, Chaoliang; Turunen, Jari; Pan, Liuzhan

2018-02-01

We investigate a class of isodiffracting pulsed beams, which are superpositions of transverse modes supported by spherical-mirror laser resonators. By employing modal weights that, for stationary light, produce a Gaussian Schell-model beam, we extend this standard model to pulsed beams. We first construct the two-frequency cross-spectral density function that characterizes the spatial coherence in the space-frequency domain. By assuming a power-exponential spectral profile, we then employ the generalized Wiener-Khintchine theorem for nonstationary light to derive the two-time mutual coherence function that describes the space-time coherence of the ensuing beams. The isodiffracting nature of the laser resonator modes permits all (paraxial-domain) calculations at any propagation distance to be performed analytically. Significant spatiotemporal coupling is revealed in subcycle, single-cycle, and few-cycle domains, where the partial spatial coherence also leads to reduced temporal coherence even though full spectral coherence is assumed.

Spectral-domain optical coherence tomography of roth spots.

PubMed

Giovinazzo, Jerome; Mrejen, Sarah; Freund, K Bailey

2013-01-01

To describe the retinal findings of subacute bacterial endocarditis, their evolution after treatment, and analysis with spectral-domain optical coherence tomography. Retrospective chart review. A 21-year-old man presented with the sudden onset of a central scotoma in his left eye because of a sub-internal limiting membrane hemorrhage overlying the left fovea. When examined 2 weeks later, Roth spots were noted in his right eye. The patient was immediately referred to his internist and diagnosed with subacute bacterial endocarditis with cultures positive for Streptococcus viridans. He subsequently underwent aortic valve replacement surgery after 4 weeks of intravenous antibiotic therapy. When examined 4 weeks after valve replacement surgery, there was regression of the Roth spots. The present case demonstrates the importance of a funduscopic examination in the early diagnosis and management of subacute bacterial endocarditis. The analysis of Roth spots with spectral-domain optical coherence tomography suggested that they were septic emboli.

Frequency domain modeling and dynamic characteristics evaluation of existing wind turbine systems

NASA Astrophysics Data System (ADS)

Chiang, Chih-Hung; Yu, Chih-Peng

2016-04-01

It is quite well accepted that frequency domain procedures are suitable for the design and dynamic analysis of wind turbine structures, especially for floating offshore wind turbines, since random wind loads and wave induced motions are most likely simulated in the frequency domain. This paper presents specific applications of an effective frequency domain scheme to the linear analysis of wind turbine structures in which a 1-D spectral element was developed based on the axially-loaded member. The solution schemes are summarized for the spectral analyses of the tower, the blades, and the combined system with selected frequency-dependent coupling effect from foundation-structure interactions. Numerical examples demonstrate that the modal frequencies obtained using spectral-element models are in good agreement with those found in the literature. A 5-element mono-pile model results in less than 0.3% deviation from an existing 160-element model. It is preliminarily concluded that the proposed scheme is relatively efficient in performing quick verification for test data obtained from the on-site vibration measurement using the microwave interferometer.

Optical coherence tomography-based decision making in exudative age-related macular degeneration: comparison of time- vs spectral-domain devices.

PubMed

Cukras, C; Wang, Y D; Meyerle, C B; Forooghian, F; Chew, E Y; Wong, W T

2010-05-01

To determine whether optical coherence tomography (OCT) device-type influences clinical grading of OCT imaging in the context of exudative age-related macular degeneration (AMD). Ninety-six paired OCT scans from 49 patients with active exudative AMD were obtained on both the time-domain Stratus OCT system and the spectral-domain Cirrus OCT system at the same visit. Three independent graders judged each scan for the presence of intraretinal fluid (IRF) or subretinal fluid (SRF). The degree of grader consensus was evaluated and the ability of the systems to detect the presence of disease activity was analysed. Cirrus OCT generated a higher degree of inter-grader consensus than Stratus OCT with higher intraclass correlation coefficients for all parameters analysed. A pair-wise comparison of Cirrus OCT with Stratus OCT systems revealed that Cirrus-based gradings more frequently reported the presence of SRF and IRF and detected overall neovascular activity at a higher rate (P<0.05) compared with Stratus-based gradings. The choice of time-domain (Stratus) vs spectra-domain (Cirrus) OCT systems has a measurable impact on clinical decision making in exudative AMD. Spectral-domain OCT systems may be able to generate more consensus in clinical interpretation and, in particular cases, detect disease activity not detected by time-domain systems. Clinical trials using OCT-based clinical evaluations of exudative AMD may need to account for these inter-system differences in planning and analysis.

Optical Coherence Tomography-Based Decision Making in Exudative Age-related Macular Degeneration: Comparison of Time- versus Spectral-Domain Devices

PubMed Central

Cukras, Catherine; Wang, Yunqing D.; Meyerle, Catherine B.; Forooghian, Farzin; Chew, Emily Y.; Wong, Wai T.

2010-01-01

Purpose To determine if optical coherence tomography (OCT) device-type influences clinical grading of OCT imaging in the context of exudative age-related macular degeneration (AMD). Methods Ninety-six paired OCT scans from 49 patients with active exudative AMD were obtained on both the time-domain Stratus™ OCT system and the spectral-domain Cirrus™ OCT system at the same visit. Three independent graders judged each scan for the presence of intraretinal fluid (IRF) or subretinal fluid (SRF). The degree of grader consensus was evaluated and the ability of the systems to detect the presence of disease activity was analyzed. Results Cirrus™ OCT generated a higher degree of inter-grader consensus than Stratus OCT with higher intraclass correlation coefficients (ICC) for all parameters analyzed. A pair-wise comparison of Cirrus™ OCT to Stratus™ OCT systems revealed that Cirrus™-based gradings more frequently reported the presence of SRF and IRF and detected overall neovascular activity at a higher rate (p<0.05) compared to Stratus™-based gradings Conclusions The choice of time-domain (Stratus™) versus spectra-domain (Cirrus™) OCT systems has a measurable impact on clinical decision making in exudative AMD. Spectral-domain OCT systems may be able to generate more consensus in clinical interpretation and, in particular cases, detect disease activity not detected by time-domain systems. Clinical trials employing OCT-based clinical evaluations of exudative AMD may need to account for these inter-system differences in planning and analysis. PMID:19696804

Joint spatial-spectral hyperspectral image clustering using block-diagonal amplified affinity matrix

NASA Astrophysics Data System (ADS)

Fan, Lei; Messinger, David W.

2018-03-01

The large number of spectral channels in a hyperspectral image (HSI) produces a fine spectral resolution to differentiate between materials in a scene. However, difficult classes that have similar spectral signatures are often confused while merely exploiting information in the spectral domain. Therefore, in addition to spectral characteristics, the spatial relationships inherent in HSIs should also be considered for incorporation into classifiers. The growing availability of high spectral and spatial resolution of remote sensors provides rich information for image clustering. Besides the discriminating power in the rich spectrum, contextual information can be extracted from the spatial domain, such as the size and the shape of the structure to which one pixel belongs. In recent years, spectral clustering has gained popularity compared to other clustering methods due to the difficulty of accurate statistical modeling of data in high dimensional space. The joint spatial-spectral information could be effectively incorporated into the proximity graph for spectral clustering approach, which provides a better data representation by discovering the inherent lower dimensionality from the input space. We embedded both spectral and spatial information into our proposed local density adaptive affinity matrix, which is able to handle multiscale data by automatically selecting the scale of analysis for every pixel according to its neighborhood of the correlated pixels. Furthermore, we explored the "conductivity method," which aims at amplifying the block diagonal structure of the affinity matrix to further improve the performance of spectral clustering on HSI datasets.

Suppressing correlations in massively parallel simulations of lattice models

NASA Astrophysics Data System (ADS)

Kelling, Jeffrey; Ódor, Géza; Gemming, Sibylle

2017-11-01

For lattice Monte Carlo simulations parallelization is crucial to make studies of large systems and long simulation time feasible, while sequential simulations remain the gold-standard for correlation-free dynamics. Here, various domain decomposition schemes are compared, concluding with one which delivers virtually correlation-free simulations on GPUs. Extensive simulations of the octahedron model for 2 + 1 dimensional Kardar-Parisi-Zhang surface growth, which is very sensitive to correlation in the site-selection dynamics, were performed to show self-consistency of the parallel runs and agreement with the sequential algorithm. We present a GPU implementation providing a speedup of about 30 × over a parallel CPU implementation on a single socket and at least 180 × with respect to the sequential reference.

Spectral optical coherence tomography for ophthalmologic applications

NASA Astrophysics Data System (ADS)

Targowski, Piotr; Bajraszewski, Tomasz; Gorczyńska, Iwona; Szkulmowska, Anna; Szkulmowski, Maciej; Wojtkowski, Maciej; Kowalczyk, Andrzej; Kaluzny, Jakub J.; Kaluzny, Bartłomiej J.

2006-09-01

The overview of the Spectral Optical Coherence Tomography an alternative method to more popular Time domain modality is given. Examples from medical practice utilizing high resolution, ultra fast SOCT device are presented.

THE SECOND BLIND SPOT: SMALL RETINAL VESSEL VASCULOPATHY AFTER VACCINATION AGAINST NEISSERIA MENINGITIDIS AND YELLOW FEVER.

PubMed

Moysidis, Stavros N; Koulisis, Nicole; Patel, Vivek R; Kashani, Amir H; Rao, Narsing A; Humayun, Mark S; Rodger, Damien C

2017-01-01

To describe a case of small retinal vessel vasculopathy postvaccination. We report the case of a 41-year-old white man who presented with a "second blind spot," describing a nasal scotoma in the right eye that started 4 days after vaccinations against Neisseria meningitidis and the yellow fever virus, and after a 2-month period of high stress and decreased sleep. Clinical examination, Humphrey visual field testing, and multimodal imaging with fundus photographs, autofluorescence, fluorescein angiography, and spectral domain optical coherence tomography and angiography were performed. Clinical examination revealed a well-circumscribed, triangular area of retinal graying of about 1-disk diameter in size, located at the border of the temporal macula. This corresponded to a deep scotoma similar in size to the physiologic blind spot on Humphrey visual field 24-2 testing. There was mild hypoautofluoresence of this lesion on autofluorescence, hypofluorescence on fluorescein angiography, and focal attenuation of a small artery just distal to the bifurcation of an artery supplying the involved area. Spectral domain optical coherence tomography through the lesion conveyed hyperreflectivity most prominent in the inner and outer plexiform layers, with extension of the hyperreflectivity into the ganglion cell and inner nuclear layers. Spectral domain optical coherence tomography angiography demonstrated arteriolar and capillary dropout, more pronounced in the superficial retinal layer compared to the deeper retinal layer. At 1-month follow-up, his scotoma improved with monitoring, with reduction from -32 dB to -7 dB on Humphrey visual field testing. There was clinical resolution of the area of graying and decreased hyperreflectivity on spectral domain optical coherence tomography, with atrophy of the inner retina. Spectral domain optical coherence tomography angiography showed progression of arteriolar and capillary dropout, more so in the superficial than in the deep capillary plexus. We describe a case of small artery occlusion in a previously healthy patient, 4 days after vaccination against N. meningitidis and yellow fever. Fluorescein angiography yielded greater diagnostic value than OCTA for evaluating the occlusion, whereas spectral domain optical coherence tomography angiography enabled better visualization of capillary dropout and layer-specific assessment. Further research is required to determine whether vaccination in general, or directed specifically at N. meningitidis or yellow fever, is associated with small vessel vasculopathy and the underlying pathogenesis.

One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy

NASA Astrophysics Data System (ADS)

Sahoo, Prasana K.; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R.

2018-01-01

Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the junctions. Our new approach offers greater flexibility and control than previous methods for continuous growth of transition-metal-dichalcogenide-based multi-junction lateral heterostructures. These findings could be extended to other families of two-dimensional materials, and establish a foundation for the development of complex and atomically thin in-plane superlattices, devices and integrated circuits.

UTILIZATION OF FUNDUS AUTOFLUORESCENCE, SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY, AND ENHANCED DEPTH IMAGING IN THE CHARACTERIZATION OF BIETTI CRYSTALLINE DYSTROPHY IN DIFFERENT STAGES.

PubMed

Li, Qian; Li, Yang; Zhang, Xiaohui; Xu, Zhangxing; Zhu, Xiaoqing; Ma, Kai; She, Haicheng; Peng, Xiaoyan

2015-10-01

To characterize Bietti crystalline dystrophy (BCD) in different stages using multiple imaging modalities. Sixteen participants clinically diagnosed as BCD were included in the retrospective study and were categorized into 3 stages according to fundus photography. Eleven patients were genetically confirmed. Fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging features of BCD were analyzed. On fundus autofluorescence, the abnormal autofluorescence was shown to enlarge in area and decrease in intensity with stages. Using spectral domain optical coherence tomography, the abnormalities in Stage 1 were observed to localize in outer retinal layers, whereas in Stage 2 and Stage 3, more extensive retinal atrophy was seen. In enhanced depth imaging, the subfoveal choroidal layers were delineated clearly in Stage 1; in Stage 2, destructions were primarily found in the choriocapillaris with associated alterations in the outer vessels; Stage 3 BCD displayed severe choroidal thinning. Choroidal neovascularization and macular edema were exhibited with high incidence. IVS6-8del17bp/inGC of the CYP4V2 gene was the most common mutant allele. Noninvasive fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging may help to characterize the chorioretinal pathology of BCD at different degrees, and therefore, we propose staging of BCD depending on those methods. Physicians should be cautious of the vision-threatening complications of the disease.

MULTIMODAL IMAGING OF DISEASE-ASSOCIATED PIGMENTARY CHANGES IN RETINITIS PIGMENTOSA.

PubMed

Schuerch, Kaspar; Marsiglia, Marcela; Lee, Winston; Tsang, Stephen H; Sparrow, Janet R

2016-12-01

Using multiple imaging modalities, we evaluated the changes in photoreceptor cells and retinal pigment epithelium (RPE) that are associated with bone spicule-shaped melanin pigmentation in retinitis pigmentosa. In a cohort of 60 patients with retinitis pigmentosa, short-wavelength autofluorescence, near-infrared autofluorescence (NIR-AF), NIR reflectance, spectral domain optical coherence tomography, and color fundus images were studied. Central AF rings were visible in both short-wavelength autofluorescence and NIR-AF images. Bone spicule pigmentation was nonreflective in NIR reflectance, hypoautofluorescent with short-wavelength autofluorescence and NIR-AF imaging, and presented as intraretinal hyperreflective foci in spectral domain optical coherence tomography images. In areas beyond the AF ring outer border, the photoreceptor ellipsoid zone band was absent in spectral domain optical coherence tomography and the visibility of choroidal vessels in short-wavelength autofluorescence, NIR-AF, and NIR reflectance images was indicative of reduced RPE pigmentation. Choroidal visibility was most pronounced in the zone approaching peripheral areas of bone spicule pigmentation; here RPE/Bruch membrane thinning became apparent in spectral domain optical coherence tomography. These findings are consistent with a process by which RPE cells vacate their monolayer and migrate into inner retina in response to photoreceptor cell degeneration. The remaining RPE spread undergo thinning and consequently become less pigmented. An explanation for the absence of NIR-AF melanin signal in relation to bone spicule pigmentation is not forthcoming.

Optimization Strategies for Bruch's Membrane Opening Minimum Rim Area Calculation: Sequential versus Simultaneous Minimization.

PubMed

Enders, Philip; Adler, Werner; Schaub, Friederike; Hermann, Manuel M; Diestelhorst, Michael; Dietlein, Thomas; Cursiefen, Claus; Heindl, Ludwig M

2017-10-24

To compare a simultaneously optimized continuous minimum rim surface parameter between Bruch's membrane opening (BMO) and the internal limiting membrane to the standard sequential minimization used for calculating the BMO minimum rim area in spectral domain optical coherence tomography (SD-OCT). In this case-control, cross-sectional study, 704 eyes of 445 participants underwent SD-OCT of the optic nerve head (ONH), visual field testing, and clinical examination. Globally and clock-hour sector-wise optimized BMO-based minimum rim area was calculated independently. Outcome parameters included BMO-globally optimized minimum rim area (BMO-gMRA) and sector-wise optimized BMO-minimum rim area (BMO-MRA). BMO area was 1.89 ± 0.05 mm 2 . Mean global BMO-MRA was 0.97 ± 0.34 mm 2 , mean global BMO-gMRA was 1.01 ± 0.36 mm 2 . Both parameters correlated with r = 0.995 (P < 0.001); mean difference was 0.04 mm 2 (P < 0.001). In all sectors, parameters differed by 3.0-4.2%. In receiver operating characteristics, the calculated area under the curve (AUC) to differentiate glaucoma was 0.873 for BMO-MRA, compared to 0.866 for BMO-gMRA (P = 0.004). Among ONH sectors, the temporal inferior location showed the highest AUC. Optimization strategies to calculate BMO-based minimum rim area led to significantly different results. Imposing an additional adjacency constraint within calculation of BMO-MRA does not improve diagnostic power. Global and temporal inferior BMO-MRA performed best in differentiating glaucoma patients.

Spectral line-by-line pulse shaping of on-chip microresonator frequency combs

NASA Astrophysics Data System (ADS)

Ferdous, Fahmida; Miao, Houxun; Leaird, Daniel E.; Srinivasan, Kartik; Wang, Jian; Chen, Lei; Varghese, Leo Tom; Weiner, Andrew M.

2011-12-01

Recently, on-chip comb generation methods based on nonlinear optical modulation in ultrahigh-quality-factor monolithic microresonators have been demonstrated, where two pump photons are transformed into sideband photons in a four-wave-mixing process mediated by Kerr nonlinearity. Here, we investigate line-by-line pulse shaping of such combs generated in silicon nitride ring resonators. We observe two distinct paths to comb formation that exhibit strikingly different time-domain behaviours. For combs formed as a cascade of sidebands spaced by a single free spectral range that spread from the pump, we are able to compress stably to nearly bandwidth-limited pulses. This indicates high coherence across the spectra and provides new data on the high passive stability of the spectral phase. For combs where the initial sidebands are spaced by multiple free spectral ranges that then fill in to give combs with single free-spectral-range spacing, the time-domain data reveal partially coherent behaviour.

Combining near-field scanning optical microscopy with spectral interferometry for local characterization of the optical electric field in photonic structures.

PubMed

Trägårdh, Johanna; Gersen, Henkjan

2013-07-15

We show how a combination of near-field scanning optical microscopy with crossed beam spectral interferometry allows a local measurement of the spectral phase and amplitude of light propagating in photonic structures. The method only requires measurement at the single point of interest and at a reference point, to correct for the relative phase of the interferometer branches, to retrieve the dispersion properties of the sample. Furthermore, since the measurement is performed in the spectral domain, the spectral phase and amplitude could be retrieved from a single camera frame, here in 70 ms for a signal power of less than 100 pW limited by the dynamic range of the 8-bit camera. The method is substantially faster than most previous time-resolved NSOM methods that are based on time-domain interferometry, which also reduced problems with drift. We demonstrate how the method can be used to measure the refractive index and group velocity in a waveguide structure.

In-vivo assessment of microvascular functional dynamics by combination of cmOCT and wavelet transform

NASA Astrophysics Data System (ADS)

Smirni, Salvatore; MacDonald, Michael P.; Robertson, Catherine P.; McNamara, Paul M.; O'Gorman, Sean; Leahy, Martin J.; Khan, Faisel

2018-02-01

The cutaneous microcirculation represents an index of the health status of the cardiovascular system. Conventional methods to evaluate skin microvascular function are based on measuring blood flow by laser Doppler in combination with reactive tests such as post-occlusive reactive hyperaemia (PORH). Moreover, the spectral analysis of blood flow signals by continuous wavelet transform (CWT) reveals nonlinear oscillations reflecting the functionality of microvascular biological factors, e.g. endothelial cells (ECs). Correlation mapping optical coherence tomography (cmOCT) has been previously described as an efficient methodology for the morphological visualisation of cutaneous micro-vessels. Here, we show that cmOCT flow maps can also provide information on the functional components of the microcirculation. A spectral domain optical coherence tomography (SD-OCT) imaging system was used to acquire 90 sequential 3D OCT volumes from the forearm of a volunteer, while challenging the micro-vessels with a PORH test. The volumes were sampled in a temporal window of 25 minutes, and were processed by cmOCT to obtain flow maps at different tissue depths. The images clearly show changes of flow in response to the applied stimulus. Furthermore, a blood flow signal was reconstructed from cmOCT maps intensities to investigate the microvascular nonlinear dynamics by CWT. The analysis revealed oscillations changing in response to PORH, associated with the activity of ECs and the sympathetic innervation. The results demonstrate that cmOCT may be potentially used as diagnostic tool for the assessment of microvascular function, with the advantage of also providing spatial resolution and structural information compared to the traditional laser Doppler techniques.

Evaluation of Central Macular Thickness and Retinal Nerve Fiber Layer Thickness using Spectral Domain Optical Coherence Tomography in a Tertiary Care Hospital

PubMed Central

Saini, VK; Gupta, Saroj; Sharma, Anjali

2014-01-01

ABSTRACT Purpose: To evaluate the normative data of macular thickness and retinal nerve fiber layer thickness (RNFL) among normal subjects using spectral domain optical coherence tomography (OCT). Materials and methods: Normal subjects presenting to a tertiary medical hospital were included in the study. All patient underwent clinical examination followed by study of macular thickness and RN FL thick ness by spectral domain Topc on OCT. The data was collected and analyzed for variations in gender and age. The data was also compared with available literature. Results: Total numbers of patients enrolled in the study were 154 (308 eyes). Numbers of males were 79 (158 eyes) and numbers of females were 75 (150 eyes). The mean age among males was 42.67 ± 12.15 years and mean age among females was 42.88 ± 11.73 years. Overall the mean mac ular thickness (central 1 mm zone) with SD - OCT was 241.75 ± 17.3 microns. The mean macular volume was 7.6 cu. mm ± 0.33. On analysis of the RNFL thickness, we observed that the RNFL was thickest in the inferior quadrant (138.58) followed by superior (122.30) nasal (116.32) and temporal quadrant (73.04). Gender-wise comparison of the data revealed no statistically significant difference for age, macular thickness parameters, volume and RFNL values except outer temporal thickness among males and females. No age-related difference was noted in the above parameters. On comparison with available norma tive data from India and elsewhere, we found significant variations with different machines. Conclusion: The study is the first to provide normative data using SD-OCT from central India. The data from spectral domain OCT correlated well with the values obtained from similar studies with SD - OCT. Values obtained from time domain OCT machines are different and are not comparable. How to cite this article: Agarwal P, Saini VK, Gupta S, Sharma A. Evaluation of Central Macular Thickness and Retinal Nerve Fiber Layer Thickness using Spectral Domain Optical Coherence Tomography in a Tertiary Care Hospital. J Curr Glaucoma Pract 2014;8(2):75-81. PMID:26997813

Structure-function relationships using spectral-domain optical coherence tomography: comparison with scanning laser polarimetry.

PubMed

Aptel, Florent; Sayous, Romain; Fortoul, Vincent; Beccat, Sylvain; Denis, Philippe

2010-12-01

To evaluate and compare the regional relationships between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness as measured by spectral-domain optical coherence tomography (OCT) and scanning laser polarimetry. Prospective cross-sectional study. One hundred and twenty eyes of 120 patients (40 with healthy eyes, 40 with suspected glaucoma, and 40 with glaucoma) were tested on Cirrus-OCT, GDx VCC, and standard automated perimetry. Raw data on RNFL thickness were extracted for 256 peripapillary sectors of 1.40625 degrees each for the OCT measurement ellipse and 64 peripapillary sectors of 5.625 degrees each for the GDx VCC measurement ellipse. Correlations between peripapillary RNFL thickness in 6 sectors and visual field sensitivity in the 6 corresponding areas were evaluated using linear and logarithmic regression analysis. Receiver operating curve areas were calculated for each instrument. With spectral-domain OCT, the correlations (r(2)) between RNFL thickness and visual field sensitivity ranged from 0.082 (nasal RNFL and corresponding visual field area, linear regression) to 0.726 (supratemporal RNFL and corresponding visual field area, logarithmic regression). By comparison, with GDx-VCC, the correlations ranged from 0.062 (temporal RNFL and corresponding visual field area, linear regression) to 0.362 (supratemporal RNFL and corresponding visual field area, logarithmic regression). In pairwise comparisons, these structure-function correlations were generally stronger with spectral-domain OCT than with GDx VCC and with logarithmic regression than with linear regression. The largest areas under the receiver operating curve were seen for OCT superior thickness (0.963 ± 0.022; P < .001) in eyes with glaucoma and for OCT average thickness (0.888 ± 0.072; P < .001) in eyes with suspected glaucoma. The structure-function relationship was significantly stronger with spectral-domain OCT than with scanning laser polarimetry, and was better expressed logarithmically than linearly. Measurements with these 2 instruments should not be considered to be interchangeable. Copyright © 2010 Elsevier Inc. All rights reserved.

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains

PubMed Central

Kowialiewski, Benjamin; Majerus, Steve

2016-01-01

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes. PMID:27992565

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains.

PubMed

Gorin, Simon; Kowialiewski, Benjamin; Majerus, Steve

2016-01-01

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

Heart rate and heart rate variability response to the transpiration of vortex-water by Begonia Eliator plants to the air in an office during visual display terminal work.

PubMed

Johansson, Benny

2008-10-01

This study explores the effects of vortex-water transpired from indoor greenery to office air, in relation to heart rate and heart rate variability during exposure to an electromagnetic field (EMF) from a visual display terminal (VDT). The study followed a randomized prospective single group cross-over design. Fifty (50) healthy volunteers, seated in any ordinary working posture in front of a VDT. Electrocardiography was measured in five 10-minute sequential tests. The VDT was turned off during the first test and switched on for the subsequent four tests. During tests 3 and 4, one of two Begonia Eliator plants, irrigated with either tap water or vortex-rotated (active) tap water during growth, was placed adjacent to the VDT. Heart rate, heart rate variability (HRV) and power spectral density (PSD) were analyzed. The heart rate was unchanged at the start of EMF exposure. The time domain measurements indicated a significant decrease in heart rate and a significant increase in HRV, accompanied by higher vagal tone in the presence, and finally in the absence, of the active plant. PSD parameters revealed significantly higher total power, as well as an increase in low frequencies (LF) and high frequencies (HF) in the condition induced by the active plant as well as after its removal. Very low frequencies (VLF) increased at EMF exposure whereas normally HF power decreased, accompanied by a rise in LF power and LF/HF ratio. HF power was higher at exposure to the active compared to the control plant. Spectral power density diagrams revealed an intensified spectral power band at frequencies of around 0.1 Hz at the condition of both plants, indicating systemic autonomic stability. The findings suggest that the parasympathetic response was associated with reduced heart rate, implicating restoration and maintenance of metabolic energy resources mediated by an involuntary adaptation to active plant-related stimuli.

Determining the von Mises stress power spectral density for frequency domain fatigue analysis including out-of-phase stress components

NASA Astrophysics Data System (ADS)

Bonte, M. H. A.; de Boer, A.; Liebregts, R.

2007-04-01

This paper provides a new formula to take into account phase differences in the determination of an equivalent von Mises stress power spectral density (PSD) from multiple random inputs. The obtained von Mises PSD can subsequently be used for fatigue analysis. The formula was derived for use in the commercial vehicle business and was implemented in combination with Finite Element software to predict and analyse fatigue failure in the frequency domain.

Improvement of lateral resolution of spectral domain optical coherence tomography images in out-of-focus regions with holographic data processing techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moiseev, A A; Gelikonov, G V; Terpelov, D A

2014-08-31

An analogy between spectral-domain optical coherence tomography (SD OCT) data and broadband digital holography data is considered. Based on this analogy, a method for processing SD OCT data, which makes it possible to construct images with a lateral resolution in the whole investigated volume equal to the resolution in the in-focus region, is developed. Several issues concerning practical application of the proposed method are discussed. (laser biophotonics)

Analysis of multimode fiber bundles for endoscopic spectral-domain optical coherence tomography

PubMed Central

Risi, Matthew D.; Makhlouf, Houssine; Rouse, Andrew R.; Gmitro, Arthur F.

2016-01-01

A theoretical analysis of the use of a fiber bundle in spectral-domain optical coherence tomography (OCT) systems is presented. The fiber bundle enables a flexible endoscopic design and provides fast, parallelized acquisition of the OCT data. However, the multimode characteristic of the fibers in the fiber bundle affects the depth sensitivity of the imaging system. A description of light interference in a multimode fiber is presented along with numerical simulations and experimental studies to illustrate the theoretical analysis. PMID:25967012

Domain Decomposition By the Advancing-Partition Method for Parallel Unstructured Grid Generation

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.; Zagaris, George

2009-01-01

A new method of domain decomposition has been developed for generating unstructured grids in subdomains either sequentially or using multiple computers in parallel. Domain decomposition is a crucial and challenging step for parallel grid generation. Prior methods are generally based on auxiliary, complex, and computationally intensive operations for defining partition interfaces and usually produce grids of lower quality than those generated in single domains. The new technique, referred to as "Advancing Partition," is based on the Advancing-Front method, which partitions a domain as part of the volume mesh generation in a consistent and "natural" way. The benefits of this approach are: 1) the process of domain decomposition is highly automated, 2) partitioning of domain does not compromise the quality of the generated grids, and 3) the computational overhead for domain decomposition is minimal. The new method has been implemented in NASA's unstructured grid generation code VGRID.

Domain Decomposition By the Advancing-Partition Method

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.

2008-01-01

A new method of domain decomposition has been developed for generating unstructured grids in subdomains either sequentially or using multiple computers in parallel. Domain decomposition is a crucial and challenging step for parallel grid generation. Prior methods are generally based on auxiliary, complex, and computationally intensive operations for defining partition interfaces and usually produce grids of lower quality than those generated in single domains. The new technique, referred to as "Advancing Partition," is based on the Advancing-Front method, which partitions a domain as part of the volume mesh generation in a consistent and "natural" way. The benefits of this approach are: 1) the process of domain decomposition is highly automated, 2) partitioning of domain does not compromise the quality of the generated grids, and 3) the computational overhead for domain decomposition is minimal. The new method has been implemented in NASA's unstructured grid generation code VGRID.

MURI: Adaptive Waveform Design for Full Spectral Dominance

DTIC Science & Technology

2011-03-11

a three- dimensional urban tracking model, based on the nonlinear measurement model (that uses the urban multipath geometry with different types of ... the time evolution of the scattering function with a high dimensional dynamic system; a multiple particle filter technique is used to sequentially...integration of space -time coding with a fixed set of beams. It complements the

Novel full-spectral flow cytometry with multiple spectrally-adjacent fluorescent proteins and fluorochromes and visualization of in vivo cellular movement.

PubMed

Futamura, Koji; Sekino, Masashi; Hata, Akihiro; Ikebuchi, Ryoyo; Nakanishi, Yasutaka; Egawa, Gyohei; Kabashima, Kenji; Watanabe, Takeshi; Furuki, Motohiro; Tomura, Michio

2015-09-01

Flow cytometric analysis with multicolor fluoroprobes is an essential method for detecting biological signatures of cells. Here, we present a new full-spectral flow cytometer (spectral-FCM). Unlike conventional flow cytometer, this spectral-FCM acquires the emitted fluorescence for all probes across the full-spectrum from each cell with 32 channels sequential PMT unit after dispersion with prism, and extracts the signals of each fluoroprobe based on the spectral shape of each fluoroprobe using unique algorithm in high speed, high sensitive, accurate, automatic and real-time. The spectral-FCM detects the continuous changes in emission spectra from green to red of the photoconvertible protein, KikGR with high-spectral resolution and separates spectrally-adjacent fluoroprobes, such as FITC (Emission peak (Em) 519 nm) and EGFP (Em 507 nm). Moreover, the spectral-FCM can measure and subtract autofluorescence of each cell providing increased signal-to-noise ratios and improved resolution of dim samples, which leads to a transformative technology for investigation of single cell state and function. These advances make it possible to perform 11-color fluorescence analysis to visualize movement of multilinage immune cells by using KikGR-expressing mice. Thus, the novel spectral flow cytometry improves the combinational use of spectrally-adjacent various FPs and multicolor fluorochromes in metabolically active cell for the investigation of not only the immune system but also other research and clinical fields of use. © 2015 International Society for Advancement of Cytometry.

Model Order Reduction Algorithm for Estimating the Absorption Spectrum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Beeumen, Roel; Williams-Young, David B.; Kasper, Joseph M.

The ab initio description of the spectral interior of the absorption spectrum poses both a theoretical and computational challenge for modern electronic structure theory. Due to the often spectrally dense character of this domain in the quantum propagator’s eigenspectrum for medium-to-large sized systems, traditional approaches based on the partial diagonalization of the propagator often encounter oscillatory and stagnating convergence. Electronic structure methods which solve the molecular response problem through the solution of spectrally shifted linear systems, such as the complex polarization propagator, offer an alternative approach which is agnostic to the underlying spectral density or domain location. This generality comesmore » at a seemingly high computational cost associated with solving a large linear system for each spectral shift in some discretization of the spectral domain of interest. In this work, we present a novel, adaptive solution to this high computational overhead based on model order reduction techniques via interpolation. Model order reduction reduces the computational complexity of mathematical models and is ubiquitous in the simulation of dynamical systems and control theory. The efficiency and effectiveness of the proposed algorithm in the ab initio prediction of X-ray absorption spectra is demonstrated using a test set of challenging water clusters which are spectrally dense in the neighborhood of the oxygen K-edge. On the basis of a single, user defined tolerance we automatically determine the order of the reduced models and approximate the absorption spectrum up to the given tolerance. We also illustrate that, for the systems studied, the automatically determined model order increases logarithmically with the problem dimension, compared to a linear increase of the number of eigenvalues within the energy window. Furthermore, we observed that the computational cost of the proposed algorithm only scales quadratically with respect to the problem dimension.« less

Topographic gravity modeling for global Bouguer maps to degree 2160: Validation of spectral and spatial domain forward modeling techniques at the 10 microGal level

NASA Astrophysics Data System (ADS)

Hirt, Christian; Reußner, Elisabeth; Rexer, Moritz; Kuhn, Michael

2016-09-01

Over the past years, spectral techniques have become a standard to model Earth's global gravity field to 10 km scales, with the EGM2008 geopotential model being a prominent example. For some geophysical applications of EGM2008, particularly Bouguer gravity computation with spectral techniques, a topographic potential model of adequate resolution is required. However, current topographic potential models have not yet been successfully validated to degree 2160, and notable discrepancies between spectral modeling and Newtonian (numerical) integration well beyond the 10 mGal level have been reported. Here we accurately compute and validate gravity implied by a degree 2160 model of Earth's topographic masses. Our experiments are based on two key strategies, both of which require advanced computational resources. First, we construct a spectrally complete model of the gravity field which is generated by the degree 2160 Earth topography model. This involves expansion of the topographic potential to the 15th integer power of the topography and modeling of short-scale gravity signals to ultrahigh degree of 21,600, translating into unprecedented fine scales of 1 km. Second, we apply Newtonian integration in the space domain with high spatial resolution to reduce discretization errors. Our numerical study demonstrates excellent agreement (8 μGgal RMS) between gravity from both forward modeling techniques and provides insight into the convergence process associated with spectral modeling of gravity signals at very short scales (few km). As key conclusion, our work successfully validates the spectral domain forward modeling technique for degree 2160 topography and increases the confidence in new high-resolution global Bouguer gravity maps.

Spectral Domain RF Fingerprinting for 802.11 Wireless Devices

DTIC Science & Technology

2010-03-01

induce unintentional modulation effects . If these effects (features) are sufficiently unique, it becomes possible to identify a device us- ing its...Previous AFIT research has demonstrated the effectiveness of RF Fin- gerprinting using 802.11A signals with 1) spectral correlation on Power Spectral...32 4.5. SD Intra-manufacturer Classification: Effects of Burst Location Error

The spectral cell method in nonlinear earthquake modeling

NASA Astrophysics Data System (ADS)

Giraldo, Daniel; Restrepo, Doriam

2017-12-01

This study examines the applicability of the spectral cell method (SCM) to compute the nonlinear earthquake response of complex basins. SCM combines fictitious-domain concepts with the spectral-version of the finite element method to solve the wave equations in heterogeneous geophysical domains. Nonlinear behavior is considered by implementing the Mohr-Coulomb and Drucker-Prager yielding criteria. We illustrate the performance of SCM with numerical examples of nonlinear basins exhibiting physically and computationally challenging conditions. The numerical experiments are benchmarked with results from overkill solutions, and using MIDAS GTS NX, a finite element software for geotechnical applications. Our findings show good agreement between the two sets of results. Traditional spectral elements implementations allow points per wavelength as low as PPW = 4.5 for high-order polynomials. Our findings show that in the presence of nonlinearity, high-order polynomials (p ≥ 3) require mesh resolutions above of PPW ≥ 10 to ensure displacement errors below 10%.

Estimation of Soil Moisture Content from the Spectral Reflectance of Bare Soils in the 0.4–2.5 μm Domain

PubMed Central

Fabre, Sophie; Briottet, Xavier; Lesaignoux, Audrey

2015-01-01

This work aims to compare the performance of new methods to estimate the Soil Moisture Content (SMC) of bare soils from their spectral signatures in the reflective domain (0.4–2.5 μm) in comparison with widely used spectral indices like Normalized Soil Moisture Index (NSMI) and Water Index SOIL (WISOIL). Indeed, these reference spectral indices use wavelengths located in the water vapour absorption bands and their performance are thus very sensitive to the quality of the atmospheric compensation. To reduce these limitations, two new spectral indices are proposed which wavelengths are defined using the determination matrix tool by taking into account the atmospheric transmission: Normalized Index of Nswir domain for Smc estimatiOn from Linear correlation (NINSOL) and Normalized Index of Nswir domain for Smc estimatiOn from Non linear correlation (NINSON). These spectral indices are completed by two new methods based on the global shape of the soil spectral signatures. These methods are the Inverse Soil semi-Empirical Reflectance model (ISER), using the inversion of an existing empirical soil model simulating the soil spectral reflectance according to soil moisture content for a given soil class, and the convex envelope model, linking the area between the envelope and the spectral signature to the SMC. All these methods are compared using a reference database built with 32 soil samples and composed of 190 spectral signatures with five or six soil moisture contents. Half of the database is used for the calibration stage and the remaining to evaluate the performance of the SMC estimation methods. The results show that the four new methods lead to similar or better performance than the one obtained by the reference indices. The RMSE is ranging from 3.8% to 6.2% and the coefficient of determination R2 varies between 0.74 and 0.91 with the best performance obtained with the ISER model. In a second step, simulated spectral radiances at the sensor level are used to analyse the sensitivity of these methods to the sensor spectral resolution and the water vapour content knowledge. The spectral signatures of the database are then used to simulate the signal at the top of atmosphere with a radiative transfer model and to compute the integrated incident signal representing the spectral radiance measurements of the HYMAP airborne hyperspectral instrument. The sensor radiances are then corrected from the atmosphere by an atmospheric compensation tool to retrieve the surface reflectances. The SMC estimation methods are then applied on the retrieve spectral reflectances. The adaptation of the spectral index wavelengths to the HyMap sensor spectral bands and the application of the convex envelope and ISER models to boarder spectral bands lead to an error on the SMC estimation. The best performance is then obtained with the ISER model (RMSE of 2.9% and R2 of 0.96) while the four other methods lead to quite similar RMSE (from 6.4% to 7.8%) and R2 (between 0.79 and 0.83) values. In the atmosphere compensation processing, an error on the water vapour content is introduced. The most robust methods to water vapour content variations are WISOIL, NINSON, NINSOL and ISER model. The convex envelope model and NSMI index require an accurate estimation of the water vapour content in the atmosphere. PMID:25648710

A novel Pareto-based Bayesian approach on extension of the infogram for extracting repetitive transients

NASA Astrophysics Data System (ADS)

Gu, Xiaohui; Yang, Shaopu; Liu, Yongqiang; Hao, Rujiang

2018-06-01

Two most important signatures of repetitive transients in the vibration signals of a faulty rotating machine are impulsiveness and cyclostationarity. In the newly proposed infogram, the time-domain and frequency-domain spectral negentropy were put forward to characterize these two aspects, respectively. However, in extension of the infogram to Bayesian inference based optimal wavelet filtering, only one spectral negentropy was employed in identifying the informative frequency band. To overcome its drawback, a novel Pareto-based Bayesian approach was proposed in this paper. The Pareto optimal solutions which can simultaneously maximize the time-domain and frequency-domain spectral negentropy were utilized in estimating the posterior wavelet parameters distributions. Moreover, the relationship between the impulsive and cyclostationary signatures was established by the domination. It can help balance the contributions due to these two aspects other than simply synthesize by the average weight in the infogram. Three instance studies including simulated and experimental signals were investigated to illustrate the effectiveness of the proposed method by challenging different noises and interferences. In addition, some comparisons with the aforementioned peer methods were also conducted to show its superiority and robustness in extracting the repetitive transients.

Defining the spectral and amplitude domain of music---a window into audio

NASA Astrophysics Data System (ADS)

Nam, Myoung W.

In terms of 'visualizing music', this thesis presents the first critical measurements for the selected musical instruments (piano, violin, cello, flute, piccolo, drums, double bass, electric bass, and electric guitar) seeking to describe their place in the spectral and amplitude domain. All data presented as a part of this research were measured with Z-weighting (un-weighted) from 12.5Hz to 20kHz along the frequency axis, in 1/3 octave bands, evaluated statistically and in equivalent sound level. Measuring musical performances can be a very subjective process. Therefore, this research proceeded under some strategically chosen conditions and limitations. The measurements were made with each musician playing at several different intensities of musical performance. Chosen musical genres were classical, pop and jazz for the selected musical instruments. To obtain data representative of real world conditions, musical instrument measurements were made mostly in professional recording studios by professional players. The results seek to define the spectral and amplitude domain occupied by these instruments when playing typical works.

RETINAL DEEP CAPILLARY ISCHEMIA ASSOCIATED WITH AN OCCLUDED CONGENITAL RETINAL MACROVESSEL.

PubMed

Hasegawa, Taiji; Ogata, Nahoko

2017-01-01

To report the case of a patient with an occluded congenital retinal macrovessel accompanied by retinal deep capillary ischemia. A 38-year-old woman presented with a 2-day history of a paracentral scotoma of her right eye. Fundus photograph showed a dilated congenital retinal macrovessel with arteriovenous anastomosis, an intravascular white region indicating the thrombus at arteriovenous anastomotic region, and an area of retinal whitening temporal to the fovea. The spectral domain optical coherence tomography images through the area of retinal whitening showed a thickening and highly reflectivity at the level of the inner nuclear layer, which is likely due to the deep capillary ischemia. After 6 weeks, spectral domain optical coherence tomography images through the same area demonstrated a thinning and atrophy of only the inner nuclear layer, and the patient's paracentral scotoma persisted. Acute capillary hemodynamic changes caused deep capillary ischemia. The spectral domain optical coherence tomography showed a highly reflective lesion at the level of the inner nuclear layer in the acute phase.

Increasing efficiency of preclinical research by group sequential designs

PubMed Central

Piper, Sophie K.; Rex, Andre; Florez-Vargas, Oscar; Karystianis, George; Schneider, Alice; Wellwood, Ian; Siegerink, Bob; Ioannidis, John P. A.; Kimmelman, Jonathan; Dirnagl, Ulrich

2017-01-01

Despite the potential benefits of sequential designs, studies evaluating treatments or experimental manipulations in preclinical experimental biomedicine almost exclusively use classical block designs. Our aim with this article is to bring the existing methodology of group sequential designs to the attention of researchers in the preclinical field and to clearly illustrate its potential utility. Group sequential designs can offer higher efficiency than traditional methods and are increasingly used in clinical trials. Using simulation of data, we demonstrate that group sequential designs have the potential to improve the efficiency of experimental studies, even when sample sizes are very small, as is currently prevalent in preclinical experimental biomedicine. When simulating data with a large effect size of d = 1 and a sample size of n = 18 per group, sequential frequentist analysis consumes in the long run only around 80% of the planned number of experimental units. In larger trials (n = 36 per group), additional stopping rules for futility lead to the saving of resources of up to 30% compared to block designs. We argue that these savings should be invested to increase sample sizes and hence power, since the currently underpowered experiments in preclinical biomedicine are a major threat to the value and predictiveness in this research domain. PMID:28282371

Sequential and simultaneous choices: testing the diet selection and sequential choice models.

PubMed

Freidin, Esteban; Aw, Justine; Kacelnik, Alex

2009-03-01

We investigate simultaneous and sequential choices in starlings, using Charnov's Diet Choice Model (DCM) and Shapiro, Siller and Kacelnik's Sequential Choice Model (SCM) to integrate function and mechanism. During a training phase, starlings encountered one food-related option per trial (A, B or R) in random sequence and with equal probability. A and B delivered food rewards after programmed delays (shorter for A), while R ('rejection') moved directly to the next trial without reward. In this phase we measured latencies to respond. In a later, choice, phase, birds encountered the pairs A-B, A-R and B-R, the first implementing a simultaneous choice and the second and third sequential choices. The DCM predicts when R should be chosen to maximize intake rate, and SCM uses latencies of the training phase to predict choices between any pair of options in the choice phase. The predictions of both models coincided, and both successfully predicted the birds' preferences. The DCM does not deal with partial preferences, while the SCM does, and experimental results were strongly correlated to this model's predictions. We believe that the SCM may expose a very general mechanism of animal choice, and that its wider domain of success reflects the greater ecological significance of sequential over simultaneous choices.

Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles.

PubMed

Grewal, D S; Brar, G S; Jain, R; Grewal, S P S

2011-05-01

To compare the performance of anterior chamber volume (ACV) and anterior chamber depth (ACD) obtained using Scheimpflug imaging with angle opening distance (AOD500) and trabecular-iris space area (TISA500) obtained using spectral domain anterior segment optical coherence tomography (SD-ASOCT) in detecting narrow angles classified using gonioscopy. In this prospective, cross-sectional observational study, 265 eyes of 265 consecutive patients underwent sequential Scheimpflug imaging, SD-ASOCT imaging, and gonioscopy. Correlations between gonioscopy grading, ACV, ACD, AOD500, and TISA500 were evaluated. Area under receiver operating characteristic curve (AUC), sensitivity, specificity, and likelihood ratios (LRs) were calculated to assess the performance of ACV, ACD, AOD500, and TISA500 in detecting narrow angles (defined as Shaffer grade ≤1 in all quadrants). SD-ASOCT images were obtained at the nasal and temporal quadrants only. Twenty-eight eyes (10.6%) were classified as narrow angles on gonioscopy. ACV correlated with gonioscopy grading (P<0.001) for temporal (r=0.204), superior (r=0.251), nasal (r=0.213), and inferior (r=0.236) quadrants. ACV correlated with TISA500 for nasal (r=0.135, P=0.029) and temporal (P=0.160, P=0.009) quadrants and also with AOD500 for nasal (r=0.498, P<0.001) and temporal (r=0.517, P<0.001) quadrants. For detection of narrow angles, ACV (AUC=0.935; 95% confidence interval (CI) =0.898-0.961) performed similar to ACD (AUC=0.88, P=0.06) and significantly better than AOD500 nasal (AUC=0.761, P=0.001), AOD500 temporal (AUC=0.808, P<0.001), TISA500 nasal (AUC=0.756, P<0.001), and TISA500 temporal (AUC=0.738, P<0.001). Using a cutoff of 113 mm(3), ACV had 90% sensitivity and 88% specificity for detecting narrow angles. Positive and negative LRs for ACV were 8.63 (95% CI=7.4-10.0) and 0.11 (95% CI=0.03-0.4), respectively. ACV measurements using Scheimpflug imaging outperformed AOD500 and TISA500 using SD-ASOCT for detecting narrow angles.

Semi-empirical model for the assessment of railway ballast using GPR

NASA Astrophysics Data System (ADS)

Giulia Brancadoro, Maria; Benedetto, Andrea

2017-04-01

Over time, railways have become a very competitive mean of transportation, especially for long distances. In order to ensure high level of safety, comfort and regularity of transportation, an efficient maintenance of the railway track-bed is crucial. In fact, the cyclic loads passing on the rails produce a progressive deterioration of railway ballast beneath the sleepers, and a breakdown of its particles that causes a general decrease of railway performances. This work aims at proposing a semi-empirical model for the characterisation of railway ballast grading, through the spectral analysis of Ground-Penetrating Radar (GPR) signal. To this effect, a theoretical study has been preliminary conducted to investigate the propagation and scattering phenomena of the electromagnetic waves within a ballast layer. To confirm the theoretical assumptions, high-frequency GPR signals have been both collected in laboratory and virtual environment. Concerning the latter, progressively more complex numerical domains have been designed and subjected to synthetic GPR test, by a Finite Different Time Domain (FTDT) procedure, run in GPR Max 2D simulator. As first simulation steps, ballast aggregates simplified through circles have been accounted for, with increasing values of radius. Subsequently, real-scale scenarios characterized by multi-size ballast particles, consistent with three different grain size distribution from railway network standards, have been reproduced by the employment of Random Sequential Adsorption - RSA algorithm. As far as the laboratory procedures, real GPR tests have been carried out on an experimental framework purposely set up, and composed of a methacrylate tank filled up with limestone-derived railway ballast. The ballast aggregates grading has been retrieved by means of an automatic image analysis algorithm, run on the lateral sight of the transparent tank. Through their spectral analysis, an empirical relationship between the position of the amplitude peak in the spectra, and the size of ballast particles was retrieved. As a result, this work opens new perspectives in railway track-bed maintenance. Indeed, it allows at monitoring the progressive evolution of ballast fragmentation and pollution phenomena, non-destructively and without need for any calibration. Acknowledgements The Authors thank COST, for funding the Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar"

Index of learning styles in a u.s. School of pharmacy.

PubMed

Teevan, Colleen J; Li, Michael; Schlesselman, Lauren S

2011-04-01

The goal of this study was to assess for a predominance of learning styles among pharmacy students at an accredited U.S. school of pharmacy. Following approval by the Institutional Review Board, the Index of Learning Styles© was administered to 210 pharmacy students. The survey provides results within 4 domains: perception, input, processing, and understanding. Analyses were conducted to determine trends in student learning styles. Within the four domains, 84% of students showed a preference toward sensory perception, 66% toward visual input, and 74% toward sequential understanding. Students showed no significant preference for active or reflective processing. Preferences were of moderate strength for the sensing, visual, and sequential learning styles. Students showed preferences for sensing, visual, and sequential learning styles with gender playing a role in learning style preferences. Faculty should be aware, despite some preferences, a mix of learning styles exists. To focus on the preferences found, instructors should focus teaching in a logical progression while adding visual aids. To account for other types of learning styles found, the instructors can offer other approaches and provide supplemental activities for those who would benefit from them. Further research is necessary to compare these learning styles to the teaching styles of pharmacy preceptors and faculty at schools of pharmacy.

Multi-objective design optimization of antenna structures using sequential domain patching with automated patch size determination

NASA Astrophysics Data System (ADS)

Koziel, Slawomir; Bekasiewicz, Adrian

2018-02-01

In this article, a simple yet efficient and reliable technique for fully automated multi-objective design optimization of antenna structures using sequential domain patching (SDP) is discussed. The optimization procedure according to SDP is a two-step process: (i) obtaining the initial set of Pareto-optimal designs representing the best possible trade-offs between considered conflicting objectives, and (ii) Pareto set refinement for yielding the optimal designs at the high-fidelity electromagnetic (EM) simulation model level. For the sake of computational efficiency, the first step is realized at the level of a low-fidelity (coarse-discretization) EM model by sequential construction and relocation of small design space segments (patches) in order to create a path connecting the extreme Pareto front designs obtained beforehand. The second stage involves response correction techniques and local response surface approximation models constructed by reusing EM simulation data acquired in the first step. A major contribution of this work is an automated procedure for determining the patch dimensions. It allows for appropriate selection of the number of patches for each geometry variable so as to ensure reliability of the optimization process while maintaining its low cost. The importance of this procedure is demonstrated by comparing it with uniform patch dimensions.

Likelihood Ratios for Glaucoma Diagnosis Using Spectral Domain Optical Coherence Tomography

PubMed Central

Lisboa, Renato; Mansouri, Kaweh; Zangwill, Linda M.; Weinreb, Robert N.; Medeiros, Felipe A.

2014-01-01

Purpose To present a methodology for calculating likelihood ratios for glaucoma diagnosis for continuous retinal nerve fiber layer (RNFL) thickness measurements from spectral domain optical coherence tomography (spectral-domain OCT). Design Observational cohort study. Methods 262 eyes of 187 patients with glaucoma and 190 eyes of 100 control subjects were included in the study. Subjects were recruited from the Diagnostic Innovations Glaucoma Study. Eyes with preperimetric and perimetric glaucomatous damage were included in the glaucoma group. The control group was composed of healthy eyes with normal visual fields from subjects recruited from the general population. All eyes underwent RNFL imaging with Spectralis spectral-domain OCT. Likelihood ratios for glaucoma diagnosis were estimated for specific global RNFL thickness measurements using a methodology based on estimating the tangents to the Receiver Operating Characteristic (ROC) curve. Results Likelihood ratios could be determined for continuous values of average RNFL thickness. Average RNFL thickness values lower than 86μm were associated with positive LRs, i.e., LRs greater than 1; whereas RNFL thickness values higher than 86μm were associated with negative LRs, i.e., LRs smaller than 1. A modified Fagan nomogram was provided to assist calculation of post-test probability of disease from the calculated likelihood ratios and pretest probability of disease. Conclusion The methodology allowed calculation of likelihood ratios for specific RNFL thickness values. By avoiding arbitrary categorization of test results, it potentially allows for an improved integration of test results into diagnostic clinical decision-making. PMID:23972303

Time domain simulation of the response of geometrically nonlinear panels subjected to random loading

NASA Technical Reports Server (NTRS)

Moyer, E. Thomas, Jr.

1988-01-01

The response of composite panels subjected to random pressure loads large enough to cause geometrically nonlinear responses is studied. A time domain simulation is employed to solve the equations of motion. An adaptive time stepping algorithm is employed to minimize intermittent transients. A modified algorithm for the prediction of response spectral density is presented which predicts smooth spectral peaks for discrete time histories. Results are presented for a number of input pressure levels and damping coefficients. Response distributions are calculated and compared with the analytical solution of the Fokker-Planck equations. RMS response is reported as a function of input pressure level and damping coefficient. Spectral densities are calculated for a number of examples.

Rapid Sequential in Situ Multiplexing with DNA Exchange Imaging in Neuronal Cells and Tissues.

PubMed

Wang, Yu; Woehrstein, Johannes B; Donoghue, Noah; Dai, Mingjie; Avendaño, Maier S; Schackmann, Ron C J; Zoeller, Jason J; Wang, Shan Shan H; Tillberg, Paul W; Park, Demian; Lapan, Sylvain W; Boyden, Edward S; Brugge, Joan S; Kaeser, Pascal S; Church, George M; Agasti, Sarit S; Jungmann, Ralf; Yin, Peng

2017-10-11

To decipher the molecular mechanisms of biological function, it is critical to map the molecular composition of individual cells or even more importantly tissue samples in the context of their biological environment in situ. Immunofluorescence (IF) provides specific labeling for molecular profiling. However, conventional IF methods have finite multiplexing capabilities due to spectral overlap of the fluorophores. Various sequential imaging methods have been developed to circumvent this spectral limit but are not widely adopted due to the common limitation of requiring multirounds of slow (typically over 2 h at room temperature to overnight at 4 °C in practice) immunostaining. We present here a practical and robust method, which we call DNA Exchange Imaging (DEI), for rapid in situ spectrally unlimited multiplexing. This technique overcomes speed restrictions by allowing for single-round immunostaining with DNA-barcoded antibodies, followed by rapid (less than 10 min) buffer exchange of fluorophore-bearing DNA imager strands. The programmability of DEI allows us to apply it to diverse microscopy platforms (with Exchange Confocal, Exchange-SIM, Exchange-STED, and Exchange-PAINT demonstrated here) at multiple desired resolution scales (from ∼300 nm down to sub-20 nm). We optimized and validated the use of DEI in complex biological samples, including primary neuron cultures and tissue sections. These results collectively suggest DNA exchange as a versatile, practical platform for rapid, highly multiplexed in situ imaging, potentially enabling new applications ranging from basic science, to drug discovery, and to clinical pathology.

Lunar Infrared Spectrometer (LIS) for Luna-Resurs and Luna-Glob missions

NASA Astrophysics Data System (ADS)

Korablev, O.; Ivanov, A.; Mantsevich, S.; Kiselev, A.; Vyazovetskiy, N.; Fedorova, A.; Evdokimova, N.; Stepanov, A.; Titov, A.; Kalinnikov, Y.

2012-09-01

Lunar Infrared Spectrometer (LIS) is an experiment onboard Luna-Glob (launch in 2015) and Luna- Resurs (launch in 2017) Russian surface missions. The experiment is dedicated to the studies of mineralogy of the lunar regolith in the vicinity of the lander. The instrument is mounted on the mechanic arm of landing module in the field of view (45°) of stereo TV camera. LIS will provide measurements of selected surface region in the spectral range of 1.15-3.3 μm. The electrically commanded acousto-optic filter scans sequentially at a desired sampling, with random access, over the entire spectral range.

Analysis of hyperspectral fluorescence images for poultry skin tumor inspection

NASA Astrophysics Data System (ADS)

Kong, Seong G.; Chen, Yud-Ren; Kim, Intaek; Kim, Moon S.

2004-02-01

We present a hyperspectral fluorescence imaging system with a fuzzy inference scheme for detecting skin tumors on poultry carcasses. Hyperspectral images reveal spatial and spectral information useful for finding pathological lesions or contaminants on agricultural products. Skin tumors are not obvious because the visual signature appears as a shape distortion rather than a discoloration. Fluorescence imaging allows the visualization of poultry skin tumors more easily than reflectance. The hyperspectral image samples obtained for this poultry tumor inspection contain 65 spectral bands of fluorescence in the visible region of the spectrum at wavelengths ranging from 425 to 711 nm. The large amount of hyperspectral image data is compressed by use of a discrete wavelet transform in the spatial domain. Principal-component analysis provides an effective compressed representation of the spectral signal of each pixel in the spectral domain. A small number of significant features are extracted from two major spectral peaks of relative fluorescence intensity that have been identified as meaningful spectral bands for detecting tumors. A fuzzy inference scheme that uses a small number of fuzzy rules and Gaussian membership functions successfully detects skin tumors on poultry carcasses. Spatial-filtering techniques are used to significantly reduce false positives.

Tunable Fano resonance using weak-value amplification with asymmetric spectral response as a natural pointer

NASA Astrophysics Data System (ADS)

Singh, Ankit K.; Ray, Subir K.; Chandel, Shubham; Pal, Semanti; Gupta, Angad; Mitra, P.; Ghosh, N.

2018-05-01

Weak measurement enables faithful amplification and high-precision measurement of small physical parameters and is under intensive investigation as an effective tool in metrology and for addressing foundational questions in quantum mechanics. Here we demonstrate weak-value amplification using the asymmetric spectral response of Fano resonance as the pointer arising naturally in precisely designed metamaterials, namely, waveguided plasmonic crystals. The weak coupling between the polarization degree of freedom and the spectral response of Fano resonance arises due to a tiny shift in the asymmetric spectral response between two orthogonal linear polarizations. By choosing the preselected and postselected polarization states to be nearly mutually orthogonal, we observe both real and imaginary weak-value amplifications manifested as a spectacular shift of the Fano-resonance peak and narrowing (or broadening) of the resonance linewidth, respectively. The remarkable control and tunability of Fano resonance in a single device enabled by weak-value amplification may enhance active Fano-resonance-based applications in the nano-optical domain. In general, weak measurements using Fano-type spectral response broadens the domain of applicability of weak measurements using natural spectral line shapes as a pointer in a wide range of physical systems.

Perceptual Grouping Affects Pitch Judgments Across Time and Frequency

PubMed Central

Borchert, Elizabeth M. O.; Micheyl, Christophe; Oxenham, Andrew J.

2010-01-01

Pitch, the perceptual correlate of fundamental frequency (F0), plays an important role in speech, music and animal vocalizations. Changes in F0 over time help define musical melodies and speech prosody, while comparisons of simultaneous F0 are important for musical harmony, and for segregating competing sound sources. This study compared listeners’ ability to detect differences in F0 between pairs of sequential or simultaneous tones that were filtered into separate, non-overlapping spectral regions. The timbre differences induced by filtering led to poor F0 discrimination in the sequential, but not the simultaneous, conditions. Temporal overlap of the two tones was not sufficient to produce good performance; instead performance appeared to depend on the two tones being integrated into the same perceptual object. The results confirm the difficulty of comparing the pitches of sequential sounds with different timbres and suggest that, for simultaneous sounds, pitch differences may be detected through a decrease in perceptual fusion rather than an explicit coding and comparison of the underlying F0s. PMID:21077719

Domain Decomposition with Local Mesh Refinement.

DTIC Science & Technology

1989-08-01

smoothi coefficients, or non-smooth solui ioni,. We eiriplov fromn 1 to 1024 tiles on problems containing irp to 161K (degrees of freedom. Though io... methodology survives such compromises and is even sequentially advantageous in many problems. The domain decomposition algorithms we employ (sertiun 3...iog( I + !J2 it - g i Ol Qunit squiare 1 he (,mai oive i> Hie outward normal. lfie sevoh iih exam pie, from [1. 27] has a smoothi solution, but rapidlY

Flat-plate techniques for measuring reflectance of macro-algae (Ulva curvata)

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina; Thomsen, Mads Solgaard; Schwarzschild, Arthur

2012-01-01

We tested the consistency and accuracy of flat-plate spectral measurements (400–1000 nm) of the marine macrophyte Ulva curvata. With sequential addition of Ulva thallus layers, the reflectance progressively increased from 6% to 9% with six thalli in the visible (VIS) and from 5% to 19% with ten thalli in the near infrared (NIR). This progressive increase was simulated by a mathematical calculation based on an Ulva thallus diffuse reflectance weighted by a transmittance power series. Experimental and simulated reflectance differences that were particularly high in the NIR most likely resulted from residual water and layering structure unevenness in the experimental progression. High spectral overlap existed between fouled and non-fouled Ulva mats and the coexistent lagoon mud in the VIS, whereas in the NIR, spectral contrast was retained but substantially dampened by fouling.

Frequency domain finite-element and spectral-element acoustic wave modeling using absorbing boundaries and perfectly matched layer

NASA Astrophysics Data System (ADS)

Rahimi Dalkhani, Amin; Javaherian, Abdolrahim; Mahdavi Basir, Hadi

2018-04-01

Wave propagation modeling as a vital tool in seismology can be done via several different numerical methods among them are finite-difference, finite-element, and spectral-element methods (FDM, FEM and SEM). Some advanced applications in seismic exploration benefit the frequency domain modeling. Regarding flexibility in complex geological models and dealing with the free surface boundary condition, we studied the frequency domain acoustic wave equation using FEM and SEM. The results demonstrated that the frequency domain FEM and SEM have a good accuracy and numerical efficiency with the second order interpolation polynomials. Furthermore, we developed the second order Clayton and Engquist absorbing boundary condition (CE-ABC2) and compared it with the perfectly matched layer (PML) for the frequency domain FEM and SEM. In spite of PML method, CE-ABC2 does not add any additional computational cost to the modeling except assembling boundary matrices. As a result, considering CE-ABC2 is more efficient than PML for the frequency domain acoustic wave propagation modeling especially when computational cost is high and high-level absorbing performance is unnecessary.

Adaptive illumination source for multispectral vision system applied to material discrimination

NASA Astrophysics Data System (ADS)

Conde, Olga M.; Cobo, Adolfo; Cantero, Paulino; Conde, David; Mirapeix, Jesús; Cubillas, Ana M.; López-Higuera, José M.

2008-04-01

A multispectral system based on a monochrome camera and an adaptive illumination source is presented in this paper. Its preliminary application is focused on material discrimination for food and beverage industries, where monochrome, color and infrared imaging have been successfully applied for this task. This work proposes a different approach, in which the relevant wavelengths for the required discrimination task are selected in advance using a Sequential Forward Floating Selection (SFFS) Algorithm. A light source, based on Light Emitting Diodes (LEDs) at these wavelengths is then used to sequentially illuminate the material under analysis, and the resulting images are captured by a CCD camera with spectral response in the entire range of the selected wavelengths. Finally, the several multispectral planes obtained are processed using a Spectral Angle Mapping (SAM) algorithm, whose output is the desired material classification. Among other advantages, this approach of controlled and specific illumination produces multispectral imaging with a simple monochrome camera, and cold illumination restricted to specific relevant wavelengths, which is desirable for the food and beverage industry. The proposed system has been tested with success for the automatic detection of foreign object in the tobacco processing industry.

Learning Sequential Composition Control.

PubMed

Najafi, Esmaeil; Babuska, Robert; Lopes, Gabriel A D

2016-11-01

Sequential composition is an effective supervisory control method for addressing control problems in nonlinear dynamical systems. It executes a set of controllers sequentially to achieve a control specification that cannot be realized by a single controller. As these controllers are designed offline, sequential composition cannot address unmodeled situations that might occur during runtime. This paper proposes a learning approach to augment the standard sequential composition framework by using online learning to handle unforeseen situations. New controllers are acquired via learning and added to the existing supervisory control structure. In the proposed setting, learning experiments are restricted to take place within the domain of attraction (DOA) of the existing controllers. This guarantees that the learning process is safe (i.e., the closed loop system is always stable). In addition, the DOA of the new learned controller is approximated after each learning trial. This keeps the learning process short as learning is terminated as soon as the DOA of the learned controller is sufficiently large. The proposed approach has been implemented on two nonlinear systems: 1) a nonlinear mass-damper system and 2) an inverted pendulum. The results show that in both cases a new controller can be rapidly learned and added to the supervisory control structure.

Analysis of spatial distribution of land cover maps accuracy

NASA Astrophysics Data System (ADS)

Khatami, R.; Mountrakis, G.; Stehman, S. V.

2017-12-01

Land cover maps have become one of the most important products of remote sensing science. However, classification errors will exist in any classified map and affect the reliability of subsequent map usage. Moreover, classification accuracy often varies over different regions of a classified map. These variations of accuracy will affect the reliability of subsequent analyses of different regions based on the classified maps. The traditional approach of map accuracy assessment based on an error matrix does not capture the spatial variation in classification accuracy. Here, per-pixel accuracy prediction methods are proposed based on interpolating accuracy values from a test sample to produce wall-to-wall accuracy maps. Different accuracy prediction methods were developed based on four factors: predictive domain (spatial versus spectral), interpolation function (constant, linear, Gaussian, and logistic), incorporation of class information (interpolating each class separately versus grouping them together), and sample size. Incorporation of spectral domain as explanatory feature spaces of classification accuracy interpolation was done for the first time in this research. Performance of the prediction methods was evaluated using 26 test blocks, with 10 km × 10 km dimensions, dispersed throughout the United States. The performance of the predictions was evaluated using the area under the curve (AUC) of the receiver operating characteristic. Relative to existing accuracy prediction methods, our proposed methods resulted in improvements of AUC of 0.15 or greater. Evaluation of the four factors comprising the accuracy prediction methods demonstrated that: i) interpolations should be done separately for each class instead of grouping all classes together; ii) if an all-classes approach is used, the spectral domain will result in substantially greater AUC than the spatial domain; iii) for the smaller sample size and per-class predictions, the spectral and spatial domain yielded similar AUC; iv) for the larger sample size (i.e., very dense spatial sample) and per-class predictions, the spatial domain yielded larger AUC; v) increasing the sample size improved accuracy predictions with a greater benefit accruing to the spatial domain; and vi) the function used for interpolation had the smallest effect on AUC.

Novel Spectral Representations and Sparsity-Driven Algorithms for Shape Modeling and Analysis

NASA Astrophysics Data System (ADS)

Zhong, Ming

In this dissertation, we focus on extending classical spectral shape analysis by incorporating spectral graph wavelets and sparsity-seeking algorithms. Defined with the graph Laplacian eigenbasis, the spectral graph wavelets are localized both in the vertex domain and graph spectral domain, and thus are very effective in describing local geometry. With a rich dictionary of elementary vectors and forcing certain sparsity constraints, a real life signal can often be well approximated by a very sparse coefficient representation. The many successful applications of sparse signal representation in computer vision and image processing inspire us to explore the idea of employing sparse modeling techniques with dictionary of spectral basis to solve various shape modeling problems. Conventional spectral mesh compression uses the eigenfunctions of mesh Laplacian as shape bases, which are highly inefficient in representing local geometry. To ameliorate, we advocate an innovative approach to 3D mesh compression using spectral graph wavelets as dictionary to encode mesh geometry. The spectral graph wavelets are locally defined at individual vertices and can better capture local shape information than Laplacian eigenbasis. The multi-scale SGWs form a redundant dictionary as shape basis, so we formulate the compression of 3D shape as a sparse approximation problem that can be readily handled by greedy pursuit algorithms. Surface inpainting refers to the completion or recovery of missing shape geometry based on the shape information that is currently available. We devise a new surface inpainting algorithm founded upon the theory and techniques of sparse signal recovery. Instead of estimating the missing geometry directly, our novel method is to find this low-dimensional representation which describes the entire original shape. More specifically, we find that, for many shapes, the vertex coordinate function can be well approximated by a very sparse coefficient representation with respect to the dictionary comprising its Laplacian eigenbasis, and it is then possible to recover this sparse representation from partial measurements of the original shape. Taking advantage of the sparsity cue, we advocate a novel variational approach for surface inpainting, integrating data fidelity constraints on the shape domain with coefficient sparsity constraints on the transformed domain. Because of the powerful properties of Laplacian eigenbasis, the inpainting results of our method tend to be globally coherent with the remaining shape. Informative and discriminative feature descriptors are vital in qualitative and quantitative shape analysis for a large variety of graphics applications. We advocate novel strategies to define generalized, user-specified features on shapes. Our new region descriptors are primarily built upon the coefficients of spectral graph wavelets that are both multi-scale and multi-level in nature, consisting of both local and global information. Based on our novel spectral feature descriptor, we developed a user-specified feature detection framework and a tensor-based shape matching algorithm. Through various experiments, we demonstrate the competitive performance of our proposed methods and the great potential of spectral basis and sparsity-driven methods for shape modeling.

Spectral behavior of a terahertz quantum-cascade laser.

PubMed

Hensley, J M; Montoya, Juan; Allen, M G; Xu, J; Mahler, L; Tredicucci, A; Beere, H E; Ritchie, D A

2009-10-26

In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.

Optical stealth transmission based on super-continuum generation in highly nonlinear fiber over WDM network.

PubMed

Zhu, Huatao; Wang, Rong; Pu, Tao; Fang, Tao; Xiang, Peng; Zheng, Jilin; Chen, Dalei

2015-06-01

In this Letter, the optical stealth transmission carried by super-continuum spectrum optical pulses generated in highly nonlinear fiber is proposed and experimentally demonstrated. In the proposed transmission scheme, super-continuum signals are reshaped in the spectral domain through a wavelength-selective switch and are temporally spread by a chromatic dispersion device to achieve the same noise-like characteristic as the noise in optical networks, so that in both the time domain and the spectral domain, the stealth signals are hidden in public channel. Our experimental results show that compared with existing schemes where stealth channels are carried by amplified spontaneous emission noise, super-continuum signal can increase the transmission performance and robustness.

A multi-domain spectral method for time-fractional differential equations

NASA Astrophysics Data System (ADS)

Chen, Feng; Xu, Qinwu; Hesthaven, Jan S.

2015-07-01

This paper proposes an approach for high-order time integration within a multi-domain setting for time-fractional differential equations. Since the kernel is singular or nearly singular, two main difficulties arise after the domain decomposition: how to properly account for the history/memory part and how to perform the integration accurately. To address these issues, we propose a novel hybrid approach for the numerical integration based on the combination of three-term-recurrence relations of Jacobi polynomials and high-order Gauss quadrature. The different approximations used in the hybrid approach are justified theoretically and through numerical examples. Based on this, we propose a new multi-domain spectral method for high-order accurate time integrations and study its stability properties by identifying the method as a generalized linear method. Numerical experiments confirm hp-convergence for both time-fractional differential equations and time-fractional partial differential equations.

Identification of bearing faults using time domain zero-crossings

NASA Astrophysics Data System (ADS)

William, P. E.; Hoffman, M. W.

2011-11-01

In this paper, zero-crossing characteristic features are employed for early detection and identification of single point bearing defects in rotating machinery. As a result of bearing defects, characteristic defect frequencies appear in the machine vibration signal, normally requiring spectral analysis or envelope analysis to identify the defect type. Zero-crossing features are extracted directly from the time domain vibration signal using only the duration between successive zero-crossing intervals and do not require estimation of the rotational frequency. The features are a time domain representation of the composite vibration signature in the spectral domain. Features are normalized by the length of the observation window and classification is performed using a multilayer feedforward neural network. The model was evaluated on vibration data recorded using an accelerometer mounted on an induction motor housing subjected to a number of single point defects with different severity levels.

A spectral power analysis of driving behavior changes during the transition from nondistraction to distraction.

PubMed

Wang, Yuan; Bao, Shan; Du, Wenjun; Ye, Zhirui; Sayer, James R

2017-11-17

This article investigated and compared frequency domain and time domain characteristics of drivers' behaviors before and after the start of distracted driving. Data from an existing naturalistic driving study were used. Fast Fourier transform (FFT) was applied for the frequency domain analysis to explore drivers' behavior pattern changes between nondistracted (prestarting of visual-manual task) and distracted (poststarting of visual-manual task) driving periods. Average relative spectral power in a low frequency range (0-0.5 Hz) and the standard deviation in a 10-s time window of vehicle control variables (i.e., lane offset, yaw rate, and acceleration) were calculated and further compared. Sensitivity analyses were also applied to examine the reliability of the time and frequency domain analyses. Results of the mixed model analyses from the time and frequency domain analyses all showed significant degradation in lateral control performance after engaging in visual-manual tasks while driving. Results of the sensitivity analyses suggested that the frequency domain analysis was less sensitive to the frequency bandwidth, whereas the time domain analysis was more sensitive to the time intervals selected for variation calculations. Different time interval selections can result in significantly different standard deviation values, whereas average spectral power analysis on yaw rate in both low and high frequency bandwidths showed consistent results, that higher variation values were observed during distracted driving when compared to nondistracted driving. This study suggests that driver state detection needs to consider the behavior changes during the prestarting periods, instead of only focusing on periods with physical presence of distraction, such as cell phone use. Lateral control measures can be a better indicator of distraction detection than longitudinal controls. In addition, frequency domain analyses proved to be a more robust and consistent method in assessing driving performance compared to time domain analyses.

A reversible fluorescence "off-on-off" sensor for sequential detection of aluminum and acetate/fluoride ions.

PubMed

Gupta, Vinod Kumar; Mergu, Naveen; Kumawat, Lokesh Kumar; Singh, Ashok Kumar

2015-11-01

A new rhodamine functionalized fluorogenic Schiff base CS was synthesized and its colorimetric and fluorescence responses toward various metal ions were explored. The sensor exhibited highly selective and sensitive colorimetric and "off-on" fluorescence response towards Al(3+) in the presence of other competing metal ions. These spectral changes are large enough in the visible region of the spectrum and thus enable naked-eye detection. Studies proved that the formation of CS-Al(3+) complex is fully reversible and can sense to AcO(-)/F(-) via dissociation. The results revealed that the sensor provides fluorescence "off-on-off" strategy for the sequential detection of Al(3+) and AcO(-)/F(-). Copyright © 2015 Elsevier B.V. All rights reserved.

Compressive Coded-Aperture Multimodal Imaging Systems

NASA Astrophysics Data System (ADS)

Rueda-Chacon, Hoover F.

Multimodal imaging refers to the framework of capturing images that span different physical domains such as space, spectrum, depth, time, polarization, and others. For instance, spectral images are modeled as 3D cubes with two spatial and one spectral coordinate. Three-dimensional cubes spanning just the space domain, are referred as depth volumes. Imaging cubes varying in time, spectra or depth, are referred as 4D-images. Nature itself spans different physical domains, thus imaging our real world demands capturing information in at least 6 different domains simultaneously, giving turn to 3D-spatial+spectral+polarized dynamic sequences. Conventional imaging devices, however, can capture dynamic sequences with up-to 3 spectral channels, in real-time, by the use of color sensors. Capturing multiple spectral channels require scanning methodologies, which demand long time. In general, to-date multimodal imaging requires a sequence of different imaging sensors, placed in tandem, to simultaneously capture the different physical properties of a scene. Then, different fusion techniques are employed to mix all the individual information into a single image. Therefore, new ways to efficiently capture more than 3 spectral channels of 3D time-varying spatial information, in a single or few sensors, are of high interest. Compressive spectral imaging (CSI) is an imaging framework that seeks to optimally capture spectral imagery (tens of spectral channels of 2D spatial information), using fewer measurements than that required by traditional sensing procedures which follows the Shannon-Nyquist sampling. Instead of capturing direct one-to-one representations of natural scenes, CSI systems acquire linear random projections of the scene and then solve an optimization algorithm to estimate the 3D spatio-spectral data cube by exploiting the theory of compressive sensing (CS). To date, the coding procedure in CSI has been realized through the use of ``block-unblock" coded apertures, commonly implemented as chrome-on-quartz photomasks. These apertures block or permit to pass the entire spectrum from the scene at given spatial locations, thus modulating the spatial characteristics of the scene. In the first part, this thesis aims to expand the framework of CSI by replacing the traditional block-unblock coded apertures by patterned optical filter arrays, referred as ``color" coded apertures. These apertures are formed by tiny pixelated optical filters, which in turn, allow the input image to be modulated not only spatially but spectrally as well, entailing more powerful coding strategies. The proposed colored coded apertures are either synthesized through linear combinations of low-pass, high-pass and band-pass filters, paired with binary pattern ensembles realized by a digital-micromirror-device (DMD), or experimentally realized through thin-film color-patterned filter arrays. The optical forward model of the proposed CSI architectures will be presented along with the design and proof-of-concept implementations, which achieve noticeable improvements in the quality of the reconstructions compared with conventional block-unblock coded aperture-based CSI architectures. On another front, due to the rich information contained in the infrared spectrum as well as the depth domain, this thesis aims to explore multimodal imaging by extending the range sensitivity of current CSI systems to a dual-band visible+near-infrared spectral domain, and also, it proposes, for the first time, a new imaging device that captures simultaneously 4D data cubes (2D spatial+1D spectral+depth imaging) with as few as a single snapshot. Due to the snapshot advantage of this camera, video sequences are possible, thus enabling the joint capture of 5D imagery. It aims to create super-human sensing that will enable the perception of our world in new and exciting ways. With this, we intend to advance in the state of the art in compressive sensing systems to extract depth while accurately capturing spatial and spectral material properties. The applications of such a sensor are self-evident in fields such as computer/robotic vision because they would allow an artificial intelligence to make informed decisions about not only the location of objects within a scene but also their material properties.

Sequential Reactions of Surface-Tethered Glycolytic Enzymes

PubMed Central

Mukai, Chinatsu; Bergkvist, Magnus; Nelson, Jacquelyn L.; Travis, Alexander J.

2014-01-01

SUMMARY The development of complex hybrid organic-inorganic devices faces several challenges, including how they can generate energy. Cells face similar challenges regarding local energy production. Mammalian sperm solve this problem by generating ATP down the flagellar principal piece by means of glycolytic enzymes, several of which are tethered to a cytoskeletal support via germ cell-specific targeting domains. Inspired by this design, we have produced recombinant hexokinase type 1 and glucose-6-phosphate isomerase capable of oriented immobilization on a nickel-nitrilotriacetic acid modified surface. Specific activities of enzymes tethered via this strategy were substantially higher than when randomly adsorbed. Furthermore, these enzymes showed sequential activities when tethered onto the same surface. This is the first demonstration of surface-tethered pathway components showing sequential enzymatic activities, and it provides a first step toward reconstitution of glycolysis on engineered hybrid devices. PMID:19778729

Domain-general neural correlates of dependency formation: Using complex tones to simulate language.

PubMed

Brilmayer, Ingmar; Sassenhagen, Jona; Bornkessel-Schlesewsky, Ina; Schlesewsky, Matthias

2017-08-01

There is an ongoing debate whether the P600 event-related potential component following syntactic anomalies reflects syntactic processes per se, or if it is an instance of the P300, a domain-general ERP component associated with attention and cognitive reorientation. A direct comparison of both components is challenging because of the huge discrepancy in experimental designs and stimulus choice between language and 'classic' P300 experiments. In the present study, we develop a new approach to mimic the interplay of sequential position as well as categorical and relational information in natural language syntax (word category and agreement) in a non-linguistic target detection paradigm using musical instruments. Participants were instructed to (covertly) detect target tones which were defined by instrument change and pitch rise between subsequent tones at the last two positions of four-tone sequences. We analysed the EEG using event-related averaging and time-frequency decomposition. Our results show striking similarities to results obtained from linguistic experiments. We found a P300 that showed sensitivity to sequential position and a late positivity sensitive to stimulus type and position. A time-frequency decomposition revealed significant effects of sequential position on the theta band and a significant influence of stimulus type on the delta band. Our results suggest that the detection of non-linguistic targets defined via complex feature conjunctions in the present study and the detection of syntactic anomalies share the same underlying processes: attentional shift and memory based matching processes that act upon multi-feature conjunctions. We discuss the results as supporting domain-general accounts of the P600 during natural language comprehension. Copyright © 2017 Elsevier Ltd. All rights reserved.

Domain decomposition preconditioners for the spectral collocation method

NASA Technical Reports Server (NTRS)

Quarteroni, Alfio; Sacchilandriani, Giovanni

1988-01-01

Several block iteration preconditioners are proposed and analyzed for the solution of elliptic problems by spectral collocation methods in a region partitioned into several rectangles. It is shown that convergence is achieved with a rate which does not depend on the polynomial degree of the spectral solution. The iterative methods here presented can be effectively implemented on multiprocessor systems due to their high degree of parallelism.

hyperspectral characterization of tissue simulating phantoms using a supercontinuum laser in a spatial frequency domain imaging instrument

NASA Astrophysics Data System (ADS)

Torabzadeh, Mohammad; Stockton, Patrick; Kennedy, Gordon T.; Saager, Rolf B.; Durkin, Anthony J.; Bartels, Randy A.; Tromberg, Bruce J.

2018-02-01

Hyperspectral Imaging (HSI) is a growing field in tissue optics due to its ability to collect continuous spectral features of a sample without a contact probe. Spatial Frequency Domain Imaging (SFDI) is a non-contact wide-field spectral imaging technique that is used to quantitatively characterize tissue structure and chromophore concentration. In this study, we designed a Hyperspectral SFDI (H-SFDI) instrument which integrated a supercontinuum laser source to a wavelength tuning optical configuration and a sCMOS camera to extract spatial (Field of View: 2cm×2cm) and broadband spectral features (580nm-950nm). A preliminary experiment was also performed to integrate the hyperspectral projection unit to a compressed single pixel camera and Light Labeling (LiLa) technique.

Causality Analysis of Neural Connectivity: Critical Examination of Existing Methods and Advances of New Methods

PubMed Central

Hu, Sanqing; Dai, Guojun; Worrell, Gregory A.; Dai, Qionghai; Liang, Hualou

2012-01-01

Granger causality (GC) is one of the most popular measures to reveal causality influence of time series and has been widely applied in economics and neuroscience. Especially, its counterpart in frequency domain, spectral GC, as well as other Granger-like causality measures have recently been applied to study causal interactions between brain areas in different frequency ranges during cognitive and perceptual tasks. In this paper, we show that: 1) GC in time domain cannot correctly determine how strongly one time series influences the other when there is directional causality between two time series, and 2) spectral GC and other Granger-like causality measures have inherent shortcomings and/or limitations because of the use of the transfer function (or its inverse matrix) and partial information of the linear regression model. On the other hand, we propose two novel causality measures (in time and frequency domains) for the linear regression model, called new causality and new spectral causality, respectively, which are more reasonable and understandable than GC or Granger-like measures. Especially, from one simple example, we point out that, in time domain, both new causality and GC adopt the concept of proportion, but they are defined on two different equations where one equation (for GC) is only part of the other (for new causality), thus the new causality is a natural extension of GC and has a sound conceptual/theoretical basis, and GC is not the desired causal influence at all. By several examples, we confirm that new causality measures have distinct advantages over GC or Granger-like measures. Finally, we conduct event-related potential causality analysis for a subject with intracranial depth electrodes undergoing evaluation for epilepsy surgery, and show that, in the frequency domain, all measures reveal significant directional event-related causality, but the result from new spectral causality is consistent with event-related time–frequency power spectrum activity. The spectral GC as well as other Granger-like measures are shown to generate misleading results. The proposed new causality measures may have wide potential applications in economics and neuroscience. PMID:21511564

Acquisition and analysis of a spectral and bidirectional database of urban materials over Toulouse (France)

NASA Astrophysics Data System (ADS)

Briottet, X.; Lachérade, S.; Pallotta, S.; Miesch, C.; Tanguy, B.; Le Men, H.

2006-05-01

This paper presents an experiment carried out in Toulouse in 2004. This campaign aims to create a specific library which will give us simultaneously information in three domains: a list of the main materials present in the city, the optical properties of each of them (spectral and directional) and their spatial variability in a given class. The spectral domain covers the entire optical domain from the visible to the Long Wave InfraRed range. Measurements have been carried out in the visible and near infrared spectral region (400-2500 nm) with an ASD spectroradiometer at a 20 cm resolution for outdoors measurements, and with a goniometer for laboratory ones at the same spatial resolution. A database of about 550 individual spectra has been created. These spectra could be divided into 4 classical urban classes like road (red asphalt, tar), pavement (red asphalt, tar), square (granite slab) and wall (brick, concrete). In addition to these "in situ" experiments, the bi-directional behaviours of urban material samples have been studied in laboratory with the Onera goniometer. Two material types have been distinguished: flat materials, which is isotropic, and textured materials, whose study is more complex. Whereas road and sidewalk materials are quite lambertian with a slight backscattering effect typical of rough surfaces, square materials like granite or concrete present a specular peak at large zenith angle. A specific study on tiles demonstrates their important anisotropic directional properties. In the infrared domain (3μm - 14μm), a SOC 400 spectroradiometer was used at a 1.27cm spatial resolution. A database of about 100 individual spectra has been created. These spectra could be divided into four classical urban classes like road (red asphalt, tar), pavement (red asphalt, tar), square (granite slab) and wall (bricks, painted walls). In each spectral domain, three variability types are considered: a physical variability which is intrinsic to the material, a contextual variability depending on the material use and a theoretical variability which is the one observed inside a chosen class.

The "New" Domain of Post-Secondary Education.

ERIC Educational Resources Information Center

Moses, Stanley

This paper argues that government agencies have traditionally been concerned with recording and reporting only the dimensions of the formal "Core" of educational activity--the sequential ladder ranging from kindergarten through graduate and professional schools. Missing is a similar recording of participation in the "Educational…

Face identification with frequency domain matched filtering in mobile environments

NASA Astrophysics Data System (ADS)

Lee, Dong-Su; Woo, Yong-Hyun; Yeom, Seokwon; Kim, Shin-Hwan

2012-06-01

Face identification at a distance is very challenging since captured images are often degraded by blur and noise. Furthermore, the computational resources and memory are often limited in the mobile environments. Thus, it is very challenging to develop a real-time face identification system on the mobile device. This paper discusses face identification based on frequency domain matched filtering in the mobile environments. Face identification is performed by the linear or phase-only matched filter and sequential verification stages. The candidate window regions are decided by the major peaks of the linear or phase-only matched filtering outputs. The sequential stages comprise a skin-color test and an edge mask filtering test, which verify color and shape information of the candidate regions in order to remove false alarms. All algorithms are built on the mobile device using Android platform. The preliminary results show that face identification of East Asian people can be performed successfully in the mobile environments.

Rational Design of Potent Antagonists to the Human Growth Hormone Receptor

NASA Astrophysics Data System (ADS)

Fuh, Germaine; Cunningham, Brian C.; Fukunaga, Rikiro; Nagata, Shigekazu; Goeddel, David V.; Wells, James A.

1992-06-01

A hybrid receptor was constructed that contained the extracellular binding domain of the human growth hormone (hGH) receptor linked to the transmembrane and intracellular domains of the murine granulocyte colony-stimulating factor receptor. Addition of hGH to a myeloid leukemia cell line (FDC-P1) that expressed the hybrid receptor caused proliferation of these cells. The mechanism for signal transduction of the hybrid receptor required dimerization because monoclonal antibodies to the hGH receptor were agonists whereas their monovalent fragments were not. Receptor dimerization occurs sequentially-a receptor binds to site 1 on hGH, and then a second receptor molecule binds to site 2 on hGH. On the basis of this sequential mechanism, which may occur in many other cytokine receptors, inactive hGH analogs were designed that were potent antagonists to hGH-induced cell proliferation. Such antagonists could be useful for treating clinical conditions of hGH excess, such as acromegaly.

Monitoring proteins using in vivo near-infrared time-domain optical imaging after 2-O-hexyldiglycerol-mediated transfer to the brain.

PubMed

Hülper, Petra; Dullin, Christian; Kugler, Wilfried; Lakomek, Max; Erdlenbruch, Bernhard

2011-04-01

The aim of the present study was to gain insight into the penetration, biodistribution, and fate of globulins in the brain after 2-O-hexyldiglycerol-induced blood-brain barrier opening. The spatial distribution of fluorescence probes was investigated after blood-brain barrier opening with intracarotid 2-O-hexyldiglycerol injection. Fluorescence intensity was visualized by microscopy (mice and rats) and by in vivo time-domain optical imaging. There was an increased 2-O-hexyldiglycerol-mediated transfer of fluorescence-labeled globulins into the ipsilateral hemisphere. Sequential in vivo measurements revealed that the increase in protein concentration lasted at least 96 h after administration. Ex vivo detection of tissue fluorescence confirmed the results obtained in vivo. Globulins enter the healthy brain in conjunction with 2-O-hexyldiglycerol. Sequential in vivo near-infrared fluorescence measurements enable the visualization of the spatial distribution of antibodies in the brain of living small animals.

Likelihood ratios for glaucoma diagnosis using spectral-domain optical coherence tomography.

PubMed

Lisboa, Renato; Mansouri, Kaweh; Zangwill, Linda M; Weinreb, Robert N; Medeiros, Felipe A

2013-11-01

To present a methodology for calculating likelihood ratios for glaucoma diagnosis for continuous retinal nerve fiber layer (RNFL) thickness measurements from spectral-domain optical coherence tomography (spectral-domain OCT). Observational cohort study. A total of 262 eyes of 187 patients with glaucoma and 190 eyes of 100 control subjects were included in the study. Subjects were recruited from the Diagnostic Innovations Glaucoma Study. Eyes with preperimetric and perimetric glaucomatous damage were included in the glaucoma group. The control group was composed of healthy eyes with normal visual fields from subjects recruited from the general population. All eyes underwent RNFL imaging with Spectralis spectral-domain OCT. Likelihood ratios for glaucoma diagnosis were estimated for specific global RNFL thickness measurements using a methodology based on estimating the tangents to the receiver operating characteristic (ROC) curve. Likelihood ratios could be determined for continuous values of average RNFL thickness. Average RNFL thickness values lower than 86 μm were associated with positive likelihood ratios (ie, likelihood ratios greater than 1), whereas RNFL thickness values higher than 86 μm were associated with negative likelihood ratios (ie, likelihood ratios smaller than 1). A modified Fagan nomogram was provided to assist calculation of posttest probability of disease from the calculated likelihood ratios and pretest probability of disease. The methodology allowed calculation of likelihood ratios for specific RNFL thickness values. By avoiding arbitrary categorization of test results, it potentially allows for an improved integration of test results into diagnostic clinical decision making. Copyright © 2013. Published by Elsevier Inc.

Spectral domain optical coherence tomography imaging of spectacular ecdysis in the royal python (Python regius).

PubMed

Tusler, Charlotte A; Maggs, David J; Kass, Philip H; Paul-Murphy, Joanne R; Schwab, Ivan R; Murphy, Christopher J

2015-01-01

To describe using spectral domain optical coherence tomography (SD-OCT), digital slit-lamp biomicroscopy, and external photography, changes in the ophidian cuticle, spectacle, and cornea during ecdysis. Four normal royal pythons (Python regius). Snakes were assessed once daily throughout a complete shed cycle using nasal, axial, and temporal SD-OCT images, digital slit-lamp biomicroscopy, and external photography. Spectral domain optical coherence tomography (SD-OCT) images reliably showed the spectacular cuticle and stroma, subcuticular space (SCS), cornea, anterior chamber, iris, and Schlemm's canal. When visible, the subspectacular space (SSS) was more distended peripherally than axially. Ocular surface changes throughout ecdysis were relatively conserved among snakes at all three regions imaged. From baseline (7 days following completion of a full cycle), the spectacle gradually thickened before separating into superficial cuticular and deep, hyper-reflective stromal components, thereby creating the SCS. During spectacular separation, the stroma regained original reflectivity, and multiple hyper-reflective foci (likely fragments from the cuticular-stromal interface) were noted within the SCS. The cornea was relatively unchanged in character or thickness throughout all stages of ecdysis. Slit-lamp images did not permit observation of these changes. Spectral domain optical coherence tomography (SD-OCT) provided excellent high-resolution images of the snake anterior segment, and especially the cuticle, spectacle, and cornea of manually restrained normal snakes at all stages of ecdysis and warrants investigation in snakes with anterior segment disease. The peripheral spectacle may be the preferred entry point for diagnostic or therapeutic injections into the SSS and for initiating spectacular surgery. © 2014 American College of Veterinary Ophthalmologists.

Allan deviation computations of a linear frequency synthesizer system using frequency domain techniques

NASA Technical Reports Server (NTRS)

Wu, Andy

1995-01-01

Allan Deviation computations of linear frequency synthesizer systems have been reported previously using real-time simulations. Even though it takes less time compared with the actual measurement, it is still very time consuming to compute the Allan Deviation for long sample times with the desired confidence level. Also noises, such as flicker phase noise and flicker frequency noise, can not be simulated precisely. The use of frequency domain techniques can overcome these drawbacks. In this paper the system error model of a fictitious linear frequency synthesizer is developed and its performance using a Cesium (Cs) atomic frequency standard (AFS) as a reference is evaluated using frequency domain techniques. For a linear timing system, the power spectral density at the system output can be computed with known system transfer functions and known power spectral densities from the input noise sources. The resulting power spectral density can then be used to compute the Allan Variance at the system output. Sensitivities of the Allan Variance at the system output to each of its independent input noises are obtained, and they are valuable for design trade-off and trouble-shooting.

Master-slave interferometry for parallel spectral domain interferometry sensing and versatile 3D optical coherence tomography.

PubMed

Podoleanu, Adrian Gh; Bradu, Adrian

2013-08-12

Conventional spectral domain interferometry (SDI) methods suffer from the need of data linearization. When applied to optical coherence tomography (OCT), conventional SDI methods are limited in their 3D capability, as they cannot deliver direct en-face cuts. Here we introduce a novel SDI method, which eliminates these disadvantages. We denote this method as Master - Slave Interferometry (MSI), because a signal is acquired by a slave interferometer for an optical path difference (OPD) value determined by a master interferometer. The MSI method radically changes the main building block of an SDI sensor and of a spectral domain OCT set-up. The serially provided signal in conventional technology is replaced by multiple signals, a signal for each OPD point in the object investigated. This opens novel avenues in parallel sensing and in parallelization of signal processing in 3D-OCT, with applications in high- resolution medical imaging and microscopy investigation of biosamples. Eliminating the need of linearization leads to lower cost OCT systems and opens potential avenues in increasing the speed of production of en-face OCT images in comparison with conventional SDI.

Plasma rotation measurement in small tokamaks using an optical spectrometer and a single photomultiplier as detector.

PubMed

Severo, J H F; Nascimento, I C; Kuznetov, Yu K; Tsypin, V S; Galvão, R M O; Tendler, M

2007-04-01

The method for plasma rotation measurement in the tokamak TCABR is reported in this article. During a discharge, an optical spectrometer is used to scan sequentially spectral lines of plasma impurities and spectral lines of a calibration lamp. Knowing the scanning velocity of the diffraction grating of the spectrometer with adequate precision, the Doppler shifts of impurity lines are determined. The photomultiplier output voltage signals are recorded with adequate sampling rate. With this method the residual poloidal and toroidal plasma rotation velocities were determined, assuming that they are the same as those of the impurity ions. The results show reasonable agreement with the neoclassical theory and with results from similar tokamaks.

Hyperspectral light sheet microscopy

NASA Astrophysics Data System (ADS)

Jahr, Wiebke; Schmid, Benjamin; Schmied, Christopher; Fahrbach, Florian O.; Huisken, Jan

2015-09-01

To study the development and interactions of cells and tissues, multiple fluorescent markers need to be imaged efficiently in a single living organism. Instead of acquiring individual colours sequentially with filters, we created a platform based on line-scanning light sheet microscopy to record the entire spectrum for each pixel in a three-dimensional volume. We evaluated data sets with varying spectral sampling and determined the optimal channel width to be around 5 nm. With the help of these data sets, we show that our setup outperforms filter-based approaches with regard to image quality and discrimination of fluorophores. By spectral unmixing we resolved overlapping fluorophores with up to nanometre resolution and removed autofluorescence in zebrafish and fruit fly embryos.

Hyperspectral light sheet microscopy.

PubMed

Jahr, Wiebke; Schmid, Benjamin; Schmied, Christopher; Fahrbach, Florian O; Huisken, Jan

2015-09-02

To study the development and interactions of cells and tissues, multiple fluorescent markers need to be imaged efficiently in a single living organism. Instead of acquiring individual colours sequentially with filters, we created a platform based on line-scanning light sheet microscopy to record the entire spectrum for each pixel in a three-dimensional volume. We evaluated data sets with varying spectral sampling and determined the optimal channel width to be around 5 nm. With the help of these data sets, we show that our setup outperforms filter-based approaches with regard to image quality and discrimination of fluorophores. By spectral unmixing we resolved overlapping fluorophores with up to nanometre resolution and removed autofluorescence in zebrafish and fruit fly embryos.

Multipurpose spectral imager.

PubMed

Sigernes, F; Lorentzen, D A; Heia, K; Svenøe, T

2000-06-20

A small spectral imaging system is presented that images static or moving objects simultaneously as a function of wavelength. The main physical principle is outlined and demonstrated. The instrument is capable of resolving both spectral and spatial information from targets throughout the entire visible region. The spectral domain has a bandpass of 12 A. One can achieve the spatial domain by rotating the system's front mirror with a high-resolution stepper motor. The spatial resolution range from millimeters to several meters depends mainly on the front optics used and whether the target is fixed (static) or movable relative to the instrument. Different applications and examples are explored, including outdoor landscapes, industrial fish-related targets, and ground-level objects observed in the more traditional way from an airborne carrier (remote sensing). Through the examples, we found that the instrument correctly classifies whether a shrimp is peeled and whether it can disclose the spectral and spatial microcharacteristics of targets such as a fish nematode (parasite). In the macroregime, we were able to distinguish a marine vessel from the surrounding sea and sky. A study of the directional spectral albedo from clouds, mountains, snow cover, and vegetation has also been included. With the airborne experiment, the imager successfully classified snow cover, leads, and new and rafted ice, as seen from 10.000 ft (3.048 m).

Using frequency-domain methods to identify XV-15 aeroelastic modes

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.; Tischler, Mark B.

1987-01-01

The XV-15 Tilt-Rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier transformed) with cross spectral and transfer function methods. Modal frequencies and damping were determined by performing curve fits to transfer function magnitude and phase data and to cross spectral magnitude data. Results are given for the XV-15 with its original metal rotor blades. Frequency and damping values are also compared with earlier predictions.

Low-dose cerebral perfusion computed tomography image restoration via low-rank and total variation regularizations

PubMed Central

Niu, Shanzhou; Zhang, Shanli; Huang, Jing; Bian, Zhaoying; Chen, Wufan; Yu, Gaohang; Liang, Zhengrong; Ma, Jianhua

2016-01-01

Cerebral perfusion x-ray computed tomography (PCT) is an important functional imaging modality for evaluating cerebrovascular diseases and has been widely used in clinics over the past decades. However, due to the protocol of PCT imaging with repeated dynamic sequential scans, the associative radiation dose unavoidably increases as compared with that used in conventional CT examinations. Minimizing the radiation exposure in PCT examination is a major task in the CT field. In this paper, considering the rich similarity redundancy information among enhanced sequential PCT images, we propose a low-dose PCT image restoration model by incorporating the low-rank and sparse matrix characteristic of sequential PCT images. Specifically, the sequential PCT images were first stacked into a matrix (i.e., low-rank matrix), and then a non-convex spectral norm/regularization and a spatio-temporal total variation norm/regularization were then built on the low-rank matrix to describe the low rank and sparsity of the sequential PCT images, respectively. Subsequently, an improved split Bregman method was adopted to minimize the associative objective function with a reasonable convergence rate. Both qualitative and quantitative studies were conducted using a digital phantom and clinical cerebral PCT datasets to evaluate the present method. Experimental results show that the presented method can achieve images with several noticeable advantages over the existing methods in terms of noise reduction and universal quality index. More importantly, the present method can produce more accurate kinetic enhanced details and diagnostic hemodynamic parameter maps. PMID:27440948

Clinical assessment of motor function: a processes oriented instrument based on a speed-accuracy trade-off paradigm.

PubMed

Christe, Blaise; Burkhard, Pierre R; Pegna, Alan J; Mayer, Eugene; Hauert, Claude-Alain

2007-01-01

In this study, we developed a digitizing tablet-based instrument for the clinical assessment of human voluntary movements targeting motor processes of planning, programming and execution. The tool was used to investigate an adaptation of Fitts' reciprocal tapping task [10], comprising four conditions, each of them modulated by three indices of difficulty related to the amplitude of movement required. Temporal, spatial and sequential constraints underlying the various conditions allowed the intricate motor processes to be dissociated. Data obtained from a group of elderly healthy subjects (N=50) were in agreement with the literature on motor control, in the temporal and spatial domains. Speed constraints generated gains in the temporal domain and costs in the spatial one, while spatial constraints generated gain in the spatial domain and costs in the temporal one; finally, sequential constraints revealed the integrative nature of the cognitive operations involved in motor production. This versatile instrument proved capable of providing quantitative, accurate and sensitive measures of the various processes sustaining voluntary movement in healthy subjects. Altogether, analyses performed in this study generated a theoretical framework and reference data which could be used in the future for the clinical assessment of patients with various movement disorders, in particular Parkinson's disease.

Surface Green's function of a piezoelectric half-space.

PubMed

Laude, Vincent; Jerez-Hanckes, Carlos F; Ballandras, Sylvain

2006-02-01

The computation of the two-dimensional harmonic spatial-domain Green's function at the surface of a piezoelectric half-space is discussed. Starting from the known form of the Green's function expressed in the spectral domain, the singular contributions are isolated and treated separately. It is found that the surface acoustic wave contributions (i.e., poles in the spectral Green's function) give rise to an anisotropic generalization of the Hankel function H0(2), the spatial Green's function for the scalar two-dimensional wave equation. The asymptotic behavior at infinity and at the origin (for the electrostatic contribution) also are explicitly treated. The remaining nonsingular part of the spectral Green's function is obtained numerically by a combination of fast Fourier transform and quadrature. Illustrations are given in the case of a substrate of Y-cut lithium niobate.

Impact of absorption in the top layer of a two layer sample on spectroscopic spectral domain interferometry of the bottom layer

NASA Astrophysics Data System (ADS)

Fleischhauer, F.; Feuchter, T.; Leick, L.; Rajendram, R.; Podoleanu, A.

2018-03-01

Spectroscopic spectral domain interferometry and spectroscopic optical coherence tomography combine depth information with spectrally-resolved localised absorption data. These additional data can improve diagnostics by giving access to functional information of the investigated sample. One possible application is measuring oxygenation levels at the retina for earlier detection of several eye diseases. Here measurements with different hollow glass tube phantoms are shown to measure the impact of a superficial absorbing layer on the precision of reconstructed attenuation spectra of a deeper layer. Measurements show that a superficial absorber has no impact on the reconstructed absorption spectrum of the deeper absorber. Even when diluting the concentration of the deeper absorber so far that an incorrect absorption maximum is obtained, still no influence of the superficially placed absorber is identified.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vay, Jean-Luc, E-mail: jlvay@lbl.gov; Haber, Irving; Godfrey, Brendan B.

Pseudo-spectral electromagnetic solvers (i.e. representing the fields in Fourier space) have extraordinary precision. In particular, Haber et al. presented in 1973 a pseudo-spectral solver that integrates analytically the solution over a finite time step, under the usual assumption that the source is constant over that time step. Yet, pseudo-spectral solvers have not been widely used, due in part to the difficulty for efficient parallelization owing to global communications associated with global FFTs on the entire computational domains. A method for the parallelization of electromagnetic pseudo-spectral solvers is proposed and tested on single electromagnetic pulses, and on Particle-In-Cell simulations of themore » wakefield formation in a laser plasma accelerator. The method takes advantage of the properties of the Discrete Fourier Transform, the linearity of Maxwell’s equations and the finite speed of light for limiting the communications of data within guard regions between neighboring computational domains. Although this requires a small approximation, test results show that no significant error is made on the test cases that have been presented. The proposed method opens the way to solvers combining the favorable parallel scaling of standard finite-difference methods with the accuracy advantages of pseudo-spectral methods.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shumway, R.H.; McQuarrie, A.D.

Robust statistical approaches to the problem of discriminating between regional earthquakes and explosions are developed. We compare linear discriminant analysis using descriptive features like amplitude and spectral ratios with signal discrimination techniques using the original signal waveforms and spectral approximations to the log likelihood function. Robust information theoretic techniques are proposed and all methods are applied to 8 earthquakes and 8 mining explosions in Scandinavia and to an event from Novaya Zemlya of unknown origin. It is noted that signal discrimination approaches based on discrimination information and Renyi entropy perform better in the test sample than conventional methods based onmore » spectral ratios involving the P and S phases. Two techniques for identifying the ripple-firing pattern for typical mining explosions are proposed and shown to work well on simulated data and on several Scandinavian earthquakes and explosions. We use both cepstral analysis in the frequency domain and a time domain method based on the autocorrelation and partial autocorrelation functions. The proposed approach strips off underlying smooth spectral and seasonal spectral components corresponding to the echo pattern induced by two simple ripple-fired models. For two mining explosions, a pattern is identified whereas for two earthquakes, no pattern is evident.« less

Multichannel spectral mode of the ALOHA up-conversion interferometer

NASA Astrophysics Data System (ADS)

Lehmann, L.; Darré, P.; Boulogne, H.; Delage, L.; Grossard, L.; Reynaud, F.

2018-06-01

In this paper, we propose a multichannel spectral configuration of the Astronomical Light Optical Hybrid Analysis (ALOHA) instrument dedicated to high-resolution imaging. A frequency conversion process is implemented in each arm of an interferometer to transfer the astronomical light to a shorter wavelength domain. Exploiting the spectral selectivity of this non-linear optical process, we propose to use a set of independent pump lasers in order to simultaneously study multiple spectral channels. This principle is experimentally demonstrated with a dual-channel configuration as a proof-of-principle.

Doppler imaging using spectrally-encoded endoscopy

PubMed Central

Yelin, Dvir; Bouma, B. E.; Rosowsky, J. J.; Tearney, G. J.

2009-01-01

The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique that utilizes a single optical fiber and miniature diffractive optics to obtain endoscopic images through small diameter probes. Using spectral-domain interferometry, SEE is furthermore capable of three-dimensional volume imaging at video rates. Here we show that by measuring relative spectral phases, this technology can additionally measure Doppler shifts. Doppler SEE is demonstrated in flowing Intralipid phantoms and vibrating middle ear ossicles. PMID:18795020

Searching Remote Homology with Spectral Clustering with Symmetry in Neighborhood Cluster Kernels

PubMed Central

Maulik, Ujjwal; Sarkar, Anasua

2013-01-01

Remote homology detection among proteins utilizing only the unlabelled sequences is a central problem in comparative genomics. The existing cluster kernel methods based on neighborhoods and profiles and the Markov clustering algorithms are currently the most popular methods for protein family recognition. The deviation from random walks with inflation or dependency on hard threshold in similarity measure in those methods requires an enhancement for homology detection among multi-domain proteins. We propose to combine spectral clustering with neighborhood kernels in Markov similarity for enhancing sensitivity in detecting homology independent of “recent” paralogs. The spectral clustering approach with new combined local alignment kernels more effectively exploits the unsupervised protein sequences globally reducing inter-cluster walks. When combined with the corrections based on modified symmetry based proximity norm deemphasizing outliers, the technique proposed in this article outperforms other state-of-the-art cluster kernels among all twelve implemented kernels. The comparison with the state-of-the-art string and mismatch kernels also show the superior performance scores provided by the proposed kernels. Similar performance improvement also is found over an existing large dataset. Therefore the proposed spectral clustering framework over combined local alignment kernels with modified symmetry based correction achieves superior performance for unsupervised remote homolog detection even in multi-domain and promiscuous domain proteins from Genolevures database families with better biological relevance. Source code available upon request. Contact: sarkar@labri.fr. PMID:23457439

Searching remote homology with spectral clustering with symmetry in neighborhood cluster kernels.

PubMed

Maulik, Ujjwal; Sarkar, Anasua

2013-01-01

Remote homology detection among proteins utilizing only the unlabelled sequences is a central problem in comparative genomics. The existing cluster kernel methods based on neighborhoods and profiles and the Markov clustering algorithms are currently the most popular methods for protein family recognition. The deviation from random walks with inflation or dependency on hard threshold in similarity measure in those methods requires an enhancement for homology detection among multi-domain proteins. We propose to combine spectral clustering with neighborhood kernels in Markov similarity for enhancing sensitivity in detecting homology independent of "recent" paralogs. The spectral clustering approach with new combined local alignment kernels more effectively exploits the unsupervised protein sequences globally reducing inter-cluster walks. When combined with the corrections based on modified symmetry based proximity norm deemphasizing outliers, the technique proposed in this article outperforms other state-of-the-art cluster kernels among all twelve implemented kernels. The comparison with the state-of-the-art string and mismatch kernels also show the superior performance scores provided by the proposed kernels. Similar performance improvement also is found over an existing large dataset. Therefore the proposed spectral clustering framework over combined local alignment kernels with modified symmetry based correction achieves superior performance for unsupervised remote homolog detection even in multi-domain and promiscuous domain proteins from Genolevures database families with better biological relevance. Source code available upon request. sarkar@labri.fr.

The Time-Domain Matched Filter and the Spectral-Domain Matched Filter in 1-Dimensional NMR Spectroscopy.

PubMed

Spencer, Richard G

2010-09-01

A type of "matched filter" (MF), used extensively in the processing of one-dimensional spectra, is defined by multiplication of a free-induction decay (FID) by a decaying exponential with the same time constant as that of the FID. This maximizes, in a sense to be defined, the signal-to-noise ratio (SNR) in the spectrum obtained after Fourier transformation. However, a different entity known also as the matched filter was introduced by van Vleck in the context of pulse detection in the 1940's and has become widely integrated into signal processing practice. These two types of matched filters appear to be quite distinct. In the NMR case, the "filter", that is, the exponential multiplication, is defined by the characteristics of, and applied to, a time domain signal in order to achieve improved SNR in the spectral domain. In signal processing, the filter is defined by the characteristics of a signal in the spectral domain, and applied in order to improve the SNR in the temporal (pulse) domain. We reconcile these two distinct implementations of the matched filter, demonstrating that the NMR "matched filter" is a special case of the matched filter more rigorously defined in the signal processing literature. In addition, two limitations in the use of the MF are highlighted. First, application of the MF distorts resonance ratios as defined by amplitudes, although not as defined by areas. Second, the MF maximizes SNR with respect to resonance amplitude, while intensities are often more appropriately defined by areas. Maximizing the SNR with respect to area requires a somewhat different approach to matched filtering.

Analysis of spectral operators in one-dimensional domains

NASA Technical Reports Server (NTRS)

Maday, Y.

1985-01-01

Results are proven concerning certain projection operators on the space of all polynomials of degree less than or equal to N with respect to a class of one-dimensional weighted Sobolev spaces. The results are useful in the theory of the approximation of partial differential equations with spectral methods.

Cell wall invertase as a regulator in determining sequential development of endosperm and embryo through glucose signaling early in seed development.

PubMed

Wang, Lu; Liao, Shengjin; Ruan, Yong-Ling

2013-01-01

Seed development depends on coordination among embryo, endosperm and seed coat. Endosperm undergoes nuclear division soon after fertilization, whereas embryo remains quiescent for a while. Such a developmental sequence is of great importance for proper seed development. However, the underlying mechanism remains unclear. Recent results on the cellular domain- and stage-specific expression of invertase genes in cotton and Arabidopsis revealed that cell wall invertase may positively and specifically regulate nuclear division of endosperm after fertilization, thereby playing a role in determining the sequential development of endosperm and embryo, probably through glucose signaling.

Analytical solution for multi-species contaminant transport in finite media with time-varying boundary conditions

USDA-ARS?s Scientific Manuscript database

Most analytical solutions available for the equations governing the advective-dispersive transport of multiple solutes undergoing sequential first-order decay reactions have been developed for infinite or semi-infinite spatial domains and steady-state boundary conditions. In this work we present an ...

Variable-Domain Functional Regression for Modeling ICU Data.

PubMed

Gellar, Jonathan E; Colantuoni, Elizabeth; Needham, Dale M; Crainiceanu, Ciprian M

2014-12-01

We introduce a class of scalar-on-function regression models with subject-specific functional predictor domains. The fundamental idea is to consider a bivariate functional parameter that depends both on the functional argument and on the width of the functional predictor domain. Both parametric and nonparametric models are introduced to fit the functional coefficient. The nonparametric model is theoretically and practically invariant to functional support transformation, or support registration. Methods were motivated by and applied to a study of association between daily measures of the Intensive Care Unit (ICU) Sequential Organ Failure Assessment (SOFA) score and two outcomes: in-hospital mortality, and physical impairment at hospital discharge among survivors. Methods are generally applicable to a large number of new studies that record a continuous variables over unequal domains.

Multiscale Modeling of Damage Processes in fcc Aluminum: From Atoms to Grains

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Saether, E.; Yamakov, V.

2008-01-01

Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, current analysis is limited to small domains and increasing the size of the MD domain quickly presents intractable computational demands. A preferred approach to surmount this computational limitation has been to combine continuum mechanics-based modeling procedures, such as the finite element method (FEM), with MD analyses thereby reducing the region of atomic scale refinement. Such multiscale modeling strategies can be divided into two broad classifications: concurrent multiscale methods that directly incorporate an atomistic domain within a continuum domain and sequential multiscale methods that extract an averaged response from the atomistic simulation for later use as a constitutive model in a continuum analysis.

Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

PubMed Central

Jia, Yali; Liu, Gangjun; Gordon, Andrew Y.; Gao, Simon S.; Pechauer, Alex D.; Stoddard, Jonathan; McGill, Trevor J.; Jayagopal, Ashwath; Huang, David

2015-01-01

We demonstrate the proof of concept of a novel Fourier-domain optical coherence tomography contrast mechanism using gold nanorod contrast agents and a spectral fractionation processing technique. The methodology detects the spectral shift of the backscattered light from the nanorods by comparing the ratio between the short and long wavelength halves of the optical coherence tomography signal intensity. Spectral fractionation further divides the halves into sub-bands to improve spectral contrast and suppress speckle noise. Herein, we show that this technique can detect gold nanorods in intralipid tissue phantoms. Furthermore, cellular labeling by gold nanorods was demonstrated using retinal pigment epithelial cells in vitro. PMID:25836459

ACUTE ZONAL OCCULT OUTER RETINOPATHY: Structural and Functional Analysis Across the Transition Zone Between Healthy and Diseased Retina.

PubMed

Duncker, Tobias; Lee, Winston; Jiang, Fan; Ramachandran, Rithambara; Hood, Donald C; Tsang, Stephen H; Sparrow, Janet R; Greenstein, Vivienne C

2018-01-01

To assess structure and function across the transition zone (TZ) between relatively healthy and diseased retina in acute zonal occult outer retinopathy. Six patients (6 eyes; age 22-71 years) with acute zonal occult outer retinopathy were studied. Spectral-domain optical coherence tomography, fundus autofluorescence, near-infrared reflectance, color fundus photography, and fundus perimetry were performed and images were registered to each other. The retinal layers of the spectral-domain optical coherence tomography scans were segmented and the thicknesses of two outer retinal layers, that is, the total receptor and outer segment plus layers, and the retinal nerve fiber layer were measured. All eyes showed a TZ on multimodal imaging. On spectral-domain optical coherence tomography, the TZ was in the nasal retina at varying distances from the fovea. For all eyes, it was associated with loss of the ellipsoid zone band, significant thinning of the two outer retinal layers, and in three eyes with thickening of the retinal nerve fiber layer. On fundus autofluorescence, all eyes had a clearly demarcated peripapillary area of abnormal fundus autofluorescence delimited by a border of high autofluorescence; the latter was associated with loss of the ellipsoid zone band and with a change from relatively normal to markedly decreased or nonrecordable visual sensitivity on fundus perimetry. The results of multimodal imaging clarified the TZ in acute zonal occult outer retinopathy. The TZ was outlined by a distinct high autofluorescence border that correlated with loss of the ellipsoid zone band on spectral-domain optical coherence tomography. However, in fundus areas that seemed healthy on fundus autofluorescence, thinning of the outer retinal layers and thickening of the retinal nerve fiber layer were observed near the TZ. The TZ was also characterized by a decrease in visual sensitivity.

PREVALENCE OF FOVEOLAR LUCENCY WITH DIFFERENT GAS TAMPONADES IN SURGICALLY CLOSED MACULAR HOLES ASSESSED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

PubMed

Zarranz-Ventura, Javier; Ellabban, Abdallah A; Sim, Dawn A; Keane, Pearse A; Kirkpatrick, James N; Sallam, Ahmed A B

2017-07-07

To evaluate the prevalence of foveolar lucency (FL) in surgically closed macular holes by spectral domain optical coherence tomography. One hundred forty-two eyes of 132 patients underwent pars plana vitrectomy, internal limiting membrane peeling, and gas tamponade in a 60-month time frame. Anatomical success and FL rates assessed by spectral domain optical coherence tomography, mean preoperative, and postoperative best-measured visual acuity and surgical details were retrospectively analyzed. Spectral domain optical coherence tomography confirmed closed holes with FL in 33.7% (34/101) of eyes at 1 month, 7.3% (9/123) at 3 months, 4.6% (6/129) at 6 months, and 3% (4/133) at 12 months. Prevalence of FL in closed holes at Month 1 was lower in C3F8-treated eyes (9.5%, 2/21) compared with C2F6 (40.9%, 18/44, P = 0.03) and SF6-treated eyes (38.9%, 14/36, P = 0.05). No differences were observed at Month 3. No differences in best-measured visual acuity change were observed between closed holes with or without FL at Month 1 (-0.14 ± 0.19 vs. -0.11 ± 0.23, P = 0.48) or any of the other time points. Temporary FL is a highly prevalent feature in successfully closed macular holes. Eyes treated with C3F8 gas had lower rates of FL at Month 1 than C2F6 and SF6-treated eyes. The presence of FL in closed holes does not seem to have any effect on the visual outcomes.

AMISH EYE STUDY: Baseline Spectral Domain Optical Coherence Tomography Characteristics of Age-Related Macular Degeneration.

PubMed

Nittala, Muneeswar G; Song, Yeunjoo E; Sardell, Rebecca; Adams, Larry D; Pan, Samuel; Velaga, Swetha B; Horst, Violet; Dana, Debra; Caywood, Laura; Laux, Renee; Fuzzell, Denise; Fuzzell, Sarada; Scott, William K; Cooke Bailey, Jessica N; Igo, Robert P; Haines, Jonathan; Pericak-Vance, Margaret A; Sadda, SriniVas R; Stambolian, Dwight

2018-05-09

To describe spectral domain optical coherence tomography (SD-OCT) findings in an Amish cohort to assess SD-OCT markers for early age-related macular degeneration (AMD). The authors performed a family-based prospective cohort study of 1,146 elderly Amish subjects (age range 50-99 years) (2,292 eyes) who had a family history of at least 1 individual with AMD. All subjects underwent complete ophthalmic examinations, SD-OCT using both Cirrus and Spectralis (20 × 20° scan area) instruments, fundus autofluorescence, infrared imaging, and color fundus photography. Spectral domain optical coherence tomography characteristics were analyzed in subjects with AMD (with and without subretinal drusenoid deposits [SDDs]) and normal healthy cohorts. Participants' mean age was 65.2 years (SD ± 11). Color fundus photographic findings in 596 (53%) subjects (1,009 eyes) were consistent with AMD; the remaining 478 (43%) subjects showed no signs of AMD. The choroid was significantly thinner on OCT (242 ± 76 µm, P < 0.001) in those with AMD compared with those without (263 ± 63 µm). Subretinal drusenoid deposits were found in 143 eyes (7%); 11 of the 143 eyes (8%) had no other manifestations of AMD. Drusen volume (P < 0.001) and area of geographic atrophy (P < 0.001) were significantly greater, and choroid was significantly (P < 0.001) thinner in subjects with SDDs versus those without SDDs. The authors describe spectral domain optical coherence tomography characteristics in an elderly Amish population with and without AMD, including the frequency of SDD. Although relatively uncommon in this population, the authors confirmed that SDDs can be found in the absence of other features of AMD and that eyes with SDDs have thinner choroids.

MULTIMODAL IMAGING OF MOSAIC RETINOPATHY IN CARRIERS OF HEREDITARY X-LINKED RECESSIVE DISEASES.

PubMed

Wu, An-Lun; Wang, Jung-Pan; Tseng, Yun-Ju; Liu, Laura; Kang, Yu-Chuan; Chen, Kuan-Jen; Chao, An-Ning; Yeh, Lung-Kun; Chen, Tun-Lu; Hwang, Yih-Shiou; Wu, Wei-Chi; Lai, Chi-Chun; Wang, Nan-Kai

2018-05-01

To investigate the clinical features in carriers of X-linked retinitis pigmentosa, X-linked ocular albinism, and choroideremia (CHM) using multimodal imaging and to assess their diagnostic value in these three mosaic retinopathies. We prospectively examined 14 carriers of 3 X-linked recessive disorders (X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM). Details of abnormalities of retinal morphology were evaluated using fundus photography, fundus autofluorescence (FAF) imaging, and spectral domain optical coherence tomography. In six X-linked retinitis pigmentosa carriers, fundus appearance varied from unremarkable to the presence of tapetal-like reflex and pigmentary changes. On FAF imaging, all carriers exhibited a bright radial reflex against a dark background. By spectral domain optical coherence tomography, loss of the ellipsoid zone in the macula was observed in 3 carriers (50%). Regarding the retinal laminar architecture, 4 carriers (66.7%) showed thinning of the outer nuclear layer and a dentate appearance of the outer plexiform layer. All five X-linked ocular albinism carriers showed a characteristic mud-splatter patterned fundus, dark radial streaks against a bright background on FAF imaging, and a normal-appearing retinal structure by spectral domain optical coherence tomography imaging. Two of the 3 CHM carriers (66.7%) showed a diffuse moth-eaten appearance of the fundus, and all 3 showed irregular hyper-FAF and hypo-FAF spots throughout the affected area. In the CHM carriers, the structural changes observed by spectral domain optical coherence tomography imaging were variable. Our findings in an Asian cohort suggest that FAF imaging is a practical diagnostic test for differentiating X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM carriers. Wide-field FAF is an easy and helpful adjunct to testing for the correct diagnosis and identification of lyonization in carriers of these three mosaic retinopathies.

Curvature of iris profile in spectral domain optical coherence tomography and dependency to refraction, age and pupil size - the MIPH Eye&Health Study.

PubMed

Schuster, Alexander K; Fischer, Joachim E; Vossmerbaeumer, Urs

2017-03-01

Optical coherence tomography (OCT) of the anterior segment allows quantitative analysis of the geometry of the iris. We performed spectral domain OCT examinations in healthy emmetropic, hyperopic and myopic subjects to investigate iris curvature and its associations. In a cross-sectional study, out of 4617 eyes (2309 subjects) those with refractive errors of <-4 or >+3 dioptres were identified by objective refraction. The iris was examined using the anterior segment mode of a spectral domain 3D OCT-2000 (Topcon Inc., Japan) in the temporal meridian, and OCT scans were investigated with respect to presence and amount of convex and concave iris configuration. Ninety-three eyes of 50 subjects served as emmetropic group (-0.5 ≤ x ≤+0.5 dioptres). Previous ocular surgery was exclusion criterion. Six hundred and sixty-eight eyes of 398 persons [292 male (76%); age range; 18-66 years] were included in the study. In the myopic group, 105 eyes had a concave iris configuration (26%), while in the hyperopic group, no eye had this configuration (0%) and in the emmetropic group five eyes (5%). Convex iris configuration was found in 96% of hyperopic, in 85% of the emmetropic and in 67% of the myopic eyes. There was an association between concave iris configuration and myopia, younger age and male gender, and with anterior chamber angle width. Spectral domain OCT images can be used for analysis of the iris structure and geometry. Our results are limited to the properties of the study population having an age range from 18 to 66 years and consisting mainly of men. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

An efficient implementation of a high-order filter for a cubed-sphere spectral element model

NASA Astrophysics Data System (ADS)

Kang, Hyun-Gyu; Cheong, Hyeong-Bin

2017-03-01

A parallel-scalable, isotropic, scale-selective spatial filter was developed for the cubed-sphere spectral element model on the sphere. The filter equation is a high-order elliptic (Helmholtz) equation based on the spherical Laplacian operator, which is transformed into cubed-sphere local coordinates. The Laplacian operator is discretized on the computational domain, i.e., on each cell, by the spectral element method with Gauss-Lobatto Lagrange interpolating polynomials (GLLIPs) as the orthogonal basis functions. On the global domain, the discrete filter equation yielded a linear system represented by a highly sparse matrix. The density of this matrix increases quadratically (linearly) with the order of GLLIP (order of the filter), and the linear system is solved in only O (Ng) operations, where Ng is the total number of grid points. The solution, obtained by a row reduction method, demonstrated the typical accuracy and convergence rate of the cubed-sphere spectral element method. To achieve computational efficiency on parallel computers, the linear system was treated by an inverse matrix method (a sparse matrix-vector multiplication). The density of the inverse matrix was lowered to only a few times of the original sparse matrix without degrading the accuracy of the solution. For better computational efficiency, a local-domain high-order filter was introduced: The filter equation is applied to multiple cells, and then the central cell was only used to reconstruct the filtered field. The parallel efficiency of applying the inverse matrix method to the global- and local-domain filter was evaluated by the scalability on a distributed-memory parallel computer. The scale-selective performance of the filter was demonstrated on Earth topography. The usefulness of the filter as a hyper-viscosity for the vorticity equation was also demonstrated.

On the maximum-entropy/autoregressive modeling of time series

NASA Technical Reports Server (NTRS)

Chao, B. F.

1984-01-01

The autoregressive (AR) model of a random process is interpreted in the light of the Prony's relation which relates a complex conjugate pair of poles of the AR process in the z-plane (or the z domain) on the one hand, to the complex frequency of one complex harmonic function in the time domain on the other. Thus the AR model of a time series is one that models the time series as a linear combination of complex harmonic functions, which include pure sinusoids and real exponentials as special cases. An AR model is completely determined by its z-domain pole configuration. The maximum-entropy/autogressive (ME/AR) spectrum, defined on the unit circle of the z-plane (or the frequency domain), is nothing but a convenient, but ambiguous visual representation. It is asserted that the position and shape of a spectral peak is determined by the corresponding complex frequency, and the height of the spectral peak contains little information about the complex amplitude of the complex harmonic functions.

Wavelet-domain de-noising technique for THz pulsed spectroscopy

NASA Astrophysics Data System (ADS)

Chernomyrdin, Nikita V.; Zaytsev, Kirill I.; Gavdush, Arsenii A.; Fokina, Irina N.; Karasik, Valeriy E.; Reshetov, Igor V.; Kudrin, Konstantin G.; Nosov, Pavel A.; Yurchenko, Stanislav O.

2014-09-01

De-noising of terahertz (THz) pulsed spectroscopy (TPS) data is an essential problem, since a noise in the TPS system data prevents correct reconstruction of the sample spectral dielectric properties and to perform the sample internal structure studying. There are certain regions in TPS signal Fourier spectrum, where Fourier-domain signal-to-noise ratio is relatively small. Effective de-noising might potentially expand the range of spectrometer spectral sensitivity and reduce the time of waveform registration, which is an essential problem for biomedical applications of TPS. In this work, it is shown how the recent progress in signal processing in wavelet-domain could be used for TPS waveforms de-noising. It demonstrates the ability to perform effective de-noising of TPS data using the algorithm of the Fast Wavelet Transform (FWT). The results of the optimal wavelet basis selection and wavelet-domain thresholding technique selection are reported. Developed technique is implemented for reconstruction of in vivo healthy and deseased skin samplesspectral characteristics at THz frequency range.

TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Tie; Wu Yuefang; Zhang Huawei

The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10{sup 3} cm{sup -3} and kinematic temperature {approx}20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed towardmore » core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.« less

Imaging of retinal and choroidal vascular tumours

PubMed Central

Heimann, H; Jmor, F; Damato, B

2013-01-01

The most common intraocular vascular tumours are choroidal haemangiomas, vasoproliferative tumours, and retinal haemangioblastomas. Rarer conditions include cavernous retinal angioma and arteriovenous malformations. Options for ablating the tumour include photodynamic therapy, argon laser photocoagulation, trans-scleral diathermy, cryotherapy, anti-angiogenic agents, plaque radiotherapy, and proton beam radiotherapy. Secondary effects are common and include retinal exudates, macular oedema, epiretinal membranes, retinal fibrosis, as well as serous and tractional retinal detachment, which are treated using standard methods (ie, intravitreal anti-angiogenic agents or steroids as well as vitreoretinal procedures, such as epiretinal membrane peeling and release of retinal traction). The detection, diagnosis, and monitoring of vascular tumours and their complications have improved considerably thanks to advances in imaging. These include spectral domain and enhanced depth imaging optical coherence tomography (SD-OCT and EDI-OCT, respectively), wide-angle photography and angiography as well as wide-angle fundus autofluorescence. Such novel imaging has provided new diagnostic clues and has profoundly influenced therapeutic strategies so that vascular tumours and secondary effects are now treated concurrently instead of sequentially, enhancing any opportunities for conserving vision and the eye. In this review, we describe how SD-OCT, EDI-OCT, autofluorescence, wide-angle photography and wide-angle angiography have facilitated the evaluation of eyes with the more common vascular tumours, that is, choroidal haemangioma, retinal vasoproliferative tumours, and retinal haemangioblastoma. PMID:23196648

Changes in the optical absorption induced by sequential exposition to short- and long-wavelength radiation in the BTO:Al crystal

NASA Astrophysics Data System (ADS)

Shandarov, S. M.; Dyu, V. G.; Kisteneva, M. G.; Khudyakova, E. S.; Smirnov, S. V.; Akrestina, A. S.; Kargin, Yu F.

2017-02-01

Modifications of the spectral dependences of the optical absorption induced in the Bi12TiO20:Al crystal as a result of sequential exposition to cw laser radiation first with the wavelength λ g = 532 nm and then with the longer wavelength λ l,n = 588, 633, 655, 658, 663, 700, 780, 871, or 1064 nm are investigated. We revealed that after the short-wavelength exposition to radiation with λg = 532 nm, the optical absorption in the crystal increases, and in the range 470-1000 nm, yields the spectrum whose form is independent of a prehistory. The subsequent exposition to longer-wavelength radiation leads to bleaching of the crystal in the examined spectral range. A maximum diminishing of the optical absorption in the crystal is observed upon exposure to radiation with the wavelength λ l,5 = 663 nm. To describe the experimentally observed reversible changes in the optical absorption spectrum in the Bi12TiO20:Al we use the impurity absorption model that takes into account the photoinduced transitions between two metastable states of a deep defect center leading to the change of its position in the crystal lattice under conditions of strong lattice relaxation.

Nebo: An efficient, parallel, and portable domain-specific language for numerically solving partial differential equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Earl, Christopher; Might, Matthew; Bagusetty, Abhishek

This study presents Nebo, a declarative domain-specific language embedded in C++ for discretizing partial differential equations for transport phenomena on multiple architectures. Application programmers use Nebo to write code that appears sequential but can be run in parallel, without editing the code. Currently Nebo supports single-thread execution, multi-thread execution, and many-core (GPU-based) execution. With single-thread execution, Nebo performs on par with code written by domain experts. With multi-thread execution, Nebo can linearly scale (with roughly 90% efficiency) up to 12 cores, compared to its single-thread execution. Moreover, Nebo’s many-core execution can be over 140x faster than its single-thread execution.

Nebo: An efficient, parallel, and portable domain-specific language for numerically solving partial differential equations

DOE PAGES

Earl, Christopher; Might, Matthew; Bagusetty, Abhishek; ...

2016-01-26

This study presents Nebo, a declarative domain-specific language embedded in C++ for discretizing partial differential equations for transport phenomena on multiple architectures. Application programmers use Nebo to write code that appears sequential but can be run in parallel, without editing the code. Currently Nebo supports single-thread execution, multi-thread execution, and many-core (GPU-based) execution. With single-thread execution, Nebo performs on par with code written by domain experts. With multi-thread execution, Nebo can linearly scale (with roughly 90% efficiency) up to 12 cores, compared to its single-thread execution. Moreover, Nebo’s many-core execution can be over 140x faster than its single-thread execution.

Solution to the indexing problem of frequency domain simulation experiments

NASA Technical Reports Server (NTRS)

Mitra, Mousumi; Park, Stephen K.

1991-01-01

A frequency domain simulation experiment is one in which selected system parameters are oscillated sinusoidally to induce oscillations in one or more system statistics of interest. A spectral (Fourier) analysis of these induced oscillations is then performed. To perform this spectral analysis, all oscillation frequencies must be referenced to a common, independent variable - an oscillation index. In a discrete-event simulation, the global simulation clock is the most natural choice for the oscillation index. However, past efforts to reference all frequencies to the simulation clock generally yielded unsatisfactory results. The reason for these unsatisfactory results is explained in this paper and a new methodology which uses the simulation clock as the oscillation index is presented. Techniques for implementing this new methodology are demonstrated by performing a frequency domain simulation experiment for a network of queues.

Long-lived coherences: Improved dispersion in the frequency domain using continuous-wave and reduced-power windowed sustaining irradiation

NASA Astrophysics Data System (ADS)

Sadet, A.; Fernandes, L.; Kateb, F.; Balzan, R.; Vasos, P. R.

2014-08-01

Long-lived coherences (LLC's) are detectable magnetisation modes with favourable relaxation times that translate as sharp resonances upon Fourier transform. The frequency domain of LLC's was previously limited to the range of J-couplings within pairs of homonuclear spins. LLC evolution at high magnetic fields needs to be sustained by radio-frequency irradiation. We show that LLC-based spectral dispersion can be extended beyond the J-couplings domain using adapted carrier offsets and introduce a new reduced-power sustaining method to preserve LLC's within the required range of offsets. Spectral resolution is enhanced as the natively narrow lines of LLC's are further dispersed, making them potential probes for the study of biomolecules featuring strong resonance overlap and for media where NMR spectroscopy is commonly hindered by line broadening.

Evaluation of skin moisturizer effects using terahertz time domain imaging

NASA Astrophysics Data System (ADS)

Martinez-Meza, L. H.; Rojas-Landeros, S. C.; Castro-Camus, E.; Alfaro-Gomez, M.

2018-02-01

We use terahertz time domain imaging for the evaluation of the effects of skin-moisturizers in vivo. We evaluate three principal substances used in commercial moisturizers: glycerin, hyaluronic acid and lanolin. We image the interaction of the forearm with each of the substances taking terahertz spectra at sequential times. With this, we are able to measure the effect of the substances on the hydration level of the skin in time, determining the feasibility of using THz imaging for the evaluation of the products and their effects on the hydration levels of the skin.

Mutational analysis of the Saccharomyces cerevisiae cytochrome c oxidase assembly protein Cox11p.

PubMed

Banting, Graham S; Glerum, D Moira

2006-03-01

Cox11p is an integral protein of the inner mitochondrial membrane that is essential for cytochrome c oxidase assembly. The bulk of the protein is located in the intermembrane space and displays high levels of evolutionary conservation. We have analyzed a collection of site-directed and random cox11 mutants in an effort to further define essential portions of the molecule. Of the alleles studied, more than half had no apparent effect on Cox11p function. Among the respiration deficiency-encoding alleles, we identified three distinct phenotypes, which included a set of mutants with a misassembled or partially assembled cytochrome oxidase, as indicated by a blue-shifted cytochrome aa(3) peak. In addition to the shifted spectral signal, these mutants also display a specific reduction in the levels of subunit 1 (Cox1p). Two of these mutations are likely to occlude a surface pocket behind the copper-binding domain in Cox11p, based on analogy with the Sinorhizobium meliloti Cox11 solution structure, thereby suggesting that this pocket is crucial for Cox11p function. Sequential deletions of the matrix portion of Cox11p suggest that this domain is not functional beyond the residues involved in mitochondrial targeting and membrane insertion. In addition, our studies indicate that Deltacox11, like Deltasco1, displays a specific hypersensitivity to hydrogen peroxide. Our studies provide the first evidence at the level of the cytochrome oxidase holoenzyme that Cox1p is the in vivo target for Cox11p and suggest that Cox11p may also have a role in the response to hydrogen peroxide exposure.

Far-Ir Spectroscopy of Neutral Gas Phase Peptides: Signatures from Combined Experiments and Simulations

NASA Astrophysics Data System (ADS)

Mahé, Jérôme; Gaigeot, Marie-Pierre; Bakker, Daniël; Jaeqx, Sander; Rijs, Anouk

2016-06-01

Within the past two decades, action vibrational spectroscopy has become an almost routine experimental method to probe the structures of molecules and clusters in the gas phase (neutral and ions). Such experiments are mainly performed in the 1000-4000 wn fingerprint regions. Though successful in many respects, these spectral domains can be however restrictive in the information provided, and sometimes reach limitations for unravelling structures without ambiguity. In a collaborative work with the group of Dr A.M. Rijs (FELIX laboratory, Radbout University, The Netherlands) we have launched a new strategy where the far-IR/Tera-Hertz domain (100-800 wn domain) is experimentally probed for neutral gas phase molecules. Our group in Paris apply finite temperature DFT-based molecular dynamics (DFT-MD) simulations in order to unravel the complex signatures arising in the far-IR domain, and provide an unambiguous assignment both of the structural conformation of the gas phase molecules (taking into account the experimental conditions) and an understanding of the spectral signatures/fingerprints. We will discuss our experimental and theoretical investigations on two neutral peptides in the 100-800 wn far-IR spectral domain, i.e. Z-Ala6 and PheGly dipeptide, that represent two systems which definitive conformational assignment was not possible without the far IR signatures. We will also present our very recent results on the Phe-X peptide series, where X stands for Gly, Ala, Pro, Val, Ser, Cys, combining experiments and DFT-MD simulations, providing a detailed understanding of the vibrational fingerprints in the far-IR domain. In all exemples, we will show how DFT-MD simulations is the proper theoretical tool to account for vibrational anharmonicities and mode couplings, of prime importance in the far-IR domain. References : J. Mahé, S. Jaeqx, A.M. Rijs, M.P. Gaigeot, Phys. Chem. Chem. Phys., 17 :25905 (2015) S. Jaeqx, J. Oomens, A. Cimas, M.P. Gaigeot, A.M. Rijs, Angew. Chemie. Int., 53 :3663 (2014)

Guided-mode resonant filters and reflectors: Principles, design, and fabrication

NASA Astrophysics Data System (ADS)

Niraula, Manoj

In this dissertation, we overview the operational principles of these resonant periodic structures, discuss the methods of their design and fabrication, and propose and demonstrate novel functionalities for spatial and spectral filtering, and unpolarized wideband reflection. Fashioned with materially sparse gratings, these optical devices are easy to fabricate and integration friendly compared to their traditional multi-layer counterparts making their research and development critical for practical applications. We study, theoretically, modal properties and parametric dependence of resonant periodic bandpass filters operating in the mid- and near-infrared spectral domains. We investigate three different device architectures consisting of single, double, and triple layers based on all-transparent dielectric and semiconductor thin films. We present three modal coupling configurations forming complex mixtures of two or three distinct leaky modes coupling at different evanescent diffraction orders. Our modal analysis demonstrates key attributes of subwavelength periodic thin-film structures in multiple-modal blending to achieve desired transmission spectra. We provide the first experimental demonstration of high-efficiency and narrow-linewidth resonant bandpass filter applying a single patterned silicon layer on a quartz substrate. Its performance corresponds to bandpass filters requiring 15 traditional Si/SiO2 thin-film layers. The feasibility of sparse narrowband, high-efficiency bandpass filters with extremely wide, flat, and low sidebands is thereby demonstrated. The proposed technology is integration-friendly and opens doors for further development in various disciplines and spectral regions where thin-film solutions are traditionally applied. We demonstrate concurrent spatial and spectral filtering as a new outstanding attribute of resonant periodic devices. This functionality is enabled by a unique, near-complete, reflection state that is discrete in both angular and spectral domains and realized with carefully crafted nanogratings operating in the non-subwavelength regime. We study the pathway and inter-modal interference effects inducing this intriguing reflection state. In a proof-of-concept experiment, we obtain angular and spectral bandwidths of 4 mrad and 1 nm, respectively. This filter concept can be used for focus-free spectral and spatial filtering in compact holographic and interferometric optical instruments. We report unpolarized broadband reflectors enabled by a serial arrangement of a pair of polarized subwavelength gratings. Optimized with inverse numerical methods, our elemental gratings consist of a partially etched crystalline-silicon film on a quartz substrate. The resulting reflectors exhibit extremely wide spectral reflection bands in one polarization. By arranging two such reflectors sequentially with orthogonal periodicities, there results an unpolarized spectral band possessing bandwidth exceeding those of the individual polarized bands. In the experiments reported herein, we achieve zero-order reflectance exceeding 97% under unpolarized light incidence over a 500-nm-wide wavelength band in the near-infrared domain. Moreover, the resonant unpolarized broadband accommodates an ultra-high-reflection band spanning 85 nm and exceeding 99.9% in efficiency. The elemental polarization-sensitive reflectors based on one-dimensional resonant gratings have simple design, robust performance, and are straightforward to fabricate. Hence, this technology is a promising alternative to traditional multilayer thin-film reflectors especially at longer wavelengths of light where multilayer deposition may be infeasible or impractical. We demonstrate an interesting attribute of resonant bandpass filters which is high angular stability for fully conical light incidence. Fashioning an experimental bandpass filter with a subwavelength silicon grating on a quartz substrate, we show that fully conical incidence provides an angular full-width at half-maximum linewidth of 9.5° compared to a linewidth of 0.1° for classical incidence. Slow angular variation of the central wavelength with full conical incidence arises via a corresponding slow angular variation of the resonant second diffraction orders driving the pertinent leaky modes. Moreover, full conical incidence maintains a profile with a single passband as opposed to the formation of two passbands characteristic of resonant subwavelength gratings under classical incidence. Our experimental results demonstrate excellent stability in angle, spectral profile, linewidth, and efficiency. Finally, we propose a novel method of design and fabrication of photonic lattices that incorporates the best of both worlds: a polarized resonant grating can be designed and converted to its unpolarized lattice equivalent using the same design parameters to obtain a similar performance. We show this in context of a single-layer polarized bandpass filter operating at 1550 nm with 100% transmission efficiency. An unpolarized square-hole lattice with identical parameters operates as a bandpass filter at 1560 nm with 70% transmission efficiency. Moreover, conventional laser interference lithography technique for mask patterning is limited to circular-hole photoresist lattice. We propose a method to lay down a metal hard-mask by lifting-off patterned photoresist in two steps for a square-hole lattice. Our comprehensive study provides new principles for easy design and fabrication of square-hole photonic lattices for unpolarized guided-mode resonance applications. (Abstract shortened by ProQuest.).

Domain decomposition methods for systems of conservation laws: Spectral collocation approximations

NASA Technical Reports Server (NTRS)

Quarteroni, Alfio

1989-01-01

Hyperbolic systems of conversation laws are considered which are discretized in space by spectral collocation methods and advanced in time by finite difference schemes. At any time-level a domain deposition method based on an iteration by subdomain procedure was introduced yielding at each step a sequence of independent subproblems (one for each subdomain) that can be solved simultaneously. The method is set for a general nonlinear problem in several space variables. The convergence analysis, however, is carried out only for a linear one-dimensional system with continuous solutions. A precise form of the error reduction factor at each iteration is derived. Although the method is applied here to the case of spectral collocation approximation only, the idea is fairly general and can be used in a different context as well. For instance, its application to space discretization by finite differences is straight forward.

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance

PubMed Central

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2017-01-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm−1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360–500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors. PMID:29201583

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance.

PubMed

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2016-03-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), S cdm (units: nm -1 ), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving S cdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of S cdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.

Self-spectral calibration for spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Zhang, Xianling; Gao, Wanrong; Bian, Haiyi; Chen, Chaoliang; Liao, Jiuling

2013-06-01

A different real-time self-wavelength calibration method for spectral domain optical coherence tomography is presented in which interference spectra measured from two arbitrary points on the tissue surface are used for calibration. The method takes advantages of two favorable conditions of optical coherence tomography (OCT) signal. First, the signal back-scattered from the tissue surface is generally much stronger than that from positions in the tissue interior, so the spectral component of the surface interference could be extracted from the measured spectrum. Second, the tissue surface is not a plane and a phase difference exists between the light reflected from two different points on the surface. Compared with the zero-crossing automatic method, the introduced method has the advantage of removing the error due to dispersion mismatch or the common phase error. The method is tested experimentally to demonstrate the improved signal-to-noise ratio, higher axial resolution, and slower sensitivity degradation with depth when compared to the use of the zero-crossing method and applied to two-dimensional cross-sectional images of human finger skin.

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

NASA Astrophysics Data System (ADS)

Lim, Yiheng; Yatagai, Toyohiko; Otani, Yukitoshi

2016-04-01

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680-940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.

Self-organization of the magnetization in ferromagnetic nanowires

NASA Astrophysics Data System (ADS)

Ivanov, A. A.; Orlov, V. A.

2017-10-01

In this work we demonstrate the occurrence of the characteristic spatial scale in the distribution of magnetization unrelated to the domain wall or crystallite size with using computer simulation of magnetization in a polycrystalline ferromagnetic nanowire. This is the stochastic domain size. We show that this length is included in the spectral density of the pinning force of domain wall on inhomogeneities of the crystallographic anisotropy. The constant and distribution of easy axes directions of the effective anisotropy of stochastic domain, are analytically calculated.

Birefringence measurement of retinal nerve fiber layer using polarization-sensitive spectral domain optical coherence tomography with Jones matrix based analysis

NASA Astrophysics Data System (ADS)

Yamanari, Masahiro; Miura, Masahiro; Makita, Shuichi; Yatagai, Toyohiko; Yasuno, Yoshiaki

2007-02-01

Birefringence of retinal nerve fiber layer is measured by polarization-sensitive spectral domain optical coherence tomography using the B-scan-oriented polarization modulation method. Birefringence of the optical fiber and the cornea is compensated by Jones matrix based analysis. Three-dimensional phase retardation map around the optic nerve head and en-face phase retardation map of the retinal nerve fiber layer are shown. Unlike scanning laser polarimetry, our system can measure the phase retardation quantitatively without using bow-tie pattern of the birefringence in the macular region, which enables diagnosis of glaucoma even if the patients have macular disease.

Feasibility of spectral-domain phase-sensitive optical coherence tomography for middle ear vibrometry

PubMed Central

Nguyen-Huynh, Anh; Wang, Ruikang K.; Jacques, Steven L.; Choudhury, Niloy; Nuttall, Alfred L.

2012-01-01

Abstract. We describe a novel application of spectral-domain phase-sensitive optical coherence tomography (SD PS-OCT) to detect the tiny motions of the middle ear structures, such as the tympanic membrane and ossicular chain, and their morphological features for differential diagnosis of CHL. This technique has the potential to provide meaningful vibration of ossicles with a vibration sensitivity of ∼0.5  nm at 1 kHz of 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 a nanometer scale. PMID:22734728

Computation of Engine Noise Propagation and Scattering Off an Aircraft

NASA Technical Reports Server (NTRS)

Xu, J.; Stanescu, D.; Hussaini, M. Y.; Farassat, F.

2003-01-01

The paper presents a comparison of experimental noise data measured in flight on a two-engine business jet aircraft with Kulite microphones placed on the suction surface of the wing with computational results. Both a time-domain discontinuous Galerkin spectral method and a frequency-domain spectral element method are used to simulate the radiation of the dominant spinning mode from the engine and its reflection and scattering by the fuselage and the wing. Both methods are implemented in computer codes that use the distributed memory model to make use of large parallel architectures. The results show that trends of the noise field are well predicted by both methods.

Extended depth of focus adaptive optics spectral domain optical coherence tomography

PubMed Central

Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

2012-01-01

We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

Extended depth of focus adaptive optics spectral domain optical coherence tomography.

PubMed

Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

2012-10-01

We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA.

Spectral-domain optical coherence tomography for endoscopic imaging

NASA Astrophysics Data System (ADS)

Chen, Xiaodong; Li, Qiao; Li, Wanhui; Wang, Yi; Yu, Daoyin

2007-02-01

Optical coherence tomography (OCT) is an emerging cross-sectional imaging technology. It uses broadband light sources to achieve axial image resolutions on the few micron scale. OCT is widely applied to medical imaging, it can get cross-sectional image of bio-tissue (transparent and turbid) with non-invasion and non-touch. In this paper, the principle of OCT is presented and the crucial parameters of the system are discussed in theory. With analysis of different methods and medical endoscopic system's feature, a design which combines the spectral domain OCT (SDOCT) technique and endoscopy is put forward. SDOCT provides direct access to the spectrum of the optical signal. It is shown to provide higher imaging speed when compared to time domain OCT. At the meantime, a novel OCT probe which uses advanced micromotor to drive reflecting prism is designed according to alimentary tract endoscopic feature. A simple optical coherence tomography system has been developed based on a fiber-based Michelson interferometer and spectrometer. An experiment which uses motor to drive prism to realize rotating imaging is done. Images obtained with this spectral interferometer are presented. The results verify the feasibility of endoscopic optical coherence tomography system with rotating scan.

Post-earthquake relaxation using a spectral element method: 2.5-D case

USGS Publications Warehouse

Pollitz, Fred

2014-01-01

The computation of quasi-static deformation for axisymmetric viscoelastic structures on a gravitating spherical earth is addressed using the spectral element method (SEM). A 2-D spectral element domain is defined with respect to spherical coordinates of radius and angular distance from a pole of symmetry, and 3-D viscoelastic structure is assumed to be azimuthally symmetric with respect to this pole. A point dislocation source that is periodic in azimuth is implemented with a truncated sequence of azimuthal order numbers. Viscoelasticity is limited to linear rheologies and is implemented with the correspondence principle in the Laplace transform domain. This leads to a series of decoupled 2-D problems which are solved with the SEM. Inverse Laplace transform of the independent 2-D solutions leads to the time-domain solution of the 3-D equations of quasi-static equilibrium imposed on a 2-D structure. The numerical procedure is verified through comparison with analytic solutions for finite faults embedded in a laterally homogeneous viscoelastic structure. This methodology is applicable to situations where the predominant structure varies in one horizontal direction, such as a structural contrast across (or parallel to) a long strike-slip fault.

CHARACTERIZING PHOTORECEPTOR CHANGES IN ACUTE POSTERIOR MULTIFOCAL PLACOID PIGMENT EPITHELIOPATHY USING ADAPTIVE OPTICS.

PubMed

Roberts, Philipp K; Nesper, Peter L; Onishi, Alex C; Skondra, Dimitra; Jampol, Lee M; Fawzi, Amani A

2018-01-01

To characterize lesions of acute posterior multifocal placoid pigment epitheliopathy (APMPPE) by multimodal imaging including adaptive optics scanning laser ophthalmoscopy (AOSLO). We included patients with APMPPE at different stages of evolution of the placoid lesions. Color fundus photography, spectral domain optical coherence tomography, infrared reflectance, fundus autofluorescence, and AOSLO images were obtained and registered to correlate microstructural changes. Eight eyes of four patients (two women) were included and analyzed by multimodal imaging. Photoreceptor reflectivity within APMPPE lesions was more heterogeneous than in adjacent healthy areas. Hyperpigmentation on color fundus photography appeared hyperreflective on infrared reflectance and on AOSLO. Irregularity of the interdigitation zone and the photoreceptor inner and outer segment junctions (IS/OS) on spectral domain optical coherence tomography was associated with photoreceptor hyporeflectivity on AOSLO. Interruption of the interdigitation zone or IS/OS was associated with loss of photoreceptor reflectivity on AOSLO. Irregularities in the reflectivity of the photoreceptor mosaic are visible on AOSLO even in inactive APMPPE lesions, where the photoreceptor bands on spectral domain optical coherence tomography have recovered. Adaptive optics scanning laser ophthalmoscopy combined with multimodal imaging has the potential to enhance our understanding of photoreceptor involvement in APMPPE.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

The Effects of Spectral Nudging on Arctic Temperature and Precipitation Extremes as Produced by the Pan-Arctic WRF

NASA Astrophysics Data System (ADS)

Glisan, J. M.; Gutowski, W. J.; Higgins, M.; Cassano, J. J.

2011-12-01

Pan-Arctic WRF (PAW) simulations produced using the 50-km wr50a domain developed for the fully-coupled Regional Arctic Climate Model (RACM) were found to produce deep atmospheric circulation biases over the northern Pacific Ocean, manifested in pressure, geopotential height, and temperature fields. Various remedies were unsuccessfully tested to correct these large biases, such as modifying the physical domain or using different initial/boundary conditions. Spectral (interior) nudging was introduced as a way of constraining the model to be more consistent with observed behavior. However, such control over numerical model behavior raises concerns over how much nudging may affect unforced variability and extremes. Strong nudging may reduce or filter out extreme events, since the nudging pushes the model toward a relatively smooth, large-scale state. The question then becomes - what is the minimum spectral nudging needed to correct the biases occurring on the RACM domain while not limiting PAW simulation of extreme events? To determine this, case studies were devised, using a six-member PAW ensemble on the RACM grid with varying spectral nudging strength. Two simulations were run, one in the cold season (January 2007) and one in a warm season (July 2007). Precipitation and 2-m temperature fields were extracted from the output and analyzed to determine how changing spectral nudging strength impacts both temporal and spatial temperature and precipitation extremes. The maximum and minimum temperatures at each point from among the ensemble members were examined, on the 95th confidence interval. The maximum and minimums over the simulation period will also be considered. Results suggest that there is a marked lack of sensitivity to the degrees of nudging. Moreover, it appears nudging strength can be considerably smaller than the standard strength and still produce reliably good simulations.

Digital filtering of plume emission spectra

NASA Technical Reports Server (NTRS)

Madzsar, George C.

1990-01-01

Fourier transformation and digital filtering techniques were used to separate the superpositioned spectral phenomena observed in the exhaust plumes of liquid propellant rocket engines. Space shuttle main engine (SSME) spectral data were used to show that extraction of spectral lines in the spatial frequency domain does not introduce error, and extraction of the background continuum introduces only minimal error. Error introduced during band extraction could not be quantified due to poor spectrometer resolution. Based on the atomic and molecular species found in the SSME plume, it was determined that spectrometer resolution must be 0.03 nm for SSME plume spectral monitoring.

Development and Application of a Stepwise Assessment Process for Rational Redesign of Sequential Skills-Based Courses.

PubMed

Gallimore, Casey E; Porter, Andrea L; Barnett, Susanne G

2016-10-25

Objective. To develop and apply a stepwise process to assess achievement of course learning objectives related to advanced pharmacy practice experiences (APPEs) preparedness and inform redesign of sequential skills-based courses. Design. Four steps comprised the assessment and redesign process: (1) identify skills critical for APPE preparedness; (2) utilize focus groups and course evaluations to determine student competence in skill performance; (3) apply course mapping to identify course deficits contributing to suboptimal skill performance; and (4) initiate course redesign to target exposed deficits. Assessment. Focus group participants perceived students were least prepared for skills within the Accreditation Council for Pharmacy Education's pre-APPE core domains of Identification and Assessment of Drug-related Problems and General Communication Abilities. Course mapping identified gaps in instruction, performance, and assessment of skills within aforementioned domains. Conclusions. A stepwise process that identified strengths and weaknesses of a course, was used to facilitate structured course redesign. Strengths of the process included input and corroboration from both preceptors and students. Limitations included feedback from a small number of pharmacy preceptors and increased workload on course coordinators.

Maximum likelihood method for estimating airplane stability and control parameters from flight data in frequency domain

NASA Technical Reports Server (NTRS)

Klein, V.

1980-01-01

A frequency domain maximum likelihood method is developed for the estimation of airplane stability and control parameters from measured data. The model of an airplane is represented by a discrete-type steady state Kalman filter with time variables replaced by their Fourier series expansions. The likelihood function of innovations is formulated, and by its maximization with respect to unknown parameters the estimation algorithm is obtained. This algorithm is then simplified to the output error estimation method with the data in the form of transformed time histories, frequency response curves, or spectral and cross-spectral densities. The development is followed by a discussion on the equivalence of the cost function in the time and frequency domains, and on advantages and disadvantages of the frequency domain approach. The algorithm developed is applied in four examples to the estimation of longitudinal parameters of a general aviation airplane using computer generated and measured data in turbulent and still air. The cost functions in the time and frequency domains are shown to be equivalent; therefore, both approaches are complementary and not contradictory. Despite some computational advantages of parameter estimation in the frequency domain, this approach is limited to linear equations of motion with constant coefficients.

A Spectral Multi-Domain Penalty Method for Elliptic Problems Arising From a Time-Splitting Algorithm For the Incompressible Navier-Stokes Equations

NASA Astrophysics Data System (ADS)

Diamantopoulos, Theodore; Rowe, Kristopher; Diamessis, Peter

2017-11-01

The Collocation Penalty Method (CPM) solves a PDE on the interior of a domain, while weakly enforcing boundary conditions at domain edges via penalty terms, and naturally lends itself to high-order and multi-domain discretization. Such spectral multi-domain penalty methods (SMPM) have been used to solve the Navier-Stokes equations. Bounds for penalty coefficients are typically derived using the energy method to guarantee stability for time-dependent problems. The choice of collocation points and penalty parameter can greatly affect the conditioning and accuracy of a solution. Effort has been made in recent years to relate various high-order methods on multiple elements or domains under the umbrella of the Correction Procedure via Reconstruction (CPR). Most applications of CPR have focused on solving the compressible Navier-Stokes equations using explicit time-stepping procedures. A particularly important aspect which is still missing in the context of the SMPM is a study of the Helmholtz equation arising in many popular time-splitting schemes for the incompressible Navier-Stokes equations. Stability and convergence results for the SMPM for the Helmholtz equation will be presented. Emphasis will be placed on the efficiency and accuracy of high-order methods.

Prototype color field sequential television lens assembly

NASA Technical Reports Server (NTRS)

1974-01-01

The design, development, and evaluation of a prototype modular lens assembly with a self-contained field sequential color wheel is presented. The design of a color wheel of maximum efficiency, the selection of spectral filters, and the design of a quiet, efficient wheel drive system are included. Design tradeoffs considered for each aspect of the modular assembly are discussed. Emphasis is placed on achieving a design which can be attached directly to an unmodified camera, thus permitting use of the assembly in evaluating various candidate camera and sensor designs. A technique is described which permits maintaining high optical efficiency with an unmodified camera. A motor synchronization system is developed which requires only the vertical synchronization signal as a reference frequency input. Equations and tradeoff curves are developed to permit optimizing the filter wheel aperture shapes for a variety of different design conditions.

A high accuracy sequential solver for simulation and active control of a longitudinal combustion instability

NASA Technical Reports Server (NTRS)

Shyy, W.; Thakur, S.; Udaykumar, H. S.

1993-01-01

A high accuracy convection scheme using a sequential solution technique has been developed and applied to simulate the longitudinal combustion instability and its active control. The scheme has been devised in the spirit of the Total Variation Diminishing (TVD) concept with special source term treatment. Due to the substantial heat release effect, a clear delineation of the key elements employed by the scheme, i.e., the adjustable damping factor and the source term treatment has been made. By comparing with the first-order upwind scheme previously utilized, the present results exhibit less damping and are free from spurious oscillations, offering improved quantitative accuracy while confirming the spectral analysis reported earlier. A simple feedback type of active control has been found to be capable of enhancing or attenuating the magnitude of the combustion instability.

A Spectral Element Ocean Model on the Cray T3D: the interannual variability of the Mediterranean Sea general circulation

NASA Astrophysics Data System (ADS)

Molcard, A. J.; Pinardi, N.; Ansaloni, R.

A new numerical model, SEOM (Spectral Element Ocean Model, (Iskandarani et al, 1994)), has been implemented in the Mediterranean Sea. Spectral element methods combine the geometric flexibility of finite element techniques with the rapid convergence rate of spectral schemes. The current version solves the shallow water equations with a fifth (or sixth) order accuracy spectral scheme and about 50.000 nodes. The domain decomposition philosophy makes it possible to exploit the power of parallel machines. The original MIMD master/slave version of SEOM, written in F90 and PVM, has been ported to the Cray T3D. When critical for performance, Cray specific high-performance one-sided communication routines (SHMEM) have been adopted to fully exploit the Cray T3D interprocessor network. Tests performed with highly unstructured and irregular grid, on up to 128 processors, show an almost linear scalability even with unoptimized domain decomposition techniques. Results from various case studies on the Mediterranean Sea are shown, involving realistic coastline geometry, and monthly mean 1000mb winds from the ECMWF's atmospheric model operational analysis from the period January 1987 to December 1994. The simulation results show that variability in the wind forcing considerably affect the circulation dynamics of the Mediterranean Sea.

Fast time-domain measurements on telecom single photons

NASA Astrophysics Data System (ADS)

Allgaier, Markus; Vigh, Gesche; Ansari, Vahid; Eigner, Christof; Quiring, Viktor; Ricken, Raimund; Brecht, Benjamin; Silberhorn, Christine

2017-09-01

Direct measurements on the temporal envelope of quantum light are a challenging task and not many examples are known because most classical pulse characterisation methods do not work on the single-photon level. Knowledge of both spectrum and timing can, however, give insights on properties that cannot be determined by the spectral intensity alone. While temporal measurements on single photons on timescales of tens of picoseconds are possible with superconducting photon detectors, and picosecond measurements have been performed using streak cameras, there are no commercial single-photon sensitive devices with femtosecond resolution available. While time-domain sampling using sum-frequency generation has already been exploited for such a measurement, inefficient conversion has necessitated long integration times to build the temporal profile. We demonstrate a highly efficient waveguided sum-frequency generation process in Lithium Niobate to measure the temporal envelope of single photons with femtosecond resolution with short enough acquisition time to provide a live-view of the measurement. We demonstrate the measurement technique and combine it with spectral measurements using a dispersive-fibre time-of-flight spectrometer to determine upper and lower bounds for the spectral purity of heralded single photons. The approach complements the joint spectral intensity measurements as a measure on the purity can be given without knowledge of the spectral phase.

Paleo-productivity changes revealed by spectral analysis performed on coccoliths assemblages

NASA Astrophysics Data System (ADS)

Palumbo, Eliana; Ornella Amore, Filomena; Perugia, Carmen

2010-05-01

Several climate changes occurred over geological time at different time-scales. Spectral analyses performed on paleo-climate data suggested that these cyclicities verify irregularly into time-space domain. Paleo-climate oscillations occur with high or low frequencies dues to the oscillation of the major orbital parameters (characterized by low frequencies and high period) and some minor high-frequencies events. During last years, analyses on frequencies domain have been performed also on coccoliths assemblages. Coccolithophores are a special phytoplankton group living today at all latitude regions within the photic zone (0-200 m of depth) (Winter & Siesser, 1994). They are sensitive indicators of environmental conditions because they directly depend on temperature, salinity and nutrients as well as the availability of sunlight (McIntyre and Bé, 1967; Giradeau et al., 1993; Winter & Siesser, 1994; Baumann & Freitag, 2004). Therefore coccolithophores quickly respond to fluctuations in climate as well as changes in surface-water conditions (Baumann & Freitag, 2004). Thus coccoliths can be clearly used as paleo-climate data because of their power of recordering and amplifying climatic change signals. In addition, primary productivity depends on the amount of insolation received by Earth surface. In this study Sun insolation has been calculated in terms of intensity and energy, in order to compare them with maximum productivity activity. Precession controls sun intensity insolation, while the energy is controlled by obliquity. Thus, the intensity depends on the duration of the insolation,while the energy is connected to the amount of insolation (Berger, 1978; Loutre et al., 2004; Huybers, 2006). In this study, spectral analyses have been performed on coccoliths data with the result of individuating high and low frequencies content in productivity signals. Auto-spectral and cross-spectral analyses have been performed through Matlab software using several available functions plus a new function created in order to evaluate cross-wavelet power spectra. Auto-spectral analysis aims to describe the distribution of variance contained in each single signal over frequency or wavelength, while cross-spectral analysis correlates two time series in the frequency domain (Trauth, 2009). We have performed spectral analyses using the complex Fourier transform and the Short time Fourier transform. Both the transforms lose any kind of time information in transforming the signal from time to frequency domain (Jenkins and Watt, 1968). These transforms don't allow us to individuate when an event occurred in the past. In order to overcome this limit we have also applied Wavelet analysis which represents frequency content of a signal over the time thus it allows us to visualize when an event occurred into time domain (Torrence and Compo, 1998; Prokoph and El Bilali, 2008; Grinsted et al., 2004). Moreover we have performed a simple cross and a cross-spectral analysis between different proxy groups to discover their possible correlations into time and frequency domains. References. Berger, A., 1978. J. Atmos. Sc., 35 (12): 2362-2367. Baumann, K.-H., and Freitag, T., 2004. Marine Micropaleontology 52: 195-215. Giraudeau, J., Monteiro, P.M.S., Nikodemus, K., 1993. Mar. Micropalaeontol. 22: 93- 110. Grinsted, A., Moore, J. C., and Jevrejeva, S., 2004. Nonlinear Processes in Geophysics 11: 561-566. Huybers, P., 2006. Science 313: 508-511. Jenkins, G. M., and Watt, D. G., 1968. Holden Day, pp. 410, Oakland. Loutre, M. F., Paillard, D., Vimeux, F., and Cortijo, E., 2004. Earth Planet. Sci. Lett., 221, 1-14. McIntyre, A., and Bè, A.H.W., 1967. Deep-Sea Res. 14, pp. 561-597. Prokoph, A., and El Bilali, H., 2008. Math Geosciences 40: 575-586. Torrence, C., and Compo, G. P., 1998. Bulletin of American Meteorological Society 79:61-78. Trauth, M.H., 2009. Springer 288 p. Winter, A., and Siesser, W., 1994. Cambridge University Press 242 p.

Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles

PubMed Central

Grewal, D S; Brar, G S; Jain, R; Grewal, S P S

2011-01-01

Purpose To compare the performance of anterior chamber volume (ACV) and anterior chamber depth (ACD) obtained using Scheimpflug imaging with angle opening distance (AOD500) and trabecular-iris space area (TISA500) obtained using spectral domain anterior segment optical coherence tomography (SD-ASOCT) in detecting narrow angles classified using gonioscopy. Methods In this prospective, cross-sectional observational study, 265 eyes of 265 consecutive patients underwent sequential Scheimpflug imaging, SD-ASOCT imaging, and gonioscopy. Correlations between gonioscopy grading, ACV, ACD, AOD500, and TISA500 were evaluated. Area under receiver operating characteristic curve (AUC), sensitivity, specificity, and likelihood ratios (LRs) were calculated to assess the performance of ACV, ACD, AOD500, and TISA500 in detecting narrow angles (defined as Shaffer grade ≤1 in all quadrants). SD-ASOCT images were obtained at the nasal and temporal quadrants only. Results Twenty-eight eyes (10.6%) were classified as narrow angles on gonioscopy. ACV correlated with gonioscopy grading (P<0.001) for temporal (r=0.204), superior (r=0.251), nasal (r=0.213), and inferior (r=0.236) quadrants. ACV correlated with TISA500 for nasal (r=0.135, P=0.029) and temporal (P=0.160, P=0.009) quadrants and also with AOD500 for nasal (r=0.498, P<0.001) and temporal (r=0.517, P<0.001) quadrants. For detection of narrow angles, ACV (AUC=0.935; 95% confidence interval (CI) =0.898–0.961) performed similar to ACD (AUC=0.88, P=0.06) and significantly better than AOD500 nasal (AUC=0.761, P=0.001), AOD500 temporal (AUC=0.808, P<0.001), TISA500 nasal (AUC=0.756, P<0.001), and TISA500 temporal (AUC=0.738, P<0.001). Using a cutoff of 113 mm3, ACV had 90% sensitivity and 88% specificity for detecting narrow angles. Positive and negative LRs for ACV were 8.63 (95% CI=7.4–10.0) and 0.11 (95% CI=0.03–0.4), respectively. Conclusions ACV measurements using Scheimpflug imaging outperformed AOD500 and TISA500 using SD-ASOCT for detecting narrow angles. PMID:21336254

Spectral domain polarization-sensitive optical coherence tomography at 850 nm

NASA Astrophysics Data System (ADS)

Cense, Barry; Chen, Teresa C.; Mujat, Mircea; Joo, Chulmin; Akkin, Taner; Park, B. H.; Pierce, Mark C.; Yun, Andy; Bouma, Brett E.; Tearney, Guillermo J.; de Boer, Johannes F.

2005-04-01

Spectral-Domain Polarization-Sensitive Optical Coherence Tomography (SD-PS-OCT) is a technique developed to measure the thickness and birefringence of the nerve fiber layer in vivo as a tool for the early diagnosis of glaucoma. A clinical SD-PS-OCT system was developed and scans were made around the optic nerve head (ONH) using ten concentric circles of increasing diameter. One healthy volunteer was imaged. Retinal nerve fiber layer thickness and birefringence information was extracted from the data. Polarization-sensitive OCT images were acquired at video rate (29 frames per second (fps), 1000 A-lines / frame) and at 7 fps (1000 A-lines / frame). The last setting improved the signal to noise ratio by approximately 6 dB. Birefringence measurements on the healthy volunteer gave similar results as earlier reported values that were obtained with a time-domain setup. The measurement time was reduced from more than a minute to less than a second.

Spectral analysis based on fast Fourier transformation (FFT) of surveillance data: the case of scarlet fever in China.

PubMed

Zhang, T; Yang, M; Xiao, X; Feng, Z; Li, C; Zhou, Z; Ren, Q; Li, X

2014-03-01

Many infectious diseases exhibit repetitive or regular behaviour over time. Time-domain approaches, such as the seasonal autoregressive integrated moving average model, are often utilized to examine the cyclical behaviour of such diseases. The limitations for time-domain approaches include over-differencing and over-fitting; furthermore, the use of these approaches is inappropriate when the assumption of linearity may not hold. In this study, we implemented a simple and efficient procedure based on the fast Fourier transformation (FFT) approach to evaluate the epidemic dynamic of scarlet fever incidence (2004-2010) in China. This method demonstrated good internal and external validities and overcame some shortcomings of time-domain approaches. The procedure also elucidated the cycling behaviour in terms of environmental factors. We concluded that, under appropriate circumstances of data structure, spectral analysis based on the FFT approach may be applicable for the study of oscillating diseases.

Laser-plasma interactions with a Fourier-Bessel particle-in-cell method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andriyash, Igor A., E-mail: igor.andriyash@gmail.com; LOA, ENSTA ParisTech, CNRS, Ecole polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau cedex; Lehe, Remi

A new spectral particle-in-cell (PIC) method for plasma modeling is presented and discussed. In the proposed scheme, the Fourier-Bessel transform is used to translate the Maxwell equations to the quasi-cylindrical spectral domain. In this domain, the equations are solved analytically in time, and the spatial derivatives are approximated with high accuracy. In contrast to the finite-difference time domain (FDTD) methods, that are used commonly in PIC, the developed method does not produce numerical dispersion and does not involve grid staggering for the electric and magnetic fields. These features are especially valuable in modeling the wakefield acceleration of particles in plasmas.more » The proposed algorithm is implemented in the code PLARES-PIC, and the test simulations of laser plasma interactions are compared to the ones done with the quasi-cylindrical FDTD PIC code CALDER-CIRC.« less

Ultra-high-speed optical coherence tomography with a stretched pulse supercontinuum source.

PubMed

Moon, Sucbei; Kim, Dug Young

2006-11-27

We introduce a new high-speed Fourier-domain optical coherence tomography (FD-OCT) scheme based on a stretched pulse supercontinuum source. A wide-band short pulse of a supercontinuum source of which output spectrum spanned a wavelength range from 1,200 nm to 1,550 nm was stretched to a long pulse of 70-ns duration by using a dispersive fiber due to the group-velocity dispersion, and it was used directly as frequency-swept light for FD-OCT. The OCT spectral interferogram was acquired in the time domain and converted into the spectral domain by the pre-calibrated time-to-wavelength relation. Using this stretched-pulse OCT (SP-OCT) scheme, we have demonstrated an ultrahigh-speed axial-line scanning rate of 5 MHz. The axial resolution of 8 microm was achieved without re-calibration of the sweep characteristic owing to the passive nature of the frequency-sweeping mechanism.

The Multi-Spectral Imaging Diagnostic on Alcator C-MOD and TCV

NASA Astrophysics Data System (ADS)

Linehan, B. L.; Mumgaard, R. T.; Duval, B. P.; Theiler, C. G.; TCV Team

2017-10-01

The Multi-Spectral Imaging (MSI) diagnostic is a new instrument that captures simultaneous spectrally filtered images from a common sight view while maintaining a large tendue and high spatial resolution. The system uses a polychromator layout where each image is sequentially filtered. This procedure yields a high transmission for each spectral channel with minimal vignetting and aberrations. A four-wavelength system was installed on Alcator C-Mod and then moved to TCV. The system uses industrial cameras to simultaneously image the divertor region at 95 frames per second at f/# 2.8 via a coherent fiber bundle (C-Mod) or a lens-based relay optic (TCV). The images are absolutely calibrated and spatially registered enabling accurate measurement of atomic line ratios and absolute line intensities. The images will be used to study divertor detachment by imaging impurities and Balmer series emissions. Furthermore, the large field of view and an ability to support many types of detectors opens the door for other novel approaches to optically measuring plasma with high temporal, spatial, and spectral resolution. Such measurements will allow for the study of Stark broadening and divertor turbulence. Here, we present the first measurements taken with this cavity imaging system. USDoE awards DE-FC02-99ER54512 and award DE-AC05-06OR23100, ORISE, administered by ORAU.

A G-quadruplex-binding macrodomain within the "SARS-unique domain" is essential for the activity of the SARS-coronavirus replication-transcription complex.

PubMed

Kusov, Yuri; Tan, Jinzhi; Alvarez, Enrique; Enjuanes, Luis; Hilgenfeld, Rolf

2015-10-01

The multi-domain non-structural protein 3 of SARS-coronavirus is a component of the viral replication/transcription complex (RTC). Among other domains, it contains three sequentially arranged macrodomains: the X domain and subdomains SUD-N as well as SUD-M within the "SARS-unique domain". The X domain was proposed to be an ADP-ribose-1"-phosphatase or a poly(ADP-ribose)-binding protein, whereas SUD-NM binds oligo(G)-nucleotides capable of forming G-quadruplexes. Here, we describe the application of a reverse genetic approach to assess the importance of these macrodomains for the activity of the SARS-CoV RTC. To this end, Renilla luciferase-encoding SARS-CoV replicons with selectively deleted macrodomains were constructed and their ability to modulate the RTC activity was examined. While the SUD-N and the X domains were found to be dispensable, the SUD-M domain was crucial for viral genome replication/transcription. Moreover, alanine replacement of charged amino-acid residues of the SUD-M domain, which are likely involved in G-quadruplex-binding, caused abrogation of RTC activity. Copyright © 2015 Elsevier Inc. All rights reserved.

Developing the Effective Method of Spectral Harmonic Energy Ratio to Analyze the Arterial Pulse Spectrum

PubMed Central

Huang, Chin-Ming; Wei, Ching-Chuan; Liao, Yin-Tzu; Chang, Hsien-Cheh; Kao, Shung-Te; Li, Tsai-Chung

2011-01-01

In this article, we analyze the arterial pulse in the spectral domain. A parameter, the spectral harmonic energy ratio (SHER), is developed to assess the features of the overly decreased spectral energy in the fourth to sixth harmonic for palpitation patients. Compared with normal subjects, the statistical results reveal that the mean value of SHER in the patient group (57.7 ± 27.9) is significantly higher than that of the normal group (39.7 ± 20.9) (P-value = .0066 < .01). This means that the total energy in the fourth to sixth harmonic of palpitation patients is significantly less than it is in normal subjects. In other words, the spectral distribution of the arterial pulse gradually decreases for normal subjects while it decreases abruptly in higher-order harmonics (the fourth, fifth and sixth harmonics) for palpitation patients. Hence, SHER is an effective method to distinguish the two groups in the spectral domain. Also, we can thus know that a “gradual decrease” might mean a “balanced” state, whereas an “abrupt decrease” might mean an “unbalanced” state in blood circulation and pulse diagnosis. By SHER, we can determine the ratio of energy distribution in different harmonic bands, and this method gives us a novel viewpoint from which to comprehend and quantify the spectral harmonic distribution of circulation information conveyed by the arterial pulse. These concepts can be further applied to improve the clinical diagnosis not only in Western medicine but also in traditional Chinese medicine (TCM). PMID:21845200

[Building Mass Spectrometry Spectral Libraries of Human Cancer Cell Lines].

PubMed

Faktor, J; Bouchal, P

Cancer research often focuses on protein quantification in model cancer cell lines and cancer tissues. SWATH (sequential windowed acquisition of all theoretical fragment ion spectra), the state of the art method, enables the quantification of all proteins included in spectral library. Spectral library contains fragmentation patterns of each detectable protein in a sample. Thorough spectral library preparation will improve quantitation of low abundant proteins which usually play an important role in cancer. Our research is focused on the optimization of spectral library preparation aimed at maximizing the number of identified proteins in MCF-7 breast cancer cell line. First, we optimized the sample preparation prior entering the mass spectrometer. We examined the effects of lysis buffer composition, peptide dissolution protocol and the material of sample vial on the number of proteins identified in spectral library. Next, we optimized mass spectrometry (MS) method for spectral library data acquisition. Our thorough optimized protocol for spectral library building enabled the identification of 1,653 proteins (FDR < 1%) in 1 µg of MCF-7 lysate. This work contributed to the enhancement of protein coverage in SWATH digital biobanks which enable quantification of arbitrary protein from physically unavailable samples. In future, high quality spectral libraries could play a key role in preparing of patient proteome digital fingerprints.Key words: biomarker - mass spectrometry - proteomics - digital biobanking - SWATH - protein quantificationThis work was supported by the project MEYS - NPS I - LO1413.The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 7. 5. 2016Accepted: 9. 6. 2016.

2.5 TW, two-cycle IR laser pulses via frequency domain optical parametric amplification.

PubMed

Gruson, V; Ernotte, G; Lassonde, P; Laramée, A; Bionta, M R; Chaker, M; Di Mauro, L; Corkum, P B; Ibrahim, H; Schmidt, B E; Legaré, F

2017-10-30

Broadband optical parametric amplification in the IR region has reached a new milestone through the use of a non-collinear Frequency domain Optical Parametric Amplification system. We report a laser source delivering 11.6 fs pulses with 30 mJ of energy at a central wavelength of 1.8 μm at 10 Hz repetition rate corresponding to a peak power of 2.5 TW. The peak power scaling is accompanied by a pulse shortening of about 20% upon amplification due to the spectral reshaping with higher gain in the spectral wings. This source paves the way for high flux soft X-ray pulses and IR-driven laser wakefield acceleration.

Assessment of Spectral-Domain Optical Coherence Tomography Findings in Three Cases of X-Linked Juvenile Retinoschisis in the Same Family.

PubMed

Doğuizi, Sibel; Şekeroğlu, Mehmet Ali; Çolak, Salih; Anayol, Mustafa Alpaslan; Yılmazbaş, Pelin

2017-10-01

X-linked juvenile retinoschisis (XLRS) is an X-linked hereditary retinal dystrophy characterized by splitting of the neurosensory retina. On fundus examination, the macula often has a spoke wheel appearance with foveal cystic lesions, and separation of the retinal layers is typical on spectral-domain optical coherence tomography (SD-OCT). Patients with XLRS can exhibit different clinical courses, stages, and SD-OCT findings, even among members of the same family. SD-OCT is an important imaging method that allows us to achieve more detailed information about XLRS. In this study, we report three patients in the same family who have different clinical features and SD-OCT findings.

Fast retinal layer segmentation of spectral domain optical coherence tomography images

NASA Astrophysics Data System (ADS)

Zhang, Tianqiao; Song, Zhangjun; Wang, Xiaogang; Zheng, Huimin; Jia, Fucang; Wu, Jianhuang; Li, Guanglin; Hu, Qingmao

2015-09-01

An approach to segment macular layer thicknesses from spectral domain optical coherence tomography has been proposed. The main contribution is to decrease computational costs while maintaining high accuracy via exploring Kalman filtering, customized active contour, and curve smoothing. Validation on 21 normal volumes shows that 8 layer boundaries could be segmented within 5.8 s with an average layer boundary error <2.35 μm. It has been compared with state-of-the-art methods for both normal and age-related macular degeneration cases to yield similar or significantly better accuracy and is 37 times faster. The proposed method could be a potential tool to clinically quantify the retinal layer boundaries.

The perturbation of tryptophan fluorescence by phenylalanine to alanine mutations identifies the hydrophobic core in a subset of bacterial Ig-like domains.

PubMed

Raman, Rajeev; Ptak, Christopher P; Hsieh, Ching-Lin; Oswald, Robert E; Chang, Yung-Fu; Sharma, Yogendra

2013-07-09

Many host-parasite interactions are mediated via surface-exposed proteins containing bacterial immunoglobulin-like (Big) domains. Here, we utilize the spectral properties of a conserved Trp to provide evidence that, along with a Phe, these residues are positioned within the hydrophobic core of a subset of Big_2 domains. The mutation of the Phe to Ala decreases Big_2 domain stability and impairs the ability of LigBCen2 to bind to the host protein, fibronectin.

Hα and Gaia-RVS domain spectroscopy of Be stars and interacting binaries with Ondřejov 2m telescope

NASA Astrophysics Data System (ADS)

Koubský, P.; Kotková, L.; Votruba, V.

2011-12-01

A long term project to investigate the spectral appearance over the Gaia RVS domain of a large sample of Be stars and interacting binaries has been undertaken. The aim of the Ondřejov project is to create sufficient amounts of training data in the RVS wavelength domain to complement the Bp/Rp classification of Be stars which may be observed with Gaia. The project's current status is described and sample spectra in both the Hα and RVS wavelength domains are presented and discussed.

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

PubMed

Velarde, Luis; Wang, Hong-Fei

2013-12-14

The lack of understanding of the temporal effects and the restricted ability to control experimental conditions in order to obtain intrinsic spectral lineshapes in surface sum-frequency generation vibrational spectroscopy (SFG-VS) have limited its applications in surface and interfacial studies. The emergence of high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS) with sub-wavenumber resolution [Velarde et al., J. Chem. Phys., 2011, 135, 241102] offers new opportunities for obtaining and understanding the spectral lineshapes and temporal effects in SFG-VS. Particularly, the high accuracy of the HR-BB-SFG-VS experimental lineshape provides detailed information on the complex coherent vibrational dynamics through direct spectral measurements. Here we present a unified formalism for the theoretical and experimental routes for obtaining an accurate lineshape of the SFG response. Then, we present a detailed analysis of a cholesterol monolayer at the air/water interface with higher and lower resolution SFG spectra along with their temporal response. With higher spectral resolution and accurate vibrational spectral lineshapes, it is shown that the parameters of the experimental SFG spectra can be used both to understand and to quantitatively reproduce the temporal effects in lower resolution SFG measurements. This perspective provides not only a unified picture but also a novel experimental approach to measuring and understanding the frequency-domain and time-domain SFG response of a complex molecular interface.

Nonlinear whistler wave model for lion roars in the Earth's magnetosheath

NASA Astrophysics Data System (ADS)

Dwivedi, N. K.; Singh, S.

2017-09-01

In the present study, we construct a nonlinear whistler wave model to explain the magnetic field spectra observed for lion roars in the Earth's magnetosheath region. We use two-fluid theory and semi-analytical approach to derive the dynamical equation of whistler wave propagating along the ambient magnetic field. We examine the magnetic field localization of parallel propagating whistler wave in the intermediate beta plasma applicable to the Earth's magnetosheath. In addition, we investigate spectral features of the magnetic field fluctuations and the spectral slope value. The magnetic field spectrum obtained by semi-analytical approach shows a spectral break point and becomes steeper at higher wave numbers. The observations of IMP 6 plasma waves and magnetometer experiment reveal the existence of short period magnetic field fluctuations in the magnetosheath. The observation shows the broadband spectrum with a spectral slope of -4.5 superimposed with a narrow band peak. The broadband fluctuations appear due to the energy cascades attributed by low-frequency magnetohydrodynamic modes, whereas, a narrow band peak is observed due to the short period lion roars bursts. The energy spectrum predicted by the present theoretical model shows a similar broadband spectrum in the wave number domain with a spectral slope of -3.2, however, it does not show any narrow band peak. Further, we present a comparison between theoretical energy spectrum and the observed spectral slope in the frequency domain. The present semi-analytical model provides exposure to the whistler wave turbulence in the Earth's magnetosheath.

The Effect of English Language Learning on Creative Thinking Skills: A Mixed Methods Case Study

ERIC Educational Resources Information Center

Sehic, Sandro

2017-01-01

The purpose of this sequential explanatory mixed-methods case study was to investigate the effects of English language learning on creative thinking skills in the domains of fluency, flexibility, originality, and elaboration as measured with the Alternate Uses Test. Unlike the previous research studies that investigated the links between English…

Signal-to-noise analysis of a birefringent spectral zooming imaging spectrometer

NASA Astrophysics Data System (ADS)

Li, Jie; Zhang, Xiaotong; Wu, Haiying; Qi, Chun

2018-05-01

Study of signal-to-noise ratio (SNR) of a novel spectral zooming imaging spectrometer (SZIS) based on two identical Wollaston prisms is conducted. According to the theory of radiometry and Fourier transform spectroscopy, we deduce the theoretical equations of SNR of SZIS in spectral domain with consideration of the incident wavelength and the adjustable spectral resolution. An example calculation of SNR of SZIS is performed over 400-1000 nm. The calculation results indicate that SNR with different spectral resolutions of SZIS can be optionally selected by changing the spacing between the two identical Wollaston prisms. This will provide theoretical basis for the design, development and engineering of the developed imaging spectrometer for broad spectrum and SNR requirements.

Clinical validity of macular ganglion cell complex by spectral domain-optical coherence tomography in advanced glaucoma.

PubMed

Sung, Mi-Sun; Kang, Byung-Wan; Kim, Hwang-Gyun; Heo, Hwan; Park, Sang-Woo

2014-08-01

To evaluate the repeatability and diagnostic power of macular ganglion cell complex (mGCC) thickness and peripapillary retinal nerve fiber layer (pRNFL) thickness using a spectral domain-optical coherence tomography in advanced glaucoma. Forty advanced glaucoma patients were enrolled. Patients were divided into 2 groups of 20 patients each, according to the MD between -20 and -10 dB, and <-20 dB. The thickness of mGCC and pRNFL were measured with spectral domain-optical coherence tomography in both the groups. The repeatability of each parameter was assessed in both the groups, and the diagnostic power of each parameter was compared with the normal controls. Comparison of diagnostic power between the pRNFL and mGCC parameters revealed that the area under the receiver operating characteristic curve was not significantly different in patients with advanced glaucoma. The repeatability of pRNFL parameters was similar, irrespective of the severity of glaucoma. However, the repeatability of mGCC parameters became lower as the severity increased in patients with advanced glaucoma. In advanced glaucoma, the measurement of mGCC thickness has similar diagnostic power as the measurement of pRNFL thickness. However, the measurement of mGCC thickness showed a lower repeatability as MD decreased.

3-D segmentation of retinal blood vessels in spectral-domain OCT volumes of the optic nerve head

NASA Astrophysics Data System (ADS)

Lee, Kyungmoo; Abràmoff, Michael D.; Niemeijer, Meindert; Garvin, Mona K.; Sonka, Milan

2010-03-01

Segmentation of retinal blood vessels can provide important information for detecting and tracking retinal vascular diseases including diabetic retinopathy, arterial hypertension, arteriosclerosis and retinopathy of prematurity (ROP). Many studies on 2-D segmentation of retinal blood vessels from a variety of medical images have been performed. However, 3-D segmentation of retinal blood vessels from spectral-domain optical coherence tomography (OCT) volumes, which is capable of providing geometrically accurate vessel models, to the best of our knowledge, has not been previously studied. The purpose of this study is to develop and evaluate a method that can automatically detect 3-D retinal blood vessels from spectral-domain OCT scans centered on the optic nerve head (ONH). The proposed method utilized a fast multiscale 3-D graph search to segment retinal surfaces as well as a triangular mesh-based 3-D graph search to detect retinal blood vessels. An experiment on 30 ONH-centered OCT scans (15 right eye scans and 15 left eye scans) from 15 subjects was performed, and the mean unsigned error in 3-D of the computer segmentations compared with the independent standard obtained from a retinal specialist was 3.4 +/- 2.5 voxels (0.10 +/- 0.07 mm).

WIDEFIELD SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING OF PERIPHERAL ROUND RETINAL HOLES WITH OR WITHOUT RETINAL DETACHMENT.

PubMed

Casswell, Edward J; Abou Ltaif, Sleiman; Carr, Thomas; Keane, Pearse A; Charteris, David G; Wickham, Louisa

2018-03-02

To describe the widefield spectral-domain optical coherence tomography features of peripheral round retinal holes, with or without associated retinal detachment (RD). Retrospective, observational study of 28 eyes with peripheral round retinal holes, with and without RD. Patients underwent imaging with a widefield 50-degree spectral-domain optical coherence tomography (Heidelberg Engineering, Germany) and Optos ultra-widefield imaging systems (Optos, United Kingdom). Vitreous attachment at the site of the retinal hole was detected in 27/28 (96.4%) cases. Cases were split into three groups: RHs with RD (n = 12); RHs with subretinal fluid (n = 5), and flat RHs (n = 11), with minimal or no subretinal fluid. 91.6% retinal holes associated with subretinal fluid or RD had vitreous attachment at the site of the hole. Eighty percent had vitreous attachment at both edges of the retinal hole, in a U-shape configuration, which appeared to exert traction. By contrast, flat retinal holes had visible vitreous attachment only at one edge of the retinal hole in 45.4%. Vitreous attachment was commonly seen at the site of round retinal holes. Vitreous attachment at both edges of the retinal hole in a U-shape configuration was more commonly seen at holes associated with subretinal fluid or RD.

Retinal thickness changes after phacoemulsification

PubMed Central

Pardianto, Gede; Moeloek, Nila; Reveny, Julia; Wage, Sutarman; Satari, Imsyah; Sembiring, Rosita; Srisamran, Nuttamon

2013-01-01

Purpose To determine the effect of phacoemulsification on macular volume and thickness using spectral domain optical coherence tomography examinations. Methods Twenty-seven eyes of 27 subjects who underwent phacoemulsification were studied. All nine areas of the macula were examined by spectral domain optical coherence tomography preoperatively and 2 months postoperatively. Effective phacoemulsification time and absolute phacoemulsification time were also recorded. Results There were statistically significant differences in macular thickness between preoperative and postoperative spectral domain optical coherence tomography examinations in nine areas including macular volume. In the paracentral macular area, the thickness of three quadrants significantly increased (superior P=0.015; temporal P=0.001; and nasal P=0.023). Peripheral macular thickness also increased significantly in the superior (P=0.05) and temporal macular areas (P<0.001). The macular volume increased significantly after phacoemulsification (P<0.001). There were no correlations between absolute/effective phacoemulsification time and macular cellular structures (P>0.05), but a significant correlation (P=0.011) was found between absolute phacoemulsification time and change in macular volume. Conclusion Macular thickness changes in the nasal, superior, and temporal quadrants of the paracentral area and the superior and temporal quadrants of the peripheral area, as well as macular volume, may be used as detailed biomarkers to measure the effects of intraocular pressure fluctuations and maneuvers in phacoemulsification intraocular surgeries. PMID:24235812

Spectral analysis using CCDs

NASA Technical Reports Server (NTRS)

Hewes, C. R.; Brodersen, R. W.; De Wit, M.; Buss, D. D.

1976-01-01

Charge-coupled devices (CCDs) are ideally suited for performing sampled-data transversal filtering operations in the analog domain. Two algorithms have been identified for performing spectral analysis in which the bulk of the computation can be performed in a CCD transversal filter; the chirp z-transform and the prime transform. CCD implementation of both these transform algorithms is presented together with performance data and applications.

Design of multivariable feedback control systems via spectral assignment. [as applied to aircraft flight control

NASA Technical Reports Server (NTRS)

Liberty, S. R.; Mielke, R. R.; Tung, L. J.

1981-01-01

Applied research in the area of spectral assignment in multivariable systems is reported. A frequency domain technique for determining the set of all stabilizing controllers for a single feedback loop multivariable system is described. It is shown that decoupling and tracking are achievable using this procedure. The technique is illustrated with a simple example.

P-HARP: A parallel dynamic spectral partitioner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sohn, A.; Biswas, R.; Simon, H.D.

1997-05-01

Partitioning unstructured graphs is central to the parallel solution of problems in computational science and engineering. The authors have introduced earlier the sequential version of an inertial spectral partitioner called HARP which maintains the quality of recursive spectral bisection (RSB) while forming the partitions an order of magnitude faster than RSB. The serial HARP is known to be the fastest spectral partitioner to date, three to four times faster than similar partitioners on a variety of meshes. This paper presents a parallel version of HARP, called P-HARP. Two types of parallelism have been exploited: loop level parallelism and recursive parallelism.more » P-HARP has been implemented in MPI on the SGI/Cray T3E and the IBM SP2. Experimental results demonstrate that P-HARP can partition a mesh of over 100,000 vertices into 256 partitions in 0.25 seconds on a 64-processor T3E. Experimental results further show that P-HARP can give nearly a 20-fold speedup on 64 processors. These results indicate that graph partitioning is no longer a major bottleneck that hinders the advancement of computational science and engineering for dynamically-changing real-world applications.« less

Wavelength-Filter Based Spectral Calibrated Wave number - Linearization in 1.3 mm Spectral Domain Optical Coherence.

PubMed

Wijeisnghe, Ruchire Eranga Henry; Cho, Nam Hyun; Park, Kibeom; Shin, Yongseung; Kim, Jeehyun

2013-12-01

In this study, we demonstrate the enhanced spectral calibration method for 1.3 μm spectral-domain optical coherence tomography (SD-OCT). The calibration method using wavelength-filter simplifies the SD-OCT system, and also the axial resolution and the entire speed of the OCT system can be dramatically improved as well. An externally connected wavelength-filter is utilized to obtain the information of the wavenumber and the pixel position. During the calibration process the wavelength-filter is placed after a broadband source by connecting through an optical circulator. The filtered spectrum with a narrow line width of 0.5 nm is detected by using a line-scan camera. The method does not require a filter or a software recalibration algorithm for imaging as it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. One of the main drawbacks of SD-OCT is the broadened point spread functions (PSFs) with increasing imaging depth can be compensated by increasing the wavenumber-linearization order. The sensitivity of our system was measured at 99.8 dB at an imaging depth of 2.1 mm compared with the uncompensated case.

Discriminant Analysis of Time Series in the Presence of Within-Group Spectral Variability.

PubMed

Krafty, Robert T

2016-07-01

Many studies record replicated time series epochs from different groups with the goal of using frequency domain properties to discriminate between the groups. In many applications, there exists variation in cyclical patterns from time series in the same group. Although a number of frequency domain methods for the discriminant analysis of time series have been explored, there is a dearth of models and methods that account for within-group spectral variability. This article proposes a model for groups of time series in which transfer functions are modeled as stochastic variables that can account for both between-group and within-group differences in spectra that are identified from individual replicates. An ensuing discriminant analysis of stochastic cepstra under this model is developed to obtain parsimonious measures of relative power that optimally separate groups in the presence of within-group spectral variability. The approach possess favorable properties in classifying new observations and can be consistently estimated through a simple discriminant analysis of a finite number of estimated cepstral coefficients. Benefits in accounting for within-group spectral variability are empirically illustrated in a simulation study and through an analysis of gait variability.

Efficient three-dimensional Poisson solvers in open rectangular conducting pipe

NASA Astrophysics Data System (ADS)

Qiang, Ji

2016-06-01

Three-dimensional (3D) Poisson solver plays an important role in the study of space-charge effects on charged particle beam dynamics in particle accelerators. In this paper, we propose three new 3D Poisson solvers for a charged particle beam in an open rectangular conducting pipe. These three solvers include a spectral integrated Green function (IGF) solver, a 3D spectral solver, and a 3D integrated Green function solver. These solvers effectively handle the longitudinal open boundary condition using a finite computational domain that contains the beam itself. This saves the computational cost of using an extra larger longitudinal domain in order to set up an appropriate finite boundary condition. Using an integrated Green function also avoids the need to resolve rapid variation of the Green function inside the beam. The numerical operational cost of the spectral IGF solver and the 3D IGF solver scales as O(N log(N)) , where N is the number of grid points. The cost of the 3D spectral solver scales as O(Nn N) , where Nn is the maximum longitudinal mode number. We compare these three solvers using several numerical examples and discuss the advantageous regime of each solver in the physical application.

Fictitious domain method for fully resolved reacting gas-solid flow simulation

NASA Astrophysics Data System (ADS)

Zhang, Longhui; Liu, Kai; You, Changfu

2015-10-01

Fully resolved simulation (FRS) for gas-solid multiphase flow considers solid objects as finite sized regions in flow fields and their behaviours are predicted by solving equations in both fluid and solid regions directly. Fixed mesh numerical methods, such as fictitious domain method, are preferred in solving FRS problems and have been widely researched. However, for reacting gas-solid flows no suitable fictitious domain numerical method has been developed. This work presents a new fictitious domain finite element method for FRS of reacting particulate flows. Low Mach number reacting flow governing equations are solved sequentially on a regular background mesh. Particles are immersed in the mesh and driven by their surface forces and torques integrated on immersed interfaces. Additional treatments on energy and surface reactions are developed. Several numerical test cases validated the method and a burning carbon particles array falling simulation proved the capability for solving moving reacting particle cluster problems.

Extracting and compensating dispersion mismatch in ultrahigh-resolution Fourier domain OCT imaging of the retina

PubMed Central

Choi, WooJhon; Baumann, Bernhard; Swanson, Eric A.; Fujimoto, James G.

2012-01-01

We present a numerical approach to extract the dispersion mismatch in ultrahigh-resolution Fourier domain optical coherence tomography (OCT) imaging of the retina. The method draws upon an analogy with a Shack-Hartmann wavefront sensor. By exploiting mathematical similarities between the expressions for aberration in optical imaging and dispersion mismatch in spectral / Fourier domain OCT, Shack-Hartmann principles can be extended from the two-dimensional paraxial wavevector space (or the x-y plane in the spatial domain) to the one-dimensional wavenumber space (or the z-axis in the spatial domain). For OCT imaging of the retina, different retinal layers, such as the retinal nerve fiber layer (RNFL), the photoreceptor inner and outer segment junction (IS/OS), or all the retinal layers near the retinal pigment epithelium (RPE) can be used as point source beacons in the axial direction, analogous to point source beacons used in conventional two-dimensional Shack-Hartman wavefront sensors for aberration characterization. Subtleties regarding speckle phenomena in optical imaging, which affect the Shack-Hartmann wavefront sensor used in adaptive optics, also occur analogously in this application. Using this approach and carefully suppressing speckle, the dispersion mismatch in spectral / Fourier domain OCT retinal imaging can be successfully extracted numerically and used for numerical dispersion compensation to generate sharper, ultrahigh-resolution OCT images. PMID:23187353

Multimodal Retinal Imaging in Incontinentia Pigmenti Including Optical Coherence Tomography Angiography: Findings From an Older Cohort With Mild Phenotype.

PubMed

Liu, Tin Yan Alvin; Han, Ian C; Goldberg, Morton F; Linz, Marguerite O; Chen, Connie J; Scott, Adrienne W

2018-05-01

Incontinentia pigmenti (IP) is a rare, X-linked dominant disease with potentially severe ocular complications that predominantly affect the peripheral retina. However, little is known about its effects on the macula. To describe the structural and vascular abnormalities observed in the maculas of patients with IP and to correlate these findings with peripheral pathologies. Prospective, cross-sectional study at Wilmer Eye Institute, Johns Hopkins University. Five participants with a clinical diagnosis of IP were included and underwent multimodal imaging with ultra-wide-field fluorescein angiography (FA), spectral-domain optical coherence tomography (OCT), and OCT angiography. The structural and vascular abnormalities observed on spectral-domain OCT and OCT angiography and their correlation with peripheral pathologies seen on ultra-wide-field FA. A total of 9 eyes from 5 patients (median age, 20.5 years; range, 8.4-54.2 years) were included. Median Snellen visual acuity was 20/32 (range, 20/16 to 20/63). ultra-wide-field FA-identified retinal vascular abnormalities in all 7 eyes in which FA was obtained. These abnormalities included microaneurysms, areas of nonperfusion, and vascular anastomoses, most of which were peripheral to the standard view of 30° FA with peripheral sweeps. Structural abnormalities were observed in 6 eyes on spectral-domain OCT, including inner retinal thinning and irregularities in the outer plexiform layer. Optical coherence tomography angiography abnormalities were noted in all 9 eyes, including decreased vascular density, abnormal vascular loops, and flow loss in the superficial and deep plexuses, which corresponded to areas of retinal thinning on spectral-domain OCT. Although our study is limited by the small sample size, the findings suggest that multimodal imaging is useful for detecting structural and vascular abnormalities that may not be apparent on ophthalmoscopy in patients with IP. Macular pathologies, especially a decrease in vascular density on OCT angiography, are common. Further studies are needed to characterize further the association between macular and peripheral abnormalities in patients with IP.

A spectral X-ray CT simulation study for quantitative determination of iron

NASA Astrophysics Data System (ADS)

Su, Ting; Kaftandjian, Valérie; Duvauchelle, Philippe; Zhu, Yuemin

2018-06-01

Iron is an essential element in the human body and disorders in iron such as iron deficiency or overload can cause serious diseases. This paper aims to explore the ability of spectral X-ray CT to quantitatively separate iron from calcium and potassium and to investigate the influence of different acquisition parameters on material decomposition performance. We simulated spectral X-ray CT imaging of a PMMA phantom filled with iron, calcium, and potassium solutions at various concentrations (15-200 mg/cc). Different acquisition parameters were considered, such as the number of energy bins (6, 10, 15, 20, 30, 60) and exposure factor per projection (0.025, 0.1, 1, 10, 100 mA s). Based on the simulation data, we investigated the performance of two regularized material decomposition approaches: projection domain method and image domain method. It was found that the former method discriminated iron from calcium, potassium and water in all cases and tended to benefit from lower number of energy bins for lower exposure factor acquisition. The latter method succeeded in iron determination only when the number of energy bins equals 60, and in this case, the contrast-to-noise ratios of the decomposed iron images are higher than those obtained using the projection domain method. The results demonstrate that both methods are able to discriminate and quantify iron from calcium, potassium and water under certain conditions. Their performances vary with the acquisition parameters of spectral CT. One can use one method or the other to benefit better performance according to the data available.

Random vibration analysis of space flight hardware using NASTRAN

NASA Technical Reports Server (NTRS)

Thampi, S. K.; Vidyasagar, S. N.

1990-01-01

During liftoff and ascent flight phases, the Space Transportation System (STS) and payloads are exposed to the random acoustic environment produced by engine exhaust plumes and aerodynamic disturbances. The analysis of payloads for randomly fluctuating loads is usually carried out using the Miles' relationship. This approximation technique computes an equivalent load factor as a function of the natural frequency of the structure, the power spectral density of the excitation, and the magnification factor at resonance. Due to the assumptions inherent in Miles' equation, random load factors are often over-estimated by this approach. In such cases, the estimates can be refined using alternate techniques such as time domain simulations or frequency domain spectral analysis. Described here is the use of NASTRAN to compute more realistic random load factors through spectral analysis. The procedure is illustrated using Spacelab Life Sciences (SLS-1) payloads and certain unique features of this problem are described. The solutions are compared with Miles' results in order to establish trends at over or under prediction.

On-line surface inspection using cylindrical lens-based spectral domain low-coherence interferometry.

PubMed

Tang, Dawei; Gao, Feng; Jiang, X

2014-08-20

We present a spectral domain low-coherence interferometry (SD-LCI) method that is effective for applications in on-line surface inspection because it can obtain a surface profile in a single shot. It has an advantage over existing spectral interferometry techniques by using cylindrical lenses as the objective lenses in a Michelson interferometric configuration to enable the measurement of long profiles. Combined with a modern high-speed CCD camera, general-purpose graphics processing unit, and multicore processors computing technology, fast measurement can be achieved. By translating the tested sample during the measurement procedure, real-time surface inspection was implemented, which is proved by the large-scale 3D surface measurement in this paper. ZEMAX software is used to simulate the SD-LCI system and analyze the alignment errors. Two step height surfaces were measured, and the captured interferograms were analyzed using a fast Fourier transform algorithm. Both 2D profile results and 3D surface maps closely align with the calibrated specifications given by the manufacturer.

Ghost Spectroscopy with Classical Thermal Light Emitted by a Superluminescent Diode

NASA Astrophysics Data System (ADS)

Janassek, Patrick; Blumenstein, Sébastien; Elsäßer, Wolfgang

2018-02-01

We propose and realize the first classical ghost-imaging (GI) experiment in the frequency or wavelength domain, thus performing ghost spectroscopy using thermal light exhibiting photon bunching. The required wavelength correlations are provided by light emitted by spectrally broadband near-infrared amplified spontaneous emission of a semiconductor-based superluminescent diode. They are characterized by wavelength-resolved intensity cross-correlation measurements utilizing two-photon-absorption interferometry. Finally, a real-world spectroscopic application of this ghost spectroscopy with a classical light scheme is demonstrated in which an absorption band of trichloromethane (chloroform) at 1214 nm is reconstructed with a spectral resolution of 10 nm as a proof-of-principle experiment. This ghost-spectroscopy work fills the gap of a hitherto missing analogy between the spatial and the spectral domain in classical GI modalities, with the expectation of contributing towards a broader dissemination of correlated photon ghost modalities, hence paving the way towards more applications which exploit the favorable advantages.

Use of spectral analogy to evaluate canopy reflectance sensitivity to leaf optical property

NASA Technical Reports Server (NTRS)

Baret, Frederic; Vanderbilt, Vern C.; Steven, Michael D.; Jacquemoud, Stephane

1993-01-01

The spectral variation of canopy reflectance is mostly governed by the absorption properties of the elements, hence the leaves, since their intrinsic scattering properties show very little spectral variation. The relationship between canopy reflectance and leaf reflectance measured at the red edge over sugar beet canopies was used to simulate canopy reflectance from leaf reflectance spectra measured over the whole spectral domain. The results show that the spectral analogies found allows accurate reconstruction of canopy reflectance spectra. Explicit assumptions about the very low spectral variation of leaf intrinsic scattering properties are thus indirectly justified. The sensitivity of canopy reflectance (rho(sub c)) to leaf optical properties can then be investigated from concurrent spectral variations of canopy (delta rho(sub c)/delta lambda) and leaf reflectance (delta rho(sub l)/delta lambda): (delta rho(sub c))/(delta rho(sub l)) = ((delta rho(sub c))/(delta lambda) ((delta rho( sub l))/(delta lambda))(sup -1)). This expression is strictly valid only when the optical properties of the soil background or the other vegetation elements such as bark are either spectrally flat or do not contribute significantly to canopy reflectance. Simulations using the SAIL and PROSPECT models demonstrate that the sensitivity of canopy reflectance to leaf reflectance is significant for large vegetation cover fractions in spectral domains where absorption is low. In these conditions, multiple, scattering enhances the leaf absorption features by a factor that can be greater than 2.0. To override the limitations of the SAIL model for the description of the canopy architecture, we tested the previous findings on experimental data. Concurrent canopy and leaf reflectance spectra were measured for a range of sugar beet canopies. The results show good agreement with the theoretical findings. Conclusions are drawn about the applicability of these findings, with particular attention to the potential detectability of leaf biochemical composition from canopy reflectance sensed from space.

Is There Spectral Variation in the Polarized Reflectance of Leaves?

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.; Daughtry, C. S. T.; Biehl, L. L.

2014-01-01

The light scattered by plant canopies depends in part on the light scattering/absorbing properties of the leaves and is key to understanding the remote sensing process in the optical domain. Here we specifically looked for evidence of fine spectral detail in the polarized portion of the light reflected from the individual leaves of five species of plants measured at Brewsters angle over the wavelength range 450 to 2300nm. Our results show no strong, unambiguous evidence of narrow band spectral variation of the polarized portion of the reflectance factor.

Is there Spectral Variation in the Polarized Reflectance of Leaves?

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.; Daughtry, C. S. T.; Biehl, L. L.

2014-01-01

The light scattered by plant canopies depends in part on the light scattering/absorbing properties of the leaves and is key to understanding the remote sensing process in the optical domain. Here we specifically looked for evidence of fine spectral detail in the polarized portion of the light reflected from the individual leaves of five species of plants measured at Brewsters angle over the wavelength range 450 to 2300nm. Our results show no strong, unambiguous evidence of narrow band spectral variation of the polarized portion of the reflectance factor.

Impact of sequential proton density fat fraction for quantification of hepatic steatosis in nonalcoholic fatty liver disease.

PubMed

Idilman, Ilkay S; Keskin, Onur; Elhan, Atilla Halil; Idilman, Ramazan; Karcaaltincaba, Musturay

2014-05-01

To determine the utility of sequential MRI-estimated proton density fat fraction (MRI-PDFF) for quantification of the longitudinal changes in liver fat content in individuals with nonalcoholic fatty liver disease (NAFLD). A total of 18 consecutive individuals (M/F: 10/8, mean age: 47.7±9.8 years) diagnosed with NAFLD, who underwent sequential PDFF calculations for the quantification of hepatic steatosis at two different time points, were included in the study. All patients underwent T1-independent volumetric multi-echo gradient-echo imaging with T2* correction and spectral fat modeling. A close correlation for quantification of hepatic steatosis between the initial MRI-PDFF and liver biopsy was observed (rs=0.758, p<0.001). The median interval between two sequential MRI-PDFF measurements was 184 days. From baseline to the end of the follow-up period, serum GGT level and homeostasis model assessment score were significantly improved (p=0.015, p=0.006, respectively), whereas BMI, serum AST, and ALT levels were slightly decreased. MRI-PDFFs were significantly improved (p=0.004). A good correlation between two sequential MRI-PDFF calculations was observed (rs=0.714, p=0.001). With linear regression analyses, only delta serum ALT levels had a significant effect on delta MRI-PDFF calculations (r2=38.6%, p=0.006). At least 5.9% improvement in MRI-PDFF is needed to achieve a normalized abnormal ALT level. The improvement of MRI-PDFF score was associated with the improvement of biochemical parameters in patients who had improvement in delta MRI-PDFF (p<0.05). MRI-PDFF can be used for the quantification of the longitudinal changes of hepatic steatosis. The changes in serum ALT levels significantly reflected changes in MRI-PDFF in patients with NAFLD.

A strategy for comprehensive identification of sequential constituents using ultra-high-performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometer, application study on chlorogenic acids in Flos Lonicerae Japonicae.

PubMed

Zhang, Jia-yu; Wang, Zi-jian; Li, Yun; Liu, Ying; Cai, Wei; Li, Chen; Lu, Jian-qiu; Qiao, Yan-jiang

2016-01-15

The analytical methodologies for evaluation of multi-component system in traditional Chinese medicines (TCMs) have been inadequate or unacceptable. As a result, the unclarity of multi-component hinders the sufficient interpretation of their bioactivities. In this paper, an ultra-high-performance liquid chromatography coupled with linear ion trap-Orbitrap (UPLC-LTQ-Orbitrap)-based strategy focused on the comprehensive identification of TCM sequential constituents was developed. The strategy was characterized by molecular design, multiple ion monitoring (MIM), targeted database hits and mass spectral trees similarity filter (MTSF), and even more isomerism discrimination. It was successfully applied in the HRMS data-acquisition and processing of chlorogenic acids (CGAs) in Flos Lonicerae Japonicae (FLJ), and a total of 115 chromatographic peaks attributed to 18 categories were characterized, allowing a comprehensive revelation of CGAs in FLJ for the first time. This demonstrated that MIM based on molecular design could improve the efficiency to trigger MS/MS fragmentation reactions. Targeted database hits and MTSF searching greatly facilitated the processing of extremely large information data. Besides, the introduction of diagnostic product ions (DPIs) discrimination, ClogP analysis, and molecular simulation, raised the efficiency and accuracy to characterize sequential constituents especially position and geometric isomers. In conclusion, the results expanded our understanding on CGAs in FLJ, and the strategy could be exemplary for future research on the comprehensive identification of sequential constituents in TCMs. Meanwhile, it may propose a novel idea for analyzing sequential constituents, and is promising for quality control and evaluation of TCMs. Copyright © 2015 Elsevier B.V. All rights reserved.

Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy

PubMed Central

Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

2016-01-01

Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident. PMID:27301319

Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy

NASA Astrophysics Data System (ADS)

Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

2016-06-01

Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident.

Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy.

PubMed

Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

2016-06-15

Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident.

Detecting and monitoring water stress states in maize crops using spectral ratios obtained in the photosynthetic domain

NASA Astrophysics Data System (ADS)

Baranoski, Gladimir V. G.; Van Leeuwen, Spencer R.

2017-07-01

The reliable detection and monitoring of changes in the water status of crops composed of plants like maize, a highly adaptable C4 species in large demand for both food and biofuel production, are longstanding remote sensing goals. Existing procedures employed to achieve these goals rely predominantly on the spectral signatures of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. It has been suggested that such procedures could be implemented using subsurface reflectance to transmittance ratios obtained in the visible (photosynthetic) domain with the assistance of polarization devices. However, the experiments leading to this proposition were performed on detached maize leaves, which were not influenced by the whole (living) plant's adaptation mechanisms to water stress. In this work, we employ predictive simulations of light-leaf interactions in the photosynthetic domain to demonstrate that the living specimens' physiological responses to dehydration stress should be taken into account in this context. Our findings also indicate that a reflectance to transmittance ratio obtained in the photosynthetic domain at a lower angle of incidence without the use of polarization devices may represent a cost-effective alternative for the assessment of water stress states in maize crops.

The on-ground calibration performances of the hyperspectral microscope MicrOmega for the Hayabusa-2 mission

NASA Astrophysics Data System (ADS)

Riu, Lucie; Bibring, Jean-Pierre; Pilorget, Cédric; Poulet, François; Hamm, Vincent

2018-03-01

The miniaturized near-infrared hyperspectral microscope MicrOmega, on board the MASCOT lander for Hayabusa-2 mission, is designed to perform in situ measurements at the grain scale of the C-type asteroid 1999 JU3 RYUGU. MicrOmega will observe samples with a field of view of a few millimeters with a spatial sampling of 25 μm and acquire near-infrared spectra by illuminating the sample sequentially with different wavelengths from 0.99 to 3.55 μm over two spectral channels with a typical spectral sampling of 20 cm-1. The on-ground calibration of MicrOmega requires a full characterization of the nominal range of operation of the instrument, both spectral (0.99-3.55 μm) and thermal (-40 °C to +40 °C) to derive the radiometric and spectral responses combined into a 4D transfer function to convert raw signal to calibrated reflectance. This specific 4D radiometric reference gives the instrument response according to the pixel location (x,y), the wavelength and the instrument temperature. This paper reports the complex computation of the 4D radiometric reference for the 0.9-2.5 μm channel. In this spectral range, the composition of the grains of a wide variety of minerals with relevance to solar system bodies can be identified through diagnostic spectral features: mafic (pyroxene, olivine…) as well as hydrated and altered minerals that are key phases for the solar system bodies' exploration.

Fourier transform methods in local gravity modeling

NASA Technical Reports Server (NTRS)

Harrison, J. C.; Dickinson, M.

1989-01-01

New algorithms were derived for computing terrain corrections, all components of the attraction of the topography at the topographic surface and the gradients of these attractions. These algoriithms utilize fast Fourier transforms, but, in contrast to methods currently in use, all divergences of the integrals are removed during the analysis. Sequential methods employing a smooth intermediate reference surface were developed to avoid the very large transforms necessary when making computations at high resolution over a wide area. A new method for the numerical solution of Molodensky's problem was developed to mitigate the convergence difficulties that occur at short wavelengths with methods based on a Taylor series expansion. A trial field on a level surface is continued analytically to the topographic surface, and compared with that predicted from gravity observations. The difference is used to compute a correction to the trial field and the process iterated. Special techniques are employed to speed convergence and prevent oscillations. Three different spectral methods for fitting a point-mass set to a gravity field given on a regular grid at constant elevation are described. Two of the methods differ in the way that the spectrum of the point-mass set, which extends to infinite wave number, is matched to that of the gravity field which is band-limited. The third method is essentially a space-domain technique in which Fourier methods are used to solve a set of simultaneous equations.

Frequency-domain nonlinear regression algorithm for spectral analysis of broadband SFG spectroscopy.

PubMed

He, Yuhan; Wang, Ying; Wang, Jingjing; Guo, Wei; Wang, Zhaohui

2016-03-01

The resonant spectral bands of the broadband sum frequency generation (BB-SFG) spectra are often distorted by the nonresonant portion and the lineshapes of the laser pulses. Frequency domain nonlinear regression (FDNLR) algorithm was proposed to retrieve the first-order polarization induced by the infrared pulse and to improve the analysis of SFG spectra through simultaneous fitting of a series of time-resolved BB-SFG spectra. The principle of FDNLR was presented, and the validity and reliability were tested by the analysis of the virtual and measured SFG spectra. The relative phase, dephasing time, and lineshapes of the resonant vibrational SFG bands can be retrieved without any preset assumptions about the SFG bands and the incident laser pulses.

Photoreceptor inner segment ellipsoid band integrity on spectral domain optical coherence tomography

PubMed Central

Saxena, Sandeep; Srivastav, Khushboo; Cheung, Chui M; Ng, Joanne YW; Lai, Timothy YY

2014-01-01

Spectral domain optical coherence tomography cross-sectional imaging of the macula has conventionally been resolved into four bands. However, some doubts were raised regarding authentication of the existence of these bands. Recently, a number of studies have suggested that the second band appeared to originate from the inner segment ellipsoids of the foveal cone photoreceptors, and therefore the previously called inner segment-outer segment junction is now referred to as inner segment ellipsoidband. Photoreceptor dysfunction may be a significant predictor of visual acuity in a spectrum of surgical and medical retinal diseases. This review aims to provide an overview and summarizes the role of the photoreceptor inner segment ellipsoid band in the management and prognostication of various vitreoretinal diseases. PMID:25525329

Acute macular neuroretinopathy: contribution of spectral-domain optical coherence tomography and multifocal ERG.

PubMed

Maschi, Célia; Schneider-Lise, Bérengère; Paoli, Vincent; Gastaud, Pierre

2011-06-01

Acute macular neuroretinopathy is a rare disease which occurs in young women and causes sudden paracentral scotoma and typical reddish-brown macular lesions. We report two cases of young women suffering from acute macular neuroretinopathy which we observed with spectral-domain Spectralis HRA-OCT and multifocal ERG at 3 and 7 months. Imaging revealed an early hyper-reflectivity of the photoreceptor layer, which changed into hyporeflectivity in the first week and remained the same in the following months, whereas visual field improved. Our findings show involvement primarly of the outer retina, and confirm OCT and mf ERG as important tools for diagnosis and follow-up of pathologic changes in AMNR, as other diagnostic tests often remain normal.

Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma.

PubMed

Priluck, Joshua C; Grover, Sandeep; Chalam, Kv

2012-01-01

To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases. Case report with images. Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20-1 OD (-2.50 + 0.25 × 090) and 20/50 OS (-8.25 + 3.25 × 075). Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography. Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases.

Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing

PubMed Central

Yaqoob, Zahid; Choi, Wonshik; Oh, Seungeun; Lue, Niyom; Park, Yongkeun; Fang-Yen, Christopher; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2010-01-01

We report a quantitative phase microscope based on spectral domain optical coherence tomography and line-field illumination. The line illumination allows self phase-referencing method to reject common-mode phase noise. The quantitative phase microscope also features a separate reference arm, permitting the use of high numerical aperture (NA > 1) microscope objectives for high resolution phase measurement at multiple points along the line of illumination. We demonstrate that the path-length sensitivity of the instrument can be as good as 41 pm/Hz, which makes it suitable for nanometer scale study of cell motility. We present the detection of natural motions of cell surface and two-dimensional surface profiling of a HeLa cell. PMID:19550464

A fluid model simulation of a simplified plasma limiter based on spectral-element time-domain method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Cheng; Ding, Dazhi, E-mail: dzding@njust.edu.cn; Fan, Zhenhong

2015-03-15

A simplified plasma limiter prototype is proposed and the fluid model coupled with Maxwell's equations is established to describe the operating mechanism of plasma limiter. A three-dimensional (3-D) simplified sandwich structure plasma limiter model is analyzed with the spectral-element time-domain (SETD) method. The field breakdown threshold of air and argon at different frequency is predicted and compared with the experimental data and there is a good agreement between them for gas microwave breakdown discharge problems. Numerical results demonstrate that the two-layer plasma limiter (plasma-slab-plasma) has better protective characteristics than a one-layer plasma limiter (slab-plasma-slab) with the same length of gasmore » chamber.« less

Spectral domain optical coherence tomography imaging of retinal diseases in Singapore.

PubMed

Singh, Mandeep; Chee, Caroline K L

2009-01-01

In this retrospective case series, the authors reviewed cases of patients with macular disorders whose eyes had been imaged using spectral domain optical coherence tomography (SD-OCT) (Cirrus HD-OCT; Carl Zeiss Meditec, Inc., Dublin, CA). SD-OCT images were obtained from patients with a variety of ocular conditions attending a tertiary retinal clinic in Singapore from August 2007 to December 2007, according to standardized protocols. Images of 428 eyes from 301 patients were reviewed. Ocular diagnoses included diabetic macular edema, exudative age-related macular degeneration, central serous chorioretinopathy, cystoid macular edema, retinal vein and artery occlusions, infective chorioretinitis, and others. The authors present four cases of particular interest to illustrate how SD-OCT was useful in complementing the clinician's assessment of macular disease.

Central serous chorioretinopathy treatment with spironolactone: a challenge-rechallenge case.

PubMed

Ryan, Edwin H; Pulido, Christine M

2015-01-01

To present a case of central serous chorioretinopathy (CSC) treatment with spironolactone in a challenge-rechallenge pattern. At presentation, fundus photography, fluorescein angiography, spectral domain optical coherence tomography, and enhanced depth imaging ocular coherence tomography were performed in both eyes. The patient was prescribed 25 mg spironolactone daily along with serum potassium monitoring. At follow-ups, spectral domain optical coherence tomography and enhanced depth imaging ocular coherence tomography were performed. A 37-year-old white male accountant presenting with CSC. Spironolactone treatment resolved the CSC. After the patient discontinued treatment, it returned. After returning to daily treatment, the CSC again resolved. Spironolactone was an effective treatment of CSC in this case. Other groups have reported similar findings with eplerenone, a similar drug.

Finite grid instability and spectral fidelity of the electrostatic Particle-In-Cell algorithm

DOE PAGES

Huang, C. -K.; Zeng, Y.; Wang, Y.; ...

2016-10-01

The origin of the Finite Grid Instability (FGI) is studied by resolving the dynamics in the 1D electrostatic Particle-In-Cell (PIC) model in the spectral domain at the single particle level and at the collective motion level. The spectral fidelity of the PIC model is contrasted with the underlying physical system or the gridless model. The systematic spectral phase and amplitude errors from the charge deposition and field interpolation are quantified for common particle shapes used in the PIC models. Lastly, it is shown through such analysis and in simulations that the lack of spectral fidelity relative to the physical systemmore » due to the existence of aliased spatial modes is the major cause of the FGI in the PIC model.« less

Temporal intensity interferometry for characterization of very narrow spectral lines

NASA Astrophysics Data System (ADS)

Tan, P. K.; Kurtsiefer, C.

2017-08-01

Some stellar objects exhibit very narrow spectral lines in the visible range additional to their blackbody radiation. Natural lasing has been suggested as a mechanism to explain narrow lines in Wolf-Rayet stars. However, the spectral resolution of conventional astronomical spectrographs is still about two orders of magnitude too low to test this hypothesis. We want to resolve the linewidth of narrow spectral emissions in starlight. A combination of spectral filtering with single-photon-level temporal correlation measurements breaks the resolution limit of wavelength-dispersing spectrographs by moving the linewidth measurement into the time domain. We demonstrate in a laboratory experiment that temporal intensity interferometry can determine a 20-MHz-wide linewidth of Doppler-broadened laser light and identify a coherent laser light contribution in a blackbody radiation background.

A study of the tolerance block approach to special stratification. [winter wheat in Kansas

NASA Technical Reports Server (NTRS)

Richardson, W. (Principal Investigator)

1979-01-01

The author has identified the following significant results. Twelve winter wheat LACIE segments in Kansas were used to compare the performance of three clustering methods: (1) BCLUST, which uses a spectral distance function to accumulate clusters; (2) blocks-alone, which divides spectral space into equally populated blocks; and (3) block-seeds, which uses spectral means of blocks-alone as seeds for accumulating distance-type clusters. Both BCLUST and block-seeds performed equally well and outperformed blocks-alone significantly. Their average variance ratio of about 0.5 showed imperfect separation of wheat from non-wheat. This result points to the need to explore the achievable crop separability in the spectral/temporal domain, and suggest evaluating derived features rather than data channels as a means to achieve purer spectral strata.

Finite grid instability and spectral fidelity of the electrostatic Particle-In-Cell algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, C. -K.; Zeng, Y.; Wang, Y.

The origin of the Finite Grid Instability (FGI) is studied by resolving the dynamics in the 1D electrostatic Particle-In-Cell (PIC) model in the spectral domain at the single particle level and at the collective motion level. The spectral fidelity of the PIC model is contrasted with the underlying physical system or the gridless model. The systematic spectral phase and amplitude errors from the charge deposition and field interpolation are quantified for common particle shapes used in the PIC models. Lastly, it is shown through such analysis and in simulations that the lack of spectral fidelity relative to the physical systemmore » due to the existence of aliased spatial modes is the major cause of the FGI in the PIC model.« less

Superpixel-Augmented Endmember Detection for Hyperspectral Images

NASA Technical Reports Server (NTRS)

Thompson, David R.; Castano, Rebecca; Gilmore, Martha

2011-01-01

Superpixels are homogeneous image regions comprised of several contiguous pixels. They are produced by shattering the image into contiguous, homogeneous regions that each cover between 20 and 100 image pixels. The segmentation aims for a many-to-one mapping from superpixels to image features; each image feature could contain several superpixels, but each superpixel occupies no more than one image feature. This conservative segmentation is relatively easy to automate in a robust fashion. Superpixel processing is related to the more general idea of improving hyperspectral analysis through spatial constraints, which can recognize subtle features at or below the level of noise by exploiting the fact that their spectral signatures are found in neighboring pixels. Recent work has explored spatial constraints for endmember extraction, showing significant advantages over techniques that ignore pixels relative positions. Methods such as AMEE (automated morphological endmember extraction) express spatial influence using fixed isometric relationships a local square window or Euclidean distance in pixel coordinates. In other words, two pixels covariances are based on their spatial proximity, but are independent of their absolute location in the scene. These isometric spatial constraints are most appropriate when spectral variation is smooth and constant over the image. Superpixels are simple to implement, efficient to compute, and are empirically effective. They can be used as a preprocessing step with any desired endmember extraction technique. Superpixels also have a solid theoretical basis in the hyperspectral linear mixing model, making them a principled approach for improving endmember extraction. Unlike existing approaches, superpixels can accommodate non-isometric covariance between image pixels (characteristic of discrete image features separated by step discontinuities). These kinds of image features are common in natural scenes. Analysts can substitute superpixels for image pixels during endmember analysis that leverages the spatial contiguity of scene features to enhance subtle spectral features. Superpixels define populations of image pixels that are independent samples from each image feature, permitting robust estimation of spectral properties, and reducing measurement noise in proportion to the area of the superpixel. This permits improved endmember extraction, and enables automated search for novel and constituent minerals in very noisy, hyperspatial images. This innovation begins with a graph-based segmentation based on the work of Felzenszwalb et al., but then expands their approach to the hyperspectral image domain with a Euclidean distance metric. Then, the mean spectrum of each segment is computed, and the resulting data cloud is used as input into sequential maximum angle convex cone (SMACC) endmember extraction.

The Development of Object Categorization in Young Children: Hierarchical Inclusiveness, Age, Perceptual Attribute, and Group versus Individual Analyses

ERIC Educational Resources Information Center

Bornstein, Marc H.; Arterberry, Martha E.

2010-01-01

Multiple levels of category inclusiveness in 4 object domains (animals, vehicles, fruit, and furniture) were examined using a sequential touching procedure and assessed in both individual and group analyses in eighty 12-, 18-, 24-, and 30-month-olds. The roles of stimulus discriminability and child motor development, fatigue, and actions were also…

Effects of Experimenting with Physical and Virtual Manipulatives on Students' Conceptual Understanding in Heat and Temperature

ERIC Educational Resources Information Center

Zacharia, Zacharias C.; Olympiou, Georgios; Papaevripidou, Marios

2008-01-01

This study aimed to investigate the comparative value of experimenting with physical manipulatives (PM) in a sequential combination with virtual manipulatives (VM), with the use of PM preceding the use of VM, and of experimenting with PM alone, with respect to changes in students' conceptual understanding in the domain of heat and temperature. A…

Hypercube matrix computation task

NASA Technical Reports Server (NTRS)

Calalo, R.; Imbriale, W.; Liewer, P.; Lyons, J.; Manshadi, F.; Patterson, J.

1987-01-01

The Hypercube Matrix Computation (Year 1986-1987) task investigated the applicability of a parallel computing architecture to the solution of large scale electromagnetic scattering problems. Two existing electromagnetic scattering codes were selected for conversion to the Mark III Hypercube concurrent computing environment. They were selected so that the underlying numerical algorithms utilized would be different thereby providing a more thorough evaluation of the appropriateness of the parallel environment for these types of problems. The first code was a frequency domain method of moments solution, NEC-2, developed at Lawrence Livermore National Laboratory. The second code was a time domain finite difference solution of Maxwell's equations to solve for the scattered fields. Once the codes were implemented on the hypercube and verified to obtain correct solutions by comparing the results with those from sequential runs, several measures were used to evaluate the performance of the two codes. First, a comparison was provided of the problem size possible on the hypercube with 128 megabytes of memory for a 32-node configuration with that available in a typical sequential user environment of 4 to 8 megabytes. Then, the performance of the codes was anlyzed for the computational speedup attained by the parallel architecture.

Gapped fermionic spectrum from a domain wall in seven dimension

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Subir; Rai, Nishal

2018-05-01

We obtain a domain wall solution in maximally gauged seven dimensional supergravity, which interpolates between two AdS spaces and spontaneously breaks a U (1) symmetry. We analyse frequency dependence of conductivity and find power law behaviour at low frequency. We consider certain fermions of supergravity in the background of this domain wall and compute holographic spectral function of the operators in the dual six dimensional theory. We find fermionic operators involving bosons with non-zero expectation value lead to gapped spectrum.

Nonconforming mortar element methods: Application to spectral discretizations

NASA Technical Reports Server (NTRS)

Maday, Yvon; Mavriplis, Cathy; Patera, Anthony

1988-01-01

Spectral element methods are p-type weighted residual techniques for partial differential equations that combine the generality of finite element methods with the accuracy of spectral methods. Presented here is a new nonconforming discretization which greatly improves the flexibility of the spectral element approach as regards automatic mesh generation and non-propagating local mesh refinement. The method is based on the introduction of an auxiliary mortar trace space, and constitutes a new approach to discretization-driven domain decomposition characterized by a clean decoupling of the local, structure-preserving residual evaluations and the transmission of boundary and continuity conditions. The flexibility of the mortar method is illustrated by several nonconforming adaptive Navier-Stokes calculations in complex geometry.

A DFFD simulation method combined with the spectral element method for solid-fluid-interaction problems

NASA Astrophysics Data System (ADS)

Chen, Li-Chieh; Huang, Mei-Jiau

2017-02-01

A 2D simulation method for a rigid body moving in an incompressible viscous fluid is proposed. It combines one of the immersed-boundary methods, the DFFD (direct forcing fictitious domain) method with the spectral element method; the former is employed for efficiently capturing the two-way FSI (fluid-structure interaction) and the geometric flexibility of the latter is utilized for any possibly co-existing stationary and complicated solid or flow boundary. A pseudo body force is imposed within the solid domain to enforce the rigid body motion and a Lagrangian mesh composed of triangular elements is employed for tracing the rigid body. In particular, a so called sub-cell scheme is proposed to smooth the discontinuity at the fluid-solid interface and to execute integrations involving Eulerian variables over the moving-solid domain. The accuracy of the proposed method is verified through an observed agreement of the simulation results of some typical flows with analytical solutions or existing literatures.

An Accurate Method for Measuring Airplane-Borne Conformal Antenna's Radar Cross Section

NASA Astrophysics Data System (ADS)

Guo, Shuxia; Zhang, Lei; Wang, Yafeng; Hu, Chufeng

2016-09-01

The airplane-borne conformal antenna attaches itself tightly with the airplane skin, so the conventional measurement method cannot determine the contribution of the airplane-borne conformal antenna to its radar cross section (RCS). This paper uses the 2D microwave imaging to isolate and extract the distribution of the reflectivity of the airplane-borne conformal antenna. It obtains the 2D spatial spectra of the conformal antenna through the wave spectral transform between the 2D spatial image and the 2D spatial spectrum. After the interpolation from the rectangular coordinate domain to the polar coordinate domain, the spectral domain data for the variation of the scatter of the conformal antenna with frequency and angle is obtained. The experimental results show that the measurement method proposed in this paper greatly enhances the airplane-borne conformal antenna's RCS measurement accuracy, essentially eliminates the influences caused by the airplane skin and more accurately reveals the airplane-borne conformal antenna's RCS scatter properties.

Ontology-based classification of remote sensing images using spectral rules

NASA Astrophysics Data System (ADS)

Andrés, Samuel; Arvor, Damien; Mougenot, Isabelle; Libourel, Thérèse; Durieux, Laurent

2017-05-01

Earth Observation data is of great interest for a wide spectrum of scientific domain applications. An enhanced access to remote sensing images for "domain" experts thus represents a great advance since it allows users to interpret remote sensing images based on their domain expert knowledge. However, such an advantage can also turn into a major limitation if this knowledge is not formalized, and thus is difficult for it to be shared with and understood by other users. In this context, knowledge representation techniques such as ontologies should play a major role in the future of remote sensing applications. We implemented an ontology-based prototype to automatically classify Landsat images based on explicit spectral rules. The ontology is designed in a very modular way in order to achieve a generic and versatile representation of concepts we think of utmost importance in remote sensing. The prototype was tested on four subsets of Landsat images and the results confirmed the potential of ontologies to formalize expert knowledge and classify remote sensing images.

A frequency domain analysis of respiratory variations in the seismocardiogram signal.

PubMed

Pandia, Keya; Inan, Omer T; Kovacs, Gregory T A

2013-01-01

The seismocardiogram (SCG) signal traditionally measured using a chest-mounted accelerometer contains low-frequency (0-100 Hz) cardiac vibrations that can be used to derive diagnostically relevant information about cardiovascular and cardiopulmonary health. This work is aimed at investigating the effects of respiration on the frequency domain characteristics of SCG signals measured from 18 healthy subjects. Toward this end, the 0-100 Hz SCG signal bandwidth of interest was sub-divided into 5 Hz and 10 Hz frequency bins to compare the spectral energy in corresponding frequency bins of the SCG signal measured during three key conditions of respiration--inspiration, expiration, and apnea. Statistically significant differences were observed between the power in ensemble averaged inspiratory and expiratory SCG beats and between ensemble averaged inspiratory and apneaic beats across the 18 subjects for multiple frequency bins in the 10-40 Hz frequency range. Accordingly, the spectral analysis methods described in this paper could provide complementary and improved classification of respiratory modulations in the SCG signal over and above time-domain SCG analysis methods.

Ultrafast spectral dynamics of dual-color-soliton intracavity collision in a mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Wei, Yuan; Li, Bowen; Wei, Xiaoming; Yu, Ying; Wong, Kenneth K. Y.

2018-02-01

The single-shot spectral dynamics of dual-color-soliton collisions inside a mode-locked laser is experimentally and numerically investigated. By using the all-optically dispersive Fourier transform, we spectrally unveil the collision-induced soliton self-reshaping process, which features dynamic spectral fringes over the soliton main lobe, and the rebuilding of Kelly sidebands with wavelength drifting. Meanwhile, the numerical simulations validate the experimental observation and provide additional insights into the physical mechanism of the collision-induced spectral dynamics from the temporal domain perspective. It is verified that the dynamic interference between the soliton and the dispersive waves is responsible for the observed collision-induced spectral evolution. These dynamic phenomena not only demonstrate the role of dispersive waves in the sophisticated soliton interaction inside the laser cavity, but also facilitate a deeper understanding of the soliton's inherent stability.

Multiband Spectral-Spatial RF Excitation for Hyperpolarized [2-13C]Dihydroxyacetone 13C-MR Metabolism Studies

PubMed Central

Marco-Rius, Irene; Cao, Peng; von Morze, Cornelius; Merrit, Matthew; Moreno, Karlos X; Chang, Gene-Yuan; Ohliger, Michael A.; Pearce, David; Kurhanewicz, John; Larson, Peder E. Z.; Vigneron, Daniel B.

2016-01-01

Purpose To develop a specialized multislice, single-acquisition approach to detect the metabolites of hyperpolarized [2-13C]dihydroxyacetone (DHAc) to probe gluconeogenesis in vivo, which have a broad 144 ppm spectral range (~4.6 KHz at 3T). A novel multiband RF excitation pulse was designed for independent flip angle control over 5-6 spectral-spatial (SPSP) excitation bands, each corrected for chemical shift misregistration effects. Methods Specialized multi-band SPSP RF pulses were designed, tested and applied to investigate hyperpolarized [2-13C]DHAc metabolism in kidney and liver of fasted rats with dynamic 13C-MRS and an optimal flip angle scheme. For comparison, experiments were also performed with narrow-band slice-selective RF pulses and a sequential change of the frequency offset to cover the five frequency bands of interest. Results The SPSP pulses provided a controllable spectral profile free of baseline distortion with improved signal to noise of the metabolite peaks, allowing for quantification of the metabolic products. We observed organ-specific differences in DHAc metabolism. There was 2-5 times more [2-13C]phosphoenolpyruvate and about 19 times more [2-13C]glycerol 3-phosphate in the liver than in the kidney. Conclusion A multiband SPSP RF pulse covering a spectral range over 144 ppm enabled in vivo characterization of HP [2-13C]dihydroxyacetone metabolism in rat liver and kidney. PMID:27017966

Unfolding of titin immunoglobulin domains by steered molecular dynamics simulation.

PubMed

Lu, H; Isralewitz, B; Krammer, A; Vogel, V; Schulten, K

1998-08-01

Titin, a 1-microm-long protein found in striated muscle myofibrils, possesses unique elastic and extensibility properties in its I-band region, which is largely composed of a PEVK region (70% proline, glutamic acid, valine, and lysine residue) and seven-strand beta-sandwich immunoglobulin-like (Ig) domains. The behavior of titin as a multistage entropic spring has been shown in atomic force microscope and optical tweezer experiments to partially depend on the reversible unfolding of individual Ig domains. We performed steered molecular dynamics simulations to stretch single titin Ig domains in solution with pulling speeds of 0.5 and 1.0 A/ps. Resulting force-extension profiles exhibit a single dominant peak for each Ig domain unfolding, consistent with the experimentally observed sequential, as opposed to concerted, unfolding of Ig domains under external stretching forces. This force peak can be attributed to an initial burst of backbone hydrogen bonds, which takes place between antiparallel beta-strands A and B and between parallel beta-strands A' and G. Additional features of the simulations, including the position of the force peak and relative unfolding resistance of different Ig domains, can be related to experimental observations.

Two zinc-binding domains in the transporter AdcA from Streptococcus pyogenes facilitate high-affinity binding and fast transport of zinc.

PubMed

Cao, Kun; Li, Nan; Wang, Hongcui; Cao, Xin; He, Jiaojiao; Zhang, Bing; He, Qing-Yu; Zhang, Gong; Sun, Xuesong

2018-04-20

Zinc is an essential metal in bacteria. One important bacterial zinc transporter is AdcA, and most bacteria possess AdcA homologs that are single-domain small proteins due to better efficiency of protein biogenesis. However, a double-domain AdcA with two zinc-binding sites is significantly overrepresented in Streptococcus species, many of which are major human pathogens. Using molecular simulation and experimental validations of AdcA from Streptococcus pyogenes , we found here that the two AdcA domains sequentially stabilize the structure upon zinc binding, indicating an organization required for both increased zinc affinity and transfer speed. This structural organization appears to endow Streptococcus species with distinct advantages in zinc-depleted environments, which would not be achieved by each single AdcA domain alone. This enhanced zinc transport mechanism sheds light on the significance of the evolution of the AdcA domain fusion, provides new insights into double-domain transporter proteins with two binding sites for the same ion, and indicates a potential target of antimicrobial drugs against pathogenic Streptococcus species. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Synthesis and Structural Characterization of Reflectin Proteins

DTIC Science & Technology

2012-02-29

constructs of interest included a reflectin 1a domain 3 (D3) monomer, a domain 3 dimer, subdomain peptides, recombinant reflectin 1b, an elastin -reflectin...diblock copolymer, and an elastin -reflectin-GFP fusion protein. After construction of the sequences of interest at the DNA level, protein expression...characterization was performed. The unique spectral properties associated with recombinant reflectin protein materials make elastin -reflectin

Emergence of CD134 cysteine-rich domain 2 (CRD2)-independent strains of feline immunodeficiency virus (FIV) is associated with disease progression in naturally infected cats.

PubMed

Bęczkowski, Paweł M; Techakriengkrai, Navapon; Logan, Nicola; McMonagle, Elizabeth; Litster, Annette; Willett, Brian J; Hosie, Margaret J

2014-11-28

Feline immunodeficiency virus (FIV) infection is mediated by sequential interactions with CD134 and CXCR4. Field strains of virus vary in their dependence on cysteine-rich domain 2 (CRD2) of CD134 for infection. Here, we analyse the receptor usage of viral variants in the blood of 39 naturally infected cats, revealing that CRD2-dependent viral variants dominate in early infection, evolving towards CRD2-independence with disease progression. These findings are consistent with a shift in CRD2 of CD134 usage with disease progression.

On the utilization of novel spectral laser scanning for three-dimensional classification of vegetation elements.

PubMed

Li, Zhan; Schaefer, Michael; Strahler, Alan; Schaaf, Crystal; Jupp, David

2018-04-06

The Dual-Wavelength Echidna Lidar (DWEL), a full waveform terrestrial laser scanner (TLS), has been used to scan a variety of forested and agricultural environments. From these scanning campaigns, we summarize the benefits and challenges given by DWEL's novel coaxial dual-wavelength scanning technology, particularly for the three-dimensional (3D) classification of vegetation elements. Simultaneous scanning at both 1064 nm and 1548 nm by DWEL instruments provides a new spectral dimension to TLS data that joins the 3D spatial dimension of lidar as an information source. Our point cloud classification algorithm explores the utilization of both spectral and spatial attributes of individual points from DWEL scans and highlights the strengths and weaknesses of each attribute domain. The spectral and spatial attributes for vegetation element classification each perform better in different parts of vegetation (canopy interior, fine branches, coarse trunks, etc.) and under different vegetation conditions (dead or live, leaf-on or leaf-off, water content, etc.). These environmental characteristics of vegetation, convolved with the lidar instrument specifications and lidar data quality, result in the actual capabilities of spectral and spatial attributes to classify vegetation elements in 3D space. The spectral and spatial information domains thus complement each other in the classification process. The joint use of both not only enhances the classification accuracy but also reduces its variance across the multiple vegetation types we have examined, highlighting the value of the DWEL as a new source of 3D spectral information. Wider deployment of the DWEL instruments is in practice currently held back by challenges in instrument development and the demands of data processing required by coaxial dual- or multi-wavelength scanning. But the simultaneous 3D acquisition of both spectral and spatial features, offered by new multispectral scanning instruments such as the DWEL, opens doors to study biophysical and biochemical properties of forested and agricultural ecosystems at more detailed scales.

[Accuracy improvement of spectral classification of crop using microwave backscatter data].

PubMed

Jia, Kun; Li, Qiang-Zi; Tian, Yi-Chen; Wu, Bing-Fang; Zhang, Fei-Fei; Meng, Ji-Hua

2011-02-01

In the present study, VV polarization microwave backscatter data used for improving accuracies of spectral classification of crop is investigated. Classification accuracy using different classifiers based on the fusion data of HJ satellite multi-spectral and Envisat ASAR VV backscatter data are compared. The results indicate that fusion data can take full advantage of spectral information of HJ multi-spectral data and the structure sensitivity feature of ASAR VV polarization data. The fusion data enlarges the spectral difference among different classifications and improves crop classification accuracy. The classification accuracy using fusion data can be increased by 5 percent compared to the single HJ data. Furthermore, ASAR VV polarization data is sensitive to non-agrarian area of planted field, and VV polarization data joined classification can effectively distinguish the field border. VV polarization data associating with multi-spectral data used in crop classification enlarges the application of satellite data and has the potential of spread in the domain of agriculture.

Compressive Spectral Method for the Simulation of the Nonlinear Gravity Waves

PubMed Central

Bayındır, Cihan

2016-01-01

In this paper an approach for decreasing the computational effort required for the spectral simulations of the fully nonlinear ocean waves is introduced. The proposed approach utilizes the compressive sampling algorithm and depends on the idea of using a smaller number of spectral components compared to the classical spectral method. After performing the time integration with a smaller number of spectral components and using the compressive sampling technique, it is shown that the ocean wave field can be reconstructed with a significantly better efficiency compared to the classical spectral method. For the sparse ocean wave model in the frequency domain the fully nonlinear ocean waves with Jonswap spectrum is considered. By implementation of a high-order spectral method it is shown that the proposed methodology can simulate the linear and the fully nonlinear ocean waves with negligible difference in the accuracy and with a great efficiency by reducing the computation time significantly especially for large time evolutions. PMID:26911357

Sensitivity of visual evoked potentials and spectral domain optical coherence tomography in early relapsing remitting multiple sclerosis.

PubMed

Behbehani, Raed; Ahmed, Samar; Al-Hashel, Jasem; Rousseff, Rossen T; Alroughani, Raed

2017-02-01

Visual evoked potentials and spectral-domain optical coherence tomography are common ancillary studies that assess the visual pathways from a functional and structural aspect, respectively. To compare prevalence of abnormalities of Visual evoked potentials (VEP) and spectral-domain optical coherence tomography (SDOCT) in patients with relapsing remitting multiple sclerosis (RRMS). A cross-sectional study of 100 eyes with disease duration of less than 5 years since the diagnosis. Correlation between retinal nerve fiber layer and ganglion-cell/inner plexiform layer with pattern-reversal visual evoked potentials amplitude and latency and contrast sensitivity was performed. The prevalence of abnormalities in pattern-reversal visual VEP was 56% while that of SOCT was 48% in all eyes. There was significant negative correlations between the average RNFL (r=-0.34, p=0.001) and GCIPL (r=-0.39, p<0.001) with VEP latency. In eyes with prior optic neuritis, a significant negative correlation was seen between average RNFL (r=-0.33, p=0.037) and GCIPL (r=-0.40, p=0.010) with VEP latency. We have found higher prevalence of VEP abnormalities than SCOCT in early relapsing-remitting multiple sclerosis. This suggests that VEP has a higher sensitivity for detecting lesions of the visual pathway in patients with early RRMS. Copyright © 2016 Elsevier B.V. All rights reserved.

Infrared scanning laser ophthalmoscope imaging of the macula and its correlation with functional loss and structural changes in patients with stargardt disease.

PubMed

Anastasakis, Anastasios; Fishman, Gerald A; Lindeman, Martin; Genead, Mohamed A; Zhou, Wensheng

2011-05-01

To correlate the degree of functional loss with structural changes in patients with Stargardt disease. Eighteen eyes of 10 patients with Stargardt disease were studied. Scanning laser ophthalmoscope infrared images were compared with corresponding spectral-domain optical coherence tomography scans. Additionally, scanning laser ophthalmoscope microperimetry was performed, and results were superimposed on scanning laser ophthalmoscope infrared images and in selected cases on fundus autofluorescence images. Seventeen of 18 eyes showed a distinct hyporeflective foveal and/or perifoveal area with distinct borders on scanning laser ophthalmoscope infrared images, which was less evident on funduscopy and incompletely depicted in fundus autofluorescence images. This hyporeflective zone corresponded to areas of significantly elevated psychophysical thresholds on microperimetry testing, in addition to thinning of the retinal pigment epithelium and disorganization or loss of the photoreceptor cell inner segment-outer segment junction and external-limiting membrane on spectral-domain optical coherence tomography. Scanning laser ophthalmoscope infrared fundus images are useful for depicting retinal structural changes in patients with Stargardt disease. A spectral-domain optical coherence tomography/scanning laser ophthalmoscope microperimetry device allows for a direct correlation of structural abnormalities with functional defects that will likely be applicable for the determination of retinal areas for potential improvement of retinal function in these patients during future clinical trials and for the monitoring of the diseases' natural history.

THE VALUE OF RETINAL IMAGING WITH INFRARED SCANNING LASER OPHTHALMOSCOPY IN PATIENTS WITH STARGARDT DISEASE

PubMed Central

Chun, Robert; Fishman, Gerald A.; Collison, Frederick T.; Stone, Edwin M.; Zernant, Jana; Allikmets, Rando

2014-01-01

Purpose To demonstrate the value of infrared scanning laser ophthalmoscopy (SLO) for determining structural retinal and choroidal changes in patients with Stargardt disease and its comparison to findings on short-wavelength fundus autofluorescence (SW-AF) imaging, spectral-domain optical coherence tomography, and microperimetry measurements. Methods Forty-four eyes of 22 patients with Stargardt disease were studied using infrared-SLO, spectral-domain optical coherence tomography, macular microperimetry, SW-AF, electroretinography, and fundus photography. Results Although SW-AF imaging outlined the regions of retinal pigment epithelial (RPE) atrophy (hypofluorescence) and enhanced the visibility of more funduscopically apparent flecks (hyperfluorescence), infrared-SLO imaging outlined the regions of choroidal, and RPE, atrophic changes. Degenerative changes in photoreceptor and RPE cell layers, evident on spectral-domain optical coherence tomography imaging, were associated with either hyporeflective or hyperreflective images on infrared-SLO imaging, depending on whether both RPE and choroidal atrophy (hyperreflectance) or solely RPE atrophy (hyporeflectance) was present. Threshold elevations on microperimetry testing corresponded to both RPE and choroidal atrophy on infrared-SLO imaging and RPE atrophy on SW-AF. Conclusion Although SW-AF identifies regions of RPE atrophy, infrared-SLO also identifies the involvement of the choroid that has important implications for the potential improvement in visual function from treatment. Thus, infrared-SLO imaging offers an additional advantage beyond that obtained with SW-AF. PMID:24317291

Spectral Domain Optical Coherence Tomography Allows the Unification of Clinical Decision Making for the Evaluation of Choroidal Neovascularization Activity.

PubMed

Volz, Cornelia; Grassmann, Felix; Greslechner, Roman; Märker, David Arthur; Peters, Patrick; Helbig, Horst; Gamulescu, Maria-Andreea

2018-06-21

This prospective observational clinical study investigated the benefits of spectral domain optical coherence tomography for specialists and residents in the management of neovascular age-related macular degeneration (AMD). The study involved 49 eyes of 44 patients. Patients were advised to present for reevaluation 4 weeks after the administration of the loading dose of vascular endothelial growth factor (VEGF)-inhibitors (3 intravitreal injections every 4 weeks after diagnosis). They were examined by residents (3-4 years' experience in ophthalmology) and specialists (> 5 years' experience). Each examiner evaluated the clinical situation and the spectral domain optical coherence tomography (SD-OCT) scan. After each evaluation, the examiners independently stated if further anti-VEGF treatment was recommended. The "true outcome" was defined as the specialist decision based on clinical evaluation and SD-OCT. Specialists and residents did not significantly differ in their accuracy in deciding on the correct treatment (p = 0.705 and p = 1), with or without the aid of SD-OCT. Both groups benefited from using SD-OCT to support their recommendations (p = 0.001 and p = 0.0002) and achieved a similar level of accuracy (p = 1 for difference). Residents benefited more than specialists by using SD-OCT to substantiate their recommendation on how to manage exudative AMD after the administration of the loading dose. © 2018 S. Karger AG, Basel.

Multiwavelength monitoring of the BL Lacertae object PKS 2155-304. 3: Ground-based observations in 1991 November

NASA Technical Reports Server (NTRS)

Courvoisier, T. J.-L.; Blecha, A.; Bouchet, P.; Bratschi, P.; Carini, M. T.; Donahue, M.; Edelson, R.; Feigelson, E. D.; Filippenko, A. V.; Glass, I. S.

1995-01-01

We present ground-based observations of the BL Lac object PKS 2155-304 during 1991 November. These data were obtained as part of a large international campaign of observations spanning the electro-magnetic spectrum from the radio waves to the X-rays. The data presented here include radio and UBVRI fluxes, as well as optical polarimetry. The U to I data show the same behavior in all bands and that only upper limits to any lag can be deduced from the cross-correlation of the light curves. The spectral slope in the U-I domain remained constant on all epochs but 2. There is no correlation between changes in the spectral slope and large variations in the total or polarized flux. The radio flux variations did not follow the same pattern of variability as the optical and infrared fluxes. The polarized flux varied by a larger factor than the total flux. The variations of the polarized flux are poorly correlated with those of the total flux in the optical (and hence UV domain; see the accompanying paper by Edelson et al.) nor with those of the soft X-rays. We conclude that the variability of PKS 2155-304 in the optical and near-infrared spectral domains are easier to understand in the context of variable geometry or bulk Lorentz factor than of variable electron acceleration and cooling rates.

Teleophthalmology with optical coherence tomography imaging in community optometry. Evaluation of a quality improvement for macular patients

PubMed Central

Kelly, Simon P; Wallwork, Ian; Haider, David; Qureshi, Kashif

2011-01-01

Purpose To describe a quality improvement for referral of National Health Service patients with macular disorders from a community optometry setting in an urban area. Methods Service evaluation of teleophthalmology consultation based on spectral domain optical coherence tomography images acquired by the community optometrist and transmitted to hospital eye services. Results Fifty patients with suspected macular conditions were managed via telemedicine consultation over 1 year. Responses were provided by hospital eye service-based ophthalmologists to the community optometrist or patient within the next day in 48 cases (96%) and in 34 (68%) patients on the same day. In the consensus opinion of the optometrist and ophthalmologist, 33 (66%) patients required further “face-to-face” medical examination and were triaged on clinical urgency. Seventeen cases (34%) were managed in the community and are a potential cost improvement. Specialty trainees were supervised in telemedicine consultations. Conclusion Innovation and quality improvement were demonstrated in both optometry to ophthalmology referrals and in primary optometric care by use of telemedicine with spectral domain optical coherence tomography images. E-referral of spectral domain optical coherence tomography images assists triage of macular patients and swifter care of urgent cases. Teleophthalmology is also, in the authors’ opinion, a tool to improve interdisciplinary professional working with community optometrists. Implications for progress are discussed. PMID:22174576

Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

NASA Astrophysics Data System (ADS)

Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

2018-06-01

Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

LORENE: Spectral methods differential equations solver

NASA Astrophysics Data System (ADS)

Gourgoulhon, Eric; Grandclément, Philippe; Marck, Jean-Alain; Novak, Jérôme; Taniguchi, Keisuke

2016-08-01

LORENE (Langage Objet pour la RElativité NumériquE) solves various problems arising in numerical relativity, and more generally in computational astrophysics. It is a set of C++ classes and provides tools to solve partial differential equations by means of multi-domain spectral methods. LORENE classes implement basic structures such as arrays and matrices, but also abstract mathematical objects, such as tensors, and astrophysical objects, such as stars and black holes.

Infiltration Processes and Flow Velocities Across the Landscape: When and Where is Macropore Flow Relevant?

NASA Astrophysics Data System (ADS)

Demand, D.; Blume, T.; Weiler, M.

2017-12-01

Preferential flow in macropores significantly affects the distributions of water and solutes in soil and many studies showed its relevance worldwide. Although some models include this process as a second pore domain, little is known about the spatial patterns and temporal dynamics. For example, while flow in the matrix is usually modeled and parameterized based on soil texture, an influence of texture on non-capillary flow for a given land-use class is poorly understood. To investigate the temporal and spatial dynamics on preferential flow we used a four-year soil moisture dataset from the mesoscale Attert catchment (288 km²) in Luxembourg. This dataset contains time series from 126 soil profiles in different textures and two land-use classes (forest, grassland). The soil moisture probes were installed in 10, 30 and 50 cm depth and measured in a 5-minute temporal resolution. Events were defined by a soil moisture increase higher than the instrument noise after a precipitation sum of more than 1 mm. Precipitation was measured next to the profiles so that each location could be associated to its unique precipitation characteristics. For every event and profile the soil moisture reaction was classified in sequential (ordered by depth) and non-sequential response. A non-sequential soil moisture reaction was used as an indicator of preferential flow. For sequential flow, the velocity was determined by the first reaction between two vertically adjacent sensors. The sensor reaction and wetting front velocity was analyzed in the context of precipitation characteristics and initial soil water content. Grassland sites showed a lower proportion of non-sequential flow than forest sites. For forest, non-sequential response is dependent on texture, rainfall intensity and initial water content. This is less distinct for the grassland sites. Furthermore, sequential reactions show higher flow velocities at sites, which also have high percentage of non-sequential response. In contrast, grassland sites show a more homogenous wetting front independent of soil texture. Compared against common modelling approaches of soil water flow, measured velocities show clear evidence of preferential flow, especially for forest soils. The analysis also shows that vegetation can alter the soil properties above the textural properties alone.

MEM spectral analysis for predicting influenza epidemics in Japan.

PubMed

Sumi, Ayako; Kamo, Ken-ichi

2012-03-01

The prediction of influenza epidemics has long been the focus of attention in epidemiology and mathematical biology. In this study, we tested whether time series analysis was useful for predicting the incidence of influenza in Japan. The method of time series analysis we used consists of spectral analysis based on the maximum entropy method (MEM) in the frequency domain and the nonlinear least squares method in the time domain. Using this time series analysis, we analyzed the incidence data of influenza in Japan from January 1948 to December 1998; these data are unique in that they covered the periods of pandemics in Japan in 1957, 1968, and 1977. On the basis of the MEM spectral analysis, we identified the periodic modes explaining the underlying variations of the incidence data. The optimum least squares fitting (LSF) curve calculated with the periodic modes reproduced the underlying variation of the incidence data. An extension of the LSF curve could be used to predict the incidence of influenza quantitatively. Our study suggested that MEM spectral analysis would allow us to model temporal variations of influenza epidemics with multiple periodic modes much more effectively than by using the method of conventional time series analysis, which has been used previously to investigate the behavior of temporal variations in influenza data.

Feature Transformation Detection Method with Best Spectral Band Selection Process for Hyper-spectral Imaging

NASA Astrophysics Data System (ADS)

Chen, Hai-Wen; McGurr, Mike; Brickhouse, Mark

2015-11-01

We present a newly developed feature transformation (FT) detection method for hyper-spectral imagery (HSI) sensors. In essence, the FT method, by transforming the original features (spectral bands) to a different feature domain, may considerably increase the statistical separation between the target and background probability density functions, and thus may significantly improve the target detection and identification performance, as evidenced by the test results in this paper. We show that by differentiating the original spectral, one can completely separate targets from the background using a single spectral band, leading to perfect detection results. In addition, we have proposed an automated best spectral band selection process with a double-threshold scheme that can rank the available spectral bands from the best to the worst for target detection. Finally, we have also proposed an automated cross-spectrum fusion process to further improve the detection performance in lower spectral range (<1000 nm) by selecting the best spectral band pair with multivariate analysis. Promising detection performance has been achieved using a small background material signature library for concept-proving, and has then been further evaluated and verified using a real background HSI scene collected by a HYDICE sensor.

Pathways for learning two languages: lexical and grammatical associations within and across languages in sequential bilingual children*

PubMed Central

PHAM, GIANG

2018-01-01

This study examines the strength and direction of lexical-grammatical associations within and between first and second languages (L1 and L2) in a longitudinal sample of sequential bilinguals. Thirty-three children who spoke Vietnamese (L1) and English (L2) completed picture-naming and story-telling tasks in each language at four yearly intervals. Hierarchical linear modeling across Years 1–4 revealed bidirectional within-language associations and a unidirectional cross-language association from the L1 to L2. Results suggest a conditional relationship between languages in which the L1 supports L2 growth, but not vice versa. Findings contribute to defining pathways for L1 and L2 learning across domains and languages. PMID:29670455

A proposed mechanism for rapid adaptation to spectrally distorted speech.

PubMed

Azadpour, Mahan; Balaban, Evan

2015-07-01

The mechanisms underlying perceptual adaptation to severely spectrally-distorted speech were studied by training participants to comprehend spectrally-rotated speech, which is obtained by inverting the speech spectrum. Spectral-rotation produces severe distortion confined to the spectral domain while preserving temporal trajectories. During five 1-hour training sessions, pairs of participants attempted to extract spoken messages from the spectrally-rotated speech of their training partner. Data on training-induced changes in comprehension of spectrally-rotated sentences and identification/discrimination of spectrally-rotated phonemes were used to evaluate the plausibility of three different classes of underlying perceptual mechanisms: (1) phonemic remapping (the formation of new phonemic categories that specifically incorporate spectrally-rotated acoustic information); (2) experience-dependent generation of a perceptual "inverse-transform" that compensates for spectral-rotation; and (3) changes in cue weighting (the identification of sets of acoustic cues least affected by spectral-rotation, followed by a rapid shift in perceptual emphasis to favour those cues, combined with the recruitment of the same type of "perceptual filling-in" mechanisms used to disambiguate speech-in-noise). Results exclusively support the third mechanism, which is the only one predicting that learning would specifically target temporally-dynamic cues that were transmitting phonetic information most stably in spite of spectral-distortion. No support was found for phonemic remapping or for inverse-transform generation.

Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shilyagin, P A; Gelikonov, G V; Gelikonov, V M

2014-07-31

We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phasemore » shift achromatism over a wide spectral range is achieved by using in the delay lines the individual elements with different dispersion characteristics. The ranges of admissible adjustment parameters of the achromatised delay line are estimated for exact and inexact conformity of the geometric characteristics of its components to those calculated. A possibility of simultaneous recording of the close-to-quadrature spectral components with a single linear photodetector element is experimentally confirmed. The suppression of the artefact mirror peak in the OCT-signal by an additional 9 dB relative to the level of its suppression is experimentally achieved when the air delay line is used. Two-dimensional images of the surface positioned at an angle to the axis of the probe beam are obtained with the correction of the 'mirror' artefact while maintaining the dynamic range of the image. (laser biophotonics)« less

Spectral-Domain Optical Coherence Tomography for Glaucoma Diagnosis

PubMed Central

Gracitelli, Carolina P.B; Abe, Ricardo Y; Medeiros, Felipe A

2015-01-01

Identification of structural damage to the optic nerve and retinal nerve fiber layer (RNFL) is an essential component of diagnosis and management of glaucoma. The introduction of spectral-domain OCT (SD-OCT) has allowed objective quantification of damage to these structures with unprecedented resolution. In addition, recent attention has been directed towards imaging the macular area for quantifying loss of neural tissue caused by the disease. Many studies have evaluated and compared the diagnostic accuracies of a variety of parameters that can be obtained from imaging these areas of the ocular fundus. In this article, we critically review the existing literature evaluating the diagnostic accuracy of SD-OCT in glaucoma and we discuss issues related to how SD-OCT results should be incorporated into clinical practice. PMID:26069519

Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma

PubMed Central

Priluck, Joshua C; Grover, Sandeep; Chalam, KV

2012-01-01

Purpose To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases. Methods Case report with images. Results Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20–1 OD (−2.50 + 0.25 × 090) and 20/50 OS (−8.25 + 3.25 × 075). Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography. Conclusions Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases. PMID:23152663

Spectral domain optical coherence tomography in Celestone® retinal toxicity.

PubMed

Marticorena-Álvarez, P; González Guijarro, J

2016-03-01

After inadvertent intravitreal injection of Celestone® (betamethasone sodium phosphate and acetate, benzalkonium chloride) in a patient, the macular spectral domain optical coherence tomography (SD-OCT) images showed hyper-reflectivity, thinning, and irregular spikes in the inner retinal layers. These early findings could explain the toxic secondary anatomical changes due to the drug itself and/or to its excipients. Late and permanent SD-OCT findings included changes in the ellipsoid zone and cystic-like spaces. In this case, SD-OCT images can help to better understand the pathophysiology of the retinal damage and to diagnose the associated complications, providing information with prognostic value. Copyright © 2015 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

Stress dependence of the Raman spectrum of polycrystalline barium titanate in presence of localized domain texture

NASA Astrophysics Data System (ADS)

Sakashita, Tatsuo; Deluca, Marco; Yamamoto, Shinsuke; Chazono, Hirokazu; Pezzotti, Giuseppe

2007-06-01

The stress dependence of the Raman spectrum of polycrystalline barium titanate (BaTiO3, BT) ceramics has been examined with microprobe polarized Raman spectroscopy. The angular dependence of the Raman spectrum of the tetragonal BT crystal has been theoretically established, enabling us to assess the stress dependence of selected spectral modes without the influence of crystallographic domain orientation. Upon considering the frequency shift of selected Raman modes as a function of orientation between the crystallographic axis and the polarization vector of incident and scattered light, a suitable instrumental configuration has been selected, which allowed a direct residual stress measurement according to a modified piezospectroscopic procedure. The analysis is based on the selection of mixed photostimulated spectral modes in two perpendicular angular orientations.

High-speed spectral domain optical coherence tomography using non-uniform fast Fourier transform

PubMed Central

Chan, Kenny K. H.; Tang, Shuo

2010-01-01

The useful imaging range in spectral domain optical coherence tomography (SD-OCT) is often limited by the depth dependent sensitivity fall-off. Processing SD-OCT data with the non-uniform fast Fourier transform (NFFT) can improve the sensitivity fall-off at maximum depth by greater than 5dB concurrently with a 30 fold decrease in processing time compared to the fast Fourier transform with cubic spline interpolation method. NFFT can also improve local signal to noise ratio (SNR) and reduce image artifacts introduced in post-processing. Combined with parallel processing, NFFT is shown to have the ability to process up to 90k A-lines per second. High-speed SD-OCT imaging is demonstrated at camera-limited 100 frames per second on an ex-vivo squid eye. PMID:21258551

Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Subhash, Hrebesh M.; Choudhury, Niloy; Jacques, Steven L.; Wang, Ruikang K.; Chen, Fangyi; Zha, Dingjun; Nuttall, Alfred L.

2012-01-01

Direct measurement of absolute vibration parameters from different locations within the mammalian organ of Corti is crucial for understanding the hearing mechanics such as how sound propagates through the cochlea and how sound stimulates the vibration of various structures of the cochlea, namely, basilar membrane (BM), recticular lamina, outer hair cells and tectorial membrane (TM). In this study we demonstrate the feasibility a modified phase-sensitive spectral domain optical coherence tomography system to provide subnanometer scale vibration information from multiple angles within the imaging beam. The system has the potential to provide depth resolved absolute vibration measurement of tissue microstructures from each of the delay-encoded vibration images with a noise floor of ~0.3nm at 200Hz.

Spectral analysis of temporal non-stationary rainfall-runoff processes

NASA Astrophysics Data System (ADS)

Chang, Ching-Min; Yeh, Hund-Der

2018-04-01

This study treats the catchment as a block box system with considering the rainfall input and runoff output being a stochastic process. The temporal rainfall-runoff relationship at the catchment scale is described by a convolution integral on a continuous time scale. Using the Fourier-Stieltjes representation approach, a frequency domain solution to the convolution integral is developed to the spectral analysis of runoff processes generated by temporal non-stationary rainfall events. It is shown that the characteristic time scale of rainfall process increases the runoff discharge variability, while the catchment mean travel time constant plays the role in reducing the variability of runoff discharge. Similar to the behavior of groundwater aquifers, catchments act as a low-pass filter in the frequency domain for the rainfall input signal.

Photoionization in the time and frequency domain

NASA Astrophysics Data System (ADS)

Isinger, M.; Squibb, R. J.; Busto, D.; Zhong, S.; Harth, A.; Kroon, D.; Nandi, S.; Arnold, C. L.; Miranda, M.; Dahlström, J. M.; Lindroth, E.; Feifel, R.; Gisselbrecht, M.; L'Huillier, A.

2017-11-01

Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10-18 seconds) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40-electron volt energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake-up, in which a second electron is left in an excited state, and obtain excellent agreement with theoretical calculations, thereby solving a puzzle raised by 7-year-old measurements.

Stability analysis of spectral methods for hyperbolic initial-boundary value systems

NASA Technical Reports Server (NTRS)

Gottlieb, D.; Lustman, L.; Tadmor, E.

1986-01-01

A constant coefficient hyperbolic system in one space variable, with zero initial data is discussed. Dissipative boundary conditions are imposed at the two points x = + or - 1. This problem is discretized by a spectral approximation in space. Sufficient conditions under which the spectral numerical solution is stable are demonstrated - moreover, these conditions have to be checked only for scalar equations. The stability theorems take the form of explicit bounds for the norm of the solution in terms of the boundary data. The dependence of these bounds on N, the number of points in the domain (or equivalently the degree of the polynomials involved), is investigated for a class of standard spectral methods, including Chebyshev and Legendre collocations.

Spectrally resolved laser interference microscopy

NASA Astrophysics Data System (ADS)

Butola, Ankit; Ahmad, Azeem; Dubey, Vishesh; Senthilkumaran, P.; Singh Mehta, Dalip

2018-07-01

We developed a new quantitative phase microscopy technique, namely, spectrally resolved laser interference microscopy (SR-LIM), with which it is possible to quantify multi-spectral phase information related to biological specimens without color crosstalk using a color CCD camera. It is a single shot technique where sequential switched on/off of red, green, and blue (RGB) wavelength light sources are not required. The method is implemented using a three-wavelength interference microscope and a customized compact grating based imaging spectrometer fitted at the output port. The results of the USAF resolution chart while employing three different light sources, namely, a halogen lamp, light emitting diodes, and lasers, are discussed and compared. The broadband light sources like the halogen lamp and light emitting diodes lead to stretching in the spectrally decomposed images, whereas it is not observed in the case of narrow-band light sources, i.e. lasers. The proposed technique is further successfully employed for single-shot quantitative phase imaging of human red blood cells at three wavelengths simultaneously without color crosstalk. Using the present technique, one can also use a monochrome camera, even though the experiments are performed using multi-color light sources. Finally, SR-LIM is not only limited to RGB wavelengths, it can be further extended to red, near infra-red, and infra-red wavelengths, which are suitable for various biological applications.

AOTF near-IR spectrometers for study of Lunar and Martian surface composition

NASA Astrophysics Data System (ADS)

Ivanov, A.; Korablev, O.; Mantsevich, S.; Vyazovetskiy, N.; Fedorova, A.; Evdokimova, N.; Stepanov, A.; Titov, A.; Kalinnikov, Y.; Kuzmin, R.; Kiselev, A.; Bazilevsky, A.; Bondarenko, A.; Dokuchaev, I.; Moiseev, P.; Victorov, A.; Berezhnoy, A.; Skorov, Y.; Bisikalo, D.; Velikodsky, Y.

2014-04-01

The series of the AOTF near-IR spectrometers is developed in Moscow Space Research Institute for study of Lunar and Martian surface composition in the vicinity of a lander or a rover. Lunar Infrared Spectrometer (LIS) is an experiment onboard Luna-Glob (launch in 2017) and Luna- Resurs (launch in 2019) Russian surface missions. It's a pencil-beam spectrometer to be pointed by a robotic arm of the landing module. The instrument's field of view (FOV) of 1° is co-aligned with the FOV(45°) of a stereo TV camera. Infrared Spectrometer for ExoMars (ISEM) is an experiment onboard ExoMars (launch in 2018) ESARoscosmos rover. It's spectrometer based on LIS with required redesign for ExoMars mission. The ISEM instrument is mounted on the rover's mast coaligned with the FOV (5°) of High Resolution camera (HRC). Spectrometers and are intended for study of the surface composition in the vicinity of the lander and rover. The spectrometers will provide measurements of selected surface areas in the spectral range of 1.15-3.3 μm. The spectral selection is provided by acoustooptic tunable filter (AOTF), which scans the spectral range sequentially. Electrical command of the AOTF allows selecting the spectral sampling, and permits a random access if needed.

Post-processing of auditory steady-state responses to correct spectral leakage.

PubMed

Felix, Leonardo Bonato; de Sá, Antonio Mauricio Ferreira Leite Miranda; Mendes, Eduardo Mazoni Andrade Marçal; Moraes, Márcio Flávio Dutra

2009-06-30

Auditory steady-state responses (ASSRs) are electrical manifestations of brain due to high rate sound stimulation. These evoked responses can be used to assess the hearing capabilities of a subject in an objective, automatic fashion. Usually, the detection protocol is accomplished by frequency-domain techniques, such as magnitude-squared coherence, whose estimation is based on the fast Fourier transform (FFT) of several data segments. In practice, the FFT-based spectrum may spread out the energy of a given frequency to its side bins and this escape of energy in the spectrum is called spectral leakage. The distortion of the spectrum due to leakage may severely compromise statistical significance of objective detection. This work presents an offline, a posteriori method for spectral leakage minimization in the frequency-domain analysis of ASSRs using coherent sampling criterion and interpolation in time. The technique was applied to the local field potentials of 10 Wistar rats and the results, together with those from simulated data, indicate that a leakage-free analysis of ASSRs is possible for any dataset if the methods showed in this paper were followed.

On the electromagnetic scattering from infinite rectangular conducting grids

NASA Technical Reports Server (NTRS)

Christodoulou, C.

1985-01-01

The study and development of two numerical techniques for the analysis of electromagnetic scattering from a rectangular wire mesh are described. Both techniques follow from one basic formulation and they are both solved in the spectral domain. These techniques were developed as a result of an investigation towards more efficient numerical computation for mesh scattering. These techniques are efficient for the following reasons: (a1) make use of the Fast Fourier Transform; (b2) they avoid any convolution problems by converting integrodifferential equations into algebraic equations; and (c3) they do not require inversions of any matrices. The first method, the SIT or Spectral Iteration Technique, is applied for regions where the spacing between wires is not less than two wavelengths. The second method, the SDCG or Spectral Domain Conjugate Gradient approach, can be used for any spacing between adjacent wires. A study of electromagnetic wave properties, such as reflection coefficient, induced currents and aperture fields, as functions of frequency, angle of incidence, polarization and thickness of wires is presented. Examples and comparisons or results with other methods are also included to support the validity of the new algorithms.

Spectral-domain low-coherence interferometry for phase-sensitive measurement of Faraday rotation at multiple depths.

PubMed

Yeh, Yi-Jou; Black, Adam J; Akkin, Taner

2013-10-10

We describe a method for differential phase measurement of Faraday rotation from multiple depth locations simultaneously. A polarization-maintaining fiber-based spectral-domain interferometer that utilizes a low-coherent light source and a single camera is developed. Light decorrelated by the orthogonal channels of the fiber is launched on a sample as two oppositely polarized circular states. These states reflect from sample surfaces and interfere with the corresponding states of the reference arm. A custom spectrometer, which is designed to simplify camera alignment, separates the orthogonal channels and records the interference-related oscillations on both spectra. Inverse Fourier transform of the spectral oscillations in k-space yields complex depth profiles, whose amplitudes and phase difference are related to reflectivity and Faraday rotation within the sample, respectively. Information along a full depth profile is produced at the camera speed without performing an axial scan for a multisurface sample. System sensitivity for the Faraday rotation measurement is 0.86 min of arc. Verdet constants of clear liquids and turbid media are measured at 687 nm.

Pixel switching of epitaxial Pd/YHx/CaF2 switchable mirrors

PubMed

Kerssemakers; van der Molen SJ; Koeman; Gunther; Griessen

2000-08-03

Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors.

Snapshot hyperspectral imaging probe with principal component analysis and confidence ellipse for classification

NASA Astrophysics Data System (ADS)

Lim, Hoong-Ta; Murukeshan, Vadakke Matham

2017-06-01

Hyperspectral imaging combines imaging and spectroscopy to provide detailed spectral information for each spatial point in the image. This gives a three-dimensional spatial-spatial-spectral datacube with hundreds of spectral images. Probe-based hyperspectral imaging systems have been developed so that they can be used in regions where conventional table-top platforms would find it difficult to access. A fiber bundle, which is made up of specially-arranged optical fibers, has recently been developed and integrated with a spectrograph-based hyperspectral imager. This forms a snapshot hyperspectral imaging probe, which is able to form a datacube using the information from each scan. Compared to the other configurations, which require sequential scanning to form a datacube, the snapshot configuration is preferred in real-time applications where motion artifacts and pixel misregistration can be minimized. Principal component analysis is a dimension-reducing technique that can be applied in hyperspectral imaging to convert the spectral information into uncorrelated variables known as principal components. A confidence ellipse can be used to define the region of each class in the principal component feature space and for classification. This paper demonstrates the use of the snapshot hyperspectral imaging probe to acquire data from samples of different colors. The spectral library of each sample was acquired and then analyzed using principal component analysis. Confidence ellipse was then applied to the principal components of each sample and used as the classification criteria. The results show that the applied analysis can be used to perform classification of the spectral data acquired using the snapshot hyperspectral imaging probe.

An Internal Signal Sequence Directs Intramembrane Proteolysis of a Cellular Immunoglobulin Domain Protein*S⃞

PubMed Central

Robakis, Thalia; Bak, Beata; Lin, Shu-huei; Bernard, Daniel J.; Scheiffele, Peter

2008-01-01

Precursor proteolysis is a crucial mechanism for regulating protein structure and function. Signal peptidase (SP) is an enzyme with a well defined role in cleaving N-terminal signal sequences but no demonstrated function in the proteolysis of cellular precursor proteins. We provide evidence that SP mediates intraprotein cleavage of IgSF1, a large cellular Ig domain protein that is processed into two separate Ig domain proteins. In addition, our results suggest the involvement of signal peptide peptidase (SPP), an intramembrane protease, which acts on substrates that have been previously cleaved by SP. We show that IgSF1 is processed through sequential proteolysis by SP and SPP. Cleavage is directed by an internal signal sequence and generates two separate Ig domain proteins from a polytopic precursor. Our findings suggest that SP and SPP function are not restricted to N-terminal signal sequence cleavage but also contribute to the processing of cellular transmembrane proteins. PMID:18981173

Spectral methods for time dependent partial differential equations

NASA Technical Reports Server (NTRS)

Gottlieb, D.; Turkel, E.

1983-01-01

The theory of spectral methods for time dependent partial differential equations is reviewed. When the domain is periodic Fourier methods are presented while for nonperiodic problems both Chebyshev and Legendre methods are discussed. The theory is presented for both hyperbolic and parabolic systems using both Galerkin and collocation procedures. While most of the review considers problems with constant coefficients the extension to nonlinear problems is also discussed. Some results for problems with shocks are presented.

A New Frequency-Domain Method for Bunch Length Measurement

NASA Astrophysics Data System (ADS)

Ferianis, M.; Pros, M.

1997-05-01

A new method for bunch length measurements has been developed at Elettra. It is based on a spectral observation of the synchrotron radiation light pulses. The single pulse spectrum is shaped by means of an optical process which gives the method an increased sensitivity compared to the usual spectral observations. Some simulations have been carried out to check the method in non-ideal conditions. The results of the first measurements are also presented.

Raman Spectroscopy of Experimental Oral Carcinogenesis: Study on Sequential Cancer Progression in Hamster Buccal Pouch Model.

PubMed

Kumar, Piyush; Bhattacharjee, Tanmoy; Ingle, Arvind; Maru, Girish; Krishna, C Murali

2016-10-01

Oral cancers suffer from poor 5-year survival rates, owing to late detection of the disease. Current diagnostic/screening tools need to be upgraded in view of disadvantages like invasiveness, tedious sample preparation, long output times, and interobserver variances. Raman spectroscopy has been shown to identify many disease conditions, including oral cancers, from healthy conditions. Further studies in exploring sequential changes in oral carcinogenesis are warranted. In this Raman spectroscopy study, sequential progression in experimental oral carcinogenesis in Hamster buccal pouch model was investigated using 3 approaches-ex vivo, in vivo sequential, and in vivo follow-up. In all these studies, spectral changes show lipid dominance in early stages while later stages and tumors showed increased protein to lipid ratio and nucleic acids. On similar lines, early weeks of 7,12-dimethylbenz(a)anthracene-treated and control groups showed higher overlap and low classification. The classification efficiency increased progressively, reached a plateau phase and subsequently increased up to 100% by 14 weeks. The misclassifications between treated and control spectra suggested some changes in controls as well, which was confirmed by a careful reexamination of histopathological slides. These findings suggests Raman spectroscopy may be able to identify microheterogeneity, which may often go unnoticed in conventional biochemistry wherein tissue extracts are employed, as well as in histopathology. In vivo findings, quite comparable to gold-standard supported ex vivo findings, give further proof of Raman spectroscopy being a promising label-free, noninvasive diagnostic adjunct for future clinical applications. © The Author(s) 2015.

Portable sequential multicolor thermal imager based on a MCT 384 x 288 focal plane array

NASA Astrophysics Data System (ADS)

Breiter, Rainer; Cabanski, Wolfgang A.; Mauk, Karl-Heinz; Rode, Werner; Ziegler, Johann

2001-10-01

AIM has developed a sequential multicolor thermal imager to provide customers with a test system to realize real-time spectral selective thermal imaging. In contrast to existing PC based laboratory units, the system is miniaturized with integrated signal processing like non-uniformity correction and post processing functions such as image subtraction of different colors to allow field tests in military applications like detection of missile plumes or camouflaged targets as well as commercial applications like detection of chemical agents, pollution control, etc. The detection module used is a 384 X 288 mercury cadmium telluride (MCT) focal plane array (FPA) available in the mid wave (MWIR) or long wave spectral band LWIR). A compact command and control electronics (CCE) provides clock and voltage supply for the detector as well as 14 bit deep digital conversion of the analog detector output. A continuous rotating wheel with four facets for filters provides spectral selectivity. The customer can choose between various types of filter characteristics, e.g. a 4.2 micrometer bandpass filter for CO2 detection in the MWIR band. The rotating wheel can be synchronized to an external source giving the rotation speed, typical 25 l/s. A position sensor generates the four frame start signals for synchronous operation of the detector -- 100 Hz framerate for the four frames per rotation. The rotating wheel is exchangeable for different configurations and also plates for a microscanner operation to improve geometrical resolution are available instead of a multicolor operation. AIM's programmable MVIP image processing unit is used for signal processing like non- uniformity correction and controlling the detector parameters. The MVIP allows to output the four subsequent images as four quarters of the video screen to prior to any observation task set the integration time for each color individually for comparable performance in each spectral color and after that also to determine separate NUC coefficients for each filter position. This procedure allows to really evaluate the pay off of spectral selectivity in the IR. The display part of the MVIP allows linear look up tables (LUT) for dynamic reduction as well as histogram equalization for automatic LUT optimization. Parallel to the video output a digital interface is provided for digital recording of the 14 bit corrected detector data. The architecture of the thermal imager with its components is presented in this paper together with some aspects on multicolor thermal imaging.

Cell Wall Architecture of the Elongating Maize Coleoptile1

PubMed Central

Carpita, Nicholas C.; Defernez, Marianne; Findlay, Kim; Wells, Brian; Shoue, Douglas A.; Catchpole, Gareth; Wilson, Reginald H.; McCann, Maureen C.

2001-01-01

The primary walls of grasses are composed of cellulose microfibrils, glucuronoarabinoxylans (GAXs), and mixed-linkage β-glucans, together with smaller amounts of xyloglucans, glucomannans, pectins, and a network of polyphenolic substances. Chemical imaging by Fourier transform infrared microspectroscopy revealed large differences in the distributions of many chemical species between different tissues of the maize (Zea mays) coleoptile. This was confirmed by chemical analyses of isolated outer epidermal tissues compared with mesophyll-enriched preparations. Glucomannans and esterified uronic acids were more abundant in the epidermis, whereas β-glucans were more abundant in the mesophyll cells. The localization of β-glucan was confirmed by immunocytochemistry in the electron microscope and quantitative biochemical assays. We used field emission scanning electron microscopy, infrared microspectroscopy, and biochemical characterization of sequentially extracted polymers to further characterize the cell wall architecture of the epidermis. Oxidation of the phenolic network followed by dilute NaOH extraction widened the pores of the wall substantially and permitted observation by scanning electron microscopy of up to six distinct microfibrillar lamellae. Sequential chemical extraction of specific polysaccharides together with enzymic digestion of β-glucans allowed us to distinguish two distinct domains in the grass primary wall. First, a β-glucan-enriched domain, coextensive with GAXs of low degrees of arabinosyl substitution and glucomannans, is tightly associated around microfibrils. Second, a GAX that is more highly substituted with arabinosyl residues and additional glucomannan provides an interstitial domain that interconnects the β-glucan-coated microfibrils. Implications for current models that attempt to explain the biochemical and biophysical mechanism of wall loosening during cell growth are discussed. PMID:11598229

Terahertz time-gated spectral imaging for content extraction through layered structures

PubMed Central

Redo-Sanchez, Albert; Heshmat, Barmak; Aghasi, Alireza; Naqvi, Salman; Zhang, Mingjie; Romberg, Justin; Raskar, Ramesh

2016-01-01

Spatial resolution, spectral contrast and occlusion are three major bottlenecks for non-invasive inspection of complex samples with current imaging technologies. We exploit the sub-picosecond time resolution along with spectral resolution provided by terahertz time-domain spectroscopy to computationally extract occluding content from layers whose thicknesses are wavelength comparable. The method uses the statistics of the reflected terahertz electric field at subwavelength gaps to lock into each layer position and then uses a time-gated spectral kurtosis to tune to highest spectral contrast of the content on that specific layer. To demonstrate, occluding textual content was successfully extracted from a packed stack of paper pages down to nine pages without human supervision. The method provides over an order of magnitude enhancement in the signal contrast and can impact inspection of structural defects in wooden objects, plastic components, composites, drugs and especially cultural artefacts with subwavelength or wavelength comparable layers. PMID:27610926

Terahertz absorption spectra of commonly used antimalarial drugs

NASA Astrophysics Data System (ADS)

Bawuah, Prince; Zeitler, J. Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

2018-06-01

Terahertz (THz) spectra from the pure forms [i.e. the active pharmaceutical ingredients (APIs)] of four commonly used antimalarial drugs are reported. The well-defined spectral fingerprints obtained for these APIs in the spectral range of 0.1 THz-3 THz show the sensitivity of the THz time-domain spectroscopic (THz-TDS) method for screening antimalarial drugs. For identification purpose, two commercially available antimalarial tablets were detected. Clear spectral fingerprints of the APIs in the antimalarial tablets were obtained even amidst the several types of excipients present in the tablets. This observation further proves the high sensitivity of the THz techniques in tracking the presence or absence of API in a pharmaceutical tablet. We envisage that the spectral data obtained for these drugs can contribute to a spectroscopic database in the far infrared spectral region and hence support the modelling of THz sensing to differentiate between genuine and counterfeit antimalarial tablets.

Digital techniques for ULF wave polarization analysis

NASA Technical Reports Server (NTRS)

Arthur, C. W.

1979-01-01

Digital power spectral and wave polarization analysis are powerful techniques for studying ULF waves in the earth's magnetosphere. Four different techniques for using the spectral matrix to perform such an analysis have been presented in the literature. Three of these techniques are similar in that they require transformation of the spectral matrix to the principal axis system prior to performing the polarization analysis. The differences in the three techniques lie in the manner in which determine this transformation. A comparative study of these three techniques using both simulated and real data has shown them to be approximately equal in quality of performance. The fourth technique does not require transformation of the spectral matrix. Rather, it uses the measured spectral matrix and state vectors for a desired wave type to design a polarization detector function in the frequency domain. The design of various detector functions and their application to both simulated and real data will be presented.

Compression of hyper-spectral images using an accelerated nonnegative tensor decomposition

NASA Astrophysics Data System (ADS)

Li, Jin; Liu, Zilong

2017-12-01

Nonnegative tensor Tucker decomposition (NTD) in a transform domain (e.g., 2D-DWT, etc) has been used in the compression of hyper-spectral images because it can remove redundancies between spectrum bands and also exploit spatial correlations of each band. However, the use of a NTD has a very high computational cost. In this paper, we propose a low complexity NTD-based compression method of hyper-spectral images. This method is based on a pair-wise multilevel grouping approach for the NTD to overcome its high computational cost. The proposed method has a low complexity under a slight decrease of the coding performance compared to conventional NTD. We experimentally confirm this method, which indicates that this method has the less processing time and keeps a better coding performance than the case that the NTD is not used. The proposed approach has a potential application in the loss compression of hyper-spectral or multi-spectral images

Global spectral graph wavelet signature for surface analysis of carpal bones

NASA Astrophysics Data System (ADS)

Masoumi, Majid; Rezaei, Mahsa; Ben Hamza, A.

2018-02-01

Quantitative shape comparison is a fundamental problem in computer vision, geometry processing and medical imaging. In this paper, we present a spectral graph wavelet approach for shape analysis of carpal bones of the human wrist. We employ spectral graph wavelets to represent the cortical surface of a carpal bone via the spectral geometric analysis of the Laplace-Beltrami operator in the discrete domain. We propose global spectral graph wavelet (GSGW) descriptor that is isometric invariant, efficient to compute, and combines the advantages of both low-pass and band-pass filters. We perform experiments on shapes of the carpal bones of ten women and ten men from a publicly-available database of wrist bones. Using one-way multivariate analysis of variance (MANOVA) and permutation testing, we show through extensive experiments that the proposed GSGW framework gives a much better performance compared to the global point signature embedding approach for comparing shapes of the carpal bones across populations.

A Review of Spectral Methods for Variable Amplitude Fatigue Prediction and New Results

NASA Technical Reports Server (NTRS)

Larsen, Curtis E.; Irvine, Tom

2013-01-01

A comprehensive review of the available methods for estimating fatigue damage from variable amplitude loading is presented. The dependence of fatigue damage accumulation on power spectral density (psd) is investigated for random processes relevant to real structures such as in offshore or aerospace applications. Beginning with the Rayleigh (or narrow band) approximation, attempts at improved approximations or corrections to the Rayleigh approximation are examined by comparison to rainflow analysis of time histories simulated from psd functions representative of simple theoretical and real world applications. Spectral methods investigated include corrections by Wirsching and Light, Ortiz and Chen, the Dirlik formula, and the Single-Moment method, among other more recent proposed methods. Good agreement is obtained between the spectral methods and the time-domain rainflow identification for most cases, with some limitations. Guidelines are given for using the several spectral methods to increase confidence in the damage estimate.

Global spectral graph wavelet signature for surface analysis of carpal bones.

PubMed

Masoumi, Majid; Rezaei, Mahsa; Ben Hamza, A

2018-02-05

Quantitative shape comparison is a fundamental problem in computer vision, geometry processing and medical imaging. In this paper, we present a spectral graph wavelet approach for shape analysis of carpal bones of the human wrist. We employ spectral graph wavelets to represent the cortical surface of a carpal bone via the spectral geometric analysis of the Laplace-Beltrami operator in the discrete domain. We propose global spectral graph wavelet (GSGW) descriptor that is isometric invariant, efficient to compute, and combines the advantages of both low-pass and band-pass filters. We perform experiments on shapes of the carpal bones of ten women and ten men from a publicly-available database of wrist bones. Using one-way multivariate analysis of variance (MANOVA) and permutation testing, we show through extensive experiments that the proposed GSGW framework gives a much better performance compared to the global point signature embedding approach for comparing shapes of the carpal bones across populations.

Terahertz absorption spectra of commonly used antimalarial drugs

NASA Astrophysics Data System (ADS)

Bawuah, Prince; Zeitler, J. Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

2018-03-01

Terahertz (THz) spectra from the pure forms [i.e. the active pharmaceutical ingredients (APIs)] of four commonly used antimalarial drugs are reported. The well-defined spectral fingerprints obtained for these APIs in the spectral range of 0.1 THz-3 THz show the sensitivity of the THz time-domain spectroscopic (THz-TDS) method for screening antimalarial drugs. For identification purpose, two commercially available antimalarial tablets were detected. Clear spectral fingerprints of the APIs in the antimalarial tablets were obtained even amidst the several types of excipients present in the tablets. This observation further proves the high sensitivity of the THz techniques in tracking the presence or absence of API in a pharmaceutical tablet. We envisage that the spectral data obtained for these drugs can contribute to a spectroscopic database in the far infrared spectral region and hence support the modelling of THz sensing to differentiate between genuine and counterfeit antimalarial tablets.

From the outside looking in: developing snapshot imaging spectro-polarimeters

NASA Astrophysics Data System (ADS)

Dereniak, E. L.

2014-09-01

The information from a scene is critical in autonomous optical systems, and the variety of information that can be extracted is determined by the application. To characterize a target, the information of interest captured is spectral (λ), polarization (S) and distance (Z). There are many technologies that capture this information in different ways to identify the target. In many fields, such as mining and military reconnaissance, there is a need for rapid data acquisition and, for this reason, a relatively new method has been devised that can obtain all this information simultaneously. The need for snapshot acquisition of data without moving parts was the goal of the research. This paper reviews the chain of novel research instruments that were sequentially developed to capture spectral and polarization information of a scene in a snapshot or flash. The distance (Z) is yet to be integrated.

Reference-free fatigue crack detection using nonlinear ultrasonic modulation under various temperature and loading conditions

NASA Astrophysics Data System (ADS)

Lim, Hyung Jin; Sohn, Hoon; DeSimio, Martin P.; Brown, Kevin

2014-04-01

This study presents a reference-free fatigue crack detection technique using nonlinear ultrasonic modulation. When low frequency (LF) and high frequency (HF) inputs generated by two surface-mounted lead zirconate titanate (PZT) transducers are applied to a structure, the presence of a fatigue crack can provide a mechanism for nonlinear ultrasonic modulation and create spectral sidebands around the frequency of the HF signal. The crack-induced spectral sidebands are isolated using a combination of linear response subtraction (LRS), synchronous demodulation (SD) and continuous wavelet transform (CWT) filtering. Then, a sequential outlier analysis is performed on the extracted sidebands to identify the crack presence without referring any baseline data obtained from the intact condition of the structure. Finally, the robustness of the proposed technique is demonstrated using actual test data obtained from simple aluminum plate and complex aircraft fitting-lug specimens under varying temperature and loading variations.

AOTF near-IR spectrometers for study of Lunar and Martian surface composition

NASA Astrophysics Data System (ADS)

Korablev, O.; Kiselev, A.; Vyazovetskiy, N.; Fedorova, A.; Evdokimova, N.; Stepanov, A.; Titov, A.; Kalinnikov, Y.; Kuzmin, R. O.; Bazilevsky, A. T.; Bondarenko, A.; Moiseev, P.

2013-09-01

The series of the AOTF near-IR spectrometers is developed in Moscow Space Research Institute for study of Lunar and Martian surface composition in the vicinity of a lander or a rover. Lunar Infrared Spectrometer (LIS) is an experiment onboard Luna-Glob (launch in 2015) and Luna-Resurs (launch in 2017) Russian surface missions. The LIS is mounted on the mechanic arm of landing module in the field of view (45°) of stereo TV camera. Infrared Spectrometer for ExoMars (ISEM) is an experiment onboard ExoMars (launch in 2018) ESARoscosmos rover. The ISEM instrument is mounted on the rover's mast together with High Resolution camera (HRC). Spectrometers will provide measurements of selected surface area in the spectral range of 1.15-3.3 μm. The electrically commanded acousto-optic filter scans sequentially at a desired sampling, with random access, over the entire spectral range.

Spectral decompositions of multiple time series: a Bayesian non-parametric approach.

PubMed

Macaro, Christian; Prado, Raquel

2014-01-01

We consider spectral decompositions of multiple time series that arise in studies where the interest lies in assessing the influence of two or more factors. We write the spectral density of each time series as a sum of the spectral densities associated to the different levels of the factors. We then use Whittle's approximation to the likelihood function and follow a Bayesian non-parametric approach to obtain posterior inference on the spectral densities based on Bernstein-Dirichlet prior distributions. The prior is strategically important as it carries identifiability conditions for the models and allows us to quantify our degree of confidence in such conditions. A Markov chain Monte Carlo (MCMC) algorithm for posterior inference within this class of frequency-domain models is presented.We illustrate the approach by analyzing simulated and real data via spectral one-way and two-way models. In particular, we present an analysis of functional magnetic resonance imaging (fMRI) brain responses measured in individuals who participated in a designed experiment to study pain perception in humans.

HARP: A Dynamic Inertial Spectral Partitioner

NASA Technical Reports Server (NTRS)

Simon, Horst D.; Sohn, Andrew; Biswas, Rupak

1997-01-01

Partitioning unstructured graphs is central to the parallel solution of computational science and engineering problems. Spectral partitioners, such recursive spectral bisection (RSB), have proven effecfive in generating high-quality partitions of realistically-sized meshes. The major problem which hindered their wide-spread use was their long execution times. This paper presents a new inertial spectral partitioner, called HARP. The main objective of the proposed approach is to quickly partition the meshes at runtime in a manner that works efficiently for real applications in the context of distributed-memory machines. The underlying principle of HARP is to find the eigenvectors of the unpartitioned vertices and then project them onto the eigerivectors of the original mesh. Results for various meshes ranging in size from 1000 to 100,000 vertices indicate that HARP can indeed partition meshes rapidly at runtime. Experimental results show that our largest mesh can be partitioned sequentially in only a few seconds on an SP2 which is several times faster than other spectral partitioners while maintaining the solution quality of the proven RSB method. A parallel WI version of HARP has also been implemented on IBM SP2 and Cray T3E. Parallel HARP, running on 64 processors SP2 and T3E, can partition a mesh containing more than 100,000 vertices into 64 subgrids in about half a second. These results indicate that graph partitioning can now be truly embedded in dynamically-changing real-world applications.

Two new xanthones from Calophyllum nodusum (Guttiferae).

PubMed

Nasir, Nadiah Mad; Rahmani, Mawardi; Shaari, Khozirah; Ee, Gwendoline Cheng Lian; Go, Rusea; Kassim, Nur Kartinee; Muhamad, Siti Noor Kamilah; Iskandar, Mohd Johadi

2011-10-25

The air-dried powdered stem bark of Calophyllum nodusum (Guttiferea) collected from Sandakan (Sabah, Malaysia), was extracted sequentially with hexane, chloroform and methanol. The solvents were removed by rotary evaporator to give dark viscous extracts. Detailed and repeated chromatographic separation of the extracts lead to isolation of two new xanthones, identified as nodusuxanthone and trapezifolixanthone A. Other common terpenoids such as betulinic acid, lupeol, stigmasterol and friedelin were also isolated from the extracts and identified. The structures of the compounds were established by detailed spectral analysis and comparison with previously reported data.

Dual-wavelength quantum cascade laser for trace gas spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jágerská, J.; Tuzson, B.; Mangold, M.

2014-10-20

We demonstrate a sequentially operating dual-wavelength quantum cascade laser with electrically separated laser sections, emitting single-mode at 5.25 and 6.25 μm. Based on a single waveguide ridge, this laser represents a considerable asset to optical sensing and trace gas spectroscopy, as it allows probing multiple gas species with spectrally distant absorption features using conventional optical setups without any beam combining optics. The laser capability was demonstrated in simultaneous NO and NO{sub 2} detection, reaching sub-ppb detection limits and selectivity comparable to conventional high-end spectroscopic systems.

Changes in the Spectral Features of Zinc Phthalocyanine Induced by Nitrogen Dioxide Gas in Solution and in Solid Polymer Nanofiber Media.

PubMed

Zugle, Ruphino; Tetteh, Samuel

2017-03-01

The changes in the spectral features of zinc phthalocyanine in the visible domain as a result of its interaction with nitrogen dioxide gas were assessed in this work. This was done both in solution and when the phthalocyanine was incorporated into a solid polystyrene polymer nanofiber matrix. The spectral changes were found to be spontaneous and marked in both cases suggesting a rapid response criterion for the detection of the gas. In particular, the functionalised nano-fabric material could serve as a practical fire alarm system as it rapidly detects the nitrogen dioxide gas generated during burning.

Spectroscopy by joint spectral and time domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Szkulmowski, Maciej; Tamborski, Szymon; Wojtkowski, Maciej

2015-03-01

We present the methodology for spectroscopic examination of absorbing media being the combination of Spectral Optical Coherence Tomography and Fourier Transform Spectroscopy. The method bases on the joint Spectral and Time OCT computational scheme and simplifies data analysis procedure as compared to the mostly used windowing-based Spectroscopic OCT methods. The proposed experimental setup is self-calibrating in terms of wavelength-pixel assignment. The performance of the method in measuring absorption spectrum was checked with the use of the reflecting phantom filled with the absorbing agent (indocyanine green). The results show quantitative accordance with the controlled exact results provided by the reference method.

Simplified signal processing for impedance spectroscopy with spectrally sparse sequences

NASA Astrophysics Data System (ADS)

Annus, P.; Land, R.; Reidla, M.; Ojarand, J.; Mughal, Y.; Min, M.

2013-04-01

Classical method for measurement of the electrical bio-impedance involves excitation with sinusoidal waveform. Sinusoidal excitation at fixed frequency points enables wide variety of signal processing options, most general of them being Fourier transform. Multiplication with two quadrature waveforms at desired frequency could be easily accomplished both in analogue and in digital domains, even simplest quadrature square waves can be considered, which reduces signal processing task in analogue domain to synchronous switching followed by low pass filter, and in digital domain requires only additions. So called spectrally sparse excitation sequences (SSS), which have been recently introduced into bio-impedance measurement domain, are very reasonable choice when simultaneous multifrequency excitation is required. They have many good properties, such as ease of generation and good crest factor compared to similar multisinusoids. Typically, the usage of discrete or fast Fourier transform in signal processing step is considered so far. Usage of simplified methods nevertheless would reduce computational burden, and enable simpler, less costly and less energy hungry signal processing platforms. Accuracy of the measurement with SSS excitation when using different waveforms for quadrature demodulation will be compared in order to evaluate the feasibility of the simplified signal processing. Sigma delta modulated sinusoid (binary signal) is considered to be a good alternative for a synchronous demodulation.

JAIL: a structure-based interface library for macromolecules.

PubMed

Günther, Stefan; von Eichborn, Joachim; May, Patrick; Preissner, Robert

2009-01-01

The increasing number of solved macromolecules provides a solid number of 3D interfaces, if all types of molecular contacts are being considered. JAIL annotates three different kinds of macromolecular interfaces, those between interacting protein domains, interfaces of different protein chains and interfaces between proteins and nucleic acids. This results in a total number of about 184,000 database entries. All the interfaces can easily be identified by a detailed search form or by a hierarchical tree that describes the protein domain architectures classified by the SCOP database. Visual inspection of the interfaces is possible via an interactive protein viewer. Furthermore, large scale analyses are supported by an implemented sequential and by a structural clustering. Similar interfaces as well as non-redundant interfaces can be easily picked out. Additionally, the sequential conservation of binding sites was also included in the database and is retrievable via Jmol. A comprehensive download section allows the composition of representative data sets with user defined parameters. The huge data set in combination with various search options allow a comprehensive view on all interfaces between macromolecules included in the Protein Data Bank (PDB). The download of the data sets supports numerous further investigations in macromolecular recognition. JAIL is publicly available at http://bioinformatics.charite.de/jail.

Depth resolved hyperspectral imaging spectrometer based on structured light illumination and Fourier transform interferometry

PubMed Central

Choi, Heejin; Wadduwage, Dushan; Matsudaira, Paul T.; So, Peter T.C.

2014-01-01

A depth resolved hyperspectral imaging spectrometer can provide depth resolved imaging both in the spatial and the spectral domain. Images acquired through a standard imaging Fourier transform spectrometer do not have the depth-resolution. By post processing the spectral cubes (x, y, λ) obtained through a Sagnac interferometer under uniform illumination and structured illumination, spectrally resolved images with depth resolution can be recovered using structured light illumination algorithms such as the HiLo method. The proposed scheme is validated with in vitro specimens including fluorescent solution and fluorescent beads with known spectra. The system is further demonstrated in quantifying spectra from 3D resolved features in biological specimens. The system has demonstrated depth resolution of 1.8 μm and spectral resolution of 7 nm respectively. PMID:25360367

Retrieval of the thickness and refractive index dispersion of parallel plate from a single interferogram recorded in both spectral and angular domains

NASA Astrophysics Data System (ADS)

Dong, Jingtao; Lu, Rongsheng

2018-04-01

The principle of retrieving the thickness and refractive index dispersion of a parallel glass plate is reported based on single interferogram recording and phase analysis. With the parallel plate illuminated by a convergent light sheet, the transmitted light interfering in both spectral and angular domains is recorded. The phase recovered from the single interferogram by Fourier analysis is used to retrieve the thickness and refractive index dispersion without periodic ambiguity. Experimental results of an optical substrate standard show that the accuracy of refractive index dispersion is less than 2.5 × 10-5 and the relative uncertainty of thickness is 6 × 10-5 (3σ). This method is confirmed to be robust against the intensity noises, indicating the capability of stable and accurate measurement.

Analysis of spatial and temporal spectra of liquid film surface in annular gas-liquid flow

NASA Astrophysics Data System (ADS)

Alekseenko, Sergey; Cherdantsev, Andrey; Heinz, Oksana; Kharlamov, Sergey; Markovich, Dmitriy

2013-09-01

Wavy structure of liquid film in annular gas-liquid flow without liquid entrainment consists of fast long-living primary waves and slow short-living secondary waves. In present paper, results of spectral analysis of this wavy structure are presented. Application of high-speed LIF technique allowed us to perform such analysis in both spatial and temporal domains. Power spectra in both domains are characterized by one-humped shape with long exponential tail. Influence of gas velocity, liquid Reynolds number, liquid viscosity and pipe diameter on frequency of the waves is investigated. When gravity effect is much lesser than the shear stress, similarity of power spectra at different gas velocities is observed. Using combination of spectral analysis and identification of characteristic lines of primary waves, frequency of generation of secondary waves by primary waves is measured.

Swept source optical coherence tomography using an all-fiber 1300-nm ring laser source.

PubMed

Choma, Michael A; Hsu, Kevin; Izatt, Joseph A

2005-01-01

The increased sensitivity of spectral domain optical coherence tomography (OCT) has driven the development of a new generation of technologies in OCT, including rapidly tunable, broad bandwidth swept laser sources and spectral domain OCT interferometer topologies. In this work, the operation of a turnkey 1300-nm swept laser source is demonstrated. This source has a fiber ring cavity with a semiconductor optical amplifier gain medium. Intracavity mode selection is achieved with an in-fiber tunable fiber Fabry-Perot filter. A novel optoelectronic technique that allows for even sampling of the swept source OCT signal in k space also is described. A differential swept source OCT system is presented, and images of in vivo human cornea and skin are presented. Lastly, the effects of analog-to-digital converter aliasing on image quality in swept source OCT are discussed.

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images

NASA Astrophysics Data System (ADS)

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N.; Zangwill, Linda M.

2014-03-01

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Quantitative Analysis of Mouse Retinal Layers Using Automated Segmentation of Spectral Domain Optical Coherence Tomography Images

PubMed Central

Dysli, Chantal; Enzmann, Volker; Sznitman, Raphael; Zinkernagel, Martin S.

2015-01-01

Purpose Quantification of retinal layers using automated segmentation of optical coherence tomography (OCT) images allows for longitudinal studies of retinal and neurological disorders in mice. The purpose of this study was to compare the performance of automated retinal layer segmentation algorithms with data from manual segmentation in mice using the Spectralis OCT. Methods Spectral domain OCT images from 55 mice from three different mouse strains were analyzed in total. The OCT scans from 22 C57Bl/6, 22 BALBc, and 11 C3A.Cg-Pde6b+Prph2Rd2/J mice were automatically segmented using three commercially available automated retinal segmentation algorithms and compared to manual segmentation. Results Fully automated segmentation performed well in mice and showed coefficients of variation (CV) of below 5% for the total retinal volume. However, all three automated segmentation algorithms yielded much thicker total retinal thickness values compared to manual segmentation data (P < 0.0001) due to segmentation errors in the basement membrane. Conclusions Whereas the automated retinal segmentation algorithms performed well for the inner layers, the retinal pigmentation epithelium (RPE) was delineated within the sclera, leading to consistently thicker measurements of the photoreceptor layer and the total retina. Translational Relevance The introduction of spectral domain OCT allows for accurate imaging of the mouse retina. Exact quantification of retinal layer thicknesses in mice is important to study layers of interest under various pathological conditions. PMID:26336634

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images.

PubMed

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N; Zangwill, Linda M

2014-03-18

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Influence of image compression on the interpretation of spectral-domain optical coherence tomography in exudative age-related macular degeneration

PubMed Central

Kim, J H; Kang, S W; Kim, J-r; Chang, Y S

2014-01-01

Purpose To evaluate the effect of image compression of spectral-domain optical coherence tomography (OCT) images in the examination of eyes with exudative age-related macular degeneration (AMD). Methods Thirty eyes from 30 patients who were diagnosed with exudative AMD were included in this retrospective observational case series. The horizontal OCT scans centered at the center of the fovea were conducted using spectral-domain OCT. The images were exported to Tag Image File Format (TIFF) and 100, 75, 50, 25 and 10% quality of Joint Photographic Experts Group (JPEG) format. OCT images were taken before and after intravitreal ranibizumab injections, and after relapse. The prevalence of subretinal and intraretinal fluids was determined. Differences in choroidal thickness between the TIFF and JPEG images were compared with the intra-observer variability. Results The prevalence of subretinal and intraretinal fluids was comparable regardless of the degree of compression. However, the chorio–scleral interface was not clearly identified in many images with a high degree of compression. In images with 25 and 10% quality of JPEG, the difference in choroidal thickness between the TIFF images and the respective JPEG images was significantly greater than the intra-observer variability of the TIFF images (P=0.029 and P=0.024, respectively). Conclusions In OCT images of eyes with AMD, 50% of the quality of the JPEG format would be an optimal degree of compression for efficient data storage and transfer without sacrificing image quality. PMID:24788012

INCREASED SERUM LEVELS OF UREA AND CREATININE ARE SURROGATE MARKERS FOR DISRUPTION OF RETINAL PHOTORECEPTOR EXTERNAL LIMITING MEMBRANE AND INNER SEGMENT ELLIPSOID ZONE IN TYPE 2 DIABETES MELLITUS.

PubMed

Saxena, Sandeep; Ruia, Surabhi; Prasad, Senthamizh; Jain, Astha; Mishra, Nibha; Natu, Shankar M; Meyer, Carsten H; Gilhotra, Jagjit S; Kruzliak, Peter; Akduman, Levent

2017-02-01

To evaluate the role of serum urea and creatinine as surrogate markers for disruption of retinal photoreceptor external limiting membrane (ELM) and inner segment ellipsoid zone (EZ) in Type 2 diabetic retinopathy (DR) using spectral-domain optical coherence tomography, for the first time. One hundred and seventeen consecutive cases of Type 2 diabetes mellitus (diabetes without retinopathy [No DR; n = 39], nonproliferative diabetic retinopathy [NPDR; n = 39], proliferative diabetic retinopathy [PDR; n = 39]) and 40 healthy control subjects were included. Serum levels of urea and creatinine were assessed using standard protocol. Spectral-domain optical coherence tomography was used to grade the disruption of ELM and EZ as follows: Grade 0, no disruption of ELM and EZ; Grade 1, ELM disrupted, EZ intact; Grade 2, ELM and EZ disrupted. Data were analyzed statistically. Increase in serum levels of urea (F = 22.93) and creatinine (F = 15.82) and increased grades of disruption of ELM and EZ (γ = 116.3) were observed with increased severity of DR (P < 0.001). Increase in serum levels of urea (F = 10.45) and creatinine (F = 6.89) was observed with increased grades of disruption of ELM and EZ (P = 0.001). Serum levels of urea and creatinine are surrogate markers for disruption of retinal photoreceptor ELM and EZ on spectral-domain optical coherence tomography in DR.

Presentation of a new BRDF measurement device

NASA Astrophysics Data System (ADS)

Serrot, Gerard; Bodilis, Madeleine; Briottet, Xavier; Cosnefroy, Helene

1998-12-01

The bi-directional reflectance distribution function (BRDF) plays a major role to evaluate or analyze signals reflected by Earth in the solar spectrum. A BRDF measurement device that covers a large spectral and directional domain was recently developed by ONERA/DOTA. It was designed to allow both laboratory and outside measurements. Its main characteristics are a spectral domain: 0.42-0.95 micrometers ; a geometrical domain: 0-60 degrees for zenith angle, 0-180 degrees for azimuth; a maximum target size for nadir measurements: 22 cm. For a given zenith angle of the source, the BRDF device needs about seven minutes to take measurements for a viewing zenith angle varying from 0-60 degrees and relative azimuth angle varying from 0-180 degrees. The performances, imperfections and properties of each component of the measurement chain are studied. A part of the work was devoted to characterize precisely the source, and particularly the spatial variability of the irradiance at the target level, the temporal stability and the spectral profile of the lamp. Some of these imperfections are modeled and taken into account in corrections of BRDF measurements. Concerning the sensor, a calibration in wavelength was done. Measurements of bi- directional reflectance of which is well known. A software was developed to convert all the raw data acquired automatically into BRDF values. To illustrate measurements taken by this device, some results are also presented here. They are taken over sand and short grass, for different wavelengths and geometrical conditions.

DCOMP Award Lecture (Metropolis): A 3D Spectral Anelastic Hydrodynamic Code for Shearing, Stratified Flows

NASA Astrophysics Data System (ADS)

Barranco, Joseph

2006-03-01

We have developed a three-dimensional (3D) spectral hydrodynamic code to study vortex dynamics in rotating, shearing, stratified systems (eg, the atmosphere of gas giant planets, protoplanetary disks around newly forming protostars). The time-independent background state is stably stratified in the vertical direction and has a unidirectional linear shear flow aligned with one horizontal axis. Superposed on this background state is an unsteady, subsonic flow that is evolved with the Euler equations subject to the anelastic approximation to filter acoustic phenomena. A Fourier-Fourier basis in a set of quasi-Lagrangian coordinates that advect with the background shear is used for spectral expansions in the two horizontal directions. For the vertical direction, two different sets of basis functions have been implemented: (1) Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev functions on an infinite domain. Use of this latter set is equivalent to transforming the infinite domain to a finite one with a cotangent mapping, and using cosine and sine expansions in the mapped coordinate. The nonlinear advection terms are time integrated explicitly, whereas the Coriolis force, buoyancy terms, and pressure/enthalpy gradient are integrated semi- implicitly. We show that internal gravity waves can be damped by adding new terms to the Euler equations. The code exhibits excellent parallel performance with the Message Passing Interface (MPI). As a demonstration of the code, we simulate vortex dynamics in protoplanetary disks and the Kelvin-Helmholtz instability in the dusty midplanes of protoplanetary disks.

A 3D spectral anelastic hydrodynamic code for shearing, stratified flows

NASA Astrophysics Data System (ADS)

Barranco, Joseph A.; Marcus, Philip S.

2006-11-01

We have developed a three-dimensional (3D) spectral hydrodynamic code to study vortex dynamics in rotating, shearing, stratified systems (e.g., the atmosphere of gas giant planets, protoplanetary disks around newly forming protostars). The time-independent background state is stably stratified in the vertical direction and has a unidirectional linear shear flow aligned with one horizontal axis. Superposed on this background state is an unsteady, subsonic flow that is evolved with the Euler equations subject to the anelastic approximation to filter acoustic phenomena. A Fourier Fourier basis in a set of quasi-Lagrangian coordinates that advect with the background shear is used for spectral expansions in the two horizontal directions. For the vertical direction, two different sets of basis functions have been implemented: (1) Chebyshev polynomials on a truncated, finite domain, and (2) rational Chebyshev functions on an infinite domain. Use of this latter set is equivalent to transforming the infinite domain to a finite one with a cotangent mapping, and using cosine and sine expansions in the mapped coordinate. The nonlinear advection terms are time-integrated explicitly, the pressure/enthalpy terms are integrated semi-implicitly, and the Coriolis force and buoyancy terms are treated semi-analytically. We show that internal gravity waves can be damped by adding new terms to the Euler equations. The code exhibits excellent parallel performance with the message passing interface (MPI). As a demonstration of the code, we simulate the merger of two 3D vortices in the midplane of a protoplanetary disk.

Early photoreceptor outer segment loss and retinoschisis in Cohen syndrome.

PubMed

Uyhazi, Katherine E; Binenbaum, Gil; Carducci, Nicholas; Zackai, Elaine H; Aleman, Tomas S

2018-06-01

To describe early structural and functional retinal changes in a patient with Cohen syndrome. A 13-month-old Caucasian girl of Irish and Spanish ancestry was noted to have micrognathia and laryngomalacia at birth, which prompted a genetic evaluation that revealed biallelic deletions in COH1 (VPS13B) (a maternally inherited 60-kb deletion involving exons 26-32 and a paternally inherited 3.5-kb deletion within exon 17) consistent with Cohen syndrome. She underwent a complete ophthalmic examination, full-field flash electroretinography and retinal imaging with spectral domain optical coherence tomography. Central vision was central, steady, and maintained. There was bilateral myopic astigmatic refractive error. Fundus exam was notable for dark foveolar pigmentation, but no obvious abnormalities of either eye. Spectral domain optical coherence tomography cross sections through the fovea revealed a normal appearing photoreceptor outer nuclear layer but loss of the interdigitation signal between the photoreceptor outer segments and the apical retinal pigment epithelium. Retinoschisis involving the inner nuclear layer of both eyes and possible ganglion cell layer thinning were also noted. There was a detectable electroretinogram with similarly reduced amplitudes of rod- (white, 0.01 cd.s.m -2 ) and cone-mediated (3 cd.s.m -2 , 30 Hz) responses. Photoreceptor outer segment abnormalities and retinoschisis may represent the earliest structural retinal change detected by spectral domain optical coherence tomography in patients with Cohen syndrome, suggesting a complex pathophysiology with primary involvement of the photoreceptor cilium and disorganization of the structural integrity of the inner retina.

Research on aviation unsafe incidents classification with improved TF-IDF algorithm

NASA Astrophysics Data System (ADS)

Wang, Yanhua; Zhang, Zhiyuan; Huo, Weigang

2016-05-01

The text content of Aviation Safety Confidential Reports contains a large number of valuable information. Term frequency-inverse document frequency algorithm is commonly used in text analysis, but it does not take into account the sequential relationship of the words in the text and its role in semantic expression. According to the seven category labels of civil aviation unsafe incidents, aiming at solving the problems of TF-IDF algorithm, this paper improved TF-IDF algorithm based on co-occurrence network; established feature words extraction and words sequential relations for classified incidents. Aviation domain lexicon was used to improve the accuracy rate of classification. Feature words network model was designed for multi-documents unsafe incidents classification, and it was used in the experiment. Finally, the classification accuracy of improved algorithm was verified by the experiments.

Effective description of domain wall strings

NASA Astrophysics Data System (ADS)

Rodrigues, Davi R.; Abanov, Ar.; Sinova, J.; Everschor-Sitte, K.

2018-04-01

The analysis of domain wall dynamics is often simplified to one-dimensional physics. For domain walls in thin films, more realistic approaches require the description as two-dimensional objects. This includes the study of vortices and curvatures along the domain walls as well as the influence of boundary effects. Here we provide a theory in terms of soft modes that allows us to analytically study the physics of extended domain walls and their stability. By considering irregularly shaped skyrmions as closed domain walls, we analyze their plasticity and compare their dynamics with those of circular skyrmions. Our theory directly provides an analytical description of the excitation modes of magnetic skyrmions, previously accessible only through sophisticated micromagnetic numerical calculations and spectral analysis. These analytical expressions provide the scaling behavior of the different physics on parameters that experiments can test.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng,Y.; Liu, J.; Zheng, Q.

Entry of SARS coronavirus into its target cell requires large-scale structural transitions in the viral spike (S) glycoprotein in order to induce fusion of the virus and cell membranes. Here we describe the identification and crystal structures of four distinct a-helical domains derived from the highly conserved heptad-repeat (HR) regions of the S2 fusion subunit. The four domains are an antiparallel four-stranded coiled coil, a parallel trimeric coiled coil, a four-helix bundle, and a six-helix bundle that is likely the final fusogenic form of the protein. When considered together, the structural and thermodynamic features of the four domains suggest amore » possible mechanism whereby the HR regions, initially sequestered in the native S glycoprotein spike, are released and refold sequentially to promote membrane fusion. Our results provide a structural framework for understanding the control of membrane fusion and should guide efforts to intervene in the SARS coronavirus entry process.« less

Multivariable frequency domain identification via 2-norm minimization

NASA Technical Reports Server (NTRS)

Bayard, David S.

1992-01-01

The author develops a computational approach to multivariable frequency domain identification, based on 2-norm minimization. In particular, a Gauss-Newton (GN) iteration is developed to minimize the 2-norm of the error between frequency domain data and a matrix fraction transfer function estimate. To improve the global performance of the optimization algorithm, the GN iteration is initialized using the solution to a particular sequentially reweighted least squares problem, denoted as the SK iteration. The least squares problems which arise from both the SK and GN iterations are shown to involve sparse matrices with identical block structure. A sparse matrix QR factorization method is developed to exploit the special block structure, and to efficiently compute the least squares solution. A numerical example involving the identification of a multiple-input multiple-output (MIMO) plant having 286 unknown parameters is given to illustrate the effectiveness of the algorithm.

Spine Patterning Is Guided by Segmentation of the Notochord Sheath.

PubMed

Wopat, Susan; Bagwell, Jennifer; Sumigray, Kaelyn D; Dickson, Amy L; Huitema, Leonie F A; Poss, Kenneth D; Schulte-Merker, Stefan; Bagnat, Michel

2018-02-20

The spine is a segmented axial structure made of alternating vertebral bodies (centra) and intervertebral discs (IVDs) assembled around the notochord. Here, we show that, prior to centra formation, the outer epithelial cell layer of the zebrafish notochord, the sheath, segments into alternating domains corresponding to the prospective centra and IVD areas. This process occurs sequentially in an anteroposterior direction via the activation of Notch signaling in alternating segments of the sheath, which transition from cartilaginous to mineralizing domains. Subsequently, osteoblasts are recruited to the mineralized domains of the notochord sheath to form mature centra. Tissue-specific manipulation of Notch signaling in sheath cells produces notochord segmentation defects that are mirrored in the spine. Together, our findings demonstrate that notochord sheath segmentation provides a template for vertebral patterning in the zebrafish spine. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Development of a low-cost, 11 µm spectral domain optical coherence tomography surface profilometry prototype

NASA Astrophysics Data System (ADS)

Suliali, Nyasha J.; Baricholo, Peter; Neethling, Pieter H.; Rohwer, Erich G.

2017-06-01

A spectral-domain Optical Coherence Tomography (OCT) surface profilometry prototype has been developed for the purpose of surface metrology of optical elements. The prototype consists of a light source, spectral interferometer, sample fixture and software currently running on Microsoft® Windows platforms. In this system, a broadband light emitting diode beam is focused into a Michelson interferometer with a plane mirror as its sample fixture. At the interferometer output, spectral interferograms of broadband sources were measured using a Czerny-Turner mount monochromator with a 2048-element complementary metal oxide semiconductor linear array as the detector. The software performs importation and interpolation of interferometer spectra to pre-condition the data for image computation. One dimensional axial OCT images were computed by Fourier transformation of the measured spectra. A first reflection surface profilometry (FRSP) algorithm was then formulated to perform imaging of step-function-surfaced samples. The algorithm re-constructs two dimensional colour-scaled slice images by concatenation of 21 and 13 axial scans to form a 10 mm and 3.0 mm slice respectively. Measured spectral interferograms, computed interference fringe signals and depth reflectivity profiles were comparable to simulations and correlated to displacements of a single reflector linearly translated about the arm null-mismatch point. Surface profile images of a double-step-function-surfaced sample, embedded with inclination and crack detail were plotted with an axial resolution of 11 μm. The surface shape, defects and misalignment relative to the incident beam were detected to the order of a micron, confirming high resolution of the developed system as compared to electro-mechanical surface profilometry techniques.

Modeling of Graphene Planar Grating in the THz Range by the Method of Singular Integral Equations

NASA Astrophysics Data System (ADS)

Kaliberda, Mstislav E.; Lytvynenko, Leonid M.; Pogarsky, Sergey A.

2018-04-01

Diffraction of the H-polarized electromagnetic wave by the planar graphene grating in the THz range is considered. The scattering and absorption characteristics are studied. The scattered field is represented in the spectral domain via unknown spectral function. The mathematical model is based on the graphene surface impedance and the method of singular integral equations. The numerical solution is obtained by the Nystrom-type method of discrete singularities.

Terascale spectral element algorithms and implementations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fischer, P. F.; Tufo, H. M.

1999-08-17

We describe the development and implementation of an efficient spectral element code for multimillion gridpoint simulations of incompressible flows in general two- and three-dimensional domains. We review basic and recently developed algorithmic underpinnings that have resulted in good parallel and vector performance on a broad range of architectures, including the terascale computing systems now coming online at the DOE labs. Sustained performance of 219 GFLOPS has been recently achieved on 2048 nodes of the Intel ASCI-Red machine at Sandia.

Signal and noise level estimation for narrow spectral width returns observed by the Indian MST radar

NASA Astrophysics Data System (ADS)

Hooper, D. A.

1999-07-01

Use is made of five sets of multibeam observations of the lower atmosphere made by the Indian mesosphere-stratosphere-troposphere (MST) radar. Two aspects of signal processing which can lead to serious underestimates of the signal-to-noise ratio are considered. First, a comparison is made of the effects of different data weighting windows applied to the inphase and quadrature components of the radar return samples prior to Fourier transformation. The relatively high degree of spectral leakage associated with the rectangular and Hamming windows can give rise to overestimates of the noise levels by up to 28 dB for the strongest signals. Use of the Hanning window is found to be the most appropriate for these particular data. Second, a technique for removing systematic dc biases from the data in the time domain is compared with the more well-known practice of correction in the frequency domain. The latter technique, which is often used to remove the effects of ground clutter, is shown to be particularly inappropriate for the characteristically narrow spectral width signals observed by the Indian MST radar. For cases of near-zero Doppler shift it can remove up to 30 dB of signal information. The consequences of noise and signal level discrepancies for studies of refractivity structures are discussed. It is shown that neither problem has a significant effect on Doppler shift or spectral width estimates.

Impact of spectral nudging on the downscaling of tropical cyclones in regional climate simulations

NASA Astrophysics Data System (ADS)

Choi, Suk-Jin; Lee, Dong-Kyou

2016-06-01

This study investigated the simulations of three months of seasonal tropical cyclone (TC) activity over the western North Pacific using the Advanced Research WRF Model. In the control experiment (CTL), the TC frequency was considerably overestimated. Additionally, the tracks of some TCs tended to have larger radii of curvature and were shifted eastward. The large-scale environments of westerly monsoon flows and subtropical Pacific highs were unreasonably simulated. The overestimated frequency of TC formation was attributed to a strengthened westerly wind field in the southern quadrants of the TC center. In comparison with the experiment with the spectral nudging method, the strengthened wind speed was mainly modulated by large-scale flow that was greater than approximately 1000 km in the model domain. The spurious formation and undesirable tracks of TCs in the CTL were considerably improved by reproducing realistic large-scale atmospheric monsoon circulation with substantial adjustment between large-scale flow in the model domain and large-scale boundary forcing modified by the spectral nudging method. The realistic monsoon circulation took a vital role in simulating realistic TCs. It revealed that, in the downscaling from large-scale fields for regional climate simulations, scale interaction between model-generated regional features and forced large-scale fields should be considered, and spectral nudging is a desirable method in the downscaling method.

Differences in time-domain and spectral indexes of skin-surface laser-Doppler signals between controls and breast-cancer subjects.

PubMed

Hsiu, Hsin; Chen, Chao-Tsung; Hung, Shuo-Hui; Chen, Guan-Zhang; Huang, Yu-Ling

2018-04-13

There is an urgent need to improve the early diagnosis of breast cancer. The present study applied spectral and beat-to-beat analyses to laser-Doppler (LDF) data sequences measured on the skin surface on the back of the right hands, with the aim of comparing the different peripheral microcirculatory-blood-flow (MBF) perfusion condition between breast-cancer and control subjects. ECG and LDF signals were obtained simultaneously and noninvasively from 23 breast-cancer patients and 23 age-matched control subjects. Time-domain beat-to-beat indexes and their variability parameters were calculated. Spectral indexes were calculated using the Morlet wavelet transform. The beat-to-beat LDF pulse width and its variability were significantly smaller in cancer patients than in the controls. The energy contributions of endothelial-, neural-, and myogenic-related frequency bands were also significantly smaller in cancer patients. The present study has revealed significant differences in the beat-to-beat and spectral indexes of skin-surface-acquired LDF signals between control subjects and breast-cancer patients. This illustrates that LDF indexes may be useful for monitoring the changes in the MBF perfusion condition induced by breast cancer. Since the breast-cancer patients were at TNM stages 0- 2, the present findings may aid the development of indexes for detecting breast cancer.

Domain architecture conservation in orthologs

PubMed Central

2011-01-01

Background As orthologous proteins are expected to retain function more often than other homologs, they are often used for functional annotation transfer between species. However, ortholog identification methods do not take into account changes in domain architecture, which are likely to modify a protein's function. By domain architecture we refer to the sequential arrangement of domains along a protein sequence. To assess the level of domain architecture conservation among orthologs, we carried out a large-scale study of such events between human and 40 other species spanning the entire evolutionary range. We designed a score to measure domain architecture similarity and used it to analyze differences in domain architecture conservation between orthologs and paralogs relative to the conservation of primary sequence. We also statistically characterized the extents of different types of domain swapping events across pairs of orthologs and paralogs. Results The analysis shows that orthologs exhibit greater domain architecture conservation than paralogous homologs, even when differences in average sequence divergence are compensated for, for homologs that have diverged beyond a certain threshold. We interpret this as an indication of a stronger selective pressure on orthologs than paralogs to retain the domain architecture required for the proteins to perform a specific function. In general, orthologs as well as the closest paralogous homologs have very similar domain architectures, even at large evolutionary separation. The most common domain architecture changes observed in both ortholog and paralog pairs involved insertion/deletion of new domains, while domain shuffling and segment duplication/deletion were very infrequent. Conclusions On the whole, our results support the hypothesis that function conservation between orthologs demands higher domain architecture conservation than other types of homologs, relative to primary sequence conservation. This supports the notion that orthologs are functionally more similar than other types of homologs at the same evolutionary distance. PMID:21819573

Three-dimensional dominant frequency mapping using autoregressive spectral analysis of atrial electrograms of patients in persistent atrial fibrillation.

PubMed

Salinet, João L; Masca, Nicholas; Stafford, Peter J; Ng, G André; Schlindwein, Fernando S

2016-03-08

Areas with high frequency activity within the atrium are thought to be 'drivers' of the rhythm in patients with atrial fibrillation (AF) and ablation of these areas seems to be an effective therapy in eliminating DF gradient and restoring sinus rhythm. Clinical groups have applied the traditional FFT-based approach to generate the three-dimensional dominant frequency (3D DF) maps during electrophysiology (EP) procedures but literature is restricted on using alternative spectral estimation techniques that can have a better frequency resolution that FFT-based spectral estimation. Autoregressive (AR) model-based spectral estimation techniques, with emphasis on selection of appropriate sampling rate and AR model order, were implemented to generate high-density 3D DF maps of atrial electrograms (AEGs) in persistent atrial fibrillation (persAF). For each patient, 2048 simultaneous AEGs were recorded for 20.478 s-long segments in the left atrium (LA) and exported for analysis, together with their anatomical locations. After the DFs were identified using AR-based spectral estimation, they were colour coded to produce sequential 3D DF maps. These maps were systematically compared with maps found using the Fourier-based approach. 3D DF maps can be obtained using AR-based spectral estimation after AEGs downsampling (DS) and the resulting maps are very similar to those obtained using FFT-based spectral estimation (mean 90.23 %). There were no significant differences between AR techniques (p = 0.62). The processing time for AR-based approach was considerably shorter (from 5.44 to 5.05 s) when lower sampling frequencies and model order values were used. Higher levels of DS presented higher rates of DF agreement (sampling frequency of 37.5 Hz). We have demonstrated the feasibility of using AR spectral estimation methods for producing 3D DF maps and characterised their differences to the maps produced using the FFT technique, offering an alternative approach for 3D DF computation in human persAF studies.

Deep data analysis via physically constrained linear unmixing: universal framework, domain examples, and a community-wide platform.

PubMed

Kannan, R; Ievlev, A V; Laanait, N; Ziatdinov, M A; Vasudevan, R K; Jesse, S; Kalinin, S V

2018-01-01

Many spectral responses in materials science, physics, and chemistry experiments can be characterized as resulting from the superposition of a number of more basic individual spectra. In this context, unmixing is defined as the problem of determining the individual spectra, given measurements of multiple spectra that are spatially resolved across samples, as well as the determination of the corresponding abundance maps indicating the local weighting of each individual spectrum. Matrix factorization is a popular linear unmixing technique that considers that the mixture model between the individual spectra and the spatial maps is linear. Here, we present a tutorial paper targeted at domain scientists to introduce linear unmixing techniques, to facilitate greater understanding of spectroscopic imaging data. We detail a matrix factorization framework that can incorporate different domain information through various parameters of the matrix factorization method. We demonstrate many domain-specific examples to explain the expressivity of the matrix factorization framework and show how the appropriate use of domain-specific constraints such as non-negativity and sum-to-one abundance result in physically meaningful spectral decompositions that are more readily interpretable. Our aim is not only to explain the off-the-shelf available tools, but to add additional constraints when ready-made algorithms are unavailable for the task. All examples use the scalable open source implementation from https://github.com/ramkikannan/nmflibrary that can run from small laptops to supercomputers, creating a user-wide platform for rapid dissemination and adoption across scientific disciplines.

Sequential Infection in Ferrets with Antigenically Distinct Seasonal H1N1 Influenza Viruses Boosts Hemagglutinin Stalk-Specific Antibodies

PubMed Central

Kirchenbaum, Greg A.; Carter, Donald M.

2015-01-01

ABSTRACT Broadly reactive antibodies targeting the conserved hemagglutinin (HA) stalk region are elicited following sequential infection or vaccination with influenza viruses belonging to divergent subtypes and/or expressing antigenically distinct HA globular head domains. Here, we demonstrate, through the use of novel chimeric HA proteins and competitive binding assays, that sequential infection of ferrets with antigenically distinct seasonal H1N1 (sH1N1) influenza virus isolates induced an HA stalk-specific antibody response. Additionally, stalk-specific antibody titers were boosted following sequential infection with antigenically distinct sH1N1 isolates in spite of preexisting, cross-reactive, HA-specific antibody titers. Despite a decline in stalk-specific serum antibody titers, sequential sH1N1 influenza virus-infected ferrets were protected from challenge with a novel H1N1 influenza virus (A/California/07/2009), and these ferrets poorly transmitted the virus to naive contacts. Collectively, these findings indicate that HA stalk-specific antibodies are commonly elicited in ferrets following sequential infection with antigenically distinct sH1N1 influenza virus isolates lacking HA receptor-binding site cross-reactivity and can protect ferrets against a pathogenic novel H1N1 virus. IMPORTANCE The influenza virus hemagglutinin (HA) is a major target of the humoral immune response following infection and/or seasonal vaccination. While antibodies targeting the receptor-binding pocket of HA possess strong neutralization capacities, these antibodies are largely strain specific and do not confer protection against antigenic drift variant or novel HA subtype-expressing viruses. In contrast, antibodies targeting the conserved stalk region of HA exhibit broader reactivity among viruses within and among influenza virus subtypes. Here, we show that sequential infection of ferrets with antigenically distinct seasonal H1N1 influenza viruses boosts the antibody responses directed at the HA stalk region. Moreover, ferrets possessing HA stalk-specific antibody were protected against novel H1N1 virus infection and did not transmit the virus to naive contacts. PMID:26559834

Effect of contact lens on optical coherence tomography imaging of rodent retina.

PubMed

Liu, Xiaojing; Wang, Chia-Hao; Dai, Cuixia; Camesa, Adam; Zhang, Hao F; Jiao, Shuliang

2013-12-01

To evaluate the effect of powerless contact lens on improving the quality of optical coherence tomography imaging of rodent retina. A spectral-domain optical coherence tomography (SD-OCT) system was built for in vivo imaging of rodent retina. The calibrated depth resolution of the system was 3 µm in tissue. A commercial powerless contact lens for rat eye was tested in the experiments. For each rat eye, the retina was imaged in vivo sequentially first without wearing contact lens and then with wearing contact lens. The lateral resolution and signal-to-noise ratio of the OCT images with and without contact lens were compared to evaluate the improvement of image quality. The fundus images generated from the measured 3D OCT datasets with contact lens showed sharper retinal blood vessels than those without contact lens. The contrast of the retinal blood vessels was also significantly enhanced in the OCT fundus images with contact lens. As high as 10 dB improvements in SNR was observed for OCT images with contact lens compared to the images of the same retinal area without contact lens. We have demonstrated that the use of powerless contact lens on rat eye can significantly improve OCT image quality of rodent retina, which is a benefit in addition to preventing cataract formation. We believe the improvement in image quality is the result of partial compensation of the optical aberrations of the rodent eye by the contact lens.

Algorithms and Application of Sparse Matrix Assembly and Equation Solvers for Aeroacoustics

NASA Technical Reports Server (NTRS)

Watson, W. R.; Nguyen, D. T.; Reddy, C. J.; Vatsa, V. N.; Tang, W. H.

2001-01-01

An algorithm for symmetric sparse equation solutions on an unstructured grid is described. Efficient, sequential sparse algorithms for degree-of-freedom reordering, supernodes, symbolic/numerical factorization, and forward backward solution phases are reviewed. Three sparse algorithms for the generation and assembly of symmetric systems of matrix equations are presented. The accuracy and numerical performance of the sequential version of the sparse algorithms are evaluated over the frequency range of interest in a three-dimensional aeroacoustics application. Results show that the solver solutions are accurate using a discretization of 12 points per wavelength. Results also show that the first assembly algorithm is impractical for high-frequency noise calculations. The second and third assembly algorithms have nearly equal performance at low values of source frequencies, but at higher values of source frequencies the third algorithm saves CPU time and RAM. The CPU time and the RAM required by the second and third assembly algorithms are two orders of magnitude smaller than that required by the sparse equation solver. A sequential version of these sparse algorithms can, therefore, be conveniently incorporated into a substructuring for domain decomposition formulation to achieve parallel computation, where different substructures are handles by different parallel processors.

Parallel heuristics for scalable community detection

DOE PAGES

Lu, Hao; Halappanavar, Mahantesh; Kalyanaraman, Ananth

2015-08-14

Community detection has become a fundamental operation in numerous graph-theoretic applications. Despite its potential for application, there is only limited support for community detection on large-scale parallel computers, largely owing to the irregular and inherently sequential nature of the underlying heuristics. In this paper, we present parallelization heuristics for fast community detection using the Louvain method as the serial template. The Louvain method is an iterative heuristic for modularity optimization. Originally developed in 2008, the method has become increasingly popular owing to its ability to detect high modularity community partitions in a fast and memory-efficient manner. However, the method ismore » also inherently sequential, thereby limiting its scalability. Here, we observe certain key properties of this method that present challenges for its parallelization, and consequently propose heuristics that are designed to break the sequential barrier. For evaluation purposes, we implemented our heuristics using OpenMP multithreading, and tested them over real world graphs derived from multiple application domains. Compared to the serial Louvain implementation, our parallel implementation is able to produce community outputs with a higher modularity for most of the inputs tested, in comparable number or fewer iterations, while providing real speedups of up to 16x using 32 threads.« less

Introduction of sequential inactivated polio vaccine-oral polio vaccine schedule for routine infant immunization in Brazil's National Immunization Program.

PubMed

Domingues, Carla Magda Allan S; de Fátima Pereira, Sirlene; Cunha Marreiros, Ana Carolina; Menezes, Nair; Flannery, Brendan

2014-11-01

In August 2012, the Brazilian Ministry of Health introduced inactivated polio vaccine (IPV) as part of sequential polio vaccination schedule for all infants beginning their primary vaccination series. The revised childhood immunization schedule included 2 doses of IPV at 2 and 4 months of age followed by 2 doses of oral polio vaccine (OPV) at 6 and 15 months of age. One annual national polio immunization day was maintained to provide OPV to all children aged 6 to 59 months. The decision to introduce IPV was based on preventing rare cases of vaccine-associated paralytic polio, financially sustaining IPV introduction, ensuring equitable access to IPV, and preparing for future OPV cessation following global eradication. Introducing IPV during a national multivaccination campaign led to rapid uptake, despite challenges with local vaccine supply due to high wastage rates. Continuous monitoring is required to achieve high coverage with the sequential polio vaccine schedule. Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Concurrent processing simulation of the space station

NASA Technical Reports Server (NTRS)

Gluck, R.; Hale, A. L.; Sunkel, John W.

1989-01-01

The development of a new capability for the time-domain simulation of multibody dynamic systems and its application to the study of a large angle rotational maneuvers of the Space Station is described. The effort was divided into three sequential tasks, which required significant advancements of the state-of-the art to accomplish. These were: (1) the development of an explicit mathematical model via symbol manipulation of a flexible, multibody dynamic system; (2) the development of a methodology for balancing the computational load of an explicit mathematical model for concurrent processing; and (3) the implementation and successful simulation of the above on a prototype Custom Architectured Parallel Processing System (CAPPS) containing eight processors. The throughput rate achieved by the CAPPS operating at only 70 percent efficiency, was 3.9 times greater than that obtained sequentially by the IBM 3090 supercomputer simulating the same problem. More significantly, analysis of the results leads to the conclusion that the relative cost effectiveness of concurrent vs. sequential digital computation will grow substantially as the computational load is increased. This is a welcomed development in an era when very complex and cumbersome mathematical models of large space vehicles must be used as substitutes for full scale testing which has become impractical.

Statistical Time Series Models of Pilot Control with Applications to Instrument Discrimination

NASA Technical Reports Server (NTRS)

Altschul, R. E.; Nagel, P. M.; Oliver, F.

1984-01-01

A general description of the methodology used in obtaining the transfer function models and verification of model fidelity, frequency domain plots of the modeled transfer functions, numerical results obtained from an analysis of poles and zeroes obtained from z plane to s-plane conversions of the transfer functions, and the results of a study on the sequential introduction of other variables, both exogenous and endogenous into the loop are contained.

Impacts of Typhoon Megi (2010) on the South China Sea

DTIC Science & Technology

2014-06-01

investigations. To obtain realistic typhoon-strength atmospheric forcing, the EASNFS applied typhoon-resolving Weather Research and Forecasting ( WRF ) model wind...EASNFS applied typhoon-resolving Weather Research and Forecasting ( WRF ) model wind field blended with global weather forecast winds from the U.S. Navy...only 1C. Sequential SST snapshots, of which only a Figure 1. The EASNFS model domain with topography and an inset covered by WRF model. Typhoon Megi’s

Spacepower Theory: Lessons from the Masters

DTIC Science & Technology

2005-04-01

3 conduct “sequential, parallel or simultaneous operations throughout the physical and information domains of the global battlespace.”11 This...of having to destroy it physically .”35 Rather than a concentrated advance, Hart advocating using a combined effect of air and land motor power to...over physical destruction of the enemy as a way to overcome the butcherous trench warfare of WWI. He said, “If a battle can be won without suffering

Visible light spectral domain optical coherence microscopy system for ex vivo imaging

NASA Astrophysics Data System (ADS)

Lichtenegger, Antonia; Harper, Danielle J.; Augustin, Marco; Eugui, Pablo; Fialová, Stanislava; Woehrer, Adelheid; Hitzenberger, Christoph K.; Baumann, Bernhard

2017-02-01

A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm2 and 0.5 x 0.5 mm2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification, resulting in a transverse resolution of 2 μm . Specification measurements showed that a -89 dB sensitivity with a 24 dB/mm roll-off could be achieved with the system. First of all the capabilities of the system were tested by investigating millimeter paper, tape and the USAF (US Air Force) 1951 resolution test target. Finally cerebral tissues from non-pathological and Alzheimer's disease affected brains were investigated. The results showed that structures, such as white and gray matter, could be distinguished. Furthermore a first effort was made to differentiate Alzheimer's disease from healthy brain tissue.

Imaging of murine embryonic cardiovascular development using optical coherence tomography (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huang, Yongyang; Degenhardt, Karl R.; Astrof, Sophie; Zhou, Chao

2016-03-01

We have demonstrated the capability of spectral domain optical coherence tomography (SDOCT) system to image full development of mouse embryonic cardiovascular system. Monitoring morphological changes of mouse embryonic heart occurred in different embryonic stages helps identify structural or functional cardiac anomalies and understand how these anomalies lead to congenital heart diseases (CHD) present at birth. In this study, mouse embryo hearts ranging from E9.5 to E15.5 were prepared and imaged in vitro. A customized spectral domain OCT system was used for imaging, with a central wavelength of 1310nm, spectral bandwidth of ~100nm and imaging speed of 47kHz A-scans/s. Axial resolution of this system was 8.3µm in air, and transverse resolution was 6.2 µm with 5X objective. Key features of mouse embryonic cardiovascular development such as vasculature remodeling into circulatory system, separation of atria and ventricles and emergence of valves could be clearly seen in three-dimensional OCT images. Optical clearing was applied to overcome the penetration limit of OCT system. With high resolution, fast imaging speed, 3D imaging capability, OCT proves to be a promising biomedical imaging modality for developmental biology studies, rivaling histology and micro-CT.

Augmenting the spectral efficiency of enhanced PAM-DMT-based optical wireless communications.

PubMed

Islim, Mohamed Sufyan; Haas, Harald

2016-05-30

The energy efficiency of pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) decreases as the modulation order of M-PAM modulation increases. Enhanced PAM-DMT (ePAM-DMT) was proposed as a solution to the reduced energy efficiency of PAM-DMT. This was achieved by allowing multiple streams of PAM-DMT to be superimposed and successively demodulated at the receiver side. In order to maintain a distortion-free unipolar ePAM-DMT system, the multiple time-domain PAM-DMT streams are required to be aligned. However, aligning the antisymmetry in ePAM-DMT is complex and results in efficiency losses. In this paper, a novel simplified method to apply the superposition modulation on M-PAM modulated discrete multitone (DMT) is introduced. Contrary to ePAM-DMT, the signal generation of the proposed system, termed augmented spectral efficiency discrete multitone (ASE-DMT), occurs in the frequency domain. This results in an improved spectral and energy efficiency. The analytical bit error rate (BER) performance bound of the proposed system is derived and compared with Monte-Carlo simulations. The system performance is shown to offer significant electrical and optical energy savings compared with ePAM-DMT and DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM).

Shot noise limited characterization of ultraweak femtosecond pulse trains.

PubMed

Schwartz, Osip; Raz, Oren; Katz, Ori; Dudovich, Nirit; Oron, Dan

2011-01-17

Ultrafast science is inherently, due to the lack of fast enough detectors and electronics, based on nonlinear interactions. Typically, however, nonlinear measurements require significant powers and often operate in a limited spectral range. Here we overcome the difficulties of ultraweak ultrafast measurements by precision time-domain localization of spectral components. We utilize this for linear self-referenced characterization of pulse trains having ∼ 1 photon per pulse, a regime in which nonlinear techniques are impractical, at a temporal resolution of ∼ 10 fs. This technique does not only set a new scale of sensitivity in ultrashort pulse characterization, but is also applicable in any spectral range from the near-infrared to the deep UV.

Measurement of atomic Stark parameters of many Mn I and Fe I spectral lines using GMAW process

NASA Astrophysics Data System (ADS)

Zielinska, S.; Pellerin, S.; Dzierzega, K.; Valensi, F.; Musiol, K.; Briand, F.

2010-11-01

The particular character of the welding arc working in pure argon, whose emission spectrum consists of many spectral lines strongly broadened by the Stark effect, has allowed measurement, sometimes for the first time, of the Stark parameters of 15 Mn I and 10 Fe I atomic spectral lines, and determination of the dependence on temperature of normalized Stark broadening in Ne = 1023 m-3 of the 542.4 nm atomic iron line. These results show that special properties of the MIG plasma may be useful in this domain because composition of the wire-electrode may be easily adapted to the needs of an experiment.

Efficient spectral-Galerkin algorithms for direct solution for second-order differential equations using Jacobi polynomials

NASA Astrophysics Data System (ADS)

Doha, E.; Bhrawy, A.

2006-06-01

It is well known that spectral methods (tau, Galerkin, collocation) have a condition number of ( is the number of retained modes of polynomial approximations). This paper presents some efficient spectral algorithms, which have a condition number of , based on the Jacobi?Galerkin methods of second-order elliptic equations in one and two space variables. The key to the efficiency of these algorithms is to construct appropriate base functions, which lead to systems with specially structured matrices that can be efficiently inverted. The complexities of the algorithms are a small multiple of operations for a -dimensional domain with unknowns, while the convergence rates of the algorithms are exponentials with smooth solutions.

Isolated pores dissected from human two-pore channel 2 are functional

PubMed Central

Penny, Christopher J.; Rahman, Taufiq; Sula, Altin; Miles, Andrew J.; Wallace, B. A.; Patel, Sandip

2016-01-01

Multi-domain voltage-gated ion channels appear to have evolved through sequential rounds of intragenic duplication from a primordial one-domain precursor. Whereas modularity within one-domain symmetrical channels is established, little is known about the roles of individual regions within more complex asymmetrical channels where the domains have undergone substantial divergence. Here we isolated and characterised both of the divergent pore regions from human TPC2, a two-domain channel that holds a key intermediate position in the evolution of voltage-gated ion channels. In HeLa cells, each pore localised to the ER and caused Ca2+ depletion, whereas an ER-targeted pore mutated at a residue that inactivates full-length TPC2 did not. Additionally, one of the pores expressed at high levels in E. coli. When purified, it formed a stable, folded tetramer. Liposomes reconstituted with the pore supported Ca2+ and Na+ uptake that was inhibited by known blockers of full-length channels. Computational modelling of the pore corroborated cationic permeability and drug interaction. Therefore, despite divergence, both pores are constitutively active in the absence of their partners and retain several properties of the wild-type pore. Such symmetrical ‘pore-only’ proteins derived from divergent channel domains may therefore provide tractable tools for probing the functional architecture of complex ion channels. PMID:27941820

Isolated pores dissected from human two-pore channel 2 are functional.

PubMed

Penny, Christopher J; Rahman, Taufiq; Sula, Altin; Miles, Andrew J; Wallace, B A; Patel, Sandip

2016-12-12

Multi-domain voltage-gated ion channels appear to have evolved through sequential rounds of intragenic duplication from a primordial one-domain precursor. Whereas modularity within one-domain symmetrical channels is established, little is known about the roles of individual regions within more complex asymmetrical channels where the domains have undergone substantial divergence. Here we isolated and characterised both of the divergent pore regions from human TPC2, a two-domain channel that holds a key intermediate position in the evolution of voltage-gated ion channels. In HeLa cells, each pore localised to the ER and caused Ca 2+ depletion, whereas an ER-targeted pore mutated at a residue that inactivates full-length TPC2 did not. Additionally, one of the pores expressed at high levels in E. coli. When purified, it formed a stable, folded tetramer. Liposomes reconstituted with the pore supported Ca 2+ and Na + uptake that was inhibited by known blockers of full-length channels. Computational modelling of the pore corroborated cationic permeability and drug interaction. Therefore, despite divergence, both pores are constitutively active in the absence of their partners and retain several properties of the wild-type pore. Such symmetrical 'pore-only' proteins derived from divergent channel domains may therefore provide tractable tools for probing the functional architecture of complex ion channels.

High-speed spectral domain polarization-sensitive OCT using a single InGaAs line-scan camera and an optical switch

NASA Astrophysics Data System (ADS)

Lee, Sang-Won; Jeong, Hyun-Woo; Kim, Beop-Min

2010-02-01

We demonstrated high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PSOCT) using a single InGaAs line-scan camera and an optical switch at 1.3-μm region. The polarization-sensitive low coherence interferometer in the system was based on the original free-space PS-OCT system published by Hee et al. The horizontal and vertical polarization light rays split by polarization beam splitter were delivered and detected via an optical switch to a single spectrometer by turns instead of dual spectrometers. The SD-PSOCT system had an axial resolution of 8.2 μm, a sensitivity of 101.5 dB, and an acquisition speed of 23,496 Alines/s. We obtained the intensity, phase retardation, and fast axis orientation images of a biological tissue. In addition, we calculated the averaged axial profiles of the phase retardation in human skin.

Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma.

PubMed

Guerra, Ricardo Luz Leitão; Marback, Eduardo Ferrari; Silva, Igor Sandes Pessoa da; Maia Junior, Otacílio de Oliveira; Marback, Roberto Lorens

2014-01-01

The authors report fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (OCT) findings of two consecutive patients who presented with optic disk melanocytoma (ODM). A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

Two-harmonic complex spectral-domain optical coherence tomography using achromatic sinusoidal phase modulation

NASA Astrophysics Data System (ADS)

Lu, Sheng-Hua; Huang, Siang-Ru; Chou, Che-Chung

2018-03-01

We resolve the complex conjugate ambiguity in spectral-domain optical coherence tomography (SD-OCT) by using achromatic two-harmonic method. Unlike previous researches, the optical phase of the fiber interferometer is modulated by an achromatic phase shifter based on an optical delay line. The achromatic phase modulation leads to a wavelength-independent scaling coefficient for the two harmonics. Dividing the mean absolute value of the first harmonic by that of the second harmonic in a B-scan interferogram directly gives the scaling coefficient. It greatly simplifies the determination of the magnitude ratio between the two harmonics without the need of third harmonic and cumbersome iterative calculations. The inverse fast Fourier transform of the complex-valued interferogram constructed with the scaling coefficient, first and second harmonics yields a full-range OCT image. Experimental results confirm the effectiveness of the proposed achromatic two-harmonic technique for suppressing the mirror artifacts in SD-OCT images.

Fourier domain low coherence interferometry for detection of early colorectal cancer development in the AOM rat model

NASA Astrophysics Data System (ADS)

Robles, Francisco E.; Zhu, Yizheng; Lee, Jin; Sharma, Sheela; Wax, Adam

2011-03-01

We present Fourier domain low coherence interferometry (fLCI) applied to the detection of preneoplastic changes in the colon using the ex-vivo azoxymethane (AOM) rat carcinogenesis model. fLCI measures depth resolved spectral oscillations, also known as local oscillations, resulting from coherent fields induced by the scattering of cell nuclei. The depth resolution of fLCI permits nuclear morphology measurements within thick tissues, making the technique sensitive to the earliest stages of precancerous development. To achieve depth resolved spectroscopic analysis, we use the dual window method, which obtains simultaneously high spectral and depth resolution and yields access to the local oscillations. The results show highly statistically significant differences between the AOM-treated and control group samples. Further, the results suggest that fLCI may be used to detect the field effect of carcinogenesis, in addition to identifying specific areas where more advanced neoplastic development has occurred.

Performance analysis of FET microwave devices by use of extended spectral-element time-domain method

NASA Astrophysics Data System (ADS)

Sheng, Yijun; Xu, Kan; Wang, Daoxiang; Chen, Rushan

2013-05-01

The extended spectral-element time-domain (SETD) method is employed to analyse field effect transistor (FET) microwave devices. In order to impose the contribution of the FET microwave devices into the electromagnetic simulation, the SETD method is extended by introducing a lumped current term into the vector Helmholtz equation. The change of currents on each lumped component can be expressed by the change of voltage via corresponding models of equivalent circuit. The electric fields around the lumped component must be influenced by the change of voltage on each lumped component, and vice versa. So a global coupling about the EM-circuit can be built directly. The fully explicit solving scheme is maintained in this extended SETD method and the CPU time can be saved spontaneously. Three practical FET microwave devices are analysed in this article. The numerical results demonstrate the ability and accuracy of this method.

3D THz hyperspectrum applied in security check-in

NASA Astrophysics Data System (ADS)

Damian, V.; Logofǎtu, P. C.; Vasile, T.

2016-12-01

We developed a measuring technology using a TDS-THz system to construct hyperspectral images of some objects, including hazardous materials. "T-rays" (the THz spectral domain of the light) have a growing importance in security and imagistic domain. Due to their property of penetrating through dielectric objects, and using non-ionizing radiations, the THz systems have become a standard for "hot-places" (airports, train stations etc.). The hyperspectral images are 3D images having 2D spatial dimension and one spectral dimension. In this way, we obtain simultaneously information about the form of the object and its molecular composition. For discriminating between substances, we must first build a database of spectra for hazardous and dangerous substances. We experiment our system on some items (among them a firecracker, a cigarette and a metal collar) and we tried to discriminate between them using the database of spectra.

High-speed spectral domain polarization- sensitive optical coherence tomography using a single camera and an optical switch at 1.3 microm.

PubMed

Lee, Sang-Won; Jeong, Hyun-Woo; Kim, Beop-Min

2010-01-01

We propose high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) using a single camera and a 1x2 optical switch at the 1.3-microm region. The PS-low coherence interferometer used in the system is constructed using free-space optics. The reflected horizontal and vertical polarization light rays are delivered via an optical switch to a single spectrometer by turns. Therefore, our system costs less to build than those that use dual spectrometers, and the processes of timing and triggering are simpler from the viewpoints of both hardware and software. Our SD-PS-OCT has a sensitivity of 101.5 dB, an axial resolution of 8.2 microm, and an acquisition speed of 23,496 A-scans per second. We obtain the intensity, phase retardation, and fast axis orientation images of a rat tail tendon ex vivo.

Three-dimensional spectral domain optical coherence tomography in X linked foveal retinoschisis

PubMed Central

Saxena, Sandeep; Manisha; Meyer, Carsten H

2013-01-01

Spectral domain optical coherence tomography (SD-OCT) was performed in two cases of bilateral X linked foveal retinoschisis of different age groups. On fundus examination spoke wheel and honeycomb pattern of cysts were observed along with retinal nerve fibre layer (RNFL) defects. On SD-OCT, schisis was observed in the outer plexiform layer. External limiting membrane disruption was observed in the subfoveal area, along with disruption of outer nuclear layer (ONL) and inner–outer segment junction. Elevation of ONL due to tractional pull of central palisade was a novel observation. Retinoschisis extended beyond the optic disc up to the nasal region. Extracted RNFL tomogram presented an unprecedented visualisation of schisis along 360° of the optic disc. Tractional elevation in the foveal area and schisis involving nasal region, not observed upon clinical examination, was highlighted on SD-OCT. This investigative modality is an important adjunct in the assessment of foveal retinoschisis. PMID:23563673

ARCH: Adaptive recurrent-convolutional hybrid networks for long-term action recognition

PubMed Central

Xin, Miao; Zhang, Hong; Wang, Helong; Sun, Mingui; Yuan, Ding

2017-01-01

Recognition of human actions from digital video is a challenging task due to complex interfering factors in uncontrolled realistic environments. In this paper, we propose a learning framework using static, dynamic and sequential mixed features to solve three fundamental problems: spatial domain variation, temporal domain polytrope, and intra- and inter-class diversities. Utilizing a cognitive-based data reduction method and a hybrid “network upon networks” architecture, we extract human action representations which are robust against spatial and temporal interferences and adaptive to variations in both action speed and duration. We evaluated our method on the UCF101 and other three challenging datasets. Our results demonstrated a superior performance of the proposed algorithm in human action recognition. PMID:29290647

Three is much more than two in coarsening dynamics of cyclic competitions

NASA Astrophysics Data System (ADS)

Mitarai, Namiko; Gunnarson, Ivar; Pedersen, Buster Niels; Rosiek, Christian Anker; Sneppen, Kim

2016-04-01

The classical game of rock-paper-scissors has inspired experiments and spatial model systems that address the robustness of biological diversity. In particular, the game nicely illustrates that cyclic interactions allow multiple strategies to coexist for long-time intervals. When formulated in terms of a one-dimensional cellular automata, the spatial distribution of strategies exhibits coarsening with algebraically growing domain size over time, while the two-dimensional version allows domains to break and thereby opens the possibility for long-time coexistence. We consider a quasi-one-dimensional implementation of the cyclic competition, and study the long-term dynamics as a function of rare invasions between parallel linear ecosystems. We find that increasing the complexity from two to three parallel subsystems allows a transition from complete coarsening to an active steady state where the domain size stays finite. We further find that this transition happens irrespective of whether the update is done in parallel for all sites simultaneously or done randomly in sequential order. In both cases, the active state is characterized by localized bursts of dislocations, followed by longer periods of coarsening. In the case of the parallel dynamics, we find that there is another phase transition between the active steady state and the coarsening state within the three-line system when the invasion rate between the subsystems is varied. We identify the critical parameter for this transition and show that the density of active boundaries has critical exponents that are consistent with the directed percolation universality class. On the other hand, numerical simulations with the random sequential dynamics suggest that the system may exhibit an active steady state as long as the invasion rate is finite.

Ca2+ binding and conformational changes in a calmodulin domain.

PubMed

Evenäs, J; Malmendal, A; Thulin, E; Carlström, G; Forsén, S

1998-09-29

Calcium activation of the C-terminal domain of calmodulin was studied using 1H and 15N NMR spectroscopy. The important role played by the conserved bidentate glutamate Ca2+ ligand in the binding loops is emphasized by the striking effects resulting from a mutation of this glutamic acid to a glutamine, i.e. E104Q in loop III and E140Q in loop IV. The study involves determination of Ca2+ binding constants, assignments, and structural characterizations of the apo, (Ca2+)1, and (Ca2+)2 states of the E104Q mutant and comparisons to the wild-type protein and the E140Q mutant [Evenäs et al. (1997) Biochemistry 36, 3448-3457]. NMR titration data show sequential Ca2+ binding in the E104Q mutant. The first Ca2+ binds to loop IV and the second to loop III, which is the order reverse to that observed for the E140Q mutant. In both mutants, the major structural changes occur upon Ca2+ binding to loop IV, which implies a different response to Ca2+ binding in the N- and C-terminal EF-hands. Spectral characteristics show that the (Ca2+)1 and (Ca2+)2 states of the E104Q mutant undergo global exchange on a 10-100 micros time scale between conformations seemingly similar to the closed and open structures of this domain in wild-type calmodulin, paralleling earlier observations for the (Ca2+)2 state of the E140Q mutant, indicating that both glutamic acid residues, E104 and E140, are required for stabilization of the open conformation in the (Ca2+)2 state. To verify that the NOE constraints cannot be fulfilled in a single structure, solution structures of the (Ca2+)2 state of the E104Q mutant are calculated. Within the ensemble of structures the precision is good. However, the clearly dynamic nature of the state, a large number of violated distance restraints, ill-defined secondary structural elements, and comparisons to the structures of calmodulin indicate that the ensemble does not provide a good picture of the (Ca2+)2 state of the E104Q mutant but rather represents the distance-averaged structure of at least two distinct different conformations.

Designed microstructure based on color filter and metallic nanoslit for multiband spectral compatible control

NASA Astrophysics Data System (ADS)

Zhan, Zhigang; Han, Yuge

2018-01-01

Controlling the spectral characteristics by regulating the geometry of microstructure has become an effective method to meet the requirements of various applications. To mediate the spectral characteristics, metallic subwavelength slits with different structures and color filters consisting of diverse materials were discussed, and then a designed microstructure composed of color filter and metallic slits, which were surrounded by grooves, was put forward for a compatible effect of controlling the spectral characteristics. Afterward, the spectral characteristics of the proposed structure were simulated by finite-difference time-domain method in the wavelength range of 300 to 10,000 nm. Additionally, the effects of geometric parameters on the spectral characteristics were studied. The results show that the presented microstructure can reflect a monochromatic color at the wavelength of 600 nm and its reflectance is ˜40%. The average absorptance near the wavelength of 1060 nm is more than 95%, and the average reflectance in the infrared band exceeds 80%. In conclusion, the compatible spectrum control in three bands (i.e., visible, near-infrared, and mid-infrared) was realized.

Supplementary motor area as key structure for domain-general sequence processing: A unified account.

PubMed

Cona, Giorgia; Semenza, Carlo

2017-01-01

The Supplementary Motor Area (SMA) is considered as an anatomically and functionally heterogeneous region and is implicated in several functions. We propose that SMA plays a crucial role in domain-general sequence processes, contributing to the integration of sequential elements into higher-order representations regardless of the nature of such elements (e.g., motor, temporal, spatial, numerical, linguistic, etc.). This review emphasizes the domain-general involvement of the SMA, as this region has been found to support sequence operations in a variety of cognitive domains that, albeit different, share an inherent sequence processing. These include action, time and spatial processing, numerical cognition, music and language processing, and working memory. In this light, we reviewed and synthesized recent neuroimaging, stimulation and electrophysiological studies in order to compare and reconcile the distinct sources of data by proposing a unifying account for the role of the SMA. We also discussed the differential contribution of the pre-SMA and SMA-proper in sequence operations, and possible neural mechanisms by which such operations are executed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spectral Estimation Model Construction of Heavy Metals in Mining Reclamation Areas

PubMed Central

Dong, Jihong; Dai, Wenting; Xu, Jiren; Li, Songnian

2016-01-01

The study reported here examined, as the research subject, surface soils in the Liuxin mining area of Xuzhou, and explored the heavy metal content and spectral data by establishing quantitative models with Multivariable Linear Regression (MLR), Generalized Regression Neural Network (GRNN) and Sequential Minimal Optimization for Support Vector Machine (SMO-SVM) methods. The study results are as follows: (1) the estimations of the spectral inversion models established based on MLR, GRNN and SMO-SVM are satisfactory, and the MLR model provides the worst estimation, with R2 of more than 0.46. This result suggests that the stress sensitive bands of heavy metal pollution contain enough effective spectral information; (2) the GRNN model can simulate the data from small samples more effectively than the MLR model, and the R2 between the contents of the five heavy metals estimated by the GRNN model and the measured values are approximately 0.7; (3) the stability and accuracy of the spectral estimation using the SMO-SVM model are obviously better than that of the GRNN and MLR models. Among all five types of heavy metals, the estimation for cadmium (Cd) is the best when using the SMO-SVM model, and its R2 value reaches 0.8628; (4) using the optimal model to invert the Cd content in wheat that are planted on mine reclamation soil, the R2 and RMSE between the measured and the estimated values are 0.6683 and 0.0489, respectively. This result suggests that the method using the SMO-SVM model to estimate the contents of heavy metals in wheat samples is feasible. PMID:27367708

Spectral Estimation Model Construction of Heavy Metals in Mining Reclamation Areas.

PubMed

Dong, Jihong; Dai, Wenting; Xu, Jiren; Li, Songnian

2016-06-28

The study reported here examined, as the research subject, surface soils in the Liuxin mining area of Xuzhou, and explored the heavy metal content and spectral data by establishing quantitative models with Multivariable Linear Regression (MLR), Generalized Regression Neural Network (GRNN) and Sequential Minimal Optimization for Support Vector Machine (SMO-SVM) methods. The study results are as follows: (1) the estimations of the spectral inversion models established based on MLR, GRNN and SMO-SVM are satisfactory, and the MLR model provides the worst estimation, with R² of more than 0.46. This result suggests that the stress sensitive bands of heavy metal pollution contain enough effective spectral information; (2) the GRNN model can simulate the data from small samples more effectively than the MLR model, and the R² between the contents of the five heavy metals estimated by the GRNN model and the measured values are approximately 0.7; (3) the stability and accuracy of the spectral estimation using the SMO-SVM model are obviously better than that of the GRNN and MLR models. Among all five types of heavy metals, the estimation for cadmium (Cd) is the best when using the SMO-SVM model, and its R² value reaches 0.8628; (4) using the optimal model to invert the Cd content in wheat that are planted on mine reclamation soil, the R² and RMSE between the measured and the estimated values are 0.6683 and 0.0489, respectively. This result suggests that the method using the SMO-SVM model to estimate the contents of heavy metals in wheat samples is feasible.

Novel full‐spectral flow cytometry with multiple spectrally‐adjacent fluorescent proteins and fluorochromes and visualization of in vivo cellular movement

PubMed Central

Futamura, Koji; Sekino, Masashi; Hata, Akihiro; Ikebuchi, Ryoyo; Nakanishi, Yasutaka; Egawa, Gyohei; Kabashima, Kenji; Watanabe, Takeshi; Furuki, Motohiro

2015-01-01

Abstract Flow cytometric analysis with multicolor fluoroprobes is an essential method for detecting biological signatures of cells. Here, we present a new full‐spectral flow cytometer (spectral‐FCM). Unlike conventional flow cytometer, this spectral‐FCM acquires the emitted fluorescence for all probes across the full‐spectrum from each cell with 32 channels sequential PMT unit after dispersion with prism, and extracts the signals of each fluoroprobe based on the spectral shape of each fluoroprobe using unique algorithm in high speed, high sensitive, accurate, automatic and real‐time. The spectral‐FCM detects the continuous changes in emission spectra from green to red of the photoconvertible protein, KikGR with high‐spectral resolution and separates spectrally‐adjacent fluoroprobes, such as FITC (Emission peak (Em) 519 nm) and EGFP (Em 507 nm). Moreover, the spectral‐FCM can measure and subtract autofluorescence of each cell providing increased signal‐to‐noise ratios and improved resolution of dim samples, which leads to a transformative technology for investigation of single cell state and function. These advances make it possible to perform 11‐color fluorescence analysis to visualize movement of multilinage immune cells by using KikGR‐expressing mice. Thus, the novel spectral flow cytometry improves the combinational use of spectrally‐adjacent various FPs and multicolor fluorochromes in metabolically active cell for the investigation of not only the immune system but also other research and clinical fields of use. © 2015 The Authors. Cytometry Part A Published by Wiley Periodicals, Inc. on behalf of ISAC PMID:26217952

A comparison of serial order short-term memory effects across verbal and musical domains.

PubMed

Gorin, Simon; Mengal, Pierre; Majerus, Steve

2018-04-01

Recent studies suggest that the mechanisms involved in the short-term retention of serial order information may be shared across short-term memory (STM) domains such as verbal and visuospatial STM. Given the intrinsic sequential organization of musical material, the study of STM for musical information may be particularly informative about serial order retention processes and their domain-generality. The present experiment examined serial order STM for verbal and musical sequences in participants with no advanced musical expertise and experienced musicians. Serial order STM for verbal information was assessed via a serial order reconstruction task for digit sequences. In the musical domain, serial order STM was assessed using a novel melodic sequence reconstruction task maximizing the retention of tone order information. We observed that performance for the verbal and musical tasks was characterized by sequence length as well as primacy and recency effects. Serial order errors in both tasks were characterized by similar transposition gradients and ratios of fill-in:infill errors. These effects were observed for both participant groups, although the transposition gradients and ratios of fill-in:infill errors showed additional specificities for musician participants in the musical task. The data support domain-general serial order STM effects but also suggest the existence of additional domain-specific effects. Implications for models of serial order STM in verbal and musical domains are discussed.

Broadband polarizing beam splitter based on the form birefringence of a subwavelength grating in the quasi-static domain.

PubMed

Yi, Deer; Yan, Yingbai; Liu, Haitao; Lu, Si; Jin, Guofan

2004-04-01

We propose a novel broadband polarizing beam splitter with a compact sandwich structure that has a subwavelength grating in the quasi-static domain as the filling. The design is based on effective-medium theory an anisotropic thin-film theory, and the performance is investigated with rigorous coupled-wave theory. The design results show that the structure can provide a high polarization extinction ratio in a broad spectral range.

Using Sentence-Level Classifiers for Cross-Domain Sentiment Analysis

DTIC Science & Technology

2014-09-01

National Defence, 2014 © Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2014 DRDC-RDDC...domain sentiment classification via spectral feature alignment. In Proceedings of the 19th international conference on World Wide Web, WWW ’10...Dennis, S. 5. DATE OF PUBLICATION (Month and year of publication of document.) September 2014 6a. NO. OF PAGES (Total containing information

Thalamic and parietal brain morphology predicts auditory category learning.

PubMed

Scharinger, Mathias; Henry, Molly J; Erb, Julia; Meyer, Lars; Obleser, Jonas

2014-01-01

Auditory categorization is a vital skill involving the attribution of meaning to acoustic events, engaging domain-specific (i.e., auditory) as well as domain-general (e.g., executive) brain networks. A listener's ability to categorize novel acoustic stimuli should therefore depend on both, with the domain-general network being particularly relevant for adaptively changing listening strategies and directing attention to relevant acoustic cues. Here we assessed adaptive listening behavior, using complex acoustic stimuli with an initially salient (but later degraded) spectral cue and a secondary, duration cue that remained nondegraded. We employed voxel-based morphometry (VBM) to identify cortical and subcortical brain structures whose individual neuroanatomy predicted task performance and the ability to optimally switch to making use of temporal cues after spectral degradation. Behavioral listening strategies were assessed by logistic regression and revealed mainly strategy switches in the expected direction, with considerable individual differences. Gray-matter probability in the left inferior parietal lobule (BA 40) and left precentral gyrus was predictive of "optimal" strategy switch, while gray-matter probability in thalamic areas, comprising the medial geniculate body, co-varied with overall performance. Taken together, our findings suggest that successful auditory categorization relies on domain-specific neural circuits in the ascending auditory pathway, while adaptive listening behavior depends more on brain structure in parietal cortex, enabling the (re)direction of attention to salient stimulus properties. © 2013 Published by Elsevier Ltd.

Compressed sensing and the reconstruction of ultrafast 2D NMR data: Principles and biomolecular applications.

PubMed

Shrot, Yoav; Frydman, Lucio

2011-04-01

A topic of active investigation in 2D NMR relates to the minimum number of scans required for acquiring this kind of spectra, particularly when these are dictated by sampling rather than by sensitivity considerations. Reductions in this minimum number of scans have been achieved by departing from the regular sampling used to monitor the indirect domain, and relying instead on non-uniform sampling and iterative reconstruction algorithms. Alternatively, so-called "ultrafast" methods can compress the minimum number of scans involved in 2D NMR all the way to a minimum number of one, by spatially encoding the indirect domain information and subsequently recovering it via oscillating field gradients. Given ultrafast NMR's simultaneous recording of the indirect- and direct-domain data, this experiment couples the spectral constraints of these orthogonal domains - often calling for the use of strong acquisition gradients and large filter widths to fulfill the desired bandwidth and resolution demands along all spectral dimensions. This study discusses a way to alleviate these demands, and thereby enhance the method's performance and applicability, by combining spatial encoding with iterative reconstruction approaches. Examples of these new principles are given based on the compressed-sensed reconstruction of biomolecular 2D HSQC ultrafast NMR data, an approach that we show enables a decrease of the gradient strengths demanded in this type of experiments by up to 80%. Copyright © 2011 Elsevier Inc. All rights reserved.

Novel methodologies for spectral classification of exon and intron sequences

NASA Astrophysics Data System (ADS)

Kwan, Hon Keung; Kwan, Benjamin Y. M.; Kwan, Jennifer Y. Y.

2012-12-01

Digital processing of a nucleotide sequence requires it to be mapped to a numerical sequence in which the choice of nucleotide to numeric mapping affects how well its biological properties can be preserved and reflected from nucleotide domain to numerical domain. Digital spectral analysis of nucleotide sequences unfolds a period-3 power spectral value which is more prominent in an exon sequence as compared to that of an intron sequence. The success of a period-3 based exon and intron classification depends on the choice of a threshold value. The main purposes of this article are to introduce novel codes for 1-sequence numerical representations for spectral analysis and compare them to existing codes to determine appropriate representation, and to introduce novel thresholding methods for more accurate period-3 based exon and intron classification of an unknown sequence. The main findings of this study are summarized as follows: Among sixteen 1-sequence numerical representations, the K-Quaternary Code I offers an attractive performance. A windowed 1-sequence numerical representation (with window length of 9, 15, and 24 bases) offers a possible speed gain over non-windowed 4-sequence Voss representation which increases as sequence length increases. A winner threshold value (chosen from the best among two defined threshold values and one other threshold value) offers a top precision for classifying an unknown sequence of specified fixed lengths. An interpolated winner threshold value applicable to an unknown and arbitrary length sequence can be estimated from the winner threshold values of fixed length sequences with a comparable performance. In general, precision increases as sequence length increases. The study contributes an effective spectral analysis of nucleotide sequences to better reveal embedded properties, and has potential applications in improved genome annotation.

Statistical learning of music- and language-like sequences and tolerance for spectral shifts.

PubMed

Daikoku, Tatsuya; Yatomi, Yutaka; Yumoto, Masato

2015-02-01

In our previous study (Daikoku, Yatomi, & Yumoto, 2014), we demonstrated that the N1m response could be a marker for the statistical learning process of pitch sequence, in which each tone was ordered by a Markov stochastic model. The aim of the present study was to investigate how the statistical learning of music- and language-like auditory sequences is reflected in the N1m responses based on the assumption that both language and music share domain generality. By using vowel sounds generated by a formant synthesizer, we devised music- and language-like auditory sequences in which higher-ordered transitional rules were embedded according to a Markov stochastic model by controlling fundamental (F0) and/or formant frequencies (F1-F2). In each sequence, F0 and/or F1-F2 were spectrally shifted in the last one-third of the tone sequence. Neuromagnetic responses to the tone sequences were recorded from 14 right-handed normal volunteers. In the music- and language-like sequences with pitch change, the N1m responses to the tones that appeared with higher transitional probability were significantly decreased compared with the responses to the tones that appeared with lower transitional probability within the first two-thirds of each sequence. Moreover, the amplitude difference was even retained within the last one-third of the sequence after the spectral shifts. However, in the language-like sequence without pitch change, no significant difference could be detected. The pitch change may facilitate the statistical learning in language and music. Statistically acquired knowledge may be appropriated to process altered auditory sequences with spectral shifts. The relative processing of spectral sequences may be a domain-general auditory mechanism that is innate to humans. Copyright © 2014 Elsevier Inc. All rights reserved.

The Anomalous Influence of Spectral Resolution on Pulsed THz Time Domain Spectroscopy under Real Conditions

PubMed Central

Trofimov, Vyacheslav A.; Varentsova, Svetlana A.

2017-01-01

We have studied the spectral resolution influence on the accuracy of the substance detection and identification at using a broadband THz pulse measured under real conditions (at a distance of more than 3 m from a THz emitter in ambient air with a relative humidity of about 50%). We show that increasing spectral resolution leads to manifestation of small-scale perturbations (random fluctuations) in the signal spectrum caused by the influence of the environment or the sample structure. Decreasing the spectral resolution allows us to exclude from consideration this small-scale modulation of the signal as well as to detect the water vapor absorption frequencies. This fact is important in practice because it allows us to increase the signal processing rate. In order to increase the detection reliability, it is advisable to decrease the spectral resolution up to values of not more than 40% of the corresponding spectral line bandwidth. The method of spectral dynamics analysis together with the integral correlation criteria is used for the substance detection and identification. Neutral substances such as chocolate and cookies are used as the samples in the physical experiment. PMID:29231895

Hyperspectral and multispectral data fusion based on linear-quadratic nonnegative matrix factorization

NASA Astrophysics Data System (ADS)

Benhalouche, Fatima Zohra; Karoui, Moussa Sofiane; Deville, Yannick; Ouamri, Abdelaziz

2017-04-01

This paper proposes three multisharpening approaches to enhance the spatial resolution of urban hyperspectral remote sensing images. These approaches, related to linear-quadratic spectral unmixing techniques, use a linear-quadratic nonnegative matrix factorization (NMF) multiplicative algorithm. These methods begin by unmixing the observable high-spectral/low-spatial resolution hyperspectral and high-spatial/low-spectral resolution multispectral images. The obtained high-spectral/high-spatial resolution features are then recombined, according to the linear-quadratic mixing model, to obtain an unobservable multisharpened high-spectral/high-spatial resolution hyperspectral image. In the first designed approach, hyperspectral and multispectral variables are independently optimized, once they have been coherently initialized. These variables are alternately updated in the second designed approach. In the third approach, the considered hyperspectral and multispectral variables are jointly updated. Experiments, using synthetic and real data, are conducted to assess the efficiency, in spatial and spectral domains, of the designed approaches and of linear NMF-based approaches from the literature. Experimental results show that the designed methods globally yield very satisfactory spectral and spatial fidelities for the multisharpened hyperspectral data. They also prove that these methods significantly outperform the used literature approaches.

Towards spectral geometric methods for Euclidean quantum gravity

NASA Astrophysics Data System (ADS)

Panine, Mikhail; Kempf, Achim

2016-04-01

The unification of general relativity with quantum theory will also require a coming together of the two quite different mathematical languages of general relativity and quantum theory, i.e., of differential geometry and functional analysis, respectively. Of particular interest in this regard is the field of spectral geometry, which studies to which extent the shape of a Riemannian manifold is describable in terms of the spectra of differential operators defined on the manifold. Spectral geometry is hard because it is highly nonlinear, but linearized spectral geometry, i.e., the task to determine small shape changes from small spectral changes, is much more tractable and may be iterated to approximate the full problem. Here, we generalize this approach, allowing, in particular, nonequal finite numbers of shape and spectral degrees of freedom. This allows us to study how well the shape degrees of freedom are encoded in the eigenvalues. We apply this strategy numerically to a class of planar domains and find that the reconstruction of small shape changes from small spectral changes is possible if enough eigenvalues are used. While isospectral nonisometric shapes are known to exist, we find evidence that generically shaped isospectral nonisometric shapes, if existing, are exceedingly rare.

Possible role for fundus autofluorescence as a predictive factor for visual acuity recovery after epiretinal membrane surgery.

PubMed

Brito, Pedro N; Gomes, Nuno L; Vieira, Marco P; Faria, Pedro A; Fernandes, Augusto V; Rocha-Sousa, Amândio; Falcão-Reis, Fernando

2014-02-01

To study the potential association between fundus autofluorescence, spectral-domain optical coherence tomography, and visual acuity in patients undergoing surgery because of epiretinal membranes. Prospective, interventional case series including 26 patients submitted to vitrectomy because of symptomatic epiretinal membranes. Preoperative evaluation consisted of a complete ophthalmologic examination, autofluorescence, and spectral-domain optical coherence tomography. Studied variables included foveal autofluorescence (fov.AF), photoreceptor inner segment/outer segment (IS/OS) junction line integrity, external limiting membrane integrity, central foveal thickness, and foveal morphology. All examinations were repeated at the first, third, and sixth postoperative months. The main outcome measures were logarithm of minimal angle resolution visual acuity, fov.AF integrity, and IS/OS integrity. All cases showing a continuous IS/OS line had an intact fov.AF, whereas patients with IS/OS disruption could have either an increased area of foveal hypoautofluorescence or an intact fov.AF, with the latter being associated with IS/OS integrity recovery in follow-up spectral-domain optical coherence tomography imaging. The only preoperative variables presenting a significant correlation with final visual acuity were baseline visual acuity (P = 0.047) and fov.AF grade (P = 0.023). Recovery of IS/OS line integrity after surgery, in patients with preoperative IS/OS disruption and normal fov.AF, can be explained by the presence of a functional retinal pigment epithelium-photoreceptor complex, supporting normal photoreceptor activity. Autofluorescence imaging provides a functional component to the study of epiretinal membranes, complementing the structural information obtained with optical coherence tomography.

Diagnostic Capability of Spectral Domain Optical Coherence Tomography for Glaucoma

PubMed Central

Wu, Huijuan; de Boer, Johannes F.; Chen, Teresa C.

2012-01-01

Purpose To determine the diagnostic capability of spectral domain optical coherence tomography (OCT) in glaucoma patients with visual field (VF) defects. Design Prospective, cross-sectional study. Methods Setting Participants were recruited from a university hospital clinic. Study Population One eye of 85 normal subjects and 61 glaucoma patients [with average VF mean deviation (MD) of -9.61 ± 8.76 dB] were randomly selected for the study. A subgroup of the glaucoma patients with early VF defects was calculated separately. Observation Procedures Spectralis OCT circular scans were performed to obtain peripapillary retinal nerve fiber layer (RNFL) thicknesses. The RNFL diagnostic parameters based on the normative database were used alone or in combination for identifying glaucomatous RNFL thinning. Main Outcome Measures To evaluate diagnostic performance, calculations included areas under the receiver operating characteristic curve (AROC), sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio. Results Overall RNFL thickness had the highest AROC value (0.952 for all patients, 0.895 for the early glaucoma subgroup). For all patients, the highest sensitivity (98.4%, CI 96.3-100%) was achieved by using two criteria: ≥1 RNFL sectors being abnormal at the < 5% level, and overall classification of borderline or outside normal limits, with specificities of 88.9% (CI 84.0-94.0%) and 87.1% (CI 81.6-92.5%) respectively for these two criteria. Conclusions Statistical parameters for evaluating the diagnostic performance of the Spectralis spectral domain OCT were good for early perimetric glaucoma and excellent for moderately-advanced perimetric glaucoma. PMID:22265147

Ultra-widefield imaging with autofluorescence and indocyanine green angiography in central serous chorioretinopathy.

PubMed

Pang, Claudine E; Shah, Vinnie P; Sarraf, David; Freund, K Bailey

2014-08-01

To describe the spectrum of ultra-widefield autofluorescence (AF) and indocyanine green (ICG) angiographic findings in central serous chorioretinopathy (CSC). Retrospective observational case series. In 37 patients, 65 eyes with CSC from 2 vitreoretinal clinical practices were imaged using ultra-widefield AF and 24 of these eyes with ultra-widefield ICG angiography. Images were correlated with clinical findings and spectral-domain optical coherence tomography (OCT). In 37 (57%) eyes, a variety of altered AF patterns, including gravitational tracts, extended beyond the posterior 50 degrees of retina. Hyper-AF corresponded to areas of subretinal fluid (SRF) on spectral-domain OCT and was found to persist in 44 (70%) eyes for up to 8 years despite resolution of SRF. These areas corresponded to outer retinal atrophy with viable retinal pigment epithelium (RPE) on spectral-domain OCT and may be explained by the unmasking of normal background RPE AF. Ultra-widefield ICG angiography revealed dilated choroidal vessels and choroidal hyperpermeability in areas corresponding to altered AF on ultra-widefield AF in all 24 eyes. In 20 (83.3%) eyes, dilated vessels were observed in association with 1 or more congested vortex veins ampullas, suggesting that outflow congestion may be a contributing factor to the pathogenesis of CSC. Ultra-widefield AF and ICG angiography in CSC revealed more widespread disease in a single image than with standard field imaging and may be useful for identifying peripheral areas of previous or ongoing SRF and choroidal hyperpermeability that can assist in the diagnosis of CSC, surveillance of recurrent disease and treatment of active disease. Copyright © 2014 Elsevier Inc. All rights reserved.

Space moving target detection using time domain feature

NASA Astrophysics Data System (ADS)

Wang, Min; Chen, Jin-yong; Gao, Feng; Zhao, Jin-yu

2018-01-01

The traditional space target detection methods mainly use the spatial characteristics of the star map to detect the targets, which can not make full use of the time domain information. This paper presents a new space moving target detection method based on time domain features. We firstly construct the time spectral data of star map, then analyze the time domain features of the main objects (target, stars and the background) in star maps, finally detect the moving targets using single pulse feature of the time domain signal. The real star map target detection experimental results show that the proposed method can effectively detect the trajectory of moving targets in the star map sequence, and the detection probability achieves 99% when the false alarm rate is about 8×10-5, which outperforms those of compared algorithms.

Complex mode indication function and its applications to spatial domain parameter estimation

NASA Astrophysics Data System (ADS)

Shih, C. Y.; Tsuei, Y. G.; Allemang, R. J.; Brown, D. L.

1988-10-01

This paper introduces the concept of the Complex Mode Indication Function (CMIF) and its application in spatial domain parameter estimation. The concept of CMIF is developed by performing singular value decomposition (SVD) of the Frequency Response Function (FRF) matrix at each spectral line. The CMIF is defined as the eigenvalues, which are the square of the singular values, solved from the normal matrix formed from the FRF matrix, [ H( jω)] H[ H( jω)], at each spectral line. The CMIF appears to be a simple and efficient method for identifying the modes of the complex system. The CMIF identifies modes by showing the physical magnitude of each mode and the damped natural frequency for each root. Since multiple reference data is applied in CMIF, repeated roots can be detected. The CMIF also gives global modal parameters, such as damped natural frequencies, mode shapes and modal participation vectors. Since CMIF works in the spatial domain, uneven frequency spacing data such as data from spatial sine testing can be used. A second-stage procedure for accurate damped natural frequency and damping estimation as well as mode shape scaling is also discussed in this paper.

Spectral narrowing and spin echo for localized carriers with heavy-tailed L evy distribution of hopping times

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Z.; Mkhitaryan, Vagharsh; Raikh, M. E.

2016-02-02

We study analytically the free induction decay and the spin echo decay originating from the localized carriers moving between the sites which host random magnetic fields. Due to disorder in the site positions and energies, the on-site residence times, , are widely spread according to the L evy distribution. The power-law tail ∝ τ -1-∝ in the distribution of does not affect the conventional spectral narrowing for α > 2, but leads to a dramatic acceleration of the free induction decay in the domain 2 > α > 1. The next abrupt acceleration of the decay takes place as becomesmore » smaller than 1. In the latter domain the decay does not follow a simple-exponent law. To capture the behavior of the average spin in this domain, we solve the evolution equation for the average spin using the approach different from the conventional approach based on the Laplace transform. Unlike the free induction decay, the tail in the distribution of the residence times leads to the slow decay of the spin echo. The echo is dominated by realizations of the carrier motion for which the number of sites, visited by the carrier, is minimal.« less

Towards Optimal Spectral and Spatial Documentation of Cultural Heritage. Cosch - AN Interdisciplinary Action in the Cost Framework

NASA Astrophysics Data System (ADS)

Boochs, F.; Bentkowska-Kafel, A.; Degringy, C.; Hautta-Kasari, M.; Rizvic, S.; Sitnik, R.; Tremeau, A.

2013-07-01

This paper introduces the aims and early activities of Colour and Space in Cultural Heritage (COSCH), an interdisciplinary European network of experts in the latest optical measuring techniques and electronic imaging applied to documentation of artefacts. COSCH is a forum open to organisations, institutions and companies interested in collaboration within the emerging field of precise spectral and spatial imaging techniques, in physical and chemical sciences applied to cultural heritage objects, as well as in research and applications to conservation and art-historical analysis of such objects. COSCH started in November 2012. Funded by COST, an intergovernmental framework for European Cooperation in Science and Technology, COSCH networking activities enable knowledge exchange and coordination of nationally-funded research on a European level with occasional contribution of experts from other countries. Funding has been made available for four years (2012-2016). Participation is open to researchers across a wide range of disciplines, including computer scientists and museum professionals, art historians and academics in heritage-related fields. COSCH is a trans-domain Action (TD1201) of the COST Domain Materials, Physics and Nanosciences (MPNS) which facilitates and promotes innovation in material science. The work of COSCH is defined in the Memorandum of Understanding between the COST Office and the Chairman of COSCH. The Memorandum is available from http://www.cost.eu/domains_actions/mpns/Actions/TD1201 alongside the latest progress report and other documents. The scientific work draws on earlier and current research of the participants and is organised around the following areas: spectral and spatial object documentation; algorithms and procedures; analysis and restoration of surfaces and objects of material culture; visualisation of cultural heritage objects and its dissemination. Up-to-date information about COSCH activities, including its scientific and training programmes, abstracts of presentations and a list of participants, can all be found on the Action website at http://www.cosch.info.

Progress on type-II InAs/GaSb superlattice (T2SL) infrared photodetector : from MWIR to VLWIR spectral domains

NASA Astrophysics Data System (ADS)

Christol, P.; Rodriguez, J.-B.

2017-11-01

Infrared photodetectors based on type-II InAs/GaSb superlattice (T2SL) material has been given a lot of attention this past decade, in particular by U.S. laboratories. Among the advantages of this material system, one can cite the possibility to span a large Infrared (IR) range (3μm to 30 μm) by tailoring the band-gap independently from the lattice constant, allowing addressing many applications by the same fabrication process and the realization of multi-color IR sensors for high performance imaging systems. Recently, the maturity of the growth of the quantum structure by molecular beam epitaxy (MBE) and progress on the processing resulted in the demonstration of high-performance mega-pixel focal plane arrays (FPA) in both the mid-wavelength (MWIR) and the long-wavelength (LWIR) infrared spectral bands [1]. Consequently, InAs/GaSb T2SL photodetector can be now considered as a new infrared technology which can be complementary to InSb, MCT or QWIPs technologies. After some reminders on InAs/GaSb T2SL quantum structure properties, we present in this communication the results obtained by the IES laboratory, from Montpellier University, France, for photodiodes operating in the MWIR spectral domains. We then complete the paper by the main results reached by others laboratories for T2SL detectors operating from MWIR to VLWIR spectral ranges.

Spectral-Domain Optical Coherence Tomography Staging and Autofluorescence Imaging in Achromatopsia

PubMed Central

Greenberg, Jonathan P.; Sherman, Jerome; Zweifel, Sandrine A.; Chen, Royce W. S.; Duncker, Tobias; Kohl, Susanne; Baumann, Britta; Wissinger, Bernd; Yannuzzi, Lawrence A.; Tsang, Stephen H.

2015-01-01

Importance Evidence is mounting that achromatopsia is a progressive retinal degeneration, and treatments for this condition are on the horizon. Objectives To categorize achromatopsia into clinically identifiable stages using spectral-domain optical coherence tomography and to describe fundus autofluorescence imaging in this condition. Design, Setting, and Participants A prospective observational study was performed between 2010 and 2012 at the Edward S. Harkness Eye Institute, New York-Presbyterian Hospital. Participants included 17 patients (aged 10-62 years) with full-field electroretinography-confirmed achromatopsia. Main outcomes and Measures Spectral-domain optical coherence tomography features and staging system, fundus autofluorescence and near-infrared reflectance features and their correlation to optical coherence tomography, and genetic mutations served as the outcomes and measures. Results Achromatopsia was categorized into 5 stages on spectral-domain optical coherence tomography: stage 1 (2 patients [12%]), intact outer retina; stage 2 (2 patients [12%]), inner segment ellipsoid line disruption; stage 3 (5 patients [29%]), presence of an optically empty space; stage 4 (5 patients [29%]), optically empty space with partial retinal pigment epithelium disruption; and stage 5 (3 patients [18%]), complete retinal pigment epithelium disruption and/or loss of the outer nuclear layer. Stage 1 patients showed isolated hyperreflectivity of the external limiting membrane in the fovea, and the external limiting membrane was hyperreflective above each optically empty space. On near infrared reflectance imaging, the fovea was normal, hyporeflective, or showed both hyporeflective and hyperreflective features. All patients demonstrated autofluorescence abnormalities in the fovea and/or parafovea: 9 participants (53%) had reduced or absent autofluorescence surrounded by increased autofluorescence, 4 individuals (24%) showed only reduced or absent autofluorescence, 3 patients (18%) displayed only increased autofluorescence, and 1 individual (6%) exhibited decreased macular pigment contrast. Inner segment ellipsoid line loss generally correlated with the area of reduced autofluorescence, but hyperautofluorescence extended into this region in 2 patients (12%). Bilateral coloboma-like atrophic macular lesions were observed in 1 patient (6%). Five novel mutations were identified (4 in the CNGA3 gene and 1 in the CNGB3 gene). Conclusions and Relevance Achromatopsia often demonstrates hyperautofluorescence suggestive of progressive retinal degeneration. The proposed staging system facilitates classification of the disease into different phases of progression and may have therapeutic implications. PMID:24504161

Spectral-domain optical coherence tomography staging and autofluorescence imaging in achromatopsia.

PubMed

Greenberg, Jonathan P; Sherman, Jerome; Zweifel, Sandrine A; Chen, Royce W S; Duncker, Tobias; Kohl, Susanne; Baumann, Britta; Wissinger, Bernd; Yannuzzi, Lawrence A; Tsang, Stephen H

2014-04-01

IMPORTANCE Evidence is mounting that achromatopsia is a progressive retinal degeneration, and treatments for this condition are on the horizon. OBJECTIVES To categorize achromatopsia into clinically identifiable stages using spectral-domain optical coherence tomography and to describe fundus autofluorescence imaging in this condition. DESIGN, SETTING, AND PARTICIPANTS A prospective observational study was performed between 2010 and 2012 at the Edward S. Harkness Eye Institute, New York-Presbyterian Hospital. Participants included 17 patients (aged 10-62 years) with full-field electroretinography-confirmed achromatopsia. MAIN OUTCOMES AND MEASURES Spectral-domain optical coherence tomography features and staging system, fundus autofluorescence and near-infrared reflectance features and their correlation to optical coherence tomography, and genetic mutations served as the outcomes and measures. RESULTS Achromatopsia was categorized into 5 stages on spectral-domain optical coherence tomography: stage 1 (2 patients [12%]), intact outer retina; stage 2 (2 patients [12%]), inner segment ellipsoid line disruption; stage 3 (5 patients [29%]), presence of an optically empty space; stage 4 (5 patients [29%]), optically empty space with partial retinal pigment epithelium disruption; and stage 5 (3 patients [18%]), complete retinal pigment epithelium disruption and/or loss of the outer nuclear layer. Stage 1 patients showed isolated hyperreflectivity of the external limiting membrane in the fovea, and the external limiting membrane was hyperreflective above each optically empty space. On near infrared reflectance imaging, the fovea was normal, hyporeflective, or showed both hyporeflective and hyperreflective features. All patients demonstrated autofluorescence abnormalities in the fovea and/or parafovea: 9 participants (53%) had reduced or absent autofluorescence surrounded by increased autofluorescence, 4 individuals (24%) showed only reduced or absent autofluorescence, 3 patients (18%) displayed only increased autofluorescence, and 1 individual (6%) exhibited decreased macular pigment contrast. Inner segment ellipsoid line loss generally correlated with the area of reduced autofluorescence, but hyperautofluorescence extended into this region in 2 patients (12%). Bilateral coloboma-like atrophic macular lesions were observed in 1 patient (6%). Five novel mutations were identified (4 in the CNGA3 gene and 1 in the CNGB3 gene). CONCLUSIONS AND RELEVANCE Achromatopsia often demonstrates hyperautofluorescence suggestive of progressive retinal degeneration. The proposed staging system facilitates classification of the disease into different phases of progression and may have therapeutic implications.

Ultra-Widefield Steering-Based Spectral-Domain Optical Coherence Tomography Imaging of the Retinal Periphery.

PubMed

Choudhry, Netan; Golding, John; Manry, Matthew W; Rao, Rajesh C

2016-06-01

To describe the spectral-domain optical coherence tomography (SD OCT) features of peripheral retinal findings using an ultra-widefield (UWF) steering technique to image the retinal periphery. Observational study. A total of 68 patients (68 eyes) with 19 peripheral retinal features. Spectral-domain OCT-based structural features. Nineteen peripheral retinal features, including vortex vein, congenital hypertrophy of the retinal pigment epithelium, pars plana, ora serrata pearl, typical cystoid degeneration (TCD), cystic retinal tuft, meridional fold, lattice and cobblestone degeneration, retinal hole, retinal tear, rhegmatogenous retinal detachment, typical degenerative senile retinoschisis, peripheral laser coagulation scars, ora tooth, cryopexy scars (retinal tear and treated retinoblastoma scar), bone spicules, white without pressure, and peripheral drusen, were identified by peripheral clinical examination. Near-infrared scanning laser ophthalmoscopy images and SD OCT of these entities were registered to UWF color photographs. Spectral-domain OCT resolved structural features of all peripheral findings. Dilated hyporeflective tubular structures within the choroid were observed in the vortex vein. Loss of retinal lamination, neural retinal attenuation, retinal pigment epithelium loss, or hypertrophy was seen in several entities, including congenital hypertrophy of the retinal pigment epithelium, ora serrata pearl, TCD, cystic retinal tuft, meridional fold, lattice, and cobblestone degenerations. Hyporeflective intraretinal spaces, indicating cystoid or schitic fluid, were seen in ora serrata pearl, ora tooth, TCD, cystic retinal tuft, meridional fold, retinal hole, and typical degenerative senile retinoschisis. The vitreoretinal interface, which often consisted of lamellae-like structures of the condensed cortical vitreous near or adherent to the neural retina, appeared clearly in most peripheral findings, confirming its association with many low-risk and vision-threatening pathologies, such as lattice degeneration, meridional folds, retinal breaks, and rhegmatogenous retinal detachments. Ultra-widefield steering-based SD OCT imaging of the retinal periphery is feasible with current commercially available devices and provides detailed anatomic information of the peripheral retina, including benign and pathologic entities, not previously imaged. This imaging technique may deepen our structural understanding of these entities and their potentially associated macular and systemic pathologies, and may influence decision-making in clinical practice, particularly in areas with teleretinal capabilities but poor access to retinal specialists. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Airphoto assessment of changes in aquatic vegetation

NASA Technical Reports Server (NTRS)

Markham, B. L.; Philipson, W. R.; Russel, A. E.

1977-01-01

Large scale, multiyear, color and color infrared aerial photographs were used to evaluate changes in aquatic vegetation that have accompanied a reduction in phosphorus inputs to a phosphorus-limited, eutrophic lake in New York State. The study showed that the distribution of emergent, floating and submersed vegetation could be determined with little or no concurrent ground data; that various emergent and floating types could be separated and, with limited field checks, identified; and that different submersed types are generally not separable. Major vegetative types are characterized by spectral and nonspectral features, and a classification is developed for compiling time-sequential vegetation maps.

Remote measurement of ClO in the stratosphere

NASA Technical Reports Server (NTRS)

Menzies, R. T.

1979-01-01

ClO has been detected in the stratosphere from observations of the solar spectrum in the infrared, in a small spectral interval near 12 micrometers. The observations were made with a balloon-borne laser heterodyne radiometer, launched from Palestine, Texas on September 20. By comparing high sun spectra with a number of sequential spectra taken during sunset, an altitude profile has been calculated in the 29-38 km altitude range. The results show a peak mixing ratio in excess of one ppb above 34 km, and a rapid decrease in mixing ratio with decreasing altitude below 34 km.

Data Field Modeling and Spectral-Spatial Feature Fusion for Hyperspectral Data Classification.

PubMed

Liu, Da; Li, Jianxun

2016-12-16

Classification is a significant subject in hyperspectral remote sensing image processing. This study proposes a spectral-spatial feature fusion algorithm for the classification of hyperspectral images (HSI). Unlike existing spectral-spatial classification methods, the influences and interactions of the surroundings on each measured pixel were taken into consideration in this paper. Data field theory was employed as the mathematical realization of the field theory concept in physics, and both the spectral and spatial domains of HSI were considered as data fields. Therefore, the inherent dependency of interacting pixels was modeled. Using data field modeling, spatial and spectral features were transformed into a unified radiation form and further fused into a new feature by using a linear model. In contrast to the current spectral-spatial classification methods, which usually simply stack spectral and spatial features together, the proposed method builds the inner connection between the spectral and spatial features, and explores the hidden information that contributed to classification. Therefore, new information is included for classification. The final classification result was obtained using a random forest (RF) classifier. The proposed method was tested with the University of Pavia and Indian Pines, two well-known standard hyperspectral datasets. The experimental results demonstrate that the proposed method has higher classification accuracies than those obtained by the traditional approaches.

Directional and Spectral Irradiance in Ocean Models: Effects on Simulated Global Phytoplankton, Nutrients, and Primary Production

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Rousseaux, Cecile S.

2016-01-01

The importance of including directional and spectral light in simulations of ocean radiative transfer was investigated using a coupled biogeochemical-circulation-radiative model of the global oceans. The effort focused on phytoplankton abundances, nutrient concentrations and vertically-integrated net primary production. The importance was approached by sequentially removing directional (i.e., direct vs. diffuse) and spectral irradiance and comparing results of the above variables to a fully directionally and spectrally-resolved model. In each case the total irradiance was kept constant; it was only the pathways and spectral nature that were changed. Assuming all irradiance was diffuse had negligible effect on global ocean primary production. Global nitrate and total chlorophyll concentrations declined by about 20% each. The largest changes occurred in the tropics and sub-tropics rather than the high latitudes, where most of the irradiance is already diffuse. Disregarding spectral irradiance had effects that depended upon the choice of attenuation wavelength. The wavelength closest to the spectrally-resolved model, 500 nm, produced lower nitrate (19%) and chlorophyll (8%) and higher primary production (2%) than the spectral model. Phytoplankton relative abundances were very sensitive to the choice of non-spectral wavelength transmittance. The combined effects of neglecting both directional and spectral irradiance exacerbated the differences, despite using attenuation at 500 nm. Global nitrate decreased 33% and chlorophyll decreased 24%. Changes in phytoplankton community structure were considerable, representing a change from chlorophytes to cyanobacteria and coccolithophores. This suggested a shift in community function, from light-limitation to nutrient limitation: lower demands for nutrients from cyanobacteria and coccolithophores favored them over the more nutrient-demanding chlorophytes. Although diatoms have the highest nutrient demands in the model, their relative abundances were generally unaffected because they only prosper in nutrient-rich regions, such as the high latitudes and upwelling regions, which showed the fewest effects from the changes in radiative simulations. The results showed that including directional and spectral irradiance when simulating the ocean light field can be important for ocean biology, but the magnitude varies with variables and regions. The quantitative results are intended to assist ocean modelers when considering improved irradiance representations relative to other processes or variables associated with the issues of interest.

Further development of the dynamic gas temperature measurement system. Volume 2: Computer program user's manual

NASA Technical Reports Server (NTRS)

Stocks, Dana R.

1986-01-01

The Dynamic Gas Temperature Measurement System compensation software accepts digitized data from two different diameter thermocouples and computes a compensated frequency response spectrum for one of the thermocouples. Detailed discussions of the physical system, analytical model, and computer software are presented in this volume and in Volume 1 of this report under Task 3. Computer program software restrictions and test cases are also presented. Compensated and uncompensated data may be presented in either the time or frequency domain. Time domain data are presented as instantaneous temperature vs time. Frequency domain data may be presented in several forms such as power spectral density vs frequency.

Crystal structure of the catalytic domain of PigE: a transaminase involved in the biosynthesis of 2-methyl-3-n-amyl-pyrrole (MAP) from Serratia sp. FS14.

PubMed

Lou, Xiangdi; Ran, Tingting; Han, Ning; Gao, Yanyan; He, Jianhua; Tang, Lin; Xu, Dongqing; Wang, Weiwu

2014-04-25

Prodigiosin, a tripyrrole red pigment synthesized by Serratia and some other microbes through a bifurcated biosynthesis pathway, MBC (4-methoxy-2,2'-bipyrrole-5-carbaldehyde) and MAP (2-methyl-3-n-amyl-pyrrole) are synthesized separately and then condensed by PigC to form prodigiosin. MAP is synthesized sequentially by PigD, PigE and PigB. PigE catalyzes the transamination of an amino group to the aldehyde group of 3-acetyloctanal, resulting in an aminoketone, which spontaneously cyclizes to form H2MAP. Here we report the crystal structure of the catalytic domain of PigE which involved in the biosynthesis of prodigiosin precursor MAP for the first time to a resolution of 2.3Å with a homodimer in the asymmetric unit. The monomer of PigE catalytic domain is composed of three domains with PLP as cofactor: a small N-terminal domain connecting the catalytic domain with the front part of PigE, a large PLP-binding domain and a C-terminal domain. The residues from both monomers build the PLP binding site at the interface of the dimer which resembles the other PLP-dependent enzymes. Structural comparison of PigE with Thermus thermophilus AcOAT showed a higher hydrophobic and smaller active site of PigE, these differences may be the reason for substrate specificity. Copyright © 2014 Elsevier Inc. All rights reserved.

Bacterial SPOR domains are recruited to septal peptidoglycan by binding to glycan strands that lack stem peptides

PubMed Central

Yahashiri, Atsushi; Jorgenson, Matthew A.; Weiss, David S.

2015-01-01

Bacterial SPOR domains bind peptidoglycan (PG) and are thought to target proteins to the cell division site by binding to “denuded” glycan strands that lack stem peptides, but uncertainties remain, in part because septal-specific binding has yet to be studied in a purified system. Here we show that fusions of GFP to SPOR domains from the Escherichia coli cell-division proteins DamX, DedD, FtsN, and RlpA all localize to septal regions of purified PG sacculi obtained from E. coli and Bacillus subtilis. Treatment of sacculi with an amidase that removes stem peptides enhanced SPOR domain binding, whereas treatment with a lytic transglycosylase that removes denuded glycans reduced SPOR domain binding. These findings demonstrate unequivocally that SPOR domains localize by binding to septal PG, that the physiologically relevant binding site is indeed a denuded glycan, and that denuded glycans are enriched in septal PG rather than distributed uniformly around the sacculus. Accumulation of denuded glycans in the septal PG of both E. coli and B. subtilis, organisms separated by 1 billion years of evolution, suggests that sequential removal of stem peptides followed by degradation of the glycan backbone is an ancient feature of PG turnover during bacterial cell division. Linking SPOR domain localization to the abundance of a structure (denuded glycans) present only transiently during biogenesis of septal PG provides a mechanism for coordinating the function of SPOR domain proteins with the progress of cell division. PMID:26305949

Genèse des séquences sédimentaires du Crétacé supérieur des Aurès (Algérie). Rôle de l'eustatisme, de la tectonique, de la subsidence: une mise au pointSedimentary sequences in the Upper Cretaceous of Aures Mountains (Algerie). Eustatsy, tectonics and subsidence: a development.

NASA Astrophysics Data System (ADS)

Herkat, Missoum; Delfaud, Jean

2000-06-01

The Upper Cretaceous of Aurès has been studied using a sedimentological approach to characterize the sequential organisation and deposits distribution in the basin. The sequential chain which was observed has been correlated to eustatic cycles defined on a global scale. Palaeogeographic reconstruction shows a basin with its south margin corresponding to a proximal platform domain with essentially carbonate deposits and toward the northeast, marly sedimentation of pelagic nature. The influence of NW-SE to WNW-ESE accidents on sedimentation control has been found preponderant. Therefore a system of tilted blocks toward the south characterizes a large part of the basin. The subsidence evolution through Upper Cretaceous is marked by a recovery of a tectonic distension during some phases (Late Albian and Lower Turonian) and an essentially thermic subsidence during the other periods. Finally some precocious tectonic phases appeared as early as the Santonian-Campanian transition. The evolution of the basin was thus controlled by the drift of the African plate during the expansion of the Atlantic ocean and also the tectonic influence which began to appear in north Alpine domain.

Recovering Protein-Protein and Domain-Domain Interactions from Aggregation of IP-MS Proteomics of Coregulator Complexes

PubMed Central

Mazloom, Amin R.; Dannenfelser, Ruth; Clark, Neil R.; Grigoryan, Arsen V.; Linder, Kathryn M.; Cardozo, Timothy J.; Bond, Julia C.; Boran, Aislyn D. W.; Iyengar, Ravi; Malovannaya, Anna; Lanz, Rainer B.; Ma'ayan, Avi

2011-01-01

Coregulator proteins (CoRegs) are part of multi-protein complexes that transiently assemble with transcription factors and chromatin modifiers to regulate gene expression. In this study we analyzed data from 3,290 immuno-precipitations (IP) followed by mass spectrometry (MS) applied to human cell lines aimed at identifying CoRegs complexes. Using the semi-quantitative spectral counts, we scored binary protein-protein and domain-domain associations with several equations. Unlike previous applications, our methods scored prey-prey protein-protein interactions regardless of the baits used. We also predicted domain-domain interactions underlying predicted protein-protein interactions. The quality of predicted protein-protein and domain-domain interactions was evaluated using known binary interactions from the literature, whereas one protein-protein interaction, between STRN and CTTNBP2NL, was validated experimentally; and one domain-domain interaction, between the HEAT domain of PPP2R1A and the Pkinase domain of STK25, was validated using molecular docking simulations. The scoring schemes presented here recovered known, and predicted many new, complexes, protein-protein, and domain-domain interactions. The networks that resulted from the predictions are provided as a web-based interactive application at http://maayanlab.net/HT-IP-MS-2-PPI-DDI/. PMID:22219718

Spectral gain profile of a multi-stack terahertz quantum cascade laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachmann, D., E-mail: dominic.bachmann@tuwien.ac.at; Deutsch, C.; Krall, M.

2014-11-03

The spectral gain of a multi-stack terahertz quantum cascade laser, composed of three active regions with emission frequencies centered at 2.3, 2.7, and 3.0 THz, is studied as a function of driving current and temperature using terahertz time-domain spectroscopy. The optical gain associated with the particular quantum cascade stacks clamps at different driving currents and saturates to different values. We attribute these observations to varying pumping efficiencies of the respective upper laser states and to frequency dependent optical losses. The multi-stack active region exhibits a spectral gain full width at half-maximum of 1.1 THz. Bandwidth and spectral position of themore » measured gain match with the broadband laser emission. As the laser action ceases with increasing operating temperature, the gain at the dominant lasing frequency of 2.65 THz degrades sharply.« less

The basal ganglia is necessary for learning spectral, but not temporal features of birdsong

PubMed Central

Ali, Farhan; Fantana, Antoniu L.; Burak, Yoram; Ölveczky, Bence P.

2013-01-01

Executing a motor skill requires the brain to control which muscles to activate at what times. How these aspects of control - motor implementation and timing - are acquired, and whether the learning processes underlying them differ, is not well understood. To address this we used a reinforcement learning paradigm to independently manipulate both spectral and temporal features of birdsong, a complex learned motor sequence, while recording and perturbing activity in underlying circuits. Our results uncovered a striking dissociation in how neural circuits underlie learning in the two domains. The basal ganglia was required for modifying spectral, but not temporal structure. This functional dissociation extended to the descending motor pathway, where recordings from a premotor cortex analogue nucleus reflected changes to temporal, but not spectral structure. Our results reveal a strategy in which the nervous system employs different and largely independent circuits to learn distinct aspects of a motor skill. PMID:24075977

Assessments of SENTINEL-2 Vegetation Red-Edge Spectral Bands for Improving Land Cover Classification

NASA Astrophysics Data System (ADS)

Qiu, S.; He, B.; Yin, C.; Liao, Z.

2017-09-01

The Multi Spectral Instrument (MSI) onboard Sentinel-2 can record the information in Vegetation Red-Edge (VRE) spectral domains. In this study, the performance of the VRE bands on improving land cover classification was evaluated based on a Sentinel-2A MSI image in East Texas, USA. Two classification scenarios were designed by excluding and including the VRE bands. A Random Forest (RF) classifier was used to generate land cover maps and evaluate the contributions of different spectral bands. The combination of VRE bands increased the overall classification accuracy by 1.40 %, which was statistically significant. Both confusion matrices and land cover maps indicated that the most beneficial increase was from vegetation-related land cover types, especially agriculture. Comparison of the relative importance of each band showed that the most beneficial VRE bands were Band 5 and Band 6. These results demonstrated the value of VRE bands for land cover classification.

Assessing plant water relations based on hidden in formation in the hyper-spectral signatures: Parameterization of olive leaf P-V curve and estimation of water potential components

NASA Astrophysics Data System (ADS)

Rallo, Giovanni; Provenzano, Giuseppe; Jones, Hamlyn G.

2015-04-01

The Soil Plant Atmosphere Continuum (SPAC) is characterized by complex structures and biophysical processes acting over a wide range of temporal and spatial scales. Additionally, in olive grove systems, the plant adaptive strategies to respond to soil water-limited conditions make the system even more complex. One of the greatest challenges in hydrological research is to quantify changing plant water relations. A promising new technology is provided by the advent of new field spectroscopy detectors, characterized by very high resolution over the spectral range between 300 and 2500 nm, allowing the detection of narrow reflectance or absorptance peaks, to separate close lying peaks and to discover new information, hidden at lower resolutions. The general objective of the present research was to investigate a range of plant state function parameters in a non-destructive and repeatable manner and to improve methodologies aimed to parameterize hydrological models describing the entire SPAC, or each single compartment (soil or plant). We have investigated the use of hyperspectral sensing for the parameterization of the hydraulic pressure-volume curve (P-V) for olive leaf and for the indirect estimation of the two principal leaf water potential components, i.e. turgor and osmotic potentials. Experiments were carried out on an olive grove in Sicily, during the mature phase of the first vegetative flush. Leaf spectral signatures and associated P-V measurements were acquired on olive leaves collected from well-irrigated plants and from plants maintained under moderate or severe water stress. Leaf spectral reflectance was monitored with a FieldSpec 4 spectro-radiometer (Analytical Spectral Device, Inc.), in a range of wavelengths from VIS to SWIR (350-2500 nm), with sampling intervals of 1.4 nm and 2.0 nm, respectively in the regions from 350 to 1000 nm and from 1000 to 2500 nm. Measurements required the use of contact probe and leaf clip (Analytical Spectral Device, Inc.), specifically designed for plant leaves. Immediately after each spectral acquisition, water potential was measured on the same leaf with a Scholander pressure chamber (Skye, Powys, UK), by following the standard procedure usually adopted to detect leaf P-V curves (Vilagrosa et al. 2003). The relationship between pressure and volume was represented by means of the Höfler diagram (Richter, 1978) and modeled following an analytical approach. In order to parameterize the the P-V curve and to estimate the leaf water potential components, spectral indices were then examined, considering the features of water absorption in SWIR domain, sensitive to changes in leaf water content, and in NIR domain of the spectrum, sensitive to changes in leaf internal structure. A number of spectral indices were found to be related to patterns in the Höfler diagram, for leaves collected under different intensities of crop water stress. Moreover, results show that a fundamental characteristic point of the Höfler diagram, the turgor loss point, can be identified when indices accounting for both SWIR and NIR domains are considered. Acknowledgements The research was carried out thanks to the Alexander Goetz support program 2014, which provided the tools for spectral measurements and technical assistance during experiments.

Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations

NASA Astrophysics Data System (ADS)

Miguez-Macho, Gonzalo; Stenchikov, Georgiy L.; Robock, Alan

2004-07-01

It is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations. Here we study the physical mechanisms of this sensitivity. We conducted simulations with the Regional Atmospheric Modeling System (RAMS) for June 2000 over North America at 50 km horizontal resolution using a 7500 km × 5400 km grid and NCEP/NCAR reanalysis as boundary conditions. The position of the domain was displaced in several directions, always maintaining the U.S. in the interior, out of the buffer zone along the lateral boundaries. Circulation biases developed a large scale structure, organized by the Rocky Mountains, resulting from a systematic shifting of the synoptic wave trains that crossed the domain. The distortion of the large-scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered. This changed the large-scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the Great Plains in the summer season. As a consequence, precipitation results varied, sometimes greatly, among the experiments with the different grid positions. To eliminate the dependence of results on the position of the domain, we used spectral nudging of waves longer than 2500 km above the boundary layer. Moisture was not nudged at any level. This constrained the synoptic scales to follow reanalysis while allowing the model to develop the small-scale dynamics responsible for the rainfall. Nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved. We suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models.

The Derivation of Simple Poles in a Transfer Function from Real Frequency Information. Part 3. Object Classification and Identification,

DTIC Science & Technology

1977-01-10

This report is the third in a series of three that evaluate a technique (frequency-domain Prony) for obtaining the poles of a transfer function. The...main objective was to assess the feasibility of classifying or identifying ship-like targets by using pole sets derived from frequency-domain data. A...predictor-correlator procedure for using spectral data and library pole sets for this purpose was developed. Also studied was an iterative method for

Numerical and experimental study of curved and planar frequency selective surfaces with arbitrary illumination. M.S. Thesis - Maryland Univ., 1989

NASA Technical Reports Server (NTRS)

Caroglanian, Armen

1991-01-01

A frequency selective surface (FSS) composed of apertures in a metallic sheet is known as the inductive FSS. The infinite inductive FSS theory is derived and the aperture fields are solved by a spectral domain formulation with method of moments solution. Both full domain and subsectional basis functions are studied. A locally planar technique (LPT) is used to determine the forward scattered field from a generally shaped inductive FSS with arbitrary illumination.

Two-tint pump-probe measurements using a femtosecond laser oscillator and sharp-edged optical filters.

PubMed

Kang, Kwangu; Koh, Yee Kan; Chiritescu, Catalin; Zheng, Xuan; Cahill, David G

2008-11-01

We describe a simple approach for rejecting unwanted scattered light in two types of time-resolved pump-probe measurements, time-domain thermoreflectance (TDTR) and time-resolved incoherent anti-Stokes Raman scattering (TRIARS). Sharp edged optical filters are used to create spectrally distinct pump and probe beams from the broad spectral output of a femtosecond Ti:sapphire laser oscillator. For TDTR, the diffusely scattered pump light is then blocked by a third optical filter. For TRIARS, depolarized scattering created by the pump is shifted in frequency by approximately 250 cm(-1) relative to the polarized scattering created by the probe; therefore, spectral features created by the pump and probe scattering can be easily distinguished.

Temperature-sensitive gating of hCx26: high-resolution Raman spectroscopy sheds light on conformational changes

PubMed Central

Kniggendorf, Ann-Kathrin; Meinhardt-Wollweber, Merve; Yuan, Xiaogang; Roth, Bernhard; Seifert, Astrid; Fertig, Niels; Zeilinger, Carsten

2014-01-01

The temperature-sensitive gating of human Connexin 26 (hCx26) was analyzed with confocal Raman microscopy. High-resolution Raman spectra covering the spectral range between 400 and 1500 rel. cm−1 with a spectral resolution of 1 cm−1 were fully annotated, revealing notable differences between the spectrum recorded from solubilized hCx26 in Ca2+-buffered POPC at 10°C and any other set of protein conditions (temperature, Ca2+ presence, POPC presence). Spectral components originating from specific amino acids show that the TM1/EL1 parahelix and probably the TM4 trans-membrane helix and the plug domain are involved in the gating process responsible for fully closing the hemichannel. PMID:25071948

Temperature-sensitive gating of hCx26: high-resolution Raman spectroscopy sheds light on conformational changes.

PubMed

Kniggendorf, Ann-Kathrin; Meinhardt-Wollweber, Merve; Yuan, Xiaogang; Roth, Bernhard; Seifert, Astrid; Fertig, Niels; Zeilinger, Carsten

2014-07-01

The temperature-sensitive gating of human Connexin 26 (hCx26) was analyzed with confocal Raman microscopy. High-resolution Raman spectra covering the spectral range between 400 and 1500 rel. cm(-1) with a spectral resolution of 1 cm(-1) were fully annotated, revealing notable differences between the spectrum recorded from solubilized hCx26 in Ca(2+)-buffered POPC at 10°C and any other set of protein conditions (temperature, Ca(2+) presence, POPC presence). Spectral components originating from specific amino acids show that the TM1/EL1 parahelix and probably the TM4 trans-membrane helix and the plug domain are involved in the gating process responsible for fully closing the hemichannel.

Spectral binning for mitigation of polarization mode dispersion artifacts in catheter-based optical frequency domain imaging

PubMed Central

Villiger, Martin; Zhang, Ellen Ziyi; Nadkarni, Seemantini K.; Oh, Wang-Yuhl; Vakoc, Benjamin J.; Bouma, Brett E.

2013-01-01

Polarization mode dispersion (PMD) has been recognized as a significant barrier to sensitive and reproducible birefringence measurements with fiber-based, polarization-sensitive optical coherence tomography systems. Here, we present a signal processing strategy that reconstructs the local retardation robustly in the presence of system PMD. The algorithm uses a spectral binning approach to limit the detrimental impact of system PMD and benefits from the final averaging of the PMD-corrected retardation vectors of the spectral bins. The algorithm was validated with numerical simulations and experimental measurements of a rubber phantom. When applied to the imaging of human cadaveric coronary arteries, the algorithm was found to yield a substantial improvement in the reconstructed birefringence maps. PMID:23938487

Coherence and dimensionality of intense spatiospectral twin beams

NASA Astrophysics Data System (ADS)

Peřina, Jan

2015-07-01

Spatiospectral properties of twin beams at their transition from low to high intensities are analyzed in parametric and paraxial approximations using decomposition into paired spatial and spectral modes. Intensity auto- and cross-correlation functions are determined and compared in the spectral and temporal domains as well as the transverse wave-vector and crystal output planes. Whereas the spectral, temporal, and transverse wave-vector coherence increases with the increasing pump intensity, coherence in the crystal output plane is almost independent of the pump intensity owing to the mode structure in this plane. The corresponding auto- and cross-correlation functions approach each other for larger pump intensities. The entanglement dimensionality of a twin beam is determined with a comparison of several approaches.

Scanning protocols dedicated to smart velocity ranging in spectral OCT.

PubMed

Grulkowski, Ireneusz; Gorczynska, Iwona; Szkulmowski, Maciej; Szlag, Daniel; Szkulmowska, Anna; Leitgeb, Rainer A; Kowalczyk, Andrzej; Wojtkowski, Maciej

2009-12-21

We introduce a new type of scanning protocols, called segmented protocols, which enable extracting multi-range flow velocity information from a single Spectral OCT data set. The protocols are evaluated using a well defined flow in a glass capillary. As an example of in vivo studies, we demonstrate two- and three-dimensional imaging of the retinal vascular system in the eyes of healthy volunteers. The flow velocity detection is performed using a method of Joint Spectral and Time domain OCT. Velocity ranging is demonstrated in imaging of retinal vasculature in the macular region and in the optic disk area characterized by different flow velocity values. Additionally, an enhanced visualization of retinal capillary network is presented in the close proximity to macula.

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, Diana; Guha, Supratik; Lee, Byeongdu

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition and selective swelling of the of the polymer template. We show that the refractive index of Al 2O 3 can be lowered from 1.76more » down to 1.1 using this method. The thickness of the Al 2O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband anti-reflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE PAGES

Berman, Diana; Guha, Supratik; Lee, Byeongdu; ...

2017-01-31

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition and selective swelling of the of the polymer template. We show that the refractive index of Al 2O 3 can be lowered from 1.76more » down to 1.1 using this method. The thickness of the Al 2O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband anti-reflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, Diana; Guha, Supratik; Lee, Byeongdu

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al2O3 can be lowered from 1.76 down tomore » 1.1 using this method. The thickness of the Al2O3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.« less

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness.

PubMed

Berman, Diana; Guha, Supratik; Lee, Byeongdu; Elam, Jeffrey W; Darling, Seth B; Shevchenko, Elena V

2017-03-28

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al 2 O 3 can be lowered from 1.76 down to 1.1 using this method. The thickness of the Al 2 O 3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.

Approaches for Achieving Broadband Achromatic Phase Shifts for Visible Nulling Coronagraphy

NASA Technical Reports Server (NTRS)

Bolcar, Matthew R.; Lyon, Richard G.

2012-01-01

Visible nulling coronagraphy is one of the few approaches to the direct detection and characterization of Jovian and Terrestrial exoplanets that works with segmented aperture telescopes. Jovian and Terrestrial planets require at least 10(exp -9) and 10(exp -10) image plane contrasts, respectively, within the spectral bandpass and thus require a nearly achromatic pi-phase difference between the arms of the interferometer. An achromatic pi-phase shift can be achieved by several techniques, including sequential angled thick glass plates of varying dispersive materials, distributed thin-film multilayer coatings, and techniques that leverage the polarization-dependent phase shift of total-internal reflections. Herein we describe two such techniques: sequential thick glass plates and Fresnel rhomb prisms. A viable technique must achieve the achromatic phase shift while simultaneously minimizing the intensity difference, chromatic beam spread and polarization variation between each arm. In this paper we describe the above techniques and report on efforts to design, model, fabricate, align the trades associated with each technique that will lead to an implementations of the most promising one in Goddard's Visible Nulling Coronagraph (VNC).

Fluence-dependent singlet exciton dynamics in length-sorted chirality-enriched single-walled carbon nanotubes.

PubMed

Park, Jaehong; Deria, Pravas; Olivier, Jean-Hubert; Therien, Michael J

2014-02-12

We utilize individualized, length-sorted (6,5)-chirality enriched single-walled carbon nanotubes (SWNTs) having dimensions of 200 and 800 nm, femtosecond transient absorption spectroscopy, and variable excitation fluences that modulate the exciton density per nanotube unit length, to interrogate nanotube exciton/biexciton dynamics. For pump fluences below 30 μJ/cm(2), transient absorption (TA) spectra of (6,5) SWNTs reveal the instantaneous emergence of the exciton to biexciton transition (E11 → E11,BX) at 1100 nm; in contrast, under excitation fluences exceeding 100 μJ/cm(2), this TA signal manifests a rise time (τ rise ∼ 250 fs), indicating that E11 state repopulation is required to produce this signal. Femtosecond transient absorption spectroscopic data acquired over the 900-1400 nm spectral region of the near-infrared (NIR) region for (6,5) SWNTs, as a function of nanotube length and exciton density, reveal that over time delays that exceed 200 fs exciton-exciton interactions do not occur over spatial domains larger than 200 nm. Furthermore, the excitation fluence dependence of the E11 → E11,BX transient absorption signal demonstrates that relaxation of the E11 biexciton state (E11,BX) gives rise to a substantial E11 state population, as increasing delay times result in a concomitant increase of E11 → E11,BX transition oscillator strength. Numerical simulations based on a three-state model are consistent with a mechanism whereby biexcitons are generated at high excitation fluences via sequential SWNT ground- and E11-state excitation that occurs within the 980 nm excitation pulse duration. These studies that investigate fluence-dependent TA spectral evolution show that SWNT ground → E11 and E11 → E11,BX excitations are coresonant and provide evidence that E11,BX → E11 relaxation constitutes a significant decay channel for the SWNT biexciton state over delay times that exceed 200 fs, a finding that runs counter to assumptions made in previous analyses of SWNT biexciton dynamical data where exciton-exciton annihilation has been assumed to play a dominant role.

Dual-mode photosensitive arrays based on the integration of liquid crystal microlenses and CMOS sensors for obtaining the intensity images and wavefronts of objects.

PubMed

Tong, Qing; Lei, Yu; Xin, Zhaowei; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

2016-02-08

In this paper, we present a kind of dual-mode photosensitive arrays (DMPAs) constructed by hybrid integration a liquid crystal microlens array (LCMLA) driven electrically and a CMOS sensor array, which can be used to measure both the conventional intensity images and corresponding wavefronts of objects. We utilize liquid crystal materials to shape the microlens array with the electrically tunable focal length. Through switching the voltage signal on and off, the wavefronts and the intensity images can be acquired through the DMPAs, sequentially. We use white light to obtain the object's wavefronts for avoiding losing important wavefront information. We separate the white light wavefronts with a large number of spectral components and then experimentally compare them with single spectral wavefronts of typical red, green and blue lasers, respectively. Then we mix the red, green and blue wavefronts to a composite wavefront containing more optical information of the object.

Calibration of Herschel SPIRE FTS observations at different spectral resolutions

NASA Astrophysics Data System (ADS)

Marchili, N.; Hopwood, R.; Fulton, T.; Polehampton, E. T.; Valtchanov, I.; Zaretski, J.; Naylor, D. A.; Griffin, M. J.; Imhof, P.; Lim, T.; Lu, N.; Makiwa, G.; Pearson, C.; Spencer, L.

2017-01-01

The SPIRE Fourier Transform Spectrometer on-board the Herschel Space Observatory had two standard spectral resolution modes for science observations: high resolution (HR) and low resolution (LR), which could also be performed in sequence (H+LR). A comparison of the HR and LR resolution spectra taken in this sequential mode revealed a systematic discrepancy in the continuum level. Analysing the data at different stages during standard pipeline processing demonstrates that the telescope and instrument emission affect HR and H+LR observations in a systematically different way. The origin of this difference is found to lie in the variation of both the telescope and instrument response functions, while it is triggered by fast variation of the instrument temperatures. As it is not possible to trace the evolution of the response functions using housekeeping data from the instrument subsystems, the calibration cannot be corrected analytically. Therefore, an empirical correction for LR spectra has been developed, which removes the systematic noise introduced by the variation of the response functions.

The experimental vibrational infrared spectrum of lemon peel and simulation of spectral properties of the plant cell wall

NASA Astrophysics Data System (ADS)

Berezin, K. V.; Shagautdinova, I. T.; Chernavina, M. L.; Novoselova, A. V.; Dvoretskii, K. N.; Likhter, A. M.

2017-09-01

The experimental vibrational IR spectra of the outer part of lemon peel are recorded in the range of 3800-650 cm-1. The effect of artificial and natural dehydration of the peel on its vibrational spectrum is studied. It is shown that the colored outer layer of lemon peel does not have a noticeable effect on the vibrational spectrum. Upon 28-day storage of a lemon under natural laboratory conditions, only sequential dehydration processes are reflected in the vibrational spectrum of the peel. Within the framework of the theoretical DFT/B3LYP/6-31G(d) method, a model of a plant cell wall is developed consisting of a number of polymeric molecules of dietary fibers like cellulose, hemicellulose, pectin, lignin, some polyphenolic compounds (hesperetin glycoside-flavonoid), and a free water cluster. Using a supermolecular approach, the spectral properties of the wall of a lemon peel cell was simulated, and a detailed theoretical interpretation of the recorded vibrational spectrum is given.

The central role of recognition in auditory perception: a neurobiological model.

PubMed

McLachlan, Neil; Wilson, Sarah

2010-01-01

The model presents neurobiologically plausible accounts of sound recognition (including absolute pitch), neural plasticity involved in pitch, loudness and location information integration, and streaming and auditory recall. It is proposed that a cortical mechanism for sound identification modulates the spectrotemporal response fields of inferior colliculus neurons and regulates the encoding of the echoic trace in the thalamus. Identification involves correlation of sequential spectral slices of the stimulus-driven neural activity with stored representations in association with multimodal memories, verbal lexicons, and contextual information. Identities are then consolidated in auditory short-term memory and bound with attribute information (usually pitch, loudness, and direction) that has been integrated according to the identities' spectral properties. Attention to, or recall of, a particular identity will excite a particular sequence in the identification hierarchies and so lead to modulation of thalamus and inferior colliculus neural spectrotemporal response fields. This operates as an adaptive filter for identities, or their attributes, and explains many puzzling human auditory behaviors, such as the cocktail party effect, selective attention, and continuity illusions.

Sequence-specific sup 1 H NMR resonance assignments of Bacillus subtilis HPr: Use of spectra obtained from mutants to resolve spectral overlap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittekind, M.; Klevit, R.E.; Reizer, J.

1990-08-07

On the basis of an analysis of two-dimensional {sup 1}H NMR spectra, the complete sequence-specific {sup 1}H NMR assignments are presented for the phosphocarrier protein HPr from the Gram-positive bacterium Bacillus subtilis. During the assignment procedure, extensive use was made of spectra obtained from point mutants of HPr in order to resolve spectral overlap and to provide verification of assignments. Regions of regular secondary structure were identified by characteristic patterns of sequential backbone proton NOEs and slowly exchanging amide protons. B subtilis HPr contains four {beta}-strands that form a single antiparallel {beta}-sheet and two well-defined {alpha}-helices. There are two stretchesmore » of extended backbone structure, one of which contains the active site His{sub 15}. The overall fold of the protein is very similar to that of Escherichia coli HPr determined by NMR studies.« less

Next Generation Driver for Attosecond and Laser-plasma Physics.

PubMed

Rivas, D E; Borot, A; Cardenas, D E; Marcus, G; Gu, X; Herrmann, D; Xu, J; Tan, J; Kormin, D; Ma, G; Dallari, W; Tsakiris, G D; Földes, I B; Chou, S-W; Weidman, M; Bergues, B; Wittmann, T; Schröder, H; Tzallas, P; Charalambidis, D; Razskazovskaya, O; Pervak, V; Krausz, F; Veisz, L

2017-07-12

The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10 20  W/cm 2 with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.